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 @anchor{add_inferior_cli}
3314 @kindex add-inferior
3315 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ] [-no-connection ]
3316 Adds @var{n} inferiors to be run using @var{executable} as the
3317 executable; @var{n} defaults to 1. If no executable is specified,
3318 the inferiors begins empty, with no program. You can still assign or
3319 change the program assigned to the inferior at any time by using the
3320 @code{file} command with the executable name as its argument.
3322 By default, the new inferior begins connected to the same target
3323 connection as the current inferior. For example, if the current
3324 inferior was connected to @code{gdbserver} with @code{target remote},
3325 then the new inferior will be connected to the same @code{gdbserver}
3326 instance. The @samp{-no-connection} option starts the new inferior
3327 with no connection yet. You can then for example use the @code{target
3328 remote} command to connect to some other @code{gdbserver} instance,
3329 use @code{run} to spawn a local program, etc.
3331 @kindex clone-inferior
3332 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
3333 Adds @var{n} inferiors ready to execute the same program as inferior
3334 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
3335 number of the current inferior. This command copies the values of the
3336 @var{args}, @w{@var{inferior-tty}} and @var{cwd} properties from the
3337 current inferior to the new one. It also propagates changes the user
3338 made to environment variables using the @w{@code{set environment}} and
3339 @w{@code{unset environment}} commands. This is a convenient command
3340 when you want to run another instance of the inferior you are debugging.
3343 (@value{GDBP}) info inferiors
3344 Num Description Connection Executable
3345 * 1 process 29964 1 (native) helloworld
3346 (@value{GDBP}) clone-inferior
3349 (@value{GDBP}) info inferiors
3350 Num Description Connection Executable
3351 * 1 process 29964 1 (native) helloworld
3352 2 <null> 1 (native) helloworld
3355 You can now simply switch focus to inferior 2 and run it.
3357 @kindex remove-inferiors
3358 @item remove-inferiors @var{infno}@dots{}
3359 Removes the inferior or inferiors @var{infno}@dots{}. It is not
3360 possible to remove an inferior that is running with this command. For
3361 those, use the @code{kill} or @code{detach} command first.
3365 To quit debugging one of the running inferiors that is not the current
3366 inferior, you can either detach from it by using the @w{@code{detach
3367 inferior}} command (allowing it to run independently), or kill it
3368 using the @w{@code{kill inferiors}} command:
3371 @kindex detach inferiors @var{infno}@dots{}
3372 @item detach inferior @var{infno}@dots{}
3373 Detach from the inferior or inferiors identified by @value{GDBN}
3374 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
3375 still stays on the list of inferiors shown by @code{info inferiors},
3376 but its Description will show @samp{<null>}.
3378 @kindex kill inferiors @var{infno}@dots{}
3379 @item kill inferiors @var{infno}@dots{}
3380 Kill the inferior or inferiors identified by @value{GDBN} inferior
3381 number(s) @var{infno}@dots{}. Note that the inferior's entry still
3382 stays on the list of inferiors shown by @code{info inferiors}, but its
3383 Description will show @samp{<null>}.
3386 After the successful completion of a command such as @code{detach},
3387 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
3388 a normal process exit, the inferior is still valid and listed with
3389 @code{info inferiors}, ready to be restarted.
3392 To be notified when inferiors are started or exit under @value{GDBN}'s
3393 control use @w{@code{set print inferior-events}}:
3396 @kindex set print inferior-events
3397 @cindex print messages on inferior start and exit
3398 @item set print inferior-events
3399 @itemx set print inferior-events on
3400 @itemx set print inferior-events off
3401 The @code{set print inferior-events} command allows you to enable or
3402 disable printing of messages when @value{GDBN} notices that new
3403 inferiors have started or that inferiors have exited or have been
3404 detached. By default, these messages will be printed.
3406 @kindex show print inferior-events
3407 @item show print inferior-events
3408 Show whether messages will be printed when @value{GDBN} detects that
3409 inferiors have started, exited or have been detached.
3412 Many commands will work the same with multiple programs as with a
3413 single program: e.g., @code{print myglobal} will simply display the
3414 value of @code{myglobal} in the current inferior.
3417 Occasionally, when debugging @value{GDBN} itself, it may be useful to
3418 get more info about the relationship of inferiors, programs, address
3419 spaces in a debug session. You can do that with the @w{@code{maint
3420 info program-spaces}} command.
3423 @kindex maint info program-spaces
3424 @item maint info program-spaces
3425 Print a list of all program spaces currently being managed by
3428 @value{GDBN} displays for each program space (in this order):
3432 the program space number assigned by @value{GDBN}
3435 the name of the executable loaded into the program space, with e.g.,
3436 the @code{file} command.
3441 An asterisk @samp{*} preceding the @value{GDBN} program space number
3442 indicates the current program space.
3444 In addition, below each program space line, @value{GDBN} prints extra
3445 information that isn't suitable to display in tabular form. For
3446 example, the list of inferiors bound to the program space.
3449 (@value{GDBP}) maint info program-spaces
3453 Bound inferiors: ID 1 (process 21561)
3456 Here we can see that no inferior is running the program @code{hello},
3457 while @code{process 21561} is running the program @code{goodbye}. On
3458 some targets, it is possible that multiple inferiors are bound to the
3459 same program space. The most common example is that of debugging both
3460 the parent and child processes of a @code{vfork} call. For example,
3463 (@value{GDBP}) maint info program-spaces
3466 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
3469 Here, both inferior 2 and inferior 1 are running in the same program
3470 space as a result of inferior 1 having executed a @code{vfork} call.
3474 @section Debugging Programs with Multiple Threads
3476 @cindex threads of execution
3477 @cindex multiple threads
3478 @cindex switching threads
3479 In some operating systems, such as GNU/Linux and Solaris, a single program
3480 may have more than one @dfn{thread} of execution. The precise semantics
3481 of threads differ from one operating system to another, but in general
3482 the threads of a single program are akin to multiple processes---except
3483 that they share one address space (that is, they can all examine and
3484 modify the same variables). On the other hand, each thread has its own
3485 registers and execution stack, and perhaps private memory.
3487 @value{GDBN} provides these facilities for debugging multi-thread
3491 @item automatic notification of new threads
3492 @item @samp{thread @var{thread-id}}, a command to switch among threads
3493 @item @samp{info threads}, a command to inquire about existing threads
3494 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
3495 a command to apply a command to a list of threads
3496 @item thread-specific breakpoints
3497 @item @samp{set print thread-events}, which controls printing of
3498 messages on thread start and exit.
3499 @item @samp{set libthread-db-search-path @var{path}}, which lets
3500 the user specify which @code{libthread_db} to use if the default choice
3501 isn't compatible with the program.
3504 @cindex focus of debugging
3505 @cindex current thread
3506 The @value{GDBN} thread debugging facility allows you to observe all
3507 threads while your program runs---but whenever @value{GDBN} takes
3508 control, one thread in particular is always the focus of debugging.
3509 This thread is called the @dfn{current thread}. Debugging commands show
3510 program information from the perspective of the current thread.
3512 @cindex @code{New} @var{systag} message
3513 @cindex thread identifier (system)
3514 @c FIXME-implementors!! It would be more helpful if the [New...] message
3515 @c included GDB's numeric thread handle, so you could just go to that
3516 @c thread without first checking `info threads'.
3517 Whenever @value{GDBN} detects a new thread in your program, it displays
3518 the target system's identification for the thread with a message in the
3519 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
3520 whose form varies depending on the particular system. For example, on
3521 @sc{gnu}/Linux, you might see
3524 [New Thread 0x41e02940 (LWP 25582)]
3528 when @value{GDBN} notices a new thread. In contrast, on other systems,
3529 the @var{systag} is simply something like @samp{process 368}, with no
3532 @c FIXME!! (1) Does the [New...] message appear even for the very first
3533 @c thread of a program, or does it only appear for the
3534 @c second---i.e.@: when it becomes obvious we have a multithread
3536 @c (2) *Is* there necessarily a first thread always? Or do some
3537 @c multithread systems permit starting a program with multiple
3538 @c threads ab initio?
3540 @anchor{thread numbers}
3541 @cindex thread number, per inferior
3542 @cindex thread identifier (GDB)
3543 For debugging purposes, @value{GDBN} associates its own thread number
3544 ---always a single integer---with each thread of an inferior. This
3545 number is unique between all threads of an inferior, but not unique
3546 between threads of different inferiors.
3548 @cindex qualified thread ID
3549 You can refer to a given thread in an inferior using the qualified
3550 @var{inferior-num}.@var{thread-num} syntax, also known as
3551 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3552 number and @var{thread-num} being the thread number of the given
3553 inferior. For example, thread @code{2.3} refers to thread number 3 of
3554 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3555 then @value{GDBN} infers you're referring to a thread of the current
3558 Until you create a second inferior, @value{GDBN} does not show the
3559 @var{inferior-num} part of thread IDs, even though you can always use
3560 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3561 of inferior 1, the initial inferior.
3563 @anchor{thread ID lists}
3564 @cindex thread ID lists
3565 Some commands accept a space-separated @dfn{thread ID list} as
3566 argument. A list element can be:
3570 A thread ID as shown in the first field of the @samp{info threads}
3571 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3575 A range of thread numbers, again with or without an inferior
3576 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3577 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3580 All threads of an inferior, specified with a star wildcard, with or
3581 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3582 @samp{1.*}) or @code{*}. The former refers to all threads of the
3583 given inferior, and the latter form without an inferior qualifier
3584 refers to all threads of the current inferior.
3588 For example, if the current inferior is 1, and inferior 7 has one
3589 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3590 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3591 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3592 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3596 @anchor{global thread numbers}
3597 @cindex global thread number
3598 @cindex global thread identifier (GDB)
3599 In addition to a @emph{per-inferior} number, each thread is also
3600 assigned a unique @emph{global} number, also known as @dfn{global
3601 thread ID}, a single integer. Unlike the thread number component of
3602 the thread ID, no two threads have the same global ID, even when
3603 you're debugging multiple inferiors.
3605 From @value{GDBN}'s perspective, a process always has at least one
3606 thread. In other words, @value{GDBN} assigns a thread number to the
3607 program's ``main thread'' even if the program is not multi-threaded.
3609 @vindex $_thread@r{, convenience variable}
3610 @vindex $_gthread@r{, convenience variable}
3611 The debugger convenience variables @samp{$_thread} and
3612 @samp{$_gthread} contain, respectively, the per-inferior thread number
3613 and the global thread number of the current thread. You may find this
3614 useful in writing breakpoint conditional expressions, command scripts,
3615 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3616 general information on convenience variables.
3618 If @value{GDBN} detects the program is multi-threaded, it augments the
3619 usual message about stopping at a breakpoint with the ID and name of
3620 the thread that hit the breakpoint.
3623 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3626 Likewise when the program receives a signal:
3629 Thread 1 "main" received signal SIGINT, Interrupt.
3633 @anchor{info_threads}
3634 @kindex info threads
3635 @item info threads @r{[}@var{thread-id-list}@r{]}
3637 Display information about one or more threads. With no arguments
3638 displays information about all threads. You can specify the list of
3639 threads that you want to display using the thread ID list syntax
3640 (@pxref{thread ID lists}).
3642 @value{GDBN} displays for each thread (in this order):
3646 the per-inferior thread number assigned by @value{GDBN}
3649 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3650 option was specified
3653 the target system's thread identifier (@var{systag})
3656 the thread's name, if one is known. A thread can either be named by
3657 the user (see @code{thread name}, below), or, in some cases, by the
3661 the current stack frame summary for that thread
3665 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3666 indicates the current thread.
3670 @c end table here to get a little more width for example
3673 (@value{GDBP}) info threads
3675 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3676 2 process 35 thread 23 0x34e5 in sigpause ()
3677 3 process 35 thread 27 0x34e5 in sigpause ()
3681 If you're debugging multiple inferiors, @value{GDBN} displays thread
3682 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3683 Otherwise, only @var{thread-num} is shown.
3685 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3686 indicating each thread's global thread ID:
3689 (@value{GDBP}) info threads
3690 Id GId Target Id Frame
3691 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3692 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3693 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3694 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3697 On Solaris, you can display more information about user threads with a
3698 Solaris-specific command:
3701 @item maint info sol-threads
3702 @kindex maint info sol-threads
3703 @cindex thread info (Solaris)
3704 Display info on Solaris user threads.
3708 @kindex thread @var{thread-id}
3709 @item thread @var{thread-id}
3710 Make thread ID @var{thread-id} the current thread. The command
3711 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3712 the first field of the @samp{info threads} display, with or without an
3713 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3715 @value{GDBN} responds by displaying the system identifier of the
3716 thread you selected, and its current stack frame summary:
3719 (@value{GDBP}) thread 2
3720 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3721 #0 some_function (ignore=0x0) at example.c:8
3722 8 printf ("hello\n");
3726 As with the @samp{[New @dots{}]} message, the form of the text after
3727 @samp{Switching to} depends on your system's conventions for identifying
3730 @anchor{thread apply all}
3731 @kindex thread apply
3732 @cindex apply command to several threads
3733 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3734 The @code{thread apply} command allows you to apply the named
3735 @var{command} to one or more threads. Specify the threads that you
3736 want affected using the thread ID list syntax (@pxref{thread ID
3737 lists}), or specify @code{all} to apply to all threads. To apply a
3738 command to all threads in descending order, type @kbd{thread apply all
3739 @var{command}}. To apply a command to all threads in ascending order,
3740 type @kbd{thread apply all -ascending @var{command}}.
3742 The @var{flag} arguments control what output to produce and how to handle
3743 errors raised when applying @var{command} to a thread. @var{flag}
3744 must start with a @code{-} directly followed by one letter in
3745 @code{qcs}. If several flags are provided, they must be given
3746 individually, such as @code{-c -q}.
3748 By default, @value{GDBN} displays some thread information before the
3749 output produced by @var{command}, and an error raised during the
3750 execution of a @var{command} will abort @code{thread apply}. The
3751 following flags can be used to fine-tune this behavior:
3755 The flag @code{-c}, which stands for @samp{continue}, causes any
3756 errors in @var{command} to be displayed, and the execution of
3757 @code{thread apply} then continues.
3759 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3760 or empty output produced by a @var{command} to be silently ignored.
3761 That is, the execution continues, but the thread information and errors
3764 The flag @code{-q} (@samp{quiet}) disables printing the thread
3768 Flags @code{-c} and @code{-s} cannot be used together.
3771 @cindex apply command to all threads (ignoring errors and empty output)
3772 @item taas [@var{option}]@dots{} @var{command}
3773 Shortcut for @code{thread apply all -s [@var{option}]@dots{} @var{command}}.
3774 Applies @var{command} on all threads, ignoring errors and empty output.
3776 The @code{taas} command accepts the same options as the @code{thread
3777 apply all} command. @xref{thread apply all}.
3780 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3781 @item tfaas [@var{option}]@dots{} @var{command}
3782 Shortcut for @code{thread apply all -s -- frame apply all -s [@var{option}]@dots{} @var{command}}.
3783 Applies @var{command} on all frames of all threads, ignoring errors
3784 and empty output. Note that the flag @code{-s} is specified twice:
3785 The first @code{-s} ensures that @code{thread apply} only shows the thread
3786 information of the threads for which @code{frame apply} produces
3787 some output. The second @code{-s} is needed to ensure that @code{frame
3788 apply} shows the frame information of a frame only if the
3789 @var{command} successfully produced some output.
3791 It can for example be used to print a local variable or a function
3792 argument without knowing the thread or frame where this variable or argument
3795 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3798 The @code{tfaas} command accepts the same options as the @code{frame
3799 apply} command. @xref{Frame Apply,,frame apply}.
3802 @cindex name a thread
3803 @item thread name [@var{name}]
3804 This command assigns a name to the current thread. If no argument is
3805 given, any existing user-specified name is removed. The thread name
3806 appears in the @samp{info threads} display.
3808 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3809 determine the name of the thread as given by the OS. On these
3810 systems, a name specified with @samp{thread name} will override the
3811 system-give name, and removing the user-specified name will cause
3812 @value{GDBN} to once again display the system-specified name.
3815 @cindex search for a thread
3816 @item thread find [@var{regexp}]
3817 Search for and display thread ids whose name or @var{systag}
3818 matches the supplied regular expression.
3820 As well as being the complement to the @samp{thread name} command,
3821 this command also allows you to identify a thread by its target
3822 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3826 (@value{GDBN}) thread find 26688
3827 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3828 (@value{GDBN}) info thread 4
3830 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3833 @kindex set print thread-events
3834 @cindex print messages on thread start and exit
3835 @item set print thread-events
3836 @itemx set print thread-events on
3837 @itemx set print thread-events off
3838 The @code{set print thread-events} command allows you to enable or
3839 disable printing of messages when @value{GDBN} notices that new threads have
3840 started or that threads have exited. By default, these messages will
3841 be printed if detection of these events is supported by the target.
3842 Note that these messages cannot be disabled on all targets.
3844 @kindex show print thread-events
3845 @item show print thread-events
3846 Show whether messages will be printed when @value{GDBN} detects that threads
3847 have started and exited.
3850 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3851 more information about how @value{GDBN} behaves when you stop and start
3852 programs with multiple threads.
3854 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3855 watchpoints in programs with multiple threads.
3857 @anchor{set libthread-db-search-path}
3859 @kindex set libthread-db-search-path
3860 @cindex search path for @code{libthread_db}
3861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3862 If this variable is set, @var{path} is a colon-separated list of
3863 directories @value{GDBN} will use to search for @code{libthread_db}.
3864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3870 @code{libthread_db} library to obtain information about threads in the
3871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3872 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3873 specific thread debugging library loading is enabled
3874 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3876 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3877 refers to the default system directories that are
3878 normally searched for loading shared libraries. The @samp{$sdir} entry
3879 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3880 (@pxref{libthread_db.so.1 file}).
3882 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3883 refers to the directory from which @code{libpthread}
3884 was loaded in the inferior process.
3886 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3887 @value{GDBN} attempts to initialize it with the current inferior process.
3888 If this initialization fails (which could happen because of a version
3889 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3890 will unload @code{libthread_db}, and continue with the next directory.
3891 If none of @code{libthread_db} libraries initialize successfully,
3892 @value{GDBN} will issue a warning and thread debugging will be disabled.
3894 Setting @code{libthread-db-search-path} is currently implemented
3895 only on some platforms.
3897 @kindex show libthread-db-search-path
3898 @item show libthread-db-search-path
3899 Display current libthread_db search path.
3901 @kindex set debug libthread-db
3902 @kindex show debug libthread-db
3903 @cindex debugging @code{libthread_db}
3904 @item set debug libthread-db
3905 @itemx show debug libthread-db
3906 Turns on or off display of @code{libthread_db}-related events.
3907 Use @code{1} to enable, @code{0} to disable.
3909 @kindex set debug threads
3910 @kindex show debug threads
3911 @cindex debugging @code{threads}
3912 @item set debug threads @r{[}on@r{|}off@r{]}
3913 @itemx show debug threads
3914 When @samp{on} @value{GDBN} will print additional messages when
3915 threads are created and deleted.
3919 @section Debugging Forks
3921 @cindex fork, debugging programs which call
3922 @cindex multiple processes
3923 @cindex processes, multiple
3924 On most systems, @value{GDBN} has no special support for debugging
3925 programs which create additional processes using the @code{fork}
3926 function. When a program forks, @value{GDBN} will continue to debug the
3927 parent process and the child process will run unimpeded. If you have
3928 set a breakpoint in any code which the child then executes, the child
3929 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3930 will cause it to terminate.
3932 However, if you want to debug the child process there is a workaround
3933 which isn't too painful. Put a call to @code{sleep} in the code which
3934 the child process executes after the fork. It may be useful to sleep
3935 only if a certain environment variable is set, or a certain file exists,
3936 so that the delay need not occur when you don't want to run @value{GDBN}
3937 on the child. While the child is sleeping, use the @code{ps} program to
3938 get its process ID. Then tell @value{GDBN} (a new invocation of
3939 @value{GDBN} if you are also debugging the parent process) to attach to
3940 the child process (@pxref{Attach}). From that point on you can debug
3941 the child process just like any other process which you attached to.
3943 On some systems, @value{GDBN} provides support for debugging programs
3944 that create additional processes using the @code{fork} or @code{vfork}
3945 functions. On @sc{gnu}/Linux platforms, this feature is supported
3946 with kernel version 2.5.46 and later.
3948 The fork debugging commands are supported in native mode and when
3949 connected to @code{gdbserver} in either @code{target remote} mode or
3950 @code{target extended-remote} mode.
3952 By default, when a program forks, @value{GDBN} will continue to debug
3953 the parent process and the child process will run unimpeded.
3955 If you want to follow the child process instead of the parent process,
3956 use the command @w{@code{set follow-fork-mode}}.
3959 @kindex set follow-fork-mode
3960 @item set follow-fork-mode @var{mode}
3961 Set the debugger response to a program call of @code{fork} or
3962 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3963 process. The @var{mode} argument can be:
3967 The original process is debugged after a fork. The child process runs
3968 unimpeded. This is the default.
3971 The new process is debugged after a fork. The parent process runs
3976 @kindex show follow-fork-mode
3977 @item show follow-fork-mode
3978 Display the current debugger response to a @code{fork} or @code{vfork} call.
3981 @cindex debugging multiple processes
3982 On Linux, if you want to debug both the parent and child processes, use the
3983 command @w{@code{set detach-on-fork}}.
3986 @kindex set detach-on-fork
3987 @item set detach-on-fork @var{mode}
3988 Tells gdb whether to detach one of the processes after a fork, or
3989 retain debugger control over them both.
3993 The child process (or parent process, depending on the value of
3994 @code{follow-fork-mode}) will be detached and allowed to run
3995 independently. This is the default.
3998 Both processes will be held under the control of @value{GDBN}.
3999 One process (child or parent, depending on the value of
4000 @code{follow-fork-mode}) is debugged as usual, while the other
4005 @kindex show detach-on-fork
4006 @item show detach-on-fork
4007 Show whether detach-on-fork mode is on/off.
4010 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
4011 will retain control of all forked processes (including nested forks).
4012 You can list the forked processes under the control of @value{GDBN} by
4013 using the @w{@code{info inferiors}} command, and switch from one fork
4014 to another by using the @code{inferior} command (@pxref{Inferiors Connections and
4015 Programs, ,Debugging Multiple Inferiors Connections and Programs}).
4017 To quit debugging one of the forked processes, you can either detach
4018 from it by using the @w{@code{detach inferiors}} command (allowing it
4019 to run independently), or kill it using the @w{@code{kill inferiors}}
4020 command. @xref{Inferiors Connections and Programs, ,Debugging
4021 Multiple Inferiors Connections and Programs}.
4023 If you ask to debug a child process and a @code{vfork} is followed by an
4024 @code{exec}, @value{GDBN} executes the new target up to the first
4025 breakpoint in the new target. If you have a breakpoint set on
4026 @code{main} in your original program, the breakpoint will also be set on
4027 the child process's @code{main}.
4029 On some systems, when a child process is spawned by @code{vfork}, you
4030 cannot debug the child or parent until an @code{exec} call completes.
4032 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
4033 call executes, the new target restarts. To restart the parent
4034 process, use the @code{file} command with the parent executable name
4035 as its argument. By default, after an @code{exec} call executes,
4036 @value{GDBN} discards the symbols of the previous executable image.
4037 You can change this behaviour with the @w{@code{set follow-exec-mode}}
4041 @kindex set follow-exec-mode
4042 @item set follow-exec-mode @var{mode}
4044 Set debugger response to a program call of @code{exec}. An
4045 @code{exec} call replaces the program image of a process.
4047 @code{follow-exec-mode} can be:
4051 @value{GDBN} creates a new inferior and rebinds the process to this
4052 new inferior. The program the process was running before the
4053 @code{exec} call can be restarted afterwards by restarting the
4059 (@value{GDBP}) info inferiors
4061 Id Description Executable
4064 process 12020 is executing new program: prog2
4065 Program exited normally.
4066 (@value{GDBP}) info inferiors
4067 Id Description Executable
4073 @value{GDBN} keeps the process bound to the same inferior. The new
4074 executable image replaces the previous executable loaded in the
4075 inferior. Restarting the inferior after the @code{exec} call, with
4076 e.g., the @code{run} command, restarts the executable the process was
4077 running after the @code{exec} call. This is the default mode.
4082 (@value{GDBP}) info inferiors
4083 Id Description Executable
4086 process 12020 is executing new program: prog2
4087 Program exited normally.
4088 (@value{GDBP}) info inferiors
4089 Id Description Executable
4096 @code{follow-exec-mode} is supported in native mode and
4097 @code{target extended-remote} mode.
4099 You can use the @code{catch} command to make @value{GDBN} stop whenever
4100 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
4101 Catchpoints, ,Setting Catchpoints}.
4103 @node Checkpoint/Restart
4104 @section Setting a @emph{Bookmark} to Return to Later
4109 @cindex snapshot of a process
4110 @cindex rewind program state
4112 On certain operating systems@footnote{Currently, only
4113 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
4114 program's state, called a @dfn{checkpoint}, and come back to it
4117 Returning to a checkpoint effectively undoes everything that has
4118 happened in the program since the @code{checkpoint} was saved. This
4119 includes changes in memory, registers, and even (within some limits)
4120 system state. Effectively, it is like going back in time to the
4121 moment when the checkpoint was saved.
4123 Thus, if you're stepping thru a program and you think you're
4124 getting close to the point where things go wrong, you can save
4125 a checkpoint. Then, if you accidentally go too far and miss
4126 the critical statement, instead of having to restart your program
4127 from the beginning, you can just go back to the checkpoint and
4128 start again from there.
4130 This can be especially useful if it takes a lot of time or
4131 steps to reach the point where you think the bug occurs.
4133 To use the @code{checkpoint}/@code{restart} method of debugging:
4138 Save a snapshot of the debugged program's current execution state.
4139 The @code{checkpoint} command takes no arguments, but each checkpoint
4140 is assigned a small integer id, similar to a breakpoint id.
4142 @kindex info checkpoints
4143 @item info checkpoints
4144 List the checkpoints that have been saved in the current debugging
4145 session. For each checkpoint, the following information will be
4152 @item Source line, or label
4155 @kindex restart @var{checkpoint-id}
4156 @item restart @var{checkpoint-id}
4157 Restore the program state that was saved as checkpoint number
4158 @var{checkpoint-id}. All program variables, registers, stack frames
4159 etc.@: will be returned to the values that they had when the checkpoint
4160 was saved. In essence, gdb will ``wind back the clock'' to the point
4161 in time when the checkpoint was saved.
4163 Note that breakpoints, @value{GDBN} variables, command history etc.
4164 are not affected by restoring a checkpoint. In general, a checkpoint
4165 only restores things that reside in the program being debugged, not in
4168 @kindex delete checkpoint @var{checkpoint-id}
4169 @item delete checkpoint @var{checkpoint-id}
4170 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
4174 Returning to a previously saved checkpoint will restore the user state
4175 of the program being debugged, plus a significant subset of the system
4176 (OS) state, including file pointers. It won't ``un-write'' data from
4177 a file, but it will rewind the file pointer to the previous location,
4178 so that the previously written data can be overwritten. For files
4179 opened in read mode, the pointer will also be restored so that the
4180 previously read data can be read again.
4182 Of course, characters that have been sent to a printer (or other
4183 external device) cannot be ``snatched back'', and characters received
4184 from eg.@: a serial device can be removed from internal program buffers,
4185 but they cannot be ``pushed back'' into the serial pipeline, ready to
4186 be received again. Similarly, the actual contents of files that have
4187 been changed cannot be restored (at this time).
4189 However, within those constraints, you actually can ``rewind'' your
4190 program to a previously saved point in time, and begin debugging it
4191 again --- and you can change the course of events so as to debug a
4192 different execution path this time.
4194 @cindex checkpoints and process id
4195 Finally, there is one bit of internal program state that will be
4196 different when you return to a checkpoint --- the program's process
4197 id. Each checkpoint will have a unique process id (or @var{pid}),
4198 and each will be different from the program's original @var{pid}.
4199 If your program has saved a local copy of its process id, this could
4200 potentially pose a problem.
4202 @subsection A Non-obvious Benefit of Using Checkpoints
4204 On some systems such as @sc{gnu}/Linux, address space randomization
4205 is performed on new processes for security reasons. This makes it
4206 difficult or impossible to set a breakpoint, or watchpoint, on an
4207 absolute address if you have to restart the program, since the
4208 absolute location of a symbol will change from one execution to the
4211 A checkpoint, however, is an @emph{identical} copy of a process.
4212 Therefore if you create a checkpoint at (eg.@:) the start of main,
4213 and simply return to that checkpoint instead of restarting the
4214 process, you can avoid the effects of address randomization and
4215 your symbols will all stay in the same place.
4218 @chapter Stopping and Continuing
4220 The principal purposes of using a debugger are so that you can stop your
4221 program before it terminates; or so that, if your program runs into
4222 trouble, you can investigate and find out why.
4224 Inside @value{GDBN}, your program may stop for any of several reasons,
4225 such as a signal, a breakpoint, or reaching a new line after a
4226 @value{GDBN} command such as @code{step}. You may then examine and
4227 change variables, set new breakpoints or remove old ones, and then
4228 continue execution. Usually, the messages shown by @value{GDBN} provide
4229 ample explanation of the status of your program---but you can also
4230 explicitly request this information at any time.
4233 @kindex info program
4235 Display information about the status of your program: whether it is
4236 running or not, what process it is, and why it stopped.
4240 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
4241 * Continuing and Stepping:: Resuming execution
4242 * Skipping Over Functions and Files::
4243 Skipping over functions and files
4245 * Thread Stops:: Stopping and starting multi-thread programs
4249 @section Breakpoints, Watchpoints, and Catchpoints
4252 A @dfn{breakpoint} makes your program stop whenever a certain point in
4253 the program is reached. For each breakpoint, you can add conditions to
4254 control in finer detail whether your program stops. You can set
4255 breakpoints with the @code{break} command and its variants (@pxref{Set
4256 Breaks, ,Setting Breakpoints}), to specify the place where your program
4257 should stop by line number, function name or exact address in the
4260 On some systems, you can set breakpoints in shared libraries before
4261 the executable is run.
4264 @cindex data breakpoints
4265 @cindex memory tracing
4266 @cindex breakpoint on memory address
4267 @cindex breakpoint on variable modification
4268 A @dfn{watchpoint} is a special breakpoint that stops your program
4269 when the value of an expression changes. The expression may be a value
4270 of a variable, or it could involve values of one or more variables
4271 combined by operators, such as @samp{a + b}. This is sometimes called
4272 @dfn{data breakpoints}. You must use a different command to set
4273 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
4274 from that, you can manage a watchpoint like any other breakpoint: you
4275 enable, disable, and delete both breakpoints and watchpoints using the
4278 You can arrange to have values from your program displayed automatically
4279 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
4283 @cindex breakpoint on events
4284 A @dfn{catchpoint} is another special breakpoint that stops your program
4285 when a certain kind of event occurs, such as the throwing of a C@t{++}
4286 exception or the loading of a library. As with watchpoints, you use a
4287 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
4288 Catchpoints}), but aside from that, you can manage a catchpoint like any
4289 other breakpoint. (To stop when your program receives a signal, use the
4290 @code{handle} command; see @ref{Signals, ,Signals}.)
4292 @cindex breakpoint numbers
4293 @cindex numbers for breakpoints
4294 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
4295 catchpoint when you create it; these numbers are successive integers
4296 starting with one. In many of the commands for controlling various
4297 features of breakpoints you use the breakpoint number to say which
4298 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
4299 @dfn{disabled}; if disabled, it has no effect on your program until you
4302 @cindex breakpoint ranges
4303 @cindex breakpoint lists
4304 @cindex ranges of breakpoints
4305 @cindex lists of breakpoints
4306 Some @value{GDBN} commands accept a space-separated list of breakpoints
4307 on which to operate. A list element can be either a single breakpoint number,
4308 like @samp{5}, or a range of such numbers, like @samp{5-7}.
4309 When a breakpoint list is given to a command, all breakpoints in that list
4313 * Set Breaks:: Setting breakpoints
4314 * Set Watchpoints:: Setting watchpoints
4315 * Set Catchpoints:: Setting catchpoints
4316 * Delete Breaks:: Deleting breakpoints
4317 * Disabling:: Disabling breakpoints
4318 * Conditions:: Break conditions
4319 * Break Commands:: Breakpoint command lists
4320 * Dynamic Printf:: Dynamic printf
4321 * Save Breakpoints:: How to save breakpoints in a file
4322 * Static Probe Points:: Listing static probe points
4323 * Error in Breakpoints:: ``Cannot insert breakpoints''
4324 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
4328 @subsection Setting Breakpoints
4330 @c FIXME LMB what does GDB do if no code on line of breakpt?
4331 @c consider in particular declaration with/without initialization.
4333 @c FIXME 2 is there stuff on this already? break at fun start, already init?
4336 @kindex b @r{(@code{break})}
4337 @vindex $bpnum@r{, convenience variable}
4338 @cindex latest breakpoint
4339 Breakpoints are set with the @code{break} command (abbreviated
4340 @code{b}). The debugger convenience variable @samp{$bpnum} records the
4341 number of the breakpoint you've set most recently; see @ref{Convenience
4342 Vars,, Convenience Variables}, for a discussion of what you can do with
4343 convenience variables.
4346 @item break @var{location}
4347 Set a breakpoint at the given @var{location}, which can specify a
4348 function name, a line number, or an address of an instruction.
4349 (@xref{Specify Location}, for a list of all the possible ways to
4350 specify a @var{location}.) The breakpoint will stop your program just
4351 before it executes any of the code in the specified @var{location}.
4353 When using source languages that permit overloading of symbols, such as
4354 C@t{++}, a function name may refer to more than one possible place to break.
4355 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
4358 It is also possible to insert a breakpoint that will stop the program
4359 only if a specific thread (@pxref{Thread-Specific Breakpoints})
4360 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
4363 When called without any arguments, @code{break} sets a breakpoint at
4364 the next instruction to be executed in the selected stack frame
4365 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
4366 innermost, this makes your program stop as soon as control
4367 returns to that frame. This is similar to the effect of a
4368 @code{finish} command in the frame inside the selected frame---except
4369 that @code{finish} does not leave an active breakpoint. If you use
4370 @code{break} without an argument in the innermost frame, @value{GDBN} stops
4371 the next time it reaches the current location; this may be useful
4374 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
4375 least one instruction has been executed. If it did not do this, you
4376 would be unable to proceed past a breakpoint without first disabling the
4377 breakpoint. This rule applies whether or not the breakpoint already
4378 existed when your program stopped.
4380 @item break @dots{} if @var{cond}
4381 Set a breakpoint with condition @var{cond}; evaluate the expression
4382 @var{cond} each time the breakpoint is reached, and stop only if the
4383 value is nonzero---that is, if @var{cond} evaluates as true.
4384 @samp{@dots{}} stands for one of the possible arguments described
4385 above (or no argument) specifying where to break. @xref{Conditions,
4386 ,Break Conditions}, for more information on breakpoint conditions.
4388 The breakpoint may be mapped to multiple locations. If the breakpoint
4389 condition @var{cond} is invalid at some but not all of the locations,
4390 the locations for which the condition is invalid are disabled. For
4391 example, @value{GDBN} reports below that two of the three locations
4395 (@value{GDBP}) break func if a == 10
4396 warning: failed to validate condition at location 0x11ce, disabling:
4397 No symbol "a" in current context.
4398 warning: failed to validate condition at location 0x11b6, disabling:
4399 No symbol "a" in current context.
4400 Breakpoint 1 at 0x11b6: func. (3 locations)
4403 Locations that are disabled because of the condition are denoted by an
4404 uppercase @code{N} in the output of the @code{info breakpoints}
4408 (@value{GDBP}) info breakpoints
4409 Num Type Disp Enb Address What
4410 1 breakpoint keep y <MULTIPLE>
4411 stop only if a == 10
4412 1.1 N* 0x00000000000011b6 in ...
4413 1.2 y 0x00000000000011c2 in ...
4414 1.3 N* 0x00000000000011ce in ...
4415 (*): Breakpoint condition is invalid at this location.
4418 If the breakpoint condition @var{cond} is invalid in the context of
4419 @emph{all} the locations of the breakpoint, @value{GDBN} refuses to
4420 define the breakpoint. For example, if variable @code{foo} is an
4424 (@value{GDBP}) break func if foo
4425 No symbol "foo" in current context.
4428 @item break @dots{} -force-condition if @var{cond}
4429 There may be cases where the condition @var{cond} is invalid at all
4430 the current locations, but the user knows that it will be valid at a
4431 future location; for example, because of a library load. In such
4432 cases, by using the @code{-force-condition} keyword before @samp{if},
4433 @value{GDBN} can be forced to define the breakpoint with the given
4434 condition expression instead of refusing it.
4437 (@value{GDBP}) break func -force-condition if foo
4438 warning: failed to validate condition at location 1, disabling:
4439 No symbol "foo" in current context.
4440 warning: failed to validate condition at location 2, disabling:
4441 No symbol "foo" in current context.
4442 warning: failed to validate condition at location 3, disabling:
4443 No symbol "foo" in current context.
4444 Breakpoint 1 at 0x1158: test.c:18. (3 locations)
4447 This causes all the present locations where the breakpoint would
4448 otherwise be inserted, to be disabled, as seen in the example above.
4449 However, if there exist locations at which the condition is valid, the
4450 @code{-force-condition} keyword has no effect.
4453 @item tbreak @var{args}
4454 Set a breakpoint enabled only for one stop. The @var{args} are the
4455 same as for the @code{break} command, and the breakpoint is set in the same
4456 way, but the breakpoint is automatically deleted after the first time your
4457 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
4460 @cindex hardware breakpoints
4461 @item hbreak @var{args}
4462 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
4463 @code{break} command and the breakpoint is set in the same way, but the
4464 breakpoint requires hardware support and some target hardware may not
4465 have this support. The main purpose of this is EPROM/ROM code
4466 debugging, so you can set a breakpoint at an instruction without
4467 changing the instruction. This can be used with the new trap-generation
4468 provided by SPARClite DSU and most x86-based targets. These targets
4469 will generate traps when a program accesses some data or instruction
4470 address that is assigned to the debug registers. However the hardware
4471 breakpoint registers can take a limited number of breakpoints. For
4472 example, on the DSU, only two data breakpoints can be set at a time, and
4473 @value{GDBN} will reject this command if more than two are used. Delete
4474 or disable unused hardware breakpoints before setting new ones
4475 (@pxref{Disabling, ,Disabling Breakpoints}).
4476 @xref{Conditions, ,Break Conditions}.
4477 For remote targets, you can restrict the number of hardware
4478 breakpoints @value{GDBN} will use, see @ref{set remote
4479 hardware-breakpoint-limit}.
4482 @item thbreak @var{args}
4483 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
4484 are the same as for the @code{hbreak} command and the breakpoint is set in
4485 the same way. However, like the @code{tbreak} command,
4486 the breakpoint is automatically deleted after the
4487 first time your program stops there. Also, like the @code{hbreak}
4488 command, the breakpoint requires hardware support and some target hardware
4489 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
4490 See also @ref{Conditions, ,Break Conditions}.
4493 @cindex regular expression
4494 @cindex breakpoints at functions matching a regexp
4495 @cindex set breakpoints in many functions
4496 @item rbreak @var{regex}
4497 Set breakpoints on all functions matching the regular expression
4498 @var{regex}. This command sets an unconditional breakpoint on all
4499 matches, printing a list of all breakpoints it set. Once these
4500 breakpoints are set, they are treated just like the breakpoints set with
4501 the @code{break} command. You can delete them, disable them, or make
4502 them conditional the same way as any other breakpoint.
4504 In programs using different languages, @value{GDBN} chooses the syntax
4505 to print the list of all breakpoints it sets according to the
4506 @samp{set language} value: using @samp{set language auto}
4507 (see @ref{Automatically, ,Set Language Automatically}) means to use the
4508 language of the breakpoint's function, other values mean to use
4509 the manually specified language (see @ref{Manually, ,Set Language Manually}).
4511 The syntax of the regular expression is the standard one used with tools
4512 like @file{grep}. Note that this is different from the syntax used by
4513 shells, so for instance @code{foo*} matches all functions that include
4514 an @code{fo} followed by zero or more @code{o}s. There is an implicit
4515 @code{.*} leading and trailing the regular expression you supply, so to
4516 match only functions that begin with @code{foo}, use @code{^foo}.
4518 @cindex non-member C@t{++} functions, set breakpoint in
4519 When debugging C@t{++} programs, @code{rbreak} is useful for setting
4520 breakpoints on overloaded functions that are not members of any special
4523 @cindex set breakpoints on all functions
4524 The @code{rbreak} command can be used to set breakpoints in
4525 @strong{all} the functions in a program, like this:
4528 (@value{GDBP}) rbreak .
4531 @item rbreak @var{file}:@var{regex}
4532 If @code{rbreak} is called with a filename qualification, it limits
4533 the search for functions matching the given regular expression to the
4534 specified @var{file}. This can be used, for example, to set breakpoints on
4535 every function in a given file:
4538 (@value{GDBP}) rbreak file.c:.
4541 The colon separating the filename qualifier from the regex may
4542 optionally be surrounded by spaces.
4544 @kindex info breakpoints
4545 @cindex @code{$_} and @code{info breakpoints}
4546 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
4547 @itemx info break @r{[}@var{list}@dots{}@r{]}
4548 Print a table of all breakpoints, watchpoints, and catchpoints set and
4549 not deleted. Optional argument @var{n} means print information only
4550 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
4551 For each breakpoint, following columns are printed:
4554 @item Breakpoint Numbers
4556 Breakpoint, watchpoint, or catchpoint.
4558 Whether the breakpoint is marked to be disabled or deleted when hit.
4559 @item Enabled or Disabled
4560 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
4561 that are not enabled.
4563 Where the breakpoint is in your program, as a memory address. For a
4564 pending breakpoint whose address is not yet known, this field will
4565 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
4566 library that has the symbol or line referred by breakpoint is loaded.
4567 See below for details. A breakpoint with several locations will
4568 have @samp{<MULTIPLE>} in this field---see below for details.
4570 Where the breakpoint is in the source for your program, as a file and
4571 line number. For a pending breakpoint, the original string passed to
4572 the breakpoint command will be listed as it cannot be resolved until
4573 the appropriate shared library is loaded in the future.
4577 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
4578 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
4579 @value{GDBN} on the host's side. If it is ``target'', then the condition
4580 is evaluated by the target. The @code{info break} command shows
4581 the condition on the line following the affected breakpoint, together with
4582 its condition evaluation mode in between parentheses.
4584 Breakpoint commands, if any, are listed after that. A pending breakpoint is
4585 allowed to have a condition specified for it. The condition is not parsed for
4586 validity until a shared library is loaded that allows the pending
4587 breakpoint to resolve to a valid location.
4590 @code{info break} with a breakpoint
4591 number @var{n} as argument lists only that breakpoint. The
4592 convenience variable @code{$_} and the default examining-address for
4593 the @code{x} command are set to the address of the last breakpoint
4594 listed (@pxref{Memory, ,Examining Memory}).
4597 @code{info break} displays a count of the number of times the breakpoint
4598 has been hit. This is especially useful in conjunction with the
4599 @code{ignore} command. You can ignore a large number of breakpoint
4600 hits, look at the breakpoint info to see how many times the breakpoint
4601 was hit, and then run again, ignoring one less than that number. This
4602 will get you quickly to the last hit of that breakpoint.
4605 For a breakpoints with an enable count (xref) greater than 1,
4606 @code{info break} also displays that count.
4610 @value{GDBN} allows you to set any number of breakpoints at the same place in
4611 your program. There is nothing silly or meaningless about this. When
4612 the breakpoints are conditional, this is even useful
4613 (@pxref{Conditions, ,Break Conditions}).
4615 @cindex multiple locations, breakpoints
4616 @cindex breakpoints, multiple locations
4617 It is possible that a breakpoint corresponds to several locations
4618 in your program. Examples of this situation are:
4622 Multiple functions in the program may have the same name.
4625 For a C@t{++} constructor, the @value{NGCC} compiler generates several
4626 instances of the function body, used in different cases.
4629 For a C@t{++} template function, a given line in the function can
4630 correspond to any number of instantiations.
4633 For an inlined function, a given source line can correspond to
4634 several places where that function is inlined.
4637 In all those cases, @value{GDBN} will insert a breakpoint at all
4638 the relevant locations.
4640 A breakpoint with multiple locations is displayed in the breakpoint
4641 table using several rows---one header row, followed by one row for
4642 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4643 address column. The rows for individual locations contain the actual
4644 addresses for locations, and show the functions to which those
4645 locations belong. The number column for a location is of the form
4646 @var{breakpoint-number}.@var{location-number}.
4651 Num Type Disp Enb Address What
4652 1 breakpoint keep y <MULTIPLE>
4654 breakpoint already hit 1 time
4655 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4656 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4659 You cannot delete the individual locations from a breakpoint. However,
4660 each location can be individually enabled or disabled by passing
4661 @var{breakpoint-number}.@var{location-number} as argument to the
4662 @code{enable} and @code{disable} commands. It's also possible to
4663 @code{enable} and @code{disable} a range of @var{location-number}
4664 locations using a @var{breakpoint-number} and two @var{location-number}s,
4665 in increasing order, separated by a hyphen, like
4666 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4667 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4668 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4669 all of the locations that belong to that breakpoint.
4671 @cindex pending breakpoints
4672 It's quite common to have a breakpoint inside a shared library.
4673 Shared libraries can be loaded and unloaded explicitly,
4674 and possibly repeatedly, as the program is executed. To support
4675 this use case, @value{GDBN} updates breakpoint locations whenever
4676 any shared library is loaded or unloaded. Typically, you would
4677 set a breakpoint in a shared library at the beginning of your
4678 debugging session, when the library is not loaded, and when the
4679 symbols from the library are not available. When you try to set
4680 breakpoint, @value{GDBN} will ask you if you want to set
4681 a so called @dfn{pending breakpoint}---breakpoint whose address
4682 is not yet resolved.
4684 After the program is run, whenever a new shared library is loaded,
4685 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4686 shared library contains the symbol or line referred to by some
4687 pending breakpoint, that breakpoint is resolved and becomes an
4688 ordinary breakpoint. When a library is unloaded, all breakpoints
4689 that refer to its symbols or source lines become pending again.
4691 This logic works for breakpoints with multiple locations, too. For
4692 example, if you have a breakpoint in a C@t{++} template function, and
4693 a newly loaded shared library has an instantiation of that template,
4694 a new location is added to the list of locations for the breakpoint.
4696 Except for having unresolved address, pending breakpoints do not
4697 differ from regular breakpoints. You can set conditions or commands,
4698 enable and disable them and perform other breakpoint operations.
4700 @value{GDBN} provides some additional commands for controlling what
4701 happens when the @samp{break} command cannot resolve breakpoint
4702 address specification to an address:
4704 @kindex set breakpoint pending
4705 @kindex show breakpoint pending
4707 @item set breakpoint pending auto
4708 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4709 location, it queries you whether a pending breakpoint should be created.
4711 @item set breakpoint pending on
4712 This indicates that an unrecognized breakpoint location should automatically
4713 result in a pending breakpoint being created.
4715 @item set breakpoint pending off
4716 This indicates that pending breakpoints are not to be created. Any
4717 unrecognized breakpoint location results in an error. This setting does
4718 not affect any pending breakpoints previously created.
4720 @item show breakpoint pending
4721 Show the current behavior setting for creating pending breakpoints.
4724 The settings above only affect the @code{break} command and its
4725 variants. Once breakpoint is set, it will be automatically updated
4726 as shared libraries are loaded and unloaded.
4728 @cindex automatic hardware breakpoints
4729 For some targets, @value{GDBN} can automatically decide if hardware or
4730 software breakpoints should be used, depending on whether the
4731 breakpoint address is read-only or read-write. This applies to
4732 breakpoints set with the @code{break} command as well as to internal
4733 breakpoints set by commands like @code{next} and @code{finish}. For
4734 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4737 You can control this automatic behaviour with the following commands:
4739 @kindex set breakpoint auto-hw
4740 @kindex show breakpoint auto-hw
4742 @item set breakpoint auto-hw on
4743 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4744 will try to use the target memory map to decide if software or hardware
4745 breakpoint must be used.
4747 @item set breakpoint auto-hw off
4748 This indicates @value{GDBN} should not automatically select breakpoint
4749 type. If the target provides a memory map, @value{GDBN} will warn when
4750 trying to set software breakpoint at a read-only address.
4753 @value{GDBN} normally implements breakpoints by replacing the program code
4754 at the breakpoint address with a special instruction, which, when
4755 executed, given control to the debugger. By default, the program
4756 code is so modified only when the program is resumed. As soon as
4757 the program stops, @value{GDBN} restores the original instructions. This
4758 behaviour guards against leaving breakpoints inserted in the
4759 target should gdb abrubptly disconnect. However, with slow remote
4760 targets, inserting and removing breakpoint can reduce the performance.
4761 This behavior can be controlled with the following commands::
4763 @kindex set breakpoint always-inserted
4764 @kindex show breakpoint always-inserted
4766 @item set breakpoint always-inserted off
4767 All breakpoints, including newly added by the user, are inserted in
4768 the target only when the target is resumed. All breakpoints are
4769 removed from the target when it stops. This is the default mode.
4771 @item set breakpoint always-inserted on
4772 Causes all breakpoints to be inserted in the target at all times. If
4773 the user adds a new breakpoint, or changes an existing breakpoint, the
4774 breakpoints in the target are updated immediately. A breakpoint is
4775 removed from the target only when breakpoint itself is deleted.
4778 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4779 when a breakpoint breaks. If the condition is true, then the process being
4780 debugged stops, otherwise the process is resumed.
4782 If the target supports evaluating conditions on its end, @value{GDBN} may
4783 download the breakpoint, together with its conditions, to it.
4785 This feature can be controlled via the following commands:
4787 @kindex set breakpoint condition-evaluation
4788 @kindex show breakpoint condition-evaluation
4790 @item set breakpoint condition-evaluation host
4791 This option commands @value{GDBN} to evaluate the breakpoint
4792 conditions on the host's side. Unconditional breakpoints are sent to
4793 the target which in turn receives the triggers and reports them back to GDB
4794 for condition evaluation. This is the standard evaluation mode.
4796 @item set breakpoint condition-evaluation target
4797 This option commands @value{GDBN} to download breakpoint conditions
4798 to the target at the moment of their insertion. The target
4799 is responsible for evaluating the conditional expression and reporting
4800 breakpoint stop events back to @value{GDBN} whenever the condition
4801 is true. Due to limitations of target-side evaluation, some conditions
4802 cannot be evaluated there, e.g., conditions that depend on local data
4803 that is only known to the host. Examples include
4804 conditional expressions involving convenience variables, complex types
4805 that cannot be handled by the agent expression parser and expressions
4806 that are too long to be sent over to the target, specially when the
4807 target is a remote system. In these cases, the conditions will be
4808 evaluated by @value{GDBN}.
4810 @item set breakpoint condition-evaluation auto
4811 This is the default mode. If the target supports evaluating breakpoint
4812 conditions on its end, @value{GDBN} will download breakpoint conditions to
4813 the target (limitations mentioned previously apply). If the target does
4814 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4815 to evaluating all these conditions on the host's side.
4819 @cindex negative breakpoint numbers
4820 @cindex internal @value{GDBN} breakpoints
4821 @value{GDBN} itself sometimes sets breakpoints in your program for
4822 special purposes, such as proper handling of @code{longjmp} (in C
4823 programs). These internal breakpoints are assigned negative numbers,
4824 starting with @code{-1}; @samp{info breakpoints} does not display them.
4825 You can see these breakpoints with the @value{GDBN} maintenance command
4826 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4829 @node Set Watchpoints
4830 @subsection Setting Watchpoints
4832 @cindex setting watchpoints
4833 You can use a watchpoint to stop execution whenever the value of an
4834 expression changes, without having to predict a particular place where
4835 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4836 The expression may be as simple as the value of a single variable, or
4837 as complex as many variables combined by operators. Examples include:
4841 A reference to the value of a single variable.
4844 An address cast to an appropriate data type. For example,
4845 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4846 address (assuming an @code{int} occupies 4 bytes).
4849 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4850 expression can use any operators valid in the program's native
4851 language (@pxref{Languages}).
4854 You can set a watchpoint on an expression even if the expression can
4855 not be evaluated yet. For instance, you can set a watchpoint on
4856 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4857 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4858 the expression produces a valid value. If the expression becomes
4859 valid in some other way than changing a variable (e.g.@: if the memory
4860 pointed to by @samp{*global_ptr} becomes readable as the result of a
4861 @code{malloc} call), @value{GDBN} may not stop until the next time
4862 the expression changes.
4864 @cindex software watchpoints
4865 @cindex hardware watchpoints
4866 Depending on your system, watchpoints may be implemented in software or
4867 hardware. @value{GDBN} does software watchpointing by single-stepping your
4868 program and testing the variable's value each time, which is hundreds of
4869 times slower than normal execution. (But this may still be worth it, to
4870 catch errors where you have no clue what part of your program is the
4873 On some systems, such as most PowerPC or x86-based targets,
4874 @value{GDBN} includes support for hardware watchpoints, which do not
4875 slow down the running of your program.
4879 @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{]}
4880 Set a watchpoint for an expression. @value{GDBN} will break when the
4881 expression @var{expr} is written into by the program and its value
4882 changes. The simplest (and the most popular) use of this command is
4883 to watch the value of a single variable:
4886 (@value{GDBP}) watch foo
4889 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4890 argument, @value{GDBN} breaks only when the thread identified by
4891 @var{thread-id} changes the value of @var{expr}. If any other threads
4892 change the value of @var{expr}, @value{GDBN} will not break. Note
4893 that watchpoints restricted to a single thread in this way only work
4894 with Hardware Watchpoints.
4896 Similarly, if the @code{task} argument is given, then the watchpoint
4897 will be specific to the indicated Ada task (@pxref{Ada Tasks}).
4899 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4900 (see below). The @code{-location} argument tells @value{GDBN} to
4901 instead watch the memory referred to by @var{expr}. In this case,
4902 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4903 and watch the memory at that address. The type of the result is used
4904 to determine the size of the watched memory. If the expression's
4905 result does not have an address, then @value{GDBN} will print an
4908 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4909 of masked watchpoints, if the current architecture supports this
4910 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4911 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4912 to an address to watch. The mask specifies that some bits of an address
4913 (the bits which are reset in the mask) should be ignored when matching
4914 the address accessed by the inferior against the watchpoint address.
4915 Thus, a masked watchpoint watches many addresses simultaneously---those
4916 addresses whose unmasked bits are identical to the unmasked bits in the
4917 watchpoint address. The @code{mask} argument implies @code{-location}.
4921 (@value{GDBP}) watch foo mask 0xffff00ff
4922 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4926 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4927 Set a watchpoint that will break when the value of @var{expr} is read
4931 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4932 Set a watchpoint that will break when @var{expr} is either read from
4933 or written into by the program.
4935 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4936 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4937 This command prints a list of watchpoints, using the same format as
4938 @code{info break} (@pxref{Set Breaks}).
4941 If you watch for a change in a numerically entered address you need to
4942 dereference it, as the address itself is just a constant number which will
4943 never change. @value{GDBN} refuses to create a watchpoint that watches
4944 a never-changing value:
4947 (@value{GDBP}) watch 0x600850
4948 Cannot watch constant value 0x600850.
4949 (@value{GDBP}) watch *(int *) 0x600850
4950 Watchpoint 1: *(int *) 6293584
4953 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4954 watchpoints execute very quickly, and the debugger reports a change in
4955 value at the exact instruction where the change occurs. If @value{GDBN}
4956 cannot set a hardware watchpoint, it sets a software watchpoint, which
4957 executes more slowly and reports the change in value at the next
4958 @emph{statement}, not the instruction, after the change occurs.
4960 @cindex use only software watchpoints
4961 You can force @value{GDBN} to use only software watchpoints with the
4962 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4963 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4964 the underlying system supports them. (Note that hardware-assisted
4965 watchpoints that were set @emph{before} setting
4966 @code{can-use-hw-watchpoints} to zero will still use the hardware
4967 mechanism of watching expression values.)
4970 @item set can-use-hw-watchpoints
4971 @kindex set can-use-hw-watchpoints
4972 Set whether or not to use hardware watchpoints.
4974 @item show can-use-hw-watchpoints
4975 @kindex show can-use-hw-watchpoints
4976 Show the current mode of using hardware watchpoints.
4979 For remote targets, you can restrict the number of hardware
4980 watchpoints @value{GDBN} will use, see @ref{set remote
4981 hardware-breakpoint-limit}.
4983 When you issue the @code{watch} command, @value{GDBN} reports
4986 Hardware watchpoint @var{num}: @var{expr}
4990 if it was able to set a hardware watchpoint.
4992 Currently, the @code{awatch} and @code{rwatch} commands can only set
4993 hardware watchpoints, because accesses to data that don't change the
4994 value of the watched expression cannot be detected without examining
4995 every instruction as it is being executed, and @value{GDBN} does not do
4996 that currently. If @value{GDBN} finds that it is unable to set a
4997 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4998 will print a message like this:
5001 Expression cannot be implemented with read/access watchpoint.
5004 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
5005 data type of the watched expression is wider than what a hardware
5006 watchpoint on the target machine can handle. For example, some systems
5007 can only watch regions that are up to 4 bytes wide; on such systems you
5008 cannot set hardware watchpoints for an expression that yields a
5009 double-precision floating-point number (which is typically 8 bytes
5010 wide). As a work-around, it might be possible to break the large region
5011 into a series of smaller ones and watch them with separate watchpoints.
5013 If you set too many hardware watchpoints, @value{GDBN} might be unable
5014 to insert all of them when you resume the execution of your program.
5015 Since the precise number of active watchpoints is unknown until such
5016 time as the program is about to be resumed, @value{GDBN} might not be
5017 able to warn you about this when you set the watchpoints, and the
5018 warning will be printed only when the program is resumed:
5021 Hardware watchpoint @var{num}: Could not insert watchpoint
5025 If this happens, delete or disable some of the watchpoints.
5027 Watching complex expressions that reference many variables can also
5028 exhaust the resources available for hardware-assisted watchpoints.
5029 That's because @value{GDBN} needs to watch every variable in the
5030 expression with separately allocated resources.
5032 If you call a function interactively using @code{print} or @code{call},
5033 any watchpoints you have set will be inactive until @value{GDBN} reaches another
5034 kind of breakpoint or the call completes.
5036 @value{GDBN} automatically deletes watchpoints that watch local
5037 (automatic) variables, or expressions that involve such variables, when
5038 they go out of scope, that is, when the execution leaves the block in
5039 which these variables were defined. In particular, when the program
5040 being debugged terminates, @emph{all} local variables go out of scope,
5041 and so only watchpoints that watch global variables remain set. If you
5042 rerun the program, you will need to set all such watchpoints again. One
5043 way of doing that would be to set a code breakpoint at the entry to the
5044 @code{main} function and when it breaks, set all the watchpoints.
5046 @cindex watchpoints and threads
5047 @cindex threads and watchpoints
5048 In multi-threaded programs, watchpoints will detect changes to the
5049 watched expression from every thread.
5052 @emph{Warning:} In multi-threaded programs, software watchpoints
5053 have only limited usefulness. If @value{GDBN} creates a software
5054 watchpoint, it can only watch the value of an expression @emph{in a
5055 single thread}. If you are confident that the expression can only
5056 change due to the current thread's activity (and if you are also
5057 confident that no other thread can become current), then you can use
5058 software watchpoints as usual. However, @value{GDBN} may not notice
5059 when a non-current thread's activity changes the expression. (Hardware
5060 watchpoints, in contrast, watch an expression in all threads.)
5063 @xref{set remote hardware-watchpoint-limit}.
5065 @node Set Catchpoints
5066 @subsection Setting Catchpoints
5067 @cindex catchpoints, setting
5068 @cindex exception handlers
5069 @cindex event handling
5071 You can use @dfn{catchpoints} to cause the debugger to stop for certain
5072 kinds of program events, such as C@t{++} exceptions or the loading of a
5073 shared library. Use the @code{catch} command to set a catchpoint.
5077 @item catch @var{event}
5078 Stop when @var{event} occurs. The @var{event} can be any of the following:
5081 @item throw @r{[}@var{regexp}@r{]}
5082 @itemx rethrow @r{[}@var{regexp}@r{]}
5083 @itemx catch @r{[}@var{regexp}@r{]}
5085 @kindex catch rethrow
5087 @cindex stop on C@t{++} exceptions
5088 The throwing, re-throwing, or catching of a C@t{++} exception.
5090 If @var{regexp} is given, then only exceptions whose type matches the
5091 regular expression will be caught.
5093 @vindex $_exception@r{, convenience variable}
5094 The convenience variable @code{$_exception} is available at an
5095 exception-related catchpoint, on some systems. This holds the
5096 exception being thrown.
5098 There are currently some limitations to C@t{++} exception handling in
5103 The support for these commands is system-dependent. Currently, only
5104 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
5108 The regular expression feature and the @code{$_exception} convenience
5109 variable rely on the presence of some SDT probes in @code{libstdc++}.
5110 If these probes are not present, then these features cannot be used.
5111 These probes were first available in the GCC 4.8 release, but whether
5112 or not they are available in your GCC also depends on how it was
5116 The @code{$_exception} convenience variable is only valid at the
5117 instruction at which an exception-related catchpoint is set.
5120 When an exception-related catchpoint is hit, @value{GDBN} stops at a
5121 location in the system library which implements runtime exception
5122 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
5123 (@pxref{Selection}) to get to your code.
5126 If you call a function interactively, @value{GDBN} normally returns
5127 control to you when the function has finished executing. If the call
5128 raises an exception, however, the call may bypass the mechanism that
5129 returns control to you and cause your program either to abort or to
5130 simply continue running until it hits a breakpoint, catches a signal
5131 that @value{GDBN} is listening for, or exits. This is the case even if
5132 you set a catchpoint for the exception; catchpoints on exceptions are
5133 disabled within interactive calls. @xref{Calling}, for information on
5134 controlling this with @code{set unwind-on-terminating-exception}.
5137 You cannot raise an exception interactively.
5140 You cannot install an exception handler interactively.
5143 @item exception @r{[}@var{name}@r{]}
5144 @kindex catch exception
5145 @cindex Ada exception catching
5146 @cindex catch Ada exceptions
5147 An Ada exception being raised. If an exception name is specified
5148 at the end of the command (eg @code{catch exception Program_Error}),
5149 the debugger will stop only when this specific exception is raised.
5150 Otherwise, the debugger stops execution when any Ada exception is raised.
5152 When inserting an exception catchpoint on a user-defined exception whose
5153 name is identical to one of the exceptions defined by the language, the
5154 fully qualified name must be used as the exception name. Otherwise,
5155 @value{GDBN} will assume that it should stop on the pre-defined exception
5156 rather than the user-defined one. For instance, assuming an exception
5157 called @code{Constraint_Error} is defined in package @code{Pck}, then
5158 the command to use to catch such exceptions is @kbd{catch exception
5159 Pck.Constraint_Error}.
5161 @vindex $_ada_exception@r{, convenience variable}
5162 The convenience variable @code{$_ada_exception} holds the address of
5163 the exception being thrown. This can be useful when setting a
5164 condition for such a catchpoint.
5166 @item exception unhandled
5167 @kindex catch exception unhandled
5168 An exception that was raised but is not handled by the program. The
5169 convenience variable @code{$_ada_exception} is set as for @code{catch
5172 @item handlers @r{[}@var{name}@r{]}
5173 @kindex catch handlers
5174 @cindex Ada exception handlers catching
5175 @cindex catch Ada exceptions when handled
5176 An Ada exception being handled. If an exception name is
5177 specified at the end of the command
5178 (eg @kbd{catch handlers Program_Error}), the debugger will stop
5179 only when this specific exception is handled.
5180 Otherwise, the debugger stops execution when any Ada exception is handled.
5182 When inserting a handlers catchpoint on a user-defined
5183 exception whose name is identical to one of the exceptions
5184 defined by the language, the fully qualified name must be used
5185 as the exception name. Otherwise, @value{GDBN} will assume that it
5186 should stop on the pre-defined exception rather than the
5187 user-defined one. For instance, assuming an exception called
5188 @code{Constraint_Error} is defined in package @code{Pck}, then the
5189 command to use to catch such exceptions handling is
5190 @kbd{catch handlers Pck.Constraint_Error}.
5192 The convenience variable @code{$_ada_exception} is set as for
5193 @code{catch exception}.
5196 @kindex catch assert
5197 A failed Ada assertion. Note that the convenience variable
5198 @code{$_ada_exception} is @emph{not} set by this catchpoint.
5202 @cindex break on fork/exec
5203 A call to @code{exec}.
5205 @anchor{catch syscall}
5207 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
5208 @kindex catch syscall
5209 @cindex break on a system call.
5210 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
5211 syscall is a mechanism for application programs to request a service
5212 from the operating system (OS) or one of the OS system services.
5213 @value{GDBN} can catch some or all of the syscalls issued by the
5214 debuggee, and show the related information for each syscall. If no
5215 argument is specified, calls to and returns from all system calls
5218 @var{name} can be any system call name that is valid for the
5219 underlying OS. Just what syscalls are valid depends on the OS. On
5220 GNU and Unix systems, you can find the full list of valid syscall
5221 names on @file{/usr/include/asm/unistd.h}.
5223 @c For MS-Windows, the syscall names and the corresponding numbers
5224 @c can be found, e.g., on this URL:
5225 @c http://www.metasploit.com/users/opcode/syscalls.html
5226 @c but we don't support Windows syscalls yet.
5228 Normally, @value{GDBN} knows in advance which syscalls are valid for
5229 each OS, so you can use the @value{GDBN} command-line completion
5230 facilities (@pxref{Completion,, command completion}) to list the
5233 You may also specify the system call numerically. A syscall's
5234 number is the value passed to the OS's syscall dispatcher to
5235 identify the requested service. When you specify the syscall by its
5236 name, @value{GDBN} uses its database of syscalls to convert the name
5237 into the corresponding numeric code, but using the number directly
5238 may be useful if @value{GDBN}'s database does not have the complete
5239 list of syscalls on your system (e.g., because @value{GDBN} lags
5240 behind the OS upgrades).
5242 You may specify a group of related syscalls to be caught at once using
5243 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
5244 instance, on some platforms @value{GDBN} allows you to catch all
5245 network related syscalls, by passing the argument @code{group:network}
5246 to @code{catch syscall}. Note that not all syscall groups are
5247 available in every system. You can use the command completion
5248 facilities (@pxref{Completion,, command completion}) to list the
5249 syscall groups available on your environment.
5251 The example below illustrates how this command works if you don't provide
5255 (@value{GDBP}) catch syscall
5256 Catchpoint 1 (syscall)
5258 Starting program: /tmp/catch-syscall
5260 Catchpoint 1 (call to syscall 'close'), \
5261 0xffffe424 in __kernel_vsyscall ()
5265 Catchpoint 1 (returned from syscall 'close'), \
5266 0xffffe424 in __kernel_vsyscall ()
5270 Here is an example of catching a system call by name:
5273 (@value{GDBP}) catch syscall chroot
5274 Catchpoint 1 (syscall 'chroot' [61])
5276 Starting program: /tmp/catch-syscall
5278 Catchpoint 1 (call to syscall 'chroot'), \
5279 0xffffe424 in __kernel_vsyscall ()
5283 Catchpoint 1 (returned from syscall 'chroot'), \
5284 0xffffe424 in __kernel_vsyscall ()
5288 An example of specifying a system call numerically. In the case
5289 below, the syscall number has a corresponding entry in the XML
5290 file, so @value{GDBN} finds its name and prints it:
5293 (@value{GDBP}) catch syscall 252
5294 Catchpoint 1 (syscall(s) 'exit_group')
5296 Starting program: /tmp/catch-syscall
5298 Catchpoint 1 (call to syscall 'exit_group'), \
5299 0xffffe424 in __kernel_vsyscall ()
5303 Program exited normally.
5307 Here is an example of catching a syscall group:
5310 (@value{GDBP}) catch syscall group:process
5311 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
5312 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
5313 'exit_group' [252] 'waitid' [284] 'unshare' [310])
5315 Starting program: /tmp/catch-syscall
5317 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
5318 from /lib64/ld-linux-x86-64.so.2
5324 However, there can be situations when there is no corresponding name
5325 in XML file for that syscall number. In this case, @value{GDBN} prints
5326 a warning message saying that it was not able to find the syscall name,
5327 but the catchpoint will be set anyway. See the example below:
5330 (@value{GDBP}) catch syscall 764
5331 warning: The number '764' does not represent a known syscall.
5332 Catchpoint 2 (syscall 764)
5336 If you configure @value{GDBN} using the @samp{--without-expat} option,
5337 it will not be able to display syscall names. Also, if your
5338 architecture does not have an XML file describing its system calls,
5339 you will not be able to see the syscall names. It is important to
5340 notice that these two features are used for accessing the syscall
5341 name database. In either case, you will see a warning like this:
5344 (@value{GDBP}) catch syscall
5345 warning: Could not open "syscalls/i386-linux.xml"
5346 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
5347 GDB will not be able to display syscall names.
5348 Catchpoint 1 (syscall)
5352 Of course, the file name will change depending on your architecture and system.
5354 Still using the example above, you can also try to catch a syscall by its
5355 number. In this case, you would see something like:
5358 (@value{GDBP}) catch syscall 252
5359 Catchpoint 1 (syscall(s) 252)
5362 Again, in this case @value{GDBN} would not be able to display syscall's names.
5366 A call to @code{fork}.
5370 A call to @code{vfork}.
5372 @item load @r{[}@var{regexp}@r{]}
5373 @itemx unload @r{[}@var{regexp}@r{]}
5375 @kindex catch unload
5376 The loading or unloading of a shared library. If @var{regexp} is
5377 given, then the catchpoint will stop only if the regular expression
5378 matches one of the affected libraries.
5380 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5381 @kindex catch signal
5382 The delivery of a signal.
5384 With no arguments, this catchpoint will catch any signal that is not
5385 used internally by @value{GDBN}, specifically, all signals except
5386 @samp{SIGTRAP} and @samp{SIGINT}.
5388 With the argument @samp{all}, all signals, including those used by
5389 @value{GDBN}, will be caught. This argument cannot be used with other
5392 Otherwise, the arguments are a list of signal names as given to
5393 @code{handle} (@pxref{Signals}). Only signals specified in this list
5396 One reason that @code{catch signal} can be more useful than
5397 @code{handle} is that you can attach commands and conditions to the
5400 When a signal is caught by a catchpoint, the signal's @code{stop} and
5401 @code{print} settings, as specified by @code{handle}, are ignored.
5402 However, whether the signal is still delivered to the inferior depends
5403 on the @code{pass} setting; this can be changed in the catchpoint's
5408 @item tcatch @var{event}
5410 Set a catchpoint that is enabled only for one stop. The catchpoint is
5411 automatically deleted after the first time the event is caught.
5415 Use the @code{info break} command to list the current catchpoints.
5419 @subsection Deleting Breakpoints
5421 @cindex clearing breakpoints, watchpoints, catchpoints
5422 @cindex deleting breakpoints, watchpoints, catchpoints
5423 It is often necessary to eliminate a breakpoint, watchpoint, or
5424 catchpoint once it has done its job and you no longer want your program
5425 to stop there. This is called @dfn{deleting} the breakpoint. A
5426 breakpoint that has been deleted no longer exists; it is forgotten.
5428 With the @code{clear} command you can delete breakpoints according to
5429 where they are in your program. With the @code{delete} command you can
5430 delete individual breakpoints, watchpoints, or catchpoints by specifying
5431 their breakpoint numbers.
5433 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
5434 automatically ignores breakpoints on the first instruction to be executed
5435 when you continue execution without changing the execution address.
5440 Delete any breakpoints at the next instruction to be executed in the
5441 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
5442 the innermost frame is selected, this is a good way to delete a
5443 breakpoint where your program just stopped.
5445 @item clear @var{location}
5446 Delete any breakpoints set at the specified @var{location}.
5447 @xref{Specify Location}, for the various forms of @var{location}; the
5448 most useful ones are listed below:
5451 @item clear @var{function}
5452 @itemx clear @var{filename}:@var{function}
5453 Delete any breakpoints set at entry to the named @var{function}.
5455 @item clear @var{linenum}
5456 @itemx clear @var{filename}:@var{linenum}
5457 Delete any breakpoints set at or within the code of the specified
5458 @var{linenum} of the specified @var{filename}.
5461 @cindex delete breakpoints
5463 @kindex d @r{(@code{delete})}
5464 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5465 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
5466 list specified as argument. If no argument is specified, delete all
5467 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
5468 confirm off}). You can abbreviate this command as @code{d}.
5472 @subsection Disabling Breakpoints
5474 @cindex enable/disable a breakpoint
5475 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
5476 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
5477 it had been deleted, but remembers the information on the breakpoint so
5478 that you can @dfn{enable} it again later.
5480 You disable and enable breakpoints, watchpoints, and catchpoints with
5481 the @code{enable} and @code{disable} commands, optionally specifying
5482 one or more breakpoint numbers as arguments. Use @code{info break} to
5483 print a list of all breakpoints, watchpoints, and catchpoints if you
5484 do not know which numbers to use.
5486 Disabling and enabling a breakpoint that has multiple locations
5487 affects all of its locations.
5489 A breakpoint, watchpoint, or catchpoint can have any of several
5490 different states of enablement:
5494 Enabled. The breakpoint stops your program. A breakpoint set
5495 with the @code{break} command starts out in this state.
5497 Disabled. The breakpoint has no effect on your program.
5499 Enabled once. The breakpoint stops your program, but then becomes
5502 Enabled for a count. The breakpoint stops your program for the next
5503 N times, then becomes disabled.
5505 Enabled for deletion. The breakpoint stops your program, but
5506 immediately after it does so it is deleted permanently. A breakpoint
5507 set with the @code{tbreak} command starts out in this state.
5510 You can use the following commands to enable or disable breakpoints,
5511 watchpoints, and catchpoints:
5515 @kindex dis @r{(@code{disable})}
5516 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5517 Disable the specified breakpoints---or all breakpoints, if none are
5518 listed. A disabled breakpoint has no effect but is not forgotten. All
5519 options such as ignore-counts, conditions and commands are remembered in
5520 case the breakpoint is enabled again later. You may abbreviate
5521 @code{disable} as @code{dis}.
5524 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
5525 Enable the specified breakpoints (or all defined breakpoints). They
5526 become effective once again in stopping your program.
5528 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
5529 Enable the specified breakpoints temporarily. @value{GDBN} disables any
5530 of these breakpoints immediately after stopping your program.
5532 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
5533 Enable the specified breakpoints temporarily. @value{GDBN} records
5534 @var{count} with each of the specified breakpoints, and decrements a
5535 breakpoint's count when it is hit. When any count reaches 0,
5536 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
5537 count (@pxref{Conditions, ,Break Conditions}), that will be
5538 decremented to 0 before @var{count} is affected.
5540 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
5541 Enable the specified breakpoints to work once, then die. @value{GDBN}
5542 deletes any of these breakpoints as soon as your program stops there.
5543 Breakpoints set by the @code{tbreak} command start out in this state.
5546 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
5547 @c confusing: tbreak is also initially enabled.
5548 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
5549 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
5550 subsequently, they become disabled or enabled only when you use one of
5551 the commands above. (The command @code{until} can set and delete a
5552 breakpoint of its own, but it does not change the state of your other
5553 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
5557 @subsection Break Conditions
5558 @cindex conditional breakpoints
5559 @cindex breakpoint conditions
5561 @c FIXME what is scope of break condition expr? Context where wanted?
5562 @c in particular for a watchpoint?
5563 The simplest sort of breakpoint breaks every time your program reaches a
5564 specified place. You can also specify a @dfn{condition} for a
5565 breakpoint. A condition is just a Boolean expression in your
5566 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
5567 a condition evaluates the expression each time your program reaches it,
5568 and your program stops only if the condition is @emph{true}.
5570 This is the converse of using assertions for program validation; in that
5571 situation, you want to stop when the assertion is violated---that is,
5572 when the condition is false. In C, if you want to test an assertion expressed
5573 by the condition @var{assert}, you should set the condition
5574 @samp{! @var{assert}} on the appropriate breakpoint.
5576 Conditions are also accepted for watchpoints; you may not need them,
5577 since a watchpoint is inspecting the value of an expression anyhow---but
5578 it might be simpler, say, to just set a watchpoint on a variable name,
5579 and specify a condition that tests whether the new value is an interesting
5582 Break conditions can have side effects, and may even call functions in
5583 your program. This can be useful, for example, to activate functions
5584 that log program progress, or to use your own print functions to
5585 format special data structures. The effects are completely predictable
5586 unless there is another enabled breakpoint at the same address. (In
5587 that case, @value{GDBN} might see the other breakpoint first and stop your
5588 program without checking the condition of this one.) Note that
5589 breakpoint commands are usually more convenient and flexible than break
5591 purpose of performing side effects when a breakpoint is reached
5592 (@pxref{Break Commands, ,Breakpoint Command Lists}).
5594 Breakpoint conditions can also be evaluated on the target's side if
5595 the target supports it. Instead of evaluating the conditions locally,
5596 @value{GDBN} encodes the expression into an agent expression
5597 (@pxref{Agent Expressions}) suitable for execution on the target,
5598 independently of @value{GDBN}. Global variables become raw memory
5599 locations, locals become stack accesses, and so forth.
5601 In this case, @value{GDBN} will only be notified of a breakpoint trigger
5602 when its condition evaluates to true. This mechanism may provide faster
5603 response times depending on the performance characteristics of the target
5604 since it does not need to keep @value{GDBN} informed about
5605 every breakpoint trigger, even those with false conditions.
5607 Break conditions can be specified when a breakpoint is set, by using
5608 @samp{if} in the arguments to the @code{break} command. @xref{Set
5609 Breaks, ,Setting Breakpoints}. They can also be changed at any time
5610 with the @code{condition} command.
5612 You can also use the @code{if} keyword with the @code{watch} command.
5613 The @code{catch} command does not recognize the @code{if} keyword;
5614 @code{condition} is the only way to impose a further condition on a
5619 @item condition @var{bnum} @var{expression}
5620 Specify @var{expression} as the break condition for breakpoint,
5621 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
5622 breakpoint @var{bnum} stops your program only if the value of
5623 @var{expression} is true (nonzero, in C). When you use
5624 @code{condition}, @value{GDBN} checks @var{expression} immediately for
5625 syntactic correctness, and to determine whether symbols in it have
5626 referents in the context of your breakpoint. If @var{expression} uses
5627 symbols not referenced in the context of the breakpoint, @value{GDBN}
5628 prints an error message:
5631 No symbol "foo" in current context.
5636 not actually evaluate @var{expression} at the time the @code{condition}
5637 command (or a command that sets a breakpoint with a condition, like
5638 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
5640 @item condition -force @var{bnum} @var{expression}
5641 When the @code{-force} flag is used, define the condition even if
5642 @var{expression} is invalid at all the current locations of breakpoint
5643 @var{bnum}. This is similar to the @code{-force-condition} option
5644 of the @code{break} command.
5646 @item condition @var{bnum}
5647 Remove the condition from breakpoint number @var{bnum}. It becomes
5648 an ordinary unconditional breakpoint.
5651 @cindex ignore count (of breakpoint)
5652 A special case of a breakpoint condition is to stop only when the
5653 breakpoint has been reached a certain number of times. This is so
5654 useful that there is a special way to do it, using the @dfn{ignore
5655 count} of the breakpoint. Every breakpoint has an ignore count, which
5656 is an integer. Most of the time, the ignore count is zero, and
5657 therefore has no effect. But if your program reaches a breakpoint whose
5658 ignore count is positive, then instead of stopping, it just decrements
5659 the ignore count by one and continues. As a result, if the ignore count
5660 value is @var{n}, the breakpoint does not stop the next @var{n} times
5661 your program reaches it.
5665 @item ignore @var{bnum} @var{count}
5666 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5667 The next @var{count} times the breakpoint is reached, your program's
5668 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5671 To make the breakpoint stop the next time it is reached, specify
5674 When you use @code{continue} to resume execution of your program from a
5675 breakpoint, you can specify an ignore count directly as an argument to
5676 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5677 Stepping,,Continuing and Stepping}.
5679 If a breakpoint has a positive ignore count and a condition, the
5680 condition is not checked. Once the ignore count reaches zero,
5681 @value{GDBN} resumes checking the condition.
5683 You could achieve the effect of the ignore count with a condition such
5684 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5685 is decremented each time. @xref{Convenience Vars, ,Convenience
5689 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5692 @node Break Commands
5693 @subsection Breakpoint Command Lists
5695 @cindex breakpoint commands
5696 You can give any breakpoint (or watchpoint or catchpoint) a series of
5697 commands to execute when your program stops due to that breakpoint. For
5698 example, you might want to print the values of certain expressions, or
5699 enable other breakpoints.
5703 @kindex end@r{ (breakpoint commands)}
5704 @item commands @r{[}@var{list}@dots{}@r{]}
5705 @itemx @dots{} @var{command-list} @dots{}
5707 Specify a list of commands for the given breakpoints. The commands
5708 themselves appear on the following lines. Type a line containing just
5709 @code{end} to terminate the commands.
5711 To remove all commands from a breakpoint, type @code{commands} and
5712 follow it immediately with @code{end}; that is, give no commands.
5714 With no argument, @code{commands} refers to the last breakpoint,
5715 watchpoint, or catchpoint set (not to the breakpoint most recently
5716 encountered). If the most recent breakpoints were set with a single
5717 command, then the @code{commands} will apply to all the breakpoints
5718 set by that command. This applies to breakpoints set by
5719 @code{rbreak}, and also applies when a single @code{break} command
5720 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5724 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5725 disabled within a @var{command-list}.
5727 You can use breakpoint commands to start your program up again. Simply
5728 use the @code{continue} command, or @code{step}, or any other command
5729 that resumes execution.
5731 Any other commands in the command list, after a command that resumes
5732 execution, are ignored. This is because any time you resume execution
5733 (even with a simple @code{next} or @code{step}), you may encounter
5734 another breakpoint---which could have its own command list, leading to
5735 ambiguities about which list to execute.
5738 If the first command you specify in a command list is @code{silent}, the
5739 usual message about stopping at a breakpoint is not printed. This may
5740 be desirable for breakpoints that are to print a specific message and
5741 then continue. If none of the remaining commands print anything, you
5742 see no sign that the breakpoint was reached. @code{silent} is
5743 meaningful only at the beginning of a breakpoint command list.
5745 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5746 print precisely controlled output, and are often useful in silent
5747 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5749 For example, here is how you could use breakpoint commands to print the
5750 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5756 printf "x is %d\n",x
5761 One application for breakpoint commands is to compensate for one bug so
5762 you can test for another. Put a breakpoint just after the erroneous line
5763 of code, give it a condition to detect the case in which something
5764 erroneous has been done, and give it commands to assign correct values
5765 to any variables that need them. End with the @code{continue} command
5766 so that your program does not stop, and start with the @code{silent}
5767 command so that no output is produced. Here is an example:
5778 @node Dynamic Printf
5779 @subsection Dynamic Printf
5781 @cindex dynamic printf
5783 The dynamic printf command @code{dprintf} combines a breakpoint with
5784 formatted printing of your program's data to give you the effect of
5785 inserting @code{printf} calls into your program on-the-fly, without
5786 having to recompile it.
5788 In its most basic form, the output goes to the GDB console. However,
5789 you can set the variable @code{dprintf-style} for alternate handling.
5790 For instance, you can ask to format the output by calling your
5791 program's @code{printf} function. This has the advantage that the
5792 characters go to the program's output device, so they can recorded in
5793 redirects to files and so forth.
5795 If you are doing remote debugging with a stub or agent, you can also
5796 ask to have the printf handled by the remote agent. In addition to
5797 ensuring that the output goes to the remote program's device along
5798 with any other output the program might produce, you can also ask that
5799 the dprintf remain active even after disconnecting from the remote
5800 target. Using the stub/agent is also more efficient, as it can do
5801 everything without needing to communicate with @value{GDBN}.
5805 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5806 Whenever execution reaches @var{location}, print the values of one or
5807 more @var{expressions} under the control of the string @var{template}.
5808 To print several values, separate them with commas.
5810 @item set dprintf-style @var{style}
5811 Set the dprintf output to be handled in one of several different
5812 styles enumerated below. A change of style affects all existing
5813 dynamic printfs immediately. (If you need individual control over the
5814 print commands, simply define normal breakpoints with
5815 explicitly-supplied command lists.)
5819 @kindex dprintf-style gdb
5820 Handle the output using the @value{GDBN} @code{printf} command.
5823 @kindex dprintf-style call
5824 Handle the output by calling a function in your program (normally
5828 @kindex dprintf-style agent
5829 Have the remote debugging agent (such as @code{gdbserver}) handle
5830 the output itself. This style is only available for agents that
5831 support running commands on the target.
5834 @item set dprintf-function @var{function}
5835 Set the function to call if the dprintf style is @code{call}. By
5836 default its value is @code{printf}. You may set it to any expression.
5837 that @value{GDBN} can evaluate to a function, as per the @code{call}
5840 @item set dprintf-channel @var{channel}
5841 Set a ``channel'' for dprintf. If set to a non-empty value,
5842 @value{GDBN} will evaluate it as an expression and pass the result as
5843 a first argument to the @code{dprintf-function}, in the manner of
5844 @code{fprintf} and similar functions. Otherwise, the dprintf format
5845 string will be the first argument, in the manner of @code{printf}.
5847 As an example, if you wanted @code{dprintf} output to go to a logfile
5848 that is a standard I/O stream assigned to the variable @code{mylog},
5849 you could do the following:
5852 (gdb) set dprintf-style call
5853 (gdb) set dprintf-function fprintf
5854 (gdb) set dprintf-channel mylog
5855 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5856 Dprintf 1 at 0x123456: file main.c, line 25.
5858 1 dprintf keep y 0x00123456 in main at main.c:25
5859 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5864 Note that the @code{info break} displays the dynamic printf commands
5865 as normal breakpoint commands; you can thus easily see the effect of
5866 the variable settings.
5868 @item set disconnected-dprintf on
5869 @itemx set disconnected-dprintf off
5870 @kindex set disconnected-dprintf
5871 Choose whether @code{dprintf} commands should continue to run if
5872 @value{GDBN} has disconnected from the target. This only applies
5873 if the @code{dprintf-style} is @code{agent}.
5875 @item show disconnected-dprintf off
5876 @kindex show disconnected-dprintf
5877 Show the current choice for disconnected @code{dprintf}.
5881 @value{GDBN} does not check the validity of function and channel,
5882 relying on you to supply values that are meaningful for the contexts
5883 in which they are being used. For instance, the function and channel
5884 may be the values of local variables, but if that is the case, then
5885 all enabled dynamic prints must be at locations within the scope of
5886 those locals. If evaluation fails, @value{GDBN} will report an error.
5888 @node Save Breakpoints
5889 @subsection How to save breakpoints to a file
5891 To save breakpoint definitions to a file use the @w{@code{save
5892 breakpoints}} command.
5895 @kindex save breakpoints
5896 @cindex save breakpoints to a file for future sessions
5897 @item save breakpoints [@var{filename}]
5898 This command saves all current breakpoint definitions together with
5899 their commands and ignore counts, into a file @file{@var{filename}}
5900 suitable for use in a later debugging session. This includes all
5901 types of breakpoints (breakpoints, watchpoints, catchpoints,
5902 tracepoints). To read the saved breakpoint definitions, use the
5903 @code{source} command (@pxref{Command Files}). Note that watchpoints
5904 with expressions involving local variables may fail to be recreated
5905 because it may not be possible to access the context where the
5906 watchpoint is valid anymore. Because the saved breakpoint definitions
5907 are simply a sequence of @value{GDBN} commands that recreate the
5908 breakpoints, you can edit the file in your favorite editing program,
5909 and remove the breakpoint definitions you're not interested in, or
5910 that can no longer be recreated.
5913 @node Static Probe Points
5914 @subsection Static Probe Points
5916 @cindex static probe point, SystemTap
5917 @cindex static probe point, DTrace
5918 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5919 for Statically Defined Tracing, and the probes are designed to have a tiny
5920 runtime code and data footprint, and no dynamic relocations.
5922 Currently, the following types of probes are supported on
5923 ELF-compatible systems:
5927 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5928 @acronym{SDT} probes@footnote{See
5929 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5930 for more information on how to add @code{SystemTap} @acronym{SDT}
5931 probes in your applications.}. @code{SystemTap} probes are usable
5932 from assembly, C and C@t{++} languages@footnote{See
5933 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5934 for a good reference on how the @acronym{SDT} probes are implemented.}.
5936 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5937 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5941 @cindex semaphores on static probe points
5942 Some @code{SystemTap} probes have an associated semaphore variable;
5943 for instance, this happens automatically if you defined your probe
5944 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5945 @value{GDBN} will automatically enable it when you specify a
5946 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5947 breakpoint at a probe's location by some other method (e.g.,
5948 @code{break file:line}), then @value{GDBN} will not automatically set
5949 the semaphore. @code{DTrace} probes do not support semaphores.
5951 You can examine the available static static probes using @code{info
5952 probes}, with optional arguments:
5956 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5957 If given, @var{type} is either @code{stap} for listing
5958 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5959 probes. If omitted all probes are listed regardless of their types.
5961 If given, @var{provider} is a regular expression used to match against provider
5962 names when selecting which probes to list. If omitted, probes by all
5963 probes from all providers are listed.
5965 If given, @var{name} is a regular expression to match against probe names
5966 when selecting which probes to list. If omitted, probe names are not
5967 considered when deciding whether to display them.
5969 If given, @var{objfile} is a regular expression used to select which
5970 object files (executable or shared libraries) to examine. If not
5971 given, all object files are considered.
5973 @item info probes all
5974 List the available static probes, from all types.
5977 @cindex enabling and disabling probes
5978 Some probe points can be enabled and/or disabled. The effect of
5979 enabling or disabling a probe depends on the type of probe being
5980 handled. Some @code{DTrace} probes can be enabled or
5981 disabled, but @code{SystemTap} probes cannot be disabled.
5983 You can enable (or disable) one or more probes using the following
5984 commands, with optional arguments:
5987 @kindex enable probes
5988 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5989 If given, @var{provider} is a regular expression used to match against
5990 provider names when selecting which probes to enable. If omitted,
5991 all probes from all providers are enabled.
5993 If given, @var{name} is a regular expression to match against probe
5994 names when selecting which probes to enable. If omitted, probe names
5995 are not considered when deciding whether to enable them.
5997 If given, @var{objfile} is a regular expression used to select which
5998 object files (executable or shared libraries) to examine. If not
5999 given, all object files are considered.
6001 @kindex disable probes
6002 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
6003 See the @code{enable probes} command above for a description of the
6004 optional arguments accepted by this command.
6007 @vindex $_probe_arg@r{, convenience variable}
6008 A probe may specify up to twelve arguments. These are available at the
6009 point at which the probe is defined---that is, when the current PC is
6010 at the probe's location. The arguments are available using the
6011 convenience variables (@pxref{Convenience Vars})
6012 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
6013 probes each probe argument is an integer of the appropriate size;
6014 types are not preserved. In @code{DTrace} probes types are preserved
6015 provided that they are recognized as such by @value{GDBN}; otherwise
6016 the value of the probe argument will be a long integer. The
6017 convenience variable @code{$_probe_argc} holds the number of arguments
6018 at the current probe point.
6020 These variables are always available, but attempts to access them at
6021 any location other than a probe point will cause @value{GDBN} to give
6025 @c @ifclear BARETARGET
6026 @node Error in Breakpoints
6027 @subsection ``Cannot insert breakpoints''
6029 If you request too many active hardware-assisted breakpoints and
6030 watchpoints, you will see this error message:
6032 @c FIXME: the precise wording of this message may change; the relevant
6033 @c source change is not committed yet (Sep 3, 1999).
6035 Stopped; cannot insert breakpoints.
6036 You may have requested too many hardware breakpoints and watchpoints.
6040 This message is printed when you attempt to resume the program, since
6041 only then @value{GDBN} knows exactly how many hardware breakpoints and
6042 watchpoints it needs to insert.
6044 When this message is printed, you need to disable or remove some of the
6045 hardware-assisted breakpoints and watchpoints, and then continue.
6047 @node Breakpoint-related Warnings
6048 @subsection ``Breakpoint address adjusted...''
6049 @cindex breakpoint address adjusted
6051 Some processor architectures place constraints on the addresses at
6052 which breakpoints may be placed. For architectures thus constrained,
6053 @value{GDBN} will attempt to adjust the breakpoint's address to comply
6054 with the constraints dictated by the architecture.
6056 One example of such an architecture is the Fujitsu FR-V. The FR-V is
6057 a VLIW architecture in which a number of RISC-like instructions may be
6058 bundled together for parallel execution. The FR-V architecture
6059 constrains the location of a breakpoint instruction within such a
6060 bundle to the instruction with the lowest address. @value{GDBN}
6061 honors this constraint by adjusting a breakpoint's address to the
6062 first in the bundle.
6064 It is not uncommon for optimized code to have bundles which contain
6065 instructions from different source statements, thus it may happen that
6066 a breakpoint's address will be adjusted from one source statement to
6067 another. Since this adjustment may significantly alter @value{GDBN}'s
6068 breakpoint related behavior from what the user expects, a warning is
6069 printed when the breakpoint is first set and also when the breakpoint
6072 A warning like the one below is printed when setting a breakpoint
6073 that's been subject to address adjustment:
6076 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
6079 Such warnings are printed both for user settable and @value{GDBN}'s
6080 internal breakpoints. If you see one of these warnings, you should
6081 verify that a breakpoint set at the adjusted address will have the
6082 desired affect. If not, the breakpoint in question may be removed and
6083 other breakpoints may be set which will have the desired behavior.
6084 E.g., it may be sufficient to place the breakpoint at a later
6085 instruction. A conditional breakpoint may also be useful in some
6086 cases to prevent the breakpoint from triggering too often.
6088 @value{GDBN} will also issue a warning when stopping at one of these
6089 adjusted breakpoints:
6092 warning: Breakpoint 1 address previously adjusted from 0x00010414
6096 When this warning is encountered, it may be too late to take remedial
6097 action except in cases where the breakpoint is hit earlier or more
6098 frequently than expected.
6100 @node Continuing and Stepping
6101 @section Continuing and Stepping
6105 @cindex resuming execution
6106 @dfn{Continuing} means resuming program execution until your program
6107 completes normally. In contrast, @dfn{stepping} means executing just
6108 one more ``step'' of your program, where ``step'' may mean either one
6109 line of source code, or one machine instruction (depending on what
6110 particular command you use). Either when continuing or when stepping,
6111 your program may stop even sooner, due to a breakpoint or a signal. (If
6112 it stops due to a signal, you may want to use @code{handle}, or use
6113 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
6114 or you may step into the signal's handler (@pxref{stepping and signal
6119 @kindex c @r{(@code{continue})}
6120 @kindex fg @r{(resume foreground execution)}
6121 @item continue @r{[}@var{ignore-count}@r{]}
6122 @itemx c @r{[}@var{ignore-count}@r{]}
6123 @itemx fg @r{[}@var{ignore-count}@r{]}
6124 Resume program execution, at the address where your program last stopped;
6125 any breakpoints set at that address are bypassed. The optional argument
6126 @var{ignore-count} allows you to specify a further number of times to
6127 ignore a breakpoint at this location; its effect is like that of
6128 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
6130 The argument @var{ignore-count} is meaningful only when your program
6131 stopped due to a breakpoint. At other times, the argument to
6132 @code{continue} is ignored.
6134 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
6135 debugged program is deemed to be the foreground program) are provided
6136 purely for convenience, and have exactly the same behavior as
6140 To resume execution at a different place, you can use @code{return}
6141 (@pxref{Returning, ,Returning from a Function}) to go back to the
6142 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
6143 Different Address}) to go to an arbitrary location in your program.
6145 A typical technique for using stepping is to set a breakpoint
6146 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
6147 beginning of the function or the section of your program where a problem
6148 is believed to lie, run your program until it stops at that breakpoint,
6149 and then step through the suspect area, examining the variables that are
6150 interesting, until you see the problem happen.
6154 @kindex s @r{(@code{step})}
6156 Continue running your program until control reaches a different source
6157 line, then stop it and return control to @value{GDBN}. This command is
6158 abbreviated @code{s}.
6161 @c "without debugging information" is imprecise; actually "without line
6162 @c numbers in the debugging information". (gcc -g1 has debugging info but
6163 @c not line numbers). But it seems complex to try to make that
6164 @c distinction here.
6165 @emph{Warning:} If you use the @code{step} command while control is
6166 within a function that was compiled without debugging information,
6167 execution proceeds until control reaches a function that does have
6168 debugging information. Likewise, it will not step into a function which
6169 is compiled without debugging information. To step through functions
6170 without debugging information, use the @code{stepi} command, described
6174 The @code{step} command only stops at the first instruction of a source
6175 line. This prevents the multiple stops that could otherwise occur in
6176 @code{switch} statements, @code{for} loops, etc. @code{step} continues
6177 to stop if a function that has debugging information is called within
6178 the line. In other words, @code{step} @emph{steps inside} any functions
6179 called within the line.
6181 Also, the @code{step} command only enters a function if there is line
6182 number information for the function. Otherwise it acts like the
6183 @code{next} command. This avoids problems when using @code{cc -gl}
6184 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
6185 was any debugging information about the routine.
6187 @item step @var{count}
6188 Continue running as in @code{step}, but do so @var{count} times. If a
6189 breakpoint is reached, or a signal not related to stepping occurs before
6190 @var{count} steps, stepping stops right away.
6193 @kindex n @r{(@code{next})}
6194 @item next @r{[}@var{count}@r{]}
6195 Continue to the next source line in the current (innermost) stack frame.
6196 This is similar to @code{step}, but function calls that appear within
6197 the line of code are executed without stopping. Execution stops when
6198 control reaches a different line of code at the original stack level
6199 that was executing when you gave the @code{next} command. This command
6200 is abbreviated @code{n}.
6202 An argument @var{count} is a repeat count, as for @code{step}.
6205 @c FIX ME!! Do we delete this, or is there a way it fits in with
6206 @c the following paragraph? --- Vctoria
6208 @c @code{next} within a function that lacks debugging information acts like
6209 @c @code{step}, but any function calls appearing within the code of the
6210 @c function are executed without stopping.
6212 The @code{next} command only stops at the first instruction of a
6213 source line. This prevents multiple stops that could otherwise occur in
6214 @code{switch} statements, @code{for} loops, etc.
6216 @kindex set step-mode
6218 @cindex functions without line info, and stepping
6219 @cindex stepping into functions with no line info
6220 @itemx set step-mode on
6221 The @code{set step-mode on} command causes the @code{step} command to
6222 stop at the first instruction of a function which contains no debug line
6223 information rather than stepping over it.
6225 This is useful in cases where you may be interested in inspecting the
6226 machine instructions of a function which has no symbolic info and do not
6227 want @value{GDBN} to automatically skip over this function.
6229 @item set step-mode off
6230 Causes the @code{step} command to step over any functions which contains no
6231 debug information. This is the default.
6233 @item show step-mode
6234 Show whether @value{GDBN} will stop in or step over functions without
6235 source line debug information.
6238 @kindex fin @r{(@code{finish})}
6240 Continue running until just after function in the selected stack frame
6241 returns. Print the returned value (if any). This command can be
6242 abbreviated as @code{fin}.
6244 Contrast this with the @code{return} command (@pxref{Returning,
6245 ,Returning from a Function}).
6247 @kindex set print finish
6248 @kindex show print finish
6249 @item set print finish @r{[}on|off@r{]}
6250 @itemx show print finish
6251 By default the @code{finish} command will show the value that is
6252 returned by the function. This can be disabled using @code{set print
6253 finish off}. When disabled, the value is still entered into the value
6254 history (@pxref{Value History}), but not displayed.
6257 @kindex u @r{(@code{until})}
6258 @cindex run until specified location
6261 Continue running until a source line past the current line, in the
6262 current stack frame, is reached. This command is used to avoid single
6263 stepping through a loop more than once. It is like the @code{next}
6264 command, except that when @code{until} encounters a jump, it
6265 automatically continues execution until the program counter is greater
6266 than the address of the jump.
6268 This means that when you reach the end of a loop after single stepping
6269 though it, @code{until} makes your program continue execution until it
6270 exits the loop. In contrast, a @code{next} command at the end of a loop
6271 simply steps back to the beginning of the loop, which forces you to step
6272 through the next iteration.
6274 @code{until} always stops your program if it attempts to exit the current
6277 @code{until} may produce somewhat counterintuitive results if the order
6278 of machine code does not match the order of the source lines. For
6279 example, in the following excerpt from a debugging session, the @code{f}
6280 (@code{frame}) command shows that execution is stopped at line
6281 @code{206}; yet when we use @code{until}, we get to line @code{195}:
6285 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
6287 (@value{GDBP}) until
6288 195 for ( ; argc > 0; NEXTARG) @{
6291 This happened because, for execution efficiency, the compiler had
6292 generated code for the loop closure test at the end, rather than the
6293 start, of the loop---even though the test in a C @code{for}-loop is
6294 written before the body of the loop. The @code{until} command appeared
6295 to step back to the beginning of the loop when it advanced to this
6296 expression; however, it has not really gone to an earlier
6297 statement---not in terms of the actual machine code.
6299 @code{until} with no argument works by means of single
6300 instruction stepping, and hence is slower than @code{until} with an
6303 @item until @var{location}
6304 @itemx u @var{location}
6305 Continue running your program until either the specified @var{location} is
6306 reached, or the current stack frame returns. The location is any of
6307 the forms described in @ref{Specify Location}.
6308 This form of the command uses temporary breakpoints, and
6309 hence is quicker than @code{until} without an argument. The specified
6310 location is actually reached only if it is in the current frame. This
6311 implies that @code{until} can be used to skip over recursive function
6312 invocations. For instance in the code below, if the current location is
6313 line @code{96}, issuing @code{until 99} will execute the program up to
6314 line @code{99} in the same invocation of factorial, i.e., after the inner
6315 invocations have returned.
6318 94 int factorial (int value)
6320 96 if (value > 1) @{
6321 97 value *= factorial (value - 1);
6328 @kindex advance @var{location}
6329 @item advance @var{location}
6330 Continue running the program up to the given @var{location}. An argument is
6331 required, which should be of one of the forms described in
6332 @ref{Specify Location}.
6333 Execution will also stop upon exit from the current stack
6334 frame. This command is similar to @code{until}, but @code{advance} will
6335 not skip over recursive function calls, and the target location doesn't
6336 have to be in the same frame as the current one.
6340 @kindex si @r{(@code{stepi})}
6342 @itemx stepi @var{arg}
6344 Execute one machine instruction, then stop and return to the debugger.
6346 It is often useful to do @samp{display/i $pc} when stepping by machine
6347 instructions. This makes @value{GDBN} automatically display the next
6348 instruction to be executed, each time your program stops. @xref{Auto
6349 Display,, Automatic Display}.
6351 An argument is a repeat count, as in @code{step}.
6355 @kindex ni @r{(@code{nexti})}
6357 @itemx nexti @var{arg}
6359 Execute one machine instruction, but if it is a function call,
6360 proceed until the function returns.
6362 An argument is a repeat count, as in @code{next}.
6366 @anchor{range stepping}
6367 @cindex range stepping
6368 @cindex target-assisted range stepping
6369 By default, and if available, @value{GDBN} makes use of
6370 target-assisted @dfn{range stepping}. In other words, whenever you
6371 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
6372 tells the target to step the corresponding range of instruction
6373 addresses instead of issuing multiple single-steps. This speeds up
6374 line stepping, particularly for remote targets. Ideally, there should
6375 be no reason you would want to turn range stepping off. However, it's
6376 possible that a bug in the debug info, a bug in the remote stub (for
6377 remote targets), or even a bug in @value{GDBN} could make line
6378 stepping behave incorrectly when target-assisted range stepping is
6379 enabled. You can use the following command to turn off range stepping
6383 @kindex set range-stepping
6384 @kindex show range-stepping
6385 @item set range-stepping
6386 @itemx show range-stepping
6387 Control whether range stepping is enabled.
6389 If @code{on}, and the target supports it, @value{GDBN} tells the
6390 target to step a range of addresses itself, instead of issuing
6391 multiple single-steps. If @code{off}, @value{GDBN} always issues
6392 single-steps, even if range stepping is supported by the target. The
6393 default is @code{on}.
6397 @node Skipping Over Functions and Files
6398 @section Skipping Over Functions and Files
6399 @cindex skipping over functions and files
6401 The program you are debugging may contain some functions which are
6402 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
6403 skip a function, all functions in a file or a particular function in
6404 a particular file when stepping.
6406 For example, consider the following C function:
6417 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
6418 are not interested in stepping through @code{boring}. If you run @code{step}
6419 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
6420 step over both @code{foo} and @code{boring}!
6422 One solution is to @code{step} into @code{boring} and use the @code{finish}
6423 command to immediately exit it. But this can become tedious if @code{boring}
6424 is called from many places.
6426 A more flexible solution is to execute @kbd{skip boring}. This instructs
6427 @value{GDBN} never to step into @code{boring}. Now when you execute
6428 @code{step} at line 103, you'll step over @code{boring} and directly into
6431 Functions may be skipped by providing either a function name, linespec
6432 (@pxref{Specify Location}), regular expression that matches the function's
6433 name, file name or a @code{glob}-style pattern that matches the file name.
6435 On Posix systems the form of the regular expression is
6436 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
6437 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
6438 expression is whatever is provided by the @code{regcomp} function of
6439 the underlying system.
6440 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
6441 description of @code{glob}-style patterns.
6445 @item skip @r{[}@var{options}@r{]}
6446 The basic form of the @code{skip} command takes zero or more options
6447 that specify what to skip.
6448 The @var{options} argument is any useful combination of the following:
6451 @item -file @var{file}
6452 @itemx -fi @var{file}
6453 Functions in @var{file} will be skipped over when stepping.
6455 @item -gfile @var{file-glob-pattern}
6456 @itemx -gfi @var{file-glob-pattern}
6457 @cindex skipping over files via glob-style patterns
6458 Functions in files matching @var{file-glob-pattern} will be skipped
6462 (gdb) skip -gfi utils/*.c
6465 @item -function @var{linespec}
6466 @itemx -fu @var{linespec}
6467 Functions named by @var{linespec} or the function containing the line
6468 named by @var{linespec} will be skipped over when stepping.
6469 @xref{Specify Location}.
6471 @item -rfunction @var{regexp}
6472 @itemx -rfu @var{regexp}
6473 @cindex skipping over functions via regular expressions
6474 Functions whose name matches @var{regexp} will be skipped over when stepping.
6476 This form is useful for complex function names.
6477 For example, there is generally no need to step into C@t{++} @code{std::string}
6478 constructors or destructors. Plus with C@t{++} templates it can be hard to
6479 write out the full name of the function, and often it doesn't matter what
6480 the template arguments are. Specifying the function to be skipped as a
6481 regular expression makes this easier.
6484 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
6487 If you want to skip every templated C@t{++} constructor and destructor
6488 in the @code{std} namespace you can do:
6491 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
6495 If no options are specified, the function you're currently debugging
6498 @kindex skip function
6499 @item skip function @r{[}@var{linespec}@r{]}
6500 After running this command, the function named by @var{linespec} or the
6501 function containing the line named by @var{linespec} will be skipped over when
6502 stepping. @xref{Specify Location}.
6504 If you do not specify @var{linespec}, the function you're currently debugging
6507 (If you have a function called @code{file} that you want to skip, use
6508 @kbd{skip function file}.)
6511 @item skip file @r{[}@var{filename}@r{]}
6512 After running this command, any function whose source lives in @var{filename}
6513 will be skipped over when stepping.
6516 (gdb) skip file boring.c
6517 File boring.c will be skipped when stepping.
6520 If you do not specify @var{filename}, functions whose source lives in the file
6521 you're currently debugging will be skipped.
6524 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
6525 These are the commands for managing your list of skips:
6529 @item info skip @r{[}@var{range}@r{]}
6530 Print details about the specified skip(s). If @var{range} is not specified,
6531 print a table with details about all functions and files marked for skipping.
6532 @code{info skip} prints the following information about each skip:
6536 A number identifying this skip.
6537 @item Enabled or Disabled
6538 Enabled skips are marked with @samp{y}.
6539 Disabled skips are marked with @samp{n}.
6541 If the file name is a @samp{glob} pattern this is @samp{y}.
6542 Otherwise it is @samp{n}.
6544 The name or @samp{glob} pattern of the file to be skipped.
6545 If no file is specified this is @samp{<none>}.
6547 If the function name is a @samp{regular expression} this is @samp{y}.
6548 Otherwise it is @samp{n}.
6550 The name or regular expression of the function to skip.
6551 If no function is specified this is @samp{<none>}.
6555 @item skip delete @r{[}@var{range}@r{]}
6556 Delete the specified skip(s). If @var{range} is not specified, delete all
6560 @item skip enable @r{[}@var{range}@r{]}
6561 Enable the specified skip(s). If @var{range} is not specified, enable all
6564 @kindex skip disable
6565 @item skip disable @r{[}@var{range}@r{]}
6566 Disable the specified skip(s). If @var{range} is not specified, disable all
6569 @kindex set debug skip
6570 @item set debug skip @r{[}on|off@r{]}
6571 Set whether to print the debug output about skipping files and functions.
6573 @kindex show debug skip
6574 @item show debug skip
6575 Show whether the debug output about skipping files and functions is printed.
6583 A signal is an asynchronous event that can happen in a program. The
6584 operating system defines the possible kinds of signals, and gives each
6585 kind a name and a number. For example, in Unix @code{SIGINT} is the
6586 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
6587 @code{SIGSEGV} is the signal a program gets from referencing a place in
6588 memory far away from all the areas in use; @code{SIGALRM} occurs when
6589 the alarm clock timer goes off (which happens only if your program has
6590 requested an alarm).
6592 @cindex fatal signals
6593 Some signals, including @code{SIGALRM}, are a normal part of the
6594 functioning of your program. Others, such as @code{SIGSEGV}, indicate
6595 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
6596 program has not specified in advance some other way to handle the signal.
6597 @code{SIGINT} does not indicate an error in your program, but it is normally
6598 fatal so it can carry out the purpose of the interrupt: to kill the program.
6600 @value{GDBN} has the ability to detect any occurrence of a signal in your
6601 program. You can tell @value{GDBN} in advance what to do for each kind of
6604 @cindex handling signals
6605 Normally, @value{GDBN} is set up to let the non-erroneous signals like
6606 @code{SIGALRM} be silently passed to your program
6607 (so as not to interfere with their role in the program's functioning)
6608 but to stop your program immediately whenever an error signal happens.
6609 You can change these settings with the @code{handle} command.
6612 @kindex info signals
6616 Print a table of all the kinds of signals and how @value{GDBN} has been told to
6617 handle each one. You can use this to see the signal numbers of all
6618 the defined types of signals.
6620 @item info signals @var{sig}
6621 Similar, but print information only about the specified signal number.
6623 @code{info handle} is an alias for @code{info signals}.
6625 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
6626 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
6627 for details about this command.
6630 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
6631 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
6632 can be the number of a signal or its name (with or without the
6633 @samp{SIG} at the beginning); a list of signal numbers of the form
6634 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
6635 known signals. Optional arguments @var{keywords}, described below,
6636 say what change to make.
6640 The keywords allowed by the @code{handle} command can be abbreviated.
6641 Their full names are:
6645 @value{GDBN} should not stop your program when this signal happens. It may
6646 still print a message telling you that the signal has come in.
6649 @value{GDBN} should stop your program when this signal happens. This implies
6650 the @code{print} keyword as well.
6653 @value{GDBN} should print a message when this signal happens.
6656 @value{GDBN} should not mention the occurrence of the signal at all. This
6657 implies the @code{nostop} keyword as well.
6661 @value{GDBN} should allow your program to see this signal; your program
6662 can handle the signal, or else it may terminate if the signal is fatal
6663 and not handled. @code{pass} and @code{noignore} are synonyms.
6667 @value{GDBN} should not allow your program to see this signal.
6668 @code{nopass} and @code{ignore} are synonyms.
6672 When a signal stops your program, the signal is not visible to the
6674 continue. Your program sees the signal then, if @code{pass} is in
6675 effect for the signal in question @emph{at that time}. In other words,
6676 after @value{GDBN} reports a signal, you can use the @code{handle}
6677 command with @code{pass} or @code{nopass} to control whether your
6678 program sees that signal when you continue.
6680 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6681 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6682 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6685 You can also use the @code{signal} command to prevent your program from
6686 seeing a signal, or cause it to see a signal it normally would not see,
6687 or to give it any signal at any time. For example, if your program stopped
6688 due to some sort of memory reference error, you might store correct
6689 values into the erroneous variables and continue, hoping to see more
6690 execution; but your program would probably terminate immediately as
6691 a result of the fatal signal once it saw the signal. To prevent this,
6692 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6695 @cindex stepping and signal handlers
6696 @anchor{stepping and signal handlers}
6698 @value{GDBN} optimizes for stepping the mainline code. If a signal
6699 that has @code{handle nostop} and @code{handle pass} set arrives while
6700 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6701 in progress, @value{GDBN} lets the signal handler run and then resumes
6702 stepping the mainline code once the signal handler returns. In other
6703 words, @value{GDBN} steps over the signal handler. This prevents
6704 signals that you've specified as not interesting (with @code{handle
6705 nostop}) from changing the focus of debugging unexpectedly. Note that
6706 the signal handler itself may still hit a breakpoint, stop for another
6707 signal that has @code{handle stop} in effect, or for any other event
6708 that normally results in stopping the stepping command sooner. Also
6709 note that @value{GDBN} still informs you that the program received a
6710 signal if @code{handle print} is set.
6712 @anchor{stepping into signal handlers}
6714 If you set @code{handle pass} for a signal, and your program sets up a
6715 handler for it, then issuing a stepping command, such as @code{step}
6716 or @code{stepi}, when your program is stopped due to the signal will
6717 step @emph{into} the signal handler (if the target supports that).
6719 Likewise, if you use the @code{queue-signal} command to queue a signal
6720 to be delivered to the current thread when execution of the thread
6721 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6722 stepping command will step into the signal handler.
6724 Here's an example, using @code{stepi} to step to the first instruction
6725 of @code{SIGUSR1}'s handler:
6728 (@value{GDBP}) handle SIGUSR1
6729 Signal Stop Print Pass to program Description
6730 SIGUSR1 Yes Yes Yes User defined signal 1
6734 Program received signal SIGUSR1, User defined signal 1.
6735 main () sigusr1.c:28
6738 sigusr1_handler () at sigusr1.c:9
6742 The same, but using @code{queue-signal} instead of waiting for the
6743 program to receive the signal first:
6748 (@value{GDBP}) queue-signal SIGUSR1
6750 sigusr1_handler () at sigusr1.c:9
6755 @cindex extra signal information
6756 @anchor{extra signal information}
6758 On some targets, @value{GDBN} can inspect extra signal information
6759 associated with the intercepted signal, before it is actually
6760 delivered to the program being debugged. This information is exported
6761 by the convenience variable @code{$_siginfo}, and consists of data
6762 that is passed by the kernel to the signal handler at the time of the
6763 receipt of a signal. The data type of the information itself is
6764 target dependent. You can see the data type using the @code{ptype
6765 $_siginfo} command. On Unix systems, it typically corresponds to the
6766 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6769 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6770 referenced address that raised a segmentation fault.
6774 (@value{GDBP}) continue
6775 Program received signal SIGSEGV, Segmentation fault.
6776 0x0000000000400766 in main ()
6778 (@value{GDBP}) ptype $_siginfo
6785 struct @{...@} _kill;
6786 struct @{...@} _timer;
6788 struct @{...@} _sigchld;
6789 struct @{...@} _sigfault;
6790 struct @{...@} _sigpoll;
6793 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6797 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6798 $1 = (void *) 0x7ffff7ff7000
6802 Depending on target support, @code{$_siginfo} may also be writable.
6804 @cindex Intel MPX boundary violations
6805 @cindex boundary violations, Intel MPX
6806 On some targets, a @code{SIGSEGV} can be caused by a boundary
6807 violation, i.e., accessing an address outside of the allowed range.
6808 In those cases @value{GDBN} may displays additional information,
6809 depending on how @value{GDBN} has been told to handle the signal.
6810 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6811 kind: "Upper" or "Lower", the memory address accessed and the
6812 bounds, while with @code{handle nostop SIGSEGV} no additional
6813 information is displayed.
6815 The usual output of a segfault is:
6817 Program received signal SIGSEGV, Segmentation fault
6818 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6819 68 value = *(p + len);
6822 While a bound violation is presented as:
6824 Program received signal SIGSEGV, Segmentation fault
6825 Upper bound violation while accessing address 0x7fffffffc3b3
6826 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6827 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6828 68 value = *(p + len);
6832 @section Stopping and Starting Multi-thread Programs
6834 @cindex stopped threads
6835 @cindex threads, stopped
6837 @cindex continuing threads
6838 @cindex threads, continuing
6840 @value{GDBN} supports debugging programs with multiple threads
6841 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6842 are two modes of controlling execution of your program within the
6843 debugger. In the default mode, referred to as @dfn{all-stop mode},
6844 when any thread in your program stops (for example, at a breakpoint
6845 or while being stepped), all other threads in the program are also stopped by
6846 @value{GDBN}. On some targets, @value{GDBN} also supports
6847 @dfn{non-stop mode}, in which other threads can continue to run freely while
6848 you examine the stopped thread in the debugger.
6851 * All-Stop Mode:: All threads stop when GDB takes control
6852 * Non-Stop Mode:: Other threads continue to execute
6853 * Background Execution:: Running your program asynchronously
6854 * Thread-Specific Breakpoints:: Controlling breakpoints
6855 * Interrupted System Calls:: GDB may interfere with system calls
6856 * Observer Mode:: GDB does not alter program behavior
6860 @subsection All-Stop Mode
6862 @cindex all-stop mode
6864 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6865 @emph{all} threads of execution stop, not just the current thread. This
6866 allows you to examine the overall state of the program, including
6867 switching between threads, without worrying that things may change
6870 Conversely, whenever you restart the program, @emph{all} threads start
6871 executing. @emph{This is true even when single-stepping} with commands
6872 like @code{step} or @code{next}.
6874 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6875 Since thread scheduling is up to your debugging target's operating
6876 system (not controlled by @value{GDBN}), other threads may
6877 execute more than one statement while the current thread completes a
6878 single step. Moreover, in general other threads stop in the middle of a
6879 statement, rather than at a clean statement boundary, when the program
6882 You might even find your program stopped in another thread after
6883 continuing or even single-stepping. This happens whenever some other
6884 thread runs into a breakpoint, a signal, or an exception before the
6885 first thread completes whatever you requested.
6887 @cindex automatic thread selection
6888 @cindex switching threads automatically
6889 @cindex threads, automatic switching
6890 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6891 signal, it automatically selects the thread where that breakpoint or
6892 signal happened. @value{GDBN} alerts you to the context switch with a
6893 message such as @samp{[Switching to Thread @var{n}]} to identify the
6896 On some OSes, you can modify @value{GDBN}'s default behavior by
6897 locking the OS scheduler to allow only a single thread to run.
6900 @item set scheduler-locking @var{mode}
6901 @cindex scheduler locking mode
6902 @cindex lock scheduler
6903 Set the scheduler locking mode. It applies to normal execution,
6904 record mode, and replay mode. If it is @code{off}, then there is no
6905 locking and any thread may run at any time. If @code{on}, then only
6906 the current thread may run when the inferior is resumed. The
6907 @code{step} mode optimizes for single-stepping; it prevents other
6908 threads from preempting the current thread while you are stepping, so
6909 that the focus of debugging does not change unexpectedly. Other
6910 threads never get a chance to run when you step, and they are
6911 completely free to run when you use commands like @samp{continue},
6912 @samp{until}, or @samp{finish}. However, unless another thread hits a
6913 breakpoint during its timeslice, @value{GDBN} does not change the
6914 current thread away from the thread that you are debugging. The
6915 @code{replay} mode behaves like @code{off} in record mode and like
6916 @code{on} in replay mode.
6918 @item show scheduler-locking
6919 Display the current scheduler locking mode.
6922 @cindex resume threads of multiple processes simultaneously
6923 By default, when you issue one of the execution commands such as
6924 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6925 threads of the current inferior to run. For example, if @value{GDBN}
6926 is attached to two inferiors, each with two threads, the
6927 @code{continue} command resumes only the two threads of the current
6928 inferior. This is useful, for example, when you debug a program that
6929 forks and you want to hold the parent stopped (so that, for instance,
6930 it doesn't run to exit), while you debug the child. In other
6931 situations, you may not be interested in inspecting the current state
6932 of any of the processes @value{GDBN} is attached to, and you may want
6933 to resume them all until some breakpoint is hit. In the latter case,
6934 you can instruct @value{GDBN} to allow all threads of all the
6935 inferiors to run with the @w{@code{set schedule-multiple}} command.
6938 @kindex set schedule-multiple
6939 @item set schedule-multiple
6940 Set the mode for allowing threads of multiple processes to be resumed
6941 when an execution command is issued. When @code{on}, all threads of
6942 all processes are allowed to run. When @code{off}, only the threads
6943 of the current process are resumed. The default is @code{off}. The
6944 @code{scheduler-locking} mode takes precedence when set to @code{on},
6945 or while you are stepping and set to @code{step}.
6947 @item show schedule-multiple
6948 Display the current mode for resuming the execution of threads of
6953 @subsection Non-Stop Mode
6955 @cindex non-stop mode
6957 @c This section is really only a place-holder, and needs to be expanded
6958 @c with more details.
6960 For some multi-threaded targets, @value{GDBN} supports an optional
6961 mode of operation in which you can examine stopped program threads in
6962 the debugger while other threads continue to execute freely. This
6963 minimizes intrusion when debugging live systems, such as programs
6964 where some threads have real-time constraints or must continue to
6965 respond to external events. This is referred to as @dfn{non-stop} mode.
6967 In non-stop mode, when a thread stops to report a debugging event,
6968 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6969 threads as well, in contrast to the all-stop mode behavior. Additionally,
6970 execution commands such as @code{continue} and @code{step} apply by default
6971 only to the current thread in non-stop mode, rather than all threads as
6972 in all-stop mode. This allows you to control threads explicitly in
6973 ways that are not possible in all-stop mode --- for example, stepping
6974 one thread while allowing others to run freely, stepping
6975 one thread while holding all others stopped, or stepping several threads
6976 independently and simultaneously.
6978 To enter non-stop mode, use this sequence of commands before you run
6979 or attach to your program:
6982 # If using the CLI, pagination breaks non-stop.
6985 # Finally, turn it on!
6989 You can use these commands to manipulate the non-stop mode setting:
6992 @kindex set non-stop
6993 @item set non-stop on
6994 Enable selection of non-stop mode.
6995 @item set non-stop off
6996 Disable selection of non-stop mode.
6997 @kindex show non-stop
6999 Show the current non-stop enablement setting.
7002 Note these commands only reflect whether non-stop mode is enabled,
7003 not whether the currently-executing program is being run in non-stop mode.
7004 In particular, the @code{set non-stop} preference is only consulted when
7005 @value{GDBN} starts or connects to the target program, and it is generally
7006 not possible to switch modes once debugging has started. Furthermore,
7007 since not all targets support non-stop mode, even when you have enabled
7008 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
7011 In non-stop mode, all execution commands apply only to the current thread
7012 by default. That is, @code{continue} only continues one thread.
7013 To continue all threads, issue @code{continue -a} or @code{c -a}.
7015 You can use @value{GDBN}'s background execution commands
7016 (@pxref{Background Execution}) to run some threads in the background
7017 while you continue to examine or step others from @value{GDBN}.
7018 The MI execution commands (@pxref{GDB/MI Program Execution}) are
7019 always executed asynchronously in non-stop mode.
7021 Suspending execution is done with the @code{interrupt} command when
7022 running in the background, or @kbd{Ctrl-c} during foreground execution.
7023 In all-stop mode, this stops the whole process;
7024 but in non-stop mode the interrupt applies only to the current thread.
7025 To stop the whole program, use @code{interrupt -a}.
7027 Other execution commands do not currently support the @code{-a} option.
7029 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
7030 that thread current, as it does in all-stop mode. This is because the
7031 thread stop notifications are asynchronous with respect to @value{GDBN}'s
7032 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
7033 changed to a different thread just as you entered a command to operate on the
7034 previously current thread.
7036 @node Background Execution
7037 @subsection Background Execution
7039 @cindex foreground execution
7040 @cindex background execution
7041 @cindex asynchronous execution
7042 @cindex execution, foreground, background and asynchronous
7044 @value{GDBN}'s execution commands have two variants: the normal
7045 foreground (synchronous) behavior, and a background
7046 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
7047 the program to report that some thread has stopped before prompting for
7048 another command. In background execution, @value{GDBN} immediately gives
7049 a command prompt so that you can issue other commands while your program runs.
7051 If the target doesn't support async mode, @value{GDBN} issues an error
7052 message if you attempt to use the background execution commands.
7054 @cindex @code{&}, background execution of commands
7055 To specify background execution, add a @code{&} to the command. For example,
7056 the background form of the @code{continue} command is @code{continue&}, or
7057 just @code{c&}. The execution commands that accept background execution
7063 @xref{Starting, , Starting your Program}.
7067 @xref{Attach, , Debugging an Already-running Process}.
7071 @xref{Continuing and Stepping, step}.
7075 @xref{Continuing and Stepping, stepi}.
7079 @xref{Continuing and Stepping, next}.
7083 @xref{Continuing and Stepping, nexti}.
7087 @xref{Continuing and Stepping, continue}.
7091 @xref{Continuing and Stepping, finish}.
7095 @xref{Continuing and Stepping, until}.
7099 Background execution is especially useful in conjunction with non-stop
7100 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
7101 However, you can also use these commands in the normal all-stop mode with
7102 the restriction that you cannot issue another execution command until the
7103 previous one finishes. Examples of commands that are valid in all-stop
7104 mode while the program is running include @code{help} and @code{info break}.
7106 You can interrupt your program while it is running in the background by
7107 using the @code{interrupt} command.
7114 Suspend execution of the running program. In all-stop mode,
7115 @code{interrupt} stops the whole process, but in non-stop mode, it stops
7116 only the current thread. To stop the whole program in non-stop mode,
7117 use @code{interrupt -a}.
7120 @node Thread-Specific Breakpoints
7121 @subsection Thread-Specific Breakpoints
7123 When your program has multiple threads (@pxref{Threads,, Debugging
7124 Programs with Multiple Threads}), you can choose whether to set
7125 breakpoints on all threads, or on a particular thread.
7128 @cindex breakpoints and threads
7129 @cindex thread breakpoints
7130 @kindex break @dots{} thread @var{thread-id}
7131 @item break @var{location} thread @var{thread-id}
7132 @itemx break @var{location} thread @var{thread-id} if @dots{}
7133 @var{location} specifies source lines; there are several ways of
7134 writing them (@pxref{Specify Location}), but the effect is always to
7135 specify some source line.
7137 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
7138 to specify that you only want @value{GDBN} to stop the program when a
7139 particular thread reaches this breakpoint. The @var{thread-id} specifier
7140 is one of the thread identifiers assigned by @value{GDBN}, shown
7141 in the first column of the @samp{info threads} display.
7143 If you do not specify @samp{thread @var{thread-id}} when you set a
7144 breakpoint, the breakpoint applies to @emph{all} threads of your
7147 You can use the @code{thread} qualifier on conditional breakpoints as
7148 well; in this case, place @samp{thread @var{thread-id}} before or
7149 after the breakpoint condition, like this:
7152 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
7157 Thread-specific breakpoints are automatically deleted when
7158 @value{GDBN} detects the corresponding thread is no longer in the
7159 thread list. For example:
7163 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
7166 There are several ways for a thread to disappear, such as a regular
7167 thread exit, but also when you detach from the process with the
7168 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
7169 Process}), or if @value{GDBN} loses the remote connection
7170 (@pxref{Remote Debugging}), etc. Note that with some targets,
7171 @value{GDBN} is only able to detect a thread has exited when the user
7172 explictly asks for the thread list with the @code{info threads}
7175 @node Interrupted System Calls
7176 @subsection Interrupted System Calls
7178 @cindex thread breakpoints and system calls
7179 @cindex system calls and thread breakpoints
7180 @cindex premature return from system calls
7181 There is an unfortunate side effect when using @value{GDBN} to debug
7182 multi-threaded programs. If one thread stops for a
7183 breakpoint, or for some other reason, and another thread is blocked in a
7184 system call, then the system call may return prematurely. This is a
7185 consequence of the interaction between multiple threads and the signals
7186 that @value{GDBN} uses to implement breakpoints and other events that
7189 To handle this problem, your program should check the return value of
7190 each system call and react appropriately. This is good programming
7193 For example, do not write code like this:
7199 The call to @code{sleep} will return early if a different thread stops
7200 at a breakpoint or for some other reason.
7202 Instead, write this:
7207 unslept = sleep (unslept);
7210 A system call is allowed to return early, so the system is still
7211 conforming to its specification. But @value{GDBN} does cause your
7212 multi-threaded program to behave differently than it would without
7215 Also, @value{GDBN} uses internal breakpoints in the thread library to
7216 monitor certain events such as thread creation and thread destruction.
7217 When such an event happens, a system call in another thread may return
7218 prematurely, even though your program does not appear to stop.
7221 @subsection Observer Mode
7223 If you want to build on non-stop mode and observe program behavior
7224 without any chance of disruption by @value{GDBN}, you can set
7225 variables to disable all of the debugger's attempts to modify state,
7226 whether by writing memory, inserting breakpoints, etc. These operate
7227 at a low level, intercepting operations from all commands.
7229 When all of these are set to @code{off}, then @value{GDBN} is said to
7230 be @dfn{observer mode}. As a convenience, the variable
7231 @code{observer} can be set to disable these, plus enable non-stop
7234 Note that @value{GDBN} will not prevent you from making nonsensical
7235 combinations of these settings. For instance, if you have enabled
7236 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
7237 then breakpoints that work by writing trap instructions into the code
7238 stream will still not be able to be placed.
7243 @item set observer on
7244 @itemx set observer off
7245 When set to @code{on}, this disables all the permission variables
7246 below (except for @code{insert-fast-tracepoints}), plus enables
7247 non-stop debugging. Setting this to @code{off} switches back to
7248 normal debugging, though remaining in non-stop mode.
7251 Show whether observer mode is on or off.
7253 @kindex may-write-registers
7254 @item set may-write-registers on
7255 @itemx set may-write-registers off
7256 This controls whether @value{GDBN} will attempt to alter the values of
7257 registers, such as with assignment expressions in @code{print}, or the
7258 @code{jump} command. It defaults to @code{on}.
7260 @item show may-write-registers
7261 Show the current permission to write registers.
7263 @kindex may-write-memory
7264 @item set may-write-memory on
7265 @itemx set may-write-memory off
7266 This controls whether @value{GDBN} will attempt to alter the contents
7267 of memory, such as with assignment expressions in @code{print}. It
7268 defaults to @code{on}.
7270 @item show may-write-memory
7271 Show the current permission to write memory.
7273 @kindex may-insert-breakpoints
7274 @item set may-insert-breakpoints on
7275 @itemx set may-insert-breakpoints off
7276 This controls whether @value{GDBN} will attempt to insert breakpoints.
7277 This affects all breakpoints, including internal breakpoints defined
7278 by @value{GDBN}. It defaults to @code{on}.
7280 @item show may-insert-breakpoints
7281 Show the current permission to insert breakpoints.
7283 @kindex may-insert-tracepoints
7284 @item set may-insert-tracepoints on
7285 @itemx set may-insert-tracepoints off
7286 This controls whether @value{GDBN} will attempt to insert (regular)
7287 tracepoints at the beginning of a tracing experiment. It affects only
7288 non-fast tracepoints, fast tracepoints being under the control of
7289 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
7291 @item show may-insert-tracepoints
7292 Show the current permission to insert tracepoints.
7294 @kindex may-insert-fast-tracepoints
7295 @item set may-insert-fast-tracepoints on
7296 @itemx set may-insert-fast-tracepoints off
7297 This controls whether @value{GDBN} will attempt to insert fast
7298 tracepoints at the beginning of a tracing experiment. It affects only
7299 fast tracepoints, regular (non-fast) tracepoints being under the
7300 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
7302 @item show may-insert-fast-tracepoints
7303 Show the current permission to insert fast tracepoints.
7305 @kindex may-interrupt
7306 @item set may-interrupt on
7307 @itemx set may-interrupt off
7308 This controls whether @value{GDBN} will attempt to interrupt or stop
7309 program execution. When this variable is @code{off}, the
7310 @code{interrupt} command will have no effect, nor will
7311 @kbd{Ctrl-c}. It defaults to @code{on}.
7313 @item show may-interrupt
7314 Show the current permission to interrupt or stop the program.
7318 @node Reverse Execution
7319 @chapter Running programs backward
7320 @cindex reverse execution
7321 @cindex running programs backward
7323 When you are debugging a program, it is not unusual to realize that
7324 you have gone too far, and some event of interest has already happened.
7325 If the target environment supports it, @value{GDBN} can allow you to
7326 ``rewind'' the program by running it backward.
7328 A target environment that supports reverse execution should be able
7329 to ``undo'' the changes in machine state that have taken place as the
7330 program was executing normally. Variables, registers etc.@: should
7331 revert to their previous values. Obviously this requires a great
7332 deal of sophistication on the part of the target environment; not
7333 all target environments can support reverse execution.
7335 When a program is executed in reverse, the instructions that
7336 have most recently been executed are ``un-executed'', in reverse
7337 order. The program counter runs backward, following the previous
7338 thread of execution in reverse. As each instruction is ``un-executed'',
7339 the values of memory and/or registers that were changed by that
7340 instruction are reverted to their previous states. After executing
7341 a piece of source code in reverse, all side effects of that code
7342 should be ``undone'', and all variables should be returned to their
7343 prior values@footnote{
7344 Note that some side effects are easier to undo than others. For instance,
7345 memory and registers are relatively easy, but device I/O is hard. Some
7346 targets may be able undo things like device I/O, and some may not.
7348 The contract between @value{GDBN} and the reverse executing target
7349 requires only that the target do something reasonable when
7350 @value{GDBN} tells it to execute backwards, and then report the
7351 results back to @value{GDBN}. Whatever the target reports back to
7352 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
7353 assumes that the memory and registers that the target reports are in a
7354 consistent state, but @value{GDBN} accepts whatever it is given.
7357 On some platforms, @value{GDBN} has built-in support for reverse
7358 execution, activated with the @code{record} or @code{record btrace}
7359 commands. @xref{Process Record and Replay}. Some remote targets,
7360 typically full system emulators, support reverse execution directly
7361 without requiring any special command.
7363 If you are debugging in a target environment that supports
7364 reverse execution, @value{GDBN} provides the following commands.
7367 @kindex reverse-continue
7368 @kindex rc @r{(@code{reverse-continue})}
7369 @item reverse-continue @r{[}@var{ignore-count}@r{]}
7370 @itemx rc @r{[}@var{ignore-count}@r{]}
7371 Beginning at the point where your program last stopped, start executing
7372 in reverse. Reverse execution will stop for breakpoints and synchronous
7373 exceptions (signals), just like normal execution. Behavior of
7374 asynchronous signals depends on the target environment.
7376 @kindex reverse-step
7377 @kindex rs @r{(@code{step})}
7378 @item reverse-step @r{[}@var{count}@r{]}
7379 Run the program backward until control reaches the start of a
7380 different source line; then stop it, and return control to @value{GDBN}.
7382 Like the @code{step} command, @code{reverse-step} will only stop
7383 at the beginning of a source line. It ``un-executes'' the previously
7384 executed source line. If the previous source line included calls to
7385 debuggable functions, @code{reverse-step} will step (backward) into
7386 the called function, stopping at the beginning of the @emph{last}
7387 statement in the called function (typically a return statement).
7389 Also, as with the @code{step} command, if non-debuggable functions are
7390 called, @code{reverse-step} will run thru them backward without stopping.
7392 @kindex reverse-stepi
7393 @kindex rsi @r{(@code{reverse-stepi})}
7394 @item reverse-stepi @r{[}@var{count}@r{]}
7395 Reverse-execute one machine instruction. Note that the instruction
7396 to be reverse-executed is @emph{not} the one pointed to by the program
7397 counter, but the instruction executed prior to that one. For instance,
7398 if the last instruction was a jump, @code{reverse-stepi} will take you
7399 back from the destination of the jump to the jump instruction itself.
7401 @kindex reverse-next
7402 @kindex rn @r{(@code{reverse-next})}
7403 @item reverse-next @r{[}@var{count}@r{]}
7404 Run backward to the beginning of the previous line executed in
7405 the current (innermost) stack frame. If the line contains function
7406 calls, they will be ``un-executed'' without stopping. Starting from
7407 the first line of a function, @code{reverse-next} will take you back
7408 to the caller of that function, @emph{before} the function was called,
7409 just as the normal @code{next} command would take you from the last
7410 line of a function back to its return to its caller
7411 @footnote{Unless the code is too heavily optimized.}.
7413 @kindex reverse-nexti
7414 @kindex rni @r{(@code{reverse-nexti})}
7415 @item reverse-nexti @r{[}@var{count}@r{]}
7416 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
7417 in reverse, except that called functions are ``un-executed'' atomically.
7418 That is, if the previously executed instruction was a return from
7419 another function, @code{reverse-nexti} will continue to execute
7420 in reverse until the call to that function (from the current stack
7423 @kindex reverse-finish
7424 @item reverse-finish
7425 Just as the @code{finish} command takes you to the point where the
7426 current function returns, @code{reverse-finish} takes you to the point
7427 where it was called. Instead of ending up at the end of the current
7428 function invocation, you end up at the beginning.
7430 @kindex set exec-direction
7431 @item set exec-direction
7432 Set the direction of target execution.
7433 @item set exec-direction reverse
7434 @cindex execute forward or backward in time
7435 @value{GDBN} will perform all execution commands in reverse, until the
7436 exec-direction mode is changed to ``forward''. Affected commands include
7437 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
7438 command cannot be used in reverse mode.
7439 @item set exec-direction forward
7440 @value{GDBN} will perform all execution commands in the normal fashion.
7441 This is the default.
7445 @node Process Record and Replay
7446 @chapter Recording Inferior's Execution and Replaying It
7447 @cindex process record and replay
7448 @cindex recording inferior's execution and replaying it
7450 On some platforms, @value{GDBN} provides a special @dfn{process record
7451 and replay} target that can record a log of the process execution, and
7452 replay it later with both forward and reverse execution commands.
7455 When this target is in use, if the execution log includes the record
7456 for the next instruction, @value{GDBN} will debug in @dfn{replay
7457 mode}. In the replay mode, the inferior does not really execute code
7458 instructions. Instead, all the events that normally happen during
7459 code execution are taken from the execution log. While code is not
7460 really executed in replay mode, the values of registers (including the
7461 program counter register) and the memory of the inferior are still
7462 changed as they normally would. Their contents are taken from the
7466 If the record for the next instruction is not in the execution log,
7467 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
7468 inferior executes normally, and @value{GDBN} records the execution log
7471 The process record and replay target supports reverse execution
7472 (@pxref{Reverse Execution}), even if the platform on which the
7473 inferior runs does not. However, the reverse execution is limited in
7474 this case by the range of the instructions recorded in the execution
7475 log. In other words, reverse execution on platforms that don't
7476 support it directly can only be done in the replay mode.
7478 When debugging in the reverse direction, @value{GDBN} will work in
7479 replay mode as long as the execution log includes the record for the
7480 previous instruction; otherwise, it will work in record mode, if the
7481 platform supports reverse execution, or stop if not.
7483 Currently, process record and replay is supported on ARM, Aarch64,
7484 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
7485 GNU/Linux. Process record and replay can be used both when native
7486 debugging, and when remote debugging via @code{gdbserver}.
7488 For architecture environments that support process record and replay,
7489 @value{GDBN} provides the following commands:
7492 @kindex target record
7493 @kindex target record-full
7494 @kindex target record-btrace
7497 @kindex record btrace
7498 @kindex record btrace bts
7499 @kindex record btrace pt
7505 @kindex rec btrace bts
7506 @kindex rec btrace pt
7509 @item record @var{method}
7510 This command starts the process record and replay target. The
7511 recording method can be specified as parameter. Without a parameter
7512 the command uses the @code{full} recording method. The following
7513 recording methods are available:
7517 Full record/replay recording using @value{GDBN}'s software record and
7518 replay implementation. This method allows replaying and reverse
7521 @item btrace @var{format}
7522 Hardware-supported instruction recording, supported on Intel
7523 processors. This method does not record data. Further, the data is
7524 collected in a ring buffer so old data will be overwritten when the
7525 buffer is full. It allows limited reverse execution. Variables and
7526 registers are not available during reverse execution. In remote
7527 debugging, recording continues on disconnect. Recorded data can be
7528 inspected after reconnecting. The recording may be stopped using
7531 The recording format can be specified as parameter. Without a parameter
7532 the command chooses the recording format. The following recording
7533 formats are available:
7537 @cindex branch trace store
7538 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
7539 this format, the processor stores a from/to record for each executed
7540 branch in the btrace ring buffer.
7543 @cindex Intel Processor Trace
7544 Use the @dfn{Intel Processor Trace} recording format. In this
7545 format, the processor stores the execution trace in a compressed form
7546 that is afterwards decoded by @value{GDBN}.
7548 The trace can be recorded with very low overhead. The compressed
7549 trace format also allows small trace buffers to already contain a big
7550 number of instructions compared to @acronym{BTS}.
7552 Decoding the recorded execution trace, on the other hand, is more
7553 expensive than decoding @acronym{BTS} trace. This is mostly due to the
7554 increased number of instructions to process. You should increase the
7555 buffer-size with care.
7558 Not all recording formats may be available on all processors.
7561 The process record and replay target can only debug a process that is
7562 already running. Therefore, you need first to start the process with
7563 the @kbd{run} or @kbd{start} commands, and then start the recording
7564 with the @kbd{record @var{method}} command.
7566 @cindex displaced stepping, and process record and replay
7567 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
7568 will be automatically disabled when process record and replay target
7569 is started. That's because the process record and replay target
7570 doesn't support displaced stepping.
7572 @cindex non-stop mode, and process record and replay
7573 @cindex asynchronous execution, and process record and replay
7574 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
7575 the asynchronous execution mode (@pxref{Background Execution}), not
7576 all recording methods are available. The @code{full} recording method
7577 does not support these two modes.
7582 Stop the process record and replay target. When process record and
7583 replay target stops, the entire execution log will be deleted and the
7584 inferior will either be terminated, or will remain in its final state.
7586 When you stop the process record and replay target in record mode (at
7587 the end of the execution log), the inferior will be stopped at the
7588 next instruction that would have been recorded. In other words, if
7589 you record for a while and then stop recording, the inferior process
7590 will be left in the same state as if the recording never happened.
7592 On the other hand, if the process record and replay target is stopped
7593 while in replay mode (that is, not at the end of the execution log,
7594 but at some earlier point), the inferior process will become ``live''
7595 at that earlier state, and it will then be possible to continue the
7596 usual ``live'' debugging of the process from that state.
7598 When the inferior process exits, or @value{GDBN} detaches from it,
7599 process record and replay target will automatically stop itself.
7603 Go to a specific location in the execution log. There are several
7604 ways to specify the location to go to:
7607 @item record goto begin
7608 @itemx record goto start
7609 Go to the beginning of the execution log.
7611 @item record goto end
7612 Go to the end of the execution log.
7614 @item record goto @var{n}
7615 Go to instruction number @var{n} in the execution log.
7619 @item record save @var{filename}
7620 Save the execution log to a file @file{@var{filename}}.
7621 Default filename is @file{gdb_record.@var{process_id}}, where
7622 @var{process_id} is the process ID of the inferior.
7624 This command may not be available for all recording methods.
7626 @kindex record restore
7627 @item record restore @var{filename}
7628 Restore the execution log from a file @file{@var{filename}}.
7629 File must have been created with @code{record save}.
7631 @kindex set record full
7632 @item set record full insn-number-max @var{limit}
7633 @itemx set record full insn-number-max unlimited
7634 Set the limit of instructions to be recorded for the @code{full}
7635 recording method. Default value is 200000.
7637 If @var{limit} is a positive number, then @value{GDBN} will start
7638 deleting instructions from the log once the number of the record
7639 instructions becomes greater than @var{limit}. For every new recorded
7640 instruction, @value{GDBN} will delete the earliest recorded
7641 instruction to keep the number of recorded instructions at the limit.
7642 (Since deleting recorded instructions loses information, @value{GDBN}
7643 lets you control what happens when the limit is reached, by means of
7644 the @code{stop-at-limit} option, described below.)
7646 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
7647 delete recorded instructions from the execution log. The number of
7648 recorded instructions is limited only by the available memory.
7650 @kindex show record full
7651 @item show record full insn-number-max
7652 Show the limit of instructions to be recorded with the @code{full}
7655 @item set record full stop-at-limit
7656 Control the behavior of the @code{full} recording method when the
7657 number of recorded instructions reaches the limit. If ON (the
7658 default), @value{GDBN} will stop when the limit is reached for the
7659 first time and ask you whether you want to stop the inferior or
7660 continue running it and recording the execution log. If you decide
7661 to continue recording, each new recorded instruction will cause the
7662 oldest one to be deleted.
7664 If this option is OFF, @value{GDBN} will automatically delete the
7665 oldest record to make room for each new one, without asking.
7667 @item show record full stop-at-limit
7668 Show the current setting of @code{stop-at-limit}.
7670 @item set record full memory-query
7671 Control the behavior when @value{GDBN} is unable to record memory
7672 changes caused by an instruction for the @code{full} recording method.
7673 If ON, @value{GDBN} will query whether to stop the inferior in that
7676 If this option is OFF (the default), @value{GDBN} will automatically
7677 ignore the effect of such instructions on memory. Later, when
7678 @value{GDBN} replays this execution log, it will mark the log of this
7679 instruction as not accessible, and it will not affect the replay
7682 @item show record full memory-query
7683 Show the current setting of @code{memory-query}.
7685 @kindex set record btrace
7686 The @code{btrace} record target does not trace data. As a
7687 convenience, when replaying, @value{GDBN} reads read-only memory off
7688 the live program directly, assuming that the addresses of the
7689 read-only areas don't change. This for example makes it possible to
7690 disassemble code while replaying, but not to print variables.
7691 In some cases, being able to inspect variables might be useful.
7692 You can use the following command for that:
7694 @item set record btrace replay-memory-access
7695 Control the behavior of the @code{btrace} recording method when
7696 accessing memory during replay. If @code{read-only} (the default),
7697 @value{GDBN} will only allow accesses to read-only memory.
7698 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7699 and to read-write memory. Beware that the accessed memory corresponds
7700 to the live target and not necessarily to the current replay
7703 @item set record btrace cpu @var{identifier}
7704 Set the processor to be used for enabling workarounds for processor
7705 errata when decoding the trace.
7707 Processor errata are defects in processor operation, caused by its
7708 design or manufacture. They can cause a trace not to match the
7709 specification. This, in turn, may cause trace decode to fail.
7710 @value{GDBN} can detect erroneous trace packets and correct them, thus
7711 avoiding the decoding failures. These corrections are known as
7712 @dfn{errata workarounds}, and are enabled based on the processor on
7713 which the trace was recorded.
7715 By default, @value{GDBN} attempts to detect the processor
7716 automatically, and apply the necessary workarounds for it. However,
7717 you may need to specify the processor if @value{GDBN} does not yet
7718 support it. This command allows you to do that, and also allows to
7719 disable the workarounds.
7721 The argument @var{identifier} identifies the @sc{cpu} and is of the
7722 form: @code{@var{vendor}:@var{processor identifier}}. In addition,
7723 there are two special identifiers, @code{none} and @code{auto}
7726 The following vendor identifiers and corresponding processor
7727 identifiers are currently supported:
7729 @multitable @columnfractions .1 .9
7732 @tab @var{family}/@var{model}[/@var{stepping}]
7736 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7737 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7739 If @var{identifier} is @code{auto}, enable errata workarounds for the
7740 processor on which the trace was recorded. If @var{identifier} is
7741 @code{none}, errata workarounds are disabled.
7743 For example, when using an old @value{GDBN} on a new system, decode
7744 may fail because @value{GDBN} does not support the new processor. It
7745 often suffices to specify an older processor that @value{GDBN}
7750 Active record target: record-btrace
7751 Recording format: Intel Processor Trace.
7753 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7754 (gdb) set record btrace cpu intel:6/158
7756 Active record target: record-btrace
7757 Recording format: Intel Processor Trace.
7759 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7762 @kindex show record btrace
7763 @item show record btrace replay-memory-access
7764 Show the current setting of @code{replay-memory-access}.
7766 @item show record btrace cpu
7767 Show the processor to be used for enabling trace decode errata
7770 @kindex set record btrace bts
7771 @item set record btrace bts buffer-size @var{size}
7772 @itemx set record btrace bts buffer-size unlimited
7773 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7774 format. Default is 64KB.
7776 If @var{size} is a positive number, then @value{GDBN} will try to
7777 allocate a buffer of at least @var{size} bytes for each new thread
7778 that uses the btrace recording method and the @acronym{BTS} format.
7779 The actually obtained buffer size may differ from the requested
7780 @var{size}. Use the @code{info record} command to see the actual
7781 buffer size for each thread that uses the btrace recording method and
7782 the @acronym{BTS} format.
7784 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7785 allocate a buffer of 4MB.
7787 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7788 also need longer to process the branch trace data before it can be used.
7790 @item show record btrace bts buffer-size @var{size}
7791 Show the current setting of the requested ring buffer size for branch
7792 tracing in @acronym{BTS} format.
7794 @kindex set record btrace pt
7795 @item set record btrace pt buffer-size @var{size}
7796 @itemx set record btrace pt buffer-size unlimited
7797 Set the requested ring buffer size for branch tracing in Intel
7798 Processor Trace format. Default is 16KB.
7800 If @var{size} is a positive number, then @value{GDBN} will try to
7801 allocate a buffer of at least @var{size} bytes for each new thread
7802 that uses the btrace recording method and the Intel Processor Trace
7803 format. The actually obtained buffer size may differ from the
7804 requested @var{size}. Use the @code{info record} command to see the
7805 actual buffer size for each thread.
7807 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7808 allocate a buffer of 4MB.
7810 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7811 also need longer to process the branch trace data before it can be used.
7813 @item show record btrace pt buffer-size @var{size}
7814 Show the current setting of the requested ring buffer size for branch
7815 tracing in Intel Processor Trace format.
7819 Show various statistics about the recording depending on the recording
7824 For the @code{full} recording method, it shows the state of process
7825 record and its in-memory execution log buffer, including:
7829 Whether in record mode or replay mode.
7831 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7833 Highest recorded instruction number.
7835 Current instruction about to be replayed (if in replay mode).
7837 Number of instructions contained in the execution log.
7839 Maximum number of instructions that may be contained in the execution log.
7843 For the @code{btrace} recording method, it shows:
7849 Number of instructions that have been recorded.
7851 Number of blocks of sequential control-flow formed by the recorded
7854 Whether in record mode or replay mode.
7857 For the @code{bts} recording format, it also shows:
7860 Size of the perf ring buffer.
7863 For the @code{pt} recording format, it also shows:
7866 Size of the perf ring buffer.
7870 @kindex record delete
7873 When record target runs in replay mode (``in the past''), delete the
7874 subsequent execution log and begin to record a new execution log starting
7875 from the current address. This means you will abandon the previously
7876 recorded ``future'' and begin recording a new ``future''.
7878 @kindex record instruction-history
7879 @kindex rec instruction-history
7880 @item record instruction-history
7881 Disassembles instructions from the recorded execution log. By
7882 default, ten instructions are disassembled. This can be changed using
7883 the @code{set record instruction-history-size} command. Instructions
7884 are printed in execution order.
7886 It can also print mixed source+disassembly if you specify the the
7887 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7888 as well as in symbolic form by specifying the @code{/r} modifier.
7890 The current position marker is printed for the instruction at the
7891 current program counter value. This instruction can appear multiple
7892 times in the trace and the current position marker will be printed
7893 every time. To omit the current position marker, specify the
7896 To better align the printed instructions when the trace contains
7897 instructions from more than one function, the function name may be
7898 omitted by specifying the @code{/f} modifier.
7900 Speculatively executed instructions are prefixed with @samp{?}. This
7901 feature is not available for all recording formats.
7903 There are several ways to specify what part of the execution log to
7907 @item record instruction-history @var{insn}
7908 Disassembles ten instructions starting from instruction number
7911 @item record instruction-history @var{insn}, +/-@var{n}
7912 Disassembles @var{n} instructions around instruction number
7913 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7914 @var{n} instructions after instruction number @var{insn}. If
7915 @var{n} is preceded with @code{-}, disassembles @var{n}
7916 instructions before instruction number @var{insn}.
7918 @item record instruction-history
7919 Disassembles ten more instructions after the last disassembly.
7921 @item record instruction-history -
7922 Disassembles ten more instructions before the last disassembly.
7924 @item record instruction-history @var{begin}, @var{end}
7925 Disassembles instructions beginning with instruction number
7926 @var{begin} until instruction number @var{end}. The instruction
7927 number @var{end} is included.
7930 This command may not be available for all recording methods.
7933 @item set record instruction-history-size @var{size}
7934 @itemx set record instruction-history-size unlimited
7935 Define how many instructions to disassemble in the @code{record
7936 instruction-history} command. The default value is 10.
7937 A @var{size} of @code{unlimited} means unlimited instructions.
7940 @item show record instruction-history-size
7941 Show how many instructions to disassemble in the @code{record
7942 instruction-history} command.
7944 @kindex record function-call-history
7945 @kindex rec function-call-history
7946 @item record function-call-history
7947 Prints the execution history at function granularity. For each sequence
7948 of instructions that belong to the same function, it prints the name of
7949 that function, the source lines for this instruction sequence (if the
7950 @code{/l} modifier is specified), and the instructions numbers that form
7951 the sequence (if the @code{/i} modifier is specified). The function names
7952 are indented to reflect the call stack depth if the @code{/c} modifier is
7953 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be given
7957 (@value{GDBP}) @b{list 1, 10}
7968 (@value{GDBP}) @b{record function-call-history /ilc}
7969 1 bar inst 1,4 at foo.c:6,8
7970 2 foo inst 5,10 at foo.c:2,3
7971 3 bar inst 11,13 at foo.c:9,10
7974 By default, ten functions are printed. This can be changed using the
7975 @code{set record function-call-history-size} command. Functions are
7976 printed in execution order. There are several ways to specify what
7980 @item record function-call-history @var{func}
7981 Prints ten functions starting from function number @var{func}.
7983 @item record function-call-history @var{func}, +/-@var{n}
7984 Prints @var{n} functions around function number @var{func}. If
7985 @var{n} is preceded with @code{+}, prints @var{n} functions after
7986 function number @var{func}. If @var{n} is preceded with @code{-},
7987 prints @var{n} functions before function number @var{func}.
7989 @item record function-call-history
7990 Prints ten more functions after the last ten-function print.
7992 @item record function-call-history -
7993 Prints ten more functions before the last ten-function print.
7995 @item record function-call-history @var{begin}, @var{end}
7996 Prints functions beginning with function number @var{begin} until
7997 function number @var{end}. The function number @var{end} is included.
8000 This command may not be available for all recording methods.
8002 @item set record function-call-history-size @var{size}
8003 @itemx set record function-call-history-size unlimited
8004 Define how many functions to print in the
8005 @code{record function-call-history} command. The default value is 10.
8006 A size of @code{unlimited} means unlimited functions.
8008 @item show record function-call-history-size
8009 Show how many functions to print in the
8010 @code{record function-call-history} command.
8015 @chapter Examining the Stack
8017 When your program has stopped, the first thing you need to know is where it
8018 stopped and how it got there.
8021 Each time your program performs a function call, information about the call
8023 That information includes the location of the call in your program,
8024 the arguments of the call,
8025 and the local variables of the function being called.
8026 The information is saved in a block of data called a @dfn{stack frame}.
8027 The stack frames are allocated in a region of memory called the @dfn{call
8030 When your program stops, the @value{GDBN} commands for examining the
8031 stack allow you to see all of this information.
8033 @cindex selected frame
8034 One of the stack frames is @dfn{selected} by @value{GDBN} and many
8035 @value{GDBN} commands refer implicitly to the selected frame. In
8036 particular, whenever you ask @value{GDBN} for the value of a variable in
8037 your program, the value is found in the selected frame. There are
8038 special @value{GDBN} commands to select whichever frame you are
8039 interested in. @xref{Selection, ,Selecting a Frame}.
8041 When your program stops, @value{GDBN} automatically selects the
8042 currently executing frame and describes it briefly, similar to the
8043 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
8046 * Frames:: Stack frames
8047 * Backtrace:: Backtraces
8048 * Selection:: Selecting a frame
8049 * Frame Info:: Information on a frame
8050 * Frame Apply:: Applying a command to several frames
8051 * Frame Filter Management:: Managing frame filters
8056 @section Stack Frames
8058 @cindex frame, definition
8060 The call stack is divided up into contiguous pieces called @dfn{stack
8061 frames}, or @dfn{frames} for short; each frame is the data associated
8062 with one call to one function. The frame contains the arguments given
8063 to the function, the function's local variables, and the address at
8064 which the function is executing.
8066 @cindex initial frame
8067 @cindex outermost frame
8068 @cindex innermost frame
8069 When your program is started, the stack has only one frame, that of the
8070 function @code{main}. This is called the @dfn{initial} frame or the
8071 @dfn{outermost} frame. Each time a function is called, a new frame is
8072 made. Each time a function returns, the frame for that function invocation
8073 is eliminated. If a function is recursive, there can be many frames for
8074 the same function. The frame for the function in which execution is
8075 actually occurring is called the @dfn{innermost} frame. This is the most
8076 recently created of all the stack frames that still exist.
8078 @cindex frame pointer
8079 Inside your program, stack frames are identified by their addresses. A
8080 stack frame consists of many bytes, each of which has its own address; each
8081 kind of computer has a convention for choosing one byte whose
8082 address serves as the address of the frame. Usually this address is kept
8083 in a register called the @dfn{frame pointer register}
8084 (@pxref{Registers, $fp}) while execution is going on in that frame.
8087 @cindex frame number
8088 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
8089 number that is zero for the innermost frame, one for the frame that
8090 called it, and so on upward. These level numbers give you a way of
8091 designating stack frames in @value{GDBN} commands. The terms
8092 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
8093 describe this number.
8095 @c The -fomit-frame-pointer below perennially causes hbox overflow
8096 @c underflow problems.
8097 @cindex frameless execution
8098 Some compilers provide a way to compile functions so that they operate
8099 without stack frames. (For example, the @value{NGCC} option
8101 @samp{-fomit-frame-pointer}
8103 generates functions without a frame.)
8104 This is occasionally done with heavily used library functions to save
8105 the frame setup time. @value{GDBN} has limited facilities for dealing
8106 with these function invocations. If the innermost function invocation
8107 has no stack frame, @value{GDBN} nevertheless regards it as though
8108 it had a separate frame, which is numbered zero as usual, allowing
8109 correct tracing of the function call chain. However, @value{GDBN} has
8110 no provision for frameless functions elsewhere in the stack.
8116 @cindex call stack traces
8117 A backtrace is a summary of how your program got where it is. It shows one
8118 line per frame, for many frames, starting with the currently executing
8119 frame (frame zero), followed by its caller (frame one), and on up the
8122 @anchor{backtrace-command}
8124 @kindex bt @r{(@code{backtrace})}
8125 To print a backtrace of the entire stack, use the @code{backtrace}
8126 command, or its alias @code{bt}. This command will print one line per
8127 frame for frames in the stack. By default, all stack frames are
8128 printed. You can stop the backtrace at any time by typing the system
8129 interrupt character, normally @kbd{Ctrl-c}.
8132 @item backtrace [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8133 @itemx bt [@var{option}]@dots{} [@var{qualifier}]@dots{} [@var{count}]
8134 Print the backtrace of the entire stack.
8136 The optional @var{count} can be one of the following:
8141 Print only the innermost @var{n} frames, where @var{n} is a positive
8146 Print only the outermost @var{n} frames, where @var{n} is a positive
8154 Print the values of the local variables also. This can be combined
8155 with the optional @var{count} to limit the number of frames shown.
8158 Do not run Python frame filters on this backtrace. @xref{Frame
8159 Filter API}, for more information. Additionally use @ref{disable
8160 frame-filter all} to turn off all frame filters. This is only
8161 relevant when @value{GDBN} has been configured with @code{Python}
8165 A Python frame filter might decide to ``elide'' some frames. Normally
8166 such elided frames are still printed, but they are indented relative
8167 to the filtered frames that cause them to be elided. The @code{-hide}
8168 option causes elided frames to not be printed at all.
8171 The @code{backtrace} command also supports a number of options that
8172 allow overriding relevant global print settings as set by @code{set
8173 backtrace} and @code{set print} subcommands:
8176 @item -past-main [@code{on}|@code{off}]
8177 Set whether backtraces should continue past @code{main}. Related setting:
8178 @ref{set backtrace past-main}.
8180 @item -past-entry [@code{on}|@code{off}]
8181 Set whether backtraces should continue past the entry point of a program.
8182 Related setting: @ref{set backtrace past-entry}.
8184 @item -entry-values @code{no}|@code{only}|@code{preferred}|@code{if-needed}|@code{both}|@code{compact}|@code{default}
8185 Set printing of function arguments at function entry.
8186 Related setting: @ref{set print entry-values}.
8188 @item -frame-arguments @code{all}|@code{scalars}|@code{none}
8189 Set printing of non-scalar frame arguments.
8190 Related setting: @ref{set print frame-arguments}.
8192 @item -raw-frame-arguments [@code{on}|@code{off}]
8193 Set whether to print frame arguments in raw form.
8194 Related setting: @ref{set print raw-frame-arguments}.
8196 @item -frame-info @code{auto}|@code{source-line}|@code{location}|@code{source-and-location}|@code{location-and-address}|@code{short-location}
8197 Set printing of frame information.
8198 Related setting: @ref{set print frame-info}.
8201 The optional @var{qualifier} is maintained for backward compatibility.
8202 It can be one of the following:
8206 Equivalent to the @code{-full} option.
8209 Equivalent to the @code{-no-filters} option.
8212 Equivalent to the @code{-hide} option.
8219 The names @code{where} and @code{info stack} (abbreviated @code{info s})
8220 are additional aliases for @code{backtrace}.
8222 @cindex multiple threads, backtrace
8223 In a multi-threaded program, @value{GDBN} by default shows the
8224 backtrace only for the current thread. To display the backtrace for
8225 several or all of the threads, use the command @code{thread apply}
8226 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
8227 apply all backtrace}, @value{GDBN} will display the backtrace for all
8228 the threads; this is handy when you debug a core dump of a
8229 multi-threaded program.
8231 Each line in the backtrace shows the frame number and the function name.
8232 The program counter value is also shown---unless you use @code{set
8233 print address off}. The backtrace also shows the source file name and
8234 line number, as well as the arguments to the function. The program
8235 counter value is omitted if it is at the beginning of the code for that
8238 Here is an example of a backtrace. It was made with the command
8239 @samp{bt 3}, so it shows the innermost three frames.
8243 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8245 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
8246 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
8248 (More stack frames follow...)
8253 The display for frame zero does not begin with a program counter
8254 value, indicating that your program has stopped at the beginning of the
8255 code for line @code{993} of @code{builtin.c}.
8258 The value of parameter @code{data} in frame 1 has been replaced by
8259 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
8260 only if it is a scalar (integer, pointer, enumeration, etc). See command
8261 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
8262 on how to configure the way function parameter values are printed.
8263 The command @kbd{set print frame-info} (@pxref{Print Settings}) controls
8264 what frame information is printed.
8266 @cindex optimized out, in backtrace
8267 @cindex function call arguments, optimized out
8268 If your program was compiled with optimizations, some compilers will
8269 optimize away arguments passed to functions if those arguments are
8270 never used after the call. Such optimizations generate code that
8271 passes arguments through registers, but doesn't store those arguments
8272 in the stack frame. @value{GDBN} has no way of displaying such
8273 arguments in stack frames other than the innermost one. Here's what
8274 such a backtrace might look like:
8278 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
8280 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
8281 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
8283 (More stack frames follow...)
8288 The values of arguments that were not saved in their stack frames are
8289 shown as @samp{<optimized out>}.
8291 If you need to display the values of such optimized-out arguments,
8292 either deduce that from other variables whose values depend on the one
8293 you are interested in, or recompile without optimizations.
8295 @cindex backtrace beyond @code{main} function
8296 @cindex program entry point
8297 @cindex startup code, and backtrace
8298 Most programs have a standard user entry point---a place where system
8299 libraries and startup code transition into user code. For C this is
8300 @code{main}@footnote{
8301 Note that embedded programs (the so-called ``free-standing''
8302 environment) are not required to have a @code{main} function as the
8303 entry point. They could even have multiple entry points.}.
8304 When @value{GDBN} finds the entry function in a backtrace
8305 it will terminate the backtrace, to avoid tracing into highly
8306 system-specific (and generally uninteresting) code.
8308 If you need to examine the startup code, or limit the number of levels
8309 in a backtrace, you can change this behavior:
8312 @item set backtrace past-main
8313 @itemx set backtrace past-main on
8314 @anchor{set backtrace past-main}
8315 @kindex set backtrace
8316 Backtraces will continue past the user entry point.
8318 @item set backtrace past-main off
8319 Backtraces will stop when they encounter the user entry point. This is the
8322 @item show backtrace past-main
8323 @kindex show backtrace
8324 Display the current user entry point backtrace policy.
8326 @item set backtrace past-entry
8327 @itemx set backtrace past-entry on
8328 @anchor{set backtrace past-entry}
8329 Backtraces will continue past the internal entry point of an application.
8330 This entry point is encoded by the linker when the application is built,
8331 and is likely before the user entry point @code{main} (or equivalent) is called.
8333 @item set backtrace past-entry off
8334 Backtraces will stop when they encounter the internal entry point of an
8335 application. This is the default.
8337 @item show backtrace past-entry
8338 Display the current internal entry point backtrace policy.
8340 @item set backtrace limit @var{n}
8341 @itemx set backtrace limit 0
8342 @itemx set backtrace limit unlimited
8343 @anchor{set backtrace limit}
8344 @cindex backtrace limit
8345 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
8346 or zero means unlimited levels.
8348 @item show backtrace limit
8349 Display the current limit on backtrace levels.
8352 You can control how file names are displayed.
8355 @item set filename-display
8356 @itemx set filename-display relative
8357 @cindex filename-display
8358 Display file names relative to the compilation directory. This is the default.
8360 @item set filename-display basename
8361 Display only basename of a filename.
8363 @item set filename-display absolute
8364 Display an absolute filename.
8366 @item show filename-display
8367 Show the current way to display filenames.
8371 @section Selecting a Frame
8373 Most commands for examining the stack and other data in your program work on
8374 whichever stack frame is selected at the moment. Here are the commands for
8375 selecting a stack frame; all of them finish by printing a brief description
8376 of the stack frame just selected.
8379 @kindex frame@r{, selecting}
8380 @kindex f @r{(@code{frame})}
8381 @item frame @r{[} @var{frame-selection-spec} @r{]}
8382 @item f @r{[} @var{frame-selection-spec} @r{]}
8383 The @command{frame} command allows different stack frames to be
8384 selected. The @var{frame-selection-spec} can be any of the following:
8389 @item level @var{num}
8390 Select frame level @var{num}. Recall that frame zero is the innermost
8391 (currently executing) frame, frame one is the frame that called the
8392 innermost one, and so on. The highest level frame is usually the one
8395 As this is the most common method of navigating the frame stack, the
8396 string @command{level} can be omitted. For example, the following two
8397 commands are equivalent:
8400 (@value{GDBP}) frame 3
8401 (@value{GDBP}) frame level 3
8404 @kindex frame address
8405 @item address @var{stack-address}
8406 Select the frame with stack address @var{stack-address}. The
8407 @var{stack-address} for a frame can be seen in the output of
8408 @command{info frame}, for example:
8412 Stack level 1, frame at 0x7fffffffda30:
8413 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
8414 tail call frame, caller of frame at 0x7fffffffda30
8415 source language c++.
8416 Arglist at unknown address.
8417 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
8420 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
8421 indicated by the line:
8424 Stack level 1, frame at 0x7fffffffda30:
8427 @kindex frame function
8428 @item function @var{function-name}
8429 Select the stack frame for function @var{function-name}. If there are
8430 multiple stack frames for function @var{function-name} then the inner
8431 most stack frame is selected.
8434 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
8435 View a frame that is not part of @value{GDBN}'s backtrace. The frame
8436 viewed has stack address @var{stack-addr}, and optionally, a program
8437 counter address of @var{pc-addr}.
8439 This is useful mainly if the chaining of stack frames has been
8440 damaged by a bug, making it impossible for @value{GDBN} to assign
8441 numbers properly to all frames. In addition, this can be useful
8442 when your program has multiple stacks and switches between them.
8444 When viewing a frame outside the current backtrace using
8445 @command{frame view} then you can always return to the original
8446 stack using one of the previous stack frame selection instructions,
8447 for example @command{frame level 0}.
8453 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
8454 numbers @var{n}, this advances toward the outermost frame, to higher
8455 frame numbers, to frames that have existed longer.
8458 @kindex do @r{(@code{down})}
8460 Move @var{n} frames down the stack; @var{n} defaults to 1. For
8461 positive numbers @var{n}, this advances toward the innermost frame, to
8462 lower frame numbers, to frames that were created more recently.
8463 You may abbreviate @code{down} as @code{do}.
8466 All of these commands end by printing two lines of output describing the
8467 frame. The first line shows the frame number, the function name, the
8468 arguments, and the source file and line number of execution in that
8469 frame. The second line shows the text of that source line.
8477 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
8479 10 read_input_file (argv[i]);
8483 After such a printout, the @code{list} command with no arguments
8484 prints ten lines centered on the point of execution in the frame.
8485 You can also edit the program at the point of execution with your favorite
8486 editing program by typing @code{edit}.
8487 @xref{List, ,Printing Source Lines},
8491 @kindex select-frame
8492 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
8493 The @code{select-frame} command is a variant of @code{frame} that does
8494 not display the new frame after selecting it. This command is
8495 intended primarily for use in @value{GDBN} command scripts, where the
8496 output might be unnecessary and distracting. The
8497 @var{frame-selection-spec} is as for the @command{frame} command
8498 described in @ref{Selection, ,Selecting a Frame}.
8500 @kindex down-silently
8502 @item up-silently @var{n}
8503 @itemx down-silently @var{n}
8504 These two commands are variants of @code{up} and @code{down},
8505 respectively; they differ in that they do their work silently, without
8506 causing display of the new frame. They are intended primarily for use
8507 in @value{GDBN} command scripts, where the output might be unnecessary and
8512 @section Information About a Frame
8514 There are several other commands to print information about the selected
8520 When used without any argument, this command does not change which
8521 frame is selected, but prints a brief description of the currently
8522 selected stack frame. It can be abbreviated @code{f}. With an
8523 argument, this command is used to select a stack frame.
8524 @xref{Selection, ,Selecting a Frame}.
8527 @kindex info f @r{(@code{info frame})}
8530 This command prints a verbose description of the selected stack frame,
8535 the address of the frame
8537 the address of the next frame down (called by this frame)
8539 the address of the next frame up (caller of this frame)
8541 the language in which the source code corresponding to this frame is written
8543 the address of the frame's arguments
8545 the address of the frame's local variables
8547 the program counter saved in it (the address of execution in the caller frame)
8549 which registers were saved in the frame
8552 @noindent The verbose description is useful when
8553 something has gone wrong that has made the stack format fail to fit
8554 the usual conventions.
8556 @item info frame @r{[} @var{frame-selection-spec} @r{]}
8557 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
8558 Print a verbose description of the frame selected by
8559 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
8560 same as for the @command{frame} command (@pxref{Selection, ,Selecting
8561 a Frame}). The selected frame remains unchanged by this command.
8564 @item info args [-q]
8565 Print the arguments of the selected frame, each on a separate line.
8567 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8568 printing header information and messages explaining why no argument
8571 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
8572 Like @kbd{info args}, but only print the arguments selected
8573 with the provided regexp(s).
8575 If @var{regexp} is provided, print only the arguments whose names
8576 match the regular expression @var{regexp}.
8578 If @var{type_regexp} is provided, print only the arguments whose
8579 types, as printed by the @code{whatis} command, match
8580 the regular expression @var{type_regexp}.
8581 If @var{type_regexp} contains space(s), it should be enclosed in
8582 quote characters. If needed, use backslash to escape the meaning
8583 of special characters or quotes.
8585 If both @var{regexp} and @var{type_regexp} are provided, an argument
8586 is printed only if its name matches @var{regexp} and its type matches
8589 @item info locals [-q]
8591 Print the local variables of the selected frame, each on a separate
8592 line. These are all variables (declared either static or automatic)
8593 accessible at the point of execution of the selected frame.
8595 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
8596 printing header information and messages explaining why no local variables
8599 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
8600 Like @kbd{info locals}, but only print the local variables selected
8601 with the provided regexp(s).
8603 If @var{regexp} is provided, print only the local variables whose names
8604 match the regular expression @var{regexp}.
8606 If @var{type_regexp} is provided, print only the local variables whose
8607 types, as printed by the @code{whatis} command, match
8608 the regular expression @var{type_regexp}.
8609 If @var{type_regexp} contains space(s), it should be enclosed in
8610 quote characters. If needed, use backslash to escape the meaning
8611 of special characters or quotes.
8613 If both @var{regexp} and @var{type_regexp} are provided, a local variable
8614 is printed only if its name matches @var{regexp} and its type matches
8617 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
8618 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
8619 For example, your program might use Resource Acquisition Is
8620 Initialization types (RAII) such as @code{lock_something_t}: each
8621 local variable of type @code{lock_something_t} automatically places a
8622 lock that is destroyed when the variable goes out of scope. You can
8623 then list all acquired locks in your program by doing
8625 thread apply all -s frame apply all -s info locals -q -t lock_something_t
8628 or the equivalent shorter form
8630 tfaas i lo -q -t lock_something_t
8636 @section Applying a Command to Several Frames.
8638 @cindex apply command to several frames
8640 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{option}]@dots{} @var{command}
8641 The @code{frame apply} command allows you to apply the named
8642 @var{command} to one or more frames.
8646 Specify @code{all} to apply @var{command} to all frames.
8649 Use @var{count} to apply @var{command} to the innermost @var{count}
8650 frames, where @var{count} is a positive number.
8653 Use @var{-count} to apply @var{command} to the outermost @var{count}
8654 frames, where @var{count} is a positive number.
8657 Use @code{level} to apply @var{command} to the set of frames identified
8658 by the @var{level} list. @var{level} is a frame level or a range of frame
8659 levels as @var{level1}-@var{level2}. The frame level is the number shown
8660 in the first field of the @samp{backtrace} command output.
8661 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
8662 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
8666 Note that the frames on which @code{frame apply} applies a command are
8667 also influenced by the @code{set backtrace} settings such as @code{set
8668 backtrace past-main} and @code{set backtrace limit N}.
8669 @xref{Backtrace,,Backtraces}.
8671 The @code{frame apply} command also supports a number of options that
8672 allow overriding relevant @code{set backtrace} settings:
8675 @item -past-main [@code{on}|@code{off}]
8676 Whether backtraces should continue past @code{main}.
8677 Related setting: @ref{set backtrace past-main}.
8679 @item -past-entry [@code{on}|@code{off}]
8680 Whether backtraces should continue past the entry point of a program.
8681 Related setting: @ref{set backtrace past-entry}.
8684 By default, @value{GDBN} displays some frame information before the
8685 output produced by @var{command}, and an error raised during the
8686 execution of a @var{command} will abort @code{frame apply}. The
8687 following options can be used to fine-tune these behaviors:
8691 The flag @code{-c}, which stands for @samp{continue}, causes any
8692 errors in @var{command} to be displayed, and the execution of
8693 @code{frame apply} then continues.
8695 The flag @code{-s}, which stands for @samp{silent}, causes any errors
8696 or empty output produced by a @var{command} to be silently ignored.
8697 That is, the execution continues, but the frame information and errors
8700 The flag @code{-q} (@samp{quiet}) disables printing the frame
8704 The following example shows how the flags @code{-c} and @code{-s} are
8705 working when applying the command @code{p j} to all frames, where
8706 variable @code{j} can only be successfully printed in the outermost
8707 @code{#1 main} frame.
8711 (gdb) frame apply all p j
8712 #0 some_function (i=5) at fun.c:4
8713 No symbol "j" in current context.
8714 (gdb) frame apply all -c p j
8715 #0 some_function (i=5) at fun.c:4
8716 No symbol "j" in current context.
8717 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8719 (gdb) frame apply all -s p j
8720 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8726 By default, @samp{frame apply}, prints the frame location
8727 information before the command output:
8731 (gdb) frame apply all p $sp
8732 #0 some_function (i=5) at fun.c:4
8733 $4 = (void *) 0xffffd1e0
8734 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8735 $5 = (void *) 0xffffd1f0
8740 If the flag @code{-q} is given, no frame information is printed:
8743 (gdb) frame apply all -q p $sp
8744 $12 = (void *) 0xffffd1e0
8745 $13 = (void *) 0xffffd1f0
8755 @cindex apply a command to all frames (ignoring errors and empty output)
8756 @item faas @var{command}
8757 Shortcut for @code{frame apply all -s @var{command}}.
8758 Applies @var{command} on all frames, ignoring errors and empty output.
8760 It can for example be used to print a local variable or a function
8761 argument without knowing the frame where this variable or argument
8764 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8767 The @code{faas} command accepts the same options as the @code{frame
8768 apply} command. @xref{Frame Apply,,frame apply}.
8770 Note that the command @code{tfaas @var{command}} applies @var{command}
8771 on all frames of all threads. See @xref{Threads,,Threads}.
8775 @node Frame Filter Management
8776 @section Management of Frame Filters.
8777 @cindex managing frame filters
8779 Frame filters are Python based utilities to manage and decorate the
8780 output of frames. @xref{Frame Filter API}, for further information.
8782 Managing frame filters is performed by several commands available
8783 within @value{GDBN}, detailed here.
8786 @kindex info frame-filter
8787 @item info frame-filter
8788 Print a list of installed frame filters from all dictionaries, showing
8789 their name, priority and enabled status.
8791 @kindex disable frame-filter
8792 @anchor{disable frame-filter all}
8793 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8794 Disable a frame filter in the dictionary matching
8795 @var{filter-dictionary} and @var{filter-name}. The
8796 @var{filter-dictionary} may be @code{all}, @code{global},
8797 @code{progspace}, or the name of the object file where the frame filter
8798 dictionary resides. When @code{all} is specified, all frame filters
8799 across all dictionaries are disabled. The @var{filter-name} is the name
8800 of the frame filter and is used when @code{all} is not the option for
8801 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8802 may be enabled again later.
8804 @kindex enable frame-filter
8805 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8806 Enable a frame filter in the dictionary matching
8807 @var{filter-dictionary} and @var{filter-name}. The
8808 @var{filter-dictionary} may be @code{all}, @code{global},
8809 @code{progspace} or the name of the object file where the frame filter
8810 dictionary resides. When @code{all} is specified, all frame filters across
8811 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8812 filter and is used when @code{all} is not the option for
8813 @var{filter-dictionary}.
8818 (gdb) info frame-filter
8820 global frame-filters:
8821 Priority Enabled Name
8822 1000 No PrimaryFunctionFilter
8825 progspace /build/test frame-filters:
8826 Priority Enabled Name
8827 100 Yes ProgspaceFilter
8829 objfile /build/test frame-filters:
8830 Priority Enabled Name
8831 999 Yes BuildProgramFilter
8833 (gdb) disable frame-filter /build/test BuildProgramFilter
8834 (gdb) info frame-filter
8836 global frame-filters:
8837 Priority Enabled Name
8838 1000 No PrimaryFunctionFilter
8841 progspace /build/test frame-filters:
8842 Priority Enabled Name
8843 100 Yes ProgspaceFilter
8845 objfile /build/test frame-filters:
8846 Priority Enabled Name
8847 999 No BuildProgramFilter
8849 (gdb) enable frame-filter global PrimaryFunctionFilter
8850 (gdb) info frame-filter
8852 global frame-filters:
8853 Priority Enabled Name
8854 1000 Yes PrimaryFunctionFilter
8857 progspace /build/test frame-filters:
8858 Priority Enabled Name
8859 100 Yes ProgspaceFilter
8861 objfile /build/test frame-filters:
8862 Priority Enabled Name
8863 999 No BuildProgramFilter
8866 @kindex set frame-filter priority
8867 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8868 Set the @var{priority} of a frame filter in the dictionary matching
8869 @var{filter-dictionary}, and the frame filter name matching
8870 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8871 @code{progspace} or the name of the object file where the frame filter
8872 dictionary resides. The @var{priority} is an integer.
8874 @kindex show frame-filter priority
8875 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8876 Show the @var{priority} of a frame filter in the dictionary matching
8877 @var{filter-dictionary}, and the frame filter name matching
8878 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8879 @code{progspace} or the name of the object file where the frame filter
8885 (gdb) info frame-filter
8887 global frame-filters:
8888 Priority Enabled Name
8889 1000 Yes PrimaryFunctionFilter
8892 progspace /build/test frame-filters:
8893 Priority Enabled Name
8894 100 Yes ProgspaceFilter
8896 objfile /build/test frame-filters:
8897 Priority Enabled Name
8898 999 No BuildProgramFilter
8900 (gdb) set frame-filter priority global Reverse 50
8901 (gdb) info frame-filter
8903 global frame-filters:
8904 Priority Enabled Name
8905 1000 Yes PrimaryFunctionFilter
8908 progspace /build/test frame-filters:
8909 Priority Enabled Name
8910 100 Yes ProgspaceFilter
8912 objfile /build/test frame-filters:
8913 Priority Enabled Name
8914 999 No BuildProgramFilter
8919 @chapter Examining Source Files
8921 @value{GDBN} can print parts of your program's source, since the debugging
8922 information recorded in the program tells @value{GDBN} what source files were
8923 used to build it. When your program stops, @value{GDBN} spontaneously prints
8924 the line where it stopped. Likewise, when you select a stack frame
8925 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8926 execution in that frame has stopped. You can print other portions of
8927 source files by explicit command.
8929 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8930 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8931 @value{GDBN} under @sc{gnu} Emacs}.
8934 * List:: Printing source lines
8935 * Specify Location:: How to specify code locations
8936 * Edit:: Editing source files
8937 * Search:: Searching source files
8938 * Source Path:: Specifying source directories
8939 * Machine Code:: Source and machine code
8940 * Disable Reading Source:: Disable Reading Source Code
8944 @section Printing Source Lines
8947 @kindex l @r{(@code{list})}
8948 To print lines from a source file, use the @code{list} command
8949 (abbreviated @code{l}). By default, ten lines are printed.
8950 There are several ways to specify what part of the file you want to
8951 print; see @ref{Specify Location}, for the full list.
8953 Here are the forms of the @code{list} command most commonly used:
8956 @item list @var{linenum}
8957 Print lines centered around line number @var{linenum} in the
8958 current source file.
8960 @item list @var{function}
8961 Print lines centered around the beginning of function
8965 Print more lines. If the last lines printed were printed with a
8966 @code{list} command, this prints lines following the last lines
8967 printed; however, if the last line printed was a solitary line printed
8968 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8969 Stack}), this prints lines centered around that line.
8972 Print lines just before the lines last printed.
8975 @cindex @code{list}, how many lines to display
8976 By default, @value{GDBN} prints ten source lines with any of these forms of
8977 the @code{list} command. You can change this using @code{set listsize}:
8980 @kindex set listsize
8981 @item set listsize @var{count}
8982 @itemx set listsize unlimited
8983 Make the @code{list} command display @var{count} source lines (unless
8984 the @code{list} argument explicitly specifies some other number).
8985 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8987 @kindex show listsize
8989 Display the number of lines that @code{list} prints.
8992 Repeating a @code{list} command with @key{RET} discards the argument,
8993 so it is equivalent to typing just @code{list}. This is more useful
8994 than listing the same lines again. An exception is made for an
8995 argument of @samp{-}; that argument is preserved in repetition so that
8996 each repetition moves up in the source file.
8998 In general, the @code{list} command expects you to supply zero, one or two
8999 @dfn{locations}. Locations specify source lines; there are several ways
9000 of writing them (@pxref{Specify Location}), but the effect is always
9001 to specify some source line.
9003 Here is a complete description of the possible arguments for @code{list}:
9006 @item list @var{location}
9007 Print lines centered around the line specified by @var{location}.
9009 @item list @var{first},@var{last}
9010 Print lines from @var{first} to @var{last}. Both arguments are
9011 locations. When a @code{list} command has two locations, and the
9012 source file of the second location is omitted, this refers to
9013 the same source file as the first location.
9015 @item list ,@var{last}
9016 Print lines ending with @var{last}.
9018 @item list @var{first},
9019 Print lines starting with @var{first}.
9022 Print lines just after the lines last printed.
9025 Print lines just before the lines last printed.
9028 As described in the preceding table.
9031 @node Specify Location
9032 @section Specifying a Location
9033 @cindex specifying location
9035 @cindex source location
9037 Several @value{GDBN} commands accept arguments that specify a location
9038 of your program's code. Since @value{GDBN} is a source-level
9039 debugger, a location usually specifies some line in the source code.
9040 Locations may be specified using three different formats:
9041 linespec locations, explicit locations, or address locations.
9044 * Linespec Locations:: Linespec locations
9045 * Explicit Locations:: Explicit locations
9046 * Address Locations:: Address locations
9049 @node Linespec Locations
9050 @subsection Linespec Locations
9051 @cindex linespec locations
9053 A @dfn{linespec} is a colon-separated list of source location parameters such
9054 as file name, function name, etc. Here are all the different ways of
9055 specifying a linespec:
9059 Specifies the line number @var{linenum} of the current source file.
9062 @itemx +@var{offset}
9063 Specifies the line @var{offset} lines before or after the @dfn{current
9064 line}. For the @code{list} command, the current line is the last one
9065 printed; for the breakpoint commands, this is the line at which
9066 execution stopped in the currently selected @dfn{stack frame}
9067 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
9068 used as the second of the two linespecs in a @code{list} command,
9069 this specifies the line @var{offset} lines up or down from the first
9072 @item @var{filename}:@var{linenum}
9073 Specifies the line @var{linenum} in the source file @var{filename}.
9074 If @var{filename} is a relative file name, then it will match any
9075 source file name with the same trailing components. For example, if
9076 @var{filename} is @samp{gcc/expr.c}, then it will match source file
9077 name of @file{/build/trunk/gcc/expr.c}, but not
9078 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
9080 @item @var{function}
9081 Specifies the line that begins the body of the function @var{function}.
9082 For example, in C, this is the line with the open brace.
9084 By default, in C@t{++} and Ada, @var{function} is interpreted as
9085 specifying all functions named @var{function} in all scopes. For
9086 C@t{++}, this means in all namespaces and classes. For Ada, this
9087 means in all packages.
9089 For example, assuming a program with C@t{++} symbols named
9090 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9091 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
9093 Commands that accept a linespec let you override this with the
9094 @code{-qualified} option. For example, @w{@kbd{break -qualified
9095 func}} sets a breakpoint on a free-function named @code{func} ignoring
9096 any C@t{++} class methods and namespace functions called @code{func}.
9098 @xref{Explicit Locations}.
9100 @item @var{function}:@var{label}
9101 Specifies the line where @var{label} appears in @var{function}.
9103 @item @var{filename}:@var{function}
9104 Specifies the line that begins the body of the function @var{function}
9105 in the file @var{filename}. You only need the file name with a
9106 function name to avoid ambiguity when there are identically named
9107 functions in different source files.
9110 Specifies the line at which the label named @var{label} appears
9111 in the function corresponding to the currently selected stack frame.
9112 If there is no current selected stack frame (for instance, if the inferior
9113 is not running), then @value{GDBN} will not search for a label.
9115 @cindex breakpoint at static probe point
9116 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
9117 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
9118 applications to embed static probes. @xref{Static Probe Points}, for more
9119 information on finding and using static probes. This form of linespec
9120 specifies the location of such a static probe.
9122 If @var{objfile} is given, only probes coming from that shared library
9123 or executable matching @var{objfile} as a regular expression are considered.
9124 If @var{provider} is given, then only probes from that provider are considered.
9125 If several probes match the spec, @value{GDBN} will insert a breakpoint at
9126 each one of those probes.
9129 @node Explicit Locations
9130 @subsection Explicit Locations
9131 @cindex explicit locations
9133 @dfn{Explicit locations} allow the user to directly specify the source
9134 location's parameters using option-value pairs.
9136 Explicit locations are useful when several functions, labels, or
9137 file names have the same name (base name for files) in the program's
9138 sources. In these cases, explicit locations point to the source
9139 line you meant more accurately and unambiguously. Also, using
9140 explicit locations might be faster in large programs.
9142 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
9143 defined in the file named @file{foo} or the label @code{bar} in a function
9144 named @code{foo}. @value{GDBN} must search either the file system or
9145 the symbol table to know.
9147 The list of valid explicit location options is summarized in the
9151 @item -source @var{filename}
9152 The value specifies the source file name. To differentiate between
9153 files with the same base name, prepend as many directories as is necessary
9154 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
9155 @value{GDBN} will use the first file it finds with the given base
9156 name. This option requires the use of either @code{-function} or @code{-line}.
9158 @item -function @var{function}
9159 The value specifies the name of a function. Operations
9160 on function locations unmodified by other options (such as @code{-label}
9161 or @code{-line}) refer to the line that begins the body of the function.
9162 In C, for example, this is the line with the open brace.
9164 By default, in C@t{++} and Ada, @var{function} is interpreted as
9165 specifying all functions named @var{function} in all scopes. For
9166 C@t{++}, this means in all namespaces and classes. For Ada, this
9167 means in all packages.
9169 For example, assuming a program with C@t{++} symbols named
9170 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
9171 -function func}} and @w{@kbd{break -function B::func}} set a
9172 breakpoint on both symbols.
9174 You can use the @kbd{-qualified} flag to override this (see below).
9178 This flag makes @value{GDBN} interpret a function name specified with
9179 @kbd{-function} as a complete fully-qualified name.
9181 For example, assuming a C@t{++} program with symbols named
9182 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
9183 -function B::func}} command sets a breakpoint on @code{B::func}, only.
9185 (Note: the @kbd{-qualified} option can precede a linespec as well
9186 (@pxref{Linespec Locations}), so the particular example above could be
9187 simplified as @w{@kbd{break -qualified B::func}}.)
9189 @item -label @var{label}
9190 The value specifies the name of a label. When the function
9191 name is not specified, the label is searched in the function of the currently
9192 selected stack frame.
9194 @item -line @var{number}
9195 The value specifies a line offset for the location. The offset may either
9196 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
9197 the command. When specified without any other options, the line offset is
9198 relative to the current line.
9201 Explicit location options may be abbreviated by omitting any non-unique
9202 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
9204 @node Address Locations
9205 @subsection Address Locations
9206 @cindex address locations
9208 @dfn{Address locations} indicate a specific program address. They have
9209 the generalized form *@var{address}.
9211 For line-oriented commands, such as @code{list} and @code{edit}, this
9212 specifies a source line that contains @var{address}. For @code{break} and
9213 other breakpoint-oriented commands, this can be used to set breakpoints in
9214 parts of your program which do not have debugging information or
9217 Here @var{address} may be any expression valid in the current working
9218 language (@pxref{Languages, working language}) that specifies a code
9219 address. In addition, as a convenience, @value{GDBN} extends the
9220 semantics of expressions used in locations to cover several situations
9221 that frequently occur during debugging. Here are the various forms
9225 @item @var{expression}
9226 Any expression valid in the current working language.
9228 @item @var{funcaddr}
9229 An address of a function or procedure derived from its name. In C,
9230 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
9231 simply the function's name @var{function} (and actually a special case
9232 of a valid expression). In Pascal and Modula-2, this is
9233 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
9234 (although the Pascal form also works).
9236 This form specifies the address of the function's first instruction,
9237 before the stack frame and arguments have been set up.
9239 @item '@var{filename}':@var{funcaddr}
9240 Like @var{funcaddr} above, but also specifies the name of the source
9241 file explicitly. This is useful if the name of the function does not
9242 specify the function unambiguously, e.g., if there are several
9243 functions with identical names in different source files.
9247 @section Editing Source Files
9248 @cindex editing source files
9251 @kindex e @r{(@code{edit})}
9252 To edit the lines in a source file, use the @code{edit} command.
9253 The editing program of your choice
9254 is invoked with the current line set to
9255 the active line in the program.
9256 Alternatively, there are several ways to specify what part of the file you
9257 want to print if you want to see other parts of the program:
9260 @item edit @var{location}
9261 Edit the source file specified by @code{location}. Editing starts at
9262 that @var{location}, e.g., at the specified source line of the
9263 specified file. @xref{Specify Location}, for all the possible forms
9264 of the @var{location} argument; here are the forms of the @code{edit}
9265 command most commonly used:
9268 @item edit @var{number}
9269 Edit the current source file with @var{number} as the active line number.
9271 @item edit @var{function}
9272 Edit the file containing @var{function} at the beginning of its definition.
9277 @subsection Choosing your Editor
9278 You can customize @value{GDBN} to use any editor you want
9280 The only restriction is that your editor (say @code{ex}), recognizes the
9281 following command-line syntax:
9283 ex +@var{number} file
9285 The optional numeric value +@var{number} specifies the number of the line in
9286 the file where to start editing.}.
9287 By default, it is @file{@value{EDITOR}}, but you can change this
9288 by setting the environment variable @env{EDITOR} before using
9289 @value{GDBN}. For example, to configure @value{GDBN} to use the
9290 @code{vi} editor, you could use these commands with the @code{sh} shell:
9296 or in the @code{csh} shell,
9298 setenv EDITOR /usr/bin/vi
9303 @section Searching Source Files
9304 @cindex searching source files
9306 There are two commands for searching through the current source file for a
9311 @kindex forward-search
9312 @kindex fo @r{(@code{forward-search})}
9313 @item forward-search @var{regexp}
9314 @itemx search @var{regexp}
9315 The command @samp{forward-search @var{regexp}} checks each line,
9316 starting with the one following the last line listed, for a match for
9317 @var{regexp}. It lists the line that is found. You can use the
9318 synonym @samp{search @var{regexp}} or abbreviate the command name as
9321 @kindex reverse-search
9322 @item reverse-search @var{regexp}
9323 The command @samp{reverse-search @var{regexp}} checks each line, starting
9324 with the one before the last line listed and going backward, for a match
9325 for @var{regexp}. It lists the line that is found. You can abbreviate
9326 this command as @code{rev}.
9330 @section Specifying Source Directories
9333 @cindex directories for source files
9334 Executable programs sometimes do not record the directories of the source
9335 files from which they were compiled, just the names. Even when they do,
9336 the directories could be moved between the compilation and your debugging
9337 session. @value{GDBN} has a list of directories to search for source files;
9338 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
9339 it tries all the directories in the list, in the order they are present
9340 in the list, until it finds a file with the desired name.
9342 For example, suppose an executable references the file
9343 @file{/usr/src/foo-1.0/lib/foo.c}, does not record a compilation
9344 directory, and the @dfn{source path} is @file{/mnt/cross}.
9345 @value{GDBN} would look for the source file in the following
9350 @item @file{/usr/src/foo-1.0/lib/foo.c}
9351 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9352 @item @file{/mnt/cross/foo.c}
9356 If the source file is not present at any of the above locations then
9357 an error is printed. @value{GDBN} does not look up the parts of the
9358 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
9359 Likewise, the subdirectories of the source path are not searched: if
9360 the source path is @file{/mnt/cross}, and the binary refers to
9361 @file{foo.c}, @value{GDBN} would not find it under
9362 @file{/mnt/cross/usr/src/foo-1.0/lib}.
9364 Plain file names, relative file names with leading directories, file
9365 names containing dots, etc.@: are all treated as described above,
9366 except that non-absolute file names are not looked up literally. If
9367 the @dfn{source path} is @file{/mnt/cross}, the source file is
9368 recorded as @file{../lib/foo.c}, and no compilation directory is
9369 recorded, then @value{GDBN} will search in the following locations:
9373 @item @file{/mnt/cross/../lib/foo.c}
9374 @item @file{/mnt/cross/foo.c}
9380 @vindex $cdir@r{, convenience variable}
9381 @vindex $cwd@r{, convenience variable}
9382 @cindex compilation directory
9383 @cindex current directory
9384 @cindex working directory
9385 @cindex directory, current
9386 @cindex directory, compilation
9387 The @dfn{source path} will always include two special entries
9388 @samp{$cdir} and @samp{$cwd}, these refer to the compilation directory
9389 (if one is recorded) and the current working directory respectively.
9391 @samp{$cdir} causes @value{GDBN} to search within the compilation
9392 directory, if one is recorded in the debug information. If no
9393 compilation directory is recorded in the debug information then
9394 @samp{$cdir} is ignored.
9396 @samp{$cwd} is not the same as @samp{.}---the former tracks the
9397 current working directory as it changes during your @value{GDBN}
9398 session, while the latter is immediately expanded to the current
9399 directory at the time you add an entry to the source path.
9401 If a compilation directory is recorded in the debug information, and
9402 @value{GDBN} has not found the source file after the first search
9403 using @dfn{source path}, then @value{GDBN} will combine the
9404 compilation directory and the filename, and then search for the source
9405 file again using the @dfn{source path}.
9407 For example, if the executable records the source file as
9408 @file{/usr/src/foo-1.0/lib/foo.c}, the compilation directory is
9409 recorded as @file{/project/build}, and the @dfn{source path} is
9410 @file{/mnt/cross:$cdir:$cwd} while the current working directory of
9411 the @value{GDBN} session is @file{/home/user}, then @value{GDBN} will
9412 search for the source file in the following locations:
9416 @item @file{/usr/src/foo-1.0/lib/foo.c}
9417 @item @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c}
9418 @item @file{/project/build/usr/src/foo-1.0/lib/foo.c}
9419 @item @file{/home/user/usr/src/foo-1.0/lib/foo.c}
9420 @item @file{/mnt/cross/project/build/usr/src/foo-1.0/lib/foo.c}
9421 @item @file{/project/build/project/build/usr/src/foo-1.0/lib/foo.c}
9422 @item @file{/home/user/project/build/usr/src/foo-1.0/lib/foo.c}
9423 @item @file{/mnt/cross/foo.c}
9424 @item @file{/project/build/foo.c}
9425 @item @file{/home/user/foo.c}
9429 If the file name in the previous example had been recorded in the
9430 executable as a relative path rather than an absolute path, then the
9431 first look up would not have occurred, but all of the remaining steps
9434 When searching for source files on MS-DOS and MS-Windows, where
9435 absolute paths start with a drive letter (e.g.@:
9436 @file{C:/project/foo.c}), @value{GDBN} will remove the drive letter
9437 from the file name before appending it to a search directory from
9438 @dfn{source path}; for instance if the executable references the
9439 source file @file{C:/project/foo.c} and @dfn{source path} is set to
9440 @file{D:/mnt/cross}, then @value{GDBN} will search in the following
9441 locations for the source file:
9445 @item @file{C:/project/foo.c}
9446 @item @file{D:/mnt/cross/project/foo.c}
9447 @item @file{D:/mnt/cross/foo.c}
9451 Note that the executable search path is @emph{not} used to locate the
9454 Whenever you reset or rearrange the source path, @value{GDBN} clears out
9455 any information it has cached about where source files are found and where
9456 each line is in the file.
9460 When you start @value{GDBN}, its source path includes only @samp{$cdir}
9461 and @samp{$cwd}, in that order.
9462 To add other directories, use the @code{directory} command.
9464 The search path is used to find both program source files and @value{GDBN}
9465 script files (read using the @samp{-command} option and @samp{source} command).
9467 In addition to the source path, @value{GDBN} provides a set of commands
9468 that manage a list of source path substitution rules. A @dfn{substitution
9469 rule} specifies how to rewrite source directories stored in the program's
9470 debug information in case the sources were moved to a different
9471 directory between compilation and debugging. A rule is made of
9472 two strings, the first specifying what needs to be rewritten in
9473 the path, and the second specifying how it should be rewritten.
9474 In @ref{set substitute-path}, we name these two parts @var{from} and
9475 @var{to} respectively. @value{GDBN} does a simple string replacement
9476 of @var{from} with @var{to} at the start of the directory part of the
9477 source file name, and uses that result instead of the original file
9478 name to look up the sources.
9480 Using the previous example, suppose the @file{foo-1.0} tree has been
9481 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
9482 @value{GDBN} to replace @file{/usr/src} in all source path names with
9483 @file{/mnt/cross}. The first lookup will then be
9484 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
9485 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
9486 substitution rule, use the @code{set substitute-path} command
9487 (@pxref{set substitute-path}).
9489 To avoid unexpected substitution results, a rule is applied only if the
9490 @var{from} part of the directory name ends at a directory separator.
9491 For instance, a rule substituting @file{/usr/source} into
9492 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
9493 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
9494 is applied only at the beginning of the directory name, this rule will
9495 not be applied to @file{/root/usr/source/baz.c} either.
9497 In many cases, you can achieve the same result using the @code{directory}
9498 command. However, @code{set substitute-path} can be more efficient in
9499 the case where the sources are organized in a complex tree with multiple
9500 subdirectories. With the @code{directory} command, you need to add each
9501 subdirectory of your project. If you moved the entire tree while
9502 preserving its internal organization, then @code{set substitute-path}
9503 allows you to direct the debugger to all the sources with one single
9506 @code{set substitute-path} is also more than just a shortcut command.
9507 The source path is only used if the file at the original location no
9508 longer exists. On the other hand, @code{set substitute-path} modifies
9509 the debugger behavior to look at the rewritten location instead. So, if
9510 for any reason a source file that is not relevant to your executable is
9511 located at the original location, a substitution rule is the only
9512 method available to point @value{GDBN} at the new location.
9514 @cindex @samp{--with-relocated-sources}
9515 @cindex default source path substitution
9516 You can configure a default source path substitution rule by
9517 configuring @value{GDBN} with the
9518 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
9519 should be the name of a directory under @value{GDBN}'s configured
9520 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
9521 directory names in debug information under @var{dir} will be adjusted
9522 automatically if the installed @value{GDBN} is moved to a new
9523 location. This is useful if @value{GDBN}, libraries or executables
9524 with debug information and corresponding source code are being moved
9528 @item directory @var{dirname} @dots{}
9529 @item dir @var{dirname} @dots{}
9530 Add directory @var{dirname} to the front of the source path. Several
9531 directory names may be given to this command, separated by @samp{:}
9532 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
9533 part of absolute file names) or
9534 whitespace. You may specify a directory that is already in the source
9535 path; this moves it forward, so @value{GDBN} searches it sooner.
9537 The special strings @samp{$cdir} (to refer to the compilation
9538 directory, if one is recorded), and @samp{$cwd} (to refer to the
9539 current working directory) can also be included in the list of
9540 directories @var{dirname}. Though these will already be in the source
9541 path they will be moved forward in the list so @value{GDBN} searches
9545 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
9547 @c RET-repeat for @code{directory} is explicitly disabled, but since
9548 @c repeating it would be a no-op we do not say that. (thanks to RMS)
9550 @item set directories @var{path-list}
9551 @kindex set directories
9552 Set the source path to @var{path-list}.
9553 @samp{$cdir:$cwd} are added if missing.
9555 @item show directories
9556 @kindex show directories
9557 Print the source path: show which directories it contains.
9559 @anchor{set substitute-path}
9560 @item set substitute-path @var{from} @var{to}
9561 @kindex set substitute-path
9562 Define a source path substitution rule, and add it at the end of the
9563 current list of existing substitution rules. If a rule with the same
9564 @var{from} was already defined, then the old rule is also deleted.
9566 For example, if the file @file{/foo/bar/baz.c} was moved to
9567 @file{/mnt/cross/baz.c}, then the command
9570 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
9574 will tell @value{GDBN} to replace @samp{/foo/bar} with
9575 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
9576 @file{baz.c} even though it was moved.
9578 In the case when more than one substitution rule have been defined,
9579 the rules are evaluated one by one in the order where they have been
9580 defined. The first one matching, if any, is selected to perform
9583 For instance, if we had entered the following commands:
9586 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
9587 (@value{GDBP}) set substitute-path /usr/src /mnt/src
9591 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
9592 @file{/mnt/include/defs.h} by using the first rule. However, it would
9593 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
9594 @file{/mnt/src/lib/foo.c}.
9597 @item unset substitute-path [path]
9598 @kindex unset substitute-path
9599 If a path is specified, search the current list of substitution rules
9600 for a rule that would rewrite that path. Delete that rule if found.
9601 A warning is emitted by the debugger if no rule could be found.
9603 If no path is specified, then all substitution rules are deleted.
9605 @item show substitute-path [path]
9606 @kindex show substitute-path
9607 If a path is specified, then print the source path substitution rule
9608 which would rewrite that path, if any.
9610 If no path is specified, then print all existing source path substitution
9615 If your source path is cluttered with directories that are no longer of
9616 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
9617 versions of source. You can correct the situation as follows:
9621 Use @code{directory} with no argument to reset the source path to its default value.
9624 Use @code{directory} with suitable arguments to reinstall the
9625 directories you want in the source path. You can add all the
9626 directories in one command.
9630 @section Source and Machine Code
9631 @cindex source line and its code address
9633 You can use the command @code{info line} to map source lines to program
9634 addresses (and vice versa), and the command @code{disassemble} to display
9635 a range of addresses as machine instructions. You can use the command
9636 @code{set disassemble-next-line} to set whether to disassemble next
9637 source line when execution stops. When run under @sc{gnu} Emacs
9638 mode, the @code{info line} command causes the arrow to point to the
9639 line specified. Also, @code{info line} prints addresses in symbolic form as
9645 @itemx info line @var{location}
9646 Print the starting and ending addresses of the compiled code for
9647 source line @var{location}. You can specify source lines in any of
9648 the ways documented in @ref{Specify Location}. With no @var{location}
9649 information about the current source line is printed.
9652 For example, we can use @code{info line} to discover the location of
9653 the object code for the first line of function
9654 @code{m4_changequote}:
9657 (@value{GDBP}) info line m4_changequote
9658 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
9659 ends at 0x6350 <m4_changequote+4>.
9663 @cindex code address and its source line
9664 We can also inquire (using @code{*@var{addr}} as the form for
9665 @var{location}) what source line covers a particular address:
9667 (@value{GDBP}) info line *0x63ff
9668 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
9669 ends at 0x6404 <m4_changequote+184>.
9672 @cindex @code{$_} and @code{info line}
9673 @cindex @code{x} command, default address
9674 @kindex x@r{(examine), and} info line
9675 After @code{info line}, the default address for the @code{x} command
9676 is changed to the starting address of the line, so that @samp{x/i} is
9677 sufficient to begin examining the machine code (@pxref{Memory,
9678 ,Examining Memory}). Also, this address is saved as the value of the
9679 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
9682 @cindex info line, repeated calls
9683 After @code{info line}, using @code{info line} again without
9684 specifying a location will display information about the next source
9689 @cindex assembly instructions
9690 @cindex instructions, assembly
9691 @cindex machine instructions
9692 @cindex listing machine instructions
9694 @itemx disassemble /m
9695 @itemx disassemble /s
9696 @itemx disassemble /r
9697 This specialized command dumps a range of memory as machine
9698 instructions. It can also print mixed source+disassembly by specifying
9699 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
9700 as well as in symbolic form by specifying the @code{/r} modifier.
9701 The default memory range is the function surrounding the
9702 program counter of the selected frame. A single argument to this
9703 command is a program counter value; @value{GDBN} dumps the function
9704 surrounding this value. When two arguments are given, they should
9705 be separated by a comma, possibly surrounded by whitespace. The
9706 arguments specify a range of addresses to dump, in one of two forms:
9709 @item @var{start},@var{end}
9710 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
9711 @item @var{start},+@var{length}
9712 the addresses from @var{start} (inclusive) to
9713 @code{@var{start}+@var{length}} (exclusive).
9717 When 2 arguments are specified, the name of the function is also
9718 printed (since there could be several functions in the given range).
9720 The argument(s) can be any expression yielding a numeric value, such as
9721 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
9723 If the range of memory being disassembled contains current program counter,
9724 the instruction at that location is shown with a @code{=>} marker.
9727 The following example shows the disassembly of a range of addresses of
9728 HP PA-RISC 2.0 code:
9731 (@value{GDBP}) disas 0x32c4, 0x32e4
9732 Dump of assembler code from 0x32c4 to 0x32e4:
9733 0x32c4 <main+204>: addil 0,dp
9734 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
9735 0x32cc <main+212>: ldil 0x3000,r31
9736 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
9737 0x32d4 <main+220>: ldo 0(r31),rp
9738 0x32d8 <main+224>: addil -0x800,dp
9739 0x32dc <main+228>: ldo 0x588(r1),r26
9740 0x32e0 <main+232>: ldil 0x3000,r31
9741 End of assembler dump.
9744 Here is an example showing mixed source+assembly for Intel x86
9745 with @code{/m} or @code{/s}, when the program is stopped just after
9746 function prologue in a non-optimized function with no inline code.
9749 (@value{GDBP}) disas /m main
9750 Dump of assembler code for function main:
9752 0x08048330 <+0>: push %ebp
9753 0x08048331 <+1>: mov %esp,%ebp
9754 0x08048333 <+3>: sub $0x8,%esp
9755 0x08048336 <+6>: and $0xfffffff0,%esp
9756 0x08048339 <+9>: sub $0x10,%esp
9758 6 printf ("Hello.\n");
9759 => 0x0804833c <+12>: movl $0x8048440,(%esp)
9760 0x08048343 <+19>: call 0x8048284 <puts@@plt>
9764 0x08048348 <+24>: mov $0x0,%eax
9765 0x0804834d <+29>: leave
9766 0x0804834e <+30>: ret
9768 End of assembler dump.
9771 The @code{/m} option is deprecated as its output is not useful when
9772 there is either inlined code or re-ordered code.
9773 The @code{/s} option is the preferred choice.
9774 Here is an example for AMD x86-64 showing the difference between
9775 @code{/m} output and @code{/s} output.
9776 This example has one inline function defined in a header file,
9777 and the code is compiled with @samp{-O2} optimization.
9778 Note how the @code{/m} output is missing the disassembly of
9779 several instructions that are present in the @code{/s} output.
9809 (@value{GDBP}) disas /m main
9810 Dump of assembler code for function main:
9814 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9815 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9819 0x000000000040041d <+29>: xor %eax,%eax
9820 0x000000000040041f <+31>: retq
9821 0x0000000000400420 <+32>: add %eax,%eax
9822 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9824 End of assembler dump.
9825 (@value{GDBP}) disas /s main
9826 Dump of assembler code for function main:
9830 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9834 0x0000000000400406 <+6>: test %eax,%eax
9835 0x0000000000400408 <+8>: js 0x400420 <main+32>
9840 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9841 0x000000000040040d <+13>: test %eax,%eax
9842 0x000000000040040f <+15>: mov $0x1,%eax
9843 0x0000000000400414 <+20>: cmovne %edx,%eax
9847 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9851 0x000000000040041d <+29>: xor %eax,%eax
9852 0x000000000040041f <+31>: retq
9856 0x0000000000400420 <+32>: add %eax,%eax
9857 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9858 End of assembler dump.
9861 Here is another example showing raw instructions in hex for AMD x86-64,
9864 (gdb) disas /r 0x400281,+10
9865 Dump of assembler code from 0x400281 to 0x40028b:
9866 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9867 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9868 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9869 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9870 End of assembler dump.
9873 Addresses cannot be specified as a location (@pxref{Specify Location}).
9874 So, for example, if you want to disassemble function @code{bar}
9875 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9876 and not @samp{disassemble foo.c:bar}.
9878 Some architectures have more than one commonly-used set of instruction
9879 mnemonics or other syntax.
9881 For programs that were dynamically linked and use shared libraries,
9882 instructions that call functions or branch to locations in the shared
9883 libraries might show a seemingly bogus location---it's actually a
9884 location of the relocation table. On some architectures, @value{GDBN}
9885 might be able to resolve these to actual function names.
9888 @kindex set disassembler-options
9889 @cindex disassembler options
9890 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9891 This command controls the passing of target specific information to
9892 the disassembler. For a list of valid options, please refer to the
9893 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9894 manual and/or the output of @kbd{objdump --help}
9895 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9896 The default value is the empty string.
9898 If it is necessary to specify more than one disassembler option, then
9899 multiple options can be placed together into a comma separated list.
9900 Currently this command is only supported on targets ARC, ARM, MIPS,
9903 @kindex show disassembler-options
9904 @item show disassembler-options
9905 Show the current setting of the disassembler options.
9909 @kindex set disassembly-flavor
9910 @cindex Intel disassembly flavor
9911 @cindex AT&T disassembly flavor
9912 @item set disassembly-flavor @var{instruction-set}
9913 Select the instruction set to use when disassembling the
9914 program via the @code{disassemble} or @code{x/i} commands.
9916 Currently this command is only defined for the Intel x86 family. You
9917 can set @var{instruction-set} to either @code{intel} or @code{att}.
9918 The default is @code{att}, the AT&T flavor used by default by Unix
9919 assemblers for x86-based targets.
9921 @kindex show disassembly-flavor
9922 @item show disassembly-flavor
9923 Show the current setting of the disassembly flavor.
9927 @kindex set disassemble-next-line
9928 @kindex show disassemble-next-line
9929 @item set disassemble-next-line
9930 @itemx show disassemble-next-line
9931 Control whether or not @value{GDBN} will disassemble the next source
9932 line or instruction when execution stops. If ON, @value{GDBN} will
9933 display disassembly of the next source line when execution of the
9934 program being debugged stops. This is @emph{in addition} to
9935 displaying the source line itself, which @value{GDBN} always does if
9936 possible. If the next source line cannot be displayed for some reason
9937 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9938 info in the debug info), @value{GDBN} will display disassembly of the
9939 next @emph{instruction} instead of showing the next source line. If
9940 AUTO, @value{GDBN} will display disassembly of next instruction only
9941 if the source line cannot be displayed. This setting causes
9942 @value{GDBN} to display some feedback when you step through a function
9943 with no line info or whose source file is unavailable. The default is
9944 OFF, which means never display the disassembly of the next line or
9948 @node Disable Reading Source
9949 @section Disable Reading Source Code
9950 @cindex source code, disable access
9952 In some cases it can be desirable to prevent @value{GDBN} from
9953 accessing source code files. One case where this might be desirable
9954 is if the source code files are located over a slow network
9957 The following command can be used to control whether @value{GDBN}
9958 should access source code files or not:
9961 @kindex set source open
9962 @kindex show source open
9963 @item set source open @r{[}on@r{|}off@r{]}
9964 @itemx show source open
9965 When this option is @code{on}, which is the default, @value{GDBN} will
9966 access source code files when needed, for example to print source
9967 lines when @value{GDBN} stops, or in response to the @code{list}
9970 When this option is @code{off}, @value{GDBN} will not access source
9975 @chapter Examining Data
9977 @cindex printing data
9978 @cindex examining data
9981 The usual way to examine data in your program is with the @code{print}
9982 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9983 evaluates and prints the value of an expression of the language your
9984 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9985 Different Languages}). It may also print the expression using a
9986 Python-based pretty-printer (@pxref{Pretty Printing}).
9989 @item print [[@var{options}] --] @var{expr}
9990 @itemx print [[@var{options}] --] /@var{f} @var{expr}
9991 @var{expr} is an expression (in the source language). By default the
9992 value of @var{expr} is printed in a format appropriate to its data type;
9993 you can choose a different format by specifying @samp{/@var{f}}, where
9994 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9997 @anchor{print options}
9998 The @code{print} command supports a number of options that allow
9999 overriding relevant global print settings as set by @code{set print}
10003 @item -address [@code{on}|@code{off}]
10004 Set printing of addresses.
10005 Related setting: @ref{set print address}.
10007 @item -array [@code{on}|@code{off}]
10008 Pretty formatting of arrays.
10009 Related setting: @ref{set print array}.
10011 @item -array-indexes [@code{on}|@code{off}]
10012 Set printing of array indexes.
10013 Related setting: @ref{set print array-indexes}.
10015 @item -elements @var{number-of-elements}|@code{unlimited}
10016 Set limit on string chars or array elements to print. The value
10017 @code{unlimited} causes there to be no limit. Related setting:
10018 @ref{set print elements}.
10020 @item -max-depth @var{depth}|@code{unlimited}
10021 Set the threshold after which nested structures are replaced with
10022 ellipsis. Related setting: @ref{set print max-depth}.
10024 @item -memory-tag-violations [@code{on}|@code{off}]
10025 Set printing of additional information about memory tag violations.
10026 @xref{set print memory-tag-violations}.
10028 @item -null-stop [@code{on}|@code{off}]
10029 Set printing of char arrays to stop at first null char. Related
10030 setting: @ref{set print null-stop}.
10032 @item -object [@code{on}|@code{off}]
10033 Set printing C@t{++} virtual function tables. Related setting:
10034 @ref{set print object}.
10036 @item -pretty [@code{on}|@code{off}]
10037 Set pretty formatting of structures. Related setting: @ref{set print
10040 @item -raw-values [@code{on}|@code{off}]
10041 Set whether to print values in raw form, bypassing any
10042 pretty-printers for that value. Related setting: @ref{set print
10045 @item -repeats @var{number-of-repeats}|@code{unlimited}
10046 Set threshold for repeated print elements. @code{unlimited} causes
10047 all elements to be individually printed. Related setting: @ref{set
10050 @item -static-members [@code{on}|@code{off}]
10051 Set printing C@t{++} static members. Related setting: @ref{set print
10054 @item -symbol [@code{on}|@code{off}]
10055 Set printing of symbol names when printing pointers. Related setting:
10056 @ref{set print symbol}.
10058 @item -union [@code{on}|@code{off}]
10059 Set printing of unions interior to structures. Related setting:
10060 @ref{set print union}.
10062 @item -vtbl [@code{on}|@code{off}]
10063 Set printing of C++ virtual function tables. Related setting:
10064 @ref{set print vtbl}.
10067 Because the @code{print} command accepts arbitrary expressions which
10068 may look like options (including abbreviations), if you specify any
10069 command option, then you must use a double dash (@code{--}) to mark
10070 the end of option processing.
10072 For example, this prints the value of the @code{-p} expression:
10075 (@value{GDBP}) print -p
10078 While this repeats the last value in the value history (see below)
10079 with the @code{-pretty} option in effect:
10082 (@value{GDBP}) print -p --
10085 Here is an example including both on option and an expression:
10089 (@value{GDBP}) print -pretty -- *myptr
10101 @item print [@var{options}]
10102 @itemx print [@var{options}] /@var{f}
10103 @cindex reprint the last value
10104 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
10105 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
10106 conveniently inspect the same value in an alternative format.
10109 If the architecture supports memory tagging, the @code{print} command will
10110 display pointer/memory tag mismatches if what is being printed is a pointer
10111 or reference type. @xref{Memory Tagging}.
10113 A more low-level way of examining data is with the @code{x} command.
10114 It examines data in memory at a specified address and prints it in a
10115 specified format. @xref{Memory, ,Examining Memory}.
10117 If you are interested in information about types, or about how the
10118 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
10119 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
10122 @cindex exploring hierarchical data structures
10124 Another way of examining values of expressions and type information is
10125 through the Python extension command @code{explore} (available only if
10126 the @value{GDBN} build is configured with @code{--with-python}). It
10127 offers an interactive way to start at the highest level (or, the most
10128 abstract level) of the data type of an expression (or, the data type
10129 itself) and explore all the way down to leaf scalar values/fields
10130 embedded in the higher level data types.
10133 @item explore @var{arg}
10134 @var{arg} is either an expression (in the source language), or a type
10135 visible in the current context of the program being debugged.
10138 The working of the @code{explore} command can be illustrated with an
10139 example. If a data type @code{struct ComplexStruct} is defined in your
10143 struct SimpleStruct
10149 struct ComplexStruct
10151 struct SimpleStruct *ss_p;
10157 followed by variable declarations as
10160 struct SimpleStruct ss = @{ 10, 1.11 @};
10161 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
10165 then, the value of the variable @code{cs} can be explored using the
10166 @code{explore} command as follows.
10170 The value of `cs' is a struct/class of type `struct ComplexStruct' with
10171 the following fields:
10173 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
10174 arr = <Enter 1 to explore this field of type `int [10]'>
10176 Enter the field number of choice:
10180 Since the fields of @code{cs} are not scalar values, you are being
10181 prompted to chose the field you want to explore. Let's say you choose
10182 the field @code{ss_p} by entering @code{0}. Then, since this field is a
10183 pointer, you will be asked if it is pointing to a single value. From
10184 the declaration of @code{cs} above, it is indeed pointing to a single
10185 value, hence you enter @code{y}. If you enter @code{n}, then you will
10186 be asked if it were pointing to an array of values, in which case this
10187 field will be explored as if it were an array.
10190 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
10191 Continue exploring it as a pointer to a single value [y/n]: y
10192 The value of `*(cs.ss_p)' is a struct/class of type `struct
10193 SimpleStruct' with the following fields:
10195 i = 10 .. (Value of type `int')
10196 d = 1.1100000000000001 .. (Value of type `double')
10198 Press enter to return to parent value:
10202 If the field @code{arr} of @code{cs} was chosen for exploration by
10203 entering @code{1} earlier, then since it is as array, you will be
10204 prompted to enter the index of the element in the array that you want
10208 `cs.arr' is an array of `int'.
10209 Enter the index of the element you want to explore in `cs.arr': 5
10211 `(cs.arr)[5]' is a scalar value of type `int'.
10215 Press enter to return to parent value:
10218 In general, at any stage of exploration, you can go deeper towards the
10219 leaf values by responding to the prompts appropriately, or hit the
10220 return key to return to the enclosing data structure (the @i{higher}
10221 level data structure).
10223 Similar to exploring values, you can use the @code{explore} command to
10224 explore types. Instead of specifying a value (which is typically a
10225 variable name or an expression valid in the current context of the
10226 program being debugged), you specify a type name. If you consider the
10227 same example as above, your can explore the type
10228 @code{struct ComplexStruct} by passing the argument
10229 @code{struct ComplexStruct} to the @code{explore} command.
10232 (gdb) explore struct ComplexStruct
10236 By responding to the prompts appropriately in the subsequent interactive
10237 session, you can explore the type @code{struct ComplexStruct} in a
10238 manner similar to how the value @code{cs} was explored in the above
10241 The @code{explore} command also has two sub-commands,
10242 @code{explore value} and @code{explore type}. The former sub-command is
10243 a way to explicitly specify that value exploration of the argument is
10244 being invoked, while the latter is a way to explicitly specify that type
10245 exploration of the argument is being invoked.
10248 @item explore value @var{expr}
10249 @cindex explore value
10250 This sub-command of @code{explore} explores the value of the
10251 expression @var{expr} (if @var{expr} is an expression valid in the
10252 current context of the program being debugged). The behavior of this
10253 command is identical to that of the behavior of the @code{explore}
10254 command being passed the argument @var{expr}.
10256 @item explore type @var{arg}
10257 @cindex explore type
10258 This sub-command of @code{explore} explores the type of @var{arg} (if
10259 @var{arg} is a type visible in the current context of program being
10260 debugged), or the type of the value/expression @var{arg} (if @var{arg}
10261 is an expression valid in the current context of the program being
10262 debugged). If @var{arg} is a type, then the behavior of this command is
10263 identical to that of the @code{explore} command being passed the
10264 argument @var{arg}. If @var{arg} is an expression, then the behavior of
10265 this command will be identical to that of the @code{explore} command
10266 being passed the type of @var{arg} as the argument.
10270 * Expressions:: Expressions
10271 * Ambiguous Expressions:: Ambiguous Expressions
10272 * Variables:: Program variables
10273 * Arrays:: Artificial arrays
10274 * Output Formats:: Output formats
10275 * Memory:: Examining memory
10276 * Memory Tagging:: Memory Tagging
10277 * Auto Display:: Automatic display
10278 * Print Settings:: Print settings
10279 * Pretty Printing:: Python pretty printing
10280 * Value History:: Value history
10281 * Convenience Vars:: Convenience variables
10282 * Convenience Funs:: Convenience functions
10283 * Registers:: Registers
10284 * Floating Point Hardware:: Floating point hardware
10285 * Vector Unit:: Vector Unit
10286 * OS Information:: Auxiliary data provided by operating system
10287 * Memory Region Attributes:: Memory region attributes
10288 * Dump/Restore Files:: Copy between memory and a file
10289 * Core File Generation:: Cause a program dump its core
10290 * Character Sets:: Debugging programs that use a different
10291 character set than GDB does
10292 * Caching Target Data:: Data caching for targets
10293 * Searching Memory:: Searching memory for a sequence of bytes
10294 * Value Sizes:: Managing memory allocated for values
10298 @section Expressions
10300 @cindex expressions
10301 @code{print} and many other @value{GDBN} commands accept an expression and
10302 compute its value. Any kind of constant, variable or operator defined
10303 by the programming language you are using is valid in an expression in
10304 @value{GDBN}. This includes conditional expressions, function calls,
10305 casts, and string constants. It also includes preprocessor macros, if
10306 you compiled your program to include this information; see
10309 @cindex arrays in expressions
10310 @value{GDBN} supports array constants in expressions input by
10311 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
10312 you can use the command @code{print @{1, 2, 3@}} to create an array
10313 of three integers. If you pass an array to a function or assign it
10314 to a program variable, @value{GDBN} copies the array to memory that
10315 is @code{malloc}ed in the target program.
10317 Because C is so widespread, most of the expressions shown in examples in
10318 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
10319 Languages}, for information on how to use expressions in other
10322 In this section, we discuss operators that you can use in @value{GDBN}
10323 expressions regardless of your programming language.
10325 @cindex casts, in expressions
10326 Casts are supported in all languages, not just in C, because it is so
10327 useful to cast a number into a pointer in order to examine a structure
10328 at that address in memory.
10329 @c FIXME: casts supported---Mod2 true?
10331 @value{GDBN} supports these operators, in addition to those common
10332 to programming languages:
10336 @samp{@@} is a binary operator for treating parts of memory as arrays.
10337 @xref{Arrays, ,Artificial Arrays}, for more information.
10340 @samp{::} allows you to specify a variable in terms of the file or
10341 function where it is defined. @xref{Variables, ,Program Variables}.
10343 @cindex @{@var{type}@}
10344 @cindex type casting memory
10345 @cindex memory, viewing as typed object
10346 @cindex casts, to view memory
10347 @item @{@var{type}@} @var{addr}
10348 Refers to an object of type @var{type} stored at address @var{addr} in
10349 memory. The address @var{addr} may be any expression whose value is
10350 an integer or pointer (but parentheses are required around binary
10351 operators, just as in a cast). This construct is allowed regardless
10352 of what kind of data is normally supposed to reside at @var{addr}.
10355 @node Ambiguous Expressions
10356 @section Ambiguous Expressions
10357 @cindex ambiguous expressions
10359 Expressions can sometimes contain some ambiguous elements. For instance,
10360 some programming languages (notably Ada, C@t{++} and Objective-C) permit
10361 a single function name to be defined several times, for application in
10362 different contexts. This is called @dfn{overloading}. Another example
10363 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
10364 templates and is typically instantiated several times, resulting in
10365 the same function name being defined in different contexts.
10367 In some cases and depending on the language, it is possible to adjust
10368 the expression to remove the ambiguity. For instance in C@t{++}, you
10369 can specify the signature of the function you want to break on, as in
10370 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
10371 qualified name of your function often makes the expression unambiguous
10374 When an ambiguity that needs to be resolved is detected, the debugger
10375 has the capability to display a menu of numbered choices for each
10376 possibility, and then waits for the selection with the prompt @samp{>}.
10377 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
10378 aborts the current command. If the command in which the expression was
10379 used allows more than one choice to be selected, the next option in the
10380 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
10383 For example, the following session excerpt shows an attempt to set a
10384 breakpoint at the overloaded symbol @code{String::after}.
10385 We choose three particular definitions of that function name:
10387 @c FIXME! This is likely to change to show arg type lists, at least
10390 (@value{GDBP}) b String::after
10393 [2] file:String.cc; line number:867
10394 [3] file:String.cc; line number:860
10395 [4] file:String.cc; line number:875
10396 [5] file:String.cc; line number:853
10397 [6] file:String.cc; line number:846
10398 [7] file:String.cc; line number:735
10400 Breakpoint 1 at 0xb26c: file String.cc, line 867.
10401 Breakpoint 2 at 0xb344: file String.cc, line 875.
10402 Breakpoint 3 at 0xafcc: file String.cc, line 846.
10403 Multiple breakpoints were set.
10404 Use the "delete" command to delete unwanted
10411 @kindex set multiple-symbols
10412 @item set multiple-symbols @var{mode}
10413 @cindex multiple-symbols menu
10415 This option allows you to adjust the debugger behavior when an expression
10418 By default, @var{mode} is set to @code{all}. If the command with which
10419 the expression is used allows more than one choice, then @value{GDBN}
10420 automatically selects all possible choices. For instance, inserting
10421 a breakpoint on a function using an ambiguous name results in a breakpoint
10422 inserted on each possible match. However, if a unique choice must be made,
10423 then @value{GDBN} uses the menu to help you disambiguate the expression.
10424 For instance, printing the address of an overloaded function will result
10425 in the use of the menu.
10427 When @var{mode} is set to @code{ask}, the debugger always uses the menu
10428 when an ambiguity is detected.
10430 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
10431 an error due to the ambiguity and the command is aborted.
10433 @kindex show multiple-symbols
10434 @item show multiple-symbols
10435 Show the current value of the @code{multiple-symbols} setting.
10439 @section Program Variables
10441 The most common kind of expression to use is the name of a variable
10444 Variables in expressions are understood in the selected stack frame
10445 (@pxref{Selection, ,Selecting a Frame}); they must be either:
10449 global (or file-static)
10456 visible according to the scope rules of the
10457 programming language from the point of execution in that frame
10460 @noindent This means that in the function
10475 you can examine and use the variable @code{a} whenever your program is
10476 executing within the function @code{foo}, but you can only use or
10477 examine the variable @code{b} while your program is executing inside
10478 the block where @code{b} is declared.
10480 @cindex variable name conflict
10481 There is an exception: you can refer to a variable or function whose
10482 scope is a single source file even if the current execution point is not
10483 in this file. But it is possible to have more than one such variable or
10484 function with the same name (in different source files). If that
10485 happens, referring to that name has unpredictable effects. If you wish,
10486 you can specify a static variable in a particular function or file by
10487 using the colon-colon (@code{::}) notation:
10489 @cindex colon-colon, context for variables/functions
10491 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
10492 @cindex @code{::}, context for variables/functions
10495 @var{file}::@var{variable}
10496 @var{function}::@var{variable}
10500 Here @var{file} or @var{function} is the name of the context for the
10501 static @var{variable}. In the case of file names, you can use quotes to
10502 make sure @value{GDBN} parses the file name as a single word---for example,
10503 to print a global value of @code{x} defined in @file{f2.c}:
10506 (@value{GDBP}) p 'f2.c'::x
10509 The @code{::} notation is normally used for referring to
10510 static variables, since you typically disambiguate uses of local variables
10511 in functions by selecting the appropriate frame and using the
10512 simple name of the variable. However, you may also use this notation
10513 to refer to local variables in frames enclosing the selected frame:
10522 process (a); /* Stop here */
10533 For example, if there is a breakpoint at the commented line,
10534 here is what you might see
10535 when the program stops after executing the call @code{bar(0)}:
10540 (@value{GDBP}) p bar::a
10542 (@value{GDBP}) up 2
10543 #2 0x080483d0 in foo (a=5) at foobar.c:12
10546 (@value{GDBP}) p bar::a
10550 @cindex C@t{++} scope resolution
10551 These uses of @samp{::} are very rarely in conflict with the very
10552 similar use of the same notation in C@t{++}. When they are in
10553 conflict, the C@t{++} meaning takes precedence; however, this can be
10554 overridden by quoting the file or function name with single quotes.
10556 For example, suppose the program is stopped in a method of a class
10557 that has a field named @code{includefile}, and there is also an
10558 include file named @file{includefile} that defines a variable,
10559 @code{some_global}.
10562 (@value{GDBP}) p includefile
10564 (@value{GDBP}) p includefile::some_global
10565 A syntax error in expression, near `'.
10566 (@value{GDBP}) p 'includefile'::some_global
10570 @cindex wrong values
10571 @cindex variable values, wrong
10572 @cindex function entry/exit, wrong values of variables
10573 @cindex optimized code, wrong values of variables
10575 @emph{Warning:} Occasionally, a local variable may appear to have the
10576 wrong value at certain points in a function---just after entry to a new
10577 scope, and just before exit.
10579 You may see this problem when you are stepping by machine instructions.
10580 This is because, on most machines, it takes more than one instruction to
10581 set up a stack frame (including local variable definitions); if you are
10582 stepping by machine instructions, variables may appear to have the wrong
10583 values until the stack frame is completely built. On exit, it usually
10584 also takes more than one machine instruction to destroy a stack frame;
10585 after you begin stepping through that group of instructions, local
10586 variable definitions may be gone.
10588 This may also happen when the compiler does significant optimizations.
10589 To be sure of always seeing accurate values, turn off all optimization
10592 @cindex ``No symbol "foo" in current context''
10593 Another possible effect of compiler optimizations is to optimize
10594 unused variables out of existence, or assign variables to registers (as
10595 opposed to memory addresses). Depending on the support for such cases
10596 offered by the debug info format used by the compiler, @value{GDBN}
10597 might not be able to display values for such local variables. If that
10598 happens, @value{GDBN} will print a message like this:
10601 No symbol "foo" in current context.
10604 To solve such problems, either recompile without optimizations, or use a
10605 different debug info format, if the compiler supports several such
10606 formats. @xref{Compilation}, for more information on choosing compiler
10607 options. @xref{C, ,C and C@t{++}}, for more information about debug
10608 info formats that are best suited to C@t{++} programs.
10610 If you ask to print an object whose contents are unknown to
10611 @value{GDBN}, e.g., because its data type is not completely specified
10612 by the debug information, @value{GDBN} will say @samp{<incomplete
10613 type>}. @xref{Symbols, incomplete type}, for more about this.
10615 @cindex no debug info variables
10616 If you try to examine or use the value of a (global) variable for
10617 which @value{GDBN} has no type information, e.g., because the program
10618 includes no debug information, @value{GDBN} displays an error message.
10619 @xref{Symbols, unknown type}, for more about unknown types. If you
10620 cast the variable to its declared type, @value{GDBN} gets the
10621 variable's value using the cast-to type as the variable's type. For
10622 example, in a C program:
10625 (@value{GDBP}) p var
10626 'var' has unknown type; cast it to its declared type
10627 (@value{GDBP}) p (float) var
10631 If you append @kbd{@@entry} string to a function parameter name you get its
10632 value at the time the function got called. If the value is not available an
10633 error message is printed. Entry values are available only with some compilers.
10634 Entry values are normally also printed at the function parameter list according
10635 to @ref{set print entry-values}.
10638 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
10644 (gdb) print i@@entry
10648 Strings are identified as arrays of @code{char} values without specified
10649 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
10650 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
10651 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
10652 defines literal string type @code{"char"} as @code{char} without a sign.
10657 signed char var1[] = "A";
10660 You get during debugging
10665 $2 = @{65 'A', 0 '\0'@}
10669 @section Artificial Arrays
10671 @cindex artificial array
10673 @kindex @@@r{, referencing memory as an array}
10674 It is often useful to print out several successive objects of the
10675 same type in memory; a section of an array, or an array of
10676 dynamically determined size for which only a pointer exists in the
10679 You can do this by referring to a contiguous span of memory as an
10680 @dfn{artificial array}, using the binary operator @samp{@@}. The left
10681 operand of @samp{@@} should be the first element of the desired array
10682 and be an individual object. The right operand should be the desired length
10683 of the array. The result is an array value whose elements are all of
10684 the type of the left argument. The first element is actually the left
10685 argument; the second element comes from bytes of memory immediately
10686 following those that hold the first element, and so on. Here is an
10687 example. If a program says
10690 int *array = (int *) malloc (len * sizeof (int));
10694 you can print the contents of @code{array} with
10700 The left operand of @samp{@@} must reside in memory. Array values made
10701 with @samp{@@} in this way behave just like other arrays in terms of
10702 subscripting, and are coerced to pointers when used in expressions.
10703 Artificial arrays most often appear in expressions via the value history
10704 (@pxref{Value History, ,Value History}), after printing one out.
10706 Another way to create an artificial array is to use a cast.
10707 This re-interprets a value as if it were an array.
10708 The value need not be in memory:
10710 (@value{GDBP}) p/x (short[2])0x12345678
10711 $1 = @{0x1234, 0x5678@}
10714 As a convenience, if you leave the array length out (as in
10715 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
10716 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
10718 (@value{GDBP}) p/x (short[])0x12345678
10719 $2 = @{0x1234, 0x5678@}
10722 Sometimes the artificial array mechanism is not quite enough; in
10723 moderately complex data structures, the elements of interest may not
10724 actually be adjacent---for example, if you are interested in the values
10725 of pointers in an array. One useful work-around in this situation is
10726 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
10727 Variables}) as a counter in an expression that prints the first
10728 interesting value, and then repeat that expression via @key{RET}. For
10729 instance, suppose you have an array @code{dtab} of pointers to
10730 structures, and you are interested in the values of a field @code{fv}
10731 in each structure. Here is an example of what you might type:
10741 @node Output Formats
10742 @section Output Formats
10744 @cindex formatted output
10745 @cindex output formats
10746 By default, @value{GDBN} prints a value according to its data type. Sometimes
10747 this is not what you want. For example, you might want to print a number
10748 in hex, or a pointer in decimal. Or you might want to view data in memory
10749 at a certain address as a character string or as an instruction. To do
10750 these things, specify an @dfn{output format} when you print a value.
10752 The simplest use of output formats is to say how to print a value
10753 already computed. This is done by starting the arguments of the
10754 @code{print} command with a slash and a format letter. The format
10755 letters supported are:
10759 Print the binary representation of the value in hexadecimal.
10762 Print the binary representation of the value in decimal.
10765 Print the binary representation of the value as an decimal, as if it
10769 Print the binary representation of the value in octal.
10772 Print the binary representation of the value in binary. The letter
10773 @samp{t} stands for ``two''. @footnote{@samp{b} cannot be used
10774 because these format letters are also used with the @code{x} command,
10775 where @samp{b} stands for ``byte''; see @ref{Memory,,Examining
10779 @cindex unknown address, locating
10780 @cindex locate address
10781 Print as an address, both absolute in hexadecimal and as an offset from
10782 the nearest preceding symbol. You can use this format used to discover
10783 where (in what function) an unknown address is located:
10786 (@value{GDBP}) p/a 0x54320
10787 $3 = 0x54320 <_initialize_vx+396>
10791 The command @code{info symbol 0x54320} yields similar results.
10792 @xref{Symbols, info symbol}.
10795 Cast the value to an integer (unlike other formats, this does not just
10796 reinterpret the underlying bits) and print it as a character constant.
10797 This prints both the numerical value and its character representation.
10798 The character representation is replaced with the octal escape
10799 @samp{\nnn} for characters outside the 7-bit @sc{ascii} range.
10801 Without this format, @value{GDBN} displays @code{char},
10802 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
10803 constants. Single-byte members of vectors are displayed as integer
10807 Regard the bits of the value as a floating point number and print
10808 using typical floating point syntax.
10811 @cindex printing strings
10812 @cindex printing byte arrays
10813 Regard as a string, if possible. With this format, pointers to single-byte
10814 data are displayed as null-terminated strings and arrays of single-byte data
10815 are displayed as fixed-length strings. Other values are displayed in their
10818 Without this format, @value{GDBN} displays pointers to and arrays of
10819 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
10820 strings. Single-byte members of a vector are displayed as an integer
10824 Like @samp{x} formatting, the value is treated as an integer and
10825 printed as hexadecimal, but leading zeros are printed to pad the value
10826 to the size of the integer type.
10829 @cindex raw printing
10830 Print using the @samp{raw} formatting. By default, @value{GDBN} will
10831 use a Python-based pretty-printer, if one is available (@pxref{Pretty
10832 Printing}). This typically results in a higher-level display of the
10833 value's contents. The @samp{r} format bypasses any Python
10834 pretty-printer which might exist.
10837 For example, to print the program counter in hex (@pxref{Registers}), type
10844 Note that no space is required before the slash; this is because command
10845 names in @value{GDBN} cannot contain a slash.
10847 To reprint the last value in the value history with a different format,
10848 you can use the @code{print} command with just a format and no
10849 expression. For example, @samp{p/x} reprints the last value in hex.
10852 @section Examining Memory
10854 You can use the command @code{x} (for ``examine'') to examine memory in
10855 any of several formats, independently of your program's data types.
10857 @cindex examining memory
10859 @kindex x @r{(examine memory)}
10860 @item x/@var{nfu} @var{addr}
10861 @itemx x @var{addr}
10863 Use the @code{x} command to examine memory.
10866 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
10867 much memory to display and how to format it; @var{addr} is an
10868 expression giving the address where you want to start displaying memory.
10869 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
10870 Several commands set convenient defaults for @var{addr}.
10873 @item @var{n}, the repeat count
10874 The repeat count is a decimal integer; the default is 1. It specifies
10875 how much memory (counting by units @var{u}) to display. If a negative
10876 number is specified, memory is examined backward from @var{addr}.
10877 @c This really is **decimal**; unaffected by 'set radix' as of GDB
10880 @item @var{f}, the display format
10881 The display format is one of the formats used by @code{print}
10882 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
10883 @samp{f}, @samp{s}), @samp{i} (for machine instructions) and
10884 @samp{m} (for displaying memory tags).
10885 The default is @samp{x} (hexadecimal) initially. The default changes
10886 each time you use either @code{x} or @code{print}.
10888 @item @var{u}, the unit size
10889 The unit size is any of
10895 Halfwords (two bytes).
10897 Words (four bytes). This is the initial default.
10899 Giant words (eight bytes).
10902 Each time you specify a unit size with @code{x}, that size becomes the
10903 default unit the next time you use @code{x}. For the @samp{i} format,
10904 the unit size is ignored and is normally not written. For the @samp{s} format,
10905 the unit size defaults to @samp{b}, unless it is explicitly given.
10906 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
10907 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
10908 Note that the results depend on the programming language of the
10909 current compilation unit. If the language is C, the @samp{s}
10910 modifier will use the UTF-16 encoding while @samp{w} will use
10911 UTF-32. The encoding is set by the programming language and cannot
10914 @item @var{addr}, starting display address
10915 @var{addr} is the address where you want @value{GDBN} to begin displaying
10916 memory. The expression need not have a pointer value (though it may);
10917 it is always interpreted as an integer address of a byte of memory.
10918 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
10919 @var{addr} is usually just after the last address examined---but several
10920 other commands also set the default address: @code{info breakpoints} (to
10921 the address of the last breakpoint listed), @code{info line} (to the
10922 starting address of a line), and @code{print} (if you use it to display
10923 a value from memory).
10926 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
10927 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
10928 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
10929 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
10930 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
10932 You can also specify a negative repeat count to examine memory backward
10933 from the given address. For example, @samp{x/-3uh 0x54320} prints three
10934 halfwords (@code{h}) at @code{0x5431a}, @code{0x5431c}, and @code{0x5431e}.
10936 Since the letters indicating unit sizes are all distinct from the
10937 letters specifying output formats, you do not have to remember whether
10938 unit size or format comes first; either order works. The output
10939 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10940 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10942 Even though the unit size @var{u} is ignored for the formats @samp{s}
10943 and @samp{i}, you might still want to use a count @var{n}; for example,
10944 @samp{3i} specifies that you want to see three machine instructions,
10945 including any operands. For convenience, especially when used with
10946 the @code{display} command, the @samp{i} format also prints branch delay
10947 slot instructions, if any, beyond the count specified, which immediately
10948 follow the last instruction that is within the count. The command
10949 @code{disassemble} gives an alternative way of inspecting machine
10950 instructions; see @ref{Machine Code,,Source and Machine Code}.
10952 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10953 the command displays null-terminated strings or instructions before the given
10954 address as many as the absolute value of the given number. For the @samp{i}
10955 format, we use line number information in the debug info to accurately locate
10956 instruction boundaries while disassembling backward. If line info is not
10957 available, the command stops examining memory with an error message.
10959 All the defaults for the arguments to @code{x} are designed to make it
10960 easy to continue scanning memory with minimal specifications each time
10961 you use @code{x}. For example, after you have inspected three machine
10962 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10963 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10964 the repeat count @var{n} is used again; the other arguments default as
10965 for successive uses of @code{x}.
10967 When examining machine instructions, the instruction at current program
10968 counter is shown with a @code{=>} marker. For example:
10971 (@value{GDBP}) x/5i $pc-6
10972 0x804837f <main+11>: mov %esp,%ebp
10973 0x8048381 <main+13>: push %ecx
10974 0x8048382 <main+14>: sub $0x4,%esp
10975 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10976 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10979 If the architecture supports memory tagging, the tags can be displayed by
10980 using @samp{m}. @xref{Memory Tagging}.
10982 The information will be displayed once per granule size
10983 (the amount of bytes a particular memory tag covers). For example, AArch64
10984 has a granule size of 16 bytes, so it will display a tag every 16 bytes.
10986 Due to the way @value{GDBN} prints information with the @code{x} command (not
10987 aligned to a particular boundary), the tag information will refer to the
10988 initial address displayed on a particular line. If a memory tag boundary
10989 is crossed in the middle of a line displayed by the @code{x} command, it
10990 will be displayed on the next line.
10992 The @samp{m} format doesn't affect any other specified formats that were
10993 passed to the @code{x} command.
10995 @cindex @code{$_}, @code{$__}, and value history
10996 The addresses and contents printed by the @code{x} command are not saved
10997 in the value history because there is often too much of them and they
10998 would get in the way. Instead, @value{GDBN} makes these values available for
10999 subsequent use in expressions as values of the convenience variables
11000 @code{$_} and @code{$__}. After an @code{x} command, the last address
11001 examined is available for use in expressions in the convenience variable
11002 @code{$_}. The contents of that address, as examined, are available in
11003 the convenience variable @code{$__}.
11005 If the @code{x} command has a repeat count, the address and contents saved
11006 are from the last memory unit printed; this is not the same as the last
11007 address printed if several units were printed on the last line of output.
11009 @anchor{addressable memory unit}
11010 @cindex addressable memory unit
11011 Most targets have an addressable memory unit size of 8 bits. This means
11012 that to each memory address are associated 8 bits of data. Some
11013 targets, however, have other addressable memory unit sizes.
11014 Within @value{GDBN} and this document, the term
11015 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
11016 when explicitly referring to a chunk of data of that size. The word
11017 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
11018 the addressable memory unit size of the target. For most systems,
11019 addressable memory unit is a synonym of byte.
11021 @cindex remote memory comparison
11022 @cindex target memory comparison
11023 @cindex verify remote memory image
11024 @cindex verify target memory image
11025 When you are debugging a program running on a remote target machine
11026 (@pxref{Remote Debugging}), you may wish to verify the program's image
11027 in the remote machine's memory against the executable file you
11028 downloaded to the target. Or, on any target, you may want to check
11029 whether the program has corrupted its own read-only sections. The
11030 @code{compare-sections} command is provided for such situations.
11033 @kindex compare-sections
11034 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
11035 Compare the data of a loadable section @var{section-name} in the
11036 executable file of the program being debugged with the same section in
11037 the target machine's memory, and report any mismatches. With no
11038 arguments, compares all loadable sections. With an argument of
11039 @code{-r}, compares all loadable read-only sections.
11041 Note: for remote targets, this command can be accelerated if the
11042 target supports computing the CRC checksum of a block of memory
11043 (@pxref{qCRC packet}).
11046 @node Memory Tagging
11047 @section Memory Tagging
11049 Memory tagging is a memory protection technology that uses a pair of tags to
11050 validate memory accesses through pointers. The tags are integer values
11051 usually comprised of a few bits, depending on the architecture.
11053 There are two types of tags that are used in this setup: logical and
11054 allocation. A logical tag is stored in the pointers themselves, usually at the
11055 higher bits of the pointers. An allocation tag is the tag associated
11056 with particular ranges of memory in the physical address space, against which
11057 the logical tags from pointers are compared.
11059 The pointer tag (logical tag) must match the memory tag (allocation tag)
11060 for the memory access to be valid. If the logical tag does not match the
11061 allocation tag, that will raise a memory violation.
11063 Allocation tags cover multiple contiguous bytes of physical memory. This
11064 range of bytes is called a memory tag granule and is architecture-specific.
11065 For example, AArch64 has a tag granule of 16 bytes, meaning each allocation
11066 tag spans 16 bytes of memory.
11068 If the underlying architecture supports memory tagging, like AArch64 MTE
11069 or SPARC ADI do, @value{GDBN} can make use of it to validate pointers
11070 against memory allocation tags.
11072 The @code{print} (@pxref{Data}) and @code{x} (@pxref{Memory}) commands will
11073 display tag information when appropriate, and a command prefix of
11074 @code{memory-tag} gives access to the various memory tagging commands.
11076 The @code{memory-tag} commands are the following:
11079 @kindex memory-tag print-logical-tag
11080 @item memory-tag print-logical-tag @var{pointer_expression}
11081 Print the logical tag stored in @var{pointer_expression}.
11082 @kindex memory-tag with-logical-tag
11083 @item memory-tag with-logical-tag @var{pointer_expression} @var{tag_bytes}
11084 Print the pointer given by @var{pointer_expression}, augmented with a logical
11085 tag of @var{tag_bytes}.
11086 @kindex memory-tag print-allocation-tag
11087 @item memory-tag print-allocation-tag @var{address_expression}
11088 Print the allocation tag associated with the memory address given by
11089 @var{address_expression}.
11090 @kindex memory-tag setatag
11091 @item memory-tag setatag @var{starting_address} @var{length} @var{tag_bytes}
11092 Set the allocation tag(s) for memory range @r{[}@var{starting_address},
11093 @var{starting_address} + @var{length}@r{)} to @var{tag_bytes}.
11094 @kindex memory-tag check
11095 @item memory-tag check @var{pointer_expression}
11096 Check if the logical tag in the pointer given by @var{pointer_expression}
11097 matches the allocation tag for the memory referenced by the pointer.
11099 This essentially emulates the hardware validation that is done when tagged
11100 memory is accessed through a pointer, but does not cause a memory fault as
11101 it would during hardware validation.
11103 It can be used to inspect potential memory tagging violations in the running
11104 process, before any faults get triggered.
11108 @section Automatic Display
11109 @cindex automatic display
11110 @cindex display of expressions
11112 If you find that you want to print the value of an expression frequently
11113 (to see how it changes), you might want to add it to the @dfn{automatic
11114 display list} so that @value{GDBN} prints its value each time your program stops.
11115 Each expression added to the list is given a number to identify it;
11116 to remove an expression from the list, you specify that number.
11117 The automatic display looks like this:
11121 3: bar[5] = (struct hack *) 0x3804
11125 This display shows item numbers, expressions and their current values. As with
11126 displays you request manually using @code{x} or @code{print}, you can
11127 specify the output format you prefer; in fact, @code{display} decides
11128 whether to use @code{print} or @code{x} depending your format
11129 specification---it uses @code{x} if you specify either the @samp{i}
11130 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
11134 @item display @var{expr}
11135 Add the expression @var{expr} to the list of expressions to display
11136 each time your program stops. @xref{Expressions, ,Expressions}.
11138 @code{display} does not repeat if you press @key{RET} again after using it.
11140 @item display/@var{fmt} @var{expr}
11141 For @var{fmt} specifying only a display format and not a size or
11142 count, add the expression @var{expr} to the auto-display list but
11143 arrange to display it each time in the specified format @var{fmt}.
11144 @xref{Output Formats,,Output Formats}.
11146 @item display/@var{fmt} @var{addr}
11147 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
11148 number of units, add the expression @var{addr} as a memory address to
11149 be examined each time your program stops. Examining means in effect
11150 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
11153 For example, @samp{display/i $pc} can be helpful, to see the machine
11154 instruction about to be executed each time execution stops (@samp{$pc}
11155 is a common name for the program counter; @pxref{Registers, ,Registers}).
11158 @kindex delete display
11160 @item undisplay @var{dnums}@dots{}
11161 @itemx delete display @var{dnums}@dots{}
11162 Remove items from the list of expressions to display. Specify the
11163 numbers of the displays that you want affected with the command
11164 argument @var{dnums}. It can be a single display number, one of the
11165 numbers shown in the first field of the @samp{info display} display;
11166 or it could be a range of display numbers, as in @code{2-4}.
11168 @code{undisplay} does not repeat if you press @key{RET} after using it.
11169 (Otherwise you would just get the error @samp{No display number @dots{}}.)
11171 @kindex disable display
11172 @item disable display @var{dnums}@dots{}
11173 Disable the display of item numbers @var{dnums}. A disabled display
11174 item is not printed automatically, but is not forgotten. It may be
11175 enabled again later. Specify the numbers of the displays that you
11176 want affected with the command argument @var{dnums}. It can be a
11177 single display number, one of the numbers shown in the first field of
11178 the @samp{info display} display; or it could be a range of display
11179 numbers, as in @code{2-4}.
11181 @kindex enable display
11182 @item enable display @var{dnums}@dots{}
11183 Enable display of item numbers @var{dnums}. It becomes effective once
11184 again in auto display of its expression, until you specify otherwise.
11185 Specify the numbers of the displays that you want affected with the
11186 command argument @var{dnums}. It can be a single display number, one
11187 of the numbers shown in the first field of the @samp{info display}
11188 display; or it could be a range of display numbers, as in @code{2-4}.
11191 Display the current values of the expressions on the list, just as is
11192 done when your program stops.
11194 @kindex info display
11196 Print the list of expressions previously set up to display
11197 automatically, each one with its item number, but without showing the
11198 values. This includes disabled expressions, which are marked as such.
11199 It also includes expressions which would not be displayed right now
11200 because they refer to automatic variables not currently available.
11203 @cindex display disabled out of scope
11204 If a display expression refers to local variables, then it does not make
11205 sense outside the lexical context for which it was set up. Such an
11206 expression is disabled when execution enters a context where one of its
11207 variables is not defined. For example, if you give the command
11208 @code{display last_char} while inside a function with an argument
11209 @code{last_char}, @value{GDBN} displays this argument while your program
11210 continues to stop inside that function. When it stops elsewhere---where
11211 there is no variable @code{last_char}---the display is disabled
11212 automatically. The next time your program stops where @code{last_char}
11213 is meaningful, you can enable the display expression once again.
11215 @node Print Settings
11216 @section Print Settings
11218 @cindex format options
11219 @cindex print settings
11220 @value{GDBN} provides the following ways to control how arrays, structures,
11221 and symbols are printed.
11224 These settings are useful for debugging programs in any language:
11228 @anchor{set print address}
11229 @item set print address
11230 @itemx set print address on
11231 @cindex print/don't print memory addresses
11232 @value{GDBN} prints memory addresses showing the location of stack
11233 traces, structure values, pointer values, breakpoints, and so forth,
11234 even when it also displays the contents of those addresses. The default
11235 is @code{on}. For example, this is what a stack frame display looks like with
11236 @code{set print address on}:
11241 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
11243 530 if (lquote != def_lquote)
11247 @item set print address off
11248 Do not print addresses when displaying their contents. For example,
11249 this is the same stack frame displayed with @code{set print address off}:
11253 (@value{GDBP}) set print addr off
11255 #0 set_quotes (lq="<<", rq=">>") at input.c:530
11256 530 if (lquote != def_lquote)
11260 You can use @samp{set print address off} to eliminate all machine
11261 dependent displays from the @value{GDBN} interface. For example, with
11262 @code{print address off}, you should get the same text for backtraces on
11263 all machines---whether or not they involve pointer arguments.
11266 @item show print address
11267 Show whether or not addresses are to be printed.
11270 When @value{GDBN} prints a symbolic address, it normally prints the
11271 closest earlier symbol plus an offset. If that symbol does not uniquely
11272 identify the address (for example, it is a name whose scope is a single
11273 source file), you may need to clarify. One way to do this is with
11274 @code{info line}, for example @samp{info line *0x4537}. Alternately,
11275 you can set @value{GDBN} to print the source file and line number when
11276 it prints a symbolic address:
11279 @item set print symbol-filename on
11280 @cindex source file and line of a symbol
11281 @cindex symbol, source file and line
11282 Tell @value{GDBN} to print the source file name and line number of a
11283 symbol in the symbolic form of an address.
11285 @item set print symbol-filename off
11286 Do not print source file name and line number of a symbol. This is the
11289 @item show print symbol-filename
11290 Show whether or not @value{GDBN} will print the source file name and
11291 line number of a symbol in the symbolic form of an address.
11294 Another situation where it is helpful to show symbol filenames and line
11295 numbers is when disassembling code; @value{GDBN} shows you the line
11296 number and source file that corresponds to each instruction.
11298 Also, you may wish to see the symbolic form only if the address being
11299 printed is reasonably close to the closest earlier symbol:
11302 @item set print max-symbolic-offset @var{max-offset}
11303 @itemx set print max-symbolic-offset unlimited
11304 @cindex maximum value for offset of closest symbol
11305 Tell @value{GDBN} to only display the symbolic form of an address if the
11306 offset between the closest earlier symbol and the address is less than
11307 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
11308 to always print the symbolic form of an address if any symbol precedes
11309 it. Zero is equivalent to @code{unlimited}.
11311 @item show print max-symbolic-offset
11312 Ask how large the maximum offset is that @value{GDBN} prints in a
11316 @cindex wild pointer, interpreting
11317 @cindex pointer, finding referent
11318 If you have a pointer and you are not sure where it points, try
11319 @samp{set print symbol-filename on}. Then you can determine the name
11320 and source file location of the variable where it points, using
11321 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
11322 For example, here @value{GDBN} shows that a variable @code{ptt} points
11323 at another variable @code{t}, defined in @file{hi2.c}:
11326 (@value{GDBP}) set print symbol-filename on
11327 (@value{GDBP}) p/a ptt
11328 $4 = 0xe008 <t in hi2.c>
11332 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
11333 does not show the symbol name and filename of the referent, even with
11334 the appropriate @code{set print} options turned on.
11337 You can also enable @samp{/a}-like formatting all the time using
11338 @samp{set print symbol on}:
11340 @anchor{set print symbol}
11342 @item set print symbol on
11343 Tell @value{GDBN} to print the symbol corresponding to an address, if
11346 @item set print symbol off
11347 Tell @value{GDBN} not to print the symbol corresponding to an
11348 address. In this mode, @value{GDBN} will still print the symbol
11349 corresponding to pointers to functions. This is the default.
11351 @item show print symbol
11352 Show whether @value{GDBN} will display the symbol corresponding to an
11356 Other settings control how different kinds of objects are printed:
11359 @anchor{set print array}
11360 @item set print array
11361 @itemx set print array on
11362 @cindex pretty print arrays
11363 Pretty print arrays. This format is more convenient to read,
11364 but uses more space. The default is off.
11366 @item set print array off
11367 Return to compressed format for arrays.
11369 @item show print array
11370 Show whether compressed or pretty format is selected for displaying
11373 @cindex print array indexes
11374 @anchor{set print array-indexes}
11375 @item set print array-indexes
11376 @itemx set print array-indexes on
11377 Print the index of each element when displaying arrays. May be more
11378 convenient to locate a given element in the array or quickly find the
11379 index of a given element in that printed array. The default is off.
11381 @item set print array-indexes off
11382 Stop printing element indexes when displaying arrays.
11384 @item show print array-indexes
11385 Show whether the index of each element is printed when displaying
11388 @anchor{set print elements}
11389 @item set print elements @var{number-of-elements}
11390 @itemx set print elements unlimited
11391 @cindex number of array elements to print
11392 @cindex limit on number of printed array elements
11393 Set a limit on how many elements of an array @value{GDBN} will print.
11394 If @value{GDBN} is printing a large array, it stops printing after it has
11395 printed the number of elements set by the @code{set print elements} command.
11396 This limit also applies to the display of strings.
11397 When @value{GDBN} starts, this limit is set to 200.
11398 Setting @var{number-of-elements} to @code{unlimited} or zero means
11399 that the number of elements to print is unlimited.
11401 @item show print elements
11402 Display the number of elements of a large array that @value{GDBN} will print.
11404 @anchor{set print frame-arguments}
11405 @item set print frame-arguments @var{value}
11406 @kindex set print frame-arguments
11407 @cindex printing frame argument values
11408 @cindex print all frame argument values
11409 @cindex print frame argument values for scalars only
11410 @cindex do not print frame arguments
11411 This command allows to control how the values of arguments are printed
11412 when the debugger prints a frame (@pxref{Frames}). The possible
11417 The values of all arguments are printed.
11420 Print the value of an argument only if it is a scalar. The value of more
11421 complex arguments such as arrays, structures, unions, etc, is replaced
11422 by @code{@dots{}}. This is the default. Here is an example where
11423 only scalar arguments are shown:
11426 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
11431 None of the argument values are printed. Instead, the value of each argument
11432 is replaced by @code{@dots{}}. In this case, the example above now becomes:
11435 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
11440 Only the presence of arguments is indicated by @code{@dots{}}.
11441 The @code{@dots{}} are not printed for function without any arguments.
11442 None of the argument names and values are printed.
11443 In this case, the example above now becomes:
11446 #1 0x08048361 in call_me (@dots{}) at frame-args.c:23
11451 By default, only scalar arguments are printed. This command can be used
11452 to configure the debugger to print the value of all arguments, regardless
11453 of their type. However, it is often advantageous to not print the value
11454 of more complex parameters. For instance, it reduces the amount of
11455 information printed in each frame, making the backtrace more readable.
11456 Also, it improves performance when displaying Ada frames, because
11457 the computation of large arguments can sometimes be CPU-intensive,
11458 especially in large applications. Setting @code{print frame-arguments}
11459 to @code{scalars} (the default), @code{none} or @code{presence} avoids
11460 this computation, thus speeding up the display of each Ada frame.
11462 @item show print frame-arguments
11463 Show how the value of arguments should be displayed when printing a frame.
11465 @anchor{set print raw-frame-arguments}
11466 @item set print raw-frame-arguments on
11467 Print frame arguments in raw, non pretty-printed, form.
11469 @item set print raw-frame-arguments off
11470 Print frame arguments in pretty-printed form, if there is a pretty-printer
11471 for the value (@pxref{Pretty Printing}),
11472 otherwise print the value in raw form.
11473 This is the default.
11475 @item show print raw-frame-arguments
11476 Show whether to print frame arguments in raw form.
11478 @anchor{set print entry-values}
11479 @item set print entry-values @var{value}
11480 @kindex set print entry-values
11481 Set printing of frame argument values at function entry. In some cases
11482 @value{GDBN} can determine the value of function argument which was passed by
11483 the function caller, even if the value was modified inside the called function
11484 and therefore is different. With optimized code, the current value could be
11485 unavailable, but the entry value may still be known.
11487 The default value is @code{default} (see below for its description). Older
11488 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
11489 this feature will behave in the @code{default} setting the same way as with the
11492 This functionality is currently supported only by DWARF 2 debugging format and
11493 the compiler has to produce @samp{DW_TAG_call_site} tags. With
11494 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11497 The @var{value} parameter can be one of the following:
11501 Print only actual parameter values, never print values from function entry
11505 #0 different (val=6)
11506 #0 lost (val=<optimized out>)
11508 #0 invalid (val=<optimized out>)
11512 Print only parameter values from function entry point. The actual parameter
11513 values are never printed.
11515 #0 equal (val@@entry=5)
11516 #0 different (val@@entry=5)
11517 #0 lost (val@@entry=5)
11518 #0 born (val@@entry=<optimized out>)
11519 #0 invalid (val@@entry=<optimized out>)
11523 Print only parameter values from function entry point. If value from function
11524 entry point is not known while the actual value is known, print the actual
11525 value for such parameter.
11527 #0 equal (val@@entry=5)
11528 #0 different (val@@entry=5)
11529 #0 lost (val@@entry=5)
11531 #0 invalid (val@@entry=<optimized out>)
11535 Print actual parameter values. If actual parameter value is not known while
11536 value from function entry point is known, print the entry point value for such
11540 #0 different (val=6)
11541 #0 lost (val@@entry=5)
11543 #0 invalid (val=<optimized out>)
11547 Always print both the actual parameter value and its value from function entry
11548 point, even if values of one or both are not available due to compiler
11551 #0 equal (val=5, val@@entry=5)
11552 #0 different (val=6, val@@entry=5)
11553 #0 lost (val=<optimized out>, val@@entry=5)
11554 #0 born (val=10, val@@entry=<optimized out>)
11555 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
11559 Print the actual parameter value if it is known and also its value from
11560 function entry point if it is known. If neither is known, print for the actual
11561 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
11562 values are known and identical, print the shortened
11563 @code{param=param@@entry=VALUE} notation.
11565 #0 equal (val=val@@entry=5)
11566 #0 different (val=6, val@@entry=5)
11567 #0 lost (val@@entry=5)
11569 #0 invalid (val=<optimized out>)
11573 Always print the actual parameter value. Print also its value from function
11574 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
11575 if both values are known and identical, print the shortened
11576 @code{param=param@@entry=VALUE} notation.
11578 #0 equal (val=val@@entry=5)
11579 #0 different (val=6, val@@entry=5)
11580 #0 lost (val=<optimized out>, val@@entry=5)
11582 #0 invalid (val=<optimized out>)
11586 For analysis messages on possible failures of frame argument values at function
11587 entry resolution see @ref{set debug entry-values}.
11589 @item show print entry-values
11590 Show the method being used for printing of frame argument values at function
11593 @anchor{set print frame-info}
11594 @item set print frame-info @var{value}
11595 @kindex set print frame-info
11596 @cindex printing frame information
11597 @cindex frame information, printing
11598 This command allows to control the information printed when
11599 the debugger prints a frame. See @ref{Frames}, @ref{Backtrace},
11600 for a general explanation about frames and frame information.
11601 Note that some other settings (such as @code{set print frame-arguments}
11602 and @code{set print address}) are also influencing if and how some frame
11603 information is displayed. In particular, the frame program counter is never
11604 printed if @code{set print address} is off.
11606 The possible values for @code{set print frame-info} are:
11608 @item short-location
11609 Print the frame level, the program counter (if not at the
11610 beginning of the location source line), the function, the function
11613 Same as @code{short-location} but also print the source file and source line
11615 @item location-and-address
11616 Same as @code{location} but print the program counter even if located at the
11617 beginning of the location source line.
11619 Print the program counter (if not at the beginning of the location
11620 source line), the line number and the source line.
11621 @item source-and-location
11622 Print what @code{location} and @code{source-line} are printing.
11624 The information printed for a frame is decided automatically
11625 by the @value{GDBN} command that prints a frame.
11626 For example, @code{frame} prints the information printed by
11627 @code{source-and-location} while @code{stepi} will switch between
11628 @code{source-line} and @code{source-and-location} depending on the program
11630 The default value is @code{auto}.
11633 @anchor{set print repeats}
11634 @item set print repeats @var{number-of-repeats}
11635 @itemx set print repeats unlimited
11636 @cindex repeated array elements
11637 Set the threshold for suppressing display of repeated array
11638 elements. When the number of consecutive identical elements of an
11639 array exceeds the threshold, @value{GDBN} prints the string
11640 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
11641 identical repetitions, instead of displaying the identical elements
11642 themselves. Setting the threshold to @code{unlimited} or zero will
11643 cause all elements to be individually printed. The default threshold
11646 @item show print repeats
11647 Display the current threshold for printing repeated identical
11650 @anchor{set print max-depth}
11651 @item set print max-depth @var{depth}
11652 @item set print max-depth unlimited
11653 @cindex printing nested structures
11654 Set the threshold after which nested structures are replaced with
11655 ellipsis, this can make visualising deeply nested structures easier.
11657 For example, given this C code
11660 typedef struct s1 @{ int a; @} s1;
11661 typedef struct s2 @{ s1 b; @} s2;
11662 typedef struct s3 @{ s2 c; @} s3;
11663 typedef struct s4 @{ s3 d; @} s4;
11665 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
11668 The following table shows how different values of @var{depth} will
11669 effect how @code{var} is printed by @value{GDBN}:
11671 @multitable @columnfractions .3 .7
11672 @headitem @var{depth} setting @tab Result of @samp{p var}
11674 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11676 @tab @code{$1 = @{...@}}
11678 @tab @code{$1 = @{d = @{...@}@}}
11680 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
11682 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
11684 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
11687 To see the contents of structures that have been hidden the user can
11688 either increase the print max-depth, or they can print the elements of
11689 the structure that are visible, for example
11692 (gdb) set print max-depth 2
11694 $1 = @{d = @{c = @{...@}@}@}
11696 $2 = @{c = @{b = @{...@}@}@}
11698 $3 = @{b = @{a = 3@}@}
11701 The pattern used to replace nested structures varies based on
11702 language, for most languages @code{@{...@}} is used, but Fortran uses
11705 @item show print max-depth
11706 Display the current threshold after which nested structures are
11707 replaces with ellipsis.
11709 @anchor{set print memory-tag-violations}
11710 @cindex printing memory tag violation information
11711 @item set print memory-tag-violations
11712 @itemx set print memory-tag-violations on
11713 Cause @value{GDBN} to display additional information about memory tag violations
11714 when printing pointers and addresses.
11716 @item set print memory-tag-violations off
11717 Stop printing memory tag violation information.
11719 @item show print memory-tag-violations
11720 Show whether memory tag violation information is displayed when printing
11721 pointers and addresses.
11723 @anchor{set print null-stop}
11724 @item set print null-stop
11725 @cindex @sc{null} elements in arrays
11726 Cause @value{GDBN} to stop printing the characters of an array when the first
11727 @sc{null} is encountered. This is useful when large arrays actually
11728 contain only short strings.
11729 The default is off.
11731 @item show print null-stop
11732 Show whether @value{GDBN} stops printing an array on the first
11733 @sc{null} character.
11735 @anchor{set print pretty}
11736 @item set print pretty on
11737 @cindex print structures in indented form
11738 @cindex indentation in structure display
11739 Cause @value{GDBN} to print structures in an indented format with one member
11740 per line, like this:
11755 @item set print pretty off
11756 Cause @value{GDBN} to print structures in a compact format, like this:
11760 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
11761 meat = 0x54 "Pork"@}
11766 This is the default format.
11768 @item show print pretty
11769 Show which format @value{GDBN} is using to print structures.
11771 @anchor{set print raw-values}
11772 @item set print raw-values on
11773 Print values in raw form, without applying the pretty
11774 printers for the value.
11776 @item set print raw-values off
11777 Print values in pretty-printed form, if there is a pretty-printer
11778 for the value (@pxref{Pretty Printing}),
11779 otherwise print the value in raw form.
11781 The default setting is ``off''.
11783 @item show print raw-values
11784 Show whether to print values in raw form.
11786 @item set print sevenbit-strings on
11787 @cindex eight-bit characters in strings
11788 @cindex octal escapes in strings
11789 Print using only seven-bit characters; if this option is set,
11790 @value{GDBN} displays any eight-bit characters (in strings or
11791 character values) using the notation @code{\}@var{nnn}. This setting is
11792 best if you are working in English (@sc{ascii}) and you use the
11793 high-order bit of characters as a marker or ``meta'' bit.
11795 @item set print sevenbit-strings off
11796 Print full eight-bit characters. This allows the use of more
11797 international character sets, and is the default.
11799 @item show print sevenbit-strings
11800 Show whether or not @value{GDBN} is printing only seven-bit characters.
11802 @anchor{set print union}
11803 @item set print union on
11804 @cindex unions in structures, printing
11805 Tell @value{GDBN} to print unions which are contained in structures
11806 and other unions. This is the default setting.
11808 @item set print union off
11809 Tell @value{GDBN} not to print unions which are contained in
11810 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
11813 @item show print union
11814 Ask @value{GDBN} whether or not it will print unions which are contained in
11815 structures and other unions.
11817 For example, given the declarations
11820 typedef enum @{Tree, Bug@} Species;
11821 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
11822 typedef enum @{Caterpillar, Cocoon, Butterfly@}
11833 struct thing foo = @{Tree, @{Acorn@}@};
11837 with @code{set print union on} in effect @samp{p foo} would print
11840 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
11844 and with @code{set print union off} in effect it would print
11847 $1 = @{it = Tree, form = @{...@}@}
11851 @code{set print union} affects programs written in C-like languages
11857 These settings are of interest when debugging C@t{++} programs:
11860 @cindex demangling C@t{++} names
11861 @item set print demangle
11862 @itemx set print demangle on
11863 Print C@t{++} names in their source form rather than in the encoded
11864 (``mangled'') form passed to the assembler and linker for type-safe
11865 linkage. The default is on.
11867 @item show print demangle
11868 Show whether C@t{++} names are printed in mangled or demangled form.
11870 @item set print asm-demangle
11871 @itemx set print asm-demangle on
11872 Print C@t{++} names in their source form rather than their mangled form, even
11873 in assembler code printouts such as instruction disassemblies.
11874 The default is off.
11876 @item show print asm-demangle
11877 Show whether C@t{++} names in assembly listings are printed in mangled
11880 @cindex C@t{++} symbol decoding style
11881 @cindex symbol decoding style, C@t{++}
11882 @kindex set demangle-style
11883 @item set demangle-style @var{style}
11884 Choose among several encoding schemes used by different compilers to represent
11885 C@t{++} names. If you omit @var{style}, you will see a list of possible
11886 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
11887 decoding style by inspecting your program.
11889 @item show demangle-style
11890 Display the encoding style currently in use for decoding C@t{++} symbols.
11892 @anchor{set print object}
11893 @item set print object
11894 @itemx set print object on
11895 @cindex derived type of an object, printing
11896 @cindex display derived types
11897 When displaying a pointer to an object, identify the @emph{actual}
11898 (derived) type of the object rather than the @emph{declared} type, using
11899 the virtual function table. Note that the virtual function table is
11900 required---this feature can only work for objects that have run-time
11901 type identification; a single virtual method in the object's declared
11902 type is sufficient. Note that this setting is also taken into account when
11903 working with variable objects via MI (@pxref{GDB/MI}).
11905 @item set print object off
11906 Display only the declared type of objects, without reference to the
11907 virtual function table. This is the default setting.
11909 @item show print object
11910 Show whether actual, or declared, object types are displayed.
11912 @anchor{set print static-members}
11913 @item set print static-members
11914 @itemx set print static-members on
11915 @cindex static members of C@t{++} objects
11916 Print static members when displaying a C@t{++} object. The default is on.
11918 @item set print static-members off
11919 Do not print static members when displaying a C@t{++} object.
11921 @item show print static-members
11922 Show whether C@t{++} static members are printed or not.
11924 @item set print pascal_static-members
11925 @itemx set print pascal_static-members on
11926 @cindex static members of Pascal objects
11927 @cindex Pascal objects, static members display
11928 Print static members when displaying a Pascal object. The default is on.
11930 @item set print pascal_static-members off
11931 Do not print static members when displaying a Pascal object.
11933 @item show print pascal_static-members
11934 Show whether Pascal static members are printed or not.
11936 @c These don't work with HP ANSI C++ yet.
11937 @anchor{set print vtbl}
11938 @item set print vtbl
11939 @itemx set print vtbl on
11940 @cindex pretty print C@t{++} virtual function tables
11941 @cindex virtual functions (C@t{++}) display
11942 @cindex VTBL display
11943 Pretty print C@t{++} virtual function tables. The default is off.
11944 (The @code{vtbl} commands do not work on programs compiled with the HP
11945 ANSI C@t{++} compiler (@code{aCC}).)
11947 @item set print vtbl off
11948 Do not pretty print C@t{++} virtual function tables.
11950 @item show print vtbl
11951 Show whether C@t{++} virtual function tables are pretty printed, or not.
11954 @node Pretty Printing
11955 @section Pretty Printing
11957 @value{GDBN} provides a mechanism to allow pretty-printing of values using
11958 Python code. It greatly simplifies the display of complex objects. This
11959 mechanism works for both MI and the CLI.
11962 * Pretty-Printer Introduction:: Introduction to pretty-printers
11963 * Pretty-Printer Example:: An example pretty-printer
11964 * Pretty-Printer Commands:: Pretty-printer commands
11967 @node Pretty-Printer Introduction
11968 @subsection Pretty-Printer Introduction
11970 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
11971 registered for the value. If there is then @value{GDBN} invokes the
11972 pretty-printer to print the value. Otherwise the value is printed normally.
11974 Pretty-printers are normally named. This makes them easy to manage.
11975 The @samp{info pretty-printer} command will list all the installed
11976 pretty-printers with their names.
11977 If a pretty-printer can handle multiple data types, then its
11978 @dfn{subprinters} are the printers for the individual data types.
11979 Each such subprinter has its own name.
11980 The format of the name is @var{printer-name};@var{subprinter-name}.
11982 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
11983 Typically they are automatically loaded and registered when the corresponding
11984 debug information is loaded, thus making them available without having to
11985 do anything special.
11987 There are three places where a pretty-printer can be registered.
11991 Pretty-printers registered globally are available when debugging
11995 Pretty-printers registered with a program space are available only
11996 when debugging that program.
11997 @xref{Progspaces In Python}, for more details on program spaces in Python.
12000 Pretty-printers registered with an objfile are loaded and unloaded
12001 with the corresponding objfile (e.g., shared library).
12002 @xref{Objfiles In Python}, for more details on objfiles in Python.
12005 @xref{Selecting Pretty-Printers}, for further information on how
12006 pretty-printers are selected,
12008 @xref{Writing a Pretty-Printer}, for implementing pretty printers
12011 @node Pretty-Printer Example
12012 @subsection Pretty-Printer Example
12014 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
12017 (@value{GDBP}) print s
12019 static npos = 4294967295,
12021 <std::allocator<char>> = @{
12022 <__gnu_cxx::new_allocator<char>> = @{
12023 <No data fields>@}, <No data fields>
12025 members of std::basic_string<char, std::char_traits<char>,
12026 std::allocator<char> >::_Alloc_hider:
12027 _M_p = 0x804a014 "abcd"
12032 With a pretty-printer for @code{std::string} only the contents are printed:
12035 (@value{GDBP}) print s
12039 @node Pretty-Printer Commands
12040 @subsection Pretty-Printer Commands
12041 @cindex pretty-printer commands
12044 @kindex info pretty-printer
12045 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12046 Print the list of installed pretty-printers.
12047 This includes disabled pretty-printers, which are marked as such.
12049 @var{object-regexp} is a regular expression matching the objects
12050 whose pretty-printers to list.
12051 Objects can be @code{global}, the program space's file
12052 (@pxref{Progspaces In Python}),
12053 and the object files within that program space (@pxref{Objfiles In Python}).
12054 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
12055 looks up a printer from these three objects.
12057 @var{name-regexp} is a regular expression matching the name of the printers
12060 @kindex disable pretty-printer
12061 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12062 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12063 A disabled pretty-printer is not forgotten, it may be enabled again later.
12065 @kindex enable pretty-printer
12066 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
12067 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
12072 Suppose we have three pretty-printers installed: one from library1.so
12073 named @code{foo} that prints objects of type @code{foo}, and
12074 another from library2.so named @code{bar} that prints two types of objects,
12075 @code{bar1} and @code{bar2}.
12078 (gdb) info pretty-printer
12085 (gdb) info pretty-printer library2
12090 (gdb) disable pretty-printer library1
12092 2 of 3 printers enabled
12093 (gdb) info pretty-printer
12100 (gdb) disable pretty-printer library2 bar;bar1
12102 1 of 3 printers enabled
12103 (gdb) info pretty-printer library2
12110 (gdb) disable pretty-printer library2 bar
12112 0 of 3 printers enabled
12113 (gdb) info pretty-printer library2
12122 Note that for @code{bar} the entire printer can be disabled,
12123 as can each individual subprinter.
12125 Printing values and frame arguments is done by default using
12126 the enabled pretty printers.
12128 The print option @code{-raw-values} and @value{GDBN} setting
12129 @code{set print raw-values} (@pxref{set print raw-values}) can be
12130 used to print values without applying the enabled pretty printers.
12132 Similarly, the backtrace option @code{-raw-frame-arguments} and
12133 @value{GDBN} setting @code{set print raw-frame-arguments}
12134 (@pxref{set print raw-frame-arguments}) can be used to ignore the
12135 enabled pretty printers when printing frame argument values.
12137 @node Value History
12138 @section Value History
12140 @cindex value history
12141 @cindex history of values printed by @value{GDBN}
12142 Values printed by the @code{print} command are saved in the @value{GDBN}
12143 @dfn{value history}. This allows you to refer to them in other expressions.
12144 Values are kept until the symbol table is re-read or discarded
12145 (for example with the @code{file} or @code{symbol-file} commands).
12146 When the symbol table changes, the value history is discarded,
12147 since the values may contain pointers back to the types defined in the
12152 @cindex history number
12153 The values printed are given @dfn{history numbers} by which you can
12154 refer to them. These are successive integers starting with one.
12155 @code{print} shows you the history number assigned to a value by
12156 printing @samp{$@var{num} = } before the value; here @var{num} is the
12159 To refer to any previous value, use @samp{$} followed by the value's
12160 history number. The way @code{print} labels its output is designed to
12161 remind you of this. Just @code{$} refers to the most recent value in
12162 the history, and @code{$$} refers to the value before that.
12163 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
12164 is the value just prior to @code{$$}, @code{$$1} is equivalent to
12165 @code{$$}, and @code{$$0} is equivalent to @code{$}.
12167 For example, suppose you have just printed a pointer to a structure and
12168 want to see the contents of the structure. It suffices to type
12174 If you have a chain of structures where the component @code{next} points
12175 to the next one, you can print the contents of the next one with this:
12182 You can print successive links in the chain by repeating this
12183 command---which you can do by just typing @key{RET}.
12185 Note that the history records values, not expressions. If the value of
12186 @code{x} is 4 and you type these commands:
12194 then the value recorded in the value history by the @code{print} command
12195 remains 4 even though the value of @code{x} has changed.
12198 @kindex show values
12200 Print the last ten values in the value history, with their item numbers.
12201 This is like @samp{p@ $$9} repeated ten times, except that @code{show
12202 values} does not change the history.
12204 @item show values @var{n}
12205 Print ten history values centered on history item number @var{n}.
12207 @item show values +
12208 Print ten history values just after the values last printed. If no more
12209 values are available, @code{show values +} produces no display.
12212 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
12213 same effect as @samp{show values +}.
12215 @node Convenience Vars
12216 @section Convenience Variables
12218 @cindex convenience variables
12219 @cindex user-defined variables
12220 @value{GDBN} provides @dfn{convenience variables} that you can use within
12221 @value{GDBN} to hold on to a value and refer to it later. These variables
12222 exist entirely within @value{GDBN}; they are not part of your program, and
12223 setting a convenience variable has no direct effect on further execution
12224 of your program. That is why you can use them freely.
12226 Convenience variables are prefixed with @samp{$}. Any name preceded by
12227 @samp{$} can be used for a convenience variable, unless it is one of
12228 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
12229 (Value history references, in contrast, are @emph{numbers} preceded
12230 by @samp{$}. @xref{Value History, ,Value History}.)
12232 You can save a value in a convenience variable with an assignment
12233 expression, just as you would set a variable in your program.
12237 set $foo = *object_ptr
12241 would save in @code{$foo} the value contained in the object pointed to by
12244 Using a convenience variable for the first time creates it, but its
12245 value is @code{void} until you assign a new value. You can alter the
12246 value with another assignment at any time.
12248 Convenience variables have no fixed types. You can assign a convenience
12249 variable any type of value, including structures and arrays, even if
12250 that variable already has a value of a different type. The convenience
12251 variable, when used as an expression, has the type of its current value.
12254 @kindex show convenience
12255 @cindex show all user variables and functions
12256 @item show convenience
12257 Print a list of convenience variables used so far, and their values,
12258 as well as a list of the convenience functions.
12259 Abbreviated @code{show conv}.
12261 @kindex init-if-undefined
12262 @cindex convenience variables, initializing
12263 @item init-if-undefined $@var{variable} = @var{expression}
12264 Set a convenience variable if it has not already been set. This is useful
12265 for user-defined commands that keep some state. It is similar, in concept,
12266 to using local static variables with initializers in C (except that
12267 convenience variables are global). It can also be used to allow users to
12268 override default values used in a command script.
12270 If the variable is already defined then the expression is not evaluated so
12271 any side-effects do not occur.
12274 One of the ways to use a convenience variable is as a counter to be
12275 incremented or a pointer to be advanced. For example, to print
12276 a field from successive elements of an array of structures:
12280 print bar[$i++]->contents
12284 Repeat that command by typing @key{RET}.
12286 Some convenience variables are created automatically by @value{GDBN} and given
12287 values likely to be useful.
12290 @vindex $_@r{, convenience variable}
12292 The variable @code{$_} is automatically set by the @code{x} command to
12293 the last address examined (@pxref{Memory, ,Examining Memory}). Other
12294 commands which provide a default address for @code{x} to examine also
12295 set @code{$_} to that address; these commands include @code{info line}
12296 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
12297 except when set by the @code{x} command, in which case it is a pointer
12298 to the type of @code{$__}.
12300 @vindex $__@r{, convenience variable}
12302 The variable @code{$__} is automatically set by the @code{x} command
12303 to the value found in the last address examined. Its type is chosen
12304 to match the format in which the data was printed.
12307 @vindex $_exitcode@r{, convenience variable}
12308 When the program being debugged terminates normally, @value{GDBN}
12309 automatically sets this variable to the exit code of the program, and
12310 resets @code{$_exitsignal} to @code{void}.
12313 @vindex $_exitsignal@r{, convenience variable}
12314 When the program being debugged dies due to an uncaught signal,
12315 @value{GDBN} automatically sets this variable to that signal's number,
12316 and resets @code{$_exitcode} to @code{void}.
12318 To distinguish between whether the program being debugged has exited
12319 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
12320 @code{$_exitsignal} is not @code{void}), the convenience function
12321 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
12322 Functions}). For example, considering the following source code:
12325 #include <signal.h>
12328 main (int argc, char *argv[])
12335 A valid way of telling whether the program being debugged has exited
12336 or signalled would be:
12339 (@value{GDBP}) define has_exited_or_signalled
12340 Type commands for definition of ``has_exited_or_signalled''.
12341 End with a line saying just ``end''.
12342 >if $_isvoid ($_exitsignal)
12343 >echo The program has exited\n
12345 >echo The program has signalled\n
12351 Program terminated with signal SIGALRM, Alarm clock.
12352 The program no longer exists.
12353 (@value{GDBP}) has_exited_or_signalled
12354 The program has signalled
12357 As can be seen, @value{GDBN} correctly informs that the program being
12358 debugged has signalled, since it calls @code{raise} and raises a
12359 @code{SIGALRM} signal. If the program being debugged had not called
12360 @code{raise}, then @value{GDBN} would report a normal exit:
12363 (@value{GDBP}) has_exited_or_signalled
12364 The program has exited
12368 The variable @code{$_exception} is set to the exception object being
12369 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
12371 @item $_ada_exception
12372 The variable @code{$_ada_exception} is set to the address of the
12373 exception being caught or thrown at an Ada exception-related
12374 catchpoint. @xref{Set Catchpoints}.
12377 @itemx $_probe_arg0@dots{}$_probe_arg11
12378 Arguments to a static probe. @xref{Static Probe Points}.
12381 @vindex $_sdata@r{, inspect, convenience variable}
12382 The variable @code{$_sdata} contains extra collected static tracepoint
12383 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
12384 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
12385 if extra static tracepoint data has not been collected.
12388 @vindex $_siginfo@r{, convenience variable}
12389 The variable @code{$_siginfo} contains extra signal information
12390 (@pxref{extra signal information}). Note that @code{$_siginfo}
12391 could be empty, if the application has not yet received any signals.
12392 For example, it will be empty before you execute the @code{run} command.
12395 @vindex $_tlb@r{, convenience variable}
12396 The variable @code{$_tlb} is automatically set when debugging
12397 applications running on MS-Windows in native mode or connected to
12398 gdbserver that supports the @code{qGetTIBAddr} request.
12399 @xref{General Query Packets}.
12400 This variable contains the address of the thread information block.
12403 The number of the current inferior. @xref{Inferiors Connections and
12404 Programs, ,Debugging Multiple Inferiors Connections and Programs}.
12407 The thread number of the current thread. @xref{thread numbers}.
12410 The global number of the current thread. @xref{global thread numbers}.
12414 @vindex $_gdb_major@r{, convenience variable}
12415 @vindex $_gdb_minor@r{, convenience variable}
12416 The major and minor version numbers of the running @value{GDBN}.
12417 Development snapshots and pretest versions have their minor version
12418 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
12419 the value 12 for @code{$_gdb_minor}. These variables allow you to
12420 write scripts that work with different versions of @value{GDBN}
12421 without errors caused by features unavailable in some of those
12424 @item $_shell_exitcode
12425 @itemx $_shell_exitsignal
12426 @vindex $_shell_exitcode@r{, convenience variable}
12427 @vindex $_shell_exitsignal@r{, convenience variable}
12428 @cindex shell command, exit code
12429 @cindex shell command, exit signal
12430 @cindex exit status of shell commands
12431 @value{GDBN} commands such as @code{shell} and @code{|} are launching
12432 shell commands. When a launched command terminates, @value{GDBN}
12433 automatically maintains the variables @code{$_shell_exitcode}
12434 and @code{$_shell_exitsignal} according to the exit status of the last
12435 launched command. These variables are set and used similarly to
12436 the variables @code{$_exitcode} and @code{$_exitsignal}.
12440 @node Convenience Funs
12441 @section Convenience Functions
12443 @cindex convenience functions
12444 @value{GDBN} also supplies some @dfn{convenience functions}. These
12445 have a syntax similar to convenience variables. A convenience
12446 function can be used in an expression just like an ordinary function;
12447 however, a convenience function is implemented internally to
12450 These functions do not require @value{GDBN} to be configured with
12451 @code{Python} support, which means that they are always available.
12455 @item $_isvoid (@var{expr})
12456 @findex $_isvoid@r{, convenience function}
12457 Return one if the expression @var{expr} is @code{void}. Otherwise it
12460 A @code{void} expression is an expression where the type of the result
12461 is @code{void}. For example, you can examine a convenience variable
12462 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
12466 (@value{GDBP}) print $_exitcode
12468 (@value{GDBP}) print $_isvoid ($_exitcode)
12471 Starting program: ./a.out
12472 [Inferior 1 (process 29572) exited normally]
12473 (@value{GDBP}) print $_exitcode
12475 (@value{GDBP}) print $_isvoid ($_exitcode)
12479 In the example above, we used @code{$_isvoid} to check whether
12480 @code{$_exitcode} is @code{void} before and after the execution of the
12481 program being debugged. Before the execution there is no exit code to
12482 be examined, therefore @code{$_exitcode} is @code{void}. After the
12483 execution the program being debugged returned zero, therefore
12484 @code{$_exitcode} is zero, which means that it is not @code{void}
12487 The @code{void} expression can also be a call of a function from the
12488 program being debugged. For example, given the following function:
12497 The result of calling it inside @value{GDBN} is @code{void}:
12500 (@value{GDBP}) print foo ()
12502 (@value{GDBP}) print $_isvoid (foo ())
12504 (@value{GDBP}) set $v = foo ()
12505 (@value{GDBP}) print $v
12507 (@value{GDBP}) print $_isvoid ($v)
12511 @item $_gdb_setting_str (@var{setting})
12512 @findex $_gdb_setting_str@r{, convenience function}
12513 Return the value of the @value{GDBN} @var{setting} as a string.
12514 @var{setting} is any setting that can be used in a @code{set} or
12515 @code{show} command (@pxref{Controlling GDB}).
12518 (@value{GDBP}) show print frame-arguments
12519 Printing of non-scalar frame arguments is "scalars".
12520 (@value{GDBP}) p $_gdb_setting_str("print frame-arguments")
12522 (@value{GDBP}) p $_gdb_setting_str("height")
12527 @item $_gdb_setting (@var{setting})
12528 @findex $_gdb_setting@r{, convenience function}
12529 Return the value of the @value{GDBN} @var{setting}.
12530 The type of the returned value depends on the setting.
12532 The value type for boolean and auto boolean settings is @code{int}.
12533 The boolean values @code{off} and @code{on} are converted to
12534 the integer values @code{0} and @code{1}. The value @code{auto} is
12535 converted to the value @code{-1}.
12537 The value type for integer settings is either @code{unsigned int}
12538 or @code{int}, depending on the setting.
12540 Some integer settings accept an @code{unlimited} value.
12541 Depending on the setting, the @code{set} command also accepts
12542 the value @code{0} or the value @code{@minus{}1} as a synonym for
12544 For example, @code{set height unlimited} is equivalent to
12545 @code{set height 0}.
12547 Some other settings that accept the @code{unlimited} value
12548 use the value @code{0} to literally mean zero.
12549 For example, @code{set history size 0} indicates to not
12550 record any @value{GDBN} commands in the command history.
12551 For such settings, @code{@minus{}1} is the synonym
12552 for @code{unlimited}.
12554 See the documentation of the corresponding @code{set} command for
12555 the numerical value equivalent to @code{unlimited}.
12557 The @code{$_gdb_setting} function converts the unlimited value
12558 to a @code{0} or a @code{@minus{}1} value according to what the
12559 @code{set} command uses.
12563 (@value{GDBP}) p $_gdb_setting_str("height")
12565 (@value{GDBP}) p $_gdb_setting("height")
12567 (@value{GDBP}) set height unlimited
12568 (@value{GDBP}) p $_gdb_setting_str("height")
12570 (@value{GDBP}) p $_gdb_setting("height")
12574 (@value{GDBP}) p $_gdb_setting_str("history size")
12576 (@value{GDBP}) p $_gdb_setting("history size")
12578 (@value{GDBP}) p $_gdb_setting_str("disassemble-next-line")
12580 (@value{GDBP}) p $_gdb_setting("disassemble-next-line")
12586 Other setting types (enum, filename, optional filename, string, string noescape)
12587 are returned as string values.
12590 @item $_gdb_maint_setting_str (@var{setting})
12591 @findex $_gdb_maint_setting_str@r{, convenience function}
12592 Like the @code{$_gdb_setting_str} function, but works with
12593 @code{maintenance set} variables.
12595 @item $_gdb_maint_setting (@var{setting})
12596 @findex $_gdb_maint_setting@r{, convenience function}
12597 Like the @code{$_gdb_setting} function, but works with
12598 @code{maintenance set} variables.
12602 The following functions require @value{GDBN} to be configured with
12603 @code{Python} support.
12607 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
12608 @findex $_memeq@r{, convenience function}
12609 Returns one if the @var{length} bytes at the addresses given by
12610 @var{buf1} and @var{buf2} are equal.
12611 Otherwise it returns zero.
12613 @item $_regex(@var{str}, @var{regex})
12614 @findex $_regex@r{, convenience function}
12615 Returns one if the string @var{str} matches the regular expression
12616 @var{regex}. Otherwise it returns zero.
12617 The syntax of the regular expression is that specified by @code{Python}'s
12618 regular expression support.
12620 @item $_streq(@var{str1}, @var{str2})
12621 @findex $_streq@r{, convenience function}
12622 Returns one if the strings @var{str1} and @var{str2} are equal.
12623 Otherwise it returns zero.
12625 @item $_strlen(@var{str})
12626 @findex $_strlen@r{, convenience function}
12627 Returns the length of string @var{str}.
12629 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12630 @findex $_caller_is@r{, convenience function}
12631 Returns one if the calling function's name is equal to @var{name}.
12632 Otherwise it returns zero.
12634 If the optional argument @var{number_of_frames} is provided,
12635 it is the number of frames up in the stack to look.
12643 at testsuite/gdb.python/py-caller-is.c:21
12644 #1 0x00000000004005a0 in middle_func ()
12645 at testsuite/gdb.python/py-caller-is.c:27
12646 #2 0x00000000004005ab in top_func ()
12647 at testsuite/gdb.python/py-caller-is.c:33
12648 #3 0x00000000004005b6 in main ()
12649 at testsuite/gdb.python/py-caller-is.c:39
12650 (gdb) print $_caller_is ("middle_func")
12652 (gdb) print $_caller_is ("top_func", 2)
12656 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12657 @findex $_caller_matches@r{, convenience function}
12658 Returns one if the calling function's name matches the regular expression
12659 @var{regexp}. Otherwise it returns zero.
12661 If the optional argument @var{number_of_frames} is provided,
12662 it is the number of frames up in the stack to look.
12665 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
12666 @findex $_any_caller_is@r{, convenience function}
12667 Returns one if any calling function's name is equal to @var{name}.
12668 Otherwise it returns zero.
12670 If the optional argument @var{number_of_frames} is provided,
12671 it is the number of frames up in the stack to look.
12674 This function differs from @code{$_caller_is} in that this function
12675 checks all stack frames from the immediate caller to the frame specified
12676 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
12677 frame specified by @var{number_of_frames}.
12679 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
12680 @findex $_any_caller_matches@r{, convenience function}
12681 Returns one if any calling function's name matches the regular expression
12682 @var{regexp}. Otherwise it returns zero.
12684 If the optional argument @var{number_of_frames} is provided,
12685 it is the number of frames up in the stack to look.
12688 This function differs from @code{$_caller_matches} in that this function
12689 checks all stack frames from the immediate caller to the frame specified
12690 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
12691 frame specified by @var{number_of_frames}.
12693 @item $_as_string(@var{value})
12694 @findex $_as_string@r{, convenience function}
12695 Return the string representation of @var{value}.
12697 This function is useful to obtain the textual label (enumerator) of an
12698 enumeration value. For example, assuming the variable @var{node} is of
12699 an enumerated type:
12702 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
12703 Visiting node of type NODE_INTEGER
12706 @item $_cimag(@var{value})
12707 @itemx $_creal(@var{value})
12708 @findex $_cimag@r{, convenience function}
12709 @findex $_creal@r{, convenience function}
12710 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
12711 the complex number @var{value}.
12713 The type of the imaginary or real part depends on the type of the
12714 complex number, e.g., using @code{$_cimag} on a @code{float complex}
12715 will return an imaginary part of type @code{float}.
12719 @value{GDBN} provides the ability to list and get help on
12720 convenience functions.
12723 @item help function
12724 @kindex help function
12725 @cindex show all convenience functions
12726 Print a list of all convenience functions.
12733 You can refer to machine register contents, in expressions, as variables
12734 with names starting with @samp{$}. The names of registers are different
12735 for each machine; use @code{info registers} to see the names used on
12739 @kindex info registers
12740 @item info registers
12741 Print the names and values of all registers except floating-point
12742 and vector registers (in the selected stack frame).
12744 @kindex info all-registers
12745 @cindex floating point registers
12746 @item info all-registers
12747 Print the names and values of all registers, including floating-point
12748 and vector registers (in the selected stack frame).
12750 @anchor{info_registers_reggroup}
12751 @item info registers @var{reggroup} @dots{}
12752 Print the name and value of the registers in each of the specified
12753 @var{reggroup}s. The @var{reggroup} can be any of those returned by
12754 @code{maint print reggroups} (@pxref{Maintenance Commands}).
12756 @item info registers @var{regname} @dots{}
12757 Print the @dfn{relativized} value of each specified register @var{regname}.
12758 As discussed in detail below, register values are normally relative to
12759 the selected stack frame. The @var{regname} may be any register name valid on
12760 the machine you are using, with or without the initial @samp{$}.
12763 @anchor{standard registers}
12764 @cindex stack pointer register
12765 @cindex program counter register
12766 @cindex process status register
12767 @cindex frame pointer register
12768 @cindex standard registers
12769 @value{GDBN} has four ``standard'' register names that are available (in
12770 expressions) on most machines---whenever they do not conflict with an
12771 architecture's canonical mnemonics for registers. The register names
12772 @code{$pc} and @code{$sp} are used for the program counter register and
12773 the stack pointer. @code{$fp} is used for a register that contains a
12774 pointer to the current stack frame, and @code{$ps} is used for a
12775 register that contains the processor status. For example,
12776 you could print the program counter in hex with
12783 or print the instruction to be executed next with
12790 or add four to the stack pointer@footnote{This is a way of removing
12791 one word from the stack, on machines where stacks grow downward in
12792 memory (most machines, nowadays). This assumes that the innermost
12793 stack frame is selected; setting @code{$sp} is not allowed when other
12794 stack frames are selected. To pop entire frames off the stack,
12795 regardless of machine architecture, use @code{return};
12796 see @ref{Returning, ,Returning from a Function}.} with
12802 Whenever possible, these four standard register names are available on
12803 your machine even though the machine has different canonical mnemonics,
12804 so long as there is no conflict. The @code{info registers} command
12805 shows the canonical names. For example, on the SPARC, @code{info
12806 registers} displays the processor status register as @code{$psr} but you
12807 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
12808 is an alias for the @sc{eflags} register.
12810 @value{GDBN} always considers the contents of an ordinary register as an
12811 integer when the register is examined in this way. Some machines have
12812 special registers which can hold nothing but floating point; these
12813 registers are considered to have floating point values. There is no way
12814 to refer to the contents of an ordinary register as floating point value
12815 (although you can @emph{print} it as a floating point value with
12816 @samp{print/f $@var{regname}}).
12818 Some registers have distinct ``raw'' and ``virtual'' data formats. This
12819 means that the data format in which the register contents are saved by
12820 the operating system is not the same one that your program normally
12821 sees. For example, the registers of the 68881 floating point
12822 coprocessor are always saved in ``extended'' (raw) format, but all C
12823 programs expect to work with ``double'' (virtual) format. In such
12824 cases, @value{GDBN} normally works with the virtual format only (the format
12825 that makes sense for your program), but the @code{info registers} command
12826 prints the data in both formats.
12828 @cindex SSE registers (x86)
12829 @cindex MMX registers (x86)
12830 Some machines have special registers whose contents can be interpreted
12831 in several different ways. For example, modern x86-based machines
12832 have SSE and MMX registers that can hold several values packed
12833 together in several different formats. @value{GDBN} refers to such
12834 registers in @code{struct} notation:
12837 (@value{GDBP}) print $xmm1
12839 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
12840 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
12841 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
12842 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
12843 v4_int32 = @{0, 20657912, 11, 13@},
12844 v2_int64 = @{88725056443645952, 55834574859@},
12845 uint128 = 0x0000000d0000000b013b36f800000000
12850 To set values of such registers, you need to tell @value{GDBN} which
12851 view of the register you wish to change, as if you were assigning
12852 value to a @code{struct} member:
12855 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
12858 Normally, register values are relative to the selected stack frame
12859 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
12860 value that the register would contain if all stack frames farther in
12861 were exited and their saved registers restored. In order to see the
12862 true contents of hardware registers, you must select the innermost
12863 frame (with @samp{frame 0}).
12865 @cindex caller-saved registers
12866 @cindex call-clobbered registers
12867 @cindex volatile registers
12868 @cindex <not saved> values
12869 Usually ABIs reserve some registers as not needed to be saved by the
12870 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
12871 registers). It may therefore not be possible for @value{GDBN} to know
12872 the value a register had before the call (in other words, in the outer
12873 frame), if the register value has since been changed by the callee.
12874 @value{GDBN} tries to deduce where the inner frame saved
12875 (``callee-saved'') registers, from the debug info, unwind info, or the
12876 machine code generated by your compiler. If some register is not
12877 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
12878 its own knowledge of the ABI, or because the debug/unwind info
12879 explicitly says the register's value is undefined), @value{GDBN}
12880 displays @w{@samp{<not saved>}} as the register's value. With targets
12881 that @value{GDBN} has no knowledge of the register saving convention,
12882 if a register was not saved by the callee, then its value and location
12883 in the outer frame are assumed to be the same of the inner frame.
12884 This is usually harmless, because if the register is call-clobbered,
12885 the caller either does not care what is in the register after the
12886 call, or has code to restore the value that it does care about. Note,
12887 however, that if you change such a register in the outer frame, you
12888 may also be affecting the inner frame. Also, the more ``outer'' the
12889 frame is you're looking at, the more likely a call-clobbered
12890 register's value is to be wrong, in the sense that it doesn't actually
12891 represent the value the register had just before the call.
12893 @node Floating Point Hardware
12894 @section Floating Point Hardware
12895 @cindex floating point
12897 Depending on the configuration, @value{GDBN} may be able to give
12898 you more information about the status of the floating point hardware.
12903 Display hardware-dependent information about the floating
12904 point unit. The exact contents and layout vary depending on the
12905 floating point chip. Currently, @samp{info float} is supported on
12906 the ARM and x86 machines.
12910 @section Vector Unit
12911 @cindex vector unit
12913 Depending on the configuration, @value{GDBN} may be able to give you
12914 more information about the status of the vector unit.
12917 @kindex info vector
12919 Display information about the vector unit. The exact contents and
12920 layout vary depending on the hardware.
12923 @node OS Information
12924 @section Operating System Auxiliary Information
12925 @cindex OS information
12927 @value{GDBN} provides interfaces to useful OS facilities that can help
12928 you debug your program.
12930 @cindex auxiliary vector
12931 @cindex vector, auxiliary
12932 Some operating systems supply an @dfn{auxiliary vector} to programs at
12933 startup. This is akin to the arguments and environment that you
12934 specify for a program, but contains a system-dependent variety of
12935 binary values that tell system libraries important details about the
12936 hardware, operating system, and process. Each value's purpose is
12937 identified by an integer tag; the meanings are well-known but system-specific.
12938 Depending on the configuration and operating system facilities,
12939 @value{GDBN} may be able to show you this information. For remote
12940 targets, this functionality may further depend on the remote stub's
12941 support of the @samp{qXfer:auxv:read} packet, see
12942 @ref{qXfer auxiliary vector read}.
12947 Display the auxiliary vector of the inferior, which can be either a
12948 live process or a core dump file. @value{GDBN} prints each tag value
12949 numerically, and also shows names and text descriptions for recognized
12950 tags. Some values in the vector are numbers, some bit masks, and some
12951 pointers to strings or other data. @value{GDBN} displays each value in the
12952 most appropriate form for a recognized tag, and in hexadecimal for
12953 an unrecognized tag.
12956 On some targets, @value{GDBN} can access operating system-specific
12957 information and show it to you. The types of information available
12958 will differ depending on the type of operating system running on the
12959 target. The mechanism used to fetch the data is described in
12960 @ref{Operating System Information}. For remote targets, this
12961 functionality depends on the remote stub's support of the
12962 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
12966 @item info os @var{infotype}
12968 Display OS information of the requested type.
12970 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
12972 @anchor{linux info os infotypes}
12974 @kindex info os cpus
12976 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
12977 the available fields from /proc/cpuinfo. For each supported architecture
12978 different fields are available. Two common entries are processor which gives
12979 CPU number and bogomips; a system constant that is calculated during
12980 kernel initialization.
12982 @kindex info os files
12984 Display the list of open file descriptors on the target. For each
12985 file descriptor, @value{GDBN} prints the identifier of the process
12986 owning the descriptor, the command of the owning process, the value
12987 of the descriptor, and the target of the descriptor.
12989 @kindex info os modules
12991 Display the list of all loaded kernel modules on the target. For each
12992 module, @value{GDBN} prints the module name, the size of the module in
12993 bytes, the number of times the module is used, the dependencies of the
12994 module, the status of the module, and the address of the loaded module
12997 @kindex info os msg
12999 Display the list of all System V message queues on the target. For each
13000 message queue, @value{GDBN} prints the message queue key, the message
13001 queue identifier, the access permissions, the current number of bytes
13002 on the queue, the current number of messages on the queue, the processes
13003 that last sent and received a message on the queue, the user and group
13004 of the owner and creator of the message queue, the times at which a
13005 message was last sent and received on the queue, and the time at which
13006 the message queue was last changed.
13008 @kindex info os processes
13010 Display the list of processes on the target. For each process,
13011 @value{GDBN} prints the process identifier, the name of the user, the
13012 command corresponding to the process, and the list of processor cores
13013 that the process is currently running on. (To understand what these
13014 properties mean, for this and the following info types, please consult
13015 the general @sc{gnu}/Linux documentation.)
13017 @kindex info os procgroups
13019 Display the list of process groups on the target. For each process,
13020 @value{GDBN} prints the identifier of the process group that it belongs
13021 to, the command corresponding to the process group leader, the process
13022 identifier, and the command line of the process. The list is sorted
13023 first by the process group identifier, then by the process identifier,
13024 so that processes belonging to the same process group are grouped together
13025 and the process group leader is listed first.
13027 @kindex info os semaphores
13029 Display the list of all System V semaphore sets on the target. For each
13030 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
13031 set identifier, the access permissions, the number of semaphores in the
13032 set, the user and group of the owner and creator of the semaphore set,
13033 and the times at which the semaphore set was operated upon and changed.
13035 @kindex info os shm
13037 Display the list of all System V shared-memory regions on the target.
13038 For each shared-memory region, @value{GDBN} prints the region key,
13039 the shared-memory identifier, the access permissions, the size of the
13040 region, the process that created the region, the process that last
13041 attached to or detached from the region, the current number of live
13042 attaches to the region, and the times at which the region was last
13043 attached to, detach from, and changed.
13045 @kindex info os sockets
13047 Display the list of Internet-domain sockets on the target. For each
13048 socket, @value{GDBN} prints the address and port of the local and
13049 remote endpoints, the current state of the connection, the creator of
13050 the socket, the IP address family of the socket, and the type of the
13053 @kindex info os threads
13055 Display the list of threads running on the target. For each thread,
13056 @value{GDBN} prints the identifier of the process that the thread
13057 belongs to, the command of the process, the thread identifier, and the
13058 processor core that it is currently running on. The main thread of a
13059 process is not listed.
13063 If @var{infotype} is omitted, then list the possible values for
13064 @var{infotype} and the kind of OS information available for each
13065 @var{infotype}. If the target does not return a list of possible
13066 types, this command will report an error.
13069 @node Memory Region Attributes
13070 @section Memory Region Attributes
13071 @cindex memory region attributes
13073 @dfn{Memory region attributes} allow you to describe special handling
13074 required by regions of your target's memory. @value{GDBN} uses
13075 attributes to determine whether to allow certain types of memory
13076 accesses; whether to use specific width accesses; and whether to cache
13077 target memory. By default the description of memory regions is
13078 fetched from the target (if the current target supports this), but the
13079 user can override the fetched regions.
13081 Defined memory regions can be individually enabled and disabled. When a
13082 memory region is disabled, @value{GDBN} uses the default attributes when
13083 accessing memory in that region. Similarly, if no memory regions have
13084 been defined, @value{GDBN} uses the default attributes when accessing
13087 When a memory region is defined, it is given a number to identify it;
13088 to enable, disable, or remove a memory region, you specify that number.
13092 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
13093 Define a memory region bounded by @var{lower} and @var{upper} with
13094 attributes @var{attributes}@dots{}, and add it to the list of regions
13095 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
13096 case: it is treated as the target's maximum memory address.
13097 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
13100 Discard any user changes to the memory regions and use target-supplied
13101 regions, if available, or no regions if the target does not support.
13104 @item delete mem @var{nums}@dots{}
13105 Remove memory regions @var{nums}@dots{} from the list of regions
13106 monitored by @value{GDBN}.
13108 @kindex disable mem
13109 @item disable mem @var{nums}@dots{}
13110 Disable monitoring of memory regions @var{nums}@dots{}.
13111 A disabled memory region is not forgotten.
13112 It may be enabled again later.
13115 @item enable mem @var{nums}@dots{}
13116 Enable monitoring of memory regions @var{nums}@dots{}.
13120 Print a table of all defined memory regions, with the following columns
13124 @item Memory Region Number
13125 @item Enabled or Disabled.
13126 Enabled memory regions are marked with @samp{y}.
13127 Disabled memory regions are marked with @samp{n}.
13130 The address defining the inclusive lower bound of the memory region.
13133 The address defining the exclusive upper bound of the memory region.
13136 The list of attributes set for this memory region.
13141 @subsection Attributes
13143 @subsubsection Memory Access Mode
13144 The access mode attributes set whether @value{GDBN} may make read or
13145 write accesses to a memory region.
13147 While these attributes prevent @value{GDBN} from performing invalid
13148 memory accesses, they do nothing to prevent the target system, I/O DMA,
13149 etc.@: from accessing memory.
13153 Memory is read only.
13155 Memory is write only.
13157 Memory is read/write. This is the default.
13160 @subsubsection Memory Access Size
13161 The access size attribute tells @value{GDBN} to use specific sized
13162 accesses in the memory region. Often memory mapped device registers
13163 require specific sized accesses. If no access size attribute is
13164 specified, @value{GDBN} may use accesses of any size.
13168 Use 8 bit memory accesses.
13170 Use 16 bit memory accesses.
13172 Use 32 bit memory accesses.
13174 Use 64 bit memory accesses.
13177 @c @subsubsection Hardware/Software Breakpoints
13178 @c The hardware/software breakpoint attributes set whether @value{GDBN}
13179 @c will use hardware or software breakpoints for the internal breakpoints
13180 @c used by the step, next, finish, until, etc. commands.
13184 @c Always use hardware breakpoints
13185 @c @item swbreak (default)
13188 @subsubsection Data Cache
13189 The data cache attributes set whether @value{GDBN} will cache target
13190 memory. While this generally improves performance by reducing debug
13191 protocol overhead, it can lead to incorrect results because @value{GDBN}
13192 does not know about volatile variables or memory mapped device
13197 Enable @value{GDBN} to cache target memory.
13199 Disable @value{GDBN} from caching target memory. This is the default.
13202 @subsection Memory Access Checking
13203 @value{GDBN} can be instructed to refuse accesses to memory that is
13204 not explicitly described. This can be useful if accessing such
13205 regions has undesired effects for a specific target, or to provide
13206 better error checking. The following commands control this behaviour.
13209 @kindex set mem inaccessible-by-default
13210 @item set mem inaccessible-by-default [on|off]
13211 If @code{on} is specified, make @value{GDBN} treat memory not
13212 explicitly described by the memory ranges as non-existent and refuse accesses
13213 to such memory. The checks are only performed if there's at least one
13214 memory range defined. If @code{off} is specified, make @value{GDBN}
13215 treat the memory not explicitly described by the memory ranges as RAM.
13216 The default value is @code{on}.
13217 @kindex show mem inaccessible-by-default
13218 @item show mem inaccessible-by-default
13219 Show the current handling of accesses to unknown memory.
13223 @c @subsubsection Memory Write Verification
13224 @c The memory write verification attributes set whether @value{GDBN}
13225 @c will re-reads data after each write to verify the write was successful.
13229 @c @item noverify (default)
13232 @node Dump/Restore Files
13233 @section Copy Between Memory and a File
13234 @cindex dump/restore files
13235 @cindex append data to a file
13236 @cindex dump data to a file
13237 @cindex restore data from a file
13239 You can use the commands @code{dump}, @code{append}, and
13240 @code{restore} to copy data between target memory and a file. The
13241 @code{dump} and @code{append} commands write data to a file, and the
13242 @code{restore} command reads data from a file back into the inferior's
13243 memory. Files may be in binary, Motorola S-record, Intel hex,
13244 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
13245 append to binary files, and cannot read from Verilog Hex files.
13250 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13251 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
13252 Dump the contents of memory from @var{start_addr} to @var{end_addr},
13253 or the value of @var{expr}, to @var{filename} in the given format.
13255 The @var{format} parameter may be any one of:
13262 Motorola S-record format.
13264 Tektronix Hex format.
13266 Verilog Hex format.
13269 @value{GDBN} uses the same definitions of these formats as the
13270 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
13271 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
13275 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
13276 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
13277 Append the contents of memory from @var{start_addr} to @var{end_addr},
13278 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
13279 (@value{GDBN} can only append data to files in raw binary form.)
13282 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
13283 Restore the contents of file @var{filename} into memory. The
13284 @code{restore} command can automatically recognize any known @sc{bfd}
13285 file format, except for raw binary. To restore a raw binary file you
13286 must specify the optional keyword @code{binary} after the filename.
13288 If @var{bias} is non-zero, its value will be added to the addresses
13289 contained in the file. Binary files always start at address zero, so
13290 they will be restored at address @var{bias}. Other bfd files have
13291 a built-in location; they will be restored at offset @var{bias}
13292 from that location.
13294 If @var{start} and/or @var{end} are non-zero, then only data between
13295 file offset @var{start} and file offset @var{end} will be restored.
13296 These offsets are relative to the addresses in the file, before
13297 the @var{bias} argument is applied.
13301 @node Core File Generation
13302 @section How to Produce a Core File from Your Program
13303 @cindex dump core from inferior
13305 A @dfn{core file} or @dfn{core dump} is a file that records the memory
13306 image of a running process and its process status (register values
13307 etc.). Its primary use is post-mortem debugging of a program that
13308 crashed while it ran outside a debugger. A program that crashes
13309 automatically produces a core file, unless this feature is disabled by
13310 the user. @xref{Files}, for information on invoking @value{GDBN} in
13311 the post-mortem debugging mode.
13313 Occasionally, you may wish to produce a core file of the program you
13314 are debugging in order to preserve a snapshot of its state.
13315 @value{GDBN} has a special command for that.
13319 @kindex generate-core-file
13320 @item generate-core-file [@var{file}]
13321 @itemx gcore [@var{file}]
13322 Produce a core dump of the inferior process. The optional argument
13323 @var{file} specifies the file name where to put the core dump. If not
13324 specified, the file name defaults to @file{core.@var{pid}}, where
13325 @var{pid} is the inferior process ID.
13327 Note that this command is implemented only for some systems (as of
13328 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
13330 On @sc{gnu}/Linux, this command can take into account the value of the
13331 file @file{/proc/@var{pid}/coredump_filter} when generating the core
13332 dump (@pxref{set use-coredump-filter}), and by default honors the
13333 @code{VM_DONTDUMP} flag for mappings where it is present in the file
13334 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
13336 @kindex set use-coredump-filter
13337 @anchor{set use-coredump-filter}
13338 @item set use-coredump-filter on
13339 @itemx set use-coredump-filter off
13340 Enable or disable the use of the file
13341 @file{/proc/@var{pid}/coredump_filter} when generating core dump
13342 files. This file is used by the Linux kernel to decide what types of
13343 memory mappings will be dumped or ignored when generating a core dump
13344 file. @var{pid} is the process ID of a currently running process.
13346 To make use of this feature, you have to write in the
13347 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
13348 which is a bit mask representing the memory mapping types. If a bit
13349 is set in the bit mask, then the memory mappings of the corresponding
13350 types will be dumped; otherwise, they will be ignored. This
13351 configuration is inherited by child processes. For more information
13352 about the bits that can be set in the
13353 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
13354 manpage of @code{core(5)}.
13356 By default, this option is @code{on}. If this option is turned
13357 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
13358 and instead uses the same default value as the Linux kernel in order
13359 to decide which pages will be dumped in the core dump file. This
13360 value is currently @code{0x33}, which means that bits @code{0}
13361 (anonymous private mappings), @code{1} (anonymous shared mappings),
13362 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
13363 This will cause these memory mappings to be dumped automatically.
13365 @kindex set dump-excluded-mappings
13366 @anchor{set dump-excluded-mappings}
13367 @item set dump-excluded-mappings on
13368 @itemx set dump-excluded-mappings off
13369 If @code{on} is specified, @value{GDBN} will dump memory mappings
13370 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
13371 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
13373 The default value is @code{off}.
13376 @node Character Sets
13377 @section Character Sets
13378 @cindex character sets
13380 @cindex translating between character sets
13381 @cindex host character set
13382 @cindex target character set
13384 If the program you are debugging uses a different character set to
13385 represent characters and strings than the one @value{GDBN} uses itself,
13386 @value{GDBN} can automatically translate between the character sets for
13387 you. The character set @value{GDBN} uses we call the @dfn{host
13388 character set}; the one the inferior program uses we call the
13389 @dfn{target character set}.
13391 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
13392 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
13393 remote protocol (@pxref{Remote Debugging}) to debug a program
13394 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
13395 then the host character set is Latin-1, and the target character set is
13396 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
13397 target-charset EBCDIC-US}, then @value{GDBN} translates between
13398 @sc{ebcdic} and Latin 1 as you print character or string values, or use
13399 character and string literals in expressions.
13401 @value{GDBN} has no way to automatically recognize which character set
13402 the inferior program uses; you must tell it, using the @code{set
13403 target-charset} command, described below.
13405 Here are the commands for controlling @value{GDBN}'s character set
13409 @item set target-charset @var{charset}
13410 @kindex set target-charset
13411 Set the current target character set to @var{charset}. To display the
13412 list of supported target character sets, type
13413 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
13415 @item set host-charset @var{charset}
13416 @kindex set host-charset
13417 Set the current host character set to @var{charset}.
13419 By default, @value{GDBN} uses a host character set appropriate to the
13420 system it is running on; you can override that default using the
13421 @code{set host-charset} command. On some systems, @value{GDBN} cannot
13422 automatically determine the appropriate host character set. In this
13423 case, @value{GDBN} uses @samp{UTF-8}.
13425 @value{GDBN} can only use certain character sets as its host character
13426 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
13427 @value{GDBN} will list the host character sets it supports.
13429 @item set charset @var{charset}
13430 @kindex set charset
13431 Set the current host and target character sets to @var{charset}. As
13432 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
13433 @value{GDBN} will list the names of the character sets that can be used
13434 for both host and target.
13437 @kindex show charset
13438 Show the names of the current host and target character sets.
13440 @item show host-charset
13441 @kindex show host-charset
13442 Show the name of the current host character set.
13444 @item show target-charset
13445 @kindex show target-charset
13446 Show the name of the current target character set.
13448 @item set target-wide-charset @var{charset}
13449 @kindex set target-wide-charset
13450 Set the current target's wide character set to @var{charset}. This is
13451 the character set used by the target's @code{wchar_t} type. To
13452 display the list of supported wide character sets, type
13453 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
13455 @item show target-wide-charset
13456 @kindex show target-wide-charset
13457 Show the name of the current target's wide character set.
13460 Here is an example of @value{GDBN}'s character set support in action.
13461 Assume that the following source code has been placed in the file
13462 @file{charset-test.c}:
13468 = @{72, 101, 108, 108, 111, 44, 32, 119,
13469 111, 114, 108, 100, 33, 10, 0@};
13470 char ibm1047_hello[]
13471 = @{200, 133, 147, 147, 150, 107, 64, 166,
13472 150, 153, 147, 132, 90, 37, 0@};
13476 printf ("Hello, world!\n");
13480 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
13481 containing the string @samp{Hello, world!} followed by a newline,
13482 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
13484 We compile the program, and invoke the debugger on it:
13487 $ gcc -g charset-test.c -o charset-test
13488 $ gdb -nw charset-test
13489 GNU gdb 2001-12-19-cvs
13490 Copyright 2001 Free Software Foundation, Inc.
13495 We can use the @code{show charset} command to see what character sets
13496 @value{GDBN} is currently using to interpret and display characters and
13500 (@value{GDBP}) show charset
13501 The current host and target character set is `ISO-8859-1'.
13505 For the sake of printing this manual, let's use @sc{ascii} as our
13506 initial character set:
13508 (@value{GDBP}) set charset ASCII
13509 (@value{GDBP}) show charset
13510 The current host and target character set is `ASCII'.
13514 Let's assume that @sc{ascii} is indeed the correct character set for our
13515 host system --- in other words, let's assume that if @value{GDBN} prints
13516 characters using the @sc{ascii} character set, our terminal will display
13517 them properly. Since our current target character set is also
13518 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
13521 (@value{GDBP}) print ascii_hello
13522 $1 = 0x401698 "Hello, world!\n"
13523 (@value{GDBP}) print ascii_hello[0]
13528 @value{GDBN} uses the target character set for character and string
13529 literals you use in expressions:
13532 (@value{GDBP}) print '+'
13537 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
13540 @value{GDBN} relies on the user to tell it which character set the
13541 target program uses. If we print @code{ibm1047_hello} while our target
13542 character set is still @sc{ascii}, we get jibberish:
13545 (@value{GDBP}) print ibm1047_hello
13546 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
13547 (@value{GDBP}) print ibm1047_hello[0]
13552 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
13553 @value{GDBN} tells us the character sets it supports:
13556 (@value{GDBP}) set target-charset
13557 ASCII EBCDIC-US IBM1047 ISO-8859-1
13558 (@value{GDBP}) set target-charset
13561 We can select @sc{ibm1047} as our target character set, and examine the
13562 program's strings again. Now the @sc{ascii} string is wrong, but
13563 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
13564 target character set, @sc{ibm1047}, to the host character set,
13565 @sc{ascii}, and they display correctly:
13568 (@value{GDBP}) set target-charset IBM1047
13569 (@value{GDBP}) show charset
13570 The current host character set is `ASCII'.
13571 The current target character set is `IBM1047'.
13572 (@value{GDBP}) print ascii_hello
13573 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
13574 (@value{GDBP}) print ascii_hello[0]
13576 (@value{GDBP}) print ibm1047_hello
13577 $8 = 0x4016a8 "Hello, world!\n"
13578 (@value{GDBP}) print ibm1047_hello[0]
13583 As above, @value{GDBN} uses the target character set for character and
13584 string literals you use in expressions:
13587 (@value{GDBP}) print '+'
13592 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
13595 @node Caching Target Data
13596 @section Caching Data of Targets
13597 @cindex caching data of targets
13599 @value{GDBN} caches data exchanged between the debugger and a target.
13600 Each cache is associated with the address space of the inferior.
13601 @xref{Inferiors Connections and Programs}, about inferior and address space.
13602 Such caching generally improves performance in remote debugging
13603 (@pxref{Remote Debugging}), because it reduces the overhead of the
13604 remote protocol by bundling memory reads and writes into large chunks.
13605 Unfortunately, simply caching everything would lead to incorrect results,
13606 since @value{GDBN} does not necessarily know anything about volatile
13607 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
13608 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
13610 Therefore, by default, @value{GDBN} only caches data
13611 known to be on the stack@footnote{In non-stop mode, it is moderately
13612 rare for a running thread to modify the stack of a stopped thread
13613 in a way that would interfere with a backtrace, and caching of
13614 stack reads provides a significant speed up of remote backtraces.} or
13615 in the code segment.
13616 Other regions of memory can be explicitly marked as
13617 cacheable; @pxref{Memory Region Attributes}.
13620 @kindex set remotecache
13621 @item set remotecache on
13622 @itemx set remotecache off
13623 This option no longer does anything; it exists for compatibility
13626 @kindex show remotecache
13627 @item show remotecache
13628 Show the current state of the obsolete remotecache flag.
13630 @kindex set stack-cache
13631 @item set stack-cache on
13632 @itemx set stack-cache off
13633 Enable or disable caching of stack accesses. When @code{on}, use
13634 caching. By default, this option is @code{on}.
13636 @kindex show stack-cache
13637 @item show stack-cache
13638 Show the current state of data caching for memory accesses.
13640 @kindex set code-cache
13641 @item set code-cache on
13642 @itemx set code-cache off
13643 Enable or disable caching of code segment accesses. When @code{on},
13644 use caching. By default, this option is @code{on}. This improves
13645 performance of disassembly in remote debugging.
13647 @kindex show code-cache
13648 @item show code-cache
13649 Show the current state of target memory cache for code segment
13652 @kindex info dcache
13653 @item info dcache @r{[}line@r{]}
13654 Print the information about the performance of data cache of the
13655 current inferior's address space. The information displayed
13656 includes the dcache width and depth, and for each cache line, its
13657 number, address, and how many times it was referenced. This
13658 command is useful for debugging the data cache operation.
13660 If a line number is specified, the contents of that line will be
13663 @item set dcache size @var{size}
13664 @cindex dcache size
13665 @kindex set dcache size
13666 Set maximum number of entries in dcache (dcache depth above).
13668 @item set dcache line-size @var{line-size}
13669 @cindex dcache line-size
13670 @kindex set dcache line-size
13671 Set number of bytes each dcache entry caches (dcache width above).
13672 Must be a power of 2.
13674 @item show dcache size
13675 @kindex show dcache size
13676 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
13678 @item show dcache line-size
13679 @kindex show dcache line-size
13680 Show default size of dcache lines.
13682 @item maint flush dcache
13683 @cindex dcache, flushing
13684 @kindex maint flush dcache
13685 Flush the contents (if any) of the dcache. This maintainer command is
13686 useful when debugging the dcache implementation.
13690 @node Searching Memory
13691 @section Search Memory
13692 @cindex searching memory
13694 Memory can be searched for a particular sequence of bytes with the
13695 @code{find} command.
13699 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13700 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
13701 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
13702 etc. The search begins at address @var{start_addr} and continues for either
13703 @var{len} bytes or through to @var{end_addr} inclusive.
13706 @var{s} and @var{n} are optional parameters.
13707 They may be specified in either order, apart or together.
13710 @item @var{s}, search query size
13711 The size of each search query value.
13717 halfwords (two bytes)
13721 giant words (eight bytes)
13724 All values are interpreted in the current language.
13725 This means, for example, that if the current source language is C/C@t{++}
13726 then searching for the string ``hello'' includes the trailing '\0'.
13727 The null terminator can be removed from searching by using casts,
13728 e.g.: @samp{@{char[5]@}"hello"}.
13730 If the value size is not specified, it is taken from the
13731 value's type in the current language.
13732 This is useful when one wants to specify the search
13733 pattern as a mixture of types.
13734 Note that this means, for example, that in the case of C-like languages
13735 a search for an untyped 0x42 will search for @samp{(int) 0x42}
13736 which is typically four bytes.
13738 @item @var{n}, maximum number of finds
13739 The maximum number of matches to print. The default is to print all finds.
13742 You can use strings as search values. Quote them with double-quotes
13744 The string value is copied into the search pattern byte by byte,
13745 regardless of the endianness of the target and the size specification.
13747 The address of each match found is printed as well as a count of the
13748 number of matches found.
13750 The address of the last value found is stored in convenience variable
13752 A count of the number of matches is stored in @samp{$numfound}.
13754 For example, if stopped at the @code{printf} in this function:
13760 static char hello[] = "hello-hello";
13761 static struct @{ char c; short s; int i; @}
13762 __attribute__ ((packed)) mixed
13763 = @{ 'c', 0x1234, 0x87654321 @};
13764 printf ("%s\n", hello);
13769 you get during debugging:
13772 (gdb) find &hello[0], +sizeof(hello), "hello"
13773 0x804956d <hello.1620+6>
13775 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
13776 0x8049567 <hello.1620>
13777 0x804956d <hello.1620+6>
13779 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
13780 0x8049567 <hello.1620>
13781 0x804956d <hello.1620+6>
13783 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
13784 0x8049567 <hello.1620>
13786 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
13787 0x8049560 <mixed.1625>
13789 (gdb) print $numfound
13792 $2 = (void *) 0x8049560
13796 @section Value Sizes
13798 Whenever @value{GDBN} prints a value memory will be allocated within
13799 @value{GDBN} to hold the contents of the value. It is possible in
13800 some languages with dynamic typing systems, that an invalid program
13801 may indicate a value that is incorrectly large, this in turn may cause
13802 @value{GDBN} to try and allocate an overly large amount of memory.
13805 @kindex set max-value-size
13806 @item set max-value-size @var{bytes}
13807 @itemx set max-value-size unlimited
13808 Set the maximum size of memory that @value{GDBN} will allocate for the
13809 contents of a value to @var{bytes}, trying to display a value that
13810 requires more memory than that will result in an error.
13812 Setting this variable does not effect values that have already been
13813 allocated within @value{GDBN}, only future allocations.
13815 There's a minimum size that @code{max-value-size} can be set to in
13816 order that @value{GDBN} can still operate correctly, this minimum is
13817 currently 16 bytes.
13819 The limit applies to the results of some subexpressions as well as to
13820 complete expressions. For example, an expression denoting a simple
13821 integer component, such as @code{x.y.z}, may fail if the size of
13822 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
13823 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
13824 @var{A} is an array variable with non-constant size, will generally
13825 succeed regardless of the bounds on @var{A}, as long as the component
13826 size is less than @var{bytes}.
13828 The default value of @code{max-value-size} is currently 64k.
13830 @kindex show max-value-size
13831 @item show max-value-size
13832 Show the maximum size of memory, in bytes, that @value{GDBN} will
13833 allocate for the contents of a value.
13836 @node Optimized Code
13837 @chapter Debugging Optimized Code
13838 @cindex optimized code, debugging
13839 @cindex debugging optimized code
13841 Almost all compilers support optimization. With optimization
13842 disabled, the compiler generates assembly code that corresponds
13843 directly to your source code, in a simplistic way. As the compiler
13844 applies more powerful optimizations, the generated assembly code
13845 diverges from your original source code. With help from debugging
13846 information generated by the compiler, @value{GDBN} can map from
13847 the running program back to constructs from your original source.
13849 @value{GDBN} is more accurate with optimization disabled. If you
13850 can recompile without optimization, it is easier to follow the
13851 progress of your program during debugging. But, there are many cases
13852 where you may need to debug an optimized version.
13854 When you debug a program compiled with @samp{-g -O}, remember that the
13855 optimizer has rearranged your code; the debugger shows you what is
13856 really there. Do not be too surprised when the execution path does not
13857 exactly match your source file! An extreme example: if you define a
13858 variable, but never use it, @value{GDBN} never sees that
13859 variable---because the compiler optimizes it out of existence.
13861 Some things do not work as well with @samp{-g -O} as with just
13862 @samp{-g}, particularly on machines with instruction scheduling. If in
13863 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
13864 please report it to us as a bug (including a test case!).
13865 @xref{Variables}, for more information about debugging optimized code.
13868 * Inline Functions:: How @value{GDBN} presents inlining
13869 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
13872 @node Inline Functions
13873 @section Inline Functions
13874 @cindex inline functions, debugging
13876 @dfn{Inlining} is an optimization that inserts a copy of the function
13877 body directly at each call site, instead of jumping to a shared
13878 routine. @value{GDBN} displays inlined functions just like
13879 non-inlined functions. They appear in backtraces. You can view their
13880 arguments and local variables, step into them with @code{step}, skip
13881 them with @code{next}, and escape from them with @code{finish}.
13882 You can check whether a function was inlined by using the
13883 @code{info frame} command.
13885 For @value{GDBN} to support inlined functions, the compiler must
13886 record information about inlining in the debug information ---
13887 @value{NGCC} using the @sc{dwarf 2} format does this, and several
13888 other compilers do also. @value{GDBN} only supports inlined functions
13889 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
13890 do not emit two required attributes (@samp{DW_AT_call_file} and
13891 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
13892 function calls with earlier versions of @value{NGCC}. It instead
13893 displays the arguments and local variables of inlined functions as
13894 local variables in the caller.
13896 The body of an inlined function is directly included at its call site;
13897 unlike a non-inlined function, there are no instructions devoted to
13898 the call. @value{GDBN} still pretends that the call site and the
13899 start of the inlined function are different instructions. Stepping to
13900 the call site shows the call site, and then stepping again shows
13901 the first line of the inlined function, even though no additional
13902 instructions are executed.
13904 This makes source-level debugging much clearer; you can see both the
13905 context of the call and then the effect of the call. Only stepping by
13906 a single instruction using @code{stepi} or @code{nexti} does not do
13907 this; single instruction steps always show the inlined body.
13909 There are some ways that @value{GDBN} does not pretend that inlined
13910 function calls are the same as normal calls:
13914 Setting breakpoints at the call site of an inlined function may not
13915 work, because the call site does not contain any code. @value{GDBN}
13916 may incorrectly move the breakpoint to the next line of the enclosing
13917 function, after the call. This limitation will be removed in a future
13918 version of @value{GDBN}; until then, set a breakpoint on an earlier line
13919 or inside the inlined function instead.
13922 @value{GDBN} cannot locate the return value of inlined calls after
13923 using the @code{finish} command. This is a limitation of compiler-generated
13924 debugging information; after @code{finish}, you can step to the next line
13925 and print a variable where your program stored the return value.
13929 @node Tail Call Frames
13930 @section Tail Call Frames
13931 @cindex tail call frames, debugging
13933 Function @code{B} can call function @code{C} in its very last statement. In
13934 unoptimized compilation the call of @code{C} is immediately followed by return
13935 instruction at the end of @code{B} code. Optimizing compiler may replace the
13936 call and return in function @code{B} into one jump to function @code{C}
13937 instead. Such use of a jump instruction is called @dfn{tail call}.
13939 During execution of function @code{C}, there will be no indication in the
13940 function call stack frames that it was tail-called from @code{B}. If function
13941 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
13942 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
13943 some cases @value{GDBN} can determine that @code{C} was tail-called from
13944 @code{B}, and it will then create fictitious call frame for that, with the
13945 return address set up as if @code{B} called @code{C} normally.
13947 This functionality is currently supported only by DWARF 2 debugging format and
13948 the compiler has to produce @samp{DW_TAG_call_site} tags. With
13949 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
13952 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
13953 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
13957 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
13959 Stack level 1, frame at 0x7fffffffda30:
13960 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
13961 tail call frame, caller of frame at 0x7fffffffda30
13962 source language c++.
13963 Arglist at unknown address.
13964 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
13967 The detection of all the possible code path executions can find them ambiguous.
13968 There is no execution history stored (possible @ref{Reverse Execution} is never
13969 used for this purpose) and the last known caller could have reached the known
13970 callee by multiple different jump sequences. In such case @value{GDBN} still
13971 tries to show at least all the unambiguous top tail callers and all the
13972 unambiguous bottom tail calees, if any.
13975 @anchor{set debug entry-values}
13976 @item set debug entry-values
13977 @kindex set debug entry-values
13978 When set to on, enables printing of analysis messages for both frame argument
13979 values at function entry and tail calls. It will show all the possible valid
13980 tail calls code paths it has considered. It will also print the intersection
13981 of them with the final unambiguous (possibly partial or even empty) code path
13984 @item show debug entry-values
13985 @kindex show debug entry-values
13986 Show the current state of analysis messages printing for both frame argument
13987 values at function entry and tail calls.
13990 The analysis messages for tail calls can for example show why the virtual tail
13991 call frame for function @code{c} has not been recognized (due to the indirect
13992 reference by variable @code{x}):
13995 static void __attribute__((noinline, noclone)) c (void);
13996 void (*x) (void) = c;
13997 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
13998 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
13999 int main (void) @{ x (); return 0; @}
14001 Breakpoint 1, DW_OP_entry_value resolving cannot find
14002 DW_TAG_call_site 0x40039a in main
14004 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
14007 #1 0x000000000040039a in main () at t.c:5
14010 Another possibility is an ambiguous virtual tail call frames resolution:
14014 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
14015 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
14016 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
14017 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
14018 static void __attribute__((noinline, noclone)) b (void)
14019 @{ if (i) c (); else e (); @}
14020 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
14021 int main (void) @{ a (); return 0; @}
14023 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
14024 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
14025 tailcall: reduced: 0x4004d2(a) |
14028 #1 0x00000000004004d2 in a () at t.c:8
14029 #2 0x0000000000400395 in main () at t.c:9
14032 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
14033 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
14035 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
14036 @ifset HAVE_MAKEINFO_CLICK
14037 @set ARROW @click{}
14038 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
14039 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
14041 @ifclear HAVE_MAKEINFO_CLICK
14043 @set CALLSEQ1B @value{CALLSEQ1A}
14044 @set CALLSEQ2B @value{CALLSEQ2A}
14047 Frames #0 and #2 are real, #1 is a virtual tail call frame.
14048 The code can have possible execution paths @value{CALLSEQ1B} or
14049 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
14051 @code{initial:} state shows some random possible calling sequence @value{GDBN}
14052 has found. It then finds another possible calling sequence - that one is
14053 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
14054 printed as the @code{reduced:} calling sequence. That one could have many
14055 further @code{compare:} and @code{reduced:} statements as long as there remain
14056 any non-ambiguous sequence entries.
14058 For the frame of function @code{b} in both cases there are different possible
14059 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
14060 also ambiguous. The only non-ambiguous frame is the one for function @code{a},
14061 therefore this one is displayed to the user while the ambiguous frames are
14064 There can be also reasons why printing of frame argument values at function
14069 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
14070 static void __attribute__((noinline, noclone)) a (int i);
14071 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
14072 static void __attribute__((noinline, noclone)) a (int i)
14073 @{ if (i) b (i - 1); else c (0); @}
14074 int main (void) @{ a (5); return 0; @}
14077 #0 c (i=i@@entry=0) at t.c:2
14078 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
14079 function "a" at 0x400420 can call itself via tail calls
14080 i=<optimized out>) at t.c:6
14081 #2 0x000000000040036e in main () at t.c:7
14084 @value{GDBN} cannot find out from the inferior state if and how many times did
14085 function @code{a} call itself (via function @code{b}) as these calls would be
14086 tail calls. Such tail calls would modify the @code{i} variable, therefore
14087 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
14088 prints @code{<optimized out>} instead.
14091 @chapter C Preprocessor Macros
14093 Some languages, such as C and C@t{++}, provide a way to define and invoke
14094 ``preprocessor macros'' which expand into strings of tokens.
14095 @value{GDBN} can evaluate expressions containing macro invocations, show
14096 the result of macro expansion, and show a macro's definition, including
14097 where it was defined.
14099 You may need to compile your program specially to provide @value{GDBN}
14100 with information about preprocessor macros. Most compilers do not
14101 include macros in their debugging information, even when you compile
14102 with the @option{-g} flag. @xref{Compilation}.
14104 A program may define a macro at one point, remove that definition later,
14105 and then provide a different definition after that. Thus, at different
14106 points in the program, a macro may have different definitions, or have
14107 no definition at all. If there is a current stack frame, @value{GDBN}
14108 uses the macros in scope at that frame's source code line. Otherwise,
14109 @value{GDBN} uses the macros in scope at the current listing location;
14112 Whenever @value{GDBN} evaluates an expression, it always expands any
14113 macro invocations present in the expression. @value{GDBN} also provides
14114 the following commands for working with macros explicitly.
14118 @kindex macro expand
14119 @cindex macro expansion, showing the results of preprocessor
14120 @cindex preprocessor macro expansion, showing the results of
14121 @cindex expanding preprocessor macros
14122 @item macro expand @var{expression}
14123 @itemx macro exp @var{expression}
14124 Show the results of expanding all preprocessor macro invocations in
14125 @var{expression}. Since @value{GDBN} simply expands macros, but does
14126 not parse the result, @var{expression} need not be a valid expression;
14127 it can be any string of tokens.
14130 @item macro expand-once @var{expression}
14131 @itemx macro exp1 @var{expression}
14132 @cindex expand macro once
14133 @i{(This command is not yet implemented.)} Show the results of
14134 expanding those preprocessor macro invocations that appear explicitly in
14135 @var{expression}. Macro invocations appearing in that expansion are
14136 left unchanged. This command allows you to see the effect of a
14137 particular macro more clearly, without being confused by further
14138 expansions. Since @value{GDBN} simply expands macros, but does not
14139 parse the result, @var{expression} need not be a valid expression; it
14140 can be any string of tokens.
14143 @cindex macro definition, showing
14144 @cindex definition of a macro, showing
14145 @cindex macros, from debug info
14146 @item info macro [-a|-all] [--] @var{macro}
14147 Show the current definition or all definitions of the named @var{macro},
14148 and describe the source location or compiler command-line where that
14149 definition was established. The optional double dash is to signify the end of
14150 argument processing and the beginning of @var{macro} for non C-like macros where
14151 the macro may begin with a hyphen.
14153 @kindex info macros
14154 @item info macros @var{location}
14155 Show all macro definitions that are in effect at the location specified
14156 by @var{location}, and describe the source location or compiler
14157 command-line where those definitions were established.
14159 @kindex macro define
14160 @cindex user-defined macros
14161 @cindex defining macros interactively
14162 @cindex macros, user-defined
14163 @item macro define @var{macro} @var{replacement-list}
14164 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
14165 Introduce a definition for a preprocessor macro named @var{macro},
14166 invocations of which are replaced by the tokens given in
14167 @var{replacement-list}. The first form of this command defines an
14168 ``object-like'' macro, which takes no arguments; the second form
14169 defines a ``function-like'' macro, which takes the arguments given in
14172 A definition introduced by this command is in scope in every
14173 expression evaluated in @value{GDBN}, until it is removed with the
14174 @code{macro undef} command, described below. The definition overrides
14175 all definitions for @var{macro} present in the program being debugged,
14176 as well as any previous user-supplied definition.
14178 @kindex macro undef
14179 @item macro undef @var{macro}
14180 Remove any user-supplied definition for the macro named @var{macro}.
14181 This command only affects definitions provided with the @code{macro
14182 define} command, described above; it cannot remove definitions present
14183 in the program being debugged.
14187 List all the macros defined using the @code{macro define} command.
14190 @cindex macros, example of debugging with
14191 Here is a transcript showing the above commands in action. First, we
14192 show our source files:
14197 #include "sample.h"
14200 #define ADD(x) (M + x)
14205 printf ("Hello, world!\n");
14207 printf ("We're so creative.\n");
14209 printf ("Goodbye, world!\n");
14216 Now, we compile the program using the @sc{gnu} C compiler,
14217 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
14218 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
14219 and @option{-gdwarf-4}; we recommend always choosing the most recent
14220 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
14221 includes information about preprocessor macros in the debugging
14225 $ gcc -gdwarf-2 -g3 sample.c -o sample
14229 Now, we start @value{GDBN} on our sample program:
14233 GNU gdb 2002-05-06-cvs
14234 Copyright 2002 Free Software Foundation, Inc.
14235 GDB is free software, @dots{}
14239 We can expand macros and examine their definitions, even when the
14240 program is not running. @value{GDBN} uses the current listing position
14241 to decide which macro definitions are in scope:
14244 (@value{GDBP}) list main
14247 5 #define ADD(x) (M + x)
14252 10 printf ("Hello, world!\n");
14254 12 printf ("We're so creative.\n");
14255 (@value{GDBP}) info macro ADD
14256 Defined at /home/jimb/gdb/macros/play/sample.c:5
14257 #define ADD(x) (M + x)
14258 (@value{GDBP}) info macro Q
14259 Defined at /home/jimb/gdb/macros/play/sample.h:1
14260 included at /home/jimb/gdb/macros/play/sample.c:2
14262 (@value{GDBP}) macro expand ADD(1)
14263 expands to: (42 + 1)
14264 (@value{GDBP}) macro expand-once ADD(1)
14265 expands to: once (M + 1)
14269 In the example above, note that @code{macro expand-once} expands only
14270 the macro invocation explicit in the original text --- the invocation of
14271 @code{ADD} --- but does not expand the invocation of the macro @code{M},
14272 which was introduced by @code{ADD}.
14274 Once the program is running, @value{GDBN} uses the macro definitions in
14275 force at the source line of the current stack frame:
14278 (@value{GDBP}) break main
14279 Breakpoint 1 at 0x8048370: file sample.c, line 10.
14281 Starting program: /home/jimb/gdb/macros/play/sample
14283 Breakpoint 1, main () at sample.c:10
14284 10 printf ("Hello, world!\n");
14288 At line 10, the definition of the macro @code{N} at line 9 is in force:
14291 (@value{GDBP}) info macro N
14292 Defined at /home/jimb/gdb/macros/play/sample.c:9
14294 (@value{GDBP}) macro expand N Q M
14295 expands to: 28 < 42
14296 (@value{GDBP}) print N Q M
14301 As we step over directives that remove @code{N}'s definition, and then
14302 give it a new definition, @value{GDBN} finds the definition (or lack
14303 thereof) in force at each point:
14306 (@value{GDBP}) next
14308 12 printf ("We're so creative.\n");
14309 (@value{GDBP}) info macro N
14310 The symbol `N' has no definition as a C/C++ preprocessor macro
14311 at /home/jimb/gdb/macros/play/sample.c:12
14312 (@value{GDBP}) next
14314 14 printf ("Goodbye, world!\n");
14315 (@value{GDBP}) info macro N
14316 Defined at /home/jimb/gdb/macros/play/sample.c:13
14318 (@value{GDBP}) macro expand N Q M
14319 expands to: 1729 < 42
14320 (@value{GDBP}) print N Q M
14325 In addition to source files, macros can be defined on the compilation command
14326 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
14327 such a way, @value{GDBN} displays the location of their definition as line zero
14328 of the source file submitted to the compiler.
14331 (@value{GDBP}) info macro __STDC__
14332 Defined at /home/jimb/gdb/macros/play/sample.c:0
14339 @chapter Tracepoints
14340 @c This chapter is based on the documentation written by Michael
14341 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
14343 @cindex tracepoints
14344 In some applications, it is not feasible for the debugger to interrupt
14345 the program's execution long enough for the developer to learn
14346 anything helpful about its behavior. If the program's correctness
14347 depends on its real-time behavior, delays introduced by a debugger
14348 might cause the program to change its behavior drastically, or perhaps
14349 fail, even when the code itself is correct. It is useful to be able
14350 to observe the program's behavior without interrupting it.
14352 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
14353 specify locations in the program, called @dfn{tracepoints}, and
14354 arbitrary expressions to evaluate when those tracepoints are reached.
14355 Later, using the @code{tfind} command, you can examine the values
14356 those expressions had when the program hit the tracepoints. The
14357 expressions may also denote objects in memory---structures or arrays,
14358 for example---whose values @value{GDBN} should record; while visiting
14359 a particular tracepoint, you may inspect those objects as if they were
14360 in memory at that moment. However, because @value{GDBN} records these
14361 values without interacting with you, it can do so quickly and
14362 unobtrusively, hopefully not disturbing the program's behavior.
14364 The tracepoint facility is currently available only for remote
14365 targets. @xref{Targets}. In addition, your remote target must know
14366 how to collect trace data. This functionality is implemented in the
14367 remote stub; however, none of the stubs distributed with @value{GDBN}
14368 support tracepoints as of this writing. The format of the remote
14369 packets used to implement tracepoints are described in @ref{Tracepoint
14372 It is also possible to get trace data from a file, in a manner reminiscent
14373 of corefiles; you specify the filename, and use @code{tfind} to search
14374 through the file. @xref{Trace Files}, for more details.
14376 This chapter describes the tracepoint commands and features.
14379 * Set Tracepoints::
14380 * Analyze Collected Data::
14381 * Tracepoint Variables::
14385 @node Set Tracepoints
14386 @section Commands to Set Tracepoints
14388 Before running such a @dfn{trace experiment}, an arbitrary number of
14389 tracepoints can be set. A tracepoint is actually a special type of
14390 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
14391 standard breakpoint commands. For instance, as with breakpoints,
14392 tracepoint numbers are successive integers starting from one, and many
14393 of the commands associated with tracepoints take the tracepoint number
14394 as their argument, to identify which tracepoint to work on.
14396 For each tracepoint, you can specify, in advance, some arbitrary set
14397 of data that you want the target to collect in the trace buffer when
14398 it hits that tracepoint. The collected data can include registers,
14399 local variables, or global data. Later, you can use @value{GDBN}
14400 commands to examine the values these data had at the time the
14401 tracepoint was hit.
14403 Tracepoints do not support every breakpoint feature. Ignore counts on
14404 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
14405 commands when they are hit. Tracepoints may not be thread-specific
14408 @cindex fast tracepoints
14409 Some targets may support @dfn{fast tracepoints}, which are inserted in
14410 a different way (such as with a jump instead of a trap), that is
14411 faster but possibly restricted in where they may be installed.
14413 @cindex static tracepoints
14414 @cindex markers, static tracepoints
14415 @cindex probing markers, static tracepoints
14416 Regular and fast tracepoints are dynamic tracing facilities, meaning
14417 that they can be used to insert tracepoints at (almost) any location
14418 in the target. Some targets may also support controlling @dfn{static
14419 tracepoints} from @value{GDBN}. With static tracing, a set of
14420 instrumentation points, also known as @dfn{markers}, are embedded in
14421 the target program, and can be activated or deactivated by name or
14422 address. These are usually placed at locations which facilitate
14423 investigating what the target is actually doing. @value{GDBN}'s
14424 support for static tracing includes being able to list instrumentation
14425 points, and attach them with @value{GDBN} defined high level
14426 tracepoints that expose the whole range of convenience of
14427 @value{GDBN}'s tracepoints support. Namely, support for collecting
14428 registers values and values of global or local (to the instrumentation
14429 point) variables; tracepoint conditions and trace state variables.
14430 The act of installing a @value{GDBN} static tracepoint on an
14431 instrumentation point, or marker, is referred to as @dfn{probing} a
14432 static tracepoint marker.
14434 @code{gdbserver} supports tracepoints on some target systems.
14435 @xref{Server,,Tracepoints support in @code{gdbserver}}.
14437 This section describes commands to set tracepoints and associated
14438 conditions and actions.
14441 * Create and Delete Tracepoints::
14442 * Enable and Disable Tracepoints::
14443 * Tracepoint Passcounts::
14444 * Tracepoint Conditions::
14445 * Trace State Variables::
14446 * Tracepoint Actions::
14447 * Listing Tracepoints::
14448 * Listing Static Tracepoint Markers::
14449 * Starting and Stopping Trace Experiments::
14450 * Tracepoint Restrictions::
14453 @node Create and Delete Tracepoints
14454 @subsection Create and Delete Tracepoints
14457 @cindex set tracepoint
14459 @item trace @var{location}
14460 The @code{trace} command is very similar to the @code{break} command.
14461 Its argument @var{location} can be any valid location.
14462 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
14463 which is a point in the target program where the debugger will briefly stop,
14464 collect some data, and then allow the program to continue. Setting a tracepoint
14465 or changing its actions takes effect immediately if the remote stub
14466 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
14468 If remote stub doesn't support the @samp{InstallInTrace} feature, all
14469 these changes don't take effect until the next @code{tstart}
14470 command, and once a trace experiment is running, further changes will
14471 not have any effect until the next trace experiment starts. In addition,
14472 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
14473 address is not yet resolved. (This is similar to pending breakpoints.)
14474 Pending tracepoints are not downloaded to the target and not installed
14475 until they are resolved. The resolution of pending tracepoints requires
14476 @value{GDBN} support---when debugging with the remote target, and
14477 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
14478 tracing}), pending tracepoints can not be resolved (and downloaded to
14479 the remote stub) while @value{GDBN} is disconnected.
14481 Here are some examples of using the @code{trace} command:
14484 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
14486 (@value{GDBP}) @b{trace +2} // 2 lines forward
14488 (@value{GDBP}) @b{trace my_function} // first source line of function
14490 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
14492 (@value{GDBP}) @b{trace *0x2117c4} // an address
14496 You can abbreviate @code{trace} as @code{tr}.
14498 @item trace @var{location} if @var{cond}
14499 Set a tracepoint with condition @var{cond}; evaluate the expression
14500 @var{cond} each time the tracepoint is reached, and collect data only
14501 if the value is nonzero---that is, if @var{cond} evaluates as true.
14502 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
14503 information on tracepoint conditions.
14505 @item ftrace @var{location} [ if @var{cond} ]
14506 @cindex set fast tracepoint
14507 @cindex fast tracepoints, setting
14509 The @code{ftrace} command sets a fast tracepoint. For targets that
14510 support them, fast tracepoints will use a more efficient but possibly
14511 less general technique to trigger data collection, such as a jump
14512 instruction instead of a trap, or some sort of hardware support. It
14513 may not be possible to create a fast tracepoint at the desired
14514 location, in which case the command will exit with an explanatory
14517 @value{GDBN} handles arguments to @code{ftrace} exactly as for
14520 On 32-bit x86-architecture systems, fast tracepoints normally need to
14521 be placed at an instruction that is 5 bytes or longer, but can be
14522 placed at 4-byte instructions if the low 64K of memory of the target
14523 program is available to install trampolines. Some Unix-type systems,
14524 such as @sc{gnu}/Linux, exclude low addresses from the program's
14525 address space; but for instance with the Linux kernel it is possible
14526 to let @value{GDBN} use this area by doing a @command{sysctl} command
14527 to set the @code{mmap_min_addr} kernel parameter, as in
14530 sudo sysctl -w vm.mmap_min_addr=32768
14534 which sets the low address to 32K, which leaves plenty of room for
14535 trampolines. The minimum address should be set to a page boundary.
14537 @item strace @var{location} [ if @var{cond} ]
14538 @cindex set static tracepoint
14539 @cindex static tracepoints, setting
14540 @cindex probe static tracepoint marker
14542 The @code{strace} command sets a static tracepoint. For targets that
14543 support it, setting a static tracepoint probes a static
14544 instrumentation point, or marker, found at @var{location}. It may not
14545 be possible to set a static tracepoint at the desired location, in
14546 which case the command will exit with an explanatory message.
14548 @value{GDBN} handles arguments to @code{strace} exactly as for
14549 @code{trace}, with the addition that the user can also specify
14550 @code{-m @var{marker}} as @var{location}. This probes the marker
14551 identified by the @var{marker} string identifier. This identifier
14552 depends on the static tracepoint backend library your program is
14553 using. You can find all the marker identifiers in the @samp{ID} field
14554 of the @code{info static-tracepoint-markers} command output.
14555 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
14556 Markers}. For example, in the following small program using the UST
14562 trace_mark(ust, bar33, "str %s", "FOOBAZ");
14567 the marker id is composed of joining the first two arguments to the
14568 @code{trace_mark} call with a slash, which translates to:
14571 (@value{GDBP}) info static-tracepoint-markers
14572 Cnt Enb ID Address What
14573 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
14579 so you may probe the marker above with:
14582 (@value{GDBP}) strace -m ust/bar33
14585 Static tracepoints accept an extra collect action --- @code{collect
14586 $_sdata}. This collects arbitrary user data passed in the probe point
14587 call to the tracing library. In the UST example above, you'll see
14588 that the third argument to @code{trace_mark} is a printf-like format
14589 string. The user data is then the result of running that formatting
14590 string against the following arguments. Note that @code{info
14591 static-tracepoint-markers} command output lists that format string in
14592 the @samp{Data:} field.
14594 You can inspect this data when analyzing the trace buffer, by printing
14595 the $_sdata variable like any other variable available to
14596 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
14599 @cindex last tracepoint number
14600 @cindex recent tracepoint number
14601 @cindex tracepoint number
14602 The convenience variable @code{$tpnum} records the tracepoint number
14603 of the most recently set tracepoint.
14605 @kindex delete tracepoint
14606 @cindex tracepoint deletion
14607 @item delete tracepoint @r{[}@var{num}@r{]}
14608 Permanently delete one or more tracepoints. With no argument, the
14609 default is to delete all tracepoints. Note that the regular
14610 @code{delete} command can remove tracepoints also.
14615 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
14617 (@value{GDBP}) @b{delete trace} // remove all tracepoints
14621 You can abbreviate this command as @code{del tr}.
14624 @node Enable and Disable Tracepoints
14625 @subsection Enable and Disable Tracepoints
14627 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
14630 @kindex disable tracepoint
14631 @item disable tracepoint @r{[}@var{num}@r{]}
14632 Disable tracepoint @var{num}, or all tracepoints if no argument
14633 @var{num} is given. A disabled tracepoint will have no effect during
14634 a trace experiment, but it is not forgotten. You can re-enable
14635 a disabled tracepoint using the @code{enable tracepoint} command.
14636 If the command is issued during a trace experiment and the debug target
14637 has support for disabling tracepoints during a trace experiment, then the
14638 change will be effective immediately. Otherwise, it will be applied to the
14639 next trace experiment.
14641 @kindex enable tracepoint
14642 @item enable tracepoint @r{[}@var{num}@r{]}
14643 Enable tracepoint @var{num}, or all tracepoints. If this command is
14644 issued during a trace experiment and the debug target supports enabling
14645 tracepoints during a trace experiment, then the enabled tracepoints will
14646 become effective immediately. Otherwise, they will become effective the
14647 next time a trace experiment is run.
14650 @node Tracepoint Passcounts
14651 @subsection Tracepoint Passcounts
14655 @cindex tracepoint pass count
14656 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
14657 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
14658 automatically stop a trace experiment. If a tracepoint's passcount is
14659 @var{n}, then the trace experiment will be automatically stopped on
14660 the @var{n}'th time that tracepoint is hit. If the tracepoint number
14661 @var{num} is not specified, the @code{passcount} command sets the
14662 passcount of the most recently defined tracepoint. If no passcount is
14663 given, the trace experiment will run until stopped explicitly by the
14669 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
14670 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
14672 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
14673 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
14674 (@value{GDBP}) @b{trace foo}
14675 (@value{GDBP}) @b{pass 3}
14676 (@value{GDBP}) @b{trace bar}
14677 (@value{GDBP}) @b{pass 2}
14678 (@value{GDBP}) @b{trace baz}
14679 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
14680 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
14681 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
14682 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
14686 @node Tracepoint Conditions
14687 @subsection Tracepoint Conditions
14688 @cindex conditional tracepoints
14689 @cindex tracepoint conditions
14691 The simplest sort of tracepoint collects data every time your program
14692 reaches a specified place. You can also specify a @dfn{condition} for
14693 a tracepoint. A condition is just a Boolean expression in your
14694 programming language (@pxref{Expressions, ,Expressions}). A
14695 tracepoint with a condition evaluates the expression each time your
14696 program reaches it, and data collection happens only if the condition
14699 Tracepoint conditions can be specified when a tracepoint is set, by
14700 using @samp{if} in the arguments to the @code{trace} command.
14701 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
14702 also be set or changed at any time with the @code{condition} command,
14703 just as with breakpoints.
14705 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
14706 the conditional expression itself. Instead, @value{GDBN} encodes the
14707 expression into an agent expression (@pxref{Agent Expressions})
14708 suitable for execution on the target, independently of @value{GDBN}.
14709 Global variables become raw memory locations, locals become stack
14710 accesses, and so forth.
14712 For instance, suppose you have a function that is usually called
14713 frequently, but should not be called after an error has occurred. You
14714 could use the following tracepoint command to collect data about calls
14715 of that function that happen while the error code is propagating
14716 through the program; an unconditional tracepoint could end up
14717 collecting thousands of useless trace frames that you would have to
14721 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
14724 @node Trace State Variables
14725 @subsection Trace State Variables
14726 @cindex trace state variables
14728 A @dfn{trace state variable} is a special type of variable that is
14729 created and managed by target-side code. The syntax is the same as
14730 that for GDB's convenience variables (a string prefixed with ``$''),
14731 but they are stored on the target. They must be created explicitly,
14732 using a @code{tvariable} command. They are always 64-bit signed
14735 Trace state variables are remembered by @value{GDBN}, and downloaded
14736 to the target along with tracepoint information when the trace
14737 experiment starts. There are no intrinsic limits on the number of
14738 trace state variables, beyond memory limitations of the target.
14740 @cindex convenience variables, and trace state variables
14741 Although trace state variables are managed by the target, you can use
14742 them in print commands and expressions as if they were convenience
14743 variables; @value{GDBN} will get the current value from the target
14744 while the trace experiment is running. Trace state variables share
14745 the same namespace as other ``$'' variables, which means that you
14746 cannot have trace state variables with names like @code{$23} or
14747 @code{$pc}, nor can you have a trace state variable and a convenience
14748 variable with the same name.
14752 @item tvariable $@var{name} [ = @var{expression} ]
14754 The @code{tvariable} command creates a new trace state variable named
14755 @code{$@var{name}}, and optionally gives it an initial value of
14756 @var{expression}. The @var{expression} is evaluated when this command is
14757 entered; the result will be converted to an integer if possible,
14758 otherwise @value{GDBN} will report an error. A subsequent
14759 @code{tvariable} command specifying the same name does not create a
14760 variable, but instead assigns the supplied initial value to the
14761 existing variable of that name, overwriting any previous initial
14762 value. The default initial value is 0.
14764 @item info tvariables
14765 @kindex info tvariables
14766 List all the trace state variables along with their initial values.
14767 Their current values may also be displayed, if the trace experiment is
14770 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
14771 @kindex delete tvariable
14772 Delete the given trace state variables, or all of them if no arguments
14777 @node Tracepoint Actions
14778 @subsection Tracepoint Action Lists
14782 @cindex tracepoint actions
14783 @item actions @r{[}@var{num}@r{]}
14784 This command will prompt for a list of actions to be taken when the
14785 tracepoint is hit. If the tracepoint number @var{num} is not
14786 specified, this command sets the actions for the one that was most
14787 recently defined (so that you can define a tracepoint and then say
14788 @code{actions} without bothering about its number). You specify the
14789 actions themselves on the following lines, one action at a time, and
14790 terminate the actions list with a line containing just @code{end}. So
14791 far, the only defined actions are @code{collect}, @code{teval}, and
14792 @code{while-stepping}.
14794 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
14795 Commands, ,Breakpoint Command Lists}), except that only the defined
14796 actions are allowed; any other @value{GDBN} command is rejected.
14798 @cindex remove actions from a tracepoint
14799 To remove all actions from a tracepoint, type @samp{actions @var{num}}
14800 and follow it immediately with @samp{end}.
14803 (@value{GDBP}) @b{collect @var{data}} // collect some data
14805 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
14807 (@value{GDBP}) @b{end} // signals the end of actions.
14810 In the following example, the action list begins with @code{collect}
14811 commands indicating the things to be collected when the tracepoint is
14812 hit. Then, in order to single-step and collect additional data
14813 following the tracepoint, a @code{while-stepping} command is used,
14814 followed by the list of things to be collected after each step in a
14815 sequence of single steps. The @code{while-stepping} command is
14816 terminated by its own separate @code{end} command. Lastly, the action
14817 list is terminated by an @code{end} command.
14820 (@value{GDBP}) @b{trace foo}
14821 (@value{GDBP}) @b{actions}
14822 Enter actions for tracepoint 1, one per line:
14825 > while-stepping 12
14826 > collect $pc, arr[i]
14831 @kindex collect @r{(tracepoints)}
14832 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
14833 Collect values of the given expressions when the tracepoint is hit.
14834 This command accepts a comma-separated list of any valid expressions.
14835 In addition to global, static, or local variables, the following
14836 special arguments are supported:
14840 Collect all registers.
14843 Collect all function arguments.
14846 Collect all local variables.
14849 Collect the return address. This is helpful if you want to see more
14852 @emph{Note:} The return address location can not always be reliably
14853 determined up front, and the wrong address / registers may end up
14854 collected instead. On some architectures the reliability is higher
14855 for tracepoints at function entry, while on others it's the opposite.
14856 When this happens, backtracing will stop because the return address is
14857 found unavailable (unless another collect rule happened to match it).
14860 Collects the number of arguments from the static probe at which the
14861 tracepoint is located.
14862 @xref{Static Probe Points}.
14864 @item $_probe_arg@var{n}
14865 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
14866 from the static probe at which the tracepoint is located.
14867 @xref{Static Probe Points}.
14870 @vindex $_sdata@r{, collect}
14871 Collect static tracepoint marker specific data. Only available for
14872 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
14873 Lists}. On the UST static tracepoints library backend, an
14874 instrumentation point resembles a @code{printf} function call. The
14875 tracing library is able to collect user specified data formatted to a
14876 character string using the format provided by the programmer that
14877 instrumented the program. Other backends have similar mechanisms.
14878 Here's an example of a UST marker call:
14881 const char master_name[] = "$your_name";
14882 trace_mark(channel1, marker1, "hello %s", master_name)
14885 In this case, collecting @code{$_sdata} collects the string
14886 @samp{hello $yourname}. When analyzing the trace buffer, you can
14887 inspect @samp{$_sdata} like any other variable available to
14891 You can give several consecutive @code{collect} commands, each one
14892 with a single argument, or one @code{collect} command with several
14893 arguments separated by commas; the effect is the same.
14895 The optional @var{mods} changes the usual handling of the arguments.
14896 @code{s} requests that pointers to chars be handled as strings, in
14897 particular collecting the contents of the memory being pointed at, up
14898 to the first zero. The upper bound is by default the value of the
14899 @code{print elements} variable; if @code{s} is followed by a decimal
14900 number, that is the upper bound instead. So for instance
14901 @samp{collect/s25 mystr} collects as many as 25 characters at
14904 The command @code{info scope} (@pxref{Symbols, info scope}) is
14905 particularly useful for figuring out what data to collect.
14907 @kindex teval @r{(tracepoints)}
14908 @item teval @var{expr1}, @var{expr2}, @dots{}
14909 Evaluate the given expressions when the tracepoint is hit. This
14910 command accepts a comma-separated list of expressions. The results
14911 are discarded, so this is mainly useful for assigning values to trace
14912 state variables (@pxref{Trace State Variables}) without adding those
14913 values to the trace buffer, as would be the case if the @code{collect}
14916 @kindex while-stepping @r{(tracepoints)}
14917 @item while-stepping @var{n}
14918 Perform @var{n} single-step instruction traces after the tracepoint,
14919 collecting new data after each step. The @code{while-stepping}
14920 command is followed by the list of what to collect while stepping
14921 (followed by its own @code{end} command):
14924 > while-stepping 12
14925 > collect $regs, myglobal
14931 Note that @code{$pc} is not automatically collected by
14932 @code{while-stepping}; you need to explicitly collect that register if
14933 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
14936 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
14937 @kindex set default-collect
14938 @cindex default collection action
14939 This variable is a list of expressions to collect at each tracepoint
14940 hit. It is effectively an additional @code{collect} action prepended
14941 to every tracepoint action list. The expressions are parsed
14942 individually for each tracepoint, so for instance a variable named
14943 @code{xyz} may be interpreted as a global for one tracepoint, and a
14944 local for another, as appropriate to the tracepoint's location.
14946 @item show default-collect
14947 @kindex show default-collect
14948 Show the list of expressions that are collected by default at each
14953 @node Listing Tracepoints
14954 @subsection Listing Tracepoints
14957 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
14958 @kindex info tp @r{[}@var{n}@dots{}@r{]}
14959 @cindex information about tracepoints
14960 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
14961 Display information about the tracepoint @var{num}. If you don't
14962 specify a tracepoint number, displays information about all the
14963 tracepoints defined so far. The format is similar to that used for
14964 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
14965 command, simply restricting itself to tracepoints.
14967 A tracepoint's listing may include additional information specific to
14972 its passcount as given by the @code{passcount @var{n}} command
14975 the state about installed on target of each location
14979 (@value{GDBP}) @b{info trace}
14980 Num Type Disp Enb Address What
14981 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
14983 collect globfoo, $regs
14988 2 tracepoint keep y <MULTIPLE>
14990 2.1 y 0x0804859c in func4 at change-loc.h:35
14991 installed on target
14992 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
14993 installed on target
14994 2.3 y <PENDING> set_tracepoint
14995 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
14996 not installed on target
15001 This command can be abbreviated @code{info tp}.
15004 @node Listing Static Tracepoint Markers
15005 @subsection Listing Static Tracepoint Markers
15008 @kindex info static-tracepoint-markers
15009 @cindex information about static tracepoint markers
15010 @item info static-tracepoint-markers
15011 Display information about all static tracepoint markers defined in the
15014 For each marker, the following columns are printed:
15018 An incrementing counter, output to help readability. This is not a
15021 The marker ID, as reported by the target.
15022 @item Enabled or Disabled
15023 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
15024 that are not enabled.
15026 Where the marker is in your program, as a memory address.
15028 Where the marker is in the source for your program, as a file and line
15029 number. If the debug information included in the program does not
15030 allow @value{GDBN} to locate the source of the marker, this column
15031 will be left blank.
15035 In addition, the following information may be printed for each marker:
15039 User data passed to the tracing library by the marker call. In the
15040 UST backend, this is the format string passed as argument to the
15042 @item Static tracepoints probing the marker
15043 The list of static tracepoints attached to the marker.
15047 (@value{GDBP}) info static-tracepoint-markers
15048 Cnt ID Enb Address What
15049 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
15050 Data: number1 %d number2 %d
15051 Probed by static tracepoints: #2
15052 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
15058 @node Starting and Stopping Trace Experiments
15059 @subsection Starting and Stopping Trace Experiments
15062 @kindex tstart [ @var{notes} ]
15063 @cindex start a new trace experiment
15064 @cindex collected data discarded
15066 This command starts the trace experiment, and begins collecting data.
15067 It has the side effect of discarding all the data collected in the
15068 trace buffer during the previous trace experiment. If any arguments
15069 are supplied, they are taken as a note and stored with the trace
15070 experiment's state. The notes may be arbitrary text, and are
15071 especially useful with disconnected tracing in a multi-user context;
15072 the notes can explain what the trace is doing, supply user contact
15073 information, and so forth.
15075 @kindex tstop [ @var{notes} ]
15076 @cindex stop a running trace experiment
15078 This command stops the trace experiment. If any arguments are
15079 supplied, they are recorded with the experiment as a note. This is
15080 useful if you are stopping a trace started by someone else, for
15081 instance if the trace is interfering with the system's behavior and
15082 needs to be stopped quickly.
15084 @strong{Note}: a trace experiment and data collection may stop
15085 automatically if any tracepoint's passcount is reached
15086 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
15089 @cindex status of trace data collection
15090 @cindex trace experiment, status of
15092 This command displays the status of the current trace data
15096 Here is an example of the commands we described so far:
15099 (@value{GDBP}) @b{trace gdb_c_test}
15100 (@value{GDBP}) @b{actions}
15101 Enter actions for tracepoint #1, one per line.
15102 > collect $regs,$locals,$args
15103 > while-stepping 11
15107 (@value{GDBP}) @b{tstart}
15108 [time passes @dots{}]
15109 (@value{GDBP}) @b{tstop}
15112 @anchor{disconnected tracing}
15113 @cindex disconnected tracing
15114 You can choose to continue running the trace experiment even if
15115 @value{GDBN} disconnects from the target, voluntarily or
15116 involuntarily. For commands such as @code{detach}, the debugger will
15117 ask what you want to do with the trace. But for unexpected
15118 terminations (@value{GDBN} crash, network outage), it would be
15119 unfortunate to lose hard-won trace data, so the variable
15120 @code{disconnected-tracing} lets you decide whether the trace should
15121 continue running without @value{GDBN}.
15124 @item set disconnected-tracing on
15125 @itemx set disconnected-tracing off
15126 @kindex set disconnected-tracing
15127 Choose whether a tracing run should continue to run if @value{GDBN}
15128 has disconnected from the target. Note that @code{detach} or
15129 @code{quit} will ask you directly what to do about a running trace no
15130 matter what this variable's setting, so the variable is mainly useful
15131 for handling unexpected situations, such as loss of the network.
15133 @item show disconnected-tracing
15134 @kindex show disconnected-tracing
15135 Show the current choice for disconnected tracing.
15139 When you reconnect to the target, the trace experiment may or may not
15140 still be running; it might have filled the trace buffer in the
15141 meantime, or stopped for one of the other reasons. If it is running,
15142 it will continue after reconnection.
15144 Upon reconnection, the target will upload information about the
15145 tracepoints in effect. @value{GDBN} will then compare that
15146 information to the set of tracepoints currently defined, and attempt
15147 to match them up, allowing for the possibility that the numbers may
15148 have changed due to creation and deletion in the meantime. If one of
15149 the target's tracepoints does not match any in @value{GDBN}, the
15150 debugger will create a new tracepoint, so that you have a number with
15151 which to specify that tracepoint. This matching-up process is
15152 necessarily heuristic, and it may result in useless tracepoints being
15153 created; you may simply delete them if they are of no use.
15155 @cindex circular trace buffer
15156 If your target agent supports a @dfn{circular trace buffer}, then you
15157 can run a trace experiment indefinitely without filling the trace
15158 buffer; when space runs out, the agent deletes already-collected trace
15159 frames, oldest first, until there is enough room to continue
15160 collecting. This is especially useful if your tracepoints are being
15161 hit too often, and your trace gets terminated prematurely because the
15162 buffer is full. To ask for a circular trace buffer, simply set
15163 @samp{circular-trace-buffer} to on. You can set this at any time,
15164 including during tracing; if the agent can do it, it will change
15165 buffer handling on the fly, otherwise it will not take effect until
15169 @item set circular-trace-buffer on
15170 @itemx set circular-trace-buffer off
15171 @kindex set circular-trace-buffer
15172 Choose whether a tracing run should use a linear or circular buffer
15173 for trace data. A linear buffer will not lose any trace data, but may
15174 fill up prematurely, while a circular buffer will discard old trace
15175 data, but it will have always room for the latest tracepoint hits.
15177 @item show circular-trace-buffer
15178 @kindex show circular-trace-buffer
15179 Show the current choice for the trace buffer. Note that this may not
15180 match the agent's current buffer handling, nor is it guaranteed to
15181 match the setting that might have been in effect during a past run,
15182 for instance if you are looking at frames from a trace file.
15187 @item set trace-buffer-size @var{n}
15188 @itemx set trace-buffer-size unlimited
15189 @kindex set trace-buffer-size
15190 Request that the target use a trace buffer of @var{n} bytes. Not all
15191 targets will honor the request; they may have a compiled-in size for
15192 the trace buffer, or some other limitation. Set to a value of
15193 @code{unlimited} or @code{-1} to let the target use whatever size it
15194 likes. This is also the default.
15196 @item show trace-buffer-size
15197 @kindex show trace-buffer-size
15198 Show the current requested size for the trace buffer. Note that this
15199 will only match the actual size if the target supports size-setting,
15200 and was able to handle the requested size. For instance, if the
15201 target can only change buffer size between runs, this variable will
15202 not reflect the change until the next run starts. Use @code{tstatus}
15203 to get a report of the actual buffer size.
15207 @item set trace-user @var{text}
15208 @kindex set trace-user
15210 @item show trace-user
15211 @kindex show trace-user
15213 @item set trace-notes @var{text}
15214 @kindex set trace-notes
15215 Set the trace run's notes.
15217 @item show trace-notes
15218 @kindex show trace-notes
15219 Show the trace run's notes.
15221 @item set trace-stop-notes @var{text}
15222 @kindex set trace-stop-notes
15223 Set the trace run's stop notes. The handling of the note is as for
15224 @code{tstop} arguments; the set command is convenient way to fix a
15225 stop note that is mistaken or incomplete.
15227 @item show trace-stop-notes
15228 @kindex show trace-stop-notes
15229 Show the trace run's stop notes.
15233 @node Tracepoint Restrictions
15234 @subsection Tracepoint Restrictions
15236 @cindex tracepoint restrictions
15237 There are a number of restrictions on the use of tracepoints. As
15238 described above, tracepoint data gathering occurs on the target
15239 without interaction from @value{GDBN}. Thus the full capabilities of
15240 the debugger are not available during data gathering, and then at data
15241 examination time, you will be limited by only having what was
15242 collected. The following items describe some common problems, but it
15243 is not exhaustive, and you may run into additional difficulties not
15249 Tracepoint expressions are intended to gather objects (lvalues). Thus
15250 the full flexibility of GDB's expression evaluator is not available.
15251 You cannot call functions, cast objects to aggregate types, access
15252 convenience variables or modify values (except by assignment to trace
15253 state variables). Some language features may implicitly call
15254 functions (for instance Objective-C fields with accessors), and therefore
15255 cannot be collected either.
15258 Collection of local variables, either individually or in bulk with
15259 @code{$locals} or @code{$args}, during @code{while-stepping} may
15260 behave erratically. The stepping action may enter a new scope (for
15261 instance by stepping into a function), or the location of the variable
15262 may change (for instance it is loaded into a register). The
15263 tracepoint data recorded uses the location information for the
15264 variables that is correct for the tracepoint location. When the
15265 tracepoint is created, it is not possible, in general, to determine
15266 where the steps of a @code{while-stepping} sequence will advance the
15267 program---particularly if a conditional branch is stepped.
15270 Collection of an incompletely-initialized or partially-destroyed object
15271 may result in something that @value{GDBN} cannot display, or displays
15272 in a misleading way.
15275 When @value{GDBN} displays a pointer to character it automatically
15276 dereferences the pointer to also display characters of the string
15277 being pointed to. However, collecting the pointer during tracing does
15278 not automatically collect the string. You need to explicitly
15279 dereference the pointer and provide size information if you want to
15280 collect not only the pointer, but the memory pointed to. For example,
15281 @code{*ptr@@50} can be used to collect the 50 element array pointed to
15285 It is not possible to collect a complete stack backtrace at a
15286 tracepoint. Instead, you may collect the registers and a few hundred
15287 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
15288 (adjust to use the name of the actual stack pointer register on your
15289 target architecture, and the amount of stack you wish to capture).
15290 Then the @code{backtrace} command will show a partial backtrace when
15291 using a trace frame. The number of stack frames that can be examined
15292 depends on the sizes of the frames in the collected stack. Note that
15293 if you ask for a block so large that it goes past the bottom of the
15294 stack, the target agent may report an error trying to read from an
15298 If you do not collect registers at a tracepoint, @value{GDBN} can
15299 infer that the value of @code{$pc} must be the same as the address of
15300 the tracepoint and use that when you are looking at a trace frame
15301 for that tracepoint. However, this cannot work if the tracepoint has
15302 multiple locations (for instance if it was set in a function that was
15303 inlined), or if it has a @code{while-stepping} loop. In those cases
15304 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
15309 @node Analyze Collected Data
15310 @section Using the Collected Data
15312 After the tracepoint experiment ends, you use @value{GDBN} commands
15313 for examining the trace data. The basic idea is that each tracepoint
15314 collects a trace @dfn{snapshot} every time it is hit and another
15315 snapshot every time it single-steps. All these snapshots are
15316 consecutively numbered from zero and go into a buffer, and you can
15317 examine them later. The way you examine them is to @dfn{focus} on a
15318 specific trace snapshot. When the remote stub is focused on a trace
15319 snapshot, it will respond to all @value{GDBN} requests for memory and
15320 registers by reading from the buffer which belongs to that snapshot,
15321 rather than from @emph{real} memory or registers of the program being
15322 debugged. This means that @strong{all} @value{GDBN} commands
15323 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
15324 behave as if we were currently debugging the program state as it was
15325 when the tracepoint occurred. Any requests for data that are not in
15326 the buffer will fail.
15329 * tfind:: How to select a trace snapshot
15330 * tdump:: How to display all data for a snapshot
15331 * save tracepoints:: How to save tracepoints for a future run
15335 @subsection @code{tfind @var{n}}
15338 @cindex select trace snapshot
15339 @cindex find trace snapshot
15340 The basic command for selecting a trace snapshot from the buffer is
15341 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
15342 counting from zero. If no argument @var{n} is given, the next
15343 snapshot is selected.
15345 Here are the various forms of using the @code{tfind} command.
15349 Find the first snapshot in the buffer. This is a synonym for
15350 @code{tfind 0} (since 0 is the number of the first snapshot).
15353 Stop debugging trace snapshots, resume @emph{live} debugging.
15356 Same as @samp{tfind none}.
15359 No argument means find the next trace snapshot or find the first
15360 one if no trace snapshot is selected.
15363 Find the previous trace snapshot before the current one. This permits
15364 retracing earlier steps.
15366 @item tfind tracepoint @var{num}
15367 Find the next snapshot associated with tracepoint @var{num}. Search
15368 proceeds forward from the last examined trace snapshot. If no
15369 argument @var{num} is given, it means find the next snapshot collected
15370 for the same tracepoint as the current snapshot.
15372 @item tfind pc @var{addr}
15373 Find the next snapshot associated with the value @var{addr} of the
15374 program counter. Search proceeds forward from the last examined trace
15375 snapshot. If no argument @var{addr} is given, it means find the next
15376 snapshot with the same value of PC as the current snapshot.
15378 @item tfind outside @var{addr1}, @var{addr2}
15379 Find the next snapshot whose PC is outside the given range of
15380 addresses (exclusive).
15382 @item tfind range @var{addr1}, @var{addr2}
15383 Find the next snapshot whose PC is between @var{addr1} and
15384 @var{addr2} (inclusive).
15386 @item tfind line @r{[}@var{file}:@r{]}@var{n}
15387 Find the next snapshot associated with the source line @var{n}. If
15388 the optional argument @var{file} is given, refer to line @var{n} in
15389 that source file. Search proceeds forward from the last examined
15390 trace snapshot. If no argument @var{n} is given, it means find the
15391 next line other than the one currently being examined; thus saying
15392 @code{tfind line} repeatedly can appear to have the same effect as
15393 stepping from line to line in a @emph{live} debugging session.
15396 The default arguments for the @code{tfind} commands are specifically
15397 designed to make it easy to scan through the trace buffer. For
15398 instance, @code{tfind} with no argument selects the next trace
15399 snapshot, and @code{tfind -} with no argument selects the previous
15400 trace snapshot. So, by giving one @code{tfind} command, and then
15401 simply hitting @key{RET} repeatedly you can examine all the trace
15402 snapshots in order. Or, by saying @code{tfind -} and then hitting
15403 @key{RET} repeatedly you can examine the snapshots in reverse order.
15404 The @code{tfind line} command with no argument selects the snapshot
15405 for the next source line executed. The @code{tfind pc} command with
15406 no argument selects the next snapshot with the same program counter
15407 (PC) as the current frame. The @code{tfind tracepoint} command with
15408 no argument selects the next trace snapshot collected by the same
15409 tracepoint as the current one.
15411 In addition to letting you scan through the trace buffer manually,
15412 these commands make it easy to construct @value{GDBN} scripts that
15413 scan through the trace buffer and print out whatever collected data
15414 you are interested in. Thus, if we want to examine the PC, FP, and SP
15415 registers from each trace frame in the buffer, we can say this:
15418 (@value{GDBP}) @b{tfind start}
15419 (@value{GDBP}) @b{while ($trace_frame != -1)}
15420 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
15421 $trace_frame, $pc, $sp, $fp
15425 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
15426 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
15427 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
15428 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
15429 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
15430 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
15431 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
15432 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
15433 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
15434 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
15435 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
15438 Or, if we want to examine the variable @code{X} at each source line in
15442 (@value{GDBP}) @b{tfind start}
15443 (@value{GDBP}) @b{while ($trace_frame != -1)}
15444 > printf "Frame %d, X == %d\n", $trace_frame, X
15454 @subsection @code{tdump}
15456 @cindex dump all data collected at tracepoint
15457 @cindex tracepoint data, display
15459 This command takes no arguments. It prints all the data collected at
15460 the current trace snapshot.
15463 (@value{GDBP}) @b{trace 444}
15464 (@value{GDBP}) @b{actions}
15465 Enter actions for tracepoint #2, one per line:
15466 > collect $regs, $locals, $args, gdb_long_test
15469 (@value{GDBP}) @b{tstart}
15471 (@value{GDBP}) @b{tfind line 444}
15472 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
15474 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
15476 (@value{GDBP}) @b{tdump}
15477 Data collected at tracepoint 2, trace frame 1:
15478 d0 0xc4aa0085 -995491707
15482 d4 0x71aea3d 119204413
15485 d7 0x380035 3670069
15486 a0 0x19e24a 1696330
15487 a1 0x3000668 50333288
15489 a3 0x322000 3284992
15490 a4 0x3000698 50333336
15491 a5 0x1ad3cc 1758156
15492 fp 0x30bf3c 0x30bf3c
15493 sp 0x30bf34 0x30bf34
15495 pc 0x20b2c8 0x20b2c8
15499 p = 0x20e5b4 "gdb-test"
15506 gdb_long_test = 17 '\021'
15511 @code{tdump} works by scanning the tracepoint's current collection
15512 actions and printing the value of each expression listed. So
15513 @code{tdump} can fail, if after a run, you change the tracepoint's
15514 actions to mention variables that were not collected during the run.
15516 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
15517 uses the collected value of @code{$pc} to distinguish between trace
15518 frames that were collected at the tracepoint hit, and frames that were
15519 collected while stepping. This allows it to correctly choose whether
15520 to display the basic list of collections, or the collections from the
15521 body of the while-stepping loop. However, if @code{$pc} was not collected,
15522 then @code{tdump} will always attempt to dump using the basic collection
15523 list, and may fail if a while-stepping frame does not include all the
15524 same data that is collected at the tracepoint hit.
15525 @c This is getting pretty arcane, example would be good.
15527 @node save tracepoints
15528 @subsection @code{save tracepoints @var{filename}}
15529 @kindex save tracepoints
15530 @kindex save-tracepoints
15531 @cindex save tracepoints for future sessions
15533 This command saves all current tracepoint definitions together with
15534 their actions and passcounts, into a file @file{@var{filename}}
15535 suitable for use in a later debugging session. To read the saved
15536 tracepoint definitions, use the @code{source} command (@pxref{Command
15537 Files}). The @w{@code{save-tracepoints}} command is a deprecated
15538 alias for @w{@code{save tracepoints}}
15540 @node Tracepoint Variables
15541 @section Convenience Variables for Tracepoints
15542 @cindex tracepoint variables
15543 @cindex convenience variables for tracepoints
15546 @vindex $trace_frame
15547 @item (int) $trace_frame
15548 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
15549 snapshot is selected.
15551 @vindex $tracepoint
15552 @item (int) $tracepoint
15553 The tracepoint for the current trace snapshot.
15555 @vindex $trace_line
15556 @item (int) $trace_line
15557 The line number for the current trace snapshot.
15559 @vindex $trace_file
15560 @item (char []) $trace_file
15561 The source file for the current trace snapshot.
15563 @vindex $trace_func
15564 @item (char []) $trace_func
15565 The name of the function containing @code{$tracepoint}.
15568 Note: @code{$trace_file} is not suitable for use in @code{printf},
15569 use @code{output} instead.
15571 Here's a simple example of using these convenience variables for
15572 stepping through all the trace snapshots and printing some of their
15573 data. Note that these are not the same as trace state variables,
15574 which are managed by the target.
15577 (@value{GDBP}) @b{tfind start}
15579 (@value{GDBP}) @b{while $trace_frame != -1}
15580 > output $trace_file
15581 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
15587 @section Using Trace Files
15588 @cindex trace files
15590 In some situations, the target running a trace experiment may no
15591 longer be available; perhaps it crashed, or the hardware was needed
15592 for a different activity. To handle these cases, you can arrange to
15593 dump the trace data into a file, and later use that file as a source
15594 of trace data, via the @code{target tfile} command.
15599 @item tsave [ -r ] @var{filename}
15600 @itemx tsave [-ctf] @var{dirname}
15601 Save the trace data to @var{filename}. By default, this command
15602 assumes that @var{filename} refers to the host filesystem, so if
15603 necessary @value{GDBN} will copy raw trace data up from the target and
15604 then save it. If the target supports it, you can also supply the
15605 optional argument @code{-r} (``remote'') to direct the target to save
15606 the data directly into @var{filename} in its own filesystem, which may be
15607 more efficient if the trace buffer is very large. (Note, however, that
15608 @code{target tfile} can only read from files accessible to the host.)
15609 By default, this command will save trace frame in tfile format.
15610 You can supply the optional argument @code{-ctf} to save data in CTF
15611 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
15612 that can be shared by multiple debugging and tracing tools. Please go to
15613 @indicateurl{http://www.efficios.com/ctf} to get more information.
15615 @kindex target tfile
15619 @item target tfile @var{filename}
15620 @itemx target ctf @var{dirname}
15621 Use the file named @var{filename} or directory named @var{dirname} as
15622 a source of trace data. Commands that examine data work as they do with
15623 a live target, but it is not possible to run any new trace experiments.
15624 @code{tstatus} will report the state of the trace run at the moment
15625 the data was saved, as well as the current trace frame you are examining.
15626 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
15630 (@value{GDBP}) target ctf ctf.ctf
15631 (@value{GDBP}) tfind
15632 Found trace frame 0, tracepoint 2
15633 39 ++a; /* set tracepoint 1 here */
15634 (@value{GDBP}) tdump
15635 Data collected at tracepoint 2, trace frame 0:
15639 c = @{"123", "456", "789", "123", "456", "789"@}
15640 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
15648 @chapter Debugging Programs That Use Overlays
15651 If your program is too large to fit completely in your target system's
15652 memory, you can sometimes use @dfn{overlays} to work around this
15653 problem. @value{GDBN} provides some support for debugging programs that
15657 * How Overlays Work:: A general explanation of overlays.
15658 * Overlay Commands:: Managing overlays in @value{GDBN}.
15659 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
15660 mapped by asking the inferior.
15661 * Overlay Sample Program:: A sample program using overlays.
15664 @node How Overlays Work
15665 @section How Overlays Work
15666 @cindex mapped overlays
15667 @cindex unmapped overlays
15668 @cindex load address, overlay's
15669 @cindex mapped address
15670 @cindex overlay area
15672 Suppose you have a computer whose instruction address space is only 64
15673 kilobytes long, but which has much more memory which can be accessed by
15674 other means: special instructions, segment registers, or memory
15675 management hardware, for example. Suppose further that you want to
15676 adapt a program which is larger than 64 kilobytes to run on this system.
15678 One solution is to identify modules of your program which are relatively
15679 independent, and need not call each other directly; call these modules
15680 @dfn{overlays}. Separate the overlays from the main program, and place
15681 their machine code in the larger memory. Place your main program in
15682 instruction memory, but leave at least enough space there to hold the
15683 largest overlay as well.
15685 Now, to call a function located in an overlay, you must first copy that
15686 overlay's machine code from the large memory into the space set aside
15687 for it in the instruction memory, and then jump to its entry point
15690 @c NB: In the below the mapped area's size is greater or equal to the
15691 @c size of all overlays. This is intentional to remind the developer
15692 @c that overlays don't necessarily need to be the same size.
15696 Data Instruction Larger
15697 Address Space Address Space Address Space
15698 +-----------+ +-----------+ +-----------+
15700 +-----------+ +-----------+ +-----------+<-- overlay 1
15701 | program | | main | .----| overlay 1 | load address
15702 | variables | | program | | +-----------+
15703 | and heap | | | | | |
15704 +-----------+ | | | +-----------+<-- overlay 2
15705 | | +-----------+ | | | load address
15706 +-----------+ | | | .-| overlay 2 |
15708 mapped --->+-----------+ | | +-----------+
15709 address | | | | | |
15710 | overlay | <-' | | |
15711 | area | <---' +-----------+<-- overlay 3
15712 | | <---. | | load address
15713 +-----------+ `--| overlay 3 |
15720 @anchor{A code overlay}A code overlay
15724 The diagram (@pxref{A code overlay}) shows a system with separate data
15725 and instruction address spaces. To map an overlay, the program copies
15726 its code from the larger address space to the instruction address space.
15727 Since the overlays shown here all use the same mapped address, only one
15728 may be mapped at a time. For a system with a single address space for
15729 data and instructions, the diagram would be similar, except that the
15730 program variables and heap would share an address space with the main
15731 program and the overlay area.
15733 An overlay loaded into instruction memory and ready for use is called a
15734 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
15735 instruction memory. An overlay not present (or only partially present)
15736 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
15737 is its address in the larger memory. The mapped address is also called
15738 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
15739 called the @dfn{load memory address}, or @dfn{LMA}.
15741 Unfortunately, overlays are not a completely transparent way to adapt a
15742 program to limited instruction memory. They introduce a new set of
15743 global constraints you must keep in mind as you design your program:
15748 Before calling or returning to a function in an overlay, your program
15749 must make sure that overlay is actually mapped. Otherwise, the call or
15750 return will transfer control to the right address, but in the wrong
15751 overlay, and your program will probably crash.
15754 If the process of mapping an overlay is expensive on your system, you
15755 will need to choose your overlays carefully to minimize their effect on
15756 your program's performance.
15759 The executable file you load onto your system must contain each
15760 overlay's instructions, appearing at the overlay's load address, not its
15761 mapped address. However, each overlay's instructions must be relocated
15762 and its symbols defined as if the overlay were at its mapped address.
15763 You can use GNU linker scripts to specify different load and relocation
15764 addresses for pieces of your program; see @ref{Overlay Description,,,
15765 ld.info, Using ld: the GNU linker}.
15768 The procedure for loading executable files onto your system must be able
15769 to load their contents into the larger address space as well as the
15770 instruction and data spaces.
15774 The overlay system described above is rather simple, and could be
15775 improved in many ways:
15780 If your system has suitable bank switch registers or memory management
15781 hardware, you could use those facilities to make an overlay's load area
15782 contents simply appear at their mapped address in instruction space.
15783 This would probably be faster than copying the overlay to its mapped
15784 area in the usual way.
15787 If your overlays are small enough, you could set aside more than one
15788 overlay area, and have more than one overlay mapped at a time.
15791 You can use overlays to manage data, as well as instructions. In
15792 general, data overlays are even less transparent to your design than
15793 code overlays: whereas code overlays only require care when you call or
15794 return to functions, data overlays require care every time you access
15795 the data. Also, if you change the contents of a data overlay, you
15796 must copy its contents back out to its load address before you can copy a
15797 different data overlay into the same mapped area.
15802 @node Overlay Commands
15803 @section Overlay Commands
15805 To use @value{GDBN}'s overlay support, each overlay in your program must
15806 correspond to a separate section of the executable file. The section's
15807 virtual memory address and load memory address must be the overlay's
15808 mapped and load addresses. Identifying overlays with sections allows
15809 @value{GDBN} to determine the appropriate address of a function or
15810 variable, depending on whether the overlay is mapped or not.
15812 @value{GDBN}'s overlay commands all start with the word @code{overlay};
15813 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
15818 Disable @value{GDBN}'s overlay support. When overlay support is
15819 disabled, @value{GDBN} assumes that all functions and variables are
15820 always present at their mapped addresses. By default, @value{GDBN}'s
15821 overlay support is disabled.
15823 @item overlay manual
15824 @cindex manual overlay debugging
15825 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
15826 relies on you to tell it which overlays are mapped, and which are not,
15827 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
15828 commands described below.
15830 @item overlay map-overlay @var{overlay}
15831 @itemx overlay map @var{overlay}
15832 @cindex map an overlay
15833 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
15834 be the name of the object file section containing the overlay. When an
15835 overlay is mapped, @value{GDBN} assumes it can find the overlay's
15836 functions and variables at their mapped addresses. @value{GDBN} assumes
15837 that any other overlays whose mapped ranges overlap that of
15838 @var{overlay} are now unmapped.
15840 @item overlay unmap-overlay @var{overlay}
15841 @itemx overlay unmap @var{overlay}
15842 @cindex unmap an overlay
15843 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
15844 must be the name of the object file section containing the overlay.
15845 When an overlay is unmapped, @value{GDBN} assumes it can find the
15846 overlay's functions and variables at their load addresses.
15849 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
15850 consults a data structure the overlay manager maintains in the inferior
15851 to see which overlays are mapped. For details, see @ref{Automatic
15852 Overlay Debugging}.
15854 @item overlay load-target
15855 @itemx overlay load
15856 @cindex reloading the overlay table
15857 Re-read the overlay table from the inferior. Normally, @value{GDBN}
15858 re-reads the table @value{GDBN} automatically each time the inferior
15859 stops, so this command should only be necessary if you have changed the
15860 overlay mapping yourself using @value{GDBN}. This command is only
15861 useful when using automatic overlay debugging.
15863 @item overlay list-overlays
15864 @itemx overlay list
15865 @cindex listing mapped overlays
15866 Display a list of the overlays currently mapped, along with their mapped
15867 addresses, load addresses, and sizes.
15871 Normally, when @value{GDBN} prints a code address, it includes the name
15872 of the function the address falls in:
15875 (@value{GDBP}) print main
15876 $3 = @{int ()@} 0x11a0 <main>
15879 When overlay debugging is enabled, @value{GDBN} recognizes code in
15880 unmapped overlays, and prints the names of unmapped functions with
15881 asterisks around them. For example, if @code{foo} is a function in an
15882 unmapped overlay, @value{GDBN} prints it this way:
15885 (@value{GDBP}) overlay list
15886 No sections are mapped.
15887 (@value{GDBP}) print foo
15888 $5 = @{int (int)@} 0x100000 <*foo*>
15891 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
15895 (@value{GDBP}) overlay list
15896 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
15897 mapped at 0x1016 - 0x104a
15898 (@value{GDBP}) print foo
15899 $6 = @{int (int)@} 0x1016 <foo>
15902 When overlay debugging is enabled, @value{GDBN} can find the correct
15903 address for functions and variables in an overlay, whether or not the
15904 overlay is mapped. This allows most @value{GDBN} commands, like
15905 @code{break} and @code{disassemble}, to work normally, even on unmapped
15906 code. However, @value{GDBN}'s breakpoint support has some limitations:
15910 @cindex breakpoints in overlays
15911 @cindex overlays, setting breakpoints in
15912 You can set breakpoints in functions in unmapped overlays, as long as
15913 @value{GDBN} can write to the overlay at its load address.
15915 @value{GDBN} can not set hardware or simulator-based breakpoints in
15916 unmapped overlays. However, if you set a breakpoint at the end of your
15917 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
15918 you are using manual overlay management), @value{GDBN} will re-set its
15919 breakpoints properly.
15923 @node Automatic Overlay Debugging
15924 @section Automatic Overlay Debugging
15925 @cindex automatic overlay debugging
15927 @value{GDBN} can automatically track which overlays are mapped and which
15928 are not, given some simple co-operation from the overlay manager in the
15929 inferior. If you enable automatic overlay debugging with the
15930 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
15931 looks in the inferior's memory for certain variables describing the
15932 current state of the overlays.
15934 Here are the variables your overlay manager must define to support
15935 @value{GDBN}'s automatic overlay debugging:
15939 @item @code{_ovly_table}:
15940 This variable must be an array of the following structures:
15945 /* The overlay's mapped address. */
15948 /* The size of the overlay, in bytes. */
15949 unsigned long size;
15951 /* The overlay's load address. */
15954 /* Non-zero if the overlay is currently mapped;
15956 unsigned long mapped;
15960 @item @code{_novlys}:
15961 This variable must be a four-byte signed integer, holding the total
15962 number of elements in @code{_ovly_table}.
15966 To decide whether a particular overlay is mapped or not, @value{GDBN}
15967 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
15968 @code{lma} members equal the VMA and LMA of the overlay's section in the
15969 executable file. When @value{GDBN} finds a matching entry, it consults
15970 the entry's @code{mapped} member to determine whether the overlay is
15973 In addition, your overlay manager may define a function called
15974 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
15975 will silently set a breakpoint there. If the overlay manager then
15976 calls this function whenever it has changed the overlay table, this
15977 will enable @value{GDBN} to accurately keep track of which overlays
15978 are in program memory, and update any breakpoints that may be set
15979 in overlays. This will allow breakpoints to work even if the
15980 overlays are kept in ROM or other non-writable memory while they
15981 are not being executed.
15983 @node Overlay Sample Program
15984 @section Overlay Sample Program
15985 @cindex overlay example program
15987 When linking a program which uses overlays, you must place the overlays
15988 at their load addresses, while relocating them to run at their mapped
15989 addresses. To do this, you must write a linker script (@pxref{Overlay
15990 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
15991 since linker scripts are specific to a particular host system, target
15992 architecture, and target memory layout, this manual cannot provide
15993 portable sample code demonstrating @value{GDBN}'s overlay support.
15995 However, the @value{GDBN} source distribution does contain an overlaid
15996 program, with linker scripts for a few systems, as part of its test
15997 suite. The program consists of the following files from
15998 @file{gdb/testsuite/gdb.base}:
16002 The main program file.
16004 A simple overlay manager, used by @file{overlays.c}.
16009 Overlay modules, loaded and used by @file{overlays.c}.
16012 Linker scripts for linking the test program on the @code{d10v-elf}
16013 and @code{m32r-elf} targets.
16016 You can build the test program using the @code{d10v-elf} GCC
16017 cross-compiler like this:
16020 $ d10v-elf-gcc -g -c overlays.c
16021 $ d10v-elf-gcc -g -c ovlymgr.c
16022 $ d10v-elf-gcc -g -c foo.c
16023 $ d10v-elf-gcc -g -c bar.c
16024 $ d10v-elf-gcc -g -c baz.c
16025 $ d10v-elf-gcc -g -c grbx.c
16026 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
16027 baz.o grbx.o -Wl,-Td10v.ld -o overlays
16030 The build process is identical for any other architecture, except that
16031 you must substitute the appropriate compiler and linker script for the
16032 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
16036 @chapter Using @value{GDBN} with Different Languages
16039 Although programming languages generally have common aspects, they are
16040 rarely expressed in the same manner. For instance, in ANSI C,
16041 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
16042 Modula-2, it is accomplished by @code{p^}. Values can also be
16043 represented (and displayed) differently. Hex numbers in C appear as
16044 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
16046 @cindex working language
16047 Language-specific information is built into @value{GDBN} for some languages,
16048 allowing you to express operations like the above in your program's
16049 native language, and allowing @value{GDBN} to output values in a manner
16050 consistent with the syntax of your program's native language. The
16051 language you use to build expressions is called the @dfn{working
16055 * Setting:: Switching between source languages
16056 * Show:: Displaying the language
16057 * Checks:: Type and range checks
16058 * Supported Languages:: Supported languages
16059 * Unsupported Languages:: Unsupported languages
16063 @section Switching Between Source Languages
16065 There are two ways to control the working language---either have @value{GDBN}
16066 set it automatically, or select it manually yourself. You can use the
16067 @code{set language} command for either purpose. On startup, @value{GDBN}
16068 defaults to setting the language automatically. The working language is
16069 used to determine how expressions you type are interpreted, how values
16072 In addition to the working language, every source file that
16073 @value{GDBN} knows about has its own working language. For some object
16074 file formats, the compiler might indicate which language a particular
16075 source file is in. However, most of the time @value{GDBN} infers the
16076 language from the name of the file. The language of a source file
16077 controls whether C@t{++} names are demangled---this way @code{backtrace} can
16078 show each frame appropriately for its own language. There is no way to
16079 set the language of a source file from within @value{GDBN}, but you can
16080 set the language associated with a filename extension. @xref{Show, ,
16081 Displaying the Language}.
16083 This is most commonly a problem when you use a program, such
16084 as @code{cfront} or @code{f2c}, that generates C but is written in
16085 another language. In that case, make the
16086 program use @code{#line} directives in its C output; that way
16087 @value{GDBN} will know the correct language of the source code of the original
16088 program, and will display that source code, not the generated C code.
16091 * Filenames:: Filename extensions and languages.
16092 * Manually:: Setting the working language manually
16093 * Automatically:: Having @value{GDBN} infer the source language
16097 @subsection List of Filename Extensions and Languages
16099 If a source file name ends in one of the following extensions, then
16100 @value{GDBN} infers that its language is the one indicated.
16118 C@t{++} source file
16124 Objective-C source file
16128 Fortran source file
16131 Modula-2 source file
16135 Assembler source file. This actually behaves almost like C, but
16136 @value{GDBN} does not skip over function prologues when stepping.
16139 In addition, you may set the language associated with a filename
16140 extension. @xref{Show, , Displaying the Language}.
16143 @subsection Setting the Working Language
16145 If you allow @value{GDBN} to set the language automatically,
16146 expressions are interpreted the same way in your debugging session and
16149 @kindex set language
16150 If you wish, you may set the language manually. To do this, issue the
16151 command @samp{set language @var{lang}}, where @var{lang} is the name of
16152 a language, such as
16153 @code{c} or @code{modula-2}.
16154 For a list of the supported languages, type @samp{set language}.
16156 Setting the language manually prevents @value{GDBN} from updating the working
16157 language automatically. This can lead to confusion if you try
16158 to debug a program when the working language is not the same as the
16159 source language, when an expression is acceptable to both
16160 languages---but means different things. For instance, if the current
16161 source file were written in C, and @value{GDBN} was parsing Modula-2, a
16169 might not have the effect you intended. In C, this means to add
16170 @code{b} and @code{c} and place the result in @code{a}. The result
16171 printed would be the value of @code{a}. In Modula-2, this means to compare
16172 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
16174 @node Automatically
16175 @subsection Having @value{GDBN} Infer the Source Language
16177 To have @value{GDBN} set the working language automatically, use
16178 @samp{set language local} or @samp{set language auto}. @value{GDBN}
16179 then infers the working language. That is, when your program stops in a
16180 frame (usually by encountering a breakpoint), @value{GDBN} sets the
16181 working language to the language recorded for the function in that
16182 frame. If the language for a frame is unknown (that is, if the function
16183 or block corresponding to the frame was defined in a source file that
16184 does not have a recognized extension), the current working language is
16185 not changed, and @value{GDBN} issues a warning.
16187 This may not seem necessary for most programs, which are written
16188 entirely in one source language. However, program modules and libraries
16189 written in one source language can be used by a main program written in
16190 a different source language. Using @samp{set language auto} in this
16191 case frees you from having to set the working language manually.
16194 @section Displaying the Language
16196 The following commands help you find out which language is the
16197 working language, and also what language source files were written in.
16200 @item show language
16201 @anchor{show language}
16202 @kindex show language
16203 Display the current working language. This is the
16204 language you can use with commands such as @code{print} to
16205 build and compute expressions that may involve variables in your program.
16208 @kindex info frame@r{, show the source language}
16209 Display the source language for this frame. This language becomes the
16210 working language if you use an identifier from this frame.
16211 @xref{Frame Info, ,Information about a Frame}, to identify the other
16212 information listed here.
16215 @kindex info source@r{, show the source language}
16216 Display the source language of this source file.
16217 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
16218 information listed here.
16221 In unusual circumstances, you may have source files with extensions
16222 not in the standard list. You can then set the extension associated
16223 with a language explicitly:
16226 @item set extension-language @var{ext} @var{language}
16227 @kindex set extension-language
16228 Tell @value{GDBN} that source files with extension @var{ext} are to be
16229 assumed as written in the source language @var{language}.
16231 @item info extensions
16232 @kindex info extensions
16233 List all the filename extensions and the associated languages.
16237 @section Type and Range Checking
16239 Some languages are designed to guard you against making seemingly common
16240 errors through a series of compile- and run-time checks. These include
16241 checking the type of arguments to functions and operators and making
16242 sure mathematical overflows are caught at run time. Checks such as
16243 these help to ensure a program's correctness once it has been compiled
16244 by eliminating type mismatches and providing active checks for range
16245 errors when your program is running.
16247 By default @value{GDBN} checks for these errors according to the
16248 rules of the current source language. Although @value{GDBN} does not check
16249 the statements in your program, it can check expressions entered directly
16250 into @value{GDBN} for evaluation via the @code{print} command, for example.
16253 * Type Checking:: An overview of type checking
16254 * Range Checking:: An overview of range checking
16257 @cindex type checking
16258 @cindex checks, type
16259 @node Type Checking
16260 @subsection An Overview of Type Checking
16262 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
16263 arguments to operators and functions have to be of the correct type,
16264 otherwise an error occurs. These checks prevent type mismatch
16265 errors from ever causing any run-time problems. For example,
16268 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
16270 (@value{GDBP}) print obj.my_method (0)
16273 (@value{GDBP}) print obj.my_method (0x1234)
16274 Cannot resolve method klass::my_method to any overloaded instance
16277 The second example fails because in C@t{++} the integer constant
16278 @samp{0x1234} is not type-compatible with the pointer parameter type.
16280 For the expressions you use in @value{GDBN} commands, you can tell
16281 @value{GDBN} to not enforce strict type checking or
16282 to treat any mismatches as errors and abandon the expression;
16283 When type checking is disabled, @value{GDBN} successfully evaluates
16284 expressions like the second example above.
16286 Even if type checking is off, there may be other reasons
16287 related to type that prevent @value{GDBN} from evaluating an expression.
16288 For instance, @value{GDBN} does not know how to add an @code{int} and
16289 a @code{struct foo}. These particular type errors have nothing to do
16290 with the language in use and usually arise from expressions which make
16291 little sense to evaluate anyway.
16293 @value{GDBN} provides some additional commands for controlling type checking:
16295 @kindex set check type
16296 @kindex show check type
16298 @item set check type on
16299 @itemx set check type off
16300 Set strict type checking on or off. If any type mismatches occur in
16301 evaluating an expression while type checking is on, @value{GDBN} prints a
16302 message and aborts evaluation of the expression.
16304 @item show check type
16305 Show the current setting of type checking and whether @value{GDBN}
16306 is enforcing strict type checking rules.
16309 @cindex range checking
16310 @cindex checks, range
16311 @node Range Checking
16312 @subsection An Overview of Range Checking
16314 In some languages (such as Modula-2), it is an error to exceed the
16315 bounds of a type; this is enforced with run-time checks. Such range
16316 checking is meant to ensure program correctness by making sure
16317 computations do not overflow, or indices on an array element access do
16318 not exceed the bounds of the array.
16320 For expressions you use in @value{GDBN} commands, you can tell
16321 @value{GDBN} to treat range errors in one of three ways: ignore them,
16322 always treat them as errors and abandon the expression, or issue
16323 warnings but evaluate the expression anyway.
16325 A range error can result from numerical overflow, from exceeding an
16326 array index bound, or when you type a constant that is not a member
16327 of any type. Some languages, however, do not treat overflows as an
16328 error. In many implementations of C, mathematical overflow causes the
16329 result to ``wrap around'' to lower values---for example, if @var{m} is
16330 the largest integer value, and @var{s} is the smallest, then
16333 @var{m} + 1 @result{} @var{s}
16336 This, too, is specific to individual languages, and in some cases
16337 specific to individual compilers or machines. @xref{Supported Languages, ,
16338 Supported Languages}, for further details on specific languages.
16340 @value{GDBN} provides some additional commands for controlling the range checker:
16342 @kindex set check range
16343 @kindex show check range
16345 @item set check range auto
16346 Set range checking on or off based on the current working language.
16347 @xref{Supported Languages, ,Supported Languages}, for the default settings for
16350 @item set check range on
16351 @itemx set check range off
16352 Set range checking on or off, overriding the default setting for the
16353 current working language. A warning is issued if the setting does not
16354 match the language default. If a range error occurs and range checking is on,
16355 then a message is printed and evaluation of the expression is aborted.
16357 @item set check range warn
16358 Output messages when the @value{GDBN} range checker detects a range error,
16359 but attempt to evaluate the expression anyway. Evaluating the
16360 expression may still be impossible for other reasons, such as accessing
16361 memory that the process does not own (a typical example from many Unix
16364 @item show check range
16365 Show the current setting of the range checker, and whether or not it is
16366 being set automatically by @value{GDBN}.
16369 @node Supported Languages
16370 @section Supported Languages
16372 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
16373 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
16374 @c This is false ...
16375 Some @value{GDBN} features may be used in expressions regardless of the
16376 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
16377 and the @samp{@{type@}addr} construct (@pxref{Expressions,
16378 ,Expressions}) can be used with the constructs of any supported
16381 The following sections detail to what degree each source language is
16382 supported by @value{GDBN}. These sections are not meant to be language
16383 tutorials or references, but serve only as a reference guide to what the
16384 @value{GDBN} expression parser accepts, and what input and output
16385 formats should look like for different languages. There are many good
16386 books written on each of these languages; please look to these for a
16387 language reference or tutorial.
16390 * C:: C and C@t{++}
16393 * Objective-C:: Objective-C
16394 * OpenCL C:: OpenCL C
16395 * Fortran:: Fortran
16398 * Modula-2:: Modula-2
16403 @subsection C and C@t{++}
16405 @cindex C and C@t{++}
16406 @cindex expressions in C or C@t{++}
16408 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
16409 to both languages. Whenever this is the case, we discuss those languages
16413 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
16414 @cindex @sc{gnu} C@t{++}
16415 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
16416 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
16417 effectively, you must compile your C@t{++} programs with a supported
16418 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
16419 compiler (@code{aCC}).
16422 * C Operators:: C and C@t{++} operators
16423 * C Constants:: C and C@t{++} constants
16424 * C Plus Plus Expressions:: C@t{++} expressions
16425 * C Defaults:: Default settings for C and C@t{++}
16426 * C Checks:: C and C@t{++} type and range checks
16427 * Debugging C:: @value{GDBN} and C
16428 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
16429 * Decimal Floating Point:: Numbers in Decimal Floating Point format
16433 @subsubsection C and C@t{++} Operators
16435 @cindex C and C@t{++} operators
16437 Operators must be defined on values of specific types. For instance,
16438 @code{+} is defined on numbers, but not on structures. Operators are
16439 often defined on groups of types.
16441 For the purposes of C and C@t{++}, the following definitions hold:
16446 @emph{Integral types} include @code{int} with any of its storage-class
16447 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
16450 @emph{Floating-point types} include @code{float}, @code{double}, and
16451 @code{long double} (if supported by the target platform).
16454 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
16457 @emph{Scalar types} include all of the above.
16462 The following operators are supported. They are listed here
16463 in order of increasing precedence:
16467 The comma or sequencing operator. Expressions in a comma-separated list
16468 are evaluated from left to right, with the result of the entire
16469 expression being the last expression evaluated.
16472 Assignment. The value of an assignment expression is the value
16473 assigned. Defined on scalar types.
16476 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
16477 and translated to @w{@code{@var{a} = @var{a op b}}}.
16478 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
16479 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
16480 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
16483 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
16484 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
16485 should be of an integral type.
16488 Logical @sc{or}. Defined on integral types.
16491 Logical @sc{and}. Defined on integral types.
16494 Bitwise @sc{or}. Defined on integral types.
16497 Bitwise exclusive-@sc{or}. Defined on integral types.
16500 Bitwise @sc{and}. Defined on integral types.
16503 Equality and inequality. Defined on scalar types. The value of these
16504 expressions is 0 for false and non-zero for true.
16506 @item <@r{, }>@r{, }<=@r{, }>=
16507 Less than, greater than, less than or equal, greater than or equal.
16508 Defined on scalar types. The value of these expressions is 0 for false
16509 and non-zero for true.
16512 left shift, and right shift. Defined on integral types.
16515 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16518 Addition and subtraction. Defined on integral types, floating-point types and
16521 @item *@r{, }/@r{, }%
16522 Multiplication, division, and modulus. Multiplication and division are
16523 defined on integral and floating-point types. Modulus is defined on
16527 Increment and decrement. When appearing before a variable, the
16528 operation is performed before the variable is used in an expression;
16529 when appearing after it, the variable's value is used before the
16530 operation takes place.
16533 Pointer dereferencing. Defined on pointer types. Same precedence as
16537 Address operator. Defined on variables. Same precedence as @code{++}.
16539 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
16540 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
16541 to examine the address
16542 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
16546 Negative. Defined on integral and floating-point types. Same
16547 precedence as @code{++}.
16550 Logical negation. Defined on integral types. Same precedence as
16554 Bitwise complement operator. Defined on integral types. Same precedence as
16559 Structure member, and pointer-to-structure member. For convenience,
16560 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
16561 pointer based on the stored type information.
16562 Defined on @code{struct} and @code{union} data.
16565 Dereferences of pointers to members.
16568 Array indexing. @code{@var{a}[@var{i}]} is defined as
16569 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
16572 Function parameter list. Same precedence as @code{->}.
16575 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
16576 and @code{class} types.
16579 Doubled colons also represent the @value{GDBN} scope operator
16580 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
16584 If an operator is redefined in the user code, @value{GDBN} usually
16585 attempts to invoke the redefined version instead of using the operator's
16586 predefined meaning.
16589 @subsubsection C and C@t{++} Constants
16591 @cindex C and C@t{++} constants
16593 @value{GDBN} allows you to express the constants of C and C@t{++} in the
16598 Integer constants are a sequence of digits. Octal constants are
16599 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
16600 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
16601 @samp{l}, specifying that the constant should be treated as a
16605 Floating point constants are a sequence of digits, followed by a decimal
16606 point, followed by a sequence of digits, and optionally followed by an
16607 exponent. An exponent is of the form:
16608 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
16609 sequence of digits. The @samp{+} is optional for positive exponents.
16610 A floating-point constant may also end with a letter @samp{f} or
16611 @samp{F}, specifying that the constant should be treated as being of
16612 the @code{float} (as opposed to the default @code{double}) type; or with
16613 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
16617 Enumerated constants consist of enumerated identifiers, or their
16618 integral equivalents.
16621 Character constants are a single character surrounded by single quotes
16622 (@code{'}), or a number---the ordinal value of the corresponding character
16623 (usually its @sc{ascii} value). Within quotes, the single character may
16624 be represented by a letter or by @dfn{escape sequences}, which are of
16625 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
16626 of the character's ordinal value; or of the form @samp{\@var{x}}, where
16627 @samp{@var{x}} is a predefined special character---for example,
16628 @samp{\n} for newline.
16630 Wide character constants can be written by prefixing a character
16631 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
16632 form of @samp{x}. The target wide character set is used when
16633 computing the value of this constant (@pxref{Character Sets}).
16636 String constants are a sequence of character constants surrounded by
16637 double quotes (@code{"}). Any valid character constant (as described
16638 above) may appear. Double quotes within the string must be preceded by
16639 a backslash, so for instance @samp{"a\"b'c"} is a string of five
16642 Wide string constants can be written by prefixing a string constant
16643 with @samp{L}, as in C. The target wide character set is used when
16644 computing the value of this constant (@pxref{Character Sets}).
16647 Pointer constants are an integral value. You can also write pointers
16648 to constants using the C operator @samp{&}.
16651 Array constants are comma-separated lists surrounded by braces @samp{@{}
16652 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
16653 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
16654 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
16657 @node C Plus Plus Expressions
16658 @subsubsection C@t{++} Expressions
16660 @cindex expressions in C@t{++}
16661 @value{GDBN} expression handling can interpret most C@t{++} expressions.
16663 @cindex debugging C@t{++} programs
16664 @cindex C@t{++} compilers
16665 @cindex debug formats and C@t{++}
16666 @cindex @value{NGCC} and C@t{++}
16668 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
16669 the proper compiler and the proper debug format. Currently,
16670 @value{GDBN} works best when debugging C@t{++} code that is compiled
16671 with the most recent version of @value{NGCC} possible. The DWARF
16672 debugging format is preferred; @value{NGCC} defaults to this on most
16673 popular platforms. Other compilers and/or debug formats are likely to
16674 work badly or not at all when using @value{GDBN} to debug C@t{++}
16675 code. @xref{Compilation}.
16680 @cindex member functions
16682 Member function calls are allowed; you can use expressions like
16685 count = aml->GetOriginal(x, y)
16688 @vindex this@r{, inside C@t{++} member functions}
16689 @cindex namespace in C@t{++}
16691 While a member function is active (in the selected stack frame), your
16692 expressions have the same namespace available as the member function;
16693 that is, @value{GDBN} allows implicit references to the class instance
16694 pointer @code{this} following the same rules as C@t{++}. @code{using}
16695 declarations in the current scope are also respected by @value{GDBN}.
16697 @cindex call overloaded functions
16698 @cindex overloaded functions, calling
16699 @cindex type conversions in C@t{++}
16701 You can call overloaded functions; @value{GDBN} resolves the function
16702 call to the right definition, with some restrictions. @value{GDBN} does not
16703 perform overload resolution involving user-defined type conversions,
16704 calls to constructors, or instantiations of templates that do not exist
16705 in the program. It also cannot handle ellipsis argument lists or
16708 It does perform integral conversions and promotions, floating-point
16709 promotions, arithmetic conversions, pointer conversions, conversions of
16710 class objects to base classes, and standard conversions such as those of
16711 functions or arrays to pointers; it requires an exact match on the
16712 number of function arguments.
16714 Overload resolution is always performed, unless you have specified
16715 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
16716 ,@value{GDBN} Features for C@t{++}}.
16718 You must specify @code{set overload-resolution off} in order to use an
16719 explicit function signature to call an overloaded function, as in
16721 p 'foo(char,int)'('x', 13)
16724 The @value{GDBN} command-completion facility can simplify this;
16725 see @ref{Completion, ,Command Completion}.
16727 @cindex reference declarations
16729 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
16730 references; you can use them in expressions just as you do in C@t{++}
16731 source---they are automatically dereferenced.
16733 In the parameter list shown when @value{GDBN} displays a frame, the values of
16734 reference variables are not displayed (unlike other variables); this
16735 avoids clutter, since references are often used for large structures.
16736 The @emph{address} of a reference variable is always shown, unless
16737 you have specified @samp{set print address off}.
16740 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
16741 expressions can use it just as expressions in your program do. Since
16742 one scope may be defined in another, you can use @code{::} repeatedly if
16743 necessary, for example in an expression like
16744 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
16745 resolving name scope by reference to source files, in both C and C@t{++}
16746 debugging (@pxref{Variables, ,Program Variables}).
16749 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
16754 @subsubsection C and C@t{++} Defaults
16756 @cindex C and C@t{++} defaults
16758 If you allow @value{GDBN} to set range checking automatically, it
16759 defaults to @code{off} whenever the working language changes to
16760 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
16761 selects the working language.
16763 If you allow @value{GDBN} to set the language automatically, it
16764 recognizes source files whose names end with @file{.c}, @file{.C}, or
16765 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
16766 these files, it sets the working language to C or C@t{++}.
16767 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
16768 for further details.
16771 @subsubsection C and C@t{++} Type and Range Checks
16773 @cindex C and C@t{++} checks
16775 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
16776 checking is used. However, if you turn type checking off, @value{GDBN}
16777 will allow certain non-standard conversions, such as promoting integer
16778 constants to pointers.
16780 Range checking, if turned on, is done on mathematical operations. Array
16781 indices are not checked, since they are often used to index a pointer
16782 that is not itself an array.
16785 @subsubsection @value{GDBN} and C
16787 The @code{set print union} and @code{show print union} commands apply to
16788 the @code{union} type. When set to @samp{on}, any @code{union} that is
16789 inside a @code{struct} or @code{class} is also printed. Otherwise, it
16790 appears as @samp{@{...@}}.
16792 The @code{@@} operator aids in the debugging of dynamic arrays, formed
16793 with pointers and a memory allocation function. @xref{Expressions,
16796 @node Debugging C Plus Plus
16797 @subsubsection @value{GDBN} Features for C@t{++}
16799 @cindex commands for C@t{++}
16801 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
16802 designed specifically for use with C@t{++}. Here is a summary:
16805 @cindex break in overloaded functions
16806 @item @r{breakpoint menus}
16807 When you want a breakpoint in a function whose name is overloaded,
16808 @value{GDBN} has the capability to display a menu of possible breakpoint
16809 locations to help you specify which function definition you want.
16810 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
16812 @cindex overloading in C@t{++}
16813 @item rbreak @var{regex}
16814 Setting breakpoints using regular expressions is helpful for setting
16815 breakpoints on overloaded functions that are not members of any special
16817 @xref{Set Breaks, ,Setting Breakpoints}.
16819 @cindex C@t{++} exception handling
16821 @itemx catch rethrow
16823 Debug C@t{++} exception handling using these commands. @xref{Set
16824 Catchpoints, , Setting Catchpoints}.
16826 @cindex inheritance
16827 @item ptype @var{typename}
16828 Print inheritance relationships as well as other information for type
16830 @xref{Symbols, ,Examining the Symbol Table}.
16832 @item info vtbl @var{expression}.
16833 The @code{info vtbl} command can be used to display the virtual
16834 method tables of the object computed by @var{expression}. This shows
16835 one entry per virtual table; there may be multiple virtual tables when
16836 multiple inheritance is in use.
16838 @cindex C@t{++} demangling
16839 @item demangle @var{name}
16840 Demangle @var{name}.
16841 @xref{Symbols}, for a more complete description of the @code{demangle} command.
16843 @cindex C@t{++} symbol display
16844 @item set print demangle
16845 @itemx show print demangle
16846 @itemx set print asm-demangle
16847 @itemx show print asm-demangle
16848 Control whether C@t{++} symbols display in their source form, both when
16849 displaying code as C@t{++} source and when displaying disassemblies.
16850 @xref{Print Settings, ,Print Settings}.
16852 @item set print object
16853 @itemx show print object
16854 Choose whether to print derived (actual) or declared types of objects.
16855 @xref{Print Settings, ,Print Settings}.
16857 @item set print vtbl
16858 @itemx show print vtbl
16859 Control the format for printing virtual function tables.
16860 @xref{Print Settings, ,Print Settings}.
16861 (The @code{vtbl} commands do not work on programs compiled with the HP
16862 ANSI C@t{++} compiler (@code{aCC}).)
16864 @kindex set overload-resolution
16865 @cindex overloaded functions, overload resolution
16866 @item set overload-resolution on
16867 Enable overload resolution for C@t{++} expression evaluation. The default
16868 is on. For overloaded functions, @value{GDBN} evaluates the arguments
16869 and searches for a function whose signature matches the argument types,
16870 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
16871 Expressions, ,C@t{++} Expressions}, for details).
16872 If it cannot find a match, it emits a message.
16874 @item set overload-resolution off
16875 Disable overload resolution for C@t{++} expression evaluation. For
16876 overloaded functions that are not class member functions, @value{GDBN}
16877 chooses the first function of the specified name that it finds in the
16878 symbol table, whether or not its arguments are of the correct type. For
16879 overloaded functions that are class member functions, @value{GDBN}
16880 searches for a function whose signature @emph{exactly} matches the
16883 @kindex show overload-resolution
16884 @item show overload-resolution
16885 Show the current setting of overload resolution.
16887 @item @r{Overloaded symbol names}
16888 You can specify a particular definition of an overloaded symbol, using
16889 the same notation that is used to declare such symbols in C@t{++}: type
16890 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
16891 also use the @value{GDBN} command-line word completion facilities to list the
16892 available choices, or to finish the type list for you.
16893 @xref{Completion,, Command Completion}, for details on how to do this.
16895 @item @r{Breakpoints in template functions}
16897 Similar to how overloaded symbols are handled, @value{GDBN} will ignore
16898 template parameter lists when it encounters a symbol which includes a
16899 C@t{++} template. This permits setting breakpoints on families of template functions
16900 or functions whose parameters include template types.
16902 The @kbd{-qualified} flag may be used to override this behavior, causing
16903 @value{GDBN} to search for a specific function or type.
16905 The @value{GDBN} command-line word completion facility also understands
16906 template parameters and may be used to list available choices or finish
16907 template parameter lists for you. @xref{Completion,, Command Completion}, for
16908 details on how to do this.
16910 @item @r{Breakpoints in functions with ABI tags}
16912 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
16913 correspond to changes in the ABI of a type, function, or variable that
16914 would not otherwise be reflected in a mangled name. See
16915 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
16918 The ABI tags are visible in C@t{++} demangled names. For example, a
16919 function that returns a std::string:
16922 std::string function(int);
16926 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
16927 tag, and @value{GDBN} displays the symbol like this:
16930 function[abi:cxx11](int)
16933 You can set a breakpoint on such functions simply as if they had no
16937 (gdb) b function(int)
16938 Breakpoint 2 at 0x40060d: file main.cc, line 10.
16939 (gdb) info breakpoints
16940 Num Type Disp Enb Address What
16941 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
16945 On the rare occasion you need to disambiguate between different ABI
16946 tags, you can do so by simply including the ABI tag in the function
16950 (@value{GDBP}) b ambiguous[abi:other_tag](int)
16954 @node Decimal Floating Point
16955 @subsubsection Decimal Floating Point format
16956 @cindex decimal floating point format
16958 @value{GDBN} can examine, set and perform computations with numbers in
16959 decimal floating point format, which in the C language correspond to the
16960 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
16961 specified by the extension to support decimal floating-point arithmetic.
16963 There are two encodings in use, depending on the architecture: BID (Binary
16964 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
16965 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
16968 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
16969 to manipulate decimal floating point numbers, it is not possible to convert
16970 (using a cast, for example) integers wider than 32-bit to decimal float.
16972 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
16973 point computations, error checking in decimal float operations ignores
16974 underflow, overflow and divide by zero exceptions.
16976 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
16977 to inspect @code{_Decimal128} values stored in floating point registers.
16978 See @ref{PowerPC,,PowerPC} for more details.
16984 @value{GDBN} can be used to debug programs written in D and compiled with
16985 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
16986 specific feature --- dynamic arrays.
16991 @cindex Go (programming language)
16992 @value{GDBN} can be used to debug programs written in Go and compiled with
16993 @file{gccgo} or @file{6g} compilers.
16995 Here is a summary of the Go-specific features and restrictions:
16998 @cindex current Go package
16999 @item The current Go package
17000 The name of the current package does not need to be specified when
17001 specifying global variables and functions.
17003 For example, given the program:
17007 var myglob = "Shall we?"
17013 When stopped inside @code{main} either of these work:
17017 (gdb) p main.myglob
17020 @cindex builtin Go types
17021 @item Builtin Go types
17022 The @code{string} type is recognized by @value{GDBN} and is printed
17025 @cindex builtin Go functions
17026 @item Builtin Go functions
17027 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
17028 function and handles it internally.
17030 @cindex restrictions on Go expressions
17031 @item Restrictions on Go expressions
17032 All Go operators are supported except @code{&^}.
17033 The Go @code{_} ``blank identifier'' is not supported.
17034 Automatic dereferencing of pointers is not supported.
17038 @subsection Objective-C
17040 @cindex Objective-C
17041 This section provides information about some commands and command
17042 options that are useful for debugging Objective-C code. See also
17043 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
17044 few more commands specific to Objective-C support.
17047 * Method Names in Commands::
17048 * The Print Command with Objective-C::
17051 @node Method Names in Commands
17052 @subsubsection Method Names in Commands
17054 The following commands have been extended to accept Objective-C method
17055 names as line specifications:
17057 @kindex clear@r{, and Objective-C}
17058 @kindex break@r{, and Objective-C}
17059 @kindex info line@r{, and Objective-C}
17060 @kindex jump@r{, and Objective-C}
17061 @kindex list@r{, and Objective-C}
17065 @item @code{info line}
17070 A fully qualified Objective-C method name is specified as
17073 -[@var{Class} @var{methodName}]
17076 where the minus sign is used to indicate an instance method and a
17077 plus sign (not shown) is used to indicate a class method. The class
17078 name @var{Class} and method name @var{methodName} are enclosed in
17079 brackets, similar to the way messages are specified in Objective-C
17080 source code. For example, to set a breakpoint at the @code{create}
17081 instance method of class @code{Fruit} in the program currently being
17085 break -[Fruit create]
17088 To list ten program lines around the @code{initialize} class method,
17092 list +[NSText initialize]
17095 In the current version of @value{GDBN}, the plus or minus sign is
17096 required. In future versions of @value{GDBN}, the plus or minus
17097 sign will be optional, but you can use it to narrow the search. It
17098 is also possible to specify just a method name:
17104 You must specify the complete method name, including any colons. If
17105 your program's source files contain more than one @code{create} method,
17106 you'll be presented with a numbered list of classes that implement that
17107 method. Indicate your choice by number, or type @samp{0} to exit if
17110 As another example, to clear a breakpoint established at the
17111 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
17114 clear -[NSWindow makeKeyAndOrderFront:]
17117 @node The Print Command with Objective-C
17118 @subsubsection The Print Command With Objective-C
17119 @cindex Objective-C, print objects
17120 @kindex print-object
17121 @kindex po @r{(@code{print-object})}
17123 The print command has also been extended to accept methods. For example:
17126 print -[@var{object} hash]
17129 @cindex print an Objective-C object description
17130 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
17132 will tell @value{GDBN} to send the @code{hash} message to @var{object}
17133 and print the result. Also, an additional command has been added,
17134 @code{print-object} or @code{po} for short, which is meant to print
17135 the description of an object. However, this command may only work
17136 with certain Objective-C libraries that have a particular hook
17137 function, @code{_NSPrintForDebugger}, defined.
17140 @subsection OpenCL C
17143 This section provides information about @value{GDBN}s OpenCL C support.
17146 * OpenCL C Datatypes::
17147 * OpenCL C Expressions::
17148 * OpenCL C Operators::
17151 @node OpenCL C Datatypes
17152 @subsubsection OpenCL C Datatypes
17154 @cindex OpenCL C Datatypes
17155 @value{GDBN} supports the builtin scalar and vector datatypes specified
17156 by OpenCL 1.1. In addition the half- and double-precision floating point
17157 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
17158 extensions are also known to @value{GDBN}.
17160 @node OpenCL C Expressions
17161 @subsubsection OpenCL C Expressions
17163 @cindex OpenCL C Expressions
17164 @value{GDBN} supports accesses to vector components including the access as
17165 lvalue where possible. Since OpenCL C is based on C99 most C expressions
17166 supported by @value{GDBN} can be used as well.
17168 @node OpenCL C Operators
17169 @subsubsection OpenCL C Operators
17171 @cindex OpenCL C Operators
17172 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
17176 @subsection Fortran
17177 @cindex Fortran-specific support in @value{GDBN}
17179 @value{GDBN} can be used to debug programs written in Fortran. Note, that not
17180 all Fortran language features are available yet.
17182 @cindex trailing underscore, in Fortran symbols
17183 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
17184 among them) append an underscore to the names of variables and
17185 functions. When you debug programs compiled by those compilers, you
17186 will need to refer to variables and functions with a trailing
17189 @cindex Fortran Defaults
17190 Fortran symbols are usually case-insensitive, so @value{GDBN} by
17191 default uses case-insensitive matching for Fortran symbols. You can
17192 change that with the @samp{set case-insensitive} command, see
17193 @ref{Symbols}, for the details.
17196 * Fortran Types:: Fortran builtin types
17197 * Fortran Operators:: Fortran operators and expressions
17198 * Fortran Intrinsics:: Fortran intrinsic functions
17199 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
17202 @node Fortran Types
17203 @subsubsection Fortran Types
17205 @cindex Fortran Types
17207 In Fortran the primitive data-types have an associated @code{KIND} type
17208 parameter, written as @samp{@var{type}*@var{kindparam}},
17209 @samp{@var{type}*@var{kindparam}}, or in the @value{GDBN}-only dialect
17210 @samp{@var{type}_@var{kindparam}}. A concrete example would be
17211 @samp{@code{Real*4}}, @samp{@code{Real(kind=4)}}, and @samp{@code{Real_4}}.
17212 The kind of a type can be retrieved by using the intrinsic function
17213 @code{KIND}, see @ref{Fortran Intrinsics}.
17215 Generally, the actual implementation of the @code{KIND} type parameter is
17216 compiler specific. In @value{GDBN} the kind parameter is implemented in
17217 accordance with its use in the @sc{gnu} @command{gfortran} compiler. Here, the
17218 kind parameter for a given @var{type} specifies its size in memory --- a
17219 Fortran @code{Integer*4} or @code{Integer(kind=4)} would be an integer type
17220 occupying 4 bytes of memory. An exception to this rule is the @code{Complex}
17221 type for which the kind of the type does not specify its entire size, but
17222 the size of each of the two @code{Real}'s it is composed of. A
17223 @code{Complex*4} would thus consist of two @code{Real*4}s and occupy 8 bytes
17226 For every type there is also a default kind associated with it, e.g.@
17227 @code{Integer} in @value{GDBN} will internally be an @code{Integer*4} (see the
17228 table below for default types). The default types are the same as in @sc{gnu}
17229 compilers but note, that the @sc{gnu} default types can actually be changed by
17230 compiler flags such as @option{-fdefault-integer-8} and
17231 @option{-fdefault-real-8}.
17233 Not every kind parameter is valid for every type and in @value{GDBN} the
17234 following type kinds are available.
17238 @code{Integer*1}, @code{Integer*2}, @code{Integer*4}, @code{Integer*8}, and
17239 @code{Integer} = @code{Integer*4}.
17242 @code{Logical*1}, @code{Logical*2}, @code{Logical*4}, @code{Logical*8}, and
17243 @code{Logical} = @code{Logical*4}.
17246 @code{Real*4}, @code{Real*8}, @code{Real*16}, and @code{Real} = @code{Real*4}.
17249 @code{Complex*4}, @code{Complex*8}, @code{Complex*16}, and @code{Complex} =
17254 @node Fortran Operators
17255 @subsubsection Fortran Operators and Expressions
17257 @cindex Fortran operators and expressions
17259 Operators must be defined on values of specific types. For instance,
17260 @code{+} is defined on numbers, but not on characters or other non-
17261 arithmetic types. Operators are often defined on groups of types.
17265 The exponentiation operator. It raises the first operand to the power
17269 The range operator. Normally used in the form of array(low:high) to
17270 represent a section of array.
17273 The access component operator. Normally used to access elements in derived
17274 types. Also suitable for unions. As unions aren't part of regular Fortran,
17275 this can only happen when accessing a register that uses a gdbarch-defined
17278 The scope operator. Normally used to access variables in modules or
17279 to set breakpoints on subroutines nested in modules or in other
17280 subroutines (internal subroutines).
17283 @node Fortran Intrinsics
17284 @subsubsection Fortran Intrinsics
17286 @cindex Fortran Intrinsics
17288 Fortran provides a large set of intrinsic procedures. @value{GDBN} implements
17289 an incomplete subset of those procedures and their overloads. Some of these
17290 procedures take an optional @code{KIND} parameter, see @ref{Fortran Types}.
17294 Computes the absolute value of its argument @var{a}. Currently not supported
17295 for @code{Complex} arguments.
17297 @item ALLOCATE(@var{array})
17298 Returns whether @var{array} is allocated or not.
17300 @item ASSOCIATED(@var{pointer} [, @var{target}])
17301 Returns the association status of the pointer @var{pointer} or, if @var{target}
17302 is present, whether @var{pointer} is associated with the target @var{target}.
17304 @item CEILING(@var{a} [, @var{kind}])
17305 Computes the least integer greater than or equal to @var{a}. The optional
17306 parameter @var{kind} specifies the kind of the return type
17307 @code{Integer(@var{kind})}.
17309 @item CMPLX(@var{x} [, @var{y} [, @var{kind}]])
17310 Returns a complex number where @var{x} is converted to the real component. If
17311 @var{y} is present it is converted to the imaginary component. If @var{y} is
17312 not present then the imaginary component is set to @code{0.0} except if @var{x}
17313 itself is of @code{Complex} type. The optional parameter @var{kind} specifies
17314 the kind of the return type @code{Complex(@var{kind})}.
17316 @item FLOOR(@var{a} [, @var{kind}])
17317 Computes the greatest integer less than or equal to @var{a}. The optional
17318 parameter @var{kind} specifies the kind of the return type
17319 @code{Integer(@var{kind})}.
17321 @item KIND(@var{a})
17322 Returns the kind value of the argument @var{a}, see @ref{Fortran Types}.
17324 @item LBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17325 Returns the lower bounds of an @var{array}, or a single lower bound along the
17326 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17327 the kind of the return type @code{Integer(@var{kind})}.
17330 Returns the address of @var{x} as an @code{Integer}.
17332 @item MOD(@var{a}, @var{p})
17333 Computes the remainder of the division of @var{a} by @var{p}.
17335 @item MODULO(@var{a}, @var{p})
17336 Computes the @var{a} modulo @var{p}.
17338 @item RANK(@var{a})
17339 Returns the rank of a scalar or array (scalars have rank @code{0}).
17341 @item SHAPE(@var{a})
17342 Returns the shape of a scalar or array (scalars have shape @samp{()}).
17344 @item SIZE(@var{array}[, @var{dim} [, @var{kind}]])
17345 Returns the extent of @var{array} along a specified dimension @var{dim}, or the
17346 total number of elements in @var{array} if @var{dim} is absent. The optional
17347 parameter @var{kind} specifies the kind of the return type
17348 @code{Integer(@var{kind})}.
17350 @item UBOUND(@var{array} [, @var{dim} [, @var{kind}]])
17351 Returns the upper bounds of an @var{array}, or a single upper bound along the
17352 @var{dim} dimension if present. The optional parameter @var{kind} specifies
17353 the kind of the return type @code{Integer(@var{kind})}.
17357 @node Special Fortran Commands
17358 @subsubsection Special Fortran Commands
17360 @cindex Special Fortran commands
17362 @value{GDBN} has some commands to support Fortran-specific features,
17363 such as displaying common blocks.
17366 @cindex @code{COMMON} blocks, Fortran
17367 @kindex info common
17368 @item info common @r{[}@var{common-name}@r{]}
17369 This command prints the values contained in the Fortran @code{COMMON}
17370 block whose name is @var{common-name}. With no argument, the names of
17371 all @code{COMMON} blocks visible at the current program location are
17373 @cindex arrays slices (Fortran)
17374 @kindex set fortran repack-array-slices
17375 @kindex show fortran repack-array-slices
17376 @item set fortran repack-array-slices [on|off]
17377 @item show fortran repack-array-slices
17378 When taking a slice from an array, a Fortran compiler can choose to
17379 either produce an array descriptor that describes the slice in place,
17380 or it may repack the slice, copying the elements of the slice into a
17381 new region of memory.
17383 When this setting is on, then @value{GDBN} will also repack array
17384 slices in some situations. When this setting is off, then
17385 @value{GDBN} will create array descriptors for slices that reference
17386 the original data in place.
17388 @value{GDBN} will never repack an array slice if the data for the
17389 slice is contiguous within the original array.
17391 @value{GDBN} will always repack string slices if the data for the
17392 slice is non-contiguous within the original string as @value{GDBN}
17393 does not support printing non-contiguous strings.
17395 The default for this setting is @code{off}.
17401 @cindex Pascal support in @value{GDBN}, limitations
17402 Debugging Pascal programs which use sets, subranges, file variables, or
17403 nested functions does not currently work. @value{GDBN} does not support
17404 entering expressions, printing values, or similar features using Pascal
17407 The Pascal-specific command @code{set print pascal_static-members}
17408 controls whether static members of Pascal objects are displayed.
17409 @xref{Print Settings, pascal_static-members}.
17414 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
17415 Programming Language}. Type- and value-printing, and expression
17416 parsing, are reasonably complete. However, there are a few
17417 peculiarities and holes to be aware of.
17421 Linespecs (@pxref{Specify Location}) are never relative to the current
17422 crate. Instead, they act as if there were a global namespace of
17423 crates, somewhat similar to the way @code{extern crate} behaves.
17425 That is, if @value{GDBN} is stopped at a breakpoint in a function in
17426 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
17427 to set a breakpoint in a function named @samp{f} in a crate named
17430 As a consequence of this approach, linespecs also cannot refer to
17431 items using @samp{self::} or @samp{super::}.
17434 Because @value{GDBN} implements Rust name-lookup semantics in
17435 expressions, it will sometimes prepend the current crate to a name.
17436 For example, if @value{GDBN} is stopped at a breakpoint in the crate
17437 @samp{K}, then @code{print ::x::y} will try to find the symbol
17440 However, since it is useful to be able to refer to other crates when
17441 debugging, @value{GDBN} provides the @code{extern} extension to
17442 circumvent this. To use the extension, just put @code{extern} before
17443 a path expression to refer to the otherwise unavailable ``global''
17446 In the above example, if you wanted to refer to the symbol @samp{y} in
17447 the crate @samp{x}, you would use @code{print extern x::y}.
17450 The Rust expression evaluator does not support ``statement-like''
17451 expressions such as @code{if} or @code{match}, or lambda expressions.
17454 Tuple expressions are not implemented.
17457 The Rust expression evaluator does not currently implement the
17458 @code{Drop} trait. Objects that may be created by the evaluator will
17459 never be destroyed.
17462 @value{GDBN} does not implement type inference for generics. In order
17463 to call generic functions or otherwise refer to generic items, you
17464 will have to specify the type parameters manually.
17467 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
17468 cases this does not cause any problems. However, in an expression
17469 context, completing a generic function name will give syntactically
17470 invalid results. This happens because Rust requires the @samp{::}
17471 operator between the function name and its generic arguments. For
17472 example, @value{GDBN} might provide a completion like
17473 @code{crate::f<u32>}, where the parser would require
17474 @code{crate::f::<u32>}.
17477 As of this writing, the Rust compiler (version 1.8) has a few holes in
17478 the debugging information it generates. These holes prevent certain
17479 features from being implemented by @value{GDBN}:
17483 Method calls cannot be made via traits.
17486 Operator overloading is not implemented.
17489 When debugging in a monomorphized function, you cannot use the generic
17493 The type @code{Self} is not available.
17496 @code{use} statements are not available, so some names may not be
17497 available in the crate.
17502 @subsection Modula-2
17504 @cindex Modula-2, @value{GDBN} support
17506 The extensions made to @value{GDBN} to support Modula-2 only support
17507 output from the @sc{gnu} Modula-2 compiler (which is currently being
17508 developed). Other Modula-2 compilers are not currently supported, and
17509 attempting to debug executables produced by them is most likely
17510 to give an error as @value{GDBN} reads in the executable's symbol
17513 @cindex expressions in Modula-2
17515 * M2 Operators:: Built-in operators
17516 * Built-In Func/Proc:: Built-in functions and procedures
17517 * M2 Constants:: Modula-2 constants
17518 * M2 Types:: Modula-2 types
17519 * M2 Defaults:: Default settings for Modula-2
17520 * Deviations:: Deviations from standard Modula-2
17521 * M2 Checks:: Modula-2 type and range checks
17522 * M2 Scope:: The scope operators @code{::} and @code{.}
17523 * GDB/M2:: @value{GDBN} and Modula-2
17527 @subsubsection Operators
17528 @cindex Modula-2 operators
17530 Operators must be defined on values of specific types. For instance,
17531 @code{+} is defined on numbers, but not on structures. Operators are
17532 often defined on groups of types. For the purposes of Modula-2, the
17533 following definitions hold:
17538 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
17542 @emph{Character types} consist of @code{CHAR} and its subranges.
17545 @emph{Floating-point types} consist of @code{REAL}.
17548 @emph{Pointer types} consist of anything declared as @code{POINTER TO
17552 @emph{Scalar types} consist of all of the above.
17555 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
17558 @emph{Boolean types} consist of @code{BOOLEAN}.
17562 The following operators are supported, and appear in order of
17563 increasing precedence:
17567 Function argument or array index separator.
17570 Assignment. The value of @var{var} @code{:=} @var{value} is
17574 Less than, greater than on integral, floating-point, or enumerated
17578 Less than or equal to, greater than or equal to
17579 on integral, floating-point and enumerated types, or set inclusion on
17580 set types. Same precedence as @code{<}.
17582 @item =@r{, }<>@r{, }#
17583 Equality and two ways of expressing inequality, valid on scalar types.
17584 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
17585 available for inequality, since @code{#} conflicts with the script
17589 Set membership. Defined on set types and the types of their members.
17590 Same precedence as @code{<}.
17593 Boolean disjunction. Defined on boolean types.
17596 Boolean conjunction. Defined on boolean types.
17599 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
17602 Addition and subtraction on integral and floating-point types, or union
17603 and difference on set types.
17606 Multiplication on integral and floating-point types, or set intersection
17610 Division on floating-point types, or symmetric set difference on set
17611 types. Same precedence as @code{*}.
17614 Integer division and remainder. Defined on integral types. Same
17615 precedence as @code{*}.
17618 Negative. Defined on @code{INTEGER} and @code{REAL} data.
17621 Pointer dereferencing. Defined on pointer types.
17624 Boolean negation. Defined on boolean types. Same precedence as
17628 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
17629 precedence as @code{^}.
17632 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
17635 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
17639 @value{GDBN} and Modula-2 scope operators.
17643 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
17644 treats the use of the operator @code{IN}, or the use of operators
17645 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
17646 @code{<=}, and @code{>=} on sets as an error.
17650 @node Built-In Func/Proc
17651 @subsubsection Built-in Functions and Procedures
17652 @cindex Modula-2 built-ins
17654 Modula-2 also makes available several built-in procedures and functions.
17655 In describing these, the following metavariables are used:
17660 represents an @code{ARRAY} variable.
17663 represents a @code{CHAR} constant or variable.
17666 represents a variable or constant of integral type.
17669 represents an identifier that belongs to a set. Generally used in the
17670 same function with the metavariable @var{s}. The type of @var{s} should
17671 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
17674 represents a variable or constant of integral or floating-point type.
17677 represents a variable or constant of floating-point type.
17683 represents a variable.
17686 represents a variable or constant of one of many types. See the
17687 explanation of the function for details.
17690 All Modula-2 built-in procedures also return a result, described below.
17694 Returns the absolute value of @var{n}.
17697 If @var{c} is a lower case letter, it returns its upper case
17698 equivalent, otherwise it returns its argument.
17701 Returns the character whose ordinal value is @var{i}.
17704 Decrements the value in the variable @var{v} by one. Returns the new value.
17706 @item DEC(@var{v},@var{i})
17707 Decrements the value in the variable @var{v} by @var{i}. Returns the
17710 @item EXCL(@var{m},@var{s})
17711 Removes the element @var{m} from the set @var{s}. Returns the new
17714 @item FLOAT(@var{i})
17715 Returns the floating point equivalent of the integer @var{i}.
17717 @item HIGH(@var{a})
17718 Returns the index of the last member of @var{a}.
17721 Increments the value in the variable @var{v} by one. Returns the new value.
17723 @item INC(@var{v},@var{i})
17724 Increments the value in the variable @var{v} by @var{i}. Returns the
17727 @item INCL(@var{m},@var{s})
17728 Adds the element @var{m} to the set @var{s} if it is not already
17729 there. Returns the new set.
17732 Returns the maximum value of the type @var{t}.
17735 Returns the minimum value of the type @var{t}.
17738 Returns boolean TRUE if @var{i} is an odd number.
17741 Returns the ordinal value of its argument. For example, the ordinal
17742 value of a character is its @sc{ascii} value (on machines supporting
17743 the @sc{ascii} character set). The argument @var{x} must be of an
17744 ordered type, which include integral, character and enumerated types.
17746 @item SIZE(@var{x})
17747 Returns the size of its argument. The argument @var{x} can be a
17748 variable or a type.
17750 @item TRUNC(@var{r})
17751 Returns the integral part of @var{r}.
17753 @item TSIZE(@var{x})
17754 Returns the size of its argument. The argument @var{x} can be a
17755 variable or a type.
17757 @item VAL(@var{t},@var{i})
17758 Returns the member of the type @var{t} whose ordinal value is @var{i}.
17762 @emph{Warning:} Sets and their operations are not yet supported, so
17763 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
17767 @cindex Modula-2 constants
17769 @subsubsection Constants
17771 @value{GDBN} allows you to express the constants of Modula-2 in the following
17777 Integer constants are simply a sequence of digits. When used in an
17778 expression, a constant is interpreted to be type-compatible with the
17779 rest of the expression. Hexadecimal integers are specified by a
17780 trailing @samp{H}, and octal integers by a trailing @samp{B}.
17783 Floating point constants appear as a sequence of digits, followed by a
17784 decimal point and another sequence of digits. An optional exponent can
17785 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
17786 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
17787 digits of the floating point constant must be valid decimal (base 10)
17791 Character constants consist of a single character enclosed by a pair of
17792 like quotes, either single (@code{'}) or double (@code{"}). They may
17793 also be expressed by their ordinal value (their @sc{ascii} value, usually)
17794 followed by a @samp{C}.
17797 String constants consist of a sequence of characters enclosed by a
17798 pair of like quotes, either single (@code{'}) or double (@code{"}).
17799 Escape sequences in the style of C are also allowed. @xref{C
17800 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
17804 Enumerated constants consist of an enumerated identifier.
17807 Boolean constants consist of the identifiers @code{TRUE} and
17811 Pointer constants consist of integral values only.
17814 Set constants are not yet supported.
17818 @subsubsection Modula-2 Types
17819 @cindex Modula-2 types
17821 Currently @value{GDBN} can print the following data types in Modula-2
17822 syntax: array types, record types, set types, pointer types, procedure
17823 types, enumerated types, subrange types and base types. You can also
17824 print the contents of variables declared using these type.
17825 This section gives a number of simple source code examples together with
17826 sample @value{GDBN} sessions.
17828 The first example contains the following section of code:
17837 and you can request @value{GDBN} to interrogate the type and value of
17838 @code{r} and @code{s}.
17841 (@value{GDBP}) print s
17843 (@value{GDBP}) ptype s
17845 (@value{GDBP}) print r
17847 (@value{GDBP}) ptype r
17852 Likewise if your source code declares @code{s} as:
17856 s: SET ['A'..'Z'] ;
17860 then you may query the type of @code{s} by:
17863 (@value{GDBP}) ptype s
17864 type = SET ['A'..'Z']
17868 Note that at present you cannot interactively manipulate set
17869 expressions using the debugger.
17871 The following example shows how you might declare an array in Modula-2
17872 and how you can interact with @value{GDBN} to print its type and contents:
17876 s: ARRAY [-10..10] OF CHAR ;
17880 (@value{GDBP}) ptype s
17881 ARRAY [-10..10] OF CHAR
17884 Note that the array handling is not yet complete and although the type
17885 is printed correctly, expression handling still assumes that all
17886 arrays have a lower bound of zero and not @code{-10} as in the example
17889 Here are some more type related Modula-2 examples:
17893 colour = (blue, red, yellow, green) ;
17894 t = [blue..yellow] ;
17902 The @value{GDBN} interaction shows how you can query the data type
17903 and value of a variable.
17906 (@value{GDBP}) print s
17908 (@value{GDBP}) ptype t
17909 type = [blue..yellow]
17913 In this example a Modula-2 array is declared and its contents
17914 displayed. Observe that the contents are written in the same way as
17915 their @code{C} counterparts.
17919 s: ARRAY [1..5] OF CARDINAL ;
17925 (@value{GDBP}) print s
17926 $1 = @{1, 0, 0, 0, 0@}
17927 (@value{GDBP}) ptype s
17928 type = ARRAY [1..5] OF CARDINAL
17931 The Modula-2 language interface to @value{GDBN} also understands
17932 pointer types as shown in this example:
17936 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
17943 and you can request that @value{GDBN} describes the type of @code{s}.
17946 (@value{GDBP}) ptype s
17947 type = POINTER TO ARRAY [1..5] OF CARDINAL
17950 @value{GDBN} handles compound types as we can see in this example.
17951 Here we combine array types, record types, pointer types and subrange
17962 myarray = ARRAY myrange OF CARDINAL ;
17963 myrange = [-2..2] ;
17965 s: POINTER TO ARRAY myrange OF foo ;
17969 and you can ask @value{GDBN} to describe the type of @code{s} as shown
17973 (@value{GDBP}) ptype s
17974 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
17977 f3 : ARRAY [-2..2] OF CARDINAL;
17982 @subsubsection Modula-2 Defaults
17983 @cindex Modula-2 defaults
17985 If type and range checking are set automatically by @value{GDBN}, they
17986 both default to @code{on} whenever the working language changes to
17987 Modula-2. This happens regardless of whether you or @value{GDBN}
17988 selected the working language.
17990 If you allow @value{GDBN} to set the language automatically, then entering
17991 code compiled from a file whose name ends with @file{.mod} sets the
17992 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
17993 Infer the Source Language}, for further details.
17996 @subsubsection Deviations from Standard Modula-2
17997 @cindex Modula-2, deviations from
17999 A few changes have been made to make Modula-2 programs easier to debug.
18000 This is done primarily via loosening its type strictness:
18004 Unlike in standard Modula-2, pointer constants can be formed by
18005 integers. This allows you to modify pointer variables during
18006 debugging. (In standard Modula-2, the actual address contained in a
18007 pointer variable is hidden from you; it can only be modified
18008 through direct assignment to another pointer variable or expression that
18009 returned a pointer.)
18012 C escape sequences can be used in strings and characters to represent
18013 non-printable characters. @value{GDBN} prints out strings with these
18014 escape sequences embedded. Single non-printable characters are
18015 printed using the @samp{CHR(@var{nnn})} format.
18018 The assignment operator (@code{:=}) returns the value of its right-hand
18022 All built-in procedures both modify @emph{and} return their argument.
18026 @subsubsection Modula-2 Type and Range Checks
18027 @cindex Modula-2 checks
18030 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
18033 @c FIXME remove warning when type/range checks added
18035 @value{GDBN} considers two Modula-2 variables type equivalent if:
18039 They are of types that have been declared equivalent via a @code{TYPE
18040 @var{t1} = @var{t2}} statement
18043 They have been declared on the same line. (Note: This is true of the
18044 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
18047 As long as type checking is enabled, any attempt to combine variables
18048 whose types are not equivalent is an error.
18050 Range checking is done on all mathematical operations, assignment, array
18051 index bounds, and all built-in functions and procedures.
18054 @subsubsection The Scope Operators @code{::} and @code{.}
18056 @cindex @code{.}, Modula-2 scope operator
18057 @cindex colon, doubled as scope operator
18059 @vindex colon-colon@r{, in Modula-2}
18060 @c Info cannot handle :: but TeX can.
18063 @vindex ::@r{, in Modula-2}
18066 There are a few subtle differences between the Modula-2 scope operator
18067 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
18072 @var{module} . @var{id}
18073 @var{scope} :: @var{id}
18077 where @var{scope} is the name of a module or a procedure,
18078 @var{module} the name of a module, and @var{id} is any declared
18079 identifier within your program, except another module.
18081 Using the @code{::} operator makes @value{GDBN} search the scope
18082 specified by @var{scope} for the identifier @var{id}. If it is not
18083 found in the specified scope, then @value{GDBN} searches all scopes
18084 enclosing the one specified by @var{scope}.
18086 Using the @code{.} operator makes @value{GDBN} search the current scope for
18087 the identifier specified by @var{id} that was imported from the
18088 definition module specified by @var{module}. With this operator, it is
18089 an error if the identifier @var{id} was not imported from definition
18090 module @var{module}, or if @var{id} is not an identifier in
18094 @subsubsection @value{GDBN} and Modula-2
18096 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
18097 Five subcommands of @code{set print} and @code{show print} apply
18098 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
18099 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
18100 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
18101 analogue in Modula-2.
18103 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
18104 with any language, is not useful with Modula-2. Its
18105 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
18106 created in Modula-2 as they can in C or C@t{++}. However, because an
18107 address can be specified by an integral constant, the construct
18108 @samp{@{@var{type}@}@var{adrexp}} is still useful.
18110 @cindex @code{#} in Modula-2
18111 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
18112 interpreted as the beginning of a comment. Use @code{<>} instead.
18118 The extensions made to @value{GDBN} for Ada only support
18119 output from the @sc{gnu} Ada (GNAT) compiler.
18120 Other Ada compilers are not currently supported, and
18121 attempting to debug executables produced by them is most likely
18125 @cindex expressions in Ada
18127 * Ada Mode Intro:: General remarks on the Ada syntax
18128 and semantics supported by Ada mode
18130 * Omissions from Ada:: Restrictions on the Ada expression syntax.
18131 * Additions to Ada:: Extensions of the Ada expression syntax.
18132 * Overloading support for Ada:: Support for expressions involving overloaded
18134 * Stopping Before Main Program:: Debugging the program during elaboration.
18135 * Ada Exceptions:: Ada Exceptions
18136 * Ada Tasks:: Listing and setting breakpoints in tasks.
18137 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
18138 * Ravenscar Profile:: Tasking Support when using the Ravenscar
18140 * Ada Source Character Set:: Character set of Ada source files.
18141 * Ada Glitches:: Known peculiarities of Ada mode.
18144 @node Ada Mode Intro
18145 @subsubsection Introduction
18146 @cindex Ada mode, general
18148 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
18149 syntax, with some extensions.
18150 The philosophy behind the design of this subset is
18154 That @value{GDBN} should provide basic literals and access to operations for
18155 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
18156 leaving more sophisticated computations to subprograms written into the
18157 program (which therefore may be called from @value{GDBN}).
18160 That type safety and strict adherence to Ada language restrictions
18161 are not particularly important to the @value{GDBN} user.
18164 That brevity is important to the @value{GDBN} user.
18167 Thus, for brevity, the debugger acts as if all names declared in
18168 user-written packages are directly visible, even if they are not visible
18169 according to Ada rules, thus making it unnecessary to fully qualify most
18170 names with their packages, regardless of context. Where this causes
18171 ambiguity, @value{GDBN} asks the user's intent.
18173 The debugger will start in Ada mode if it detects an Ada main program.
18174 As for other languages, it will enter Ada mode when stopped in a program that
18175 was translated from an Ada source file.
18177 While in Ada mode, you may use `@t{--}' for comments. This is useful
18178 mostly for documenting command files. The standard @value{GDBN} comment
18179 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
18180 middle (to allow based literals).
18182 @node Omissions from Ada
18183 @subsubsection Omissions from Ada
18184 @cindex Ada, omissions from
18186 Here are the notable omissions from the subset:
18190 Only a subset of the attributes are supported:
18194 @t{'First}, @t{'Last}, and @t{'Length}
18195 on array objects (not on types and subtypes).
18198 @t{'Min} and @t{'Max}.
18201 @t{'Pos} and @t{'Val}.
18207 @t{'Range} on array objects (not subtypes), but only as the right
18208 operand of the membership (@code{in}) operator.
18211 @t{'Access}, @t{'Unchecked_Access}, and
18212 @t{'Unrestricted_Access} (a GNAT extension).
18219 The names in @code{Characters.Latin_1} are not available.
18222 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
18223 equality of representations. They will generally work correctly
18224 for strings and arrays whose elements have integer or enumeration types.
18225 They may not work correctly for arrays whose element
18226 types have user-defined equality, for arrays of real values
18227 (in particular, IEEE-conformant floating point, because of negative
18228 zeroes and NaNs), and for arrays whose elements contain unused bits with
18229 indeterminate values.
18232 The other component-by-component array operations (@code{and}, @code{or},
18233 @code{xor}, @code{not}, and relational tests other than equality)
18234 are not implemented.
18237 @cindex array aggregates (Ada)
18238 @cindex record aggregates (Ada)
18239 @cindex aggregates (Ada)
18240 There is limited support for array and record aggregates. They are
18241 permitted only on the right sides of assignments, as in these examples:
18244 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
18245 (@value{GDBP}) set An_Array := (1, others => 0)
18246 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
18247 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
18248 (@value{GDBP}) set A_Record := (1, "Peter", True);
18249 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
18253 discriminant's value by assigning an aggregate has an
18254 undefined effect if that discriminant is used within the record.
18255 However, you can first modify discriminants by directly assigning to
18256 them (which normally would not be allowed in Ada), and then performing an
18257 aggregate assignment. For example, given a variable @code{A_Rec}
18258 declared to have a type such as:
18261 type Rec (Len : Small_Integer := 0) is record
18263 Vals : IntArray (1 .. Len);
18267 you can assign a value with a different size of @code{Vals} with two
18271 (@value{GDBP}) set A_Rec.Len := 4
18272 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
18275 As this example also illustrates, @value{GDBN} is very loose about the usual
18276 rules concerning aggregates. You may leave out some of the
18277 components of an array or record aggregate (such as the @code{Len}
18278 component in the assignment to @code{A_Rec} above); they will retain their
18279 original values upon assignment. You may freely use dynamic values as
18280 indices in component associations. You may even use overlapping or
18281 redundant component associations, although which component values are
18282 assigned in such cases is not defined.
18285 Calls to dispatching subprograms are not implemented.
18288 The overloading algorithm is much more limited (i.e., less selective)
18289 than that of real Ada. It makes only limited use of the context in
18290 which a subexpression appears to resolve its meaning, and it is much
18291 looser in its rules for allowing type matches. As a result, some
18292 function calls will be ambiguous, and the user will be asked to choose
18293 the proper resolution.
18296 The @code{new} operator is not implemented.
18299 Entry calls are not implemented.
18302 Aside from printing, arithmetic operations on the native VAX floating-point
18303 formats are not supported.
18306 It is not possible to slice a packed array.
18309 The names @code{True} and @code{False}, when not part of a qualified name,
18310 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
18312 Should your program
18313 redefine these names in a package or procedure (at best a dubious practice),
18314 you will have to use fully qualified names to access their new definitions.
18317 Based real literals are not implemented.
18320 @node Additions to Ada
18321 @subsubsection Additions to Ada
18322 @cindex Ada, deviations from
18324 As it does for other languages, @value{GDBN} makes certain generic
18325 extensions to Ada (@pxref{Expressions}):
18329 If the expression @var{E} is a variable residing in memory (typically
18330 a local variable or array element) and @var{N} is a positive integer,
18331 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
18332 @var{N}-1 adjacent variables following it in memory as an array. In
18333 Ada, this operator is generally not necessary, since its prime use is
18334 in displaying parts of an array, and slicing will usually do this in
18335 Ada. However, there are occasional uses when debugging programs in
18336 which certain debugging information has been optimized away.
18339 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
18340 appears in function or file @var{B}.'' When @var{B} is a file name,
18341 you must typically surround it in single quotes.
18344 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
18345 @var{type} that appears at address @var{addr}.''
18348 A name starting with @samp{$} is a convenience variable
18349 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
18352 In addition, @value{GDBN} provides a few other shortcuts and outright
18353 additions specific to Ada:
18357 The assignment statement is allowed as an expression, returning
18358 its right-hand operand as its value. Thus, you may enter
18361 (@value{GDBP}) set x := y + 3
18362 (@value{GDBP}) print A(tmp := y + 1)
18366 The semicolon is allowed as an ``operator,'' returning as its value
18367 the value of its right-hand operand.
18368 This allows, for example,
18369 complex conditional breaks:
18372 (@value{GDBP}) break f
18373 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
18377 An extension to based literals can be used to specify the exact byte
18378 contents of a floating-point literal. After the base, you can use
18379 from zero to two @samp{l} characters, followed by an @samp{f}. The
18380 number of @samp{l} characters controls the width of the resulting real
18381 constant: zero means @code{Float} is used, one means
18382 @code{Long_Float}, and two means @code{Long_Long_Float}.
18385 (@value{GDBP}) print 16f#41b80000#
18390 Rather than use catenation and symbolic character names to introduce special
18391 characters into strings, one may instead use a special bracket notation,
18392 which is also used to print strings. A sequence of characters of the form
18393 @samp{["@var{XX}"]} within a string or character literal denotes the
18394 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
18395 sequence of characters @samp{["""]} also denotes a single quotation mark
18396 in strings. For example,
18398 "One line.["0a"]Next line.["0a"]"
18401 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
18405 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
18406 @t{'Max} is optional (and is ignored in any case). For example, it is valid
18410 (@value{GDBP}) print 'max(x, y)
18414 When printing arrays, @value{GDBN} uses positional notation when the
18415 array has a lower bound of 1, and uses a modified named notation otherwise.
18416 For example, a one-dimensional array of three integers with a lower bound
18417 of 3 might print as
18424 That is, in contrast to valid Ada, only the first component has a @code{=>}
18428 You may abbreviate attributes in expressions with any unique,
18429 multi-character subsequence of
18430 their names (an exact match gets preference).
18431 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
18432 in place of @t{a'length}.
18435 @cindex quoting Ada internal identifiers
18436 Since Ada is case-insensitive, the debugger normally maps identifiers you type
18437 to lower case. The GNAT compiler uses upper-case characters for
18438 some of its internal identifiers, which are normally of no interest to users.
18439 For the rare occasions when you actually have to look at them,
18440 enclose them in angle brackets to avoid the lower-case mapping.
18443 (@value{GDBP}) print <JMPBUF_SAVE>[0]
18447 Printing an object of class-wide type or dereferencing an
18448 access-to-class-wide value will display all the components of the object's
18449 specific type (as indicated by its run-time tag). Likewise, component
18450 selection on such a value will operate on the specific type of the
18455 @node Overloading support for Ada
18456 @subsubsection Overloading support for Ada
18457 @cindex overloading, Ada
18459 The debugger supports limited overloading. Given a subprogram call in which
18460 the function symbol has multiple definitions, it will use the number of
18461 actual parameters and some information about their types to attempt to narrow
18462 the set of definitions. It also makes very limited use of context, preferring
18463 procedures to functions in the context of the @code{call} command, and
18464 functions to procedures elsewhere.
18466 If, after narrowing, the set of matching definitions still contains more than
18467 one definition, @value{GDBN} will display a menu to query which one it should
18471 (@value{GDBP}) print f(1)
18472 Multiple matches for f
18474 [1] foo.f (integer) return boolean at foo.adb:23
18475 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
18479 In this case, just select one menu entry either to cancel expression evaluation
18480 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
18481 instance (type the corresponding number and press @key{RET}).
18483 Here are a couple of commands to customize @value{GDBN}'s behavior in this
18488 @kindex set ada print-signatures
18489 @item set ada print-signatures
18490 Control whether parameter types and return types are displayed in overloads
18491 selection menus. It is @code{on} by default.
18492 @xref{Overloading support for Ada}.
18494 @kindex show ada print-signatures
18495 @item show ada print-signatures
18496 Show the current setting for displaying parameter types and return types in
18497 overloads selection menu.
18498 @xref{Overloading support for Ada}.
18502 @node Stopping Before Main Program
18503 @subsubsection Stopping at the Very Beginning
18505 @cindex breakpointing Ada elaboration code
18506 It is sometimes necessary to debug the program during elaboration, and
18507 before reaching the main procedure.
18508 As defined in the Ada Reference
18509 Manual, the elaboration code is invoked from a procedure called
18510 @code{adainit}. To run your program up to the beginning of
18511 elaboration, simply use the following two commands:
18512 @code{tbreak adainit} and @code{run}.
18514 @node Ada Exceptions
18515 @subsubsection Ada Exceptions
18517 A command is provided to list all Ada exceptions:
18520 @kindex info exceptions
18521 @item info exceptions
18522 @itemx info exceptions @var{regexp}
18523 The @code{info exceptions} command allows you to list all Ada exceptions
18524 defined within the program being debugged, as well as their addresses.
18525 With a regular expression, @var{regexp}, as argument, only those exceptions
18526 whose names match @var{regexp} are listed.
18529 Below is a small example, showing how the command can be used, first
18530 without argument, and next with a regular expression passed as an
18534 (@value{GDBP}) info exceptions
18535 All defined Ada exceptions:
18536 constraint_error: 0x613da0
18537 program_error: 0x613d20
18538 storage_error: 0x613ce0
18539 tasking_error: 0x613ca0
18540 const.aint_global_e: 0x613b00
18541 (@value{GDBP}) info exceptions const.aint
18542 All Ada exceptions matching regular expression "const.aint":
18543 constraint_error: 0x613da0
18544 const.aint_global_e: 0x613b00
18547 It is also possible to ask @value{GDBN} to stop your program's execution
18548 when an exception is raised. For more details, see @ref{Set Catchpoints}.
18551 @subsubsection Extensions for Ada Tasks
18552 @cindex Ada, tasking
18554 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
18555 @value{GDBN} provides the following task-related commands:
18560 This command shows a list of current Ada tasks, as in the following example:
18567 (@value{GDBP}) info tasks
18568 ID TID P-ID Pri State Name
18569 1 8088000 0 15 Child Activation Wait main_task
18570 2 80a4000 1 15 Accept Statement b
18571 3 809a800 1 15 Child Activation Wait a
18572 * 4 80ae800 3 15 Runnable c
18577 In this listing, the asterisk before the last task indicates it to be the
18578 task currently being inspected.
18582 Represents @value{GDBN}'s internal task number.
18588 The parent's task ID (@value{GDBN}'s internal task number).
18591 The base priority of the task.
18594 Current state of the task.
18598 The task has been created but has not been activated. It cannot be
18602 The task is not blocked for any reason known to Ada. (It may be waiting
18603 for a mutex, though.) It is conceptually "executing" in normal mode.
18606 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
18607 that were waiting on terminate alternatives have been awakened and have
18608 terminated themselves.
18610 @item Child Activation Wait
18611 The task is waiting for created tasks to complete activation.
18613 @item Accept Statement
18614 The task is waiting on an accept or selective wait statement.
18616 @item Waiting on entry call
18617 The task is waiting on an entry call.
18619 @item Async Select Wait
18620 The task is waiting to start the abortable part of an asynchronous
18624 The task is waiting on a select statement with only a delay
18627 @item Child Termination Wait
18628 The task is sleeping having completed a master within itself, and is
18629 waiting for the tasks dependent on that master to become terminated or
18630 waiting on a terminate Phase.
18632 @item Wait Child in Term Alt
18633 The task is sleeping waiting for tasks on terminate alternatives to
18634 finish terminating.
18636 @item Accepting RV with @var{taskno}
18637 The task is accepting a rendez-vous with the task @var{taskno}.
18641 Name of the task in the program.
18645 @kindex info task @var{taskno}
18646 @item info task @var{taskno}
18647 This command shows detailed informations on the specified task, as in
18648 the following example:
18653 (@value{GDBP}) info tasks
18654 ID TID P-ID Pri State Name
18655 1 8077880 0 15 Child Activation Wait main_task
18656 * 2 807c468 1 15 Runnable task_1
18657 (@value{GDBP}) info task 2
18658 Ada Task: 0x807c468
18662 Parent: 1 ("main_task")
18668 @kindex task@r{ (Ada)}
18669 @cindex current Ada task ID
18670 This command prints the ID and name of the current task.
18676 (@value{GDBP}) info tasks
18677 ID TID P-ID Pri State Name
18678 1 8077870 0 15 Child Activation Wait main_task
18679 * 2 807c458 1 15 Runnable some_task
18680 (@value{GDBP}) task
18681 [Current task is 2 "some_task"]
18684 @item task @var{taskno}
18685 @cindex Ada task switching
18686 This command is like the @code{thread @var{thread-id}}
18687 command (@pxref{Threads}). It switches the context of debugging
18688 from the current task to the given task.
18694 (@value{GDBP}) info tasks
18695 ID TID P-ID Pri State Name
18696 1 8077870 0 15 Child Activation Wait main_task
18697 * 2 807c458 1 15 Runnable some_task
18698 (@value{GDBP}) task 1
18699 [Switching to task 1 "main_task"]
18700 #0 0x8067726 in pthread_cond_wait ()
18702 #0 0x8067726 in pthread_cond_wait ()
18703 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
18704 #2 0x805cb63 in system.task_primitives.operations.sleep ()
18705 #3 0x806153e in system.tasking.stages.activate_tasks ()
18706 #4 0x804aacc in un () at un.adb:5
18709 @item task apply [@var{task-id-list} | all] [@var{flag}]@dots{} @var{command}
18710 The @code{task apply} command is the Ada tasking analogue of
18711 @code{thread apply} (@pxref{Threads}). It allows you to apply the
18712 named @var{command} to one or more tasks. Specify the tasks that you
18713 want affected using a list of task IDs, or specify @code{all} to apply
18716 The @var{flag} arguments control what output to produce and how to
18717 handle errors raised when applying @var{command} to a task.
18718 @var{flag} must start with a @code{-} directly followed by one letter
18719 in @code{qcs}. If several flags are provided, they must be given
18720 individually, such as @code{-c -q}.
18722 By default, @value{GDBN} displays some task information before the
18723 output produced by @var{command}, and an error raised during the
18724 execution of a @var{command} will abort @code{task apply}. The
18725 following flags can be used to fine-tune this behavior:
18729 The flag @code{-c}, which stands for @samp{continue}, causes any
18730 errors in @var{command} to be displayed, and the execution of
18731 @code{task apply} then continues.
18733 The flag @code{-s}, which stands for @samp{silent}, causes any errors
18734 or empty output produced by a @var{command} to be silently ignored.
18735 That is, the execution continues, but the task information and errors
18738 The flag @code{-q} (@samp{quiet}) disables printing the task
18742 Flags @code{-c} and @code{-s} cannot be used together.
18744 @item break @var{location} task @var{taskno}
18745 @itemx break @var{location} task @var{taskno} if @dots{}
18746 @cindex breakpoints and tasks, in Ada
18747 @cindex task breakpoints, in Ada
18748 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
18749 These commands are like the @code{break @dots{} thread @dots{}}
18750 command (@pxref{Thread Stops}). The
18751 @var{location} argument specifies source lines, as described
18752 in @ref{Specify Location}.
18754 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
18755 to specify that you only want @value{GDBN} to stop the program when a
18756 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
18757 numeric task identifiers assigned by @value{GDBN}, shown in the first
18758 column of the @samp{info tasks} display.
18760 If you do not specify @samp{task @var{taskno}} when you set a
18761 breakpoint, the breakpoint applies to @emph{all} tasks of your
18764 You can use the @code{task} qualifier on conditional breakpoints as
18765 well; in this case, place @samp{task @var{taskno}} before the
18766 breakpoint condition (before the @code{if}).
18774 (@value{GDBP}) info tasks
18775 ID TID P-ID Pri State Name
18776 1 140022020 0 15 Child Activation Wait main_task
18777 2 140045060 1 15 Accept/Select Wait t2
18778 3 140044840 1 15 Runnable t1
18779 * 4 140056040 1 15 Runnable t3
18780 (@value{GDBP}) b 15 task 2
18781 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
18782 (@value{GDBP}) cont
18787 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
18789 (@value{GDBP}) info tasks
18790 ID TID P-ID Pri State Name
18791 1 140022020 0 15 Child Activation Wait main_task
18792 * 2 140045060 1 15 Runnable t2
18793 3 140044840 1 15 Runnable t1
18794 4 140056040 1 15 Delay Sleep t3
18798 @node Ada Tasks and Core Files
18799 @subsubsection Tasking Support when Debugging Core Files
18800 @cindex Ada tasking and core file debugging
18802 When inspecting a core file, as opposed to debugging a live program,
18803 tasking support may be limited or even unavailable, depending on
18804 the platform being used.
18805 For instance, on x86-linux, the list of tasks is available, but task
18806 switching is not supported.
18808 On certain platforms, the debugger needs to perform some
18809 memory writes in order to provide Ada tasking support. When inspecting
18810 a core file, this means that the core file must be opened with read-write
18811 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
18812 Under these circumstances, you should make a backup copy of the core
18813 file before inspecting it with @value{GDBN}.
18815 @node Ravenscar Profile
18816 @subsubsection Tasking Support when using the Ravenscar Profile
18817 @cindex Ravenscar Profile
18819 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
18820 specifically designed for systems with safety-critical real-time
18824 @kindex set ravenscar task-switching on
18825 @cindex task switching with program using Ravenscar Profile
18826 @item set ravenscar task-switching on
18827 Allows task switching when debugging a program that uses the Ravenscar
18828 Profile. This is the default.
18830 @kindex set ravenscar task-switching off
18831 @item set ravenscar task-switching off
18832 Turn off task switching when debugging a program that uses the Ravenscar
18833 Profile. This is mostly intended to disable the code that adds support
18834 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
18835 the Ravenscar runtime is preventing @value{GDBN} from working properly.
18836 To be effective, this command should be run before the program is started.
18838 @kindex show ravenscar task-switching
18839 @item show ravenscar task-switching
18840 Show whether it is possible to switch from task to task in a program
18841 using the Ravenscar Profile.
18845 @cindex Ravenscar thread
18846 When Ravenscar task-switching is enabled, Ravenscar tasks are
18847 announced by @value{GDBN} as if they were threads:
18851 [New Ravenscar Thread 0x2b8f0]
18854 Both Ravenscar tasks and the underlying CPU threads will show up in
18855 the output of @code{info threads}:
18860 1 Thread 1 (CPU#0 [running]) simple () at simple.adb:10
18861 2 Thread 2 (CPU#1 [running]) 0x0000000000003d34 in __gnat_initialize_cpu_devices ()
18862 3 Thread 3 (CPU#2 [running]) 0x0000000000003d28 in __gnat_initialize_cpu_devices ()
18863 4 Thread 4 (CPU#3 [halted ]) 0x000000000000c6ec in system.task_primitives.operations.idle ()
18864 * 5 Ravenscar Thread 0x2b8f0 simple () at simple.adb:10
18865 6 Ravenscar Thread 0x2f150 0x000000000000c6ec in system.task_primitives.operations.idle ()
18868 One known limitation of the Ravenscar support in @value{GDBN} is that
18869 it isn't currently possible to single-step through the runtime
18870 initialization sequence. If you need to debug this code, you should
18871 use @code{set ravenscar task-switching off}.
18873 @node Ada Source Character Set
18874 @subsubsection Ada Source Character Set
18875 @cindex Ada, source character set
18877 The GNAT compiler supports a number of character sets for source
18878 files. @xref{Character Set Control, , Character Set Control,
18879 gnat_ugn}. @value{GDBN} includes support for this as well.
18882 @item set ada source-charset @var{charset}
18883 @kindex set ada source-charset
18884 Set the source character set for Ada. The character set must be
18885 supported by GNAT. Because this setting affects the decoding of
18886 symbols coming from the debug information in your program, the setting
18887 should be set as early as possible. The default is @code{ISO-8859-1},
18888 because that is also GNAT's default.
18890 @item show ada source-charset
18891 @kindex show ada source-charset
18892 Show the current source character set for Ada.
18896 @subsubsection Known Peculiarities of Ada Mode
18897 @cindex Ada, problems
18899 Besides the omissions listed previously (@pxref{Omissions from Ada}),
18900 we know of several problems with and limitations of Ada mode in
18902 some of which will be fixed with planned future releases of the debugger
18903 and the GNU Ada compiler.
18907 Static constants that the compiler chooses not to materialize as objects in
18908 storage are invisible to the debugger.
18911 Named parameter associations in function argument lists are ignored (the
18912 argument lists are treated as positional).
18915 Many useful library packages are currently invisible to the debugger.
18918 Fixed-point arithmetic, conversions, input, and output is carried out using
18919 floating-point arithmetic, and may give results that only approximate those on
18923 The GNAT compiler never generates the prefix @code{Standard} for any of
18924 the standard symbols defined by the Ada language. @value{GDBN} knows about
18925 this: it will strip the prefix from names when you use it, and will never
18926 look for a name you have so qualified among local symbols, nor match against
18927 symbols in other packages or subprograms. If you have
18928 defined entities anywhere in your program other than parameters and
18929 local variables whose simple names match names in @code{Standard},
18930 GNAT's lack of qualification here can cause confusion. When this happens,
18931 you can usually resolve the confusion
18932 by qualifying the problematic names with package
18933 @code{Standard} explicitly.
18936 Older versions of the compiler sometimes generate erroneous debugging
18937 information, resulting in the debugger incorrectly printing the value
18938 of affected entities. In some cases, the debugger is able to work
18939 around an issue automatically. In other cases, the debugger is able
18940 to work around the issue, but the work-around has to be specifically
18943 @kindex set ada trust-PAD-over-XVS
18944 @kindex show ada trust-PAD-over-XVS
18947 @item set ada trust-PAD-over-XVS on
18948 Configure GDB to strictly follow the GNAT encoding when computing the
18949 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
18950 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
18951 a complete description of the encoding used by the GNAT compiler).
18952 This is the default.
18954 @item set ada trust-PAD-over-XVS off
18955 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
18956 sometimes prints the wrong value for certain entities, changing @code{ada
18957 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
18958 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
18959 @code{off}, but this incurs a slight performance penalty, so it is
18960 recommended to leave this setting to @code{on} unless necessary.
18964 @cindex GNAT descriptive types
18965 @cindex GNAT encoding
18966 Internally, the debugger also relies on the compiler following a number
18967 of conventions known as the @samp{GNAT Encoding}, all documented in
18968 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
18969 how the debugging information should be generated for certain types.
18970 In particular, this convention makes use of @dfn{descriptive types},
18971 which are artificial types generated purely to help the debugger.
18973 These encodings were defined at a time when the debugging information
18974 format used was not powerful enough to describe some of the more complex
18975 types available in Ada. Since DWARF allows us to express nearly all
18976 Ada features, the long-term goal is to slowly replace these descriptive
18977 types by their pure DWARF equivalent. To facilitate that transition,
18978 a new maintenance option is available to force the debugger to ignore
18979 those descriptive types. It allows the user to quickly evaluate how
18980 well @value{GDBN} works without them.
18984 @kindex maint ada set ignore-descriptive-types
18985 @item maintenance ada set ignore-descriptive-types [on|off]
18986 Control whether the debugger should ignore descriptive types.
18987 The default is not to ignore descriptives types (@code{off}).
18989 @kindex maint ada show ignore-descriptive-types
18990 @item maintenance ada show ignore-descriptive-types
18991 Show if descriptive types are ignored by @value{GDBN}.
18995 @node Unsupported Languages
18996 @section Unsupported Languages
18998 @cindex unsupported languages
18999 @cindex minimal language
19000 In addition to the other fully-supported programming languages,
19001 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
19002 It does not represent a real programming language, but provides a set
19003 of capabilities close to what the C or assembly languages provide.
19004 This should allow most simple operations to be performed while debugging
19005 an application that uses a language currently not supported by @value{GDBN}.
19007 If the language is set to @code{auto}, @value{GDBN} will automatically
19008 select this language if the current frame corresponds to an unsupported
19012 @chapter Examining the Symbol Table
19014 The commands described in this chapter allow you to inquire about the
19015 symbols (names of variables, functions and types) defined in your
19016 program. This information is inherent in the text of your program and
19017 does not change as your program executes. @value{GDBN} finds it in your
19018 program's symbol table, in the file indicated when you started @value{GDBN}
19019 (@pxref{File Options, ,Choosing Files}), or by one of the
19020 file-management commands (@pxref{Files, ,Commands to Specify Files}).
19022 @cindex symbol names
19023 @cindex names of symbols
19024 @cindex quoting names
19025 @anchor{quoting names}
19026 Occasionally, you may need to refer to symbols that contain unusual
19027 characters, which @value{GDBN} ordinarily treats as word delimiters. The
19028 most frequent case is in referring to static variables in other
19029 source files (@pxref{Variables,,Program Variables}). File names
19030 are recorded in object files as debugging symbols, but @value{GDBN} would
19031 ordinarily parse a typical file name, like @file{foo.c}, as the three words
19032 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
19033 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
19040 looks up the value of @code{x} in the scope of the file @file{foo.c}.
19043 @cindex case-insensitive symbol names
19044 @cindex case sensitivity in symbol names
19045 @kindex set case-sensitive
19046 @item set case-sensitive on
19047 @itemx set case-sensitive off
19048 @itemx set case-sensitive auto
19049 Normally, when @value{GDBN} looks up symbols, it matches their names
19050 with case sensitivity determined by the current source language.
19051 Occasionally, you may wish to control that. The command @code{set
19052 case-sensitive} lets you do that by specifying @code{on} for
19053 case-sensitive matches or @code{off} for case-insensitive ones. If
19054 you specify @code{auto}, case sensitivity is reset to the default
19055 suitable for the source language. The default is case-sensitive
19056 matches for all languages except for Fortran, for which the default is
19057 case-insensitive matches.
19059 @kindex show case-sensitive
19060 @item show case-sensitive
19061 This command shows the current setting of case sensitivity for symbols
19064 @kindex set print type methods
19065 @item set print type methods
19066 @itemx set print type methods on
19067 @itemx set print type methods off
19068 Normally, when @value{GDBN} prints a class, it displays any methods
19069 declared in that class. You can control this behavior either by
19070 passing the appropriate flag to @code{ptype}, or using @command{set
19071 print type methods}. Specifying @code{on} will cause @value{GDBN} to
19072 display the methods; this is the default. Specifying @code{off} will
19073 cause @value{GDBN} to omit the methods.
19075 @kindex show print type methods
19076 @item show print type methods
19077 This command shows the current setting of method display when printing
19080 @kindex set print type nested-type-limit
19081 @item set print type nested-type-limit @var{limit}
19082 @itemx set print type nested-type-limit unlimited
19083 Set the limit of displayed nested types that the type printer will
19084 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
19085 nested definitions. By default, the type printer will not show any nested
19086 types defined in classes.
19088 @kindex show print type nested-type-limit
19089 @item show print type nested-type-limit
19090 This command shows the current display limit of nested types when
19093 @kindex set print type typedefs
19094 @item set print type typedefs
19095 @itemx set print type typedefs on
19096 @itemx set print type typedefs off
19098 Normally, when @value{GDBN} prints a class, it displays any typedefs
19099 defined in that class. You can control this behavior either by
19100 passing the appropriate flag to @code{ptype}, or using @command{set
19101 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
19102 display the typedef definitions; this is the default. Specifying
19103 @code{off} will cause @value{GDBN} to omit the typedef definitions.
19104 Note that this controls whether the typedef definition itself is
19105 printed, not whether typedef names are substituted when printing other
19108 @kindex show print type typedefs
19109 @item show print type typedefs
19110 This command shows the current setting of typedef display when
19113 @kindex set print type hex
19114 @item set print type hex
19115 @itemx set print type hex on
19116 @itemx set print type hex off
19118 When @value{GDBN} prints sizes and offsets of struct members, it can use
19119 either the decimal or hexadecimal notation. You can select one or the
19120 other either by passing the appropriate flag to @code{ptype}, or by using
19121 the @command{set print type hex} command.
19123 @kindex show print type hex
19124 @item show print type hex
19125 This command shows whether the sizes and offsets of struct members are
19126 printed in decimal or hexadecimal notation.
19128 @kindex info address
19129 @cindex address of a symbol
19130 @item info address @var{symbol}
19131 Describe where the data for @var{symbol} is stored. For a register
19132 variable, this says which register it is kept in. For a non-register
19133 local variable, this prints the stack-frame offset at which the variable
19136 Note the contrast with @samp{print &@var{symbol}}, which does not work
19137 at all for a register variable, and for a stack local variable prints
19138 the exact address of the current instantiation of the variable.
19140 @kindex info symbol
19141 @cindex symbol from address
19142 @cindex closest symbol and offset for an address
19143 @item info symbol @var{addr}
19144 Print the name of a symbol which is stored at the address @var{addr}.
19145 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
19146 nearest symbol and an offset from it:
19149 (@value{GDBP}) info symbol 0x54320
19150 _initialize_vx + 396 in section .text
19154 This is the opposite of the @code{info address} command. You can use
19155 it to find out the name of a variable or a function given its address.
19157 For dynamically linked executables, the name of executable or shared
19158 library containing the symbol is also printed:
19161 (@value{GDBP}) info symbol 0x400225
19162 _start + 5 in section .text of /tmp/a.out
19163 (@value{GDBP}) info symbol 0x2aaaac2811cf
19164 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
19169 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
19170 Demangle @var{name}.
19171 If @var{language} is provided it is the name of the language to demangle
19172 @var{name} in. Otherwise @var{name} is demangled in the current language.
19174 The @samp{--} option specifies the end of options,
19175 and is useful when @var{name} begins with a dash.
19177 The parameter @code{demangle-style} specifies how to interpret the kind
19178 of mangling used. @xref{Print Settings}.
19181 @item whatis[/@var{flags}] [@var{arg}]
19182 Print the data type of @var{arg}, which can be either an expression
19183 or a name of a data type. With no argument, print the data type of
19184 @code{$}, the last value in the value history.
19186 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
19187 is not actually evaluated, and any side-effecting operations (such as
19188 assignments or function calls) inside it do not take place.
19190 If @var{arg} is a variable or an expression, @code{whatis} prints its
19191 literal type as it is used in the source code. If the type was
19192 defined using a @code{typedef}, @code{whatis} will @emph{not} print
19193 the data type underlying the @code{typedef}. If the type of the
19194 variable or the expression is a compound data type, such as
19195 @code{struct} or @code{class}, @code{whatis} never prints their
19196 fields or methods. It just prints the @code{struct}/@code{class}
19197 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
19198 such a compound data type, use @code{ptype}.
19200 If @var{arg} is a type name that was defined using @code{typedef},
19201 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
19202 Unrolling means that @code{whatis} will show the underlying type used
19203 in the @code{typedef} declaration of @var{arg}. However, if that
19204 underlying type is also a @code{typedef}, @code{whatis} will not
19207 For C code, the type names may also have the form @samp{class
19208 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
19209 @var{union-tag}} or @samp{enum @var{enum-tag}}.
19211 @var{flags} can be used to modify how the type is displayed.
19212 Available flags are:
19216 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
19217 parameters and typedefs defined in a class when printing the class'
19218 members. The @code{/r} flag disables this.
19221 Do not print methods defined in the class.
19224 Print methods defined in the class. This is the default, but the flag
19225 exists in case you change the default with @command{set print type methods}.
19228 Do not print typedefs defined in the class. Note that this controls
19229 whether the typedef definition itself is printed, not whether typedef
19230 names are substituted when printing other types.
19233 Print typedefs defined in the class. This is the default, but the flag
19234 exists in case you change the default with @command{set print type typedefs}.
19237 Print the offsets and sizes of fields in a struct, similar to what the
19238 @command{pahole} tool does. This option implies the @code{/tm} flags.
19241 Use hexadecimal notation when printing offsets and sizes of fields in a
19245 Use decimal notation when printing offsets and sizes of fields in a
19248 For example, given the following declarations:
19284 Issuing a @kbd{ptype /o struct tuv} command would print:
19287 (@value{GDBP}) ptype /o struct tuv
19288 /* offset | size */ type = struct tuv @{
19289 /* 0 | 4 */ int a1;
19290 /* XXX 4-byte hole */
19291 /* 8 | 8 */ char *a2;
19292 /* 16 | 4 */ int a3;
19294 /* total size (bytes): 24 */
19298 Notice the format of the first column of comments. There, you can
19299 find two parts separated by the @samp{|} character: the @emph{offset},
19300 which indicates where the field is located inside the struct, in
19301 bytes, and the @emph{size} of the field. Another interesting line is
19302 the marker of a @emph{hole} in the struct, indicating that it may be
19303 possible to pack the struct and make it use less space by reorganizing
19306 It is also possible to print offsets inside an union:
19309 (@value{GDBP}) ptype /o union qwe
19310 /* offset | size */ type = union qwe @{
19311 /* 24 */ struct tuv @{
19312 /* 0 | 4 */ int a1;
19313 /* XXX 4-byte hole */
19314 /* 8 | 8 */ char *a2;
19315 /* 16 | 4 */ int a3;
19317 /* total size (bytes): 24 */
19319 /* 40 */ struct xyz @{
19320 /* 0 | 4 */ int f1;
19321 /* 4 | 1 */ char f2;
19322 /* XXX 3-byte hole */
19323 /* 8 | 8 */ void *f3;
19324 /* 16 | 24 */ struct tuv @{
19325 /* 16 | 4 */ int a1;
19326 /* XXX 4-byte hole */
19327 /* 24 | 8 */ char *a2;
19328 /* 32 | 4 */ int a3;
19330 /* total size (bytes): 24 */
19333 /* total size (bytes): 40 */
19336 /* total size (bytes): 40 */
19340 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
19341 same space (because we are dealing with an union), the offset is not
19342 printed for them. However, you can still examine the offset of each
19343 of these structures' fields.
19345 Another useful scenario is printing the offsets of a struct containing
19349 (@value{GDBP}) ptype /o struct tyu
19350 /* offset | size */ type = struct tyu @{
19351 /* 0:31 | 4 */ int a1 : 1;
19352 /* 0:28 | 4 */ int a2 : 3;
19353 /* 0: 5 | 4 */ int a3 : 23;
19354 /* 3: 3 | 1 */ signed char a4 : 2;
19355 /* XXX 3-bit hole */
19356 /* XXX 4-byte hole */
19357 /* 8 | 8 */ int64_t a5;
19358 /* 16: 0 | 4 */ int a6 : 5;
19359 /* 16: 5 | 8 */ int64_t a7 : 3;
19360 /* XXX 7-byte padding */
19362 /* total size (bytes): 24 */
19366 Note how the offset information is now extended to also include the
19367 first bit of the bitfield.
19371 @item ptype[/@var{flags}] [@var{arg}]
19372 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
19373 detailed description of the type, instead of just the name of the type.
19374 @xref{Expressions, ,Expressions}.
19376 Contrary to @code{whatis}, @code{ptype} always unrolls any
19377 @code{typedef}s in its argument declaration, whether the argument is
19378 a variable, expression, or a data type. This means that @code{ptype}
19379 of a variable or an expression will not print literally its type as
19380 present in the source code---use @code{whatis} for that. @code{typedef}s at
19381 the pointer or reference targets are also unrolled. Only @code{typedef}s of
19382 fields, methods and inner @code{class typedef}s of @code{struct}s,
19383 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
19385 For example, for this variable declaration:
19388 typedef double real_t;
19389 struct complex @{ real_t real; double imag; @};
19390 typedef struct complex complex_t;
19392 real_t *real_pointer_var;
19396 the two commands give this output:
19400 (@value{GDBP}) whatis var
19402 (@value{GDBP}) ptype var
19403 type = struct complex @{
19407 (@value{GDBP}) whatis complex_t
19408 type = struct complex
19409 (@value{GDBP}) whatis struct complex
19410 type = struct complex
19411 (@value{GDBP}) ptype struct complex
19412 type = struct complex @{
19416 (@value{GDBP}) whatis real_pointer_var
19418 (@value{GDBP}) ptype real_pointer_var
19424 As with @code{whatis}, using @code{ptype} without an argument refers to
19425 the type of @code{$}, the last value in the value history.
19427 @cindex incomplete type
19428 Sometimes, programs use opaque data types or incomplete specifications
19429 of complex data structure. If the debug information included in the
19430 program does not allow @value{GDBN} to display a full declaration of
19431 the data type, it will say @samp{<incomplete type>}. For example,
19432 given these declarations:
19436 struct foo *fooptr;
19440 but no definition for @code{struct foo} itself, @value{GDBN} will say:
19443 (@value{GDBP}) ptype foo
19444 $1 = <incomplete type>
19448 ``Incomplete type'' is C terminology for data types that are not
19449 completely specified.
19451 @cindex unknown type
19452 Othertimes, information about a variable's type is completely absent
19453 from the debug information included in the program. This most often
19454 happens when the program or library where the variable is defined
19455 includes no debug information at all. @value{GDBN} knows the variable
19456 exists from inspecting the linker/loader symbol table (e.g., the ELF
19457 dynamic symbol table), but such symbols do not contain type
19458 information. Inspecting the type of a (global) variable for which
19459 @value{GDBN} has no type information shows:
19462 (@value{GDBP}) ptype var
19463 type = <data variable, no debug info>
19466 @xref{Variables, no debug info variables}, for how to print the values
19470 @item info types [-q] [@var{regexp}]
19471 Print a brief description of all types whose names match the regular
19472 expression @var{regexp} (or all types in your program, if you supply
19473 no argument). Each complete typename is matched as though it were a
19474 complete line; thus, @samp{i type value} gives information on all
19475 types in your program whose names include the string @code{value}, but
19476 @samp{i type ^value$} gives information only on types whose complete
19477 name is @code{value}.
19479 In programs using different languages, @value{GDBN} chooses the syntax
19480 to print the type description according to the
19481 @samp{set language} value: using @samp{set language auto}
19482 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19483 language of the type, other values mean to use
19484 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19486 This command differs from @code{ptype} in two ways: first, like
19487 @code{whatis}, it does not print a detailed description; second, it
19488 lists all source files and line numbers where a type is defined.
19490 The output from @samp{into types} is proceeded with a header line
19491 describing what types are being listed. The optional flag @samp{-q},
19492 which stands for @samp{quiet}, disables printing this header
19495 @kindex info type-printers
19496 @item info type-printers
19497 Versions of @value{GDBN} that ship with Python scripting enabled may
19498 have ``type printers'' available. When using @command{ptype} or
19499 @command{whatis}, these printers are consulted when the name of a type
19500 is needed. @xref{Type Printing API}, for more information on writing
19503 @code{info type-printers} displays all the available type printers.
19505 @kindex enable type-printer
19506 @kindex disable type-printer
19507 @item enable type-printer @var{name}@dots{}
19508 @item disable type-printer @var{name}@dots{}
19509 These commands can be used to enable or disable type printers.
19512 @cindex local variables
19513 @item info scope @var{location}
19514 List all the variables local to a particular scope. This command
19515 accepts a @var{location} argument---a function name, a source line, or
19516 an address preceded by a @samp{*}, and prints all the variables local
19517 to the scope defined by that location. (@xref{Specify Location}, for
19518 details about supported forms of @var{location}.) For example:
19521 (@value{GDBP}) @b{info scope command_line_handler}
19522 Scope for command_line_handler:
19523 Symbol rl is an argument at stack/frame offset 8, length 4.
19524 Symbol linebuffer is in static storage at address 0x150a18, length 4.
19525 Symbol linelength is in static storage at address 0x150a1c, length 4.
19526 Symbol p is a local variable in register $esi, length 4.
19527 Symbol p1 is a local variable in register $ebx, length 4.
19528 Symbol nline is a local variable in register $edx, length 4.
19529 Symbol repeat is a local variable at frame offset -8, length 4.
19533 This command is especially useful for determining what data to collect
19534 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
19537 @kindex info source
19539 Show information about the current source file---that is, the source file for
19540 the function containing the current point of execution:
19543 the name of the source file, and the directory containing it,
19545 the directory it was compiled in,
19547 its length, in lines,
19549 which programming language it is written in,
19551 if the debug information provides it, the program that compiled the file
19552 (which may include, e.g., the compiler version and command line arguments),
19554 whether the executable includes debugging information for that file, and
19555 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
19557 whether the debugging information includes information about
19558 preprocessor macros.
19562 @kindex info sources
19563 @item info sources @r{[}-dirname | -basename@r{]} @r{[}--@r{]} @r{[}@var{regexp}@r{]}
19566 With no options @samp{info sources} prints the names of all source
19567 files in your program for which there is debugging information. The
19568 source files are presented based on a list of object files
19569 (executables and libraries) currently loaded into @value{GDBN}. For
19570 each object file all of the associated source files are listed.
19572 Each source file will only be printed once for each object file, but a
19573 single source file can be repeated in the output if it is part of
19574 multiple object files.
19576 If the optional @var{regexp} is provided, then only source files that
19577 match the regular expression will be printed. The matching is
19578 case-sensitive, except on operating systems that have case-insensitive
19579 filesystem (e.g., MS-Windows). @samp{--} can be used before
19580 @var{regexp} to prevent @value{GDBN} interpreting @var{regexp} as a
19581 command option (e.g. if @var{regexp} starts with @samp{-}).
19583 By default, the @var{regexp} is used to match anywhere in the
19584 filename. If @code{-dirname}, only files having a dirname matching
19585 @var{regexp} are shown. If @code{-basename}, only files having a
19586 basename matching @var{regexp} are shown.
19588 It is possible that an object file may be printed in the list with no
19589 associated source files. This can happen when either no source files
19590 match @var{regexp}, or, the object file was compiled without debug
19591 information and so @value{GDBN} is unable to find any source file
19594 @kindex info functions
19595 @item info functions [-q] [-n]
19596 Print the names and data types of all defined functions.
19597 Similarly to @samp{info types}, this command groups its output by source
19598 files and annotates each function definition with its source line
19601 In programs using different languages, @value{GDBN} chooses the syntax
19602 to print the function name and type according to the
19603 @samp{set language} value: using @samp{set language auto}
19604 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19605 language of the function, other values mean to use
19606 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19608 The @samp{-n} flag excludes @dfn{non-debugging symbols} from the
19609 results. A non-debugging symbol is a symbol that comes from the
19610 executable's symbol table, not from the debug information (for
19611 example, DWARF) associated with the executable.
19613 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19614 printing header information and messages explaining why no functions
19617 @item info functions [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19618 Like @samp{info functions}, but only print the names and data types
19619 of the functions selected with the provided regexp(s).
19621 If @var{regexp} is provided, print only the functions whose names
19622 match the regular expression @var{regexp}.
19623 Thus, @samp{info fun step} finds all functions whose
19624 names include @code{step}; @samp{info fun ^step} finds those whose names
19625 start with @code{step}. If a function name contains characters that
19626 conflict with the regular expression language (e.g.@:
19627 @samp{operator*()}), they may be quoted with a backslash.
19629 If @var{type_regexp} is provided, print only the functions whose
19630 types, as printed by the @code{whatis} command, match
19631 the regular expression @var{type_regexp}.
19632 If @var{type_regexp} contains space(s), it should be enclosed in
19633 quote characters. If needed, use backslash to escape the meaning
19634 of special characters or quotes.
19635 Thus, @samp{info fun -t '^int ('} finds the functions that return
19636 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
19637 have an argument type containing int; @samp{info fun -t '^int (' ^step}
19638 finds the functions whose names start with @code{step} and that return
19641 If both @var{regexp} and @var{type_regexp} are provided, a function
19642 is printed only if its name matches @var{regexp} and its type matches
19646 @kindex info variables
19647 @item info variables [-q] [-n]
19648 Print the names and data types of all variables that are defined
19649 outside of functions (i.e.@: excluding local variables).
19650 The printed variables are grouped by source files and annotated with
19651 their respective source line numbers.
19653 In programs using different languages, @value{GDBN} chooses the syntax
19654 to print the variable name and type according to the
19655 @samp{set language} value: using @samp{set language auto}
19656 (see @ref{Automatically, ,Set Language Automatically}) means to use the
19657 language of the variable, other values mean to use
19658 the manually specified language (see @ref{Manually, ,Set Language Manually}).
19660 The @samp{-n} flag excludes non-debugging symbols from the results.
19662 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19663 printing header information and messages explaining why no variables
19666 @item info variables [-q] [-n] [-t @var{type_regexp}] [@var{regexp}]
19667 Like @kbd{info variables}, but only print the variables selected
19668 with the provided regexp(s).
19670 If @var{regexp} is provided, print only the variables whose names
19671 match the regular expression @var{regexp}.
19673 If @var{type_regexp} is provided, print only the variables whose
19674 types, as printed by the @code{whatis} command, match
19675 the regular expression @var{type_regexp}.
19676 If @var{type_regexp} contains space(s), it should be enclosed in
19677 quote characters. If needed, use backslash to escape the meaning
19678 of special characters or quotes.
19680 If both @var{regexp} and @var{type_regexp} are provided, an argument
19681 is printed only if its name matches @var{regexp} and its type matches
19684 @kindex info modules
19686 @item info modules @r{[}-q@r{]} @r{[}@var{regexp}@r{]}
19687 List all Fortran modules in the program, or all modules matching the
19688 optional regular expression @var{regexp}.
19690 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19691 printing header information and messages explaining why no modules
19694 @kindex info module
19695 @cindex Fortran modules, information about
19696 @cindex functions and variables by Fortran module
19697 @cindex module functions and variables
19698 @item info module functions @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19699 @itemx info module variables @r{[}-q@r{]} @r{[}-m @var{module-regexp}@r{]} @r{[}-t @var{type-regexp}@r{]} @r{[}@var{regexp}@r{]}
19700 List all functions or variables within all Fortran modules. The set
19701 of functions or variables listed can be limited by providing some or
19702 all of the optional regular expressions. If @var{module-regexp} is
19703 provided, then only Fortran modules matching @var{module-regexp} will
19704 be searched. Only functions or variables whose type matches the
19705 optional regular expression @var{type-regexp} will be listed. And
19706 only functions or variables whose name matches the optional regular
19707 expression @var{regexp} will be listed.
19709 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
19710 printing header information and messages explaining why no functions
19711 or variables have been printed.
19713 @kindex info classes
19714 @cindex Objective-C, classes and selectors
19716 @itemx info classes @var{regexp}
19717 Display all Objective-C classes in your program, or
19718 (with the @var{regexp} argument) all those matching a particular regular
19721 @kindex info selectors
19722 @item info selectors
19723 @itemx info selectors @var{regexp}
19724 Display all Objective-C selectors in your program, or
19725 (with the @var{regexp} argument) all those matching a particular regular
19729 This was never implemented.
19730 @kindex info methods
19732 @itemx info methods @var{regexp}
19733 The @code{info methods} command permits the user to examine all defined
19734 methods within C@t{++} program, or (with the @var{regexp} argument) a
19735 specific set of methods found in the various C@t{++} classes. Many
19736 C@t{++} classes provide a large number of methods. Thus, the output
19737 from the @code{ptype} command can be overwhelming and hard to use. The
19738 @code{info-methods} command filters the methods, printing only those
19739 which match the regular-expression @var{regexp}.
19742 @cindex opaque data types
19743 @kindex set opaque-type-resolution
19744 @item set opaque-type-resolution on
19745 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
19746 declared as a pointer to a @code{struct}, @code{class}, or
19747 @code{union}---for example, @code{struct MyType *}---that is used in one
19748 source file although the full declaration of @code{struct MyType} is in
19749 another source file. The default is on.
19751 A change in the setting of this subcommand will not take effect until
19752 the next time symbols for a file are loaded.
19754 @item set opaque-type-resolution off
19755 Tell @value{GDBN} not to resolve opaque types. In this case, the type
19756 is printed as follows:
19758 @{<no data fields>@}
19761 @kindex show opaque-type-resolution
19762 @item show opaque-type-resolution
19763 Show whether opaque types are resolved or not.
19765 @kindex set print symbol-loading
19766 @cindex print messages when symbols are loaded
19767 @item set print symbol-loading
19768 @itemx set print symbol-loading full
19769 @itemx set print symbol-loading brief
19770 @itemx set print symbol-loading off
19771 The @code{set print symbol-loading} command allows you to control the
19772 printing of messages when @value{GDBN} loads symbol information.
19773 By default a message is printed for the executable and one for each
19774 shared library, and normally this is what you want. However, when
19775 debugging apps with large numbers of shared libraries these messages
19777 When set to @code{brief} a message is printed for each executable,
19778 and when @value{GDBN} loads a collection of shared libraries at once
19779 it will only print one message regardless of the number of shared
19780 libraries. When set to @code{off} no messages are printed.
19782 @kindex show print symbol-loading
19783 @item show print symbol-loading
19784 Show whether messages will be printed when a @value{GDBN} command
19785 entered from the keyboard causes symbol information to be loaded.
19787 @kindex maint print symbols
19788 @cindex symbol dump
19789 @kindex maint print psymbols
19790 @cindex partial symbol dump
19791 @kindex maint print msymbols
19792 @cindex minimal symbol dump
19793 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
19794 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19795 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19796 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19797 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
19798 Write a dump of debugging symbol data into the file @var{filename} or
19799 the terminal if @var{filename} is unspecified.
19800 If @code{-objfile @var{objfile}} is specified, only dump symbols for
19802 If @code{-pc @var{address}} is specified, only dump symbols for the file
19803 with code at that address. Note that @var{address} may be a symbol like
19805 If @code{-source @var{source}} is specified, only dump symbols for that
19808 These commands are used to debug the @value{GDBN} symbol-reading code.
19809 These commands do not modify internal @value{GDBN} state, therefore
19810 @samp{maint print symbols} will only print symbols for already expanded symbol
19812 You can use the command @code{info sources} to find out which files these are.
19813 If you use @samp{maint print psymbols} instead, the dump shows information
19814 about symbols that @value{GDBN} only knows partially---that is, symbols
19815 defined in files that @value{GDBN} has skimmed, but not yet read completely.
19816 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
19819 @xref{Files, ,Commands to Specify Files}, for a discussion of how
19820 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
19822 @kindex maint info symtabs
19823 @kindex maint info psymtabs
19824 @cindex listing @value{GDBN}'s internal symbol tables
19825 @cindex symbol tables, listing @value{GDBN}'s internal
19826 @cindex full symbol tables, listing @value{GDBN}'s internal
19827 @cindex partial symbol tables, listing @value{GDBN}'s internal
19828 @item maint info symtabs @r{[} @var{regexp} @r{]}
19829 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
19831 List the @code{struct symtab} or @code{struct partial_symtab}
19832 structures whose names match @var{regexp}. If @var{regexp} is not
19833 given, list them all. The output includes expressions which you can
19834 copy into a @value{GDBN} debugging this one to examine a particular
19835 structure in more detail. For example:
19838 (@value{GDBP}) maint info psymtabs dwarf2read
19839 @{ objfile /home/gnu/build/gdb/gdb
19840 ((struct objfile *) 0x82e69d0)
19841 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
19842 ((struct partial_symtab *) 0x8474b10)
19845 text addresses 0x814d3c8 -- 0x8158074
19846 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
19847 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
19848 dependencies (none)
19851 (@value{GDBP}) maint info symtabs
19855 We see that there is one partial symbol table whose filename contains
19856 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
19857 and we see that @value{GDBN} has not read in any symtabs yet at all.
19858 If we set a breakpoint on a function, that will cause @value{GDBN} to
19859 read the symtab for the compilation unit containing that function:
19862 (@value{GDBP}) break dwarf2_psymtab_to_symtab
19863 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
19865 (@value{GDBP}) maint info symtabs
19866 @{ objfile /home/gnu/build/gdb/gdb
19867 ((struct objfile *) 0x82e69d0)
19868 @{ symtab /home/gnu/src/gdb/dwarf2read.c
19869 ((struct symtab *) 0x86c1f38)
19872 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
19873 linetable ((struct linetable *) 0x8370fa0)
19874 debugformat DWARF 2
19880 @kindex maint info line-table
19881 @cindex listing @value{GDBN}'s internal line tables
19882 @cindex line tables, listing @value{GDBN}'s internal
19883 @item maint info line-table @r{[} @var{regexp} @r{]}
19885 List the @code{struct linetable} from all @code{struct symtab}
19886 instances whose name matches @var{regexp}. If @var{regexp} is not
19887 given, list the @code{struct linetable} from all @code{struct symtab}.
19891 (@value{GDBP}) maint info line-table
19892 objfile: /home/gnu/build/a.out ((struct objfile *) 0x6120000e0d40)
19893 compunit_symtab: simple.cpp ((struct compunit_symtab *) 0x6210000ff450)
19894 symtab: /home/gnu/src/simple.cpp ((struct symtab *) 0x6210000ff4d0)
19895 linetable: ((struct linetable *) 0x62100012b760):
19896 INDEX LINE ADDRESS IS-STMT PROLOGUE-END
19897 0 3 0x0000000000401110 Y
19898 1 4 0x0000000000401114 Y Y
19899 2 9 0x0000000000401120 Y
19900 3 10 0x0000000000401124 Y Y
19901 4 10 0x0000000000401129
19902 5 15 0x0000000000401130 Y
19903 6 16 0x0000000000401134 Y Y
19904 7 16 0x0000000000401139
19905 8 21 0x0000000000401140 Y
19906 9 22 0x000000000040114f Y Y
19907 10 22 0x0000000000401154
19908 11 END 0x000000000040115a Y
19911 The @samp{IS-STMT} column indicates if the address is a recommended breakpoint
19912 location to represent a line or a statement. The @samp{PROLOGUE-END} column
19913 indicates that a given address is an adequate place to set a breakpoint at the
19914 first instruction following a function prologue.
19916 @kindex maint set symbol-cache-size
19917 @cindex symbol cache size
19918 @item maint set symbol-cache-size @var{size}
19919 Set the size of the symbol cache to @var{size}.
19920 The default size is intended to be good enough for debugging
19921 most applications. This option exists to allow for experimenting
19922 with different sizes.
19924 @kindex maint show symbol-cache-size
19925 @item maint show symbol-cache-size
19926 Show the size of the symbol cache.
19928 @kindex maint print symbol-cache
19929 @cindex symbol cache, printing its contents
19930 @item maint print symbol-cache
19931 Print the contents of the symbol cache.
19932 This is useful when debugging symbol cache issues.
19934 @kindex maint print symbol-cache-statistics
19935 @cindex symbol cache, printing usage statistics
19936 @item maint print symbol-cache-statistics
19937 Print symbol cache usage statistics.
19938 This helps determine how well the cache is being utilized.
19940 @kindex maint flush symbol-cache
19941 @kindex maint flush-symbol-cache
19942 @cindex symbol cache, flushing
19943 @item maint flush symbol-cache
19944 @itemx maint flush-symbol-cache
19945 Flush the contents of the symbol cache, all entries are removed. This
19946 command is useful when debugging the symbol cache. It is also useful
19947 when collecting performance data. The command @code{maint
19948 flush-symbol-cache} is deprecated in favor of @code{maint flush
19951 @kindex maint set ignore-prologue-end-flag
19952 @cindex prologue-end
19953 @item maint set ignore-prologue-end-flag [on|off]
19954 Enable or disable the use of the @samp{PROLOGUE-END} flag from the line-table.
19955 When @samp{off} (the default), @value{GDBN} uses the @samp{PROLOGUE-END} flag
19956 to place breakpoints past the end of a function prologue. When @samp{on},
19957 @value{GDBN} ignores the flag and relies on prologue analyzers to skip function
19960 @kindex maint show ignore-prologue-end-flag
19961 @item maint show ignore-prologue-end-flag
19962 Show whether @value{GDBN} will ignore the @samp{PROLOGUE-END} flag.
19967 @chapter Altering Execution
19969 Once you think you have found an error in your program, you might want to
19970 find out for certain whether correcting the apparent error would lead to
19971 correct results in the rest of the run. You can find the answer by
19972 experiment, using the @value{GDBN} features for altering execution of the
19975 For example, you can store new values into variables or memory
19976 locations, give your program a signal, restart it at a different
19977 address, or even return prematurely from a function.
19980 * Assignment:: Assignment to variables
19981 * Jumping:: Continuing at a different address
19982 * Signaling:: Giving your program a signal
19983 * Returning:: Returning from a function
19984 * Calling:: Calling your program's functions
19985 * Patching:: Patching your program
19986 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
19990 @section Assignment to Variables
19993 @cindex setting variables
19994 To alter the value of a variable, evaluate an assignment expression.
19995 @xref{Expressions, ,Expressions}. For example,
20002 stores the value 4 into the variable @code{x}, and then prints the
20003 value of the assignment expression (which is 4).
20004 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
20005 information on operators in supported languages.
20007 @kindex set variable
20008 @cindex variables, setting
20009 If you are not interested in seeing the value of the assignment, use the
20010 @code{set} command instead of the @code{print} command. @code{set} is
20011 really the same as @code{print} except that the expression's value is
20012 not printed and is not put in the value history (@pxref{Value History,
20013 ,Value History}). The expression is evaluated only for its effects.
20015 If the beginning of the argument string of the @code{set} command
20016 appears identical to a @code{set} subcommand, use the @code{set
20017 variable} command instead of just @code{set}. This command is identical
20018 to @code{set} except for its lack of subcommands. For example, if your
20019 program has a variable @code{width}, you get an error if you try to set
20020 a new value with just @samp{set width=13}, because @value{GDBN} has the
20021 command @code{set width}:
20024 (@value{GDBP}) whatis width
20026 (@value{GDBP}) p width
20028 (@value{GDBP}) set width=47
20029 Invalid syntax in expression.
20033 The invalid expression, of course, is @samp{=47}. In
20034 order to actually set the program's variable @code{width}, use
20037 (@value{GDBP}) set var width=47
20040 Because the @code{set} command has many subcommands that can conflict
20041 with the names of program variables, it is a good idea to use the
20042 @code{set variable} command instead of just @code{set}. For example, if
20043 your program has a variable @code{g}, you run into problems if you try
20044 to set a new value with just @samp{set g=4}, because @value{GDBN} has
20045 the command @code{set gnutarget}, abbreviated @code{set g}:
20049 (@value{GDBP}) whatis g
20053 (@value{GDBP}) set g=4
20057 The program being debugged has been started already.
20058 Start it from the beginning? (y or n) y
20059 Starting program: /home/smith/cc_progs/a.out
20060 "/home/smith/cc_progs/a.out": can't open to read symbols:
20061 Invalid bfd target.
20062 (@value{GDBP}) show g
20063 The current BFD target is "=4".
20068 The program variable @code{g} did not change, and you silently set the
20069 @code{gnutarget} to an invalid value. In order to set the variable
20073 (@value{GDBP}) set var g=4
20076 @value{GDBN} allows more implicit conversions in assignments than C; you can
20077 freely store an integer value into a pointer variable or vice versa,
20078 and you can convert any structure to any other structure that is the
20079 same length or shorter.
20080 @comment FIXME: how do structs align/pad in these conversions?
20081 @comment /doc@cygnus.com 18dec1990
20083 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
20084 construct to generate a value of specified type at a specified address
20085 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
20086 to memory location @code{0x83040} as an integer (which implies a certain size
20087 and representation in memory), and
20090 set @{int@}0x83040 = 4
20094 stores the value 4 into that memory location.
20097 @section Continuing at a Different Address
20099 Ordinarily, when you continue your program, you do so at the place where
20100 it stopped, with the @code{continue} command. You can instead continue at
20101 an address of your own choosing, with the following commands:
20105 @kindex j @r{(@code{jump})}
20106 @item jump @var{location}
20107 @itemx j @var{location}
20108 Resume execution at @var{location}. Execution stops again immediately
20109 if there is a breakpoint there. @xref{Specify Location}, for a description
20110 of the different forms of @var{location}. It is common
20111 practice to use the @code{tbreak} command in conjunction with
20112 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
20114 The @code{jump} command does not change the current stack frame, or
20115 the stack pointer, or the contents of any memory location or any
20116 register other than the program counter. If @var{location} is in
20117 a different function from the one currently executing, the results may
20118 be bizarre if the two functions expect different patterns of arguments or
20119 of local variables. For this reason, the @code{jump} command requests
20120 confirmation if the specified line is not in the function currently
20121 executing. However, even bizarre results are predictable if you are
20122 well acquainted with the machine-language code of your program.
20125 On many systems, you can get much the same effect as the @code{jump}
20126 command by storing a new value into the register @code{$pc}. The
20127 difference is that this does not start your program running; it only
20128 changes the address of where it @emph{will} run when you continue. For
20136 makes the next @code{continue} command or stepping command execute at
20137 address @code{0x485}, rather than at the address where your program stopped.
20138 @xref{Continuing and Stepping, ,Continuing and Stepping}.
20140 The most common occasion to use the @code{jump} command is to back
20141 up---perhaps with more breakpoints set---over a portion of a program
20142 that has already executed, in order to examine its execution in more
20147 @section Giving your Program a Signal
20148 @cindex deliver a signal to a program
20152 @item signal @var{signal}
20153 Resume execution where your program is stopped, but immediately give it the
20154 signal @var{signal}. The @var{signal} can be the name or the number of a
20155 signal. For example, on many systems @code{signal 2} and @code{signal
20156 SIGINT} are both ways of sending an interrupt signal.
20158 Alternatively, if @var{signal} is zero, continue execution without
20159 giving a signal. This is useful when your program stopped on account of
20160 a signal and would ordinarily see the signal when resumed with the
20161 @code{continue} command; @samp{signal 0} causes it to resume without a
20164 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
20165 delivered to the currently selected thread, not the thread that last
20166 reported a stop. This includes the situation where a thread was
20167 stopped due to a signal. So if you want to continue execution
20168 suppressing the signal that stopped a thread, you should select that
20169 same thread before issuing the @samp{signal 0} command. If you issue
20170 the @samp{signal 0} command with another thread as the selected one,
20171 @value{GDBN} detects that and asks for confirmation.
20173 Invoking the @code{signal} command is not the same as invoking the
20174 @code{kill} utility from the shell. Sending a signal with @code{kill}
20175 causes @value{GDBN} to decide what to do with the signal depending on
20176 the signal handling tables (@pxref{Signals}). The @code{signal} command
20177 passes the signal directly to your program.
20179 @code{signal} does not repeat when you press @key{RET} a second time
20180 after executing the command.
20182 @kindex queue-signal
20183 @item queue-signal @var{signal}
20184 Queue @var{signal} to be delivered immediately to the current thread
20185 when execution of the thread resumes. The @var{signal} can be the name or
20186 the number of a signal. For example, on many systems @code{signal 2} and
20187 @code{signal SIGINT} are both ways of sending an interrupt signal.
20188 The handling of the signal must be set to pass the signal to the program,
20189 otherwise @value{GDBN} will report an error.
20190 You can control the handling of signals from @value{GDBN} with the
20191 @code{handle} command (@pxref{Signals}).
20193 Alternatively, if @var{signal} is zero, any currently queued signal
20194 for the current thread is discarded and when execution resumes no signal
20195 will be delivered. This is useful when your program stopped on account
20196 of a signal and would ordinarily see the signal when resumed with the
20197 @code{continue} command.
20199 This command differs from the @code{signal} command in that the signal
20200 is just queued, execution is not resumed. And @code{queue-signal} cannot
20201 be used to pass a signal whose handling state has been set to @code{nopass}
20206 @xref{stepping into signal handlers}, for information on how stepping
20207 commands behave when the thread has a signal queued.
20210 @section Returning from a Function
20213 @cindex returning from a function
20216 @itemx return @var{expression}
20217 You can cancel execution of a function call with the @code{return}
20218 command. If you give an
20219 @var{expression} argument, its value is used as the function's return
20223 When you use @code{return}, @value{GDBN} discards the selected stack frame
20224 (and all frames within it). You can think of this as making the
20225 discarded frame return prematurely. If you wish to specify a value to
20226 be returned, give that value as the argument to @code{return}.
20228 This pops the selected stack frame (@pxref{Selection, ,Selecting a
20229 Frame}), and any other frames inside of it, leaving its caller as the
20230 innermost remaining frame. That frame becomes selected. The
20231 specified value is stored in the registers used for returning values
20234 The @code{return} command does not resume execution; it leaves the
20235 program stopped in the state that would exist if the function had just
20236 returned. In contrast, the @code{finish} command (@pxref{Continuing
20237 and Stepping, ,Continuing and Stepping}) resumes execution until the
20238 selected stack frame returns naturally.
20240 @value{GDBN} needs to know how the @var{expression} argument should be set for
20241 the inferior. The concrete registers assignment depends on the OS ABI and the
20242 type being returned by the selected stack frame. For example it is common for
20243 OS ABI to return floating point values in FPU registers while integer values in
20244 CPU registers. Still some ABIs return even floating point values in CPU
20245 registers. Larger integer widths (such as @code{long long int}) also have
20246 specific placement rules. @value{GDBN} already knows the OS ABI from its
20247 current target so it needs to find out also the type being returned to make the
20248 assignment into the right register(s).
20250 Normally, the selected stack frame has debug info. @value{GDBN} will always
20251 use the debug info instead of the implicit type of @var{expression} when the
20252 debug info is available. For example, if you type @kbd{return -1}, and the
20253 function in the current stack frame is declared to return a @code{long long
20254 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
20255 into a @code{long long int}:
20258 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
20260 (@value{GDBP}) return -1
20261 Make func return now? (y or n) y
20262 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
20263 43 printf ("result=%lld\n", func ());
20267 However, if the selected stack frame does not have a debug info, e.g., if the
20268 function was compiled without debug info, @value{GDBN} has to find out the type
20269 to return from user. Specifying a different type by mistake may set the value
20270 in different inferior registers than the caller code expects. For example,
20271 typing @kbd{return -1} with its implicit type @code{int} would set only a part
20272 of a @code{long long int} result for a debug info less function (on 32-bit
20273 architectures). Therefore the user is required to specify the return type by
20274 an appropriate cast explicitly:
20277 Breakpoint 2, 0x0040050b in func ()
20278 (@value{GDBP}) return -1
20279 Return value type not available for selected stack frame.
20280 Please use an explicit cast of the value to return.
20281 (@value{GDBP}) return (long long int) -1
20282 Make selected stack frame return now? (y or n) y
20283 #0 0x00400526 in main ()
20288 @section Calling Program Functions
20291 @cindex calling functions
20292 @cindex inferior functions, calling
20293 @item print @var{expr}
20294 Evaluate the expression @var{expr} and display the resulting value.
20295 The expression may include calls to functions in the program being
20299 @item call @var{expr}
20300 Evaluate the expression @var{expr} without displaying @code{void}
20303 You can use this variant of the @code{print} command if you want to
20304 execute a function from your program that does not return anything
20305 (a.k.a.@: @dfn{a void function}), but without cluttering the output
20306 with @code{void} returned values that @value{GDBN} will otherwise
20307 print. If the result is not void, it is printed and saved in the
20311 It is possible for the function you call via the @code{print} or
20312 @code{call} command to generate a signal (e.g., if there's a bug in
20313 the function, or if you passed it incorrect arguments). What happens
20314 in that case is controlled by the @code{set unwindonsignal} command.
20316 Similarly, with a C@t{++} program it is possible for the function you
20317 call via the @code{print} or @code{call} command to generate an
20318 exception that is not handled due to the constraints of the dummy
20319 frame. In this case, any exception that is raised in the frame, but has
20320 an out-of-frame exception handler will not be found. GDB builds a
20321 dummy-frame for the inferior function call, and the unwinder cannot
20322 seek for exception handlers outside of this dummy-frame. What happens
20323 in that case is controlled by the
20324 @code{set unwind-on-terminating-exception} command.
20327 @item set unwindonsignal
20328 @kindex set unwindonsignal
20329 @cindex unwind stack in called functions
20330 @cindex call dummy stack unwinding
20331 Set unwinding of the stack if a signal is received while in a function
20332 that @value{GDBN} called in the program being debugged. If set to on,
20333 @value{GDBN} unwinds the stack it created for the call and restores
20334 the context to what it was before the call. If set to off (the
20335 default), @value{GDBN} stops in the frame where the signal was
20338 @item show unwindonsignal
20339 @kindex show unwindonsignal
20340 Show the current setting of stack unwinding in the functions called by
20343 @item set unwind-on-terminating-exception
20344 @kindex set unwind-on-terminating-exception
20345 @cindex unwind stack in called functions with unhandled exceptions
20346 @cindex call dummy stack unwinding on unhandled exception.
20347 Set unwinding of the stack if a C@t{++} exception is raised, but left
20348 unhandled while in a function that @value{GDBN} called in the program being
20349 debugged. If set to on (the default), @value{GDBN} unwinds the stack
20350 it created for the call and restores the context to what it was before
20351 the call. If set to off, @value{GDBN} the exception is delivered to
20352 the default C@t{++} exception handler and the inferior terminated.
20354 @item show unwind-on-terminating-exception
20355 @kindex show unwind-on-terminating-exception
20356 Show the current setting of stack unwinding in the functions called by
20359 @item set may-call-functions
20360 @kindex set may-call-functions
20361 @cindex disabling calling functions in the program
20362 @cindex calling functions in the program, disabling
20363 Set permission to call functions in the program.
20364 This controls whether @value{GDBN} will attempt to call functions in
20365 the program, such as with expressions in the @code{print} command. It
20366 defaults to @code{on}.
20368 To call a function in the program, @value{GDBN} has to temporarily
20369 modify the state of the inferior. This has potentially undesired side
20370 effects. Also, having @value{GDBN} call nested functions is likely to
20371 be erroneous and may even crash the program being debugged. You can
20372 avoid such hazards by forbidding @value{GDBN} from calling functions
20373 in the program being debugged. If calling functions in the program
20374 is forbidden, GDB will throw an error when a command (such as printing
20375 an expression) starts a function call in the program.
20377 @item show may-call-functions
20378 @kindex show may-call-functions
20379 Show permission to call functions in the program.
20383 @subsection Calling functions with no debug info
20385 @cindex no debug info functions
20386 Sometimes, a function you wish to call is missing debug information.
20387 In such case, @value{GDBN} does not know the type of the function,
20388 including the types of the function's parameters. To avoid calling
20389 the inferior function incorrectly, which could result in the called
20390 function functioning erroneously and even crash, @value{GDBN} refuses
20391 to call the function unless you tell it the type of the function.
20393 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
20394 to do that. The simplest is to cast the call to the function's
20395 declared return type. For example:
20398 (@value{GDBP}) p getenv ("PATH")
20399 'getenv' has unknown return type; cast the call to its declared return type
20400 (@value{GDBP}) p (char *) getenv ("PATH")
20401 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
20404 Casting the return type of a no-debug function is equivalent to
20405 casting the function to a pointer to a prototyped function that has a
20406 prototype that matches the types of the passed-in arguments, and
20407 calling that. I.e., the call above is equivalent to:
20410 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
20414 and given this prototyped C or C++ function with float parameters:
20417 float multiply (float v1, float v2) @{ return v1 * v2; @}
20421 these calls are equivalent:
20424 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
20425 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
20428 If the function you wish to call is declared as unprototyped (i.e.@:
20429 old K&R style), you must use the cast-to-function-pointer syntax, so
20430 that @value{GDBN} knows that it needs to apply default argument
20431 promotions (promote float arguments to double). @xref{ABI, float
20432 promotion}. For example, given this unprototyped C function with
20433 float parameters, and no debug info:
20437 multiply_noproto (v1, v2)
20445 you call it like this:
20448 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
20452 @section Patching Programs
20454 @cindex patching binaries
20455 @cindex writing into executables
20456 @cindex writing into corefiles
20458 By default, @value{GDBN} opens the file containing your program's
20459 executable code (or the corefile) read-only. This prevents accidental
20460 alterations to machine code; but it also prevents you from intentionally
20461 patching your program's binary.
20463 If you'd like to be able to patch the binary, you can specify that
20464 explicitly with the @code{set write} command. For example, you might
20465 want to turn on internal debugging flags, or even to make emergency
20471 @itemx set write off
20472 If you specify @samp{set write on}, @value{GDBN} opens executable and
20473 core files for both reading and writing; if you specify @kbd{set write
20474 off} (the default), @value{GDBN} opens them read-only.
20476 If you have already loaded a file, you must load it again (using the
20477 @code{exec-file} or @code{core-file} command) after changing @code{set
20478 write}, for your new setting to take effect.
20482 Display whether executable files and core files are opened for writing
20483 as well as reading.
20486 @node Compiling and Injecting Code
20487 @section Compiling and injecting code in @value{GDBN}
20488 @cindex injecting code
20489 @cindex writing into executables
20490 @cindex compiling code
20492 @value{GDBN} supports on-demand compilation and code injection into
20493 programs running under @value{GDBN}. GCC 5.0 or higher built with
20494 @file{libcc1.so} must be installed for this functionality to be enabled.
20495 This functionality is implemented with the following commands.
20498 @kindex compile code
20499 @item compile code @var{source-code}
20500 @itemx compile code -raw @var{--} @var{source-code}
20501 Compile @var{source-code} with the compiler language found as the current
20502 language in @value{GDBN} (@pxref{Languages}). If compilation and
20503 injection is not supported with the current language specified in
20504 @value{GDBN}, or the compiler does not support this feature, an error
20505 message will be printed. If @var{source-code} compiles and links
20506 successfully, @value{GDBN} will load the object-code emitted,
20507 and execute it within the context of the currently selected inferior.
20508 It is important to note that the compiled code is executed immediately.
20509 After execution, the compiled code is removed from @value{GDBN} and any
20510 new types or variables you have defined will be deleted.
20512 The command allows you to specify @var{source-code} in two ways.
20513 The simplest method is to provide a single line of code to the command.
20517 compile code printf ("hello world\n");
20520 If you specify options on the command line as well as source code, they
20521 may conflict. The @samp{--} delimiter can be used to separate options
20522 from actual source code. E.g.:
20525 compile code -r -- printf ("hello world\n");
20528 Alternatively you can enter source code as multiple lines of text. To
20529 enter this mode, invoke the @samp{compile code} command without any text
20530 following the command. This will start the multiple-line editor and
20531 allow you to type as many lines of source code as required. When you
20532 have completed typing, enter @samp{end} on its own line to exit the
20537 >printf ("hello\n");
20538 >printf ("world\n");
20542 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
20543 provided @var{source-code} in a callable scope. In this case, you must
20544 specify the entry point of the code by defining a function named
20545 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
20546 inferior. Using @samp{-raw} option may be needed for example when
20547 @var{source-code} requires @samp{#include} lines which may conflict with
20548 inferior symbols otherwise.
20550 @kindex compile file
20551 @item compile file @var{filename}
20552 @itemx compile file -raw @var{filename}
20553 Like @code{compile code}, but take the source code from @var{filename}.
20556 compile file /home/user/example.c
20561 @item compile print [[@var{options}] --] @var{expr}
20562 @itemx compile print [[@var{options}] --] /@var{f} @var{expr}
20563 Compile and execute @var{expr} with the compiler language found as the
20564 current language in @value{GDBN} (@pxref{Languages}). By default the
20565 value of @var{expr} is printed in a format appropriate to its data type;
20566 you can choose a different format by specifying @samp{/@var{f}}, where
20567 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
20568 Formats}. The @code{compile print} command accepts the same options
20569 as the @code{print} command; see @ref{print options}.
20571 @item compile print [[@var{options}] --]
20572 @itemx compile print [[@var{options}] --] /@var{f}
20573 @cindex reprint the last value
20574 Alternatively you can enter the expression (source code producing it) as
20575 multiple lines of text. To enter this mode, invoke the @samp{compile print}
20576 command without any text following the command. This will start the
20577 multiple-line editor.
20581 The process of compiling and injecting the code can be inspected using:
20584 @anchor{set debug compile}
20585 @item set debug compile
20586 @cindex compile command debugging info
20587 Turns on or off display of @value{GDBN} process of compiling and
20588 injecting the code. The default is off.
20590 @item show debug compile
20591 Displays the current state of displaying @value{GDBN} process of
20592 compiling and injecting the code.
20594 @anchor{set debug compile-cplus-types}
20595 @item set debug compile-cplus-types
20596 @cindex compile C@t{++} type conversion
20597 Turns on or off the display of C@t{++} type conversion debugging information.
20598 The default is off.
20600 @item show debug compile-cplus-types
20601 Displays the current state of displaying debugging information for
20602 C@t{++} type conversion.
20605 @subsection Compilation options for the @code{compile} command
20607 @value{GDBN} needs to specify the right compilation options for the code
20608 to be injected, in part to make its ABI compatible with the inferior
20609 and in part to make the injected code compatible with @value{GDBN}'s
20613 The options used, in increasing precedence:
20616 @item target architecture and OS options (@code{gdbarch})
20617 These options depend on target processor type and target operating
20618 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
20619 (@code{-m64}) compilation option.
20621 @item compilation options recorded in the target
20622 @value{NGCC} (since version 4.7) stores the options used for compilation
20623 into @code{DW_AT_producer} part of DWARF debugging information according
20624 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
20625 explicitly specify @code{-g} during inferior compilation otherwise
20626 @value{NGCC} produces no DWARF. This feature is only relevant for
20627 platforms where @code{-g} produces DWARF by default, otherwise one may
20628 try to enforce DWARF by using @code{-gdwarf-4}.
20630 @item compilation options set by @code{set compile-args}
20634 You can override compilation options using the following command:
20637 @item set compile-args
20638 @cindex compile command options override
20639 Set compilation options used for compiling and injecting code with the
20640 @code{compile} commands. These options override any conflicting ones
20641 from the target architecture and/or options stored during inferior
20644 @item show compile-args
20645 Displays the current state of compilation options override.
20646 This does not show all the options actually used during compilation,
20647 use @ref{set debug compile} for that.
20650 @subsection Caveats when using the @code{compile} command
20652 There are a few caveats to keep in mind when using the @code{compile}
20653 command. As the caveats are different per language, the table below
20654 highlights specific issues on a per language basis.
20657 @item C code examples and caveats
20658 When the language in @value{GDBN} is set to @samp{C}, the compiler will
20659 attempt to compile the source code with a @samp{C} compiler. The source
20660 code provided to the @code{compile} command will have much the same
20661 access to variables and types as it normally would if it were part of
20662 the program currently being debugged in @value{GDBN}.
20664 Below is a sample program that forms the basis of the examples that
20665 follow. This program has been compiled and loaded into @value{GDBN},
20666 much like any other normal debugging session.
20669 void function1 (void)
20672 printf ("function 1\n");
20675 void function2 (void)
20690 For the purposes of the examples in this section, the program above has
20691 been compiled, loaded into @value{GDBN}, stopped at the function
20692 @code{main}, and @value{GDBN} is awaiting input from the user.
20694 To access variables and types for any program in @value{GDBN}, the
20695 program must be compiled and packaged with debug information. The
20696 @code{compile} command is not an exception to this rule. Without debug
20697 information, you can still use the @code{compile} command, but you will
20698 be very limited in what variables and types you can access.
20700 So with that in mind, the example above has been compiled with debug
20701 information enabled. The @code{compile} command will have access to
20702 all variables and types (except those that may have been optimized
20703 out). Currently, as @value{GDBN} has stopped the program in the
20704 @code{main} function, the @code{compile} command would have access to
20705 the variable @code{k}. You could invoke the @code{compile} command
20706 and type some source code to set the value of @code{k}. You can also
20707 read it, or do anything with that variable you would normally do in
20708 @code{C}. Be aware that changes to inferior variables in the
20709 @code{compile} command are persistent. In the following example:
20712 compile code k = 3;
20716 the variable @code{k} is now 3. It will retain that value until
20717 something else in the example program changes it, or another
20718 @code{compile} command changes it.
20720 Normal scope and access rules apply to source code compiled and
20721 injected by the @code{compile} command. In the example, the variables
20722 @code{j} and @code{k} are not accessible yet, because the program is
20723 currently stopped in the @code{main} function, where these variables
20724 are not in scope. Therefore, the following command
20727 compile code j = 3;
20731 will result in a compilation error message.
20733 Once the program is continued, execution will bring these variables in
20734 scope, and they will become accessible; then the code you specify via
20735 the @code{compile} command will be able to access them.
20737 You can create variables and types with the @code{compile} command as
20738 part of your source code. Variables and types that are created as part
20739 of the @code{compile} command are not visible to the rest of the program for
20740 the duration of its run. This example is valid:
20743 compile code int ff = 5; printf ("ff is %d\n", ff);
20746 However, if you were to type the following into @value{GDBN} after that
20747 command has completed:
20750 compile code printf ("ff is %d\n'', ff);
20754 a compiler error would be raised as the variable @code{ff} no longer
20755 exists. Object code generated and injected by the @code{compile}
20756 command is removed when its execution ends. Caution is advised
20757 when assigning to program variables values of variables created by the
20758 code submitted to the @code{compile} command. This example is valid:
20761 compile code int ff = 5; k = ff;
20764 The value of the variable @code{ff} is assigned to @code{k}. The variable
20765 @code{k} does not require the existence of @code{ff} to maintain the value
20766 it has been assigned. However, pointers require particular care in
20767 assignment. If the source code compiled with the @code{compile} command
20768 changed the address of a pointer in the example program, perhaps to a
20769 variable created in the @code{compile} command, that pointer would point
20770 to an invalid location when the command exits. The following example
20771 would likely cause issues with your debugged program:
20774 compile code int ff = 5; p = &ff;
20777 In this example, @code{p} would point to @code{ff} when the
20778 @code{compile} command is executing the source code provided to it.
20779 However, as variables in the (example) program persist with their
20780 assigned values, the variable @code{p} would point to an invalid
20781 location when the command exists. A general rule should be followed
20782 in that you should either assign @code{NULL} to any assigned pointers,
20783 or restore a valid location to the pointer before the command exits.
20785 Similar caution must be exercised with any structs, unions, and typedefs
20786 defined in @code{compile} command. Types defined in the @code{compile}
20787 command will no longer be available in the next @code{compile} command.
20788 Therefore, if you cast a variable to a type defined in the
20789 @code{compile} command, care must be taken to ensure that any future
20790 need to resolve the type can be achieved.
20793 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
20794 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
20795 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
20796 Compilation failed.
20797 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
20801 Variables that have been optimized away by the compiler are not
20802 accessible to the code submitted to the @code{compile} command.
20803 Access to those variables will generate a compiler error which @value{GDBN}
20804 will print to the console.
20807 @subsection Compiler search for the @code{compile} command
20809 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
20810 which may not be obvious for remote targets of different architecture
20811 than where @value{GDBN} is running. Environment variable @env{PATH} on
20812 @value{GDBN} host is searched for @value{NGCC} binary matching the
20813 target architecture and operating system. This search can be overriden
20814 by @code{set compile-gcc} @value{GDBN} command below. @env{PATH} is
20815 taken from shell that executed @value{GDBN}, it is not the value set by
20816 @value{GDBN} command @code{set environment}). @xref{Environment}.
20819 Specifically @env{PATH} is searched for binaries matching regular expression
20820 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
20821 debugged. @var{arch} is processor name --- multiarch is supported, so for
20822 example both @code{i386} and @code{x86_64} targets look for pattern
20823 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
20824 for pattern @code{s390x?}. @var{os} is currently supported only for
20825 pattern @code{linux(-gnu)?}.
20827 On Posix hosts the compiler driver @value{GDBN} needs to find also
20828 shared library @file{libcc1.so} from the compiler. It is searched in
20829 default shared library search path (overridable with usual environment
20830 variable @env{LD_LIBRARY_PATH}), unrelated to @env{PATH} or @code{set
20831 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
20832 according to the installation of the found compiler --- as possibly
20833 specified by the @code{set compile-gcc} command.
20836 @item set compile-gcc
20837 @cindex compile command driver filename override
20838 Set compilation command used for compiling and injecting code with the
20839 @code{compile} commands. If this option is not set (it is set to
20840 an empty string), the search described above will occur --- that is the
20843 @item show compile-gcc
20844 Displays the current compile command @value{NGCC} driver filename.
20845 If set, it is the main command @command{gcc}, found usually for example
20846 under name @file{x86_64-linux-gnu-gcc}.
20850 @chapter @value{GDBN} Files
20852 @value{GDBN} needs to know the file name of the program to be debugged,
20853 both in order to read its symbol table and in order to start your
20854 program. To debug a core dump of a previous run, you must also tell
20855 @value{GDBN} the name of the core dump file.
20858 * Files:: Commands to specify files
20859 * File Caching:: Information about @value{GDBN}'s file caching
20860 * Separate Debug Files:: Debugging information in separate files
20861 * MiniDebugInfo:: Debugging information in a special section
20862 * Index Files:: Index files speed up GDB
20863 * Symbol Errors:: Errors reading symbol files
20864 * Data Files:: GDB data files
20868 @section Commands to Specify Files
20870 @cindex symbol table
20871 @cindex core dump file
20873 You may want to specify executable and core dump file names. The usual
20874 way to do this is at start-up time, using the arguments to
20875 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
20876 Out of @value{GDBN}}).
20878 Occasionally it is necessary to change to a different file during a
20879 @value{GDBN} session. Or you may run @value{GDBN} and forget to
20880 specify a file you want to use. Or you are debugging a remote target
20881 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
20882 Program}). In these situations the @value{GDBN} commands to specify
20883 new files are useful.
20886 @cindex executable file
20888 @item file @var{filename}
20889 Use @var{filename} as the program to be debugged. It is read for its
20890 symbols and for the contents of pure memory. It is also the program
20891 executed when you use the @code{run} command. If you do not specify a
20892 directory and the file is not found in the @value{GDBN} working directory,
20893 @value{GDBN} uses the environment variable @env{PATH} as a list of
20894 directories to search, just as the shell does when looking for a program
20895 to run. You can change the value of this variable, for both @value{GDBN}
20896 and your program, using the @code{path} command.
20898 @cindex unlinked object files
20899 @cindex patching object files
20900 You can load unlinked object @file{.o} files into @value{GDBN} using
20901 the @code{file} command. You will not be able to ``run'' an object
20902 file, but you can disassemble functions and inspect variables. Also,
20903 if the underlying BFD functionality supports it, you could use
20904 @kbd{gdb -write} to patch object files using this technique. Note
20905 that @value{GDBN} can neither interpret nor modify relocations in this
20906 case, so branches and some initialized variables will appear to go to
20907 the wrong place. But this feature is still handy from time to time.
20910 @code{file} with no argument makes @value{GDBN} discard any information it
20911 has on both executable file and the symbol table.
20914 @item exec-file @r{[} @var{filename} @r{]}
20915 Specify that the program to be run (but not the symbol table) is found
20916 in @var{filename}. @value{GDBN} searches the environment variable @env{PATH}
20917 if necessary to locate your program. Omitting @var{filename} means to
20918 discard information on the executable file.
20920 @kindex symbol-file
20921 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
20922 Read symbol table information from file @var{filename}. @env{PATH} is
20923 searched when necessary. Use the @code{file} command to get both symbol
20924 table and program to run from the same file.
20926 If an optional @var{offset} is specified, it is added to the start
20927 address of each section in the symbol file. This is useful if the
20928 program is relocated at runtime, such as the Linux kernel with kASLR
20931 @code{symbol-file} with no argument clears out @value{GDBN} information on your
20932 program's symbol table.
20934 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
20935 some breakpoints and auto-display expressions. This is because they may
20936 contain pointers to the internal data recording symbols and data types,
20937 which are part of the old symbol table data being discarded inside
20940 @code{symbol-file} does not repeat if you press @key{RET} again after
20943 When @value{GDBN} is configured for a particular environment, it
20944 understands debugging information in whatever format is the standard
20945 generated for that environment; you may use either a @sc{gnu} compiler, or
20946 other compilers that adhere to the local conventions.
20947 Best results are usually obtained from @sc{gnu} compilers; for example,
20948 using @code{@value{NGCC}} you can generate debugging information for
20951 For most kinds of object files, with the exception of old SVR3 systems
20952 using COFF, the @code{symbol-file} command does not normally read the
20953 symbol table in full right away. Instead, it scans the symbol table
20954 quickly to find which source files and which symbols are present. The
20955 details are read later, one source file at a time, as they are needed.
20957 The purpose of this two-stage reading strategy is to make @value{GDBN}
20958 start up faster. For the most part, it is invisible except for
20959 occasional pauses while the symbol table details for a particular source
20960 file are being read. (The @code{set verbose} command can turn these
20961 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
20962 Warnings and Messages}.)
20964 We have not implemented the two-stage strategy for COFF yet. When the
20965 symbol table is stored in COFF format, @code{symbol-file} reads the
20966 symbol table data in full right away. Note that ``stabs-in-COFF''
20967 still does the two-stage strategy, since the debug info is actually
20971 @cindex reading symbols immediately
20972 @cindex symbols, reading immediately
20973 @item symbol-file @r{[} -readnow @r{]} @var{filename}
20974 @itemx file @r{[} -readnow @r{]} @var{filename}
20975 You can override the @value{GDBN} two-stage strategy for reading symbol
20976 tables by using the @samp{-readnow} option with any of the commands that
20977 load symbol table information, if you want to be sure @value{GDBN} has the
20978 entire symbol table available.
20980 @cindex @code{-readnever}, option for symbol-file command
20981 @cindex never read symbols
20982 @cindex symbols, never read
20983 @item symbol-file @r{[} -readnever @r{]} @var{filename}
20984 @itemx file @r{[} -readnever @r{]} @var{filename}
20985 You can instruct @value{GDBN} to never read the symbolic information
20986 contained in @var{filename} by using the @samp{-readnever} option.
20987 @xref{--readnever}.
20989 @c FIXME: for now no mention of directories, since this seems to be in
20990 @c flux. 13mar1992 status is that in theory GDB would look either in
20991 @c current dir or in same dir as myprog; but issues like competing
20992 @c GDB's, or clutter in system dirs, mean that in practice right now
20993 @c only current dir is used. FFish says maybe a special GDB hierarchy
20994 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
20998 @item core-file @r{[}@var{filename}@r{]}
21000 Specify the whereabouts of a core dump file to be used as the ``contents
21001 of memory''. Traditionally, core files contain only some parts of the
21002 address space of the process that generated them; @value{GDBN} can access the
21003 executable file itself for other parts.
21005 @code{core-file} with no argument specifies that no core file is
21008 Note that the core file is ignored when your program is actually running
21009 under @value{GDBN}. So, if you have been running your program and you
21010 wish to debug a core file instead, you must kill the subprocess in which
21011 the program is running. To do this, use the @code{kill} command
21012 (@pxref{Kill Process, ,Killing the Child Process}).
21014 @kindex add-symbol-file
21015 @cindex dynamic linking
21016 @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{]}
21017 The @code{add-symbol-file} command reads additional symbol table
21018 information from the file @var{filename}. You would use this command
21019 when @var{filename} has been dynamically loaded (by some other means)
21020 into the program that is running. The @var{textaddress} parameter gives
21021 the memory address at which the file's text section has been loaded.
21022 You can additionally specify the base address of other sections using
21023 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
21024 If a section is omitted, @value{GDBN} will use its default addresses
21025 as found in @var{filename}. Any @var{address} or @var{textaddress}
21026 can be given as an expression.
21028 If an optional @var{offset} is specified, it is added to the start
21029 address of each section, except those for which the address was
21030 specified explicitly.
21032 The symbol table of the file @var{filename} is added to the symbol table
21033 originally read with the @code{symbol-file} command. You can use the
21034 @code{add-symbol-file} command any number of times; the new symbol data
21035 thus read is kept in addition to the old.
21037 Changes can be reverted using the command @code{remove-symbol-file}.
21039 @cindex relocatable object files, reading symbols from
21040 @cindex object files, relocatable, reading symbols from
21041 @cindex reading symbols from relocatable object files
21042 @cindex symbols, reading from relocatable object files
21043 @cindex @file{.o} files, reading symbols from
21044 Although @var{filename} is typically a shared library file, an
21045 executable file, or some other object file which has been fully
21046 relocated for loading into a process, you can also load symbolic
21047 information from relocatable @file{.o} files, as long as:
21051 the file's symbolic information refers only to linker symbols defined in
21052 that file, not to symbols defined by other object files,
21054 every section the file's symbolic information refers to has actually
21055 been loaded into the inferior, as it appears in the file, and
21057 you can determine the address at which every section was loaded, and
21058 provide these to the @code{add-symbol-file} command.
21062 Some embedded operating systems, like Sun Chorus and VxWorks, can load
21063 relocatable files into an already running program; such systems
21064 typically make the requirements above easy to meet. However, it's
21065 important to recognize that many native systems use complex link
21066 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
21067 assembly, for example) that make the requirements difficult to meet. In
21068 general, one cannot assume that using @code{add-symbol-file} to read a
21069 relocatable object file's symbolic information will have the same effect
21070 as linking the relocatable object file into the program in the normal
21073 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
21075 @kindex remove-symbol-file
21076 @item remove-symbol-file @var{filename}
21077 @item remove-symbol-file -a @var{address}
21078 Remove a symbol file added via the @code{add-symbol-file} command. The
21079 file to remove can be identified by its @var{filename} or by an @var{address}
21080 that lies within the boundaries of this symbol file in memory. Example:
21083 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
21084 add symbol table from file "/home/user/gdb/mylib.so" at
21085 .text_addr = 0x7ffff7ff9480
21087 Reading symbols from /home/user/gdb/mylib.so...
21088 (gdb) remove-symbol-file -a 0x7ffff7ff9480
21089 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
21094 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
21096 @kindex add-symbol-file-from-memory
21097 @cindex @code{syscall DSO}
21098 @cindex load symbols from memory
21099 @item add-symbol-file-from-memory @var{address}
21100 Load symbols from the given @var{address} in a dynamically loaded
21101 object file whose image is mapped directly into the inferior's memory.
21102 For example, the Linux kernel maps a @code{syscall DSO} into each
21103 process's address space; this DSO provides kernel-specific code for
21104 some system calls. The argument can be any expression whose
21105 evaluation yields the address of the file's shared object file header.
21106 For this command to work, you must have used @code{symbol-file} or
21107 @code{exec-file} commands in advance.
21110 @item section @var{section} @var{addr}
21111 The @code{section} command changes the base address of the named
21112 @var{section} of the exec file to @var{addr}. This can be used if the
21113 exec file does not contain section addresses, (such as in the
21114 @code{a.out} format), or when the addresses specified in the file
21115 itself are wrong. Each section must be changed separately. The
21116 @code{info files} command, described below, lists all the sections and
21120 @kindex info target
21123 @code{info files} and @code{info target} are synonymous; both print the
21124 current target (@pxref{Targets, ,Specifying a Debugging Target}),
21125 including the names of the executable and core dump files currently in
21126 use by @value{GDBN}, and the files from which symbols were loaded. The
21127 command @code{help target} lists all possible targets rather than
21130 @kindex maint info sections
21131 @item maint info sections @r{[}-all-objects@r{]} @r{[}@var{filter-list}@r{]}
21132 Another command that can give you extra information about program sections
21133 is @code{maint info sections}. In addition to the section information
21134 displayed by @code{info files}, this command displays the flags and file
21135 offset of each section in the executable and core dump files.
21137 When @samp{-all-objects} is passed then sections from all loaded object
21138 files, including shared libraries, are printed.
21140 The optional @var{filter-list} is a space separated list of filter
21141 keywords. Sections that match any one of the filter criteria will be
21142 printed. There are two types of filter:
21145 @item @var{section-name}
21146 Display information about any section named @var{section-name}.
21147 @item @var{section-flag}
21148 Display information for any section with @var{section-flag}. The
21149 section flags that @value{GDBN} currently knows about are:
21152 Section will have space allocated in the process when loaded.
21153 Set for all sections except those containing debug information.
21155 Section will be loaded from the file into the child process memory.
21156 Set for pre-initialized code and data, clear for @code{.bss} sections.
21158 Section needs to be relocated before loading.
21160 Section cannot be modified by the child process.
21162 Section contains executable code only.
21164 Section contains data only (no executable code).
21166 Section will reside in ROM.
21168 Section contains data for constructor/destructor lists.
21170 Section is not empty.
21172 An instruction to the linker to not output the section.
21173 @item COFF_SHARED_LIBRARY
21174 A notification to the linker that the section contains
21175 COFF shared library information.
21177 Section contains common symbols.
21181 @kindex maint info target-sections
21182 @item maint info target-sections
21183 This command prints @value{GDBN}'s internal section table. For each
21184 target @value{GDBN} maintains a table containing the allocatable
21185 sections from all currently mapped objects, along with information
21186 about where the section is mapped.
21188 @kindex set trust-readonly-sections
21189 @cindex read-only sections
21190 @item set trust-readonly-sections on
21191 Tell @value{GDBN} that readonly sections in your object file
21192 really are read-only (i.e.@: that their contents will not change).
21193 In that case, @value{GDBN} can fetch values from these sections
21194 out of the object file, rather than from the target program.
21195 For some targets (notably embedded ones), this can be a significant
21196 enhancement to debugging performance.
21198 The default is off.
21200 @item set trust-readonly-sections off
21201 Tell @value{GDBN} not to trust readonly sections. This means that
21202 the contents of the section might change while the program is running,
21203 and must therefore be fetched from the target when needed.
21205 @item show trust-readonly-sections
21206 Show the current setting of trusting readonly sections.
21209 All file-specifying commands allow both absolute and relative file names
21210 as arguments. @value{GDBN} always converts the file name to an absolute file
21211 name and remembers it that way.
21213 @cindex shared libraries
21214 @anchor{Shared Libraries}
21215 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
21216 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
21217 DSBT (TIC6X) shared libraries.
21219 On MS-Windows @value{GDBN} must be linked with the Expat library to support
21220 shared libraries. @xref{Expat}.
21222 @value{GDBN} automatically loads symbol definitions from shared libraries
21223 when you use the @code{run} command, or when you examine a core file.
21224 (Before you issue the @code{run} command, @value{GDBN} does not understand
21225 references to a function in a shared library, however---unless you are
21226 debugging a core file).
21228 @c FIXME: some @value{GDBN} release may permit some refs to undef
21229 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
21230 @c FIXME...lib; check this from time to time when updating manual
21232 There are times, however, when you may wish to not automatically load
21233 symbol definitions from shared libraries, such as when they are
21234 particularly large or there are many of them.
21236 To control the automatic loading of shared library symbols, use the
21240 @kindex set auto-solib-add
21241 @item set auto-solib-add @var{mode}
21242 If @var{mode} is @code{on}, symbols from all shared object libraries
21243 will be loaded automatically when the inferior begins execution, you
21244 attach to an independently started inferior, or when the dynamic linker
21245 informs @value{GDBN} that a new library has been loaded. If @var{mode}
21246 is @code{off}, symbols must be loaded manually, using the
21247 @code{sharedlibrary} command. The default value is @code{on}.
21249 @cindex memory used for symbol tables
21250 If your program uses lots of shared libraries with debug info that
21251 takes large amounts of memory, you can decrease the @value{GDBN}
21252 memory footprint by preventing it from automatically loading the
21253 symbols from shared libraries. To that end, type @kbd{set
21254 auto-solib-add off} before running the inferior, then load each
21255 library whose debug symbols you do need with @kbd{sharedlibrary
21256 @var{regexp}}, where @var{regexp} is a regular expression that matches
21257 the libraries whose symbols you want to be loaded.
21259 @kindex show auto-solib-add
21260 @item show auto-solib-add
21261 Display the current autoloading mode.
21264 @cindex load shared library
21265 To explicitly load shared library symbols, use the @code{sharedlibrary}
21269 @kindex info sharedlibrary
21271 @item info share @var{regex}
21272 @itemx info sharedlibrary @var{regex}
21273 Print the names of the shared libraries which are currently loaded
21274 that match @var{regex}. If @var{regex} is omitted then print
21275 all shared libraries that are loaded.
21278 @item info dll @var{regex}
21279 This is an alias of @code{info sharedlibrary}.
21281 @kindex sharedlibrary
21283 @item sharedlibrary @var{regex}
21284 @itemx share @var{regex}
21285 Load shared object library symbols for files matching a
21286 Unix regular expression.
21287 As with files loaded automatically, it only loads shared libraries
21288 required by your program for a core file or after typing @code{run}. If
21289 @var{regex} is omitted all shared libraries required by your program are
21292 @item nosharedlibrary
21293 @kindex nosharedlibrary
21294 @cindex unload symbols from shared libraries
21295 Unload all shared object library symbols. This discards all symbols
21296 that have been loaded from all shared libraries. Symbols from shared
21297 libraries that were loaded by explicit user requests are not
21301 Sometimes you may wish that @value{GDBN} stops and gives you control
21302 when any of shared library events happen. The best way to do this is
21303 to use @code{catch load} and @code{catch unload} (@pxref{Set
21306 @value{GDBN} also supports the @code{set stop-on-solib-events}
21307 command for this. This command exists for historical reasons. It is
21308 less useful than setting a catchpoint, because it does not allow for
21309 conditions or commands as a catchpoint does.
21312 @item set stop-on-solib-events
21313 @kindex set stop-on-solib-events
21314 This command controls whether @value{GDBN} should give you control
21315 when the dynamic linker notifies it about some shared library event.
21316 The most common event of interest is loading or unloading of a new
21319 @item show stop-on-solib-events
21320 @kindex show stop-on-solib-events
21321 Show whether @value{GDBN} stops and gives you control when shared
21322 library events happen.
21325 Shared libraries are also supported in many cross or remote debugging
21326 configurations. @value{GDBN} needs to have access to the target's libraries;
21327 this can be accomplished either by providing copies of the libraries
21328 on the host system, or by asking @value{GDBN} to automatically retrieve the
21329 libraries from the target. If copies of the target libraries are
21330 provided, they need to be the same as the target libraries, although the
21331 copies on the target can be stripped as long as the copies on the host are
21334 @cindex where to look for shared libraries
21335 For remote debugging, you need to tell @value{GDBN} where the target
21336 libraries are, so that it can load the correct copies---otherwise, it
21337 may try to load the host's libraries. @value{GDBN} has two variables
21338 to specify the search directories for target libraries.
21341 @cindex prefix for executable and shared library file names
21342 @cindex system root, alternate
21343 @kindex set solib-absolute-prefix
21344 @kindex set sysroot
21345 @item set sysroot @var{path}
21346 Use @var{path} as the system root for the program being debugged. Any
21347 absolute shared library paths will be prefixed with @var{path}; many
21348 runtime loaders store the absolute paths to the shared library in the
21349 target program's memory. When starting processes remotely, and when
21350 attaching to already-running processes (local or remote), their
21351 executable filenames will be prefixed with @var{path} if reported to
21352 @value{GDBN} as absolute by the operating system. If you use
21353 @code{set sysroot} to find executables and shared libraries, they need
21354 to be laid out in the same way that they are on the target, with
21355 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
21358 If @var{path} starts with the sequence @file{target:} and the target
21359 system is remote then @value{GDBN} will retrieve the target binaries
21360 from the remote system. This is only supported when using a remote
21361 target that supports the @code{remote get} command (@pxref{File
21362 Transfer,,Sending files to a remote system}). The part of @var{path}
21363 following the initial @file{target:} (if present) is used as system
21364 root prefix on the remote file system. If @var{path} starts with the
21365 sequence @file{remote:} this is converted to the sequence
21366 @file{target:} by @code{set sysroot}@footnote{Historically the
21367 functionality to retrieve binaries from the remote system was
21368 provided by prefixing @var{path} with @file{remote:}}. If you want
21369 to specify a local system root using a directory that happens to be
21370 named @file{target:} or @file{remote:}, you need to use some
21371 equivalent variant of the name like @file{./target:}.
21373 For targets with an MS-DOS based filesystem, such as MS-Windows,
21374 @value{GDBN} tries prefixing a few variants of the target
21375 absolute file name with @var{path}. But first, on Unix hosts,
21376 @value{GDBN} converts all backslash directory separators into forward
21377 slashes, because the backslash is not a directory separator on Unix:
21380 c:\foo\bar.dll @result{} c:/foo/bar.dll
21383 Then, @value{GDBN} attempts prefixing the target file name with
21384 @var{path}, and looks for the resulting file name in the host file
21388 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
21391 If that does not find the binary, @value{GDBN} tries removing
21392 the @samp{:} character from the drive spec, both for convenience, and,
21393 for the case of the host file system not supporting file names with
21397 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
21400 This makes it possible to have a system root that mirrors a target
21401 with more than one drive. E.g., you may want to setup your local
21402 copies of the target system shared libraries like so (note @samp{c} vs
21406 @file{/path/to/sysroot/c/sys/bin/foo.dll}
21407 @file{/path/to/sysroot/c/sys/bin/bar.dll}
21408 @file{/path/to/sysroot/z/sys/bin/bar.dll}
21412 and point the system root at @file{/path/to/sysroot}, so that
21413 @value{GDBN} can find the correct copies of both
21414 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
21416 If that still does not find the binary, @value{GDBN} tries
21417 removing the whole drive spec from the target file name:
21420 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
21423 This last lookup makes it possible to not care about the drive name,
21424 if you don't want or need to.
21426 The @code{set solib-absolute-prefix} command is an alias for @code{set
21429 @cindex default system root
21430 @cindex @samp{--with-sysroot}
21431 You can set the default system root by using the configure-time
21432 @samp{--with-sysroot} option. If the system root is inside
21433 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
21434 @samp{--exec-prefix}), then the default system root will be updated
21435 automatically if the installed @value{GDBN} is moved to a new
21438 @kindex show sysroot
21440 Display the current executable and shared library prefix.
21442 @kindex set solib-search-path
21443 @item set solib-search-path @var{path}
21444 If this variable is set, @var{path} is a colon-separated list of
21445 directories to search for shared libraries. @samp{solib-search-path}
21446 is used after @samp{sysroot} fails to locate the library, or if the
21447 path to the library is relative instead of absolute. If you want to
21448 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
21449 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
21450 finding your host's libraries. @samp{sysroot} is preferred; setting
21451 it to a nonexistent directory may interfere with automatic loading
21452 of shared library symbols.
21454 @kindex show solib-search-path
21455 @item show solib-search-path
21456 Display the current shared library search path.
21458 @cindex DOS file-name semantics of file names.
21459 @kindex set target-file-system-kind (unix|dos-based|auto)
21460 @kindex show target-file-system-kind
21461 @item set target-file-system-kind @var{kind}
21462 Set assumed file system kind for target reported file names.
21464 Shared library file names as reported by the target system may not
21465 make sense as is on the system @value{GDBN} is running on. For
21466 example, when remote debugging a target that has MS-DOS based file
21467 system semantics, from a Unix host, the target may be reporting to
21468 @value{GDBN} a list of loaded shared libraries with file names such as
21469 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
21470 drive letters, so the @samp{c:\} prefix is not normally understood as
21471 indicating an absolute file name, and neither is the backslash
21472 normally considered a directory separator character. In that case,
21473 the native file system would interpret this whole absolute file name
21474 as a relative file name with no directory components. This would make
21475 it impossible to point @value{GDBN} at a copy of the remote target's
21476 shared libraries on the host using @code{set sysroot}, and impractical
21477 with @code{set solib-search-path}. Setting
21478 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
21479 to interpret such file names similarly to how the target would, and to
21480 map them to file names valid on @value{GDBN}'s native file system
21481 semantics. The value of @var{kind} can be @code{"auto"}, in addition
21482 to one of the supported file system kinds. In that case, @value{GDBN}
21483 tries to determine the appropriate file system variant based on the
21484 current target's operating system (@pxref{ABI, ,Configuring the
21485 Current ABI}). The supported file system settings are:
21489 Instruct @value{GDBN} to assume the target file system is of Unix
21490 kind. Only file names starting the forward slash (@samp{/}) character
21491 are considered absolute, and the directory separator character is also
21495 Instruct @value{GDBN} to assume the target file system is DOS based.
21496 File names starting with either a forward slash, or a drive letter
21497 followed by a colon (e.g., @samp{c:}), are considered absolute, and
21498 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
21499 considered directory separators.
21502 Instruct @value{GDBN} to use the file system kind associated with the
21503 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
21504 This is the default.
21508 @cindex file name canonicalization
21509 @cindex base name differences
21510 When processing file names provided by the user, @value{GDBN}
21511 frequently needs to compare them to the file names recorded in the
21512 program's debug info. Normally, @value{GDBN} compares just the
21513 @dfn{base names} of the files as strings, which is reasonably fast
21514 even for very large programs. (The base name of a file is the last
21515 portion of its name, after stripping all the leading directories.)
21516 This shortcut in comparison is based upon the assumption that files
21517 cannot have more than one base name. This is usually true, but
21518 references to files that use symlinks or similar filesystem
21519 facilities violate that assumption. If your program records files
21520 using such facilities, or if you provide file names to @value{GDBN}
21521 using symlinks etc., you can set @code{basenames-may-differ} to
21522 @code{true} to instruct @value{GDBN} to completely canonicalize each
21523 pair of file names it needs to compare. This will make file-name
21524 comparisons accurate, but at a price of a significant slowdown.
21527 @item set basenames-may-differ
21528 @kindex set basenames-may-differ
21529 Set whether a source file may have multiple base names.
21531 @item show basenames-may-differ
21532 @kindex show basenames-may-differ
21533 Show whether a source file may have multiple base names.
21537 @section File Caching
21538 @cindex caching of opened files
21539 @cindex caching of bfd objects
21541 To speed up file loading, and reduce memory usage, @value{GDBN} will
21542 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
21543 BFD, bfd, The Binary File Descriptor Library}. The following commands
21544 allow visibility and control of the caching behavior.
21547 @kindex maint info bfds
21548 @item maint info bfds
21549 This prints information about each @code{bfd} object that is known to
21552 @kindex maint set bfd-sharing
21553 @kindex maint show bfd-sharing
21554 @kindex bfd caching
21555 @item maint set bfd-sharing
21556 @item maint show bfd-sharing
21557 Control whether @code{bfd} objects can be shared. When sharing is
21558 enabled @value{GDBN} reuses already open @code{bfd} objects rather
21559 than reopening the same file. Turning sharing off does not cause
21560 already shared @code{bfd} objects to be unshared, but all future files
21561 that are opened will create a new @code{bfd} object. Similarly,
21562 re-enabling sharing does not cause multiple existing @code{bfd}
21563 objects to be collapsed into a single shared @code{bfd} object.
21565 @kindex set debug bfd-cache @var{level}
21566 @kindex bfd caching
21567 @item set debug bfd-cache @var{level}
21568 Turns on debugging of the bfd cache, setting the level to @var{level}.
21570 @kindex show debug bfd-cache
21571 @kindex bfd caching
21572 @item show debug bfd-cache
21573 Show the current debugging level of the bfd cache.
21576 @node Separate Debug Files
21577 @section Debugging Information in Separate Files
21578 @cindex separate debugging information files
21579 @cindex debugging information in separate files
21580 @cindex @file{.debug} subdirectories
21581 @cindex debugging information directory, global
21582 @cindex global debugging information directories
21583 @cindex build ID, and separate debugging files
21584 @cindex @file{.build-id} directory
21586 @value{GDBN} allows you to put a program's debugging information in a
21587 file separate from the executable itself, in a way that allows
21588 @value{GDBN} to find and load the debugging information automatically.
21589 Since debugging information can be very large---sometimes larger
21590 than the executable code itself---some systems distribute debugging
21591 information for their executables in separate files, which users can
21592 install only when they need to debug a problem.
21594 @value{GDBN} supports two ways of specifying the separate debug info
21599 The executable contains a @dfn{debug link} that specifies the name of
21600 the separate debug info file. The separate debug file's name is
21601 usually @file{@var{executable}.debug}, where @var{executable} is the
21602 name of the corresponding executable file without leading directories
21603 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
21604 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
21605 checksum for the debug file, which @value{GDBN} uses to validate that
21606 the executable and the debug file came from the same build.
21610 The executable contains a @dfn{build ID}, a unique bit string that is
21611 also present in the corresponding debug info file. (This is supported
21612 only on some operating systems, when using the ELF or PE file formats
21613 for binary files and the @sc{gnu} Binutils.) For more details about
21614 this feature, see the description of the @option{--build-id}
21615 command-line option in @ref{Options, , Command Line Options, ld,
21616 The GNU Linker}. The debug info file's name is not specified
21617 explicitly by the build ID, but can be computed from the build ID, see
21621 Depending on the way the debug info file is specified, @value{GDBN}
21622 uses two different methods of looking for the debug file:
21626 For the ``debug link'' method, @value{GDBN} looks up the named file in
21627 the directory of the executable file, then in a subdirectory of that
21628 directory named @file{.debug}, and finally under each one of the
21629 global debug directories, in a subdirectory whose name is identical to
21630 the leading directories of the executable's absolute file name. (On
21631 MS-Windows/MS-DOS, the drive letter of the executable's leading
21632 directories is converted to a one-letter subdirectory, i.e.@:
21633 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
21634 filesystems disallow colons in file names.)
21637 For the ``build ID'' method, @value{GDBN} looks in the
21638 @file{.build-id} subdirectory of each one of the global debug directories for
21639 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
21640 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
21641 are the rest of the bit string. (Real build ID strings are 32 or more
21642 hex characters, not 10.) @value{GDBN} can automatically query
21643 @code{debuginfod} servers using build IDs in order to download separate debug
21644 files that cannot be found locally. For more information see @ref{Debuginfod}.
21647 So, for example, suppose you ask @value{GDBN} to debug
21648 @file{/usr/bin/ls}, which has a debug link that specifies the
21649 file @file{ls.debug}, and a build ID whose value in hex is
21650 @code{abcdef1234}. If the list of the global debug directories includes
21651 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
21652 debug information files, in the indicated order:
21656 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
21658 @file{/usr/bin/ls.debug}
21660 @file{/usr/bin/.debug/ls.debug}
21662 @file{/usr/lib/debug/usr/bin/ls.debug}.
21665 If the debug file still has not been found and @code{debuginfod}
21666 (@pxref{Debuginfod}) is enabled, @value{GDBN} will attempt to download the
21667 file from @code{debuginfod} servers.
21669 @anchor{debug-file-directory}
21670 Global debugging info directories default to what is set by @value{GDBN}
21671 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
21672 you can also set the global debugging info directories, and view the list
21673 @value{GDBN} is currently using.
21677 @kindex set debug-file-directory
21678 @item set debug-file-directory @var{directories}
21679 Set the directories which @value{GDBN} searches for separate debugging
21680 information files to @var{directory}. Multiple path components can be set
21681 concatenating them by a path separator.
21683 @kindex show debug-file-directory
21684 @item show debug-file-directory
21685 Show the directories @value{GDBN} searches for separate debugging
21690 @cindex @code{.gnu_debuglink} sections
21691 @cindex debug link sections
21692 A debug link is a special section of the executable file named
21693 @code{.gnu_debuglink}. The section must contain:
21697 A filename, with any leading directory components removed, followed by
21700 zero to three bytes of padding, as needed to reach the next four-byte
21701 boundary within the section, and
21703 a four-byte CRC checksum, stored in the same endianness used for the
21704 executable file itself. The checksum is computed on the debugging
21705 information file's full contents by the function given below, passing
21706 zero as the @var{crc} argument.
21709 Any executable file format can carry a debug link, as long as it can
21710 contain a section named @code{.gnu_debuglink} with the contents
21713 @cindex @code{.note.gnu.build-id} sections
21714 @cindex build ID sections
21715 The build ID is a special section in the executable file (and in other
21716 ELF binary files that @value{GDBN} may consider). This section is
21717 often named @code{.note.gnu.build-id}, but that name is not mandatory.
21718 It contains unique identification for the built files---the ID remains
21719 the same across multiple builds of the same build tree. The default
21720 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
21721 content for the build ID string. The same section with an identical
21722 value is present in the original built binary with symbols, in its
21723 stripped variant, and in the separate debugging information file.
21725 The debugging information file itself should be an ordinary
21726 executable, containing a full set of linker symbols, sections, and
21727 debugging information. The sections of the debugging information file
21728 should have the same names, addresses, and sizes as the original file,
21729 but they need not contain any data---much like a @code{.bss} section
21730 in an ordinary executable.
21732 The @sc{gnu} binary utilities (Binutils) package includes the
21733 @samp{objcopy} utility that can produce
21734 the separated executable / debugging information file pairs using the
21735 following commands:
21738 @kbd{objcopy --only-keep-debug foo foo.debug}
21743 These commands remove the debugging
21744 information from the executable file @file{foo} and place it in the file
21745 @file{foo.debug}. You can use the first, second or both methods to link the
21750 The debug link method needs the following additional command to also leave
21751 behind a debug link in @file{foo}:
21754 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
21757 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
21758 a version of the @code{strip} command such that the command @kbd{strip foo -f
21759 foo.debug} has the same functionality as the two @code{objcopy} commands and
21760 the @code{ln -s} command above, together.
21763 Build ID gets embedded into the main executable using @code{ld --build-id} or
21764 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
21765 compatibility fixes for debug files separation are present in @sc{gnu} binary
21766 utilities (Binutils) package since version 2.18.
21771 @cindex CRC algorithm definition
21772 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
21773 IEEE 802.3 using the polynomial:
21775 @c TexInfo requires naked braces for multi-digit exponents for Tex
21776 @c output, but this causes HTML output to barf. HTML has to be set using
21777 @c raw commands. So we end up having to specify this equation in 2
21782 <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>
21783 + <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
21789 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
21790 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
21794 The function is computed byte at a time, taking the least
21795 significant bit of each byte first. The initial pattern
21796 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
21797 the final result is inverted to ensure trailing zeros also affect the
21800 @emph{Note:} This is the same CRC polynomial as used in handling the
21801 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
21802 However in the case of the Remote Serial Protocol, the CRC is computed
21803 @emph{most} significant bit first, and the result is not inverted, so
21804 trailing zeros have no effect on the CRC value.
21806 To complete the description, we show below the code of the function
21807 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
21808 initially supplied @code{crc} argument means that an initial call to
21809 this function passing in zero will start computing the CRC using
21812 @kindex gnu_debuglink_crc32
21815 gnu_debuglink_crc32 (unsigned long crc,
21816 unsigned char *buf, size_t len)
21818 static const unsigned long crc32_table[256] =
21820 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
21821 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
21822 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
21823 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
21824 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
21825 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
21826 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
21827 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
21828 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
21829 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
21830 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
21831 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
21832 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
21833 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
21834 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
21835 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
21836 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
21837 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
21838 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
21839 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
21840 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
21841 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
21842 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
21843 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
21844 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
21845 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
21846 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
21847 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
21848 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
21849 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
21850 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
21851 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
21852 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
21853 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
21854 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
21855 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
21856 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
21857 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
21858 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
21859 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
21860 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
21861 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
21862 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
21863 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
21864 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
21865 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
21866 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
21867 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
21868 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
21869 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
21870 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
21873 unsigned char *end;
21875 crc = ~crc & 0xffffffff;
21876 for (end = buf + len; buf < end; ++buf)
21877 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
21878 return ~crc & 0xffffffff;
21883 This computation does not apply to the ``build ID'' method.
21885 @node MiniDebugInfo
21886 @section Debugging information in a special section
21887 @cindex separate debug sections
21888 @cindex @samp{.gnu_debugdata} section
21890 Some systems ship pre-built executables and libraries that have a
21891 special @samp{.gnu_debugdata} section. This feature is called
21892 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
21893 is used to supply extra symbols for backtraces.
21895 The intent of this section is to provide extra minimal debugging
21896 information for use in simple backtraces. It is not intended to be a
21897 replacement for full separate debugging information (@pxref{Separate
21898 Debug Files}). The example below shows the intended use; however,
21899 @value{GDBN} does not currently put restrictions on what sort of
21900 debugging information might be included in the section.
21902 @value{GDBN} has support for this extension. If the section exists,
21903 then it is used provided that no other source of debugging information
21904 can be found, and that @value{GDBN} was configured with LZMA support.
21906 This section can be easily created using @command{objcopy} and other
21907 standard utilities:
21910 # Extract the dynamic symbols from the main binary, there is no need
21911 # to also have these in the normal symbol table.
21912 nm -D @var{binary} --format=posix --defined-only \
21913 | awk '@{ print $1 @}' | sort > dynsyms
21915 # Extract all the text (i.e. function) symbols from the debuginfo.
21916 # (Note that we actually also accept "D" symbols, for the benefit
21917 # of platforms like PowerPC64 that use function descriptors.)
21918 nm @var{binary} --format=posix --defined-only \
21919 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
21922 # Keep all the function symbols not already in the dynamic symbol
21924 comm -13 dynsyms funcsyms > keep_symbols
21926 # Separate full debug info into debug binary.
21927 objcopy --only-keep-debug @var{binary} debug
21929 # Copy the full debuginfo, keeping only a minimal set of symbols and
21930 # removing some unnecessary sections.
21931 objcopy -S --remove-section .gdb_index --remove-section .comment \
21932 --keep-symbols=keep_symbols debug mini_debuginfo
21934 # Drop the full debug info from the original binary.
21935 strip --strip-all -R .comment @var{binary}
21937 # Inject the compressed data into the .gnu_debugdata section of the
21940 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
21944 @section Index Files Speed Up @value{GDBN}
21945 @cindex index files
21946 @cindex @samp{.gdb_index} section
21948 When @value{GDBN} finds a symbol file, it scans the symbols in the
21949 file in order to construct an internal symbol table. This lets most
21950 @value{GDBN} operations work quickly---at the cost of a delay early
21951 on. For large programs, this delay can be quite lengthy, so
21952 @value{GDBN} provides a way to build an index, which speeds up
21955 For convenience, @value{GDBN} comes with a program,
21956 @command{gdb-add-index}, which can be used to add the index to a
21957 symbol file. It takes the symbol file as its only argument:
21960 $ gdb-add-index symfile
21963 @xref{gdb-add-index}.
21965 It is also possible to do the work manually. Here is what
21966 @command{gdb-add-index} does behind the curtains.
21968 The index is stored as a section in the symbol file. @value{GDBN} can
21969 write the index to a file, then you can put it into the symbol file
21970 using @command{objcopy}.
21972 To create an index file, use the @code{save gdb-index} command:
21975 @item save gdb-index [-dwarf-5] @var{directory}
21976 @kindex save gdb-index
21977 Create index files for all symbol files currently known by
21978 @value{GDBN}. For each known @var{symbol-file}, this command by
21979 default creates it produces a single file
21980 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
21981 the @option{-dwarf-5} option, it produces 2 files:
21982 @file{@var{symbol-file}.debug_names} and
21983 @file{@var{symbol-file}.debug_str}. The files are created in the
21984 given @var{directory}.
21987 Once you have created an index file you can merge it into your symbol
21988 file, here named @file{symfile}, using @command{objcopy}:
21991 $ objcopy --add-section .gdb_index=symfile.gdb-index \
21992 --set-section-flags .gdb_index=readonly symfile symfile
21995 Or for @code{-dwarf-5}:
21998 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
21999 $ cat symfile.debug_str >>symfile.debug_str.new
22000 $ objcopy --add-section .debug_names=symfile.gdb-index \
22001 --set-section-flags .debug_names=readonly \
22002 --update-section .debug_str=symfile.debug_str.new symfile symfile
22005 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
22006 sections that have been deprecated. Usually they are deprecated because
22007 they are missing a new feature or have performance issues.
22008 To tell @value{GDBN} to use a deprecated index section anyway
22009 specify @code{set use-deprecated-index-sections on}.
22010 The default is @code{off}.
22011 This can speed up startup, but may result in some functionality being lost.
22012 @xref{Index Section Format}.
22014 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
22015 must be done before gdb reads the file. The following will not work:
22018 $ gdb -ex "set use-deprecated-index-sections on" <program>
22021 Instead you must do, for example,
22024 $ gdb -iex "set use-deprecated-index-sections on" <program>
22027 Indices only work when using DWARF debugging information, not stabs.
22029 @subsection Automatic symbol index cache
22031 @cindex automatic symbol index cache
22032 It is possible for @value{GDBN} to automatically save a copy of this index in a
22033 cache on disk and retrieve it from there when loading the same binary in the
22034 future. This feature can be turned on with @kbd{set index-cache enabled on}.
22035 The following commands can be used to tweak the behavior of the index cache.
22039 @kindex set index-cache
22040 @item set index-cache enabled on
22041 @itemx set index-cache enabled off
22042 Enable or disable the use of the symbol index cache.
22044 @item set index-cache directory @var{directory}
22045 @kindex show index-cache
22046 @itemx show index-cache directory
22047 Set/show the directory where index files will be saved.
22049 The default value for this directory depends on the host platform. On
22050 most systems, the index is cached in the @file{gdb} subdirectory of
22051 the directory pointed to by the @env{XDG_CACHE_HOME} environment
22052 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
22053 of your home directory. However, on some systems, the default may
22054 differ according to local convention.
22056 There is no limit on the disk space used by index cache. It is perfectly safe
22057 to delete the content of that directory to free up disk space.
22059 @item show index-cache stats
22060 Print the number of cache hits and misses since the launch of @value{GDBN}.
22064 @node Symbol Errors
22065 @section Errors Reading Symbol Files
22067 While reading a symbol file, @value{GDBN} occasionally encounters problems,
22068 such as symbol types it does not recognize, or known bugs in compiler
22069 output. By default, @value{GDBN} does not notify you of such problems, since
22070 they are relatively common and primarily of interest to people
22071 debugging compilers. If you are interested in seeing information
22072 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
22073 only one message about each such type of problem, no matter how many
22074 times the problem occurs; or you can ask @value{GDBN} to print more messages,
22075 to see how many times the problems occur, with the @code{set
22076 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
22079 The messages currently printed, and their meanings, include:
22082 @item inner block not inside outer block in @var{symbol}
22084 The symbol information shows where symbol scopes begin and end
22085 (such as at the start of a function or a block of statements). This
22086 error indicates that an inner scope block is not fully contained
22087 in its outer scope blocks.
22089 @value{GDBN} circumvents the problem by treating the inner block as if it had
22090 the same scope as the outer block. In the error message, @var{symbol}
22091 may be shown as ``@code{(don't know)}'' if the outer block is not a
22094 @item block at @var{address} out of order
22096 The symbol information for symbol scope blocks should occur in
22097 order of increasing addresses. This error indicates that it does not
22100 @value{GDBN} does not circumvent this problem, and has trouble
22101 locating symbols in the source file whose symbols it is reading. (You
22102 can often determine what source file is affected by specifying
22103 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
22106 @item bad block start address patched
22108 The symbol information for a symbol scope block has a start address
22109 smaller than the address of the preceding source line. This is known
22110 to occur in the SunOS 4.1.1 (and earlier) C compiler.
22112 @value{GDBN} circumvents the problem by treating the symbol scope block as
22113 starting on the previous source line.
22115 @item bad string table offset in symbol @var{n}
22118 Symbol number @var{n} contains a pointer into the string table which is
22119 larger than the size of the string table.
22121 @value{GDBN} circumvents the problem by considering the symbol to have the
22122 name @code{foo}, which may cause other problems if many symbols end up
22125 @item unknown symbol type @code{0x@var{nn}}
22127 The symbol information contains new data types that @value{GDBN} does
22128 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
22129 uncomprehended information, in hexadecimal.
22131 @value{GDBN} circumvents the error by ignoring this symbol information.
22132 This usually allows you to debug your program, though certain symbols
22133 are not accessible. If you encounter such a problem and feel like
22134 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
22135 on @code{complain}, then go up to the function @code{read_dbx_symtab}
22136 and examine @code{*bufp} to see the symbol.
22138 @item stub type has NULL name
22140 @value{GDBN} could not find the full definition for a struct or class.
22142 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
22143 The symbol information for a C@t{++} member function is missing some
22144 information that recent versions of the compiler should have output for
22147 @item info mismatch between compiler and debugger
22149 @value{GDBN} could not parse a type specification output by the compiler.
22154 @section GDB Data Files
22156 @cindex prefix for data files
22157 @value{GDBN} will sometimes read an auxiliary data file. These files
22158 are kept in a directory known as the @dfn{data directory}.
22160 You can set the data directory's name, and view the name @value{GDBN}
22161 is currently using.
22164 @kindex set data-directory
22165 @item set data-directory @var{directory}
22166 Set the directory which @value{GDBN} searches for auxiliary data files
22167 to @var{directory}.
22169 @kindex show data-directory
22170 @item show data-directory
22171 Show the directory @value{GDBN} searches for auxiliary data files.
22174 @cindex default data directory
22175 @cindex @samp{--with-gdb-datadir}
22176 You can set the default data directory by using the configure-time
22177 @samp{--with-gdb-datadir} option. If the data directory is inside
22178 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
22179 @samp{--exec-prefix}), then the default data directory will be updated
22180 automatically if the installed @value{GDBN} is moved to a new
22183 The data directory may also be specified with the
22184 @code{--data-directory} command line option.
22185 @xref{Mode Options}.
22188 @chapter Specifying a Debugging Target
22190 @cindex debugging target
22191 A @dfn{target} is the execution environment occupied by your program.
22193 Often, @value{GDBN} runs in the same host environment as your program;
22194 in that case, the debugging target is specified as a side effect when
22195 you use the @code{file} or @code{core} commands. When you need more
22196 flexibility---for example, running @value{GDBN} on a physically separate
22197 host, or controlling a standalone system over a serial port or a
22198 realtime system over a TCP/IP connection---you can use the @code{target}
22199 command to specify one of the target types configured for @value{GDBN}
22200 (@pxref{Target Commands, ,Commands for Managing Targets}).
22202 @cindex target architecture
22203 It is possible to build @value{GDBN} for several different @dfn{target
22204 architectures}. When @value{GDBN} is built like that, you can choose
22205 one of the available architectures with the @kbd{set architecture}
22209 @kindex set architecture
22210 @kindex show architecture
22211 @item set architecture @var{arch}
22212 This command sets the current target architecture to @var{arch}. The
22213 value of @var{arch} can be @code{"auto"}, in addition to one of the
22214 supported architectures.
22216 @item show architecture
22217 Show the current target architecture.
22219 @item set processor
22221 @kindex set processor
22222 @kindex show processor
22223 These are alias commands for, respectively, @code{set architecture}
22224 and @code{show architecture}.
22228 * Active Targets:: Active targets
22229 * Target Commands:: Commands for managing targets
22230 * Byte Order:: Choosing target byte order
22233 @node Active Targets
22234 @section Active Targets
22236 @cindex stacking targets
22237 @cindex active targets
22238 @cindex multiple targets
22240 There are multiple classes of targets such as: processes, executable files or
22241 recording sessions. Core files belong to the process class, making core file
22242 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
22243 on multiple active targets, one in each class. This allows you to (for
22244 example) start a process and inspect its activity, while still having access to
22245 the executable file after the process finishes. Or if you start process
22246 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
22247 presented a virtual layer of the recording target, while the process target
22248 remains stopped at the chronologically last point of the process execution.
22250 Use the @code{core-file} and @code{exec-file} commands to select a new core
22251 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
22252 specify as a target a process that is already running, use the @code{attach}
22253 command (@pxref{Attach, ,Debugging an Already-running Process}).
22255 @node Target Commands
22256 @section Commands for Managing Targets
22259 @item target @var{type} @var{parameters}
22260 Connects the @value{GDBN} host environment to a target machine or
22261 process. A target is typically a protocol for talking to debugging
22262 facilities. You use the argument @var{type} to specify the type or
22263 protocol of the target machine.
22265 Further @var{parameters} are interpreted by the target protocol, but
22266 typically include things like device names or host names to connect
22267 with, process numbers, and baud rates.
22269 The @code{target} command does not repeat if you press @key{RET} again
22270 after executing the command.
22272 @kindex help target
22274 Displays the names of all targets available. To display targets
22275 currently selected, use either @code{info target} or @code{info files}
22276 (@pxref{Files, ,Commands to Specify Files}).
22278 @item help target @var{name}
22279 Describe a particular target, including any parameters necessary to
22282 @kindex set gnutarget
22283 @item set gnutarget @var{args}
22284 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
22285 knows whether it is reading an @dfn{executable},
22286 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
22287 with the @code{set gnutarget} command. Unlike most @code{target} commands,
22288 with @code{gnutarget} the @code{target} refers to a program, not a machine.
22291 @emph{Warning:} To specify a file format with @code{set gnutarget},
22292 you must know the actual BFD name.
22296 @xref{Files, , Commands to Specify Files}.
22298 @kindex show gnutarget
22299 @item show gnutarget
22300 Use the @code{show gnutarget} command to display what file format
22301 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
22302 @value{GDBN} will determine the file format for each file automatically,
22303 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
22306 @cindex common targets
22307 Here are some common targets (available, or not, depending on the GDB
22312 @item target exec @var{program}
22313 @cindex executable file target
22314 An executable file. @samp{target exec @var{program}} is the same as
22315 @samp{exec-file @var{program}}.
22317 @item target core @var{filename}
22318 @cindex core dump file target
22319 A core dump file. @samp{target core @var{filename}} is the same as
22320 @samp{core-file @var{filename}}.
22322 @item target remote @var{medium}
22323 @cindex remote target
22324 A remote system connected to @value{GDBN} via a serial line or network
22325 connection. This command tells @value{GDBN} to use its own remote
22326 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
22328 For example, if you have a board connected to @file{/dev/ttya} on the
22329 machine running @value{GDBN}, you could say:
22332 target remote /dev/ttya
22335 @code{target remote} supports the @code{load} command. This is only
22336 useful if you have some other way of getting the stub to the target
22337 system, and you can put it somewhere in memory where it won't get
22338 clobbered by the download.
22340 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22341 @cindex built-in simulator target
22342 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
22350 works; however, you cannot assume that a specific memory map, device
22351 drivers, or even basic I/O is available, although some simulators do
22352 provide these. For info about any processor-specific simulator details,
22353 see the appropriate section in @ref{Embedded Processors, ,Embedded
22356 @item target native
22357 @cindex native target
22358 Setup for local/native process debugging. Useful to make the
22359 @code{run} command spawn native processes (likewise @code{attach},
22360 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
22361 (@pxref{set auto-connect-native-target}).
22365 Different targets are available on different configurations of @value{GDBN};
22366 your configuration may have more or fewer targets.
22368 Many remote targets require you to download the executable's code once
22369 you've successfully established a connection. You may wish to control
22370 various aspects of this process.
22375 @kindex set hash@r{, for remote monitors}
22376 @cindex hash mark while downloading
22377 This command controls whether a hash mark @samp{#} is displayed while
22378 downloading a file to the remote monitor. If on, a hash mark is
22379 displayed after each S-record is successfully downloaded to the
22383 @kindex show hash@r{, for remote monitors}
22384 Show the current status of displaying the hash mark.
22386 @item set debug monitor
22387 @kindex set debug monitor
22388 @cindex display remote monitor communications
22389 Enable or disable display of communications messages between
22390 @value{GDBN} and the remote monitor.
22392 @item show debug monitor
22393 @kindex show debug monitor
22394 Show the current status of displaying communications between
22395 @value{GDBN} and the remote monitor.
22400 @kindex load @var{filename} @var{offset}
22401 @item load @var{filename} @var{offset}
22403 Depending on what remote debugging facilities are configured into
22404 @value{GDBN}, the @code{load} command may be available. Where it exists, it
22405 is meant to make @var{filename} (an executable) available for debugging
22406 on the remote system---by downloading, or dynamic linking, for example.
22407 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
22408 the @code{add-symbol-file} command.
22410 If your @value{GDBN} does not have a @code{load} command, attempting to
22411 execute it gets the error message ``@code{You can't do that when your
22412 target is @dots{}}''
22414 The file is loaded at whatever address is specified in the executable.
22415 For some object file formats, you can specify the load address when you
22416 link the program; for other formats, like a.out, the object file format
22417 specifies a fixed address.
22418 @c FIXME! This would be a good place for an xref to the GNU linker doc.
22420 It is also possible to tell @value{GDBN} to load the executable file at a
22421 specific offset described by the optional argument @var{offset}. When
22422 @var{offset} is provided, @var{filename} must also be provided.
22424 Depending on the remote side capabilities, @value{GDBN} may be able to
22425 load programs into flash memory.
22427 @code{load} does not repeat if you press @key{RET} again after using it.
22432 @kindex flash-erase
22434 @anchor{flash-erase}
22436 Erases all known flash memory regions on the target.
22441 @section Choosing Target Byte Order
22443 @cindex choosing target byte order
22444 @cindex target byte order
22446 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
22447 offer the ability to run either big-endian or little-endian byte
22448 orders. Usually the executable or symbol will include a bit to
22449 designate the endian-ness, and you will not need to worry about
22450 which to use. However, you may still find it useful to adjust
22451 @value{GDBN}'s idea of processor endian-ness manually.
22455 @item set endian big
22456 Instruct @value{GDBN} to assume the target is big-endian.
22458 @item set endian little
22459 Instruct @value{GDBN} to assume the target is little-endian.
22461 @item set endian auto
22462 Instruct @value{GDBN} to use the byte order associated with the
22466 Display @value{GDBN}'s current idea of the target byte order.
22470 If the @code{set endian auto} mode is in effect and no executable has
22471 been selected, then the endianness used is the last one chosen either
22472 by one of the @code{set endian big} and @code{set endian little}
22473 commands or by inferring from the last executable used. If no
22474 endianness has been previously chosen, then the default for this mode
22475 is inferred from the target @value{GDBN} has been built for, and is
22476 @code{little} if the name of the target CPU has an @code{el} suffix
22477 and @code{big} otherwise.
22479 Note that these commands merely adjust interpretation of symbolic
22480 data on the host, and that they have absolutely no effect on the
22484 @node Remote Debugging
22485 @chapter Debugging Remote Programs
22486 @cindex remote debugging
22488 If you are trying to debug a program running on a machine that cannot run
22489 @value{GDBN} in the usual way, it is often useful to use remote debugging.
22490 For example, you might use remote debugging on an operating system kernel,
22491 or on a small system which does not have a general purpose operating system
22492 powerful enough to run a full-featured debugger.
22494 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
22495 to make this work with particular debugging targets. In addition,
22496 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
22497 but not specific to any particular target system) which you can use if you
22498 write the remote stubs---the code that runs on the remote system to
22499 communicate with @value{GDBN}.
22501 Other remote targets may be available in your
22502 configuration of @value{GDBN}; use @code{help target} to list them.
22505 * Connecting:: Connecting to a remote target
22506 * File Transfer:: Sending files to a remote system
22507 * Server:: Using the gdbserver program
22508 * Remote Configuration:: Remote configuration
22509 * Remote Stub:: Implementing a remote stub
22513 @section Connecting to a Remote Target
22514 @cindex remote debugging, connecting
22515 @cindex @code{gdbserver}, connecting
22516 @cindex remote debugging, types of connections
22517 @cindex @code{gdbserver}, types of connections
22518 @cindex @code{gdbserver}, @code{target remote} mode
22519 @cindex @code{gdbserver}, @code{target extended-remote} mode
22521 This section describes how to connect to a remote target, including the
22522 types of connections and their differences, how to set up executable and
22523 symbol files on the host and target, and the commands used for
22524 connecting to and disconnecting from the remote target.
22526 @subsection Types of Remote Connections
22528 @value{GDBN} supports two types of remote connections, @code{target remote}
22529 mode and @code{target extended-remote} mode. Note that many remote targets
22530 support only @code{target remote} mode. There are several major
22531 differences between the two types of connections, enumerated here:
22535 @cindex remote debugging, detach and program exit
22536 @item Result of detach or program exit
22537 @strong{With target remote mode:} When the debugged program exits or you
22538 detach from it, @value{GDBN} disconnects from the target. When using
22539 @code{gdbserver}, @code{gdbserver} will exit.
22541 @strong{With target extended-remote mode:} When the debugged program exits or
22542 you detach from it, @value{GDBN} remains connected to the target, even
22543 though no program is running. You can rerun the program, attach to a
22544 running program, or use @code{monitor} commands specific to the target.
22546 When using @code{gdbserver} in this case, it does not exit unless it was
22547 invoked using the @option{--once} option. If the @option{--once} option
22548 was not used, you can ask @code{gdbserver} to exit using the
22549 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
22551 @item Specifying the program to debug
22552 For both connection types you use the @code{file} command to specify the
22553 program on the host system. If you are using @code{gdbserver} there are
22554 some differences in how to specify the location of the program on the
22557 @strong{With target remote mode:} You must either specify the program to debug
22558 on the @code{gdbserver} command line or use the @option{--attach} option
22559 (@pxref{Attaching to a program,,Attaching to a Running Program}).
22561 @cindex @option{--multi}, @code{gdbserver} option
22562 @strong{With target extended-remote mode:} You may specify the program to debug
22563 on the @code{gdbserver} command line, or you can load the program or attach
22564 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
22566 @anchor{--multi Option in Types of Remote Connnections}
22567 You can start @code{gdbserver} without supplying an initial command to run
22568 or process ID to attach. To do this, use the @option{--multi} command line
22569 option. Then you can connect using @code{target extended-remote} and start
22570 the program you want to debug (see below for details on using the
22571 @code{run} command in this scenario). Note that the conditions under which
22572 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
22573 (@code{target remote} or @code{target extended-remote}). The
22574 @option{--multi} option to @code{gdbserver} has no influence on that.
22576 @item The @code{run} command
22577 @strong{With target remote mode:} The @code{run} command is not
22578 supported. Once a connection has been established, you can use all
22579 the usual @value{GDBN} commands to examine and change data. The
22580 remote program is already running, so you can use commands like
22581 @kbd{step} and @kbd{continue}.
22583 @strong{With target extended-remote mode:} The @code{run} command is
22584 supported. The @code{run} command uses the value set by
22585 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
22586 the program to run. Command line arguments are supported, except for
22587 wildcard expansion and I/O redirection (@pxref{Arguments}).
22589 If you specify the program to debug on the command line, then the
22590 @code{run} command is not required to start execution, and you can
22591 resume using commands like @kbd{step} and @kbd{continue} as with
22592 @code{target remote} mode.
22594 @anchor{Attaching in Types of Remote Connections}
22596 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
22597 not supported. To attach to a running program using @code{gdbserver}, you
22598 must use the @option{--attach} option (@pxref{Running gdbserver}).
22600 @strong{With target extended-remote mode:} To attach to a running program,
22601 you may use the @code{attach} command after the connection has been
22602 established. If you are using @code{gdbserver}, you may also invoke
22603 @code{gdbserver} using the @option{--attach} option
22604 (@pxref{Running gdbserver}).
22606 Some remote targets allow @value{GDBN} to determine the executable file running
22607 in the process the debugger is attaching to. In such a case, @value{GDBN}
22608 uses the value of @code{exec-file-mismatch} to handle a possible mismatch
22609 between the executable file name running in the process and the name of the
22610 current exec-file loaded by @value{GDBN} (@pxref{set exec-file-mismatch}).
22614 @anchor{Host and target files}
22615 @subsection Host and Target Files
22616 @cindex remote debugging, symbol files
22617 @cindex symbol files, remote debugging
22619 @value{GDBN}, running on the host, needs access to symbol and debugging
22620 information for your program running on the target. This requires
22621 access to an unstripped copy of your program, and possibly any associated
22622 symbol files. Note that this section applies equally to both @code{target
22623 remote} mode and @code{target extended-remote} mode.
22625 Some remote targets (@pxref{qXfer executable filename read}, and
22626 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
22627 the same connection used to communicate with @value{GDBN}. With such a
22628 target, if the remote program is unstripped, the only command you need is
22629 @code{target remote} (or @code{target extended-remote}).
22631 If the remote program is stripped, or the target does not support remote
22632 program file access, start up @value{GDBN} using the name of the local
22633 unstripped copy of your program as the first argument, or use the
22634 @code{file} command. Use @code{set sysroot} to specify the location (on
22635 the host) of target libraries (unless your @value{GDBN} was compiled with
22636 the correct sysroot using @code{--with-sysroot}). Alternatively, you
22637 may use @code{set solib-search-path} to specify how @value{GDBN} locates
22640 The symbol file and target libraries must exactly match the executable
22641 and libraries on the target, with one exception: the files on the host
22642 system should not be stripped, even if the files on the target system
22643 are. Mismatched or missing files will lead to confusing results
22644 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
22645 files may also prevent @code{gdbserver} from debugging multi-threaded
22648 @subsection Remote Connection Commands
22649 @cindex remote connection commands
22650 @value{GDBN} can communicate with the target over a serial line, a
22651 local Unix domain socket, or
22652 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
22653 each case, @value{GDBN} uses the same protocol for debugging your
22654 program; only the medium carrying the debugging packets varies. The
22655 @code{target remote} and @code{target extended-remote} commands
22656 establish a connection to the target. Both commands accept the same
22657 arguments, which indicate the medium to use:
22661 @item target remote @var{serial-device}
22662 @itemx target extended-remote @var{serial-device}
22663 @cindex serial line, @code{target remote}
22664 Use @var{serial-device} to communicate with the target. For example,
22665 to use a serial line connected to the device named @file{/dev/ttyb}:
22668 target remote /dev/ttyb
22671 If you're using a serial line, you may want to give @value{GDBN} the
22672 @samp{--baud} option, or use the @code{set serial baud} command
22673 (@pxref{Remote Configuration, set serial baud}) before the
22674 @code{target} command.
22676 @item target remote @var{local-socket}
22677 @itemx target extended-remote @var{local-socket}
22678 @cindex local socket, @code{target remote}
22679 @cindex Unix domain socket
22680 Use @var{local-socket} to communicate with the target. For example,
22681 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
22684 target remote /tmp/gdb-socket0
22687 Note that this command has the same form as the command to connect
22688 to a serial line. @value{GDBN} will automatically determine which
22689 kind of file you have specified and will make the appropriate kind
22691 This feature is not available if the host system does not support
22692 Unix domain sockets.
22694 @item target remote @code{@var{host}:@var{port}}
22695 @itemx target remote @code{[@var{host}]:@var{port}}
22696 @itemx target remote @code{tcp:@var{host}:@var{port}}
22697 @itemx target remote @code{tcp:[@var{host}]:@var{port}}
22698 @itemx target remote @code{tcp4:@var{host}:@var{port}}
22699 @itemx target remote @code{tcp6:@var{host}:@var{port}}
22700 @itemx target remote @code{tcp6:[@var{host}]:@var{port}}
22701 @itemx target extended-remote @code{@var{host}:@var{port}}
22702 @itemx target extended-remote @code{[@var{host}]:@var{port}}
22703 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
22704 @itemx target extended-remote @code{tcp:[@var{host}]:@var{port}}
22705 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
22706 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
22707 @itemx target extended-remote @code{tcp6:[@var{host}]:@var{port}}
22708 @cindex @acronym{TCP} port, @code{target remote}
22709 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
22710 The @var{host} may be either a host name, a numeric @acronym{IPv4}
22711 address, or a numeric @acronym{IPv6} address (with or without the
22712 square brackets to separate the address from the port); @var{port}
22713 must be a decimal number. The @var{host} could be the target machine
22714 itself, if it is directly connected to the net, or it might be a
22715 terminal server which in turn has a serial line to the target.
22717 For example, to connect to port 2828 on a terminal server named
22721 target remote manyfarms:2828
22724 To connect to port 2828 on a terminal server whose address is
22725 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
22726 square bracket syntax:
22729 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
22733 or explicitly specify the @acronym{IPv6} protocol:
22736 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
22739 This last example may be confusing to the reader, because there is no
22740 visible separation between the hostname and the port number.
22741 Therefore, we recommend the user to provide @acronym{IPv6} addresses
22742 using square brackets for clarity. However, it is important to
22743 mention that for @value{GDBN} there is no ambiguity: the number after
22744 the last colon is considered to be the port number.
22746 If your remote target is actually running on the same machine as your
22747 debugger session (e.g.@: a simulator for your target running on the
22748 same host), you can omit the hostname. For example, to connect to
22749 port 1234 on your local machine:
22752 target remote :1234
22756 Note that the colon is still required here.
22758 @item target remote @code{udp:@var{host}:@var{port}}
22759 @itemx target remote @code{udp:[@var{host}]:@var{port}}
22760 @itemx target remote @code{udp4:@var{host}:@var{port}}
22761 @itemx target remote @code{udp6:[@var{host}]:@var{port}}
22762 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22763 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
22764 @itemx target extended-remote @code{udp:[@var{host}]:@var{port}}
22765 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
22766 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
22767 @itemx target extended-remote @code{udp6:[@var{host}]:@var{port}}
22768 @cindex @acronym{UDP} port, @code{target remote}
22769 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
22770 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
22773 target remote udp:manyfarms:2828
22776 When using a @acronym{UDP} connection for remote debugging, you should
22777 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
22778 can silently drop packets on busy or unreliable networks, which will
22779 cause havoc with your debugging session.
22781 @item target remote | @var{command}
22782 @itemx target extended-remote | @var{command}
22783 @cindex pipe, @code{target remote} to
22784 Run @var{command} in the background and communicate with it using a
22785 pipe. The @var{command} is a shell command, to be parsed and expanded
22786 by the system's command shell, @code{/bin/sh}; it should expect remote
22787 protocol packets on its standard input, and send replies on its
22788 standard output. You could use this to run a stand-alone simulator
22789 that speaks the remote debugging protocol, to make net connections
22790 using programs like @code{ssh}, or for other similar tricks.
22792 If @var{command} closes its standard output (perhaps by exiting),
22793 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
22794 program has already exited, this will have no effect.)
22798 @cindex interrupting remote programs
22799 @cindex remote programs, interrupting
22800 Whenever @value{GDBN} is waiting for the remote program, if you type the
22801 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
22802 program. This may or may not succeed, depending in part on the hardware
22803 and the serial drivers the remote system uses. If you type the
22804 interrupt character once again, @value{GDBN} displays this prompt:
22807 Interrupted while waiting for the program.
22808 Give up (and stop debugging it)? (y or n)
22811 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
22812 the remote debugging session. (If you decide you want to try again later,
22813 you can use @kbd{target remote} again to connect once more.) If you type
22814 @kbd{n}, @value{GDBN} goes back to waiting.
22816 In @code{target extended-remote} mode, typing @kbd{n} will leave
22817 @value{GDBN} connected to the target.
22820 @kindex detach (remote)
22822 When you have finished debugging the remote program, you can use the
22823 @code{detach} command to release it from @value{GDBN} control.
22824 Detaching from the target normally resumes its execution, but the results
22825 will depend on your particular remote stub. After the @code{detach}
22826 command in @code{target remote} mode, @value{GDBN} is free to connect to
22827 another target. In @code{target extended-remote} mode, @value{GDBN} is
22828 still connected to the target.
22832 The @code{disconnect} command closes the connection to the target, and
22833 the target is generally not resumed. It will wait for @value{GDBN}
22834 (this instance or another one) to connect and continue debugging. After
22835 the @code{disconnect} command, @value{GDBN} is again free to connect to
22838 @cindex send command to remote monitor
22839 @cindex extend @value{GDBN} for remote targets
22840 @cindex add new commands for external monitor
22842 @item monitor @var{cmd}
22843 This command allows you to send arbitrary commands directly to the
22844 remote monitor. Since @value{GDBN} doesn't care about the commands it
22845 sends like this, this command is the way to extend @value{GDBN}---you
22846 can add new commands that only the external monitor will understand
22850 @node File Transfer
22851 @section Sending files to a remote system
22852 @cindex remote target, file transfer
22853 @cindex file transfer
22854 @cindex sending files to remote systems
22856 Some remote targets offer the ability to transfer files over the same
22857 connection used to communicate with @value{GDBN}. This is convenient
22858 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
22859 running @code{gdbserver} over a network interface. For other targets,
22860 e.g.@: embedded devices with only a single serial port, this may be
22861 the only way to upload or download files.
22863 Not all remote targets support these commands.
22867 @item remote put @var{hostfile} @var{targetfile}
22868 Copy file @var{hostfile} from the host system (the machine running
22869 @value{GDBN}) to @var{targetfile} on the target system.
22872 @item remote get @var{targetfile} @var{hostfile}
22873 Copy file @var{targetfile} from the target system to @var{hostfile}
22874 on the host system.
22876 @kindex remote delete
22877 @item remote delete @var{targetfile}
22878 Delete @var{targetfile} from the target system.
22883 @section Using the @code{gdbserver} Program
22886 @cindex remote connection without stubs
22887 @code{gdbserver} is a control program for Unix-like systems, which
22888 allows you to connect your program with a remote @value{GDBN} via
22889 @code{target remote} or @code{target extended-remote}---but without
22890 linking in the usual debugging stub.
22892 @code{gdbserver} is not a complete replacement for the debugging stubs,
22893 because it requires essentially the same operating-system facilities
22894 that @value{GDBN} itself does. In fact, a system that can run
22895 @code{gdbserver} to connect to a remote @value{GDBN} could also run
22896 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
22897 because it is a much smaller program than @value{GDBN} itself. It is
22898 also easier to port than all of @value{GDBN}, so you may be able to get
22899 started more quickly on a new system by using @code{gdbserver}.
22900 Finally, if you develop code for real-time systems, you may find that
22901 the tradeoffs involved in real-time operation make it more convenient to
22902 do as much development work as possible on another system, for example
22903 by cross-compiling. You can use @code{gdbserver} to make a similar
22904 choice for debugging.
22906 @value{GDBN} and @code{gdbserver} communicate via either a serial line
22907 or a TCP connection, using the standard @value{GDBN} remote serial
22911 @emph{Warning:} @code{gdbserver} does not have any built-in security.
22912 Do not run @code{gdbserver} connected to any public network; a
22913 @value{GDBN} connection to @code{gdbserver} provides access to the
22914 target system with the same privileges as the user running
22918 @anchor{Running gdbserver}
22919 @subsection Running @code{gdbserver}
22920 @cindex arguments, to @code{gdbserver}
22921 @cindex @code{gdbserver}, command-line arguments
22923 Run @code{gdbserver} on the target system. You need a copy of the
22924 program you want to debug, including any libraries it requires.
22925 @code{gdbserver} does not need your program's symbol table, so you can
22926 strip the program if necessary to save space. @value{GDBN} on the host
22927 system does all the symbol handling.
22929 To use the server, you must tell it how to communicate with @value{GDBN};
22930 the name of your program; and the arguments for your program. The usual
22934 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
22937 @var{comm} is either a device name (to use a serial line), or a TCP
22938 hostname and portnumber, or @code{-} or @code{stdio} to use
22939 stdin/stdout of @code{gdbserver}.
22940 For example, to debug Emacs with the argument
22941 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
22945 target> gdbserver /dev/com1 emacs foo.txt
22948 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
22951 To use a TCP connection instead of a serial line:
22954 target> gdbserver host:2345 emacs foo.txt
22957 The only difference from the previous example is the first argument,
22958 specifying that you are communicating with the host @value{GDBN} via
22959 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
22960 expect a TCP connection from machine @samp{host} to local TCP port 2345.
22961 (Currently, the @samp{host} part is ignored.) You can choose any number
22962 you want for the port number as long as it does not conflict with any
22963 TCP ports already in use on the target system (for example, @code{23} is
22964 reserved for @code{telnet}).@footnote{If you choose a port number that
22965 conflicts with another service, @code{gdbserver} prints an error message
22966 and exits.} You must use the same port number with the host @value{GDBN}
22967 @code{target remote} command.
22969 The @code{stdio} connection is useful when starting @code{gdbserver}
22973 (gdb) target remote | ssh -T hostname gdbserver - hello
22976 The @samp{-T} option to ssh is provided because we don't need a remote pty,
22977 and we don't want escape-character handling. Ssh does this by default when
22978 a command is provided, the flag is provided to make it explicit.
22979 You could elide it if you want to.
22981 Programs started with stdio-connected gdbserver have @file{/dev/null} for
22982 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
22983 display through a pipe connected to gdbserver.
22984 Both @code{stdout} and @code{stderr} use the same pipe.
22986 @anchor{Attaching to a program}
22987 @subsubsection Attaching to a Running Program
22988 @cindex attach to a program, @code{gdbserver}
22989 @cindex @option{--attach}, @code{gdbserver} option
22991 On some targets, @code{gdbserver} can also attach to running programs.
22992 This is accomplished via the @code{--attach} argument. The syntax is:
22995 target> gdbserver --attach @var{comm} @var{pid}
22998 @var{pid} is the process ID of a currently running process. It isn't
22999 necessary to point @code{gdbserver} at a binary for the running process.
23001 In @code{target extended-remote} mode, you can also attach using the
23002 @value{GDBN} attach command
23003 (@pxref{Attaching in Types of Remote Connections}).
23006 You can debug processes by name instead of process ID if your target has the
23007 @code{pidof} utility:
23010 target> gdbserver --attach @var{comm} `pidof @var{program}`
23013 In case more than one copy of @var{program} is running, or @var{program}
23014 has multiple threads, most versions of @code{pidof} support the
23015 @code{-s} option to only return the first process ID.
23017 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
23019 This section applies only when @code{gdbserver} is run to listen on a TCP
23022 @code{gdbserver} normally terminates after all of its debugged processes have
23023 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
23024 extended-remote}, @code{gdbserver} stays running even with no processes left.
23025 @value{GDBN} normally terminates the spawned debugged process on its exit,
23026 which normally also terminates @code{gdbserver} in the @kbd{target remote}
23027 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
23028 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
23029 stays running even in the @kbd{target remote} mode.
23031 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
23032 Such reconnecting is useful for features like @ref{disconnected tracing}. For
23033 completeness, at most one @value{GDBN} can be connected at a time.
23035 @cindex @option{--once}, @code{gdbserver} option
23036 By default, @code{gdbserver} keeps the listening TCP port open, so that
23037 subsequent connections are possible. However, if you start @code{gdbserver}
23038 with the @option{--once} option, it will stop listening for any further
23039 connection attempts after connecting to the first @value{GDBN} session. This
23040 means no further connections to @code{gdbserver} will be possible after the
23041 first one. It also means @code{gdbserver} will terminate after the first
23042 connection with remote @value{GDBN} has closed, even for unexpectedly closed
23043 connections and even in the @kbd{target extended-remote} mode. The
23044 @option{--once} option allows reusing the same port number for connecting to
23045 multiple instances of @code{gdbserver} running on the same host, since each
23046 instance closes its port after the first connection.
23048 @anchor{Other Command-Line Arguments for gdbserver}
23049 @subsubsection Other Command-Line Arguments for @code{gdbserver}
23051 You can use the @option{--multi} option to start @code{gdbserver} without
23052 specifying a program to debug or a process to attach to. Then you can
23053 attach in @code{target extended-remote} mode and run or attach to a
23054 program. For more information,
23055 @pxref{--multi Option in Types of Remote Connnections}.
23057 @cindex @option{--debug}, @code{gdbserver} option
23058 The @option{--debug} option tells @code{gdbserver} to display extra
23059 status information about the debugging process.
23060 @cindex @option{--remote-debug}, @code{gdbserver} option
23061 The @option{--remote-debug} option tells @code{gdbserver} to display
23062 remote protocol debug output.
23063 @cindex @option{--debug-file}, @code{gdbserver} option
23064 @cindex @code{gdbserver}, send all debug output to a single file
23065 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
23066 write any debug output to the given @var{filename}. These options are intended
23067 for @code{gdbserver} development and for bug reports to the developers.
23069 @cindex @option{--debug-format}, @code{gdbserver} option
23070 The @option{--debug-format=option1[,option2,...]} option tells
23071 @code{gdbserver} to include additional information in each output.
23072 Possible options are:
23076 Turn off all extra information in debugging output.
23078 Turn on all extra information in debugging output.
23080 Include a timestamp in each line of debugging output.
23083 Options are processed in order. Thus, for example, if @option{none}
23084 appears last then no additional information is added to debugging output.
23086 @cindex @option{--wrapper}, @code{gdbserver} option
23087 The @option{--wrapper} option specifies a wrapper to launch programs
23088 for debugging. The option should be followed by the name of the
23089 wrapper, then any command-line arguments to pass to the wrapper, then
23090 @kbd{--} indicating the end of the wrapper arguments.
23092 @code{gdbserver} runs the specified wrapper program with a combined
23093 command line including the wrapper arguments, then the name of the
23094 program to debug, then any arguments to the program. The wrapper
23095 runs until it executes your program, and then @value{GDBN} gains control.
23097 You can use any program that eventually calls @code{execve} with
23098 its arguments as a wrapper. Several standard Unix utilities do
23099 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
23100 with @code{exec "$@@"} will also work.
23102 For example, you can use @code{env} to pass an environment variable to
23103 the debugged program, without setting the variable in @code{gdbserver}'s
23107 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
23110 @cindex @option{--selftest}
23111 The @option{--selftest} option runs the self tests in @code{gdbserver}:
23114 $ gdbserver --selftest
23115 Ran 2 unit tests, 0 failed
23118 These tests are disabled in release.
23119 @subsection Connecting to @code{gdbserver}
23121 The basic procedure for connecting to the remote target is:
23125 Run @value{GDBN} on the host system.
23128 Make sure you have the necessary symbol files
23129 (@pxref{Host and target files}).
23130 Load symbols for your application using the @code{file} command before you
23131 connect. Use @code{set sysroot} to locate target libraries (unless your
23132 @value{GDBN} was compiled with the correct sysroot using
23133 @code{--with-sysroot}).
23136 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
23137 For TCP connections, you must start up @code{gdbserver} prior to using
23138 the @code{target} command. Otherwise you may get an error whose
23139 text depends on the host system, but which usually looks something like
23140 @samp{Connection refused}. Don't use the @code{load}
23141 command in @value{GDBN} when using @code{target remote} mode, since the
23142 program is already on the target.
23146 @anchor{Monitor Commands for gdbserver}
23147 @subsection Monitor Commands for @code{gdbserver}
23148 @cindex monitor commands, for @code{gdbserver}
23150 During a @value{GDBN} session using @code{gdbserver}, you can use the
23151 @code{monitor} command to send special requests to @code{gdbserver}.
23152 Here are the available commands.
23156 List the available monitor commands.
23158 @item monitor set debug 0
23159 @itemx monitor set debug 1
23160 Disable or enable general debugging messages.
23162 @item monitor set remote-debug 0
23163 @itemx monitor set remote-debug 1
23164 Disable or enable specific debugging messages associated with the remote
23165 protocol (@pxref{Remote Protocol}).
23167 @item monitor set debug-file filename
23168 @itemx monitor set debug-file
23169 Send any debug output to the given file, or to stderr.
23171 @item monitor set debug-format option1@r{[},option2,...@r{]}
23172 Specify additional text to add to debugging messages.
23173 Possible options are:
23177 Turn off all extra information in debugging output.
23179 Turn on all extra information in debugging output.
23181 Include a timestamp in each line of debugging output.
23184 Options are processed in order. Thus, for example, if @option{none}
23185 appears last then no additional information is added to debugging output.
23187 @item monitor set libthread-db-search-path [PATH]
23188 @cindex gdbserver, search path for @code{libthread_db}
23189 When this command is issued, @var{path} is a colon-separated list of
23190 directories to search for @code{libthread_db} (@pxref{Threads,,set
23191 libthread-db-search-path}). If you omit @var{path},
23192 @samp{libthread-db-search-path} will be reset to its default value.
23194 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
23195 not supported in @code{gdbserver}.
23198 Tell gdbserver to exit immediately. This command should be followed by
23199 @code{disconnect} to close the debugging session. @code{gdbserver} will
23200 detach from any attached processes and kill any processes it created.
23201 Use @code{monitor exit} to terminate @code{gdbserver} at the end
23202 of a multi-process mode debug session.
23206 @subsection Tracepoints support in @code{gdbserver}
23207 @cindex tracepoints support in @code{gdbserver}
23209 On some targets, @code{gdbserver} supports tracepoints, fast
23210 tracepoints and static tracepoints.
23212 For fast or static tracepoints to work, a special library called the
23213 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
23214 This library is built and distributed as an integral part of
23215 @code{gdbserver}. In addition, support for static tracepoints
23216 requires building the in-process agent library with static tracepoints
23217 support. At present, the UST (LTTng Userspace Tracer,
23218 @url{http://lttng.org/ust}) tracing engine is supported. This support
23219 is automatically available if UST development headers are found in the
23220 standard include path when @code{gdbserver} is built, or if
23221 @code{gdbserver} was explicitly configured using @option{--with-ust}
23222 to point at such headers. You can explicitly disable the support
23223 using @option{--with-ust=no}.
23225 There are several ways to load the in-process agent in your program:
23228 @item Specifying it as dependency at link time
23230 You can link your program dynamically with the in-process agent
23231 library. On most systems, this is accomplished by adding
23232 @code{-linproctrace} to the link command.
23234 @item Using the system's preloading mechanisms
23236 You can force loading the in-process agent at startup time by using
23237 your system's support for preloading shared libraries. Many Unixes
23238 support the concept of preloading user defined libraries. In most
23239 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
23240 in the environment. See also the description of @code{gdbserver}'s
23241 @option{--wrapper} command line option.
23243 @item Using @value{GDBN} to force loading the agent at run time
23245 On some systems, you can force the inferior to load a shared library,
23246 by calling a dynamic loader function in the inferior that takes care
23247 of dynamically looking up and loading a shared library. On most Unix
23248 systems, the function is @code{dlopen}. You'll use the @code{call}
23249 command for that. For example:
23252 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
23255 Note that on most Unix systems, for the @code{dlopen} function to be
23256 available, the program needs to be linked with @code{-ldl}.
23259 On systems that have a userspace dynamic loader, like most Unix
23260 systems, when you connect to @code{gdbserver} using @code{target
23261 remote}, you'll find that the program is stopped at the dynamic
23262 loader's entry point, and no shared library has been loaded in the
23263 program's address space yet, including the in-process agent. In that
23264 case, before being able to use any of the fast or static tracepoints
23265 features, you need to let the loader run and load the shared
23266 libraries. The simplest way to do that is to run the program to the
23267 main procedure. E.g., if debugging a C or C@t{++} program, start
23268 @code{gdbserver} like so:
23271 $ gdbserver :9999 myprogram
23274 Start GDB and connect to @code{gdbserver} like so, and run to main:
23278 (@value{GDBP}) target remote myhost:9999
23279 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
23280 (@value{GDBP}) b main
23281 (@value{GDBP}) continue
23284 The in-process tracing agent library should now be loaded into the
23285 process; you can confirm it with the @code{info sharedlibrary}
23286 command, which will list @file{libinproctrace.so} as loaded in the
23287 process. You are now ready to install fast tracepoints, list static
23288 tracepoint markers, probe static tracepoints markers, and start
23291 @node Remote Configuration
23292 @section Remote Configuration
23295 @kindex show remote
23296 This section documents the configuration options available when
23297 debugging remote programs. For the options related to the File I/O
23298 extensions of the remote protocol, see @ref{system,
23299 system-call-allowed}.
23302 @item set remoteaddresssize @var{bits}
23303 @cindex address size for remote targets
23304 @cindex bits in remote address
23305 Set the maximum size of address in a memory packet to the specified
23306 number of bits. @value{GDBN} will mask off the address bits above
23307 that number, when it passes addresses to the remote target. The
23308 default value is the number of bits in the target's address.
23310 @item show remoteaddresssize
23311 Show the current value of remote address size in bits.
23313 @item set serial baud @var{n}
23314 @cindex baud rate for remote targets
23315 Set the baud rate for the remote serial I/O to @var{n} baud. The
23316 value is used to set the speed of the serial port used for debugging
23319 @item show serial baud
23320 Show the current speed of the remote connection.
23322 @item set serial parity @var{parity}
23323 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
23324 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
23326 @item show serial parity
23327 Show the current parity of the serial port.
23329 @item set remotebreak
23330 @cindex interrupt remote programs
23331 @cindex BREAK signal instead of Ctrl-C
23332 @anchor{set remotebreak}
23333 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
23334 when you type @kbd{Ctrl-c} to interrupt the program running
23335 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
23336 character instead. The default is off, since most remote systems
23337 expect to see @samp{Ctrl-C} as the interrupt signal.
23339 @item show remotebreak
23340 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
23341 interrupt the remote program.
23343 @item set remoteflow on
23344 @itemx set remoteflow off
23345 @kindex set remoteflow
23346 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
23347 on the serial port used to communicate to the remote target.
23349 @item show remoteflow
23350 @kindex show remoteflow
23351 Show the current setting of hardware flow control.
23353 @item set remotelogbase @var{base}
23354 Set the base (a.k.a.@: radix) of logging serial protocol
23355 communications to @var{base}. Supported values of @var{base} are:
23356 @code{ascii}, @code{octal}, and @code{hex}. The default is
23359 @item show remotelogbase
23360 Show the current setting of the radix for logging remote serial
23363 @item set remotelogfile @var{file}
23364 @cindex record serial communications on file
23365 Record remote serial communications on the named @var{file}. The
23366 default is not to record at all.
23368 @item show remotelogfile
23369 Show the current setting of the file name on which to record the
23370 serial communications.
23372 @item set remotetimeout @var{num}
23373 @cindex timeout for serial communications
23374 @cindex remote timeout
23375 Set the timeout limit to wait for the remote target to respond to
23376 @var{num} seconds. The default is 2 seconds.
23378 @item show remotetimeout
23379 Show the current number of seconds to wait for the remote target
23382 @cindex limit hardware breakpoints and watchpoints
23383 @cindex remote target, limit break- and watchpoints
23384 @anchor{set remote hardware-watchpoint-limit}
23385 @anchor{set remote hardware-breakpoint-limit}
23386 @item set remote hardware-watchpoint-limit @var{limit}
23387 @itemx set remote hardware-breakpoint-limit @var{limit}
23388 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
23389 or breakpoints. The @var{limit} can be set to 0 to disable hardware
23390 watchpoints or breakpoints, and @code{unlimited} for unlimited
23391 watchpoints or breakpoints.
23393 @item show remote hardware-watchpoint-limit
23394 @itemx show remote hardware-breakpoint-limit
23395 Show the current limit for the number of hardware watchpoints or
23396 breakpoints that @value{GDBN} can use.
23398 @cindex limit hardware watchpoints length
23399 @cindex remote target, limit watchpoints length
23400 @anchor{set remote hardware-watchpoint-length-limit}
23401 @item set remote hardware-watchpoint-length-limit @var{limit}
23402 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
23403 length of a remote hardware watchpoint. A @var{limit} of 0 disables
23404 hardware watchpoints and @code{unlimited} allows watchpoints of any
23407 @item show remote hardware-watchpoint-length-limit
23408 Show the current limit (in bytes) of the maximum length of
23409 a remote hardware watchpoint.
23411 @item set remote exec-file @var{filename}
23412 @itemx show remote exec-file
23413 @anchor{set remote exec-file}
23414 @cindex executable file, for remote target
23415 Select the file used for @code{run} with @code{target
23416 extended-remote}. This should be set to a filename valid on the
23417 target system. If it is not set, the target will use a default
23418 filename (e.g.@: the last program run).
23420 @item set remote interrupt-sequence
23421 @cindex interrupt remote programs
23422 @cindex select Ctrl-C, BREAK or BREAK-g
23423 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
23424 @samp{BREAK-g} as the
23425 sequence to the remote target in order to interrupt the execution.
23426 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
23427 is high level of serial line for some certain time.
23428 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
23429 It is @code{BREAK} signal followed by character @code{g}.
23431 @item show remote interrupt-sequence
23432 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
23433 is sent by @value{GDBN} to interrupt the remote program.
23434 @code{BREAK-g} is BREAK signal followed by @code{g} and
23435 also known as Magic SysRq g.
23437 @item set remote interrupt-on-connect
23438 @cindex send interrupt-sequence on start
23439 Specify whether interrupt-sequence is sent to remote target when
23440 @value{GDBN} connects to it. This is mostly needed when you debug
23441 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
23442 which is known as Magic SysRq g in order to connect @value{GDBN}.
23444 @item show remote interrupt-on-connect
23445 Show whether interrupt-sequence is sent
23446 to remote target when @value{GDBN} connects to it.
23450 @item set tcp auto-retry on
23451 @cindex auto-retry, for remote TCP target
23452 Enable auto-retry for remote TCP connections. This is useful if the remote
23453 debugging agent is launched in parallel with @value{GDBN}; there is a race
23454 condition because the agent may not become ready to accept the connection
23455 before @value{GDBN} attempts to connect. When auto-retry is
23456 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
23457 to establish the connection using the timeout specified by
23458 @code{set tcp connect-timeout}.
23460 @item set tcp auto-retry off
23461 Do not auto-retry failed TCP connections.
23463 @item show tcp auto-retry
23464 Show the current auto-retry setting.
23466 @item set tcp connect-timeout @var{seconds}
23467 @itemx set tcp connect-timeout unlimited
23468 @cindex connection timeout, for remote TCP target
23469 @cindex timeout, for remote target connection
23470 Set the timeout for establishing a TCP connection to the remote target to
23471 @var{seconds}. The timeout affects both polling to retry failed connections
23472 (enabled by @code{set tcp auto-retry on}) and waiting for connections
23473 that are merely slow to complete, and represents an approximate cumulative
23474 value. If @var{seconds} is @code{unlimited}, there is no timeout and
23475 @value{GDBN} will keep attempting to establish a connection forever,
23476 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
23478 @item show tcp connect-timeout
23479 Show the current connection timeout setting.
23482 @cindex remote packets, enabling and disabling
23483 The @value{GDBN} remote protocol autodetects the packets supported by
23484 your debugging stub. If you need to override the autodetection, you
23485 can use these commands to enable or disable individual packets. Each
23486 packet can be set to @samp{on} (the remote target supports this
23487 packet), @samp{off} (the remote target does not support this packet),
23488 or @samp{auto} (detect remote target support for this packet). They
23489 all default to @samp{auto}. For more information about each packet,
23490 see @ref{Remote Protocol}.
23492 During normal use, you should not have to use any of these commands.
23493 If you do, that may be a bug in your remote debugging stub, or a bug
23494 in @value{GDBN}. You may want to report the problem to the
23495 @value{GDBN} developers.
23497 For each packet @var{name}, the command to enable or disable the
23498 packet is @code{set remote @var{name}-packet}. The available settings
23501 @multitable @columnfractions 0.28 0.32 0.25
23504 @tab Related Features
23506 @item @code{fetch-register}
23508 @tab @code{info registers}
23510 @item @code{set-register}
23514 @item @code{binary-download}
23516 @tab @code{load}, @code{set}
23518 @item @code{read-aux-vector}
23519 @tab @code{qXfer:auxv:read}
23520 @tab @code{info auxv}
23522 @item @code{symbol-lookup}
23523 @tab @code{qSymbol}
23524 @tab Detecting multiple threads
23526 @item @code{attach}
23527 @tab @code{vAttach}
23530 @item @code{verbose-resume}
23532 @tab Stepping or resuming multiple threads
23538 @item @code{software-breakpoint}
23542 @item @code{hardware-breakpoint}
23546 @item @code{write-watchpoint}
23550 @item @code{read-watchpoint}
23554 @item @code{access-watchpoint}
23558 @item @code{pid-to-exec-file}
23559 @tab @code{qXfer:exec-file:read}
23560 @tab @code{attach}, @code{run}
23562 @item @code{target-features}
23563 @tab @code{qXfer:features:read}
23564 @tab @code{set architecture}
23566 @item @code{library-info}
23567 @tab @code{qXfer:libraries:read}
23568 @tab @code{info sharedlibrary}
23570 @item @code{memory-map}
23571 @tab @code{qXfer:memory-map:read}
23572 @tab @code{info mem}
23574 @item @code{read-sdata-object}
23575 @tab @code{qXfer:sdata:read}
23576 @tab @code{print $_sdata}
23578 @item @code{read-siginfo-object}
23579 @tab @code{qXfer:siginfo:read}
23580 @tab @code{print $_siginfo}
23582 @item @code{write-siginfo-object}
23583 @tab @code{qXfer:siginfo:write}
23584 @tab @code{set $_siginfo}
23586 @item @code{threads}
23587 @tab @code{qXfer:threads:read}
23588 @tab @code{info threads}
23590 @item @code{get-thread-local-@*storage-address}
23591 @tab @code{qGetTLSAddr}
23592 @tab Displaying @code{__thread} variables
23594 @item @code{get-thread-information-block-address}
23595 @tab @code{qGetTIBAddr}
23596 @tab Display MS-Windows Thread Information Block.
23598 @item @code{search-memory}
23599 @tab @code{qSearch:memory}
23602 @item @code{supported-packets}
23603 @tab @code{qSupported}
23604 @tab Remote communications parameters
23606 @item @code{catch-syscalls}
23607 @tab @code{QCatchSyscalls}
23608 @tab @code{catch syscall}
23610 @item @code{pass-signals}
23611 @tab @code{QPassSignals}
23612 @tab @code{handle @var{signal}}
23614 @item @code{program-signals}
23615 @tab @code{QProgramSignals}
23616 @tab @code{handle @var{signal}}
23618 @item @code{hostio-close-packet}
23619 @tab @code{vFile:close}
23620 @tab @code{remote get}, @code{remote put}
23622 @item @code{hostio-open-packet}
23623 @tab @code{vFile:open}
23624 @tab @code{remote get}, @code{remote put}
23626 @item @code{hostio-pread-packet}
23627 @tab @code{vFile:pread}
23628 @tab @code{remote get}, @code{remote put}
23630 @item @code{hostio-pwrite-packet}
23631 @tab @code{vFile:pwrite}
23632 @tab @code{remote get}, @code{remote put}
23634 @item @code{hostio-unlink-packet}
23635 @tab @code{vFile:unlink}
23636 @tab @code{remote delete}
23638 @item @code{hostio-readlink-packet}
23639 @tab @code{vFile:readlink}
23642 @item @code{hostio-fstat-packet}
23643 @tab @code{vFile:fstat}
23646 @item @code{hostio-setfs-packet}
23647 @tab @code{vFile:setfs}
23650 @item @code{noack-packet}
23651 @tab @code{QStartNoAckMode}
23652 @tab Packet acknowledgment
23654 @item @code{osdata}
23655 @tab @code{qXfer:osdata:read}
23656 @tab @code{info os}
23658 @item @code{query-attached}
23659 @tab @code{qAttached}
23660 @tab Querying remote process attach state.
23662 @item @code{trace-buffer-size}
23663 @tab @code{QTBuffer:size}
23664 @tab @code{set trace-buffer-size}
23666 @item @code{trace-status}
23667 @tab @code{qTStatus}
23668 @tab @code{tstatus}
23670 @item @code{traceframe-info}
23671 @tab @code{qXfer:traceframe-info:read}
23672 @tab Traceframe info
23674 @item @code{install-in-trace}
23675 @tab @code{InstallInTrace}
23676 @tab Install tracepoint in tracing
23678 @item @code{disable-randomization}
23679 @tab @code{QDisableRandomization}
23680 @tab @code{set disable-randomization}
23682 @item @code{startup-with-shell}
23683 @tab @code{QStartupWithShell}
23684 @tab @code{set startup-with-shell}
23686 @item @code{environment-hex-encoded}
23687 @tab @code{QEnvironmentHexEncoded}
23688 @tab @code{set environment}
23690 @item @code{environment-unset}
23691 @tab @code{QEnvironmentUnset}
23692 @tab @code{unset environment}
23694 @item @code{environment-reset}
23695 @tab @code{QEnvironmentReset}
23696 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
23698 @item @code{set-working-dir}
23699 @tab @code{QSetWorkingDir}
23700 @tab @code{set cwd}
23702 @item @code{conditional-breakpoints-packet}
23703 @tab @code{Z0 and Z1}
23704 @tab @code{Support for target-side breakpoint condition evaluation}
23706 @item @code{multiprocess-extensions}
23707 @tab @code{multiprocess extensions}
23708 @tab Debug multiple processes and remote process PID awareness
23710 @item @code{swbreak-feature}
23711 @tab @code{swbreak stop reason}
23714 @item @code{hwbreak-feature}
23715 @tab @code{hwbreak stop reason}
23718 @item @code{fork-event-feature}
23719 @tab @code{fork stop reason}
23722 @item @code{vfork-event-feature}
23723 @tab @code{vfork stop reason}
23726 @item @code{exec-event-feature}
23727 @tab @code{exec stop reason}
23730 @item @code{thread-events}
23731 @tab @code{QThreadEvents}
23732 @tab Tracking thread lifetime.
23734 @item @code{no-resumed-stop-reply}
23735 @tab @code{no resumed thread left stop reply}
23736 @tab Tracking thread lifetime.
23741 @section Implementing a Remote Stub
23743 @cindex debugging stub, example
23744 @cindex remote stub, example
23745 @cindex stub example, remote debugging
23746 The stub files provided with @value{GDBN} implement the target side of the
23747 communication protocol, and the @value{GDBN} side is implemented in the
23748 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
23749 these subroutines to communicate, and ignore the details. (If you're
23750 implementing your own stub file, you can still ignore the details: start
23751 with one of the existing stub files. @file{sparc-stub.c} is the best
23752 organized, and therefore the easiest to read.)
23754 @cindex remote serial debugging, overview
23755 To debug a program running on another machine (the debugging
23756 @dfn{target} machine), you must first arrange for all the usual
23757 prerequisites for the program to run by itself. For example, for a C
23762 A startup routine to set up the C runtime environment; these usually
23763 have a name like @file{crt0}. The startup routine may be supplied by
23764 your hardware supplier, or you may have to write your own.
23767 A C subroutine library to support your program's
23768 subroutine calls, notably managing input and output.
23771 A way of getting your program to the other machine---for example, a
23772 download program. These are often supplied by the hardware
23773 manufacturer, but you may have to write your own from hardware
23777 The next step is to arrange for your program to use a serial port to
23778 communicate with the machine where @value{GDBN} is running (the @dfn{host}
23779 machine). In general terms, the scheme looks like this:
23783 @value{GDBN} already understands how to use this protocol; when everything
23784 else is set up, you can simply use the @samp{target remote} command
23785 (@pxref{Targets,,Specifying a Debugging Target}).
23787 @item On the target,
23788 you must link with your program a few special-purpose subroutines that
23789 implement the @value{GDBN} remote serial protocol. The file containing these
23790 subroutines is called a @dfn{debugging stub}.
23792 On certain remote targets, you can use an auxiliary program
23793 @code{gdbserver} instead of linking a stub into your program.
23794 @xref{Server,,Using the @code{gdbserver} Program}, for details.
23797 The debugging stub is specific to the architecture of the remote
23798 machine; for example, use @file{sparc-stub.c} to debug programs on
23801 @cindex remote serial stub list
23802 These working remote stubs are distributed with @value{GDBN}:
23807 @cindex @file{i386-stub.c}
23810 For Intel 386 and compatible architectures.
23813 @cindex @file{m68k-stub.c}
23814 @cindex Motorola 680x0
23816 For Motorola 680x0 architectures.
23819 @cindex @file{sh-stub.c}
23822 For Renesas SH architectures.
23825 @cindex @file{sparc-stub.c}
23827 For @sc{sparc} architectures.
23829 @item sparcl-stub.c
23830 @cindex @file{sparcl-stub.c}
23833 For Fujitsu @sc{sparclite} architectures.
23837 The @file{README} file in the @value{GDBN} distribution may list other
23838 recently added stubs.
23841 * Stub Contents:: What the stub can do for you
23842 * Bootstrapping:: What you must do for the stub
23843 * Debug Session:: Putting it all together
23846 @node Stub Contents
23847 @subsection What the Stub Can Do for You
23849 @cindex remote serial stub
23850 The debugging stub for your architecture supplies these three
23854 @item set_debug_traps
23855 @findex set_debug_traps
23856 @cindex remote serial stub, initialization
23857 This routine arranges for @code{handle_exception} to run when your
23858 program stops. You must call this subroutine explicitly in your
23859 program's startup code.
23861 @item handle_exception
23862 @findex handle_exception
23863 @cindex remote serial stub, main routine
23864 This is the central workhorse, but your program never calls it
23865 explicitly---the setup code arranges for @code{handle_exception} to
23866 run when a trap is triggered.
23868 @code{handle_exception} takes control when your program stops during
23869 execution (for example, on a breakpoint), and mediates communications
23870 with @value{GDBN} on the host machine. This is where the communications
23871 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
23872 representative on the target machine. It begins by sending summary
23873 information on the state of your program, then continues to execute,
23874 retrieving and transmitting any information @value{GDBN} needs, until you
23875 execute a @value{GDBN} command that makes your program resume; at that point,
23876 @code{handle_exception} returns control to your own code on the target
23880 @cindex @code{breakpoint} subroutine, remote
23881 Use this auxiliary subroutine to make your program contain a
23882 breakpoint. Depending on the particular situation, this may be the only
23883 way for @value{GDBN} to get control. For instance, if your target
23884 machine has some sort of interrupt button, you won't need to call this;
23885 pressing the interrupt button transfers control to
23886 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
23887 simply receiving characters on the serial port may also trigger a trap;
23888 again, in that situation, you don't need to call @code{breakpoint} from
23889 your own program---simply running @samp{target remote} from the host
23890 @value{GDBN} session gets control.
23892 Call @code{breakpoint} if none of these is true, or if you simply want
23893 to make certain your program stops at a predetermined point for the
23894 start of your debugging session.
23897 @node Bootstrapping
23898 @subsection What You Must Do for the Stub
23900 @cindex remote stub, support routines
23901 The debugging stubs that come with @value{GDBN} are set up for a particular
23902 chip architecture, but they have no information about the rest of your
23903 debugging target machine.
23905 First of all you need to tell the stub how to communicate with the
23909 @item int getDebugChar()
23910 @findex getDebugChar
23911 Write this subroutine to read a single character from the serial port.
23912 It may be identical to @code{getchar} for your target system; a
23913 different name is used to allow you to distinguish the two if you wish.
23915 @item void putDebugChar(int)
23916 @findex putDebugChar
23917 Write this subroutine to write a single character to the serial port.
23918 It may be identical to @code{putchar} for your target system; a
23919 different name is used to allow you to distinguish the two if you wish.
23922 @cindex control C, and remote debugging
23923 @cindex interrupting remote targets
23924 If you want @value{GDBN} to be able to stop your program while it is
23925 running, you need to use an interrupt-driven serial driver, and arrange
23926 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
23927 character). That is the character which @value{GDBN} uses to tell the
23928 remote system to stop.
23930 Getting the debugging target to return the proper status to @value{GDBN}
23931 probably requires changes to the standard stub; one quick and dirty way
23932 is to just execute a breakpoint instruction (the ``dirty'' part is that
23933 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
23935 Other routines you need to supply are:
23938 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
23939 @findex exceptionHandler
23940 Write this function to install @var{exception_address} in the exception
23941 handling tables. You need to do this because the stub does not have any
23942 way of knowing what the exception handling tables on your target system
23943 are like (for example, the processor's table might be in @sc{rom},
23944 containing entries which point to a table in @sc{ram}).
23945 The @var{exception_number} specifies the exception which should be changed;
23946 its meaning is architecture-dependent (for example, different numbers
23947 might represent divide by zero, misaligned access, etc). When this
23948 exception occurs, control should be transferred directly to
23949 @var{exception_address}, and the processor state (stack, registers,
23950 and so on) should be just as it is when a processor exception occurs. So if
23951 you want to use a jump instruction to reach @var{exception_address}, it
23952 should be a simple jump, not a jump to subroutine.
23954 For the 386, @var{exception_address} should be installed as an interrupt
23955 gate so that interrupts are masked while the handler runs. The gate
23956 should be at privilege level 0 (the most privileged level). The
23957 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
23958 help from @code{exceptionHandler}.
23960 @item void flush_i_cache()
23961 @findex flush_i_cache
23962 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
23963 instruction cache, if any, on your target machine. If there is no
23964 instruction cache, this subroutine may be a no-op.
23966 On target machines that have instruction caches, @value{GDBN} requires this
23967 function to make certain that the state of your program is stable.
23971 You must also make sure this library routine is available:
23974 @item void *memset(void *, int, int)
23976 This is the standard library function @code{memset} that sets an area of
23977 memory to a known value. If you have one of the free versions of
23978 @code{libc.a}, @code{memset} can be found there; otherwise, you must
23979 either obtain it from your hardware manufacturer, or write your own.
23982 If you do not use the GNU C compiler, you may need other standard
23983 library subroutines as well; this varies from one stub to another,
23984 but in general the stubs are likely to use any of the common library
23985 subroutines which @code{@value{NGCC}} generates as inline code.
23988 @node Debug Session
23989 @subsection Putting it All Together
23991 @cindex remote serial debugging summary
23992 In summary, when your program is ready to debug, you must follow these
23997 Make sure you have defined the supporting low-level routines
23998 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
24000 @code{getDebugChar}, @code{putDebugChar},
24001 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
24005 Insert these lines in your program's startup code, before the main
24006 procedure is called:
24013 On some machines, when a breakpoint trap is raised, the hardware
24014 automatically makes the PC point to the instruction after the
24015 breakpoint. If your machine doesn't do that, you may need to adjust
24016 @code{handle_exception} to arrange for it to return to the instruction
24017 after the breakpoint on this first invocation, so that your program
24018 doesn't keep hitting the initial breakpoint instead of making
24022 For the 680x0 stub only, you need to provide a variable called
24023 @code{exceptionHook}. Normally you just use:
24026 void (*exceptionHook)() = 0;
24030 but if before calling @code{set_debug_traps}, you set it to point to a
24031 function in your program, that function is called when
24032 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
24033 error). The function indicated by @code{exceptionHook} is called with
24034 one parameter: an @code{int} which is the exception number.
24037 Compile and link together: your program, the @value{GDBN} debugging stub for
24038 your target architecture, and the supporting subroutines.
24041 Make sure you have a serial connection between your target machine and
24042 the @value{GDBN} host, and identify the serial port on the host.
24045 @c The "remote" target now provides a `load' command, so we should
24046 @c document that. FIXME.
24047 Download your program to your target machine (or get it there by
24048 whatever means the manufacturer provides), and start it.
24051 Start @value{GDBN} on the host, and connect to the target
24052 (@pxref{Connecting,,Connecting to a Remote Target}).
24056 @node Configurations
24057 @chapter Configuration-Specific Information
24059 While nearly all @value{GDBN} commands are available for all native and
24060 cross versions of the debugger, there are some exceptions. This chapter
24061 describes things that are only available in certain configurations.
24063 There are three major categories of configurations: native
24064 configurations, where the host and target are the same, embedded
24065 operating system configurations, which are usually the same for several
24066 different processor architectures, and bare embedded processors, which
24067 are quite different from each other.
24072 * Embedded Processors::
24079 This section describes details specific to particular native
24083 * BSD libkvm Interface:: Debugging BSD kernel memory images
24084 * Process Information:: Process information
24085 * DJGPP Native:: Features specific to the DJGPP port
24086 * Cygwin Native:: Features specific to the Cygwin port
24087 * Hurd Native:: Features specific to @sc{gnu} Hurd
24088 * Darwin:: Features specific to Darwin
24089 * FreeBSD:: Features specific to FreeBSD
24092 @node BSD libkvm Interface
24093 @subsection BSD libkvm Interface
24096 @cindex kernel memory image
24097 @cindex kernel crash dump
24099 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
24100 interface that provides a uniform interface for accessing kernel virtual
24101 memory images, including live systems and crash dumps. @value{GDBN}
24102 uses this interface to allow you to debug live kernels and kernel crash
24103 dumps on many native BSD configurations. This is implemented as a
24104 special @code{kvm} debugging target. For debugging a live system, load
24105 the currently running kernel into @value{GDBN} and connect to the
24109 (@value{GDBP}) @b{target kvm}
24112 For debugging crash dumps, provide the file name of the crash dump as an
24116 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
24119 Once connected to the @code{kvm} target, the following commands are
24125 Set current context from the @dfn{Process Control Block} (PCB) address.
24128 Set current context from proc address. This command isn't available on
24129 modern FreeBSD systems.
24132 @node Process Information
24133 @subsection Process Information
24135 @cindex examine process image
24136 @cindex process info via @file{/proc}
24138 Some operating systems provide interfaces to fetch additional
24139 information about running processes beyond memory and per-thread
24140 register state. If @value{GDBN} is configured for an operating system
24141 with a supported interface, the command @code{info proc} is available
24142 to report information about the process running your program, or about
24143 any process running on your system.
24145 One supported interface is a facility called @samp{/proc} that can be
24146 used to examine the image of a running process using file-system
24147 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
24150 On FreeBSD and NetBSD systems, system control nodes are used to query
24151 process information.
24153 In addition, some systems may provide additional process information
24154 in core files. Note that a core file may include a subset of the
24155 information available from a live process. Process information is
24156 currently available from cores created on @sc{gnu}/Linux and FreeBSD
24163 @itemx info proc @var{process-id}
24164 Summarize available information about a process. If a
24165 process ID is specified by @var{process-id}, display information about
24166 that process; otherwise display information about the program being
24167 debugged. The summary includes the debugged process ID, the command
24168 line used to invoke it, its current working directory, and its
24169 executable file's absolute file name.
24171 On some systems, @var{process-id} can be of the form
24172 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
24173 within a process. If the optional @var{pid} part is missing, it means
24174 a thread from the process being debugged (the leading @samp{/} still
24175 needs to be present, or else @value{GDBN} will interpret the number as
24176 a process ID rather than a thread ID).
24178 @item info proc cmdline
24179 @cindex info proc cmdline
24180 Show the original command line of the process. This command is
24181 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24183 @item info proc cwd
24184 @cindex info proc cwd
24185 Show the current working directory of the process. This command is
24186 supported on @sc{gnu}/Linux, FreeBSD and NetBSD.
24188 @item info proc exe
24189 @cindex info proc exe
24190 Show the name of executable of the process. This command is supported
24191 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24193 @item info proc files
24194 @cindex info proc files
24195 Show the file descriptors open by the process. For each open file
24196 descriptor, @value{GDBN} shows its number, type (file, directory,
24197 character device, socket), file pointer offset, and the name of the
24198 resource open on the descriptor. The resource name can be a file name
24199 (for files, directories, and devices) or a protocol followed by socket
24200 address (for network connections). This command is supported on
24203 This example shows the open file descriptors for a process using a
24204 tty for standard input and output as well as two network sockets:
24207 (gdb) info proc files 22136
24211 FD Type Offset Flags Name
24212 text file - r-------- /usr/bin/ssh
24213 ctty chr - rw------- /dev/pts/20
24214 cwd dir - r-------- /usr/home/john
24215 root dir - r-------- /
24216 0 chr 0x32933a4 rw------- /dev/pts/20
24217 1 chr 0x32933a4 rw------- /dev/pts/20
24218 2 chr 0x32933a4 rw------- /dev/pts/20
24219 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
24220 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
24223 @item info proc mappings
24224 @cindex memory address space mappings
24225 Report the memory address space ranges accessible in a process. On
24226 Solaris, FreeBSD and NetBSD systems, each memory range includes information
24227 on whether the process has read, write, or execute access rights to each
24228 range. On @sc{gnu}/Linux, FreeBSD and NetBSD systems, each memory range
24229 includes the object file which is mapped to that range.
24231 @item info proc stat
24232 @itemx info proc status
24233 @cindex process detailed status information
24234 Show additional process-related information, including the user ID and
24235 group ID; virtual memory usage; the signals that are pending, blocked,
24236 and ignored; its TTY; its consumption of system and user time; its
24237 stack size; its @samp{nice} value; etc. These commands are supported
24238 on @sc{gnu}/Linux, FreeBSD and NetBSD.
24240 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
24241 information (type @kbd{man 5 proc} from your shell prompt).
24243 For FreeBSD and NetBSD systems, @code{info proc stat} is an alias for
24244 @code{info proc status}.
24246 @item info proc all
24247 Show all the information about the process described under all of the
24248 above @code{info proc} subcommands.
24251 @comment These sub-options of 'info proc' were not included when
24252 @comment procfs.c was re-written. Keep their descriptions around
24253 @comment against the day when someone finds the time to put them back in.
24254 @kindex info proc times
24255 @item info proc times
24256 Starting time, user CPU time, and system CPU time for your program and
24259 @kindex info proc id
24261 Report on the process IDs related to your program: its own process ID,
24262 the ID of its parent, the process group ID, and the session ID.
24265 @item set procfs-trace
24266 @kindex set procfs-trace
24267 @cindex @code{procfs} API calls
24268 This command enables and disables tracing of @code{procfs} API calls.
24270 @item show procfs-trace
24271 @kindex show procfs-trace
24272 Show the current state of @code{procfs} API call tracing.
24274 @item set procfs-file @var{file}
24275 @kindex set procfs-file
24276 Tell @value{GDBN} to write @code{procfs} API trace to the named
24277 @var{file}. @value{GDBN} appends the trace info to the previous
24278 contents of the file. The default is to display the trace on the
24281 @item show procfs-file
24282 @kindex show procfs-file
24283 Show the file to which @code{procfs} API trace is written.
24285 @item proc-trace-entry
24286 @itemx proc-trace-exit
24287 @itemx proc-untrace-entry
24288 @itemx proc-untrace-exit
24289 @kindex proc-trace-entry
24290 @kindex proc-trace-exit
24291 @kindex proc-untrace-entry
24292 @kindex proc-untrace-exit
24293 These commands enable and disable tracing of entries into and exits
24294 from the @code{syscall} interface.
24297 @kindex info pidlist
24298 @cindex process list, QNX Neutrino
24299 For QNX Neutrino only, this command displays the list of all the
24300 processes and all the threads within each process.
24303 @kindex info meminfo
24304 @cindex mapinfo list, QNX Neutrino
24305 For QNX Neutrino only, this command displays the list of all mapinfos.
24309 @subsection Features for Debugging @sc{djgpp} Programs
24310 @cindex @sc{djgpp} debugging
24311 @cindex native @sc{djgpp} debugging
24312 @cindex MS-DOS-specific commands
24315 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
24316 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
24317 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
24318 top of real-mode DOS systems and their emulations.
24320 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
24321 defines a few commands specific to the @sc{djgpp} port. This
24322 subsection describes those commands.
24327 This is a prefix of @sc{djgpp}-specific commands which print
24328 information about the target system and important OS structures.
24331 @cindex MS-DOS system info
24332 @cindex free memory information (MS-DOS)
24333 @item info dos sysinfo
24334 This command displays assorted information about the underlying
24335 platform: the CPU type and features, the OS version and flavor, the
24336 DPMI version, and the available conventional and DPMI memory.
24341 @cindex segment descriptor tables
24342 @cindex descriptor tables display
24344 @itemx info dos ldt
24345 @itemx info dos idt
24346 These 3 commands display entries from, respectively, Global, Local,
24347 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
24348 tables are data structures which store a descriptor for each segment
24349 that is currently in use. The segment's selector is an index into a
24350 descriptor table; the table entry for that index holds the
24351 descriptor's base address and limit, and its attributes and access
24354 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
24355 segment (used for both data and the stack), and a DOS segment (which
24356 allows access to DOS/BIOS data structures and absolute addresses in
24357 conventional memory). However, the DPMI host will usually define
24358 additional segments in order to support the DPMI environment.
24360 @cindex garbled pointers
24361 These commands allow to display entries from the descriptor tables.
24362 Without an argument, all entries from the specified table are
24363 displayed. An argument, which should be an integer expression, means
24364 display a single entry whose index is given by the argument. For
24365 example, here's a convenient way to display information about the
24366 debugged program's data segment:
24369 @exdent @code{(@value{GDBP}) info dos ldt $ds}
24370 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
24374 This comes in handy when you want to see whether a pointer is outside
24375 the data segment's limit (i.e.@: @dfn{garbled}).
24377 @cindex page tables display (MS-DOS)
24379 @itemx info dos pte
24380 These two commands display entries from, respectively, the Page
24381 Directory and the Page Tables. Page Directories and Page Tables are
24382 data structures which control how virtual memory addresses are mapped
24383 into physical addresses. A Page Table includes an entry for every
24384 page of memory that is mapped into the program's address space; there
24385 may be several Page Tables, each one holding up to 4096 entries. A
24386 Page Directory has up to 4096 entries, one each for every Page Table
24387 that is currently in use.
24389 Without an argument, @kbd{info dos pde} displays the entire Page
24390 Directory, and @kbd{info dos pte} displays all the entries in all of
24391 the Page Tables. An argument, an integer expression, given to the
24392 @kbd{info dos pde} command means display only that entry from the Page
24393 Directory table. An argument given to the @kbd{info dos pte} command
24394 means display entries from a single Page Table, the one pointed to by
24395 the specified entry in the Page Directory.
24397 @cindex direct memory access (DMA) on MS-DOS
24398 These commands are useful when your program uses @dfn{DMA} (Direct
24399 Memory Access), which needs physical addresses to program the DMA
24402 These commands are supported only with some DPMI servers.
24404 @cindex physical address from linear address
24405 @item info dos address-pte @var{addr}
24406 This command displays the Page Table entry for a specified linear
24407 address. The argument @var{addr} is a linear address which should
24408 already have the appropriate segment's base address added to it,
24409 because this command accepts addresses which may belong to @emph{any}
24410 segment. For example, here's how to display the Page Table entry for
24411 the page where a variable @code{i} is stored:
24414 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
24415 @exdent @code{Page Table entry for address 0x11a00d30:}
24416 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
24420 This says that @code{i} is stored at offset @code{0xd30} from the page
24421 whose physical base address is @code{0x02698000}, and shows all the
24422 attributes of that page.
24424 Note that you must cast the addresses of variables to a @code{char *},
24425 since otherwise the value of @code{__djgpp_base_address}, the base
24426 address of all variables and functions in a @sc{djgpp} program, will
24427 be added using the rules of C pointer arithmetics: if @code{i} is
24428 declared an @code{int}, @value{GDBN} will add 4 times the value of
24429 @code{__djgpp_base_address} to the address of @code{i}.
24431 Here's another example, it displays the Page Table entry for the
24435 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
24436 @exdent @code{Page Table entry for address 0x29110:}
24437 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
24441 (The @code{+ 3} offset is because the transfer buffer's address is the
24442 3rd member of the @code{_go32_info_block} structure.) The output
24443 clearly shows that this DPMI server maps the addresses in conventional
24444 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
24445 linear (@code{0x29110}) addresses are identical.
24447 This command is supported only with some DPMI servers.
24450 @cindex DOS serial data link, remote debugging
24451 In addition to native debugging, the DJGPP port supports remote
24452 debugging via a serial data link. The following commands are specific
24453 to remote serial debugging in the DJGPP port of @value{GDBN}.
24456 @kindex set com1base
24457 @kindex set com1irq
24458 @kindex set com2base
24459 @kindex set com2irq
24460 @kindex set com3base
24461 @kindex set com3irq
24462 @kindex set com4base
24463 @kindex set com4irq
24464 @item set com1base @var{addr}
24465 This command sets the base I/O port address of the @file{COM1} serial
24468 @item set com1irq @var{irq}
24469 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
24470 for the @file{COM1} serial port.
24472 There are similar commands @samp{set com2base}, @samp{set com3irq},
24473 etc.@: for setting the port address and the @code{IRQ} lines for the
24476 @kindex show com1base
24477 @kindex show com1irq
24478 @kindex show com2base
24479 @kindex show com2irq
24480 @kindex show com3base
24481 @kindex show com3irq
24482 @kindex show com4base
24483 @kindex show com4irq
24484 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
24485 display the current settings of the base address and the @code{IRQ}
24486 lines used by the COM ports.
24489 @kindex info serial
24490 @cindex DOS serial port status
24491 This command prints the status of the 4 DOS serial ports. For each
24492 port, it prints whether it's active or not, its I/O base address and
24493 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
24494 counts of various errors encountered so far.
24498 @node Cygwin Native
24499 @subsection Features for Debugging MS Windows PE Executables
24500 @cindex MS Windows debugging
24501 @cindex native Cygwin debugging
24502 @cindex Cygwin-specific commands
24504 @value{GDBN} supports native debugging of MS Windows programs, including
24505 DLLs with and without symbolic debugging information.
24507 @cindex Ctrl-BREAK, MS-Windows
24508 @cindex interrupt debuggee on MS-Windows
24509 MS-Windows programs that call @code{SetConsoleMode} to switch off the
24510 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
24511 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
24512 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
24513 sequence, which can be used to interrupt the debuggee even if it
24516 There are various additional Cygwin-specific commands, described in
24517 this section. Working with DLLs that have no debugging symbols is
24518 described in @ref{Non-debug DLL Symbols}.
24523 This is a prefix of MS Windows-specific commands which print
24524 information about the target system and important OS structures.
24526 @item info w32 selector
24527 This command displays information returned by
24528 the Win32 API @code{GetThreadSelectorEntry} function.
24529 It takes an optional argument that is evaluated to
24530 a long value to give the information about this given selector.
24531 Without argument, this command displays information
24532 about the six segment registers.
24534 @item info w32 thread-information-block
24535 This command displays thread specific information stored in the
24536 Thread Information Block (readable on the X86 CPU family using @code{$fs}
24537 selector for 32-bit programs and @code{$gs} for 64-bit programs).
24539 @kindex signal-event
24540 @item signal-event @var{id}
24541 This command signals an event with user-provided @var{id}. Used to resume
24542 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
24544 To use it, create or edit the following keys in
24545 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
24546 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
24547 (for x86_64 versions):
24551 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
24552 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
24553 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
24555 The first @code{%ld} will be replaced by the process ID of the
24556 crashing process, the second @code{%ld} will be replaced by the ID of
24557 the event that blocks the crashing process, waiting for @value{GDBN}
24561 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
24562 make the system run debugger specified by the Debugger key
24563 automatically, @code{0} will cause a dialog box with ``OK'' and
24564 ``Cancel'' buttons to appear, which allows the user to either
24565 terminate the crashing process (OK) or debug it (Cancel).
24568 @kindex set cygwin-exceptions
24569 @cindex debugging the Cygwin DLL
24570 @cindex Cygwin DLL, debugging
24571 @item set cygwin-exceptions @var{mode}
24572 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
24573 happen inside the Cygwin DLL. If @var{mode} is @code{off},
24574 @value{GDBN} will delay recognition of exceptions, and may ignore some
24575 exceptions which seem to be caused by internal Cygwin DLL
24576 ``bookkeeping''. This option is meant primarily for debugging the
24577 Cygwin DLL itself; the default value is @code{off} to avoid annoying
24578 @value{GDBN} users with false @code{SIGSEGV} signals.
24580 @kindex show cygwin-exceptions
24581 @item show cygwin-exceptions
24582 Displays whether @value{GDBN} will break on exceptions that happen
24583 inside the Cygwin DLL itself.
24585 @kindex set new-console
24586 @item set new-console @var{mode}
24587 If @var{mode} is @code{on} the debuggee will
24588 be started in a new console on next start.
24589 If @var{mode} is @code{off}, the debuggee will
24590 be started in the same console as the debugger.
24592 @kindex show new-console
24593 @item show new-console
24594 Displays whether a new console is used
24595 when the debuggee is started.
24597 @kindex set new-group
24598 @item set new-group @var{mode}
24599 This boolean value controls whether the debuggee should
24600 start a new group or stay in the same group as the debugger.
24601 This affects the way the Windows OS handles
24604 @kindex show new-group
24605 @item show new-group
24606 Displays current value of new-group boolean.
24608 @kindex set debugevents
24609 @item set debugevents
24610 This boolean value adds debug output concerning kernel events related
24611 to the debuggee seen by the debugger. This includes events that
24612 signal thread and process creation and exit, DLL loading and
24613 unloading, console interrupts, and debugging messages produced by the
24614 Windows @code{OutputDebugString} API call.
24616 @kindex set debugexec
24617 @item set debugexec
24618 This boolean value adds debug output concerning execute events
24619 (such as resume thread) seen by the debugger.
24621 @kindex set debugexceptions
24622 @item set debugexceptions
24623 This boolean value adds debug output concerning exceptions in the
24624 debuggee seen by the debugger.
24626 @kindex set debugmemory
24627 @item set debugmemory
24628 This boolean value adds debug output concerning debuggee memory reads
24629 and writes by the debugger.
24633 This boolean values specifies whether the debuggee is called
24634 via a shell or directly (default value is on).
24638 Displays if the debuggee will be started with a shell.
24643 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
24646 @node Non-debug DLL Symbols
24647 @subsubsection Support for DLLs without Debugging Symbols
24648 @cindex DLLs with no debugging symbols
24649 @cindex Minimal symbols and DLLs
24651 Very often on windows, some of the DLLs that your program relies on do
24652 not include symbolic debugging information (for example,
24653 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
24654 symbols in a DLL, it relies on the minimal amount of symbolic
24655 information contained in the DLL's export table. This section
24656 describes working with such symbols, known internally to @value{GDBN} as
24657 ``minimal symbols''.
24659 Note that before the debugged program has started execution, no DLLs
24660 will have been loaded. The easiest way around this problem is simply to
24661 start the program --- either by setting a breakpoint or letting the
24662 program run once to completion.
24664 @subsubsection DLL Name Prefixes
24666 In keeping with the naming conventions used by the Microsoft debugging
24667 tools, DLL export symbols are made available with a prefix based on the
24668 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
24669 also entered into the symbol table, so @code{CreateFileA} is often
24670 sufficient. In some cases there will be name clashes within a program
24671 (particularly if the executable itself includes full debugging symbols)
24672 necessitating the use of the fully qualified name when referring to the
24673 contents of the DLL. Use single-quotes around the name to avoid the
24674 exclamation mark (``!'') being interpreted as a language operator.
24676 Note that the internal name of the DLL may be all upper-case, even
24677 though the file name of the DLL is lower-case, or vice-versa. Since
24678 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
24679 some confusion. If in doubt, try the @code{info functions} and
24680 @code{info variables} commands or even @code{maint print msymbols}
24681 (@pxref{Symbols}). Here's an example:
24684 (@value{GDBP}) info function CreateFileA
24685 All functions matching regular expression "CreateFileA":
24687 Non-debugging symbols:
24688 0x77e885f4 CreateFileA
24689 0x77e885f4 KERNEL32!CreateFileA
24693 (@value{GDBP}) info function !
24694 All functions matching regular expression "!":
24696 Non-debugging symbols:
24697 0x6100114c cygwin1!__assert
24698 0x61004034 cygwin1!_dll_crt0@@0
24699 0x61004240 cygwin1!dll_crt0(per_process *)
24703 @subsubsection Working with Minimal Symbols
24705 Symbols extracted from a DLL's export table do not contain very much
24706 type information. All that @value{GDBN} can do is guess whether a symbol
24707 refers to a function or variable depending on the linker section that
24708 contains the symbol. Also note that the actual contents of the memory
24709 contained in a DLL are not available unless the program is running. This
24710 means that you cannot examine the contents of a variable or disassemble
24711 a function within a DLL without a running program.
24713 Variables are generally treated as pointers and dereferenced
24714 automatically. For this reason, it is often necessary to prefix a
24715 variable name with the address-of operator (``&'') and provide explicit
24716 type information in the command. Here's an example of the type of
24720 (@value{GDBP}) print 'cygwin1!__argv'
24721 'cygwin1!__argv' has unknown type; cast it to its declared type
24725 (@value{GDBP}) x 'cygwin1!__argv'
24726 'cygwin1!__argv' has unknown type; cast it to its declared type
24729 And two possible solutions:
24732 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
24733 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
24737 (@value{GDBP}) x/2x &'cygwin1!__argv'
24738 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
24739 (@value{GDBP}) x/x 0x10021608
24740 0x10021608: 0x0022fd98
24741 (@value{GDBP}) x/s 0x0022fd98
24742 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
24745 Setting a break point within a DLL is possible even before the program
24746 starts execution. However, under these circumstances, @value{GDBN} can't
24747 examine the initial instructions of the function in order to skip the
24748 function's frame set-up code. You can work around this by using ``*&''
24749 to set the breakpoint at a raw memory address:
24752 (@value{GDBP}) break *&'python22!PyOS_Readline'
24753 Breakpoint 1 at 0x1e04eff0
24756 The author of these extensions is not entirely convinced that setting a
24757 break point within a shared DLL like @file{kernel32.dll} is completely
24761 @subsection Commands Specific to @sc{gnu} Hurd Systems
24762 @cindex @sc{gnu} Hurd debugging
24764 This subsection describes @value{GDBN} commands specific to the
24765 @sc{gnu} Hurd native debugging.
24770 @kindex set signals@r{, Hurd command}
24771 @kindex set sigs@r{, Hurd command}
24772 This command toggles the state of inferior signal interception by
24773 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
24774 affected by this command. @code{sigs} is a shorthand alias for
24779 @kindex show signals@r{, Hurd command}
24780 @kindex show sigs@r{, Hurd command}
24781 Show the current state of intercepting inferior's signals.
24783 @item set signal-thread
24784 @itemx set sigthread
24785 @kindex set signal-thread
24786 @kindex set sigthread
24787 This command tells @value{GDBN} which thread is the @code{libc} signal
24788 thread. That thread is run when a signal is delivered to a running
24789 process. @code{set sigthread} is the shorthand alias of @code{set
24792 @item show signal-thread
24793 @itemx show sigthread
24794 @kindex show signal-thread
24795 @kindex show sigthread
24796 These two commands show which thread will run when the inferior is
24797 delivered a signal.
24800 @kindex set stopped@r{, Hurd command}
24801 This commands tells @value{GDBN} that the inferior process is stopped,
24802 as with the @code{SIGSTOP} signal. The stopped process can be
24803 continued by delivering a signal to it.
24806 @kindex show stopped@r{, Hurd command}
24807 This command shows whether @value{GDBN} thinks the debuggee is
24810 @item set exceptions
24811 @kindex set exceptions@r{, Hurd command}
24812 Use this command to turn off trapping of exceptions in the inferior.
24813 When exception trapping is off, neither breakpoints nor
24814 single-stepping will work. To restore the default, set exception
24817 @item show exceptions
24818 @kindex show exceptions@r{, Hurd command}
24819 Show the current state of trapping exceptions in the inferior.
24821 @item set task pause
24822 @kindex set task@r{, Hurd commands}
24823 @cindex task attributes (@sc{gnu} Hurd)
24824 @cindex pause current task (@sc{gnu} Hurd)
24825 This command toggles task suspension when @value{GDBN} has control.
24826 Setting it to on takes effect immediately, and the task is suspended
24827 whenever @value{GDBN} gets control. Setting it to off will take
24828 effect the next time the inferior is continued. If this option is set
24829 to off, you can use @code{set thread default pause on} or @code{set
24830 thread pause on} (see below) to pause individual threads.
24832 @item show task pause
24833 @kindex show task@r{, Hurd commands}
24834 Show the current state of task suspension.
24836 @item set task detach-suspend-count
24837 @cindex task suspend count
24838 @cindex detach from task, @sc{gnu} Hurd
24839 This command sets the suspend count the task will be left with when
24840 @value{GDBN} detaches from it.
24842 @item show task detach-suspend-count
24843 Show the suspend count the task will be left with when detaching.
24845 @item set task exception-port
24846 @itemx set task excp
24847 @cindex task exception port, @sc{gnu} Hurd
24848 This command sets the task exception port to which @value{GDBN} will
24849 forward exceptions. The argument should be the value of the @dfn{send
24850 rights} of the task. @code{set task excp} is a shorthand alias.
24852 @item set noninvasive
24853 @cindex noninvasive task options
24854 This command switches @value{GDBN} to a mode that is the least
24855 invasive as far as interfering with the inferior is concerned. This
24856 is the same as using @code{set task pause}, @code{set exceptions}, and
24857 @code{set signals} to values opposite to the defaults.
24859 @item info send-rights
24860 @itemx info receive-rights
24861 @itemx info port-rights
24862 @itemx info port-sets
24863 @itemx info dead-names
24866 @cindex send rights, @sc{gnu} Hurd
24867 @cindex receive rights, @sc{gnu} Hurd
24868 @cindex port rights, @sc{gnu} Hurd
24869 @cindex port sets, @sc{gnu} Hurd
24870 @cindex dead names, @sc{gnu} Hurd
24871 These commands display information about, respectively, send rights,
24872 receive rights, port rights, port sets, and dead names of a task.
24873 There are also shorthand aliases: @code{info ports} for @code{info
24874 port-rights} and @code{info psets} for @code{info port-sets}.
24876 @item set thread pause
24877 @kindex set thread@r{, Hurd command}
24878 @cindex thread properties, @sc{gnu} Hurd
24879 @cindex pause current thread (@sc{gnu} Hurd)
24880 This command toggles current thread suspension when @value{GDBN} has
24881 control. Setting it to on takes effect immediately, and the current
24882 thread is suspended whenever @value{GDBN} gets control. Setting it to
24883 off will take effect the next time the inferior is continued.
24884 Normally, this command has no effect, since when @value{GDBN} has
24885 control, the whole task is suspended. However, if you used @code{set
24886 task pause off} (see above), this command comes in handy to suspend
24887 only the current thread.
24889 @item show thread pause
24890 @kindex show thread@r{, Hurd command}
24891 This command shows the state of current thread suspension.
24893 @item set thread run
24894 This command sets whether the current thread is allowed to run.
24896 @item show thread run
24897 Show whether the current thread is allowed to run.
24899 @item set thread detach-suspend-count
24900 @cindex thread suspend count, @sc{gnu} Hurd
24901 @cindex detach from thread, @sc{gnu} Hurd
24902 This command sets the suspend count @value{GDBN} will leave on a
24903 thread when detaching. This number is relative to the suspend count
24904 found by @value{GDBN} when it notices the thread; use @code{set thread
24905 takeover-suspend-count} to force it to an absolute value.
24907 @item show thread detach-suspend-count
24908 Show the suspend count @value{GDBN} will leave on the thread when
24911 @item set thread exception-port
24912 @itemx set thread excp
24913 Set the thread exception port to which to forward exceptions. This
24914 overrides the port set by @code{set task exception-port} (see above).
24915 @code{set thread excp} is the shorthand alias.
24917 @item set thread takeover-suspend-count
24918 Normally, @value{GDBN}'s thread suspend counts are relative to the
24919 value @value{GDBN} finds when it notices each thread. This command
24920 changes the suspend counts to be absolute instead.
24922 @item set thread default
24923 @itemx show thread default
24924 @cindex thread default settings, @sc{gnu} Hurd
24925 Each of the above @code{set thread} commands has a @code{set thread
24926 default} counterpart (e.g., @code{set thread default pause}, @code{set
24927 thread default exception-port}, etc.). The @code{thread default}
24928 variety of commands sets the default thread properties for all
24929 threads; you can then change the properties of individual threads with
24930 the non-default commands.
24937 @value{GDBN} provides the following commands specific to the Darwin target:
24940 @item set debug darwin @var{num}
24941 @kindex set debug darwin
24942 When set to a non zero value, enables debugging messages specific to
24943 the Darwin support. Higher values produce more verbose output.
24945 @item show debug darwin
24946 @kindex show debug darwin
24947 Show the current state of Darwin messages.
24949 @item set debug mach-o @var{num}
24950 @kindex set debug mach-o
24951 When set to a non zero value, enables debugging messages while
24952 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
24953 file format used on Darwin for object and executable files.) Higher
24954 values produce more verbose output. This is a command to diagnose
24955 problems internal to @value{GDBN} and should not be needed in normal
24958 @item show debug mach-o
24959 @kindex show debug mach-o
24960 Show the current state of Mach-O file messages.
24962 @item set mach-exceptions on
24963 @itemx set mach-exceptions off
24964 @kindex set mach-exceptions
24965 On Darwin, faults are first reported as a Mach exception and are then
24966 mapped to a Posix signal. Use this command to turn on trapping of
24967 Mach exceptions in the inferior. This might be sometimes useful to
24968 better understand the cause of a fault. The default is off.
24970 @item show mach-exceptions
24971 @kindex show mach-exceptions
24972 Show the current state of exceptions trapping.
24976 @subsection FreeBSD
24979 When the ABI of a system call is changed in the FreeBSD kernel, this
24980 is implemented by leaving a compatibility system call using the old
24981 ABI at the existing number and allocating a new system call number for
24982 the version using the new ABI. As a convenience, when a system call
24983 is caught by name (@pxref{catch syscall}), compatibility system calls
24986 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
24987 system call and catching the @code{kevent} system call by name catches
24991 (@value{GDBP}) catch syscall kevent
24992 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
24998 @section Embedded Operating Systems
25000 This section describes configurations involving the debugging of
25001 embedded operating systems that are available for several different
25004 @value{GDBN} includes the ability to debug programs running on
25005 various real-time operating systems.
25007 @node Embedded Processors
25008 @section Embedded Processors
25010 This section goes into details specific to particular embedded
25013 @cindex send command to simulator
25014 Whenever a specific embedded processor has a simulator, @value{GDBN}
25015 allows to send an arbitrary command to the simulator.
25018 @item sim @var{command}
25019 @kindex sim@r{, a command}
25020 Send an arbitrary @var{command} string to the simulator. Consult the
25021 documentation for the specific simulator in use for information about
25022 acceptable commands.
25027 * ARC:: Synopsys ARC
25030 * M68K:: Motorola M68K
25031 * MicroBlaze:: Xilinx MicroBlaze
25032 * MIPS Embedded:: MIPS Embedded
25033 * OpenRISC 1000:: OpenRISC 1000 (or1k)
25034 * PowerPC Embedded:: PowerPC Embedded
25037 * Super-H:: Renesas Super-H
25041 @subsection Synopsys ARC
25042 @cindex Synopsys ARC
25043 @cindex ARC specific commands
25049 @value{GDBN} provides the following ARC-specific commands:
25052 @item set debug arc
25053 @kindex set debug arc
25054 Control the level of ARC specific debug messages. Use 0 for no messages (the
25055 default), 1 for debug messages, and 2 for even more debug messages.
25057 @item show debug arc
25058 @kindex show debug arc
25059 Show the level of ARC specific debugging in operation.
25061 @item maint print arc arc-instruction @var{address}
25062 @kindex maint print arc arc-instruction
25063 Print internal disassembler information about instruction at a given address.
25070 @value{GDBN} provides the following ARM-specific commands:
25073 @item set arm disassembler
25075 This commands selects from a list of disassembly styles. The
25076 @code{"std"} style is the standard style.
25078 @item show arm disassembler
25080 Show the current disassembly style.
25082 @item set arm apcs32
25083 @cindex ARM 32-bit mode
25084 This command toggles ARM operation mode between 32-bit and 26-bit.
25086 @item show arm apcs32
25087 Display the current usage of the ARM 32-bit mode.
25089 @item set arm fpu @var{fputype}
25090 This command sets the ARM floating-point unit (FPU) type. The
25091 argument @var{fputype} can be one of these:
25095 Determine the FPU type by querying the OS ABI.
25097 Software FPU, with mixed-endian doubles on little-endian ARM
25100 GCC-compiled FPA co-processor.
25102 Software FPU with pure-endian doubles.
25108 Show the current type of the FPU.
25111 This command forces @value{GDBN} to use the specified ABI.
25114 Show the currently used ABI.
25116 @item set arm fallback-mode (arm|thumb|auto)
25117 @value{GDBN} uses the symbol table, when available, to determine
25118 whether instructions are ARM or Thumb. This command controls
25119 @value{GDBN}'s default behavior when the symbol table is not
25120 available. The default is @samp{auto}, which causes @value{GDBN} to
25121 use the current execution mode (from the @code{T} bit in the @code{CPSR}
25124 @item show arm fallback-mode
25125 Show the current fallback instruction mode.
25127 @item set arm force-mode (arm|thumb|auto)
25128 This command overrides use of the symbol table to determine whether
25129 instructions are ARM or Thumb. The default is @samp{auto}, which
25130 causes @value{GDBN} to use the symbol table and then the setting
25131 of @samp{set arm fallback-mode}.
25133 @item show arm force-mode
25134 Show the current forced instruction mode.
25136 @item set debug arm
25137 Toggle whether to display ARM-specific debugging messages from the ARM
25138 target support subsystem.
25140 @item show debug arm
25141 Show whether ARM-specific debugging messages are enabled.
25145 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25146 The @value{GDBN} ARM simulator accepts the following optional arguments.
25149 @item --swi-support=@var{type}
25150 Tell the simulator which SWI interfaces to support. The argument
25151 @var{type} may be a comma separated list of the following values.
25152 The default value is @code{all}.
25168 @item target sim @r{[}@var{simargs}@r{]} @dots{}
25169 The @value{GDBN} BPF simulator accepts the following optional arguments.
25172 @item --skb-data-offset=@var{offset}
25173 Tell the simulator the offset, measured in bytes, of the
25174 @code{skb_data} field in the kernel @code{struct sk_buff} structure.
25175 This offset is used by some BPF specific-purpose load/store
25176 instructions. Defaults to 0.
25183 The Motorola m68k configuration includes ColdFire support.
25186 @subsection MicroBlaze
25187 @cindex Xilinx MicroBlaze
25188 @cindex XMD, Xilinx Microprocessor Debugger
25190 The MicroBlaze is a soft-core processor supported on various Xilinx
25191 FPGAs, such as Spartan or Virtex series. Boards with these processors
25192 usually have JTAG ports which connect to a host system running the Xilinx
25193 Embedded Development Kit (EDK) or Software Development Kit (SDK).
25194 This host system is used to download the configuration bitstream to
25195 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
25196 communicates with the target board using the JTAG interface and
25197 presents a @code{gdbserver} interface to the board. By default
25198 @code{xmd} uses port @code{1234}. (While it is possible to change
25199 this default port, it requires the use of undocumented @code{xmd}
25200 commands. Contact Xilinx support if you need to do this.)
25202 Use these GDB commands to connect to the MicroBlaze target processor.
25205 @item target remote :1234
25206 Use this command to connect to the target if you are running @value{GDBN}
25207 on the same system as @code{xmd}.
25209 @item target remote @var{xmd-host}:1234
25210 Use this command to connect to the target if it is connected to @code{xmd}
25211 running on a different system named @var{xmd-host}.
25214 Use this command to download a program to the MicroBlaze target.
25216 @item set debug microblaze @var{n}
25217 Enable MicroBlaze-specific debugging messages if non-zero.
25219 @item show debug microblaze @var{n}
25220 Show MicroBlaze-specific debugging level.
25223 @node MIPS Embedded
25224 @subsection @acronym{MIPS} Embedded
25227 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
25230 @item set mipsfpu double
25231 @itemx set mipsfpu single
25232 @itemx set mipsfpu none
25233 @itemx set mipsfpu auto
25234 @itemx show mipsfpu
25235 @kindex set mipsfpu
25236 @kindex show mipsfpu
25237 @cindex @acronym{MIPS} remote floating point
25238 @cindex floating point, @acronym{MIPS} remote
25239 If your target board does not support the @acronym{MIPS} floating point
25240 coprocessor, you should use the command @samp{set mipsfpu none} (if you
25241 need this, you may wish to put the command in your @value{GDBN} init
25242 file). This tells @value{GDBN} how to find the return value of
25243 functions which return floating point values. It also allows
25244 @value{GDBN} to avoid saving the floating point registers when calling
25245 functions on the board. If you are using a floating point coprocessor
25246 with only single precision floating point support, as on the @sc{r4650}
25247 processor, use the command @samp{set mipsfpu single}. The default
25248 double precision floating point coprocessor may be selected using
25249 @samp{set mipsfpu double}.
25251 In previous versions the only choices were double precision or no
25252 floating point, so @samp{set mipsfpu on} will select double precision
25253 and @samp{set mipsfpu off} will select no floating point.
25255 As usual, you can inquire about the @code{mipsfpu} variable with
25256 @samp{show mipsfpu}.
25259 @node OpenRISC 1000
25260 @subsection OpenRISC 1000
25261 @cindex OpenRISC 1000
25264 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
25265 mainly provided as a soft-core which can run on Xilinx, Altera and other
25268 @value{GDBN} for OpenRISC supports the below commands when connecting to
25276 Runs the builtin CPU simulator which can run very basic
25277 programs but does not support most hardware functions like MMU.
25278 For more complex use cases the user is advised to run an external
25279 target, and connect using @samp{target remote}.
25281 Example: @code{target sim}
25283 @item set debug or1k
25284 Toggle whether to display OpenRISC-specific debugging messages from the
25285 OpenRISC target support subsystem.
25287 @item show debug or1k
25288 Show whether OpenRISC-specific debugging messages are enabled.
25291 @node PowerPC Embedded
25292 @subsection PowerPC Embedded
25294 @cindex DVC register
25295 @value{GDBN} supports using the DVC (Data Value Compare) register to
25296 implement in hardware simple hardware watchpoint conditions of the form:
25299 (@value{GDBP}) watch @var{address|variable} \
25300 if @var{address|variable} == @var{constant expression}
25303 The DVC register will be automatically used when @value{GDBN} detects
25304 such pattern in a condition expression, and the created watchpoint uses one
25305 debug register (either the @code{exact-watchpoints} option is on and the
25306 variable is scalar, or the variable has a length of one byte). This feature
25307 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
25310 When running on PowerPC embedded processors, @value{GDBN} automatically uses
25311 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
25312 in which case watchpoints using only one debug register are created when
25313 watching variables of scalar types.
25315 You can create an artificial array to watch an arbitrary memory
25316 region using one of the following commands (@pxref{Expressions}):
25319 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
25320 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
25323 PowerPC embedded processors support masked watchpoints. See the discussion
25324 about the @code{mask} argument in @ref{Set Watchpoints}.
25326 @cindex ranged breakpoint
25327 PowerPC embedded processors support hardware accelerated
25328 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
25329 the inferior whenever it executes an instruction at any address within
25330 the range it specifies. To set a ranged breakpoint in @value{GDBN},
25331 use the @code{break-range} command.
25333 @value{GDBN} provides the following PowerPC-specific commands:
25336 @kindex break-range
25337 @item break-range @var{start-location}, @var{end-location}
25338 Set a breakpoint for an address range given by
25339 @var{start-location} and @var{end-location}, which can specify a function name,
25340 a line number, an offset of lines from the current line or from the start
25341 location, or an address of an instruction (see @ref{Specify Location},
25342 for a list of all the possible ways to specify a @var{location}.)
25343 The breakpoint will stop execution of the inferior whenever it
25344 executes an instruction at any address within the specified range,
25345 (including @var{start-location} and @var{end-location}.)
25347 @kindex set powerpc
25348 @item set powerpc soft-float
25349 @itemx show powerpc soft-float
25350 Force @value{GDBN} to use (or not use) a software floating point calling
25351 convention. By default, @value{GDBN} selects the calling convention based
25352 on the selected architecture and the provided executable file.
25354 @item set powerpc vector-abi
25355 @itemx show powerpc vector-abi
25356 Force @value{GDBN} to use the specified calling convention for vector
25357 arguments and return values. The valid options are @samp{auto};
25358 @samp{generic}, to avoid vector registers even if they are present;
25359 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
25360 registers. By default, @value{GDBN} selects the calling convention
25361 based on the selected architecture and the provided executable file.
25363 @item set powerpc exact-watchpoints
25364 @itemx show powerpc exact-watchpoints
25365 Allow @value{GDBN} to use only one debug register when watching a variable
25366 of scalar type, thus assuming that the variable is accessed through the
25367 address of its first byte.
25372 @subsection Atmel AVR
25375 When configured for debugging the Atmel AVR, @value{GDBN} supports the
25376 following AVR-specific commands:
25379 @item info io_registers
25380 @kindex info io_registers@r{, AVR}
25381 @cindex I/O registers (Atmel AVR)
25382 This command displays information about the AVR I/O registers. For
25383 each register, @value{GDBN} prints its number and value.
25390 When configured for debugging CRIS, @value{GDBN} provides the
25391 following CRIS-specific commands:
25394 @item set cris-version @var{ver}
25395 @cindex CRIS version
25396 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
25397 The CRIS version affects register names and sizes. This command is useful in
25398 case autodetection of the CRIS version fails.
25400 @item show cris-version
25401 Show the current CRIS version.
25403 @item set cris-dwarf2-cfi
25404 @cindex DWARF-2 CFI and CRIS
25405 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
25406 Change to @samp{off} when using @code{gcc-cris} whose version is below
25409 @item show cris-dwarf2-cfi
25410 Show the current state of using DWARF-2 CFI.
25412 @item set cris-mode @var{mode}
25414 Set the current CRIS mode to @var{mode}. It should only be changed when
25415 debugging in guru mode, in which case it should be set to
25416 @samp{guru} (the default is @samp{normal}).
25418 @item show cris-mode
25419 Show the current CRIS mode.
25423 @subsection Renesas Super-H
25426 For the Renesas Super-H processor, @value{GDBN} provides these
25430 @item set sh calling-convention @var{convention}
25431 @kindex set sh calling-convention
25432 Set the calling-convention used when calling functions from @value{GDBN}.
25433 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
25434 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
25435 convention. If the DWARF-2 information of the called function specifies
25436 that the function follows the Renesas calling convention, the function
25437 is called using the Renesas calling convention. If the calling convention
25438 is set to @samp{renesas}, the Renesas calling convention is always used,
25439 regardless of the DWARF-2 information. This can be used to override the
25440 default of @samp{gcc} if debug information is missing, or the compiler
25441 does not emit the DWARF-2 calling convention entry for a function.
25443 @item show sh calling-convention
25444 @kindex show sh calling-convention
25445 Show the current calling convention setting.
25450 @node Architectures
25451 @section Architectures
25453 This section describes characteristics of architectures that affect
25454 all uses of @value{GDBN} with the architecture, both native and cross.
25461 * HPPA:: HP PA architecture
25469 @subsection AArch64
25470 @cindex AArch64 support
25472 When @value{GDBN} is debugging the AArch64 architecture, it provides the
25473 following special commands:
25476 @item set debug aarch64
25477 @kindex set debug aarch64
25478 This command determines whether AArch64 architecture-specific debugging
25479 messages are to be displayed.
25481 @item show debug aarch64
25482 Show whether AArch64 debugging messages are displayed.
25486 @subsubsection AArch64 SVE.
25487 @cindex AArch64 SVE.
25489 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
25490 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
25491 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
25492 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
25493 @code{$vg} will be provided. This is the vector granule for the current thread
25494 and represents the number of 64-bit chunks in an SVE @code{z} register.
25496 If the vector length changes, then the @code{$vg} register will be updated,
25497 but the lengths of the @code{z} and @code{p} registers will not change. This
25498 is a known limitation of @value{GDBN} and does not affect the execution of the
25501 @subsubsection AArch64 Pointer Authentication.
25502 @cindex AArch64 Pointer Authentication.
25503 @anchor{AArch64 PAC}
25505 When @value{GDBN} is debugging the AArch64 architecture, and the program is
25506 using the v8.3-A feature Pointer Authentication (PAC), then whenever the link
25507 register @code{$lr} is pointing to an PAC function its value will be masked.
25508 When GDB prints a backtrace, any addresses that required unmasking will be
25509 postfixed with the marker [PAC]. When using the MI, this is printed as part
25510 of the @code{addr_flags} field.
25512 @subsubsection AArch64 Memory Tagging Extension.
25513 @cindex AArch64 Memory Tagging Extension.
25515 When @value{GDBN} is debugging the AArch64 architecture, the program is
25516 using the v8.5-A feature Memory Tagging Extension (MTE) and there is support
25517 in the kernel for MTE, @value{GDBN} will make memory tagging functionality
25518 available for inspection and editing of logical and allocation tags.
25519 @xref{Memory Tagging}.
25521 To aid debugging, @value{GDBN} will output additional information when SIGSEGV
25522 signals are generated as a result of memory tag failures.
25524 If the tag violation is synchronous, the following will be shown:
25527 Program received signal SIGSEGV, Segmentation fault
25528 Memory tag violation while accessing address 0x0500fffff7ff8000
25533 If the tag violation is asynchronous, the fault address is not available.
25534 In this case @value{GDBN} will show the following:
25537 Program received signal SIGSEGV, Segmentation fault
25538 Memory tag violation
25539 Fault address unavailable.
25542 A special register, @code{tag_ctl}, is made available through the
25543 @code{org.gnu.gdb.aarch64.mte} feature. This register exposes some
25544 options that can be controlled at runtime and emulates the @code{prctl}
25545 option @code{PR_SET_TAGGED_ADDR_CTRL}. For further information, see the
25546 documentation in the Linux kernel.
25549 @subsection x86 Architecture-specific Issues
25552 @item set struct-convention @var{mode}
25553 @kindex set struct-convention
25554 @cindex struct return convention
25555 @cindex struct/union returned in registers
25556 Set the convention used by the inferior to return @code{struct}s and
25557 @code{union}s from functions to @var{mode}. Possible values of
25558 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
25559 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
25560 are returned on the stack, while @code{"reg"} means that a
25561 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
25562 be returned in a register.
25564 @item show struct-convention
25565 @kindex show struct-convention
25566 Show the current setting of the convention to return @code{struct}s
25571 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
25572 @cindex Intel Memory Protection Extensions (MPX).
25574 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
25575 @footnote{The register named with capital letters represent the architecture
25576 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
25577 which are the lower bound and upper bound. Bounds are effective addresses or
25578 memory locations. The upper bounds are architecturally represented in 1's
25579 complement form. A bound having lower bound = 0, and upper bound = 0
25580 (1's complement of all bits set) will allow access to the entire address space.
25582 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
25583 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
25584 display the upper bound performing the complement of one operation on the
25585 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
25586 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
25587 can also be noted that the upper bounds are inclusive.
25589 As an example, assume that the register BND0 holds bounds for a pointer having
25590 access allowed for the range between 0x32 and 0x71. The values present on
25591 bnd0raw and bnd registers are presented as follows:
25594 bnd0raw = @{0x32, 0xffffffff8e@}
25595 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
25598 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
25599 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
25600 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
25601 Python, the display includes the memory size, in bits, accessible to
25604 Bounds can also be stored in bounds tables, which are stored in
25605 application memory. These tables store bounds for pointers by specifying
25606 the bounds pointer's value along with its bounds. Evaluating and changing
25607 bounds located in bound tables is therefore interesting while investigating
25608 bugs on MPX context. @value{GDBN} provides commands for this purpose:
25611 @item show mpx bound @var{pointer}
25612 @kindex show mpx bound
25613 Display bounds of the given @var{pointer}.
25615 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
25616 @kindex set mpx bound
25617 Set the bounds of a pointer in the bound table.
25618 This command takes three parameters: @var{pointer} is the pointers
25619 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
25620 for lower and upper bounds respectively.
25623 When you call an inferior function on an Intel MPX enabled program,
25624 GDB sets the inferior's bound registers to the init (disabled) state
25625 before calling the function. As a consequence, bounds checks for the
25626 pointer arguments passed to the function will always pass.
25628 This is necessary because when you call an inferior function, the
25629 program is usually in the middle of the execution of other function.
25630 Since at that point bound registers are in an arbitrary state, not
25631 clearing them would lead to random bound violations in the called
25634 You can still examine the influence of the bound registers on the
25635 execution of the called function by stopping the execution of the
25636 called function at its prologue, setting bound registers, and
25637 continuing the execution. For example:
25641 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
25642 $ print upper (a, b, c, d, 1)
25643 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
25645 @{lbound = 0x0, ubound = ffffffff@} : size -1
25648 At this last step the value of bnd0 can be changed for investigation of bound
25649 violations caused along the execution of the call. In order to know how to
25650 set the bound registers or bound table for the call consult the ABI.
25655 See the following section.
25658 @subsection @acronym{MIPS}
25660 @cindex stack on Alpha
25661 @cindex stack on @acronym{MIPS}
25662 @cindex Alpha stack
25663 @cindex @acronym{MIPS} stack
25664 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
25665 sometimes requires @value{GDBN} to search backward in the object code to
25666 find the beginning of a function.
25668 @cindex response time, @acronym{MIPS} debugging
25669 To improve response time (especially for embedded applications, where
25670 @value{GDBN} may be restricted to a slow serial line for this search)
25671 you may want to limit the size of this search, using one of these
25675 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
25676 @item set heuristic-fence-post @var{limit}
25677 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
25678 search for the beginning of a function. A value of @var{0} (the
25679 default) means there is no limit. However, except for @var{0}, the
25680 larger the limit the more bytes @code{heuristic-fence-post} must search
25681 and therefore the longer it takes to run. You should only need to use
25682 this command when debugging a stripped executable.
25684 @item show heuristic-fence-post
25685 Display the current limit.
25689 These commands are available @emph{only} when @value{GDBN} is configured
25690 for debugging programs on Alpha or @acronym{MIPS} processors.
25692 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
25696 @item set mips abi @var{arg}
25697 @kindex set mips abi
25698 @cindex set ABI for @acronym{MIPS}
25699 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
25700 values of @var{arg} are:
25704 The default ABI associated with the current binary (this is the
25714 @item show mips abi
25715 @kindex show mips abi
25716 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
25718 @item set mips compression @var{arg}
25719 @kindex set mips compression
25720 @cindex code compression, @acronym{MIPS}
25721 Tell @value{GDBN} which @acronym{MIPS} compressed
25722 @acronym{ISA, Instruction Set Architecture} encoding is used by the
25723 inferior. @value{GDBN} uses this for code disassembly and other
25724 internal interpretation purposes. This setting is only referred to
25725 when no executable has been associated with the debugging session or
25726 the executable does not provide information about the encoding it uses.
25727 Otherwise this setting is automatically updated from information
25728 provided by the executable.
25730 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
25731 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
25732 executables containing @acronym{MIPS16} code frequently are not
25733 identified as such.
25735 This setting is ``sticky''; that is, it retains its value across
25736 debugging sessions until reset either explicitly with this command or
25737 implicitly from an executable.
25739 The compiler and/or assembler typically add symbol table annotations to
25740 identify functions compiled for the @acronym{MIPS16} or
25741 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
25742 are present, @value{GDBN} uses them in preference to the global
25743 compressed @acronym{ISA} encoding setting.
25745 @item show mips compression
25746 @kindex show mips compression
25747 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
25748 @value{GDBN} to debug the inferior.
25751 @itemx show mipsfpu
25752 @xref{MIPS Embedded, set mipsfpu}.
25754 @item set mips mask-address @var{arg}
25755 @kindex set mips mask-address
25756 @cindex @acronym{MIPS} addresses, masking
25757 This command determines whether the most-significant 32 bits of 64-bit
25758 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
25759 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
25760 setting, which lets @value{GDBN} determine the correct value.
25762 @item show mips mask-address
25763 @kindex show mips mask-address
25764 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
25767 @item set remote-mips64-transfers-32bit-regs
25768 @kindex set remote-mips64-transfers-32bit-regs
25769 This command controls compatibility with 64-bit @acronym{MIPS} targets that
25770 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
25771 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
25772 and 64 bits for other registers, set this option to @samp{on}.
25774 @item show remote-mips64-transfers-32bit-regs
25775 @kindex show remote-mips64-transfers-32bit-regs
25776 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
25778 @item set debug mips
25779 @kindex set debug mips
25780 This command turns on and off debugging messages for the @acronym{MIPS}-specific
25781 target code in @value{GDBN}.
25783 @item show debug mips
25784 @kindex show debug mips
25785 Show the current setting of @acronym{MIPS} debugging messages.
25791 @cindex HPPA support
25793 When @value{GDBN} is debugging the HP PA architecture, it provides the
25794 following special commands:
25797 @item set debug hppa
25798 @kindex set debug hppa
25799 This command determines whether HPPA architecture-specific debugging
25800 messages are to be displayed.
25802 @item show debug hppa
25803 Show whether HPPA debugging messages are displayed.
25805 @item maint print unwind @var{address}
25806 @kindex maint print unwind@r{, HPPA}
25807 This command displays the contents of the unwind table entry at the
25808 given @var{address}.
25814 @subsection PowerPC
25815 @cindex PowerPC architecture
25817 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
25818 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
25819 numbers stored in the floating point registers. These values must be stored
25820 in two consecutive registers, always starting at an even register like
25821 @code{f0} or @code{f2}.
25823 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
25824 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
25825 @code{f2} and @code{f3} for @code{$dl1} and so on.
25827 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
25828 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
25831 @subsection Nios II
25832 @cindex Nios II architecture
25834 When @value{GDBN} is debugging the Nios II architecture,
25835 it provides the following special commands:
25839 @item set debug nios2
25840 @kindex set debug nios2
25841 This command turns on and off debugging messages for the Nios II
25842 target code in @value{GDBN}.
25844 @item show debug nios2
25845 @kindex show debug nios2
25846 Show the current setting of Nios II debugging messages.
25850 @subsection Sparc64
25851 @cindex Sparc64 support
25852 @cindex Application Data Integrity
25853 @subsubsection ADI Support
25855 The M7 processor supports an Application Data Integrity (ADI) feature that
25856 detects invalid data accesses. When software allocates memory and enables
25857 ADI on the allocated memory, it chooses a 4-bit version number, sets the
25858 version in the upper 4 bits of the 64-bit pointer to that data, and stores
25859 the 4-bit version in every cacheline of that data. Hardware saves the latter
25860 in spare bits in the cache and memory hierarchy. On each load and store,
25861 the processor compares the upper 4 VA (virtual address) bits to the
25862 cacheline's version. If there is a mismatch, the processor generates a
25863 version mismatch trap which can be either precise or disrupting. The trap
25864 is an error condition which the kernel delivers to the process as a SIGSEGV
25867 Note that only 64-bit applications can use ADI and need to be built with
25870 Values of the ADI version tags, which are in granularity of a
25871 cacheline (64 bytes), can be viewed or modified.
25875 @kindex adi examine
25876 @item adi (examine | x) [ / @var{n} ] @var{addr}
25878 The @code{adi examine} command displays the value of one ADI version tag per
25881 @var{n} is a decimal integer specifying the number in bytes; the default
25882 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
25883 block size, to display.
25885 @var{addr} is the address in user address space where you want @value{GDBN}
25886 to begin displaying the ADI version tags.
25888 Below is an example of displaying ADI versions of variable "shmaddr".
25891 (@value{GDBP}) adi x/100 shmaddr
25892 0xfff800010002c000: 0 0
25896 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
25898 The @code{adi assign} command is used to assign new ADI version tag
25901 @var{n} is a decimal integer specifying the number in bytes;
25902 the default is 1. It specifies how much ADI version information, at the
25903 ratio of 1:ADI block size, to modify.
25905 @var{addr} is the address in user address space where you want @value{GDBN}
25906 to begin modifying the ADI version tags.
25908 @var{tag} is the new ADI version tag.
25910 For example, do the following to modify then verify ADI versions of
25911 variable "shmaddr":
25914 (@value{GDBP}) adi a/100 shmaddr = 7
25915 (@value{GDBP}) adi x/100 shmaddr
25916 0xfff800010002c000: 7 7
25923 @cindex S12Z support
25925 When @value{GDBN} is debugging the S12Z architecture,
25926 it provides the following special command:
25929 @item maint info bdccsr
25930 @kindex maint info bdccsr@r{, S12Z}
25931 This command displays the current value of the microprocessor's
25936 @node Controlling GDB
25937 @chapter Controlling @value{GDBN}
25939 You can alter the way @value{GDBN} interacts with you by using the
25940 @code{set} command. For commands controlling how @value{GDBN} displays
25941 data, see @ref{Print Settings, ,Print Settings}. Other settings are
25946 * Editing:: Command editing
25947 * Command History:: Command history
25948 * Screen Size:: Screen size
25949 * Output Styling:: Output styling
25950 * Numbers:: Numbers
25951 * ABI:: Configuring the current ABI
25952 * Auto-loading:: Automatically loading associated files
25953 * Messages/Warnings:: Optional warnings and messages
25954 * Debugging Output:: Optional messages about internal happenings
25955 * Other Misc Settings:: Other Miscellaneous Settings
25963 @value{GDBN} indicates its readiness to read a command by printing a string
25964 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
25965 can change the prompt string with the @code{set prompt} command. For
25966 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
25967 the prompt in one of the @value{GDBN} sessions so that you can always tell
25968 which one you are talking to.
25970 @emph{Note:} @code{set prompt} does not add a space for you after the
25971 prompt you set. This allows you to set a prompt which ends in a space
25972 or a prompt that does not.
25976 @item set prompt @var{newprompt}
25977 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
25979 @kindex show prompt
25981 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
25984 Versions of @value{GDBN} that ship with Python scripting enabled have
25985 prompt extensions. The commands for interacting with these extensions
25989 @kindex set extended-prompt
25990 @item set extended-prompt @var{prompt}
25991 Set an extended prompt that allows for substitutions.
25992 @xref{gdb.prompt}, for a list of escape sequences that can be used for
25993 substitution. Any escape sequences specified as part of the prompt
25994 string are replaced with the corresponding strings each time the prompt
26000 set extended-prompt Current working directory: \w (gdb)
26003 Note that when an extended-prompt is set, it takes control of the
26004 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
26006 @kindex show extended-prompt
26007 @item show extended-prompt
26008 Prints the extended prompt. Any escape sequences specified as part of
26009 the prompt string with @code{set extended-prompt}, are replaced with the
26010 corresponding strings each time the prompt is displayed.
26014 @section Command Editing
26016 @cindex command line editing
26018 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
26019 @sc{gnu} library provides consistent behavior for programs which provide a
26020 command line interface to the user. Advantages are @sc{gnu} Emacs-style
26021 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
26022 substitution, and a storage and recall of command history across
26023 debugging sessions.
26025 You may control the behavior of command line editing in @value{GDBN} with the
26026 command @code{set}.
26029 @kindex set editing
26032 @itemx set editing on
26033 Enable command line editing (enabled by default).
26035 @item set editing off
26036 Disable command line editing.
26038 @kindex show editing
26040 Show whether command line editing is enabled.
26043 @ifset SYSTEM_READLINE
26044 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
26046 @ifclear SYSTEM_READLINE
26047 @xref{Command Line Editing},
26049 for more details about the Readline
26050 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
26051 encouraged to read that chapter.
26053 @cindex Readline application name
26054 @value{GDBN} sets the Readline application name to @samp{gdb}. This
26055 is useful for conditions in @file{.inputrc}.
26057 @cindex operate-and-get-next
26058 @value{GDBN} defines a bindable Readline command,
26059 @code{operate-and-get-next}. This is bound to @kbd{C-o} by default.
26060 This command accepts the current line for execution and fetches the
26061 next line relative to the current line from the history for editing.
26062 Any argument is ignored.
26064 @node Command History
26065 @section Command History
26066 @cindex command history
26068 @value{GDBN} can keep track of the commands you type during your
26069 debugging sessions, so that you can be certain of precisely what
26070 happened. Use these commands to manage the @value{GDBN} command
26073 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
26074 package, to provide the history facility.
26075 @ifset SYSTEM_READLINE
26076 @xref{Using History Interactively, , , history, GNU History Library},
26078 @ifclear SYSTEM_READLINE
26079 @xref{Using History Interactively},
26081 for the detailed description of the History library.
26083 To issue a command to @value{GDBN} without affecting certain aspects of
26084 the state which is seen by users, prefix it with @samp{server }
26085 (@pxref{Server Prefix}). This
26086 means that this command will not affect the command history, nor will it
26087 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
26088 pressed on a line by itself.
26090 @cindex @code{server}, command prefix
26091 The server prefix does not affect the recording of values into the value
26092 history; to print a value without recording it into the value history,
26093 use the @code{output} command instead of the @code{print} command.
26095 Here is the description of @value{GDBN} commands related to command
26099 @cindex history substitution
26100 @cindex history file
26101 @kindex set history filename
26102 @cindex @env{GDBHISTFILE}, environment variable
26103 @item set history filename @r{[}@var{fname}@r{]}
26104 Set the name of the @value{GDBN} command history file to @var{fname}.
26105 This is the file where @value{GDBN} reads an initial command history
26106 list, and where it writes the command history from this session when it
26107 exits. You can access this list through history expansion or through
26108 the history command editing characters listed below. This file defaults
26109 to the value of the environment variable @env{GDBHISTFILE}, or to
26110 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
26113 The @env{GDBHISTFILE} environment variable is read after processing
26114 any @value{GDBN} initialization files (@pxref{Startup}) and after
26115 processing any commands passed using command line options (for
26116 example, @code{-ex}).
26118 If the @var{fname} argument is not given, or if the @env{GDBHISTFILE}
26119 is the empty string then @value{GDBN} will neither try to load an
26120 existing history file, nor will it try to save the history on exit.
26122 @cindex save command history
26123 @kindex set history save
26124 @item set history save
26125 @itemx set history save on
26126 Record command history in a file, whose name may be specified with the
26127 @code{set history filename} command. By default, this option is
26128 disabled. The command history will be recorded when @value{GDBN}
26129 exits. If @code{set history filename} is set to the empty string then
26130 history saving is disabled, even when @code{set history save} is
26133 @item set history save off
26134 Don't record the command history into the file specified by @code{set
26135 history filename} when @value{GDBN} exits.
26137 @cindex history size
26138 @kindex set history size
26139 @cindex @env{GDBHISTSIZE}, environment variable
26140 @item set history size @var{size}
26141 @itemx set history size unlimited
26142 Set the number of commands which @value{GDBN} keeps in its history list.
26143 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
26144 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
26145 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
26146 either a negative number or the empty string, then the number of commands
26147 @value{GDBN} keeps in the history list is unlimited.
26149 The @env{GDBHISTSIZE} environment variable is read after processing
26150 any @value{GDBN} initialization files (@pxref{Startup}) and after
26151 processing any commands passed using command line options (for
26152 example, @code{-ex}).
26154 @cindex remove duplicate history
26155 @kindex set history remove-duplicates
26156 @item set history remove-duplicates @var{count}
26157 @itemx set history remove-duplicates unlimited
26158 Control the removal of duplicate history entries in the command history list.
26159 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
26160 history entries and remove the first entry that is a duplicate of the current
26161 entry being added to the command history list. If @var{count} is
26162 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
26163 removal of duplicate history entries is disabled.
26165 Only history entries added during the current session are considered for
26166 removal. This option is set to 0 by default.
26170 History expansion assigns special meaning to the character @kbd{!}.
26171 @ifset SYSTEM_READLINE
26172 @xref{Event Designators, , , history, GNU History Library},
26174 @ifclear SYSTEM_READLINE
26175 @xref{Event Designators},
26179 @cindex history expansion, turn on/off
26180 Since @kbd{!} is also the logical not operator in C, history expansion
26181 is off by default. If you decide to enable history expansion with the
26182 @code{set history expansion on} command, you may sometimes need to
26183 follow @kbd{!} (when it is used as logical not, in an expression) with
26184 a space or a tab to prevent it from being expanded. The readline
26185 history facilities do not attempt substitution on the strings
26186 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
26188 The commands to control history expansion are:
26191 @item set history expansion on
26192 @itemx set history expansion
26193 @kindex set history expansion
26194 Enable history expansion. History expansion is off by default.
26196 @item set history expansion off
26197 Disable history expansion.
26200 @kindex show history
26202 @itemx show history filename
26203 @itemx show history save
26204 @itemx show history size
26205 @itemx show history expansion
26206 These commands display the state of the @value{GDBN} history parameters.
26207 @code{show history} by itself displays all four states.
26212 @kindex show commands
26213 @cindex show last commands
26214 @cindex display command history
26215 @item show commands
26216 Display the last ten commands in the command history.
26218 @item show commands @var{n}
26219 Print ten commands centered on command number @var{n}.
26221 @item show commands +
26222 Print ten commands just after the commands last printed.
26226 @section Screen Size
26227 @cindex size of screen
26228 @cindex screen size
26231 @cindex pauses in output
26233 Certain commands to @value{GDBN} may produce large amounts of
26234 information output to the screen. To help you read all of it,
26235 @value{GDBN} pauses and asks you for input at the end of each page of
26236 output. Type @key{RET} when you want to see one more page of output,
26237 @kbd{q} to discard the remaining output, or @kbd{c} to continue
26238 without paging for the rest of the current command. Also, the screen
26239 width setting determines when to wrap lines of output. Depending on
26240 what is being printed, @value{GDBN} tries to break the line at a
26241 readable place, rather than simply letting it overflow onto the
26244 Normally @value{GDBN} knows the size of the screen from the terminal
26245 driver software. For example, on Unix @value{GDBN} uses the termcap data base
26246 together with the value of the @env{TERM} environment variable and the
26247 @code{stty rows} and @code{stty cols} settings. If this is not correct,
26248 you can override it with the @code{set height} and @code{set
26255 @kindex show height
26256 @item set height @var{lpp}
26257 @itemx set height unlimited
26259 @itemx set width @var{cpl}
26260 @itemx set width unlimited
26262 These @code{set} commands specify a screen height of @var{lpp} lines and
26263 a screen width of @var{cpl} characters. The associated @code{show}
26264 commands display the current settings.
26266 If you specify a height of either @code{unlimited} or zero lines,
26267 @value{GDBN} does not pause during output no matter how long the
26268 output is. This is useful if output is to a file or to an editor
26271 Likewise, you can specify @samp{set width unlimited} or @samp{set
26272 width 0} to prevent @value{GDBN} from wrapping its output.
26274 @item set pagination on
26275 @itemx set pagination off
26276 @kindex set pagination
26277 Turn the output pagination on or off; the default is on. Turning
26278 pagination off is the alternative to @code{set height unlimited}. Note that
26279 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
26280 Options, -batch}) also automatically disables pagination.
26282 @item show pagination
26283 @kindex show pagination
26284 Show the current pagination mode.
26287 @node Output Styling
26288 @section Output Styling
26294 @value{GDBN} can style its output on a capable terminal. This is
26295 enabled by default on most systems, but disabled by default when in
26296 batch mode (@pxref{Mode Options}). Various style settings are available;
26297 and styles can also be disabled entirely.
26300 @item set style enabled @samp{on|off}
26301 Enable or disable all styling. The default is host-dependent, with
26302 most hosts defaulting to @samp{on}.
26304 @item show style enabled
26305 Show the current state of styling.
26307 @item set style sources @samp{on|off}
26308 Enable or disable source code styling. This affects whether source
26309 code, such as the output of the @code{list} command, is styled. The
26310 default is @samp{on}. Note that source styling only works if styling
26311 in general is enabled, and if a source highlighting library is
26312 available to @value{GDBN}.
26314 There are two ways that highlighting can be done. First, if
26315 @value{GDBN} was linked with the GNU Source Highlight library, then it
26316 is used. Otherwise, if @value{GDBN} was configured with Python
26317 scripting support, and if the Python Pygments package is available,
26318 then it will be used.
26320 @item show style sources
26321 Show the current state of source code styling.
26323 @item set style disassembler enabled @samp{on|off}
26324 Enable or disable disassembler styling. This affects whether
26325 disassembler output, such as the output of the @code{disassemble}
26326 command, is styled. Disassembler styling only works if styling in
26327 general is enabled (with @code{set style enabled on}), and if a source
26328 highlighting library is available to @value{GDBN}.
26330 To highlight disassembler output, @value{GDBN} must be compiled with
26331 Python support, and the Python Pygments package must be available. If
26332 these requirements are not met then @value{GDBN} will not highlight
26333 disassembler output, even when this option is @samp{on}.
26335 @item show style disassembler enabled
26336 Show the current state of disassembler styling.
26339 Subcommands of @code{set style} control specific forms of styling.
26340 These subcommands all follow the same pattern: each style-able object
26341 can be styled with a foreground color, a background color, and an
26344 For example, the style of file names can be controlled using the
26345 @code{set style filename} group of commands:
26348 @item set style filename background @var{color}
26349 Set the background to @var{color}. Valid colors are @samp{none}
26350 (meaning the terminal's default color), @samp{black}, @samp{red},
26351 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26354 @item set style filename foreground @var{color}
26355 Set the foreground to @var{color}. Valid colors are @samp{none}
26356 (meaning the terminal's default color), @samp{black}, @samp{red},
26357 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
26360 @item set style filename intensity @var{value}
26361 Set the intensity to @var{value}. Valid intensities are @samp{normal}
26362 (the default), @samp{bold}, and @samp{dim}.
26365 The @code{show style} command and its subcommands are styling
26366 a style name in their output using its own style.
26367 So, use @command{show style} to see the complete list of styles,
26368 their characteristics and the visual aspect of each style.
26370 The style-able objects are:
26373 Control the styling of file names and URLs. By default, this style's
26374 foreground color is green.
26377 Control the styling of function names. These are managed with the
26378 @code{set style function} family of commands. By default, this
26379 style's foreground color is yellow.
26382 Control the styling of variable names. These are managed with the
26383 @code{set style variable} family of commands. By default, this style's
26384 foreground color is cyan.
26387 Control the styling of addresses. These are managed with the
26388 @code{set style address} family of commands. By default, this style's
26389 foreground color is blue.
26392 Control the styling of @value{GDBN}'s version number text. By
26393 default, this style's foreground color is magenta and it has bold
26394 intensity. The version number is displayed in two places, the output
26395 of @command{show version}, and when @value{GDBN} starts up.
26397 In order to control how @value{GDBN} styles the version number at
26398 startup, add the @code{set style version} family of commands to the
26399 early initialization command file (@pxref{Initialization
26403 Control the styling of titles. These are managed with the
26404 @code{set style title} family of commands. By default, this style's
26405 intensity is bold. Commands are using the title style to improve
26406 the readability of large output. For example, the commands
26407 @command{apropos} and @command{help} are using the title style
26408 for the command names.
26411 Control the styling of highlightings. These are managed with the
26412 @code{set style highlight} family of commands. By default, this style's
26413 foreground color is red. Commands are using the highlight style to draw
26414 the user attention to some specific parts of their output. For example,
26415 the command @command{apropos -v REGEXP} uses the highlight style to
26416 mark the documentation parts matching @var{regexp}.
26419 Control the styling of the TUI border. Note that, unlike other
26420 styling options, only the color of the border can be controlled via
26421 @code{set style}. This was done for compatibility reasons, as TUI
26422 controls to set the border's intensity predated the addition of
26423 general styling to @value{GDBN}. @xref{TUI Configuration}.
26425 @item tui-active-border
26426 Control the styling of the active TUI border; that is, the TUI window
26427 that has the focus.
26433 @cindex number representation
26434 @cindex entering numbers
26436 You can always enter numbers in octal, decimal, or hexadecimal in
26437 @value{GDBN} by the usual conventions: octal numbers begin with
26438 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
26439 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
26440 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
26441 10; likewise, the default display for numbers---when no particular
26442 format is specified---is base 10. You can change the default base for
26443 both input and output with the commands described below.
26446 @kindex set input-radix
26447 @item set input-radix @var{base}
26448 Set the default base for numeric input. Supported choices
26449 for @var{base} are decimal 8, 10, or 16. The base must itself be
26450 specified either unambiguously or using the current input radix; for
26454 set input-radix 012
26455 set input-radix 10.
26456 set input-radix 0xa
26460 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
26461 leaves the input radix unchanged, no matter what it was, since
26462 @samp{10}, being without any leading or trailing signs of its base, is
26463 interpreted in the current radix. Thus, if the current radix is 16,
26464 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
26467 @kindex set output-radix
26468 @item set output-radix @var{base}
26469 Set the default base for numeric display. Supported choices
26470 for @var{base} are decimal 8, 10, or 16. The base must itself be
26471 specified either unambiguously or using the current input radix.
26473 @kindex show input-radix
26474 @item show input-radix
26475 Display the current default base for numeric input.
26477 @kindex show output-radix
26478 @item show output-radix
26479 Display the current default base for numeric display.
26481 @item set radix @r{[}@var{base}@r{]}
26485 These commands set and show the default base for both input and output
26486 of numbers. @code{set radix} sets the radix of input and output to
26487 the same base; without an argument, it resets the radix back to its
26488 default value of 10.
26493 @section Configuring the Current ABI
26495 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
26496 application automatically. However, sometimes you need to override its
26497 conclusions. Use these commands to manage @value{GDBN}'s view of the
26503 @cindex Newlib OS ABI and its influence on the longjmp handling
26505 One @value{GDBN} configuration can debug binaries for multiple operating
26506 system targets, either via remote debugging or native emulation.
26507 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
26508 but you can override its conclusion using the @code{set osabi} command.
26509 One example where this is useful is in debugging of binaries which use
26510 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
26511 not have the same identifying marks that the standard C library for your
26514 When @value{GDBN} is debugging the AArch64 architecture, it provides a
26515 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
26516 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
26517 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
26521 Show the OS ABI currently in use.
26524 With no argument, show the list of registered available OS ABI's.
26526 @item set osabi @var{abi}
26527 Set the current OS ABI to @var{abi}.
26530 @cindex float promotion
26532 Generally, the way that an argument of type @code{float} is passed to a
26533 function depends on whether the function is prototyped. For a prototyped
26534 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
26535 according to the architecture's convention for @code{float}. For unprototyped
26536 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
26537 @code{double} and then passed.
26539 Unfortunately, some forms of debug information do not reliably indicate whether
26540 a function is prototyped. If @value{GDBN} calls a function that is not marked
26541 as prototyped, it consults @kbd{set coerce-float-to-double}.
26544 @kindex set coerce-float-to-double
26545 @item set coerce-float-to-double
26546 @itemx set coerce-float-to-double on
26547 Arguments of type @code{float} will be promoted to @code{double} when passed
26548 to an unprototyped function. This is the default setting.
26550 @item set coerce-float-to-double off
26551 Arguments of type @code{float} will be passed directly to unprototyped
26554 @kindex show coerce-float-to-double
26555 @item show coerce-float-to-double
26556 Show the current setting of promoting @code{float} to @code{double}.
26560 @kindex show cp-abi
26561 @value{GDBN} needs to know the ABI used for your program's C@t{++}
26562 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
26563 used to build your application. @value{GDBN} only fully supports
26564 programs with a single C@t{++} ABI; if your program contains code using
26565 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
26566 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
26567 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
26568 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
26569 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
26570 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
26575 Show the C@t{++} ABI currently in use.
26578 With no argument, show the list of supported C@t{++} ABI's.
26580 @item set cp-abi @var{abi}
26581 @itemx set cp-abi auto
26582 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
26586 @section Automatically loading associated files
26587 @cindex auto-loading
26589 @value{GDBN} sometimes reads files with commands and settings automatically,
26590 without being explicitly told so by the user. We call this feature
26591 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
26592 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
26593 results or introduce security risks (e.g., if the file comes from untrusted
26596 There are various kinds of files @value{GDBN} can automatically load.
26597 In addition to these files, @value{GDBN} supports auto-loading code written
26598 in various extension languages. @xref{Auto-loading extensions}.
26600 Note that loading of these associated files (including the local @file{.gdbinit}
26601 file) requires accordingly configured @code{auto-load safe-path}
26602 (@pxref{Auto-loading safe path}).
26604 For these reasons, @value{GDBN} includes commands and options to let you
26605 control when to auto-load files and which files should be auto-loaded.
26608 @anchor{set auto-load off}
26609 @kindex set auto-load off
26610 @item set auto-load off
26611 Globally disable loading of all auto-loaded files.
26612 You may want to use this command with the @samp{-iex} option
26613 (@pxref{Option -init-eval-command}) such as:
26615 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
26618 Be aware that system init file (@pxref{System-wide configuration})
26619 and init files from your home directory (@pxref{Home Directory Init File})
26620 still get read (as they come from generally trusted directories).
26621 To prevent @value{GDBN} from auto-loading even those init files, use the
26622 @option{-nx} option (@pxref{Mode Options}), in addition to
26623 @code{set auto-load no}.
26625 @anchor{show auto-load}
26626 @kindex show auto-load
26627 @item show auto-load
26628 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
26632 (gdb) show auto-load
26633 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
26634 libthread-db: Auto-loading of inferior specific libthread_db is on.
26635 local-gdbinit: Auto-loading of .gdbinit script from current directory
26637 python-scripts: Auto-loading of Python scripts is on.
26638 safe-path: List of directories from which it is safe to auto-load files
26639 is $debugdir:$datadir/auto-load.
26640 scripts-directory: List of directories from which to load auto-loaded scripts
26641 is $debugdir:$datadir/auto-load.
26644 @anchor{info auto-load}
26645 @kindex info auto-load
26646 @item info auto-load
26647 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
26651 (gdb) info auto-load
26654 Yes /home/user/gdb/gdb-gdb.gdb
26655 libthread-db: No auto-loaded libthread-db.
26656 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
26660 Yes /home/user/gdb/gdb-gdb.py
26664 These are @value{GDBN} control commands for the auto-loading:
26666 @multitable @columnfractions .5 .5
26667 @item @xref{set auto-load off}.
26668 @tab Disable auto-loading globally.
26669 @item @xref{show auto-load}.
26670 @tab Show setting of all kinds of files.
26671 @item @xref{info auto-load}.
26672 @tab Show state of all kinds of files.
26673 @item @xref{set auto-load gdb-scripts}.
26674 @tab Control for @value{GDBN} command scripts.
26675 @item @xref{show auto-load gdb-scripts}.
26676 @tab Show setting of @value{GDBN} command scripts.
26677 @item @xref{info auto-load gdb-scripts}.
26678 @tab Show state of @value{GDBN} command scripts.
26679 @item @xref{set auto-load python-scripts}.
26680 @tab Control for @value{GDBN} Python scripts.
26681 @item @xref{show auto-load python-scripts}.
26682 @tab Show setting of @value{GDBN} Python scripts.
26683 @item @xref{info auto-load python-scripts}.
26684 @tab Show state of @value{GDBN} Python scripts.
26685 @item @xref{set auto-load guile-scripts}.
26686 @tab Control for @value{GDBN} Guile scripts.
26687 @item @xref{show auto-load guile-scripts}.
26688 @tab Show setting of @value{GDBN} Guile scripts.
26689 @item @xref{info auto-load guile-scripts}.
26690 @tab Show state of @value{GDBN} Guile scripts.
26691 @item @xref{set auto-load scripts-directory}.
26692 @tab Control for @value{GDBN} auto-loaded scripts location.
26693 @item @xref{show auto-load scripts-directory}.
26694 @tab Show @value{GDBN} auto-loaded scripts location.
26695 @item @xref{add-auto-load-scripts-directory}.
26696 @tab Add directory for auto-loaded scripts location list.
26697 @item @xref{set auto-load local-gdbinit}.
26698 @tab Control for init file in the current directory.
26699 @item @xref{show auto-load local-gdbinit}.
26700 @tab Show setting of init file in the current directory.
26701 @item @xref{info auto-load local-gdbinit}.
26702 @tab Show state of init file in the current directory.
26703 @item @xref{set auto-load libthread-db}.
26704 @tab Control for thread debugging library.
26705 @item @xref{show auto-load libthread-db}.
26706 @tab Show setting of thread debugging library.
26707 @item @xref{info auto-load libthread-db}.
26708 @tab Show state of thread debugging library.
26709 @item @xref{set auto-load safe-path}.
26710 @tab Control directories trusted for automatic loading.
26711 @item @xref{show auto-load safe-path}.
26712 @tab Show directories trusted for automatic loading.
26713 @item @xref{add-auto-load-safe-path}.
26714 @tab Add directory trusted for automatic loading.
26718 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
26719 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
26721 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
26722 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
26725 @node Init File in the Current Directory
26726 @subsection Automatically loading init file in the current directory
26727 @cindex auto-loading init file in the current directory
26729 By default, @value{GDBN} reads and executes the canned sequences of commands
26730 from init file (if any) in the current working directory,
26731 see @ref{Init File in the Current Directory during Startup}.
26733 Note that loading of this local @file{.gdbinit} file also requires accordingly
26734 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26737 @anchor{set auto-load local-gdbinit}
26738 @kindex set auto-load local-gdbinit
26739 @item set auto-load local-gdbinit [on|off]
26740 Enable or disable the auto-loading of canned sequences of commands
26741 (@pxref{Sequences}) found in init file in the current directory.
26743 @anchor{show auto-load local-gdbinit}
26744 @kindex show auto-load local-gdbinit
26745 @item show auto-load local-gdbinit
26746 Show whether auto-loading of canned sequences of commands from init file in the
26747 current directory is enabled or disabled.
26749 @anchor{info auto-load local-gdbinit}
26750 @kindex info auto-load local-gdbinit
26751 @item info auto-load local-gdbinit
26752 Print whether canned sequences of commands from init file in the
26753 current directory have been auto-loaded.
26756 @node libthread_db.so.1 file
26757 @subsection Automatically loading thread debugging library
26758 @cindex auto-loading libthread_db.so.1
26760 This feature is currently present only on @sc{gnu}/Linux native hosts.
26762 @value{GDBN} reads in some cases thread debugging library from places specific
26763 to the inferior (@pxref{set libthread-db-search-path}).
26765 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
26766 without checking this @samp{set auto-load libthread-db} switch as system
26767 libraries have to be trusted in general. In all other cases of
26768 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
26769 auto-load libthread-db} is enabled before trying to open such thread debugging
26772 Note that loading of this debugging library also requires accordingly configured
26773 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26776 @anchor{set auto-load libthread-db}
26777 @kindex set auto-load libthread-db
26778 @item set auto-load libthread-db [on|off]
26779 Enable or disable the auto-loading of inferior specific thread debugging library.
26781 @anchor{show auto-load libthread-db}
26782 @kindex show auto-load libthread-db
26783 @item show auto-load libthread-db
26784 Show whether auto-loading of inferior specific thread debugging library is
26785 enabled or disabled.
26787 @anchor{info auto-load libthread-db}
26788 @kindex info auto-load libthread-db
26789 @item info auto-load libthread-db
26790 Print the list of all loaded inferior specific thread debugging libraries and
26791 for each such library print list of inferior @var{pid}s using it.
26794 @node Auto-loading safe path
26795 @subsection Security restriction for auto-loading
26796 @cindex auto-loading safe-path
26798 As the files of inferior can come from untrusted source (such as submitted by
26799 an application user) @value{GDBN} does not always load any files automatically.
26800 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
26801 directories trusted for loading files not explicitly requested by user.
26802 Each directory can also be a shell wildcard pattern.
26804 If the path is not set properly you will see a warning and the file will not
26809 Reading symbols from /home/user/gdb/gdb...
26810 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
26811 declined by your `auto-load safe-path' set
26812 to "$debugdir:$datadir/auto-load".
26813 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
26814 declined by your `auto-load safe-path' set
26815 to "$debugdir:$datadir/auto-load".
26819 To instruct @value{GDBN} to go ahead and use the init files anyway,
26820 invoke @value{GDBN} like this:
26823 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
26826 The list of trusted directories is controlled by the following commands:
26829 @anchor{set auto-load safe-path}
26830 @kindex set auto-load safe-path
26831 @item set auto-load safe-path @r{[}@var{directories}@r{]}
26832 Set the list of directories (and their subdirectories) trusted for automatic
26833 loading and execution of scripts. You can also enter a specific trusted file.
26834 Each directory can also be a shell wildcard pattern; wildcards do not match
26835 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
26836 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
26837 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
26838 its default value as specified during @value{GDBN} compilation.
26840 The list of directories uses path separator (@samp{:} on GNU and Unix
26841 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26842 to the @env{PATH} environment variable.
26844 @anchor{show auto-load safe-path}
26845 @kindex show auto-load safe-path
26846 @item show auto-load safe-path
26847 Show the list of directories trusted for automatic loading and execution of
26850 @anchor{add-auto-load-safe-path}
26851 @kindex add-auto-load-safe-path
26852 @item add-auto-load-safe-path
26853 Add an entry (or list of entries) to the list of directories trusted for
26854 automatic loading and execution of scripts. Multiple entries may be delimited
26855 by the host platform path separator in use.
26858 This variable defaults to what @code{--with-auto-load-dir} has been configured
26859 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
26860 substitution applies the same as for @ref{set auto-load scripts-directory}.
26861 The default @code{set auto-load safe-path} value can be also overriden by
26862 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
26864 Setting this variable to @file{/} disables this security protection,
26865 corresponding @value{GDBN} configuration option is
26866 @option{--without-auto-load-safe-path}.
26867 This variable is supposed to be set to the system directories writable by the
26868 system superuser only. Users can add their source directories in init files in
26869 their home directories (@pxref{Home Directory Init File}). See also deprecated
26870 init file in the current directory
26871 (@pxref{Init File in the Current Directory during Startup}).
26873 To force @value{GDBN} to load the files it declined to load in the previous
26874 example, you could use one of the following ways:
26877 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
26878 Specify this trusted directory (or a file) as additional component of the list.
26879 You have to specify also any existing directories displayed by
26880 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
26882 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
26883 Specify this directory as in the previous case but just for a single
26884 @value{GDBN} session.
26886 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
26887 Disable auto-loading safety for a single @value{GDBN} session.
26888 This assumes all the files you debug during this @value{GDBN} session will come
26889 from trusted sources.
26891 @item @kbd{./configure --without-auto-load-safe-path}
26892 During compilation of @value{GDBN} you may disable any auto-loading safety.
26893 This assumes all the files you will ever debug with this @value{GDBN} come from
26897 On the other hand you can also explicitly forbid automatic files loading which
26898 also suppresses any such warning messages:
26901 @item @kbd{gdb -iex "set auto-load no" @dots{}}
26902 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
26904 @item @file{~/.gdbinit}: @samp{set auto-load no}
26905 Disable auto-loading globally for the user
26906 (@pxref{Home Directory Init File}). While it is improbable, you could also
26907 use system init file instead (@pxref{System-wide configuration}).
26910 This setting applies to the file names as entered by user. If no entry matches
26911 @value{GDBN} tries as a last resort to also resolve all the file names into
26912 their canonical form (typically resolving symbolic links) and compare the
26913 entries again. @value{GDBN} already canonicalizes most of the filenames on its
26914 own before starting the comparison so a canonical form of directories is
26915 recommended to be entered.
26917 @node Auto-loading verbose mode
26918 @subsection Displaying files tried for auto-load
26919 @cindex auto-loading verbose mode
26921 For better visibility of all the file locations where you can place scripts to
26922 be auto-loaded with inferior --- or to protect yourself against accidental
26923 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
26924 all the files attempted to be loaded. Both existing and non-existing files may
26927 For example the list of directories from which it is safe to auto-load files
26928 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
26929 may not be too obvious while setting it up.
26932 (gdb) set debug auto-load on
26933 (gdb) file ~/src/t/true
26934 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
26935 for objfile "/tmp/true".
26936 auto-load: Updating directories of "/usr:/opt".
26937 auto-load: Using directory "/usr".
26938 auto-load: Using directory "/opt".
26939 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
26940 by your `auto-load safe-path' set to "/usr:/opt".
26944 @anchor{set debug auto-load}
26945 @kindex set debug auto-load
26946 @item set debug auto-load [on|off]
26947 Set whether to print the filenames attempted to be auto-loaded.
26949 @anchor{show debug auto-load}
26950 @kindex show debug auto-load
26951 @item show debug auto-load
26952 Show whether printing of the filenames attempted to be auto-loaded is turned
26956 @node Messages/Warnings
26957 @section Optional Warnings and Messages
26959 @cindex verbose operation
26960 @cindex optional warnings
26961 By default, @value{GDBN} is silent about its inner workings. If you are
26962 running on a slow machine, you may want to use the @code{set verbose}
26963 command. This makes @value{GDBN} tell you when it does a lengthy
26964 internal operation, so you will not think it has crashed.
26966 Currently, the messages controlled by @code{set verbose} are those
26967 which announce that the symbol table for a source file is being read;
26968 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
26971 @kindex set verbose
26972 @item set verbose on
26973 Enables @value{GDBN} output of certain informational messages.
26975 @item set verbose off
26976 Disables @value{GDBN} output of certain informational messages.
26978 @kindex show verbose
26980 Displays whether @code{set verbose} is on or off.
26983 By default, if @value{GDBN} encounters bugs in the symbol table of an
26984 object file, it is silent; but if you are debugging a compiler, you may
26985 find this information useful (@pxref{Symbol Errors, ,Errors Reading
26990 @kindex set complaints
26991 @item set complaints @var{limit}
26992 Permits @value{GDBN} to output @var{limit} complaints about each type of
26993 unusual symbols before becoming silent about the problem. Set
26994 @var{limit} to zero to suppress all complaints; set it to a large number
26995 to prevent complaints from being suppressed.
26997 @kindex show complaints
26998 @item show complaints
26999 Displays how many symbol complaints @value{GDBN} is permitted to produce.
27003 @anchor{confirmation requests}
27004 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
27005 lot of stupid questions to confirm certain commands. For example, if
27006 you try to run a program which is already running:
27010 The program being debugged has been started already.
27011 Start it from the beginning? (y or n)
27014 If you are willing to unflinchingly face the consequences of your own
27015 commands, you can disable this ``feature'':
27019 @kindex set confirm
27021 @cindex confirmation
27022 @cindex stupid questions
27023 @item set confirm off
27024 Disables confirmation requests. Note that running @value{GDBN} with
27025 the @option{--batch} option (@pxref{Mode Options, -batch}) also
27026 automatically disables confirmation requests.
27028 @item set confirm on
27029 Enables confirmation requests (the default).
27031 @kindex show confirm
27033 Displays state of confirmation requests.
27037 @cindex command tracing
27038 If you need to debug user-defined commands or sourced files you may find it
27039 useful to enable @dfn{command tracing}. In this mode each command will be
27040 printed as it is executed, prefixed with one or more @samp{+} symbols, the
27041 quantity denoting the call depth of each command.
27044 @kindex set trace-commands
27045 @cindex command scripts, debugging
27046 @item set trace-commands on
27047 Enable command tracing.
27048 @item set trace-commands off
27049 Disable command tracing.
27050 @item show trace-commands
27051 Display the current state of command tracing.
27054 @node Debugging Output
27055 @section Optional Messages about Internal Happenings
27056 @cindex optional debugging messages
27058 @value{GDBN} has commands that enable optional debugging messages from
27059 various @value{GDBN} subsystems; normally these commands are of
27060 interest to @value{GDBN} maintainers, or when reporting a bug. This
27061 section documents those commands.
27064 @kindex set exec-done-display
27065 @item set exec-done-display
27066 Turns on or off the notification of asynchronous commands'
27067 completion. When on, @value{GDBN} will print a message when an
27068 asynchronous command finishes its execution. The default is off.
27069 @kindex show exec-done-display
27070 @item show exec-done-display
27071 Displays the current setting of asynchronous command completion
27075 @cindex ARM AArch64
27076 @item set debug aarch64
27077 Turns on or off display of debugging messages related to ARM AArch64.
27078 The default is off.
27080 @item show debug aarch64
27081 Displays the current state of displaying debugging messages related to
27084 @cindex gdbarch debugging info
27085 @cindex architecture debugging info
27086 @item set debug arch
27087 Turns on or off display of gdbarch debugging info. The default is off
27088 @item show debug arch
27089 Displays the current state of displaying gdbarch debugging info.
27091 @item set debug aix-solib
27092 @cindex AIX shared library debugging
27093 Control display of debugging messages from the AIX shared library
27094 support module. The default is off.
27095 @item show debug aix-solib
27096 Show the current state of displaying AIX shared library debugging messages.
27098 @item set debug aix-thread
27099 @cindex AIX threads
27100 Display debugging messages about inner workings of the AIX thread
27102 @item show debug aix-thread
27103 Show the current state of AIX thread debugging info display.
27105 @item set debug check-physname
27107 Check the results of the ``physname'' computation. When reading DWARF
27108 debugging information for C@t{++}, @value{GDBN} attempts to compute
27109 each entity's name. @value{GDBN} can do this computation in two
27110 different ways, depending on exactly what information is present.
27111 When enabled, this setting causes @value{GDBN} to compute the names
27112 both ways and display any discrepancies.
27113 @item show debug check-physname
27114 Show the current state of ``physname'' checking.
27116 @item set debug coff-pe-read
27117 @cindex COFF/PE exported symbols
27118 Control display of debugging messages related to reading of COFF/PE
27119 exported symbols. The default is off.
27120 @item show debug coff-pe-read
27121 Displays the current state of displaying debugging messages related to
27122 reading of COFF/PE exported symbols.
27124 @item set debug dwarf-die
27126 Dump DWARF DIEs after they are read in.
27127 The value is the number of nesting levels to print.
27128 A value of zero turns off the display.
27129 @item show debug dwarf-die
27130 Show the current state of DWARF DIE debugging.
27132 @item set debug dwarf-line
27133 @cindex DWARF Line Tables
27134 Turns on or off display of debugging messages related to reading
27135 DWARF line tables. The default is 0 (off).
27136 A value of 1 provides basic information.
27137 A value greater than 1 provides more verbose information.
27138 @item show debug dwarf-line
27139 Show the current state of DWARF line table debugging.
27141 @item set debug dwarf-read
27142 @cindex DWARF Reading
27143 Turns on or off display of debugging messages related to reading
27144 DWARF debug info. The default is 0 (off).
27145 A value of 1 provides basic information.
27146 A value greater than 1 provides more verbose information.
27147 @item show debug dwarf-read
27148 Show the current state of DWARF reader debugging.
27150 @item set debug displaced
27151 @cindex displaced stepping debugging info
27152 Turns on or off display of @value{GDBN} debugging info for the
27153 displaced stepping support. The default is off.
27154 @item show debug displaced
27155 Displays the current state of displaying @value{GDBN} debugging info
27156 related to displaced stepping.
27158 @item set debug event
27159 @cindex event debugging info
27160 Turns on or off display of @value{GDBN} event debugging info. The
27162 @item show debug event
27163 Displays the current state of displaying @value{GDBN} event debugging
27166 @item set debug event-loop
27167 @cindex event-loop debugging
27168 Controls output of debugging info about the event loop. The possible
27169 values are @samp{off}, @samp{all} (shows all debugging info) and
27170 @samp{all-except-ui} (shows all debugging info except those about
27171 UI-related events).
27172 @item show debug event-loop
27173 Shows the current state of displaying debugging info about the event
27176 @item set debug expression
27177 @cindex expression debugging info
27178 Turns on or off display of debugging info about @value{GDBN}
27179 expression parsing. The default is off.
27180 @item show debug expression
27181 Displays the current state of displaying debugging info about
27182 @value{GDBN} expression parsing.
27184 @item set debug fbsd-lwp
27185 @cindex FreeBSD LWP debug messages
27186 Turns on or off debugging messages from the FreeBSD LWP debug support.
27187 @item show debug fbsd-lwp
27188 Show the current state of FreeBSD LWP debugging messages.
27190 @item set debug fbsd-nat
27191 @cindex FreeBSD native target debug messages
27192 Turns on or off debugging messages from the FreeBSD native target.
27193 @item show debug fbsd-nat
27194 Show the current state of FreeBSD native target debugging messages.
27196 @item set debug fortran-array-slicing
27197 @cindex fortran array slicing debugging info
27198 Turns on or off display of @value{GDBN} Fortran array slicing
27199 debugging info. The default is off.
27201 @item show debug fortran-array-slicing
27202 Displays the current state of displaying @value{GDBN} Fortran array
27203 slicing debugging info.
27205 @item set debug frame
27206 @cindex frame debugging info
27207 Turns on or off display of @value{GDBN} frame debugging info. The
27209 @item show debug frame
27210 Displays the current state of displaying @value{GDBN} frame debugging
27213 @item set debug gnu-nat
27214 @cindex @sc{gnu}/Hurd debug messages
27215 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
27216 @item show debug gnu-nat
27217 Show the current state of @sc{gnu}/Hurd debugging messages.
27219 @item set debug infrun
27220 @cindex inferior debugging info
27221 Turns on or off display of @value{GDBN} debugging info for running the inferior.
27222 The default is off. @file{infrun.c} contains GDB's runtime state machine used
27223 for implementing operations such as single-stepping the inferior.
27224 @item show debug infrun
27225 Displays the current state of @value{GDBN} inferior debugging.
27227 @item set debug jit
27228 @cindex just-in-time compilation, debugging messages
27229 Turn on or off debugging messages from JIT debug support.
27230 @item show debug jit
27231 Displays the current state of @value{GDBN} JIT debugging.
27233 @item set debug linux-nat @r{[}on@r{|}off@r{]}
27234 @cindex @sc{gnu}/Linux native target debug messages
27235 @cindex Linux native targets
27236 Turn on or off debugging messages from the Linux native target debug support.
27237 @item show debug linux-nat
27238 Show the current state of Linux native target debugging messages.
27240 @item set debug linux-namespaces
27241 @cindex @sc{gnu}/Linux namespaces debug messages
27242 Turn on or off debugging messages from the Linux namespaces debug support.
27243 @item show debug linux-namespaces
27244 Show the current state of Linux namespaces debugging messages.
27246 @item set debug mach-o
27247 @cindex Mach-O symbols processing
27248 Control display of debugging messages related to Mach-O symbols
27249 processing. The default is off.
27250 @item show debug mach-o
27251 Displays the current state of displaying debugging messages related to
27252 reading of COFF/PE exported symbols.
27254 @item set debug notification
27255 @cindex remote async notification debugging info
27256 Turn on or off debugging messages about remote async notification.
27257 The default is off.
27258 @item show debug notification
27259 Displays the current state of remote async notification debugging messages.
27261 @item set debug observer
27262 @cindex observer debugging info
27263 Turns on or off display of @value{GDBN} observer debugging. This
27264 includes info such as the notification of observable events.
27265 @item show debug observer
27266 Displays the current state of observer debugging.
27268 @item set debug overload
27269 @cindex C@t{++} overload debugging info
27270 Turns on or off display of @value{GDBN} C@t{++} overload debugging
27271 info. This includes info such as ranking of functions, etc. The default
27273 @item show debug overload
27274 Displays the current state of displaying @value{GDBN} C@t{++} overload
27277 @cindex expression parser, debugging info
27278 @cindex debug expression parser
27279 @item set debug parser
27280 Turns on or off the display of expression parser debugging output.
27281 Internally, this sets the @code{yydebug} variable in the expression
27282 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
27283 details. The default is off.
27284 @item show debug parser
27285 Show the current state of expression parser debugging.
27287 @cindex packets, reporting on stdout
27288 @cindex serial connections, debugging
27289 @cindex debug remote protocol
27290 @cindex remote protocol debugging
27291 @cindex display remote packets
27292 @item set debug remote
27293 Turns on or off display of reports on all packets sent back and forth across
27294 the serial line to the remote machine. The info is printed on the
27295 @value{GDBN} standard output stream. The default is off.
27296 @item show debug remote
27297 Displays the state of display of remote packets.
27299 @item set debug remote-packet-max-chars
27300 Sets the maximum number of characters to display for each remote packet when
27301 @code{set debug remote} is on. This is useful to prevent @value{GDBN} from
27302 displaying lengthy remote packets and polluting the console.
27304 The default value is @code{512}, which means @value{GDBN} will truncate each
27305 remote packet after 512 bytes.
27307 Setting this option to @code{unlimited} will disable truncation and will output
27308 the full length of the remote packets.
27309 @item show debug remote-packet-max-chars
27310 Displays the number of bytes to output for remote packet debugging.
27312 @item set debug separate-debug-file
27313 Turns on or off display of debug output about separate debug file search.
27314 @item show debug separate-debug-file
27315 Displays the state of separate debug file search debug output.
27317 @item set debug serial
27318 Turns on or off display of @value{GDBN} serial debugging info. The
27320 @item show debug serial
27321 Displays the current state of displaying @value{GDBN} serial debugging
27324 @item set debug solib-frv
27325 @cindex FR-V shared-library debugging
27326 Turn on or off debugging messages for FR-V shared-library code.
27327 @item show debug solib-frv
27328 Display the current state of FR-V shared-library code debugging
27331 @item set debug symbol-lookup
27332 @cindex symbol lookup
27333 Turns on or off display of debugging messages related to symbol lookup.
27334 The default is 0 (off).
27335 A value of 1 provides basic information.
27336 A value greater than 1 provides more verbose information.
27337 @item show debug symbol-lookup
27338 Show the current state of symbol lookup debugging messages.
27340 @item set debug symfile
27341 @cindex symbol file functions
27342 Turns on or off display of debugging messages related to symbol file functions.
27343 The default is off. @xref{Files}.
27344 @item show debug symfile
27345 Show the current state of symbol file debugging messages.
27347 @item set debug symtab-create
27348 @cindex symbol table creation
27349 Turns on or off display of debugging messages related to symbol table creation.
27350 The default is 0 (off).
27351 A value of 1 provides basic information.
27352 A value greater than 1 provides more verbose information.
27353 @item show debug symtab-create
27354 Show the current state of symbol table creation debugging.
27356 @item set debug target
27357 @cindex target debugging info
27358 Turns on or off display of @value{GDBN} target debugging info. This info
27359 includes what is going on at the target level of GDB, as it happens. The
27360 default is 0. Set it to 1 to track events, and to 2 to also track the
27361 value of large memory transfers.
27362 @item show debug target
27363 Displays the current state of displaying @value{GDBN} target debugging
27366 @item set debug timestamp
27367 @cindex timestamping debugging info
27368 Turns on or off display of timestamps with @value{GDBN} debugging info.
27369 When enabled, seconds and microseconds are displayed before each debugging
27371 @item show debug timestamp
27372 Displays the current state of displaying timestamps with @value{GDBN}
27375 @item set debug varobj
27376 @cindex variable object debugging info
27377 Turns on or off display of @value{GDBN} variable object debugging
27378 info. The default is off.
27379 @item show debug varobj
27380 Displays the current state of displaying @value{GDBN} variable object
27383 @item set debug xml
27384 @cindex XML parser debugging
27385 Turn on or off debugging messages for built-in XML parsers.
27386 @item show debug xml
27387 Displays the current state of XML debugging messages.
27390 @node Other Misc Settings
27391 @section Other Miscellaneous Settings
27392 @cindex miscellaneous settings
27395 @kindex set interactive-mode
27396 @item set interactive-mode
27397 If @code{on}, forces @value{GDBN} to assume that GDB was started
27398 in a terminal. In practice, this means that @value{GDBN} should wait
27399 for the user to answer queries generated by commands entered at
27400 the command prompt. If @code{off}, forces @value{GDBN} to operate
27401 in the opposite mode, and it uses the default answers to all queries.
27402 If @code{auto} (the default), @value{GDBN} tries to determine whether
27403 its standard input is a terminal, and works in interactive-mode if it
27404 is, non-interactively otherwise.
27406 In the vast majority of cases, the debugger should be able to guess
27407 correctly which mode should be used. But this setting can be useful
27408 in certain specific cases, such as running a MinGW @value{GDBN}
27409 inside a cygwin window.
27411 @kindex show interactive-mode
27412 @item show interactive-mode
27413 Displays whether the debugger is operating in interactive mode or not.
27417 @kindex set suppress-cli-notifications
27418 @item set suppress-cli-notifications
27419 If @code{on}, command-line-interface (CLI) notifications that are
27420 printed by @value{GDBN} are suppressed. If @code{off}, the
27421 notifications are printed as usual. The default value is @code{off}.
27422 CLI notifications occur when you change the selected context or when
27423 the program being debugged stops, as detailed below.
27426 @item User-selected context changes:
27427 When you change the selected context (i.e.@: the current inferior,
27428 thread and/or the frame), @value{GDBN} prints information about the
27429 new context. For example, the default behavior is below:
27433 [Switching to inferior 1 [process 634] (/tmp/test)]
27434 [Switching to thread 1 (process 634)]
27435 #0 main () at test.c:3
27440 When the notifications are suppressed, the new context is not printed:
27443 (gdb) set suppress-cli-notifications on
27448 @item The program being debugged stops:
27449 When the program you are debugging stops (e.g.@: because of hitting a
27450 breakpoint, completing source-stepping, an interrupt, etc.),
27451 @value{GDBN} prints information about the stop event. For example,
27452 below is a breakpoint hit:
27455 (gdb) break test.c:3
27456 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27460 Breakpoint 2, main () at test.c:3
27465 When the notifications are suppressed, the output becomes:
27468 (gdb) break test.c:3
27469 Breakpoint 2 at 0x555555555155: file test.c, line 3.
27470 (gdb) set suppress-cli-notifications on
27476 Suppressing CLI notifications may be useful in scripts to obtain a
27477 reduced output from a list of commands.
27480 @kindex show suppress-cli-notifications
27481 @item show suppress-cli-notifications
27482 Displays whether printing CLI notifications is suppressed or not.
27485 @node Extending GDB
27486 @chapter Extending @value{GDBN}
27487 @cindex extending GDB
27489 @value{GDBN} provides several mechanisms for extension.
27490 @value{GDBN} also provides the ability to automatically load
27491 extensions when it reads a file for debugging. This allows the
27492 user to automatically customize @value{GDBN} for the program
27495 To facilitate the use of extension languages, @value{GDBN} is capable
27496 of evaluating the contents of a file. When doing so, @value{GDBN}
27497 can recognize which extension language is being used by looking at
27498 the filename extension. Files with an unrecognized filename extension
27499 are always treated as a @value{GDBN} Command Files.
27500 @xref{Command Files,, Command files}.
27502 You can control how @value{GDBN} evaluates these files with the following
27506 @kindex set script-extension
27507 @kindex show script-extension
27508 @item set script-extension off
27509 All scripts are always evaluated as @value{GDBN} Command Files.
27511 @item set script-extension soft
27512 The debugger determines the scripting language based on filename
27513 extension. If this scripting language is supported, @value{GDBN}
27514 evaluates the script using that language. Otherwise, it evaluates
27515 the file as a @value{GDBN} Command File.
27517 @item set script-extension strict
27518 The debugger determines the scripting language based on filename
27519 extension, and evaluates the script using that language. If the
27520 language is not supported, then the evaluation fails.
27522 @item show script-extension
27523 Display the current value of the @code{script-extension} option.
27527 @ifset SYSTEM_GDBINIT_DIR
27528 This setting is not used for files in the system-wide gdbinit directory.
27529 Files in that directory must have an extension matching their language,
27530 or have a @file{.gdb} extension to be interpreted as regular @value{GDBN}
27531 commands. @xref{Startup}.
27535 * Sequences:: Canned Sequences of @value{GDBN} Commands
27536 * Aliases:: Command Aliases
27537 * Python:: Extending @value{GDBN} using Python
27538 * Guile:: Extending @value{GDBN} using Guile
27539 * Auto-loading extensions:: Automatically loading extensions
27540 * Multiple Extension Languages:: Working with multiple extension languages
27544 @section Canned Sequences of Commands
27546 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
27547 Command Lists}), @value{GDBN} provides two ways to store sequences of
27548 commands for execution as a unit: user-defined commands and command
27552 * Define:: How to define your own commands
27553 * Hooks:: Hooks for user-defined commands
27554 * Command Files:: How to write scripts of commands to be stored in a file
27555 * Output:: Commands for controlled output
27556 * Auto-loading sequences:: Controlling auto-loaded command files
27560 @subsection User-defined Commands
27562 @cindex user-defined command
27563 @cindex arguments, to user-defined commands
27564 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
27565 which you assign a new name as a command. This is done with the
27566 @code{define} command. User commands may accept an unlimited number of arguments
27567 separated by whitespace. Arguments are accessed within the user command
27568 via @code{$arg0@dots{}$argN}. A trivial example:
27572 print $arg0 + $arg1 + $arg2
27577 To execute the command use:
27584 This defines the command @code{adder}, which prints the sum of
27585 its three arguments. Note the arguments are text substitutions, so they may
27586 reference variables, use complex expressions, or even perform inferior
27589 @cindex argument count in user-defined commands
27590 @cindex how many arguments (user-defined commands)
27591 In addition, @code{$argc} may be used to find out how many arguments have
27597 print $arg0 + $arg1
27600 print $arg0 + $arg1 + $arg2
27605 Combining with the @code{eval} command (@pxref{eval}) makes it easier
27606 to process a variable number of arguments:
27613 eval "set $sum = $sum + $arg%d", $i
27623 @item define @var{commandname}
27624 Define a command named @var{commandname}. If there is already a command
27625 by that name, you are asked to confirm that you want to redefine it.
27626 The argument @var{commandname} may be a bare command name consisting of letters,
27627 numbers, dashes, dots, and underscores. It may also start with any
27628 predefined or user-defined prefix command.
27629 For example, @samp{define target my-target} creates
27630 a user-defined @samp{target my-target} command.
27632 The definition of the command is made up of other @value{GDBN} command lines,
27633 which are given following the @code{define} command. The end of these
27634 commands is marked by a line containing @code{end}.
27637 @kindex end@r{ (user-defined commands)}
27638 @item document @var{commandname}
27639 Document the user-defined command @var{commandname}, so that it can be
27640 accessed by @code{help}. The command @var{commandname} must already be
27641 defined. This command reads lines of documentation just as @code{define}
27642 reads the lines of the command definition, ending with @code{end}.
27643 After the @code{document} command is finished, @code{help} on command
27644 @var{commandname} displays the documentation you have written.
27646 You may use the @code{document} command again to change the
27647 documentation of a command. Redefining the command with @code{define}
27648 does not change the documentation.
27650 @kindex define-prefix
27651 @item define-prefix @var{commandname}
27652 Define or mark the command @var{commandname} as a user-defined prefix
27653 command. Once marked, @var{commandname} can be used as prefix command
27654 by the @code{define} command.
27655 Note that @code{define-prefix} can be used with a not yet defined
27656 @var{commandname}. In such a case, @var{commandname} is defined as
27657 an empty user-defined command.
27658 In case you redefine a command that was marked as a user-defined
27659 prefix command, the subcommands of the redefined command are kept
27660 (and @value{GDBN} indicates so to the user).
27664 (gdb) define-prefix abc
27665 (gdb) define-prefix abc def
27666 (gdb) define abc def
27667 Type commands for definition of "abc def".
27668 End with a line saying just "end".
27669 >echo command initial def\n
27671 (gdb) define abc def ghi
27672 Type commands for definition of "abc def ghi".
27673 End with a line saying just "end".
27674 >echo command ghi\n
27676 (gdb) define abc def
27677 Keeping subcommands of prefix command "def".
27678 Redefine command "def"? (y or n) y
27679 Type commands for definition of "abc def".
27680 End with a line saying just "end".
27681 >echo command def\n
27690 @kindex dont-repeat
27691 @cindex don't repeat command
27693 Used inside a user-defined command, this tells @value{GDBN} that this
27694 command should not be repeated when the user hits @key{RET}
27695 (@pxref{Command Syntax, repeat last command}).
27697 @kindex help user-defined
27698 @item help user-defined
27699 List all user-defined commands and all python commands defined in class
27700 COMMAND_USER. The first line of the documentation or docstring is
27705 @itemx show user @var{commandname}
27706 Display the @value{GDBN} commands used to define @var{commandname} (but
27707 not its documentation). If no @var{commandname} is given, display the
27708 definitions for all user-defined commands.
27709 This does not work for user-defined python commands.
27711 @cindex infinite recursion in user-defined commands
27712 @kindex show max-user-call-depth
27713 @kindex set max-user-call-depth
27714 @item show max-user-call-depth
27715 @itemx set max-user-call-depth
27716 The value of @code{max-user-call-depth} controls how many recursion
27717 levels are allowed in user-defined commands before @value{GDBN} suspects an
27718 infinite recursion and aborts the command.
27719 This does not apply to user-defined python commands.
27722 In addition to the above commands, user-defined commands frequently
27723 use control flow commands, described in @ref{Command Files}.
27725 When user-defined commands are executed, the
27726 commands of the definition are not printed. An error in any command
27727 stops execution of the user-defined command.
27729 If used interactively, commands that would ask for confirmation proceed
27730 without asking when used inside a user-defined command. Many @value{GDBN}
27731 commands that normally print messages to say what they are doing omit the
27732 messages when used in a user-defined command.
27735 @subsection User-defined Command Hooks
27736 @cindex command hooks
27737 @cindex hooks, for commands
27738 @cindex hooks, pre-command
27741 You may define @dfn{hooks}, which are a special kind of user-defined
27742 command. Whenever you run the command @samp{foo}, if the user-defined
27743 command @samp{hook-foo} exists, it is executed (with no arguments)
27744 before that command.
27746 @cindex hooks, post-command
27748 A hook may also be defined which is run after the command you executed.
27749 Whenever you run the command @samp{foo}, if the user-defined command
27750 @samp{hookpost-foo} exists, it is executed (with no arguments) after
27751 that command. Post-execution hooks may exist simultaneously with
27752 pre-execution hooks, for the same command.
27754 It is valid for a hook to call the command which it hooks. If this
27755 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
27757 @c It would be nice if hookpost could be passed a parameter indicating
27758 @c if the command it hooks executed properly or not. FIXME!
27760 @kindex stop@r{, a pseudo-command}
27761 In addition, a pseudo-command, @samp{stop} exists. Defining
27762 (@samp{hook-stop}) makes the associated commands execute every time
27763 execution stops in your program: before breakpoint commands are run,
27764 displays are printed, or the stack frame is printed.
27766 For example, to ignore @code{SIGALRM} signals while
27767 single-stepping, but treat them normally during normal execution,
27772 handle SIGALRM nopass
27776 handle SIGALRM pass
27779 define hook-continue
27780 handle SIGALRM pass
27784 As a further example, to hook at the beginning and end of the @code{echo}
27785 command, and to add extra text to the beginning and end of the message,
27793 define hookpost-echo
27797 (@value{GDBP}) echo Hello World
27798 <<<---Hello World--->>>
27803 You can define a hook for any single-word command in @value{GDBN}, but
27804 not for command aliases; you should define a hook for the basic command
27805 name, e.g.@: @code{backtrace} rather than @code{bt}.
27806 @c FIXME! So how does Joe User discover whether a command is an alias
27808 You can hook a multi-word command by adding @code{hook-} or
27809 @code{hookpost-} to the last word of the command, e.g.@:
27810 @samp{define target hook-remote} to add a hook to @samp{target remote}.
27812 If an error occurs during the execution of your hook, execution of
27813 @value{GDBN} commands stops and @value{GDBN} issues a prompt
27814 (before the command that you actually typed had a chance to run).
27816 If you try to define a hook which does not match any known command, you
27817 get a warning from the @code{define} command.
27819 @node Command Files
27820 @subsection Command Files
27822 @cindex command files
27823 @cindex scripting commands
27824 A command file for @value{GDBN} is a text file made of lines that are
27825 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
27826 also be included. An empty line in a command file does nothing; it
27827 does not mean to repeat the last command, as it would from the
27830 You can request the execution of a command file with the @code{source}
27831 command. Note that the @code{source} command is also used to evaluate
27832 scripts that are not Command Files. The exact behavior can be configured
27833 using the @code{script-extension} setting.
27834 @xref{Extending GDB,, Extending GDB}.
27838 @cindex execute commands from a file
27839 @item source [-s] [-v] @var{filename}
27840 Execute the command file @var{filename}.
27843 The lines in a command file are generally executed sequentially,
27844 unless the order of execution is changed by one of the
27845 @emph{flow-control commands} described below. The commands are not
27846 printed as they are executed. An error in any command terminates
27847 execution of the command file and control is returned to the console.
27849 @value{GDBN} first searches for @var{filename} in the current directory.
27850 If the file is not found there, and @var{filename} does not specify a
27851 directory, then @value{GDBN} also looks for the file on the source search path
27852 (specified with the @samp{directory} command);
27853 except that @file{$cdir} is not searched because the compilation directory
27854 is not relevant to scripts.
27856 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
27857 on the search path even if @var{filename} specifies a directory.
27858 The search is done by appending @var{filename} to each element of the
27859 search path. So, for example, if @var{filename} is @file{mylib/myscript}
27860 and the search path contains @file{/home/user} then @value{GDBN} will
27861 look for the script @file{/home/user/mylib/myscript}.
27862 The search is also done if @var{filename} is an absolute path.
27863 For example, if @var{filename} is @file{/tmp/myscript} and
27864 the search path contains @file{/home/user} then @value{GDBN} will
27865 look for the script @file{/home/user/tmp/myscript}.
27866 For DOS-like systems, if @var{filename} contains a drive specification,
27867 it is stripped before concatenation. For example, if @var{filename} is
27868 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
27869 will look for the script @file{c:/tmp/myscript}.
27871 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
27872 each command as it is executed. The option must be given before
27873 @var{filename}, and is interpreted as part of the filename anywhere else.
27875 Commands that would ask for confirmation if used interactively proceed
27876 without asking when used in a command file. Many @value{GDBN} commands that
27877 normally print messages to say what they are doing omit the messages
27878 when called from command files.
27880 @value{GDBN} also accepts command input from standard input. In this
27881 mode, normal output goes to standard output and error output goes to
27882 standard error. Errors in a command file supplied on standard input do
27883 not terminate execution of the command file---execution continues with
27887 gdb < cmds > log 2>&1
27890 (The syntax above will vary depending on the shell used.) This example
27891 will execute commands from the file @file{cmds}. All output and errors
27892 would be directed to @file{log}.
27894 Since commands stored on command files tend to be more general than
27895 commands typed interactively, they frequently need to deal with
27896 complicated situations, such as different or unexpected values of
27897 variables and symbols, changes in how the program being debugged is
27898 built, etc. @value{GDBN} provides a set of flow-control commands to
27899 deal with these complexities. Using these commands, you can write
27900 complex scripts that loop over data structures, execute commands
27901 conditionally, etc.
27908 This command allows to include in your script conditionally executed
27909 commands. The @code{if} command takes a single argument, which is an
27910 expression to evaluate. It is followed by a series of commands that
27911 are executed only if the expression is true (its value is nonzero).
27912 There can then optionally be an @code{else} line, followed by a series
27913 of commands that are only executed if the expression was false. The
27914 end of the list is marked by a line containing @code{end}.
27918 This command allows to write loops. Its syntax is similar to
27919 @code{if}: the command takes a single argument, which is an expression
27920 to evaluate, and must be followed by the commands to execute, one per
27921 line, terminated by an @code{end}. These commands are called the
27922 @dfn{body} of the loop. The commands in the body of @code{while} are
27923 executed repeatedly as long as the expression evaluates to true.
27927 This command exits the @code{while} loop in whose body it is included.
27928 Execution of the script continues after that @code{while}s @code{end}
27931 @kindex loop_continue
27932 @item loop_continue
27933 This command skips the execution of the rest of the body of commands
27934 in the @code{while} loop in whose body it is included. Execution
27935 branches to the beginning of the @code{while} loop, where it evaluates
27936 the controlling expression.
27938 @kindex end@r{ (if/else/while commands)}
27940 Terminate the block of commands that are the body of @code{if},
27941 @code{else}, or @code{while} flow-control commands.
27946 @subsection Commands for Controlled Output
27948 During the execution of a command file or a user-defined command, normal
27949 @value{GDBN} output is suppressed; the only output that appears is what is
27950 explicitly printed by the commands in the definition. This section
27951 describes three commands useful for generating exactly the output you
27956 @item echo @var{text}
27957 @c I do not consider backslash-space a standard C escape sequence
27958 @c because it is not in ANSI.
27959 Print @var{text}. Nonprinting characters can be included in
27960 @var{text} using C escape sequences, such as @samp{\n} to print a
27961 newline. @strong{No newline is printed unless you specify one.}
27962 In addition to the standard C escape sequences, a backslash followed
27963 by a space stands for a space. This is useful for displaying a
27964 string with spaces at the beginning or the end, since leading and
27965 trailing spaces are otherwise trimmed from all arguments.
27966 To print @samp{@w{ }and foo =@w{ }}, use the command
27967 @samp{echo \@w{ }and foo = \@w{ }}.
27969 A backslash at the end of @var{text} can be used, as in C, to continue
27970 the command onto subsequent lines. For example,
27973 echo This is some text\n\
27974 which is continued\n\
27975 onto several lines.\n
27978 produces the same output as
27981 echo This is some text\n
27982 echo which is continued\n
27983 echo onto several lines.\n
27987 @item output @var{expression}
27988 Print the value of @var{expression} and nothing but that value: no
27989 newlines, no @samp{$@var{nn} = }. The value is not entered in the
27990 value history either. @xref{Expressions, ,Expressions}, for more information
27993 @item output/@var{fmt} @var{expression}
27994 Print the value of @var{expression} in format @var{fmt}. You can use
27995 the same formats as for @code{print}. @xref{Output Formats,,Output
27996 Formats}, for more information.
27999 @item printf @var{template}, @var{expressions}@dots{}
28000 Print the values of one or more @var{expressions} under the control of
28001 the string @var{template}. To print several values, make
28002 @var{expressions} be a comma-separated list of individual expressions,
28003 which may be either numbers or pointers. Their values are printed as
28004 specified by @var{template}, exactly as a C program would do by
28005 executing the code below:
28008 printf (@var{template}, @var{expressions}@dots{});
28011 As in @code{C} @code{printf}, ordinary characters in @var{template}
28012 are printed verbatim, while @dfn{conversion specification} introduced
28013 by the @samp{%} character cause subsequent @var{expressions} to be
28014 evaluated, their values converted and formatted according to type and
28015 style information encoded in the conversion specifications, and then
28018 For example, you can print two values in hex like this:
28021 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
28024 @code{printf} supports all the standard @code{C} conversion
28025 specifications, including the flags and modifiers between the @samp{%}
28026 character and the conversion letter, with the following exceptions:
28030 The argument-ordering modifiers, such as @samp{2$}, are not supported.
28033 The modifier @samp{*} is not supported for specifying precision or
28037 The @samp{'} flag (for separation of digits into groups according to
28038 @code{LC_NUMERIC'}) is not supported.
28041 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
28045 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
28048 The conversion letters @samp{a} and @samp{A} are not supported.
28052 Note that the @samp{ll} type modifier is supported only if the
28053 underlying @code{C} implementation used to build @value{GDBN} supports
28054 the @code{long long int} type, and the @samp{L} type modifier is
28055 supported only if @code{long double} type is available.
28057 As in @code{C}, @code{printf} supports simple backslash-escape
28058 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
28059 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
28060 single character. Octal and hexadecimal escape sequences are not
28063 Additionally, @code{printf} supports conversion specifications for DFP
28064 (@dfn{Decimal Floating Point}) types using the following length modifiers
28065 together with a floating point specifier.
28070 @samp{H} for printing @code{Decimal32} types.
28073 @samp{D} for printing @code{Decimal64} types.
28076 @samp{DD} for printing @code{Decimal128} types.
28079 If the underlying @code{C} implementation used to build @value{GDBN} has
28080 support for the three length modifiers for DFP types, other modifiers
28081 such as width and precision will also be available for @value{GDBN} to use.
28083 In case there is no such @code{C} support, no additional modifiers will be
28084 available and the value will be printed in the standard way.
28086 Here's an example of printing DFP types using the above conversion letters:
28088 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
28093 @item eval @var{template}, @var{expressions}@dots{}
28094 Convert the values of one or more @var{expressions} under the control of
28095 the string @var{template} to a command line, and call it.
28099 @node Auto-loading sequences
28100 @subsection Controlling auto-loading native @value{GDBN} scripts
28101 @cindex native script auto-loading
28103 When a new object file is read (for example, due to the @code{file}
28104 command, or because the inferior has loaded a shared library),
28105 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
28106 @xref{Auto-loading extensions}.
28108 Auto-loading can be enabled or disabled,
28109 and the list of auto-loaded scripts can be printed.
28112 @anchor{set auto-load gdb-scripts}
28113 @kindex set auto-load gdb-scripts
28114 @item set auto-load gdb-scripts [on|off]
28115 Enable or disable the auto-loading of canned sequences of commands scripts.
28117 @anchor{show auto-load gdb-scripts}
28118 @kindex show auto-load gdb-scripts
28119 @item show auto-load gdb-scripts
28120 Show whether auto-loading of canned sequences of commands scripts is enabled or
28123 @anchor{info auto-load gdb-scripts}
28124 @kindex info auto-load gdb-scripts
28125 @cindex print list of auto-loaded canned sequences of commands scripts
28126 @item info auto-load gdb-scripts [@var{regexp}]
28127 Print the list of all canned sequences of commands scripts that @value{GDBN}
28131 If @var{regexp} is supplied only canned sequences of commands scripts with
28132 matching names are printed.
28135 @section Command Aliases
28136 @cindex aliases for commands
28138 Aliases allow you to define alternate spellings for existing commands.
28139 For example, if a new @value{GDBN} command defined in Python
28140 (@pxref{Python}) has a long name, it is handy to have an abbreviated
28141 version of it that involves less typing.
28143 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28144 of the @samp{step} command even though it is otherwise an ambiguous
28145 abbreviation of other commands like @samp{set} and @samp{show}.
28147 Aliases are also used to provide shortened or more common versions
28148 of multi-word commands. For example, @value{GDBN} provides the
28149 @samp{tty} alias of the @samp{set inferior-tty} command.
28151 You can define a new alias with the @samp{alias} command.
28156 @item alias [-a] [--] @var{alias} = @var{command} [@var{default-args}]
28160 @var{alias} specifies the name of the new alias. Each word of
28161 @var{alias} must consist of letters, numbers, dashes and underscores.
28163 @var{command} specifies the name of an existing command
28164 that is being aliased.
28166 @var{command} can also be the name of an existing alias. In this
28167 case, @var{command} cannot be an alias that has default arguments.
28169 The @samp{-a} option specifies that the new alias is an abbreviation
28170 of the command. Abbreviations are not used in command completion.
28172 The @samp{--} option specifies the end of options,
28173 and is useful when @var{alias} begins with a dash.
28175 You can specify @var{default-args} for your alias. These
28176 @var{default-args} will be automatically added before the alias
28177 arguments typed explicitly on the command line.
28179 For example, the below defines an alias @code{btfullall} that shows all local
28180 variables and all frame arguments:
28182 (@value{GDBP}) alias btfullall = backtrace -full -frame-arguments all
28185 For more information about @var{default-args}, see @ref{Command
28186 aliases default args, ,Default Arguments}.
28188 Here is a simple example showing how to make an abbreviation of a
28189 command so that there is less to type. Suppose you were tired of
28190 typing @samp{disas}, the current shortest unambiguous abbreviation of
28191 the @samp{disassemble} command and you wanted an even shorter version
28192 named @samp{di}. The following will accomplish this.
28195 (gdb) alias -a di = disas
28198 Note that aliases are different from user-defined commands. With a
28199 user-defined command, you also need to write documentation for it with
28200 the @samp{document} command. An alias automatically picks up the
28201 documentation of the existing command.
28203 Here is an example where we make @samp{elms} an abbreviation of
28204 @samp{elements} in the @samp{set print elements} command.
28205 This is to show that you can make an abbreviation of any part
28209 (gdb) alias -a set print elms = set print elements
28210 (gdb) alias -a show print elms = show print elements
28211 (gdb) set p elms 200
28213 Limit on string chars or array elements to print is 200.
28216 Note that if you are defining an alias of a @samp{set} command,
28217 and you want to have an alias for the corresponding @samp{show}
28218 command, then you need to define the latter separately.
28220 Unambiguously abbreviated commands are allowed in @var{command} and
28221 @var{alias}, just as they are normally.
28224 (gdb) alias -a set pr elms = set p ele
28227 Finally, here is an example showing the creation of a one word
28228 alias for a more complex command.
28229 This creates alias @samp{spe} of the command @samp{set print elements}.
28232 (gdb) alias spe = set print elements
28237 * Command aliases default args:: Default arguments for aliases
28240 @node Command aliases default args
28241 @subsection Default Arguments
28242 @cindex aliases for commands, default arguments
28244 You can tell @value{GDBN} to always prepend some default arguments to
28245 the list of arguments provided explicitly by the user when using a
28246 user-defined alias.
28248 If you repeatedly use the same arguments or options for a command, you
28249 can define an alias for this command and tell @value{GDBN} to
28250 automatically prepend these arguments or options to the list of
28251 arguments you type explicitly when using the alias@footnote{@value{GDBN}
28252 could easily accept default arguments for pre-defined commands and aliases,
28253 but it was deemed this would be confusing, and so is not allowed.}.
28255 For example, if you often use the command @code{thread apply all}
28256 specifying to work on the threads in ascending order and to continue in case it
28257 encounters an error, you can tell @value{GDBN} to automatically preprend
28258 the @code{-ascending} and @code{-c} options by using:
28261 (@value{GDBP}) alias thread apply asc-all = thread apply all -ascending -c
28264 Once you have defined this alias with its default args, any time you type
28265 the @code{thread apply asc-all} followed by @code{some arguments},
28266 @value{GDBN} will execute @code{thread apply all -ascending -c some arguments}.
28268 To have even less to type, you can also define a one word alias:
28270 (@value{GDBP}) alias t_a_c = thread apply all -ascending -c
28273 As usual, unambiguous abbreviations can be used for @var{alias}
28274 and @var{default-args}.
28276 The different aliases of a command do not share their default args.
28277 For example, you define a new alias @code{bt_ALL} showing all possible
28278 information and another alias @code{bt_SMALL} showing very limited information
28281 (@value{GDBP}) alias bt_ALL = backtrace -entry-values both -frame-arg all \
28282 -past-main -past-entry -full
28283 (@value{GDBP}) alias bt_SMALL = backtrace -entry-values no -frame-arg none \
28284 -past-main off -past-entry off
28287 (For more on using the @code{alias} command, see @ref{Aliases}.)
28289 Default args are not limited to the arguments and options of @var{command},
28290 but can specify nested commands if @var{command} accepts such a nested command
28292 For example, the below defines @code{faalocalsoftype} that lists the
28293 frames having locals of a certain type, together with the matching
28296 (@value{GDBP}) alias faalocalsoftype = frame apply all info locals -q -t
28297 (@value{GDBP}) faalocalsoftype int
28298 #1 0x55554f5e in sleeper_or_burner (v=0xdf50) at sleepers.c:86
28303 This is also very useful to define an alias for a set of nested @code{with}
28304 commands to have a particular combination of temporary settings. For example,
28305 the below defines the alias @code{pp10} that pretty prints an expression
28306 argument, with a maximum of 10 elements if the expression is a string or
28309 (@value{GDBP}) alias pp10 = with print pretty -- with print elements 10 -- print
28311 This defines the alias @code{pp10} as being a sequence of 3 commands.
28312 The first part @code{with print pretty --} temporarily activates the setting
28313 @code{set print pretty}, then launches the command that follows the separator
28315 The command following the first part is also a @code{with} command that
28316 temporarily changes the setting @code{set print elements} to 10, then
28317 launches the command that follows the second separator @code{--}.
28318 The third part @code{print} is the command the @code{pp10} alias will launch,
28319 using the temporary values of the settings and the arguments explicitly given
28321 For more information about the @code{with} command usage,
28322 see @ref{Command Settings}.
28324 @c Python docs live in a separate file.
28325 @include python.texi
28327 @c Guile docs live in a separate file.
28328 @include guile.texi
28330 @node Auto-loading extensions
28331 @section Auto-loading extensions
28332 @cindex auto-loading extensions
28334 @value{GDBN} provides two mechanisms for automatically loading
28335 extensions when a new object file is read (for example, due to the
28336 @code{file} command, or because the inferior has loaded a shared
28337 library): @file{@var{objfile}-gdb.@var{ext}} (@pxref{objfile-gdbdotext
28338 file,,The @file{@var{objfile}-gdb.@var{ext}} file}) and the
28339 @code{.debug_gdb_scripts} section of modern file formats like ELF
28340 (@pxref{dotdebug_gdb_scripts section,,The @code{.debug_gdb_scripts}
28341 section}). For a discussion of the differences between these two
28342 approaches see @ref{Which flavor to choose?}.
28344 The auto-loading feature is useful for supplying application-specific
28345 debugging commands and features.
28347 Auto-loading can be enabled or disabled,
28348 and the list of auto-loaded scripts can be printed.
28349 See the @samp{auto-loading} section of each extension language
28350 for more information.
28351 For @value{GDBN} command files see @ref{Auto-loading sequences}.
28352 For Python files see @ref{Python Auto-loading}.
28354 Note that loading of this script file also requires accordingly configured
28355 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28358 * objfile-gdbdotext file:: The @file{@var{objfile}-gdb.@var{ext}} file
28359 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
28360 * Which flavor to choose?:: Choosing between these approaches
28363 @node objfile-gdbdotext file
28364 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
28365 @cindex @file{@var{objfile}-gdb.gdb}
28366 @cindex @file{@var{objfile}-gdb.py}
28367 @cindex @file{@var{objfile}-gdb.scm}
28369 When a new object file is read, @value{GDBN} looks for a file named
28370 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
28371 where @var{objfile} is the object file's name and
28372 where @var{ext} is the file extension for the extension language:
28375 @item @file{@var{objfile}-gdb.gdb}
28376 GDB's own command language
28377 @item @file{@var{objfile}-gdb.py}
28379 @item @file{@var{objfile}-gdb.scm}
28383 @var{script-name} is formed by ensuring that the file name of @var{objfile}
28384 is absolute, following all symlinks, and resolving @code{.} and @code{..}
28385 components, and appending the @file{-gdb.@var{ext}} suffix.
28386 If this file exists and is readable, @value{GDBN} will evaluate it as a
28387 script in the specified extension language.
28389 If this file does not exist, then @value{GDBN} will look for
28390 @var{script-name} file in all of the directories as specified below.
28391 (On MS-Windows/MS-DOS, the drive letter of the executable's leading
28392 directories is converted to a one-letter subdirectory, i.e.@:
28393 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
28394 filesystems disallow colons in file names.)
28396 Note that loading of these files requires an accordingly configured
28397 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28399 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
28400 scripts normally according to its @file{.exe} filename. But if no scripts are
28401 found @value{GDBN} also tries script filenames matching the object file without
28402 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
28403 is attempted on any platform. This makes the script filenames compatible
28404 between Unix and MS-Windows hosts.
28407 @anchor{set auto-load scripts-directory}
28408 @kindex set auto-load scripts-directory
28409 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
28410 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
28411 may be delimited by the host platform path separator in use
28412 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
28414 Each entry here needs to be covered also by the security setting
28415 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
28417 @anchor{with-auto-load-dir}
28418 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
28419 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
28420 configuration option @option{--with-auto-load-dir}.
28422 Any reference to @file{$debugdir} will get replaced by
28423 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
28424 reference to @file{$datadir} will get replaced by @var{data-directory} which is
28425 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
28426 @file{$datadir} must be placed as a directory component --- either alone or
28427 delimited by @file{/} or @file{\} directory separators, depending on the host
28430 The list of directories uses path separator (@samp{:} on GNU and Unix
28431 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
28432 to the @env{PATH} environment variable.
28434 @anchor{show auto-load scripts-directory}
28435 @kindex show auto-load scripts-directory
28436 @item show auto-load scripts-directory
28437 Show @value{GDBN} auto-loaded scripts location.
28439 @anchor{add-auto-load-scripts-directory}
28440 @kindex add-auto-load-scripts-directory
28441 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
28442 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
28443 Multiple entries may be delimited by the host platform path separator in use.
28446 @value{GDBN} does not track which files it has already auto-loaded this way.
28447 @value{GDBN} will load the associated script every time the corresponding
28448 @var{objfile} is opened.
28449 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
28450 is evaluated more than once.
28452 @node dotdebug_gdb_scripts section
28453 @subsection The @code{.debug_gdb_scripts} section
28454 @cindex @code{.debug_gdb_scripts} section
28456 For systems using file formats like ELF and COFF,
28457 when @value{GDBN} loads a new object file
28458 it will look for a special section named @code{.debug_gdb_scripts}.
28459 If this section exists, its contents is a list of null-terminated entries
28460 specifying scripts to load. Each entry begins with a non-null prefix byte that
28461 specifies the kind of entry, typically the extension language and whether the
28462 script is in a file or inlined in @code{.debug_gdb_scripts}.
28464 The following entries are supported:
28467 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
28468 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
28469 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
28470 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
28473 @subsubsection Script File Entries
28475 If the entry specifies a file, @value{GDBN} will look for the file first
28476 in the current directory and then along the source search path
28477 (@pxref{Source Path, ,Specifying Source Directories}),
28478 except that @file{$cdir} is not searched, since the compilation
28479 directory is not relevant to scripts.
28481 File entries can be placed in section @code{.debug_gdb_scripts} with,
28482 for example, this GCC macro for Python scripts.
28485 /* Note: The "MS" section flags are to remove duplicates. */
28486 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28488 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28489 .byte 1 /* Python */\n\
28490 .asciz \"" script_name "\"\n\
28496 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
28497 Then one can reference the macro in a header or source file like this:
28500 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28503 The script name may include directories if desired.
28505 Note that loading of this script file also requires accordingly configured
28506 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28508 If the macro invocation is put in a header, any application or library
28509 using this header will get a reference to the specified script,
28510 and with the use of @code{"MS"} attributes on the section, the linker
28511 will remove duplicates.
28513 @subsubsection Script Text Entries
28515 Script text entries allow to put the executable script in the entry
28516 itself instead of loading it from a file.
28517 The first line of the entry, everything after the prefix byte and up to
28518 the first newline (@code{0xa}) character, is the script name, and must not
28519 contain any kind of space character, e.g., spaces or tabs.
28520 The rest of the entry, up to the trailing null byte, is the script to
28521 execute in the specified language. The name needs to be unique among
28522 all script names, as @value{GDBN} executes each script only once based
28525 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
28529 #include "symcat.h"
28530 #include "gdb/section-scripts.h"
28532 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
28533 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
28534 ".ascii \"gdb.inlined-script\\n\"\n"
28535 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
28536 ".ascii \" def __init__ (self):\\n\"\n"
28537 ".ascii \" super (test_cmd, self).__init__ ("
28538 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
28539 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
28540 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
28541 ".ascii \"test_cmd ()\\n\"\n"
28547 Loading of inlined scripts requires a properly configured
28548 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28549 The path to specify in @code{auto-load safe-path} is the path of the file
28550 containing the @code{.debug_gdb_scripts} section.
28552 @node Which flavor to choose?
28553 @subsection Which flavor to choose?
28555 Given the multiple ways of auto-loading extensions, it might not always
28556 be clear which one to choose. This section provides some guidance.
28559 Benefits of the @file{-gdb.@var{ext}} way:
28563 Can be used with file formats that don't support multiple sections.
28566 Ease of finding scripts for public libraries.
28568 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28569 in the source search path.
28570 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28571 isn't a source directory in which to find the script.
28574 Doesn't require source code additions.
28578 Benefits of the @code{.debug_gdb_scripts} way:
28582 Works with static linking.
28584 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28585 trigger their loading. When an application is statically linked the only
28586 objfile available is the executable, and it is cumbersome to attach all the
28587 scripts from all the input libraries to the executable's
28588 @file{-gdb.@var{ext}} script.
28591 Works with classes that are entirely inlined.
28593 Some classes can be entirely inlined, and thus there may not be an associated
28594 shared library to attach a @file{-gdb.@var{ext}} script to.
28597 Scripts needn't be copied out of the source tree.
28599 In some circumstances, apps can be built out of large collections of internal
28600 libraries, and the build infrastructure necessary to install the
28601 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28602 cumbersome. It may be easier to specify the scripts in the
28603 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28604 top of the source tree to the source search path.
28607 @node Multiple Extension Languages
28608 @section Multiple Extension Languages
28610 The Guile and Python extension languages do not share any state,
28611 and generally do not interfere with each other.
28612 There are some things to be aware of, however.
28614 @subsection Python comes first
28616 Python was @value{GDBN}'s first extension language, and to avoid breaking
28617 existing behaviour Python comes first. This is generally solved by the
28618 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
28619 extension languages, and when it makes a call to an extension language,
28620 (say to pretty-print a value), it tries each in turn until an extension
28621 language indicates it has performed the request (e.g., has returned the
28622 pretty-printed form of a value).
28623 This extends to errors while performing such requests: If an error happens
28624 while, for example, trying to pretty-print an object then the error is
28625 reported and any following extension languages are not tried.
28628 @chapter Command Interpreters
28629 @cindex command interpreters
28631 @value{GDBN} supports multiple command interpreters, and some command
28632 infrastructure to allow users or user interface writers to switch
28633 between interpreters or run commands in other interpreters.
28635 @value{GDBN} currently supports two command interpreters, the console
28636 interpreter (sometimes called the command-line interpreter or @sc{cli})
28637 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28638 describes both of these interfaces in great detail.
28640 By default, @value{GDBN} will start with the console interpreter.
28641 However, the user may choose to start @value{GDBN} with another
28642 interpreter by specifying the @option{-i} or @option{--interpreter}
28643 startup options. Defined interpreters include:
28647 @cindex console interpreter
28648 The traditional console or command-line interpreter. This is the most often
28649 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28650 @value{GDBN} will use this interpreter.
28653 @cindex mi interpreter
28654 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
28655 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28656 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28660 @cindex mi3 interpreter
28661 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
28664 @cindex mi2 interpreter
28665 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
28668 @cindex mi1 interpreter
28669 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
28673 @cindex invoke another interpreter
28675 @kindex interpreter-exec
28676 You may execute commands in any interpreter from the current
28677 interpreter using the appropriate command. If you are running the
28678 console interpreter, simply use the @code{interpreter-exec} command:
28681 interpreter-exec mi "-data-list-register-names"
28684 @sc{gdb/mi} has a similar command, although it is only available in versions of
28685 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28687 Note that @code{interpreter-exec} only changes the interpreter for the
28688 duration of the specified command. It does not change the interpreter
28691 @cindex start a new independent interpreter
28693 Although you may only choose a single interpreter at startup, it is
28694 possible to run an independent interpreter on a specified input/output
28695 device (usually a tty).
28697 For example, consider a debugger GUI or IDE that wants to provide a
28698 @value{GDBN} console view. It may do so by embedding a terminal
28699 emulator widget in its GUI, starting @value{GDBN} in the traditional
28700 command-line mode with stdin/stdout/stderr redirected to that
28701 terminal, and then creating an MI interpreter running on a specified
28702 input/output device. The console interpreter created by @value{GDBN}
28703 at startup handles commands the user types in the terminal widget,
28704 while the GUI controls and synchronizes state with @value{GDBN} using
28705 the separate MI interpreter.
28707 To start a new secondary @dfn{user interface} running MI, use the
28708 @code{new-ui} command:
28711 @cindex new user interface
28713 new-ui @var{interpreter} @var{tty}
28716 The @var{interpreter} parameter specifies the interpreter to run.
28717 This accepts the same values as the @code{interpreter-exec} command.
28718 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
28719 @var{tty} parameter specifies the name of the bidirectional file the
28720 interpreter uses for input/output, usually the name of a
28721 pseudoterminal slave on Unix systems. For example:
28724 (@value{GDBP}) new-ui mi /dev/pts/9
28728 runs an MI interpreter on @file{/dev/pts/9}.
28731 @chapter @value{GDBN} Text User Interface
28733 @cindex Text User Interface
28735 The @value{GDBN} Text User Interface (TUI) is a terminal
28736 interface which uses the @code{curses} library to show the source
28737 file, the assembly output, the program registers and @value{GDBN}
28738 commands in separate text windows. The TUI mode is supported only
28739 on platforms where a suitable version of the @code{curses} library
28742 The TUI mode is enabled by default when you invoke @value{GDBN} as
28743 @samp{@value{GDBP} -tui}.
28744 You can also switch in and out of TUI mode while @value{GDBN} runs by
28745 using various TUI commands and key bindings, such as @command{tui
28746 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
28747 @ref{TUI Keys, ,TUI Key Bindings}.
28750 * TUI Overview:: TUI overview
28751 * TUI Keys:: TUI key bindings
28752 * TUI Single Key Mode:: TUI single key mode
28753 * TUI Mouse Support:: TUI mouse support
28754 * TUI Commands:: TUI-specific commands
28755 * TUI Configuration:: TUI configuration variables
28759 @section TUI Overview
28761 In TUI mode, @value{GDBN} can display several text windows:
28765 This window is the @value{GDBN} command window with the @value{GDBN}
28766 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28767 managed using readline.
28770 The source window shows the source file of the program. The current
28771 line and active breakpoints are displayed in this window.
28774 The assembly window shows the disassembly output of the program.
28777 This window shows the processor registers. Registers are highlighted
28778 when their values change.
28781 The source and assembly windows show the current program position
28782 by highlighting the current line and marking it with a @samp{>} marker.
28783 Breakpoints are indicated with two markers. The first marker
28784 indicates the breakpoint type:
28788 Breakpoint which was hit at least once.
28791 Breakpoint which was never hit.
28794 Hardware breakpoint which was hit at least once.
28797 Hardware breakpoint which was never hit.
28800 The second marker indicates whether the breakpoint is enabled or not:
28804 Breakpoint is enabled.
28807 Breakpoint is disabled.
28810 The source, assembly and register windows are updated when the current
28811 thread changes, when the frame changes, or when the program counter
28814 These windows are not all visible at the same time. The command
28815 window is always visible. The others can be arranged in several
28826 source and assembly,
28829 source and registers, or
28832 assembly and registers.
28835 These are the standard layouts, but other layouts can be defined.
28837 A status line above the command window shows the following information:
28841 Indicates the current @value{GDBN} target.
28842 (@pxref{Targets, ,Specifying a Debugging Target}).
28845 Gives the current process or thread number.
28846 When no process is being debugged, this field is set to @code{No process}.
28849 Gives the current function name for the selected frame.
28850 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28851 When there is no symbol corresponding to the current program counter,
28852 the string @code{??} is displayed.
28855 Indicates the current line number for the selected frame.
28856 When the current line number is not known, the string @code{??} is displayed.
28859 Indicates the current program counter address.
28863 @section TUI Key Bindings
28864 @cindex TUI key bindings
28866 The TUI installs several key bindings in the readline keymaps
28867 @ifset SYSTEM_READLINE
28868 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28870 @ifclear SYSTEM_READLINE
28871 (@pxref{Command Line Editing}).
28873 The following key bindings are installed for both TUI mode and the
28874 @value{GDBN} standard mode.
28883 Enter or leave the TUI mode. When leaving the TUI mode,
28884 the curses window management stops and @value{GDBN} operates using
28885 its standard mode, writing on the terminal directly. When reentering
28886 the TUI mode, control is given back to the curses windows.
28887 The screen is then refreshed.
28889 This key binding uses the bindable Readline function
28890 @code{tui-switch-mode}.
28894 Use a TUI layout with only one window. The layout will
28895 either be @samp{source} or @samp{assembly}. When the TUI mode
28896 is not active, it will switch to the TUI mode.
28898 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28900 This key binding uses the bindable Readline function
28901 @code{tui-delete-other-windows}.
28905 Use a TUI layout with at least two windows. When the current
28906 layout already has two windows, the next layout with two windows is used.
28907 When a new layout is chosen, one window will always be common to the
28908 previous layout and the new one.
28910 Think of it as the Emacs @kbd{C-x 2} binding.
28912 This key binding uses the bindable Readline function
28913 @code{tui-change-windows}.
28917 Change the active window. The TUI associates several key bindings
28918 (like scrolling and arrow keys) with the active window. This command
28919 gives the focus to the next TUI window.
28921 Think of it as the Emacs @kbd{C-x o} binding.
28923 This key binding uses the bindable Readline function
28924 @code{tui-other-window}.
28928 Switch in and out of the TUI SingleKey mode that binds single
28929 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28931 This key binding uses the bindable Readline function
28932 @code{next-keymap}.
28935 The following key bindings only work in the TUI mode:
28940 Scroll the active window one page up.
28944 Scroll the active window one page down.
28948 Scroll the active window one line up.
28952 Scroll the active window one line down.
28956 Scroll the active window one column left.
28960 Scroll the active window one column right.
28964 Refresh the screen.
28967 Because the arrow keys scroll the active window in the TUI mode, they
28968 are not available for their normal use by readline unless the command
28969 window has the focus. When another window is active, you must use
28970 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28971 and @kbd{C-f} to control the command window.
28973 @node TUI Single Key Mode
28974 @section TUI Single Key Mode
28975 @cindex TUI single key mode
28977 The TUI also provides a @dfn{SingleKey} mode, which binds several
28978 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28979 switch into this mode, where the following key bindings are used:
28982 @kindex c @r{(SingleKey TUI key)}
28986 @kindex d @r{(SingleKey TUI key)}
28990 @kindex f @r{(SingleKey TUI key)}
28994 @kindex n @r{(SingleKey TUI key)}
28998 @kindex o @r{(SingleKey TUI key)}
29000 nexti. The shortcut letter @samp{o} stands for ``step Over''.
29002 @kindex q @r{(SingleKey TUI key)}
29004 exit the SingleKey mode.
29006 @kindex r @r{(SingleKey TUI key)}
29010 @kindex s @r{(SingleKey TUI key)}
29014 @kindex i @r{(SingleKey TUI key)}
29016 stepi. The shortcut letter @samp{i} stands for ``step Into''.
29018 @kindex u @r{(SingleKey TUI key)}
29022 @kindex v @r{(SingleKey TUI key)}
29026 @kindex w @r{(SingleKey TUI key)}
29031 Other keys temporarily switch to the @value{GDBN} command prompt.
29032 The key that was pressed is inserted in the editing buffer so that
29033 it is possible to type most @value{GDBN} commands without interaction
29034 with the TUI SingleKey mode. Once the command is entered the TUI
29035 SingleKey mode is restored. The only way to permanently leave
29036 this mode is by typing @kbd{q} or @kbd{C-x s}.
29038 @cindex SingleKey keymap name
29039 If @value{GDBN} was built with Readline 8.0 or later, the TUI
29040 SingleKey keymap will be named @samp{SingleKey}. This can be used in
29041 @file{.inputrc} to add additional bindings to this keymap.
29043 @node TUI Mouse Support
29044 @section TUI Mouse Support
29045 @cindex TUI mouse support
29047 If the curses library supports the mouse, the TUI supports mouse
29050 The mouse wheel scrolls the appropriate window under the mouse cursor.
29052 The TUI itself does not directly support copying/pasting with the
29053 mouse. However, on Unix terminals, you can typically press and hold
29054 the @key{SHIFT} key on your keyboard to temporarily bypass
29055 @value{GDBN}'s TUI and access the terminal's native mouse copy/paste
29056 functionality (commonly, click-drag-release or double-click to select
29057 text, middle-click to paste). This copy/paste works with the
29058 terminal's selection buffer, as opposed to the TUI's buffer.
29061 @section TUI-specific Commands
29062 @cindex TUI commands
29064 The TUI has specific commands to control the text windows.
29065 These commands are always available, even when @value{GDBN} is not in
29066 the TUI mode. When @value{GDBN} is in the standard mode, most
29067 of these commands will automatically switch to the TUI mode.
29069 Note that if @value{GDBN}'s @code{stdout} is not connected to a
29070 terminal, or @value{GDBN} has been started with the machine interface
29071 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
29072 these commands will fail with an error, because it would not be
29073 possible or desirable to enable curses window management.
29078 Activate TUI mode. The last active TUI window layout will be used if
29079 TUI mode has previously been used in the current debugging session,
29080 otherwise a default layout is used.
29083 @kindex tui disable
29084 Disable TUI mode, returning to the console interpreter.
29086 @anchor{info_win_command}
29089 List the names and sizes of all currently displayed windows.
29091 @item tui new-layout @var{name} @var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}
29092 @kindex tui new-layout
29093 Create a new TUI layout. The new layout will be named @var{name}, and
29094 can be accessed using the @code{layout} command (see below).
29096 Each @var{window} parameter is either the name of a window to display,
29097 or a window description. The windows will be displayed from top to
29098 bottom in the order listed.
29100 The names of the windows are the same as the ones given to the
29101 @code{focus} command (see below); additional, the @code{status}
29102 window can be specified. Note that, because it is of fixed height,
29103 the weight assigned to the status window is of no importance. It is
29104 conventional to use @samp{0} here.
29106 A window description looks a bit like an invocation of @code{tui
29107 new-layout}, and is of the form
29108 @{@r{[}@code{-horizontal}@r{]}@var{window} @var{weight} @r{[}@var{window} @var{weight}@dots{}@r{]}@}.
29110 This specifies a sub-layout. If @code{-horizontal} is given, the
29111 windows in this description will be arranged side-by-side, rather than
29114 Each @var{weight} is an integer. It is the weight of this window
29115 relative to all the other windows in the layout. These numbers are
29116 used to calculate how much of the screen is given to each window.
29121 (gdb) tui new-layout example src 1 regs 1 status 0 cmd 1
29124 Here, the new layout is called @samp{example}. It shows the source
29125 and register windows, followed by the status window, and then finally
29126 the command window. The non-status windows all have the same weight,
29127 so the terminal will be split into three roughly equal sections.
29129 Here is a more complex example, showing a horizontal layout:
29132 (gdb) tui new-layout example @{-horizontal src 1 asm 1@} 2 status 0 cmd 1
29135 This will result in side-by-side source and assembly windows; with the
29136 status and command window being beneath these, filling the entire
29137 width of the terminal. Because they have weight 2, the source and
29138 assembly windows will be twice the height of the command window.
29142 @item tui layout @var{name}
29143 @itemx layout @var{name}
29144 Changes which TUI windows are displayed. The @var{name} parameter
29145 controls which layout is shown. It can be either one of the built-in
29146 layout names, or the name of a layout defined by the user using
29147 @code{tui new-layout}.
29149 The built-in layouts are as follows:
29153 Display the next layout.
29156 Display the previous layout.
29159 Display the source and command windows.
29162 Display the assembly and command windows.
29165 Display the source, assembly, and command windows.
29168 When in @code{src} layout display the register, source, and command
29169 windows. When in @code{asm} or @code{split} layout display the
29170 register, assembler, and command windows.
29174 @item tui focus @var{name}
29175 @itemx focus @var{name}
29176 Changes which TUI window is currently active for scrolling. The
29177 @var{name} parameter can be any of the following:
29181 Make the next window active for scrolling.
29184 Make the previous window active for scrolling.
29187 Make the source window active for scrolling.
29190 Make the assembly window active for scrolling.
29193 Make the register window active for scrolling.
29196 Make the command window active for scrolling.
29199 @kindex tui refresh
29203 Refresh the screen. This is similar to typing @kbd{C-L}.
29205 @item tui reg @var{group}
29207 Changes the register group displayed in the tui register window to
29208 @var{group}. If the register window is not currently displayed this
29209 command will cause the register window to be displayed. The list of
29210 register groups, as well as their order is target specific. The
29211 following groups are available on most targets:
29214 Repeatedly selecting this group will cause the display to cycle
29215 through all of the available register groups.
29218 Repeatedly selecting this group will cause the display to cycle
29219 through all of the available register groups in the reverse order to
29223 Display the general registers.
29225 Display the floating point registers.
29227 Display the system registers.
29229 Display the vector registers.
29231 Display all registers.
29236 Update the source window and the current execution point.
29238 @kindex tui window height
29240 @item tui window height @var{name} +@var{count}
29241 @itemx tui window height @var{name} -@var{count}
29242 @itemx winheight @var{name} +@var{count}
29243 @itemx winheight @var{name} -@var{count}
29244 Change the height of the window @var{name} by @var{count} lines.
29245 Positive counts increase the height, while negative counts decrease
29246 it. The @var{name} parameter can be the name of any currently visible
29247 window. The names of the currently visible windows can be discovered
29248 using @kbd{info win} (@pxref{info_win_command,,info win}).
29250 The set of currently visible windows must always fill the terminal,
29251 and so, it is only possible to resize on window if there are other
29252 visible windows that can either give or receive the extra terminal
29255 @kindex tui window width
29257 @item tui window width @var{name} +@var{count}
29258 @itemx tui window width @var{name} -@var{count}
29259 @itemx winwidth @var{name} +@var{count}
29260 @itemx winwidth @var{name} -@var{count}
29261 Change the width of the window @var{name} by @var{count} columns.
29262 Positive counts increase the width, while negative counts decrease it.
29263 The @var{name} parameter can be the name of any currently visible
29264 window. The names of the currently visible windows can be discovered
29265 using @code{info win} (@pxref{info_win_command,,info win}).
29267 The set of currently visible windows must always fill the terminal,
29268 and so, it is only possible to resize on window if there are other
29269 visible windows that can either give or receive the extra terminal
29273 @node TUI Configuration
29274 @section TUI Configuration Variables
29275 @cindex TUI configuration variables
29277 Several configuration variables control the appearance of TUI windows.
29280 @item set tui border-kind @var{kind}
29281 @kindex set tui border-kind
29282 Select the border appearance for the source, assembly and register windows.
29283 The possible values are the following:
29286 Use a space character to draw the border.
29289 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
29292 Use the Alternate Character Set to draw the border. The border is
29293 drawn using character line graphics if the terminal supports them.
29296 @item set tui border-mode @var{mode}
29297 @kindex set tui border-mode
29298 @itemx set tui active-border-mode @var{mode}
29299 @kindex set tui active-border-mode
29300 Select the display attributes for the borders of the inactive windows
29301 or the active window. The @var{mode} can be one of the following:
29304 Use normal attributes to display the border.
29310 Use reverse video mode.
29313 Use half bright mode.
29315 @item half-standout
29316 Use half bright and standout mode.
29319 Use extra bright or bold mode.
29321 @item bold-standout
29322 Use extra bright or bold and standout mode.
29325 @item set tui tab-width @var{nchars}
29326 @kindex set tui tab-width
29328 Set the width of tab stops to be @var{nchars} characters. This
29329 setting affects the display of TAB characters in the source and
29332 @item set tui compact-source @r{[}on@r{|}off@r{]}
29333 @kindex set tui compact-source
29334 Set whether the TUI source window is displayed in ``compact'' form.
29335 The default display uses more space for line numbers and starts the
29336 source text at the next tab stop; the compact display uses only as
29337 much space as is needed for the line numbers in the current file, and
29338 only a single space to separate the line numbers from the source.
29340 @kindex set debug tui
29341 @item set debug tui @r{[}on|off@r{]}
29342 Turn on or off display of @value{GDBN} internal debug messages relating
29345 @kindex show debug tui
29346 @item show debug tui
29347 Show the current status of displaying @value{GDBN} internal debug
29348 messages relating to the TUI.
29352 Note that the colors of the TUI borders can be controlled using the
29353 appropriate @code{set style} commands. @xref{Output Styling}.
29356 @chapter Using @value{GDBN} under @sc{gnu} Emacs
29359 @cindex @sc{gnu} Emacs
29360 A special interface allows you to use @sc{gnu} Emacs to view (and
29361 edit) the source files for the program you are debugging with
29364 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
29365 executable file you want to debug as an argument. This command starts
29366 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
29367 created Emacs buffer.
29368 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
29370 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
29375 All ``terminal'' input and output goes through an Emacs buffer, called
29378 This applies both to @value{GDBN} commands and their output, and to the input
29379 and output done by the program you are debugging.
29381 This is useful because it means that you can copy the text of previous
29382 commands and input them again; you can even use parts of the output
29385 All the facilities of Emacs' Shell mode are available for interacting
29386 with your program. In particular, you can send signals the usual
29387 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
29391 @value{GDBN} displays source code through Emacs.
29393 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
29394 source file for that frame and puts an arrow (@samp{=>}) at the
29395 left margin of the current line. Emacs uses a separate buffer for
29396 source display, and splits the screen to show both your @value{GDBN} session
29399 Explicit @value{GDBN} @code{list} or search commands still produce output as
29400 usual, but you probably have no reason to use them from Emacs.
29403 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
29404 a graphical mode, enabled by default, which provides further buffers
29405 that can control the execution and describe the state of your program.
29406 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
29408 If you specify an absolute file name when prompted for the @kbd{M-x
29409 gdb} argument, then Emacs sets your current working directory to where
29410 your program resides. If you only specify the file name, then Emacs
29411 sets your current working directory to the directory associated
29412 with the previous buffer. In this case, @value{GDBN} may find your
29413 program by searching your environment's @env{PATH} variable, but on
29414 some operating systems it might not find the source. So, although the
29415 @value{GDBN} input and output session proceeds normally, the auxiliary
29416 buffer does not display the current source and line of execution.
29418 The initial working directory of @value{GDBN} is printed on the top
29419 line of the GUD buffer and this serves as a default for the commands
29420 that specify files for @value{GDBN} to operate on. @xref{Files,
29421 ,Commands to Specify Files}.
29423 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
29424 need to call @value{GDBN} by a different name (for example, if you
29425 keep several configurations around, with different names) you can
29426 customize the Emacs variable @code{gud-gdb-command-name} to run the
29429 In the GUD buffer, you can use these special Emacs commands in
29430 addition to the standard Shell mode commands:
29434 Describe the features of Emacs' GUD Mode.
29437 Execute to another source line, like the @value{GDBN} @code{step} command; also
29438 update the display window to show the current file and location.
29441 Execute to next source line in this function, skipping all function
29442 calls, like the @value{GDBN} @code{next} command. Then update the display window
29443 to show the current file and location.
29446 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
29447 display window accordingly.
29450 Execute until exit from the selected stack frame, like the @value{GDBN}
29451 @code{finish} command.
29454 Continue execution of your program, like the @value{GDBN} @code{continue}
29458 Go up the number of frames indicated by the numeric argument
29459 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
29460 like the @value{GDBN} @code{up} command.
29463 Go down the number of frames indicated by the numeric argument, like the
29464 @value{GDBN} @code{down} command.
29467 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
29468 tells @value{GDBN} to set a breakpoint on the source line point is on.
29470 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
29471 separate frame which shows a backtrace when the GUD buffer is current.
29472 Move point to any frame in the stack and type @key{RET} to make it
29473 become the current frame and display the associated source in the
29474 source buffer. Alternatively, click @kbd{Mouse-2} to make the
29475 selected frame become the current one. In graphical mode, the
29476 speedbar displays watch expressions.
29478 If you accidentally delete the source-display buffer, an easy way to get
29479 it back is to type the command @code{f} in the @value{GDBN} buffer, to
29480 request a frame display; when you run under Emacs, this recreates
29481 the source buffer if necessary to show you the context of the current
29484 The source files displayed in Emacs are in ordinary Emacs buffers
29485 which are visiting the source files in the usual way. You can edit
29486 the files with these buffers if you wish; but keep in mind that @value{GDBN}
29487 communicates with Emacs in terms of line numbers. If you add or
29488 delete lines from the text, the line numbers that @value{GDBN} knows cease
29489 to correspond properly with the code.
29491 A more detailed description of Emacs' interaction with @value{GDBN} is
29492 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
29496 @chapter The @sc{gdb/mi} Interface
29498 @unnumberedsec Function and Purpose
29500 @cindex @sc{gdb/mi}, its purpose
29501 @sc{gdb/mi} is a line based machine oriented text interface to
29502 @value{GDBN} and is activated by specifying using the
29503 @option{--interpreter} command line option (@pxref{Mode Options}). It
29504 is specifically intended to support the development of systems which
29505 use the debugger as just one small component of a larger system.
29507 This chapter is a specification of the @sc{gdb/mi} interface. It is written
29508 in the form of a reference manual.
29510 Note that @sc{gdb/mi} is still under construction, so some of the
29511 features described below are incomplete and subject to change
29512 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
29514 @unnumberedsec Notation and Terminology
29516 @cindex notational conventions, for @sc{gdb/mi}
29517 This chapter uses the following notation:
29521 @code{|} separates two alternatives.
29524 @code{[ @var{something} ]} indicates that @var{something} is optional:
29525 it may or may not be given.
29528 @code{( @var{group} )*} means that @var{group} inside the parentheses
29529 may repeat zero or more times.
29532 @code{( @var{group} )+} means that @var{group} inside the parentheses
29533 may repeat one or more times.
29536 @code{"@var{string}"} means a literal @var{string}.
29540 @heading Dependencies
29544 * GDB/MI General Design::
29545 * GDB/MI Command Syntax::
29546 * GDB/MI Compatibility with CLI::
29547 * GDB/MI Development and Front Ends::
29548 * GDB/MI Output Records::
29549 * GDB/MI Simple Examples::
29550 * GDB/MI Command Description Format::
29551 * GDB/MI Breakpoint Commands::
29552 * GDB/MI Catchpoint Commands::
29553 * GDB/MI Program Context::
29554 * GDB/MI Thread Commands::
29555 * GDB/MI Ada Tasking Commands::
29556 * GDB/MI Program Execution::
29557 * GDB/MI Stack Manipulation::
29558 * GDB/MI Variable Objects::
29559 * GDB/MI Data Manipulation::
29560 * GDB/MI Tracepoint Commands::
29561 * GDB/MI Symbol Query::
29562 * GDB/MI File Commands::
29564 * GDB/MI Kod Commands::
29565 * GDB/MI Memory Overlay Commands::
29566 * GDB/MI Signal Handling Commands::
29568 * GDB/MI Target Manipulation::
29569 * GDB/MI File Transfer Commands::
29570 * GDB/MI Ada Exceptions Commands::
29571 * GDB/MI Support Commands::
29572 * GDB/MI Miscellaneous Commands::
29575 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29576 @node GDB/MI General Design
29577 @section @sc{gdb/mi} General Design
29578 @cindex GDB/MI General Design
29580 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
29581 parts---commands sent to @value{GDBN}, responses to those commands
29582 and notifications. Each command results in exactly one response,
29583 indicating either successful completion of the command, or an error.
29584 For the commands that do not resume the target, the response contains the
29585 requested information. For the commands that resume the target, the
29586 response only indicates whether the target was successfully resumed.
29587 Notifications is the mechanism for reporting changes in the state of the
29588 target, or in @value{GDBN} state, that cannot conveniently be associated with
29589 a command and reported as part of that command response.
29591 The important examples of notifications are:
29595 Exec notifications. These are used to report changes in
29596 target state---when a target is resumed, or stopped. It would not
29597 be feasible to include this information in response of resuming
29598 commands, because one resume commands can result in multiple events in
29599 different threads. Also, quite some time may pass before any event
29600 happens in the target, while a frontend needs to know whether the resuming
29601 command itself was successfully executed.
29604 Console output, and status notifications. Console output
29605 notifications are used to report output of CLI commands, as well as
29606 diagnostics for other commands. Status notifications are used to
29607 report the progress of a long-running operation. Naturally, including
29608 this information in command response would mean no output is produced
29609 until the command is finished, which is undesirable.
29612 General notifications. Commands may have various side effects on
29613 the @value{GDBN} or target state beyond their official purpose. For example,
29614 a command may change the selected thread. Although such changes can
29615 be included in command response, using notification allows for more
29616 orthogonal frontend design.
29620 There's no guarantee that whenever an MI command reports an error,
29621 @value{GDBN} or the target are in any specific state, and especially,
29622 the state is not reverted to the state before the MI command was
29623 processed. Therefore, whenever an MI command results in an error,
29624 we recommend that the frontend refreshes all the information shown in
29625 the user interface.
29629 * Context management::
29630 * Asynchronous and non-stop modes::
29634 @node Context management
29635 @subsection Context management
29637 @subsubsection Threads and Frames
29639 In most cases when @value{GDBN} accesses the target, this access is
29640 done in context of a specific thread and frame (@pxref{Frames}).
29641 Often, even when accessing global data, the target requires that a thread
29642 be specified. The CLI interface maintains the selected thread and frame,
29643 and supplies them to target on each command. This is convenient,
29644 because a command line user would not want to specify that information
29645 explicitly on each command, and because user interacts with
29646 @value{GDBN} via a single terminal, so no confusion is possible as
29647 to what thread and frame are the current ones.
29649 In the case of MI, the concept of selected thread and frame is less
29650 useful. First, a frontend can easily remember this information
29651 itself. Second, a graphical frontend can have more than one window,
29652 each one used for debugging a different thread, and the frontend might
29653 want to access additional threads for internal purposes. This
29654 increases the risk that by relying on implicitly selected thread, the
29655 frontend may be operating on a wrong one. Therefore, each MI command
29656 should explicitly specify which thread and frame to operate on. To
29657 make it possible, each MI command accepts the @samp{--thread} and
29658 @samp{--frame} options, the value to each is @value{GDBN} global
29659 identifier for thread and frame to operate on.
29661 Usually, each top-level window in a frontend allows the user to select
29662 a thread and a frame, and remembers the user selection for further
29663 operations. However, in some cases @value{GDBN} may suggest that the
29664 current thread or frame be changed. For example, when stopping on a
29665 breakpoint it is reasonable to switch to the thread where breakpoint is
29666 hit. For another example, if the user issues the CLI @samp{thread} or
29667 @samp{frame} commands via the frontend, it is desirable to change the
29668 frontend's selection to the one specified by user. @value{GDBN}
29669 communicates the suggestion to change current thread and frame using the
29670 @samp{=thread-selected} notification.
29672 Note that historically, MI shares the selected thread with CLI, so
29673 frontends used the @code{-thread-select} to execute commands in the
29674 right context. However, getting this to work right is cumbersome. The
29675 simplest way is for frontend to emit @code{-thread-select} command
29676 before every command. This doubles the number of commands that need
29677 to be sent. The alternative approach is to suppress @code{-thread-select}
29678 if the selected thread in @value{GDBN} is supposed to be identical to the
29679 thread the frontend wants to operate on. However, getting this
29680 optimization right can be tricky. In particular, if the frontend
29681 sends several commands to @value{GDBN}, and one of the commands changes the
29682 selected thread, then the behaviour of subsequent commands will
29683 change. So, a frontend should either wait for response from such
29684 problematic commands, or explicitly add @code{-thread-select} for
29685 all subsequent commands. No frontend is known to do this exactly
29686 right, so it is suggested to just always pass the @samp{--thread} and
29687 @samp{--frame} options.
29689 @subsubsection Language
29691 The execution of several commands depends on which language is selected.
29692 By default, the current language (@pxref{show language}) is used.
29693 But for commands known to be language-sensitive, it is recommended
29694 to use the @samp{--language} option. This option takes one argument,
29695 which is the name of the language to use while executing the command.
29699 -data-evaluate-expression --language c "sizeof (void*)"
29704 The valid language names are the same names accepted by the
29705 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29706 @samp{local} or @samp{unknown}.
29708 @node Asynchronous and non-stop modes
29709 @subsection Asynchronous command execution and non-stop mode
29711 On some targets, @value{GDBN} is capable of processing MI commands
29712 even while the target is running. This is called @dfn{asynchronous
29713 command execution} (@pxref{Background Execution}). The frontend may
29714 specify a preference for asynchronous execution using the
29715 @code{-gdb-set mi-async 1} command, which should be emitted before
29716 either running the executable or attaching to the target. After the
29717 frontend has started the executable or attached to the target, it can
29718 find if asynchronous execution is enabled using the
29719 @code{-list-target-features} command.
29722 @cindex foreground execution
29723 @cindex background execution
29724 @cindex asynchronous execution
29725 @cindex execution, foreground, background and asynchronous
29726 @kindex set mi-async
29727 @item -gdb-set mi-async @r{[}on@r{|}off@r{]}
29728 Set whether MI is in asynchronous mode.
29730 When @code{off}, which is the default, MI execution commands (e.g.,
29731 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
29732 for the program to stop before processing further commands.
29734 When @code{on}, MI execution commands are background execution
29735 commands (e.g., @code{-exec-continue} becomes the equivalent of the
29736 @code{c&} CLI command), and so @value{GDBN} is capable of processing
29737 MI commands even while the target is running.
29739 @kindex show mi-async
29740 @item -gdb-show mi-async
29741 Show whether MI asynchronous mode is enabled.
29744 Note: In @value{GDBN} version 7.7 and earlier, this option was called
29745 @code{target-async} instead of @code{mi-async}, and it had the effect
29746 of both putting MI in asynchronous mode and making CLI background
29747 commands possible. CLI background commands are now always possible
29748 ``out of the box'' if the target supports them. The old spelling is
29749 kept as a deprecated alias for backwards compatibility.
29751 Even if @value{GDBN} can accept a command while target is running,
29752 many commands that access the target do not work when the target is
29753 running. Therefore, asynchronous command execution is most useful
29754 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29755 it is possible to examine the state of one thread, while other threads
29758 When a given thread is running, MI commands that try to access the
29759 target in the context of that thread may not work, or may work only on
29760 some targets. In particular, commands that try to operate on thread's
29761 stack will not work, on any target. Commands that read memory, or
29762 modify breakpoints, may work or not work, depending on the target. Note
29763 that even commands that operate on global state, such as @code{print},
29764 @code{set}, and breakpoint commands, still access the target in the
29765 context of a specific thread, so frontend should try to find a
29766 stopped thread and perform the operation on that thread (using the
29767 @samp{--thread} option).
29769 Which commands will work in the context of a running thread is
29770 highly target dependent. However, the two commands
29771 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29772 to find the state of a thread, will always work.
29774 @node Thread groups
29775 @subsection Thread groups
29776 @value{GDBN} may be used to debug several processes at the same time.
29777 On some platforms, @value{GDBN} may support debugging of several
29778 hardware systems, each one having several cores with several different
29779 processes running on each core. This section describes the MI
29780 mechanism to support such debugging scenarios.
29782 The key observation is that regardless of the structure of the
29783 target, MI can have a global list of threads, because most commands that
29784 accept the @samp{--thread} option do not need to know what process that
29785 thread belongs to. Therefore, it is not necessary to introduce
29786 neither additional @samp{--process} option, nor an notion of the
29787 current process in the MI interface. The only strictly new feature
29788 that is required is the ability to find how the threads are grouped
29791 To allow the user to discover such grouping, and to support arbitrary
29792 hierarchy of machines/cores/processes, MI introduces the concept of a
29793 @dfn{thread group}. Thread group is a collection of threads and other
29794 thread groups. A thread group always has a string identifier, a type,
29795 and may have additional attributes specific to the type. A new
29796 command, @code{-list-thread-groups}, returns the list of top-level
29797 thread groups, which correspond to processes that @value{GDBN} is
29798 debugging at the moment. By passing an identifier of a thread group
29799 to the @code{-list-thread-groups} command, it is possible to obtain
29800 the members of specific thread group.
29802 To allow the user to easily discover processes, and other objects, he
29803 wishes to debug, a concept of @dfn{available thread group} is
29804 introduced. Available thread group is an thread group that
29805 @value{GDBN} is not debugging, but that can be attached to, using the
29806 @code{-target-attach} command. The list of available top-level thread
29807 groups can be obtained using @samp{-list-thread-groups --available}.
29808 In general, the content of a thread group may be only retrieved only
29809 after attaching to that thread group.
29811 Thread groups are related to inferiors (@pxref{Inferiors Connections and
29812 Programs}). Each inferior corresponds to a thread group of a special
29813 type @samp{process}, and some additional operations are permitted on
29814 such thread groups.
29816 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29817 @node GDB/MI Command Syntax
29818 @section @sc{gdb/mi} Command Syntax
29821 * GDB/MI Input Syntax::
29822 * GDB/MI Output Syntax::
29825 @node GDB/MI Input Syntax
29826 @subsection @sc{gdb/mi} Input Syntax
29828 @cindex input syntax for @sc{gdb/mi}
29829 @cindex @sc{gdb/mi}, input syntax
29831 @item @var{command} @expansion{}
29832 @code{@var{cli-command} | @var{mi-command}}
29834 @item @var{cli-command} @expansion{}
29835 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29836 @var{cli-command} is any existing @value{GDBN} CLI command.
29838 @item @var{mi-command} @expansion{}
29839 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29840 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29842 @item @var{token} @expansion{}
29843 "any sequence of digits"
29845 @item @var{option} @expansion{}
29846 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29848 @item @var{parameter} @expansion{}
29849 @code{@var{non-blank-sequence} | @var{c-string}}
29851 @item @var{operation} @expansion{}
29852 @emph{any of the operations described in this chapter}
29854 @item @var{non-blank-sequence} @expansion{}
29855 @emph{anything, provided it doesn't contain special characters such as
29856 "-", @var{nl}, """ and of course " "}
29858 @item @var{c-string} @expansion{}
29859 @code{""" @var{seven-bit-iso-c-string-content} """}
29861 @item @var{nl} @expansion{}
29870 The CLI commands are still handled by the @sc{mi} interpreter; their
29871 output is described below.
29874 The @code{@var{token}}, when present, is passed back when the command
29878 Some @sc{mi} commands accept optional arguments as part of the parameter
29879 list. Each option is identified by a leading @samp{-} (dash) and may be
29880 followed by an optional argument parameter. Options occur first in the
29881 parameter list and can be delimited from normal parameters using
29882 @samp{--} (this is useful when some parameters begin with a dash).
29889 We want easy access to the existing CLI syntax (for debugging).
29892 We want it to be easy to spot a @sc{mi} operation.
29895 @node GDB/MI Output Syntax
29896 @subsection @sc{gdb/mi} Output Syntax
29898 @cindex output syntax of @sc{gdb/mi}
29899 @cindex @sc{gdb/mi}, output syntax
29900 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29901 followed, optionally, by a single result record. This result record
29902 is for the most recent command. The sequence of output records is
29903 terminated by @samp{(gdb)}.
29905 If an input command was prefixed with a @code{@var{token}} then the
29906 corresponding output for that command will also be prefixed by that same
29910 @item @var{output} @expansion{}
29911 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29913 @item @var{result-record} @expansion{}
29914 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29916 @item @var{out-of-band-record} @expansion{}
29917 @code{@var{async-record} | @var{stream-record}}
29919 @item @var{async-record} @expansion{}
29920 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29922 @item @var{exec-async-output} @expansion{}
29923 @code{[ @var{token} ] "*" @var{async-output nl}}
29925 @item @var{status-async-output} @expansion{}
29926 @code{[ @var{token} ] "+" @var{async-output nl}}
29928 @item @var{notify-async-output} @expansion{}
29929 @code{[ @var{token} ] "=" @var{async-output nl}}
29931 @item @var{async-output} @expansion{}
29932 @code{@var{async-class} ( "," @var{result} )*}
29934 @item @var{result-class} @expansion{}
29935 @code{"done" | "running" | "connected" | "error" | "exit"}
29937 @item @var{async-class} @expansion{}
29938 @code{"stopped" | @var{others}} (where @var{others} will be added
29939 depending on the needs---this is still in development).
29941 @item @var{result} @expansion{}
29942 @code{ @var{variable} "=" @var{value}}
29944 @item @var{variable} @expansion{}
29945 @code{ @var{string} }
29947 @item @var{value} @expansion{}
29948 @code{ @var{const} | @var{tuple} | @var{list} }
29950 @item @var{const} @expansion{}
29951 @code{@var{c-string}}
29953 @item @var{tuple} @expansion{}
29954 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29956 @item @var{list} @expansion{}
29957 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29958 @var{result} ( "," @var{result} )* "]" }
29960 @item @var{stream-record} @expansion{}
29961 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29963 @item @var{console-stream-output} @expansion{}
29964 @code{"~" @var{c-string nl}}
29966 @item @var{target-stream-output} @expansion{}
29967 @code{"@@" @var{c-string nl}}
29969 @item @var{log-stream-output} @expansion{}
29970 @code{"&" @var{c-string nl}}
29972 @item @var{nl} @expansion{}
29975 @item @var{token} @expansion{}
29976 @emph{any sequence of digits}.
29984 All output sequences end in a single line containing a period.
29987 The @code{@var{token}} is from the corresponding request. Note that
29988 for all async output, while the token is allowed by the grammar and
29989 may be output by future versions of @value{GDBN} for select async
29990 output messages, it is generally omitted. Frontends should treat
29991 all async output as reporting general changes in the state of the
29992 target and there should be no need to associate async output to any
29996 @cindex status output in @sc{gdb/mi}
29997 @var{status-async-output} contains on-going status information about the
29998 progress of a slow operation. It can be discarded. All status output is
29999 prefixed by @samp{+}.
30002 @cindex async output in @sc{gdb/mi}
30003 @var{exec-async-output} contains asynchronous state change on the target
30004 (stopped, started, disappeared). All async output is prefixed by
30008 @cindex notify output in @sc{gdb/mi}
30009 @var{notify-async-output} contains supplementary information that the
30010 client should handle (e.g., a new breakpoint information). All notify
30011 output is prefixed by @samp{=}.
30014 @cindex console output in @sc{gdb/mi}
30015 @var{console-stream-output} is output that should be displayed as is in the
30016 console. It is the textual response to a CLI command. All the console
30017 output is prefixed by @samp{~}.
30020 @cindex target output in @sc{gdb/mi}
30021 @var{target-stream-output} is the output produced by the target program.
30022 All the target output is prefixed by @samp{@@}.
30025 @cindex log output in @sc{gdb/mi}
30026 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
30027 instance messages that should be displayed as part of an error log. All
30028 the log output is prefixed by @samp{&}.
30031 @cindex list output in @sc{gdb/mi}
30032 New @sc{gdb/mi} commands should only output @var{lists} containing
30038 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
30039 details about the various output records.
30041 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30042 @node GDB/MI Compatibility with CLI
30043 @section @sc{gdb/mi} Compatibility with CLI
30045 @cindex compatibility, @sc{gdb/mi} and CLI
30046 @cindex @sc{gdb/mi}, compatibility with CLI
30048 For the developers convenience CLI commands can be entered directly,
30049 but there may be some unexpected behaviour. For example, commands
30050 that query the user will behave as if the user replied yes, breakpoint
30051 command lists are not executed and some CLI commands, such as
30052 @code{if}, @code{when} and @code{define}, prompt for further input with
30053 @samp{>}, which is not valid MI output.
30055 This feature may be removed at some stage in the future and it is
30056 recommended that front ends use the @code{-interpreter-exec} command
30057 (@pxref{-interpreter-exec}).
30059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30060 @node GDB/MI Development and Front Ends
30061 @section @sc{gdb/mi} Development and Front Ends
30062 @cindex @sc{gdb/mi} development
30064 The application which takes the MI output and presents the state of the
30065 program being debugged to the user is called a @dfn{front end}.
30067 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
30068 to the MI interface may break existing usage. This section describes how the
30069 protocol changes and how to request previous version of the protocol when it
30072 Some changes in MI need not break a carefully designed front end, and
30073 for these the MI version will remain unchanged. The following is a
30074 list of changes that may occur within one level, so front ends should
30075 parse MI output in a way that can handle them:
30079 New MI commands may be added.
30082 New fields may be added to the output of any MI command.
30085 The range of values for fields with specified values, e.g.,
30086 @code{in_scope} (@pxref{-var-update}) may be extended.
30088 @c The format of field's content e.g type prefix, may change so parse it
30089 @c at your own risk. Yes, in general?
30091 @c The order of fields may change? Shouldn't really matter but it might
30092 @c resolve inconsistencies.
30095 If the changes are likely to break front ends, the MI version level
30096 will be increased by one. The new versions of the MI protocol are not compatible
30097 with the old versions. Old versions of MI remain available, allowing front ends
30098 to keep using them until they are modified to use the latest MI version.
30100 Since @code{--interpreter=mi} always points to the latest MI version, it is
30101 recommended that front ends request a specific version of MI when launching
30102 @value{GDBN} (e.g.@: @code{--interpreter=mi2}) to make sure they get an
30103 interpreter with the MI version they expect.
30105 The following table gives a summary of the released versions of the MI
30106 interface: the version number, the version of GDB in which it first appeared
30107 and the breaking changes compared to the previous version.
30109 @multitable @columnfractions .05 .05 .9
30110 @headitem MI version @tab GDB version @tab Breaking changes
30127 The @code{-environment-pwd}, @code{-environment-directory} and
30128 @code{-environment-path} commands now returns values using the MI output
30129 syntax, rather than CLI output syntax.
30132 @code{-var-list-children}'s @code{children} result field is now a list, rather
30136 @code{-var-update}'s @code{changelist} result field is now a list, rather than
30148 The output of information about multi-location breakpoints has changed in the
30149 responses to the @code{-break-insert} and @code{-break-info} commands, as well
30150 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
30151 The multiple locations are now placed in a @code{locations} field, whose value
30157 If your front end cannot yet migrate to a more recent version of the
30158 MI protocol, you can nevertheless selectively enable specific features
30159 available in those recent MI versions, using the following commands:
30163 @item -fix-multi-location-breakpoint-output
30164 Use the output for multi-location breakpoints which was introduced by
30165 MI 3, even when using MI versions 2 or 1. This command has no
30166 effect when using MI version 3 or later.
30170 The best way to avoid unexpected changes in MI that might break your front
30171 end is to make your project known to @value{GDBN} developers and
30172 follow development on @email{gdb@@sourceware.org} and
30173 @email{gdb-patches@@sourceware.org}.
30174 @cindex mailing lists
30176 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30177 @node GDB/MI Output Records
30178 @section @sc{gdb/mi} Output Records
30181 * GDB/MI Result Records::
30182 * GDB/MI Stream Records::
30183 * GDB/MI Async Records::
30184 * GDB/MI Breakpoint Information::
30185 * GDB/MI Frame Information::
30186 * GDB/MI Thread Information::
30187 * GDB/MI Ada Exception Information::
30190 @node GDB/MI Result Records
30191 @subsection @sc{gdb/mi} Result Records
30193 @cindex result records in @sc{gdb/mi}
30194 @cindex @sc{gdb/mi}, result records
30195 In addition to a number of out-of-band notifications, the response to a
30196 @sc{gdb/mi} command includes one of the following result indications:
30200 @item "^done" [ "," @var{results} ]
30201 The synchronous operation was successful, @code{@var{results}} are the return
30206 This result record is equivalent to @samp{^done}. Historically, it
30207 was output instead of @samp{^done} if the command has resumed the
30208 target. This behaviour is maintained for backward compatibility, but
30209 all frontends should treat @samp{^done} and @samp{^running}
30210 identically and rely on the @samp{*running} output record to determine
30211 which threads are resumed.
30215 @value{GDBN} has connected to a remote target.
30217 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
30219 The operation failed. The @code{msg=@var{c-string}} variable contains
30220 the corresponding error message.
30222 If present, the @code{code=@var{c-string}} variable provides an error
30223 code on which consumers can rely on to detect the corresponding
30224 error condition. At present, only one error code is defined:
30227 @item "undefined-command"
30228 Indicates that the command causing the error does not exist.
30233 @value{GDBN} has terminated.
30237 @node GDB/MI Stream Records
30238 @subsection @sc{gdb/mi} Stream Records
30240 @cindex @sc{gdb/mi}, stream records
30241 @cindex stream records in @sc{gdb/mi}
30242 @value{GDBN} internally maintains a number of output streams: the console, the
30243 target, and the log. The output intended for each of these streams is
30244 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
30246 Each stream record begins with a unique @dfn{prefix character} which
30247 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
30248 Syntax}). In addition to the prefix, each stream record contains a
30249 @code{@var{string-output}}. This is either raw text (with an implicit new
30250 line) or a quoted C string (which does not contain an implicit newline).
30253 @item "~" @var{string-output}
30254 The console output stream contains text that should be displayed in the
30255 CLI console window. It contains the textual responses to CLI commands.
30257 @item "@@" @var{string-output}
30258 The target output stream contains any textual output from the running
30259 target. This is only present when GDB's event loop is truly
30260 asynchronous, which is currently only the case for remote targets.
30262 @item "&" @var{string-output}
30263 The log stream contains debugging messages being produced by @value{GDBN}'s
30267 @node GDB/MI Async Records
30268 @subsection @sc{gdb/mi} Async Records
30270 @cindex async records in @sc{gdb/mi}
30271 @cindex @sc{gdb/mi}, async records
30272 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
30273 additional changes that have occurred. Those changes can either be a
30274 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
30275 target activity (e.g., target stopped).
30277 The following is the list of possible async records:
30281 @item *running,thread-id="@var{thread}"
30282 The target is now running. The @var{thread} field can be the global
30283 thread ID of the thread that is now running, and it can be
30284 @samp{all} if all threads are running. The frontend should assume
30285 that no interaction with a running thread is possible after this
30286 notification is produced. The frontend should not assume that this
30287 notification is output only once for any command. @value{GDBN} may
30288 emit this notification several times, either for different threads,
30289 because it cannot resume all threads together, or even for a single
30290 thread, if the thread must be stepped though some code before letting
30293 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
30294 The target has stopped. The @var{reason} field can have one of the
30298 @item breakpoint-hit
30299 A breakpoint was reached.
30300 @item watchpoint-trigger
30301 A watchpoint was triggered.
30302 @item read-watchpoint-trigger
30303 A read watchpoint was triggered.
30304 @item access-watchpoint-trigger
30305 An access watchpoint was triggered.
30306 @item function-finished
30307 An -exec-finish or similar CLI command was accomplished.
30308 @item location-reached
30309 An -exec-until or similar CLI command was accomplished.
30310 @item watchpoint-scope
30311 A watchpoint has gone out of scope.
30312 @item end-stepping-range
30313 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
30314 similar CLI command was accomplished.
30315 @item exited-signalled
30316 The inferior exited because of a signal.
30318 The inferior exited.
30319 @item exited-normally
30320 The inferior exited normally.
30321 @item signal-received
30322 A signal was received by the inferior.
30324 The inferior has stopped due to a library being loaded or unloaded.
30325 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
30326 set or when a @code{catch load} or @code{catch unload} catchpoint is
30327 in use (@pxref{Set Catchpoints}).
30329 The inferior has forked. This is reported when @code{catch fork}
30330 (@pxref{Set Catchpoints}) has been used.
30332 The inferior has vforked. This is reported in when @code{catch vfork}
30333 (@pxref{Set Catchpoints}) has been used.
30334 @item syscall-entry
30335 The inferior entered a system call. This is reported when @code{catch
30336 syscall} (@pxref{Set Catchpoints}) has been used.
30337 @item syscall-return
30338 The inferior returned from a system call. This is reported when
30339 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
30341 The inferior called @code{exec}. This is reported when @code{catch exec}
30342 (@pxref{Set Catchpoints}) has been used.
30345 The @var{id} field identifies the global thread ID of the thread
30346 that directly caused the stop -- for example by hitting a breakpoint.
30347 Depending on whether all-stop
30348 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
30349 stop all threads, or only the thread that directly triggered the stop.
30350 If all threads are stopped, the @var{stopped} field will have the
30351 value of @code{"all"}. Otherwise, the value of the @var{stopped}
30352 field will be a list of thread identifiers. Presently, this list will
30353 always include a single thread, but frontend should be prepared to see
30354 several threads in the list. The @var{core} field reports the
30355 processor core on which the stop event has happened. This field may be absent
30356 if such information is not available.
30358 @item =thread-group-added,id="@var{id}"
30359 @itemx =thread-group-removed,id="@var{id}"
30360 A thread group was either added or removed. The @var{id} field
30361 contains the @value{GDBN} identifier of the thread group. When a thread
30362 group is added, it generally might not be associated with a running
30363 process. When a thread group is removed, its id becomes invalid and
30364 cannot be used in any way.
30366 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
30367 A thread group became associated with a running program,
30368 either because the program was just started or the thread group
30369 was attached to a program. The @var{id} field contains the
30370 @value{GDBN} identifier of the thread group. The @var{pid} field
30371 contains process identifier, specific to the operating system.
30373 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
30374 A thread group is no longer associated with a running program,
30375 either because the program has exited, or because it was detached
30376 from. The @var{id} field contains the @value{GDBN} identifier of the
30377 thread group. The @var{code} field is the exit code of the inferior; it exists
30378 only when the inferior exited with some code.
30380 @item =thread-created,id="@var{id}",group-id="@var{gid}"
30381 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
30382 A thread either was created, or has exited. The @var{id} field
30383 contains the global @value{GDBN} identifier of the thread. The @var{gid}
30384 field identifies the thread group this thread belongs to.
30386 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
30387 Informs that the selected thread or frame were changed. This notification
30388 is not emitted as result of the @code{-thread-select} or
30389 @code{-stack-select-frame} commands, but is emitted whenever an MI command
30390 that is not documented to change the selected thread and frame actually
30391 changes them. In particular, invoking, directly or indirectly
30392 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
30393 will generate this notification. Changing the thread or frame from another
30394 user interface (see @ref{Interpreters}) will also generate this notification.
30396 The @var{frame} field is only present if the newly selected thread is
30397 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
30399 We suggest that in response to this notification, front ends
30400 highlight the selected thread and cause subsequent commands to apply to
30403 @item =library-loaded,...
30404 Reports that a new library file was loaded by the program. This
30405 notification has 5 fields---@var{id}, @var{target-name},
30406 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
30407 opaque identifier of the library. For remote debugging case,
30408 @var{target-name} and @var{host-name} fields give the name of the
30409 library file on the target, and on the host respectively. For native
30410 debugging, both those fields have the same value. The
30411 @var{symbols-loaded} field is emitted only for backward compatibility
30412 and should not be relied on to convey any useful information. The
30413 @var{thread-group} field, if present, specifies the id of the thread
30414 group in whose context the library was loaded. If the field is
30415 absent, it means the library was loaded in the context of all present
30416 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
30419 @item =library-unloaded,...
30420 Reports that a library was unloaded by the program. This notification
30421 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
30422 the same meaning as for the @code{=library-loaded} notification.
30423 The @var{thread-group} field, if present, specifies the id of the
30424 thread group in whose context the library was unloaded. If the field is
30425 absent, it means the library was unloaded in the context of all present
30428 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
30429 @itemx =traceframe-changed,end
30430 Reports that the trace frame was changed and its new number is
30431 @var{tfnum}. The number of the tracepoint associated with this trace
30432 frame is @var{tpnum}.
30434 @item =tsv-created,name=@var{name},initial=@var{initial}
30435 Reports that the new trace state variable @var{name} is created with
30436 initial value @var{initial}.
30438 @item =tsv-deleted,name=@var{name}
30439 @itemx =tsv-deleted
30440 Reports that the trace state variable @var{name} is deleted or all
30441 trace state variables are deleted.
30443 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
30444 Reports that the trace state variable @var{name} is modified with
30445 the initial value @var{initial}. The current value @var{current} of
30446 trace state variable is optional and is reported if the current
30447 value of trace state variable is known.
30449 @item =breakpoint-created,bkpt=@{...@}
30450 @itemx =breakpoint-modified,bkpt=@{...@}
30451 @itemx =breakpoint-deleted,id=@var{number}
30452 Reports that a breakpoint was created, modified, or deleted,
30453 respectively. Only user-visible breakpoints are reported to the MI
30456 The @var{bkpt} argument is of the same form as returned by the various
30457 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
30458 @var{number} is the ordinal number of the breakpoint.
30460 Note that if a breakpoint is emitted in the result record of a
30461 command, then it will not also be emitted in an async record.
30463 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
30464 @itemx =record-stopped,thread-group="@var{id}"
30465 Execution log recording was either started or stopped on an
30466 inferior. The @var{id} is the @value{GDBN} identifier of the thread
30467 group corresponding to the affected inferior.
30469 The @var{method} field indicates the method used to record execution. If the
30470 method in use supports multiple recording formats, @var{format} will be present
30471 and contain the currently used format. @xref{Process Record and Replay},
30472 for existing method and format values.
30474 @item =cmd-param-changed,param=@var{param},value=@var{value}
30475 Reports that a parameter of the command @code{set @var{param}} is
30476 changed to @var{value}. In the multi-word @code{set} command,
30477 the @var{param} is the whole parameter list to @code{set} command.
30478 For example, In command @code{set check type on}, @var{param}
30479 is @code{check type} and @var{value} is @code{on}.
30481 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
30482 Reports that bytes from @var{addr} to @var{data} + @var{len} were
30483 written in an inferior. The @var{id} is the identifier of the
30484 thread group corresponding to the affected inferior. The optional
30485 @code{type="code"} part is reported if the memory written to holds
30489 @node GDB/MI Breakpoint Information
30490 @subsection @sc{gdb/mi} Breakpoint Information
30492 When @value{GDBN} reports information about a breakpoint, a
30493 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
30498 The breakpoint number.
30501 The type of the breakpoint. For ordinary breakpoints this will be
30502 @samp{breakpoint}, but many values are possible.
30505 If the type of the breakpoint is @samp{catchpoint}, then this
30506 indicates the exact type of catchpoint.
30509 This is the breakpoint disposition---either @samp{del}, meaning that
30510 the breakpoint will be deleted at the next stop, or @samp{keep},
30511 meaning that the breakpoint will not be deleted.
30514 This indicates whether the breakpoint is enabled, in which case the
30515 value is @samp{y}, or disabled, in which case the value is @samp{n}.
30516 Note that this is not the same as the field @code{enable}.
30519 The address of the breakpoint. This may be a hexidecimal number,
30520 giving the address; or the string @samp{<PENDING>}, for a pending
30521 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
30522 multiple locations. This field will not be present if no address can
30523 be determined. For example, a watchpoint does not have an address.
30526 Optional field containing any flags related to the address. These flags are
30527 architecture-dependent; see @ref{Architectures} for their meaning for a
30531 If known, the function in which the breakpoint appears.
30532 If not known, this field is not present.
30535 The name of the source file which contains this function, if known.
30536 If not known, this field is not present.
30539 The full file name of the source file which contains this function, if
30540 known. If not known, this field is not present.
30543 The line number at which this breakpoint appears, if known.
30544 If not known, this field is not present.
30547 If the source file is not known, this field may be provided. If
30548 provided, this holds the address of the breakpoint, possibly followed
30552 If this breakpoint is pending, this field is present and holds the
30553 text used to set the breakpoint, as entered by the user.
30556 Where this breakpoint's condition is evaluated, either @samp{host} or
30560 If this is a thread-specific breakpoint, then this identifies the
30561 thread in which the breakpoint can trigger.
30564 If this breakpoint is restricted to a particular Ada task, then this
30565 field will hold the task identifier.
30568 If the breakpoint is conditional, this is the condition expression.
30571 The ignore count of the breakpoint.
30574 The enable count of the breakpoint.
30576 @item traceframe-usage
30579 @item static-tracepoint-marker-string-id
30580 For a static tracepoint, the name of the static tracepoint marker.
30583 For a masked watchpoint, this is the mask.
30586 A tracepoint's pass count.
30588 @item original-location
30589 The location of the breakpoint as originally specified by the user.
30590 This field is optional.
30593 The number of times the breakpoint has been hit.
30596 This field is only given for tracepoints. This is either @samp{y},
30597 meaning that the tracepoint is installed, or @samp{n}, meaning that it
30601 Some extra data, the exact contents of which are type-dependent.
30604 This field is present if the breakpoint has multiple locations. It is also
30605 exceptionally present if the breakpoint is enabled and has a single, disabled
30608 The value is a list of locations. The format of a location is described below.
30612 A location in a multi-location breakpoint is represented as a tuple with the
30618 The location number as a dotted pair, like @samp{1.2}. The first digit is the
30619 number of the parent breakpoint. The second digit is the number of the
30620 location within that breakpoint.
30623 There are three possible values, with the following meanings:
30626 The location is enabled.
30628 The location is disabled by the user.
30630 The location is disabled because the breakpoint condition is invalid
30635 The address of this location as an hexidecimal number.
30638 Optional field containing any flags related to the address. These flags are
30639 architecture-dependent; see @ref{Architectures} for their meaning for a
30643 If known, the function in which the location appears.
30644 If not known, this field is not present.
30647 The name of the source file which contains this location, if known.
30648 If not known, this field is not present.
30651 The full file name of the source file which contains this location, if
30652 known. If not known, this field is not present.
30655 The line number at which this location appears, if known.
30656 If not known, this field is not present.
30658 @item thread-groups
30659 The thread groups this location is in.
30663 For example, here is what the output of @code{-break-insert}
30664 (@pxref{GDB/MI Breakpoint Commands}) might be:
30667 -> -break-insert main
30668 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30669 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30670 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30675 @node GDB/MI Frame Information
30676 @subsection @sc{gdb/mi} Frame Information
30678 Response from many MI commands includes an information about stack
30679 frame. This information is a tuple that may have the following
30684 The level of the stack frame. The innermost frame has the level of
30685 zero. This field is always present.
30688 The name of the function corresponding to the frame. This field may
30689 be absent if @value{GDBN} is unable to determine the function name.
30692 The code address for the frame. This field is always present.
30695 Optional field containing any flags related to the address. These flags are
30696 architecture-dependent; see @ref{Architectures} for their meaning for a
30700 The name of the source files that correspond to the frame's code
30701 address. This field may be absent.
30704 The source line corresponding to the frames' code address. This field
30708 The name of the binary file (either executable or shared library) the
30709 corresponds to the frame's code address. This field may be absent.
30713 @node GDB/MI Thread Information
30714 @subsection @sc{gdb/mi} Thread Information
30716 Whenever @value{GDBN} has to report an information about a thread, it
30717 uses a tuple with the following fields. The fields are always present unless
30722 The global numeric id assigned to the thread by @value{GDBN}.
30725 The target-specific string identifying the thread.
30728 Additional information about the thread provided by the target.
30729 It is supposed to be human-readable and not interpreted by the
30730 frontend. This field is optional.
30733 The name of the thread. If the user specified a name using the
30734 @code{thread name} command, then this name is given. Otherwise, if
30735 @value{GDBN} can extract the thread name from the target, then that
30736 name is given. If @value{GDBN} cannot find the thread name, then this
30740 The execution state of the thread, either @samp{stopped} or @samp{running},
30741 depending on whether the thread is presently running.
30744 The stack frame currently executing in the thread. This field is only present
30745 if the thread is stopped. Its format is documented in
30746 @ref{GDB/MI Frame Information}.
30749 The value of this field is an integer number of the processor core the
30750 thread was last seen on. This field is optional.
30753 @node GDB/MI Ada Exception Information
30754 @subsection @sc{gdb/mi} Ada Exception Information
30756 Whenever a @code{*stopped} record is emitted because the program
30757 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
30758 @value{GDBN} provides the name of the exception that was raised via
30759 the @code{exception-name} field. Also, for exceptions that were raised
30760 with an exception message, @value{GDBN} provides that message via
30761 the @code{exception-message} field.
30763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30764 @node GDB/MI Simple Examples
30765 @section Simple Examples of @sc{gdb/mi} Interaction
30766 @cindex @sc{gdb/mi}, simple examples
30768 This subsection presents several simple examples of interaction using
30769 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
30770 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
30771 the output received from @sc{gdb/mi}.
30773 Note the line breaks shown in the examples are here only for
30774 readability, they don't appear in the real output.
30776 @subheading Setting a Breakpoint
30778 Setting a breakpoint generates synchronous output which contains detailed
30779 information of the breakpoint.
30782 -> -break-insert main
30783 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30784 enabled="y",addr="0x08048564",func="main",file="myprog.c",
30785 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
30790 @subheading Program Execution
30792 Program execution generates asynchronous records and MI gives the
30793 reason that execution stopped.
30799 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30800 frame=@{addr="0x08048564",func="main",
30801 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
30802 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
30803 arch="i386:x86_64"@}
30808 <- *stopped,reason="exited-normally"
30812 @subheading Quitting @value{GDBN}
30814 Quitting @value{GDBN} just prints the result class @samp{^exit}.
30822 Please note that @samp{^exit} is printed immediately, but it might
30823 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
30824 performs necessary cleanups, including killing programs being debugged
30825 or disconnecting from debug hardware, so the frontend should wait till
30826 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
30827 fails to exit in reasonable time.
30829 @subheading A Bad Command
30831 Here's what happens if you pass a non-existent command:
30835 <- ^error,msg="Undefined MI command: rubbish"
30840 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30841 @node GDB/MI Command Description Format
30842 @section @sc{gdb/mi} Command Description Format
30844 The remaining sections describe blocks of commands. Each block of
30845 commands is laid out in a fashion similar to this section.
30847 @subheading Motivation
30849 The motivation for this collection of commands.
30851 @subheading Introduction
30853 A brief introduction to this collection of commands as a whole.
30855 @subheading Commands
30857 For each command in the block, the following is described:
30859 @subsubheading Synopsis
30862 -command @var{args}@dots{}
30865 @subsubheading Result
30867 @subsubheading @value{GDBN} Command
30869 The corresponding @value{GDBN} CLI command(s), if any.
30871 @subsubheading Example
30873 Example(s) formatted for readability. Some of the described commands have
30874 not been implemented yet and these are labeled N.A.@: (not available).
30877 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30878 @node GDB/MI Breakpoint Commands
30879 @section @sc{gdb/mi} Breakpoint Commands
30881 @cindex breakpoint commands for @sc{gdb/mi}
30882 @cindex @sc{gdb/mi}, breakpoint commands
30883 This section documents @sc{gdb/mi} commands for manipulating
30886 @subheading The @code{-break-after} Command
30887 @findex -break-after
30889 @subsubheading Synopsis
30892 -break-after @var{number} @var{count}
30895 The breakpoint number @var{number} is not in effect until it has been
30896 hit @var{count} times. To see how this is reflected in the output of
30897 the @samp{-break-list} command, see the description of the
30898 @samp{-break-list} command below.
30900 @subsubheading @value{GDBN} Command
30902 The corresponding @value{GDBN} command is @samp{ignore}.
30904 @subsubheading Example
30909 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30910 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30911 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30919 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30920 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30921 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30922 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30923 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30924 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30925 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30926 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30927 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30928 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30933 @subheading The @code{-break-catch} Command
30934 @findex -break-catch
30937 @subheading The @code{-break-commands} Command
30938 @findex -break-commands
30940 @subsubheading Synopsis
30943 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30946 Specifies the CLI commands that should be executed when breakpoint
30947 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30948 are the commands. If no command is specified, any previously-set
30949 commands are cleared. @xref{Break Commands}. Typical use of this
30950 functionality is tracing a program, that is, printing of values of
30951 some variables whenever breakpoint is hit and then continuing.
30953 @subsubheading @value{GDBN} Command
30955 The corresponding @value{GDBN} command is @samp{commands}.
30957 @subsubheading Example
30962 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30963 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30964 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30967 -break-commands 1 "print v" "continue"
30972 @subheading The @code{-break-condition} Command
30973 @findex -break-condition
30975 @subsubheading Synopsis
30978 -break-condition [ --force ] @var{number} [ @var{expr} ]
30981 Breakpoint @var{number} will stop the program only if the condition in
30982 @var{expr} is true. The condition becomes part of the
30983 @samp{-break-list} output (see the description of the @samp{-break-list}
30984 command below). If the @samp{--force} flag is passed, the condition
30985 is forcibly defined even when it is invalid for all locations of
30986 breakpoint @var{number}. If the @var{expr} argument is omitted,
30987 breakpoint @var{number} becomes unconditional.
30989 @subsubheading @value{GDBN} Command
30991 The corresponding @value{GDBN} command is @samp{condition}.
30993 @subsubheading Example
30997 -break-condition 1 1
31001 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31002 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31003 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31004 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31005 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31006 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31007 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31008 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31009 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31010 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
31014 @subheading The @code{-break-delete} Command
31015 @findex -break-delete
31017 @subsubheading Synopsis
31020 -break-delete ( @var{breakpoint} )+
31023 Delete the breakpoint(s) whose number(s) are specified in the argument
31024 list. This is obviously reflected in the breakpoint list.
31026 @subsubheading @value{GDBN} Command
31028 The corresponding @value{GDBN} command is @samp{delete}.
31030 @subsubheading Example
31038 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31039 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31040 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31041 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31042 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31043 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31044 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31049 @subheading The @code{-break-disable} Command
31050 @findex -break-disable
31052 @subsubheading Synopsis
31055 -break-disable ( @var{breakpoint} )+
31058 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
31059 break list is now set to @samp{n} for the named @var{breakpoint}(s).
31061 @subsubheading @value{GDBN} Command
31063 The corresponding @value{GDBN} command is @samp{disable}.
31065 @subsubheading Example
31073 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31074 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31075 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31076 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31077 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31078 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31079 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31080 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
31081 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31082 line="5",thread-groups=["i1"],times="0"@}]@}
31086 @subheading The @code{-break-enable} Command
31087 @findex -break-enable
31089 @subsubheading Synopsis
31092 -break-enable ( @var{breakpoint} )+
31095 Enable (previously disabled) @var{breakpoint}(s).
31097 @subsubheading @value{GDBN} Command
31099 The corresponding @value{GDBN} command is @samp{enable}.
31101 @subsubheading Example
31109 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31110 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31111 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31112 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31113 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31114 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31115 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31116 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31117 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
31118 line="5",thread-groups=["i1"],times="0"@}]@}
31122 @subheading The @code{-break-info} Command
31123 @findex -break-info
31125 @subsubheading Synopsis
31128 -break-info @var{breakpoint}
31132 Get information about a single breakpoint.
31134 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
31135 Information}, for details on the format of each breakpoint in the
31138 @subsubheading @value{GDBN} Command
31140 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
31142 @subsubheading Example
31145 @subheading The @code{-break-insert} Command
31146 @findex -break-insert
31147 @anchor{-break-insert}
31149 @subsubheading Synopsis
31152 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ] [ --qualified ]
31153 [ -c @var{condition} ] [ --force-condition ] [ -i @var{ignore-count} ]
31154 [ -p @var{thread-id} ] [ @var{location} ]
31158 If specified, @var{location}, can be one of:
31161 @item linespec location
31162 A linespec location. @xref{Linespec Locations}.
31164 @item explicit location
31165 An explicit location. @sc{gdb/mi} explicit locations are
31166 analogous to the CLI's explicit locations using the option names
31167 listed below. @xref{Explicit Locations}.
31170 @item --source @var{filename}
31171 The source file name of the location. This option requires the use
31172 of either @samp{--function} or @samp{--line}.
31174 @item --function @var{function}
31175 The name of a function or method.
31177 @item --label @var{label}
31178 The name of a label.
31180 @item --line @var{lineoffset}
31181 An absolute or relative line offset from the start of the location.
31184 @item address location
31185 An address location, *@var{address}. @xref{Address Locations}.
31189 The possible optional parameters of this command are:
31193 Insert a temporary breakpoint.
31195 Insert a hardware breakpoint.
31197 If @var{location} cannot be parsed (for example if it
31198 refers to unknown files or functions), create a pending
31199 breakpoint. Without this flag, @value{GDBN} will report
31200 an error, and won't create a breakpoint, if @var{location}
31203 Create a disabled breakpoint.
31205 Create a tracepoint. @xref{Tracepoints}. When this parameter
31206 is used together with @samp{-h}, a fast tracepoint is created.
31207 @item -c @var{condition}
31208 Make the breakpoint conditional on @var{condition}.
31209 @item --force-condition
31210 Forcibly define the breakpoint even if the condition is invalid at
31211 all of the breakpoint locations.
31212 @item -i @var{ignore-count}
31213 Initialize the @var{ignore-count}.
31214 @item -p @var{thread-id}
31215 Restrict the breakpoint to the thread with the specified global
31218 This option makes @value{GDBN} interpret a function name specified as
31219 a complete fully-qualified name.
31222 @subsubheading Result
31224 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31225 resulting breakpoint.
31227 Note: this format is open to change.
31228 @c An out-of-band breakpoint instead of part of the result?
31230 @subsubheading @value{GDBN} Command
31232 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
31233 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
31235 @subsubheading Example
31240 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
31241 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
31244 -break-insert -t foo
31245 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
31246 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
31250 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31251 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31252 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31253 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31254 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31255 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31256 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31257 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31258 addr="0x0001072c", func="main",file="recursive2.c",
31259 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
31261 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
31262 addr="0x00010774",func="foo",file="recursive2.c",
31263 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31266 @c -break-insert -r foo.*
31267 @c ~int foo(int, int);
31268 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
31269 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
31274 @subheading The @code{-dprintf-insert} Command
31275 @findex -dprintf-insert
31277 @subsubheading Synopsis
31280 -dprintf-insert [ -t ] [ -f ] [ -d ] [ --qualified ]
31281 [ -c @var{condition} ] [--force-condition] [ -i @var{ignore-count} ]
31282 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
31287 If supplied, @var{location} and @code{--qualified} may be specified
31288 the same way as for the @code{-break-insert} command.
31289 @xref{-break-insert}.
31291 The possible optional parameters of this command are:
31295 Insert a temporary breakpoint.
31297 If @var{location} cannot be parsed (for example, if it
31298 refers to unknown files or functions), create a pending
31299 breakpoint. Without this flag, @value{GDBN} will report
31300 an error, and won't create a breakpoint, if @var{location}
31303 Create a disabled breakpoint.
31304 @item -c @var{condition}
31305 Make the breakpoint conditional on @var{condition}.
31306 @item --force-condition
31307 Forcibly define the breakpoint even if the condition is invalid at
31308 all of the breakpoint locations.
31309 @item -i @var{ignore-count}
31310 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
31311 to @var{ignore-count}.
31312 @item -p @var{thread-id}
31313 Restrict the breakpoint to the thread with the specified global
31317 @subsubheading Result
31319 @xref{GDB/MI Breakpoint Information}, for details on the format of the
31320 resulting breakpoint.
31322 @c An out-of-band breakpoint instead of part of the result?
31324 @subsubheading @value{GDBN} Command
31326 The corresponding @value{GDBN} command is @samp{dprintf}.
31328 @subsubheading Example
31332 4-dprintf-insert foo "At foo entry\n"
31333 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
31334 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
31335 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
31336 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
31337 original-location="foo"@}
31339 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
31340 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
31341 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
31342 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
31343 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
31344 original-location="mi-dprintf.c:26"@}
31348 @subheading The @code{-break-list} Command
31349 @findex -break-list
31351 @subsubheading Synopsis
31357 Displays the list of inserted breakpoints, showing the following fields:
31361 number of the breakpoint
31363 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
31365 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
31368 is the breakpoint enabled or no: @samp{y} or @samp{n}
31370 memory location at which the breakpoint is set
31372 logical location of the breakpoint, expressed by function name, file
31374 @item Thread-groups
31375 list of thread groups to which this breakpoint applies
31377 number of times the breakpoint has been hit
31380 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
31381 @code{body} field is an empty list.
31383 @subsubheading @value{GDBN} Command
31385 The corresponding @value{GDBN} command is @samp{info break}.
31387 @subsubheading Example
31392 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31393 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31394 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31395 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31396 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31397 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31398 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31399 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31400 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
31402 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
31403 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
31404 line="13",thread-groups=["i1"],times="0"@}]@}
31408 Here's an example of the result when there are no breakpoints:
31413 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
31414 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31415 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31416 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31417 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31418 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31419 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31424 @subheading The @code{-break-passcount} Command
31425 @findex -break-passcount
31427 @subsubheading Synopsis
31430 -break-passcount @var{tracepoint-number} @var{passcount}
31433 Set the passcount for tracepoint @var{tracepoint-number} to
31434 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
31435 is not a tracepoint, error is emitted. This corresponds to CLI
31436 command @samp{passcount}.
31438 @subheading The @code{-break-watch} Command
31439 @findex -break-watch
31441 @subsubheading Synopsis
31444 -break-watch [ -a | -r ]
31447 Create a watchpoint. With the @samp{-a} option it will create an
31448 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
31449 read from or on a write to the memory location. With the @samp{-r}
31450 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
31451 trigger only when the memory location is accessed for reading. Without
31452 either of the options, the watchpoint created is a regular watchpoint,
31453 i.e., it will trigger when the memory location is accessed for writing.
31454 @xref{Set Watchpoints, , Setting Watchpoints}.
31456 Note that @samp{-break-list} will report a single list of watchpoints and
31457 breakpoints inserted.
31459 @subsubheading @value{GDBN} Command
31461 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
31464 @subsubheading Example
31466 Setting a watchpoint on a variable in the @code{main} function:
31471 ^done,wpt=@{number="2",exp="x"@}
31476 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
31477 value=@{old="-268439212",new="55"@},
31478 frame=@{func="main",args=[],file="recursive2.c",
31479 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
31483 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
31484 the program execution twice: first for the variable changing value, then
31485 for the watchpoint going out of scope.
31490 ^done,wpt=@{number="5",exp="C"@}
31495 *stopped,reason="watchpoint-trigger",
31496 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
31497 frame=@{func="callee4",args=[],
31498 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31499 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31500 arch="i386:x86_64"@}
31505 *stopped,reason="watchpoint-scope",wpnum="5",
31506 frame=@{func="callee3",args=[@{name="strarg",
31507 value="0x11940 \"A string argument.\""@}],
31508 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31509 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31510 arch="i386:x86_64"@}
31514 Listing breakpoints and watchpoints, at different points in the program
31515 execution. Note that once the watchpoint goes out of scope, it is
31521 ^done,wpt=@{number="2",exp="C"@}
31524 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31525 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31526 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31527 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31528 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31529 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31530 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31531 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31532 addr="0x00010734",func="callee4",
31533 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31534 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
31536 bkpt=@{number="2",type="watchpoint",disp="keep",
31537 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
31542 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
31543 value=@{old="-276895068",new="3"@},
31544 frame=@{func="callee4",args=[],
31545 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31546 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
31547 arch="i386:x86_64"@}
31550 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
31551 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31552 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31553 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31554 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31555 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31556 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31557 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31558 addr="0x00010734",func="callee4",
31559 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31560 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
31562 bkpt=@{number="2",type="watchpoint",disp="keep",
31563 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
31567 ^done,reason="watchpoint-scope",wpnum="2",
31568 frame=@{func="callee3",args=[@{name="strarg",
31569 value="0x11940 \"A string argument.\""@}],
31570 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31571 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
31572 arch="i386:x86_64"@}
31575 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
31576 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
31577 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
31578 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
31579 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
31580 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
31581 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
31582 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31583 addr="0x00010734",func="callee4",
31584 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31585 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
31586 thread-groups=["i1"],times="1"@}]@}
31591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31592 @node GDB/MI Catchpoint Commands
31593 @section @sc{gdb/mi} Catchpoint Commands
31595 This section documents @sc{gdb/mi} commands for manipulating
31599 * Shared Library GDB/MI Catchpoint Commands::
31600 * Ada Exception GDB/MI Catchpoint Commands::
31601 * C++ Exception GDB/MI Catchpoint Commands::
31604 @node Shared Library GDB/MI Catchpoint Commands
31605 @subsection Shared Library @sc{gdb/mi} Catchpoints
31607 @subheading The @code{-catch-load} Command
31608 @findex -catch-load
31610 @subsubheading Synopsis
31613 -catch-load [ -t ] [ -d ] @var{regexp}
31616 Add a catchpoint for library load events. If the @samp{-t} option is used,
31617 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31618 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
31619 in a disabled state. The @samp{regexp} argument is a regular
31620 expression used to match the name of the loaded library.
31623 @subsubheading @value{GDBN} Command
31625 The corresponding @value{GDBN} command is @samp{catch load}.
31627 @subsubheading Example
31630 -catch-load -t foo.so
31631 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
31632 what="load of library matching foo.so",catch-type="load",times="0"@}
31637 @subheading The @code{-catch-unload} Command
31638 @findex -catch-unload
31640 @subsubheading Synopsis
31643 -catch-unload [ -t ] [ -d ] @var{regexp}
31646 Add a catchpoint for library unload events. If the @samp{-t} option is
31647 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
31648 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
31649 created in a disabled state. The @samp{regexp} argument is a regular
31650 expression used to match the name of the unloaded library.
31652 @subsubheading @value{GDBN} Command
31654 The corresponding @value{GDBN} command is @samp{catch unload}.
31656 @subsubheading Example
31659 -catch-unload -d bar.so
31660 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
31661 what="load of library matching bar.so",catch-type="unload",times="0"@}
31665 @node Ada Exception GDB/MI Catchpoint Commands
31666 @subsection Ada Exception @sc{gdb/mi} Catchpoints
31668 The following @sc{gdb/mi} commands can be used to create catchpoints
31669 that stop the execution when Ada exceptions are being raised.
31671 @subheading The @code{-catch-assert} Command
31672 @findex -catch-assert
31674 @subsubheading Synopsis
31677 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
31680 Add a catchpoint for failed Ada assertions.
31682 The possible optional parameters for this command are:
31685 @item -c @var{condition}
31686 Make the catchpoint conditional on @var{condition}.
31688 Create a disabled catchpoint.
31690 Create a temporary catchpoint.
31693 @subsubheading @value{GDBN} Command
31695 The corresponding @value{GDBN} command is @samp{catch assert}.
31697 @subsubheading Example
31701 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
31702 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
31703 thread-groups=["i1"],times="0",
31704 original-location="__gnat_debug_raise_assert_failure"@}
31708 @subheading The @code{-catch-exception} Command
31709 @findex -catch-exception
31711 @subsubheading Synopsis
31714 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31718 Add a catchpoint stopping when Ada exceptions are raised.
31719 By default, the command stops the program when any Ada exception
31720 gets raised. But it is also possible, by using some of the
31721 optional parameters described below, to create more selective
31724 The possible optional parameters for this command are:
31727 @item -c @var{condition}
31728 Make the catchpoint conditional on @var{condition}.
31730 Create a disabled catchpoint.
31731 @item -e @var{exception-name}
31732 Only stop when @var{exception-name} is raised. This option cannot
31733 be used combined with @samp{-u}.
31735 Create a temporary catchpoint.
31737 Stop only when an unhandled exception gets raised. This option
31738 cannot be used combined with @samp{-e}.
31741 @subsubheading @value{GDBN} Command
31743 The corresponding @value{GDBN} commands are @samp{catch exception}
31744 and @samp{catch exception unhandled}.
31746 @subsubheading Example
31749 -catch-exception -e Program_Error
31750 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31751 enabled="y",addr="0x0000000000404874",
31752 what="`Program_Error' Ada exception", thread-groups=["i1"],
31753 times="0",original-location="__gnat_debug_raise_exception"@}
31757 @subheading The @code{-catch-handlers} Command
31758 @findex -catch-handlers
31760 @subsubheading Synopsis
31763 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
31767 Add a catchpoint stopping when Ada exceptions are handled.
31768 By default, the command stops the program when any Ada exception
31769 gets handled. But it is also possible, by using some of the
31770 optional parameters described below, to create more selective
31773 The possible optional parameters for this command are:
31776 @item -c @var{condition}
31777 Make the catchpoint conditional on @var{condition}.
31779 Create a disabled catchpoint.
31780 @item -e @var{exception-name}
31781 Only stop when @var{exception-name} is handled.
31783 Create a temporary catchpoint.
31786 @subsubheading @value{GDBN} Command
31788 The corresponding @value{GDBN} command is @samp{catch handlers}.
31790 @subsubheading Example
31793 -catch-handlers -e Constraint_Error
31794 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
31795 enabled="y",addr="0x0000000000402f68",
31796 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
31797 times="0",original-location="__gnat_begin_handler"@}
31801 @node C++ Exception GDB/MI Catchpoint Commands
31802 @subsection C@t{++} Exception @sc{gdb/mi} Catchpoints
31804 The following @sc{gdb/mi} commands can be used to create catchpoints
31805 that stop the execution when C@t{++} exceptions are being throw, rethrown,
31808 @subheading The @code{-catch-throw} Command
31809 @findex -catch-throw
31811 @subsubheading Synopsis
31814 -catch-throw [ -t ] [ -r @var{regexp}]
31817 Stop when the debuggee throws a C@t{++} exception. If @var{regexp} is
31818 given, then only exceptions whose type matches the regular expression
31821 If @samp{-t} is given, then the catchpoint is enabled only for one
31822 stop, the catchpoint is automatically deleted after stopping once for
31825 @subsubheading @value{GDBN} Command
31827 The corresponding @value{GDBN} commands are @samp{catch throw}
31828 and @samp{tcatch throw} (@pxref{Set Catchpoints}).
31830 @subsubheading Example
31833 -catch-throw -r exception_type
31834 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31835 what="exception throw",catch-type="throw",
31836 thread-groups=["i1"],
31837 regexp="exception_type",times="0"@}
31843 ~"Catchpoint 1 (exception thrown), 0x00007ffff7ae00ed
31844 in __cxa_throw () from /lib64/libstdc++.so.6\n"
31845 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31846 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_throw",
31847 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31848 thread-id="1",stopped-threads="all",core="6"
31852 @subheading The @code{-catch-rethrow} Command
31853 @findex -catch-rethrow
31855 @subsubheading Synopsis
31858 -catch-rethrow [ -t ] [ -r @var{regexp}]
31861 Stop when a C@t{++} exception is re-thrown. If @var{regexp} is given,
31862 then only exceptions whose type matches the regular expression will be
31865 If @samp{-t} is given, then the catchpoint is enabled only for one
31866 stop, the catchpoint is automatically deleted after the first event is
31869 @subsubheading @value{GDBN} Command
31871 The corresponding @value{GDBN} commands are @samp{catch rethrow}
31872 and @samp{tcatch rethrow} (@pxref{Set Catchpoints}).
31874 @subsubheading Example
31877 -catch-rethrow -r exception_type
31878 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31879 what="exception rethrow",catch-type="rethrow",
31880 thread-groups=["i1"],
31881 regexp="exception_type",times="0"@}
31887 ~"Catchpoint 1 (exception rethrown), 0x00007ffff7ae00ed
31888 in __cxa_rethrow () from /lib64/libstdc++.so.6\n"
31889 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31890 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_rethrow",
31891 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31892 thread-id="1",stopped-threads="all",core="6"
31896 @subheading The @code{-catch-catch} Command
31897 @findex -catch-catch
31899 @subsubheading Synopsis
31902 -catch-catch [ -t ] [ -r @var{regexp}]
31905 Stop when the debuggee catches a C@t{++} exception. If @var{regexp}
31906 is given, then only exceptions whose type matches the regular
31907 expression will be caught.
31909 If @samp{-t} is given, then the catchpoint is enabled only for one
31910 stop, the catchpoint is automatically deleted after the first event is
31913 @subsubheading @value{GDBN} Command
31915 The corresponding @value{GDBN} commands are @samp{catch catch}
31916 and @samp{tcatch catch} (@pxref{Set Catchpoints}).
31918 @subsubheading Example
31921 -catch-catch -r exception_type
31922 ^done,bkpt=@{number="1",type="catchpoint",disp="keep",enabled="y",
31923 what="exception catch",catch-type="catch",
31924 thread-groups=["i1"],
31925 regexp="exception_type",times="0"@}
31931 ~"Catchpoint 1 (exception caught), 0x00007ffff7ae00ed
31932 in __cxa_begin_catch () from /lib64/libstdc++.so.6\n"
31933 *stopped,bkptno="1",reason="breakpoint-hit",disp="keep",
31934 frame=@{addr="0x00007ffff7ae00ed",func="__cxa_begin_catch",
31935 args=[],from="/lib64/libstdc++.so.6",arch="i386:x86-64"@},
31936 thread-id="1",stopped-threads="all",core="6"
31940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31941 @node GDB/MI Program Context
31942 @section @sc{gdb/mi} Program Context
31944 @subheading The @code{-exec-arguments} Command
31945 @findex -exec-arguments
31948 @subsubheading Synopsis
31951 -exec-arguments @var{args}
31954 Set the inferior program arguments, to be used in the next
31957 @subsubheading @value{GDBN} Command
31959 The corresponding @value{GDBN} command is @samp{set args}.
31961 @subsubheading Example
31965 -exec-arguments -v word
31972 @subheading The @code{-exec-show-arguments} Command
31973 @findex -exec-show-arguments
31975 @subsubheading Synopsis
31978 -exec-show-arguments
31981 Print the arguments of the program.
31983 @subsubheading @value{GDBN} Command
31985 The corresponding @value{GDBN} command is @samp{show args}.
31987 @subsubheading Example
31992 @subheading The @code{-environment-cd} Command
31993 @findex -environment-cd
31995 @subsubheading Synopsis
31998 -environment-cd @var{pathdir}
32001 Set @value{GDBN}'s working directory.
32003 @subsubheading @value{GDBN} Command
32005 The corresponding @value{GDBN} command is @samp{cd}.
32007 @subsubheading Example
32011 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32017 @subheading The @code{-environment-directory} Command
32018 @findex -environment-directory
32020 @subsubheading Synopsis
32023 -environment-directory [ -r ] [ @var{pathdir} ]+
32026 Add directories @var{pathdir} to beginning of search path for source files.
32027 If the @samp{-r} option is used, the search path is reset to the default
32028 search path. If directories @var{pathdir} are supplied in addition to the
32029 @samp{-r} option, the search path is first reset and then addition
32031 Multiple directories may be specified, separated by blanks. Specifying
32032 multiple directories in a single command
32033 results in the directories added to the beginning of the
32034 search path in the same order they were presented in the command.
32035 If blanks are needed as
32036 part of a directory name, double-quotes should be used around
32037 the name. In the command output, the path will show up separated
32038 by the system directory-separator character. The directory-separator
32039 character must not be used
32040 in any directory name.
32041 If no directories are specified, the current search path is displayed.
32043 @subsubheading @value{GDBN} Command
32045 The corresponding @value{GDBN} command is @samp{dir}.
32047 @subsubheading Example
32051 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
32052 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32054 -environment-directory ""
32055 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
32057 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
32058 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
32060 -environment-directory -r
32061 ^done,source-path="$cdir:$cwd"
32066 @subheading The @code{-environment-path} Command
32067 @findex -environment-path
32069 @subsubheading Synopsis
32072 -environment-path [ -r ] [ @var{pathdir} ]+
32075 Add directories @var{pathdir} to beginning of search path for object files.
32076 If the @samp{-r} option is used, the search path is reset to the original
32077 search path that existed at gdb start-up. If directories @var{pathdir} are
32078 supplied in addition to the
32079 @samp{-r} option, the search path is first reset and then addition
32081 Multiple directories may be specified, separated by blanks. Specifying
32082 multiple directories in a single command
32083 results in the directories added to the beginning of the
32084 search path in the same order they were presented in the command.
32085 If blanks are needed as
32086 part of a directory name, double-quotes should be used around
32087 the name. In the command output, the path will show up separated
32088 by the system directory-separator character. The directory-separator
32089 character must not be used
32090 in any directory name.
32091 If no directories are specified, the current path is displayed.
32094 @subsubheading @value{GDBN} Command
32096 The corresponding @value{GDBN} command is @samp{path}.
32098 @subsubheading Example
32103 ^done,path="/usr/bin"
32105 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
32106 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
32108 -environment-path -r /usr/local/bin
32109 ^done,path="/usr/local/bin:/usr/bin"
32114 @subheading The @code{-environment-pwd} Command
32115 @findex -environment-pwd
32117 @subsubheading Synopsis
32123 Show the current working directory.
32125 @subsubheading @value{GDBN} Command
32127 The corresponding @value{GDBN} command is @samp{pwd}.
32129 @subsubheading Example
32134 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
32138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32139 @node GDB/MI Thread Commands
32140 @section @sc{gdb/mi} Thread Commands
32143 @subheading The @code{-thread-info} Command
32144 @findex -thread-info
32146 @subsubheading Synopsis
32149 -thread-info [ @var{thread-id} ]
32152 Reports information about either a specific thread, if the
32153 @var{thread-id} parameter is present, or about all threads.
32154 @var{thread-id} is the thread's global thread ID. When printing
32155 information about all threads, also reports the global ID of the
32158 @subsubheading @value{GDBN} Command
32160 The @samp{info thread} command prints the same information
32163 @subsubheading Result
32165 The result contains the following attributes:
32169 A list of threads. The format of the elements of the list is described in
32170 @ref{GDB/MI Thread Information}.
32172 @item current-thread-id
32173 The global id of the currently selected thread. This field is omitted if there
32174 is no selected thread (for example, when the selected inferior is not running,
32175 and therefore has no threads) or if a @var{thread-id} argument was passed to
32180 @subsubheading Example
32185 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32186 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
32187 args=[]@},state="running"@},
32188 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32189 frame=@{level="0",addr="0x0804891f",func="foo",
32190 args=[@{name="i",value="10"@}],
32191 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
32192 state="running"@}],
32193 current-thread-id="1"
32197 @subheading The @code{-thread-list-ids} Command
32198 @findex -thread-list-ids
32200 @subsubheading Synopsis
32206 Produces a list of the currently known global @value{GDBN} thread ids.
32207 At the end of the list it also prints the total number of such
32210 This command is retained for historical reasons, the
32211 @code{-thread-info} command should be used instead.
32213 @subsubheading @value{GDBN} Command
32215 Part of @samp{info threads} supplies the same information.
32217 @subsubheading Example
32222 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32223 current-thread-id="1",number-of-threads="3"
32228 @subheading The @code{-thread-select} Command
32229 @findex -thread-select
32231 @subsubheading Synopsis
32234 -thread-select @var{thread-id}
32237 Make thread with global thread number @var{thread-id} the current
32238 thread. It prints the number of the new current thread, and the
32239 topmost frame for that thread.
32241 This command is deprecated in favor of explicitly using the
32242 @samp{--thread} option to each command.
32244 @subsubheading @value{GDBN} Command
32246 The corresponding @value{GDBN} command is @samp{thread}.
32248 @subsubheading Example
32255 *stopped,reason="end-stepping-range",thread-id="2",line="187",
32256 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
32260 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
32261 number-of-threads="3"
32264 ^done,new-thread-id="3",
32265 frame=@{level="0",func="vprintf",
32266 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
32267 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
32271 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32272 @node GDB/MI Ada Tasking Commands
32273 @section @sc{gdb/mi} Ada Tasking Commands
32275 @subheading The @code{-ada-task-info} Command
32276 @findex -ada-task-info
32278 @subsubheading Synopsis
32281 -ada-task-info [ @var{task-id} ]
32284 Reports information about either a specific Ada task, if the
32285 @var{task-id} parameter is present, or about all Ada tasks.
32287 @subsubheading @value{GDBN} Command
32289 The @samp{info tasks} command prints the same information
32290 about all Ada tasks (@pxref{Ada Tasks}).
32292 @subsubheading Result
32294 The result is a table of Ada tasks. The following columns are
32295 defined for each Ada task:
32299 This field exists only for the current thread. It has the value @samp{*}.
32302 The identifier that @value{GDBN} uses to refer to the Ada task.
32305 The identifier that the target uses to refer to the Ada task.
32308 The global thread identifier of the thread corresponding to the Ada
32311 This field should always exist, as Ada tasks are always implemented
32312 on top of a thread. But if @value{GDBN} cannot find this corresponding
32313 thread for any reason, the field is omitted.
32316 This field exists only when the task was created by another task.
32317 In this case, it provides the ID of the parent task.
32320 The base priority of the task.
32323 The current state of the task. For a detailed description of the
32324 possible states, see @ref{Ada Tasks}.
32327 The name of the task.
32331 @subsubheading Example
32335 ^done,tasks=@{nr_rows="3",nr_cols="8",
32336 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
32337 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
32338 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
32339 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
32340 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
32341 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
32342 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
32343 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
32344 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
32345 state="Child Termination Wait",name="main_task"@}]@}
32349 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32350 @node GDB/MI Program Execution
32351 @section @sc{gdb/mi} Program Execution
32353 These are the asynchronous commands which generate the out-of-band
32354 record @samp{*stopped}. Currently @value{GDBN} only really executes
32355 asynchronously with remote targets and this interaction is mimicked in
32358 @subheading The @code{-exec-continue} Command
32359 @findex -exec-continue
32361 @subsubheading Synopsis
32364 -exec-continue [--reverse] [--all|--thread-group N]
32367 Resumes the execution of the inferior program, which will continue
32368 to execute until it reaches a debugger stop event. If the
32369 @samp{--reverse} option is specified, execution resumes in reverse until
32370 it reaches a stop event. Stop events may include
32373 breakpoints or watchpoints
32375 signals or exceptions
32377 the end of the process (or its beginning under @samp{--reverse})
32379 the end or beginning of a replay log if one is being used.
32381 In all-stop mode (@pxref{All-Stop
32382 Mode}), may resume only one thread, or all threads, depending on the
32383 value of the @samp{scheduler-locking} variable. If @samp{--all} is
32384 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
32385 ignored in all-stop mode. If the @samp{--thread-group} options is
32386 specified, then all threads in that thread group are resumed.
32388 @subsubheading @value{GDBN} Command
32390 The corresponding @value{GDBN} corresponding is @samp{continue}.
32392 @subsubheading Example
32399 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
32400 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
32401 line="13",arch="i386:x86_64"@}
32406 @subheading The @code{-exec-finish} Command
32407 @findex -exec-finish
32409 @subsubheading Synopsis
32412 -exec-finish [--reverse]
32415 Resumes the execution of the inferior program until the current
32416 function is exited. Displays the results returned by the function.
32417 If the @samp{--reverse} option is specified, resumes the reverse
32418 execution of the inferior program until the point where current
32419 function was called.
32421 @subsubheading @value{GDBN} Command
32423 The corresponding @value{GDBN} command is @samp{finish}.
32425 @subsubheading Example
32427 Function returning @code{void}.
32434 *stopped,reason="function-finished",frame=@{func="main",args=[],
32435 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
32439 Function returning other than @code{void}. The name of the internal
32440 @value{GDBN} variable storing the result is printed, together with the
32447 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
32448 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
32449 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
32450 arch="i386:x86_64"@},
32451 gdb-result-var="$1",return-value="0"
32456 @subheading The @code{-exec-interrupt} Command
32457 @findex -exec-interrupt
32459 @subsubheading Synopsis
32462 -exec-interrupt [--all|--thread-group N]
32465 Interrupts the background execution of the target. Note how the token
32466 associated with the stop message is the one for the execution command
32467 that has been interrupted. The token for the interrupt itself only
32468 appears in the @samp{^done} output. If the user is trying to
32469 interrupt a non-running program, an error message will be printed.
32471 Note that when asynchronous execution is enabled, this command is
32472 asynchronous just like other execution commands. That is, first the
32473 @samp{^done} response will be printed, and the target stop will be
32474 reported after that using the @samp{*stopped} notification.
32476 In non-stop mode, only the context thread is interrupted by default.
32477 All threads (in all inferiors) will be interrupted if the
32478 @samp{--all} option is specified. If the @samp{--thread-group}
32479 option is specified, all threads in that group will be interrupted.
32481 @subsubheading @value{GDBN} Command
32483 The corresponding @value{GDBN} command is @samp{interrupt}.
32485 @subsubheading Example
32496 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
32497 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
32498 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
32503 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
32507 @subheading The @code{-exec-jump} Command
32510 @subsubheading Synopsis
32513 -exec-jump @var{location}
32516 Resumes execution of the inferior program at the location specified by
32517 parameter. @xref{Specify Location}, for a description of the
32518 different forms of @var{location}.
32520 @subsubheading @value{GDBN} Command
32522 The corresponding @value{GDBN} command is @samp{jump}.
32524 @subsubheading Example
32527 -exec-jump foo.c:10
32528 *running,thread-id="all"
32533 @subheading The @code{-exec-next} Command
32536 @subsubheading Synopsis
32539 -exec-next [--reverse]
32542 Resumes execution of the inferior program, stopping when the beginning
32543 of the next source line is reached.
32545 If the @samp{--reverse} option is specified, resumes reverse execution
32546 of the inferior program, stopping at the beginning of the previous
32547 source line. If you issue this command on the first line of a
32548 function, it will take you back to the caller of that function, to the
32549 source line where the function was called.
32552 @subsubheading @value{GDBN} Command
32554 The corresponding @value{GDBN} command is @samp{next}.
32556 @subsubheading Example
32562 *stopped,reason="end-stepping-range",line="8",file="hello.c"
32567 @subheading The @code{-exec-next-instruction} Command
32568 @findex -exec-next-instruction
32570 @subsubheading Synopsis
32573 -exec-next-instruction [--reverse]
32576 Executes one machine instruction. If the instruction is a function
32577 call, continues until the function returns. If the program stops at an
32578 instruction in the middle of a source line, the address will be
32581 If the @samp{--reverse} option is specified, resumes reverse execution
32582 of the inferior program, stopping at the previous instruction. If the
32583 previously executed instruction was a return from another function,
32584 it will continue to execute in reverse until the call to that function
32585 (from the current stack frame) is reached.
32587 @subsubheading @value{GDBN} Command
32589 The corresponding @value{GDBN} command is @samp{nexti}.
32591 @subsubheading Example
32595 -exec-next-instruction
32599 *stopped,reason="end-stepping-range",
32600 addr="0x000100d4",line="5",file="hello.c"
32605 @subheading The @code{-exec-return} Command
32606 @findex -exec-return
32608 @subsubheading Synopsis
32614 Makes current function return immediately. Doesn't execute the inferior.
32615 Displays the new current frame.
32617 @subsubheading @value{GDBN} Command
32619 The corresponding @value{GDBN} command is @samp{return}.
32621 @subsubheading Example
32625 200-break-insert callee4
32626 200^done,bkpt=@{number="1",addr="0x00010734",
32627 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
32632 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32633 frame=@{func="callee4",args=[],
32634 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32635 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
32636 arch="i386:x86_64"@}
32642 111^done,frame=@{level="0",func="callee3",
32643 args=[@{name="strarg",
32644 value="0x11940 \"A string argument.\""@}],
32645 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32646 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
32647 arch="i386:x86_64"@}
32652 @subheading The @code{-exec-run} Command
32655 @subsubheading Synopsis
32658 -exec-run [ --all | --thread-group N ] [ --start ]
32661 Starts execution of the inferior from the beginning. The inferior
32662 executes until either a breakpoint is encountered or the program
32663 exits. In the latter case the output will include an exit code, if
32664 the program has exited exceptionally.
32666 When neither the @samp{--all} nor the @samp{--thread-group} option
32667 is specified, the current inferior is started. If the
32668 @samp{--thread-group} option is specified, it should refer to a thread
32669 group of type @samp{process}, and that thread group will be started.
32670 If the @samp{--all} option is specified, then all inferiors will be started.
32672 Using the @samp{--start} option instructs the debugger to stop
32673 the execution at the start of the inferior's main subprogram,
32674 following the same behavior as the @code{start} command
32675 (@pxref{Starting}).
32677 @subsubheading @value{GDBN} Command
32679 The corresponding @value{GDBN} command is @samp{run}.
32681 @subsubheading Examples
32686 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
32691 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
32692 frame=@{func="main",args=[],file="recursive2.c",
32693 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
32698 Program exited normally:
32706 *stopped,reason="exited-normally"
32711 Program exited exceptionally:
32719 *stopped,reason="exited",exit-code="01"
32723 Another way the program can terminate is if it receives a signal such as
32724 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
32728 *stopped,reason="exited-signalled",signal-name="SIGINT",
32729 signal-meaning="Interrupt"
32733 @c @subheading -exec-signal
32736 @subheading The @code{-exec-step} Command
32739 @subsubheading Synopsis
32742 -exec-step [--reverse]
32745 Resumes execution of the inferior program, stopping when the beginning
32746 of the next source line is reached, if the next source line is not a
32747 function call. If it is, stop at the first instruction of the called
32748 function. If the @samp{--reverse} option is specified, resumes reverse
32749 execution of the inferior program, stopping at the beginning of the
32750 previously executed source line.
32752 @subsubheading @value{GDBN} Command
32754 The corresponding @value{GDBN} command is @samp{step}.
32756 @subsubheading Example
32758 Stepping into a function:
32764 *stopped,reason="end-stepping-range",
32765 frame=@{func="foo",args=[@{name="a",value="10"@},
32766 @{name="b",value="0"@}],file="recursive2.c",
32767 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
32777 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
32782 @subheading The @code{-exec-step-instruction} Command
32783 @findex -exec-step-instruction
32785 @subsubheading Synopsis
32788 -exec-step-instruction [--reverse]
32791 Resumes the inferior which executes one machine instruction. If the
32792 @samp{--reverse} option is specified, resumes reverse execution of the
32793 inferior program, stopping at the previously executed instruction.
32794 The output, once @value{GDBN} has stopped, will vary depending on
32795 whether we have stopped in the middle of a source line or not. In the
32796 former case, the address at which the program stopped will be printed
32799 @subsubheading @value{GDBN} Command
32801 The corresponding @value{GDBN} command is @samp{stepi}.
32803 @subsubheading Example
32807 -exec-step-instruction
32811 *stopped,reason="end-stepping-range",
32812 frame=@{func="foo",args=[],file="try.c",
32813 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32815 -exec-step-instruction
32819 *stopped,reason="end-stepping-range",
32820 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
32821 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
32826 @subheading The @code{-exec-until} Command
32827 @findex -exec-until
32829 @subsubheading Synopsis
32832 -exec-until [ @var{location} ]
32835 Executes the inferior until the @var{location} specified in the
32836 argument is reached. If there is no argument, the inferior executes
32837 until a source line greater than the current one is reached. The
32838 reason for stopping in this case will be @samp{location-reached}.
32840 @subsubheading @value{GDBN} Command
32842 The corresponding @value{GDBN} command is @samp{until}.
32844 @subsubheading Example
32848 -exec-until recursive2.c:6
32852 *stopped,reason="location-reached",frame=@{func="main",args=[],
32853 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
32854 arch="i386:x86_64"@}
32859 @subheading -file-clear
32860 Is this going away????
32863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32864 @node GDB/MI Stack Manipulation
32865 @section @sc{gdb/mi} Stack Manipulation Commands
32867 @subheading The @code{-enable-frame-filters} Command
32868 @findex -enable-frame-filters
32871 -enable-frame-filters
32874 @value{GDBN} allows Python-based frame filters to affect the output of
32875 the MI commands relating to stack traces. As there is no way to
32876 implement this in a fully backward-compatible way, a front end must
32877 request that this functionality be enabled.
32879 Once enabled, this feature cannot be disabled.
32881 Note that if Python support has not been compiled into @value{GDBN},
32882 this command will still succeed (and do nothing).
32884 @subheading The @code{-stack-info-frame} Command
32885 @findex -stack-info-frame
32887 @subsubheading Synopsis
32893 Get info on the selected frame.
32895 @subsubheading @value{GDBN} Command
32897 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
32898 (without arguments).
32900 @subsubheading Example
32905 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
32906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
32907 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
32908 arch="i386:x86_64"@}
32912 @subheading The @code{-stack-info-depth} Command
32913 @findex -stack-info-depth
32915 @subsubheading Synopsis
32918 -stack-info-depth [ @var{max-depth} ]
32921 Return the depth of the stack. If the integer argument @var{max-depth}
32922 is specified, do not count beyond @var{max-depth} frames.
32924 @subsubheading @value{GDBN} Command
32926 There's no equivalent @value{GDBN} command.
32928 @subsubheading Example
32930 For a stack with frame levels 0 through 11:
32937 -stack-info-depth 4
32940 -stack-info-depth 12
32943 -stack-info-depth 11
32946 -stack-info-depth 13
32951 @anchor{-stack-list-arguments}
32952 @subheading The @code{-stack-list-arguments} Command
32953 @findex -stack-list-arguments
32955 @subsubheading Synopsis
32958 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32959 [ @var{low-frame} @var{high-frame} ]
32962 Display a list of the arguments for the frames between @var{low-frame}
32963 and @var{high-frame} (inclusive). If @var{low-frame} and
32964 @var{high-frame} are not provided, list the arguments for the whole
32965 call stack. If the two arguments are equal, show the single frame
32966 at the corresponding level. It is an error if @var{low-frame} is
32967 larger than the actual number of frames. On the other hand,
32968 @var{high-frame} may be larger than the actual number of frames, in
32969 which case only existing frames will be returned.
32971 If @var{print-values} is 0 or @code{--no-values}, print only the names of
32972 the variables; if it is 1 or @code{--all-values}, print also their
32973 values; and if it is 2 or @code{--simple-values}, print the name,
32974 type and value for simple data types, and the name and type for arrays,
32975 structures and unions. If the option @code{--no-frame-filters} is
32976 supplied, then Python frame filters will not be executed.
32978 If the @code{--skip-unavailable} option is specified, arguments that
32979 are not available are not listed. Partially available arguments
32980 are still displayed, however.
32982 Use of this command to obtain arguments in a single frame is
32983 deprecated in favor of the @samp{-stack-list-variables} command.
32985 @subsubheading @value{GDBN} Command
32987 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
32988 @samp{gdb_get_args} command which partially overlaps with the
32989 functionality of @samp{-stack-list-arguments}.
32991 @subsubheading Example
32998 frame=@{level="0",addr="0x00010734",func="callee4",
32999 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33000 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
33001 arch="i386:x86_64"@},
33002 frame=@{level="1",addr="0x0001076c",func="callee3",
33003 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33004 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
33005 arch="i386:x86_64"@},
33006 frame=@{level="2",addr="0x0001078c",func="callee2",
33007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
33009 arch="i386:x86_64"@},
33010 frame=@{level="3",addr="0x000107b4",func="callee1",
33011 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33012 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
33013 arch="i386:x86_64"@},
33014 frame=@{level="4",addr="0x000107e0",func="main",
33015 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
33016 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
33017 arch="i386:x86_64"@}]
33019 -stack-list-arguments 0
33022 frame=@{level="0",args=[]@},
33023 frame=@{level="1",args=[name="strarg"]@},
33024 frame=@{level="2",args=[name="intarg",name="strarg"]@},
33025 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
33026 frame=@{level="4",args=[]@}]
33028 -stack-list-arguments 1
33031 frame=@{level="0",args=[]@},
33033 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33034 frame=@{level="2",args=[
33035 @{name="intarg",value="2"@},
33036 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
33037 @{frame=@{level="3",args=[
33038 @{name="intarg",value="2"@},
33039 @{name="strarg",value="0x11940 \"A string argument.\""@},
33040 @{name="fltarg",value="3.5"@}]@},
33041 frame=@{level="4",args=[]@}]
33043 -stack-list-arguments 0 2 2
33044 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
33046 -stack-list-arguments 1 2 2
33047 ^done,stack-args=[frame=@{level="2",
33048 args=[@{name="intarg",value="2"@},
33049 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
33053 @c @subheading -stack-list-exception-handlers
33056 @anchor{-stack-list-frames}
33057 @subheading The @code{-stack-list-frames} Command
33058 @findex -stack-list-frames
33060 @subsubheading Synopsis
33063 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
33066 List the frames currently on the stack. For each frame it displays the
33071 The frame number, 0 being the topmost frame, i.e., the innermost function.
33073 The @code{$pc} value for that frame.
33077 File name of the source file where the function lives.
33078 @item @var{fullname}
33079 The full file name of the source file where the function lives.
33081 Line number corresponding to the @code{$pc}.
33083 The shared library where this function is defined. This is only given
33084 if the frame's function is not known.
33086 Frame's architecture.
33089 If invoked without arguments, this command prints a backtrace for the
33090 whole stack. If given two integer arguments, it shows the frames whose
33091 levels are between the two arguments (inclusive). If the two arguments
33092 are equal, it shows the single frame at the corresponding level. It is
33093 an error if @var{low-frame} is larger than the actual number of
33094 frames. On the other hand, @var{high-frame} may be larger than the
33095 actual number of frames, in which case only existing frames will be
33096 returned. If the option @code{--no-frame-filters} is supplied, then
33097 Python frame filters will not be executed.
33099 @subsubheading @value{GDBN} Command
33101 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
33103 @subsubheading Example
33105 Full stack backtrace:
33111 [frame=@{level="0",addr="0x0001076c",func="foo",
33112 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
33113 arch="i386:x86_64"@},
33114 frame=@{level="1",addr="0x000107a4",func="foo",
33115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33116 arch="i386:x86_64"@},
33117 frame=@{level="2",addr="0x000107a4",func="foo",
33118 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33119 arch="i386:x86_64"@},
33120 frame=@{level="3",addr="0x000107a4",func="foo",
33121 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33122 arch="i386:x86_64"@},
33123 frame=@{level="4",addr="0x000107a4",func="foo",
33124 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33125 arch="i386:x86_64"@},
33126 frame=@{level="5",addr="0x000107a4",func="foo",
33127 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33128 arch="i386:x86_64"@},
33129 frame=@{level="6",addr="0x000107a4",func="foo",
33130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33131 arch="i386:x86_64"@},
33132 frame=@{level="7",addr="0x000107a4",func="foo",
33133 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33134 arch="i386:x86_64"@},
33135 frame=@{level="8",addr="0x000107a4",func="foo",
33136 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33137 arch="i386:x86_64"@},
33138 frame=@{level="9",addr="0x000107a4",func="foo",
33139 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33140 arch="i386:x86_64"@},
33141 frame=@{level="10",addr="0x000107a4",func="foo",
33142 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33143 arch="i386:x86_64"@},
33144 frame=@{level="11",addr="0x00010738",func="main",
33145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
33146 arch="i386:x86_64"@}]
33150 Show frames between @var{low_frame} and @var{high_frame}:
33154 -stack-list-frames 3 5
33156 [frame=@{level="3",addr="0x000107a4",func="foo",
33157 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33158 arch="i386:x86_64"@},
33159 frame=@{level="4",addr="0x000107a4",func="foo",
33160 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33161 arch="i386:x86_64"@},
33162 frame=@{level="5",addr="0x000107a4",func="foo",
33163 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33164 arch="i386:x86_64"@}]
33168 Show a single frame:
33172 -stack-list-frames 3 3
33174 [frame=@{level="3",addr="0x000107a4",func="foo",
33175 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
33176 arch="i386:x86_64"@}]
33181 @subheading The @code{-stack-list-locals} Command
33182 @findex -stack-list-locals
33183 @anchor{-stack-list-locals}
33185 @subsubheading Synopsis
33188 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33191 Display the local variable names for the selected frame. If
33192 @var{print-values} is 0 or @code{--no-values}, print only the names of
33193 the variables; if it is 1 or @code{--all-values}, print also their
33194 values; and if it is 2 or @code{--simple-values}, print the name,
33195 type and value for simple data types, and the name and type for arrays,
33196 structures and unions. In this last case, a frontend can immediately
33197 display the value of simple data types and create variable objects for
33198 other data types when the user wishes to explore their values in
33199 more detail. If the option @code{--no-frame-filters} is supplied, then
33200 Python frame filters will not be executed.
33202 If the @code{--skip-unavailable} option is specified, local variables
33203 that are not available are not listed. Partially available local
33204 variables are still displayed, however.
33206 This command is deprecated in favor of the
33207 @samp{-stack-list-variables} command.
33209 @subsubheading @value{GDBN} Command
33211 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
33213 @subsubheading Example
33217 -stack-list-locals 0
33218 ^done,locals=[name="A",name="B",name="C"]
33220 -stack-list-locals --all-values
33221 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
33222 @{name="C",value="@{1, 2, 3@}"@}]
33223 -stack-list-locals --simple-values
33224 ^done,locals=[@{name="A",type="int",value="1"@},
33225 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
33229 @anchor{-stack-list-variables}
33230 @subheading The @code{-stack-list-variables} Command
33231 @findex -stack-list-variables
33233 @subsubheading Synopsis
33236 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
33239 Display the names of local variables and function arguments for the selected frame. If
33240 @var{print-values} is 0 or @code{--no-values}, print only the names of
33241 the variables; if it is 1 or @code{--all-values}, print also their
33242 values; and if it is 2 or @code{--simple-values}, print the name,
33243 type and value for simple data types, and the name and type for arrays,
33244 structures and unions. If the option @code{--no-frame-filters} is
33245 supplied, then Python frame filters will not be executed.
33247 If the @code{--skip-unavailable} option is specified, local variables
33248 and arguments that are not available are not listed. Partially
33249 available arguments and local variables are still displayed, however.
33251 @subsubheading Example
33255 -stack-list-variables --thread 1 --frame 0 --all-values
33256 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
33261 @subheading The @code{-stack-select-frame} Command
33262 @findex -stack-select-frame
33264 @subsubheading Synopsis
33267 -stack-select-frame @var{framenum}
33270 Change the selected frame. Select a different frame @var{framenum} on
33273 This command in deprecated in favor of passing the @samp{--frame}
33274 option to every command.
33276 @subsubheading @value{GDBN} Command
33278 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
33279 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
33281 @subsubheading Example
33285 -stack-select-frame 2
33290 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33291 @node GDB/MI Variable Objects
33292 @section @sc{gdb/mi} Variable Objects
33296 @subheading Motivation for Variable Objects in @sc{gdb/mi}
33298 For the implementation of a variable debugger window (locals, watched
33299 expressions, etc.), we are proposing the adaptation of the existing code
33300 used by @code{Insight}.
33302 The two main reasons for that are:
33306 It has been proven in practice (it is already on its second generation).
33309 It will shorten development time (needless to say how important it is
33313 The original interface was designed to be used by Tcl code, so it was
33314 slightly changed so it could be used through @sc{gdb/mi}. This section
33315 describes the @sc{gdb/mi} operations that will be available and gives some
33316 hints about their use.
33318 @emph{Note}: In addition to the set of operations described here, we
33319 expect the @sc{gui} implementation of a variable window to require, at
33320 least, the following operations:
33323 @item @code{-gdb-show} @code{output-radix}
33324 @item @code{-stack-list-arguments}
33325 @item @code{-stack-list-locals}
33326 @item @code{-stack-select-frame}
33331 @subheading Introduction to Variable Objects
33333 @cindex variable objects in @sc{gdb/mi}
33335 Variable objects are "object-oriented" MI interface for examining and
33336 changing values of expressions. Unlike some other MI interfaces that
33337 work with expressions, variable objects are specifically designed for
33338 simple and efficient presentation in the frontend. A variable object
33339 is identified by string name. When a variable object is created, the
33340 frontend specifies the expression for that variable object. The
33341 expression can be a simple variable, or it can be an arbitrary complex
33342 expression, and can even involve CPU registers. After creating a
33343 variable object, the frontend can invoke other variable object
33344 operations---for example to obtain or change the value of a variable
33345 object, or to change display format.
33347 Variable objects have hierarchical tree structure. Any variable object
33348 that corresponds to a composite type, such as structure in C, has
33349 a number of child variable objects, for example corresponding to each
33350 element of a structure. A child variable object can itself have
33351 children, recursively. Recursion ends when we reach
33352 leaf variable objects, which always have built-in types. Child variable
33353 objects are created only by explicit request, so if a frontend
33354 is not interested in the children of a particular variable object, no
33355 child will be created.
33357 For a leaf variable object it is possible to obtain its value as a
33358 string, or set the value from a string. String value can be also
33359 obtained for a non-leaf variable object, but it's generally a string
33360 that only indicates the type of the object, and does not list its
33361 contents. Assignment to a non-leaf variable object is not allowed.
33363 A frontend does not need to read the values of all variable objects each time
33364 the program stops. Instead, MI provides an update command that lists all
33365 variable objects whose values has changed since the last update
33366 operation. This considerably reduces the amount of data that must
33367 be transferred to the frontend. As noted above, children variable
33368 objects are created on demand, and only leaf variable objects have a
33369 real value. As result, gdb will read target memory only for leaf
33370 variables that frontend has created.
33372 The automatic update is not always desirable. For example, a frontend
33373 might want to keep a value of some expression for future reference,
33374 and never update it. For another example, fetching memory is
33375 relatively slow for embedded targets, so a frontend might want
33376 to disable automatic update for the variables that are either not
33377 visible on the screen, or ``closed''. This is possible using so
33378 called ``frozen variable objects''. Such variable objects are never
33379 implicitly updated.
33381 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
33382 fixed variable object, the expression is parsed when the variable
33383 object is created, including associating identifiers to specific
33384 variables. The meaning of expression never changes. For a floating
33385 variable object the values of variables whose names appear in the
33386 expressions are re-evaluated every time in the context of the current
33387 frame. Consider this example:
33392 struct work_state state;
33399 If a fixed variable object for the @code{state} variable is created in
33400 this function, and we enter the recursive call, the variable
33401 object will report the value of @code{state} in the top-level
33402 @code{do_work} invocation. On the other hand, a floating variable
33403 object will report the value of @code{state} in the current frame.
33405 If an expression specified when creating a fixed variable object
33406 refers to a local variable, the variable object becomes bound to the
33407 thread and frame in which the variable object is created. When such
33408 variable object is updated, @value{GDBN} makes sure that the
33409 thread/frame combination the variable object is bound to still exists,
33410 and re-evaluates the variable object in context of that thread/frame.
33412 The following is the complete set of @sc{gdb/mi} operations defined to
33413 access this functionality:
33415 @multitable @columnfractions .4 .6
33416 @item @strong{Operation}
33417 @tab @strong{Description}
33419 @item @code{-enable-pretty-printing}
33420 @tab enable Python-based pretty-printing
33421 @item @code{-var-create}
33422 @tab create a variable object
33423 @item @code{-var-delete}
33424 @tab delete the variable object and/or its children
33425 @item @code{-var-set-format}
33426 @tab set the display format of this variable
33427 @item @code{-var-show-format}
33428 @tab show the display format of this variable
33429 @item @code{-var-info-num-children}
33430 @tab tells how many children this object has
33431 @item @code{-var-list-children}
33432 @tab return a list of the object's children
33433 @item @code{-var-info-type}
33434 @tab show the type of this variable object
33435 @item @code{-var-info-expression}
33436 @tab print parent-relative expression that this variable object represents
33437 @item @code{-var-info-path-expression}
33438 @tab print full expression that this variable object represents
33439 @item @code{-var-show-attributes}
33440 @tab is this variable editable? does it exist here?
33441 @item @code{-var-evaluate-expression}
33442 @tab get the value of this variable
33443 @item @code{-var-assign}
33444 @tab set the value of this variable
33445 @item @code{-var-update}
33446 @tab update the variable and its children
33447 @item @code{-var-set-frozen}
33448 @tab set frozenness attribute
33449 @item @code{-var-set-update-range}
33450 @tab set range of children to display on update
33453 In the next subsection we describe each operation in detail and suggest
33454 how it can be used.
33456 @subheading Description And Use of Operations on Variable Objects
33458 @subheading The @code{-enable-pretty-printing} Command
33459 @findex -enable-pretty-printing
33462 -enable-pretty-printing
33465 @value{GDBN} allows Python-based visualizers to affect the output of the
33466 MI variable object commands. However, because there was no way to
33467 implement this in a fully backward-compatible way, a front end must
33468 request that this functionality be enabled.
33470 Once enabled, this feature cannot be disabled.
33472 Note that if Python support has not been compiled into @value{GDBN},
33473 this command will still succeed (and do nothing).
33475 This feature is currently (as of @value{GDBN} 7.0) experimental, and
33476 may work differently in future versions of @value{GDBN}.
33478 @subheading The @code{-var-create} Command
33479 @findex -var-create
33481 @subsubheading Synopsis
33484 -var-create @{@var{name} | "-"@}
33485 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
33488 This operation creates a variable object, which allows the monitoring of
33489 a variable, the result of an expression, a memory cell or a CPU
33492 The @var{name} parameter is the string by which the object can be
33493 referenced. It must be unique. If @samp{-} is specified, the varobj
33494 system will generate a string ``varNNNNNN'' automatically. It will be
33495 unique provided that one does not specify @var{name} of that format.
33496 The command fails if a duplicate name is found.
33498 The frame under which the expression should be evaluated can be
33499 specified by @var{frame-addr}. A @samp{*} indicates that the current
33500 frame should be used. A @samp{@@} indicates that a floating variable
33501 object must be created.
33503 @var{expression} is any expression valid on the current language set (must not
33504 begin with a @samp{*}), or one of the following:
33508 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
33511 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
33514 @samp{$@var{regname}} --- a CPU register name
33517 @cindex dynamic varobj
33518 A varobj's contents may be provided by a Python-based pretty-printer. In this
33519 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
33520 have slightly different semantics in some cases. If the
33521 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
33522 will never create a dynamic varobj. This ensures backward
33523 compatibility for existing clients.
33525 @subsubheading Result
33527 This operation returns attributes of the newly-created varobj. These
33532 The name of the varobj.
33535 The number of children of the varobj. This number is not necessarily
33536 reliable for a dynamic varobj. Instead, you must examine the
33537 @samp{has_more} attribute.
33540 The varobj's scalar value. For a varobj whose type is some sort of
33541 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
33542 will not be interesting.
33545 The varobj's type. This is a string representation of the type, as
33546 would be printed by the @value{GDBN} CLI. If @samp{print object}
33547 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33548 @emph{actual} (derived) type of the object is shown rather than the
33549 @emph{declared} one.
33552 If a variable object is bound to a specific thread, then this is the
33553 thread's global identifier.
33556 For a dynamic varobj, this indicates whether there appear to be any
33557 children available. For a non-dynamic varobj, this will be 0.
33560 This attribute will be present and have the value @samp{1} if the
33561 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33562 then this attribute will not be present.
33565 A dynamic varobj can supply a display hint to the front end. The
33566 value comes directly from the Python pretty-printer object's
33567 @code{display_hint} method. @xref{Pretty Printing API}.
33570 Typical output will look like this:
33573 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
33574 has_more="@var{has_more}"
33578 @subheading The @code{-var-delete} Command
33579 @findex -var-delete
33581 @subsubheading Synopsis
33584 -var-delete [ -c ] @var{name}
33587 Deletes a previously created variable object and all of its children.
33588 With the @samp{-c} option, just deletes the children.
33590 Returns an error if the object @var{name} is not found.
33593 @subheading The @code{-var-set-format} Command
33594 @findex -var-set-format
33596 @subsubheading Synopsis
33599 -var-set-format @var{name} @var{format-spec}
33602 Sets the output format for the value of the object @var{name} to be
33605 @anchor{-var-set-format}
33606 The syntax for the @var{format-spec} is as follows:
33609 @var{format-spec} @expansion{}
33610 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
33613 The natural format is the default format choosen automatically
33614 based on the variable type (like decimal for an @code{int}, hex
33615 for pointers, etc.).
33617 The zero-hexadecimal format has a representation similar to hexadecimal
33618 but with padding zeroes to the left of the value. For example, a 32-bit
33619 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
33620 zero-hexadecimal format.
33622 For a variable with children, the format is set only on the
33623 variable itself, and the children are not affected.
33625 @subheading The @code{-var-show-format} Command
33626 @findex -var-show-format
33628 @subsubheading Synopsis
33631 -var-show-format @var{name}
33634 Returns the format used to display the value of the object @var{name}.
33637 @var{format} @expansion{}
33642 @subheading The @code{-var-info-num-children} Command
33643 @findex -var-info-num-children
33645 @subsubheading Synopsis
33648 -var-info-num-children @var{name}
33651 Returns the number of children of a variable object @var{name}:
33657 Note that this number is not completely reliable for a dynamic varobj.
33658 It will return the current number of children, but more children may
33662 @subheading The @code{-var-list-children} Command
33663 @findex -var-list-children
33665 @subsubheading Synopsis
33668 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
33670 @anchor{-var-list-children}
33672 Return a list of the children of the specified variable object and
33673 create variable objects for them, if they do not already exist. With
33674 a single argument or if @var{print-values} has a value of 0 or
33675 @code{--no-values}, print only the names of the variables; if
33676 @var{print-values} is 1 or @code{--all-values}, also print their
33677 values; and if it is 2 or @code{--simple-values} print the name and
33678 value for simple data types and just the name for arrays, structures
33681 @var{from} and @var{to}, if specified, indicate the range of children
33682 to report. If @var{from} or @var{to} is less than zero, the range is
33683 reset and all children will be reported. Otherwise, children starting
33684 at @var{from} (zero-based) and up to and excluding @var{to} will be
33687 If a child range is requested, it will only affect the current call to
33688 @code{-var-list-children}, but not future calls to @code{-var-update}.
33689 For this, you must instead use @code{-var-set-update-range}. The
33690 intent of this approach is to enable a front end to implement any
33691 update approach it likes; for example, scrolling a view may cause the
33692 front end to request more children with @code{-var-list-children}, and
33693 then the front end could call @code{-var-set-update-range} with a
33694 different range to ensure that future updates are restricted to just
33697 For each child the following results are returned:
33702 Name of the variable object created for this child.
33705 The expression to be shown to the user by the front end to designate this child.
33706 For example this may be the name of a structure member.
33708 For a dynamic varobj, this value cannot be used to form an
33709 expression. There is no way to do this at all with a dynamic varobj.
33711 For C/C@t{++} structures there are several pseudo children returned to
33712 designate access qualifiers. For these pseudo children @var{exp} is
33713 @samp{public}, @samp{private}, or @samp{protected}. In this case the
33714 type and value are not present.
33716 A dynamic varobj will not report the access qualifying
33717 pseudo-children, regardless of the language. This information is not
33718 available at all with a dynamic varobj.
33721 Number of children this child has. For a dynamic varobj, this will be
33725 The type of the child. If @samp{print object}
33726 (@pxref{Print Settings, set print object}) is set to @code{on}, the
33727 @emph{actual} (derived) type of the object is shown rather than the
33728 @emph{declared} one.
33731 If values were requested, this is the value.
33734 If this variable object is associated with a thread, this is the
33735 thread's global thread id. Otherwise this result is not present.
33738 If the variable object is frozen, this variable will be present with a value of 1.
33741 A dynamic varobj can supply a display hint to the front end. The
33742 value comes directly from the Python pretty-printer object's
33743 @code{display_hint} method. @xref{Pretty Printing API}.
33746 This attribute will be present and have the value @samp{1} if the
33747 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
33748 then this attribute will not be present.
33752 The result may have its own attributes:
33756 A dynamic varobj can supply a display hint to the front end. The
33757 value comes directly from the Python pretty-printer object's
33758 @code{display_hint} method. @xref{Pretty Printing API}.
33761 This is an integer attribute which is nonzero if there are children
33762 remaining after the end of the selected range.
33765 @subsubheading Example
33769 -var-list-children n
33770 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33771 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
33773 -var-list-children --all-values n
33774 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
33775 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
33779 @subheading The @code{-var-info-type} Command
33780 @findex -var-info-type
33782 @subsubheading Synopsis
33785 -var-info-type @var{name}
33788 Returns the type of the specified variable @var{name}. The type is
33789 returned as a string in the same format as it is output by the
33793 type=@var{typename}
33797 @subheading The @code{-var-info-expression} Command
33798 @findex -var-info-expression
33800 @subsubheading Synopsis
33803 -var-info-expression @var{name}
33806 Returns a string that is suitable for presenting this
33807 variable object in user interface. The string is generally
33808 not valid expression in the current language, and cannot be evaluated.
33810 For example, if @code{a} is an array, and variable object
33811 @code{A} was created for @code{a}, then we'll get this output:
33814 (gdb) -var-info-expression A.1
33815 ^done,lang="C",exp="1"
33819 Here, the value of @code{lang} is the language name, which can be
33820 found in @ref{Supported Languages}.
33822 Note that the output of the @code{-var-list-children} command also
33823 includes those expressions, so the @code{-var-info-expression} command
33826 @subheading The @code{-var-info-path-expression} Command
33827 @findex -var-info-path-expression
33829 @subsubheading Synopsis
33832 -var-info-path-expression @var{name}
33835 Returns an expression that can be evaluated in the current
33836 context and will yield the same value that a variable object has.
33837 Compare this with the @code{-var-info-expression} command, which
33838 result can be used only for UI presentation. Typical use of
33839 the @code{-var-info-path-expression} command is creating a
33840 watchpoint from a variable object.
33842 This command is currently not valid for children of a dynamic varobj,
33843 and will give an error when invoked on one.
33845 For example, suppose @code{C} is a C@t{++} class, derived from class
33846 @code{Base}, and that the @code{Base} class has a member called
33847 @code{m_size}. Assume a variable @code{c} is has the type of
33848 @code{C} and a variable object @code{C} was created for variable
33849 @code{c}. Then, we'll get this output:
33851 (gdb) -var-info-path-expression C.Base.public.m_size
33852 ^done,path_expr=((Base)c).m_size)
33855 @subheading The @code{-var-show-attributes} Command
33856 @findex -var-show-attributes
33858 @subsubheading Synopsis
33861 -var-show-attributes @var{name}
33864 List attributes of the specified variable object @var{name}:
33867 status=@var{attr} [ ( ,@var{attr} )* ]
33871 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
33873 @subheading The @code{-var-evaluate-expression} Command
33874 @findex -var-evaluate-expression
33876 @subsubheading Synopsis
33879 -var-evaluate-expression [-f @var{format-spec}] @var{name}
33882 Evaluates the expression that is represented by the specified variable
33883 object and returns its value as a string. The format of the string
33884 can be specified with the @samp{-f} option. The possible values of
33885 this option are the same as for @code{-var-set-format}
33886 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
33887 the current display format will be used. The current display format
33888 can be changed using the @code{-var-set-format} command.
33894 Note that one must invoke @code{-var-list-children} for a variable
33895 before the value of a child variable can be evaluated.
33897 @subheading The @code{-var-assign} Command
33898 @findex -var-assign
33900 @subsubheading Synopsis
33903 -var-assign @var{name} @var{expression}
33906 Assigns the value of @var{expression} to the variable object specified
33907 by @var{name}. The object must be @samp{editable}. If the variable's
33908 value is altered by the assign, the variable will show up in any
33909 subsequent @code{-var-update} list.
33911 @subsubheading Example
33919 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
33923 @subheading The @code{-var-update} Command
33924 @findex -var-update
33926 @subsubheading Synopsis
33929 -var-update [@var{print-values}] @{@var{name} | "*"@}
33932 Reevaluate the expressions corresponding to the variable object
33933 @var{name} and all its direct and indirect children, and return the
33934 list of variable objects whose values have changed; @var{name} must
33935 be a root variable object. Here, ``changed'' means that the result of
33936 @code{-var-evaluate-expression} before and after the
33937 @code{-var-update} is different. If @samp{*} is used as the variable
33938 object names, all existing variable objects are updated, except
33939 for frozen ones (@pxref{-var-set-frozen}). The option
33940 @var{print-values} determines whether both names and values, or just
33941 names are printed. The possible values of this option are the same
33942 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
33943 recommended to use the @samp{--all-values} option, to reduce the
33944 number of MI commands needed on each program stop.
33946 With the @samp{*} parameter, if a variable object is bound to a
33947 currently running thread, it will not be updated, without any
33950 If @code{-var-set-update-range} was previously used on a varobj, then
33951 only the selected range of children will be reported.
33953 @code{-var-update} reports all the changed varobjs in a tuple named
33956 Each item in the change list is itself a tuple holding:
33960 The name of the varobj.
33963 If values were requested for this update, then this field will be
33964 present and will hold the value of the varobj.
33967 @anchor{-var-update}
33968 This field is a string which may take one of three values:
33972 The variable object's current value is valid.
33975 The variable object does not currently hold a valid value but it may
33976 hold one in the future if its associated expression comes back into
33980 The variable object no longer holds a valid value.
33981 This can occur when the executable file being debugged has changed,
33982 either through recompilation or by using the @value{GDBN} @code{file}
33983 command. The front end should normally choose to delete these variable
33987 In the future new values may be added to this list so the front should
33988 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
33991 This is only present if the varobj is still valid. If the type
33992 changed, then this will be the string @samp{true}; otherwise it will
33995 When a varobj's type changes, its children are also likely to have
33996 become incorrect. Therefore, the varobj's children are automatically
33997 deleted when this attribute is @samp{true}. Also, the varobj's update
33998 range, when set using the @code{-var-set-update-range} command, is
34002 If the varobj's type changed, then this field will be present and will
34005 @item new_num_children
34006 For a dynamic varobj, if the number of children changed, or if the
34007 type changed, this will be the new number of children.
34009 The @samp{numchild} field in other varobj responses is generally not
34010 valid for a dynamic varobj -- it will show the number of children that
34011 @value{GDBN} knows about, but because dynamic varobjs lazily
34012 instantiate their children, this will not reflect the number of
34013 children which may be available.
34015 The @samp{new_num_children} attribute only reports changes to the
34016 number of children known by @value{GDBN}. This is the only way to
34017 detect whether an update has removed children (which necessarily can
34018 only happen at the end of the update range).
34021 The display hint, if any.
34024 This is an integer value, which will be 1 if there are more children
34025 available outside the varobj's update range.
34028 This attribute will be present and have the value @samp{1} if the
34029 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
34030 then this attribute will not be present.
34033 If new children were added to a dynamic varobj within the selected
34034 update range (as set by @code{-var-set-update-range}), then they will
34035 be listed in this attribute.
34038 @subsubheading Example
34045 -var-update --all-values var1
34046 ^done,changelist=[@{name="var1",value="3",in_scope="true",
34047 type_changed="false"@}]
34051 @subheading The @code{-var-set-frozen} Command
34052 @findex -var-set-frozen
34053 @anchor{-var-set-frozen}
34055 @subsubheading Synopsis
34058 -var-set-frozen @var{name} @var{flag}
34061 Set the frozenness flag on the variable object @var{name}. The
34062 @var{flag} parameter should be either @samp{1} to make the variable
34063 frozen or @samp{0} to make it unfrozen. If a variable object is
34064 frozen, then neither itself, nor any of its children, are
34065 implicitly updated by @code{-var-update} of
34066 a parent variable or by @code{-var-update *}. Only
34067 @code{-var-update} of the variable itself will update its value and
34068 values of its children. After a variable object is unfrozen, it is
34069 implicitly updated by all subsequent @code{-var-update} operations.
34070 Unfreezing a variable does not update it, only subsequent
34071 @code{-var-update} does.
34073 @subsubheading Example
34077 -var-set-frozen V 1
34082 @subheading The @code{-var-set-update-range} command
34083 @findex -var-set-update-range
34084 @anchor{-var-set-update-range}
34086 @subsubheading Synopsis
34089 -var-set-update-range @var{name} @var{from} @var{to}
34092 Set the range of children to be returned by future invocations of
34093 @code{-var-update}.
34095 @var{from} and @var{to} indicate the range of children to report. If
34096 @var{from} or @var{to} is less than zero, the range is reset and all
34097 children will be reported. Otherwise, children starting at @var{from}
34098 (zero-based) and up to and excluding @var{to} will be reported.
34100 @subsubheading Example
34104 -var-set-update-range V 1 2
34108 @subheading The @code{-var-set-visualizer} command
34109 @findex -var-set-visualizer
34110 @anchor{-var-set-visualizer}
34112 @subsubheading Synopsis
34115 -var-set-visualizer @var{name} @var{visualizer}
34118 Set a visualizer for the variable object @var{name}.
34120 @var{visualizer} is the visualizer to use. The special value
34121 @samp{None} means to disable any visualizer in use.
34123 If not @samp{None}, @var{visualizer} must be a Python expression.
34124 This expression must evaluate to a callable object which accepts a
34125 single argument. @value{GDBN} will call this object with the value of
34126 the varobj @var{name} as an argument (this is done so that the same
34127 Python pretty-printing code can be used for both the CLI and MI).
34128 When called, this object must return an object which conforms to the
34129 pretty-printing interface (@pxref{Pretty Printing API}).
34131 The pre-defined function @code{gdb.default_visualizer} may be used to
34132 select a visualizer by following the built-in process
34133 (@pxref{Selecting Pretty-Printers}). This is done automatically when
34134 a varobj is created, and so ordinarily is not needed.
34136 This feature is only available if Python support is enabled. The MI
34137 command @code{-list-features} (@pxref{GDB/MI Support Commands})
34138 can be used to check this.
34140 @subsubheading Example
34142 Resetting the visualizer:
34146 -var-set-visualizer V None
34150 Reselecting the default (type-based) visualizer:
34154 -var-set-visualizer V gdb.default_visualizer
34158 Suppose @code{SomeClass} is a visualizer class. A lambda expression
34159 can be used to instantiate this class for a varobj:
34163 -var-set-visualizer V "lambda val: SomeClass()"
34167 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34168 @node GDB/MI Data Manipulation
34169 @section @sc{gdb/mi} Data Manipulation
34171 @cindex data manipulation, in @sc{gdb/mi}
34172 @cindex @sc{gdb/mi}, data manipulation
34173 This section describes the @sc{gdb/mi} commands that manipulate data:
34174 examine memory and registers, evaluate expressions, etc.
34176 For details about what an addressable memory unit is,
34177 @pxref{addressable memory unit}.
34179 @c REMOVED FROM THE INTERFACE.
34180 @c @subheading -data-assign
34181 @c Change the value of a program variable. Plenty of side effects.
34182 @c @subsubheading GDB Command
34184 @c @subsubheading Example
34187 @subheading The @code{-data-disassemble} Command
34188 @findex -data-disassemble
34190 @subsubheading Synopsis
34194 [ -s @var{start-addr} -e @var{end-addr} ]
34195 | [ -a @var{addr} ]
34196 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
34204 @item @var{start-addr}
34205 is the beginning address (or @code{$pc})
34206 @item @var{end-addr}
34209 is an address anywhere within (or the name of) the function to
34210 disassemble. If an address is specified, the whole function
34211 surrounding that address will be disassembled. If a name is
34212 specified, the whole function with that name will be disassembled.
34213 @item @var{filename}
34214 is the name of the file to disassemble
34215 @item @var{linenum}
34216 is the line number to disassemble around
34218 is the number of disassembly lines to be produced. If it is -1,
34219 the whole function will be disassembled, in case no @var{end-addr} is
34220 specified. If @var{end-addr} is specified as a non-zero value, and
34221 @var{lines} is lower than the number of disassembly lines between
34222 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
34223 displayed; if @var{lines} is higher than the number of lines between
34224 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
34229 @item 0 disassembly only
34230 @item 1 mixed source and disassembly (deprecated)
34231 @item 2 disassembly with raw opcodes
34232 @item 3 mixed source and disassembly with raw opcodes (deprecated)
34233 @item 4 mixed source and disassembly
34234 @item 5 mixed source and disassembly with raw opcodes
34237 Modes 1 and 3 are deprecated. The output is ``source centric''
34238 which hasn't proved useful in practice.
34239 @xref{Machine Code}, for a discussion of the difference between
34240 @code{/m} and @code{/s} output of the @code{disassemble} command.
34243 @subsubheading Result
34245 The result of the @code{-data-disassemble} command will be a list named
34246 @samp{asm_insns}, the contents of this list depend on the @var{mode}
34247 used with the @code{-data-disassemble} command.
34249 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
34254 The address at which this instruction was disassembled.
34257 The name of the function this instruction is within.
34260 The decimal offset in bytes from the start of @samp{func-name}.
34263 The text disassembly for this @samp{address}.
34266 This field is only present for modes 2, 3 and 5. This contains the raw opcode
34267 bytes for the @samp{inst} field.
34271 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
34272 @samp{src_and_asm_line}, each of which has the following fields:
34276 The line number within @samp{file}.
34279 The file name from the compilation unit. This might be an absolute
34280 file name or a relative file name depending on the compile command
34284 Absolute file name of @samp{file}. It is converted to a canonical form
34285 using the source file search path
34286 (@pxref{Source Path, ,Specifying Source Directories})
34287 and after resolving all the symbolic links.
34289 If the source file is not found this field will contain the path as
34290 present in the debug information.
34292 @item line_asm_insn
34293 This is a list of tuples containing the disassembly for @samp{line} in
34294 @samp{file}. The fields of each tuple are the same as for
34295 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
34296 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
34301 Note that whatever included in the @samp{inst} field, is not
34302 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
34305 @subsubheading @value{GDBN} Command
34307 The corresponding @value{GDBN} command is @samp{disassemble}.
34309 @subsubheading Example
34311 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
34315 -data-disassemble -s $pc -e "$pc + 20" -- 0
34318 @{address="0x000107c0",func-name="main",offset="4",
34319 inst="mov 2, %o0"@},
34320 @{address="0x000107c4",func-name="main",offset="8",
34321 inst="sethi %hi(0x11800), %o2"@},
34322 @{address="0x000107c8",func-name="main",offset="12",
34323 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
34324 @{address="0x000107cc",func-name="main",offset="16",
34325 inst="sethi %hi(0x11800), %o2"@},
34326 @{address="0x000107d0",func-name="main",offset="20",
34327 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
34331 Disassemble the whole @code{main} function. Line 32 is part of
34335 -data-disassemble -f basics.c -l 32 -- 0
34337 @{address="0x000107bc",func-name="main",offset="0",
34338 inst="save %sp, -112, %sp"@},
34339 @{address="0x000107c0",func-name="main",offset="4",
34340 inst="mov 2, %o0"@},
34341 @{address="0x000107c4",func-name="main",offset="8",
34342 inst="sethi %hi(0x11800), %o2"@},
34344 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
34345 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
34349 Disassemble 3 instructions from the start of @code{main}:
34353 -data-disassemble -f basics.c -l 32 -n 3 -- 0
34355 @{address="0x000107bc",func-name="main",offset="0",
34356 inst="save %sp, -112, %sp"@},
34357 @{address="0x000107c0",func-name="main",offset="4",
34358 inst="mov 2, %o0"@},
34359 @{address="0x000107c4",func-name="main",offset="8",
34360 inst="sethi %hi(0x11800), %o2"@}]
34364 Disassemble 3 instructions from the start of @code{main} in mixed mode:
34368 -data-disassemble -f basics.c -l 32 -n 3 -- 1
34370 src_and_asm_line=@{line="31",
34371 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34372 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34373 line_asm_insn=[@{address="0x000107bc",
34374 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
34375 src_and_asm_line=@{line="32",
34376 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
34377 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
34378 line_asm_insn=[@{address="0x000107c0",
34379 func-name="main",offset="4",inst="mov 2, %o0"@},
34380 @{address="0x000107c4",func-name="main",offset="8",
34381 inst="sethi %hi(0x11800), %o2"@}]@}]
34386 @subheading The @code{-data-evaluate-expression} Command
34387 @findex -data-evaluate-expression
34389 @subsubheading Synopsis
34392 -data-evaluate-expression @var{expr}
34395 Evaluate @var{expr} as an expression. The expression could contain an
34396 inferior function call. The function call will execute synchronously.
34397 If the expression contains spaces, it must be enclosed in double quotes.
34399 @subsubheading @value{GDBN} Command
34401 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
34402 @samp{call}. In @code{gdbtk} only, there's a corresponding
34403 @samp{gdb_eval} command.
34405 @subsubheading Example
34407 In the following example, the numbers that precede the commands are the
34408 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
34409 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
34413 211-data-evaluate-expression A
34416 311-data-evaluate-expression &A
34417 311^done,value="0xefffeb7c"
34419 411-data-evaluate-expression A+3
34422 511-data-evaluate-expression "A + 3"
34428 @subheading The @code{-data-list-changed-registers} Command
34429 @findex -data-list-changed-registers
34431 @subsubheading Synopsis
34434 -data-list-changed-registers
34437 Display a list of the registers that have changed.
34439 @subsubheading @value{GDBN} Command
34441 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
34442 has the corresponding command @samp{gdb_changed_register_list}.
34444 @subsubheading Example
34446 On a PPC MBX board:
34454 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
34455 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
34456 line="5",arch="powerpc"@}
34458 -data-list-changed-registers
34459 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
34460 "10","11","13","14","15","16","17","18","19","20","21","22","23",
34461 "24","25","26","27","28","30","31","64","65","66","67","69"]
34466 @subheading The @code{-data-list-register-names} Command
34467 @findex -data-list-register-names
34469 @subsubheading Synopsis
34472 -data-list-register-names [ ( @var{regno} )+ ]
34475 Show a list of register names for the current target. If no arguments
34476 are given, it shows a list of the names of all the registers. If
34477 integer numbers are given as arguments, it will print a list of the
34478 names of the registers corresponding to the arguments. To ensure
34479 consistency between a register name and its number, the output list may
34480 include empty register names.
34482 @subsubheading @value{GDBN} Command
34484 @value{GDBN} does not have a command which corresponds to
34485 @samp{-data-list-register-names}. In @code{gdbtk} there is a
34486 corresponding command @samp{gdb_regnames}.
34488 @subsubheading Example
34490 For the PPC MBX board:
34493 -data-list-register-names
34494 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
34495 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
34496 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
34497 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
34498 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
34499 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
34500 "", "pc","ps","cr","lr","ctr","xer"]
34502 -data-list-register-names 1 2 3
34503 ^done,register-names=["r1","r2","r3"]
34507 @subheading The @code{-data-list-register-values} Command
34508 @findex -data-list-register-values
34510 @subsubheading Synopsis
34513 -data-list-register-values
34514 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
34517 Display the registers' contents. The format according to which the
34518 registers' contents are to be returned is given by @var{fmt}, followed
34519 by an optional list of numbers specifying the registers to display. A
34520 missing list of numbers indicates that the contents of all the
34521 registers must be returned. The @code{--skip-unavailable} option
34522 indicates that only the available registers are to be returned.
34524 Allowed formats for @var{fmt} are:
34541 @subsubheading @value{GDBN} Command
34543 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
34544 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
34546 @subsubheading Example
34548 For a PPC MBX board (note: line breaks are for readability only, they
34549 don't appear in the actual output):
34553 -data-list-register-values r 64 65
34554 ^done,register-values=[@{number="64",value="0xfe00a300"@},
34555 @{number="65",value="0x00029002"@}]
34557 -data-list-register-values x
34558 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
34559 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
34560 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
34561 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
34562 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
34563 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
34564 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
34565 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
34566 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
34567 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
34568 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
34569 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
34570 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
34571 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
34572 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
34573 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
34574 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
34575 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
34576 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
34577 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
34578 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
34579 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
34580 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
34581 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
34582 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
34583 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
34584 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
34585 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
34586 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
34587 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
34588 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
34589 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
34590 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
34591 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
34592 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
34593 @{number="69",value="0x20002b03"@}]
34598 @subheading The @code{-data-read-memory} Command
34599 @findex -data-read-memory
34601 This command is deprecated, use @code{-data-read-memory-bytes} instead.
34603 @subsubheading Synopsis
34606 -data-read-memory [ -o @var{byte-offset} ]
34607 @var{address} @var{word-format} @var{word-size}
34608 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
34615 @item @var{address}
34616 An expression specifying the address of the first memory word to be
34617 read. Complex expressions containing embedded white space should be
34618 quoted using the C convention.
34620 @item @var{word-format}
34621 The format to be used to print the memory words. The notation is the
34622 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
34625 @item @var{word-size}
34626 The size of each memory word in bytes.
34628 @item @var{nr-rows}
34629 The number of rows in the output table.
34631 @item @var{nr-cols}
34632 The number of columns in the output table.
34635 If present, indicates that each row should include an @sc{ascii} dump. The
34636 value of @var{aschar} is used as a padding character when a byte is not a
34637 member of the printable @sc{ascii} character set (printable @sc{ascii}
34638 characters are those whose code is between 32 and 126, inclusively).
34640 @item @var{byte-offset}
34641 An offset to add to the @var{address} before fetching memory.
34644 This command displays memory contents as a table of @var{nr-rows} by
34645 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
34646 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
34647 (returned as @samp{total-bytes}). Should less than the requested number
34648 of bytes be returned by the target, the missing words are identified
34649 using @samp{N/A}. The number of bytes read from the target is returned
34650 in @samp{nr-bytes} and the starting address used to read memory in
34653 The address of the next/previous row or page is available in
34654 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
34657 @subsubheading @value{GDBN} Command
34659 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
34660 @samp{gdb_get_mem} memory read command.
34662 @subsubheading Example
34664 Read six bytes of memory starting at @code{bytes+6} but then offset by
34665 @code{-6} bytes. Format as three rows of two columns. One byte per
34666 word. Display each word in hex.
34670 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
34671 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
34672 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
34673 prev-page="0x0000138a",memory=[
34674 @{addr="0x00001390",data=["0x00","0x01"]@},
34675 @{addr="0x00001392",data=["0x02","0x03"]@},
34676 @{addr="0x00001394",data=["0x04","0x05"]@}]
34680 Read two bytes of memory starting at address @code{shorts + 64} and
34681 display as a single word formatted in decimal.
34685 5-data-read-memory shorts+64 d 2 1 1
34686 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
34687 next-row="0x00001512",prev-row="0x0000150e",
34688 next-page="0x00001512",prev-page="0x0000150e",memory=[
34689 @{addr="0x00001510",data=["128"]@}]
34693 Read thirty two bytes of memory starting at @code{bytes+16} and format
34694 as eight rows of four columns. Include a string encoding with @samp{x}
34695 used as the non-printable character.
34699 4-data-read-memory bytes+16 x 1 8 4 x
34700 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
34701 next-row="0x000013c0",prev-row="0x0000139c",
34702 next-page="0x000013c0",prev-page="0x00001380",memory=[
34703 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
34704 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
34705 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
34706 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
34707 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
34708 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
34709 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
34710 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
34714 @subheading The @code{-data-read-memory-bytes} Command
34715 @findex -data-read-memory-bytes
34717 @subsubheading Synopsis
34720 -data-read-memory-bytes [ -o @var{offset} ]
34721 @var{address} @var{count}
34728 @item @var{address}
34729 An expression specifying the address of the first addressable memory unit
34730 to be read. Complex expressions containing embedded white space should be
34731 quoted using the C convention.
34734 The number of addressable memory units to read. This should be an integer
34738 The offset relative to @var{address} at which to start reading. This
34739 should be an integer literal. This option is provided so that a frontend
34740 is not required to first evaluate address and then perform address
34741 arithmetics itself.
34745 This command attempts to read all accessible memory regions in the
34746 specified range. First, all regions marked as unreadable in the memory
34747 map (if one is defined) will be skipped. @xref{Memory Region
34748 Attributes}. Second, @value{GDBN} will attempt to read the remaining
34749 regions. For each one, if reading full region results in an errors,
34750 @value{GDBN} will try to read a subset of the region.
34752 In general, every single memory unit in the region may be readable or not,
34753 and the only way to read every readable unit is to try a read at
34754 every address, which is not practical. Therefore, @value{GDBN} will
34755 attempt to read all accessible memory units at either beginning or the end
34756 of the region, using a binary division scheme. This heuristic works
34757 well for reading across a memory map boundary. Note that if a region
34758 has a readable range that is neither at the beginning or the end,
34759 @value{GDBN} will not read it.
34761 The result record (@pxref{GDB/MI Result Records}) that is output of
34762 the command includes a field named @samp{memory} whose content is a
34763 list of tuples. Each tuple represent a successfully read memory block
34764 and has the following fields:
34768 The start address of the memory block, as hexadecimal literal.
34771 The end address of the memory block, as hexadecimal literal.
34774 The offset of the memory block, as hexadecimal literal, relative to
34775 the start address passed to @code{-data-read-memory-bytes}.
34778 The contents of the memory block, in hex.
34784 @subsubheading @value{GDBN} Command
34786 The corresponding @value{GDBN} command is @samp{x}.
34788 @subsubheading Example
34792 -data-read-memory-bytes &a 10
34793 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
34795 contents="01000000020000000300"@}]
34800 @subheading The @code{-data-write-memory-bytes} Command
34801 @findex -data-write-memory-bytes
34803 @subsubheading Synopsis
34806 -data-write-memory-bytes @var{address} @var{contents}
34807 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
34814 @item @var{address}
34815 An expression specifying the address of the first addressable memory unit
34816 to be written. Complex expressions containing embedded white space should
34817 be quoted using the C convention.
34819 @item @var{contents}
34820 The hex-encoded data to write. It is an error if @var{contents} does
34821 not represent an integral number of addressable memory units.
34824 Optional argument indicating the number of addressable memory units to be
34825 written. If @var{count} is greater than @var{contents}' length,
34826 @value{GDBN} will repeatedly write @var{contents} until it fills
34827 @var{count} memory units.
34831 @subsubheading @value{GDBN} Command
34833 There's no corresponding @value{GDBN} command.
34835 @subsubheading Example
34839 -data-write-memory-bytes &a "aabbccdd"
34846 -data-write-memory-bytes &a "aabbccdd" 16e
34851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34852 @node GDB/MI Tracepoint Commands
34853 @section @sc{gdb/mi} Tracepoint Commands
34855 The commands defined in this section implement MI support for
34856 tracepoints. For detailed introduction, see @ref{Tracepoints}.
34858 @subheading The @code{-trace-find} Command
34859 @findex -trace-find
34861 @subsubheading Synopsis
34864 -trace-find @var{mode} [@var{parameters}@dots{}]
34867 Find a trace frame using criteria defined by @var{mode} and
34868 @var{parameters}. The following table lists permissible
34869 modes and their parameters. For details of operation, see @ref{tfind}.
34874 No parameters are required. Stops examining trace frames.
34877 An integer is required as parameter. Selects tracepoint frame with
34880 @item tracepoint-number
34881 An integer is required as parameter. Finds next
34882 trace frame that corresponds to tracepoint with the specified number.
34885 An address is required as parameter. Finds
34886 next trace frame that corresponds to any tracepoint at the specified
34889 @item pc-inside-range
34890 Two addresses are required as parameters. Finds next trace
34891 frame that corresponds to a tracepoint at an address inside the
34892 specified range. Both bounds are considered to be inside the range.
34894 @item pc-outside-range
34895 Two addresses are required as parameters. Finds
34896 next trace frame that corresponds to a tracepoint at an address outside
34897 the specified range. Both bounds are considered to be inside the range.
34900 Line specification is required as parameter. @xref{Specify Location}.
34901 Finds next trace frame that corresponds to a tracepoint at
34902 the specified location.
34906 If @samp{none} was passed as @var{mode}, the response does not
34907 have fields. Otherwise, the response may have the following fields:
34911 This field has either @samp{0} or @samp{1} as the value, depending
34912 on whether a matching tracepoint was found.
34915 The index of the found traceframe. This field is present iff
34916 the @samp{found} field has value of @samp{1}.
34919 The index of the found tracepoint. This field is present iff
34920 the @samp{found} field has value of @samp{1}.
34923 The information about the frame corresponding to the found trace
34924 frame. This field is present only if a trace frame was found.
34925 @xref{GDB/MI Frame Information}, for description of this field.
34929 @subsubheading @value{GDBN} Command
34931 The corresponding @value{GDBN} command is @samp{tfind}.
34933 @subheading -trace-define-variable
34934 @findex -trace-define-variable
34936 @subsubheading Synopsis
34939 -trace-define-variable @var{name} [ @var{value} ]
34942 Create trace variable @var{name} if it does not exist. If
34943 @var{value} is specified, sets the initial value of the specified
34944 trace variable to that value. Note that the @var{name} should start
34945 with the @samp{$} character.
34947 @subsubheading @value{GDBN} Command
34949 The corresponding @value{GDBN} command is @samp{tvariable}.
34951 @subheading The @code{-trace-frame-collected} Command
34952 @findex -trace-frame-collected
34954 @subsubheading Synopsis
34957 -trace-frame-collected
34958 [--var-print-values @var{var_pval}]
34959 [--comp-print-values @var{comp_pval}]
34960 [--registers-format @var{regformat}]
34961 [--memory-contents]
34964 This command returns the set of collected objects, register names,
34965 trace state variable names, memory ranges and computed expressions
34966 that have been collected at a particular trace frame. The optional
34967 parameters to the command affect the output format in different ways.
34968 See the output description table below for more details.
34970 The reported names can be used in the normal manner to create
34971 varobjs and inspect the objects themselves. The items returned by
34972 this command are categorized so that it is clear which is a variable,
34973 which is a register, which is a trace state variable, which is a
34974 memory range and which is a computed expression.
34976 For instance, if the actions were
34978 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
34979 collect *(int*)0xaf02bef0@@40
34983 the object collected in its entirety would be @code{myVar}. The
34984 object @code{myArray} would be partially collected, because only the
34985 element at index @code{myIndex} would be collected. The remaining
34986 objects would be computed expressions.
34988 An example output would be:
34992 -trace-frame-collected
34994 explicit-variables=[@{name="myVar",value="1"@}],
34995 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
34996 @{name="myObj.field",value="0"@},
34997 @{name="myPtr->field",value="1"@},
34998 @{name="myCount + 2",value="3"@},
34999 @{name="$tvar1 + 1",value="43970027"@}],
35000 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
35001 @{number="1",value="0x0"@},
35002 @{number="2",value="0x4"@},
35004 @{number="125",value="0x0"@}],
35005 tvars=[@{name="$tvar1",current="43970026"@}],
35006 memory=[@{address="0x0000000000602264",length="4"@},
35007 @{address="0x0000000000615bc0",length="4"@}]
35014 @item explicit-variables
35015 The set of objects that have been collected in their entirety (as
35016 opposed to collecting just a few elements of an array or a few struct
35017 members). For each object, its name and value are printed.
35018 The @code{--var-print-values} option affects how or whether the value
35019 field is output. If @var{var_pval} is 0, then print only the names;
35020 if it is 1, print also their values; and if it is 2, print the name,
35021 type and value for simple data types, and the name and type for
35022 arrays, structures and unions.
35024 @item computed-expressions
35025 The set of computed expressions that have been collected at the
35026 current trace frame. The @code{--comp-print-values} option affects
35027 this set like the @code{--var-print-values} option affects the
35028 @code{explicit-variables} set. See above.
35031 The registers that have been collected at the current trace frame.
35032 For each register collected, the name and current value are returned.
35033 The value is formatted according to the @code{--registers-format}
35034 option. See the @command{-data-list-register-values} command for a
35035 list of the allowed formats. The default is @samp{x}.
35038 The trace state variables that have been collected at the current
35039 trace frame. For each trace state variable collected, the name and
35040 current value are returned.
35043 The set of memory ranges that have been collected at the current trace
35044 frame. Its content is a list of tuples. Each tuple represents a
35045 collected memory range and has the following fields:
35049 The start address of the memory range, as hexadecimal literal.
35052 The length of the memory range, as decimal literal.
35055 The contents of the memory block, in hex. This field is only present
35056 if the @code{--memory-contents} option is specified.
35062 @subsubheading @value{GDBN} Command
35064 There is no corresponding @value{GDBN} command.
35066 @subsubheading Example
35068 @subheading -trace-list-variables
35069 @findex -trace-list-variables
35071 @subsubheading Synopsis
35074 -trace-list-variables
35077 Return a table of all defined trace variables. Each element of the
35078 table has the following fields:
35082 The name of the trace variable. This field is always present.
35085 The initial value. This is a 64-bit signed integer. This
35086 field is always present.
35089 The value the trace variable has at the moment. This is a 64-bit
35090 signed integer. This field is absent iff current value is
35091 not defined, for example if the trace was never run, or is
35096 @subsubheading @value{GDBN} Command
35098 The corresponding @value{GDBN} command is @samp{tvariables}.
35100 @subsubheading Example
35104 -trace-list-variables
35105 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
35106 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
35107 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
35108 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
35109 body=[variable=@{name="$trace_timestamp",initial="0"@}
35110 variable=@{name="$foo",initial="10",current="15"@}]@}
35114 @subheading -trace-save
35115 @findex -trace-save
35117 @subsubheading Synopsis
35120 -trace-save [ -r ] [ -ctf ] @var{filename}
35123 Saves the collected trace data to @var{filename}. Without the
35124 @samp{-r} option, the data is downloaded from the target and saved
35125 in a local file. With the @samp{-r} option the target is asked
35126 to perform the save.
35128 By default, this command will save the trace in the tfile format. You can
35129 supply the optional @samp{-ctf} argument to save it the CTF format. See
35130 @ref{Trace Files} for more information about CTF.
35132 @subsubheading @value{GDBN} Command
35134 The corresponding @value{GDBN} command is @samp{tsave}.
35137 @subheading -trace-start
35138 @findex -trace-start
35140 @subsubheading Synopsis
35146 Starts a tracing experiment. The result of this command does not
35149 @subsubheading @value{GDBN} Command
35151 The corresponding @value{GDBN} command is @samp{tstart}.
35153 @subheading -trace-status
35154 @findex -trace-status
35156 @subsubheading Synopsis
35162 Obtains the status of a tracing experiment. The result may include
35163 the following fields:
35168 May have a value of either @samp{0}, when no tracing operations are
35169 supported, @samp{1}, when all tracing operations are supported, or
35170 @samp{file} when examining trace file. In the latter case, examining
35171 of trace frame is possible but new tracing experiement cannot be
35172 started. This field is always present.
35175 May have a value of either @samp{0} or @samp{1} depending on whether
35176 tracing experiement is in progress on target. This field is present
35177 if @samp{supported} field is not @samp{0}.
35180 Report the reason why the tracing was stopped last time. This field
35181 may be absent iff tracing was never stopped on target yet. The
35182 value of @samp{request} means the tracing was stopped as result of
35183 the @code{-trace-stop} command. The value of @samp{overflow} means
35184 the tracing buffer is full. The value of @samp{disconnection} means
35185 tracing was automatically stopped when @value{GDBN} has disconnected.
35186 The value of @samp{passcount} means tracing was stopped when a
35187 tracepoint was passed a maximal number of times for that tracepoint.
35188 This field is present if @samp{supported} field is not @samp{0}.
35190 @item stopping-tracepoint
35191 The number of tracepoint whose passcount as exceeded. This field is
35192 present iff the @samp{stop-reason} field has the value of
35196 @itemx frames-created
35197 The @samp{frames} field is a count of the total number of trace frames
35198 in the trace buffer, while @samp{frames-created} is the total created
35199 during the run, including ones that were discarded, such as when a
35200 circular trace buffer filled up. Both fields are optional.
35204 These fields tell the current size of the tracing buffer and the
35205 remaining space. These fields are optional.
35208 The value of the circular trace buffer flag. @code{1} means that the
35209 trace buffer is circular and old trace frames will be discarded if
35210 necessary to make room, @code{0} means that the trace buffer is linear
35214 The value of the disconnected tracing flag. @code{1} means that
35215 tracing will continue after @value{GDBN} disconnects, @code{0} means
35216 that the trace run will stop.
35219 The filename of the trace file being examined. This field is
35220 optional, and only present when examining a trace file.
35224 @subsubheading @value{GDBN} Command
35226 The corresponding @value{GDBN} command is @samp{tstatus}.
35228 @subheading -trace-stop
35229 @findex -trace-stop
35231 @subsubheading Synopsis
35237 Stops a tracing experiment. The result of this command has the same
35238 fields as @code{-trace-status}, except that the @samp{supported} and
35239 @samp{running} fields are not output.
35241 @subsubheading @value{GDBN} Command
35243 The corresponding @value{GDBN} command is @samp{tstop}.
35246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35247 @node GDB/MI Symbol Query
35248 @section @sc{gdb/mi} Symbol Query Commands
35252 @subheading The @code{-symbol-info-address} Command
35253 @findex -symbol-info-address
35255 @subsubheading Synopsis
35258 -symbol-info-address @var{symbol}
35261 Describe where @var{symbol} is stored.
35263 @subsubheading @value{GDBN} Command
35265 The corresponding @value{GDBN} command is @samp{info address}.
35267 @subsubheading Example
35271 @subheading The @code{-symbol-info-file} Command
35272 @findex -symbol-info-file
35274 @subsubheading Synopsis
35280 Show the file for the symbol.
35282 @subsubheading @value{GDBN} Command
35284 There's no equivalent @value{GDBN} command. @code{gdbtk} has
35285 @samp{gdb_find_file}.
35287 @subsubheading Example
35291 @subheading The @code{-symbol-info-functions} Command
35292 @findex -symbol-info-functions
35293 @anchor{-symbol-info-functions}
35295 @subsubheading Synopsis
35298 -symbol-info-functions [--include-nondebug]
35299 [--type @var{type_regexp}]
35300 [--name @var{name_regexp}]
35301 [--max-results @var{limit}]
35305 Return a list containing the names and types for all global functions
35306 taken from the debug information. The functions are grouped by source
35307 file, and shown with the line number on which each function is
35310 The @code{--include-nondebug} option causes the output to include
35311 code symbols from the symbol table.
35313 The options @code{--type} and @code{--name} allow the symbols returned
35314 to be filtered based on either the name of the function, or the type
35315 signature of the function.
35317 The option @code{--max-results} restricts the command to return no
35318 more than @var{limit} results. If exactly @var{limit} results are
35319 returned then there might be additional results available if a higher
35322 @subsubheading @value{GDBN} Command
35324 The corresponding @value{GDBN} command is @samp{info functions}.
35326 @subsubheading Example
35330 -symbol-info-functions
35333 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35334 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35335 symbols=[@{line="36", name="f4", type="void (int *)",
35336 description="void f4(int *);"@},
35337 @{line="42", name="main", type="int ()",
35338 description="int main();"@},
35339 @{line="30", name="f1", type="my_int_t (int, int)",
35340 description="static my_int_t f1(int, int);"@}]@},
35341 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35342 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35343 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35344 description="float f2(another_float_t);"@},
35345 @{line="39", name="f3", type="int (another_int_t)",
35346 description="int f3(another_int_t);"@},
35347 @{line="27", name="f1", type="another_float_t (int)",
35348 description="static another_float_t f1(int);"@}]@}]@}
35352 -symbol-info-functions --name f1
35355 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35356 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35357 symbols=[@{line="30", name="f1", type="my_int_t (int, int)",
35358 description="static my_int_t f1(int, int);"@}]@},
35359 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35360 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35361 symbols=[@{line="27", name="f1", type="another_float_t (int)",
35362 description="static another_float_t f1(int);"@}]@}]@}
35366 -symbol-info-functions --type void
35369 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35370 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35371 symbols=[@{line="36", name="f4", type="void (int *)",
35372 description="void f4(int *);"@}]@}]@}
35376 -symbol-info-functions --include-nondebug
35379 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35380 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35381 symbols=[@{line="36", name="f4", type="void (int *)",
35382 description="void f4(int *);"@},
35383 @{line="42", name="main", type="int ()",
35384 description="int main();"@},
35385 @{line="30", name="f1", type="my_int_t (int, int)",
35386 description="static my_int_t f1(int, int);"@}]@},
35387 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35388 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35389 symbols=[@{line="33", name="f2", type="float (another_float_t)",
35390 description="float f2(another_float_t);"@},
35391 @{line="39", name="f3", type="int (another_int_t)",
35392 description="int f3(another_int_t);"@},
35393 @{line="27", name="f1", type="another_float_t (int)",
35394 description="static another_float_t f1(int);"@}]@}],
35396 [@{address="0x0000000000400398",name="_init"@},
35397 @{address="0x00000000004003b0",name="_start"@},
35403 @subheading The @code{-symbol-info-module-functions} Command
35404 @findex -symbol-info-module-functions
35405 @anchor{-symbol-info-module-functions}
35407 @subsubheading Synopsis
35410 -symbol-info-module-functions [--module @var{module_regexp}]
35411 [--name @var{name_regexp}]
35412 [--type @var{type_regexp}]
35416 Return a list containing the names of all known functions within all
35417 know Fortran modules. The functions are grouped by source file and
35418 containing module, and shown with the line number on which each
35419 function is defined.
35421 The option @code{--module} only returns results for modules matching
35422 @var{module_regexp}. The option @code{--name} only returns functions
35423 whose name matches @var{name_regexp}, and @code{--type} only returns
35424 functions whose type matches @var{type_regexp}.
35426 @subsubheading @value{GDBN} Command
35428 The corresponding @value{GDBN} command is @samp{info module functions}.
35430 @subsubheading Example
35435 -symbol-info-module-functions
35438 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35439 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35440 symbols=[@{line="21",name="mod1::check_all",type="void (void)",
35441 description="void mod1::check_all(void);"@}]@}]@},
35443 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35444 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35445 symbols=[@{line="30",name="mod2::check_var_i",type="void (void)",
35446 description="void mod2::check_var_i(void);"@}]@}]@},
35448 files=[@{filename="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35449 fullname="/projec/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35450 symbols=[@{line="21",name="mod3::check_all",type="void (void)",
35451 description="void mod3::check_all(void);"@},
35452 @{line="27",name="mod3::check_mod2",type="void (void)",
35453 description="void mod3::check_mod2(void);"@}]@}]@},
35454 @{module="modmany",
35455 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35456 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35457 symbols=[@{line="35",name="modmany::check_some",type="void (void)",
35458 description="void modmany::check_some(void);"@}]@}]@},
35460 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35461 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35462 symbols=[@{line="44",name="moduse::check_all",type="void (void)",
35463 description="void moduse::check_all(void);"@},
35464 @{line="49",name="moduse::check_var_x",type="void (void)",
35465 description="void moduse::check_var_x(void);"@}]@}]@}]
35469 @subheading The @code{-symbol-info-module-variables} Command
35470 @findex -symbol-info-module-variables
35471 @anchor{-symbol-info-module-variables}
35473 @subsubheading Synopsis
35476 -symbol-info-module-variables [--module @var{module_regexp}]
35477 [--name @var{name_regexp}]
35478 [--type @var{type_regexp}]
35482 Return a list containing the names of all known variables within all
35483 know Fortran modules. The variables are grouped by source file and
35484 containing module, and shown with the line number on which each
35485 variable is defined.
35487 The option @code{--module} only returns results for modules matching
35488 @var{module_regexp}. The option @code{--name} only returns variables
35489 whose name matches @var{name_regexp}, and @code{--type} only returns
35490 variables whose type matches @var{type_regexp}.
35492 @subsubheading @value{GDBN} Command
35494 The corresponding @value{GDBN} command is @samp{info module variables}.
35496 @subsubheading Example
35501 -symbol-info-module-variables
35504 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35505 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35506 symbols=[@{line="18",name="mod1::var_const",type="integer(kind=4)",
35507 description="integer(kind=4) mod1::var_const;"@},
35508 @{line="17",name="mod1::var_i",type="integer(kind=4)",
35509 description="integer(kind=4) mod1::var_i;"@}]@}]@},
35511 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35512 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35513 symbols=[@{line="28",name="mod2::var_i",type="integer(kind=4)",
35514 description="integer(kind=4) mod2::var_i;"@}]@}]@},
35516 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35517 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35518 symbols=[@{line="18",name="mod3::mod1",type="integer(kind=4)",
35519 description="integer(kind=4) mod3::mod1;"@},
35520 @{line="17",name="mod3::mod2",type="integer(kind=4)",
35521 description="integer(kind=4) mod3::mod2;"@},
35522 @{line="19",name="mod3::var_i",type="integer(kind=4)",
35523 description="integer(kind=4) mod3::var_i;"@}]@}]@},
35524 @{module="modmany",
35525 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35526 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35527 symbols=[@{line="33",name="modmany::var_a",type="integer(kind=4)",
35528 description="integer(kind=4) modmany::var_a;"@},
35529 @{line="33",name="modmany::var_b",type="integer(kind=4)",
35530 description="integer(kind=4) modmany::var_b;"@},
35531 @{line="33",name="modmany::var_c",type="integer(kind=4)",
35532 description="integer(kind=4) modmany::var_c;"@},
35533 @{line="33",name="modmany::var_i",type="integer(kind=4)",
35534 description="integer(kind=4) modmany::var_i;"@}]@}]@},
35536 files=[@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35537 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35538 symbols=[@{line="42",name="moduse::var_x",type="integer(kind=4)",
35539 description="integer(kind=4) moduse::var_x;"@},
35540 @{line="42",name="moduse::var_y",type="integer(kind=4)",
35541 description="integer(kind=4) moduse::var_y;"@}]@}]@}]
35545 @subheading The @code{-symbol-info-modules} Command
35546 @findex -symbol-info-modules
35547 @anchor{-symbol-info-modules}
35549 @subsubheading Synopsis
35552 -symbol-info-modules [--name @var{name_regexp}]
35553 [--max-results @var{limit}]
35558 Return a list containing the names of all known Fortran modules. The
35559 modules are grouped by source file, and shown with the line number on
35560 which each modules is defined.
35562 The option @code{--name} allows the modules returned to be filtered
35563 based the name of the module.
35565 The option @code{--max-results} restricts the command to return no
35566 more than @var{limit} results. If exactly @var{limit} results are
35567 returned then there might be additional results available if a higher
35570 @subsubheading @value{GDBN} Command
35572 The corresponding @value{GDBN} command is @samp{info modules}.
35574 @subsubheading Example
35578 -symbol-info-modules
35581 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35582 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35583 symbols=[@{line="16",name="mod1"@},
35584 @{line="22",name="mod2"@}]@},
35585 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35586 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35587 symbols=[@{line="16",name="mod3"@},
35588 @{line="22",name="modmany"@},
35589 @{line="26",name="moduse"@}]@}]@}
35593 -symbol-info-modules --name mod[123]
35596 [@{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35597 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules-2.f90",
35598 symbols=[@{line="16",name="mod1"@},
35599 @{line="22",name="mod2"@}]@},
35600 @{filename="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35601 fullname="/project/gdb/testsuite/gdb.mi/mi-fortran-modules.f90",
35602 symbols=[@{line="16",name="mod3"@}]@}]@}
35606 @subheading The @code{-symbol-info-types} Command
35607 @findex -symbol-info-types
35608 @anchor{-symbol-info-types}
35610 @subsubheading Synopsis
35613 -symbol-info-types [--name @var{name_regexp}]
35614 [--max-results @var{limit}]
35619 Return a list of all defined types. The types are grouped by source
35620 file, and shown with the line number on which each user defined type
35621 is defined. Some base types are not defined in the source code but
35622 are added to the debug information by the compiler, for example
35623 @code{int}, @code{float}, etc.; these types do not have an associated
35626 The option @code{--name} allows the list of types returned to be
35629 The option @code{--max-results} restricts the command to return no
35630 more than @var{limit} results. If exactly @var{limit} results are
35631 returned then there might be additional results available if a higher
35634 @subsubheading @value{GDBN} Command
35636 The corresponding @value{GDBN} command is @samp{info types}.
35638 @subsubheading Example
35645 [@{filename="gdb.mi/mi-sym-info-1.c",
35646 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35647 symbols=[@{name="float"@},
35649 @{line="27",name="typedef int my_int_t;"@}]@},
35650 @{filename="gdb.mi/mi-sym-info-2.c",
35651 fullname="/project/gdb.mi/mi-sym-info-2.c",
35652 symbols=[@{line="24",name="typedef float another_float_t;"@},
35653 @{line="23",name="typedef int another_int_t;"@},
35655 @{name="int"@}]@}]@}
35659 -symbol-info-types --name _int_
35662 [@{filename="gdb.mi/mi-sym-info-1.c",
35663 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35664 symbols=[@{line="27",name="typedef int my_int_t;"@}]@},
35665 @{filename="gdb.mi/mi-sym-info-2.c",
35666 fullname="/project/gdb.mi/mi-sym-info-2.c",
35667 symbols=[@{line="23",name="typedef int another_int_t;"@}]@}]@}
35671 @subheading The @code{-symbol-info-variables} Command
35672 @findex -symbol-info-variables
35673 @anchor{-symbol-info-variables}
35675 @subsubheading Synopsis
35678 -symbol-info-variables [--include-nondebug]
35679 [--type @var{type_regexp}]
35680 [--name @var{name_regexp}]
35681 [--max-results @var{limit}]
35686 Return a list containing the names and types for all global variables
35687 taken from the debug information. The variables are grouped by source
35688 file, and shown with the line number on which each variable is
35691 The @code{--include-nondebug} option causes the output to include
35692 data symbols from the symbol table.
35694 The options @code{--type} and @code{--name} allow the symbols returned
35695 to be filtered based on either the name of the variable, or the type
35698 The option @code{--max-results} restricts the command to return no
35699 more than @var{limit} results. If exactly @var{limit} results are
35700 returned then there might be additional results available if a higher
35703 @subsubheading @value{GDBN} Command
35705 The corresponding @value{GDBN} command is @samp{info variables}.
35707 @subsubheading Example
35711 -symbol-info-variables
35714 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35715 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35716 symbols=[@{line="25",name="global_f1",type="float",
35717 description="static float global_f1;"@},
35718 @{line="24",name="global_i1",type="int",
35719 description="static int global_i1;"@}]@},
35720 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35721 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35722 symbols=[@{line="21",name="global_f2",type="int",
35723 description="int global_f2;"@},
35724 @{line="20",name="global_i2",type="int",
35725 description="int global_i2;"@},
35726 @{line="19",name="global_f1",type="float",
35727 description="static float global_f1;"@},
35728 @{line="18",name="global_i1",type="int",
35729 description="static int global_i1;"@}]@}]@}
35733 -symbol-info-variables --name f1
35736 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35737 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35738 symbols=[@{line="25",name="global_f1",type="float",
35739 description="static float global_f1;"@}]@},
35740 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35741 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35742 symbols=[@{line="19",name="global_f1",type="float",
35743 description="static float global_f1;"@}]@}]@}
35747 -symbol-info-variables --type float
35750 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35751 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35752 symbols=[@{line="25",name="global_f1",type="float",
35753 description="static float global_f1;"@}]@},
35754 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35755 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35756 symbols=[@{line="19",name="global_f1",type="float",
35757 description="static float global_f1;"@}]@}]@}
35761 -symbol-info-variables --include-nondebug
35764 [@{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35765 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-1.c",
35766 symbols=[@{line="25",name="global_f1",type="float",
35767 description="static float global_f1;"@},
35768 @{line="24",name="global_i1",type="int",
35769 description="static int global_i1;"@}]@},
35770 @{filename="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35771 fullname="/project/gdb/testsuite/gdb.mi/mi-sym-info-2.c",
35772 symbols=[@{line="21",name="global_f2",type="int",
35773 description="int global_f2;"@},
35774 @{line="20",name="global_i2",type="int",
35775 description="int global_i2;"@},
35776 @{line="19",name="global_f1",type="float",
35777 description="static float global_f1;"@},
35778 @{line="18",name="global_i1",type="int",
35779 description="static int global_i1;"@}]@}],
35781 [@{address="0x00000000004005d0",name="_IO_stdin_used"@},
35782 @{address="0x00000000004005d8",name="__dso_handle"@}
35789 @subheading The @code{-symbol-info-line} Command
35790 @findex -symbol-info-line
35792 @subsubheading Synopsis
35798 Show the core addresses of the code for a source line.
35800 @subsubheading @value{GDBN} Command
35802 The corresponding @value{GDBN} command is @samp{info line}.
35803 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
35805 @subsubheading Example
35809 @subheading The @code{-symbol-info-symbol} Command
35810 @findex -symbol-info-symbol
35812 @subsubheading Synopsis
35815 -symbol-info-symbol @var{addr}
35818 Describe what symbol is at location @var{addr}.
35820 @subsubheading @value{GDBN} Command
35822 The corresponding @value{GDBN} command is @samp{info symbol}.
35824 @subsubheading Example
35828 @subheading The @code{-symbol-list-functions} Command
35829 @findex -symbol-list-functions
35831 @subsubheading Synopsis
35834 -symbol-list-functions
35837 List the functions in the executable.
35839 @subsubheading @value{GDBN} Command
35841 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
35842 @samp{gdb_search} in @code{gdbtk}.
35844 @subsubheading Example
35849 @subheading The @code{-symbol-list-lines} Command
35850 @findex -symbol-list-lines
35852 @subsubheading Synopsis
35855 -symbol-list-lines @var{filename}
35858 Print the list of lines that contain code and their associated program
35859 addresses for the given source filename. The entries are sorted in
35860 ascending PC order.
35862 @subsubheading @value{GDBN} Command
35864 There is no corresponding @value{GDBN} command.
35866 @subsubheading Example
35869 -symbol-list-lines basics.c
35870 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
35876 @subheading The @code{-symbol-list-types} Command
35877 @findex -symbol-list-types
35879 @subsubheading Synopsis
35885 List all the type names.
35887 @subsubheading @value{GDBN} Command
35889 The corresponding commands are @samp{info types} in @value{GDBN},
35890 @samp{gdb_search} in @code{gdbtk}.
35892 @subsubheading Example
35896 @subheading The @code{-symbol-list-variables} Command
35897 @findex -symbol-list-variables
35899 @subsubheading Synopsis
35902 -symbol-list-variables
35905 List all the global and static variable names.
35907 @subsubheading @value{GDBN} Command
35909 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
35911 @subsubheading Example
35915 @subheading The @code{-symbol-locate} Command
35916 @findex -symbol-locate
35918 @subsubheading Synopsis
35924 @subsubheading @value{GDBN} Command
35926 @samp{gdb_loc} in @code{gdbtk}.
35928 @subsubheading Example
35932 @subheading The @code{-symbol-type} Command
35933 @findex -symbol-type
35935 @subsubheading Synopsis
35938 -symbol-type @var{variable}
35941 Show type of @var{variable}.
35943 @subsubheading @value{GDBN} Command
35945 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
35946 @samp{gdb_obj_variable}.
35948 @subsubheading Example
35953 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35954 @node GDB/MI File Commands
35955 @section @sc{gdb/mi} File Commands
35957 This section describes the GDB/MI commands to specify executable file names
35958 and to read in and obtain symbol table information.
35960 @subheading The @code{-file-exec-and-symbols} Command
35961 @findex -file-exec-and-symbols
35963 @subsubheading Synopsis
35966 -file-exec-and-symbols @var{file}
35969 Specify the executable file to be debugged. This file is the one from
35970 which the symbol table is also read. If no file is specified, the
35971 command clears the executable and symbol information. If breakpoints
35972 are set when using this command with no arguments, @value{GDBN} will produce
35973 error messages. Otherwise, no output is produced, except a completion
35976 @subsubheading @value{GDBN} Command
35978 The corresponding @value{GDBN} command is @samp{file}.
35980 @subsubheading Example
35984 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
35990 @subheading The @code{-file-exec-file} Command
35991 @findex -file-exec-file
35993 @subsubheading Synopsis
35996 -file-exec-file @var{file}
35999 Specify the executable file to be debugged. Unlike
36000 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
36001 from this file. If used without argument, @value{GDBN} clears the information
36002 about the executable file. No output is produced, except a completion
36005 @subsubheading @value{GDBN} Command
36007 The corresponding @value{GDBN} command is @samp{exec-file}.
36009 @subsubheading Example
36013 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36020 @subheading The @code{-file-list-exec-sections} Command
36021 @findex -file-list-exec-sections
36023 @subsubheading Synopsis
36026 -file-list-exec-sections
36029 List the sections of the current executable file.
36031 @subsubheading @value{GDBN} Command
36033 The @value{GDBN} command @samp{info file} shows, among the rest, the same
36034 information as this command. @code{gdbtk} has a corresponding command
36035 @samp{gdb_load_info}.
36037 @subsubheading Example
36042 @subheading The @code{-file-list-exec-source-file} Command
36043 @findex -file-list-exec-source-file
36045 @subsubheading Synopsis
36048 -file-list-exec-source-file
36051 List the line number, the current source file, and the absolute path
36052 to the current source file for the current executable. The macro
36053 information field has a value of @samp{1} or @samp{0} depending on
36054 whether or not the file includes preprocessor macro information.
36056 @subsubheading @value{GDBN} Command
36058 The @value{GDBN} equivalent is @samp{info source}
36060 @subsubheading Example
36064 123-file-list-exec-source-file
36065 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
36070 @subheading The @code{-file-list-exec-source-files} Command
36071 @kindex info sources
36072 @findex -file-list-exec-source-files
36074 @subsubheading Synopsis
36077 -file-list-exec-source-files @r{[} @var{--group-by-objfile} @r{]}
36078 @r{[} @var{--dirname} @r{|} @var{--basename} @r{]}
36080 @r{[} @var{regexp} @r{]}
36083 This command returns information about the source files @value{GDBN}
36084 knows about, it will output both the filename and fullname (absolute
36085 file name) of a source file, though the fullname can be elided if this
36086 information is not known to @value{GDBN}.
36088 With no arguments this command returns a list of source files. Each
36089 source file is represented by a tuple with the fields; @var{file},
36090 @var{fullname}, and @var{debug-fully-read}. The @var{file} is the
36091 display name for the file, while @var{fullname} is the absolute name
36092 of the file. The @var{fullname} field can be elided if the absolute
36093 name of the source file can't be computed. The field
36094 @var{debug-fully-read} will be a string, either @code{true} or
36095 @code{false}. When @code{true}, this indicates the full debug
36096 information for the compilation unit describing this file has been
36097 read in. When @code{false}, the full debug information has not yet
36098 been read in. While reading in the full debug information it is
36099 possible that @value{GDBN} could become aware of additional source
36102 The optional @var{regexp} can be used to filter the list of source
36103 files returned. The @var{regexp} will be matched against the full
36104 source file name. The matching is case-sensitive, except on operating
36105 systems that have case-insensitive filesystem (e.g.,
36106 MS-Windows). @samp{--} can be used before @var{regexp} to prevent
36107 @value{GDBN} interpreting @var{regexp} as a command option (e.g.@: if
36108 @var{regexp} starts with @samp{-}).
36110 If @code{--dirname} is provided, then @var{regexp} is matched only
36111 against the directory name of each source file. If @code{--basename}
36112 is provided, then @var{regexp} is matched against the basename of each
36113 source file. Only one of @code{--dirname} or @code{--basename} may be
36114 given, and if either is given then @var{regexp} is required.
36116 If @code{--group-by-objfile} is used then the format of the results is
36117 changed. The results will now be a list of tuples, with each tuple
36118 representing an object file (executable or shared library) loaded into
36119 @value{GDBN}. The fields of these tuples are; @var{filename},
36120 @var{debug-info}, and @var{sources}. The @var{filename} is the
36121 absolute name of the object file, @var{debug-info} is a string with
36122 one of the following values:
36126 This object file has no debug information.
36127 @item partially-read
36128 This object file has debug information, but it is not fully read in
36129 yet. When it is read in later, GDB might become aware of additional
36132 This object file has debug information, and this information is fully
36133 read into GDB. The list of source files is complete.
36136 The @var{sources} is a list or tuples, with each tuple describing a
36137 single source file with the same fields as described previously. The
36138 @var{sources} list can be empty for object files that have no debug
36141 @subsubheading @value{GDBN} Command
36143 The @value{GDBN} equivalent is @samp{info sources}.
36144 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
36146 @subsubheading Example
36149 -file-list-exec-source-files
36150 ^done,files=[@{file="foo.c",fullname="/home/foo.c",debug-fully-read="true"@},
36151 @{file="/home/bar.c",fullname="/home/bar.c",debug-fully-read="true"@},
36152 @{file="gdb_could_not_find_fullpath.c",debug-fully-read="true"@}]
36154 -file-list-exec-source-files
36155 ^done,files=[@{file="test.c",
36156 fullname="/tmp/info-sources/test.c",
36157 debug-fully-read="true"@},
36158 @{file="/usr/include/stdc-predef.h",
36159 fullname="/usr/include/stdc-predef.h",
36160 debug-fully-read="true"@},
36162 fullname="/tmp/info-sources/header.h",
36163 debug-fully-read="true"@},
36165 fullname="/tmp/info-sources/helper.c",
36166 debug-fully-read="true"@}]
36168 -file-list-exec-source-files -- \\.c
36169 ^done,files=[@{file="test.c",
36170 fullname="/tmp/info-sources/test.c",
36171 debug-fully-read="true"@},
36173 fullname="/tmp/info-sources/helper.c",
36174 debug-fully-read="true"@}]
36176 -file-list-exec-source-files --group-by-objfile
36177 ^done,files=[@{filename="/tmp/info-sources/test.x",
36178 debug-info="fully-read",
36179 sources=[@{file="test.c",
36180 fullname="/tmp/info-sources/test.c",
36181 debug-fully-read="true"@},
36182 @{file="/usr/include/stdc-predef.h",
36183 fullname="/usr/include/stdc-predef.h",
36184 debug-fully-read="true"@},
36186 fullname="/tmp/info-sources/header.h",
36187 debug-fully-read="true"@}]@},
36188 @{filename="/lib64/ld-linux-x86-64.so.2",
36191 @{filename="system-supplied DSO at 0x7ffff7fcf000",
36194 @{filename="/tmp/info-sources/libhelper.so",
36195 debug-info="fully-read",
36196 sources=[@{file="helper.c",
36197 fullname="/tmp/info-sources/helper.c",
36198 debug-fully-read="true"@},
36199 @{file="/usr/include/stdc-predef.h",
36200 fullname="/usr/include/stdc-predef.h",
36201 debug-fully-read="true"@},
36203 fullname="/tmp/info-sources/header.h",
36204 debug-fully-read="true"@}]@},
36205 @{filename="/lib64/libc.so.6",
36210 @subheading The @code{-file-list-shared-libraries} Command
36211 @findex -file-list-shared-libraries
36213 @subsubheading Synopsis
36216 -file-list-shared-libraries [ @var{regexp} ]
36219 List the shared libraries in the program.
36220 With a regular expression @var{regexp}, only those libraries whose
36221 names match @var{regexp} are listed.
36223 @subsubheading @value{GDBN} Command
36225 The corresponding @value{GDBN} command is @samp{info shared}. The fields
36226 have a similar meaning to the @code{=library-loaded} notification.
36227 The @code{ranges} field specifies the multiple segments belonging to this
36228 library. Each range has the following fields:
36232 The address defining the inclusive lower bound of the segment.
36234 The address defining the exclusive upper bound of the segment.
36237 @subsubheading Example
36240 -file-list-exec-source-files
36241 ^done,shared-libraries=[
36242 @{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"@}]@},
36243 @{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"@}]@}]
36249 @subheading The @code{-file-list-symbol-files} Command
36250 @findex -file-list-symbol-files
36252 @subsubheading Synopsis
36255 -file-list-symbol-files
36260 @subsubheading @value{GDBN} Command
36262 The corresponding @value{GDBN} command is @samp{info file} (part of it).
36264 @subsubheading Example
36269 @subheading The @code{-file-symbol-file} Command
36270 @findex -file-symbol-file
36272 @subsubheading Synopsis
36275 -file-symbol-file @var{file}
36278 Read symbol table info from the specified @var{file} argument. When
36279 used without arguments, clears @value{GDBN}'s symbol table info. No output is
36280 produced, except for a completion notification.
36282 @subsubheading @value{GDBN} Command
36284 The corresponding @value{GDBN} command is @samp{symbol-file}.
36286 @subsubheading Example
36290 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
36296 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36297 @node GDB/MI Memory Overlay Commands
36298 @section @sc{gdb/mi} Memory Overlay Commands
36300 The memory overlay commands are not implemented.
36302 @c @subheading -overlay-auto
36304 @c @subheading -overlay-list-mapping-state
36306 @c @subheading -overlay-list-overlays
36308 @c @subheading -overlay-map
36310 @c @subheading -overlay-off
36312 @c @subheading -overlay-on
36314 @c @subheading -overlay-unmap
36316 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36317 @node GDB/MI Signal Handling Commands
36318 @section @sc{gdb/mi} Signal Handling Commands
36320 Signal handling commands are not implemented.
36322 @c @subheading -signal-handle
36324 @c @subheading -signal-list-handle-actions
36326 @c @subheading -signal-list-signal-types
36330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36331 @node GDB/MI Target Manipulation
36332 @section @sc{gdb/mi} Target Manipulation Commands
36335 @subheading The @code{-target-attach} Command
36336 @findex -target-attach
36338 @subsubheading Synopsis
36341 -target-attach @var{pid} | @var{gid} | @var{file}
36344 Attach to a process @var{pid} or a file @var{file} outside of
36345 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
36346 group, the id previously returned by
36347 @samp{-list-thread-groups --available} must be used.
36349 @subsubheading @value{GDBN} Command
36351 The corresponding @value{GDBN} command is @samp{attach}.
36353 @subsubheading Example
36357 =thread-created,id="1"
36358 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
36364 @subheading The @code{-target-compare-sections} Command
36365 @findex -target-compare-sections
36367 @subsubheading Synopsis
36370 -target-compare-sections [ @var{section} ]
36373 Compare data of section @var{section} on target to the exec file.
36374 Without the argument, all sections are compared.
36376 @subsubheading @value{GDBN} Command
36378 The @value{GDBN} equivalent is @samp{compare-sections}.
36380 @subsubheading Example
36385 @subheading The @code{-target-detach} Command
36386 @findex -target-detach
36388 @subsubheading Synopsis
36391 -target-detach [ @var{pid} | @var{gid} ]
36394 Detach from the remote target which normally resumes its execution.
36395 If either @var{pid} or @var{gid} is specified, detaches from either
36396 the specified process, or specified thread group. There's no output.
36398 @subsubheading @value{GDBN} Command
36400 The corresponding @value{GDBN} command is @samp{detach}.
36402 @subsubheading Example
36412 @subheading The @code{-target-disconnect} Command
36413 @findex -target-disconnect
36415 @subsubheading Synopsis
36421 Disconnect from the remote target. There's no output and the target is
36422 generally not resumed.
36424 @subsubheading @value{GDBN} Command
36426 The corresponding @value{GDBN} command is @samp{disconnect}.
36428 @subsubheading Example
36438 @subheading The @code{-target-download} Command
36439 @findex -target-download
36441 @subsubheading Synopsis
36447 Loads the executable onto the remote target.
36448 It prints out an update message every half second, which includes the fields:
36452 The name of the section.
36454 The size of what has been sent so far for that section.
36456 The size of the section.
36458 The total size of what was sent so far (the current and the previous sections).
36460 The size of the overall executable to download.
36464 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
36465 @sc{gdb/mi} Output Syntax}).
36467 In addition, it prints the name and size of the sections, as they are
36468 downloaded. These messages include the following fields:
36472 The name of the section.
36474 The size of the section.
36476 The size of the overall executable to download.
36480 At the end, a summary is printed.
36482 @subsubheading @value{GDBN} Command
36484 The corresponding @value{GDBN} command is @samp{load}.
36486 @subsubheading Example
36488 Note: each status message appears on a single line. Here the messages
36489 have been broken down so that they can fit onto a page.
36494 +download,@{section=".text",section-size="6668",total-size="9880"@}
36495 +download,@{section=".text",section-sent="512",section-size="6668",
36496 total-sent="512",total-size="9880"@}
36497 +download,@{section=".text",section-sent="1024",section-size="6668",
36498 total-sent="1024",total-size="9880"@}
36499 +download,@{section=".text",section-sent="1536",section-size="6668",
36500 total-sent="1536",total-size="9880"@}
36501 +download,@{section=".text",section-sent="2048",section-size="6668",
36502 total-sent="2048",total-size="9880"@}
36503 +download,@{section=".text",section-sent="2560",section-size="6668",
36504 total-sent="2560",total-size="9880"@}
36505 +download,@{section=".text",section-sent="3072",section-size="6668",
36506 total-sent="3072",total-size="9880"@}
36507 +download,@{section=".text",section-sent="3584",section-size="6668",
36508 total-sent="3584",total-size="9880"@}
36509 +download,@{section=".text",section-sent="4096",section-size="6668",
36510 total-sent="4096",total-size="9880"@}
36511 +download,@{section=".text",section-sent="4608",section-size="6668",
36512 total-sent="4608",total-size="9880"@}
36513 +download,@{section=".text",section-sent="5120",section-size="6668",
36514 total-sent="5120",total-size="9880"@}
36515 +download,@{section=".text",section-sent="5632",section-size="6668",
36516 total-sent="5632",total-size="9880"@}
36517 +download,@{section=".text",section-sent="6144",section-size="6668",
36518 total-sent="6144",total-size="9880"@}
36519 +download,@{section=".text",section-sent="6656",section-size="6668",
36520 total-sent="6656",total-size="9880"@}
36521 +download,@{section=".init",section-size="28",total-size="9880"@}
36522 +download,@{section=".fini",section-size="28",total-size="9880"@}
36523 +download,@{section=".data",section-size="3156",total-size="9880"@}
36524 +download,@{section=".data",section-sent="512",section-size="3156",
36525 total-sent="7236",total-size="9880"@}
36526 +download,@{section=".data",section-sent="1024",section-size="3156",
36527 total-sent="7748",total-size="9880"@}
36528 +download,@{section=".data",section-sent="1536",section-size="3156",
36529 total-sent="8260",total-size="9880"@}
36530 +download,@{section=".data",section-sent="2048",section-size="3156",
36531 total-sent="8772",total-size="9880"@}
36532 +download,@{section=".data",section-sent="2560",section-size="3156",
36533 total-sent="9284",total-size="9880"@}
36534 +download,@{section=".data",section-sent="3072",section-size="3156",
36535 total-sent="9796",total-size="9880"@}
36536 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
36543 @subheading The @code{-target-exec-status} Command
36544 @findex -target-exec-status
36546 @subsubheading Synopsis
36549 -target-exec-status
36552 Provide information on the state of the target (whether it is running or
36553 not, for instance).
36555 @subsubheading @value{GDBN} Command
36557 There's no equivalent @value{GDBN} command.
36559 @subsubheading Example
36563 @subheading The @code{-target-list-available-targets} Command
36564 @findex -target-list-available-targets
36566 @subsubheading Synopsis
36569 -target-list-available-targets
36572 List the possible targets to connect to.
36574 @subsubheading @value{GDBN} Command
36576 The corresponding @value{GDBN} command is @samp{help target}.
36578 @subsubheading Example
36582 @subheading The @code{-target-list-current-targets} Command
36583 @findex -target-list-current-targets
36585 @subsubheading Synopsis
36588 -target-list-current-targets
36591 Describe the current target.
36593 @subsubheading @value{GDBN} Command
36595 The corresponding information is printed by @samp{info file} (among
36598 @subsubheading Example
36602 @subheading The @code{-target-list-parameters} Command
36603 @findex -target-list-parameters
36605 @subsubheading Synopsis
36608 -target-list-parameters
36614 @subsubheading @value{GDBN} Command
36618 @subsubheading Example
36621 @subheading The @code{-target-flash-erase} Command
36622 @findex -target-flash-erase
36624 @subsubheading Synopsis
36627 -target-flash-erase
36630 Erases all known flash memory regions on the target.
36632 The corresponding @value{GDBN} command is @samp{flash-erase}.
36634 The output is a list of flash regions that have been erased, with starting
36635 addresses and memory region sizes.
36639 -target-flash-erase
36640 ^done,erased-regions=@{address="0x0",size="0x40000"@}
36644 @subheading The @code{-target-select} Command
36645 @findex -target-select
36647 @subsubheading Synopsis
36650 -target-select @var{type} @var{parameters @dots{}}
36653 Connect @value{GDBN} to the remote target. This command takes two args:
36657 The type of target, for instance @samp{remote}, etc.
36658 @item @var{parameters}
36659 Device names, host names and the like. @xref{Target Commands, ,
36660 Commands for Managing Targets}, for more details.
36663 The output is a connection notification, followed by the address at
36664 which the target program is, in the following form:
36667 ^connected,addr="@var{address}",func="@var{function name}",
36668 args=[@var{arg list}]
36671 @subsubheading @value{GDBN} Command
36673 The corresponding @value{GDBN} command is @samp{target}.
36675 @subsubheading Example
36679 -target-select remote /dev/ttya
36680 ^connected,addr="0xfe00a300",func="??",args=[]
36684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36685 @node GDB/MI File Transfer Commands
36686 @section @sc{gdb/mi} File Transfer Commands
36689 @subheading The @code{-target-file-put} Command
36690 @findex -target-file-put
36692 @subsubheading Synopsis
36695 -target-file-put @var{hostfile} @var{targetfile}
36698 Copy file @var{hostfile} from the host system (the machine running
36699 @value{GDBN}) to @var{targetfile} on the target system.
36701 @subsubheading @value{GDBN} Command
36703 The corresponding @value{GDBN} command is @samp{remote put}.
36705 @subsubheading Example
36709 -target-file-put localfile remotefile
36715 @subheading The @code{-target-file-get} Command
36716 @findex -target-file-get
36718 @subsubheading Synopsis
36721 -target-file-get @var{targetfile} @var{hostfile}
36724 Copy file @var{targetfile} from the target system to @var{hostfile}
36725 on the host system.
36727 @subsubheading @value{GDBN} Command
36729 The corresponding @value{GDBN} command is @samp{remote get}.
36731 @subsubheading Example
36735 -target-file-get remotefile localfile
36741 @subheading The @code{-target-file-delete} Command
36742 @findex -target-file-delete
36744 @subsubheading Synopsis
36747 -target-file-delete @var{targetfile}
36750 Delete @var{targetfile} from the target system.
36752 @subsubheading @value{GDBN} Command
36754 The corresponding @value{GDBN} command is @samp{remote delete}.
36756 @subsubheading Example
36760 -target-file-delete remotefile
36766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36767 @node GDB/MI Ada Exceptions Commands
36768 @section Ada Exceptions @sc{gdb/mi} Commands
36770 @subheading The @code{-info-ada-exceptions} Command
36771 @findex -info-ada-exceptions
36773 @subsubheading Synopsis
36776 -info-ada-exceptions [ @var{regexp}]
36779 List all Ada exceptions defined within the program being debugged.
36780 With a regular expression @var{regexp}, only those exceptions whose
36781 names match @var{regexp} are listed.
36783 @subsubheading @value{GDBN} Command
36785 The corresponding @value{GDBN} command is @samp{info exceptions}.
36787 @subsubheading Result
36789 The result is a table of Ada exceptions. The following columns are
36790 defined for each exception:
36794 The name of the exception.
36797 The address of the exception.
36801 @subsubheading Example
36804 -info-ada-exceptions aint
36805 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
36806 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
36807 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
36808 body=[@{name="constraint_error",address="0x0000000000613da0"@},
36809 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
36812 @subheading Catching Ada Exceptions
36814 The commands describing how to ask @value{GDBN} to stop when a program
36815 raises an exception are described at @ref{Ada Exception GDB/MI
36816 Catchpoint Commands}.
36819 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36820 @node GDB/MI Support Commands
36821 @section @sc{gdb/mi} Support Commands
36823 Since new commands and features get regularly added to @sc{gdb/mi},
36824 some commands are available to help front-ends query the debugger
36825 about support for these capabilities. Similarly, it is also possible
36826 to query @value{GDBN} about target support of certain features.
36828 @subheading The @code{-info-gdb-mi-command} Command
36829 @cindex @code{-info-gdb-mi-command}
36830 @findex -info-gdb-mi-command
36832 @subsubheading Synopsis
36835 -info-gdb-mi-command @var{cmd_name}
36838 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
36840 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
36841 is technically not part of the command name (@pxref{GDB/MI Input
36842 Syntax}), and thus should be omitted in @var{cmd_name}. However,
36843 for ease of use, this command also accepts the form with the leading
36846 @subsubheading @value{GDBN} Command
36848 There is no corresponding @value{GDBN} command.
36850 @subsubheading Result
36852 The result is a tuple. There is currently only one field:
36856 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
36857 @code{"false"} otherwise.
36861 @subsubheading Example
36863 Here is an example where the @sc{gdb/mi} command does not exist:
36866 -info-gdb-mi-command unsupported-command
36867 ^done,command=@{exists="false"@}
36871 And here is an example where the @sc{gdb/mi} command is known
36875 -info-gdb-mi-command symbol-list-lines
36876 ^done,command=@{exists="true"@}
36879 @subheading The @code{-list-features} Command
36880 @findex -list-features
36881 @cindex supported @sc{gdb/mi} features, list
36883 Returns a list of particular features of the MI protocol that
36884 this version of gdb implements. A feature can be a command,
36885 or a new field in an output of some command, or even an
36886 important bugfix. While a frontend can sometimes detect presence
36887 of a feature at runtime, it is easier to perform detection at debugger
36890 The command returns a list of strings, with each string naming an
36891 available feature. Each returned string is just a name, it does not
36892 have any internal structure. The list of possible feature names
36898 (gdb) -list-features
36899 ^done,result=["feature1","feature2"]
36902 The current list of features is:
36905 @item frozen-varobjs
36906 Indicates support for the @code{-var-set-frozen} command, as well
36907 as possible presence of the @code{frozen} field in the output
36908 of @code{-varobj-create}.
36909 @item pending-breakpoints
36910 Indicates support for the @option{-f} option to the @code{-break-insert}
36913 Indicates Python scripting support, Python-based
36914 pretty-printing commands, and possible presence of the
36915 @samp{display_hint} field in the output of @code{-var-list-children}
36917 Indicates support for the @code{-thread-info} command.
36918 @item data-read-memory-bytes
36919 Indicates support for the @code{-data-read-memory-bytes} and the
36920 @code{-data-write-memory-bytes} commands.
36921 @item breakpoint-notifications
36922 Indicates that changes to breakpoints and breakpoints created via the
36923 CLI will be announced via async records.
36924 @item ada-task-info
36925 Indicates support for the @code{-ada-task-info} command.
36926 @item language-option
36927 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
36928 option (@pxref{Context management}).
36929 @item info-gdb-mi-command
36930 Indicates support for the @code{-info-gdb-mi-command} command.
36931 @item undefined-command-error-code
36932 Indicates support for the "undefined-command" error code in error result
36933 records, produced when trying to execute an undefined @sc{gdb/mi} command
36934 (@pxref{GDB/MI Result Records}).
36935 @item exec-run-start-option
36936 Indicates that the @code{-exec-run} command supports the @option{--start}
36937 option (@pxref{GDB/MI Program Execution}).
36938 @item data-disassemble-a-option
36939 Indicates that the @code{-data-disassemble} command supports the @option{-a}
36940 option (@pxref{GDB/MI Data Manipulation}).
36943 @subheading The @code{-list-target-features} Command
36944 @findex -list-target-features
36946 Returns a list of particular features that are supported by the
36947 target. Those features affect the permitted MI commands, but
36948 unlike the features reported by the @code{-list-features} command, the
36949 features depend on which target GDB is using at the moment. Whenever
36950 a target can change, due to commands such as @code{-target-select},
36951 @code{-target-attach} or @code{-exec-run}, the list of target features
36952 may change, and the frontend should obtain it again.
36956 (gdb) -list-target-features
36957 ^done,result=["async"]
36960 The current list of features is:
36964 Indicates that the target is capable of asynchronous command
36965 execution, which means that @value{GDBN} will accept further commands
36966 while the target is running.
36969 Indicates that the target is capable of reverse execution.
36970 @xref{Reverse Execution}, for more information.
36974 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
36975 @node GDB/MI Miscellaneous Commands
36976 @section Miscellaneous @sc{gdb/mi} Commands
36978 @c @subheading -gdb-complete
36980 @subheading The @code{-gdb-exit} Command
36983 @subsubheading Synopsis
36989 Exit @value{GDBN} immediately.
36991 @subsubheading @value{GDBN} Command
36993 Approximately corresponds to @samp{quit}.
36995 @subsubheading Example
37005 @subheading The @code{-exec-abort} Command
37006 @findex -exec-abort
37008 @subsubheading Synopsis
37014 Kill the inferior running program.
37016 @subsubheading @value{GDBN} Command
37018 The corresponding @value{GDBN} command is @samp{kill}.
37020 @subsubheading Example
37025 @subheading The @code{-gdb-set} Command
37028 @subsubheading Synopsis
37034 Set an internal @value{GDBN} variable.
37035 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
37037 @subsubheading @value{GDBN} Command
37039 The corresponding @value{GDBN} command is @samp{set}.
37041 @subsubheading Example
37051 @subheading The @code{-gdb-show} Command
37054 @subsubheading Synopsis
37060 Show the current value of a @value{GDBN} variable.
37062 @subsubheading @value{GDBN} Command
37064 The corresponding @value{GDBN} command is @samp{show}.
37066 @subsubheading Example
37075 @c @subheading -gdb-source
37078 @subheading The @code{-gdb-version} Command
37079 @findex -gdb-version
37081 @subsubheading Synopsis
37087 Show version information for @value{GDBN}. Used mostly in testing.
37089 @subsubheading @value{GDBN} Command
37091 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
37092 default shows this information when you start an interactive session.
37094 @subsubheading Example
37096 @c This example modifies the actual output from GDB to avoid overfull
37102 ~Copyright 2000 Free Software Foundation, Inc.
37103 ~GDB is free software, covered by the GNU General Public License, and
37104 ~you are welcome to change it and/or distribute copies of it under
37105 ~ certain conditions.
37106 ~Type "show copying" to see the conditions.
37107 ~There is absolutely no warranty for GDB. Type "show warranty" for
37109 ~This GDB was configured as
37110 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
37115 @subheading The @code{-list-thread-groups} Command
37116 @findex -list-thread-groups
37118 @subheading Synopsis
37121 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
37124 Lists thread groups (@pxref{Thread groups}). When a single thread
37125 group is passed as the argument, lists the children of that group.
37126 When several thread group are passed, lists information about those
37127 thread groups. Without any parameters, lists information about all
37128 top-level thread groups.
37130 Normally, thread groups that are being debugged are reported.
37131 With the @samp{--available} option, @value{GDBN} reports thread groups
37132 available on the target.
37134 The output of this command may have either a @samp{threads} result or
37135 a @samp{groups} result. The @samp{thread} result has a list of tuples
37136 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
37137 Information}). The @samp{groups} result has a list of tuples as value,
37138 each tuple describing a thread group. If top-level groups are
37139 requested (that is, no parameter is passed), or when several groups
37140 are passed, the output always has a @samp{groups} result. The format
37141 of the @samp{group} result is described below.
37143 To reduce the number of roundtrips it's possible to list thread groups
37144 together with their children, by passing the @samp{--recurse} option
37145 and the recursion depth. Presently, only recursion depth of 1 is
37146 permitted. If this option is present, then every reported thread group
37147 will also include its children, either as @samp{group} or
37148 @samp{threads} field.
37150 In general, any combination of option and parameters is permitted, with
37151 the following caveats:
37155 When a single thread group is passed, the output will typically
37156 be the @samp{threads} result. Because threads may not contain
37157 anything, the @samp{recurse} option will be ignored.
37160 When the @samp{--available} option is passed, limited information may
37161 be available. In particular, the list of threads of a process might
37162 be inaccessible. Further, specifying specific thread groups might
37163 not give any performance advantage over listing all thread groups.
37164 The frontend should assume that @samp{-list-thread-groups --available}
37165 is always an expensive operation and cache the results.
37169 The @samp{groups} result is a list of tuples, where each tuple may
37170 have the following fields:
37174 Identifier of the thread group. This field is always present.
37175 The identifier is an opaque string; frontends should not try to
37176 convert it to an integer, even though it might look like one.
37179 The type of the thread group. At present, only @samp{process} is a
37183 The target-specific process identifier. This field is only present
37184 for thread groups of type @samp{process} and only if the process exists.
37187 The exit code of this group's last exited thread, formatted in octal.
37188 This field is only present for thread groups of type @samp{process} and
37189 only if the process is not running.
37192 The number of children this thread group has. This field may be
37193 absent for an available thread group.
37196 This field has a list of tuples as value, each tuple describing a
37197 thread. It may be present if the @samp{--recurse} option is
37198 specified, and it's actually possible to obtain the threads.
37201 This field is a list of integers, each identifying a core that one
37202 thread of the group is running on. This field may be absent if
37203 such information is not available.
37206 The name of the executable file that corresponds to this thread group.
37207 The field is only present for thread groups of type @samp{process},
37208 and only if there is a corresponding executable file.
37212 @subheading Example
37216 -list-thread-groups
37217 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
37218 -list-thread-groups 17
37219 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
37220 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
37221 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
37222 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
37223 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
37224 -list-thread-groups --available
37225 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
37226 -list-thread-groups --available --recurse 1
37227 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37228 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37229 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
37230 -list-thread-groups --available --recurse 1 17 18
37231 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
37232 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
37233 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
37236 @subheading The @code{-info-os} Command
37239 @subsubheading Synopsis
37242 -info-os [ @var{type} ]
37245 If no argument is supplied, the command returns a table of available
37246 operating-system-specific information types. If one of these types is
37247 supplied as an argument @var{type}, then the command returns a table
37248 of data of that type.
37250 The types of information available depend on the target operating
37253 @subsubheading @value{GDBN} Command
37255 The corresponding @value{GDBN} command is @samp{info os}.
37257 @subsubheading Example
37259 When run on a @sc{gnu}/Linux system, the output will look something
37265 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
37266 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
37267 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
37268 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
37269 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
37271 item=@{col0="files",col1="Listing of all file descriptors",
37272 col2="File descriptors"@},
37273 item=@{col0="modules",col1="Listing of all loaded kernel modules",
37274 col2="Kernel modules"@},
37275 item=@{col0="msg",col1="Listing of all message queues",
37276 col2="Message queues"@},
37277 item=@{col0="processes",col1="Listing of all processes",
37278 col2="Processes"@},
37279 item=@{col0="procgroups",col1="Listing of all process groups",
37280 col2="Process groups"@},
37281 item=@{col0="semaphores",col1="Listing of all semaphores",
37282 col2="Semaphores"@},
37283 item=@{col0="shm",col1="Listing of all shared-memory regions",
37284 col2="Shared-memory regions"@},
37285 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
37287 item=@{col0="threads",col1="Listing of all threads",
37291 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
37292 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
37293 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
37294 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
37295 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
37296 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
37297 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
37298 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
37300 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
37301 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
37305 (Note that the MI output here includes a @code{"Title"} column that
37306 does not appear in command-line @code{info os}; this column is useful
37307 for MI clients that want to enumerate the types of data, such as in a
37308 popup menu, but is needless clutter on the command line, and
37309 @code{info os} omits it.)
37311 @subheading The @code{-add-inferior} Command
37312 @findex -add-inferior
37314 @subheading Synopsis
37317 -add-inferior [ --no-connection ]
37320 Creates a new inferior (@pxref{Inferiors Connections and Programs}). The created
37321 inferior is not associated with any executable. Such association may
37322 be established with the @samp{-file-exec-and-symbols} command
37323 (@pxref{GDB/MI File Commands}).
37325 By default, the new inferior begins connected to the same target
37326 connection as the current inferior. For example, if the current
37327 inferior was connected to @code{gdbserver} with @code{target remote},
37328 then the new inferior will be connected to the same @code{gdbserver}
37329 instance. The @samp{--no-connection} option starts the new inferior
37330 with no connection yet. You can then for example use the
37331 @code{-target-select remote} command to connect to some other
37332 @code{gdbserver} instance, use @code{-exec-run} to spawn a local
37335 The command response always has a field, @var{inferior}, whose value
37336 is the identifier of the thread group corresponding to the new
37339 An additional section field, @var{connection}, is optional. This
37340 field will only exist if the new inferior has a target connection. If
37341 this field exists, then its value will be a tuple containing the
37346 The number of the connection used for the new inferior.
37349 The name of the connection type used for the new inferior.
37352 @subheading @value{GDBN} Command
37354 The corresponding @value{GDBN} command is @samp{add-inferior}
37355 (@pxref{add_inferior_cli,,@samp{add-inferior}}).
37357 @subheading Example
37362 ^done,inferior="i3"
37365 @subheading The @code{-interpreter-exec} Command
37366 @findex -interpreter-exec
37368 @subheading Synopsis
37371 -interpreter-exec @var{interpreter} @var{command}
37373 @anchor{-interpreter-exec}
37375 Execute the specified @var{command} in the given @var{interpreter}.
37377 @subheading @value{GDBN} Command
37379 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
37381 @subheading Example
37385 -interpreter-exec console "break main"
37386 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
37387 &"During symbol reading, bad structure-type format.\n"
37388 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
37393 @subheading The @code{-inferior-tty-set} Command
37394 @findex -inferior-tty-set
37396 @subheading Synopsis
37399 -inferior-tty-set /dev/pts/1
37402 Set terminal for future runs of the program being debugged.
37404 @subheading @value{GDBN} Command
37406 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
37408 @subheading Example
37412 -inferior-tty-set /dev/pts/1
37417 @subheading The @code{-inferior-tty-show} Command
37418 @findex -inferior-tty-show
37420 @subheading Synopsis
37426 Show terminal for future runs of program being debugged.
37428 @subheading @value{GDBN} Command
37430 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
37432 @subheading Example
37436 -inferior-tty-set /dev/pts/1
37440 ^done,inferior_tty_terminal="/dev/pts/1"
37444 @subheading The @code{-enable-timings} Command
37445 @findex -enable-timings
37447 @subheading Synopsis
37450 -enable-timings [yes | no]
37453 Toggle the printing of the wallclock, user and system times for an MI
37454 command as a field in its output. This command is to help frontend
37455 developers optimize the performance of their code. No argument is
37456 equivalent to @samp{yes}.
37458 @subheading @value{GDBN} Command
37462 @subheading Example
37470 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
37471 addr="0x080484ed",func="main",file="myprog.c",
37472 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
37474 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
37482 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
37483 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
37484 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
37485 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
37489 @subheading The @code{-complete} Command
37492 @subheading Synopsis
37495 -complete @var{command}
37498 Show a list of completions for partially typed CLI @var{command}.
37500 This command is intended for @sc{gdb/mi} frontends that cannot use two separate
37501 CLI and MI channels --- for example: because of lack of PTYs like on Windows or
37502 because @value{GDBN} is used remotely via a SSH connection.
37506 The result consists of two or three fields:
37510 This field contains the completed @var{command}. If @var{command}
37511 has no known completions, this field is omitted.
37514 This field contains a (possibly empty) array of matches. It is always present.
37516 @item max_completions_reached
37517 This field contains @code{1} if number of known completions is above
37518 @code{max-completions} limit (@pxref{Completion}), otherwise it contains
37519 @code{0}. It is always present.
37523 @subheading @value{GDBN} Command
37525 The corresponding @value{GDBN} command is @samp{complete}.
37527 @subheading Example
37532 ^done,completion="break",
37533 matches=["break","break-range"],
37534 max_completions_reached="0"
37537 ^done,completion="b ma",
37538 matches=["b madvise","b main"],max_completions_reached="0"
37540 -complete "b push_b"
37541 ^done,completion="b push_back(",
37543 "b A::push_back(void*)",
37544 "b std::string::push_back(char)",
37545 "b std::vector<int, std::allocator<int> >::push_back(int&&)"],
37546 max_completions_reached="0"
37548 -complete "nonexist"
37549 ^done,matches=[],max_completions_reached="0"
37555 @chapter @value{GDBN} Annotations
37557 This chapter describes annotations in @value{GDBN}. Annotations were
37558 designed to interface @value{GDBN} to graphical user interfaces or other
37559 similar programs which want to interact with @value{GDBN} at a
37560 relatively high level.
37562 The annotation mechanism has largely been superseded by @sc{gdb/mi}
37566 This is Edition @value{EDITION}, @value{DATE}.
37570 * Annotations Overview:: What annotations are; the general syntax.
37571 * Server Prefix:: Issuing a command without affecting user state.
37572 * Prompting:: Annotations marking @value{GDBN}'s need for input.
37573 * Errors:: Annotations for error messages.
37574 * Invalidation:: Some annotations describe things now invalid.
37575 * Annotations for Running::
37576 Whether the program is running, how it stopped, etc.
37577 * Source Annotations:: Annotations describing source code.
37580 @node Annotations Overview
37581 @section What is an Annotation?
37582 @cindex annotations
37584 Annotations start with a newline character, two @samp{control-z}
37585 characters, and the name of the annotation. If there is no additional
37586 information associated with this annotation, the name of the annotation
37587 is followed immediately by a newline. If there is additional
37588 information, the name of the annotation is followed by a space, the
37589 additional information, and a newline. The additional information
37590 cannot contain newline characters.
37592 Any output not beginning with a newline and two @samp{control-z}
37593 characters denotes literal output from @value{GDBN}. Currently there is
37594 no need for @value{GDBN} to output a newline followed by two
37595 @samp{control-z} characters, but if there was such a need, the
37596 annotations could be extended with an @samp{escape} annotation which
37597 means those three characters as output.
37599 The annotation @var{level}, which is specified using the
37600 @option{--annotate} command line option (@pxref{Mode Options}), controls
37601 how much information @value{GDBN} prints together with its prompt,
37602 values of expressions, source lines, and other types of output. Level 0
37603 is for no annotations, level 1 is for use when @value{GDBN} is run as a
37604 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
37605 for programs that control @value{GDBN}, and level 2 annotations have
37606 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
37607 Interface, annotate, GDB's Obsolete Annotations}).
37610 @kindex set annotate
37611 @item set annotate @var{level}
37612 The @value{GDBN} command @code{set annotate} sets the level of
37613 annotations to the specified @var{level}.
37615 @item show annotate
37616 @kindex show annotate
37617 Show the current annotation level.
37620 This chapter describes level 3 annotations.
37622 A simple example of starting up @value{GDBN} with annotations is:
37625 $ @kbd{gdb --annotate=3}
37627 Copyright 2003 Free Software Foundation, Inc.
37628 GDB is free software, covered by the GNU General Public License,
37629 and you are welcome to change it and/or distribute copies of it
37630 under certain conditions.
37631 Type "show copying" to see the conditions.
37632 There is absolutely no warranty for GDB. Type "show warranty"
37634 This GDB was configured as "i386-pc-linux-gnu"
37645 Here @samp{quit} is input to @value{GDBN}; the rest is output from
37646 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
37647 denotes a @samp{control-z} character) are annotations; the rest is
37648 output from @value{GDBN}.
37650 @node Server Prefix
37651 @section The Server Prefix
37652 @cindex server prefix
37654 If you prefix a command with @samp{server } then it will not affect
37655 the command history, nor will it affect @value{GDBN}'s notion of which
37656 command to repeat if @key{RET} is pressed on a line by itself. This
37657 means that commands can be run behind a user's back by a front-end in
37658 a transparent manner.
37660 The @code{server } prefix does not affect the recording of values into
37661 the value history; to print a value without recording it into the
37662 value history, use the @code{output} command instead of the
37663 @code{print} command.
37665 Using this prefix also disables confirmation requests
37666 (@pxref{confirmation requests}).
37669 @section Annotation for @value{GDBN} Input
37671 @cindex annotations for prompts
37672 When @value{GDBN} prompts for input, it annotates this fact so it is possible
37673 to know when to send output, when the output from a given command is
37676 Different kinds of input each have a different @dfn{input type}. Each
37677 input type has three annotations: a @code{pre-} annotation, which
37678 denotes the beginning of any prompt which is being output, a plain
37679 annotation, which denotes the end of the prompt, and then a @code{post-}
37680 annotation which denotes the end of any echo which may (or may not) be
37681 associated with the input. For example, the @code{prompt} input type
37682 features the following annotations:
37690 The input types are
37693 @findex pre-prompt annotation
37694 @findex prompt annotation
37695 @findex post-prompt annotation
37697 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
37699 @findex pre-commands annotation
37700 @findex commands annotation
37701 @findex post-commands annotation
37703 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
37704 command. The annotations are repeated for each command which is input.
37706 @findex pre-overload-choice annotation
37707 @findex overload-choice annotation
37708 @findex post-overload-choice annotation
37709 @item overload-choice
37710 When @value{GDBN} wants the user to select between various overloaded functions.
37712 @findex pre-query annotation
37713 @findex query annotation
37714 @findex post-query annotation
37716 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
37718 @findex pre-prompt-for-continue annotation
37719 @findex prompt-for-continue annotation
37720 @findex post-prompt-for-continue annotation
37721 @item prompt-for-continue
37722 When @value{GDBN} is asking the user to press return to continue. Note: Don't
37723 expect this to work well; instead use @code{set height 0} to disable
37724 prompting. This is because the counting of lines is buggy in the
37725 presence of annotations.
37730 @cindex annotations for errors, warnings and interrupts
37732 @findex quit annotation
37737 This annotation occurs right before @value{GDBN} responds to an interrupt.
37739 @findex error annotation
37744 This annotation occurs right before @value{GDBN} responds to an error.
37746 Quit and error annotations indicate that any annotations which @value{GDBN} was
37747 in the middle of may end abruptly. For example, if a
37748 @code{value-history-begin} annotation is followed by a @code{error}, one
37749 cannot expect to receive the matching @code{value-history-end}. One
37750 cannot expect not to receive it either, however; an error annotation
37751 does not necessarily mean that @value{GDBN} is immediately returning all the way
37754 @findex error-begin annotation
37755 A quit or error annotation may be preceded by
37761 Any output between that and the quit or error annotation is the error
37764 Warning messages are not yet annotated.
37765 @c If we want to change that, need to fix warning(), type_error(),
37766 @c range_error(), and possibly other places.
37769 @section Invalidation Notices
37771 @cindex annotations for invalidation messages
37772 The following annotations say that certain pieces of state may have
37776 @findex frames-invalid annotation
37777 @item ^Z^Zframes-invalid
37779 The frames (for example, output from the @code{backtrace} command) may
37782 @findex breakpoints-invalid annotation
37783 @item ^Z^Zbreakpoints-invalid
37785 The breakpoints may have changed. For example, the user just added or
37786 deleted a breakpoint.
37789 @node Annotations for Running
37790 @section Running the Program
37791 @cindex annotations for running programs
37793 @findex starting annotation
37794 @findex stopping annotation
37795 When the program starts executing due to a @value{GDBN} command such as
37796 @code{step} or @code{continue},
37802 is output. When the program stops,
37808 is output. Before the @code{stopped} annotation, a variety of
37809 annotations describe how the program stopped.
37812 @findex exited annotation
37813 @item ^Z^Zexited @var{exit-status}
37814 The program exited, and @var{exit-status} is the exit status (zero for
37815 successful exit, otherwise nonzero).
37817 @findex signalled annotation
37818 @findex signal-name annotation
37819 @findex signal-name-end annotation
37820 @findex signal-string annotation
37821 @findex signal-string-end annotation
37822 @item ^Z^Zsignalled
37823 The program exited with a signal. After the @code{^Z^Zsignalled}, the
37824 annotation continues:
37830 ^Z^Zsignal-name-end
37834 ^Z^Zsignal-string-end
37839 where @var{name} is the name of the signal, such as @code{SIGILL} or
37840 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
37841 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
37842 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
37843 user's benefit and have no particular format.
37845 @findex signal annotation
37847 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
37848 just saying that the program received the signal, not that it was
37849 terminated with it.
37851 @findex breakpoint annotation
37852 @item ^Z^Zbreakpoint @var{number}
37853 The program hit breakpoint number @var{number}.
37855 @findex watchpoint annotation
37856 @item ^Z^Zwatchpoint @var{number}
37857 The program hit watchpoint number @var{number}.
37860 @node Source Annotations
37861 @section Displaying Source
37862 @cindex annotations for source display
37864 @findex source annotation
37865 The following annotation is used instead of displaying source code:
37868 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
37871 where @var{filename} is an absolute file name indicating which source
37872 file, @var{line} is the line number within that file (where 1 is the
37873 first line in the file), @var{character} is the character position
37874 within the file (where 0 is the first character in the file) (for most
37875 debug formats this will necessarily point to the beginning of a line),
37876 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
37877 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
37878 @var{addr} is the address in the target program associated with the
37879 source which is being displayed. The @var{addr} is in the form @samp{0x}
37880 followed by one or more lowercase hex digits (note that this does not
37881 depend on the language).
37883 @node JIT Interface
37884 @chapter JIT Compilation Interface
37885 @cindex just-in-time compilation
37886 @cindex JIT compilation interface
37888 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
37889 interface. A JIT compiler is a program or library that generates native
37890 executable code at runtime and executes it, usually in order to achieve good
37891 performance while maintaining platform independence.
37893 Programs that use JIT compilation are normally difficult to debug because
37894 portions of their code are generated at runtime, instead of being loaded from
37895 object files, which is where @value{GDBN} normally finds the program's symbols
37896 and debug information. In order to debug programs that use JIT compilation,
37897 @value{GDBN} has an interface that allows the program to register in-memory
37898 symbol files with @value{GDBN} at runtime.
37900 If you are using @value{GDBN} to debug a program that uses this interface, then
37901 it should work transparently so long as you have not stripped the binary. If
37902 you are developing a JIT compiler, then the interface is documented in the rest
37903 of this chapter. At this time, the only known client of this interface is the
37906 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
37907 JIT compiler communicates with @value{GDBN} by writing data into a global
37908 variable and calling a function at a well-known symbol. When @value{GDBN}
37909 attaches, it reads a linked list of symbol files from the global variable to
37910 find existing code, and puts a breakpoint in the function so that it can find
37911 out about additional code.
37914 * Declarations:: Relevant C struct declarations
37915 * Registering Code:: Steps to register code
37916 * Unregistering Code:: Steps to unregister code
37917 * Custom Debug Info:: Emit debug information in a custom format
37921 @section JIT Declarations
37923 These are the relevant struct declarations that a C program should include to
37924 implement the interface:
37934 struct jit_code_entry
37936 struct jit_code_entry *next_entry;
37937 struct jit_code_entry *prev_entry;
37938 const char *symfile_addr;
37939 uint64_t symfile_size;
37942 struct jit_descriptor
37945 /* This type should be jit_actions_t, but we use uint32_t
37946 to be explicit about the bitwidth. */
37947 uint32_t action_flag;
37948 struct jit_code_entry *relevant_entry;
37949 struct jit_code_entry *first_entry;
37952 /* GDB puts a breakpoint in this function. */
37953 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
37955 /* Make sure to specify the version statically, because the
37956 debugger may check the version before we can set it. */
37957 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
37960 If the JIT is multi-threaded, then it is important that the JIT synchronize any
37961 modifications to this global data properly, which can easily be done by putting
37962 a global mutex around modifications to these structures.
37964 @node Registering Code
37965 @section Registering Code
37967 To register code with @value{GDBN}, the JIT should follow this protocol:
37971 Generate an object file in memory with symbols and other desired debug
37972 information. The file must include the virtual addresses of the sections.
37975 Create a code entry for the file, which gives the start and size of the symbol
37979 Add it to the linked list in the JIT descriptor.
37982 Point the relevant_entry field of the descriptor at the entry.
37985 Set @code{action_flag} to @code{JIT_REGISTER} and call
37986 @code{__jit_debug_register_code}.
37989 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
37990 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
37991 new code. However, the linked list must still be maintained in order to allow
37992 @value{GDBN} to attach to a running process and still find the symbol files.
37994 @node Unregistering Code
37995 @section Unregistering Code
37997 If code is freed, then the JIT should use the following protocol:
38001 Remove the code entry corresponding to the code from the linked list.
38004 Point the @code{relevant_entry} field of the descriptor at the code entry.
38007 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
38008 @code{__jit_debug_register_code}.
38011 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
38012 and the JIT will leak the memory used for the associated symbol files.
38014 @node Custom Debug Info
38015 @section Custom Debug Info
38016 @cindex custom JIT debug info
38017 @cindex JIT debug info reader
38019 Generating debug information in platform-native file formats (like ELF
38020 or COFF) may be an overkill for JIT compilers; especially if all the
38021 debug info is used for is displaying a meaningful backtrace. The
38022 issue can be resolved by having the JIT writers decide on a debug info
38023 format and also provide a reader that parses the debug info generated
38024 by the JIT compiler. This section gives a brief overview on writing
38025 such a parser. More specific details can be found in the source file
38026 @file{gdb/jit-reader.in}, which is also installed as a header at
38027 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
38029 The reader is implemented as a shared object (so this functionality is
38030 not available on platforms which don't allow loading shared objects at
38031 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
38032 @code{jit-reader-unload} are provided, to be used to load and unload
38033 the readers from a preconfigured directory. Once loaded, the shared
38034 object is used the parse the debug information emitted by the JIT
38038 * Using JIT Debug Info Readers:: How to use supplied readers correctly
38039 * Writing JIT Debug Info Readers:: Creating a debug-info reader
38042 @node Using JIT Debug Info Readers
38043 @subsection Using JIT Debug Info Readers
38044 @kindex jit-reader-load
38045 @kindex jit-reader-unload
38047 Readers can be loaded and unloaded using the @code{jit-reader-load}
38048 and @code{jit-reader-unload} commands.
38051 @item jit-reader-load @var{reader}
38052 Load the JIT reader named @var{reader}, which is a shared
38053 object specified as either an absolute or a relative file name. In
38054 the latter case, @value{GDBN} will try to load the reader from a
38055 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
38056 system (here @var{libdir} is the system library directory, often
38057 @file{/usr/local/lib}).
38059 Only one reader can be active at a time; trying to load a second
38060 reader when one is already loaded will result in @value{GDBN}
38061 reporting an error. A new JIT reader can be loaded by first unloading
38062 the current one using @code{jit-reader-unload} and then invoking
38063 @code{jit-reader-load}.
38065 @item jit-reader-unload
38066 Unload the currently loaded JIT reader.
38070 @node Writing JIT Debug Info Readers
38071 @subsection Writing JIT Debug Info Readers
38072 @cindex writing JIT debug info readers
38074 As mentioned, a reader is essentially a shared object conforming to a
38075 certain ABI. This ABI is described in @file{jit-reader.h}.
38077 @file{jit-reader.h} defines the structures, macros and functions
38078 required to write a reader. It is installed (along with
38079 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
38080 the system include directory.
38082 Readers need to be released under a GPL compatible license. A reader
38083 can be declared as released under such a license by placing the macro
38084 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
38086 The entry point for readers is the symbol @code{gdb_init_reader},
38087 which is expected to be a function with the prototype
38089 @findex gdb_init_reader
38091 extern struct gdb_reader_funcs *gdb_init_reader (void);
38094 @cindex @code{struct gdb_reader_funcs}
38096 @code{struct gdb_reader_funcs} contains a set of pointers to callback
38097 functions. These functions are executed to read the debug info
38098 generated by the JIT compiler (@code{read}), to unwind stack frames
38099 (@code{unwind}) and to create canonical frame IDs
38100 (@code{get_frame_id}). It also has a callback that is called when the
38101 reader is being unloaded (@code{destroy}). The struct looks like this
38104 struct gdb_reader_funcs
38106 /* Must be set to GDB_READER_INTERFACE_VERSION. */
38107 int reader_version;
38109 /* For use by the reader. */
38112 gdb_read_debug_info *read;
38113 gdb_unwind_frame *unwind;
38114 gdb_get_frame_id *get_frame_id;
38115 gdb_destroy_reader *destroy;
38119 @cindex @code{struct gdb_symbol_callbacks}
38120 @cindex @code{struct gdb_unwind_callbacks}
38122 The callbacks are provided with another set of callbacks by
38123 @value{GDBN} to do their job. For @code{read}, these callbacks are
38124 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
38125 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
38126 @code{struct gdb_symbol_callbacks} has callbacks to create new object
38127 files and new symbol tables inside those object files. @code{struct
38128 gdb_unwind_callbacks} has callbacks to read registers off the current
38129 frame and to write out the values of the registers in the previous
38130 frame. Both have a callback (@code{target_read}) to read bytes off the
38131 target's address space.
38133 @node In-Process Agent
38134 @chapter In-Process Agent
38135 @cindex debugging agent
38136 The traditional debugging model is conceptually low-speed, but works fine,
38137 because most bugs can be reproduced in debugging-mode execution. However,
38138 as multi-core or many-core processors are becoming mainstream, and
38139 multi-threaded programs become more and more popular, there should be more
38140 and more bugs that only manifest themselves at normal-mode execution, for
38141 example, thread races, because debugger's interference with the program's
38142 timing may conceal the bugs. On the other hand, in some applications,
38143 it is not feasible for the debugger to interrupt the program's execution
38144 long enough for the developer to learn anything helpful about its behavior.
38145 If the program's correctness depends on its real-time behavior, delays
38146 introduced by a debugger might cause the program to fail, even when the
38147 code itself is correct. It is useful to be able to observe the program's
38148 behavior without interrupting it.
38150 Therefore, traditional debugging model is too intrusive to reproduce
38151 some bugs. In order to reduce the interference with the program, we can
38152 reduce the number of operations performed by debugger. The
38153 @dfn{In-Process Agent}, a shared library, is running within the same
38154 process with inferior, and is able to perform some debugging operations
38155 itself. As a result, debugger is only involved when necessary, and
38156 performance of debugging can be improved accordingly. Note that
38157 interference with program can be reduced but can't be removed completely,
38158 because the in-process agent will still stop or slow down the program.
38160 The in-process agent can interpret and execute Agent Expressions
38161 (@pxref{Agent Expressions}) during performing debugging operations. The
38162 agent expressions can be used for different purposes, such as collecting
38163 data in tracepoints, and condition evaluation in breakpoints.
38165 @anchor{Control Agent}
38166 You can control whether the in-process agent is used as an aid for
38167 debugging with the following commands:
38170 @kindex set agent on
38172 Causes the in-process agent to perform some operations on behalf of the
38173 debugger. Just which operations requested by the user will be done
38174 by the in-process agent depends on the its capabilities. For example,
38175 if you request to evaluate breakpoint conditions in the in-process agent,
38176 and the in-process agent has such capability as well, then breakpoint
38177 conditions will be evaluated in the in-process agent.
38179 @kindex set agent off
38180 @item set agent off
38181 Disables execution of debugging operations by the in-process agent. All
38182 of the operations will be performed by @value{GDBN}.
38186 Display the current setting of execution of debugging operations by
38187 the in-process agent.
38191 * In-Process Agent Protocol::
38194 @node In-Process Agent Protocol
38195 @section In-Process Agent Protocol
38196 @cindex in-process agent protocol
38198 The in-process agent is able to communicate with both @value{GDBN} and
38199 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
38200 used for communications between @value{GDBN} or GDBserver and the IPA.
38201 In general, @value{GDBN} or GDBserver sends commands
38202 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
38203 in-process agent replies back with the return result of the command, or
38204 some other information. The data sent to in-process agent is composed
38205 of primitive data types, such as 4-byte or 8-byte type, and composite
38206 types, which are called objects (@pxref{IPA Protocol Objects}).
38209 * IPA Protocol Objects::
38210 * IPA Protocol Commands::
38213 @node IPA Protocol Objects
38214 @subsection IPA Protocol Objects
38215 @cindex ipa protocol objects
38217 The commands sent to and results received from agent may contain some
38218 complex data types called @dfn{objects}.
38220 The in-process agent is running on the same machine with @value{GDBN}
38221 or GDBserver, so it doesn't have to handle as much differences between
38222 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
38223 However, there are still some differences of two ends in two processes:
38227 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
38228 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
38230 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
38231 GDBserver is compiled with one, and in-process agent is compiled with
38235 Here are the IPA Protocol Objects:
38239 agent expression object. It represents an agent expression
38240 (@pxref{Agent Expressions}).
38241 @anchor{agent expression object}
38243 tracepoint action object. It represents a tracepoint action
38244 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
38245 memory, static trace data and to evaluate expression.
38246 @anchor{tracepoint action object}
38248 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
38249 @anchor{tracepoint object}
38253 The following table describes important attributes of each IPA protocol
38256 @multitable @columnfractions .30 .20 .50
38257 @headitem Name @tab Size @tab Description
38258 @item @emph{agent expression object} @tab @tab
38259 @item length @tab 4 @tab length of bytes code
38260 @item byte code @tab @var{length} @tab contents of byte code
38261 @item @emph{tracepoint action for collecting memory} @tab @tab
38262 @item 'M' @tab 1 @tab type of tracepoint action
38263 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
38264 address of the lowest byte to collect, otherwise @var{addr} is the offset
38265 of @var{basereg} for memory collecting.
38266 @item len @tab 8 @tab length of memory for collecting
38267 @item basereg @tab 4 @tab the register number containing the starting
38268 memory address for collecting.
38269 @item @emph{tracepoint action for collecting registers} @tab @tab
38270 @item 'R' @tab 1 @tab type of tracepoint action
38271 @item @emph{tracepoint action for collecting static trace data} @tab @tab
38272 @item 'L' @tab 1 @tab type of tracepoint action
38273 @item @emph{tracepoint action for expression evaluation} @tab @tab
38274 @item 'X' @tab 1 @tab type of tracepoint action
38275 @item agent expression @tab length of @tab @ref{agent expression object}
38276 @item @emph{tracepoint object} @tab @tab
38277 @item number @tab 4 @tab number of tracepoint
38278 @item address @tab 8 @tab address of tracepoint inserted on
38279 @item type @tab 4 @tab type of tracepoint
38280 @item enabled @tab 1 @tab enable or disable of tracepoint
38281 @item step_count @tab 8 @tab step
38282 @item pass_count @tab 8 @tab pass
38283 @item numactions @tab 4 @tab number of tracepoint actions
38284 @item hit count @tab 8 @tab hit count
38285 @item trace frame usage @tab 8 @tab trace frame usage
38286 @item compiled_cond @tab 8 @tab compiled condition
38287 @item orig_size @tab 8 @tab orig size
38288 @item condition @tab 4 if condition is NULL otherwise length of
38289 @ref{agent expression object}
38290 @tab zero if condition is NULL, otherwise is
38291 @ref{agent expression object}
38292 @item actions @tab variable
38293 @tab numactions number of @ref{tracepoint action object}
38296 @node IPA Protocol Commands
38297 @subsection IPA Protocol Commands
38298 @cindex ipa protocol commands
38300 The spaces in each command are delimiters to ease reading this commands
38301 specification. They don't exist in real commands.
38305 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
38306 Installs a new fast tracepoint described by @var{tracepoint_object}
38307 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
38308 head of @dfn{jumppad}, which is used to jump to data collection routine
38313 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
38314 @var{target_address} is address of tracepoint in the inferior.
38315 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
38316 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
38317 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
38318 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
38325 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
38326 is about to kill inferiors.
38334 @item probe_marker_at:@var{address}
38335 Asks in-process agent to probe the marker at @var{address}.
38342 @item unprobe_marker_at:@var{address}
38343 Asks in-process agent to unprobe the marker at @var{address}.
38347 @chapter Reporting Bugs in @value{GDBN}
38348 @cindex bugs in @value{GDBN}
38349 @cindex reporting bugs in @value{GDBN}
38351 Your bug reports play an essential role in making @value{GDBN} reliable.
38353 Reporting a bug may help you by bringing a solution to your problem, or it
38354 may not. But in any case the principal function of a bug report is to help
38355 the entire community by making the next version of @value{GDBN} work better. Bug
38356 reports are your contribution to the maintenance of @value{GDBN}.
38358 In order for a bug report to serve its purpose, you must include the
38359 information that enables us to fix the bug.
38362 * Bug Criteria:: Have you found a bug?
38363 * Bug Reporting:: How to report bugs
38367 @section Have You Found a Bug?
38368 @cindex bug criteria
38370 If you are not sure whether you have found a bug, here are some guidelines:
38373 @cindex fatal signal
38374 @cindex debugger crash
38375 @cindex crash of debugger
38377 If the debugger gets a fatal signal, for any input whatever, that is a
38378 @value{GDBN} bug. Reliable debuggers never crash.
38380 @cindex error on valid input
38382 If @value{GDBN} produces an error message for valid input, that is a
38383 bug. (Note that if you're cross debugging, the problem may also be
38384 somewhere in the connection to the target.)
38386 @cindex invalid input
38388 If @value{GDBN} does not produce an error message for invalid input,
38389 that is a bug. However, you should note that your idea of
38390 ``invalid input'' might be our idea of ``an extension'' or ``support
38391 for traditional practice''.
38394 If you are an experienced user of debugging tools, your suggestions
38395 for improvement of @value{GDBN} are welcome in any case.
38398 @node Bug Reporting
38399 @section How to Report Bugs
38400 @cindex bug reports
38401 @cindex @value{GDBN} bugs, reporting
38403 A number of companies and individuals offer support for @sc{gnu} products.
38404 If you obtained @value{GDBN} from a support organization, we recommend you
38405 contact that organization first.
38407 You can find contact information for many support companies and
38408 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
38410 @c should add a web page ref...
38413 @ifset BUGURL_DEFAULT
38414 In any event, we also recommend that you submit bug reports for
38415 @value{GDBN}. The preferred method is to submit them directly using
38416 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
38417 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
38420 @strong{Do not send bug reports to @samp{info-gdb}, or to
38421 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
38422 not want to receive bug reports. Those that do have arranged to receive
38425 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
38426 serves as a repeater. The mailing list and the newsgroup carry exactly
38427 the same messages. Often people think of posting bug reports to the
38428 newsgroup instead of mailing them. This appears to work, but it has one
38429 problem which can be crucial: a newsgroup posting often lacks a mail
38430 path back to the sender. Thus, if we need to ask for more information,
38431 we may be unable to reach you. For this reason, it is better to send
38432 bug reports to the mailing list.
38434 @ifclear BUGURL_DEFAULT
38435 In any event, we also recommend that you submit bug reports for
38436 @value{GDBN} to @value{BUGURL}.
38440 The fundamental principle of reporting bugs usefully is this:
38441 @strong{report all the facts}. If you are not sure whether to state a
38442 fact or leave it out, state it!
38444 Often people omit facts because they think they know what causes the
38445 problem and assume that some details do not matter. Thus, you might
38446 assume that the name of the variable you use in an example does not matter.
38447 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
38448 stray memory reference which happens to fetch from the location where that
38449 name is stored in memory; perhaps, if the name were different, the contents
38450 of that location would fool the debugger into doing the right thing despite
38451 the bug. Play it safe and give a specific, complete example. That is the
38452 easiest thing for you to do, and the most helpful.
38454 Keep in mind that the purpose of a bug report is to enable us to fix the
38455 bug. It may be that the bug has been reported previously, but neither
38456 you nor we can know that unless your bug report is complete and
38459 Sometimes people give a few sketchy facts and ask, ``Does this ring a
38460 bell?'' Those bug reports are useless, and we urge everyone to
38461 @emph{refuse to respond to them} except to chide the sender to report
38464 To enable us to fix the bug, you should include all these things:
38468 The version of @value{GDBN}. @value{GDBN} announces it if you start
38469 with no arguments; you can also print it at any time using @code{show
38472 Without this, we will not know whether there is any point in looking for
38473 the bug in the current version of @value{GDBN}.
38476 The type of machine you are using, and the operating system name and
38480 The details of the @value{GDBN} build-time configuration.
38481 @value{GDBN} shows these details if you invoke it with the
38482 @option{--configuration} command-line option, or if you type
38483 @code{show configuration} at @value{GDBN}'s prompt.
38486 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
38487 ``@value{GCC}--2.8.1''.
38490 What compiler (and its version) was used to compile the program you are
38491 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
38492 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
38493 to get this information; for other compilers, see the documentation for
38497 The command arguments you gave the compiler to compile your example and
38498 observe the bug. For example, did you use @samp{-O}? To guarantee
38499 you will not omit something important, list them all. A copy of the
38500 Makefile (or the output from make) is sufficient.
38502 If we were to try to guess the arguments, we would probably guess wrong
38503 and then we might not encounter the bug.
38506 A complete input script, and all necessary source files, that will
38510 A description of what behavior you observe that you believe is
38511 incorrect. For example, ``It gets a fatal signal.''
38513 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
38514 will certainly notice it. But if the bug is incorrect output, we might
38515 not notice unless it is glaringly wrong. You might as well not give us
38516 a chance to make a mistake.
38518 Even if the problem you experience is a fatal signal, you should still
38519 say so explicitly. Suppose something strange is going on, such as, your
38520 copy of @value{GDBN} is out of synch, or you have encountered a bug in
38521 the C library on your system. (This has happened!) Your copy might
38522 crash and ours would not. If you told us to expect a crash, then when
38523 ours fails to crash, we would know that the bug was not happening for
38524 us. If you had not told us to expect a crash, then we would not be able
38525 to draw any conclusion from our observations.
38528 @cindex recording a session script
38529 To collect all this information, you can use a session recording program
38530 such as @command{script}, which is available on many Unix systems.
38531 Just run your @value{GDBN} session inside @command{script} and then
38532 include the @file{typescript} file with your bug report.
38534 Another way to record a @value{GDBN} session is to run @value{GDBN}
38535 inside Emacs and then save the entire buffer to a file.
38538 If you wish to suggest changes to the @value{GDBN} source, send us context
38539 diffs. If you even discuss something in the @value{GDBN} source, refer to
38540 it by context, not by line number.
38542 The line numbers in our development sources will not match those in your
38543 sources. Your line numbers would convey no useful information to us.
38547 Here are some things that are not necessary:
38551 A description of the envelope of the bug.
38553 Often people who encounter a bug spend a lot of time investigating
38554 which changes to the input file will make the bug go away and which
38555 changes will not affect it.
38557 This is often time consuming and not very useful, because the way we
38558 will find the bug is by running a single example under the debugger
38559 with breakpoints, not by pure deduction from a series of examples.
38560 We recommend that you save your time for something else.
38562 Of course, if you can find a simpler example to report @emph{instead}
38563 of the original one, that is a convenience for us. Errors in the
38564 output will be easier to spot, running under the debugger will take
38565 less time, and so on.
38567 However, simplification is not vital; if you do not want to do this,
38568 report the bug anyway and send us the entire test case you used.
38571 A patch for the bug.
38573 A patch for the bug does help us if it is a good one. But do not omit
38574 the necessary information, such as the test case, on the assumption that
38575 a patch is all we need. We might see problems with your patch and decide
38576 to fix the problem another way, or we might not understand it at all.
38578 Sometimes with a program as complicated as @value{GDBN} it is very hard to
38579 construct an example that will make the program follow a certain path
38580 through the code. If you do not send us the example, we will not be able
38581 to construct one, so we will not be able to verify that the bug is fixed.
38583 And if we cannot understand what bug you are trying to fix, or why your
38584 patch should be an improvement, we will not install it. A test case will
38585 help us to understand.
38588 A guess about what the bug is or what it depends on.
38590 Such guesses are usually wrong. Even we cannot guess right about such
38591 things without first using the debugger to find the facts.
38594 @c The readline documentation is distributed with the readline code
38595 @c and consists of the two following files:
38598 @c Use -I with makeinfo to point to the appropriate directory,
38599 @c environment var TEXINPUTS with TeX.
38600 @ifclear SYSTEM_READLINE
38601 @include rluser.texi
38602 @include hsuser.texi
38606 @appendix In Memoriam
38608 The @value{GDBN} project mourns the loss of the following long-time
38613 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
38614 to Free Software in general. Outside of @value{GDBN}, he was known in
38615 the Amiga world for his series of Fish Disks, and the GeekGadget project.
38617 @item Michael Snyder
38618 Michael was one of the Global Maintainers of the @value{GDBN} project,
38619 with contributions recorded as early as 1996, until 2011. In addition
38620 to his day to day participation, he was a large driving force behind
38621 adding Reverse Debugging to @value{GDBN}.
38624 Beyond their technical contributions to the project, they were also
38625 enjoyable members of the Free Software Community. We will miss them.
38627 @node Formatting Documentation
38628 @appendix Formatting Documentation
38630 @cindex @value{GDBN} reference card
38631 @cindex reference card
38632 The @value{GDBN} 4 release includes an already-formatted reference card, ready
38633 for printing with PostScript or Ghostscript, in the @file{gdb}
38634 subdirectory of the main source directory@footnote{In
38635 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
38636 release.}. If you can use PostScript or Ghostscript with your printer,
38637 you can print the reference card immediately with @file{refcard.ps}.
38639 The release also includes the source for the reference card. You
38640 can format it, using @TeX{}, by typing:
38646 The @value{GDBN} reference card is designed to print in @dfn{landscape}
38647 mode on US ``letter'' size paper;
38648 that is, on a sheet 11 inches wide by 8.5 inches
38649 high. You will need to specify this form of printing as an option to
38650 your @sc{dvi} output program.
38652 @cindex documentation
38654 All the documentation for @value{GDBN} comes as part of the machine-readable
38655 distribution. The documentation is written in Texinfo format, which is
38656 a documentation system that uses a single source file to produce both
38657 on-line information and a printed manual. You can use one of the Info
38658 formatting commands to create the on-line version of the documentation
38659 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
38661 @value{GDBN} includes an already formatted copy of the on-line Info
38662 version of this manual in the @file{gdb} subdirectory. The main Info
38663 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
38664 subordinate files matching @samp{gdb.info*} in the same directory. If
38665 necessary, you can print out these files, or read them with any editor;
38666 but they are easier to read using the @code{info} subsystem in @sc{gnu}
38667 Emacs or the standalone @code{info} program, available as part of the
38668 @sc{gnu} Texinfo distribution.
38670 If you want to format these Info files yourself, you need one of the
38671 Info formatting programs, such as @code{texinfo-format-buffer} or
38674 If you have @code{makeinfo} installed, and are in the top level
38675 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
38676 version @value{GDBVN}), you can make the Info file by typing:
38683 If you want to typeset and print copies of this manual, you need @TeX{},
38684 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
38685 Texinfo definitions file.
38687 @TeX{} is a typesetting program; it does not print files directly, but
38688 produces output files called @sc{dvi} files. To print a typeset
38689 document, you need a program to print @sc{dvi} files. If your system
38690 has @TeX{} installed, chances are it has such a program. The precise
38691 command to use depends on your system; @kbd{lpr -d} is common; another
38692 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
38693 require a file name without any extension or a @samp{.dvi} extension.
38695 @TeX{} also requires a macro definitions file called
38696 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
38697 written in Texinfo format. On its own, @TeX{} cannot either read or
38698 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
38699 and is located in the @file{gdb-@var{version-number}/texinfo}
38702 If you have @TeX{} and a @sc{dvi} printer program installed, you can
38703 typeset and print this manual. First switch to the @file{gdb}
38704 subdirectory of the main source directory (for example, to
38705 @file{gdb-@value{GDBVN}/gdb}) and type:
38711 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
38713 @node Installing GDB
38714 @appendix Installing @value{GDBN}
38715 @cindex installation
38718 * Requirements:: Requirements for building @value{GDBN}
38719 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
38720 * Separate Objdir:: Compiling @value{GDBN} in another directory
38721 * Config Names:: Specifying names for hosts and targets
38722 * Configure Options:: Summary of options for configure
38723 * System-wide configuration:: Having a system-wide init file
38727 @section Requirements for Building @value{GDBN}
38728 @cindex building @value{GDBN}, requirements for
38730 Building @value{GDBN} requires various tools and packages to be available.
38731 Other packages will be used only if they are found.
38733 @heading Tools/Packages Necessary for Building @value{GDBN}
38735 @item C@t{++}11 compiler
38736 @value{GDBN} is written in C@t{++}11. It should be buildable with any
38737 recent C@t{++}11 compiler, e.g.@: GCC.
38740 @value{GDBN}'s build system relies on features only found in the GNU
38741 make program. Other variants of @code{make} will not work.
38743 @item GMP (The GNU Multiple Precision Arithmetic Library)
38744 @value{GDBN} now uses GMP to perform some of its arithmetics.
38745 This library may be included with your operating system distribution;
38746 if it is not, you can get the latest version from
38747 @url{https://gmplib.org/}. If GMP is installed at an unusual path,
38748 you can use the @option{--with-libgmp-prefix} option to specify
38753 @heading Tools/Packages Optional for Building @value{GDBN}
38757 @value{GDBN} can use the Expat XML parsing library. This library may be
38758 included with your operating system distribution; if it is not, you
38759 can get the latest version from @url{http://expat.sourceforge.net}.
38760 The @file{configure} script will search for this library in several
38761 standard locations; if it is installed in an unusual path, you can
38762 use the @option{--with-libexpat-prefix} option to specify its location.
38768 Remote protocol memory maps (@pxref{Memory Map Format})
38770 Target descriptions (@pxref{Target Descriptions})
38772 Remote shared library lists (@xref{Library List Format},
38773 or alternatively @pxref{Library List Format for SVR4 Targets})
38775 MS-Windows shared libraries (@pxref{Shared Libraries})
38777 Traceframe info (@pxref{Traceframe Info Format})
38779 Branch trace (@pxref{Branch Trace Format},
38780 @pxref{Branch Trace Configuration Format})
38784 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
38785 default, @value{GDBN} will be compiled if the Guile libraries are
38786 installed and are found by @file{configure}. You can use the
38787 @code{--with-guile} option to request Guile, and pass either the Guile
38788 version number or the file name of the relevant @code{pkg-config}
38789 program to choose a particular version of Guile.
38792 @value{GDBN}'s features related to character sets (@pxref{Character
38793 Sets}) require a functioning @code{iconv} implementation. If you are
38794 on a GNU system, then this is provided by the GNU C Library. Some
38795 other systems also provide a working @code{iconv}.
38797 If @value{GDBN} is using the @code{iconv} program which is installed
38798 in a non-standard place, you will need to tell @value{GDBN} where to
38799 find it. This is done with @option{--with-iconv-bin} which specifies
38800 the directory that contains the @code{iconv} program. This program is
38801 run in order to make a list of the available character sets.
38803 On systems without @code{iconv}, you can install GNU Libiconv. If
38804 Libiconv is installed in a standard place, @value{GDBN} will
38805 automatically use it if it is needed. If you have previously
38806 installed Libiconv in a non-standard place, you can use the
38807 @option{--with-libiconv-prefix} option to @file{configure}.
38809 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
38810 arrange to build Libiconv if a directory named @file{libiconv} appears
38811 in the top-most source directory. If Libiconv is built this way, and
38812 if the operating system does not provide a suitable @code{iconv}
38813 implementation, then the just-built library will automatically be used
38814 by @value{GDBN}. One easy way to set this up is to download GNU
38815 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
38816 source tree, and then rename the directory holding the Libiconv source
38817 code to @samp{libiconv}.
38820 @value{GDBN} can support debugging sections that are compressed with
38821 the LZMA library. @xref{MiniDebugInfo}. If this library is not
38822 included with your operating system, you can find it in the xz package
38823 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
38824 the usual place, then the @file{configure} script will use it
38825 automatically. If it is installed in an unusual path, you can use the
38826 @option{--with-liblzma-prefix} option to specify its location.
38830 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
38831 library. This library may be included with your operating system
38832 distribution; if it is not, you can get the latest version from
38833 @url{http://www.mpfr.org}. The @file{configure} script will search
38834 for this library in several standard locations; if it is installed
38835 in an unusual path, you can use the @option{--with-libmpfr-prefix}
38836 option to specify its location.
38838 GNU MPFR is used to emulate target floating-point arithmetic during
38839 expression evaluation when the target uses different floating-point
38840 formats than the host. If GNU MPFR it is not available, @value{GDBN}
38841 will fall back to using host floating-point arithmetic.
38844 @value{GDBN} can be scripted using Python language. @xref{Python}.
38845 By default, @value{GDBN} will be compiled if the Python libraries are
38846 installed and are found by @file{configure}. You can use the
38847 @code{--with-python} option to request Python, and pass either the
38848 file name of the relevant @code{python} executable, or the name of the
38849 directory in which Python is installed, to choose a particular
38850 installation of Python.
38853 @cindex compressed debug sections
38854 @value{GDBN} will use the @samp{zlib} library, if available, to read
38855 compressed debug sections. Some linkers, such as GNU gold, are capable
38856 of producing binaries with compressed debug sections. If @value{GDBN}
38857 is compiled with @samp{zlib}, it will be able to read the debug
38858 information in such binaries.
38860 The @samp{zlib} library is likely included with your operating system
38861 distribution; if it is not, you can get the latest version from
38862 @url{http://zlib.net}.
38865 @node Running Configure
38866 @section Invoking the @value{GDBN} @file{configure} Script
38867 @cindex configuring @value{GDBN}
38868 @value{GDBN} comes with a @file{configure} script that automates the process
38869 of preparing @value{GDBN} for installation; you can then use @code{make} to
38870 build the @code{gdb} program.
38872 @c irrelevant in info file; it's as current as the code it lives with.
38873 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
38874 look at the @file{README} file in the sources; we may have improved the
38875 installation procedures since publishing this manual.}
38878 The @value{GDBN} distribution includes all the source code you need for
38879 @value{GDBN} in a single directory, whose name is usually composed by
38880 appending the version number to @samp{gdb}.
38882 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
38883 @file{gdb-@value{GDBVN}} directory. That directory contains:
38886 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
38887 script for configuring @value{GDBN} and all its supporting libraries
38889 @item gdb-@value{GDBVN}/gdb
38890 the source specific to @value{GDBN} itself
38892 @item gdb-@value{GDBVN}/bfd
38893 source for the Binary File Descriptor library
38895 @item gdb-@value{GDBVN}/include
38896 @sc{gnu} include files
38898 @item gdb-@value{GDBVN}/libiberty
38899 source for the @samp{-liberty} free software library
38901 @item gdb-@value{GDBVN}/opcodes
38902 source for the library of opcode tables and disassemblers
38904 @item gdb-@value{GDBVN}/readline
38905 source for the @sc{gnu} command-line interface
38908 There may be other subdirectories as well.
38910 The simplest way to configure and build @value{GDBN} is to run @file{configure}
38911 from the @file{gdb-@var{version-number}} source directory, which in
38912 this example is the @file{gdb-@value{GDBVN}} directory.
38914 First switch to the @file{gdb-@var{version-number}} source directory
38915 if you are not already in it; then run @file{configure}. Pass the
38916 identifier for the platform on which @value{GDBN} will run as an
38922 cd gdb-@value{GDBVN}
38927 Running @samp{configure} and then running @code{make} builds the
38928 included supporting libraries, then @code{gdb} itself. The configured
38929 source files, and the binaries, are left in the corresponding source
38933 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
38934 system does not recognize this automatically when you run a different
38935 shell, you may need to run @code{sh} on it explicitly:
38941 You should run the @file{configure} script from the top directory in the
38942 source tree, the @file{gdb-@var{version-number}} directory. If you run
38943 @file{configure} from one of the subdirectories, you will configure only
38944 that subdirectory. That is usually not what you want. In particular,
38945 if you run the first @file{configure} from the @file{gdb} subdirectory
38946 of the @file{gdb-@var{version-number}} directory, you will omit the
38947 configuration of @file{bfd}, @file{readline}, and other sibling
38948 directories of the @file{gdb} subdirectory. This leads to build errors
38949 about missing include files such as @file{bfd/bfd.h}.
38951 You can install @code{@value{GDBN}} anywhere. The best way to do this
38952 is to pass the @code{--prefix} option to @code{configure}, and then
38953 install it with @code{make install}.
38955 @node Separate Objdir
38956 @section Compiling @value{GDBN} in Another Directory
38958 If you want to run @value{GDBN} versions for several host or target machines,
38959 you need a different @code{gdb} compiled for each combination of
38960 host and target. @file{configure} is designed to make this easy by
38961 allowing you to generate each configuration in a separate subdirectory,
38962 rather than in the source directory. If your @code{make} program
38963 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
38964 @code{make} in each of these directories builds the @code{gdb}
38965 program specified there.
38967 To build @code{gdb} in a separate directory, run @file{configure}
38968 with the @samp{--srcdir} option to specify where to find the source.
38969 (You also need to specify a path to find @file{configure}
38970 itself from your working directory. If the path to @file{configure}
38971 would be the same as the argument to @samp{--srcdir}, you can leave out
38972 the @samp{--srcdir} option; it is assumed.)
38974 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
38975 separate directory for a Sun 4 like this:
38979 cd gdb-@value{GDBVN}
38982 ../gdb-@value{GDBVN}/configure
38987 When @file{configure} builds a configuration using a remote source
38988 directory, it creates a tree for the binaries with the same structure
38989 (and using the same names) as the tree under the source directory. In
38990 the example, you'd find the Sun 4 library @file{libiberty.a} in the
38991 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
38992 @file{gdb-sun4/gdb}.
38994 Make sure that your path to the @file{configure} script has just one
38995 instance of @file{gdb} in it. If your path to @file{configure} looks
38996 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
38997 one subdirectory of @value{GDBN}, not the whole package. This leads to
38998 build errors about missing include files such as @file{bfd/bfd.h}.
39000 One popular reason to build several @value{GDBN} configurations in separate
39001 directories is to configure @value{GDBN} for cross-compiling (where
39002 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
39003 programs that run on another machine---the @dfn{target}).
39004 You specify a cross-debugging target by
39005 giving the @samp{--target=@var{target}} option to @file{configure}.
39007 When you run @code{make} to build a program or library, you must run
39008 it in a configured directory---whatever directory you were in when you
39009 called @file{configure} (or one of its subdirectories).
39011 The @code{Makefile} that @file{configure} generates in each source
39012 directory also runs recursively. If you type @code{make} in a source
39013 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
39014 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
39015 will build all the required libraries, and then build GDB.
39017 When you have multiple hosts or targets configured in separate
39018 directories, you can run @code{make} on them in parallel (for example,
39019 if they are NFS-mounted on each of the hosts); they will not interfere
39023 @section Specifying Names for Hosts and Targets
39025 The specifications used for hosts and targets in the @file{configure}
39026 script are based on a three-part naming scheme, but some short predefined
39027 aliases are also supported. The full naming scheme encodes three pieces
39028 of information in the following pattern:
39031 @var{architecture}-@var{vendor}-@var{os}
39034 For example, you can use the alias @code{sun4} as a @var{host} argument,
39035 or as the value for @var{target} in a @code{--target=@var{target}}
39036 option. The equivalent full name is @samp{sparc-sun-sunos4}.
39038 The @file{configure} script accompanying @value{GDBN} does not provide
39039 any query facility to list all supported host and target names or
39040 aliases. @file{configure} calls the Bourne shell script
39041 @code{config.sub} to map abbreviations to full names; you can read the
39042 script, if you wish, or you can use it to test your guesses on
39043 abbreviations---for example:
39046 % sh config.sub i386-linux
39048 % sh config.sub alpha-linux
39049 alpha-unknown-linux-gnu
39050 % sh config.sub hp9k700
39052 % sh config.sub sun4
39053 sparc-sun-sunos4.1.1
39054 % sh config.sub sun3
39055 m68k-sun-sunos4.1.1
39056 % sh config.sub i986v
39057 Invalid configuration `i986v': machine `i986v' not recognized
39061 @code{config.sub} is also distributed in the @value{GDBN} source
39062 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
39064 @node Configure Options
39065 @section @file{configure} Options
39067 Here is a summary of the @file{configure} options and arguments that
39068 are most often useful for building @value{GDBN}. @file{configure}
39069 also has several other options not listed here. @xref{Running
39070 configure Scripts,,,autoconf}, for a full
39071 explanation of @file{configure}.
39074 configure @r{[}--help@r{]}
39075 @r{[}--prefix=@var{dir}@r{]}
39076 @r{[}--exec-prefix=@var{dir}@r{]}
39077 @r{[}--srcdir=@var{dirname}@r{]}
39078 @r{[}--target=@var{target}@r{]}
39082 You may introduce options with a single @samp{-} rather than
39083 @samp{--} if you prefer; but you may abbreviate option names if you use
39088 Display a quick summary of how to invoke @file{configure}.
39090 @item --prefix=@var{dir}
39091 Configure the source to install programs and files under directory
39094 @item --exec-prefix=@var{dir}
39095 Configure the source to install programs under directory
39098 @c avoid splitting the warning from the explanation:
39100 @item --srcdir=@var{dirname}
39101 Use this option to make configurations in directories separate from the
39102 @value{GDBN} source directories. Among other things, you can use this to
39103 build (or maintain) several configurations simultaneously, in separate
39104 directories. @file{configure} writes configuration-specific files in
39105 the current directory, but arranges for them to use the source in the
39106 directory @var{dirname}. @file{configure} creates directories under
39107 the working directory in parallel to the source directories below
39110 @item --target=@var{target}
39111 Configure @value{GDBN} for cross-debugging programs running on the specified
39112 @var{target}. Without this option, @value{GDBN} is configured to debug
39113 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
39115 There is no convenient way to generate a list of all available
39116 targets. Also see the @code{--enable-targets} option, below.
39119 There are many other options that are specific to @value{GDBN}. This
39120 lists just the most common ones; there are some very specialized
39121 options not described here.
39124 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
39125 @itemx --enable-targets=all
39126 Configure @value{GDBN} for cross-debugging programs running on the
39127 specified list of targets. The special value @samp{all} configures
39128 @value{GDBN} for debugging programs running on any target it supports.
39130 @item --with-gdb-datadir=@var{path}
39131 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
39132 here for certain supporting files or scripts. This defaults to the
39133 @file{gdb} subdirectory of @samp{datadir} (which can be set using
39136 @item --with-relocated-sources=@var{dir}
39137 Sets up the default source path substitution rule so that directory
39138 names recorded in debug information will be automatically adjusted for
39139 any directory under @var{dir}. @var{dir} should be a subdirectory of
39140 @value{GDBN}'s configured prefix, the one mentioned in the
39141 @code{--prefix} or @code{--exec-prefix} options to configure. This
39142 option is useful if GDB is supposed to be moved to a different place
39145 @item --enable-64-bit-bfd
39146 Enable 64-bit support in BFD on 32-bit hosts.
39148 @item --disable-gdbmi
39149 Build @value{GDBN} without the GDB/MI machine interface
39153 Build @value{GDBN} with the text-mode full-screen user interface
39154 (TUI). Requires a curses library (ncurses and cursesX are also
39157 @item --with-curses
39158 Use the curses library instead of the termcap library, for text-mode
39159 terminal operations.
39161 @item --with-debuginfod
39162 Build @value{GDBN} with @file{libdebuginfod}, the @code{debuginfod} client
39163 library. Used to automatically fetch ELF, DWARF and source files from
39164 @code{debuginfod} servers using build IDs associated with any missing
39165 files. Enabled by default if @file{libdebuginfod} is installed and found
39166 at configure time. For more information regarding @code{debuginfod} see
39169 @item --with-libunwind-ia64
39170 Use the libunwind library for unwinding function call stack on ia64
39171 target platforms. See http://www.nongnu.org/libunwind/index.html for
39174 @item --with-system-readline
39175 Use the readline library installed on the host, rather than the
39176 library supplied as part of @value{GDBN}. Readline 7 or newer is
39177 required; this is enforced by the build system.
39179 @item --with-system-zlib
39180 Use the zlib library installed on the host, rather than the library
39181 supplied as part of @value{GDBN}.
39184 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
39185 default if libexpat is installed and found at configure time.) This
39186 library is used to read XML files supplied with @value{GDBN}. If it
39187 is unavailable, some features, such as remote protocol memory maps,
39188 target descriptions, and shared library lists, that are based on XML
39189 files, will not be available in @value{GDBN}. If your host does not
39190 have libexpat installed, you can get the latest version from
39191 `http://expat.sourceforge.net'.
39193 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
39195 Build @value{GDBN} with GNU libiconv, a character set encoding
39196 conversion library. This is not done by default, as on GNU systems
39197 the @code{iconv} that is built in to the C library is sufficient. If
39198 your host does not have a working @code{iconv}, you can get the latest
39199 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
39201 @value{GDBN}'s build system also supports building GNU libiconv as
39202 part of the overall build. @xref{Requirements}.
39205 Build @value{GDBN} with LZMA, a compression library. (Done by default
39206 if liblzma is installed and found at configure time.) LZMA is used by
39207 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
39208 platforms using the ELF object file format. If your host does not
39209 have liblzma installed, you can get the latest version from
39210 `https://tukaani.org/xz/'.
39213 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
39214 floating-point computation with correct rounding. (Done by default if
39215 GNU MPFR is installed and found at configure time.) This library is
39216 used to emulate target floating-point arithmetic during expression
39217 evaluation when the target uses different floating-point formats than
39218 the host. If GNU MPFR is not available, @value{GDBN} will fall back
39219 to using host floating-point arithmetic. If your host does not have
39220 GNU MPFR installed, you can get the latest version from
39221 `http://www.mpfr.org'.
39223 @item --with-python@r{[}=@var{python}@r{]}
39224 Build @value{GDBN} with Python scripting support. (Done by default if
39225 libpython is present and found at configure time.) Python makes
39226 @value{GDBN} scripting much more powerful than the restricted CLI
39227 scripting language. If your host does not have Python installed, you
39228 can find it on `http://www.python.org/download/'. The oldest version
39229 of Python supported by GDB is 2.6. The optional argument @var{python}
39230 is used to find the Python headers and libraries. It can be either
39231 the name of a Python executable, or the name of the directory in which
39232 Python is installed.
39234 @item --with-guile[=GUILE]'
39235 Build @value{GDBN} with GNU Guile scripting support. (Done by default
39236 if libguile is present and found at configure time.) If your host
39237 does not have Guile installed, you can find it at
39238 `https://www.gnu.org/software/guile/'. The optional argument GUILE
39239 can be a version number, which will cause @code{configure} to try to
39240 use that version of Guile; or the file name of a @code{pkg-config}
39241 executable, which will be queried to find the information needed to
39242 compile and link against Guile.
39244 @item --without-included-regex
39245 Don't use the regex library included with @value{GDBN} (as part of the
39246 libiberty library). This is the default on hosts with version 2 of
39249 @item --with-sysroot=@var{dir}
39250 Use @var{dir} as the default system root directory for libraries whose
39251 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
39252 @var{dir} can be modified at run time by using the @command{set
39253 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
39254 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
39255 default system root will be automatically adjusted if and when
39256 @value{GDBN} is moved to a different location.
39258 @item --with-system-gdbinit=@var{file}
39259 Configure @value{GDBN} to automatically load a system-wide init file.
39260 @var{file} should be an absolute file name. If @var{file} is in a
39261 directory under the configured prefix, and @value{GDBN} is moved to
39262 another location after being built, the location of the system-wide
39263 init file will be adjusted accordingly.
39265 @item --with-system-gdbinit-dir=@var{directory}
39266 Configure @value{GDBN} to automatically load init files from a
39267 system-wide directory. @var{directory} should be an absolute directory
39268 name. If @var{directory} is in a directory under the configured
39269 prefix, and @value{GDBN} is moved to another location after being
39270 built, the location of the system-wide init directory will be
39271 adjusted accordingly.
39273 @item --enable-build-warnings
39274 When building the @value{GDBN} sources, ask the compiler to warn about
39275 any code which looks even vaguely suspicious. It passes many
39276 different warning flags, depending on the exact version of the
39277 compiler you are using.
39279 @item --enable-werror
39280 Treat compiler warnings as errors. It adds the @code{-Werror} flag
39281 to the compiler, which will fail the compilation if the compiler
39282 outputs any warning messages.
39284 @item --enable-ubsan
39285 Enable the GCC undefined behavior sanitizer. This is disabled by
39286 default, but passing @code{--enable-ubsan=yes} or
39287 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
39288 undefined behavior sanitizer checks for C@t{++} undefined behavior.
39289 It has a performance cost, so if you are looking at @value{GDBN}'s
39290 performance, you should disable it. The undefined behavior sanitizer
39291 was first introduced in GCC 4.9.
39294 @node System-wide configuration
39295 @section System-wide configuration and settings
39296 @cindex system-wide init file
39298 @value{GDBN} can be configured to have a system-wide init file and a
39299 system-wide init file directory; this file and files in that directory
39300 (if they have a recognized file extension) will be read and executed at
39301 startup (@pxref{Startup, , What @value{GDBN} does during startup}).
39303 Here are the corresponding configure options:
39306 @item --with-system-gdbinit=@var{file}
39307 Specify that the default location of the system-wide init file is
39309 @item --with-system-gdbinit-dir=@var{directory}
39310 Specify that the default location of the system-wide init file directory
39311 is @var{directory}.
39314 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
39315 they may be subject to relocation. Two possible cases:
39319 If the default location of this init file/directory contains @file{$prefix},
39320 it will be subject to relocation. Suppose that the configure options
39321 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
39322 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
39323 init file is looked for as @file{$install/etc/gdbinit} instead of
39324 @file{$prefix/etc/gdbinit}.
39327 By contrast, if the default location does not contain the prefix,
39328 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
39329 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
39330 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
39331 wherever @value{GDBN} is installed.
39334 If the configured location of the system-wide init file (as given by the
39335 @option{--with-system-gdbinit} option at configure time) is in the
39336 data-directory (as specified by @option{--with-gdb-datadir} at configure
39337 time) or in one of its subdirectories, then @value{GDBN} will look for the
39338 system-wide init file in the directory specified by the
39339 @option{--data-directory} command-line option.
39340 Note that the system-wide init file is only read once, during @value{GDBN}
39341 initialization. If the data-directory is changed after @value{GDBN} has
39342 started with the @code{set data-directory} command, the file will not be
39345 This applies similarly to the system-wide directory specified in
39346 @option{--with-system-gdbinit-dir}.
39348 Any supported scripting language can be used for these init files, as long
39349 as the file extension matches the scripting language. To be interpreted
39350 as regular @value{GDBN} commands, the files needs to have a @file{.gdb}
39354 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
39357 @node System-wide Configuration Scripts
39358 @subsection Installed System-wide Configuration Scripts
39359 @cindex system-wide configuration scripts
39361 The @file{system-gdbinit} directory, located inside the data-directory
39362 (as specified by @option{--with-gdb-datadir} at configure time) contains
39363 a number of scripts which can be used as system-wide init files. To
39364 automatically source those scripts at startup, @value{GDBN} should be
39365 configured with @option{--with-system-gdbinit}. Otherwise, any user
39366 should be able to source them by hand as needed.
39368 The following scripts are currently available:
39371 @item @file{elinos.py}
39373 @cindex ELinOS system-wide configuration script
39374 This script is useful when debugging a program on an ELinOS target.
39375 It takes advantage of the environment variables defined in a standard
39376 ELinOS environment in order to determine the location of the system
39377 shared libraries, and then sets the @samp{solib-absolute-prefix}
39378 and @samp{solib-search-path} variables appropriately.
39380 @item @file{wrs-linux.py}
39381 @pindex wrs-linux.py
39382 @cindex Wind River Linux system-wide configuration script
39383 This script is useful when debugging a program on a target running
39384 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
39385 the host-side sysroot used by the target system.
39389 @node Maintenance Commands
39390 @appendix Maintenance Commands
39391 @cindex maintenance commands
39392 @cindex internal commands
39394 In addition to commands intended for @value{GDBN} users, @value{GDBN}
39395 includes a number of commands intended for @value{GDBN} developers,
39396 that are not documented elsewhere in this manual. These commands are
39397 provided here for reference. (For commands that turn on debugging
39398 messages, see @ref{Debugging Output}.)
39401 @kindex maint agent
39402 @kindex maint agent-eval
39403 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39404 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
39405 Translate the given @var{expression} into remote agent bytecodes.
39406 This command is useful for debugging the Agent Expression mechanism
39407 (@pxref{Agent Expressions}). The @samp{agent} version produces an
39408 expression useful for data collection, such as by tracepoints, while
39409 @samp{maint agent-eval} produces an expression that evaluates directly
39410 to a result. For instance, a collection expression for @code{globa +
39411 globb} will include bytecodes to record four bytes of memory at each
39412 of the addresses of @code{globa} and @code{globb}, while discarding
39413 the result of the addition, while an evaluation expression will do the
39414 addition and return the sum.
39415 If @code{-at} is given, generate remote agent bytecode for @var{location}.
39416 If not, generate remote agent bytecode for current frame PC address.
39418 @kindex maint agent-printf
39419 @item maint agent-printf @var{format},@var{expr},...
39420 Translate the given format string and list of argument expressions
39421 into remote agent bytecodes and display them as a disassembled list.
39422 This command is useful for debugging the agent version of dynamic
39423 printf (@pxref{Dynamic Printf}).
39425 @kindex maint info breakpoints
39426 @item @anchor{maint info breakpoints}maint info breakpoints
39427 Using the same format as @samp{info breakpoints}, display both the
39428 breakpoints you've set explicitly, and those @value{GDBN} is using for
39429 internal purposes. Internal breakpoints are shown with negative
39430 breakpoint numbers. The type column identifies what kind of breakpoint
39435 Normal, explicitly set breakpoint.
39438 Normal, explicitly set watchpoint.
39441 Internal breakpoint, used to handle correctly stepping through
39442 @code{longjmp} calls.
39444 @item longjmp resume
39445 Internal breakpoint at the target of a @code{longjmp}.
39448 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
39451 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
39454 Shared library events.
39458 @kindex maint info btrace
39459 @item maint info btrace
39460 Pint information about raw branch tracing data.
39462 @kindex maint btrace packet-history
39463 @item maint btrace packet-history
39464 Print the raw branch trace packets that are used to compute the
39465 execution history for the @samp{record btrace} command. Both the
39466 information and the format in which it is printed depend on the btrace
39471 For the BTS recording format, print a list of blocks of sequential
39472 code. For each block, the following information is printed:
39476 Newer blocks have higher numbers. The oldest block has number zero.
39477 @item Lowest @samp{PC}
39478 @item Highest @samp{PC}
39482 For the Intel Processor Trace recording format, print a list of
39483 Intel Processor Trace packets. For each packet, the following
39484 information is printed:
39487 @item Packet number
39488 Newer packets have higher numbers. The oldest packet has number zero.
39490 The packet's offset in the trace stream.
39491 @item Packet opcode and payload
39495 @kindex maint btrace clear-packet-history
39496 @item maint btrace clear-packet-history
39497 Discards the cached packet history printed by the @samp{maint btrace
39498 packet-history} command. The history will be computed again when
39501 @kindex maint btrace clear
39502 @item maint btrace clear
39503 Discard the branch trace data. The data will be fetched anew and the
39504 branch trace will be recomputed when needed.
39506 This implicitly truncates the branch trace to a single branch trace
39507 buffer. When updating branch trace incrementally, the branch trace
39508 available to @value{GDBN} may be bigger than a single branch trace
39511 @kindex maint set btrace pt skip-pad
39512 @item maint set btrace pt skip-pad
39513 @kindex maint show btrace pt skip-pad
39514 @item maint show btrace pt skip-pad
39515 Control whether @value{GDBN} will skip PAD packets when computing the
39518 @kindex maint info jit
39519 @item maint info jit
39520 Print information about JIT code objects loaded in the current inferior.
39522 @kindex set displaced-stepping
39523 @kindex show displaced-stepping
39524 @cindex displaced stepping support
39525 @cindex out-of-line single-stepping
39526 @item set displaced-stepping
39527 @itemx show displaced-stepping
39528 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
39529 if the target supports it. Displaced stepping is a way to single-step
39530 over breakpoints without removing them from the inferior, by executing
39531 an out-of-line copy of the instruction that was originally at the
39532 breakpoint location. It is also known as out-of-line single-stepping.
39535 @item set displaced-stepping on
39536 If the target architecture supports it, @value{GDBN} will use
39537 displaced stepping to step over breakpoints.
39539 @item set displaced-stepping off
39540 @value{GDBN} will not use displaced stepping to step over breakpoints,
39541 even if such is supported by the target architecture.
39543 @cindex non-stop mode, and @samp{set displaced-stepping}
39544 @item set displaced-stepping auto
39545 This is the default mode. @value{GDBN} will use displaced stepping
39546 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
39547 architecture supports displaced stepping.
39550 @kindex maint check-psymtabs
39551 @item maint check-psymtabs
39552 Check the consistency of currently expanded psymtabs versus symtabs.
39553 Use this to check, for example, whether a symbol is in one but not the other.
39555 @kindex maint check-symtabs
39556 @item maint check-symtabs
39557 Check the consistency of currently expanded symtabs.
39559 @kindex maint expand-symtabs
39560 @item maint expand-symtabs [@var{regexp}]
39561 Expand symbol tables.
39562 If @var{regexp} is specified, only expand symbol tables for file
39563 names matching @var{regexp}.
39565 @kindex maint set catch-demangler-crashes
39566 @kindex maint show catch-demangler-crashes
39567 @cindex demangler crashes
39568 @item maint set catch-demangler-crashes [on|off]
39569 @itemx maint show catch-demangler-crashes
39570 Control whether @value{GDBN} should attempt to catch crashes in the
39571 symbol name demangler. The default is to attempt to catch crashes.
39572 If enabled, the first time a crash is caught, a core file is created,
39573 the offending symbol is displayed and the user is presented with the
39574 option to terminate the current session.
39576 @kindex maint cplus first_component
39577 @item maint cplus first_component @var{name}
39578 Print the first C@t{++} class/namespace component of @var{name}.
39580 @kindex maint cplus namespace
39581 @item maint cplus namespace
39582 Print the list of possible C@t{++} namespaces.
39584 @kindex maint deprecate
39585 @kindex maint undeprecate
39586 @cindex deprecated commands
39587 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
39588 @itemx maint undeprecate @var{command}
39589 Deprecate or undeprecate the named @var{command}. Deprecated commands
39590 cause @value{GDBN} to issue a warning when you use them. The optional
39591 argument @var{replacement} says which newer command should be used in
39592 favor of the deprecated one; if it is given, @value{GDBN} will mention
39593 the replacement as part of the warning.
39595 @kindex maint dump-me
39596 @item maint dump-me
39597 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
39598 Cause a fatal signal in the debugger and force it to dump its core.
39599 This is supported only on systems which support aborting a program
39600 with the @code{SIGQUIT} signal.
39602 @kindex maint internal-error
39603 @kindex maint internal-warning
39604 @kindex maint demangler-warning
39605 @cindex demangler crashes
39606 @item maint internal-error @r{[}@var{message-text}@r{]}
39607 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
39608 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
39610 Cause @value{GDBN} to call the internal function @code{internal_error},
39611 @code{internal_warning} or @code{demangler_warning} and hence behave
39612 as though an internal problem has been detected. In addition to
39613 reporting the internal problem, these functions give the user the
39614 opportunity to either quit @value{GDBN} or (for @code{internal_error}
39615 and @code{internal_warning}) create a core file of the current
39616 @value{GDBN} session.
39618 These commands take an optional parameter @var{message-text} that is
39619 used as the text of the error or warning message.
39621 Here's an example of using @code{internal-error}:
39624 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
39625 @dots{}/maint.c:121: internal-error: testing, 1, 2
39626 A problem internal to GDB has been detected. Further
39627 debugging may prove unreliable.
39628 Quit this debugging session? (y or n) @kbd{n}
39629 Create a core file? (y or n) @kbd{n}
39633 @cindex @value{GDBN} internal error
39634 @cindex internal errors, control of @value{GDBN} behavior
39635 @cindex demangler crashes
39637 @kindex maint set internal-error
39638 @kindex maint show internal-error
39639 @kindex maint set internal-warning
39640 @kindex maint show internal-warning
39641 @kindex maint set demangler-warning
39642 @kindex maint show demangler-warning
39643 @item maint set internal-error @var{action} [ask|yes|no]
39644 @itemx maint show internal-error @var{action}
39645 @itemx maint set internal-warning @var{action} [ask|yes|no]
39646 @itemx maint show internal-warning @var{action}
39647 @itemx maint set demangler-warning @var{action} [ask|yes|no]
39648 @itemx maint show demangler-warning @var{action}
39649 When @value{GDBN} reports an internal problem (error or warning) it
39650 gives the user the opportunity to both quit @value{GDBN} and create a
39651 core file of the current @value{GDBN} session. These commands let you
39652 override the default behaviour for each particular @var{action},
39653 described in the table below.
39657 You can specify that @value{GDBN} should always (yes) or never (no)
39658 quit. The default is to ask the user what to do.
39661 You can specify that @value{GDBN} should always (yes) or never (no)
39662 create a core file. The default is to ask the user what to do. Note
39663 that there is no @code{corefile} option for @code{demangler-warning}:
39664 demangler warnings always create a core file and this cannot be
39668 @kindex maint set internal-error
39669 @kindex maint show internal-error
39670 @kindex maint set internal-warning
39671 @kindex maint show internal-warning
39672 @item maint set internal-error backtrace @r{[}on|off@r{]}
39673 @itemx maint show internal-error backtrace
39674 @itemx maint set internal-warning backtrace @r{[}on|off@r{]}
39675 @itemx maint show internal-warning backtrace
39676 When @value{GDBN} reports an internal problem (error or warning) it is
39677 possible to have a backtrace of @value{GDBN} printed to the standard
39678 error stream. This is @samp{on} by default for @code{internal-error}
39679 and @samp{off} by default for @code{internal-warning}.
39681 @anchor{maint packet}
39682 @kindex maint packet
39683 @item maint packet @var{text}
39684 If @value{GDBN} is talking to an inferior via the serial protocol,
39685 then this command sends the string @var{text} to the inferior, and
39686 displays the response packet. @value{GDBN} supplies the initial
39687 @samp{$} character, the terminating @samp{#} character, and the
39690 Any non-printable characters in the reply are printed as escaped hex,
39691 e.g. @samp{\x00}, @samp{\x01}, etc.
39693 @kindex maint print architecture
39694 @item maint print architecture @r{[}@var{file}@r{]}
39695 Print the entire architecture configuration. The optional argument
39696 @var{file} names the file where the output goes.
39698 @kindex maint print c-tdesc
39699 @item maint print c-tdesc @r{[}-single-feature@r{]} @r{[}@var{file}@r{]}
39700 Print the target description (@pxref{Target Descriptions}) as
39701 a C source file. By default, the target description is for the current
39702 target, but if the optional argument @var{file} is provided, that file
39703 is used to produce the description. The @var{file} should be an XML
39704 document, of the form described in @ref{Target Description Format}.
39705 The created source file is built into @value{GDBN} when @value{GDBN} is
39706 built again. This command is used by developers after they add or
39707 modify XML target descriptions.
39709 When the optional flag @samp{-single-feature} is provided then the
39710 target description being processed (either the default, or from
39711 @var{file}) must only contain a single feature. The source file
39712 produced is different in this case.
39714 @kindex maint print xml-tdesc
39715 @item maint print xml-tdesc @r{[}@var{file}@r{]}
39716 Print the target description (@pxref{Target Descriptions}) as an XML
39717 file. By default print the target description for the current target,
39718 but if the optional argument @var{file} is provided, then that file is
39719 read in by GDB and then used to produce the description. The
39720 @var{file} should be an XML document, of the form described in
39721 @ref{Target Description Format}.
39723 @kindex maint check xml-descriptions
39724 @item maint check xml-descriptions @var{dir}
39725 Check that the target descriptions dynamically created by @value{GDBN}
39726 equal the descriptions created from XML files found in @var{dir}.
39728 @anchor{maint check libthread-db}
39729 @kindex maint check libthread-db
39730 @item maint check libthread-db
39731 Run integrity checks on the current inferior's thread debugging
39732 library. This exercises all @code{libthread_db} functionality used by
39733 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
39734 @code{proc_service} functions provided by @value{GDBN} that
39735 @code{libthread_db} uses. Note that parts of the test may be skipped
39736 on some platforms when debugging core files.
39738 @kindex maint print core-file-backed-mappings
39739 @cindex memory address space mappings
39740 @item maint print core-file-backed-mappings
39741 Print the file-backed mappings which were loaded from a core file note.
39742 This output represents state internal to @value{GDBN} and should be
39743 similar to the mappings displayed by the @code{info proc mappings}
39746 @kindex maint print dummy-frames
39747 @item maint print dummy-frames
39748 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
39751 (@value{GDBP}) @kbd{b add}
39753 (@value{GDBP}) @kbd{print add(2,3)}
39754 Breakpoint 2, add (a=2, b=3) at @dots{}
39756 The program being debugged stopped while in a function called from GDB.
39758 (@value{GDBP}) @kbd{maint print dummy-frames}
39759 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
39763 Takes an optional file parameter.
39765 @kindex maint print registers
39766 @kindex maint print raw-registers
39767 @kindex maint print cooked-registers
39768 @kindex maint print register-groups
39769 @kindex maint print remote-registers
39770 @item maint print registers @r{[}@var{file}@r{]}
39771 @itemx maint print raw-registers @r{[}@var{file}@r{]}
39772 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
39773 @itemx maint print register-groups @r{[}@var{file}@r{]}
39774 @itemx maint print remote-registers @r{[}@var{file}@r{]}
39775 Print @value{GDBN}'s internal register data structures.
39777 The command @code{maint print raw-registers} includes the contents of
39778 the raw register cache; the command @code{maint print
39779 cooked-registers} includes the (cooked) value of all registers,
39780 including registers which aren't available on the target nor visible
39781 to user; the command @code{maint print register-groups} includes the
39782 groups that each register is a member of; and the command @code{maint
39783 print remote-registers} includes the remote target's register numbers
39784 and offsets in the `G' packets.
39786 These commands take an optional parameter, a file name to which to
39787 write the information.
39789 @kindex maint print reggroups
39790 @item maint print reggroups @r{[}@var{file}@r{]}
39791 Print @value{GDBN}'s internal register group data structures. The
39792 optional argument @var{file} tells to what file to write the
39795 The register groups info looks like this:
39798 (@value{GDBP}) @kbd{maint print reggroups}
39809 @kindex maint flush register-cache
39811 @cindex register cache, flushing
39812 @item maint flush register-cache
39814 Flush the contents of the register cache and as a consequence the
39815 frame cache. This command is useful when debugging issues related to
39816 register fetching, or frame unwinding. The command @code{flushregs}
39817 is deprecated in favor of @code{maint flush register-cache}.
39819 @kindex maint flush source-cache
39820 @cindex source code, caching
39821 @item maint flush source-cache
39822 Flush @value{GDBN}'s cache of source code file contents. After
39823 @value{GDBN} reads a source file, and optionally applies styling
39824 (@pxref{Output Styling}), the file contents are cached. This command
39825 clears that cache. The next time @value{GDBN} wants to show lines
39826 from a source file, the content will be re-read.
39828 This command is useful when debugging issues related to source code
39829 styling. After flushing the cache any source code displayed by
39830 @value{GDBN} will be re-read and re-styled.
39832 @kindex maint print objfiles
39833 @cindex info for known object files
39834 @item maint print objfiles @r{[}@var{regexp}@r{]}
39835 Print a dump of all known object files.
39836 If @var{regexp} is specified, only print object files whose names
39837 match @var{regexp}. For each object file, this command prints its name,
39838 address in memory, and all of its psymtabs and symtabs.
39840 @kindex maint print user-registers
39841 @cindex user registers
39842 @item maint print user-registers
39843 List all currently available @dfn{user registers}. User registers
39844 typically provide alternate names for actual hardware registers. They
39845 include the four ``standard'' registers @code{$fp}, @code{$pc},
39846 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
39847 registers can be used in expressions in the same way as the canonical
39848 register names, but only the latter are listed by the @code{info
39849 registers} and @code{maint print registers} commands.
39851 @kindex maint print section-scripts
39852 @cindex info for known .debug_gdb_scripts-loaded scripts
39853 @item maint print section-scripts [@var{regexp}]
39854 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
39855 If @var{regexp} is specified, only print scripts loaded by object files
39856 matching @var{regexp}.
39857 For each script, this command prints its name as specified in the objfile,
39858 and the full path if known.
39859 @xref{dotdebug_gdb_scripts section}.
39861 @kindex maint print statistics
39862 @cindex bcache statistics
39863 @item maint print statistics
39864 This command prints, for each object file in the program, various data
39865 about that object file followed by the byte cache (@dfn{bcache})
39866 statistics for the object file. The objfile data includes the number
39867 of minimal, partial, full, and stabs symbols, the number of types
39868 defined by the objfile, the number of as yet unexpanded psym tables,
39869 the number of line tables and string tables, and the amount of memory
39870 used by the various tables. The bcache statistics include the counts,
39871 sizes, and counts of duplicates of all and unique objects, max,
39872 average, and median entry size, total memory used and its overhead and
39873 savings, and various measures of the hash table size and chain
39876 @kindex maint print target-stack
39877 @cindex target stack description
39878 @item maint print target-stack
39879 A @dfn{target} is an interface between the debugger and a particular
39880 kind of file or process. Targets can be stacked in @dfn{strata},
39881 so that more than one target can potentially respond to a request.
39882 In particular, memory accesses will walk down the stack of targets
39883 until they find a target that is interested in handling that particular
39886 This command prints a short description of each layer that was pushed on
39887 the @dfn{target stack}, starting from the top layer down to the bottom one.
39889 @kindex maint print type
39890 @cindex type chain of a data type
39891 @item maint print type @var{expr}
39892 Print the type chain for a type specified by @var{expr}. The argument
39893 can be either a type name or a symbol. If it is a symbol, the type of
39894 that symbol is described. The type chain produced by this command is
39895 a recursive definition of the data type as stored in @value{GDBN}'s
39896 data structures, including its flags and contained types.
39898 @kindex maint selftest
39900 @item maint selftest @r{[}-verbose@r{]} @r{[}@var{filter}@r{]}
39901 Run any self tests that were compiled in to @value{GDBN}. This will
39902 print a message showing how many tests were run, and how many failed.
39903 If a @var{filter} is passed, only the tests with @var{filter} in their
39904 name will be ran. If @code{-verbose} is passed, the self tests can be
39907 @kindex maint set selftest verbose
39908 @kindex maint show selftest verbose
39910 @item maint set selftest verbose
39911 @item maint show selftest verbose
39912 Control whether self tests are run verbosely or not.
39914 @kindex maint info selftests
39916 @item maint info selftests
39917 List the selftests compiled in to @value{GDBN}.
39919 @kindex maint set dwarf always-disassemble
39920 @kindex maint show dwarf always-disassemble
39921 @item maint set dwarf always-disassemble
39922 @item maint show dwarf always-disassemble
39923 Control the behavior of @code{info address} when using DWARF debugging
39926 The default is @code{off}, which means that @value{GDBN} should try to
39927 describe a variable's location in an easily readable format. When
39928 @code{on}, @value{GDBN} will instead display the DWARF location
39929 expression in an assembly-like format. Note that some locations are
39930 too complex for @value{GDBN} to describe simply; in this case you will
39931 always see the disassembly form.
39933 Here is an example of the resulting disassembly:
39936 (gdb) info addr argc
39937 Symbol "argc" is a complex DWARF expression:
39941 For more information on these expressions, see
39942 @uref{http://www.dwarfstd.org/, the DWARF standard}.
39944 @kindex maint set dwarf max-cache-age
39945 @kindex maint show dwarf max-cache-age
39946 @item maint set dwarf max-cache-age
39947 @itemx maint show dwarf max-cache-age
39948 Control the DWARF compilation unit cache.
39950 @cindex DWARF compilation units cache
39951 In object files with inter-compilation-unit references, such as those
39952 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
39953 reader needs to frequently refer to previously read compilation units.
39954 This setting controls how long a compilation unit will remain in the
39955 cache if it is not referenced. A higher limit means that cached
39956 compilation units will be stored in memory longer, and more total
39957 memory will be used. Setting it to zero disables caching, which will
39958 slow down @value{GDBN} startup, but reduce memory consumption.
39960 @kindex maint set dwarf unwinders
39961 @kindex maint show dwarf unwinders
39962 @item maint set dwarf unwinders
39963 @itemx maint show dwarf unwinders
39964 Control use of the DWARF frame unwinders.
39966 @cindex DWARF frame unwinders
39967 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
39968 frame unwinders to build the backtrace. Many of these targets will
39969 also have a second mechanism for building the backtrace for use in
39970 cases where DWARF information is not available, this second mechanism
39971 is often an analysis of a function's prologue.
39973 In order to extend testing coverage of the second level stack
39974 unwinding mechanisms it is helpful to be able to disable the DWARF
39975 stack unwinders, this can be done with this switch.
39977 In normal use of @value{GDBN} disabling the DWARF unwinders is not
39978 advisable, there are cases that are better handled through DWARF than
39979 prologue analysis, and the debug experience is likely to be better
39980 with the DWARF frame unwinders enabled.
39982 If DWARF frame unwinders are not supported for a particular target
39983 architecture, then enabling this flag does not cause them to be used.
39985 @kindex maint set worker-threads
39986 @kindex maint show worker-threads
39987 @item maint set worker-threads
39988 @item maint show worker-threads
39989 Control the number of worker threads that may be used by @value{GDBN}.
39990 On capable hosts, @value{GDBN} may use multiple threads to speed up
39991 certain CPU-intensive operations, such as demangling symbol names.
39992 While the number of threads used by @value{GDBN} may vary, this
39993 command can be used to set an upper bound on this number. The default
39994 is @code{unlimited}, which lets @value{GDBN} choose a reasonable
39995 number. Note that this only controls worker threads started by
39996 @value{GDBN} itself; libraries used by @value{GDBN} may start threads
39999 @kindex maint set profile
40000 @kindex maint show profile
40001 @cindex profiling GDB
40002 @item maint set profile
40003 @itemx maint show profile
40004 Control profiling of @value{GDBN}.
40006 Profiling will be disabled until you use the @samp{maint set profile}
40007 command to enable it. When you enable profiling, the system will begin
40008 collecting timing and execution count data; when you disable profiling or
40009 exit @value{GDBN}, the results will be written to a log file. Remember that
40010 if you use profiling, @value{GDBN} will overwrite the profiling log file
40011 (often called @file{gmon.out}). If you have a record of important profiling
40012 data in a @file{gmon.out} file, be sure to move it to a safe location.
40014 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
40015 compiled with the @samp{-pg} compiler option.
40017 @kindex maint set show-debug-regs
40018 @kindex maint show show-debug-regs
40019 @cindex hardware debug registers
40020 @item maint set show-debug-regs
40021 @itemx maint show show-debug-regs
40022 Control whether to show variables that mirror the hardware debug
40023 registers. Use @code{on} to enable, @code{off} to disable. If
40024 enabled, the debug registers values are shown when @value{GDBN} inserts or
40025 removes a hardware breakpoint or watchpoint, and when the inferior
40026 triggers a hardware-assisted breakpoint or watchpoint.
40028 @kindex maint set show-all-tib
40029 @kindex maint show show-all-tib
40030 @item maint set show-all-tib
40031 @itemx maint show show-all-tib
40032 Control whether to show all non zero areas within a 1k block starting
40033 at thread local base, when using the @samp{info w32 thread-information-block}
40036 @kindex maint set target-async
40037 @kindex maint show target-async
40038 @item maint set target-async
40039 @itemx maint show target-async
40040 This controls whether @value{GDBN} targets operate in synchronous or
40041 asynchronous mode (@pxref{Background Execution}). Normally the
40042 default is asynchronous, if it is available; but this can be changed
40043 to more easily debug problems occurring only in synchronous mode.
40045 @kindex maint set target-non-stop @var{mode} [on|off|auto]
40046 @kindex maint show target-non-stop
40047 @item maint set target-non-stop
40048 @itemx maint show target-non-stop
40050 This controls whether @value{GDBN} targets always operate in non-stop
40051 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
40052 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
40053 if supported by the target.
40056 @item maint set target-non-stop auto
40057 This is the default mode. @value{GDBN} controls the target in
40058 non-stop mode if the target supports it.
40060 @item maint set target-non-stop on
40061 @value{GDBN} controls the target in non-stop mode even if the target
40062 does not indicate support.
40064 @item maint set target-non-stop off
40065 @value{GDBN} does not control the target in non-stop mode even if the
40066 target supports it.
40069 @kindex maint set tui-resize-message
40070 @kindex maint show tui-resize-message
40071 @item maint set tui-resize-message
40072 @item maint show tui-resize-message
40073 Control whether @value{GDBN} displays a message each time the terminal
40074 is resized when in TUI mode. The default is @code{off}, which means
40075 that @value{GDBN} is silent during resizes. When @code{on},
40076 @value{GDBN} will display a message after a resize is completed; the
40077 message will include a number indicating how many times the terminal
40078 has been resized. This setting is intended for use by the test suite,
40079 where it would otherwise be difficult to determine when a resize and
40080 refresh has been completed.
40082 @kindex maint set per-command
40083 @kindex maint show per-command
40084 @item maint set per-command
40085 @itemx maint show per-command
40086 @cindex resources used by commands
40088 @value{GDBN} can display the resources used by each command.
40089 This is useful in debugging performance problems.
40092 @item maint set per-command space [on|off]
40093 @itemx maint show per-command space
40094 Enable or disable the printing of the memory used by GDB for each command.
40095 If enabled, @value{GDBN} will display how much memory each command
40096 took, following the command's own output.
40097 This can also be requested by invoking @value{GDBN} with the
40098 @option{--statistics} command-line switch (@pxref{Mode Options}).
40100 @item maint set per-command time [on|off]
40101 @itemx maint show per-command time
40102 Enable or disable the printing of the execution time of @value{GDBN}
40104 If enabled, @value{GDBN} will display how much time it
40105 took to execute each command, following the command's own output.
40106 Both CPU time and wallclock time are printed.
40107 Printing both is useful when trying to determine whether the cost is
40108 CPU or, e.g., disk/network latency.
40109 Note that the CPU time printed is for @value{GDBN} only, it does not include
40110 the execution time of the inferior because there's no mechanism currently
40111 to compute how much time was spent by @value{GDBN} and how much time was
40112 spent by the program been debugged.
40113 This can also be requested by invoking @value{GDBN} with the
40114 @option{--statistics} command-line switch (@pxref{Mode Options}).
40116 @item maint set per-command symtab [on|off]
40117 @itemx maint show per-command symtab
40118 Enable or disable the printing of basic symbol table statistics
40120 If enabled, @value{GDBN} will display the following information:
40124 number of symbol tables
40126 number of primary symbol tables
40128 number of blocks in the blockvector
40132 @kindex maint set check-libthread-db
40133 @kindex maint show check-libthread-db
40134 @item maint set check-libthread-db [on|off]
40135 @itemx maint show check-libthread-db
40136 Control whether @value{GDBN} should run integrity checks on inferior
40137 specific thread debugging libraries as they are loaded. The default
40138 is not to perform such checks. If any check fails @value{GDBN} will
40139 unload the library and continue searching for a suitable candidate as
40140 described in @ref{set libthread-db-search-path}. For more information
40141 about the tests, see @ref{maint check libthread-db}.
40143 @kindex maint set gnu-source-highlight enabled
40144 @kindex maint show gnu-source-highlight enabled
40145 @item maint set gnu-source-highlight enabled @r{[}on|off@r{]}
40146 @itemx maint show gnu-source-highlight enabled
40147 Control whether @value{GDBN} should use the GNU Source Highlight
40148 library for applying styling to source code (@pxref{Output Styling}).
40149 This will be @samp{on} by default if the GNU Source Highlight library
40150 is available. If the GNU Source Highlight library is not available,
40151 then this will be @samp{off} by default, and attempting to change this
40152 value to @samp{on} will give an error.
40154 If the GNU Source Highlight library is not being used, then
40155 @value{GDBN} will use the Python Pygments package for source code
40156 styling, if it is available.
40158 This option is useful for debugging @value{GDBN}'s use of the Pygments
40159 library when @value{GDBN} is linked against the GNU Source Highlight
40162 @kindex maint space
40163 @cindex memory used by commands
40164 @item maint space @var{value}
40165 An alias for @code{maint set per-command space}.
40166 A non-zero value enables it, zero disables it.
40169 @cindex time of command execution
40170 @item maint time @var{value}
40171 An alias for @code{maint set per-command time}.
40172 A non-zero value enables it, zero disables it.
40174 @kindex maint translate-address
40175 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
40176 Find the symbol stored at the location specified by the address
40177 @var{addr} and an optional section name @var{section}. If found,
40178 @value{GDBN} prints the name of the closest symbol and an offset from
40179 the symbol's location to the specified address. This is similar to
40180 the @code{info address} command (@pxref{Symbols}), except that this
40181 command also allows to find symbols in other sections.
40183 If section was not specified, the section in which the symbol was found
40184 is also printed. For dynamically linked executables, the name of
40185 executable or shared library containing the symbol is printed as well.
40187 @kindex maint test-options
40188 @item maint test-options require-delimiter
40189 @itemx maint test-options unknown-is-error
40190 @itemx maint test-options unknown-is-operand
40191 These commands are used by the testsuite to validate the command
40192 options framework. The @code{require-delimiter} variant requires a
40193 double-dash delimiter to indicate end of options. The
40194 @code{unknown-is-error} and @code{unknown-is-operand} do not. The
40195 @code{unknown-is-error} variant throws an error on unknown option,
40196 while @code{unknown-is-operand} treats unknown options as the start of
40197 the command's operands. When run, the commands output the result of
40198 the processed options. When completed, the commands store the
40199 internal result of completion in a variable exposed by the @code{maint
40200 show test-options-completion-result} command.
40202 @kindex maint show test-options-completion-result
40203 @item maint show test-options-completion-result
40204 Shows the result of completing the @code{maint test-options}
40205 subcommands. This is used by the testsuite to validate completion
40206 support in the command options framework.
40208 @kindex maint set test-settings
40209 @kindex maint show test-settings
40210 @item maint set test-settings @var{kind}
40211 @itemx maint show test-settings @var{kind}
40212 These are representative commands for each @var{kind} of setting type
40213 @value{GDBN} supports. They are used by the testsuite for exercising
40214 the settings infrastructure.
40216 @kindex maint set backtrace-on-fatal-signal
40217 @kindex maint show backtrace-on-fatal-signal
40218 @item maint set backtrace-on-fatal-signal [on|off]
40219 @itemx maint show backtrace-on-fatal-signal
40220 When this setting is @code{on}, if @value{GDBN} itself terminates with
40221 a fatal signal (e.g.@: SIGSEGV), then a limited backtrace will be
40222 printed to the standard error stream. This backtrace can be used to
40223 help diagnose crashes within @value{GDBN} in situations where a user
40224 is unable to share a corefile with the @value{GDBN} developers.
40226 If the functionality to provide this backtrace is not available for
40227 the platform on which GDB is running then this feature will be
40228 @code{off} by default, and attempting to turn this feature on will
40231 For platforms that do support creating the backtrace this feature is
40232 @code{on} by default.
40235 @item maint with @var{setting} [@var{value}] [-- @var{command}]
40236 Like the @code{with} command, but works with @code{maintenance set}
40237 variables. This is used by the testsuite to exercise the @code{with}
40238 command's infrastructure.
40242 The following command is useful for non-interactive invocations of
40243 @value{GDBN}, such as in the test suite.
40246 @item set watchdog @var{nsec}
40247 @kindex set watchdog
40248 @cindex watchdog timer
40249 @cindex timeout for commands
40250 Set the maximum number of seconds @value{GDBN} will wait for the
40251 target operation to finish. If this time expires, @value{GDBN}
40252 reports and error and the command is aborted.
40254 @item show watchdog
40255 Show the current setting of the target wait timeout.
40258 @node Remote Protocol
40259 @appendix @value{GDBN} Remote Serial Protocol
40264 * Stop Reply Packets::
40265 * General Query Packets::
40266 * Architecture-Specific Protocol Details::
40267 * Tracepoint Packets::
40268 * Host I/O Packets::
40270 * Notification Packets::
40271 * Remote Non-Stop::
40272 * Packet Acknowledgment::
40274 * File-I/O Remote Protocol Extension::
40275 * Library List Format::
40276 * Library List Format for SVR4 Targets::
40277 * Memory Map Format::
40278 * Thread List Format::
40279 * Traceframe Info Format::
40280 * Branch Trace Format::
40281 * Branch Trace Configuration Format::
40287 There may be occasions when you need to know something about the
40288 protocol---for example, if there is only one serial port to your target
40289 machine, you might want your program to do something special if it
40290 recognizes a packet meant for @value{GDBN}.
40292 In the examples below, @samp{->} and @samp{<-} are used to indicate
40293 transmitted and received data, respectively.
40295 @cindex protocol, @value{GDBN} remote serial
40296 @cindex serial protocol, @value{GDBN} remote
40297 @cindex remote serial protocol
40298 All @value{GDBN} commands and responses (other than acknowledgments
40299 and notifications, see @ref{Notification Packets}) are sent as a
40300 @var{packet}. A @var{packet} is introduced with the character
40301 @samp{$}, the actual @var{packet-data}, and the terminating character
40302 @samp{#} followed by a two-digit @var{checksum}:
40305 @code{$}@var{packet-data}@code{#}@var{checksum}
40309 @cindex checksum, for @value{GDBN} remote
40311 The two-digit @var{checksum} is computed as the modulo 256 sum of all
40312 characters between the leading @samp{$} and the trailing @samp{#} (an
40313 eight bit unsigned checksum).
40315 Implementors should note that prior to @value{GDBN} 5.0 the protocol
40316 specification also included an optional two-digit @var{sequence-id}:
40319 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
40322 @cindex sequence-id, for @value{GDBN} remote
40324 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
40325 has never output @var{sequence-id}s. Stubs that handle packets added
40326 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
40328 When either the host or the target machine receives a packet, the first
40329 response expected is an acknowledgment: either @samp{+} (to indicate
40330 the package was received correctly) or @samp{-} (to request
40334 -> @code{$}@var{packet-data}@code{#}@var{checksum}
40339 The @samp{+}/@samp{-} acknowledgments can be disabled
40340 once a connection is established.
40341 @xref{Packet Acknowledgment}, for details.
40343 The host (@value{GDBN}) sends @var{command}s, and the target (the
40344 debugging stub incorporated in your program) sends a @var{response}. In
40345 the case of step and continue @var{command}s, the response is only sent
40346 when the operation has completed, and the target has again stopped all
40347 threads in all attached processes. This is the default all-stop mode
40348 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
40349 execution mode; see @ref{Remote Non-Stop}, for details.
40351 @var{packet-data} consists of a sequence of characters with the
40352 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
40355 @cindex remote protocol, field separator
40356 Fields within the packet should be separated using @samp{,} @samp{;} or
40357 @samp{:}. Except where otherwise noted all numbers are represented in
40358 @sc{hex} with leading zeros suppressed.
40360 Implementors should note that prior to @value{GDBN} 5.0, the character
40361 @samp{:} could not appear as the third character in a packet (as it
40362 would potentially conflict with the @var{sequence-id}).
40364 @cindex remote protocol, binary data
40365 @anchor{Binary Data}
40366 Binary data in most packets is encoded either as two hexadecimal
40367 digits per byte of binary data. This allowed the traditional remote
40368 protocol to work over connections which were only seven-bit clean.
40369 Some packets designed more recently assume an eight-bit clean
40370 connection, and use a more efficient encoding to send and receive
40373 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
40374 as an escape character. Any escaped byte is transmitted as the escape
40375 character followed by the original character XORed with @code{0x20}.
40376 For example, the byte @code{0x7d} would be transmitted as the two
40377 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
40378 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
40379 @samp{@}}) must always be escaped. Responses sent by the stub
40380 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
40381 is not interpreted as the start of a run-length encoded sequence
40384 Response @var{data} can be run-length encoded to save space.
40385 Run-length encoding replaces runs of identical characters with one
40386 instance of the repeated character, followed by a @samp{*} and a
40387 repeat count. The repeat count is itself sent encoded, to avoid
40388 binary characters in @var{data}: a value of @var{n} is sent as
40389 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
40390 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
40391 code 32) for a repeat count of 3. (This is because run-length
40392 encoding starts to win for counts 3 or more.) Thus, for example,
40393 @samp{0* } is a run-length encoding of ``0000'': the space character
40394 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
40397 The printable characters @samp{#} and @samp{$} or with a numeric value
40398 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
40399 seven repeats (@samp{$}) can be expanded using a repeat count of only
40400 five (@samp{"}). For example, @samp{00000000} can be encoded as
40403 The error response returned for some packets includes a two character
40404 error number. That number is not well defined.
40406 @cindex empty response, for unsupported packets
40407 For any @var{command} not supported by the stub, an empty response
40408 (@samp{$#00}) should be returned. That way it is possible to extend the
40409 protocol. A newer @value{GDBN} can tell if a packet is supported based
40412 At a minimum, a stub is required to support the @samp{?} command to
40413 tell @value{GDBN} the reason for halting, @samp{g} and @samp{G}
40414 commands for register access, and the @samp{m} and @samp{M} commands
40415 for memory access. Stubs that only control single-threaded targets
40416 can implement run control with the @samp{c} (continue) command, and if
40417 the target architecture supports hardware-assisted single-stepping,
40418 the @samp{s} (step) command. Stubs that support multi-threading
40419 targets should support the @samp{vCont} command. All other commands
40425 The following table provides a complete list of all currently defined
40426 @var{command}s and their corresponding response @var{data}.
40427 @xref{File-I/O Remote Protocol Extension}, for details about the File
40428 I/O extension of the remote protocol.
40430 Each packet's description has a template showing the packet's overall
40431 syntax, followed by an explanation of the packet's meaning. We
40432 include spaces in some of the templates for clarity; these are not
40433 part of the packet's syntax. No @value{GDBN} packet uses spaces to
40434 separate its components. For example, a template like @samp{foo
40435 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
40436 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
40437 @var{baz}. @value{GDBN} does not transmit a space character between the
40438 @samp{foo} and the @var{bar}, or between the @var{bar} and the
40441 @cindex @var{thread-id}, in remote protocol
40442 @anchor{thread-id syntax}
40443 Several packets and replies include a @var{thread-id} field to identify
40444 a thread. Normally these are positive numbers with a target-specific
40445 interpretation, formatted as big-endian hex strings. A @var{thread-id}
40446 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
40449 In addition, the remote protocol supports a multiprocess feature in
40450 which the @var{thread-id} syntax is extended to optionally include both
40451 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
40452 The @var{pid} (process) and @var{tid} (thread) components each have the
40453 format described above: a positive number with target-specific
40454 interpretation formatted as a big-endian hex string, literal @samp{-1}
40455 to indicate all processes or threads (respectively), or @samp{0} to
40456 indicate an arbitrary process or thread. Specifying just a process, as
40457 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
40458 error to specify all processes but a specific thread, such as
40459 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
40460 for those packets and replies explicitly documented to include a process
40461 ID, rather than a @var{thread-id}.
40463 The multiprocess @var{thread-id} syntax extensions are only used if both
40464 @value{GDBN} and the stub report support for the @samp{multiprocess}
40465 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
40468 Note that all packet forms beginning with an upper- or lower-case
40469 letter, other than those described here, are reserved for future use.
40471 Here are the packet descriptions.
40476 @cindex @samp{!} packet
40477 @anchor{extended mode}
40478 Enable extended mode. In extended mode, the remote server is made
40479 persistent. The @samp{R} packet is used to restart the program being
40485 The remote target both supports and has enabled extended mode.
40489 @cindex @samp{?} packet
40491 This is sent when connection is first established to query the reason
40492 the target halted. The reply is the same as for step and continue.
40493 This packet has a special interpretation when the target is in
40494 non-stop mode; see @ref{Remote Non-Stop}.
40497 @xref{Stop Reply Packets}, for the reply specifications.
40499 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
40500 @cindex @samp{A} packet
40501 Initialized @code{argv[]} array passed into program. @var{arglen}
40502 specifies the number of bytes in the hex encoded byte stream
40503 @var{arg}. See @code{gdbserver} for more details.
40508 The arguments were set.
40514 @cindex @samp{b} packet
40515 (Don't use this packet; its behavior is not well-defined.)
40516 Change the serial line speed to @var{baud}.
40518 JTC: @emph{When does the transport layer state change? When it's
40519 received, or after the ACK is transmitted. In either case, there are
40520 problems if the command or the acknowledgment packet is dropped.}
40522 Stan: @emph{If people really wanted to add something like this, and get
40523 it working for the first time, they ought to modify ser-unix.c to send
40524 some kind of out-of-band message to a specially-setup stub and have the
40525 switch happen "in between" packets, so that from remote protocol's point
40526 of view, nothing actually happened.}
40528 @item B @var{addr},@var{mode}
40529 @cindex @samp{B} packet
40530 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
40531 breakpoint at @var{addr}.
40533 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
40534 (@pxref{insert breakpoint or watchpoint packet}).
40536 @cindex @samp{bc} packet
40539 Backward continue. Execute the target system in reverse. No parameter.
40540 @xref{Reverse Execution}, for more information.
40543 @xref{Stop Reply Packets}, for the reply specifications.
40545 @cindex @samp{bs} packet
40548 Backward single step. Execute one instruction in reverse. No parameter.
40549 @xref{Reverse Execution}, for more information.
40552 @xref{Stop Reply Packets}, for the reply specifications.
40554 @item c @r{[}@var{addr}@r{]}
40555 @cindex @samp{c} packet
40556 Continue at @var{addr}, which is the address to resume. If @var{addr}
40557 is omitted, resume at current address.
40559 This packet is deprecated for multi-threading support. @xref{vCont
40563 @xref{Stop Reply Packets}, for the reply specifications.
40565 @item C @var{sig}@r{[};@var{addr}@r{]}
40566 @cindex @samp{C} packet
40567 Continue with signal @var{sig} (hex signal number). If
40568 @samp{;@var{addr}} is omitted, resume at same address.
40570 This packet is deprecated for multi-threading support. @xref{vCont
40574 @xref{Stop Reply Packets}, for the reply specifications.
40577 @cindex @samp{d} packet
40580 Don't use this packet; instead, define a general set packet
40581 (@pxref{General Query Packets}).
40585 @cindex @samp{D} packet
40586 The first form of the packet is used to detach @value{GDBN} from the
40587 remote system. It is sent to the remote target
40588 before @value{GDBN} disconnects via the @code{detach} command.
40590 The second form, including a process ID, is used when multiprocess
40591 protocol extensions are enabled (@pxref{multiprocess extensions}), to
40592 detach only a specific process. The @var{pid} is specified as a
40593 big-endian hex string.
40603 @item F @var{RC},@var{EE},@var{CF};@var{XX}
40604 @cindex @samp{F} packet
40605 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
40606 This is part of the File-I/O protocol extension. @xref{File-I/O
40607 Remote Protocol Extension}, for the specification.
40610 @anchor{read registers packet}
40611 @cindex @samp{g} packet
40612 Read general registers.
40616 @item @var{XX@dots{}}
40617 Each byte of register data is described by two hex digits. The bytes
40618 with the register are transmitted in target byte order. The size of
40619 each register and their position within the @samp{g} packet are
40620 determined by the @value{GDBN} internal gdbarch functions
40621 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
40623 When reading registers from a trace frame (@pxref{Analyze Collected
40624 Data,,Using the Collected Data}), the stub may also return a string of
40625 literal @samp{x}'s in place of the register data digits, to indicate
40626 that the corresponding register has not been collected, thus its value
40627 is unavailable. For example, for an architecture with 4 registers of
40628 4 bytes each, the following reply indicates to @value{GDBN} that
40629 registers 0 and 2 have not been collected, while registers 1 and 3
40630 have been collected, and both have zero value:
40634 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
40641 @item G @var{XX@dots{}}
40642 @cindex @samp{G} packet
40643 Write general registers. @xref{read registers packet}, for a
40644 description of the @var{XX@dots{}} data.
40654 @item H @var{op} @var{thread-id}
40655 @cindex @samp{H} packet
40656 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
40657 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
40658 should be @samp{c} for step and continue operations (note that this
40659 is deprecated, supporting the @samp{vCont} command is a better
40660 option), and @samp{g} for other operations. The thread designator
40661 @var{thread-id} has the format and interpretation described in
40662 @ref{thread-id syntax}.
40673 @c 'H': How restrictive (or permissive) is the thread model. If a
40674 @c thread is selected and stopped, are other threads allowed
40675 @c to continue to execute? As I mentioned above, I think the
40676 @c semantics of each command when a thread is selected must be
40677 @c described. For example:
40679 @c 'g': If the stub supports threads and a specific thread is
40680 @c selected, returns the register block from that thread;
40681 @c otherwise returns current registers.
40683 @c 'G' If the stub supports threads and a specific thread is
40684 @c selected, sets the registers of the register block of
40685 @c that thread; otherwise sets current registers.
40687 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
40688 @anchor{cycle step packet}
40689 @cindex @samp{i} packet
40690 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
40691 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
40692 step starting at that address.
40695 @cindex @samp{I} packet
40696 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
40700 @cindex @samp{k} packet
40703 The exact effect of this packet is not specified.
40705 For a bare-metal target, it may power cycle or reset the target
40706 system. For that reason, the @samp{k} packet has no reply.
40708 For a single-process target, it may kill that process if possible.
40710 A multiple-process target may choose to kill just one process, or all
40711 that are under @value{GDBN}'s control. For more precise control, use
40712 the vKill packet (@pxref{vKill packet}).
40714 If the target system immediately closes the connection in response to
40715 @samp{k}, @value{GDBN} does not consider the lack of packet
40716 acknowledgment to be an error, and assumes the kill was successful.
40718 If connected using @kbd{target extended-remote}, and the target does
40719 not close the connection in response to a kill request, @value{GDBN}
40720 probes the target state as if a new connection was opened
40721 (@pxref{? packet}).
40723 @item m @var{addr},@var{length}
40724 @cindex @samp{m} packet
40725 Read @var{length} addressable memory units starting at address @var{addr}
40726 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
40727 any particular boundary.
40729 The stub need not use any particular size or alignment when gathering
40730 data from memory for the response; even if @var{addr} is word-aligned
40731 and @var{length} is a multiple of the word size, the stub is free to
40732 use byte accesses, or not. For this reason, this packet may not be
40733 suitable for accessing memory-mapped I/O devices.
40734 @cindex alignment of remote memory accesses
40735 @cindex size of remote memory accesses
40736 @cindex memory, alignment and size of remote accesses
40740 @item @var{XX@dots{}}
40741 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
40742 The reply may contain fewer addressable memory units than requested if the
40743 server was able to read only part of the region of memory.
40748 @item M @var{addr},@var{length}:@var{XX@dots{}}
40749 @cindex @samp{M} packet
40750 Write @var{length} addressable memory units starting at address @var{addr}
40751 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
40752 byte is transmitted as a two-digit hexadecimal number.
40759 for an error (this includes the case where only part of the data was
40764 @cindex @samp{p} packet
40765 Read the value of register @var{n}; @var{n} is in hex.
40766 @xref{read registers packet}, for a description of how the returned
40767 register value is encoded.
40771 @item @var{XX@dots{}}
40772 the register's value
40776 Indicating an unrecognized @var{query}.
40779 @item P @var{n@dots{}}=@var{r@dots{}}
40780 @anchor{write register packet}
40781 @cindex @samp{P} packet
40782 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
40783 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
40784 digits for each byte in the register (target byte order).
40794 @item q @var{name} @var{params}@dots{}
40795 @itemx Q @var{name} @var{params}@dots{}
40796 @cindex @samp{q} packet
40797 @cindex @samp{Q} packet
40798 General query (@samp{q}) and set (@samp{Q}). These packets are
40799 described fully in @ref{General Query Packets}.
40802 @cindex @samp{r} packet
40803 Reset the entire system.
40805 Don't use this packet; use the @samp{R} packet instead.
40808 @cindex @samp{R} packet
40809 Restart the program being debugged. The @var{XX}, while needed, is ignored.
40810 This packet is only available in extended mode (@pxref{extended mode}).
40812 The @samp{R} packet has no reply.
40814 @item s @r{[}@var{addr}@r{]}
40815 @cindex @samp{s} packet
40816 Single step, resuming at @var{addr}. If
40817 @var{addr} is omitted, resume at same address.
40819 This packet is deprecated for multi-threading support. @xref{vCont
40823 @xref{Stop Reply Packets}, for the reply specifications.
40825 @item S @var{sig}@r{[};@var{addr}@r{]}
40826 @anchor{step with signal packet}
40827 @cindex @samp{S} packet
40828 Step with signal. This is analogous to the @samp{C} packet, but
40829 requests a single-step, rather than a normal resumption of execution.
40831 This packet is deprecated for multi-threading support. @xref{vCont
40835 @xref{Stop Reply Packets}, for the reply specifications.
40837 @item t @var{addr}:@var{PP},@var{MM}
40838 @cindex @samp{t} packet
40839 Search backwards starting at address @var{addr} for a match with pattern
40840 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
40841 There must be at least 3 digits in @var{addr}.
40843 @item T @var{thread-id}
40844 @cindex @samp{T} packet
40845 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
40850 thread is still alive
40856 Packets starting with @samp{v} are identified by a multi-letter name,
40857 up to the first @samp{;} or @samp{?} (or the end of the packet).
40859 @item vAttach;@var{pid}
40860 @cindex @samp{vAttach} packet
40861 Attach to a new process with the specified process ID @var{pid}.
40862 The process ID is a
40863 hexadecimal integer identifying the process. In all-stop mode, all
40864 threads in the attached process are stopped; in non-stop mode, it may be
40865 attached without being stopped if that is supported by the target.
40867 @c In non-stop mode, on a successful vAttach, the stub should set the
40868 @c current thread to a thread of the newly-attached process. After
40869 @c attaching, GDB queries for the attached process's thread ID with qC.
40870 @c Also note that, from a user perspective, whether or not the
40871 @c target is stopped on attach in non-stop mode depends on whether you
40872 @c use the foreground or background version of the attach command, not
40873 @c on what vAttach does; GDB does the right thing with respect to either
40874 @c stopping or restarting threads.
40876 This packet is only available in extended mode (@pxref{extended mode}).
40882 @item @r{Any stop packet}
40883 for success in all-stop mode (@pxref{Stop Reply Packets})
40885 for success in non-stop mode (@pxref{Remote Non-Stop})
40888 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
40889 @cindex @samp{vCont} packet
40890 @anchor{vCont packet}
40891 Resume the inferior, specifying different actions for each thread.
40893 For each inferior thread, the leftmost action with a matching
40894 @var{thread-id} is applied. Threads that don't match any action
40895 remain in their current state. Thread IDs are specified using the
40896 syntax described in @ref{thread-id syntax}. If multiprocess
40897 extensions (@pxref{multiprocess extensions}) are supported, actions
40898 can be specified to match all threads in a process by using the
40899 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
40900 @var{thread-id} matches all threads. Specifying no actions is an
40903 Currently supported actions are:
40909 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
40913 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
40916 @item r @var{start},@var{end}
40917 Step once, and then keep stepping as long as the thread stops at
40918 addresses between @var{start} (inclusive) and @var{end} (exclusive).
40919 The remote stub reports a stop reply when either the thread goes out
40920 of the range or is stopped due to an unrelated reason, such as hitting
40921 a breakpoint. @xref{range stepping}.
40923 If the range is empty (@var{start} == @var{end}), then the action
40924 becomes equivalent to the @samp{s} action. In other words,
40925 single-step once, and report the stop (even if the stepped instruction
40926 jumps to @var{start}).
40928 (A stop reply may be sent at any point even if the PC is still within
40929 the stepping range; for example, it is valid to implement this packet
40930 in a degenerate way as a single instruction step operation.)
40934 The optional argument @var{addr} normally associated with the
40935 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
40936 not supported in @samp{vCont}.
40938 The @samp{t} action is only relevant in non-stop mode
40939 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
40940 A stop reply should be generated for any affected thread not already stopped.
40941 When a thread is stopped by means of a @samp{t} action,
40942 the corresponding stop reply should indicate that the thread has stopped with
40943 signal @samp{0}, regardless of whether the target uses some other signal
40944 as an implementation detail.
40946 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
40947 @samp{r} actions for threads that are already running. Conversely,
40948 the server must ignore @samp{t} actions for threads that are already
40951 @emph{Note:} In non-stop mode, a thread is considered running until
40952 @value{GDBN} acknowledges an asynchronous stop notification for it with
40953 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
40955 The stub must support @samp{vCont} if it reports support for
40956 multiprocess extensions (@pxref{multiprocess extensions}).
40959 @xref{Stop Reply Packets}, for the reply specifications.
40962 @cindex @samp{vCont?} packet
40963 Request a list of actions supported by the @samp{vCont} packet.
40967 @item vCont@r{[};@var{action}@dots{}@r{]}
40968 The @samp{vCont} packet is supported. Each @var{action} is a supported
40969 command in the @samp{vCont} packet.
40971 The @samp{vCont} packet is not supported.
40974 @anchor{vCtrlC packet}
40976 @cindex @samp{vCtrlC} packet
40977 Interrupt remote target as if a control-C was pressed on the remote
40978 terminal. This is the equivalent to reacting to the @code{^C}
40979 (@samp{\003}, the control-C character) character in all-stop mode
40980 while the target is running, except this works in non-stop mode.
40981 @xref{interrupting remote targets}, for more info on the all-stop
40992 @item vFile:@var{operation}:@var{parameter}@dots{}
40993 @cindex @samp{vFile} packet
40994 Perform a file operation on the target system. For details,
40995 see @ref{Host I/O Packets}.
40997 @item vFlashErase:@var{addr},@var{length}
40998 @cindex @samp{vFlashErase} packet
40999 Direct the stub to erase @var{length} bytes of flash starting at
41000 @var{addr}. The region may enclose any number of flash blocks, but
41001 its start and end must fall on block boundaries, as indicated by the
41002 flash block size appearing in the memory map (@pxref{Memory Map
41003 Format}). @value{GDBN} groups flash memory programming operations
41004 together, and sends a @samp{vFlashDone} request after each group; the
41005 stub is allowed to delay erase operation until the @samp{vFlashDone}
41006 packet is received.
41016 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
41017 @cindex @samp{vFlashWrite} packet
41018 Direct the stub to write data to flash address @var{addr}. The data
41019 is passed in binary form using the same encoding as for the @samp{X}
41020 packet (@pxref{Binary Data}). The memory ranges specified by
41021 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
41022 not overlap, and must appear in order of increasing addresses
41023 (although @samp{vFlashErase} packets for higher addresses may already
41024 have been received; the ordering is guaranteed only between
41025 @samp{vFlashWrite} packets). If a packet writes to an address that was
41026 neither erased by a preceding @samp{vFlashErase} packet nor by some other
41027 target-specific method, the results are unpredictable.
41035 for vFlashWrite addressing non-flash memory
41041 @cindex @samp{vFlashDone} packet
41042 Indicate to the stub that flash programming operation is finished.
41043 The stub is permitted to delay or batch the effects of a group of
41044 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
41045 @samp{vFlashDone} packet is received. The contents of the affected
41046 regions of flash memory are unpredictable until the @samp{vFlashDone}
41047 request is completed.
41049 @item vKill;@var{pid}
41050 @cindex @samp{vKill} packet
41051 @anchor{vKill packet}
41052 Kill the process with the specified process ID @var{pid}, which is a
41053 hexadecimal integer identifying the process. This packet is used in
41054 preference to @samp{k} when multiprocess protocol extensions are
41055 supported; see @ref{multiprocess extensions}.
41065 @item vMustReplyEmpty
41066 @cindex @samp{vMustReplyEmpty} packet
41067 The correct reply to an unknown @samp{v} packet is to return the empty
41068 string, however, some older versions of @command{gdbserver} would
41069 incorrectly return @samp{OK} for unknown @samp{v} packets.
41071 The @samp{vMustReplyEmpty} is used as a feature test to check how
41072 @command{gdbserver} handles unknown packets, it is important that this
41073 packet be handled in the same way as other unknown @samp{v} packets.
41074 If this packet is handled differently to other unknown @samp{v}
41075 packets then it is possible that @value{GDBN} may run into problems in
41076 other areas, specifically around use of @samp{vFile:setfs:}.
41078 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
41079 @cindex @samp{vRun} packet
41080 Run the program @var{filename}, passing it each @var{argument} on its
41081 command line. The file and arguments are hex-encoded strings. If
41082 @var{filename} is an empty string, the stub may use a default program
41083 (e.g.@: the last program run). The program is created in the stopped
41086 @c FIXME: What about non-stop mode?
41088 This packet is only available in extended mode (@pxref{extended mode}).
41094 @item @r{Any stop packet}
41095 for success (@pxref{Stop Reply Packets})
41099 @cindex @samp{vStopped} packet
41100 @xref{Notification Packets}.
41102 @item X @var{addr},@var{length}:@var{XX@dots{}}
41104 @cindex @samp{X} packet
41105 Write data to memory, where the data is transmitted in binary.
41106 Memory is specified by its address @var{addr} and number of addressable memory
41107 units @var{length} (@pxref{addressable memory unit});
41108 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
41118 @item z @var{type},@var{addr},@var{kind}
41119 @itemx Z @var{type},@var{addr},@var{kind}
41120 @anchor{insert breakpoint or watchpoint packet}
41121 @cindex @samp{z} packet
41122 @cindex @samp{Z} packets
41123 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
41124 watchpoint starting at address @var{address} of kind @var{kind}.
41126 Each breakpoint and watchpoint packet @var{type} is documented
41129 @emph{Implementation notes: A remote target shall return an empty string
41130 for an unrecognized breakpoint or watchpoint packet @var{type}. A
41131 remote target shall support either both or neither of a given
41132 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
41133 avoid potential problems with duplicate packets, the operations should
41134 be implemented in an idempotent way.}
41136 @item z0,@var{addr},@var{kind}
41137 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41138 @cindex @samp{z0} packet
41139 @cindex @samp{Z0} packet
41140 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
41141 @var{addr} of type @var{kind}.
41143 A software breakpoint is implemented by replacing the instruction at
41144 @var{addr} with a software breakpoint or trap instruction. The
41145 @var{kind} is target-specific and typically indicates the size of the
41146 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
41147 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
41148 architectures have additional meanings for @var{kind}
41149 (@pxref{Architecture-Specific Protocol Details}); if no
41150 architecture-specific value is being used, it should be @samp{0}.
41151 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
41152 conditional expressions in bytecode form that should be evaluated on
41153 the target's side. These are the conditions that should be taken into
41154 consideration when deciding if the breakpoint trigger should be
41155 reported back to @value{GDBN}.
41157 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
41158 for how to best report a software breakpoint event to @value{GDBN}.
41160 The @var{cond_list} parameter is comprised of a series of expressions,
41161 concatenated without separators. Each expression has the following form:
41165 @item X @var{len},@var{expr}
41166 @var{len} is the length of the bytecode expression and @var{expr} is the
41167 actual conditional expression in bytecode form.
41171 The optional @var{cmd_list} parameter introduces commands that may be
41172 run on the target, rather than being reported back to @value{GDBN}.
41173 The parameter starts with a numeric flag @var{persist}; if the flag is
41174 nonzero, then the breakpoint may remain active and the commands
41175 continue to be run even when @value{GDBN} disconnects from the target.
41176 Following this flag is a series of expressions concatenated with no
41177 separators. Each expression has the following form:
41181 @item X @var{len},@var{expr}
41182 @var{len} is the length of the bytecode expression and @var{expr} is the
41183 actual commands expression in bytecode form.
41187 @emph{Implementation note: It is possible for a target to copy or move
41188 code that contains software breakpoints (e.g., when implementing
41189 overlays). The behavior of this packet, in the presence of such a
41190 target, is not defined.}
41202 @item z1,@var{addr},@var{kind}
41203 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
41204 @cindex @samp{z1} packet
41205 @cindex @samp{Z1} packet
41206 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
41207 address @var{addr}.
41209 A hardware breakpoint is implemented using a mechanism that is not
41210 dependent on being able to modify the target's memory. The
41211 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
41212 same meaning as in @samp{Z0} packets.
41214 @emph{Implementation note: A hardware breakpoint is not affected by code
41227 @item z2,@var{addr},@var{kind}
41228 @itemx Z2,@var{addr},@var{kind}
41229 @cindex @samp{z2} packet
41230 @cindex @samp{Z2} packet
41231 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
41232 The number of bytes to watch is specified by @var{kind}.
41244 @item z3,@var{addr},@var{kind}
41245 @itemx Z3,@var{addr},@var{kind}
41246 @cindex @samp{z3} packet
41247 @cindex @samp{Z3} packet
41248 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
41249 The number of bytes to watch is specified by @var{kind}.
41261 @item z4,@var{addr},@var{kind}
41262 @itemx Z4,@var{addr},@var{kind}
41263 @cindex @samp{z4} packet
41264 @cindex @samp{Z4} packet
41265 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
41266 The number of bytes to watch is specified by @var{kind}.
41280 @node Stop Reply Packets
41281 @section Stop Reply Packets
41282 @cindex stop reply packets
41284 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
41285 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
41286 receive any of the below as a reply. Except for @samp{?}
41287 and @samp{vStopped}, that reply is only returned
41288 when the target halts. In the below the exact meaning of @dfn{signal
41289 number} is defined by the header @file{include/gdb/signals.h} in the
41290 @value{GDBN} source code.
41292 In non-stop mode, the server will simply reply @samp{OK} to commands
41293 such as @samp{vCont}; any stop will be the subject of a future
41294 notification. @xref{Remote Non-Stop}.
41296 As in the description of request packets, we include spaces in the
41297 reply templates for clarity; these are not part of the reply packet's
41298 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
41304 The program received signal number @var{AA} (a two-digit hexadecimal
41305 number). This is equivalent to a @samp{T} response with no
41306 @var{n}:@var{r} pairs.
41308 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
41309 @cindex @samp{T} packet reply
41310 The program received signal number @var{AA} (a two-digit hexadecimal
41311 number). This is equivalent to an @samp{S} response, except that the
41312 @samp{@var{n}:@var{r}} pairs can carry values of important registers
41313 and other information directly in the stop reply packet, reducing
41314 round-trip latency. Single-step and breakpoint traps are reported
41315 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
41319 If @var{n} is a hexadecimal number, it is a register number, and the
41320 corresponding @var{r} gives that register's value. The data @var{r} is a
41321 series of bytes in target byte order, with each byte given by a
41322 two-digit hex number.
41325 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
41326 the stopped thread, as specified in @ref{thread-id syntax}.
41329 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
41330 the core on which the stop event was detected.
41333 If @var{n} is a recognized @dfn{stop reason}, it describes a more
41334 specific event that stopped the target. The currently defined stop
41335 reasons are listed below. The @var{aa} should be @samp{05}, the trap
41336 signal. At most one stop reason should be present.
41339 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
41340 and go on to the next; this allows us to extend the protocol in the
41344 The currently defined stop reasons are:
41350 The packet indicates a watchpoint hit, and @var{r} is the data address, in
41353 @item syscall_entry
41354 @itemx syscall_return
41355 The packet indicates a syscall entry or return, and @var{r} is the
41356 syscall number, in hex.
41358 @cindex shared library events, remote reply
41360 The packet indicates that the loaded libraries have changed.
41361 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
41362 list of loaded libraries. The @var{r} part is ignored.
41364 @cindex replay log events, remote reply
41366 The packet indicates that the target cannot continue replaying
41367 logged execution events, because it has reached the end (or the
41368 beginning when executing backward) of the log. The value of @var{r}
41369 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
41370 for more information.
41373 @anchor{swbreak stop reason}
41374 The packet indicates a software breakpoint instruction was executed,
41375 irrespective of whether it was @value{GDBN} that planted the
41376 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
41377 part must be left empty.
41379 On some architectures, such as x86, at the architecture level, when a
41380 breakpoint instruction executes the program counter points at the
41381 breakpoint address plus an offset. On such targets, the stub is
41382 responsible for adjusting the PC to point back at the breakpoint
41385 This packet should not be sent by default; older @value{GDBN} versions
41386 did not support it. @value{GDBN} requests it, by supplying an
41387 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41388 remote stub must also supply the appropriate @samp{qSupported} feature
41389 indicating support.
41391 This packet is required for correct non-stop mode operation.
41394 The packet indicates the target stopped for a hardware breakpoint.
41395 The @var{r} part must be left empty.
41397 The same remarks about @samp{qSupported} and non-stop mode above
41400 @cindex fork events, remote reply
41402 The packet indicates that @code{fork} was called, and @var{r}
41403 is the thread ID of the new child process. Refer to
41404 @ref{thread-id syntax} for the format of the @var{thread-id}
41405 field. This packet is only applicable to targets that support
41408 This packet should not be sent by default; older @value{GDBN} versions
41409 did not support it. @value{GDBN} requests it, by supplying an
41410 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41411 remote stub must also supply the appropriate @samp{qSupported} feature
41412 indicating support.
41414 @cindex vfork events, remote reply
41416 The packet indicates that @code{vfork} was called, and @var{r}
41417 is the thread ID of the new child process. Refer to
41418 @ref{thread-id syntax} for the format of the @var{thread-id}
41419 field. This packet is only applicable to targets that support
41422 This packet should not be sent by default; older @value{GDBN} versions
41423 did not support it. @value{GDBN} requests it, by supplying an
41424 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41425 remote stub must also supply the appropriate @samp{qSupported} feature
41426 indicating support.
41428 @cindex vforkdone events, remote reply
41430 The packet indicates that a child process created by a vfork
41431 has either called @code{exec} or terminated, so that the
41432 address spaces of the parent and child process are no longer
41433 shared. The @var{r} part is ignored. This packet is only
41434 applicable to targets that support vforkdone events.
41436 This packet should not be sent by default; older @value{GDBN} versions
41437 did not support it. @value{GDBN} requests it, by supplying an
41438 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41439 remote stub must also supply the appropriate @samp{qSupported} feature
41440 indicating support.
41442 @cindex exec events, remote reply
41444 The packet indicates that @code{execve} was called, and @var{r}
41445 is the absolute pathname of the file that was executed, in hex.
41446 This packet is only applicable to targets that support exec events.
41448 This packet should not be sent by default; older @value{GDBN} versions
41449 did not support it. @value{GDBN} requests it, by supplying an
41450 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
41451 remote stub must also supply the appropriate @samp{qSupported} feature
41452 indicating support.
41454 @cindex thread create event, remote reply
41455 @anchor{thread create event}
41457 The packet indicates that the thread was just created. The new thread
41458 is stopped until @value{GDBN} sets it running with a resumption packet
41459 (@pxref{vCont packet}). This packet should not be sent by default;
41460 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
41461 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
41462 @var{r} part is ignored.
41467 @itemx W @var{AA} ; process:@var{pid}
41468 The process exited, and @var{AA} is the exit status. This is only
41469 applicable to certain targets.
41471 The second form of the response, including the process ID of the
41472 exited process, can be used only when @value{GDBN} has reported
41473 support for multiprocess protocol extensions; see @ref{multiprocess
41474 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41478 @itemx X @var{AA} ; process:@var{pid}
41479 The process terminated with signal @var{AA}.
41481 The second form of the response, including the process ID of the
41482 terminated process, can be used only when @value{GDBN} has reported
41483 support for multiprocess protocol extensions; see @ref{multiprocess
41484 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
41487 @anchor{thread exit event}
41488 @cindex thread exit event, remote reply
41489 @item w @var{AA} ; @var{tid}
41491 The thread exited, and @var{AA} is the exit status. This response
41492 should not be sent by default; @value{GDBN} requests it with the
41493 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
41494 @var{AA} is formatted as a big-endian hex string.
41497 There are no resumed threads left in the target. In other words, even
41498 though the process is alive, the last resumed thread has exited. For
41499 example, say the target process has two threads: thread 1 and thread
41500 2. The client leaves thread 1 stopped, and resumes thread 2, which
41501 subsequently exits. At this point, even though the process is still
41502 alive, and thus no @samp{W} stop reply is sent, no thread is actually
41503 executing either. The @samp{N} stop reply thus informs the client
41504 that it can stop waiting for stop replies. This packet should not be
41505 sent by default; older @value{GDBN} versions did not support it.
41506 @value{GDBN} requests it, by supplying an appropriate
41507 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
41508 also supply the appropriate @samp{qSupported} feature indicating
41511 @item O @var{XX}@dots{}
41512 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
41513 written as the program's console output. This can happen at any time
41514 while the program is running and the debugger should continue to wait
41515 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
41517 @item F @var{call-id},@var{parameter}@dots{}
41518 @var{call-id} is the identifier which says which host system call should
41519 be called. This is just the name of the function. Translation into the
41520 correct system call is only applicable as it's defined in @value{GDBN}.
41521 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
41524 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
41525 this very system call.
41527 The target replies with this packet when it expects @value{GDBN} to
41528 call a host system call on behalf of the target. @value{GDBN} replies
41529 with an appropriate @samp{F} packet and keeps up waiting for the next
41530 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
41531 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
41532 Protocol Extension}, for more details.
41536 @node General Query Packets
41537 @section General Query Packets
41538 @cindex remote query requests
41540 Packets starting with @samp{q} are @dfn{general query packets};
41541 packets starting with @samp{Q} are @dfn{general set packets}. General
41542 query and set packets are a semi-unified form for retrieving and
41543 sending information to and from the stub.
41545 The initial letter of a query or set packet is followed by a name
41546 indicating what sort of thing the packet applies to. For example,
41547 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
41548 definitions with the stub. These packet names follow some
41553 The name must not contain commas, colons or semicolons.
41555 Most @value{GDBN} query and set packets have a leading upper case
41558 The names of custom vendor packets should use a company prefix, in
41559 lower case, followed by a period. For example, packets designed at
41560 the Acme Corporation might begin with @samp{qacme.foo} (for querying
41561 foos) or @samp{Qacme.bar} (for setting bars).
41564 The name of a query or set packet should be separated from any
41565 parameters by a @samp{:}; the parameters themselves should be
41566 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
41567 full packet name, and check for a separator or the end of the packet,
41568 in case two packet names share a common prefix. New packets should not begin
41569 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
41570 packets predate these conventions, and have arguments without any terminator
41571 for the packet name; we suspect they are in widespread use in places that
41572 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
41573 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
41576 Like the descriptions of the other packets, each description here
41577 has a template showing the packet's overall syntax, followed by an
41578 explanation of the packet's meaning. We include spaces in some of the
41579 templates for clarity; these are not part of the packet's syntax. No
41580 @value{GDBN} packet uses spaces to separate its components.
41582 Here are the currently defined query and set packets:
41588 Turn on or off the agent as a helper to perform some debugging operations
41589 delegated from @value{GDBN} (@pxref{Control Agent}).
41591 @item QAllow:@var{op}:@var{val}@dots{}
41592 @cindex @samp{QAllow} packet
41593 Specify which operations @value{GDBN} expects to request of the
41594 target, as a semicolon-separated list of operation name and value
41595 pairs. Possible values for @var{op} include @samp{WriteReg},
41596 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
41597 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
41598 indicating that @value{GDBN} will not request the operation, or 1,
41599 indicating that it may. (The target can then use this to set up its
41600 own internals optimally, for instance if the debugger never expects to
41601 insert breakpoints, it may not need to install its own trap handler.)
41604 @cindex current thread, remote request
41605 @cindex @samp{qC} packet
41606 Return the current thread ID.
41610 @item QC @var{thread-id}
41611 Where @var{thread-id} is a thread ID as documented in
41612 @ref{thread-id syntax}.
41613 @item @r{(anything else)}
41614 Any other reply implies the old thread ID.
41617 @item qCRC:@var{addr},@var{length}
41618 @cindex CRC of memory block, remote request
41619 @cindex @samp{qCRC} packet
41620 @anchor{qCRC packet}
41621 Compute the CRC checksum of a block of memory using CRC-32 defined in
41622 IEEE 802.3. The CRC is computed byte at a time, taking the most
41623 significant bit of each byte first. The initial pattern code
41624 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
41626 @emph{Note:} This is the same CRC used in validating separate debug
41627 files (@pxref{Separate Debug Files, , Debugging Information in Separate
41628 Files}). However the algorithm is slightly different. When validating
41629 separate debug files, the CRC is computed taking the @emph{least}
41630 significant bit of each byte first, and the final result is inverted to
41631 detect trailing zeros.
41636 An error (such as memory fault)
41637 @item C @var{crc32}
41638 The specified memory region's checksum is @var{crc32}.
41641 @item QDisableRandomization:@var{value}
41642 @cindex disable address space randomization, remote request
41643 @cindex @samp{QDisableRandomization} packet
41644 Some target operating systems will randomize the virtual address space
41645 of the inferior process as a security feature, but provide a feature
41646 to disable such randomization, e.g.@: to allow for a more deterministic
41647 debugging experience. On such systems, this packet with a @var{value}
41648 of 1 directs the target to disable address space randomization for
41649 processes subsequently started via @samp{vRun} packets, while a packet
41650 with a @var{value} of 0 tells the target to enable address space
41653 This packet is only available in extended mode (@pxref{extended mode}).
41658 The request succeeded.
41661 An error occurred. The error number @var{nn} is given as hex digits.
41664 An empty reply indicates that @samp{QDisableRandomization} is not supported
41668 This packet is not probed by default; the remote stub must request it,
41669 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
41670 This should only be done on targets that actually support disabling
41671 address space randomization.
41673 @item QStartupWithShell:@var{value}
41674 @cindex startup with shell, remote request
41675 @cindex @samp{QStartupWithShell} packet
41676 On UNIX-like targets, it is possible to start the inferior using a
41677 shell program. This is the default behavior on both @value{GDBN} and
41678 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
41679 used to inform @command{gdbserver} whether it should start the
41680 inferior using a shell or not.
41682 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
41683 to start the inferior. If @var{value} is @samp{1},
41684 @command{gdbserver} will use a shell to start the inferior. All other
41685 values are considered an error.
41687 This packet is only available in extended mode (@pxref{extended
41693 The request succeeded.
41696 An error occurred. The error number @var{nn} is given as hex digits.
41699 This packet is not probed by default; the remote stub must request it,
41700 by supplying an appropriate @samp{qSupported} response
41701 (@pxref{qSupported}). This should only be done on targets that
41702 actually support starting the inferior using a shell.
41704 Use of this packet is controlled by the @code{set startup-with-shell}
41705 command; @pxref{set startup-with-shell}.
41707 @item QEnvironmentHexEncoded:@var{hex-value}
41708 @anchor{QEnvironmentHexEncoded}
41709 @cindex set environment variable, remote request
41710 @cindex @samp{QEnvironmentHexEncoded} packet
41711 On UNIX-like targets, it is possible to set environment variables that
41712 will be passed to the inferior during the startup process. This
41713 packet is used to inform @command{gdbserver} of an environment
41714 variable that has been defined by the user on @value{GDBN} (@pxref{set
41717 The packet is composed by @var{hex-value}, an hex encoded
41718 representation of the @var{name=value} format representing an
41719 environment variable. The name of the environment variable is
41720 represented by @var{name}, and the value to be assigned to the
41721 environment variable is represented by @var{value}. If the variable
41722 has no value (i.e., the value is @code{null}), then @var{value} will
41725 This packet is only available in extended mode (@pxref{extended
41731 The request succeeded.
41734 This packet is not probed by default; the remote stub must request it,
41735 by supplying an appropriate @samp{qSupported} response
41736 (@pxref{qSupported}). This should only be done on targets that
41737 actually support passing environment variables to the starting
41740 This packet is related to the @code{set environment} command;
41741 @pxref{set environment}.
41743 @item QEnvironmentUnset:@var{hex-value}
41744 @anchor{QEnvironmentUnset}
41745 @cindex unset environment variable, remote request
41746 @cindex @samp{QEnvironmentUnset} packet
41747 On UNIX-like targets, it is possible to unset environment variables
41748 before starting the inferior in the remote target. This packet is
41749 used to inform @command{gdbserver} of an environment variable that has
41750 been unset by the user on @value{GDBN} (@pxref{unset environment}).
41752 The packet is composed by @var{hex-value}, an hex encoded
41753 representation of the name of the environment variable to be unset.
41755 This packet is only available in extended mode (@pxref{extended
41761 The request succeeded.
41764 This packet is not probed by default; the remote stub must request it,
41765 by supplying an appropriate @samp{qSupported} response
41766 (@pxref{qSupported}). This should only be done on targets that
41767 actually support passing environment variables to the starting
41770 This packet is related to the @code{unset environment} command;
41771 @pxref{unset environment}.
41773 @item QEnvironmentReset
41774 @anchor{QEnvironmentReset}
41775 @cindex reset environment, remote request
41776 @cindex @samp{QEnvironmentReset} packet
41777 On UNIX-like targets, this packet is used to reset the state of
41778 environment variables in the remote target before starting the
41779 inferior. In this context, reset means unsetting all environment
41780 variables that were previously set by the user (i.e., were not
41781 initially present in the environment). It is sent to
41782 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
41783 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
41784 (@pxref{QEnvironmentUnset}) packets.
41786 This packet is only available in extended mode (@pxref{extended
41792 The request succeeded.
41795 This packet is not probed by default; the remote stub must request it,
41796 by supplying an appropriate @samp{qSupported} response
41797 (@pxref{qSupported}). This should only be done on targets that
41798 actually support passing environment variables to the starting
41801 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
41802 @anchor{QSetWorkingDir packet}
41803 @cindex set working directory, remote request
41804 @cindex @samp{QSetWorkingDir} packet
41805 This packet is used to inform the remote server of the intended
41806 current working directory for programs that are going to be executed.
41808 The packet is composed by @var{directory}, an hex encoded
41809 representation of the directory that the remote inferior will use as
41810 its current working directory. If @var{directory} is an empty string,
41811 the remote server should reset the inferior's current working
41812 directory to its original, empty value.
41814 This packet is only available in extended mode (@pxref{extended
41820 The request succeeded.
41824 @itemx qsThreadInfo
41825 @cindex list active threads, remote request
41826 @cindex @samp{qfThreadInfo} packet
41827 @cindex @samp{qsThreadInfo} packet
41828 Obtain a list of all active thread IDs from the target (OS). Since there
41829 may be too many active threads to fit into one reply packet, this query
41830 works iteratively: it may require more than one query/reply sequence to
41831 obtain the entire list of threads. The first query of the sequence will
41832 be the @samp{qfThreadInfo} query; subsequent queries in the
41833 sequence will be the @samp{qsThreadInfo} query.
41835 NOTE: This packet replaces the @samp{qL} query (see below).
41839 @item m @var{thread-id}
41841 @item m @var{thread-id},@var{thread-id}@dots{}
41842 a comma-separated list of thread IDs
41844 (lower case letter @samp{L}) denotes end of list.
41847 In response to each query, the target will reply with a list of one or
41848 more thread IDs, separated by commas.
41849 @value{GDBN} will respond to each reply with a request for more thread
41850 ids (using the @samp{qs} form of the query), until the target responds
41851 with @samp{l} (lower-case ell, for @dfn{last}).
41852 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
41855 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
41856 initial connection with the remote target, and the very first thread ID
41857 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
41858 message. Therefore, the stub should ensure that the first thread ID in
41859 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
41861 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
41862 @cindex get thread-local storage address, remote request
41863 @cindex @samp{qGetTLSAddr} packet
41864 Fetch the address associated with thread local storage specified
41865 by @var{thread-id}, @var{offset}, and @var{lm}.
41867 @var{thread-id} is the thread ID associated with the
41868 thread for which to fetch the TLS address. @xref{thread-id syntax}.
41870 @var{offset} is the (big endian, hex encoded) offset associated with the
41871 thread local variable. (This offset is obtained from the debug
41872 information associated with the variable.)
41874 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
41875 load module associated with the thread local storage. For example,
41876 a @sc{gnu}/Linux system will pass the link map address of the shared
41877 object associated with the thread local storage under consideration.
41878 Other operating environments may choose to represent the load module
41879 differently, so the precise meaning of this parameter will vary.
41883 @item @var{XX}@dots{}
41884 Hex encoded (big endian) bytes representing the address of the thread
41885 local storage requested.
41888 An error occurred. The error number @var{nn} is given as hex digits.
41891 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
41894 @item qGetTIBAddr:@var{thread-id}
41895 @cindex get thread information block address
41896 @cindex @samp{qGetTIBAddr} packet
41897 Fetch address of the Windows OS specific Thread Information Block.
41899 @var{thread-id} is the thread ID associated with the thread.
41903 @item @var{XX}@dots{}
41904 Hex encoded (big endian) bytes representing the linear address of the
41905 thread information block.
41908 An error occured. This means that either the thread was not found, or the
41909 address could not be retrieved.
41912 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
41915 @item qL @var{startflag} @var{threadcount} @var{nextthread}
41916 Obtain thread information from RTOS. Where: @var{startflag} (one hex
41917 digit) is one to indicate the first query and zero to indicate a
41918 subsequent query; @var{threadcount} (two hex digits) is the maximum
41919 number of threads the response packet can contain; and @var{nextthread}
41920 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
41921 returned in the response as @var{argthread}.
41923 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
41927 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
41928 Where: @var{count} (two hex digits) is the number of threads being
41929 returned; @var{done} (one hex digit) is zero to indicate more threads
41930 and one indicates no further threads; @var{argthreadid} (eight hex
41931 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
41932 is a sequence of thread IDs, @var{threadid} (eight hex
41933 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
41936 @item qMemTags:@var{start address},@var{length}:@var{type}
41938 @cindex fetch memory tags
41939 @cindex @samp{qMemTags} packet
41940 Fetch memory tags of type @var{type} from the address range
41941 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41942 target is responsible for calculating how many tags will be returned, as this
41943 is architecture-specific.
41945 @var{start address} is the starting address of the memory range.
41947 @var{length} is the length, in bytes, of the memory range.
41949 @var{type} is the type of tag the request wants to fetch. The type is a signed
41954 @item @var{mxx}@dots{}
41955 Hex encoded sequence of uninterpreted bytes, @var{xx}@dots{}, representing the
41956 tags found in the requested memory range.
41959 An error occured. This means that fetching of memory tags failed for some
41963 An empty reply indicates that @samp{qMemTags} is not supported by the stub,
41964 although this should not happen given @value{GDBN} will only send this packet
41965 if the stub has advertised support for memory tagging via @samp{qSupported}.
41968 @item QMemTags:@var{start address},@var{length}:@var{type}:@var{tag bytes}
41970 @cindex store memory tags
41971 @cindex @samp{QMemTags} packet
41972 Store memory tags of type @var{type} to the address range
41973 @w{@r{[}@var{start address}, @var{start address} + @var{length}@r{)}}. The
41974 target is responsible for interpreting the type, the tag bytes and modifying
41975 the memory tag granules accordingly, given this is architecture-specific.
41977 The interpretation of how many tags (@var{nt}) should be written to how many
41978 memory tag granules (@var{ng}) is also architecture-specific. The behavior is
41979 implementation-specific, but the following is suggested.
41981 If the number of memory tags, @var{nt}, is greater than or equal to the
41982 number of memory tag granules, @var{ng}, only @var{ng} tags will be
41985 If @var{nt} is less than @var{ng}, the behavior is that of a fill operation,
41986 and the tag bytes will be used as a pattern that will get repeated until
41987 @var{ng} tags are stored.
41989 @var{start address} is the starting address of the memory range. The address
41990 does not have any restriction on alignment or size.
41992 @var{length} is the length, in bytes, of the memory range.
41994 @var{type} is the type of tag the request wants to fetch. The type is a signed
41997 @var{tag bytes} is a sequence of hex encoded uninterpreted bytes which will be
41998 interpreted by the target. Each pair of hex digits is interpreted as a
42004 The request was successful and the memory tag granules were modified
42008 An error occured. This means that modifying the memory tag granules failed
42012 An empty reply indicates that @samp{QMemTags} is not supported by the stub,
42013 although this should not happen given @value{GDBN} will only send this packet
42014 if the stub has advertised support for memory tagging via @samp{qSupported}.
42018 @cindex section offsets, remote request
42019 @cindex @samp{qOffsets} packet
42020 Get section offsets that the target used when relocating the downloaded
42025 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
42026 Relocate the @code{Text} section by @var{xxx} from its original address.
42027 Relocate the @code{Data} section by @var{yyy} from its original address.
42028 If the object file format provides segment information (e.g.@: @sc{elf}
42029 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
42030 segments by the supplied offsets.
42032 @emph{Note: while a @code{Bss} offset may be included in the response,
42033 @value{GDBN} ignores this and instead applies the @code{Data} offset
42034 to the @code{Bss} section.}
42036 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
42037 Relocate the first segment of the object file, which conventionally
42038 contains program code, to a starting address of @var{xxx}. If
42039 @samp{DataSeg} is specified, relocate the second segment, which
42040 conventionally contains modifiable data, to a starting address of
42041 @var{yyy}. @value{GDBN} will report an error if the object file
42042 does not contain segment information, or does not contain at least
42043 as many segments as mentioned in the reply. Extra segments are
42044 kept at fixed offsets relative to the last relocated segment.
42047 @item qP @var{mode} @var{thread-id}
42048 @cindex thread information, remote request
42049 @cindex @samp{qP} packet
42050 Returns information on @var{thread-id}. Where: @var{mode} is a hex
42051 encoded 32 bit mode; @var{thread-id} is a thread ID
42052 (@pxref{thread-id syntax}).
42054 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
42057 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
42061 @cindex non-stop mode, remote request
42062 @cindex @samp{QNonStop} packet
42064 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
42065 @xref{Remote Non-Stop}, for more information.
42070 The request succeeded.
42073 An error occurred. The error number @var{nn} is given as hex digits.
42076 An empty reply indicates that @samp{QNonStop} is not supported by
42080 This packet is not probed by default; the remote stub must request it,
42081 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42082 Use of this packet is controlled by the @code{set non-stop} command;
42083 @pxref{Non-Stop Mode}.
42085 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
42086 @itemx QCatchSyscalls:0
42087 @cindex catch syscalls from inferior, remote request
42088 @cindex @samp{QCatchSyscalls} packet
42089 @anchor{QCatchSyscalls}
42090 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
42091 catching syscalls from the inferior process.
42093 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
42094 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
42095 is listed, every system call should be reported.
42097 Note that if a syscall not in the list is reported, @value{GDBN} will
42098 still filter the event according to its own list from all corresponding
42099 @code{catch syscall} commands. However, it is more efficient to only
42100 report the requested syscalls.
42102 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
42103 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
42105 If the inferior process execs, the state of @samp{QCatchSyscalls} is
42106 kept for the new process too. On targets where exec may affect syscall
42107 numbers, for example with exec between 32 and 64-bit processes, the
42108 client should send a new packet with the new syscall list.
42113 The request succeeded.
42116 An error occurred. @var{nn} are hex digits.
42119 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
42123 Use of this packet is controlled by the @code{set remote catch-syscalls}
42124 command (@pxref{Remote Configuration, set remote catch-syscalls}).
42125 This packet is not probed by default; the remote stub must request it,
42126 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42128 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42129 @cindex pass signals to inferior, remote request
42130 @cindex @samp{QPassSignals} packet
42131 @anchor{QPassSignals}
42132 Each listed @var{signal} should be passed directly to the inferior process.
42133 Signals are numbered identically to continue packets and stop replies
42134 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42135 strictly greater than the previous item. These signals do not need to stop
42136 the inferior, or be reported to @value{GDBN}. All other signals should be
42137 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
42138 combine; any earlier @samp{QPassSignals} list is completely replaced by the
42139 new list. This packet improves performance when using @samp{handle
42140 @var{signal} nostop noprint pass}.
42145 The request succeeded.
42148 An error occurred. The error number @var{nn} is given as hex digits.
42151 An empty reply indicates that @samp{QPassSignals} is not supported by
42155 Use of this packet is controlled by the @code{set remote pass-signals}
42156 command (@pxref{Remote Configuration, set remote pass-signals}).
42157 This packet is not probed by default; the remote stub must request it,
42158 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42160 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
42161 @cindex signals the inferior may see, remote request
42162 @cindex @samp{QProgramSignals} packet
42163 @anchor{QProgramSignals}
42164 Each listed @var{signal} may be delivered to the inferior process.
42165 Others should be silently discarded.
42167 In some cases, the remote stub may need to decide whether to deliver a
42168 signal to the program or not without @value{GDBN} involvement. One
42169 example of that is while detaching --- the program's threads may have
42170 stopped for signals that haven't yet had a chance of being reported to
42171 @value{GDBN}, and so the remote stub can use the signal list specified
42172 by this packet to know whether to deliver or ignore those pending
42175 This does not influence whether to deliver a signal as requested by a
42176 resumption packet (@pxref{vCont packet}).
42178 Signals are numbered identically to continue packets and stop replies
42179 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
42180 strictly greater than the previous item. Multiple
42181 @samp{QProgramSignals} packets do not combine; any earlier
42182 @samp{QProgramSignals} list is completely replaced by the new list.
42187 The request succeeded.
42190 An error occurred. The error number @var{nn} is given as hex digits.
42193 An empty reply indicates that @samp{QProgramSignals} is not supported
42197 Use of this packet is controlled by the @code{set remote program-signals}
42198 command (@pxref{Remote Configuration, set remote program-signals}).
42199 This packet is not probed by default; the remote stub must request it,
42200 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
42202 @anchor{QThreadEvents}
42203 @item QThreadEvents:1
42204 @itemx QThreadEvents:0
42205 @cindex thread create/exit events, remote request
42206 @cindex @samp{QThreadEvents} packet
42208 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
42209 reporting of thread create and exit events. @xref{thread create
42210 event}, for the reply specifications. For example, this is used in
42211 non-stop mode when @value{GDBN} stops a set of threads and
42212 synchronously waits for the their corresponding stop replies. Without
42213 exit events, if one of the threads exits, @value{GDBN} would hang
42214 forever not knowing that it should no longer expect a stop for that
42215 same thread. @value{GDBN} does not enable this feature unless the
42216 stub reports that it supports it by including @samp{QThreadEvents+} in
42217 its @samp{qSupported} reply.
42222 The request succeeded.
42225 An error occurred. The error number @var{nn} is given as hex digits.
42228 An empty reply indicates that @samp{QThreadEvents} is not supported by
42232 Use of this packet is controlled by the @code{set remote thread-events}
42233 command (@pxref{Remote Configuration, set remote thread-events}).
42235 @item qRcmd,@var{command}
42236 @cindex execute remote command, remote request
42237 @cindex @samp{qRcmd} packet
42238 @var{command} (hex encoded) is passed to the local interpreter for
42239 execution. Invalid commands should be reported using the output
42240 string. Before the final result packet, the target may also respond
42241 with a number of intermediate @samp{O@var{output}} console output
42242 packets. @emph{Implementors should note that providing access to a
42243 stubs's interpreter may have security implications}.
42248 A command response with no output.
42250 A command response with the hex encoded output string @var{OUTPUT}.
42252 Indicate a badly formed request. The error number @var{NN} is given as
42255 An empty reply indicates that @samp{qRcmd} is not recognized.
42258 (Note that the @code{qRcmd} packet's name is separated from the
42259 command by a @samp{,}, not a @samp{:}, contrary to the naming
42260 conventions above. Please don't use this packet as a model for new
42263 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
42264 @cindex searching memory, in remote debugging
42266 @cindex @samp{qSearch:memory} packet
42268 @cindex @samp{qSearch memory} packet
42269 @anchor{qSearch memory}
42270 Search @var{length} bytes at @var{address} for @var{search-pattern}.
42271 Both @var{address} and @var{length} are encoded in hex;
42272 @var{search-pattern} is a sequence of bytes, also hex encoded.
42277 The pattern was not found.
42279 The pattern was found at @var{address}.
42281 A badly formed request or an error was encountered while searching memory.
42283 An empty reply indicates that @samp{qSearch:memory} is not recognized.
42286 @item QStartNoAckMode
42287 @cindex @samp{QStartNoAckMode} packet
42288 @anchor{QStartNoAckMode}
42289 Request that the remote stub disable the normal @samp{+}/@samp{-}
42290 protocol acknowledgments (@pxref{Packet Acknowledgment}).
42295 The stub has switched to no-acknowledgment mode.
42296 @value{GDBN} acknowledges this response,
42297 but neither the stub nor @value{GDBN} shall send or expect further
42298 @samp{+}/@samp{-} acknowledgments in the current connection.
42300 An empty reply indicates that the stub does not support no-acknowledgment mode.
42303 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
42304 @cindex supported packets, remote query
42305 @cindex features of the remote protocol
42306 @cindex @samp{qSupported} packet
42307 @anchor{qSupported}
42308 Tell the remote stub about features supported by @value{GDBN}, and
42309 query the stub for features it supports. This packet allows
42310 @value{GDBN} and the remote stub to take advantage of each others'
42311 features. @samp{qSupported} also consolidates multiple feature probes
42312 at startup, to improve @value{GDBN} performance---a single larger
42313 packet performs better than multiple smaller probe packets on
42314 high-latency links. Some features may enable behavior which must not
42315 be on by default, e.g.@: because it would confuse older clients or
42316 stubs. Other features may describe packets which could be
42317 automatically probed for, but are not. These features must be
42318 reported before @value{GDBN} will use them. This ``default
42319 unsupported'' behavior is not appropriate for all packets, but it
42320 helps to keep the initial connection time under control with new
42321 versions of @value{GDBN} which support increasing numbers of packets.
42325 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
42326 The stub supports or does not support each returned @var{stubfeature},
42327 depending on the form of each @var{stubfeature} (see below for the
42330 An empty reply indicates that @samp{qSupported} is not recognized,
42331 or that no features needed to be reported to @value{GDBN}.
42334 The allowed forms for each feature (either a @var{gdbfeature} in the
42335 @samp{qSupported} packet, or a @var{stubfeature} in the response)
42339 @item @var{name}=@var{value}
42340 The remote protocol feature @var{name} is supported, and associated
42341 with the specified @var{value}. The format of @var{value} depends
42342 on the feature, but it must not include a semicolon.
42344 The remote protocol feature @var{name} is supported, and does not
42345 need an associated value.
42347 The remote protocol feature @var{name} is not supported.
42349 The remote protocol feature @var{name} may be supported, and
42350 @value{GDBN} should auto-detect support in some other way when it is
42351 needed. This form will not be used for @var{gdbfeature} notifications,
42352 but may be used for @var{stubfeature} responses.
42355 Whenever the stub receives a @samp{qSupported} request, the
42356 supplied set of @value{GDBN} features should override any previous
42357 request. This allows @value{GDBN} to put the stub in a known
42358 state, even if the stub had previously been communicating with
42359 a different version of @value{GDBN}.
42361 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
42366 This feature indicates whether @value{GDBN} supports multiprocess
42367 extensions to the remote protocol. @value{GDBN} does not use such
42368 extensions unless the stub also reports that it supports them by
42369 including @samp{multiprocess+} in its @samp{qSupported} reply.
42370 @xref{multiprocess extensions}, for details.
42373 This feature indicates that @value{GDBN} supports the XML target
42374 description. If the stub sees @samp{xmlRegisters=} with target
42375 specific strings separated by a comma, it will report register
42379 This feature indicates whether @value{GDBN} supports the
42380 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
42381 instruction reply packet}).
42384 This feature indicates whether @value{GDBN} supports the swbreak stop
42385 reason in stop replies. @xref{swbreak stop reason}, for details.
42388 This feature indicates whether @value{GDBN} supports the hwbreak stop
42389 reason in stop replies. @xref{swbreak stop reason}, for details.
42392 This feature indicates whether @value{GDBN} supports fork event
42393 extensions to the remote protocol. @value{GDBN} does not use such
42394 extensions unless the stub also reports that it supports them by
42395 including @samp{fork-events+} in its @samp{qSupported} reply.
42398 This feature indicates whether @value{GDBN} supports vfork event
42399 extensions to the remote protocol. @value{GDBN} does not use such
42400 extensions unless the stub also reports that it supports them by
42401 including @samp{vfork-events+} in its @samp{qSupported} reply.
42404 This feature indicates whether @value{GDBN} supports exec event
42405 extensions to the remote protocol. @value{GDBN} does not use such
42406 extensions unless the stub also reports that it supports them by
42407 including @samp{exec-events+} in its @samp{qSupported} reply.
42409 @item vContSupported
42410 This feature indicates whether @value{GDBN} wants to know the
42411 supported actions in the reply to @samp{vCont?} packet.
42414 Stubs should ignore any unknown values for
42415 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
42416 packet supports receiving packets of unlimited length (earlier
42417 versions of @value{GDBN} may reject overly long responses). Additional values
42418 for @var{gdbfeature} may be defined in the future to let the stub take
42419 advantage of new features in @value{GDBN}, e.g.@: incompatible
42420 improvements in the remote protocol---the @samp{multiprocess} feature is
42421 an example of such a feature. The stub's reply should be independent
42422 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
42423 describes all the features it supports, and then the stub replies with
42424 all the features it supports.
42426 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
42427 responses, as long as each response uses one of the standard forms.
42429 Some features are flags. A stub which supports a flag feature
42430 should respond with a @samp{+} form response. Other features
42431 require values, and the stub should respond with an @samp{=}
42434 Each feature has a default value, which @value{GDBN} will use if
42435 @samp{qSupported} is not available or if the feature is not mentioned
42436 in the @samp{qSupported} response. The default values are fixed; a
42437 stub is free to omit any feature responses that match the defaults.
42439 Not all features can be probed, but for those which can, the probing
42440 mechanism is useful: in some cases, a stub's internal
42441 architecture may not allow the protocol layer to know some information
42442 about the underlying target in advance. This is especially common in
42443 stubs which may be configured for multiple targets.
42445 These are the currently defined stub features and their properties:
42447 @multitable @columnfractions 0.35 0.2 0.12 0.2
42448 @c NOTE: The first row should be @headitem, but we do not yet require
42449 @c a new enough version of Texinfo (4.7) to use @headitem.
42451 @tab Value Required
42455 @item @samp{PacketSize}
42460 @item @samp{qXfer:auxv:read}
42465 @item @samp{qXfer:btrace:read}
42470 @item @samp{qXfer:btrace-conf:read}
42475 @item @samp{qXfer:exec-file:read}
42480 @item @samp{qXfer:features:read}
42485 @item @samp{qXfer:libraries:read}
42490 @item @samp{qXfer:libraries-svr4:read}
42495 @item @samp{augmented-libraries-svr4-read}
42500 @item @samp{qXfer:memory-map:read}
42505 @item @samp{qXfer:sdata:read}
42510 @item @samp{qXfer:siginfo:read}
42515 @item @samp{qXfer:siginfo:write}
42520 @item @samp{qXfer:threads:read}
42525 @item @samp{qXfer:traceframe-info:read}
42530 @item @samp{qXfer:uib:read}
42535 @item @samp{qXfer:fdpic:read}
42540 @item @samp{Qbtrace:off}
42545 @item @samp{Qbtrace:bts}
42550 @item @samp{Qbtrace:pt}
42555 @item @samp{Qbtrace-conf:bts:size}
42560 @item @samp{Qbtrace-conf:pt:size}
42565 @item @samp{QNonStop}
42570 @item @samp{QCatchSyscalls}
42575 @item @samp{QPassSignals}
42580 @item @samp{QStartNoAckMode}
42585 @item @samp{multiprocess}
42590 @item @samp{ConditionalBreakpoints}
42595 @item @samp{ConditionalTracepoints}
42600 @item @samp{ReverseContinue}
42605 @item @samp{ReverseStep}
42610 @item @samp{TracepointSource}
42615 @item @samp{QAgent}
42620 @item @samp{QAllow}
42625 @item @samp{QDisableRandomization}
42630 @item @samp{EnableDisableTracepoints}
42635 @item @samp{QTBuffer:size}
42640 @item @samp{tracenz}
42645 @item @samp{BreakpointCommands}
42650 @item @samp{swbreak}
42655 @item @samp{hwbreak}
42660 @item @samp{fork-events}
42665 @item @samp{vfork-events}
42670 @item @samp{exec-events}
42675 @item @samp{QThreadEvents}
42680 @item @samp{no-resumed}
42685 @item @samp{memory-tagging}
42692 These are the currently defined stub features, in more detail:
42695 @cindex packet size, remote protocol
42696 @item PacketSize=@var{bytes}
42697 The remote stub can accept packets up to at least @var{bytes} in
42698 length. @value{GDBN} will send packets up to this size for bulk
42699 transfers, and will never send larger packets. This is a limit on the
42700 data characters in the packet, including the frame and checksum.
42701 There is no trailing NUL byte in a remote protocol packet; if the stub
42702 stores packets in a NUL-terminated format, it should allow an extra
42703 byte in its buffer for the NUL. If this stub feature is not supported,
42704 @value{GDBN} guesses based on the size of the @samp{g} packet response.
42706 @item qXfer:auxv:read
42707 The remote stub understands the @samp{qXfer:auxv:read} packet
42708 (@pxref{qXfer auxiliary vector read}).
42710 @item qXfer:btrace:read
42711 The remote stub understands the @samp{qXfer:btrace:read}
42712 packet (@pxref{qXfer btrace read}).
42714 @item qXfer:btrace-conf:read
42715 The remote stub understands the @samp{qXfer:btrace-conf:read}
42716 packet (@pxref{qXfer btrace-conf read}).
42718 @item qXfer:exec-file:read
42719 The remote stub understands the @samp{qXfer:exec-file:read} packet
42720 (@pxref{qXfer executable filename read}).
42722 @item qXfer:features:read
42723 The remote stub understands the @samp{qXfer:features:read} packet
42724 (@pxref{qXfer target description read}).
42726 @item qXfer:libraries:read
42727 The remote stub understands the @samp{qXfer:libraries:read} packet
42728 (@pxref{qXfer library list read}).
42730 @item qXfer:libraries-svr4:read
42731 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
42732 (@pxref{qXfer svr4 library list read}).
42734 @item augmented-libraries-svr4-read
42735 The remote stub understands the augmented form of the
42736 @samp{qXfer:libraries-svr4:read} packet
42737 (@pxref{qXfer svr4 library list read}).
42739 @item qXfer:memory-map:read
42740 The remote stub understands the @samp{qXfer:memory-map:read} packet
42741 (@pxref{qXfer memory map read}).
42743 @item qXfer:sdata:read
42744 The remote stub understands the @samp{qXfer:sdata:read} packet
42745 (@pxref{qXfer sdata read}).
42747 @item qXfer:siginfo:read
42748 The remote stub understands the @samp{qXfer:siginfo:read} packet
42749 (@pxref{qXfer siginfo read}).
42751 @item qXfer:siginfo:write
42752 The remote stub understands the @samp{qXfer:siginfo:write} packet
42753 (@pxref{qXfer siginfo write}).
42755 @item qXfer:threads:read
42756 The remote stub understands the @samp{qXfer:threads:read} packet
42757 (@pxref{qXfer threads read}).
42759 @item qXfer:traceframe-info:read
42760 The remote stub understands the @samp{qXfer:traceframe-info:read}
42761 packet (@pxref{qXfer traceframe info read}).
42763 @item qXfer:uib:read
42764 The remote stub understands the @samp{qXfer:uib:read}
42765 packet (@pxref{qXfer unwind info block}).
42767 @item qXfer:fdpic:read
42768 The remote stub understands the @samp{qXfer:fdpic:read}
42769 packet (@pxref{qXfer fdpic loadmap read}).
42772 The remote stub understands the @samp{QNonStop} packet
42773 (@pxref{QNonStop}).
42775 @item QCatchSyscalls
42776 The remote stub understands the @samp{QCatchSyscalls} packet
42777 (@pxref{QCatchSyscalls}).
42780 The remote stub understands the @samp{QPassSignals} packet
42781 (@pxref{QPassSignals}).
42783 @item QStartNoAckMode
42784 The remote stub understands the @samp{QStartNoAckMode} packet and
42785 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
42788 @anchor{multiprocess extensions}
42789 @cindex multiprocess extensions, in remote protocol
42790 The remote stub understands the multiprocess extensions to the remote
42791 protocol syntax. The multiprocess extensions affect the syntax of
42792 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
42793 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
42794 replies. Note that reporting this feature indicates support for the
42795 syntactic extensions only, not that the stub necessarily supports
42796 debugging of more than one process at a time. The stub must not use
42797 multiprocess extensions in packet replies unless @value{GDBN} has also
42798 indicated it supports them in its @samp{qSupported} request.
42800 @item qXfer:osdata:read
42801 The remote stub understands the @samp{qXfer:osdata:read} packet
42802 ((@pxref{qXfer osdata read}).
42804 @item ConditionalBreakpoints
42805 The target accepts and implements evaluation of conditional expressions
42806 defined for breakpoints. The target will only report breakpoint triggers
42807 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
42809 @item ConditionalTracepoints
42810 The remote stub accepts and implements conditional expressions defined
42811 for tracepoints (@pxref{Tracepoint Conditions}).
42813 @item ReverseContinue
42814 The remote stub accepts and implements the reverse continue packet
42818 The remote stub accepts and implements the reverse step packet
42821 @item TracepointSource
42822 The remote stub understands the @samp{QTDPsrc} packet that supplies
42823 the source form of tracepoint definitions.
42826 The remote stub understands the @samp{QAgent} packet.
42829 The remote stub understands the @samp{QAllow} packet.
42831 @item QDisableRandomization
42832 The remote stub understands the @samp{QDisableRandomization} packet.
42834 @item StaticTracepoint
42835 @cindex static tracepoints, in remote protocol
42836 The remote stub supports static tracepoints.
42838 @item InstallInTrace
42839 @anchor{install tracepoint in tracing}
42840 The remote stub supports installing tracepoint in tracing.
42842 @item EnableDisableTracepoints
42843 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
42844 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
42845 to be enabled and disabled while a trace experiment is running.
42847 @item QTBuffer:size
42848 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
42849 packet that allows to change the size of the trace buffer.
42852 @cindex string tracing, in remote protocol
42853 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
42854 See @ref{Bytecode Descriptions} for details about the bytecode.
42856 @item BreakpointCommands
42857 @cindex breakpoint commands, in remote protocol
42858 The remote stub supports running a breakpoint's command list itself,
42859 rather than reporting the hit to @value{GDBN}.
42862 The remote stub understands the @samp{Qbtrace:off} packet.
42865 The remote stub understands the @samp{Qbtrace:bts} packet.
42868 The remote stub understands the @samp{Qbtrace:pt} packet.
42870 @item Qbtrace-conf:bts:size
42871 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
42873 @item Qbtrace-conf:pt:size
42874 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
42877 The remote stub reports the @samp{swbreak} stop reason for memory
42881 The remote stub reports the @samp{hwbreak} stop reason for hardware
42885 The remote stub reports the @samp{fork} stop reason for fork events.
42888 The remote stub reports the @samp{vfork} stop reason for vfork events
42889 and vforkdone events.
42892 The remote stub reports the @samp{exec} stop reason for exec events.
42894 @item vContSupported
42895 The remote stub reports the supported actions in the reply to
42896 @samp{vCont?} packet.
42898 @item QThreadEvents
42899 The remote stub understands the @samp{QThreadEvents} packet.
42902 The remote stub reports the @samp{N} stop reply.
42905 @item memory-tagging
42906 The remote stub supports and implements the required memory tagging
42907 functionality and understands the @samp{qMemTags} (@pxref{qMemTags}) and
42908 @samp{QMemTags} (@pxref{QMemTags}) packets.
42910 For AArch64 GNU/Linux systems, this feature also requires access to the
42911 @file{/proc/@var{pid}/smaps} file so memory mapping page flags can be inspected.
42912 This is done via the @samp{vFile} requests.
42917 @cindex symbol lookup, remote request
42918 @cindex @samp{qSymbol} packet
42919 Notify the target that @value{GDBN} is prepared to serve symbol lookup
42920 requests. Accept requests from the target for the values of symbols.
42925 The target does not need to look up any (more) symbols.
42926 @item qSymbol:@var{sym_name}
42927 The target requests the value of symbol @var{sym_name} (hex encoded).
42928 @value{GDBN} may provide the value by using the
42929 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
42933 @item qSymbol:@var{sym_value}:@var{sym_name}
42934 Set the value of @var{sym_name} to @var{sym_value}.
42936 @var{sym_name} (hex encoded) is the name of a symbol whose value the
42937 target has previously requested.
42939 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
42940 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
42946 The target does not need to look up any (more) symbols.
42947 @item qSymbol:@var{sym_name}
42948 The target requests the value of a new symbol @var{sym_name} (hex
42949 encoded). @value{GDBN} will continue to supply the values of symbols
42950 (if available), until the target ceases to request them.
42955 @itemx QTDisconnected
42962 @itemx qTMinFTPILen
42964 @xref{Tracepoint Packets}.
42966 @anchor{qThreadExtraInfo}
42967 @item qThreadExtraInfo,@var{thread-id}
42968 @cindex thread attributes info, remote request
42969 @cindex @samp{qThreadExtraInfo} packet
42970 Obtain from the target OS a printable string description of thread
42971 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
42972 for the forms of @var{thread-id}. This
42973 string may contain anything that the target OS thinks is interesting
42974 for @value{GDBN} to tell the user about the thread. The string is
42975 displayed in @value{GDBN}'s @code{info threads} display. Some
42976 examples of possible thread extra info strings are @samp{Runnable}, or
42977 @samp{Blocked on Mutex}.
42981 @item @var{XX}@dots{}
42982 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
42983 comprising the printable string containing the extra information about
42984 the thread's attributes.
42987 (Note that the @code{qThreadExtraInfo} packet's name is separated from
42988 the command by a @samp{,}, not a @samp{:}, contrary to the naming
42989 conventions above. Please don't use this packet as a model for new
43008 @xref{Tracepoint Packets}.
43010 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
43011 @cindex read special object, remote request
43012 @cindex @samp{qXfer} packet
43013 @anchor{qXfer read}
43014 Read uninterpreted bytes from the target's special data area
43015 identified by the keyword @var{object}. Request @var{length} bytes
43016 starting at @var{offset} bytes into the data. The content and
43017 encoding of @var{annex} is specific to @var{object}; it can supply
43018 additional details about what data to access.
43023 Data @var{data} (@pxref{Binary Data}) has been read from the
43024 target. There may be more data at a higher address (although
43025 it is permitted to return @samp{m} even for the last valid
43026 block of data, as long as at least one byte of data was read).
43027 It is possible for @var{data} to have fewer bytes than the @var{length} in the
43031 Data @var{data} (@pxref{Binary Data}) has been read from the target.
43032 There is no more data to be read. It is possible for @var{data} to
43033 have fewer bytes than the @var{length} in the request.
43036 The @var{offset} in the request is at the end of the data.
43037 There is no more data to be read.
43040 The request was malformed, or @var{annex} was invalid.
43043 The offset was invalid, or there was an error encountered reading the data.
43044 The @var{nn} part is a hex-encoded @code{errno} value.
43047 An empty reply indicates the @var{object} string was not recognized by
43048 the stub, or that the object does not support reading.
43051 Here are the specific requests of this form defined so far. All the
43052 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
43053 formats, listed above.
43056 @item qXfer:auxv:read::@var{offset},@var{length}
43057 @anchor{qXfer auxiliary vector read}
43058 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
43059 auxiliary vector}. Note @var{annex} must be empty.
43061 This packet is not probed by default; the remote stub must request it,
43062 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43064 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
43065 @anchor{qXfer btrace read}
43067 Return a description of the current branch trace.
43068 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
43069 packet may have one of the following values:
43073 Returns all available branch trace.
43076 Returns all available branch trace if the branch trace changed since
43077 the last read request.
43080 Returns the new branch trace since the last read request. Adds a new
43081 block to the end of the trace that begins at zero and ends at the source
43082 location of the first branch in the trace buffer. This extra block is
43083 used to stitch traces together.
43085 If the trace buffer overflowed, returns an error indicating the overflow.
43088 This packet is not probed by default; the remote stub must request it
43089 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43091 @item qXfer:btrace-conf:read::@var{offset},@var{length}
43092 @anchor{qXfer btrace-conf read}
43094 Return a description of the current branch trace configuration.
43095 @xref{Branch Trace Configuration Format}.
43097 This packet is not probed by default; the remote stub must request it
43098 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43100 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
43101 @anchor{qXfer executable filename read}
43102 Return the full absolute name of the file that was executed to create
43103 a process running on the remote system. The annex specifies the
43104 numeric process ID of the process to query, encoded as a hexadecimal
43105 number. If the annex part is empty the remote stub should return the
43106 filename corresponding to the currently executing process.
43108 This packet is not probed by default; the remote stub must request it,
43109 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43111 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
43112 @anchor{qXfer target description read}
43113 Access the @dfn{target description}. @xref{Target Descriptions}. The
43114 annex specifies which XML document to access. The main description is
43115 always loaded from the @samp{target.xml} annex.
43117 This packet is not probed by default; the remote stub must request it,
43118 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43120 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
43121 @anchor{qXfer library list read}
43122 Access the target's list of loaded libraries. @xref{Library List Format}.
43123 The annex part of the generic @samp{qXfer} packet must be empty
43124 (@pxref{qXfer read}).
43126 Targets which maintain a list of libraries in the program's memory do
43127 not need to implement this packet; it is designed for platforms where
43128 the operating system manages the list of loaded libraries.
43130 This packet is not probed by default; the remote stub must request it,
43131 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43133 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
43134 @anchor{qXfer svr4 library list read}
43135 Access the target's list of loaded libraries when the target is an SVR4
43136 platform. @xref{Library List Format for SVR4 Targets}. The annex part
43137 of the generic @samp{qXfer} packet must be empty unless the remote
43138 stub indicated it supports the augmented form of this packet
43139 by supplying an appropriate @samp{qSupported} response
43140 (@pxref{qXfer read}, @ref{qSupported}).
43142 This packet is optional for better performance on SVR4 targets.
43143 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
43145 This packet is not probed by default; the remote stub must request it,
43146 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43148 If the remote stub indicates it supports the augmented form of this
43149 packet then the annex part of the generic @samp{qXfer} packet may
43150 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
43151 arguments. The currently supported arguments are:
43154 @item start=@var{address}
43155 A hexadecimal number specifying the address of the @samp{struct
43156 link_map} to start reading the library list from. If unset or zero
43157 then the first @samp{struct link_map} in the library list will be
43158 chosen as the starting point.
43160 @item prev=@var{address}
43161 A hexadecimal number specifying the address of the @samp{struct
43162 link_map} immediately preceding the @samp{struct link_map}
43163 specified by the @samp{start} argument. If unset or zero then
43164 the remote stub will expect that no @samp{struct link_map}
43165 exists prior to the starting point.
43169 Arguments that are not understood by the remote stub will be silently
43172 @item qXfer:memory-map:read::@var{offset},@var{length}
43173 @anchor{qXfer memory map read}
43174 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
43175 annex part of the generic @samp{qXfer} packet must be empty
43176 (@pxref{qXfer read}).
43178 This packet is not probed by default; the remote stub must request it,
43179 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43181 @item qXfer:sdata:read::@var{offset},@var{length}
43182 @anchor{qXfer sdata read}
43184 Read contents of the extra collected static tracepoint marker
43185 information. The annex part of the generic @samp{qXfer} packet must
43186 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
43189 This packet is not probed by default; the remote stub must request it,
43190 by supplying an appropriate @samp{qSupported} response
43191 (@pxref{qSupported}).
43193 @item qXfer:siginfo:read::@var{offset},@var{length}
43194 @anchor{qXfer siginfo read}
43195 Read contents of the extra signal information on the target
43196 system. The annex part of the generic @samp{qXfer} packet must be
43197 empty (@pxref{qXfer read}).
43199 This packet is not probed by default; the remote stub must request it,
43200 by supplying an appropriate @samp{qSupported} response
43201 (@pxref{qSupported}).
43203 @item qXfer:threads:read::@var{offset},@var{length}
43204 @anchor{qXfer threads read}
43205 Access the list of threads on target. @xref{Thread List Format}. The
43206 annex part of the generic @samp{qXfer} packet must be empty
43207 (@pxref{qXfer read}).
43209 This packet is not probed by default; the remote stub must request it,
43210 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43212 @item qXfer:traceframe-info:read::@var{offset},@var{length}
43213 @anchor{qXfer traceframe info read}
43215 Return a description of the current traceframe's contents.
43216 @xref{Traceframe Info Format}. The annex part of the generic
43217 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
43219 This packet is not probed by default; the remote stub must request it,
43220 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43222 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
43223 @anchor{qXfer unwind info block}
43225 Return the unwind information block for @var{pc}. This packet is used
43226 on OpenVMS/ia64 to ask the kernel unwind information.
43228 This packet is not probed by default.
43230 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
43231 @anchor{qXfer fdpic loadmap read}
43232 Read contents of @code{loadmap}s on the target system. The
43233 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
43234 executable @code{loadmap} or interpreter @code{loadmap} to read.
43236 This packet is not probed by default; the remote stub must request it,
43237 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
43239 @item qXfer:osdata:read::@var{offset},@var{length}
43240 @anchor{qXfer osdata read}
43241 Access the target's @dfn{operating system information}.
43242 @xref{Operating System Information}.
43246 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
43247 @cindex write data into object, remote request
43248 @anchor{qXfer write}
43249 Write uninterpreted bytes into the target's special data area
43250 identified by the keyword @var{object}, starting at @var{offset} bytes
43251 into the data. The binary-encoded data (@pxref{Binary Data}) to be
43252 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
43253 is specific to @var{object}; it can supply additional details about what data
43259 @var{nn} (hex encoded) is the number of bytes written.
43260 This may be fewer bytes than supplied in the request.
43263 The request was malformed, or @var{annex} was invalid.
43266 The offset was invalid, or there was an error encountered writing the data.
43267 The @var{nn} part is a hex-encoded @code{errno} value.
43270 An empty reply indicates the @var{object} string was not
43271 recognized by the stub, or that the object does not support writing.
43274 Here are the specific requests of this form defined so far. All the
43275 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
43276 formats, listed above.
43279 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
43280 @anchor{qXfer siginfo write}
43281 Write @var{data} to the extra signal information on the target system.
43282 The annex part of the generic @samp{qXfer} packet must be
43283 empty (@pxref{qXfer write}).
43285 This packet is not probed by default; the remote stub must request it,
43286 by supplying an appropriate @samp{qSupported} response
43287 (@pxref{qSupported}).
43290 @item qXfer:@var{object}:@var{operation}:@dots{}
43291 Requests of this form may be added in the future. When a stub does
43292 not recognize the @var{object} keyword, or its support for
43293 @var{object} does not recognize the @var{operation} keyword, the stub
43294 must respond with an empty packet.
43296 @item qAttached:@var{pid}
43297 @cindex query attached, remote request
43298 @cindex @samp{qAttached} packet
43299 Return an indication of whether the remote server attached to an
43300 existing process or created a new process. When the multiprocess
43301 protocol extensions are supported (@pxref{multiprocess extensions}),
43302 @var{pid} is an integer in hexadecimal format identifying the target
43303 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
43304 the query packet will be simplified as @samp{qAttached}.
43306 This query is used, for example, to know whether the remote process
43307 should be detached or killed when a @value{GDBN} session is ended with
43308 the @code{quit} command.
43313 The remote server attached to an existing process.
43315 The remote server created a new process.
43317 A badly formed request or an error was encountered.
43321 Enable branch tracing for the current thread using Branch Trace Store.
43326 Branch tracing has been enabled.
43328 A badly formed request or an error was encountered.
43332 Enable branch tracing for the current thread using Intel Processor Trace.
43337 Branch tracing has been enabled.
43339 A badly formed request or an error was encountered.
43343 Disable branch tracing for the current thread.
43348 Branch tracing has been disabled.
43350 A badly formed request or an error was encountered.
43353 @item Qbtrace-conf:bts:size=@var{value}
43354 Set the requested ring buffer size for new threads that use the
43355 btrace recording method in bts format.
43360 The ring buffer size has been set.
43362 A badly formed request or an error was encountered.
43365 @item Qbtrace-conf:pt:size=@var{value}
43366 Set the requested ring buffer size for new threads that use the
43367 btrace recording method in pt format.
43372 The ring buffer size has been set.
43374 A badly formed request or an error was encountered.
43379 @node Architecture-Specific Protocol Details
43380 @section Architecture-Specific Protocol Details
43382 This section describes how the remote protocol is applied to specific
43383 target architectures. Also see @ref{Standard Target Features}, for
43384 details of XML target descriptions for each architecture.
43387 * ARM-Specific Protocol Details::
43388 * MIPS-Specific Protocol Details::
43391 @node ARM-Specific Protocol Details
43392 @subsection @acronym{ARM}-specific Protocol Details
43395 * ARM Breakpoint Kinds::
43396 * ARM Memory Tag Types::
43399 @node ARM Breakpoint Kinds
43400 @subsubsection @acronym{ARM} Breakpoint Kinds
43401 @cindex breakpoint kinds, @acronym{ARM}
43403 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43408 16-bit Thumb mode breakpoint.
43411 32-bit Thumb mode (Thumb-2) breakpoint.
43414 32-bit @acronym{ARM} mode breakpoint.
43418 @node ARM Memory Tag Types
43419 @subsubsection @acronym{ARM} Memory Tag Types
43420 @cindex memory tag types, @acronym{ARM}
43422 These memory tag types are defined for the @samp{qMemTag} and @samp{QMemTag}
43435 @node MIPS-Specific Protocol Details
43436 @subsection @acronym{MIPS}-specific Protocol Details
43439 * MIPS Register packet Format::
43440 * MIPS Breakpoint Kinds::
43443 @node MIPS Register packet Format
43444 @subsubsection @acronym{MIPS} Register Packet Format
43445 @cindex register packet format, @acronym{MIPS}
43447 The following @code{g}/@code{G} packets have previously been defined.
43448 In the below, some thirty-two bit registers are transferred as
43449 sixty-four bits. Those registers should be zero/sign extended (which?)
43450 to fill the space allocated. Register bytes are transferred in target
43451 byte order. The two nibbles within a register byte are transferred
43452 most-significant -- least-significant.
43457 All registers are transferred as thirty-two bit quantities in the order:
43458 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
43459 registers; fsr; fir; fp.
43462 All registers are transferred as sixty-four bit quantities (including
43463 thirty-two bit registers such as @code{sr}). The ordering is the same
43468 @node MIPS Breakpoint Kinds
43469 @subsubsection @acronym{MIPS} Breakpoint Kinds
43470 @cindex breakpoint kinds, @acronym{MIPS}
43472 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
43477 16-bit @acronym{MIPS16} mode breakpoint.
43480 16-bit @acronym{microMIPS} mode breakpoint.
43483 32-bit standard @acronym{MIPS} mode breakpoint.
43486 32-bit @acronym{microMIPS} mode breakpoint.
43490 @node Tracepoint Packets
43491 @section Tracepoint Packets
43492 @cindex tracepoint packets
43493 @cindex packets, tracepoint
43495 Here we describe the packets @value{GDBN} uses to implement
43496 tracepoints (@pxref{Tracepoints}).
43500 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
43501 @cindex @samp{QTDP} packet
43502 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
43503 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
43504 the tracepoint is disabled. The @var{step} gives the tracepoint's step
43505 count, and @var{pass} gives its pass count. If an @samp{F} is present,
43506 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
43507 the number of bytes that the target should copy elsewhere to make room
43508 for the tracepoint. If an @samp{X} is present, it introduces a
43509 tracepoint condition, which consists of a hexadecimal length, followed
43510 by a comma and hex-encoded bytes, in a manner similar to action
43511 encodings as described below. If the trailing @samp{-} is present,
43512 further @samp{QTDP} packets will follow to specify this tracepoint's
43518 The packet was understood and carried out.
43520 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43522 The packet was not recognized.
43525 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
43526 Define actions to be taken when a tracepoint is hit. The @var{n} and
43527 @var{addr} must be the same as in the initial @samp{QTDP} packet for
43528 this tracepoint. This packet may only be sent immediately after
43529 another @samp{QTDP} packet that ended with a @samp{-}. If the
43530 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
43531 specifying more actions for this tracepoint.
43533 In the series of action packets for a given tracepoint, at most one
43534 can have an @samp{S} before its first @var{action}. If such a packet
43535 is sent, it and the following packets define ``while-stepping''
43536 actions. Any prior packets define ordinary actions --- that is, those
43537 taken when the tracepoint is first hit. If no action packet has an
43538 @samp{S}, then all the packets in the series specify ordinary
43539 tracepoint actions.
43541 The @samp{@var{action}@dots{}} portion of the packet is a series of
43542 actions, concatenated without separators. Each action has one of the
43548 Collect the registers whose bits are set in @var{mask},
43549 a hexadecimal number whose @var{i}'th bit is set if register number
43550 @var{i} should be collected. (The least significant bit is numbered
43551 zero.) Note that @var{mask} may be any number of digits long; it may
43552 not fit in a 32-bit word.
43554 @item M @var{basereg},@var{offset},@var{len}
43555 Collect @var{len} bytes of memory starting at the address in register
43556 number @var{basereg}, plus @var{offset}. If @var{basereg} is
43557 @samp{-1}, then the range has a fixed address: @var{offset} is the
43558 address of the lowest byte to collect. The @var{basereg},
43559 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
43560 values (the @samp{-1} value for @var{basereg} is a special case).
43562 @item X @var{len},@var{expr}
43563 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
43564 it directs. The agent expression @var{expr} is as described in
43565 @ref{Agent Expressions}. Each byte of the expression is encoded as a
43566 two-digit hex number in the packet; @var{len} is the number of bytes
43567 in the expression (and thus one-half the number of hex digits in the
43572 Any number of actions may be packed together in a single @samp{QTDP}
43573 packet, as long as the packet does not exceed the maximum packet
43574 length (400 bytes, for many stubs). There may be only one @samp{R}
43575 action per tracepoint, and it must precede any @samp{M} or @samp{X}
43576 actions. Any registers referred to by @samp{M} and @samp{X} actions
43577 must be collected by a preceding @samp{R} action. (The
43578 ``while-stepping'' actions are treated as if they were attached to a
43579 separate tracepoint, as far as these restrictions are concerned.)
43584 The packet was understood and carried out.
43586 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
43588 The packet was not recognized.
43591 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
43592 @cindex @samp{QTDPsrc} packet
43593 Specify a source string of tracepoint @var{n} at address @var{addr}.
43594 This is useful to get accurate reproduction of the tracepoints
43595 originally downloaded at the beginning of the trace run. The @var{type}
43596 is the name of the tracepoint part, such as @samp{cond} for the
43597 tracepoint's conditional expression (see below for a list of types), while
43598 @var{bytes} is the string, encoded in hexadecimal.
43600 @var{start} is the offset of the @var{bytes} within the overall source
43601 string, while @var{slen} is the total length of the source string.
43602 This is intended for handling source strings that are longer than will
43603 fit in a single packet.
43604 @c Add detailed example when this info is moved into a dedicated
43605 @c tracepoint descriptions section.
43607 The available string types are @samp{at} for the location,
43608 @samp{cond} for the conditional, and @samp{cmd} for an action command.
43609 @value{GDBN} sends a separate packet for each command in the action
43610 list, in the same order in which the commands are stored in the list.
43612 The target does not need to do anything with source strings except
43613 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
43616 Although this packet is optional, and @value{GDBN} will only send it
43617 if the target replies with @samp{TracepointSource} @xref{General
43618 Query Packets}, it makes both disconnected tracing and trace files
43619 much easier to use. Otherwise the user must be careful that the
43620 tracepoints in effect while looking at trace frames are identical to
43621 the ones in effect during the trace run; even a small discrepancy
43622 could cause @samp{tdump} not to work, or a particular trace frame not
43625 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
43626 @cindex define trace state variable, remote request
43627 @cindex @samp{QTDV} packet
43628 Create a new trace state variable, number @var{n}, with an initial
43629 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
43630 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
43631 the option of not using this packet for initial values of zero; the
43632 target should simply create the trace state variables as they are
43633 mentioned in expressions. The value @var{builtin} should be 1 (one)
43634 if the trace state variable is builtin and 0 (zero) if it is not builtin.
43635 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
43636 @samp{qTsV} packet had it set. The contents of @var{name} is the
43637 hex-encoded name (without the leading @samp{$}) of the trace state
43640 @item QTFrame:@var{n}
43641 @cindex @samp{QTFrame} packet
43642 Select the @var{n}'th tracepoint frame from the buffer, and use the
43643 register and memory contents recorded there to answer subsequent
43644 request packets from @value{GDBN}.
43646 A successful reply from the stub indicates that the stub has found the
43647 requested frame. The response is a series of parts, concatenated
43648 without separators, describing the frame we selected. Each part has
43649 one of the following forms:
43653 The selected frame is number @var{n} in the trace frame buffer;
43654 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
43655 was no frame matching the criteria in the request packet.
43658 The selected trace frame records a hit of tracepoint number @var{t};
43659 @var{t} is a hexadecimal number.
43663 @item QTFrame:pc:@var{addr}
43664 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43665 currently selected frame whose PC is @var{addr};
43666 @var{addr} is a hexadecimal number.
43668 @item QTFrame:tdp:@var{t}
43669 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43670 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
43671 is a hexadecimal number.
43673 @item QTFrame:range:@var{start}:@var{end}
43674 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
43675 currently selected frame whose PC is between @var{start} (inclusive)
43676 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
43679 @item QTFrame:outside:@var{start}:@var{end}
43680 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
43681 frame @emph{outside} the given range of addresses (exclusive).
43684 @cindex @samp{qTMinFTPILen} packet
43685 This packet requests the minimum length of instruction at which a fast
43686 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
43687 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
43688 it depends on the target system being able to create trampolines in
43689 the first 64K of memory, which might or might not be possible for that
43690 system. So the reply to this packet will be 4 if it is able to
43697 The minimum instruction length is currently unknown.
43699 The minimum instruction length is @var{length}, where @var{length}
43700 is a hexadecimal number greater or equal to 1. A reply
43701 of 1 means that a fast tracepoint may be placed on any instruction
43702 regardless of size.
43704 An error has occurred.
43706 An empty reply indicates that the request is not supported by the stub.
43710 @cindex @samp{QTStart} packet
43711 Begin the tracepoint experiment. Begin collecting data from
43712 tracepoint hits in the trace frame buffer. This packet supports the
43713 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
43714 instruction reply packet}).
43717 @cindex @samp{QTStop} packet
43718 End the tracepoint experiment. Stop collecting trace frames.
43720 @item QTEnable:@var{n}:@var{addr}
43722 @cindex @samp{QTEnable} packet
43723 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
43724 experiment. If the tracepoint was previously disabled, then collection
43725 of data from it will resume.
43727 @item QTDisable:@var{n}:@var{addr}
43729 @cindex @samp{QTDisable} packet
43730 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
43731 experiment. No more data will be collected from the tracepoint unless
43732 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
43735 @cindex @samp{QTinit} packet
43736 Clear the table of tracepoints, and empty the trace frame buffer.
43738 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
43739 @cindex @samp{QTro} packet
43740 Establish the given ranges of memory as ``transparent''. The stub
43741 will answer requests for these ranges from memory's current contents,
43742 if they were not collected as part of the tracepoint hit.
43744 @value{GDBN} uses this to mark read-only regions of memory, like those
43745 containing program code. Since these areas never change, they should
43746 still have the same contents they did when the tracepoint was hit, so
43747 there's no reason for the stub to refuse to provide their contents.
43749 @item QTDisconnected:@var{value}
43750 @cindex @samp{QTDisconnected} packet
43751 Set the choice to what to do with the tracing run when @value{GDBN}
43752 disconnects from the target. A @var{value} of 1 directs the target to
43753 continue the tracing run, while 0 tells the target to stop tracing if
43754 @value{GDBN} is no longer in the picture.
43757 @cindex @samp{qTStatus} packet
43758 Ask the stub if there is a trace experiment running right now.
43760 The reply has the form:
43764 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
43765 @var{running} is a single digit @code{1} if the trace is presently
43766 running, or @code{0} if not. It is followed by semicolon-separated
43767 optional fields that an agent may use to report additional status.
43771 If the trace is not running, the agent may report any of several
43772 explanations as one of the optional fields:
43777 No trace has been run yet.
43779 @item tstop[:@var{text}]:0
43780 The trace was stopped by a user-originated stop command. The optional
43781 @var{text} field is a user-supplied string supplied as part of the
43782 stop command (for instance, an explanation of why the trace was
43783 stopped manually). It is hex-encoded.
43786 The trace stopped because the trace buffer filled up.
43788 @item tdisconnected:0
43789 The trace stopped because @value{GDBN} disconnected from the target.
43791 @item tpasscount:@var{tpnum}
43792 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
43794 @item terror:@var{text}:@var{tpnum}
43795 The trace stopped because tracepoint @var{tpnum} had an error. The
43796 string @var{text} is available to describe the nature of the error
43797 (for instance, a divide by zero in the condition expression); it
43801 The trace stopped for some other reason.
43805 Additional optional fields supply statistical and other information.
43806 Although not required, they are extremely useful for users monitoring
43807 the progress of a trace run. If a trace has stopped, and these
43808 numbers are reported, they must reflect the state of the just-stopped
43813 @item tframes:@var{n}
43814 The number of trace frames in the buffer.
43816 @item tcreated:@var{n}
43817 The total number of trace frames created during the run. This may
43818 be larger than the trace frame count, if the buffer is circular.
43820 @item tsize:@var{n}
43821 The total size of the trace buffer, in bytes.
43823 @item tfree:@var{n}
43824 The number of bytes still unused in the buffer.
43826 @item circular:@var{n}
43827 The value of the circular trace buffer flag. @code{1} means that the
43828 trace buffer is circular and old trace frames will be discarded if
43829 necessary to make room, @code{0} means that the trace buffer is linear
43832 @item disconn:@var{n}
43833 The value of the disconnected tracing flag. @code{1} means that
43834 tracing will continue after @value{GDBN} disconnects, @code{0} means
43835 that the trace run will stop.
43839 @item qTP:@var{tp}:@var{addr}
43840 @cindex tracepoint status, remote request
43841 @cindex @samp{qTP} packet
43842 Ask the stub for the current state of tracepoint number @var{tp} at
43843 address @var{addr}.
43847 @item V@var{hits}:@var{usage}
43848 The tracepoint has been hit @var{hits} times so far during the trace
43849 run, and accounts for @var{usage} in the trace buffer. Note that
43850 @code{while-stepping} steps are not counted as separate hits, but the
43851 steps' space consumption is added into the usage number.
43855 @item qTV:@var{var}
43856 @cindex trace state variable value, remote request
43857 @cindex @samp{qTV} packet
43858 Ask the stub for the value of the trace state variable number @var{var}.
43863 The value of the variable is @var{value}. This will be the current
43864 value of the variable if the user is examining a running target, or a
43865 saved value if the variable was collected in the trace frame that the
43866 user is looking at. Note that multiple requests may result in
43867 different reply values, such as when requesting values while the
43868 program is running.
43871 The value of the variable is unknown. This would occur, for example,
43872 if the user is examining a trace frame in which the requested variable
43877 @cindex @samp{qTfP} packet
43879 @cindex @samp{qTsP} packet
43880 These packets request data about tracepoints that are being used by
43881 the target. @value{GDBN} sends @code{qTfP} to get the first piece
43882 of data, and multiple @code{qTsP} to get additional pieces. Replies
43883 to these packets generally take the form of the @code{QTDP} packets
43884 that define tracepoints. (FIXME add detailed syntax)
43887 @cindex @samp{qTfV} packet
43889 @cindex @samp{qTsV} packet
43890 These packets request data about trace state variables that are on the
43891 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
43892 and multiple @code{qTsV} to get additional variables. Replies to
43893 these packets follow the syntax of the @code{QTDV} packets that define
43894 trace state variables.
43900 @cindex @samp{qTfSTM} packet
43901 @cindex @samp{qTsSTM} packet
43902 These packets request data about static tracepoint markers that exist
43903 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
43904 first piece of data, and multiple @code{qTsSTM} to get additional
43905 pieces. Replies to these packets take the following form:
43909 @item m @var{address}:@var{id}:@var{extra}
43911 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
43912 a comma-separated list of markers
43914 (lower case letter @samp{L}) denotes end of list.
43916 An error occurred. The error number @var{nn} is given as hex digits.
43918 An empty reply indicates that the request is not supported by the
43922 The @var{address} is encoded in hex;
43923 @var{id} and @var{extra} are strings encoded in hex.
43925 In response to each query, the target will reply with a list of one or
43926 more markers, separated by commas. @value{GDBN} will respond to each
43927 reply with a request for more markers (using the @samp{qs} form of the
43928 query), until the target responds with @samp{l} (lower-case ell, for
43931 @item qTSTMat:@var{address}
43933 @cindex @samp{qTSTMat} packet
43934 This packets requests data about static tracepoint markers in the
43935 target program at @var{address}. Replies to this packet follow the
43936 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
43937 tracepoint markers.
43939 @item QTSave:@var{filename}
43940 @cindex @samp{QTSave} packet
43941 This packet directs the target to save trace data to the file name
43942 @var{filename} in the target's filesystem. The @var{filename} is encoded
43943 as a hex string; the interpretation of the file name (relative vs
43944 absolute, wild cards, etc) is up to the target.
43946 @item qTBuffer:@var{offset},@var{len}
43947 @cindex @samp{qTBuffer} packet
43948 Return up to @var{len} bytes of the current contents of trace buffer,
43949 starting at @var{offset}. The trace buffer is treated as if it were
43950 a contiguous collection of traceframes, as per the trace file format.
43951 The reply consists as many hex-encoded bytes as the target can deliver
43952 in a packet; it is not an error to return fewer than were asked for.
43953 A reply consisting of just @code{l} indicates that no bytes are
43956 @item QTBuffer:circular:@var{value}
43957 This packet directs the target to use a circular trace buffer if
43958 @var{value} is 1, or a linear buffer if the value is 0.
43960 @item QTBuffer:size:@var{size}
43961 @anchor{QTBuffer-size}
43962 @cindex @samp{QTBuffer size} packet
43963 This packet directs the target to make the trace buffer be of size
43964 @var{size} if possible. A value of @code{-1} tells the target to
43965 use whatever size it prefers.
43967 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
43968 @cindex @samp{QTNotes} packet
43969 This packet adds optional textual notes to the trace run. Allowable
43970 types include @code{user}, @code{notes}, and @code{tstop}, the
43971 @var{text} fields are arbitrary strings, hex-encoded.
43975 @subsection Relocate instruction reply packet
43976 When installing fast tracepoints in memory, the target may need to
43977 relocate the instruction currently at the tracepoint address to a
43978 different address in memory. For most instructions, a simple copy is
43979 enough, but, for example, call instructions that implicitly push the
43980 return address on the stack, and relative branches or other
43981 PC-relative instructions require offset adjustment, so that the effect
43982 of executing the instruction at a different address is the same as if
43983 it had executed in the original location.
43985 In response to several of the tracepoint packets, the target may also
43986 respond with a number of intermediate @samp{qRelocInsn} request
43987 packets before the final result packet, to have @value{GDBN} handle
43988 this relocation operation. If a packet supports this mechanism, its
43989 documentation will explicitly say so. See for example the above
43990 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
43991 format of the request is:
43994 @item qRelocInsn:@var{from};@var{to}
43996 This requests @value{GDBN} to copy instruction at address @var{from}
43997 to address @var{to}, possibly adjusted so that executing the
43998 instruction at @var{to} has the same effect as executing it at
43999 @var{from}. @value{GDBN} writes the adjusted instruction to target
44000 memory starting at @var{to}.
44005 @item qRelocInsn:@var{adjusted_size}
44006 Informs the stub the relocation is complete. The @var{adjusted_size} is
44007 the length in bytes of resulting relocated instruction sequence.
44009 A badly formed request was detected, or an error was encountered while
44010 relocating the instruction.
44013 @node Host I/O Packets
44014 @section Host I/O Packets
44015 @cindex Host I/O, remote protocol
44016 @cindex file transfer, remote protocol
44018 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
44019 operations on the far side of a remote link. For example, Host I/O is
44020 used to upload and download files to a remote target with its own
44021 filesystem. Host I/O uses the same constant values and data structure
44022 layout as the target-initiated File-I/O protocol. However, the
44023 Host I/O packets are structured differently. The target-initiated
44024 protocol relies on target memory to store parameters and buffers.
44025 Host I/O requests are initiated by @value{GDBN}, and the
44026 target's memory is not involved. @xref{File-I/O Remote Protocol
44027 Extension}, for more details on the target-initiated protocol.
44029 The Host I/O request packets all encode a single operation along with
44030 its arguments. They have this format:
44034 @item vFile:@var{operation}: @var{parameter}@dots{}
44035 @var{operation} is the name of the particular request; the target
44036 should compare the entire packet name up to the second colon when checking
44037 for a supported operation. The format of @var{parameter} depends on
44038 the operation. Numbers are always passed in hexadecimal. Negative
44039 numbers have an explicit minus sign (i.e.@: two's complement is not
44040 used). Strings (e.g.@: filenames) are encoded as a series of
44041 hexadecimal bytes. The last argument to a system call may be a
44042 buffer of escaped binary data (@pxref{Binary Data}).
44046 The valid responses to Host I/O packets are:
44050 @item F @var{result} [, @var{errno}] [; @var{attachment}]
44051 @var{result} is the integer value returned by this operation, usually
44052 non-negative for success and -1 for errors. If an error has occured,
44053 @var{errno} will be included in the result specifying a
44054 value defined by the File-I/O protocol (@pxref{Errno Values}). For
44055 operations which return data, @var{attachment} supplies the data as a
44056 binary buffer. Binary buffers in response packets are escaped in the
44057 normal way (@pxref{Binary Data}). See the individual packet
44058 documentation for the interpretation of @var{result} and
44062 An empty response indicates that this operation is not recognized.
44066 These are the supported Host I/O operations:
44069 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
44070 Open a file at @var{filename} and return a file descriptor for it, or
44071 return -1 if an error occurs. The @var{filename} is a string,
44072 @var{flags} is an integer indicating a mask of open flags
44073 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
44074 of mode bits to use if the file is created (@pxref{mode_t Values}).
44075 @xref{open}, for details of the open flags and mode values.
44077 @item vFile:close: @var{fd}
44078 Close the open file corresponding to @var{fd} and return 0, or
44079 -1 if an error occurs.
44081 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
44082 Read data from the open file corresponding to @var{fd}. Up to
44083 @var{count} bytes will be read from the file, starting at @var{offset}
44084 relative to the start of the file. The target may read fewer bytes;
44085 common reasons include packet size limits and an end-of-file
44086 condition. The number of bytes read is returned. Zero should only be
44087 returned for a successful read at the end of the file, or if
44088 @var{count} was zero.
44090 The data read should be returned as a binary attachment on success.
44091 If zero bytes were read, the response should include an empty binary
44092 attachment (i.e.@: a trailing semicolon). The return value is the
44093 number of target bytes read; the binary attachment may be longer if
44094 some characters were escaped.
44096 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
44097 Write @var{data} (a binary buffer) to the open file corresponding
44098 to @var{fd}. Start the write at @var{offset} from the start of the
44099 file. Unlike many @code{write} system calls, there is no
44100 separate @var{count} argument; the length of @var{data} in the
44101 packet is used. @samp{vFile:pwrite} returns the number of bytes written,
44102 which may be shorter than the length of @var{data}, or -1 if an
44105 @item vFile:fstat: @var{fd}
44106 Get information about the open file corresponding to @var{fd}.
44107 On success the information is returned as a binary attachment
44108 and the return value is the size of this attachment in bytes.
44109 If an error occurs the return value is -1. The format of the
44110 returned binary attachment is as described in @ref{struct stat}.
44112 @item vFile:unlink: @var{filename}
44113 Delete the file at @var{filename} on the target. Return 0,
44114 or -1 if an error occurs. The @var{filename} is a string.
44116 @item vFile:readlink: @var{filename}
44117 Read value of symbolic link @var{filename} on the target. Return
44118 the number of bytes read, or -1 if an error occurs.
44120 The data read should be returned as a binary attachment on success.
44121 If zero bytes were read, the response should include an empty binary
44122 attachment (i.e.@: a trailing semicolon). The return value is the
44123 number of target bytes read; the binary attachment may be longer if
44124 some characters were escaped.
44126 @item vFile:setfs: @var{pid}
44127 Select the filesystem on which @code{vFile} operations with
44128 @var{filename} arguments will operate. This is required for
44129 @value{GDBN} to be able to access files on remote targets where
44130 the remote stub does not share a common filesystem with the
44133 If @var{pid} is nonzero, select the filesystem as seen by process
44134 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
44135 the remote stub. Return 0 on success, or -1 if an error occurs.
44136 If @code{vFile:setfs:} indicates success, the selected filesystem
44137 remains selected until the next successful @code{vFile:setfs:}
44143 @section Interrupts
44144 @cindex interrupts (remote protocol)
44145 @anchor{interrupting remote targets}
44147 In all-stop mode, when a program on the remote target is running,
44148 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
44149 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
44150 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
44152 The precise meaning of @code{BREAK} is defined by the transport
44153 mechanism and may, in fact, be undefined. @value{GDBN} does not
44154 currently define a @code{BREAK} mechanism for any of the network
44155 interfaces except for TCP, in which case @value{GDBN} sends the
44156 @code{telnet} BREAK sequence.
44158 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
44159 transport mechanisms. It is represented by sending the single byte
44160 @code{0x03} without any of the usual packet overhead described in
44161 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
44162 transmitted as part of a packet, it is considered to be packet data
44163 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
44164 (@pxref{X packet}), used for binary downloads, may include an unescaped
44165 @code{0x03} as part of its packet.
44167 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
44168 When Linux kernel receives this sequence from serial port,
44169 it stops execution and connects to gdb.
44171 In non-stop mode, because packet resumptions are asynchronous
44172 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
44173 command to the remote stub, even when the target is running. For that
44174 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
44175 packet}) with the usual packet framing instead of the single byte
44178 Stubs are not required to recognize these interrupt mechanisms and the
44179 precise meaning associated with receipt of the interrupt is
44180 implementation defined. If the target supports debugging of multiple
44181 threads and/or processes, it should attempt to interrupt all
44182 currently-executing threads and processes.
44183 If the stub is successful at interrupting the
44184 running program, it should send one of the stop
44185 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
44186 of successfully stopping the program in all-stop mode, and a stop reply
44187 for each stopped thread in non-stop mode.
44188 Interrupts received while the
44189 program is stopped are queued and the program will be interrupted when
44190 it is resumed next time.
44192 @node Notification Packets
44193 @section Notification Packets
44194 @cindex notification packets
44195 @cindex packets, notification
44197 The @value{GDBN} remote serial protocol includes @dfn{notifications},
44198 packets that require no acknowledgment. Both the GDB and the stub
44199 may send notifications (although the only notifications defined at
44200 present are sent by the stub). Notifications carry information
44201 without incurring the round-trip latency of an acknowledgment, and so
44202 are useful for low-impact communications where occasional packet loss
44205 A notification packet has the form @samp{% @var{data} #
44206 @var{checksum}}, where @var{data} is the content of the notification,
44207 and @var{checksum} is a checksum of @var{data}, computed and formatted
44208 as for ordinary @value{GDBN} packets. A notification's @var{data}
44209 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
44210 receiving a notification, the recipient sends no @samp{+} or @samp{-}
44211 to acknowledge the notification's receipt or to report its corruption.
44213 Every notification's @var{data} begins with a name, which contains no
44214 colon characters, followed by a colon character.
44216 Recipients should silently ignore corrupted notifications and
44217 notifications they do not understand. Recipients should restart
44218 timeout periods on receipt of a well-formed notification, whether or
44219 not they understand it.
44221 Senders should only send the notifications described here when this
44222 protocol description specifies that they are permitted. In the
44223 future, we may extend the protocol to permit existing notifications in
44224 new contexts; this rule helps older senders avoid confusing newer
44227 (Older versions of @value{GDBN} ignore bytes received until they see
44228 the @samp{$} byte that begins an ordinary packet, so new stubs may
44229 transmit notifications without fear of confusing older clients. There
44230 are no notifications defined for @value{GDBN} to send at the moment, but we
44231 assume that most older stubs would ignore them, as well.)
44233 Each notification is comprised of three parts:
44235 @item @var{name}:@var{event}
44236 The notification packet is sent by the side that initiates the
44237 exchange (currently, only the stub does that), with @var{event}
44238 carrying the specific information about the notification, and
44239 @var{name} specifying the name of the notification.
44241 The acknowledge sent by the other side, usually @value{GDBN}, to
44242 acknowledge the exchange and request the event.
44245 The purpose of an asynchronous notification mechanism is to report to
44246 @value{GDBN} that something interesting happened in the remote stub.
44248 The remote stub may send notification @var{name}:@var{event}
44249 at any time, but @value{GDBN} acknowledges the notification when
44250 appropriate. The notification event is pending before @value{GDBN}
44251 acknowledges. Only one notification at a time may be pending; if
44252 additional events occur before @value{GDBN} has acknowledged the
44253 previous notification, they must be queued by the stub for later
44254 synchronous transmission in response to @var{ack} packets from
44255 @value{GDBN}. Because the notification mechanism is unreliable,
44256 the stub is permitted to resend a notification if it believes
44257 @value{GDBN} may not have received it.
44259 Specifically, notifications may appear when @value{GDBN} is not
44260 otherwise reading input from the stub, or when @value{GDBN} is
44261 expecting to read a normal synchronous response or a
44262 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
44263 Notification packets are distinct from any other communication from
44264 the stub so there is no ambiguity.
44266 After receiving a notification, @value{GDBN} shall acknowledge it by
44267 sending a @var{ack} packet as a regular, synchronous request to the
44268 stub. Such acknowledgment is not required to happen immediately, as
44269 @value{GDBN} is permitted to send other, unrelated packets to the
44270 stub first, which the stub should process normally.
44272 Upon receiving a @var{ack} packet, if the stub has other queued
44273 events to report to @value{GDBN}, it shall respond by sending a
44274 normal @var{event}. @value{GDBN} shall then send another @var{ack}
44275 packet to solicit further responses; again, it is permitted to send
44276 other, unrelated packets as well which the stub should process
44279 If the stub receives a @var{ack} packet and there are no additional
44280 @var{event} to report, the stub shall return an @samp{OK} response.
44281 At this point, @value{GDBN} has finished processing a notification
44282 and the stub has completed sending any queued events. @value{GDBN}
44283 won't accept any new notifications until the final @samp{OK} is
44284 received . If further notification events occur, the stub shall send
44285 a new notification, @value{GDBN} shall accept the notification, and
44286 the process shall be repeated.
44288 The process of asynchronous notification can be illustrated by the
44291 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
44294 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
44296 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
44301 The following notifications are defined:
44302 @multitable @columnfractions 0.12 0.12 0.38 0.38
44311 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
44312 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
44313 for information on how these notifications are acknowledged by
44315 @tab Report an asynchronous stop event in non-stop mode.
44319 @node Remote Non-Stop
44320 @section Remote Protocol Support for Non-Stop Mode
44322 @value{GDBN}'s remote protocol supports non-stop debugging of
44323 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
44324 supports non-stop mode, it should report that to @value{GDBN} by including
44325 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
44327 @value{GDBN} typically sends a @samp{QNonStop} packet only when
44328 establishing a new connection with the stub. Entering non-stop mode
44329 does not alter the state of any currently-running threads, but targets
44330 must stop all threads in any already-attached processes when entering
44331 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
44332 probe the target state after a mode change.
44334 In non-stop mode, when an attached process encounters an event that
44335 would otherwise be reported with a stop reply, it uses the
44336 asynchronous notification mechanism (@pxref{Notification Packets}) to
44337 inform @value{GDBN}. In contrast to all-stop mode, where all threads
44338 in all processes are stopped when a stop reply is sent, in non-stop
44339 mode only the thread reporting the stop event is stopped. That is,
44340 when reporting a @samp{S} or @samp{T} response to indicate completion
44341 of a step operation, hitting a breakpoint, or a fault, only the
44342 affected thread is stopped; any other still-running threads continue
44343 to run. When reporting a @samp{W} or @samp{X} response, all running
44344 threads belonging to other attached processes continue to run.
44346 In non-stop mode, the target shall respond to the @samp{?} packet as
44347 follows. First, any incomplete stop reply notification/@samp{vStopped}
44348 sequence in progress is abandoned. The target must begin a new
44349 sequence reporting stop events for all stopped threads, whether or not
44350 it has previously reported those events to @value{GDBN}. The first
44351 stop reply is sent as a synchronous reply to the @samp{?} packet, and
44352 subsequent stop replies are sent as responses to @samp{vStopped} packets
44353 using the mechanism described above. The target must not send
44354 asynchronous stop reply notifications until the sequence is complete.
44355 If all threads are running when the target receives the @samp{?} packet,
44356 or if the target is not attached to any process, it shall respond
44359 If the stub supports non-stop mode, it should also support the
44360 @samp{swbreak} stop reason if software breakpoints are supported, and
44361 the @samp{hwbreak} stop reason if hardware breakpoints are supported
44362 (@pxref{swbreak stop reason}). This is because given the asynchronous
44363 nature of non-stop mode, between the time a thread hits a breakpoint
44364 and the time the event is finally processed by @value{GDBN}, the
44365 breakpoint may have already been removed from the target. Due to
44366 this, @value{GDBN} needs to be able to tell whether a trap stop was
44367 caused by a delayed breakpoint event, which should be ignored, as
44368 opposed to a random trap signal, which should be reported to the user.
44369 Note the @samp{swbreak} feature implies that the target is responsible
44370 for adjusting the PC when a software breakpoint triggers, if
44371 necessary, such as on the x86 architecture.
44373 @node Packet Acknowledgment
44374 @section Packet Acknowledgment
44376 @cindex acknowledgment, for @value{GDBN} remote
44377 @cindex packet acknowledgment, for @value{GDBN} remote
44378 By default, when either the host or the target machine receives a packet,
44379 the first response expected is an acknowledgment: either @samp{+} (to indicate
44380 the package was received correctly) or @samp{-} (to request retransmission).
44381 This mechanism allows the @value{GDBN} remote protocol to operate over
44382 unreliable transport mechanisms, such as a serial line.
44384 In cases where the transport mechanism is itself reliable (such as a pipe or
44385 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
44386 It may be desirable to disable them in that case to reduce communication
44387 overhead, or for other reasons. This can be accomplished by means of the
44388 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
44390 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
44391 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
44392 and response format still includes the normal checksum, as described in
44393 @ref{Overview}, but the checksum may be ignored by the receiver.
44395 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
44396 no-acknowledgment mode, it should report that to @value{GDBN}
44397 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
44398 @pxref{qSupported}.
44399 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
44400 disabled via the @code{set remote noack-packet off} command
44401 (@pxref{Remote Configuration}),
44402 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
44403 Only then may the stub actually turn off packet acknowledgments.
44404 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
44405 response, which can be safely ignored by the stub.
44407 Note that @code{set remote noack-packet} command only affects negotiation
44408 between @value{GDBN} and the stub when subsequent connections are made;
44409 it does not affect the protocol acknowledgment state for any current
44411 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
44412 new connection is established,
44413 there is also no protocol request to re-enable the acknowledgments
44414 for the current connection, once disabled.
44419 Example sequence of a target being re-started. Notice how the restart
44420 does not get any direct output:
44425 @emph{target restarts}
44428 <- @code{T001:1234123412341234}
44432 Example sequence of a target being stepped by a single instruction:
44435 -> @code{G1445@dots{}}
44440 <- @code{T001:1234123412341234}
44444 <- @code{1455@dots{}}
44448 @node File-I/O Remote Protocol Extension
44449 @section File-I/O Remote Protocol Extension
44450 @cindex File-I/O remote protocol extension
44453 * File-I/O Overview::
44454 * Protocol Basics::
44455 * The F Request Packet::
44456 * The F Reply Packet::
44457 * The Ctrl-C Message::
44459 * List of Supported Calls::
44460 * Protocol-specific Representation of Datatypes::
44462 * File-I/O Examples::
44465 @node File-I/O Overview
44466 @subsection File-I/O Overview
44467 @cindex file-i/o overview
44469 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
44470 target to use the host's file system and console I/O to perform various
44471 system calls. System calls on the target system are translated into a
44472 remote protocol packet to the host system, which then performs the needed
44473 actions and returns a response packet to the target system.
44474 This simulates file system operations even on targets that lack file systems.
44476 The protocol is defined to be independent of both the host and target systems.
44477 It uses its own internal representation of datatypes and values. Both
44478 @value{GDBN} and the target's @value{GDBN} stub are responsible for
44479 translating the system-dependent value representations into the internal
44480 protocol representations when data is transmitted.
44482 The communication is synchronous. A system call is possible only when
44483 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
44484 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
44485 the target is stopped to allow deterministic access to the target's
44486 memory. Therefore File-I/O is not interruptible by target signals. On
44487 the other hand, it is possible to interrupt File-I/O by a user interrupt
44488 (@samp{Ctrl-C}) within @value{GDBN}.
44490 The target's request to perform a host system call does not finish
44491 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
44492 after finishing the system call, the target returns to continuing the
44493 previous activity (continue, step). No additional continue or step
44494 request from @value{GDBN} is required.
44497 (@value{GDBP}) continue
44498 <- target requests 'system call X'
44499 target is stopped, @value{GDBN} executes system call
44500 -> @value{GDBN} returns result
44501 ... target continues, @value{GDBN} returns to wait for the target
44502 <- target hits breakpoint and sends a Txx packet
44505 The protocol only supports I/O on the console and to regular files on
44506 the host file system. Character or block special devices, pipes,
44507 named pipes, sockets or any other communication method on the host
44508 system are not supported by this protocol.
44510 File I/O is not supported in non-stop mode.
44512 @node Protocol Basics
44513 @subsection Protocol Basics
44514 @cindex protocol basics, file-i/o
44516 The File-I/O protocol uses the @code{F} packet as the request as well
44517 as reply packet. Since a File-I/O system call can only occur when
44518 @value{GDBN} is waiting for a response from the continuing or stepping target,
44519 the File-I/O request is a reply that @value{GDBN} has to expect as a result
44520 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
44521 This @code{F} packet contains all information needed to allow @value{GDBN}
44522 to call the appropriate host system call:
44526 A unique identifier for the requested system call.
44529 All parameters to the system call. Pointers are given as addresses
44530 in the target memory address space. Pointers to strings are given as
44531 pointer/length pair. Numerical values are given as they are.
44532 Numerical control flags are given in a protocol-specific representation.
44536 At this point, @value{GDBN} has to perform the following actions.
44540 If the parameters include pointer values to data needed as input to a
44541 system call, @value{GDBN} requests this data from the target with a
44542 standard @code{m} packet request. This additional communication has to be
44543 expected by the target implementation and is handled as any other @code{m}
44547 @value{GDBN} translates all value from protocol representation to host
44548 representation as needed. Datatypes are coerced into the host types.
44551 @value{GDBN} calls the system call.
44554 It then coerces datatypes back to protocol representation.
44557 If the system call is expected to return data in buffer space specified
44558 by pointer parameters to the call, the data is transmitted to the
44559 target using a @code{M} or @code{X} packet. This packet has to be expected
44560 by the target implementation and is handled as any other @code{M} or @code{X}
44565 Eventually @value{GDBN} replies with another @code{F} packet which contains all
44566 necessary information for the target to continue. This at least contains
44573 @code{errno}, if has been changed by the system call.
44580 After having done the needed type and value coercion, the target continues
44581 the latest continue or step action.
44583 @node The F Request Packet
44584 @subsection The @code{F} Request Packet
44585 @cindex file-i/o request packet
44586 @cindex @code{F} request packet
44588 The @code{F} request packet has the following format:
44591 @item F@var{call-id},@var{parameter@dots{}}
44593 @var{call-id} is the identifier to indicate the host system call to be called.
44594 This is just the name of the function.
44596 @var{parameter@dots{}} are the parameters to the system call.
44597 Parameters are hexadecimal integer values, either the actual values in case
44598 of scalar datatypes, pointers to target buffer space in case of compound
44599 datatypes and unspecified memory areas, or pointer/length pairs in case
44600 of string parameters. These are appended to the @var{call-id} as a
44601 comma-delimited list. All values are transmitted in ASCII
44602 string representation, pointer/length pairs separated by a slash.
44608 @node The F Reply Packet
44609 @subsection The @code{F} Reply Packet
44610 @cindex file-i/o reply packet
44611 @cindex @code{F} reply packet
44613 The @code{F} reply packet has the following format:
44617 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
44619 @var{retcode} is the return code of the system call as hexadecimal value.
44621 @var{errno} is the @code{errno} set by the call, in protocol-specific
44623 This parameter can be omitted if the call was successful.
44625 @var{Ctrl-C flag} is only sent if the user requested a break. In this
44626 case, @var{errno} must be sent as well, even if the call was successful.
44627 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
44634 or, if the call was interrupted before the host call has been performed:
44641 assuming 4 is the protocol-specific representation of @code{EINTR}.
44646 @node The Ctrl-C Message
44647 @subsection The @samp{Ctrl-C} Message
44648 @cindex ctrl-c message, in file-i/o protocol
44650 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
44651 reply packet (@pxref{The F Reply Packet}),
44652 the target should behave as if it had
44653 gotten a break message. The meaning for the target is ``system call
44654 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
44655 (as with a break message) and return to @value{GDBN} with a @code{T02}
44658 It's important for the target to know in which
44659 state the system call was interrupted. There are two possible cases:
44663 The system call hasn't been performed on the host yet.
44666 The system call on the host has been finished.
44670 These two states can be distinguished by the target by the value of the
44671 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
44672 call hasn't been performed. This is equivalent to the @code{EINTR} handling
44673 on POSIX systems. In any other case, the target may presume that the
44674 system call has been finished --- successfully or not --- and should behave
44675 as if the break message arrived right after the system call.
44677 @value{GDBN} must behave reliably. If the system call has not been called
44678 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
44679 @code{errno} in the packet. If the system call on the host has been finished
44680 before the user requests a break, the full action must be finished by
44681 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
44682 The @code{F} packet may only be sent when either nothing has happened
44683 or the full action has been completed.
44686 @subsection Console I/O
44687 @cindex console i/o as part of file-i/o
44689 By default and if not explicitly closed by the target system, the file
44690 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
44691 on the @value{GDBN} console is handled as any other file output operation
44692 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
44693 by @value{GDBN} so that after the target read request from file descriptor
44694 0 all following typing is buffered until either one of the following
44699 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
44701 system call is treated as finished.
44704 The user presses @key{RET}. This is treated as end of input with a trailing
44708 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
44709 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
44713 If the user has typed more characters than fit in the buffer given to
44714 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
44715 either another @code{read(0, @dots{})} is requested by the target, or debugging
44716 is stopped at the user's request.
44719 @node List of Supported Calls
44720 @subsection List of Supported Calls
44721 @cindex list of supported file-i/o calls
44738 @unnumberedsubsubsec open
44739 @cindex open, file-i/o system call
44744 int open(const char *pathname, int flags);
44745 int open(const char *pathname, int flags, mode_t mode);
44749 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
44752 @var{flags} is the bitwise @code{OR} of the following values:
44756 If the file does not exist it will be created. The host
44757 rules apply as far as file ownership and time stamps
44761 When used with @code{O_CREAT}, if the file already exists it is
44762 an error and open() fails.
44765 If the file already exists and the open mode allows
44766 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
44767 truncated to zero length.
44770 The file is opened in append mode.
44773 The file is opened for reading only.
44776 The file is opened for writing only.
44779 The file is opened for reading and writing.
44783 Other bits are silently ignored.
44787 @var{mode} is the bitwise @code{OR} of the following values:
44791 User has read permission.
44794 User has write permission.
44797 Group has read permission.
44800 Group has write permission.
44803 Others have read permission.
44806 Others have write permission.
44810 Other bits are silently ignored.
44813 @item Return value:
44814 @code{open} returns the new file descriptor or -1 if an error
44821 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
44824 @var{pathname} refers to a directory.
44827 The requested access is not allowed.
44830 @var{pathname} was too long.
44833 A directory component in @var{pathname} does not exist.
44836 @var{pathname} refers to a device, pipe, named pipe or socket.
44839 @var{pathname} refers to a file on a read-only filesystem and
44840 write access was requested.
44843 @var{pathname} is an invalid pointer value.
44846 No space on device to create the file.
44849 The process already has the maximum number of files open.
44852 The limit on the total number of files open on the system
44856 The call was interrupted by the user.
44862 @unnumberedsubsubsec close
44863 @cindex close, file-i/o system call
44872 @samp{Fclose,@var{fd}}
44874 @item Return value:
44875 @code{close} returns zero on success, or -1 if an error occurred.
44881 @var{fd} isn't a valid open file descriptor.
44884 The call was interrupted by the user.
44890 @unnumberedsubsubsec read
44891 @cindex read, file-i/o system call
44896 int read(int fd, void *buf, unsigned int count);
44900 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
44902 @item Return value:
44903 On success, the number of bytes read is returned.
44904 Zero indicates end of file. If count is zero, read
44905 returns zero as well. On error, -1 is returned.
44911 @var{fd} is not a valid file descriptor or is not open for
44915 @var{bufptr} is an invalid pointer value.
44918 The call was interrupted by the user.
44924 @unnumberedsubsubsec write
44925 @cindex write, file-i/o system call
44930 int write(int fd, const void *buf, unsigned int count);
44934 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
44936 @item Return value:
44937 On success, the number of bytes written are returned.
44938 Zero indicates nothing was written. On error, -1
44945 @var{fd} is not a valid file descriptor or is not open for
44949 @var{bufptr} is an invalid pointer value.
44952 An attempt was made to write a file that exceeds the
44953 host-specific maximum file size allowed.
44956 No space on device to write the data.
44959 The call was interrupted by the user.
44965 @unnumberedsubsubsec lseek
44966 @cindex lseek, file-i/o system call
44971 long lseek (int fd, long offset, int flag);
44975 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
44977 @var{flag} is one of:
44981 The offset is set to @var{offset} bytes.
44984 The offset is set to its current location plus @var{offset}
44988 The offset is set to the size of the file plus @var{offset}
44992 @item Return value:
44993 On success, the resulting unsigned offset in bytes from
44994 the beginning of the file is returned. Otherwise, a
44995 value of -1 is returned.
45001 @var{fd} is not a valid open file descriptor.
45004 @var{fd} is associated with the @value{GDBN} console.
45007 @var{flag} is not a proper value.
45010 The call was interrupted by the user.
45016 @unnumberedsubsubsec rename
45017 @cindex rename, file-i/o system call
45022 int rename(const char *oldpath, const char *newpath);
45026 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
45028 @item Return value:
45029 On success, zero is returned. On error, -1 is returned.
45035 @var{newpath} is an existing directory, but @var{oldpath} is not a
45039 @var{newpath} is a non-empty directory.
45042 @var{oldpath} or @var{newpath} is a directory that is in use by some
45046 An attempt was made to make a directory a subdirectory
45050 A component used as a directory in @var{oldpath} or new
45051 path is not a directory. Or @var{oldpath} is a directory
45052 and @var{newpath} exists but is not a directory.
45055 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
45058 No access to the file or the path of the file.
45062 @var{oldpath} or @var{newpath} was too long.
45065 A directory component in @var{oldpath} or @var{newpath} does not exist.
45068 The file is on a read-only filesystem.
45071 The device containing the file has no room for the new
45075 The call was interrupted by the user.
45081 @unnumberedsubsubsec unlink
45082 @cindex unlink, file-i/o system call
45087 int unlink(const char *pathname);
45091 @samp{Funlink,@var{pathnameptr}/@var{len}}
45093 @item Return value:
45094 On success, zero is returned. On error, -1 is returned.
45100 No access to the file or the path of the file.
45103 The system does not allow unlinking of directories.
45106 The file @var{pathname} cannot be unlinked because it's
45107 being used by another process.
45110 @var{pathnameptr} is an invalid pointer value.
45113 @var{pathname} was too long.
45116 A directory component in @var{pathname} does not exist.
45119 A component of the path is not a directory.
45122 The file is on a read-only filesystem.
45125 The call was interrupted by the user.
45131 @unnumberedsubsubsec stat/fstat
45132 @cindex fstat, file-i/o system call
45133 @cindex stat, file-i/o system call
45138 int stat(const char *pathname, struct stat *buf);
45139 int fstat(int fd, struct stat *buf);
45143 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
45144 @samp{Ffstat,@var{fd},@var{bufptr}}
45146 @item Return value:
45147 On success, zero is returned. On error, -1 is returned.
45153 @var{fd} is not a valid open file.
45156 A directory component in @var{pathname} does not exist or the
45157 path is an empty string.
45160 A component of the path is not a directory.
45163 @var{pathnameptr} is an invalid pointer value.
45166 No access to the file or the path of the file.
45169 @var{pathname} was too long.
45172 The call was interrupted by the user.
45178 @unnumberedsubsubsec gettimeofday
45179 @cindex gettimeofday, file-i/o system call
45184 int gettimeofday(struct timeval *tv, void *tz);
45188 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
45190 @item Return value:
45191 On success, 0 is returned, -1 otherwise.
45197 @var{tz} is a non-NULL pointer.
45200 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
45206 @unnumberedsubsubsec isatty
45207 @cindex isatty, file-i/o system call
45212 int isatty(int fd);
45216 @samp{Fisatty,@var{fd}}
45218 @item Return value:
45219 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
45225 The call was interrupted by the user.
45230 Note that the @code{isatty} call is treated as a special case: it returns
45231 1 to the target if the file descriptor is attached
45232 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
45233 would require implementing @code{ioctl} and would be more complex than
45238 @unnumberedsubsubsec system
45239 @cindex system, file-i/o system call
45244 int system(const char *command);
45248 @samp{Fsystem,@var{commandptr}/@var{len}}
45250 @item Return value:
45251 If @var{len} is zero, the return value indicates whether a shell is
45252 available. A zero return value indicates a shell is not available.
45253 For non-zero @var{len}, the value returned is -1 on error and the
45254 return status of the command otherwise. Only the exit status of the
45255 command is returned, which is extracted from the host's @code{system}
45256 return value by calling @code{WEXITSTATUS(retval)}. In case
45257 @file{/bin/sh} could not be executed, 127 is returned.
45263 The call was interrupted by the user.
45268 @value{GDBN} takes over the full task of calling the necessary host calls
45269 to perform the @code{system} call. The return value of @code{system} on
45270 the host is simplified before it's returned
45271 to the target. Any termination signal information from the child process
45272 is discarded, and the return value consists
45273 entirely of the exit status of the called command.
45275 Due to security concerns, the @code{system} call is by default refused
45276 by @value{GDBN}. The user has to allow this call explicitly with the
45277 @code{set remote system-call-allowed 1} command.
45280 @item set remote system-call-allowed
45281 @kindex set remote system-call-allowed
45282 Control whether to allow the @code{system} calls in the File I/O
45283 protocol for the remote target. The default is zero (disabled).
45285 @item show remote system-call-allowed
45286 @kindex show remote system-call-allowed
45287 Show whether the @code{system} calls are allowed in the File I/O
45291 @node Protocol-specific Representation of Datatypes
45292 @subsection Protocol-specific Representation of Datatypes
45293 @cindex protocol-specific representation of datatypes, in file-i/o protocol
45296 * Integral Datatypes::
45298 * Memory Transfer::
45303 @node Integral Datatypes
45304 @unnumberedsubsubsec Integral Datatypes
45305 @cindex integral datatypes, in file-i/o protocol
45307 The integral datatypes used in the system calls are @code{int},
45308 @code{unsigned int}, @code{long}, @code{unsigned long},
45309 @code{mode_t}, and @code{time_t}.
45311 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
45312 implemented as 32 bit values in this protocol.
45314 @code{long} and @code{unsigned long} are implemented as 64 bit types.
45316 @xref{Limits}, for corresponding MIN and MAX values (similar to those
45317 in @file{limits.h}) to allow range checking on host and target.
45319 @code{time_t} datatypes are defined as seconds since the Epoch.
45321 All integral datatypes transferred as part of a memory read or write of a
45322 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
45325 @node Pointer Values
45326 @unnumberedsubsubsec Pointer Values
45327 @cindex pointer values, in file-i/o protocol
45329 Pointers to target data are transmitted as they are. An exception
45330 is made for pointers to buffers for which the length isn't
45331 transmitted as part of the function call, namely strings. Strings
45332 are transmitted as a pointer/length pair, both as hex values, e.g.@:
45339 which is a pointer to data of length 18 bytes at position 0x1aaf.
45340 The length is defined as the full string length in bytes, including
45341 the trailing null byte. For example, the string @code{"hello world"}
45342 at address 0x123456 is transmitted as
45348 @node Memory Transfer
45349 @unnumberedsubsubsec Memory Transfer
45350 @cindex memory transfer, in file-i/o protocol
45352 Structured data which is transferred using a memory read or write (for
45353 example, a @code{struct stat}) is expected to be in a protocol-specific format
45354 with all scalar multibyte datatypes being big endian. Translation to
45355 this representation needs to be done both by the target before the @code{F}
45356 packet is sent, and by @value{GDBN} before
45357 it transfers memory to the target. Transferred pointers to structured
45358 data should point to the already-coerced data at any time.
45362 @unnumberedsubsubsec struct stat
45363 @cindex struct stat, in file-i/o protocol
45365 The buffer of type @code{struct stat} used by the target and @value{GDBN}
45366 is defined as follows:
45370 unsigned int st_dev; /* device */
45371 unsigned int st_ino; /* inode */
45372 mode_t st_mode; /* protection */
45373 unsigned int st_nlink; /* number of hard links */
45374 unsigned int st_uid; /* user ID of owner */
45375 unsigned int st_gid; /* group ID of owner */
45376 unsigned int st_rdev; /* device type (if inode device) */
45377 unsigned long st_size; /* total size, in bytes */
45378 unsigned long st_blksize; /* blocksize for filesystem I/O */
45379 unsigned long st_blocks; /* number of blocks allocated */
45380 time_t st_atime; /* time of last access */
45381 time_t st_mtime; /* time of last modification */
45382 time_t st_ctime; /* time of last change */
45386 The integral datatypes conform to the definitions given in the
45387 appropriate section (see @ref{Integral Datatypes}, for details) so this
45388 structure is of size 64 bytes.
45390 The values of several fields have a restricted meaning and/or
45396 A value of 0 represents a file, 1 the console.
45399 No valid meaning for the target. Transmitted unchanged.
45402 Valid mode bits are described in @ref{Constants}. Any other
45403 bits have currently no meaning for the target.
45408 No valid meaning for the target. Transmitted unchanged.
45413 These values have a host and file system dependent
45414 accuracy. Especially on Windows hosts, the file system may not
45415 support exact timing values.
45418 The target gets a @code{struct stat} of the above representation and is
45419 responsible for coercing it to the target representation before
45422 Note that due to size differences between the host, target, and protocol
45423 representations of @code{struct stat} members, these members could eventually
45424 get truncated on the target.
45426 @node struct timeval
45427 @unnumberedsubsubsec struct timeval
45428 @cindex struct timeval, in file-i/o protocol
45430 The buffer of type @code{struct timeval} used by the File-I/O protocol
45431 is defined as follows:
45435 time_t tv_sec; /* second */
45436 long tv_usec; /* microsecond */
45440 The integral datatypes conform to the definitions given in the
45441 appropriate section (see @ref{Integral Datatypes}, for details) so this
45442 structure is of size 8 bytes.
45445 @subsection Constants
45446 @cindex constants, in file-i/o protocol
45448 The following values are used for the constants inside of the
45449 protocol. @value{GDBN} and target are responsible for translating these
45450 values before and after the call as needed.
45461 @unnumberedsubsubsec Open Flags
45462 @cindex open flags, in file-i/o protocol
45464 All values are given in hexadecimal representation.
45476 @node mode_t Values
45477 @unnumberedsubsubsec mode_t Values
45478 @cindex mode_t values, in file-i/o protocol
45480 All values are given in octal representation.
45497 @unnumberedsubsubsec Errno Values
45498 @cindex errno values, in file-i/o protocol
45500 All values are given in decimal representation.
45525 @code{EUNKNOWN} is used as a fallback error value if a host system returns
45526 any error value not in the list of supported error numbers.
45529 @unnumberedsubsubsec Lseek Flags
45530 @cindex lseek flags, in file-i/o protocol
45539 @unnumberedsubsubsec Limits
45540 @cindex limits, in file-i/o protocol
45542 All values are given in decimal representation.
45545 INT_MIN -2147483648
45547 UINT_MAX 4294967295
45548 LONG_MIN -9223372036854775808
45549 LONG_MAX 9223372036854775807
45550 ULONG_MAX 18446744073709551615
45553 @node File-I/O Examples
45554 @subsection File-I/O Examples
45555 @cindex file-i/o examples
45557 Example sequence of a write call, file descriptor 3, buffer is at target
45558 address 0x1234, 6 bytes should be written:
45561 <- @code{Fwrite,3,1234,6}
45562 @emph{request memory read from target}
45565 @emph{return "6 bytes written"}
45569 Example sequence of a read call, file descriptor 3, buffer is at target
45570 address 0x1234, 6 bytes should be read:
45573 <- @code{Fread,3,1234,6}
45574 @emph{request memory write to target}
45575 -> @code{X1234,6:XXXXXX}
45576 @emph{return "6 bytes read"}
45580 Example sequence of a read call, call fails on the host due to invalid
45581 file descriptor (@code{EBADF}):
45584 <- @code{Fread,3,1234,6}
45588 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
45592 <- @code{Fread,3,1234,6}
45597 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
45601 <- @code{Fread,3,1234,6}
45602 -> @code{X1234,6:XXXXXX}
45606 @node Library List Format
45607 @section Library List Format
45608 @cindex library list format, remote protocol
45610 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
45611 same process as your application to manage libraries. In this case,
45612 @value{GDBN} can use the loader's symbol table and normal memory
45613 operations to maintain a list of shared libraries. On other
45614 platforms, the operating system manages loaded libraries.
45615 @value{GDBN} can not retrieve the list of currently loaded libraries
45616 through memory operations, so it uses the @samp{qXfer:libraries:read}
45617 packet (@pxref{qXfer library list read}) instead. The remote stub
45618 queries the target's operating system and reports which libraries
45621 The @samp{qXfer:libraries:read} packet returns an XML document which
45622 lists loaded libraries and their offsets. Each library has an
45623 associated name and one or more segment or section base addresses,
45624 which report where the library was loaded in memory.
45626 For the common case of libraries that are fully linked binaries, the
45627 library should have a list of segments. If the target supports
45628 dynamic linking of a relocatable object file, its library XML element
45629 should instead include a list of allocated sections. The segment or
45630 section bases are start addresses, not relocation offsets; they do not
45631 depend on the library's link-time base addresses.
45633 @value{GDBN} must be linked with the Expat library to support XML
45634 library lists. @xref{Expat}.
45636 A simple memory map, with one loaded library relocated by a single
45637 offset, looks like this:
45641 <library name="/lib/libc.so.6">
45642 <segment address="0x10000000"/>
45647 Another simple memory map, with one loaded library with three
45648 allocated sections (.text, .data, .bss), looks like this:
45652 <library name="sharedlib.o">
45653 <section address="0x10000000"/>
45654 <section address="0x20000000"/>
45655 <section address="0x30000000"/>
45660 The format of a library list is described by this DTD:
45663 <!-- library-list: Root element with versioning -->
45664 <!ELEMENT library-list (library)*>
45665 <!ATTLIST library-list version CDATA #FIXED "1.0">
45666 <!ELEMENT library (segment*, section*)>
45667 <!ATTLIST library name CDATA #REQUIRED>
45668 <!ELEMENT segment EMPTY>
45669 <!ATTLIST segment address CDATA #REQUIRED>
45670 <!ELEMENT section EMPTY>
45671 <!ATTLIST section address CDATA #REQUIRED>
45674 In addition, segments and section descriptors cannot be mixed within a
45675 single library element, and you must supply at least one segment or
45676 section for each library.
45678 @node Library List Format for SVR4 Targets
45679 @section Library List Format for SVR4 Targets
45680 @cindex library list format, remote protocol
45682 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
45683 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
45684 shared libraries. Still a special library list provided by this packet is
45685 more efficient for the @value{GDBN} remote protocol.
45687 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
45688 loaded libraries and their SVR4 linker parameters. For each library on SVR4
45689 target, the following parameters are reported:
45693 @code{name}, the absolute file name from the @code{l_name} field of
45694 @code{struct link_map}.
45696 @code{lm} with address of @code{struct link_map} used for TLS
45697 (Thread Local Storage) access.
45699 @code{l_addr}, the displacement as read from the field @code{l_addr} of
45700 @code{struct link_map}. For prelinked libraries this is not an absolute
45701 memory address. It is a displacement of absolute memory address against
45702 address the file was prelinked to during the library load.
45704 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
45707 Additionally the single @code{main-lm} attribute specifies address of
45708 @code{struct link_map} used for the main executable. This parameter is used
45709 for TLS access and its presence is optional.
45711 @value{GDBN} must be linked with the Expat library to support XML
45712 SVR4 library lists. @xref{Expat}.
45714 A simple memory map, with two loaded libraries (which do not use prelink),
45718 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
45719 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
45721 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
45723 </library-list-svr>
45726 The format of an SVR4 library list is described by this DTD:
45729 <!-- library-list-svr4: Root element with versioning -->
45730 <!ELEMENT library-list-svr4 (library)*>
45731 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
45732 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
45733 <!ELEMENT library EMPTY>
45734 <!ATTLIST library name CDATA #REQUIRED>
45735 <!ATTLIST library lm CDATA #REQUIRED>
45736 <!ATTLIST library l_addr CDATA #REQUIRED>
45737 <!ATTLIST library l_ld CDATA #REQUIRED>
45740 @node Memory Map Format
45741 @section Memory Map Format
45742 @cindex memory map format
45744 To be able to write into flash memory, @value{GDBN} needs to obtain a
45745 memory map from the target. This section describes the format of the
45748 The memory map is obtained using the @samp{qXfer:memory-map:read}
45749 (@pxref{qXfer memory map read}) packet and is an XML document that
45750 lists memory regions.
45752 @value{GDBN} must be linked with the Expat library to support XML
45753 memory maps. @xref{Expat}.
45755 The top-level structure of the document is shown below:
45758 <?xml version="1.0"?>
45759 <!DOCTYPE memory-map
45760 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45761 "http://sourceware.org/gdb/gdb-memory-map.dtd">
45767 Each region can be either:
45772 A region of RAM starting at @var{addr} and extending for @var{length}
45776 <memory type="ram" start="@var{addr}" length="@var{length}"/>
45781 A region of read-only memory:
45784 <memory type="rom" start="@var{addr}" length="@var{length}"/>
45789 A region of flash memory, with erasure blocks @var{blocksize}
45793 <memory type="flash" start="@var{addr}" length="@var{length}">
45794 <property name="blocksize">@var{blocksize}</property>
45800 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
45801 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
45802 packets to write to addresses in such ranges.
45804 The formal DTD for memory map format is given below:
45807 <!-- ................................................... -->
45808 <!-- Memory Map XML DTD ................................ -->
45809 <!-- File: memory-map.dtd .............................. -->
45810 <!-- .................................... .............. -->
45811 <!-- memory-map.dtd -->
45812 <!-- memory-map: Root element with versioning -->
45813 <!ELEMENT memory-map (memory)*>
45814 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
45815 <!ELEMENT memory (property)*>
45816 <!-- memory: Specifies a memory region,
45817 and its type, or device. -->
45818 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
45819 start CDATA #REQUIRED
45820 length CDATA #REQUIRED>
45821 <!-- property: Generic attribute tag -->
45822 <!ELEMENT property (#PCDATA | property)*>
45823 <!ATTLIST property name (blocksize) #REQUIRED>
45826 @node Thread List Format
45827 @section Thread List Format
45828 @cindex thread list format
45830 To efficiently update the list of threads and their attributes,
45831 @value{GDBN} issues the @samp{qXfer:threads:read} packet
45832 (@pxref{qXfer threads read}) and obtains the XML document with
45833 the following structure:
45836 <?xml version="1.0"?>
45838 <thread id="id" core="0" name="name">
45839 ... description ...
45844 Each @samp{thread} element must have the @samp{id} attribute that
45845 identifies the thread (@pxref{thread-id syntax}). The
45846 @samp{core} attribute, if present, specifies which processor core
45847 the thread was last executing on. The @samp{name} attribute, if
45848 present, specifies the human-readable name of the thread. The content
45849 of the of @samp{thread} element is interpreted as human-readable
45850 auxiliary information. The @samp{handle} attribute, if present,
45851 is a hex encoded representation of the thread handle.
45854 @node Traceframe Info Format
45855 @section Traceframe Info Format
45856 @cindex traceframe info format
45858 To be able to know which objects in the inferior can be examined when
45859 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
45860 memory ranges, registers and trace state variables that have been
45861 collected in a traceframe.
45863 This list is obtained using the @samp{qXfer:traceframe-info:read}
45864 (@pxref{qXfer traceframe info read}) packet and is an XML document.
45866 @value{GDBN} must be linked with the Expat library to support XML
45867 traceframe info discovery. @xref{Expat}.
45869 The top-level structure of the document is shown below:
45872 <?xml version="1.0"?>
45873 <!DOCTYPE traceframe-info
45874 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
45875 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
45881 Each traceframe block can be either:
45886 A region of collected memory starting at @var{addr} and extending for
45887 @var{length} bytes from there:
45890 <memory start="@var{addr}" length="@var{length}"/>
45894 A block indicating trace state variable numbered @var{number} has been
45898 <tvar id="@var{number}"/>
45903 The formal DTD for the traceframe info format is given below:
45906 <!ELEMENT traceframe-info (memory | tvar)* >
45907 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
45909 <!ELEMENT memory EMPTY>
45910 <!ATTLIST memory start CDATA #REQUIRED
45911 length CDATA #REQUIRED>
45913 <!ATTLIST tvar id CDATA #REQUIRED>
45916 @node Branch Trace Format
45917 @section Branch Trace Format
45918 @cindex branch trace format
45920 In order to display the branch trace of an inferior thread,
45921 @value{GDBN} needs to obtain the list of branches. This list is
45922 represented as list of sequential code blocks that are connected via
45923 branches. The code in each block has been executed sequentially.
45925 This list is obtained using the @samp{qXfer:btrace:read}
45926 (@pxref{qXfer btrace read}) packet and is an XML document.
45928 @value{GDBN} must be linked with the Expat library to support XML
45929 traceframe info discovery. @xref{Expat}.
45931 The top-level structure of the document is shown below:
45934 <?xml version="1.0"?>
45936 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
45937 "http://sourceware.org/gdb/gdb-btrace.dtd">
45946 A block of sequentially executed instructions starting at @var{begin}
45947 and ending at @var{end}:
45950 <block begin="@var{begin}" end="@var{end}"/>
45955 The formal DTD for the branch trace format is given below:
45958 <!ELEMENT btrace (block* | pt) >
45959 <!ATTLIST btrace version CDATA #FIXED "1.0">
45961 <!ELEMENT block EMPTY>
45962 <!ATTLIST block begin CDATA #REQUIRED
45963 end CDATA #REQUIRED>
45965 <!ELEMENT pt (pt-config?, raw?)>
45967 <!ELEMENT pt-config (cpu?)>
45969 <!ELEMENT cpu EMPTY>
45970 <!ATTLIST cpu vendor CDATA #REQUIRED
45971 family CDATA #REQUIRED
45972 model CDATA #REQUIRED
45973 stepping CDATA #REQUIRED>
45975 <!ELEMENT raw (#PCDATA)>
45978 @node Branch Trace Configuration Format
45979 @section Branch Trace Configuration Format
45980 @cindex branch trace configuration format
45982 For each inferior thread, @value{GDBN} can obtain the branch trace
45983 configuration using the @samp{qXfer:btrace-conf:read}
45984 (@pxref{qXfer btrace-conf read}) packet.
45986 The configuration describes the branch trace format and configuration
45987 settings for that format. The following information is described:
45991 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
45994 The size of the @acronym{BTS} ring buffer in bytes.
45997 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
46001 The size of the @acronym{Intel PT} ring buffer in bytes.
46005 @value{GDBN} must be linked with the Expat library to support XML
46006 branch trace configuration discovery. @xref{Expat}.
46008 The formal DTD for the branch trace configuration format is given below:
46011 <!ELEMENT btrace-conf (bts?, pt?)>
46012 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
46014 <!ELEMENT bts EMPTY>
46015 <!ATTLIST bts size CDATA #IMPLIED>
46017 <!ELEMENT pt EMPTY>
46018 <!ATTLIST pt size CDATA #IMPLIED>
46021 @include agentexpr.texi
46023 @node Target Descriptions
46024 @appendix Target Descriptions
46025 @cindex target descriptions
46027 One of the challenges of using @value{GDBN} to debug embedded systems
46028 is that there are so many minor variants of each processor
46029 architecture in use. It is common practice for vendors to start with
46030 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
46031 and then make changes to adapt it to a particular market niche. Some
46032 architectures have hundreds of variants, available from dozens of
46033 vendors. This leads to a number of problems:
46037 With so many different customized processors, it is difficult for
46038 the @value{GDBN} maintainers to keep up with the changes.
46040 Since individual variants may have short lifetimes or limited
46041 audiences, it may not be worthwhile to carry information about every
46042 variant in the @value{GDBN} source tree.
46044 When @value{GDBN} does support the architecture of the embedded system
46045 at hand, the task of finding the correct architecture name to give the
46046 @command{set architecture} command can be error-prone.
46049 To address these problems, the @value{GDBN} remote protocol allows a
46050 target system to not only identify itself to @value{GDBN}, but to
46051 actually describe its own features. This lets @value{GDBN} support
46052 processor variants it has never seen before --- to the extent that the
46053 descriptions are accurate, and that @value{GDBN} understands them.
46055 @value{GDBN} must be linked with the Expat library to support XML
46056 target descriptions. @xref{Expat}.
46059 * Retrieving Descriptions:: How descriptions are fetched from a target.
46060 * Target Description Format:: The contents of a target description.
46061 * Predefined Target Types:: Standard types available for target
46063 * Enum Target Types:: How to define enum target types.
46064 * Standard Target Features:: Features @value{GDBN} knows about.
46067 @node Retrieving Descriptions
46068 @section Retrieving Descriptions
46070 Target descriptions can be read from the target automatically, or
46071 specified by the user manually. The default behavior is to read the
46072 description from the target. @value{GDBN} retrieves it via the remote
46073 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
46074 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
46075 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
46076 XML document, of the form described in @ref{Target Description
46079 Alternatively, you can specify a file to read for the target description.
46080 If a file is set, the target will not be queried. The commands to
46081 specify a file are:
46084 @cindex set tdesc filename
46085 @item set tdesc filename @var{path}
46086 Read the target description from @var{path}.
46088 @cindex unset tdesc filename
46089 @item unset tdesc filename
46090 Do not read the XML target description from a file. @value{GDBN}
46091 will use the description supplied by the current target.
46093 @cindex show tdesc filename
46094 @item show tdesc filename
46095 Show the filename to read for a target description, if any.
46099 @node Target Description Format
46100 @section Target Description Format
46101 @cindex target descriptions, XML format
46103 A target description annex is an @uref{http://www.w3.org/XML/, XML}
46104 document which complies with the Document Type Definition provided in
46105 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
46106 means you can use generally available tools like @command{xmllint} to
46107 check that your feature descriptions are well-formed and valid.
46108 However, to help people unfamiliar with XML write descriptions for
46109 their targets, we also describe the grammar here.
46111 Target descriptions can identify the architecture of the remote target
46112 and (for some architectures) provide information about custom register
46113 sets. They can also identify the OS ABI of the remote target.
46114 @value{GDBN} can use this information to autoconfigure for your
46115 target, or to warn you if you connect to an unsupported target.
46117 Here is a simple target description:
46120 <target version="1.0">
46121 <architecture>i386:x86-64</architecture>
46126 This minimal description only says that the target uses
46127 the x86-64 architecture.
46129 A target description has the following overall form, with [ ] marking
46130 optional elements and @dots{} marking repeatable elements. The elements
46131 are explained further below.
46134 <?xml version="1.0"?>
46135 <!DOCTYPE target SYSTEM "gdb-target.dtd">
46136 <target version="1.0">
46137 @r{[}@var{architecture}@r{]}
46138 @r{[}@var{osabi}@r{]}
46139 @r{[}@var{compatible}@r{]}
46140 @r{[}@var{feature}@dots{}@r{]}
46145 The description is generally insensitive to whitespace and line
46146 breaks, under the usual common-sense rules. The XML version
46147 declaration and document type declaration can generally be omitted
46148 (@value{GDBN} does not require them), but specifying them may be
46149 useful for XML validation tools. The @samp{version} attribute for
46150 @samp{<target>} may also be omitted, but we recommend
46151 including it; if future versions of @value{GDBN} use an incompatible
46152 revision of @file{gdb-target.dtd}, they will detect and report
46153 the version mismatch.
46155 @subsection Inclusion
46156 @cindex target descriptions, inclusion
46159 @cindex <xi:include>
46162 It can sometimes be valuable to split a target description up into
46163 several different annexes, either for organizational purposes, or to
46164 share files between different possible target descriptions. You can
46165 divide a description into multiple files by replacing any element of
46166 the target description with an inclusion directive of the form:
46169 <xi:include href="@var{document}"/>
46173 When @value{GDBN} encounters an element of this form, it will retrieve
46174 the named XML @var{document}, and replace the inclusion directive with
46175 the contents of that document. If the current description was read
46176 using @samp{qXfer}, then so will be the included document;
46177 @var{document} will be interpreted as the name of an annex. If the
46178 current description was read from a file, @value{GDBN} will look for
46179 @var{document} as a file in the same directory where it found the
46180 original description.
46182 @subsection Architecture
46183 @cindex <architecture>
46185 An @samp{<architecture>} element has this form:
46188 <architecture>@var{arch}</architecture>
46191 @var{arch} is one of the architectures from the set accepted by
46192 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46195 @cindex @code{<osabi>}
46197 This optional field was introduced in @value{GDBN} version 7.0.
46198 Previous versions of @value{GDBN} ignore it.
46200 An @samp{<osabi>} element has this form:
46203 <osabi>@var{abi-name}</osabi>
46206 @var{abi-name} is an OS ABI name from the same selection accepted by
46207 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
46209 @subsection Compatible Architecture
46210 @cindex @code{<compatible>}
46212 This optional field was introduced in @value{GDBN} version 7.0.
46213 Previous versions of @value{GDBN} ignore it.
46215 A @samp{<compatible>} element has this form:
46218 <compatible>@var{arch}</compatible>
46221 @var{arch} is one of the architectures from the set accepted by
46222 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
46224 A @samp{<compatible>} element is used to specify that the target
46225 is able to run binaries in some other than the main target architecture
46226 given by the @samp{<architecture>} element. For example, on the
46227 Cell Broadband Engine, the main architecture is @code{powerpc:common}
46228 or @code{powerpc:common64}, but the system is able to run binaries
46229 in the @code{spu} architecture as well. The way to describe this
46230 capability with @samp{<compatible>} is as follows:
46233 <architecture>powerpc:common</architecture>
46234 <compatible>spu</compatible>
46237 @subsection Features
46240 Each @samp{<feature>} describes some logical portion of the target
46241 system. Features are currently used to describe available CPU
46242 registers and the types of their contents. A @samp{<feature>} element
46246 <feature name="@var{name}">
46247 @r{[}@var{type}@dots{}@r{]}
46253 Each feature's name should be unique within the description. The name
46254 of a feature does not matter unless @value{GDBN} has some special
46255 knowledge of the contents of that feature; if it does, the feature
46256 should have its standard name. @xref{Standard Target Features}.
46260 Any register's value is a collection of bits which @value{GDBN} must
46261 interpret. The default interpretation is a two's complement integer,
46262 but other types can be requested by name in the register description.
46263 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
46264 Target Types}), and the description can define additional composite
46267 Each type element must have an @samp{id} attribute, which gives
46268 a unique (within the containing @samp{<feature>}) name to the type.
46269 Types must be defined before they are used.
46272 Some targets offer vector registers, which can be treated as arrays
46273 of scalar elements. These types are written as @samp{<vector>} elements,
46274 specifying the array element type, @var{type}, and the number of elements,
46278 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
46282 If a register's value is usefully viewed in multiple ways, define it
46283 with a union type containing the useful representations. The
46284 @samp{<union>} element contains one or more @samp{<field>} elements,
46285 each of which has a @var{name} and a @var{type}:
46288 <union id="@var{id}">
46289 <field name="@var{name}" type="@var{type}"/>
46296 If a register's value is composed from several separate values, define
46297 it with either a structure type or a flags type.
46298 A flags type may only contain bitfields.
46299 A structure type may either contain only bitfields or contain no bitfields.
46300 If the value contains only bitfields, its total size in bytes must be
46303 Non-bitfield values have a @var{name} and @var{type}.
46306 <struct id="@var{id}">
46307 <field name="@var{name}" type="@var{type}"/>
46312 Both @var{name} and @var{type} values are required.
46313 No implicit padding is added.
46315 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
46318 <struct id="@var{id}" size="@var{size}">
46319 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46325 <flags id="@var{id}" size="@var{size}">
46326 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
46331 The @var{name} value is required.
46332 Bitfield values may be named with the empty string, @samp{""},
46333 in which case the field is ``filler'' and its value is not printed.
46334 Not all bits need to be specified, so ``filler'' fields are optional.
46336 The @var{start} and @var{end} values are required, and @var{type}
46338 The field's @var{start} must be less than or equal to its @var{end},
46339 and zero represents the least significant bit.
46341 The default value of @var{type} is @code{bool} for single bit fields,
46342 and an unsigned integer otherwise.
46344 Which to choose? Structures or flags?
46346 Registers defined with @samp{flags} have these advantages over
46347 defining them with @samp{struct}:
46351 Arithmetic may be performed on them as if they were integers.
46353 They are printed in a more readable fashion.
46356 Registers defined with @samp{struct} have one advantage over
46357 defining them with @samp{flags}:
46361 One can fetch individual fields like in @samp{C}.
46364 (gdb) print $my_struct_reg.field3
46370 @subsection Registers
46373 Each register is represented as an element with this form:
46376 <reg name="@var{name}"
46377 bitsize="@var{size}"
46378 @r{[}regnum="@var{num}"@r{]}
46379 @r{[}save-restore="@var{save-restore}"@r{]}
46380 @r{[}type="@var{type}"@r{]}
46381 @r{[}group="@var{group}"@r{]}/>
46385 The components are as follows:
46390 The register's name; it must be unique within the target description.
46393 The register's size, in bits.
46396 The register's number. If omitted, a register's number is one greater
46397 than that of the previous register (either in the current feature or in
46398 a preceding feature); the first register in the target description
46399 defaults to zero. This register number is used to read or write
46400 the register; e.g.@: it is used in the remote @code{p} and @code{P}
46401 packets, and registers appear in the @code{g} and @code{G} packets
46402 in order of increasing register number.
46405 Whether the register should be preserved across inferior function
46406 calls; this must be either @code{yes} or @code{no}. The default is
46407 @code{yes}, which is appropriate for most registers except for
46408 some system control registers; this is not related to the target's
46412 The type of the register. It may be a predefined type, a type
46413 defined in the current feature, or one of the special types @code{int}
46414 and @code{float}. @code{int} is an integer type of the correct size
46415 for @var{bitsize}, and @code{float} is a floating point type (in the
46416 architecture's normal floating point format) of the correct size for
46417 @var{bitsize}. The default is @code{int}.
46420 The register group to which this register belongs. It can be one of the
46421 standard register groups @code{general}, @code{float}, @code{vector} or an
46422 arbitrary string. Group names should be limited to alphanumeric characters.
46423 If a group name is made up of multiple words the words may be separated by
46424 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
46425 @var{group} is specified, @value{GDBN} will not display the register in
46426 @code{info registers}.
46430 @node Predefined Target Types
46431 @section Predefined Target Types
46432 @cindex target descriptions, predefined types
46434 Type definitions in the self-description can build up composite types
46435 from basic building blocks, but can not define fundamental types. Instead,
46436 standard identifiers are provided by @value{GDBN} for the fundamental
46437 types. The currently supported types are:
46442 Boolean type, occupying a single bit.
46450 Signed integer types holding the specified number of bits.
46458 Unsigned integer types holding the specified number of bits.
46462 Pointers to unspecified code and data. The program counter and
46463 any dedicated return address register may be marked as code
46464 pointers; printing a code pointer converts it into a symbolic
46465 address. The stack pointer and any dedicated address registers
46466 may be marked as data pointers.
46469 Half precision IEEE floating point.
46472 Single precision IEEE floating point.
46475 Double precision IEEE floating point.
46478 The 16-bit @dfn{brain floating point} format used e.g.@: by x86 and ARM.
46481 The 12-byte extended precision format used by ARM FPA registers.
46484 The 10-byte extended precision format used by x87 registers.
46487 32bit @sc{eflags} register used by x86.
46490 32bit @sc{mxcsr} register used by x86.
46494 @node Enum Target Types
46495 @section Enum Target Types
46496 @cindex target descriptions, enum types
46498 Enum target types are useful in @samp{struct} and @samp{flags}
46499 register descriptions. @xref{Target Description Format}.
46501 Enum types have a name, size and a list of name/value pairs.
46504 <enum id="@var{id}" size="@var{size}">
46505 <evalue name="@var{name}" value="@var{value}"/>
46510 Enums must be defined before they are used.
46513 <enum id="levels_type" size="4">
46514 <evalue name="low" value="0"/>
46515 <evalue name="high" value="1"/>
46517 <flags id="flags_type" size="4">
46518 <field name="X" start="0"/>
46519 <field name="LEVEL" start="1" end="1" type="levels_type"/>
46521 <reg name="flags" bitsize="32" type="flags_type"/>
46524 Given that description, a value of 3 for the @samp{flags} register
46525 would be printed as:
46528 (gdb) info register flags
46529 flags 0x3 [ X LEVEL=high ]
46532 @node Standard Target Features
46533 @section Standard Target Features
46534 @cindex target descriptions, standard features
46536 A target description must contain either no registers or all the
46537 target's registers. If the description contains no registers, then
46538 @value{GDBN} will assume a default register layout, selected based on
46539 the architecture. If the description contains any registers, the
46540 default layout will not be used; the standard registers must be
46541 described in the target description, in such a way that @value{GDBN}
46542 can recognize them.
46544 This is accomplished by giving specific names to feature elements
46545 which contain standard registers. @value{GDBN} will look for features
46546 with those names and verify that they contain the expected registers;
46547 if any known feature is missing required registers, or if any required
46548 feature is missing, @value{GDBN} will reject the target
46549 description. You can add additional registers to any of the
46550 standard features --- @value{GDBN} will display them just as if
46551 they were added to an unrecognized feature.
46553 This section lists the known features and their expected contents.
46554 Sample XML documents for these features are included in the
46555 @value{GDBN} source tree, in the directory @file{gdb/features}.
46557 Names recognized by @value{GDBN} should include the name of the
46558 company or organization which selected the name, and the overall
46559 architecture to which the feature applies; so e.g.@: the feature
46560 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
46562 The names of registers are not case sensitive for the purpose
46563 of recognizing standard features, but @value{GDBN} will only display
46564 registers using the capitalization used in the description.
46567 * AArch64 Features::
46571 * LoongArch Features::
46572 * MicroBlaze Features::
46576 * Nios II Features::
46577 * OpenRISC 1000 Features::
46578 * PowerPC Features::
46579 * RISC-V Features::
46581 * S/390 and System z Features::
46587 @node AArch64 Features
46588 @subsection AArch64 Features
46589 @cindex target descriptions, AArch64 features
46591 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
46592 targets. It should contain registers @samp{x0} through @samp{x30},
46593 @samp{sp}, @samp{pc}, and @samp{cpsr}.
46595 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
46596 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
46599 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
46600 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
46601 through @samp{p15}, @samp{ffr} and @samp{vg}.
46603 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
46604 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
46607 @subsection ARC Features
46608 @cindex target descriptions, ARC Features
46610 ARC processors are so configurable that even core registers and their numbers
46611 are not predetermined completely. Moreover, @emph{flags} and @emph{PC}
46612 registers, which are important to @value{GDBN}, are not ``core'' registers in
46613 ARC. Therefore, there are two features that their presence is mandatory:
46614 @samp{org.gnu.gdb.arc.core} and @samp{org.gnu.gdb.arc.aux}.
46616 The @samp{org.gnu.gdb.arc.core} feature is required for all targets. It must
46621 @samp{r0} through @samp{r25} for normal register file targets.
46623 @samp{r0} through @samp{r3}, and @samp{r10} through @samp{r15} for reduced
46624 register file targets.
46626 @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}@footnote{Not necessary for ARCv1.},
46627 @samp{blink}, @samp{lp_count}, @samp{pcl}.
46630 In case of an ARCompact target (ARCv1 ISA), the @samp{org.gnu.gdb.arc.core}
46631 feature may contain registers @samp{ilink1} and @samp{ilink2}. While in case
46632 of ARC EM and ARC HS targets (ARCv2 ISA), register @samp{ilink} may be present.
46633 The difference between ARCv1 and ARCv2 is the naming of registers @emph{29th}
46634 and @emph{30th}. They are called @samp{ilink1} and @samp{ilink2} for ARCv1 and
46635 are optional. For ARCv2, they are called @samp{ilink} and @samp{r30} and only
46636 @samp{ilink} is optional. The optionality of @samp{ilink*} registers is
46637 because of their inaccessibility during user space debugging sessions.
46639 Extension core registers @samp{r32} through @samp{r59} are optional and their
46640 existence depends on the configuration. When debugging GNU/Linux applications,
46641 i.e.@: user space debugging, these core registers are not available.
46643 The @samp{org.gnu.gdb.arc.aux} feature is required for all ARC targets. Here
46644 is the list of registers pertinent to this feature:
46648 mandatory: @samp{pc} and @samp{status32}.
46650 optional: @samp{lp_start}, @samp{lp_end}, and @samp{bta}.
46654 @subsection ARM Features
46655 @cindex target descriptions, ARM features
46657 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
46659 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
46660 @samp{lr}, @samp{pc}, and @samp{cpsr}.
46662 For M-profile targets (e.g.@: Cortex-M3), the @samp{org.gnu.gdb.arm.core}
46663 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
46664 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
46667 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
46668 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
46670 The @samp{org.gnu.gdb.arm.m-profile-mve} feature is optional. If present, it
46671 must contain register @samp{vpr}.
46673 If the @samp{org.gnu.gdb.arm.m-profile-mve} feature is available, @value{GDBN}
46674 will synthesize the @samp{p0} pseudo register from @samp{vpr} contents.
46676 If the @samp{org.gnu.gdb.arm.vfp} feature is available alongside the
46677 @samp{org.gnu.gdb.arm.m-profile-mve} feature, @value{GDBN} will
46678 synthesize the @samp{q} pseudo registers from @samp{d} register
46681 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
46682 it should contain at least registers @samp{wR0} through @samp{wR15} and
46683 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
46684 @samp{wCSSF}, and @samp{wCASF} registers are optional.
46686 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
46687 should contain at least registers @samp{d0} through @samp{d15}. If
46688 they are present, @samp{d16} through @samp{d31} should also be included.
46689 @value{GDBN} will synthesize the single-precision registers from
46690 halves of the double-precision registers.
46692 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
46693 need to contain registers; it instructs @value{GDBN} to display the
46694 VFP double-precision registers as vectors and to synthesize the
46695 quad-precision registers from pairs of double-precision registers.
46696 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
46697 be present and include 32 double-precision registers.
46699 The @samp{org.gnu.gdb.arm.m-profile-pacbti} feature is optional, and
46700 acknowledges support for the ARMv8.1-m PACBTI extensions. @value{GDBN}
46701 will track return address signing states and will decorate backtraces using
46702 the [PAC] marker, similar to AArch64's PAC extension.
46703 @xref{AArch64 PAC}.
46705 @node i386 Features
46706 @subsection i386 Features
46707 @cindex target descriptions, i386 features
46709 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
46710 targets. It should describe the following registers:
46714 @samp{eax} through @samp{edi} plus @samp{eip} for i386
46716 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
46718 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
46719 @samp{fs}, @samp{gs}
46721 @samp{st0} through @samp{st7}
46723 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
46724 @samp{foseg}, @samp{fooff} and @samp{fop}
46727 The register sets may be different, depending on the target.
46729 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
46730 describe registers:
46734 @samp{xmm0} through @samp{xmm7} for i386
46736 @samp{xmm0} through @samp{xmm15} for amd64
46741 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
46742 @samp{org.gnu.gdb.i386.sse} feature. It should
46743 describe the upper 128 bits of @sc{ymm} registers:
46747 @samp{ymm0h} through @samp{ymm7h} for i386
46749 @samp{ymm0h} through @samp{ymm15h} for amd64
46752 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
46753 Memory Protection Extension (MPX). It should describe the following registers:
46757 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
46759 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
46762 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
46763 describe a single register, @samp{orig_eax}.
46765 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
46766 describe two system registers: @samp{fs_base} and @samp{gs_base}.
46768 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
46769 @samp{org.gnu.gdb.i386.avx} feature. It should
46770 describe additional @sc{xmm} registers:
46774 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
46777 It should describe the upper 128 bits of additional @sc{ymm} registers:
46781 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
46785 describe the upper 256 bits of @sc{zmm} registers:
46789 @samp{zmm0h} through @samp{zmm7h} for i386.
46791 @samp{zmm0h} through @samp{zmm15h} for amd64.
46795 describe the additional @sc{zmm} registers:
46799 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
46802 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
46803 describe a single register, @samp{pkru}. It is a 32-bit register
46804 valid for i386 and amd64.
46806 @node LoongArch Features
46807 @subsection LoongArch Features
46808 @cindex target descriptions, LoongArch Features
46810 The @samp{org.gnu.gdb.loongarch.base} feature is required for LoongArch
46811 targets. It should contain the registers @samp{r0} through @samp{r31},
46812 @samp{pc}, and @samp{badv}. Either the architectural names (@samp{r0},
46813 @samp{r1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra}, etc).
46815 @node MicroBlaze Features
46816 @subsection MicroBlaze Features
46817 @cindex target descriptions, MicroBlaze features
46819 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
46820 targets. It should contain registers @samp{r0} through @samp{r31},
46821 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
46822 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
46823 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
46825 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
46826 If present, it should contain registers @samp{rshr} and @samp{rslr}
46828 @node MIPS Features
46829 @subsection @acronym{MIPS} Features
46830 @cindex target descriptions, @acronym{MIPS} features
46832 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
46833 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
46834 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
46837 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
46838 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
46839 registers. They may be 32-bit or 64-bit depending on the target.
46841 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
46842 it may be optional in a future version of @value{GDBN}. It should
46843 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
46844 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
46846 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
46847 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
46848 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
46849 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
46851 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
46852 contain a single register, @samp{restart}, which is used by the
46853 Linux kernel to control restartable syscalls.
46855 @node M68K Features
46856 @subsection M68K Features
46857 @cindex target descriptions, M68K features
46860 @item @samp{org.gnu.gdb.m68k.core}
46861 @itemx @samp{org.gnu.gdb.coldfire.core}
46862 @itemx @samp{org.gnu.gdb.fido.core}
46863 One of those features must be always present.
46864 The feature that is present determines which flavor of m68k is
46865 used. The feature that is present should contain registers
46866 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
46867 @samp{sp}, @samp{ps} and @samp{pc}.
46869 @item @samp{org.gnu.gdb.coldfire.fp}
46870 This feature is optional. If present, it should contain registers
46871 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
46874 Note that, despite the fact that this feature's name says
46875 @samp{coldfire}, it is used to describe any floating point registers.
46876 The size of the registers must match the main m68k flavor; so, for
46877 example, if the primary feature is reported as @samp{coldfire}, then
46878 64-bit floating point registers are required.
46881 @node NDS32 Features
46882 @subsection NDS32 Features
46883 @cindex target descriptions, NDS32 features
46885 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
46886 targets. It should contain at least registers @samp{r0} through
46887 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
46890 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
46891 it should contain 64-bit double-precision floating-point registers
46892 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
46893 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
46895 @emph{Note:} The first sixteen 64-bit double-precision floating-point
46896 registers are overlapped with the thirty-two 32-bit single-precision
46897 floating-point registers. The 32-bit single-precision registers, if
46898 not being listed explicitly, will be synthesized from halves of the
46899 overlapping 64-bit double-precision registers. Listing 32-bit
46900 single-precision registers explicitly is deprecated, and the
46901 support to it could be totally removed some day.
46903 @node Nios II Features
46904 @subsection Nios II Features
46905 @cindex target descriptions, Nios II features
46907 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
46908 targets. It should contain the 32 core registers (@samp{zero},
46909 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
46910 @samp{pc}, and the 16 control registers (@samp{status} through
46913 @node OpenRISC 1000 Features
46914 @subsection Openrisc 1000 Features
46915 @cindex target descriptions, OpenRISC 1000 features
46917 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
46918 targets. It should contain the 32 general purpose registers (@samp{r0}
46919 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
46921 @node PowerPC Features
46922 @subsection PowerPC Features
46923 @cindex target descriptions, PowerPC features
46925 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
46926 targets. It should contain registers @samp{r0} through @samp{r31},
46927 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
46928 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
46930 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
46931 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
46933 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
46934 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
46935 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
46936 through @samp{v31} as aliases for the corresponding @samp{vrX}
46939 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
46940 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
46941 combine these registers with the floating point registers (@samp{f0}
46942 through @samp{f31}) and the altivec registers (@samp{vr0} through
46943 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
46944 @samp{vs63}, the set of vector-scalar registers for POWER7.
46945 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
46946 @samp{org.gnu.gdb.power.altivec}.
46948 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
46949 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
46950 @samp{spefscr}. SPE targets should provide 32-bit registers in
46951 @samp{org.gnu.gdb.power.core} and provide the upper halves in
46952 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
46953 these to present registers @samp{ev0} through @samp{ev31} to the
46956 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
46957 contain the 64-bit register @samp{ppr}.
46959 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
46960 contain the 64-bit register @samp{dscr}.
46962 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
46963 contain the 64-bit register @samp{tar}.
46965 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
46966 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
46969 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
46970 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
46971 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
46972 server PMU registers provided by @sc{gnu}/Linux.
46974 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
46975 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
46978 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
46979 contain the checkpointed general-purpose registers @samp{cr0} through
46980 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
46981 @samp{cctr}. These registers may all be either 32-bit or 64-bit
46982 depending on the target. It should also contain the checkpointed
46983 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
46986 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
46987 contain the checkpointed 64-bit floating-point registers @samp{cf0}
46988 through @samp{cf31}, as well as the checkpointed 64-bit register
46991 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
46992 should contain the checkpointed altivec registers @samp{cvr0} through
46993 @samp{cvr31}, all 128-bit wide. It should also contain the
46994 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
46997 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
46998 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
46999 will combine these registers with the checkpointed floating point
47000 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
47001 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
47002 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
47003 @samp{cvs63}. Therefore, this feature requires both
47004 @samp{org.gnu.gdb.power.htm.altivec} and
47005 @samp{org.gnu.gdb.power.htm.fpu}.
47007 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
47008 contain the 64-bit checkpointed register @samp{cppr}.
47010 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
47011 contain the 64-bit checkpointed register @samp{cdscr}.
47013 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
47014 contain the 64-bit checkpointed register @samp{ctar}.
47017 @node RISC-V Features
47018 @subsection RISC-V Features
47019 @cindex target descriptions, RISC-V Features
47021 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
47022 targets. It should contain the registers @samp{x0} through
47023 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
47024 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
47027 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
47028 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
47029 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
47030 architectural register names, or the ABI names can be used.
47032 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
47033 it should contain registers that are not backed by real registers on
47034 the target, but are instead virtual, where the register value is
47035 derived from other target state. In many ways these are like
47036 @value{GDBN}s pseudo-registers, except implemented by the target.
47037 Currently the only register expected in this set is the one byte
47038 @samp{priv} register that contains the target's privilege level in the
47039 least significant two bits.
47041 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
47042 should contain all of the target's standard CSRs. Standard CSRs are
47043 those defined in the RISC-V specification documents. There is some
47044 overlap between this feature and the fpu feature; the @samp{fflags},
47045 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
47046 expectation is that these registers will be in the fpu feature if the
47047 target has floating point hardware, but can be moved into the csr
47048 feature if the target has the floating point control registers, but no
47049 other floating point hardware.
47051 The @samp{org.gnu.gdb.riscv.vector} feature is optional. If present,
47052 it should contain registers @samp{v0} through @samp{v31}, all of which
47053 must be the same size. These requirements are based on the v0.10
47054 draft vector extension, as the vector extension is not yet final. In
47055 the event that the register set of the vector extension changes for
47056 the final specification, the requirements given here could change for
47057 future releases of @value{GDBN}.
47060 @subsection RX Features
47061 @cindex target descriptions, RX Features
47063 The @samp{org.gnu.gdb.rx.core} feature is required for RX
47064 targets. It should contain the registers @samp{r0} through
47065 @samp{r15}, @samp{usp}, @samp{isp}, @samp{psw}, @samp{pc}, @samp{intb},
47066 @samp{bpsw}, @samp{bpc}, @samp{fintv}, @samp{fpsw}, and @samp{acc}.
47068 @node S/390 and System z Features
47069 @subsection S/390 and System z Features
47070 @cindex target descriptions, S/390 features
47071 @cindex target descriptions, System z features
47073 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
47074 System z targets. It should contain the PSW and the 16 general
47075 registers. In particular, System z targets should provide the 64-bit
47076 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
47077 S/390 targets should provide the 32-bit versions of these registers.
47078 A System z target that runs in 31-bit addressing mode should provide
47079 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
47080 register's upper halves @samp{r0h} through @samp{r15h}, and their
47081 lower halves @samp{r0l} through @samp{r15l}.
47083 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
47084 contain the 64-bit registers @samp{f0} through @samp{f15}, and
47087 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
47088 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
47090 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
47091 contain the register @samp{orig_r2}, which is 64-bit wide on System z
47092 targets and 32-bit otherwise. In addition, the feature may contain
47093 the @samp{last_break} register, whose width depends on the addressing
47094 mode, as well as the @samp{system_call} register, which is always
47097 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
47098 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
47099 @samp{atia}, and @samp{tr0} through @samp{tr15}.
47101 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
47102 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
47103 combined by @value{GDBN} with the floating point registers @samp{f0}
47104 through @samp{f15} to present the 128-bit wide vector registers
47105 @samp{v0} through @samp{v15}. In addition, this feature should
47106 contain the 128-bit wide vector registers @samp{v16} through
47109 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
47110 the 64-bit wide guarded-storage-control registers @samp{gsd},
47111 @samp{gssm}, and @samp{gsepla}.
47113 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
47114 the 64-bit wide guarded-storage broadcast control registers
47115 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
47117 @node Sparc Features
47118 @subsection Sparc Features
47119 @cindex target descriptions, sparc32 features
47120 @cindex target descriptions, sparc64 features
47121 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
47122 targets. It should describe the following registers:
47126 @samp{g0} through @samp{g7}
47128 @samp{o0} through @samp{o7}
47130 @samp{l0} through @samp{l7}
47132 @samp{i0} through @samp{i7}
47135 They may be 32-bit or 64-bit depending on the target.
47137 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
47138 targets. It should describe the following registers:
47142 @samp{f0} through @samp{f31}
47144 @samp{f32} through @samp{f62} for sparc64
47147 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
47148 targets. It should describe the following registers:
47152 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
47153 @samp{fsr}, and @samp{csr} for sparc32
47155 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
47159 @node TIC6x Features
47160 @subsection TMS320C6x Features
47161 @cindex target descriptions, TIC6x features
47162 @cindex target descriptions, TMS320C6x features
47163 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
47164 targets. It should contain registers @samp{A0} through @samp{A15},
47165 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
47167 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
47168 contain registers @samp{A16} through @samp{A31} and @samp{B16}
47169 through @samp{B31}.
47171 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
47172 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
47174 @node Operating System Information
47175 @appendix Operating System Information
47176 @cindex operating system information
47178 Users of @value{GDBN} often wish to obtain information about the state of
47179 the operating system running on the target---for example the list of
47180 processes, or the list of open files. This section describes the
47181 mechanism that makes it possible. This mechanism is similar to the
47182 target features mechanism (@pxref{Target Descriptions}), but focuses
47183 on a different aspect of target.
47185 Operating system information is retrieved from the target via the
47186 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
47187 read}). The object name in the request should be @samp{osdata}, and
47188 the @var{annex} identifies the data to be fetched.
47195 @appendixsection Process list
47196 @cindex operating system information, process list
47198 When requesting the process list, the @var{annex} field in the
47199 @samp{qXfer} request should be @samp{processes}. The returned data is
47200 an XML document. The formal syntax of this document is defined in
47201 @file{gdb/features/osdata.dtd}.
47203 An example document is:
47206 <?xml version="1.0"?>
47207 <!DOCTYPE target SYSTEM "osdata.dtd">
47208 <osdata type="processes">
47210 <column name="pid">1</column>
47211 <column name="user">root</column>
47212 <column name="command">/sbin/init</column>
47213 <column name="cores">1,2,3</column>
47218 Each item should include a column whose name is @samp{pid}. The value
47219 of that column should identify the process on the target. The
47220 @samp{user} and @samp{command} columns are optional, and will be
47221 displayed by @value{GDBN}. The @samp{cores} column, if present,
47222 should contain a comma-separated list of cores that this process
47223 is running on. Target may provide additional columns,
47224 which @value{GDBN} currently ignores.
47226 @node Trace File Format
47227 @appendix Trace File Format
47228 @cindex trace file format
47230 The trace file comes in three parts: a header, a textual description
47231 section, and a trace frame section with binary data.
47233 The header has the form @code{\x7fTRACE0\n}. The first byte is
47234 @code{0x7f} so as to indicate that the file contains binary data,
47235 while the @code{0} is a version number that may have different values
47238 The description section consists of multiple lines of @sc{ascii} text
47239 separated by newline characters (@code{0xa}). The lines may include a
47240 variety of optional descriptive or context-setting information, such
47241 as tracepoint definitions or register set size. @value{GDBN} will
47242 ignore any line that it does not recognize. An empty line marks the end
47247 Specifies the size of a register block in bytes. This is equal to the
47248 size of a @code{g} packet payload in the remote protocol. @var{size}
47249 is an ascii decimal number. There should be only one such line in
47250 a single trace file.
47252 @item status @var{status}
47253 Trace status. @var{status} has the same format as a @code{qTStatus}
47254 remote packet reply. There should be only one such line in a single trace
47257 @item tp @var{payload}
47258 Tracepoint definition. The @var{payload} has the same format as
47259 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
47260 may take multiple lines of definition, corresponding to the multiple
47263 @item tsv @var{payload}
47264 Trace state variable definition. The @var{payload} has the same format as
47265 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
47266 may take multiple lines of definition, corresponding to the multiple
47269 @item tdesc @var{payload}
47270 Target description in XML format. The @var{payload} is a single line of
47271 the XML file. All such lines should be concatenated together to get
47272 the original XML file. This file is in the same format as @code{qXfer}
47273 @code{features} payload, and corresponds to the main @code{target.xml}
47274 file. Includes are not allowed.
47278 The trace frame section consists of a number of consecutive frames.
47279 Each frame begins with a two-byte tracepoint number, followed by a
47280 four-byte size giving the amount of data in the frame. The data in
47281 the frame consists of a number of blocks, each introduced by a
47282 character indicating its type (at least register, memory, and trace
47283 state variable). The data in this section is raw binary, not a
47284 hexadecimal or other encoding; its endianness matches the target's
47287 @c FIXME bi-arch may require endianness/arch info in description section
47290 @item R @var{bytes}
47291 Register block. The number and ordering of bytes matches that of a
47292 @code{g} packet in the remote protocol. Note that these are the
47293 actual bytes, in target order, not a hexadecimal encoding.
47295 @item M @var{address} @var{length} @var{bytes}...
47296 Memory block. This is a contiguous block of memory, at the 8-byte
47297 address @var{address}, with a 2-byte length @var{length}, followed by
47298 @var{length} bytes.
47300 @item V @var{number} @var{value}
47301 Trace state variable block. This records the 8-byte signed value
47302 @var{value} of trace state variable numbered @var{number}.
47306 Future enhancements of the trace file format may include additional types
47309 @node Index Section Format
47310 @appendix @code{.gdb_index} section format
47311 @cindex .gdb_index section format
47312 @cindex index section format
47314 This section documents the index section that is created by @code{save
47315 gdb-index} (@pxref{Index Files}). The index section is
47316 DWARF-specific; some knowledge of DWARF is assumed in this
47319 The mapped index file format is designed to be directly
47320 @code{mmap}able on any architecture. In most cases, a datum is
47321 represented using a little-endian 32-bit integer value, called an
47322 @code{offset_type}. Big endian machines must byte-swap the values
47323 before using them. Exceptions to this rule are noted. The data is
47324 laid out such that alignment is always respected.
47326 A mapped index consists of several areas, laid out in order.
47330 The file header. This is a sequence of values, of @code{offset_type}
47331 unless otherwise noted:
47335 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
47336 Version 4 uses a different hashing function from versions 5 and 6.
47337 Version 6 includes symbols for inlined functions, whereas versions 4
47338 and 5 do not. Version 7 adds attributes to the CU indices in the
47339 symbol table. Version 8 specifies that symbols from DWARF type units
47340 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
47341 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
47343 @value{GDBN} will only read version 4, 5, or 6 indices
47344 by specifying @code{set use-deprecated-index-sections on}.
47345 GDB has a workaround for potentially broken version 7 indices so it is
47346 currently not flagged as deprecated.
47349 The offset, from the start of the file, of the CU list.
47352 The offset, from the start of the file, of the types CU list. Note
47353 that this area can be empty, in which case this offset will be equal
47354 to the next offset.
47357 The offset, from the start of the file, of the address area.
47360 The offset, from the start of the file, of the symbol table.
47363 The offset, from the start of the file, of the constant pool.
47367 The CU list. This is a sequence of pairs of 64-bit little-endian
47368 values, sorted by the CU offset. The first element in each pair is
47369 the offset of a CU in the @code{.debug_info} section. The second
47370 element in each pair is the length of that CU. References to a CU
47371 elsewhere in the map are done using a CU index, which is just the
47372 0-based index into this table. Note that if there are type CUs, then
47373 conceptually CUs and type CUs form a single list for the purposes of
47377 The types CU list. This is a sequence of triplets of 64-bit
47378 little-endian values. In a triplet, the first value is the CU offset,
47379 the second value is the type offset in the CU, and the third value is
47380 the type signature. The types CU list is not sorted.
47383 The address area. The address area consists of a sequence of address
47384 entries. Each address entry has three elements:
47388 The low address. This is a 64-bit little-endian value.
47391 The high address. This is a 64-bit little-endian value. Like
47392 @code{DW_AT_high_pc}, the value is one byte beyond the end.
47395 The CU index. This is an @code{offset_type} value.
47399 The symbol table. This is an open-addressed hash table. The size of
47400 the hash table is always a power of 2.
47402 Each slot in the hash table consists of a pair of @code{offset_type}
47403 values. The first value is the offset of the symbol's name in the
47404 constant pool. The second value is the offset of the CU vector in the
47407 If both values are 0, then this slot in the hash table is empty. This
47408 is ok because while 0 is a valid constant pool index, it cannot be a
47409 valid index for both a string and a CU vector.
47411 The hash value for a table entry is computed by applying an
47412 iterative hash function to the symbol's name. Starting with an
47413 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
47414 the string is incorporated into the hash using the formula depending on the
47419 The formula is @code{r = r * 67 + c - 113}.
47421 @item Versions 5 to 7
47422 The formula is @code{r = r * 67 + tolower (c) - 113}.
47425 The terminating @samp{\0} is not incorporated into the hash.
47427 The step size used in the hash table is computed via
47428 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
47429 value, and @samp{size} is the size of the hash table. The step size
47430 is used to find the next candidate slot when handling a hash
47433 The names of C@t{++} symbols in the hash table are canonicalized. We
47434 don't currently have a simple description of the canonicalization
47435 algorithm; if you intend to create new index sections, you must read
47439 The constant pool. This is simply a bunch of bytes. It is organized
47440 so that alignment is correct: CU vectors are stored first, followed by
47443 A CU vector in the constant pool is a sequence of @code{offset_type}
47444 values. The first value is the number of CU indices in the vector.
47445 Each subsequent value is the index and symbol attributes of a CU in
47446 the CU list. This element in the hash table is used to indicate which
47447 CUs define the symbol and how the symbol is used.
47448 See below for the format of each CU index+attributes entry.
47450 A string in the constant pool is zero-terminated.
47453 Attributes were added to CU index values in @code{.gdb_index} version 7.
47454 If a symbol has multiple uses within a CU then there is one
47455 CU index+attributes value for each use.
47457 The format of each CU index+attributes entry is as follows
47463 This is the index of the CU in the CU list.
47465 These bits are reserved for future purposes and must be zero.
47467 The kind of the symbol in the CU.
47471 This value is reserved and should not be used.
47472 By reserving zero the full @code{offset_type} value is backwards compatible
47473 with previous versions of the index.
47475 The symbol is a type.
47477 The symbol is a variable or an enum value.
47479 The symbol is a function.
47481 Any other kind of symbol.
47483 These values are reserved.
47487 This bit is zero if the value is global and one if it is static.
47489 The determination of whether a symbol is global or static is complicated.
47490 The authorative reference is the file @file{dwarf2read.c} in
47491 @value{GDBN} sources.
47495 This pseudo-code describes the computation of a symbol's kind and
47496 global/static attributes in the index.
47499 is_external = get_attribute (die, DW_AT_external);
47500 language = get_attribute (cu_die, DW_AT_language);
47503 case DW_TAG_typedef:
47504 case DW_TAG_base_type:
47505 case DW_TAG_subrange_type:
47509 case DW_TAG_enumerator:
47511 is_static = language != CPLUS;
47513 case DW_TAG_subprogram:
47515 is_static = ! (is_external || language == ADA);
47517 case DW_TAG_constant:
47519 is_static = ! is_external;
47521 case DW_TAG_variable:
47523 is_static = ! is_external;
47525 case DW_TAG_namespace:
47529 case DW_TAG_class_type:
47530 case DW_TAG_interface_type:
47531 case DW_TAG_structure_type:
47532 case DW_TAG_union_type:
47533 case DW_TAG_enumeration_type:
47535 is_static = language != CPLUS;
47543 @appendix Download debugging resources with Debuginfod
47546 @code{debuginfod} is an HTTP server for distributing ELF, DWARF and source
47549 With the @code{debuginfod} client library, @file{libdebuginfod}, @value{GDBN}
47550 can query servers using the build IDs associated with missing debug info,
47551 executables and source files in order to download them on demand.
47553 For instructions on building @value{GDBN} with @file{libdebuginfod},
47554 @pxref{Configure Options,,--with-debuginfod}. @code{debuginfod} is packaged
47555 with @code{elfutils}, starting with version 0.178. See
47556 @uref{https://sourceware.org/elfutils/Debuginfod.html} for more information
47557 regarding @code{debuginfod}.
47560 * Debuginfod Settings:: Configuring debuginfod with @value{GDBN}
47563 @node Debuginfod Settings
47564 @section Debuginfod Settings
47566 @value{GDBN} provides the following commands for configuring @code{debuginfod}.
47569 @kindex set debuginfod enabled
47570 @anchor{set debuginfod enabled}
47571 @item set debuginfod enabled
47572 @itemx set debuginfod enabled on
47573 @cindex enable debuginfod
47574 @value{GDBN} will attempt to query @code{debuginfod} servers when missing debug
47575 info or source files.
47577 @item set debuginfod enabled off
47578 @value{GDBN} will not attempt to query @code{debuginfod} servers when missing
47579 debug info or source files. By default, @code{debuginfod enabled} is set to
47580 @code{off} for non-interactive sessions.
47582 @item set debuginfod enabled ask
47583 @value{GDBN} will prompt the user to enable or disable @code{debuginfod} before
47584 attempting to perform the next query. By default, @code{debuginfod enabled}
47585 is set to @code{ask} for interactive sessions.
47587 @kindex show debuginfod enabled
47588 @item show debuginfod enabled
47589 Display whether @code{debuginfod enabled} is set to @code{on}, @code{off} or
47592 @kindex set debuginfod urls
47593 @cindex configure debuginfod URLs
47594 @item set debuginfod urls
47595 @itemx set debuginfod urls @var{urls}
47596 Set the space-separated list of URLs that @code{debuginfod} will attempt to
47597 query. Only @code{http://}, @code{https://} and @code{file://} protocols
47598 should be used. The default value of @code{debuginfod urls} is copied from
47599 the @var{DEBUGINFOD_URLS} environment variable.
47601 @kindex show debuginfod urls
47602 @item show debuginfod urls
47603 Display the list of URLs that @code{debuginfod} will attempt to query.
47605 @kindex set debuginfod verbose
47606 @cindex debuginfod verbosity
47607 @item set debuginfod verbose
47608 @itemx set debuginfod verbose @var{n}
47609 Enable or disable @code{debuginfod}-related output. Use a non-zero value
47610 to enable and @code{0} to disable. @code{debuginfod} output is shown by
47613 @kindex show debuginfod verbose
47614 @item show debuginfod verbose
47615 Show the current verbosity setting.
47620 @appendix Manual pages
47624 * gdb man:: The GNU Debugger man page
47625 * gdbserver man:: Remote Server for the GNU Debugger man page
47626 * gcore man:: Generate a core file of a running program
47627 * gdbinit man:: gdbinit scripts
47628 * gdb-add-index man:: Add index files to speed up GDB
47634 @c man title gdb The GNU Debugger
47636 @c man begin SYNOPSIS gdb
47637 gdb [OPTIONS] [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
47640 @c man begin DESCRIPTION gdb
47641 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
47642 going on ``inside'' another program while it executes -- or what another
47643 program was doing at the moment it crashed.
47645 @value{GDBN} can do four main kinds of things (plus other things in support of
47646 these) to help you catch bugs in the act:
47650 Start your program, specifying anything that might affect its behavior.
47653 Make your program stop on specified conditions.
47656 Examine what has happened, when your program has stopped.
47659 Change things in your program, so you can experiment with correcting the
47660 effects of one bug and go on to learn about another.
47663 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
47666 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
47667 commands from the terminal until you tell it to exit with the @value{GDBN}
47668 command @code{quit} or @code{exit}. You can get online help from @value{GDBN} itself
47669 by using the command @code{help}.
47671 You can run @code{gdb} with no arguments or options; but the most
47672 usual way to start @value{GDBN} is with one argument or two, specifying an
47673 executable program as the argument:
47679 You can also start with both an executable program and a core file specified:
47685 You can, instead, specify a process ID as a second argument or use option
47686 @code{-p}, if you want to debug a running process:
47694 would attach @value{GDBN} to process @code{1234}. With option @option{-p} you
47695 can omit the @var{program} filename.
47697 Here are some of the most frequently needed @value{GDBN} commands:
47699 @c pod2man highlights the right hand side of the @item lines.
47701 @item break [@var{file}:][@var{function}|@var{line}]
47702 Set a breakpoint at @var{function} or @var{line} (in @var{file}).
47704 @item run [@var{arglist}]
47705 Start your program (with @var{arglist}, if specified).
47708 Backtrace: display the program stack.
47710 @item print @var{expr}
47711 Display the value of an expression.
47714 Continue running your program (after stopping, e.g.@: at a breakpoint).
47717 Execute next program line (after stopping); step @emph{over} any
47718 function calls in the line.
47720 @item edit [@var{file}:]@var{function}
47721 look at the program line where it is presently stopped.
47723 @item list [@var{file}:]@var{function}
47724 type the text of the program in the vicinity of where it is presently stopped.
47727 Execute next program line (after stopping); step @emph{into} any
47728 function calls in the line.
47730 @item help [@var{name}]
47731 Show information about @value{GDBN} command @var{name}, or general information
47732 about using @value{GDBN}.
47736 Exit from @value{GDBN}.
47740 For full details on @value{GDBN},
47741 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47742 by Richard M. Stallman and Roland H. Pesch. The same text is available online
47743 as the @code{gdb} entry in the @code{info} program.
47747 @c man begin OPTIONS gdb
47748 Any arguments other than options specify an executable
47749 file and core file (or process ID); that is, the first argument
47750 encountered with no
47751 associated option flag is equivalent to a @option{--se} option, and the second,
47752 if any, is equivalent to a @option{-c} option if it's the name of a file.
47754 both long and abbreviated forms; both are shown here. The long forms are also
47755 recognized if you truncate them, so long as enough of the option is
47756 present to be unambiguous.
47758 The abbreviated forms are shown here with @samp{-} and long forms are shown
47759 with @samp{--} to reflect how they are shown in @option{--help}. However,
47760 @value{GDBN} recognizes all of the following conventions for most options:
47763 @item --option=@var{value}
47764 @item --option @var{value}
47765 @item -option=@var{value}
47766 @item -option @var{value}
47767 @item --o=@var{value}
47768 @item --o @var{value}
47769 @item -o=@var{value}
47770 @item -o @var{value}
47773 All the options and command line arguments you give are processed
47774 in sequential order. The order makes a difference when the @option{-x}
47780 List all options, with brief explanations.
47782 @item --symbols=@var{file}
47783 @itemx -s @var{file}
47784 Read symbol table from @var{file}.
47787 Enable writing into executable and core files.
47789 @item --exec=@var{file}
47790 @itemx -e @var{file}
47791 Use @var{file} as the executable file to execute when
47792 appropriate, and for examining pure data in conjunction with a core
47795 @item --se=@var{file}
47796 Read symbol table from @var{file} and use it as the executable
47799 @item --core=@var{file}
47800 @itemx -c @var{file}
47801 Use @var{file} as a core dump to examine.
47803 @item --command=@var{file}
47804 @itemx -x @var{file}
47805 Execute @value{GDBN} commands from @var{file}.
47807 @item --eval-command=@var{command}
47808 @item -ex @var{command}
47809 Execute given @value{GDBN} @var{command}.
47811 @item --init-eval-command=@var{command}
47813 Execute @value{GDBN} @var{command} before loading the inferior.
47815 @item --directory=@var{directory}
47816 @itemx -d @var{directory}
47817 Add @var{directory} to the path to search for source files.
47820 Do not execute commands from @file{~/.config/gdb/gdbinit},
47821 @file{~/.gdbinit}, @file{~/.config/gdb/gdbearlyinit}, or
47822 @file{~/.gdbearlyinit}
47826 Do not execute commands from any @file{.gdbinit} or
47827 @file{.gdbearlyinit} initialization files.
47832 ``Quiet''. Do not print the introductory and copyright messages. These
47833 messages are also suppressed in batch mode.
47836 Run in batch mode. Exit with status @code{0} after processing all the command
47837 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
47838 Exit with nonzero status if an error occurs in executing the @value{GDBN}
47839 commands in the command files.
47841 Batch mode may be useful for running @value{GDBN} as a filter, for example to
47842 download and run a program on another computer; in order to make this
47843 more useful, the message
47846 Program exited normally.
47850 (which is ordinarily issued whenever a program running under @value{GDBN} control
47851 terminates) is not issued when running in batch mode.
47853 @item --batch-silent
47854 Run in batch mode, just like @option{--batch}, but totally silent. All @value{GDBN}
47855 output is supressed (stderr is unaffected). This is much quieter than
47856 @option{--silent} and would be useless for an interactive session.
47858 This is particularly useful when using targets that give @samp{Loading section}
47859 messages, for example.
47861 Note that targets that give their output via @value{GDBN}, as opposed to writing
47862 directly to @code{stdout}, will also be made silent.
47864 @item --args @var{prog} [@var{arglist}]
47865 Change interpretation of command line so that arguments following this
47866 option are passed as arguments to the inferior. As an example, take
47867 the following command:
47874 It would start @value{GDBN} with @option{-q}, not printing the introductory message. On
47875 the other hand, using:
47878 gdb --args ./a.out -q
47882 starts @value{GDBN} with the introductory message, and passes the option to the inferior.
47884 @item --pid=@var{pid}
47885 Attach @value{GDBN} to an already running program, with the PID @var{pid}.
47888 Open the terminal user interface.
47891 Read all symbols from the given symfile on the first access.
47894 Do not read symbol files.
47896 @item --return-child-result
47897 @value{GDBN}'s exit code will be the same as the child's exit code.
47899 @item --configuration
47900 Print details about GDB configuration and then exit.
47903 Print version information and then exit.
47905 @item --cd=@var{directory}
47906 Run @value{GDBN} using @var{directory} as its working directory,
47907 instead of the current directory.
47909 @item --data-directory=@var{directory}
47911 Run @value{GDBN} using @var{directory} as its data directory. The data
47912 directory is where @value{GDBN} searches for its auxiliary files.
47916 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
47917 @value{GDBN} to output the full file name and line number in a standard,
47918 recognizable fashion each time a stack frame is displayed (which
47919 includes each time the program stops). This recognizable format looks
47920 like two @samp{\032} characters, followed by the file name, line number
47921 and character position separated by colons, and a newline. The
47922 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
47923 characters as a signal to display the source code for the frame.
47925 @item -b @var{baudrate}
47926 Set the line speed (baud rate or bits per second) of any serial
47927 interface used by @value{GDBN} for remote debugging.
47929 @item -l @var{timeout}
47930 Set timeout, in seconds, for remote debugging.
47932 @item --tty=@var{device}
47933 Run using @var{device} for your program's standard input and output.
47937 @c man begin SEEALSO gdb
47939 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
47940 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
47941 documentation are properly installed at your site, the command
47948 should give you access to the complete manual.
47950 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
47951 Richard M. Stallman and Roland H. Pesch, July 1991.
47955 @node gdbserver man
47956 @heading gdbserver man
47958 @c man title gdbserver Remote Server for the GNU Debugger
47960 @c man begin SYNOPSIS gdbserver
47961 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
47963 gdbserver --attach @var{comm} @var{pid}
47965 gdbserver --multi @var{comm}
47969 @c man begin DESCRIPTION gdbserver
47970 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
47971 than the one which is running the program being debugged.
47974 @subheading Usage (server (target) side)
47977 Usage (server (target) side):
47980 First, you need to have a copy of the program you want to debug put onto
47981 the target system. The program can be stripped to save space if needed, as
47982 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
47983 the @value{GDBN} running on the host system.
47985 To use the server, you log on to the target system, and run the @command{gdbserver}
47986 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
47987 your program, and (c) its arguments. The general syntax is:
47990 target> gdbserver @var{comm} @var{program} [@var{args} ...]
47993 For example, using a serial port, you might say:
47997 @c @file would wrap it as F</dev/com1>.
47998 target> gdbserver /dev/com1 emacs foo.txt
48001 target> gdbserver @file{/dev/com1} emacs foo.txt
48005 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
48006 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
48007 waits patiently for the host @value{GDBN} to communicate with it.
48009 To use a TCP connection, you could say:
48012 target> gdbserver host:2345 emacs foo.txt
48015 This says pretty much the same thing as the last example, except that we are
48016 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
48017 that we are expecting to see a TCP connection from @code{host} to local TCP port
48018 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
48019 want for the port number as long as it does not conflict with any existing TCP
48020 ports on the target system. This same port number must be used in the host
48021 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
48022 you chose a port number that conflicts with another service, @command{gdbserver} will
48023 print an error message and exit.
48025 @command{gdbserver} can also attach to running programs.
48026 This is accomplished via the @option{--attach} argument. The syntax is:
48029 target> gdbserver --attach @var{comm} @var{pid}
48032 @var{pid} is the process ID of a currently running process. It isn't
48033 necessary to point @command{gdbserver} at a binary for the running process.
48035 To start @code{gdbserver} without supplying an initial command to run
48036 or process ID to attach, use the @option{--multi} command line option.
48037 In such case you should connect using @kbd{target extended-remote} to start
48038 the program you want to debug.
48041 target> gdbserver --multi @var{comm}
48045 @subheading Usage (host side)
48051 You need an unstripped copy of the target program on your host system, since
48052 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
48053 would, with the target program as the first argument. (You may need to use the
48054 @option{--baud} option if the serial line is running at anything except 9600 baud.)
48055 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
48056 new command you need to know about is @code{target remote}
48057 (or @code{target extended-remote}). Its argument is either
48058 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
48059 descriptor. For example:
48063 @c @file would wrap it as F</dev/ttyb>.
48064 (gdb) target remote /dev/ttyb
48067 (gdb) target remote @file{/dev/ttyb}
48072 communicates with the server via serial line @file{/dev/ttyb}, and:
48075 (gdb) target remote the-target:2345
48079 communicates via a TCP connection to port 2345 on host `the-target', where
48080 you previously started up @command{gdbserver} with the same port number. Note that for
48081 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
48082 command, otherwise you may get an error that looks something like
48083 `Connection refused'.
48085 @command{gdbserver} can also debug multiple inferiors at once,
48088 the @value{GDBN} manual in node @code{Inferiors Connections and Programs}
48089 -- shell command @code{info -f gdb -n 'Inferiors Connections and Programs'}.
48092 @ref{Inferiors Connections and Programs}.
48094 In such case use the @code{extended-remote} @value{GDBN} command variant:
48097 (gdb) target extended-remote the-target:2345
48100 The @command{gdbserver} option @option{--multi} may or may not be used in such
48104 @c man begin OPTIONS gdbserver
48105 There are three different modes for invoking @command{gdbserver}:
48110 Debug a specific program specified by its program name:
48113 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
48116 The @var{comm} parameter specifies how should the server communicate
48117 with @value{GDBN}; it is either a device name (to use a serial line),
48118 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
48119 stdin/stdout of @code{gdbserver}. Specify the name of the program to
48120 debug in @var{prog}. Any remaining arguments will be passed to the
48121 program verbatim. When the program exits, @value{GDBN} will close the
48122 connection, and @code{gdbserver} will exit.
48125 Debug a specific program by specifying the process ID of a running
48129 gdbserver --attach @var{comm} @var{pid}
48132 The @var{comm} parameter is as described above. Supply the process ID
48133 of a running program in @var{pid}; @value{GDBN} will do everything
48134 else. Like with the previous mode, when the process @var{pid} exits,
48135 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
48138 Multi-process mode -- debug more than one program/process:
48141 gdbserver --multi @var{comm}
48144 In this mode, @value{GDBN} can instruct @command{gdbserver} which
48145 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
48146 close the connection when a process being debugged exits, so you can
48147 debug several processes in the same session.
48150 In each of the modes you may specify these options:
48155 List all options, with brief explanations.
48158 This option causes @command{gdbserver} to print its version number and exit.
48161 @command{gdbserver} will attach to a running program. The syntax is:
48164 target> gdbserver --attach @var{comm} @var{pid}
48167 @var{pid} is the process ID of a currently running process. It isn't
48168 necessary to point @command{gdbserver} at a binary for the running process.
48171 To start @code{gdbserver} without supplying an initial command to run
48172 or process ID to attach, use this command line option.
48173 Then you can connect using @kbd{target extended-remote} and start
48174 the program you want to debug. The syntax is:
48177 target> gdbserver --multi @var{comm}
48181 Instruct @code{gdbserver} to display extra status information about the debugging
48183 This option is intended for @code{gdbserver} development and for bug reports to
48186 @item --remote-debug
48187 Instruct @code{gdbserver} to display remote protocol debug output.
48188 This option is intended for @code{gdbserver} development and for bug reports to
48191 @item --debug-file=@var{filename}
48192 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
48193 This option is intended for @code{gdbserver} development and for bug reports to
48196 @item --debug-format=option1@r{[},option2,...@r{]}
48197 Instruct @code{gdbserver} to include extra information in each line
48198 of debugging output.
48199 @xref{Other Command-Line Arguments for gdbserver}.
48202 Specify a wrapper to launch programs
48203 for debugging. The option should be followed by the name of the
48204 wrapper, then any command-line arguments to pass to the wrapper, then
48205 @kbd{--} indicating the end of the wrapper arguments.
48208 By default, @command{gdbserver} keeps the listening TCP port open, so that
48209 additional connections are possible. However, if you start @code{gdbserver}
48210 with the @option{--once} option, it will stop listening for any further
48211 connection attempts after connecting to the first @value{GDBN} session.
48213 @c --disable-packet is not documented for users.
48215 @c --disable-randomization and --no-disable-randomization are superseded by
48216 @c QDisableRandomization.
48221 @c man begin SEEALSO gdbserver
48223 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48224 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48225 documentation are properly installed at your site, the command
48231 should give you access to the complete manual.
48233 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48234 Richard M. Stallman and Roland H. Pesch, July 1991.
48241 @c man title gcore Generate a core file of a running program
48244 @c man begin SYNOPSIS gcore
48245 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
48249 @c man begin DESCRIPTION gcore
48250 Generate core dumps of one or more running programs with process IDs
48251 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
48252 is equivalent to one produced by the kernel when the process crashes
48253 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
48254 limit). However, unlike after a crash, after @command{gcore} finishes
48255 its job the program remains running without any change.
48258 @c man begin OPTIONS gcore
48261 Dump all memory mappings. The actual effect of this option depends on
48262 the Operating System. On @sc{gnu}/Linux, it will disable
48263 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
48264 enable @code{dump-excluded-mappings} (@pxref{set
48265 dump-excluded-mappings}).
48267 @item -o @var{prefix}
48268 The optional argument @var{prefix} specifies the prefix to be used
48269 when composing the file names of the core dumps. The file name is
48270 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
48271 process ID of the running program being analyzed by @command{gcore}.
48272 If not specified, @var{prefix} defaults to @var{gcore}.
48276 @c man begin SEEALSO gcore
48278 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48279 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48280 documentation are properly installed at your site, the command
48287 should give you access to the complete manual.
48289 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48290 Richard M. Stallman and Roland H. Pesch, July 1991.
48297 @c man title gdbinit GDB initialization scripts
48300 @c man begin SYNOPSIS gdbinit
48301 @ifset SYSTEM_GDBINIT
48302 @value{SYSTEM_GDBINIT}
48305 @ifset SYSTEM_GDBINIT_DIR
48306 @value{SYSTEM_GDBINIT_DIR}/*
48309 ~/.config/gdb/gdbinit
48317 @c man begin DESCRIPTION gdbinit
48318 These files contain @value{GDBN} commands to automatically execute during
48319 @value{GDBN} startup. The lines of contents are canned sequences of commands,
48322 the @value{GDBN} manual in node @code{Sequences}
48323 -- shell command @code{info -f gdb -n Sequences}.
48329 Please read more in
48331 the @value{GDBN} manual in node @code{Startup}
48332 -- shell command @code{info -f gdb -n Startup}.
48339 @ifset SYSTEM_GDBINIT
48340 @item @value{SYSTEM_GDBINIT}
48342 @ifclear SYSTEM_GDBINIT
48343 @item (not enabled with @code{--with-system-gdbinit} during compilation)
48345 System-wide initialization file. It is executed unless user specified
48346 @value{GDBN} option @code{-nx} or @code{-n}.
48349 the @value{GDBN} manual in node @code{System-wide configuration}
48350 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48352 @ifset SYSTEM_GDBINIT_DIR
48353 @item @value{SYSTEM_GDBINIT_DIR}
48355 @ifclear SYSTEM_GDBINIT_DIR
48356 @item (not enabled with @code{--with-system-gdbinit-dir} during compilation)
48358 System-wide initialization directory. All files in this directory are
48359 executed on startup unless user specified @value{GDBN} option @code{-nx} or
48360 @code{-n}, as long as they have a recognized file extension.
48363 the @value{GDBN} manual in node @code{System-wide configuration}
48364 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
48367 @ref{System-wide configuration}.
48370 @item @file{~/.config/gdb/gdbinit} or @file{~/.gdbinit}
48371 User initialization file. It is executed unless user specified
48372 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
48374 @item @file{.gdbinit}
48375 Initialization file for current directory. It may need to be enabled with
48376 @value{GDBN} security command @code{set auto-load local-gdbinit}.
48379 the @value{GDBN} manual in node @code{Init File in the Current Directory}
48380 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
48383 @ref{Init File in the Current Directory}.
48388 @c man begin SEEALSO gdbinit
48390 gdb(1), @code{info -f gdb -n Startup}
48392 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48393 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48394 documentation are properly installed at your site, the command
48400 should give you access to the complete manual.
48402 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48403 Richard M. Stallman and Roland H. Pesch, July 1991.
48407 @node gdb-add-index man
48408 @heading gdb-add-index
48409 @pindex gdb-add-index
48410 @anchor{gdb-add-index}
48412 @c man title gdb-add-index Add index files to speed up GDB
48414 @c man begin SYNOPSIS gdb-add-index
48415 gdb-add-index @var{filename}
48418 @c man begin DESCRIPTION gdb-add-index
48419 When @value{GDBN} finds a symbol file, it scans the symbols in the
48420 file in order to construct an internal symbol table. This lets most
48421 @value{GDBN} operations work quickly--at the cost of a delay early on.
48422 For large programs, this delay can be quite lengthy, so @value{GDBN}
48423 provides a way to build an index, which speeds up startup.
48425 To determine whether a file contains such an index, use the command
48426 @kbd{readelf -S filename}: the index is stored in a section named
48427 @code{.gdb_index}. The index file can only be produced on systems
48428 which use ELF binaries and DWARF debug information (i.e., sections
48429 named @code{.debug_*}).
48431 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
48432 in the @env{PATH} environment variable. If you want to use different
48433 versions of these programs, you can specify them through the
48434 @env{GDB} and @env{OBJDUMP} environment variables.
48438 the @value{GDBN} manual in node @code{Index Files}
48439 -- shell command @kbd{info -f gdb -n "Index Files"}.
48446 @c man begin SEEALSO gdb-add-index
48448 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
48449 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
48450 documentation are properly installed at your site, the command
48456 should give you access to the complete manual.
48458 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
48459 Richard M. Stallman and Roland H. Pesch, July 1991.
48465 @node GNU Free Documentation License
48466 @appendix GNU Free Documentation License
48469 @node Concept Index
48470 @unnumbered Concept Index
48474 @node Command and Variable Index
48475 @unnumbered Command, Variable, and Function Index
48480 % I think something like @@colophon should be in texinfo. In the
48482 \long\def\colophon{\hbox to0pt{}\vfill
48483 \centerline{The body of this manual is set in}
48484 \centerline{\fontname\tenrm,}
48485 \centerline{with headings in {\bf\fontname\tenbf}}
48486 \centerline{and examples in {\tt\fontname\tentt}.}
48487 \centerline{{\it\fontname\tenit\/},}
48488 \centerline{{\bf\fontname\tenbf}, and}
48489 \centerline{{\sl\fontname\tensl\/}}
48490 \centerline{are used for emphasis.}\vfill}
48492 % Blame: doc@@cygnus.com, 1991.