1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988--2022 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2022 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2022 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Debuginfod:: Download debugging resources with @code{debuginfod}
188 * Man Pages:: Manual pages
189 * Copying:: GNU General Public License says
190 how you can copy and share GDB
191 * GNU Free Documentation License:: The license for this documentation
192 * Concept Index:: Index of @value{GDBN} concepts
193 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
194 functions, and Python data types
202 @unnumbered Summary of @value{GDBN}
204 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
205 going on ``inside'' another program while it executes---or what another
206 program was doing at the moment it crashed.
208 @value{GDBN} can do four main kinds of things (plus other things in support of
209 these) to help you catch bugs in the act:
213 Start your program, specifying anything that might affect its behavior.
216 Make your program stop on specified conditions.
219 Examine what has happened, when your program has stopped.
222 Change things in your program, so you can experiment with correcting the
223 effects of one bug and go on to learn about another.
226 You can use @value{GDBN} to debug programs written in C and C@t{++}.
227 For more information, see @ref{Supported Languages,,Supported Languages}.
228 For more information, see @ref{C,,C and C++}.
230 Support for D is partial. For information on D, see
234 Support for Modula-2 is partial. For information on Modula-2, see
235 @ref{Modula-2,,Modula-2}.
237 Support for OpenCL C is partial. For information on OpenCL C, see
238 @ref{OpenCL C,,OpenCL C}.
241 Debugging Pascal programs which use sets, subranges, file variables, or
242 nested functions does not currently work. @value{GDBN} does not support
243 entering expressions, printing values, or similar features using Pascal
247 @value{GDBN} can be used to debug programs written in Fortran, although
248 it may be necessary to refer to some variables with a trailing
251 @value{GDBN} can be used to debug programs written in Objective-C,
252 using either the Apple/NeXT or the GNU Objective-C runtime.
255 * Free Software:: Freely redistributable software
256 * Free Documentation:: Free Software Needs Free Documentation
257 * Contributors:: Contributors to GDB
261 @unnumberedsec Free Software
263 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
264 General Public License
265 (GPL). The GPL gives you the freedom to copy or adapt a licensed
266 program---but every person getting a copy also gets with it the
267 freedom to modify that copy (which means that they must get access to
268 the source code), and the freedom to distribute further copies.
269 Typical software companies use copyrights to limit your freedoms; the
270 Free Software Foundation uses the GPL to preserve these freedoms.
272 Fundamentally, the General Public License is a license which says that
273 you have these freedoms and that you cannot take these freedoms away
276 @node Free Documentation
277 @unnumberedsec Free Software Needs Free Documentation
279 The biggest deficiency in the free software community today is not in
280 the software---it is the lack of good free documentation that we can
281 include with the free software. Many of our most important
282 programs do not come with free reference manuals and free introductory
283 texts. Documentation is an essential part of any software package;
284 when an important free software package does not come with a free
285 manual and a free tutorial, that is a major gap. We have many such
288 Consider Perl, for instance. The tutorial manuals that people
289 normally use are non-free. How did this come about? Because the
290 authors of those manuals published them with restrictive terms---no
291 copying, no modification, source files not available---which exclude
292 them from the free software world.
294 That wasn't the first time this sort of thing happened, and it was far
295 from the last. Many times we have heard a GNU user eagerly describe a
296 manual that he is writing, his intended contribution to the community,
297 only to learn that he had ruined everything by signing a publication
298 contract to make it non-free.
300 Free documentation, like free software, is a matter of freedom, not
301 price. The problem with the non-free manual is not that publishers
302 charge a price for printed copies---that in itself is fine. (The Free
303 Software Foundation sells printed copies of manuals, too.) The
304 problem is the restrictions on the use of the manual. Free manuals
305 are available in source code form, and give you permission to copy and
306 modify. Non-free manuals do not allow this.
308 The criteria of freedom for a free manual are roughly the same as for
309 free software. Redistribution (including the normal kinds of
310 commercial redistribution) must be permitted, so that the manual can
311 accompany every copy of the program, both on-line and on paper.
313 Permission for modification of the technical content is crucial too.
314 When people modify the software, adding or changing features, if they
315 are conscientious they will change the manual too---so they can
316 provide accurate and clear documentation for the modified program. A
317 manual that leaves you no choice but to write a new manual to document
318 a changed version of the program is not really available to our
321 Some kinds of limits on the way modification is handled are
322 acceptable. For example, requirements to preserve the original
323 author's copyright notice, the distribution terms, or the list of
324 authors, are ok. It is also no problem to require modified versions
325 to include notice that they were modified. Even entire sections that
326 may not be deleted or changed are acceptable, as long as they deal
327 with nontechnical topics (like this one). These kinds of restrictions
328 are acceptable because they don't obstruct the community's normal use
331 However, it must be possible to modify all the @emph{technical}
332 content of the manual, and then distribute the result in all the usual
333 media, through all the usual channels. Otherwise, the restrictions
334 obstruct the use of the manual, it is not free, and we need another
335 manual to replace it.
337 Please spread the word about this issue. Our community continues to
338 lose manuals to proprietary publishing. If we spread the word that
339 free software needs free reference manuals and free tutorials, perhaps
340 the next person who wants to contribute by writing documentation will
341 realize, before it is too late, that only free manuals contribute to
342 the free software community.
344 If you are writing documentation, please insist on publishing it under
345 the GNU Free Documentation License or another free documentation
346 license. Remember that this decision requires your approval---you
347 don't have to let the publisher decide. Some commercial publishers
348 will use a free license if you insist, but they will not propose the
349 option; it is up to you to raise the issue and say firmly that this is
350 what you want. If the publisher you are dealing with refuses, please
351 try other publishers. If you're not sure whether a proposed license
352 is free, write to @email{licensing@@gnu.org}.
354 You can encourage commercial publishers to sell more free, copylefted
355 manuals and tutorials by buying them, and particularly by buying
356 copies from the publishers that paid for their writing or for major
357 improvements. Meanwhile, try to avoid buying non-free documentation
358 at all. Check the distribution terms of a manual before you buy it,
359 and insist that whoever seeks your business must respect your freedom.
360 Check the history of the book, and try to reward the publishers that
361 have paid or pay the authors to work on it.
363 The Free Software Foundation maintains a list of free documentation
364 published by other publishers, at
365 @url{http://www.fsf.org/doc/other-free-books.html}.
368 @unnumberedsec Contributors to @value{GDBN}
370 Richard Stallman was the original author of @value{GDBN}, and of many
371 other @sc{gnu} programs. Many others have contributed to its
372 development. This section attempts to credit major contributors. One
373 of the virtues of free software is that everyone is free to contribute
374 to it; with regret, we cannot actually acknowledge everyone here. The
375 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
376 blow-by-blow account.
378 Changes much prior to version 2.0 are lost in the mists of time.
381 @emph{Plea:} Additions to this section are particularly welcome. If you
382 or your friends (or enemies, to be evenhanded) have been unfairly
383 omitted from this list, we would like to add your names!
386 So that they may not regard their many labors as thankless, we
387 particularly thank those who shepherded @value{GDBN} through major
389 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
390 Jim Blandy (release 4.18);
391 Jason Molenda (release 4.17);
392 Stan Shebs (release 4.14);
393 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
394 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
395 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
396 Jim Kingdon (releases 3.5, 3.4, and 3.3);
397 and Randy Smith (releases 3.2, 3.1, and 3.0).
399 Richard Stallman, assisted at various times by Peter TerMaat, Chris
400 Hanson, and Richard Mlynarik, handled releases through 2.8.
402 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
403 in @value{GDBN}, with significant additional contributions from Per
404 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
405 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
406 much general update work leading to release 3.0).
408 @value{GDBN} uses the BFD subroutine library to examine multiple
409 object-file formats; BFD was a joint project of David V.
410 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
412 David Johnson wrote the original COFF support; Pace Willison did
413 the original support for encapsulated COFF.
415 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
417 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
418 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
420 Jean-Daniel Fekete contributed Sun 386i support.
421 Chris Hanson improved the HP9000 support.
422 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
423 David Johnson contributed Encore Umax support.
424 Jyrki Kuoppala contributed Altos 3068 support.
425 Jeff Law contributed HP PA and SOM support.
426 Keith Packard contributed NS32K support.
427 Doug Rabson contributed Acorn Risc Machine support.
428 Bob Rusk contributed Harris Nighthawk CX-UX support.
429 Chris Smith contributed Convex support (and Fortran debugging).
430 Jonathan Stone contributed Pyramid support.
431 Michael Tiemann contributed SPARC support.
432 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
433 Pace Willison contributed Intel 386 support.
434 Jay Vosburgh contributed Symmetry support.
435 Marko Mlinar contributed OpenRISC 1000 support.
437 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
439 Rich Schaefer and Peter Schauer helped with support of SunOS shared
442 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
443 about several machine instruction sets.
445 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
446 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
447 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
448 and RDI targets, respectively.
450 Brian Fox is the author of the readline libraries providing
451 command-line editing and command history.
453 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
454 Modula-2 support, and contributed the Languages chapter of this manual.
456 Fred Fish wrote most of the support for Unix System Vr4.
457 He also enhanced the command-completion support to cover C@t{++} overloaded
460 Hitachi America (now Renesas America), Ltd. sponsored the support for
461 H8/300, H8/500, and Super-H processors.
463 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
465 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
468 Toshiba sponsored the support for the TX39 Mips processor.
470 Matsushita sponsored the support for the MN10200 and MN10300 processors.
472 Fujitsu sponsored the support for SPARClite and FR30 processors.
474 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
477 Michael Snyder added support for tracepoints.
479 Stu Grossman wrote gdbserver.
481 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
482 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
484 The following people at the Hewlett-Packard Company contributed
485 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
486 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
487 compiler, and the Text User Interface (nee Terminal User Interface):
488 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
489 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
490 provided HP-specific information in this manual.
492 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
493 Robert Hoehne made significant contributions to the DJGPP port.
495 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
496 development since 1991. Cygnus engineers who have worked on @value{GDBN}
497 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
498 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
499 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
500 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
501 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
502 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
503 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
504 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
505 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
506 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
507 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
508 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
509 Zuhn have made contributions both large and small.
511 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
512 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
514 Jim Blandy added support for preprocessor macros, while working for Red
517 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
518 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
519 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
520 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
521 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
522 with the migration of old architectures to this new framework.
524 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
525 unwinder framework, this consisting of a fresh new design featuring
526 frame IDs, independent frame sniffers, and the sentinel frame. Mark
527 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
528 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
529 trad unwinders. The architecture-specific changes, each involving a
530 complete rewrite of the architecture's frame code, were carried out by
531 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
532 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
533 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
534 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
537 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
538 Tensilica, Inc.@: contributed support for Xtensa processors. Others
539 who have worked on the Xtensa port of @value{GDBN} in the past include
540 Steve Tjiang, John Newlin, and Scott Foehner.
542 Michael Eager and staff of Xilinx, Inc., contributed support for the
543 Xilinx MicroBlaze architecture.
545 Initial support for the FreeBSD/mips target and native configuration
546 was developed by SRI International and the University of Cambridge
547 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
548 ("CTSRD"), as part of the DARPA CRASH research programme.
550 Initial support for the FreeBSD/riscv target and native configuration
551 was developed by SRI International and the University of Cambridge
552 Computer Laboratory (Department of Computer Science and Technology)
553 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
554 SSITH research programme.
556 The original port to the OpenRISC 1000 is believed to be due to
557 Alessandro Forin and Per Bothner. More recent ports have been the work
558 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 Weimin Pan, David Faust and Jose E. Marchesi contributed support for
562 the Linux kernel BPF virtual architecture. This work was sponsored by
566 @chapter A Sample @value{GDBN} Session
568 You can use this manual at your leisure to read all about @value{GDBN}.
569 However, a handful of commands are enough to get started using the
570 debugger. This chapter illustrates those commands.
573 In this sample session, we emphasize user input like this: @b{input},
574 to make it easier to pick out from the surrounding output.
577 @c FIXME: this example may not be appropriate for some configs, where
578 @c FIXME...primary interest is in remote use.
580 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
581 processor) exhibits the following bug: sometimes, when we change its
582 quote strings from the default, the commands used to capture one macro
583 definition within another stop working. In the following short @code{m4}
584 session, we define a macro @code{foo} which expands to @code{0000}; we
585 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
586 same thing. However, when we change the open quote string to
587 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
588 procedure fails to define a new synonym @code{baz}:
597 @b{define(bar,defn(`foo'))}
601 @b{changequote(<QUOTE>,<UNQUOTE>)}
603 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
606 m4: End of input: 0: fatal error: EOF in string
610 Let us use @value{GDBN} to try to see what is going on.
613 $ @b{@value{GDBP} m4}
614 @c FIXME: this falsifies the exact text played out, to permit smallbook
615 @c FIXME... format to come out better.
616 @value{GDBN} is free software and you are welcome to distribute copies
617 of it under certain conditions; type "show copying" to see
619 There is absolutely no warranty for @value{GDBN}; type "show warranty"
622 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
627 @value{GDBN} reads only enough symbol data to know where to find the
628 rest when needed; as a result, the first prompt comes up very quickly.
629 We now tell @value{GDBN} to use a narrower display width than usual, so
630 that examples fit in this manual.
633 (@value{GDBP}) @b{set width 70}
637 We need to see how the @code{m4} built-in @code{changequote} works.
638 Having looked at the source, we know the relevant subroutine is
639 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
640 @code{break} command.
643 (@value{GDBP}) @b{break m4_changequote}
644 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
648 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
649 control; as long as control does not reach the @code{m4_changequote}
650 subroutine, the program runs as usual:
653 (@value{GDBP}) @b{run}
654 Starting program: /work/Editorial/gdb/gnu/m4/m4
662 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
663 suspends execution of @code{m4}, displaying information about the
664 context where it stops.
667 @b{changequote(<QUOTE>,<UNQUOTE>)}
669 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
671 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
675 Now we use the command @code{n} (@code{next}) to advance execution to
676 the next line of the current function.
680 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
685 @code{set_quotes} looks like a promising subroutine. We can go into it
686 by using the command @code{s} (@code{step}) instead of @code{next}.
687 @code{step} goes to the next line to be executed in @emph{any}
688 subroutine, so it steps into @code{set_quotes}.
692 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
694 530 if (lquote != def_lquote)
698 The display that shows the subroutine where @code{m4} is now
699 suspended (and its arguments) is called a stack frame display. It
700 shows a summary of the stack. We can use the @code{backtrace}
701 command (which can also be spelled @code{bt}), to see where we are
702 in the stack as a whole: the @code{backtrace} command displays a
703 stack frame for each active subroutine.
706 (@value{GDBP}) @b{bt}
707 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
709 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
711 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
712 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
714 #4 0x79dc in expand_input () at macro.c:40
715 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
719 We step through a few more lines to see what happens. The first two
720 times, we can use @samp{s}; the next two times we use @code{n} to avoid
721 falling into the @code{xstrdup} subroutine.
725 0x3b5c 532 if (rquote != def_rquote)
727 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
728 def_lquote : xstrdup(lq);
730 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
733 538 len_lquote = strlen(rquote);
737 The last line displayed looks a little odd; we can examine the variables
738 @code{lquote} and @code{rquote} to see if they are in fact the new left
739 and right quotes we specified. We use the command @code{p}
740 (@code{print}) to see their values.
743 (@value{GDBP}) @b{p lquote}
744 $1 = 0x35d40 "<QUOTE>"
745 (@value{GDBP}) @b{p rquote}
746 $2 = 0x35d50 "<UNQUOTE>"
750 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
751 To look at some context, we can display ten lines of source
752 surrounding the current line with the @code{l} (@code{list}) command.
758 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
760 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
763 538 len_lquote = strlen(rquote);
764 539 len_rquote = strlen(lquote);
771 Let us step past the two lines that set @code{len_lquote} and
772 @code{len_rquote}, and then examine the values of those variables.
776 539 len_rquote = strlen(lquote);
779 (@value{GDBP}) @b{p len_lquote}
781 (@value{GDBP}) @b{p len_rquote}
786 That certainly looks wrong, assuming @code{len_lquote} and
787 @code{len_rquote} are meant to be the lengths of @code{lquote} and
788 @code{rquote} respectively. We can set them to better values using
789 the @code{p} command, since it can print the value of
790 any expression---and that expression can include subroutine calls and
794 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
796 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
801 Is that enough to fix the problem of using the new quotes with the
802 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
803 executing with the @code{c} (@code{continue}) command, and then try the
804 example that caused trouble initially:
810 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
817 Success! The new quotes now work just as well as the default ones. The
818 problem seems to have been just the two typos defining the wrong
819 lengths. We allow @code{m4} exit by giving it an EOF as input:
823 Program exited normally.
827 The message @samp{Program exited normally.} is from @value{GDBN}; it
828 indicates @code{m4} has finished executing. We can end our @value{GDBN}
829 session with the @value{GDBN} @code{quit} command.
832 (@value{GDBP}) @b{quit}
836 @chapter Getting In and Out of @value{GDBN}
838 This chapter discusses how to start @value{GDBN}, and how to get out of it.
842 type @samp{@value{GDBP}} to start @value{GDBN}.
844 type @kbd{quit}, @kbd{exit} or @kbd{Ctrl-d} to exit.
848 * Invoking GDB:: How to start @value{GDBN}
849 * Quitting GDB:: How to quit @value{GDBN}
850 * Shell Commands:: How to use shell commands inside @value{GDBN}
851 * Logging Output:: How to log @value{GDBN}'s output to a file
855 @section Invoking @value{GDBN}
857 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
858 @value{GDBN} reads commands from the terminal until you tell it to exit.
860 You can also run @code{@value{GDBP}} with a variety of arguments and options,
861 to specify more of your debugging environment at the outset.
863 The command-line options described here are designed
864 to cover a variety of situations; in some environments, some of these
865 options may effectively be unavailable.
867 The most usual way to start @value{GDBN} is with one argument,
868 specifying an executable program:
871 @value{GDBP} @var{program}
875 You can also start with both an executable program and a core file
879 @value{GDBP} @var{program} @var{core}
882 You can, instead, specify a process ID as a second argument or use option
883 @code{-p}, if you want to debug a running process:
886 @value{GDBP} @var{program} 1234
891 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
892 can omit the @var{program} filename.
894 Taking advantage of the second command-line argument requires a fairly
895 complete operating system; when you use @value{GDBN} as a remote
896 debugger attached to a bare board, there may not be any notion of
897 ``process'', and there is often no way to get a core dump. @value{GDBN}
898 will warn you if it is unable to attach or to read core dumps.
900 You can optionally have @code{@value{GDBP}} pass any arguments after the
901 executable file to the inferior using @code{--args}. This option stops
904 @value{GDBP} --args gcc -O2 -c foo.c
906 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
907 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
909 You can run @code{@value{GDBP}} without printing the front material, which describes
910 @value{GDBN}'s non-warranty, by specifying @code{--silent}
911 (or @code{-q}/@code{--quiet}):
914 @value{GDBP} --silent
918 You can further control how @value{GDBN} starts up by using command-line
919 options. @value{GDBN} itself can remind you of the options available.
929 to display all available options and briefly describe their use
930 (@samp{@value{GDBP} -h} is a shorter equivalent).
932 All options and command line arguments you give are processed
933 in sequential order. The order makes a difference when the
934 @samp{-x} option is used.
938 * File Options:: Choosing files
939 * Mode Options:: Choosing modes
940 * Startup:: What @value{GDBN} does during startup
941 * Initialization Files:: Initialization Files
945 @subsection Choosing Files
947 When @value{GDBN} starts, it reads any arguments other than options as
948 specifying an executable file and core file (or process ID). This is
949 the same as if the arguments were specified by the @samp{-se} and
950 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
951 first argument that does not have an associated option flag as
952 equivalent to the @samp{-se} option followed by that argument; and the
953 second argument that does not have an associated option flag, if any, as
954 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
955 If the second argument begins with a decimal digit, @value{GDBN} will
956 first attempt to attach to it as a process, and if that fails, attempt
957 to open it as a corefile. If you have a corefile whose name begins with
958 a digit, you can prevent @value{GDBN} from treating it as a pid by
959 prefixing it with @file{./}, e.g.@: @file{./12345}.
961 If @value{GDBN} has not been configured to included core file support,
962 such as for most embedded targets, then it will complain about a second
963 argument and ignore it.
965 Many options have both long and short forms; both are shown in the
966 following list. @value{GDBN} also recognizes the long forms if you truncate
967 them, so long as enough of the option is present to be unambiguous.
968 (If you prefer, you can flag option arguments with @samp{--} rather
969 than @samp{-}, though we illustrate the more usual convention.)
971 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
972 @c way, both those who look for -foo and --foo in the index, will find
976 @item -symbols @var{file}
978 @cindex @code{--symbols}
980 Read symbol table from file @var{file}.
982 @item -exec @var{file}
984 @cindex @code{--exec}
986 Use file @var{file} as the executable file to execute when appropriate,
987 and for examining pure data in conjunction with a core dump.
991 Read symbol table from file @var{file} and use it as the executable
994 @item -core @var{file}
996 @cindex @code{--core}
998 Use file @var{file} as a core dump to examine.
1000 @item -pid @var{number}
1001 @itemx -p @var{number}
1002 @cindex @code{--pid}
1004 Connect to process ID @var{number}, as with the @code{attach} command.
1006 @item -command @var{file}
1007 @itemx -x @var{file}
1008 @cindex @code{--command}
1010 Execute commands from file @var{file}. The contents of this file is
1011 evaluated exactly as the @code{source} command would.
1012 @xref{Command Files,, Command files}.
1014 @item -eval-command @var{command}
1015 @itemx -ex @var{command}
1016 @cindex @code{--eval-command}
1018 Execute a single @value{GDBN} command.
1020 This option may be used multiple times to call multiple commands. It may
1021 also be interleaved with @samp{-command} as required.
1024 @value{GDBP} -ex 'target sim' -ex 'load' \
1025 -x setbreakpoints -ex 'run' a.out
1028 @item -init-command @var{file}
1029 @itemx -ix @var{file}
1030 @cindex @code{--init-command}
1032 Execute commands from file @var{file} before loading the inferior (but
1033 after loading gdbinit files).
1036 @item -init-eval-command @var{command}
1037 @itemx -iex @var{command}
1038 @cindex @code{--init-eval-command}
1040 Execute a single @value{GDBN} command before loading the inferior (but
1041 after loading gdbinit files).
1044 @item -early-init-command @var{file}
1045 @itemx -eix @var{file}
1046 @cindex @code{--early-init-command}
1048 Execute commands from @var{file} very early in the initialization
1049 process, before any output is produced. @xref{Startup}.
1051 @item -early-init-eval-command @var{command}
1052 @itemx -eiex @var{command}
1053 @cindex @code{--early-init-eval-command}
1054 @cindex @code{-eiex}
1055 Execute a single @value{GDBN} command very early in the initialization
1056 process, before any output is produced.
1058 @item -directory @var{directory}
1059 @itemx -d @var{directory}
1060 @cindex @code{--directory}
1062 Add @var{directory} to the path to search for source and script files.
1066 @cindex @code{--readnow}
1068 Read each symbol file's entire symbol table immediately, rather than
1069 the default, which is to read it incrementally as it is needed.
1070 This makes startup slower, but makes future operations faster.
1073 @anchor{--readnever}
1074 @cindex @code{--readnever}, command-line option
1075 Do not read each symbol file's symbolic debug information. This makes
1076 startup faster but at the expense of not being able to perform
1077 symbolic debugging. DWARF unwind information is also not read,
1078 meaning backtraces may become incomplete or inaccurate. One use of
1079 this is when a user simply wants to do the following sequence: attach,
1080 dump core, detach. Loading the debugging information in this case is
1081 an unnecessary cause of delay.
1085 @subsection Choosing Modes
1087 You can run @value{GDBN} in various alternative modes---for example, in
1088 batch mode or quiet mode.
1096 Do not execute commands found in any initialization files
1097 (@pxref{Initialization Files}).
1102 Do not execute commands found in any home directory initialization
1103 file (@pxref{Initialization Files,,Home directory initialization
1104 file}). The system wide and current directory initialization files
1110 @cindex @code{--quiet}
1111 @cindex @code{--silent}
1113 ``Quiet''. Do not print the introductory and copyright messages. These
1114 messages are also suppressed in batch mode.
1116 @kindex set startup-quietly
1117 @kindex show startup-quietly
1118 This can also be enabled using @code{set startup-quietly on}. The
1119 default is @code{off}. Use @code{show startup-quietly} to see the
1120 current setting. Place @code{set startup-quietly on} into your early
1121 initialization file (@pxref{Initialization Files,,Initialization
1122 Files}) to have future @value{GDBN} sessions startup quietly.
1125 @cindex @code{--batch}
1126 Run in batch mode. Exit with status @code{0} after processing all the
1127 command files specified with @samp{-x} (and all commands from
1128 initialization files, if not inhibited with @samp{-n}). Exit with
1129 nonzero status if an error occurs in executing the @value{GDBN} commands
1130 in the command files. Batch mode also disables pagination, sets unlimited
1131 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1132 off} were in effect (@pxref{Messages/Warnings}).
1134 Batch mode may be useful for running @value{GDBN} as a filter, for
1135 example to download and run a program on another computer; in order to
1136 make this more useful, the message
1139 Program exited normally.
1143 (which is ordinarily issued whenever a program running under
1144 @value{GDBN} control terminates) is not issued when running in batch
1148 @cindex @code{--batch-silent}
1149 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1150 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1151 unaffected). This is much quieter than @samp{-silent} and would be useless
1152 for an interactive session.
1154 This is particularly useful when using targets that give @samp{Loading section}
1155 messages, for example.
1157 Note that targets that give their output via @value{GDBN}, as opposed to
1158 writing directly to @code{stdout}, will also be made silent.
1160 @item -return-child-result
1161 @cindex @code{--return-child-result}
1162 The return code from @value{GDBN} will be the return code from the child
1163 process (the process being debugged), with the following exceptions:
1167 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1168 internal error. In this case the exit code is the same as it would have been
1169 without @samp{-return-child-result}.
1171 The user quits with an explicit value. E.g., @samp{quit 1}.
1173 The child process never runs, or is not allowed to terminate, in which case
1174 the exit code will be -1.
1177 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1178 when @value{GDBN} is being used as a remote program loader or simulator
1183 @cindex @code{--nowindows}
1185 ``No windows''. If @value{GDBN} comes with a graphical user interface
1186 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1187 interface. If no GUI is available, this option has no effect.
1191 @cindex @code{--windows}
1193 If @value{GDBN} includes a GUI, then this option requires it to be
1196 @item -cd @var{directory}
1198 Run @value{GDBN} using @var{directory} as its working directory,
1199 instead of the current directory.
1201 @item -data-directory @var{directory}
1202 @itemx -D @var{directory}
1203 @cindex @code{--data-directory}
1205 Run @value{GDBN} using @var{directory} as its data directory.
1206 The data directory is where @value{GDBN} searches for its
1207 auxiliary files. @xref{Data Files}.
1211 @cindex @code{--fullname}
1213 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1214 subprocess. It tells @value{GDBN} to output the full file name and line
1215 number in a standard, recognizable fashion each time a stack frame is
1216 displayed (which includes each time your program stops). This
1217 recognizable format looks like two @samp{\032} characters, followed by
1218 the file name, line number and character position separated by colons,
1219 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1220 @samp{\032} characters as a signal to display the source code for the
1223 @item -annotate @var{level}
1224 @cindex @code{--annotate}
1225 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1226 effect is identical to using @samp{set annotate @var{level}}
1227 (@pxref{Annotations}). The annotation @var{level} controls how much
1228 information @value{GDBN} prints together with its prompt, values of
1229 expressions, source lines, and other types of output. Level 0 is the
1230 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1231 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1232 that control @value{GDBN}, and level 2 has been deprecated.
1234 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1238 @cindex @code{--args}
1239 Change interpretation of command line so that arguments following the
1240 executable file are passed as command line arguments to the inferior.
1241 This option stops option processing.
1243 @item -baud @var{bps}
1245 @cindex @code{--baud}
1247 Set the line speed (baud rate or bits per second) of any serial
1248 interface used by @value{GDBN} for remote debugging.
1250 @item -l @var{timeout}
1252 Set the timeout (in seconds) of any communication used by @value{GDBN}
1253 for remote debugging.
1255 @item -tty @var{device}
1256 @itemx -t @var{device}
1257 @cindex @code{--tty}
1259 Run using @var{device} for your program's standard input and output.
1260 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1262 @c resolve the situation of these eventually
1264 @cindex @code{--tui}
1265 Activate the @dfn{Text User Interface} when starting. The Text User
1266 Interface manages several text windows on the terminal, showing
1267 source, assembly, registers and @value{GDBN} command outputs
1268 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1269 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1270 Using @value{GDBN} under @sc{gnu} Emacs}).
1272 @item -interpreter @var{interp}
1273 @cindex @code{--interpreter}
1274 Use the interpreter @var{interp} for interface with the controlling
1275 program or device. This option is meant to be set by programs which
1276 communicate with @value{GDBN} using it as a back end.
1277 @xref{Interpreters, , Command Interpreters}.
1279 @samp{--interpreter=mi} (or @samp{--interpreter=mi3}) causes
1280 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1281 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1282 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1283 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1284 interfaces are no longer supported.
1287 @cindex @code{--write}
1288 Open the executable and core files for both reading and writing. This
1289 is equivalent to the @samp{set write on} command inside @value{GDBN}
1293 @cindex @code{--statistics}
1294 This option causes @value{GDBN} to print statistics about time and
1295 memory usage after it completes each command and returns to the prompt.
1298 @cindex @code{--version}
1299 This option causes @value{GDBN} to print its version number and
1300 no-warranty blurb, and exit.
1302 @item -configuration
1303 @cindex @code{--configuration}
1304 This option causes @value{GDBN} to print details about its build-time
1305 configuration parameters, and then exit. These details can be
1306 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1311 @subsection What @value{GDBN} Does During Startup
1312 @cindex @value{GDBN} startup
1314 Here's the description of what @value{GDBN} does during session startup:
1319 Performs minimal setup required to initialize basic internal state.
1322 @cindex early initialization file
1323 Reads commands from the early initialization file (if any) in your
1324 home directory. Only a restricted set of commands can be placed into
1325 an early initialization file, see @ref{Initialization Files}, for
1329 Executes commands and command files specified by the @samp{-eiex} and
1330 @samp{-eix} command line options in their specified order. Only a
1331 restricted set of commands can be used with @samp{-eiex} and
1332 @samp{eix}, see @ref{Initialization Files}, for details.
1335 Sets up the command interpreter as specified by the command line
1336 (@pxref{Mode Options, interpreter}).
1340 Reads the system wide initialization file and the files from the
1341 system wide initialization directory, @pxref{System Wide Init Files}.
1344 Reads the initialization file (if any) in your home directory and
1345 executes all the commands in that file, @pxref{Home Directory Init
1348 @anchor{Option -init-eval-command}
1350 Executes commands and command files specified by the @samp{-iex} and
1351 @samp{-ix} options in their specified order. Usually you should use the
1352 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1353 settings before @value{GDBN} init files get executed and before inferior
1357 Processes command line options and operands.
1360 Reads and executes the commands from the initialization file (if any)
1361 in the current working directory as long as @samp{set auto-load
1362 local-gdbinit} is set to @samp{on} (@pxref{Init File in the Current
1363 Directory}). This is only done if the current directory is different
1364 from your home directory. Thus, you can have more than one init file,
1365 one generic in your home directory, and another, specific to the
1366 program you are debugging, in the directory where you invoke
1367 @value{GDBN}. @xref{Init File in the Current Directory during
1371 If the command line specified a program to debug, or a process to
1372 attach to, or a core file, @value{GDBN} loads any auto-loaded
1373 scripts provided for the program or for its loaded shared libraries.
1374 @xref{Auto-loading}.
1376 If you wish to disable the auto-loading during startup,
1377 you must do something like the following:
1380 $ gdb -iex "set auto-load python-scripts off" myprogram
1383 Option @samp{-ex} does not work because the auto-loading is then turned
1387 Executes commands and command files specified by the @samp{-ex} and
1388 @samp{-x} options in their specified order. @xref{Command Files}, for
1389 more details about @value{GDBN} command files.
1392 Reads the command history recorded in the @dfn{history file}.
1393 @xref{Command History}, for more details about the command history and the
1394 files where @value{GDBN} records it.
1397 @node Initialization Files
1398 @subsection Initialization Files
1399 @cindex init file name
1401 During startup (@pxref{Startup}) @value{GDBN} will execute commands
1402 from several initialization files. These initialization files use the
1403 same syntax as @dfn{command files} (@pxref{Command Files}) and are
1404 processed by @value{GDBN} in the same way.
1406 To display the list of initialization files loaded by @value{GDBN} at
1407 startup, in the order they will be loaded, you can use @kbd{gdb
1410 @cindex early initialization
1411 The @dfn{early initialization} file is loaded very early in
1412 @value{GDBN}'s initialization process, before the interpreter
1413 (@pxref{Interpreters}) has been initialized, and before the default
1414 target (@pxref{Targets}) is initialized. Only @code{set} or
1415 @code{source} commands should be placed into an early initialization
1416 file, and the only @code{set} commands that can be used are those that
1417 control how @value{GDBN} starts up.
1419 Commands that can be placed into an early initialization file will be
1420 documented as such throughout this manual. Any command that is not
1421 documented as being suitable for an early initialization file should
1422 instead be placed into a general initialization file. Command files
1423 passed to @code{--early-init-command} or @code{-eix} are also early
1424 initialization files, with the same command restrictions. Only
1425 commands that can appear in an early initialization file should be
1426 passed to @code{--early-init-eval-command} or @code{-eiex}.
1428 @cindex general initialization
1429 In contrast, the @dfn{general initialization} files are processed
1430 later, after @value{GDBN} has finished its own internal initialization
1431 process, any valid command can be used in these files.
1433 @cindex initialization file
1434 Throughout the rest of this document the term @dfn{initialization
1435 file} refers to one of the general initialization files, not the early
1436 initialization file. Any discussion of the early initialization file
1437 will specifically mention that it is the early initialization file
1440 As the system wide and home directory initialization files are
1441 processed before most command line options, changes to settings
1442 (e.g.@: @samp{set complaints}) can affect subsequent processing of
1443 command line options and operands.
1445 The following sections describe where @value{GDBN} looks for the early
1446 initialization and initialization files, and the order that the files
1449 @subsubsection Home directory early initialization files
1451 @value{GDBN} initially looks for an early initialization file in the
1452 users home directory@footnote{On DOS/Windows systems, the home
1453 directory is the one pointed to by the @env{HOME} environment
1454 variable.}. There are a number of locations that @value{GDBN} will
1455 search in the home directory, these locations are searched in order
1456 and @value{GDBN} will load the first file that it finds, and
1457 subsequent locations will not be checked.
1459 On non-macOS hosts the locations searched are:
1462 The file @file{gdb/gdbearlyinit} within the directory pointed to by the
1463 environment variable @env{XDG_CONFIG_HOME}, if it is defined.
1465 The file @file{.config/gdb/gdbearlyinit} within the directory pointed to
1466 by the environment variable @env{HOME}, if it is defined.
1468 The file @file{.gdbearlyinit} within the directory pointed to by the
1469 environment variable @env{HOME}, if it is defined.
1472 By contrast, on macOS hosts the locations searched are:
1475 The file @file{Library/Preferences/gdb/gdbearlyinit} within the
1476 directory pointed to by the environment variable @env{HOME}, if it is
1479 The file @file{.gdbearlyinit} within the directory pointed to by the
1480 environment variable @env{HOME}, if it is defined.
1483 It is possible to prevent the home directory early initialization file
1484 from being loaded using the @samp{-nx} or @samp{-nh} command line
1485 options, @pxref{Mode Options,,Choosing Modes}.
1487 @anchor{System Wide Init Files}
1488 @subsubsection System wide initialization files
1490 There are two locations that are searched for system wide
1491 initialization files. Both of these locations are always checked:
1495 @item @file{system.gdbinit}
1496 This is a single system-wide initialization file. Its location is
1497 specified with the @code{--with-system-gdbinit} configure option
1498 (@pxref{System-wide configuration}). It is loaded first when
1499 @value{GDBN} starts, before command line options have been processed.
1501 @item @file{system.gdbinit.d}
1502 This is the system-wide initialization directory. Its location is
1503 specified with the @code{--with-system-gdbinit-dir} configure option
1504 (@pxref{System-wide configuration}). Files in this directory are
1505 loaded in alphabetical order immediately after @file{system.gdbinit}
1506 (if enabled) when @value{GDBN} starts, before command line options
1507 have been processed. Files need to have a recognized scripting
1508 language extension (@file{.py}/@file{.scm}) or be named with a
1509 @file{.gdb} extension to be interpreted as regular @value{GDBN}
1510 commands. @value{GDBN} will not recurse into any subdirectories of
1515 It is possible to prevent the system wide initialization files from
1516 being loaded using the @samp{-nx} command line option, @pxref{Mode
1517 Options,,Choosing Modes}.
1519 @anchor{Home Directory Init File}
1520 @subsubsection Home directory initialization file
1521 @cindex @file{gdbinit}
1522 @cindex @file{.gdbinit}
1523 @cindex @file{gdb.ini}
1525 After loading the system wide initialization files @value{GDBN} will
1526 look for an initialization file in the users home
1527 directory@footnote{On DOS/Windows systems, the home directory is the
1528 one pointed to by the @env{HOME} environment variable.}. There are a
1529 number of locations that @value{GDBN} will search in the home
1530 directory, these locations are searched in order and @value{GDBN} will
1531 load the first file that it finds, and subsequent locations will not
1534 On non-Apple hosts the locations searched are:
1536 @item $XDG_CONFIG_HOME/gdb/gdbinit
1537 @item $HOME/.config/gdb/gdbinit
1538 @item $HOME/.gdbinit
1541 While on Apple hosts the locations searched are:
1543 @item $HOME/Library/Preferences/gdb/gdbinit
1544 @item $HOME/.gdbinit
1547 It is possible to prevent the home directory initialization file from
1548 being loaded using the @samp{-nx} or @samp{-nh} command line options,
1549 @pxref{Mode Options,,Choosing Modes}.
1551 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini} instead of
1552 @file{.gdbinit} or @file{gdbinit}, due to the limitations of file
1553 names imposed by DOS filesystems. The Windows port of @value{GDBN}
1554 uses the standard name, but if it finds a @file{gdb.ini} file in your
1555 home directory, it warns you about that and suggests to rename the
1556 file to the standard name.
1558 @anchor{Init File in the Current Directory during Startup}
1559 @subsubsection Local directory initialization file
1561 @value{GDBN} will check the current directory for a file called
1562 @file{.gdbinit}. It is loaded last, after command line options
1563 other than @samp{-x} and @samp{-ex} have been processed. The command
1564 line options @samp{-x} and @samp{-ex} are processed last, after
1565 @file{.gdbinit} has been loaded, @pxref{File Options,,Choosing
1568 If the file in the current directory was already loaded as the home
1569 directory initialization file then it will not be loaded a second
1572 It is possible to prevent the local directory initialization file from
1573 being loaded using the @samp{-nx} command line option, @pxref{Mode
1574 Options,,Choosing Modes}.
1577 @section Quitting @value{GDBN}
1578 @cindex exiting @value{GDBN}
1579 @cindex leaving @value{GDBN}
1582 @kindex quit @r{[}@var{expression}@r{]}
1583 @kindex exit @r{[}@var{expression}@r{]}
1584 @kindex q @r{(@code{quit})}
1585 @item quit @r{[}@var{expression}@r{]}
1586 @itemx exit @r{[}@var{expression}@r{]}
1588 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1589 @code{q}), the @code{exit} command, or type an end-of-file
1590 character (usually @kbd{Ctrl-d}). If you do not supply @var{expression},
1591 @value{GDBN} will terminate normally; otherwise it will terminate using
1592 the result of @var{expression} as the error code.
1596 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1597 terminates the action of any @value{GDBN} command that is in progress and
1598 returns to @value{GDBN} command level. It is safe to type the interrupt
1599 character at any time because @value{GDBN} does not allow it to take effect
1600 until a time when it is safe.
1602 If you have been using @value{GDBN} to control an attached process or
1603 device, you can release it with the @code{detach} command
1604 (@pxref{Attach, ,Debugging an Already-running Process}).
1606 @node Shell Commands
1607 @section Shell Commands
1609 If you need to execute occasional shell commands during your
1610 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1611 just use the @code{shell} command.
1616 @cindex shell escape
1617 @item shell @var{command-string}
1618 @itemx !@var{command-string}
1619 Invoke a standard shell to execute @var{command-string}.
1620 Note that no space is needed between @code{!} and @var{command-string}.
1621 On GNU and Unix systems, the environment variable @env{SHELL}, if it
1622 exists, determines which shell to run. Otherwise @value{GDBN} uses
1623 the default shell (@file{/bin/sh} on GNU and Unix systems,
1624 @file{cmd.exe} on MS-Windows, @file{COMMAND.COM} on MS-DOS, etc.).
1627 The utility @code{make} is often needed in development environments.
1628 You do not have to use the @code{shell} command for this purpose in
1633 @cindex calling make
1634 @item make @var{make-args}
1635 Execute the @code{make} program with the specified
1636 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1642 @cindex send the output of a gdb command to a shell command
1644 @item pipe [@var{command}] | @var{shell_command}
1645 @itemx | [@var{command}] | @var{shell_command}
1646 @itemx pipe -d @var{delim} @var{command} @var{delim} @var{shell_command}
1647 @itemx | -d @var{delim} @var{command} @var{delim} @var{shell_command}
1648 Executes @var{command} and sends its output to @var{shell_command}.
1649 Note that no space is needed around @code{|}.
1650 If no @var{command} is provided, the last command executed is repeated.
1652 In case the @var{command} contains a @code{|}, the option @code{-d @var{delim}}
1653 can be used to specify an alternate delimiter string @var{delim} that separates
1654 the @var{command} from the @var{shell_command}.
1687 (gdb) | -d ! echo this contains a | char\n ! sed -e 's/|/PIPE/'
1688 this contains a PIPE char
1689 (gdb) | -d xxx echo this contains a | char!\n xxx sed -e 's/|/PIPE/'
1690 this contains a PIPE char!
1696 The convenience variables @code{$_shell_exitcode} and @code{$_shell_exitsignal}
1697 can be used to examine the exit status of the last shell command launched
1698 by @code{shell}, @code{make}, @code{pipe} and @code{|}.
1699 @xref{Convenience Vars,, Convenience Variables}.
1701 @node Logging Output
1702 @section Logging Output
1703 @cindex logging @value{GDBN} output
1704 @cindex save @value{GDBN} output to a file
1706 You may want to save the output of @value{GDBN} commands to a file.
1707 There are several commands to control @value{GDBN}'s logging.
1710 @kindex set logging enabled
1711 @item set logging enabled [on|off]
1712 Enable or disable logging.
1713 @cindex logging file name
1714 @item set logging file @var{file}
1715 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1716 @item set logging overwrite [on|off]
1717 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1718 you want @code{set logging enabled on} to overwrite the logfile instead.
1719 @item set logging redirect [on|off]
1720 By default, @value{GDBN} output will go to both the terminal and the logfile.
1721 Set @code{redirect} if you want output to go only to the log file.
1722 @item set logging debugredirect [on|off]
1723 By default, @value{GDBN} debug output will go to both the terminal and the logfile.
1724 Set @code{debugredirect} if you want debug output to go only to the log file.
1725 @kindex show logging
1727 Show the current values of the logging settings.
1730 You can also redirect the output of a @value{GDBN} command to a
1731 shell command. @xref{pipe}.
1733 @chapter @value{GDBN} Commands
1735 You can abbreviate a @value{GDBN} command to the first few letters of the command
1736 name, if that abbreviation is unambiguous; and you can repeat certain
1737 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1738 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1739 show you the alternatives available, if there is more than one possibility).
1742 * Command Syntax:: How to give commands to @value{GDBN}
1743 * Command Settings:: How to change default behavior of commands
1744 * Completion:: Command completion
1745 * Command Options:: Command options
1746 * Help:: How to ask @value{GDBN} for help
1749 @node Command Syntax
1750 @section Command Syntax
1752 A @value{GDBN} command is a single line of input. There is no limit on
1753 how long it can be. It starts with a command name, which is followed by
1754 arguments whose meaning depends on the command name. For example, the
1755 command @code{step} accepts an argument which is the number of times to
1756 step, as in @samp{step 5}. You can also use the @code{step} command
1757 with no arguments. Some commands do not allow any arguments.
1759 @cindex abbreviation
1760 @value{GDBN} command names may always be truncated if that abbreviation is
1761 unambiguous. Other possible command abbreviations are listed in the
1762 documentation for individual commands. In some cases, even ambiguous
1763 abbreviations are allowed; for example, @code{s} is specially defined as
1764 equivalent to @code{step} even though there are other commands whose
1765 names start with @code{s}. You can test abbreviations by using them as
1766 arguments to the @code{help} command.
1768 @cindex repeating commands
1769 @kindex RET @r{(repeat last command)}
1770 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1771 repeat the previous command. Certain commands (for example, @code{run})
1772 will not repeat this way; these are commands whose unintentional
1773 repetition might cause trouble and which you are unlikely to want to
1774 repeat. User-defined commands can disable this feature; see
1775 @ref{Define, dont-repeat}.
1777 The @code{list} and @code{x} commands, when you repeat them with
1778 @key{RET}, construct new arguments rather than repeating
1779 exactly as typed. This permits easy scanning of source or memory.
1781 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1782 output, in a way similar to the common utility @code{more}
1783 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1784 @key{RET} too many in this situation, @value{GDBN} disables command
1785 repetition after any command that generates this sort of display.
1787 @kindex # @r{(a comment)}
1789 Any text from a @kbd{#} to the end of the line is a comment; it does
1790 nothing. This is useful mainly in command files (@pxref{Command
1791 Files,,Command Files}).
1793 @cindex repeating command sequences
1794 @kindex Ctrl-o @r{(operate-and-get-next)}
1795 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1796 commands. This command accepts the current line, like @key{RET}, and
1797 then fetches the next line relative to the current line from the history
1801 @node Command Settings
1802 @section Command Settings
1803 @cindex default behavior of commands, changing
1804 @cindex default settings, changing
1806 Many commands change their behavior according to command-specific
1807 variables or settings. These settings can be changed with the
1808 @code{set} subcommands. For example, the @code{print} command
1809 (@pxref{Data, ,Examining Data}) prints arrays differently depending on
1810 settings changeable with the commands @code{set print elements
1811 NUMBER-OF-ELEMENTS} and @code{set print array-indexes}, among others.
1813 You can change these settings to your preference in the gdbinit files
1814 loaded at @value{GDBN} startup. @xref{Startup}.
1816 The settings can also be changed interactively during the debugging
1817 session. For example, to change the limit of array elements to print,
1818 you can do the following:
1820 (@value{GDBN}) set print elements 10
1821 (@value{GDBN}) print some_array
1822 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1825 The above @code{set print elements 10} command changes the number of
1826 elements to print from the default of 200 to 10. If you only intend
1827 this limit of 10 to be used for printing @code{some_array}, then you
1828 must restore the limit back to 200, with @code{set print elements
1831 Some commands allow overriding settings with command options. For
1832 example, the @code{print} command supports a number of options that
1833 allow overriding relevant global print settings as set by @code{set
1834 print} subcommands. @xref{print options}. The example above could be
1837 (@value{GDBN}) print -elements 10 -- some_array
1838 $1 = @{0, 10, 20, 30, 40, 50, 60, 70, 80, 90...@}
1841 Alternatively, you can use the @code{with} command to change a setting
1842 temporarily, for the duration of a command invocation.
1845 @kindex with command
1846 @kindex w @r{(@code{with})}
1848 @cindex temporarily change settings
1849 @item with @var{setting} [@var{value}] [-- @var{command}]
1850 @itemx w @var{setting} [@var{value}] [-- @var{command}]
1851 Temporarily set @var{setting} to @var{value} for the duration of
1854 @var{setting} is any setting you can change with the @code{set}
1855 subcommands. @var{value} is the value to assign to @code{setting}
1856 while running @code{command}.
1858 If no @var{command} is provided, the last command executed is
1861 If a @var{command} is provided, it must be preceded by a double dash
1862 (@code{--}) separator. This is required because some settings accept
1863 free-form arguments, such as expressions or filenames.
1865 For example, the command
1867 (@value{GDBN}) with print array on -- print some_array
1870 is equivalent to the following 3 commands:
1872 (@value{GDBN}) set print array on
1873 (@value{GDBN}) print some_array
1874 (@value{GDBN}) set print array off
1877 The @code{with} command is particularly useful when you want to
1878 override a setting while running user-defined commands, or commands
1879 defined in Python or Guile. @xref{Extending GDB,, Extending GDB}.
1882 (@value{GDBN}) with print pretty on -- my_complex_command
1885 To change several settings for the same command, you can nest
1886 @code{with} commands. For example, @code{with language ada -- with
1887 print elements 10} temporarily changes the language to Ada and sets a
1888 limit of 10 elements to print for arrays and strings.
1893 @section Command Completion
1896 @cindex word completion
1897 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1898 only one possibility; it can also show you what the valid possibilities
1899 are for the next word in a command, at any time. This works for @value{GDBN}
1900 commands, @value{GDBN} subcommands, command options, and the names of symbols
1903 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1904 of a word. If there is only one possibility, @value{GDBN} fills in the
1905 word, and waits for you to finish the command (or press @key{RET} to
1906 enter it). For example, if you type
1908 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1909 @c complete accuracy in these examples; space introduced for clarity.
1910 @c If texinfo enhancements make it unnecessary, it would be nice to
1911 @c replace " @key" by "@key" in the following...
1913 (@value{GDBP}) info bre @key{TAB}
1917 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1918 the only @code{info} subcommand beginning with @samp{bre}:
1921 (@value{GDBP}) info breakpoints
1925 You can either press @key{RET} at this point, to run the @code{info
1926 breakpoints} command, or backspace and enter something else, if
1927 @samp{breakpoints} does not look like the command you expected. (If you
1928 were sure you wanted @code{info breakpoints} in the first place, you
1929 might as well just type @key{RET} immediately after @samp{info bre},
1930 to exploit command abbreviations rather than command completion).
1932 If there is more than one possibility for the next word when you press
1933 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1934 characters and try again, or just press @key{TAB} a second time;
1935 @value{GDBN} displays all the possible completions for that word. For
1936 example, you might want to set a breakpoint on a subroutine whose name
1937 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1938 just sounds the bell. Typing @key{TAB} again displays all the
1939 function names in your program that begin with those characters, for
1943 (@value{GDBP}) b make_ @key{TAB}
1944 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1945 make_a_section_from_file make_environ
1946 make_abs_section make_function_type
1947 make_blockvector make_pointer_type
1948 make_cleanup make_reference_type
1949 make_command make_symbol_completion_list
1950 (@value{GDBP}) b make_
1954 After displaying the available possibilities, @value{GDBN} copies your
1955 partial input (@samp{b make_} in the example) so you can finish the
1958 If you just want to see the list of alternatives in the first place, you
1959 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1960 means @kbd{@key{META} ?}. You can type this either by holding down a
1961 key designated as the @key{META} shift on your keyboard (if there is
1962 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1964 If the number of possible completions is large, @value{GDBN} will
1965 print as much of the list as it has collected, as well as a message
1966 indicating that the list may be truncated.
1969 (@value{GDBP}) b m@key{TAB}@key{TAB}
1971 <... the rest of the possible completions ...>
1972 *** List may be truncated, max-completions reached. ***
1977 This behavior can be controlled with the following commands:
1980 @kindex set max-completions
1981 @item set max-completions @var{limit}
1982 @itemx set max-completions unlimited
1983 Set the maximum number of completion candidates. @value{GDBN} will
1984 stop looking for more completions once it collects this many candidates.
1985 This is useful when completing on things like function names as collecting
1986 all the possible candidates can be time consuming.
1987 The default value is 200. A value of zero disables tab-completion.
1988 Note that setting either no limit or a very large limit can make
1990 @kindex show max-completions
1991 @item show max-completions
1992 Show the maximum number of candidates that @value{GDBN} will collect and show
1996 @cindex quotes in commands
1997 @cindex completion of quoted strings
1998 Sometimes the string you need, while logically a ``word'', may contain
1999 parentheses or other characters that @value{GDBN} normally excludes from
2000 its notion of a word. To permit word completion to work in this
2001 situation, you may enclose words in @code{'} (single quote marks) in
2002 @value{GDBN} commands.
2004 A likely situation where you might need this is in typing an
2005 expression that involves a C@t{++} symbol name with template
2006 parameters. This is because when completing expressions, GDB treats
2007 the @samp{<} character as word delimiter, assuming that it's the
2008 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
2011 For example, when you want to call a C@t{++} template function
2012 interactively using the @code{print} or @code{call} commands, you may
2013 need to distinguish whether you mean the version of @code{name} that
2014 was specialized for @code{int}, @code{name<int>()}, or the version
2015 that was specialized for @code{float}, @code{name<float>()}. To use
2016 the word-completion facilities in this situation, type a single quote
2017 @code{'} at the beginning of the function name. This alerts
2018 @value{GDBN} that it may need to consider more information than usual
2019 when you press @key{TAB} or @kbd{M-?} to request word completion:
2022 (@value{GDBP}) p 'func< @kbd{M-?}
2023 func<int>() func<float>()
2024 (@value{GDBP}) p 'func<
2027 When setting breakpoints however (@pxref{Specify Location}), you don't
2028 usually need to type a quote before the function name, because
2029 @value{GDBN} understands that you want to set a breakpoint on a
2033 (@value{GDBP}) b func< @kbd{M-?}
2034 func<int>() func<float>()
2035 (@value{GDBP}) b func<
2038 This is true even in the case of typing the name of C@t{++} overloaded
2039 functions (multiple definitions of the same function, distinguished by
2040 argument type). For example, when you want to set a breakpoint you
2041 don't need to distinguish whether you mean the version of @code{name}
2042 that takes an @code{int} parameter, @code{name(int)}, or the version
2043 that takes a @code{float} parameter, @code{name(float)}.
2046 (@value{GDBP}) b bubble( @kbd{M-?}
2047 bubble(int) bubble(double)
2048 (@value{GDBP}) b bubble(dou @kbd{M-?}
2052 See @ref{quoting names} for a description of other scenarios that
2055 For more information about overloaded functions, see @ref{C Plus Plus
2056 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
2057 overload-resolution off} to disable overload resolution;
2058 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
2060 @cindex completion of structure field names
2061 @cindex structure field name completion
2062 @cindex completion of union field names
2063 @cindex union field name completion
2064 When completing in an expression which looks up a field in a
2065 structure, @value{GDBN} also tries@footnote{The completer can be
2066 confused by certain kinds of invalid expressions. Also, it only
2067 examines the static type of the expression, not the dynamic type.} to
2068 limit completions to the field names available in the type of the
2072 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
2073 magic to_fputs to_rewind
2074 to_data to_isatty to_write
2075 to_delete to_put to_write_async_safe
2080 This is because the @code{gdb_stdout} is a variable of the type
2081 @code{struct ui_file} that is defined in @value{GDBN} sources as
2088 ui_file_flush_ftype *to_flush;
2089 ui_file_write_ftype *to_write;
2090 ui_file_write_async_safe_ftype *to_write_async_safe;
2091 ui_file_fputs_ftype *to_fputs;
2092 ui_file_read_ftype *to_read;
2093 ui_file_delete_ftype *to_delete;
2094 ui_file_isatty_ftype *to_isatty;
2095 ui_file_rewind_ftype *to_rewind;
2096 ui_file_put_ftype *to_put;
2101 @node Command Options
2102 @section Command options
2104 @cindex command options
2105 Some commands accept options starting with a leading dash. For
2106 example, @code{print -pretty}. Similarly to command names, you can
2107 abbreviate a @value{GDBN} option to the first few letters of the
2108 option name, if that abbreviation is unambiguous, and you can also use
2109 the @key{TAB} key to get @value{GDBN} to fill out the rest of a word
2110 in an option (or to show you the alternatives available, if there is
2111 more than one possibility).
2113 @cindex command options, raw input
2114 Some commands take raw input as argument. For example, the print
2115 command processes arbitrary expressions in any of the languages
2116 supported by @value{GDBN}. With such commands, because raw input may
2117 start with a leading dash that would be confused with an option or any
2118 of its abbreviations, e.g.@: @code{print -p} (short for @code{print
2119 -pretty} or printing negative @code{p}?), if you specify any command
2120 option, then you must use a double-dash (@code{--}) delimiter to
2121 indicate the end of options.
2123 @cindex command options, boolean
2125 Some options are described as accepting an argument which can be
2126 either @code{on} or @code{off}. These are known as @dfn{boolean
2127 options}. Similarly to boolean settings commands---@code{on} and
2128 @code{off} are the typical values, but any of @code{1}, @code{yes} and
2129 @code{enable} can also be used as ``true'' value, and any of @code{0},
2130 @code{no} and @code{disable} can also be used as ``false'' value. You
2131 can also omit a ``true'' value, as it is implied by default.
2133 For example, these are equivalent:
2136 (@value{GDBP}) print -object on -pretty off -element unlimited -- *myptr
2137 (@value{GDBP}) p -o -p 0 -e u -- *myptr
2140 You can discover the set of options some command accepts by completing
2141 on @code{-} after the command name. For example:
2144 (@value{GDBP}) print -@key{TAB}@key{TAB}
2145 -address -max-depth -pretty -symbol
2146 -array -memory-tag-violations -raw-values -union
2147 -array-indexes -null-stop -repeats -vtbl
2148 -elements -object -static-members
2151 Completion will in some cases guide you with a suggestion of what kind
2152 of argument an option expects. For example:
2155 (@value{GDBP}) print -elements @key{TAB}@key{TAB}
2159 Here, the option expects a number (e.g., @code{100}), not literal
2160 @code{NUMBER}. Such metasyntactical arguments are always presented in
2163 (For more on using the @code{print} command, see @ref{Data, ,Examining
2167 @section Getting Help
2168 @cindex online documentation
2171 You can always ask @value{GDBN} itself for information on its commands,
2172 using the command @code{help}.
2175 @kindex h @r{(@code{help})}
2178 You can use @code{help} (abbreviated @code{h}) with no arguments to
2179 display a short list of named classes of commands:
2183 List of classes of commands:
2185 aliases -- User-defined aliases of other commands
2186 breakpoints -- Making program stop at certain points
2187 data -- Examining data
2188 files -- Specifying and examining files
2189 internals -- Maintenance commands
2190 obscure -- Obscure features
2191 running -- Running the program
2192 stack -- Examining the stack
2193 status -- Status inquiries
2194 support -- Support facilities
2195 tracepoints -- Tracing of program execution without
2196 stopping the program
2197 user-defined -- User-defined commands
2199 Type "help" followed by a class name for a list of
2200 commands in that class.
2201 Type "help" followed by command name for full
2203 Command name abbreviations are allowed if unambiguous.
2206 @c the above line break eliminates huge line overfull...
2208 @item help @var{class}
2209 Using one of the general help classes as an argument, you can get a
2210 list of the individual commands in that class. If a command has
2211 aliases, the aliases are given after the command name, separated by
2212 commas. If an alias has default arguments, the full definition of
2213 the alias is given after the first line.
2214 For example, here is the help display for the class @code{status}:
2217 (@value{GDBP}) help status
2222 @c Line break in "show" line falsifies real output, but needed
2223 @c to fit in smallbook page size.
2224 info, inf, i -- Generic command for showing things
2225 about the program being debugged
2226 info address, iamain -- Describe where symbol SYM is stored.
2227 alias iamain = info address main
2228 info all-registers -- List of all registers and their contents,
2229 for selected stack frame.
2231 show, info set -- Generic command for showing things
2234 Type "help" followed by command name for full
2236 Command name abbreviations are allowed if unambiguous.
2240 @item help @var{command}
2241 With a command name as @code{help} argument, @value{GDBN} displays a
2242 short paragraph on how to use that command. If that command has
2243 one or more aliases, @value{GDBN} will display a first line with
2244 the command name and all its aliases separated by commas.
2245 This first line will be followed by the full definition of all aliases
2246 having default arguments.
2249 @item apropos [-v] @var{regexp}
2250 The @code{apropos} command searches through all of the @value{GDBN}
2251 commands, and their documentation, for the regular expression specified in
2252 @var{args}. It prints out all matches found. The optional flag @samp{-v},
2253 which stands for @samp{verbose}, indicates to output the full documentation
2254 of the matching commands and highlight the parts of the documentation
2255 matching @var{regexp}. For example:
2266 alias -- Define a new command that is an alias of an existing command
2267 aliases -- User-defined aliases of other commands
2275 apropos -v cut.*thread apply
2279 results in the below output, where @samp{cut for 'thread apply}
2280 is highlighted if styling is enabled.
2284 taas -- Apply a command to all threads (ignoring errors
2287 shortcut for 'thread apply all -s COMMAND'
2289 tfaas -- Apply a command to all frames of all threads
2290 (ignoring errors and empty output).
2291 Usage: tfaas COMMAND
2292 shortcut for 'thread apply all -s frame apply all -s COMMAND'
2297 @item complete @var{args}
2298 The @code{complete @var{args}} command lists all the possible completions
2299 for the beginning of a command. Use @var{args} to specify the beginning of the
2300 command you want completed. For example:
2306 @noindent results in:
2317 @noindent This is intended for use by @sc{gnu} Emacs.
2320 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
2321 and @code{show} to inquire about the state of your program, or the state
2322 of @value{GDBN} itself. Each command supports many topics of inquiry; this
2323 manual introduces each of them in the appropriate context. The listings
2324 under @code{info} and under @code{show} in the Command, Variable, and
2325 Function Index point to all the sub-commands. @xref{Command and Variable
2331 @kindex i @r{(@code{info})}
2333 This command (abbreviated @code{i}) is for describing the state of your
2334 program. For example, you can show the arguments passed to a function
2335 with @code{info args}, list the registers currently in use with @code{info
2336 registers}, or list the breakpoints you have set with @code{info breakpoints}.
2337 You can get a complete list of the @code{info} sub-commands with
2338 @w{@code{help info}}.
2342 You can assign the result of an expression to an environment variable with
2343 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
2344 @code{set prompt $}.
2348 In contrast to @code{info}, @code{show} is for describing the state of
2349 @value{GDBN} itself.
2350 You can change most of the things you can @code{show}, by using the
2351 related command @code{set}; for example, you can control what number
2352 system is used for displays with @code{set radix}, or simply inquire
2353 which is currently in use with @code{show radix}.
2356 To display all the settable parameters and their current
2357 values, you can use @code{show} with no arguments; you may also use
2358 @code{info set}. Both commands produce the same display.
2359 @c FIXME: "info set" violates the rule that "info" is for state of
2360 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
2361 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
2365 Here are several miscellaneous @code{show} subcommands, all of which are
2366 exceptional in lacking corresponding @code{set} commands:
2369 @kindex show version
2370 @cindex @value{GDBN} version number
2372 Show what version of @value{GDBN} is running. You should include this
2373 information in @value{GDBN} bug-reports. If multiple versions of
2374 @value{GDBN} are in use at your site, you may need to determine which
2375 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
2376 commands are introduced, and old ones may wither away. Also, many
2377 system vendors ship variant versions of @value{GDBN}, and there are
2378 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
2379 The version number is the same as the one announced when you start
2382 @kindex show copying
2383 @kindex info copying
2384 @cindex display @value{GDBN} copyright
2387 Display information about permission for copying @value{GDBN}.
2389 @kindex show warranty
2390 @kindex info warranty
2392 @itemx info warranty
2393 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
2394 if your version of @value{GDBN} comes with one.
2396 @kindex show configuration
2397 @item show configuration
2398 Display detailed information about the way @value{GDBN} was configured
2399 when it was built. This displays the optional arguments passed to the
2400 @file{configure} script and also configuration parameters detected
2401 automatically by @command{configure}. When reporting a @value{GDBN}
2402 bug (@pxref{GDB Bugs}), it is important to include this information in
2408 @chapter Running Programs Under @value{GDBN}
2410 When you run a program under @value{GDBN}, you must first generate
2411 debugging information when you compile it.
2413 You may start @value{GDBN} with its arguments, if any, in an environment
2414 of your choice. If you are doing native debugging, you may redirect
2415 your program's input and output, debug an already running process, or
2416 kill a child process.
2419 * Compilation:: Compiling for debugging
2420 * Starting:: Starting your program
2421 * Arguments:: Your program's arguments
2422 * Environment:: Your program's environment
2424 * Working Directory:: Your program's working directory
2425 * Input/Output:: Your program's input and output
2426 * Attach:: Debugging an already-running process
2427 * Kill Process:: Killing the child process
2428 * Inferiors Connections and Programs:: Debugging multiple inferiors
2429 connections and programs
2430 * Threads:: Debugging programs with multiple threads
2431 * Forks:: Debugging forks
2432 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
2436 @section Compiling for Debugging
2438 In order to debug a program effectively, you need to generate
2439 debugging information when you compile it. This debugging information
2440 is stored in the object file; it describes the data type of each
2441 variable or function and the correspondence between source line numbers
2442 and addresses in the executable code.
2444 To request debugging information, specify the @samp{-g} option when you run
2447 Programs that are to be shipped to your customers are compiled with
2448 optimizations, using the @samp{-O} compiler option. However, some
2449 compilers are unable to handle the @samp{-g} and @samp{-O} options
2450 together. Using those compilers, you cannot generate optimized
2451 executables containing debugging information.
2453 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2454 without @samp{-O}, making it possible to debug optimized code. We
2455 recommend that you @emph{always} use @samp{-g} whenever you compile a
2456 program. You may think your program is correct, but there is no sense
2457 in pushing your luck. For more information, see @ref{Optimized Code}.
2459 Older versions of the @sc{gnu} C compiler permitted a variant option
2460 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2461 format; if your @sc{gnu} C compiler has this option, do not use it.
2463 @value{GDBN} knows about preprocessor macros and can show you their
2464 expansion (@pxref{Macros}). Most compilers do not include information
2465 about preprocessor macros in the debugging information if you specify
2466 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2467 the @sc{gnu} C compiler, provides macro information if you are using
2468 the DWARF debugging format, and specify the option @option{-g3}.
2470 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2471 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2472 information on @value{NGCC} options affecting debug information.
2474 You will have the best debugging experience if you use the latest
2475 version of the DWARF debugging format that your compiler supports.
2476 DWARF is currently the most expressive and best supported debugging
2477 format in @value{GDBN}.
2481 @section Starting your Program
2487 @kindex r @r{(@code{run})}
2490 Use the @code{run} command to start your program under @value{GDBN}.
2491 You must first specify the program name with an argument to
2492 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2493 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2494 command (@pxref{Files, ,Commands to Specify Files}).
2498 If you are running your program in an execution environment that
2499 supports processes, @code{run} creates an inferior process and makes
2500 that process run your program. In some environments without processes,
2501 @code{run} jumps to the start of your program. Other targets,
2502 like @samp{remote}, are always running. If you get an error
2503 message like this one:
2506 The "remote" target does not support "run".
2507 Try "help target" or "continue".
2511 then use @code{continue} to run your program. You may need @code{load}
2512 first (@pxref{load}).
2514 The execution of a program is affected by certain information it
2515 receives from its superior. @value{GDBN} provides ways to specify this
2516 information, which you must do @emph{before} starting your program. (You
2517 can change it after starting your program, but such changes only affect
2518 your program the next time you start it.) This information may be
2519 divided into four categories:
2522 @item The @emph{arguments.}
2523 Specify the arguments to give your program as the arguments of the
2524 @code{run} command. If a shell is available on your target, the shell
2525 is used to pass the arguments, so that you may use normal conventions
2526 (such as wildcard expansion or variable substitution) in describing
2528 In Unix systems, you can control which shell is used with the
2529 @env{SHELL} environment variable. If you do not define @env{SHELL},
2530 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2531 use of any shell with the @code{set startup-with-shell} command (see
2534 @item The @emph{environment.}
2535 Your program normally inherits its environment from @value{GDBN}, but you can
2536 use the @value{GDBN} commands @code{set environment} and @code{unset
2537 environment} to change parts of the environment that affect
2538 your program. @xref{Environment, ,Your Program's Environment}.
2540 @item The @emph{working directory.}
2541 You can set your program's working directory with the command
2542 @kbd{set cwd}. If you do not set any working directory with this
2543 command, your program will inherit @value{GDBN}'s working directory if
2544 native debugging, or the remote server's working directory if remote
2545 debugging. @xref{Working Directory, ,Your Program's Working
2548 @item The @emph{standard input and output.}
2549 Your program normally uses the same device for standard input and
2550 standard output as @value{GDBN} is using. You can redirect input and output
2551 in the @code{run} command line, or you can use the @code{tty} command to
2552 set a different device for your program.
2553 @xref{Input/Output, ,Your Program's Input and Output}.
2556 @emph{Warning:} While input and output redirection work, you cannot use
2557 pipes to pass the output of the program you are debugging to another
2558 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2562 When you issue the @code{run} command, your program begins to execute
2563 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2564 of how to arrange for your program to stop. Once your program has
2565 stopped, you may call functions in your program, using the @code{print}
2566 or @code{call} commands. @xref{Data, ,Examining Data}.
2568 If the modification time of your symbol file has changed since the last
2569 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2570 table, and reads it again. When it does this, @value{GDBN} tries to retain
2571 your current breakpoints.
2576 @cindex run to main procedure
2577 The name of the main procedure can vary from language to language.
2578 With C or C@t{++}, the main procedure name is always @code{main}, but
2579 other languages such as Ada do not require a specific name for their
2580 main procedure. The debugger provides a convenient way to start the
2581 execution of the program and to stop at the beginning of the main
2582 procedure, depending on the language used.
2584 The @samp{start} command does the equivalent of setting a temporary
2585 breakpoint at the beginning of the main procedure and then invoking
2586 the @samp{run} command.
2588 @cindex elaboration phase
2589 Some programs contain an @dfn{elaboration} phase where some startup code is
2590 executed before the main procedure is called. This depends on the
2591 languages used to write your program. In C@t{++}, for instance,
2592 constructors for static and global objects are executed before
2593 @code{main} is called. It is therefore possible that the debugger stops
2594 before reaching the main procedure. However, the temporary breakpoint
2595 will remain to halt execution.
2597 Specify the arguments to give to your program as arguments to the
2598 @samp{start} command. These arguments will be given verbatim to the
2599 underlying @samp{run} command. Note that the same arguments will be
2600 reused if no argument is provided during subsequent calls to
2601 @samp{start} or @samp{run}.
2603 It is sometimes necessary to debug the program during elaboration. In
2604 these cases, using the @code{start} command would stop the execution
2605 of your program too late, as the program would have already completed
2606 the elaboration phase. Under these circumstances, either insert
2607 breakpoints in your elaboration code before running your program or
2608 use the @code{starti} command.
2612 @cindex run to first instruction
2613 The @samp{starti} command does the equivalent of setting a temporary
2614 breakpoint at the first instruction of a program's execution and then
2615 invoking the @samp{run} command. For programs containing an
2616 elaboration phase, the @code{starti} command will stop execution at
2617 the start of the elaboration phase.
2619 @anchor{set exec-wrapper}
2620 @kindex set exec-wrapper
2621 @item set exec-wrapper @var{wrapper}
2622 @itemx show exec-wrapper
2623 @itemx unset exec-wrapper
2624 When @samp{exec-wrapper} is set, the specified wrapper is used to
2625 launch programs for debugging. @value{GDBN} starts your program
2626 with a shell command of the form @kbd{exec @var{wrapper}
2627 @var{program}}. Quoting is added to @var{program} and its
2628 arguments, but not to @var{wrapper}, so you should add quotes if
2629 appropriate for your shell. The wrapper runs until it executes
2630 your program, and then @value{GDBN} takes control.
2632 You can use any program that eventually calls @code{execve} with
2633 its arguments as a wrapper. Several standard Unix utilities do
2634 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2635 with @code{exec "$@@"} will also work.
2637 For example, you can use @code{env} to pass an environment variable to
2638 the debugged program, without setting the variable in your shell's
2642 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2646 This command is available when debugging locally on most targets, excluding
2647 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2649 @kindex set startup-with-shell
2650 @anchor{set startup-with-shell}
2651 @item set startup-with-shell
2652 @itemx set startup-with-shell on
2653 @itemx set startup-with-shell off
2654 @itemx show startup-with-shell
2655 On Unix systems, by default, if a shell is available on your target,
2656 @value{GDBN}) uses it to start your program. Arguments of the
2657 @code{run} command are passed to the shell, which does variable
2658 substitution, expands wildcard characters and performs redirection of
2659 I/O. In some circumstances, it may be useful to disable such use of a
2660 shell, for example, when debugging the shell itself or diagnosing
2661 startup failures such as:
2665 Starting program: ./a.out
2666 During startup program terminated with signal SIGSEGV, Segmentation fault.
2670 which indicates the shell or the wrapper specified with
2671 @samp{exec-wrapper} crashed, not your program. Most often, this is
2672 caused by something odd in your shell's non-interactive mode
2673 initialization file---such as @file{.cshrc} for C-shell,
2674 $@file{.zshenv} for the Z shell, or the file specified in the
2675 @env{BASH_ENV} environment variable for BASH.
2677 @anchor{set auto-connect-native-target}
2678 @kindex set auto-connect-native-target
2679 @item set auto-connect-native-target
2680 @itemx set auto-connect-native-target on
2681 @itemx set auto-connect-native-target off
2682 @itemx show auto-connect-native-target
2684 By default, if the current inferior is not connected to any target yet
2685 (e.g., with @code{target remote}), the @code{run} command starts your
2686 program as a native process under @value{GDBN}, on your local machine.
2687 If you're sure you don't want to debug programs on your local machine,
2688 you can tell @value{GDBN} to not connect to the native target
2689 automatically with the @code{set auto-connect-native-target off}
2692 If @code{on}, which is the default, and if the current inferior is not
2693 connected to a target already, the @code{run} command automaticaly
2694 connects to the native target, if one is available.
2696 If @code{off}, and if the current inferior is not connected to a
2697 target already, the @code{run} command fails with an error:
2701 Don't know how to run. Try "help target".
2704 If the current inferior is already connected to a target, @value{GDBN}
2705 always uses it with the @code{run} command.
2707 In any case, you can explicitly connect to the native target with the
2708 @code{target native} command. For example,
2711 (@value{GDBP}) set auto-connect-native-target off
2713 Don't know how to run. Try "help target".
2714 (@value{GDBP}) target native
2716 Starting program: ./a.out
2717 [Inferior 1 (process 10421) exited normally]
2720 In case you connected explicitly to the @code{native} target,
2721 @value{GDBN} remains connected even if all inferiors exit, ready for
2722 the next @code{run} command. Use the @code{disconnect} command to
2725 Examples of other commands that likewise respect the
2726 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2727 proc}, @code{info os}.
2729 @kindex set disable-randomization
2730 @item set disable-randomization
2731 @itemx set disable-randomization on
2732 This option (enabled by default in @value{GDBN}) will turn off the native
2733 randomization of the virtual address space of the started program. This option
2734 is useful for multiple debugging sessions to make the execution better
2735 reproducible and memory addresses reusable across debugging sessions.
2737 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2738 On @sc{gnu}/Linux you can get the same behavior using
2741 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2744 @item set disable-randomization off
2745 Leave the behavior of the started executable unchanged. Some bugs rear their
2746 ugly heads only when the program is loaded at certain addresses. If your bug
2747 disappears when you run the program under @value{GDBN}, that might be because
2748 @value{GDBN} by default disables the address randomization on platforms, such
2749 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2750 disable-randomization off} to try to reproduce such elusive bugs.
2752 On targets where it is available, virtual address space randomization
2753 protects the programs against certain kinds of security attacks. In these
2754 cases the attacker needs to know the exact location of a concrete executable
2755 code. Randomizing its location makes it impossible to inject jumps misusing
2756 a code at its expected addresses.
2758 Prelinking shared libraries provides a startup performance advantage but it
2759 makes addresses in these libraries predictable for privileged processes by
2760 having just unprivileged access at the target system. Reading the shared
2761 library binary gives enough information for assembling the malicious code
2762 misusing it. Still even a prelinked shared library can get loaded at a new
2763 random address just requiring the regular relocation process during the
2764 startup. Shared libraries not already prelinked are always loaded at
2765 a randomly chosen address.
2767 Position independent executables (PIE) contain position independent code
2768 similar to the shared libraries and therefore such executables get loaded at
2769 a randomly chosen address upon startup. PIE executables always load even
2770 already prelinked shared libraries at a random address. You can build such
2771 executable using @command{gcc -fPIE -pie}.
2773 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2774 (as long as the randomization is enabled).
2776 @item show disable-randomization
2777 Show the current setting of the explicit disable of the native randomization of
2778 the virtual address space of the started program.
2783 @section Your Program's Arguments
2785 @cindex arguments (to your program)
2786 The arguments to your program can be specified by the arguments of the
2788 They are passed to a shell, which expands wildcard characters and
2789 performs redirection of I/O, and thence to your program. Your
2790 @env{SHELL} environment variable (if it exists) specifies what shell
2791 @value{GDBN} uses. If you do not define @env{SHELL}, @value{GDBN} uses
2792 the default shell (@file{/bin/sh} on Unix).
2794 On non-Unix systems, the program is usually invoked directly by
2795 @value{GDBN}, which emulates I/O redirection via the appropriate system
2796 calls, and the wildcard characters are expanded by the startup code of
2797 the program, not by the shell.
2799 @code{run} with no arguments uses the same arguments used by the previous
2800 @code{run}, or those set by the @code{set args} command.
2805 Specify the arguments to be used the next time your program is run. If
2806 @code{set args} has no arguments, @code{run} executes your program
2807 with no arguments. Once you have run your program with arguments,
2808 using @code{set args} before the next @code{run} is the only way to run
2809 it again without arguments.
2813 Show the arguments to give your program when it is started.
2817 @section Your Program's Environment
2819 @cindex environment (of your program)
2820 The @dfn{environment} consists of a set of environment variables and
2821 their values. Environment variables conventionally record such things as
2822 your user name, your home directory, your terminal type, and your search
2823 path for programs to run. Usually you set up environment variables with
2824 the shell and they are inherited by all the other programs you run. When
2825 debugging, it can be useful to try running your program with a modified
2826 environment without having to start @value{GDBN} over again.
2830 @item path @var{directory}
2831 Add @var{directory} to the front of the @env{PATH} environment variable
2832 (the search path for executables) that will be passed to your program.
2833 The value of @env{PATH} used by @value{GDBN} does not change.
2834 You may specify several directory names, separated by whitespace or by a
2835 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2836 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2837 is moved to the front, so it is searched sooner.
2839 You can use the string @samp{$cwd} to refer to whatever is the current
2840 working directory at the time @value{GDBN} searches the path. If you
2841 use @samp{.} instead, it refers to the directory where you executed the
2842 @code{path} command. @value{GDBN} replaces @samp{.} in the
2843 @var{directory} argument (with the current path) before adding
2844 @var{directory} to the search path.
2845 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2846 @c document that, since repeating it would be a no-op.
2850 Display the list of search paths for executables (the @env{PATH}
2851 environment variable).
2853 @kindex show environment
2854 @item show environment @r{[}@var{varname}@r{]}
2855 Print the value of environment variable @var{varname} to be given to
2856 your program when it starts. If you do not supply @var{varname},
2857 print the names and values of all environment variables to be given to
2858 your program. You can abbreviate @code{environment} as @code{env}.
2860 @kindex set environment
2861 @anchor{set environment}
2862 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2863 Set environment variable @var{varname} to @var{value}. The value
2864 changes for your program (and the shell @value{GDBN} uses to launch
2865 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2866 values of environment variables are just strings, and any
2867 interpretation is supplied by your program itself. The @var{value}
2868 parameter is optional; if it is eliminated, the variable is set to a
2870 @c "any string" here does not include leading, trailing
2871 @c blanks. Gnu asks: does anyone care?
2873 For example, this command:
2880 tells the debugged program, when subsequently run, that its user is named
2881 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2882 are not actually required.)
2884 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2885 which also inherits the environment set with @code{set environment}.
2886 If necessary, you can avoid that by using the @samp{env} program as a
2887 wrapper instead of using @code{set environment}. @xref{set
2888 exec-wrapper}, for an example doing just that.
2890 Environment variables that are set by the user are also transmitted to
2891 @command{gdbserver} to be used when starting the remote inferior.
2892 @pxref{QEnvironmentHexEncoded}.
2894 @kindex unset environment
2895 @anchor{unset environment}
2896 @item unset environment @var{varname}
2897 Remove variable @var{varname} from the environment to be passed to your
2898 program. This is different from @samp{set env @var{varname} =};
2899 @code{unset environment} removes the variable from the environment,
2900 rather than assigning it an empty value.
2902 Environment variables that are unset by the user are also unset on
2903 @command{gdbserver} when starting the remote inferior.
2904 @pxref{QEnvironmentUnset}.
2907 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2908 the shell indicated by your @env{SHELL} environment variable if it
2909 exists (or @code{/bin/sh} if not). If your @env{SHELL} variable
2910 names a shell that runs an initialization file when started
2911 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2912 for the Z shell, or the file specified in the @env{BASH_ENV}
2913 environment variable for BASH---any variables you set in that file
2914 affect your program. You may wish to move setting of environment
2915 variables to files that are only run when you sign on, such as
2916 @file{.login} or @file{.profile}.
2918 @node Working Directory
2919 @section Your Program's Working Directory
2921 @cindex working directory (of your program)
2922 Each time you start your program with @code{run}, the inferior will be
2923 initialized with the current working directory specified by the
2924 @kbd{set cwd} command. If no directory has been specified by this
2925 command, then the inferior will inherit @value{GDBN}'s current working
2926 directory as its working directory if native debugging, or it will
2927 inherit the remote server's current working directory if remote
2932 @cindex change inferior's working directory
2933 @anchor{set cwd command}
2934 @item set cwd @r{[}@var{directory}@r{]}
2935 Set the inferior's working directory to @var{directory}, which will be
2936 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2937 argument has been specified, the command clears the setting and resets
2938 it to an empty state. This setting has no effect on @value{GDBN}'s
2939 working directory, and it only takes effect the next time you start
2940 the inferior. The @file{~} in @var{directory} is a short for the
2941 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2942 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2943 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2946 You can also change @value{GDBN}'s current working directory by using
2947 the @code{cd} command.
2951 @cindex show inferior's working directory
2953 Show the inferior's working directory. If no directory has been
2954 specified by @kbd{set cwd}, then the default inferior's working
2955 directory is the same as @value{GDBN}'s working directory.
2958 @cindex change @value{GDBN}'s working directory
2960 @item cd @r{[}@var{directory}@r{]}
2961 Set the @value{GDBN} working directory to @var{directory}. If not
2962 given, @var{directory} uses @file{'~'}.
2964 The @value{GDBN} working directory serves as a default for the
2965 commands that specify files for @value{GDBN} to operate on.
2966 @xref{Files, ,Commands to Specify Files}.
2967 @xref{set cwd command}.
2971 Print the @value{GDBN} working directory.
2974 It is generally impossible to find the current working directory of
2975 the process being debugged (since a program can change its directory
2976 during its run). If you work on a system where @value{GDBN} supports
2977 the @code{info proc} command (@pxref{Process Information}), you can
2978 use the @code{info proc} command to find out the
2979 current working directory of the debuggee.
2982 @section Your Program's Input and Output
2987 By default, the program you run under @value{GDBN} does input and output to
2988 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2989 to its own terminal modes to interact with you, but it records the terminal
2990 modes your program was using and switches back to them when you continue
2991 running your program.
2994 @kindex info terminal
2996 Displays information recorded by @value{GDBN} about the terminal modes your
3000 You can redirect your program's input and/or output using shell
3001 redirection with the @code{run} command. For example,
3008 starts your program, diverting its output to the file @file{outfile}.
3011 @cindex controlling terminal
3012 Another way to specify where your program should do input and output is
3013 with the @code{tty} command. This command accepts a file name as
3014 argument, and causes this file to be the default for future @code{run}
3015 commands. It also resets the controlling terminal for the child
3016 process, for future @code{run} commands. For example,
3023 directs that processes started with subsequent @code{run} commands
3024 default to do input and output on the terminal @file{/dev/ttyb} and have
3025 that as their controlling terminal.
3027 An explicit redirection in @code{run} overrides the @code{tty} command's
3028 effect on the input/output device, but not its effect on the controlling
3031 When you use the @code{tty} command or redirect input in the @code{run}
3032 command, only the input @emph{for your program} is affected. The input
3033 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
3034 for @code{set inferior-tty}.
3036 @cindex inferior tty
3037 @cindex set inferior controlling terminal
3038 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
3039 display the name of the terminal that will be used for future runs of your
3043 @item set inferior-tty [ @var{tty} ]
3044 @kindex set inferior-tty
3045 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
3046 restores the default behavior, which is to use the same terminal as
3049 @item show inferior-tty
3050 @kindex show inferior-tty
3051 Show the current tty for the program being debugged.
3055 @section Debugging an Already-running Process
3060 @item attach @var{process-id}
3061 This command attaches to a running process---one that was started
3062 outside @value{GDBN}. (@code{info files} shows your active
3063 targets.) The command takes as argument a process ID. The usual way to
3064 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
3065 or with the @samp{jobs -l} shell command.
3067 @code{attach} does not repeat if you press @key{RET} a second time after
3068 executing the command.
3071 To use @code{attach}, your program must be running in an environment
3072 which supports processes; for example, @code{attach} does not work for
3073 programs on bare-board targets that lack an operating system. You must
3074 also have permission to send the process a signal.
3076 When you use @code{attach}, the debugger finds the program running in
3077 the process first by looking in the current working directory, then (if
3078 the program is not found) by using the source file search path
3079 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
3080 the @code{file} command to load the program. @xref{Files, ,Commands to
3083 @anchor{set exec-file-mismatch}
3084 If the debugger can determine that the executable file running in the
3085 process it is attaching to does not match the current exec-file loaded
3086 by @value{GDBN}, the option @code{exec-file-mismatch} specifies how to
3087 handle the mismatch. @value{GDBN} tries to compare the files by
3088 comparing their build IDs (@pxref{build ID}), if available.
3091 @kindex exec-file-mismatch
3092 @cindex set exec-file-mismatch
3093 @item set exec-file-mismatch @samp{ask|warn|off}
3095 Whether to detect mismatch between the current executable file loaded
3096 by @value{GDBN} and the executable file used to start the process. If
3097 @samp{ask}, the default, display a warning and ask the user whether to
3098 load the process executable file; if @samp{warn}, just display a
3099 warning; if @samp{off}, don't attempt to detect a mismatch.
3100 If the user confirms loading the process executable file, then its symbols
3101 will be loaded as well.
3103 @cindex show exec-file-mismatch
3104 @item show exec-file-mismatch
3105 Show the current value of @code{exec-file-mismatch}.
3109 The first thing @value{GDBN} does after arranging to debug the specified
3110 process is to stop it. You can examine and modify an attached process
3111 with all the @value{GDBN} commands that are ordinarily available when
3112 you start processes with @code{run}. You can insert breakpoints; you
3113 can step and continue; you can modify storage. If you would rather the
3114 process continue running, you may use the @code{continue} command after
3115 attaching @value{GDBN} to the process.
3120 When you have finished debugging the attached process, you can use the
3121 @code{detach} command to release it from @value{GDBN} control. Detaching
3122 the process continues its execution. After the @code{detach} command,
3123 that process and @value{GDBN} become completely independent once more, and you
3124 are ready to @code{attach} another process or start one with @code{run}.
3125 @code{detach} does not repeat if you press @key{RET} again after
3126 executing the command.
3129 If you exit @value{GDBN} while you have an attached process, you detach
3130 that process. If you use the @code{run} command, you kill that process.
3131 By default, @value{GDBN} asks for confirmation if you try to do either of these
3132 things; you can control whether or not you need to confirm by using the
3133 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
3137 @section Killing the Child Process
3142 Kill the child process in which your program is running under @value{GDBN}.
3145 This command is useful if you wish to debug a core dump instead of a
3146 running process. @value{GDBN} ignores any core dump file while your program
3149 On some operating systems, a program cannot be executed outside @value{GDBN}
3150 while you have breakpoints set on it inside @value{GDBN}. You can use the
3151 @code{kill} command in this situation to permit running your program
3152 outside the debugger.
3154 The @code{kill} command is also useful if you wish to recompile and
3155 relink your program, since on many systems it is impossible to modify an
3156 executable file while it is running in a process. In this case, when you
3157 next type @code{run}, @value{GDBN} notices that the file has changed, and
3158 reads the symbol table again (while trying to preserve your current
3159 breakpoint settings).
3161 @node Inferiors Connections and Programs
3162 @section Debugging Multiple Inferiors Connections and Programs
3164 @value{GDBN} lets you run and debug multiple programs in a single
3165 session. In addition, @value{GDBN} on some systems may let you run
3166 several programs simultaneously (otherwise you have to exit from one
3167 before starting another). On some systems @value{GDBN} may even let
3168 you debug several programs simultaneously on different remote systems.
3169 In the most general case, you can have multiple threads of execution
3170 in each of multiple processes, launched from multiple executables,
3171 running on different machines.
3174 @value{GDBN} represents the state of each program execution with an
3175 object called an @dfn{inferior}. An inferior typically corresponds to
3176 a process, but is more general and applies also to targets that do not
3177 have processes. Inferiors may be created before a process runs, and
3178 may be retained after a process exits. Inferiors have unique
3179 identifiers that are different from process ids. Usually each
3180 inferior will also have its own distinct address space, although some
3181 embedded targets may have several inferiors running in different parts
3182 of a single address space. Each inferior may in turn have multiple
3183 threads running in it.
3185 To find out what inferiors exist at any moment, use @w{@code{info
3189 @kindex info inferiors [ @var{id}@dots{} ]
3190 @item info inferiors
3191 Print a list of all inferiors currently being managed by @value{GDBN}.
3192 By default all inferiors are printed, but the argument @var{id}@dots{}
3193 -- a space separated list of inferior numbers -- can be used to limit
3194 the display to just the requested inferiors.
3196 @value{GDBN} displays for each inferior (in this order):
3200 the inferior number assigned by @value{GDBN}
3203 the target system's inferior identifier
3206 the target connection the inferior is bound to, including the unique
3207 connection number assigned by @value{GDBN}, and the protocol used by
3211 the name of the executable the inferior is running.
3216 An asterisk @samp{*} preceding the @value{GDBN} inferior number
3217 indicates the current inferior.
3221 @c end table here to get a little more width for example
3224 (@value{GDBP}) info inferiors
3225 Num Description Connection Executable
3226 * 1 process 3401 1 (native) goodbye
3227 2 process 2307 2 (extended-remote host:10000) hello
3230 To get informations about the current inferior, use @code{inferior}:
3235 Shows information about the current inferior.
3239 @c end table here to get a little more width for example
3242 (@value{GDBP}) inferior
3243 [Current inferior is 1 [process 3401] (helloworld)]
3246 To find out what open target connections exist at any moment, use
3247 @w{@code{info connections}}:
3250 @kindex info connections [ @var{id}@dots{} ]
3251 @item info connections
3252 Print a list of all open target connections currently being managed by
3253 @value{GDBN}. By default all connections are printed, but the
3254 argument @var{id}@dots{} -- a space separated list of connections
3255 numbers -- can be used to limit the display to just the requested
3258 @value{GDBN} displays for each connection (in this order):
3262 the connection number assigned by @value{GDBN}.
3265 the protocol used by the connection.
3268 a textual description of the protocol used by the connection.
3273 An asterisk @samp{*} preceding the connection number indicates the
3274 connection of the current inferior.
3278 @c end table here to get a little more width for example
3281 (@value{GDBP}) info connections
3282 Num What Description
3283 * 1 extended-remote host:10000 Extended remote serial target in gdb-specific protocol
3284 2 native Native process
3285 3 core Local core dump file
3288 To switch focus between inferiors, use the @code{inferior} command:
3291 @kindex inferior @var{infno}
3292 @item inferior @var{infno}
3293 Make inferior number @var{infno} the current inferior. The argument
3294 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
3295 in the first field of the @samp{info inferiors} display.
3298 @vindex $_inferior@r{, convenience variable}
3299 The debugger convenience variable @samp{$_inferior} contains the
3300 number of the current inferior. You may find this useful in writing
3301 breakpoint conditional expressions, command scripts, and so forth.
3302 @xref{Convenience Vars,, Convenience Variables}, for general
3303 information on convenience variables.
3305 You can get multiple executables into a debugging session via the
3306 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
3307 systems @value{GDBN} can add inferiors to the debug session
3308 automatically by following calls to @code{fork} and @code{exec}. To
3309 remove inferiors from the debugging session use the
3310 @w{@code{remove-inferiors}} command.
3313 @kindex add-inferior
3314 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3315 Adds @var{n} inferiors to be run using @var{executable} as the
3316 executable; @var{n} defaults to 1. If no executable is specified,
3317 the inferiors begins empty, with no program. You can still assign or
3318 change the program assigned to the inferior at any time by using the
3319 @code{file} command with the executable name as its argument.
3321 By default, the new inferior begins connected to the same target
3322 connection as the current inferior. For example, if the current
3323 inferior was connected to @code{gdbserver} with @code{target remote},
3324 then the new inferior will be connected to the same @code{gdbserver}
3325 instance. The @samp{-no-connection} option starts the new inferior
3326 with no connection yet. You can then for example use the @code{target
3327 remote} command to connect to some other @code{gdbserver} instance,
3328 use @code{run} to spawn a local program, etc.
3330 @kindex clone-inferior
3331 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3332 Adds @var{n} inferiors ready to execute the same program as inferior
3333 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3334 number of the current inferior. This command copies the values of the
3335 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3336 current inferior to the new one. It also propagates changes the user
3337 made to environment variables using the @w{@code{set environment}} and
3338 @w{@code{unset environment}} commands. This is a convenient command
3339 when you want to run another instance of the inferior you are debugging.
3342 (@value{GDBP}) info inferiors
3343 Num Description Connection Executable
3344 * 1 process 29964 1 (native) helloworld
3345 (@value{GDBP}) clone-inferior
3348 (@value{GDBP}) info inferiors
3349 Num Description Connection Executable
3350 * 1 process 29964 1 (native) helloworld
3351 2 <null> 1 (native) helloworld
3354 You can now simply switch focus to inferior 2 and run it.
3356 @kindex remove-inferiors
3357 @item remove-inferiors @var{infno}@dots{}
3358 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3359 possible to remove an inferior that is running with this command. For
3360 those, use the @code{kill} or @code{detach} command first.
3364 To quit debugging one of the running inferiors that is not the current
3365 inferior, you can either detach from it by using the @w{@code{detach
3366 inferior}} command (allowing it to run independently), or kill it
3367 using the @w{@code{kill inferiors}} command:
3370 @kindex detach inferiors @var{infno}@dots{}
3371 @item detach inferior @var{infno}@dots{}
3372 Detach from the inferior or inferiors identified by @value{GDBN}
3373 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3374 still stays on the list of inferiors shown by @code{info inferiors},
3375 but its Description will show @samp{<null>}.
3377 @kindex kill inferiors @var{infno}@dots{}
3378 @item kill inferiors @var{infno}@dots{}
3379 Kill the inferior or inferiors identified by @value{GDBN} inferior
3380 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3381 stays on the list of inferiors shown by @code{info inferiors}, but its
3382 Description will show @samp{<null>}.
3385 After the successful completion of a command such as @code{detach},
3386 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3387 a normal process exit, the inferior is still valid and listed with
3388 @code{info inferiors}, ready to be restarted.
3391 To be notified when inferiors are started or exit under @value{GDBN}'s
3392 control use @w{@code{set print inferior-events}}:
3395 @kindex set print inferior-events
3396 @cindex print messages on inferior start and exit
3397 @item set print inferior-events
3398 @itemx set print inferior-events on
3399 @itemx set print inferior-events off
3400 The @code{set print inferior-events} command allows you to enable or
3401 disable printing of messages when @value{GDBN} notices that new
3402 inferiors have started or that inferiors have exited or have been
3403 detached. By default, these messages will be printed.
3405 @kindex show print inferior-events
3406 @item show print inferior-events
3407 Show whether messages will be printed when @value{GDBN} detects that
3408 inferiors have started, exited or have been detached.
3411 Many commands will work the same with multiple programs as with a
3412 single program: e.g., @code{print myglobal} will simply display the
3413 value of @code{myglobal} in the current inferior.
3416 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3417 get more info about the relationship of inferiors, programs, address
3418 spaces in a debug session. You can do that with the @w{@code{maint
3419 info program-spaces}} command.
3422 @kindex maint info program-spaces
3423 @item maint info program-spaces
3424 Print a list of all program spaces currently being managed by
3427 @value{GDBN} displays for each program space (in this order):
3431 the program space number assigned by @value{GDBN}
3434 the name of the executable loaded into the program space, with e.g.,
3435 the @code{file} command.
3440 An asterisk @samp{*} preceding the @value{GDBN} program space number
3441 indicates the current program space.
3443 In addition, below each program space line, @value{GDBN} prints extra
3444 information that isn't suitable to display in tabular form. For
3445 example, the list of inferiors bound to the program space.
3448 (@value{GDBP}) maint info program-spaces
3452 Bound inferiors: ID 1 (process 21561)
3455 Here we can see that no inferior is running the program @code{hello},
3456 while @code{process 21561} is running the program @code{goodbye}. On
3457 some targets, it is possible that multiple inferiors are bound to the
3458 same program space. The most common example is that of debugging both
3459 the parent and child processes of a @code{vfork} call. For example,
3462 (@value{GDBP}) maint info program-spaces
3465 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3468 Here, both inferior 2 and inferior 1 are running in the same program
3469 space as a result of inferior 1 having executed a @code{vfork} call.
3473 @section Debugging Programs with Multiple Threads
3475 @cindex threads of execution
3476 @cindex multiple threads
3477 @cindex switching threads
3478 In some operating systems, such as GNU/Linux and Solaris, a single program
3479 may have more than one @dfn{thread} of execution. The precise semantics
3480 of threads differ from one operating system to another, but in general
3481 the threads of a single program are akin to multiple processes---except
3482 that they share one address space (that is, they can all examine and
3483 modify the same variables). On the other hand, each thread has its own
3484 registers and execution stack, and perhaps private memory.
3486 @value{GDBN} provides these facilities for debugging multi-thread
3490 @item automatic notification of new threads
3491 @item @samp{thread @var{thread-id}}, a command to switch among threads
3492 @item @samp{info threads}, a command to inquire about existing threads
3493 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3494 a command to apply a command to a list of threads
3495 @item thread-specific breakpoints
3496 @item @samp{set print thread-events}, which controls printing of
3497 messages on thread start and exit.
3498 @item @samp{set libthread-db-search-path @var{path}}, which lets
3499 the user specify which @code{libthread_db} to use if the default choice
3500 isn't compatible with the program.
3503 @cindex focus of debugging
3504 @cindex current thread
3505 The @value{GDBN} thread debugging facility allows you to observe all
3506 threads while your program runs---but whenever @value{GDBN} takes
3507 control, one thread in particular is always the focus of debugging.
3508 This thread is called the @dfn{current thread}. Debugging commands show
3509 program information from the perspective of the current thread.
3511 @cindex @code{New} @var{systag} message
3512 @cindex thread identifier (system)
3513 @c FIXME-implementors!! It would be more helpful if the [New...] message
3514 @c included GDB's numeric thread handle, so you could just go to that
3515 @c thread without first checking `info threads'.
3516 Whenever @value{GDBN} detects a new thread in your program, it displays
3517 the target system's identification for the thread with a message in the
3518 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3519 whose form varies depending on the particular system. For example, on
3520 @sc{gnu}/Linux, you might see
3523 [New Thread 0x41e02940 (LWP 25582)]
3527 when @value{GDBN} notices a new thread. In contrast, on other systems,
3528 the @var{systag} is simply something like @samp{process 368}, with no
3531 @c FIXME!! (1) Does the [New...] message appear even for the very first
3532 @c thread of a program, or does it only appear for the
3533 @c second---i.e.@: when it becomes obvious we have a multithread
3535 @c (2) *Is* there necessarily a first thread always? Or do some
3536 @c multithread systems permit starting a program with multiple
3537 @c threads ab initio?
3539 @anchor{thread numbers}
3540 @cindex thread number, per inferior
3541 @cindex thread identifier (GDB)
3542 For debugging purposes, @value{GDBN} associates its own thread number
3543 ---always a single integer---with each thread of an inferior. This
3544 number is unique between all threads of an inferior, but not unique
3545 between threads of different inferiors.
3547 @cindex qualified thread ID
3548 You can refer to a given thread in an inferior using the qualified
3549 @var{inferior-num}.@var{thread-num} syntax, also known as
3550 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3551 number and @var{thread-num} being the thread number of the given
3552 inferior. For example, thread @code{2.3} refers to thread number 3 of
3553 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3554 then @value{GDBN} infers you're referring to a thread of the current
3557 Until you create a second inferior, @value{GDBN} does not show the
3558 @var{inferior-num} part of thread IDs, even though you can always use
3559 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3560 of inferior 1, the initial inferior.
3562 @anchor{thread ID lists}
3563 @cindex thread ID lists
3564 Some commands accept a space-separated @dfn{thread ID list} as
3565 argument. A list element can be:
3569 A thread ID as shown in the first field of the @samp{info threads}
3570 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3574 A range of thread numbers, again with or without an inferior
3575 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3576 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3579 All threads of an inferior, specified with a star wildcard, with or
3580 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3581 @samp{1.*}) or @code{*}. The former refers to all threads of the
3582 given inferior, and the latter form without an inferior qualifier
3583 refers to all threads of the current inferior.
3587 For example, if the current inferior is 1, and inferior 7 has one
3588 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3589 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3590 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3591 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3595 @anchor{global thread numbers}
3596 @cindex global thread number
3597 @cindex global thread identifier (GDB)
3598 In addition to a @emph{per-inferior} number, each thread is also
3599 assigned a unique @emph{global} number, also known as @dfn{global
3600 thread ID}, a single integer. Unlike the thread number component of
3601 the thread ID, no two threads have the same global ID, even when
3602 you're debugging multiple inferiors.
3604 From @value{GDBN}'s perspective, a process always has at least one
3605 thread. In other words, @value{GDBN} assigns a thread number to the
3606 program's ``main thread'' even if the program is not multi-threaded.
3608 @vindex $_thread@r{, convenience variable}
3609 @vindex $_gthread@r{, convenience variable}
3610 The debugger convenience variables @samp{$_thread} and
3611 @samp{$_gthread} contain, respectively, the per-inferior thread number
3612 and the global thread number of the current thread. You may find this
3613 useful in writing breakpoint conditional expressions, command scripts,
3614 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3615 general information on convenience variables.
3617 If @value{GDBN} detects the program is multi-threaded, it augments the
3618 usual message about stopping at a breakpoint with the ID and name of
3619 the thread that hit the breakpoint.
3622 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3625 Likewise when the program receives a signal:
3628 Thread 1 "main" received signal SIGINT, Interrupt.
3632 @anchor{info_threads}
3633 @kindex info threads
3634 @item info threads @r{[}@var{thread-id-list}@r{]}
3636 Display information about one or more threads. With no arguments
3637 displays information about all threads. You can specify the list of
3638 threads that you want to display using the thread ID list syntax
3639 (@pxref{thread ID lists}).
3641 @value{GDBN} displays for each thread (in this order):
3645 the per-inferior thread number assigned by @value{GDBN}
3648 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3649 option was specified
3652 the target system's thread identifier (@var{systag})
3655 the thread's name, if one is known. A thread can either be named by
3656 the user (see @code{thread name}, below), or, in some cases, by the
3660 the current stack frame summary for that thread
3664 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3665 indicates the current thread.
3669 @c end table here to get a little more width for example
3672 (@value{GDBP}) info threads
3674 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3675 2 process 35 thread 23 0x34e5 in sigpause ()
3676 3 process 35 thread 27 0x34e5 in sigpause ()
3680 If you're debugging multiple inferiors, @value{GDBN} displays thread
3681 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3682 Otherwise, only @var{thread-num} is shown.
3684 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3685 indicating each thread's global thread ID:
3688 (@value{GDBP}) info threads
3689 Id GId Target Id Frame
3690 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3691 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3692 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3693 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3696 On Solaris, you can display more information about user threads with a
3697 Solaris-specific command:
3700 @item maint info sol-threads
3701 @kindex maint info sol-threads
3702 @cindex thread info (Solaris)
3703 Display info on Solaris user threads.
3707 @kindex thread @var{thread-id}
3708 @item thread @var{thread-id}
3709 Make thread ID @var{thread-id} the current thread. The command
3710 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3711 the first field of the @samp{info threads} display, with or without an
3712 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3714 @value{GDBN} responds by displaying the system identifier of the
3715 thread you selected, and its current stack frame summary:
3718 (@value{GDBP}) thread 2
3719 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3720 #0 some_function (ignore=0x0) at example.c:8
3721 8 printf ("hello\n");
3725 As with the @samp{[New @dots{}]} message, the form of the text after
3726 @samp{Switching to} depends on your system's conventions for identifying
3729 @anchor{thread apply all}
3730 @kindex thread apply
3731 @cindex apply command to several threads
3732 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3733 The @code{thread apply} command allows you to apply the named
3734 @var{command} to one or more threads. Specify the threads that you
3735 want affected using the thread ID list syntax (@pxref{thread ID
3736 lists}), or specify @code{all} to apply to all threads. To apply a
3737 command to all threads in descending order, type @kbd{thread apply all
3738 @var{command}}. To apply a command to all threads in ascending order,
3739 type @kbd{thread apply all -ascending @var{command}}.
3741 The @var{flag} arguments control what output to produce and how to handle
3742 errors raised when applying @var{command} to a thread. @var{flag}
3743 must start with a @code{-} directly followed by one letter in
3744 @code{qcs}. If several flags are provided, they must be given
3745 individually, such as @code{-c -q}.
3747 By default, @value{GDBN} displays some thread information before the
3748 output produced by @var{command}, and an error raised during the
3749 execution of a @var{command} will abort @code{thread apply}. The
3750 following flags can be used to fine-tune this behavior:
3754 The flag @code{-c}, which stands for @samp{continue}, causes any
3755 errors in @var{command} to be displayed, and the execution of
3756 @code{thread apply} then continues.
3758 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3759 or empty output produced by a @var{command} to be silently ignored.
3760 That is, the execution continues, but the thread information and errors
3763 The flag @code{-q} (@samp{quiet}) disables printing the thread
3767 Flags @code{-c} and @code{-s} cannot be used together.
3770 @cindex apply command to all threads (ignoring errors and empty output)
3771 @item taas [@var{option}]@dots{} @var{command}
3772 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3773 Applies @var{command} on all threads, ignoring errors and empty output.
3775 The @code{taas} command accepts the same options as the @code{thread
3776 apply all} command. @xref{thread apply all}.
3779 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3780 @item tfaas [@var{option}]@dots{} @var{command}
3781 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3782 Applies @var{command} on all frames of all threads, ignoring errors
3783 and empty output. Note that the flag @code{-s} is specified twice:
3784 The first @code{-s} ensures that @code{thread apply} only shows the thread
3785 information of the threads for which @code{frame apply} produces
3786 some output. The second @code{-s} is needed to ensure that @code{frame
3787 apply} shows the frame information of a frame only if the
3788 @var{command} successfully produced some output.
3790 It can for example be used to print a local variable or a function
3791 argument without knowing the thread or frame where this variable or argument
3794 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3797 The @code{tfaas} command accepts the same options as the @code{frame
3798 apply} command. @xref{Frame Apply,,frame apply}.
3801 @cindex name a thread
3802 @item thread name [@var{name}]
3803 This command assigns a name to the current thread. If no argument is
3804 given, any existing user-specified name is removed. The thread name
3805 appears in the @samp{info threads} display.
3807 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3808 determine the name of the thread as given by the OS. On these
3809 systems, a name specified with @samp{thread name} will override the
3810 system-give name, and removing the user-specified name will cause
3811 @value{GDBN} to once again display the system-specified name.
3814 @cindex search for a thread
3815 @item thread find [@var{regexp}]
3816 Search for and display thread ids whose name or @var{systag}
3817 matches the supplied regular expression.
3819 As well as being the complement to the @samp{thread name} command,
3820 this command also allows you to identify a thread by its target
3821 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3825 (@value{GDBN}) thread find 26688
3826 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3827 (@value{GDBN}) info thread 4
3829 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3832 @kindex set print thread-events
3833 @cindex print messages on thread start and exit
3834 @item set print thread-events
3835 @itemx set print thread-events on
3836 @itemx set print thread-events off
3837 The @code{set print thread-events} command allows you to enable or
3838 disable printing of messages when @value{GDBN} notices that new threads have
3839 started or that threads have exited. By default, these messages will
3840 be printed if detection of these events is supported by the target.
3841 Note that these messages cannot be disabled on all targets.
3843 @kindex show print thread-events
3844 @item show print thread-events
3845 Show whether messages will be printed when @value{GDBN} detects that threads
3846 have started and exited.
3849 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3850 more information about how @value{GDBN} behaves when you stop and start
3851 programs with multiple threads.
3853 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3854 watchpoints in programs with multiple threads.
3856 @anchor{set libthread-db-search-path}
3858 @kindex set libthread-db-search-path
3859 @cindex search path for @code{libthread_db}
3860 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3861 If this variable is set, @var{path} is a colon-separated list of
3862 directories @value{GDBN} will use to search for @code{libthread_db}.
3863 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3864 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3865 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3868 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3869 @code{libthread_db} library to obtain information about threads in the
3870 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3871 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3872 specific thread debugging library loading is enabled
3873 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3875 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3876 refers to the default system directories that are
3877 normally searched for loading shared libraries. The @samp{$sdir} entry
3878 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3879 (@pxref{libthread_db.so.1 file}).
3881 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3882 refers to the directory from which @code{libpthread}
3883 was loaded in the inferior process.
3885 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3886 @value{GDBN} attempts to initialize it with the current inferior process.
3887 If this initialization fails (which could happen because of a version
3888 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3889 will unload @code{libthread_db}, and continue with the next directory.
3890 If none of @code{libthread_db} libraries initialize successfully,
3891 @value{GDBN} will issue a warning and thread debugging will be disabled.
3893 Setting @code{libthread-db-search-path} is currently implemented
3894 only on some platforms.
3896 @kindex show libthread-db-search-path
3897 @item show libthread-db-search-path
3898 Display current libthread_db search path.
3900 @kindex set debug libthread-db
3901 @kindex show debug libthread-db
3902 @cindex debugging @code{libthread_db}
3903 @item set debug libthread-db
3904 @itemx show debug libthread-db
3905 Turns on or off display of @code{libthread_db}-related events.
3906 Use @code{1} to enable, @code{0} to disable.
3908 @kindex set debug threads
3909 @kindex show debug threads
3910 @cindex debugging @code{threads}
3911 @item set debug threads @r{[}on@r{|}off@r{]}
3912 @itemx show debug threads
3913 When @samp{on} @value{GDBN} will print additional messages when
3914 threads are created and deleted.
3918 @section Debugging Forks
3920 @cindex fork, debugging programs which call
3921 @cindex multiple processes
3922 @cindex processes, multiple
3923 On most systems, @value{GDBN} has no special support for debugging
3924 programs which create additional processes using the @code{fork}
3925 function. When a program forks, @value{GDBN} will continue to debug the
3926 parent process and the child process will run unimpeded. If you have
3927 set a breakpoint in any code which the child then executes, the child
3928 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3929 will cause it to terminate.
3931 However, if you want to debug the child process there is a workaround
3932 which isn't too painful. Put a call to @code{sleep} in the code which
3933 the child process executes after the fork. It may be useful to sleep
3934 only if a certain environment variable is set, or a certain file exists,
3935 so that the delay need not occur when you don't want to run @value{GDBN}
3936 on the child. While the child is sleeping, use the @code{ps} program to
3937 get its process ID. Then tell @value{GDBN} (a new invocation of
3938 @value{GDBN} if you are also debugging the parent process) to attach to
3939 the child process (@pxref{Attach}). From that point on you can debug
3940 the child process just like any other process which you attached to.
3942 On some systems, @value{GDBN} provides support for debugging programs
3943 that create additional processes using the @code{fork} or @code{vfork}
3944 functions. On @sc{gnu}/Linux platforms, this feature is supported
3945 with kernel version 2.5.46 and later.
3947 The fork debugging commands are supported in native mode and when
3948 connected to @code{gdbserver} in either @code{target remote} mode or
3949 @code{target extended-remote} mode.
3951 By default, when a program forks, @value{GDBN} will continue to debug
3952 the parent process and the child process will run unimpeded.
3954 If you want to follow the child process instead of the parent process,
3955 use the command @w{@code{set follow-fork-mode}}.
3958 @kindex set follow-fork-mode
3959 @item set follow-fork-mode @var{mode}
3960 Set the debugger response to a program call of @code{fork} or
3961 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3962 process. The @var{mode} argument can be:
3966 The original process is debugged after a fork. The child process runs
3967 unimpeded. This is the default.
3970 The new process is debugged after a fork. The parent process runs
3975 @kindex show follow-fork-mode
3976 @item show follow-fork-mode
3977 Display the current debugger response to a @code{fork} or @code{vfork} call.
3980 @cindex debugging multiple processes
3981 On Linux, if you want to debug both the parent and child processes, use the
3982 command @w{@code{set detach-on-fork}}.
3985 @kindex set detach-on-fork
3986 @item set detach-on-fork @var{mode}
3987 Tells gdb whether to detach one of the processes after a fork, or
3988 retain debugger control over them both.
3992 The child process (or parent process, depending on the value of
3993 @code{follow-fork-mode}) will be detached and allowed to run
3994 independently. This is the default.
3997 Both processes will be held under the control of @value{GDBN}.
3998 One process (child or parent, depending on the value of
3999 @code{follow-fork-mode}) is debugged as usual, while the other
4004 @kindex show detach-on-fork
4005 @item show detach-on-fork
4006 Show whether detach-on-fork mode is on/off.
4009 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4010 will retain control of all forked processes (including nested forks).
4011 You can list the forked processes under the control of @value{GDBN} by
4012 using the @w{@code{info inferiors}} command, and switch from one fork
4013 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4014 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4016 To quit debugging one of the forked processes, you can either detach
4017 from it by using the @w{@code{detach inferiors}} command (allowing it
4018 to run independently), or kill it using the @w{@code{kill inferiors}}
4019 command. @xref{Inferiors Connections and Programs, ,Debugging
4020 Multiple Inferiors Connections and Programs}.
4022 If you ask to debug a child process and a @code{vfork} is followed by an
4023 @code{exec}, @value{GDBN} executes the new target up to the first
4024 breakpoint in the new target. If you have a breakpoint set on
4025 @code{main} in your original program, the breakpoint will also be set on
4026 the child process's @code{main}.
4028 On some systems, when a child process is spawned by @code{vfork}, you
4029 cannot debug the child or parent until an @code{exec} call completes.
4031 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4032 call executes, the new target restarts. To restart the parent
4033 process, use the @code{file} command with the parent executable name
4034 as its argument. By default, after an @code{exec} call executes,
4035 @value{GDBN} discards the symbols of the previous executable image.
4036 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4040 @kindex set follow-exec-mode
4041 @item set follow-exec-mode @var{mode}
4043 Set debugger response to a program call of @code{exec}. An
4044 @code{exec} call replaces the program image of a process.
4046 @code{follow-exec-mode} can be:
4050 @value{GDBN} creates a new inferior and rebinds the process to this
4051 new inferior. The program the process was running before the
4052 @code{exec} call can be restarted afterwards by restarting the
4058 (@value{GDBP}) info inferiors
4060 Id Description Executable
4063 process 12020 is executing new program: prog2
4064 Program exited normally.
4065 (@value{GDBP}) info inferiors
4066 Id Description Executable
4072 @value{GDBN} keeps the process bound to the same inferior. The new
4073 executable image replaces the previous executable loaded in the
4074 inferior. Restarting the inferior after the @code{exec} call, with
4075 e.g., the @code{run} command, restarts the executable the process was
4076 running after the @code{exec} call. This is the default mode.
4081 (@value{GDBP}) info inferiors
4082 Id Description Executable
4085 process 12020 is executing new program: prog2
4086 Program exited normally.
4087 (@value{GDBP}) info inferiors
4088 Id Description Executable
4095 @code{follow-exec-mode} is supported in native mode and
4096 @code{target extended-remote} mode.
4098 You can use the @code{catch} command to make @value{GDBN} stop whenever
4099 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4100 Catchpoints, ,Setting Catchpoints}.
4102 @node Checkpoint/Restart
4103 @section Setting a @emph{Bookmark} to Return to Later
4108 @cindex snapshot of a process
4109 @cindex rewind program state
4111 On certain operating systems@footnote{Currently, only
4112 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4113 program's state, called a @dfn{checkpoint}, and come back to it
4116 Returning to a checkpoint effectively undoes everything that has
4117 happened in the program since the @code{checkpoint} was saved. This
4118 includes changes in memory, registers, and even (within some limits)
4119 system state. Effectively, it is like going back in time to the
4120 moment when the checkpoint was saved.
4122 Thus, if you're stepping thru a program and you think you're
4123 getting close to the point where things go wrong, you can save
4124 a checkpoint. Then, if you accidentally go too far and miss
4125 the critical statement, instead of having to restart your program
4126 from the beginning, you can just go back to the checkpoint and
4127 start again from there.
4129 This can be especially useful if it takes a lot of time or
4130 steps to reach the point where you think the bug occurs.
4132 To use the @code{checkpoint}/@code{restart} method of debugging:
4137 Save a snapshot of the debugged program's current execution state.
4138 The @code{checkpoint} command takes no arguments, but each checkpoint
4139 is assigned a small integer id, similar to a breakpoint id.
4141 @kindex info checkpoints
4142 @item info checkpoints
4143 List the checkpoints that have been saved in the current debugging
4144 session. For each checkpoint, the following information will be
4151 @item Source line, or label
4154 @kindex restart @var{checkpoint-id}
4155 @item restart @var{checkpoint-id}
4156 Restore the program state that was saved as checkpoint number
4157 @var{checkpoint-id}. All program variables, registers, stack frames
4158 etc.@: will be returned to the values that they had when the checkpoint
4159 was saved. In essence, gdb will ``wind back the clock'' to the point
4160 in time when the checkpoint was saved.
4162 Note that breakpoints, @value{GDBN} variables, command history etc.
4163 are not affected by restoring a checkpoint. In general, a checkpoint
4164 only restores things that reside in the program being debugged, not in
4167 @kindex delete checkpoint @var{checkpoint-id}
4168 @item delete checkpoint @var{checkpoint-id}
4169 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4173 Returning to a previously saved checkpoint will restore the user state
4174 of the program being debugged, plus a significant subset of the system
4175 (OS) state, including file pointers. It won't ``un-write'' data from
4176 a file, but it will rewind the file pointer to the previous location,
4177 so that the previously written data can be overwritten. For files
4178 opened in read mode, the pointer will also be restored so that the
4179 previously read data can be read again.
4181 Of course, characters that have been sent to a printer (or other
4182 external device) cannot be ``snatched back'', and characters received
4183 from eg.@: a serial device can be removed from internal program buffers,
4184 but they cannot be ``pushed back'' into the serial pipeline, ready to
4185 be received again. Similarly, the actual contents of files that have
4186 been changed cannot be restored (at this time).
4188 However, within those constraints, you actually can ``rewind'' your
4189 program to a previously saved point in time, and begin debugging it
4190 again --- and you can change the course of events so as to debug a
4191 different execution path this time.
4193 @cindex checkpoints and process id
4194 Finally, there is one bit of internal program state that will be
4195 different when you return to a checkpoint --- the program's process
4196 id. Each checkpoint will have a unique process id (or @var{pid}),
4197 and each will be different from the program's original @var{pid}.
4198 If your program has saved a local copy of its process id, this could
4199 potentially pose a problem.
4201 @subsection A Non-obvious Benefit of Using Checkpoints
4203 On some systems such as @sc{gnu}/Linux, address space randomization
4204 is performed on new processes for security reasons. This makes it
4205 difficult or impossible to set a breakpoint, or watchpoint, on an
4206 absolute address if you have to restart the program, since the
4207 absolute location of a symbol will change from one execution to the
4210 A checkpoint, however, is an @emph{identical} copy of a process.
4211 Therefore if you create a checkpoint at (eg.@:) the start of main,
4212 and simply return to that checkpoint instead of restarting the
4213 process, you can avoid the effects of address randomization and
4214 your symbols will all stay in the same place.
4217 @chapter Stopping and Continuing
4219 The principal purposes of using a debugger are so that you can stop your
4220 program before it terminates; or so that, if your program runs into
4221 trouble, you can investigate and find out why.
4223 Inside @value{GDBN}, your program may stop for any of several reasons,
4224 such as a signal, a breakpoint, or reaching a new line after a
4225 @value{GDBN} command such as @code{step}. You may then examine and
4226 change variables, set new breakpoints or remove old ones, and then
4227 continue execution. Usually, the messages shown by @value{GDBN} provide
4228 ample explanation of the status of your program---but you can also
4229 explicitly request this information at any time.
4232 @kindex info program
4234 Display information about the status of your program: whether it is
4235 running or not, what process it is, and why it stopped.
4239 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4240 * Continuing and Stepping:: Resuming execution
4241 * Skipping Over Functions and Files::
4242 Skipping over functions and files
4244 * Thread Stops:: Stopping and starting multi-thread programs
4248 @section Breakpoints, Watchpoints, and Catchpoints
4251 A @dfn{breakpoint} makes your program stop whenever a certain point in
4252 the program is reached. For each breakpoint, you can add conditions to
4253 control in finer detail whether your program stops. You can set
4254 breakpoints with the @code{break} command and its variants (@pxref{Set
4255 Breaks, ,Setting Breakpoints}), to specify the place where your program
4256 should stop by line number, function name or exact address in the
4259 On some systems, you can set breakpoints in shared libraries before
4260 the executable is run.
4263 @cindex data breakpoints
4264 @cindex memory tracing
4265 @cindex breakpoint on memory address
4266 @cindex breakpoint on variable modification
4267 A @dfn{watchpoint} is a special breakpoint that stops your program
4268 when the value of an expression changes. The expression may be a value
4269 of a variable, or it could involve values of one or more variables
4270 combined by operators, such as @samp{a + b}. This is sometimes called
4271 @dfn{data breakpoints}. You must use a different command to set
4272 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4273 from that, you can manage a watchpoint like any other breakpoint: you
4274 enable, disable, and delete both breakpoints and watchpoints using the
4277 You can arrange to have values from your program displayed automatically
4278 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4282 @cindex breakpoint on events
4283 A @dfn{catchpoint} is another special breakpoint that stops your program
4284 when a certain kind of event occurs, such as the throwing of a C@t{++}
4285 exception or the loading of a library. As with watchpoints, you use a
4286 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4287 Catchpoints}), but aside from that, you can manage a catchpoint like any
4288 other breakpoint. (To stop when your program receives a signal, use the
4289 @code{handle} command; see @ref{Signals, ,Signals}.)
4291 @cindex breakpoint numbers
4292 @cindex numbers for breakpoints
4293 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4294 catchpoint when you create it; these numbers are successive integers
4295 starting with one. In many of the commands for controlling various
4296 features of breakpoints you use the breakpoint number to say which
4297 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4298 @dfn{disabled}; if disabled, it has no effect on your program until you
4301 @cindex breakpoint ranges
4302 @cindex breakpoint lists
4303 @cindex ranges of breakpoints
4304 @cindex lists of breakpoints
4305 Some @value{GDBN} commands accept a space-separated list of breakpoints
4306 on which to operate. A list element can be either a single breakpoint number,
4307 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4308 When a breakpoint list is given to a command, all breakpoints in that list
4312 * Set Breaks:: Setting breakpoints
4313 * Set Watchpoints:: Setting watchpoints
4314 * Set Catchpoints:: Setting catchpoints
4315 * Delete Breaks:: Deleting breakpoints
4316 * Disabling:: Disabling breakpoints
4317 * Conditions:: Break conditions
4318 * Break Commands:: Breakpoint command lists
4319 * Dynamic Printf:: Dynamic printf
4320 * Save Breakpoints:: How to save breakpoints in a file
4321 * Static Probe Points:: Listing static probe points
4322 * Error in Breakpoints:: ``Cannot insert breakpoints''
4323 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4327 @subsection Setting Breakpoints
4329 @c FIXME LMB what does GDB do if no code on line of breakpt?
4330 @c consider in particular declaration with/without initialization.
4332 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4335 @kindex b @r{(@code{break})}
4336 @vindex $bpnum@r{, convenience variable}
4337 @cindex latest breakpoint
4338 Breakpoints are set with the @code{break} command (abbreviated
4339 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4340 number of the breakpoint you've set most recently; see @ref{Convenience
4341 Vars,, Convenience Variables}, for a discussion of what you can do with
4342 convenience variables.
4345 @item break @var{location}
4346 Set a breakpoint at the given @var{location}, which can specify a
4347 function name, a line number, or an address of an instruction.
4348 (@xref{Specify Location}, for a list of all the possible ways to
4349 specify a @var{location}.) The breakpoint will stop your program just
4350 before it executes any of the code in the specified @var{location}.
4352 When using source languages that permit overloading of symbols, such as
4353 C@t{++}, a function name may refer to more than one possible place to break.
4354 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4357 It is also possible to insert a breakpoint that will stop the program
4358 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4359 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4362 When called without any arguments, @code{break} sets a breakpoint at
4363 the next instruction to be executed in the selected stack frame
4364 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4365 innermost, this makes your program stop as soon as control
4366 returns to that frame. This is similar to the effect of a
4367 @code{finish} command in the frame inside the selected frame---except
4368 that @code{finish} does not leave an active breakpoint. If you use
4369 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4370 the next time it reaches the current location; this may be useful
4373 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4374 least one instruction has been executed. If it did not do this, you
4375 would be unable to proceed past a breakpoint without first disabling the
4376 breakpoint. This rule applies whether or not the breakpoint already
4377 existed when your program stopped.
4379 @item break @dots{} if @var{cond}
4380 Set a breakpoint with condition @var{cond}; evaluate the expression
4381 @var{cond} each time the breakpoint is reached, and stop only if the
4382 value is nonzero---that is, if @var{cond} evaluates as true.
4383 @samp{@dots{}} stands for one of the possible arguments described
4384 above (or no argument) specifying where to break. @xref{Conditions,
4385 ,Break Conditions}, for more information on breakpoint conditions.
4387 The breakpoint may be mapped to multiple locations. If the breakpoint
4388 condition @var{cond} is invalid at some but not all of the locations,
4389 the locations for which the condition is invalid are disabled. For
4390 example, @value{GDBN} reports below that two of the three locations
4394 (@value{GDBP}) break func if a == 10
4395 warning: failed to validate condition at location 0x11ce, disabling:
4396 No symbol "a" in current context.
4397 warning: failed to validate condition at location 0x11b6, disabling:
4398 No symbol "a" in current context.
4399 Breakpoint 1 at 0x11b6: func. (3 locations)
4402 Locations that are disabled because of the condition are denoted by an
4403 uppercase @code{N} in the output of the @code{info breakpoints}
4407 (@value{GDBP}) info breakpoints
4408 Num Type Disp Enb Address What
4409 1 breakpoint keep y <MULTIPLE>
4410 stop only if a == 10
4411 1.1 N* 0x00000000000011b6 in ...
4412 1.2 y 0x00000000000011c2 in ...
4413 1.3 N* 0x00000000000011ce in ...
4414 (*): Breakpoint condition is invalid at this location.
4417 If the breakpoint condition @var{cond} is invalid in the context of
4418 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4419 define the breakpoint. For example, if variable @code{foo} is an
4423 (@value{GDBP}) break func if foo
4424 No symbol "foo" in current context.
4427 @item break @dots{} -force-condition if @var{cond}
4428 There may be cases where the condition @var{cond} is invalid at all
4429 the current locations, but the user knows that it will be valid at a
4430 future location; for example, because of a library load. In such
4431 cases, by using the @code{-force-condition} keyword before @samp{if},
4432 @value{GDBN} can be forced to define the breakpoint with the given
4433 condition expression instead of refusing it.
4436 (@value{GDBP}) break func -force-condition if foo
4437 warning: failed to validate condition at location 1, disabling:
4438 No symbol "foo" in current context.
4439 warning: failed to validate condition at location 2, disabling:
4440 No symbol "foo" in current context.
4441 warning: failed to validate condition at location 3, disabling:
4442 No symbol "foo" in current context.
4443 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4446 This causes all the present locations where the breakpoint would
4447 otherwise be inserted, to be disabled, as seen in the example above.
4448 However, if there exist locations at which the condition is valid, the
4449 @code{-force-condition} keyword has no effect.
4452 @item tbreak @var{args}
4453 Set a breakpoint enabled only for one stop. The @var{args} are the
4454 same as for the @code{break} command, and the breakpoint is set in the same
4455 way, but the breakpoint is automatically deleted after the first time your
4456 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4459 @cindex hardware breakpoints
4460 @item hbreak @var{args}
4461 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4462 @code{break} command and the breakpoint is set in the same way, but the
4463 breakpoint requires hardware support and some target hardware may not
4464 have this support. The main purpose of this is EPROM/ROM code
4465 debugging, so you can set a breakpoint at an instruction without
4466 changing the instruction. This can be used with the new trap-generation
4467 provided by SPARClite DSU and most x86-based targets. These targets
4468 will generate traps when a program accesses some data or instruction
4469 address that is assigned to the debug registers. However the hardware
4470 breakpoint registers can take a limited number of breakpoints. For
4471 example, on the DSU, only two data breakpoints can be set at a time, and
4472 @value{GDBN} will reject this command if more than two are used. Delete
4473 or disable unused hardware breakpoints before setting new ones
4474 (@pxref{Disabling, ,Disabling Breakpoints}).
4475 @xref{Conditions, ,Break Conditions}.
4476 For remote targets, you can restrict the number of hardware
4477 breakpoints @value{GDBN} will use, see @ref{set remote
4478 hardware-breakpoint-limit}.
4481 @item thbreak @var{args}
4482 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4483 are the same as for the @code{hbreak} command and the breakpoint is set in
4484 the same way. However, like the @code{tbreak} command,
4485 the breakpoint is automatically deleted after the
4486 first time your program stops there. Also, like the @code{hbreak}
4487 command, the breakpoint requires hardware support and some target hardware
4488 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4489 See also @ref{Conditions, ,Break Conditions}.
4492 @cindex regular expression
4493 @cindex breakpoints at functions matching a regexp
4494 @cindex set breakpoints in many functions
4495 @item rbreak @var{regex}
4496 Set breakpoints on all functions matching the regular expression
4497 @var{regex}. This command sets an unconditional breakpoint on all
4498 matches, printing a list of all breakpoints it set. Once these
4499 breakpoints are set, they are treated just like the breakpoints set with
4500 the @code{break} command. You can delete them, disable them, or make
4501 them conditional the same way as any other breakpoint.
4503 In programs using different languages, @value{GDBN} chooses the syntax
4504 to print the list of all breakpoints it sets according to the
4505 @samp{set language} value: using @samp{set language auto}
4506 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4507 language of the breakpoint's function, other values mean to use
4508 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4510 The syntax of the regular expression is the standard one used with tools
4511 like @file{grep}. Note that this is different from the syntax used by
4512 shells, so for instance @code{foo*} matches all functions that include
4513 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4514 @code{.*} leading and trailing the regular expression you supply, so to
4515 match only functions that begin with @code{foo}, use @code{^foo}.
4517 @cindex non-member C@t{++} functions, set breakpoint in
4518 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4519 breakpoints on overloaded functions that are not members of any special
4522 @cindex set breakpoints on all functions
4523 The @code{rbreak} command can be used to set breakpoints in
4524 @strong{all} the functions in a program, like this:
4527 (@value{GDBP}) rbreak .
4530 @item rbreak @var{file}:@var{regex}
4531 If @code{rbreak} is called with a filename qualification, it limits
4532 the search for functions matching the given regular expression to the
4533 specified @var{file}. This can be used, for example, to set breakpoints on
4534 every function in a given file:
4537 (@value{GDBP}) rbreak file.c:.
4540 The colon separating the filename qualifier from the regex may
4541 optionally be surrounded by spaces.
4543 @kindex info breakpoints
4544 @cindex @code{$_} and @code{info breakpoints}
4545 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4546 @itemx info break @r{[}@var{list}@dots{}@r{]}
4547 Print a table of all breakpoints, watchpoints, and catchpoints set and
4548 not deleted. Optional argument @var{n} means print information only
4549 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4550 For each breakpoint, following columns are printed:
4553 @item Breakpoint Numbers
4555 Breakpoint, watchpoint, or catchpoint.
4557 Whether the breakpoint is marked to be disabled or deleted when hit.
4558 @item Enabled or Disabled
4559 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4560 that are not enabled.
4562 Where the breakpoint is in your program, as a memory address. For a
4563 pending breakpoint whose address is not yet known, this field will
4564 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4565 library that has the symbol or line referred by breakpoint is loaded.
4566 See below for details. A breakpoint with several locations will
4567 have @samp{<MULTIPLE>} in this field---see below for details.
4569 Where the breakpoint is in the source for your program, as a file and
4570 line number. For a pending breakpoint, the original string passed to
4571 the breakpoint command will be listed as it cannot be resolved until
4572 the appropriate shared library is loaded in the future.
4576 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4577 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4578 @value{GDBN} on the host's side. If it is ``target'', then the condition
4579 is evaluated by the target. The @code{info break} command shows
4580 the condition on the line following the affected breakpoint, together with
4581 its condition evaluation mode in between parentheses.
4583 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4584 allowed to have a condition specified for it. The condition is not parsed for
4585 validity until a shared library is loaded that allows the pending
4586 breakpoint to resolve to a valid location.
4589 @code{info break} with a breakpoint
4590 number @var{n} as argument lists only that breakpoint. The
4591 convenience variable @code{$_} and the default examining-address for
4592 the @code{x} command are set to the address of the last breakpoint
4593 listed (@pxref{Memory, ,Examining Memory}).
4596 @code{info break} displays a count of the number of times the breakpoint
4597 has been hit. This is especially useful in conjunction with the
4598 @code{ignore} command. You can ignore a large number of breakpoint
4599 hits, look at the breakpoint info to see how many times the breakpoint
4600 was hit, and then run again, ignoring one less than that number. This
4601 will get you quickly to the last hit of that breakpoint.
4604 For a breakpoints with an enable count (xref) greater than 1,
4605 @code{info break} also displays that count.
4609 @value{GDBN} allows you to set any number of breakpoints at the same place in
4610 your program. There is nothing silly or meaningless about this. When
4611 the breakpoints are conditional, this is even useful
4612 (@pxref{Conditions, ,Break Conditions}).
4614 @cindex multiple locations, breakpoints
4615 @cindex breakpoints, multiple locations
4616 It is possible that a breakpoint corresponds to several locations
4617 in your program. Examples of this situation are:
4621 Multiple functions in the program may have the same name.
4624 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4625 instances of the function body, used in different cases.
4628 For a C@t{++} template function, a given line in the function can
4629 correspond to any number of instantiations.
4632 For an inlined function, a given source line can correspond to
4633 several places where that function is inlined.
4636 In all those cases, @value{GDBN} will insert a breakpoint at all
4637 the relevant locations.
4639 A breakpoint with multiple locations is displayed in the breakpoint
4640 table using several rows---one header row, followed by one row for
4641 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4642 address column. The rows for individual locations contain the actual
4643 addresses for locations, and show the functions to which those
4644 locations belong. The number column for a location is of the form
4645 @var{breakpoint-number}.@var{location-number}.
4650 Num Type Disp Enb Address What
4651 1 breakpoint keep y <MULTIPLE>
4653 breakpoint already hit 1 time
4654 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4655 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4658 You cannot delete the individual locations from a breakpoint. However,
4659 each location can be individually enabled or disabled by passing
4660 @var{breakpoint-number}.@var{location-number} as argument to the
4661 @code{enable} and @code{disable} commands. It's also possible to
4662 @code{enable} and @code{disable} a range of @var{location-number}
4663 locations using a @var{breakpoint-number} and two @var{location-number}s,
4664 in increasing order, separated by a hyphen, like
4665 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4666 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4667 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4668 all of the locations that belong to that breakpoint.
4670 @cindex pending breakpoints
4671 It's quite common to have a breakpoint inside a shared library.
4672 Shared libraries can be loaded and unloaded explicitly,
4673 and possibly repeatedly, as the program is executed. To support
4674 this use case, @value{GDBN} updates breakpoint locations whenever
4675 any shared library is loaded or unloaded. Typically, you would
4676 set a breakpoint in a shared library at the beginning of your
4677 debugging session, when the library is not loaded, and when the
4678 symbols from the library are not available. When you try to set
4679 breakpoint, @value{GDBN} will ask you if you want to set
4680 a so called @dfn{pending breakpoint}---breakpoint whose address
4681 is not yet resolved.
4683 After the program is run, whenever a new shared library is loaded,
4684 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4685 shared library contains the symbol or line referred to by some
4686 pending breakpoint, that breakpoint is resolved and becomes an
4687 ordinary breakpoint. When a library is unloaded, all breakpoints
4688 that refer to its symbols or source lines become pending again.
4690 This logic works for breakpoints with multiple locations, too. For
4691 example, if you have a breakpoint in a C@t{++} template function, and
4692 a newly loaded shared library has an instantiation of that template,
4693 a new location is added to the list of locations for the breakpoint.
4695 Except for having unresolved address, pending breakpoints do not
4696 differ from regular breakpoints. You can set conditions or commands,
4697 enable and disable them and perform other breakpoint operations.
4699 @value{GDBN} provides some additional commands for controlling what
4700 happens when the @samp{break} command cannot resolve breakpoint
4701 address specification to an address:
4703 @kindex set breakpoint pending
4704 @kindex show breakpoint pending
4706 @item set breakpoint pending auto
4707 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4708 location, it queries you whether a pending breakpoint should be created.
4710 @item set breakpoint pending on
4711 This indicates that an unrecognized breakpoint location should automatically
4712 result in a pending breakpoint being created.
4714 @item set breakpoint pending off
4715 This indicates that pending breakpoints are not to be created. Any
4716 unrecognized breakpoint location results in an error. This setting does
4717 not affect any pending breakpoints previously created.
4719 @item show breakpoint pending
4720 Show the current behavior setting for creating pending breakpoints.
4723 The settings above only affect the @code{break} command and its
4724 variants. Once breakpoint is set, it will be automatically updated
4725 as shared libraries are loaded and unloaded.
4727 @cindex automatic hardware breakpoints
4728 For some targets, @value{GDBN} can automatically decide if hardware or
4729 software breakpoints should be used, depending on whether the
4730 breakpoint address is read-only or read-write. This applies to
4731 breakpoints set with the @code{break} command as well as to internal
4732 breakpoints set by commands like @code{next} and @code{finish}. For
4733 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4736 You can control this automatic behaviour with the following commands:
4738 @kindex set breakpoint auto-hw
4739 @kindex show breakpoint auto-hw
4741 @item set breakpoint auto-hw on
4742 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4743 will try to use the target memory map to decide if software or hardware
4744 breakpoint must be used.
4746 @item set breakpoint auto-hw off
4747 This indicates @value{GDBN} should not automatically select breakpoint
4748 type. If the target provides a memory map, @value{GDBN} will warn when
4749 trying to set software breakpoint at a read-only address.
4752 @value{GDBN} normally implements breakpoints by replacing the program code
4753 at the breakpoint address with a special instruction, which, when
4754 executed, given control to the debugger. By default, the program
4755 code is so modified only when the program is resumed. As soon as
4756 the program stops, @value{GDBN} restores the original instructions. This
4757 behaviour guards against leaving breakpoints inserted in the
4758 target should gdb abrubptly disconnect. However, with slow remote
4759 targets, inserting and removing breakpoint can reduce the performance.
4760 This behavior can be controlled with the following commands::
4762 @kindex set breakpoint always-inserted
4763 @kindex show breakpoint always-inserted
4765 @item set breakpoint always-inserted off
4766 All breakpoints, including newly added by the user, are inserted in
4767 the target only when the target is resumed. All breakpoints are
4768 removed from the target when it stops. This is the default mode.
4770 @item set breakpoint always-inserted on
4771 Causes all breakpoints to be inserted in the target at all times. If
4772 the user adds a new breakpoint, or changes an existing breakpoint, the
4773 breakpoints in the target are updated immediately. A breakpoint is
4774 removed from the target only when breakpoint itself is deleted.
4777 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4778 when a breakpoint breaks. If the condition is true, then the process being
4779 debugged stops, otherwise the process is resumed.
4781 If the target supports evaluating conditions on its end, @value{GDBN} may
4782 download the breakpoint, together with its conditions, to it.
4784 This feature can be controlled via the following commands:
4786 @kindex set breakpoint condition-evaluation
4787 @kindex show breakpoint condition-evaluation
4789 @item set breakpoint condition-evaluation host
4790 This option commands @value{GDBN} to evaluate the breakpoint
4791 conditions on the host's side. Unconditional breakpoints are sent to
4792 the target which in turn receives the triggers and reports them back to GDB
4793 for condition evaluation. This is the standard evaluation mode.
4795 @item set breakpoint condition-evaluation target
4796 This option commands @value{GDBN} to download breakpoint conditions
4797 to the target at the moment of their insertion. The target
4798 is responsible for evaluating the conditional expression and reporting
4799 breakpoint stop events back to @value{GDBN} whenever the condition
4800 is true. Due to limitations of target-side evaluation, some conditions
4801 cannot be evaluated there, e.g., conditions that depend on local data
4802 that is only known to the host. Examples include
4803 conditional expressions involving convenience variables, complex types
4804 that cannot be handled by the agent expression parser and expressions
4805 that are too long to be sent over to the target, specially when the
4806 target is a remote system. In these cases, the conditions will be
4807 evaluated by @value{GDBN}.
4809 @item set breakpoint condition-evaluation auto
4810 This is the default mode. If the target supports evaluating breakpoint
4811 conditions on its end, @value{GDBN} will download breakpoint conditions to
4812 the target (limitations mentioned previously apply). If the target does
4813 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4814 to evaluating all these conditions on the host's side.
4818 @cindex negative breakpoint numbers
4819 @cindex internal @value{GDBN} breakpoints
4820 @value{GDBN} itself sometimes sets breakpoints in your program for
4821 special purposes, such as proper handling of @code{longjmp} (in C
4822 programs). These internal breakpoints are assigned negative numbers,
4823 starting with @code{-1}; @samp{info breakpoints} does not display them.
4824 You can see these breakpoints with the @value{GDBN} maintenance command
4825 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4828 @node Set Watchpoints
4829 @subsection Setting Watchpoints
4831 @cindex setting watchpoints
4832 You can use a watchpoint to stop execution whenever the value of an
4833 expression changes, without having to predict a particular place where
4834 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4835 The expression may be as simple as the value of a single variable, or
4836 as complex as many variables combined by operators. Examples include:
4840 A reference to the value of a single variable.
4843 An address cast to an appropriate data type. For example,
4844 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4845 address (assuming an @code{int} occupies 4 bytes).
4848 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4849 expression can use any operators valid in the program's native
4850 language (@pxref{Languages}).
4853 You can set a watchpoint on an expression even if the expression can
4854 not be evaluated yet. For instance, you can set a watchpoint on
4855 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4856 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4857 the expression produces a valid value. If the expression becomes
4858 valid in some other way than changing a variable (e.g.@: if the memory
4859 pointed to by @samp{*global_ptr} becomes readable as the result of a
4860 @code{malloc} call), @value{GDBN} may not stop until the next time
4861 the expression changes.
4863 @cindex software watchpoints
4864 @cindex hardware watchpoints
4865 Depending on your system, watchpoints may be implemented in software or
4866 hardware. @value{GDBN} does software watchpointing by single-stepping your
4867 program and testing the variable's value each time, which is hundreds of
4868 times slower than normal execution. (But this may still be worth it, to
4869 catch errors where you have no clue what part of your program is the
4872 On some systems, such as most PowerPC or x86-based targets,
4873 @value{GDBN} includes support for hardware watchpoints, which do not
4874 slow down the running of your program.
4878 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]} @r{[}task @var{task-id}@r{]}
4879 Set a watchpoint for an expression. @value{GDBN} will break when the
4880 expression @var{expr} is written into by the program and its value
4881 changes. The simplest (and the most popular) use of this command is
4882 to watch the value of a single variable:
4885 (@value{GDBP}) watch foo
4888 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4889 argument, @value{GDBN} breaks only when the thread identified by
4890 @var{thread-id} changes the value of @var{expr}. If any other threads
4891 change the value of @var{expr}, @value{GDBN} will not break. Note
4892 that watchpoints restricted to a single thread in this way only work
4893 with Hardware Watchpoints.
4895 Similarly, if the @code{task} argument is given, then the watchpoint
4896 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4898 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4899 (see below). The @code{-location} argument tells @value{GDBN} to
4900 instead watch the memory referred to by @var{expr}. In this case,
4901 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4902 and watch the memory at that address. The type of the result is used
4903 to determine the size of the watched memory. If the expression's
4904 result does not have an address, then @value{GDBN} will print an
4907 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4908 of masked watchpoints, if the current architecture supports this
4909 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4910 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4911 to an address to watch. The mask specifies that some bits of an address
4912 (the bits which are reset in the mask) should be ignored when matching
4913 the address accessed by the inferior against the watchpoint address.
4914 Thus, a masked watchpoint watches many addresses simultaneously---those
4915 addresses whose unmasked bits are identical to the unmasked bits in the
4916 watchpoint address. The @code{mask} argument implies @code{-location}.
4920 (@value{GDBP}) watch foo mask 0xffff00ff
4921 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4925 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4926 Set a watchpoint that will break when the value of @var{expr} is read
4930 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4931 Set a watchpoint that will break when @var{expr} is either read from
4932 or written into by the program.
4934 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4935 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4936 This command prints a list of watchpoints, using the same format as
4937 @code{info break} (@pxref{Set Breaks}).
4940 If you watch for a change in a numerically entered address you need to
4941 dereference it, as the address itself is just a constant number which will
4942 never change. @value{GDBN} refuses to create a watchpoint that watches
4943 a never-changing value:
4946 (@value{GDBP}) watch 0x600850
4947 Cannot watch constant value 0x600850.
4948 (@value{GDBP}) watch *(int *) 0x600850
4949 Watchpoint 1: *(int *) 6293584
4952 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4953 watchpoints execute very quickly, and the debugger reports a change in
4954 value at the exact instruction where the change occurs. If @value{GDBN}
4955 cannot set a hardware watchpoint, it sets a software watchpoint, which
4956 executes more slowly and reports the change in value at the next
4957 @emph{statement}, not the instruction, after the change occurs.
4959 @cindex use only software watchpoints
4960 You can force @value{GDBN} to use only software watchpoints with the
4961 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4962 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4963 the underlying system supports them. (Note that hardware-assisted
4964 watchpoints that were set @emph{before} setting
4965 @code{can-use-hw-watchpoints} to zero will still use the hardware
4966 mechanism of watching expression values.)
4969 @item set can-use-hw-watchpoints
4970 @kindex set can-use-hw-watchpoints
4971 Set whether or not to use hardware watchpoints.
4973 @item show can-use-hw-watchpoints
4974 @kindex show can-use-hw-watchpoints
4975 Show the current mode of using hardware watchpoints.
4978 For remote targets, you can restrict the number of hardware
4979 watchpoints @value{GDBN} will use, see @ref{set remote
4980 hardware-breakpoint-limit}.
4982 When you issue the @code{watch} command, @value{GDBN} reports
4985 Hardware watchpoint @var{num}: @var{expr}
4989 if it was able to set a hardware watchpoint.
4991 Currently, the @code{awatch} and @code{rwatch} commands can only set
4992 hardware watchpoints, because accesses to data that don't change the
4993 value of the watched expression cannot be detected without examining
4994 every instruction as it is being executed, and @value{GDBN} does not do
4995 that currently. If @value{GDBN} finds that it is unable to set a
4996 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4997 will print a message like this:
5000 Expression cannot be implemented with read/access watchpoint.
5003 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5004 data type of the watched expression is wider than what a hardware
5005 watchpoint on the target machine can handle. For example, some systems
5006 can only watch regions that are up to 4 bytes wide; on such systems you
5007 cannot set hardware watchpoints for an expression that yields a
5008 double-precision floating-point number (which is typically 8 bytes
5009 wide). As a work-around, it might be possible to break the large region
5010 into a series of smaller ones and watch them with separate watchpoints.
5012 If you set too many hardware watchpoints, @value{GDBN} might be unable
5013 to insert all of them when you resume the execution of your program.
5014 Since the precise number of active watchpoints is unknown until such
5015 time as the program is about to be resumed, @value{GDBN} might not be
5016 able to warn you about this when you set the watchpoints, and the
5017 warning will be printed only when the program is resumed:
5020 Hardware watchpoint @var{num}: Could not insert watchpoint
5024 If this happens, delete or disable some of the watchpoints.
5026 Watching complex expressions that reference many variables can also
5027 exhaust the resources available for hardware-assisted watchpoints.
5028 That's because @value{GDBN} needs to watch every variable in the
5029 expression with separately allocated resources.
5031 If you call a function interactively using @code{print} or @code{call},
5032 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5033 kind of breakpoint or the call completes.
5035 @value{GDBN} automatically deletes watchpoints that watch local
5036 (automatic) variables, or expressions that involve such variables, when
5037 they go out of scope, that is, when the execution leaves the block in
5038 which these variables were defined. In particular, when the program
5039 being debugged terminates, @emph{all} local variables go out of scope,
5040 and so only watchpoints that watch global variables remain set. If you
5041 rerun the program, you will need to set all such watchpoints again. One
5042 way of doing that would be to set a code breakpoint at the entry to the
5043 @code{main} function and when it breaks, set all the watchpoints.
5045 @cindex watchpoints and threads
5046 @cindex threads and watchpoints
5047 In multi-threaded programs, watchpoints will detect changes to the
5048 watched expression from every thread.
5051 @emph{Warning:} In multi-threaded programs, software watchpoints
5052 have only limited usefulness. If @value{GDBN} creates a software
5053 watchpoint, it can only watch the value of an expression @emph{in a
5054 single thread}. If you are confident that the expression can only
5055 change due to the current thread's activity (and if you are also
5056 confident that no other thread can become current), then you can use
5057 software watchpoints as usual. However, @value{GDBN} may not notice
5058 when a non-current thread's activity changes the expression. (Hardware
5059 watchpoints, in contrast, watch an expression in all threads.)
5062 @xref{set remote hardware-watchpoint-limit}.
5064 @node Set Catchpoints
5065 @subsection Setting Catchpoints
5066 @cindex catchpoints, setting
5067 @cindex exception handlers
5068 @cindex event handling
5070 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5071 kinds of program events, such as C@t{++} exceptions or the loading of a
5072 shared library. Use the @code{catch} command to set a catchpoint.
5076 @item catch @var{event}
5077 Stop when @var{event} occurs. The @var{event} can be any of the following:
5080 @item throw @r{[}@var{regexp}@r{]}
5081 @itemx rethrow @r{[}@var{regexp}@r{]}
5082 @itemx catch @r{[}@var{regexp}@r{]}
5084 @kindex catch rethrow
5086 @cindex stop on C@t{++} exceptions
5087 The throwing, re-throwing, or catching of a C@t{++} exception.
5089 If @var{regexp} is given, then only exceptions whose type matches the
5090 regular expression will be caught.
5092 @vindex $_exception@r{, convenience variable}
5093 The convenience variable @code{$_exception} is available at an
5094 exception-related catchpoint, on some systems. This holds the
5095 exception being thrown.
5097 There are currently some limitations to C@t{++} exception handling in
5102 The support for these commands is system-dependent. Currently, only
5103 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5107 The regular expression feature and the @code{$_exception} convenience
5108 variable rely on the presence of some SDT probes in @code{libstdc++}.
5109 If these probes are not present, then these features cannot be used.
5110 These probes were first available in the GCC 4.8 release, but whether
5111 or not they are available in your GCC also depends on how it was
5115 The @code{$_exception} convenience variable is only valid at the
5116 instruction at which an exception-related catchpoint is set.
5119 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5120 location in the system library which implements runtime exception
5121 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5122 (@pxref{Selection}) to get to your code.
5125 If you call a function interactively, @value{GDBN} normally returns
5126 control to you when the function has finished executing. If the call
5127 raises an exception, however, the call may bypass the mechanism that
5128 returns control to you and cause your program either to abort or to
5129 simply continue running until it hits a breakpoint, catches a signal
5130 that @value{GDBN} is listening for, or exits. This is the case even if
5131 you set a catchpoint for the exception; catchpoints on exceptions are
5132 disabled within interactive calls. @xref{Calling}, for information on
5133 controlling this with @code{set unwind-on-terminating-exception}.
5136 You cannot raise an exception interactively.
5139 You cannot install an exception handler interactively.
5142 @item exception @r{[}@var{name}@r{]}
5143 @kindex catch exception
5144 @cindex Ada exception catching
5145 @cindex catch Ada exceptions
5146 An Ada exception being raised. If an exception name is specified
5147 at the end of the command (eg @code{catch exception Program_Error}),
5148 the debugger will stop only when this specific exception is raised.
5149 Otherwise, the debugger stops execution when any Ada exception is raised.
5151 When inserting an exception catchpoint on a user-defined exception whose
5152 name is identical to one of the exceptions defined by the language, the
5153 fully qualified name must be used as the exception name. Otherwise,
5154 @value{GDBN} will assume that it should stop on the pre-defined exception
5155 rather than the user-defined one. For instance, assuming an exception
5156 called @code{Constraint_Error} is defined in package @code{Pck}, then
5157 the command to use to catch such exceptions is @kbd{catch exception
5158 Pck.Constraint_Error}.
5160 @vindex $_ada_exception@r{, convenience variable}
5161 The convenience variable @code{$_ada_exception} holds the address of
5162 the exception being thrown. This can be useful when setting a
5163 condition for such a catchpoint.
5165 @item exception unhandled
5166 @kindex catch exception unhandled
5167 An exception that was raised but is not handled by the program. The
5168 convenience variable @code{$_ada_exception} is set as for @code{catch
5171 @item handlers @r{[}@var{name}@r{]}
5172 @kindex catch handlers
5173 @cindex Ada exception handlers catching
5174 @cindex catch Ada exceptions when handled
5175 An Ada exception being handled. If an exception name is
5176 specified at the end of the command
5177 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5178 only when this specific exception is handled.
5179 Otherwise, the debugger stops execution when any Ada exception is handled.
5181 When inserting a handlers catchpoint on a user-defined
5182 exception whose name is identical to one of the exceptions
5183 defined by the language, the fully qualified name must be used
5184 as the exception name. Otherwise, @value{GDBN} will assume that it
5185 should stop on the pre-defined exception rather than the
5186 user-defined one. For instance, assuming an exception called
5187 @code{Constraint_Error} is defined in package @code{Pck}, then the
5188 command to use to catch such exceptions handling is
5189 @kbd{catch handlers Pck.Constraint_Error}.
5191 The convenience variable @code{$_ada_exception} is set as for
5192 @code{catch exception}.
5195 @kindex catch assert
5196 A failed Ada assertion. Note that the convenience variable
5197 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5201 @cindex break on fork/exec
5202 A call to @code{exec}.
5204 @anchor{catch syscall}
5206 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5207 @kindex catch syscall
5208 @cindex break on a system call.
5209 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5210 syscall is a mechanism for application programs to request a service
5211 from the operating system (OS) or one of the OS system services.
5212 @value{GDBN} can catch some or all of the syscalls issued by the
5213 debuggee, and show the related information for each syscall. If no
5214 argument is specified, calls to and returns from all system calls
5217 @var{name} can be any system call name that is valid for the
5218 underlying OS. Just what syscalls are valid depends on the OS. On
5219 GNU and Unix systems, you can find the full list of valid syscall
5220 names on @file{/usr/include/asm/unistd.h}.
5222 @c For MS-Windows, the syscall names and the corresponding numbers
5223 @c can be found, e.g., on this URL:
5224 @c http://www.metasploit.com/users/opcode/syscalls.html
5225 @c but we don't support Windows syscalls yet.
5227 Normally, @value{GDBN} knows in advance which syscalls are valid for
5228 each OS, so you can use the @value{GDBN} command-line completion
5229 facilities (@pxref{Completion,, command completion}) to list the
5232 You may also specify the system call numerically. A syscall's
5233 number is the value passed to the OS's syscall dispatcher to
5234 identify the requested service. When you specify the syscall by its
5235 name, @value{GDBN} uses its database of syscalls to convert the name
5236 into the corresponding numeric code, but using the number directly
5237 may be useful if @value{GDBN}'s database does not have the complete
5238 list of syscalls on your system (e.g., because @value{GDBN} lags
5239 behind the OS upgrades).
5241 You may specify a group of related syscalls to be caught at once using
5242 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5243 instance, on some platforms @value{GDBN} allows you to catch all
5244 network related syscalls, by passing the argument @code{group:network}
5245 to @code{catch syscall}. Note that not all syscall groups are
5246 available in every system. You can use the command completion
5247 facilities (@pxref{Completion,, command completion}) to list the
5248 syscall groups available on your environment.
5250 The example below illustrates how this command works if you don't provide
5254 (@value{GDBP}) catch syscall
5255 Catchpoint 1 (syscall)
5257 Starting program: /tmp/catch-syscall
5259 Catchpoint 1 (call to syscall 'close'), \
5260 0xffffe424 in __kernel_vsyscall ()
5264 Catchpoint 1 (returned from syscall 'close'), \
5265 0xffffe424 in __kernel_vsyscall ()
5269 Here is an example of catching a system call by name:
5272 (@value{GDBP}) catch syscall chroot
5273 Catchpoint 1 (syscall 'chroot' [61])
5275 Starting program: /tmp/catch-syscall
5277 Catchpoint 1 (call to syscall 'chroot'), \
5278 0xffffe424 in __kernel_vsyscall ()
5282 Catchpoint 1 (returned from syscall 'chroot'), \
5283 0xffffe424 in __kernel_vsyscall ()
5287 An example of specifying a system call numerically. In the case
5288 below, the syscall number has a corresponding entry in the XML
5289 file, so @value{GDBN} finds its name and prints it:
5292 (@value{GDBP}) catch syscall 252
5293 Catchpoint 1 (syscall(s) 'exit_group')
5295 Starting program: /tmp/catch-syscall
5297 Catchpoint 1 (call to syscall 'exit_group'), \
5298 0xffffe424 in __kernel_vsyscall ()
5302 Program exited normally.
5306 Here is an example of catching a syscall group:
5309 (@value{GDBP}) catch syscall group:process
5310 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5311 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5312 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5314 Starting program: /tmp/catch-syscall
5316 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5317 from /lib64/ld-linux-x86-64.so.2
5323 However, there can be situations when there is no corresponding name
5324 in XML file for that syscall number. In this case, @value{GDBN} prints
5325 a warning message saying that it was not able to find the syscall name,
5326 but the catchpoint will be set anyway. See the example below:
5329 (@value{GDBP}) catch syscall 764
5330 warning: The number '764' does not represent a known syscall.
5331 Catchpoint 2 (syscall 764)
5335 If you configure @value{GDBN} using the @samp{--without-expat} option,
5336 it will not be able to display syscall names. Also, if your
5337 architecture does not have an XML file describing its system calls,
5338 you will not be able to see the syscall names. It is important to
5339 notice that these two features are used for accessing the syscall
5340 name database. In either case, you will see a warning like this:
5343 (@value{GDBP}) catch syscall
5344 warning: Could not open "syscalls/i386-linux.xml"
5345 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5346 GDB will not be able to display syscall names.
5347 Catchpoint 1 (syscall)
5351 Of course, the file name will change depending on your architecture and system.
5353 Still using the example above, you can also try to catch a syscall by its
5354 number. In this case, you would see something like:
5357 (@value{GDBP}) catch syscall 252
5358 Catchpoint 1 (syscall(s) 252)
5361 Again, in this case @value{GDBN} would not be able to display syscall's names.
5365 A call to @code{fork}.
5369 A call to @code{vfork}.
5371 @item load @r{[}@var{regexp}@r{]}
5372 @itemx unload @r{[}@var{regexp}@r{]}
5374 @kindex catch unload
5375 The loading or unloading of a shared library. If @var{regexp} is
5376 given, then the catchpoint will stop only if the regular expression
5377 matches one of the affected libraries.
5379 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5380 @kindex catch signal
5381 The delivery of a signal.
5383 With no arguments, this catchpoint will catch any signal that is not
5384 used internally by @value{GDBN}, specifically, all signals except
5385 @samp{SIGTRAP} and @samp{SIGINT}.
5387 With the argument @samp{all}, all signals, including those used by
5388 @value{GDBN}, will be caught. This argument cannot be used with other
5391 Otherwise, the arguments are a list of signal names as given to
5392 @code{handle} (@pxref{Signals}). Only signals specified in this list
5395 One reason that @code{catch signal} can be more useful than
5396 @code{handle} is that you can attach commands and conditions to the
5399 When a signal is caught by a catchpoint, the signal's @code{stop} and
5400 @code{print} settings, as specified by @code{handle}, are ignored.
5401 However, whether the signal is still delivered to the inferior depends
5402 on the @code{pass} setting; this can be changed in the catchpoint's
5407 @item tcatch @var{event}
5409 Set a catchpoint that is enabled only for one stop. The catchpoint is
5410 automatically deleted after the first time the event is caught.
5414 Use the @code{info break} command to list the current catchpoints.
5418 @subsection Deleting Breakpoints
5420 @cindex clearing breakpoints, watchpoints, catchpoints
5421 @cindex deleting breakpoints, watchpoints, catchpoints
5422 It is often necessary to eliminate a breakpoint, watchpoint, or
5423 catchpoint once it has done its job and you no longer want your program
5424 to stop there. This is called @dfn{deleting} the breakpoint. A
5425 breakpoint that has been deleted no longer exists; it is forgotten.
5427 With the @code{clear} command you can delete breakpoints according to
5428 where they are in your program. With the @code{delete} command you can
5429 delete individual breakpoints, watchpoints, or catchpoints by specifying
5430 their breakpoint numbers.
5432 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5433 automatically ignores breakpoints on the first instruction to be executed
5434 when you continue execution without changing the execution address.
5439 Delete any breakpoints at the next instruction to be executed in the
5440 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5441 the innermost frame is selected, this is a good way to delete a
5442 breakpoint where your program just stopped.
5444 @item clear @var{location}
5445 Delete any breakpoints set at the specified @var{location}.
5446 @xref{Specify Location}, for the various forms of @var{location}; the
5447 most useful ones are listed below:
5450 @item clear @var{function}
5451 @itemx clear @var{filename}:@var{function}
5452 Delete any breakpoints set at entry to the named @var{function}.
5454 @item clear @var{linenum}
5455 @itemx clear @var{filename}:@var{linenum}
5456 Delete any breakpoints set at or within the code of the specified
5457 @var{linenum} of the specified @var{filename}.
5460 @cindex delete breakpoints
5462 @kindex d @r{(@code{delete})}
5463 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5464 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5465 list specified as argument. If no argument is specified, delete all
5466 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5467 confirm off}). You can abbreviate this command as @code{d}.
5471 @subsection Disabling Breakpoints
5473 @cindex enable/disable a breakpoint
5474 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5475 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5476 it had been deleted, but remembers the information on the breakpoint so
5477 that you can @dfn{enable} it again later.
5479 You disable and enable breakpoints, watchpoints, and catchpoints with
5480 the @code{enable} and @code{disable} commands, optionally specifying
5481 one or more breakpoint numbers as arguments. Use @code{info break} to
5482 print a list of all breakpoints, watchpoints, and catchpoints if you
5483 do not know which numbers to use.
5485 Disabling and enabling a breakpoint that has multiple locations
5486 affects all of its locations.
5488 A breakpoint, watchpoint, or catchpoint can have any of several
5489 different states of enablement:
5493 Enabled. The breakpoint stops your program. A breakpoint set
5494 with the @code{break} command starts out in this state.
5496 Disabled. The breakpoint has no effect on your program.
5498 Enabled once. The breakpoint stops your program, but then becomes
5501 Enabled for a count. The breakpoint stops your program for the next
5502 N times, then becomes disabled.
5504 Enabled for deletion. The breakpoint stops your program, but
5505 immediately after it does so it is deleted permanently. A breakpoint
5506 set with the @code{tbreak} command starts out in this state.
5509 You can use the following commands to enable or disable breakpoints,
5510 watchpoints, and catchpoints:
5514 @kindex dis @r{(@code{disable})}
5515 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5516 Disable the specified breakpoints---or all breakpoints, if none are
5517 listed. A disabled breakpoint has no effect but is not forgotten. All
5518 options such as ignore-counts, conditions and commands are remembered in
5519 case the breakpoint is enabled again later. You may abbreviate
5520 @code{disable} as @code{dis}.
5523 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5524 Enable the specified breakpoints (or all defined breakpoints). They
5525 become effective once again in stopping your program.
5527 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5528 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5529 of these breakpoints immediately after stopping your program.
5531 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5532 Enable the specified breakpoints temporarily. @value{GDBN} records
5533 @var{count} with each of the specified breakpoints, and decrements a
5534 breakpoint's count when it is hit. When any count reaches 0,
5535 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5536 count (@pxref{Conditions, ,Break Conditions}), that will be
5537 decremented to 0 before @var{count} is affected.
5539 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5540 Enable the specified breakpoints to work once, then die. @value{GDBN}
5541 deletes any of these breakpoints as soon as your program stops there.
5542 Breakpoints set by the @code{tbreak} command start out in this state.
5545 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5546 @c confusing: tbreak is also initially enabled.
5547 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5548 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5549 subsequently, they become disabled or enabled only when you use one of
5550 the commands above. (The command @code{until} can set and delete a
5551 breakpoint of its own, but it does not change the state of your other
5552 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5556 @subsection Break Conditions
5557 @cindex conditional breakpoints
5558 @cindex breakpoint conditions
5560 @c FIXME what is scope of break condition expr? Context where wanted?
5561 @c in particular for a watchpoint?
5562 The simplest sort of breakpoint breaks every time your program reaches a
5563 specified place. You can also specify a @dfn{condition} for a
5564 breakpoint. A condition is just a Boolean expression in your
5565 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5566 a condition evaluates the expression each time your program reaches it,
5567 and your program stops only if the condition is @emph{true}.
5569 This is the converse of using assertions for program validation; in that
5570 situation, you want to stop when the assertion is violated---that is,
5571 when the condition is false. In C, if you want to test an assertion expressed
5572 by the condition @var{assert}, you should set the condition
5573 @samp{! @var{assert}} on the appropriate breakpoint.
5575 Conditions are also accepted for watchpoints; you may not need them,
5576 since a watchpoint is inspecting the value of an expression anyhow---but
5577 it might be simpler, say, to just set a watchpoint on a variable name,
5578 and specify a condition that tests whether the new value is an interesting
5581 Break conditions can have side effects, and may even call functions in
5582 your program. This can be useful, for example, to activate functions
5583 that log program progress, or to use your own print functions to
5584 format special data structures. The effects are completely predictable
5585 unless there is another enabled breakpoint at the same address. (In
5586 that case, @value{GDBN} might see the other breakpoint first and stop your
5587 program without checking the condition of this one.) Note that
5588 breakpoint commands are usually more convenient and flexible than break
5590 purpose of performing side effects when a breakpoint is reached
5591 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5593 Breakpoint conditions can also be evaluated on the target's side if
5594 the target supports it. Instead of evaluating the conditions locally,
5595 @value{GDBN} encodes the expression into an agent expression
5596 (@pxref{Agent Expressions}) suitable for execution on the target,
5597 independently of @value{GDBN}. Global variables become raw memory
5598 locations, locals become stack accesses, and so forth.
5600 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5601 when its condition evaluates to true. This mechanism may provide faster
5602 response times depending on the performance characteristics of the target
5603 since it does not need to keep @value{GDBN} informed about
5604 every breakpoint trigger, even those with false conditions.
5606 Break conditions can be specified when a breakpoint is set, by using
5607 @samp{if} in the arguments to the @code{break} command. @xref{Set
5608 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5609 with the @code{condition} command.
5611 You can also use the @code{if} keyword with the @code{watch} command.
5612 The @code{catch} command does not recognize the @code{if} keyword;
5613 @code{condition} is the only way to impose a further condition on a
5618 @item condition @var{bnum} @var{expression}
5619 Specify @var{expression} as the break condition for breakpoint,
5620 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5621 breakpoint @var{bnum} stops your program only if the value of
5622 @var{expression} is true (nonzero, in C). When you use
5623 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5624 syntactic correctness, and to determine whether symbols in it have
5625 referents in the context of your breakpoint. If @var{expression} uses
5626 symbols not referenced in the context of the breakpoint, @value{GDBN}
5627 prints an error message:
5630 No symbol "foo" in current context.
5635 not actually evaluate @var{expression} at the time the @code{condition}
5636 command (or a command that sets a breakpoint with a condition, like
5637 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5639 @item condition -force @var{bnum} @var{expression}
5640 When the @code{-force} flag is used, define the condition even if
5641 @var{expression} is invalid at all the current locations of breakpoint
5642 @var{bnum}. This is similar to the @code{-force-condition} option
5643 of the @code{break} command.
5645 @item condition @var{bnum}
5646 Remove the condition from breakpoint number @var{bnum}. It becomes
5647 an ordinary unconditional breakpoint.
5650 @cindex ignore count (of breakpoint)
5651 A special case of a breakpoint condition is to stop only when the
5652 breakpoint has been reached a certain number of times. This is so
5653 useful that there is a special way to do it, using the @dfn{ignore
5654 count} of the breakpoint. Every breakpoint has an ignore count, which
5655 is an integer. Most of the time, the ignore count is zero, and
5656 therefore has no effect. But if your program reaches a breakpoint whose
5657 ignore count is positive, then instead of stopping, it just decrements
5658 the ignore count by one and continues. As a result, if the ignore count
5659 value is @var{n}, the breakpoint does not stop the next @var{n} times
5660 your program reaches it.
5664 @item ignore @var{bnum} @var{count}
5665 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5666 The next @var{count} times the breakpoint is reached, your program's
5667 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5670 To make the breakpoint stop the next time it is reached, specify
5673 When you use @code{continue} to resume execution of your program from a
5674 breakpoint, you can specify an ignore count directly as an argument to
5675 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5676 Stepping,,Continuing and Stepping}.
5678 If a breakpoint has a positive ignore count and a condition, the
5679 condition is not checked. Once the ignore count reaches zero,
5680 @value{GDBN} resumes checking the condition.
5682 You could achieve the effect of the ignore count with a condition such
5683 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5684 is decremented each time. @xref{Convenience Vars, ,Convenience
5688 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5691 @node Break Commands
5692 @subsection Breakpoint Command Lists
5694 @cindex breakpoint commands
5695 You can give any breakpoint (or watchpoint or catchpoint) a series of
5696 commands to execute when your program stops due to that breakpoint. For
5697 example, you might want to print the values of certain expressions, or
5698 enable other breakpoints.
5702 @kindex end@r{ (breakpoint commands)}
5703 @item commands @r{[}@var{list}@dots{}@r{]}
5704 @itemx @dots{} @var{command-list} @dots{}
5706 Specify a list of commands for the given breakpoints. The commands
5707 themselves appear on the following lines. Type a line containing just
5708 @code{end} to terminate the commands.
5710 To remove all commands from a breakpoint, type @code{commands} and
5711 follow it immediately with @code{end}; that is, give no commands.
5713 With no argument, @code{commands} refers to the last breakpoint,
5714 watchpoint, or catchpoint set (not to the breakpoint most recently
5715 encountered). If the most recent breakpoints were set with a single
5716 command, then the @code{commands} will apply to all the breakpoints
5717 set by that command. This applies to breakpoints set by
5718 @code{rbreak}, and also applies when a single @code{break} command
5719 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5723 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5724 disabled within a @var{command-list}.
5726 You can use breakpoint commands to start your program up again. Simply
5727 use the @code{continue} command, or @code{step}, or any other command
5728 that resumes execution.
5730 Any other commands in the command list, after a command that resumes
5731 execution, are ignored. This is because any time you resume execution
5732 (even with a simple @code{next} or @code{step}), you may encounter
5733 another breakpoint---which could have its own command list, leading to
5734 ambiguities about which list to execute.
5737 If the first command you specify in a command list is @code{silent}, the
5738 usual message about stopping at a breakpoint is not printed. This may
5739 be desirable for breakpoints that are to print a specific message and
5740 then continue. If none of the remaining commands print anything, you
5741 see no sign that the breakpoint was reached. @code{silent} is
5742 meaningful only at the beginning of a breakpoint command list.
5744 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5745 print precisely controlled output, and are often useful in silent
5746 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5748 For example, here is how you could use breakpoint commands to print the
5749 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5755 printf "x is %d\n",x
5760 One application for breakpoint commands is to compensate for one bug so
5761 you can test for another. Put a breakpoint just after the erroneous line
5762 of code, give it a condition to detect the case in which something
5763 erroneous has been done, and give it commands to assign correct values
5764 to any variables that need them. End with the @code{continue} command
5765 so that your program does not stop, and start with the @code{silent}
5766 command so that no output is produced. Here is an example:
5777 @node Dynamic Printf
5778 @subsection Dynamic Printf
5780 @cindex dynamic printf
5782 The dynamic printf command @code{dprintf} combines a breakpoint with
5783 formatted printing of your program's data to give you the effect of
5784 inserting @code{printf} calls into your program on-the-fly, without
5785 having to recompile it.
5787 In its most basic form, the output goes to the GDB console. However,
5788 you can set the variable @code{dprintf-style} for alternate handling.
5789 For instance, you can ask to format the output by calling your
5790 program's @code{printf} function. This has the advantage that the
5791 characters go to the program's output device, so they can recorded in
5792 redirects to files and so forth.
5794 If you are doing remote debugging with a stub or agent, you can also
5795 ask to have the printf handled by the remote agent. In addition to
5796 ensuring that the output goes to the remote program's device along
5797 with any other output the program might produce, you can also ask that
5798 the dprintf remain active even after disconnecting from the remote
5799 target. Using the stub/agent is also more efficient, as it can do
5800 everything without needing to communicate with @value{GDBN}.
5804 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5805 Whenever execution reaches @var{location}, print the values of one or
5806 more @var{expressions} under the control of the string @var{template}.
5807 To print several values, separate them with commas.
5809 @item set dprintf-style @var{style}
5810 Set the dprintf output to be handled in one of several different
5811 styles enumerated below. A change of style affects all existing
5812 dynamic printfs immediately. (If you need individual control over the
5813 print commands, simply define normal breakpoints with
5814 explicitly-supplied command lists.)
5818 @kindex dprintf-style gdb
5819 Handle the output using the @value{GDBN} @code{printf} command.
5822 @kindex dprintf-style call
5823 Handle the output by calling a function in your program (normally
5827 @kindex dprintf-style agent
5828 Have the remote debugging agent (such as @code{gdbserver}) handle
5829 the output itself. This style is only available for agents that
5830 support running commands on the target.
5833 @item set dprintf-function @var{function}
5834 Set the function to call if the dprintf style is @code{call}. By
5835 default its value is @code{printf}. You may set it to any expression.
5836 that @value{GDBN} can evaluate to a function, as per the @code{call}
5839 @item set dprintf-channel @var{channel}
5840 Set a ``channel'' for dprintf. If set to a non-empty value,
5841 @value{GDBN} will evaluate it as an expression and pass the result as
5842 a first argument to the @code{dprintf-function}, in the manner of
5843 @code{fprintf} and similar functions. Otherwise, the dprintf format
5844 string will be the first argument, in the manner of @code{printf}.
5846 As an example, if you wanted @code{dprintf} output to go to a logfile
5847 that is a standard I/O stream assigned to the variable @code{mylog},
5848 you could do the following:
5851 (gdb) set dprintf-style call
5852 (gdb) set dprintf-function fprintf
5853 (gdb) set dprintf-channel mylog
5854 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5855 Dprintf 1 at 0x123456: file main.c, line 25.
5857 1 dprintf keep y 0x00123456 in main at main.c:25
5858 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5863 Note that the @code{info break} displays the dynamic printf commands
5864 as normal breakpoint commands; you can thus easily see the effect of
5865 the variable settings.
5867 @item set disconnected-dprintf on
5868 @itemx set disconnected-dprintf off
5869 @kindex set disconnected-dprintf
5870 Choose whether @code{dprintf} commands should continue to run if
5871 @value{GDBN} has disconnected from the target. This only applies
5872 if the @code{dprintf-style} is @code{agent}.
5874 @item show disconnected-dprintf off
5875 @kindex show disconnected-dprintf
5876 Show the current choice for disconnected @code{dprintf}.
5880 @value{GDBN} does not check the validity of function and channel,
5881 relying on you to supply values that are meaningful for the contexts
5882 in which they are being used. For instance, the function and channel
5883 may be the values of local variables, but if that is the case, then
5884 all enabled dynamic prints must be at locations within the scope of
5885 those locals. If evaluation fails, @value{GDBN} will report an error.
5887 @node Save Breakpoints
5888 @subsection How to save breakpoints to a file
5890 To save breakpoint definitions to a file use the @w{@code{save
5891 breakpoints}} command.
5894 @kindex save breakpoints
5895 @cindex save breakpoints to a file for future sessions
5896 @item save breakpoints [@var{filename}]
5897 This command saves all current breakpoint definitions together with
5898 their commands and ignore counts, into a file @file{@var{filename}}
5899 suitable for use in a later debugging session. This includes all
5900 types of breakpoints (breakpoints, watchpoints, catchpoints,
5901 tracepoints). To read the saved breakpoint definitions, use the
5902 @code{source} command (@pxref{Command Files}). Note that watchpoints
5903 with expressions involving local variables may fail to be recreated
5904 because it may not be possible to access the context where the
5905 watchpoint is valid anymore. Because the saved breakpoint definitions
5906 are simply a sequence of @value{GDBN} commands that recreate the
5907 breakpoints, you can edit the file in your favorite editing program,
5908 and remove the breakpoint definitions you're not interested in, or
5909 that can no longer be recreated.
5912 @node Static Probe Points
5913 @subsection Static Probe Points
5915 @cindex static probe point, SystemTap
5916 @cindex static probe point, DTrace
5917 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5918 for Statically Defined Tracing, and the probes are designed to have a tiny
5919 runtime code and data footprint, and no dynamic relocations.
5921 Currently, the following types of probes are supported on
5922 ELF-compatible systems:
5926 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5927 @acronym{SDT} probes@footnote{See
5928 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5929 for more information on how to add @code{SystemTap} @acronym{SDT}
5930 probes in your applications.}. @code{SystemTap} probes are usable
5931 from assembly, C and C@t{++} languages@footnote{See
5932 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5933 for a good reference on how the @acronym{SDT} probes are implemented.}.
5935 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5936 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5940 @cindex semaphores on static probe points
5941 Some @code{SystemTap} probes have an associated semaphore variable;
5942 for instance, this happens automatically if you defined your probe
5943 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5944 @value{GDBN} will automatically enable it when you specify a
5945 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5946 breakpoint at a probe's location by some other method (e.g.,
5947 @code{break file:line}), then @value{GDBN} will not automatically set
5948 the semaphore. @code{DTrace} probes do not support semaphores.
5950 You can examine the available static static probes using @code{info
5951 probes}, with optional arguments:
5955 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5956 If given, @var{type} is either @code{stap} for listing
5957 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5958 probes. If omitted all probes are listed regardless of their types.
5960 If given, @var{provider} is a regular expression used to match against provider
5961 names when selecting which probes to list. If omitted, probes by all
5962 probes from all providers are listed.
5964 If given, @var{name} is a regular expression to match against probe names
5965 when selecting which probes to list. If omitted, probe names are not
5966 considered when deciding whether to display them.
5968 If given, @var{objfile} is a regular expression used to select which
5969 object files (executable or shared libraries) to examine. If not
5970 given, all object files are considered.
5972 @item info probes all
5973 List the available static probes, from all types.
5976 @cindex enabling and disabling probes
5977 Some probe points can be enabled and/or disabled. The effect of
5978 enabling or disabling a probe depends on the type of probe being
5979 handled. Some @code{DTrace} probes can be enabled or
5980 disabled, but @code{SystemTap} probes cannot be disabled.
5982 You can enable (or disable) one or more probes using the following
5983 commands, with optional arguments:
5986 @kindex enable probes
5987 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5988 If given, @var{provider} is a regular expression used to match against
5989 provider names when selecting which probes to enable. If omitted,
5990 all probes from all providers are enabled.
5992 If given, @var{name} is a regular expression to match against probe
5993 names when selecting which probes to enable. If omitted, probe names
5994 are not considered when deciding whether to enable them.
5996 If given, @var{objfile} is a regular expression used to select which
5997 object files (executable or shared libraries) to examine. If not
5998 given, all object files are considered.
6000 @kindex disable probes
6001 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6002 See the @code{enable probes} command above for a description of the
6003 optional arguments accepted by this command.
6006 @vindex $_probe_arg@r{, convenience variable}
6007 A probe may specify up to twelve arguments. These are available at the
6008 point at which the probe is defined---that is, when the current PC is
6009 at the probe's location. The arguments are available using the
6010 convenience variables (@pxref{Convenience Vars})
6011 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6012 probes each probe argument is an integer of the appropriate size;
6013 types are not preserved. In @code{DTrace} probes types are preserved
6014 provided that they are recognized as such by @value{GDBN}; otherwise
6015 the value of the probe argument will be a long integer. The
6016 convenience variable @code{$_probe_argc} holds the number of arguments
6017 at the current probe point.
6019 These variables are always available, but attempts to access them at
6020 any location other than a probe point will cause @value{GDBN} to give
6024 @c @ifclear BARETARGET
6025 @node Error in Breakpoints
6026 @subsection ``Cannot insert breakpoints''
6028 If you request too many active hardware-assisted breakpoints and
6029 watchpoints, you will see this error message:
6031 @c FIXME: the precise wording of this message may change; the relevant
6032 @c source change is not committed yet (Sep 3, 1999).
6034 Stopped; cannot insert breakpoints.
6035 You may have requested too many hardware breakpoints and watchpoints.
6039 This message is printed when you attempt to resume the program, since
6040 only then @value{GDBN} knows exactly how many hardware breakpoints and
6041 watchpoints it needs to insert.
6043 When this message is printed, you need to disable or remove some of the
6044 hardware-assisted breakpoints and watchpoints, and then continue.
6046 @node Breakpoint-related Warnings
6047 @subsection ``Breakpoint address adjusted...''
6048 @cindex breakpoint address adjusted
6050 Some processor architectures place constraints on the addresses at
6051 which breakpoints may be placed. For architectures thus constrained,
6052 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6053 with the constraints dictated by the architecture.
6055 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6056 a VLIW architecture in which a number of RISC-like instructions may be
6057 bundled together for parallel execution. The FR-V architecture
6058 constrains the location of a breakpoint instruction within such a
6059 bundle to the instruction with the lowest address. @value{GDBN}
6060 honors this constraint by adjusting a breakpoint's address to the
6061 first in the bundle.
6063 It is not uncommon for optimized code to have bundles which contain
6064 instructions from different source statements, thus it may happen that
6065 a breakpoint's address will be adjusted from one source statement to
6066 another. Since this adjustment may significantly alter @value{GDBN}'s
6067 breakpoint related behavior from what the user expects, a warning is
6068 printed when the breakpoint is first set and also when the breakpoint
6071 A warning like the one below is printed when setting a breakpoint
6072 that's been subject to address adjustment:
6075 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6078 Such warnings are printed both for user settable and @value{GDBN}'s
6079 internal breakpoints. If you see one of these warnings, you should
6080 verify that a breakpoint set at the adjusted address will have the
6081 desired affect. If not, the breakpoint in question may be removed and
6082 other breakpoints may be set which will have the desired behavior.
6083 E.g., it may be sufficient to place the breakpoint at a later
6084 instruction. A conditional breakpoint may also be useful in some
6085 cases to prevent the breakpoint from triggering too often.
6087 @value{GDBN} will also issue a warning when stopping at one of these
6088 adjusted breakpoints:
6091 warning: Breakpoint 1 address previously adjusted from 0x00010414
6095 When this warning is encountered, it may be too late to take remedial
6096 action except in cases where the breakpoint is hit earlier or more
6097 frequently than expected.
6099 @node Continuing and Stepping
6100 @section Continuing and Stepping
6104 @cindex resuming execution
6105 @dfn{Continuing} means resuming program execution until your program
6106 completes normally. In contrast, @dfn{stepping} means executing just
6107 one more ``step'' of your program, where ``step'' may mean either one
6108 line of source code, or one machine instruction (depending on what
6109 particular command you use). Either when continuing or when stepping,
6110 your program may stop even sooner, due to a breakpoint or a signal. (If
6111 it stops due to a signal, you may want to use @code{handle}, or use
6112 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6113 or you may step into the signal's handler (@pxref{stepping and signal
6118 @kindex c @r{(@code{continue})}
6119 @kindex fg @r{(resume foreground execution)}
6120 @item continue @r{[}@var{ignore-count}@r{]}
6121 @itemx c @r{[}@var{ignore-count}@r{]}
6122 @itemx fg @r{[}@var{ignore-count}@r{]}
6123 Resume program execution, at the address where your program last stopped;
6124 any breakpoints set at that address are bypassed. The optional argument
6125 @var{ignore-count} allows you to specify a further number of times to
6126 ignore a breakpoint at this location; its effect is like that of
6127 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6129 The argument @var{ignore-count} is meaningful only when your program
6130 stopped due to a breakpoint. At other times, the argument to
6131 @code{continue} is ignored.
6133 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6134 debugged program is deemed to be the foreground program) are provided
6135 purely for convenience, and have exactly the same behavior as
6139 To resume execution at a different place, you can use @code{return}
6140 (@pxref{Returning, ,Returning from a Function}) to go back to the
6141 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6142 Different Address}) to go to an arbitrary location in your program.
6144 A typical technique for using stepping is to set a breakpoint
6145 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6146 beginning of the function or the section of your program where a problem
6147 is believed to lie, run your program until it stops at that breakpoint,
6148 and then step through the suspect area, examining the variables that are
6149 interesting, until you see the problem happen.
6153 @kindex s @r{(@code{step})}
6155 Continue running your program until control reaches a different source
6156 line, then stop it and return control to @value{GDBN}. This command is
6157 abbreviated @code{s}.
6160 @c "without debugging information" is imprecise; actually "without line
6161 @c numbers in the debugging information". (gcc -g1 has debugging info but
6162 @c not line numbers). But it seems complex to try to make that
6163 @c distinction here.
6164 @emph{Warning:} If you use the @code{step} command while control is
6165 within a function that was compiled without debugging information,
6166 execution proceeds until control reaches a function that does have
6167 debugging information. Likewise, it will not step into a function which
6168 is compiled without debugging information. To step through functions
6169 without debugging information, use the @code{stepi} command, described
6173 The @code{step} command only stops at the first instruction of a source
6174 line. This prevents the multiple stops that could otherwise occur in
6175 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6176 to stop if a function that has debugging information is called within
6177 the line. In other words, @code{step} @emph{steps inside} any functions
6178 called within the line.
6180 Also, the @code{step} command only enters a function if there is line
6181 number information for the function. Otherwise it acts like the
6182 @code{next} command. This avoids problems when using @code{cc -gl}
6183 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6184 was any debugging information about the routine.
6186 @item step @var{count}
6187 Continue running as in @code{step}, but do so @var{count} times. If a
6188 breakpoint is reached, or a signal not related to stepping occurs before
6189 @var{count} steps, stepping stops right away.
6192 @kindex n @r{(@code{next})}
6193 @item next @r{[}@var{count}@r{]}
6194 Continue to the next source line in the current (innermost) stack frame.
6195 This is similar to @code{step}, but function calls that appear within
6196 the line of code are executed without stopping. Execution stops when
6197 control reaches a different line of code at the original stack level
6198 that was executing when you gave the @code{next} command. This command
6199 is abbreviated @code{n}.
6201 An argument @var{count} is a repeat count, as for @code{step}.
6204 @c FIX ME!! Do we delete this, or is there a way it fits in with
6205 @c the following paragraph? --- Vctoria
6207 @c @code{next} within a function that lacks debugging information acts like
6208 @c @code{step}, but any function calls appearing within the code of the
6209 @c function are executed without stopping.
6211 The @code{next} command only stops at the first instruction of a
6212 source line. This prevents multiple stops that could otherwise occur in
6213 @code{switch} statements, @code{for} loops, etc.
6215 @kindex set step-mode
6217 @cindex functions without line info, and stepping
6218 @cindex stepping into functions with no line info
6219 @itemx set step-mode on
6220 The @code{set step-mode on} command causes the @code{step} command to
6221 stop at the first instruction of a function which contains no debug line
6222 information rather than stepping over it.
6224 This is useful in cases where you may be interested in inspecting the
6225 machine instructions of a function which has no symbolic info and do not
6226 want @value{GDBN} to automatically skip over this function.
6228 @item set step-mode off
6229 Causes the @code{step} command to step over any functions which contains no
6230 debug information. This is the default.
6232 @item show step-mode
6233 Show whether @value{GDBN} will stop in or step over functions without
6234 source line debug information.
6237 @kindex fin @r{(@code{finish})}
6239 Continue running until just after function in the selected stack frame
6240 returns. Print the returned value (if any). This command can be
6241 abbreviated as @code{fin}.
6243 Contrast this with the @code{return} command (@pxref{Returning,
6244 ,Returning from a Function}).
6246 @kindex set print finish
6247 @kindex show print finish
6248 @item set print finish @r{[}on|off@r{]}
6249 @itemx show print finish
6250 By default the @code{finish} command will show the value that is
6251 returned by the function. This can be disabled using @code{set print
6252 finish off}. When disabled, the value is still entered into the value
6253 history (@pxref{Value History}), but not displayed.
6256 @kindex u @r{(@code{until})}
6257 @cindex run until specified location
6260 Continue running until a source line past the current line, in the
6261 current stack frame, is reached. This command is used to avoid single
6262 stepping through a loop more than once. It is like the @code{next}
6263 command, except that when @code{until} encounters a jump, it
6264 automatically continues execution until the program counter is greater
6265 than the address of the jump.
6267 This means that when you reach the end of a loop after single stepping
6268 though it, @code{until} makes your program continue execution until it
6269 exits the loop. In contrast, a @code{next} command at the end of a loop
6270 simply steps back to the beginning of the loop, which forces you to step
6271 through the next iteration.
6273 @code{until} always stops your program if it attempts to exit the current
6276 @code{until} may produce somewhat counterintuitive results if the order
6277 of machine code does not match the order of the source lines. For
6278 example, in the following excerpt from a debugging session, the @code{f}
6279 (@code{frame}) command shows that execution is stopped at line
6280 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6284 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6286 (@value{GDBP}) until
6287 195 for ( ; argc > 0; NEXTARG) @{
6290 This happened because, for execution efficiency, the compiler had
6291 generated code for the loop closure test at the end, rather than the
6292 start, of the loop---even though the test in a C @code{for}-loop is
6293 written before the body of the loop. The @code{until} command appeared
6294 to step back to the beginning of the loop when it advanced to this
6295 expression; however, it has not really gone to an earlier
6296 statement---not in terms of the actual machine code.
6298 @code{until} with no argument works by means of single
6299 instruction stepping, and hence is slower than @code{until} with an
6302 @item until @var{location}
6303 @itemx u @var{location}
6304 Continue running your program until either the specified @var{location} is
6305 reached, or the current stack frame returns. The location is any of
6306 the forms described in @ref{Specify Location}.
6307 This form of the command uses temporary breakpoints, and
6308 hence is quicker than @code{until} without an argument. The specified
6309 location is actually reached only if it is in the current frame. This
6310 implies that @code{until} can be used to skip over recursive function
6311 invocations. For instance in the code below, if the current location is
6312 line @code{96}, issuing @code{until 99} will execute the program up to
6313 line @code{99} in the same invocation of factorial, i.e., after the inner
6314 invocations have returned.
6317 94 int factorial (int value)
6319 96 if (value > 1) @{
6320 97 value *= factorial (value - 1);
6327 @kindex advance @var{location}
6328 @item advance @var{location}
6329 Continue running the program up to the given @var{location}. An argument is
6330 required, which should be of one of the forms described in
6331 @ref{Specify Location}.
6332 Execution will also stop upon exit from the current stack
6333 frame. This command is similar to @code{until}, but @code{advance} will
6334 not skip over recursive function calls, and the target location doesn't
6335 have to be in the same frame as the current one.
6339 @kindex si @r{(@code{stepi})}
6341 @itemx stepi @var{arg}
6343 Execute one machine instruction, then stop and return to the debugger.
6345 It is often useful to do @samp{display/i $pc} when stepping by machine
6346 instructions. This makes @value{GDBN} automatically display the next
6347 instruction to be executed, each time your program stops. @xref{Auto
6348 Display,, Automatic Display}.
6350 An argument is a repeat count, as in @code{step}.
6354 @kindex ni @r{(@code{nexti})}
6356 @itemx nexti @var{arg}
6358 Execute one machine instruction, but if it is a function call,
6359 proceed until the function returns.
6361 An argument is a repeat count, as in @code{next}.
6365 @anchor{range stepping}
6366 @cindex range stepping
6367 @cindex target-assisted range stepping
6368 By default, and if available, @value{GDBN} makes use of
6369 target-assisted @dfn{range stepping}. In other words, whenever you
6370 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6371 tells the target to step the corresponding range of instruction
6372 addresses instead of issuing multiple single-steps. This speeds up
6373 line stepping, particularly for remote targets. Ideally, there should
6374 be no reason you would want to turn range stepping off. However, it's
6375 possible that a bug in the debug info, a bug in the remote stub (for
6376 remote targets), or even a bug in @value{GDBN} could make line
6377 stepping behave incorrectly when target-assisted range stepping is
6378 enabled. You can use the following command to turn off range stepping
6382 @kindex set range-stepping
6383 @kindex show range-stepping
6384 @item set range-stepping
6385 @itemx show range-stepping
6386 Control whether range stepping is enabled.
6388 If @code{on}, and the target supports it, @value{GDBN} tells the
6389 target to step a range of addresses itself, instead of issuing
6390 multiple single-steps. If @code{off}, @value{GDBN} always issues
6391 single-steps, even if range stepping is supported by the target. The
6392 default is @code{on}.
6396 @node Skipping Over Functions and Files
6397 @section Skipping Over Functions and Files
6398 @cindex skipping over functions and files
6400 The program you are debugging may contain some functions which are
6401 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6402 skip a function, all functions in a file or a particular function in
6403 a particular file when stepping.
6405 For example, consider the following C function:
6416 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6417 are not interested in stepping through @code{boring}. If you run @code{step}
6418 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6419 step over both @code{foo} and @code{boring}!
6421 One solution is to @code{step} into @code{boring} and use the @code{finish}
6422 command to immediately exit it. But this can become tedious if @code{boring}
6423 is called from many places.
6425 A more flexible solution is to execute @kbd{skip boring}. This instructs
6426 @value{GDBN} never to step into @code{boring}. Now when you execute
6427 @code{step} at line 103, you'll step over @code{boring} and directly into
6430 Functions may be skipped by providing either a function name, linespec
6431 (@pxref{Specify Location}), regular expression that matches the function's
6432 name, file name or a @code{glob}-style pattern that matches the file name.
6434 On Posix systems the form of the regular expression is
6435 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6436 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6437 expression is whatever is provided by the @code{regcomp} function of
6438 the underlying system.
6439 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6440 description of @code{glob}-style patterns.
6444 @item skip @r{[}@var{options}@r{]}
6445 The basic form of the @code{skip} command takes zero or more options
6446 that specify what to skip.
6447 The @var{options} argument is any useful combination of the following:
6450 @item -file @var{file}
6451 @itemx -fi @var{file}
6452 Functions in @var{file} will be skipped over when stepping.
6454 @item -gfile @var{file-glob-pattern}
6455 @itemx -gfi @var{file-glob-pattern}
6456 @cindex skipping over files via glob-style patterns
6457 Functions in files matching @var{file-glob-pattern} will be skipped
6461 (gdb) skip -gfi utils/*.c
6464 @item -function @var{linespec}
6465 @itemx -fu @var{linespec}
6466 Functions named by @var{linespec} or the function containing the line
6467 named by @var{linespec} will be skipped over when stepping.
6468 @xref{Specify Location}.
6470 @item -rfunction @var{regexp}
6471 @itemx -rfu @var{regexp}
6472 @cindex skipping over functions via regular expressions
6473 Functions whose name matches @var{regexp} will be skipped over when stepping.
6475 This form is useful for complex function names.
6476 For example, there is generally no need to step into C@t{++} @code{std::string}
6477 constructors or destructors. Plus with C@t{++} templates it can be hard to
6478 write out the full name of the function, and often it doesn't matter what
6479 the template arguments are. Specifying the function to be skipped as a
6480 regular expression makes this easier.
6483 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6486 If you want to skip every templated C@t{++} constructor and destructor
6487 in the @code{std} namespace you can do:
6490 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6494 If no options are specified, the function you're currently debugging
6497 @kindex skip function
6498 @item skip function @r{[}@var{linespec}@r{]}
6499 After running this command, the function named by @var{linespec} or the
6500 function containing the line named by @var{linespec} will be skipped over when
6501 stepping. @xref{Specify Location}.
6503 If you do not specify @var{linespec}, the function you're currently debugging
6506 (If you have a function called @code{file} that you want to skip, use
6507 @kbd{skip function file}.)
6510 @item skip file @r{[}@var{filename}@r{]}
6511 After running this command, any function whose source lives in @var{filename}
6512 will be skipped over when stepping.
6515 (gdb) skip file boring.c
6516 File boring.c will be skipped when stepping.
6519 If you do not specify @var{filename}, functions whose source lives in the file
6520 you're currently debugging will be skipped.
6523 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6524 These are the commands for managing your list of skips:
6528 @item info skip @r{[}@var{range}@r{]}
6529 Print details about the specified skip(s). If @var{range} is not specified,
6530 print a table with details about all functions and files marked for skipping.
6531 @code{info skip} prints the following information about each skip:
6535 A number identifying this skip.
6536 @item Enabled or Disabled
6537 Enabled skips are marked with @samp{y}.
6538 Disabled skips are marked with @samp{n}.
6540 If the file name is a @samp{glob} pattern this is @samp{y}.
6541 Otherwise it is @samp{n}.
6543 The name or @samp{glob} pattern of the file to be skipped.
6544 If no file is specified this is @samp{<none>}.
6546 If the function name is a @samp{regular expression} this is @samp{y}.
6547 Otherwise it is @samp{n}.
6549 The name or regular expression of the function to skip.
6550 If no function is specified this is @samp{<none>}.
6554 @item skip delete @r{[}@var{range}@r{]}
6555 Delete the specified skip(s). If @var{range} is not specified, delete all
6559 @item skip enable @r{[}@var{range}@r{]}
6560 Enable the specified skip(s). If @var{range} is not specified, enable all
6563 @kindex skip disable
6564 @item skip disable @r{[}@var{range}@r{]}
6565 Disable the specified skip(s). If @var{range} is not specified, disable all
6568 @kindex set debug skip
6569 @item set debug skip @r{[}on|off@r{]}
6570 Set whether to print the debug output about skipping files and functions.
6572 @kindex show debug skip
6573 @item show debug skip
6574 Show whether the debug output about skipping files and functions is printed.
6582 A signal is an asynchronous event that can happen in a program. The
6583 operating system defines the possible kinds of signals, and gives each
6584 kind a name and a number. For example, in Unix @code{SIGINT} is the
6585 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6586 @code{SIGSEGV} is the signal a program gets from referencing a place in
6587 memory far away from all the areas in use; @code{SIGALRM} occurs when
6588 the alarm clock timer goes off (which happens only if your program has
6589 requested an alarm).
6591 @cindex fatal signals
6592 Some signals, including @code{SIGALRM}, are a normal part of the
6593 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6594 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6595 program has not specified in advance some other way to handle the signal.
6596 @code{SIGINT} does not indicate an error in your program, but it is normally
6597 fatal so it can carry out the purpose of the interrupt: to kill the program.
6599 @value{GDBN} has the ability to detect any occurrence of a signal in your
6600 program. You can tell @value{GDBN} in advance what to do for each kind of
6603 @cindex handling signals
6604 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6605 @code{SIGALRM} be silently passed to your program
6606 (so as not to interfere with their role in the program's functioning)
6607 but to stop your program immediately whenever an error signal happens.
6608 You can change these settings with the @code{handle} command.
6611 @kindex info signals
6615 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6616 handle each one. You can use this to see the signal numbers of all
6617 the defined types of signals.
6619 @item info signals @var{sig}
6620 Similar, but print information only about the specified signal number.
6622 @code{info handle} is an alias for @code{info signals}.
6624 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6625 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6626 for details about this command.
6629 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6630 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6631 can be the number of a signal or its name (with or without the
6632 @samp{SIG} at the beginning); a list of signal numbers of the form
6633 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6634 known signals. Optional arguments @var{keywords}, described below,
6635 say what change to make.
6639 The keywords allowed by the @code{handle} command can be abbreviated.
6640 Their full names are:
6644 @value{GDBN} should not stop your program when this signal happens. It may
6645 still print a message telling you that the signal has come in.
6648 @value{GDBN} should stop your program when this signal happens. This implies
6649 the @code{print} keyword as well.
6652 @value{GDBN} should print a message when this signal happens.
6655 @value{GDBN} should not mention the occurrence of the signal at all. This
6656 implies the @code{nostop} keyword as well.
6660 @value{GDBN} should allow your program to see this signal; your program
6661 can handle the signal, or else it may terminate if the signal is fatal
6662 and not handled. @code{pass} and @code{noignore} are synonyms.
6666 @value{GDBN} should not allow your program to see this signal.
6667 @code{nopass} and @code{ignore} are synonyms.
6671 When a signal stops your program, the signal is not visible to the
6673 continue. Your program sees the signal then, if @code{pass} is in
6674 effect for the signal in question @emph{at that time}. In other words,
6675 after @value{GDBN} reports a signal, you can use the @code{handle}
6676 command with @code{pass} or @code{nopass} to control whether your
6677 program sees that signal when you continue.
6679 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6680 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6681 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6684 You can also use the @code{signal} command to prevent your program from
6685 seeing a signal, or cause it to see a signal it normally would not see,
6686 or to give it any signal at any time. For example, if your program stopped
6687 due to some sort of memory reference error, you might store correct
6688 values into the erroneous variables and continue, hoping to see more
6689 execution; but your program would probably terminate immediately as
6690 a result of the fatal signal once it saw the signal. To prevent this,
6691 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6694 @cindex stepping and signal handlers
6695 @anchor{stepping and signal handlers}
6697 @value{GDBN} optimizes for stepping the mainline code. If a signal
6698 that has @code{handle nostop} and @code{handle pass} set arrives while
6699 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6700 in progress, @value{GDBN} lets the signal handler run and then resumes
6701 stepping the mainline code once the signal handler returns. In other
6702 words, @value{GDBN} steps over the signal handler. This prevents
6703 signals that you've specified as not interesting (with @code{handle
6704 nostop}) from changing the focus of debugging unexpectedly. Note that
6705 the signal handler itself may still hit a breakpoint, stop for another
6706 signal that has @code{handle stop} in effect, or for any other event
6707 that normally results in stopping the stepping command sooner. Also
6708 note that @value{GDBN} still informs you that the program received a
6709 signal if @code{handle print} is set.
6711 @anchor{stepping into signal handlers}
6713 If you set @code{handle pass} for a signal, and your program sets up a
6714 handler for it, then issuing a stepping command, such as @code{step}
6715 or @code{stepi}, when your program is stopped due to the signal will
6716 step @emph{into} the signal handler (if the target supports that).
6718 Likewise, if you use the @code{queue-signal} command to queue a signal
6719 to be delivered to the current thread when execution of the thread
6720 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6721 stepping command will step into the signal handler.
6723 Here's an example, using @code{stepi} to step to the first instruction
6724 of @code{SIGUSR1}'s handler:
6727 (@value{GDBP}) handle SIGUSR1
6728 Signal Stop Print Pass to program Description
6729 SIGUSR1 Yes Yes Yes User defined signal 1
6733 Program received signal SIGUSR1, User defined signal 1.
6734 main () sigusr1.c:28
6737 sigusr1_handler () at sigusr1.c:9
6741 The same, but using @code{queue-signal} instead of waiting for the
6742 program to receive the signal first:
6747 (@value{GDBP}) queue-signal SIGUSR1
6749 sigusr1_handler () at sigusr1.c:9
6754 @cindex extra signal information
6755 @anchor{extra signal information}
6757 On some targets, @value{GDBN} can inspect extra signal information
6758 associated with the intercepted signal, before it is actually
6759 delivered to the program being debugged. This information is exported
6760 by the convenience variable @code{$_siginfo}, and consists of data
6761 that is passed by the kernel to the signal handler at the time of the
6762 receipt of a signal. The data type of the information itself is
6763 target dependent. You can see the data type using the @code{ptype
6764 $_siginfo} command. On Unix systems, it typically corresponds to the
6765 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6768 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6769 referenced address that raised a segmentation fault.
6773 (@value{GDBP}) continue
6774 Program received signal SIGSEGV, Segmentation fault.
6775 0x0000000000400766 in main ()
6777 (@value{GDBP}) ptype $_siginfo
6784 struct @{...@} _kill;
6785 struct @{...@} _timer;
6787 struct @{...@} _sigchld;
6788 struct @{...@} _sigfault;
6789 struct @{...@} _sigpoll;
6792 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6796 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6797 $1 = (void *) 0x7ffff7ff7000
6801 Depending on target support, @code{$_siginfo} may also be writable.
6803 @cindex Intel MPX boundary violations
6804 @cindex boundary violations, Intel MPX
6805 On some targets, a @code{SIGSEGV} can be caused by a boundary
6806 violation, i.e., accessing an address outside of the allowed range.
6807 In those cases @value{GDBN} may displays additional information,
6808 depending on how @value{GDBN} has been told to handle the signal.
6809 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6810 kind: "Upper" or "Lower", the memory address accessed and the
6811 bounds, while with @code{handle nostop SIGSEGV} no additional
6812 information is displayed.
6814 The usual output of a segfault is:
6816 Program received signal SIGSEGV, Segmentation fault
6817 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6818 68 value = *(p + len);
6821 While a bound violation is presented as:
6823 Program received signal SIGSEGV, Segmentation fault
6824 Upper bound violation while accessing address 0x7fffffffc3b3
6825 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6826 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6827 68 value = *(p + len);
6831 @section Stopping and Starting Multi-thread Programs
6833 @cindex stopped threads
6834 @cindex threads, stopped
6836 @cindex continuing threads
6837 @cindex threads, continuing
6839 @value{GDBN} supports debugging programs with multiple threads
6840 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6841 are two modes of controlling execution of your program within the
6842 debugger. In the default mode, referred to as @dfn{all-stop mode},
6843 when any thread in your program stops (for example, at a breakpoint
6844 or while being stepped), all other threads in the program are also stopped by
6845 @value{GDBN}. On some targets, @value{GDBN} also supports
6846 @dfn{non-stop mode}, in which other threads can continue to run freely while
6847 you examine the stopped thread in the debugger.
6850 * All-Stop Mode:: All threads stop when GDB takes control
6851 * Non-Stop Mode:: Other threads continue to execute
6852 * Background Execution:: Running your program asynchronously
6853 * Thread-Specific Breakpoints:: Controlling breakpoints
6854 * Interrupted System Calls:: GDB may interfere with system calls
6855 * Observer Mode:: GDB does not alter program behavior
6859 @subsection All-Stop Mode
6861 @cindex all-stop mode
6863 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6864 @emph{all} threads of execution stop, not just the current thread. This
6865 allows you to examine the overall state of the program, including
6866 switching between threads, without worrying that things may change
6869 Conversely, whenever you restart the program, @emph{all} threads start
6870 executing. @emph{This is true even when single-stepping} with commands
6871 like @code{step} or @code{next}.
6873 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6874 Since thread scheduling is up to your debugging target's operating
6875 system (not controlled by @value{GDBN}), other threads may
6876 execute more than one statement while the current thread completes a
6877 single step. Moreover, in general other threads stop in the middle of a
6878 statement, rather than at a clean statement boundary, when the program
6881 You might even find your program stopped in another thread after
6882 continuing or even single-stepping. This happens whenever some other
6883 thread runs into a breakpoint, a signal, or an exception before the
6884 first thread completes whatever you requested.
6886 @cindex automatic thread selection
6887 @cindex switching threads automatically
6888 @cindex threads, automatic switching
6889 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6890 signal, it automatically selects the thread where that breakpoint or
6891 signal happened. @value{GDBN} alerts you to the context switch with a
6892 message such as @samp{[Switching to Thread @var{n}]} to identify the
6895 On some OSes, you can modify @value{GDBN}'s default behavior by
6896 locking the OS scheduler to allow only a single thread to run.
6899 @item set scheduler-locking @var{mode}
6900 @cindex scheduler locking mode
6901 @cindex lock scheduler
6902 Set the scheduler locking mode. It applies to normal execution,
6903 record mode, and replay mode. If it is @code{off}, then there is no
6904 locking and any thread may run at any time. If @code{on}, then only
6905 the current thread may run when the inferior is resumed. The
6906 @code{step} mode optimizes for single-stepping; it prevents other
6907 threads from preempting the current thread while you are stepping, so
6908 that the focus of debugging does not change unexpectedly. Other
6909 threads never get a chance to run when you step, and they are
6910 completely free to run when you use commands like @samp{continue},
6911 @samp{until}, or @samp{finish}. However, unless another thread hits a
6912 breakpoint during its timeslice, @value{GDBN} does not change the
6913 current thread away from the thread that you are debugging. The
6914 @code{replay} mode behaves like @code{off} in record mode and like
6915 @code{on} in replay mode.
6917 @item show scheduler-locking
6918 Display the current scheduler locking mode.
6921 @cindex resume threads of multiple processes simultaneously
6922 By default, when you issue one of the execution commands such as
6923 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6924 threads of the current inferior to run. For example, if @value{GDBN}
6925 is attached to two inferiors, each with two threads, the
6926 @code{continue} command resumes only the two threads of the current
6927 inferior. This is useful, for example, when you debug a program that
6928 forks and you want to hold the parent stopped (so that, for instance,
6929 it doesn't run to exit), while you debug the child. In other
6930 situations, you may not be interested in inspecting the current state
6931 of any of the processes @value{GDBN} is attached to, and you may want
6932 to resume them all until some breakpoint is hit. In the latter case,
6933 you can instruct @value{GDBN} to allow all threads of all the
6934 inferiors to run with the @w{@code{set schedule-multiple}} command.
6937 @kindex set schedule-multiple
6938 @item set schedule-multiple
6939 Set the mode for allowing threads of multiple processes to be resumed
6940 when an execution command is issued. When @code{on}, all threads of
6941 all processes are allowed to run. When @code{off}, only the threads
6942 of the current process are resumed. The default is @code{off}. The
6943 @code{scheduler-locking} mode takes precedence when set to @code{on},
6944 or while you are stepping and set to @code{step}.
6946 @item show schedule-multiple
6947 Display the current mode for resuming the execution of threads of
6952 @subsection Non-Stop Mode
6954 @cindex non-stop mode
6956 @c This section is really only a place-holder, and needs to be expanded
6957 @c with more details.
6959 For some multi-threaded targets, @value{GDBN} supports an optional
6960 mode of operation in which you can examine stopped program threads in
6961 the debugger while other threads continue to execute freely. This
6962 minimizes intrusion when debugging live systems, such as programs
6963 where some threads have real-time constraints or must continue to
6964 respond to external events. This is referred to as @dfn{non-stop} mode.
6966 In non-stop mode, when a thread stops to report a debugging event,
6967 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6968 threads as well, in contrast to the all-stop mode behavior. Additionally,
6969 execution commands such as @code{continue} and @code{step} apply by default
6970 only to the current thread in non-stop mode, rather than all threads as
6971 in all-stop mode. This allows you to control threads explicitly in
6972 ways that are not possible in all-stop mode --- for example, stepping
6973 one thread while allowing others to run freely, stepping
6974 one thread while holding all others stopped, or stepping several threads
6975 independently and simultaneously.
6977 To enter non-stop mode, use this sequence of commands before you run
6978 or attach to your program:
6981 # If using the CLI, pagination breaks non-stop.
6984 # Finally, turn it on!
6988 You can use these commands to manipulate the non-stop mode setting:
6991 @kindex set non-stop
6992 @item set non-stop on
6993 Enable selection of non-stop mode.
6994 @item set non-stop off
6995 Disable selection of non-stop mode.
6996 @kindex show non-stop
6998 Show the current non-stop enablement setting.
7001 Note these commands only reflect whether non-stop mode is enabled,
7002 not whether the currently-executing program is being run in non-stop mode.
7003 In particular, the @code{set non-stop} preference is only consulted when
7004 @value{GDBN} starts or connects to the target program, and it is generally
7005 not possible to switch modes once debugging has started. Furthermore,
7006 since not all targets support non-stop mode, even when you have enabled
7007 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7010 In non-stop mode, all execution commands apply only to the current thread
7011 by default. That is, @code{continue} only continues one thread.
7012 To continue all threads, issue @code{continue -a} or @code{c -a}.
7014 You can use @value{GDBN}'s background execution commands
7015 (@pxref{Background Execution}) to run some threads in the background
7016 while you continue to examine or step others from @value{GDBN}.
7017 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7018 always executed asynchronously in non-stop mode.
7020 Suspending execution is done with the @code{interrupt} command when
7021 running in the background, or @kbd{Ctrl-c} during foreground execution.
7022 In all-stop mode, this stops the whole process;
7023 but in non-stop mode the interrupt applies only to the current thread.
7024 To stop the whole program, use @code{interrupt -a}.
7026 Other execution commands do not currently support the @code{-a} option.
7028 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7029 that thread current, as it does in all-stop mode. This is because the
7030 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7031 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7032 changed to a different thread just as you entered a command to operate on the
7033 previously current thread.
7035 @node Background Execution
7036 @subsection Background Execution
7038 @cindex foreground execution
7039 @cindex background execution
7040 @cindex asynchronous execution
7041 @cindex execution, foreground, background and asynchronous
7043 @value{GDBN}'s execution commands have two variants: the normal
7044 foreground (synchronous) behavior, and a background
7045 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7046 the program to report that some thread has stopped before prompting for
7047 another command. In background execution, @value{GDBN} immediately gives
7048 a command prompt so that you can issue other commands while your program runs.
7050 If the target doesn't support async mode, @value{GDBN} issues an error
7051 message if you attempt to use the background execution commands.
7053 @cindex @code{&}, background execution of commands
7054 To specify background execution, add a @code{&} to the command. For example,
7055 the background form of the @code{continue} command is @code{continue&}, or
7056 just @code{c&}. The execution commands that accept background execution
7062 @xref{Starting, , Starting your Program}.
7066 @xref{Attach, , Debugging an Already-running Process}.
7070 @xref{Continuing and Stepping, step}.
7074 @xref{Continuing and Stepping, stepi}.
7078 @xref{Continuing and Stepping, next}.
7082 @xref{Continuing and Stepping, nexti}.
7086 @xref{Continuing and Stepping, continue}.
7090 @xref{Continuing and Stepping, finish}.
7094 @xref{Continuing and Stepping, until}.
7098 Background execution is especially useful in conjunction with non-stop
7099 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7100 However, you can also use these commands in the normal all-stop mode with
7101 the restriction that you cannot issue another execution command until the
7102 previous one finishes. Examples of commands that are valid in all-stop
7103 mode while the program is running include @code{help} and @code{info break}.
7105 You can interrupt your program while it is running in the background by
7106 using the @code{interrupt} command.
7113 Suspend execution of the running program. In all-stop mode,
7114 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7115 only the current thread. To stop the whole program in non-stop mode,
7116 use @code{interrupt -a}.
7119 @node Thread-Specific Breakpoints
7120 @subsection Thread-Specific Breakpoints
7122 When your program has multiple threads (@pxref{Threads,, Debugging
7123 Programs with Multiple Threads}), you can choose whether to set
7124 breakpoints on all threads, or on a particular thread.
7127 @cindex breakpoints and threads
7128 @cindex thread breakpoints
7129 @kindex break @dots{} thread @var{thread-id}
7130 @item break @var{location} thread @var{thread-id}
7131 @itemx break @var{location} thread @var{thread-id} if @dots{}
7132 @var{location} specifies source lines; there are several ways of
7133 writing them (@pxref{Specify Location}), but the effect is always to
7134 specify some source line.
7136 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7137 to specify that you only want @value{GDBN} to stop the program when a
7138 particular thread reaches this breakpoint. The @var{thread-id} specifier
7139 is one of the thread identifiers assigned by @value{GDBN}, shown
7140 in the first column of the @samp{info threads} display.
7142 If you do not specify @samp{thread @var{thread-id}} when you set a
7143 breakpoint, the breakpoint applies to @emph{all} threads of your
7146 You can use the @code{thread} qualifier on conditional breakpoints as
7147 well; in this case, place @samp{thread @var{thread-id}} before or
7148 after the breakpoint condition, like this:
7151 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7156 Thread-specific breakpoints are automatically deleted when
7157 @value{GDBN} detects the corresponding thread is no longer in the
7158 thread list. For example:
7162 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7165 There are several ways for a thread to disappear, such as a regular
7166 thread exit, but also when you detach from the process with the
7167 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7168 Process}), or if @value{GDBN} loses the remote connection
7169 (@pxref{Remote Debugging}), etc. Note that with some targets,
7170 @value{GDBN} is only able to detect a thread has exited when the user
7171 explictly asks for the thread list with the @code{info threads}
7174 @node Interrupted System Calls
7175 @subsection Interrupted System Calls
7177 @cindex thread breakpoints and system calls
7178 @cindex system calls and thread breakpoints
7179 @cindex premature return from system calls
7180 There is an unfortunate side effect when using @value{GDBN} to debug
7181 multi-threaded programs. If one thread stops for a
7182 breakpoint, or for some other reason, and another thread is blocked in a
7183 system call, then the system call may return prematurely. This is a
7184 consequence of the interaction between multiple threads and the signals
7185 that @value{GDBN} uses to implement breakpoints and other events that
7188 To handle this problem, your program should check the return value of
7189 each system call and react appropriately. This is good programming
7192 For example, do not write code like this:
7198 The call to @code{sleep} will return early if a different thread stops
7199 at a breakpoint or for some other reason.
7201 Instead, write this:
7206 unslept = sleep (unslept);
7209 A system call is allowed to return early, so the system is still
7210 conforming to its specification. But @value{GDBN} does cause your
7211 multi-threaded program to behave differently than it would without
7214 Also, @value{GDBN} uses internal breakpoints in the thread library to
7215 monitor certain events such as thread creation and thread destruction.
7216 When such an event happens, a system call in another thread may return
7217 prematurely, even though your program does not appear to stop.
7220 @subsection Observer Mode
7222 If you want to build on non-stop mode and observe program behavior
7223 without any chance of disruption by @value{GDBN}, you can set
7224 variables to disable all of the debugger's attempts to modify state,
7225 whether by writing memory, inserting breakpoints, etc. These operate
7226 at a low level, intercepting operations from all commands.
7228 When all of these are set to @code{off}, then @value{GDBN} is said to
7229 be @dfn{observer mode}. As a convenience, the variable
7230 @code{observer} can be set to disable these, plus enable non-stop
7233 Note that @value{GDBN} will not prevent you from making nonsensical
7234 combinations of these settings. For instance, if you have enabled
7235 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7236 then breakpoints that work by writing trap instructions into the code
7237 stream will still not be able to be placed.
7242 @item set observer on
7243 @itemx set observer off
7244 When set to @code{on}, this disables all the permission variables
7245 below (except for @code{insert-fast-tracepoints}), plus enables
7246 non-stop debugging. Setting this to @code{off} switches back to
7247 normal debugging, though remaining in non-stop mode.
7250 Show whether observer mode is on or off.
7252 @kindex may-write-registers
7253 @item set may-write-registers on
7254 @itemx set may-write-registers off
7255 This controls whether @value{GDBN} will attempt to alter the values of
7256 registers, such as with assignment expressions in @code{print}, or the
7257 @code{jump} command. It defaults to @code{on}.
7259 @item show may-write-registers
7260 Show the current permission to write registers.
7262 @kindex may-write-memory
7263 @item set may-write-memory on
7264 @itemx set may-write-memory off
7265 This controls whether @value{GDBN} will attempt to alter the contents
7266 of memory, such as with assignment expressions in @code{print}. It
7267 defaults to @code{on}.
7269 @item show may-write-memory
7270 Show the current permission to write memory.
7272 @kindex may-insert-breakpoints
7273 @item set may-insert-breakpoints on
7274 @itemx set may-insert-breakpoints off
7275 This controls whether @value{GDBN} will attempt to insert breakpoints.
7276 This affects all breakpoints, including internal breakpoints defined
7277 by @value{GDBN}. It defaults to @code{on}.
7279 @item show may-insert-breakpoints
7280 Show the current permission to insert breakpoints.
7282 @kindex may-insert-tracepoints
7283 @item set may-insert-tracepoints on
7284 @itemx set may-insert-tracepoints off
7285 This controls whether @value{GDBN} will attempt to insert (regular)
7286 tracepoints at the beginning of a tracing experiment. It affects only
7287 non-fast tracepoints, fast tracepoints being under the control of
7288 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7290 @item show may-insert-tracepoints
7291 Show the current permission to insert tracepoints.
7293 @kindex may-insert-fast-tracepoints
7294 @item set may-insert-fast-tracepoints on
7295 @itemx set may-insert-fast-tracepoints off
7296 This controls whether @value{GDBN} will attempt to insert fast
7297 tracepoints at the beginning of a tracing experiment. It affects only
7298 fast tracepoints, regular (non-fast) tracepoints being under the
7299 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7301 @item show may-insert-fast-tracepoints
7302 Show the current permission to insert fast tracepoints.
7304 @kindex may-interrupt
7305 @item set may-interrupt on
7306 @itemx set may-interrupt off
7307 This controls whether @value{GDBN} will attempt to interrupt or stop
7308 program execution. When this variable is @code{off}, the
7309 @code{interrupt} command will have no effect, nor will
7310 @kbd{Ctrl-c}. It defaults to @code{on}.
7312 @item show may-interrupt
7313 Show the current permission to interrupt or stop the program.
7317 @node Reverse Execution
7318 @chapter Running programs backward
7319 @cindex reverse execution
7320 @cindex running programs backward
7322 When you are debugging a program, it is not unusual to realize that
7323 you have gone too far, and some event of interest has already happened.
7324 If the target environment supports it, @value{GDBN} can allow you to
7325 ``rewind'' the program by running it backward.
7327 A target environment that supports reverse execution should be able
7328 to ``undo'' the changes in machine state that have taken place as the
7329 program was executing normally. Variables, registers etc.@: should
7330 revert to their previous values. Obviously this requires a great
7331 deal of sophistication on the part of the target environment; not
7332 all target environments can support reverse execution.
7334 When a program is executed in reverse, the instructions that
7335 have most recently been executed are ``un-executed'', in reverse
7336 order. The program counter runs backward, following the previous
7337 thread of execution in reverse. As each instruction is ``un-executed'',
7338 the values of memory and/or registers that were changed by that
7339 instruction are reverted to their previous states. After executing
7340 a piece of source code in reverse, all side effects of that code
7341 should be ``undone'', and all variables should be returned to their
7342 prior values@footnote{
7343 Note that some side effects are easier to undo than others. For instance,
7344 memory and registers are relatively easy, but device I/O is hard. Some
7345 targets may be able undo things like device I/O, and some may not.
7347 The contract between @value{GDBN} and the reverse executing target
7348 requires only that the target do something reasonable when
7349 @value{GDBN} tells it to execute backwards, and then report the
7350 results back to @value{GDBN}. Whatever the target reports back to
7351 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7352 assumes that the memory and registers that the target reports are in a
7353 consistent state, but @value{GDBN} accepts whatever it is given.
7356 On some platforms, @value{GDBN} has built-in support for reverse
7357 execution, activated with the @code{record} or @code{record btrace}
7358 commands. @xref{Process Record and Replay}. Some remote targets,
7359 typically full system emulators, support reverse execution directly
7360 without requiring any special command.
7362 If you are debugging in a target environment that supports
7363 reverse execution, @value{GDBN} provides the following commands.
7366 @kindex reverse-continue
7367 @kindex rc @r{(@code{reverse-continue})}
7368 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7369 @itemx rc @r{[}@var{ignore-count}@r{]}
7370 Beginning at the point where your program last stopped, start executing
7371 in reverse. Reverse execution will stop for breakpoints and synchronous
7372 exceptions (signals), just like normal execution. Behavior of
7373 asynchronous signals depends on the target environment.
7375 @kindex reverse-step
7376 @kindex rs @r{(@code{step})}
7377 @item reverse-step @r{[}@var{count}@r{]}
7378 Run the program backward until control reaches the start of a
7379 different source line; then stop it, and return control to @value{GDBN}.
7381 Like the @code{step} command, @code{reverse-step} will only stop
7382 at the beginning of a source line. It ``un-executes'' the previously
7383 executed source line. If the previous source line included calls to
7384 debuggable functions, @code{reverse-step} will step (backward) into
7385 the called function, stopping at the beginning of the @emph{last}
7386 statement in the called function (typically a return statement).
7388 Also, as with the @code{step} command, if non-debuggable functions are
7389 called, @code{reverse-step} will run thru them backward without stopping.
7391 @kindex reverse-stepi
7392 @kindex rsi @r{(@code{reverse-stepi})}
7393 @item reverse-stepi @r{[}@var{count}@r{]}
7394 Reverse-execute one machine instruction. Note that the instruction
7395 to be reverse-executed is @emph{not} the one pointed to by the program
7396 counter, but the instruction executed prior to that one. For instance,
7397 if the last instruction was a jump, @code{reverse-stepi} will take you
7398 back from the destination of the jump to the jump instruction itself.
7400 @kindex reverse-next
7401 @kindex rn @r{(@code{reverse-next})}
7402 @item reverse-next @r{[}@var{count}@r{]}
7403 Run backward to the beginning of the previous line executed in
7404 the current (innermost) stack frame. If the line contains function
7405 calls, they will be ``un-executed'' without stopping. Starting from
7406 the first line of a function, @code{reverse-next} will take you back
7407 to the caller of that function, @emph{before} the function was called,
7408 just as the normal @code{next} command would take you from the last
7409 line of a function back to its return to its caller
7410 @footnote{Unless the code is too heavily optimized.}.
7412 @kindex reverse-nexti
7413 @kindex rni @r{(@code{reverse-nexti})}
7414 @item reverse-nexti @r{[}@var{count}@r{]}
7415 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7416 in reverse, except that called functions are ``un-executed'' atomically.
7417 That is, if the previously executed instruction was a return from
7418 another function, @code{reverse-nexti} will continue to execute
7419 in reverse until the call to that function (from the current stack
7422 @kindex reverse-finish
7423 @item reverse-finish
7424 Just as the @code{finish} command takes you to the point where the
7425 current function returns, @code{reverse-finish} takes you to the point
7426 where it was called. Instead of ending up at the end of the current
7427 function invocation, you end up at the beginning.
7429 @kindex set exec-direction
7430 @item set exec-direction
7431 Set the direction of target execution.
7432 @item set exec-direction reverse
7433 @cindex execute forward or backward in time
7434 @value{GDBN} will perform all execution commands in reverse, until the
7435 exec-direction mode is changed to ``forward''. Affected commands include
7436 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7437 command cannot be used in reverse mode.
7438 @item set exec-direction forward
7439 @value{GDBN} will perform all execution commands in the normal fashion.
7440 This is the default.
7444 @node Process Record and Replay
7445 @chapter Recording Inferior's Execution and Replaying It
7446 @cindex process record and replay
7447 @cindex recording inferior's execution and replaying it
7449 On some platforms, @value{GDBN} provides a special @dfn{process record
7450 and replay} target that can record a log of the process execution, and
7451 replay it later with both forward and reverse execution commands.
7454 When this target is in use, if the execution log includes the record
7455 for the next instruction, @value{GDBN} will debug in @dfn{replay
7456 mode}. In the replay mode, the inferior does not really execute code
7457 instructions. Instead, all the events that normally happen during
7458 code execution are taken from the execution log. While code is not
7459 really executed in replay mode, the values of registers (including the
7460 program counter register) and the memory of the inferior are still
7461 changed as they normally would. Their contents are taken from the
7465 If the record for the next instruction is not in the execution log,
7466 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7467 inferior executes normally, and @value{GDBN} records the execution log
7470 The process record and replay target supports reverse execution
7471 (@pxref{Reverse Execution}), even if the platform on which the
7472 inferior runs does not. However, the reverse execution is limited in
7473 this case by the range of the instructions recorded in the execution
7474 log. In other words, reverse execution on platforms that don't
7475 support it directly can only be done in the replay mode.
7477 When debugging in the reverse direction, @value{GDBN} will work in
7478 replay mode as long as the execution log includes the record for the
7479 previous instruction; otherwise, it will work in record mode, if the
7480 platform supports reverse execution, or stop if not.
7482 Currently, process record and replay is supported on ARM, Aarch64,
7483 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7484 GNU/Linux. Process record and replay can be used both when native
7485 debugging, and when remote debugging via @code{gdbserver}.
7487 For architecture environments that support process record and replay,
7488 @value{GDBN} provides the following commands:
7491 @kindex target record
7492 @kindex target record-full
7493 @kindex target record-btrace
7496 @kindex record btrace
7497 @kindex record btrace bts
7498 @kindex record btrace pt
7504 @kindex rec btrace bts
7505 @kindex rec btrace pt
7508 @item record @var{method}
7509 This command starts the process record and replay target. The
7510 recording method can be specified as parameter. Without a parameter
7511 the command uses the @code{full} recording method. The following
7512 recording methods are available:
7516 Full record/replay recording using @value{GDBN}'s software record and
7517 replay implementation. This method allows replaying and reverse
7520 @item btrace @var{format}
7521 Hardware-supported instruction recording, supported on Intel
7522 processors. This method does not record data. Further, the data is
7523 collected in a ring buffer so old data will be overwritten when the
7524 buffer is full. It allows limited reverse execution. Variables and
7525 registers are not available during reverse execution. In remote
7526 debugging, recording continues on disconnect. Recorded data can be
7527 inspected after reconnecting. The recording may be stopped using
7530 The recording format can be specified as parameter. Without a parameter
7531 the command chooses the recording format. The following recording
7532 formats are available:
7536 @cindex branch trace store
7537 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7538 this format, the processor stores a from/to record for each executed
7539 branch in the btrace ring buffer.
7542 @cindex Intel Processor Trace
7543 Use the @dfn{Intel Processor Trace} recording format. In this
7544 format, the processor stores the execution trace in a compressed form
7545 that is afterwards decoded by @value{GDBN}.
7547 The trace can be recorded with very low overhead. The compressed
7548 trace format also allows small trace buffers to already contain a big
7549 number of instructions compared to @acronym{BTS}.
7551 Decoding the recorded execution trace, on the other hand, is more
7552 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7553 increased number of instructions to process. You should increase the
7554 buffer-size with care.
7557 Not all recording formats may be available on all processors.
7560 The process record and replay target can only debug a process that is
7561 already running. Therefore, you need first to start the process with
7562 the @kbd{run} or @kbd{start} commands, and then start the recording
7563 with the @kbd{record @var{method}} command.
7565 @cindex displaced stepping, and process record and replay
7566 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7567 will be automatically disabled when process record and replay target
7568 is started. That's because the process record and replay target
7569 doesn't support displaced stepping.
7571 @cindex non-stop mode, and process record and replay
7572 @cindex asynchronous execution, and process record and replay
7573 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7574 the asynchronous execution mode (@pxref{Background Execution}), not
7575 all recording methods are available. The @code{full} recording method
7576 does not support these two modes.
7581 Stop the process record and replay target. When process record and
7582 replay target stops, the entire execution log will be deleted and the
7583 inferior will either be terminated, or will remain in its final state.
7585 When you stop the process record and replay target in record mode (at
7586 the end of the execution log), the inferior will be stopped at the
7587 next instruction that would have been recorded. In other words, if
7588 you record for a while and then stop recording, the inferior process
7589 will be left in the same state as if the recording never happened.
7591 On the other hand, if the process record and replay target is stopped
7592 while in replay mode (that is, not at the end of the execution log,
7593 but at some earlier point), the inferior process will become ``live''
7594 at that earlier state, and it will then be possible to continue the
7595 usual ``live'' debugging of the process from that state.
7597 When the inferior process exits, or @value{GDBN} detaches from it,
7598 process record and replay target will automatically stop itself.
7602 Go to a specific location in the execution log. There are several
7603 ways to specify the location to go to:
7606 @item record goto begin
7607 @itemx record goto start
7608 Go to the beginning of the execution log.
7610 @item record goto end
7611 Go to the end of the execution log.
7613 @item record goto @var{n}
7614 Go to instruction number @var{n} in the execution log.
7618 @item record save @var{filename}
7619 Save the execution log to a file @file{@var{filename}}.
7620 Default filename is @file{gdb_record.@var{process_id}}, where
7621 @var{process_id} is the process ID of the inferior.
7623 This command may not be available for all recording methods.
7625 @kindex record restore
7626 @item record restore @var{filename}
7627 Restore the execution log from a file @file{@var{filename}}.
7628 File must have been created with @code{record save}.
7630 @kindex set record full
7631 @item set record full insn-number-max @var{limit}
7632 @itemx set record full insn-number-max unlimited
7633 Set the limit of instructions to be recorded for the @code{full}
7634 recording method. Default value is 200000.
7636 If @var{limit} is a positive number, then @value{GDBN} will start
7637 deleting instructions from the log once the number of the record
7638 instructions becomes greater than @var{limit}. For every new recorded
7639 instruction, @value{GDBN} will delete the earliest recorded
7640 instruction to keep the number of recorded instructions at the limit.
7641 (Since deleting recorded instructions loses information, @value{GDBN}
7642 lets you control what happens when the limit is reached, by means of
7643 the @code{stop-at-limit} option, described below.)
7645 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7646 delete recorded instructions from the execution log. The number of
7647 recorded instructions is limited only by the available memory.
7649 @kindex show record full
7650 @item show record full insn-number-max
7651 Show the limit of instructions to be recorded with the @code{full}
7654 @item set record full stop-at-limit
7655 Control the behavior of the @code{full} recording method when the
7656 number of recorded instructions reaches the limit. If ON (the
7657 default), @value{GDBN} will stop when the limit is reached for the
7658 first time and ask you whether you want to stop the inferior or
7659 continue running it and recording the execution log. If you decide
7660 to continue recording, each new recorded instruction will cause the
7661 oldest one to be deleted.
7663 If this option is OFF, @value{GDBN} will automatically delete the
7664 oldest record to make room for each new one, without asking.
7666 @item show record full stop-at-limit
7667 Show the current setting of @code{stop-at-limit}.
7669 @item set record full memory-query
7670 Control the behavior when @value{GDBN} is unable to record memory
7671 changes caused by an instruction for the @code{full} recording method.
7672 If ON, @value{GDBN} will query whether to stop the inferior in that
7675 If this option is OFF (the default), @value{GDBN} will automatically
7676 ignore the effect of such instructions on memory. Later, when
7677 @value{GDBN} replays this execution log, it will mark the log of this
7678 instruction as not accessible, and it will not affect the replay
7681 @item show record full memory-query
7682 Show the current setting of @code{memory-query}.
7684 @kindex set record btrace
7685 The @code{btrace} record target does not trace data. As a
7686 convenience, when replaying, @value{GDBN} reads read-only memory off
7687 the live program directly, assuming that the addresses of the
7688 read-only areas don't change. This for example makes it possible to
7689 disassemble code while replaying, but not to print variables.
7690 In some cases, being able to inspect variables might be useful.
7691 You can use the following command for that:
7693 @item set record btrace replay-memory-access
7694 Control the behavior of the @code{btrace} recording method when
7695 accessing memory during replay. If @code{read-only} (the default),
7696 @value{GDBN} will only allow accesses to read-only memory.
7697 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7698 and to read-write memory. Beware that the accessed memory corresponds
7699 to the live target and not necessarily to the current replay
7702 @item set record btrace cpu @var{identifier}
7703 Set the processor to be used for enabling workarounds for processor
7704 errata when decoding the trace.
7706 Processor errata are defects in processor operation, caused by its
7707 design or manufacture. They can cause a trace not to match the
7708 specification. This, in turn, may cause trace decode to fail.
7709 @value{GDBN} can detect erroneous trace packets and correct them, thus
7710 avoiding the decoding failures. These corrections are known as
7711 @dfn{errata workarounds}, and are enabled based on the processor on
7712 which the trace was recorded.
7714 By default, @value{GDBN} attempts to detect the processor
7715 automatically, and apply the necessary workarounds for it. However,
7716 you may need to specify the processor if @value{GDBN} does not yet
7717 support it. This command allows you to do that, and also allows to
7718 disable the workarounds.
7720 The argument @var{identifier} identifies the @sc{cpu} and is of the
7721 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7722 there are two special identifiers, @code{none} and @code{auto}
7725 The following vendor identifiers and corresponding processor
7726 identifiers are currently supported:
7728 @multitable @columnfractions .1 .9
7731 @tab @var{family}/@var{model}[/@var{stepping}]
7735 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7736 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7738 If @var{identifier} is @code{auto}, enable errata workarounds for the
7739 processor on which the trace was recorded. If @var{identifier} is
7740 @code{none}, errata workarounds are disabled.
7742 For example, when using an old @value{GDBN} on a new system, decode
7743 may fail because @value{GDBN} does not support the new processor. It
7744 often suffices to specify an older processor that @value{GDBN}
7749 Active record target: record-btrace
7750 Recording format: Intel Processor Trace.
7752 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7753 (gdb) set record btrace cpu intel:6/158
7755 Active record target: record-btrace
7756 Recording format: Intel Processor Trace.
7758 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7761 @kindex show record btrace
7762 @item show record btrace replay-memory-access
7763 Show the current setting of @code{replay-memory-access}.
7765 @item show record btrace cpu
7766 Show the processor to be used for enabling trace decode errata
7769 @kindex set record btrace bts
7770 @item set record btrace bts buffer-size @var{size}
7771 @itemx set record btrace bts buffer-size unlimited
7772 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7773 format. Default is 64KB.
7775 If @var{size} is a positive number, then @value{GDBN} will try to
7776 allocate a buffer of at least @var{size} bytes for each new thread
7777 that uses the btrace recording method and the @acronym{BTS} format.
7778 The actually obtained buffer size may differ from the requested
7779 @var{size}. Use the @code{info record} command to see the actual
7780 buffer size for each thread that uses the btrace recording method and
7781 the @acronym{BTS} format.
7783 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7784 allocate a buffer of 4MB.
7786 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7787 also need longer to process the branch trace data before it can be used.
7789 @item show record btrace bts buffer-size @var{size}
7790 Show the current setting of the requested ring buffer size for branch
7791 tracing in @acronym{BTS} format.
7793 @kindex set record btrace pt
7794 @item set record btrace pt buffer-size @var{size}
7795 @itemx set record btrace pt buffer-size unlimited
7796 Set the requested ring buffer size for branch tracing in Intel
7797 Processor Trace format. Default is 16KB.
7799 If @var{size} is a positive number, then @value{GDBN} will try to
7800 allocate a buffer of at least @var{size} bytes for each new thread
7801 that uses the btrace recording method and the Intel Processor Trace
7802 format. The actually obtained buffer size may differ from the
7803 requested @var{size}. Use the @code{info record} command to see the
7804 actual buffer size for each thread.
7806 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7807 allocate a buffer of 4MB.
7809 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7810 also need longer to process the branch trace data before it can be used.
7812 @item show record btrace pt buffer-size @var{size}
7813 Show the current setting of the requested ring buffer size for branch
7814 tracing in Intel Processor Trace format.
7818 Show various statistics about the recording depending on the recording
7823 For the @code{full} recording method, it shows the state of process
7824 record and its in-memory execution log buffer, including:
7828 Whether in record mode or replay mode.
7830 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7832 Highest recorded instruction number.
7834 Current instruction about to be replayed (if in replay mode).
7836 Number of instructions contained in the execution log.
7838 Maximum number of instructions that may be contained in the execution log.
7842 For the @code{btrace} recording method, it shows:
7848 Number of instructions that have been recorded.
7850 Number of blocks of sequential control-flow formed by the recorded
7853 Whether in record mode or replay mode.
7856 For the @code{bts} recording format, it also shows:
7859 Size of the perf ring buffer.
7862 For the @code{pt} recording format, it also shows:
7865 Size of the perf ring buffer.
7869 @kindex record delete
7872 When record target runs in replay mode (``in the past''), delete the
7873 subsequent execution log and begin to record a new execution log starting
7874 from the current address. This means you will abandon the previously
7875 recorded ``future'' and begin recording a new ``future''.
7877 @kindex record instruction-history
7878 @kindex rec instruction-history
7879 @item record instruction-history
7880 Disassembles instructions from the recorded execution log. By
7881 default, ten instructions are disassembled. This can be changed using
7882 the @code{set record instruction-history-size} command. Instructions
7883 are printed in execution order.
7885 It can also print mixed source+disassembly if you specify the the
7886 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7887 as well as in symbolic form by specifying the @code{/r} modifier.
7889 The current position marker is printed for the instruction at the
7890 current program counter value. This instruction can appear multiple
7891 times in the trace and the current position marker will be printed
7892 every time. To omit the current position marker, specify the
7895 To better align the printed instructions when the trace contains
7896 instructions from more than one function, the function name may be
7897 omitted by specifying the @code{/f} modifier.
7899 Speculatively executed instructions are prefixed with @samp{?}. This
7900 feature is not available for all recording formats.
7902 There are several ways to specify what part of the execution log to
7906 @item record instruction-history @var{insn}
7907 Disassembles ten instructions starting from instruction number
7910 @item record instruction-history @var{insn}, +/-@var{n}
7911 Disassembles @var{n} instructions around instruction number
7912 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7913 @var{n} instructions after instruction number @var{insn}. If
7914 @var{n} is preceded with @code{-}, disassembles @var{n}
7915 instructions before instruction number @var{insn}.
7917 @item record instruction-history
7918 Disassembles ten more instructions after the last disassembly.
7920 @item record instruction-history -
7921 Disassembles ten more instructions before the last disassembly.
7923 @item record instruction-history @var{begin}, @var{end}
7924 Disassembles instructions beginning with instruction number
7925 @var{begin} until instruction number @var{end}. The instruction
7926 number @var{end} is included.
7929 This command may not be available for all recording methods.
7932 @item set record instruction-history-size @var{size}
7933 @itemx set record instruction-history-size unlimited
7934 Define how many instructions to disassemble in the @code{record
7935 instruction-history} command. The default value is 10.
7936 A @var{size} of @code{unlimited} means unlimited instructions.
7939 @item show record instruction-history-size
7940 Show how many instructions to disassemble in the @code{record
7941 instruction-history} command.
7943 @kindex record function-call-history
7944 @kindex rec function-call-history
7945 @item record function-call-history
7946 Prints the execution history at function granularity. For each sequence
7947 of instructions that belong to the same function, it prints the name of
7948 that function, the source lines for this instruction sequence (if the
7949 @code{/l} modifier is specified), and the instructions numbers that form
7950 the sequence (if the @code{/i} modifier is specified). The function names
7951 are indented to reflect the call stack depth if the @code{/c} modifier is
7952 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
7956 (@value{GDBP}) @b{list 1, 10}
7967 (@value{GDBP}) @b{record function-call-history /ilc}
7968 1 bar inst 1,4 at foo.c:6,8
7969 2 foo inst 5,10 at foo.c:2,3
7970 3 bar inst 11,13 at foo.c:9,10
7973 By default, ten functions are printed. This can be changed using the
7974 @code{set record function-call-history-size} command. Functions are
7975 printed in execution order. There are several ways to specify what
7979 @item record function-call-history @var{func}
7980 Prints ten functions starting from function number @var{func}.
7982 @item record function-call-history @var{func}, +/-@var{n}
7983 Prints @var{n} functions around function number @var{func}. If
7984 @var{n} is preceded with @code{+}, prints @var{n} functions after
7985 function number @var{func}. If @var{n} is preceded with @code{-},
7986 prints @var{n} functions before function number @var{func}.
7988 @item record function-call-history
7989 Prints ten more functions after the last ten-function print.
7991 @item record function-call-history -
7992 Prints ten more functions before the last ten-function print.
7994 @item record function-call-history @var{begin}, @var{end}
7995 Prints functions beginning with function number @var{begin} until
7996 function number @var{end}. The function number @var{end} is included.
7999 This command may not be available for all recording methods.
8001 @item set record function-call-history-size @var{size}
8002 @itemx set record function-call-history-size unlimited
8003 Define how many functions to print in the
8004 @code{record function-call-history} command. The default value is 10.
8005 A size of @code{unlimited} means unlimited functions.
8007 @item show record function-call-history-size
8008 Show how many functions to print in the
8009 @code{record function-call-history} command.
8014 @chapter Examining the Stack
8016 When your program has stopped, the first thing you need to know is where it
8017 stopped and how it got there.
8020 Each time your program performs a function call, information about the call
8022 That information includes the location of the call in your program,
8023 the arguments of the call,
8024 and the local variables of the function being called.
8025 The information is saved in a block of data called a @dfn{stack frame}.
8026 The stack frames are allocated in a region of memory called the @dfn{call
8029 When your program stops, the @value{GDBN} commands for examining the
8030 stack allow you to see all of this information.
8032 @cindex selected frame
8033 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8034 @value{GDBN} commands refer implicitly to the selected frame. In
8035 particular, whenever you ask @value{GDBN} for the value of a variable in
8036 your program, the value is found in the selected frame. There are
8037 special @value{GDBN} commands to select whichever frame you are
8038 interested in. @xref{Selection, ,Selecting a Frame}.
8040 When your program stops, @value{GDBN} automatically selects the
8041 currently executing frame and describes it briefly, similar to the
8042 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8045 * Frames:: Stack frames
8046 * Backtrace:: Backtraces
8047 * Selection:: Selecting a frame
8048 * Frame Info:: Information on a frame
8049 * Frame Apply:: Applying a command to several frames
8050 * Frame Filter Management:: Managing frame filters
8055 @section Stack Frames
8057 @cindex frame, definition
8059 The call stack is divided up into contiguous pieces called @dfn{stack
8060 frames}, or @dfn{frames} for short; each frame is the data associated
8061 with one call to one function. The frame contains the arguments given
8062 to the function, the function's local variables, and the address at
8063 which the function is executing.
8065 @cindex initial frame
8066 @cindex outermost frame
8067 @cindex innermost frame
8068 When your program is started, the stack has only one frame, that of the
8069 function @code{main}. This is called the @dfn{initial} frame or the
8070 @dfn{outermost} frame. Each time a function is called, a new frame is
8071 made. Each time a function returns, the frame for that function invocation
8072 is eliminated. If a function is recursive, there can be many frames for
8073 the same function. The frame for the function in which execution is
8074 actually occurring is called the @dfn{innermost} frame. This is the most
8075 recently created of all the stack frames that still exist.
8077 @cindex frame pointer
8078 Inside your program, stack frames are identified by their addresses. A
8079 stack frame consists of many bytes, each of which has its own address; each
8080 kind of computer has a convention for choosing one byte whose
8081 address serves as the address of the frame. Usually this address is kept
8082 in a register called the @dfn{frame pointer register}
8083 (@pxref{Registers, $fp}) while execution is going on in that frame.
8086 @cindex frame number
8087 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8088 number that is zero for the innermost frame, one for the frame that
8089 called it, and so on upward. These level numbers give you a way of
8090 designating stack frames in @value{GDBN} commands. The terms
8091 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8092 describe this number.
8094 @c The -fomit-frame-pointer below perennially causes hbox overflow
8095 @c underflow problems.
8096 @cindex frameless execution
8097 Some compilers provide a way to compile functions so that they operate
8098 without stack frames. (For example, the @value{NGCC} option
8100 @samp{-fomit-frame-pointer}
8102 generates functions without a frame.)
8103 This is occasionally done with heavily used library functions to save
8104 the frame setup time. @value{GDBN} has limited facilities for dealing
8105 with these function invocations. If the innermost function invocation
8106 has no stack frame, @value{GDBN} nevertheless regards it as though
8107 it had a separate frame, which is numbered zero as usual, allowing
8108 correct tracing of the function call chain. However, @value{GDBN} has
8109 no provision for frameless functions elsewhere in the stack.
8115 @cindex call stack traces
8116 A backtrace is a summary of how your program got where it is. It shows one
8117 line per frame, for many frames, starting with the currently executing
8118 frame (frame zero), followed by its caller (frame one), and on up the
8121 @anchor{backtrace-command}
8123 @kindex bt @r{(@code{backtrace})}
8124 To print a backtrace of the entire stack, use the @code{backtrace}
8125 command, or its alias @code{bt}. This command will print one line per
8126 frame for frames in the stack. By default, all stack frames are
8127 printed. You can stop the backtrace at any time by typing the system
8128 interrupt character, normally @kbd{Ctrl-c}.
8131 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8132 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8133 Print the backtrace of the entire stack.
8135 The optional @var{count} can be one of the following:
8140 Print only the innermost @var{n} frames, where @var{n} is a positive
8145 Print only the outermost @var{n} frames, where @var{n} is a positive
8153 Print the values of the local variables also. This can be combined
8154 with the optional @var{count} to limit the number of frames shown.
8157 Do not run Python frame filters on this backtrace. @xref{Frame
8158 Filter API}, for more information. Additionally use @ref{disable
8159 frame-filter all} to turn off all frame filters. This is only
8160 relevant when @value{GDBN} has been configured with @code{Python}
8164 A Python frame filter might decide to ``elide'' some frames. Normally
8165 such elided frames are still printed, but they are indented relative
8166 to the filtered frames that cause them to be elided. The @code{-hide}
8167 option causes elided frames to not be printed at all.
8170 The @code{backtrace} command also supports a number of options that
8171 allow overriding relevant global print settings as set by @code{set
8172 backtrace} and @code{set print} subcommands:
8175 @item -past-main [@code{on}|@code{off}]
8176 Set whether backtraces should continue past @code{main}. Related setting:
8177 @ref{set backtrace past-main}.
8179 @item -past-entry [@code{on}|@code{off}]
8180 Set whether backtraces should continue past the entry point of a program.
8181 Related setting: @ref{set backtrace past-entry}.
8183 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8184 Set printing of function arguments at function entry.
8185 Related setting: @ref{set print entry-values}.
8187 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8188 Set printing of non-scalar frame arguments.
8189 Related setting: @ref{set print frame-arguments}.
8191 @item -raw-frame-arguments [@code{on}|@code{off}]
8192 Set whether to print frame arguments in raw form.
8193 Related setting: @ref{set print raw-frame-arguments}.
8195 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8196 Set printing of frame information.
8197 Related setting: @ref{set print frame-info}.
8200 The optional @var{qualifier} is maintained for backward compatibility.
8201 It can be one of the following:
8205 Equivalent to the @code{-full} option.
8208 Equivalent to the @code{-no-filters} option.
8211 Equivalent to the @code{-hide} option.
8218 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8219 are additional aliases for @code{backtrace}.
8221 @cindex multiple threads, backtrace
8222 In a multi-threaded program, @value{GDBN} by default shows the
8223 backtrace only for the current thread. To display the backtrace for
8224 several or all of the threads, use the command @code{thread apply}
8225 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8226 apply all backtrace}, @value{GDBN} will display the backtrace for all
8227 the threads; this is handy when you debug a core dump of a
8228 multi-threaded program.
8230 Each line in the backtrace shows the frame number and the function name.
8231 The program counter value is also shown---unless you use @code{set
8232 print address off}. The backtrace also shows the source file name and
8233 line number, as well as the arguments to the function. The program
8234 counter value is omitted if it is at the beginning of the code for that
8237 Here is an example of a backtrace. It was made with the command
8238 @samp{bt 3}, so it shows the innermost three frames.
8242 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8244 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8245 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8247 (More stack frames follow...)
8252 The display for frame zero does not begin with a program counter
8253 value, indicating that your program has stopped at the beginning of the
8254 code for line @code{993} of @code{builtin.c}.
8257 The value of parameter @code{data} in frame 1 has been replaced by
8258 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8259 only if it is a scalar (integer, pointer, enumeration, etc). See command
8260 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8261 on how to configure the way function parameter values are printed.
8262 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8263 what frame information is printed.
8265 @cindex optimized out, in backtrace
8266 @cindex function call arguments, optimized out
8267 If your program was compiled with optimizations, some compilers will
8268 optimize away arguments passed to functions if those arguments are
8269 never used after the call. Such optimizations generate code that
8270 passes arguments through registers, but doesn't store those arguments
8271 in the stack frame. @value{GDBN} has no way of displaying such
8272 arguments in stack frames other than the innermost one. Here's what
8273 such a backtrace might look like:
8277 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8279 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8280 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8282 (More stack frames follow...)
8287 The values of arguments that were not saved in their stack frames are
8288 shown as @samp{<optimized out>}.
8290 If you need to display the values of such optimized-out arguments,
8291 either deduce that from other variables whose values depend on the one
8292 you are interested in, or recompile without optimizations.
8294 @cindex backtrace beyond @code{main} function
8295 @cindex program entry point
8296 @cindex startup code, and backtrace
8297 Most programs have a standard user entry point---a place where system
8298 libraries and startup code transition into user code. For C this is
8299 @code{main}@footnote{
8300 Note that embedded programs (the so-called ``free-standing''
8301 environment) are not required to have a @code{main} function as the
8302 entry point. They could even have multiple entry points.}.
8303 When @value{GDBN} finds the entry function in a backtrace
8304 it will terminate the backtrace, to avoid tracing into highly
8305 system-specific (and generally uninteresting) code.
8307 If you need to examine the startup code, or limit the number of levels
8308 in a backtrace, you can change this behavior:
8311 @item set backtrace past-main
8312 @itemx set backtrace past-main on
8313 @anchor{set backtrace past-main}
8314 @kindex set backtrace
8315 Backtraces will continue past the user entry point.
8317 @item set backtrace past-main off
8318 Backtraces will stop when they encounter the user entry point. This is the
8321 @item show backtrace past-main
8322 @kindex show backtrace
8323 Display the current user entry point backtrace policy.
8325 @item set backtrace past-entry
8326 @itemx set backtrace past-entry on
8327 @anchor{set backtrace past-entry}
8328 Backtraces will continue past the internal entry point of an application.
8329 This entry point is encoded by the linker when the application is built,
8330 and is likely before the user entry point @code{main} (or equivalent) is called.
8332 @item set backtrace past-entry off
8333 Backtraces will stop when they encounter the internal entry point of an
8334 application. This is the default.
8336 @item show backtrace past-entry
8337 Display the current internal entry point backtrace policy.
8339 @item set backtrace limit @var{n}
8340 @itemx set backtrace limit 0
8341 @itemx set backtrace limit unlimited
8342 @anchor{set backtrace limit}
8343 @cindex backtrace limit
8344 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8345 or zero means unlimited levels.
8347 @item show backtrace limit
8348 Display the current limit on backtrace levels.
8351 You can control how file names are displayed.
8354 @item set filename-display
8355 @itemx set filename-display relative
8356 @cindex filename-display
8357 Display file names relative to the compilation directory. This is the default.
8359 @item set filename-display basename
8360 Display only basename of a filename.
8362 @item set filename-display absolute
8363 Display an absolute filename.
8365 @item show filename-display
8366 Show the current way to display filenames.
8370 @section Selecting a Frame
8372 Most commands for examining the stack and other data in your program work on
8373 whichever stack frame is selected at the moment. Here are the commands for
8374 selecting a stack frame; all of them finish by printing a brief description
8375 of the stack frame just selected.
8378 @kindex frame@r{, selecting}
8379 @kindex f @r{(@code{frame})}
8380 @item frame @r{[} @var{frame-selection-spec} @r{]}
8381 @item f @r{[} @var{frame-selection-spec} @r{]}
8382 The @command{frame} command allows different stack frames to be
8383 selected. The @var{frame-selection-spec} can be any of the following:
8388 @item level @var{num}
8389 Select frame level @var{num}. Recall that frame zero is the innermost
8390 (currently executing) frame, frame one is the frame that called the
8391 innermost one, and so on. The highest level frame is usually the one
8394 As this is the most common method of navigating the frame stack, the
8395 string @command{level} can be omitted. For example, the following two
8396 commands are equivalent:
8399 (@value{GDBP}) frame 3
8400 (@value{GDBP}) frame level 3
8403 @kindex frame address
8404 @item address @var{stack-address}
8405 Select the frame with stack address @var{stack-address}. The
8406 @var{stack-address} for a frame can be seen in the output of
8407 @command{info frame}, for example:
8411 Stack level 1, frame at 0x7fffffffda30:
8412 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8413 tail call frame, caller of frame at 0x7fffffffda30
8414 source language c++.
8415 Arglist at unknown address.
8416 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8419 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8420 indicated by the line:
8423 Stack level 1, frame at 0x7fffffffda30:
8426 @kindex frame function
8427 @item function @var{function-name}
8428 Select the stack frame for function @var{function-name}. If there are
8429 multiple stack frames for function @var{function-name} then the inner
8430 most stack frame is selected.
8433 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8434 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8435 viewed has stack address @var{stack-addr}, and optionally, a program
8436 counter address of @var{pc-addr}.
8438 This is useful mainly if the chaining of stack frames has been
8439 damaged by a bug, making it impossible for @value{GDBN} to assign
8440 numbers properly to all frames. In addition, this can be useful
8441 when your program has multiple stacks and switches between them.
8443 When viewing a frame outside the current backtrace using
8444 @command{frame view} then you can always return to the original
8445 stack using one of the previous stack frame selection instructions,
8446 for example @command{frame level 0}.
8452 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8453 numbers @var{n}, this advances toward the outermost frame, to higher
8454 frame numbers, to frames that have existed longer.
8457 @kindex do @r{(@code{down})}
8459 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8460 positive numbers @var{n}, this advances toward the innermost frame, to
8461 lower frame numbers, to frames that were created more recently.
8462 You may abbreviate @code{down} as @code{do}.
8465 All of these commands end by printing two lines of output describing the
8466 frame. The first line shows the frame number, the function name, the
8467 arguments, and the source file and line number of execution in that
8468 frame. The second line shows the text of that source line.
8476 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8478 10 read_input_file (argv[i]);
8482 After such a printout, the @code{list} command with no arguments
8483 prints ten lines centered on the point of execution in the frame.
8484 You can also edit the program at the point of execution with your favorite
8485 editing program by typing @code{edit}.
8486 @xref{List, ,Printing Source Lines},
8490 @kindex select-frame
8491 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8492 The @code{select-frame} command is a variant of @code{frame} that does
8493 not display the new frame after selecting it. This command is
8494 intended primarily for use in @value{GDBN} command scripts, where the
8495 output might be unnecessary and distracting. The
8496 @var{frame-selection-spec} is as for the @command{frame} command
8497 described in @ref{Selection, ,Selecting a Frame}.
8499 @kindex down-silently
8501 @item up-silently @var{n}
8502 @itemx down-silently @var{n}
8503 These two commands are variants of @code{up} and @code{down},
8504 respectively; they differ in that they do their work silently, without
8505 causing display of the new frame. They are intended primarily for use
8506 in @value{GDBN} command scripts, where the output might be unnecessary and
8511 @section Information About a Frame
8513 There are several other commands to print information about the selected
8519 When used without any argument, this command does not change which
8520 frame is selected, but prints a brief description of the currently
8521 selected stack frame. It can be abbreviated @code{f}. With an
8522 argument, this command is used to select a stack frame.
8523 @xref{Selection, ,Selecting a Frame}.
8526 @kindex info f @r{(@code{info frame})}
8529 This command prints a verbose description of the selected stack frame,
8534 the address of the frame
8536 the address of the next frame down (called by this frame)
8538 the address of the next frame up (caller of this frame)
8540 the language in which the source code corresponding to this frame is written
8542 the address of the frame's arguments
8544 the address of the frame's local variables
8546 the program counter saved in it (the address of execution in the caller frame)
8548 which registers were saved in the frame
8551 @noindent The verbose description is useful when
8552 something has gone wrong that has made the stack format fail to fit
8553 the usual conventions.
8555 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8556 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8557 Print a verbose description of the frame selected by
8558 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8559 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8560 a Frame}). The selected frame remains unchanged by this command.
8563 @item info args [-q]
8564 Print the arguments of the selected frame, each on a separate line.
8566 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8567 printing header information and messages explaining why no argument
8570 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8571 Like @kbd{info args}, but only print the arguments selected
8572 with the provided regexp(s).
8574 If @var{regexp} is provided, print only the arguments whose names
8575 match the regular expression @var{regexp}.
8577 If @var{type_regexp} is provided, print only the arguments whose
8578 types, as printed by the @code{whatis} command, match
8579 the regular expression @var{type_regexp}.
8580 If @var{type_regexp} contains space(s), it should be enclosed in
8581 quote characters. If needed, use backslash to escape the meaning
8582 of special characters or quotes.
8584 If both @var{regexp} and @var{type_regexp} are provided, an argument
8585 is printed only if its name matches @var{regexp} and its type matches
8588 @item info locals [-q]
8590 Print the local variables of the selected frame, each on a separate
8591 line. These are all variables (declared either static or automatic)
8592 accessible at the point of execution of the selected frame.
8594 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8595 printing header information and messages explaining why no local variables
8598 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8599 Like @kbd{info locals}, but only print the local variables selected
8600 with the provided regexp(s).
8602 If @var{regexp} is provided, print only the local variables whose names
8603 match the regular expression @var{regexp}.
8605 If @var{type_regexp} is provided, print only the local variables whose
8606 types, as printed by the @code{whatis} command, match
8607 the regular expression @var{type_regexp}.
8608 If @var{type_regexp} contains space(s), it should be enclosed in
8609 quote characters. If needed, use backslash to escape the meaning
8610 of special characters or quotes.
8612 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8613 is printed only if its name matches @var{regexp} and its type matches
8616 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8617 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8618 For example, your program might use Resource Acquisition Is
8619 Initialization types (RAII) such as @code{lock_something_t}: each
8620 local variable of type @code{lock_something_t} automatically places a
8621 lock that is destroyed when the variable goes out of scope. You can
8622 then list all acquired locks in your program by doing
8624 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8627 or the equivalent shorter form
8629 tfaas i lo -q -t lock_something_t
8635 @section Applying a Command to Several Frames.
8637 @cindex apply command to several frames
8639 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8640 The @code{frame apply} command allows you to apply the named
8641 @var{command} to one or more frames.
8645 Specify @code{all} to apply @var{command} to all frames.
8648 Use @var{count} to apply @var{command} to the innermost @var{count}
8649 frames, where @var{count} is a positive number.
8652 Use @var{-count} to apply @var{command} to the outermost @var{count}
8653 frames, where @var{count} is a positive number.
8656 Use @code{level} to apply @var{command} to the set of frames identified
8657 by the @var{level} list. @var{level} is a frame level or a range of frame
8658 levels as @var{level1}-@var{level2}. The frame level is the number shown
8659 in the first field of the @samp{backtrace} command output.
8660 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8661 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8665 Note that the frames on which @code{frame apply} applies a command are
8666 also influenced by the @code{set backtrace} settings such as @code{set
8667 backtrace past-main} and @code{set backtrace limit N}.
8668 @xref{Backtrace,,Backtraces}.
8670 The @code{frame apply} command also supports a number of options that
8671 allow overriding relevant @code{set backtrace} settings:
8674 @item -past-main [@code{on}|@code{off}]
8675 Whether backtraces should continue past @code{main}.
8676 Related setting: @ref{set backtrace past-main}.
8678 @item -past-entry [@code{on}|@code{off}]
8679 Whether backtraces should continue past the entry point of a program.
8680 Related setting: @ref{set backtrace past-entry}.
8683 By default, @value{GDBN} displays some frame information before the
8684 output produced by @var{command}, and an error raised during the
8685 execution of a @var{command} will abort @code{frame apply}. The
8686 following options can be used to fine-tune these behaviors:
8690 The flag @code{-c}, which stands for @samp{continue}, causes any
8691 errors in @var{command} to be displayed, and the execution of
8692 @code{frame apply} then continues.
8694 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8695 or empty output produced by a @var{command} to be silently ignored.
8696 That is, the execution continues, but the frame information and errors
8699 The flag @code{-q} (@samp{quiet}) disables printing the frame
8703 The following example shows how the flags @code{-c} and @code{-s} are
8704 working when applying the command @code{p j} to all frames, where
8705 variable @code{j} can only be successfully printed in the outermost
8706 @code{#1 main} frame.
8710 (gdb) frame apply all p j
8711 #0 some_function (i=5) at fun.c:4
8712 No symbol "j" in current context.
8713 (gdb) frame apply all -c p j
8714 #0 some_function (i=5) at fun.c:4
8715 No symbol "j" in current context.
8716 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8718 (gdb) frame apply all -s p j
8719 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8725 By default, @samp{frame apply}, prints the frame location
8726 information before the command output:
8730 (gdb) frame apply all p $sp
8731 #0 some_function (i=5) at fun.c:4
8732 $4 = (void *) 0xffffd1e0
8733 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8734 $5 = (void *) 0xffffd1f0
8739 If the flag @code{-q} is given, no frame information is printed:
8742 (gdb) frame apply all -q p $sp
8743 $12 = (void *) 0xffffd1e0
8744 $13 = (void *) 0xffffd1f0
8754 @cindex apply a command to all frames (ignoring errors and empty output)
8755 @item faas @var{command}
8756 Shortcut for @code{frame apply all -s @var{command}}.
8757 Applies @var{command} on all frames, ignoring errors and empty output.
8759 It can for example be used to print a local variable or a function
8760 argument without knowing the frame where this variable or argument
8763 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8766 The @code{faas} command accepts the same options as the @code{frame
8767 apply} command. @xref{Frame Apply,,frame apply}.
8769 Note that the command @code{tfaas @var{command}} applies @var{command}
8770 on all frames of all threads. See @xref{Threads,,Threads}.
8774 @node Frame Filter Management
8775 @section Management of Frame Filters.
8776 @cindex managing frame filters
8778 Frame filters are Python based utilities to manage and decorate the
8779 output of frames. @xref{Frame Filter API}, for further information.
8781 Managing frame filters is performed by several commands available
8782 within @value{GDBN}, detailed here.
8785 @kindex info frame-filter
8786 @item info frame-filter
8787 Print a list of installed frame filters from all dictionaries, showing
8788 their name, priority and enabled status.
8790 @kindex disable frame-filter
8791 @anchor{disable frame-filter all}
8792 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8793 Disable a frame filter in the dictionary matching
8794 @var{filter-dictionary} and @var{filter-name}. The
8795 @var{filter-dictionary} may be @code{all}, @code{global},
8796 @code{progspace}, or the name of the object file where the frame filter
8797 dictionary resides. When @code{all} is specified, all frame filters
8798 across all dictionaries are disabled. The @var{filter-name} is the name
8799 of the frame filter and is used when @code{all} is not the option for
8800 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8801 may be enabled again later.
8803 @kindex enable frame-filter
8804 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8805 Enable a frame filter in the dictionary matching
8806 @var{filter-dictionary} and @var{filter-name}. The
8807 @var{filter-dictionary} may be @code{all}, @code{global},
8808 @code{progspace} or the name of the object file where the frame filter
8809 dictionary resides. When @code{all} is specified, all frame filters across
8810 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8811 filter and is used when @code{all} is not the option for
8812 @var{filter-dictionary}.
8817 (gdb) info frame-filter
8819 global frame-filters:
8820 Priority Enabled Name
8821 1000 No PrimaryFunctionFilter
8824 progspace /build/test frame-filters:
8825 Priority Enabled Name
8826 100 Yes ProgspaceFilter
8828 objfile /build/test frame-filters:
8829 Priority Enabled Name
8830 999 Yes BuildProgramFilter
8832 (gdb) disable frame-filter /build/test BuildProgramFilter
8833 (gdb) info frame-filter
8835 global frame-filters:
8836 Priority Enabled Name
8837 1000 No PrimaryFunctionFilter
8840 progspace /build/test frame-filters:
8841 Priority Enabled Name
8842 100 Yes ProgspaceFilter
8844 objfile /build/test frame-filters:
8845 Priority Enabled Name
8846 999 No BuildProgramFilter
8848 (gdb) enable frame-filter global PrimaryFunctionFilter
8849 (gdb) info frame-filter
8851 global frame-filters:
8852 Priority Enabled Name
8853 1000 Yes PrimaryFunctionFilter
8856 progspace /build/test frame-filters:
8857 Priority Enabled Name
8858 100 Yes ProgspaceFilter
8860 objfile /build/test frame-filters:
8861 Priority Enabled Name
8862 999 No BuildProgramFilter
8865 @kindex set frame-filter priority
8866 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8867 Set the @var{priority} of a frame filter in the dictionary matching
8868 @var{filter-dictionary}, and the frame filter name matching
8869 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8870 @code{progspace} or the name of the object file where the frame filter
8871 dictionary resides. The @var{priority} is an integer.
8873 @kindex show frame-filter priority
8874 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8875 Show the @var{priority} of a frame filter in the dictionary matching
8876 @var{filter-dictionary}, and the frame filter name matching
8877 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8878 @code{progspace} or the name of the object file where the frame filter
8884 (gdb) info frame-filter
8886 global frame-filters:
8887 Priority Enabled Name
8888 1000 Yes PrimaryFunctionFilter
8891 progspace /build/test frame-filters:
8892 Priority Enabled Name
8893 100 Yes ProgspaceFilter
8895 objfile /build/test frame-filters:
8896 Priority Enabled Name
8897 999 No BuildProgramFilter
8899 (gdb) set frame-filter priority global Reverse 50
8900 (gdb) info frame-filter
8902 global frame-filters:
8903 Priority Enabled Name
8904 1000 Yes PrimaryFunctionFilter
8907 progspace /build/test frame-filters:
8908 Priority Enabled Name
8909 100 Yes ProgspaceFilter
8911 objfile /build/test frame-filters:
8912 Priority Enabled Name
8913 999 No BuildProgramFilter
8918 @chapter Examining Source Files
8920 @value{GDBN} can print parts of your program's source, since the debugging
8921 information recorded in the program tells @value{GDBN} what source files were
8922 used to build it. When your program stops, @value{GDBN} spontaneously prints
8923 the line where it stopped. Likewise, when you select a stack frame
8924 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8925 execution in that frame has stopped. You can print other portions of
8926 source files by explicit command.
8928 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8929 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8930 @value{GDBN} under @sc{gnu} Emacs}.
8933 * List:: Printing source lines
8934 * Specify Location:: How to specify code locations
8935 * Edit:: Editing source files
8936 * Search:: Searching source files
8937 * Source Path:: Specifying source directories
8938 * Machine Code:: Source and machine code
8939 * Disable Reading Source:: Disable Reading Source Code
8943 @section Printing Source Lines
8946 @kindex l @r{(@code{list})}
8947 To print lines from a source file, use the @code{list} command
8948 (abbreviated @code{l}). By default, ten lines are printed.
8949 There are several ways to specify what part of the file you want to
8950 print; see @ref{Specify Location}, for the full list.
8952 Here are the forms of the @code{list} command most commonly used:
8955 @item list @var{linenum}
8956 Print lines centered around line number @var{linenum} in the
8957 current source file.
8959 @item list @var{function}
8960 Print lines centered around the beginning of function
8964 Print more lines. If the last lines printed were printed with a
8965 @code{list} command, this prints lines following the last lines
8966 printed; however, if the last line printed was a solitary line printed
8967 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8968 Stack}), this prints lines centered around that line.
8971 Print lines just before the lines last printed.
8974 @cindex @code{list}, how many lines to display
8975 By default, @value{GDBN} prints ten source lines with any of these forms of
8976 the @code{list} command. You can change this using @code{set listsize}:
8979 @kindex set listsize
8980 @item set listsize @var{count}
8981 @itemx set listsize unlimited
8982 Make the @code{list} command display @var{count} source lines (unless
8983 the @code{list} argument explicitly specifies some other number).
8984 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8986 @kindex show listsize
8988 Display the number of lines that @code{list} prints.
8991 Repeating a @code{list} command with @key{RET} discards the argument,
8992 so it is equivalent to typing just @code{list}. This is more useful
8993 than listing the same lines again. An exception is made for an
8994 argument of @samp{-}; that argument is preserved in repetition so that
8995 each repetition moves up in the source file.
8997 In general, the @code{list} command expects you to supply zero, one or two
8998 @dfn{locations}. Locations specify source lines; there are several ways
8999 of writing them (@pxref{Specify Location}), but the effect is always
9000 to specify some source line.
9002 Here is a complete description of the possible arguments for @code{list}:
9005 @item list @var{location}
9006 Print lines centered around the line specified by @var{location}.
9008 @item list @var{first},@var{last}
9009 Print lines from @var{first} to @var{last}. Both arguments are
9010 locations. When a @code{list} command has two locations, and the
9011 source file of the second location is omitted, this refers to
9012 the same source file as the first location.
9014 @item list ,@var{last}
9015 Print lines ending with @var{last}.
9017 @item list @var{first},
9018 Print lines starting with @var{first}.
9021 Print lines just after the lines last printed.
9024 Print lines just before the lines last printed.
9027 As described in the preceding table.
9030 @node Specify Location
9031 @section Specifying a Location
9032 @cindex specifying location
9034 @cindex source location
9036 Several @value{GDBN} commands accept arguments that specify a location
9037 of your program's code. Since @value{GDBN} is a source-level
9038 debugger, a location usually specifies some line in the source code.
9039 Locations may be specified using three different formats:
9040 linespec locations, explicit locations, or address locations.
9043 * Linespec Locations:: Linespec locations
9044 * Explicit Locations:: Explicit locations
9045 * Address Locations:: Address locations
9048 @node Linespec Locations
9049 @subsection Linespec Locations
9050 @cindex linespec locations
9052 A @dfn{linespec} is a colon-separated list of source location parameters such
9053 as file name, function name, etc. Here are all the different ways of
9054 specifying a linespec:
9058 Specifies the line number @var{linenum} of the current source file.
9061 @itemx +@var{offset}
9062 Specifies the line @var{offset} lines before or after the @dfn{current
9063 line}. For the @code{list} command, the current line is the last one
9064 printed; for the breakpoint commands, this is the line at which
9065 execution stopped in the currently selected @dfn{stack frame}
9066 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9067 used as the second of the two linespecs in a @code{list} command,
9068 this specifies the line @var{offset} lines up or down from the first
9071 @item @var{filename}:@var{linenum}
9072 Specifies the line @var{linenum} in the source file @var{filename}.
9073 If @var{filename} is a relative file name, then it will match any
9074 source file name with the same trailing components. For example, if
9075 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9076 name of @file{/build/trunk/gcc/expr.c}, but not
9077 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9079 @item @var{function}
9080 Specifies the line that begins the body of the function @var{function}.
9081 For example, in C, this is the line with the open brace.
9083 By default, in C@t{++} and Ada, @var{function} is interpreted as
9084 specifying all functions named @var{function} in all scopes. For
9085 C@t{++}, this means in all namespaces and classes. For Ada, this
9086 means in all packages.
9088 For example, assuming a program with C@t{++} symbols named
9089 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9090 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9092 Commands that accept a linespec let you override this with the
9093 @code{-qualified} option. For example, @w{@kbd{break -qualified
9094 func}} sets a breakpoint on a free-function named @code{func} ignoring
9095 any C@t{++} class methods and namespace functions called @code{func}.
9097 @xref{Explicit Locations}.
9099 @item @var{function}:@var{label}
9100 Specifies the line where @var{label} appears in @var{function}.
9102 @item @var{filename}:@var{function}
9103 Specifies the line that begins the body of the function @var{function}
9104 in the file @var{filename}. You only need the file name with a
9105 function name to avoid ambiguity when there are identically named
9106 functions in different source files.
9109 Specifies the line at which the label named @var{label} appears
9110 in the function corresponding to the currently selected stack frame.
9111 If there is no current selected stack frame (for instance, if the inferior
9112 is not running), then @value{GDBN} will not search for a label.
9114 @cindex breakpoint at static probe point
9115 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9116 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9117 applications to embed static probes. @xref{Static Probe Points}, for more
9118 information on finding and using static probes. This form of linespec
9119 specifies the location of such a static probe.
9121 If @var{objfile} is given, only probes coming from that shared library
9122 or executable matching @var{objfile} as a regular expression are considered.
9123 If @var{provider} is given, then only probes from that provider are considered.
9124 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9125 each one of those probes.
9128 @node Explicit Locations
9129 @subsection Explicit Locations
9130 @cindex explicit locations
9132 @dfn{Explicit locations} allow the user to directly specify the source
9133 location's parameters using option-value pairs.
9135 Explicit locations are useful when several functions, labels, or
9136 file names have the same name (base name for files) in the program's
9137 sources. In these cases, explicit locations point to the source
9138 line you meant more accurately and unambiguously. Also, using
9139 explicit locations might be faster in large programs.
9141 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9142 defined in the file named @file{foo} or the label @code{bar} in a function
9143 named @code{foo}. @value{GDBN} must search either the file system or
9144 the symbol table to know.
9146 The list of valid explicit location options is summarized in the
9150 @item -source @var{filename}
9151 The value specifies the source file name. To differentiate between
9152 files with the same base name, prepend as many directories as is necessary
9153 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9154 @value{GDBN} will use the first file it finds with the given base
9155 name. This option requires the use of either @code{-function} or @code{-line}.
9157 @item -function @var{function}
9158 The value specifies the name of a function. Operations
9159 on function locations unmodified by other options (such as @code{-label}
9160 or @code{-line}) refer to the line that begins the body of the function.
9161 In C, for example, this is the line with the open brace.
9163 By default, in C@t{++} and Ada, @var{function} is interpreted as
9164 specifying all functions named @var{function} in all scopes. For
9165 C@t{++}, this means in all namespaces and classes. For Ada, this
9166 means in all packages.
9168 For example, assuming a program with C@t{++} symbols named
9169 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9170 -function func}} and @w{@kbd{break -function B::func}} set a
9171 breakpoint on both symbols.
9173 You can use the @kbd{-qualified} flag to override this (see below).
9177 This flag makes @value{GDBN} interpret a function name specified with
9178 @kbd{-function} as a complete fully-qualified name.
9180 For example, assuming a C@t{++} program with symbols named
9181 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9182 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9184 (Note: the @kbd{-qualified} option can precede a linespec as well
9185 (@pxref{Linespec Locations}), so the particular example above could be
9186 simplified as @w{@kbd{break -qualified B::func}}.)
9188 @item -label @var{label}
9189 The value specifies the name of a label. When the function
9190 name is not specified, the label is searched in the function of the currently
9191 selected stack frame.
9193 @item -line @var{number}
9194 The value specifies a line offset for the location. The offset may either
9195 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9196 the command. When specified without any other options, the line offset is
9197 relative to the current line.
9200 Explicit location options may be abbreviated by omitting any non-unique
9201 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9203 @node Address Locations
9204 @subsection Address Locations
9205 @cindex address locations
9207 @dfn{Address locations} indicate a specific program address. They have
9208 the generalized form *@var{address}.
9210 For line-oriented commands, such as @code{list} and @code{edit}, this
9211 specifies a source line that contains @var{address}. For @code{break} and
9212 other breakpoint-oriented commands, this can be used to set breakpoints in
9213 parts of your program which do not have debugging information or
9216 Here @var{address} may be any expression valid in the current working
9217 language (@pxref{Languages, working language}) that specifies a code
9218 address. In addition, as a convenience, @value{GDBN} extends the
9219 semantics of expressions used in locations to cover several situations
9220 that frequently occur during debugging. Here are the various forms
9224 @item @var{expression}
9225 Any expression valid in the current working language.
9227 @item @var{funcaddr}
9228 An address of a function or procedure derived from its name. In C,
9229 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9230 simply the function's name @var{function} (and actually a special case
9231 of a valid expression). In Pascal and Modula-2, this is
9232 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9233 (although the Pascal form also works).
9235 This form specifies the address of the function's first instruction,
9236 before the stack frame and arguments have been set up.
9238 @item '@var{filename}':@var{funcaddr}
9239 Like @var{funcaddr} above, but also specifies the name of the source
9240 file explicitly. This is useful if the name of the function does not
9241 specify the function unambiguously, e.g., if there are several
9242 functions with identical names in different source files.
9246 @section Editing Source Files
9247 @cindex editing source files
9250 @kindex e @r{(@code{edit})}
9251 To edit the lines in a source file, use the @code{edit} command.
9252 The editing program of your choice
9253 is invoked with the current line set to
9254 the active line in the program.
9255 Alternatively, there are several ways to specify what part of the file you
9256 want to print if you want to see other parts of the program:
9259 @item edit @var{location}
9260 Edit the source file specified by @code{location}. Editing starts at
9261 that @var{location}, e.g., at the specified source line of the
9262 specified file. @xref{Specify Location}, for all the possible forms
9263 of the @var{location} argument; here are the forms of the @code{edit}
9264 command most commonly used:
9267 @item edit @var{number}
9268 Edit the current source file with @var{number} as the active line number.
9270 @item edit @var{function}
9271 Edit the file containing @var{function} at the beginning of its definition.
9276 @subsection Choosing your Editor
9277 You can customize @value{GDBN} to use any editor you want
9279 The only restriction is that your editor (say @code{ex}), recognizes the
9280 following command-line syntax:
9282 ex +@var{number} file
9284 The optional numeric value +@var{number} specifies the number of the line in
9285 the file where to start editing.}.
9286 By default, it is @file{@value{EDITOR}}, but you can change this
9287 by setting the environment variable @env{EDITOR} before using
9288 @value{GDBN}. For example, to configure @value{GDBN} to use the
9289 @code{vi} editor, you could use these commands with the @code{sh} shell:
9295 or in the @code{csh} shell,
9297 setenv EDITOR /usr/bin/vi
9302 @section Searching Source Files
9303 @cindex searching source files
9305 There are two commands for searching through the current source file for a
9310 @kindex forward-search
9311 @kindex fo @r{(@code{forward-search})}
9312 @item forward-search @var{regexp}
9313 @itemx search @var{regexp}
9314 The command @samp{forward-search @var{regexp}} checks each line,
9315 starting with the one following the last line listed, for a match for
9316 @var{regexp}. It lists the line that is found. You can use the
9317 synonym @samp{search @var{regexp}} or abbreviate the command name as
9320 @kindex reverse-search
9321 @item reverse-search @var{regexp}
9322 The command @samp{reverse-search @var{regexp}} checks each line, starting
9323 with the one before the last line listed and going backward, for a match
9324 for @var{regexp}. It lists the line that is found. You can abbreviate
9325 this command as @code{rev}.
9329 @section Specifying Source Directories
9332 @cindex directories for source files
9333 Executable programs sometimes do not record the directories of the source
9334 files from which they were compiled, just the names. Even when they do,
9335 the directories could be moved between the compilation and your debugging
9336 session. @value{GDBN} has a list of directories to search for source files;
9337 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9338 it tries all the directories in the list, in the order they are present
9339 in the list, until it finds a file with the desired name.
9341 For example, suppose an executable references the file
9342 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9343 directory, and the @dfn{source path} is @file{/mnt/cross}.
9344 @value{GDBN} would look for the source file in the following
9349 @item @file{/usr/src/foo-1.0/lib/foo.c}
9350 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9351 @item @file{/mnt/cross/foo.c}
9355 If the source file is not present at any of the above locations then
9356 an error is printed. @value{GDBN} does not look up the parts of the
9357 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9358 Likewise, the subdirectories of the source path are not searched: if
9359 the source path is @file{/mnt/cross}, and the binary refers to
9360 @file{foo.c}, @value{GDBN} would not find it under
9361 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9363 Plain file names, relative file names with leading directories, file
9364 names containing dots, etc.@: are all treated as described above,
9365 except that non-absolute file names are not looked up literally. If
9366 the @dfn{source path} is @file{/mnt/cross}, the source file is
9367 recorded as @file{../lib/foo.c}, and no compilation directory is
9368 recorded, then @value{GDBN} will search in the following locations:
9372 @item @file{/mnt/cross/../lib/foo.c}
9373 @item @file{/mnt/cross/foo.c}
9379 @vindex $cdir@r{, convenience variable}
9380 @vindex $cwd@r{, convenience variable}
9381 @cindex compilation directory
9382 @cindex current directory
9383 @cindex working directory
9384 @cindex directory, current
9385 @cindex directory, compilation
9386 The @dfn{source path} will always include two special entries
9387 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9388 (if one is recorded) and the current working directory respectively.
9390 @samp{$cdir} causes @value{GDBN} to search within the compilation
9391 directory, if one is recorded in the debug information. If no
9392 compilation directory is recorded in the debug information then
9393 @samp{$cdir} is ignored.
9395 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9396 current working directory as it changes during your @value{GDBN}
9397 session, while the latter is immediately expanded to the current
9398 directory at the time you add an entry to the source path.
9400 If a compilation directory is recorded in the debug information, and
9401 @value{GDBN} has not found the source file after the first search
9402 using @dfn{source path}, then @value{GDBN} will combine the
9403 compilation directory and the filename, and then search for the source
9404 file again using the @dfn{source path}.
9406 For example, if the executable records the source file as
9407 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9408 recorded as @file{/project/build}, and the @dfn{source path} is
9409 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9410 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9411 search for the source file in the following locations:
9415 @item @file{/usr/src/foo-1.0/lib/foo.c}
9416 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9417 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9418 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9419 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9420 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9421 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9422 @item @file{/mnt/cross/foo.c}
9423 @item @file{/project/build/foo.c}
9424 @item @file{/home/user/foo.c}
9428 If the file name in the previous example had been recorded in the
9429 executable as a relative path rather than an absolute path, then the
9430 first look up would not have occurred, but all of the remaining steps
9433 When searching for source files on MS-DOS and MS-Windows, where
9434 absolute paths start with a drive letter (e.g.@:
9435 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9436 from the file name before appending it to a search directory from
9437 @dfn{source path}; for instance if the executable references the
9438 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9439 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9440 locations for the source file:
9444 @item @file{C:/project/foo.c}
9445 @item @file{D:/mnt/cross/project/foo.c}
9446 @item @file{D:/mnt/cross/foo.c}
9450 Note that the executable search path is @emph{not} used to locate the
9453 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9454 any information it has cached about where source files are found and where
9455 each line is in the file.
9459 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9460 and @samp{$cwd}, in that order.
9461 To add other directories, use the @code{directory} command.
9463 The search path is used to find both program source files and @value{GDBN}
9464 script files (read using the @samp{-command} option and @samp{source} command).
9466 In addition to the source path, @value{GDBN} provides a set of commands
9467 that manage a list of source path substitution rules. A @dfn{substitution
9468 rule} specifies how to rewrite source directories stored in the program's
9469 debug information in case the sources were moved to a different
9470 directory between compilation and debugging. A rule is made of
9471 two strings, the first specifying what needs to be rewritten in
9472 the path, and the second specifying how it should be rewritten.
9473 In @ref{set substitute-path}, we name these two parts @var{from} and
9474 @var{to} respectively. @value{GDBN} does a simple string replacement
9475 of @var{from} with @var{to} at the start of the directory part of the
9476 source file name, and uses that result instead of the original file
9477 name to look up the sources.
9479 Using the previous example, suppose the @file{foo-1.0} tree has been
9480 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9481 @value{GDBN} to replace @file{/usr/src} in all source path names with
9482 @file{/mnt/cross}. The first lookup will then be
9483 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9484 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9485 substitution rule, use the @code{set substitute-path} command
9486 (@pxref{set substitute-path}).
9488 To avoid unexpected substitution results, a rule is applied only if the
9489 @var{from} part of the directory name ends at a directory separator.
9490 For instance, a rule substituting @file{/usr/source} into
9491 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9492 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9493 is applied only at the beginning of the directory name, this rule will
9494 not be applied to @file{/root/usr/source/baz.c} either.
9496 In many cases, you can achieve the same result using the @code{directory}
9497 command. However, @code{set substitute-path} can be more efficient in
9498 the case where the sources are organized in a complex tree with multiple
9499 subdirectories. With the @code{directory} command, you need to add each
9500 subdirectory of your project. If you moved the entire tree while
9501 preserving its internal organization, then @code{set substitute-path}
9502 allows you to direct the debugger to all the sources with one single
9505 @code{set substitute-path} is also more than just a shortcut command.
9506 The source path is only used if the file at the original location no
9507 longer exists. On the other hand, @code{set substitute-path} modifies
9508 the debugger behavior to look at the rewritten location instead. So, if
9509 for any reason a source file that is not relevant to your executable is
9510 located at the original location, a substitution rule is the only
9511 method available to point @value{GDBN} at the new location.
9513 @cindex @samp{--with-relocated-sources}
9514 @cindex default source path substitution
9515 You can configure a default source path substitution rule by
9516 configuring @value{GDBN} with the
9517 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9518 should be the name of a directory under @value{GDBN}'s configured
9519 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9520 directory names in debug information under @var{dir} will be adjusted
9521 automatically if the installed @value{GDBN} is moved to a new
9522 location. This is useful if @value{GDBN}, libraries or executables
9523 with debug information and corresponding source code are being moved
9527 @item directory @var{dirname} @dots{}
9528 @item dir @var{dirname} @dots{}
9529 Add directory @var{dirname} to the front of the source path. Several
9530 directory names may be given to this command, separated by @samp{:}
9531 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9532 part of absolute file names) or
9533 whitespace. You may specify a directory that is already in the source
9534 path; this moves it forward, so @value{GDBN} searches it sooner.
9536 The special strings @samp{$cdir} (to refer to the compilation
9537 directory, if one is recorded), and @samp{$cwd} (to refer to the
9538 current working directory) can also be included in the list of
9539 directories @var{dirname}. Though these will already be in the source
9540 path they will be moved forward in the list so @value{GDBN} searches
9544 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9546 @c RET-repeat for @code{directory} is explicitly disabled, but since
9547 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9549 @item set directories @var{path-list}
9550 @kindex set directories
9551 Set the source path to @var{path-list}.
9552 @samp{$cdir:$cwd} are added if missing.
9554 @item show directories
9555 @kindex show directories
9556 Print the source path: show which directories it contains.
9558 @anchor{set substitute-path}
9559 @item set substitute-path @var{from} @var{to}
9560 @kindex set substitute-path
9561 Define a source path substitution rule, and add it at the end of the
9562 current list of existing substitution rules. If a rule with the same
9563 @var{from} was already defined, then the old rule is also deleted.
9565 For example, if the file @file{/foo/bar/baz.c} was moved to
9566 @file{/mnt/cross/baz.c}, then the command
9569 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9573 will tell @value{GDBN} to replace @samp{/foo/bar} with
9574 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9575 @file{baz.c} even though it was moved.
9577 In the case when more than one substitution rule have been defined,
9578 the rules are evaluated one by one in the order where they have been
9579 defined. The first one matching, if any, is selected to perform
9582 For instance, if we had entered the following commands:
9585 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9586 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9590 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9591 @file{/mnt/include/defs.h} by using the first rule. However, it would
9592 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9593 @file{/mnt/src/lib/foo.c}.
9596 @item unset substitute-path [path]
9597 @kindex unset substitute-path
9598 If a path is specified, search the current list of substitution rules
9599 for a rule that would rewrite that path. Delete that rule if found.
9600 A warning is emitted by the debugger if no rule could be found.
9602 If no path is specified, then all substitution rules are deleted.
9604 @item show substitute-path [path]
9605 @kindex show substitute-path
9606 If a path is specified, then print the source path substitution rule
9607 which would rewrite that path, if any.
9609 If no path is specified, then print all existing source path substitution
9614 If your source path is cluttered with directories that are no longer of
9615 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9616 versions of source. You can correct the situation as follows:
9620 Use @code{directory} with no argument to reset the source path to its default value.
9623 Use @code{directory} with suitable arguments to reinstall the
9624 directories you want in the source path. You can add all the
9625 directories in one command.
9629 @section Source and Machine Code
9630 @cindex source line and its code address
9632 You can use the command @code{info line} to map source lines to program
9633 addresses (and vice versa), and the command @code{disassemble} to display
9634 a range of addresses as machine instructions. You can use the command
9635 @code{set disassemble-next-line} to set whether to disassemble next
9636 source line when execution stops. When run under @sc{gnu} Emacs
9637 mode, the @code{info line} command causes the arrow to point to the
9638 line specified. Also, @code{info line} prints addresses in symbolic form as
9644 @itemx info line @var{location}
9645 Print the starting and ending addresses of the compiled code for
9646 source line @var{location}. You can specify source lines in any of
9647 the ways documented in @ref{Specify Location}. With no @var{location}
9648 information about the current source line is printed.
9651 For example, we can use @code{info line} to discover the location of
9652 the object code for the first line of function
9653 @code{m4_changequote}:
9656 (@value{GDBP}) info line m4_changequote
9657 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9658 ends at 0x6350 <m4_changequote+4>.
9662 @cindex code address and its source line
9663 We can also inquire (using @code{*@var{addr}} as the form for
9664 @var{location}) what source line covers a particular address:
9666 (@value{GDBP}) info line *0x63ff
9667 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9668 ends at 0x6404 <m4_changequote+184>.
9671 @cindex @code{$_} and @code{info line}
9672 @cindex @code{x} command, default address
9673 @kindex x@r{(examine), and} info line
9674 After @code{info line}, the default address for the @code{x} command
9675 is changed to the starting address of the line, so that @samp{x/i} is
9676 sufficient to begin examining the machine code (@pxref{Memory,
9677 ,Examining Memory}). Also, this address is saved as the value of the
9678 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9681 @cindex info line, repeated calls
9682 After @code{info line}, using @code{info line} again without
9683 specifying a location will display information about the next source
9688 @cindex assembly instructions
9689 @cindex instructions, assembly
9690 @cindex machine instructions
9691 @cindex listing machine instructions
9693 @itemx disassemble /m
9694 @itemx disassemble /s
9695 @itemx disassemble /r
9696 This specialized command dumps a range of memory as machine
9697 instructions. It can also print mixed source+disassembly by specifying
9698 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9699 as well as in symbolic form by specifying the @code{/r} modifier.
9700 The default memory range is the function surrounding the
9701 program counter of the selected frame. A single argument to this
9702 command is a program counter value; @value{GDBN} dumps the function
9703 surrounding this value. When two arguments are given, they should
9704 be separated by a comma, possibly surrounded by whitespace. The
9705 arguments specify a range of addresses to dump, in one of two forms:
9708 @item @var{start},@var{end}
9709 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9710 @item @var{start},+@var{length}
9711 the addresses from @var{start} (inclusive) to
9712 @code{@var{start}+@var{length}} (exclusive).
9716 When 2 arguments are specified, the name of the function is also
9717 printed (since there could be several functions in the given range).
9719 The argument(s) can be any expression yielding a numeric value, such as
9720 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9722 If the range of memory being disassembled contains current program counter,
9723 the instruction at that location is shown with a @code{=>} marker.
9726 The following example shows the disassembly of a range of addresses of
9727 HP PA-RISC 2.0 code:
9730 (@value{GDBP}) disas 0x32c4, 0x32e4
9731 Dump of assembler code from 0x32c4 to 0x32e4:
9732 0x32c4 <main+204>: addil 0,dp
9733 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9734 0x32cc <main+212>: ldil 0x3000,r31
9735 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9736 0x32d4 <main+220>: ldo 0(r31),rp
9737 0x32d8 <main+224>: addil -0x800,dp
9738 0x32dc <main+228>: ldo 0x588(r1),r26
9739 0x32e0 <main+232>: ldil 0x3000,r31
9740 End of assembler dump.
9743 Here is an example showing mixed source+assembly for Intel x86
9744 with @code{/m} or @code{/s}, when the program is stopped just after
9745 function prologue in a non-optimized function with no inline code.
9748 (@value{GDBP}) disas /m main
9749 Dump of assembler code for function main:
9751 0x08048330 <+0>: push %ebp
9752 0x08048331 <+1>: mov %esp,%ebp
9753 0x08048333 <+3>: sub $0x8,%esp
9754 0x08048336 <+6>: and $0xfffffff0,%esp
9755 0x08048339 <+9>: sub $0x10,%esp
9757 6 printf ("Hello.\n");
9758 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9759 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9763 0x08048348 <+24>: mov $0x0,%eax
9764 0x0804834d <+29>: leave
9765 0x0804834e <+30>: ret
9767 End of assembler dump.
9770 The @code{/m} option is deprecated as its output is not useful when
9771 there is either inlined code or re-ordered code.
9772 The @code{/s} option is the preferred choice.
9773 Here is an example for AMD x86-64 showing the difference between
9774 @code{/m} output and @code{/s} output.
9775 This example has one inline function defined in a header file,
9776 and the code is compiled with @samp{-O2} optimization.
9777 Note how the @code{/m} output is missing the disassembly of
9778 several instructions that are present in the @code{/s} output.
9808 (@value{GDBP}) disas /m main
9809 Dump of assembler code for function main:
9813 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9814 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9818 0x000000000040041d <+29>: xor %eax,%eax
9819 0x000000000040041f <+31>: retq
9820 0x0000000000400420 <+32>: add %eax,%eax
9821 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9823 End of assembler dump.
9824 (@value{GDBP}) disas /s main
9825 Dump of assembler code for function main:
9829 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9833 0x0000000000400406 <+6>: test %eax,%eax
9834 0x0000000000400408 <+8>: js 0x400420 <main+32>
9839 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9840 0x000000000040040d <+13>: test %eax,%eax
9841 0x000000000040040f <+15>: mov $0x1,%eax
9842 0x0000000000400414 <+20>: cmovne %edx,%eax
9846 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9850 0x000000000040041d <+29>: xor %eax,%eax
9851 0x000000000040041f <+31>: retq
9855 0x0000000000400420 <+32>: add %eax,%eax
9856 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9857 End of assembler dump.
9860 Here is another example showing raw instructions in hex for AMD x86-64,
9863 (gdb) disas /r 0x400281,+10
9864 Dump of assembler code from 0x400281 to 0x40028b:
9865 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9866 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9867 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9868 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9869 End of assembler dump.
9872 Addresses cannot be specified as a location (@pxref{Specify Location}).
9873 So, for example, if you want to disassemble function @code{bar}
9874 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9875 and not @samp{disassemble foo.c:bar}.
9877 Some architectures have more than one commonly-used set of instruction
9878 mnemonics or other syntax.
9880 For programs that were dynamically linked and use shared libraries,
9881 instructions that call functions or branch to locations in the shared
9882 libraries might show a seemingly bogus location---it's actually a
9883 location of the relocation table. On some architectures, @value{GDBN}
9884 might be able to resolve these to actual function names.
9887 @kindex set disassembler-options
9888 @cindex disassembler options
9889 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9890 This command controls the passing of target specific information to
9891 the disassembler. For a list of valid options, please refer to the
9892 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9893 manual and/or the output of @kbd{objdump --help}
9894 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9895 The default value is the empty string.
9897 If it is necessary to specify more than one disassembler option, then
9898 multiple options can be placed together into a comma separated list.
9899 Currently this command is only supported on targets ARC, ARM, MIPS,
9902 @kindex show disassembler-options
9903 @item show disassembler-options
9904 Show the current setting of the disassembler options.
9908 @kindex set disassembly-flavor
9909 @cindex Intel disassembly flavor
9910 @cindex AT&T disassembly flavor
9911 @item set disassembly-flavor @var{instruction-set}
9912 Select the instruction set to use when disassembling the
9913 program via the @code{disassemble} or @code{x/i} commands.
9915 Currently this command is only defined for the Intel x86 family. You
9916 can set @var{instruction-set} to either @code{intel} or @code{att}.
9917 The default is @code{att}, the AT&T flavor used by default by Unix
9918 assemblers for x86-based targets.
9920 @kindex show disassembly-flavor
9921 @item show disassembly-flavor
9922 Show the current setting of the disassembly flavor.
9926 @kindex set disassemble-next-line
9927 @kindex show disassemble-next-line
9928 @item set disassemble-next-line
9929 @itemx show disassemble-next-line
9930 Control whether or not @value{GDBN} will disassemble the next source
9931 line or instruction when execution stops. If ON, @value{GDBN} will
9932 display disassembly of the next source line when execution of the
9933 program being debugged stops. This is @emph{in addition} to
9934 displaying the source line itself, which @value{GDBN} always does if
9935 possible. If the next source line cannot be displayed for some reason
9936 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9937 info in the debug info), @value{GDBN} will display disassembly of the
9938 next @emph{instruction} instead of showing the next source line. If
9939 AUTO, @value{GDBN} will display disassembly of next instruction only
9940 if the source line cannot be displayed. This setting causes
9941 @value{GDBN} to display some feedback when you step through a function
9942 with no line info or whose source file is unavailable. The default is
9943 OFF, which means never display the disassembly of the next line or
9947 @node Disable Reading Source
9948 @section Disable Reading Source Code
9949 @cindex source code, disable access
9951 In some cases it can be desirable to prevent @value{GDBN} from
9952 accessing source code files. One case where this might be desirable
9953 is if the source code files are located over a slow network
9956 The following command can be used to control whether @value{GDBN}
9957 should access source code files or not:
9960 @kindex set source open
9961 @kindex show source open
9962 @item set source open @r{[}on@r{|}off@r{]}
9963 @itemx show source open
9964 When this option is @code{on}, which is the default, @value{GDBN} will
9965 access source code files when needed, for example to print source
9966 lines when @value{GDBN} stops, or in response to the @code{list}
9969 When this option is @code{off}, @value{GDBN} will not access source
9974 @chapter Examining Data
9976 @cindex printing data
9977 @cindex examining data
9980 The usual way to examine data in your program is with the @code{print}
9981 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9982 evaluates and prints the value of an expression of the language your
9983 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9984 Different Languages}). It may also print the expression using a
9985 Python-based pretty-printer (@pxref{Pretty Printing}).
9988 @item print [[@var{options}] --] @var{expr}
9989 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9990 @var{expr} is an expression (in the source language). By default the
9991 value of @var{expr} is printed in a format appropriate to its data type;
9992 you can choose a different format by specifying @samp{/@var{f}}, where
9993 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9996 @anchor{print options}
9997 The @code{print} command supports a number of options that allow
9998 overriding relevant global print settings as set by @code{set print}
10002 @item -address [@code{on}|@code{off}]
10003 Set printing of addresses.
10004 Related setting: @ref{set print address}.
10006 @item -array [@code{on}|@code{off}]
10007 Pretty formatting of arrays.
10008 Related setting: @ref{set print array}.
10010 @item -array-indexes [@code{on}|@code{off}]
10011 Set printing of array indexes.
10012 Related setting: @ref{set print array-indexes}.
10014 @item -elements @var{number-of-elements}|@code{unlimited}
10015 Set limit on string chars or array elements to print. The value
10016 @code{unlimited} causes there to be no limit. Related setting:
10017 @ref{set print elements}.
10019 @item -max-depth @var{depth}|@code{unlimited}
10020 Set the threshold after which nested structures are replaced with
10021 ellipsis. Related setting: @ref{set print max-depth}.
10023 @item -memory-tag-violations [@code{on}|@code{off}]
10024 Set printing of additional information about memory tag violations.
10025 @xref{set print memory-tag-violations}.
10027 @item -null-stop [@code{on}|@code{off}]
10028 Set printing of char arrays to stop at first null char. Related
10029 setting: @ref{set print null-stop}.
10031 @item -object [@code{on}|@code{off}]
10032 Set printing C@t{++} virtual function tables. Related setting:
10033 @ref{set print object}.
10035 @item -pretty [@code{on}|@code{off}]
10036 Set pretty formatting of structures. Related setting: @ref{set print
10039 @item -raw-values [@code{on}|@code{off}]
10040 Set whether to print values in raw form, bypassing any
10041 pretty-printers for that value. Related setting: @ref{set print
10044 @item -repeats @var{number-of-repeats}|@code{unlimited}
10045 Set threshold for repeated print elements. @code{unlimited} causes
10046 all elements to be individually printed. Related setting: @ref{set
10049 @item -static-members [@code{on}|@code{off}]
10050 Set printing C@t{++} static members. Related setting: @ref{set print
10053 @item -symbol [@code{on}|@code{off}]
10054 Set printing of symbol names when printing pointers. Related setting:
10055 @ref{set print symbol}.
10057 @item -union [@code{on}|@code{off}]
10058 Set printing of unions interior to structures. Related setting:
10059 @ref{set print union}.
10061 @item -vtbl [@code{on}|@code{off}]
10062 Set printing of C++ virtual function tables. Related setting:
10063 @ref{set print vtbl}.
10066 Because the @code{print} command accepts arbitrary expressions which
10067 may look like options (including abbreviations), if you specify any
10068 command option, then you must use a double dash (@code{--}) to mark
10069 the end of option processing.
10071 For example, this prints the value of the @code{-p} expression:
10074 (@value{GDBP}) print -p
10077 While this repeats the last value in the value history (see below)
10078 with the @code{-pretty} option in effect:
10081 (@value{GDBP}) print -p --
10084 Here is an example including both on option and an expression:
10088 (@value{GDBP}) print -pretty -- *myptr
10100 @item print [@var{options}]
10101 @itemx print [@var{options}] /@var{f}
10102 @cindex reprint the last value
10103 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10104 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10105 conveniently inspect the same value in an alternative format.
10108 If the architecture supports memory tagging, the @code{print} command will
10109 display pointer/memory tag mismatches if what is being printed is a pointer
10110 or reference type. @xref{Memory Tagging}.
10112 A more low-level way of examining data is with the @code{x} command.
10113 It examines data in memory at a specified address and prints it in a
10114 specified format. @xref{Memory, ,Examining Memory}.
10116 If you are interested in information about types, or about how the
10117 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
10118 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10121 @cindex exploring hierarchical data structures
10123 Another way of examining values of expressions and type information is
10124 through the Python extension command @code{explore} (available only if
10125 the @value{GDBN} build is configured with @code{--with-python}). It
10126 offers an interactive way to start at the highest level (or, the most
10127 abstract level) of the data type of an expression (or, the data type
10128 itself) and explore all the way down to leaf scalar values/fields
10129 embedded in the higher level data types.
10132 @item explore @var{arg}
10133 @var{arg} is either an expression (in the source language), or a type
10134 visible in the current context of the program being debugged.
10137 The working of the @code{explore} command can be illustrated with an
10138 example. If a data type @code{struct ComplexStruct} is defined in your
10142 struct SimpleStruct
10148 struct ComplexStruct
10150 struct SimpleStruct *ss_p;
10156 followed by variable declarations as
10159 struct SimpleStruct ss = @{ 10, 1.11 @};
10160 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10164 then, the value of the variable @code{cs} can be explored using the
10165 @code{explore} command as follows.
10169 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10170 the following fields:
10172 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10173 arr = <Enter 1 to explore this field of type `int [10]'>
10175 Enter the field number of choice:
10179 Since the fields of @code{cs} are not scalar values, you are being
10180 prompted to chose the field you want to explore. Let's say you choose
10181 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10182 pointer, you will be asked if it is pointing to a single value. From
10183 the declaration of @code{cs} above, it is indeed pointing to a single
10184 value, hence you enter @code{y}. If you enter @code{n}, then you will
10185 be asked if it were pointing to an array of values, in which case this
10186 field will be explored as if it were an array.
10189 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10190 Continue exploring it as a pointer to a single value [y/n]: y
10191 The value of `*(cs.ss_p)' is a struct/class of type `struct
10192 SimpleStruct' with the following fields:
10194 i = 10 .. (Value of type `int')
10195 d = 1.1100000000000001 .. (Value of type `double')
10197 Press enter to return to parent value:
10201 If the field @code{arr} of @code{cs} was chosen for exploration by
10202 entering @code{1} earlier, then since it is as array, you will be
10203 prompted to enter the index of the element in the array that you want
10207 `cs.arr' is an array of `int'.
10208 Enter the index of the element you want to explore in `cs.arr': 5
10210 `(cs.arr)[5]' is a scalar value of type `int'.
10214 Press enter to return to parent value:
10217 In general, at any stage of exploration, you can go deeper towards the
10218 leaf values by responding to the prompts appropriately, or hit the
10219 return key to return to the enclosing data structure (the @i{higher}
10220 level data structure).
10222 Similar to exploring values, you can use the @code{explore} command to
10223 explore types. Instead of specifying a value (which is typically a
10224 variable name or an expression valid in the current context of the
10225 program being debugged), you specify a type name. If you consider the
10226 same example as above, your can explore the type
10227 @code{struct ComplexStruct} by passing the argument
10228 @code{struct ComplexStruct} to the @code{explore} command.
10231 (gdb) explore struct ComplexStruct
10235 By responding to the prompts appropriately in the subsequent interactive
10236 session, you can explore the type @code{struct ComplexStruct} in a
10237 manner similar to how the value @code{cs} was explored in the above
10240 The @code{explore} command also has two sub-commands,
10241 @code{explore value} and @code{explore type}. The former sub-command is
10242 a way to explicitly specify that value exploration of the argument is
10243 being invoked, while the latter is a way to explicitly specify that type
10244 exploration of the argument is being invoked.
10247 @item explore value @var{expr}
10248 @cindex explore value
10249 This sub-command of @code{explore} explores the value of the
10250 expression @var{expr} (if @var{expr} is an expression valid in the
10251 current context of the program being debugged). The behavior of this
10252 command is identical to that of the behavior of the @code{explore}
10253 command being passed the argument @var{expr}.
10255 @item explore type @var{arg}
10256 @cindex explore type
10257 This sub-command of @code{explore} explores the type of @var{arg} (if
10258 @var{arg} is a type visible in the current context of program being
10259 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10260 is an expression valid in the current context of the program being
10261 debugged). If @var{arg} is a type, then the behavior of this command is
10262 identical to that of the @code{explore} command being passed the
10263 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10264 this command will be identical to that of the @code{explore} command
10265 being passed the type of @var{arg} as the argument.
10269 * Expressions:: Expressions
10270 * Ambiguous Expressions:: Ambiguous Expressions
10271 * Variables:: Program variables
10272 * Arrays:: Artificial arrays
10273 * Output Formats:: Output formats
10274 * Memory:: Examining memory
10275 * Memory Tagging:: Memory Tagging
10276 * Auto Display:: Automatic display
10277 * Print Settings:: Print settings
10278 * Pretty Printing:: Python pretty printing
10279 * Value History:: Value history
10280 * Convenience Vars:: Convenience variables
10281 * Convenience Funs:: Convenience functions
10282 * Registers:: Registers
10283 * Floating Point Hardware:: Floating point hardware
10284 * Vector Unit:: Vector Unit
10285 * OS Information:: Auxiliary data provided by operating system
10286 * Memory Region Attributes:: Memory region attributes
10287 * Dump/Restore Files:: Copy between memory and a file
10288 * Core File Generation:: Cause a program dump its core
10289 * Character Sets:: Debugging programs that use a different
10290 character set than GDB does
10291 * Caching Target Data:: Data caching for targets
10292 * Searching Memory:: Searching memory for a sequence of bytes
10293 * Value Sizes:: Managing memory allocated for values
10297 @section Expressions
10299 @cindex expressions
10300 @code{print} and many other @value{GDBN} commands accept an expression and
10301 compute its value. Any kind of constant, variable or operator defined
10302 by the programming language you are using is valid in an expression in
10303 @value{GDBN}. This includes conditional expressions, function calls,
10304 casts, and string constants. It also includes preprocessor macros, if
10305 you compiled your program to include this information; see
10308 @cindex arrays in expressions
10309 @value{GDBN} supports array constants in expressions input by
10310 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10311 you can use the command @code{print @{1, 2, 3@}} to create an array
10312 of three integers. If you pass an array to a function or assign it
10313 to a program variable, @value{GDBN} copies the array to memory that
10314 is @code{malloc}ed in the target program.
10316 Because C is so widespread, most of the expressions shown in examples in
10317 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10318 Languages}, for information on how to use expressions in other
10321 In this section, we discuss operators that you can use in @value{GDBN}
10322 expressions regardless of your programming language.
10324 @cindex casts, in expressions
10325 Casts are supported in all languages, not just in C, because it is so
10326 useful to cast a number into a pointer in order to examine a structure
10327 at that address in memory.
10328 @c FIXME: casts supported---Mod2 true?
10330 @value{GDBN} supports these operators, in addition to those common
10331 to programming languages:
10335 @samp{@@} is a binary operator for treating parts of memory as arrays.
10336 @xref{Arrays, ,Artificial Arrays}, for more information.
10339 @samp{::} allows you to specify a variable in terms of the file or
10340 function where it is defined. @xref{Variables, ,Program Variables}.
10342 @cindex @{@var{type}@}
10343 @cindex type casting memory
10344 @cindex memory, viewing as typed object
10345 @cindex casts, to view memory
10346 @item @{@var{type}@} @var{addr}
10347 Refers to an object of type @var{type} stored at address @var{addr} in
10348 memory. The address @var{addr} may be any expression whose value is
10349 an integer or pointer (but parentheses are required around binary
10350 operators, just as in a cast). This construct is allowed regardless
10351 of what kind of data is normally supposed to reside at @var{addr}.
10354 @node Ambiguous Expressions
10355 @section Ambiguous Expressions
10356 @cindex ambiguous expressions
10358 Expressions can sometimes contain some ambiguous elements. For instance,
10359 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10360 a single function name to be defined several times, for application in
10361 different contexts. This is called @dfn{overloading}. Another example
10362 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10363 templates and is typically instantiated several times, resulting in
10364 the same function name being defined in different contexts.
10366 In some cases and depending on the language, it is possible to adjust
10367 the expression to remove the ambiguity. For instance in C@t{++}, you
10368 can specify the signature of the function you want to break on, as in
10369 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10370 qualified name of your function often makes the expression unambiguous
10373 When an ambiguity that needs to be resolved is detected, the debugger
10374 has the capability to display a menu of numbered choices for each
10375 possibility, and then waits for the selection with the prompt @samp{>}.
10376 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10377 aborts the current command. If the command in which the expression was
10378 used allows more than one choice to be selected, the next option in the
10379 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10382 For example, the following session excerpt shows an attempt to set a
10383 breakpoint at the overloaded symbol @code{String::after}.
10384 We choose three particular definitions of that function name:
10386 @c FIXME! This is likely to change to show arg type lists, at least
10389 (@value{GDBP}) b String::after
10392 [2] file:String.cc; line number:867
10393 [3] file:String.cc; line number:860
10394 [4] file:String.cc; line number:875
10395 [5] file:String.cc; line number:853
10396 [6] file:String.cc; line number:846
10397 [7] file:String.cc; line number:735
10399 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10400 Breakpoint 2 at 0xb344: file String.cc, line 875.
10401 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10402 Multiple breakpoints were set.
10403 Use the "delete" command to delete unwanted
10410 @kindex set multiple-symbols
10411 @item set multiple-symbols @var{mode}
10412 @cindex multiple-symbols menu
10414 This option allows you to adjust the debugger behavior when an expression
10417 By default, @var{mode} is set to @code{all}. If the command with which
10418 the expression is used allows more than one choice, then @value{GDBN}
10419 automatically selects all possible choices. For instance, inserting
10420 a breakpoint on a function using an ambiguous name results in a breakpoint
10421 inserted on each possible match. However, if a unique choice must be made,
10422 then @value{GDBN} uses the menu to help you disambiguate the expression.
10423 For instance, printing the address of an overloaded function will result
10424 in the use of the menu.
10426 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10427 when an ambiguity is detected.
10429 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10430 an error due to the ambiguity and the command is aborted.
10432 @kindex show multiple-symbols
10433 @item show multiple-symbols
10434 Show the current value of the @code{multiple-symbols} setting.
10438 @section Program Variables
10440 The most common kind of expression to use is the name of a variable
10443 Variables in expressions are understood in the selected stack frame
10444 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10448 global (or file-static)
10455 visible according to the scope rules of the
10456 programming language from the point of execution in that frame
10459 @noindent This means that in the function
10474 you can examine and use the variable @code{a} whenever your program is
10475 executing within the function @code{foo}, but you can only use or
10476 examine the variable @code{b} while your program is executing inside
10477 the block where @code{b} is declared.
10479 @cindex variable name conflict
10480 There is an exception: you can refer to a variable or function whose
10481 scope is a single source file even if the current execution point is not
10482 in this file. But it is possible to have more than one such variable or
10483 function with the same name (in different source files). If that
10484 happens, referring to that name has unpredictable effects. If you wish,
10485 you can specify a static variable in a particular function or file by
10486 using the colon-colon (@code{::}) notation:
10488 @cindex colon-colon, context for variables/functions
10490 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10491 @cindex @code{::}, context for variables/functions
10494 @var{file}::@var{variable}
10495 @var{function}::@var{variable}
10499 Here @var{file} or @var{function} is the name of the context for the
10500 static @var{variable}. In the case of file names, you can use quotes to
10501 make sure @value{GDBN} parses the file name as a single word---for example,
10502 to print a global value of @code{x} defined in @file{f2.c}:
10505 (@value{GDBP}) p 'f2.c'::x
10508 The @code{::} notation is normally used for referring to
10509 static variables, since you typically disambiguate uses of local variables
10510 in functions by selecting the appropriate frame and using the
10511 simple name of the variable. However, you may also use this notation
10512 to refer to local variables in frames enclosing the selected frame:
10521 process (a); /* Stop here */
10532 For example, if there is a breakpoint at the commented line,
10533 here is what you might see
10534 when the program stops after executing the call @code{bar(0)}:
10539 (@value{GDBP}) p bar::a
10541 (@value{GDBP}) up 2
10542 #2 0x080483d0 in foo (a=5) at foobar.c:12
10545 (@value{GDBP}) p bar::a
10549 @cindex C@t{++} scope resolution
10550 These uses of @samp{::} are very rarely in conflict with the very
10551 similar use of the same notation in C@t{++}. When they are in
10552 conflict, the C@t{++} meaning takes precedence; however, this can be
10553 overridden by quoting the file or function name with single quotes.
10555 For example, suppose the program is stopped in a method of a class
10556 that has a field named @code{includefile}, and there is also an
10557 include file named @file{includefile} that defines a variable,
10558 @code{some_global}.
10561 (@value{GDBP}) p includefile
10563 (@value{GDBP}) p includefile::some_global
10564 A syntax error in expression, near `'.
10565 (@value{GDBP}) p 'includefile'::some_global
10569 @cindex wrong values
10570 @cindex variable values, wrong
10571 @cindex function entry/exit, wrong values of variables
10572 @cindex optimized code, wrong values of variables
10574 @emph{Warning:} Occasionally, a local variable may appear to have the
10575 wrong value at certain points in a function---just after entry to a new
10576 scope, and just before exit.
10578 You may see this problem when you are stepping by machine instructions.
10579 This is because, on most machines, it takes more than one instruction to
10580 set up a stack frame (including local variable definitions); if you are
10581 stepping by machine instructions, variables may appear to have the wrong
10582 values until the stack frame is completely built. On exit, it usually
10583 also takes more than one machine instruction to destroy a stack frame;
10584 after you begin stepping through that group of instructions, local
10585 variable definitions may be gone.
10587 This may also happen when the compiler does significant optimizations.
10588 To be sure of always seeing accurate values, turn off all optimization
10591 @cindex ``No symbol "foo" in current context''
10592 Another possible effect of compiler optimizations is to optimize
10593 unused variables out of existence, or assign variables to registers (as
10594 opposed to memory addresses). Depending on the support for such cases
10595 offered by the debug info format used by the compiler, @value{GDBN}
10596 might not be able to display values for such local variables. If that
10597 happens, @value{GDBN} will print a message like this:
10600 No symbol "foo" in current context.
10603 To solve such problems, either recompile without optimizations, or use a
10604 different debug info format, if the compiler supports several such
10605 formats. @xref{Compilation}, for more information on choosing compiler
10606 options. @xref{C, ,C and C@t{++}}, for more information about debug
10607 info formats that are best suited to C@t{++} programs.
10609 If you ask to print an object whose contents are unknown to
10610 @value{GDBN}, e.g., because its data type is not completely specified
10611 by the debug information, @value{GDBN} will say @samp{<incomplete
10612 type>}. @xref{Symbols, incomplete type}, for more about this.
10614 @cindex no debug info variables
10615 If you try to examine or use the value of a (global) variable for
10616 which @value{GDBN} has no type information, e.g., because the program
10617 includes no debug information, @value{GDBN} displays an error message.
10618 @xref{Symbols, unknown type}, for more about unknown types. If you
10619 cast the variable to its declared type, @value{GDBN} gets the
10620 variable's value using the cast-to type as the variable's type. For
10621 example, in a C program:
10624 (@value{GDBP}) p var
10625 'var' has unknown type; cast it to its declared type
10626 (@value{GDBP}) p (float) var
10630 If you append @kbd{@@entry} string to a function parameter name you get its
10631 value at the time the function got called. If the value is not available an
10632 error message is printed. Entry values are available only with some compilers.
10633 Entry values are normally also printed at the function parameter list according
10634 to @ref{set print entry-values}.
10637 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10643 (gdb) print i@@entry
10647 Strings are identified as arrays of @code{char} values without specified
10648 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10649 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10650 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10651 defines literal string type @code{"char"} as @code{char} without a sign.
10656 signed char var1[] = "A";
10659 You get during debugging
10664 $2 = @{65 'A', 0 '\0'@}
10668 @section Artificial Arrays
10670 @cindex artificial array
10672 @kindex @@@r{, referencing memory as an array}
10673 It is often useful to print out several successive objects of the
10674 same type in memory; a section of an array, or an array of
10675 dynamically determined size for which only a pointer exists in the
10678 You can do this by referring to a contiguous span of memory as an
10679 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10680 operand of @samp{@@} should be the first element of the desired array
10681 and be an individual object. The right operand should be the desired length
10682 of the array. The result is an array value whose elements are all of
10683 the type of the left argument. The first element is actually the left
10684 argument; the second element comes from bytes of memory immediately
10685 following those that hold the first element, and so on. Here is an
10686 example. If a program says
10689 int *array = (int *) malloc (len * sizeof (int));
10693 you can print the contents of @code{array} with
10699 The left operand of @samp{@@} must reside in memory. Array values made
10700 with @samp{@@} in this way behave just like other arrays in terms of
10701 subscripting, and are coerced to pointers when used in expressions.
10702 Artificial arrays most often appear in expressions via the value history
10703 (@pxref{Value History, ,Value History}), after printing one out.
10705 Another way to create an artificial array is to use a cast.
10706 This re-interprets a value as if it were an array.
10707 The value need not be in memory:
10709 (@value{GDBP}) p/x (short[2])0x12345678
10710 $1 = @{0x1234, 0x5678@}
10713 As a convenience, if you leave the array length out (as in
10714 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10715 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10717 (@value{GDBP}) p/x (short[])0x12345678
10718 $2 = @{0x1234, 0x5678@}
10721 Sometimes the artificial array mechanism is not quite enough; in
10722 moderately complex data structures, the elements of interest may not
10723 actually be adjacent---for example, if you are interested in the values
10724 of pointers in an array. One useful work-around in this situation is
10725 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10726 Variables}) as a counter in an expression that prints the first
10727 interesting value, and then repeat that expression via @key{RET}. For
10728 instance, suppose you have an array @code{dtab} of pointers to
10729 structures, and you are interested in the values of a field @code{fv}
10730 in each structure. Here is an example of what you might type:
10740 @node Output Formats
10741 @section Output Formats
10743 @cindex formatted output
10744 @cindex output formats
10745 By default, @value{GDBN} prints a value according to its data type. Sometimes
10746 this is not what you want. For example, you might want to print a number
10747 in hex, or a pointer in decimal. Or you might want to view data in memory
10748 at a certain address as a character string or as an instruction. To do
10749 these things, specify an @dfn{output format} when you print a value.
10751 The simplest use of output formats is to say how to print a value
10752 already computed. This is done by starting the arguments of the
10753 @code{print} command with a slash and a format letter. The format
10754 letters supported are:
10758 Regard the bits of the value as an integer, and print the integer in
10762 Print as integer in signed decimal.
10765 Print as integer in unsigned decimal.
10768 Print as integer in octal.
10771 Print as integer in binary. The letter @samp{t} stands for ``two''.
10772 @footnote{@samp{b} cannot be used because these format letters are also
10773 used with the @code{x} command, where @samp{b} stands for ``byte'';
10774 see @ref{Memory,,Examining Memory}.}
10777 @cindex unknown address, locating
10778 @cindex locate address
10779 Print as an address, both absolute in hexadecimal and as an offset from
10780 the nearest preceding symbol. You can use this format used to discover
10781 where (in what function) an unknown address is located:
10784 (@value{GDBP}) p/a 0x54320
10785 $3 = 0x54320 <_initialize_vx+396>
10789 The command @code{info symbol 0x54320} yields similar results.
10790 @xref{Symbols, info symbol}.
10793 Regard as an integer and print it as a character constant. This
10794 prints both the numerical value and its character representation. The
10795 character representation is replaced with the octal escape @samp{\nnn}
10796 for characters outside the 7-bit @sc{ascii} range.
10798 Without this format, @value{GDBN} displays @code{char},
10799 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10800 constants. Single-byte members of vectors are displayed as integer
10804 Regard the bits of the value as a floating point number and print
10805 using typical floating point syntax.
10808 @cindex printing strings
10809 @cindex printing byte arrays
10810 Regard as a string, if possible. With this format, pointers to single-byte
10811 data are displayed as null-terminated strings and arrays of single-byte data
10812 are displayed as fixed-length strings. Other values are displayed in their
10815 Without this format, @value{GDBN} displays pointers to and arrays of
10816 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10817 strings. Single-byte members of a vector are displayed as an integer
10821 Like @samp{x} formatting, the value is treated as an integer and
10822 printed as hexadecimal, but leading zeros are printed to pad the value
10823 to the size of the integer type.
10826 @cindex raw printing
10827 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10828 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10829 Printing}). This typically results in a higher-level display of the
10830 value's contents. The @samp{r} format bypasses any Python
10831 pretty-printer which might exist.
10834 For example, to print the program counter in hex (@pxref{Registers}), type
10841 Note that no space is required before the slash; this is because command
10842 names in @value{GDBN} cannot contain a slash.
10844 To reprint the last value in the value history with a different format,
10845 you can use the @code{print} command with just a format and no
10846 expression. For example, @samp{p/x} reprints the last value in hex.
10849 @section Examining Memory
10851 You can use the command @code{x} (for ``examine'') to examine memory in
10852 any of several formats, independently of your program's data types.
10854 @cindex examining memory
10856 @kindex x @r{(examine memory)}
10857 @item x/@var{nfu} @var{addr}
10858 @itemx x @var{addr}
10860 Use the @code{x} command to examine memory.
10863 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10864 much memory to display and how to format it; @var{addr} is an
10865 expression giving the address where you want to start displaying memory.
10866 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10867 Several commands set convenient defaults for @var{addr}.
10870 @item @var{n}, the repeat count
10871 The repeat count is a decimal integer; the default is 1. It specifies
10872 how much memory (counting by units @var{u}) to display. If a negative
10873 number is specified, memory is examined backward from @var{addr}.
10874 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10877 @item @var{f}, the display format
10878 The display format is one of the formats used by @code{print}
10879 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10880 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
10881 @samp{m} (for displaying memory tags).
10882 The default is @samp{x} (hexadecimal) initially. The default changes
10883 each time you use either @code{x} or @code{print}.
10885 @item @var{u}, the unit size
10886 The unit size is any of
10892 Halfwords (two bytes).
10894 Words (four bytes). This is the initial default.
10896 Giant words (eight bytes).
10899 Each time you specify a unit size with @code{x}, that size becomes the
10900 default unit the next time you use @code{x}. For the @samp{i} format,
10901 the unit size is ignored and is normally not written. For the @samp{s} format,
10902 the unit size defaults to @samp{b}, unless it is explicitly given.
10903 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10904 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10905 Note that the results depend on the programming language of the
10906 current compilation unit. If the language is C, the @samp{s}
10907 modifier will use the UTF-16 encoding while @samp{w} will use
10908 UTF-32. The encoding is set by the programming language and cannot
10911 @item @var{addr}, starting display address
10912 @var{addr} is the address where you want @value{GDBN} to begin displaying
10913 memory. The expression need not have a pointer value (though it may);
10914 it is always interpreted as an integer address of a byte of memory.
10915 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10916 @var{addr} is usually just after the last address examined---but several
10917 other commands also set the default address: @code{info breakpoints} (to
10918 the address of the last breakpoint listed), @code{info line} (to the
10919 starting address of a line), and @code{print} (if you use it to display
10920 a value from memory).
10923 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10924 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10925 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10926 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10927 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10929 You can also specify a negative repeat count to examine memory backward
10930 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10931 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
10933 Since the letters indicating unit sizes are all distinct from the
10934 letters specifying output formats, you do not have to remember whether
10935 unit size or format comes first; either order works. The output
10936 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10937 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10939 Even though the unit size @var{u} is ignored for the formats @samp{s}
10940 and @samp{i}, you might still want to use a count @var{n}; for example,
10941 @samp{3i} specifies that you want to see three machine instructions,
10942 including any operands. For convenience, especially when used with
10943 the @code{display} command, the @samp{i} format also prints branch delay
10944 slot instructions, if any, beyond the count specified, which immediately
10945 follow the last instruction that is within the count. The command
10946 @code{disassemble} gives an alternative way of inspecting machine
10947 instructions; see @ref{Machine Code,,Source and Machine Code}.
10949 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10950 the command displays null-terminated strings or instructions before the given
10951 address as many as the absolute value of the given number. For the @samp{i}
10952 format, we use line number information in the debug info to accurately locate
10953 instruction boundaries while disassembling backward. If line info is not
10954 available, the command stops examining memory with an error message.
10956 All the defaults for the arguments to @code{x} are designed to make it
10957 easy to continue scanning memory with minimal specifications each time
10958 you use @code{x}. For example, after you have inspected three machine
10959 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10960 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10961 the repeat count @var{n} is used again; the other arguments default as
10962 for successive uses of @code{x}.
10964 When examining machine instructions, the instruction at current program
10965 counter is shown with a @code{=>} marker. For example:
10968 (@value{GDBP}) x/5i $pc-6
10969 0x804837f <main+11>: mov %esp,%ebp
10970 0x8048381 <main+13>: push %ecx
10971 0x8048382 <main+14>: sub $0x4,%esp
10972 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10973 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10976 If the architecture supports memory tagging, the tags can be displayed by
10977 using @samp{m}. @xref{Memory Tagging}.
10979 The information will be displayed once per granule size
10980 (the amount of bytes a particular memory tag covers). For example, AArch64
10981 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
10983 Due to the way @value{GDBN} prints information with the @code{x} command (not
10984 aligned to a particular boundary), the tag information will refer to the
10985 initial address displayed on a particular line. If a memory tag boundary
10986 is crossed in the middle of a line displayed by the @code{x} command, it
10987 will be displayed on the next line.
10989 The @samp{m} format doesn't affect any other specified formats that were
10990 passed to the @code{x} command.
10992 @cindex @code{$_}, @code{$__}, and value history
10993 The addresses and contents printed by the @code{x} command are not saved
10994 in the value history because there is often too much of them and they
10995 would get in the way. Instead, @value{GDBN} makes these values available for
10996 subsequent use in expressions as values of the convenience variables
10997 @code{$_} and @code{$__}. After an @code{x} command, the last address
10998 examined is available for use in expressions in the convenience variable
10999 @code{$_}. The contents of that address, as examined, are available in
11000 the convenience variable @code{$__}.
11002 If the @code{x} command has a repeat count, the address and contents saved
11003 are from the last memory unit printed; this is not the same as the last
11004 address printed if several units were printed on the last line of output.
11006 @anchor{addressable memory unit}
11007 @cindex addressable memory unit
11008 Most targets have an addressable memory unit size of 8 bits. This means
11009 that to each memory address are associated 8 bits of data. Some
11010 targets, however, have other addressable memory unit sizes.
11011 Within @value{GDBN} and this document, the term
11012 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11013 when explicitly referring to a chunk of data of that size. The word
11014 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11015 the addressable memory unit size of the target. For most systems,
11016 addressable memory unit is a synonym of byte.
11018 @cindex remote memory comparison
11019 @cindex target memory comparison
11020 @cindex verify remote memory image
11021 @cindex verify target memory image
11022 When you are debugging a program running on a remote target machine
11023 (@pxref{Remote Debugging}), you may wish to verify the program's image
11024 in the remote machine's memory against the executable file you
11025 downloaded to the target. Or, on any target, you may want to check
11026 whether the program has corrupted its own read-only sections. The
11027 @code{compare-sections} command is provided for such situations.
11030 @kindex compare-sections
11031 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11032 Compare the data of a loadable section @var{section-name} in the
11033 executable file of the program being debugged with the same section in
11034 the target machine's memory, and report any mismatches. With no
11035 arguments, compares all loadable sections. With an argument of
11036 @code{-r}, compares all loadable read-only sections.
11038 Note: for remote targets, this command can be accelerated if the
11039 target supports computing the CRC checksum of a block of memory
11040 (@pxref{qCRC packet}).
11043 @node Memory Tagging
11044 @section Memory Tagging
11046 Memory tagging is a memory protection technology that uses a pair of tags to
11047 validate memory accesses through pointers. The tags are integer values
11048 usually comprised of a few bits, depending on the architecture.
11050 There are two types of tags that are used in this setup: logical and
11051 allocation. A logical tag is stored in the pointers themselves, usually at the
11052 higher bits of the pointers. An allocation tag is the tag associated
11053 with particular ranges of memory in the physical address space, against which
11054 the logical tags from pointers are compared.
11056 The pointer tag (logical tag) must match the memory tag (allocation tag)
11057 for the memory access to be valid. If the logical tag does not match the
11058 allocation tag, that will raise a memory violation.
11060 Allocation tags cover multiple contiguous bytes of physical memory. This
11061 range of bytes is called a memory tag granule and is architecture-specific.
11062 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11063 tag spans 16 bytes of memory.
11065 If the underlying architecture supports memory tagging, like AArch64 MTE
11066 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11067 against memory allocation tags.
11069 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11070 display tag information when appropriate, and a command prefix of
11071 @code{memory-tag} gives access to the various memory tagging commands.
11073 The @code{memory-tag} commands are the following:
11076 @kindex memory-tag print-logical-tag
11077 @item memory-tag print-logical-tag @var{pointer_expression}
11078 Print the logical tag stored in @var{pointer_expression}.
11079 @kindex memory-tag with-logical-tag
11080 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11081 Print the pointer given by @var{pointer_expression}, augmented with a logical
11082 tag of @var{tag_bytes}.
11083 @kindex memory-tag print-allocation-tag
11084 @item memory-tag print-allocation-tag @var{address_expression}
11085 Print the allocation tag associated with the memory address given by
11086 @var{address_expression}.
11087 @kindex memory-tag setatag
11088 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11089 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11090 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11091 @kindex memory-tag check
11092 @item memory-tag check @var{pointer_expression}
11093 Check if the logical tag in the pointer given by @var{pointer_expression}
11094 matches the allocation tag for the memory referenced by the pointer.
11096 This essentially emulates the hardware validation that is done when tagged
11097 memory is accessed through a pointer, but does not cause a memory fault as
11098 it would during hardware validation.
11100 It can be used to inspect potential memory tagging violations in the running
11101 process, before any faults get triggered.
11105 @section Automatic Display
11106 @cindex automatic display
11107 @cindex display of expressions
11109 If you find that you want to print the value of an expression frequently
11110 (to see how it changes), you might want to add it to the @dfn{automatic
11111 display list} so that @value{GDBN} prints its value each time your program stops.
11112 Each expression added to the list is given a number to identify it;
11113 to remove an expression from the list, you specify that number.
11114 The automatic display looks like this:
11118 3: bar[5] = (struct hack *) 0x3804
11122 This display shows item numbers, expressions and their current values. As with
11123 displays you request manually using @code{x} or @code{print}, you can
11124 specify the output format you prefer; in fact, @code{display} decides
11125 whether to use @code{print} or @code{x} depending your format
11126 specification---it uses @code{x} if you specify either the @samp{i}
11127 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11131 @item display @var{expr}
11132 Add the expression @var{expr} to the list of expressions to display
11133 each time your program stops. @xref{Expressions, ,Expressions}.
11135 @code{display} does not repeat if you press @key{RET} again after using it.
11137 @item display/@var{fmt} @var{expr}
11138 For @var{fmt} specifying only a display format and not a size or
11139 count, add the expression @var{expr} to the auto-display list but
11140 arrange to display it each time in the specified format @var{fmt}.
11141 @xref{Output Formats,,Output Formats}.
11143 @item display/@var{fmt} @var{addr}
11144 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11145 number of units, add the expression @var{addr} as a memory address to
11146 be examined each time your program stops. Examining means in effect
11147 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11150 For example, @samp{display/i $pc} can be helpful, to see the machine
11151 instruction about to be executed each time execution stops (@samp{$pc}
11152 is a common name for the program counter; @pxref{Registers, ,Registers}).
11155 @kindex delete display
11157 @item undisplay @var{dnums}@dots{}
11158 @itemx delete display @var{dnums}@dots{}
11159 Remove items from the list of expressions to display. Specify the
11160 numbers of the displays that you want affected with the command
11161 argument @var{dnums}. It can be a single display number, one of the
11162 numbers shown in the first field of the @samp{info display} display;
11163 or it could be a range of display numbers, as in @code{2-4}.
11165 @code{undisplay} does not repeat if you press @key{RET} after using it.
11166 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11168 @kindex disable display
11169 @item disable display @var{dnums}@dots{}
11170 Disable the display of item numbers @var{dnums}. A disabled display
11171 item is not printed automatically, but is not forgotten. It may be
11172 enabled again later. Specify the numbers of the displays that you
11173 want affected with the command argument @var{dnums}. It can be a
11174 single display number, one of the numbers shown in the first field of
11175 the @samp{info display} display; or it could be a range of display
11176 numbers, as in @code{2-4}.
11178 @kindex enable display
11179 @item enable display @var{dnums}@dots{}
11180 Enable display of item numbers @var{dnums}. It becomes effective once
11181 again in auto display of its expression, until you specify otherwise.
11182 Specify the numbers of the displays that you want affected with the
11183 command argument @var{dnums}. It can be a single display number, one
11184 of the numbers shown in the first field of the @samp{info display}
11185 display; or it could be a range of display numbers, as in @code{2-4}.
11188 Display the current values of the expressions on the list, just as is
11189 done when your program stops.
11191 @kindex info display
11193 Print the list of expressions previously set up to display
11194 automatically, each one with its item number, but without showing the
11195 values. This includes disabled expressions, which are marked as such.
11196 It also includes expressions which would not be displayed right now
11197 because they refer to automatic variables not currently available.
11200 @cindex display disabled out of scope
11201 If a display expression refers to local variables, then it does not make
11202 sense outside the lexical context for which it was set up. Such an
11203 expression is disabled when execution enters a context where one of its
11204 variables is not defined. For example, if you give the command
11205 @code{display last_char} while inside a function with an argument
11206 @code{last_char}, @value{GDBN} displays this argument while your program
11207 continues to stop inside that function. When it stops elsewhere---where
11208 there is no variable @code{last_char}---the display is disabled
11209 automatically. The next time your program stops where @code{last_char}
11210 is meaningful, you can enable the display expression once again.
11212 @node Print Settings
11213 @section Print Settings
11215 @cindex format options
11216 @cindex print settings
11217 @value{GDBN} provides the following ways to control how arrays, structures,
11218 and symbols are printed.
11221 These settings are useful for debugging programs in any language:
11225 @anchor{set print address}
11226 @item set print address
11227 @itemx set print address on
11228 @cindex print/don't print memory addresses
11229 @value{GDBN} prints memory addresses showing the location of stack
11230 traces, structure values, pointer values, breakpoints, and so forth,
11231 even when it also displays the contents of those addresses. The default
11232 is @code{on}. For example, this is what a stack frame display looks like with
11233 @code{set print address on}:
11238 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11240 530 if (lquote != def_lquote)
11244 @item set print address off
11245 Do not print addresses when displaying their contents. For example,
11246 this is the same stack frame displayed with @code{set print address off}:
11250 (@value{GDBP}) set print addr off
11252 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11253 530 if (lquote != def_lquote)
11257 You can use @samp{set print address off} to eliminate all machine
11258 dependent displays from the @value{GDBN} interface. For example, with
11259 @code{print address off}, you should get the same text for backtraces on
11260 all machines---whether or not they involve pointer arguments.
11263 @item show print address
11264 Show whether or not addresses are to be printed.
11267 When @value{GDBN} prints a symbolic address, it normally prints the
11268 closest earlier symbol plus an offset. If that symbol does not uniquely
11269 identify the address (for example, it is a name whose scope is a single
11270 source file), you may need to clarify. One way to do this is with
11271 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11272 you can set @value{GDBN} to print the source file and line number when
11273 it prints a symbolic address:
11276 @item set print symbol-filename on
11277 @cindex source file and line of a symbol
11278 @cindex symbol, source file and line
11279 Tell @value{GDBN} to print the source file name and line number of a
11280 symbol in the symbolic form of an address.
11282 @item set print symbol-filename off
11283 Do not print source file name and line number of a symbol. This is the
11286 @item show print symbol-filename
11287 Show whether or not @value{GDBN} will print the source file name and
11288 line number of a symbol in the symbolic form of an address.
11291 Another situation where it is helpful to show symbol filenames and line
11292 numbers is when disassembling code; @value{GDBN} shows you the line
11293 number and source file that corresponds to each instruction.
11295 Also, you may wish to see the symbolic form only if the address being
11296 printed is reasonably close to the closest earlier symbol:
11299 @item set print max-symbolic-offset @var{max-offset}
11300 @itemx set print max-symbolic-offset unlimited
11301 @cindex maximum value for offset of closest symbol
11302 Tell @value{GDBN} to only display the symbolic form of an address if the
11303 offset between the closest earlier symbol and the address is less than
11304 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11305 to always print the symbolic form of an address if any symbol precedes
11306 it. Zero is equivalent to @code{unlimited}.
11308 @item show print max-symbolic-offset
11309 Ask how large the maximum offset is that @value{GDBN} prints in a
11313 @cindex wild pointer, interpreting
11314 @cindex pointer, finding referent
11315 If you have a pointer and you are not sure where it points, try
11316 @samp{set print symbol-filename on}. Then you can determine the name
11317 and source file location of the variable where it points, using
11318 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11319 For example, here @value{GDBN} shows that a variable @code{ptt} points
11320 at another variable @code{t}, defined in @file{hi2.c}:
11323 (@value{GDBP}) set print symbol-filename on
11324 (@value{GDBP}) p/a ptt
11325 $4 = 0xe008 <t in hi2.c>
11329 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11330 does not show the symbol name and filename of the referent, even with
11331 the appropriate @code{set print} options turned on.
11334 You can also enable @samp{/a}-like formatting all the time using
11335 @samp{set print symbol on}:
11337 @anchor{set print symbol}
11339 @item set print symbol on
11340 Tell @value{GDBN} to print the symbol corresponding to an address, if
11343 @item set print symbol off
11344 Tell @value{GDBN} not to print the symbol corresponding to an
11345 address. In this mode, @value{GDBN} will still print the symbol
11346 corresponding to pointers to functions. This is the default.
11348 @item show print symbol
11349 Show whether @value{GDBN} will display the symbol corresponding to an
11353 Other settings control how different kinds of objects are printed:
11356 @anchor{set print array}
11357 @item set print array
11358 @itemx set print array on
11359 @cindex pretty print arrays
11360 Pretty print arrays. This format is more convenient to read,
11361 but uses more space. The default is off.
11363 @item set print array off
11364 Return to compressed format for arrays.
11366 @item show print array
11367 Show whether compressed or pretty format is selected for displaying
11370 @cindex print array indexes
11371 @anchor{set print array-indexes}
11372 @item set print array-indexes
11373 @itemx set print array-indexes on
11374 Print the index of each element when displaying arrays. May be more
11375 convenient to locate a given element in the array or quickly find the
11376 index of a given element in that printed array. The default is off.
11378 @item set print array-indexes off
11379 Stop printing element indexes when displaying arrays.
11381 @item show print array-indexes
11382 Show whether the index of each element is printed when displaying
11385 @anchor{set print elements}
11386 @item set print elements @var{number-of-elements}
11387 @itemx set print elements unlimited
11388 @cindex number of array elements to print
11389 @cindex limit on number of printed array elements
11390 Set a limit on how many elements of an array @value{GDBN} will print.
11391 If @value{GDBN} is printing a large array, it stops printing after it has
11392 printed the number of elements set by the @code{set print elements} command.
11393 This limit also applies to the display of strings.
11394 When @value{GDBN} starts, this limit is set to 200.
11395 Setting @var{number-of-elements} to @code{unlimited} or zero means
11396 that the number of elements to print is unlimited.
11398 @item show print elements
11399 Display the number of elements of a large array that @value{GDBN} will print.
11401 @anchor{set print frame-arguments}
11402 @item set print frame-arguments @var{value}
11403 @kindex set print frame-arguments
11404 @cindex printing frame argument values
11405 @cindex print all frame argument values
11406 @cindex print frame argument values for scalars only
11407 @cindex do not print frame arguments
11408 This command allows to control how the values of arguments are printed
11409 when the debugger prints a frame (@pxref{Frames}). The possible
11414 The values of all arguments are printed.
11417 Print the value of an argument only if it is a scalar. The value of more
11418 complex arguments such as arrays, structures, unions, etc, is replaced
11419 by @code{@dots{}}. This is the default. Here is an example where
11420 only scalar arguments are shown:
11423 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11428 None of the argument values are printed. Instead, the value of each argument
11429 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11432 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11437 Only the presence of arguments is indicated by @code{@dots{}}.
11438 The @code{@dots{}} are not printed for function without any arguments.
11439 None of the argument names and values are printed.
11440 In this case, the example above now becomes:
11443 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11448 By default, only scalar arguments are printed. This command can be used
11449 to configure the debugger to print the value of all arguments, regardless
11450 of their type. However, it is often advantageous to not print the value
11451 of more complex parameters. For instance, it reduces the amount of
11452 information printed in each frame, making the backtrace more readable.
11453 Also, it improves performance when displaying Ada frames, because
11454 the computation of large arguments can sometimes be CPU-intensive,
11455 especially in large applications. Setting @code{print frame-arguments}
11456 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11457 this computation, thus speeding up the display of each Ada frame.
11459 @item show print frame-arguments
11460 Show how the value of arguments should be displayed when printing a frame.
11462 @anchor{set print raw-frame-arguments}
11463 @item set print raw-frame-arguments on
11464 Print frame arguments in raw, non pretty-printed, form.
11466 @item set print raw-frame-arguments off
11467 Print frame arguments in pretty-printed form, if there is a pretty-printer
11468 for the value (@pxref{Pretty Printing}),
11469 otherwise print the value in raw form.
11470 This is the default.
11472 @item show print raw-frame-arguments
11473 Show whether to print frame arguments in raw form.
11475 @anchor{set print entry-values}
11476 @item set print entry-values @var{value}
11477 @kindex set print entry-values
11478 Set printing of frame argument values at function entry. In some cases
11479 @value{GDBN} can determine the value of function argument which was passed by
11480 the function caller, even if the value was modified inside the called function
11481 and therefore is different. With optimized code, the current value could be
11482 unavailable, but the entry value may still be known.
11484 The default value is @code{default} (see below for its description). Older
11485 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11486 this feature will behave in the @code{default} setting the same way as with the
11489 This functionality is currently supported only by DWARF 2 debugging format and
11490 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11491 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11494 The @var{value} parameter can be one of the following:
11498 Print only actual parameter values, never print values from function entry
11502 #0 different (val=6)
11503 #0 lost (val=<optimized out>)
11505 #0 invalid (val=<optimized out>)
11509 Print only parameter values from function entry point. The actual parameter
11510 values are never printed.
11512 #0 equal (val@@entry=5)
11513 #0 different (val@@entry=5)
11514 #0 lost (val@@entry=5)
11515 #0 born (val@@entry=<optimized out>)
11516 #0 invalid (val@@entry=<optimized out>)
11520 Print only parameter values from function entry point. If value from function
11521 entry point is not known while the actual value is known, print the actual
11522 value for such parameter.
11524 #0 equal (val@@entry=5)
11525 #0 different (val@@entry=5)
11526 #0 lost (val@@entry=5)
11528 #0 invalid (val@@entry=<optimized out>)
11532 Print actual parameter values. If actual parameter value is not known while
11533 value from function entry point is known, print the entry point value for such
11537 #0 different (val=6)
11538 #0 lost (val@@entry=5)
11540 #0 invalid (val=<optimized out>)
11544 Always print both the actual parameter value and its value from function entry
11545 point, even if values of one or both are not available due to compiler
11548 #0 equal (val=5, val@@entry=5)
11549 #0 different (val=6, val@@entry=5)
11550 #0 lost (val=<optimized out>, val@@entry=5)
11551 #0 born (val=10, val@@entry=<optimized out>)
11552 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11556 Print the actual parameter value if it is known and also its value from
11557 function entry point if it is known. If neither is known, print for the actual
11558 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11559 values are known and identical, print the shortened
11560 @code{param=param@@entry=VALUE} notation.
11562 #0 equal (val=val@@entry=5)
11563 #0 different (val=6, val@@entry=5)
11564 #0 lost (val@@entry=5)
11566 #0 invalid (val=<optimized out>)
11570 Always print the actual parameter value. Print also its value from function
11571 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11572 if both values are known and identical, print the shortened
11573 @code{param=param@@entry=VALUE} notation.
11575 #0 equal (val=val@@entry=5)
11576 #0 different (val=6, val@@entry=5)
11577 #0 lost (val=<optimized out>, val@@entry=5)
11579 #0 invalid (val=<optimized out>)
11583 For analysis messages on possible failures of frame argument values at function
11584 entry resolution see @ref{set debug entry-values}.
11586 @item show print entry-values
11587 Show the method being used for printing of frame argument values at function
11590 @anchor{set print frame-info}
11591 @item set print frame-info @var{value}
11592 @kindex set print frame-info
11593 @cindex printing frame information
11594 @cindex frame information, printing
11595 This command allows to control the information printed when
11596 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11597 for a general explanation about frames and frame information.
11598 Note that some other settings (such as @code{set print frame-arguments}
11599 and @code{set print address}) are also influencing if and how some frame
11600 information is displayed. In particular, the frame program counter is never
11601 printed if @code{set print address} is off.
11603 The possible values for @code{set print frame-info} are:
11605 @item short-location
11606 Print the frame level, the program counter (if not at the
11607 beginning of the location source line), the function, the function
11610 Same as @code{short-location} but also print the source file and source line
11612 @item location-and-address
11613 Same as @code{location} but print the program counter even if located at the
11614 beginning of the location source line.
11616 Print the program counter (if not at the beginning of the location
11617 source line), the line number and the source line.
11618 @item source-and-location
11619 Print what @code{location} and @code{source-line} are printing.
11621 The information printed for a frame is decided automatically
11622 by the @value{GDBN} command that prints a frame.
11623 For example, @code{frame} prints the information printed by
11624 @code{source-and-location} while @code{stepi} will switch between
11625 @code{source-line} and @code{source-and-location} depending on the program
11627 The default value is @code{auto}.
11630 @anchor{set print repeats}
11631 @item set print repeats @var{number-of-repeats}
11632 @itemx set print repeats unlimited
11633 @cindex repeated array elements
11634 Set the threshold for suppressing display of repeated array
11635 elements. When the number of consecutive identical elements of an
11636 array exceeds the threshold, @value{GDBN} prints the string
11637 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11638 identical repetitions, instead of displaying the identical elements
11639 themselves. Setting the threshold to @code{unlimited} or zero will
11640 cause all elements to be individually printed. The default threshold
11643 @item show print repeats
11644 Display the current threshold for printing repeated identical
11647 @anchor{set print max-depth}
11648 @item set print max-depth @var{depth}
11649 @item set print max-depth unlimited
11650 @cindex printing nested structures
11651 Set the threshold after which nested structures are replaced with
11652 ellipsis, this can make visualising deeply nested structures easier.
11654 For example, given this C code
11657 typedef struct s1 @{ int a; @} s1;
11658 typedef struct s2 @{ s1 b; @} s2;
11659 typedef struct s3 @{ s2 c; @} s3;
11660 typedef struct s4 @{ s3 d; @} s4;
11662 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11665 The following table shows how different values of @var{depth} will
11666 effect how @code{var} is printed by @value{GDBN}:
11668 @multitable @columnfractions .3 .7
11669 @headitem @var{depth} setting @tab Result of @samp{p var}
11671 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11673 @tab @code{$1 = @{...@}}
11675 @tab @code{$1 = @{d = @{...@}@}}
11677 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11679 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11681 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11684 To see the contents of structures that have been hidden the user can
11685 either increase the print max-depth, or they can print the elements of
11686 the structure that are visible, for example
11689 (gdb) set print max-depth 2
11691 $1 = @{d = @{c = @{...@}@}@}
11693 $2 = @{c = @{b = @{...@}@}@}
11695 $3 = @{b = @{a = 3@}@}
11698 The pattern used to replace nested structures varies based on
11699 language, for most languages @code{@{...@}} is used, but Fortran uses
11702 @item show print max-depth
11703 Display the current threshold after which nested structures are
11704 replaces with ellipsis.
11706 @anchor{set print memory-tag-violations}
11707 @cindex printing memory tag violation information
11708 @item set print memory-tag-violations
11709 @itemx set print memory-tag-violations on
11710 Cause @value{GDBN} to display additional information about memory tag violations
11711 when printing pointers and addresses.
11713 @item set print memory-tag-violations off
11714 Stop printing memory tag violation information.
11716 @item show print memory-tag-violations
11717 Show whether memory tag violation information is displayed when printing
11718 pointers and addresses.
11720 @anchor{set print null-stop}
11721 @item set print null-stop
11722 @cindex @sc{null} elements in arrays
11723 Cause @value{GDBN} to stop printing the characters of an array when the first
11724 @sc{null} is encountered. This is useful when large arrays actually
11725 contain only short strings.
11726 The default is off.
11728 @item show print null-stop
11729 Show whether @value{GDBN} stops printing an array on the first
11730 @sc{null} character.
11732 @anchor{set print pretty}
11733 @item set print pretty on
11734 @cindex print structures in indented form
11735 @cindex indentation in structure display
11736 Cause @value{GDBN} to print structures in an indented format with one member
11737 per line, like this:
11752 @item set print pretty off
11753 Cause @value{GDBN} to print structures in a compact format, like this:
11757 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11758 meat = 0x54 "Pork"@}
11763 This is the default format.
11765 @item show print pretty
11766 Show which format @value{GDBN} is using to print structures.
11768 @anchor{set print raw-values}
11769 @item set print raw-values on
11770 Print values in raw form, without applying the pretty
11771 printers for the value.
11773 @item set print raw-values off
11774 Print values in pretty-printed form, if there is a pretty-printer
11775 for the value (@pxref{Pretty Printing}),
11776 otherwise print the value in raw form.
11778 The default setting is ``off''.
11780 @item show print raw-values
11781 Show whether to print values in raw form.
11783 @item set print sevenbit-strings on
11784 @cindex eight-bit characters in strings
11785 @cindex octal escapes in strings
11786 Print using only seven-bit characters; if this option is set,
11787 @value{GDBN} displays any eight-bit characters (in strings or
11788 character values) using the notation @code{\}@var{nnn}. This setting is
11789 best if you are working in English (@sc{ascii}) and you use the
11790 high-order bit of characters as a marker or ``meta'' bit.
11792 @item set print sevenbit-strings off
11793 Print full eight-bit characters. This allows the use of more
11794 international character sets, and is the default.
11796 @item show print sevenbit-strings
11797 Show whether or not @value{GDBN} is printing only seven-bit characters.
11799 @anchor{set print union}
11800 @item set print union on
11801 @cindex unions in structures, printing
11802 Tell @value{GDBN} to print unions which are contained in structures
11803 and other unions. This is the default setting.
11805 @item set print union off
11806 Tell @value{GDBN} not to print unions which are contained in
11807 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11810 @item show print union
11811 Ask @value{GDBN} whether or not it will print unions which are contained in
11812 structures and other unions.
11814 For example, given the declarations
11817 typedef enum @{Tree, Bug@} Species;
11818 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11819 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11830 struct thing foo = @{Tree, @{Acorn@}@};
11834 with @code{set print union on} in effect @samp{p foo} would print
11837 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11841 and with @code{set print union off} in effect it would print
11844 $1 = @{it = Tree, form = @{...@}@}
11848 @code{set print union} affects programs written in C-like languages
11854 These settings are of interest when debugging C@t{++} programs:
11857 @cindex demangling C@t{++} names
11858 @item set print demangle
11859 @itemx set print demangle on
11860 Print C@t{++} names in their source form rather than in the encoded
11861 (``mangled'') form passed to the assembler and linker for type-safe
11862 linkage. The default is on.
11864 @item show print demangle
11865 Show whether C@t{++} names are printed in mangled or demangled form.
11867 @item set print asm-demangle
11868 @itemx set print asm-demangle on
11869 Print C@t{++} names in their source form rather than their mangled form, even
11870 in assembler code printouts such as instruction disassemblies.
11871 The default is off.
11873 @item show print asm-demangle
11874 Show whether C@t{++} names in assembly listings are printed in mangled
11877 @cindex C@t{++} symbol decoding style
11878 @cindex symbol decoding style, C@t{++}
11879 @kindex set demangle-style
11880 @item set demangle-style @var{style}
11881 Choose among several encoding schemes used by different compilers to represent
11882 C@t{++} names. If you omit @var{style}, you will see a list of possible
11883 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11884 decoding style by inspecting your program.
11886 @item show demangle-style
11887 Display the encoding style currently in use for decoding C@t{++} symbols.
11889 @anchor{set print object}
11890 @item set print object
11891 @itemx set print object on
11892 @cindex derived type of an object, printing
11893 @cindex display derived types
11894 When displaying a pointer to an object, identify the @emph{actual}
11895 (derived) type of the object rather than the @emph{declared} type, using
11896 the virtual function table. Note that the virtual function table is
11897 required---this feature can only work for objects that have run-time
11898 type identification; a single virtual method in the object's declared
11899 type is sufficient. Note that this setting is also taken into account when
11900 working with variable objects via MI (@pxref{GDB/MI}).
11902 @item set print object off
11903 Display only the declared type of objects, without reference to the
11904 virtual function table. This is the default setting.
11906 @item show print object
11907 Show whether actual, or declared, object types are displayed.
11909 @anchor{set print static-members}
11910 @item set print static-members
11911 @itemx set print static-members on
11912 @cindex static members of C@t{++} objects
11913 Print static members when displaying a C@t{++} object. The default is on.
11915 @item set print static-members off
11916 Do not print static members when displaying a C@t{++} object.
11918 @item show print static-members
11919 Show whether C@t{++} static members are printed or not.
11921 @item set print pascal_static-members
11922 @itemx set print pascal_static-members on
11923 @cindex static members of Pascal objects
11924 @cindex Pascal objects, static members display
11925 Print static members when displaying a Pascal object. The default is on.
11927 @item set print pascal_static-members off
11928 Do not print static members when displaying a Pascal object.
11930 @item show print pascal_static-members
11931 Show whether Pascal static members are printed or not.
11933 @c These don't work with HP ANSI C++ yet.
11934 @anchor{set print vtbl}
11935 @item set print vtbl
11936 @itemx set print vtbl on
11937 @cindex pretty print C@t{++} virtual function tables
11938 @cindex virtual functions (C@t{++}) display
11939 @cindex VTBL display
11940 Pretty print C@t{++} virtual function tables. The default is off.
11941 (The @code{vtbl} commands do not work on programs compiled with the HP
11942 ANSI C@t{++} compiler (@code{aCC}).)
11944 @item set print vtbl off
11945 Do not pretty print C@t{++} virtual function tables.
11947 @item show print vtbl
11948 Show whether C@t{++} virtual function tables are pretty printed, or not.
11951 @node Pretty Printing
11952 @section Pretty Printing
11954 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11955 Python code. It greatly simplifies the display of complex objects. This
11956 mechanism works for both MI and the CLI.
11959 * Pretty-Printer Introduction:: Introduction to pretty-printers
11960 * Pretty-Printer Example:: An example pretty-printer
11961 * Pretty-Printer Commands:: Pretty-printer commands
11964 @node Pretty-Printer Introduction
11965 @subsection Pretty-Printer Introduction
11967 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11968 registered for the value. If there is then @value{GDBN} invokes the
11969 pretty-printer to print the value. Otherwise the value is printed normally.
11971 Pretty-printers are normally named. This makes them easy to manage.
11972 The @samp{info pretty-printer} command will list all the installed
11973 pretty-printers with their names.
11974 If a pretty-printer can handle multiple data types, then its
11975 @dfn{subprinters} are the printers for the individual data types.
11976 Each such subprinter has its own name.
11977 The format of the name is @var{printer-name};@var{subprinter-name}.
11979 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11980 Typically they are automatically loaded and registered when the corresponding
11981 debug information is loaded, thus making them available without having to
11982 do anything special.
11984 There are three places where a pretty-printer can be registered.
11988 Pretty-printers registered globally are available when debugging
11992 Pretty-printers registered with a program space are available only
11993 when debugging that program.
11994 @xref{Progspaces In Python}, for more details on program spaces in Python.
11997 Pretty-printers registered with an objfile are loaded and unloaded
11998 with the corresponding objfile (e.g., shared library).
11999 @xref{Objfiles In Python}, for more details on objfiles in Python.
12002 @xref{Selecting Pretty-Printers}, for further information on how
12003 pretty-printers are selected,
12005 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12008 @node Pretty-Printer Example
12009 @subsection Pretty-Printer Example
12011 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12014 (@value{GDBP}) print s
12016 static npos = 4294967295,
12018 <std::allocator<char>> = @{
12019 <__gnu_cxx::new_allocator<char>> = @{
12020 <No data fields>@}, <No data fields>
12022 members of std::basic_string<char, std::char_traits<char>,
12023 std::allocator<char> >::_Alloc_hider:
12024 _M_p = 0x804a014 "abcd"
12029 With a pretty-printer for @code{std::string} only the contents are printed:
12032 (@value{GDBP}) print s
12036 @node Pretty-Printer Commands
12037 @subsection Pretty-Printer Commands
12038 @cindex pretty-printer commands
12041 @kindex info pretty-printer
12042 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12043 Print the list of installed pretty-printers.
12044 This includes disabled pretty-printers, which are marked as such.
12046 @var{object-regexp} is a regular expression matching the objects
12047 whose pretty-printers to list.
12048 Objects can be @code{global}, the program space's file
12049 (@pxref{Progspaces In Python}),
12050 and the object files within that program space (@pxref{Objfiles In Python}).
12051 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12052 looks up a printer from these three objects.
12054 @var{name-regexp} is a regular expression matching the name of the printers
12057 @kindex disable pretty-printer
12058 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12059 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12060 A disabled pretty-printer is not forgotten, it may be enabled again later.
12062 @kindex enable pretty-printer
12063 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12064 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12069 Suppose we have three pretty-printers installed: one from library1.so
12070 named @code{foo} that prints objects of type @code{foo}, and
12071 another from library2.so named @code{bar} that prints two types of objects,
12072 @code{bar1} and @code{bar2}.
12075 (gdb) info pretty-printer
12082 (gdb) info pretty-printer library2
12087 (gdb) disable pretty-printer library1
12089 2 of 3 printers enabled
12090 (gdb) info pretty-printer
12097 (gdb) disable pretty-printer library2 bar;bar1
12099 1 of 3 printers enabled
12100 (gdb) info pretty-printer library2
12107 (gdb) disable pretty-printer library2 bar
12109 0 of 3 printers enabled
12110 (gdb) info pretty-printer library2
12119 Note that for @code{bar} the entire printer can be disabled,
12120 as can each individual subprinter.
12122 Printing values and frame arguments is done by default using
12123 the enabled pretty printers.
12125 The print option @code{-raw-values} and @value{GDBN} setting
12126 @code{set print raw-values} (@pxref{set print raw-values}) can be
12127 used to print values without applying the enabled pretty printers.
12129 Similarly, the backtrace option @code{-raw-frame-arguments} and
12130 @value{GDBN} setting @code{set print raw-frame-arguments}
12131 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12132 enabled pretty printers when printing frame argument values.
12134 @node Value History
12135 @section Value History
12137 @cindex value history
12138 @cindex history of values printed by @value{GDBN}
12139 Values printed by the @code{print} command are saved in the @value{GDBN}
12140 @dfn{value history}. This allows you to refer to them in other expressions.
12141 Values are kept until the symbol table is re-read or discarded
12142 (for example with the @code{file} or @code{symbol-file} commands).
12143 When the symbol table changes, the value history is discarded,
12144 since the values may contain pointers back to the types defined in the
12149 @cindex history number
12150 The values printed are given @dfn{history numbers} by which you can
12151 refer to them. These are successive integers starting with one.
12152 @code{print} shows you the history number assigned to a value by
12153 printing @samp{$@var{num} = } before the value; here @var{num} is the
12156 To refer to any previous value, use @samp{$} followed by the value's
12157 history number. The way @code{print} labels its output is designed to
12158 remind you of this. Just @code{$} refers to the most recent value in
12159 the history, and @code{$$} refers to the value before that.
12160 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12161 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12162 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12164 For example, suppose you have just printed a pointer to a structure and
12165 want to see the contents of the structure. It suffices to type
12171 If you have a chain of structures where the component @code{next} points
12172 to the next one, you can print the contents of the next one with this:
12179 You can print successive links in the chain by repeating this
12180 command---which you can do by just typing @key{RET}.
12182 Note that the history records values, not expressions. If the value of
12183 @code{x} is 4 and you type these commands:
12191 then the value recorded in the value history by the @code{print} command
12192 remains 4 even though the value of @code{x} has changed.
12195 @kindex show values
12197 Print the last ten values in the value history, with their item numbers.
12198 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12199 values} does not change the history.
12201 @item show values @var{n}
12202 Print ten history values centered on history item number @var{n}.
12204 @item show values +
12205 Print ten history values just after the values last printed. If no more
12206 values are available, @code{show values +} produces no display.
12209 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12210 same effect as @samp{show values +}.
12212 @node Convenience Vars
12213 @section Convenience Variables
12215 @cindex convenience variables
12216 @cindex user-defined variables
12217 @value{GDBN} provides @dfn{convenience variables} that you can use within
12218 @value{GDBN} to hold on to a value and refer to it later. These variables
12219 exist entirely within @value{GDBN}; they are not part of your program, and
12220 setting a convenience variable has no direct effect on further execution
12221 of your program. That is why you can use them freely.
12223 Convenience variables are prefixed with @samp{$}. Any name preceded by
12224 @samp{$} can be used for a convenience variable, unless it is one of
12225 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12226 (Value history references, in contrast, are @emph{numbers} preceded
12227 by @samp{$}. @xref{Value History, ,Value History}.)
12229 You can save a value in a convenience variable with an assignment
12230 expression, just as you would set a variable in your program.
12234 set $foo = *object_ptr
12238 would save in @code{$foo} the value contained in the object pointed to by
12241 Using a convenience variable for the first time creates it, but its
12242 value is @code{void} until you assign a new value. You can alter the
12243 value with another assignment at any time.
12245 Convenience variables have no fixed types. You can assign a convenience
12246 variable any type of value, including structures and arrays, even if
12247 that variable already has a value of a different type. The convenience
12248 variable, when used as an expression, has the type of its current value.
12251 @kindex show convenience
12252 @cindex show all user variables and functions
12253 @item show convenience
12254 Print a list of convenience variables used so far, and their values,
12255 as well as a list of the convenience functions.
12256 Abbreviated @code{show conv}.
12258 @kindex init-if-undefined
12259 @cindex convenience variables, initializing
12260 @item init-if-undefined $@var{variable} = @var{expression}
12261 Set a convenience variable if it has not already been set. This is useful
12262 for user-defined commands that keep some state. It is similar, in concept,
12263 to using local static variables with initializers in C (except that
12264 convenience variables are global). It can also be used to allow users to
12265 override default values used in a command script.
12267 If the variable is already defined then the expression is not evaluated so
12268 any side-effects do not occur.
12271 One of the ways to use a convenience variable is as a counter to be
12272 incremented or a pointer to be advanced. For example, to print
12273 a field from successive elements of an array of structures:
12277 print bar[$i++]->contents
12281 Repeat that command by typing @key{RET}.
12283 Some convenience variables are created automatically by @value{GDBN} and given
12284 values likely to be useful.
12287 @vindex $_@r{, convenience variable}
12289 The variable @code{$_} is automatically set by the @code{x} command to
12290 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12291 commands which provide a default address for @code{x} to examine also
12292 set @code{$_} to that address; these commands include @code{info line}
12293 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12294 except when set by the @code{x} command, in which case it is a pointer
12295 to the type of @code{$__}.
12297 @vindex $__@r{, convenience variable}
12299 The variable @code{$__} is automatically set by the @code{x} command
12300 to the value found in the last address examined. Its type is chosen
12301 to match the format in which the data was printed.
12304 @vindex $_exitcode@r{, convenience variable}
12305 When the program being debugged terminates normally, @value{GDBN}
12306 automatically sets this variable to the exit code of the program, and
12307 resets @code{$_exitsignal} to @code{void}.
12310 @vindex $_exitsignal@r{, convenience variable}
12311 When the program being debugged dies due to an uncaught signal,
12312 @value{GDBN} automatically sets this variable to that signal's number,
12313 and resets @code{$_exitcode} to @code{void}.
12315 To distinguish between whether the program being debugged has exited
12316 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12317 @code{$_exitsignal} is not @code{void}), the convenience function
12318 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12319 Functions}). For example, considering the following source code:
12322 #include <signal.h>
12325 main (int argc, char *argv[])
12332 A valid way of telling whether the program being debugged has exited
12333 or signalled would be:
12336 (@value{GDBP}) define has_exited_or_signalled
12337 Type commands for definition of ``has_exited_or_signalled''.
12338 End with a line saying just ``end''.
12339 >if $_isvoid ($_exitsignal)
12340 >echo The program has exited\n
12342 >echo The program has signalled\n
12348 Program terminated with signal SIGALRM, Alarm clock.
12349 The program no longer exists.
12350 (@value{GDBP}) has_exited_or_signalled
12351 The program has signalled
12354 As can be seen, @value{GDBN} correctly informs that the program being
12355 debugged has signalled, since it calls @code{raise} and raises a
12356 @code{SIGALRM} signal. If the program being debugged had not called
12357 @code{raise}, then @value{GDBN} would report a normal exit:
12360 (@value{GDBP}) has_exited_or_signalled
12361 The program has exited
12365 The variable @code{$_exception} is set to the exception object being
12366 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12368 @item $_ada_exception
12369 The variable @code{$_ada_exception} is set to the address of the
12370 exception being caught or thrown at an Ada exception-related
12371 catchpoint. @xref{Set Catchpoints}.
12374 @itemx $_probe_arg0@dots{}$_probe_arg11
12375 Arguments to a static probe. @xref{Static Probe Points}.
12378 @vindex $_sdata@r{, inspect, convenience variable}
12379 The variable @code{$_sdata} contains extra collected static tracepoint
12380 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12381 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12382 if extra static tracepoint data has not been collected.
12385 @vindex $_siginfo@r{, convenience variable}
12386 The variable @code{$_siginfo} contains extra signal information
12387 (@pxref{extra signal information}). Note that @code{$_siginfo}
12388 could be empty, if the application has not yet received any signals.
12389 For example, it will be empty before you execute the @code{run} command.
12392 @vindex $_tlb@r{, convenience variable}
12393 The variable @code{$_tlb} is automatically set when debugging
12394 applications running on MS-Windows in native mode or connected to
12395 gdbserver that supports the @code{qGetTIBAddr} request.
12396 @xref{General Query Packets}.
12397 This variable contains the address of the thread information block.
12400 The number of the current inferior. @xref{Inferiors Connections and
12401 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12404 The thread number of the current thread. @xref{thread numbers}.
12407 The global number of the current thread. @xref{global thread numbers}.
12411 @vindex $_gdb_major@r{, convenience variable}
12412 @vindex $_gdb_minor@r{, convenience variable}
12413 The major and minor version numbers of the running @value{GDBN}.
12414 Development snapshots and pretest versions have their minor version
12415 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12416 the value 12 for @code{$_gdb_minor}. These variables allow you to
12417 write scripts that work with different versions of @value{GDBN}
12418 without errors caused by features unavailable in some of those
12421 @item $_shell_exitcode
12422 @itemx $_shell_exitsignal
12423 @vindex $_shell_exitcode@r{, convenience variable}
12424 @vindex $_shell_exitsignal@r{, convenience variable}
12425 @cindex shell command, exit code
12426 @cindex shell command, exit signal
12427 @cindex exit status of shell commands
12428 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12429 shell commands. When a launched command terminates, @value{GDBN}
12430 automatically maintains the variables @code{$_shell_exitcode}
12431 and @code{$_shell_exitsignal} according to the exit status of the last
12432 launched command. These variables are set and used similarly to
12433 the variables @code{$_exitcode} and @code{$_exitsignal}.
12437 @node Convenience Funs
12438 @section Convenience Functions
12440 @cindex convenience functions
12441 @value{GDBN} also supplies some @dfn{convenience functions}. These
12442 have a syntax similar to convenience variables. A convenience
12443 function can be used in an expression just like an ordinary function;
12444 however, a convenience function is implemented internally to
12447 These functions do not require @value{GDBN} to be configured with
12448 @code{Python} support, which means that they are always available.
12452 @item $_isvoid (@var{expr})
12453 @findex $_isvoid@r{, convenience function}
12454 Return one if the expression @var{expr} is @code{void}. Otherwise it
12457 A @code{void} expression is an expression where the type of the result
12458 is @code{void}. For example, you can examine a convenience variable
12459 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12463 (@value{GDBP}) print $_exitcode
12465 (@value{GDBP}) print $_isvoid ($_exitcode)
12468 Starting program: ./a.out
12469 [Inferior 1 (process 29572) exited normally]
12470 (@value{GDBP}) print $_exitcode
12472 (@value{GDBP}) print $_isvoid ($_exitcode)
12476 In the example above, we used @code{$_isvoid} to check whether
12477 @code{$_exitcode} is @code{void} before and after the execution of the
12478 program being debugged. Before the execution there is no exit code to
12479 be examined, therefore @code{$_exitcode} is @code{void}. After the
12480 execution the program being debugged returned zero, therefore
12481 @code{$_exitcode} is zero, which means that it is not @code{void}
12484 The @code{void} expression can also be a call of a function from the
12485 program being debugged. For example, given the following function:
12494 The result of calling it inside @value{GDBN} is @code{void}:
12497 (@value{GDBP}) print foo ()
12499 (@value{GDBP}) print $_isvoid (foo ())
12501 (@value{GDBP}) set $v = foo ()
12502 (@value{GDBP}) print $v
12504 (@value{GDBP}) print $_isvoid ($v)
12508 @item $_gdb_setting_str (@var{setting})
12509 @findex $_gdb_setting_str@r{, convenience function}
12510 Return the value of the @value{GDBN} @var{setting} as a string.
12511 @var{setting} is any setting that can be used in a @code{set} or
12512 @code{show} command (@pxref{Controlling GDB}).
12515 (@value{GDBP}) show print frame-arguments
12516 Printing of non-scalar frame arguments is "scalars".
12517 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12519 (@value{GDBP}) p $_gdb_setting_str("height")
12524 @item $_gdb_setting (@var{setting})
12525 @findex $_gdb_setting@r{, convenience function}
12526 Return the value of the @value{GDBN} @var{setting}.
12527 The type of the returned value depends on the setting.
12529 The value type for boolean and auto boolean settings is @code{int}.
12530 The boolean values @code{off} and @code{on} are converted to
12531 the integer values @code{0} and @code{1}. The value @code{auto} is
12532 converted to the value @code{-1}.
12534 The value type for integer settings is either @code{unsigned int}
12535 or @code{int}, depending on the setting.
12537 Some integer settings accept an @code{unlimited} value.
12538 Depending on the setting, the @code{set} command also accepts
12539 the value @code{0} or the value @code{@minus{}1} as a synonym for
12541 For example, @code{set height unlimited} is equivalent to
12542 @code{set height 0}.
12544 Some other settings that accept the @code{unlimited} value
12545 use the value @code{0} to literally mean zero.
12546 For example, @code{set history size 0} indicates to not
12547 record any @value{GDBN} commands in the command history.
12548 For such settings, @code{@minus{}1} is the synonym
12549 for @code{unlimited}.
12551 See the documentation of the corresponding @code{set} command for
12552 the numerical value equivalent to @code{unlimited}.
12554 The @code{$_gdb_setting} function converts the unlimited value
12555 to a @code{0} or a @code{@minus{}1} value according to what the
12556 @code{set} command uses.
12560 (@value{GDBP}) p $_gdb_setting_str("height")
12562 (@value{GDBP}) p $_gdb_setting("height")
12564 (@value{GDBP}) set height unlimited
12565 (@value{GDBP}) p $_gdb_setting_str("height")
12567 (@value{GDBP}) p $_gdb_setting("height")
12571 (@value{GDBP}) p $_gdb_setting_str("history size")
12573 (@value{GDBP}) p $_gdb_setting("history size")
12575 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12577 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12583 Other setting types (enum, filename, optional filename, string, string noescape)
12584 are returned as string values.
12587 @item $_gdb_maint_setting_str (@var{setting})
12588 @findex $_gdb_maint_setting_str@r{, convenience function}
12589 Like the @code{$_gdb_setting_str} function, but works with
12590 @code{maintenance set} variables.
12592 @item $_gdb_maint_setting (@var{setting})
12593 @findex $_gdb_maint_setting@r{, convenience function}
12594 Like the @code{$_gdb_setting} function, but works with
12595 @code{maintenance set} variables.
12599 The following functions require @value{GDBN} to be configured with
12600 @code{Python} support.
12604 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12605 @findex $_memeq@r{, convenience function}
12606 Returns one if the @var{length} bytes at the addresses given by
12607 @var{buf1} and @var{buf2} are equal.
12608 Otherwise it returns zero.
12610 @item $_regex(@var{str}, @var{regex})
12611 @findex $_regex@r{, convenience function}
12612 Returns one if the string @var{str} matches the regular expression
12613 @var{regex}. Otherwise it returns zero.
12614 The syntax of the regular expression is that specified by @code{Python}'s
12615 regular expression support.
12617 @item $_streq(@var{str1}, @var{str2})
12618 @findex $_streq@r{, convenience function}
12619 Returns one if the strings @var{str1} and @var{str2} are equal.
12620 Otherwise it returns zero.
12622 @item $_strlen(@var{str})
12623 @findex $_strlen@r{, convenience function}
12624 Returns the length of string @var{str}.
12626 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12627 @findex $_caller_is@r{, convenience function}
12628 Returns one if the calling function's name is equal to @var{name}.
12629 Otherwise it returns zero.
12631 If the optional argument @var{number_of_frames} is provided,
12632 it is the number of frames up in the stack to look.
12640 at testsuite/gdb.python/py-caller-is.c:21
12641 #1 0x00000000004005a0 in middle_func ()
12642 at testsuite/gdb.python/py-caller-is.c:27
12643 #2 0x00000000004005ab in top_func ()
12644 at testsuite/gdb.python/py-caller-is.c:33
12645 #3 0x00000000004005b6 in main ()
12646 at testsuite/gdb.python/py-caller-is.c:39
12647 (gdb) print $_caller_is ("middle_func")
12649 (gdb) print $_caller_is ("top_func", 2)
12653 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12654 @findex $_caller_matches@r{, convenience function}
12655 Returns one if the calling function's name matches the regular expression
12656 @var{regexp}. Otherwise it returns zero.
12658 If the optional argument @var{number_of_frames} is provided,
12659 it is the number of frames up in the stack to look.
12662 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12663 @findex $_any_caller_is@r{, convenience function}
12664 Returns one if any calling function's name is equal to @var{name}.
12665 Otherwise it returns zero.
12667 If the optional argument @var{number_of_frames} is provided,
12668 it is the number of frames up in the stack to look.
12671 This function differs from @code{$_caller_is} in that this function
12672 checks all stack frames from the immediate caller to the frame specified
12673 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12674 frame specified by @var{number_of_frames}.
12676 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12677 @findex $_any_caller_matches@r{, convenience function}
12678 Returns one if any calling function's name matches the regular expression
12679 @var{regexp}. Otherwise it returns zero.
12681 If the optional argument @var{number_of_frames} is provided,
12682 it is the number of frames up in the stack to look.
12685 This function differs from @code{$_caller_matches} in that this function
12686 checks all stack frames from the immediate caller to the frame specified
12687 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12688 frame specified by @var{number_of_frames}.
12690 @item $_as_string(@var{value})
12691 @findex $_as_string@r{, convenience function}
12692 Return the string representation of @var{value}.
12694 This function is useful to obtain the textual label (enumerator) of an
12695 enumeration value. For example, assuming the variable @var{node} is of
12696 an enumerated type:
12699 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12700 Visiting node of type NODE_INTEGER
12703 @item $_cimag(@var{value})
12704 @itemx $_creal(@var{value})
12705 @findex $_cimag@r{, convenience function}
12706 @findex $_creal@r{, convenience function}
12707 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12708 the complex number @var{value}.
12710 The type of the imaginary or real part depends on the type of the
12711 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12712 will return an imaginary part of type @code{float}.
12716 @value{GDBN} provides the ability to list and get help on
12717 convenience functions.
12720 @item help function
12721 @kindex help function
12722 @cindex show all convenience functions
12723 Print a list of all convenience functions.
12730 You can refer to machine register contents, in expressions, as variables
12731 with names starting with @samp{$}. The names of registers are different
12732 for each machine; use @code{info registers} to see the names used on
12736 @kindex info registers
12737 @item info registers
12738 Print the names and values of all registers except floating-point
12739 and vector registers (in the selected stack frame).
12741 @kindex info all-registers
12742 @cindex floating point registers
12743 @item info all-registers
12744 Print the names and values of all registers, including floating-point
12745 and vector registers (in the selected stack frame).
12747 @anchor{info_registers_reggroup}
12748 @item info registers @var{reggroup} @dots{}
12749 Print the name and value of the registers in each of the specified
12750 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12751 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12753 @item info registers @var{regname} @dots{}
12754 Print the @dfn{relativized} value of each specified register @var{regname}.
12755 As discussed in detail below, register values are normally relative to
12756 the selected stack frame. The @var{regname} may be any register name valid on
12757 the machine you are using, with or without the initial @samp{$}.
12760 @anchor{standard registers}
12761 @cindex stack pointer register
12762 @cindex program counter register
12763 @cindex process status register
12764 @cindex frame pointer register
12765 @cindex standard registers
12766 @value{GDBN} has four ``standard'' register names that are available (in
12767 expressions) on most machines---whenever they do not conflict with an
12768 architecture's canonical mnemonics for registers. The register names
12769 @code{$pc} and @code{$sp} are used for the program counter register and
12770 the stack pointer. @code{$fp} is used for a register that contains a
12771 pointer to the current stack frame, and @code{$ps} is used for a
12772 register that contains the processor status. For example,
12773 you could print the program counter in hex with
12780 or print the instruction to be executed next with
12787 or add four to the stack pointer@footnote{This is a way of removing
12788 one word from the stack, on machines where stacks grow downward in
12789 memory (most machines, nowadays). This assumes that the innermost
12790 stack frame is selected; setting @code{$sp} is not allowed when other
12791 stack frames are selected. To pop entire frames off the stack,
12792 regardless of machine architecture, use @code{return};
12793 see @ref{Returning, ,Returning from a Function}.} with
12799 Whenever possible, these four standard register names are available on
12800 your machine even though the machine has different canonical mnemonics,
12801 so long as there is no conflict. The @code{info registers} command
12802 shows the canonical names. For example, on the SPARC, @code{info
12803 registers} displays the processor status register as @code{$psr} but you
12804 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12805 is an alias for the @sc{eflags} register.
12807 @value{GDBN} always considers the contents of an ordinary register as an
12808 integer when the register is examined in this way. Some machines have
12809 special registers which can hold nothing but floating point; these
12810 registers are considered to have floating point values. There is no way
12811 to refer to the contents of an ordinary register as floating point value
12812 (although you can @emph{print} it as a floating point value with
12813 @samp{print/f $@var{regname}}).
12815 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12816 means that the data format in which the register contents are saved by
12817 the operating system is not the same one that your program normally
12818 sees. For example, the registers of the 68881 floating point
12819 coprocessor are always saved in ``extended'' (raw) format, but all C
12820 programs expect to work with ``double'' (virtual) format. In such
12821 cases, @value{GDBN} normally works with the virtual format only (the format
12822 that makes sense for your program), but the @code{info registers} command
12823 prints the data in both formats.
12825 @cindex SSE registers (x86)
12826 @cindex MMX registers (x86)
12827 Some machines have special registers whose contents can be interpreted
12828 in several different ways. For example, modern x86-based machines
12829 have SSE and MMX registers that can hold several values packed
12830 together in several different formats. @value{GDBN} refers to such
12831 registers in @code{struct} notation:
12834 (@value{GDBP}) print $xmm1
12836 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12837 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12838 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12839 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12840 v4_int32 = @{0, 20657912, 11, 13@},
12841 v2_int64 = @{88725056443645952, 55834574859@},
12842 uint128 = 0x0000000d0000000b013b36f800000000
12847 To set values of such registers, you need to tell @value{GDBN} which
12848 view of the register you wish to change, as if you were assigning
12849 value to a @code{struct} member:
12852 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12855 Normally, register values are relative to the selected stack frame
12856 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12857 value that the register would contain if all stack frames farther in
12858 were exited and their saved registers restored. In order to see the
12859 true contents of hardware registers, you must select the innermost
12860 frame (with @samp{frame 0}).
12862 @cindex caller-saved registers
12863 @cindex call-clobbered registers
12864 @cindex volatile registers
12865 @cindex <not saved> values
12866 Usually ABIs reserve some registers as not needed to be saved by the
12867 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12868 registers). It may therefore not be possible for @value{GDBN} to know
12869 the value a register had before the call (in other words, in the outer
12870 frame), if the register value has since been changed by the callee.
12871 @value{GDBN} tries to deduce where the inner frame saved
12872 (``callee-saved'') registers, from the debug info, unwind info, or the
12873 machine code generated by your compiler. If some register is not
12874 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12875 its own knowledge of the ABI, or because the debug/unwind info
12876 explicitly says the register's value is undefined), @value{GDBN}
12877 displays @w{@samp{<not saved>}} as the register's value. With targets
12878 that @value{GDBN} has no knowledge of the register saving convention,
12879 if a register was not saved by the callee, then its value and location
12880 in the outer frame are assumed to be the same of the inner frame.
12881 This is usually harmless, because if the register is call-clobbered,
12882 the caller either does not care what is in the register after the
12883 call, or has code to restore the value that it does care about. Note,
12884 however, that if you change such a register in the outer frame, you
12885 may also be affecting the inner frame. Also, the more ``outer'' the
12886 frame is you're looking at, the more likely a call-clobbered
12887 register's value is to be wrong, in the sense that it doesn't actually
12888 represent the value the register had just before the call.
12890 @node Floating Point Hardware
12891 @section Floating Point Hardware
12892 @cindex floating point
12894 Depending on the configuration, @value{GDBN} may be able to give
12895 you more information about the status of the floating point hardware.
12900 Display hardware-dependent information about the floating
12901 point unit. The exact contents and layout vary depending on the
12902 floating point chip. Currently, @samp{info float} is supported on
12903 the ARM and x86 machines.
12907 @section Vector Unit
12908 @cindex vector unit
12910 Depending on the configuration, @value{GDBN} may be able to give you
12911 more information about the status of the vector unit.
12914 @kindex info vector
12916 Display information about the vector unit. The exact contents and
12917 layout vary depending on the hardware.
12920 @node OS Information
12921 @section Operating System Auxiliary Information
12922 @cindex OS information
12924 @value{GDBN} provides interfaces to useful OS facilities that can help
12925 you debug your program.
12927 @cindex auxiliary vector
12928 @cindex vector, auxiliary
12929 Some operating systems supply an @dfn{auxiliary vector} to programs at
12930 startup. This is akin to the arguments and environment that you
12931 specify for a program, but contains a system-dependent variety of
12932 binary values that tell system libraries important details about the
12933 hardware, operating system, and process. Each value's purpose is
12934 identified by an integer tag; the meanings are well-known but system-specific.
12935 Depending on the configuration and operating system facilities,
12936 @value{GDBN} may be able to show you this information. For remote
12937 targets, this functionality may further depend on the remote stub's
12938 support of the @samp{qXfer:auxv:read} packet, see
12939 @ref{qXfer auxiliary vector read}.
12944 Display the auxiliary vector of the inferior, which can be either a
12945 live process or a core dump file. @value{GDBN} prints each tag value
12946 numerically, and also shows names and text descriptions for recognized
12947 tags. Some values in the vector are numbers, some bit masks, and some
12948 pointers to strings or other data. @value{GDBN} displays each value in the
12949 most appropriate form for a recognized tag, and in hexadecimal for
12950 an unrecognized tag.
12953 On some targets, @value{GDBN} can access operating system-specific
12954 information and show it to you. The types of information available
12955 will differ depending on the type of operating system running on the
12956 target. The mechanism used to fetch the data is described in
12957 @ref{Operating System Information}. For remote targets, this
12958 functionality depends on the remote stub's support of the
12959 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12963 @item info os @var{infotype}
12965 Display OS information of the requested type.
12967 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12969 @anchor{linux info os infotypes}
12971 @kindex info os cpus
12973 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12974 the available fields from /proc/cpuinfo. For each supported architecture
12975 different fields are available. Two common entries are processor which gives
12976 CPU number and bogomips; a system constant that is calculated during
12977 kernel initialization.
12979 @kindex info os files
12981 Display the list of open file descriptors on the target. For each
12982 file descriptor, @value{GDBN} prints the identifier of the process
12983 owning the descriptor, the command of the owning process, the value
12984 of the descriptor, and the target of the descriptor.
12986 @kindex info os modules
12988 Display the list of all loaded kernel modules on the target. For each
12989 module, @value{GDBN} prints the module name, the size of the module in
12990 bytes, the number of times the module is used, the dependencies of the
12991 module, the status of the module, and the address of the loaded module
12994 @kindex info os msg
12996 Display the list of all System V message queues on the target. For each
12997 message queue, @value{GDBN} prints the message queue key, the message
12998 queue identifier, the access permissions, the current number of bytes
12999 on the queue, the current number of messages on the queue, the processes
13000 that last sent and received a message on the queue, the user and group
13001 of the owner and creator of the message queue, the times at which a
13002 message was last sent and received on the queue, and the time at which
13003 the message queue was last changed.
13005 @kindex info os processes
13007 Display the list of processes on the target. For each process,
13008 @value{GDBN} prints the process identifier, the name of the user, the
13009 command corresponding to the process, and the list of processor cores
13010 that the process is currently running on. (To understand what these
13011 properties mean, for this and the following info types, please consult
13012 the general @sc{gnu}/Linux documentation.)
13014 @kindex info os procgroups
13016 Display the list of process groups on the target. For each process,
13017 @value{GDBN} prints the identifier of the process group that it belongs
13018 to, the command corresponding to the process group leader, the process
13019 identifier, and the command line of the process. The list is sorted
13020 first by the process group identifier, then by the process identifier,
13021 so that processes belonging to the same process group are grouped together
13022 and the process group leader is listed first.
13024 @kindex info os semaphores
13026 Display the list of all System V semaphore sets on the target. For each
13027 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13028 set identifier, the access permissions, the number of semaphores in the
13029 set, the user and group of the owner and creator of the semaphore set,
13030 and the times at which the semaphore set was operated upon and changed.
13032 @kindex info os shm
13034 Display the list of all System V shared-memory regions on the target.
13035 For each shared-memory region, @value{GDBN} prints the region key,
13036 the shared-memory identifier, the access permissions, the size of the
13037 region, the process that created the region, the process that last
13038 attached to or detached from the region, the current number of live
13039 attaches to the region, and the times at which the region was last
13040 attached to, detach from, and changed.
13042 @kindex info os sockets
13044 Display the list of Internet-domain sockets on the target. For each
13045 socket, @value{GDBN} prints the address and port of the local and
13046 remote endpoints, the current state of the connection, the creator of
13047 the socket, the IP address family of the socket, and the type of the
13050 @kindex info os threads
13052 Display the list of threads running on the target. For each thread,
13053 @value{GDBN} prints the identifier of the process that the thread
13054 belongs to, the command of the process, the thread identifier, and the
13055 processor core that it is currently running on. The main thread of a
13056 process is not listed.
13060 If @var{infotype} is omitted, then list the possible values for
13061 @var{infotype} and the kind of OS information available for each
13062 @var{infotype}. If the target does not return a list of possible
13063 types, this command will report an error.
13066 @node Memory Region Attributes
13067 @section Memory Region Attributes
13068 @cindex memory region attributes
13070 @dfn{Memory region attributes} allow you to describe special handling
13071 required by regions of your target's memory. @value{GDBN} uses
13072 attributes to determine whether to allow certain types of memory
13073 accesses; whether to use specific width accesses; and whether to cache
13074 target memory. By default the description of memory regions is
13075 fetched from the target (if the current target supports this), but the
13076 user can override the fetched regions.
13078 Defined memory regions can be individually enabled and disabled. When a
13079 memory region is disabled, @value{GDBN} uses the default attributes when
13080 accessing memory in that region. Similarly, if no memory regions have
13081 been defined, @value{GDBN} uses the default attributes when accessing
13084 When a memory region is defined, it is given a number to identify it;
13085 to enable, disable, or remove a memory region, you specify that number.
13089 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13090 Define a memory region bounded by @var{lower} and @var{upper} with
13091 attributes @var{attributes}@dots{}, and add it to the list of regions
13092 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13093 case: it is treated as the target's maximum memory address.
13094 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13097 Discard any user changes to the memory regions and use target-supplied
13098 regions, if available, or no regions if the target does not support.
13101 @item delete mem @var{nums}@dots{}
13102 Remove memory regions @var{nums}@dots{} from the list of regions
13103 monitored by @value{GDBN}.
13105 @kindex disable mem
13106 @item disable mem @var{nums}@dots{}
13107 Disable monitoring of memory regions @var{nums}@dots{}.
13108 A disabled memory region is not forgotten.
13109 It may be enabled again later.
13112 @item enable mem @var{nums}@dots{}
13113 Enable monitoring of memory regions @var{nums}@dots{}.
13117 Print a table of all defined memory regions, with the following columns
13121 @item Memory Region Number
13122 @item Enabled or Disabled.
13123 Enabled memory regions are marked with @samp{y}.
13124 Disabled memory regions are marked with @samp{n}.
13127 The address defining the inclusive lower bound of the memory region.
13130 The address defining the exclusive upper bound of the memory region.
13133 The list of attributes set for this memory region.
13138 @subsection Attributes
13140 @subsubsection Memory Access Mode
13141 The access mode attributes set whether @value{GDBN} may make read or
13142 write accesses to a memory region.
13144 While these attributes prevent @value{GDBN} from performing invalid
13145 memory accesses, they do nothing to prevent the target system, I/O DMA,
13146 etc.@: from accessing memory.
13150 Memory is read only.
13152 Memory is write only.
13154 Memory is read/write. This is the default.
13157 @subsubsection Memory Access Size
13158 The access size attribute tells @value{GDBN} to use specific sized
13159 accesses in the memory region. Often memory mapped device registers
13160 require specific sized accesses. If no access size attribute is
13161 specified, @value{GDBN} may use accesses of any size.
13165 Use 8 bit memory accesses.
13167 Use 16 bit memory accesses.
13169 Use 32 bit memory accesses.
13171 Use 64 bit memory accesses.
13174 @c @subsubsection Hardware/Software Breakpoints
13175 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13176 @c will use hardware or software breakpoints for the internal breakpoints
13177 @c used by the step, next, finish, until, etc. commands.
13181 @c Always use hardware breakpoints
13182 @c @item swbreak (default)
13185 @subsubsection Data Cache
13186 The data cache attributes set whether @value{GDBN} will cache target
13187 memory. While this generally improves performance by reducing debug
13188 protocol overhead, it can lead to incorrect results because @value{GDBN}
13189 does not know about volatile variables or memory mapped device
13194 Enable @value{GDBN} to cache target memory.
13196 Disable @value{GDBN} from caching target memory. This is the default.
13199 @subsection Memory Access Checking
13200 @value{GDBN} can be instructed to refuse accesses to memory that is
13201 not explicitly described. This can be useful if accessing such
13202 regions has undesired effects for a specific target, or to provide
13203 better error checking. The following commands control this behaviour.
13206 @kindex set mem inaccessible-by-default
13207 @item set mem inaccessible-by-default [on|off]
13208 If @code{on} is specified, make @value{GDBN} treat memory not
13209 explicitly described by the memory ranges as non-existent and refuse accesses
13210 to such memory. The checks are only performed if there's at least one
13211 memory range defined. If @code{off} is specified, make @value{GDBN}
13212 treat the memory not explicitly described by the memory ranges as RAM.
13213 The default value is @code{on}.
13214 @kindex show mem inaccessible-by-default
13215 @item show mem inaccessible-by-default
13216 Show the current handling of accesses to unknown memory.
13220 @c @subsubsection Memory Write Verification
13221 @c The memory write verification attributes set whether @value{GDBN}
13222 @c will re-reads data after each write to verify the write was successful.
13226 @c @item noverify (default)
13229 @node Dump/Restore Files
13230 @section Copy Between Memory and a File
13231 @cindex dump/restore files
13232 @cindex append data to a file
13233 @cindex dump data to a file
13234 @cindex restore data from a file
13236 You can use the commands @code{dump}, @code{append}, and
13237 @code{restore} to copy data between target memory and a file. The
13238 @code{dump} and @code{append} commands write data to a file, and the
13239 @code{restore} command reads data from a file back into the inferior's
13240 memory. Files may be in binary, Motorola S-record, Intel hex,
13241 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13242 append to binary files, and cannot read from Verilog Hex files.
13247 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13248 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13249 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13250 or the value of @var{expr}, to @var{filename} in the given format.
13252 The @var{format} parameter may be any one of:
13259 Motorola S-record format.
13261 Tektronix Hex format.
13263 Verilog Hex format.
13266 @value{GDBN} uses the same definitions of these formats as the
13267 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13268 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13272 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13273 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13274 Append the contents of memory from @var{start_addr} to @var{end_addr},
13275 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13276 (@value{GDBN} can only append data to files in raw binary form.)
13279 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13280 Restore the contents of file @var{filename} into memory. The
13281 @code{restore} command can automatically recognize any known @sc{bfd}
13282 file format, except for raw binary. To restore a raw binary file you
13283 must specify the optional keyword @code{binary} after the filename.
13285 If @var{bias} is non-zero, its value will be added to the addresses
13286 contained in the file. Binary files always start at address zero, so
13287 they will be restored at address @var{bias}. Other bfd files have
13288 a built-in location; they will be restored at offset @var{bias}
13289 from that location.
13291 If @var{start} and/or @var{end} are non-zero, then only data between
13292 file offset @var{start} and file offset @var{end} will be restored.
13293 These offsets are relative to the addresses in the file, before
13294 the @var{bias} argument is applied.
13298 @node Core File Generation
13299 @section How to Produce a Core File from Your Program
13300 @cindex dump core from inferior
13302 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13303 image of a running process and its process status (register values
13304 etc.). Its primary use is post-mortem debugging of a program that
13305 crashed while it ran outside a debugger. A program that crashes
13306 automatically produces a core file, unless this feature is disabled by
13307 the user. @xref{Files}, for information on invoking @value{GDBN} in
13308 the post-mortem debugging mode.
13310 Occasionally, you may wish to produce a core file of the program you
13311 are debugging in order to preserve a snapshot of its state.
13312 @value{GDBN} has a special command for that.
13316 @kindex generate-core-file
13317 @item generate-core-file [@var{file}]
13318 @itemx gcore [@var{file}]
13319 Produce a core dump of the inferior process. The optional argument
13320 @var{file} specifies the file name where to put the core dump. If not
13321 specified, the file name defaults to @file{core.@var{pid}}, where
13322 @var{pid} is the inferior process ID.
13324 Note that this command is implemented only for some systems (as of
13325 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13327 On @sc{gnu}/Linux, this command can take into account the value of the
13328 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13329 dump (@pxref{set use-coredump-filter}), and by default honors the
13330 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13331 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13333 @kindex set use-coredump-filter
13334 @anchor{set use-coredump-filter}
13335 @item set use-coredump-filter on
13336 @itemx set use-coredump-filter off
13337 Enable or disable the use of the file
13338 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13339 files. This file is used by the Linux kernel to decide what types of
13340 memory mappings will be dumped or ignored when generating a core dump
13341 file. @var{pid} is the process ID of a currently running process.
13343 To make use of this feature, you have to write in the
13344 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13345 which is a bit mask representing the memory mapping types. If a bit
13346 is set in the bit mask, then the memory mappings of the corresponding
13347 types will be dumped; otherwise, they will be ignored. This
13348 configuration is inherited by child processes. For more information
13349 about the bits that can be set in the
13350 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13351 manpage of @code{core(5)}.
13353 By default, this option is @code{on}. If this option is turned
13354 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13355 and instead uses the same default value as the Linux kernel in order
13356 to decide which pages will be dumped in the core dump file. This
13357 value is currently @code{0x33}, which means that bits @code{0}
13358 (anonymous private mappings), @code{1} (anonymous shared mappings),
13359 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13360 This will cause these memory mappings to be dumped automatically.
13362 @kindex set dump-excluded-mappings
13363 @anchor{set dump-excluded-mappings}
13364 @item set dump-excluded-mappings on
13365 @itemx set dump-excluded-mappings off
13366 If @code{on} is specified, @value{GDBN} will dump memory mappings
13367 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13368 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13370 The default value is @code{off}.
13373 @node Character Sets
13374 @section Character Sets
13375 @cindex character sets
13377 @cindex translating between character sets
13378 @cindex host character set
13379 @cindex target character set
13381 If the program you are debugging uses a different character set to
13382 represent characters and strings than the one @value{GDBN} uses itself,
13383 @value{GDBN} can automatically translate between the character sets for
13384 you. The character set @value{GDBN} uses we call the @dfn{host
13385 character set}; the one the inferior program uses we call the
13386 @dfn{target character set}.
13388 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13389 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13390 remote protocol (@pxref{Remote Debugging}) to debug a program
13391 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13392 then the host character set is Latin-1, and the target character set is
13393 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13394 target-charset EBCDIC-US}, then @value{GDBN} translates between
13395 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13396 character and string literals in expressions.
13398 @value{GDBN} has no way to automatically recognize which character set
13399 the inferior program uses; you must tell it, using the @code{set
13400 target-charset} command, described below.
13402 Here are the commands for controlling @value{GDBN}'s character set
13406 @item set target-charset @var{charset}
13407 @kindex set target-charset
13408 Set the current target character set to @var{charset}. To display the
13409 list of supported target character sets, type
13410 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13412 @item set host-charset @var{charset}
13413 @kindex set host-charset
13414 Set the current host character set to @var{charset}.
13416 By default, @value{GDBN} uses a host character set appropriate to the
13417 system it is running on; you can override that default using the
13418 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13419 automatically determine the appropriate host character set. In this
13420 case, @value{GDBN} uses @samp{UTF-8}.
13422 @value{GDBN} can only use certain character sets as its host character
13423 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13424 @value{GDBN} will list the host character sets it supports.
13426 @item set charset @var{charset}
13427 @kindex set charset
13428 Set the current host and target character sets to @var{charset}. As
13429 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13430 @value{GDBN} will list the names of the character sets that can be used
13431 for both host and target.
13434 @kindex show charset
13435 Show the names of the current host and target character sets.
13437 @item show host-charset
13438 @kindex show host-charset
13439 Show the name of the current host character set.
13441 @item show target-charset
13442 @kindex show target-charset
13443 Show the name of the current target character set.
13445 @item set target-wide-charset @var{charset}
13446 @kindex set target-wide-charset
13447 Set the current target's wide character set to @var{charset}. This is
13448 the character set used by the target's @code{wchar_t} type. To
13449 display the list of supported wide character sets, type
13450 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13452 @item show target-wide-charset
13453 @kindex show target-wide-charset
13454 Show the name of the current target's wide character set.
13457 Here is an example of @value{GDBN}'s character set support in action.
13458 Assume that the following source code has been placed in the file
13459 @file{charset-test.c}:
13465 = @{72, 101, 108, 108, 111, 44, 32, 119,
13466 111, 114, 108, 100, 33, 10, 0@};
13467 char ibm1047_hello[]
13468 = @{200, 133, 147, 147, 150, 107, 64, 166,
13469 150, 153, 147, 132, 90, 37, 0@};
13473 printf ("Hello, world!\n");
13477 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13478 containing the string @samp{Hello, world!} followed by a newline,
13479 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13481 We compile the program, and invoke the debugger on it:
13484 $ gcc -g charset-test.c -o charset-test
13485 $ gdb -nw charset-test
13486 GNU gdb 2001-12-19-cvs
13487 Copyright 2001 Free Software Foundation, Inc.
13492 We can use the @code{show charset} command to see what character sets
13493 @value{GDBN} is currently using to interpret and display characters and
13497 (@value{GDBP}) show charset
13498 The current host and target character set is `ISO-8859-1'.
13502 For the sake of printing this manual, let's use @sc{ascii} as our
13503 initial character set:
13505 (@value{GDBP}) set charset ASCII
13506 (@value{GDBP}) show charset
13507 The current host and target character set is `ASCII'.
13511 Let's assume that @sc{ascii} is indeed the correct character set for our
13512 host system --- in other words, let's assume that if @value{GDBN} prints
13513 characters using the @sc{ascii} character set, our terminal will display
13514 them properly. Since our current target character set is also
13515 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13518 (@value{GDBP}) print ascii_hello
13519 $1 = 0x401698 "Hello, world!\n"
13520 (@value{GDBP}) print ascii_hello[0]
13525 @value{GDBN} uses the target character set for character and string
13526 literals you use in expressions:
13529 (@value{GDBP}) print '+'
13534 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13537 @value{GDBN} relies on the user to tell it which character set the
13538 target program uses. If we print @code{ibm1047_hello} while our target
13539 character set is still @sc{ascii}, we get jibberish:
13542 (@value{GDBP}) print ibm1047_hello
13543 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13544 (@value{GDBP}) print ibm1047_hello[0]
13549 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13550 @value{GDBN} tells us the character sets it supports:
13553 (@value{GDBP}) set target-charset
13554 ASCII EBCDIC-US IBM1047 ISO-8859-1
13555 (@value{GDBP}) set target-charset
13558 We can select @sc{ibm1047} as our target character set, and examine the
13559 program's strings again. Now the @sc{ascii} string is wrong, but
13560 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13561 target character set, @sc{ibm1047}, to the host character set,
13562 @sc{ascii}, and they display correctly:
13565 (@value{GDBP}) set target-charset IBM1047
13566 (@value{GDBP}) show charset
13567 The current host character set is `ASCII'.
13568 The current target character set is `IBM1047'.
13569 (@value{GDBP}) print ascii_hello
13570 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13571 (@value{GDBP}) print ascii_hello[0]
13573 (@value{GDBP}) print ibm1047_hello
13574 $8 = 0x4016a8 "Hello, world!\n"
13575 (@value{GDBP}) print ibm1047_hello[0]
13580 As above, @value{GDBN} uses the target character set for character and
13581 string literals you use in expressions:
13584 (@value{GDBP}) print '+'
13589 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13592 @node Caching Target Data
13593 @section Caching Data of Targets
13594 @cindex caching data of targets
13596 @value{GDBN} caches data exchanged between the debugger and a target.
13597 Each cache is associated with the address space of the inferior.
13598 @xref{Inferiors Connections and Programs}, about inferior and address space.
13599 Such caching generally improves performance in remote debugging
13600 (@pxref{Remote Debugging}), because it reduces the overhead of the
13601 remote protocol by bundling memory reads and writes into large chunks.
13602 Unfortunately, simply caching everything would lead to incorrect results,
13603 since @value{GDBN} does not necessarily know anything about volatile
13604 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13605 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13607 Therefore, by default, @value{GDBN} only caches data
13608 known to be on the stack@footnote{In non-stop mode, it is moderately
13609 rare for a running thread to modify the stack of a stopped thread
13610 in a way that would interfere with a backtrace, and caching of
13611 stack reads provides a significant speed up of remote backtraces.} or
13612 in the code segment.
13613 Other regions of memory can be explicitly marked as
13614 cacheable; @pxref{Memory Region Attributes}.
13617 @kindex set remotecache
13618 @item set remotecache on
13619 @itemx set remotecache off
13620 This option no longer does anything; it exists for compatibility
13623 @kindex show remotecache
13624 @item show remotecache
13625 Show the current state of the obsolete remotecache flag.
13627 @kindex set stack-cache
13628 @item set stack-cache on
13629 @itemx set stack-cache off
13630 Enable or disable caching of stack accesses. When @code{on}, use
13631 caching. By default, this option is @code{on}.
13633 @kindex show stack-cache
13634 @item show stack-cache
13635 Show the current state of data caching for memory accesses.
13637 @kindex set code-cache
13638 @item set code-cache on
13639 @itemx set code-cache off
13640 Enable or disable caching of code segment accesses. When @code{on},
13641 use caching. By default, this option is @code{on}. This improves
13642 performance of disassembly in remote debugging.
13644 @kindex show code-cache
13645 @item show code-cache
13646 Show the current state of target memory cache for code segment
13649 @kindex info dcache
13650 @item info dcache @r{[}line@r{]}
13651 Print the information about the performance of data cache of the
13652 current inferior's address space. The information displayed
13653 includes the dcache width and depth, and for each cache line, its
13654 number, address, and how many times it was referenced. This
13655 command is useful for debugging the data cache operation.
13657 If a line number is specified, the contents of that line will be
13660 @item set dcache size @var{size}
13661 @cindex dcache size
13662 @kindex set dcache size
13663 Set maximum number of entries in dcache (dcache depth above).
13665 @item set dcache line-size @var{line-size}
13666 @cindex dcache line-size
13667 @kindex set dcache line-size
13668 Set number of bytes each dcache entry caches (dcache width above).
13669 Must be a power of 2.
13671 @item show dcache size
13672 @kindex show dcache size
13673 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13675 @item show dcache line-size
13676 @kindex show dcache line-size
13677 Show default size of dcache lines.
13679 @item maint flush dcache
13680 @cindex dcache, flushing
13681 @kindex maint flush dcache
13682 Flush the contents (if any) of the dcache. This maintainer command is
13683 useful when debugging the dcache implementation.
13687 @node Searching Memory
13688 @section Search Memory
13689 @cindex searching memory
13691 Memory can be searched for a particular sequence of bytes with the
13692 @code{find} command.
13696 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13697 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13698 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13699 etc. The search begins at address @var{start_addr} and continues for either
13700 @var{len} bytes or through to @var{end_addr} inclusive.
13703 @var{s} and @var{n} are optional parameters.
13704 They may be specified in either order, apart or together.
13707 @item @var{s}, search query size
13708 The size of each search query value.
13714 halfwords (two bytes)
13718 giant words (eight bytes)
13721 All values are interpreted in the current language.
13722 This means, for example, that if the current source language is C/C@t{++}
13723 then searching for the string ``hello'' includes the trailing '\0'.
13724 The null terminator can be removed from searching by using casts,
13725 e.g.: @samp{@{char[5]@}"hello"}.
13727 If the value size is not specified, it is taken from the
13728 value's type in the current language.
13729 This is useful when one wants to specify the search
13730 pattern as a mixture of types.
13731 Note that this means, for example, that in the case of C-like languages
13732 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13733 which is typically four bytes.
13735 @item @var{n}, maximum number of finds
13736 The maximum number of matches to print. The default is to print all finds.
13739 You can use strings as search values. Quote them with double-quotes
13741 The string value is copied into the search pattern byte by byte,
13742 regardless of the endianness of the target and the size specification.
13744 The address of each match found is printed as well as a count of the
13745 number of matches found.
13747 The address of the last value found is stored in convenience variable
13749 A count of the number of matches is stored in @samp{$numfound}.
13751 For example, if stopped at the @code{printf} in this function:
13757 static char hello[] = "hello-hello";
13758 static struct @{ char c; short s; int i; @}
13759 __attribute__ ((packed)) mixed
13760 = @{ 'c', 0x1234, 0x87654321 @};
13761 printf ("%s\n", hello);
13766 you get during debugging:
13769 (gdb) find &hello[0], +sizeof(hello), "hello"
13770 0x804956d <hello.1620+6>
13772 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13773 0x8049567 <hello.1620>
13774 0x804956d <hello.1620+6>
13776 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13777 0x8049567 <hello.1620>
13778 0x804956d <hello.1620+6>
13780 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13781 0x8049567 <hello.1620>
13783 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13784 0x8049560 <mixed.1625>
13786 (gdb) print $numfound
13789 $2 = (void *) 0x8049560
13793 @section Value Sizes
13795 Whenever @value{GDBN} prints a value memory will be allocated within
13796 @value{GDBN} to hold the contents of the value. It is possible in
13797 some languages with dynamic typing systems, that an invalid program
13798 may indicate a value that is incorrectly large, this in turn may cause
13799 @value{GDBN} to try and allocate an overly large amount of memory.
13802 @kindex set max-value-size
13803 @item set max-value-size @var{bytes}
13804 @itemx set max-value-size unlimited
13805 Set the maximum size of memory that @value{GDBN} will allocate for the
13806 contents of a value to @var{bytes}, trying to display a value that
13807 requires more memory than that will result in an error.
13809 Setting this variable does not effect values that have already been
13810 allocated within @value{GDBN}, only future allocations.
13812 There's a minimum size that @code{max-value-size} can be set to in
13813 order that @value{GDBN} can still operate correctly, this minimum is
13814 currently 16 bytes.
13816 The limit applies to the results of some subexpressions as well as to
13817 complete expressions. For example, an expression denoting a simple
13818 integer component, such as @code{x.y.z}, may fail if the size of
13819 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13820 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13821 @var{A} is an array variable with non-constant size, will generally
13822 succeed regardless of the bounds on @var{A}, as long as the component
13823 size is less than @var{bytes}.
13825 The default value of @code{max-value-size} is currently 64k.
13827 @kindex show max-value-size
13828 @item show max-value-size
13829 Show the maximum size of memory, in bytes, that @value{GDBN} will
13830 allocate for the contents of a value.
13833 @node Optimized Code
13834 @chapter Debugging Optimized Code
13835 @cindex optimized code, debugging
13836 @cindex debugging optimized code
13838 Almost all compilers support optimization. With optimization
13839 disabled, the compiler generates assembly code that corresponds
13840 directly to your source code, in a simplistic way. As the compiler
13841 applies more powerful optimizations, the generated assembly code
13842 diverges from your original source code. With help from debugging
13843 information generated by the compiler, @value{GDBN} can map from
13844 the running program back to constructs from your original source.
13846 @value{GDBN} is more accurate with optimization disabled. If you
13847 can recompile without optimization, it is easier to follow the
13848 progress of your program during debugging. But, there are many cases
13849 where you may need to debug an optimized version.
13851 When you debug a program compiled with @samp{-g -O}, remember that the
13852 optimizer has rearranged your code; the debugger shows you what is
13853 really there. Do not be too surprised when the execution path does not
13854 exactly match your source file! An extreme example: if you define a
13855 variable, but never use it, @value{GDBN} never sees that
13856 variable---because the compiler optimizes it out of existence.
13858 Some things do not work as well with @samp{-g -O} as with just
13859 @samp{-g}, particularly on machines with instruction scheduling. If in
13860 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13861 please report it to us as a bug (including a test case!).
13862 @xref{Variables}, for more information about debugging optimized code.
13865 * Inline Functions:: How @value{GDBN} presents inlining
13866 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13869 @node Inline Functions
13870 @section Inline Functions
13871 @cindex inline functions, debugging
13873 @dfn{Inlining} is an optimization that inserts a copy of the function
13874 body directly at each call site, instead of jumping to a shared
13875 routine. @value{GDBN} displays inlined functions just like
13876 non-inlined functions. They appear in backtraces. You can view their
13877 arguments and local variables, step into them with @code{step}, skip
13878 them with @code{next}, and escape from them with @code{finish}.
13879 You can check whether a function was inlined by using the
13880 @code{info frame} command.
13882 For @value{GDBN} to support inlined functions, the compiler must
13883 record information about inlining in the debug information ---
13884 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13885 other compilers do also. @value{GDBN} only supports inlined functions
13886 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13887 do not emit two required attributes (@samp{DW_AT_call_file} and
13888 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13889 function calls with earlier versions of @value{NGCC}. It instead
13890 displays the arguments and local variables of inlined functions as
13891 local variables in the caller.
13893 The body of an inlined function is directly included at its call site;
13894 unlike a non-inlined function, there are no instructions devoted to
13895 the call. @value{GDBN} still pretends that the call site and the
13896 start of the inlined function are different instructions. Stepping to
13897 the call site shows the call site, and then stepping again shows
13898 the first line of the inlined function, even though no additional
13899 instructions are executed.
13901 This makes source-level debugging much clearer; you can see both the
13902 context of the call and then the effect of the call. Only stepping by
13903 a single instruction using @code{stepi} or @code{nexti} does not do
13904 this; single instruction steps always show the inlined body.
13906 There are some ways that @value{GDBN} does not pretend that inlined
13907 function calls are the same as normal calls:
13911 Setting breakpoints at the call site of an inlined function may not
13912 work, because the call site does not contain any code. @value{GDBN}
13913 may incorrectly move the breakpoint to the next line of the enclosing
13914 function, after the call. This limitation will be removed in a future
13915 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13916 or inside the inlined function instead.
13919 @value{GDBN} cannot locate the return value of inlined calls after
13920 using the @code{finish} command. This is a limitation of compiler-generated
13921 debugging information; after @code{finish}, you can step to the next line
13922 and print a variable where your program stored the return value.
13926 @node Tail Call Frames
13927 @section Tail Call Frames
13928 @cindex tail call frames, debugging
13930 Function @code{B} can call function @code{C} in its very last statement. In
13931 unoptimized compilation the call of @code{C} is immediately followed by return
13932 instruction at the end of @code{B} code. Optimizing compiler may replace the
13933 call and return in function @code{B} into one jump to function @code{C}
13934 instead. Such use of a jump instruction is called @dfn{tail call}.
13936 During execution of function @code{C}, there will be no indication in the
13937 function call stack frames that it was tail-called from @code{B}. If function
13938 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13939 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13940 some cases @value{GDBN} can determine that @code{C} was tail-called from
13941 @code{B}, and it will then create fictitious call frame for that, with the
13942 return address set up as if @code{B} called @code{C} normally.
13944 This functionality is currently supported only by DWARF 2 debugging format and
13945 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13946 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13949 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13950 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13954 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13956 Stack level 1, frame at 0x7fffffffda30:
13957 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13958 tail call frame, caller of frame at 0x7fffffffda30
13959 source language c++.
13960 Arglist at unknown address.
13961 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13964 The detection of all the possible code path executions can find them ambiguous.
13965 There is no execution history stored (possible @ref{Reverse Execution} is never
13966 used for this purpose) and the last known caller could have reached the known
13967 callee by multiple different jump sequences. In such case @value{GDBN} still
13968 tries to show at least all the unambiguous top tail callers and all the
13969 unambiguous bottom tail calees, if any.
13972 @anchor{set debug entry-values}
13973 @item set debug entry-values
13974 @kindex set debug entry-values
13975 When set to on, enables printing of analysis messages for both frame argument
13976 values at function entry and tail calls. It will show all the possible valid
13977 tail calls code paths it has considered. It will also print the intersection
13978 of them with the final unambiguous (possibly partial or even empty) code path
13981 @item show debug entry-values
13982 @kindex show debug entry-values
13983 Show the current state of analysis messages printing for both frame argument
13984 values at function entry and tail calls.
13987 The analysis messages for tail calls can for example show why the virtual tail
13988 call frame for function @code{c} has not been recognized (due to the indirect
13989 reference by variable @code{x}):
13992 static void __attribute__((noinline, noclone)) c (void);
13993 void (*x) (void) = c;
13994 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13995 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13996 int main (void) @{ x (); return 0; @}
13998 Breakpoint 1, DW_OP_entry_value resolving cannot find
13999 DW_TAG_call_site 0x40039a in main
14001 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14004 #1 0x000000000040039a in main () at t.c:5
14007 Another possibility is an ambiguous virtual tail call frames resolution:
14011 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14012 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14013 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14014 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14015 static void __attribute__((noinline, noclone)) b (void)
14016 @{ if (i) c (); else e (); @}
14017 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14018 int main (void) @{ a (); return 0; @}
14020 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14021 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14022 tailcall: reduced: 0x4004d2(a) |
14025 #1 0x00000000004004d2 in a () at t.c:8
14026 #2 0x0000000000400395 in main () at t.c:9
14029 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14030 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14032 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14033 @ifset HAVE_MAKEINFO_CLICK
14034 @set ARROW @click{}
14035 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14036 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14038 @ifclear HAVE_MAKEINFO_CLICK
14040 @set CALLSEQ1B @value{CALLSEQ1A}
14041 @set CALLSEQ2B @value{CALLSEQ2A}
14044 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14045 The code can have possible execution paths @value{CALLSEQ1B} or
14046 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14048 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14049 has found. It then finds another possible calling sequence - that one is
14050 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14051 printed as the @code{reduced:} calling sequence. That one could have many
14052 further @code{compare:} and @code{reduced:} statements as long as there remain
14053 any non-ambiguous sequence entries.
14055 For the frame of function @code{b} in both cases there are different possible
14056 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14057 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14058 therefore this one is displayed to the user while the ambiguous frames are
14061 There can be also reasons why printing of frame argument values at function
14066 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14067 static void __attribute__((noinline, noclone)) a (int i);
14068 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14069 static void __attribute__((noinline, noclone)) a (int i)
14070 @{ if (i) b (i - 1); else c (0); @}
14071 int main (void) @{ a (5); return 0; @}
14074 #0 c (i=i@@entry=0) at t.c:2
14075 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14076 function "a" at 0x400420 can call itself via tail calls
14077 i=<optimized out>) at t.c:6
14078 #2 0x000000000040036e in main () at t.c:7
14081 @value{GDBN} cannot find out from the inferior state if and how many times did
14082 function @code{a} call itself (via function @code{b}) as these calls would be
14083 tail calls. Such tail calls would modify the @code{i} variable, therefore
14084 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14085 prints @code{<optimized out>} instead.
14088 @chapter C Preprocessor Macros
14090 Some languages, such as C and C@t{++}, provide a way to define and invoke
14091 ``preprocessor macros'' which expand into strings of tokens.
14092 @value{GDBN} can evaluate expressions containing macro invocations, show
14093 the result of macro expansion, and show a macro's definition, including
14094 where it was defined.
14096 You may need to compile your program specially to provide @value{GDBN}
14097 with information about preprocessor macros. Most compilers do not
14098 include macros in their debugging information, even when you compile
14099 with the @option{-g} flag. @xref{Compilation}.
14101 A program may define a macro at one point, remove that definition later,
14102 and then provide a different definition after that. Thus, at different
14103 points in the program, a macro may have different definitions, or have
14104 no definition at all. If there is a current stack frame, @value{GDBN}
14105 uses the macros in scope at that frame's source code line. Otherwise,
14106 @value{GDBN} uses the macros in scope at the current listing location;
14109 Whenever @value{GDBN} evaluates an expression, it always expands any
14110 macro invocations present in the expression. @value{GDBN} also provides
14111 the following commands for working with macros explicitly.
14115 @kindex macro expand
14116 @cindex macro expansion, showing the results of preprocessor
14117 @cindex preprocessor macro expansion, showing the results of
14118 @cindex expanding preprocessor macros
14119 @item macro expand @var{expression}
14120 @itemx macro exp @var{expression}
14121 Show the results of expanding all preprocessor macro invocations in
14122 @var{expression}. Since @value{GDBN} simply expands macros, but does
14123 not parse the result, @var{expression} need not be a valid expression;
14124 it can be any string of tokens.
14127 @item macro expand-once @var{expression}
14128 @itemx macro exp1 @var{expression}
14129 @cindex expand macro once
14130 @i{(This command is not yet implemented.)} Show the results of
14131 expanding those preprocessor macro invocations that appear explicitly in
14132 @var{expression}. Macro invocations appearing in that expansion are
14133 left unchanged. This command allows you to see the effect of a
14134 particular macro more clearly, without being confused by further
14135 expansions. Since @value{GDBN} simply expands macros, but does not
14136 parse the result, @var{expression} need not be a valid expression; it
14137 can be any string of tokens.
14140 @cindex macro definition, showing
14141 @cindex definition of a macro, showing
14142 @cindex macros, from debug info
14143 @item info macro [-a|-all] [--] @var{macro}
14144 Show the current definition or all definitions of the named @var{macro},
14145 and describe the source location or compiler command-line where that
14146 definition was established. The optional double dash is to signify the end of
14147 argument processing and the beginning of @var{macro} for non C-like macros where
14148 the macro may begin with a hyphen.
14150 @kindex info macros
14151 @item info macros @var{location}
14152 Show all macro definitions that are in effect at the location specified
14153 by @var{location}, and describe the source location or compiler
14154 command-line where those definitions were established.
14156 @kindex macro define
14157 @cindex user-defined macros
14158 @cindex defining macros interactively
14159 @cindex macros, user-defined
14160 @item macro define @var{macro} @var{replacement-list}
14161 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14162 Introduce a definition for a preprocessor macro named @var{macro},
14163 invocations of which are replaced by the tokens given in
14164 @var{replacement-list}. The first form of this command defines an
14165 ``object-like'' macro, which takes no arguments; the second form
14166 defines a ``function-like'' macro, which takes the arguments given in
14169 A definition introduced by this command is in scope in every
14170 expression evaluated in @value{GDBN}, until it is removed with the
14171 @code{macro undef} command, described below. The definition overrides
14172 all definitions for @var{macro} present in the program being debugged,
14173 as well as any previous user-supplied definition.
14175 @kindex macro undef
14176 @item macro undef @var{macro}
14177 Remove any user-supplied definition for the macro named @var{macro}.
14178 This command only affects definitions provided with the @code{macro
14179 define} command, described above; it cannot remove definitions present
14180 in the program being debugged.
14184 List all the macros defined using the @code{macro define} command.
14187 @cindex macros, example of debugging with
14188 Here is a transcript showing the above commands in action. First, we
14189 show our source files:
14194 #include "sample.h"
14197 #define ADD(x) (M + x)
14202 printf ("Hello, world!\n");
14204 printf ("We're so creative.\n");
14206 printf ("Goodbye, world!\n");
14213 Now, we compile the program using the @sc{gnu} C compiler,
14214 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14215 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14216 and @option{-gdwarf-4}; we recommend always choosing the most recent
14217 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14218 includes information about preprocessor macros in the debugging
14222 $ gcc -gdwarf-2 -g3 sample.c -o sample
14226 Now, we start @value{GDBN} on our sample program:
14230 GNU gdb 2002-05-06-cvs
14231 Copyright 2002 Free Software Foundation, Inc.
14232 GDB is free software, @dots{}
14236 We can expand macros and examine their definitions, even when the
14237 program is not running. @value{GDBN} uses the current listing position
14238 to decide which macro definitions are in scope:
14241 (@value{GDBP}) list main
14244 5 #define ADD(x) (M + x)
14249 10 printf ("Hello, world!\n");
14251 12 printf ("We're so creative.\n");
14252 (@value{GDBP}) info macro ADD
14253 Defined at /home/jimb/gdb/macros/play/sample.c:5
14254 #define ADD(x) (M + x)
14255 (@value{GDBP}) info macro Q
14256 Defined at /home/jimb/gdb/macros/play/sample.h:1
14257 included at /home/jimb/gdb/macros/play/sample.c:2
14259 (@value{GDBP}) macro expand ADD(1)
14260 expands to: (42 + 1)
14261 (@value{GDBP}) macro expand-once ADD(1)
14262 expands to: once (M + 1)
14266 In the example above, note that @code{macro expand-once} expands only
14267 the macro invocation explicit in the original text --- the invocation of
14268 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14269 which was introduced by @code{ADD}.
14271 Once the program is running, @value{GDBN} uses the macro definitions in
14272 force at the source line of the current stack frame:
14275 (@value{GDBP}) break main
14276 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14278 Starting program: /home/jimb/gdb/macros/play/sample
14280 Breakpoint 1, main () at sample.c:10
14281 10 printf ("Hello, world!\n");
14285 At line 10, the definition of the macro @code{N} at line 9 is in force:
14288 (@value{GDBP}) info macro N
14289 Defined at /home/jimb/gdb/macros/play/sample.c:9
14291 (@value{GDBP}) macro expand N Q M
14292 expands to: 28 < 42
14293 (@value{GDBP}) print N Q M
14298 As we step over directives that remove @code{N}'s definition, and then
14299 give it a new definition, @value{GDBN} finds the definition (or lack
14300 thereof) in force at each point:
14303 (@value{GDBP}) next
14305 12 printf ("We're so creative.\n");
14306 (@value{GDBP}) info macro N
14307 The symbol `N' has no definition as a C/C++ preprocessor macro
14308 at /home/jimb/gdb/macros/play/sample.c:12
14309 (@value{GDBP}) next
14311 14 printf ("Goodbye, world!\n");
14312 (@value{GDBP}) info macro N
14313 Defined at /home/jimb/gdb/macros/play/sample.c:13
14315 (@value{GDBP}) macro expand N Q M
14316 expands to: 1729 < 42
14317 (@value{GDBP}) print N Q M
14322 In addition to source files, macros can be defined on the compilation command
14323 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14324 such a way, @value{GDBN} displays the location of their definition as line zero
14325 of the source file submitted to the compiler.
14328 (@value{GDBP}) info macro __STDC__
14329 Defined at /home/jimb/gdb/macros/play/sample.c:0
14336 @chapter Tracepoints
14337 @c This chapter is based on the documentation written by Michael
14338 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14340 @cindex tracepoints
14341 In some applications, it is not feasible for the debugger to interrupt
14342 the program's execution long enough for the developer to learn
14343 anything helpful about its behavior. If the program's correctness
14344 depends on its real-time behavior, delays introduced by a debugger
14345 might cause the program to change its behavior drastically, or perhaps
14346 fail, even when the code itself is correct. It is useful to be able
14347 to observe the program's behavior without interrupting it.
14349 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14350 specify locations in the program, called @dfn{tracepoints}, and
14351 arbitrary expressions to evaluate when those tracepoints are reached.
14352 Later, using the @code{tfind} command, you can examine the values
14353 those expressions had when the program hit the tracepoints. The
14354 expressions may also denote objects in memory---structures or arrays,
14355 for example---whose values @value{GDBN} should record; while visiting
14356 a particular tracepoint, you may inspect those objects as if they were
14357 in memory at that moment. However, because @value{GDBN} records these
14358 values without interacting with you, it can do so quickly and
14359 unobtrusively, hopefully not disturbing the program's behavior.
14361 The tracepoint facility is currently available only for remote
14362 targets. @xref{Targets}. In addition, your remote target must know
14363 how to collect trace data. This functionality is implemented in the
14364 remote stub; however, none of the stubs distributed with @value{GDBN}
14365 support tracepoints as of this writing. The format of the remote
14366 packets used to implement tracepoints are described in @ref{Tracepoint
14369 It is also possible to get trace data from a file, in a manner reminiscent
14370 of corefiles; you specify the filename, and use @code{tfind} to search
14371 through the file. @xref{Trace Files}, for more details.
14373 This chapter describes the tracepoint commands and features.
14376 * Set Tracepoints::
14377 * Analyze Collected Data::
14378 * Tracepoint Variables::
14382 @node Set Tracepoints
14383 @section Commands to Set Tracepoints
14385 Before running such a @dfn{trace experiment}, an arbitrary number of
14386 tracepoints can be set. A tracepoint is actually a special type of
14387 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14388 standard breakpoint commands. For instance, as with breakpoints,
14389 tracepoint numbers are successive integers starting from one, and many
14390 of the commands associated with tracepoints take the tracepoint number
14391 as their argument, to identify which tracepoint to work on.
14393 For each tracepoint, you can specify, in advance, some arbitrary set
14394 of data that you want the target to collect in the trace buffer when
14395 it hits that tracepoint. The collected data can include registers,
14396 local variables, or global data. Later, you can use @value{GDBN}
14397 commands to examine the values these data had at the time the
14398 tracepoint was hit.
14400 Tracepoints do not support every breakpoint feature. Ignore counts on
14401 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14402 commands when they are hit. Tracepoints may not be thread-specific
14405 @cindex fast tracepoints
14406 Some targets may support @dfn{fast tracepoints}, which are inserted in
14407 a different way (such as with a jump instead of a trap), that is
14408 faster but possibly restricted in where they may be installed.
14410 @cindex static tracepoints
14411 @cindex markers, static tracepoints
14412 @cindex probing markers, static tracepoints
14413 Regular and fast tracepoints are dynamic tracing facilities, meaning
14414 that they can be used to insert tracepoints at (almost) any location
14415 in the target. Some targets may also support controlling @dfn{static
14416 tracepoints} from @value{GDBN}. With static tracing, a set of
14417 instrumentation points, also known as @dfn{markers}, are embedded in
14418 the target program, and can be activated or deactivated by name or
14419 address. These are usually placed at locations which facilitate
14420 investigating what the target is actually doing. @value{GDBN}'s
14421 support for static tracing includes being able to list instrumentation
14422 points, and attach them with @value{GDBN} defined high level
14423 tracepoints that expose the whole range of convenience of
14424 @value{GDBN}'s tracepoints support. Namely, support for collecting
14425 registers values and values of global or local (to the instrumentation
14426 point) variables; tracepoint conditions and trace state variables.
14427 The act of installing a @value{GDBN} static tracepoint on an
14428 instrumentation point, or marker, is referred to as @dfn{probing} a
14429 static tracepoint marker.
14431 @code{gdbserver} supports tracepoints on some target systems.
14432 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14434 This section describes commands to set tracepoints and associated
14435 conditions and actions.
14438 * Create and Delete Tracepoints::
14439 * Enable and Disable Tracepoints::
14440 * Tracepoint Passcounts::
14441 * Tracepoint Conditions::
14442 * Trace State Variables::
14443 * Tracepoint Actions::
14444 * Listing Tracepoints::
14445 * Listing Static Tracepoint Markers::
14446 * Starting and Stopping Trace Experiments::
14447 * Tracepoint Restrictions::
14450 @node Create and Delete Tracepoints
14451 @subsection Create and Delete Tracepoints
14454 @cindex set tracepoint
14456 @item trace @var{location}
14457 The @code{trace} command is very similar to the @code{break} command.
14458 Its argument @var{location} can be any valid location.
14459 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14460 which is a point in the target program where the debugger will briefly stop,
14461 collect some data, and then allow the program to continue. Setting a tracepoint
14462 or changing its actions takes effect immediately if the remote stub
14463 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14465 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14466 these changes don't take effect until the next @code{tstart}
14467 command, and once a trace experiment is running, further changes will
14468 not have any effect until the next trace experiment starts. In addition,
14469 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14470 address is not yet resolved. (This is similar to pending breakpoints.)
14471 Pending tracepoints are not downloaded to the target and not installed
14472 until they are resolved. The resolution of pending tracepoints requires
14473 @value{GDBN} support---when debugging with the remote target, and
14474 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14475 tracing}), pending tracepoints can not be resolved (and downloaded to
14476 the remote stub) while @value{GDBN} is disconnected.
14478 Here are some examples of using the @code{trace} command:
14481 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14483 (@value{GDBP}) @b{trace +2} // 2 lines forward
14485 (@value{GDBP}) @b{trace my_function} // first source line of function
14487 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14489 (@value{GDBP}) @b{trace *0x2117c4} // an address
14493 You can abbreviate @code{trace} as @code{tr}.
14495 @item trace @var{location} if @var{cond}
14496 Set a tracepoint with condition @var{cond}; evaluate the expression
14497 @var{cond} each time the tracepoint is reached, and collect data only
14498 if the value is nonzero---that is, if @var{cond} evaluates as true.
14499 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14500 information on tracepoint conditions.
14502 @item ftrace @var{location} [ if @var{cond} ]
14503 @cindex set fast tracepoint
14504 @cindex fast tracepoints, setting
14506 The @code{ftrace} command sets a fast tracepoint. For targets that
14507 support them, fast tracepoints will use a more efficient but possibly
14508 less general technique to trigger data collection, such as a jump
14509 instruction instead of a trap, or some sort of hardware support. It
14510 may not be possible to create a fast tracepoint at the desired
14511 location, in which case the command will exit with an explanatory
14514 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14517 On 32-bit x86-architecture systems, fast tracepoints normally need to
14518 be placed at an instruction that is 5 bytes or longer, but can be
14519 placed at 4-byte instructions if the low 64K of memory of the target
14520 program is available to install trampolines. Some Unix-type systems,
14521 such as @sc{gnu}/Linux, exclude low addresses from the program's
14522 address space; but for instance with the Linux kernel it is possible
14523 to let @value{GDBN} use this area by doing a @command{sysctl} command
14524 to set the @code{mmap_min_addr} kernel parameter, as in
14527 sudo sysctl -w vm.mmap_min_addr=32768
14531 which sets the low address to 32K, which leaves plenty of room for
14532 trampolines. The minimum address should be set to a page boundary.
14534 @item strace @var{location} [ if @var{cond} ]
14535 @cindex set static tracepoint
14536 @cindex static tracepoints, setting
14537 @cindex probe static tracepoint marker
14539 The @code{strace} command sets a static tracepoint. For targets that
14540 support it, setting a static tracepoint probes a static
14541 instrumentation point, or marker, found at @var{location}. It may not
14542 be possible to set a static tracepoint at the desired location, in
14543 which case the command will exit with an explanatory message.
14545 @value{GDBN} handles arguments to @code{strace} exactly as for
14546 @code{trace}, with the addition that the user can also specify
14547 @code{-m @var{marker}} as @var{location}. This probes the marker
14548 identified by the @var{marker} string identifier. This identifier
14549 depends on the static tracepoint backend library your program is
14550 using. You can find all the marker identifiers in the @samp{ID} field
14551 of the @code{info static-tracepoint-markers} command output.
14552 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14553 Markers}. For example, in the following small program using the UST
14559 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14564 the marker id is composed of joining the first two arguments to the
14565 @code{trace_mark} call with a slash, which translates to:
14568 (@value{GDBP}) info static-tracepoint-markers
14569 Cnt Enb ID Address What
14570 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14576 so you may probe the marker above with:
14579 (@value{GDBP}) strace -m ust/bar33
14582 Static tracepoints accept an extra collect action --- @code{collect
14583 $_sdata}. This collects arbitrary user data passed in the probe point
14584 call to the tracing library. In the UST example above, you'll see
14585 that the third argument to @code{trace_mark} is a printf-like format
14586 string. The user data is then the result of running that formatting
14587 string against the following arguments. Note that @code{info
14588 static-tracepoint-markers} command output lists that format string in
14589 the @samp{Data:} field.
14591 You can inspect this data when analyzing the trace buffer, by printing
14592 the $_sdata variable like any other variable available to
14593 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14596 @cindex last tracepoint number
14597 @cindex recent tracepoint number
14598 @cindex tracepoint number
14599 The convenience variable @code{$tpnum} records the tracepoint number
14600 of the most recently set tracepoint.
14602 @kindex delete tracepoint
14603 @cindex tracepoint deletion
14604 @item delete tracepoint @r{[}@var{num}@r{]}
14605 Permanently delete one or more tracepoints. With no argument, the
14606 default is to delete all tracepoints. Note that the regular
14607 @code{delete} command can remove tracepoints also.
14612 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14614 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14618 You can abbreviate this command as @code{del tr}.
14621 @node Enable and Disable Tracepoints
14622 @subsection Enable and Disable Tracepoints
14624 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14627 @kindex disable tracepoint
14628 @item disable tracepoint @r{[}@var{num}@r{]}
14629 Disable tracepoint @var{num}, or all tracepoints if no argument
14630 @var{num} is given. A disabled tracepoint will have no effect during
14631 a trace experiment, but it is not forgotten. You can re-enable
14632 a disabled tracepoint using the @code{enable tracepoint} command.
14633 If the command is issued during a trace experiment and the debug target
14634 has support for disabling tracepoints during a trace experiment, then the
14635 change will be effective immediately. Otherwise, it will be applied to the
14636 next trace experiment.
14638 @kindex enable tracepoint
14639 @item enable tracepoint @r{[}@var{num}@r{]}
14640 Enable tracepoint @var{num}, or all tracepoints. If this command is
14641 issued during a trace experiment and the debug target supports enabling
14642 tracepoints during a trace experiment, then the enabled tracepoints will
14643 become effective immediately. Otherwise, they will become effective the
14644 next time a trace experiment is run.
14647 @node Tracepoint Passcounts
14648 @subsection Tracepoint Passcounts
14652 @cindex tracepoint pass count
14653 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14654 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14655 automatically stop a trace experiment. If a tracepoint's passcount is
14656 @var{n}, then the trace experiment will be automatically stopped on
14657 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14658 @var{num} is not specified, the @code{passcount} command sets the
14659 passcount of the most recently defined tracepoint. If no passcount is
14660 given, the trace experiment will run until stopped explicitly by the
14666 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14667 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14669 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14670 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14671 (@value{GDBP}) @b{trace foo}
14672 (@value{GDBP}) @b{pass 3}
14673 (@value{GDBP}) @b{trace bar}
14674 (@value{GDBP}) @b{pass 2}
14675 (@value{GDBP}) @b{trace baz}
14676 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14677 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14678 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14679 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14683 @node Tracepoint Conditions
14684 @subsection Tracepoint Conditions
14685 @cindex conditional tracepoints
14686 @cindex tracepoint conditions
14688 The simplest sort of tracepoint collects data every time your program
14689 reaches a specified place. You can also specify a @dfn{condition} for
14690 a tracepoint. A condition is just a Boolean expression in your
14691 programming language (@pxref{Expressions, ,Expressions}). A
14692 tracepoint with a condition evaluates the expression each time your
14693 program reaches it, and data collection happens only if the condition
14696 Tracepoint conditions can be specified when a tracepoint is set, by
14697 using @samp{if} in the arguments to the @code{trace} command.
14698 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14699 also be set or changed at any time with the @code{condition} command,
14700 just as with breakpoints.
14702 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14703 the conditional expression itself. Instead, @value{GDBN} encodes the
14704 expression into an agent expression (@pxref{Agent Expressions})
14705 suitable for execution on the target, independently of @value{GDBN}.
14706 Global variables become raw memory locations, locals become stack
14707 accesses, and so forth.
14709 For instance, suppose you have a function that is usually called
14710 frequently, but should not be called after an error has occurred. You
14711 could use the following tracepoint command to collect data about calls
14712 of that function that happen while the error code is propagating
14713 through the program; an unconditional tracepoint could end up
14714 collecting thousands of useless trace frames that you would have to
14718 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14721 @node Trace State Variables
14722 @subsection Trace State Variables
14723 @cindex trace state variables
14725 A @dfn{trace state variable} is a special type of variable that is
14726 created and managed by target-side code. The syntax is the same as
14727 that for GDB's convenience variables (a string prefixed with ``$''),
14728 but they are stored on the target. They must be created explicitly,
14729 using a @code{tvariable} command. They are always 64-bit signed
14732 Trace state variables are remembered by @value{GDBN}, and downloaded
14733 to the target along with tracepoint information when the trace
14734 experiment starts. There are no intrinsic limits on the number of
14735 trace state variables, beyond memory limitations of the target.
14737 @cindex convenience variables, and trace state variables
14738 Although trace state variables are managed by the target, you can use
14739 them in print commands and expressions as if they were convenience
14740 variables; @value{GDBN} will get the current value from the target
14741 while the trace experiment is running. Trace state variables share
14742 the same namespace as other ``$'' variables, which means that you
14743 cannot have trace state variables with names like @code{$23} or
14744 @code{$pc}, nor can you have a trace state variable and a convenience
14745 variable with the same name.
14749 @item tvariable $@var{name} [ = @var{expression} ]
14751 The @code{tvariable} command creates a new trace state variable named
14752 @code{$@var{name}}, and optionally gives it an initial value of
14753 @var{expression}. The @var{expression} is evaluated when this command is
14754 entered; the result will be converted to an integer if possible,
14755 otherwise @value{GDBN} will report an error. A subsequent
14756 @code{tvariable} command specifying the same name does not create a
14757 variable, but instead assigns the supplied initial value to the
14758 existing variable of that name, overwriting any previous initial
14759 value. The default initial value is 0.
14761 @item info tvariables
14762 @kindex info tvariables
14763 List all the trace state variables along with their initial values.
14764 Their current values may also be displayed, if the trace experiment is
14767 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14768 @kindex delete tvariable
14769 Delete the given trace state variables, or all of them if no arguments
14774 @node Tracepoint Actions
14775 @subsection Tracepoint Action Lists
14779 @cindex tracepoint actions
14780 @item actions @r{[}@var{num}@r{]}
14781 This command will prompt for a list of actions to be taken when the
14782 tracepoint is hit. If the tracepoint number @var{num} is not
14783 specified, this command sets the actions for the one that was most
14784 recently defined (so that you can define a tracepoint and then say
14785 @code{actions} without bothering about its number). You specify the
14786 actions themselves on the following lines, one action at a time, and
14787 terminate the actions list with a line containing just @code{end}. So
14788 far, the only defined actions are @code{collect}, @code{teval}, and
14789 @code{while-stepping}.
14791 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14792 Commands, ,Breakpoint Command Lists}), except that only the defined
14793 actions are allowed; any other @value{GDBN} command is rejected.
14795 @cindex remove actions from a tracepoint
14796 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14797 and follow it immediately with @samp{end}.
14800 (@value{GDBP}) @b{collect @var{data}} // collect some data
14802 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14804 (@value{GDBP}) @b{end} // signals the end of actions.
14807 In the following example, the action list begins with @code{collect}
14808 commands indicating the things to be collected when the tracepoint is
14809 hit. Then, in order to single-step and collect additional data
14810 following the tracepoint, a @code{while-stepping} command is used,
14811 followed by the list of things to be collected after each step in a
14812 sequence of single steps. The @code{while-stepping} command is
14813 terminated by its own separate @code{end} command. Lastly, the action
14814 list is terminated by an @code{end} command.
14817 (@value{GDBP}) @b{trace foo}
14818 (@value{GDBP}) @b{actions}
14819 Enter actions for tracepoint 1, one per line:
14822 > while-stepping 12
14823 > collect $pc, arr[i]
14828 @kindex collect @r{(tracepoints)}
14829 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14830 Collect values of the given expressions when the tracepoint is hit.
14831 This command accepts a comma-separated list of any valid expressions.
14832 In addition to global, static, or local variables, the following
14833 special arguments are supported:
14837 Collect all registers.
14840 Collect all function arguments.
14843 Collect all local variables.
14846 Collect the return address. This is helpful if you want to see more
14849 @emph{Note:} The return address location can not always be reliably
14850 determined up front, and the wrong address / registers may end up
14851 collected instead. On some architectures the reliability is higher
14852 for tracepoints at function entry, while on others it's the opposite.
14853 When this happens, backtracing will stop because the return address is
14854 found unavailable (unless another collect rule happened to match it).
14857 Collects the number of arguments from the static probe at which the
14858 tracepoint is located.
14859 @xref{Static Probe Points}.
14861 @item $_probe_arg@var{n}
14862 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14863 from the static probe at which the tracepoint is located.
14864 @xref{Static Probe Points}.
14867 @vindex $_sdata@r{, collect}
14868 Collect static tracepoint marker specific data. Only available for
14869 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14870 Lists}. On the UST static tracepoints library backend, an
14871 instrumentation point resembles a @code{printf} function call. The
14872 tracing library is able to collect user specified data formatted to a
14873 character string using the format provided by the programmer that
14874 instrumented the program. Other backends have similar mechanisms.
14875 Here's an example of a UST marker call:
14878 const char master_name[] = "$your_name";
14879 trace_mark(channel1, marker1, "hello %s", master_name)
14882 In this case, collecting @code{$_sdata} collects the string
14883 @samp{hello $yourname}. When analyzing the trace buffer, you can
14884 inspect @samp{$_sdata} like any other variable available to
14888 You can give several consecutive @code{collect} commands, each one
14889 with a single argument, or one @code{collect} command with several
14890 arguments separated by commas; the effect is the same.
14892 The optional @var{mods} changes the usual handling of the arguments.
14893 @code{s} requests that pointers to chars be handled as strings, in
14894 particular collecting the contents of the memory being pointed at, up
14895 to the first zero. The upper bound is by default the value of the
14896 @code{print elements} variable; if @code{s} is followed by a decimal
14897 number, that is the upper bound instead. So for instance
14898 @samp{collect/s25 mystr} collects as many as 25 characters at
14901 The command @code{info scope} (@pxref{Symbols, info scope}) is
14902 particularly useful for figuring out what data to collect.
14904 @kindex teval @r{(tracepoints)}
14905 @item teval @var{expr1}, @var{expr2}, @dots{}
14906 Evaluate the given expressions when the tracepoint is hit. This
14907 command accepts a comma-separated list of expressions. The results
14908 are discarded, so this is mainly useful for assigning values to trace
14909 state variables (@pxref{Trace State Variables}) without adding those
14910 values to the trace buffer, as would be the case if the @code{collect}
14913 @kindex while-stepping @r{(tracepoints)}
14914 @item while-stepping @var{n}
14915 Perform @var{n} single-step instruction traces after the tracepoint,
14916 collecting new data after each step. The @code{while-stepping}
14917 command is followed by the list of what to collect while stepping
14918 (followed by its own @code{end} command):
14921 > while-stepping 12
14922 > collect $regs, myglobal
14928 Note that @code{$pc} is not automatically collected by
14929 @code{while-stepping}; you need to explicitly collect that register if
14930 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14933 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14934 @kindex set default-collect
14935 @cindex default collection action
14936 This variable is a list of expressions to collect at each tracepoint
14937 hit. It is effectively an additional @code{collect} action prepended
14938 to every tracepoint action list. The expressions are parsed
14939 individually for each tracepoint, so for instance a variable named
14940 @code{xyz} may be interpreted as a global for one tracepoint, and a
14941 local for another, as appropriate to the tracepoint's location.
14943 @item show default-collect
14944 @kindex show default-collect
14945 Show the list of expressions that are collected by default at each
14950 @node Listing Tracepoints
14951 @subsection Listing Tracepoints
14954 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14955 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14956 @cindex information about tracepoints
14957 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14958 Display information about the tracepoint @var{num}. If you don't
14959 specify a tracepoint number, displays information about all the
14960 tracepoints defined so far. The format is similar to that used for
14961 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14962 command, simply restricting itself to tracepoints.
14964 A tracepoint's listing may include additional information specific to
14969 its passcount as given by the @code{passcount @var{n}} command
14972 the state about installed on target of each location
14976 (@value{GDBP}) @b{info trace}
14977 Num Type Disp Enb Address What
14978 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14980 collect globfoo, $regs
14985 2 tracepoint keep y <MULTIPLE>
14987 2.1 y 0x0804859c in func4 at change-loc.h:35
14988 installed on target
14989 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14990 installed on target
14991 2.3 y <PENDING> set_tracepoint
14992 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14993 not installed on target
14998 This command can be abbreviated @code{info tp}.
15001 @node Listing Static Tracepoint Markers
15002 @subsection Listing Static Tracepoint Markers
15005 @kindex info static-tracepoint-markers
15006 @cindex information about static tracepoint markers
15007 @item info static-tracepoint-markers
15008 Display information about all static tracepoint markers defined in the
15011 For each marker, the following columns are printed:
15015 An incrementing counter, output to help readability. This is not a
15018 The marker ID, as reported by the target.
15019 @item Enabled or Disabled
15020 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15021 that are not enabled.
15023 Where the marker is in your program, as a memory address.
15025 Where the marker is in the source for your program, as a file and line
15026 number. If the debug information included in the program does not
15027 allow @value{GDBN} to locate the source of the marker, this column
15028 will be left blank.
15032 In addition, the following information may be printed for each marker:
15036 User data passed to the tracing library by the marker call. In the
15037 UST backend, this is the format string passed as argument to the
15039 @item Static tracepoints probing the marker
15040 The list of static tracepoints attached to the marker.
15044 (@value{GDBP}) info static-tracepoint-markers
15045 Cnt ID Enb Address What
15046 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15047 Data: number1 %d number2 %d
15048 Probed by static tracepoints: #2
15049 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15055 @node Starting and Stopping Trace Experiments
15056 @subsection Starting and Stopping Trace Experiments
15059 @kindex tstart [ @var{notes} ]
15060 @cindex start a new trace experiment
15061 @cindex collected data discarded
15063 This command starts the trace experiment, and begins collecting data.
15064 It has the side effect of discarding all the data collected in the
15065 trace buffer during the previous trace experiment. If any arguments
15066 are supplied, they are taken as a note and stored with the trace
15067 experiment's state. The notes may be arbitrary text, and are
15068 especially useful with disconnected tracing in a multi-user context;
15069 the notes can explain what the trace is doing, supply user contact
15070 information, and so forth.
15072 @kindex tstop [ @var{notes} ]
15073 @cindex stop a running trace experiment
15075 This command stops the trace experiment. If any arguments are
15076 supplied, they are recorded with the experiment as a note. This is
15077 useful if you are stopping a trace started by someone else, for
15078 instance if the trace is interfering with the system's behavior and
15079 needs to be stopped quickly.
15081 @strong{Note}: a trace experiment and data collection may stop
15082 automatically if any tracepoint's passcount is reached
15083 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15086 @cindex status of trace data collection
15087 @cindex trace experiment, status of
15089 This command displays the status of the current trace data
15093 Here is an example of the commands we described so far:
15096 (@value{GDBP}) @b{trace gdb_c_test}
15097 (@value{GDBP}) @b{actions}
15098 Enter actions for tracepoint #1, one per line.
15099 > collect $regs,$locals,$args
15100 > while-stepping 11
15104 (@value{GDBP}) @b{tstart}
15105 [time passes @dots{}]
15106 (@value{GDBP}) @b{tstop}
15109 @anchor{disconnected tracing}
15110 @cindex disconnected tracing
15111 You can choose to continue running the trace experiment even if
15112 @value{GDBN} disconnects from the target, voluntarily or
15113 involuntarily. For commands such as @code{detach}, the debugger will
15114 ask what you want to do with the trace. But for unexpected
15115 terminations (@value{GDBN} crash, network outage), it would be
15116 unfortunate to lose hard-won trace data, so the variable
15117 @code{disconnected-tracing} lets you decide whether the trace should
15118 continue running without @value{GDBN}.
15121 @item set disconnected-tracing on
15122 @itemx set disconnected-tracing off
15123 @kindex set disconnected-tracing
15124 Choose whether a tracing run should continue to run if @value{GDBN}
15125 has disconnected from the target. Note that @code{detach} or
15126 @code{quit} will ask you directly what to do about a running trace no
15127 matter what this variable's setting, so the variable is mainly useful
15128 for handling unexpected situations, such as loss of the network.
15130 @item show disconnected-tracing
15131 @kindex show disconnected-tracing
15132 Show the current choice for disconnected tracing.
15136 When you reconnect to the target, the trace experiment may or may not
15137 still be running; it might have filled the trace buffer in the
15138 meantime, or stopped for one of the other reasons. If it is running,
15139 it will continue after reconnection.
15141 Upon reconnection, the target will upload information about the
15142 tracepoints in effect. @value{GDBN} will then compare that
15143 information to the set of tracepoints currently defined, and attempt
15144 to match them up, allowing for the possibility that the numbers may
15145 have changed due to creation and deletion in the meantime. If one of
15146 the target's tracepoints does not match any in @value{GDBN}, the
15147 debugger will create a new tracepoint, so that you have a number with
15148 which to specify that tracepoint. This matching-up process is
15149 necessarily heuristic, and it may result in useless tracepoints being
15150 created; you may simply delete them if they are of no use.
15152 @cindex circular trace buffer
15153 If your target agent supports a @dfn{circular trace buffer}, then you
15154 can run a trace experiment indefinitely without filling the trace
15155 buffer; when space runs out, the agent deletes already-collected trace
15156 frames, oldest first, until there is enough room to continue
15157 collecting. This is especially useful if your tracepoints are being
15158 hit too often, and your trace gets terminated prematurely because the
15159 buffer is full. To ask for a circular trace buffer, simply set
15160 @samp{circular-trace-buffer} to on. You can set this at any time,
15161 including during tracing; if the agent can do it, it will change
15162 buffer handling on the fly, otherwise it will not take effect until
15166 @item set circular-trace-buffer on
15167 @itemx set circular-trace-buffer off
15168 @kindex set circular-trace-buffer
15169 Choose whether a tracing run should use a linear or circular buffer
15170 for trace data. A linear buffer will not lose any trace data, but may
15171 fill up prematurely, while a circular buffer will discard old trace
15172 data, but it will have always room for the latest tracepoint hits.
15174 @item show circular-trace-buffer
15175 @kindex show circular-trace-buffer
15176 Show the current choice for the trace buffer. Note that this may not
15177 match the agent's current buffer handling, nor is it guaranteed to
15178 match the setting that might have been in effect during a past run,
15179 for instance if you are looking at frames from a trace file.
15184 @item set trace-buffer-size @var{n}
15185 @itemx set trace-buffer-size unlimited
15186 @kindex set trace-buffer-size
15187 Request that the target use a trace buffer of @var{n} bytes. Not all
15188 targets will honor the request; they may have a compiled-in size for
15189 the trace buffer, or some other limitation. Set to a value of
15190 @code{unlimited} or @code{-1} to let the target use whatever size it
15191 likes. This is also the default.
15193 @item show trace-buffer-size
15194 @kindex show trace-buffer-size
15195 Show the current requested size for the trace buffer. Note that this
15196 will only match the actual size if the target supports size-setting,
15197 and was able to handle the requested size. For instance, if the
15198 target can only change buffer size between runs, this variable will
15199 not reflect the change until the next run starts. Use @code{tstatus}
15200 to get a report of the actual buffer size.
15204 @item set trace-user @var{text}
15205 @kindex set trace-user
15207 @item show trace-user
15208 @kindex show trace-user
15210 @item set trace-notes @var{text}
15211 @kindex set trace-notes
15212 Set the trace run's notes.
15214 @item show trace-notes
15215 @kindex show trace-notes
15216 Show the trace run's notes.
15218 @item set trace-stop-notes @var{text}
15219 @kindex set trace-stop-notes
15220 Set the trace run's stop notes. The handling of the note is as for
15221 @code{tstop} arguments; the set command is convenient way to fix a
15222 stop note that is mistaken or incomplete.
15224 @item show trace-stop-notes
15225 @kindex show trace-stop-notes
15226 Show the trace run's stop notes.
15230 @node Tracepoint Restrictions
15231 @subsection Tracepoint Restrictions
15233 @cindex tracepoint restrictions
15234 There are a number of restrictions on the use of tracepoints. As
15235 described above, tracepoint data gathering occurs on the target
15236 without interaction from @value{GDBN}. Thus the full capabilities of
15237 the debugger are not available during data gathering, and then at data
15238 examination time, you will be limited by only having what was
15239 collected. The following items describe some common problems, but it
15240 is not exhaustive, and you may run into additional difficulties not
15246 Tracepoint expressions are intended to gather objects (lvalues). Thus
15247 the full flexibility of GDB's expression evaluator is not available.
15248 You cannot call functions, cast objects to aggregate types, access
15249 convenience variables or modify values (except by assignment to trace
15250 state variables). Some language features may implicitly call
15251 functions (for instance Objective-C fields with accessors), and therefore
15252 cannot be collected either.
15255 Collection of local variables, either individually or in bulk with
15256 @code{$locals} or @code{$args}, during @code{while-stepping} may
15257 behave erratically. The stepping action may enter a new scope (for
15258 instance by stepping into a function), or the location of the variable
15259 may change (for instance it is loaded into a register). The
15260 tracepoint data recorded uses the location information for the
15261 variables that is correct for the tracepoint location. When the
15262 tracepoint is created, it is not possible, in general, to determine
15263 where the steps of a @code{while-stepping} sequence will advance the
15264 program---particularly if a conditional branch is stepped.
15267 Collection of an incompletely-initialized or partially-destroyed object
15268 may result in something that @value{GDBN} cannot display, or displays
15269 in a misleading way.
15272 When @value{GDBN} displays a pointer to character it automatically
15273 dereferences the pointer to also display characters of the string
15274 being pointed to. However, collecting the pointer during tracing does
15275 not automatically collect the string. You need to explicitly
15276 dereference the pointer and provide size information if you want to
15277 collect not only the pointer, but the memory pointed to. For example,
15278 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15282 It is not possible to collect a complete stack backtrace at a
15283 tracepoint. Instead, you may collect the registers and a few hundred
15284 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15285 (adjust to use the name of the actual stack pointer register on your
15286 target architecture, and the amount of stack you wish to capture).
15287 Then the @code{backtrace} command will show a partial backtrace when
15288 using a trace frame. The number of stack frames that can be examined
15289 depends on the sizes of the frames in the collected stack. Note that
15290 if you ask for a block so large that it goes past the bottom of the
15291 stack, the target agent may report an error trying to read from an
15295 If you do not collect registers at a tracepoint, @value{GDBN} can
15296 infer that the value of @code{$pc} must be the same as the address of
15297 the tracepoint and use that when you are looking at a trace frame
15298 for that tracepoint. However, this cannot work if the tracepoint has
15299 multiple locations (for instance if it was set in a function that was
15300 inlined), or if it has a @code{while-stepping} loop. In those cases
15301 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15306 @node Analyze Collected Data
15307 @section Using the Collected Data
15309 After the tracepoint experiment ends, you use @value{GDBN} commands
15310 for examining the trace data. The basic idea is that each tracepoint
15311 collects a trace @dfn{snapshot} every time it is hit and another
15312 snapshot every time it single-steps. All these snapshots are
15313 consecutively numbered from zero and go into a buffer, and you can
15314 examine them later. The way you examine them is to @dfn{focus} on a
15315 specific trace snapshot. When the remote stub is focused on a trace
15316 snapshot, it will respond to all @value{GDBN} requests for memory and
15317 registers by reading from the buffer which belongs to that snapshot,
15318 rather than from @emph{real} memory or registers of the program being
15319 debugged. This means that @strong{all} @value{GDBN} commands
15320 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15321 behave as if we were currently debugging the program state as it was
15322 when the tracepoint occurred. Any requests for data that are not in
15323 the buffer will fail.
15326 * tfind:: How to select a trace snapshot
15327 * tdump:: How to display all data for a snapshot
15328 * save tracepoints:: How to save tracepoints for a future run
15332 @subsection @code{tfind @var{n}}
15335 @cindex select trace snapshot
15336 @cindex find trace snapshot
15337 The basic command for selecting a trace snapshot from the buffer is
15338 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15339 counting from zero. If no argument @var{n} is given, the next
15340 snapshot is selected.
15342 Here are the various forms of using the @code{tfind} command.
15346 Find the first snapshot in the buffer. This is a synonym for
15347 @code{tfind 0} (since 0 is the number of the first snapshot).
15350 Stop debugging trace snapshots, resume @emph{live} debugging.
15353 Same as @samp{tfind none}.
15356 No argument means find the next trace snapshot or find the first
15357 one if no trace snapshot is selected.
15360 Find the previous trace snapshot before the current one. This permits
15361 retracing earlier steps.
15363 @item tfind tracepoint @var{num}
15364 Find the next snapshot associated with tracepoint @var{num}. Search
15365 proceeds forward from the last examined trace snapshot. If no
15366 argument @var{num} is given, it means find the next snapshot collected
15367 for the same tracepoint as the current snapshot.
15369 @item tfind pc @var{addr}
15370 Find the next snapshot associated with the value @var{addr} of the
15371 program counter. Search proceeds forward from the last examined trace
15372 snapshot. If no argument @var{addr} is given, it means find the next
15373 snapshot with the same value of PC as the current snapshot.
15375 @item tfind outside @var{addr1}, @var{addr2}
15376 Find the next snapshot whose PC is outside the given range of
15377 addresses (exclusive).
15379 @item tfind range @var{addr1}, @var{addr2}
15380 Find the next snapshot whose PC is between @var{addr1} and
15381 @var{addr2} (inclusive).
15383 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15384 Find the next snapshot associated with the source line @var{n}. If
15385 the optional argument @var{file} is given, refer to line @var{n} in
15386 that source file. Search proceeds forward from the last examined
15387 trace snapshot. If no argument @var{n} is given, it means find the
15388 next line other than the one currently being examined; thus saying
15389 @code{tfind line} repeatedly can appear to have the same effect as
15390 stepping from line to line in a @emph{live} debugging session.
15393 The default arguments for the @code{tfind} commands are specifically
15394 designed to make it easy to scan through the trace buffer. For
15395 instance, @code{tfind} with no argument selects the next trace
15396 snapshot, and @code{tfind -} with no argument selects the previous
15397 trace snapshot. So, by giving one @code{tfind} command, and then
15398 simply hitting @key{RET} repeatedly you can examine all the trace
15399 snapshots in order. Or, by saying @code{tfind -} and then hitting
15400 @key{RET} repeatedly you can examine the snapshots in reverse order.
15401 The @code{tfind line} command with no argument selects the snapshot
15402 for the next source line executed. The @code{tfind pc} command with
15403 no argument selects the next snapshot with the same program counter
15404 (PC) as the current frame. The @code{tfind tracepoint} command with
15405 no argument selects the next trace snapshot collected by the same
15406 tracepoint as the current one.
15408 In addition to letting you scan through the trace buffer manually,
15409 these commands make it easy to construct @value{GDBN} scripts that
15410 scan through the trace buffer and print out whatever collected data
15411 you are interested in. Thus, if we want to examine the PC, FP, and SP
15412 registers from each trace frame in the buffer, we can say this:
15415 (@value{GDBP}) @b{tfind start}
15416 (@value{GDBP}) @b{while ($trace_frame != -1)}
15417 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15418 $trace_frame, $pc, $sp, $fp
15422 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15423 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15424 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15425 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15426 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15427 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15428 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15429 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15430 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15431 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15432 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15435 Or, if we want to examine the variable @code{X} at each source line in
15439 (@value{GDBP}) @b{tfind start}
15440 (@value{GDBP}) @b{while ($trace_frame != -1)}
15441 > printf "Frame %d, X == %d\n", $trace_frame, X
15451 @subsection @code{tdump}
15453 @cindex dump all data collected at tracepoint
15454 @cindex tracepoint data, display
15456 This command takes no arguments. It prints all the data collected at
15457 the current trace snapshot.
15460 (@value{GDBP}) @b{trace 444}
15461 (@value{GDBP}) @b{actions}
15462 Enter actions for tracepoint #2, one per line:
15463 > collect $regs, $locals, $args, gdb_long_test
15466 (@value{GDBP}) @b{tstart}
15468 (@value{GDBP}) @b{tfind line 444}
15469 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15471 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15473 (@value{GDBP}) @b{tdump}
15474 Data collected at tracepoint 2, trace frame 1:
15475 d0 0xc4aa0085 -995491707
15479 d4 0x71aea3d 119204413
15482 d7 0x380035 3670069
15483 a0 0x19e24a 1696330
15484 a1 0x3000668 50333288
15486 a3 0x322000 3284992
15487 a4 0x3000698 50333336
15488 a5 0x1ad3cc 1758156
15489 fp 0x30bf3c 0x30bf3c
15490 sp 0x30bf34 0x30bf34
15492 pc 0x20b2c8 0x20b2c8
15496 p = 0x20e5b4 "gdb-test"
15503 gdb_long_test = 17 '\021'
15508 @code{tdump} works by scanning the tracepoint's current collection
15509 actions and printing the value of each expression listed. So
15510 @code{tdump} can fail, if after a run, you change the tracepoint's
15511 actions to mention variables that were not collected during the run.
15513 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15514 uses the collected value of @code{$pc} to distinguish between trace
15515 frames that were collected at the tracepoint hit, and frames that were
15516 collected while stepping. This allows it to correctly choose whether
15517 to display the basic list of collections, or the collections from the
15518 body of the while-stepping loop. However, if @code{$pc} was not collected,
15519 then @code{tdump} will always attempt to dump using the basic collection
15520 list, and may fail if a while-stepping frame does not include all the
15521 same data that is collected at the tracepoint hit.
15522 @c This is getting pretty arcane, example would be good.
15524 @node save tracepoints
15525 @subsection @code{save tracepoints @var{filename}}
15526 @kindex save tracepoints
15527 @kindex save-tracepoints
15528 @cindex save tracepoints for future sessions
15530 This command saves all current tracepoint definitions together with
15531 their actions and passcounts, into a file @file{@var{filename}}
15532 suitable for use in a later debugging session. To read the saved
15533 tracepoint definitions, use the @code{source} command (@pxref{Command
15534 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15535 alias for @w{@code{save tracepoints}}
15537 @node Tracepoint Variables
15538 @section Convenience Variables for Tracepoints
15539 @cindex tracepoint variables
15540 @cindex convenience variables for tracepoints
15543 @vindex $trace_frame
15544 @item (int) $trace_frame
15545 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15546 snapshot is selected.
15548 @vindex $tracepoint
15549 @item (int) $tracepoint
15550 The tracepoint for the current trace snapshot.
15552 @vindex $trace_line
15553 @item (int) $trace_line
15554 The line number for the current trace snapshot.
15556 @vindex $trace_file
15557 @item (char []) $trace_file
15558 The source file for the current trace snapshot.
15560 @vindex $trace_func
15561 @item (char []) $trace_func
15562 The name of the function containing @code{$tracepoint}.
15565 Note: @code{$trace_file} is not suitable for use in @code{printf},
15566 use @code{output} instead.
15568 Here's a simple example of using these convenience variables for
15569 stepping through all the trace snapshots and printing some of their
15570 data. Note that these are not the same as trace state variables,
15571 which are managed by the target.
15574 (@value{GDBP}) @b{tfind start}
15576 (@value{GDBP}) @b{while $trace_frame != -1}
15577 > output $trace_file
15578 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15584 @section Using Trace Files
15585 @cindex trace files
15587 In some situations, the target running a trace experiment may no
15588 longer be available; perhaps it crashed, or the hardware was needed
15589 for a different activity. To handle these cases, you can arrange to
15590 dump the trace data into a file, and later use that file as a source
15591 of trace data, via the @code{target tfile} command.
15596 @item tsave [ -r ] @var{filename}
15597 @itemx tsave [-ctf] @var{dirname}
15598 Save the trace data to @var{filename}. By default, this command
15599 assumes that @var{filename} refers to the host filesystem, so if
15600 necessary @value{GDBN} will copy raw trace data up from the target and
15601 then save it. If the target supports it, you can also supply the
15602 optional argument @code{-r} (``remote'') to direct the target to save
15603 the data directly into @var{filename} in its own filesystem, which may be
15604 more efficient if the trace buffer is very large. (Note, however, that
15605 @code{target tfile} can only read from files accessible to the host.)
15606 By default, this command will save trace frame in tfile format.
15607 You can supply the optional argument @code{-ctf} to save data in CTF
15608 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15609 that can be shared by multiple debugging and tracing tools. Please go to
15610 @indicateurl{http://www.efficios.com/ctf} to get more information.
15612 @kindex target tfile
15616 @item target tfile @var{filename}
15617 @itemx target ctf @var{dirname}
15618 Use the file named @var{filename} or directory named @var{dirname} as
15619 a source of trace data. Commands that examine data work as they do with
15620 a live target, but it is not possible to run any new trace experiments.
15621 @code{tstatus} will report the state of the trace run at the moment
15622 the data was saved, as well as the current trace frame you are examining.
15623 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15627 (@value{GDBP}) target ctf ctf.ctf
15628 (@value{GDBP}) tfind
15629 Found trace frame 0, tracepoint 2
15630 39 ++a; /* set tracepoint 1 here */
15631 (@value{GDBP}) tdump
15632 Data collected at tracepoint 2, trace frame 0:
15636 c = @{"123", "456", "789", "123", "456", "789"@}
15637 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15645 @chapter Debugging Programs That Use Overlays
15648 If your program is too large to fit completely in your target system's
15649 memory, you can sometimes use @dfn{overlays} to work around this
15650 problem. @value{GDBN} provides some support for debugging programs that
15654 * How Overlays Work:: A general explanation of overlays.
15655 * Overlay Commands:: Managing overlays in @value{GDBN}.
15656 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15657 mapped by asking the inferior.
15658 * Overlay Sample Program:: A sample program using overlays.
15661 @node How Overlays Work
15662 @section How Overlays Work
15663 @cindex mapped overlays
15664 @cindex unmapped overlays
15665 @cindex load address, overlay's
15666 @cindex mapped address
15667 @cindex overlay area
15669 Suppose you have a computer whose instruction address space is only 64
15670 kilobytes long, but which has much more memory which can be accessed by
15671 other means: special instructions, segment registers, or memory
15672 management hardware, for example. Suppose further that you want to
15673 adapt a program which is larger than 64 kilobytes to run on this system.
15675 One solution is to identify modules of your program which are relatively
15676 independent, and need not call each other directly; call these modules
15677 @dfn{overlays}. Separate the overlays from the main program, and place
15678 their machine code in the larger memory. Place your main program in
15679 instruction memory, but leave at least enough space there to hold the
15680 largest overlay as well.
15682 Now, to call a function located in an overlay, you must first copy that
15683 overlay's machine code from the large memory into the space set aside
15684 for it in the instruction memory, and then jump to its entry point
15687 @c NB: In the below the mapped area's size is greater or equal to the
15688 @c size of all overlays. This is intentional to remind the developer
15689 @c that overlays don't necessarily need to be the same size.
15693 Data Instruction Larger
15694 Address Space Address Space Address Space
15695 +-----------+ +-----------+ +-----------+
15697 +-----------+ +-----------+ +-----------+<-- overlay 1
15698 | program | | main | .----| overlay 1 | load address
15699 | variables | | program | | +-----------+
15700 | and heap | | | | | |
15701 +-----------+ | | | +-----------+<-- overlay 2
15702 | | +-----------+ | | | load address
15703 +-----------+ | | | .-| overlay 2 |
15705 mapped --->+-----------+ | | +-----------+
15706 address | | | | | |
15707 | overlay | <-' | | |
15708 | area | <---' +-----------+<-- overlay 3
15709 | | <---. | | load address
15710 +-----------+ `--| overlay 3 |
15717 @anchor{A code overlay}A code overlay
15721 The diagram (@pxref{A code overlay}) shows a system with separate data
15722 and instruction address spaces. To map an overlay, the program copies
15723 its code from the larger address space to the instruction address space.
15724 Since the overlays shown here all use the same mapped address, only one
15725 may be mapped at a time. For a system with a single address space for
15726 data and instructions, the diagram would be similar, except that the
15727 program variables and heap would share an address space with the main
15728 program and the overlay area.
15730 An overlay loaded into instruction memory and ready for use is called a
15731 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15732 instruction memory. An overlay not present (or only partially present)
15733 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15734 is its address in the larger memory. The mapped address is also called
15735 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15736 called the @dfn{load memory address}, or @dfn{LMA}.
15738 Unfortunately, overlays are not a completely transparent way to adapt a
15739 program to limited instruction memory. They introduce a new set of
15740 global constraints you must keep in mind as you design your program:
15745 Before calling or returning to a function in an overlay, your program
15746 must make sure that overlay is actually mapped. Otherwise, the call or
15747 return will transfer control to the right address, but in the wrong
15748 overlay, and your program will probably crash.
15751 If the process of mapping an overlay is expensive on your system, you
15752 will need to choose your overlays carefully to minimize their effect on
15753 your program's performance.
15756 The executable file you load onto your system must contain each
15757 overlay's instructions, appearing at the overlay's load address, not its
15758 mapped address. However, each overlay's instructions must be relocated
15759 and its symbols defined as if the overlay were at its mapped address.
15760 You can use GNU linker scripts to specify different load and relocation
15761 addresses for pieces of your program; see @ref{Overlay Description,,,
15762 ld.info, Using ld: the GNU linker}.
15765 The procedure for loading executable files onto your system must be able
15766 to load their contents into the larger address space as well as the
15767 instruction and data spaces.
15771 The overlay system described above is rather simple, and could be
15772 improved in many ways:
15777 If your system has suitable bank switch registers or memory management
15778 hardware, you could use those facilities to make an overlay's load area
15779 contents simply appear at their mapped address in instruction space.
15780 This would probably be faster than copying the overlay to its mapped
15781 area in the usual way.
15784 If your overlays are small enough, you could set aside more than one
15785 overlay area, and have more than one overlay mapped at a time.
15788 You can use overlays to manage data, as well as instructions. In
15789 general, data overlays are even less transparent to your design than
15790 code overlays: whereas code overlays only require care when you call or
15791 return to functions, data overlays require care every time you access
15792 the data. Also, if you change the contents of a data overlay, you
15793 must copy its contents back out to its load address before you can copy a
15794 different data overlay into the same mapped area.
15799 @node Overlay Commands
15800 @section Overlay Commands
15802 To use @value{GDBN}'s overlay support, each overlay in your program must
15803 correspond to a separate section of the executable file. The section's
15804 virtual memory address and load memory address must be the overlay's
15805 mapped and load addresses. Identifying overlays with sections allows
15806 @value{GDBN} to determine the appropriate address of a function or
15807 variable, depending on whether the overlay is mapped or not.
15809 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15810 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15815 Disable @value{GDBN}'s overlay support. When overlay support is
15816 disabled, @value{GDBN} assumes that all functions and variables are
15817 always present at their mapped addresses. By default, @value{GDBN}'s
15818 overlay support is disabled.
15820 @item overlay manual
15821 @cindex manual overlay debugging
15822 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15823 relies on you to tell it which overlays are mapped, and which are not,
15824 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15825 commands described below.
15827 @item overlay map-overlay @var{overlay}
15828 @itemx overlay map @var{overlay}
15829 @cindex map an overlay
15830 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15831 be the name of the object file section containing the overlay. When an
15832 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15833 functions and variables at their mapped addresses. @value{GDBN} assumes
15834 that any other overlays whose mapped ranges overlap that of
15835 @var{overlay} are now unmapped.
15837 @item overlay unmap-overlay @var{overlay}
15838 @itemx overlay unmap @var{overlay}
15839 @cindex unmap an overlay
15840 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15841 must be the name of the object file section containing the overlay.
15842 When an overlay is unmapped, @value{GDBN} assumes it can find the
15843 overlay's functions and variables at their load addresses.
15846 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15847 consults a data structure the overlay manager maintains in the inferior
15848 to see which overlays are mapped. For details, see @ref{Automatic
15849 Overlay Debugging}.
15851 @item overlay load-target
15852 @itemx overlay load
15853 @cindex reloading the overlay table
15854 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15855 re-reads the table @value{GDBN} automatically each time the inferior
15856 stops, so this command should only be necessary if you have changed the
15857 overlay mapping yourself using @value{GDBN}. This command is only
15858 useful when using automatic overlay debugging.
15860 @item overlay list-overlays
15861 @itemx overlay list
15862 @cindex listing mapped overlays
15863 Display a list of the overlays currently mapped, along with their mapped
15864 addresses, load addresses, and sizes.
15868 Normally, when @value{GDBN} prints a code address, it includes the name
15869 of the function the address falls in:
15872 (@value{GDBP}) print main
15873 $3 = @{int ()@} 0x11a0 <main>
15876 When overlay debugging is enabled, @value{GDBN} recognizes code in
15877 unmapped overlays, and prints the names of unmapped functions with
15878 asterisks around them. For example, if @code{foo} is a function in an
15879 unmapped overlay, @value{GDBN} prints it this way:
15882 (@value{GDBP}) overlay list
15883 No sections are mapped.
15884 (@value{GDBP}) print foo
15885 $5 = @{int (int)@} 0x100000 <*foo*>
15888 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15892 (@value{GDBP}) overlay list
15893 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15894 mapped at 0x1016 - 0x104a
15895 (@value{GDBP}) print foo
15896 $6 = @{int (int)@} 0x1016 <foo>
15899 When overlay debugging is enabled, @value{GDBN} can find the correct
15900 address for functions and variables in an overlay, whether or not the
15901 overlay is mapped. This allows most @value{GDBN} commands, like
15902 @code{break} and @code{disassemble}, to work normally, even on unmapped
15903 code. However, @value{GDBN}'s breakpoint support has some limitations:
15907 @cindex breakpoints in overlays
15908 @cindex overlays, setting breakpoints in
15909 You can set breakpoints in functions in unmapped overlays, as long as
15910 @value{GDBN} can write to the overlay at its load address.
15912 @value{GDBN} can not set hardware or simulator-based breakpoints in
15913 unmapped overlays. However, if you set a breakpoint at the end of your
15914 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15915 you are using manual overlay management), @value{GDBN} will re-set its
15916 breakpoints properly.
15920 @node Automatic Overlay Debugging
15921 @section Automatic Overlay Debugging
15922 @cindex automatic overlay debugging
15924 @value{GDBN} can automatically track which overlays are mapped and which
15925 are not, given some simple co-operation from the overlay manager in the
15926 inferior. If you enable automatic overlay debugging with the
15927 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15928 looks in the inferior's memory for certain variables describing the
15929 current state of the overlays.
15931 Here are the variables your overlay manager must define to support
15932 @value{GDBN}'s automatic overlay debugging:
15936 @item @code{_ovly_table}:
15937 This variable must be an array of the following structures:
15942 /* The overlay's mapped address. */
15945 /* The size of the overlay, in bytes. */
15946 unsigned long size;
15948 /* The overlay's load address. */
15951 /* Non-zero if the overlay is currently mapped;
15953 unsigned long mapped;
15957 @item @code{_novlys}:
15958 This variable must be a four-byte signed integer, holding the total
15959 number of elements in @code{_ovly_table}.
15963 To decide whether a particular overlay is mapped or not, @value{GDBN}
15964 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15965 @code{lma} members equal the VMA and LMA of the overlay's section in the
15966 executable file. When @value{GDBN} finds a matching entry, it consults
15967 the entry's @code{mapped} member to determine whether the overlay is
15970 In addition, your overlay manager may define a function called
15971 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15972 will silently set a breakpoint there. If the overlay manager then
15973 calls this function whenever it has changed the overlay table, this
15974 will enable @value{GDBN} to accurately keep track of which overlays
15975 are in program memory, and update any breakpoints that may be set
15976 in overlays. This will allow breakpoints to work even if the
15977 overlays are kept in ROM or other non-writable memory while they
15978 are not being executed.
15980 @node Overlay Sample Program
15981 @section Overlay Sample Program
15982 @cindex overlay example program
15984 When linking a program which uses overlays, you must place the overlays
15985 at their load addresses, while relocating them to run at their mapped
15986 addresses. To do this, you must write a linker script (@pxref{Overlay
15987 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15988 since linker scripts are specific to a particular host system, target
15989 architecture, and target memory layout, this manual cannot provide
15990 portable sample code demonstrating @value{GDBN}'s overlay support.
15992 However, the @value{GDBN} source distribution does contain an overlaid
15993 program, with linker scripts for a few systems, as part of its test
15994 suite. The program consists of the following files from
15995 @file{gdb/testsuite/gdb.base}:
15999 The main program file.
16001 A simple overlay manager, used by @file{overlays.c}.
16006 Overlay modules, loaded and used by @file{overlays.c}.
16009 Linker scripts for linking the test program on the @code{d10v-elf}
16010 and @code{m32r-elf} targets.
16013 You can build the test program using the @code{d10v-elf} GCC
16014 cross-compiler like this:
16017 $ d10v-elf-gcc -g -c overlays.c
16018 $ d10v-elf-gcc -g -c ovlymgr.c
16019 $ d10v-elf-gcc -g -c foo.c
16020 $ d10v-elf-gcc -g -c bar.c
16021 $ d10v-elf-gcc -g -c baz.c
16022 $ d10v-elf-gcc -g -c grbx.c
16023 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16024 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16027 The build process is identical for any other architecture, except that
16028 you must substitute the appropriate compiler and linker script for the
16029 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16033 @chapter Using @value{GDBN} with Different Languages
16036 Although programming languages generally have common aspects, they are
16037 rarely expressed in the same manner. For instance, in ANSI C,
16038 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16039 Modula-2, it is accomplished by @code{p^}. Values can also be
16040 represented (and displayed) differently. Hex numbers in C appear as
16041 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16043 @cindex working language
16044 Language-specific information is built into @value{GDBN} for some languages,
16045 allowing you to express operations like the above in your program's
16046 native language, and allowing @value{GDBN} to output values in a manner
16047 consistent with the syntax of your program's native language. The
16048 language you use to build expressions is called the @dfn{working
16052 * Setting:: Switching between source languages
16053 * Show:: Displaying the language
16054 * Checks:: Type and range checks
16055 * Supported Languages:: Supported languages
16056 * Unsupported Languages:: Unsupported languages
16060 @section Switching Between Source Languages
16062 There are two ways to control the working language---either have @value{GDBN}
16063 set it automatically, or select it manually yourself. You can use the
16064 @code{set language} command for either purpose. On startup, @value{GDBN}
16065 defaults to setting the language automatically. The working language is
16066 used to determine how expressions you type are interpreted, how values
16069 In addition to the working language, every source file that
16070 @value{GDBN} knows about has its own working language. For some object
16071 file formats, the compiler might indicate which language a particular
16072 source file is in. However, most of the time @value{GDBN} infers the
16073 language from the name of the file. The language of a source file
16074 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16075 show each frame appropriately for its own language. There is no way to
16076 set the language of a source file from within @value{GDBN}, but you can
16077 set the language associated with a filename extension. @xref{Show, ,
16078 Displaying the Language}.
16080 This is most commonly a problem when you use a program, such
16081 as @code{cfront} or @code{f2c}, that generates C but is written in
16082 another language. In that case, make the
16083 program use @code{#line} directives in its C output; that way
16084 @value{GDBN} will know the correct language of the source code of the original
16085 program, and will display that source code, not the generated C code.
16088 * Filenames:: Filename extensions and languages.
16089 * Manually:: Setting the working language manually
16090 * Automatically:: Having @value{GDBN} infer the source language
16094 @subsection List of Filename Extensions and Languages
16096 If a source file name ends in one of the following extensions, then
16097 @value{GDBN} infers that its language is the one indicated.
16115 C@t{++} source file
16121 Objective-C source file
16125 Fortran source file
16128 Modula-2 source file
16132 Assembler source file. This actually behaves almost like C, but
16133 @value{GDBN} does not skip over function prologues when stepping.
16136 In addition, you may set the language associated with a filename
16137 extension. @xref{Show, , Displaying the Language}.
16140 @subsection Setting the Working Language
16142 If you allow @value{GDBN} to set the language automatically,
16143 expressions are interpreted the same way in your debugging session and
16146 @kindex set language
16147 If you wish, you may set the language manually. To do this, issue the
16148 command @samp{set language @var{lang}}, where @var{lang} is the name of
16149 a language, such as
16150 @code{c} or @code{modula-2}.
16151 For a list of the supported languages, type @samp{set language}.
16153 Setting the language manually prevents @value{GDBN} from updating the working
16154 language automatically. This can lead to confusion if you try
16155 to debug a program when the working language is not the same as the
16156 source language, when an expression is acceptable to both
16157 languages---but means different things. For instance, if the current
16158 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16166 might not have the effect you intended. In C, this means to add
16167 @code{b} and @code{c} and place the result in @code{a}. The result
16168 printed would be the value of @code{a}. In Modula-2, this means to compare
16169 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16171 @node Automatically
16172 @subsection Having @value{GDBN} Infer the Source Language
16174 To have @value{GDBN} set the working language automatically, use
16175 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16176 then infers the working language. That is, when your program stops in a
16177 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16178 working language to the language recorded for the function in that
16179 frame. If the language for a frame is unknown (that is, if the function
16180 or block corresponding to the frame was defined in a source file that
16181 does not have a recognized extension), the current working language is
16182 not changed, and @value{GDBN} issues a warning.
16184 This may not seem necessary for most programs, which are written
16185 entirely in one source language. However, program modules and libraries
16186 written in one source language can be used by a main program written in
16187 a different source language. Using @samp{set language auto} in this
16188 case frees you from having to set the working language manually.
16191 @section Displaying the Language
16193 The following commands help you find out which language is the
16194 working language, and also what language source files were written in.
16197 @item show language
16198 @anchor{show language}
16199 @kindex show language
16200 Display the current working language. This is the
16201 language you can use with commands such as @code{print} to
16202 build and compute expressions that may involve variables in your program.
16205 @kindex info frame@r{, show the source language}
16206 Display the source language for this frame. This language becomes the
16207 working language if you use an identifier from this frame.
16208 @xref{Frame Info, ,Information about a Frame}, to identify the other
16209 information listed here.
16212 @kindex info source@r{, show the source language}
16213 Display the source language of this source file.
16214 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16215 information listed here.
16218 In unusual circumstances, you may have source files with extensions
16219 not in the standard list. You can then set the extension associated
16220 with a language explicitly:
16223 @item set extension-language @var{ext} @var{language}
16224 @kindex set extension-language
16225 Tell @value{GDBN} that source files with extension @var{ext} are to be
16226 assumed as written in the source language @var{language}.
16228 @item info extensions
16229 @kindex info extensions
16230 List all the filename extensions and the associated languages.
16234 @section Type and Range Checking
16236 Some languages are designed to guard you against making seemingly common
16237 errors through a series of compile- and run-time checks. These include
16238 checking the type of arguments to functions and operators and making
16239 sure mathematical overflows are caught at run time. Checks such as
16240 these help to ensure a program's correctness once it has been compiled
16241 by eliminating type mismatches and providing active checks for range
16242 errors when your program is running.
16244 By default @value{GDBN} checks for these errors according to the
16245 rules of the current source language. Although @value{GDBN} does not check
16246 the statements in your program, it can check expressions entered directly
16247 into @value{GDBN} for evaluation via the @code{print} command, for example.
16250 * Type Checking:: An overview of type checking
16251 * Range Checking:: An overview of range checking
16254 @cindex type checking
16255 @cindex checks, type
16256 @node Type Checking
16257 @subsection An Overview of Type Checking
16259 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16260 arguments to operators and functions have to be of the correct type,
16261 otherwise an error occurs. These checks prevent type mismatch
16262 errors from ever causing any run-time problems. For example,
16265 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16267 (@value{GDBP}) print obj.my_method (0)
16270 (@value{GDBP}) print obj.my_method (0x1234)
16271 Cannot resolve method klass::my_method to any overloaded instance
16274 The second example fails because in C@t{++} the integer constant
16275 @samp{0x1234} is not type-compatible with the pointer parameter type.
16277 For the expressions you use in @value{GDBN} commands, you can tell
16278 @value{GDBN} to not enforce strict type checking or
16279 to treat any mismatches as errors and abandon the expression;
16280 When type checking is disabled, @value{GDBN} successfully evaluates
16281 expressions like the second example above.
16283 Even if type checking is off, there may be other reasons
16284 related to type that prevent @value{GDBN} from evaluating an expression.
16285 For instance, @value{GDBN} does not know how to add an @code{int} and
16286 a @code{struct foo}. These particular type errors have nothing to do
16287 with the language in use and usually arise from expressions which make
16288 little sense to evaluate anyway.
16290 @value{GDBN} provides some additional commands for controlling type checking:
16292 @kindex set check type
16293 @kindex show check type
16295 @item set check type on
16296 @itemx set check type off
16297 Set strict type checking on or off. If any type mismatches occur in
16298 evaluating an expression while type checking is on, @value{GDBN} prints a
16299 message and aborts evaluation of the expression.
16301 @item show check type
16302 Show the current setting of type checking and whether @value{GDBN}
16303 is enforcing strict type checking rules.
16306 @cindex range checking
16307 @cindex checks, range
16308 @node Range Checking
16309 @subsection An Overview of Range Checking
16311 In some languages (such as Modula-2), it is an error to exceed the
16312 bounds of a type; this is enforced with run-time checks. Such range
16313 checking is meant to ensure program correctness by making sure
16314 computations do not overflow, or indices on an array element access do
16315 not exceed the bounds of the array.
16317 For expressions you use in @value{GDBN} commands, you can tell
16318 @value{GDBN} to treat range errors in one of three ways: ignore them,
16319 always treat them as errors and abandon the expression, or issue
16320 warnings but evaluate the expression anyway.
16322 A range error can result from numerical overflow, from exceeding an
16323 array index bound, or when you type a constant that is not a member
16324 of any type. Some languages, however, do not treat overflows as an
16325 error. In many implementations of C, mathematical overflow causes the
16326 result to ``wrap around'' to lower values---for example, if @var{m} is
16327 the largest integer value, and @var{s} is the smallest, then
16330 @var{m} + 1 @result{} @var{s}
16333 This, too, is specific to individual languages, and in some cases
16334 specific to individual compilers or machines. @xref{Supported Languages, ,
16335 Supported Languages}, for further details on specific languages.
16337 @value{GDBN} provides some additional commands for controlling the range checker:
16339 @kindex set check range
16340 @kindex show check range
16342 @item set check range auto
16343 Set range checking on or off based on the current working language.
16344 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16347 @item set check range on
16348 @itemx set check range off
16349 Set range checking on or off, overriding the default setting for the
16350 current working language. A warning is issued if the setting does not
16351 match the language default. If a range error occurs and range checking is on,
16352 then a message is printed and evaluation of the expression is aborted.
16354 @item set check range warn
16355 Output messages when the @value{GDBN} range checker detects a range error,
16356 but attempt to evaluate the expression anyway. Evaluating the
16357 expression may still be impossible for other reasons, such as accessing
16358 memory that the process does not own (a typical example from many Unix
16361 @item show check range
16362 Show the current setting of the range checker, and whether or not it is
16363 being set automatically by @value{GDBN}.
16366 @node Supported Languages
16367 @section Supported Languages
16369 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16370 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16371 @c This is false ...
16372 Some @value{GDBN} features may be used in expressions regardless of the
16373 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16374 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16375 ,Expressions}) can be used with the constructs of any supported
16378 The following sections detail to what degree each source language is
16379 supported by @value{GDBN}. These sections are not meant to be language
16380 tutorials or references, but serve only as a reference guide to what the
16381 @value{GDBN} expression parser accepts, and what input and output
16382 formats should look like for different languages. There are many good
16383 books written on each of these languages; please look to these for a
16384 language reference or tutorial.
16387 * C:: C and C@t{++}
16390 * Objective-C:: Objective-C
16391 * OpenCL C:: OpenCL C
16392 * Fortran:: Fortran
16395 * Modula-2:: Modula-2
16400 @subsection C and C@t{++}
16402 @cindex C and C@t{++}
16403 @cindex expressions in C or C@t{++}
16405 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16406 to both languages. Whenever this is the case, we discuss those languages
16410 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16411 @cindex @sc{gnu} C@t{++}
16412 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16413 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16414 effectively, you must compile your C@t{++} programs with a supported
16415 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16416 compiler (@code{aCC}).
16419 * C Operators:: C and C@t{++} operators
16420 * C Constants:: C and C@t{++} constants
16421 * C Plus Plus Expressions:: C@t{++} expressions
16422 * C Defaults:: Default settings for C and C@t{++}
16423 * C Checks:: C and C@t{++} type and range checks
16424 * Debugging C:: @value{GDBN} and C
16425 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16426 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16430 @subsubsection C and C@t{++} Operators
16432 @cindex C and C@t{++} operators
16434 Operators must be defined on values of specific types. For instance,
16435 @code{+} is defined on numbers, but not on structures. Operators are
16436 often defined on groups of types.
16438 For the purposes of C and C@t{++}, the following definitions hold:
16443 @emph{Integral types} include @code{int} with any of its storage-class
16444 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16447 @emph{Floating-point types} include @code{float}, @code{double}, and
16448 @code{long double} (if supported by the target platform).
16451 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16454 @emph{Scalar types} include all of the above.
16459 The following operators are supported. They are listed here
16460 in order of increasing precedence:
16464 The comma or sequencing operator. Expressions in a comma-separated list
16465 are evaluated from left to right, with the result of the entire
16466 expression being the last expression evaluated.
16469 Assignment. The value of an assignment expression is the value
16470 assigned. Defined on scalar types.
16473 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16474 and translated to @w{@code{@var{a} = @var{a op b}}}.
16475 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16476 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16477 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16480 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16481 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16482 should be of an integral type.
16485 Logical @sc{or}. Defined on integral types.
16488 Logical @sc{and}. Defined on integral types.
16491 Bitwise @sc{or}. Defined on integral types.
16494 Bitwise exclusive-@sc{or}. Defined on integral types.
16497 Bitwise @sc{and}. Defined on integral types.
16500 Equality and inequality. Defined on scalar types. The value of these
16501 expressions is 0 for false and non-zero for true.
16503 @item <@r{, }>@r{, }<=@r{, }>=
16504 Less than, greater than, less than or equal, greater than or equal.
16505 Defined on scalar types. The value of these expressions is 0 for false
16506 and non-zero for true.
16509 left shift, and right shift. Defined on integral types.
16512 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16515 Addition and subtraction. Defined on integral types, floating-point types and
16518 @item *@r{, }/@r{, }%
16519 Multiplication, division, and modulus. Multiplication and division are
16520 defined on integral and floating-point types. Modulus is defined on
16524 Increment and decrement. When appearing before a variable, the
16525 operation is performed before the variable is used in an expression;
16526 when appearing after it, the variable's value is used before the
16527 operation takes place.
16530 Pointer dereferencing. Defined on pointer types. Same precedence as
16534 Address operator. Defined on variables. Same precedence as @code{++}.
16536 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16537 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16538 to examine the address
16539 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16543 Negative. Defined on integral and floating-point types. Same
16544 precedence as @code{++}.
16547 Logical negation. Defined on integral types. Same precedence as
16551 Bitwise complement operator. Defined on integral types. Same precedence as
16556 Structure member, and pointer-to-structure member. For convenience,
16557 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16558 pointer based on the stored type information.
16559 Defined on @code{struct} and @code{union} data.
16562 Dereferences of pointers to members.
16565 Array indexing. @code{@var{a}[@var{i}]} is defined as
16566 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16569 Function parameter list. Same precedence as @code{->}.
16572 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16573 and @code{class} types.
16576 Doubled colons also represent the @value{GDBN} scope operator
16577 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16581 If an operator is redefined in the user code, @value{GDBN} usually
16582 attempts to invoke the redefined version instead of using the operator's
16583 predefined meaning.
16586 @subsubsection C and C@t{++} Constants
16588 @cindex C and C@t{++} constants
16590 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16595 Integer constants are a sequence of digits. Octal constants are
16596 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16597 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16598 @samp{l}, specifying that the constant should be treated as a
16602 Floating point constants are a sequence of digits, followed by a decimal
16603 point, followed by a sequence of digits, and optionally followed by an
16604 exponent. An exponent is of the form:
16605 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16606 sequence of digits. The @samp{+} is optional for positive exponents.
16607 A floating-point constant may also end with a letter @samp{f} or
16608 @samp{F}, specifying that the constant should be treated as being of
16609 the @code{float} (as opposed to the default @code{double}) type; or with
16610 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16614 Enumerated constants consist of enumerated identifiers, or their
16615 integral equivalents.
16618 Character constants are a single character surrounded by single quotes
16619 (@code{'}), or a number---the ordinal value of the corresponding character
16620 (usually its @sc{ascii} value). Within quotes, the single character may
16621 be represented by a letter or by @dfn{escape sequences}, which are of
16622 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16623 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16624 @samp{@var{x}} is a predefined special character---for example,
16625 @samp{\n} for newline.
16627 Wide character constants can be written by prefixing a character
16628 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16629 form of @samp{x}. The target wide character set is used when
16630 computing the value of this constant (@pxref{Character Sets}).
16633 String constants are a sequence of character constants surrounded by
16634 double quotes (@code{"}). Any valid character constant (as described
16635 above) may appear. Double quotes within the string must be preceded by
16636 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16639 Wide string constants can be written by prefixing a string constant
16640 with @samp{L}, as in C. The target wide character set is used when
16641 computing the value of this constant (@pxref{Character Sets}).
16644 Pointer constants are an integral value. You can also write pointers
16645 to constants using the C operator @samp{&}.
16648 Array constants are comma-separated lists surrounded by braces @samp{@{}
16649 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16650 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16651 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16654 @node C Plus Plus Expressions
16655 @subsubsection C@t{++} Expressions
16657 @cindex expressions in C@t{++}
16658 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16660 @cindex debugging C@t{++} programs
16661 @cindex C@t{++} compilers
16662 @cindex debug formats and C@t{++}
16663 @cindex @value{NGCC} and C@t{++}
16665 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16666 the proper compiler and the proper debug format. Currently,
16667 @value{GDBN} works best when debugging C@t{++} code that is compiled
16668 with the most recent version of @value{NGCC} possible. The DWARF
16669 debugging format is preferred; @value{NGCC} defaults to this on most
16670 popular platforms. Other compilers and/or debug formats are likely to
16671 work badly or not at all when using @value{GDBN} to debug C@t{++}
16672 code. @xref{Compilation}.
16677 @cindex member functions
16679 Member function calls are allowed; you can use expressions like
16682 count = aml->GetOriginal(x, y)
16685 @vindex this@r{, inside C@t{++} member functions}
16686 @cindex namespace in C@t{++}
16688 While a member function is active (in the selected stack frame), your
16689 expressions have the same namespace available as the member function;
16690 that is, @value{GDBN} allows implicit references to the class instance
16691 pointer @code{this} following the same rules as C@t{++}. @code{using}
16692 declarations in the current scope are also respected by @value{GDBN}.
16694 @cindex call overloaded functions
16695 @cindex overloaded functions, calling
16696 @cindex type conversions in C@t{++}
16698 You can call overloaded functions; @value{GDBN} resolves the function
16699 call to the right definition, with some restrictions. @value{GDBN} does not
16700 perform overload resolution involving user-defined type conversions,
16701 calls to constructors, or instantiations of templates that do not exist
16702 in the program. It also cannot handle ellipsis argument lists or
16705 It does perform integral conversions and promotions, floating-point
16706 promotions, arithmetic conversions, pointer conversions, conversions of
16707 class objects to base classes, and standard conversions such as those of
16708 functions or arrays to pointers; it requires an exact match on the
16709 number of function arguments.
16711 Overload resolution is always performed, unless you have specified
16712 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16713 ,@value{GDBN} Features for C@t{++}}.
16715 You must specify @code{set overload-resolution off} in order to use an
16716 explicit function signature to call an overloaded function, as in
16718 p 'foo(char,int)'('x', 13)
16721 The @value{GDBN} command-completion facility can simplify this;
16722 see @ref{Completion, ,Command Completion}.
16724 @cindex reference declarations
16726 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16727 references; you can use them in expressions just as you do in C@t{++}
16728 source---they are automatically dereferenced.
16730 In the parameter list shown when @value{GDBN} displays a frame, the values of
16731 reference variables are not displayed (unlike other variables); this
16732 avoids clutter, since references are often used for large structures.
16733 The @emph{address} of a reference variable is always shown, unless
16734 you have specified @samp{set print address off}.
16737 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16738 expressions can use it just as expressions in your program do. Since
16739 one scope may be defined in another, you can use @code{::} repeatedly if
16740 necessary, for example in an expression like
16741 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16742 resolving name scope by reference to source files, in both C and C@t{++}
16743 debugging (@pxref{Variables, ,Program Variables}).
16746 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16751 @subsubsection C and C@t{++} Defaults
16753 @cindex C and C@t{++} defaults
16755 If you allow @value{GDBN} to set range checking automatically, it
16756 defaults to @code{off} whenever the working language changes to
16757 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16758 selects the working language.
16760 If you allow @value{GDBN} to set the language automatically, it
16761 recognizes source files whose names end with @file{.c}, @file{.C}, or
16762 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16763 these files, it sets the working language to C or C@t{++}.
16764 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16765 for further details.
16768 @subsubsection C and C@t{++} Type and Range Checks
16770 @cindex C and C@t{++} checks
16772 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16773 checking is used. However, if you turn type checking off, @value{GDBN}
16774 will allow certain non-standard conversions, such as promoting integer
16775 constants to pointers.
16777 Range checking, if turned on, is done on mathematical operations. Array
16778 indices are not checked, since they are often used to index a pointer
16779 that is not itself an array.
16782 @subsubsection @value{GDBN} and C
16784 The @code{set print union} and @code{show print union} commands apply to
16785 the @code{union} type. When set to @samp{on}, any @code{union} that is
16786 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16787 appears as @samp{@{...@}}.
16789 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16790 with pointers and a memory allocation function. @xref{Expressions,
16793 @node Debugging C Plus Plus
16794 @subsubsection @value{GDBN} Features for C@t{++}
16796 @cindex commands for C@t{++}
16798 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16799 designed specifically for use with C@t{++}. Here is a summary:
16802 @cindex break in overloaded functions
16803 @item @r{breakpoint menus}
16804 When you want a breakpoint in a function whose name is overloaded,
16805 @value{GDBN} has the capability to display a menu of possible breakpoint
16806 locations to help you specify which function definition you want.
16807 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16809 @cindex overloading in C@t{++}
16810 @item rbreak @var{regex}
16811 Setting breakpoints using regular expressions is helpful for setting
16812 breakpoints on overloaded functions that are not members of any special
16814 @xref{Set Breaks, ,Setting Breakpoints}.
16816 @cindex C@t{++} exception handling
16818 @itemx catch rethrow
16820 Debug C@t{++} exception handling using these commands. @xref{Set
16821 Catchpoints, , Setting Catchpoints}.
16823 @cindex inheritance
16824 @item ptype @var{typename}
16825 Print inheritance relationships as well as other information for type
16827 @xref{Symbols, ,Examining the Symbol Table}.
16829 @item info vtbl @var{expression}.
16830 The @code{info vtbl} command can be used to display the virtual
16831 method tables of the object computed by @var{expression}. This shows
16832 one entry per virtual table; there may be multiple virtual tables when
16833 multiple inheritance is in use.
16835 @cindex C@t{++} demangling
16836 @item demangle @var{name}
16837 Demangle @var{name}.
16838 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16840 @cindex C@t{++} symbol display
16841 @item set print demangle
16842 @itemx show print demangle
16843 @itemx set print asm-demangle
16844 @itemx show print asm-demangle
16845 Control whether C@t{++} symbols display in their source form, both when
16846 displaying code as C@t{++} source and when displaying disassemblies.
16847 @xref{Print Settings, ,Print Settings}.
16849 @item set print object
16850 @itemx show print object
16851 Choose whether to print derived (actual) or declared types of objects.
16852 @xref{Print Settings, ,Print Settings}.
16854 @item set print vtbl
16855 @itemx show print vtbl
16856 Control the format for printing virtual function tables.
16857 @xref{Print Settings, ,Print Settings}.
16858 (The @code{vtbl} commands do not work on programs compiled with the HP
16859 ANSI C@t{++} compiler (@code{aCC}).)
16861 @kindex set overload-resolution
16862 @cindex overloaded functions, overload resolution
16863 @item set overload-resolution on
16864 Enable overload resolution for C@t{++} expression evaluation. The default
16865 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16866 and searches for a function whose signature matches the argument types,
16867 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16868 Expressions, ,C@t{++} Expressions}, for details).
16869 If it cannot find a match, it emits a message.
16871 @item set overload-resolution off
16872 Disable overload resolution for C@t{++} expression evaluation. For
16873 overloaded functions that are not class member functions, @value{GDBN}
16874 chooses the first function of the specified name that it finds in the
16875 symbol table, whether or not its arguments are of the correct type. For
16876 overloaded functions that are class member functions, @value{GDBN}
16877 searches for a function whose signature @emph{exactly} matches the
16880 @kindex show overload-resolution
16881 @item show overload-resolution
16882 Show the current setting of overload resolution.
16884 @item @r{Overloaded symbol names}
16885 You can specify a particular definition of an overloaded symbol, using
16886 the same notation that is used to declare such symbols in C@t{++}: type
16887 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16888 also use the @value{GDBN} command-line word completion facilities to list the
16889 available choices, or to finish the type list for you.
16890 @xref{Completion,, Command Completion}, for details on how to do this.
16892 @item @r{Breakpoints in template functions}
16894 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
16895 template parameter lists when it encounters a symbol which includes a
16896 C@t{++} template. This permits setting breakpoints on families of template functions
16897 or functions whose parameters include template types.
16899 The @kbd{-qualified} flag may be used to override this behavior, causing
16900 @value{GDBN} to search for a specific function or type.
16902 The @value{GDBN} command-line word completion facility also understands
16903 template parameters and may be used to list available choices or finish
16904 template parameter lists for you. @xref{Completion,, Command Completion}, for
16905 details on how to do this.
16907 @item @r{Breakpoints in functions with ABI tags}
16909 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16910 correspond to changes in the ABI of a type, function, or variable that
16911 would not otherwise be reflected in a mangled name. See
16912 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16915 The ABI tags are visible in C@t{++} demangled names. For example, a
16916 function that returns a std::string:
16919 std::string function(int);
16923 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16924 tag, and @value{GDBN} displays the symbol like this:
16927 function[abi:cxx11](int)
16930 You can set a breakpoint on such functions simply as if they had no
16934 (gdb) b function(int)
16935 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16936 (gdb) info breakpoints
16937 Num Type Disp Enb Address What
16938 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16942 On the rare occasion you need to disambiguate between different ABI
16943 tags, you can do so by simply including the ABI tag in the function
16947 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16951 @node Decimal Floating Point
16952 @subsubsection Decimal Floating Point format
16953 @cindex decimal floating point format
16955 @value{GDBN} can examine, set and perform computations with numbers in
16956 decimal floating point format, which in the C language correspond to the
16957 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16958 specified by the extension to support decimal floating-point arithmetic.
16960 There are two encodings in use, depending on the architecture: BID (Binary
16961 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16962 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16965 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16966 to manipulate decimal floating point numbers, it is not possible to convert
16967 (using a cast, for example) integers wider than 32-bit to decimal float.
16969 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16970 point computations, error checking in decimal float operations ignores
16971 underflow, overflow and divide by zero exceptions.
16973 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16974 to inspect @code{_Decimal128} values stored in floating point registers.
16975 See @ref{PowerPC,,PowerPC} for more details.
16981 @value{GDBN} can be used to debug programs written in D and compiled with
16982 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16983 specific feature --- dynamic arrays.
16988 @cindex Go (programming language)
16989 @value{GDBN} can be used to debug programs written in Go and compiled with
16990 @file{gccgo} or @file{6g} compilers.
16992 Here is a summary of the Go-specific features and restrictions:
16995 @cindex current Go package
16996 @item The current Go package
16997 The name of the current package does not need to be specified when
16998 specifying global variables and functions.
17000 For example, given the program:
17004 var myglob = "Shall we?"
17010 When stopped inside @code{main} either of these work:
17014 (gdb) p main.myglob
17017 @cindex builtin Go types
17018 @item Builtin Go types
17019 The @code{string} type is recognized by @value{GDBN} and is printed
17022 @cindex builtin Go functions
17023 @item Builtin Go functions
17024 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17025 function and handles it internally.
17027 @cindex restrictions on Go expressions
17028 @item Restrictions on Go expressions
17029 All Go operators are supported except @code{&^}.
17030 The Go @code{_} ``blank identifier'' is not supported.
17031 Automatic dereferencing of pointers is not supported.
17035 @subsection Objective-C
17037 @cindex Objective-C
17038 This section provides information about some commands and command
17039 options that are useful for debugging Objective-C code. See also
17040 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17041 few more commands specific to Objective-C support.
17044 * Method Names in Commands::
17045 * The Print Command with Objective-C::
17048 @node Method Names in Commands
17049 @subsubsection Method Names in Commands
17051 The following commands have been extended to accept Objective-C method
17052 names as line specifications:
17054 @kindex clear@r{, and Objective-C}
17055 @kindex break@r{, and Objective-C}
17056 @kindex info line@r{, and Objective-C}
17057 @kindex jump@r{, and Objective-C}
17058 @kindex list@r{, and Objective-C}
17062 @item @code{info line}
17067 A fully qualified Objective-C method name is specified as
17070 -[@var{Class} @var{methodName}]
17073 where the minus sign is used to indicate an instance method and a
17074 plus sign (not shown) is used to indicate a class method. The class
17075 name @var{Class} and method name @var{methodName} are enclosed in
17076 brackets, similar to the way messages are specified in Objective-C
17077 source code. For example, to set a breakpoint at the @code{create}
17078 instance method of class @code{Fruit} in the program currently being
17082 break -[Fruit create]
17085 To list ten program lines around the @code{initialize} class method,
17089 list +[NSText initialize]
17092 In the current version of @value{GDBN}, the plus or minus sign is
17093 required. In future versions of @value{GDBN}, the plus or minus
17094 sign will be optional, but you can use it to narrow the search. It
17095 is also possible to specify just a method name:
17101 You must specify the complete method name, including any colons. If
17102 your program's source files contain more than one @code{create} method,
17103 you'll be presented with a numbered list of classes that implement that
17104 method. Indicate your choice by number, or type @samp{0} to exit if
17107 As another example, to clear a breakpoint established at the
17108 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17111 clear -[NSWindow makeKeyAndOrderFront:]
17114 @node The Print Command with Objective-C
17115 @subsubsection The Print Command With Objective-C
17116 @cindex Objective-C, print objects
17117 @kindex print-object
17118 @kindex po @r{(@code{print-object})}
17120 The print command has also been extended to accept methods. For example:
17123 print -[@var{object} hash]
17126 @cindex print an Objective-C object description
17127 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17129 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17130 and print the result. Also, an additional command has been added,
17131 @code{print-object} or @code{po} for short, which is meant to print
17132 the description of an object. However, this command may only work
17133 with certain Objective-C libraries that have a particular hook
17134 function, @code{_NSPrintForDebugger}, defined.
17137 @subsection OpenCL C
17140 This section provides information about @value{GDBN}s OpenCL C support.
17143 * OpenCL C Datatypes::
17144 * OpenCL C Expressions::
17145 * OpenCL C Operators::
17148 @node OpenCL C Datatypes
17149 @subsubsection OpenCL C Datatypes
17151 @cindex OpenCL C Datatypes
17152 @value{GDBN} supports the builtin scalar and vector datatypes specified
17153 by OpenCL 1.1. In addition the half- and double-precision floating point
17154 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17155 extensions are also known to @value{GDBN}.
17157 @node OpenCL C Expressions
17158 @subsubsection OpenCL C Expressions
17160 @cindex OpenCL C Expressions
17161 @value{GDBN} supports accesses to vector components including the access as
17162 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17163 supported by @value{GDBN} can be used as well.
17165 @node OpenCL C Operators
17166 @subsubsection OpenCL C Operators
17168 @cindex OpenCL C Operators
17169 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17173 @subsection Fortran
17174 @cindex Fortran-specific support in @value{GDBN}
17176 @value{GDBN} can be used to debug programs written in Fortran, but it
17177 currently supports only the features of Fortran 77 language.
17179 @cindex trailing underscore, in Fortran symbols
17180 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17181 among them) append an underscore to the names of variables and
17182 functions. When you debug programs compiled by those compilers, you
17183 will need to refer to variables and functions with a trailing
17187 * Fortran Operators:: Fortran operators and expressions
17188 * Fortran Defaults:: Default settings for Fortran
17189 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17192 @node Fortran Operators
17193 @subsubsection Fortran Operators and Expressions
17195 @cindex Fortran operators and expressions
17197 Operators must be defined on values of specific types. For instance,
17198 @code{+} is defined on numbers, but not on characters or other non-
17199 arithmetic types. Operators are often defined on groups of types.
17203 The exponentiation operator. It raises the first operand to the power
17207 The range operator. Normally used in the form of array(low:high) to
17208 represent a section of array.
17211 The access component operator. Normally used to access elements in derived
17212 types. Also suitable for unions. As unions aren't part of regular Fortran,
17213 this can only happen when accessing a register that uses a gdbarch-defined
17216 The scope operator. Normally used to access variables in modules or
17217 to set breakpoints on subroutines nested in modules or in other
17218 subroutines (internal subroutines).
17221 @node Fortran Defaults
17222 @subsubsection Fortran Defaults
17224 @cindex Fortran Defaults
17226 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17227 default uses case-insensitive matches for Fortran symbols. You can
17228 change that with the @samp{set case-insensitive} command, see
17229 @ref{Symbols}, for the details.
17231 @node Special Fortran Commands
17232 @subsubsection Special Fortran Commands
17234 @cindex Special Fortran commands
17236 @value{GDBN} has some commands to support Fortran-specific features,
17237 such as displaying common blocks.
17240 @cindex @code{COMMON} blocks, Fortran
17241 @kindex info common
17242 @item info common @r{[}@var{common-name}@r{]}
17243 This command prints the values contained in the Fortran @code{COMMON}
17244 block whose name is @var{common-name}. With no argument, the names of
17245 all @code{COMMON} blocks visible at the current program location are
17247 @cindex arrays slices (Fortran)
17248 @kindex set fortran repack-array-slices
17249 @kindex show fortran repack-array-slices
17250 @item set fortran repack-array-slices [on|off]
17251 @item show fortran repack-array-slices
17252 When taking a slice from an array, a Fortran compiler can choose to
17253 either produce an array descriptor that describes the slice in place,
17254 or it may repack the slice, copying the elements of the slice into a
17255 new region of memory.
17257 When this setting is on, then @value{GDBN} will also repack array
17258 slices in some situations. When this setting is off, then
17259 @value{GDBN} will create array descriptors for slices that reference
17260 the original data in place.
17262 @value{GDBN} will never repack an array slice if the data for the
17263 slice is contiguous within the original array.
17265 @value{GDBN} will always repack string slices if the data for the
17266 slice is non-contiguous within the original string as @value{GDBN}
17267 does not support printing non-contiguous strings.
17269 The default for this setting is @code{off}.
17275 @cindex Pascal support in @value{GDBN}, limitations
17276 Debugging Pascal programs which use sets, subranges, file variables, or
17277 nested functions does not currently work. @value{GDBN} does not support
17278 entering expressions, printing values, or similar features using Pascal
17281 The Pascal-specific command @code{set print pascal_static-members}
17282 controls whether static members of Pascal objects are displayed.
17283 @xref{Print Settings, pascal_static-members}.
17288 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17289 Programming Language}. Type- and value-printing, and expression
17290 parsing, are reasonably complete. However, there are a few
17291 peculiarities and holes to be aware of.
17295 Linespecs (@pxref{Specify Location}) are never relative to the current
17296 crate. Instead, they act as if there were a global namespace of
17297 crates, somewhat similar to the way @code{extern crate} behaves.
17299 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17300 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17301 to set a breakpoint in a function named @samp{f} in a crate named
17304 As a consequence of this approach, linespecs also cannot refer to
17305 items using @samp{self::} or @samp{super::}.
17308 Because @value{GDBN} implements Rust name-lookup semantics in
17309 expressions, it will sometimes prepend the current crate to a name.
17310 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17311 @samp{K}, then @code{print ::x::y} will try to find the symbol
17314 However, since it is useful to be able to refer to other crates when
17315 debugging, @value{GDBN} provides the @code{extern} extension to
17316 circumvent this. To use the extension, just put @code{extern} before
17317 a path expression to refer to the otherwise unavailable ``global''
17320 In the above example, if you wanted to refer to the symbol @samp{y} in
17321 the crate @samp{x}, you would use @code{print extern x::y}.
17324 The Rust expression evaluator does not support ``statement-like''
17325 expressions such as @code{if} or @code{match}, or lambda expressions.
17328 Tuple expressions are not implemented.
17331 The Rust expression evaluator does not currently implement the
17332 @code{Drop} trait. Objects that may be created by the evaluator will
17333 never be destroyed.
17336 @value{GDBN} does not implement type inference for generics. In order
17337 to call generic functions or otherwise refer to generic items, you
17338 will have to specify the type parameters manually.
17341 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17342 cases this does not cause any problems. However, in an expression
17343 context, completing a generic function name will give syntactically
17344 invalid results. This happens because Rust requires the @samp{::}
17345 operator between the function name and its generic arguments. For
17346 example, @value{GDBN} might provide a completion like
17347 @code{crate::f<u32>}, where the parser would require
17348 @code{crate::f::<u32>}.
17351 As of this writing, the Rust compiler (version 1.8) has a few holes in
17352 the debugging information it generates. These holes prevent certain
17353 features from being implemented by @value{GDBN}:
17357 Method calls cannot be made via traits.
17360 Operator overloading is not implemented.
17363 When debugging in a monomorphized function, you cannot use the generic
17367 The type @code{Self} is not available.
17370 @code{use} statements are not available, so some names may not be
17371 available in the crate.
17376 @subsection Modula-2
17378 @cindex Modula-2, @value{GDBN} support
17380 The extensions made to @value{GDBN} to support Modula-2 only support
17381 output from the @sc{gnu} Modula-2 compiler (which is currently being
17382 developed). Other Modula-2 compilers are not currently supported, and
17383 attempting to debug executables produced by them is most likely
17384 to give an error as @value{GDBN} reads in the executable's symbol
17387 @cindex expressions in Modula-2
17389 * M2 Operators:: Built-in operators
17390 * Built-In Func/Proc:: Built-in functions and procedures
17391 * M2 Constants:: Modula-2 constants
17392 * M2 Types:: Modula-2 types
17393 * M2 Defaults:: Default settings for Modula-2
17394 * Deviations:: Deviations from standard Modula-2
17395 * M2 Checks:: Modula-2 type and range checks
17396 * M2 Scope:: The scope operators @code{::} and @code{.}
17397 * GDB/M2:: @value{GDBN} and Modula-2
17401 @subsubsection Operators
17402 @cindex Modula-2 operators
17404 Operators must be defined on values of specific types. For instance,
17405 @code{+} is defined on numbers, but not on structures. Operators are
17406 often defined on groups of types. For the purposes of Modula-2, the
17407 following definitions hold:
17412 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17416 @emph{Character types} consist of @code{CHAR} and its subranges.
17419 @emph{Floating-point types} consist of @code{REAL}.
17422 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17426 @emph{Scalar types} consist of all of the above.
17429 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17432 @emph{Boolean types} consist of @code{BOOLEAN}.
17436 The following operators are supported, and appear in order of
17437 increasing precedence:
17441 Function argument or array index separator.
17444 Assignment. The value of @var{var} @code{:=} @var{value} is
17448 Less than, greater than on integral, floating-point, or enumerated
17452 Less than or equal to, greater than or equal to
17453 on integral, floating-point and enumerated types, or set inclusion on
17454 set types. Same precedence as @code{<}.
17456 @item =@r{, }<>@r{, }#
17457 Equality and two ways of expressing inequality, valid on scalar types.
17458 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17459 available for inequality, since @code{#} conflicts with the script
17463 Set membership. Defined on set types and the types of their members.
17464 Same precedence as @code{<}.
17467 Boolean disjunction. Defined on boolean types.
17470 Boolean conjunction. Defined on boolean types.
17473 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17476 Addition and subtraction on integral and floating-point types, or union
17477 and difference on set types.
17480 Multiplication on integral and floating-point types, or set intersection
17484 Division on floating-point types, or symmetric set difference on set
17485 types. Same precedence as @code{*}.
17488 Integer division and remainder. Defined on integral types. Same
17489 precedence as @code{*}.
17492 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17495 Pointer dereferencing. Defined on pointer types.
17498 Boolean negation. Defined on boolean types. Same precedence as
17502 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17503 precedence as @code{^}.
17506 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17509 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17513 @value{GDBN} and Modula-2 scope operators.
17517 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17518 treats the use of the operator @code{IN}, or the use of operators
17519 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17520 @code{<=}, and @code{>=} on sets as an error.
17524 @node Built-In Func/Proc
17525 @subsubsection Built-in Functions and Procedures
17526 @cindex Modula-2 built-ins
17528 Modula-2 also makes available several built-in procedures and functions.
17529 In describing these, the following metavariables are used:
17534 represents an @code{ARRAY} variable.
17537 represents a @code{CHAR} constant or variable.
17540 represents a variable or constant of integral type.
17543 represents an identifier that belongs to a set. Generally used in the
17544 same function with the metavariable @var{s}. The type of @var{s} should
17545 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17548 represents a variable or constant of integral or floating-point type.
17551 represents a variable or constant of floating-point type.
17557 represents a variable.
17560 represents a variable or constant of one of many types. See the
17561 explanation of the function for details.
17564 All Modula-2 built-in procedures also return a result, described below.
17568 Returns the absolute value of @var{n}.
17571 If @var{c} is a lower case letter, it returns its upper case
17572 equivalent, otherwise it returns its argument.
17575 Returns the character whose ordinal value is @var{i}.
17578 Decrements the value in the variable @var{v} by one. Returns the new value.
17580 @item DEC(@var{v},@var{i})
17581 Decrements the value in the variable @var{v} by @var{i}. Returns the
17584 @item EXCL(@var{m},@var{s})
17585 Removes the element @var{m} from the set @var{s}. Returns the new
17588 @item FLOAT(@var{i})
17589 Returns the floating point equivalent of the integer @var{i}.
17591 @item HIGH(@var{a})
17592 Returns the index of the last member of @var{a}.
17595 Increments the value in the variable @var{v} by one. Returns the new value.
17597 @item INC(@var{v},@var{i})
17598 Increments the value in the variable @var{v} by @var{i}. Returns the
17601 @item INCL(@var{m},@var{s})
17602 Adds the element @var{m} to the set @var{s} if it is not already
17603 there. Returns the new set.
17606 Returns the maximum value of the type @var{t}.
17609 Returns the minimum value of the type @var{t}.
17612 Returns boolean TRUE if @var{i} is an odd number.
17615 Returns the ordinal value of its argument. For example, the ordinal
17616 value of a character is its @sc{ascii} value (on machines supporting
17617 the @sc{ascii} character set). The argument @var{x} must be of an
17618 ordered type, which include integral, character and enumerated types.
17620 @item SIZE(@var{x})
17621 Returns the size of its argument. The argument @var{x} can be a
17622 variable or a type.
17624 @item TRUNC(@var{r})
17625 Returns the integral part of @var{r}.
17627 @item TSIZE(@var{x})
17628 Returns the size of its argument. The argument @var{x} can be a
17629 variable or a type.
17631 @item VAL(@var{t},@var{i})
17632 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17636 @emph{Warning:} Sets and their operations are not yet supported, so
17637 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17641 @cindex Modula-2 constants
17643 @subsubsection Constants
17645 @value{GDBN} allows you to express the constants of Modula-2 in the following
17651 Integer constants are simply a sequence of digits. When used in an
17652 expression, a constant is interpreted to be type-compatible with the
17653 rest of the expression. Hexadecimal integers are specified by a
17654 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17657 Floating point constants appear as a sequence of digits, followed by a
17658 decimal point and another sequence of digits. An optional exponent can
17659 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17660 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17661 digits of the floating point constant must be valid decimal (base 10)
17665 Character constants consist of a single character enclosed by a pair of
17666 like quotes, either single (@code{'}) or double (@code{"}). They may
17667 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17668 followed by a @samp{C}.
17671 String constants consist of a sequence of characters enclosed by a
17672 pair of like quotes, either single (@code{'}) or double (@code{"}).
17673 Escape sequences in the style of C are also allowed. @xref{C
17674 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17678 Enumerated constants consist of an enumerated identifier.
17681 Boolean constants consist of the identifiers @code{TRUE} and
17685 Pointer constants consist of integral values only.
17688 Set constants are not yet supported.
17692 @subsubsection Modula-2 Types
17693 @cindex Modula-2 types
17695 Currently @value{GDBN} can print the following data types in Modula-2
17696 syntax: array types, record types, set types, pointer types, procedure
17697 types, enumerated types, subrange types and base types. You can also
17698 print the contents of variables declared using these type.
17699 This section gives a number of simple source code examples together with
17700 sample @value{GDBN} sessions.
17702 The first example contains the following section of code:
17711 and you can request @value{GDBN} to interrogate the type and value of
17712 @code{r} and @code{s}.
17715 (@value{GDBP}) print s
17717 (@value{GDBP}) ptype s
17719 (@value{GDBP}) print r
17721 (@value{GDBP}) ptype r
17726 Likewise if your source code declares @code{s} as:
17730 s: SET ['A'..'Z'] ;
17734 then you may query the type of @code{s} by:
17737 (@value{GDBP}) ptype s
17738 type = SET ['A'..'Z']
17742 Note that at present you cannot interactively manipulate set
17743 expressions using the debugger.
17745 The following example shows how you might declare an array in Modula-2
17746 and how you can interact with @value{GDBN} to print its type and contents:
17750 s: ARRAY [-10..10] OF CHAR ;
17754 (@value{GDBP}) ptype s
17755 ARRAY [-10..10] OF CHAR
17758 Note that the array handling is not yet complete and although the type
17759 is printed correctly, expression handling still assumes that all
17760 arrays have a lower bound of zero and not @code{-10} as in the example
17763 Here are some more type related Modula-2 examples:
17767 colour = (blue, red, yellow, green) ;
17768 t = [blue..yellow] ;
17776 The @value{GDBN} interaction shows how you can query the data type
17777 and value of a variable.
17780 (@value{GDBP}) print s
17782 (@value{GDBP}) ptype t
17783 type = [blue..yellow]
17787 In this example a Modula-2 array is declared and its contents
17788 displayed. Observe that the contents are written in the same way as
17789 their @code{C} counterparts.
17793 s: ARRAY [1..5] OF CARDINAL ;
17799 (@value{GDBP}) print s
17800 $1 = @{1, 0, 0, 0, 0@}
17801 (@value{GDBP}) ptype s
17802 type = ARRAY [1..5] OF CARDINAL
17805 The Modula-2 language interface to @value{GDBN} also understands
17806 pointer types as shown in this example:
17810 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17817 and you can request that @value{GDBN} describes the type of @code{s}.
17820 (@value{GDBP}) ptype s
17821 type = POINTER TO ARRAY [1..5] OF CARDINAL
17824 @value{GDBN} handles compound types as we can see in this example.
17825 Here we combine array types, record types, pointer types and subrange
17836 myarray = ARRAY myrange OF CARDINAL ;
17837 myrange = [-2..2] ;
17839 s: POINTER TO ARRAY myrange OF foo ;
17843 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17847 (@value{GDBP}) ptype s
17848 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17851 f3 : ARRAY [-2..2] OF CARDINAL;
17856 @subsubsection Modula-2 Defaults
17857 @cindex Modula-2 defaults
17859 If type and range checking are set automatically by @value{GDBN}, they
17860 both default to @code{on} whenever the working language changes to
17861 Modula-2. This happens regardless of whether you or @value{GDBN}
17862 selected the working language.
17864 If you allow @value{GDBN} to set the language automatically, then entering
17865 code compiled from a file whose name ends with @file{.mod} sets the
17866 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17867 Infer the Source Language}, for further details.
17870 @subsubsection Deviations from Standard Modula-2
17871 @cindex Modula-2, deviations from
17873 A few changes have been made to make Modula-2 programs easier to debug.
17874 This is done primarily via loosening its type strictness:
17878 Unlike in standard Modula-2, pointer constants can be formed by
17879 integers. This allows you to modify pointer variables during
17880 debugging. (In standard Modula-2, the actual address contained in a
17881 pointer variable is hidden from you; it can only be modified
17882 through direct assignment to another pointer variable or expression that
17883 returned a pointer.)
17886 C escape sequences can be used in strings and characters to represent
17887 non-printable characters. @value{GDBN} prints out strings with these
17888 escape sequences embedded. Single non-printable characters are
17889 printed using the @samp{CHR(@var{nnn})} format.
17892 The assignment operator (@code{:=}) returns the value of its right-hand
17896 All built-in procedures both modify @emph{and} return their argument.
17900 @subsubsection Modula-2 Type and Range Checks
17901 @cindex Modula-2 checks
17904 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
17907 @c FIXME remove warning when type/range checks added
17909 @value{GDBN} considers two Modula-2 variables type equivalent if:
17913 They are of types that have been declared equivalent via a @code{TYPE
17914 @var{t1} = @var{t2}} statement
17917 They have been declared on the same line. (Note: This is true of the
17918 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
17921 As long as type checking is enabled, any attempt to combine variables
17922 whose types are not equivalent is an error.
17924 Range checking is done on all mathematical operations, assignment, array
17925 index bounds, and all built-in functions and procedures.
17928 @subsubsection The Scope Operators @code{::} and @code{.}
17930 @cindex @code{.}, Modula-2 scope operator
17931 @cindex colon, doubled as scope operator
17933 @vindex colon-colon@r{, in Modula-2}
17934 @c Info cannot handle :: but TeX can.
17937 @vindex ::@r{, in Modula-2}
17940 There are a few subtle differences between the Modula-2 scope operator
17941 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
17946 @var{module} . @var{id}
17947 @var{scope} :: @var{id}
17951 where @var{scope} is the name of a module or a procedure,
17952 @var{module} the name of a module, and @var{id} is any declared
17953 identifier within your program, except another module.
17955 Using the @code{::} operator makes @value{GDBN} search the scope
17956 specified by @var{scope} for the identifier @var{id}. If it is not
17957 found in the specified scope, then @value{GDBN} searches all scopes
17958 enclosing the one specified by @var{scope}.
17960 Using the @code{.} operator makes @value{GDBN} search the current scope for
17961 the identifier specified by @var{id} that was imported from the
17962 definition module specified by @var{module}. With this operator, it is
17963 an error if the identifier @var{id} was not imported from definition
17964 module @var{module}, or if @var{id} is not an identifier in
17968 @subsubsection @value{GDBN} and Modula-2
17970 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
17971 Five subcommands of @code{set print} and @code{show print} apply
17972 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
17973 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
17974 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
17975 analogue in Modula-2.
17977 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
17978 with any language, is not useful with Modula-2. Its
17979 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
17980 created in Modula-2 as they can in C or C@t{++}. However, because an
17981 address can be specified by an integral constant, the construct
17982 @samp{@{@var{type}@}@var{adrexp}} is still useful.
17984 @cindex @code{#} in Modula-2
17985 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
17986 interpreted as the beginning of a comment. Use @code{<>} instead.
17992 The extensions made to @value{GDBN} for Ada only support
17993 output from the @sc{gnu} Ada (GNAT) compiler.
17994 Other Ada compilers are not currently supported, and
17995 attempting to debug executables produced by them is most likely
17999 @cindex expressions in Ada
18001 * Ada Mode Intro:: General remarks on the Ada syntax
18002 and semantics supported by Ada mode
18004 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18005 * Additions to Ada:: Extensions of the Ada expression syntax.
18006 * Overloading support for Ada:: Support for expressions involving overloaded
18008 * Stopping Before Main Program:: Debugging the program during elaboration.
18009 * Ada Exceptions:: Ada Exceptions
18010 * Ada Tasks:: Listing and setting breakpoints in tasks.
18011 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18012 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18014 * Ada Settings:: New settable GDB parameters for Ada.
18015 * Ada Source Character Set:: Character set of Ada source files.
18016 * Ada Glitches:: Known peculiarities of Ada mode.
18019 @node Ada Mode Intro
18020 @subsubsection Introduction
18021 @cindex Ada mode, general
18023 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18024 syntax, with some extensions.
18025 The philosophy behind the design of this subset is
18029 That @value{GDBN} should provide basic literals and access to operations for
18030 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18031 leaving more sophisticated computations to subprograms written into the
18032 program (which therefore may be called from @value{GDBN}).
18035 That type safety and strict adherence to Ada language restrictions
18036 are not particularly important to the @value{GDBN} user.
18039 That brevity is important to the @value{GDBN} user.
18042 Thus, for brevity, the debugger acts as if all names declared in
18043 user-written packages are directly visible, even if they are not visible
18044 according to Ada rules, thus making it unnecessary to fully qualify most
18045 names with their packages, regardless of context. Where this causes
18046 ambiguity, @value{GDBN} asks the user's intent.
18048 The debugger will start in Ada mode if it detects an Ada main program.
18049 As for other languages, it will enter Ada mode when stopped in a program that
18050 was translated from an Ada source file.
18052 While in Ada mode, you may use `@t{--}' for comments. This is useful
18053 mostly for documenting command files. The standard @value{GDBN} comment
18054 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18055 middle (to allow based literals).
18057 @node Omissions from Ada
18058 @subsubsection Omissions from Ada
18059 @cindex Ada, omissions from
18061 Here are the notable omissions from the subset:
18065 Only a subset of the attributes are supported:
18069 @t{'First}, @t{'Last}, and @t{'Length}
18070 on array objects (not on types and subtypes).
18073 @t{'Min} and @t{'Max}.
18076 @t{'Pos} and @t{'Val}.
18082 @t{'Range} on array objects (not subtypes), but only as the right
18083 operand of the membership (@code{in}) operator.
18086 @t{'Access}, @t{'Unchecked_Access}, and
18087 @t{'Unrestricted_Access} (a GNAT extension).
18095 @code{Characters.Latin_1} are not available and
18096 concatenation is not implemented. Thus, escape characters in strings are
18097 not currently available.
18100 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18101 equality of representations. They will generally work correctly
18102 for strings and arrays whose elements have integer or enumeration types.
18103 They may not work correctly for arrays whose element
18104 types have user-defined equality, for arrays of real values
18105 (in particular, IEEE-conformant floating point, because of negative
18106 zeroes and NaNs), and for arrays whose elements contain unused bits with
18107 indeterminate values.
18110 The other component-by-component array operations (@code{and}, @code{or},
18111 @code{xor}, @code{not}, and relational tests other than equality)
18112 are not implemented.
18115 @cindex array aggregates (Ada)
18116 @cindex record aggregates (Ada)
18117 @cindex aggregates (Ada)
18118 There is limited support for array and record aggregates. They are
18119 permitted only on the right sides of assignments, as in these examples:
18122 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18123 (@value{GDBP}) set An_Array := (1, others => 0)
18124 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18125 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18126 (@value{GDBP}) set A_Record := (1, "Peter", True);
18127 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18131 discriminant's value by assigning an aggregate has an
18132 undefined effect if that discriminant is used within the record.
18133 However, you can first modify discriminants by directly assigning to
18134 them (which normally would not be allowed in Ada), and then performing an
18135 aggregate assignment. For example, given a variable @code{A_Rec}
18136 declared to have a type such as:
18139 type Rec (Len : Small_Integer := 0) is record
18141 Vals : IntArray (1 .. Len);
18145 you can assign a value with a different size of @code{Vals} with two
18149 (@value{GDBP}) set A_Rec.Len := 4
18150 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18153 As this example also illustrates, @value{GDBN} is very loose about the usual
18154 rules concerning aggregates. You may leave out some of the
18155 components of an array or record aggregate (such as the @code{Len}
18156 component in the assignment to @code{A_Rec} above); they will retain their
18157 original values upon assignment. You may freely use dynamic values as
18158 indices in component associations. You may even use overlapping or
18159 redundant component associations, although which component values are
18160 assigned in such cases is not defined.
18163 Calls to dispatching subprograms are not implemented.
18166 The overloading algorithm is much more limited (i.e., less selective)
18167 than that of real Ada. It makes only limited use of the context in
18168 which a subexpression appears to resolve its meaning, and it is much
18169 looser in its rules for allowing type matches. As a result, some
18170 function calls will be ambiguous, and the user will be asked to choose
18171 the proper resolution.
18174 The @code{new} operator is not implemented.
18177 Entry calls are not implemented.
18180 Aside from printing, arithmetic operations on the native VAX floating-point
18181 formats are not supported.
18184 It is not possible to slice a packed array.
18187 The names @code{True} and @code{False}, when not part of a qualified name,
18188 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18190 Should your program
18191 redefine these names in a package or procedure (at best a dubious practice),
18192 you will have to use fully qualified names to access their new definitions.
18195 @node Additions to Ada
18196 @subsubsection Additions to Ada
18197 @cindex Ada, deviations from
18199 As it does for other languages, @value{GDBN} makes certain generic
18200 extensions to Ada (@pxref{Expressions}):
18204 If the expression @var{E} is a variable residing in memory (typically
18205 a local variable or array element) and @var{N} is a positive integer,
18206 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18207 @var{N}-1 adjacent variables following it in memory as an array. In
18208 Ada, this operator is generally not necessary, since its prime use is
18209 in displaying parts of an array, and slicing will usually do this in
18210 Ada. However, there are occasional uses when debugging programs in
18211 which certain debugging information has been optimized away.
18214 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18215 appears in function or file @var{B}.'' When @var{B} is a file name,
18216 you must typically surround it in single quotes.
18219 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18220 @var{type} that appears at address @var{addr}.''
18223 A name starting with @samp{$} is a convenience variable
18224 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18227 In addition, @value{GDBN} provides a few other shortcuts and outright
18228 additions specific to Ada:
18232 The assignment statement is allowed as an expression, returning
18233 its right-hand operand as its value. Thus, you may enter
18236 (@value{GDBP}) set x := y + 3
18237 (@value{GDBP}) print A(tmp := y + 1)
18241 The semicolon is allowed as an ``operator,'' returning as its value
18242 the value of its right-hand operand.
18243 This allows, for example,
18244 complex conditional breaks:
18247 (@value{GDBP}) break f
18248 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18252 Rather than use catenation and symbolic character names to introduce special
18253 characters into strings, one may instead use a special bracket notation,
18254 which is also used to print strings. A sequence of characters of the form
18255 @samp{["@var{XX}"]} within a string or character literal denotes the
18256 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18257 sequence of characters @samp{["""]} also denotes a single quotation mark
18258 in strings. For example,
18260 "One line.["0a"]Next line.["0a"]"
18263 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18267 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18268 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18272 (@value{GDBP}) print 'max(x, y)
18276 When printing arrays, @value{GDBN} uses positional notation when the
18277 array has a lower bound of 1, and uses a modified named notation otherwise.
18278 For example, a one-dimensional array of three integers with a lower bound
18279 of 3 might print as
18286 That is, in contrast to valid Ada, only the first component has a @code{=>}
18290 You may abbreviate attributes in expressions with any unique,
18291 multi-character subsequence of
18292 their names (an exact match gets preference).
18293 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18294 in place of @t{a'length}.
18297 @cindex quoting Ada internal identifiers
18298 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18299 to lower case. The GNAT compiler uses upper-case characters for
18300 some of its internal identifiers, which are normally of no interest to users.
18301 For the rare occasions when you actually have to look at them,
18302 enclose them in angle brackets to avoid the lower-case mapping.
18305 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18309 Printing an object of class-wide type or dereferencing an
18310 access-to-class-wide value will display all the components of the object's
18311 specific type (as indicated by its run-time tag). Likewise, component
18312 selection on such a value will operate on the specific type of the
18317 @node Overloading support for Ada
18318 @subsubsection Overloading support for Ada
18319 @cindex overloading, Ada
18321 The debugger supports limited overloading. Given a subprogram call in which
18322 the function symbol has multiple definitions, it will use the number of
18323 actual parameters and some information about their types to attempt to narrow
18324 the set of definitions. It also makes very limited use of context, preferring
18325 procedures to functions in the context of the @code{call} command, and
18326 functions to procedures elsewhere.
18328 If, after narrowing, the set of matching definitions still contains more than
18329 one definition, @value{GDBN} will display a menu to query which one it should
18333 (@value{GDBP}) print f(1)
18334 Multiple matches for f
18336 [1] foo.f (integer) return boolean at foo.adb:23
18337 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18341 In this case, just select one menu entry either to cancel expression evaluation
18342 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18343 instance (type the corresponding number and press @key{RET}).
18345 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18350 @kindex set ada print-signatures
18351 @item set ada print-signatures
18352 Control whether parameter types and return types are displayed in overloads
18353 selection menus. It is @code{on} by default.
18354 @xref{Overloading support for Ada}.
18356 @kindex show ada print-signatures
18357 @item show ada print-signatures
18358 Show the current setting for displaying parameter types and return types in
18359 overloads selection menu.
18360 @xref{Overloading support for Ada}.
18364 @node Stopping Before Main Program
18365 @subsubsection Stopping at the Very Beginning
18367 @cindex breakpointing Ada elaboration code
18368 It is sometimes necessary to debug the program during elaboration, and
18369 before reaching the main procedure.
18370 As defined in the Ada Reference
18371 Manual, the elaboration code is invoked from a procedure called
18372 @code{adainit}. To run your program up to the beginning of
18373 elaboration, simply use the following two commands:
18374 @code{tbreak adainit} and @code{run}.
18376 @node Ada Exceptions
18377 @subsubsection Ada Exceptions
18379 A command is provided to list all Ada exceptions:
18382 @kindex info exceptions
18383 @item info exceptions
18384 @itemx info exceptions @var{regexp}
18385 The @code{info exceptions} command allows you to list all Ada exceptions
18386 defined within the program being debugged, as well as their addresses.
18387 With a regular expression, @var{regexp}, as argument, only those exceptions
18388 whose names match @var{regexp} are listed.
18391 Below is a small example, showing how the command can be used, first
18392 without argument, and next with a regular expression passed as an
18396 (@value{GDBP}) info exceptions
18397 All defined Ada exceptions:
18398 constraint_error: 0x613da0
18399 program_error: 0x613d20
18400 storage_error: 0x613ce0
18401 tasking_error: 0x613ca0
18402 const.aint_global_e: 0x613b00
18403 (@value{GDBP}) info exceptions const.aint
18404 All Ada exceptions matching regular expression "const.aint":
18405 constraint_error: 0x613da0
18406 const.aint_global_e: 0x613b00
18409 It is also possible to ask @value{GDBN} to stop your program's execution
18410 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18413 @subsubsection Extensions for Ada Tasks
18414 @cindex Ada, tasking
18416 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18417 @value{GDBN} provides the following task-related commands:
18422 This command shows a list of current Ada tasks, as in the following example:
18429 (@value{GDBP}) info tasks
18430 ID TID P-ID Pri State Name
18431 1 8088000 0 15 Child Activation Wait main_task
18432 2 80a4000 1 15 Accept Statement b
18433 3 809a800 1 15 Child Activation Wait a
18434 * 4 80ae800 3 15 Runnable c
18439 In this listing, the asterisk before the last task indicates it to be the
18440 task currently being inspected.
18444 Represents @value{GDBN}'s internal task number.
18450 The parent's task ID (@value{GDBN}'s internal task number).
18453 The base priority of the task.
18456 Current state of the task.
18460 The task has been created but has not been activated. It cannot be
18464 The task is not blocked for any reason known to Ada. (It may be waiting
18465 for a mutex, though.) It is conceptually "executing" in normal mode.
18468 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18469 that were waiting on terminate alternatives have been awakened and have
18470 terminated themselves.
18472 @item Child Activation Wait
18473 The task is waiting for created tasks to complete activation.
18475 @item Accept Statement
18476 The task is waiting on an accept or selective wait statement.
18478 @item Waiting on entry call
18479 The task is waiting on an entry call.
18481 @item Async Select Wait
18482 The task is waiting to start the abortable part of an asynchronous
18486 The task is waiting on a select statement with only a delay
18489 @item Child Termination Wait
18490 The task is sleeping having completed a master within itself, and is
18491 waiting for the tasks dependent on that master to become terminated or
18492 waiting on a terminate Phase.
18494 @item Wait Child in Term Alt
18495 The task is sleeping waiting for tasks on terminate alternatives to
18496 finish terminating.
18498 @item Accepting RV with @var{taskno}
18499 The task is accepting a rendez-vous with the task @var{taskno}.
18503 Name of the task in the program.
18507 @kindex info task @var{taskno}
18508 @item info task @var{taskno}
18509 This command shows detailed informations on the specified task, as in
18510 the following example:
18515 (@value{GDBP}) info tasks
18516 ID TID P-ID Pri State Name
18517 1 8077880 0 15 Child Activation Wait main_task
18518 * 2 807c468 1 15 Runnable task_1
18519 (@value{GDBP}) info task 2
18520 Ada Task: 0x807c468
18524 Parent: 1 ("main_task")
18530 @kindex task@r{ (Ada)}
18531 @cindex current Ada task ID
18532 This command prints the ID and name of the current task.
18538 (@value{GDBP}) info tasks
18539 ID TID P-ID Pri State Name
18540 1 8077870 0 15 Child Activation Wait main_task
18541 * 2 807c458 1 15 Runnable some_task
18542 (@value{GDBP}) task
18543 [Current task is 2 "some_task"]
18546 @item task @var{taskno}
18547 @cindex Ada task switching
18548 This command is like the @code{thread @var{thread-id}}
18549 command (@pxref{Threads}). It switches the context of debugging
18550 from the current task to the given task.
18556 (@value{GDBP}) info tasks
18557 ID TID P-ID Pri State Name
18558 1 8077870 0 15 Child Activation Wait main_task
18559 * 2 807c458 1 15 Runnable some_task
18560 (@value{GDBP}) task 1
18561 [Switching to task 1 "main_task"]
18562 #0 0x8067726 in pthread_cond_wait ()
18564 #0 0x8067726 in pthread_cond_wait ()
18565 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18566 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18567 #3 0x806153e in system.tasking.stages.activate_tasks ()
18568 #4 0x804aacc in un () at un.adb:5
18571 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18572 The @code{task apply} command is the Ada tasking analogue of
18573 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18574 named @var{command} to one or more tasks. Specify the tasks that you
18575 want affected using a list of task IDs, or specify @code{all} to apply
18578 The @var{flag} arguments control what output to produce and how to
18579 handle errors raised when applying @var{command} to a task.
18580 @var{flag} must start with a @code{-} directly followed by one letter
18581 in @code{qcs}. If several flags are provided, they must be given
18582 individually, such as @code{-c -q}.
18584 By default, @value{GDBN} displays some task information before the
18585 output produced by @var{command}, and an error raised during the
18586 execution of a @var{command} will abort @code{task apply}. The
18587 following flags can be used to fine-tune this behavior:
18591 The flag @code{-c}, which stands for @samp{continue}, causes any
18592 errors in @var{command} to be displayed, and the execution of
18593 @code{task apply} then continues.
18595 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18596 or empty output produced by a @var{command} to be silently ignored.
18597 That is, the execution continues, but the task information and errors
18600 The flag @code{-q} (@samp{quiet}) disables printing the task
18604 Flags @code{-c} and @code{-s} cannot be used together.
18606 @item break @var{location} task @var{taskno}
18607 @itemx break @var{location} task @var{taskno} if @dots{}
18608 @cindex breakpoints and tasks, in Ada
18609 @cindex task breakpoints, in Ada
18610 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18611 These commands are like the @code{break @dots{} thread @dots{}}
18612 command (@pxref{Thread Stops}). The
18613 @var{location} argument specifies source lines, as described
18614 in @ref{Specify Location}.
18616 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18617 to specify that you only want @value{GDBN} to stop the program when a
18618 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18619 numeric task identifiers assigned by @value{GDBN}, shown in the first
18620 column of the @samp{info tasks} display.
18622 If you do not specify @samp{task @var{taskno}} when you set a
18623 breakpoint, the breakpoint applies to @emph{all} tasks of your
18626 You can use the @code{task} qualifier on conditional breakpoints as
18627 well; in this case, place @samp{task @var{taskno}} before the
18628 breakpoint condition (before the @code{if}).
18636 (@value{GDBP}) info tasks
18637 ID TID P-ID Pri State Name
18638 1 140022020 0 15 Child Activation Wait main_task
18639 2 140045060 1 15 Accept/Select Wait t2
18640 3 140044840 1 15 Runnable t1
18641 * 4 140056040 1 15 Runnable t3
18642 (@value{GDBP}) b 15 task 2
18643 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18644 (@value{GDBP}) cont
18649 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18651 (@value{GDBP}) info tasks
18652 ID TID P-ID Pri State Name
18653 1 140022020 0 15 Child Activation Wait main_task
18654 * 2 140045060 1 15 Runnable t2
18655 3 140044840 1 15 Runnable t1
18656 4 140056040 1 15 Delay Sleep t3
18660 @node Ada Tasks and Core Files
18661 @subsubsection Tasking Support when Debugging Core Files
18662 @cindex Ada tasking and core file debugging
18664 When inspecting a core file, as opposed to debugging a live program,
18665 tasking support may be limited or even unavailable, depending on
18666 the platform being used.
18667 For instance, on x86-linux, the list of tasks is available, but task
18668 switching is not supported.
18670 On certain platforms, the debugger needs to perform some
18671 memory writes in order to provide Ada tasking support. When inspecting
18672 a core file, this means that the core file must be opened with read-write
18673 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18674 Under these circumstances, you should make a backup copy of the core
18675 file before inspecting it with @value{GDBN}.
18677 @node Ravenscar Profile
18678 @subsubsection Tasking Support when using the Ravenscar Profile
18679 @cindex Ravenscar Profile
18681 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18682 specifically designed for systems with safety-critical real-time
18686 @kindex set ravenscar task-switching on
18687 @cindex task switching with program using Ravenscar Profile
18688 @item set ravenscar task-switching on
18689 Allows task switching when debugging a program that uses the Ravenscar
18690 Profile. This is the default.
18692 @kindex set ravenscar task-switching off
18693 @item set ravenscar task-switching off
18694 Turn off task switching when debugging a program that uses the Ravenscar
18695 Profile. This is mostly intended to disable the code that adds support
18696 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18697 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18698 To be effective, this command should be run before the program is started.
18700 @kindex show ravenscar task-switching
18701 @item show ravenscar task-switching
18702 Show whether it is possible to switch from task to task in a program
18703 using the Ravenscar Profile.
18707 @cindex Ravenscar thread
18708 When Ravenscar task-switching is enabled, Ravenscar tasks are
18709 announced by @value{GDBN} as if they were threads:
18713 [New Ravenscar Thread 0x2b8f0]
18716 Both Ravenscar tasks and the underlying CPU threads will show up in
18717 the output of @code{info threads}:
18722 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18723 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18724 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18725 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18726 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18727 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18730 One known limitation of the Ravenscar support in @value{GDBN} is that
18731 it isn't currently possible to single-step through the runtime
18732 initialization sequence. If you need to debug this code, you should
18733 use @code{set ravenscar task-switching off}.
18736 @subsubsection Ada Settings
18737 @cindex Ada settings
18740 @kindex set varsize-limit
18741 @item set varsize-limit @var{size}
18742 Prevent @value{GDBN} from attempting to evaluate objects whose size
18743 is above the given limit (@var{size}) when those sizes are computed
18744 from run-time quantities. This is typically the case when the object
18745 has a variable size, such as an array whose bounds are not known at
18746 compile time for example. Setting @var{size} to @code{unlimited}
18747 removes the size limitation. By default, the limit is about 65KB.
18749 The purpose of having such a limit is to prevent @value{GDBN} from
18750 trying to grab enormous chunks of virtual memory when asked to evaluate
18751 a quantity whose bounds have been corrupted or have not yet been fully
18752 initialized. The limit applies to the results of some subexpressions
18753 as well as to complete expressions. For example, an expression denoting
18754 a simple integer component, such as @code{x.y.z}, may fail if the size of
18755 @code{x.y} is variable and exceeds @code{size}. On the other hand,
18756 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
18757 @code{A} is an array variable with non-constant size, will generally
18758 succeed regardless of the bounds on @code{A}, as long as the component
18759 size is less than @var{size}.
18761 @kindex show varsize-limit
18762 @item show varsize-limit
18763 Show the limit on types whose size is determined by run-time quantities.
18766 @node Ada Source Character Set
18767 @subsubsection Ada Source Character Set
18768 @cindex Ada, source character set
18770 The GNAT compiler supports a number of character sets for source
18771 files. @xref{Character Set Control, , Character Set Control,
18772 gnat_ugn}. @value{GDBN} includes support for this as well.
18775 @item set ada source-charset @var{charset}
18776 @kindex set ada source-charset
18777 Set the source character set for Ada. The character set must be
18778 supported by GNAT. Because this setting affects the decoding of
18779 symbols coming from the debug information in your program, the setting
18780 should be set as early as possible. The default is @code{ISO-8859-1},
18781 because that is also GNAT's default.
18783 @item show ada source-charset
18784 @kindex show ada source-charset
18785 Show the current source character set for Ada.
18789 @subsubsection Known Peculiarities of Ada Mode
18790 @cindex Ada, problems
18792 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18793 we know of several problems with and limitations of Ada mode in
18795 some of which will be fixed with planned future releases of the debugger
18796 and the GNU Ada compiler.
18800 Static constants that the compiler chooses not to materialize as objects in
18801 storage are invisible to the debugger.
18804 Named parameter associations in function argument lists are ignored (the
18805 argument lists are treated as positional).
18808 Many useful library packages are currently invisible to the debugger.
18811 Fixed-point arithmetic, conversions, input, and output is carried out using
18812 floating-point arithmetic, and may give results that only approximate those on
18816 The GNAT compiler never generates the prefix @code{Standard} for any of
18817 the standard symbols defined by the Ada language. @value{GDBN} knows about
18818 this: it will strip the prefix from names when you use it, and will never
18819 look for a name you have so qualified among local symbols, nor match against
18820 symbols in other packages or subprograms. If you have
18821 defined entities anywhere in your program other than parameters and
18822 local variables whose simple names match names in @code{Standard},
18823 GNAT's lack of qualification here can cause confusion. When this happens,
18824 you can usually resolve the confusion
18825 by qualifying the problematic names with package
18826 @code{Standard} explicitly.
18829 Older versions of the compiler sometimes generate erroneous debugging
18830 information, resulting in the debugger incorrectly printing the value
18831 of affected entities. In some cases, the debugger is able to work
18832 around an issue automatically. In other cases, the debugger is able
18833 to work around the issue, but the work-around has to be specifically
18836 @kindex set ada trust-PAD-over-XVS
18837 @kindex show ada trust-PAD-over-XVS
18840 @item set ada trust-PAD-over-XVS on
18841 Configure GDB to strictly follow the GNAT encoding when computing the
18842 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18843 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18844 a complete description of the encoding used by the GNAT compiler).
18845 This is the default.
18847 @item set ada trust-PAD-over-XVS off
18848 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18849 sometimes prints the wrong value for certain entities, changing @code{ada
18850 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18851 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18852 @code{off}, but this incurs a slight performance penalty, so it is
18853 recommended to leave this setting to @code{on} unless necessary.
18857 @cindex GNAT descriptive types
18858 @cindex GNAT encoding
18859 Internally, the debugger also relies on the compiler following a number
18860 of conventions known as the @samp{GNAT Encoding}, all documented in
18861 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18862 how the debugging information should be generated for certain types.
18863 In particular, this convention makes use of @dfn{descriptive types},
18864 which are artificial types generated purely to help the debugger.
18866 These encodings were defined at a time when the debugging information
18867 format used was not powerful enough to describe some of the more complex
18868 types available in Ada. Since DWARF allows us to express nearly all
18869 Ada features, the long-term goal is to slowly replace these descriptive
18870 types by their pure DWARF equivalent. To facilitate that transition,
18871 a new maintenance option is available to force the debugger to ignore
18872 those descriptive types. It allows the user to quickly evaluate how
18873 well @value{GDBN} works without them.
18877 @kindex maint ada set ignore-descriptive-types
18878 @item maintenance ada set ignore-descriptive-types [on|off]
18879 Control whether the debugger should ignore descriptive types.
18880 The default is not to ignore descriptives types (@code{off}).
18882 @kindex maint ada show ignore-descriptive-types
18883 @item maintenance ada show ignore-descriptive-types
18884 Show if descriptive types are ignored by @value{GDBN}.
18888 @node Unsupported Languages
18889 @section Unsupported Languages
18891 @cindex unsupported languages
18892 @cindex minimal language
18893 In addition to the other fully-supported programming languages,
18894 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
18895 It does not represent a real programming language, but provides a set
18896 of capabilities close to what the C or assembly languages provide.
18897 This should allow most simple operations to be performed while debugging
18898 an application that uses a language currently not supported by @value{GDBN}.
18900 If the language is set to @code{auto}, @value{GDBN} will automatically
18901 select this language if the current frame corresponds to an unsupported
18905 @chapter Examining the Symbol Table
18907 The commands described in this chapter allow you to inquire about the
18908 symbols (names of variables, functions and types) defined in your
18909 program. This information is inherent in the text of your program and
18910 does not change as your program executes. @value{GDBN} finds it in your
18911 program's symbol table, in the file indicated when you started @value{GDBN}
18912 (@pxref{File Options, ,Choosing Files}), or by one of the
18913 file-management commands (@pxref{Files, ,Commands to Specify Files}).
18915 @cindex symbol names
18916 @cindex names of symbols
18917 @cindex quoting names
18918 @anchor{quoting names}
18919 Occasionally, you may need to refer to symbols that contain unusual
18920 characters, which @value{GDBN} ordinarily treats as word delimiters. The
18921 most frequent case is in referring to static variables in other
18922 source files (@pxref{Variables,,Program Variables}). File names
18923 are recorded in object files as debugging symbols, but @value{GDBN} would
18924 ordinarily parse a typical file name, like @file{foo.c}, as the three words
18925 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
18926 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
18933 looks up the value of @code{x} in the scope of the file @file{foo.c}.
18936 @cindex case-insensitive symbol names
18937 @cindex case sensitivity in symbol names
18938 @kindex set case-sensitive
18939 @item set case-sensitive on
18940 @itemx set case-sensitive off
18941 @itemx set case-sensitive auto
18942 Normally, when @value{GDBN} looks up symbols, it matches their names
18943 with case sensitivity determined by the current source language.
18944 Occasionally, you may wish to control that. The command @code{set
18945 case-sensitive} lets you do that by specifying @code{on} for
18946 case-sensitive matches or @code{off} for case-insensitive ones. If
18947 you specify @code{auto}, case sensitivity is reset to the default
18948 suitable for the source language. The default is case-sensitive
18949 matches for all languages except for Fortran, for which the default is
18950 case-insensitive matches.
18952 @kindex show case-sensitive
18953 @item show case-sensitive
18954 This command shows the current setting of case sensitivity for symbols
18957 @kindex set print type methods
18958 @item set print type methods
18959 @itemx set print type methods on
18960 @itemx set print type methods off
18961 Normally, when @value{GDBN} prints a class, it displays any methods
18962 declared in that class. You can control this behavior either by
18963 passing the appropriate flag to @code{ptype}, or using @command{set
18964 print type methods}. Specifying @code{on} will cause @value{GDBN} to
18965 display the methods; this is the default. Specifying @code{off} will
18966 cause @value{GDBN} to omit the methods.
18968 @kindex show print type methods
18969 @item show print type methods
18970 This command shows the current setting of method display when printing
18973 @kindex set print type nested-type-limit
18974 @item set print type nested-type-limit @var{limit}
18975 @itemx set print type nested-type-limit unlimited
18976 Set the limit of displayed nested types that the type printer will
18977 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
18978 nested definitions. By default, the type printer will not show any nested
18979 types defined in classes.
18981 @kindex show print type nested-type-limit
18982 @item show print type nested-type-limit
18983 This command shows the current display limit of nested types when
18986 @kindex set print type typedefs
18987 @item set print type typedefs
18988 @itemx set print type typedefs on
18989 @itemx set print type typedefs off
18991 Normally, when @value{GDBN} prints a class, it displays any typedefs
18992 defined in that class. You can control this behavior either by
18993 passing the appropriate flag to @code{ptype}, or using @command{set
18994 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
18995 display the typedef definitions; this is the default. Specifying
18996 @code{off} will cause @value{GDBN} to omit the typedef definitions.
18997 Note that this controls whether the typedef definition itself is
18998 printed, not whether typedef names are substituted when printing other
19001 @kindex show print type typedefs
19002 @item show print type typedefs
19003 This command shows the current setting of typedef display when
19006 @kindex set print type hex
19007 @item set print type hex
19008 @itemx set print type hex on
19009 @itemx set print type hex off
19011 When @value{GDBN} prints sizes and offsets of struct members, it can use
19012 either the decimal or hexadecimal notation. You can select one or the
19013 other either by passing the appropriate flag to @code{ptype}, or by using
19014 the @command{set print type hex} command.
19016 @kindex show print type hex
19017 @item show print type hex
19018 This command shows whether the sizes and offsets of struct members are
19019 printed in decimal or hexadecimal notation.
19021 @kindex info address
19022 @cindex address of a symbol
19023 @item info address @var{symbol}
19024 Describe where the data for @var{symbol} is stored. For a register
19025 variable, this says which register it is kept in. For a non-register
19026 local variable, this prints the stack-frame offset at which the variable
19029 Note the contrast with @samp{print &@var{symbol}}, which does not work
19030 at all for a register variable, and for a stack local variable prints
19031 the exact address of the current instantiation of the variable.
19033 @kindex info symbol
19034 @cindex symbol from address
19035 @cindex closest symbol and offset for an address
19036 @item info symbol @var{addr}
19037 Print the name of a symbol which is stored at the address @var{addr}.
19038 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19039 nearest symbol and an offset from it:
19042 (@value{GDBP}) info symbol 0x54320
19043 _initialize_vx + 396 in section .text
19047 This is the opposite of the @code{info address} command. You can use
19048 it to find out the name of a variable or a function given its address.
19050 For dynamically linked executables, the name of executable or shared
19051 library containing the symbol is also printed:
19054 (@value{GDBP}) info symbol 0x400225
19055 _start + 5 in section .text of /tmp/a.out
19056 (@value{GDBP}) info symbol 0x2aaaac2811cf
19057 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19062 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19063 Demangle @var{name}.
19064 If @var{language} is provided it is the name of the language to demangle
19065 @var{name} in. Otherwise @var{name} is demangled in the current language.
19067 The @samp{--} option specifies the end of options,
19068 and is useful when @var{name} begins with a dash.
19070 The parameter @code{demangle-style} specifies how to interpret the kind
19071 of mangling used. @xref{Print Settings}.
19074 @item whatis[/@var{flags}] [@var{arg}]
19075 Print the data type of @var{arg}, which can be either an expression
19076 or a name of a data type. With no argument, print the data type of
19077 @code{$}, the last value in the value history.
19079 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19080 is not actually evaluated, and any side-effecting operations (such as
19081 assignments or function calls) inside it do not take place.
19083 If @var{arg} is a variable or an expression, @code{whatis} prints its
19084 literal type as it is used in the source code. If the type was
19085 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19086 the data type underlying the @code{typedef}. If the type of the
19087 variable or the expression is a compound data type, such as
19088 @code{struct} or @code{class}, @code{whatis} never prints their
19089 fields or methods. It just prints the @code{struct}/@code{class}
19090 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19091 such a compound data type, use @code{ptype}.
19093 If @var{arg} is a type name that was defined using @code{typedef},
19094 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19095 Unrolling means that @code{whatis} will show the underlying type used
19096 in the @code{typedef} declaration of @var{arg}. However, if that
19097 underlying type is also a @code{typedef}, @code{whatis} will not
19100 For C code, the type names may also have the form @samp{class
19101 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19102 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19104 @var{flags} can be used to modify how the type is displayed.
19105 Available flags are:
19109 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19110 parameters and typedefs defined in a class when printing the class'
19111 members. The @code{/r} flag disables this.
19114 Do not print methods defined in the class.
19117 Print methods defined in the class. This is the default, but the flag
19118 exists in case you change the default with @command{set print type methods}.
19121 Do not print typedefs defined in the class. Note that this controls
19122 whether the typedef definition itself is printed, not whether typedef
19123 names are substituted when printing other types.
19126 Print typedefs defined in the class. This is the default, but the flag
19127 exists in case you change the default with @command{set print type typedefs}.
19130 Print the offsets and sizes of fields in a struct, similar to what the
19131 @command{pahole} tool does. This option implies the @code{/tm} flags.
19134 Use hexadecimal notation when printing offsets and sizes of fields in a
19138 Use decimal notation when printing offsets and sizes of fields in a
19141 For example, given the following declarations:
19177 Issuing a @kbd{ptype /o struct tuv} command would print:
19180 (@value{GDBP}) ptype /o struct tuv
19181 /* offset | size */ type = struct tuv @{
19182 /* 0 | 4 */ int a1;
19183 /* XXX 4-byte hole */
19184 /* 8 | 8 */ char *a2;
19185 /* 16 | 4 */ int a3;
19187 /* total size (bytes): 24 */
19191 Notice the format of the first column of comments. There, you can
19192 find two parts separated by the @samp{|} character: the @emph{offset},
19193 which indicates where the field is located inside the struct, in
19194 bytes, and the @emph{size} of the field. Another interesting line is
19195 the marker of a @emph{hole} in the struct, indicating that it may be
19196 possible to pack the struct and make it use less space by reorganizing
19199 It is also possible to print offsets inside an union:
19202 (@value{GDBP}) ptype /o union qwe
19203 /* offset | size */ type = union qwe @{
19204 /* 24 */ struct tuv @{
19205 /* 0 | 4 */ int a1;
19206 /* XXX 4-byte hole */
19207 /* 8 | 8 */ char *a2;
19208 /* 16 | 4 */ int a3;
19210 /* total size (bytes): 24 */
19212 /* 40 */ struct xyz @{
19213 /* 0 | 4 */ int f1;
19214 /* 4 | 1 */ char f2;
19215 /* XXX 3-byte hole */
19216 /* 8 | 8 */ void *f3;
19217 /* 16 | 24 */ struct tuv @{
19218 /* 16 | 4 */ int a1;
19219 /* XXX 4-byte hole */
19220 /* 24 | 8 */ char *a2;
19221 /* 32 | 4 */ int a3;
19223 /* total size (bytes): 24 */
19226 /* total size (bytes): 40 */
19229 /* total size (bytes): 40 */
19233 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19234 same space (because we are dealing with an union), the offset is not
19235 printed for them. However, you can still examine the offset of each
19236 of these structures' fields.
19238 Another useful scenario is printing the offsets of a struct containing
19242 (@value{GDBP}) ptype /o struct tyu
19243 /* offset | size */ type = struct tyu @{
19244 /* 0:31 | 4 */ int a1 : 1;
19245 /* 0:28 | 4 */ int a2 : 3;
19246 /* 0: 5 | 4 */ int a3 : 23;
19247 /* 3: 3 | 1 */ signed char a4 : 2;
19248 /* XXX 3-bit hole */
19249 /* XXX 4-byte hole */
19250 /* 8 | 8 */ int64_t a5;
19251 /* 16: 0 | 4 */ int a6 : 5;
19252 /* 16: 5 | 8 */ int64_t a7 : 3;
19253 /* XXX 7-byte padding */
19255 /* total size (bytes): 24 */
19259 Note how the offset information is now extended to also include the
19260 first bit of the bitfield.
19264 @item ptype[/@var{flags}] [@var{arg}]
19265 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19266 detailed description of the type, instead of just the name of the type.
19267 @xref{Expressions, ,Expressions}.
19269 Contrary to @code{whatis}, @code{ptype} always unrolls any
19270 @code{typedef}s in its argument declaration, whether the argument is
19271 a variable, expression, or a data type. This means that @code{ptype}
19272 of a variable or an expression will not print literally its type as
19273 present in the source code---use @code{whatis} for that. @code{typedef}s at
19274 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19275 fields, methods and inner @code{class typedef}s of @code{struct}s,
19276 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19278 For example, for this variable declaration:
19281 typedef double real_t;
19282 struct complex @{ real_t real; double imag; @};
19283 typedef struct complex complex_t;
19285 real_t *real_pointer_var;
19289 the two commands give this output:
19293 (@value{GDBP}) whatis var
19295 (@value{GDBP}) ptype var
19296 type = struct complex @{
19300 (@value{GDBP}) whatis complex_t
19301 type = struct complex
19302 (@value{GDBP}) whatis struct complex
19303 type = struct complex
19304 (@value{GDBP}) ptype struct complex
19305 type = struct complex @{
19309 (@value{GDBP}) whatis real_pointer_var
19311 (@value{GDBP}) ptype real_pointer_var
19317 As with @code{whatis}, using @code{ptype} without an argument refers to
19318 the type of @code{$}, the last value in the value history.
19320 @cindex incomplete type
19321 Sometimes, programs use opaque data types or incomplete specifications
19322 of complex data structure. If the debug information included in the
19323 program does not allow @value{GDBN} to display a full declaration of
19324 the data type, it will say @samp{<incomplete type>}. For example,
19325 given these declarations:
19329 struct foo *fooptr;
19333 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19336 (@value{GDBP}) ptype foo
19337 $1 = <incomplete type>
19341 ``Incomplete type'' is C terminology for data types that are not
19342 completely specified.
19344 @cindex unknown type
19345 Othertimes, information about a variable's type is completely absent
19346 from the debug information included in the program. This most often
19347 happens when the program or library where the variable is defined
19348 includes no debug information at all. @value{GDBN} knows the variable
19349 exists from inspecting the linker/loader symbol table (e.g., the ELF
19350 dynamic symbol table), but such symbols do not contain type
19351 information. Inspecting the type of a (global) variable for which
19352 @value{GDBN} has no type information shows:
19355 (@value{GDBP}) ptype var
19356 type = <data variable, no debug info>
19359 @xref{Variables, no debug info variables}, for how to print the values
19363 @item info types [-q] [@var{regexp}]
19364 Print a brief description of all types whose names match the regular
19365 expression @var{regexp} (or all types in your program, if you supply
19366 no argument). Each complete typename is matched as though it were a
19367 complete line; thus, @samp{i type value} gives information on all
19368 types in your program whose names include the string @code{value}, but
19369 @samp{i type ^value$} gives information only on types whose complete
19370 name is @code{value}.
19372 In programs using different languages, @value{GDBN} chooses the syntax
19373 to print the type description according to the
19374 @samp{set language} value: using @samp{set language auto}
19375 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19376 language of the type, other values mean to use
19377 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19379 This command differs from @code{ptype} in two ways: first, like
19380 @code{whatis}, it does not print a detailed description; second, it
19381 lists all source files and line numbers where a type is defined.
19383 The output from @samp{into types} is proceeded with a header line
19384 describing what types are being listed. The optional flag @samp{-q},
19385 which stands for @samp{quiet}, disables printing this header
19388 @kindex info type-printers
19389 @item info type-printers
19390 Versions of @value{GDBN} that ship with Python scripting enabled may
19391 have ``type printers'' available. When using @command{ptype} or
19392 @command{whatis}, these printers are consulted when the name of a type
19393 is needed. @xref{Type Printing API}, for more information on writing
19396 @code{info type-printers} displays all the available type printers.
19398 @kindex enable type-printer
19399 @kindex disable type-printer
19400 @item enable type-printer @var{name}@dots{}
19401 @item disable type-printer @var{name}@dots{}
19402 These commands can be used to enable or disable type printers.
19405 @cindex local variables
19406 @item info scope @var{location}
19407 List all the variables local to a particular scope. This command
19408 accepts a @var{location} argument---a function name, a source line, or
19409 an address preceded by a @samp{*}, and prints all the variables local
19410 to the scope defined by that location. (@xref{Specify Location}, for
19411 details about supported forms of @var{location}.) For example:
19414 (@value{GDBP}) @b{info scope command_line_handler}
19415 Scope for command_line_handler:
19416 Symbol rl is an argument at stack/frame offset 8, length 4.
19417 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19418 Symbol linelength is in static storage at address 0x150a1c, length 4.
19419 Symbol p is a local variable in register $esi, length 4.
19420 Symbol p1 is a local variable in register $ebx, length 4.
19421 Symbol nline is a local variable in register $edx, length 4.
19422 Symbol repeat is a local variable at frame offset -8, length 4.
19426 This command is especially useful for determining what data to collect
19427 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19430 @kindex info source
19432 Show information about the current source file---that is, the source file for
19433 the function containing the current point of execution:
19436 the name of the source file, and the directory containing it,
19438 the directory it was compiled in,
19440 its length, in lines,
19442 which programming language it is written in,
19444 if the debug information provides it, the program that compiled the file
19445 (which may include, e.g., the compiler version and command line arguments),
19447 whether the executable includes debugging information for that file, and
19448 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19450 whether the debugging information includes information about
19451 preprocessor macros.
19455 @kindex info sources
19456 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19459 With no options @samp{info sources} prints the names of all source
19460 files in your program for which there is debugging information. The
19461 source files are presented based on a list of object files
19462 (executables and libraries) currently loaded into @value{GDBN}. For
19463 each object file all of the associated source files are listed.
19465 Each source file will only be printed once for each object file, but a
19466 single source file can be repeated in the output if it is part of
19467 multiple object files.
19469 If the optional @var{regexp} is provided, then only source files that
19470 match the regular expression will be printed. The matching is
19471 case-sensitive, except on operating systems that have case-insensitive
19472 filesystem (e.g., MS-Windows). @samp{--} can be used before
19473 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19474 command option (e.g. if @var{regexp} starts with @samp{-}).
19476 By default, the @var{regexp} is used to match anywhere in the
19477 filename. If @code{-dirname}, only files having a dirname matching
19478 @var{regexp} are shown. If @code{-basename}, only files having a
19479 basename matching @var{regexp} are shown.
19481 It is possible that an object file may be printed in the list with no
19482 associated source files. This can happen when either no source files
19483 match @var{regexp}, or, the object file was compiled without debug
19484 information and so @value{GDBN} is unable to find any source file
19487 @kindex info functions
19488 @item info functions [-q] [-n]
19489 Print the names and data types of all defined functions.
19490 Similarly to @samp{info types}, this command groups its output by source
19491 files and annotates each function definition with its source line
19494 In programs using different languages, @value{GDBN} chooses the syntax
19495 to print the function name and type according to the
19496 @samp{set language} value: using @samp{set language auto}
19497 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19498 language of the function, other values mean to use
19499 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19501 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19502 results. A non-debugging symbol is a symbol that comes from the
19503 executable's symbol table, not from the debug information (for
19504 example, DWARF) associated with the executable.
19506 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19507 printing header information and messages explaining why no functions
19510 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19511 Like @samp{info functions}, but only print the names and data types
19512 of the functions selected with the provided regexp(s).
19514 If @var{regexp} is provided, print only the functions whose names
19515 match the regular expression @var{regexp}.
19516 Thus, @samp{info fun step} finds all functions whose
19517 names include @code{step}; @samp{info fun ^step} finds those whose names
19518 start with @code{step}. If a function name contains characters that
19519 conflict with the regular expression language (e.g.@:
19520 @samp{operator*()}), they may be quoted with a backslash.
19522 If @var{type_regexp} is provided, print only the functions whose
19523 types, as printed by the @code{whatis} command, match
19524 the regular expression @var{type_regexp}.
19525 If @var{type_regexp} contains space(s), it should be enclosed in
19526 quote characters. If needed, use backslash to escape the meaning
19527 of special characters or quotes.
19528 Thus, @samp{info fun -t '^int ('} finds the functions that return
19529 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19530 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19531 finds the functions whose names start with @code{step} and that return
19534 If both @var{regexp} and @var{type_regexp} are provided, a function
19535 is printed only if its name matches @var{regexp} and its type matches
19539 @kindex info variables
19540 @item info variables [-q] [-n]
19541 Print the names and data types of all variables that are defined
19542 outside of functions (i.e.@: excluding local variables).
19543 The printed variables are grouped by source files and annotated with
19544 their respective source line numbers.
19546 In programs using different languages, @value{GDBN} chooses the syntax
19547 to print the variable name and type according to the
19548 @samp{set language} value: using @samp{set language auto}
19549 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19550 language of the variable, other values mean to use
19551 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19553 The @samp{-n} flag excludes non-debugging symbols from the results.
19555 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19556 printing header information and messages explaining why no variables
19559 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19560 Like @kbd{info variables}, but only print the variables selected
19561 with the provided regexp(s).
19563 If @var{regexp} is provided, print only the variables whose names
19564 match the regular expression @var{regexp}.
19566 If @var{type_regexp} is provided, print only the variables whose
19567 types, as printed by the @code{whatis} command, match
19568 the regular expression @var{type_regexp}.
19569 If @var{type_regexp} contains space(s), it should be enclosed in
19570 quote characters. If needed, use backslash to escape the meaning
19571 of special characters or quotes.
19573 If both @var{regexp} and @var{type_regexp} are provided, an argument
19574 is printed only if its name matches @var{regexp} and its type matches
19577 @kindex info modules
19579 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19580 List all Fortran modules in the program, or all modules matching the
19581 optional regular expression @var{regexp}.
19583 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19584 printing header information and messages explaining why no modules
19587 @kindex info module
19588 @cindex Fortran modules, information about
19589 @cindex functions and variables by Fortran module
19590 @cindex module functions and variables
19591 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19592 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19593 List all functions or variables within all Fortran modules. The set
19594 of functions or variables listed can be limited by providing some or
19595 all of the optional regular expressions. If @var{module-regexp} is
19596 provided, then only Fortran modules matching @var{module-regexp} will
19597 be searched. Only functions or variables whose type matches the
19598 optional regular expression @var{type-regexp} will be listed. And
19599 only functions or variables whose name matches the optional regular
19600 expression @var{regexp} will be listed.
19602 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19603 printing header information and messages explaining why no functions
19604 or variables have been printed.
19606 @kindex info classes
19607 @cindex Objective-C, classes and selectors
19609 @itemx info classes @var{regexp}
19610 Display all Objective-C classes in your program, or
19611 (with the @var{regexp} argument) all those matching a particular regular
19614 @kindex info selectors
19615 @item info selectors
19616 @itemx info selectors @var{regexp}
19617 Display all Objective-C selectors in your program, or
19618 (with the @var{regexp} argument) all those matching a particular regular
19622 This was never implemented.
19623 @kindex info methods
19625 @itemx info methods @var{regexp}
19626 The @code{info methods} command permits the user to examine all defined
19627 methods within C@t{++} program, or (with the @var{regexp} argument) a
19628 specific set of methods found in the various C@t{++} classes. Many
19629 C@t{++} classes provide a large number of methods. Thus, the output
19630 from the @code{ptype} command can be overwhelming and hard to use. The
19631 @code{info-methods} command filters the methods, printing only those
19632 which match the regular-expression @var{regexp}.
19635 @cindex opaque data types
19636 @kindex set opaque-type-resolution
19637 @item set opaque-type-resolution on
19638 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19639 declared as a pointer to a @code{struct}, @code{class}, or
19640 @code{union}---for example, @code{struct MyType *}---that is used in one
19641 source file although the full declaration of @code{struct MyType} is in
19642 another source file. The default is on.
19644 A change in the setting of this subcommand will not take effect until
19645 the next time symbols for a file are loaded.
19647 @item set opaque-type-resolution off
19648 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19649 is printed as follows:
19651 @{<no data fields>@}
19654 @kindex show opaque-type-resolution
19655 @item show opaque-type-resolution
19656 Show whether opaque types are resolved or not.
19658 @kindex set print symbol-loading
19659 @cindex print messages when symbols are loaded
19660 @item set print symbol-loading
19661 @itemx set print symbol-loading full
19662 @itemx set print symbol-loading brief
19663 @itemx set print symbol-loading off
19664 The @code{set print symbol-loading} command allows you to control the
19665 printing of messages when @value{GDBN} loads symbol information.
19666 By default a message is printed for the executable and one for each
19667 shared library, and normally this is what you want. However, when
19668 debugging apps with large numbers of shared libraries these messages
19670 When set to @code{brief} a message is printed for each executable,
19671 and when @value{GDBN} loads a collection of shared libraries at once
19672 it will only print one message regardless of the number of shared
19673 libraries. When set to @code{off} no messages are printed.
19675 @kindex show print symbol-loading
19676 @item show print symbol-loading
19677 Show whether messages will be printed when a @value{GDBN} command
19678 entered from the keyboard causes symbol information to be loaded.
19680 @kindex maint print symbols
19681 @cindex symbol dump
19682 @kindex maint print psymbols
19683 @cindex partial symbol dump
19684 @kindex maint print msymbols
19685 @cindex minimal symbol dump
19686 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19687 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19688 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19689 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19690 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19691 Write a dump of debugging symbol data into the file @var{filename} or
19692 the terminal if @var{filename} is unspecified.
19693 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19695 If @code{-pc @var{address}} is specified, only dump symbols for the file
19696 with code at that address. Note that @var{address} may be a symbol like
19698 If @code{-source @var{source}} is specified, only dump symbols for that
19701 These commands are used to debug the @value{GDBN} symbol-reading code.
19702 These commands do not modify internal @value{GDBN} state, therefore
19703 @samp{maint print symbols} will only print symbols for already expanded symbol
19705 You can use the command @code{info sources} to find out which files these are.
19706 If you use @samp{maint print psymbols} instead, the dump shows information
19707 about symbols that @value{GDBN} only knows partially---that is, symbols
19708 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19709 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19712 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19713 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19715 @kindex maint info symtabs
19716 @kindex maint info psymtabs
19717 @cindex listing @value{GDBN}'s internal symbol tables
19718 @cindex symbol tables, listing @value{GDBN}'s internal
19719 @cindex full symbol tables, listing @value{GDBN}'s internal
19720 @cindex partial symbol tables, listing @value{GDBN}'s internal
19721 @item maint info symtabs @r{[} @var{regexp} @r{]}
19722 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19724 List the @code{struct symtab} or @code{struct partial_symtab}
19725 structures whose names match @var{regexp}. If @var{regexp} is not
19726 given, list them all. The output includes expressions which you can
19727 copy into a @value{GDBN} debugging this one to examine a particular
19728 structure in more detail. For example:
19731 (@value{GDBP}) maint info psymtabs dwarf2read
19732 @{ objfile /home/gnu/build/gdb/gdb
19733 ((struct objfile *) 0x82e69d0)
19734 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19735 ((struct partial_symtab *) 0x8474b10)
19738 text addresses 0x814d3c8 -- 0x8158074
19739 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19740 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19741 dependencies (none)
19744 (@value{GDBP}) maint info symtabs
19748 We see that there is one partial symbol table whose filename contains
19749 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19750 and we see that @value{GDBN} has not read in any symtabs yet at all.
19751 If we set a breakpoint on a function, that will cause @value{GDBN} to
19752 read the symtab for the compilation unit containing that function:
19755 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19756 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19758 (@value{GDBP}) maint info symtabs
19759 @{ objfile /home/gnu/build/gdb/gdb
19760 ((struct objfile *) 0x82e69d0)
19761 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19762 ((struct symtab *) 0x86c1f38)
19765 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19766 linetable ((struct linetable *) 0x8370fa0)
19767 debugformat DWARF 2
19773 @kindex maint info line-table
19774 @cindex listing @value{GDBN}'s internal line tables
19775 @cindex line tables, listing @value{GDBN}'s internal
19776 @item maint info line-table @r{[} @var{regexp} @r{]}
19778 List the @code{struct linetable} from all @code{struct symtab}
19779 instances whose name matches @var{regexp}. If @var{regexp} is not
19780 given, list the @code{struct linetable} from all @code{struct symtab}.
19782 @kindex maint set symbol-cache-size
19783 @cindex symbol cache size
19784 @item maint set symbol-cache-size @var{size}
19785 Set the size of the symbol cache to @var{size}.
19786 The default size is intended to be good enough for debugging
19787 most applications. This option exists to allow for experimenting
19788 with different sizes.
19790 @kindex maint show symbol-cache-size
19791 @item maint show symbol-cache-size
19792 Show the size of the symbol cache.
19794 @kindex maint print symbol-cache
19795 @cindex symbol cache, printing its contents
19796 @item maint print symbol-cache
19797 Print the contents of the symbol cache.
19798 This is useful when debugging symbol cache issues.
19800 @kindex maint print symbol-cache-statistics
19801 @cindex symbol cache, printing usage statistics
19802 @item maint print symbol-cache-statistics
19803 Print symbol cache usage statistics.
19804 This helps determine how well the cache is being utilized.
19806 @kindex maint flush symbol-cache
19807 @kindex maint flush-symbol-cache
19808 @cindex symbol cache, flushing
19809 @item maint flush symbol-cache
19810 @itemx maint flush-symbol-cache
19811 Flush the contents of the symbol cache, all entries are removed. This
19812 command is useful when debugging the symbol cache. It is also useful
19813 when collecting performance data. The command @code{maint
19814 flush-symbol-cache} is deprecated in favor of @code{maint flush
19820 @chapter Altering Execution
19822 Once you think you have found an error in your program, you might want to
19823 find out for certain whether correcting the apparent error would lead to
19824 correct results in the rest of the run. You can find the answer by
19825 experiment, using the @value{GDBN} features for altering execution of the
19828 For example, you can store new values into variables or memory
19829 locations, give your program a signal, restart it at a different
19830 address, or even return prematurely from a function.
19833 * Assignment:: Assignment to variables
19834 * Jumping:: Continuing at a different address
19835 * Signaling:: Giving your program a signal
19836 * Returning:: Returning from a function
19837 * Calling:: Calling your program's functions
19838 * Patching:: Patching your program
19839 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19843 @section Assignment to Variables
19846 @cindex setting variables
19847 To alter the value of a variable, evaluate an assignment expression.
19848 @xref{Expressions, ,Expressions}. For example,
19855 stores the value 4 into the variable @code{x}, and then prints the
19856 value of the assignment expression (which is 4).
19857 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
19858 information on operators in supported languages.
19860 @kindex set variable
19861 @cindex variables, setting
19862 If you are not interested in seeing the value of the assignment, use the
19863 @code{set} command instead of the @code{print} command. @code{set} is
19864 really the same as @code{print} except that the expression's value is
19865 not printed and is not put in the value history (@pxref{Value History,
19866 ,Value History}). The expression is evaluated only for its effects.
19868 If the beginning of the argument string of the @code{set} command
19869 appears identical to a @code{set} subcommand, use the @code{set
19870 variable} command instead of just @code{set}. This command is identical
19871 to @code{set} except for its lack of subcommands. For example, if your
19872 program has a variable @code{width}, you get an error if you try to set
19873 a new value with just @samp{set width=13}, because @value{GDBN} has the
19874 command @code{set width}:
19877 (@value{GDBP}) whatis width
19879 (@value{GDBP}) p width
19881 (@value{GDBP}) set width=47
19882 Invalid syntax in expression.
19886 The invalid expression, of course, is @samp{=47}. In
19887 order to actually set the program's variable @code{width}, use
19890 (@value{GDBP}) set var width=47
19893 Because the @code{set} command has many subcommands that can conflict
19894 with the names of program variables, it is a good idea to use the
19895 @code{set variable} command instead of just @code{set}. For example, if
19896 your program has a variable @code{g}, you run into problems if you try
19897 to set a new value with just @samp{set g=4}, because @value{GDBN} has
19898 the command @code{set gnutarget}, abbreviated @code{set g}:
19902 (@value{GDBP}) whatis g
19906 (@value{GDBP}) set g=4
19910 The program being debugged has been started already.
19911 Start it from the beginning? (y or n) y
19912 Starting program: /home/smith/cc_progs/a.out
19913 "/home/smith/cc_progs/a.out": can't open to read symbols:
19914 Invalid bfd target.
19915 (@value{GDBP}) show g
19916 The current BFD target is "=4".
19921 The program variable @code{g} did not change, and you silently set the
19922 @code{gnutarget} to an invalid value. In order to set the variable
19926 (@value{GDBP}) set var g=4
19929 @value{GDBN} allows more implicit conversions in assignments than C; you can
19930 freely store an integer value into a pointer variable or vice versa,
19931 and you can convert any structure to any other structure that is the
19932 same length or shorter.
19933 @comment FIXME: how do structs align/pad in these conversions?
19934 @comment /doc@cygnus.com 18dec1990
19936 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
19937 construct to generate a value of specified type at a specified address
19938 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
19939 to memory location @code{0x83040} as an integer (which implies a certain size
19940 and representation in memory), and
19943 set @{int@}0x83040 = 4
19947 stores the value 4 into that memory location.
19950 @section Continuing at a Different Address
19952 Ordinarily, when you continue your program, you do so at the place where
19953 it stopped, with the @code{continue} command. You can instead continue at
19954 an address of your own choosing, with the following commands:
19958 @kindex j @r{(@code{jump})}
19959 @item jump @var{location}
19960 @itemx j @var{location}
19961 Resume execution at @var{location}. Execution stops again immediately
19962 if there is a breakpoint there. @xref{Specify Location}, for a description
19963 of the different forms of @var{location}. It is common
19964 practice to use the @code{tbreak} command in conjunction with
19965 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
19967 The @code{jump} command does not change the current stack frame, or
19968 the stack pointer, or the contents of any memory location or any
19969 register other than the program counter. If @var{location} is in
19970 a different function from the one currently executing, the results may
19971 be bizarre if the two functions expect different patterns of arguments or
19972 of local variables. For this reason, the @code{jump} command requests
19973 confirmation if the specified line is not in the function currently
19974 executing. However, even bizarre results are predictable if you are
19975 well acquainted with the machine-language code of your program.
19978 On many systems, you can get much the same effect as the @code{jump}
19979 command by storing a new value into the register @code{$pc}. The
19980 difference is that this does not start your program running; it only
19981 changes the address of where it @emph{will} run when you continue. For
19989 makes the next @code{continue} command or stepping command execute at
19990 address @code{0x485}, rather than at the address where your program stopped.
19991 @xref{Continuing and Stepping, ,Continuing and Stepping}.
19993 The most common occasion to use the @code{jump} command is to back
19994 up---perhaps with more breakpoints set---over a portion of a program
19995 that has already executed, in order to examine its execution in more
20000 @section Giving your Program a Signal
20001 @cindex deliver a signal to a program
20005 @item signal @var{signal}
20006 Resume execution where your program is stopped, but immediately give it the
20007 signal @var{signal}. The @var{signal} can be the name or the number of a
20008 signal. For example, on many systems @code{signal 2} and @code{signal
20009 SIGINT} are both ways of sending an interrupt signal.
20011 Alternatively, if @var{signal} is zero, continue execution without
20012 giving a signal. This is useful when your program stopped on account of
20013 a signal and would ordinarily see the signal when resumed with the
20014 @code{continue} command; @samp{signal 0} causes it to resume without a
20017 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20018 delivered to the currently selected thread, not the thread that last
20019 reported a stop. This includes the situation where a thread was
20020 stopped due to a signal. So if you want to continue execution
20021 suppressing the signal that stopped a thread, you should select that
20022 same thread before issuing the @samp{signal 0} command. If you issue
20023 the @samp{signal 0} command with another thread as the selected one,
20024 @value{GDBN} detects that and asks for confirmation.
20026 Invoking the @code{signal} command is not the same as invoking the
20027 @code{kill} utility from the shell. Sending a signal with @code{kill}
20028 causes @value{GDBN} to decide what to do with the signal depending on
20029 the signal handling tables (@pxref{Signals}). The @code{signal} command
20030 passes the signal directly to your program.
20032 @code{signal} does not repeat when you press @key{RET} a second time
20033 after executing the command.
20035 @kindex queue-signal
20036 @item queue-signal @var{signal}
20037 Queue @var{signal} to be delivered immediately to the current thread
20038 when execution of the thread resumes. The @var{signal} can be the name or
20039 the number of a signal. For example, on many systems @code{signal 2} and
20040 @code{signal SIGINT} are both ways of sending an interrupt signal.
20041 The handling of the signal must be set to pass the signal to the program,
20042 otherwise @value{GDBN} will report an error.
20043 You can control the handling of signals from @value{GDBN} with the
20044 @code{handle} command (@pxref{Signals}).
20046 Alternatively, if @var{signal} is zero, any currently queued signal
20047 for the current thread is discarded and when execution resumes no signal
20048 will be delivered. This is useful when your program stopped on account
20049 of a signal and would ordinarily see the signal when resumed with the
20050 @code{continue} command.
20052 This command differs from the @code{signal} command in that the signal
20053 is just queued, execution is not resumed. And @code{queue-signal} cannot
20054 be used to pass a signal whose handling state has been set to @code{nopass}
20059 @xref{stepping into signal handlers}, for information on how stepping
20060 commands behave when the thread has a signal queued.
20063 @section Returning from a Function
20066 @cindex returning from a function
20069 @itemx return @var{expression}
20070 You can cancel execution of a function call with the @code{return}
20071 command. If you give an
20072 @var{expression} argument, its value is used as the function's return
20076 When you use @code{return}, @value{GDBN} discards the selected stack frame
20077 (and all frames within it). You can think of this as making the
20078 discarded frame return prematurely. If you wish to specify a value to
20079 be returned, give that value as the argument to @code{return}.
20081 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20082 Frame}), and any other frames inside of it, leaving its caller as the
20083 innermost remaining frame. That frame becomes selected. The
20084 specified value is stored in the registers used for returning values
20087 The @code{return} command does not resume execution; it leaves the
20088 program stopped in the state that would exist if the function had just
20089 returned. In contrast, the @code{finish} command (@pxref{Continuing
20090 and Stepping, ,Continuing and Stepping}) resumes execution until the
20091 selected stack frame returns naturally.
20093 @value{GDBN} needs to know how the @var{expression} argument should be set for
20094 the inferior. The concrete registers assignment depends on the OS ABI and the
20095 type being returned by the selected stack frame. For example it is common for
20096 OS ABI to return floating point values in FPU registers while integer values in
20097 CPU registers. Still some ABIs return even floating point values in CPU
20098 registers. Larger integer widths (such as @code{long long int}) also have
20099 specific placement rules. @value{GDBN} already knows the OS ABI from its
20100 current target so it needs to find out also the type being returned to make the
20101 assignment into the right register(s).
20103 Normally, the selected stack frame has debug info. @value{GDBN} will always
20104 use the debug info instead of the implicit type of @var{expression} when the
20105 debug info is available. For example, if you type @kbd{return -1}, and the
20106 function in the current stack frame is declared to return a @code{long long
20107 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20108 into a @code{long long int}:
20111 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20113 (@value{GDBP}) return -1
20114 Make func return now? (y or n) y
20115 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20116 43 printf ("result=%lld\n", func ());
20120 However, if the selected stack frame does not have a debug info, e.g., if the
20121 function was compiled without debug info, @value{GDBN} has to find out the type
20122 to return from user. Specifying a different type by mistake may set the value
20123 in different inferior registers than the caller code expects. For example,
20124 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20125 of a @code{long long int} result for a debug info less function (on 32-bit
20126 architectures). Therefore the user is required to specify the return type by
20127 an appropriate cast explicitly:
20130 Breakpoint 2, 0x0040050b in func ()
20131 (@value{GDBP}) return -1
20132 Return value type not available for selected stack frame.
20133 Please use an explicit cast of the value to return.
20134 (@value{GDBP}) return (long long int) -1
20135 Make selected stack frame return now? (y or n) y
20136 #0 0x00400526 in main ()
20141 @section Calling Program Functions
20144 @cindex calling functions
20145 @cindex inferior functions, calling
20146 @item print @var{expr}
20147 Evaluate the expression @var{expr} and display the resulting value.
20148 The expression may include calls to functions in the program being
20152 @item call @var{expr}
20153 Evaluate the expression @var{expr} without displaying @code{void}
20156 You can use this variant of the @code{print} command if you want to
20157 execute a function from your program that does not return anything
20158 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20159 with @code{void} returned values that @value{GDBN} will otherwise
20160 print. If the result is not void, it is printed and saved in the
20164 It is possible for the function you call via the @code{print} or
20165 @code{call} command to generate a signal (e.g., if there's a bug in
20166 the function, or if you passed it incorrect arguments). What happens
20167 in that case is controlled by the @code{set unwindonsignal} command.
20169 Similarly, with a C@t{++} program it is possible for the function you
20170 call via the @code{print} or @code{call} command to generate an
20171 exception that is not handled due to the constraints of the dummy
20172 frame. In this case, any exception that is raised in the frame, but has
20173 an out-of-frame exception handler will not be found. GDB builds a
20174 dummy-frame for the inferior function call, and the unwinder cannot
20175 seek for exception handlers outside of this dummy-frame. What happens
20176 in that case is controlled by the
20177 @code{set unwind-on-terminating-exception} command.
20180 @item set unwindonsignal
20181 @kindex set unwindonsignal
20182 @cindex unwind stack in called functions
20183 @cindex call dummy stack unwinding
20184 Set unwinding of the stack if a signal is received while in a function
20185 that @value{GDBN} called in the program being debugged. If set to on,
20186 @value{GDBN} unwinds the stack it created for the call and restores
20187 the context to what it was before the call. If set to off (the
20188 default), @value{GDBN} stops in the frame where the signal was
20191 @item show unwindonsignal
20192 @kindex show unwindonsignal
20193 Show the current setting of stack unwinding in the functions called by
20196 @item set unwind-on-terminating-exception
20197 @kindex set unwind-on-terminating-exception
20198 @cindex unwind stack in called functions with unhandled exceptions
20199 @cindex call dummy stack unwinding on unhandled exception.
20200 Set unwinding of the stack if a C@t{++} exception is raised, but left
20201 unhandled while in a function that @value{GDBN} called in the program being
20202 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20203 it created for the call and restores the context to what it was before
20204 the call. If set to off, @value{GDBN} the exception is delivered to
20205 the default C@t{++} exception handler and the inferior terminated.
20207 @item show unwind-on-terminating-exception
20208 @kindex show unwind-on-terminating-exception
20209 Show the current setting of stack unwinding in the functions called by
20212 @item set may-call-functions
20213 @kindex set may-call-functions
20214 @cindex disabling calling functions in the program
20215 @cindex calling functions in the program, disabling
20216 Set permission to call functions in the program.
20217 This controls whether @value{GDBN} will attempt to call functions in
20218 the program, such as with expressions in the @code{print} command. It
20219 defaults to @code{on}.
20221 To call a function in the program, @value{GDBN} has to temporarily
20222 modify the state of the inferior. This has potentially undesired side
20223 effects. Also, having @value{GDBN} call nested functions is likely to
20224 be erroneous and may even crash the program being debugged. You can
20225 avoid such hazards by forbidding @value{GDBN} from calling functions
20226 in the program being debugged. If calling functions in the program
20227 is forbidden, GDB will throw an error when a command (such as printing
20228 an expression) starts a function call in the program.
20230 @item show may-call-functions
20231 @kindex show may-call-functions
20232 Show permission to call functions in the program.
20236 @subsection Calling functions with no debug info
20238 @cindex no debug info functions
20239 Sometimes, a function you wish to call is missing debug information.
20240 In such case, @value{GDBN} does not know the type of the function,
20241 including the types of the function's parameters. To avoid calling
20242 the inferior function incorrectly, which could result in the called
20243 function functioning erroneously and even crash, @value{GDBN} refuses
20244 to call the function unless you tell it the type of the function.
20246 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20247 to do that. The simplest is to cast the call to the function's
20248 declared return type. For example:
20251 (@value{GDBP}) p getenv ("PATH")
20252 'getenv' has unknown return type; cast the call to its declared return type
20253 (@value{GDBP}) p (char *) getenv ("PATH")
20254 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20257 Casting the return type of a no-debug function is equivalent to
20258 casting the function to a pointer to a prototyped function that has a
20259 prototype that matches the types of the passed-in arguments, and
20260 calling that. I.e., the call above is equivalent to:
20263 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20267 and given this prototyped C or C++ function with float parameters:
20270 float multiply (float v1, float v2) @{ return v1 * v2; @}
20274 these calls are equivalent:
20277 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20278 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20281 If the function you wish to call is declared as unprototyped (i.e.@:
20282 old K&R style), you must use the cast-to-function-pointer syntax, so
20283 that @value{GDBN} knows that it needs to apply default argument
20284 promotions (promote float arguments to double). @xref{ABI, float
20285 promotion}. For example, given this unprototyped C function with
20286 float parameters, and no debug info:
20290 multiply_noproto (v1, v2)
20298 you call it like this:
20301 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20305 @section Patching Programs
20307 @cindex patching binaries
20308 @cindex writing into executables
20309 @cindex writing into corefiles
20311 By default, @value{GDBN} opens the file containing your program's
20312 executable code (or the corefile) read-only. This prevents accidental
20313 alterations to machine code; but it also prevents you from intentionally
20314 patching your program's binary.
20316 If you'd like to be able to patch the binary, you can specify that
20317 explicitly with the @code{set write} command. For example, you might
20318 want to turn on internal debugging flags, or even to make emergency
20324 @itemx set write off
20325 If you specify @samp{set write on}, @value{GDBN} opens executable and
20326 core files for both reading and writing; if you specify @kbd{set write
20327 off} (the default), @value{GDBN} opens them read-only.
20329 If you have already loaded a file, you must load it again (using the
20330 @code{exec-file} or @code{core-file} command) after changing @code{set
20331 write}, for your new setting to take effect.
20335 Display whether executable files and core files are opened for writing
20336 as well as reading.
20339 @node Compiling and Injecting Code
20340 @section Compiling and injecting code in @value{GDBN}
20341 @cindex injecting code
20342 @cindex writing into executables
20343 @cindex compiling code
20345 @value{GDBN} supports on-demand compilation and code injection into
20346 programs running under @value{GDBN}. GCC 5.0 or higher built with
20347 @file{libcc1.so} must be installed for this functionality to be enabled.
20348 This functionality is implemented with the following commands.
20351 @kindex compile code
20352 @item compile code @var{source-code}
20353 @itemx compile code -raw @var{--} @var{source-code}
20354 Compile @var{source-code} with the compiler language found as the current
20355 language in @value{GDBN} (@pxref{Languages}). If compilation and
20356 injection is not supported with the current language specified in
20357 @value{GDBN}, or the compiler does not support this feature, an error
20358 message will be printed. If @var{source-code} compiles and links
20359 successfully, @value{GDBN} will load the object-code emitted,
20360 and execute it within the context of the currently selected inferior.
20361 It is important to note that the compiled code is executed immediately.
20362 After execution, the compiled code is removed from @value{GDBN} and any
20363 new types or variables you have defined will be deleted.
20365 The command allows you to specify @var{source-code} in two ways.
20366 The simplest method is to provide a single line of code to the command.
20370 compile code printf ("hello world\n");
20373 If you specify options on the command line as well as source code, they
20374 may conflict. The @samp{--} delimiter can be used to separate options
20375 from actual source code. E.g.:
20378 compile code -r -- printf ("hello world\n");
20381 Alternatively you can enter source code as multiple lines of text. To
20382 enter this mode, invoke the @samp{compile code} command without any text
20383 following the command. This will start the multiple-line editor and
20384 allow you to type as many lines of source code as required. When you
20385 have completed typing, enter @samp{end} on its own line to exit the
20390 >printf ("hello\n");
20391 >printf ("world\n");
20395 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20396 provided @var{source-code} in a callable scope. In this case, you must
20397 specify the entry point of the code by defining a function named
20398 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20399 inferior. Using @samp{-raw} option may be needed for example when
20400 @var{source-code} requires @samp{#include} lines which may conflict with
20401 inferior symbols otherwise.
20403 @kindex compile file
20404 @item compile file @var{filename}
20405 @itemx compile file -raw @var{filename}
20406 Like @code{compile code}, but take the source code from @var{filename}.
20409 compile file /home/user/example.c
20414 @item compile print [[@var{options}] --] @var{expr}
20415 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20416 Compile and execute @var{expr} with the compiler language found as the
20417 current language in @value{GDBN} (@pxref{Languages}). By default the
20418 value of @var{expr} is printed in a format appropriate to its data type;
20419 you can choose a different format by specifying @samp{/@var{f}}, where
20420 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20421 Formats}. The @code{compile print} command accepts the same options
20422 as the @code{print} command; see @ref{print options}.
20424 @item compile print [[@var{options}] --]
20425 @itemx compile print [[@var{options}] --] /@var{f}
20426 @cindex reprint the last value
20427 Alternatively you can enter the expression (source code producing it) as
20428 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20429 command without any text following the command. This will start the
20430 multiple-line editor.
20434 The process of compiling and injecting the code can be inspected using:
20437 @anchor{set debug compile}
20438 @item set debug compile
20439 @cindex compile command debugging info
20440 Turns on or off display of @value{GDBN} process of compiling and
20441 injecting the code. The default is off.
20443 @item show debug compile
20444 Displays the current state of displaying @value{GDBN} process of
20445 compiling and injecting the code.
20447 @anchor{set debug compile-cplus-types}
20448 @item set debug compile-cplus-types
20449 @cindex compile C@t{++} type conversion
20450 Turns on or off the display of C@t{++} type conversion debugging information.
20451 The default is off.
20453 @item show debug compile-cplus-types
20454 Displays the current state of displaying debugging information for
20455 C@t{++} type conversion.
20458 @subsection Compilation options for the @code{compile} command
20460 @value{GDBN} needs to specify the right compilation options for the code
20461 to be injected, in part to make its ABI compatible with the inferior
20462 and in part to make the injected code compatible with @value{GDBN}'s
20466 The options used, in increasing precedence:
20469 @item target architecture and OS options (@code{gdbarch})
20470 These options depend on target processor type and target operating
20471 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20472 (@code{-m64}) compilation option.
20474 @item compilation options recorded in the target
20475 @value{NGCC} (since version 4.7) stores the options used for compilation
20476 into @code{DW_AT_producer} part of DWARF debugging information according
20477 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20478 explicitly specify @code{-g} during inferior compilation otherwise
20479 @value{NGCC} produces no DWARF. This feature is only relevant for
20480 platforms where @code{-g} produces DWARF by default, otherwise one may
20481 try to enforce DWARF by using @code{-gdwarf-4}.
20483 @item compilation options set by @code{set compile-args}
20487 You can override compilation options using the following command:
20490 @item set compile-args
20491 @cindex compile command options override
20492 Set compilation options used for compiling and injecting code with the
20493 @code{compile} commands. These options override any conflicting ones
20494 from the target architecture and/or options stored during inferior
20497 @item show compile-args
20498 Displays the current state of compilation options override.
20499 This does not show all the options actually used during compilation,
20500 use @ref{set debug compile} for that.
20503 @subsection Caveats when using the @code{compile} command
20505 There are a few caveats to keep in mind when using the @code{compile}
20506 command. As the caveats are different per language, the table below
20507 highlights specific issues on a per language basis.
20510 @item C code examples and caveats
20511 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20512 attempt to compile the source code with a @samp{C} compiler. The source
20513 code provided to the @code{compile} command will have much the same
20514 access to variables and types as it normally would if it were part of
20515 the program currently being debugged in @value{GDBN}.
20517 Below is a sample program that forms the basis of the examples that
20518 follow. This program has been compiled and loaded into @value{GDBN},
20519 much like any other normal debugging session.
20522 void function1 (void)
20525 printf ("function 1\n");
20528 void function2 (void)
20543 For the purposes of the examples in this section, the program above has
20544 been compiled, loaded into @value{GDBN}, stopped at the function
20545 @code{main}, and @value{GDBN} is awaiting input from the user.
20547 To access variables and types for any program in @value{GDBN}, the
20548 program must be compiled and packaged with debug information. The
20549 @code{compile} command is not an exception to this rule. Without debug
20550 information, you can still use the @code{compile} command, but you will
20551 be very limited in what variables and types you can access.
20553 So with that in mind, the example above has been compiled with debug
20554 information enabled. The @code{compile} command will have access to
20555 all variables and types (except those that may have been optimized
20556 out). Currently, as @value{GDBN} has stopped the program in the
20557 @code{main} function, the @code{compile} command would have access to
20558 the variable @code{k}. You could invoke the @code{compile} command
20559 and type some source code to set the value of @code{k}. You can also
20560 read it, or do anything with that variable you would normally do in
20561 @code{C}. Be aware that changes to inferior variables in the
20562 @code{compile} command are persistent. In the following example:
20565 compile code k = 3;
20569 the variable @code{k} is now 3. It will retain that value until
20570 something else in the example program changes it, or another
20571 @code{compile} command changes it.
20573 Normal scope and access rules apply to source code compiled and
20574 injected by the @code{compile} command. In the example, the variables
20575 @code{j} and @code{k} are not accessible yet, because the program is
20576 currently stopped in the @code{main} function, where these variables
20577 are not in scope. Therefore, the following command
20580 compile code j = 3;
20584 will result in a compilation error message.
20586 Once the program is continued, execution will bring these variables in
20587 scope, and they will become accessible; then the code you specify via
20588 the @code{compile} command will be able to access them.
20590 You can create variables and types with the @code{compile} command as
20591 part of your source code. Variables and types that are created as part
20592 of the @code{compile} command are not visible to the rest of the program for
20593 the duration of its run. This example is valid:
20596 compile code int ff = 5; printf ("ff is %d\n", ff);
20599 However, if you were to type the following into @value{GDBN} after that
20600 command has completed:
20603 compile code printf ("ff is %d\n'', ff);
20607 a compiler error would be raised as the variable @code{ff} no longer
20608 exists. Object code generated and injected by the @code{compile}
20609 command is removed when its execution ends. Caution is advised
20610 when assigning to program variables values of variables created by the
20611 code submitted to the @code{compile} command. This example is valid:
20614 compile code int ff = 5; k = ff;
20617 The value of the variable @code{ff} is assigned to @code{k}. The variable
20618 @code{k} does not require the existence of @code{ff} to maintain the value
20619 it has been assigned. However, pointers require particular care in
20620 assignment. If the source code compiled with the @code{compile} command
20621 changed the address of a pointer in the example program, perhaps to a
20622 variable created in the @code{compile} command, that pointer would point
20623 to an invalid location when the command exits. The following example
20624 would likely cause issues with your debugged program:
20627 compile code int ff = 5; p = &ff;
20630 In this example, @code{p} would point to @code{ff} when the
20631 @code{compile} command is executing the source code provided to it.
20632 However, as variables in the (example) program persist with their
20633 assigned values, the variable @code{p} would point to an invalid
20634 location when the command exists. A general rule should be followed
20635 in that you should either assign @code{NULL} to any assigned pointers,
20636 or restore a valid location to the pointer before the command exits.
20638 Similar caution must be exercised with any structs, unions, and typedefs
20639 defined in @code{compile} command. Types defined in the @code{compile}
20640 command will no longer be available in the next @code{compile} command.
20641 Therefore, if you cast a variable to a type defined in the
20642 @code{compile} command, care must be taken to ensure that any future
20643 need to resolve the type can be achieved.
20646 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20647 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20648 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20649 Compilation failed.
20650 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20654 Variables that have been optimized away by the compiler are not
20655 accessible to the code submitted to the @code{compile} command.
20656 Access to those variables will generate a compiler error which @value{GDBN}
20657 will print to the console.
20660 @subsection Compiler search for the @code{compile} command
20662 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20663 which may not be obvious for remote targets of different architecture
20664 than where @value{GDBN} is running. Environment variable @env{PATH} on
20665 @value{GDBN} host is searched for @value{NGCC} binary matching the
20666 target architecture and operating system. This search can be overriden
20667 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
20668 taken from shell that executed @value{GDBN}, it is not the value set by
20669 @value{GDBN} command @code{set environment}). @xref{Environment}.
20672 Specifically @env{PATH} is searched for binaries matching regular expression
20673 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20674 debugged. @var{arch} is processor name --- multiarch is supported, so for
20675 example both @code{i386} and @code{x86_64} targets look for pattern
20676 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20677 for pattern @code{s390x?}. @var{os} is currently supported only for
20678 pattern @code{linux(-gnu)?}.
20680 On Posix hosts the compiler driver @value{GDBN} needs to find also
20681 shared library @file{libcc1.so} from the compiler. It is searched in
20682 default shared library search path (overridable with usual environment
20683 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
20684 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20685 according to the installation of the found compiler --- as possibly
20686 specified by the @code{set compile-gcc} command.
20689 @item set compile-gcc
20690 @cindex compile command driver filename override
20691 Set compilation command used for compiling and injecting code with the
20692 @code{compile} commands. If this option is not set (it is set to
20693 an empty string), the search described above will occur --- that is the
20696 @item show compile-gcc
20697 Displays the current compile command @value{NGCC} driver filename.
20698 If set, it is the main command @command{gcc}, found usually for example
20699 under name @file{x86_64-linux-gnu-gcc}.
20703 @chapter @value{GDBN} Files
20705 @value{GDBN} needs to know the file name of the program to be debugged,
20706 both in order to read its symbol table and in order to start your
20707 program. To debug a core dump of a previous run, you must also tell
20708 @value{GDBN} the name of the core dump file.
20711 * Files:: Commands to specify files
20712 * File Caching:: Information about @value{GDBN}'s file caching
20713 * Separate Debug Files:: Debugging information in separate files
20714 * MiniDebugInfo:: Debugging information in a special section
20715 * Index Files:: Index files speed up GDB
20716 * Symbol Errors:: Errors reading symbol files
20717 * Data Files:: GDB data files
20721 @section Commands to Specify Files
20723 @cindex symbol table
20724 @cindex core dump file
20726 You may want to specify executable and core dump file names. The usual
20727 way to do this is at start-up time, using the arguments to
20728 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20729 Out of @value{GDBN}}).
20731 Occasionally it is necessary to change to a different file during a
20732 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20733 specify a file you want to use. Or you are debugging a remote target
20734 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20735 Program}). In these situations the @value{GDBN} commands to specify
20736 new files are useful.
20739 @cindex executable file
20741 @item file @var{filename}
20742 Use @var{filename} as the program to be debugged. It is read for its
20743 symbols and for the contents of pure memory. It is also the program
20744 executed when you use the @code{run} command. If you do not specify a
20745 directory and the file is not found in the @value{GDBN} working directory,
20746 @value{GDBN} uses the environment variable @env{PATH} as a list of
20747 directories to search, just as the shell does when looking for a program
20748 to run. You can change the value of this variable, for both @value{GDBN}
20749 and your program, using the @code{path} command.
20751 @cindex unlinked object files
20752 @cindex patching object files
20753 You can load unlinked object @file{.o} files into @value{GDBN} using
20754 the @code{file} command. You will not be able to ``run'' an object
20755 file, but you can disassemble functions and inspect variables. Also,
20756 if the underlying BFD functionality supports it, you could use
20757 @kbd{gdb -write} to patch object files using this technique. Note
20758 that @value{GDBN} can neither interpret nor modify relocations in this
20759 case, so branches and some initialized variables will appear to go to
20760 the wrong place. But this feature is still handy from time to time.
20763 @code{file} with no argument makes @value{GDBN} discard any information it
20764 has on both executable file and the symbol table.
20767 @item exec-file @r{[} @var{filename} @r{]}
20768 Specify that the program to be run (but not the symbol table) is found
20769 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
20770 if necessary to locate your program. Omitting @var{filename} means to
20771 discard information on the executable file.
20773 @kindex symbol-file
20774 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20775 Read symbol table information from file @var{filename}. @env{PATH} is
20776 searched when necessary. Use the @code{file} command to get both symbol
20777 table and program to run from the same file.
20779 If an optional @var{offset} is specified, it is added to the start
20780 address of each section in the symbol file. This is useful if the
20781 program is relocated at runtime, such as the Linux kernel with kASLR
20784 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20785 program's symbol table.
20787 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20788 some breakpoints and auto-display expressions. This is because they may
20789 contain pointers to the internal data recording symbols and data types,
20790 which are part of the old symbol table data being discarded inside
20793 @code{symbol-file} does not repeat if you press @key{RET} again after
20796 When @value{GDBN} is configured for a particular environment, it
20797 understands debugging information in whatever format is the standard
20798 generated for that environment; you may use either a @sc{gnu} compiler, or
20799 other compilers that adhere to the local conventions.
20800 Best results are usually obtained from @sc{gnu} compilers; for example,
20801 using @code{@value{NGCC}} you can generate debugging information for
20804 For most kinds of object files, with the exception of old SVR3 systems
20805 using COFF, the @code{symbol-file} command does not normally read the
20806 symbol table in full right away. Instead, it scans the symbol table
20807 quickly to find which source files and which symbols are present. The
20808 details are read later, one source file at a time, as they are needed.
20810 The purpose of this two-stage reading strategy is to make @value{GDBN}
20811 start up faster. For the most part, it is invisible except for
20812 occasional pauses while the symbol table details for a particular source
20813 file are being read. (The @code{set verbose} command can turn these
20814 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20815 Warnings and Messages}.)
20817 We have not implemented the two-stage strategy for COFF yet. When the
20818 symbol table is stored in COFF format, @code{symbol-file} reads the
20819 symbol table data in full right away. Note that ``stabs-in-COFF''
20820 still does the two-stage strategy, since the debug info is actually
20824 @cindex reading symbols immediately
20825 @cindex symbols, reading immediately
20826 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20827 @itemx file @r{[} -readnow @r{]} @var{filename}
20828 You can override the @value{GDBN} two-stage strategy for reading symbol
20829 tables by using the @samp{-readnow} option with any of the commands that
20830 load symbol table information, if you want to be sure @value{GDBN} has the
20831 entire symbol table available.
20833 @cindex @code{-readnever}, option for symbol-file command
20834 @cindex never read symbols
20835 @cindex symbols, never read
20836 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20837 @itemx file @r{[} -readnever @r{]} @var{filename}
20838 You can instruct @value{GDBN} to never read the symbolic information
20839 contained in @var{filename} by using the @samp{-readnever} option.
20840 @xref{--readnever}.
20842 @c FIXME: for now no mention of directories, since this seems to be in
20843 @c flux. 13mar1992 status is that in theory GDB would look either in
20844 @c current dir or in same dir as myprog; but issues like competing
20845 @c GDB's, or clutter in system dirs, mean that in practice right now
20846 @c only current dir is used. FFish says maybe a special GDB hierarchy
20847 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20851 @item core-file @r{[}@var{filename}@r{]}
20853 Specify the whereabouts of a core dump file to be used as the ``contents
20854 of memory''. Traditionally, core files contain only some parts of the
20855 address space of the process that generated them; @value{GDBN} can access the
20856 executable file itself for other parts.
20858 @code{core-file} with no argument specifies that no core file is
20861 Note that the core file is ignored when your program is actually running
20862 under @value{GDBN}. So, if you have been running your program and you
20863 wish to debug a core file instead, you must kill the subprocess in which
20864 the program is running. To do this, use the @code{kill} command
20865 (@pxref{Kill Process, ,Killing the Child Process}).
20867 @kindex add-symbol-file
20868 @cindex dynamic linking
20869 @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{]}
20870 The @code{add-symbol-file} command reads additional symbol table
20871 information from the file @var{filename}. You would use this command
20872 when @var{filename} has been dynamically loaded (by some other means)
20873 into the program that is running. The @var{textaddress} parameter gives
20874 the memory address at which the file's text section has been loaded.
20875 You can additionally specify the base address of other sections using
20876 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
20877 If a section is omitted, @value{GDBN} will use its default addresses
20878 as found in @var{filename}. Any @var{address} or @var{textaddress}
20879 can be given as an expression.
20881 If an optional @var{offset} is specified, it is added to the start
20882 address of each section, except those for which the address was
20883 specified explicitly.
20885 The symbol table of the file @var{filename} is added to the symbol table
20886 originally read with the @code{symbol-file} command. You can use the
20887 @code{add-symbol-file} command any number of times; the new symbol data
20888 thus read is kept in addition to the old.
20890 Changes can be reverted using the command @code{remove-symbol-file}.
20892 @cindex relocatable object files, reading symbols from
20893 @cindex object files, relocatable, reading symbols from
20894 @cindex reading symbols from relocatable object files
20895 @cindex symbols, reading from relocatable object files
20896 @cindex @file{.o} files, reading symbols from
20897 Although @var{filename} is typically a shared library file, an
20898 executable file, or some other object file which has been fully
20899 relocated for loading into a process, you can also load symbolic
20900 information from relocatable @file{.o} files, as long as:
20904 the file's symbolic information refers only to linker symbols defined in
20905 that file, not to symbols defined by other object files,
20907 every section the file's symbolic information refers to has actually
20908 been loaded into the inferior, as it appears in the file, and
20910 you can determine the address at which every section was loaded, and
20911 provide these to the @code{add-symbol-file} command.
20915 Some embedded operating systems, like Sun Chorus and VxWorks, can load
20916 relocatable files into an already running program; such systems
20917 typically make the requirements above easy to meet. However, it's
20918 important to recognize that many native systems use complex link
20919 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
20920 assembly, for example) that make the requirements difficult to meet. In
20921 general, one cannot assume that using @code{add-symbol-file} to read a
20922 relocatable object file's symbolic information will have the same effect
20923 as linking the relocatable object file into the program in the normal
20926 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
20928 @kindex remove-symbol-file
20929 @item remove-symbol-file @var{filename}
20930 @item remove-symbol-file -a @var{address}
20931 Remove a symbol file added via the @code{add-symbol-file} command. The
20932 file to remove can be identified by its @var{filename} or by an @var{address}
20933 that lies within the boundaries of this symbol file in memory. Example:
20936 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
20937 add symbol table from file "/home/user/gdb/mylib.so" at
20938 .text_addr = 0x7ffff7ff9480
20940 Reading symbols from /home/user/gdb/mylib.so...
20941 (gdb) remove-symbol-file -a 0x7ffff7ff9480
20942 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
20947 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
20949 @kindex add-symbol-file-from-memory
20950 @cindex @code{syscall DSO}
20951 @cindex load symbols from memory
20952 @item add-symbol-file-from-memory @var{address}
20953 Load symbols from the given @var{address} in a dynamically loaded
20954 object file whose image is mapped directly into the inferior's memory.
20955 For example, the Linux kernel maps a @code{syscall DSO} into each
20956 process's address space; this DSO provides kernel-specific code for
20957 some system calls. The argument can be any expression whose
20958 evaluation yields the address of the file's shared object file header.
20959 For this command to work, you must have used @code{symbol-file} or
20960 @code{exec-file} commands in advance.
20963 @item section @var{section} @var{addr}
20964 The @code{section} command changes the base address of the named
20965 @var{section} of the exec file to @var{addr}. This can be used if the
20966 exec file does not contain section addresses, (such as in the
20967 @code{a.out} format), or when the addresses specified in the file
20968 itself are wrong. Each section must be changed separately. The
20969 @code{info files} command, described below, lists all the sections and
20973 @kindex info target
20976 @code{info files} and @code{info target} are synonymous; both print the
20977 current target (@pxref{Targets, ,Specifying a Debugging Target}),
20978 including the names of the executable and core dump files currently in
20979 use by @value{GDBN}, and the files from which symbols were loaded. The
20980 command @code{help target} lists all possible targets rather than
20983 @kindex maint info sections
20984 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
20985 Another command that can give you extra information about program sections
20986 is @code{maint info sections}. In addition to the section information
20987 displayed by @code{info files}, this command displays the flags and file
20988 offset of each section in the executable and core dump files.
20990 When @samp{-all-objects} is passed then sections from all loaded object
20991 files, including shared libraries, are printed.
20993 The optional @var{filter-list} is a space separated list of filter
20994 keywords. Sections that match any one of the filter criteria will be
20995 printed. There are two types of filter:
20998 @item @var{section-name}
20999 Display information about any section named @var{section-name}.
21000 @item @var{section-flag}
21001 Display information for any section with @var{section-flag}. The
21002 section flags that @value{GDBN} currently knows about are:
21005 Section will have space allocated in the process when loaded.
21006 Set for all sections except those containing debug information.
21008 Section will be loaded from the file into the child process memory.
21009 Set for pre-initialized code and data, clear for @code{.bss} sections.
21011 Section needs to be relocated before loading.
21013 Section cannot be modified by the child process.
21015 Section contains executable code only.
21017 Section contains data only (no executable code).
21019 Section will reside in ROM.
21021 Section contains data for constructor/destructor lists.
21023 Section is not empty.
21025 An instruction to the linker to not output the section.
21026 @item COFF_SHARED_LIBRARY
21027 A notification to the linker that the section contains
21028 COFF shared library information.
21030 Section contains common symbols.
21034 @kindex maint info target-sections
21035 @item maint info target-sections
21036 This command prints @value{GDBN}'s internal section table. For each
21037 target @value{GDBN} maintains a table containing the allocatable
21038 sections from all currently mapped objects, along with information
21039 about where the section is mapped.
21041 @kindex set trust-readonly-sections
21042 @cindex read-only sections
21043 @item set trust-readonly-sections on
21044 Tell @value{GDBN} that readonly sections in your object file
21045 really are read-only (i.e.@: that their contents will not change).
21046 In that case, @value{GDBN} can fetch values from these sections
21047 out of the object file, rather than from the target program.
21048 For some targets (notably embedded ones), this can be a significant
21049 enhancement to debugging performance.
21051 The default is off.
21053 @item set trust-readonly-sections off
21054 Tell @value{GDBN} not to trust readonly sections. This means that
21055 the contents of the section might change while the program is running,
21056 and must therefore be fetched from the target when needed.
21058 @item show trust-readonly-sections
21059 Show the current setting of trusting readonly sections.
21062 All file-specifying commands allow both absolute and relative file names
21063 as arguments. @value{GDBN} always converts the file name to an absolute file
21064 name and remembers it that way.
21066 @cindex shared libraries
21067 @anchor{Shared Libraries}
21068 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21069 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21070 DSBT (TIC6X) shared libraries.
21072 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21073 shared libraries. @xref{Expat}.
21075 @value{GDBN} automatically loads symbol definitions from shared libraries
21076 when you use the @code{run} command, or when you examine a core file.
21077 (Before you issue the @code{run} command, @value{GDBN} does not understand
21078 references to a function in a shared library, however---unless you are
21079 debugging a core file).
21081 @c FIXME: some @value{GDBN} release may permit some refs to undef
21082 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21083 @c FIXME...lib; check this from time to time when updating manual
21085 There are times, however, when you may wish to not automatically load
21086 symbol definitions from shared libraries, such as when they are
21087 particularly large or there are many of them.
21089 To control the automatic loading of shared library symbols, use the
21093 @kindex set auto-solib-add
21094 @item set auto-solib-add @var{mode}
21095 If @var{mode} is @code{on}, symbols from all shared object libraries
21096 will be loaded automatically when the inferior begins execution, you
21097 attach to an independently started inferior, or when the dynamic linker
21098 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21099 is @code{off}, symbols must be loaded manually, using the
21100 @code{sharedlibrary} command. The default value is @code{on}.
21102 @cindex memory used for symbol tables
21103 If your program uses lots of shared libraries with debug info that
21104 takes large amounts of memory, you can decrease the @value{GDBN}
21105 memory footprint by preventing it from automatically loading the
21106 symbols from shared libraries. To that end, type @kbd{set
21107 auto-solib-add off} before running the inferior, then load each
21108 library whose debug symbols you do need with @kbd{sharedlibrary
21109 @var{regexp}}, where @var{regexp} is a regular expression that matches
21110 the libraries whose symbols you want to be loaded.
21112 @kindex show auto-solib-add
21113 @item show auto-solib-add
21114 Display the current autoloading mode.
21117 @cindex load shared library
21118 To explicitly load shared library symbols, use the @code{sharedlibrary}
21122 @kindex info sharedlibrary
21124 @item info share @var{regex}
21125 @itemx info sharedlibrary @var{regex}
21126 Print the names of the shared libraries which are currently loaded
21127 that match @var{regex}. If @var{regex} is omitted then print
21128 all shared libraries that are loaded.
21131 @item info dll @var{regex}
21132 This is an alias of @code{info sharedlibrary}.
21134 @kindex sharedlibrary
21136 @item sharedlibrary @var{regex}
21137 @itemx share @var{regex}
21138 Load shared object library symbols for files matching a
21139 Unix regular expression.
21140 As with files loaded automatically, it only loads shared libraries
21141 required by your program for a core file or after typing @code{run}. If
21142 @var{regex} is omitted all shared libraries required by your program are
21145 @item nosharedlibrary
21146 @kindex nosharedlibrary
21147 @cindex unload symbols from shared libraries
21148 Unload all shared object library symbols. This discards all symbols
21149 that have been loaded from all shared libraries. Symbols from shared
21150 libraries that were loaded by explicit user requests are not
21154 Sometimes you may wish that @value{GDBN} stops and gives you control
21155 when any of shared library events happen. The best way to do this is
21156 to use @code{catch load} and @code{catch unload} (@pxref{Set
21159 @value{GDBN} also supports the @code{set stop-on-solib-events}
21160 command for this. This command exists for historical reasons. It is
21161 less useful than setting a catchpoint, because it does not allow for
21162 conditions or commands as a catchpoint does.
21165 @item set stop-on-solib-events
21166 @kindex set stop-on-solib-events
21167 This command controls whether @value{GDBN} should give you control
21168 when the dynamic linker notifies it about some shared library event.
21169 The most common event of interest is loading or unloading of a new
21172 @item show stop-on-solib-events
21173 @kindex show stop-on-solib-events
21174 Show whether @value{GDBN} stops and gives you control when shared
21175 library events happen.
21178 Shared libraries are also supported in many cross or remote debugging
21179 configurations. @value{GDBN} needs to have access to the target's libraries;
21180 this can be accomplished either by providing copies of the libraries
21181 on the host system, or by asking @value{GDBN} to automatically retrieve the
21182 libraries from the target. If copies of the target libraries are
21183 provided, they need to be the same as the target libraries, although the
21184 copies on the target can be stripped as long as the copies on the host are
21187 @cindex where to look for shared libraries
21188 For remote debugging, you need to tell @value{GDBN} where the target
21189 libraries are, so that it can load the correct copies---otherwise, it
21190 may try to load the host's libraries. @value{GDBN} has two variables
21191 to specify the search directories for target libraries.
21194 @cindex prefix for executable and shared library file names
21195 @cindex system root, alternate
21196 @kindex set solib-absolute-prefix
21197 @kindex set sysroot
21198 @item set sysroot @var{path}
21199 Use @var{path} as the system root for the program being debugged. Any
21200 absolute shared library paths will be prefixed with @var{path}; many
21201 runtime loaders store the absolute paths to the shared library in the
21202 target program's memory. When starting processes remotely, and when
21203 attaching to already-running processes (local or remote), their
21204 executable filenames will be prefixed with @var{path} if reported to
21205 @value{GDBN} as absolute by the operating system. If you use
21206 @code{set sysroot} to find executables and shared libraries, they need
21207 to be laid out in the same way that they are on the target, with
21208 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21211 If @var{path} starts with the sequence @file{target:} and the target
21212 system is remote then @value{GDBN} will retrieve the target binaries
21213 from the remote system. This is only supported when using a remote
21214 target that supports the @code{remote get} command (@pxref{File
21215 Transfer,,Sending files to a remote system}). The part of @var{path}
21216 following the initial @file{target:} (if present) is used as system
21217 root prefix on the remote file system. If @var{path} starts with the
21218 sequence @file{remote:} this is converted to the sequence
21219 @file{target:} by @code{set sysroot}@footnote{Historically the
21220 functionality to retrieve binaries from the remote system was
21221 provided by prefixing @var{path} with @file{remote:}}. If you want
21222 to specify a local system root using a directory that happens to be
21223 named @file{target:} or @file{remote:}, you need to use some
21224 equivalent variant of the name like @file{./target:}.
21226 For targets with an MS-DOS based filesystem, such as MS-Windows,
21227 @value{GDBN} tries prefixing a few variants of the target
21228 absolute file name with @var{path}. But first, on Unix hosts,
21229 @value{GDBN} converts all backslash directory separators into forward
21230 slashes, because the backslash is not a directory separator on Unix:
21233 c:\foo\bar.dll @result{} c:/foo/bar.dll
21236 Then, @value{GDBN} attempts prefixing the target file name with
21237 @var{path}, and looks for the resulting file name in the host file
21241 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21244 If that does not find the binary, @value{GDBN} tries removing
21245 the @samp{:} character from the drive spec, both for convenience, and,
21246 for the case of the host file system not supporting file names with
21250 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21253 This makes it possible to have a system root that mirrors a target
21254 with more than one drive. E.g., you may want to setup your local
21255 copies of the target system shared libraries like so (note @samp{c} vs
21259 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21260 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21261 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21265 and point the system root at @file{/path/to/sysroot}, so that
21266 @value{GDBN} can find the correct copies of both
21267 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21269 If that still does not find the binary, @value{GDBN} tries
21270 removing the whole drive spec from the target file name:
21273 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21276 This last lookup makes it possible to not care about the drive name,
21277 if you don't want or need to.
21279 The @code{set solib-absolute-prefix} command is an alias for @code{set
21282 @cindex default system root
21283 @cindex @samp{--with-sysroot}
21284 You can set the default system root by using the configure-time
21285 @samp{--with-sysroot} option. If the system root is inside
21286 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21287 @samp{--exec-prefix}), then the default system root will be updated
21288 automatically if the installed @value{GDBN} is moved to a new
21291 @kindex show sysroot
21293 Display the current executable and shared library prefix.
21295 @kindex set solib-search-path
21296 @item set solib-search-path @var{path}
21297 If this variable is set, @var{path} is a colon-separated list of
21298 directories to search for shared libraries. @samp{solib-search-path}
21299 is used after @samp{sysroot} fails to locate the library, or if the
21300 path to the library is relative instead of absolute. If you want to
21301 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21302 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21303 finding your host's libraries. @samp{sysroot} is preferred; setting
21304 it to a nonexistent directory may interfere with automatic loading
21305 of shared library symbols.
21307 @kindex show solib-search-path
21308 @item show solib-search-path
21309 Display the current shared library search path.
21311 @cindex DOS file-name semantics of file names.
21312 @kindex set target-file-system-kind (unix|dos-based|auto)
21313 @kindex show target-file-system-kind
21314 @item set target-file-system-kind @var{kind}
21315 Set assumed file system kind for target reported file names.
21317 Shared library file names as reported by the target system may not
21318 make sense as is on the system @value{GDBN} is running on. For
21319 example, when remote debugging a target that has MS-DOS based file
21320 system semantics, from a Unix host, the target may be reporting to
21321 @value{GDBN} a list of loaded shared libraries with file names such as
21322 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21323 drive letters, so the @samp{c:\} prefix is not normally understood as
21324 indicating an absolute file name, and neither is the backslash
21325 normally considered a directory separator character. In that case,
21326 the native file system would interpret this whole absolute file name
21327 as a relative file name with no directory components. This would make
21328 it impossible to point @value{GDBN} at a copy of the remote target's
21329 shared libraries on the host using @code{set sysroot}, and impractical
21330 with @code{set solib-search-path}. Setting
21331 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21332 to interpret such file names similarly to how the target would, and to
21333 map them to file names valid on @value{GDBN}'s native file system
21334 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21335 to one of the supported file system kinds. In that case, @value{GDBN}
21336 tries to determine the appropriate file system variant based on the
21337 current target's operating system (@pxref{ABI, ,Configuring the
21338 Current ABI}). The supported file system settings are:
21342 Instruct @value{GDBN} to assume the target file system is of Unix
21343 kind. Only file names starting the forward slash (@samp{/}) character
21344 are considered absolute, and the directory separator character is also
21348 Instruct @value{GDBN} to assume the target file system is DOS based.
21349 File names starting with either a forward slash, or a drive letter
21350 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21351 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21352 considered directory separators.
21355 Instruct @value{GDBN} to use the file system kind associated with the
21356 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21357 This is the default.
21361 @cindex file name canonicalization
21362 @cindex base name differences
21363 When processing file names provided by the user, @value{GDBN}
21364 frequently needs to compare them to the file names recorded in the
21365 program's debug info. Normally, @value{GDBN} compares just the
21366 @dfn{base names} of the files as strings, which is reasonably fast
21367 even for very large programs. (The base name of a file is the last
21368 portion of its name, after stripping all the leading directories.)
21369 This shortcut in comparison is based upon the assumption that files
21370 cannot have more than one base name. This is usually true, but
21371 references to files that use symlinks or similar filesystem
21372 facilities violate that assumption. If your program records files
21373 using such facilities, or if you provide file names to @value{GDBN}
21374 using symlinks etc., you can set @code{basenames-may-differ} to
21375 @code{true} to instruct @value{GDBN} to completely canonicalize each
21376 pair of file names it needs to compare. This will make file-name
21377 comparisons accurate, but at a price of a significant slowdown.
21380 @item set basenames-may-differ
21381 @kindex set basenames-may-differ
21382 Set whether a source file may have multiple base names.
21384 @item show basenames-may-differ
21385 @kindex show basenames-may-differ
21386 Show whether a source file may have multiple base names.
21390 @section File Caching
21391 @cindex caching of opened files
21392 @cindex caching of bfd objects
21394 To speed up file loading, and reduce memory usage, @value{GDBN} will
21395 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21396 BFD, bfd, The Binary File Descriptor Library}. The following commands
21397 allow visibility and control of the caching behavior.
21400 @kindex maint info bfds
21401 @item maint info bfds
21402 This prints information about each @code{bfd} object that is known to
21405 @kindex maint set bfd-sharing
21406 @kindex maint show bfd-sharing
21407 @kindex bfd caching
21408 @item maint set bfd-sharing
21409 @item maint show bfd-sharing
21410 Control whether @code{bfd} objects can be shared. When sharing is
21411 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21412 than reopening the same file. Turning sharing off does not cause
21413 already shared @code{bfd} objects to be unshared, but all future files
21414 that are opened will create a new @code{bfd} object. Similarly,
21415 re-enabling sharing does not cause multiple existing @code{bfd}
21416 objects to be collapsed into a single shared @code{bfd} object.
21418 @kindex set debug bfd-cache @var{level}
21419 @kindex bfd caching
21420 @item set debug bfd-cache @var{level}
21421 Turns on debugging of the bfd cache, setting the level to @var{level}.
21423 @kindex show debug bfd-cache
21424 @kindex bfd caching
21425 @item show debug bfd-cache
21426 Show the current debugging level of the bfd cache.
21429 @node Separate Debug Files
21430 @section Debugging Information in Separate Files
21431 @cindex separate debugging information files
21432 @cindex debugging information in separate files
21433 @cindex @file{.debug} subdirectories
21434 @cindex debugging information directory, global
21435 @cindex global debugging information directories
21436 @cindex build ID, and separate debugging files
21437 @cindex @file{.build-id} directory
21439 @value{GDBN} allows you to put a program's debugging information in a
21440 file separate from the executable itself, in a way that allows
21441 @value{GDBN} to find and load the debugging information automatically.
21442 Since debugging information can be very large---sometimes larger
21443 than the executable code itself---some systems distribute debugging
21444 information for their executables in separate files, which users can
21445 install only when they need to debug a problem.
21447 @value{GDBN} supports two ways of specifying the separate debug info
21452 The executable contains a @dfn{debug link} that specifies the name of
21453 the separate debug info file. The separate debug file's name is
21454 usually @file{@var{executable}.debug}, where @var{executable} is the
21455 name of the corresponding executable file without leading directories
21456 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21457 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21458 checksum for the debug file, which @value{GDBN} uses to validate that
21459 the executable and the debug file came from the same build.
21463 The executable contains a @dfn{build ID}, a unique bit string that is
21464 also present in the corresponding debug info file. (This is supported
21465 only on some operating systems, when using the ELF or PE file formats
21466 for binary files and the @sc{gnu} Binutils.) For more details about
21467 this feature, see the description of the @option{--build-id}
21468 command-line option in @ref{Options, , Command Line Options, ld,
21469 The GNU Linker}. The debug info file's name is not specified
21470 explicitly by the build ID, but can be computed from the build ID, see
21474 Depending on the way the debug info file is specified, @value{GDBN}
21475 uses two different methods of looking for the debug file:
21479 For the ``debug link'' method, @value{GDBN} looks up the named file in
21480 the directory of the executable file, then in a subdirectory of that
21481 directory named @file{.debug}, and finally under each one of the
21482 global debug directories, in a subdirectory whose name is identical to
21483 the leading directories of the executable's absolute file name. (On
21484 MS-Windows/MS-DOS, the drive letter of the executable's leading
21485 directories is converted to a one-letter subdirectory, i.e.@:
21486 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21487 filesystems disallow colons in file names.)
21490 For the ``build ID'' method, @value{GDBN} looks in the
21491 @file{.build-id} subdirectory of each one of the global debug directories for
21492 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21493 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21494 are the rest of the bit string. (Real build ID strings are 32 or more
21495 hex characters, not 10.) @value{GDBN} can automatically query
21496 @code{debuginfod} servers using build IDs in order to download separate debug
21497 files that cannot be found locally. For more information see @ref{Debuginfod}.
21500 So, for example, suppose you ask @value{GDBN} to debug
21501 @file{/usr/bin/ls}, which has a debug link that specifies the
21502 file @file{ls.debug}, and a build ID whose value in hex is
21503 @code{abcdef1234}. If the list of the global debug directories includes
21504 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21505 debug information files, in the indicated order:
21509 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21511 @file{/usr/bin/ls.debug}
21513 @file{/usr/bin/.debug/ls.debug}
21515 @file{/usr/lib/debug/usr/bin/ls.debug}.
21518 If the debug file still has not been found and @code{debuginfod}
21519 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21520 file from @code{debuginfod} servers.
21522 @anchor{debug-file-directory}
21523 Global debugging info directories default to what is set by @value{GDBN}
21524 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21525 you can also set the global debugging info directories, and view the list
21526 @value{GDBN} is currently using.
21530 @kindex set debug-file-directory
21531 @item set debug-file-directory @var{directories}
21532 Set the directories which @value{GDBN} searches for separate debugging
21533 information files to @var{directory}. Multiple path components can be set
21534 concatenating them by a path separator.
21536 @kindex show debug-file-directory
21537 @item show debug-file-directory
21538 Show the directories @value{GDBN} searches for separate debugging
21543 @cindex @code{.gnu_debuglink} sections
21544 @cindex debug link sections
21545 A debug link is a special section of the executable file named
21546 @code{.gnu_debuglink}. The section must contain:
21550 A filename, with any leading directory components removed, followed by
21553 zero to three bytes of padding, as needed to reach the next four-byte
21554 boundary within the section, and
21556 a four-byte CRC checksum, stored in the same endianness used for the
21557 executable file itself. The checksum is computed on the debugging
21558 information file's full contents by the function given below, passing
21559 zero as the @var{crc} argument.
21562 Any executable file format can carry a debug link, as long as it can
21563 contain a section named @code{.gnu_debuglink} with the contents
21566 @cindex @code{.note.gnu.build-id} sections
21567 @cindex build ID sections
21568 The build ID is a special section in the executable file (and in other
21569 ELF binary files that @value{GDBN} may consider). This section is
21570 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21571 It contains unique identification for the built files---the ID remains
21572 the same across multiple builds of the same build tree. The default
21573 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21574 content for the build ID string. The same section with an identical
21575 value is present in the original built binary with symbols, in its
21576 stripped variant, and in the separate debugging information file.
21578 The debugging information file itself should be an ordinary
21579 executable, containing a full set of linker symbols, sections, and
21580 debugging information. The sections of the debugging information file
21581 should have the same names, addresses, and sizes as the original file,
21582 but they need not contain any data---much like a @code{.bss} section
21583 in an ordinary executable.
21585 The @sc{gnu} binary utilities (Binutils) package includes the
21586 @samp{objcopy} utility that can produce
21587 the separated executable / debugging information file pairs using the
21588 following commands:
21591 @kbd{objcopy --only-keep-debug foo foo.debug}
21596 These commands remove the debugging
21597 information from the executable file @file{foo} and place it in the file
21598 @file{foo.debug}. You can use the first, second or both methods to link the
21603 The debug link method needs the following additional command to also leave
21604 behind a debug link in @file{foo}:
21607 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21610 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21611 a version of the @code{strip} command such that the command @kbd{strip foo -f
21612 foo.debug} has the same functionality as the two @code{objcopy} commands and
21613 the @code{ln -s} command above, together.
21616 Build ID gets embedded into the main executable using @code{ld --build-id} or
21617 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21618 compatibility fixes for debug files separation are present in @sc{gnu} binary
21619 utilities (Binutils) package since version 2.18.
21624 @cindex CRC algorithm definition
21625 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21626 IEEE 802.3 using the polynomial:
21628 @c TexInfo requires naked braces for multi-digit exponents for Tex
21629 @c output, but this causes HTML output to barf. HTML has to be set using
21630 @c raw commands. So we end up having to specify this equation in 2
21635 <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>
21636 + <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
21642 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21643 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21647 The function is computed byte at a time, taking the least
21648 significant bit of each byte first. The initial pattern
21649 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21650 the final result is inverted to ensure trailing zeros also affect the
21653 @emph{Note:} This is the same CRC polynomial as used in handling the
21654 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21655 However in the case of the Remote Serial Protocol, the CRC is computed
21656 @emph{most} significant bit first, and the result is not inverted, so
21657 trailing zeros have no effect on the CRC value.
21659 To complete the description, we show below the code of the function
21660 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21661 initially supplied @code{crc} argument means that an initial call to
21662 this function passing in zero will start computing the CRC using
21665 @kindex gnu_debuglink_crc32
21668 gnu_debuglink_crc32 (unsigned long crc,
21669 unsigned char *buf, size_t len)
21671 static const unsigned long crc32_table[256] =
21673 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21674 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21675 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21676 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21677 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21678 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21679 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21680 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21681 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21682 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21683 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21684 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21685 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21686 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21687 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21688 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21689 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21690 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21691 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21692 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21693 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21694 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21695 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21696 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21697 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21698 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21699 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21700 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21701 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21702 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21703 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21704 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21705 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21706 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21707 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21708 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21709 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21710 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21711 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21712 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21713 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21714 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21715 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21716 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21717 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21718 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21719 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21720 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21721 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21722 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21723 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21726 unsigned char *end;
21728 crc = ~crc & 0xffffffff;
21729 for (end = buf + len; buf < end; ++buf)
21730 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21731 return ~crc & 0xffffffff;
21736 This computation does not apply to the ``build ID'' method.
21738 @node MiniDebugInfo
21739 @section Debugging information in a special section
21740 @cindex separate debug sections
21741 @cindex @samp{.gnu_debugdata} section
21743 Some systems ship pre-built executables and libraries that have a
21744 special @samp{.gnu_debugdata} section. This feature is called
21745 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21746 is used to supply extra symbols for backtraces.
21748 The intent of this section is to provide extra minimal debugging
21749 information for use in simple backtraces. It is not intended to be a
21750 replacement for full separate debugging information (@pxref{Separate
21751 Debug Files}). The example below shows the intended use; however,
21752 @value{GDBN} does not currently put restrictions on what sort of
21753 debugging information might be included in the section.
21755 @value{GDBN} has support for this extension. If the section exists,
21756 then it is used provided that no other source of debugging information
21757 can be found, and that @value{GDBN} was configured with LZMA support.
21759 This section can be easily created using @command{objcopy} and other
21760 standard utilities:
21763 # Extract the dynamic symbols from the main binary, there is no need
21764 # to also have these in the normal symbol table.
21765 nm -D @var{binary} --format=posix --defined-only \
21766 | awk '@{ print $1 @}' | sort > dynsyms
21768 # Extract all the text (i.e. function) symbols from the debuginfo.
21769 # (Note that we actually also accept "D" symbols, for the benefit
21770 # of platforms like PowerPC64 that use function descriptors.)
21771 nm @var{binary} --format=posix --defined-only \
21772 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21775 # Keep all the function symbols not already in the dynamic symbol
21777 comm -13 dynsyms funcsyms > keep_symbols
21779 # Separate full debug info into debug binary.
21780 objcopy --only-keep-debug @var{binary} debug
21782 # Copy the full debuginfo, keeping only a minimal set of symbols and
21783 # removing some unnecessary sections.
21784 objcopy -S --remove-section .gdb_index --remove-section .comment \
21785 --keep-symbols=keep_symbols debug mini_debuginfo
21787 # Drop the full debug info from the original binary.
21788 strip --strip-all -R .comment @var{binary}
21790 # Inject the compressed data into the .gnu_debugdata section of the
21793 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21797 @section Index Files Speed Up @value{GDBN}
21798 @cindex index files
21799 @cindex @samp{.gdb_index} section
21801 When @value{GDBN} finds a symbol file, it scans the symbols in the
21802 file in order to construct an internal symbol table. This lets most
21803 @value{GDBN} operations work quickly---at the cost of a delay early
21804 on. For large programs, this delay can be quite lengthy, so
21805 @value{GDBN} provides a way to build an index, which speeds up
21808 For convenience, @value{GDBN} comes with a program,
21809 @command{gdb-add-index}, which can be used to add the index to a
21810 symbol file. It takes the symbol file as its only argument:
21813 $ gdb-add-index symfile
21816 @xref{gdb-add-index}.
21818 It is also possible to do the work manually. Here is what
21819 @command{gdb-add-index} does behind the curtains.
21821 The index is stored as a section in the symbol file. @value{GDBN} can
21822 write the index to a file, then you can put it into the symbol file
21823 using @command{objcopy}.
21825 To create an index file, use the @code{save gdb-index} command:
21828 @item save gdb-index [-dwarf-5] @var{directory}
21829 @kindex save gdb-index
21830 Create index files for all symbol files currently known by
21831 @value{GDBN}. For each known @var{symbol-file}, this command by
21832 default creates it produces a single file
21833 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21834 the @option{-dwarf-5} option, it produces 2 files:
21835 @file{@var{symbol-file}.debug_names} and
21836 @file{@var{symbol-file}.debug_str}. The files are created in the
21837 given @var{directory}.
21840 Once you have created an index file you can merge it into your symbol
21841 file, here named @file{symfile}, using @command{objcopy}:
21844 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21845 --set-section-flags .gdb_index=readonly symfile symfile
21848 Or for @code{-dwarf-5}:
21851 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21852 $ cat symfile.debug_str >>symfile.debug_str.new
21853 $ objcopy --add-section .debug_names=symfile.gdb-index \
21854 --set-section-flags .debug_names=readonly \
21855 --update-section .debug_str=symfile.debug_str.new symfile symfile
21858 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
21859 sections that have been deprecated. Usually they are deprecated because
21860 they are missing a new feature or have performance issues.
21861 To tell @value{GDBN} to use a deprecated index section anyway
21862 specify @code{set use-deprecated-index-sections on}.
21863 The default is @code{off}.
21864 This can speed up startup, but may result in some functionality being lost.
21865 @xref{Index Section Format}.
21867 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
21868 must be done before gdb reads the file. The following will not work:
21871 $ gdb -ex "set use-deprecated-index-sections on" <program>
21874 Instead you must do, for example,
21877 $ gdb -iex "set use-deprecated-index-sections on" <program>
21880 Indices only work when using DWARF debugging information, not stabs.
21882 @subsection Automatic symbol index cache
21884 @cindex automatic symbol index cache
21885 It is possible for @value{GDBN} to automatically save a copy of this index in a
21886 cache on disk and retrieve it from there when loading the same binary in the
21887 future. This feature can be turned on with @kbd{set index-cache enabled on}.
21888 The following commands can be used to tweak the behavior of the index cache.
21892 @kindex set index-cache
21893 @item set index-cache enabled on
21894 @itemx set index-cache enabled off
21895 Enable or disable the use of the symbol index cache.
21897 @item set index-cache directory @var{directory}
21898 @kindex show index-cache
21899 @itemx show index-cache directory
21900 Set/show the directory where index files will be saved.
21902 The default value for this directory depends on the host platform. On
21903 most systems, the index is cached in the @file{gdb} subdirectory of
21904 the directory pointed to by the @env{XDG_CACHE_HOME} environment
21905 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
21906 of your home directory. However, on some systems, the default may
21907 differ according to local convention.
21909 There is no limit on the disk space used by index cache. It is perfectly safe
21910 to delete the content of that directory to free up disk space.
21912 @item show index-cache stats
21913 Print the number of cache hits and misses since the launch of @value{GDBN}.
21917 @node Symbol Errors
21918 @section Errors Reading Symbol Files
21920 While reading a symbol file, @value{GDBN} occasionally encounters problems,
21921 such as symbol types it does not recognize, or known bugs in compiler
21922 output. By default, @value{GDBN} does not notify you of such problems, since
21923 they are relatively common and primarily of interest to people
21924 debugging compilers. If you are interested in seeing information
21925 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
21926 only one message about each such type of problem, no matter how many
21927 times the problem occurs; or you can ask @value{GDBN} to print more messages,
21928 to see how many times the problems occur, with the @code{set
21929 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
21932 The messages currently printed, and their meanings, include:
21935 @item inner block not inside outer block in @var{symbol}
21937 The symbol information shows where symbol scopes begin and end
21938 (such as at the start of a function or a block of statements). This
21939 error indicates that an inner scope block is not fully contained
21940 in its outer scope blocks.
21942 @value{GDBN} circumvents the problem by treating the inner block as if it had
21943 the same scope as the outer block. In the error message, @var{symbol}
21944 may be shown as ``@code{(don't know)}'' if the outer block is not a
21947 @item block at @var{address} out of order
21949 The symbol information for symbol scope blocks should occur in
21950 order of increasing addresses. This error indicates that it does not
21953 @value{GDBN} does not circumvent this problem, and has trouble
21954 locating symbols in the source file whose symbols it is reading. (You
21955 can often determine what source file is affected by specifying
21956 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
21959 @item bad block start address patched
21961 The symbol information for a symbol scope block has a start address
21962 smaller than the address of the preceding source line. This is known
21963 to occur in the SunOS 4.1.1 (and earlier) C compiler.
21965 @value{GDBN} circumvents the problem by treating the symbol scope block as
21966 starting on the previous source line.
21968 @item bad string table offset in symbol @var{n}
21971 Symbol number @var{n} contains a pointer into the string table which is
21972 larger than the size of the string table.
21974 @value{GDBN} circumvents the problem by considering the symbol to have the
21975 name @code{foo}, which may cause other problems if many symbols end up
21978 @item unknown symbol type @code{0x@var{nn}}
21980 The symbol information contains new data types that @value{GDBN} does
21981 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
21982 uncomprehended information, in hexadecimal.
21984 @value{GDBN} circumvents the error by ignoring this symbol information.
21985 This usually allows you to debug your program, though certain symbols
21986 are not accessible. If you encounter such a problem and feel like
21987 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
21988 on @code{complain}, then go up to the function @code{read_dbx_symtab}
21989 and examine @code{*bufp} to see the symbol.
21991 @item stub type has NULL name
21993 @value{GDBN} could not find the full definition for a struct or class.
21995 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
21996 The symbol information for a C@t{++} member function is missing some
21997 information that recent versions of the compiler should have output for
22000 @item info mismatch between compiler and debugger
22002 @value{GDBN} could not parse a type specification output by the compiler.
22007 @section GDB Data Files
22009 @cindex prefix for data files
22010 @value{GDBN} will sometimes read an auxiliary data file. These files
22011 are kept in a directory known as the @dfn{data directory}.
22013 You can set the data directory's name, and view the name @value{GDBN}
22014 is currently using.
22017 @kindex set data-directory
22018 @item set data-directory @var{directory}
22019 Set the directory which @value{GDBN} searches for auxiliary data files
22020 to @var{directory}.
22022 @kindex show data-directory
22023 @item show data-directory
22024 Show the directory @value{GDBN} searches for auxiliary data files.
22027 @cindex default data directory
22028 @cindex @samp{--with-gdb-datadir}
22029 You can set the default data directory by using the configure-time
22030 @samp{--with-gdb-datadir} option. If the data directory is inside
22031 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22032 @samp{--exec-prefix}), then the default data directory will be updated
22033 automatically if the installed @value{GDBN} is moved to a new
22036 The data directory may also be specified with the
22037 @code{--data-directory} command line option.
22038 @xref{Mode Options}.
22041 @chapter Specifying a Debugging Target
22043 @cindex debugging target
22044 A @dfn{target} is the execution environment occupied by your program.
22046 Often, @value{GDBN} runs in the same host environment as your program;
22047 in that case, the debugging target is specified as a side effect when
22048 you use the @code{file} or @code{core} commands. When you need more
22049 flexibility---for example, running @value{GDBN} on a physically separate
22050 host, or controlling a standalone system over a serial port or a
22051 realtime system over a TCP/IP connection---you can use the @code{target}
22052 command to specify one of the target types configured for @value{GDBN}
22053 (@pxref{Target Commands, ,Commands for Managing Targets}).
22055 @cindex target architecture
22056 It is possible to build @value{GDBN} for several different @dfn{target
22057 architectures}. When @value{GDBN} is built like that, you can choose
22058 one of the available architectures with the @kbd{set architecture}
22062 @kindex set architecture
22063 @kindex show architecture
22064 @item set architecture @var{arch}
22065 This command sets the current target architecture to @var{arch}. The
22066 value of @var{arch} can be @code{"auto"}, in addition to one of the
22067 supported architectures.
22069 @item show architecture
22070 Show the current target architecture.
22072 @item set processor
22074 @kindex set processor
22075 @kindex show processor
22076 These are alias commands for, respectively, @code{set architecture}
22077 and @code{show architecture}.
22081 * Active Targets:: Active targets
22082 * Target Commands:: Commands for managing targets
22083 * Byte Order:: Choosing target byte order
22086 @node Active Targets
22087 @section Active Targets
22089 @cindex stacking targets
22090 @cindex active targets
22091 @cindex multiple targets
22093 There are multiple classes of targets such as: processes, executable files or
22094 recording sessions. Core files belong to the process class, making core file
22095 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22096 on multiple active targets, one in each class. This allows you to (for
22097 example) start a process and inspect its activity, while still having access to
22098 the executable file after the process finishes. Or if you start process
22099 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22100 presented a virtual layer of the recording target, while the process target
22101 remains stopped at the chronologically last point of the process execution.
22103 Use the @code{core-file} and @code{exec-file} commands to select a new core
22104 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22105 specify as a target a process that is already running, use the @code{attach}
22106 command (@pxref{Attach, ,Debugging an Already-running Process}).
22108 @node Target Commands
22109 @section Commands for Managing Targets
22112 @item target @var{type} @var{parameters}
22113 Connects the @value{GDBN} host environment to a target machine or
22114 process. A target is typically a protocol for talking to debugging
22115 facilities. You use the argument @var{type} to specify the type or
22116 protocol of the target machine.
22118 Further @var{parameters} are interpreted by the target protocol, but
22119 typically include things like device names or host names to connect
22120 with, process numbers, and baud rates.
22122 The @code{target} command does not repeat if you press @key{RET} again
22123 after executing the command.
22125 @kindex help target
22127 Displays the names of all targets available. To display targets
22128 currently selected, use either @code{info target} or @code{info files}
22129 (@pxref{Files, ,Commands to Specify Files}).
22131 @item help target @var{name}
22132 Describe a particular target, including any parameters necessary to
22135 @kindex set gnutarget
22136 @item set gnutarget @var{args}
22137 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22138 knows whether it is reading an @dfn{executable},
22139 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22140 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22141 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22144 @emph{Warning:} To specify a file format with @code{set gnutarget},
22145 you must know the actual BFD name.
22149 @xref{Files, , Commands to Specify Files}.
22151 @kindex show gnutarget
22152 @item show gnutarget
22153 Use the @code{show gnutarget} command to display what file format
22154 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22155 @value{GDBN} will determine the file format for each file automatically,
22156 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22159 @cindex common targets
22160 Here are some common targets (available, or not, depending on the GDB
22165 @item target exec @var{program}
22166 @cindex executable file target
22167 An executable file. @samp{target exec @var{program}} is the same as
22168 @samp{exec-file @var{program}}.
22170 @item target core @var{filename}
22171 @cindex core dump file target
22172 A core dump file. @samp{target core @var{filename}} is the same as
22173 @samp{core-file @var{filename}}.
22175 @item target remote @var{medium}
22176 @cindex remote target
22177 A remote system connected to @value{GDBN} via a serial line or network
22178 connection. This command tells @value{GDBN} to use its own remote
22179 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22181 For example, if you have a board connected to @file{/dev/ttya} on the
22182 machine running @value{GDBN}, you could say:
22185 target remote /dev/ttya
22188 @code{target remote} supports the @code{load} command. This is only
22189 useful if you have some other way of getting the stub to the target
22190 system, and you can put it somewhere in memory where it won't get
22191 clobbered by the download.
22193 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22194 @cindex built-in simulator target
22195 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22203 works; however, you cannot assume that a specific memory map, device
22204 drivers, or even basic I/O is available, although some simulators do
22205 provide these. For info about any processor-specific simulator details,
22206 see the appropriate section in @ref{Embedded Processors, ,Embedded
22209 @item target native
22210 @cindex native target
22211 Setup for local/native process debugging. Useful to make the
22212 @code{run} command spawn native processes (likewise @code{attach},
22213 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22214 (@pxref{set auto-connect-native-target}).
22218 Different targets are available on different configurations of @value{GDBN};
22219 your configuration may have more or fewer targets.
22221 Many remote targets require you to download the executable's code once
22222 you've successfully established a connection. You may wish to control
22223 various aspects of this process.
22228 @kindex set hash@r{, for remote monitors}
22229 @cindex hash mark while downloading
22230 This command controls whether a hash mark @samp{#} is displayed while
22231 downloading a file to the remote monitor. If on, a hash mark is
22232 displayed after each S-record is successfully downloaded to the
22236 @kindex show hash@r{, for remote monitors}
22237 Show the current status of displaying the hash mark.
22239 @item set debug monitor
22240 @kindex set debug monitor
22241 @cindex display remote monitor communications
22242 Enable or disable display of communications messages between
22243 @value{GDBN} and the remote monitor.
22245 @item show debug monitor
22246 @kindex show debug monitor
22247 Show the current status of displaying communications between
22248 @value{GDBN} and the remote monitor.
22253 @kindex load @var{filename} @var{offset}
22254 @item load @var{filename} @var{offset}
22256 Depending on what remote debugging facilities are configured into
22257 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22258 is meant to make @var{filename} (an executable) available for debugging
22259 on the remote system---by downloading, or dynamic linking, for example.
22260 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22261 the @code{add-symbol-file} command.
22263 If your @value{GDBN} does not have a @code{load} command, attempting to
22264 execute it gets the error message ``@code{You can't do that when your
22265 target is @dots{}}''
22267 The file is loaded at whatever address is specified in the executable.
22268 For some object file formats, you can specify the load address when you
22269 link the program; for other formats, like a.out, the object file format
22270 specifies a fixed address.
22271 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22273 It is also possible to tell @value{GDBN} to load the executable file at a
22274 specific offset described by the optional argument @var{offset}. When
22275 @var{offset} is provided, @var{filename} must also be provided.
22277 Depending on the remote side capabilities, @value{GDBN} may be able to
22278 load programs into flash memory.
22280 @code{load} does not repeat if you press @key{RET} again after using it.
22285 @kindex flash-erase
22287 @anchor{flash-erase}
22289 Erases all known flash memory regions on the target.
22294 @section Choosing Target Byte Order
22296 @cindex choosing target byte order
22297 @cindex target byte order
22299 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22300 offer the ability to run either big-endian or little-endian byte
22301 orders. Usually the executable or symbol will include a bit to
22302 designate the endian-ness, and you will not need to worry about
22303 which to use. However, you may still find it useful to adjust
22304 @value{GDBN}'s idea of processor endian-ness manually.
22308 @item set endian big
22309 Instruct @value{GDBN} to assume the target is big-endian.
22311 @item set endian little
22312 Instruct @value{GDBN} to assume the target is little-endian.
22314 @item set endian auto
22315 Instruct @value{GDBN} to use the byte order associated with the
22319 Display @value{GDBN}'s current idea of the target byte order.
22323 If the @code{set endian auto} mode is in effect and no executable has
22324 been selected, then the endianness used is the last one chosen either
22325 by one of the @code{set endian big} and @code{set endian little}
22326 commands or by inferring from the last executable used. If no
22327 endianness has been previously chosen, then the default for this mode
22328 is inferred from the target @value{GDBN} has been built for, and is
22329 @code{little} if the name of the target CPU has an @code{el} suffix
22330 and @code{big} otherwise.
22332 Note that these commands merely adjust interpretation of symbolic
22333 data on the host, and that they have absolutely no effect on the
22337 @node Remote Debugging
22338 @chapter Debugging Remote Programs
22339 @cindex remote debugging
22341 If you are trying to debug a program running on a machine that cannot run
22342 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22343 For example, you might use remote debugging on an operating system kernel,
22344 or on a small system which does not have a general purpose operating system
22345 powerful enough to run a full-featured debugger.
22347 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22348 to make this work with particular debugging targets. In addition,
22349 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22350 but not specific to any particular target system) which you can use if you
22351 write the remote stubs---the code that runs on the remote system to
22352 communicate with @value{GDBN}.
22354 Other remote targets may be available in your
22355 configuration of @value{GDBN}; use @code{help target} to list them.
22358 * Connecting:: Connecting to a remote target
22359 * File Transfer:: Sending files to a remote system
22360 * Server:: Using the gdbserver program
22361 * Remote Configuration:: Remote configuration
22362 * Remote Stub:: Implementing a remote stub
22366 @section Connecting to a Remote Target
22367 @cindex remote debugging, connecting
22368 @cindex @code{gdbserver}, connecting
22369 @cindex remote debugging, types of connections
22370 @cindex @code{gdbserver}, types of connections
22371 @cindex @code{gdbserver}, @code{target remote} mode
22372 @cindex @code{gdbserver}, @code{target extended-remote} mode
22374 This section describes how to connect to a remote target, including the
22375 types of connections and their differences, how to set up executable and
22376 symbol files on the host and target, and the commands used for
22377 connecting to and disconnecting from the remote target.
22379 @subsection Types of Remote Connections
22381 @value{GDBN} supports two types of remote connections, @code{target remote}
22382 mode and @code{target extended-remote} mode. Note that many remote targets
22383 support only @code{target remote} mode. There are several major
22384 differences between the two types of connections, enumerated here:
22388 @cindex remote debugging, detach and program exit
22389 @item Result of detach or program exit
22390 @strong{With target remote mode:} When the debugged program exits or you
22391 detach from it, @value{GDBN} disconnects from the target. When using
22392 @code{gdbserver}, @code{gdbserver} will exit.
22394 @strong{With target extended-remote mode:} When the debugged program exits or
22395 you detach from it, @value{GDBN} remains connected to the target, even
22396 though no program is running. You can rerun the program, attach to a
22397 running program, or use @code{monitor} commands specific to the target.
22399 When using @code{gdbserver} in this case, it does not exit unless it was
22400 invoked using the @option{--once} option. If the @option{--once} option
22401 was not used, you can ask @code{gdbserver} to exit using the
22402 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22404 @item Specifying the program to debug
22405 For both connection types you use the @code{file} command to specify the
22406 program on the host system. If you are using @code{gdbserver} there are
22407 some differences in how to specify the location of the program on the
22410 @strong{With target remote mode:} You must either specify the program to debug
22411 on the @code{gdbserver} command line or use the @option{--attach} option
22412 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22414 @cindex @option{--multi}, @code{gdbserver} option
22415 @strong{With target extended-remote mode:} You may specify the program to debug
22416 on the @code{gdbserver} command line, or you can load the program or attach
22417 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22419 @anchor{--multi Option in Types of Remote Connnections}
22420 You can start @code{gdbserver} without supplying an initial command to run
22421 or process ID to attach. To do this, use the @option{--multi} command line
22422 option. Then you can connect using @code{target extended-remote} and start
22423 the program you want to debug (see below for details on using the
22424 @code{run} command in this scenario). Note that the conditions under which
22425 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22426 (@code{target remote} or @code{target extended-remote}). The
22427 @option{--multi} option to @code{gdbserver} has no influence on that.
22429 @item The @code{run} command
22430 @strong{With target remote mode:} The @code{run} command is not
22431 supported. Once a connection has been established, you can use all
22432 the usual @value{GDBN} commands to examine and change data. The
22433 remote program is already running, so you can use commands like
22434 @kbd{step} and @kbd{continue}.
22436 @strong{With target extended-remote mode:} The @code{run} command is
22437 supported. The @code{run} command uses the value set by
22438 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22439 the program to run. Command line arguments are supported, except for
22440 wildcard expansion and I/O redirection (@pxref{Arguments}).
22442 If you specify the program to debug on the command line, then the
22443 @code{run} command is not required to start execution, and you can
22444 resume using commands like @kbd{step} and @kbd{continue} as with
22445 @code{target remote} mode.
22447 @anchor{Attaching in Types of Remote Connections}
22449 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22450 not supported. To attach to a running program using @code{gdbserver}, you
22451 must use the @option{--attach} option (@pxref{Running gdbserver}).
22453 @strong{With target extended-remote mode:} To attach to a running program,
22454 you may use the @code{attach} command after the connection has been
22455 established. If you are using @code{gdbserver}, you may also invoke
22456 @code{gdbserver} using the @option{--attach} option
22457 (@pxref{Running gdbserver}).
22459 Some remote targets allow @value{GDBN} to determine the executable file running
22460 in the process the debugger is attaching to. In such a case, @value{GDBN}
22461 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22462 between the executable file name running in the process and the name of the
22463 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22467 @anchor{Host and target files}
22468 @subsection Host and Target Files
22469 @cindex remote debugging, symbol files
22470 @cindex symbol files, remote debugging
22472 @value{GDBN}, running on the host, needs access to symbol and debugging
22473 information for your program running on the target. This requires
22474 access to an unstripped copy of your program, and possibly any associated
22475 symbol files. Note that this section applies equally to both @code{target
22476 remote} mode and @code{target extended-remote} mode.
22478 Some remote targets (@pxref{qXfer executable filename read}, and
22479 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22480 the same connection used to communicate with @value{GDBN}. With such a
22481 target, if the remote program is unstripped, the only command you need is
22482 @code{target remote} (or @code{target extended-remote}).
22484 If the remote program is stripped, or the target does not support remote
22485 program file access, start up @value{GDBN} using the name of the local
22486 unstripped copy of your program as the first argument, or use the
22487 @code{file} command. Use @code{set sysroot} to specify the location (on
22488 the host) of target libraries (unless your @value{GDBN} was compiled with
22489 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22490 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22493 The symbol file and target libraries must exactly match the executable
22494 and libraries on the target, with one exception: the files on the host
22495 system should not be stripped, even if the files on the target system
22496 are. Mismatched or missing files will lead to confusing results
22497 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22498 files may also prevent @code{gdbserver} from debugging multi-threaded
22501 @subsection Remote Connection Commands
22502 @cindex remote connection commands
22503 @value{GDBN} can communicate with the target over a serial line, a
22504 local Unix domain socket, or
22505 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22506 each case, @value{GDBN} uses the same protocol for debugging your
22507 program; only the medium carrying the debugging packets varies. The
22508 @code{target remote} and @code{target extended-remote} commands
22509 establish a connection to the target. Both commands accept the same
22510 arguments, which indicate the medium to use:
22514 @item target remote @var{serial-device}
22515 @itemx target extended-remote @var{serial-device}
22516 @cindex serial line, @code{target remote}
22517 Use @var{serial-device} to communicate with the target. For example,
22518 to use a serial line connected to the device named @file{/dev/ttyb}:
22521 target remote /dev/ttyb
22524 If you're using a serial line, you may want to give @value{GDBN} the
22525 @samp{--baud} option, or use the @code{set serial baud} command
22526 (@pxref{Remote Configuration, set serial baud}) before the
22527 @code{target} command.
22529 @item target remote @var{local-socket}
22530 @itemx target extended-remote @var{local-socket}
22531 @cindex local socket, @code{target remote}
22532 @cindex Unix domain socket
22533 Use @var{local-socket} to communicate with the target. For example,
22534 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22537 target remote /tmp/gdb-socket0
22540 Note that this command has the same form as the command to connect
22541 to a serial line. @value{GDBN} will automatically determine which
22542 kind of file you have specified and will make the appropriate kind
22544 This feature is not available if the host system does not support
22545 Unix domain sockets.
22547 @item target remote @code{@var{host}:@var{port}}
22548 @itemx target remote @code{[@var{host}]:@var{port}}
22549 @itemx target remote @code{tcp:@var{host}:@var{port}}
22550 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22551 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22552 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22553 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22554 @itemx target extended-remote @code{@var{host}:@var{port}}
22555 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22556 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22557 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22558 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22559 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22560 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22561 @cindex @acronym{TCP} port, @code{target remote}
22562 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22563 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22564 address, or a numeric @acronym{IPv6} address (with or without the
22565 square brackets to separate the address from the port); @var{port}
22566 must be a decimal number. The @var{host} could be the target machine
22567 itself, if it is directly connected to the net, or it might be a
22568 terminal server which in turn has a serial line to the target.
22570 For example, to connect to port 2828 on a terminal server named
22574 target remote manyfarms:2828
22577 To connect to port 2828 on a terminal server whose address is
22578 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22579 square bracket syntax:
22582 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22586 or explicitly specify the @acronym{IPv6} protocol:
22589 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22592 This last example may be confusing to the reader, because there is no
22593 visible separation between the hostname and the port number.
22594 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22595 using square brackets for clarity. However, it is important to
22596 mention that for @value{GDBN} there is no ambiguity: the number after
22597 the last colon is considered to be the port number.
22599 If your remote target is actually running on the same machine as your
22600 debugger session (e.g.@: a simulator for your target running on the
22601 same host), you can omit the hostname. For example, to connect to
22602 port 1234 on your local machine:
22605 target remote :1234
22609 Note that the colon is still required here.
22611 @item target remote @code{udp:@var{host}:@var{port}}
22612 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22613 @itemx target remote @code{udp4:@var{host}:@var{port}}
22614 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22615 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22616 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22617 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22618 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22619 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22620 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22621 @cindex @acronym{UDP} port, @code{target remote}
22622 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22623 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22626 target remote udp:manyfarms:2828
22629 When using a @acronym{UDP} connection for remote debugging, you should
22630 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22631 can silently drop packets on busy or unreliable networks, which will
22632 cause havoc with your debugging session.
22634 @item target remote | @var{command}
22635 @itemx target extended-remote | @var{command}
22636 @cindex pipe, @code{target remote} to
22637 Run @var{command} in the background and communicate with it using a
22638 pipe. The @var{command} is a shell command, to be parsed and expanded
22639 by the system's command shell, @code{/bin/sh}; it should expect remote
22640 protocol packets on its standard input, and send replies on its
22641 standard output. You could use this to run a stand-alone simulator
22642 that speaks the remote debugging protocol, to make net connections
22643 using programs like @code{ssh}, or for other similar tricks.
22645 If @var{command} closes its standard output (perhaps by exiting),
22646 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22647 program has already exited, this will have no effect.)
22651 @cindex interrupting remote programs
22652 @cindex remote programs, interrupting
22653 Whenever @value{GDBN} is waiting for the remote program, if you type the
22654 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22655 program. This may or may not succeed, depending in part on the hardware
22656 and the serial drivers the remote system uses. If you type the
22657 interrupt character once again, @value{GDBN} displays this prompt:
22660 Interrupted while waiting for the program.
22661 Give up (and stop debugging it)? (y or n)
22664 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22665 the remote debugging session. (If you decide you want to try again later,
22666 you can use @kbd{target remote} again to connect once more.) If you type
22667 @kbd{n}, @value{GDBN} goes back to waiting.
22669 In @code{target extended-remote} mode, typing @kbd{n} will leave
22670 @value{GDBN} connected to the target.
22673 @kindex detach (remote)
22675 When you have finished debugging the remote program, you can use the
22676 @code{detach} command to release it from @value{GDBN} control.
22677 Detaching from the target normally resumes its execution, but the results
22678 will depend on your particular remote stub. After the @code{detach}
22679 command in @code{target remote} mode, @value{GDBN} is free to connect to
22680 another target. In @code{target extended-remote} mode, @value{GDBN} is
22681 still connected to the target.
22685 The @code{disconnect} command closes the connection to the target, and
22686 the target is generally not resumed. It will wait for @value{GDBN}
22687 (this instance or another one) to connect and continue debugging. After
22688 the @code{disconnect} command, @value{GDBN} is again free to connect to
22691 @cindex send command to remote monitor
22692 @cindex extend @value{GDBN} for remote targets
22693 @cindex add new commands for external monitor
22695 @item monitor @var{cmd}
22696 This command allows you to send arbitrary commands directly to the
22697 remote monitor. Since @value{GDBN} doesn't care about the commands it
22698 sends like this, this command is the way to extend @value{GDBN}---you
22699 can add new commands that only the external monitor will understand
22703 @node File Transfer
22704 @section Sending files to a remote system
22705 @cindex remote target, file transfer
22706 @cindex file transfer
22707 @cindex sending files to remote systems
22709 Some remote targets offer the ability to transfer files over the same
22710 connection used to communicate with @value{GDBN}. This is convenient
22711 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22712 running @code{gdbserver} over a network interface. For other targets,
22713 e.g.@: embedded devices with only a single serial port, this may be
22714 the only way to upload or download files.
22716 Not all remote targets support these commands.
22720 @item remote put @var{hostfile} @var{targetfile}
22721 Copy file @var{hostfile} from the host system (the machine running
22722 @value{GDBN}) to @var{targetfile} on the target system.
22725 @item remote get @var{targetfile} @var{hostfile}
22726 Copy file @var{targetfile} from the target system to @var{hostfile}
22727 on the host system.
22729 @kindex remote delete
22730 @item remote delete @var{targetfile}
22731 Delete @var{targetfile} from the target system.
22736 @section Using the @code{gdbserver} Program
22739 @cindex remote connection without stubs
22740 @code{gdbserver} is a control program for Unix-like systems, which
22741 allows you to connect your program with a remote @value{GDBN} via
22742 @code{target remote} or @code{target extended-remote}---but without
22743 linking in the usual debugging stub.
22745 @code{gdbserver} is not a complete replacement for the debugging stubs,
22746 because it requires essentially the same operating-system facilities
22747 that @value{GDBN} itself does. In fact, a system that can run
22748 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22749 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22750 because it is a much smaller program than @value{GDBN} itself. It is
22751 also easier to port than all of @value{GDBN}, so you may be able to get
22752 started more quickly on a new system by using @code{gdbserver}.
22753 Finally, if you develop code for real-time systems, you may find that
22754 the tradeoffs involved in real-time operation make it more convenient to
22755 do as much development work as possible on another system, for example
22756 by cross-compiling. You can use @code{gdbserver} to make a similar
22757 choice for debugging.
22759 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22760 or a TCP connection, using the standard @value{GDBN} remote serial
22764 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22765 Do not run @code{gdbserver} connected to any public network; a
22766 @value{GDBN} connection to @code{gdbserver} provides access to the
22767 target system with the same privileges as the user running
22771 @anchor{Running gdbserver}
22772 @subsection Running @code{gdbserver}
22773 @cindex arguments, to @code{gdbserver}
22774 @cindex @code{gdbserver}, command-line arguments
22776 Run @code{gdbserver} on the target system. You need a copy of the
22777 program you want to debug, including any libraries it requires.
22778 @code{gdbserver} does not need your program's symbol table, so you can
22779 strip the program if necessary to save space. @value{GDBN} on the host
22780 system does all the symbol handling.
22782 To use the server, you must tell it how to communicate with @value{GDBN};
22783 the name of your program; and the arguments for your program. The usual
22787 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22790 @var{comm} is either a device name (to use a serial line), or a TCP
22791 hostname and portnumber, or @code{-} or @code{stdio} to use
22792 stdin/stdout of @code{gdbserver}.
22793 For example, to debug Emacs with the argument
22794 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22798 target> gdbserver /dev/com1 emacs foo.txt
22801 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22804 To use a TCP connection instead of a serial line:
22807 target> gdbserver host:2345 emacs foo.txt
22810 The only difference from the previous example is the first argument,
22811 specifying that you are communicating with the host @value{GDBN} via
22812 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22813 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22814 (Currently, the @samp{host} part is ignored.) You can choose any number
22815 you want for the port number as long as it does not conflict with any
22816 TCP ports already in use on the target system (for example, @code{23} is
22817 reserved for @code{telnet}).@footnote{If you choose a port number that
22818 conflicts with another service, @code{gdbserver} prints an error message
22819 and exits.} You must use the same port number with the host @value{GDBN}
22820 @code{target remote} command.
22822 The @code{stdio} connection is useful when starting @code{gdbserver}
22826 (gdb) target remote | ssh -T hostname gdbserver - hello
22829 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22830 and we don't want escape-character handling. Ssh does this by default when
22831 a command is provided, the flag is provided to make it explicit.
22832 You could elide it if you want to.
22834 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22835 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22836 display through a pipe connected to gdbserver.
22837 Both @code{stdout} and @code{stderr} use the same pipe.
22839 @anchor{Attaching to a program}
22840 @subsubsection Attaching to a Running Program
22841 @cindex attach to a program, @code{gdbserver}
22842 @cindex @option{--attach}, @code{gdbserver} option
22844 On some targets, @code{gdbserver} can also attach to running programs.
22845 This is accomplished via the @code{--attach} argument. The syntax is:
22848 target> gdbserver --attach @var{comm} @var{pid}
22851 @var{pid} is the process ID of a currently running process. It isn't
22852 necessary to point @code{gdbserver} at a binary for the running process.
22854 In @code{target extended-remote} mode, you can also attach using the
22855 @value{GDBN} attach command
22856 (@pxref{Attaching in Types of Remote Connections}).
22859 You can debug processes by name instead of process ID if your target has the
22860 @code{pidof} utility:
22863 target> gdbserver --attach @var{comm} `pidof @var{program}`
22866 In case more than one copy of @var{program} is running, or @var{program}
22867 has multiple threads, most versions of @code{pidof} support the
22868 @code{-s} option to only return the first process ID.
22870 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
22872 This section applies only when @code{gdbserver} is run to listen on a TCP
22875 @code{gdbserver} normally terminates after all of its debugged processes have
22876 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
22877 extended-remote}, @code{gdbserver} stays running even with no processes left.
22878 @value{GDBN} normally terminates the spawned debugged process on its exit,
22879 which normally also terminates @code{gdbserver} in the @kbd{target remote}
22880 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
22881 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
22882 stays running even in the @kbd{target remote} mode.
22884 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
22885 Such reconnecting is useful for features like @ref{disconnected tracing}. For
22886 completeness, at most one @value{GDBN} can be connected at a time.
22888 @cindex @option{--once}, @code{gdbserver} option
22889 By default, @code{gdbserver} keeps the listening TCP port open, so that
22890 subsequent connections are possible. However, if you start @code{gdbserver}
22891 with the @option{--once} option, it will stop listening for any further
22892 connection attempts after connecting to the first @value{GDBN} session. This
22893 means no further connections to @code{gdbserver} will be possible after the
22894 first one. It also means @code{gdbserver} will terminate after the first
22895 connection with remote @value{GDBN} has closed, even for unexpectedly closed
22896 connections and even in the @kbd{target extended-remote} mode. The
22897 @option{--once} option allows reusing the same port number for connecting to
22898 multiple instances of @code{gdbserver} running on the same host, since each
22899 instance closes its port after the first connection.
22901 @anchor{Other Command-Line Arguments for gdbserver}
22902 @subsubsection Other Command-Line Arguments for @code{gdbserver}
22904 You can use the @option{--multi} option to start @code{gdbserver} without
22905 specifying a program to debug or a process to attach to. Then you can
22906 attach in @code{target extended-remote} mode and run or attach to a
22907 program. For more information,
22908 @pxref{--multi Option in Types of Remote Connnections}.
22910 @cindex @option{--debug}, @code{gdbserver} option
22911 The @option{--debug} option tells @code{gdbserver} to display extra
22912 status information about the debugging process.
22913 @cindex @option{--remote-debug}, @code{gdbserver} option
22914 The @option{--remote-debug} option tells @code{gdbserver} to display
22915 remote protocol debug output.
22916 @cindex @option{--debug-file}, @code{gdbserver} option
22917 @cindex @code{gdbserver}, send all debug output to a single file
22918 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
22919 write any debug output to the given @var{filename}. These options are intended
22920 for @code{gdbserver} development and for bug reports to the developers.
22922 @cindex @option{--debug-format}, @code{gdbserver} option
22923 The @option{--debug-format=option1[,option2,...]} option tells
22924 @code{gdbserver} to include additional information in each output.
22925 Possible options are:
22929 Turn off all extra information in debugging output.
22931 Turn on all extra information in debugging output.
22933 Include a timestamp in each line of debugging output.
22936 Options are processed in order. Thus, for example, if @option{none}
22937 appears last then no additional information is added to debugging output.
22939 @cindex @option{--wrapper}, @code{gdbserver} option
22940 The @option{--wrapper} option specifies a wrapper to launch programs
22941 for debugging. The option should be followed by the name of the
22942 wrapper, then any command-line arguments to pass to the wrapper, then
22943 @kbd{--} indicating the end of the wrapper arguments.
22945 @code{gdbserver} runs the specified wrapper program with a combined
22946 command line including the wrapper arguments, then the name of the
22947 program to debug, then any arguments to the program. The wrapper
22948 runs until it executes your program, and then @value{GDBN} gains control.
22950 You can use any program that eventually calls @code{execve} with
22951 its arguments as a wrapper. Several standard Unix utilities do
22952 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
22953 with @code{exec "$@@"} will also work.
22955 For example, you can use @code{env} to pass an environment variable to
22956 the debugged program, without setting the variable in @code{gdbserver}'s
22960 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
22963 @cindex @option{--selftest}
22964 The @option{--selftest} option runs the self tests in @code{gdbserver}:
22967 $ gdbserver --selftest
22968 Ran 2 unit tests, 0 failed
22971 These tests are disabled in release.
22972 @subsection Connecting to @code{gdbserver}
22974 The basic procedure for connecting to the remote target is:
22978 Run @value{GDBN} on the host system.
22981 Make sure you have the necessary symbol files
22982 (@pxref{Host and target files}).
22983 Load symbols for your application using the @code{file} command before you
22984 connect. Use @code{set sysroot} to locate target libraries (unless your
22985 @value{GDBN} was compiled with the correct sysroot using
22986 @code{--with-sysroot}).
22989 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
22990 For TCP connections, you must start up @code{gdbserver} prior to using
22991 the @code{target} command. Otherwise you may get an error whose
22992 text depends on the host system, but which usually looks something like
22993 @samp{Connection refused}. Don't use the @code{load}
22994 command in @value{GDBN} when using @code{target remote} mode, since the
22995 program is already on the target.
22999 @anchor{Monitor Commands for gdbserver}
23000 @subsection Monitor Commands for @code{gdbserver}
23001 @cindex monitor commands, for @code{gdbserver}
23003 During a @value{GDBN} session using @code{gdbserver}, you can use the
23004 @code{monitor} command to send special requests to @code{gdbserver}.
23005 Here are the available commands.
23009 List the available monitor commands.
23011 @item monitor set debug 0
23012 @itemx monitor set debug 1
23013 Disable or enable general debugging messages.
23015 @item monitor set remote-debug 0
23016 @itemx monitor set remote-debug 1
23017 Disable or enable specific debugging messages associated with the remote
23018 protocol (@pxref{Remote Protocol}).
23020 @item monitor set debug-file filename
23021 @itemx monitor set debug-file
23022 Send any debug output to the given file, or to stderr.
23024 @item monitor set debug-format option1@r{[},option2,...@r{]}
23025 Specify additional text to add to debugging messages.
23026 Possible options are:
23030 Turn off all extra information in debugging output.
23032 Turn on all extra information in debugging output.
23034 Include a timestamp in each line of debugging output.
23037 Options are processed in order. Thus, for example, if @option{none}
23038 appears last then no additional information is added to debugging output.
23040 @item monitor set libthread-db-search-path [PATH]
23041 @cindex gdbserver, search path for @code{libthread_db}
23042 When this command is issued, @var{path} is a colon-separated list of
23043 directories to search for @code{libthread_db} (@pxref{Threads,,set
23044 libthread-db-search-path}). If you omit @var{path},
23045 @samp{libthread-db-search-path} will be reset to its default value.
23047 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23048 not supported in @code{gdbserver}.
23051 Tell gdbserver to exit immediately. This command should be followed by
23052 @code{disconnect} to close the debugging session. @code{gdbserver} will
23053 detach from any attached processes and kill any processes it created.
23054 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23055 of a multi-process mode debug session.
23059 @subsection Tracepoints support in @code{gdbserver}
23060 @cindex tracepoints support in @code{gdbserver}
23062 On some targets, @code{gdbserver} supports tracepoints, fast
23063 tracepoints and static tracepoints.
23065 For fast or static tracepoints to work, a special library called the
23066 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23067 This library is built and distributed as an integral part of
23068 @code{gdbserver}. In addition, support for static tracepoints
23069 requires building the in-process agent library with static tracepoints
23070 support. At present, the UST (LTTng Userspace Tracer,
23071 @url{http://lttng.org/ust}) tracing engine is supported. This support
23072 is automatically available if UST development headers are found in the
23073 standard include path when @code{gdbserver} is built, or if
23074 @code{gdbserver} was explicitly configured using @option{--with-ust}
23075 to point at such headers. You can explicitly disable the support
23076 using @option{--with-ust=no}.
23078 There are several ways to load the in-process agent in your program:
23081 @item Specifying it as dependency at link time
23083 You can link your program dynamically with the in-process agent
23084 library. On most systems, this is accomplished by adding
23085 @code{-linproctrace} to the link command.
23087 @item Using the system's preloading mechanisms
23089 You can force loading the in-process agent at startup time by using
23090 your system's support for preloading shared libraries. Many Unixes
23091 support the concept of preloading user defined libraries. In most
23092 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23093 in the environment. See also the description of @code{gdbserver}'s
23094 @option{--wrapper} command line option.
23096 @item Using @value{GDBN} to force loading the agent at run time
23098 On some systems, you can force the inferior to load a shared library,
23099 by calling a dynamic loader function in the inferior that takes care
23100 of dynamically looking up and loading a shared library. On most Unix
23101 systems, the function is @code{dlopen}. You'll use the @code{call}
23102 command for that. For example:
23105 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23108 Note that on most Unix systems, for the @code{dlopen} function to be
23109 available, the program needs to be linked with @code{-ldl}.
23112 On systems that have a userspace dynamic loader, like most Unix
23113 systems, when you connect to @code{gdbserver} using @code{target
23114 remote}, you'll find that the program is stopped at the dynamic
23115 loader's entry point, and no shared library has been loaded in the
23116 program's address space yet, including the in-process agent. In that
23117 case, before being able to use any of the fast or static tracepoints
23118 features, you need to let the loader run and load the shared
23119 libraries. The simplest way to do that is to run the program to the
23120 main procedure. E.g., if debugging a C or C@t{++} program, start
23121 @code{gdbserver} like so:
23124 $ gdbserver :9999 myprogram
23127 Start GDB and connect to @code{gdbserver} like so, and run to main:
23131 (@value{GDBP}) target remote myhost:9999
23132 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23133 (@value{GDBP}) b main
23134 (@value{GDBP}) continue
23137 The in-process tracing agent library should now be loaded into the
23138 process; you can confirm it with the @code{info sharedlibrary}
23139 command, which will list @file{libinproctrace.so} as loaded in the
23140 process. You are now ready to install fast tracepoints, list static
23141 tracepoint markers, probe static tracepoints markers, and start
23144 @node Remote Configuration
23145 @section Remote Configuration
23148 @kindex show remote
23149 This section documents the configuration options available when
23150 debugging remote programs. For the options related to the File I/O
23151 extensions of the remote protocol, see @ref{system,
23152 system-call-allowed}.
23155 @item set remoteaddresssize @var{bits}
23156 @cindex address size for remote targets
23157 @cindex bits in remote address
23158 Set the maximum size of address in a memory packet to the specified
23159 number of bits. @value{GDBN} will mask off the address bits above
23160 that number, when it passes addresses to the remote target. The
23161 default value is the number of bits in the target's address.
23163 @item show remoteaddresssize
23164 Show the current value of remote address size in bits.
23166 @item set serial baud @var{n}
23167 @cindex baud rate for remote targets
23168 Set the baud rate for the remote serial I/O to @var{n} baud. The
23169 value is used to set the speed of the serial port used for debugging
23172 @item show serial baud
23173 Show the current speed of the remote connection.
23175 @item set serial parity @var{parity}
23176 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23177 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23179 @item show serial parity
23180 Show the current parity of the serial port.
23182 @item set remotebreak
23183 @cindex interrupt remote programs
23184 @cindex BREAK signal instead of Ctrl-C
23185 @anchor{set remotebreak}
23186 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23187 when you type @kbd{Ctrl-c} to interrupt the program running
23188 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23189 character instead. The default is off, since most remote systems
23190 expect to see @samp{Ctrl-C} as the interrupt signal.
23192 @item show remotebreak
23193 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23194 interrupt the remote program.
23196 @item set remoteflow on
23197 @itemx set remoteflow off
23198 @kindex set remoteflow
23199 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23200 on the serial port used to communicate to the remote target.
23202 @item show remoteflow
23203 @kindex show remoteflow
23204 Show the current setting of hardware flow control.
23206 @item set remotelogbase @var{base}
23207 Set the base (a.k.a.@: radix) of logging serial protocol
23208 communications to @var{base}. Supported values of @var{base} are:
23209 @code{ascii}, @code{octal}, and @code{hex}. The default is
23212 @item show remotelogbase
23213 Show the current setting of the radix for logging remote serial
23216 @item set remotelogfile @var{file}
23217 @cindex record serial communications on file
23218 Record remote serial communications on the named @var{file}. The
23219 default is not to record at all.
23221 @item show remotelogfile
23222 Show the current setting of the file name on which to record the
23223 serial communications.
23225 @item set remotetimeout @var{num}
23226 @cindex timeout for serial communications
23227 @cindex remote timeout
23228 Set the timeout limit to wait for the remote target to respond to
23229 @var{num} seconds. The default is 2 seconds.
23231 @item show remotetimeout
23232 Show the current number of seconds to wait for the remote target
23235 @cindex limit hardware breakpoints and watchpoints
23236 @cindex remote target, limit break- and watchpoints
23237 @anchor{set remote hardware-watchpoint-limit}
23238 @anchor{set remote hardware-breakpoint-limit}
23239 @item set remote hardware-watchpoint-limit @var{limit}
23240 @itemx set remote hardware-breakpoint-limit @var{limit}
23241 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23242 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23243 watchpoints or breakpoints, and @code{unlimited} for unlimited
23244 watchpoints or breakpoints.
23246 @item show remote hardware-watchpoint-limit
23247 @itemx show remote hardware-breakpoint-limit
23248 Show the current limit for the number of hardware watchpoints or
23249 breakpoints that @value{GDBN} can use.
23251 @cindex limit hardware watchpoints length
23252 @cindex remote target, limit watchpoints length
23253 @anchor{set remote hardware-watchpoint-length-limit}
23254 @item set remote hardware-watchpoint-length-limit @var{limit}
23255 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23256 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23257 hardware watchpoints and @code{unlimited} allows watchpoints of any
23260 @item show remote hardware-watchpoint-length-limit
23261 Show the current limit (in bytes) of the maximum length of
23262 a remote hardware watchpoint.
23264 @item set remote exec-file @var{filename}
23265 @itemx show remote exec-file
23266 @anchor{set remote exec-file}
23267 @cindex executable file, for remote target
23268 Select the file used for @code{run} with @code{target
23269 extended-remote}. This should be set to a filename valid on the
23270 target system. If it is not set, the target will use a default
23271 filename (e.g.@: the last program run).
23273 @item set remote interrupt-sequence
23274 @cindex interrupt remote programs
23275 @cindex select Ctrl-C, BREAK or BREAK-g
23276 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23277 @samp{BREAK-g} as the
23278 sequence to the remote target in order to interrupt the execution.
23279 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23280 is high level of serial line for some certain time.
23281 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23282 It is @code{BREAK} signal followed by character @code{g}.
23284 @item show remote interrupt-sequence
23285 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23286 is sent by @value{GDBN} to interrupt the remote program.
23287 @code{BREAK-g} is BREAK signal followed by @code{g} and
23288 also known as Magic SysRq g.
23290 @item set remote interrupt-on-connect
23291 @cindex send interrupt-sequence on start
23292 Specify whether interrupt-sequence is sent to remote target when
23293 @value{GDBN} connects to it. This is mostly needed when you debug
23294 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23295 which is known as Magic SysRq g in order to connect @value{GDBN}.
23297 @item show remote interrupt-on-connect
23298 Show whether interrupt-sequence is sent
23299 to remote target when @value{GDBN} connects to it.
23303 @item set tcp auto-retry on
23304 @cindex auto-retry, for remote TCP target
23305 Enable auto-retry for remote TCP connections. This is useful if the remote
23306 debugging agent is launched in parallel with @value{GDBN}; there is a race
23307 condition because the agent may not become ready to accept the connection
23308 before @value{GDBN} attempts to connect. When auto-retry is
23309 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23310 to establish the connection using the timeout specified by
23311 @code{set tcp connect-timeout}.
23313 @item set tcp auto-retry off
23314 Do not auto-retry failed TCP connections.
23316 @item show tcp auto-retry
23317 Show the current auto-retry setting.
23319 @item set tcp connect-timeout @var{seconds}
23320 @itemx set tcp connect-timeout unlimited
23321 @cindex connection timeout, for remote TCP target
23322 @cindex timeout, for remote target connection
23323 Set the timeout for establishing a TCP connection to the remote target to
23324 @var{seconds}. The timeout affects both polling to retry failed connections
23325 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23326 that are merely slow to complete, and represents an approximate cumulative
23327 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23328 @value{GDBN} will keep attempting to establish a connection forever,
23329 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23331 @item show tcp connect-timeout
23332 Show the current connection timeout setting.
23335 @cindex remote packets, enabling and disabling
23336 The @value{GDBN} remote protocol autodetects the packets supported by
23337 your debugging stub. If you need to override the autodetection, you
23338 can use these commands to enable or disable individual packets. Each
23339 packet can be set to @samp{on} (the remote target supports this
23340 packet), @samp{off} (the remote target does not support this packet),
23341 or @samp{auto} (detect remote target support for this packet). They
23342 all default to @samp{auto}. For more information about each packet,
23343 see @ref{Remote Protocol}.
23345 During normal use, you should not have to use any of these commands.
23346 If you do, that may be a bug in your remote debugging stub, or a bug
23347 in @value{GDBN}. You may want to report the problem to the
23348 @value{GDBN} developers.
23350 For each packet @var{name}, the command to enable or disable the
23351 packet is @code{set remote @var{name}-packet}. The available settings
23354 @multitable @columnfractions 0.28 0.32 0.25
23357 @tab Related Features
23359 @item @code{fetch-register}
23361 @tab @code{info registers}
23363 @item @code{set-register}
23367 @item @code{binary-download}
23369 @tab @code{load}, @code{set}
23371 @item @code{read-aux-vector}
23372 @tab @code{qXfer:auxv:read}
23373 @tab @code{info auxv}
23375 @item @code{symbol-lookup}
23376 @tab @code{qSymbol}
23377 @tab Detecting multiple threads
23379 @item @code{attach}
23380 @tab @code{vAttach}
23383 @item @code{verbose-resume}
23385 @tab Stepping or resuming multiple threads
23391 @item @code{software-breakpoint}
23395 @item @code{hardware-breakpoint}
23399 @item @code{write-watchpoint}
23403 @item @code{read-watchpoint}
23407 @item @code{access-watchpoint}
23411 @item @code{pid-to-exec-file}
23412 @tab @code{qXfer:exec-file:read}
23413 @tab @code{attach}, @code{run}
23415 @item @code{target-features}
23416 @tab @code{qXfer:features:read}
23417 @tab @code{set architecture}
23419 @item @code{library-info}
23420 @tab @code{qXfer:libraries:read}
23421 @tab @code{info sharedlibrary}
23423 @item @code{memory-map}
23424 @tab @code{qXfer:memory-map:read}
23425 @tab @code{info mem}
23427 @item @code{read-sdata-object}
23428 @tab @code{qXfer:sdata:read}
23429 @tab @code{print $_sdata}
23431 @item @code{read-siginfo-object}
23432 @tab @code{qXfer:siginfo:read}
23433 @tab @code{print $_siginfo}
23435 @item @code{write-siginfo-object}
23436 @tab @code{qXfer:siginfo:write}
23437 @tab @code{set $_siginfo}
23439 @item @code{threads}
23440 @tab @code{qXfer:threads:read}
23441 @tab @code{info threads}
23443 @item @code{get-thread-local-@*storage-address}
23444 @tab @code{qGetTLSAddr}
23445 @tab Displaying @code{__thread} variables
23447 @item @code{get-thread-information-block-address}
23448 @tab @code{qGetTIBAddr}
23449 @tab Display MS-Windows Thread Information Block.
23451 @item @code{search-memory}
23452 @tab @code{qSearch:memory}
23455 @item @code{supported-packets}
23456 @tab @code{qSupported}
23457 @tab Remote communications parameters
23459 @item @code{catch-syscalls}
23460 @tab @code{QCatchSyscalls}
23461 @tab @code{catch syscall}
23463 @item @code{pass-signals}
23464 @tab @code{QPassSignals}
23465 @tab @code{handle @var{signal}}
23467 @item @code{program-signals}
23468 @tab @code{QProgramSignals}
23469 @tab @code{handle @var{signal}}
23471 @item @code{hostio-close-packet}
23472 @tab @code{vFile:close}
23473 @tab @code{remote get}, @code{remote put}
23475 @item @code{hostio-open-packet}
23476 @tab @code{vFile:open}
23477 @tab @code{remote get}, @code{remote put}
23479 @item @code{hostio-pread-packet}
23480 @tab @code{vFile:pread}
23481 @tab @code{remote get}, @code{remote put}
23483 @item @code{hostio-pwrite-packet}
23484 @tab @code{vFile:pwrite}
23485 @tab @code{remote get}, @code{remote put}
23487 @item @code{hostio-unlink-packet}
23488 @tab @code{vFile:unlink}
23489 @tab @code{remote delete}
23491 @item @code{hostio-readlink-packet}
23492 @tab @code{vFile:readlink}
23495 @item @code{hostio-fstat-packet}
23496 @tab @code{vFile:fstat}
23499 @item @code{hostio-setfs-packet}
23500 @tab @code{vFile:setfs}
23503 @item @code{noack-packet}
23504 @tab @code{QStartNoAckMode}
23505 @tab Packet acknowledgment
23507 @item @code{osdata}
23508 @tab @code{qXfer:osdata:read}
23509 @tab @code{info os}
23511 @item @code{query-attached}
23512 @tab @code{qAttached}
23513 @tab Querying remote process attach state.
23515 @item @code{trace-buffer-size}
23516 @tab @code{QTBuffer:size}
23517 @tab @code{set trace-buffer-size}
23519 @item @code{trace-status}
23520 @tab @code{qTStatus}
23521 @tab @code{tstatus}
23523 @item @code{traceframe-info}
23524 @tab @code{qXfer:traceframe-info:read}
23525 @tab Traceframe info
23527 @item @code{install-in-trace}
23528 @tab @code{InstallInTrace}
23529 @tab Install tracepoint in tracing
23531 @item @code{disable-randomization}
23532 @tab @code{QDisableRandomization}
23533 @tab @code{set disable-randomization}
23535 @item @code{startup-with-shell}
23536 @tab @code{QStartupWithShell}
23537 @tab @code{set startup-with-shell}
23539 @item @code{environment-hex-encoded}
23540 @tab @code{QEnvironmentHexEncoded}
23541 @tab @code{set environment}
23543 @item @code{environment-unset}
23544 @tab @code{QEnvironmentUnset}
23545 @tab @code{unset environment}
23547 @item @code{environment-reset}
23548 @tab @code{QEnvironmentReset}
23549 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23551 @item @code{set-working-dir}
23552 @tab @code{QSetWorkingDir}
23553 @tab @code{set cwd}
23555 @item @code{conditional-breakpoints-packet}
23556 @tab @code{Z0 and Z1}
23557 @tab @code{Support for target-side breakpoint condition evaluation}
23559 @item @code{multiprocess-extensions}
23560 @tab @code{multiprocess extensions}
23561 @tab Debug multiple processes and remote process PID awareness
23563 @item @code{swbreak-feature}
23564 @tab @code{swbreak stop reason}
23567 @item @code{hwbreak-feature}
23568 @tab @code{hwbreak stop reason}
23571 @item @code{fork-event-feature}
23572 @tab @code{fork stop reason}
23575 @item @code{vfork-event-feature}
23576 @tab @code{vfork stop reason}
23579 @item @code{exec-event-feature}
23580 @tab @code{exec stop reason}
23583 @item @code{thread-events}
23584 @tab @code{QThreadEvents}
23585 @tab Tracking thread lifetime.
23587 @item @code{no-resumed-stop-reply}
23588 @tab @code{no resumed thread left stop reply}
23589 @tab Tracking thread lifetime.
23594 @section Implementing a Remote Stub
23596 @cindex debugging stub, example
23597 @cindex remote stub, example
23598 @cindex stub example, remote debugging
23599 The stub files provided with @value{GDBN} implement the target side of the
23600 communication protocol, and the @value{GDBN} side is implemented in the
23601 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23602 these subroutines to communicate, and ignore the details. (If you're
23603 implementing your own stub file, you can still ignore the details: start
23604 with one of the existing stub files. @file{sparc-stub.c} is the best
23605 organized, and therefore the easiest to read.)
23607 @cindex remote serial debugging, overview
23608 To debug a program running on another machine (the debugging
23609 @dfn{target} machine), you must first arrange for all the usual
23610 prerequisites for the program to run by itself. For example, for a C
23615 A startup routine to set up the C runtime environment; these usually
23616 have a name like @file{crt0}. The startup routine may be supplied by
23617 your hardware supplier, or you may have to write your own.
23620 A C subroutine library to support your program's
23621 subroutine calls, notably managing input and output.
23624 A way of getting your program to the other machine---for example, a
23625 download program. These are often supplied by the hardware
23626 manufacturer, but you may have to write your own from hardware
23630 The next step is to arrange for your program to use a serial port to
23631 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23632 machine). In general terms, the scheme looks like this:
23636 @value{GDBN} already understands how to use this protocol; when everything
23637 else is set up, you can simply use the @samp{target remote} command
23638 (@pxref{Targets,,Specifying a Debugging Target}).
23640 @item On the target,
23641 you must link with your program a few special-purpose subroutines that
23642 implement the @value{GDBN} remote serial protocol. The file containing these
23643 subroutines is called a @dfn{debugging stub}.
23645 On certain remote targets, you can use an auxiliary program
23646 @code{gdbserver} instead of linking a stub into your program.
23647 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23650 The debugging stub is specific to the architecture of the remote
23651 machine; for example, use @file{sparc-stub.c} to debug programs on
23654 @cindex remote serial stub list
23655 These working remote stubs are distributed with @value{GDBN}:
23660 @cindex @file{i386-stub.c}
23663 For Intel 386 and compatible architectures.
23666 @cindex @file{m68k-stub.c}
23667 @cindex Motorola 680x0
23669 For Motorola 680x0 architectures.
23672 @cindex @file{sh-stub.c}
23675 For Renesas SH architectures.
23678 @cindex @file{sparc-stub.c}
23680 For @sc{sparc} architectures.
23682 @item sparcl-stub.c
23683 @cindex @file{sparcl-stub.c}
23686 For Fujitsu @sc{sparclite} architectures.
23690 The @file{README} file in the @value{GDBN} distribution may list other
23691 recently added stubs.
23694 * Stub Contents:: What the stub can do for you
23695 * Bootstrapping:: What you must do for the stub
23696 * Debug Session:: Putting it all together
23699 @node Stub Contents
23700 @subsection What the Stub Can Do for You
23702 @cindex remote serial stub
23703 The debugging stub for your architecture supplies these three
23707 @item set_debug_traps
23708 @findex set_debug_traps
23709 @cindex remote serial stub, initialization
23710 This routine arranges for @code{handle_exception} to run when your
23711 program stops. You must call this subroutine explicitly in your
23712 program's startup code.
23714 @item handle_exception
23715 @findex handle_exception
23716 @cindex remote serial stub, main routine
23717 This is the central workhorse, but your program never calls it
23718 explicitly---the setup code arranges for @code{handle_exception} to
23719 run when a trap is triggered.
23721 @code{handle_exception} takes control when your program stops during
23722 execution (for example, on a breakpoint), and mediates communications
23723 with @value{GDBN} on the host machine. This is where the communications
23724 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23725 representative on the target machine. It begins by sending summary
23726 information on the state of your program, then continues to execute,
23727 retrieving and transmitting any information @value{GDBN} needs, until you
23728 execute a @value{GDBN} command that makes your program resume; at that point,
23729 @code{handle_exception} returns control to your own code on the target
23733 @cindex @code{breakpoint} subroutine, remote
23734 Use this auxiliary subroutine to make your program contain a
23735 breakpoint. Depending on the particular situation, this may be the only
23736 way for @value{GDBN} to get control. For instance, if your target
23737 machine has some sort of interrupt button, you won't need to call this;
23738 pressing the interrupt button transfers control to
23739 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23740 simply receiving characters on the serial port may also trigger a trap;
23741 again, in that situation, you don't need to call @code{breakpoint} from
23742 your own program---simply running @samp{target remote} from the host
23743 @value{GDBN} session gets control.
23745 Call @code{breakpoint} if none of these is true, or if you simply want
23746 to make certain your program stops at a predetermined point for the
23747 start of your debugging session.
23750 @node Bootstrapping
23751 @subsection What You Must Do for the Stub
23753 @cindex remote stub, support routines
23754 The debugging stubs that come with @value{GDBN} are set up for a particular
23755 chip architecture, but they have no information about the rest of your
23756 debugging target machine.
23758 First of all you need to tell the stub how to communicate with the
23762 @item int getDebugChar()
23763 @findex getDebugChar
23764 Write this subroutine to read a single character from the serial port.
23765 It may be identical to @code{getchar} for your target system; a
23766 different name is used to allow you to distinguish the two if you wish.
23768 @item void putDebugChar(int)
23769 @findex putDebugChar
23770 Write this subroutine to write a single character to the serial port.
23771 It may be identical to @code{putchar} for your target system; a
23772 different name is used to allow you to distinguish the two if you wish.
23775 @cindex control C, and remote debugging
23776 @cindex interrupting remote targets
23777 If you want @value{GDBN} to be able to stop your program while it is
23778 running, you need to use an interrupt-driven serial driver, and arrange
23779 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23780 character). That is the character which @value{GDBN} uses to tell the
23781 remote system to stop.
23783 Getting the debugging target to return the proper status to @value{GDBN}
23784 probably requires changes to the standard stub; one quick and dirty way
23785 is to just execute a breakpoint instruction (the ``dirty'' part is that
23786 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23788 Other routines you need to supply are:
23791 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23792 @findex exceptionHandler
23793 Write this function to install @var{exception_address} in the exception
23794 handling tables. You need to do this because the stub does not have any
23795 way of knowing what the exception handling tables on your target system
23796 are like (for example, the processor's table might be in @sc{rom},
23797 containing entries which point to a table in @sc{ram}).
23798 The @var{exception_number} specifies the exception which should be changed;
23799 its meaning is architecture-dependent (for example, different numbers
23800 might represent divide by zero, misaligned access, etc). When this
23801 exception occurs, control should be transferred directly to
23802 @var{exception_address}, and the processor state (stack, registers,
23803 and so on) should be just as it is when a processor exception occurs. So if
23804 you want to use a jump instruction to reach @var{exception_address}, it
23805 should be a simple jump, not a jump to subroutine.
23807 For the 386, @var{exception_address} should be installed as an interrupt
23808 gate so that interrupts are masked while the handler runs. The gate
23809 should be at privilege level 0 (the most privileged level). The
23810 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23811 help from @code{exceptionHandler}.
23813 @item void flush_i_cache()
23814 @findex flush_i_cache
23815 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23816 instruction cache, if any, on your target machine. If there is no
23817 instruction cache, this subroutine may be a no-op.
23819 On target machines that have instruction caches, @value{GDBN} requires this
23820 function to make certain that the state of your program is stable.
23824 You must also make sure this library routine is available:
23827 @item void *memset(void *, int, int)
23829 This is the standard library function @code{memset} that sets an area of
23830 memory to a known value. If you have one of the free versions of
23831 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23832 either obtain it from your hardware manufacturer, or write your own.
23835 If you do not use the GNU C compiler, you may need other standard
23836 library subroutines as well; this varies from one stub to another,
23837 but in general the stubs are likely to use any of the common library
23838 subroutines which @code{@value{NGCC}} generates as inline code.
23841 @node Debug Session
23842 @subsection Putting it All Together
23844 @cindex remote serial debugging summary
23845 In summary, when your program is ready to debug, you must follow these
23850 Make sure you have defined the supporting low-level routines
23851 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
23853 @code{getDebugChar}, @code{putDebugChar},
23854 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
23858 Insert these lines in your program's startup code, before the main
23859 procedure is called:
23866 On some machines, when a breakpoint trap is raised, the hardware
23867 automatically makes the PC point to the instruction after the
23868 breakpoint. If your machine doesn't do that, you may need to adjust
23869 @code{handle_exception} to arrange for it to return to the instruction
23870 after the breakpoint on this first invocation, so that your program
23871 doesn't keep hitting the initial breakpoint instead of making
23875 For the 680x0 stub only, you need to provide a variable called
23876 @code{exceptionHook}. Normally you just use:
23879 void (*exceptionHook)() = 0;
23883 but if before calling @code{set_debug_traps}, you set it to point to a
23884 function in your program, that function is called when
23885 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
23886 error). The function indicated by @code{exceptionHook} is called with
23887 one parameter: an @code{int} which is the exception number.
23890 Compile and link together: your program, the @value{GDBN} debugging stub for
23891 your target architecture, and the supporting subroutines.
23894 Make sure you have a serial connection between your target machine and
23895 the @value{GDBN} host, and identify the serial port on the host.
23898 @c The "remote" target now provides a `load' command, so we should
23899 @c document that. FIXME.
23900 Download your program to your target machine (or get it there by
23901 whatever means the manufacturer provides), and start it.
23904 Start @value{GDBN} on the host, and connect to the target
23905 (@pxref{Connecting,,Connecting to a Remote Target}).
23909 @node Configurations
23910 @chapter Configuration-Specific Information
23912 While nearly all @value{GDBN} commands are available for all native and
23913 cross versions of the debugger, there are some exceptions. This chapter
23914 describes things that are only available in certain configurations.
23916 There are three major categories of configurations: native
23917 configurations, where the host and target are the same, embedded
23918 operating system configurations, which are usually the same for several
23919 different processor architectures, and bare embedded processors, which
23920 are quite different from each other.
23925 * Embedded Processors::
23932 This section describes details specific to particular native
23936 * BSD libkvm Interface:: Debugging BSD kernel memory images
23937 * Process Information:: Process information
23938 * DJGPP Native:: Features specific to the DJGPP port
23939 * Cygwin Native:: Features specific to the Cygwin port
23940 * Hurd Native:: Features specific to @sc{gnu} Hurd
23941 * Darwin:: Features specific to Darwin
23942 * FreeBSD:: Features specific to FreeBSD
23945 @node BSD libkvm Interface
23946 @subsection BSD libkvm Interface
23949 @cindex kernel memory image
23950 @cindex kernel crash dump
23952 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
23953 interface that provides a uniform interface for accessing kernel virtual
23954 memory images, including live systems and crash dumps. @value{GDBN}
23955 uses this interface to allow you to debug live kernels and kernel crash
23956 dumps on many native BSD configurations. This is implemented as a
23957 special @code{kvm} debugging target. For debugging a live system, load
23958 the currently running kernel into @value{GDBN} and connect to the
23962 (@value{GDBP}) @b{target kvm}
23965 For debugging crash dumps, provide the file name of the crash dump as an
23969 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
23972 Once connected to the @code{kvm} target, the following commands are
23978 Set current context from the @dfn{Process Control Block} (PCB) address.
23981 Set current context from proc address. This command isn't available on
23982 modern FreeBSD systems.
23985 @node Process Information
23986 @subsection Process Information
23988 @cindex examine process image
23989 @cindex process info via @file{/proc}
23991 Some operating systems provide interfaces to fetch additional
23992 information about running processes beyond memory and per-thread
23993 register state. If @value{GDBN} is configured for an operating system
23994 with a supported interface, the command @code{info proc} is available
23995 to report information about the process running your program, or about
23996 any process running on your system.
23998 One supported interface is a facility called @samp{/proc} that can be
23999 used to examine the image of a running process using file-system
24000 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24003 On FreeBSD and NetBSD systems, system control nodes are used to query
24004 process information.
24006 In addition, some systems may provide additional process information
24007 in core files. Note that a core file may include a subset of the
24008 information available from a live process. Process information is
24009 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24016 @itemx info proc @var{process-id}
24017 Summarize available information about a process. If a
24018 process ID is specified by @var{process-id}, display information about
24019 that process; otherwise display information about the program being
24020 debugged. The summary includes the debugged process ID, the command
24021 line used to invoke it, its current working directory, and its
24022 executable file's absolute file name.
24024 On some systems, @var{process-id} can be of the form
24025 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24026 within a process. If the optional @var{pid} part is missing, it means
24027 a thread from the process being debugged (the leading @samp{/} still
24028 needs to be present, or else @value{GDBN} will interpret the number as
24029 a process ID rather than a thread ID).
24031 @item info proc cmdline
24032 @cindex info proc cmdline
24033 Show the original command line of the process. This command is
24034 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24036 @item info proc cwd
24037 @cindex info proc cwd
24038 Show the current working directory of the process. This command is
24039 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24041 @item info proc exe
24042 @cindex info proc exe
24043 Show the name of executable of the process. This command is supported
24044 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24046 @item info proc files
24047 @cindex info proc files
24048 Show the file descriptors open by the process. For each open file
24049 descriptor, @value{GDBN} shows its number, type (file, directory,
24050 character device, socket), file pointer offset, and the name of the
24051 resource open on the descriptor. The resource name can be a file name
24052 (for files, directories, and devices) or a protocol followed by socket
24053 address (for network connections). This command is supported on
24056 This example shows the open file descriptors for a process using a
24057 tty for standard input and output as well as two network sockets:
24060 (gdb) info proc files 22136
24064 FD Type Offset Flags Name
24065 text file - r-------- /usr/bin/ssh
24066 ctty chr - rw------- /dev/pts/20
24067 cwd dir - r-------- /usr/home/john
24068 root dir - r-------- /
24069 0 chr 0x32933a4 rw------- /dev/pts/20
24070 1 chr 0x32933a4 rw------- /dev/pts/20
24071 2 chr 0x32933a4 rw------- /dev/pts/20
24072 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24073 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24076 @item info proc mappings
24077 @cindex memory address space mappings
24078 Report the memory address space ranges accessible in a process. On
24079 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24080 on whether the process has read, write, or execute access rights to each
24081 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24082 includes the object file which is mapped to that range.
24084 @item info proc stat
24085 @itemx info proc status
24086 @cindex process detailed status information
24087 Show additional process-related information, including the user ID and
24088 group ID; virtual memory usage; the signals that are pending, blocked,
24089 and ignored; its TTY; its consumption of system and user time; its
24090 stack size; its @samp{nice} value; etc. These commands are supported
24091 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24093 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24094 information (type @kbd{man 5 proc} from your shell prompt).
24096 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24097 @code{info proc status}.
24099 @item info proc all
24100 Show all the information about the process described under all of the
24101 above @code{info proc} subcommands.
24104 @comment These sub-options of 'info proc' were not included when
24105 @comment procfs.c was re-written. Keep their descriptions around
24106 @comment against the day when someone finds the time to put them back in.
24107 @kindex info proc times
24108 @item info proc times
24109 Starting time, user CPU time, and system CPU time for your program and
24112 @kindex info proc id
24114 Report on the process IDs related to your program: its own process ID,
24115 the ID of its parent, the process group ID, and the session ID.
24118 @item set procfs-trace
24119 @kindex set procfs-trace
24120 @cindex @code{procfs} API calls
24121 This command enables and disables tracing of @code{procfs} API calls.
24123 @item show procfs-trace
24124 @kindex show procfs-trace
24125 Show the current state of @code{procfs} API call tracing.
24127 @item set procfs-file @var{file}
24128 @kindex set procfs-file
24129 Tell @value{GDBN} to write @code{procfs} API trace to the named
24130 @var{file}. @value{GDBN} appends the trace info to the previous
24131 contents of the file. The default is to display the trace on the
24134 @item show procfs-file
24135 @kindex show procfs-file
24136 Show the file to which @code{procfs} API trace is written.
24138 @item proc-trace-entry
24139 @itemx proc-trace-exit
24140 @itemx proc-untrace-entry
24141 @itemx proc-untrace-exit
24142 @kindex proc-trace-entry
24143 @kindex proc-trace-exit
24144 @kindex proc-untrace-entry
24145 @kindex proc-untrace-exit
24146 These commands enable and disable tracing of entries into and exits
24147 from the @code{syscall} interface.
24150 @kindex info pidlist
24151 @cindex process list, QNX Neutrino
24152 For QNX Neutrino only, this command displays the list of all the
24153 processes and all the threads within each process.
24156 @kindex info meminfo
24157 @cindex mapinfo list, QNX Neutrino
24158 For QNX Neutrino only, this command displays the list of all mapinfos.
24162 @subsection Features for Debugging @sc{djgpp} Programs
24163 @cindex @sc{djgpp} debugging
24164 @cindex native @sc{djgpp} debugging
24165 @cindex MS-DOS-specific commands
24168 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24169 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24170 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24171 top of real-mode DOS systems and their emulations.
24173 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24174 defines a few commands specific to the @sc{djgpp} port. This
24175 subsection describes those commands.
24180 This is a prefix of @sc{djgpp}-specific commands which print
24181 information about the target system and important OS structures.
24184 @cindex MS-DOS system info
24185 @cindex free memory information (MS-DOS)
24186 @item info dos sysinfo
24187 This command displays assorted information about the underlying
24188 platform: the CPU type and features, the OS version and flavor, the
24189 DPMI version, and the available conventional and DPMI memory.
24194 @cindex segment descriptor tables
24195 @cindex descriptor tables display
24197 @itemx info dos ldt
24198 @itemx info dos idt
24199 These 3 commands display entries from, respectively, Global, Local,
24200 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24201 tables are data structures which store a descriptor for each segment
24202 that is currently in use. The segment's selector is an index into a
24203 descriptor table; the table entry for that index holds the
24204 descriptor's base address and limit, and its attributes and access
24207 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24208 segment (used for both data and the stack), and a DOS segment (which
24209 allows access to DOS/BIOS data structures and absolute addresses in
24210 conventional memory). However, the DPMI host will usually define
24211 additional segments in order to support the DPMI environment.
24213 @cindex garbled pointers
24214 These commands allow to display entries from the descriptor tables.
24215 Without an argument, all entries from the specified table are
24216 displayed. An argument, which should be an integer expression, means
24217 display a single entry whose index is given by the argument. For
24218 example, here's a convenient way to display information about the
24219 debugged program's data segment:
24222 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24223 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24227 This comes in handy when you want to see whether a pointer is outside
24228 the data segment's limit (i.e.@: @dfn{garbled}).
24230 @cindex page tables display (MS-DOS)
24232 @itemx info dos pte
24233 These two commands display entries from, respectively, the Page
24234 Directory and the Page Tables. Page Directories and Page Tables are
24235 data structures which control how virtual memory addresses are mapped
24236 into physical addresses. A Page Table includes an entry for every
24237 page of memory that is mapped into the program's address space; there
24238 may be several Page Tables, each one holding up to 4096 entries. A
24239 Page Directory has up to 4096 entries, one each for every Page Table
24240 that is currently in use.
24242 Without an argument, @kbd{info dos pde} displays the entire Page
24243 Directory, and @kbd{info dos pte} displays all the entries in all of
24244 the Page Tables. An argument, an integer expression, given to the
24245 @kbd{info dos pde} command means display only that entry from the Page
24246 Directory table. An argument given to the @kbd{info dos pte} command
24247 means display entries from a single Page Table, the one pointed to by
24248 the specified entry in the Page Directory.
24250 @cindex direct memory access (DMA) on MS-DOS
24251 These commands are useful when your program uses @dfn{DMA} (Direct
24252 Memory Access), which needs physical addresses to program the DMA
24255 These commands are supported only with some DPMI servers.
24257 @cindex physical address from linear address
24258 @item info dos address-pte @var{addr}
24259 This command displays the Page Table entry for a specified linear
24260 address. The argument @var{addr} is a linear address which should
24261 already have the appropriate segment's base address added to it,
24262 because this command accepts addresses which may belong to @emph{any}
24263 segment. For example, here's how to display the Page Table entry for
24264 the page where a variable @code{i} is stored:
24267 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24268 @exdent @code{Page Table entry for address 0x11a00d30:}
24269 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24273 This says that @code{i} is stored at offset @code{0xd30} from the page
24274 whose physical base address is @code{0x02698000}, and shows all the
24275 attributes of that page.
24277 Note that you must cast the addresses of variables to a @code{char *},
24278 since otherwise the value of @code{__djgpp_base_address}, the base
24279 address of all variables and functions in a @sc{djgpp} program, will
24280 be added using the rules of C pointer arithmetics: if @code{i} is
24281 declared an @code{int}, @value{GDBN} will add 4 times the value of
24282 @code{__djgpp_base_address} to the address of @code{i}.
24284 Here's another example, it displays the Page Table entry for the
24288 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24289 @exdent @code{Page Table entry for address 0x29110:}
24290 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24294 (The @code{+ 3} offset is because the transfer buffer's address is the
24295 3rd member of the @code{_go32_info_block} structure.) The output
24296 clearly shows that this DPMI server maps the addresses in conventional
24297 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24298 linear (@code{0x29110}) addresses are identical.
24300 This command is supported only with some DPMI servers.
24303 @cindex DOS serial data link, remote debugging
24304 In addition to native debugging, the DJGPP port supports remote
24305 debugging via a serial data link. The following commands are specific
24306 to remote serial debugging in the DJGPP port of @value{GDBN}.
24309 @kindex set com1base
24310 @kindex set com1irq
24311 @kindex set com2base
24312 @kindex set com2irq
24313 @kindex set com3base
24314 @kindex set com3irq
24315 @kindex set com4base
24316 @kindex set com4irq
24317 @item set com1base @var{addr}
24318 This command sets the base I/O port address of the @file{COM1} serial
24321 @item set com1irq @var{irq}
24322 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24323 for the @file{COM1} serial port.
24325 There are similar commands @samp{set com2base}, @samp{set com3irq},
24326 etc.@: for setting the port address and the @code{IRQ} lines for the
24329 @kindex show com1base
24330 @kindex show com1irq
24331 @kindex show com2base
24332 @kindex show com2irq
24333 @kindex show com3base
24334 @kindex show com3irq
24335 @kindex show com4base
24336 @kindex show com4irq
24337 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24338 display the current settings of the base address and the @code{IRQ}
24339 lines used by the COM ports.
24342 @kindex info serial
24343 @cindex DOS serial port status
24344 This command prints the status of the 4 DOS serial ports. For each
24345 port, it prints whether it's active or not, its I/O base address and
24346 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24347 counts of various errors encountered so far.
24351 @node Cygwin Native
24352 @subsection Features for Debugging MS Windows PE Executables
24353 @cindex MS Windows debugging
24354 @cindex native Cygwin debugging
24355 @cindex Cygwin-specific commands
24357 @value{GDBN} supports native debugging of MS Windows programs, including
24358 DLLs with and without symbolic debugging information.
24360 @cindex Ctrl-BREAK, MS-Windows
24361 @cindex interrupt debuggee on MS-Windows
24362 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24363 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24364 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24365 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24366 sequence, which can be used to interrupt the debuggee even if it
24369 There are various additional Cygwin-specific commands, described in
24370 this section. Working with DLLs that have no debugging symbols is
24371 described in @ref{Non-debug DLL Symbols}.
24376 This is a prefix of MS Windows-specific commands which print
24377 information about the target system and important OS structures.
24379 @item info w32 selector
24380 This command displays information returned by
24381 the Win32 API @code{GetThreadSelectorEntry} function.
24382 It takes an optional argument that is evaluated to
24383 a long value to give the information about this given selector.
24384 Without argument, this command displays information
24385 about the six segment registers.
24387 @item info w32 thread-information-block
24388 This command displays thread specific information stored in the
24389 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24390 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24392 @kindex signal-event
24393 @item signal-event @var{id}
24394 This command signals an event with user-provided @var{id}. Used to resume
24395 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24397 To use it, create or edit the following keys in
24398 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24399 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24400 (for x86_64 versions):
24404 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24405 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24406 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24408 The first @code{%ld} will be replaced by the process ID of the
24409 crashing process, the second @code{%ld} will be replaced by the ID of
24410 the event that blocks the crashing process, waiting for @value{GDBN}
24414 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24415 make the system run debugger specified by the Debugger key
24416 automatically, @code{0} will cause a dialog box with ``OK'' and
24417 ``Cancel'' buttons to appear, which allows the user to either
24418 terminate the crashing process (OK) or debug it (Cancel).
24421 @kindex set cygwin-exceptions
24422 @cindex debugging the Cygwin DLL
24423 @cindex Cygwin DLL, debugging
24424 @item set cygwin-exceptions @var{mode}
24425 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24426 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24427 @value{GDBN} will delay recognition of exceptions, and may ignore some
24428 exceptions which seem to be caused by internal Cygwin DLL
24429 ``bookkeeping''. This option is meant primarily for debugging the
24430 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24431 @value{GDBN} users with false @code{SIGSEGV} signals.
24433 @kindex show cygwin-exceptions
24434 @item show cygwin-exceptions
24435 Displays whether @value{GDBN} will break on exceptions that happen
24436 inside the Cygwin DLL itself.
24438 @kindex set new-console
24439 @item set new-console @var{mode}
24440 If @var{mode} is @code{on} the debuggee will
24441 be started in a new console on next start.
24442 If @var{mode} is @code{off}, the debuggee will
24443 be started in the same console as the debugger.
24445 @kindex show new-console
24446 @item show new-console
24447 Displays whether a new console is used
24448 when the debuggee is started.
24450 @kindex set new-group
24451 @item set new-group @var{mode}
24452 This boolean value controls whether the debuggee should
24453 start a new group or stay in the same group as the debugger.
24454 This affects the way the Windows OS handles
24457 @kindex show new-group
24458 @item show new-group
24459 Displays current value of new-group boolean.
24461 @kindex set debugevents
24462 @item set debugevents
24463 This boolean value adds debug output concerning kernel events related
24464 to the debuggee seen by the debugger. This includes events that
24465 signal thread and process creation and exit, DLL loading and
24466 unloading, console interrupts, and debugging messages produced by the
24467 Windows @code{OutputDebugString} API call.
24469 @kindex set debugexec
24470 @item set debugexec
24471 This boolean value adds debug output concerning execute events
24472 (such as resume thread) seen by the debugger.
24474 @kindex set debugexceptions
24475 @item set debugexceptions
24476 This boolean value adds debug output concerning exceptions in the
24477 debuggee seen by the debugger.
24479 @kindex set debugmemory
24480 @item set debugmemory
24481 This boolean value adds debug output concerning debuggee memory reads
24482 and writes by the debugger.
24486 This boolean values specifies whether the debuggee is called
24487 via a shell or directly (default value is on).
24491 Displays if the debuggee will be started with a shell.
24496 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24499 @node Non-debug DLL Symbols
24500 @subsubsection Support for DLLs without Debugging Symbols
24501 @cindex DLLs with no debugging symbols
24502 @cindex Minimal symbols and DLLs
24504 Very often on windows, some of the DLLs that your program relies on do
24505 not include symbolic debugging information (for example,
24506 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24507 symbols in a DLL, it relies on the minimal amount of symbolic
24508 information contained in the DLL's export table. This section
24509 describes working with such symbols, known internally to @value{GDBN} as
24510 ``minimal symbols''.
24512 Note that before the debugged program has started execution, no DLLs
24513 will have been loaded. The easiest way around this problem is simply to
24514 start the program --- either by setting a breakpoint or letting the
24515 program run once to completion.
24517 @subsubsection DLL Name Prefixes
24519 In keeping with the naming conventions used by the Microsoft debugging
24520 tools, DLL export symbols are made available with a prefix based on the
24521 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24522 also entered into the symbol table, so @code{CreateFileA} is often
24523 sufficient. In some cases there will be name clashes within a program
24524 (particularly if the executable itself includes full debugging symbols)
24525 necessitating the use of the fully qualified name when referring to the
24526 contents of the DLL. Use single-quotes around the name to avoid the
24527 exclamation mark (``!'') being interpreted as a language operator.
24529 Note that the internal name of the DLL may be all upper-case, even
24530 though the file name of the DLL is lower-case, or vice-versa. Since
24531 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24532 some confusion. If in doubt, try the @code{info functions} and
24533 @code{info variables} commands or even @code{maint print msymbols}
24534 (@pxref{Symbols}). Here's an example:
24537 (@value{GDBP}) info function CreateFileA
24538 All functions matching regular expression "CreateFileA":
24540 Non-debugging symbols:
24541 0x77e885f4 CreateFileA
24542 0x77e885f4 KERNEL32!CreateFileA
24546 (@value{GDBP}) info function !
24547 All functions matching regular expression "!":
24549 Non-debugging symbols:
24550 0x6100114c cygwin1!__assert
24551 0x61004034 cygwin1!_dll_crt0@@0
24552 0x61004240 cygwin1!dll_crt0(per_process *)
24556 @subsubsection Working with Minimal Symbols
24558 Symbols extracted from a DLL's export table do not contain very much
24559 type information. All that @value{GDBN} can do is guess whether a symbol
24560 refers to a function or variable depending on the linker section that
24561 contains the symbol. Also note that the actual contents of the memory
24562 contained in a DLL are not available unless the program is running. This
24563 means that you cannot examine the contents of a variable or disassemble
24564 a function within a DLL without a running program.
24566 Variables are generally treated as pointers and dereferenced
24567 automatically. For this reason, it is often necessary to prefix a
24568 variable name with the address-of operator (``&'') and provide explicit
24569 type information in the command. Here's an example of the type of
24573 (@value{GDBP}) print 'cygwin1!__argv'
24574 'cygwin1!__argv' has unknown type; cast it to its declared type
24578 (@value{GDBP}) x 'cygwin1!__argv'
24579 'cygwin1!__argv' has unknown type; cast it to its declared type
24582 And two possible solutions:
24585 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24586 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24590 (@value{GDBP}) x/2x &'cygwin1!__argv'
24591 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24592 (@value{GDBP}) x/x 0x10021608
24593 0x10021608: 0x0022fd98
24594 (@value{GDBP}) x/s 0x0022fd98
24595 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24598 Setting a break point within a DLL is possible even before the program
24599 starts execution. However, under these circumstances, @value{GDBN} can't
24600 examine the initial instructions of the function in order to skip the
24601 function's frame set-up code. You can work around this by using ``*&''
24602 to set the breakpoint at a raw memory address:
24605 (@value{GDBP}) break *&'python22!PyOS_Readline'
24606 Breakpoint 1 at 0x1e04eff0
24609 The author of these extensions is not entirely convinced that setting a
24610 break point within a shared DLL like @file{kernel32.dll} is completely
24614 @subsection Commands Specific to @sc{gnu} Hurd Systems
24615 @cindex @sc{gnu} Hurd debugging
24617 This subsection describes @value{GDBN} commands specific to the
24618 @sc{gnu} Hurd native debugging.
24623 @kindex set signals@r{, Hurd command}
24624 @kindex set sigs@r{, Hurd command}
24625 This command toggles the state of inferior signal interception by
24626 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24627 affected by this command. @code{sigs} is a shorthand alias for
24632 @kindex show signals@r{, Hurd command}
24633 @kindex show sigs@r{, Hurd command}
24634 Show the current state of intercepting inferior's signals.
24636 @item set signal-thread
24637 @itemx set sigthread
24638 @kindex set signal-thread
24639 @kindex set sigthread
24640 This command tells @value{GDBN} which thread is the @code{libc} signal
24641 thread. That thread is run when a signal is delivered to a running
24642 process. @code{set sigthread} is the shorthand alias of @code{set
24645 @item show signal-thread
24646 @itemx show sigthread
24647 @kindex show signal-thread
24648 @kindex show sigthread
24649 These two commands show which thread will run when the inferior is
24650 delivered a signal.
24653 @kindex set stopped@r{, Hurd command}
24654 This commands tells @value{GDBN} that the inferior process is stopped,
24655 as with the @code{SIGSTOP} signal. The stopped process can be
24656 continued by delivering a signal to it.
24659 @kindex show stopped@r{, Hurd command}
24660 This command shows whether @value{GDBN} thinks the debuggee is
24663 @item set exceptions
24664 @kindex set exceptions@r{, Hurd command}
24665 Use this command to turn off trapping of exceptions in the inferior.
24666 When exception trapping is off, neither breakpoints nor
24667 single-stepping will work. To restore the default, set exception
24670 @item show exceptions
24671 @kindex show exceptions@r{, Hurd command}
24672 Show the current state of trapping exceptions in the inferior.
24674 @item set task pause
24675 @kindex set task@r{, Hurd commands}
24676 @cindex task attributes (@sc{gnu} Hurd)
24677 @cindex pause current task (@sc{gnu} Hurd)
24678 This command toggles task suspension when @value{GDBN} has control.
24679 Setting it to on takes effect immediately, and the task is suspended
24680 whenever @value{GDBN} gets control. Setting it to off will take
24681 effect the next time the inferior is continued. If this option is set
24682 to off, you can use @code{set thread default pause on} or @code{set
24683 thread pause on} (see below) to pause individual threads.
24685 @item show task pause
24686 @kindex show task@r{, Hurd commands}
24687 Show the current state of task suspension.
24689 @item set task detach-suspend-count
24690 @cindex task suspend count
24691 @cindex detach from task, @sc{gnu} Hurd
24692 This command sets the suspend count the task will be left with when
24693 @value{GDBN} detaches from it.
24695 @item show task detach-suspend-count
24696 Show the suspend count the task will be left with when detaching.
24698 @item set task exception-port
24699 @itemx set task excp
24700 @cindex task exception port, @sc{gnu} Hurd
24701 This command sets the task exception port to which @value{GDBN} will
24702 forward exceptions. The argument should be the value of the @dfn{send
24703 rights} of the task. @code{set task excp} is a shorthand alias.
24705 @item set noninvasive
24706 @cindex noninvasive task options
24707 This command switches @value{GDBN} to a mode that is the least
24708 invasive as far as interfering with the inferior is concerned. This
24709 is the same as using @code{set task pause}, @code{set exceptions}, and
24710 @code{set signals} to values opposite to the defaults.
24712 @item info send-rights
24713 @itemx info receive-rights
24714 @itemx info port-rights
24715 @itemx info port-sets
24716 @itemx info dead-names
24719 @cindex send rights, @sc{gnu} Hurd
24720 @cindex receive rights, @sc{gnu} Hurd
24721 @cindex port rights, @sc{gnu} Hurd
24722 @cindex port sets, @sc{gnu} Hurd
24723 @cindex dead names, @sc{gnu} Hurd
24724 These commands display information about, respectively, send rights,
24725 receive rights, port rights, port sets, and dead names of a task.
24726 There are also shorthand aliases: @code{info ports} for @code{info
24727 port-rights} and @code{info psets} for @code{info port-sets}.
24729 @item set thread pause
24730 @kindex set thread@r{, Hurd command}
24731 @cindex thread properties, @sc{gnu} Hurd
24732 @cindex pause current thread (@sc{gnu} Hurd)
24733 This command toggles current thread suspension when @value{GDBN} has
24734 control. Setting it to on takes effect immediately, and the current
24735 thread is suspended whenever @value{GDBN} gets control. Setting it to
24736 off will take effect the next time the inferior is continued.
24737 Normally, this command has no effect, since when @value{GDBN} has
24738 control, the whole task is suspended. However, if you used @code{set
24739 task pause off} (see above), this command comes in handy to suspend
24740 only the current thread.
24742 @item show thread pause
24743 @kindex show thread@r{, Hurd command}
24744 This command shows the state of current thread suspension.
24746 @item set thread run
24747 This command sets whether the current thread is allowed to run.
24749 @item show thread run
24750 Show whether the current thread is allowed to run.
24752 @item set thread detach-suspend-count
24753 @cindex thread suspend count, @sc{gnu} Hurd
24754 @cindex detach from thread, @sc{gnu} Hurd
24755 This command sets the suspend count @value{GDBN} will leave on a
24756 thread when detaching. This number is relative to the suspend count
24757 found by @value{GDBN} when it notices the thread; use @code{set thread
24758 takeover-suspend-count} to force it to an absolute value.
24760 @item show thread detach-suspend-count
24761 Show the suspend count @value{GDBN} will leave on the thread when
24764 @item set thread exception-port
24765 @itemx set thread excp
24766 Set the thread exception port to which to forward exceptions. This
24767 overrides the port set by @code{set task exception-port} (see above).
24768 @code{set thread excp} is the shorthand alias.
24770 @item set thread takeover-suspend-count
24771 Normally, @value{GDBN}'s thread suspend counts are relative to the
24772 value @value{GDBN} finds when it notices each thread. This command
24773 changes the suspend counts to be absolute instead.
24775 @item set thread default
24776 @itemx show thread default
24777 @cindex thread default settings, @sc{gnu} Hurd
24778 Each of the above @code{set thread} commands has a @code{set thread
24779 default} counterpart (e.g., @code{set thread default pause}, @code{set
24780 thread default exception-port}, etc.). The @code{thread default}
24781 variety of commands sets the default thread properties for all
24782 threads; you can then change the properties of individual threads with
24783 the non-default commands.
24790 @value{GDBN} provides the following commands specific to the Darwin target:
24793 @item set debug darwin @var{num}
24794 @kindex set debug darwin
24795 When set to a non zero value, enables debugging messages specific to
24796 the Darwin support. Higher values produce more verbose output.
24798 @item show debug darwin
24799 @kindex show debug darwin
24800 Show the current state of Darwin messages.
24802 @item set debug mach-o @var{num}
24803 @kindex set debug mach-o
24804 When set to a non zero value, enables debugging messages while
24805 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24806 file format used on Darwin for object and executable files.) Higher
24807 values produce more verbose output. This is a command to diagnose
24808 problems internal to @value{GDBN} and should not be needed in normal
24811 @item show debug mach-o
24812 @kindex show debug mach-o
24813 Show the current state of Mach-O file messages.
24815 @item set mach-exceptions on
24816 @itemx set mach-exceptions off
24817 @kindex set mach-exceptions
24818 On Darwin, faults are first reported as a Mach exception and are then
24819 mapped to a Posix signal. Use this command to turn on trapping of
24820 Mach exceptions in the inferior. This might be sometimes useful to
24821 better understand the cause of a fault. The default is off.
24823 @item show mach-exceptions
24824 @kindex show mach-exceptions
24825 Show the current state of exceptions trapping.
24829 @subsection FreeBSD
24832 When the ABI of a system call is changed in the FreeBSD kernel, this
24833 is implemented by leaving a compatibility system call using the old
24834 ABI at the existing number and allocating a new system call number for
24835 the version using the new ABI. As a convenience, when a system call
24836 is caught by name (@pxref{catch syscall}), compatibility system calls
24839 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24840 system call and catching the @code{kevent} system call by name catches
24844 (@value{GDBP}) catch syscall kevent
24845 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24851 @section Embedded Operating Systems
24853 This section describes configurations involving the debugging of
24854 embedded operating systems that are available for several different
24857 @value{GDBN} includes the ability to debug programs running on
24858 various real-time operating systems.
24860 @node Embedded Processors
24861 @section Embedded Processors
24863 This section goes into details specific to particular embedded
24866 @cindex send command to simulator
24867 Whenever a specific embedded processor has a simulator, @value{GDBN}
24868 allows to send an arbitrary command to the simulator.
24871 @item sim @var{command}
24872 @kindex sim@r{, a command}
24873 Send an arbitrary @var{command} string to the simulator. Consult the
24874 documentation for the specific simulator in use for information about
24875 acceptable commands.
24880 * ARC:: Synopsys ARC
24883 * M68K:: Motorola M68K
24884 * MicroBlaze:: Xilinx MicroBlaze
24885 * MIPS Embedded:: MIPS Embedded
24886 * OpenRISC 1000:: OpenRISC 1000 (or1k)
24887 * PowerPC Embedded:: PowerPC Embedded
24890 * Super-H:: Renesas Super-H
24894 @subsection Synopsys ARC
24895 @cindex Synopsys ARC
24896 @cindex ARC specific commands
24902 @value{GDBN} provides the following ARC-specific commands:
24905 @item set debug arc
24906 @kindex set debug arc
24907 Control the level of ARC specific debug messages. Use 0 for no messages (the
24908 default), 1 for debug messages, and 2 for even more debug messages.
24910 @item show debug arc
24911 @kindex show debug arc
24912 Show the level of ARC specific debugging in operation.
24914 @item maint print arc arc-instruction @var{address}
24915 @kindex maint print arc arc-instruction
24916 Print internal disassembler information about instruction at a given address.
24923 @value{GDBN} provides the following ARM-specific commands:
24926 @item set arm disassembler
24928 This commands selects from a list of disassembly styles. The
24929 @code{"std"} style is the standard style.
24931 @item show arm disassembler
24933 Show the current disassembly style.
24935 @item set arm apcs32
24936 @cindex ARM 32-bit mode
24937 This command toggles ARM operation mode between 32-bit and 26-bit.
24939 @item show arm apcs32
24940 Display the current usage of the ARM 32-bit mode.
24942 @item set arm fpu @var{fputype}
24943 This command sets the ARM floating-point unit (FPU) type. The
24944 argument @var{fputype} can be one of these:
24948 Determine the FPU type by querying the OS ABI.
24950 Software FPU, with mixed-endian doubles on little-endian ARM
24953 GCC-compiled FPA co-processor.
24955 Software FPU with pure-endian doubles.
24961 Show the current type of the FPU.
24964 This command forces @value{GDBN} to use the specified ABI.
24967 Show the currently used ABI.
24969 @item set arm fallback-mode (arm|thumb|auto)
24970 @value{GDBN} uses the symbol table, when available, to determine
24971 whether instructions are ARM or Thumb. This command controls
24972 @value{GDBN}'s default behavior when the symbol table is not
24973 available. The default is @samp{auto}, which causes @value{GDBN} to
24974 use the current execution mode (from the @code{T} bit in the @code{CPSR}
24977 @item show arm fallback-mode
24978 Show the current fallback instruction mode.
24980 @item set arm force-mode (arm|thumb|auto)
24981 This command overrides use of the symbol table to determine whether
24982 instructions are ARM or Thumb. The default is @samp{auto}, which
24983 causes @value{GDBN} to use the symbol table and then the setting
24984 of @samp{set arm fallback-mode}.
24986 @item show arm force-mode
24987 Show the current forced instruction mode.
24989 @item set debug arm
24990 Toggle whether to display ARM-specific debugging messages from the ARM
24991 target support subsystem.
24993 @item show debug arm
24994 Show whether ARM-specific debugging messages are enabled.
24998 @item target sim @r{[}@var{simargs}@r{]} @dots{}
24999 The @value{GDBN} ARM simulator accepts the following optional arguments.
25002 @item --swi-support=@var{type}
25003 Tell the simulator which SWI interfaces to support. The argument
25004 @var{type} may be a comma separated list of the following values.
25005 The default value is @code{all}.
25021 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25022 The @value{GDBN} BPF simulator accepts the following optional arguments.
25025 @item --skb-data-offset=@var{offset}
25026 Tell the simulator the offset, measured in bytes, of the
25027 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25028 This offset is used by some BPF specific-purpose load/store
25029 instructions. Defaults to 0.
25036 The Motorola m68k configuration includes ColdFire support.
25039 @subsection MicroBlaze
25040 @cindex Xilinx MicroBlaze
25041 @cindex XMD, Xilinx Microprocessor Debugger
25043 The MicroBlaze is a soft-core processor supported on various Xilinx
25044 FPGAs, such as Spartan or Virtex series. Boards with these processors
25045 usually have JTAG ports which connect to a host system running the Xilinx
25046 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25047 This host system is used to download the configuration bitstream to
25048 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25049 communicates with the target board using the JTAG interface and
25050 presents a @code{gdbserver} interface to the board. By default
25051 @code{xmd} uses port @code{1234}. (While it is possible to change
25052 this default port, it requires the use of undocumented @code{xmd}
25053 commands. Contact Xilinx support if you need to do this.)
25055 Use these GDB commands to connect to the MicroBlaze target processor.
25058 @item target remote :1234
25059 Use this command to connect to the target if you are running @value{GDBN}
25060 on the same system as @code{xmd}.
25062 @item target remote @var{xmd-host}:1234
25063 Use this command to connect to the target if it is connected to @code{xmd}
25064 running on a different system named @var{xmd-host}.
25067 Use this command to download a program to the MicroBlaze target.
25069 @item set debug microblaze @var{n}
25070 Enable MicroBlaze-specific debugging messages if non-zero.
25072 @item show debug microblaze @var{n}
25073 Show MicroBlaze-specific debugging level.
25076 @node MIPS Embedded
25077 @subsection @acronym{MIPS} Embedded
25080 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25083 @item set mipsfpu double
25084 @itemx set mipsfpu single
25085 @itemx set mipsfpu none
25086 @itemx set mipsfpu auto
25087 @itemx show mipsfpu
25088 @kindex set mipsfpu
25089 @kindex show mipsfpu
25090 @cindex @acronym{MIPS} remote floating point
25091 @cindex floating point, @acronym{MIPS} remote
25092 If your target board does not support the @acronym{MIPS} floating point
25093 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25094 need this, you may wish to put the command in your @value{GDBN} init
25095 file). This tells @value{GDBN} how to find the return value of
25096 functions which return floating point values. It also allows
25097 @value{GDBN} to avoid saving the floating point registers when calling
25098 functions on the board. If you are using a floating point coprocessor
25099 with only single precision floating point support, as on the @sc{r4650}
25100 processor, use the command @samp{set mipsfpu single}. The default
25101 double precision floating point coprocessor may be selected using
25102 @samp{set mipsfpu double}.
25104 In previous versions the only choices were double precision or no
25105 floating point, so @samp{set mipsfpu on} will select double precision
25106 and @samp{set mipsfpu off} will select no floating point.
25108 As usual, you can inquire about the @code{mipsfpu} variable with
25109 @samp{show mipsfpu}.
25112 @node OpenRISC 1000
25113 @subsection OpenRISC 1000
25114 @cindex OpenRISC 1000
25117 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25118 mainly provided as a soft-core which can run on Xilinx, Altera and other
25121 @value{GDBN} for OpenRISC supports the below commands when connecting to
25129 Runs the builtin CPU simulator which can run very basic
25130 programs but does not support most hardware functions like MMU.
25131 For more complex use cases the user is advised to run an external
25132 target, and connect using @samp{target remote}.
25134 Example: @code{target sim}
25136 @item set debug or1k
25137 Toggle whether to display OpenRISC-specific debugging messages from the
25138 OpenRISC target support subsystem.
25140 @item show debug or1k
25141 Show whether OpenRISC-specific debugging messages are enabled.
25144 @node PowerPC Embedded
25145 @subsection PowerPC Embedded
25147 @cindex DVC register
25148 @value{GDBN} supports using the DVC (Data Value Compare) register to
25149 implement in hardware simple hardware watchpoint conditions of the form:
25152 (@value{GDBP}) watch @var{address|variable} \
25153 if @var{address|variable} == @var{constant expression}
25156 The DVC register will be automatically used when @value{GDBN} detects
25157 such pattern in a condition expression, and the created watchpoint uses one
25158 debug register (either the @code{exact-watchpoints} option is on and the
25159 variable is scalar, or the variable has a length of one byte). This feature
25160 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25163 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25164 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25165 in which case watchpoints using only one debug register are created when
25166 watching variables of scalar types.
25168 You can create an artificial array to watch an arbitrary memory
25169 region using one of the following commands (@pxref{Expressions}):
25172 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25173 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25176 PowerPC embedded processors support masked watchpoints. See the discussion
25177 about the @code{mask} argument in @ref{Set Watchpoints}.
25179 @cindex ranged breakpoint
25180 PowerPC embedded processors support hardware accelerated
25181 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25182 the inferior whenever it executes an instruction at any address within
25183 the range it specifies. To set a ranged breakpoint in @value{GDBN},
25184 use the @code{break-range} command.
25186 @value{GDBN} provides the following PowerPC-specific commands:
25189 @kindex break-range
25190 @item break-range @var{start-location}, @var{end-location}
25191 Set a breakpoint for an address range given by
25192 @var{start-location} and @var{end-location}, which can specify a function name,
25193 a line number, an offset of lines from the current line or from the start
25194 location, or an address of an instruction (see @ref{Specify Location},
25195 for a list of all the possible ways to specify a @var{location}.)
25196 The breakpoint will stop execution of the inferior whenever it
25197 executes an instruction at any address within the specified range,
25198 (including @var{start-location} and @var{end-location}.)
25200 @kindex set powerpc
25201 @item set powerpc soft-float
25202 @itemx show powerpc soft-float
25203 Force @value{GDBN} to use (or not use) a software floating point calling
25204 convention. By default, @value{GDBN} selects the calling convention based
25205 on the selected architecture and the provided executable file.
25207 @item set powerpc vector-abi
25208 @itemx show powerpc vector-abi
25209 Force @value{GDBN} to use the specified calling convention for vector
25210 arguments and return values. The valid options are @samp{auto};
25211 @samp{generic}, to avoid vector registers even if they are present;
25212 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25213 registers. By default, @value{GDBN} selects the calling convention
25214 based on the selected architecture and the provided executable file.
25216 @item set powerpc exact-watchpoints
25217 @itemx show powerpc exact-watchpoints
25218 Allow @value{GDBN} to use only one debug register when watching a variable
25219 of scalar type, thus assuming that the variable is accessed through the
25220 address of its first byte.
25225 @subsection Atmel AVR
25228 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25229 following AVR-specific commands:
25232 @item info io_registers
25233 @kindex info io_registers@r{, AVR}
25234 @cindex I/O registers (Atmel AVR)
25235 This command displays information about the AVR I/O registers. For
25236 each register, @value{GDBN} prints its number and value.
25243 When configured for debugging CRIS, @value{GDBN} provides the
25244 following CRIS-specific commands:
25247 @item set cris-version @var{ver}
25248 @cindex CRIS version
25249 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25250 The CRIS version affects register names and sizes. This command is useful in
25251 case autodetection of the CRIS version fails.
25253 @item show cris-version
25254 Show the current CRIS version.
25256 @item set cris-dwarf2-cfi
25257 @cindex DWARF-2 CFI and CRIS
25258 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25259 Change to @samp{off} when using @code{gcc-cris} whose version is below
25262 @item show cris-dwarf2-cfi
25263 Show the current state of using DWARF-2 CFI.
25265 @item set cris-mode @var{mode}
25267 Set the current CRIS mode to @var{mode}. It should only be changed when
25268 debugging in guru mode, in which case it should be set to
25269 @samp{guru} (the default is @samp{normal}).
25271 @item show cris-mode
25272 Show the current CRIS mode.
25276 @subsection Renesas Super-H
25279 For the Renesas Super-H processor, @value{GDBN} provides these
25283 @item set sh calling-convention @var{convention}
25284 @kindex set sh calling-convention
25285 Set the calling-convention used when calling functions from @value{GDBN}.
25286 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25287 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25288 convention. If the DWARF-2 information of the called function specifies
25289 that the function follows the Renesas calling convention, the function
25290 is called using the Renesas calling convention. If the calling convention
25291 is set to @samp{renesas}, the Renesas calling convention is always used,
25292 regardless of the DWARF-2 information. This can be used to override the
25293 default of @samp{gcc} if debug information is missing, or the compiler
25294 does not emit the DWARF-2 calling convention entry for a function.
25296 @item show sh calling-convention
25297 @kindex show sh calling-convention
25298 Show the current calling convention setting.
25303 @node Architectures
25304 @section Architectures
25306 This section describes characteristics of architectures that affect
25307 all uses of @value{GDBN} with the architecture, both native and cross.
25314 * HPPA:: HP PA architecture
25322 @subsection AArch64
25323 @cindex AArch64 support
25325 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25326 following special commands:
25329 @item set debug aarch64
25330 @kindex set debug aarch64
25331 This command determines whether AArch64 architecture-specific debugging
25332 messages are to be displayed.
25334 @item show debug aarch64
25335 Show whether AArch64 debugging messages are displayed.
25339 @subsubsection AArch64 SVE.
25340 @cindex AArch64 SVE.
25342 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25343 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25344 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25345 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25346 @code{$vg} will be provided. This is the vector granule for the current thread
25347 and represents the number of 64-bit chunks in an SVE @code{z} register.
25349 If the vector length changes, then the @code{$vg} register will be updated,
25350 but the lengths of the @code{z} and @code{p} registers will not change. This
25351 is a known limitation of @value{GDBN} and does not affect the execution of the
25354 @subsubsection AArch64 Pointer Authentication.
25355 @cindex AArch64 Pointer Authentication.
25357 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25358 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25359 register @code{$lr} is pointing to an PAC function its value will be masked.
25360 When GDB prints a backtrace, any addresses that required unmasking will be
25361 postfixed with the marker [PAC]. When using the MI, this is printed as part
25362 of the @code{addr_flags} field.
25364 @subsubsection AArch64 Memory Tagging Extension.
25365 @cindex AArch64 Memory Tagging Extension.
25367 When @value{GDBN} is debugging the AArch64 architecture, the program is
25368 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25369 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25370 available for inspection and editing of logical and allocation tags.
25371 @xref{Memory Tagging}.
25373 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25374 signals are generated as a result of memory tag failures.
25376 If the tag violation is synchronous, the following will be shown:
25379 Program received signal SIGSEGV, Segmentation fault
25380 Memory tag violation while accessing address 0x0500fffff7ff8000
25385 If the tag violation is asynchronous, the fault address is not available.
25386 In this case @value{GDBN} will show the following:
25389 Program received signal SIGSEGV, Segmentation fault
25390 Memory tag violation
25391 Fault address unavailable.
25394 A special register, @code{tag_ctl}, is made available through the
25395 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25396 options that can be controlled at runtime and emulates the @code{prctl}
25397 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25398 documentation in the Linux kernel.
25401 @subsection x86 Architecture-specific Issues
25404 @item set struct-convention @var{mode}
25405 @kindex set struct-convention
25406 @cindex struct return convention
25407 @cindex struct/union returned in registers
25408 Set the convention used by the inferior to return @code{struct}s and
25409 @code{union}s from functions to @var{mode}. Possible values of
25410 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25411 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25412 are returned on the stack, while @code{"reg"} means that a
25413 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25414 be returned in a register.
25416 @item show struct-convention
25417 @kindex show struct-convention
25418 Show the current setting of the convention to return @code{struct}s
25423 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25424 @cindex Intel Memory Protection Extensions (MPX).
25426 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25427 @footnote{The register named with capital letters represent the architecture
25428 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25429 which are the lower bound and upper bound. Bounds are effective addresses or
25430 memory locations. The upper bounds are architecturally represented in 1's
25431 complement form. A bound having lower bound = 0, and upper bound = 0
25432 (1's complement of all bits set) will allow access to the entire address space.
25434 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25435 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25436 display the upper bound performing the complement of one operation on the
25437 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25438 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25439 can also be noted that the upper bounds are inclusive.
25441 As an example, assume that the register BND0 holds bounds for a pointer having
25442 access allowed for the range between 0x32 and 0x71. The values present on
25443 bnd0raw and bnd registers are presented as follows:
25446 bnd0raw = @{0x32, 0xffffffff8e@}
25447 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25450 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25451 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25452 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25453 Python, the display includes the memory size, in bits, accessible to
25456 Bounds can also be stored in bounds tables, which are stored in
25457 application memory. These tables store bounds for pointers by specifying
25458 the bounds pointer's value along with its bounds. Evaluating and changing
25459 bounds located in bound tables is therefore interesting while investigating
25460 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25463 @item show mpx bound @var{pointer}
25464 @kindex show mpx bound
25465 Display bounds of the given @var{pointer}.
25467 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25468 @kindex set mpx bound
25469 Set the bounds of a pointer in the bound table.
25470 This command takes three parameters: @var{pointer} is the pointers
25471 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25472 for lower and upper bounds respectively.
25475 When you call an inferior function on an Intel MPX enabled program,
25476 GDB sets the inferior's bound registers to the init (disabled) state
25477 before calling the function. As a consequence, bounds checks for the
25478 pointer arguments passed to the function will always pass.
25480 This is necessary because when you call an inferior function, the
25481 program is usually in the middle of the execution of other function.
25482 Since at that point bound registers are in an arbitrary state, not
25483 clearing them would lead to random bound violations in the called
25486 You can still examine the influence of the bound registers on the
25487 execution of the called function by stopping the execution of the
25488 called function at its prologue, setting bound registers, and
25489 continuing the execution. For example:
25493 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25494 $ print upper (a, b, c, d, 1)
25495 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25497 @{lbound = 0x0, ubound = ffffffff@} : size -1
25500 At this last step the value of bnd0 can be changed for investigation of bound
25501 violations caused along the execution of the call. In order to know how to
25502 set the bound registers or bound table for the call consult the ABI.
25507 See the following section.
25510 @subsection @acronym{MIPS}
25512 @cindex stack on Alpha
25513 @cindex stack on @acronym{MIPS}
25514 @cindex Alpha stack
25515 @cindex @acronym{MIPS} stack
25516 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25517 sometimes requires @value{GDBN} to search backward in the object code to
25518 find the beginning of a function.
25520 @cindex response time, @acronym{MIPS} debugging
25521 To improve response time (especially for embedded applications, where
25522 @value{GDBN} may be restricted to a slow serial line for this search)
25523 you may want to limit the size of this search, using one of these
25527 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25528 @item set heuristic-fence-post @var{limit}
25529 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25530 search for the beginning of a function. A value of @var{0} (the
25531 default) means there is no limit. However, except for @var{0}, the
25532 larger the limit the more bytes @code{heuristic-fence-post} must search
25533 and therefore the longer it takes to run. You should only need to use
25534 this command when debugging a stripped executable.
25536 @item show heuristic-fence-post
25537 Display the current limit.
25541 These commands are available @emph{only} when @value{GDBN} is configured
25542 for debugging programs on Alpha or @acronym{MIPS} processors.
25544 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25548 @item set mips abi @var{arg}
25549 @kindex set mips abi
25550 @cindex set ABI for @acronym{MIPS}
25551 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25552 values of @var{arg} are:
25556 The default ABI associated with the current binary (this is the
25566 @item show mips abi
25567 @kindex show mips abi
25568 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25570 @item set mips compression @var{arg}
25571 @kindex set mips compression
25572 @cindex code compression, @acronym{MIPS}
25573 Tell @value{GDBN} which @acronym{MIPS} compressed
25574 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25575 inferior. @value{GDBN} uses this for code disassembly and other
25576 internal interpretation purposes. This setting is only referred to
25577 when no executable has been associated with the debugging session or
25578 the executable does not provide information about the encoding it uses.
25579 Otherwise this setting is automatically updated from information
25580 provided by the executable.
25582 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25583 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25584 executables containing @acronym{MIPS16} code frequently are not
25585 identified as such.
25587 This setting is ``sticky''; that is, it retains its value across
25588 debugging sessions until reset either explicitly with this command or
25589 implicitly from an executable.
25591 The compiler and/or assembler typically add symbol table annotations to
25592 identify functions compiled for the @acronym{MIPS16} or
25593 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25594 are present, @value{GDBN} uses them in preference to the global
25595 compressed @acronym{ISA} encoding setting.
25597 @item show mips compression
25598 @kindex show mips compression
25599 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25600 @value{GDBN} to debug the inferior.
25603 @itemx show mipsfpu
25604 @xref{MIPS Embedded, set mipsfpu}.
25606 @item set mips mask-address @var{arg}
25607 @kindex set mips mask-address
25608 @cindex @acronym{MIPS} addresses, masking
25609 This command determines whether the most-significant 32 bits of 64-bit
25610 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25611 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25612 setting, which lets @value{GDBN} determine the correct value.
25614 @item show mips mask-address
25615 @kindex show mips mask-address
25616 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25619 @item set remote-mips64-transfers-32bit-regs
25620 @kindex set remote-mips64-transfers-32bit-regs
25621 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25622 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25623 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25624 and 64 bits for other registers, set this option to @samp{on}.
25626 @item show remote-mips64-transfers-32bit-regs
25627 @kindex show remote-mips64-transfers-32bit-regs
25628 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25630 @item set debug mips
25631 @kindex set debug mips
25632 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25633 target code in @value{GDBN}.
25635 @item show debug mips
25636 @kindex show debug mips
25637 Show the current setting of @acronym{MIPS} debugging messages.
25643 @cindex HPPA support
25645 When @value{GDBN} is debugging the HP PA architecture, it provides the
25646 following special commands:
25649 @item set debug hppa
25650 @kindex set debug hppa
25651 This command determines whether HPPA architecture-specific debugging
25652 messages are to be displayed.
25654 @item show debug hppa
25655 Show whether HPPA debugging messages are displayed.
25657 @item maint print unwind @var{address}
25658 @kindex maint print unwind@r{, HPPA}
25659 This command displays the contents of the unwind table entry at the
25660 given @var{address}.
25666 @subsection PowerPC
25667 @cindex PowerPC architecture
25669 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25670 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25671 numbers stored in the floating point registers. These values must be stored
25672 in two consecutive registers, always starting at an even register like
25673 @code{f0} or @code{f2}.
25675 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25676 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25677 @code{f2} and @code{f3} for @code{$dl1} and so on.
25679 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25680 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25683 @subsection Nios II
25684 @cindex Nios II architecture
25686 When @value{GDBN} is debugging the Nios II architecture,
25687 it provides the following special commands:
25691 @item set debug nios2
25692 @kindex set debug nios2
25693 This command turns on and off debugging messages for the Nios II
25694 target code in @value{GDBN}.
25696 @item show debug nios2
25697 @kindex show debug nios2
25698 Show the current setting of Nios II debugging messages.
25702 @subsection Sparc64
25703 @cindex Sparc64 support
25704 @cindex Application Data Integrity
25705 @subsubsection ADI Support
25707 The M7 processor supports an Application Data Integrity (ADI) feature that
25708 detects invalid data accesses. When software allocates memory and enables
25709 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25710 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25711 the 4-bit version in every cacheline of that data. Hardware saves the latter
25712 in spare bits in the cache and memory hierarchy. On each load and store,
25713 the processor compares the upper 4 VA (virtual address) bits to the
25714 cacheline's version. If there is a mismatch, the processor generates a
25715 version mismatch trap which can be either precise or disrupting. The trap
25716 is an error condition which the kernel delivers to the process as a SIGSEGV
25719 Note that only 64-bit applications can use ADI and need to be built with
25722 Values of the ADI version tags, which are in granularity of a
25723 cacheline (64 bytes), can be viewed or modified.
25727 @kindex adi examine
25728 @item adi (examine | x) [ / @var{n} ] @var{addr}
25730 The @code{adi examine} command displays the value of one ADI version tag per
25733 @var{n} is a decimal integer specifying the number in bytes; the default
25734 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25735 block size, to display.
25737 @var{addr} is the address in user address space where you want @value{GDBN}
25738 to begin displaying the ADI version tags.
25740 Below is an example of displaying ADI versions of variable "shmaddr".
25743 (@value{GDBP}) adi x/100 shmaddr
25744 0xfff800010002c000: 0 0
25748 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25750 The @code{adi assign} command is used to assign new ADI version tag
25753 @var{n} is a decimal integer specifying the number in bytes;
25754 the default is 1. It specifies how much ADI version information, at the
25755 ratio of 1:ADI block size, to modify.
25757 @var{addr} is the address in user address space where you want @value{GDBN}
25758 to begin modifying the ADI version tags.
25760 @var{tag} is the new ADI version tag.
25762 For example, do the following to modify then verify ADI versions of
25763 variable "shmaddr":
25766 (@value{GDBP}) adi a/100 shmaddr = 7
25767 (@value{GDBP}) adi x/100 shmaddr
25768 0xfff800010002c000: 7 7
25775 @cindex S12Z support
25777 When @value{GDBN} is debugging the S12Z architecture,
25778 it provides the following special command:
25781 @item maint info bdccsr
25782 @kindex maint info bdccsr@r{, S12Z}
25783 This command displays the current value of the microprocessor's
25788 @node Controlling GDB
25789 @chapter Controlling @value{GDBN}
25791 You can alter the way @value{GDBN} interacts with you by using the
25792 @code{set} command. For commands controlling how @value{GDBN} displays
25793 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25798 * Editing:: Command editing
25799 * Command History:: Command history
25800 * Screen Size:: Screen size
25801 * Output Styling:: Output styling
25802 * Numbers:: Numbers
25803 * ABI:: Configuring the current ABI
25804 * Auto-loading:: Automatically loading associated files
25805 * Messages/Warnings:: Optional warnings and messages
25806 * Debugging Output:: Optional messages about internal happenings
25807 * Other Misc Settings:: Other Miscellaneous Settings
25815 @value{GDBN} indicates its readiness to read a command by printing a string
25816 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25817 can change the prompt string with the @code{set prompt} command. For
25818 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25819 the prompt in one of the @value{GDBN} sessions so that you can always tell
25820 which one you are talking to.
25822 @emph{Note:} @code{set prompt} does not add a space for you after the
25823 prompt you set. This allows you to set a prompt which ends in a space
25824 or a prompt that does not.
25828 @item set prompt @var{newprompt}
25829 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25831 @kindex show prompt
25833 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25836 Versions of @value{GDBN} that ship with Python scripting enabled have
25837 prompt extensions. The commands for interacting with these extensions
25841 @kindex set extended-prompt
25842 @item set extended-prompt @var{prompt}
25843 Set an extended prompt that allows for substitutions.
25844 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25845 substitution. Any escape sequences specified as part of the prompt
25846 string are replaced with the corresponding strings each time the prompt
25852 set extended-prompt Current working directory: \w (gdb)
25855 Note that when an extended-prompt is set, it takes control of the
25856 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
25858 @kindex show extended-prompt
25859 @item show extended-prompt
25860 Prints the extended prompt. Any escape sequences specified as part of
25861 the prompt string with @code{set extended-prompt}, are replaced with the
25862 corresponding strings each time the prompt is displayed.
25866 @section Command Editing
25868 @cindex command line editing
25870 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
25871 @sc{gnu} library provides consistent behavior for programs which provide a
25872 command line interface to the user. Advantages are @sc{gnu} Emacs-style
25873 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
25874 substitution, and a storage and recall of command history across
25875 debugging sessions.
25877 You may control the behavior of command line editing in @value{GDBN} with the
25878 command @code{set}.
25881 @kindex set editing
25884 @itemx set editing on
25885 Enable command line editing (enabled by default).
25887 @item set editing off
25888 Disable command line editing.
25890 @kindex show editing
25892 Show whether command line editing is enabled.
25895 @ifset SYSTEM_READLINE
25896 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
25898 @ifclear SYSTEM_READLINE
25899 @xref{Command Line Editing},
25901 for more details about the Readline
25902 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
25903 encouraged to read that chapter.
25905 @cindex Readline application name
25906 @value{GDBN} sets the Readline application name to @samp{gdb}. This
25907 is useful for conditions in @file{.inputrc}.
25909 @cindex operate-and-get-next
25910 @value{GDBN} defines a bindable Readline command,
25911 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
25912 This command accepts the current line for execution and fetches the
25913 next line relative to the current line from the history for editing.
25914 Any argument is ignored.
25916 @node Command History
25917 @section Command History
25918 @cindex command history
25920 @value{GDBN} can keep track of the commands you type during your
25921 debugging sessions, so that you can be certain of precisely what
25922 happened. Use these commands to manage the @value{GDBN} command
25925 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
25926 package, to provide the history facility.
25927 @ifset SYSTEM_READLINE
25928 @xref{Using History Interactively, , , history, GNU History Library},
25930 @ifclear SYSTEM_READLINE
25931 @xref{Using History Interactively},
25933 for the detailed description of the History library.
25935 To issue a command to @value{GDBN} without affecting certain aspects of
25936 the state which is seen by users, prefix it with @samp{server }
25937 (@pxref{Server Prefix}). This
25938 means that this command will not affect the command history, nor will it
25939 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
25940 pressed on a line by itself.
25942 @cindex @code{server}, command prefix
25943 The server prefix does not affect the recording of values into the value
25944 history; to print a value without recording it into the value history,
25945 use the @code{output} command instead of the @code{print} command.
25947 Here is the description of @value{GDBN} commands related to command
25951 @cindex history substitution
25952 @cindex history file
25953 @kindex set history filename
25954 @cindex @env{GDBHISTFILE}, environment variable
25955 @item set history filename @r{[}@var{fname}@r{]}
25956 Set the name of the @value{GDBN} command history file to @var{fname}.
25957 This is the file where @value{GDBN} reads an initial command history
25958 list, and where it writes the command history from this session when it
25959 exits. You can access this list through history expansion or through
25960 the history command editing characters listed below. This file defaults
25961 to the value of the environment variable @env{GDBHISTFILE}, or to
25962 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
25965 The @env{GDBHISTFILE} environment variable is read after processing
25966 any @value{GDBN} initialization files (@pxref{Startup}) and after
25967 processing any commands passed using command line options (for
25968 example, @code{-ex}).
25970 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
25971 is the empty string then @value{GDBN} will neither try to load an
25972 existing history file, nor will it try to save the history on exit.
25974 @cindex save command history
25975 @kindex set history save
25976 @item set history save
25977 @itemx set history save on
25978 Record command history in a file, whose name may be specified with the
25979 @code{set history filename} command. By default, this option is
25980 disabled. The command history will be recorded when @value{GDBN}
25981 exits. If @code{set history filename} is set to the empty string then
25982 history saving is disabled, even when @code{set history save} is
25985 @item set history save off
25986 Don't record the command history into the file specified by @code{set
25987 history filename} when @value{GDBN} exits.
25989 @cindex history size
25990 @kindex set history size
25991 @cindex @env{GDBHISTSIZE}, environment variable
25992 @item set history size @var{size}
25993 @itemx set history size unlimited
25994 Set the number of commands which @value{GDBN} keeps in its history list.
25995 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
25996 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
25997 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
25998 either a negative number or the empty string, then the number of commands
25999 @value{GDBN} keeps in the history list is unlimited.
26001 The @env{GDBHISTSIZE} environment variable is read after processing
26002 any @value{GDBN} initialization files (@pxref{Startup}) and after
26003 processing any commands passed using command line options (for
26004 example, @code{-ex}).
26006 @cindex remove duplicate history
26007 @kindex set history remove-duplicates
26008 @item set history remove-duplicates @var{count}
26009 @itemx set history remove-duplicates unlimited
26010 Control the removal of duplicate history entries in the command history list.
26011 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26012 history entries and remove the first entry that is a duplicate of the current
26013 entry being added to the command history list. If @var{count} is
26014 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26015 removal of duplicate history entries is disabled.
26017 Only history entries added during the current session are considered for
26018 removal. This option is set to 0 by default.
26022 History expansion assigns special meaning to the character @kbd{!}.
26023 @ifset SYSTEM_READLINE
26024 @xref{Event Designators, , , history, GNU History Library},
26026 @ifclear SYSTEM_READLINE
26027 @xref{Event Designators},
26031 @cindex history expansion, turn on/off
26032 Since @kbd{!} is also the logical not operator in C, history expansion
26033 is off by default. If you decide to enable history expansion with the
26034 @code{set history expansion on} command, you may sometimes need to
26035 follow @kbd{!} (when it is used as logical not, in an expression) with
26036 a space or a tab to prevent it from being expanded. The readline
26037 history facilities do not attempt substitution on the strings
26038 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26040 The commands to control history expansion are:
26043 @item set history expansion on
26044 @itemx set history expansion
26045 @kindex set history expansion
26046 Enable history expansion. History expansion is off by default.
26048 @item set history expansion off
26049 Disable history expansion.
26052 @kindex show history
26054 @itemx show history filename
26055 @itemx show history save
26056 @itemx show history size
26057 @itemx show history expansion
26058 These commands display the state of the @value{GDBN} history parameters.
26059 @code{show history} by itself displays all four states.
26064 @kindex show commands
26065 @cindex show last commands
26066 @cindex display command history
26067 @item show commands
26068 Display the last ten commands in the command history.
26070 @item show commands @var{n}
26071 Print ten commands centered on command number @var{n}.
26073 @item show commands +
26074 Print ten commands just after the commands last printed.
26078 @section Screen Size
26079 @cindex size of screen
26080 @cindex screen size
26083 @cindex pauses in output
26085 Certain commands to @value{GDBN} may produce large amounts of
26086 information output to the screen. To help you read all of it,
26087 @value{GDBN} pauses and asks you for input at the end of each page of
26088 output. Type @key{RET} when you want to see one more page of output,
26089 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26090 without paging for the rest of the current command. Also, the screen
26091 width setting determines when to wrap lines of output. Depending on
26092 what is being printed, @value{GDBN} tries to break the line at a
26093 readable place, rather than simply letting it overflow onto the
26096 Normally @value{GDBN} knows the size of the screen from the terminal
26097 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26098 together with the value of the @env{TERM} environment variable and the
26099 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26100 you can override it with the @code{set height} and @code{set
26107 @kindex show height
26108 @item set height @var{lpp}
26109 @itemx set height unlimited
26111 @itemx set width @var{cpl}
26112 @itemx set width unlimited
26114 These @code{set} commands specify a screen height of @var{lpp} lines and
26115 a screen width of @var{cpl} characters. The associated @code{show}
26116 commands display the current settings.
26118 If you specify a height of either @code{unlimited} or zero lines,
26119 @value{GDBN} does not pause during output no matter how long the
26120 output is. This is useful if output is to a file or to an editor
26123 Likewise, you can specify @samp{set width unlimited} or @samp{set
26124 width 0} to prevent @value{GDBN} from wrapping its output.
26126 @item set pagination on
26127 @itemx set pagination off
26128 @kindex set pagination
26129 Turn the output pagination on or off; the default is on. Turning
26130 pagination off is the alternative to @code{set height unlimited}. Note that
26131 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26132 Options, -batch}) also automatically disables pagination.
26134 @item show pagination
26135 @kindex show pagination
26136 Show the current pagination mode.
26139 @node Output Styling
26140 @section Output Styling
26146 @value{GDBN} can style its output on a capable terminal. This is
26147 enabled by default on most systems, but disabled by default when in
26148 batch mode (@pxref{Mode Options}). Various style settings are available;
26149 and styles can also be disabled entirely.
26152 @item set style enabled @samp{on|off}
26153 Enable or disable all styling. The default is host-dependent, with
26154 most hosts defaulting to @samp{on}.
26156 @item show style enabled
26157 Show the current state of styling.
26159 @item set style sources @samp{on|off}
26160 Enable or disable source code styling. This affects whether source
26161 code, such as the output of the @code{list} command, is styled. The
26162 default is @samp{on}. Note that source styling only works if styling
26163 in general is enabled, and if a source highlighting library is
26164 available to @value{GDBN}.
26166 There are two ways that highlighting can be done. First, if
26167 @value{GDBN} was linked with the GNU Source Highlight library, then it
26168 is used. Otherwise, if @value{GDBN} was configured with Python
26169 scripting support, and if the Python Pygments package is available,
26170 then it will be used.
26172 @item show style sources
26173 Show the current state of source code styling.
26175 @item set style disassembler enabled @samp{on|off}
26176 Enable or disable disassembler styling. This affects whether
26177 disassembler output, such as the output of the @code{disassemble}
26178 command, is styled. Disassembler styling only works if styling in
26179 general is enabled (with @code{set style enabled on}), and if a source
26180 highlighting library is available to @value{GDBN}.
26182 To highlight disassembler output, @value{GDBN} must be compiled with
26183 Python support, and the Python Pygments package must be available. If
26184 these requirements are not met then @value{GDBN} will not highlight
26185 disassembler output, even when this option is @samp{on}.
26187 @item show style disassembler enabled
26188 Show the current state of disassembler styling.
26191 Subcommands of @code{set style} control specific forms of styling.
26192 These subcommands all follow the same pattern: each style-able object
26193 can be styled with a foreground color, a background color, and an
26196 For example, the style of file names can be controlled using the
26197 @code{set style filename} group of commands:
26200 @item set style filename background @var{color}
26201 Set the background to @var{color}. Valid colors are @samp{none}
26202 (meaning the terminal's default color), @samp{black}, @samp{red},
26203 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26206 @item set style filename foreground @var{color}
26207 Set the foreground to @var{color}. Valid colors are @samp{none}
26208 (meaning the terminal's default color), @samp{black}, @samp{red},
26209 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26212 @item set style filename intensity @var{value}
26213 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26214 (the default), @samp{bold}, and @samp{dim}.
26217 The @code{show style} command and its subcommands are styling
26218 a style name in their output using its own style.
26219 So, use @command{show style} to see the complete list of styles,
26220 their characteristics and the visual aspect of each style.
26222 The style-able objects are:
26225 Control the styling of file names. By default, this style's
26226 foreground color is green.
26229 Control the styling of function names. These are managed with the
26230 @code{set style function} family of commands. By default, this
26231 style's foreground color is yellow.
26234 Control the styling of variable names. These are managed with the
26235 @code{set style variable} family of commands. By default, this style's
26236 foreground color is cyan.
26239 Control the styling of addresses. These are managed with the
26240 @code{set style address} family of commands. By default, this style's
26241 foreground color is blue.
26244 Control the styling of @value{GDBN}'s version number text. By
26245 default, this style's foreground color is magenta and it has bold
26246 intensity. The version number is displayed in two places, the output
26247 of @command{show version}, and when @value{GDBN} starts up.
26249 In order to control how @value{GDBN} styles the version number at
26250 startup, add the @code{set style version} family of commands to the
26251 early initialization command file (@pxref{Initialization
26255 Control the styling of titles. These are managed with the
26256 @code{set style title} family of commands. By default, this style's
26257 intensity is bold. Commands are using the title style to improve
26258 the readability of large output. For example, the commands
26259 @command{apropos} and @command{help} are using the title style
26260 for the command names.
26263 Control the styling of highlightings. These are managed with the
26264 @code{set style highlight} family of commands. By default, this style's
26265 foreground color is red. Commands are using the highlight style to draw
26266 the user attention to some specific parts of their output. For example,
26267 the command @command{apropos -v REGEXP} uses the highlight style to
26268 mark the documentation parts matching @var{regexp}.
26271 Control the styling of the TUI border. Note that, unlike other
26272 styling options, only the color of the border can be controlled via
26273 @code{set style}. This was done for compatibility reasons, as TUI
26274 controls to set the border's intensity predated the addition of
26275 general styling to @value{GDBN}. @xref{TUI Configuration}.
26277 @item tui-active-border
26278 Control the styling of the active TUI border; that is, the TUI window
26279 that has the focus.
26285 @cindex number representation
26286 @cindex entering numbers
26288 You can always enter numbers in octal, decimal, or hexadecimal in
26289 @value{GDBN} by the usual conventions: octal numbers begin with
26290 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26291 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26292 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26293 10; likewise, the default display for numbers---when no particular
26294 format is specified---is base 10. You can change the default base for
26295 both input and output with the commands described below.
26298 @kindex set input-radix
26299 @item set input-radix @var{base}
26300 Set the default base for numeric input. Supported choices
26301 for @var{base} are decimal 8, 10, or 16. The base must itself be
26302 specified either unambiguously or using the current input radix; for
26306 set input-radix 012
26307 set input-radix 10.
26308 set input-radix 0xa
26312 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26313 leaves the input radix unchanged, no matter what it was, since
26314 @samp{10}, being without any leading or trailing signs of its base, is
26315 interpreted in the current radix. Thus, if the current radix is 16,
26316 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26319 @kindex set output-radix
26320 @item set output-radix @var{base}
26321 Set the default base for numeric display. Supported choices
26322 for @var{base} are decimal 8, 10, or 16. The base must itself be
26323 specified either unambiguously or using the current input radix.
26325 @kindex show input-radix
26326 @item show input-radix
26327 Display the current default base for numeric input.
26329 @kindex show output-radix
26330 @item show output-radix
26331 Display the current default base for numeric display.
26333 @item set radix @r{[}@var{base}@r{]}
26337 These commands set and show the default base for both input and output
26338 of numbers. @code{set radix} sets the radix of input and output to
26339 the same base; without an argument, it resets the radix back to its
26340 default value of 10.
26345 @section Configuring the Current ABI
26347 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26348 application automatically. However, sometimes you need to override its
26349 conclusions. Use these commands to manage @value{GDBN}'s view of the
26355 @cindex Newlib OS ABI and its influence on the longjmp handling
26357 One @value{GDBN} configuration can debug binaries for multiple operating
26358 system targets, either via remote debugging or native emulation.
26359 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26360 but you can override its conclusion using the @code{set osabi} command.
26361 One example where this is useful is in debugging of binaries which use
26362 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26363 not have the same identifying marks that the standard C library for your
26366 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26367 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26368 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26369 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26373 Show the OS ABI currently in use.
26376 With no argument, show the list of registered available OS ABI's.
26378 @item set osabi @var{abi}
26379 Set the current OS ABI to @var{abi}.
26382 @cindex float promotion
26384 Generally, the way that an argument of type @code{float} is passed to a
26385 function depends on whether the function is prototyped. For a prototyped
26386 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26387 according to the architecture's convention for @code{float}. For unprototyped
26388 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26389 @code{double} and then passed.
26391 Unfortunately, some forms of debug information do not reliably indicate whether
26392 a function is prototyped. If @value{GDBN} calls a function that is not marked
26393 as prototyped, it consults @kbd{set coerce-float-to-double}.
26396 @kindex set coerce-float-to-double
26397 @item set coerce-float-to-double
26398 @itemx set coerce-float-to-double on
26399 Arguments of type @code{float} will be promoted to @code{double} when passed
26400 to an unprototyped function. This is the default setting.
26402 @item set coerce-float-to-double off
26403 Arguments of type @code{float} will be passed directly to unprototyped
26406 @kindex show coerce-float-to-double
26407 @item show coerce-float-to-double
26408 Show the current setting of promoting @code{float} to @code{double}.
26412 @kindex show cp-abi
26413 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26414 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26415 used to build your application. @value{GDBN} only fully supports
26416 programs with a single C@t{++} ABI; if your program contains code using
26417 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26418 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26419 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26420 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26421 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26422 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26427 Show the C@t{++} ABI currently in use.
26430 With no argument, show the list of supported C@t{++} ABI's.
26432 @item set cp-abi @var{abi}
26433 @itemx set cp-abi auto
26434 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26438 @section Automatically loading associated files
26439 @cindex auto-loading
26441 @value{GDBN} sometimes reads files with commands and settings automatically,
26442 without being explicitly told so by the user. We call this feature
26443 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26444 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26445 results or introduce security risks (e.g., if the file comes from untrusted
26448 There are various kinds of files @value{GDBN} can automatically load.
26449 In addition to these files, @value{GDBN} supports auto-loading code written
26450 in various extension languages. @xref{Auto-loading extensions}.
26452 Note that loading of these associated files (including the local @file{.gdbinit}
26453 file) requires accordingly configured @code{auto-load safe-path}
26454 (@pxref{Auto-loading safe path}).
26456 For these reasons, @value{GDBN} includes commands and options to let you
26457 control when to auto-load files and which files should be auto-loaded.
26460 @anchor{set auto-load off}
26461 @kindex set auto-load off
26462 @item set auto-load off
26463 Globally disable loading of all auto-loaded files.
26464 You may want to use this command with the @samp{-iex} option
26465 (@pxref{Option -init-eval-command}) such as:
26467 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26470 Be aware that system init file (@pxref{System-wide configuration})
26471 and init files from your home directory (@pxref{Home Directory Init File})
26472 still get read (as they come from generally trusted directories).
26473 To prevent @value{GDBN} from auto-loading even those init files, use the
26474 @option{-nx} option (@pxref{Mode Options}), in addition to
26475 @code{set auto-load no}.
26477 @anchor{show auto-load}
26478 @kindex show auto-load
26479 @item show auto-load
26480 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26484 (gdb) show auto-load
26485 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26486 libthread-db: Auto-loading of inferior specific libthread_db is on.
26487 local-gdbinit: Auto-loading of .gdbinit script from current directory
26489 python-scripts: Auto-loading of Python scripts is on.
26490 safe-path: List of directories from which it is safe to auto-load files
26491 is $debugdir:$datadir/auto-load.
26492 scripts-directory: List of directories from which to load auto-loaded scripts
26493 is $debugdir:$datadir/auto-load.
26496 @anchor{info auto-load}
26497 @kindex info auto-load
26498 @item info auto-load
26499 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26503 (gdb) info auto-load
26506 Yes /home/user/gdb/gdb-gdb.gdb
26507 libthread-db: No auto-loaded libthread-db.
26508 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26512 Yes /home/user/gdb/gdb-gdb.py
26516 These are @value{GDBN} control commands for the auto-loading:
26518 @multitable @columnfractions .5 .5
26519 @item @xref{set auto-load off}.
26520 @tab Disable auto-loading globally.
26521 @item @xref{show auto-load}.
26522 @tab Show setting of all kinds of files.
26523 @item @xref{info auto-load}.
26524 @tab Show state of all kinds of files.
26525 @item @xref{set auto-load gdb-scripts}.
26526 @tab Control for @value{GDBN} command scripts.
26527 @item @xref{show auto-load gdb-scripts}.
26528 @tab Show setting of @value{GDBN} command scripts.
26529 @item @xref{info auto-load gdb-scripts}.
26530 @tab Show state of @value{GDBN} command scripts.
26531 @item @xref{set auto-load python-scripts}.
26532 @tab Control for @value{GDBN} Python scripts.
26533 @item @xref{show auto-load python-scripts}.
26534 @tab Show setting of @value{GDBN} Python scripts.
26535 @item @xref{info auto-load python-scripts}.
26536 @tab Show state of @value{GDBN} Python scripts.
26537 @item @xref{set auto-load guile-scripts}.
26538 @tab Control for @value{GDBN} Guile scripts.
26539 @item @xref{show auto-load guile-scripts}.
26540 @tab Show setting of @value{GDBN} Guile scripts.
26541 @item @xref{info auto-load guile-scripts}.
26542 @tab Show state of @value{GDBN} Guile scripts.
26543 @item @xref{set auto-load scripts-directory}.
26544 @tab Control for @value{GDBN} auto-loaded scripts location.
26545 @item @xref{show auto-load scripts-directory}.
26546 @tab Show @value{GDBN} auto-loaded scripts location.
26547 @item @xref{add-auto-load-scripts-directory}.
26548 @tab Add directory for auto-loaded scripts location list.
26549 @item @xref{set auto-load local-gdbinit}.
26550 @tab Control for init file in the current directory.
26551 @item @xref{show auto-load local-gdbinit}.
26552 @tab Show setting of init file in the current directory.
26553 @item @xref{info auto-load local-gdbinit}.
26554 @tab Show state of init file in the current directory.
26555 @item @xref{set auto-load libthread-db}.
26556 @tab Control for thread debugging library.
26557 @item @xref{show auto-load libthread-db}.
26558 @tab Show setting of thread debugging library.
26559 @item @xref{info auto-load libthread-db}.
26560 @tab Show state of thread debugging library.
26561 @item @xref{set auto-load safe-path}.
26562 @tab Control directories trusted for automatic loading.
26563 @item @xref{show auto-load safe-path}.
26564 @tab Show directories trusted for automatic loading.
26565 @item @xref{add-auto-load-safe-path}.
26566 @tab Add directory trusted for automatic loading.
26570 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26571 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26573 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26574 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26577 @node Init File in the Current Directory
26578 @subsection Automatically loading init file in the current directory
26579 @cindex auto-loading init file in the current directory
26581 By default, @value{GDBN} reads and executes the canned sequences of commands
26582 from init file (if any) in the current working directory,
26583 see @ref{Init File in the Current Directory during Startup}.
26585 Note that loading of this local @file{.gdbinit} file also requires accordingly
26586 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26589 @anchor{set auto-load local-gdbinit}
26590 @kindex set auto-load local-gdbinit
26591 @item set auto-load local-gdbinit [on|off]
26592 Enable or disable the auto-loading of canned sequences of commands
26593 (@pxref{Sequences}) found in init file in the current directory.
26595 @anchor{show auto-load local-gdbinit}
26596 @kindex show auto-load local-gdbinit
26597 @item show auto-load local-gdbinit
26598 Show whether auto-loading of canned sequences of commands from init file in the
26599 current directory is enabled or disabled.
26601 @anchor{info auto-load local-gdbinit}
26602 @kindex info auto-load local-gdbinit
26603 @item info auto-load local-gdbinit
26604 Print whether canned sequences of commands from init file in the
26605 current directory have been auto-loaded.
26608 @node libthread_db.so.1 file
26609 @subsection Automatically loading thread debugging library
26610 @cindex auto-loading libthread_db.so.1
26612 This feature is currently present only on @sc{gnu}/Linux native hosts.
26614 @value{GDBN} reads in some cases thread debugging library from places specific
26615 to the inferior (@pxref{set libthread-db-search-path}).
26617 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26618 without checking this @samp{set auto-load libthread-db} switch as system
26619 libraries have to be trusted in general. In all other cases of
26620 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26621 auto-load libthread-db} is enabled before trying to open such thread debugging
26624 Note that loading of this debugging library also requires accordingly configured
26625 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26628 @anchor{set auto-load libthread-db}
26629 @kindex set auto-load libthread-db
26630 @item set auto-load libthread-db [on|off]
26631 Enable or disable the auto-loading of inferior specific thread debugging library.
26633 @anchor{show auto-load libthread-db}
26634 @kindex show auto-load libthread-db
26635 @item show auto-load libthread-db
26636 Show whether auto-loading of inferior specific thread debugging library is
26637 enabled or disabled.
26639 @anchor{info auto-load libthread-db}
26640 @kindex info auto-load libthread-db
26641 @item info auto-load libthread-db
26642 Print the list of all loaded inferior specific thread debugging libraries and
26643 for each such library print list of inferior @var{pid}s using it.
26646 @node Auto-loading safe path
26647 @subsection Security restriction for auto-loading
26648 @cindex auto-loading safe-path
26650 As the files of inferior can come from untrusted source (such as submitted by
26651 an application user) @value{GDBN} does not always load any files automatically.
26652 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26653 directories trusted for loading files not explicitly requested by user.
26654 Each directory can also be a shell wildcard pattern.
26656 If the path is not set properly you will see a warning and the file will not
26661 Reading symbols from /home/user/gdb/gdb...
26662 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26663 declined by your `auto-load safe-path' set
26664 to "$debugdir:$datadir/auto-load".
26665 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26666 declined by your `auto-load safe-path' set
26667 to "$debugdir:$datadir/auto-load".
26671 To instruct @value{GDBN} to go ahead and use the init files anyway,
26672 invoke @value{GDBN} like this:
26675 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26678 The list of trusted directories is controlled by the following commands:
26681 @anchor{set auto-load safe-path}
26682 @kindex set auto-load safe-path
26683 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26684 Set the list of directories (and their subdirectories) trusted for automatic
26685 loading and execution of scripts. You can also enter a specific trusted file.
26686 Each directory can also be a shell wildcard pattern; wildcards do not match
26687 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26688 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26689 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26690 its default value as specified during @value{GDBN} compilation.
26692 The list of directories uses path separator (@samp{:} on GNU and Unix
26693 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26694 to the @env{PATH} environment variable.
26696 @anchor{show auto-load safe-path}
26697 @kindex show auto-load safe-path
26698 @item show auto-load safe-path
26699 Show the list of directories trusted for automatic loading and execution of
26702 @anchor{add-auto-load-safe-path}
26703 @kindex add-auto-load-safe-path
26704 @item add-auto-load-safe-path
26705 Add an entry (or list of entries) to the list of directories trusted for
26706 automatic loading and execution of scripts. Multiple entries may be delimited
26707 by the host platform path separator in use.
26710 This variable defaults to what @code{--with-auto-load-dir} has been configured
26711 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26712 substitution applies the same as for @ref{set auto-load scripts-directory}.
26713 The default @code{set auto-load safe-path} value can be also overriden by
26714 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26716 Setting this variable to @file{/} disables this security protection,
26717 corresponding @value{GDBN} configuration option is
26718 @option{--without-auto-load-safe-path}.
26719 This variable is supposed to be set to the system directories writable by the
26720 system superuser only. Users can add their source directories in init files in
26721 their home directories (@pxref{Home Directory Init File}). See also deprecated
26722 init file in the current directory
26723 (@pxref{Init File in the Current Directory during Startup}).
26725 To force @value{GDBN} to load the files it declined to load in the previous
26726 example, you could use one of the following ways:
26729 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26730 Specify this trusted directory (or a file) as additional component of the list.
26731 You have to specify also any existing directories displayed by
26732 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26734 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26735 Specify this directory as in the previous case but just for a single
26736 @value{GDBN} session.
26738 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26739 Disable auto-loading safety for a single @value{GDBN} session.
26740 This assumes all the files you debug during this @value{GDBN} session will come
26741 from trusted sources.
26743 @item @kbd{./configure --without-auto-load-safe-path}
26744 During compilation of @value{GDBN} you may disable any auto-loading safety.
26745 This assumes all the files you will ever debug with this @value{GDBN} come from
26749 On the other hand you can also explicitly forbid automatic files loading which
26750 also suppresses any such warning messages:
26753 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26754 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26756 @item @file{~/.gdbinit}: @samp{set auto-load no}
26757 Disable auto-loading globally for the user
26758 (@pxref{Home Directory Init File}). While it is improbable, you could also
26759 use system init file instead (@pxref{System-wide configuration}).
26762 This setting applies to the file names as entered by user. If no entry matches
26763 @value{GDBN} tries as a last resort to also resolve all the file names into
26764 their canonical form (typically resolving symbolic links) and compare the
26765 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26766 own before starting the comparison so a canonical form of directories is
26767 recommended to be entered.
26769 @node Auto-loading verbose mode
26770 @subsection Displaying files tried for auto-load
26771 @cindex auto-loading verbose mode
26773 For better visibility of all the file locations where you can place scripts to
26774 be auto-loaded with inferior --- or to protect yourself against accidental
26775 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26776 all the files attempted to be loaded. Both existing and non-existing files may
26779 For example the list of directories from which it is safe to auto-load files
26780 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26781 may not be too obvious while setting it up.
26784 (gdb) set debug auto-load on
26785 (gdb) file ~/src/t/true
26786 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26787 for objfile "/tmp/true".
26788 auto-load: Updating directories of "/usr:/opt".
26789 auto-load: Using directory "/usr".
26790 auto-load: Using directory "/opt".
26791 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26792 by your `auto-load safe-path' set to "/usr:/opt".
26796 @anchor{set debug auto-load}
26797 @kindex set debug auto-load
26798 @item set debug auto-load [on|off]
26799 Set whether to print the filenames attempted to be auto-loaded.
26801 @anchor{show debug auto-load}
26802 @kindex show debug auto-load
26803 @item show debug auto-load
26804 Show whether printing of the filenames attempted to be auto-loaded is turned
26808 @node Messages/Warnings
26809 @section Optional Warnings and Messages
26811 @cindex verbose operation
26812 @cindex optional warnings
26813 By default, @value{GDBN} is silent about its inner workings. If you are
26814 running on a slow machine, you may want to use the @code{set verbose}
26815 command. This makes @value{GDBN} tell you when it does a lengthy
26816 internal operation, so you will not think it has crashed.
26818 Currently, the messages controlled by @code{set verbose} are those
26819 which announce that the symbol table for a source file is being read;
26820 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26823 @kindex set verbose
26824 @item set verbose on
26825 Enables @value{GDBN} output of certain informational messages.
26827 @item set verbose off
26828 Disables @value{GDBN} output of certain informational messages.
26830 @kindex show verbose
26832 Displays whether @code{set verbose} is on or off.
26835 By default, if @value{GDBN} encounters bugs in the symbol table of an
26836 object file, it is silent; but if you are debugging a compiler, you may
26837 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26842 @kindex set complaints
26843 @item set complaints @var{limit}
26844 Permits @value{GDBN} to output @var{limit} complaints about each type of
26845 unusual symbols before becoming silent about the problem. Set
26846 @var{limit} to zero to suppress all complaints; set it to a large number
26847 to prevent complaints from being suppressed.
26849 @kindex show complaints
26850 @item show complaints
26851 Displays how many symbol complaints @value{GDBN} is permitted to produce.
26855 @anchor{confirmation requests}
26856 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
26857 lot of stupid questions to confirm certain commands. For example, if
26858 you try to run a program which is already running:
26862 The program being debugged has been started already.
26863 Start it from the beginning? (y or n)
26866 If you are willing to unflinchingly face the consequences of your own
26867 commands, you can disable this ``feature'':
26871 @kindex set confirm
26873 @cindex confirmation
26874 @cindex stupid questions
26875 @item set confirm off
26876 Disables confirmation requests. Note that running @value{GDBN} with
26877 the @option{--batch} option (@pxref{Mode Options, -batch}) also
26878 automatically disables confirmation requests.
26880 @item set confirm on
26881 Enables confirmation requests (the default).
26883 @kindex show confirm
26885 Displays state of confirmation requests.
26889 @cindex command tracing
26890 If you need to debug user-defined commands or sourced files you may find it
26891 useful to enable @dfn{command tracing}. In this mode each command will be
26892 printed as it is executed, prefixed with one or more @samp{+} symbols, the
26893 quantity denoting the call depth of each command.
26896 @kindex set trace-commands
26897 @cindex command scripts, debugging
26898 @item set trace-commands on
26899 Enable command tracing.
26900 @item set trace-commands off
26901 Disable command tracing.
26902 @item show trace-commands
26903 Display the current state of command tracing.
26906 @node Debugging Output
26907 @section Optional Messages about Internal Happenings
26908 @cindex optional debugging messages
26910 @value{GDBN} has commands that enable optional debugging messages from
26911 various @value{GDBN} subsystems; normally these commands are of
26912 interest to @value{GDBN} maintainers, or when reporting a bug. This
26913 section documents those commands.
26916 @kindex set exec-done-display
26917 @item set exec-done-display
26918 Turns on or off the notification of asynchronous commands'
26919 completion. When on, @value{GDBN} will print a message when an
26920 asynchronous command finishes its execution. The default is off.
26921 @kindex show exec-done-display
26922 @item show exec-done-display
26923 Displays the current setting of asynchronous command completion
26927 @cindex ARM AArch64
26928 @item set debug aarch64
26929 Turns on or off display of debugging messages related to ARM AArch64.
26930 The default is off.
26932 @item show debug aarch64
26933 Displays the current state of displaying debugging messages related to
26936 @cindex gdbarch debugging info
26937 @cindex architecture debugging info
26938 @item set debug arch
26939 Turns on or off display of gdbarch debugging info. The default is off
26940 @item show debug arch
26941 Displays the current state of displaying gdbarch debugging info.
26943 @item set debug aix-solib
26944 @cindex AIX shared library debugging
26945 Control display of debugging messages from the AIX shared library
26946 support module. The default is off.
26947 @item show debug aix-solib
26948 Show the current state of displaying AIX shared library debugging messages.
26950 @item set debug aix-thread
26951 @cindex AIX threads
26952 Display debugging messages about inner workings of the AIX thread
26954 @item show debug aix-thread
26955 Show the current state of AIX thread debugging info display.
26957 @item set debug check-physname
26959 Check the results of the ``physname'' computation. When reading DWARF
26960 debugging information for C@t{++}, @value{GDBN} attempts to compute
26961 each entity's name. @value{GDBN} can do this computation in two
26962 different ways, depending on exactly what information is present.
26963 When enabled, this setting causes @value{GDBN} to compute the names
26964 both ways and display any discrepancies.
26965 @item show debug check-physname
26966 Show the current state of ``physname'' checking.
26968 @item set debug coff-pe-read
26969 @cindex COFF/PE exported symbols
26970 Control display of debugging messages related to reading of COFF/PE
26971 exported symbols. The default is off.
26972 @item show debug coff-pe-read
26973 Displays the current state of displaying debugging messages related to
26974 reading of COFF/PE exported symbols.
26976 @item set debug dwarf-die
26978 Dump DWARF DIEs after they are read in.
26979 The value is the number of nesting levels to print.
26980 A value of zero turns off the display.
26981 @item show debug dwarf-die
26982 Show the current state of DWARF DIE debugging.
26984 @item set debug dwarf-line
26985 @cindex DWARF Line Tables
26986 Turns on or off display of debugging messages related to reading
26987 DWARF line tables. The default is 0 (off).
26988 A value of 1 provides basic information.
26989 A value greater than 1 provides more verbose information.
26990 @item show debug dwarf-line
26991 Show the current state of DWARF line table debugging.
26993 @item set debug dwarf-read
26994 @cindex DWARF Reading
26995 Turns on or off display of debugging messages related to reading
26996 DWARF debug info. The default is 0 (off).
26997 A value of 1 provides basic information.
26998 A value greater than 1 provides more verbose information.
26999 @item show debug dwarf-read
27000 Show the current state of DWARF reader debugging.
27002 @item set debug displaced
27003 @cindex displaced stepping debugging info
27004 Turns on or off display of @value{GDBN} debugging info for the
27005 displaced stepping support. The default is off.
27006 @item show debug displaced
27007 Displays the current state of displaying @value{GDBN} debugging info
27008 related to displaced stepping.
27010 @item set debug event
27011 @cindex event debugging info
27012 Turns on or off display of @value{GDBN} event debugging info. The
27014 @item show debug event
27015 Displays the current state of displaying @value{GDBN} event debugging
27018 @item set debug event-loop
27019 @cindex event-loop debugging
27020 Controls output of debugging info about the event loop. The possible
27021 values are @samp{off}, @samp{all} (shows all debugging info) and
27022 @samp{all-except-ui} (shows all debugging info except those about
27023 UI-related events).
27024 @item show debug event-loop
27025 Shows the current state of displaying debugging info about the event
27028 @item set debug expression
27029 @cindex expression debugging info
27030 Turns on or off display of debugging info about @value{GDBN}
27031 expression parsing. The default is off.
27032 @item show debug expression
27033 Displays the current state of displaying debugging info about
27034 @value{GDBN} expression parsing.
27036 @item set debug fbsd-lwp
27037 @cindex FreeBSD LWP debug messages
27038 Turns on or off debugging messages from the FreeBSD LWP debug support.
27039 @item show debug fbsd-lwp
27040 Show the current state of FreeBSD LWP debugging messages.
27042 @item set debug fbsd-nat
27043 @cindex FreeBSD native target debug messages
27044 Turns on or off debugging messages from the FreeBSD native target.
27045 @item show debug fbsd-nat
27046 Show the current state of FreeBSD native target debugging messages.
27048 @item set debug fortran-array-slicing
27049 @cindex fortran array slicing debugging info
27050 Turns on or off display of @value{GDBN} Fortran array slicing
27051 debugging info. The default is off.
27053 @item show debug fortran-array-slicing
27054 Displays the current state of displaying @value{GDBN} Fortran array
27055 slicing debugging info.
27057 @item set debug frame
27058 @cindex frame debugging info
27059 Turns on or off display of @value{GDBN} frame debugging info. The
27061 @item show debug frame
27062 Displays the current state of displaying @value{GDBN} frame debugging
27065 @item set debug gnu-nat
27066 @cindex @sc{gnu}/Hurd debug messages
27067 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27068 @item show debug gnu-nat
27069 Show the current state of @sc{gnu}/Hurd debugging messages.
27071 @item set debug infrun
27072 @cindex inferior debugging info
27073 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27074 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27075 for implementing operations such as single-stepping the inferior.
27076 @item show debug infrun
27077 Displays the current state of @value{GDBN} inferior debugging.
27079 @item set debug jit
27080 @cindex just-in-time compilation, debugging messages
27081 Turn on or off debugging messages from JIT debug support.
27082 @item show debug jit
27083 Displays the current state of @value{GDBN} JIT debugging.
27085 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27086 @cindex @sc{gnu}/Linux native target debug messages
27087 @cindex Linux native targets
27088 Turn on or off debugging messages from the Linux native target debug support.
27089 @item show debug linux-nat
27090 Show the current state of Linux native target debugging messages.
27092 @item set debug linux-namespaces
27093 @cindex @sc{gnu}/Linux namespaces debug messages
27094 Turn on or off debugging messages from the Linux namespaces debug support.
27095 @item show debug linux-namespaces
27096 Show the current state of Linux namespaces debugging messages.
27098 @item set debug mach-o
27099 @cindex Mach-O symbols processing
27100 Control display of debugging messages related to Mach-O symbols
27101 processing. The default is off.
27102 @item show debug mach-o
27103 Displays the current state of displaying debugging messages related to
27104 reading of COFF/PE exported symbols.
27106 @item set debug notification
27107 @cindex remote async notification debugging info
27108 Turn on or off debugging messages about remote async notification.
27109 The default is off.
27110 @item show debug notification
27111 Displays the current state of remote async notification debugging messages.
27113 @item set debug observer
27114 @cindex observer debugging info
27115 Turns on or off display of @value{GDBN} observer debugging. This
27116 includes info such as the notification of observable events.
27117 @item show debug observer
27118 Displays the current state of observer debugging.
27120 @item set debug overload
27121 @cindex C@t{++} overload debugging info
27122 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27123 info. This includes info such as ranking of functions, etc. The default
27125 @item show debug overload
27126 Displays the current state of displaying @value{GDBN} C@t{++} overload
27129 @cindex expression parser, debugging info
27130 @cindex debug expression parser
27131 @item set debug parser
27132 Turns on or off the display of expression parser debugging output.
27133 Internally, this sets the @code{yydebug} variable in the expression
27134 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27135 details. The default is off.
27136 @item show debug parser
27137 Show the current state of expression parser debugging.
27139 @cindex packets, reporting on stdout
27140 @cindex serial connections, debugging
27141 @cindex debug remote protocol
27142 @cindex remote protocol debugging
27143 @cindex display remote packets
27144 @item set debug remote
27145 Turns on or off display of reports on all packets sent back and forth across
27146 the serial line to the remote machine. The info is printed on the
27147 @value{GDBN} standard output stream. The default is off.
27148 @item show debug remote
27149 Displays the state of display of remote packets.
27151 @item set debug remote-packet-max-chars
27152 Sets the maximum number of characters to display for each remote packet when
27153 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27154 displaying lengthy remote packets and polluting the console.
27156 The default value is @code{512}, which means @value{GDBN} will truncate each
27157 remote packet after 512 bytes.
27159 Setting this option to @code{unlimited} will disable truncation and will output
27160 the full length of the remote packets.
27161 @item show debug remote-packet-max-chars
27162 Displays the number of bytes to output for remote packet debugging.
27164 @item set debug separate-debug-file
27165 Turns on or off display of debug output about separate debug file search.
27166 @item show debug separate-debug-file
27167 Displays the state of separate debug file search debug output.
27169 @item set debug serial
27170 Turns on or off display of @value{GDBN} serial debugging info. The
27172 @item show debug serial
27173 Displays the current state of displaying @value{GDBN} serial debugging
27176 @item set debug solib-frv
27177 @cindex FR-V shared-library debugging
27178 Turn on or off debugging messages for FR-V shared-library code.
27179 @item show debug solib-frv
27180 Display the current state of FR-V shared-library code debugging
27183 @item set debug symbol-lookup
27184 @cindex symbol lookup
27185 Turns on or off display of debugging messages related to symbol lookup.
27186 The default is 0 (off).
27187 A value of 1 provides basic information.
27188 A value greater than 1 provides more verbose information.
27189 @item show debug symbol-lookup
27190 Show the current state of symbol lookup debugging messages.
27192 @item set debug symfile
27193 @cindex symbol file functions
27194 Turns on or off display of debugging messages related to symbol file functions.
27195 The default is off. @xref{Files}.
27196 @item show debug symfile
27197 Show the current state of symbol file debugging messages.
27199 @item set debug symtab-create
27200 @cindex symbol table creation
27201 Turns on or off display of debugging messages related to symbol table creation.
27202 The default is 0 (off).
27203 A value of 1 provides basic information.
27204 A value greater than 1 provides more verbose information.
27205 @item show debug symtab-create
27206 Show the current state of symbol table creation debugging.
27208 @item set debug target
27209 @cindex target debugging info
27210 Turns on or off display of @value{GDBN} target debugging info. This info
27211 includes what is going on at the target level of GDB, as it happens. The
27212 default is 0. Set it to 1 to track events, and to 2 to also track the
27213 value of large memory transfers.
27214 @item show debug target
27215 Displays the current state of displaying @value{GDBN} target debugging
27218 @item set debug timestamp
27219 @cindex timestamping debugging info
27220 Turns on or off display of timestamps with @value{GDBN} debugging info.
27221 When enabled, seconds and microseconds are displayed before each debugging
27223 @item show debug timestamp
27224 Displays the current state of displaying timestamps with @value{GDBN}
27227 @item set debug varobj
27228 @cindex variable object debugging info
27229 Turns on or off display of @value{GDBN} variable object debugging
27230 info. The default is off.
27231 @item show debug varobj
27232 Displays the current state of displaying @value{GDBN} variable object
27235 @item set debug xml
27236 @cindex XML parser debugging
27237 Turn on or off debugging messages for built-in XML parsers.
27238 @item show debug xml
27239 Displays the current state of XML debugging messages.
27242 @node Other Misc Settings
27243 @section Other Miscellaneous Settings
27244 @cindex miscellaneous settings
27247 @kindex set interactive-mode
27248 @item set interactive-mode
27249 If @code{on}, forces @value{GDBN} to assume that GDB was started
27250 in a terminal. In practice, this means that @value{GDBN} should wait
27251 for the user to answer queries generated by commands entered at
27252 the command prompt. If @code{off}, forces @value{GDBN} to operate
27253 in the opposite mode, and it uses the default answers to all queries.
27254 If @code{auto} (the default), @value{GDBN} tries to determine whether
27255 its standard input is a terminal, and works in interactive-mode if it
27256 is, non-interactively otherwise.
27258 In the vast majority of cases, the debugger should be able to guess
27259 correctly which mode should be used. But this setting can be useful
27260 in certain specific cases, such as running a MinGW @value{GDBN}
27261 inside a cygwin window.
27263 @kindex show interactive-mode
27264 @item show interactive-mode
27265 Displays whether the debugger is operating in interactive mode or not.
27269 @kindex set suppress-cli-notifications
27270 @item set suppress-cli-notifications
27271 If @code{on}, command-line-interface (CLI) notifications that are
27272 printed by @value{GDBN} are suppressed. If @code{off}, the
27273 notifications are printed as usual. The default value is @code{off}.
27274 CLI notifications occur when you change the selected context or when
27275 the program being debugged stops, as detailed below.
27278 @item User-selected context changes:
27279 When you change the selected context (i.e.@: the current inferior,
27280 thread and/or the frame), @value{GDBN} prints information about the
27281 new context. For example, the default behavior is below:
27285 [Switching to inferior 1 [process 634] (/tmp/test)]
27286 [Switching to thread 1 (process 634)]
27287 #0 main () at test.c:3
27292 When the notifications are suppressed, the new context is not printed:
27295 (gdb) set suppress-cli-notifications on
27300 @item The program being debugged stops:
27301 When the program you are debugging stops (e.g.@: because of hitting a
27302 breakpoint, completing source-stepping, an interrupt, etc.),
27303 @value{GDBN} prints information about the stop event. For example,
27304 below is a breakpoint hit:
27307 (gdb) break test.c:3
27308 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27312 Breakpoint 2, main () at test.c:3
27317 When the notifications are suppressed, the output becomes:
27320 (gdb) break test.c:3
27321 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27322 (gdb) set suppress-cli-notifications on
27328 Suppressing CLI notifications may be useful in scripts to obtain a
27329 reduced output from a list of commands.
27332 @kindex show suppress-cli-notifications
27333 @item show suppress-cli-notifications
27334 Displays whether printing CLI notifications is suppressed or not.
27337 @node Extending GDB
27338 @chapter Extending @value{GDBN}
27339 @cindex extending GDB
27341 @value{GDBN} provides several mechanisms for extension.
27342 @value{GDBN} also provides the ability to automatically load
27343 extensions when it reads a file for debugging. This allows the
27344 user to automatically customize @value{GDBN} for the program
27347 To facilitate the use of extension languages, @value{GDBN} is capable
27348 of evaluating the contents of a file. When doing so, @value{GDBN}
27349 can recognize which extension language is being used by looking at
27350 the filename extension. Files with an unrecognized filename extension
27351 are always treated as a @value{GDBN} Command Files.
27352 @xref{Command Files,, Command files}.
27354 You can control how @value{GDBN} evaluates these files with the following
27358 @kindex set script-extension
27359 @kindex show script-extension
27360 @item set script-extension off
27361 All scripts are always evaluated as @value{GDBN} Command Files.
27363 @item set script-extension soft
27364 The debugger determines the scripting language based on filename
27365 extension. If this scripting language is supported, @value{GDBN}
27366 evaluates the script using that language. Otherwise, it evaluates
27367 the file as a @value{GDBN} Command File.
27369 @item set script-extension strict
27370 The debugger determines the scripting language based on filename
27371 extension, and evaluates the script using that language. If the
27372 language is not supported, then the evaluation fails.
27374 @item show script-extension
27375 Display the current value of the @code{script-extension} option.
27379 @ifset SYSTEM_GDBINIT_DIR
27380 This setting is not used for files in the system-wide gdbinit directory.
27381 Files in that directory must have an extension matching their language,
27382 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27383 commands. @xref{Startup}.
27387 * Sequences:: Canned Sequences of @value{GDBN} Commands
27388 * Aliases:: Command Aliases
27389 * Python:: Extending @value{GDBN} using Python
27390 * Guile:: Extending @value{GDBN} using Guile
27391 * Auto-loading extensions:: Automatically loading extensions
27392 * Multiple Extension Languages:: Working with multiple extension languages
27396 @section Canned Sequences of Commands
27398 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27399 Command Lists}), @value{GDBN} provides two ways to store sequences of
27400 commands for execution as a unit: user-defined commands and command
27404 * Define:: How to define your own commands
27405 * Hooks:: Hooks for user-defined commands
27406 * Command Files:: How to write scripts of commands to be stored in a file
27407 * Output:: Commands for controlled output
27408 * Auto-loading sequences:: Controlling auto-loaded command files
27412 @subsection User-defined Commands
27414 @cindex user-defined command
27415 @cindex arguments, to user-defined commands
27416 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27417 which you assign a new name as a command. This is done with the
27418 @code{define} command. User commands may accept an unlimited number of arguments
27419 separated by whitespace. Arguments are accessed within the user command
27420 via @code{$arg0@dots{}$argN}. A trivial example:
27424 print $arg0 + $arg1 + $arg2
27429 To execute the command use:
27436 This defines the command @code{adder}, which prints the sum of
27437 its three arguments. Note the arguments are text substitutions, so they may
27438 reference variables, use complex expressions, or even perform inferior
27441 @cindex argument count in user-defined commands
27442 @cindex how many arguments (user-defined commands)
27443 In addition, @code{$argc} may be used to find out how many arguments have
27449 print $arg0 + $arg1
27452 print $arg0 + $arg1 + $arg2
27457 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27458 to process a variable number of arguments:
27465 eval "set $sum = $sum + $arg%d", $i
27475 @item define @var{commandname}
27476 Define a command named @var{commandname}. If there is already a command
27477 by that name, you are asked to confirm that you want to redefine it.
27478 The argument @var{commandname} may be a bare command name consisting of letters,
27479 numbers, dashes, dots, and underscores. It may also start with any
27480 predefined or user-defined prefix command.
27481 For example, @samp{define target my-target} creates
27482 a user-defined @samp{target my-target} command.
27484 The definition of the command is made up of other @value{GDBN} command lines,
27485 which are given following the @code{define} command. The end of these
27486 commands is marked by a line containing @code{end}.
27489 @kindex end@r{ (user-defined commands)}
27490 @item document @var{commandname}
27491 Document the user-defined command @var{commandname}, so that it can be
27492 accessed by @code{help}. The command @var{commandname} must already be
27493 defined. This command reads lines of documentation just as @code{define}
27494 reads the lines of the command definition, ending with @code{end}.
27495 After the @code{document} command is finished, @code{help} on command
27496 @var{commandname} displays the documentation you have written.
27498 You may use the @code{document} command again to change the
27499 documentation of a command. Redefining the command with @code{define}
27500 does not change the documentation.
27502 @kindex define-prefix
27503 @item define-prefix @var{commandname}
27504 Define or mark the command @var{commandname} as a user-defined prefix
27505 command. Once marked, @var{commandname} can be used as prefix command
27506 by the @code{define} command.
27507 Note that @code{define-prefix} can be used with a not yet defined
27508 @var{commandname}. In such a case, @var{commandname} is defined as
27509 an empty user-defined command.
27510 In case you redefine a command that was marked as a user-defined
27511 prefix command, the subcommands of the redefined command are kept
27512 (and @value{GDBN} indicates so to the user).
27516 (gdb) define-prefix abc
27517 (gdb) define-prefix abc def
27518 (gdb) define abc def
27519 Type commands for definition of "abc def".
27520 End with a line saying just "end".
27521 >echo command initial def\n
27523 (gdb) define abc def ghi
27524 Type commands for definition of "abc def ghi".
27525 End with a line saying just "end".
27526 >echo command ghi\n
27528 (gdb) define abc def
27529 Keeping subcommands of prefix command "def".
27530 Redefine command "def"? (y or n) y
27531 Type commands for definition of "abc def".
27532 End with a line saying just "end".
27533 >echo command def\n
27542 @kindex dont-repeat
27543 @cindex don't repeat command
27545 Used inside a user-defined command, this tells @value{GDBN} that this
27546 command should not be repeated when the user hits @key{RET}
27547 (@pxref{Command Syntax, repeat last command}).
27549 @kindex help user-defined
27550 @item help user-defined
27551 List all user-defined commands and all python commands defined in class
27552 COMMAND_USER. The first line of the documentation or docstring is
27557 @itemx show user @var{commandname}
27558 Display the @value{GDBN} commands used to define @var{commandname} (but
27559 not its documentation). If no @var{commandname} is given, display the
27560 definitions for all user-defined commands.
27561 This does not work for user-defined python commands.
27563 @cindex infinite recursion in user-defined commands
27564 @kindex show max-user-call-depth
27565 @kindex set max-user-call-depth
27566 @item show max-user-call-depth
27567 @itemx set max-user-call-depth
27568 The value of @code{max-user-call-depth} controls how many recursion
27569 levels are allowed in user-defined commands before @value{GDBN} suspects an
27570 infinite recursion and aborts the command.
27571 This does not apply to user-defined python commands.
27574 In addition to the above commands, user-defined commands frequently
27575 use control flow commands, described in @ref{Command Files}.
27577 When user-defined commands are executed, the
27578 commands of the definition are not printed. An error in any command
27579 stops execution of the user-defined command.
27581 If used interactively, commands that would ask for confirmation proceed
27582 without asking when used inside a user-defined command. Many @value{GDBN}
27583 commands that normally print messages to say what they are doing omit the
27584 messages when used in a user-defined command.
27587 @subsection User-defined Command Hooks
27588 @cindex command hooks
27589 @cindex hooks, for commands
27590 @cindex hooks, pre-command
27593 You may define @dfn{hooks}, which are a special kind of user-defined
27594 command. Whenever you run the command @samp{foo}, if the user-defined
27595 command @samp{hook-foo} exists, it is executed (with no arguments)
27596 before that command.
27598 @cindex hooks, post-command
27600 A hook may also be defined which is run after the command you executed.
27601 Whenever you run the command @samp{foo}, if the user-defined command
27602 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27603 that command. Post-execution hooks may exist simultaneously with
27604 pre-execution hooks, for the same command.
27606 It is valid for a hook to call the command which it hooks. If this
27607 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27609 @c It would be nice if hookpost could be passed a parameter indicating
27610 @c if the command it hooks executed properly or not. FIXME!
27612 @kindex stop@r{, a pseudo-command}
27613 In addition, a pseudo-command, @samp{stop} exists. Defining
27614 (@samp{hook-stop}) makes the associated commands execute every time
27615 execution stops in your program: before breakpoint commands are run,
27616 displays are printed, or the stack frame is printed.
27618 For example, to ignore @code{SIGALRM} signals while
27619 single-stepping, but treat them normally during normal execution,
27624 handle SIGALRM nopass
27628 handle SIGALRM pass
27631 define hook-continue
27632 handle SIGALRM pass
27636 As a further example, to hook at the beginning and end of the @code{echo}
27637 command, and to add extra text to the beginning and end of the message,
27645 define hookpost-echo
27649 (@value{GDBP}) echo Hello World
27650 <<<---Hello World--->>>
27655 You can define a hook for any single-word command in @value{GDBN}, but
27656 not for command aliases; you should define a hook for the basic command
27657 name, e.g.@: @code{backtrace} rather than @code{bt}.
27658 @c FIXME! So how does Joe User discover whether a command is an alias
27660 You can hook a multi-word command by adding @code{hook-} or
27661 @code{hookpost-} to the last word of the command, e.g.@:
27662 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27664 If an error occurs during the execution of your hook, execution of
27665 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27666 (before the command that you actually typed had a chance to run).
27668 If you try to define a hook which does not match any known command, you
27669 get a warning from the @code{define} command.
27671 @node Command Files
27672 @subsection Command Files
27674 @cindex command files
27675 @cindex scripting commands
27676 A command file for @value{GDBN} is a text file made of lines that are
27677 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27678 also be included. An empty line in a command file does nothing; it
27679 does not mean to repeat the last command, as it would from the
27682 You can request the execution of a command file with the @code{source}
27683 command. Note that the @code{source} command is also used to evaluate
27684 scripts that are not Command Files. The exact behavior can be configured
27685 using the @code{script-extension} setting.
27686 @xref{Extending GDB,, Extending GDB}.
27690 @cindex execute commands from a file
27691 @item source [-s] [-v] @var{filename}
27692 Execute the command file @var{filename}.
27695 The lines in a command file are generally executed sequentially,
27696 unless the order of execution is changed by one of the
27697 @emph{flow-control commands} described below. The commands are not
27698 printed as they are executed. An error in any command terminates
27699 execution of the command file and control is returned to the console.
27701 @value{GDBN} first searches for @var{filename} in the current directory.
27702 If the file is not found there, and @var{filename} does not specify a
27703 directory, then @value{GDBN} also looks for the file on the source search path
27704 (specified with the @samp{directory} command);
27705 except that @file{$cdir} is not searched because the compilation directory
27706 is not relevant to scripts.
27708 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27709 on the search path even if @var{filename} specifies a directory.
27710 The search is done by appending @var{filename} to each element of the
27711 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27712 and the search path contains @file{/home/user} then @value{GDBN} will
27713 look for the script @file{/home/user/mylib/myscript}.
27714 The search is also done if @var{filename} is an absolute path.
27715 For example, if @var{filename} is @file{/tmp/myscript} and
27716 the search path contains @file{/home/user} then @value{GDBN} will
27717 look for the script @file{/home/user/tmp/myscript}.
27718 For DOS-like systems, if @var{filename} contains a drive specification,
27719 it is stripped before concatenation. For example, if @var{filename} is
27720 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27721 will look for the script @file{c:/tmp/myscript}.
27723 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27724 each command as it is executed. The option must be given before
27725 @var{filename}, and is interpreted as part of the filename anywhere else.
27727 Commands that would ask for confirmation if used interactively proceed
27728 without asking when used in a command file. Many @value{GDBN} commands that
27729 normally print messages to say what they are doing omit the messages
27730 when called from command files.
27732 @value{GDBN} also accepts command input from standard input. In this
27733 mode, normal output goes to standard output and error output goes to
27734 standard error. Errors in a command file supplied on standard input do
27735 not terminate execution of the command file---execution continues with
27739 gdb < cmds > log 2>&1
27742 (The syntax above will vary depending on the shell used.) This example
27743 will execute commands from the file @file{cmds}. All output and errors
27744 would be directed to @file{log}.
27746 Since commands stored on command files tend to be more general than
27747 commands typed interactively, they frequently need to deal with
27748 complicated situations, such as different or unexpected values of
27749 variables and symbols, changes in how the program being debugged is
27750 built, etc. @value{GDBN} provides a set of flow-control commands to
27751 deal with these complexities. Using these commands, you can write
27752 complex scripts that loop over data structures, execute commands
27753 conditionally, etc.
27760 This command allows to include in your script conditionally executed
27761 commands. The @code{if} command takes a single argument, which is an
27762 expression to evaluate. It is followed by a series of commands that
27763 are executed only if the expression is true (its value is nonzero).
27764 There can then optionally be an @code{else} line, followed by a series
27765 of commands that are only executed if the expression was false. The
27766 end of the list is marked by a line containing @code{end}.
27770 This command allows to write loops. Its syntax is similar to
27771 @code{if}: the command takes a single argument, which is an expression
27772 to evaluate, and must be followed by the commands to execute, one per
27773 line, terminated by an @code{end}. These commands are called the
27774 @dfn{body} of the loop. The commands in the body of @code{while} are
27775 executed repeatedly as long as the expression evaluates to true.
27779 This command exits the @code{while} loop in whose body it is included.
27780 Execution of the script continues after that @code{while}s @code{end}
27783 @kindex loop_continue
27784 @item loop_continue
27785 This command skips the execution of the rest of the body of commands
27786 in the @code{while} loop in whose body it is included. Execution
27787 branches to the beginning of the @code{while} loop, where it evaluates
27788 the controlling expression.
27790 @kindex end@r{ (if/else/while commands)}
27792 Terminate the block of commands that are the body of @code{if},
27793 @code{else}, or @code{while} flow-control commands.
27798 @subsection Commands for Controlled Output
27800 During the execution of a command file or a user-defined command, normal
27801 @value{GDBN} output is suppressed; the only output that appears is what is
27802 explicitly printed by the commands in the definition. This section
27803 describes three commands useful for generating exactly the output you
27808 @item echo @var{text}
27809 @c I do not consider backslash-space a standard C escape sequence
27810 @c because it is not in ANSI.
27811 Print @var{text}. Nonprinting characters can be included in
27812 @var{text} using C escape sequences, such as @samp{\n} to print a
27813 newline. @strong{No newline is printed unless you specify one.}
27814 In addition to the standard C escape sequences, a backslash followed
27815 by a space stands for a space. This is useful for displaying a
27816 string with spaces at the beginning or the end, since leading and
27817 trailing spaces are otherwise trimmed from all arguments.
27818 To print @samp{@w{ }and foo =@w{ }}, use the command
27819 @samp{echo \@w{ }and foo = \@w{ }}.
27821 A backslash at the end of @var{text} can be used, as in C, to continue
27822 the command onto subsequent lines. For example,
27825 echo This is some text\n\
27826 which is continued\n\
27827 onto several lines.\n
27830 produces the same output as
27833 echo This is some text\n
27834 echo which is continued\n
27835 echo onto several lines.\n
27839 @item output @var{expression}
27840 Print the value of @var{expression} and nothing but that value: no
27841 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27842 value history either. @xref{Expressions, ,Expressions}, for more information
27845 @item output/@var{fmt} @var{expression}
27846 Print the value of @var{expression} in format @var{fmt}. You can use
27847 the same formats as for @code{print}. @xref{Output Formats,,Output
27848 Formats}, for more information.
27851 @item printf @var{template}, @var{expressions}@dots{}
27852 Print the values of one or more @var{expressions} under the control of
27853 the string @var{template}. To print several values, make
27854 @var{expressions} be a comma-separated list of individual expressions,
27855 which may be either numbers or pointers. Their values are printed as
27856 specified by @var{template}, exactly as a C program would do by
27857 executing the code below:
27860 printf (@var{template}, @var{expressions}@dots{});
27863 As in @code{C} @code{printf}, ordinary characters in @var{template}
27864 are printed verbatim, while @dfn{conversion specification} introduced
27865 by the @samp{%} character cause subsequent @var{expressions} to be
27866 evaluated, their values converted and formatted according to type and
27867 style information encoded in the conversion specifications, and then
27870 For example, you can print two values in hex like this:
27873 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
27876 @code{printf} supports all the standard @code{C} conversion
27877 specifications, including the flags and modifiers between the @samp{%}
27878 character and the conversion letter, with the following exceptions:
27882 The argument-ordering modifiers, such as @samp{2$}, are not supported.
27885 The modifier @samp{*} is not supported for specifying precision or
27889 The @samp{'} flag (for separation of digits into groups according to
27890 @code{LC_NUMERIC'}) is not supported.
27893 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
27897 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
27900 The conversion letters @samp{a} and @samp{A} are not supported.
27904 Note that the @samp{ll} type modifier is supported only if the
27905 underlying @code{C} implementation used to build @value{GDBN} supports
27906 the @code{long long int} type, and the @samp{L} type modifier is
27907 supported only if @code{long double} type is available.
27909 As in @code{C}, @code{printf} supports simple backslash-escape
27910 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
27911 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
27912 single character. Octal and hexadecimal escape sequences are not
27915 Additionally, @code{printf} supports conversion specifications for DFP
27916 (@dfn{Decimal Floating Point}) types using the following length modifiers
27917 together with a floating point specifier.
27922 @samp{H} for printing @code{Decimal32} types.
27925 @samp{D} for printing @code{Decimal64} types.
27928 @samp{DD} for printing @code{Decimal128} types.
27931 If the underlying @code{C} implementation used to build @value{GDBN} has
27932 support for the three length modifiers for DFP types, other modifiers
27933 such as width and precision will also be available for @value{GDBN} to use.
27935 In case there is no such @code{C} support, no additional modifiers will be
27936 available and the value will be printed in the standard way.
27938 Here's an example of printing DFP types using the above conversion letters:
27940 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
27945 @item eval @var{template}, @var{expressions}@dots{}
27946 Convert the values of one or more @var{expressions} under the control of
27947 the string @var{template} to a command line, and call it.
27951 @node Auto-loading sequences
27952 @subsection Controlling auto-loading native @value{GDBN} scripts
27953 @cindex native script auto-loading
27955 When a new object file is read (for example, due to the @code{file}
27956 command, or because the inferior has loaded a shared library),
27957 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
27958 @xref{Auto-loading extensions}.
27960 Auto-loading can be enabled or disabled,
27961 and the list of auto-loaded scripts can be printed.
27964 @anchor{set auto-load gdb-scripts}
27965 @kindex set auto-load gdb-scripts
27966 @item set auto-load gdb-scripts [on|off]
27967 Enable or disable the auto-loading of canned sequences of commands scripts.
27969 @anchor{show auto-load gdb-scripts}
27970 @kindex show auto-load gdb-scripts
27971 @item show auto-load gdb-scripts
27972 Show whether auto-loading of canned sequences of commands scripts is enabled or
27975 @anchor{info auto-load gdb-scripts}
27976 @kindex info auto-load gdb-scripts
27977 @cindex print list of auto-loaded canned sequences of commands scripts
27978 @item info auto-load gdb-scripts [@var{regexp}]
27979 Print the list of all canned sequences of commands scripts that @value{GDBN}
27983 If @var{regexp} is supplied only canned sequences of commands scripts with
27984 matching names are printed.
27987 @section Command Aliases
27988 @cindex aliases for commands
27990 Aliases allow you to define alternate spellings for existing commands.
27991 For example, if a new @value{GDBN} command defined in Python
27992 (@pxref{Python}) has a long name, it is handy to have an abbreviated
27993 version of it that involves less typing.
27995 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27996 of the @samp{step} command even though it is otherwise an ambiguous
27997 abbreviation of other commands like @samp{set} and @samp{show}.
27999 Aliases are also used to provide shortened or more common versions
28000 of multi-word commands. For example, @value{GDBN} provides the
28001 @samp{tty} alias of the @samp{set inferior-tty} command.
28003 You can define a new alias with the @samp{alias} command.
28008 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28012 @var{alias} specifies the name of the new alias. Each word of
28013 @var{alias} must consist of letters, numbers, dashes and underscores.
28015 @var{command} specifies the name of an existing command
28016 that is being aliased.
28018 @var{command} can also be the name of an existing alias. In this
28019 case, @var{command} cannot be an alias that has default arguments.
28021 The @samp{-a} option specifies that the new alias is an abbreviation
28022 of the command. Abbreviations are not used in command completion.
28024 The @samp{--} option specifies the end of options,
28025 and is useful when @var{alias} begins with a dash.
28027 You can specify @var{default-args} for your alias. These
28028 @var{default-args} will be automatically added before the alias
28029 arguments typed explicitly on the command line.
28031 For example, the below defines an alias @code{btfullall} that shows all local
28032 variables and all frame arguments:
28034 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28037 For more information about @var{default-args}, see @ref{Command
28038 aliases default args, ,Default Arguments}.
28040 Here is a simple example showing how to make an abbreviation of a
28041 command so that there is less to type. Suppose you were tired of
28042 typing @samp{disas}, the current shortest unambiguous abbreviation of
28043 the @samp{disassemble} command and you wanted an even shorter version
28044 named @samp{di}. The following will accomplish this.
28047 (gdb) alias -a di = disas
28050 Note that aliases are different from user-defined commands. With a
28051 user-defined command, you also need to write documentation for it with
28052 the @samp{document} command. An alias automatically picks up the
28053 documentation of the existing command.
28055 Here is an example where we make @samp{elms} an abbreviation of
28056 @samp{elements} in the @samp{set print elements} command.
28057 This is to show that you can make an abbreviation of any part
28061 (gdb) alias -a set print elms = set print elements
28062 (gdb) alias -a show print elms = show print elements
28063 (gdb) set p elms 200
28065 Limit on string chars or array elements to print is 200.
28068 Note that if you are defining an alias of a @samp{set} command,
28069 and you want to have an alias for the corresponding @samp{show}
28070 command, then you need to define the latter separately.
28072 Unambiguously abbreviated commands are allowed in @var{command} and
28073 @var{alias}, just as they are normally.
28076 (gdb) alias -a set pr elms = set p ele
28079 Finally, here is an example showing the creation of a one word
28080 alias for a more complex command.
28081 This creates alias @samp{spe} of the command @samp{set print elements}.
28084 (gdb) alias spe = set print elements
28089 * Command aliases default args:: Default arguments for aliases
28092 @node Command aliases default args
28093 @subsection Default Arguments
28094 @cindex aliases for commands, default arguments
28096 You can tell @value{GDBN} to always prepend some default arguments to
28097 the list of arguments provided explicitly by the user when using a
28098 user-defined alias.
28100 If you repeatedly use the same arguments or options for a command, you
28101 can define an alias for this command and tell @value{GDBN} to
28102 automatically prepend these arguments or options to the list of
28103 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28104 could easily accept default arguments for pre-defined commands and aliases,
28105 but it was deemed this would be confusing, and so is not allowed.}.
28107 For example, if you often use the command @code{thread apply all}
28108 specifying to work on the threads in ascending order and to continue in case it
28109 encounters an error, you can tell @value{GDBN} to automatically preprend
28110 the @code{-ascending} and @code{-c} options by using:
28113 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28116 Once you have defined this alias with its default args, any time you type
28117 the @code{thread apply asc-all} followed by @code{some arguments},
28118 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28120 To have even less to type, you can also define a one word alias:
28122 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28125 As usual, unambiguous abbreviations can be used for @var{alias}
28126 and @var{default-args}.
28128 The different aliases of a command do not share their default args.
28129 For example, you define a new alias @code{bt_ALL} showing all possible
28130 information and another alias @code{bt_SMALL} showing very limited information
28133 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28134 -past-main -past-entry -full
28135 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28136 -past-main off -past-entry off
28139 (For more on using the @code{alias} command, see @ref{Aliases}.)
28141 Default args are not limited to the arguments and options of @var{command},
28142 but can specify nested commands if @var{command} accepts such a nested command
28144 For example, the below defines @code{faalocalsoftype} that lists the
28145 frames having locals of a certain type, together with the matching
28148 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28149 (@value{GDBP}) faalocalsoftype int
28150 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28155 This is also very useful to define an alias for a set of nested @code{with}
28156 commands to have a particular combination of temporary settings. For example,
28157 the below defines the alias @code{pp10} that pretty prints an expression
28158 argument, with a maximum of 10 elements if the expression is a string or
28161 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28163 This defines the alias @code{pp10} as being a sequence of 3 commands.
28164 The first part @code{with print pretty --} temporarily activates the setting
28165 @code{set print pretty}, then launches the command that follows the separator
28167 The command following the first part is also a @code{with} command that
28168 temporarily changes the setting @code{set print elements} to 10, then
28169 launches the command that follows the second separator @code{--}.
28170 The third part @code{print} is the command the @code{pp10} alias will launch,
28171 using the temporary values of the settings and the arguments explicitly given
28173 For more information about the @code{with} command usage,
28174 see @ref{Command Settings}.
28176 @c Python docs live in a separate file.
28177 @include python.texi
28179 @c Guile docs live in a separate file.
28180 @include guile.texi
28182 @node Auto-loading extensions
28183 @section Auto-loading extensions
28184 @cindex auto-loading extensions
28186 @value{GDBN} provides two mechanisms for automatically loading
28187 extensions when a new object file is read (for example, due to the
28188 @code{file} command, or because the inferior has loaded a shared
28189 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28190 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28191 @code{.debug_gdb_scripts} section of modern file formats like ELF
28192 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28193 section}). For a discussion of the differences between these two
28194 approaches see @ref{Which flavor to choose?}.
28196 The auto-loading feature is useful for supplying application-specific
28197 debugging commands and features.
28199 Auto-loading can be enabled or disabled,
28200 and the list of auto-loaded scripts can be printed.
28201 See the @samp{auto-loading} section of each extension language
28202 for more information.
28203 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28204 For Python files see @ref{Python Auto-loading}.
28206 Note that loading of this script file also requires accordingly configured
28207 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28210 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28211 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28212 * Which flavor to choose?:: Choosing between these approaches
28215 @node objfile-gdbdotext file
28216 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28217 @cindex @file{@var{objfile}-gdb.gdb}
28218 @cindex @file{@var{objfile}-gdb.py}
28219 @cindex @file{@var{objfile}-gdb.scm}
28221 When a new object file is read, @value{GDBN} looks for a file named
28222 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28223 where @var{objfile} is the object file's name and
28224 where @var{ext} is the file extension for the extension language:
28227 @item @file{@var{objfile}-gdb.gdb}
28228 GDB's own command language
28229 @item @file{@var{objfile}-gdb.py}
28231 @item @file{@var{objfile}-gdb.scm}
28235 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28236 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28237 components, and appending the @file{-gdb.@var{ext}} suffix.
28238 If this file exists and is readable, @value{GDBN} will evaluate it as a
28239 script in the specified extension language.
28241 If this file does not exist, then @value{GDBN} will look for
28242 @var{script-name} file in all of the directories as specified below.
28243 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28244 directories is converted to a one-letter subdirectory, i.e.@:
28245 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28246 filesystems disallow colons in file names.)
28248 Note that loading of these files requires an accordingly configured
28249 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28251 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28252 scripts normally according to its @file{.exe} filename. But if no scripts are
28253 found @value{GDBN} also tries script filenames matching the object file without
28254 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28255 is attempted on any platform. This makes the script filenames compatible
28256 between Unix and MS-Windows hosts.
28259 @anchor{set auto-load scripts-directory}
28260 @kindex set auto-load scripts-directory
28261 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28262 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28263 may be delimited by the host platform path separator in use
28264 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28266 Each entry here needs to be covered also by the security setting
28267 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28269 @anchor{with-auto-load-dir}
28270 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28271 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28272 configuration option @option{--with-auto-load-dir}.
28274 Any reference to @file{$debugdir} will get replaced by
28275 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28276 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28277 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28278 @file{$datadir} must be placed as a directory component --- either alone or
28279 delimited by @file{/} or @file{\} directory separators, depending on the host
28282 The list of directories uses path separator (@samp{:} on GNU and Unix
28283 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28284 to the @env{PATH} environment variable.
28286 @anchor{show auto-load scripts-directory}
28287 @kindex show auto-load scripts-directory
28288 @item show auto-load scripts-directory
28289 Show @value{GDBN} auto-loaded scripts location.
28291 @anchor{add-auto-load-scripts-directory}
28292 @kindex add-auto-load-scripts-directory
28293 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28294 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28295 Multiple entries may be delimited by the host platform path separator in use.
28298 @value{GDBN} does not track which files it has already auto-loaded this way.
28299 @value{GDBN} will load the associated script every time the corresponding
28300 @var{objfile} is opened.
28301 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28302 is evaluated more than once.
28304 @node dotdebug_gdb_scripts section
28305 @subsection The @code{.debug_gdb_scripts} section
28306 @cindex @code{.debug_gdb_scripts} section
28308 For systems using file formats like ELF and COFF,
28309 when @value{GDBN} loads a new object file
28310 it will look for a special section named @code{.debug_gdb_scripts}.
28311 If this section exists, its contents is a list of null-terminated entries
28312 specifying scripts to load. Each entry begins with a non-null prefix byte that
28313 specifies the kind of entry, typically the extension language and whether the
28314 script is in a file or inlined in @code{.debug_gdb_scripts}.
28316 The following entries are supported:
28319 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28320 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28321 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28322 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28325 @subsubsection Script File Entries
28327 If the entry specifies a file, @value{GDBN} will look for the file first
28328 in the current directory and then along the source search path
28329 (@pxref{Source Path, ,Specifying Source Directories}),
28330 except that @file{$cdir} is not searched, since the compilation
28331 directory is not relevant to scripts.
28333 File entries can be placed in section @code{.debug_gdb_scripts} with,
28334 for example, this GCC macro for Python scripts.
28337 /* Note: The "MS" section flags are to remove duplicates. */
28338 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28340 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28341 .byte 1 /* Python */\n\
28342 .asciz \"" script_name "\"\n\
28348 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28349 Then one can reference the macro in a header or source file like this:
28352 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28355 The script name may include directories if desired.
28357 Note that loading of this script file also requires accordingly configured
28358 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28360 If the macro invocation is put in a header, any application or library
28361 using this header will get a reference to the specified script,
28362 and with the use of @code{"MS"} attributes on the section, the linker
28363 will remove duplicates.
28365 @subsubsection Script Text Entries
28367 Script text entries allow to put the executable script in the entry
28368 itself instead of loading it from a file.
28369 The first line of the entry, everything after the prefix byte and up to
28370 the first newline (@code{0xa}) character, is the script name, and must not
28371 contain any kind of space character, e.g., spaces or tabs.
28372 The rest of the entry, up to the trailing null byte, is the script to
28373 execute in the specified language. The name needs to be unique among
28374 all script names, as @value{GDBN} executes each script only once based
28377 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28381 #include "symcat.h"
28382 #include "gdb/section-scripts.h"
28384 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28385 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28386 ".ascii \"gdb.inlined-script\\n\"\n"
28387 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28388 ".ascii \" def __init__ (self):\\n\"\n"
28389 ".ascii \" super (test_cmd, self).__init__ ("
28390 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28391 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28392 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28393 ".ascii \"test_cmd ()\\n\"\n"
28399 Loading of inlined scripts requires a properly configured
28400 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28401 The path to specify in @code{auto-load safe-path} is the path of the file
28402 containing the @code{.debug_gdb_scripts} section.
28404 @node Which flavor to choose?
28405 @subsection Which flavor to choose?
28407 Given the multiple ways of auto-loading extensions, it might not always
28408 be clear which one to choose. This section provides some guidance.
28411 Benefits of the @file{-gdb.@var{ext}} way:
28415 Can be used with file formats that don't support multiple sections.
28418 Ease of finding scripts for public libraries.
28420 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28421 in the source search path.
28422 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28423 isn't a source directory in which to find the script.
28426 Doesn't require source code additions.
28430 Benefits of the @code{.debug_gdb_scripts} way:
28434 Works with static linking.
28436 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28437 trigger their loading. When an application is statically linked the only
28438 objfile available is the executable, and it is cumbersome to attach all the
28439 scripts from all the input libraries to the executable's
28440 @file{-gdb.@var{ext}} script.
28443 Works with classes that are entirely inlined.
28445 Some classes can be entirely inlined, and thus there may not be an associated
28446 shared library to attach a @file{-gdb.@var{ext}} script to.
28449 Scripts needn't be copied out of the source tree.
28451 In some circumstances, apps can be built out of large collections of internal
28452 libraries, and the build infrastructure necessary to install the
28453 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28454 cumbersome. It may be easier to specify the scripts in the
28455 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28456 top of the source tree to the source search path.
28459 @node Multiple Extension Languages
28460 @section Multiple Extension Languages
28462 The Guile and Python extension languages do not share any state,
28463 and generally do not interfere with each other.
28464 There are some things to be aware of, however.
28466 @subsection Python comes first
28468 Python was @value{GDBN}'s first extension language, and to avoid breaking
28469 existing behaviour Python comes first. This is generally solved by the
28470 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28471 extension languages, and when it makes a call to an extension language,
28472 (say to pretty-print a value), it tries each in turn until an extension
28473 language indicates it has performed the request (e.g., has returned the
28474 pretty-printed form of a value).
28475 This extends to errors while performing such requests: If an error happens
28476 while, for example, trying to pretty-print an object then the error is
28477 reported and any following extension languages are not tried.
28480 @chapter Command Interpreters
28481 @cindex command interpreters
28483 @value{GDBN} supports multiple command interpreters, and some command
28484 infrastructure to allow users or user interface writers to switch
28485 between interpreters or run commands in other interpreters.
28487 @value{GDBN} currently supports two command interpreters, the console
28488 interpreter (sometimes called the command-line interpreter or @sc{cli})
28489 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28490 describes both of these interfaces in great detail.
28492 By default, @value{GDBN} will start with the console interpreter.
28493 However, the user may choose to start @value{GDBN} with another
28494 interpreter by specifying the @option{-i} or @option{--interpreter}
28495 startup options. Defined interpreters include:
28499 @cindex console interpreter
28500 The traditional console or command-line interpreter. This is the most often
28501 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28502 @value{GDBN} will use this interpreter.
28505 @cindex mi interpreter
28506 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28507 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28508 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28512 @cindex mi3 interpreter
28513 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28516 @cindex mi2 interpreter
28517 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28520 @cindex mi1 interpreter
28521 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28525 @cindex invoke another interpreter
28527 @kindex interpreter-exec
28528 You may execute commands in any interpreter from the current
28529 interpreter using the appropriate command. If you are running the
28530 console interpreter, simply use the @code{interpreter-exec} command:
28533 interpreter-exec mi "-data-list-register-names"
28536 @sc{gdb/mi} has a similar command, although it is only available in versions of
28537 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28539 Note that @code{interpreter-exec} only changes the interpreter for the
28540 duration of the specified command. It does not change the interpreter
28543 @cindex start a new independent interpreter
28545 Although you may only choose a single interpreter at startup, it is
28546 possible to run an independent interpreter on a specified input/output
28547 device (usually a tty).
28549 For example, consider a debugger GUI or IDE that wants to provide a
28550 @value{GDBN} console view. It may do so by embedding a terminal
28551 emulator widget in its GUI, starting @value{GDBN} in the traditional
28552 command-line mode with stdin/stdout/stderr redirected to that
28553 terminal, and then creating an MI interpreter running on a specified
28554 input/output device. The console interpreter created by @value{GDBN}
28555 at startup handles commands the user types in the terminal widget,
28556 while the GUI controls and synchronizes state with @value{GDBN} using
28557 the separate MI interpreter.
28559 To start a new secondary @dfn{user interface} running MI, use the
28560 @code{new-ui} command:
28563 @cindex new user interface
28565 new-ui @var{interpreter} @var{tty}
28568 The @var{interpreter} parameter specifies the interpreter to run.
28569 This accepts the same values as the @code{interpreter-exec} command.
28570 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28571 @var{tty} parameter specifies the name of the bidirectional file the
28572 interpreter uses for input/output, usually the name of a
28573 pseudoterminal slave on Unix systems. For example:
28576 (@value{GDBP}) new-ui mi /dev/pts/9
28580 runs an MI interpreter on @file{/dev/pts/9}.
28583 @chapter @value{GDBN} Text User Interface
28585 @cindex Text User Interface
28587 The @value{GDBN} Text User Interface (TUI) is a terminal
28588 interface which uses the @code{curses} library to show the source
28589 file, the assembly output, the program registers and @value{GDBN}
28590 commands in separate text windows. The TUI mode is supported only
28591 on platforms where a suitable version of the @code{curses} library
28594 The TUI mode is enabled by default when you invoke @value{GDBN} as
28595 @samp{@value{GDBP} -tui}.
28596 You can also switch in and out of TUI mode while @value{GDBN} runs by
28597 using various TUI commands and key bindings, such as @command{tui
28598 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28599 @ref{TUI Keys, ,TUI Key Bindings}.
28602 * TUI Overview:: TUI overview
28603 * TUI Keys:: TUI key bindings
28604 * TUI Single Key Mode:: TUI single key mode
28605 * TUI Mouse Support:: TUI mouse support
28606 * TUI Commands:: TUI-specific commands
28607 * TUI Configuration:: TUI configuration variables
28611 @section TUI Overview
28613 In TUI mode, @value{GDBN} can display several text windows:
28617 This window is the @value{GDBN} command window with the @value{GDBN}
28618 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28619 managed using readline.
28622 The source window shows the source file of the program. The current
28623 line and active breakpoints are displayed in this window.
28626 The assembly window shows the disassembly output of the program.
28629 This window shows the processor registers. Registers are highlighted
28630 when their values change.
28633 The source and assembly windows show the current program position
28634 by highlighting the current line and marking it with a @samp{>} marker.
28635 Breakpoints are indicated with two markers. The first marker
28636 indicates the breakpoint type:
28640 Breakpoint which was hit at least once.
28643 Breakpoint which was never hit.
28646 Hardware breakpoint which was hit at least once.
28649 Hardware breakpoint which was never hit.
28652 The second marker indicates whether the breakpoint is enabled or not:
28656 Breakpoint is enabled.
28659 Breakpoint is disabled.
28662 The source, assembly and register windows are updated when the current
28663 thread changes, when the frame changes, or when the program counter
28666 These windows are not all visible at the same time. The command
28667 window is always visible. The others can be arranged in several
28678 source and assembly,
28681 source and registers, or
28684 assembly and registers.
28687 These are the standard layouts, but other layouts can be defined.
28689 A status line above the command window shows the following information:
28693 Indicates the current @value{GDBN} target.
28694 (@pxref{Targets, ,Specifying a Debugging Target}).
28697 Gives the current process or thread number.
28698 When no process is being debugged, this field is set to @code{No process}.
28701 Gives the current function name for the selected frame.
28702 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28703 When there is no symbol corresponding to the current program counter,
28704 the string @code{??} is displayed.
28707 Indicates the current line number for the selected frame.
28708 When the current line number is not known, the string @code{??} is displayed.
28711 Indicates the current program counter address.
28715 @section TUI Key Bindings
28716 @cindex TUI key bindings
28718 The TUI installs several key bindings in the readline keymaps
28719 @ifset SYSTEM_READLINE
28720 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28722 @ifclear SYSTEM_READLINE
28723 (@pxref{Command Line Editing}).
28725 The following key bindings are installed for both TUI mode and the
28726 @value{GDBN} standard mode.
28735 Enter or leave the TUI mode. When leaving the TUI mode,
28736 the curses window management stops and @value{GDBN} operates using
28737 its standard mode, writing on the terminal directly. When reentering
28738 the TUI mode, control is given back to the curses windows.
28739 The screen is then refreshed.
28741 This key binding uses the bindable Readline function
28742 @code{tui-switch-mode}.
28746 Use a TUI layout with only one window. The layout will
28747 either be @samp{source} or @samp{assembly}. When the TUI mode
28748 is not active, it will switch to the TUI mode.
28750 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28752 This key binding uses the bindable Readline function
28753 @code{tui-delete-other-windows}.
28757 Use a TUI layout with at least two windows. When the current
28758 layout already has two windows, the next layout with two windows is used.
28759 When a new layout is chosen, one window will always be common to the
28760 previous layout and the new one.
28762 Think of it as the Emacs @kbd{C-x 2} binding.
28764 This key binding uses the bindable Readline function
28765 @code{tui-change-windows}.
28769 Change the active window. The TUI associates several key bindings
28770 (like scrolling and arrow keys) with the active window. This command
28771 gives the focus to the next TUI window.
28773 Think of it as the Emacs @kbd{C-x o} binding.
28775 This key binding uses the bindable Readline function
28776 @code{tui-other-window}.
28780 Switch in and out of the TUI SingleKey mode that binds single
28781 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28783 This key binding uses the bindable Readline function
28784 @code{next-keymap}.
28787 The following key bindings only work in the TUI mode:
28792 Scroll the active window one page up.
28796 Scroll the active window one page down.
28800 Scroll the active window one line up.
28804 Scroll the active window one line down.
28808 Scroll the active window one column left.
28812 Scroll the active window one column right.
28816 Refresh the screen.
28819 Because the arrow keys scroll the active window in the TUI mode, they
28820 are not available for their normal use by readline unless the command
28821 window has the focus. When another window is active, you must use
28822 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28823 and @kbd{C-f} to control the command window.
28825 @node TUI Single Key Mode
28826 @section TUI Single Key Mode
28827 @cindex TUI single key mode
28829 The TUI also provides a @dfn{SingleKey} mode, which binds several
28830 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28831 switch into this mode, where the following key bindings are used:
28834 @kindex c @r{(SingleKey TUI key)}
28838 @kindex d @r{(SingleKey TUI key)}
28842 @kindex f @r{(SingleKey TUI key)}
28846 @kindex n @r{(SingleKey TUI key)}
28850 @kindex o @r{(SingleKey TUI key)}
28852 nexti. The shortcut letter @samp{o} stands for ``step Over''.
28854 @kindex q @r{(SingleKey TUI key)}
28856 exit the SingleKey mode.
28858 @kindex r @r{(SingleKey TUI key)}
28862 @kindex s @r{(SingleKey TUI key)}
28866 @kindex i @r{(SingleKey TUI key)}
28868 stepi. The shortcut letter @samp{i} stands for ``step Into''.
28870 @kindex u @r{(SingleKey TUI key)}
28874 @kindex v @r{(SingleKey TUI key)}
28878 @kindex w @r{(SingleKey TUI key)}
28883 Other keys temporarily switch to the @value{GDBN} command prompt.
28884 The key that was pressed is inserted in the editing buffer so that
28885 it is possible to type most @value{GDBN} commands without interaction
28886 with the TUI SingleKey mode. Once the command is entered the TUI
28887 SingleKey mode is restored. The only way to permanently leave
28888 this mode is by typing @kbd{q} or @kbd{C-x s}.
28890 @cindex SingleKey keymap name
28891 If @value{GDBN} was built with Readline 8.0 or later, the TUI
28892 SingleKey keymap will be named @samp{SingleKey}. This can be used in
28893 @file{.inputrc} to add additional bindings to this keymap.
28895 @node TUI Mouse Support
28896 @section TUI Mouse Support
28897 @cindex TUI mouse support
28899 If the curses library supports the mouse, the TUI supports mouse
28902 The mouse wheel scrolls the appropriate window under the mouse cursor.
28904 The TUI itself does not directly support copying/pasting with the
28905 mouse. However, on Unix terminals, you can typically press and hold
28906 the @key{SHIFT} key on your keyboard to temporarily bypass
28907 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
28908 functionality (commonly, click-drag-release or double-click to select
28909 text, middle-click to paste). This copy/paste works with the
28910 terminal's selection buffer, as opposed to the TUI's buffer.
28913 @section TUI-specific Commands
28914 @cindex TUI commands
28916 The TUI has specific commands to control the text windows.
28917 These commands are always available, even when @value{GDBN} is not in
28918 the TUI mode. When @value{GDBN} is in the standard mode, most
28919 of these commands will automatically switch to the TUI mode.
28921 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28922 terminal, or @value{GDBN} has been started with the machine interface
28923 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28924 these commands will fail with an error, because it would not be
28925 possible or desirable to enable curses window management.
28930 Activate TUI mode. The last active TUI window layout will be used if
28931 TUI mode has previously been used in the current debugging session,
28932 otherwise a default layout is used.
28935 @kindex tui disable
28936 Disable TUI mode, returning to the console interpreter.
28938 @anchor{info_win_command}
28941 List the names and sizes of all currently displayed windows.
28943 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
28944 @kindex tui new-layout
28945 Create a new TUI layout. The new layout will be named @var{name}, and
28946 can be accessed using the @code{layout} command (see below).
28948 Each @var{window} parameter is either the name of a window to display,
28949 or a window description. The windows will be displayed from top to
28950 bottom in the order listed.
28952 The names of the windows are the same as the ones given to the
28953 @code{focus} command (see below); additional, the @code{status}
28954 window can be specified. Note that, because it is of fixed height,
28955 the weight assigned to the status window is of no importance. It is
28956 conventional to use @samp{0} here.
28958 A window description looks a bit like an invocation of @code{tui
28959 new-layout}, and is of the form
28960 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
28962 This specifies a sub-layout. If @code{-horizontal} is given, the
28963 windows in this description will be arranged side-by-side, rather than
28966 Each @var{weight} is an integer. It is the weight of this window
28967 relative to all the other windows in the layout. These numbers are
28968 used to calculate how much of the screen is given to each window.
28973 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
28976 Here, the new layout is called @samp{example}. It shows the source
28977 and register windows, followed by the status window, and then finally
28978 the command window. The non-status windows all have the same weight,
28979 so the terminal will be split into three roughly equal sections.
28981 Here is a more complex example, showing a horizontal layout:
28984 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
28987 This will result in side-by-side source and assembly windows; with the
28988 status and command window being beneath these, filling the entire
28989 width of the terminal. Because they have weight 2, the source and
28990 assembly windows will be twice the height of the command window.
28992 @item layout @var{name}
28994 Changes which TUI windows are displayed. The @var{name} parameter
28995 controls which layout is shown. It can be either one of the built-in
28996 layout names, or the name of a layout defined by the user using
28997 @code{tui new-layout}.
28999 The built-in layouts are as follows:
29003 Display the next layout.
29006 Display the previous layout.
29009 Display the source and command windows.
29012 Display the assembly and command windows.
29015 Display the source, assembly, and command windows.
29018 When in @code{src} layout display the register, source, and command
29019 windows. When in @code{asm} or @code{split} layout display the
29020 register, assembler, and command windows.
29023 @item focus @var{name}
29025 Changes which TUI window is currently active for scrolling. The
29026 @var{name} parameter can be any of the following:
29030 Make the next window active for scrolling.
29033 Make the previous window active for scrolling.
29036 Make the source window active for scrolling.
29039 Make the assembly window active for scrolling.
29042 Make the register window active for scrolling.
29045 Make the command window active for scrolling.
29050 Refresh the screen. This is similar to typing @kbd{C-L}.
29052 @item tui reg @var{group}
29054 Changes the register group displayed in the tui register window to
29055 @var{group}. If the register window is not currently displayed this
29056 command will cause the register window to be displayed. The list of
29057 register groups, as well as their order is target specific. The
29058 following groups are available on most targets:
29061 Repeatedly selecting this group will cause the display to cycle
29062 through all of the available register groups.
29065 Repeatedly selecting this group will cause the display to cycle
29066 through all of the available register groups in the reverse order to
29070 Display the general registers.
29072 Display the floating point registers.
29074 Display the system registers.
29076 Display the vector registers.
29078 Display all registers.
29083 Update the source window and the current execution point.
29085 @item winheight @var{name} +@var{count}
29086 @itemx winheight @var{name} -@var{count}
29088 Change the height of the window @var{name} by @var{count} lines.
29089 Positive counts increase the height, while negative counts decrease
29090 it. The @var{name} parameter can be the name of any currently visible
29091 window. The names of the currently visible windows can be discovered
29092 using @kbd{info win} (@pxref{info_win_command,,info win}).
29095 @node TUI Configuration
29096 @section TUI Configuration Variables
29097 @cindex TUI configuration variables
29099 Several configuration variables control the appearance of TUI windows.
29102 @item set tui border-kind @var{kind}
29103 @kindex set tui border-kind
29104 Select the border appearance for the source, assembly and register windows.
29105 The possible values are the following:
29108 Use a space character to draw the border.
29111 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29114 Use the Alternate Character Set to draw the border. The border is
29115 drawn using character line graphics if the terminal supports them.
29118 @item set tui border-mode @var{mode}
29119 @kindex set tui border-mode
29120 @itemx set tui active-border-mode @var{mode}
29121 @kindex set tui active-border-mode
29122 Select the display attributes for the borders of the inactive windows
29123 or the active window. The @var{mode} can be one of the following:
29126 Use normal attributes to display the border.
29132 Use reverse video mode.
29135 Use half bright mode.
29137 @item half-standout
29138 Use half bright and standout mode.
29141 Use extra bright or bold mode.
29143 @item bold-standout
29144 Use extra bright or bold and standout mode.
29147 @item set tui tab-width @var{nchars}
29148 @kindex set tui tab-width
29150 Set the width of tab stops to be @var{nchars} characters. This
29151 setting affects the display of TAB characters in the source and
29154 @item set tui compact-source @r{[}on@r{|}off@r{]}
29155 @kindex set tui compact-source
29156 Set whether the TUI source window is displayed in ``compact'' form.
29157 The default display uses more space for line numbers and starts the
29158 source text at the next tab stop; the compact display uses only as
29159 much space as is needed for the line numbers in the current file, and
29160 only a single space to separate the line numbers from the source.
29163 Note that the colors of the TUI borders can be controlled using the
29164 appropriate @code{set style} commands. @xref{Output Styling}.
29167 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29170 @cindex @sc{gnu} Emacs
29171 A special interface allows you to use @sc{gnu} Emacs to view (and
29172 edit) the source files for the program you are debugging with
29175 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29176 executable file you want to debug as an argument. This command starts
29177 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29178 created Emacs buffer.
29179 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29181 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29186 All ``terminal'' input and output goes through an Emacs buffer, called
29189 This applies both to @value{GDBN} commands and their output, and to the input
29190 and output done by the program you are debugging.
29192 This is useful because it means that you can copy the text of previous
29193 commands and input them again; you can even use parts of the output
29196 All the facilities of Emacs' Shell mode are available for interacting
29197 with your program. In particular, you can send signals the usual
29198 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29202 @value{GDBN} displays source code through Emacs.
29204 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29205 source file for that frame and puts an arrow (@samp{=>}) at the
29206 left margin of the current line. Emacs uses a separate buffer for
29207 source display, and splits the screen to show both your @value{GDBN} session
29210 Explicit @value{GDBN} @code{list} or search commands still produce output as
29211 usual, but you probably have no reason to use them from Emacs.
29214 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29215 a graphical mode, enabled by default, which provides further buffers
29216 that can control the execution and describe the state of your program.
29217 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29219 If you specify an absolute file name when prompted for the @kbd{M-x
29220 gdb} argument, then Emacs sets your current working directory to where
29221 your program resides. If you only specify the file name, then Emacs
29222 sets your current working directory to the directory associated
29223 with the previous buffer. In this case, @value{GDBN} may find your
29224 program by searching your environment's @env{PATH} variable, but on
29225 some operating systems it might not find the source. So, although the
29226 @value{GDBN} input and output session proceeds normally, the auxiliary
29227 buffer does not display the current source and line of execution.
29229 The initial working directory of @value{GDBN} is printed on the top
29230 line of the GUD buffer and this serves as a default for the commands
29231 that specify files for @value{GDBN} to operate on. @xref{Files,
29232 ,Commands to Specify Files}.
29234 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29235 need to call @value{GDBN} by a different name (for example, if you
29236 keep several configurations around, with different names) you can
29237 customize the Emacs variable @code{gud-gdb-command-name} to run the
29240 In the GUD buffer, you can use these special Emacs commands in
29241 addition to the standard Shell mode commands:
29245 Describe the features of Emacs' GUD Mode.
29248 Execute to another source line, like the @value{GDBN} @code{step} command; also
29249 update the display window to show the current file and location.
29252 Execute to next source line in this function, skipping all function
29253 calls, like the @value{GDBN} @code{next} command. Then update the display window
29254 to show the current file and location.
29257 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29258 display window accordingly.
29261 Execute until exit from the selected stack frame, like the @value{GDBN}
29262 @code{finish} command.
29265 Continue execution of your program, like the @value{GDBN} @code{continue}
29269 Go up the number of frames indicated by the numeric argument
29270 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29271 like the @value{GDBN} @code{up} command.
29274 Go down the number of frames indicated by the numeric argument, like the
29275 @value{GDBN} @code{down} command.
29278 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29279 tells @value{GDBN} to set a breakpoint on the source line point is on.
29281 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29282 separate frame which shows a backtrace when the GUD buffer is current.
29283 Move point to any frame in the stack and type @key{RET} to make it
29284 become the current frame and display the associated source in the
29285 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29286 selected frame become the current one. In graphical mode, the
29287 speedbar displays watch expressions.
29289 If you accidentally delete the source-display buffer, an easy way to get
29290 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29291 request a frame display; when you run under Emacs, this recreates
29292 the source buffer if necessary to show you the context of the current
29295 The source files displayed in Emacs are in ordinary Emacs buffers
29296 which are visiting the source files in the usual way. You can edit
29297 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29298 communicates with Emacs in terms of line numbers. If you add or
29299 delete lines from the text, the line numbers that @value{GDBN} knows cease
29300 to correspond properly with the code.
29302 A more detailed description of Emacs' interaction with @value{GDBN} is
29303 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29307 @chapter The @sc{gdb/mi} Interface
29309 @unnumberedsec Function and Purpose
29311 @cindex @sc{gdb/mi}, its purpose
29312 @sc{gdb/mi} is a line based machine oriented text interface to
29313 @value{GDBN} and is activated by specifying using the
29314 @option{--interpreter} command line option (@pxref{Mode Options}). It
29315 is specifically intended to support the development of systems which
29316 use the debugger as just one small component of a larger system.
29318 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29319 in the form of a reference manual.
29321 Note that @sc{gdb/mi} is still under construction, so some of the
29322 features described below are incomplete and subject to change
29323 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29325 @unnumberedsec Notation and Terminology
29327 @cindex notational conventions, for @sc{gdb/mi}
29328 This chapter uses the following notation:
29332 @code{|} separates two alternatives.
29335 @code{[ @var{something} ]} indicates that @var{something} is optional:
29336 it may or may not be given.
29339 @code{( @var{group} )*} means that @var{group} inside the parentheses
29340 may repeat zero or more times.
29343 @code{( @var{group} )+} means that @var{group} inside the parentheses
29344 may repeat one or more times.
29347 @code{"@var{string}"} means a literal @var{string}.
29351 @heading Dependencies
29355 * GDB/MI General Design::
29356 * GDB/MI Command Syntax::
29357 * GDB/MI Compatibility with CLI::
29358 * GDB/MI Development and Front Ends::
29359 * GDB/MI Output Records::
29360 * GDB/MI Simple Examples::
29361 * GDB/MI Command Description Format::
29362 * GDB/MI Breakpoint Commands::
29363 * GDB/MI Catchpoint Commands::
29364 * GDB/MI Program Context::
29365 * GDB/MI Thread Commands::
29366 * GDB/MI Ada Tasking Commands::
29367 * GDB/MI Program Execution::
29368 * GDB/MI Stack Manipulation::
29369 * GDB/MI Variable Objects::
29370 * GDB/MI Data Manipulation::
29371 * GDB/MI Tracepoint Commands::
29372 * GDB/MI Symbol Query::
29373 * GDB/MI File Commands::
29375 * GDB/MI Kod Commands::
29376 * GDB/MI Memory Overlay Commands::
29377 * GDB/MI Signal Handling Commands::
29379 * GDB/MI Target Manipulation::
29380 * GDB/MI File Transfer Commands::
29381 * GDB/MI Ada Exceptions Commands::
29382 * GDB/MI Support Commands::
29383 * GDB/MI Miscellaneous Commands::
29386 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29387 @node GDB/MI General Design
29388 @section @sc{gdb/mi} General Design
29389 @cindex GDB/MI General Design
29391 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29392 parts---commands sent to @value{GDBN}, responses to those commands
29393 and notifications. Each command results in exactly one response,
29394 indicating either successful completion of the command, or an error.
29395 For the commands that do not resume the target, the response contains the
29396 requested information. For the commands that resume the target, the
29397 response only indicates whether the target was successfully resumed.
29398 Notifications is the mechanism for reporting changes in the state of the
29399 target, or in @value{GDBN} state, that cannot conveniently be associated with
29400 a command and reported as part of that command response.
29402 The important examples of notifications are:
29406 Exec notifications. These are used to report changes in
29407 target state---when a target is resumed, or stopped. It would not
29408 be feasible to include this information in response of resuming
29409 commands, because one resume commands can result in multiple events in
29410 different threads. Also, quite some time may pass before any event
29411 happens in the target, while a frontend needs to know whether the resuming
29412 command itself was successfully executed.
29415 Console output, and status notifications. Console output
29416 notifications are used to report output of CLI commands, as well as
29417 diagnostics for other commands. Status notifications are used to
29418 report the progress of a long-running operation. Naturally, including
29419 this information in command response would mean no output is produced
29420 until the command is finished, which is undesirable.
29423 General notifications. Commands may have various side effects on
29424 the @value{GDBN} or target state beyond their official purpose. For example,
29425 a command may change the selected thread. Although such changes can
29426 be included in command response, using notification allows for more
29427 orthogonal frontend design.
29431 There's no guarantee that whenever an MI command reports an error,
29432 @value{GDBN} or the target are in any specific state, and especially,
29433 the state is not reverted to the state before the MI command was
29434 processed. Therefore, whenever an MI command results in an error,
29435 we recommend that the frontend refreshes all the information shown in
29436 the user interface.
29440 * Context management::
29441 * Asynchronous and non-stop modes::
29445 @node Context management
29446 @subsection Context management
29448 @subsubsection Threads and Frames
29450 In most cases when @value{GDBN} accesses the target, this access is
29451 done in context of a specific thread and frame (@pxref{Frames}).
29452 Often, even when accessing global data, the target requires that a thread
29453 be specified. The CLI interface maintains the selected thread and frame,
29454 and supplies them to target on each command. This is convenient,
29455 because a command line user would not want to specify that information
29456 explicitly on each command, and because user interacts with
29457 @value{GDBN} via a single terminal, so no confusion is possible as
29458 to what thread and frame are the current ones.
29460 In the case of MI, the concept of selected thread and frame is less
29461 useful. First, a frontend can easily remember this information
29462 itself. Second, a graphical frontend can have more than one window,
29463 each one used for debugging a different thread, and the frontend might
29464 want to access additional threads for internal purposes. This
29465 increases the risk that by relying on implicitly selected thread, the
29466 frontend may be operating on a wrong one. Therefore, each MI command
29467 should explicitly specify which thread and frame to operate on. To
29468 make it possible, each MI command accepts the @samp{--thread} and
29469 @samp{--frame} options, the value to each is @value{GDBN} global
29470 identifier for thread and frame to operate on.
29472 Usually, each top-level window in a frontend allows the user to select
29473 a thread and a frame, and remembers the user selection for further
29474 operations. However, in some cases @value{GDBN} may suggest that the
29475 current thread or frame be changed. For example, when stopping on a
29476 breakpoint it is reasonable to switch to the thread where breakpoint is
29477 hit. For another example, if the user issues the CLI @samp{thread} or
29478 @samp{frame} commands via the frontend, it is desirable to change the
29479 frontend's selection to the one specified by user. @value{GDBN}
29480 communicates the suggestion to change current thread and frame using the
29481 @samp{=thread-selected} notification.
29483 Note that historically, MI shares the selected thread with CLI, so
29484 frontends used the @code{-thread-select} to execute commands in the
29485 right context. However, getting this to work right is cumbersome. The
29486 simplest way is for frontend to emit @code{-thread-select} command
29487 before every command. This doubles the number of commands that need
29488 to be sent. The alternative approach is to suppress @code{-thread-select}
29489 if the selected thread in @value{GDBN} is supposed to be identical to the
29490 thread the frontend wants to operate on. However, getting this
29491 optimization right can be tricky. In particular, if the frontend
29492 sends several commands to @value{GDBN}, and one of the commands changes the
29493 selected thread, then the behaviour of subsequent commands will
29494 change. So, a frontend should either wait for response from such
29495 problematic commands, or explicitly add @code{-thread-select} for
29496 all subsequent commands. No frontend is known to do this exactly
29497 right, so it is suggested to just always pass the @samp{--thread} and
29498 @samp{--frame} options.
29500 @subsubsection Language
29502 The execution of several commands depends on which language is selected.
29503 By default, the current language (@pxref{show language}) is used.
29504 But for commands known to be language-sensitive, it is recommended
29505 to use the @samp{--language} option. This option takes one argument,
29506 which is the name of the language to use while executing the command.
29510 -data-evaluate-expression --language c "sizeof (void*)"
29515 The valid language names are the same names accepted by the
29516 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29517 @samp{local} or @samp{unknown}.
29519 @node Asynchronous and non-stop modes
29520 @subsection Asynchronous command execution and non-stop mode
29522 On some targets, @value{GDBN} is capable of processing MI commands
29523 even while the target is running. This is called @dfn{asynchronous
29524 command execution} (@pxref{Background Execution}). The frontend may
29525 specify a preference for asynchronous execution using the
29526 @code{-gdb-set mi-async 1} command, which should be emitted before
29527 either running the executable or attaching to the target. After the
29528 frontend has started the executable or attached to the target, it can
29529 find if asynchronous execution is enabled using the
29530 @code{-list-target-features} command.
29533 @cindex foreground execution
29534 @cindex background execution
29535 @cindex asynchronous execution
29536 @cindex execution, foreground, background and asynchronous
29537 @kindex set mi-async
29538 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
29539 Set whether MI is in asynchronous mode.
29541 When @code{off}, which is the default, MI execution commands (e.g.,
29542 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29543 for the program to stop before processing further commands.
29545 When @code{on}, MI execution commands are background execution
29546 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29547 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29548 MI commands even while the target is running.
29550 @kindex show mi-async
29551 @item -gdb-show mi-async
29552 Show whether MI asynchronous mode is enabled.
29555 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29556 @code{target-async} instead of @code{mi-async}, and it had the effect
29557 of both putting MI in asynchronous mode and making CLI background
29558 commands possible. CLI background commands are now always possible
29559 ``out of the box'' if the target supports them. The old spelling is
29560 kept as a deprecated alias for backwards compatibility.
29562 Even if @value{GDBN} can accept a command while target is running,
29563 many commands that access the target do not work when the target is
29564 running. Therefore, asynchronous command execution is most useful
29565 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29566 it is possible to examine the state of one thread, while other threads
29569 When a given thread is running, MI commands that try to access the
29570 target in the context of that thread may not work, or may work only on
29571 some targets. In particular, commands that try to operate on thread's
29572 stack will not work, on any target. Commands that read memory, or
29573 modify breakpoints, may work or not work, depending on the target. Note
29574 that even commands that operate on global state, such as @code{print},
29575 @code{set}, and breakpoint commands, still access the target in the
29576 context of a specific thread, so frontend should try to find a
29577 stopped thread and perform the operation on that thread (using the
29578 @samp{--thread} option).
29580 Which commands will work in the context of a running thread is
29581 highly target dependent. However, the two commands
29582 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29583 to find the state of a thread, will always work.
29585 @node Thread groups
29586 @subsection Thread groups
29587 @value{GDBN} may be used to debug several processes at the same time.
29588 On some platforms, @value{GDBN} may support debugging of several
29589 hardware systems, each one having several cores with several different
29590 processes running on each core. This section describes the MI
29591 mechanism to support such debugging scenarios.
29593 The key observation is that regardless of the structure of the
29594 target, MI can have a global list of threads, because most commands that
29595 accept the @samp{--thread} option do not need to know what process that
29596 thread belongs to. Therefore, it is not necessary to introduce
29597 neither additional @samp{--process} option, nor an notion of the
29598 current process in the MI interface. The only strictly new feature
29599 that is required is the ability to find how the threads are grouped
29602 To allow the user to discover such grouping, and to support arbitrary
29603 hierarchy of machines/cores/processes, MI introduces the concept of a
29604 @dfn{thread group}. Thread group is a collection of threads and other
29605 thread groups. A thread group always has a string identifier, a type,
29606 and may have additional attributes specific to the type. A new
29607 command, @code{-list-thread-groups}, returns the list of top-level
29608 thread groups, which correspond to processes that @value{GDBN} is
29609 debugging at the moment. By passing an identifier of a thread group
29610 to the @code{-list-thread-groups} command, it is possible to obtain
29611 the members of specific thread group.
29613 To allow the user to easily discover processes, and other objects, he
29614 wishes to debug, a concept of @dfn{available thread group} is
29615 introduced. Available thread group is an thread group that
29616 @value{GDBN} is not debugging, but that can be attached to, using the
29617 @code{-target-attach} command. The list of available top-level thread
29618 groups can be obtained using @samp{-list-thread-groups --available}.
29619 In general, the content of a thread group may be only retrieved only
29620 after attaching to that thread group.
29622 Thread groups are related to inferiors (@pxref{Inferiors Connections and
29623 Programs}). Each inferior corresponds to a thread group of a special
29624 type @samp{process}, and some additional operations are permitted on
29625 such thread groups.
29627 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29628 @node GDB/MI Command Syntax
29629 @section @sc{gdb/mi} Command Syntax
29632 * GDB/MI Input Syntax::
29633 * GDB/MI Output Syntax::
29636 @node GDB/MI Input Syntax
29637 @subsection @sc{gdb/mi} Input Syntax
29639 @cindex input syntax for @sc{gdb/mi}
29640 @cindex @sc{gdb/mi}, input syntax
29642 @item @var{command} @expansion{}
29643 @code{@var{cli-command} | @var{mi-command}}
29645 @item @var{cli-command} @expansion{}
29646 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29647 @var{cli-command} is any existing @value{GDBN} CLI command.
29649 @item @var{mi-command} @expansion{}
29650 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29651 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29653 @item @var{token} @expansion{}
29654 "any sequence of digits"
29656 @item @var{option} @expansion{}
29657 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29659 @item @var{parameter} @expansion{}
29660 @code{@var{non-blank-sequence} | @var{c-string}}
29662 @item @var{operation} @expansion{}
29663 @emph{any of the operations described in this chapter}
29665 @item @var{non-blank-sequence} @expansion{}
29666 @emph{anything, provided it doesn't contain special characters such as
29667 "-", @var{nl}, """ and of course " "}
29669 @item @var{c-string} @expansion{}
29670 @code{""" @var{seven-bit-iso-c-string-content} """}
29672 @item @var{nl} @expansion{}
29681 The CLI commands are still handled by the @sc{mi} interpreter; their
29682 output is described below.
29685 The @code{@var{token}}, when present, is passed back when the command
29689 Some @sc{mi} commands accept optional arguments as part of the parameter
29690 list. Each option is identified by a leading @samp{-} (dash) and may be
29691 followed by an optional argument parameter. Options occur first in the
29692 parameter list and can be delimited from normal parameters using
29693 @samp{--} (this is useful when some parameters begin with a dash).
29700 We want easy access to the existing CLI syntax (for debugging).
29703 We want it to be easy to spot a @sc{mi} operation.
29706 @node GDB/MI Output Syntax
29707 @subsection @sc{gdb/mi} Output Syntax
29709 @cindex output syntax of @sc{gdb/mi}
29710 @cindex @sc{gdb/mi}, output syntax
29711 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29712 followed, optionally, by a single result record. This result record
29713 is for the most recent command. The sequence of output records is
29714 terminated by @samp{(gdb)}.
29716 If an input command was prefixed with a @code{@var{token}} then the
29717 corresponding output for that command will also be prefixed by that same
29721 @item @var{output} @expansion{}
29722 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29724 @item @var{result-record} @expansion{}
29725 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29727 @item @var{out-of-band-record} @expansion{}
29728 @code{@var{async-record} | @var{stream-record}}
29730 @item @var{async-record} @expansion{}
29731 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29733 @item @var{exec-async-output} @expansion{}
29734 @code{[ @var{token} ] "*" @var{async-output nl}}
29736 @item @var{status-async-output} @expansion{}
29737 @code{[ @var{token} ] "+" @var{async-output nl}}
29739 @item @var{notify-async-output} @expansion{}
29740 @code{[ @var{token} ] "=" @var{async-output nl}}
29742 @item @var{async-output} @expansion{}
29743 @code{@var{async-class} ( "," @var{result} )*}
29745 @item @var{result-class} @expansion{}
29746 @code{"done" | "running" | "connected" | "error" | "exit"}
29748 @item @var{async-class} @expansion{}
29749 @code{"stopped" | @var{others}} (where @var{others} will be added
29750 depending on the needs---this is still in development).
29752 @item @var{result} @expansion{}
29753 @code{ @var{variable} "=" @var{value}}
29755 @item @var{variable} @expansion{}
29756 @code{ @var{string} }
29758 @item @var{value} @expansion{}
29759 @code{ @var{const} | @var{tuple} | @var{list} }
29761 @item @var{const} @expansion{}
29762 @code{@var{c-string}}
29764 @item @var{tuple} @expansion{}
29765 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29767 @item @var{list} @expansion{}
29768 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29769 @var{result} ( "," @var{result} )* "]" }
29771 @item @var{stream-record} @expansion{}
29772 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29774 @item @var{console-stream-output} @expansion{}
29775 @code{"~" @var{c-string nl}}
29777 @item @var{target-stream-output} @expansion{}
29778 @code{"@@" @var{c-string nl}}
29780 @item @var{log-stream-output} @expansion{}
29781 @code{"&" @var{c-string nl}}
29783 @item @var{nl} @expansion{}
29786 @item @var{token} @expansion{}
29787 @emph{any sequence of digits}.
29795 All output sequences end in a single line containing a period.
29798 The @code{@var{token}} is from the corresponding request. Note that
29799 for all async output, while the token is allowed by the grammar and
29800 may be output by future versions of @value{GDBN} for select async
29801 output messages, it is generally omitted. Frontends should treat
29802 all async output as reporting general changes in the state of the
29803 target and there should be no need to associate async output to any
29807 @cindex status output in @sc{gdb/mi}
29808 @var{status-async-output} contains on-going status information about the
29809 progress of a slow operation. It can be discarded. All status output is
29810 prefixed by @samp{+}.
29813 @cindex async output in @sc{gdb/mi}
29814 @var{exec-async-output} contains asynchronous state change on the target
29815 (stopped, started, disappeared). All async output is prefixed by
29819 @cindex notify output in @sc{gdb/mi}
29820 @var{notify-async-output} contains supplementary information that the
29821 client should handle (e.g., a new breakpoint information). All notify
29822 output is prefixed by @samp{=}.
29825 @cindex console output in @sc{gdb/mi}
29826 @var{console-stream-output} is output that should be displayed as is in the
29827 console. It is the textual response to a CLI command. All the console
29828 output is prefixed by @samp{~}.
29831 @cindex target output in @sc{gdb/mi}
29832 @var{target-stream-output} is the output produced by the target program.
29833 All the target output is prefixed by @samp{@@}.
29836 @cindex log output in @sc{gdb/mi}
29837 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29838 instance messages that should be displayed as part of an error log. All
29839 the log output is prefixed by @samp{&}.
29842 @cindex list output in @sc{gdb/mi}
29843 New @sc{gdb/mi} commands should only output @var{lists} containing
29849 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29850 details about the various output records.
29852 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29853 @node GDB/MI Compatibility with CLI
29854 @section @sc{gdb/mi} Compatibility with CLI
29856 @cindex compatibility, @sc{gdb/mi} and CLI
29857 @cindex @sc{gdb/mi}, compatibility with CLI
29859 For the developers convenience CLI commands can be entered directly,
29860 but there may be some unexpected behaviour. For example, commands
29861 that query the user will behave as if the user replied yes, breakpoint
29862 command lists are not executed and some CLI commands, such as
29863 @code{if}, @code{when} and @code{define}, prompt for further input with
29864 @samp{>}, which is not valid MI output.
29866 This feature may be removed at some stage in the future and it is
29867 recommended that front ends use the @code{-interpreter-exec} command
29868 (@pxref{-interpreter-exec}).
29870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29871 @node GDB/MI Development and Front Ends
29872 @section @sc{gdb/mi} Development and Front Ends
29873 @cindex @sc{gdb/mi} development
29875 The application which takes the MI output and presents the state of the
29876 program being debugged to the user is called a @dfn{front end}.
29878 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
29879 to the MI interface may break existing usage. This section describes how the
29880 protocol changes and how to request previous version of the protocol when it
29883 Some changes in MI need not break a carefully designed front end, and
29884 for these the MI version will remain unchanged. The following is a
29885 list of changes that may occur within one level, so front ends should
29886 parse MI output in a way that can handle them:
29890 New MI commands may be added.
29893 New fields may be added to the output of any MI command.
29896 The range of values for fields with specified values, e.g.,
29897 @code{in_scope} (@pxref{-var-update}) may be extended.
29899 @c The format of field's content e.g type prefix, may change so parse it
29900 @c at your own risk. Yes, in general?
29902 @c The order of fields may change? Shouldn't really matter but it might
29903 @c resolve inconsistencies.
29906 If the changes are likely to break front ends, the MI version level
29907 will be increased by one. The new versions of the MI protocol are not compatible
29908 with the old versions. Old versions of MI remain available, allowing front ends
29909 to keep using them until they are modified to use the latest MI version.
29911 Since @code{--interpreter=mi} always points to the latest MI version, it is
29912 recommended that front ends request a specific version of MI when launching
29913 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
29914 interpreter with the MI version they expect.
29916 The following table gives a summary of the released versions of the MI
29917 interface: the version number, the version of GDB in which it first appeared
29918 and the breaking changes compared to the previous version.
29920 @multitable @columnfractions .05 .05 .9
29921 @headitem MI version @tab GDB version @tab Breaking changes
29938 The @code{-environment-pwd}, @code{-environment-directory} and
29939 @code{-environment-path} commands now returns values using the MI output
29940 syntax, rather than CLI output syntax.
29943 @code{-var-list-children}'s @code{children} result field is now a list, rather
29947 @code{-var-update}'s @code{changelist} result field is now a list, rather than
29959 The output of information about multi-location breakpoints has changed in the
29960 responses to the @code{-break-insert} and @code{-break-info} commands, as well
29961 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
29962 The multiple locations are now placed in a @code{locations} field, whose value
29968 If your front end cannot yet migrate to a more recent version of the
29969 MI protocol, you can nevertheless selectively enable specific features
29970 available in those recent MI versions, using the following commands:
29974 @item -fix-multi-location-breakpoint-output
29975 Use the output for multi-location breakpoints which was introduced by
29976 MI 3, even when using MI versions 2 or 1. This command has no
29977 effect when using MI version 3 or later.
29981 The best way to avoid unexpected changes in MI that might break your front
29982 end is to make your project known to @value{GDBN} developers and
29983 follow development on @email{gdb@@sourceware.org} and
29984 @email{gdb-patches@@sourceware.org}.
29985 @cindex mailing lists
29987 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29988 @node GDB/MI Output Records
29989 @section @sc{gdb/mi} Output Records
29992 * GDB/MI Result Records::
29993 * GDB/MI Stream Records::
29994 * GDB/MI Async Records::
29995 * GDB/MI Breakpoint Information::
29996 * GDB/MI Frame Information::
29997 * GDB/MI Thread Information::
29998 * GDB/MI Ada Exception Information::
30001 @node GDB/MI Result Records
30002 @subsection @sc{gdb/mi} Result Records
30004 @cindex result records in @sc{gdb/mi}
30005 @cindex @sc{gdb/mi}, result records
30006 In addition to a number of out-of-band notifications, the response to a
30007 @sc{gdb/mi} command includes one of the following result indications:
30011 @item "^done" [ "," @var{results} ]
30012 The synchronous operation was successful, @code{@var{results}} are the return
30017 This result record is equivalent to @samp{^done}. Historically, it
30018 was output instead of @samp{^done} if the command has resumed the
30019 target. This behaviour is maintained for backward compatibility, but
30020 all frontends should treat @samp{^done} and @samp{^running}
30021 identically and rely on the @samp{*running} output record to determine
30022 which threads are resumed.
30026 @value{GDBN} has connected to a remote target.
30028 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30030 The operation failed. The @code{msg=@var{c-string}} variable contains
30031 the corresponding error message.
30033 If present, the @code{code=@var{c-string}} variable provides an error
30034 code on which consumers can rely on to detect the corresponding
30035 error condition. At present, only one error code is defined:
30038 @item "undefined-command"
30039 Indicates that the command causing the error does not exist.
30044 @value{GDBN} has terminated.
30048 @node GDB/MI Stream Records
30049 @subsection @sc{gdb/mi} Stream Records
30051 @cindex @sc{gdb/mi}, stream records
30052 @cindex stream records in @sc{gdb/mi}
30053 @value{GDBN} internally maintains a number of output streams: the console, the
30054 target, and the log. The output intended for each of these streams is
30055 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30057 Each stream record begins with a unique @dfn{prefix character} which
30058 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30059 Syntax}). In addition to the prefix, each stream record contains a
30060 @code{@var{string-output}}. This is either raw text (with an implicit new
30061 line) or a quoted C string (which does not contain an implicit newline).
30064 @item "~" @var{string-output}
30065 The console output stream contains text that should be displayed in the
30066 CLI console window. It contains the textual responses to CLI commands.
30068 @item "@@" @var{string-output}
30069 The target output stream contains any textual output from the running
30070 target. This is only present when GDB's event loop is truly
30071 asynchronous, which is currently only the case for remote targets.
30073 @item "&" @var{string-output}
30074 The log stream contains debugging messages being produced by @value{GDBN}'s
30078 @node GDB/MI Async Records
30079 @subsection @sc{gdb/mi} Async Records
30081 @cindex async records in @sc{gdb/mi}
30082 @cindex @sc{gdb/mi}, async records
30083 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30084 additional changes that have occurred. Those changes can either be a
30085 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30086 target activity (e.g., target stopped).
30088 The following is the list of possible async records:
30092 @item *running,thread-id="@var{thread}"
30093 The target is now running. The @var{thread} field can be the global
30094 thread ID of the thread that is now running, and it can be
30095 @samp{all} if all threads are running. The frontend should assume
30096 that no interaction with a running thread is possible after this
30097 notification is produced. The frontend should not assume that this
30098 notification is output only once for any command. @value{GDBN} may
30099 emit this notification several times, either for different threads,
30100 because it cannot resume all threads together, or even for a single
30101 thread, if the thread must be stepped though some code before letting
30104 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30105 The target has stopped. The @var{reason} field can have one of the
30109 @item breakpoint-hit
30110 A breakpoint was reached.
30111 @item watchpoint-trigger
30112 A watchpoint was triggered.
30113 @item read-watchpoint-trigger
30114 A read watchpoint was triggered.
30115 @item access-watchpoint-trigger
30116 An access watchpoint was triggered.
30117 @item function-finished
30118 An -exec-finish or similar CLI command was accomplished.
30119 @item location-reached
30120 An -exec-until or similar CLI command was accomplished.
30121 @item watchpoint-scope
30122 A watchpoint has gone out of scope.
30123 @item end-stepping-range
30124 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30125 similar CLI command was accomplished.
30126 @item exited-signalled
30127 The inferior exited because of a signal.
30129 The inferior exited.
30130 @item exited-normally
30131 The inferior exited normally.
30132 @item signal-received
30133 A signal was received by the inferior.
30135 The inferior has stopped due to a library being loaded or unloaded.
30136 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30137 set or when a @code{catch load} or @code{catch unload} catchpoint is
30138 in use (@pxref{Set Catchpoints}).
30140 The inferior has forked. This is reported when @code{catch fork}
30141 (@pxref{Set Catchpoints}) has been used.
30143 The inferior has vforked. This is reported in when @code{catch vfork}
30144 (@pxref{Set Catchpoints}) has been used.
30145 @item syscall-entry
30146 The inferior entered a system call. This is reported when @code{catch
30147 syscall} (@pxref{Set Catchpoints}) has been used.
30148 @item syscall-return
30149 The inferior returned from a system call. This is reported when
30150 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30152 The inferior called @code{exec}. This is reported when @code{catch exec}
30153 (@pxref{Set Catchpoints}) has been used.
30156 The @var{id} field identifies the global thread ID of the thread
30157 that directly caused the stop -- for example by hitting a breakpoint.
30158 Depending on whether all-stop
30159 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30160 stop all threads, or only the thread that directly triggered the stop.
30161 If all threads are stopped, the @var{stopped} field will have the
30162 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30163 field will be a list of thread identifiers. Presently, this list will
30164 always include a single thread, but frontend should be prepared to see
30165 several threads in the list. The @var{core} field reports the
30166 processor core on which the stop event has happened. This field may be absent
30167 if such information is not available.
30169 @item =thread-group-added,id="@var{id}"
30170 @itemx =thread-group-removed,id="@var{id}"
30171 A thread group was either added or removed. The @var{id} field
30172 contains the @value{GDBN} identifier of the thread group. When a thread
30173 group is added, it generally might not be associated with a running
30174 process. When a thread group is removed, its id becomes invalid and
30175 cannot be used in any way.
30177 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30178 A thread group became associated with a running program,
30179 either because the program was just started or the thread group
30180 was attached to a program. The @var{id} field contains the
30181 @value{GDBN} identifier of the thread group. The @var{pid} field
30182 contains process identifier, specific to the operating system.
30184 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30185 A thread group is no longer associated with a running program,
30186 either because the program has exited, or because it was detached
30187 from. The @var{id} field contains the @value{GDBN} identifier of the
30188 thread group. The @var{code} field is the exit code of the inferior; it exists
30189 only when the inferior exited with some code.
30191 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30192 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30193 A thread either was created, or has exited. The @var{id} field
30194 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30195 field identifies the thread group this thread belongs to.
30197 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30198 Informs that the selected thread or frame were changed. This notification
30199 is not emitted as result of the @code{-thread-select} or
30200 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30201 that is not documented to change the selected thread and frame actually
30202 changes them. In particular, invoking, directly or indirectly
30203 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30204 will generate this notification. Changing the thread or frame from another
30205 user interface (see @ref{Interpreters}) will also generate this notification.
30207 The @var{frame} field is only present if the newly selected thread is
30208 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30210 We suggest that in response to this notification, front ends
30211 highlight the selected thread and cause subsequent commands to apply to
30214 @item =library-loaded,...
30215 Reports that a new library file was loaded by the program. This
30216 notification has 5 fields---@var{id}, @var{target-name},
30217 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30218 opaque identifier of the library. For remote debugging case,
30219 @var{target-name} and @var{host-name} fields give the name of the
30220 library file on the target, and on the host respectively. For native
30221 debugging, both those fields have the same value. The
30222 @var{symbols-loaded} field is emitted only for backward compatibility
30223 and should not be relied on to convey any useful information. The
30224 @var{thread-group} field, if present, specifies the id of the thread
30225 group in whose context the library was loaded. If the field is
30226 absent, it means the library was loaded in the context of all present
30227 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30230 @item =library-unloaded,...
30231 Reports that a library was unloaded by the program. This notification
30232 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30233 the same meaning as for the @code{=library-loaded} notification.
30234 The @var{thread-group} field, if present, specifies the id of the
30235 thread group in whose context the library was unloaded. If the field is
30236 absent, it means the library was unloaded in the context of all present
30239 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30240 @itemx =traceframe-changed,end
30241 Reports that the trace frame was changed and its new number is
30242 @var{tfnum}. The number of the tracepoint associated with this trace
30243 frame is @var{tpnum}.
30245 @item =tsv-created,name=@var{name},initial=@var{initial}
30246 Reports that the new trace state variable @var{name} is created with
30247 initial value @var{initial}.
30249 @item =tsv-deleted,name=@var{name}
30250 @itemx =tsv-deleted
30251 Reports that the trace state variable @var{name} is deleted or all
30252 trace state variables are deleted.
30254 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30255 Reports that the trace state variable @var{name} is modified with
30256 the initial value @var{initial}. The current value @var{current} of
30257 trace state variable is optional and is reported if the current
30258 value of trace state variable is known.
30260 @item =breakpoint-created,bkpt=@{...@}
30261 @itemx =breakpoint-modified,bkpt=@{...@}
30262 @itemx =breakpoint-deleted,id=@var{number}
30263 Reports that a breakpoint was created, modified, or deleted,
30264 respectively. Only user-visible breakpoints are reported to the MI
30267 The @var{bkpt} argument is of the same form as returned by the various
30268 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30269 @var{number} is the ordinal number of the breakpoint.
30271 Note that if a breakpoint is emitted in the result record of a
30272 command, then it will not also be emitted in an async record.
30274 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30275 @itemx =record-stopped,thread-group="@var{id}"
30276 Execution log recording was either started or stopped on an
30277 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30278 group corresponding to the affected inferior.
30280 The @var{method} field indicates the method used to record execution. If the
30281 method in use supports multiple recording formats, @var{format} will be present
30282 and contain the currently used format. @xref{Process Record and Replay},
30283 for existing method and format values.
30285 @item =cmd-param-changed,param=@var{param},value=@var{value}
30286 Reports that a parameter of the command @code{set @var{param}} is
30287 changed to @var{value}. In the multi-word @code{set} command,
30288 the @var{param} is the whole parameter list to @code{set} command.
30289 For example, In command @code{set check type on}, @var{param}
30290 is @code{check type} and @var{value} is @code{on}.
30292 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30293 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30294 written in an inferior. The @var{id} is the identifier of the
30295 thread group corresponding to the affected inferior. The optional
30296 @code{type="code"} part is reported if the memory written to holds
30300 @node GDB/MI Breakpoint Information
30301 @subsection @sc{gdb/mi} Breakpoint Information
30303 When @value{GDBN} reports information about a breakpoint, a
30304 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30309 The breakpoint number.
30312 The type of the breakpoint. For ordinary breakpoints this will be
30313 @samp{breakpoint}, but many values are possible.
30316 If the type of the breakpoint is @samp{catchpoint}, then this
30317 indicates the exact type of catchpoint.
30320 This is the breakpoint disposition---either @samp{del}, meaning that
30321 the breakpoint will be deleted at the next stop, or @samp{keep},
30322 meaning that the breakpoint will not be deleted.
30325 This indicates whether the breakpoint is enabled, in which case the
30326 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30327 Note that this is not the same as the field @code{enable}.
30330 The address of the breakpoint. This may be a hexidecimal number,
30331 giving the address; or the string @samp{<PENDING>}, for a pending
30332 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30333 multiple locations. This field will not be present if no address can
30334 be determined. For example, a watchpoint does not have an address.
30337 Optional field containing any flags related to the address. These flags are
30338 architecture-dependent; see @ref{Architectures} for their meaning for a
30342 If known, the function in which the breakpoint appears.
30343 If not known, this field is not present.
30346 The name of the source file which contains this function, if known.
30347 If not known, this field is not present.
30350 The full file name of the source file which contains this function, if
30351 known. If not known, this field is not present.
30354 The line number at which this breakpoint appears, if known.
30355 If not known, this field is not present.
30358 If the source file is not known, this field may be provided. If
30359 provided, this holds the address of the breakpoint, possibly followed
30363 If this breakpoint is pending, this field is present and holds the
30364 text used to set the breakpoint, as entered by the user.
30367 Where this breakpoint's condition is evaluated, either @samp{host} or
30371 If this is a thread-specific breakpoint, then this identifies the
30372 thread in which the breakpoint can trigger.
30375 If this breakpoint is restricted to a particular Ada task, then this
30376 field will hold the task identifier.
30379 If the breakpoint is conditional, this is the condition expression.
30382 The ignore count of the breakpoint.
30385 The enable count of the breakpoint.
30387 @item traceframe-usage
30390 @item static-tracepoint-marker-string-id
30391 For a static tracepoint, the name of the static tracepoint marker.
30394 For a masked watchpoint, this is the mask.
30397 A tracepoint's pass count.
30399 @item original-location
30400 The location of the breakpoint as originally specified by the user.
30401 This field is optional.
30404 The number of times the breakpoint has been hit.
30407 This field is only given for tracepoints. This is either @samp{y},
30408 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30412 Some extra data, the exact contents of which are type-dependent.
30415 This field is present if the breakpoint has multiple locations. It is also
30416 exceptionally present if the breakpoint is enabled and has a single, disabled
30419 The value is a list of locations. The format of a location is described below.
30423 A location in a multi-location breakpoint is represented as a tuple with the
30429 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30430 number of the parent breakpoint. The second digit is the number of the
30431 location within that breakpoint.
30434 There are three possible values, with the following meanings:
30437 The location is enabled.
30439 The location is disabled by the user.
30441 The location is disabled because the breakpoint condition is invalid
30446 The address of this location as an hexidecimal number.
30449 Optional field containing any flags related to the address. These flags are
30450 architecture-dependent; see @ref{Architectures} for their meaning for a
30454 If known, the function in which the location appears.
30455 If not known, this field is not present.
30458 The name of the source file which contains this location, if known.
30459 If not known, this field is not present.
30462 The full file name of the source file which contains this location, if
30463 known. If not known, this field is not present.
30466 The line number at which this location appears, if known.
30467 If not known, this field is not present.
30469 @item thread-groups
30470 The thread groups this location is in.
30474 For example, here is what the output of @code{-break-insert}
30475 (@pxref{GDB/MI Breakpoint Commands}) might be:
30478 -> -break-insert main
30479 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30480 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30481 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30486 @node GDB/MI Frame Information
30487 @subsection @sc{gdb/mi} Frame Information
30489 Response from many MI commands includes an information about stack
30490 frame. This information is a tuple that may have the following
30495 The level of the stack frame. The innermost frame has the level of
30496 zero. This field is always present.
30499 The name of the function corresponding to the frame. This field may
30500 be absent if @value{GDBN} is unable to determine the function name.
30503 The code address for the frame. This field is always present.
30506 Optional field containing any flags related to the address. These flags are
30507 architecture-dependent; see @ref{Architectures} for their meaning for a
30511 The name of the source files that correspond to the frame's code
30512 address. This field may be absent.
30515 The source line corresponding to the frames' code address. This field
30519 The name of the binary file (either executable or shared library) the
30520 corresponds to the frame's code address. This field may be absent.
30524 @node GDB/MI Thread Information
30525 @subsection @sc{gdb/mi} Thread Information
30527 Whenever @value{GDBN} has to report an information about a thread, it
30528 uses a tuple with the following fields. The fields are always present unless
30533 The global numeric id assigned to the thread by @value{GDBN}.
30536 The target-specific string identifying the thread.
30539 Additional information about the thread provided by the target.
30540 It is supposed to be human-readable and not interpreted by the
30541 frontend. This field is optional.
30544 The name of the thread. If the user specified a name using the
30545 @code{thread name} command, then this name is given. Otherwise, if
30546 @value{GDBN} can extract the thread name from the target, then that
30547 name is given. If @value{GDBN} cannot find the thread name, then this
30551 The execution state of the thread, either @samp{stopped} or @samp{running},
30552 depending on whether the thread is presently running.
30555 The stack frame currently executing in the thread. This field is only present
30556 if the thread is stopped. Its format is documented in
30557 @ref{GDB/MI Frame Information}.
30560 The value of this field is an integer number of the processor core the
30561 thread was last seen on. This field is optional.
30564 @node GDB/MI Ada Exception Information
30565 @subsection @sc{gdb/mi} Ada Exception Information
30567 Whenever a @code{*stopped} record is emitted because the program
30568 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30569 @value{GDBN} provides the name of the exception that was raised via
30570 the @code{exception-name} field. Also, for exceptions that were raised
30571 with an exception message, @value{GDBN} provides that message via
30572 the @code{exception-message} field.
30574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30575 @node GDB/MI Simple Examples
30576 @section Simple Examples of @sc{gdb/mi} Interaction
30577 @cindex @sc{gdb/mi}, simple examples
30579 This subsection presents several simple examples of interaction using
30580 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30581 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30582 the output received from @sc{gdb/mi}.
30584 Note the line breaks shown in the examples are here only for
30585 readability, they don't appear in the real output.
30587 @subheading Setting a Breakpoint
30589 Setting a breakpoint generates synchronous output which contains detailed
30590 information of the breakpoint.
30593 -> -break-insert main
30594 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30595 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30596 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30601 @subheading Program Execution
30603 Program execution generates asynchronous records and MI gives the
30604 reason that execution stopped.
30610 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30611 frame=@{addr="0x08048564",func="main",
30612 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
30613 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
30614 arch="i386:x86_64"@}
30619 <- *stopped,reason="exited-normally"
30623 @subheading Quitting @value{GDBN}
30625 Quitting @value{GDBN} just prints the result class @samp{^exit}.
30633 Please note that @samp{^exit} is printed immediately, but it might
30634 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
30635 performs necessary cleanups, including killing programs being debugged
30636 or disconnecting from debug hardware, so the frontend should wait till
30637 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
30638 fails to exit in reasonable time.
30640 @subheading A Bad Command
30642 Here's what happens if you pass a non-existent command:
30646 <- ^error,msg="Undefined MI command: rubbish"
30651 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30652 @node GDB/MI Command Description Format
30653 @section @sc{gdb/mi} Command Description Format
30655 The remaining sections describe blocks of commands. Each block of
30656 commands is laid out in a fashion similar to this section.
30658 @subheading Motivation
30660 The motivation for this collection of commands.
30662 @subheading Introduction
30664 A brief introduction to this collection of commands as a whole.
30666 @subheading Commands
30668 For each command in the block, the following is described:
30670 @subsubheading Synopsis
30673 -command @var{args}@dots{}
30676 @subsubheading Result
30678 @subsubheading @value{GDBN} Command
30680 The corresponding @value{GDBN} CLI command(s), if any.
30682 @subsubheading Example
30684 Example(s) formatted for readability. Some of the described commands have
30685 not been implemented yet and these are labeled N.A.@: (not available).
30688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30689 @node GDB/MI Breakpoint Commands
30690 @section @sc{gdb/mi} Breakpoint Commands
30692 @cindex breakpoint commands for @sc{gdb/mi}
30693 @cindex @sc{gdb/mi}, breakpoint commands
30694 This section documents @sc{gdb/mi} commands for manipulating
30697 @subheading The @code{-break-after} Command
30698 @findex -break-after
30700 @subsubheading Synopsis
30703 -break-after @var{number} @var{count}
30706 The breakpoint number @var{number} is not in effect until it has been
30707 hit @var{count} times. To see how this is reflected in the output of
30708 the @samp{-break-list} command, see the description of the
30709 @samp{-break-list} command below.
30711 @subsubheading @value{GDBN} Command
30713 The corresponding @value{GDBN} command is @samp{ignore}.
30715 @subsubheading Example
30720 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30721 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30722 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30730 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30731 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30732 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30733 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30734 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30735 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30736 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30737 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30738 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30739 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30744 @subheading The @code{-break-catch} Command
30745 @findex -break-catch
30748 @subheading The @code{-break-commands} Command
30749 @findex -break-commands
30751 @subsubheading Synopsis
30754 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30757 Specifies the CLI commands that should be executed when breakpoint
30758 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30759 are the commands. If no command is specified, any previously-set
30760 commands are cleared. @xref{Break Commands}. Typical use of this
30761 functionality is tracing a program, that is, printing of values of
30762 some variables whenever breakpoint is hit and then continuing.
30764 @subsubheading @value{GDBN} Command
30766 The corresponding @value{GDBN} command is @samp{commands}.
30768 @subsubheading Example
30773 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30774 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30775 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30778 -break-commands 1 "print v" "continue"
30783 @subheading The @code{-break-condition} Command
30784 @findex -break-condition
30786 @subsubheading Synopsis
30789 -break-condition [ --force ] @var{number} [ @var{expr} ]
30792 Breakpoint @var{number} will stop the program only if the condition in
30793 @var{expr} is true. The condition becomes part of the
30794 @samp{-break-list} output (see the description of the @samp{-break-list}
30795 command below). If the @samp{--force} flag is passed, the condition
30796 is forcibly defined even when it is invalid for all locations of
30797 breakpoint @var{number}. If the @var{expr} argument is omitted,
30798 breakpoint @var{number} becomes unconditional.
30800 @subsubheading @value{GDBN} Command
30802 The corresponding @value{GDBN} command is @samp{condition}.
30804 @subsubheading Example
30808 -break-condition 1 1
30812 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30813 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30814 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30815 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30816 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30817 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30818 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30819 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30820 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30821 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30825 @subheading The @code{-break-delete} Command
30826 @findex -break-delete
30828 @subsubheading Synopsis
30831 -break-delete ( @var{breakpoint} )+
30834 Delete the breakpoint(s) whose number(s) are specified in the argument
30835 list. This is obviously reflected in the breakpoint list.
30837 @subsubheading @value{GDBN} Command
30839 The corresponding @value{GDBN} command is @samp{delete}.
30841 @subsubheading Example
30849 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30850 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30851 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30852 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30853 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30854 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30855 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30860 @subheading The @code{-break-disable} Command
30861 @findex -break-disable
30863 @subsubheading Synopsis
30866 -break-disable ( @var{breakpoint} )+
30869 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30870 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30872 @subsubheading @value{GDBN} Command
30874 The corresponding @value{GDBN} command is @samp{disable}.
30876 @subsubheading Example
30884 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30885 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30886 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30887 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30888 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30889 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30890 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30891 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30892 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30893 line="5",thread-groups=["i1"],times="0"@}]@}
30897 @subheading The @code{-break-enable} Command
30898 @findex -break-enable
30900 @subsubheading Synopsis
30903 -break-enable ( @var{breakpoint} )+
30906 Enable (previously disabled) @var{breakpoint}(s).
30908 @subsubheading @value{GDBN} Command
30910 The corresponding @value{GDBN} command is @samp{enable}.
30912 @subsubheading Example
30920 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30921 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30922 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30923 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30924 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30925 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30926 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30927 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30928 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30929 line="5",thread-groups=["i1"],times="0"@}]@}
30933 @subheading The @code{-break-info} Command
30934 @findex -break-info
30936 @subsubheading Synopsis
30939 -break-info @var{breakpoint}
30943 Get information about a single breakpoint.
30945 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30946 Information}, for details on the format of each breakpoint in the
30949 @subsubheading @value{GDBN} Command
30951 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30953 @subsubheading Example
30956 @subheading The @code{-break-insert} Command
30957 @findex -break-insert
30958 @anchor{-break-insert}
30960 @subsubheading Synopsis
30963 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
30964 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
30965 [ -p @var{thread-id} ] [ @var{location} ]
30969 If specified, @var{location}, can be one of:
30972 @item linespec location
30973 A linespec location. @xref{Linespec Locations}.
30975 @item explicit location
30976 An explicit location. @sc{gdb/mi} explicit locations are
30977 analogous to the CLI's explicit locations using the option names
30978 listed below. @xref{Explicit Locations}.
30981 @item --source @var{filename}
30982 The source file name of the location. This option requires the use
30983 of either @samp{--function} or @samp{--line}.
30985 @item --function @var{function}
30986 The name of a function or method.
30988 @item --label @var{label}
30989 The name of a label.
30991 @item --line @var{lineoffset}
30992 An absolute or relative line offset from the start of the location.
30995 @item address location
30996 An address location, *@var{address}. @xref{Address Locations}.
31000 The possible optional parameters of this command are:
31004 Insert a temporary breakpoint.
31006 Insert a hardware breakpoint.
31008 If @var{location} cannot be parsed (for example if it
31009 refers to unknown files or functions), create a pending
31010 breakpoint. Without this flag, @value{GDBN} will report
31011 an error, and won't create a breakpoint, if @var{location}
31014 Create a disabled breakpoint.
31016 Create a tracepoint. @xref{Tracepoints}. When this parameter
31017 is used together with @samp{-h}, a fast tracepoint is created.
31018 @item -c @var{condition}
31019 Make the breakpoint conditional on @var{condition}.
31020 @item --force-condition
31021 Forcibly define the breakpoint even if the condition is invalid at
31022 all of the breakpoint locations.
31023 @item -i @var{ignore-count}
31024 Initialize the @var{ignore-count}.
31025 @item -p @var{thread-id}
31026 Restrict the breakpoint to the thread with the specified global
31029 This option makes @value{GDBN} interpret a function name specified as
31030 a complete fully-qualified name.
31033 @subsubheading Result
31035 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31036 resulting breakpoint.
31038 Note: this format is open to change.
31039 @c An out-of-band breakpoint instead of part of the result?
31041 @subsubheading @value{GDBN} Command
31043 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31044 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31046 @subsubheading Example
31051 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31052 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31055 -break-insert -t foo
31056 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31057 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31061 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31062 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31063 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31064 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31065 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31066 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31067 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31068 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31069 addr="0x0001072c", func="main",file="recursive2.c",
31070 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31072 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31073 addr="0x00010774",func="foo",file="recursive2.c",
31074 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31077 @c -break-insert -r foo.*
31078 @c ~int foo(int, int);
31079 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
31080 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31085 @subheading The @code{-dprintf-insert} Command
31086 @findex -dprintf-insert
31088 @subsubheading Synopsis
31091 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31092 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31093 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
31098 If supplied, @var{location} and @code{--qualified} may be specified
31099 the same way as for the @code{-break-insert} command.
31100 @xref{-break-insert}.
31102 The possible optional parameters of this command are:
31106 Insert a temporary breakpoint.
31108 If @var{location} cannot be parsed (for example, if it
31109 refers to unknown files or functions), create a pending
31110 breakpoint. Without this flag, @value{GDBN} will report
31111 an error, and won't create a breakpoint, if @var{location}
31114 Create a disabled breakpoint.
31115 @item -c @var{condition}
31116 Make the breakpoint conditional on @var{condition}.
31117 @item --force-condition
31118 Forcibly define the breakpoint even if the condition is invalid at
31119 all of the breakpoint locations.
31120 @item -i @var{ignore-count}
31121 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31122 to @var{ignore-count}.
31123 @item -p @var{thread-id}
31124 Restrict the breakpoint to the thread with the specified global
31128 @subsubheading Result
31130 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31131 resulting breakpoint.
31133 @c An out-of-band breakpoint instead of part of the result?
31135 @subsubheading @value{GDBN} Command
31137 The corresponding @value{GDBN} command is @samp{dprintf}.
31139 @subsubheading Example
31143 4-dprintf-insert foo "At foo entry\n"
31144 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31145 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31146 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31147 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
31148 original-location="foo"@}
31150 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31151 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31152 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31153 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31154 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
31155 original-location="mi-dprintf.c:26"@}
31159 @subheading The @code{-break-list} Command
31160 @findex -break-list
31162 @subsubheading Synopsis
31168 Displays the list of inserted breakpoints, showing the following fields:
31172 number of the breakpoint
31174 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31176 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31179 is the breakpoint enabled or no: @samp{y} or @samp{n}
31181 memory location at which the breakpoint is set
31183 logical location of the breakpoint, expressed by function name, file
31185 @item Thread-groups
31186 list of thread groups to which this breakpoint applies
31188 number of times the breakpoint has been hit
31191 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31192 @code{body} field is an empty list.
31194 @subsubheading @value{GDBN} Command
31196 The corresponding @value{GDBN} command is @samp{info break}.
31198 @subsubheading Example
31203 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31204 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31205 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31206 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31207 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31208 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31209 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31210 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31211 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31213 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31214 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31215 line="13",thread-groups=["i1"],times="0"@}]@}
31219 Here's an example of the result when there are no breakpoints:
31224 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31225 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31226 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31227 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31228 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31229 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31230 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31235 @subheading The @code{-break-passcount} Command
31236 @findex -break-passcount
31238 @subsubheading Synopsis
31241 -break-passcount @var{tracepoint-number} @var{passcount}
31244 Set the passcount for tracepoint @var{tracepoint-number} to
31245 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31246 is not a tracepoint, error is emitted. This corresponds to CLI
31247 command @samp{passcount}.
31249 @subheading The @code{-break-watch} Command
31250 @findex -break-watch
31252 @subsubheading Synopsis
31255 -break-watch [ -a | -r ]
31258 Create a watchpoint. With the @samp{-a} option it will create an
31259 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31260 read from or on a write to the memory location. With the @samp{-r}
31261 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31262 trigger only when the memory location is accessed for reading. Without
31263 either of the options, the watchpoint created is a regular watchpoint,
31264 i.e., it will trigger when the memory location is accessed for writing.
31265 @xref{Set Watchpoints, , Setting Watchpoints}.
31267 Note that @samp{-break-list} will report a single list of watchpoints and
31268 breakpoints inserted.
31270 @subsubheading @value{GDBN} Command
31272 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31275 @subsubheading Example
31277 Setting a watchpoint on a variable in the @code{main} function:
31282 ^done,wpt=@{number="2",exp="x"@}
31287 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31288 value=@{old="-268439212",new="55"@},
31289 frame=@{func="main",args=[],file="recursive2.c",
31290 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31294 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31295 the program execution twice: first for the variable changing value, then
31296 for the watchpoint going out of scope.
31301 ^done,wpt=@{number="5",exp="C"@}
31306 *stopped,reason="watchpoint-trigger",
31307 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31308 frame=@{func="callee4",args=[],
31309 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31310 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31311 arch="i386:x86_64"@}
31316 *stopped,reason="watchpoint-scope",wpnum="5",
31317 frame=@{func="callee3",args=[@{name="strarg",
31318 value="0x11940 \"A string argument.\""@}],
31319 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31320 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31321 arch="i386:x86_64"@}
31325 Listing breakpoints and watchpoints, at different points in the program
31326 execution. Note that once the watchpoint goes out of scope, it is
31332 ^done,wpt=@{number="2",exp="C"@}
31335 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31336 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31337 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31338 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31339 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31340 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31341 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31342 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31343 addr="0x00010734",func="callee4",
31344 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31345 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31347 bkpt=@{number="2",type="watchpoint",disp="keep",
31348 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31353 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31354 value=@{old="-276895068",new="3"@},
31355 frame=@{func="callee4",args=[],
31356 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31357 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31358 arch="i386:x86_64"@}
31361 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31362 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31363 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31364 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31365 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31366 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31367 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31368 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31369 addr="0x00010734",func="callee4",
31370 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31371 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31373 bkpt=@{number="2",type="watchpoint",disp="keep",
31374 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31378 ^done,reason="watchpoint-scope",wpnum="2",
31379 frame=@{func="callee3",args=[@{name="strarg",
31380 value="0x11940 \"A string argument.\""@}],
31381 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31382 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31383 arch="i386:x86_64"@}
31386 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31387 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31388 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31389 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31390 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31391 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31392 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31393 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31394 addr="0x00010734",func="callee4",
31395 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31396 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31397 thread-groups=["i1"],times="1"@}]@}
31402 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31403 @node GDB/MI Catchpoint Commands
31404 @section @sc{gdb/mi} Catchpoint Commands
31406 This section documents @sc{gdb/mi} commands for manipulating
31410 * Shared Library GDB/MI Catchpoint Commands::
31411 * Ada Exception GDB/MI Catchpoint Commands::
31412 * C++ Exception GDB/MI Catchpoint Commands::
31415 @node Shared Library GDB/MI Catchpoint Commands
31416 @subsection Shared Library @sc{gdb/mi} Catchpoints
31418 @subheading The @code{-catch-load} Command
31419 @findex -catch-load
31421 @subsubheading Synopsis
31424 -catch-load [ -t ] [ -d ] @var{regexp}
31427 Add a catchpoint for library load events. If the @samp{-t} option is used,
31428 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31429 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31430 in a disabled state. The @samp{regexp} argument is a regular
31431 expression used to match the name of the loaded library.
31434 @subsubheading @value{GDBN} Command
31436 The corresponding @value{GDBN} command is @samp{catch load}.
31438 @subsubheading Example
31441 -catch-load -t foo.so
31442 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31443 what="load of library matching foo.so",catch-type="load",times="0"@}
31448 @subheading The @code{-catch-unload} Command
31449 @findex -catch-unload
31451 @subsubheading Synopsis
31454 -catch-unload [ -t ] [ -d ] @var{regexp}
31457 Add a catchpoint for library unload events. If the @samp{-t} option is
31458 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31459 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31460 created in a disabled state. The @samp{regexp} argument is a regular
31461 expression used to match the name of the unloaded library.
31463 @subsubheading @value{GDBN} Command
31465 The corresponding @value{GDBN} command is @samp{catch unload}.
31467 @subsubheading Example
31470 -catch-unload -d bar.so
31471 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31472 what="load of library matching bar.so",catch-type="unload",times="0"@}
31476 @node Ada Exception GDB/MI Catchpoint Commands
31477 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31479 The following @sc{gdb/mi} commands can be used to create catchpoints
31480 that stop the execution when Ada exceptions are being raised.
31482 @subheading The @code{-catch-assert} Command
31483 @findex -catch-assert
31485 @subsubheading Synopsis
31488 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31491 Add a catchpoint for failed Ada assertions.
31493 The possible optional parameters for this command are:
31496 @item -c @var{condition}
31497 Make the catchpoint conditional on @var{condition}.
31499 Create a disabled catchpoint.
31501 Create a temporary catchpoint.
31504 @subsubheading @value{GDBN} Command
31506 The corresponding @value{GDBN} command is @samp{catch assert}.
31508 @subsubheading Example
31512 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31513 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31514 thread-groups=["i1"],times="0",
31515 original-location="__gnat_debug_raise_assert_failure"@}
31519 @subheading The @code{-catch-exception} Command
31520 @findex -catch-exception
31522 @subsubheading Synopsis
31525 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31529 Add a catchpoint stopping when Ada exceptions are raised.
31530 By default, the command stops the program when any Ada exception
31531 gets raised. But it is also possible, by using some of the
31532 optional parameters described below, to create more selective
31535 The possible optional parameters for this command are:
31538 @item -c @var{condition}
31539 Make the catchpoint conditional on @var{condition}.
31541 Create a disabled catchpoint.
31542 @item -e @var{exception-name}
31543 Only stop when @var{exception-name} is raised. This option cannot
31544 be used combined with @samp{-u}.
31546 Create a temporary catchpoint.
31548 Stop only when an unhandled exception gets raised. This option
31549 cannot be used combined with @samp{-e}.
31552 @subsubheading @value{GDBN} Command
31554 The corresponding @value{GDBN} commands are @samp{catch exception}
31555 and @samp{catch exception unhandled}.
31557 @subsubheading Example
31560 -catch-exception -e Program_Error
31561 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31562 enabled="y",addr="0x0000000000404874",
31563 what="`Program_Error' Ada exception", thread-groups=["i1"],
31564 times="0",original-location="__gnat_debug_raise_exception"@}
31568 @subheading The @code{-catch-handlers} Command
31569 @findex -catch-handlers
31571 @subsubheading Synopsis
31574 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31578 Add a catchpoint stopping when Ada exceptions are handled.
31579 By default, the command stops the program when any Ada exception
31580 gets handled. But it is also possible, by using some of the
31581 optional parameters described below, to create more selective
31584 The possible optional parameters for this command are:
31587 @item -c @var{condition}
31588 Make the catchpoint conditional on @var{condition}.
31590 Create a disabled catchpoint.
31591 @item -e @var{exception-name}
31592 Only stop when @var{exception-name} is handled.
31594 Create a temporary catchpoint.
31597 @subsubheading @value{GDBN} Command
31599 The corresponding @value{GDBN} command is @samp{catch handlers}.
31601 @subsubheading Example
31604 -catch-handlers -e Constraint_Error
31605 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31606 enabled="y",addr="0x0000000000402f68",
31607 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
31608 times="0",original-location="__gnat_begin_handler"@}
31612 @node C++ Exception GDB/MI Catchpoint Commands
31613 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
31615 The following @sc{gdb/mi} commands can be used to create catchpoints
31616 that stop the execution when C@t{++} exceptions are being throw, rethrown,
31619 @subheading The @code{-catch-throw} Command
31620 @findex -catch-throw
31622 @subsubheading Synopsis
31625 -catch-throw [ -t ] [ -r @var{regexp}]
31628 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
31629 given, then only exceptions whose type matches the regular expression
31632 If @samp{-t} is given, then the catchpoint is enabled only for one
31633 stop, the catchpoint is automatically deleted after stopping once for
31636 @subsubheading @value{GDBN} Command
31638 The corresponding @value{GDBN} commands are @samp{catch throw}
31639 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
31641 @subsubheading Example
31644 -catch-throw -r exception_type
31645 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31646 what="exception throw",catch-type="throw",
31647 thread-groups=["i1"],
31648 regexp="exception_type",times="0"@}
31654 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
31655 in __cxa_throw () from /lib64/libstdc++.so.6\n"
31656 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31657 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
31658 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31659 thread-id="1",stopped-threads="all",core="6"
31663 @subheading The @code{-catch-rethrow} Command
31664 @findex -catch-rethrow
31666 @subsubheading Synopsis
31669 -catch-rethrow [ -t ] [ -r @var{regexp}]
31672 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
31673 then only exceptions whose type matches the regular expression will be
31676 If @samp{-t} is given, then the catchpoint is enabled only for one
31677 stop, the catchpoint is automatically deleted after the first event is
31680 @subsubheading @value{GDBN} Command
31682 The corresponding @value{GDBN} commands are @samp{catch rethrow}
31683 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
31685 @subsubheading Example
31688 -catch-rethrow -r exception_type
31689 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31690 what="exception rethrow",catch-type="rethrow",
31691 thread-groups=["i1"],
31692 regexp="exception_type",times="0"@}
31698 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
31699 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
31700 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31701 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
31702 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31703 thread-id="1",stopped-threads="all",core="6"
31707 @subheading The @code{-catch-catch} Command
31708 @findex -catch-catch
31710 @subsubheading Synopsis
31713 -catch-catch [ -t ] [ -r @var{regexp}]
31716 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
31717 is given, then only exceptions whose type matches the regular
31718 expression will be caught.
31720 If @samp{-t} is given, then the catchpoint is enabled only for one
31721 stop, the catchpoint is automatically deleted after the first event is
31724 @subsubheading @value{GDBN} Command
31726 The corresponding @value{GDBN} commands are @samp{catch catch}
31727 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
31729 @subsubheading Example
31732 -catch-catch -r exception_type
31733 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31734 what="exception catch",catch-type="catch",
31735 thread-groups=["i1"],
31736 regexp="exception_type",times="0"@}
31742 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
31743 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
31744 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31745 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
31746 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31747 thread-id="1",stopped-threads="all",core="6"
31751 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31752 @node GDB/MI Program Context
31753 @section @sc{gdb/mi} Program Context
31755 @subheading The @code{-exec-arguments} Command
31756 @findex -exec-arguments
31759 @subsubheading Synopsis
31762 -exec-arguments @var{args}
31765 Set the inferior program arguments, to be used in the next
31768 @subsubheading @value{GDBN} Command
31770 The corresponding @value{GDBN} command is @samp{set args}.
31772 @subsubheading Example
31776 -exec-arguments -v word
31783 @subheading The @code{-exec-show-arguments} Command
31784 @findex -exec-show-arguments
31786 @subsubheading Synopsis
31789 -exec-show-arguments
31792 Print the arguments of the program.
31794 @subsubheading @value{GDBN} Command
31796 The corresponding @value{GDBN} command is @samp{show args}.
31798 @subsubheading Example
31803 @subheading The @code{-environment-cd} Command
31804 @findex -environment-cd
31806 @subsubheading Synopsis
31809 -environment-cd @var{pathdir}
31812 Set @value{GDBN}'s working directory.
31814 @subsubheading @value{GDBN} Command
31816 The corresponding @value{GDBN} command is @samp{cd}.
31818 @subsubheading Example
31822 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31828 @subheading The @code{-environment-directory} Command
31829 @findex -environment-directory
31831 @subsubheading Synopsis
31834 -environment-directory [ -r ] [ @var{pathdir} ]+
31837 Add directories @var{pathdir} to beginning of search path for source files.
31838 If the @samp{-r} option is used, the search path is reset to the default
31839 search path. If directories @var{pathdir} are supplied in addition to the
31840 @samp{-r} option, the search path is first reset and then addition
31842 Multiple directories may be specified, separated by blanks. Specifying
31843 multiple directories in a single command
31844 results in the directories added to the beginning of the
31845 search path in the same order they were presented in the command.
31846 If blanks are needed as
31847 part of a directory name, double-quotes should be used around
31848 the name. In the command output, the path will show up separated
31849 by the system directory-separator character. The directory-separator
31850 character must not be used
31851 in any directory name.
31852 If no directories are specified, the current search path is displayed.
31854 @subsubheading @value{GDBN} Command
31856 The corresponding @value{GDBN} command is @samp{dir}.
31858 @subsubheading Example
31862 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
31863 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31865 -environment-directory ""
31866 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
31868 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
31869 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
31871 -environment-directory -r
31872 ^done,source-path="$cdir:$cwd"
31877 @subheading The @code{-environment-path} Command
31878 @findex -environment-path
31880 @subsubheading Synopsis
31883 -environment-path [ -r ] [ @var{pathdir} ]+
31886 Add directories @var{pathdir} to beginning of search path for object files.
31887 If the @samp{-r} option is used, the search path is reset to the original
31888 search path that existed at gdb start-up. If directories @var{pathdir} are
31889 supplied in addition to the
31890 @samp{-r} option, the search path is first reset and then addition
31892 Multiple directories may be specified, separated by blanks. Specifying
31893 multiple directories in a single command
31894 results in the directories added to the beginning of the
31895 search path in the same order they were presented in the command.
31896 If blanks are needed as
31897 part of a directory name, double-quotes should be used around
31898 the name. In the command output, the path will show up separated
31899 by the system directory-separator character. The directory-separator
31900 character must not be used
31901 in any directory name.
31902 If no directories are specified, the current path is displayed.
31905 @subsubheading @value{GDBN} Command
31907 The corresponding @value{GDBN} command is @samp{path}.
31909 @subsubheading Example
31914 ^done,path="/usr/bin"
31916 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31917 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31919 -environment-path -r /usr/local/bin
31920 ^done,path="/usr/local/bin:/usr/bin"
31925 @subheading The @code{-environment-pwd} Command
31926 @findex -environment-pwd
31928 @subsubheading Synopsis
31934 Show the current working directory.
31936 @subsubheading @value{GDBN} Command
31938 The corresponding @value{GDBN} command is @samp{pwd}.
31940 @subsubheading Example
31945 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31949 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31950 @node GDB/MI Thread Commands
31951 @section @sc{gdb/mi} Thread Commands
31954 @subheading The @code{-thread-info} Command
31955 @findex -thread-info
31957 @subsubheading Synopsis
31960 -thread-info [ @var{thread-id} ]
31963 Reports information about either a specific thread, if the
31964 @var{thread-id} parameter is present, or about all threads.
31965 @var{thread-id} is the thread's global thread ID. When printing
31966 information about all threads, also reports the global ID of the
31969 @subsubheading @value{GDBN} Command
31971 The @samp{info thread} command prints the same information
31974 @subsubheading Result
31976 The result contains the following attributes:
31980 A list of threads. The format of the elements of the list is described in
31981 @ref{GDB/MI Thread Information}.
31983 @item current-thread-id
31984 The global id of the currently selected thread. This field is omitted if there
31985 is no selected thread (for example, when the selected inferior is not running,
31986 and therefore has no threads) or if a @var{thread-id} argument was passed to
31991 @subsubheading Example
31996 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31997 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31998 args=[]@},state="running"@},
31999 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32000 frame=@{level="0",addr="0x0804891f",func="foo",
32001 args=[@{name="i",value="10"@}],
32002 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32003 state="running"@}],
32004 current-thread-id="1"
32008 @subheading The @code{-thread-list-ids} Command
32009 @findex -thread-list-ids
32011 @subsubheading Synopsis
32017 Produces a list of the currently known global @value{GDBN} thread ids.
32018 At the end of the list it also prints the total number of such
32021 This command is retained for historical reasons, the
32022 @code{-thread-info} command should be used instead.
32024 @subsubheading @value{GDBN} Command
32026 Part of @samp{info threads} supplies the same information.
32028 @subsubheading Example
32033 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32034 current-thread-id="1",number-of-threads="3"
32039 @subheading The @code{-thread-select} Command
32040 @findex -thread-select
32042 @subsubheading Synopsis
32045 -thread-select @var{thread-id}
32048 Make thread with global thread number @var{thread-id} the current
32049 thread. It prints the number of the new current thread, and the
32050 topmost frame for that thread.
32052 This command is deprecated in favor of explicitly using the
32053 @samp{--thread} option to each command.
32055 @subsubheading @value{GDBN} Command
32057 The corresponding @value{GDBN} command is @samp{thread}.
32059 @subsubheading Example
32066 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32067 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32071 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32072 number-of-threads="3"
32075 ^done,new-thread-id="3",
32076 frame=@{level="0",func="vprintf",
32077 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32078 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32083 @node GDB/MI Ada Tasking Commands
32084 @section @sc{gdb/mi} Ada Tasking Commands
32086 @subheading The @code{-ada-task-info} Command
32087 @findex -ada-task-info
32089 @subsubheading Synopsis
32092 -ada-task-info [ @var{task-id} ]
32095 Reports information about either a specific Ada task, if the
32096 @var{task-id} parameter is present, or about all Ada tasks.
32098 @subsubheading @value{GDBN} Command
32100 The @samp{info tasks} command prints the same information
32101 about all Ada tasks (@pxref{Ada Tasks}).
32103 @subsubheading Result
32105 The result is a table of Ada tasks. The following columns are
32106 defined for each Ada task:
32110 This field exists only for the current thread. It has the value @samp{*}.
32113 The identifier that @value{GDBN} uses to refer to the Ada task.
32116 The identifier that the target uses to refer to the Ada task.
32119 The global thread identifier of the thread corresponding to the Ada
32122 This field should always exist, as Ada tasks are always implemented
32123 on top of a thread. But if @value{GDBN} cannot find this corresponding
32124 thread for any reason, the field is omitted.
32127 This field exists only when the task was created by another task.
32128 In this case, it provides the ID of the parent task.
32131 The base priority of the task.
32134 The current state of the task. For a detailed description of the
32135 possible states, see @ref{Ada Tasks}.
32138 The name of the task.
32142 @subsubheading Example
32146 ^done,tasks=@{nr_rows="3",nr_cols="8",
32147 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32148 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32149 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32150 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32151 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32152 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32153 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32154 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32155 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32156 state="Child Termination Wait",name="main_task"@}]@}
32160 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32161 @node GDB/MI Program Execution
32162 @section @sc{gdb/mi} Program Execution
32164 These are the asynchronous commands which generate the out-of-band
32165 record @samp{*stopped}. Currently @value{GDBN} only really executes
32166 asynchronously with remote targets and this interaction is mimicked in
32169 @subheading The @code{-exec-continue} Command
32170 @findex -exec-continue
32172 @subsubheading Synopsis
32175 -exec-continue [--reverse] [--all|--thread-group N]
32178 Resumes the execution of the inferior program, which will continue
32179 to execute until it reaches a debugger stop event. If the
32180 @samp{--reverse} option is specified, execution resumes in reverse until
32181 it reaches a stop event. Stop events may include
32184 breakpoints or watchpoints
32186 signals or exceptions
32188 the end of the process (or its beginning under @samp{--reverse})
32190 the end or beginning of a replay log if one is being used.
32192 In all-stop mode (@pxref{All-Stop
32193 Mode}), may resume only one thread, or all threads, depending on the
32194 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32195 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32196 ignored in all-stop mode. If the @samp{--thread-group} options is
32197 specified, then all threads in that thread group are resumed.
32199 @subsubheading @value{GDBN} Command
32201 The corresponding @value{GDBN} corresponding is @samp{continue}.
32203 @subsubheading Example
32210 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32211 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32212 line="13",arch="i386:x86_64"@}
32217 @subheading The @code{-exec-finish} Command
32218 @findex -exec-finish
32220 @subsubheading Synopsis
32223 -exec-finish [--reverse]
32226 Resumes the execution of the inferior program until the current
32227 function is exited. Displays the results returned by the function.
32228 If the @samp{--reverse} option is specified, resumes the reverse
32229 execution of the inferior program until the point where current
32230 function was called.
32232 @subsubheading @value{GDBN} Command
32234 The corresponding @value{GDBN} command is @samp{finish}.
32236 @subsubheading Example
32238 Function returning @code{void}.
32245 *stopped,reason="function-finished",frame=@{func="main",args=[],
32246 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32250 Function returning other than @code{void}. The name of the internal
32251 @value{GDBN} variable storing the result is printed, together with the
32258 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32259 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32260 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32261 arch="i386:x86_64"@},
32262 gdb-result-var="$1",return-value="0"
32267 @subheading The @code{-exec-interrupt} Command
32268 @findex -exec-interrupt
32270 @subsubheading Synopsis
32273 -exec-interrupt [--all|--thread-group N]
32276 Interrupts the background execution of the target. Note how the token
32277 associated with the stop message is the one for the execution command
32278 that has been interrupted. The token for the interrupt itself only
32279 appears in the @samp{^done} output. If the user is trying to
32280 interrupt a non-running program, an error message will be printed.
32282 Note that when asynchronous execution is enabled, this command is
32283 asynchronous just like other execution commands. That is, first the
32284 @samp{^done} response will be printed, and the target stop will be
32285 reported after that using the @samp{*stopped} notification.
32287 In non-stop mode, only the context thread is interrupted by default.
32288 All threads (in all inferiors) will be interrupted if the
32289 @samp{--all} option is specified. If the @samp{--thread-group}
32290 option is specified, all threads in that group will be interrupted.
32292 @subsubheading @value{GDBN} Command
32294 The corresponding @value{GDBN} command is @samp{interrupt}.
32296 @subsubheading Example
32307 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32308 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32309 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32314 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32318 @subheading The @code{-exec-jump} Command
32321 @subsubheading Synopsis
32324 -exec-jump @var{location}
32327 Resumes execution of the inferior program at the location specified by
32328 parameter. @xref{Specify Location}, for a description of the
32329 different forms of @var{location}.
32331 @subsubheading @value{GDBN} Command
32333 The corresponding @value{GDBN} command is @samp{jump}.
32335 @subsubheading Example
32338 -exec-jump foo.c:10
32339 *running,thread-id="all"
32344 @subheading The @code{-exec-next} Command
32347 @subsubheading Synopsis
32350 -exec-next [--reverse]
32353 Resumes execution of the inferior program, stopping when the beginning
32354 of the next source line is reached.
32356 If the @samp{--reverse} option is specified, resumes reverse execution
32357 of the inferior program, stopping at the beginning of the previous
32358 source line. If you issue this command on the first line of a
32359 function, it will take you back to the caller of that function, to the
32360 source line where the function was called.
32363 @subsubheading @value{GDBN} Command
32365 The corresponding @value{GDBN} command is @samp{next}.
32367 @subsubheading Example
32373 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32378 @subheading The @code{-exec-next-instruction} Command
32379 @findex -exec-next-instruction
32381 @subsubheading Synopsis
32384 -exec-next-instruction [--reverse]
32387 Executes one machine instruction. If the instruction is a function
32388 call, continues until the function returns. If the program stops at an
32389 instruction in the middle of a source line, the address will be
32392 If the @samp{--reverse} option is specified, resumes reverse execution
32393 of the inferior program, stopping at the previous instruction. If the
32394 previously executed instruction was a return from another function,
32395 it will continue to execute in reverse until the call to that function
32396 (from the current stack frame) is reached.
32398 @subsubheading @value{GDBN} Command
32400 The corresponding @value{GDBN} command is @samp{nexti}.
32402 @subsubheading Example
32406 -exec-next-instruction
32410 *stopped,reason="end-stepping-range",
32411 addr="0x000100d4",line="5",file="hello.c"
32416 @subheading The @code{-exec-return} Command
32417 @findex -exec-return
32419 @subsubheading Synopsis
32425 Makes current function return immediately. Doesn't execute the inferior.
32426 Displays the new current frame.
32428 @subsubheading @value{GDBN} Command
32430 The corresponding @value{GDBN} command is @samp{return}.
32432 @subsubheading Example
32436 200-break-insert callee4
32437 200^done,bkpt=@{number="1",addr="0x00010734",
32438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32443 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32444 frame=@{func="callee4",args=[],
32445 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32446 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32447 arch="i386:x86_64"@}
32453 111^done,frame=@{level="0",func="callee3",
32454 args=[@{name="strarg",
32455 value="0x11940 \"A string argument.\""@}],
32456 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32457 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32458 arch="i386:x86_64"@}
32463 @subheading The @code{-exec-run} Command
32466 @subsubheading Synopsis
32469 -exec-run [ --all | --thread-group N ] [ --start ]
32472 Starts execution of the inferior from the beginning. The inferior
32473 executes until either a breakpoint is encountered or the program
32474 exits. In the latter case the output will include an exit code, if
32475 the program has exited exceptionally.
32477 When neither the @samp{--all} nor the @samp{--thread-group} option
32478 is specified, the current inferior is started. If the
32479 @samp{--thread-group} option is specified, it should refer to a thread
32480 group of type @samp{process}, and that thread group will be started.
32481 If the @samp{--all} option is specified, then all inferiors will be started.
32483 Using the @samp{--start} option instructs the debugger to stop
32484 the execution at the start of the inferior's main subprogram,
32485 following the same behavior as the @code{start} command
32486 (@pxref{Starting}).
32488 @subsubheading @value{GDBN} Command
32490 The corresponding @value{GDBN} command is @samp{run}.
32492 @subsubheading Examples
32497 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32502 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32503 frame=@{func="main",args=[],file="recursive2.c",
32504 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32509 Program exited normally:
32517 *stopped,reason="exited-normally"
32522 Program exited exceptionally:
32530 *stopped,reason="exited",exit-code="01"
32534 Another way the program can terminate is if it receives a signal such as
32535 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
32539 *stopped,reason="exited-signalled",signal-name="SIGINT",
32540 signal-meaning="Interrupt"
32544 @c @subheading -exec-signal
32547 @subheading The @code{-exec-step} Command
32550 @subsubheading Synopsis
32553 -exec-step [--reverse]
32556 Resumes execution of the inferior program, stopping when the beginning
32557 of the next source line is reached, if the next source line is not a
32558 function call. If it is, stop at the first instruction of the called
32559 function. If the @samp{--reverse} option is specified, resumes reverse
32560 execution of the inferior program, stopping at the beginning of the
32561 previously executed source line.
32563 @subsubheading @value{GDBN} Command
32565 The corresponding @value{GDBN} command is @samp{step}.
32567 @subsubheading Example
32569 Stepping into a function:
32575 *stopped,reason="end-stepping-range",
32576 frame=@{func="foo",args=[@{name="a",value="10"@},
32577 @{name="b",value="0"@}],file="recursive2.c",
32578 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32588 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32593 @subheading The @code{-exec-step-instruction} Command
32594 @findex -exec-step-instruction
32596 @subsubheading Synopsis
32599 -exec-step-instruction [--reverse]
32602 Resumes the inferior which executes one machine instruction. If the
32603 @samp{--reverse} option is specified, resumes reverse execution of the
32604 inferior program, stopping at the previously executed instruction.
32605 The output, once @value{GDBN} has stopped, will vary depending on
32606 whether we have stopped in the middle of a source line or not. In the
32607 former case, the address at which the program stopped will be printed
32610 @subsubheading @value{GDBN} Command
32612 The corresponding @value{GDBN} command is @samp{stepi}.
32614 @subsubheading Example
32618 -exec-step-instruction
32622 *stopped,reason="end-stepping-range",
32623 frame=@{func="foo",args=[],file="try.c",
32624 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32626 -exec-step-instruction
32630 *stopped,reason="end-stepping-range",
32631 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
32632 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32637 @subheading The @code{-exec-until} Command
32638 @findex -exec-until
32640 @subsubheading Synopsis
32643 -exec-until [ @var{location} ]
32646 Executes the inferior until the @var{location} specified in the
32647 argument is reached. If there is no argument, the inferior executes
32648 until a source line greater than the current one is reached. The
32649 reason for stopping in this case will be @samp{location-reached}.
32651 @subsubheading @value{GDBN} Command
32653 The corresponding @value{GDBN} command is @samp{until}.
32655 @subsubheading Example
32659 -exec-until recursive2.c:6
32663 *stopped,reason="location-reached",frame=@{func="main",args=[],
32664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
32665 arch="i386:x86_64"@}
32670 @subheading -file-clear
32671 Is this going away????
32674 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32675 @node GDB/MI Stack Manipulation
32676 @section @sc{gdb/mi} Stack Manipulation Commands
32678 @subheading The @code{-enable-frame-filters} Command
32679 @findex -enable-frame-filters
32682 -enable-frame-filters
32685 @value{GDBN} allows Python-based frame filters to affect the output of
32686 the MI commands relating to stack traces. As there is no way to
32687 implement this in a fully backward-compatible way, a front end must
32688 request that this functionality be enabled.
32690 Once enabled, this feature cannot be disabled.
32692 Note that if Python support has not been compiled into @value{GDBN},
32693 this command will still succeed (and do nothing).
32695 @subheading The @code{-stack-info-frame} Command
32696 @findex -stack-info-frame
32698 @subsubheading Synopsis
32704 Get info on the selected frame.
32706 @subsubheading @value{GDBN} Command
32708 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
32709 (without arguments).
32711 @subsubheading Example
32716 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
32717 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32718 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32719 arch="i386:x86_64"@}
32723 @subheading The @code{-stack-info-depth} Command
32724 @findex -stack-info-depth
32726 @subsubheading Synopsis
32729 -stack-info-depth [ @var{max-depth} ]
32732 Return the depth of the stack. If the integer argument @var{max-depth}
32733 is specified, do not count beyond @var{max-depth} frames.
32735 @subsubheading @value{GDBN} Command
32737 There's no equivalent @value{GDBN} command.
32739 @subsubheading Example
32741 For a stack with frame levels 0 through 11:
32748 -stack-info-depth 4
32751 -stack-info-depth 12
32754 -stack-info-depth 11
32757 -stack-info-depth 13
32762 @anchor{-stack-list-arguments}
32763 @subheading The @code{-stack-list-arguments} Command
32764 @findex -stack-list-arguments
32766 @subsubheading Synopsis
32769 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32770 [ @var{low-frame} @var{high-frame} ]
32773 Display a list of the arguments for the frames between @var{low-frame}
32774 and @var{high-frame} (inclusive). If @var{low-frame} and
32775 @var{high-frame} are not provided, list the arguments for the whole
32776 call stack. If the two arguments are equal, show the single frame
32777 at the corresponding level. It is an error if @var{low-frame} is
32778 larger than the actual number of frames. On the other hand,
32779 @var{high-frame} may be larger than the actual number of frames, in
32780 which case only existing frames will be returned.
32782 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32783 the variables; if it is 1 or @code{--all-values}, print also their
32784 values; and if it is 2 or @code{--simple-values}, print the name,
32785 type and value for simple data types, and the name and type for arrays,
32786 structures and unions. If the option @code{--no-frame-filters} is
32787 supplied, then Python frame filters will not be executed.
32789 If the @code{--skip-unavailable} option is specified, arguments that
32790 are not available are not listed. Partially available arguments
32791 are still displayed, however.
32793 Use of this command to obtain arguments in a single frame is
32794 deprecated in favor of the @samp{-stack-list-variables} command.
32796 @subsubheading @value{GDBN} Command
32798 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32799 @samp{gdb_get_args} command which partially overlaps with the
32800 functionality of @samp{-stack-list-arguments}.
32802 @subsubheading Example
32809 frame=@{level="0",addr="0x00010734",func="callee4",
32810 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32811 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32812 arch="i386:x86_64"@},
32813 frame=@{level="1",addr="0x0001076c",func="callee3",
32814 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32815 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32816 arch="i386:x86_64"@},
32817 frame=@{level="2",addr="0x0001078c",func="callee2",
32818 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32819 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
32820 arch="i386:x86_64"@},
32821 frame=@{level="3",addr="0x000107b4",func="callee1",
32822 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32823 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
32824 arch="i386:x86_64"@},
32825 frame=@{level="4",addr="0x000107e0",func="main",
32826 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32827 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
32828 arch="i386:x86_64"@}]
32830 -stack-list-arguments 0
32833 frame=@{level="0",args=[]@},
32834 frame=@{level="1",args=[name="strarg"]@},
32835 frame=@{level="2",args=[name="intarg",name="strarg"]@},
32836 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
32837 frame=@{level="4",args=[]@}]
32839 -stack-list-arguments 1
32842 frame=@{level="0",args=[]@},
32844 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32845 frame=@{level="2",args=[
32846 @{name="intarg",value="2"@},
32847 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
32848 @{frame=@{level="3",args=[
32849 @{name="intarg",value="2"@},
32850 @{name="strarg",value="0x11940 \"A string argument.\""@},
32851 @{name="fltarg",value="3.5"@}]@},
32852 frame=@{level="4",args=[]@}]
32854 -stack-list-arguments 0 2 2
32855 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
32857 -stack-list-arguments 1 2 2
32858 ^done,stack-args=[frame=@{level="2",
32859 args=[@{name="intarg",value="2"@},
32860 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
32864 @c @subheading -stack-list-exception-handlers
32867 @anchor{-stack-list-frames}
32868 @subheading The @code{-stack-list-frames} Command
32869 @findex -stack-list-frames
32871 @subsubheading Synopsis
32874 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32877 List the frames currently on the stack. For each frame it displays the
32882 The frame number, 0 being the topmost frame, i.e., the innermost function.
32884 The @code{$pc} value for that frame.
32888 File name of the source file where the function lives.
32889 @item @var{fullname}
32890 The full file name of the source file where the function lives.
32892 Line number corresponding to the @code{$pc}.
32894 The shared library where this function is defined. This is only given
32895 if the frame's function is not known.
32897 Frame's architecture.
32900 If invoked without arguments, this command prints a backtrace for the
32901 whole stack. If given two integer arguments, it shows the frames whose
32902 levels are between the two arguments (inclusive). If the two arguments
32903 are equal, it shows the single frame at the corresponding level. It is
32904 an error if @var{low-frame} is larger than the actual number of
32905 frames. On the other hand, @var{high-frame} may be larger than the
32906 actual number of frames, in which case only existing frames will be
32907 returned. If the option @code{--no-frame-filters} is supplied, then
32908 Python frame filters will not be executed.
32910 @subsubheading @value{GDBN} Command
32912 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32914 @subsubheading Example
32916 Full stack backtrace:
32922 [frame=@{level="0",addr="0x0001076c",func="foo",
32923 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
32924 arch="i386:x86_64"@},
32925 frame=@{level="1",addr="0x000107a4",func="foo",
32926 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32927 arch="i386:x86_64"@},
32928 frame=@{level="2",addr="0x000107a4",func="foo",
32929 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32930 arch="i386:x86_64"@},
32931 frame=@{level="3",addr="0x000107a4",func="foo",
32932 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32933 arch="i386:x86_64"@},
32934 frame=@{level="4",addr="0x000107a4",func="foo",
32935 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32936 arch="i386:x86_64"@},
32937 frame=@{level="5",addr="0x000107a4",func="foo",
32938 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32939 arch="i386:x86_64"@},
32940 frame=@{level="6",addr="0x000107a4",func="foo",
32941 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32942 arch="i386:x86_64"@},
32943 frame=@{level="7",addr="0x000107a4",func="foo",
32944 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32945 arch="i386:x86_64"@},
32946 frame=@{level="8",addr="0x000107a4",func="foo",
32947 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32948 arch="i386:x86_64"@},
32949 frame=@{level="9",addr="0x000107a4",func="foo",
32950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32951 arch="i386:x86_64"@},
32952 frame=@{level="10",addr="0x000107a4",func="foo",
32953 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32954 arch="i386:x86_64"@},
32955 frame=@{level="11",addr="0x00010738",func="main",
32956 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
32957 arch="i386:x86_64"@}]
32961 Show frames between @var{low_frame} and @var{high_frame}:
32965 -stack-list-frames 3 5
32967 [frame=@{level="3",addr="0x000107a4",func="foo",
32968 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32969 arch="i386:x86_64"@},
32970 frame=@{level="4",addr="0x000107a4",func="foo",
32971 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32972 arch="i386:x86_64"@},
32973 frame=@{level="5",addr="0x000107a4",func="foo",
32974 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32975 arch="i386:x86_64"@}]
32979 Show a single frame:
32983 -stack-list-frames 3 3
32985 [frame=@{level="3",addr="0x000107a4",func="foo",
32986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32987 arch="i386:x86_64"@}]
32992 @subheading The @code{-stack-list-locals} Command
32993 @findex -stack-list-locals
32994 @anchor{-stack-list-locals}
32996 @subsubheading Synopsis
32999 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33002 Display the local variable names for the selected frame. If
33003 @var{print-values} is 0 or @code{--no-values}, print only the names of
33004 the variables; if it is 1 or @code{--all-values}, print also their
33005 values; and if it is 2 or @code{--simple-values}, print the name,
33006 type and value for simple data types, and the name and type for arrays,
33007 structures and unions. In this last case, a frontend can immediately
33008 display the value of simple data types and create variable objects for
33009 other data types when the user wishes to explore their values in
33010 more detail. If the option @code{--no-frame-filters} is supplied, then
33011 Python frame filters will not be executed.
33013 If the @code{--skip-unavailable} option is specified, local variables
33014 that are not available are not listed. Partially available local
33015 variables are still displayed, however.
33017 This command is deprecated in favor of the
33018 @samp{-stack-list-variables} command.
33020 @subsubheading @value{GDBN} Command
33022 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33024 @subsubheading Example
33028 -stack-list-locals 0
33029 ^done,locals=[name="A",name="B",name="C"]
33031 -stack-list-locals --all-values
33032 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33033 @{name="C",value="@{1, 2, 3@}"@}]
33034 -stack-list-locals --simple-values
33035 ^done,locals=[@{name="A",type="int",value="1"@},
33036 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33040 @anchor{-stack-list-variables}
33041 @subheading The @code{-stack-list-variables} Command
33042 @findex -stack-list-variables
33044 @subsubheading Synopsis
33047 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33050 Display the names of local variables and function arguments for the selected frame. If
33051 @var{print-values} is 0 or @code{--no-values}, print only the names of
33052 the variables; if it is 1 or @code{--all-values}, print also their
33053 values; and if it is 2 or @code{--simple-values}, print the name,
33054 type and value for simple data types, and the name and type for arrays,
33055 structures and unions. If the option @code{--no-frame-filters} is
33056 supplied, then Python frame filters will not be executed.
33058 If the @code{--skip-unavailable} option is specified, local variables
33059 and arguments that are not available are not listed. Partially
33060 available arguments and local variables are still displayed, however.
33062 @subsubheading Example
33066 -stack-list-variables --thread 1 --frame 0 --all-values
33067 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33072 @subheading The @code{-stack-select-frame} Command
33073 @findex -stack-select-frame
33075 @subsubheading Synopsis
33078 -stack-select-frame @var{framenum}
33081 Change the selected frame. Select a different frame @var{framenum} on
33084 This command in deprecated in favor of passing the @samp{--frame}
33085 option to every command.
33087 @subsubheading @value{GDBN} Command
33089 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33090 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33092 @subsubheading Example
33096 -stack-select-frame 2
33101 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33102 @node GDB/MI Variable Objects
33103 @section @sc{gdb/mi} Variable Objects
33107 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33109 For the implementation of a variable debugger window (locals, watched
33110 expressions, etc.), we are proposing the adaptation of the existing code
33111 used by @code{Insight}.
33113 The two main reasons for that are:
33117 It has been proven in practice (it is already on its second generation).
33120 It will shorten development time (needless to say how important it is
33124 The original interface was designed to be used by Tcl code, so it was
33125 slightly changed so it could be used through @sc{gdb/mi}. This section
33126 describes the @sc{gdb/mi} operations that will be available and gives some
33127 hints about their use.
33129 @emph{Note}: In addition to the set of operations described here, we
33130 expect the @sc{gui} implementation of a variable window to require, at
33131 least, the following operations:
33134 @item @code{-gdb-show} @code{output-radix}
33135 @item @code{-stack-list-arguments}
33136 @item @code{-stack-list-locals}
33137 @item @code{-stack-select-frame}
33142 @subheading Introduction to Variable Objects
33144 @cindex variable objects in @sc{gdb/mi}
33146 Variable objects are "object-oriented" MI interface for examining and
33147 changing values of expressions. Unlike some other MI interfaces that
33148 work with expressions, variable objects are specifically designed for
33149 simple and efficient presentation in the frontend. A variable object
33150 is identified by string name. When a variable object is created, the
33151 frontend specifies the expression for that variable object. The
33152 expression can be a simple variable, or it can be an arbitrary complex
33153 expression, and can even involve CPU registers. After creating a
33154 variable object, the frontend can invoke other variable object
33155 operations---for example to obtain or change the value of a variable
33156 object, or to change display format.
33158 Variable objects have hierarchical tree structure. Any variable object
33159 that corresponds to a composite type, such as structure in C, has
33160 a number of child variable objects, for example corresponding to each
33161 element of a structure. A child variable object can itself have
33162 children, recursively. Recursion ends when we reach
33163 leaf variable objects, which always have built-in types. Child variable
33164 objects are created only by explicit request, so if a frontend
33165 is not interested in the children of a particular variable object, no
33166 child will be created.
33168 For a leaf variable object it is possible to obtain its value as a
33169 string, or set the value from a string. String value can be also
33170 obtained for a non-leaf variable object, but it's generally a string
33171 that only indicates the type of the object, and does not list its
33172 contents. Assignment to a non-leaf variable object is not allowed.
33174 A frontend does not need to read the values of all variable objects each time
33175 the program stops. Instead, MI provides an update command that lists all
33176 variable objects whose values has changed since the last update
33177 operation. This considerably reduces the amount of data that must
33178 be transferred to the frontend. As noted above, children variable
33179 objects are created on demand, and only leaf variable objects have a
33180 real value. As result, gdb will read target memory only for leaf
33181 variables that frontend has created.
33183 The automatic update is not always desirable. For example, a frontend
33184 might want to keep a value of some expression for future reference,
33185 and never update it. For another example, fetching memory is
33186 relatively slow for embedded targets, so a frontend might want
33187 to disable automatic update for the variables that are either not
33188 visible on the screen, or ``closed''. This is possible using so
33189 called ``frozen variable objects''. Such variable objects are never
33190 implicitly updated.
33192 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33193 fixed variable object, the expression is parsed when the variable
33194 object is created, including associating identifiers to specific
33195 variables. The meaning of expression never changes. For a floating
33196 variable object the values of variables whose names appear in the
33197 expressions are re-evaluated every time in the context of the current
33198 frame. Consider this example:
33203 struct work_state state;
33210 If a fixed variable object for the @code{state} variable is created in
33211 this function, and we enter the recursive call, the variable
33212 object will report the value of @code{state} in the top-level
33213 @code{do_work} invocation. On the other hand, a floating variable
33214 object will report the value of @code{state} in the current frame.
33216 If an expression specified when creating a fixed variable object
33217 refers to a local variable, the variable object becomes bound to the
33218 thread and frame in which the variable object is created. When such
33219 variable object is updated, @value{GDBN} makes sure that the
33220 thread/frame combination the variable object is bound to still exists,
33221 and re-evaluates the variable object in context of that thread/frame.
33223 The following is the complete set of @sc{gdb/mi} operations defined to
33224 access this functionality:
33226 @multitable @columnfractions .4 .6
33227 @item @strong{Operation}
33228 @tab @strong{Description}
33230 @item @code{-enable-pretty-printing}
33231 @tab enable Python-based pretty-printing
33232 @item @code{-var-create}
33233 @tab create a variable object
33234 @item @code{-var-delete}
33235 @tab delete the variable object and/or its children
33236 @item @code{-var-set-format}
33237 @tab set the display format of this variable
33238 @item @code{-var-show-format}
33239 @tab show the display format of this variable
33240 @item @code{-var-info-num-children}
33241 @tab tells how many children this object has
33242 @item @code{-var-list-children}
33243 @tab return a list of the object's children
33244 @item @code{-var-info-type}
33245 @tab show the type of this variable object
33246 @item @code{-var-info-expression}
33247 @tab print parent-relative expression that this variable object represents
33248 @item @code{-var-info-path-expression}
33249 @tab print full expression that this variable object represents
33250 @item @code{-var-show-attributes}
33251 @tab is this variable editable? does it exist here?
33252 @item @code{-var-evaluate-expression}
33253 @tab get the value of this variable
33254 @item @code{-var-assign}
33255 @tab set the value of this variable
33256 @item @code{-var-update}
33257 @tab update the variable and its children
33258 @item @code{-var-set-frozen}
33259 @tab set frozenness attribute
33260 @item @code{-var-set-update-range}
33261 @tab set range of children to display on update
33264 In the next subsection we describe each operation in detail and suggest
33265 how it can be used.
33267 @subheading Description And Use of Operations on Variable Objects
33269 @subheading The @code{-enable-pretty-printing} Command
33270 @findex -enable-pretty-printing
33273 -enable-pretty-printing
33276 @value{GDBN} allows Python-based visualizers to affect the output of the
33277 MI variable object commands. However, because there was no way to
33278 implement this in a fully backward-compatible way, a front end must
33279 request that this functionality be enabled.
33281 Once enabled, this feature cannot be disabled.
33283 Note that if Python support has not been compiled into @value{GDBN},
33284 this command will still succeed (and do nothing).
33286 This feature is currently (as of @value{GDBN} 7.0) experimental, and
33287 may work differently in future versions of @value{GDBN}.
33289 @subheading The @code{-var-create} Command
33290 @findex -var-create
33292 @subsubheading Synopsis
33295 -var-create @{@var{name} | "-"@}
33296 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33299 This operation creates a variable object, which allows the monitoring of
33300 a variable, the result of an expression, a memory cell or a CPU
33303 The @var{name} parameter is the string by which the object can be
33304 referenced. It must be unique. If @samp{-} is specified, the varobj
33305 system will generate a string ``varNNNNNN'' automatically. It will be
33306 unique provided that one does not specify @var{name} of that format.
33307 The command fails if a duplicate name is found.
33309 The frame under which the expression should be evaluated can be
33310 specified by @var{frame-addr}. A @samp{*} indicates that the current
33311 frame should be used. A @samp{@@} indicates that a floating variable
33312 object must be created.
33314 @var{expression} is any expression valid on the current language set (must not
33315 begin with a @samp{*}), or one of the following:
33319 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33322 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33325 @samp{$@var{regname}} --- a CPU register name
33328 @cindex dynamic varobj
33329 A varobj's contents may be provided by a Python-based pretty-printer. In this
33330 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33331 have slightly different semantics in some cases. If the
33332 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33333 will never create a dynamic varobj. This ensures backward
33334 compatibility for existing clients.
33336 @subsubheading Result
33338 This operation returns attributes of the newly-created varobj. These
33343 The name of the varobj.
33346 The number of children of the varobj. This number is not necessarily
33347 reliable for a dynamic varobj. Instead, you must examine the
33348 @samp{has_more} attribute.
33351 The varobj's scalar value. For a varobj whose type is some sort of
33352 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33353 will not be interesting.
33356 The varobj's type. This is a string representation of the type, as
33357 would be printed by the @value{GDBN} CLI. If @samp{print object}
33358 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33359 @emph{actual} (derived) type of the object is shown rather than the
33360 @emph{declared} one.
33363 If a variable object is bound to a specific thread, then this is the
33364 thread's global identifier.
33367 For a dynamic varobj, this indicates whether there appear to be any
33368 children available. For a non-dynamic varobj, this will be 0.
33371 This attribute will be present and have the value @samp{1} if the
33372 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33373 then this attribute will not be present.
33376 A dynamic varobj can supply a display hint to the front end. The
33377 value comes directly from the Python pretty-printer object's
33378 @code{display_hint} method. @xref{Pretty Printing API}.
33381 Typical output will look like this:
33384 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33385 has_more="@var{has_more}"
33389 @subheading The @code{-var-delete} Command
33390 @findex -var-delete
33392 @subsubheading Synopsis
33395 -var-delete [ -c ] @var{name}
33398 Deletes a previously created variable object and all of its children.
33399 With the @samp{-c} option, just deletes the children.
33401 Returns an error if the object @var{name} is not found.
33404 @subheading The @code{-var-set-format} Command
33405 @findex -var-set-format
33407 @subsubheading Synopsis
33410 -var-set-format @var{name} @var{format-spec}
33413 Sets the output format for the value of the object @var{name} to be
33416 @anchor{-var-set-format}
33417 The syntax for the @var{format-spec} is as follows:
33420 @var{format-spec} @expansion{}
33421 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33424 The natural format is the default format choosen automatically
33425 based on the variable type (like decimal for an @code{int}, hex
33426 for pointers, etc.).
33428 The zero-hexadecimal format has a representation similar to hexadecimal
33429 but with padding zeroes to the left of the value. For example, a 32-bit
33430 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33431 zero-hexadecimal format.
33433 For a variable with children, the format is set only on the
33434 variable itself, and the children are not affected.
33436 @subheading The @code{-var-show-format} Command
33437 @findex -var-show-format
33439 @subsubheading Synopsis
33442 -var-show-format @var{name}
33445 Returns the format used to display the value of the object @var{name}.
33448 @var{format} @expansion{}
33453 @subheading The @code{-var-info-num-children} Command
33454 @findex -var-info-num-children
33456 @subsubheading Synopsis
33459 -var-info-num-children @var{name}
33462 Returns the number of children of a variable object @var{name}:
33468 Note that this number is not completely reliable for a dynamic varobj.
33469 It will return the current number of children, but more children may
33473 @subheading The @code{-var-list-children} Command
33474 @findex -var-list-children
33476 @subsubheading Synopsis
33479 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33481 @anchor{-var-list-children}
33483 Return a list of the children of the specified variable object and
33484 create variable objects for them, if they do not already exist. With
33485 a single argument or if @var{print-values} has a value of 0 or
33486 @code{--no-values}, print only the names of the variables; if
33487 @var{print-values} is 1 or @code{--all-values}, also print their
33488 values; and if it is 2 or @code{--simple-values} print the name and
33489 value for simple data types and just the name for arrays, structures
33492 @var{from} and @var{to}, if specified, indicate the range of children
33493 to report. If @var{from} or @var{to} is less than zero, the range is
33494 reset and all children will be reported. Otherwise, children starting
33495 at @var{from} (zero-based) and up to and excluding @var{to} will be
33498 If a child range is requested, it will only affect the current call to
33499 @code{-var-list-children}, but not future calls to @code{-var-update}.
33500 For this, you must instead use @code{-var-set-update-range}. The
33501 intent of this approach is to enable a front end to implement any
33502 update approach it likes; for example, scrolling a view may cause the
33503 front end to request more children with @code{-var-list-children}, and
33504 then the front end could call @code{-var-set-update-range} with a
33505 different range to ensure that future updates are restricted to just
33508 For each child the following results are returned:
33513 Name of the variable object created for this child.
33516 The expression to be shown to the user by the front end to designate this child.
33517 For example this may be the name of a structure member.
33519 For a dynamic varobj, this value cannot be used to form an
33520 expression. There is no way to do this at all with a dynamic varobj.
33522 For C/C@t{++} structures there are several pseudo children returned to
33523 designate access qualifiers. For these pseudo children @var{exp} is
33524 @samp{public}, @samp{private}, or @samp{protected}. In this case the
33525 type and value are not present.
33527 A dynamic varobj will not report the access qualifying
33528 pseudo-children, regardless of the language. This information is not
33529 available at all with a dynamic varobj.
33532 Number of children this child has. For a dynamic varobj, this will be
33536 The type of the child. If @samp{print object}
33537 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33538 @emph{actual} (derived) type of the object is shown rather than the
33539 @emph{declared} one.
33542 If values were requested, this is the value.
33545 If this variable object is associated with a thread, this is the
33546 thread's global thread id. Otherwise this result is not present.
33549 If the variable object is frozen, this variable will be present with a value of 1.
33552 A dynamic varobj can supply a display hint to the front end. The
33553 value comes directly from the Python pretty-printer object's
33554 @code{display_hint} method. @xref{Pretty Printing API}.
33557 This attribute will be present and have the value @samp{1} if the
33558 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33559 then this attribute will not be present.
33563 The result may have its own attributes:
33567 A dynamic varobj can supply a display hint to the front end. The
33568 value comes directly from the Python pretty-printer object's
33569 @code{display_hint} method. @xref{Pretty Printing API}.
33572 This is an integer attribute which is nonzero if there are children
33573 remaining after the end of the selected range.
33576 @subsubheading Example
33580 -var-list-children n
33581 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33582 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33584 -var-list-children --all-values n
33585 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33586 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33590 @subheading The @code{-var-info-type} Command
33591 @findex -var-info-type
33593 @subsubheading Synopsis
33596 -var-info-type @var{name}
33599 Returns the type of the specified variable @var{name}. The type is
33600 returned as a string in the same format as it is output by the
33604 type=@var{typename}
33608 @subheading The @code{-var-info-expression} Command
33609 @findex -var-info-expression
33611 @subsubheading Synopsis
33614 -var-info-expression @var{name}
33617 Returns a string that is suitable for presenting this
33618 variable object in user interface. The string is generally
33619 not valid expression in the current language, and cannot be evaluated.
33621 For example, if @code{a} is an array, and variable object
33622 @code{A} was created for @code{a}, then we'll get this output:
33625 (gdb) -var-info-expression A.1
33626 ^done,lang="C",exp="1"
33630 Here, the value of @code{lang} is the language name, which can be
33631 found in @ref{Supported Languages}.
33633 Note that the output of the @code{-var-list-children} command also
33634 includes those expressions, so the @code{-var-info-expression} command
33637 @subheading The @code{-var-info-path-expression} Command
33638 @findex -var-info-path-expression
33640 @subsubheading Synopsis
33643 -var-info-path-expression @var{name}
33646 Returns an expression that can be evaluated in the current
33647 context and will yield the same value that a variable object has.
33648 Compare this with the @code{-var-info-expression} command, which
33649 result can be used only for UI presentation. Typical use of
33650 the @code{-var-info-path-expression} command is creating a
33651 watchpoint from a variable object.
33653 This command is currently not valid for children of a dynamic varobj,
33654 and will give an error when invoked on one.
33656 For example, suppose @code{C} is a C@t{++} class, derived from class
33657 @code{Base}, and that the @code{Base} class has a member called
33658 @code{m_size}. Assume a variable @code{c} is has the type of
33659 @code{C} and a variable object @code{C} was created for variable
33660 @code{c}. Then, we'll get this output:
33662 (gdb) -var-info-path-expression C.Base.public.m_size
33663 ^done,path_expr=((Base)c).m_size)
33666 @subheading The @code{-var-show-attributes} Command
33667 @findex -var-show-attributes
33669 @subsubheading Synopsis
33672 -var-show-attributes @var{name}
33675 List attributes of the specified variable object @var{name}:
33678 status=@var{attr} [ ( ,@var{attr} )* ]
33682 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
33684 @subheading The @code{-var-evaluate-expression} Command
33685 @findex -var-evaluate-expression
33687 @subsubheading Synopsis
33690 -var-evaluate-expression [-f @var{format-spec}] @var{name}
33693 Evaluates the expression that is represented by the specified variable
33694 object and returns its value as a string. The format of the string
33695 can be specified with the @samp{-f} option. The possible values of
33696 this option are the same as for @code{-var-set-format}
33697 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
33698 the current display format will be used. The current display format
33699 can be changed using the @code{-var-set-format} command.
33705 Note that one must invoke @code{-var-list-children} for a variable
33706 before the value of a child variable can be evaluated.
33708 @subheading The @code{-var-assign} Command
33709 @findex -var-assign
33711 @subsubheading Synopsis
33714 -var-assign @var{name} @var{expression}
33717 Assigns the value of @var{expression} to the variable object specified
33718 by @var{name}. The object must be @samp{editable}. If the variable's
33719 value is altered by the assign, the variable will show up in any
33720 subsequent @code{-var-update} list.
33722 @subsubheading Example
33730 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
33734 @subheading The @code{-var-update} Command
33735 @findex -var-update
33737 @subsubheading Synopsis
33740 -var-update [@var{print-values}] @{@var{name} | "*"@}
33743 Reevaluate the expressions corresponding to the variable object
33744 @var{name} and all its direct and indirect children, and return the
33745 list of variable objects whose values have changed; @var{name} must
33746 be a root variable object. Here, ``changed'' means that the result of
33747 @code{-var-evaluate-expression} before and after the
33748 @code{-var-update} is different. If @samp{*} is used as the variable
33749 object names, all existing variable objects are updated, except
33750 for frozen ones (@pxref{-var-set-frozen}). The option
33751 @var{print-values} determines whether both names and values, or just
33752 names are printed. The possible values of this option are the same
33753 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33754 recommended to use the @samp{--all-values} option, to reduce the
33755 number of MI commands needed on each program stop.
33757 With the @samp{*} parameter, if a variable object is bound to a
33758 currently running thread, it will not be updated, without any
33761 If @code{-var-set-update-range} was previously used on a varobj, then
33762 only the selected range of children will be reported.
33764 @code{-var-update} reports all the changed varobjs in a tuple named
33767 Each item in the change list is itself a tuple holding:
33771 The name of the varobj.
33774 If values were requested for this update, then this field will be
33775 present and will hold the value of the varobj.
33778 @anchor{-var-update}
33779 This field is a string which may take one of three values:
33783 The variable object's current value is valid.
33786 The variable object does not currently hold a valid value but it may
33787 hold one in the future if its associated expression comes back into
33791 The variable object no longer holds a valid value.
33792 This can occur when the executable file being debugged has changed,
33793 either through recompilation or by using the @value{GDBN} @code{file}
33794 command. The front end should normally choose to delete these variable
33798 In the future new values may be added to this list so the front should
33799 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33802 This is only present if the varobj is still valid. If the type
33803 changed, then this will be the string @samp{true}; otherwise it will
33806 When a varobj's type changes, its children are also likely to have
33807 become incorrect. Therefore, the varobj's children are automatically
33808 deleted when this attribute is @samp{true}. Also, the varobj's update
33809 range, when set using the @code{-var-set-update-range} command, is
33813 If the varobj's type changed, then this field will be present and will
33816 @item new_num_children
33817 For a dynamic varobj, if the number of children changed, or if the
33818 type changed, this will be the new number of children.
33820 The @samp{numchild} field in other varobj responses is generally not
33821 valid for a dynamic varobj -- it will show the number of children that
33822 @value{GDBN} knows about, but because dynamic varobjs lazily
33823 instantiate their children, this will not reflect the number of
33824 children which may be available.
33826 The @samp{new_num_children} attribute only reports changes to the
33827 number of children known by @value{GDBN}. This is the only way to
33828 detect whether an update has removed children (which necessarily can
33829 only happen at the end of the update range).
33832 The display hint, if any.
33835 This is an integer value, which will be 1 if there are more children
33836 available outside the varobj's update range.
33839 This attribute will be present and have the value @samp{1} if the
33840 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33841 then this attribute will not be present.
33844 If new children were added to a dynamic varobj within the selected
33845 update range (as set by @code{-var-set-update-range}), then they will
33846 be listed in this attribute.
33849 @subsubheading Example
33856 -var-update --all-values var1
33857 ^done,changelist=[@{name="var1",value="3",in_scope="true",
33858 type_changed="false"@}]
33862 @subheading The @code{-var-set-frozen} Command
33863 @findex -var-set-frozen
33864 @anchor{-var-set-frozen}
33866 @subsubheading Synopsis
33869 -var-set-frozen @var{name} @var{flag}
33872 Set the frozenness flag on the variable object @var{name}. The
33873 @var{flag} parameter should be either @samp{1} to make the variable
33874 frozen or @samp{0} to make it unfrozen. If a variable object is
33875 frozen, then neither itself, nor any of its children, are
33876 implicitly updated by @code{-var-update} of
33877 a parent variable or by @code{-var-update *}. Only
33878 @code{-var-update} of the variable itself will update its value and
33879 values of its children. After a variable object is unfrozen, it is
33880 implicitly updated by all subsequent @code{-var-update} operations.
33881 Unfreezing a variable does not update it, only subsequent
33882 @code{-var-update} does.
33884 @subsubheading Example
33888 -var-set-frozen V 1
33893 @subheading The @code{-var-set-update-range} command
33894 @findex -var-set-update-range
33895 @anchor{-var-set-update-range}
33897 @subsubheading Synopsis
33900 -var-set-update-range @var{name} @var{from} @var{to}
33903 Set the range of children to be returned by future invocations of
33904 @code{-var-update}.
33906 @var{from} and @var{to} indicate the range of children to report. If
33907 @var{from} or @var{to} is less than zero, the range is reset and all
33908 children will be reported. Otherwise, children starting at @var{from}
33909 (zero-based) and up to and excluding @var{to} will be reported.
33911 @subsubheading Example
33915 -var-set-update-range V 1 2
33919 @subheading The @code{-var-set-visualizer} command
33920 @findex -var-set-visualizer
33921 @anchor{-var-set-visualizer}
33923 @subsubheading Synopsis
33926 -var-set-visualizer @var{name} @var{visualizer}
33929 Set a visualizer for the variable object @var{name}.
33931 @var{visualizer} is the visualizer to use. The special value
33932 @samp{None} means to disable any visualizer in use.
33934 If not @samp{None}, @var{visualizer} must be a Python expression.
33935 This expression must evaluate to a callable object which accepts a
33936 single argument. @value{GDBN} will call this object with the value of
33937 the varobj @var{name} as an argument (this is done so that the same
33938 Python pretty-printing code can be used for both the CLI and MI).
33939 When called, this object must return an object which conforms to the
33940 pretty-printing interface (@pxref{Pretty Printing API}).
33942 The pre-defined function @code{gdb.default_visualizer} may be used to
33943 select a visualizer by following the built-in process
33944 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33945 a varobj is created, and so ordinarily is not needed.
33947 This feature is only available if Python support is enabled. The MI
33948 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33949 can be used to check this.
33951 @subsubheading Example
33953 Resetting the visualizer:
33957 -var-set-visualizer V None
33961 Reselecting the default (type-based) visualizer:
33965 -var-set-visualizer V gdb.default_visualizer
33969 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33970 can be used to instantiate this class for a varobj:
33974 -var-set-visualizer V "lambda val: SomeClass()"
33978 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33979 @node GDB/MI Data Manipulation
33980 @section @sc{gdb/mi} Data Manipulation
33982 @cindex data manipulation, in @sc{gdb/mi}
33983 @cindex @sc{gdb/mi}, data manipulation
33984 This section describes the @sc{gdb/mi} commands that manipulate data:
33985 examine memory and registers, evaluate expressions, etc.
33987 For details about what an addressable memory unit is,
33988 @pxref{addressable memory unit}.
33990 @c REMOVED FROM THE INTERFACE.
33991 @c @subheading -data-assign
33992 @c Change the value of a program variable. Plenty of side effects.
33993 @c @subsubheading GDB Command
33995 @c @subsubheading Example
33998 @subheading The @code{-data-disassemble} Command
33999 @findex -data-disassemble
34001 @subsubheading Synopsis
34005 [ -s @var{start-addr} -e @var{end-addr} ]
34006 | [ -a @var{addr} ]
34007 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
34015 @item @var{start-addr}
34016 is the beginning address (or @code{$pc})
34017 @item @var{end-addr}
34020 is an address anywhere within (or the name of) the function to
34021 disassemble. If an address is specified, the whole function
34022 surrounding that address will be disassembled. If a name is
34023 specified, the whole function with that name will be disassembled.
34024 @item @var{filename}
34025 is the name of the file to disassemble
34026 @item @var{linenum}
34027 is the line number to disassemble around
34029 is the number of disassembly lines to be produced. If it is -1,
34030 the whole function will be disassembled, in case no @var{end-addr} is
34031 specified. If @var{end-addr} is specified as a non-zero value, and
34032 @var{lines} is lower than the number of disassembly lines between
34033 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34034 displayed; if @var{lines} is higher than the number of lines between
34035 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34040 @item 0 disassembly only
34041 @item 1 mixed source and disassembly (deprecated)
34042 @item 2 disassembly with raw opcodes
34043 @item 3 mixed source and disassembly with raw opcodes (deprecated)
34044 @item 4 mixed source and disassembly
34045 @item 5 mixed source and disassembly with raw opcodes
34048 Modes 1 and 3 are deprecated. The output is ``source centric''
34049 which hasn't proved useful in practice.
34050 @xref{Machine Code}, for a discussion of the difference between
34051 @code{/m} and @code{/s} output of the @code{disassemble} command.
34054 @subsubheading Result
34056 The result of the @code{-data-disassemble} command will be a list named
34057 @samp{asm_insns}, the contents of this list depend on the @var{mode}
34058 used with the @code{-data-disassemble} command.
34060 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
34065 The address at which this instruction was disassembled.
34068 The name of the function this instruction is within.
34071 The decimal offset in bytes from the start of @samp{func-name}.
34074 The text disassembly for this @samp{address}.
34077 This field is only present for modes 2, 3 and 5. This contains the raw opcode
34078 bytes for the @samp{inst} field.
34082 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
34083 @samp{src_and_asm_line}, each of which has the following fields:
34087 The line number within @samp{file}.
34090 The file name from the compilation unit. This might be an absolute
34091 file name or a relative file name depending on the compile command
34095 Absolute file name of @samp{file}. It is converted to a canonical form
34096 using the source file search path
34097 (@pxref{Source Path, ,Specifying Source Directories})
34098 and after resolving all the symbolic links.
34100 If the source file is not found this field will contain the path as
34101 present in the debug information.
34103 @item line_asm_insn
34104 This is a list of tuples containing the disassembly for @samp{line} in
34105 @samp{file}. The fields of each tuple are the same as for
34106 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34107 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34112 Note that whatever included in the @samp{inst} field, is not
34113 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34116 @subsubheading @value{GDBN} Command
34118 The corresponding @value{GDBN} command is @samp{disassemble}.
34120 @subsubheading Example
34122 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34126 -data-disassemble -s $pc -e "$pc + 20" -- 0
34129 @{address="0x000107c0",func-name="main",offset="4",
34130 inst="mov 2, %o0"@},
34131 @{address="0x000107c4",func-name="main",offset="8",
34132 inst="sethi %hi(0x11800), %o2"@},
34133 @{address="0x000107c8",func-name="main",offset="12",
34134 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34135 @{address="0x000107cc",func-name="main",offset="16",
34136 inst="sethi %hi(0x11800), %o2"@},
34137 @{address="0x000107d0",func-name="main",offset="20",
34138 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34142 Disassemble the whole @code{main} function. Line 32 is part of
34146 -data-disassemble -f basics.c -l 32 -- 0
34148 @{address="0x000107bc",func-name="main",offset="0",
34149 inst="save %sp, -112, %sp"@},
34150 @{address="0x000107c0",func-name="main",offset="4",
34151 inst="mov 2, %o0"@},
34152 @{address="0x000107c4",func-name="main",offset="8",
34153 inst="sethi %hi(0x11800), %o2"@},
34155 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34156 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34160 Disassemble 3 instructions from the start of @code{main}:
34164 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34166 @{address="0x000107bc",func-name="main",offset="0",
34167 inst="save %sp, -112, %sp"@},
34168 @{address="0x000107c0",func-name="main",offset="4",
34169 inst="mov 2, %o0"@},
34170 @{address="0x000107c4",func-name="main",offset="8",
34171 inst="sethi %hi(0x11800), %o2"@}]
34175 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34179 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34181 src_and_asm_line=@{line="31",
34182 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34183 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34184 line_asm_insn=[@{address="0x000107bc",
34185 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34186 src_and_asm_line=@{line="32",
34187 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34188 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34189 line_asm_insn=[@{address="0x000107c0",
34190 func-name="main",offset="4",inst="mov 2, %o0"@},
34191 @{address="0x000107c4",func-name="main",offset="8",
34192 inst="sethi %hi(0x11800), %o2"@}]@}]
34197 @subheading The @code{-data-evaluate-expression} Command
34198 @findex -data-evaluate-expression
34200 @subsubheading Synopsis
34203 -data-evaluate-expression @var{expr}
34206 Evaluate @var{expr} as an expression. The expression could contain an
34207 inferior function call. The function call will execute synchronously.
34208 If the expression contains spaces, it must be enclosed in double quotes.
34210 @subsubheading @value{GDBN} Command
34212 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34213 @samp{call}. In @code{gdbtk} only, there's a corresponding
34214 @samp{gdb_eval} command.
34216 @subsubheading Example
34218 In the following example, the numbers that precede the commands are the
34219 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34220 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34224 211-data-evaluate-expression A
34227 311-data-evaluate-expression &A
34228 311^done,value="0xefffeb7c"
34230 411-data-evaluate-expression A+3
34233 511-data-evaluate-expression "A + 3"
34239 @subheading The @code{-data-list-changed-registers} Command
34240 @findex -data-list-changed-registers
34242 @subsubheading Synopsis
34245 -data-list-changed-registers
34248 Display a list of the registers that have changed.
34250 @subsubheading @value{GDBN} Command
34252 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34253 has the corresponding command @samp{gdb_changed_register_list}.
34255 @subsubheading Example
34257 On a PPC MBX board:
34265 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34266 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34267 line="5",arch="powerpc"@}
34269 -data-list-changed-registers
34270 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34271 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34272 "24","25","26","27","28","30","31","64","65","66","67","69"]
34277 @subheading The @code{-data-list-register-names} Command
34278 @findex -data-list-register-names
34280 @subsubheading Synopsis
34283 -data-list-register-names [ ( @var{regno} )+ ]
34286 Show a list of register names for the current target. If no arguments
34287 are given, it shows a list of the names of all the registers. If
34288 integer numbers are given as arguments, it will print a list of the
34289 names of the registers corresponding to the arguments. To ensure
34290 consistency between a register name and its number, the output list may
34291 include empty register names.
34293 @subsubheading @value{GDBN} Command
34295 @value{GDBN} does not have a command which corresponds to
34296 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34297 corresponding command @samp{gdb_regnames}.
34299 @subsubheading Example
34301 For the PPC MBX board:
34304 -data-list-register-names
34305 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34306 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34307 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34308 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34309 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34310 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34311 "", "pc","ps","cr","lr","ctr","xer"]
34313 -data-list-register-names 1 2 3
34314 ^done,register-names=["r1","r2","r3"]
34318 @subheading The @code{-data-list-register-values} Command
34319 @findex -data-list-register-values
34321 @subsubheading Synopsis
34324 -data-list-register-values
34325 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34328 Display the registers' contents. The format according to which the
34329 registers' contents are to be returned is given by @var{fmt}, followed
34330 by an optional list of numbers specifying the registers to display. A
34331 missing list of numbers indicates that the contents of all the
34332 registers must be returned. The @code{--skip-unavailable} option
34333 indicates that only the available registers are to be returned.
34335 Allowed formats for @var{fmt} are:
34352 @subsubheading @value{GDBN} Command
34354 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34355 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34357 @subsubheading Example
34359 For a PPC MBX board (note: line breaks are for readability only, they
34360 don't appear in the actual output):
34364 -data-list-register-values r 64 65
34365 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34366 @{number="65",value="0x00029002"@}]
34368 -data-list-register-values x
34369 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34370 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34371 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34372 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34373 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34374 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34375 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34376 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34377 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34378 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34379 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34380 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34381 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34382 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34383 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34384 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34385 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34386 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34387 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34388 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34389 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34390 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34391 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34392 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34393 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34394 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34395 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34396 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34397 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34398 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34399 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34400 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34401 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34402 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34403 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34404 @{number="69",value="0x20002b03"@}]
34409 @subheading The @code{-data-read-memory} Command
34410 @findex -data-read-memory
34412 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34414 @subsubheading Synopsis
34417 -data-read-memory [ -o @var{byte-offset} ]
34418 @var{address} @var{word-format} @var{word-size}
34419 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34426 @item @var{address}
34427 An expression specifying the address of the first memory word to be
34428 read. Complex expressions containing embedded white space should be
34429 quoted using the C convention.
34431 @item @var{word-format}
34432 The format to be used to print the memory words. The notation is the
34433 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34436 @item @var{word-size}
34437 The size of each memory word in bytes.
34439 @item @var{nr-rows}
34440 The number of rows in the output table.
34442 @item @var{nr-cols}
34443 The number of columns in the output table.
34446 If present, indicates that each row should include an @sc{ascii} dump. The
34447 value of @var{aschar} is used as a padding character when a byte is not a
34448 member of the printable @sc{ascii} character set (printable @sc{ascii}
34449 characters are those whose code is between 32 and 126, inclusively).
34451 @item @var{byte-offset}
34452 An offset to add to the @var{address} before fetching memory.
34455 This command displays memory contents as a table of @var{nr-rows} by
34456 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34457 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34458 (returned as @samp{total-bytes}). Should less than the requested number
34459 of bytes be returned by the target, the missing words are identified
34460 using @samp{N/A}. The number of bytes read from the target is returned
34461 in @samp{nr-bytes} and the starting address used to read memory in
34464 The address of the next/previous row or page is available in
34465 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34468 @subsubheading @value{GDBN} Command
34470 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34471 @samp{gdb_get_mem} memory read command.
34473 @subsubheading Example
34475 Read six bytes of memory starting at @code{bytes+6} but then offset by
34476 @code{-6} bytes. Format as three rows of two columns. One byte per
34477 word. Display each word in hex.
34481 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34482 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34483 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34484 prev-page="0x0000138a",memory=[
34485 @{addr="0x00001390",data=["0x00","0x01"]@},
34486 @{addr="0x00001392",data=["0x02","0x03"]@},
34487 @{addr="0x00001394",data=["0x04","0x05"]@}]
34491 Read two bytes of memory starting at address @code{shorts + 64} and
34492 display as a single word formatted in decimal.
34496 5-data-read-memory shorts+64 d 2 1 1
34497 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34498 next-row="0x00001512",prev-row="0x0000150e",
34499 next-page="0x00001512",prev-page="0x0000150e",memory=[
34500 @{addr="0x00001510",data=["128"]@}]
34504 Read thirty two bytes of memory starting at @code{bytes+16} and format
34505 as eight rows of four columns. Include a string encoding with @samp{x}
34506 used as the non-printable character.
34510 4-data-read-memory bytes+16 x 1 8 4 x
34511 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34512 next-row="0x000013c0",prev-row="0x0000139c",
34513 next-page="0x000013c0",prev-page="0x00001380",memory=[
34514 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34515 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34516 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
34517 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
34518 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
34519 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
34520 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
34521 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
34525 @subheading The @code{-data-read-memory-bytes} Command
34526 @findex -data-read-memory-bytes
34528 @subsubheading Synopsis
34531 -data-read-memory-bytes [ -o @var{offset} ]
34532 @var{address} @var{count}
34539 @item @var{address}
34540 An expression specifying the address of the first addressable memory unit
34541 to be read. Complex expressions containing embedded white space should be
34542 quoted using the C convention.
34545 The number of addressable memory units to read. This should be an integer
34549 The offset relative to @var{address} at which to start reading. This
34550 should be an integer literal. This option is provided so that a frontend
34551 is not required to first evaluate address and then perform address
34552 arithmetics itself.
34556 This command attempts to read all accessible memory regions in the
34557 specified range. First, all regions marked as unreadable in the memory
34558 map (if one is defined) will be skipped. @xref{Memory Region
34559 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34560 regions. For each one, if reading full region results in an errors,
34561 @value{GDBN} will try to read a subset of the region.
34563 In general, every single memory unit in the region may be readable or not,
34564 and the only way to read every readable unit is to try a read at
34565 every address, which is not practical. Therefore, @value{GDBN} will
34566 attempt to read all accessible memory units at either beginning or the end
34567 of the region, using a binary division scheme. This heuristic works
34568 well for reading across a memory map boundary. Note that if a region
34569 has a readable range that is neither at the beginning or the end,
34570 @value{GDBN} will not read it.
34572 The result record (@pxref{GDB/MI Result Records}) that is output of
34573 the command includes a field named @samp{memory} whose content is a
34574 list of tuples. Each tuple represent a successfully read memory block
34575 and has the following fields:
34579 The start address of the memory block, as hexadecimal literal.
34582 The end address of the memory block, as hexadecimal literal.
34585 The offset of the memory block, as hexadecimal literal, relative to
34586 the start address passed to @code{-data-read-memory-bytes}.
34589 The contents of the memory block, in hex.
34595 @subsubheading @value{GDBN} Command
34597 The corresponding @value{GDBN} command is @samp{x}.
34599 @subsubheading Example
34603 -data-read-memory-bytes &a 10
34604 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
34606 contents="01000000020000000300"@}]
34611 @subheading The @code{-data-write-memory-bytes} Command
34612 @findex -data-write-memory-bytes
34614 @subsubheading Synopsis
34617 -data-write-memory-bytes @var{address} @var{contents}
34618 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
34625 @item @var{address}
34626 An expression specifying the address of the first addressable memory unit
34627 to be written. Complex expressions containing embedded white space should
34628 be quoted using the C convention.
34630 @item @var{contents}
34631 The hex-encoded data to write. It is an error if @var{contents} does
34632 not represent an integral number of addressable memory units.
34635 Optional argument indicating the number of addressable memory units to be
34636 written. If @var{count} is greater than @var{contents}' length,
34637 @value{GDBN} will repeatedly write @var{contents} until it fills
34638 @var{count} memory units.
34642 @subsubheading @value{GDBN} Command
34644 There's no corresponding @value{GDBN} command.
34646 @subsubheading Example
34650 -data-write-memory-bytes &a "aabbccdd"
34657 -data-write-memory-bytes &a "aabbccdd" 16e
34662 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34663 @node GDB/MI Tracepoint Commands
34664 @section @sc{gdb/mi} Tracepoint Commands
34666 The commands defined in this section implement MI support for
34667 tracepoints. For detailed introduction, see @ref{Tracepoints}.
34669 @subheading The @code{-trace-find} Command
34670 @findex -trace-find
34672 @subsubheading Synopsis
34675 -trace-find @var{mode} [@var{parameters}@dots{}]
34678 Find a trace frame using criteria defined by @var{mode} and
34679 @var{parameters}. The following table lists permissible
34680 modes and their parameters. For details of operation, see @ref{tfind}.
34685 No parameters are required. Stops examining trace frames.
34688 An integer is required as parameter. Selects tracepoint frame with
34691 @item tracepoint-number
34692 An integer is required as parameter. Finds next
34693 trace frame that corresponds to tracepoint with the specified number.
34696 An address is required as parameter. Finds
34697 next trace frame that corresponds to any tracepoint at the specified
34700 @item pc-inside-range
34701 Two addresses are required as parameters. Finds next trace
34702 frame that corresponds to a tracepoint at an address inside the
34703 specified range. Both bounds are considered to be inside the range.
34705 @item pc-outside-range
34706 Two addresses are required as parameters. Finds
34707 next trace frame that corresponds to a tracepoint at an address outside
34708 the specified range. Both bounds are considered to be inside the range.
34711 Line specification is required as parameter. @xref{Specify Location}.
34712 Finds next trace frame that corresponds to a tracepoint at
34713 the specified location.
34717 If @samp{none} was passed as @var{mode}, the response does not
34718 have fields. Otherwise, the response may have the following fields:
34722 This field has either @samp{0} or @samp{1} as the value, depending
34723 on whether a matching tracepoint was found.
34726 The index of the found traceframe. This field is present iff
34727 the @samp{found} field has value of @samp{1}.
34730 The index of the found tracepoint. This field is present iff
34731 the @samp{found} field has value of @samp{1}.
34734 The information about the frame corresponding to the found trace
34735 frame. This field is present only if a trace frame was found.
34736 @xref{GDB/MI Frame Information}, for description of this field.
34740 @subsubheading @value{GDBN} Command
34742 The corresponding @value{GDBN} command is @samp{tfind}.
34744 @subheading -trace-define-variable
34745 @findex -trace-define-variable
34747 @subsubheading Synopsis
34750 -trace-define-variable @var{name} [ @var{value} ]
34753 Create trace variable @var{name} if it does not exist. If
34754 @var{value} is specified, sets the initial value of the specified
34755 trace variable to that value. Note that the @var{name} should start
34756 with the @samp{$} character.
34758 @subsubheading @value{GDBN} Command
34760 The corresponding @value{GDBN} command is @samp{tvariable}.
34762 @subheading The @code{-trace-frame-collected} Command
34763 @findex -trace-frame-collected
34765 @subsubheading Synopsis
34768 -trace-frame-collected
34769 [--var-print-values @var{var_pval}]
34770 [--comp-print-values @var{comp_pval}]
34771 [--registers-format @var{regformat}]
34772 [--memory-contents]
34775 This command returns the set of collected objects, register names,
34776 trace state variable names, memory ranges and computed expressions
34777 that have been collected at a particular trace frame. The optional
34778 parameters to the command affect the output format in different ways.
34779 See the output description table below for more details.
34781 The reported names can be used in the normal manner to create
34782 varobjs and inspect the objects themselves. The items returned by
34783 this command are categorized so that it is clear which is a variable,
34784 which is a register, which is a trace state variable, which is a
34785 memory range and which is a computed expression.
34787 For instance, if the actions were
34789 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34790 collect *(int*)0xaf02bef0@@40
34794 the object collected in its entirety would be @code{myVar}. The
34795 object @code{myArray} would be partially collected, because only the
34796 element at index @code{myIndex} would be collected. The remaining
34797 objects would be computed expressions.
34799 An example output would be:
34803 -trace-frame-collected
34805 explicit-variables=[@{name="myVar",value="1"@}],
34806 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34807 @{name="myObj.field",value="0"@},
34808 @{name="myPtr->field",value="1"@},
34809 @{name="myCount + 2",value="3"@},
34810 @{name="$tvar1 + 1",value="43970027"@}],
34811 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
34812 @{number="1",value="0x0"@},
34813 @{number="2",value="0x4"@},
34815 @{number="125",value="0x0"@}],
34816 tvars=[@{name="$tvar1",current="43970026"@}],
34817 memory=[@{address="0x0000000000602264",length="4"@},
34818 @{address="0x0000000000615bc0",length="4"@}]
34825 @item explicit-variables
34826 The set of objects that have been collected in their entirety (as
34827 opposed to collecting just a few elements of an array or a few struct
34828 members). For each object, its name and value are printed.
34829 The @code{--var-print-values} option affects how or whether the value
34830 field is output. If @var{var_pval} is 0, then print only the names;
34831 if it is 1, print also their values; and if it is 2, print the name,
34832 type and value for simple data types, and the name and type for
34833 arrays, structures and unions.
34835 @item computed-expressions
34836 The set of computed expressions that have been collected at the
34837 current trace frame. The @code{--comp-print-values} option affects
34838 this set like the @code{--var-print-values} option affects the
34839 @code{explicit-variables} set. See above.
34842 The registers that have been collected at the current trace frame.
34843 For each register collected, the name and current value are returned.
34844 The value is formatted according to the @code{--registers-format}
34845 option. See the @command{-data-list-register-values} command for a
34846 list of the allowed formats. The default is @samp{x}.
34849 The trace state variables that have been collected at the current
34850 trace frame. For each trace state variable collected, the name and
34851 current value are returned.
34854 The set of memory ranges that have been collected at the current trace
34855 frame. Its content is a list of tuples. Each tuple represents a
34856 collected memory range and has the following fields:
34860 The start address of the memory range, as hexadecimal literal.
34863 The length of the memory range, as decimal literal.
34866 The contents of the memory block, in hex. This field is only present
34867 if the @code{--memory-contents} option is specified.
34873 @subsubheading @value{GDBN} Command
34875 There is no corresponding @value{GDBN} command.
34877 @subsubheading Example
34879 @subheading -trace-list-variables
34880 @findex -trace-list-variables
34882 @subsubheading Synopsis
34885 -trace-list-variables
34888 Return a table of all defined trace variables. Each element of the
34889 table has the following fields:
34893 The name of the trace variable. This field is always present.
34896 The initial value. This is a 64-bit signed integer. This
34897 field is always present.
34900 The value the trace variable has at the moment. This is a 64-bit
34901 signed integer. This field is absent iff current value is
34902 not defined, for example if the trace was never run, or is
34907 @subsubheading @value{GDBN} Command
34909 The corresponding @value{GDBN} command is @samp{tvariables}.
34911 @subsubheading Example
34915 -trace-list-variables
34916 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
34917 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
34918 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34919 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34920 body=[variable=@{name="$trace_timestamp",initial="0"@}
34921 variable=@{name="$foo",initial="10",current="15"@}]@}
34925 @subheading -trace-save
34926 @findex -trace-save
34928 @subsubheading Synopsis
34931 -trace-save [ -r ] [ -ctf ] @var{filename}
34934 Saves the collected trace data to @var{filename}. Without the
34935 @samp{-r} option, the data is downloaded from the target and saved
34936 in a local file. With the @samp{-r} option the target is asked
34937 to perform the save.
34939 By default, this command will save the trace in the tfile format. You can
34940 supply the optional @samp{-ctf} argument to save it the CTF format. See
34941 @ref{Trace Files} for more information about CTF.
34943 @subsubheading @value{GDBN} Command
34945 The corresponding @value{GDBN} command is @samp{tsave}.
34948 @subheading -trace-start
34949 @findex -trace-start
34951 @subsubheading Synopsis
34957 Starts a tracing experiment. The result of this command does not
34960 @subsubheading @value{GDBN} Command
34962 The corresponding @value{GDBN} command is @samp{tstart}.
34964 @subheading -trace-status
34965 @findex -trace-status
34967 @subsubheading Synopsis
34973 Obtains the status of a tracing experiment. The result may include
34974 the following fields:
34979 May have a value of either @samp{0}, when no tracing operations are
34980 supported, @samp{1}, when all tracing operations are supported, or
34981 @samp{file} when examining trace file. In the latter case, examining
34982 of trace frame is possible but new tracing experiement cannot be
34983 started. This field is always present.
34986 May have a value of either @samp{0} or @samp{1} depending on whether
34987 tracing experiement is in progress on target. This field is present
34988 if @samp{supported} field is not @samp{0}.
34991 Report the reason why the tracing was stopped last time. This field
34992 may be absent iff tracing was never stopped on target yet. The
34993 value of @samp{request} means the tracing was stopped as result of
34994 the @code{-trace-stop} command. The value of @samp{overflow} means
34995 the tracing buffer is full. The value of @samp{disconnection} means
34996 tracing was automatically stopped when @value{GDBN} has disconnected.
34997 The value of @samp{passcount} means tracing was stopped when a
34998 tracepoint was passed a maximal number of times for that tracepoint.
34999 This field is present if @samp{supported} field is not @samp{0}.
35001 @item stopping-tracepoint
35002 The number of tracepoint whose passcount as exceeded. This field is
35003 present iff the @samp{stop-reason} field has the value of
35007 @itemx frames-created
35008 The @samp{frames} field is a count of the total number of trace frames
35009 in the trace buffer, while @samp{frames-created} is the total created
35010 during the run, including ones that were discarded, such as when a
35011 circular trace buffer filled up. Both fields are optional.
35015 These fields tell the current size of the tracing buffer and the
35016 remaining space. These fields are optional.
35019 The value of the circular trace buffer flag. @code{1} means that the
35020 trace buffer is circular and old trace frames will be discarded if
35021 necessary to make room, @code{0} means that the trace buffer is linear
35025 The value of the disconnected tracing flag. @code{1} means that
35026 tracing will continue after @value{GDBN} disconnects, @code{0} means
35027 that the trace run will stop.
35030 The filename of the trace file being examined. This field is
35031 optional, and only present when examining a trace file.
35035 @subsubheading @value{GDBN} Command
35037 The corresponding @value{GDBN} command is @samp{tstatus}.
35039 @subheading -trace-stop
35040 @findex -trace-stop
35042 @subsubheading Synopsis
35048 Stops a tracing experiment. The result of this command has the same
35049 fields as @code{-trace-status}, except that the @samp{supported} and
35050 @samp{running} fields are not output.
35052 @subsubheading @value{GDBN} Command
35054 The corresponding @value{GDBN} command is @samp{tstop}.
35057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35058 @node GDB/MI Symbol Query
35059 @section @sc{gdb/mi} Symbol Query Commands
35063 @subheading The @code{-symbol-info-address} Command
35064 @findex -symbol-info-address
35066 @subsubheading Synopsis
35069 -symbol-info-address @var{symbol}
35072 Describe where @var{symbol} is stored.
35074 @subsubheading @value{GDBN} Command
35076 The corresponding @value{GDBN} command is @samp{info address}.
35078 @subsubheading Example
35082 @subheading The @code{-symbol-info-file} Command
35083 @findex -symbol-info-file
35085 @subsubheading Synopsis
35091 Show the file for the symbol.
35093 @subsubheading @value{GDBN} Command
35095 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35096 @samp{gdb_find_file}.
35098 @subsubheading Example
35102 @subheading The @code{-symbol-info-functions} Command
35103 @findex -symbol-info-functions
35104 @anchor{-symbol-info-functions}
35106 @subsubheading Synopsis
35109 -symbol-info-functions [--include-nondebug]
35110 [--type @var{type_regexp}]
35111 [--name @var{name_regexp}]
35112 [--max-results @var{limit}]
35116 Return a list containing the names and types for all global functions
35117 taken from the debug information. The functions are grouped by source
35118 file, and shown with the line number on which each function is
35121 The @code{--include-nondebug} option causes the output to include
35122 code symbols from the symbol table.
35124 The options @code{--type} and @code{--name} allow the symbols returned
35125 to be filtered based on either the name of the function, or the type
35126 signature of the function.
35128 The option @code{--max-results} restricts the command to return no
35129 more than @var{limit} results. If exactly @var{limit} results are
35130 returned then there might be additional results available if a higher
35133 @subsubheading @value{GDBN} Command
35135 The corresponding @value{GDBN} command is @samp{info functions}.
35137 @subsubheading Example
35141 -symbol-info-functions
35144 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35145 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35146 symbols=[@{line="36", name="f4", type="void (int *)",
35147 description="void f4(int *);"@},
35148 @{line="42", name="main", type="int ()",
35149 description="int main();"@},
35150 @{line="30", name="f1", type="my_int_t (int, int)",
35151 description="static my_int_t f1(int, int);"@}]@},
35152 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35153 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35154 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35155 description="float f2(another_float_t);"@},
35156 @{line="39", name="f3", type="int (another_int_t)",
35157 description="int f3(another_int_t);"@},
35158 @{line="27", name="f1", type="another_float_t (int)",
35159 description="static another_float_t f1(int);"@}]@}]@}
35163 -symbol-info-functions --name f1
35166 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35167 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35168 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35169 description="static my_int_t f1(int, int);"@}]@},
35170 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35171 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35172 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35173 description="static another_float_t f1(int);"@}]@}]@}
35177 -symbol-info-functions --type void
35180 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35181 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35182 symbols=[@{line="36", name="f4", type="void (int *)",
35183 description="void f4(int *);"@}]@}]@}
35187 -symbol-info-functions --include-nondebug
35190 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35191 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35192 symbols=[@{line="36", name="f4", type="void (int *)",
35193 description="void f4(int *);"@},
35194 @{line="42", name="main", type="int ()",
35195 description="int main();"@},
35196 @{line="30", name="f1", type="my_int_t (int, int)",
35197 description="static my_int_t f1(int, int);"@}]@},
35198 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35199 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35200 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35201 description="float f2(another_float_t);"@},
35202 @{line="39", name="f3", type="int (another_int_t)",
35203 description="int f3(another_int_t);"@},
35204 @{line="27", name="f1", type="another_float_t (int)",
35205 description="static another_float_t f1(int);"@}]@}],
35207 [@{address="0x0000000000400398",name="_init"@},
35208 @{address="0x00000000004003b0",name="_start"@},
35214 @subheading The @code{-symbol-info-module-functions} Command
35215 @findex -symbol-info-module-functions
35216 @anchor{-symbol-info-module-functions}
35218 @subsubheading Synopsis
35221 -symbol-info-module-functions [--module @var{module_regexp}]
35222 [--name @var{name_regexp}]
35223 [--type @var{type_regexp}]
35227 Return a list containing the names of all known functions within all
35228 know Fortran modules. The functions are grouped by source file and
35229 containing module, and shown with the line number on which each
35230 function is defined.
35232 The option @code{--module} only returns results for modules matching
35233 @var{module_regexp}. The option @code{--name} only returns functions
35234 whose name matches @var{name_regexp}, and @code{--type} only returns
35235 functions whose type matches @var{type_regexp}.
35237 @subsubheading @value{GDBN} Command
35239 The corresponding @value{GDBN} command is @samp{info module functions}.
35241 @subsubheading Example
35246 -symbol-info-module-functions
35249 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35250 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35251 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35252 description="void mod1::check_all(void);"@}]@}]@},
35254 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35255 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35256 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35257 description="void mod2::check_var_i(void);"@}]@}]@},
35259 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35260 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35261 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35262 description="void mod3::check_all(void);"@},
35263 @{line="27",name="mod3::check_mod2",type="void (void)",
35264 description="void mod3::check_mod2(void);"@}]@}]@},
35265 @{module="modmany",
35266 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35267 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35268 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35269 description="void modmany::check_some(void);"@}]@}]@},
35271 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35272 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35273 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35274 description="void moduse::check_all(void);"@},
35275 @{line="49",name="moduse::check_var_x",type="void (void)",
35276 description="void moduse::check_var_x(void);"@}]@}]@}]
35280 @subheading The @code{-symbol-info-module-variables} Command
35281 @findex -symbol-info-module-variables
35282 @anchor{-symbol-info-module-variables}
35284 @subsubheading Synopsis
35287 -symbol-info-module-variables [--module @var{module_regexp}]
35288 [--name @var{name_regexp}]
35289 [--type @var{type_regexp}]
35293 Return a list containing the names of all known variables within all
35294 know Fortran modules. The variables are grouped by source file and
35295 containing module, and shown with the line number on which each
35296 variable is defined.
35298 The option @code{--module} only returns results for modules matching
35299 @var{module_regexp}. The option @code{--name} only returns variables
35300 whose name matches @var{name_regexp}, and @code{--type} only returns
35301 variables whose type matches @var{type_regexp}.
35303 @subsubheading @value{GDBN} Command
35305 The corresponding @value{GDBN} command is @samp{info module variables}.
35307 @subsubheading Example
35312 -symbol-info-module-variables
35315 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35316 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35317 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35318 description="integer(kind=4) mod1::var_const;"@},
35319 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35320 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35322 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35323 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35324 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35325 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35327 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35328 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35329 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35330 description="integer(kind=4) mod3::mod1;"@},
35331 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35332 description="integer(kind=4) mod3::mod2;"@},
35333 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35334 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35335 @{module="modmany",
35336 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35337 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35338 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35339 description="integer(kind=4) modmany::var_a;"@},
35340 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35341 description="integer(kind=4) modmany::var_b;"@},
35342 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35343 description="integer(kind=4) modmany::var_c;"@},
35344 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35345 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35347 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35348 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35349 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35350 description="integer(kind=4) moduse::var_x;"@},
35351 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35352 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35356 @subheading The @code{-symbol-info-modules} Command
35357 @findex -symbol-info-modules
35358 @anchor{-symbol-info-modules}
35360 @subsubheading Synopsis
35363 -symbol-info-modules [--name @var{name_regexp}]
35364 [--max-results @var{limit}]
35369 Return a list containing the names of all known Fortran modules. The
35370 modules are grouped by source file, and shown with the line number on
35371 which each modules is defined.
35373 The option @code{--name} allows the modules returned to be filtered
35374 based the name of the module.
35376 The option @code{--max-results} restricts the command to return no
35377 more than @var{limit} results. If exactly @var{limit} results are
35378 returned then there might be additional results available if a higher
35381 @subsubheading @value{GDBN} Command
35383 The corresponding @value{GDBN} command is @samp{info modules}.
35385 @subsubheading Example
35389 -symbol-info-modules
35392 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35393 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35394 symbols=[@{line="16",name="mod1"@},
35395 @{line="22",name="mod2"@}]@},
35396 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35397 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35398 symbols=[@{line="16",name="mod3"@},
35399 @{line="22",name="modmany"@},
35400 @{line="26",name="moduse"@}]@}]@}
35404 -symbol-info-modules --name mod[123]
35407 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35408 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35409 symbols=[@{line="16",name="mod1"@},
35410 @{line="22",name="mod2"@}]@},
35411 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35412 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35413 symbols=[@{line="16",name="mod3"@}]@}]@}
35417 @subheading The @code{-symbol-info-types} Command
35418 @findex -symbol-info-types
35419 @anchor{-symbol-info-types}
35421 @subsubheading Synopsis
35424 -symbol-info-types [--name @var{name_regexp}]
35425 [--max-results @var{limit}]
35430 Return a list of all defined types. The types are grouped by source
35431 file, and shown with the line number on which each user defined type
35432 is defined. Some base types are not defined in the source code but
35433 are added to the debug information by the compiler, for example
35434 @code{int}, @code{float}, etc.; these types do not have an associated
35437 The option @code{--name} allows the list of types returned to be
35440 The option @code{--max-results} restricts the command to return no
35441 more than @var{limit} results. If exactly @var{limit} results are
35442 returned then there might be additional results available if a higher
35445 @subsubheading @value{GDBN} Command
35447 The corresponding @value{GDBN} command is @samp{info types}.
35449 @subsubheading Example
35456 [@{filename="gdb.mi/mi-sym-info-1.c",
35457 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35458 symbols=[@{name="float"@},
35460 @{line="27",name="typedef int my_int_t;"@}]@},
35461 @{filename="gdb.mi/mi-sym-info-2.c",
35462 fullname="/project/gdb.mi/mi-sym-info-2.c",
35463 symbols=[@{line="24",name="typedef float another_float_t;"@},
35464 @{line="23",name="typedef int another_int_t;"@},
35466 @{name="int"@}]@}]@}
35470 -symbol-info-types --name _int_
35473 [@{filename="gdb.mi/mi-sym-info-1.c",
35474 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35475 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35476 @{filename="gdb.mi/mi-sym-info-2.c",
35477 fullname="/project/gdb.mi/mi-sym-info-2.c",
35478 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35482 @subheading The @code{-symbol-info-variables} Command
35483 @findex -symbol-info-variables
35484 @anchor{-symbol-info-variables}
35486 @subsubheading Synopsis
35489 -symbol-info-variables [--include-nondebug]
35490 [--type @var{type_regexp}]
35491 [--name @var{name_regexp}]
35492 [--max-results @var{limit}]
35497 Return a list containing the names and types for all global variables
35498 taken from the debug information. The variables are grouped by source
35499 file, and shown with the line number on which each variable is
35502 The @code{--include-nondebug} option causes the output to include
35503 data symbols from the symbol table.
35505 The options @code{--type} and @code{--name} allow the symbols returned
35506 to be filtered based on either the name of the variable, or the type
35509 The option @code{--max-results} restricts the command to return no
35510 more than @var{limit} results. If exactly @var{limit} results are
35511 returned then there might be additional results available if a higher
35514 @subsubheading @value{GDBN} Command
35516 The corresponding @value{GDBN} command is @samp{info variables}.
35518 @subsubheading Example
35522 -symbol-info-variables
35525 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35526 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35527 symbols=[@{line="25",name="global_f1",type="float",
35528 description="static float global_f1;"@},
35529 @{line="24",name="global_i1",type="int",
35530 description="static int global_i1;"@}]@},
35531 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35532 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35533 symbols=[@{line="21",name="global_f2",type="int",
35534 description="int global_f2;"@},
35535 @{line="20",name="global_i2",type="int",
35536 description="int global_i2;"@},
35537 @{line="19",name="global_f1",type="float",
35538 description="static float global_f1;"@},
35539 @{line="18",name="global_i1",type="int",
35540 description="static int global_i1;"@}]@}]@}
35544 -symbol-info-variables --name f1
35547 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35548 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35549 symbols=[@{line="25",name="global_f1",type="float",
35550 description="static float global_f1;"@}]@},
35551 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35552 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35553 symbols=[@{line="19",name="global_f1",type="float",
35554 description="static float global_f1;"@}]@}]@}
35558 -symbol-info-variables --type float
35561 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35562 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35563 symbols=[@{line="25",name="global_f1",type="float",
35564 description="static float global_f1;"@}]@},
35565 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35566 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35567 symbols=[@{line="19",name="global_f1",type="float",
35568 description="static float global_f1;"@}]@}]@}
35572 -symbol-info-variables --include-nondebug
35575 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35576 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35577 symbols=[@{line="25",name="global_f1",type="float",
35578 description="static float global_f1;"@},
35579 @{line="24",name="global_i1",type="int",
35580 description="static int global_i1;"@}]@},
35581 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35582 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35583 symbols=[@{line="21",name="global_f2",type="int",
35584 description="int global_f2;"@},
35585 @{line="20",name="global_i2",type="int",
35586 description="int global_i2;"@},
35587 @{line="19",name="global_f1",type="float",
35588 description="static float global_f1;"@},
35589 @{line="18",name="global_i1",type="int",
35590 description="static int global_i1;"@}]@}],
35592 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35593 @{address="0x00000000004005d8",name="__dso_handle"@}
35600 @subheading The @code{-symbol-info-line} Command
35601 @findex -symbol-info-line
35603 @subsubheading Synopsis
35609 Show the core addresses of the code for a source line.
35611 @subsubheading @value{GDBN} Command
35613 The corresponding @value{GDBN} command is @samp{info line}.
35614 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
35616 @subsubheading Example
35620 @subheading The @code{-symbol-info-symbol} Command
35621 @findex -symbol-info-symbol
35623 @subsubheading Synopsis
35626 -symbol-info-symbol @var{addr}
35629 Describe what symbol is at location @var{addr}.
35631 @subsubheading @value{GDBN} Command
35633 The corresponding @value{GDBN} command is @samp{info symbol}.
35635 @subsubheading Example
35639 @subheading The @code{-symbol-list-functions} Command
35640 @findex -symbol-list-functions
35642 @subsubheading Synopsis
35645 -symbol-list-functions
35648 List the functions in the executable.
35650 @subsubheading @value{GDBN} Command
35652 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
35653 @samp{gdb_search} in @code{gdbtk}.
35655 @subsubheading Example
35660 @subheading The @code{-symbol-list-lines} Command
35661 @findex -symbol-list-lines
35663 @subsubheading Synopsis
35666 -symbol-list-lines @var{filename}
35669 Print the list of lines that contain code and their associated program
35670 addresses for the given source filename. The entries are sorted in
35671 ascending PC order.
35673 @subsubheading @value{GDBN} Command
35675 There is no corresponding @value{GDBN} command.
35677 @subsubheading Example
35680 -symbol-list-lines basics.c
35681 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
35687 @subheading The @code{-symbol-list-types} Command
35688 @findex -symbol-list-types
35690 @subsubheading Synopsis
35696 List all the type names.
35698 @subsubheading @value{GDBN} Command
35700 The corresponding commands are @samp{info types} in @value{GDBN},
35701 @samp{gdb_search} in @code{gdbtk}.
35703 @subsubheading Example
35707 @subheading The @code{-symbol-list-variables} Command
35708 @findex -symbol-list-variables
35710 @subsubheading Synopsis
35713 -symbol-list-variables
35716 List all the global and static variable names.
35718 @subsubheading @value{GDBN} Command
35720 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
35722 @subsubheading Example
35726 @subheading The @code{-symbol-locate} Command
35727 @findex -symbol-locate
35729 @subsubheading Synopsis
35735 @subsubheading @value{GDBN} Command
35737 @samp{gdb_loc} in @code{gdbtk}.
35739 @subsubheading Example
35743 @subheading The @code{-symbol-type} Command
35744 @findex -symbol-type
35746 @subsubheading Synopsis
35749 -symbol-type @var{variable}
35752 Show type of @var{variable}.
35754 @subsubheading @value{GDBN} Command
35756 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35757 @samp{gdb_obj_variable}.
35759 @subsubheading Example
35764 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35765 @node GDB/MI File Commands
35766 @section @sc{gdb/mi} File Commands
35768 This section describes the GDB/MI commands to specify executable file names
35769 and to read in and obtain symbol table information.
35771 @subheading The @code{-file-exec-and-symbols} Command
35772 @findex -file-exec-and-symbols
35774 @subsubheading Synopsis
35777 -file-exec-and-symbols @var{file}
35780 Specify the executable file to be debugged. This file is the one from
35781 which the symbol table is also read. If no file is specified, the
35782 command clears the executable and symbol information. If breakpoints
35783 are set when using this command with no arguments, @value{GDBN} will produce
35784 error messages. Otherwise, no output is produced, except a completion
35787 @subsubheading @value{GDBN} Command
35789 The corresponding @value{GDBN} command is @samp{file}.
35791 @subsubheading Example
35795 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35801 @subheading The @code{-file-exec-file} Command
35802 @findex -file-exec-file
35804 @subsubheading Synopsis
35807 -file-exec-file @var{file}
35810 Specify the executable file to be debugged. Unlike
35811 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
35812 from this file. If used without argument, @value{GDBN} clears the information
35813 about the executable file. No output is produced, except a completion
35816 @subsubheading @value{GDBN} Command
35818 The corresponding @value{GDBN} command is @samp{exec-file}.
35820 @subsubheading Example
35824 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35831 @subheading The @code{-file-list-exec-sections} Command
35832 @findex -file-list-exec-sections
35834 @subsubheading Synopsis
35837 -file-list-exec-sections
35840 List the sections of the current executable file.
35842 @subsubheading @value{GDBN} Command
35844 The @value{GDBN} command @samp{info file} shows, among the rest, the same
35845 information as this command. @code{gdbtk} has a corresponding command
35846 @samp{gdb_load_info}.
35848 @subsubheading Example
35853 @subheading The @code{-file-list-exec-source-file} Command
35854 @findex -file-list-exec-source-file
35856 @subsubheading Synopsis
35859 -file-list-exec-source-file
35862 List the line number, the current source file, and the absolute path
35863 to the current source file for the current executable. The macro
35864 information field has a value of @samp{1} or @samp{0} depending on
35865 whether or not the file includes preprocessor macro information.
35867 @subsubheading @value{GDBN} Command
35869 The @value{GDBN} equivalent is @samp{info source}
35871 @subsubheading Example
35875 123-file-list-exec-source-file
35876 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
35881 @subheading The @code{-file-list-exec-source-files} Command
35882 @kindex info sources
35883 @findex -file-list-exec-source-files
35885 @subsubheading Synopsis
35888 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
35889 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
35891 @r{[} @var{regexp} @r{]}
35894 This command returns information about the source files @value{GDBN}
35895 knows about, it will output both the filename and fullname (absolute
35896 file name) of a source file, though the fullname can be elided if this
35897 information is not known to @value{GDBN}.
35899 With no arguments this command returns a list of source files. Each
35900 source file is represented by a tuple with the fields; @var{file},
35901 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
35902 display name for the file, while @var{fullname} is the absolute name
35903 of the file. The @var{fullname} field can be elided if the absolute
35904 name of the source file can't be computed. The field
35905 @var{debug-fully-read} will be a string, either @code{true} or
35906 @code{false}. When @code{true}, this indicates the full debug
35907 information for the compilation unit describing this file has been
35908 read in. When @code{false}, the full debug information has not yet
35909 been read in. While reading in the full debug information it is
35910 possible that @value{GDBN} could become aware of additional source
35913 The optional @var{regexp} can be used to filter the list of source
35914 files returned. The @var{regexp} will be matched against the full
35915 source file name. The matching is case-sensitive, except on operating
35916 systems that have case-insensitive filesystem (e.g.,
35917 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
35918 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
35919 @var{regexp} starts with @samp{-}).
35921 If @code{--dirname} is provided, then @var{regexp} is matched only
35922 against the directory name of each source file. If @code{--basename}
35923 is provided, then @var{regexp} is matched against the basename of each
35924 source file. Only one of @code{--dirname} or @code{--basename} may be
35925 given, and if either is given then @var{regexp} is required.
35927 If @code{--group-by-objfile} is used then the format of the results is
35928 changed. The results will now be a list of tuples, with each tuple
35929 representing an object file (executable or shared library) loaded into
35930 @value{GDBN}. The fields of these tuples are; @var{filename},
35931 @var{debug-info}, and @var{sources}. The @var{filename} is the
35932 absolute name of the object file, @var{debug-info} is a string with
35933 one of the following values:
35937 This object file has no debug information.
35938 @item partially-read
35939 This object file has debug information, but it is not fully read in
35940 yet. When it is read in later, GDB might become aware of additional
35943 This object file has debug information, and this information is fully
35944 read into GDB. The list of source files is complete.
35947 The @var{sources} is a list or tuples, with each tuple describing a
35948 single source file with the same fields as described previously. The
35949 @var{sources} list can be empty for object files that have no debug
35952 @subsubheading @value{GDBN} Command
35954 The @value{GDBN} equivalent is @samp{info sources}.
35955 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
35957 @subsubheading Example
35960 -file-list-exec-source-files
35961 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
35962 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
35963 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
35965 -file-list-exec-source-files
35966 ^done,files=[@{file="test.c",
35967 fullname="/tmp/info-sources/test.c",
35968 debug-fully-read="true"@},
35969 @{file="/usr/include/stdc-predef.h",
35970 fullname="/usr/include/stdc-predef.h",
35971 debug-fully-read="true"@},
35973 fullname="/tmp/info-sources/header.h",
35974 debug-fully-read="true"@},
35976 fullname="/tmp/info-sources/helper.c",
35977 debug-fully-read="true"@}]
35979 -file-list-exec-source-files -- \\.c
35980 ^done,files=[@{file="test.c",
35981 fullname="/tmp/info-sources/test.c",
35982 debug-fully-read="true"@},
35984 fullname="/tmp/info-sources/helper.c",
35985 debug-fully-read="true"@}]
35987 -file-list-exec-source-files --group-by-objfile
35988 ^done,files=[@{filename="/tmp/info-sources/test.x",
35989 debug-info="fully-read",
35990 sources=[@{file="test.c",
35991 fullname="/tmp/info-sources/test.c",
35992 debug-fully-read="true"@},
35993 @{file="/usr/include/stdc-predef.h",
35994 fullname="/usr/include/stdc-predef.h",
35995 debug-fully-read="true"@},
35997 fullname="/tmp/info-sources/header.h",
35998 debug-fully-read="true"@}]@},
35999 @{filename="/lib64/ld-linux-x86-64.so.2",
36002 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36005 @{filename="/tmp/info-sources/libhelper.so",
36006 debug-info="fully-read",
36007 sources=[@{file="helper.c",
36008 fullname="/tmp/info-sources/helper.c",
36009 debug-fully-read="true"@},
36010 @{file="/usr/include/stdc-predef.h",
36011 fullname="/usr/include/stdc-predef.h",
36012 debug-fully-read="true"@},
36014 fullname="/tmp/info-sources/header.h",
36015 debug-fully-read="true"@}]@},
36016 @{filename="/lib64/libc.so.6",
36021 @subheading The @code{-file-list-shared-libraries} Command
36022 @findex -file-list-shared-libraries
36024 @subsubheading Synopsis
36027 -file-list-shared-libraries [ @var{regexp} ]
36030 List the shared libraries in the program.
36031 With a regular expression @var{regexp}, only those libraries whose
36032 names match @var{regexp} are listed.
36034 @subsubheading @value{GDBN} Command
36036 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36037 have a similar meaning to the @code{=library-loaded} notification.
36038 The @code{ranges} field specifies the multiple segments belonging to this
36039 library. Each range has the following fields:
36043 The address defining the inclusive lower bound of the segment.
36045 The address defining the exclusive upper bound of the segment.
36048 @subsubheading Example
36051 -file-list-exec-source-files
36052 ^done,shared-libraries=[
36053 @{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"@}]@},
36054 @{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"@}]@}]
36060 @subheading The @code{-file-list-symbol-files} Command
36061 @findex -file-list-symbol-files
36063 @subsubheading Synopsis
36066 -file-list-symbol-files
36071 @subsubheading @value{GDBN} Command
36073 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36075 @subsubheading Example
36080 @subheading The @code{-file-symbol-file} Command
36081 @findex -file-symbol-file
36083 @subsubheading Synopsis
36086 -file-symbol-file @var{file}
36089 Read symbol table info from the specified @var{file} argument. When
36090 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36091 produced, except for a completion notification.
36093 @subsubheading @value{GDBN} Command
36095 The corresponding @value{GDBN} command is @samp{symbol-file}.
36097 @subsubheading Example
36101 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36107 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36108 @node GDB/MI Memory Overlay Commands
36109 @section @sc{gdb/mi} Memory Overlay Commands
36111 The memory overlay commands are not implemented.
36113 @c @subheading -overlay-auto
36115 @c @subheading -overlay-list-mapping-state
36117 @c @subheading -overlay-list-overlays
36119 @c @subheading -overlay-map
36121 @c @subheading -overlay-off
36123 @c @subheading -overlay-on
36125 @c @subheading -overlay-unmap
36127 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36128 @node GDB/MI Signal Handling Commands
36129 @section @sc{gdb/mi} Signal Handling Commands
36131 Signal handling commands are not implemented.
36133 @c @subheading -signal-handle
36135 @c @subheading -signal-list-handle-actions
36137 @c @subheading -signal-list-signal-types
36141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36142 @node GDB/MI Target Manipulation
36143 @section @sc{gdb/mi} Target Manipulation Commands
36146 @subheading The @code{-target-attach} Command
36147 @findex -target-attach
36149 @subsubheading Synopsis
36152 -target-attach @var{pid} | @var{gid} | @var{file}
36155 Attach to a process @var{pid} or a file @var{file} outside of
36156 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36157 group, the id previously returned by
36158 @samp{-list-thread-groups --available} must be used.
36160 @subsubheading @value{GDBN} Command
36162 The corresponding @value{GDBN} command is @samp{attach}.
36164 @subsubheading Example
36168 =thread-created,id="1"
36169 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36175 @subheading The @code{-target-compare-sections} Command
36176 @findex -target-compare-sections
36178 @subsubheading Synopsis
36181 -target-compare-sections [ @var{section} ]
36184 Compare data of section @var{section} on target to the exec file.
36185 Without the argument, all sections are compared.
36187 @subsubheading @value{GDBN} Command
36189 The @value{GDBN} equivalent is @samp{compare-sections}.
36191 @subsubheading Example
36196 @subheading The @code{-target-detach} Command
36197 @findex -target-detach
36199 @subsubheading Synopsis
36202 -target-detach [ @var{pid} | @var{gid} ]
36205 Detach from the remote target which normally resumes its execution.
36206 If either @var{pid} or @var{gid} is specified, detaches from either
36207 the specified process, or specified thread group. There's no output.
36209 @subsubheading @value{GDBN} Command
36211 The corresponding @value{GDBN} command is @samp{detach}.
36213 @subsubheading Example
36223 @subheading The @code{-target-disconnect} Command
36224 @findex -target-disconnect
36226 @subsubheading Synopsis
36232 Disconnect from the remote target. There's no output and the target is
36233 generally not resumed.
36235 @subsubheading @value{GDBN} Command
36237 The corresponding @value{GDBN} command is @samp{disconnect}.
36239 @subsubheading Example
36249 @subheading The @code{-target-download} Command
36250 @findex -target-download
36252 @subsubheading Synopsis
36258 Loads the executable onto the remote target.
36259 It prints out an update message every half second, which includes the fields:
36263 The name of the section.
36265 The size of what has been sent so far for that section.
36267 The size of the section.
36269 The total size of what was sent so far (the current and the previous sections).
36271 The size of the overall executable to download.
36275 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36276 @sc{gdb/mi} Output Syntax}).
36278 In addition, it prints the name and size of the sections, as they are
36279 downloaded. These messages include the following fields:
36283 The name of the section.
36285 The size of the section.
36287 The size of the overall executable to download.
36291 At the end, a summary is printed.
36293 @subsubheading @value{GDBN} Command
36295 The corresponding @value{GDBN} command is @samp{load}.
36297 @subsubheading Example
36299 Note: each status message appears on a single line. Here the messages
36300 have been broken down so that they can fit onto a page.
36305 +download,@{section=".text",section-size="6668",total-size="9880"@}
36306 +download,@{section=".text",section-sent="512",section-size="6668",
36307 total-sent="512",total-size="9880"@}
36308 +download,@{section=".text",section-sent="1024",section-size="6668",
36309 total-sent="1024",total-size="9880"@}
36310 +download,@{section=".text",section-sent="1536",section-size="6668",
36311 total-sent="1536",total-size="9880"@}
36312 +download,@{section=".text",section-sent="2048",section-size="6668",
36313 total-sent="2048",total-size="9880"@}
36314 +download,@{section=".text",section-sent="2560",section-size="6668",
36315 total-sent="2560",total-size="9880"@}
36316 +download,@{section=".text",section-sent="3072",section-size="6668",
36317 total-sent="3072",total-size="9880"@}
36318 +download,@{section=".text",section-sent="3584",section-size="6668",
36319 total-sent="3584",total-size="9880"@}
36320 +download,@{section=".text",section-sent="4096",section-size="6668",
36321 total-sent="4096",total-size="9880"@}
36322 +download,@{section=".text",section-sent="4608",section-size="6668",
36323 total-sent="4608",total-size="9880"@}
36324 +download,@{section=".text",section-sent="5120",section-size="6668",
36325 total-sent="5120",total-size="9880"@}
36326 +download,@{section=".text",section-sent="5632",section-size="6668",
36327 total-sent="5632",total-size="9880"@}
36328 +download,@{section=".text",section-sent="6144",section-size="6668",
36329 total-sent="6144",total-size="9880"@}
36330 +download,@{section=".text",section-sent="6656",section-size="6668",
36331 total-sent="6656",total-size="9880"@}
36332 +download,@{section=".init",section-size="28",total-size="9880"@}
36333 +download,@{section=".fini",section-size="28",total-size="9880"@}
36334 +download,@{section=".data",section-size="3156",total-size="9880"@}
36335 +download,@{section=".data",section-sent="512",section-size="3156",
36336 total-sent="7236",total-size="9880"@}
36337 +download,@{section=".data",section-sent="1024",section-size="3156",
36338 total-sent="7748",total-size="9880"@}
36339 +download,@{section=".data",section-sent="1536",section-size="3156",
36340 total-sent="8260",total-size="9880"@}
36341 +download,@{section=".data",section-sent="2048",section-size="3156",
36342 total-sent="8772",total-size="9880"@}
36343 +download,@{section=".data",section-sent="2560",section-size="3156",
36344 total-sent="9284",total-size="9880"@}
36345 +download,@{section=".data",section-sent="3072",section-size="3156",
36346 total-sent="9796",total-size="9880"@}
36347 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36354 @subheading The @code{-target-exec-status} Command
36355 @findex -target-exec-status
36357 @subsubheading Synopsis
36360 -target-exec-status
36363 Provide information on the state of the target (whether it is running or
36364 not, for instance).
36366 @subsubheading @value{GDBN} Command
36368 There's no equivalent @value{GDBN} command.
36370 @subsubheading Example
36374 @subheading The @code{-target-list-available-targets} Command
36375 @findex -target-list-available-targets
36377 @subsubheading Synopsis
36380 -target-list-available-targets
36383 List the possible targets to connect to.
36385 @subsubheading @value{GDBN} Command
36387 The corresponding @value{GDBN} command is @samp{help target}.
36389 @subsubheading Example
36393 @subheading The @code{-target-list-current-targets} Command
36394 @findex -target-list-current-targets
36396 @subsubheading Synopsis
36399 -target-list-current-targets
36402 Describe the current target.
36404 @subsubheading @value{GDBN} Command
36406 The corresponding information is printed by @samp{info file} (among
36409 @subsubheading Example
36413 @subheading The @code{-target-list-parameters} Command
36414 @findex -target-list-parameters
36416 @subsubheading Synopsis
36419 -target-list-parameters
36425 @subsubheading @value{GDBN} Command
36429 @subsubheading Example
36432 @subheading The @code{-target-flash-erase} Command
36433 @findex -target-flash-erase
36435 @subsubheading Synopsis
36438 -target-flash-erase
36441 Erases all known flash memory regions on the target.
36443 The corresponding @value{GDBN} command is @samp{flash-erase}.
36445 The output is a list of flash regions that have been erased, with starting
36446 addresses and memory region sizes.
36450 -target-flash-erase
36451 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36455 @subheading The @code{-target-select} Command
36456 @findex -target-select
36458 @subsubheading Synopsis
36461 -target-select @var{type} @var{parameters @dots{}}
36464 Connect @value{GDBN} to the remote target. This command takes two args:
36468 The type of target, for instance @samp{remote}, etc.
36469 @item @var{parameters}
36470 Device names, host names and the like. @xref{Target Commands, ,
36471 Commands for Managing Targets}, for more details.
36474 The output is a connection notification, followed by the address at
36475 which the target program is, in the following form:
36478 ^connected,addr="@var{address}",func="@var{function name}",
36479 args=[@var{arg list}]
36482 @subsubheading @value{GDBN} Command
36484 The corresponding @value{GDBN} command is @samp{target}.
36486 @subsubheading Example
36490 -target-select remote /dev/ttya
36491 ^connected,addr="0xfe00a300",func="??",args=[]
36495 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36496 @node GDB/MI File Transfer Commands
36497 @section @sc{gdb/mi} File Transfer Commands
36500 @subheading The @code{-target-file-put} Command
36501 @findex -target-file-put
36503 @subsubheading Synopsis
36506 -target-file-put @var{hostfile} @var{targetfile}
36509 Copy file @var{hostfile} from the host system (the machine running
36510 @value{GDBN}) to @var{targetfile} on the target system.
36512 @subsubheading @value{GDBN} Command
36514 The corresponding @value{GDBN} command is @samp{remote put}.
36516 @subsubheading Example
36520 -target-file-put localfile remotefile
36526 @subheading The @code{-target-file-get} Command
36527 @findex -target-file-get
36529 @subsubheading Synopsis
36532 -target-file-get @var{targetfile} @var{hostfile}
36535 Copy file @var{targetfile} from the target system to @var{hostfile}
36536 on the host system.
36538 @subsubheading @value{GDBN} Command
36540 The corresponding @value{GDBN} command is @samp{remote get}.
36542 @subsubheading Example
36546 -target-file-get remotefile localfile
36552 @subheading The @code{-target-file-delete} Command
36553 @findex -target-file-delete
36555 @subsubheading Synopsis
36558 -target-file-delete @var{targetfile}
36561 Delete @var{targetfile} from the target system.
36563 @subsubheading @value{GDBN} Command
36565 The corresponding @value{GDBN} command is @samp{remote delete}.
36567 @subsubheading Example
36571 -target-file-delete remotefile
36577 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36578 @node GDB/MI Ada Exceptions Commands
36579 @section Ada Exceptions @sc{gdb/mi} Commands
36581 @subheading The @code{-info-ada-exceptions} Command
36582 @findex -info-ada-exceptions
36584 @subsubheading Synopsis
36587 -info-ada-exceptions [ @var{regexp}]
36590 List all Ada exceptions defined within the program being debugged.
36591 With a regular expression @var{regexp}, only those exceptions whose
36592 names match @var{regexp} are listed.
36594 @subsubheading @value{GDBN} Command
36596 The corresponding @value{GDBN} command is @samp{info exceptions}.
36598 @subsubheading Result
36600 The result is a table of Ada exceptions. The following columns are
36601 defined for each exception:
36605 The name of the exception.
36608 The address of the exception.
36612 @subsubheading Example
36615 -info-ada-exceptions aint
36616 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
36617 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
36618 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
36619 body=[@{name="constraint_error",address="0x0000000000613da0"@},
36620 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
36623 @subheading Catching Ada Exceptions
36625 The commands describing how to ask @value{GDBN} to stop when a program
36626 raises an exception are described at @ref{Ada Exception GDB/MI
36627 Catchpoint Commands}.
36630 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36631 @node GDB/MI Support Commands
36632 @section @sc{gdb/mi} Support Commands
36634 Since new commands and features get regularly added to @sc{gdb/mi},
36635 some commands are available to help front-ends query the debugger
36636 about support for these capabilities. Similarly, it is also possible
36637 to query @value{GDBN} about target support of certain features.
36639 @subheading The @code{-info-gdb-mi-command} Command
36640 @cindex @code{-info-gdb-mi-command}
36641 @findex -info-gdb-mi-command
36643 @subsubheading Synopsis
36646 -info-gdb-mi-command @var{cmd_name}
36649 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
36651 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
36652 is technically not part of the command name (@pxref{GDB/MI Input
36653 Syntax}), and thus should be omitted in @var{cmd_name}. However,
36654 for ease of use, this command also accepts the form with the leading
36657 @subsubheading @value{GDBN} Command
36659 There is no corresponding @value{GDBN} command.
36661 @subsubheading Result
36663 The result is a tuple. There is currently only one field:
36667 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
36668 @code{"false"} otherwise.
36672 @subsubheading Example
36674 Here is an example where the @sc{gdb/mi} command does not exist:
36677 -info-gdb-mi-command unsupported-command
36678 ^done,command=@{exists="false"@}
36682 And here is an example where the @sc{gdb/mi} command is known
36686 -info-gdb-mi-command symbol-list-lines
36687 ^done,command=@{exists="true"@}
36690 @subheading The @code{-list-features} Command
36691 @findex -list-features
36692 @cindex supported @sc{gdb/mi} features, list
36694 Returns a list of particular features of the MI protocol that
36695 this version of gdb implements. A feature can be a command,
36696 or a new field in an output of some command, or even an
36697 important bugfix. While a frontend can sometimes detect presence
36698 of a feature at runtime, it is easier to perform detection at debugger
36701 The command returns a list of strings, with each string naming an
36702 available feature. Each returned string is just a name, it does not
36703 have any internal structure. The list of possible feature names
36709 (gdb) -list-features
36710 ^done,result=["feature1","feature2"]
36713 The current list of features is:
36716 @item frozen-varobjs
36717 Indicates support for the @code{-var-set-frozen} command, as well
36718 as possible presence of the @code{frozen} field in the output
36719 of @code{-varobj-create}.
36720 @item pending-breakpoints
36721 Indicates support for the @option{-f} option to the @code{-break-insert}
36724 Indicates Python scripting support, Python-based
36725 pretty-printing commands, and possible presence of the
36726 @samp{display_hint} field in the output of @code{-var-list-children}
36728 Indicates support for the @code{-thread-info} command.
36729 @item data-read-memory-bytes
36730 Indicates support for the @code{-data-read-memory-bytes} and the
36731 @code{-data-write-memory-bytes} commands.
36732 @item breakpoint-notifications
36733 Indicates that changes to breakpoints and breakpoints created via the
36734 CLI will be announced via async records.
36735 @item ada-task-info
36736 Indicates support for the @code{-ada-task-info} command.
36737 @item language-option
36738 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
36739 option (@pxref{Context management}).
36740 @item info-gdb-mi-command
36741 Indicates support for the @code{-info-gdb-mi-command} command.
36742 @item undefined-command-error-code
36743 Indicates support for the "undefined-command" error code in error result
36744 records, produced when trying to execute an undefined @sc{gdb/mi} command
36745 (@pxref{GDB/MI Result Records}).
36746 @item exec-run-start-option
36747 Indicates that the @code{-exec-run} command supports the @option{--start}
36748 option (@pxref{GDB/MI Program Execution}).
36749 @item data-disassemble-a-option
36750 Indicates that the @code{-data-disassemble} command supports the @option{-a}
36751 option (@pxref{GDB/MI Data Manipulation}).
36754 @subheading The @code{-list-target-features} Command
36755 @findex -list-target-features
36757 Returns a list of particular features that are supported by the
36758 target. Those features affect the permitted MI commands, but
36759 unlike the features reported by the @code{-list-features} command, the
36760 features depend on which target GDB is using at the moment. Whenever
36761 a target can change, due to commands such as @code{-target-select},
36762 @code{-target-attach} or @code{-exec-run}, the list of target features
36763 may change, and the frontend should obtain it again.
36767 (gdb) -list-target-features
36768 ^done,result=["async"]
36771 The current list of features is:
36775 Indicates that the target is capable of asynchronous command
36776 execution, which means that @value{GDBN} will accept further commands
36777 while the target is running.
36780 Indicates that the target is capable of reverse execution.
36781 @xref{Reverse Execution}, for more information.
36785 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36786 @node GDB/MI Miscellaneous Commands
36787 @section Miscellaneous @sc{gdb/mi} Commands
36789 @c @subheading -gdb-complete
36791 @subheading The @code{-gdb-exit} Command
36794 @subsubheading Synopsis
36800 Exit @value{GDBN} immediately.
36802 @subsubheading @value{GDBN} Command
36804 Approximately corresponds to @samp{quit}.
36806 @subsubheading Example
36816 @subheading The @code{-exec-abort} Command
36817 @findex -exec-abort
36819 @subsubheading Synopsis
36825 Kill the inferior running program.
36827 @subsubheading @value{GDBN} Command
36829 The corresponding @value{GDBN} command is @samp{kill}.
36831 @subsubheading Example
36836 @subheading The @code{-gdb-set} Command
36839 @subsubheading Synopsis
36845 Set an internal @value{GDBN} variable.
36846 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
36848 @subsubheading @value{GDBN} Command
36850 The corresponding @value{GDBN} command is @samp{set}.
36852 @subsubheading Example
36862 @subheading The @code{-gdb-show} Command
36865 @subsubheading Synopsis
36871 Show the current value of a @value{GDBN} variable.
36873 @subsubheading @value{GDBN} Command
36875 The corresponding @value{GDBN} command is @samp{show}.
36877 @subsubheading Example
36886 @c @subheading -gdb-source
36889 @subheading The @code{-gdb-version} Command
36890 @findex -gdb-version
36892 @subsubheading Synopsis
36898 Show version information for @value{GDBN}. Used mostly in testing.
36900 @subsubheading @value{GDBN} Command
36902 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
36903 default shows this information when you start an interactive session.
36905 @subsubheading Example
36907 @c This example modifies the actual output from GDB to avoid overfull
36913 ~Copyright 2000 Free Software Foundation, Inc.
36914 ~GDB is free software, covered by the GNU General Public License, and
36915 ~you are welcome to change it and/or distribute copies of it under
36916 ~ certain conditions.
36917 ~Type "show copying" to see the conditions.
36918 ~There is absolutely no warranty for GDB. Type "show warranty" for
36920 ~This GDB was configured as
36921 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
36926 @subheading The @code{-list-thread-groups} Command
36927 @findex -list-thread-groups
36929 @subheading Synopsis
36932 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
36935 Lists thread groups (@pxref{Thread groups}). When a single thread
36936 group is passed as the argument, lists the children of that group.
36937 When several thread group are passed, lists information about those
36938 thread groups. Without any parameters, lists information about all
36939 top-level thread groups.
36941 Normally, thread groups that are being debugged are reported.
36942 With the @samp{--available} option, @value{GDBN} reports thread groups
36943 available on the target.
36945 The output of this command may have either a @samp{threads} result or
36946 a @samp{groups} result. The @samp{thread} result has a list of tuples
36947 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
36948 Information}). The @samp{groups} result has a list of tuples as value,
36949 each tuple describing a thread group. If top-level groups are
36950 requested (that is, no parameter is passed), or when several groups
36951 are passed, the output always has a @samp{groups} result. The format
36952 of the @samp{group} result is described below.
36954 To reduce the number of roundtrips it's possible to list thread groups
36955 together with their children, by passing the @samp{--recurse} option
36956 and the recursion depth. Presently, only recursion depth of 1 is
36957 permitted. If this option is present, then every reported thread group
36958 will also include its children, either as @samp{group} or
36959 @samp{threads} field.
36961 In general, any combination of option and parameters is permitted, with
36962 the following caveats:
36966 When a single thread group is passed, the output will typically
36967 be the @samp{threads} result. Because threads may not contain
36968 anything, the @samp{recurse} option will be ignored.
36971 When the @samp{--available} option is passed, limited information may
36972 be available. In particular, the list of threads of a process might
36973 be inaccessible. Further, specifying specific thread groups might
36974 not give any performance advantage over listing all thread groups.
36975 The frontend should assume that @samp{-list-thread-groups --available}
36976 is always an expensive operation and cache the results.
36980 The @samp{groups} result is a list of tuples, where each tuple may
36981 have the following fields:
36985 Identifier of the thread group. This field is always present.
36986 The identifier is an opaque string; frontends should not try to
36987 convert it to an integer, even though it might look like one.
36990 The type of the thread group. At present, only @samp{process} is a
36994 The target-specific process identifier. This field is only present
36995 for thread groups of type @samp{process} and only if the process exists.
36998 The exit code of this group's last exited thread, formatted in octal.
36999 This field is only present for thread groups of type @samp{process} and
37000 only if the process is not running.
37003 The number of children this thread group has. This field may be
37004 absent for an available thread group.
37007 This field has a list of tuples as value, each tuple describing a
37008 thread. It may be present if the @samp{--recurse} option is
37009 specified, and it's actually possible to obtain the threads.
37012 This field is a list of integers, each identifying a core that one
37013 thread of the group is running on. This field may be absent if
37014 such information is not available.
37017 The name of the executable file that corresponds to this thread group.
37018 The field is only present for thread groups of type @samp{process},
37019 and only if there is a corresponding executable file.
37023 @subheading Example
37027 -list-thread-groups
37028 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37029 -list-thread-groups 17
37030 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37031 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37032 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37033 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37034 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37035 -list-thread-groups --available
37036 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37037 -list-thread-groups --available --recurse 1
37038 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37039 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37040 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37041 -list-thread-groups --available --recurse 1 17 18
37042 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37043 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37044 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37047 @subheading The @code{-info-os} Command
37050 @subsubheading Synopsis
37053 -info-os [ @var{type} ]
37056 If no argument is supplied, the command returns a table of available
37057 operating-system-specific information types. If one of these types is
37058 supplied as an argument @var{type}, then the command returns a table
37059 of data of that type.
37061 The types of information available depend on the target operating
37064 @subsubheading @value{GDBN} Command
37066 The corresponding @value{GDBN} command is @samp{info os}.
37068 @subsubheading Example
37070 When run on a @sc{gnu}/Linux system, the output will look something
37076 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37077 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37078 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37079 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37080 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37082 item=@{col0="files",col1="Listing of all file descriptors",
37083 col2="File descriptors"@},
37084 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37085 col2="Kernel modules"@},
37086 item=@{col0="msg",col1="Listing of all message queues",
37087 col2="Message queues"@},
37088 item=@{col0="processes",col1="Listing of all processes",
37089 col2="Processes"@},
37090 item=@{col0="procgroups",col1="Listing of all process groups",
37091 col2="Process groups"@},
37092 item=@{col0="semaphores",col1="Listing of all semaphores",
37093 col2="Semaphores"@},
37094 item=@{col0="shm",col1="Listing of all shared-memory regions",
37095 col2="Shared-memory regions"@},
37096 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37098 item=@{col0="threads",col1="Listing of all threads",
37102 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37103 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37104 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37105 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37106 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37107 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37108 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37109 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37111 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37112 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37116 (Note that the MI output here includes a @code{"Title"} column that
37117 does not appear in command-line @code{info os}; this column is useful
37118 for MI clients that want to enumerate the types of data, such as in a
37119 popup menu, but is needless clutter on the command line, and
37120 @code{info os} omits it.)
37122 @subheading The @code{-add-inferior} Command
37123 @findex -add-inferior
37125 @subheading Synopsis
37131 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37132 inferior is not associated with any executable. Such association may
37133 be established with the @samp{-file-exec-and-symbols} command
37134 (@pxref{GDB/MI File Commands}). The command response has a single
37135 field, @samp{inferior}, whose value is the identifier of the
37136 thread group corresponding to the new inferior.
37138 @subheading Example
37143 ^done,inferior="i3"
37146 @subheading The @code{-interpreter-exec} Command
37147 @findex -interpreter-exec
37149 @subheading Synopsis
37152 -interpreter-exec @var{interpreter} @var{command}
37154 @anchor{-interpreter-exec}
37156 Execute the specified @var{command} in the given @var{interpreter}.
37158 @subheading @value{GDBN} Command
37160 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37162 @subheading Example
37166 -interpreter-exec console "break main"
37167 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37168 &"During symbol reading, bad structure-type format.\n"
37169 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37174 @subheading The @code{-inferior-tty-set} Command
37175 @findex -inferior-tty-set
37177 @subheading Synopsis
37180 -inferior-tty-set /dev/pts/1
37183 Set terminal for future runs of the program being debugged.
37185 @subheading @value{GDBN} Command
37187 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37189 @subheading Example
37193 -inferior-tty-set /dev/pts/1
37198 @subheading The @code{-inferior-tty-show} Command
37199 @findex -inferior-tty-show
37201 @subheading Synopsis
37207 Show terminal for future runs of program being debugged.
37209 @subheading @value{GDBN} Command
37211 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37213 @subheading Example
37217 -inferior-tty-set /dev/pts/1
37221 ^done,inferior_tty_terminal="/dev/pts/1"
37225 @subheading The @code{-enable-timings} Command
37226 @findex -enable-timings
37228 @subheading Synopsis
37231 -enable-timings [yes | no]
37234 Toggle the printing of the wallclock, user and system times for an MI
37235 command as a field in its output. This command is to help frontend
37236 developers optimize the performance of their code. No argument is
37237 equivalent to @samp{yes}.
37239 @subheading @value{GDBN} Command
37243 @subheading Example
37251 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37252 addr="0x080484ed",func="main",file="myprog.c",
37253 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37255 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37263 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37264 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37265 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37266 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37270 @subheading The @code{-complete} Command
37273 @subheading Synopsis
37276 -complete @var{command}
37279 Show a list of completions for partially typed CLI @var{command}.
37281 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37282 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37283 because @value{GDBN} is used remotely via a SSH connection.
37287 The result consists of two or three fields:
37291 This field contains the completed @var{command}. If @var{command}
37292 has no known completions, this field is omitted.
37295 This field contains a (possibly empty) array of matches. It is always present.
37297 @item max_completions_reached
37298 This field contains @code{1} if number of known completions is above
37299 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37300 @code{0}. It is always present.
37304 @subheading @value{GDBN} Command
37306 The corresponding @value{GDBN} command is @samp{complete}.
37308 @subheading Example
37313 ^done,completion="break",
37314 matches=["break","break-range"],
37315 max_completions_reached="0"
37318 ^done,completion="b ma",
37319 matches=["b madvise","b main"],max_completions_reached="0"
37321 -complete "b push_b"
37322 ^done,completion="b push_back(",
37324 "b A::push_back(void*)",
37325 "b std::string::push_back(char)",
37326 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37327 max_completions_reached="0"
37329 -complete "nonexist"
37330 ^done,matches=[],max_completions_reached="0"
37336 @chapter @value{GDBN} Annotations
37338 This chapter describes annotations in @value{GDBN}. Annotations were
37339 designed to interface @value{GDBN} to graphical user interfaces or other
37340 similar programs which want to interact with @value{GDBN} at a
37341 relatively high level.
37343 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37347 This is Edition @value{EDITION}, @value{DATE}.
37351 * Annotations Overview:: What annotations are; the general syntax.
37352 * Server Prefix:: Issuing a command without affecting user state.
37353 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37354 * Errors:: Annotations for error messages.
37355 * Invalidation:: Some annotations describe things now invalid.
37356 * Annotations for Running::
37357 Whether the program is running, how it stopped, etc.
37358 * Source Annotations:: Annotations describing source code.
37361 @node Annotations Overview
37362 @section What is an Annotation?
37363 @cindex annotations
37365 Annotations start with a newline character, two @samp{control-z}
37366 characters, and the name of the annotation. If there is no additional
37367 information associated with this annotation, the name of the annotation
37368 is followed immediately by a newline. If there is additional
37369 information, the name of the annotation is followed by a space, the
37370 additional information, and a newline. The additional information
37371 cannot contain newline characters.
37373 Any output not beginning with a newline and two @samp{control-z}
37374 characters denotes literal output from @value{GDBN}. Currently there is
37375 no need for @value{GDBN} to output a newline followed by two
37376 @samp{control-z} characters, but if there was such a need, the
37377 annotations could be extended with an @samp{escape} annotation which
37378 means those three characters as output.
37380 The annotation @var{level}, which is specified using the
37381 @option{--annotate} command line option (@pxref{Mode Options}), controls
37382 how much information @value{GDBN} prints together with its prompt,
37383 values of expressions, source lines, and other types of output. Level 0
37384 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37385 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37386 for programs that control @value{GDBN}, and level 2 annotations have
37387 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37388 Interface, annotate, GDB's Obsolete Annotations}).
37391 @kindex set annotate
37392 @item set annotate @var{level}
37393 The @value{GDBN} command @code{set annotate} sets the level of
37394 annotations to the specified @var{level}.
37396 @item show annotate
37397 @kindex show annotate
37398 Show the current annotation level.
37401 This chapter describes level 3 annotations.
37403 A simple example of starting up @value{GDBN} with annotations is:
37406 $ @kbd{gdb --annotate=3}
37408 Copyright 2003 Free Software Foundation, Inc.
37409 GDB is free software, covered by the GNU General Public License,
37410 and you are welcome to change it and/or distribute copies of it
37411 under certain conditions.
37412 Type "show copying" to see the conditions.
37413 There is absolutely no warranty for GDB. Type "show warranty"
37415 This GDB was configured as "i386-pc-linux-gnu"
37426 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37427 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37428 denotes a @samp{control-z} character) are annotations; the rest is
37429 output from @value{GDBN}.
37431 @node Server Prefix
37432 @section The Server Prefix
37433 @cindex server prefix
37435 If you prefix a command with @samp{server } then it will not affect
37436 the command history, nor will it affect @value{GDBN}'s notion of which
37437 command to repeat if @key{RET} is pressed on a line by itself. This
37438 means that commands can be run behind a user's back by a front-end in
37439 a transparent manner.
37441 The @code{server } prefix does not affect the recording of values into
37442 the value history; to print a value without recording it into the
37443 value history, use the @code{output} command instead of the
37444 @code{print} command.
37446 Using this prefix also disables confirmation requests
37447 (@pxref{confirmation requests}).
37450 @section Annotation for @value{GDBN} Input
37452 @cindex annotations for prompts
37453 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37454 to know when to send output, when the output from a given command is
37457 Different kinds of input each have a different @dfn{input type}. Each
37458 input type has three annotations: a @code{pre-} annotation, which
37459 denotes the beginning of any prompt which is being output, a plain
37460 annotation, which denotes the end of the prompt, and then a @code{post-}
37461 annotation which denotes the end of any echo which may (or may not) be
37462 associated with the input. For example, the @code{prompt} input type
37463 features the following annotations:
37471 The input types are
37474 @findex pre-prompt annotation
37475 @findex prompt annotation
37476 @findex post-prompt annotation
37478 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37480 @findex pre-commands annotation
37481 @findex commands annotation
37482 @findex post-commands annotation
37484 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37485 command. The annotations are repeated for each command which is input.
37487 @findex pre-overload-choice annotation
37488 @findex overload-choice annotation
37489 @findex post-overload-choice annotation
37490 @item overload-choice
37491 When @value{GDBN} wants the user to select between various overloaded functions.
37493 @findex pre-query annotation
37494 @findex query annotation
37495 @findex post-query annotation
37497 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
37499 @findex pre-prompt-for-continue annotation
37500 @findex prompt-for-continue annotation
37501 @findex post-prompt-for-continue annotation
37502 @item prompt-for-continue
37503 When @value{GDBN} is asking the user to press return to continue. Note: Don't
37504 expect this to work well; instead use @code{set height 0} to disable
37505 prompting. This is because the counting of lines is buggy in the
37506 presence of annotations.
37511 @cindex annotations for errors, warnings and interrupts
37513 @findex quit annotation
37518 This annotation occurs right before @value{GDBN} responds to an interrupt.
37520 @findex error annotation
37525 This annotation occurs right before @value{GDBN} responds to an error.
37527 Quit and error annotations indicate that any annotations which @value{GDBN} was
37528 in the middle of may end abruptly. For example, if a
37529 @code{value-history-begin} annotation is followed by a @code{error}, one
37530 cannot expect to receive the matching @code{value-history-end}. One
37531 cannot expect not to receive it either, however; an error annotation
37532 does not necessarily mean that @value{GDBN} is immediately returning all the way
37535 @findex error-begin annotation
37536 A quit or error annotation may be preceded by
37542 Any output between that and the quit or error annotation is the error
37545 Warning messages are not yet annotated.
37546 @c If we want to change that, need to fix warning(), type_error(),
37547 @c range_error(), and possibly other places.
37550 @section Invalidation Notices
37552 @cindex annotations for invalidation messages
37553 The following annotations say that certain pieces of state may have
37557 @findex frames-invalid annotation
37558 @item ^Z^Zframes-invalid
37560 The frames (for example, output from the @code{backtrace} command) may
37563 @findex breakpoints-invalid annotation
37564 @item ^Z^Zbreakpoints-invalid
37566 The breakpoints may have changed. For example, the user just added or
37567 deleted a breakpoint.
37570 @node Annotations for Running
37571 @section Running the Program
37572 @cindex annotations for running programs
37574 @findex starting annotation
37575 @findex stopping annotation
37576 When the program starts executing due to a @value{GDBN} command such as
37577 @code{step} or @code{continue},
37583 is output. When the program stops,
37589 is output. Before the @code{stopped} annotation, a variety of
37590 annotations describe how the program stopped.
37593 @findex exited annotation
37594 @item ^Z^Zexited @var{exit-status}
37595 The program exited, and @var{exit-status} is the exit status (zero for
37596 successful exit, otherwise nonzero).
37598 @findex signalled annotation
37599 @findex signal-name annotation
37600 @findex signal-name-end annotation
37601 @findex signal-string annotation
37602 @findex signal-string-end annotation
37603 @item ^Z^Zsignalled
37604 The program exited with a signal. After the @code{^Z^Zsignalled}, the
37605 annotation continues:
37611 ^Z^Zsignal-name-end
37615 ^Z^Zsignal-string-end
37620 where @var{name} is the name of the signal, such as @code{SIGILL} or
37621 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
37622 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
37623 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
37624 user's benefit and have no particular format.
37626 @findex signal annotation
37628 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
37629 just saying that the program received the signal, not that it was
37630 terminated with it.
37632 @findex breakpoint annotation
37633 @item ^Z^Zbreakpoint @var{number}
37634 The program hit breakpoint number @var{number}.
37636 @findex watchpoint annotation
37637 @item ^Z^Zwatchpoint @var{number}
37638 The program hit watchpoint number @var{number}.
37641 @node Source Annotations
37642 @section Displaying Source
37643 @cindex annotations for source display
37645 @findex source annotation
37646 The following annotation is used instead of displaying source code:
37649 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
37652 where @var{filename} is an absolute file name indicating which source
37653 file, @var{line} is the line number within that file (where 1 is the
37654 first line in the file), @var{character} is the character position
37655 within the file (where 0 is the first character in the file) (for most
37656 debug formats this will necessarily point to the beginning of a line),
37657 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
37658 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
37659 @var{addr} is the address in the target program associated with the
37660 source which is being displayed. The @var{addr} is in the form @samp{0x}
37661 followed by one or more lowercase hex digits (note that this does not
37662 depend on the language).
37664 @node JIT Interface
37665 @chapter JIT Compilation Interface
37666 @cindex just-in-time compilation
37667 @cindex JIT compilation interface
37669 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
37670 interface. A JIT compiler is a program or library that generates native
37671 executable code at runtime and executes it, usually in order to achieve good
37672 performance while maintaining platform independence.
37674 Programs that use JIT compilation are normally difficult to debug because
37675 portions of their code are generated at runtime, instead of being loaded from
37676 object files, which is where @value{GDBN} normally finds the program's symbols
37677 and debug information. In order to debug programs that use JIT compilation,
37678 @value{GDBN} has an interface that allows the program to register in-memory
37679 symbol files with @value{GDBN} at runtime.
37681 If you are using @value{GDBN} to debug a program that uses this interface, then
37682 it should work transparently so long as you have not stripped the binary. If
37683 you are developing a JIT compiler, then the interface is documented in the rest
37684 of this chapter. At this time, the only known client of this interface is the
37687 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
37688 JIT compiler communicates with @value{GDBN} by writing data into a global
37689 variable and calling a function at a well-known symbol. When @value{GDBN}
37690 attaches, it reads a linked list of symbol files from the global variable to
37691 find existing code, and puts a breakpoint in the function so that it can find
37692 out about additional code.
37695 * Declarations:: Relevant C struct declarations
37696 * Registering Code:: Steps to register code
37697 * Unregistering Code:: Steps to unregister code
37698 * Custom Debug Info:: Emit debug information in a custom format
37702 @section JIT Declarations
37704 These are the relevant struct declarations that a C program should include to
37705 implement the interface:
37715 struct jit_code_entry
37717 struct jit_code_entry *next_entry;
37718 struct jit_code_entry *prev_entry;
37719 const char *symfile_addr;
37720 uint64_t symfile_size;
37723 struct jit_descriptor
37726 /* This type should be jit_actions_t, but we use uint32_t
37727 to be explicit about the bitwidth. */
37728 uint32_t action_flag;
37729 struct jit_code_entry *relevant_entry;
37730 struct jit_code_entry *first_entry;
37733 /* GDB puts a breakpoint in this function. */
37734 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
37736 /* Make sure to specify the version statically, because the
37737 debugger may check the version before we can set it. */
37738 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
37741 If the JIT is multi-threaded, then it is important that the JIT synchronize any
37742 modifications to this global data properly, which can easily be done by putting
37743 a global mutex around modifications to these structures.
37745 @node Registering Code
37746 @section Registering Code
37748 To register code with @value{GDBN}, the JIT should follow this protocol:
37752 Generate an object file in memory with symbols and other desired debug
37753 information. The file must include the virtual addresses of the sections.
37756 Create a code entry for the file, which gives the start and size of the symbol
37760 Add it to the linked list in the JIT descriptor.
37763 Point the relevant_entry field of the descriptor at the entry.
37766 Set @code{action_flag} to @code{JIT_REGISTER} and call
37767 @code{__jit_debug_register_code}.
37770 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
37771 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
37772 new code. However, the linked list must still be maintained in order to allow
37773 @value{GDBN} to attach to a running process and still find the symbol files.
37775 @node Unregistering Code
37776 @section Unregistering Code
37778 If code is freed, then the JIT should use the following protocol:
37782 Remove the code entry corresponding to the code from the linked list.
37785 Point the @code{relevant_entry} field of the descriptor at the code entry.
37788 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
37789 @code{__jit_debug_register_code}.
37792 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
37793 and the JIT will leak the memory used for the associated symbol files.
37795 @node Custom Debug Info
37796 @section Custom Debug Info
37797 @cindex custom JIT debug info
37798 @cindex JIT debug info reader
37800 Generating debug information in platform-native file formats (like ELF
37801 or COFF) may be an overkill for JIT compilers; especially if all the
37802 debug info is used for is displaying a meaningful backtrace. The
37803 issue can be resolved by having the JIT writers decide on a debug info
37804 format and also provide a reader that parses the debug info generated
37805 by the JIT compiler. This section gives a brief overview on writing
37806 such a parser. More specific details can be found in the source file
37807 @file{gdb/jit-reader.in}, which is also installed as a header at
37808 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
37810 The reader is implemented as a shared object (so this functionality is
37811 not available on platforms which don't allow loading shared objects at
37812 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
37813 @code{jit-reader-unload} are provided, to be used to load and unload
37814 the readers from a preconfigured directory. Once loaded, the shared
37815 object is used the parse the debug information emitted by the JIT
37819 * Using JIT Debug Info Readers:: How to use supplied readers correctly
37820 * Writing JIT Debug Info Readers:: Creating a debug-info reader
37823 @node Using JIT Debug Info Readers
37824 @subsection Using JIT Debug Info Readers
37825 @kindex jit-reader-load
37826 @kindex jit-reader-unload
37828 Readers can be loaded and unloaded using the @code{jit-reader-load}
37829 and @code{jit-reader-unload} commands.
37832 @item jit-reader-load @var{reader}
37833 Load the JIT reader named @var{reader}, which is a shared
37834 object specified as either an absolute or a relative file name. In
37835 the latter case, @value{GDBN} will try to load the reader from a
37836 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
37837 system (here @var{libdir} is the system library directory, often
37838 @file{/usr/local/lib}).
37840 Only one reader can be active at a time; trying to load a second
37841 reader when one is already loaded will result in @value{GDBN}
37842 reporting an error. A new JIT reader can be loaded by first unloading
37843 the current one using @code{jit-reader-unload} and then invoking
37844 @code{jit-reader-load}.
37846 @item jit-reader-unload
37847 Unload the currently loaded JIT reader.
37851 @node Writing JIT Debug Info Readers
37852 @subsection Writing JIT Debug Info Readers
37853 @cindex writing JIT debug info readers
37855 As mentioned, a reader is essentially a shared object conforming to a
37856 certain ABI. This ABI is described in @file{jit-reader.h}.
37858 @file{jit-reader.h} defines the structures, macros and functions
37859 required to write a reader. It is installed (along with
37860 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
37861 the system include directory.
37863 Readers need to be released under a GPL compatible license. A reader
37864 can be declared as released under such a license by placing the macro
37865 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
37867 The entry point for readers is the symbol @code{gdb_init_reader},
37868 which is expected to be a function with the prototype
37870 @findex gdb_init_reader
37872 extern struct gdb_reader_funcs *gdb_init_reader (void);
37875 @cindex @code{struct gdb_reader_funcs}
37877 @code{struct gdb_reader_funcs} contains a set of pointers to callback
37878 functions. These functions are executed to read the debug info
37879 generated by the JIT compiler (@code{read}), to unwind stack frames
37880 (@code{unwind}) and to create canonical frame IDs
37881 (@code{get_frame_id}). It also has a callback that is called when the
37882 reader is being unloaded (@code{destroy}). The struct looks like this
37885 struct gdb_reader_funcs
37887 /* Must be set to GDB_READER_INTERFACE_VERSION. */
37888 int reader_version;
37890 /* For use by the reader. */
37893 gdb_read_debug_info *read;
37894 gdb_unwind_frame *unwind;
37895 gdb_get_frame_id *get_frame_id;
37896 gdb_destroy_reader *destroy;
37900 @cindex @code{struct gdb_symbol_callbacks}
37901 @cindex @code{struct gdb_unwind_callbacks}
37903 The callbacks are provided with another set of callbacks by
37904 @value{GDBN} to do their job. For @code{read}, these callbacks are
37905 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
37906 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
37907 @code{struct gdb_symbol_callbacks} has callbacks to create new object
37908 files and new symbol tables inside those object files. @code{struct
37909 gdb_unwind_callbacks} has callbacks to read registers off the current
37910 frame and to write out the values of the registers in the previous
37911 frame. Both have a callback (@code{target_read}) to read bytes off the
37912 target's address space.
37914 @node In-Process Agent
37915 @chapter In-Process Agent
37916 @cindex debugging agent
37917 The traditional debugging model is conceptually low-speed, but works fine,
37918 because most bugs can be reproduced in debugging-mode execution. However,
37919 as multi-core or many-core processors are becoming mainstream, and
37920 multi-threaded programs become more and more popular, there should be more
37921 and more bugs that only manifest themselves at normal-mode execution, for
37922 example, thread races, because debugger's interference with the program's
37923 timing may conceal the bugs. On the other hand, in some applications,
37924 it is not feasible for the debugger to interrupt the program's execution
37925 long enough for the developer to learn anything helpful about its behavior.
37926 If the program's correctness depends on its real-time behavior, delays
37927 introduced by a debugger might cause the program to fail, even when the
37928 code itself is correct. It is useful to be able to observe the program's
37929 behavior without interrupting it.
37931 Therefore, traditional debugging model is too intrusive to reproduce
37932 some bugs. In order to reduce the interference with the program, we can
37933 reduce the number of operations performed by debugger. The
37934 @dfn{In-Process Agent}, a shared library, is running within the same
37935 process with inferior, and is able to perform some debugging operations
37936 itself. As a result, debugger is only involved when necessary, and
37937 performance of debugging can be improved accordingly. Note that
37938 interference with program can be reduced but can't be removed completely,
37939 because the in-process agent will still stop or slow down the program.
37941 The in-process agent can interpret and execute Agent Expressions
37942 (@pxref{Agent Expressions}) during performing debugging operations. The
37943 agent expressions can be used for different purposes, such as collecting
37944 data in tracepoints, and condition evaluation in breakpoints.
37946 @anchor{Control Agent}
37947 You can control whether the in-process agent is used as an aid for
37948 debugging with the following commands:
37951 @kindex set agent on
37953 Causes the in-process agent to perform some operations on behalf of the
37954 debugger. Just which operations requested by the user will be done
37955 by the in-process agent depends on the its capabilities. For example,
37956 if you request to evaluate breakpoint conditions in the in-process agent,
37957 and the in-process agent has such capability as well, then breakpoint
37958 conditions will be evaluated in the in-process agent.
37960 @kindex set agent off
37961 @item set agent off
37962 Disables execution of debugging operations by the in-process agent. All
37963 of the operations will be performed by @value{GDBN}.
37967 Display the current setting of execution of debugging operations by
37968 the in-process agent.
37972 * In-Process Agent Protocol::
37975 @node In-Process Agent Protocol
37976 @section In-Process Agent Protocol
37977 @cindex in-process agent protocol
37979 The in-process agent is able to communicate with both @value{GDBN} and
37980 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
37981 used for communications between @value{GDBN} or GDBserver and the IPA.
37982 In general, @value{GDBN} or GDBserver sends commands
37983 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
37984 in-process agent replies back with the return result of the command, or
37985 some other information. The data sent to in-process agent is composed
37986 of primitive data types, such as 4-byte or 8-byte type, and composite
37987 types, which are called objects (@pxref{IPA Protocol Objects}).
37990 * IPA Protocol Objects::
37991 * IPA Protocol Commands::
37994 @node IPA Protocol Objects
37995 @subsection IPA Protocol Objects
37996 @cindex ipa protocol objects
37998 The commands sent to and results received from agent may contain some
37999 complex data types called @dfn{objects}.
38001 The in-process agent is running on the same machine with @value{GDBN}
38002 or GDBserver, so it doesn't have to handle as much differences between
38003 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38004 However, there are still some differences of two ends in two processes:
38008 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38009 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38011 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38012 GDBserver is compiled with one, and in-process agent is compiled with
38016 Here are the IPA Protocol Objects:
38020 agent expression object. It represents an agent expression
38021 (@pxref{Agent Expressions}).
38022 @anchor{agent expression object}
38024 tracepoint action object. It represents a tracepoint action
38025 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38026 memory, static trace data and to evaluate expression.
38027 @anchor{tracepoint action object}
38029 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38030 @anchor{tracepoint object}
38034 The following table describes important attributes of each IPA protocol
38037 @multitable @columnfractions .30 .20 .50
38038 @headitem Name @tab Size @tab Description
38039 @item @emph{agent expression object} @tab @tab
38040 @item length @tab 4 @tab length of bytes code
38041 @item byte code @tab @var{length} @tab contents of byte code
38042 @item @emph{tracepoint action for collecting memory} @tab @tab
38043 @item 'M' @tab 1 @tab type of tracepoint action
38044 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38045 address of the lowest byte to collect, otherwise @var{addr} is the offset
38046 of @var{basereg} for memory collecting.
38047 @item len @tab 8 @tab length of memory for collecting
38048 @item basereg @tab 4 @tab the register number containing the starting
38049 memory address for collecting.
38050 @item @emph{tracepoint action for collecting registers} @tab @tab
38051 @item 'R' @tab 1 @tab type of tracepoint action
38052 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38053 @item 'L' @tab 1 @tab type of tracepoint action
38054 @item @emph{tracepoint action for expression evaluation} @tab @tab
38055 @item 'X' @tab 1 @tab type of tracepoint action
38056 @item agent expression @tab length of @tab @ref{agent expression object}
38057 @item @emph{tracepoint object} @tab @tab
38058 @item number @tab 4 @tab number of tracepoint
38059 @item address @tab 8 @tab address of tracepoint inserted on
38060 @item type @tab 4 @tab type of tracepoint
38061 @item enabled @tab 1 @tab enable or disable of tracepoint
38062 @item step_count @tab 8 @tab step
38063 @item pass_count @tab 8 @tab pass
38064 @item numactions @tab 4 @tab number of tracepoint actions
38065 @item hit count @tab 8 @tab hit count
38066 @item trace frame usage @tab 8 @tab trace frame usage
38067 @item compiled_cond @tab 8 @tab compiled condition
38068 @item orig_size @tab 8 @tab orig size
38069 @item condition @tab 4 if condition is NULL otherwise length of
38070 @ref{agent expression object}
38071 @tab zero if condition is NULL, otherwise is
38072 @ref{agent expression object}
38073 @item actions @tab variable
38074 @tab numactions number of @ref{tracepoint action object}
38077 @node IPA Protocol Commands
38078 @subsection IPA Protocol Commands
38079 @cindex ipa protocol commands
38081 The spaces in each command are delimiters to ease reading this commands
38082 specification. They don't exist in real commands.
38086 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38087 Installs a new fast tracepoint described by @var{tracepoint_object}
38088 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38089 head of @dfn{jumppad}, which is used to jump to data collection routine
38094 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38095 @var{target_address} is address of tracepoint in the inferior.
38096 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38097 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38098 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38099 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38106 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38107 is about to kill inferiors.
38115 @item probe_marker_at:@var{address}
38116 Asks in-process agent to probe the marker at @var{address}.
38123 @item unprobe_marker_at:@var{address}
38124 Asks in-process agent to unprobe the marker at @var{address}.
38128 @chapter Reporting Bugs in @value{GDBN}
38129 @cindex bugs in @value{GDBN}
38130 @cindex reporting bugs in @value{GDBN}
38132 Your bug reports play an essential role in making @value{GDBN} reliable.
38134 Reporting a bug may help you by bringing a solution to your problem, or it
38135 may not. But in any case the principal function of a bug report is to help
38136 the entire community by making the next version of @value{GDBN} work better. Bug
38137 reports are your contribution to the maintenance of @value{GDBN}.
38139 In order for a bug report to serve its purpose, you must include the
38140 information that enables us to fix the bug.
38143 * Bug Criteria:: Have you found a bug?
38144 * Bug Reporting:: How to report bugs
38148 @section Have You Found a Bug?
38149 @cindex bug criteria
38151 If you are not sure whether you have found a bug, here are some guidelines:
38154 @cindex fatal signal
38155 @cindex debugger crash
38156 @cindex crash of debugger
38158 If the debugger gets a fatal signal, for any input whatever, that is a
38159 @value{GDBN} bug. Reliable debuggers never crash.
38161 @cindex error on valid input
38163 If @value{GDBN} produces an error message for valid input, that is a
38164 bug. (Note that if you're cross debugging, the problem may also be
38165 somewhere in the connection to the target.)
38167 @cindex invalid input
38169 If @value{GDBN} does not produce an error message for invalid input,
38170 that is a bug. However, you should note that your idea of
38171 ``invalid input'' might be our idea of ``an extension'' or ``support
38172 for traditional practice''.
38175 If you are an experienced user of debugging tools, your suggestions
38176 for improvement of @value{GDBN} are welcome in any case.
38179 @node Bug Reporting
38180 @section How to Report Bugs
38181 @cindex bug reports
38182 @cindex @value{GDBN} bugs, reporting
38184 A number of companies and individuals offer support for @sc{gnu} products.
38185 If you obtained @value{GDBN} from a support organization, we recommend you
38186 contact that organization first.
38188 You can find contact information for many support companies and
38189 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38191 @c should add a web page ref...
38194 @ifset BUGURL_DEFAULT
38195 In any event, we also recommend that you submit bug reports for
38196 @value{GDBN}. The preferred method is to submit them directly using
38197 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38198 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38201 @strong{Do not send bug reports to @samp{info-gdb}, or to
38202 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38203 not want to receive bug reports. Those that do have arranged to receive
38206 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38207 serves as a repeater. The mailing list and the newsgroup carry exactly
38208 the same messages. Often people think of posting bug reports to the
38209 newsgroup instead of mailing them. This appears to work, but it has one
38210 problem which can be crucial: a newsgroup posting often lacks a mail
38211 path back to the sender. Thus, if we need to ask for more information,
38212 we may be unable to reach you. For this reason, it is better to send
38213 bug reports to the mailing list.
38215 @ifclear BUGURL_DEFAULT
38216 In any event, we also recommend that you submit bug reports for
38217 @value{GDBN} to @value{BUGURL}.
38221 The fundamental principle of reporting bugs usefully is this:
38222 @strong{report all the facts}. If you are not sure whether to state a
38223 fact or leave it out, state it!
38225 Often people omit facts because they think they know what causes the
38226 problem and assume that some details do not matter. Thus, you might
38227 assume that the name of the variable you use in an example does not matter.
38228 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38229 stray memory reference which happens to fetch from the location where that
38230 name is stored in memory; perhaps, if the name were different, the contents
38231 of that location would fool the debugger into doing the right thing despite
38232 the bug. Play it safe and give a specific, complete example. That is the
38233 easiest thing for you to do, and the most helpful.
38235 Keep in mind that the purpose of a bug report is to enable us to fix the
38236 bug. It may be that the bug has been reported previously, but neither
38237 you nor we can know that unless your bug report is complete and
38240 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38241 bell?'' Those bug reports are useless, and we urge everyone to
38242 @emph{refuse to respond to them} except to chide the sender to report
38245 To enable us to fix the bug, you should include all these things:
38249 The version of @value{GDBN}. @value{GDBN} announces it if you start
38250 with no arguments; you can also print it at any time using @code{show
38253 Without this, we will not know whether there is any point in looking for
38254 the bug in the current version of @value{GDBN}.
38257 The type of machine you are using, and the operating system name and
38261 The details of the @value{GDBN} build-time configuration.
38262 @value{GDBN} shows these details if you invoke it with the
38263 @option{--configuration} command-line option, or if you type
38264 @code{show configuration} at @value{GDBN}'s prompt.
38267 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38268 ``@value{GCC}--2.8.1''.
38271 What compiler (and its version) was used to compile the program you are
38272 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38273 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38274 to get this information; for other compilers, see the documentation for
38278 The command arguments you gave the compiler to compile your example and
38279 observe the bug. For example, did you use @samp{-O}? To guarantee
38280 you will not omit something important, list them all. A copy of the
38281 Makefile (or the output from make) is sufficient.
38283 If we were to try to guess the arguments, we would probably guess wrong
38284 and then we might not encounter the bug.
38287 A complete input script, and all necessary source files, that will
38291 A description of what behavior you observe that you believe is
38292 incorrect. For example, ``It gets a fatal signal.''
38294 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38295 will certainly notice it. But if the bug is incorrect output, we might
38296 not notice unless it is glaringly wrong. You might as well not give us
38297 a chance to make a mistake.
38299 Even if the problem you experience is a fatal signal, you should still
38300 say so explicitly. Suppose something strange is going on, such as, your
38301 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38302 the C library on your system. (This has happened!) Your copy might
38303 crash and ours would not. If you told us to expect a crash, then when
38304 ours fails to crash, we would know that the bug was not happening for
38305 us. If you had not told us to expect a crash, then we would not be able
38306 to draw any conclusion from our observations.
38309 @cindex recording a session script
38310 To collect all this information, you can use a session recording program
38311 such as @command{script}, which is available on many Unix systems.
38312 Just run your @value{GDBN} session inside @command{script} and then
38313 include the @file{typescript} file with your bug report.
38315 Another way to record a @value{GDBN} session is to run @value{GDBN}
38316 inside Emacs and then save the entire buffer to a file.
38319 If you wish to suggest changes to the @value{GDBN} source, send us context
38320 diffs. If you even discuss something in the @value{GDBN} source, refer to
38321 it by context, not by line number.
38323 The line numbers in our development sources will not match those in your
38324 sources. Your line numbers would convey no useful information to us.
38328 Here are some things that are not necessary:
38332 A description of the envelope of the bug.
38334 Often people who encounter a bug spend a lot of time investigating
38335 which changes to the input file will make the bug go away and which
38336 changes will not affect it.
38338 This is often time consuming and not very useful, because the way we
38339 will find the bug is by running a single example under the debugger
38340 with breakpoints, not by pure deduction from a series of examples.
38341 We recommend that you save your time for something else.
38343 Of course, if you can find a simpler example to report @emph{instead}
38344 of the original one, that is a convenience for us. Errors in the
38345 output will be easier to spot, running under the debugger will take
38346 less time, and so on.
38348 However, simplification is not vital; if you do not want to do this,
38349 report the bug anyway and send us the entire test case you used.
38352 A patch for the bug.
38354 A patch for the bug does help us if it is a good one. But do not omit
38355 the necessary information, such as the test case, on the assumption that
38356 a patch is all we need. We might see problems with your patch and decide
38357 to fix the problem another way, or we might not understand it at all.
38359 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38360 construct an example that will make the program follow a certain path
38361 through the code. If you do not send us the example, we will not be able
38362 to construct one, so we will not be able to verify that the bug is fixed.
38364 And if we cannot understand what bug you are trying to fix, or why your
38365 patch should be an improvement, we will not install it. A test case will
38366 help us to understand.
38369 A guess about what the bug is or what it depends on.
38371 Such guesses are usually wrong. Even we cannot guess right about such
38372 things without first using the debugger to find the facts.
38375 @c The readline documentation is distributed with the readline code
38376 @c and consists of the two following files:
38379 @c Use -I with makeinfo to point to the appropriate directory,
38380 @c environment var TEXINPUTS with TeX.
38381 @ifclear SYSTEM_READLINE
38382 @include rluser.texi
38383 @include hsuser.texi
38387 @appendix In Memoriam
38389 The @value{GDBN} project mourns the loss of the following long-time
38394 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38395 to Free Software in general. Outside of @value{GDBN}, he was known in
38396 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38398 @item Michael Snyder
38399 Michael was one of the Global Maintainers of the @value{GDBN} project,
38400 with contributions recorded as early as 1996, until 2011. In addition
38401 to his day to day participation, he was a large driving force behind
38402 adding Reverse Debugging to @value{GDBN}.
38405 Beyond their technical contributions to the project, they were also
38406 enjoyable members of the Free Software Community. We will miss them.
38408 @node Formatting Documentation
38409 @appendix Formatting Documentation
38411 @cindex @value{GDBN} reference card
38412 @cindex reference card
38413 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38414 for printing with PostScript or Ghostscript, in the @file{gdb}
38415 subdirectory of the main source directory@footnote{In
38416 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38417 release.}. If you can use PostScript or Ghostscript with your printer,
38418 you can print the reference card immediately with @file{refcard.ps}.
38420 The release also includes the source for the reference card. You
38421 can format it, using @TeX{}, by typing:
38427 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38428 mode on US ``letter'' size paper;
38429 that is, on a sheet 11 inches wide by 8.5 inches
38430 high. You will need to specify this form of printing as an option to
38431 your @sc{dvi} output program.
38433 @cindex documentation
38435 All the documentation for @value{GDBN} comes as part of the machine-readable
38436 distribution. The documentation is written in Texinfo format, which is
38437 a documentation system that uses a single source file to produce both
38438 on-line information and a printed manual. You can use one of the Info
38439 formatting commands to create the on-line version of the documentation
38440 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38442 @value{GDBN} includes an already formatted copy of the on-line Info
38443 version of this manual in the @file{gdb} subdirectory. The main Info
38444 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38445 subordinate files matching @samp{gdb.info*} in the same directory. If
38446 necessary, you can print out these files, or read them with any editor;
38447 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38448 Emacs or the standalone @code{info} program, available as part of the
38449 @sc{gnu} Texinfo distribution.
38451 If you want to format these Info files yourself, you need one of the
38452 Info formatting programs, such as @code{texinfo-format-buffer} or
38455 If you have @code{makeinfo} installed, and are in the top level
38456 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38457 version @value{GDBVN}), you can make the Info file by typing:
38464 If you want to typeset and print copies of this manual, you need @TeX{},
38465 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38466 Texinfo definitions file.
38468 @TeX{} is a typesetting program; it does not print files directly, but
38469 produces output files called @sc{dvi} files. To print a typeset
38470 document, you need a program to print @sc{dvi} files. If your system
38471 has @TeX{} installed, chances are it has such a program. The precise
38472 command to use depends on your system; @kbd{lpr -d} is common; another
38473 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38474 require a file name without any extension or a @samp{.dvi} extension.
38476 @TeX{} also requires a macro definitions file called
38477 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38478 written in Texinfo format. On its own, @TeX{} cannot either read or
38479 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38480 and is located in the @file{gdb-@var{version-number}/texinfo}
38483 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38484 typeset and print this manual. First switch to the @file{gdb}
38485 subdirectory of the main source directory (for example, to
38486 @file{gdb-@value{GDBVN}/gdb}) and type:
38492 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
38494 @node Installing GDB
38495 @appendix Installing @value{GDBN}
38496 @cindex installation
38499 * Requirements:: Requirements for building @value{GDBN}
38500 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
38501 * Separate Objdir:: Compiling @value{GDBN} in another directory
38502 * Config Names:: Specifying names for hosts and targets
38503 * Configure Options:: Summary of options for configure
38504 * System-wide configuration:: Having a system-wide init file
38508 @section Requirements for Building @value{GDBN}
38509 @cindex building @value{GDBN}, requirements for
38511 Building @value{GDBN} requires various tools and packages to be available.
38512 Other packages will be used only if they are found.
38514 @heading Tools/Packages Necessary for Building @value{GDBN}
38516 @item C@t{++}11 compiler
38517 @value{GDBN} is written in C@t{++}11. It should be buildable with any
38518 recent C@t{++}11 compiler, e.g.@: GCC.
38521 @value{GDBN}'s build system relies on features only found in the GNU
38522 make program. Other variants of @code{make} will not work.
38524 @item GMP (The GNU Multiple Precision Arithmetic Library)
38525 @value{GDBN} now uses GMP to perform some of its arithmetics.
38526 This library may be included with your operating system distribution;
38527 if it is not, you can get the latest version from
38528 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
38529 you can use the @option{--with-libgmp-prefix} option to specify
38534 @heading Tools/Packages Optional for Building @value{GDBN}
38538 @value{GDBN} can use the Expat XML parsing library. This library may be
38539 included with your operating system distribution; if it is not, you
38540 can get the latest version from @url{http://expat.sourceforge.net}.
38541 The @file{configure} script will search for this library in several
38542 standard locations; if it is installed in an unusual path, you can
38543 use the @option{--with-libexpat-prefix} option to specify its location.
38549 Remote protocol memory maps (@pxref{Memory Map Format})
38551 Target descriptions (@pxref{Target Descriptions})
38553 Remote shared library lists (@xref{Library List Format},
38554 or alternatively @pxref{Library List Format for SVR4 Targets})
38556 MS-Windows shared libraries (@pxref{Shared Libraries})
38558 Traceframe info (@pxref{Traceframe Info Format})
38560 Branch trace (@pxref{Branch Trace Format},
38561 @pxref{Branch Trace Configuration Format})
38565 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
38566 default, @value{GDBN} will be compiled if the Guile libraries are
38567 installed and are found by @file{configure}. You can use the
38568 @code{--with-guile} option to request Guile, and pass either the Guile
38569 version number or the file name of the relevant @code{pkg-config}
38570 program to choose a particular version of Guile.
38573 @value{GDBN}'s features related to character sets (@pxref{Character
38574 Sets}) require a functioning @code{iconv} implementation. If you are
38575 on a GNU system, then this is provided by the GNU C Library. Some
38576 other systems also provide a working @code{iconv}.
38578 If @value{GDBN} is using the @code{iconv} program which is installed
38579 in a non-standard place, you will need to tell @value{GDBN} where to
38580 find it. This is done with @option{--with-iconv-bin} which specifies
38581 the directory that contains the @code{iconv} program. This program is
38582 run in order to make a list of the available character sets.
38584 On systems without @code{iconv}, you can install GNU Libiconv. If
38585 Libiconv is installed in a standard place, @value{GDBN} will
38586 automatically use it if it is needed. If you have previously
38587 installed Libiconv in a non-standard place, you can use the
38588 @option{--with-libiconv-prefix} option to @file{configure}.
38590 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
38591 arrange to build Libiconv if a directory named @file{libiconv} appears
38592 in the top-most source directory. If Libiconv is built this way, and
38593 if the operating system does not provide a suitable @code{iconv}
38594 implementation, then the just-built library will automatically be used
38595 by @value{GDBN}. One easy way to set this up is to download GNU
38596 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
38597 source tree, and then rename the directory holding the Libiconv source
38598 code to @samp{libiconv}.
38601 @value{GDBN} can support debugging sections that are compressed with
38602 the LZMA library. @xref{MiniDebugInfo}. If this library is not
38603 included with your operating system, you can find it in the xz package
38604 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
38605 the usual place, then the @file{configure} script will use it
38606 automatically. If it is installed in an unusual path, you can use the
38607 @option{--with-lzma-prefix} option to specify its location.
38611 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
38612 library. This library may be included with your operating system
38613 distribution; if it is not, you can get the latest version from
38614 @url{http://www.mpfr.org}. The @file{configure} script will search
38615 for this library in several standard locations; if it is installed
38616 in an unusual path, you can use the @option{--with-libmpfr-prefix}
38617 option to specify its location.
38619 GNU MPFR is used to emulate target floating-point arithmetic during
38620 expression evaluation when the target uses different floating-point
38621 formats than the host. If GNU MPFR it is not available, @value{GDBN}
38622 will fall back to using host floating-point arithmetic.
38625 @value{GDBN} can be scripted using Python language. @xref{Python}.
38626 By default, @value{GDBN} will be compiled if the Python libraries are
38627 installed and are found by @file{configure}. You can use the
38628 @code{--with-python} option to request Python, and pass either the
38629 file name of the relevant @code{python} executable, or the name of the
38630 directory in which Python is installed, to choose a particular
38631 installation of Python.
38634 @cindex compressed debug sections
38635 @value{GDBN} will use the @samp{zlib} library, if available, to read
38636 compressed debug sections. Some linkers, such as GNU gold, are capable
38637 of producing binaries with compressed debug sections. If @value{GDBN}
38638 is compiled with @samp{zlib}, it will be able to read the debug
38639 information in such binaries.
38641 The @samp{zlib} library is likely included with your operating system
38642 distribution; if it is not, you can get the latest version from
38643 @url{http://zlib.net}.
38646 @node Running Configure
38647 @section Invoking the @value{GDBN} @file{configure} Script
38648 @cindex configuring @value{GDBN}
38649 @value{GDBN} comes with a @file{configure} script that automates the process
38650 of preparing @value{GDBN} for installation; you can then use @code{make} to
38651 build the @code{gdb} program.
38653 @c irrelevant in info file; it's as current as the code it lives with.
38654 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
38655 look at the @file{README} file in the sources; we may have improved the
38656 installation procedures since publishing this manual.}
38659 The @value{GDBN} distribution includes all the source code you need for
38660 @value{GDBN} in a single directory, whose name is usually composed by
38661 appending the version number to @samp{gdb}.
38663 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
38664 @file{gdb-@value{GDBVN}} directory. That directory contains:
38667 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
38668 script for configuring @value{GDBN} and all its supporting libraries
38670 @item gdb-@value{GDBVN}/gdb
38671 the source specific to @value{GDBN} itself
38673 @item gdb-@value{GDBVN}/bfd
38674 source for the Binary File Descriptor library
38676 @item gdb-@value{GDBVN}/include
38677 @sc{gnu} include files
38679 @item gdb-@value{GDBVN}/libiberty
38680 source for the @samp{-liberty} free software library
38682 @item gdb-@value{GDBVN}/opcodes
38683 source for the library of opcode tables and disassemblers
38685 @item gdb-@value{GDBVN}/readline
38686 source for the @sc{gnu} command-line interface
38689 There may be other subdirectories as well.
38691 The simplest way to configure and build @value{GDBN} is to run @file{configure}
38692 from the @file{gdb-@var{version-number}} source directory, which in
38693 this example is the @file{gdb-@value{GDBVN}} directory.
38695 First switch to the @file{gdb-@var{version-number}} source directory
38696 if you are not already in it; then run @file{configure}. Pass the
38697 identifier for the platform on which @value{GDBN} will run as an
38703 cd gdb-@value{GDBVN}
38708 Running @samp{configure} and then running @code{make} builds the
38709 included supporting libraries, then @code{gdb} itself. The configured
38710 source files, and the binaries, are left in the corresponding source
38714 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
38715 system does not recognize this automatically when you run a different
38716 shell, you may need to run @code{sh} on it explicitly:
38722 You should run the @file{configure} script from the top directory in the
38723 source tree, the @file{gdb-@var{version-number}} directory. If you run
38724 @file{configure} from one of the subdirectories, you will configure only
38725 that subdirectory. That is usually not what you want. In particular,
38726 if you run the first @file{configure} from the @file{gdb} subdirectory
38727 of the @file{gdb-@var{version-number}} directory, you will omit the
38728 configuration of @file{bfd}, @file{readline}, and other sibling
38729 directories of the @file{gdb} subdirectory. This leads to build errors
38730 about missing include files such as @file{bfd/bfd.h}.
38732 You can install @code{@value{GDBN}} anywhere. The best way to do this
38733 is to pass the @code{--prefix} option to @code{configure}, and then
38734 install it with @code{make install}.
38736 @node Separate Objdir
38737 @section Compiling @value{GDBN} in Another Directory
38739 If you want to run @value{GDBN} versions for several host or target machines,
38740 you need a different @code{gdb} compiled for each combination of
38741 host and target. @file{configure} is designed to make this easy by
38742 allowing you to generate each configuration in a separate subdirectory,
38743 rather than in the source directory. If your @code{make} program
38744 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
38745 @code{make} in each of these directories builds the @code{gdb}
38746 program specified there.
38748 To build @code{gdb} in a separate directory, run @file{configure}
38749 with the @samp{--srcdir} option to specify where to find the source.
38750 (You also need to specify a path to find @file{configure}
38751 itself from your working directory. If the path to @file{configure}
38752 would be the same as the argument to @samp{--srcdir}, you can leave out
38753 the @samp{--srcdir} option; it is assumed.)
38755 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
38756 separate directory for a Sun 4 like this:
38760 cd gdb-@value{GDBVN}
38763 ../gdb-@value{GDBVN}/configure
38768 When @file{configure} builds a configuration using a remote source
38769 directory, it creates a tree for the binaries with the same structure
38770 (and using the same names) as the tree under the source directory. In
38771 the example, you'd find the Sun 4 library @file{libiberty.a} in the
38772 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
38773 @file{gdb-sun4/gdb}.
38775 Make sure that your path to the @file{configure} script has just one
38776 instance of @file{gdb} in it. If your path to @file{configure} looks
38777 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
38778 one subdirectory of @value{GDBN}, not the whole package. This leads to
38779 build errors about missing include files such as @file{bfd/bfd.h}.
38781 One popular reason to build several @value{GDBN} configurations in separate
38782 directories is to configure @value{GDBN} for cross-compiling (where
38783 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
38784 programs that run on another machine---the @dfn{target}).
38785 You specify a cross-debugging target by
38786 giving the @samp{--target=@var{target}} option to @file{configure}.
38788 When you run @code{make} to build a program or library, you must run
38789 it in a configured directory---whatever directory you were in when you
38790 called @file{configure} (or one of its subdirectories).
38792 The @code{Makefile} that @file{configure} generates in each source
38793 directory also runs recursively. If you type @code{make} in a source
38794 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
38795 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
38796 will build all the required libraries, and then build GDB.
38798 When you have multiple hosts or targets configured in separate
38799 directories, you can run @code{make} on them in parallel (for example,
38800 if they are NFS-mounted on each of the hosts); they will not interfere
38804 @section Specifying Names for Hosts and Targets
38806 The specifications used for hosts and targets in the @file{configure}
38807 script are based on a three-part naming scheme, but some short predefined
38808 aliases are also supported. The full naming scheme encodes three pieces
38809 of information in the following pattern:
38812 @var{architecture}-@var{vendor}-@var{os}
38815 For example, you can use the alias @code{sun4} as a @var{host} argument,
38816 or as the value for @var{target} in a @code{--target=@var{target}}
38817 option. The equivalent full name is @samp{sparc-sun-sunos4}.
38819 The @file{configure} script accompanying @value{GDBN} does not provide
38820 any query facility to list all supported host and target names or
38821 aliases. @file{configure} calls the Bourne shell script
38822 @code{config.sub} to map abbreviations to full names; you can read the
38823 script, if you wish, or you can use it to test your guesses on
38824 abbreviations---for example:
38827 % sh config.sub i386-linux
38829 % sh config.sub alpha-linux
38830 alpha-unknown-linux-gnu
38831 % sh config.sub hp9k700
38833 % sh config.sub sun4
38834 sparc-sun-sunos4.1.1
38835 % sh config.sub sun3
38836 m68k-sun-sunos4.1.1
38837 % sh config.sub i986v
38838 Invalid configuration `i986v': machine `i986v' not recognized
38842 @code{config.sub} is also distributed in the @value{GDBN} source
38843 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
38845 @node Configure Options
38846 @section @file{configure} Options
38848 Here is a summary of the @file{configure} options and arguments that
38849 are most often useful for building @value{GDBN}. @file{configure}
38850 also has several other options not listed here. @xref{Running
38851 configure Scripts,,,autoconf}, for a full
38852 explanation of @file{configure}.
38855 configure @r{[}--help@r{]}
38856 @r{[}--prefix=@var{dir}@r{]}
38857 @r{[}--exec-prefix=@var{dir}@r{]}
38858 @r{[}--srcdir=@var{dirname}@r{]}
38859 @r{[}--target=@var{target}@r{]}
38863 You may introduce options with a single @samp{-} rather than
38864 @samp{--} if you prefer; but you may abbreviate option names if you use
38869 Display a quick summary of how to invoke @file{configure}.
38871 @item --prefix=@var{dir}
38872 Configure the source to install programs and files under directory
38875 @item --exec-prefix=@var{dir}
38876 Configure the source to install programs under directory
38879 @c avoid splitting the warning from the explanation:
38881 @item --srcdir=@var{dirname}
38882 Use this option to make configurations in directories separate from the
38883 @value{GDBN} source directories. Among other things, you can use this to
38884 build (or maintain) several configurations simultaneously, in separate
38885 directories. @file{configure} writes configuration-specific files in
38886 the current directory, but arranges for them to use the source in the
38887 directory @var{dirname}. @file{configure} creates directories under
38888 the working directory in parallel to the source directories below
38891 @item --target=@var{target}
38892 Configure @value{GDBN} for cross-debugging programs running on the specified
38893 @var{target}. Without this option, @value{GDBN} is configured to debug
38894 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
38896 There is no convenient way to generate a list of all available
38897 targets. Also see the @code{--enable-targets} option, below.
38900 There are many other options that are specific to @value{GDBN}. This
38901 lists just the most common ones; there are some very specialized
38902 options not described here.
38905 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
38906 @itemx --enable-targets=all
38907 Configure @value{GDBN} for cross-debugging programs running on the
38908 specified list of targets. The special value @samp{all} configures
38909 @value{GDBN} for debugging programs running on any target it supports.
38911 @item --with-gdb-datadir=@var{path}
38912 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
38913 here for certain supporting files or scripts. This defaults to the
38914 @file{gdb} subdirectory of @samp{datadir} (which can be set using
38917 @item --with-relocated-sources=@var{dir}
38918 Sets up the default source path substitution rule so that directory
38919 names recorded in debug information will be automatically adjusted for
38920 any directory under @var{dir}. @var{dir} should be a subdirectory of
38921 @value{GDBN}'s configured prefix, the one mentioned in the
38922 @code{--prefix} or @code{--exec-prefix} options to configure. This
38923 option is useful if GDB is supposed to be moved to a different place
38926 @item --enable-64-bit-bfd
38927 Enable 64-bit support in BFD on 32-bit hosts.
38929 @item --disable-gdbmi
38930 Build @value{GDBN} without the GDB/MI machine interface
38934 Build @value{GDBN} with the text-mode full-screen user interface
38935 (TUI). Requires a curses library (ncurses and cursesX are also
38938 @item --with-curses
38939 Use the curses library instead of the termcap library, for text-mode
38940 terminal operations.
38942 @item --with-debuginfod
38943 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
38944 library. Used to automatically fetch ELF, DWARF and source files from
38945 @code{debuginfod} servers using build IDs associated with any missing
38946 files. Enabled by default if @file{libdebuginfod} is installed and found
38947 at configure time. For more information regarding @code{debuginfod} see
38950 @item --with-libunwind-ia64
38951 Use the libunwind library for unwinding function call stack on ia64
38952 target platforms. See http://www.nongnu.org/libunwind/index.html for
38955 @item --with-system-readline
38956 Use the readline library installed on the host, rather than the
38957 library supplied as part of @value{GDBN}. Readline 7 or newer is
38958 required; this is enforced by the build system.
38960 @item --with-system-zlib
38961 Use the zlib library installed on the host, rather than the library
38962 supplied as part of @value{GDBN}.
38965 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
38966 default if libexpat is installed and found at configure time.) This
38967 library is used to read XML files supplied with @value{GDBN}. If it
38968 is unavailable, some features, such as remote protocol memory maps,
38969 target descriptions, and shared library lists, that are based on XML
38970 files, will not be available in @value{GDBN}. If your host does not
38971 have libexpat installed, you can get the latest version from
38972 `http://expat.sourceforge.net'.
38974 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
38976 Build @value{GDBN} with GNU libiconv, a character set encoding
38977 conversion library. This is not done by default, as on GNU systems
38978 the @code{iconv} that is built in to the C library is sufficient. If
38979 your host does not have a working @code{iconv}, you can get the latest
38980 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
38982 @value{GDBN}'s build system also supports building GNU libiconv as
38983 part of the overall build. @xref{Requirements}.
38986 Build @value{GDBN} with LZMA, a compression library. (Done by default
38987 if liblzma is installed and found at configure time.) LZMA is used by
38988 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
38989 platforms using the ELF object file format. If your host does not
38990 have liblzma installed, you can get the latest version from
38991 `https://tukaani.org/xz/'.
38994 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
38995 floating-point computation with correct rounding. (Done by default if
38996 GNU MPFR is installed and found at configure time.) This library is
38997 used to emulate target floating-point arithmetic during expression
38998 evaluation when the target uses different floating-point formats than
38999 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39000 to using host floating-point arithmetic. If your host does not have
39001 GNU MPFR installed, you can get the latest version from
39002 `http://www.mpfr.org'.
39004 @item --with-python@r{[}=@var{python}@r{]}
39005 Build @value{GDBN} with Python scripting support. (Done by default if
39006 libpython is present and found at configure time.) Python makes
39007 @value{GDBN} scripting much more powerful than the restricted CLI
39008 scripting language. If your host does not have Python installed, you
39009 can find it on `http://www.python.org/download/'. The oldest version
39010 of Python supported by GDB is 2.6. The optional argument @var{python}
39011 is used to find the Python headers and libraries. It can be either
39012 the name of a Python executable, or the name of the directory in which
39013 Python is installed.
39015 @item --with-guile[=GUILE]'
39016 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39017 if libguile is present and found at configure time.) If your host
39018 does not have Guile installed, you can find it at
39019 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39020 can be a version number, which will cause @code{configure} to try to
39021 use that version of Guile; or the file name of a @code{pkg-config}
39022 executable, which will be queried to find the information needed to
39023 compile and link against Guile.
39025 @item --without-included-regex
39026 Don't use the regex library included with @value{GDBN} (as part of the
39027 libiberty library). This is the default on hosts with version 2 of
39030 @item --with-sysroot=@var{dir}
39031 Use @var{dir} as the default system root directory for libraries whose
39032 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39033 @var{dir} can be modified at run time by using the @command{set
39034 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39035 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39036 default system root will be automatically adjusted if and when
39037 @value{GDBN} is moved to a different location.
39039 @item --with-system-gdbinit=@var{file}
39040 Configure @value{GDBN} to automatically load a system-wide init file.
39041 @var{file} should be an absolute file name. If @var{file} is in a
39042 directory under the configured prefix, and @value{GDBN} is moved to
39043 another location after being built, the location of the system-wide
39044 init file will be adjusted accordingly.
39046 @item --with-system-gdbinit-dir=@var{directory}
39047 Configure @value{GDBN} to automatically load init files from a
39048 system-wide directory. @var{directory} should be an absolute directory
39049 name. If @var{directory} is in a directory under the configured
39050 prefix, and @value{GDBN} is moved to another location after being
39051 built, the location of the system-wide init directory will be
39052 adjusted accordingly.
39054 @item --enable-build-warnings
39055 When building the @value{GDBN} sources, ask the compiler to warn about
39056 any code which looks even vaguely suspicious. It passes many
39057 different warning flags, depending on the exact version of the
39058 compiler you are using.
39060 @item --enable-werror
39061 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39062 to the compiler, which will fail the compilation if the compiler
39063 outputs any warning messages.
39065 @item --enable-ubsan
39066 Enable the GCC undefined behavior sanitizer. This is disabled by
39067 default, but passing @code{--enable-ubsan=yes} or
39068 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39069 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39070 It has a performance cost, so if you are looking at @value{GDBN}'s
39071 performance, you should disable it. The undefined behavior sanitizer
39072 was first introduced in GCC 4.9.
39075 @node System-wide configuration
39076 @section System-wide configuration and settings
39077 @cindex system-wide init file
39079 @value{GDBN} can be configured to have a system-wide init file and a
39080 system-wide init file directory; this file and files in that directory
39081 (if they have a recognized file extension) will be read and executed at
39082 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39084 Here are the corresponding configure options:
39087 @item --with-system-gdbinit=@var{file}
39088 Specify that the default location of the system-wide init file is
39090 @item --with-system-gdbinit-dir=@var{directory}
39091 Specify that the default location of the system-wide init file directory
39092 is @var{directory}.
39095 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39096 they may be subject to relocation. Two possible cases:
39100 If the default location of this init file/directory contains @file{$prefix},
39101 it will be subject to relocation. Suppose that the configure options
39102 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39103 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39104 init file is looked for as @file{$install/etc/gdbinit} instead of
39105 @file{$prefix/etc/gdbinit}.
39108 By contrast, if the default location does not contain the prefix,
39109 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39110 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39111 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39112 wherever @value{GDBN} is installed.
39115 If the configured location of the system-wide init file (as given by the
39116 @option{--with-system-gdbinit} option at configure time) is in the
39117 data-directory (as specified by @option{--with-gdb-datadir} at configure
39118 time) or in one of its subdirectories, then @value{GDBN} will look for the
39119 system-wide init file in the directory specified by the
39120 @option{--data-directory} command-line option.
39121 Note that the system-wide init file is only read once, during @value{GDBN}
39122 initialization. If the data-directory is changed after @value{GDBN} has
39123 started with the @code{set data-directory} command, the file will not be
39126 This applies similarly to the system-wide directory specified in
39127 @option{--with-system-gdbinit-dir}.
39129 Any supported scripting language can be used for these init files, as long
39130 as the file extension matches the scripting language. To be interpreted
39131 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39135 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39138 @node System-wide Configuration Scripts
39139 @subsection Installed System-wide Configuration Scripts
39140 @cindex system-wide configuration scripts
39142 The @file{system-gdbinit} directory, located inside the data-directory
39143 (as specified by @option{--with-gdb-datadir} at configure time) contains
39144 a number of scripts which can be used as system-wide init files. To
39145 automatically source those scripts at startup, @value{GDBN} should be
39146 configured with @option{--with-system-gdbinit}. Otherwise, any user
39147 should be able to source them by hand as needed.
39149 The following scripts are currently available:
39152 @item @file{elinos.py}
39154 @cindex ELinOS system-wide configuration script
39155 This script is useful when debugging a program on an ELinOS target.
39156 It takes advantage of the environment variables defined in a standard
39157 ELinOS environment in order to determine the location of the system
39158 shared libraries, and then sets the @samp{solib-absolute-prefix}
39159 and @samp{solib-search-path} variables appropriately.
39161 @item @file{wrs-linux.py}
39162 @pindex wrs-linux.py
39163 @cindex Wind River Linux system-wide configuration script
39164 This script is useful when debugging a program on a target running
39165 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39166 the host-side sysroot used by the target system.
39170 @node Maintenance Commands
39171 @appendix Maintenance Commands
39172 @cindex maintenance commands
39173 @cindex internal commands
39175 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39176 includes a number of commands intended for @value{GDBN} developers,
39177 that are not documented elsewhere in this manual. These commands are
39178 provided here for reference. (For commands that turn on debugging
39179 messages, see @ref{Debugging Output}.)
39182 @kindex maint agent
39183 @kindex maint agent-eval
39184 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39185 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39186 Translate the given @var{expression} into remote agent bytecodes.
39187 This command is useful for debugging the Agent Expression mechanism
39188 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39189 expression useful for data collection, such as by tracepoints, while
39190 @samp{maint agent-eval} produces an expression that evaluates directly
39191 to a result. For instance, a collection expression for @code{globa +
39192 globb} will include bytecodes to record four bytes of memory at each
39193 of the addresses of @code{globa} and @code{globb}, while discarding
39194 the result of the addition, while an evaluation expression will do the
39195 addition and return the sum.
39196 If @code{-at} is given, generate remote agent bytecode for @var{location}.
39197 If not, generate remote agent bytecode for current frame PC address.
39199 @kindex maint agent-printf
39200 @item maint agent-printf @var{format},@var{expr},...
39201 Translate the given format string and list of argument expressions
39202 into remote agent bytecodes and display them as a disassembled list.
39203 This command is useful for debugging the agent version of dynamic
39204 printf (@pxref{Dynamic Printf}).
39206 @kindex maint info breakpoints
39207 @item @anchor{maint info breakpoints}maint info breakpoints
39208 Using the same format as @samp{info breakpoints}, display both the
39209 breakpoints you've set explicitly, and those @value{GDBN} is using for
39210 internal purposes. Internal breakpoints are shown with negative
39211 breakpoint numbers. The type column identifies what kind of breakpoint
39216 Normal, explicitly set breakpoint.
39219 Normal, explicitly set watchpoint.
39222 Internal breakpoint, used to handle correctly stepping through
39223 @code{longjmp} calls.
39225 @item longjmp resume
39226 Internal breakpoint at the target of a @code{longjmp}.
39229 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39232 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39235 Shared library events.
39239 @kindex maint info btrace
39240 @item maint info btrace
39241 Pint information about raw branch tracing data.
39243 @kindex maint btrace packet-history
39244 @item maint btrace packet-history
39245 Print the raw branch trace packets that are used to compute the
39246 execution history for the @samp{record btrace} command. Both the
39247 information and the format in which it is printed depend on the btrace
39252 For the BTS recording format, print a list of blocks of sequential
39253 code. For each block, the following information is printed:
39257 Newer blocks have higher numbers. The oldest block has number zero.
39258 @item Lowest @samp{PC}
39259 @item Highest @samp{PC}
39263 For the Intel Processor Trace recording format, print a list of
39264 Intel Processor Trace packets. For each packet, the following
39265 information is printed:
39268 @item Packet number
39269 Newer packets have higher numbers. The oldest packet has number zero.
39271 The packet's offset in the trace stream.
39272 @item Packet opcode and payload
39276 @kindex maint btrace clear-packet-history
39277 @item maint btrace clear-packet-history
39278 Discards the cached packet history printed by the @samp{maint btrace
39279 packet-history} command. The history will be computed again when
39282 @kindex maint btrace clear
39283 @item maint btrace clear
39284 Discard the branch trace data. The data will be fetched anew and the
39285 branch trace will be recomputed when needed.
39287 This implicitly truncates the branch trace to a single branch trace
39288 buffer. When updating branch trace incrementally, the branch trace
39289 available to @value{GDBN} may be bigger than a single branch trace
39292 @kindex maint set btrace pt skip-pad
39293 @item maint set btrace pt skip-pad
39294 @kindex maint show btrace pt skip-pad
39295 @item maint show btrace pt skip-pad
39296 Control whether @value{GDBN} will skip PAD packets when computing the
39299 @kindex maint info jit
39300 @item maint info jit
39301 Print information about JIT code objects loaded in the current inferior.
39303 @kindex set displaced-stepping
39304 @kindex show displaced-stepping
39305 @cindex displaced stepping support
39306 @cindex out-of-line single-stepping
39307 @item set displaced-stepping
39308 @itemx show displaced-stepping
39309 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39310 if the target supports it. Displaced stepping is a way to single-step
39311 over breakpoints without removing them from the inferior, by executing
39312 an out-of-line copy of the instruction that was originally at the
39313 breakpoint location. It is also known as out-of-line single-stepping.
39316 @item set displaced-stepping on
39317 If the target architecture supports it, @value{GDBN} will use
39318 displaced stepping to step over breakpoints.
39320 @item set displaced-stepping off
39321 @value{GDBN} will not use displaced stepping to step over breakpoints,
39322 even if such is supported by the target architecture.
39324 @cindex non-stop mode, and @samp{set displaced-stepping}
39325 @item set displaced-stepping auto
39326 This is the default mode. @value{GDBN} will use displaced stepping
39327 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39328 architecture supports displaced stepping.
39331 @kindex maint check-psymtabs
39332 @item maint check-psymtabs
39333 Check the consistency of currently expanded psymtabs versus symtabs.
39334 Use this to check, for example, whether a symbol is in one but not the other.
39336 @kindex maint check-symtabs
39337 @item maint check-symtabs
39338 Check the consistency of currently expanded symtabs.
39340 @kindex maint expand-symtabs
39341 @item maint expand-symtabs [@var{regexp}]
39342 Expand symbol tables.
39343 If @var{regexp} is specified, only expand symbol tables for file
39344 names matching @var{regexp}.
39346 @kindex maint set catch-demangler-crashes
39347 @kindex maint show catch-demangler-crashes
39348 @cindex demangler crashes
39349 @item maint set catch-demangler-crashes [on|off]
39350 @itemx maint show catch-demangler-crashes
39351 Control whether @value{GDBN} should attempt to catch crashes in the
39352 symbol name demangler. The default is to attempt to catch crashes.
39353 If enabled, the first time a crash is caught, a core file is created,
39354 the offending symbol is displayed and the user is presented with the
39355 option to terminate the current session.
39357 @kindex maint cplus first_component
39358 @item maint cplus first_component @var{name}
39359 Print the first C@t{++} class/namespace component of @var{name}.
39361 @kindex maint cplus namespace
39362 @item maint cplus namespace
39363 Print the list of possible C@t{++} namespaces.
39365 @kindex maint deprecate
39366 @kindex maint undeprecate
39367 @cindex deprecated commands
39368 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39369 @itemx maint undeprecate @var{command}
39370 Deprecate or undeprecate the named @var{command}. Deprecated commands
39371 cause @value{GDBN} to issue a warning when you use them. The optional
39372 argument @var{replacement} says which newer command should be used in
39373 favor of the deprecated one; if it is given, @value{GDBN} will mention
39374 the replacement as part of the warning.
39376 @kindex maint dump-me
39377 @item maint dump-me
39378 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39379 Cause a fatal signal in the debugger and force it to dump its core.
39380 This is supported only on systems which support aborting a program
39381 with the @code{SIGQUIT} signal.
39383 @kindex maint internal-error
39384 @kindex maint internal-warning
39385 @kindex maint demangler-warning
39386 @cindex demangler crashes
39387 @item maint internal-error @r{[}@var{message-text}@r{]}
39388 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39389 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39391 Cause @value{GDBN} to call the internal function @code{internal_error},
39392 @code{internal_warning} or @code{demangler_warning} and hence behave
39393 as though an internal problem has been detected. In addition to
39394 reporting the internal problem, these functions give the user the
39395 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39396 and @code{internal_warning}) create a core file of the current
39397 @value{GDBN} session.
39399 These commands take an optional parameter @var{message-text} that is
39400 used as the text of the error or warning message.
39402 Here's an example of using @code{internal-error}:
39405 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39406 @dots{}/maint.c:121: internal-error: testing, 1, 2
39407 A problem internal to GDB has been detected. Further
39408 debugging may prove unreliable.
39409 Quit this debugging session? (y or n) @kbd{n}
39410 Create a core file? (y or n) @kbd{n}
39414 @cindex @value{GDBN} internal error
39415 @cindex internal errors, control of @value{GDBN} behavior
39416 @cindex demangler crashes
39418 @kindex maint set internal-error
39419 @kindex maint show internal-error
39420 @kindex maint set internal-warning
39421 @kindex maint show internal-warning
39422 @kindex maint set demangler-warning
39423 @kindex maint show demangler-warning
39424 @item maint set internal-error @var{action} [ask|yes|no]
39425 @itemx maint show internal-error @var{action}
39426 @itemx maint set internal-warning @var{action} [ask|yes|no]
39427 @itemx maint show internal-warning @var{action}
39428 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39429 @itemx maint show demangler-warning @var{action}
39430 When @value{GDBN} reports an internal problem (error or warning) it
39431 gives the user the opportunity to both quit @value{GDBN} and create a
39432 core file of the current @value{GDBN} session. These commands let you
39433 override the default behaviour for each particular @var{action},
39434 described in the table below.
39438 You can specify that @value{GDBN} should always (yes) or never (no)
39439 quit. The default is to ask the user what to do.
39442 You can specify that @value{GDBN} should always (yes) or never (no)
39443 create a core file. The default is to ask the user what to do. Note
39444 that there is no @code{corefile} option for @code{demangler-warning}:
39445 demangler warnings always create a core file and this cannot be
39449 @kindex maint set internal-error
39450 @kindex maint show internal-error
39451 @kindex maint set internal-warning
39452 @kindex maint show internal-warning
39453 @item maint set internal-error backtrace @r{[}on|off@r{]}
39454 @itemx maint show internal-error backtrace
39455 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
39456 @itemx maint show internal-warning backtrace
39457 When @value{GDBN} reports an internal problem (error or warning) it is
39458 possible to have a backtrace of @value{GDBN} printed to the standard
39459 error stream. This is @samp{on} by default for @code{internal-error}
39460 and @samp{off} by default for @code{internal-warning}.
39462 @anchor{maint packet}
39463 @kindex maint packet
39464 @item maint packet @var{text}
39465 If @value{GDBN} is talking to an inferior via the serial protocol,
39466 then this command sends the string @var{text} to the inferior, and
39467 displays the response packet. @value{GDBN} supplies the initial
39468 @samp{$} character, the terminating @samp{#} character, and the
39471 Any non-printable characters in the reply are printed as escaped hex,
39472 e.g. @samp{\x00}, @samp{\x01}, etc.
39474 @kindex maint print architecture
39475 @item maint print architecture @r{[}@var{file}@r{]}
39476 Print the entire architecture configuration. The optional argument
39477 @var{file} names the file where the output goes.
39479 @kindex maint print c-tdesc
39480 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
39481 Print the target description (@pxref{Target Descriptions}) as
39482 a C source file. By default, the target description is for the current
39483 target, but if the optional argument @var{file} is provided, that file
39484 is used to produce the description. The @var{file} should be an XML
39485 document, of the form described in @ref{Target Description Format}.
39486 The created source file is built into @value{GDBN} when @value{GDBN} is
39487 built again. This command is used by developers after they add or
39488 modify XML target descriptions.
39490 When the optional flag @samp{-single-feature} is provided then the
39491 target description being processed (either the default, or from
39492 @var{file}) must only contain a single feature. The source file
39493 produced is different in this case.
39495 @kindex maint print xml-tdesc
39496 @item maint print xml-tdesc @r{[}@var{file}@r{]}
39497 Print the target description (@pxref{Target Descriptions}) as an XML
39498 file. By default print the target description for the current target,
39499 but if the optional argument @var{file} is provided, then that file is
39500 read in by GDB and then used to produce the description. The
39501 @var{file} should be an XML document, of the form described in
39502 @ref{Target Description Format}.
39504 @kindex maint check xml-descriptions
39505 @item maint check xml-descriptions @var{dir}
39506 Check that the target descriptions dynamically created by @value{GDBN}
39507 equal the descriptions created from XML files found in @var{dir}.
39509 @anchor{maint check libthread-db}
39510 @kindex maint check libthread-db
39511 @item maint check libthread-db
39512 Run integrity checks on the current inferior's thread debugging
39513 library. This exercises all @code{libthread_db} functionality used by
39514 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
39515 @code{proc_service} functions provided by @value{GDBN} that
39516 @code{libthread_db} uses. Note that parts of the test may be skipped
39517 on some platforms when debugging core files.
39519 @kindex maint print core-file-backed-mappings
39520 @cindex memory address space mappings
39521 @item maint print core-file-backed-mappings
39522 Print the file-backed mappings which were loaded from a core file note.
39523 This output represents state internal to @value{GDBN} and should be
39524 similar to the mappings displayed by the @code{info proc mappings}
39527 @kindex maint print dummy-frames
39528 @item maint print dummy-frames
39529 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
39532 (@value{GDBP}) @kbd{b add}
39534 (@value{GDBP}) @kbd{print add(2,3)}
39535 Breakpoint 2, add (a=2, b=3) at @dots{}
39537 The program being debugged stopped while in a function called from GDB.
39539 (@value{GDBP}) @kbd{maint print dummy-frames}
39540 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
39544 Takes an optional file parameter.
39546 @kindex maint print registers
39547 @kindex maint print raw-registers
39548 @kindex maint print cooked-registers
39549 @kindex maint print register-groups
39550 @kindex maint print remote-registers
39551 @item maint print registers @r{[}@var{file}@r{]}
39552 @itemx maint print raw-registers @r{[}@var{file}@r{]}
39553 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
39554 @itemx maint print register-groups @r{[}@var{file}@r{]}
39555 @itemx maint print remote-registers @r{[}@var{file}@r{]}
39556 Print @value{GDBN}'s internal register data structures.
39558 The command @code{maint print raw-registers} includes the contents of
39559 the raw register cache; the command @code{maint print
39560 cooked-registers} includes the (cooked) value of all registers,
39561 including registers which aren't available on the target nor visible
39562 to user; the command @code{maint print register-groups} includes the
39563 groups that each register is a member of; and the command @code{maint
39564 print remote-registers} includes the remote target's register numbers
39565 and offsets in the `G' packets.
39567 These commands take an optional parameter, a file name to which to
39568 write the information.
39570 @kindex maint print reggroups
39571 @item maint print reggroups @r{[}@var{file}@r{]}
39572 Print @value{GDBN}'s internal register group data structures. The
39573 optional argument @var{file} tells to what file to write the
39576 The register groups info looks like this:
39579 (@value{GDBP}) @kbd{maint print reggroups}
39590 @kindex maint flush register-cache
39592 @cindex register cache, flushing
39593 @item maint flush register-cache
39595 Flush the contents of the register cache and as a consequence the
39596 frame cache. This command is useful when debugging issues related to
39597 register fetching, or frame unwinding. The command @code{flushregs}
39598 is deprecated in favor of @code{maint flush register-cache}.
39600 @kindex maint flush source-cache
39601 @cindex source code, caching
39602 @item maint flush source-cache
39603 Flush @value{GDBN}'s cache of source code file contents. After
39604 @value{GDBN} reads a source file, and optionally applies styling
39605 (@pxref{Output Styling}), the file contents are cached. This command
39606 clears that cache. The next time @value{GDBN} wants to show lines
39607 from a source file, the content will be re-read.
39609 This command is useful when debugging issues related to source code
39610 styling. After flushing the cache any source code displayed by
39611 @value{GDBN} will be re-read and re-styled.
39613 @kindex maint print objfiles
39614 @cindex info for known object files
39615 @item maint print objfiles @r{[}@var{regexp}@r{]}
39616 Print a dump of all known object files.
39617 If @var{regexp} is specified, only print object files whose names
39618 match @var{regexp}. For each object file, this command prints its name,
39619 address in memory, and all of its psymtabs and symtabs.
39621 @kindex maint print user-registers
39622 @cindex user registers
39623 @item maint print user-registers
39624 List all currently available @dfn{user registers}. User registers
39625 typically provide alternate names for actual hardware registers. They
39626 include the four ``standard'' registers @code{$fp}, @code{$pc},
39627 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
39628 registers can be used in expressions in the same way as the canonical
39629 register names, but only the latter are listed by the @code{info
39630 registers} and @code{maint print registers} commands.
39632 @kindex maint print section-scripts
39633 @cindex info for known .debug_gdb_scripts-loaded scripts
39634 @item maint print section-scripts [@var{regexp}]
39635 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
39636 If @var{regexp} is specified, only print scripts loaded by object files
39637 matching @var{regexp}.
39638 For each script, this command prints its name as specified in the objfile,
39639 and the full path if known.
39640 @xref{dotdebug_gdb_scripts section}.
39642 @kindex maint print statistics
39643 @cindex bcache statistics
39644 @item maint print statistics
39645 This command prints, for each object file in the program, various data
39646 about that object file followed by the byte cache (@dfn{bcache})
39647 statistics for the object file. The objfile data includes the number
39648 of minimal, partial, full, and stabs symbols, the number of types
39649 defined by the objfile, the number of as yet unexpanded psym tables,
39650 the number of line tables and string tables, and the amount of memory
39651 used by the various tables. The bcache statistics include the counts,
39652 sizes, and counts of duplicates of all and unique objects, max,
39653 average, and median entry size, total memory used and its overhead and
39654 savings, and various measures of the hash table size and chain
39657 @kindex maint print target-stack
39658 @cindex target stack description
39659 @item maint print target-stack
39660 A @dfn{target} is an interface between the debugger and a particular
39661 kind of file or process. Targets can be stacked in @dfn{strata},
39662 so that more than one target can potentially respond to a request.
39663 In particular, memory accesses will walk down the stack of targets
39664 until they find a target that is interested in handling that particular
39667 This command prints a short description of each layer that was pushed on
39668 the @dfn{target stack}, starting from the top layer down to the bottom one.
39670 @kindex maint print type
39671 @cindex type chain of a data type
39672 @item maint print type @var{expr}
39673 Print the type chain for a type specified by @var{expr}. The argument
39674 can be either a type name or a symbol. If it is a symbol, the type of
39675 that symbol is described. The type chain produced by this command is
39676 a recursive definition of the data type as stored in @value{GDBN}'s
39677 data structures, including its flags and contained types.
39679 @kindex maint selftest
39681 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
39682 Run any self tests that were compiled in to @value{GDBN}. This will
39683 print a message showing how many tests were run, and how many failed.
39684 If a @var{filter} is passed, only the tests with @var{filter} in their
39685 name will be ran. If @code{-verbose} is passed, the self tests can be
39688 @kindex maint set selftest verbose
39689 @kindex maint show selftest verbose
39691 @item maint set selftest verbose
39692 @item maint show selftest verbose
39693 Control whether self tests are run verbosely or not.
39695 @kindex maint info selftests
39697 @item maint info selftests
39698 List the selftests compiled in to @value{GDBN}.
39700 @kindex maint set dwarf always-disassemble
39701 @kindex maint show dwarf always-disassemble
39702 @item maint set dwarf always-disassemble
39703 @item maint show dwarf always-disassemble
39704 Control the behavior of @code{info address} when using DWARF debugging
39707 The default is @code{off}, which means that @value{GDBN} should try to
39708 describe a variable's location in an easily readable format. When
39709 @code{on}, @value{GDBN} will instead display the DWARF location
39710 expression in an assembly-like format. Note that some locations are
39711 too complex for @value{GDBN} to describe simply; in this case you will
39712 always see the disassembly form.
39714 Here is an example of the resulting disassembly:
39717 (gdb) info addr argc
39718 Symbol "argc" is a complex DWARF expression:
39722 For more information on these expressions, see
39723 @uref{http://www.dwarfstd.org/, the DWARF standard}.
39725 @kindex maint set dwarf max-cache-age
39726 @kindex maint show dwarf max-cache-age
39727 @item maint set dwarf max-cache-age
39728 @itemx maint show dwarf max-cache-age
39729 Control the DWARF compilation unit cache.
39731 @cindex DWARF compilation units cache
39732 In object files with inter-compilation-unit references, such as those
39733 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
39734 reader needs to frequently refer to previously read compilation units.
39735 This setting controls how long a compilation unit will remain in the
39736 cache if it is not referenced. A higher limit means that cached
39737 compilation units will be stored in memory longer, and more total
39738 memory will be used. Setting it to zero disables caching, which will
39739 slow down @value{GDBN} startup, but reduce memory consumption.
39741 @kindex maint set dwarf unwinders
39742 @kindex maint show dwarf unwinders
39743 @item maint set dwarf unwinders
39744 @itemx maint show dwarf unwinders
39745 Control use of the DWARF frame unwinders.
39747 @cindex DWARF frame unwinders
39748 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
39749 frame unwinders to build the backtrace. Many of these targets will
39750 also have a second mechanism for building the backtrace for use in
39751 cases where DWARF information is not available, this second mechanism
39752 is often an analysis of a function's prologue.
39754 In order to extend testing coverage of the second level stack
39755 unwinding mechanisms it is helpful to be able to disable the DWARF
39756 stack unwinders, this can be done with this switch.
39758 In normal use of @value{GDBN} disabling the DWARF unwinders is not
39759 advisable, there are cases that are better handled through DWARF than
39760 prologue analysis, and the debug experience is likely to be better
39761 with the DWARF frame unwinders enabled.
39763 If DWARF frame unwinders are not supported for a particular target
39764 architecture, then enabling this flag does not cause them to be used.
39766 @kindex maint set worker-threads
39767 @kindex maint show worker-threads
39768 @item maint set worker-threads
39769 @item maint show worker-threads
39770 Control the number of worker threads that may be used by @value{GDBN}.
39771 On capable hosts, @value{GDBN} may use multiple threads to speed up
39772 certain CPU-intensive operations, such as demangling symbol names.
39773 While the number of threads used by @value{GDBN} may vary, this
39774 command can be used to set an upper bound on this number. The default
39775 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
39776 number. Note that this only controls worker threads started by
39777 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
39780 @kindex maint set profile
39781 @kindex maint show profile
39782 @cindex profiling GDB
39783 @item maint set profile
39784 @itemx maint show profile
39785 Control profiling of @value{GDBN}.
39787 Profiling will be disabled until you use the @samp{maint set profile}
39788 command to enable it. When you enable profiling, the system will begin
39789 collecting timing and execution count data; when you disable profiling or
39790 exit @value{GDBN}, the results will be written to a log file. Remember that
39791 if you use profiling, @value{GDBN} will overwrite the profiling log file
39792 (often called @file{gmon.out}). If you have a record of important profiling
39793 data in a @file{gmon.out} file, be sure to move it to a safe location.
39795 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
39796 compiled with the @samp{-pg} compiler option.
39798 @kindex maint set show-debug-regs
39799 @kindex maint show show-debug-regs
39800 @cindex hardware debug registers
39801 @item maint set show-debug-regs
39802 @itemx maint show show-debug-regs
39803 Control whether to show variables that mirror the hardware debug
39804 registers. Use @code{on} to enable, @code{off} to disable. If
39805 enabled, the debug registers values are shown when @value{GDBN} inserts or
39806 removes a hardware breakpoint or watchpoint, and when the inferior
39807 triggers a hardware-assisted breakpoint or watchpoint.
39809 @kindex maint set show-all-tib
39810 @kindex maint show show-all-tib
39811 @item maint set show-all-tib
39812 @itemx maint show show-all-tib
39813 Control whether to show all non zero areas within a 1k block starting
39814 at thread local base, when using the @samp{info w32 thread-information-block}
39817 @kindex maint set target-async
39818 @kindex maint show target-async
39819 @item maint set target-async
39820 @itemx maint show target-async
39821 This controls whether @value{GDBN} targets operate in synchronous or
39822 asynchronous mode (@pxref{Background Execution}). Normally the
39823 default is asynchronous, if it is available; but this can be changed
39824 to more easily debug problems occurring only in synchronous mode.
39826 @kindex maint set target-non-stop @var{mode} [on|off|auto]
39827 @kindex maint show target-non-stop
39828 @item maint set target-non-stop
39829 @itemx maint show target-non-stop
39831 This controls whether @value{GDBN} targets always operate in non-stop
39832 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
39833 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
39834 if supported by the target.
39837 @item maint set target-non-stop auto
39838 This is the default mode. @value{GDBN} controls the target in
39839 non-stop mode if the target supports it.
39841 @item maint set target-non-stop on
39842 @value{GDBN} controls the target in non-stop mode even if the target
39843 does not indicate support.
39845 @item maint set target-non-stop off
39846 @value{GDBN} does not control the target in non-stop mode even if the
39847 target supports it.
39850 @kindex maint set tui-resize-message
39851 @kindex maint show tui-resize-message
39852 @item maint set tui-resize-message
39853 @item maint show tui-resize-message
39854 Control whether @value{GDBN} displays a message each time the terminal
39855 is resized when in TUI mode. The default is @code{off}, which means
39856 that @value{GDBN} is silent during resizes. When @code{on},
39857 @value{GDBN} will display a message after a resize is completed; the
39858 message will include a number indicating how many times the terminal
39859 has been resized. This setting is intended for use by the test suite,
39860 where it would otherwise be difficult to determine when a resize and
39861 refresh has been completed.
39863 @kindex maint set per-command
39864 @kindex maint show per-command
39865 @item maint set per-command
39866 @itemx maint show per-command
39867 @cindex resources used by commands
39869 @value{GDBN} can display the resources used by each command.
39870 This is useful in debugging performance problems.
39873 @item maint set per-command space [on|off]
39874 @itemx maint show per-command space
39875 Enable or disable the printing of the memory used by GDB for each command.
39876 If enabled, @value{GDBN} will display how much memory each command
39877 took, following the command's own output.
39878 This can also be requested by invoking @value{GDBN} with the
39879 @option{--statistics} command-line switch (@pxref{Mode Options}).
39881 @item maint set per-command time [on|off]
39882 @itemx maint show per-command time
39883 Enable or disable the printing of the execution time of @value{GDBN}
39885 If enabled, @value{GDBN} will display how much time it
39886 took to execute each command, following the command's own output.
39887 Both CPU time and wallclock time are printed.
39888 Printing both is useful when trying to determine whether the cost is
39889 CPU or, e.g., disk/network latency.
39890 Note that the CPU time printed is for @value{GDBN} only, it does not include
39891 the execution time of the inferior because there's no mechanism currently
39892 to compute how much time was spent by @value{GDBN} and how much time was
39893 spent by the program been debugged.
39894 This can also be requested by invoking @value{GDBN} with the
39895 @option{--statistics} command-line switch (@pxref{Mode Options}).
39897 @item maint set per-command symtab [on|off]
39898 @itemx maint show per-command symtab
39899 Enable or disable the printing of basic symbol table statistics
39901 If enabled, @value{GDBN} will display the following information:
39905 number of symbol tables
39907 number of primary symbol tables
39909 number of blocks in the blockvector
39913 @kindex maint set check-libthread-db
39914 @kindex maint show check-libthread-db
39915 @item maint set check-libthread-db [on|off]
39916 @itemx maint show check-libthread-db
39917 Control whether @value{GDBN} should run integrity checks on inferior
39918 specific thread debugging libraries as they are loaded. The default
39919 is not to perform such checks. If any check fails @value{GDBN} will
39920 unload the library and continue searching for a suitable candidate as
39921 described in @ref{set libthread-db-search-path}. For more information
39922 about the tests, see @ref{maint check libthread-db}.
39924 @kindex maint set gnu-source-highlight enabled
39925 @kindex maint show gnu-source-highlight enabled
39926 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
39927 @itemx maint show gnu-source-highlight enabled
39928 Control whether @value{GDBN} should use the GNU Source Highlight
39929 library for applying styling to source code (@pxref{Output Styling}).
39930 This will be @samp{on} by default if the GNU Source Highlight library
39931 is available. If the GNU Source Highlight library is not available,
39932 then this will be @samp{off} by default, and attempting to change this
39933 value to @samp{on} will give an error.
39935 If the GNU Source Highlight library is not being used, then
39936 @value{GDBN} will use the Python Pygments package for source code
39937 styling, if it is available.
39939 This option is useful for debugging @value{GDBN}'s use of the Pygments
39940 library when @value{GDBN} is linked against the GNU Source Highlight
39943 @kindex maint space
39944 @cindex memory used by commands
39945 @item maint space @var{value}
39946 An alias for @code{maint set per-command space}.
39947 A non-zero value enables it, zero disables it.
39950 @cindex time of command execution
39951 @item maint time @var{value}
39952 An alias for @code{maint set per-command time}.
39953 A non-zero value enables it, zero disables it.
39955 @kindex maint translate-address
39956 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
39957 Find the symbol stored at the location specified by the address
39958 @var{addr} and an optional section name @var{section}. If found,
39959 @value{GDBN} prints the name of the closest symbol and an offset from
39960 the symbol's location to the specified address. This is similar to
39961 the @code{info address} command (@pxref{Symbols}), except that this
39962 command also allows to find symbols in other sections.
39964 If section was not specified, the section in which the symbol was found
39965 is also printed. For dynamically linked executables, the name of
39966 executable or shared library containing the symbol is printed as well.
39968 @kindex maint test-options
39969 @item maint test-options require-delimiter
39970 @itemx maint test-options unknown-is-error
39971 @itemx maint test-options unknown-is-operand
39972 These commands are used by the testsuite to validate the command
39973 options framework. The @code{require-delimiter} variant requires a
39974 double-dash delimiter to indicate end of options. The
39975 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
39976 @code{unknown-is-error} variant throws an error on unknown option,
39977 while @code{unknown-is-operand} treats unknown options as the start of
39978 the command's operands. When run, the commands output the result of
39979 the processed options. When completed, the commands store the
39980 internal result of completion in a variable exposed by the @code{maint
39981 show test-options-completion-result} command.
39983 @kindex maint show test-options-completion-result
39984 @item maint show test-options-completion-result
39985 Shows the result of completing the @code{maint test-options}
39986 subcommands. This is used by the testsuite to validate completion
39987 support in the command options framework.
39989 @kindex maint set test-settings
39990 @kindex maint show test-settings
39991 @item maint set test-settings @var{kind}
39992 @itemx maint show test-settings @var{kind}
39993 These are representative commands for each @var{kind} of setting type
39994 @value{GDBN} supports. They are used by the testsuite for exercising
39995 the settings infrastructure.
39997 @kindex maint set backtrace-on-fatal-signal
39998 @kindex maint show backtrace-on-fatal-signal
39999 @item maint set backtrace-on-fatal-signal [on|off]
40000 @itemx maint show backtrace-on-fatal-signal
40001 When this setting is @code{on}, if @value{GDBN} itself terminates with
40002 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40003 printed to the standard error stream. This backtrace can be used to
40004 help diagnose crashes within @value{GDBN} in situations where a user
40005 is unable to share a corefile with the @value{GDBN} developers.
40007 If the functionality to provide this backtrace is not available for
40008 the platform on which GDB is running then this feature will be
40009 @code{off} by default, and attempting to turn this feature on will
40012 For platforms that do support creating the backtrace this feature is
40013 @code{on} by default.
40016 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40017 Like the @code{with} command, but works with @code{maintenance set}
40018 variables. This is used by the testsuite to exercise the @code{with}
40019 command's infrastructure.
40023 The following command is useful for non-interactive invocations of
40024 @value{GDBN}, such as in the test suite.
40027 @item set watchdog @var{nsec}
40028 @kindex set watchdog
40029 @cindex watchdog timer
40030 @cindex timeout for commands
40031 Set the maximum number of seconds @value{GDBN} will wait for the
40032 target operation to finish. If this time expires, @value{GDBN}
40033 reports and error and the command is aborted.
40035 @item show watchdog
40036 Show the current setting of the target wait timeout.
40039 @node Remote Protocol
40040 @appendix @value{GDBN} Remote Serial Protocol
40045 * Stop Reply Packets::
40046 * General Query Packets::
40047 * Architecture-Specific Protocol Details::
40048 * Tracepoint Packets::
40049 * Host I/O Packets::
40051 * Notification Packets::
40052 * Remote Non-Stop::
40053 * Packet Acknowledgment::
40055 * File-I/O Remote Protocol Extension::
40056 * Library List Format::
40057 * Library List Format for SVR4 Targets::
40058 * Memory Map Format::
40059 * Thread List Format::
40060 * Traceframe Info Format::
40061 * Branch Trace Format::
40062 * Branch Trace Configuration Format::
40068 There may be occasions when you need to know something about the
40069 protocol---for example, if there is only one serial port to your target
40070 machine, you might want your program to do something special if it
40071 recognizes a packet meant for @value{GDBN}.
40073 In the examples below, @samp{->} and @samp{<-} are used to indicate
40074 transmitted and received data, respectively.
40076 @cindex protocol, @value{GDBN} remote serial
40077 @cindex serial protocol, @value{GDBN} remote
40078 @cindex remote serial protocol
40079 All @value{GDBN} commands and responses (other than acknowledgments
40080 and notifications, see @ref{Notification Packets}) are sent as a
40081 @var{packet}. A @var{packet} is introduced with the character
40082 @samp{$}, the actual @var{packet-data}, and the terminating character
40083 @samp{#} followed by a two-digit @var{checksum}:
40086 @code{$}@var{packet-data}@code{#}@var{checksum}
40090 @cindex checksum, for @value{GDBN} remote
40092 The two-digit @var{checksum} is computed as the modulo 256 sum of all
40093 characters between the leading @samp{$} and the trailing @samp{#} (an
40094 eight bit unsigned checksum).
40096 Implementors should note that prior to @value{GDBN} 5.0 the protocol
40097 specification also included an optional two-digit @var{sequence-id}:
40100 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
40103 @cindex sequence-id, for @value{GDBN} remote
40105 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
40106 has never output @var{sequence-id}s. Stubs that handle packets added
40107 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
40109 When either the host or the target machine receives a packet, the first
40110 response expected is an acknowledgment: either @samp{+} (to indicate
40111 the package was received correctly) or @samp{-} (to request
40115 -> @code{$}@var{packet-data}@code{#}@var{checksum}
40120 The @samp{+}/@samp{-} acknowledgments can be disabled
40121 once a connection is established.
40122 @xref{Packet Acknowledgment}, for details.
40124 The host (@value{GDBN}) sends @var{command}s, and the target (the
40125 debugging stub incorporated in your program) sends a @var{response}. In
40126 the case of step and continue @var{command}s, the response is only sent
40127 when the operation has completed, and the target has again stopped all
40128 threads in all attached processes. This is the default all-stop mode
40129 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
40130 execution mode; see @ref{Remote Non-Stop}, for details.
40132 @var{packet-data} consists of a sequence of characters with the
40133 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
40136 @cindex remote protocol, field separator
40137 Fields within the packet should be separated using @samp{,} @samp{;} or
40138 @samp{:}. Except where otherwise noted all numbers are represented in
40139 @sc{hex} with leading zeros suppressed.
40141 Implementors should note that prior to @value{GDBN} 5.0, the character
40142 @samp{:} could not appear as the third character in a packet (as it
40143 would potentially conflict with the @var{sequence-id}).
40145 @cindex remote protocol, binary data
40146 @anchor{Binary Data}
40147 Binary data in most packets is encoded either as two hexadecimal
40148 digits per byte of binary data. This allowed the traditional remote
40149 protocol to work over connections which were only seven-bit clean.
40150 Some packets designed more recently assume an eight-bit clean
40151 connection, and use a more efficient encoding to send and receive
40154 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
40155 as an escape character. Any escaped byte is transmitted as the escape
40156 character followed by the original character XORed with @code{0x20}.
40157 For example, the byte @code{0x7d} would be transmitted as the two
40158 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
40159 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
40160 @samp{@}}) must always be escaped. Responses sent by the stub
40161 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
40162 is not interpreted as the start of a run-length encoded sequence
40165 Response @var{data} can be run-length encoded to save space.
40166 Run-length encoding replaces runs of identical characters with one
40167 instance of the repeated character, followed by a @samp{*} and a
40168 repeat count. The repeat count is itself sent encoded, to avoid
40169 binary characters in @var{data}: a value of @var{n} is sent as
40170 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40171 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40172 code 32) for a repeat count of 3. (This is because run-length
40173 encoding starts to win for counts 3 or more.) Thus, for example,
40174 @samp{0* } is a run-length encoding of ``0000'': the space character
40175 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40178 The printable characters @samp{#} and @samp{$} or with a numeric value
40179 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40180 seven repeats (@samp{$}) can be expanded using a repeat count of only
40181 five (@samp{"}). For example, @samp{00000000} can be encoded as
40184 The error response returned for some packets includes a two character
40185 error number. That number is not well defined.
40187 @cindex empty response, for unsupported packets
40188 For any @var{command} not supported by the stub, an empty response
40189 (@samp{$#00}) should be returned. That way it is possible to extend the
40190 protocol. A newer @value{GDBN} can tell if a packet is supported based
40193 At a minimum, a stub is required to support the @samp{?} command to
40194 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40195 commands for register access, and the @samp{m} and @samp{M} commands
40196 for memory access. Stubs that only control single-threaded targets
40197 can implement run control with the @samp{c} (continue) command, and if
40198 the target architecture supports hardware-assisted single-stepping,
40199 the @samp{s} (step) command. Stubs that support multi-threading
40200 targets should support the @samp{vCont} command. All other commands
40206 The following table provides a complete list of all currently defined
40207 @var{command}s and their corresponding response @var{data}.
40208 @xref{File-I/O Remote Protocol Extension}, for details about the File
40209 I/O extension of the remote protocol.
40211 Each packet's description has a template showing the packet's overall
40212 syntax, followed by an explanation of the packet's meaning. We
40213 include spaces in some of the templates for clarity; these are not
40214 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40215 separate its components. For example, a template like @samp{foo
40216 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40217 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40218 @var{baz}. @value{GDBN} does not transmit a space character between the
40219 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40222 @cindex @var{thread-id}, in remote protocol
40223 @anchor{thread-id syntax}
40224 Several packets and replies include a @var{thread-id} field to identify
40225 a thread. Normally these are positive numbers with a target-specific
40226 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40227 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40230 In addition, the remote protocol supports a multiprocess feature in
40231 which the @var{thread-id} syntax is extended to optionally include both
40232 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40233 The @var{pid} (process) and @var{tid} (thread) components each have the
40234 format described above: a positive number with target-specific
40235 interpretation formatted as a big-endian hex string, literal @samp{-1}
40236 to indicate all processes or threads (respectively), or @samp{0} to
40237 indicate an arbitrary process or thread. Specifying just a process, as
40238 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40239 error to specify all processes but a specific thread, such as
40240 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40241 for those packets and replies explicitly documented to include a process
40242 ID, rather than a @var{thread-id}.
40244 The multiprocess @var{thread-id} syntax extensions are only used if both
40245 @value{GDBN} and the stub report support for the @samp{multiprocess}
40246 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40249 Note that all packet forms beginning with an upper- or lower-case
40250 letter, other than those described here, are reserved for future use.
40252 Here are the packet descriptions.
40257 @cindex @samp{!} packet
40258 @anchor{extended mode}
40259 Enable extended mode. In extended mode, the remote server is made
40260 persistent. The @samp{R} packet is used to restart the program being
40266 The remote target both supports and has enabled extended mode.
40270 @cindex @samp{?} packet
40272 This is sent when connection is first established to query the reason
40273 the target halted. The reply is the same as for step and continue.
40274 This packet has a special interpretation when the target is in
40275 non-stop mode; see @ref{Remote Non-Stop}.
40278 @xref{Stop Reply Packets}, for the reply specifications.
40280 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40281 @cindex @samp{A} packet
40282 Initialized @code{argv[]} array passed into program. @var{arglen}
40283 specifies the number of bytes in the hex encoded byte stream
40284 @var{arg}. See @code{gdbserver} for more details.
40289 The arguments were set.
40295 @cindex @samp{b} packet
40296 (Don't use this packet; its behavior is not well-defined.)
40297 Change the serial line speed to @var{baud}.
40299 JTC: @emph{When does the transport layer state change? When it's
40300 received, or after the ACK is transmitted. In either case, there are
40301 problems if the command or the acknowledgment packet is dropped.}
40303 Stan: @emph{If people really wanted to add something like this, and get
40304 it working for the first time, they ought to modify ser-unix.c to send
40305 some kind of out-of-band message to a specially-setup stub and have the
40306 switch happen "in between" packets, so that from remote protocol's point
40307 of view, nothing actually happened.}
40309 @item B @var{addr},@var{mode}
40310 @cindex @samp{B} packet
40311 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
40312 breakpoint at @var{addr}.
40314 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
40315 (@pxref{insert breakpoint or watchpoint packet}).
40317 @cindex @samp{bc} packet
40320 Backward continue. Execute the target system in reverse. No parameter.
40321 @xref{Reverse Execution}, for more information.
40324 @xref{Stop Reply Packets}, for the reply specifications.
40326 @cindex @samp{bs} packet
40329 Backward single step. Execute one instruction in reverse. No parameter.
40330 @xref{Reverse Execution}, for more information.
40333 @xref{Stop Reply Packets}, for the reply specifications.
40335 @item c @r{[}@var{addr}@r{]}
40336 @cindex @samp{c} packet
40337 Continue at @var{addr}, which is the address to resume. If @var{addr}
40338 is omitted, resume at current address.
40340 This packet is deprecated for multi-threading support. @xref{vCont
40344 @xref{Stop Reply Packets}, for the reply specifications.
40346 @item C @var{sig}@r{[};@var{addr}@r{]}
40347 @cindex @samp{C} packet
40348 Continue with signal @var{sig} (hex signal number). If
40349 @samp{;@var{addr}} is omitted, resume at same address.
40351 This packet is deprecated for multi-threading support. @xref{vCont
40355 @xref{Stop Reply Packets}, for the reply specifications.
40358 @cindex @samp{d} packet
40361 Don't use this packet; instead, define a general set packet
40362 (@pxref{General Query Packets}).
40366 @cindex @samp{D} packet
40367 The first form of the packet is used to detach @value{GDBN} from the
40368 remote system. It is sent to the remote target
40369 before @value{GDBN} disconnects via the @code{detach} command.
40371 The second form, including a process ID, is used when multiprocess
40372 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40373 detach only a specific process. The @var{pid} is specified as a
40374 big-endian hex string.
40384 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40385 @cindex @samp{F} packet
40386 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40387 This is part of the File-I/O protocol extension. @xref{File-I/O
40388 Remote Protocol Extension}, for the specification.
40391 @anchor{read registers packet}
40392 @cindex @samp{g} packet
40393 Read general registers.
40397 @item @var{XX@dots{}}
40398 Each byte of register data is described by two hex digits. The bytes
40399 with the register are transmitted in target byte order. The size of
40400 each register and their position within the @samp{g} packet are
40401 determined by the @value{GDBN} internal gdbarch functions
40402 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40404 When reading registers from a trace frame (@pxref{Analyze Collected
40405 Data,,Using the Collected Data}), the stub may also return a string of
40406 literal @samp{x}'s in place of the register data digits, to indicate
40407 that the corresponding register has not been collected, thus its value
40408 is unavailable. For example, for an architecture with 4 registers of
40409 4 bytes each, the following reply indicates to @value{GDBN} that
40410 registers 0 and 2 have not been collected, while registers 1 and 3
40411 have been collected, and both have zero value:
40415 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
40422 @item G @var{XX@dots{}}
40423 @cindex @samp{G} packet
40424 Write general registers. @xref{read registers packet}, for a
40425 description of the @var{XX@dots{}} data.
40435 @item H @var{op} @var{thread-id}
40436 @cindex @samp{H} packet
40437 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
40438 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
40439 should be @samp{c} for step and continue operations (note that this
40440 is deprecated, supporting the @samp{vCont} command is a better
40441 option), and @samp{g} for other operations. The thread designator
40442 @var{thread-id} has the format and interpretation described in
40443 @ref{thread-id syntax}.
40454 @c 'H': How restrictive (or permissive) is the thread model. If a
40455 @c thread is selected and stopped, are other threads allowed
40456 @c to continue to execute? As I mentioned above, I think the
40457 @c semantics of each command when a thread is selected must be
40458 @c described. For example:
40460 @c 'g': If the stub supports threads and a specific thread is
40461 @c selected, returns the register block from that thread;
40462 @c otherwise returns current registers.
40464 @c 'G' If the stub supports threads and a specific thread is
40465 @c selected, sets the registers of the register block of
40466 @c that thread; otherwise sets current registers.
40468 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
40469 @anchor{cycle step packet}
40470 @cindex @samp{i} packet
40471 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
40472 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
40473 step starting at that address.
40476 @cindex @samp{I} packet
40477 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
40481 @cindex @samp{k} packet
40484 The exact effect of this packet is not specified.
40486 For a bare-metal target, it may power cycle or reset the target
40487 system. For that reason, the @samp{k} packet has no reply.
40489 For a single-process target, it may kill that process if possible.
40491 A multiple-process target may choose to kill just one process, or all
40492 that are under @value{GDBN}'s control. For more precise control, use
40493 the vKill packet (@pxref{vKill packet}).
40495 If the target system immediately closes the connection in response to
40496 @samp{k}, @value{GDBN} does not consider the lack of packet
40497 acknowledgment to be an error, and assumes the kill was successful.
40499 If connected using @kbd{target extended-remote}, and the target does
40500 not close the connection in response to a kill request, @value{GDBN}
40501 probes the target state as if a new connection was opened
40502 (@pxref{? packet}).
40504 @item m @var{addr},@var{length}
40505 @cindex @samp{m} packet
40506 Read @var{length} addressable memory units starting at address @var{addr}
40507 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
40508 any particular boundary.
40510 The stub need not use any particular size or alignment when gathering
40511 data from memory for the response; even if @var{addr} is word-aligned
40512 and @var{length} is a multiple of the word size, the stub is free to
40513 use byte accesses, or not. For this reason, this packet may not be
40514 suitable for accessing memory-mapped I/O devices.
40515 @cindex alignment of remote memory accesses
40516 @cindex size of remote memory accesses
40517 @cindex memory, alignment and size of remote accesses
40521 @item @var{XX@dots{}}
40522 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
40523 The reply may contain fewer addressable memory units than requested if the
40524 server was able to read only part of the region of memory.
40529 @item M @var{addr},@var{length}:@var{XX@dots{}}
40530 @cindex @samp{M} packet
40531 Write @var{length} addressable memory units starting at address @var{addr}
40532 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
40533 byte is transmitted as a two-digit hexadecimal number.
40540 for an error (this includes the case where only part of the data was
40545 @cindex @samp{p} packet
40546 Read the value of register @var{n}; @var{n} is in hex.
40547 @xref{read registers packet}, for a description of how the returned
40548 register value is encoded.
40552 @item @var{XX@dots{}}
40553 the register's value
40557 Indicating an unrecognized @var{query}.
40560 @item P @var{n@dots{}}=@var{r@dots{}}
40561 @anchor{write register packet}
40562 @cindex @samp{P} packet
40563 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
40564 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
40565 digits for each byte in the register (target byte order).
40575 @item q @var{name} @var{params}@dots{}
40576 @itemx Q @var{name} @var{params}@dots{}
40577 @cindex @samp{q} packet
40578 @cindex @samp{Q} packet
40579 General query (@samp{q}) and set (@samp{Q}). These packets are
40580 described fully in @ref{General Query Packets}.
40583 @cindex @samp{r} packet
40584 Reset the entire system.
40586 Don't use this packet; use the @samp{R} packet instead.
40589 @cindex @samp{R} packet
40590 Restart the program being debugged. The @var{XX}, while needed, is ignored.
40591 This packet is only available in extended mode (@pxref{extended mode}).
40593 The @samp{R} packet has no reply.
40595 @item s @r{[}@var{addr}@r{]}
40596 @cindex @samp{s} packet
40597 Single step, resuming at @var{addr}. If
40598 @var{addr} is omitted, resume at same address.
40600 This packet is deprecated for multi-threading support. @xref{vCont
40604 @xref{Stop Reply Packets}, for the reply specifications.
40606 @item S @var{sig}@r{[};@var{addr}@r{]}
40607 @anchor{step with signal packet}
40608 @cindex @samp{S} packet
40609 Step with signal. This is analogous to the @samp{C} packet, but
40610 requests a single-step, rather than a normal resumption of execution.
40612 This packet is deprecated for multi-threading support. @xref{vCont
40616 @xref{Stop Reply Packets}, for the reply specifications.
40618 @item t @var{addr}:@var{PP},@var{MM}
40619 @cindex @samp{t} packet
40620 Search backwards starting at address @var{addr} for a match with pattern
40621 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
40622 There must be at least 3 digits in @var{addr}.
40624 @item T @var{thread-id}
40625 @cindex @samp{T} packet
40626 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
40631 thread is still alive
40637 Packets starting with @samp{v} are identified by a multi-letter name,
40638 up to the first @samp{;} or @samp{?} (or the end of the packet).
40640 @item vAttach;@var{pid}
40641 @cindex @samp{vAttach} packet
40642 Attach to a new process with the specified process ID @var{pid}.
40643 The process ID is a
40644 hexadecimal integer identifying the process. In all-stop mode, all
40645 threads in the attached process are stopped; in non-stop mode, it may be
40646 attached without being stopped if that is supported by the target.
40648 @c In non-stop mode, on a successful vAttach, the stub should set the
40649 @c current thread to a thread of the newly-attached process. After
40650 @c attaching, GDB queries for the attached process's thread ID with qC.
40651 @c Also note that, from a user perspective, whether or not the
40652 @c target is stopped on attach in non-stop mode depends on whether you
40653 @c use the foreground or background version of the attach command, not
40654 @c on what vAttach does; GDB does the right thing with respect to either
40655 @c stopping or restarting threads.
40657 This packet is only available in extended mode (@pxref{extended mode}).
40663 @item @r{Any stop packet}
40664 for success in all-stop mode (@pxref{Stop Reply Packets})
40666 for success in non-stop mode (@pxref{Remote Non-Stop})
40669 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
40670 @cindex @samp{vCont} packet
40671 @anchor{vCont packet}
40672 Resume the inferior, specifying different actions for each thread.
40674 For each inferior thread, the leftmost action with a matching
40675 @var{thread-id} is applied. Threads that don't match any action
40676 remain in their current state. Thread IDs are specified using the
40677 syntax described in @ref{thread-id syntax}. If multiprocess
40678 extensions (@pxref{multiprocess extensions}) are supported, actions
40679 can be specified to match all threads in a process by using the
40680 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
40681 @var{thread-id} matches all threads. Specifying no actions is an
40684 Currently supported actions are:
40690 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
40694 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
40697 @item r @var{start},@var{end}
40698 Step once, and then keep stepping as long as the thread stops at
40699 addresses between @var{start} (inclusive) and @var{end} (exclusive).
40700 The remote stub reports a stop reply when either the thread goes out
40701 of the range or is stopped due to an unrelated reason, such as hitting
40702 a breakpoint. @xref{range stepping}.
40704 If the range is empty (@var{start} == @var{end}), then the action
40705 becomes equivalent to the @samp{s} action. In other words,
40706 single-step once, and report the stop (even if the stepped instruction
40707 jumps to @var{start}).
40709 (A stop reply may be sent at any point even if the PC is still within
40710 the stepping range; for example, it is valid to implement this packet
40711 in a degenerate way as a single instruction step operation.)
40715 The optional argument @var{addr} normally associated with the
40716 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
40717 not supported in @samp{vCont}.
40719 The @samp{t} action is only relevant in non-stop mode
40720 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
40721 A stop reply should be generated for any affected thread not already stopped.
40722 When a thread is stopped by means of a @samp{t} action,
40723 the corresponding stop reply should indicate that the thread has stopped with
40724 signal @samp{0}, regardless of whether the target uses some other signal
40725 as an implementation detail.
40727 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
40728 @samp{r} actions for threads that are already running. Conversely,
40729 the server must ignore @samp{t} actions for threads that are already
40732 @emph{Note:} In non-stop mode, a thread is considered running until
40733 @value{GDBN} acknowledges an asynchronous stop notification for it with
40734 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
40736 The stub must support @samp{vCont} if it reports support for
40737 multiprocess extensions (@pxref{multiprocess extensions}).
40740 @xref{Stop Reply Packets}, for the reply specifications.
40743 @cindex @samp{vCont?} packet
40744 Request a list of actions supported by the @samp{vCont} packet.
40748 @item vCont@r{[};@var{action}@dots{}@r{]}
40749 The @samp{vCont} packet is supported. Each @var{action} is a supported
40750 command in the @samp{vCont} packet.
40752 The @samp{vCont} packet is not supported.
40755 @anchor{vCtrlC packet}
40757 @cindex @samp{vCtrlC} packet
40758 Interrupt remote target as if a control-C was pressed on the remote
40759 terminal. This is the equivalent to reacting to the @code{^C}
40760 (@samp{\003}, the control-C character) character in all-stop mode
40761 while the target is running, except this works in non-stop mode.
40762 @xref{interrupting remote targets}, for more info on the all-stop
40773 @item vFile:@var{operation}:@var{parameter}@dots{}
40774 @cindex @samp{vFile} packet
40775 Perform a file operation on the target system. For details,
40776 see @ref{Host I/O Packets}.
40778 @item vFlashErase:@var{addr},@var{length}
40779 @cindex @samp{vFlashErase} packet
40780 Direct the stub to erase @var{length} bytes of flash starting at
40781 @var{addr}. The region may enclose any number of flash blocks, but
40782 its start and end must fall on block boundaries, as indicated by the
40783 flash block size appearing in the memory map (@pxref{Memory Map
40784 Format}). @value{GDBN} groups flash memory programming operations
40785 together, and sends a @samp{vFlashDone} request after each group; the
40786 stub is allowed to delay erase operation until the @samp{vFlashDone}
40787 packet is received.
40797 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
40798 @cindex @samp{vFlashWrite} packet
40799 Direct the stub to write data to flash address @var{addr}. The data
40800 is passed in binary form using the same encoding as for the @samp{X}
40801 packet (@pxref{Binary Data}). The memory ranges specified by
40802 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
40803 not overlap, and must appear in order of increasing addresses
40804 (although @samp{vFlashErase} packets for higher addresses may already
40805 have been received; the ordering is guaranteed only between
40806 @samp{vFlashWrite} packets). If a packet writes to an address that was
40807 neither erased by a preceding @samp{vFlashErase} packet nor by some other
40808 target-specific method, the results are unpredictable.
40816 for vFlashWrite addressing non-flash memory
40822 @cindex @samp{vFlashDone} packet
40823 Indicate to the stub that flash programming operation is finished.
40824 The stub is permitted to delay or batch the effects of a group of
40825 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
40826 @samp{vFlashDone} packet is received. The contents of the affected
40827 regions of flash memory are unpredictable until the @samp{vFlashDone}
40828 request is completed.
40830 @item vKill;@var{pid}
40831 @cindex @samp{vKill} packet
40832 @anchor{vKill packet}
40833 Kill the process with the specified process ID @var{pid}, which is a
40834 hexadecimal integer identifying the process. This packet is used in
40835 preference to @samp{k} when multiprocess protocol extensions are
40836 supported; see @ref{multiprocess extensions}.
40846 @item vMustReplyEmpty
40847 @cindex @samp{vMustReplyEmpty} packet
40848 The correct reply to an unknown @samp{v} packet is to return the empty
40849 string, however, some older versions of @command{gdbserver} would
40850 incorrectly return @samp{OK} for unknown @samp{v} packets.
40852 The @samp{vMustReplyEmpty} is used as a feature test to check how
40853 @command{gdbserver} handles unknown packets, it is important that this
40854 packet be handled in the same way as other unknown @samp{v} packets.
40855 If this packet is handled differently to other unknown @samp{v}
40856 packets then it is possible that @value{GDBN} may run into problems in
40857 other areas, specifically around use of @samp{vFile:setfs:}.
40859 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
40860 @cindex @samp{vRun} packet
40861 Run the program @var{filename}, passing it each @var{argument} on its
40862 command line. The file and arguments are hex-encoded strings. If
40863 @var{filename} is an empty string, the stub may use a default program
40864 (e.g.@: the last program run). The program is created in the stopped
40867 @c FIXME: What about non-stop mode?
40869 This packet is only available in extended mode (@pxref{extended mode}).
40875 @item @r{Any stop packet}
40876 for success (@pxref{Stop Reply Packets})
40880 @cindex @samp{vStopped} packet
40881 @xref{Notification Packets}.
40883 @item X @var{addr},@var{length}:@var{XX@dots{}}
40885 @cindex @samp{X} packet
40886 Write data to memory, where the data is transmitted in binary.
40887 Memory is specified by its address @var{addr} and number of addressable memory
40888 units @var{length} (@pxref{addressable memory unit});
40889 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
40899 @item z @var{type},@var{addr},@var{kind}
40900 @itemx Z @var{type},@var{addr},@var{kind}
40901 @anchor{insert breakpoint or watchpoint packet}
40902 @cindex @samp{z} packet
40903 @cindex @samp{Z} packets
40904 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
40905 watchpoint starting at address @var{address} of kind @var{kind}.
40907 Each breakpoint and watchpoint packet @var{type} is documented
40910 @emph{Implementation notes: A remote target shall return an empty string
40911 for an unrecognized breakpoint or watchpoint packet @var{type}. A
40912 remote target shall support either both or neither of a given
40913 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
40914 avoid potential problems with duplicate packets, the operations should
40915 be implemented in an idempotent way.}
40917 @item z0,@var{addr},@var{kind}
40918 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40919 @cindex @samp{z0} packet
40920 @cindex @samp{Z0} packet
40921 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
40922 @var{addr} of type @var{kind}.
40924 A software breakpoint is implemented by replacing the instruction at
40925 @var{addr} with a software breakpoint or trap instruction. The
40926 @var{kind} is target-specific and typically indicates the size of the
40927 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
40928 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
40929 architectures have additional meanings for @var{kind}
40930 (@pxref{Architecture-Specific Protocol Details}); if no
40931 architecture-specific value is being used, it should be @samp{0}.
40932 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
40933 conditional expressions in bytecode form that should be evaluated on
40934 the target's side. These are the conditions that should be taken into
40935 consideration when deciding if the breakpoint trigger should be
40936 reported back to @value{GDBN}.
40938 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
40939 for how to best report a software breakpoint event to @value{GDBN}.
40941 The @var{cond_list} parameter is comprised of a series of expressions,
40942 concatenated without separators. Each expression has the following form:
40946 @item X @var{len},@var{expr}
40947 @var{len} is the length of the bytecode expression and @var{expr} is the
40948 actual conditional expression in bytecode form.
40952 The optional @var{cmd_list} parameter introduces commands that may be
40953 run on the target, rather than being reported back to @value{GDBN}.
40954 The parameter starts with a numeric flag @var{persist}; if the flag is
40955 nonzero, then the breakpoint may remain active and the commands
40956 continue to be run even when @value{GDBN} disconnects from the target.
40957 Following this flag is a series of expressions concatenated with no
40958 separators. Each expression has the following form:
40962 @item X @var{len},@var{expr}
40963 @var{len} is the length of the bytecode expression and @var{expr} is the
40964 actual commands expression in bytecode form.
40968 @emph{Implementation note: It is possible for a target to copy or move
40969 code that contains software breakpoints (e.g., when implementing
40970 overlays). The behavior of this packet, in the presence of such a
40971 target, is not defined.}
40983 @item z1,@var{addr},@var{kind}
40984 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
40985 @cindex @samp{z1} packet
40986 @cindex @samp{Z1} packet
40987 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
40988 address @var{addr}.
40990 A hardware breakpoint is implemented using a mechanism that is not
40991 dependent on being able to modify the target's memory. The
40992 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
40993 same meaning as in @samp{Z0} packets.
40995 @emph{Implementation note: A hardware breakpoint is not affected by code
41008 @item z2,@var{addr},@var{kind}
41009 @itemx Z2,@var{addr},@var{kind}
41010 @cindex @samp{z2} packet
41011 @cindex @samp{Z2} packet
41012 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41013 The number of bytes to watch is specified by @var{kind}.
41025 @item z3,@var{addr},@var{kind}
41026 @itemx Z3,@var{addr},@var{kind}
41027 @cindex @samp{z3} packet
41028 @cindex @samp{Z3} packet
41029 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41030 The number of bytes to watch is specified by @var{kind}.
41042 @item z4,@var{addr},@var{kind}
41043 @itemx Z4,@var{addr},@var{kind}
41044 @cindex @samp{z4} packet
41045 @cindex @samp{Z4} packet
41046 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41047 The number of bytes to watch is specified by @var{kind}.
41061 @node Stop Reply Packets
41062 @section Stop Reply Packets
41063 @cindex stop reply packets
41065 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41066 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41067 receive any of the below as a reply. Except for @samp{?}
41068 and @samp{vStopped}, that reply is only returned
41069 when the target halts. In the below the exact meaning of @dfn{signal
41070 number} is defined by the header @file{include/gdb/signals.h} in the
41071 @value{GDBN} source code.
41073 In non-stop mode, the server will simply reply @samp{OK} to commands
41074 such as @samp{vCont}; any stop will be the subject of a future
41075 notification. @xref{Remote Non-Stop}.
41077 As in the description of request packets, we include spaces in the
41078 reply templates for clarity; these are not part of the reply packet's
41079 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41085 The program received signal number @var{AA} (a two-digit hexadecimal
41086 number). This is equivalent to a @samp{T} response with no
41087 @var{n}:@var{r} pairs.
41089 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
41090 @cindex @samp{T} packet reply
41091 The program received signal number @var{AA} (a two-digit hexadecimal
41092 number). This is equivalent to an @samp{S} response, except that the
41093 @samp{@var{n}:@var{r}} pairs can carry values of important registers
41094 and other information directly in the stop reply packet, reducing
41095 round-trip latency. Single-step and breakpoint traps are reported
41096 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
41100 If @var{n} is a hexadecimal number, it is a register number, and the
41101 corresponding @var{r} gives that register's value. The data @var{r} is a
41102 series of bytes in target byte order, with each byte given by a
41103 two-digit hex number.
41106 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
41107 the stopped thread, as specified in @ref{thread-id syntax}.
41110 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
41111 the core on which the stop event was detected.
41114 If @var{n} is a recognized @dfn{stop reason}, it describes a more
41115 specific event that stopped the target. The currently defined stop
41116 reasons are listed below. The @var{aa} should be @samp{05}, the trap
41117 signal. At most one stop reason should be present.
41120 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
41121 and go on to the next; this allows us to extend the protocol in the
41125 The currently defined stop reasons are:
41131 The packet indicates a watchpoint hit, and @var{r} is the data address, in
41134 @item syscall_entry
41135 @itemx syscall_return
41136 The packet indicates a syscall entry or return, and @var{r} is the
41137 syscall number, in hex.
41139 @cindex shared library events, remote reply
41141 The packet indicates that the loaded libraries have changed.
41142 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
41143 list of loaded libraries. The @var{r} part is ignored.
41145 @cindex replay log events, remote reply
41147 The packet indicates that the target cannot continue replaying
41148 logged execution events, because it has reached the end (or the
41149 beginning when executing backward) of the log. The value of @var{r}
41150 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
41151 for more information.
41154 @anchor{swbreak stop reason}
41155 The packet indicates a software breakpoint instruction was executed,
41156 irrespective of whether it was @value{GDBN} that planted the
41157 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
41158 part must be left empty.
41160 On some architectures, such as x86, at the architecture level, when a
41161 breakpoint instruction executes the program counter points at the
41162 breakpoint address plus an offset. On such targets, the stub is
41163 responsible for adjusting the PC to point back at the breakpoint
41166 This packet should not be sent by default; older @value{GDBN} versions
41167 did not support it. @value{GDBN} requests it, by supplying an
41168 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41169 remote stub must also supply the appropriate @samp{qSupported} feature
41170 indicating support.
41172 This packet is required for correct non-stop mode operation.
41175 The packet indicates the target stopped for a hardware breakpoint.
41176 The @var{r} part must be left empty.
41178 The same remarks about @samp{qSupported} and non-stop mode above
41181 @cindex fork events, remote reply
41183 The packet indicates that @code{fork} was called, and @var{r}
41184 is the thread ID of the new child process. Refer to
41185 @ref{thread-id syntax} for the format of the @var{thread-id}
41186 field. This packet is only applicable to targets that support
41189 This packet should not be sent by default; older @value{GDBN} versions
41190 did not support it. @value{GDBN} requests it, by supplying an
41191 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41192 remote stub must also supply the appropriate @samp{qSupported} feature
41193 indicating support.
41195 @cindex vfork events, remote reply
41197 The packet indicates that @code{vfork} was called, and @var{r}
41198 is the thread ID of the new child process. Refer to
41199 @ref{thread-id syntax} for the format of the @var{thread-id}
41200 field. This packet is only applicable to targets that support
41203 This packet should not be sent by default; older @value{GDBN} versions
41204 did not support it. @value{GDBN} requests it, by supplying an
41205 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41206 remote stub must also supply the appropriate @samp{qSupported} feature
41207 indicating support.
41209 @cindex vforkdone events, remote reply
41211 The packet indicates that a child process created by a vfork
41212 has either called @code{exec} or terminated, so that the
41213 address spaces of the parent and child process are no longer
41214 shared. The @var{r} part is ignored. This packet is only
41215 applicable to targets that support vforkdone events.
41217 This packet should not be sent by default; older @value{GDBN} versions
41218 did not support it. @value{GDBN} requests it, by supplying an
41219 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41220 remote stub must also supply the appropriate @samp{qSupported} feature
41221 indicating support.
41223 @cindex exec events, remote reply
41225 The packet indicates that @code{execve} was called, and @var{r}
41226 is the absolute pathname of the file that was executed, in hex.
41227 This packet is only applicable to targets that support exec events.
41229 This packet should not be sent by default; older @value{GDBN} versions
41230 did not support it. @value{GDBN} requests it, by supplying an
41231 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41232 remote stub must also supply the appropriate @samp{qSupported} feature
41233 indicating support.
41235 @cindex thread create event, remote reply
41236 @anchor{thread create event}
41238 The packet indicates that the thread was just created. The new thread
41239 is stopped until @value{GDBN} sets it running with a resumption packet
41240 (@pxref{vCont packet}). This packet should not be sent by default;
41241 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41242 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41243 @var{r} part is ignored.
41248 @itemx W @var{AA} ; process:@var{pid}
41249 The process exited, and @var{AA} is the exit status. This is only
41250 applicable to certain targets.
41252 The second form of the response, including the process ID of the
41253 exited process, can be used only when @value{GDBN} has reported
41254 support for multiprocess protocol extensions; see @ref{multiprocess
41255 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41259 @itemx X @var{AA} ; process:@var{pid}
41260 The process terminated with signal @var{AA}.
41262 The second form of the response, including the process ID of the
41263 terminated process, can be used only when @value{GDBN} has reported
41264 support for multiprocess protocol extensions; see @ref{multiprocess
41265 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41268 @anchor{thread exit event}
41269 @cindex thread exit event, remote reply
41270 @item w @var{AA} ; @var{tid}
41272 The thread exited, and @var{AA} is the exit status. This response
41273 should not be sent by default; @value{GDBN} requests it with the
41274 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41275 @var{AA} is formatted as a big-endian hex string.
41278 There are no resumed threads left in the target. In other words, even
41279 though the process is alive, the last resumed thread has exited. For
41280 example, say the target process has two threads: thread 1 and thread
41281 2. The client leaves thread 1 stopped, and resumes thread 2, which
41282 subsequently exits. At this point, even though the process is still
41283 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41284 executing either. The @samp{N} stop reply thus informs the client
41285 that it can stop waiting for stop replies. This packet should not be
41286 sent by default; older @value{GDBN} versions did not support it.
41287 @value{GDBN} requests it, by supplying an appropriate
41288 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41289 also supply the appropriate @samp{qSupported} feature indicating
41292 @item O @var{XX}@dots{}
41293 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41294 written as the program's console output. This can happen at any time
41295 while the program is running and the debugger should continue to wait
41296 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41298 @item F @var{call-id},@var{parameter}@dots{}
41299 @var{call-id} is the identifier which says which host system call should
41300 be called. This is just the name of the function. Translation into the
41301 correct system call is only applicable as it's defined in @value{GDBN}.
41302 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
41305 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
41306 this very system call.
41308 The target replies with this packet when it expects @value{GDBN} to
41309 call a host system call on behalf of the target. @value{GDBN} replies
41310 with an appropriate @samp{F} packet and keeps up waiting for the next
41311 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
41312 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
41313 Protocol Extension}, for more details.
41317 @node General Query Packets
41318 @section General Query Packets
41319 @cindex remote query requests
41321 Packets starting with @samp{q} are @dfn{general query packets};
41322 packets starting with @samp{Q} are @dfn{general set packets}. General
41323 query and set packets are a semi-unified form for retrieving and
41324 sending information to and from the stub.
41326 The initial letter of a query or set packet is followed by a name
41327 indicating what sort of thing the packet applies to. For example,
41328 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
41329 definitions with the stub. These packet names follow some
41334 The name must not contain commas, colons or semicolons.
41336 Most @value{GDBN} query and set packets have a leading upper case
41339 The names of custom vendor packets should use a company prefix, in
41340 lower case, followed by a period. For example, packets designed at
41341 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41342 foos) or @samp{Qacme.bar} (for setting bars).
41345 The name of a query or set packet should be separated from any
41346 parameters by a @samp{:}; the parameters themselves should be
41347 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41348 full packet name, and check for a separator or the end of the packet,
41349 in case two packet names share a common prefix. New packets should not begin
41350 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41351 packets predate these conventions, and have arguments without any terminator
41352 for the packet name; we suspect they are in widespread use in places that
41353 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41354 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41357 Like the descriptions of the other packets, each description here
41358 has a template showing the packet's overall syntax, followed by an
41359 explanation of the packet's meaning. We include spaces in some of the
41360 templates for clarity; these are not part of the packet's syntax. No
41361 @value{GDBN} packet uses spaces to separate its components.
41363 Here are the currently defined query and set packets:
41369 Turn on or off the agent as a helper to perform some debugging operations
41370 delegated from @value{GDBN} (@pxref{Control Agent}).
41372 @item QAllow:@var{op}:@var{val}@dots{}
41373 @cindex @samp{QAllow} packet
41374 Specify which operations @value{GDBN} expects to request of the
41375 target, as a semicolon-separated list of operation name and value
41376 pairs. Possible values for @var{op} include @samp{WriteReg},
41377 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41378 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41379 indicating that @value{GDBN} will not request the operation, or 1,
41380 indicating that it may. (The target can then use this to set up its
41381 own internals optimally, for instance if the debugger never expects to
41382 insert breakpoints, it may not need to install its own trap handler.)
41385 @cindex current thread, remote request
41386 @cindex @samp{qC} packet
41387 Return the current thread ID.
41391 @item QC @var{thread-id}
41392 Where @var{thread-id} is a thread ID as documented in
41393 @ref{thread-id syntax}.
41394 @item @r{(anything else)}
41395 Any other reply implies the old thread ID.
41398 @item qCRC:@var{addr},@var{length}
41399 @cindex CRC of memory block, remote request
41400 @cindex @samp{qCRC} packet
41401 @anchor{qCRC packet}
41402 Compute the CRC checksum of a block of memory using CRC-32 defined in
41403 IEEE 802.3. The CRC is computed byte at a time, taking the most
41404 significant bit of each byte first. The initial pattern code
41405 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41407 @emph{Note:} This is the same CRC used in validating separate debug
41408 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41409 Files}). However the algorithm is slightly different. When validating
41410 separate debug files, the CRC is computed taking the @emph{least}
41411 significant bit of each byte first, and the final result is inverted to
41412 detect trailing zeros.
41417 An error (such as memory fault)
41418 @item C @var{crc32}
41419 The specified memory region's checksum is @var{crc32}.
41422 @item QDisableRandomization:@var{value}
41423 @cindex disable address space randomization, remote request
41424 @cindex @samp{QDisableRandomization} packet
41425 Some target operating systems will randomize the virtual address space
41426 of the inferior process as a security feature, but provide a feature
41427 to disable such randomization, e.g.@: to allow for a more deterministic
41428 debugging experience. On such systems, this packet with a @var{value}
41429 of 1 directs the target to disable address space randomization for
41430 processes subsequently started via @samp{vRun} packets, while a packet
41431 with a @var{value} of 0 tells the target to enable address space
41434 This packet is only available in extended mode (@pxref{extended mode}).
41439 The request succeeded.
41442 An error occurred. The error number @var{nn} is given as hex digits.
41445 An empty reply indicates that @samp{QDisableRandomization} is not supported
41449 This packet is not probed by default; the remote stub must request it,
41450 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41451 This should only be done on targets that actually support disabling
41452 address space randomization.
41454 @item QStartupWithShell:@var{value}
41455 @cindex startup with shell, remote request
41456 @cindex @samp{QStartupWithShell} packet
41457 On UNIX-like targets, it is possible to start the inferior using a
41458 shell program. This is the default behavior on both @value{GDBN} and
41459 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
41460 used to inform @command{gdbserver} whether it should start the
41461 inferior using a shell or not.
41463 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
41464 to start the inferior. If @var{value} is @samp{1},
41465 @command{gdbserver} will use a shell to start the inferior. All other
41466 values are considered an error.
41468 This packet is only available in extended mode (@pxref{extended
41474 The request succeeded.
41477 An error occurred. The error number @var{nn} is given as hex digits.
41480 This packet is not probed by default; the remote stub must request it,
41481 by supplying an appropriate @samp{qSupported} response
41482 (@pxref{qSupported}). This should only be done on targets that
41483 actually support starting the inferior using a shell.
41485 Use of this packet is controlled by the @code{set startup-with-shell}
41486 command; @pxref{set startup-with-shell}.
41488 @item QEnvironmentHexEncoded:@var{hex-value}
41489 @anchor{QEnvironmentHexEncoded}
41490 @cindex set environment variable, remote request
41491 @cindex @samp{QEnvironmentHexEncoded} packet
41492 On UNIX-like targets, it is possible to set environment variables that
41493 will be passed to the inferior during the startup process. This
41494 packet is used to inform @command{gdbserver} of an environment
41495 variable that has been defined by the user on @value{GDBN} (@pxref{set
41498 The packet is composed by @var{hex-value}, an hex encoded
41499 representation of the @var{name=value} format representing an
41500 environment variable. The name of the environment variable is
41501 represented by @var{name}, and the value to be assigned to the
41502 environment variable is represented by @var{value}. If the variable
41503 has no value (i.e., the value is @code{null}), then @var{value} will
41506 This packet is only available in extended mode (@pxref{extended
41512 The request succeeded.
41515 This packet is not probed by default; the remote stub must request it,
41516 by supplying an appropriate @samp{qSupported} response
41517 (@pxref{qSupported}). This should only be done on targets that
41518 actually support passing environment variables to the starting
41521 This packet is related to the @code{set environment} command;
41522 @pxref{set environment}.
41524 @item QEnvironmentUnset:@var{hex-value}
41525 @anchor{QEnvironmentUnset}
41526 @cindex unset environment variable, remote request
41527 @cindex @samp{QEnvironmentUnset} packet
41528 On UNIX-like targets, it is possible to unset environment variables
41529 before starting the inferior in the remote target. This packet is
41530 used to inform @command{gdbserver} of an environment variable that has
41531 been unset by the user on @value{GDBN} (@pxref{unset environment}).
41533 The packet is composed by @var{hex-value}, an hex encoded
41534 representation of the name of the environment variable to be unset.
41536 This packet is only available in extended mode (@pxref{extended
41542 The request succeeded.
41545 This packet is not probed by default; the remote stub must request it,
41546 by supplying an appropriate @samp{qSupported} response
41547 (@pxref{qSupported}). This should only be done on targets that
41548 actually support passing environment variables to the starting
41551 This packet is related to the @code{unset environment} command;
41552 @pxref{unset environment}.
41554 @item QEnvironmentReset
41555 @anchor{QEnvironmentReset}
41556 @cindex reset environment, remote request
41557 @cindex @samp{QEnvironmentReset} packet
41558 On UNIX-like targets, this packet is used to reset the state of
41559 environment variables in the remote target before starting the
41560 inferior. In this context, reset means unsetting all environment
41561 variables that were previously set by the user (i.e., were not
41562 initially present in the environment). It is sent to
41563 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
41564 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
41565 (@pxref{QEnvironmentUnset}) packets.
41567 This packet is only available in extended mode (@pxref{extended
41573 The request succeeded.
41576 This packet is not probed by default; the remote stub must request it,
41577 by supplying an appropriate @samp{qSupported} response
41578 (@pxref{qSupported}). This should only be done on targets that
41579 actually support passing environment variables to the starting
41582 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
41583 @anchor{QSetWorkingDir packet}
41584 @cindex set working directory, remote request
41585 @cindex @samp{QSetWorkingDir} packet
41586 This packet is used to inform the remote server of the intended
41587 current working directory for programs that are going to be executed.
41589 The packet is composed by @var{directory}, an hex encoded
41590 representation of the directory that the remote inferior will use as
41591 its current working directory. If @var{directory} is an empty string,
41592 the remote server should reset the inferior's current working
41593 directory to its original, empty value.
41595 This packet is only available in extended mode (@pxref{extended
41601 The request succeeded.
41605 @itemx qsThreadInfo
41606 @cindex list active threads, remote request
41607 @cindex @samp{qfThreadInfo} packet
41608 @cindex @samp{qsThreadInfo} packet
41609 Obtain a list of all active thread IDs from the target (OS). Since there
41610 may be too many active threads to fit into one reply packet, this query
41611 works iteratively: it may require more than one query/reply sequence to
41612 obtain the entire list of threads. The first query of the sequence will
41613 be the @samp{qfThreadInfo} query; subsequent queries in the
41614 sequence will be the @samp{qsThreadInfo} query.
41616 NOTE: This packet replaces the @samp{qL} query (see below).
41620 @item m @var{thread-id}
41622 @item m @var{thread-id},@var{thread-id}@dots{}
41623 a comma-separated list of thread IDs
41625 (lower case letter @samp{L}) denotes end of list.
41628 In response to each query, the target will reply with a list of one or
41629 more thread IDs, separated by commas.
41630 @value{GDBN} will respond to each reply with a request for more thread
41631 ids (using the @samp{qs} form of the query), until the target responds
41632 with @samp{l} (lower-case ell, for @dfn{last}).
41633 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
41636 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
41637 initial connection with the remote target, and the very first thread ID
41638 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
41639 message. Therefore, the stub should ensure that the first thread ID in
41640 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
41642 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
41643 @cindex get thread-local storage address, remote request
41644 @cindex @samp{qGetTLSAddr} packet
41645 Fetch the address associated with thread local storage specified
41646 by @var{thread-id}, @var{offset}, and @var{lm}.
41648 @var{thread-id} is the thread ID associated with the
41649 thread for which to fetch the TLS address. @xref{thread-id syntax}.
41651 @var{offset} is the (big endian, hex encoded) offset associated with the
41652 thread local variable. (This offset is obtained from the debug
41653 information associated with the variable.)
41655 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
41656 load module associated with the thread local storage. For example,
41657 a @sc{gnu}/Linux system will pass the link map address of the shared
41658 object associated with the thread local storage under consideration.
41659 Other operating environments may choose to represent the load module
41660 differently, so the precise meaning of this parameter will vary.
41664 @item @var{XX}@dots{}
41665 Hex encoded (big endian) bytes representing the address of the thread
41666 local storage requested.
41669 An error occurred. The error number @var{nn} is given as hex digits.
41672 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
41675 @item qGetTIBAddr:@var{thread-id}
41676 @cindex get thread information block address
41677 @cindex @samp{qGetTIBAddr} packet
41678 Fetch address of the Windows OS specific Thread Information Block.
41680 @var{thread-id} is the thread ID associated with the thread.
41684 @item @var{XX}@dots{}
41685 Hex encoded (big endian) bytes representing the linear address of the
41686 thread information block.
41689 An error occured. This means that either the thread was not found, or the
41690 address could not be retrieved.
41693 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
41696 @item qL @var{startflag} @var{threadcount} @var{nextthread}
41697 Obtain thread information from RTOS. Where: @var{startflag} (one hex
41698 digit) is one to indicate the first query and zero to indicate a
41699 subsequent query; @var{threadcount} (two hex digits) is the maximum
41700 number of threads the response packet can contain; and @var{nextthread}
41701 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
41702 returned in the response as @var{argthread}.
41704 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
41708 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
41709 Where: @var{count} (two hex digits) is the number of threads being
41710 returned; @var{done} (one hex digit) is zero to indicate more threads
41711 and one indicates no further threads; @var{argthreadid} (eight hex
41712 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
41713 is a sequence of thread IDs, @var{threadid} (eight hex
41714 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
41717 @item qMemTags:@var{start address},@var{length}:@var{type}
41719 @cindex fetch memory tags
41720 @cindex @samp{qMemTags} packet
41721 Fetch memory tags of type @var{type} from the address range
41722 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41723 target is responsible for calculating how many tags will be returned, as this
41724 is architecture-specific.
41726 @var{start address} is the starting address of the memory range.
41728 @var{length} is the length, in bytes, of the memory range.
41730 @var{type} is the type of tag the request wants to fetch. The type is a signed
41735 @item @var{mxx}@dots{}
41736 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
41737 tags found in the requested memory range.
41740 An error occured. This means that fetching of memory tags failed for some
41744 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
41745 although this should not happen given @value{GDBN} will only send this packet
41746 if the stub has advertised support for memory tagging via @samp{qSupported}.
41749 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
41751 @cindex store memory tags
41752 @cindex @samp{QMemTags} packet
41753 Store memory tags of type @var{type} to the address range
41754 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41755 target is responsible for interpreting the type, the tag bytes and modifying
41756 the memory tag granules accordingly, given this is architecture-specific.
41758 The interpretation of how many tags (@var{nt}) should be written to how many
41759 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
41760 implementation-specific, but the following is suggested.
41762 If the number of memory tags, @var{nt}, is greater than or equal to the
41763 number of memory tag granules, @var{ng}, only @var{ng} tags will be
41766 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
41767 and the tag bytes will be used as a pattern that will get repeated until
41768 @var{ng} tags are stored.
41770 @var{start address} is the starting address of the memory range. The address
41771 does not have any restriction on alignment or size.
41773 @var{length} is the length, in bytes, of the memory range.
41775 @var{type} is the type of tag the request wants to fetch. The type is a signed
41778 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
41779 interpreted by the target. Each pair of hex digits is interpreted as a
41785 The request was successful and the memory tag granules were modified
41789 An error occured. This means that modifying the memory tag granules failed
41793 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
41794 although this should not happen given @value{GDBN} will only send this packet
41795 if the stub has advertised support for memory tagging via @samp{qSupported}.
41799 @cindex section offsets, remote request
41800 @cindex @samp{qOffsets} packet
41801 Get section offsets that the target used when relocating the downloaded
41806 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
41807 Relocate the @code{Text} section by @var{xxx} from its original address.
41808 Relocate the @code{Data} section by @var{yyy} from its original address.
41809 If the object file format provides segment information (e.g.@: @sc{elf}
41810 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
41811 segments by the supplied offsets.
41813 @emph{Note: while a @code{Bss} offset may be included in the response,
41814 @value{GDBN} ignores this and instead applies the @code{Data} offset
41815 to the @code{Bss} section.}
41817 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
41818 Relocate the first segment of the object file, which conventionally
41819 contains program code, to a starting address of @var{xxx}. If
41820 @samp{DataSeg} is specified, relocate the second segment, which
41821 conventionally contains modifiable data, to a starting address of
41822 @var{yyy}. @value{GDBN} will report an error if the object file
41823 does not contain segment information, or does not contain at least
41824 as many segments as mentioned in the reply. Extra segments are
41825 kept at fixed offsets relative to the last relocated segment.
41828 @item qP @var{mode} @var{thread-id}
41829 @cindex thread information, remote request
41830 @cindex @samp{qP} packet
41831 Returns information on @var{thread-id}. Where: @var{mode} is a hex
41832 encoded 32 bit mode; @var{thread-id} is a thread ID
41833 (@pxref{thread-id syntax}).
41835 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
41838 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
41842 @cindex non-stop mode, remote request
41843 @cindex @samp{QNonStop} packet
41845 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
41846 @xref{Remote Non-Stop}, for more information.
41851 The request succeeded.
41854 An error occurred. The error number @var{nn} is given as hex digits.
41857 An empty reply indicates that @samp{QNonStop} is not supported by
41861 This packet is not probed by default; the remote stub must request it,
41862 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41863 Use of this packet is controlled by the @code{set non-stop} command;
41864 @pxref{Non-Stop Mode}.
41866 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
41867 @itemx QCatchSyscalls:0
41868 @cindex catch syscalls from inferior, remote request
41869 @cindex @samp{QCatchSyscalls} packet
41870 @anchor{QCatchSyscalls}
41871 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
41872 catching syscalls from the inferior process.
41874 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
41875 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
41876 is listed, every system call should be reported.
41878 Note that if a syscall not in the list is reported, @value{GDBN} will
41879 still filter the event according to its own list from all corresponding
41880 @code{catch syscall} commands. However, it is more efficient to only
41881 report the requested syscalls.
41883 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
41884 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
41886 If the inferior process execs, the state of @samp{QCatchSyscalls} is
41887 kept for the new process too. On targets where exec may affect syscall
41888 numbers, for example with exec between 32 and 64-bit processes, the
41889 client should send a new packet with the new syscall list.
41894 The request succeeded.
41897 An error occurred. @var{nn} are hex digits.
41900 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
41904 Use of this packet is controlled by the @code{set remote catch-syscalls}
41905 command (@pxref{Remote Configuration, set remote catch-syscalls}).
41906 This packet is not probed by default; the remote stub must request it,
41907 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41909 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41910 @cindex pass signals to inferior, remote request
41911 @cindex @samp{QPassSignals} packet
41912 @anchor{QPassSignals}
41913 Each listed @var{signal} should be passed directly to the inferior process.
41914 Signals are numbered identically to continue packets and stop replies
41915 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41916 strictly greater than the previous item. These signals do not need to stop
41917 the inferior, or be reported to @value{GDBN}. All other signals should be
41918 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
41919 combine; any earlier @samp{QPassSignals} list is completely replaced by the
41920 new list. This packet improves performance when using @samp{handle
41921 @var{signal} nostop noprint pass}.
41926 The request succeeded.
41929 An error occurred. The error number @var{nn} is given as hex digits.
41932 An empty reply indicates that @samp{QPassSignals} is not supported by
41936 Use of this packet is controlled by the @code{set remote pass-signals}
41937 command (@pxref{Remote Configuration, set remote pass-signals}).
41938 This packet is not probed by default; the remote stub must request it,
41939 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41941 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
41942 @cindex signals the inferior may see, remote request
41943 @cindex @samp{QProgramSignals} packet
41944 @anchor{QProgramSignals}
41945 Each listed @var{signal} may be delivered to the inferior process.
41946 Others should be silently discarded.
41948 In some cases, the remote stub may need to decide whether to deliver a
41949 signal to the program or not without @value{GDBN} involvement. One
41950 example of that is while detaching --- the program's threads may have
41951 stopped for signals that haven't yet had a chance of being reported to
41952 @value{GDBN}, and so the remote stub can use the signal list specified
41953 by this packet to know whether to deliver or ignore those pending
41956 This does not influence whether to deliver a signal as requested by a
41957 resumption packet (@pxref{vCont packet}).
41959 Signals are numbered identically to continue packets and stop replies
41960 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
41961 strictly greater than the previous item. Multiple
41962 @samp{QProgramSignals} packets do not combine; any earlier
41963 @samp{QProgramSignals} list is completely replaced by the new list.
41968 The request succeeded.
41971 An error occurred. The error number @var{nn} is given as hex digits.
41974 An empty reply indicates that @samp{QProgramSignals} is not supported
41978 Use of this packet is controlled by the @code{set remote program-signals}
41979 command (@pxref{Remote Configuration, set remote program-signals}).
41980 This packet is not probed by default; the remote stub must request it,
41981 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41983 @anchor{QThreadEvents}
41984 @item QThreadEvents:1
41985 @itemx QThreadEvents:0
41986 @cindex thread create/exit events, remote request
41987 @cindex @samp{QThreadEvents} packet
41989 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
41990 reporting of thread create and exit events. @xref{thread create
41991 event}, for the reply specifications. For example, this is used in
41992 non-stop mode when @value{GDBN} stops a set of threads and
41993 synchronously waits for the their corresponding stop replies. Without
41994 exit events, if one of the threads exits, @value{GDBN} would hang
41995 forever not knowing that it should no longer expect a stop for that
41996 same thread. @value{GDBN} does not enable this feature unless the
41997 stub reports that it supports it by including @samp{QThreadEvents+} in
41998 its @samp{qSupported} reply.
42003 The request succeeded.
42006 An error occurred. The error number @var{nn} is given as hex digits.
42009 An empty reply indicates that @samp{QThreadEvents} is not supported by
42013 Use of this packet is controlled by the @code{set remote thread-events}
42014 command (@pxref{Remote Configuration, set remote thread-events}).
42016 @item qRcmd,@var{command}
42017 @cindex execute remote command, remote request
42018 @cindex @samp{qRcmd} packet
42019 @var{command} (hex encoded) is passed to the local interpreter for
42020 execution. Invalid commands should be reported using the output
42021 string. Before the final result packet, the target may also respond
42022 with a number of intermediate @samp{O@var{output}} console output
42023 packets. @emph{Implementors should note that providing access to a
42024 stubs's interpreter may have security implications}.
42029 A command response with no output.
42031 A command response with the hex encoded output string @var{OUTPUT}.
42033 Indicate a badly formed request.
42035 An empty reply indicates that @samp{qRcmd} is not recognized.
42038 (Note that the @code{qRcmd} packet's name is separated from the
42039 command by a @samp{,}, not a @samp{:}, contrary to the naming
42040 conventions above. Please don't use this packet as a model for new
42043 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42044 @cindex searching memory, in remote debugging
42046 @cindex @samp{qSearch:memory} packet
42048 @cindex @samp{qSearch memory} packet
42049 @anchor{qSearch memory}
42050 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42051 Both @var{address} and @var{length} are encoded in hex;
42052 @var{search-pattern} is a sequence of bytes, also hex encoded.
42057 The pattern was not found.
42059 The pattern was found at @var{address}.
42061 A badly formed request or an error was encountered while searching memory.
42063 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42066 @item QStartNoAckMode
42067 @cindex @samp{QStartNoAckMode} packet
42068 @anchor{QStartNoAckMode}
42069 Request that the remote stub disable the normal @samp{+}/@samp{-}
42070 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42075 The stub has switched to no-acknowledgment mode.
42076 @value{GDBN} acknowledges this response,
42077 but neither the stub nor @value{GDBN} shall send or expect further
42078 @samp{+}/@samp{-} acknowledgments in the current connection.
42080 An empty reply indicates that the stub does not support no-acknowledgment mode.
42083 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42084 @cindex supported packets, remote query
42085 @cindex features of the remote protocol
42086 @cindex @samp{qSupported} packet
42087 @anchor{qSupported}
42088 Tell the remote stub about features supported by @value{GDBN}, and
42089 query the stub for features it supports. This packet allows
42090 @value{GDBN} and the remote stub to take advantage of each others'
42091 features. @samp{qSupported} also consolidates multiple feature probes
42092 at startup, to improve @value{GDBN} performance---a single larger
42093 packet performs better than multiple smaller probe packets on
42094 high-latency links. Some features may enable behavior which must not
42095 be on by default, e.g.@: because it would confuse older clients or
42096 stubs. Other features may describe packets which could be
42097 automatically probed for, but are not. These features must be
42098 reported before @value{GDBN} will use them. This ``default
42099 unsupported'' behavior is not appropriate for all packets, but it
42100 helps to keep the initial connection time under control with new
42101 versions of @value{GDBN} which support increasing numbers of packets.
42105 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
42106 The stub supports or does not support each returned @var{stubfeature},
42107 depending on the form of each @var{stubfeature} (see below for the
42110 An empty reply indicates that @samp{qSupported} is not recognized,
42111 or that no features needed to be reported to @value{GDBN}.
42114 The allowed forms for each feature (either a @var{gdbfeature} in the
42115 @samp{qSupported} packet, or a @var{stubfeature} in the response)
42119 @item @var{name}=@var{value}
42120 The remote protocol feature @var{name} is supported, and associated
42121 with the specified @var{value}. The format of @var{value} depends
42122 on the feature, but it must not include a semicolon.
42124 The remote protocol feature @var{name} is supported, and does not
42125 need an associated value.
42127 The remote protocol feature @var{name} is not supported.
42129 The remote protocol feature @var{name} may be supported, and
42130 @value{GDBN} should auto-detect support in some other way when it is
42131 needed. This form will not be used for @var{gdbfeature} notifications,
42132 but may be used for @var{stubfeature} responses.
42135 Whenever the stub receives a @samp{qSupported} request, the
42136 supplied set of @value{GDBN} features should override any previous
42137 request. This allows @value{GDBN} to put the stub in a known
42138 state, even if the stub had previously been communicating with
42139 a different version of @value{GDBN}.
42141 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
42146 This feature indicates whether @value{GDBN} supports multiprocess
42147 extensions to the remote protocol. @value{GDBN} does not use such
42148 extensions unless the stub also reports that it supports them by
42149 including @samp{multiprocess+} in its @samp{qSupported} reply.
42150 @xref{multiprocess extensions}, for details.
42153 This feature indicates that @value{GDBN} supports the XML target
42154 description. If the stub sees @samp{xmlRegisters=} with target
42155 specific strings separated by a comma, it will report register
42159 This feature indicates whether @value{GDBN} supports the
42160 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
42161 instruction reply packet}).
42164 This feature indicates whether @value{GDBN} supports the swbreak stop
42165 reason in stop replies. @xref{swbreak stop reason}, for details.
42168 This feature indicates whether @value{GDBN} supports the hwbreak stop
42169 reason in stop replies. @xref{swbreak stop reason}, for details.
42172 This feature indicates whether @value{GDBN} supports fork event
42173 extensions to the remote protocol. @value{GDBN} does not use such
42174 extensions unless the stub also reports that it supports them by
42175 including @samp{fork-events+} in its @samp{qSupported} reply.
42178 This feature indicates whether @value{GDBN} supports vfork event
42179 extensions to the remote protocol. @value{GDBN} does not use such
42180 extensions unless the stub also reports that it supports them by
42181 including @samp{vfork-events+} in its @samp{qSupported} reply.
42184 This feature indicates whether @value{GDBN} supports exec event
42185 extensions to the remote protocol. @value{GDBN} does not use such
42186 extensions unless the stub also reports that it supports them by
42187 including @samp{exec-events+} in its @samp{qSupported} reply.
42189 @item vContSupported
42190 This feature indicates whether @value{GDBN} wants to know the
42191 supported actions in the reply to @samp{vCont?} packet.
42194 Stubs should ignore any unknown values for
42195 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42196 packet supports receiving packets of unlimited length (earlier
42197 versions of @value{GDBN} may reject overly long responses). Additional values
42198 for @var{gdbfeature} may be defined in the future to let the stub take
42199 advantage of new features in @value{GDBN}, e.g.@: incompatible
42200 improvements in the remote protocol---the @samp{multiprocess} feature is
42201 an example of such a feature. The stub's reply should be independent
42202 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42203 describes all the features it supports, and then the stub replies with
42204 all the features it supports.
42206 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42207 responses, as long as each response uses one of the standard forms.
42209 Some features are flags. A stub which supports a flag feature
42210 should respond with a @samp{+} form response. Other features
42211 require values, and the stub should respond with an @samp{=}
42214 Each feature has a default value, which @value{GDBN} will use if
42215 @samp{qSupported} is not available or if the feature is not mentioned
42216 in the @samp{qSupported} response. The default values are fixed; a
42217 stub is free to omit any feature responses that match the defaults.
42219 Not all features can be probed, but for those which can, the probing
42220 mechanism is useful: in some cases, a stub's internal
42221 architecture may not allow the protocol layer to know some information
42222 about the underlying target in advance. This is especially common in
42223 stubs which may be configured for multiple targets.
42225 These are the currently defined stub features and their properties:
42227 @multitable @columnfractions 0.35 0.2 0.12 0.2
42228 @c NOTE: The first row should be @headitem, but we do not yet require
42229 @c a new enough version of Texinfo (4.7) to use @headitem.
42231 @tab Value Required
42235 @item @samp{PacketSize}
42240 @item @samp{qXfer:auxv:read}
42245 @item @samp{qXfer:btrace:read}
42250 @item @samp{qXfer:btrace-conf:read}
42255 @item @samp{qXfer:exec-file:read}
42260 @item @samp{qXfer:features:read}
42265 @item @samp{qXfer:libraries:read}
42270 @item @samp{qXfer:libraries-svr4:read}
42275 @item @samp{augmented-libraries-svr4-read}
42280 @item @samp{qXfer:memory-map:read}
42285 @item @samp{qXfer:sdata:read}
42290 @item @samp{qXfer:siginfo:read}
42295 @item @samp{qXfer:siginfo:write}
42300 @item @samp{qXfer:threads:read}
42305 @item @samp{qXfer:traceframe-info:read}
42310 @item @samp{qXfer:uib:read}
42315 @item @samp{qXfer:fdpic:read}
42320 @item @samp{Qbtrace:off}
42325 @item @samp{Qbtrace:bts}
42330 @item @samp{Qbtrace:pt}
42335 @item @samp{Qbtrace-conf:bts:size}
42340 @item @samp{Qbtrace-conf:pt:size}
42345 @item @samp{QNonStop}
42350 @item @samp{QCatchSyscalls}
42355 @item @samp{QPassSignals}
42360 @item @samp{QStartNoAckMode}
42365 @item @samp{multiprocess}
42370 @item @samp{ConditionalBreakpoints}
42375 @item @samp{ConditionalTracepoints}
42380 @item @samp{ReverseContinue}
42385 @item @samp{ReverseStep}
42390 @item @samp{TracepointSource}
42395 @item @samp{QAgent}
42400 @item @samp{QAllow}
42405 @item @samp{QDisableRandomization}
42410 @item @samp{EnableDisableTracepoints}
42415 @item @samp{QTBuffer:size}
42420 @item @samp{tracenz}
42425 @item @samp{BreakpointCommands}
42430 @item @samp{swbreak}
42435 @item @samp{hwbreak}
42440 @item @samp{fork-events}
42445 @item @samp{vfork-events}
42450 @item @samp{exec-events}
42455 @item @samp{QThreadEvents}
42460 @item @samp{no-resumed}
42465 @item @samp{memory-tagging}
42472 These are the currently defined stub features, in more detail:
42475 @cindex packet size, remote protocol
42476 @item PacketSize=@var{bytes}
42477 The remote stub can accept packets up to at least @var{bytes} in
42478 length. @value{GDBN} will send packets up to this size for bulk
42479 transfers, and will never send larger packets. This is a limit on the
42480 data characters in the packet, including the frame and checksum.
42481 There is no trailing NUL byte in a remote protocol packet; if the stub
42482 stores packets in a NUL-terminated format, it should allow an extra
42483 byte in its buffer for the NUL. If this stub feature is not supported,
42484 @value{GDBN} guesses based on the size of the @samp{g} packet response.
42486 @item qXfer:auxv:read
42487 The remote stub understands the @samp{qXfer:auxv:read} packet
42488 (@pxref{qXfer auxiliary vector read}).
42490 @item qXfer:btrace:read
42491 The remote stub understands the @samp{qXfer:btrace:read}
42492 packet (@pxref{qXfer btrace read}).
42494 @item qXfer:btrace-conf:read
42495 The remote stub understands the @samp{qXfer:btrace-conf:read}
42496 packet (@pxref{qXfer btrace-conf read}).
42498 @item qXfer:exec-file:read
42499 The remote stub understands the @samp{qXfer:exec-file:read} packet
42500 (@pxref{qXfer executable filename read}).
42502 @item qXfer:features:read
42503 The remote stub understands the @samp{qXfer:features:read} packet
42504 (@pxref{qXfer target description read}).
42506 @item qXfer:libraries:read
42507 The remote stub understands the @samp{qXfer:libraries:read} packet
42508 (@pxref{qXfer library list read}).
42510 @item qXfer:libraries-svr4:read
42511 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
42512 (@pxref{qXfer svr4 library list read}).
42514 @item augmented-libraries-svr4-read
42515 The remote stub understands the augmented form of the
42516 @samp{qXfer:libraries-svr4:read} packet
42517 (@pxref{qXfer svr4 library list read}).
42519 @item qXfer:memory-map:read
42520 The remote stub understands the @samp{qXfer:memory-map:read} packet
42521 (@pxref{qXfer memory map read}).
42523 @item qXfer:sdata:read
42524 The remote stub understands the @samp{qXfer:sdata:read} packet
42525 (@pxref{qXfer sdata read}).
42527 @item qXfer:siginfo:read
42528 The remote stub understands the @samp{qXfer:siginfo:read} packet
42529 (@pxref{qXfer siginfo read}).
42531 @item qXfer:siginfo:write
42532 The remote stub understands the @samp{qXfer:siginfo:write} packet
42533 (@pxref{qXfer siginfo write}).
42535 @item qXfer:threads:read
42536 The remote stub understands the @samp{qXfer:threads:read} packet
42537 (@pxref{qXfer threads read}).
42539 @item qXfer:traceframe-info:read
42540 The remote stub understands the @samp{qXfer:traceframe-info:read}
42541 packet (@pxref{qXfer traceframe info read}).
42543 @item qXfer:uib:read
42544 The remote stub understands the @samp{qXfer:uib:read}
42545 packet (@pxref{qXfer unwind info block}).
42547 @item qXfer:fdpic:read
42548 The remote stub understands the @samp{qXfer:fdpic:read}
42549 packet (@pxref{qXfer fdpic loadmap read}).
42552 The remote stub understands the @samp{QNonStop} packet
42553 (@pxref{QNonStop}).
42555 @item QCatchSyscalls
42556 The remote stub understands the @samp{QCatchSyscalls} packet
42557 (@pxref{QCatchSyscalls}).
42560 The remote stub understands the @samp{QPassSignals} packet
42561 (@pxref{QPassSignals}).
42563 @item QStartNoAckMode
42564 The remote stub understands the @samp{QStartNoAckMode} packet and
42565 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
42568 @anchor{multiprocess extensions}
42569 @cindex multiprocess extensions, in remote protocol
42570 The remote stub understands the multiprocess extensions to the remote
42571 protocol syntax. The multiprocess extensions affect the syntax of
42572 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
42573 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
42574 replies. Note that reporting this feature indicates support for the
42575 syntactic extensions only, not that the stub necessarily supports
42576 debugging of more than one process at a time. The stub must not use
42577 multiprocess extensions in packet replies unless @value{GDBN} has also
42578 indicated it supports them in its @samp{qSupported} request.
42580 @item qXfer:osdata:read
42581 The remote stub understands the @samp{qXfer:osdata:read} packet
42582 ((@pxref{qXfer osdata read}).
42584 @item ConditionalBreakpoints
42585 The target accepts and implements evaluation of conditional expressions
42586 defined for breakpoints. The target will only report breakpoint triggers
42587 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
42589 @item ConditionalTracepoints
42590 The remote stub accepts and implements conditional expressions defined
42591 for tracepoints (@pxref{Tracepoint Conditions}).
42593 @item ReverseContinue
42594 The remote stub accepts and implements the reverse continue packet
42598 The remote stub accepts and implements the reverse step packet
42601 @item TracepointSource
42602 The remote stub understands the @samp{QTDPsrc} packet that supplies
42603 the source form of tracepoint definitions.
42606 The remote stub understands the @samp{QAgent} packet.
42609 The remote stub understands the @samp{QAllow} packet.
42611 @item QDisableRandomization
42612 The remote stub understands the @samp{QDisableRandomization} packet.
42614 @item StaticTracepoint
42615 @cindex static tracepoints, in remote protocol
42616 The remote stub supports static tracepoints.
42618 @item InstallInTrace
42619 @anchor{install tracepoint in tracing}
42620 The remote stub supports installing tracepoint in tracing.
42622 @item EnableDisableTracepoints
42623 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
42624 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
42625 to be enabled and disabled while a trace experiment is running.
42627 @item QTBuffer:size
42628 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
42629 packet that allows to change the size of the trace buffer.
42632 @cindex string tracing, in remote protocol
42633 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
42634 See @ref{Bytecode Descriptions} for details about the bytecode.
42636 @item BreakpointCommands
42637 @cindex breakpoint commands, in remote protocol
42638 The remote stub supports running a breakpoint's command list itself,
42639 rather than reporting the hit to @value{GDBN}.
42642 The remote stub understands the @samp{Qbtrace:off} packet.
42645 The remote stub understands the @samp{Qbtrace:bts} packet.
42648 The remote stub understands the @samp{Qbtrace:pt} packet.
42650 @item Qbtrace-conf:bts:size
42651 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
42653 @item Qbtrace-conf:pt:size
42654 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
42657 The remote stub reports the @samp{swbreak} stop reason for memory
42661 The remote stub reports the @samp{hwbreak} stop reason for hardware
42665 The remote stub reports the @samp{fork} stop reason for fork events.
42668 The remote stub reports the @samp{vfork} stop reason for vfork events
42669 and vforkdone events.
42672 The remote stub reports the @samp{exec} stop reason for exec events.
42674 @item vContSupported
42675 The remote stub reports the supported actions in the reply to
42676 @samp{vCont?} packet.
42678 @item QThreadEvents
42679 The remote stub understands the @samp{QThreadEvents} packet.
42682 The remote stub reports the @samp{N} stop reply.
42685 @item memory-tagging
42686 The remote stub supports and implements the required memory tagging
42687 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
42688 @samp{QMemTags} (@pxref{QMemTags}) packets.
42690 For AArch64 GNU/Linux systems, this feature also requires access to the
42691 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
42692 This is done via the @samp{vFile} requests.
42697 @cindex symbol lookup, remote request
42698 @cindex @samp{qSymbol} packet
42699 Notify the target that @value{GDBN} is prepared to serve symbol lookup
42700 requests. Accept requests from the target for the values of symbols.
42705 The target does not need to look up any (more) symbols.
42706 @item qSymbol:@var{sym_name}
42707 The target requests the value of symbol @var{sym_name} (hex encoded).
42708 @value{GDBN} may provide the value by using the
42709 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
42713 @item qSymbol:@var{sym_value}:@var{sym_name}
42714 Set the value of @var{sym_name} to @var{sym_value}.
42716 @var{sym_name} (hex encoded) is the name of a symbol whose value the
42717 target has previously requested.
42719 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
42720 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
42726 The target does not need to look up any (more) symbols.
42727 @item qSymbol:@var{sym_name}
42728 The target requests the value of a new symbol @var{sym_name} (hex
42729 encoded). @value{GDBN} will continue to supply the values of symbols
42730 (if available), until the target ceases to request them.
42735 @itemx QTDisconnected
42742 @itemx qTMinFTPILen
42744 @xref{Tracepoint Packets}.
42746 @anchor{qThreadExtraInfo}
42747 @item qThreadExtraInfo,@var{thread-id}
42748 @cindex thread attributes info, remote request
42749 @cindex @samp{qThreadExtraInfo} packet
42750 Obtain from the target OS a printable string description of thread
42751 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
42752 for the forms of @var{thread-id}. This
42753 string may contain anything that the target OS thinks is interesting
42754 for @value{GDBN} to tell the user about the thread. The string is
42755 displayed in @value{GDBN}'s @code{info threads} display. Some
42756 examples of possible thread extra info strings are @samp{Runnable}, or
42757 @samp{Blocked on Mutex}.
42761 @item @var{XX}@dots{}
42762 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
42763 comprising the printable string containing the extra information about
42764 the thread's attributes.
42767 (Note that the @code{qThreadExtraInfo} packet's name is separated from
42768 the command by a @samp{,}, not a @samp{:}, contrary to the naming
42769 conventions above. Please don't use this packet as a model for new
42788 @xref{Tracepoint Packets}.
42790 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
42791 @cindex read special object, remote request
42792 @cindex @samp{qXfer} packet
42793 @anchor{qXfer read}
42794 Read uninterpreted bytes from the target's special data area
42795 identified by the keyword @var{object}. Request @var{length} bytes
42796 starting at @var{offset} bytes into the data. The content and
42797 encoding of @var{annex} is specific to @var{object}; it can supply
42798 additional details about what data to access.
42803 Data @var{data} (@pxref{Binary Data}) has been read from the
42804 target. There may be more data at a higher address (although
42805 it is permitted to return @samp{m} even for the last valid
42806 block of data, as long as at least one byte of data was read).
42807 It is possible for @var{data} to have fewer bytes than the @var{length} in the
42811 Data @var{data} (@pxref{Binary Data}) has been read from the target.
42812 There is no more data to be read. It is possible for @var{data} to
42813 have fewer bytes than the @var{length} in the request.
42816 The @var{offset} in the request is at the end of the data.
42817 There is no more data to be read.
42820 The request was malformed, or @var{annex} was invalid.
42823 The offset was invalid, or there was an error encountered reading the data.
42824 The @var{nn} part is a hex-encoded @code{errno} value.
42827 An empty reply indicates the @var{object} string was not recognized by
42828 the stub, or that the object does not support reading.
42831 Here are the specific requests of this form defined so far. All the
42832 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
42833 formats, listed above.
42836 @item qXfer:auxv:read::@var{offset},@var{length}
42837 @anchor{qXfer auxiliary vector read}
42838 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
42839 auxiliary vector}. Note @var{annex} must be empty.
42841 This packet is not probed by default; the remote stub must request it,
42842 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42844 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
42845 @anchor{qXfer btrace read}
42847 Return a description of the current branch trace.
42848 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
42849 packet may have one of the following values:
42853 Returns all available branch trace.
42856 Returns all available branch trace if the branch trace changed since
42857 the last read request.
42860 Returns the new branch trace since the last read request. Adds a new
42861 block to the end of the trace that begins at zero and ends at the source
42862 location of the first branch in the trace buffer. This extra block is
42863 used to stitch traces together.
42865 If the trace buffer overflowed, returns an error indicating the overflow.
42868 This packet is not probed by default; the remote stub must request it
42869 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42871 @item qXfer:btrace-conf:read::@var{offset},@var{length}
42872 @anchor{qXfer btrace-conf read}
42874 Return a description of the current branch trace configuration.
42875 @xref{Branch Trace Configuration Format}.
42877 This packet is not probed by default; the remote stub must request it
42878 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42880 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
42881 @anchor{qXfer executable filename read}
42882 Return the full absolute name of the file that was executed to create
42883 a process running on the remote system. The annex specifies the
42884 numeric process ID of the process to query, encoded as a hexadecimal
42885 number. If the annex part is empty the remote stub should return the
42886 filename corresponding to the currently executing process.
42888 This packet is not probed by default; the remote stub must request it,
42889 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42891 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
42892 @anchor{qXfer target description read}
42893 Access the @dfn{target description}. @xref{Target Descriptions}. The
42894 annex specifies which XML document to access. The main description is
42895 always loaded from the @samp{target.xml} annex.
42897 This packet is not probed by default; the remote stub must request it,
42898 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42900 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
42901 @anchor{qXfer library list read}
42902 Access the target's list of loaded libraries. @xref{Library List Format}.
42903 The annex part of the generic @samp{qXfer} packet must be empty
42904 (@pxref{qXfer read}).
42906 Targets which maintain a list of libraries in the program's memory do
42907 not need to implement this packet; it is designed for platforms where
42908 the operating system manages the list of loaded libraries.
42910 This packet is not probed by default; the remote stub must request it,
42911 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42913 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
42914 @anchor{qXfer svr4 library list read}
42915 Access the target's list of loaded libraries when the target is an SVR4
42916 platform. @xref{Library List Format for SVR4 Targets}. The annex part
42917 of the generic @samp{qXfer} packet must be empty unless the remote
42918 stub indicated it supports the augmented form of this packet
42919 by supplying an appropriate @samp{qSupported} response
42920 (@pxref{qXfer read}, @ref{qSupported}).
42922 This packet is optional for better performance on SVR4 targets.
42923 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
42925 This packet is not probed by default; the remote stub must request it,
42926 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42928 If the remote stub indicates it supports the augmented form of this
42929 packet then the annex part of the generic @samp{qXfer} packet may
42930 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
42931 arguments. The currently supported arguments are:
42934 @item start=@var{address}
42935 A hexadecimal number specifying the address of the @samp{struct
42936 link_map} to start reading the library list from. If unset or zero
42937 then the first @samp{struct link_map} in the library list will be
42938 chosen as the starting point.
42940 @item prev=@var{address}
42941 A hexadecimal number specifying the address of the @samp{struct
42942 link_map} immediately preceding the @samp{struct link_map}
42943 specified by the @samp{start} argument. If unset or zero then
42944 the remote stub will expect that no @samp{struct link_map}
42945 exists prior to the starting point.
42949 Arguments that are not understood by the remote stub will be silently
42952 @item qXfer:memory-map:read::@var{offset},@var{length}
42953 @anchor{qXfer memory map read}
42954 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
42955 annex part of the generic @samp{qXfer} packet must be empty
42956 (@pxref{qXfer read}).
42958 This packet is not probed by default; the remote stub must request it,
42959 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42961 @item qXfer:sdata:read::@var{offset},@var{length}
42962 @anchor{qXfer sdata read}
42964 Read contents of the extra collected static tracepoint marker
42965 information. The annex part of the generic @samp{qXfer} packet must
42966 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
42969 This packet is not probed by default; the remote stub must request it,
42970 by supplying an appropriate @samp{qSupported} response
42971 (@pxref{qSupported}).
42973 @item qXfer:siginfo:read::@var{offset},@var{length}
42974 @anchor{qXfer siginfo read}
42975 Read contents of the extra signal information on the target
42976 system. The annex part of the generic @samp{qXfer} packet must be
42977 empty (@pxref{qXfer read}).
42979 This packet is not probed by default; the remote stub must request it,
42980 by supplying an appropriate @samp{qSupported} response
42981 (@pxref{qSupported}).
42983 @item qXfer:threads:read::@var{offset},@var{length}
42984 @anchor{qXfer threads read}
42985 Access the list of threads on target. @xref{Thread List Format}. The
42986 annex part of the generic @samp{qXfer} packet must be empty
42987 (@pxref{qXfer read}).
42989 This packet is not probed by default; the remote stub must request it,
42990 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42992 @item qXfer:traceframe-info:read::@var{offset},@var{length}
42993 @anchor{qXfer traceframe info read}
42995 Return a description of the current traceframe's contents.
42996 @xref{Traceframe Info Format}. The annex part of the generic
42997 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
42999 This packet is not probed by default; the remote stub must request it,
43000 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43002 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43003 @anchor{qXfer unwind info block}
43005 Return the unwind information block for @var{pc}. This packet is used
43006 on OpenVMS/ia64 to ask the kernel unwind information.
43008 This packet is not probed by default.
43010 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43011 @anchor{qXfer fdpic loadmap read}
43012 Read contents of @code{loadmap}s on the target system. The
43013 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43014 executable @code{loadmap} or interpreter @code{loadmap} to read.
43016 This packet is not probed by default; the remote stub must request it,
43017 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43019 @item qXfer:osdata:read::@var{offset},@var{length}
43020 @anchor{qXfer osdata read}
43021 Access the target's @dfn{operating system information}.
43022 @xref{Operating System Information}.
43026 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43027 @cindex write data into object, remote request
43028 @anchor{qXfer write}
43029 Write uninterpreted bytes into the target's special data area
43030 identified by the keyword @var{object}, starting at @var{offset} bytes
43031 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43032 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43033 is specific to @var{object}; it can supply additional details about what data
43039 @var{nn} (hex encoded) is the number of bytes written.
43040 This may be fewer bytes than supplied in the request.
43043 The request was malformed, or @var{annex} was invalid.
43046 The offset was invalid, or there was an error encountered writing the data.
43047 The @var{nn} part is a hex-encoded @code{errno} value.
43050 An empty reply indicates the @var{object} string was not
43051 recognized by the stub, or that the object does not support writing.
43054 Here are the specific requests of this form defined so far. All the
43055 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43056 formats, listed above.
43059 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43060 @anchor{qXfer siginfo write}
43061 Write @var{data} to the extra signal information on the target system.
43062 The annex part of the generic @samp{qXfer} packet must be
43063 empty (@pxref{qXfer write}).
43065 This packet is not probed by default; the remote stub must request it,
43066 by supplying an appropriate @samp{qSupported} response
43067 (@pxref{qSupported}).
43070 @item qXfer:@var{object}:@var{operation}:@dots{}
43071 Requests of this form may be added in the future. When a stub does
43072 not recognize the @var{object} keyword, or its support for
43073 @var{object} does not recognize the @var{operation} keyword, the stub
43074 must respond with an empty packet.
43076 @item qAttached:@var{pid}
43077 @cindex query attached, remote request
43078 @cindex @samp{qAttached} packet
43079 Return an indication of whether the remote server attached to an
43080 existing process or created a new process. When the multiprocess
43081 protocol extensions are supported (@pxref{multiprocess extensions}),
43082 @var{pid} is an integer in hexadecimal format identifying the target
43083 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43084 the query packet will be simplified as @samp{qAttached}.
43086 This query is used, for example, to know whether the remote process
43087 should be detached or killed when a @value{GDBN} session is ended with
43088 the @code{quit} command.
43093 The remote server attached to an existing process.
43095 The remote server created a new process.
43097 A badly formed request or an error was encountered.
43101 Enable branch tracing for the current thread using Branch Trace Store.
43106 Branch tracing has been enabled.
43108 A badly formed request or an error was encountered.
43112 Enable branch tracing for the current thread using Intel Processor Trace.
43117 Branch tracing has been enabled.
43119 A badly formed request or an error was encountered.
43123 Disable branch tracing for the current thread.
43128 Branch tracing has been disabled.
43130 A badly formed request or an error was encountered.
43133 @item Qbtrace-conf:bts:size=@var{value}
43134 Set the requested ring buffer size for new threads that use the
43135 btrace recording method in bts format.
43140 The ring buffer size has been set.
43142 A badly formed request or an error was encountered.
43145 @item Qbtrace-conf:pt:size=@var{value}
43146 Set the requested ring buffer size for new threads that use the
43147 btrace recording method in pt format.
43152 The ring buffer size has been set.
43154 A badly formed request or an error was encountered.
43159 @node Architecture-Specific Protocol Details
43160 @section Architecture-Specific Protocol Details
43162 This section describes how the remote protocol is applied to specific
43163 target architectures. Also see @ref{Standard Target Features}, for
43164 details of XML target descriptions for each architecture.
43167 * ARM-Specific Protocol Details::
43168 * MIPS-Specific Protocol Details::
43171 @node ARM-Specific Protocol Details
43172 @subsection @acronym{ARM}-specific Protocol Details
43175 * ARM Breakpoint Kinds::
43176 * ARM Memory Tag Types::
43179 @node ARM Breakpoint Kinds
43180 @subsubsection @acronym{ARM} Breakpoint Kinds
43181 @cindex breakpoint kinds, @acronym{ARM}
43183 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43188 16-bit Thumb mode breakpoint.
43191 32-bit Thumb mode (Thumb-2) breakpoint.
43194 32-bit @acronym{ARM} mode breakpoint.
43198 @node ARM Memory Tag Types
43199 @subsubsection @acronym{ARM} Memory Tag Types
43200 @cindex memory tag types, @acronym{ARM}
43202 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43215 @node MIPS-Specific Protocol Details
43216 @subsection @acronym{MIPS}-specific Protocol Details
43219 * MIPS Register packet Format::
43220 * MIPS Breakpoint Kinds::
43223 @node MIPS Register packet Format
43224 @subsubsection @acronym{MIPS} Register Packet Format
43225 @cindex register packet format, @acronym{MIPS}
43227 The following @code{g}/@code{G} packets have previously been defined.
43228 In the below, some thirty-two bit registers are transferred as
43229 sixty-four bits. Those registers should be zero/sign extended (which?)
43230 to fill the space allocated. Register bytes are transferred in target
43231 byte order. The two nibbles within a register byte are transferred
43232 most-significant -- least-significant.
43237 All registers are transferred as thirty-two bit quantities in the order:
43238 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43239 registers; fsr; fir; fp.
43242 All registers are transferred as sixty-four bit quantities (including
43243 thirty-two bit registers such as @code{sr}). The ordering is the same
43248 @node MIPS Breakpoint Kinds
43249 @subsubsection @acronym{MIPS} Breakpoint Kinds
43250 @cindex breakpoint kinds, @acronym{MIPS}
43252 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43257 16-bit @acronym{MIPS16} mode breakpoint.
43260 16-bit @acronym{microMIPS} mode breakpoint.
43263 32-bit standard @acronym{MIPS} mode breakpoint.
43266 32-bit @acronym{microMIPS} mode breakpoint.
43270 @node Tracepoint Packets
43271 @section Tracepoint Packets
43272 @cindex tracepoint packets
43273 @cindex packets, tracepoint
43275 Here we describe the packets @value{GDBN} uses to implement
43276 tracepoints (@pxref{Tracepoints}).
43280 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43281 @cindex @samp{QTDP} packet
43282 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43283 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43284 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43285 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43286 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43287 the number of bytes that the target should copy elsewhere to make room
43288 for the tracepoint. If an @samp{X} is present, it introduces a
43289 tracepoint condition, which consists of a hexadecimal length, followed
43290 by a comma and hex-encoded bytes, in a manner similar to action
43291 encodings as described below. If the trailing @samp{-} is present,
43292 further @samp{QTDP} packets will follow to specify this tracepoint's
43298 The packet was understood and carried out.
43300 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43302 The packet was not recognized.
43305 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
43306 Define actions to be taken when a tracepoint is hit. The @var{n} and
43307 @var{addr} must be the same as in the initial @samp{QTDP} packet for
43308 this tracepoint. This packet may only be sent immediately after
43309 another @samp{QTDP} packet that ended with a @samp{-}. If the
43310 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
43311 specifying more actions for this tracepoint.
43313 In the series of action packets for a given tracepoint, at most one
43314 can have an @samp{S} before its first @var{action}. If such a packet
43315 is sent, it and the following packets define ``while-stepping''
43316 actions. Any prior packets define ordinary actions --- that is, those
43317 taken when the tracepoint is first hit. If no action packet has an
43318 @samp{S}, then all the packets in the series specify ordinary
43319 tracepoint actions.
43321 The @samp{@var{action}@dots{}} portion of the packet is a series of
43322 actions, concatenated without separators. Each action has one of the
43328 Collect the registers whose bits are set in @var{mask},
43329 a hexadecimal number whose @var{i}'th bit is set if register number
43330 @var{i} should be collected. (The least significant bit is numbered
43331 zero.) Note that @var{mask} may be any number of digits long; it may
43332 not fit in a 32-bit word.
43334 @item M @var{basereg},@var{offset},@var{len}
43335 Collect @var{len} bytes of memory starting at the address in register
43336 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43337 @samp{-1}, then the range has a fixed address: @var{offset} is the
43338 address of the lowest byte to collect. The @var{basereg},
43339 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43340 values (the @samp{-1} value for @var{basereg} is a special case).
43342 @item X @var{len},@var{expr}
43343 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43344 it directs. The agent expression @var{expr} is as described in
43345 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43346 two-digit hex number in the packet; @var{len} is the number of bytes
43347 in the expression (and thus one-half the number of hex digits in the
43352 Any number of actions may be packed together in a single @samp{QTDP}
43353 packet, as long as the packet does not exceed the maximum packet
43354 length (400 bytes, for many stubs). There may be only one @samp{R}
43355 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43356 actions. Any registers referred to by @samp{M} and @samp{X} actions
43357 must be collected by a preceding @samp{R} action. (The
43358 ``while-stepping'' actions are treated as if they were attached to a
43359 separate tracepoint, as far as these restrictions are concerned.)
43364 The packet was understood and carried out.
43366 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43368 The packet was not recognized.
43371 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43372 @cindex @samp{QTDPsrc} packet
43373 Specify a source string of tracepoint @var{n} at address @var{addr}.
43374 This is useful to get accurate reproduction of the tracepoints
43375 originally downloaded at the beginning of the trace run. The @var{type}
43376 is the name of the tracepoint part, such as @samp{cond} for the
43377 tracepoint's conditional expression (see below for a list of types), while
43378 @var{bytes} is the string, encoded in hexadecimal.
43380 @var{start} is the offset of the @var{bytes} within the overall source
43381 string, while @var{slen} is the total length of the source string.
43382 This is intended for handling source strings that are longer than will
43383 fit in a single packet.
43384 @c Add detailed example when this info is moved into a dedicated
43385 @c tracepoint descriptions section.
43387 The available string types are @samp{at} for the location,
43388 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43389 @value{GDBN} sends a separate packet for each command in the action
43390 list, in the same order in which the commands are stored in the list.
43392 The target does not need to do anything with source strings except
43393 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43396 Although this packet is optional, and @value{GDBN} will only send it
43397 if the target replies with @samp{TracepointSource} @xref{General
43398 Query Packets}, it makes both disconnected tracing and trace files
43399 much easier to use. Otherwise the user must be careful that the
43400 tracepoints in effect while looking at trace frames are identical to
43401 the ones in effect during the trace run; even a small discrepancy
43402 could cause @samp{tdump} not to work, or a particular trace frame not
43405 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43406 @cindex define trace state variable, remote request
43407 @cindex @samp{QTDV} packet
43408 Create a new trace state variable, number @var{n}, with an initial
43409 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43410 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43411 the option of not using this packet for initial values of zero; the
43412 target should simply create the trace state variables as they are
43413 mentioned in expressions. The value @var{builtin} should be 1 (one)
43414 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43415 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43416 @samp{qTsV} packet had it set. The contents of @var{name} is the
43417 hex-encoded name (without the leading @samp{$}) of the trace state
43420 @item QTFrame:@var{n}
43421 @cindex @samp{QTFrame} packet
43422 Select the @var{n}'th tracepoint frame from the buffer, and use the
43423 register and memory contents recorded there to answer subsequent
43424 request packets from @value{GDBN}.
43426 A successful reply from the stub indicates that the stub has found the
43427 requested frame. The response is a series of parts, concatenated
43428 without separators, describing the frame we selected. Each part has
43429 one of the following forms:
43433 The selected frame is number @var{n} in the trace frame buffer;
43434 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
43435 was no frame matching the criteria in the request packet.
43438 The selected trace frame records a hit of tracepoint number @var{t};
43439 @var{t} is a hexadecimal number.
43443 @item QTFrame:pc:@var{addr}
43444 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43445 currently selected frame whose PC is @var{addr};
43446 @var{addr} is a hexadecimal number.
43448 @item QTFrame:tdp:@var{t}
43449 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43450 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
43451 is a hexadecimal number.
43453 @item QTFrame:range:@var{start}:@var{end}
43454 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43455 currently selected frame whose PC is between @var{start} (inclusive)
43456 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
43459 @item QTFrame:outside:@var{start}:@var{end}
43460 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
43461 frame @emph{outside} the given range of addresses (exclusive).
43464 @cindex @samp{qTMinFTPILen} packet
43465 This packet requests the minimum length of instruction at which a fast
43466 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
43467 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
43468 it depends on the target system being able to create trampolines in
43469 the first 64K of memory, which might or might not be possible for that
43470 system. So the reply to this packet will be 4 if it is able to
43477 The minimum instruction length is currently unknown.
43479 The minimum instruction length is @var{length}, where @var{length}
43480 is a hexadecimal number greater or equal to 1. A reply
43481 of 1 means that a fast tracepoint may be placed on any instruction
43482 regardless of size.
43484 An error has occurred.
43486 An empty reply indicates that the request is not supported by the stub.
43490 @cindex @samp{QTStart} packet
43491 Begin the tracepoint experiment. Begin collecting data from
43492 tracepoint hits in the trace frame buffer. This packet supports the
43493 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
43494 instruction reply packet}).
43497 @cindex @samp{QTStop} packet
43498 End the tracepoint experiment. Stop collecting trace frames.
43500 @item QTEnable:@var{n}:@var{addr}
43502 @cindex @samp{QTEnable} packet
43503 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
43504 experiment. If the tracepoint was previously disabled, then collection
43505 of data from it will resume.
43507 @item QTDisable:@var{n}:@var{addr}
43509 @cindex @samp{QTDisable} packet
43510 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
43511 experiment. No more data will be collected from the tracepoint unless
43512 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
43515 @cindex @samp{QTinit} packet
43516 Clear the table of tracepoints, and empty the trace frame buffer.
43518 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
43519 @cindex @samp{QTro} packet
43520 Establish the given ranges of memory as ``transparent''. The stub
43521 will answer requests for these ranges from memory's current contents,
43522 if they were not collected as part of the tracepoint hit.
43524 @value{GDBN} uses this to mark read-only regions of memory, like those
43525 containing program code. Since these areas never change, they should
43526 still have the same contents they did when the tracepoint was hit, so
43527 there's no reason for the stub to refuse to provide their contents.
43529 @item QTDisconnected:@var{value}
43530 @cindex @samp{QTDisconnected} packet
43531 Set the choice to what to do with the tracing run when @value{GDBN}
43532 disconnects from the target. A @var{value} of 1 directs the target to
43533 continue the tracing run, while 0 tells the target to stop tracing if
43534 @value{GDBN} is no longer in the picture.
43537 @cindex @samp{qTStatus} packet
43538 Ask the stub if there is a trace experiment running right now.
43540 The reply has the form:
43544 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
43545 @var{running} is a single digit @code{1} if the trace is presently
43546 running, or @code{0} if not. It is followed by semicolon-separated
43547 optional fields that an agent may use to report additional status.
43551 If the trace is not running, the agent may report any of several
43552 explanations as one of the optional fields:
43557 No trace has been run yet.
43559 @item tstop[:@var{text}]:0
43560 The trace was stopped by a user-originated stop command. The optional
43561 @var{text} field is a user-supplied string supplied as part of the
43562 stop command (for instance, an explanation of why the trace was
43563 stopped manually). It is hex-encoded.
43566 The trace stopped because the trace buffer filled up.
43568 @item tdisconnected:0
43569 The trace stopped because @value{GDBN} disconnected from the target.
43571 @item tpasscount:@var{tpnum}
43572 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
43574 @item terror:@var{text}:@var{tpnum}
43575 The trace stopped because tracepoint @var{tpnum} had an error. The
43576 string @var{text} is available to describe the nature of the error
43577 (for instance, a divide by zero in the condition expression); it
43581 The trace stopped for some other reason.
43585 Additional optional fields supply statistical and other information.
43586 Although not required, they are extremely useful for users monitoring
43587 the progress of a trace run. If a trace has stopped, and these
43588 numbers are reported, they must reflect the state of the just-stopped
43593 @item tframes:@var{n}
43594 The number of trace frames in the buffer.
43596 @item tcreated:@var{n}
43597 The total number of trace frames created during the run. This may
43598 be larger than the trace frame count, if the buffer is circular.
43600 @item tsize:@var{n}
43601 The total size of the trace buffer, in bytes.
43603 @item tfree:@var{n}
43604 The number of bytes still unused in the buffer.
43606 @item circular:@var{n}
43607 The value of the circular trace buffer flag. @code{1} means that the
43608 trace buffer is circular and old trace frames will be discarded if
43609 necessary to make room, @code{0} means that the trace buffer is linear
43612 @item disconn:@var{n}
43613 The value of the disconnected tracing flag. @code{1} means that
43614 tracing will continue after @value{GDBN} disconnects, @code{0} means
43615 that the trace run will stop.
43619 @item qTP:@var{tp}:@var{addr}
43620 @cindex tracepoint status, remote request
43621 @cindex @samp{qTP} packet
43622 Ask the stub for the current state of tracepoint number @var{tp} at
43623 address @var{addr}.
43627 @item V@var{hits}:@var{usage}
43628 The tracepoint has been hit @var{hits} times so far during the trace
43629 run, and accounts for @var{usage} in the trace buffer. Note that
43630 @code{while-stepping} steps are not counted as separate hits, but the
43631 steps' space consumption is added into the usage number.
43635 @item qTV:@var{var}
43636 @cindex trace state variable value, remote request
43637 @cindex @samp{qTV} packet
43638 Ask the stub for the value of the trace state variable number @var{var}.
43643 The value of the variable is @var{value}. This will be the current
43644 value of the variable if the user is examining a running target, or a
43645 saved value if the variable was collected in the trace frame that the
43646 user is looking at. Note that multiple requests may result in
43647 different reply values, such as when requesting values while the
43648 program is running.
43651 The value of the variable is unknown. This would occur, for example,
43652 if the user is examining a trace frame in which the requested variable
43657 @cindex @samp{qTfP} packet
43659 @cindex @samp{qTsP} packet
43660 These packets request data about tracepoints that are being used by
43661 the target. @value{GDBN} sends @code{qTfP} to get the first piece
43662 of data, and multiple @code{qTsP} to get additional pieces. Replies
43663 to these packets generally take the form of the @code{QTDP} packets
43664 that define tracepoints. (FIXME add detailed syntax)
43667 @cindex @samp{qTfV} packet
43669 @cindex @samp{qTsV} packet
43670 These packets request data about trace state variables that are on the
43671 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
43672 and multiple @code{qTsV} to get additional variables. Replies to
43673 these packets follow the syntax of the @code{QTDV} packets that define
43674 trace state variables.
43680 @cindex @samp{qTfSTM} packet
43681 @cindex @samp{qTsSTM} packet
43682 These packets request data about static tracepoint markers that exist
43683 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
43684 first piece of data, and multiple @code{qTsSTM} to get additional
43685 pieces. Replies to these packets take the following form:
43689 @item m @var{address}:@var{id}:@var{extra}
43691 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
43692 a comma-separated list of markers
43694 (lower case letter @samp{L}) denotes end of list.
43696 An error occurred. The error number @var{nn} is given as hex digits.
43698 An empty reply indicates that the request is not supported by the
43702 The @var{address} is encoded in hex;
43703 @var{id} and @var{extra} are strings encoded in hex.
43705 In response to each query, the target will reply with a list of one or
43706 more markers, separated by commas. @value{GDBN} will respond to each
43707 reply with a request for more markers (using the @samp{qs} form of the
43708 query), until the target responds with @samp{l} (lower-case ell, for
43711 @item qTSTMat:@var{address}
43713 @cindex @samp{qTSTMat} packet
43714 This packets requests data about static tracepoint markers in the
43715 target program at @var{address}. Replies to this packet follow the
43716 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
43717 tracepoint markers.
43719 @item QTSave:@var{filename}
43720 @cindex @samp{QTSave} packet
43721 This packet directs the target to save trace data to the file name
43722 @var{filename} in the target's filesystem. The @var{filename} is encoded
43723 as a hex string; the interpretation of the file name (relative vs
43724 absolute, wild cards, etc) is up to the target.
43726 @item qTBuffer:@var{offset},@var{len}
43727 @cindex @samp{qTBuffer} packet
43728 Return up to @var{len} bytes of the current contents of trace buffer,
43729 starting at @var{offset}. The trace buffer is treated as if it were
43730 a contiguous collection of traceframes, as per the trace file format.
43731 The reply consists as many hex-encoded bytes as the target can deliver
43732 in a packet; it is not an error to return fewer than were asked for.
43733 A reply consisting of just @code{l} indicates that no bytes are
43736 @item QTBuffer:circular:@var{value}
43737 This packet directs the target to use a circular trace buffer if
43738 @var{value} is 1, or a linear buffer if the value is 0.
43740 @item QTBuffer:size:@var{size}
43741 @anchor{QTBuffer-size}
43742 @cindex @samp{QTBuffer size} packet
43743 This packet directs the target to make the trace buffer be of size
43744 @var{size} if possible. A value of @code{-1} tells the target to
43745 use whatever size it prefers.
43747 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
43748 @cindex @samp{QTNotes} packet
43749 This packet adds optional textual notes to the trace run. Allowable
43750 types include @code{user}, @code{notes}, and @code{tstop}, the
43751 @var{text} fields are arbitrary strings, hex-encoded.
43755 @subsection Relocate instruction reply packet
43756 When installing fast tracepoints in memory, the target may need to
43757 relocate the instruction currently at the tracepoint address to a
43758 different address in memory. For most instructions, a simple copy is
43759 enough, but, for example, call instructions that implicitly push the
43760 return address on the stack, and relative branches or other
43761 PC-relative instructions require offset adjustment, so that the effect
43762 of executing the instruction at a different address is the same as if
43763 it had executed in the original location.
43765 In response to several of the tracepoint packets, the target may also
43766 respond with a number of intermediate @samp{qRelocInsn} request
43767 packets before the final result packet, to have @value{GDBN} handle
43768 this relocation operation. If a packet supports this mechanism, its
43769 documentation will explicitly say so. See for example the above
43770 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
43771 format of the request is:
43774 @item qRelocInsn:@var{from};@var{to}
43776 This requests @value{GDBN} to copy instruction at address @var{from}
43777 to address @var{to}, possibly adjusted so that executing the
43778 instruction at @var{to} has the same effect as executing it at
43779 @var{from}. @value{GDBN} writes the adjusted instruction to target
43780 memory starting at @var{to}.
43785 @item qRelocInsn:@var{adjusted_size}
43786 Informs the stub the relocation is complete. The @var{adjusted_size} is
43787 the length in bytes of resulting relocated instruction sequence.
43789 A badly formed request was detected, or an error was encountered while
43790 relocating the instruction.
43793 @node Host I/O Packets
43794 @section Host I/O Packets
43795 @cindex Host I/O, remote protocol
43796 @cindex file transfer, remote protocol
43798 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
43799 operations on the far side of a remote link. For example, Host I/O is
43800 used to upload and download files to a remote target with its own
43801 filesystem. Host I/O uses the same constant values and data structure
43802 layout as the target-initiated File-I/O protocol. However, the
43803 Host I/O packets are structured differently. The target-initiated
43804 protocol relies on target memory to store parameters and buffers.
43805 Host I/O requests are initiated by @value{GDBN}, and the
43806 target's memory is not involved. @xref{File-I/O Remote Protocol
43807 Extension}, for more details on the target-initiated protocol.
43809 The Host I/O request packets all encode a single operation along with
43810 its arguments. They have this format:
43814 @item vFile:@var{operation}: @var{parameter}@dots{}
43815 @var{operation} is the name of the particular request; the target
43816 should compare the entire packet name up to the second colon when checking
43817 for a supported operation. The format of @var{parameter} depends on
43818 the operation. Numbers are always passed in hexadecimal. Negative
43819 numbers have an explicit minus sign (i.e.@: two's complement is not
43820 used). Strings (e.g.@: filenames) are encoded as a series of
43821 hexadecimal bytes. The last argument to a system call may be a
43822 buffer of escaped binary data (@pxref{Binary Data}).
43826 The valid responses to Host I/O packets are:
43830 @item F @var{result} [, @var{errno}] [; @var{attachment}]
43831 @var{result} is the integer value returned by this operation, usually
43832 non-negative for success and -1 for errors. If an error has occured,
43833 @var{errno} will be included in the result specifying a
43834 value defined by the File-I/O protocol (@pxref{Errno Values}). For
43835 operations which return data, @var{attachment} supplies the data as a
43836 binary buffer. Binary buffers in response packets are escaped in the
43837 normal way (@pxref{Binary Data}). See the individual packet
43838 documentation for the interpretation of @var{result} and
43842 An empty response indicates that this operation is not recognized.
43846 These are the supported Host I/O operations:
43849 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
43850 Open a file at @var{filename} and return a file descriptor for it, or
43851 return -1 if an error occurs. The @var{filename} is a string,
43852 @var{flags} is an integer indicating a mask of open flags
43853 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
43854 of mode bits to use if the file is created (@pxref{mode_t Values}).
43855 @xref{open}, for details of the open flags and mode values.
43857 @item vFile:close: @var{fd}
43858 Close the open file corresponding to @var{fd} and return 0, or
43859 -1 if an error occurs.
43861 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
43862 Read data from the open file corresponding to @var{fd}. Up to
43863 @var{count} bytes will be read from the file, starting at @var{offset}
43864 relative to the start of the file. The target may read fewer bytes;
43865 common reasons include packet size limits and an end-of-file
43866 condition. The number of bytes read is returned. Zero should only be
43867 returned for a successful read at the end of the file, or if
43868 @var{count} was zero.
43870 The data read should be returned as a binary attachment on success.
43871 If zero bytes were read, the response should include an empty binary
43872 attachment (i.e.@: a trailing semicolon). The return value is the
43873 number of target bytes read; the binary attachment may be longer if
43874 some characters were escaped.
43876 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
43877 Write @var{data} (a binary buffer) to the open file corresponding
43878 to @var{fd}. Start the write at @var{offset} from the start of the
43879 file. Unlike many @code{write} system calls, there is no
43880 separate @var{count} argument; the length of @var{data} in the
43881 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
43882 which may be shorter than the length of @var{data}, or -1 if an
43885 @item vFile:fstat: @var{fd}
43886 Get information about the open file corresponding to @var{fd}.
43887 On success the information is returned as a binary attachment
43888 and the return value is the size of this attachment in bytes.
43889 If an error occurs the return value is -1. The format of the
43890 returned binary attachment is as described in @ref{struct stat}.
43892 @item vFile:unlink: @var{filename}
43893 Delete the file at @var{filename} on the target. Return 0,
43894 or -1 if an error occurs. The @var{filename} is a string.
43896 @item vFile:readlink: @var{filename}
43897 Read value of symbolic link @var{filename} on the target. Return
43898 the number of bytes read, or -1 if an error occurs.
43900 The data read should be returned as a binary attachment on success.
43901 If zero bytes were read, the response should include an empty binary
43902 attachment (i.e.@: a trailing semicolon). The return value is the
43903 number of target bytes read; the binary attachment may be longer if
43904 some characters were escaped.
43906 @item vFile:setfs: @var{pid}
43907 Select the filesystem on which @code{vFile} operations with
43908 @var{filename} arguments will operate. This is required for
43909 @value{GDBN} to be able to access files on remote targets where
43910 the remote stub does not share a common filesystem with the
43913 If @var{pid} is nonzero, select the filesystem as seen by process
43914 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
43915 the remote stub. Return 0 on success, or -1 if an error occurs.
43916 If @code{vFile:setfs:} indicates success, the selected filesystem
43917 remains selected until the next successful @code{vFile:setfs:}
43923 @section Interrupts
43924 @cindex interrupts (remote protocol)
43925 @anchor{interrupting remote targets}
43927 In all-stop mode, when a program on the remote target is running,
43928 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
43929 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
43930 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
43932 The precise meaning of @code{BREAK} is defined by the transport
43933 mechanism and may, in fact, be undefined. @value{GDBN} does not
43934 currently define a @code{BREAK} mechanism for any of the network
43935 interfaces except for TCP, in which case @value{GDBN} sends the
43936 @code{telnet} BREAK sequence.
43938 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
43939 transport mechanisms. It is represented by sending the single byte
43940 @code{0x03} without any of the usual packet overhead described in
43941 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
43942 transmitted as part of a packet, it is considered to be packet data
43943 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
43944 (@pxref{X packet}), used for binary downloads, may include an unescaped
43945 @code{0x03} as part of its packet.
43947 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
43948 When Linux kernel receives this sequence from serial port,
43949 it stops execution and connects to gdb.
43951 In non-stop mode, because packet resumptions are asynchronous
43952 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
43953 command to the remote stub, even when the target is running. For that
43954 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
43955 packet}) with the usual packet framing instead of the single byte
43958 Stubs are not required to recognize these interrupt mechanisms and the
43959 precise meaning associated with receipt of the interrupt is
43960 implementation defined. If the target supports debugging of multiple
43961 threads and/or processes, it should attempt to interrupt all
43962 currently-executing threads and processes.
43963 If the stub is successful at interrupting the
43964 running program, it should send one of the stop
43965 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
43966 of successfully stopping the program in all-stop mode, and a stop reply
43967 for each stopped thread in non-stop mode.
43968 Interrupts received while the
43969 program is stopped are queued and the program will be interrupted when
43970 it is resumed next time.
43972 @node Notification Packets
43973 @section Notification Packets
43974 @cindex notification packets
43975 @cindex packets, notification
43977 The @value{GDBN} remote serial protocol includes @dfn{notifications},
43978 packets that require no acknowledgment. Both the GDB and the stub
43979 may send notifications (although the only notifications defined at
43980 present are sent by the stub). Notifications carry information
43981 without incurring the round-trip latency of an acknowledgment, and so
43982 are useful for low-impact communications where occasional packet loss
43985 A notification packet has the form @samp{% @var{data} #
43986 @var{checksum}}, where @var{data} is the content of the notification,
43987 and @var{checksum} is a checksum of @var{data}, computed and formatted
43988 as for ordinary @value{GDBN} packets. A notification's @var{data}
43989 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
43990 receiving a notification, the recipient sends no @samp{+} or @samp{-}
43991 to acknowledge the notification's receipt or to report its corruption.
43993 Every notification's @var{data} begins with a name, which contains no
43994 colon characters, followed by a colon character.
43996 Recipients should silently ignore corrupted notifications and
43997 notifications they do not understand. Recipients should restart
43998 timeout periods on receipt of a well-formed notification, whether or
43999 not they understand it.
44001 Senders should only send the notifications described here when this
44002 protocol description specifies that they are permitted. In the
44003 future, we may extend the protocol to permit existing notifications in
44004 new contexts; this rule helps older senders avoid confusing newer
44007 (Older versions of @value{GDBN} ignore bytes received until they see
44008 the @samp{$} byte that begins an ordinary packet, so new stubs may
44009 transmit notifications without fear of confusing older clients. There
44010 are no notifications defined for @value{GDBN} to send at the moment, but we
44011 assume that most older stubs would ignore them, as well.)
44013 Each notification is comprised of three parts:
44015 @item @var{name}:@var{event}
44016 The notification packet is sent by the side that initiates the
44017 exchange (currently, only the stub does that), with @var{event}
44018 carrying the specific information about the notification, and
44019 @var{name} specifying the name of the notification.
44021 The acknowledge sent by the other side, usually @value{GDBN}, to
44022 acknowledge the exchange and request the event.
44025 The purpose of an asynchronous notification mechanism is to report to
44026 @value{GDBN} that something interesting happened in the remote stub.
44028 The remote stub may send notification @var{name}:@var{event}
44029 at any time, but @value{GDBN} acknowledges the notification when
44030 appropriate. The notification event is pending before @value{GDBN}
44031 acknowledges. Only one notification at a time may be pending; if
44032 additional events occur before @value{GDBN} has acknowledged the
44033 previous notification, they must be queued by the stub for later
44034 synchronous transmission in response to @var{ack} packets from
44035 @value{GDBN}. Because the notification mechanism is unreliable,
44036 the stub is permitted to resend a notification if it believes
44037 @value{GDBN} may not have received it.
44039 Specifically, notifications may appear when @value{GDBN} is not
44040 otherwise reading input from the stub, or when @value{GDBN} is
44041 expecting to read a normal synchronous response or a
44042 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44043 Notification packets are distinct from any other communication from
44044 the stub so there is no ambiguity.
44046 After receiving a notification, @value{GDBN} shall acknowledge it by
44047 sending a @var{ack} packet as a regular, synchronous request to the
44048 stub. Such acknowledgment is not required to happen immediately, as
44049 @value{GDBN} is permitted to send other, unrelated packets to the
44050 stub first, which the stub should process normally.
44052 Upon receiving a @var{ack} packet, if the stub has other queued
44053 events to report to @value{GDBN}, it shall respond by sending a
44054 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44055 packet to solicit further responses; again, it is permitted to send
44056 other, unrelated packets as well which the stub should process
44059 If the stub receives a @var{ack} packet and there are no additional
44060 @var{event} to report, the stub shall return an @samp{OK} response.
44061 At this point, @value{GDBN} has finished processing a notification
44062 and the stub has completed sending any queued events. @value{GDBN}
44063 won't accept any new notifications until the final @samp{OK} is
44064 received . If further notification events occur, the stub shall send
44065 a new notification, @value{GDBN} shall accept the notification, and
44066 the process shall be repeated.
44068 The process of asynchronous notification can be illustrated by the
44071 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44074 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44076 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44081 The following notifications are defined:
44082 @multitable @columnfractions 0.12 0.12 0.38 0.38
44091 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
44092 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
44093 for information on how these notifications are acknowledged by
44095 @tab Report an asynchronous stop event in non-stop mode.
44099 @node Remote Non-Stop
44100 @section Remote Protocol Support for Non-Stop Mode
44102 @value{GDBN}'s remote protocol supports non-stop debugging of
44103 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
44104 supports non-stop mode, it should report that to @value{GDBN} by including
44105 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
44107 @value{GDBN} typically sends a @samp{QNonStop} packet only when
44108 establishing a new connection with the stub. Entering non-stop mode
44109 does not alter the state of any currently-running threads, but targets
44110 must stop all threads in any already-attached processes when entering
44111 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
44112 probe the target state after a mode change.
44114 In non-stop mode, when an attached process encounters an event that
44115 would otherwise be reported with a stop reply, it uses the
44116 asynchronous notification mechanism (@pxref{Notification Packets}) to
44117 inform @value{GDBN}. In contrast to all-stop mode, where all threads
44118 in all processes are stopped when a stop reply is sent, in non-stop
44119 mode only the thread reporting the stop event is stopped. That is,
44120 when reporting a @samp{S} or @samp{T} response to indicate completion
44121 of a step operation, hitting a breakpoint, or a fault, only the
44122 affected thread is stopped; any other still-running threads continue
44123 to run. When reporting a @samp{W} or @samp{X} response, all running
44124 threads belonging to other attached processes continue to run.
44126 In non-stop mode, the target shall respond to the @samp{?} packet as
44127 follows. First, any incomplete stop reply notification/@samp{vStopped}
44128 sequence in progress is abandoned. The target must begin a new
44129 sequence reporting stop events for all stopped threads, whether or not
44130 it has previously reported those events to @value{GDBN}. The first
44131 stop reply is sent as a synchronous reply to the @samp{?} packet, and
44132 subsequent stop replies are sent as responses to @samp{vStopped} packets
44133 using the mechanism described above. The target must not send
44134 asynchronous stop reply notifications until the sequence is complete.
44135 If all threads are running when the target receives the @samp{?} packet,
44136 or if the target is not attached to any process, it shall respond
44139 If the stub supports non-stop mode, it should also support the
44140 @samp{swbreak} stop reason if software breakpoints are supported, and
44141 the @samp{hwbreak} stop reason if hardware breakpoints are supported
44142 (@pxref{swbreak stop reason}). This is because given the asynchronous
44143 nature of non-stop mode, between the time a thread hits a breakpoint
44144 and the time the event is finally processed by @value{GDBN}, the
44145 breakpoint may have already been removed from the target. Due to
44146 this, @value{GDBN} needs to be able to tell whether a trap stop was
44147 caused by a delayed breakpoint event, which should be ignored, as
44148 opposed to a random trap signal, which should be reported to the user.
44149 Note the @samp{swbreak} feature implies that the target is responsible
44150 for adjusting the PC when a software breakpoint triggers, if
44151 necessary, such as on the x86 architecture.
44153 @node Packet Acknowledgment
44154 @section Packet Acknowledgment
44156 @cindex acknowledgment, for @value{GDBN} remote
44157 @cindex packet acknowledgment, for @value{GDBN} remote
44158 By default, when either the host or the target machine receives a packet,
44159 the first response expected is an acknowledgment: either @samp{+} (to indicate
44160 the package was received correctly) or @samp{-} (to request retransmission).
44161 This mechanism allows the @value{GDBN} remote protocol to operate over
44162 unreliable transport mechanisms, such as a serial line.
44164 In cases where the transport mechanism is itself reliable (such as a pipe or
44165 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44166 It may be desirable to disable them in that case to reduce communication
44167 overhead, or for other reasons. This can be accomplished by means of the
44168 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44170 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44171 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44172 and response format still includes the normal checksum, as described in
44173 @ref{Overview}, but the checksum may be ignored by the receiver.
44175 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44176 no-acknowledgment mode, it should report that to @value{GDBN}
44177 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44178 @pxref{qSupported}.
44179 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44180 disabled via the @code{set remote noack-packet off} command
44181 (@pxref{Remote Configuration}),
44182 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44183 Only then may the stub actually turn off packet acknowledgments.
44184 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44185 response, which can be safely ignored by the stub.
44187 Note that @code{set remote noack-packet} command only affects negotiation
44188 between @value{GDBN} and the stub when subsequent connections are made;
44189 it does not affect the protocol acknowledgment state for any current
44191 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44192 new connection is established,
44193 there is also no protocol request to re-enable the acknowledgments
44194 for the current connection, once disabled.
44199 Example sequence of a target being re-started. Notice how the restart
44200 does not get any direct output:
44205 @emph{target restarts}
44208 <- @code{T001:1234123412341234}
44212 Example sequence of a target being stepped by a single instruction:
44215 -> @code{G1445@dots{}}
44220 <- @code{T001:1234123412341234}
44224 <- @code{1455@dots{}}
44228 @node File-I/O Remote Protocol Extension
44229 @section File-I/O Remote Protocol Extension
44230 @cindex File-I/O remote protocol extension
44233 * File-I/O Overview::
44234 * Protocol Basics::
44235 * The F Request Packet::
44236 * The F Reply Packet::
44237 * The Ctrl-C Message::
44239 * List of Supported Calls::
44240 * Protocol-specific Representation of Datatypes::
44242 * File-I/O Examples::
44245 @node File-I/O Overview
44246 @subsection File-I/O Overview
44247 @cindex file-i/o overview
44249 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44250 target to use the host's file system and console I/O to perform various
44251 system calls. System calls on the target system are translated into a
44252 remote protocol packet to the host system, which then performs the needed
44253 actions and returns a response packet to the target system.
44254 This simulates file system operations even on targets that lack file systems.
44256 The protocol is defined to be independent of both the host and target systems.
44257 It uses its own internal representation of datatypes and values. Both
44258 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44259 translating the system-dependent value representations into the internal
44260 protocol representations when data is transmitted.
44262 The communication is synchronous. A system call is possible only when
44263 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44264 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44265 the target is stopped to allow deterministic access to the target's
44266 memory. Therefore File-I/O is not interruptible by target signals. On
44267 the other hand, it is possible to interrupt File-I/O by a user interrupt
44268 (@samp{Ctrl-C}) within @value{GDBN}.
44270 The target's request to perform a host system call does not finish
44271 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44272 after finishing the system call, the target returns to continuing the
44273 previous activity (continue, step). No additional continue or step
44274 request from @value{GDBN} is required.
44277 (@value{GDBP}) continue
44278 <- target requests 'system call X'
44279 target is stopped, @value{GDBN} executes system call
44280 -> @value{GDBN} returns result
44281 ... target continues, @value{GDBN} returns to wait for the target
44282 <- target hits breakpoint and sends a Txx packet
44285 The protocol only supports I/O on the console and to regular files on
44286 the host file system. Character or block special devices, pipes,
44287 named pipes, sockets or any other communication method on the host
44288 system are not supported by this protocol.
44290 File I/O is not supported in non-stop mode.
44292 @node Protocol Basics
44293 @subsection Protocol Basics
44294 @cindex protocol basics, file-i/o
44296 The File-I/O protocol uses the @code{F} packet as the request as well
44297 as reply packet. Since a File-I/O system call can only occur when
44298 @value{GDBN} is waiting for a response from the continuing or stepping target,
44299 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44300 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44301 This @code{F} packet contains all information needed to allow @value{GDBN}
44302 to call the appropriate host system call:
44306 A unique identifier for the requested system call.
44309 All parameters to the system call. Pointers are given as addresses
44310 in the target memory address space. Pointers to strings are given as
44311 pointer/length pair. Numerical values are given as they are.
44312 Numerical control flags are given in a protocol-specific representation.
44316 At this point, @value{GDBN} has to perform the following actions.
44320 If the parameters include pointer values to data needed as input to a
44321 system call, @value{GDBN} requests this data from the target with a
44322 standard @code{m} packet request. This additional communication has to be
44323 expected by the target implementation and is handled as any other @code{m}
44327 @value{GDBN} translates all value from protocol representation to host
44328 representation as needed. Datatypes are coerced into the host types.
44331 @value{GDBN} calls the system call.
44334 It then coerces datatypes back to protocol representation.
44337 If the system call is expected to return data in buffer space specified
44338 by pointer parameters to the call, the data is transmitted to the
44339 target using a @code{M} or @code{X} packet. This packet has to be expected
44340 by the target implementation and is handled as any other @code{M} or @code{X}
44345 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44346 necessary information for the target to continue. This at least contains
44353 @code{errno}, if has been changed by the system call.
44360 After having done the needed type and value coercion, the target continues
44361 the latest continue or step action.
44363 @node The F Request Packet
44364 @subsection The @code{F} Request Packet
44365 @cindex file-i/o request packet
44366 @cindex @code{F} request packet
44368 The @code{F} request packet has the following format:
44371 @item F@var{call-id},@var{parameter@dots{}}
44373 @var{call-id} is the identifier to indicate the host system call to be called.
44374 This is just the name of the function.
44376 @var{parameter@dots{}} are the parameters to the system call.
44377 Parameters are hexadecimal integer values, either the actual values in case
44378 of scalar datatypes, pointers to target buffer space in case of compound
44379 datatypes and unspecified memory areas, or pointer/length pairs in case
44380 of string parameters. These are appended to the @var{call-id} as a
44381 comma-delimited list. All values are transmitted in ASCII
44382 string representation, pointer/length pairs separated by a slash.
44388 @node The F Reply Packet
44389 @subsection The @code{F} Reply Packet
44390 @cindex file-i/o reply packet
44391 @cindex @code{F} reply packet
44393 The @code{F} reply packet has the following format:
44397 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44399 @var{retcode} is the return code of the system call as hexadecimal value.
44401 @var{errno} is the @code{errno} set by the call, in protocol-specific
44403 This parameter can be omitted if the call was successful.
44405 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44406 case, @var{errno} must be sent as well, even if the call was successful.
44407 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44414 or, if the call was interrupted before the host call has been performed:
44421 assuming 4 is the protocol-specific representation of @code{EINTR}.
44426 @node The Ctrl-C Message
44427 @subsection The @samp{Ctrl-C} Message
44428 @cindex ctrl-c message, in file-i/o protocol
44430 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
44431 reply packet (@pxref{The F Reply Packet}),
44432 the target should behave as if it had
44433 gotten a break message. The meaning for the target is ``system call
44434 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
44435 (as with a break message) and return to @value{GDBN} with a @code{T02}
44438 It's important for the target to know in which
44439 state the system call was interrupted. There are two possible cases:
44443 The system call hasn't been performed on the host yet.
44446 The system call on the host has been finished.
44450 These two states can be distinguished by the target by the value of the
44451 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
44452 call hasn't been performed. This is equivalent to the @code{EINTR} handling
44453 on POSIX systems. In any other case, the target may presume that the
44454 system call has been finished --- successfully or not --- and should behave
44455 as if the break message arrived right after the system call.
44457 @value{GDBN} must behave reliably. If the system call has not been called
44458 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
44459 @code{errno} in the packet. If the system call on the host has been finished
44460 before the user requests a break, the full action must be finished by
44461 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
44462 The @code{F} packet may only be sent when either nothing has happened
44463 or the full action has been completed.
44466 @subsection Console I/O
44467 @cindex console i/o as part of file-i/o
44469 By default and if not explicitly closed by the target system, the file
44470 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
44471 on the @value{GDBN} console is handled as any other file output operation
44472 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
44473 by @value{GDBN} so that after the target read request from file descriptor
44474 0 all following typing is buffered until either one of the following
44479 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
44481 system call is treated as finished.
44484 The user presses @key{RET}. This is treated as end of input with a trailing
44488 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
44489 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
44493 If the user has typed more characters than fit in the buffer given to
44494 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
44495 either another @code{read(0, @dots{})} is requested by the target, or debugging
44496 is stopped at the user's request.
44499 @node List of Supported Calls
44500 @subsection List of Supported Calls
44501 @cindex list of supported file-i/o calls
44518 @unnumberedsubsubsec open
44519 @cindex open, file-i/o system call
44524 int open(const char *pathname, int flags);
44525 int open(const char *pathname, int flags, mode_t mode);
44529 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
44532 @var{flags} is the bitwise @code{OR} of the following values:
44536 If the file does not exist it will be created. The host
44537 rules apply as far as file ownership and time stamps
44541 When used with @code{O_CREAT}, if the file already exists it is
44542 an error and open() fails.
44545 If the file already exists and the open mode allows
44546 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
44547 truncated to zero length.
44550 The file is opened in append mode.
44553 The file is opened for reading only.
44556 The file is opened for writing only.
44559 The file is opened for reading and writing.
44563 Other bits are silently ignored.
44567 @var{mode} is the bitwise @code{OR} of the following values:
44571 User has read permission.
44574 User has write permission.
44577 Group has read permission.
44580 Group has write permission.
44583 Others have read permission.
44586 Others have write permission.
44590 Other bits are silently ignored.
44593 @item Return value:
44594 @code{open} returns the new file descriptor or -1 if an error
44601 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
44604 @var{pathname} refers to a directory.
44607 The requested access is not allowed.
44610 @var{pathname} was too long.
44613 A directory component in @var{pathname} does not exist.
44616 @var{pathname} refers to a device, pipe, named pipe or socket.
44619 @var{pathname} refers to a file on a read-only filesystem and
44620 write access was requested.
44623 @var{pathname} is an invalid pointer value.
44626 No space on device to create the file.
44629 The process already has the maximum number of files open.
44632 The limit on the total number of files open on the system
44636 The call was interrupted by the user.
44642 @unnumberedsubsubsec close
44643 @cindex close, file-i/o system call
44652 @samp{Fclose,@var{fd}}
44654 @item Return value:
44655 @code{close} returns zero on success, or -1 if an error occurred.
44661 @var{fd} isn't a valid open file descriptor.
44664 The call was interrupted by the user.
44670 @unnumberedsubsubsec read
44671 @cindex read, file-i/o system call
44676 int read(int fd, void *buf, unsigned int count);
44680 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
44682 @item Return value:
44683 On success, the number of bytes read is returned.
44684 Zero indicates end of file. If count is zero, read
44685 returns zero as well. On error, -1 is returned.
44691 @var{fd} is not a valid file descriptor or is not open for
44695 @var{bufptr} is an invalid pointer value.
44698 The call was interrupted by the user.
44704 @unnumberedsubsubsec write
44705 @cindex write, file-i/o system call
44710 int write(int fd, const void *buf, unsigned int count);
44714 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
44716 @item Return value:
44717 On success, the number of bytes written are returned.
44718 Zero indicates nothing was written. On error, -1
44725 @var{fd} is not a valid file descriptor or is not open for
44729 @var{bufptr} is an invalid pointer value.
44732 An attempt was made to write a file that exceeds the
44733 host-specific maximum file size allowed.
44736 No space on device to write the data.
44739 The call was interrupted by the user.
44745 @unnumberedsubsubsec lseek
44746 @cindex lseek, file-i/o system call
44751 long lseek (int fd, long offset, int flag);
44755 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
44757 @var{flag} is one of:
44761 The offset is set to @var{offset} bytes.
44764 The offset is set to its current location plus @var{offset}
44768 The offset is set to the size of the file plus @var{offset}
44772 @item Return value:
44773 On success, the resulting unsigned offset in bytes from
44774 the beginning of the file is returned. Otherwise, a
44775 value of -1 is returned.
44781 @var{fd} is not a valid open file descriptor.
44784 @var{fd} is associated with the @value{GDBN} console.
44787 @var{flag} is not a proper value.
44790 The call was interrupted by the user.
44796 @unnumberedsubsubsec rename
44797 @cindex rename, file-i/o system call
44802 int rename(const char *oldpath, const char *newpath);
44806 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
44808 @item Return value:
44809 On success, zero is returned. On error, -1 is returned.
44815 @var{newpath} is an existing directory, but @var{oldpath} is not a
44819 @var{newpath} is a non-empty directory.
44822 @var{oldpath} or @var{newpath} is a directory that is in use by some
44826 An attempt was made to make a directory a subdirectory
44830 A component used as a directory in @var{oldpath} or new
44831 path is not a directory. Or @var{oldpath} is a directory
44832 and @var{newpath} exists but is not a directory.
44835 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
44838 No access to the file or the path of the file.
44842 @var{oldpath} or @var{newpath} was too long.
44845 A directory component in @var{oldpath} or @var{newpath} does not exist.
44848 The file is on a read-only filesystem.
44851 The device containing the file has no room for the new
44855 The call was interrupted by the user.
44861 @unnumberedsubsubsec unlink
44862 @cindex unlink, file-i/o system call
44867 int unlink(const char *pathname);
44871 @samp{Funlink,@var{pathnameptr}/@var{len}}
44873 @item Return value:
44874 On success, zero is returned. On error, -1 is returned.
44880 No access to the file or the path of the file.
44883 The system does not allow unlinking of directories.
44886 The file @var{pathname} cannot be unlinked because it's
44887 being used by another process.
44890 @var{pathnameptr} is an invalid pointer value.
44893 @var{pathname} was too long.
44896 A directory component in @var{pathname} does not exist.
44899 A component of the path is not a directory.
44902 The file is on a read-only filesystem.
44905 The call was interrupted by the user.
44911 @unnumberedsubsubsec stat/fstat
44912 @cindex fstat, file-i/o system call
44913 @cindex stat, file-i/o system call
44918 int stat(const char *pathname, struct stat *buf);
44919 int fstat(int fd, struct stat *buf);
44923 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
44924 @samp{Ffstat,@var{fd},@var{bufptr}}
44926 @item Return value:
44927 On success, zero is returned. On error, -1 is returned.
44933 @var{fd} is not a valid open file.
44936 A directory component in @var{pathname} does not exist or the
44937 path is an empty string.
44940 A component of the path is not a directory.
44943 @var{pathnameptr} is an invalid pointer value.
44946 No access to the file or the path of the file.
44949 @var{pathname} was too long.
44952 The call was interrupted by the user.
44958 @unnumberedsubsubsec gettimeofday
44959 @cindex gettimeofday, file-i/o system call
44964 int gettimeofday(struct timeval *tv, void *tz);
44968 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
44970 @item Return value:
44971 On success, 0 is returned, -1 otherwise.
44977 @var{tz} is a non-NULL pointer.
44980 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
44986 @unnumberedsubsubsec isatty
44987 @cindex isatty, file-i/o system call
44992 int isatty(int fd);
44996 @samp{Fisatty,@var{fd}}
44998 @item Return value:
44999 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45005 The call was interrupted by the user.
45010 Note that the @code{isatty} call is treated as a special case: it returns
45011 1 to the target if the file descriptor is attached
45012 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45013 would require implementing @code{ioctl} and would be more complex than
45018 @unnumberedsubsubsec system
45019 @cindex system, file-i/o system call
45024 int system(const char *command);
45028 @samp{Fsystem,@var{commandptr}/@var{len}}
45030 @item Return value:
45031 If @var{len} is zero, the return value indicates whether a shell is
45032 available. A zero return value indicates a shell is not available.
45033 For non-zero @var{len}, the value returned is -1 on error and the
45034 return status of the command otherwise. Only the exit status of the
45035 command is returned, which is extracted from the host's @code{system}
45036 return value by calling @code{WEXITSTATUS(retval)}. In case
45037 @file{/bin/sh} could not be executed, 127 is returned.
45043 The call was interrupted by the user.
45048 @value{GDBN} takes over the full task of calling the necessary host calls
45049 to perform the @code{system} call. The return value of @code{system} on
45050 the host is simplified before it's returned
45051 to the target. Any termination signal information from the child process
45052 is discarded, and the return value consists
45053 entirely of the exit status of the called command.
45055 Due to security concerns, the @code{system} call is by default refused
45056 by @value{GDBN}. The user has to allow this call explicitly with the
45057 @code{set remote system-call-allowed 1} command.
45060 @item set remote system-call-allowed
45061 @kindex set remote system-call-allowed
45062 Control whether to allow the @code{system} calls in the File I/O
45063 protocol for the remote target. The default is zero (disabled).
45065 @item show remote system-call-allowed
45066 @kindex show remote system-call-allowed
45067 Show whether the @code{system} calls are allowed in the File I/O
45071 @node Protocol-specific Representation of Datatypes
45072 @subsection Protocol-specific Representation of Datatypes
45073 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45076 * Integral Datatypes::
45078 * Memory Transfer::
45083 @node Integral Datatypes
45084 @unnumberedsubsubsec Integral Datatypes
45085 @cindex integral datatypes, in file-i/o protocol
45087 The integral datatypes used in the system calls are @code{int},
45088 @code{unsigned int}, @code{long}, @code{unsigned long},
45089 @code{mode_t}, and @code{time_t}.
45091 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
45092 implemented as 32 bit values in this protocol.
45094 @code{long} and @code{unsigned long} are implemented as 64 bit types.
45096 @xref{Limits}, for corresponding MIN and MAX values (similar to those
45097 in @file{limits.h}) to allow range checking on host and target.
45099 @code{time_t} datatypes are defined as seconds since the Epoch.
45101 All integral datatypes transferred as part of a memory read or write of a
45102 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
45105 @node Pointer Values
45106 @unnumberedsubsubsec Pointer Values
45107 @cindex pointer values, in file-i/o protocol
45109 Pointers to target data are transmitted as they are. An exception
45110 is made for pointers to buffers for which the length isn't
45111 transmitted as part of the function call, namely strings. Strings
45112 are transmitted as a pointer/length pair, both as hex values, e.g.@:
45119 which is a pointer to data of length 18 bytes at position 0x1aaf.
45120 The length is defined as the full string length in bytes, including
45121 the trailing null byte. For example, the string @code{"hello world"}
45122 at address 0x123456 is transmitted as
45128 @node Memory Transfer
45129 @unnumberedsubsubsec Memory Transfer
45130 @cindex memory transfer, in file-i/o protocol
45132 Structured data which is transferred using a memory read or write (for
45133 example, a @code{struct stat}) is expected to be in a protocol-specific format
45134 with all scalar multibyte datatypes being big endian. Translation to
45135 this representation needs to be done both by the target before the @code{F}
45136 packet is sent, and by @value{GDBN} before
45137 it transfers memory to the target. Transferred pointers to structured
45138 data should point to the already-coerced data at any time.
45142 @unnumberedsubsubsec struct stat
45143 @cindex struct stat, in file-i/o protocol
45145 The buffer of type @code{struct stat} used by the target and @value{GDBN}
45146 is defined as follows:
45150 unsigned int st_dev; /* device */
45151 unsigned int st_ino; /* inode */
45152 mode_t st_mode; /* protection */
45153 unsigned int st_nlink; /* number of hard links */
45154 unsigned int st_uid; /* user ID of owner */
45155 unsigned int st_gid; /* group ID of owner */
45156 unsigned int st_rdev; /* device type (if inode device) */
45157 unsigned long st_size; /* total size, in bytes */
45158 unsigned long st_blksize; /* blocksize for filesystem I/O */
45159 unsigned long st_blocks; /* number of blocks allocated */
45160 time_t st_atime; /* time of last access */
45161 time_t st_mtime; /* time of last modification */
45162 time_t st_ctime; /* time of last change */
45166 The integral datatypes conform to the definitions given in the
45167 appropriate section (see @ref{Integral Datatypes}, for details) so this
45168 structure is of size 64 bytes.
45170 The values of several fields have a restricted meaning and/or
45176 A value of 0 represents a file, 1 the console.
45179 No valid meaning for the target. Transmitted unchanged.
45182 Valid mode bits are described in @ref{Constants}. Any other
45183 bits have currently no meaning for the target.
45188 No valid meaning for the target. Transmitted unchanged.
45193 These values have a host and file system dependent
45194 accuracy. Especially on Windows hosts, the file system may not
45195 support exact timing values.
45198 The target gets a @code{struct stat} of the above representation and is
45199 responsible for coercing it to the target representation before
45202 Note that due to size differences between the host, target, and protocol
45203 representations of @code{struct stat} members, these members could eventually
45204 get truncated on the target.
45206 @node struct timeval
45207 @unnumberedsubsubsec struct timeval
45208 @cindex struct timeval, in file-i/o protocol
45210 The buffer of type @code{struct timeval} used by the File-I/O protocol
45211 is defined as follows:
45215 time_t tv_sec; /* second */
45216 long tv_usec; /* microsecond */
45220 The integral datatypes conform to the definitions given in the
45221 appropriate section (see @ref{Integral Datatypes}, for details) so this
45222 structure is of size 8 bytes.
45225 @subsection Constants
45226 @cindex constants, in file-i/o protocol
45228 The following values are used for the constants inside of the
45229 protocol. @value{GDBN} and target are responsible for translating these
45230 values before and after the call as needed.
45241 @unnumberedsubsubsec Open Flags
45242 @cindex open flags, in file-i/o protocol
45244 All values are given in hexadecimal representation.
45256 @node mode_t Values
45257 @unnumberedsubsubsec mode_t Values
45258 @cindex mode_t values, in file-i/o protocol
45260 All values are given in octal representation.
45277 @unnumberedsubsubsec Errno Values
45278 @cindex errno values, in file-i/o protocol
45280 All values are given in decimal representation.
45305 @code{EUNKNOWN} is used as a fallback error value if a host system returns
45306 any error value not in the list of supported error numbers.
45309 @unnumberedsubsubsec Lseek Flags
45310 @cindex lseek flags, in file-i/o protocol
45319 @unnumberedsubsubsec Limits
45320 @cindex limits, in file-i/o protocol
45322 All values are given in decimal representation.
45325 INT_MIN -2147483648
45327 UINT_MAX 4294967295
45328 LONG_MIN -9223372036854775808
45329 LONG_MAX 9223372036854775807
45330 ULONG_MAX 18446744073709551615
45333 @node File-I/O Examples
45334 @subsection File-I/O Examples
45335 @cindex file-i/o examples
45337 Example sequence of a write call, file descriptor 3, buffer is at target
45338 address 0x1234, 6 bytes should be written:
45341 <- @code{Fwrite,3,1234,6}
45342 @emph{request memory read from target}
45345 @emph{return "6 bytes written"}
45349 Example sequence of a read call, file descriptor 3, buffer is at target
45350 address 0x1234, 6 bytes should be read:
45353 <- @code{Fread,3,1234,6}
45354 @emph{request memory write to target}
45355 -> @code{X1234,6:XXXXXX}
45356 @emph{return "6 bytes read"}
45360 Example sequence of a read call, call fails on the host due to invalid
45361 file descriptor (@code{EBADF}):
45364 <- @code{Fread,3,1234,6}
45368 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45372 <- @code{Fread,3,1234,6}
45377 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45381 <- @code{Fread,3,1234,6}
45382 -> @code{X1234,6:XXXXXX}
45386 @node Library List Format
45387 @section Library List Format
45388 @cindex library list format, remote protocol
45390 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45391 same process as your application to manage libraries. In this case,
45392 @value{GDBN} can use the loader's symbol table and normal memory
45393 operations to maintain a list of shared libraries. On other
45394 platforms, the operating system manages loaded libraries.
45395 @value{GDBN} can not retrieve the list of currently loaded libraries
45396 through memory operations, so it uses the @samp{qXfer:libraries:read}
45397 packet (@pxref{qXfer library list read}) instead. The remote stub
45398 queries the target's operating system and reports which libraries
45401 The @samp{qXfer:libraries:read} packet returns an XML document which
45402 lists loaded libraries and their offsets. Each library has an
45403 associated name and one or more segment or section base addresses,
45404 which report where the library was loaded in memory.
45406 For the common case of libraries that are fully linked binaries, the
45407 library should have a list of segments. If the target supports
45408 dynamic linking of a relocatable object file, its library XML element
45409 should instead include a list of allocated sections. The segment or
45410 section bases are start addresses, not relocation offsets; they do not
45411 depend on the library's link-time base addresses.
45413 @value{GDBN} must be linked with the Expat library to support XML
45414 library lists. @xref{Expat}.
45416 A simple memory map, with one loaded library relocated by a single
45417 offset, looks like this:
45421 <library name="/lib/libc.so.6">
45422 <segment address="0x10000000"/>
45427 Another simple memory map, with one loaded library with three
45428 allocated sections (.text, .data, .bss), looks like this:
45432 <library name="sharedlib.o">
45433 <section address="0x10000000"/>
45434 <section address="0x20000000"/>
45435 <section address="0x30000000"/>
45440 The format of a library list is described by this DTD:
45443 <!-- library-list: Root element with versioning -->
45444 <!ELEMENT library-list (library)*>
45445 <!ATTLIST library-list version CDATA #FIXED "1.0">
45446 <!ELEMENT library (segment*, section*)>
45447 <!ATTLIST library name CDATA #REQUIRED>
45448 <!ELEMENT segment EMPTY>
45449 <!ATTLIST segment address CDATA #REQUIRED>
45450 <!ELEMENT section EMPTY>
45451 <!ATTLIST section address CDATA #REQUIRED>
45454 In addition, segments and section descriptors cannot be mixed within a
45455 single library element, and you must supply at least one segment or
45456 section for each library.
45458 @node Library List Format for SVR4 Targets
45459 @section Library List Format for SVR4 Targets
45460 @cindex library list format, remote protocol
45462 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
45463 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
45464 shared libraries. Still a special library list provided by this packet is
45465 more efficient for the @value{GDBN} remote protocol.
45467 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
45468 loaded libraries and their SVR4 linker parameters. For each library on SVR4
45469 target, the following parameters are reported:
45473 @code{name}, the absolute file name from the @code{l_name} field of
45474 @code{struct link_map}.
45476 @code{lm} with address of @code{struct link_map} used for TLS
45477 (Thread Local Storage) access.
45479 @code{l_addr}, the displacement as read from the field @code{l_addr} of
45480 @code{struct link_map}. For prelinked libraries this is not an absolute
45481 memory address. It is a displacement of absolute memory address against
45482 address the file was prelinked to during the library load.
45484 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
45487 Additionally the single @code{main-lm} attribute specifies address of
45488 @code{struct link_map} used for the main executable. This parameter is used
45489 for TLS access and its presence is optional.
45491 @value{GDBN} must be linked with the Expat library to support XML
45492 SVR4 library lists. @xref{Expat}.
45494 A simple memory map, with two loaded libraries (which do not use prelink),
45498 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
45499 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
45501 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
45503 </library-list-svr>
45506 The format of an SVR4 library list is described by this DTD:
45509 <!-- library-list-svr4: Root element with versioning -->
45510 <!ELEMENT library-list-svr4 (library)*>
45511 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
45512 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
45513 <!ELEMENT library EMPTY>
45514 <!ATTLIST library name CDATA #REQUIRED>
45515 <!ATTLIST library lm CDATA #REQUIRED>
45516 <!ATTLIST library l_addr CDATA #REQUIRED>
45517 <!ATTLIST library l_ld CDATA #REQUIRED>
45520 @node Memory Map Format
45521 @section Memory Map Format
45522 @cindex memory map format
45524 To be able to write into flash memory, @value{GDBN} needs to obtain a
45525 memory map from the target. This section describes the format of the
45528 The memory map is obtained using the @samp{qXfer:memory-map:read}
45529 (@pxref{qXfer memory map read}) packet and is an XML document that
45530 lists memory regions.
45532 @value{GDBN} must be linked with the Expat library to support XML
45533 memory maps. @xref{Expat}.
45535 The top-level structure of the document is shown below:
45538 <?xml version="1.0"?>
45539 <!DOCTYPE memory-map
45540 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45541 "http://sourceware.org/gdb/gdb-memory-map.dtd">
45547 Each region can be either:
45552 A region of RAM starting at @var{addr} and extending for @var{length}
45556 <memory type="ram" start="@var{addr}" length="@var{length}"/>
45561 A region of read-only memory:
45564 <memory type="rom" start="@var{addr}" length="@var{length}"/>
45569 A region of flash memory, with erasure blocks @var{blocksize}
45573 <memory type="flash" start="@var{addr}" length="@var{length}">
45574 <property name="blocksize">@var{blocksize}</property>
45580 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
45581 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
45582 packets to write to addresses in such ranges.
45584 The formal DTD for memory map format is given below:
45587 <!-- ................................................... -->
45588 <!-- Memory Map XML DTD ................................ -->
45589 <!-- File: memory-map.dtd .............................. -->
45590 <!-- .................................... .............. -->
45591 <!-- memory-map.dtd -->
45592 <!-- memory-map: Root element with versioning -->
45593 <!ELEMENT memory-map (memory)*>
45594 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
45595 <!ELEMENT memory (property)*>
45596 <!-- memory: Specifies a memory region,
45597 and its type, or device. -->
45598 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
45599 start CDATA #REQUIRED
45600 length CDATA #REQUIRED>
45601 <!-- property: Generic attribute tag -->
45602 <!ELEMENT property (#PCDATA | property)*>
45603 <!ATTLIST property name (blocksize) #REQUIRED>
45606 @node Thread List Format
45607 @section Thread List Format
45608 @cindex thread list format
45610 To efficiently update the list of threads and their attributes,
45611 @value{GDBN} issues the @samp{qXfer:threads:read} packet
45612 (@pxref{qXfer threads read}) and obtains the XML document with
45613 the following structure:
45616 <?xml version="1.0"?>
45618 <thread id="id" core="0" name="name">
45619 ... description ...
45624 Each @samp{thread} element must have the @samp{id} attribute that
45625 identifies the thread (@pxref{thread-id syntax}). The
45626 @samp{core} attribute, if present, specifies which processor core
45627 the thread was last executing on. The @samp{name} attribute, if
45628 present, specifies the human-readable name of the thread. The content
45629 of the of @samp{thread} element is interpreted as human-readable
45630 auxiliary information. The @samp{handle} attribute, if present,
45631 is a hex encoded representation of the thread handle.
45634 @node Traceframe Info Format
45635 @section Traceframe Info Format
45636 @cindex traceframe info format
45638 To be able to know which objects in the inferior can be examined when
45639 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
45640 memory ranges, registers and trace state variables that have been
45641 collected in a traceframe.
45643 This list is obtained using the @samp{qXfer:traceframe-info:read}
45644 (@pxref{qXfer traceframe info read}) packet and is an XML document.
45646 @value{GDBN} must be linked with the Expat library to support XML
45647 traceframe info discovery. @xref{Expat}.
45649 The top-level structure of the document is shown below:
45652 <?xml version="1.0"?>
45653 <!DOCTYPE traceframe-info
45654 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45655 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
45661 Each traceframe block can be either:
45666 A region of collected memory starting at @var{addr} and extending for
45667 @var{length} bytes from there:
45670 <memory start="@var{addr}" length="@var{length}"/>
45674 A block indicating trace state variable numbered @var{number} has been
45678 <tvar id="@var{number}"/>
45683 The formal DTD for the traceframe info format is given below:
45686 <!ELEMENT traceframe-info (memory | tvar)* >
45687 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
45689 <!ELEMENT memory EMPTY>
45690 <!ATTLIST memory start CDATA #REQUIRED
45691 length CDATA #REQUIRED>
45693 <!ATTLIST tvar id CDATA #REQUIRED>
45696 @node Branch Trace Format
45697 @section Branch Trace Format
45698 @cindex branch trace format
45700 In order to display the branch trace of an inferior thread,
45701 @value{GDBN} needs to obtain the list of branches. This list is
45702 represented as list of sequential code blocks that are connected via
45703 branches. The code in each block has been executed sequentially.
45705 This list is obtained using the @samp{qXfer:btrace:read}
45706 (@pxref{qXfer btrace read}) packet and is an XML document.
45708 @value{GDBN} must be linked with the Expat library to support XML
45709 traceframe info discovery. @xref{Expat}.
45711 The top-level structure of the document is shown below:
45714 <?xml version="1.0"?>
45716 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
45717 "http://sourceware.org/gdb/gdb-btrace.dtd">
45726 A block of sequentially executed instructions starting at @var{begin}
45727 and ending at @var{end}:
45730 <block begin="@var{begin}" end="@var{end}"/>
45735 The formal DTD for the branch trace format is given below:
45738 <!ELEMENT btrace (block* | pt) >
45739 <!ATTLIST btrace version CDATA #FIXED "1.0">
45741 <!ELEMENT block EMPTY>
45742 <!ATTLIST block begin CDATA #REQUIRED
45743 end CDATA #REQUIRED>
45745 <!ELEMENT pt (pt-config?, raw?)>
45747 <!ELEMENT pt-config (cpu?)>
45749 <!ELEMENT cpu EMPTY>
45750 <!ATTLIST cpu vendor CDATA #REQUIRED
45751 family CDATA #REQUIRED
45752 model CDATA #REQUIRED
45753 stepping CDATA #REQUIRED>
45755 <!ELEMENT raw (#PCDATA)>
45758 @node Branch Trace Configuration Format
45759 @section Branch Trace Configuration Format
45760 @cindex branch trace configuration format
45762 For each inferior thread, @value{GDBN} can obtain the branch trace
45763 configuration using the @samp{qXfer:btrace-conf:read}
45764 (@pxref{qXfer btrace-conf read}) packet.
45766 The configuration describes the branch trace format and configuration
45767 settings for that format. The following information is described:
45771 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
45774 The size of the @acronym{BTS} ring buffer in bytes.
45777 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
45781 The size of the @acronym{Intel PT} ring buffer in bytes.
45785 @value{GDBN} must be linked with the Expat library to support XML
45786 branch trace configuration discovery. @xref{Expat}.
45788 The formal DTD for the branch trace configuration format is given below:
45791 <!ELEMENT btrace-conf (bts?, pt?)>
45792 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
45794 <!ELEMENT bts EMPTY>
45795 <!ATTLIST bts size CDATA #IMPLIED>
45797 <!ELEMENT pt EMPTY>
45798 <!ATTLIST pt size CDATA #IMPLIED>
45801 @include agentexpr.texi
45803 @node Target Descriptions
45804 @appendix Target Descriptions
45805 @cindex target descriptions
45807 One of the challenges of using @value{GDBN} to debug embedded systems
45808 is that there are so many minor variants of each processor
45809 architecture in use. It is common practice for vendors to start with
45810 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
45811 and then make changes to adapt it to a particular market niche. Some
45812 architectures have hundreds of variants, available from dozens of
45813 vendors. This leads to a number of problems:
45817 With so many different customized processors, it is difficult for
45818 the @value{GDBN} maintainers to keep up with the changes.
45820 Since individual variants may have short lifetimes or limited
45821 audiences, it may not be worthwhile to carry information about every
45822 variant in the @value{GDBN} source tree.
45824 When @value{GDBN} does support the architecture of the embedded system
45825 at hand, the task of finding the correct architecture name to give the
45826 @command{set architecture} command can be error-prone.
45829 To address these problems, the @value{GDBN} remote protocol allows a
45830 target system to not only identify itself to @value{GDBN}, but to
45831 actually describe its own features. This lets @value{GDBN} support
45832 processor variants it has never seen before --- to the extent that the
45833 descriptions are accurate, and that @value{GDBN} understands them.
45835 @value{GDBN} must be linked with the Expat library to support XML
45836 target descriptions. @xref{Expat}.
45839 * Retrieving Descriptions:: How descriptions are fetched from a target.
45840 * Target Description Format:: The contents of a target description.
45841 * Predefined Target Types:: Standard types available for target
45843 * Enum Target Types:: How to define enum target types.
45844 * Standard Target Features:: Features @value{GDBN} knows about.
45847 @node Retrieving Descriptions
45848 @section Retrieving Descriptions
45850 Target descriptions can be read from the target automatically, or
45851 specified by the user manually. The default behavior is to read the
45852 description from the target. @value{GDBN} retrieves it via the remote
45853 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
45854 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
45855 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
45856 XML document, of the form described in @ref{Target Description
45859 Alternatively, you can specify a file to read for the target description.
45860 If a file is set, the target will not be queried. The commands to
45861 specify a file are:
45864 @cindex set tdesc filename
45865 @item set tdesc filename @var{path}
45866 Read the target description from @var{path}.
45868 @cindex unset tdesc filename
45869 @item unset tdesc filename
45870 Do not read the XML target description from a file. @value{GDBN}
45871 will use the description supplied by the current target.
45873 @cindex show tdesc filename
45874 @item show tdesc filename
45875 Show the filename to read for a target description, if any.
45879 @node Target Description Format
45880 @section Target Description Format
45881 @cindex target descriptions, XML format
45883 A target description annex is an @uref{http://www.w3.org/XML/, XML}
45884 document which complies with the Document Type Definition provided in
45885 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
45886 means you can use generally available tools like @command{xmllint} to
45887 check that your feature descriptions are well-formed and valid.
45888 However, to help people unfamiliar with XML write descriptions for
45889 their targets, we also describe the grammar here.
45891 Target descriptions can identify the architecture of the remote target
45892 and (for some architectures) provide information about custom register
45893 sets. They can also identify the OS ABI of the remote target.
45894 @value{GDBN} can use this information to autoconfigure for your
45895 target, or to warn you if you connect to an unsupported target.
45897 Here is a simple target description:
45900 <target version="1.0">
45901 <architecture>i386:x86-64</architecture>
45906 This minimal description only says that the target uses
45907 the x86-64 architecture.
45909 A target description has the following overall form, with [ ] marking
45910 optional elements and @dots{} marking repeatable elements. The elements
45911 are explained further below.
45914 <?xml version="1.0"?>
45915 <!DOCTYPE target SYSTEM "gdb-target.dtd">
45916 <target version="1.0">
45917 @r{[}@var{architecture}@r{]}
45918 @r{[}@var{osabi}@r{]}
45919 @r{[}@var{compatible}@r{]}
45920 @r{[}@var{feature}@dots{}@r{]}
45925 The description is generally insensitive to whitespace and line
45926 breaks, under the usual common-sense rules. The XML version
45927 declaration and document type declaration can generally be omitted
45928 (@value{GDBN} does not require them), but specifying them may be
45929 useful for XML validation tools. The @samp{version} attribute for
45930 @samp{<target>} may also be omitted, but we recommend
45931 including it; if future versions of @value{GDBN} use an incompatible
45932 revision of @file{gdb-target.dtd}, they will detect and report
45933 the version mismatch.
45935 @subsection Inclusion
45936 @cindex target descriptions, inclusion
45939 @cindex <xi:include>
45942 It can sometimes be valuable to split a target description up into
45943 several different annexes, either for organizational purposes, or to
45944 share files between different possible target descriptions. You can
45945 divide a description into multiple files by replacing any element of
45946 the target description with an inclusion directive of the form:
45949 <xi:include href="@var{document}"/>
45953 When @value{GDBN} encounters an element of this form, it will retrieve
45954 the named XML @var{document}, and replace the inclusion directive with
45955 the contents of that document. If the current description was read
45956 using @samp{qXfer}, then so will be the included document;
45957 @var{document} will be interpreted as the name of an annex. If the
45958 current description was read from a file, @value{GDBN} will look for
45959 @var{document} as a file in the same directory where it found the
45960 original description.
45962 @subsection Architecture
45963 @cindex <architecture>
45965 An @samp{<architecture>} element has this form:
45968 <architecture>@var{arch}</architecture>
45971 @var{arch} is one of the architectures from the set accepted by
45972 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
45975 @cindex @code{<osabi>}
45977 This optional field was introduced in @value{GDBN} version 7.0.
45978 Previous versions of @value{GDBN} ignore it.
45980 An @samp{<osabi>} element has this form:
45983 <osabi>@var{abi-name}</osabi>
45986 @var{abi-name} is an OS ABI name from the same selection accepted by
45987 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
45989 @subsection Compatible Architecture
45990 @cindex @code{<compatible>}
45992 This optional field was introduced in @value{GDBN} version 7.0.
45993 Previous versions of @value{GDBN} ignore it.
45995 A @samp{<compatible>} element has this form:
45998 <compatible>@var{arch}</compatible>
46001 @var{arch} is one of the architectures from the set accepted by
46002 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46004 A @samp{<compatible>} element is used to specify that the target
46005 is able to run binaries in some other than the main target architecture
46006 given by the @samp{<architecture>} element. For example, on the
46007 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46008 or @code{powerpc:common64}, but the system is able to run binaries
46009 in the @code{spu} architecture as well. The way to describe this
46010 capability with @samp{<compatible>} is as follows:
46013 <architecture>powerpc:common</architecture>
46014 <compatible>spu</compatible>
46017 @subsection Features
46020 Each @samp{<feature>} describes some logical portion of the target
46021 system. Features are currently used to describe available CPU
46022 registers and the types of their contents. A @samp{<feature>} element
46026 <feature name="@var{name}">
46027 @r{[}@var{type}@dots{}@r{]}
46033 Each feature's name should be unique within the description. The name
46034 of a feature does not matter unless @value{GDBN} has some special
46035 knowledge of the contents of that feature; if it does, the feature
46036 should have its standard name. @xref{Standard Target Features}.
46040 Any register's value is a collection of bits which @value{GDBN} must
46041 interpret. The default interpretation is a two's complement integer,
46042 but other types can be requested by name in the register description.
46043 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46044 Target Types}), and the description can define additional composite
46047 Each type element must have an @samp{id} attribute, which gives
46048 a unique (within the containing @samp{<feature>}) name to the type.
46049 Types must be defined before they are used.
46052 Some targets offer vector registers, which can be treated as arrays
46053 of scalar elements. These types are written as @samp{<vector>} elements,
46054 specifying the array element type, @var{type}, and the number of elements,
46058 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46062 If a register's value is usefully viewed in multiple ways, define it
46063 with a union type containing the useful representations. The
46064 @samp{<union>} element contains one or more @samp{<field>} elements,
46065 each of which has a @var{name} and a @var{type}:
46068 <union id="@var{id}">
46069 <field name="@var{name}" type="@var{type}"/>
46076 If a register's value is composed from several separate values, define
46077 it with either a structure type or a flags type.
46078 A flags type may only contain bitfields.
46079 A structure type may either contain only bitfields or contain no bitfields.
46080 If the value contains only bitfields, its total size in bytes must be
46083 Non-bitfield values have a @var{name} and @var{type}.
46086 <struct id="@var{id}">
46087 <field name="@var{name}" type="@var{type}"/>
46092 Both @var{name} and @var{type} values are required.
46093 No implicit padding is added.
46095 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
46098 <struct id="@var{id}" size="@var{size}">
46099 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46105 <flags id="@var{id}" size="@var{size}">
46106 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46111 The @var{name} value is required.
46112 Bitfield values may be named with the empty string, @samp{""},
46113 in which case the field is ``filler'' and its value is not printed.
46114 Not all bits need to be specified, so ``filler'' fields are optional.
46116 The @var{start} and @var{end} values are required, and @var{type}
46118 The field's @var{start} must be less than or equal to its @var{end},
46119 and zero represents the least significant bit.
46121 The default value of @var{type} is @code{bool} for single bit fields,
46122 and an unsigned integer otherwise.
46124 Which to choose? Structures or flags?
46126 Registers defined with @samp{flags} have these advantages over
46127 defining them with @samp{struct}:
46131 Arithmetic may be performed on them as if they were integers.
46133 They are printed in a more readable fashion.
46136 Registers defined with @samp{struct} have one advantage over
46137 defining them with @samp{flags}:
46141 One can fetch individual fields like in @samp{C}.
46144 (gdb) print $my_struct_reg.field3
46150 @subsection Registers
46153 Each register is represented as an element with this form:
46156 <reg name="@var{name}"
46157 bitsize="@var{size}"
46158 @r{[}regnum="@var{num}"@r{]}
46159 @r{[}save-restore="@var{save-restore}"@r{]}
46160 @r{[}type="@var{type}"@r{]}
46161 @r{[}group="@var{group}"@r{]}/>
46165 The components are as follows:
46170 The register's name; it must be unique within the target description.
46173 The register's size, in bits.
46176 The register's number. If omitted, a register's number is one greater
46177 than that of the previous register (either in the current feature or in
46178 a preceding feature); the first register in the target description
46179 defaults to zero. This register number is used to read or write
46180 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46181 packets, and registers appear in the @code{g} and @code{G} packets
46182 in order of increasing register number.
46185 Whether the register should be preserved across inferior function
46186 calls; this must be either @code{yes} or @code{no}. The default is
46187 @code{yes}, which is appropriate for most registers except for
46188 some system control registers; this is not related to the target's
46192 The type of the register. It may be a predefined type, a type
46193 defined in the current feature, or one of the special types @code{int}
46194 and @code{float}. @code{int} is an integer type of the correct size
46195 for @var{bitsize}, and @code{float} is a floating point type (in the
46196 architecture's normal floating point format) of the correct size for
46197 @var{bitsize}. The default is @code{int}.
46200 The register group to which this register belongs. It can be one of the
46201 standard register groups @code{general}, @code{float}, @code{vector} or an
46202 arbitrary string. Group names should be limited to alphanumeric characters.
46203 If a group name is made up of multiple words the words may be separated by
46204 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46205 @var{group} is specified, @value{GDBN} will not display the register in
46206 @code{info registers}.
46210 @node Predefined Target Types
46211 @section Predefined Target Types
46212 @cindex target descriptions, predefined types
46214 Type definitions in the self-description can build up composite types
46215 from basic building blocks, but can not define fundamental types. Instead,
46216 standard identifiers are provided by @value{GDBN} for the fundamental
46217 types. The currently supported types are:
46222 Boolean type, occupying a single bit.
46230 Signed integer types holding the specified number of bits.
46238 Unsigned integer types holding the specified number of bits.
46242 Pointers to unspecified code and data. The program counter and
46243 any dedicated return address register may be marked as code
46244 pointers; printing a code pointer converts it into a symbolic
46245 address. The stack pointer and any dedicated address registers
46246 may be marked as data pointers.
46249 Half precision IEEE floating point.
46252 Single precision IEEE floating point.
46255 Double precision IEEE floating point.
46258 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46261 The 12-byte extended precision format used by ARM FPA registers.
46264 The 10-byte extended precision format used by x87 registers.
46267 32bit @sc{eflags} register used by x86.
46270 32bit @sc{mxcsr} register used by x86.
46274 @node Enum Target Types
46275 @section Enum Target Types
46276 @cindex target descriptions, enum types
46278 Enum target types are useful in @samp{struct} and @samp{flags}
46279 register descriptions. @xref{Target Description Format}.
46281 Enum types have a name, size and a list of name/value pairs.
46284 <enum id="@var{id}" size="@var{size}">
46285 <evalue name="@var{name}" value="@var{value}"/>
46290 Enums must be defined before they are used.
46293 <enum id="levels_type" size="4">
46294 <evalue name="low" value="0"/>
46295 <evalue name="high" value="1"/>
46297 <flags id="flags_type" size="4">
46298 <field name="X" start="0"/>
46299 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46301 <reg name="flags" bitsize="32" type="flags_type"/>
46304 Given that description, a value of 3 for the @samp{flags} register
46305 would be printed as:
46308 (gdb) info register flags
46309 flags 0x3 [ X LEVEL=high ]
46312 @node Standard Target Features
46313 @section Standard Target Features
46314 @cindex target descriptions, standard features
46316 A target description must contain either no registers or all the
46317 target's registers. If the description contains no registers, then
46318 @value{GDBN} will assume a default register layout, selected based on
46319 the architecture. If the description contains any registers, the
46320 default layout will not be used; the standard registers must be
46321 described in the target description, in such a way that @value{GDBN}
46322 can recognize them.
46324 This is accomplished by giving specific names to feature elements
46325 which contain standard registers. @value{GDBN} will look for features
46326 with those names and verify that they contain the expected registers;
46327 if any known feature is missing required registers, or if any required
46328 feature is missing, @value{GDBN} will reject the target
46329 description. You can add additional registers to any of the
46330 standard features --- @value{GDBN} will display them just as if
46331 they were added to an unrecognized feature.
46333 This section lists the known features and their expected contents.
46334 Sample XML documents for these features are included in the
46335 @value{GDBN} source tree, in the directory @file{gdb/features}.
46337 Names recognized by @value{GDBN} should include the name of the
46338 company or organization which selected the name, and the overall
46339 architecture to which the feature applies; so e.g.@: the feature
46340 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46342 The names of registers are not case sensitive for the purpose
46343 of recognizing standard features, but @value{GDBN} will only display
46344 registers using the capitalization used in the description.
46347 * AArch64 Features::
46351 * LoongArch Features::
46352 * MicroBlaze Features::
46356 * Nios II Features::
46357 * OpenRISC 1000 Features::
46358 * PowerPC Features::
46359 * RISC-V Features::
46361 * S/390 and System z Features::
46367 @node AArch64 Features
46368 @subsection AArch64 Features
46369 @cindex target descriptions, AArch64 features
46371 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46372 targets. It should contain registers @samp{x0} through @samp{x30},
46373 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46375 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46376 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46379 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46380 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46381 through @samp{p15}, @samp{ffr} and @samp{vg}.
46383 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46384 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46387 @subsection ARC Features
46388 @cindex target descriptions, ARC Features
46390 ARC processors are so configurable that even core registers and their numbers
46391 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46392 registers, which are important to @value{GDBN}, are not ``core'' registers in
46393 ARC. Therefore, there are two features that their presence is mandatory:
46394 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46396 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46401 @samp{r0} through @samp{r25} for normal register file targets.
46403 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46404 register file targets.
46406 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46407 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46410 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46411 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46412 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46413 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46414 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46415 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46416 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46417 because of their inaccessibility during user space debugging sessions.
46419 Extension core registers @samp{r32} through @samp{r59} are optional and their
46420 existence depends on the configuration. When debugging GNU/Linux applications,
46421 i.e.@: user space debugging, these core registers are not available.
46423 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
46424 is the list of registers pertinent to this feature:
46428 mandatory: @samp{pc} and @samp{status32}.
46430 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
46434 @subsection ARM Features
46435 @cindex target descriptions, ARM features
46437 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
46439 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
46440 @samp{lr}, @samp{pc}, and @samp{cpsr}.
46442 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
46443 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
46444 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
46447 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
46448 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
46450 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
46451 must contain register @samp{vpr}.
46453 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
46454 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
46456 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
46457 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
46458 synthesize the @samp{q} pseudo registers from @samp{d} register
46461 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
46462 it should contain at least registers @samp{wR0} through @samp{wR15} and
46463 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
46464 @samp{wCSSF}, and @samp{wCASF} registers are optional.
46466 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
46467 should contain at least registers @samp{d0} through @samp{d15}. If
46468 they are present, @samp{d16} through @samp{d31} should also be included.
46469 @value{GDBN} will synthesize the single-precision registers from
46470 halves of the double-precision registers.
46472 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
46473 need to contain registers; it instructs @value{GDBN} to display the
46474 VFP double-precision registers as vectors and to synthesize the
46475 quad-precision registers from pairs of double-precision registers.
46476 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
46477 be present and include 32 double-precision registers.
46479 @node i386 Features
46480 @subsection i386 Features
46481 @cindex target descriptions, i386 features
46483 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
46484 targets. It should describe the following registers:
46488 @samp{eax} through @samp{edi} plus @samp{eip} for i386
46490 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
46492 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
46493 @samp{fs}, @samp{gs}
46495 @samp{st0} through @samp{st7}
46497 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
46498 @samp{foseg}, @samp{fooff} and @samp{fop}
46501 The register sets may be different, depending on the target.
46503 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
46504 describe registers:
46508 @samp{xmm0} through @samp{xmm7} for i386
46510 @samp{xmm0} through @samp{xmm15} for amd64
46515 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
46516 @samp{org.gnu.gdb.i386.sse} feature. It should
46517 describe the upper 128 bits of @sc{ymm} registers:
46521 @samp{ymm0h} through @samp{ymm7h} for i386
46523 @samp{ymm0h} through @samp{ymm15h} for amd64
46526 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
46527 Memory Protection Extension (MPX). It should describe the following registers:
46531 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
46533 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
46536 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
46537 describe a single register, @samp{orig_eax}.
46539 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
46540 describe two system registers: @samp{fs_base} and @samp{gs_base}.
46542 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
46543 @samp{org.gnu.gdb.i386.avx} feature. It should
46544 describe additional @sc{xmm} registers:
46548 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
46551 It should describe the upper 128 bits of additional @sc{ymm} registers:
46555 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
46559 describe the upper 256 bits of @sc{zmm} registers:
46563 @samp{zmm0h} through @samp{zmm7h} for i386.
46565 @samp{zmm0h} through @samp{zmm15h} for amd64.
46569 describe the additional @sc{zmm} registers:
46573 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
46576 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
46577 describe a single register, @samp{pkru}. It is a 32-bit register
46578 valid for i386 and amd64.
46580 @node LoongArch Features
46581 @subsection LoongArch Features
46582 @cindex target descriptions, LoongArch Features
46584 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
46585 targets. It should contain the registers @samp{r0} through @samp{r31},
46586 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
46587 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
46589 @node MicroBlaze Features
46590 @subsection MicroBlaze Features
46591 @cindex target descriptions, MicroBlaze features
46593 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
46594 targets. It should contain registers @samp{r0} through @samp{r31},
46595 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
46596 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
46597 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
46599 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
46600 If present, it should contain registers @samp{rshr} and @samp{rslr}
46602 @node MIPS Features
46603 @subsection @acronym{MIPS} Features
46604 @cindex target descriptions, @acronym{MIPS} features
46606 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
46607 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
46608 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
46611 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
46612 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
46613 registers. They may be 32-bit or 64-bit depending on the target.
46615 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
46616 it may be optional in a future version of @value{GDBN}. It should
46617 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
46618 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
46620 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
46621 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
46622 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
46623 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
46625 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
46626 contain a single register, @samp{restart}, which is used by the
46627 Linux kernel to control restartable syscalls.
46629 @node M68K Features
46630 @subsection M68K Features
46631 @cindex target descriptions, M68K features
46634 @item @samp{org.gnu.gdb.m68k.core}
46635 @itemx @samp{org.gnu.gdb.coldfire.core}
46636 @itemx @samp{org.gnu.gdb.fido.core}
46637 One of those features must be always present.
46638 The feature that is present determines which flavor of m68k is
46639 used. The feature that is present should contain registers
46640 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
46641 @samp{sp}, @samp{ps} and @samp{pc}.
46643 @item @samp{org.gnu.gdb.coldfire.fp}
46644 This feature is optional. If present, it should contain registers
46645 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
46648 Note that, despite the fact that this feature's name says
46649 @samp{coldfire}, it is used to describe any floating point registers.
46650 The size of the registers must match the main m68k flavor; so, for
46651 example, if the primary feature is reported as @samp{coldfire}, then
46652 64-bit floating point registers are required.
46655 @node NDS32 Features
46656 @subsection NDS32 Features
46657 @cindex target descriptions, NDS32 features
46659 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
46660 targets. It should contain at least registers @samp{r0} through
46661 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
46664 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
46665 it should contain 64-bit double-precision floating-point registers
46666 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
46667 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
46669 @emph{Note:} The first sixteen 64-bit double-precision floating-point
46670 registers are overlapped with the thirty-two 32-bit single-precision
46671 floating-point registers. The 32-bit single-precision registers, if
46672 not being listed explicitly, will be synthesized from halves of the
46673 overlapping 64-bit double-precision registers. Listing 32-bit
46674 single-precision registers explicitly is deprecated, and the
46675 support to it could be totally removed some day.
46677 @node Nios II Features
46678 @subsection Nios II Features
46679 @cindex target descriptions, Nios II features
46681 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
46682 targets. It should contain the 32 core registers (@samp{zero},
46683 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
46684 @samp{pc}, and the 16 control registers (@samp{status} through
46687 @node OpenRISC 1000 Features
46688 @subsection Openrisc 1000 Features
46689 @cindex target descriptions, OpenRISC 1000 features
46691 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
46692 targets. It should contain the 32 general purpose registers (@samp{r0}
46693 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
46695 @node PowerPC Features
46696 @subsection PowerPC Features
46697 @cindex target descriptions, PowerPC features
46699 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
46700 targets. It should contain registers @samp{r0} through @samp{r31},
46701 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
46702 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
46704 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
46705 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
46707 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
46708 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
46709 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
46710 through @samp{v31} as aliases for the corresponding @samp{vrX}
46713 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
46714 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
46715 combine these registers with the floating point registers (@samp{f0}
46716 through @samp{f31}) and the altivec registers (@samp{vr0} through
46717 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
46718 @samp{vs63}, the set of vector-scalar registers for POWER7.
46719 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
46720 @samp{org.gnu.gdb.power.altivec}.
46722 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
46723 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
46724 @samp{spefscr}. SPE targets should provide 32-bit registers in
46725 @samp{org.gnu.gdb.power.core} and provide the upper halves in
46726 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
46727 these to present registers @samp{ev0} through @samp{ev31} to the
46730 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
46731 contain the 64-bit register @samp{ppr}.
46733 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
46734 contain the 64-bit register @samp{dscr}.
46736 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
46737 contain the 64-bit register @samp{tar}.
46739 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
46740 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
46743 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
46744 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
46745 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
46746 server PMU registers provided by @sc{gnu}/Linux.
46748 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
46749 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
46752 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
46753 contain the checkpointed general-purpose registers @samp{cr0} through
46754 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
46755 @samp{cctr}. These registers may all be either 32-bit or 64-bit
46756 depending on the target. It should also contain the checkpointed
46757 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
46760 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
46761 contain the checkpointed 64-bit floating-point registers @samp{cf0}
46762 through @samp{cf31}, as well as the checkpointed 64-bit register
46765 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
46766 should contain the checkpointed altivec registers @samp{cvr0} through
46767 @samp{cvr31}, all 128-bit wide. It should also contain the
46768 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
46771 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
46772 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
46773 will combine these registers with the checkpointed floating point
46774 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
46775 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
46776 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
46777 @samp{cvs63}. Therefore, this feature requires both
46778 @samp{org.gnu.gdb.power.htm.altivec} and
46779 @samp{org.gnu.gdb.power.htm.fpu}.
46781 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
46782 contain the 64-bit checkpointed register @samp{cppr}.
46784 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
46785 contain the 64-bit checkpointed register @samp{cdscr}.
46787 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
46788 contain the 64-bit checkpointed register @samp{ctar}.
46791 @node RISC-V Features
46792 @subsection RISC-V Features
46793 @cindex target descriptions, RISC-V Features
46795 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
46796 targets. It should contain the registers @samp{x0} through
46797 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
46798 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
46801 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
46802 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
46803 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
46804 architectural register names, or the ABI names can be used.
46806 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
46807 it should contain registers that are not backed by real registers on
46808 the target, but are instead virtual, where the register value is
46809 derived from other target state. In many ways these are like
46810 @value{GDBN}s pseudo-registers, except implemented by the target.
46811 Currently the only register expected in this set is the one byte
46812 @samp{priv} register that contains the target's privilege level in the
46813 least significant two bits.
46815 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
46816 should contain all of the target's standard CSRs. Standard CSRs are
46817 those defined in the RISC-V specification documents. There is some
46818 overlap between this feature and the fpu feature; the @samp{fflags},
46819 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
46820 expectation is that these registers will be in the fpu feature if the
46821 target has floating point hardware, but can be moved into the csr
46822 feature if the target has the floating point control registers, but no
46823 other floating point hardware.
46825 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
46826 it should contain registers @samp{v0} through @samp{v31}, all of which
46827 must be the same size. These requirements are based on the v0.10
46828 draft vector extension, as the vector extension is not yet final. In
46829 the event that the register set of the vector extension changes for
46830 the final specification, the requirements given here could change for
46831 future releases of @value{GDBN}.
46834 @subsection RX Features
46835 @cindex target descriptions, RX Features
46837 The @samp{org.gnu.gdb.rx.core} feature is required for RX
46838 targets. It should contain the registers @samp{r0} through
46839 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
46840 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
46842 @node S/390 and System z Features
46843 @subsection S/390 and System z Features
46844 @cindex target descriptions, S/390 features
46845 @cindex target descriptions, System z features
46847 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
46848 System z targets. It should contain the PSW and the 16 general
46849 registers. In particular, System z targets should provide the 64-bit
46850 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
46851 S/390 targets should provide the 32-bit versions of these registers.
46852 A System z target that runs in 31-bit addressing mode should provide
46853 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
46854 register's upper halves @samp{r0h} through @samp{r15h}, and their
46855 lower halves @samp{r0l} through @samp{r15l}.
46857 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
46858 contain the 64-bit registers @samp{f0} through @samp{f15}, and
46861 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
46862 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
46864 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
46865 contain the register @samp{orig_r2}, which is 64-bit wide on System z
46866 targets and 32-bit otherwise. In addition, the feature may contain
46867 the @samp{last_break} register, whose width depends on the addressing
46868 mode, as well as the @samp{system_call} register, which is always
46871 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
46872 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
46873 @samp{atia}, and @samp{tr0} through @samp{tr15}.
46875 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
46876 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
46877 combined by @value{GDBN} with the floating point registers @samp{f0}
46878 through @samp{f15} to present the 128-bit wide vector registers
46879 @samp{v0} through @samp{v15}. In addition, this feature should
46880 contain the 128-bit wide vector registers @samp{v16} through
46883 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
46884 the 64-bit wide guarded-storage-control registers @samp{gsd},
46885 @samp{gssm}, and @samp{gsepla}.
46887 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
46888 the 64-bit wide guarded-storage broadcast control registers
46889 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
46891 @node Sparc Features
46892 @subsection Sparc Features
46893 @cindex target descriptions, sparc32 features
46894 @cindex target descriptions, sparc64 features
46895 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
46896 targets. It should describe the following registers:
46900 @samp{g0} through @samp{g7}
46902 @samp{o0} through @samp{o7}
46904 @samp{l0} through @samp{l7}
46906 @samp{i0} through @samp{i7}
46909 They may be 32-bit or 64-bit depending on the target.
46911 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
46912 targets. It should describe the following registers:
46916 @samp{f0} through @samp{f31}
46918 @samp{f32} through @samp{f62} for sparc64
46921 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
46922 targets. It should describe the following registers:
46926 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
46927 @samp{fsr}, and @samp{csr} for sparc32
46929 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
46933 @node TIC6x Features
46934 @subsection TMS320C6x Features
46935 @cindex target descriptions, TIC6x features
46936 @cindex target descriptions, TMS320C6x features
46937 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
46938 targets. It should contain registers @samp{A0} through @samp{A15},
46939 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
46941 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
46942 contain registers @samp{A16} through @samp{A31} and @samp{B16}
46943 through @samp{B31}.
46945 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
46946 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
46948 @node Operating System Information
46949 @appendix Operating System Information
46950 @cindex operating system information
46952 Users of @value{GDBN} often wish to obtain information about the state of
46953 the operating system running on the target---for example the list of
46954 processes, or the list of open files. This section describes the
46955 mechanism that makes it possible. This mechanism is similar to the
46956 target features mechanism (@pxref{Target Descriptions}), but focuses
46957 on a different aspect of target.
46959 Operating system information is retrieved from the target via the
46960 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
46961 read}). The object name in the request should be @samp{osdata}, and
46962 the @var{annex} identifies the data to be fetched.
46969 @appendixsection Process list
46970 @cindex operating system information, process list
46972 When requesting the process list, the @var{annex} field in the
46973 @samp{qXfer} request should be @samp{processes}. The returned data is
46974 an XML document. The formal syntax of this document is defined in
46975 @file{gdb/features/osdata.dtd}.
46977 An example document is:
46980 <?xml version="1.0"?>
46981 <!DOCTYPE target SYSTEM "osdata.dtd">
46982 <osdata type="processes">
46984 <column name="pid">1</column>
46985 <column name="user">root</column>
46986 <column name="command">/sbin/init</column>
46987 <column name="cores">1,2,3</column>
46992 Each item should include a column whose name is @samp{pid}. The value
46993 of that column should identify the process on the target. The
46994 @samp{user} and @samp{command} columns are optional, and will be
46995 displayed by @value{GDBN}. The @samp{cores} column, if present,
46996 should contain a comma-separated list of cores that this process
46997 is running on. Target may provide additional columns,
46998 which @value{GDBN} currently ignores.
47000 @node Trace File Format
47001 @appendix Trace File Format
47002 @cindex trace file format
47004 The trace file comes in three parts: a header, a textual description
47005 section, and a trace frame section with binary data.
47007 The header has the form @code{\x7fTRACE0\n}. The first byte is
47008 @code{0x7f} so as to indicate that the file contains binary data,
47009 while the @code{0} is a version number that may have different values
47012 The description section consists of multiple lines of @sc{ascii} text
47013 separated by newline characters (@code{0xa}). The lines may include a
47014 variety of optional descriptive or context-setting information, such
47015 as tracepoint definitions or register set size. @value{GDBN} will
47016 ignore any line that it does not recognize. An empty line marks the end
47021 Specifies the size of a register block in bytes. This is equal to the
47022 size of a @code{g} packet payload in the remote protocol. @var{size}
47023 is an ascii decimal number. There should be only one such line in
47024 a single trace file.
47026 @item status @var{status}
47027 Trace status. @var{status} has the same format as a @code{qTStatus}
47028 remote packet reply. There should be only one such line in a single trace
47031 @item tp @var{payload}
47032 Tracepoint definition. The @var{payload} has the same format as
47033 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47034 may take multiple lines of definition, corresponding to the multiple
47037 @item tsv @var{payload}
47038 Trace state variable definition. The @var{payload} has the same format as
47039 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47040 may take multiple lines of definition, corresponding to the multiple
47043 @item tdesc @var{payload}
47044 Target description in XML format. The @var{payload} is a single line of
47045 the XML file. All such lines should be concatenated together to get
47046 the original XML file. This file is in the same format as @code{qXfer}
47047 @code{features} payload, and corresponds to the main @code{target.xml}
47048 file. Includes are not allowed.
47052 The trace frame section consists of a number of consecutive frames.
47053 Each frame begins with a two-byte tracepoint number, followed by a
47054 four-byte size giving the amount of data in the frame. The data in
47055 the frame consists of a number of blocks, each introduced by a
47056 character indicating its type (at least register, memory, and trace
47057 state variable). The data in this section is raw binary, not a
47058 hexadecimal or other encoding; its endianness matches the target's
47061 @c FIXME bi-arch may require endianness/arch info in description section
47064 @item R @var{bytes}
47065 Register block. The number and ordering of bytes matches that of a
47066 @code{g} packet in the remote protocol. Note that these are the
47067 actual bytes, in target order, not a hexadecimal encoding.
47069 @item M @var{address} @var{length} @var{bytes}...
47070 Memory block. This is a contiguous block of memory, at the 8-byte
47071 address @var{address}, with a 2-byte length @var{length}, followed by
47072 @var{length} bytes.
47074 @item V @var{number} @var{value}
47075 Trace state variable block. This records the 8-byte signed value
47076 @var{value} of trace state variable numbered @var{number}.
47080 Future enhancements of the trace file format may include additional types
47083 @node Index Section Format
47084 @appendix @code{.gdb_index} section format
47085 @cindex .gdb_index section format
47086 @cindex index section format
47088 This section documents the index section that is created by @code{save
47089 gdb-index} (@pxref{Index Files}). The index section is
47090 DWARF-specific; some knowledge of DWARF is assumed in this
47093 The mapped index file format is designed to be directly
47094 @code{mmap}able on any architecture. In most cases, a datum is
47095 represented using a little-endian 32-bit integer value, called an
47096 @code{offset_type}. Big endian machines must byte-swap the values
47097 before using them. Exceptions to this rule are noted. The data is
47098 laid out such that alignment is always respected.
47100 A mapped index consists of several areas, laid out in order.
47104 The file header. This is a sequence of values, of @code{offset_type}
47105 unless otherwise noted:
47109 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
47110 Version 4 uses a different hashing function from versions 5 and 6.
47111 Version 6 includes symbols for inlined functions, whereas versions 4
47112 and 5 do not. Version 7 adds attributes to the CU indices in the
47113 symbol table. Version 8 specifies that symbols from DWARF type units
47114 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
47115 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
47117 @value{GDBN} will only read version 4, 5, or 6 indices
47118 by specifying @code{set use-deprecated-index-sections on}.
47119 GDB has a workaround for potentially broken version 7 indices so it is
47120 currently not flagged as deprecated.
47123 The offset, from the start of the file, of the CU list.
47126 The offset, from the start of the file, of the types CU list. Note
47127 that this area can be empty, in which case this offset will be equal
47128 to the next offset.
47131 The offset, from the start of the file, of the address area.
47134 The offset, from the start of the file, of the symbol table.
47137 The offset, from the start of the file, of the constant pool.
47141 The CU list. This is a sequence of pairs of 64-bit little-endian
47142 values, sorted by the CU offset. The first element in each pair is
47143 the offset of a CU in the @code{.debug_info} section. The second
47144 element in each pair is the length of that CU. References to a CU
47145 elsewhere in the map are done using a CU index, which is just the
47146 0-based index into this table. Note that if there are type CUs, then
47147 conceptually CUs and type CUs form a single list for the purposes of
47151 The types CU list. This is a sequence of triplets of 64-bit
47152 little-endian values. In a triplet, the first value is the CU offset,
47153 the second value is the type offset in the CU, and the third value is
47154 the type signature. The types CU list is not sorted.
47157 The address area. The address area consists of a sequence of address
47158 entries. Each address entry has three elements:
47162 The low address. This is a 64-bit little-endian value.
47165 The high address. This is a 64-bit little-endian value. Like
47166 @code{DW_AT_high_pc}, the value is one byte beyond the end.
47169 The CU index. This is an @code{offset_type} value.
47173 The symbol table. This is an open-addressed hash table. The size of
47174 the hash table is always a power of 2.
47176 Each slot in the hash table consists of a pair of @code{offset_type}
47177 values. The first value is the offset of the symbol's name in the
47178 constant pool. The second value is the offset of the CU vector in the
47181 If both values are 0, then this slot in the hash table is empty. This
47182 is ok because while 0 is a valid constant pool index, it cannot be a
47183 valid index for both a string and a CU vector.
47185 The hash value for a table entry is computed by applying an
47186 iterative hash function to the symbol's name. Starting with an
47187 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47188 the string is incorporated into the hash using the formula depending on the
47193 The formula is @code{r = r * 67 + c - 113}.
47195 @item Versions 5 to 7
47196 The formula is @code{r = r * 67 + tolower (c) - 113}.
47199 The terminating @samp{\0} is not incorporated into the hash.
47201 The step size used in the hash table is computed via
47202 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47203 value, and @samp{size} is the size of the hash table. The step size
47204 is used to find the next candidate slot when handling a hash
47207 The names of C@t{++} symbols in the hash table are canonicalized. We
47208 don't currently have a simple description of the canonicalization
47209 algorithm; if you intend to create new index sections, you must read
47213 The constant pool. This is simply a bunch of bytes. It is organized
47214 so that alignment is correct: CU vectors are stored first, followed by
47217 A CU vector in the constant pool is a sequence of @code{offset_type}
47218 values. The first value is the number of CU indices in the vector.
47219 Each subsequent value is the index and symbol attributes of a CU in
47220 the CU list. This element in the hash table is used to indicate which
47221 CUs define the symbol and how the symbol is used.
47222 See below for the format of each CU index+attributes entry.
47224 A string in the constant pool is zero-terminated.
47227 Attributes were added to CU index values in @code{.gdb_index} version 7.
47228 If a symbol has multiple uses within a CU then there is one
47229 CU index+attributes value for each use.
47231 The format of each CU index+attributes entry is as follows
47237 This is the index of the CU in the CU list.
47239 These bits are reserved for future purposes and must be zero.
47241 The kind of the symbol in the CU.
47245 This value is reserved and should not be used.
47246 By reserving zero the full @code{offset_type} value is backwards compatible
47247 with previous versions of the index.
47249 The symbol is a type.
47251 The symbol is a variable or an enum value.
47253 The symbol is a function.
47255 Any other kind of symbol.
47257 These values are reserved.
47261 This bit is zero if the value is global and one if it is static.
47263 The determination of whether a symbol is global or static is complicated.
47264 The authorative reference is the file @file{dwarf2read.c} in
47265 @value{GDBN} sources.
47269 This pseudo-code describes the computation of a symbol's kind and
47270 global/static attributes in the index.
47273 is_external = get_attribute (die, DW_AT_external);
47274 language = get_attribute (cu_die, DW_AT_language);
47277 case DW_TAG_typedef:
47278 case DW_TAG_base_type:
47279 case DW_TAG_subrange_type:
47283 case DW_TAG_enumerator:
47285 is_static = language != CPLUS;
47287 case DW_TAG_subprogram:
47289 is_static = ! (is_external || language == ADA);
47291 case DW_TAG_constant:
47293 is_static = ! is_external;
47295 case DW_TAG_variable:
47297 is_static = ! is_external;
47299 case DW_TAG_namespace:
47303 case DW_TAG_class_type:
47304 case DW_TAG_interface_type:
47305 case DW_TAG_structure_type:
47306 case DW_TAG_union_type:
47307 case DW_TAG_enumeration_type:
47309 is_static = language != CPLUS;
47317 @appendix Download debugging resources with Debuginfod
47320 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
47323 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
47324 can query servers using the build IDs associated with missing debug info,
47325 executables and source files in order to download them on demand.
47327 For instructions on building @value{GDBN} with @file{libdebuginfod},
47328 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
47329 with @code{elfutils}, starting with version 0.178. See
47330 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
47331 regarding @code{debuginfod}.
47334 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
47337 @node Debuginfod Settings
47338 @section Debuginfod Settings
47340 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
47343 @kindex set debuginfod enabled
47344 @anchor{set debuginfod enabled}
47345 @item set debuginfod enabled
47346 @itemx set debuginfod enabled on
47347 @cindex enable debuginfod
47348 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
47349 info or source files.
47351 @item set debuginfod enabled off
47352 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
47353 debug info or source files. By default, @code{debuginfod enabled} is set to
47354 @code{off} for non-interactive sessions.
47356 @item set debuginfod enabled ask
47357 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
47358 attempting to perform the next query. By default, @code{debuginfod enabled}
47359 is set to @code{ask} for interactive sessions.
47361 @kindex show debuginfod enabled
47362 @item show debuginfod enabled
47363 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
47366 @kindex set debuginfod urls
47367 @cindex configure debuginfod URLs
47368 @item set debuginfod urls
47369 @itemx set debuginfod urls @var{urls}
47370 Set the space-separated list of URLs that @code{debuginfod} will attempt to
47371 query. Only @code{http://}, @code{https://} and @code{file://} protocols
47372 should be used. The default value of @code{debuginfod urls} is copied from
47373 the @var{DEBUGINFOD_URLS} environment variable.
47375 @kindex show debuginfod urls
47376 @item show debuginfod urls
47377 Display the list of URLs that @code{debuginfod} will attempt to query.
47379 @kindex set debuginfod verbose
47380 @cindex debuginfod verbosity
47381 @item set debuginfod verbose
47382 @itemx set debuginfod verbose @var{n}
47383 Enable or disable @code{debuginfod}-related output. Use a non-zero value
47384 to enable and @code{0} to disable. @code{debuginfod} output is shown by
47387 @kindex show debuginfod verbose
47388 @item show debuginfod verbose
47389 Show the current verbosity setting.
47394 @appendix Manual pages
47398 * gdb man:: The GNU Debugger man page
47399 * gdbserver man:: Remote Server for the GNU Debugger man page
47400 * gcore man:: Generate a core file of a running program
47401 * gdbinit man:: gdbinit scripts
47402 * gdb-add-index man:: Add index files to speed up GDB
47408 @c man title gdb The GNU Debugger
47410 @c man begin SYNOPSIS gdb
47411 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
47414 @c man begin DESCRIPTION gdb
47415 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
47416 going on ``inside'' another program while it executes -- or what another
47417 program was doing at the moment it crashed.
47419 @value{GDBN} can do four main kinds of things (plus other things in support of
47420 these) to help you catch bugs in the act:
47424 Start your program, specifying anything that might affect its behavior.
47427 Make your program stop on specified conditions.
47430 Examine what has happened, when your program has stopped.
47433 Change things in your program, so you can experiment with correcting the
47434 effects of one bug and go on to learn about another.
47437 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
47440 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
47441 commands from the terminal until you tell it to exit with the @value{GDBN}
47442 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
47443 by using the command @code{help}.
47445 You can run @code{gdb} with no arguments or options; but the most
47446 usual way to start @value{GDBN} is with one argument or two, specifying an
47447 executable program as the argument:
47453 You can also start with both an executable program and a core file specified:
47459 You can, instead, specify a process ID as a second argument or use option
47460 @code{-p}, if you want to debug a running process:
47468 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
47469 can omit the @var{program} filename.
47471 Here are some of the most frequently needed @value{GDBN} commands:
47473 @c pod2man highlights the right hand side of the @item lines.
47475 @item break [@var{file}:][@var{function}|@var{line}]
47476 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
47478 @item run [@var{arglist}]
47479 Start your program (with @var{arglist}, if specified).
47482 Backtrace: display the program stack.
47484 @item print @var{expr}
47485 Display the value of an expression.
47488 Continue running your program (after stopping, e.g.@: at a breakpoint).
47491 Execute next program line (after stopping); step @emph{over} any
47492 function calls in the line.
47494 @item edit [@var{file}:]@var{function}
47495 look at the program line where it is presently stopped.
47497 @item list [@var{file}:]@var{function}
47498 type the text of the program in the vicinity of where it is presently stopped.
47501 Execute next program line (after stopping); step @emph{into} any
47502 function calls in the line.
47504 @item help [@var{name}]
47505 Show information about @value{GDBN} command @var{name}, or general information
47506 about using @value{GDBN}.
47510 Exit from @value{GDBN}.
47514 For full details on @value{GDBN},
47515 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47516 by Richard M. Stallman and Roland H. Pesch. The same text is available online
47517 as the @code{gdb} entry in the @code{info} program.
47521 @c man begin OPTIONS gdb
47522 Any arguments other than options specify an executable
47523 file and core file (or process ID); that is, the first argument
47524 encountered with no
47525 associated option flag is equivalent to a @option{--se} option, and the second,
47526 if any, is equivalent to a @option{-c} option if it's the name of a file.
47528 both long and abbreviated forms; both are shown here. The long forms are also
47529 recognized if you truncate them, so long as enough of the option is
47530 present to be unambiguous.
47532 The abbreviated forms are shown here with @samp{-} and long forms are shown
47533 with @samp{--} to reflect how they are shown in @option{--help}. However,
47534 @value{GDBN} recognizes all of the following conventions for most options:
47537 @item --option=@var{value}
47538 @item --option @var{value}
47539 @item -option=@var{value}
47540 @item -option @var{value}
47541 @item --o=@var{value}
47542 @item --o @var{value}
47543 @item -o=@var{value}
47544 @item -o @var{value}
47547 All the options and command line arguments you give are processed
47548 in sequential order. The order makes a difference when the @option{-x}
47554 List all options, with brief explanations.
47556 @item --symbols=@var{file}
47557 @itemx -s @var{file}
47558 Read symbol table from @var{file}.
47561 Enable writing into executable and core files.
47563 @item --exec=@var{file}
47564 @itemx -e @var{file}
47565 Use @var{file} as the executable file to execute when
47566 appropriate, and for examining pure data in conjunction with a core
47569 @item --se=@var{file}
47570 Read symbol table from @var{file} and use it as the executable
47573 @item --core=@var{file}
47574 @itemx -c @var{file}
47575 Use @var{file} as a core dump to examine.
47577 @item --command=@var{file}
47578 @itemx -x @var{file}
47579 Execute @value{GDBN} commands from @var{file}.
47581 @item --eval-command=@var{command}
47582 @item -ex @var{command}
47583 Execute given @value{GDBN} @var{command}.
47585 @item --init-eval-command=@var{command}
47587 Execute @value{GDBN} @var{command} before loading the inferior.
47589 @item --directory=@var{directory}
47590 @itemx -d @var{directory}
47591 Add @var{directory} to the path to search for source files.
47594 Do not execute commands from @file{~/.config/gdb/gdbinit},
47595 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
47596 @file{~/.gdbearlyinit}
47600 Do not execute commands from any @file{.gdbinit} or
47601 @file{.gdbearlyinit} initialization files.
47606 ``Quiet''. Do not print the introductory and copyright messages. These
47607 messages are also suppressed in batch mode.
47610 Run in batch mode. Exit with status @code{0} after processing all the command
47611 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
47612 Exit with nonzero status if an error occurs in executing the @value{GDBN}
47613 commands in the command files.
47615 Batch mode may be useful for running @value{GDBN} as a filter, for example to
47616 download and run a program on another computer; in order to make this
47617 more useful, the message
47620 Program exited normally.
47624 (which is ordinarily issued whenever a program running under @value{GDBN} control
47625 terminates) is not issued when running in batch mode.
47627 @item --batch-silent
47628 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
47629 output is supressed (stderr is unaffected). This is much quieter than
47630 @option{--silent} and would be useless for an interactive session.
47632 This is particularly useful when using targets that give @samp{Loading section}
47633 messages, for example.
47635 Note that targets that give their output via @value{GDBN}, as opposed to writing
47636 directly to @code{stdout}, will also be made silent.
47638 @item --args @var{prog} [@var{arglist}]
47639 Change interpretation of command line so that arguments following this
47640 option are passed as arguments to the inferior. As an example, take
47641 the following command:
47648 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
47649 the other hand, using:
47652 gdb --args ./a.out -q
47656 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
47658 @item --pid=@var{pid}
47659 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
47662 Open the terminal user interface.
47665 Read all symbols from the given symfile on the first access.
47668 Do not read symbol files.
47671 Run in DBX compatibility mode.
47673 @item --return-child-result
47674 @value{GDBN}'s exit code will be the same as the child's exit code.
47676 @item --configuration
47677 Print details about GDB configuration and then exit.
47680 Print version information and then exit.
47682 @item --cd=@var{directory}
47683 Run @value{GDBN} using @var{directory} as its working directory,
47684 instead of the current directory.
47686 @item --data-directory=@var{directory}
47688 Run @value{GDBN} using @var{directory} as its data directory. The data
47689 directory is where @value{GDBN} searches for its auxiliary files.
47693 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
47694 @value{GDBN} to output the full file name and line number in a standard,
47695 recognizable fashion each time a stack frame is displayed (which
47696 includes each time the program stops). This recognizable format looks
47697 like two @samp{\032} characters, followed by the file name, line number
47698 and character position separated by colons, and a newline. The
47699 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
47700 characters as a signal to display the source code for the frame.
47702 @item -b @var{baudrate}
47703 Set the line speed (baud rate or bits per second) of any serial
47704 interface used by @value{GDBN} for remote debugging.
47706 @item -l @var{timeout}
47707 Set timeout, in seconds, for remote debugging.
47709 @item --tty=@var{device}
47710 Run using @var{device} for your program's standard input and output.
47714 @c man begin SEEALSO gdb
47716 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47717 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47718 documentation are properly installed at your site, the command
47725 should give you access to the complete manual.
47727 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47728 Richard M. Stallman and Roland H. Pesch, July 1991.
47732 @node gdbserver man
47733 @heading gdbserver man
47735 @c man title gdbserver Remote Server for the GNU Debugger
47737 @c man begin SYNOPSIS gdbserver
47738 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47740 gdbserver --attach @var{comm} @var{pid}
47742 gdbserver --multi @var{comm}
47746 @c man begin DESCRIPTION gdbserver
47747 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
47748 than the one which is running the program being debugged.
47751 @subheading Usage (server (target) side)
47754 Usage (server (target) side):
47757 First, you need to have a copy of the program you want to debug put onto
47758 the target system. The program can be stripped to save space if needed, as
47759 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
47760 the @value{GDBN} running on the host system.
47762 To use the server, you log on to the target system, and run the @command{gdbserver}
47763 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
47764 your program, and (c) its arguments. The general syntax is:
47767 target> gdbserver @var{comm} @var{program} [@var{args} ...]
47770 For example, using a serial port, you might say:
47774 @c @file would wrap it as F</dev/com1>.
47775 target> gdbserver /dev/com1 emacs foo.txt
47778 target> gdbserver @file{/dev/com1} emacs foo.txt
47782 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
47783 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
47784 waits patiently for the host @value{GDBN} to communicate with it.
47786 To use a TCP connection, you could say:
47789 target> gdbserver host:2345 emacs foo.txt
47792 This says pretty much the same thing as the last example, except that we are
47793 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
47794 that we are expecting to see a TCP connection from @code{host} to local TCP port
47795 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
47796 want for the port number as long as it does not conflict with any existing TCP
47797 ports on the target system. This same port number must be used in the host
47798 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
47799 you chose a port number that conflicts with another service, @command{gdbserver} will
47800 print an error message and exit.
47802 @command{gdbserver} can also attach to running programs.
47803 This is accomplished via the @option{--attach} argument. The syntax is:
47806 target> gdbserver --attach @var{comm} @var{pid}
47809 @var{pid} is the process ID of a currently running process. It isn't
47810 necessary to point @command{gdbserver} at a binary for the running process.
47812 To start @code{gdbserver} without supplying an initial command to run
47813 or process ID to attach, use the @option{--multi} command line option.
47814 In such case you should connect using @kbd{target extended-remote} to start
47815 the program you want to debug.
47818 target> gdbserver --multi @var{comm}
47822 @subheading Usage (host side)
47828 You need an unstripped copy of the target program on your host system, since
47829 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
47830 would, with the target program as the first argument. (You may need to use the
47831 @option{--baud} option if the serial line is running at anything except 9600 baud.)
47832 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
47833 new command you need to know about is @code{target remote}
47834 (or @code{target extended-remote}). Its argument is either
47835 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
47836 descriptor. For example:
47840 @c @file would wrap it as F</dev/ttyb>.
47841 (gdb) target remote /dev/ttyb
47844 (gdb) target remote @file{/dev/ttyb}
47849 communicates with the server via serial line @file{/dev/ttyb}, and:
47852 (gdb) target remote the-target:2345
47856 communicates via a TCP connection to port 2345 on host `the-target', where
47857 you previously started up @command{gdbserver} with the same port number. Note that for
47858 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
47859 command, otherwise you may get an error that looks something like
47860 `Connection refused'.
47862 @command{gdbserver} can also debug multiple inferiors at once,
47865 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
47866 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
47869 @ref{Inferiors Connections and Programs}.
47871 In such case use the @code{extended-remote} @value{GDBN} command variant:
47874 (gdb) target extended-remote the-target:2345
47877 The @command{gdbserver} option @option{--multi} may or may not be used in such
47881 @c man begin OPTIONS gdbserver
47882 There are three different modes for invoking @command{gdbserver}:
47887 Debug a specific program specified by its program name:
47890 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47893 The @var{comm} parameter specifies how should the server communicate
47894 with @value{GDBN}; it is either a device name (to use a serial line),
47895 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
47896 stdin/stdout of @code{gdbserver}. Specify the name of the program to
47897 debug in @var{prog}. Any remaining arguments will be passed to the
47898 program verbatim. When the program exits, @value{GDBN} will close the
47899 connection, and @code{gdbserver} will exit.
47902 Debug a specific program by specifying the process ID of a running
47906 gdbserver --attach @var{comm} @var{pid}
47909 The @var{comm} parameter is as described above. Supply the process ID
47910 of a running program in @var{pid}; @value{GDBN} will do everything
47911 else. Like with the previous mode, when the process @var{pid} exits,
47912 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
47915 Multi-process mode -- debug more than one program/process:
47918 gdbserver --multi @var{comm}
47921 In this mode, @value{GDBN} can instruct @command{gdbserver} which
47922 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
47923 close the connection when a process being debugged exits, so you can
47924 debug several processes in the same session.
47927 In each of the modes you may specify these options:
47932 List all options, with brief explanations.
47935 This option causes @command{gdbserver} to print its version number and exit.
47938 @command{gdbserver} will attach to a running program. The syntax is:
47941 target> gdbserver --attach @var{comm} @var{pid}
47944 @var{pid} is the process ID of a currently running process. It isn't
47945 necessary to point @command{gdbserver} at a binary for the running process.
47948 To start @code{gdbserver} without supplying an initial command to run
47949 or process ID to attach, use this command line option.
47950 Then you can connect using @kbd{target extended-remote} and start
47951 the program you want to debug. The syntax is:
47954 target> gdbserver --multi @var{comm}
47958 Instruct @code{gdbserver} to display extra status information about the debugging
47960 This option is intended for @code{gdbserver} development and for bug reports to
47963 @item --remote-debug
47964 Instruct @code{gdbserver} to display remote protocol debug output.
47965 This option is intended for @code{gdbserver} development and for bug reports to
47968 @item --debug-file=@var{filename}
47969 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
47970 This option is intended for @code{gdbserver} development and for bug reports to
47973 @item --debug-format=option1@r{[},option2,...@r{]}
47974 Instruct @code{gdbserver} to include extra information in each line
47975 of debugging output.
47976 @xref{Other Command-Line Arguments for gdbserver}.
47979 Specify a wrapper to launch programs
47980 for debugging. The option should be followed by the name of the
47981 wrapper, then any command-line arguments to pass to the wrapper, then
47982 @kbd{--} indicating the end of the wrapper arguments.
47985 By default, @command{gdbserver} keeps the listening TCP port open, so that
47986 additional connections are possible. However, if you start @code{gdbserver}
47987 with the @option{--once} option, it will stop listening for any further
47988 connection attempts after connecting to the first @value{GDBN} session.
47990 @c --disable-packet is not documented for users.
47992 @c --disable-randomization and --no-disable-randomization are superseded by
47993 @c QDisableRandomization.
47998 @c man begin SEEALSO gdbserver
48000 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48001 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48002 documentation are properly installed at your site, the command
48008 should give you access to the complete manual.
48010 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48011 Richard M. Stallman and Roland H. Pesch, July 1991.
48018 @c man title gcore Generate a core file of a running program
48021 @c man begin SYNOPSIS gcore
48022 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48026 @c man begin DESCRIPTION gcore
48027 Generate core dumps of one or more running programs with process IDs
48028 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48029 is equivalent to one produced by the kernel when the process crashes
48030 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48031 limit). However, unlike after a crash, after @command{gcore} finishes
48032 its job the program remains running without any change.
48035 @c man begin OPTIONS gcore
48038 Dump all memory mappings. The actual effect of this option depends on
48039 the Operating System. On @sc{gnu}/Linux, it will disable
48040 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48041 enable @code{dump-excluded-mappings} (@pxref{set
48042 dump-excluded-mappings}).
48044 @item -o @var{prefix}
48045 The optional argument @var{prefix} specifies the prefix to be used
48046 when composing the file names of the core dumps. The file name is
48047 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48048 process ID of the running program being analyzed by @command{gcore}.
48049 If not specified, @var{prefix} defaults to @var{gcore}.
48053 @c man begin SEEALSO gcore
48055 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48056 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48057 documentation are properly installed at your site, the command
48064 should give you access to the complete manual.
48066 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48067 Richard M. Stallman and Roland H. Pesch, July 1991.
48074 @c man title gdbinit GDB initialization scripts
48077 @c man begin SYNOPSIS gdbinit
48078 @ifset SYSTEM_GDBINIT
48079 @value{SYSTEM_GDBINIT}
48082 @ifset SYSTEM_GDBINIT_DIR
48083 @value{SYSTEM_GDBINIT_DIR}/*
48086 ~/.config/gdb/gdbinit
48094 @c man begin DESCRIPTION gdbinit
48095 These files contain @value{GDBN} commands to automatically execute during
48096 @value{GDBN} startup. The lines of contents are canned sequences of commands,
48099 the @value{GDBN} manual in node @code{Sequences}
48100 -- shell command @code{info -f gdb -n Sequences}.
48106 Please read more in
48108 the @value{GDBN} manual in node @code{Startup}
48109 -- shell command @code{info -f gdb -n Startup}.
48116 @ifset SYSTEM_GDBINIT
48117 @item @value{SYSTEM_GDBINIT}
48119 @ifclear SYSTEM_GDBINIT
48120 @item (not enabled with @code{--with-system-gdbinit} during compilation)
48122 System-wide initialization file. It is executed unless user specified
48123 @value{GDBN} option @code{-nx} or @code{-n}.
48126 the @value{GDBN} manual in node @code{System-wide configuration}
48127 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48129 @ifset SYSTEM_GDBINIT_DIR
48130 @item @value{SYSTEM_GDBINIT_DIR}
48132 @ifclear SYSTEM_GDBINIT_DIR
48133 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
48135 System-wide initialization directory. All files in this directory are
48136 executed on startup unless user specified @value{GDBN} option @code{-nx} or
48137 @code{-n}, as long as they have a recognized file extension.
48140 the @value{GDBN} manual in node @code{System-wide configuration}
48141 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48144 @ref{System-wide configuration}.
48147 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
48148 User initialization file. It is executed unless user specified
48149 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
48151 @item @file{.gdbinit}
48152 Initialization file for current directory. It may need to be enabled with
48153 @value{GDBN} security command @code{set auto-load local-gdbinit}.
48156 the @value{GDBN} manual in node @code{Init File in the Current Directory}
48157 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
48160 @ref{Init File in the Current Directory}.
48165 @c man begin SEEALSO gdbinit
48167 gdb(1), @code{info -f gdb -n Startup}
48169 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48170 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48171 documentation are properly installed at your site, the command
48177 should give you access to the complete manual.
48179 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48180 Richard M. Stallman and Roland H. Pesch, July 1991.
48184 @node gdb-add-index man
48185 @heading gdb-add-index
48186 @pindex gdb-add-index
48187 @anchor{gdb-add-index}
48189 @c man title gdb-add-index Add index files to speed up GDB
48191 @c man begin SYNOPSIS gdb-add-index
48192 gdb-add-index @var{filename}
48195 @c man begin DESCRIPTION gdb-add-index
48196 When @value{GDBN} finds a symbol file, it scans the symbols in the
48197 file in order to construct an internal symbol table. This lets most
48198 @value{GDBN} operations work quickly--at the cost of a delay early on.
48199 For large programs, this delay can be quite lengthy, so @value{GDBN}
48200 provides a way to build an index, which speeds up startup.
48202 To determine whether a file contains such an index, use the command
48203 @kbd{readelf -S filename}: the index is stored in a section named
48204 @code{.gdb_index}. The index file can only be produced on systems
48205 which use ELF binaries and DWARF debug information (i.e., sections
48206 named @code{.debug_*}).
48208 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48209 in the @env{PATH} environment variable. If you want to use different
48210 versions of these programs, you can specify them through the
48211 @env{GDB} and @env{OBJDUMP} environment variables.
48215 the @value{GDBN} manual in node @code{Index Files}
48216 -- shell command @kbd{info -f gdb -n "Index Files"}.
48223 @c man begin SEEALSO gdb-add-index
48225 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48226 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48227 documentation are properly installed at your site, the command
48233 should give you access to the complete manual.
48235 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48236 Richard M. Stallman and Roland H. Pesch, July 1991.
48242 @node GNU Free Documentation License
48243 @appendix GNU Free Documentation License
48246 @node Concept Index
48247 @unnumbered Concept Index
48251 @node Command and Variable Index
48252 @unnumbered Command, Variable, and Function Index
48257 % I think something like @@colophon should be in texinfo. In the
48259 \long\def\colophon{\hbox to0pt{}\vfill
48260 \centerline{The body of this manual is set in}
48261 \centerline{\fontname\tenrm,}
48262 \centerline{with headings in {\bf\fontname\tenbf}}
48263 \centerline{and examples in {\tt\fontname\tentt}.}
48264 \centerline{{\it\fontname\tenit\/},}
48265 \centerline{{\bf\fontname\tenbf}, and}
48266 \centerline{{\sl\fontname\tensl\/}}
48267 \centerline{are used for emphasis.}\vfill}
48269 % Blame: doc@@cygnus.com, 1991.