1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2018 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{} 1988-2018 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 @*
111 @node Top, Summary, (dir), (dir)
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) 1988-2018 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
544 Initial support for the FreeBSD/mips target and native configuration
545 was developed by SRI International and the University of Cambridge
546 Computer Laboratory under DARPA/AFRL contract FA8750-10-C-0237
547 ("CTSRD"), as part of the DARPA CRASH research programme.
549 Initial support for the FreeBSD/riscv target and native configuration
550 was developed by SRI International and the University of Cambridge
551 Computer Laboratory (Department of Computer Science and Technology)
552 under DARPA contract HR0011-18-C-0016 ("ECATS"), as part of the DARPA
553 SSITH research programme.
555 The original port to the OpenRISC 1000 is believed to be due to
556 Alessandro Forin and Per Bothner. More recent ports have been the work
557 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
561 @chapter A Sample @value{GDBN} Session
563 You can use this manual at your leisure to read all about @value{GDBN}.
564 However, a handful of commands are enough to get started using the
565 debugger. This chapter illustrates those commands.
568 In this sample session, we emphasize user input like this: @b{input},
569 to make it easier to pick out from the surrounding output.
572 @c FIXME: this example may not be appropriate for some configs, where
573 @c FIXME...primary interest is in remote use.
575 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
576 processor) exhibits the following bug: sometimes, when we change its
577 quote strings from the default, the commands used to capture one macro
578 definition within another stop working. In the following short @code{m4}
579 session, we define a macro @code{foo} which expands to @code{0000}; we
580 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
581 same thing. However, when we change the open quote string to
582 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
583 procedure fails to define a new synonym @code{baz}:
592 @b{define(bar,defn(`foo'))}
596 @b{changequote(<QUOTE>,<UNQUOTE>)}
598 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
601 m4: End of input: 0: fatal error: EOF in string
605 Let us use @value{GDBN} to try to see what is going on.
608 $ @b{@value{GDBP} m4}
609 @c FIXME: this falsifies the exact text played out, to permit smallbook
610 @c FIXME... format to come out better.
611 @value{GDBN} is free software and you are welcome to distribute copies
612 of it under certain conditions; type "show copying" to see
614 There is absolutely no warranty for @value{GDBN}; type "show warranty"
617 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
622 @value{GDBN} reads only enough symbol data to know where to find the
623 rest when needed; as a result, the first prompt comes up very quickly.
624 We now tell @value{GDBN} to use a narrower display width than usual, so
625 that examples fit in this manual.
628 (@value{GDBP}) @b{set width 70}
632 We need to see how the @code{m4} built-in @code{changequote} works.
633 Having looked at the source, we know the relevant subroutine is
634 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
635 @code{break} command.
638 (@value{GDBP}) @b{break m4_changequote}
639 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
643 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
644 control; as long as control does not reach the @code{m4_changequote}
645 subroutine, the program runs as usual:
648 (@value{GDBP}) @b{run}
649 Starting program: /work/Editorial/gdb/gnu/m4/m4
657 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
658 suspends execution of @code{m4}, displaying information about the
659 context where it stops.
662 @b{changequote(<QUOTE>,<UNQUOTE>)}
664 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
666 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
670 Now we use the command @code{n} (@code{next}) to advance execution to
671 the next line of the current function.
675 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
680 @code{set_quotes} looks like a promising subroutine. We can go into it
681 by using the command @code{s} (@code{step}) instead of @code{next}.
682 @code{step} goes to the next line to be executed in @emph{any}
683 subroutine, so it steps into @code{set_quotes}.
687 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
689 530 if (lquote != def_lquote)
693 The display that shows the subroutine where @code{m4} is now
694 suspended (and its arguments) is called a stack frame display. It
695 shows a summary of the stack. We can use the @code{backtrace}
696 command (which can also be spelled @code{bt}), to see where we are
697 in the stack as a whole: the @code{backtrace} command displays a
698 stack frame for each active subroutine.
701 (@value{GDBP}) @b{bt}
702 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
704 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
706 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
707 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
709 #4 0x79dc in expand_input () at macro.c:40
710 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
714 We step through a few more lines to see what happens. The first two
715 times, we can use @samp{s}; the next two times we use @code{n} to avoid
716 falling into the @code{xstrdup} subroutine.
720 0x3b5c 532 if (rquote != def_rquote)
722 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
723 def_lquote : xstrdup(lq);
725 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
728 538 len_lquote = strlen(rquote);
732 The last line displayed looks a little odd; we can examine the variables
733 @code{lquote} and @code{rquote} to see if they are in fact the new left
734 and right quotes we specified. We use the command @code{p}
735 (@code{print}) to see their values.
738 (@value{GDBP}) @b{p lquote}
739 $1 = 0x35d40 "<QUOTE>"
740 (@value{GDBP}) @b{p rquote}
741 $2 = 0x35d50 "<UNQUOTE>"
745 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
746 To look at some context, we can display ten lines of source
747 surrounding the current line with the @code{l} (@code{list}) command.
753 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
755 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
758 538 len_lquote = strlen(rquote);
759 539 len_rquote = strlen(lquote);
766 Let us step past the two lines that set @code{len_lquote} and
767 @code{len_rquote}, and then examine the values of those variables.
771 539 len_rquote = strlen(lquote);
774 (@value{GDBP}) @b{p len_lquote}
776 (@value{GDBP}) @b{p len_rquote}
781 That certainly looks wrong, assuming @code{len_lquote} and
782 @code{len_rquote} are meant to be the lengths of @code{lquote} and
783 @code{rquote} respectively. We can set them to better values using
784 the @code{p} command, since it can print the value of
785 any expression---and that expression can include subroutine calls and
789 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
791 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
796 Is that enough to fix the problem of using the new quotes with the
797 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
798 executing with the @code{c} (@code{continue}) command, and then try the
799 example that caused trouble initially:
805 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
812 Success! The new quotes now work just as well as the default ones. The
813 problem seems to have been just the two typos defining the wrong
814 lengths. We allow @code{m4} exit by giving it an EOF as input:
818 Program exited normally.
822 The message @samp{Program exited normally.} is from @value{GDBN}; it
823 indicates @code{m4} has finished executing. We can end our @value{GDBN}
824 session with the @value{GDBN} @code{quit} command.
827 (@value{GDBP}) @b{quit}
831 @chapter Getting In and Out of @value{GDBN}
833 This chapter discusses how to start @value{GDBN}, and how to get out of it.
837 type @samp{@value{GDBP}} to start @value{GDBN}.
839 type @kbd{quit} or @kbd{Ctrl-d} to exit.
843 * Invoking GDB:: How to start @value{GDBN}
844 * Quitting GDB:: How to quit @value{GDBN}
845 * Shell Commands:: How to use shell commands inside @value{GDBN}
846 * Logging Output:: How to log @value{GDBN}'s output to a file
850 @section Invoking @value{GDBN}
852 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
853 @value{GDBN} reads commands from the terminal until you tell it to exit.
855 You can also run @code{@value{GDBP}} with a variety of arguments and options,
856 to specify more of your debugging environment at the outset.
858 The command-line options described here are designed
859 to cover a variety of situations; in some environments, some of these
860 options may effectively be unavailable.
862 The most usual way to start @value{GDBN} is with one argument,
863 specifying an executable program:
866 @value{GDBP} @var{program}
870 You can also start with both an executable program and a core file
874 @value{GDBP} @var{program} @var{core}
877 You can, instead, specify a process ID as a second argument, if you want
878 to debug a running process:
881 @value{GDBP} @var{program} 1234
885 would attach @value{GDBN} to process @code{1234} (unless you also have a file
886 named @file{1234}; @value{GDBN} does check for a core file first).
888 Taking advantage of the second command-line argument requires a fairly
889 complete operating system; when you use @value{GDBN} as a remote
890 debugger attached to a bare board, there may not be any notion of
891 ``process'', and there is often no way to get a core dump. @value{GDBN}
892 will warn you if it is unable to attach or to read core dumps.
894 You can optionally have @code{@value{GDBP}} pass any arguments after the
895 executable file to the inferior using @code{--args}. This option stops
898 @value{GDBP} --args gcc -O2 -c foo.c
900 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
901 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
903 You can run @code{@value{GDBP}} without printing the front material, which describes
904 @value{GDBN}'s non-warranty, by specifying @code{--silent}
905 (or @code{-q}/@code{--quiet}):
908 @value{GDBP} --silent
912 You can further control how @value{GDBN} starts up by using command-line
913 options. @value{GDBN} itself can remind you of the options available.
923 to display all available options and briefly describe their use
924 (@samp{@value{GDBP} -h} is a shorter equivalent).
926 All options and command line arguments you give are processed
927 in sequential order. The order makes a difference when the
928 @samp{-x} option is used.
932 * File Options:: Choosing files
933 * Mode Options:: Choosing modes
934 * Startup:: What @value{GDBN} does during startup
938 @subsection Choosing Files
940 When @value{GDBN} starts, it reads any arguments other than options as
941 specifying an executable file and core file (or process ID). This is
942 the same as if the arguments were specified by the @samp{-se} and
943 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
944 first argument that does not have an associated option flag as
945 equivalent to the @samp{-se} option followed by that argument; and the
946 second argument that does not have an associated option flag, if any, as
947 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
948 If the second argument begins with a decimal digit, @value{GDBN} will
949 first attempt to attach to it as a process, and if that fails, attempt
950 to open it as a corefile. If you have a corefile whose name begins with
951 a digit, you can prevent @value{GDBN} from treating it as a pid by
952 prefixing it with @file{./}, e.g.@: @file{./12345}.
954 If @value{GDBN} has not been configured to included core file support,
955 such as for most embedded targets, then it will complain about a second
956 argument and ignore it.
958 Many options have both long and short forms; both are shown in the
959 following list. @value{GDBN} also recognizes the long forms if you truncate
960 them, so long as enough of the option is present to be unambiguous.
961 (If you prefer, you can flag option arguments with @samp{--} rather
962 than @samp{-}, though we illustrate the more usual convention.)
964 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
965 @c way, both those who look for -foo and --foo in the index, will find
969 @item -symbols @var{file}
971 @cindex @code{--symbols}
973 Read symbol table from file @var{file}.
975 @item -exec @var{file}
977 @cindex @code{--exec}
979 Use file @var{file} as the executable file to execute when appropriate,
980 and for examining pure data in conjunction with a core dump.
984 Read symbol table from file @var{file} and use it as the executable
987 @item -core @var{file}
989 @cindex @code{--core}
991 Use file @var{file} as a core dump to examine.
993 @item -pid @var{number}
994 @itemx -p @var{number}
997 Connect to process ID @var{number}, as with the @code{attach} command.
999 @item -command @var{file}
1000 @itemx -x @var{file}
1001 @cindex @code{--command}
1003 Execute commands from file @var{file}. The contents of this file is
1004 evaluated exactly as the @code{source} command would.
1005 @xref{Command Files,, Command files}.
1007 @item -eval-command @var{command}
1008 @itemx -ex @var{command}
1009 @cindex @code{--eval-command}
1011 Execute a single @value{GDBN} command.
1013 This option may be used multiple times to call multiple commands. It may
1014 also be interleaved with @samp{-command} as required.
1017 @value{GDBP} -ex 'target sim' -ex 'load' \
1018 -x setbreakpoints -ex 'run' a.out
1021 @item -init-command @var{file}
1022 @itemx -ix @var{file}
1023 @cindex @code{--init-command}
1025 Execute commands from file @var{file} before loading the inferior (but
1026 after loading gdbinit files).
1029 @item -init-eval-command @var{command}
1030 @itemx -iex @var{command}
1031 @cindex @code{--init-eval-command}
1033 Execute a single @value{GDBN} command before loading the inferior (but
1034 after loading gdbinit files).
1037 @item -directory @var{directory}
1038 @itemx -d @var{directory}
1039 @cindex @code{--directory}
1041 Add @var{directory} to the path to search for source and script files.
1045 @cindex @code{--readnow}
1047 Read each symbol file's entire symbol table immediately, rather than
1048 the default, which is to read it incrementally as it is needed.
1049 This makes startup slower, but makes future operations faster.
1052 @anchor{--readnever}
1053 @cindex @code{--readnever}, command-line option
1054 Do not read each symbol file's symbolic debug information. This makes
1055 startup faster but at the expense of not being able to perform
1056 symbolic debugging. DWARF unwind information is also not read,
1057 meaning backtraces may become incomplete or inaccurate. One use of
1058 this is when a user simply wants to do the following sequence: attach,
1059 dump core, detach. Loading the debugging information in this case is
1060 an unnecessary cause of delay.
1064 @subsection Choosing Modes
1066 You can run @value{GDBN} in various alternative modes---for example, in
1067 batch mode or quiet mode.
1075 Do not execute commands found in any initialization file.
1076 There are three init files, loaded in the following order:
1079 @item @file{system.gdbinit}
1080 This is the system-wide init file.
1081 Its location is specified with the @code{--with-system-gdbinit}
1082 configure option (@pxref{System-wide configuration}).
1083 It is loaded first when @value{GDBN} starts, before command line options
1084 have been processed.
1085 @item @file{~/.gdbinit}
1086 This is the init file in your home directory.
1087 It is loaded next, after @file{system.gdbinit}, and before
1088 command options have been processed.
1089 @item @file{./.gdbinit}
1090 This is the init file in the current directory.
1091 It is loaded last, after command line options other than @code{-x} and
1092 @code{-ex} have been processed. Command line options @code{-x} and
1093 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1096 For further documentation on startup processing, @xref{Startup}.
1097 For documentation on how to write command files,
1098 @xref{Command Files,,Command Files}.
1103 Do not execute commands found in @file{~/.gdbinit}, the init file
1104 in your home directory.
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.
1117 @cindex @code{--batch}
1118 Run in batch mode. Exit with status @code{0} after processing all the
1119 command files specified with @samp{-x} (and all commands from
1120 initialization files, if not inhibited with @samp{-n}). Exit with
1121 nonzero status if an error occurs in executing the @value{GDBN} commands
1122 in the command files. Batch mode also disables pagination, sets unlimited
1123 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1124 off} were in effect (@pxref{Messages/Warnings}).
1126 Batch mode may be useful for running @value{GDBN} as a filter, for
1127 example to download and run a program on another computer; in order to
1128 make this more useful, the message
1131 Program exited normally.
1135 (which is ordinarily issued whenever a program running under
1136 @value{GDBN} control terminates) is not issued when running in batch
1140 @cindex @code{--batch-silent}
1141 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1142 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1143 unaffected). This is much quieter than @samp{-silent} and would be useless
1144 for an interactive session.
1146 This is particularly useful when using targets that give @samp{Loading section}
1147 messages, for example.
1149 Note that targets that give their output via @value{GDBN}, as opposed to
1150 writing directly to @code{stdout}, will also be made silent.
1152 @item -return-child-result
1153 @cindex @code{--return-child-result}
1154 The return code from @value{GDBN} will be the return code from the child
1155 process (the process being debugged), with the following exceptions:
1159 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1160 internal error. In this case the exit code is the same as it would have been
1161 without @samp{-return-child-result}.
1163 The user quits with an explicit value. E.g., @samp{quit 1}.
1165 The child process never runs, or is not allowed to terminate, in which case
1166 the exit code will be -1.
1169 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1170 when @value{GDBN} is being used as a remote program loader or simulator
1175 @cindex @code{--nowindows}
1177 ``No windows''. If @value{GDBN} comes with a graphical user interface
1178 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1179 interface. If no GUI is available, this option has no effect.
1183 @cindex @code{--windows}
1185 If @value{GDBN} includes a GUI, then this option requires it to be
1188 @item -cd @var{directory}
1190 Run @value{GDBN} using @var{directory} as its working directory,
1191 instead of the current directory.
1193 @item -data-directory @var{directory}
1194 @itemx -D @var{directory}
1195 @cindex @code{--data-directory}
1197 Run @value{GDBN} using @var{directory} as its data directory.
1198 The data directory is where @value{GDBN} searches for its
1199 auxiliary files. @xref{Data Files}.
1203 @cindex @code{--fullname}
1205 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1206 subprocess. It tells @value{GDBN} to output the full file name and line
1207 number in a standard, recognizable fashion each time a stack frame is
1208 displayed (which includes each time your program stops). This
1209 recognizable format looks like two @samp{\032} characters, followed by
1210 the file name, line number and character position separated by colons,
1211 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1212 @samp{\032} characters as a signal to display the source code for the
1215 @item -annotate @var{level}
1216 @cindex @code{--annotate}
1217 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1218 effect is identical to using @samp{set annotate @var{level}}
1219 (@pxref{Annotations}). The annotation @var{level} controls how much
1220 information @value{GDBN} prints together with its prompt, values of
1221 expressions, source lines, and other types of output. Level 0 is the
1222 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1223 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1224 that control @value{GDBN}, and level 2 has been deprecated.
1226 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1230 @cindex @code{--args}
1231 Change interpretation of command line so that arguments following the
1232 executable file are passed as command line arguments to the inferior.
1233 This option stops option processing.
1235 @item -baud @var{bps}
1237 @cindex @code{--baud}
1239 Set the line speed (baud rate or bits per second) of any serial
1240 interface used by @value{GDBN} for remote debugging.
1242 @item -l @var{timeout}
1244 Set the timeout (in seconds) of any communication used by @value{GDBN}
1245 for remote debugging.
1247 @item -tty @var{device}
1248 @itemx -t @var{device}
1249 @cindex @code{--tty}
1251 Run using @var{device} for your program's standard input and output.
1252 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1254 @c resolve the situation of these eventually
1256 @cindex @code{--tui}
1257 Activate the @dfn{Text User Interface} when starting. The Text User
1258 Interface manages several text windows on the terminal, showing
1259 source, assembly, registers and @value{GDBN} command outputs
1260 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1261 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1262 Using @value{GDBN} under @sc{gnu} Emacs}).
1264 @item -interpreter @var{interp}
1265 @cindex @code{--interpreter}
1266 Use the interpreter @var{interp} for interface with the controlling
1267 program or device. This option is meant to be set by programs which
1268 communicate with @value{GDBN} using it as a back end.
1269 @xref{Interpreters, , Command Interpreters}.
1271 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1272 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1273 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1274 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1275 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1276 @sc{gdb/mi} interfaces are no longer supported.
1279 @cindex @code{--write}
1280 Open the executable and core files for both reading and writing. This
1281 is equivalent to the @samp{set write on} command inside @value{GDBN}
1285 @cindex @code{--statistics}
1286 This option causes @value{GDBN} to print statistics about time and
1287 memory usage after it completes each command and returns to the prompt.
1290 @cindex @code{--version}
1291 This option causes @value{GDBN} to print its version number and
1292 no-warranty blurb, and exit.
1294 @item -configuration
1295 @cindex @code{--configuration}
1296 This option causes @value{GDBN} to print details about its build-time
1297 configuration parameters, and then exit. These details can be
1298 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1303 @subsection What @value{GDBN} Does During Startup
1304 @cindex @value{GDBN} startup
1306 Here's the description of what @value{GDBN} does during session startup:
1310 Sets up the command interpreter as specified by the command line
1311 (@pxref{Mode Options, interpreter}).
1315 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1316 used when building @value{GDBN}; @pxref{System-wide configuration,
1317 ,System-wide configuration and settings}) and executes all the commands in
1320 @anchor{Home Directory Init File}
1322 Reads the init file (if any) in your home directory@footnote{On
1323 DOS/Windows systems, the home directory is the one pointed to by the
1324 @code{HOME} environment variable.} and executes all the commands in
1327 @anchor{Option -init-eval-command}
1329 Executes commands and command files specified by the @samp{-iex} and
1330 @samp{-ix} options in their specified order. Usually you should use the
1331 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1332 settings before @value{GDBN} init files get executed and before inferior
1336 Processes command line options and operands.
1338 @anchor{Init File in the Current Directory during Startup}
1340 Reads and executes the commands from init file (if any) in the current
1341 working directory as long as @samp{set auto-load local-gdbinit} is set to
1342 @samp{on} (@pxref{Init File in the Current Directory}).
1343 This is only done if the current directory is
1344 different from your home directory. Thus, you can have more than one
1345 init file, one generic in your home directory, and another, specific
1346 to the program you are debugging, in the directory where you invoke
1350 If the command line specified a program to debug, or a process to
1351 attach to, or a core file, @value{GDBN} loads any auto-loaded
1352 scripts provided for the program or for its loaded shared libraries.
1353 @xref{Auto-loading}.
1355 If you wish to disable the auto-loading during startup,
1356 you must do something like the following:
1359 $ gdb -iex "set auto-load python-scripts off" myprogram
1362 Option @samp{-ex} does not work because the auto-loading is then turned
1366 Executes commands and command files specified by the @samp{-ex} and
1367 @samp{-x} options in their specified order. @xref{Command Files}, for
1368 more details about @value{GDBN} command files.
1371 Reads the command history recorded in the @dfn{history file}.
1372 @xref{Command History}, for more details about the command history and the
1373 files where @value{GDBN} records it.
1376 Init files use the same syntax as @dfn{command files} (@pxref{Command
1377 Files}) and are processed by @value{GDBN} in the same way. The init
1378 file in your home directory can set options (such as @samp{set
1379 complaints}) that affect subsequent processing of command line options
1380 and operands. Init files are not executed if you use the @samp{-nx}
1381 option (@pxref{Mode Options, ,Choosing Modes}).
1383 To display the list of init files loaded by gdb at startup, you
1384 can use @kbd{gdb --help}.
1386 @cindex init file name
1387 @cindex @file{.gdbinit}
1388 @cindex @file{gdb.ini}
1389 The @value{GDBN} init files are normally called @file{.gdbinit}.
1390 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1391 the limitations of file names imposed by DOS filesystems. The Windows
1392 port of @value{GDBN} uses the standard name, but if it finds a
1393 @file{gdb.ini} file in your home directory, it warns you about that
1394 and suggests to rename the file to the standard name.
1398 @section Quitting @value{GDBN}
1399 @cindex exiting @value{GDBN}
1400 @cindex leaving @value{GDBN}
1403 @kindex quit @r{[}@var{expression}@r{]}
1404 @kindex q @r{(@code{quit})}
1405 @item quit @r{[}@var{expression}@r{]}
1407 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1408 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1409 do not supply @var{expression}, @value{GDBN} will terminate normally;
1410 otherwise it will terminate using the result of @var{expression} as the
1415 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1416 terminates the action of any @value{GDBN} command that is in progress and
1417 returns to @value{GDBN} command level. It is safe to type the interrupt
1418 character at any time because @value{GDBN} does not allow it to take effect
1419 until a time when it is safe.
1421 If you have been using @value{GDBN} to control an attached process or
1422 device, you can release it with the @code{detach} command
1423 (@pxref{Attach, ,Debugging an Already-running Process}).
1425 @node Shell Commands
1426 @section Shell Commands
1428 If you need to execute occasional shell commands during your
1429 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1430 just use the @code{shell} command.
1435 @cindex shell escape
1436 @item shell @var{command-string}
1437 @itemx !@var{command-string}
1438 Invoke a standard shell to execute @var{command-string}.
1439 Note that no space is needed between @code{!} and @var{command-string}.
1440 If it exists, the environment variable @code{SHELL} determines which
1441 shell to run. Otherwise @value{GDBN} uses the default shell
1442 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1445 The utility @code{make} is often needed in development environments.
1446 You do not have to use the @code{shell} command for this purpose in
1451 @cindex calling make
1452 @item make @var{make-args}
1453 Execute the @code{make} program with the specified
1454 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1457 @node Logging Output
1458 @section Logging Output
1459 @cindex logging @value{GDBN} output
1460 @cindex save @value{GDBN} output to a file
1462 You may want to save the output of @value{GDBN} commands to a file.
1463 There are several commands to control @value{GDBN}'s logging.
1467 @item set logging on
1469 @item set logging off
1471 @cindex logging file name
1472 @item set logging file @var{file}
1473 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1474 @item set logging overwrite [on|off]
1475 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1476 you want @code{set logging on} to overwrite the logfile instead.
1477 @item set logging redirect [on|off]
1478 By default, @value{GDBN} output will go to both the terminal and the logfile.
1479 Set @code{redirect} if you want output to go only to the log file.
1480 @kindex show logging
1482 Show the current values of the logging settings.
1486 @chapter @value{GDBN} Commands
1488 You can abbreviate a @value{GDBN} command to the first few letters of the command
1489 name, if that abbreviation is unambiguous; and you can repeat certain
1490 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1491 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1492 show you the alternatives available, if there is more than one possibility).
1495 * Command Syntax:: How to give commands to @value{GDBN}
1496 * Completion:: Command completion
1497 * Help:: How to ask @value{GDBN} for help
1500 @node Command Syntax
1501 @section Command Syntax
1503 A @value{GDBN} command is a single line of input. There is no limit on
1504 how long it can be. It starts with a command name, which is followed by
1505 arguments whose meaning depends on the command name. For example, the
1506 command @code{step} accepts an argument which is the number of times to
1507 step, as in @samp{step 5}. You can also use the @code{step} command
1508 with no arguments. Some commands do not allow any arguments.
1510 @cindex abbreviation
1511 @value{GDBN} command names may always be truncated if that abbreviation is
1512 unambiguous. Other possible command abbreviations are listed in the
1513 documentation for individual commands. In some cases, even ambiguous
1514 abbreviations are allowed; for example, @code{s} is specially defined as
1515 equivalent to @code{step} even though there are other commands whose
1516 names start with @code{s}. You can test abbreviations by using them as
1517 arguments to the @code{help} command.
1519 @cindex repeating commands
1520 @kindex RET @r{(repeat last command)}
1521 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1522 repeat the previous command. Certain commands (for example, @code{run})
1523 will not repeat this way; these are commands whose unintentional
1524 repetition might cause trouble and which you are unlikely to want to
1525 repeat. User-defined commands can disable this feature; see
1526 @ref{Define, dont-repeat}.
1528 The @code{list} and @code{x} commands, when you repeat them with
1529 @key{RET}, construct new arguments rather than repeating
1530 exactly as typed. This permits easy scanning of source or memory.
1532 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1533 output, in a way similar to the common utility @code{more}
1534 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1535 @key{RET} too many in this situation, @value{GDBN} disables command
1536 repetition after any command that generates this sort of display.
1538 @kindex # @r{(a comment)}
1540 Any text from a @kbd{#} to the end of the line is a comment; it does
1541 nothing. This is useful mainly in command files (@pxref{Command
1542 Files,,Command Files}).
1544 @cindex repeating command sequences
1545 @kindex Ctrl-o @r{(operate-and-get-next)}
1546 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1547 commands. This command accepts the current line, like @key{RET}, and
1548 then fetches the next line relative to the current line from the history
1552 @section Command Completion
1555 @cindex word completion
1556 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1557 only one possibility; it can also show you what the valid possibilities
1558 are for the next word in a command, at any time. This works for @value{GDBN}
1559 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1561 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1562 of a word. If there is only one possibility, @value{GDBN} fills in the
1563 word, and waits for you to finish the command (or press @key{RET} to
1564 enter it). For example, if you type
1566 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1567 @c complete accuracy in these examples; space introduced for clarity.
1568 @c If texinfo enhancements make it unnecessary, it would be nice to
1569 @c replace " @key" by "@key" in the following...
1571 (@value{GDBP}) info bre @key{TAB}
1575 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1576 the only @code{info} subcommand beginning with @samp{bre}:
1579 (@value{GDBP}) info breakpoints
1583 You can either press @key{RET} at this point, to run the @code{info
1584 breakpoints} command, or backspace and enter something else, if
1585 @samp{breakpoints} does not look like the command you expected. (If you
1586 were sure you wanted @code{info breakpoints} in the first place, you
1587 might as well just type @key{RET} immediately after @samp{info bre},
1588 to exploit command abbreviations rather than command completion).
1590 If there is more than one possibility for the next word when you press
1591 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1592 characters and try again, or just press @key{TAB} a second time;
1593 @value{GDBN} displays all the possible completions for that word. For
1594 example, you might want to set a breakpoint on a subroutine whose name
1595 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1596 just sounds the bell. Typing @key{TAB} again displays all the
1597 function names in your program that begin with those characters, for
1601 (@value{GDBP}) b make_ @key{TAB}
1602 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1603 make_a_section_from_file make_environ
1604 make_abs_section make_function_type
1605 make_blockvector make_pointer_type
1606 make_cleanup make_reference_type
1607 make_command make_symbol_completion_list
1608 (@value{GDBP}) b make_
1612 After displaying the available possibilities, @value{GDBN} copies your
1613 partial input (@samp{b make_} in the example) so you can finish the
1616 If you just want to see the list of alternatives in the first place, you
1617 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1618 means @kbd{@key{META} ?}. You can type this either by holding down a
1619 key designated as the @key{META} shift on your keyboard (if there is
1620 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1622 If the number of possible completions is large, @value{GDBN} will
1623 print as much of the list as it has collected, as well as a message
1624 indicating that the list may be truncated.
1627 (@value{GDBP}) b m@key{TAB}@key{TAB}
1629 <... the rest of the possible completions ...>
1630 *** List may be truncated, max-completions reached. ***
1635 This behavior can be controlled with the following commands:
1638 @kindex set max-completions
1639 @item set max-completions @var{limit}
1640 @itemx set max-completions unlimited
1641 Set the maximum number of completion candidates. @value{GDBN} will
1642 stop looking for more completions once it collects this many candidates.
1643 This is useful when completing on things like function names as collecting
1644 all the possible candidates can be time consuming.
1645 The default value is 200. A value of zero disables tab-completion.
1646 Note that setting either no limit or a very large limit can make
1648 @kindex show max-completions
1649 @item show max-completions
1650 Show the maximum number of candidates that @value{GDBN} will collect and show
1654 @cindex quotes in commands
1655 @cindex completion of quoted strings
1656 Sometimes the string you need, while logically a ``word'', may contain
1657 parentheses or other characters that @value{GDBN} normally excludes from
1658 its notion of a word. To permit word completion to work in this
1659 situation, you may enclose words in @code{'} (single quote marks) in
1660 @value{GDBN} commands.
1662 A likely situation where you might need this is in typing an
1663 expression that involves a C@t{++} symbol name with template
1664 parameters. This is because when completing expressions, GDB treats
1665 the @samp{<} character as word delimiter, assuming that it's the
1666 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1669 For example, when you want to call a C@t{++} template function
1670 interactively using the @code{print} or @code{call} commands, you may
1671 need to distinguish whether you mean the version of @code{name} that
1672 was specialized for @code{int}, @code{name<int>()}, or the version
1673 that was specialized for @code{float}, @code{name<float>()}. To use
1674 the word-completion facilities in this situation, type a single quote
1675 @code{'} at the beginning of the function name. This alerts
1676 @value{GDBN} that it may need to consider more information than usual
1677 when you press @key{TAB} or @kbd{M-?} to request word completion:
1680 (@value{GDBP}) p 'func< @kbd{M-?}
1681 func<int>() func<float>()
1682 (@value{GDBP}) p 'func<
1685 When setting breakpoints however (@pxref{Specify Location}), you don't
1686 usually need to type a quote before the function name, because
1687 @value{GDBN} understands that you want to set a breakpoint on a
1691 (@value{GDBP}) b func< @kbd{M-?}
1692 func<int>() func<float>()
1693 (@value{GDBP}) b func<
1696 This is true even in the case of typing the name of C@t{++} overloaded
1697 functions (multiple definitions of the same function, distinguished by
1698 argument type). For example, when you want to set a breakpoint you
1699 don't need to distinguish whether you mean the version of @code{name}
1700 that takes an @code{int} parameter, @code{name(int)}, or the version
1701 that takes a @code{float} parameter, @code{name(float)}.
1704 (@value{GDBP}) b bubble( @kbd{M-?}
1705 bubble(int) bubble(double)
1706 (@value{GDBP}) b bubble(dou @kbd{M-?}
1710 See @ref{quoting names} for a description of other scenarios that
1713 For more information about overloaded functions, see @ref{C Plus Plus
1714 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1715 overload-resolution off} to disable overload resolution;
1716 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1718 @cindex completion of structure field names
1719 @cindex structure field name completion
1720 @cindex completion of union field names
1721 @cindex union field name completion
1722 When completing in an expression which looks up a field in a
1723 structure, @value{GDBN} also tries@footnote{The completer can be
1724 confused by certain kinds of invalid expressions. Also, it only
1725 examines the static type of the expression, not the dynamic type.} to
1726 limit completions to the field names available in the type of the
1730 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1731 magic to_fputs to_rewind
1732 to_data to_isatty to_write
1733 to_delete to_put to_write_async_safe
1738 This is because the @code{gdb_stdout} is a variable of the type
1739 @code{struct ui_file} that is defined in @value{GDBN} sources as
1746 ui_file_flush_ftype *to_flush;
1747 ui_file_write_ftype *to_write;
1748 ui_file_write_async_safe_ftype *to_write_async_safe;
1749 ui_file_fputs_ftype *to_fputs;
1750 ui_file_read_ftype *to_read;
1751 ui_file_delete_ftype *to_delete;
1752 ui_file_isatty_ftype *to_isatty;
1753 ui_file_rewind_ftype *to_rewind;
1754 ui_file_put_ftype *to_put;
1761 @section Getting Help
1762 @cindex online documentation
1765 You can always ask @value{GDBN} itself for information on its commands,
1766 using the command @code{help}.
1769 @kindex h @r{(@code{help})}
1772 You can use @code{help} (abbreviated @code{h}) with no arguments to
1773 display a short list of named classes of commands:
1777 List of classes of commands:
1779 aliases -- Aliases of other commands
1780 breakpoints -- Making program stop at certain points
1781 data -- Examining data
1782 files -- Specifying and examining files
1783 internals -- Maintenance commands
1784 obscure -- Obscure features
1785 running -- Running the program
1786 stack -- Examining the stack
1787 status -- Status inquiries
1788 support -- Support facilities
1789 tracepoints -- Tracing of program execution without
1790 stopping the program
1791 user-defined -- User-defined commands
1793 Type "help" followed by a class name for a list of
1794 commands in that class.
1795 Type "help" followed by command name for full
1797 Command name abbreviations are allowed if unambiguous.
1800 @c the above line break eliminates huge line overfull...
1802 @item help @var{class}
1803 Using one of the general help classes as an argument, you can get a
1804 list of the individual commands in that class. For example, here is the
1805 help display for the class @code{status}:
1808 (@value{GDBP}) help status
1813 @c Line break in "show" line falsifies real output, but needed
1814 @c to fit in smallbook page size.
1815 info -- Generic command for showing things
1816 about the program being debugged
1817 show -- Generic command for showing things
1820 Type "help" followed by command name for full
1822 Command name abbreviations are allowed if unambiguous.
1826 @item help @var{command}
1827 With a command name as @code{help} argument, @value{GDBN} displays a
1828 short paragraph on how to use that command.
1831 @item apropos @var{args}
1832 The @code{apropos} command searches through all of the @value{GDBN}
1833 commands, and their documentation, for the regular expression specified in
1834 @var{args}. It prints out all matches found. For example:
1845 alias -- Define a new command that is an alias of an existing command
1846 aliases -- Aliases of other commands
1847 d -- Delete some breakpoints or auto-display expressions
1848 del -- Delete some breakpoints or auto-display expressions
1849 delete -- Delete some breakpoints or auto-display expressions
1854 @item complete @var{args}
1855 The @code{complete @var{args}} command lists all the possible completions
1856 for the beginning of a command. Use @var{args} to specify the beginning of the
1857 command you want completed. For example:
1863 @noindent results in:
1874 @noindent This is intended for use by @sc{gnu} Emacs.
1877 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1878 and @code{show} to inquire about the state of your program, or the state
1879 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1880 manual introduces each of them in the appropriate context. The listings
1881 under @code{info} and under @code{show} in the Command, Variable, and
1882 Function Index point to all the sub-commands. @xref{Command and Variable
1888 @kindex i @r{(@code{info})}
1890 This command (abbreviated @code{i}) is for describing the state of your
1891 program. For example, you can show the arguments passed to a function
1892 with @code{info args}, list the registers currently in use with @code{info
1893 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1894 You can get a complete list of the @code{info} sub-commands with
1895 @w{@code{help info}}.
1899 You can assign the result of an expression to an environment variable with
1900 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1901 @code{set prompt $}.
1905 In contrast to @code{info}, @code{show} is for describing the state of
1906 @value{GDBN} itself.
1907 You can change most of the things you can @code{show}, by using the
1908 related command @code{set}; for example, you can control what number
1909 system is used for displays with @code{set radix}, or simply inquire
1910 which is currently in use with @code{show radix}.
1913 To display all the settable parameters and their current
1914 values, you can use @code{show} with no arguments; you may also use
1915 @code{info set}. Both commands produce the same display.
1916 @c FIXME: "info set" violates the rule that "info" is for state of
1917 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1918 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1922 Here are several miscellaneous @code{show} subcommands, all of which are
1923 exceptional in lacking corresponding @code{set} commands:
1926 @kindex show version
1927 @cindex @value{GDBN} version number
1929 Show what version of @value{GDBN} is running. You should include this
1930 information in @value{GDBN} bug-reports. If multiple versions of
1931 @value{GDBN} are in use at your site, you may need to determine which
1932 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1933 commands are introduced, and old ones may wither away. Also, many
1934 system vendors ship variant versions of @value{GDBN}, and there are
1935 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1936 The version number is the same as the one announced when you start
1939 @kindex show copying
1940 @kindex info copying
1941 @cindex display @value{GDBN} copyright
1944 Display information about permission for copying @value{GDBN}.
1946 @kindex show warranty
1947 @kindex info warranty
1949 @itemx info warranty
1950 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1951 if your version of @value{GDBN} comes with one.
1953 @kindex show configuration
1954 @item show configuration
1955 Display detailed information about the way @value{GDBN} was configured
1956 when it was built. This displays the optional arguments passed to the
1957 @file{configure} script and also configuration parameters detected
1958 automatically by @command{configure}. When reporting a @value{GDBN}
1959 bug (@pxref{GDB Bugs}), it is important to include this information in
1965 @chapter Running Programs Under @value{GDBN}
1967 When you run a program under @value{GDBN}, you must first generate
1968 debugging information when you compile it.
1970 You may start @value{GDBN} with its arguments, if any, in an environment
1971 of your choice. If you are doing native debugging, you may redirect
1972 your program's input and output, debug an already running process, or
1973 kill a child process.
1976 * Compilation:: Compiling for debugging
1977 * Starting:: Starting your program
1978 * Arguments:: Your program's arguments
1979 * Environment:: Your program's environment
1981 * Working Directory:: Your program's working directory
1982 * Input/Output:: Your program's input and output
1983 * Attach:: Debugging an already-running process
1984 * Kill Process:: Killing the child process
1986 * Inferiors and Programs:: Debugging multiple inferiors and programs
1987 * Threads:: Debugging programs with multiple threads
1988 * Forks:: Debugging forks
1989 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1993 @section Compiling for Debugging
1995 In order to debug a program effectively, you need to generate
1996 debugging information when you compile it. This debugging information
1997 is stored in the object file; it describes the data type of each
1998 variable or function and the correspondence between source line numbers
1999 and addresses in the executable code.
2001 To request debugging information, specify the @samp{-g} option when you run
2004 Programs that are to be shipped to your customers are compiled with
2005 optimizations, using the @samp{-O} compiler option. However, some
2006 compilers are unable to handle the @samp{-g} and @samp{-O} options
2007 together. Using those compilers, you cannot generate optimized
2008 executables containing debugging information.
2010 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2011 without @samp{-O}, making it possible to debug optimized code. We
2012 recommend that you @emph{always} use @samp{-g} whenever you compile a
2013 program. You may think your program is correct, but there is no sense
2014 in pushing your luck. For more information, see @ref{Optimized Code}.
2016 Older versions of the @sc{gnu} C compiler permitted a variant option
2017 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2018 format; if your @sc{gnu} C compiler has this option, do not use it.
2020 @value{GDBN} knows about preprocessor macros and can show you their
2021 expansion (@pxref{Macros}). Most compilers do not include information
2022 about preprocessor macros in the debugging information if you specify
2023 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2024 the @sc{gnu} C compiler, provides macro information if you are using
2025 the DWARF debugging format, and specify the option @option{-g3}.
2027 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2028 gcc, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2029 information on @value{NGCC} options affecting debug information.
2031 You will have the best debugging experience if you use the latest
2032 version of the DWARF debugging format that your compiler supports.
2033 DWARF is currently the most expressive and best supported debugging
2034 format in @value{GDBN}.
2038 @section Starting your Program
2044 @kindex r @r{(@code{run})}
2047 Use the @code{run} command to start your program under @value{GDBN}.
2048 You must first specify the program name with an argument to
2049 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2050 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2051 command (@pxref{Files, ,Commands to Specify Files}).
2055 If you are running your program in an execution environment that
2056 supports processes, @code{run} creates an inferior process and makes
2057 that process run your program. In some environments without processes,
2058 @code{run} jumps to the start of your program. Other targets,
2059 like @samp{remote}, are always running. If you get an error
2060 message like this one:
2063 The "remote" target does not support "run".
2064 Try "help target" or "continue".
2068 then use @code{continue} to run your program. You may need @code{load}
2069 first (@pxref{load}).
2071 The execution of a program is affected by certain information it
2072 receives from its superior. @value{GDBN} provides ways to specify this
2073 information, which you must do @emph{before} starting your program. (You
2074 can change it after starting your program, but such changes only affect
2075 your program the next time you start it.) This information may be
2076 divided into four categories:
2079 @item The @emph{arguments.}
2080 Specify the arguments to give your program as the arguments of the
2081 @code{run} command. If a shell is available on your target, the shell
2082 is used to pass the arguments, so that you may use normal conventions
2083 (such as wildcard expansion or variable substitution) in describing
2085 In Unix systems, you can control which shell is used with the
2086 @code{SHELL} environment variable. If you do not define @code{SHELL},
2087 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2088 use of any shell with the @code{set startup-with-shell} command (see
2091 @item The @emph{environment.}
2092 Your program normally inherits its environment from @value{GDBN}, but you can
2093 use the @value{GDBN} commands @code{set environment} and @code{unset
2094 environment} to change parts of the environment that affect
2095 your program. @xref{Environment, ,Your Program's Environment}.
2097 @item The @emph{working directory.}
2098 You can set your program's working directory with the command
2099 @kbd{set cwd}. If you do not set any working directory with this
2100 command, your program will inherit @value{GDBN}'s working directory if
2101 native debugging, or the remote server's working directory if remote
2102 debugging. @xref{Working Directory, ,Your Program's Working
2105 @item The @emph{standard input and output.}
2106 Your program normally uses the same device for standard input and
2107 standard output as @value{GDBN} is using. You can redirect input and output
2108 in the @code{run} command line, or you can use the @code{tty} command to
2109 set a different device for your program.
2110 @xref{Input/Output, ,Your Program's Input and Output}.
2113 @emph{Warning:} While input and output redirection work, you cannot use
2114 pipes to pass the output of the program you are debugging to another
2115 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2119 When you issue the @code{run} command, your program begins to execute
2120 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2121 of how to arrange for your program to stop. Once your program has
2122 stopped, you may call functions in your program, using the @code{print}
2123 or @code{call} commands. @xref{Data, ,Examining Data}.
2125 If the modification time of your symbol file has changed since the last
2126 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2127 table, and reads it again. When it does this, @value{GDBN} tries to retain
2128 your current breakpoints.
2133 @cindex run to main procedure
2134 The name of the main procedure can vary from language to language.
2135 With C or C@t{++}, the main procedure name is always @code{main}, but
2136 other languages such as Ada do not require a specific name for their
2137 main procedure. The debugger provides a convenient way to start the
2138 execution of the program and to stop at the beginning of the main
2139 procedure, depending on the language used.
2141 The @samp{start} command does the equivalent of setting a temporary
2142 breakpoint at the beginning of the main procedure and then invoking
2143 the @samp{run} command.
2145 @cindex elaboration phase
2146 Some programs contain an @dfn{elaboration} phase where some startup code is
2147 executed before the main procedure is called. This depends on the
2148 languages used to write your program. In C@t{++}, for instance,
2149 constructors for static and global objects are executed before
2150 @code{main} is called. It is therefore possible that the debugger stops
2151 before reaching the main procedure. However, the temporary breakpoint
2152 will remain to halt execution.
2154 Specify the arguments to give to your program as arguments to the
2155 @samp{start} command. These arguments will be given verbatim to the
2156 underlying @samp{run} command. Note that the same arguments will be
2157 reused if no argument is provided during subsequent calls to
2158 @samp{start} or @samp{run}.
2160 It is sometimes necessary to debug the program during elaboration. In
2161 these cases, using the @code{start} command would stop the execution
2162 of your program too late, as the program would have already completed
2163 the elaboration phase. Under these circumstances, either insert
2164 breakpoints in your elaboration code before running your program or
2165 use the @code{starti} command.
2169 @cindex run to first instruction
2170 The @samp{starti} command does the equivalent of setting a temporary
2171 breakpoint at the first instruction of a program's execution and then
2172 invoking the @samp{run} command. For programs containing an
2173 elaboration phase, the @code{starti} command will stop execution at
2174 the start of the elaboration phase.
2176 @anchor{set exec-wrapper}
2177 @kindex set exec-wrapper
2178 @item set exec-wrapper @var{wrapper}
2179 @itemx show exec-wrapper
2180 @itemx unset exec-wrapper
2181 When @samp{exec-wrapper} is set, the specified wrapper is used to
2182 launch programs for debugging. @value{GDBN} starts your program
2183 with a shell command of the form @kbd{exec @var{wrapper}
2184 @var{program}}. Quoting is added to @var{program} and its
2185 arguments, but not to @var{wrapper}, so you should add quotes if
2186 appropriate for your shell. The wrapper runs until it executes
2187 your program, and then @value{GDBN} takes control.
2189 You can use any program that eventually calls @code{execve} with
2190 its arguments as a wrapper. Several standard Unix utilities do
2191 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2192 with @code{exec "$@@"} will also work.
2194 For example, you can use @code{env} to pass an environment variable to
2195 the debugged program, without setting the variable in your shell's
2199 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2203 This command is available when debugging locally on most targets, excluding
2204 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2206 @kindex set startup-with-shell
2207 @anchor{set startup-with-shell}
2208 @item set startup-with-shell
2209 @itemx set startup-with-shell on
2210 @itemx set startup-with-shell off
2211 @itemx show startup-with-shell
2212 On Unix systems, by default, if a shell is available on your target,
2213 @value{GDBN}) uses it to start your program. Arguments of the
2214 @code{run} command are passed to the shell, which does variable
2215 substitution, expands wildcard characters and performs redirection of
2216 I/O. In some circumstances, it may be useful to disable such use of a
2217 shell, for example, when debugging the shell itself or diagnosing
2218 startup failures such as:
2222 Starting program: ./a.out
2223 During startup program terminated with signal SIGSEGV, Segmentation fault.
2227 which indicates the shell or the wrapper specified with
2228 @samp{exec-wrapper} crashed, not your program. Most often, this is
2229 caused by something odd in your shell's non-interactive mode
2230 initialization file---such as @file{.cshrc} for C-shell,
2231 $@file{.zshenv} for the Z shell, or the file specified in the
2232 @samp{BASH_ENV} environment variable for BASH.
2234 @anchor{set auto-connect-native-target}
2235 @kindex set auto-connect-native-target
2236 @item set auto-connect-native-target
2237 @itemx set auto-connect-native-target on
2238 @itemx set auto-connect-native-target off
2239 @itemx show auto-connect-native-target
2241 By default, if not connected to any target yet (e.g., with
2242 @code{target remote}), the @code{run} command starts your program as a
2243 native process under @value{GDBN}, on your local machine. If you're
2244 sure you don't want to debug programs on your local machine, you can
2245 tell @value{GDBN} to not connect to the native target automatically
2246 with the @code{set auto-connect-native-target off} command.
2248 If @code{on}, which is the default, and if @value{GDBN} is not
2249 connected to a target already, the @code{run} command automaticaly
2250 connects to the native target, if one is available.
2252 If @code{off}, and if @value{GDBN} is not connected to a target
2253 already, the @code{run} command fails with an error:
2257 Don't know how to run. Try "help target".
2260 If @value{GDBN} is already connected to a target, @value{GDBN} always
2261 uses it with the @code{run} command.
2263 In any case, you can explicitly connect to the native target with the
2264 @code{target native} command. For example,
2267 (@value{GDBP}) set auto-connect-native-target off
2269 Don't know how to run. Try "help target".
2270 (@value{GDBP}) target native
2272 Starting program: ./a.out
2273 [Inferior 1 (process 10421) exited normally]
2276 In case you connected explicitly to the @code{native} target,
2277 @value{GDBN} remains connected even if all inferiors exit, ready for
2278 the next @code{run} command. Use the @code{disconnect} command to
2281 Examples of other commands that likewise respect the
2282 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2283 proc}, @code{info os}.
2285 @kindex set disable-randomization
2286 @item set disable-randomization
2287 @itemx set disable-randomization on
2288 This option (enabled by default in @value{GDBN}) will turn off the native
2289 randomization of the virtual address space of the started program. This option
2290 is useful for multiple debugging sessions to make the execution better
2291 reproducible and memory addresses reusable across debugging sessions.
2293 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2294 On @sc{gnu}/Linux you can get the same behavior using
2297 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2300 @item set disable-randomization off
2301 Leave the behavior of the started executable unchanged. Some bugs rear their
2302 ugly heads only when the program is loaded at certain addresses. If your bug
2303 disappears when you run the program under @value{GDBN}, that might be because
2304 @value{GDBN} by default disables the address randomization on platforms, such
2305 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2306 disable-randomization off} to try to reproduce such elusive bugs.
2308 On targets where it is available, virtual address space randomization
2309 protects the programs against certain kinds of security attacks. In these
2310 cases the attacker needs to know the exact location of a concrete executable
2311 code. Randomizing its location makes it impossible to inject jumps misusing
2312 a code at its expected addresses.
2314 Prelinking shared libraries provides a startup performance advantage but it
2315 makes addresses in these libraries predictable for privileged processes by
2316 having just unprivileged access at the target system. Reading the shared
2317 library binary gives enough information for assembling the malicious code
2318 misusing it. Still even a prelinked shared library can get loaded at a new
2319 random address just requiring the regular relocation process during the
2320 startup. Shared libraries not already prelinked are always loaded at
2321 a randomly chosen address.
2323 Position independent executables (PIE) contain position independent code
2324 similar to the shared libraries and therefore such executables get loaded at
2325 a randomly chosen address upon startup. PIE executables always load even
2326 already prelinked shared libraries at a random address. You can build such
2327 executable using @command{gcc -fPIE -pie}.
2329 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2330 (as long as the randomization is enabled).
2332 @item show disable-randomization
2333 Show the current setting of the explicit disable of the native randomization of
2334 the virtual address space of the started program.
2339 @section Your Program's Arguments
2341 @cindex arguments (to your program)
2342 The arguments to your program can be specified by the arguments of the
2344 They are passed to a shell, which expands wildcard characters and
2345 performs redirection of I/O, and thence to your program. Your
2346 @code{SHELL} environment variable (if it exists) specifies what shell
2347 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2348 the default shell (@file{/bin/sh} on Unix).
2350 On non-Unix systems, the program is usually invoked directly by
2351 @value{GDBN}, which emulates I/O redirection via the appropriate system
2352 calls, and the wildcard characters are expanded by the startup code of
2353 the program, not by the shell.
2355 @code{run} with no arguments uses the same arguments used by the previous
2356 @code{run}, or those set by the @code{set args} command.
2361 Specify the arguments to be used the next time your program is run. If
2362 @code{set args} has no arguments, @code{run} executes your program
2363 with no arguments. Once you have run your program with arguments,
2364 using @code{set args} before the next @code{run} is the only way to run
2365 it again without arguments.
2369 Show the arguments to give your program when it is started.
2373 @section Your Program's Environment
2375 @cindex environment (of your program)
2376 The @dfn{environment} consists of a set of environment variables and
2377 their values. Environment variables conventionally record such things as
2378 your user name, your home directory, your terminal type, and your search
2379 path for programs to run. Usually you set up environment variables with
2380 the shell and they are inherited by all the other programs you run. When
2381 debugging, it can be useful to try running your program with a modified
2382 environment without having to start @value{GDBN} over again.
2386 @item path @var{directory}
2387 Add @var{directory} to the front of the @code{PATH} environment variable
2388 (the search path for executables) that will be passed to your program.
2389 The value of @code{PATH} used by @value{GDBN} does not change.
2390 You may specify several directory names, separated by whitespace or by a
2391 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2392 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2393 is moved to the front, so it is searched sooner.
2395 You can use the string @samp{$cwd} to refer to whatever is the current
2396 working directory at the time @value{GDBN} searches the path. If you
2397 use @samp{.} instead, it refers to the directory where you executed the
2398 @code{path} command. @value{GDBN} replaces @samp{.} in the
2399 @var{directory} argument (with the current path) before adding
2400 @var{directory} to the search path.
2401 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2402 @c document that, since repeating it would be a no-op.
2406 Display the list of search paths for executables (the @code{PATH}
2407 environment variable).
2409 @kindex show environment
2410 @item show environment @r{[}@var{varname}@r{]}
2411 Print the value of environment variable @var{varname} to be given to
2412 your program when it starts. If you do not supply @var{varname},
2413 print the names and values of all environment variables to be given to
2414 your program. You can abbreviate @code{environment} as @code{env}.
2416 @kindex set environment
2417 @anchor{set environment}
2418 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2419 Set environment variable @var{varname} to @var{value}. The value
2420 changes for your program (and the shell @value{GDBN} uses to launch
2421 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2422 values of environment variables are just strings, and any
2423 interpretation is supplied by your program itself. The @var{value}
2424 parameter is optional; if it is eliminated, the variable is set to a
2426 @c "any string" here does not include leading, trailing
2427 @c blanks. Gnu asks: does anyone care?
2429 For example, this command:
2436 tells the debugged program, when subsequently run, that its user is named
2437 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2438 are not actually required.)
2440 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2441 which also inherits the environment set with @code{set environment}.
2442 If necessary, you can avoid that by using the @samp{env} program as a
2443 wrapper instead of using @code{set environment}. @xref{set
2444 exec-wrapper}, for an example doing just that.
2446 Environment variables that are set by the user are also transmitted to
2447 @command{gdbserver} to be used when starting the remote inferior.
2448 @pxref{QEnvironmentHexEncoded}.
2450 @kindex unset environment
2451 @anchor{unset environment}
2452 @item unset environment @var{varname}
2453 Remove variable @var{varname} from the environment to be passed to your
2454 program. This is different from @samp{set env @var{varname} =};
2455 @code{unset environment} removes the variable from the environment,
2456 rather than assigning it an empty value.
2458 Environment variables that are unset by the user are also unset on
2459 @command{gdbserver} when starting the remote inferior.
2460 @pxref{QEnvironmentUnset}.
2463 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2464 the shell indicated by your @code{SHELL} environment variable if it
2465 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2466 names a shell that runs an initialization file when started
2467 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2468 for the Z shell, or the file specified in the @samp{BASH_ENV}
2469 environment variable for BASH---any variables you set in that file
2470 affect your program. You may wish to move setting of environment
2471 variables to files that are only run when you sign on, such as
2472 @file{.login} or @file{.profile}.
2474 @node Working Directory
2475 @section Your Program's Working Directory
2477 @cindex working directory (of your program)
2478 Each time you start your program with @code{run}, the inferior will be
2479 initialized with the current working directory specified by the
2480 @kbd{set cwd} command. If no directory has been specified by this
2481 command, then the inferior will inherit @value{GDBN}'s current working
2482 directory as its working directory if native debugging, or it will
2483 inherit the remote server's current working directory if remote
2488 @cindex change inferior's working directory
2489 @anchor{set cwd command}
2490 @item set cwd @r{[}@var{directory}@r{]}
2491 Set the inferior's working directory to @var{directory}, which will be
2492 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2493 argument has been specified, the command clears the setting and resets
2494 it to an empty state. This setting has no effect on @value{GDBN}'s
2495 working directory, and it only takes effect the next time you start
2496 the inferior. The @file{~} in @var{directory} is a short for the
2497 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2498 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2499 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2502 You can also change @value{GDBN}'s current working directory by using
2503 the @code{cd} command.
2507 @cindex show inferior's working directory
2509 Show the inferior's working directory. If no directory has been
2510 specified by @kbd{set cwd}, then the default inferior's working
2511 directory is the same as @value{GDBN}'s working directory.
2514 @cindex change @value{GDBN}'s working directory
2516 @item cd @r{[}@var{directory}@r{]}
2517 Set the @value{GDBN} working directory to @var{directory}. If not
2518 given, @var{directory} uses @file{'~'}.
2520 The @value{GDBN} working directory serves as a default for the
2521 commands that specify files for @value{GDBN} to operate on.
2522 @xref{Files, ,Commands to Specify Files}.
2523 @xref{set cwd command}.
2527 Print the @value{GDBN} working directory.
2530 It is generally impossible to find the current working directory of
2531 the process being debugged (since a program can change its directory
2532 during its run). If you work on a system where @value{GDBN} supports
2533 the @code{info proc} command (@pxref{Process Information}), you can
2534 use the @code{info proc} command to find out the
2535 current working directory of the debuggee.
2538 @section Your Program's Input and Output
2543 By default, the program you run under @value{GDBN} does input and output to
2544 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2545 to its own terminal modes to interact with you, but it records the terminal
2546 modes your program was using and switches back to them when you continue
2547 running your program.
2550 @kindex info terminal
2552 Displays information recorded by @value{GDBN} about the terminal modes your
2556 You can redirect your program's input and/or output using shell
2557 redirection with the @code{run} command. For example,
2564 starts your program, diverting its output to the file @file{outfile}.
2567 @cindex controlling terminal
2568 Another way to specify where your program should do input and output is
2569 with the @code{tty} command. This command accepts a file name as
2570 argument, and causes this file to be the default for future @code{run}
2571 commands. It also resets the controlling terminal for the child
2572 process, for future @code{run} commands. For example,
2579 directs that processes started with subsequent @code{run} commands
2580 default to do input and output on the terminal @file{/dev/ttyb} and have
2581 that as their controlling terminal.
2583 An explicit redirection in @code{run} overrides the @code{tty} command's
2584 effect on the input/output device, but not its effect on the controlling
2587 When you use the @code{tty} command or redirect input in the @code{run}
2588 command, only the input @emph{for your program} is affected. The input
2589 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2590 for @code{set inferior-tty}.
2592 @cindex inferior tty
2593 @cindex set inferior controlling terminal
2594 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2595 display the name of the terminal that will be used for future runs of your
2599 @item set inferior-tty [ @var{tty} ]
2600 @kindex set inferior-tty
2601 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2602 restores the default behavior, which is to use the same terminal as
2605 @item show inferior-tty
2606 @kindex show inferior-tty
2607 Show the current tty for the program being debugged.
2611 @section Debugging an Already-running Process
2616 @item attach @var{process-id}
2617 This command attaches to a running process---one that was started
2618 outside @value{GDBN}. (@code{info files} shows your active
2619 targets.) The command takes as argument a process ID. The usual way to
2620 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2621 or with the @samp{jobs -l} shell command.
2623 @code{attach} does not repeat if you press @key{RET} a second time after
2624 executing the command.
2627 To use @code{attach}, your program must be running in an environment
2628 which supports processes; for example, @code{attach} does not work for
2629 programs on bare-board targets that lack an operating system. You must
2630 also have permission to send the process a signal.
2632 When you use @code{attach}, the debugger finds the program running in
2633 the process first by looking in the current working directory, then (if
2634 the program is not found) by using the source file search path
2635 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2636 the @code{file} command to load the program. @xref{Files, ,Commands to
2639 The first thing @value{GDBN} does after arranging to debug the specified
2640 process is to stop it. You can examine and modify an attached process
2641 with all the @value{GDBN} commands that are ordinarily available when
2642 you start processes with @code{run}. You can insert breakpoints; you
2643 can step and continue; you can modify storage. If you would rather the
2644 process continue running, you may use the @code{continue} command after
2645 attaching @value{GDBN} to the process.
2650 When you have finished debugging the attached process, you can use the
2651 @code{detach} command to release it from @value{GDBN} control. Detaching
2652 the process continues its execution. After the @code{detach} command,
2653 that process and @value{GDBN} become completely independent once more, and you
2654 are ready to @code{attach} another process or start one with @code{run}.
2655 @code{detach} does not repeat if you press @key{RET} again after
2656 executing the command.
2659 If you exit @value{GDBN} while you have an attached process, you detach
2660 that process. If you use the @code{run} command, you kill that process.
2661 By default, @value{GDBN} asks for confirmation if you try to do either of these
2662 things; you can control whether or not you need to confirm by using the
2663 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2667 @section Killing the Child Process
2672 Kill the child process in which your program is running under @value{GDBN}.
2675 This command is useful if you wish to debug a core dump instead of a
2676 running process. @value{GDBN} ignores any core dump file while your program
2679 On some operating systems, a program cannot be executed outside @value{GDBN}
2680 while you have breakpoints set on it inside @value{GDBN}. You can use the
2681 @code{kill} command in this situation to permit running your program
2682 outside the debugger.
2684 The @code{kill} command is also useful if you wish to recompile and
2685 relink your program, since on many systems it is impossible to modify an
2686 executable file while it is running in a process. In this case, when you
2687 next type @code{run}, @value{GDBN} notices that the file has changed, and
2688 reads the symbol table again (while trying to preserve your current
2689 breakpoint settings).
2691 @node Inferiors and Programs
2692 @section Debugging Multiple Inferiors and Programs
2694 @value{GDBN} lets you run and debug multiple programs in a single
2695 session. In addition, @value{GDBN} on some systems may let you run
2696 several programs simultaneously (otherwise you have to exit from one
2697 before starting another). In the most general case, you can have
2698 multiple threads of execution in each of multiple processes, launched
2699 from multiple executables.
2702 @value{GDBN} represents the state of each program execution with an
2703 object called an @dfn{inferior}. An inferior typically corresponds to
2704 a process, but is more general and applies also to targets that do not
2705 have processes. Inferiors may be created before a process runs, and
2706 may be retained after a process exits. Inferiors have unique
2707 identifiers that are different from process ids. Usually each
2708 inferior will also have its own distinct address space, although some
2709 embedded targets may have several inferiors running in different parts
2710 of a single address space. Each inferior may in turn have multiple
2711 threads running in it.
2713 To find out what inferiors exist at any moment, use @w{@code{info
2717 @kindex info inferiors [ @var{id}@dots{} ]
2718 @item info inferiors
2719 Print a list of all inferiors currently being managed by @value{GDBN}.
2720 By default all inferiors are printed, but the argument @var{id}@dots{}
2721 -- a space separated list of inferior numbers -- can be used to limit
2722 the display to just the requested inferiors.
2724 @value{GDBN} displays for each inferior (in this order):
2728 the inferior number assigned by @value{GDBN}
2731 the target system's inferior identifier
2734 the name of the executable the inferior is running.
2739 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2740 indicates the current inferior.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info inferiors
2748 Num Description Executable
2749 2 process 2307 hello
2750 * 1 process 3401 goodbye
2753 To switch focus between inferiors, use the @code{inferior} command:
2756 @kindex inferior @var{infno}
2757 @item inferior @var{infno}
2758 Make inferior number @var{infno} the current inferior. The argument
2759 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2760 in the first field of the @samp{info inferiors} display.
2763 @vindex $_inferior@r{, convenience variable}
2764 The debugger convenience variable @samp{$_inferior} contains the
2765 number of the current inferior. You may find this useful in writing
2766 breakpoint conditional expressions, command scripts, and so forth.
2767 @xref{Convenience Vars,, Convenience Variables}, for general
2768 information on convenience variables.
2770 You can get multiple executables into a debugging session via the
2771 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2772 systems @value{GDBN} can add inferiors to the debug session
2773 automatically by following calls to @code{fork} and @code{exec}. To
2774 remove inferiors from the debugging session use the
2775 @w{@code{remove-inferiors}} command.
2778 @kindex add-inferior
2779 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2780 Adds @var{n} inferiors to be run using @var{executable} as the
2781 executable; @var{n} defaults to 1. If no executable is specified,
2782 the inferiors begins empty, with no program. You can still assign or
2783 change the program assigned to the inferior at any time by using the
2784 @code{file} command with the executable name as its argument.
2786 @kindex clone-inferior
2787 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2788 Adds @var{n} inferiors ready to execute the same program as inferior
2789 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2790 number of the current inferior. This is a convenient command when you
2791 want to run another instance of the inferior you are debugging.
2794 (@value{GDBP}) info inferiors
2795 Num Description Executable
2796 * 1 process 29964 helloworld
2797 (@value{GDBP}) clone-inferior
2800 (@value{GDBP}) info inferiors
2801 Num Description Executable
2803 * 1 process 29964 helloworld
2806 You can now simply switch focus to inferior 2 and run it.
2808 @kindex remove-inferiors
2809 @item remove-inferiors @var{infno}@dots{}
2810 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2811 possible to remove an inferior that is running with this command. For
2812 those, use the @code{kill} or @code{detach} command first.
2816 To quit debugging one of the running inferiors that is not the current
2817 inferior, you can either detach from it by using the @w{@code{detach
2818 inferior}} command (allowing it to run independently), or kill it
2819 using the @w{@code{kill inferiors}} command:
2822 @kindex detach inferiors @var{infno}@dots{}
2823 @item detach inferior @var{infno}@dots{}
2824 Detach from the inferior or inferiors identified by @value{GDBN}
2825 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2826 still stays on the list of inferiors shown by @code{info inferiors},
2827 but its Description will show @samp{<null>}.
2829 @kindex kill inferiors @var{infno}@dots{}
2830 @item kill inferiors @var{infno}@dots{}
2831 Kill the inferior or inferiors identified by @value{GDBN} inferior
2832 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2833 stays on the list of inferiors shown by @code{info inferiors}, but its
2834 Description will show @samp{<null>}.
2837 After the successful completion of a command such as @code{detach},
2838 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2839 a normal process exit, the inferior is still valid and listed with
2840 @code{info inferiors}, ready to be restarted.
2843 To be notified when inferiors are started or exit under @value{GDBN}'s
2844 control use @w{@code{set print inferior-events}}:
2847 @kindex set print inferior-events
2848 @cindex print messages on inferior start and exit
2849 @item set print inferior-events
2850 @itemx set print inferior-events on
2851 @itemx set print inferior-events off
2852 The @code{set print inferior-events} command allows you to enable or
2853 disable printing of messages when @value{GDBN} notices that new
2854 inferiors have started or that inferiors have exited or have been
2855 detached. By default, these messages will not be printed.
2857 @kindex show print inferior-events
2858 @item show print inferior-events
2859 Show whether messages will be printed when @value{GDBN} detects that
2860 inferiors have started, exited or have been detached.
2863 Many commands will work the same with multiple programs as with a
2864 single program: e.g., @code{print myglobal} will simply display the
2865 value of @code{myglobal} in the current inferior.
2868 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2869 get more info about the relationship of inferiors, programs, address
2870 spaces in a debug session. You can do that with the @w{@code{maint
2871 info program-spaces}} command.
2874 @kindex maint info program-spaces
2875 @item maint info program-spaces
2876 Print a list of all program spaces currently being managed by
2879 @value{GDBN} displays for each program space (in this order):
2883 the program space number assigned by @value{GDBN}
2886 the name of the executable loaded into the program space, with e.g.,
2887 the @code{file} command.
2892 An asterisk @samp{*} preceding the @value{GDBN} program space number
2893 indicates the current program space.
2895 In addition, below each program space line, @value{GDBN} prints extra
2896 information that isn't suitable to display in tabular form. For
2897 example, the list of inferiors bound to the program space.
2900 (@value{GDBP}) maint info program-spaces
2904 Bound inferiors: ID 1 (process 21561)
2907 Here we can see that no inferior is running the program @code{hello},
2908 while @code{process 21561} is running the program @code{goodbye}. On
2909 some targets, it is possible that multiple inferiors are bound to the
2910 same program space. The most common example is that of debugging both
2911 the parent and child processes of a @code{vfork} call. For example,
2914 (@value{GDBP}) maint info program-spaces
2917 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2920 Here, both inferior 2 and inferior 1 are running in the same program
2921 space as a result of inferior 1 having executed a @code{vfork} call.
2925 @section Debugging Programs with Multiple Threads
2927 @cindex threads of execution
2928 @cindex multiple threads
2929 @cindex switching threads
2930 In some operating systems, such as GNU/Linux and Solaris, a single program
2931 may have more than one @dfn{thread} of execution. The precise semantics
2932 of threads differ from one operating system to another, but in general
2933 the threads of a single program are akin to multiple processes---except
2934 that they share one address space (that is, they can all examine and
2935 modify the same variables). On the other hand, each thread has its own
2936 registers and execution stack, and perhaps private memory.
2938 @value{GDBN} provides these facilities for debugging multi-thread
2942 @item automatic notification of new threads
2943 @item @samp{thread @var{thread-id}}, a command to switch among threads
2944 @item @samp{info threads}, a command to inquire about existing threads
2945 @item @samp{thread apply [@var{thread-id-list} | all] @var{args}},
2946 a command to apply a command to a list of threads
2947 @item thread-specific breakpoints
2948 @item @samp{set print thread-events}, which controls printing of
2949 messages on thread start and exit.
2950 @item @samp{set libthread-db-search-path @var{path}}, which lets
2951 the user specify which @code{libthread_db} to use if the default choice
2952 isn't compatible with the program.
2955 @cindex focus of debugging
2956 @cindex current thread
2957 The @value{GDBN} thread debugging facility allows you to observe all
2958 threads while your program runs---but whenever @value{GDBN} takes
2959 control, one thread in particular is always the focus of debugging.
2960 This thread is called the @dfn{current thread}. Debugging commands show
2961 program information from the perspective of the current thread.
2963 @cindex @code{New} @var{systag} message
2964 @cindex thread identifier (system)
2965 @c FIXME-implementors!! It would be more helpful if the [New...] message
2966 @c included GDB's numeric thread handle, so you could just go to that
2967 @c thread without first checking `info threads'.
2968 Whenever @value{GDBN} detects a new thread in your program, it displays
2969 the target system's identification for the thread with a message in the
2970 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2971 whose form varies depending on the particular system. For example, on
2972 @sc{gnu}/Linux, you might see
2975 [New Thread 0x41e02940 (LWP 25582)]
2979 when @value{GDBN} notices a new thread. In contrast, on other systems,
2980 the @var{systag} is simply something like @samp{process 368}, with no
2983 @c FIXME!! (1) Does the [New...] message appear even for the very first
2984 @c thread of a program, or does it only appear for the
2985 @c second---i.e.@: when it becomes obvious we have a multithread
2987 @c (2) *Is* there necessarily a first thread always? Or do some
2988 @c multithread systems permit starting a program with multiple
2989 @c threads ab initio?
2991 @anchor{thread numbers}
2992 @cindex thread number, per inferior
2993 @cindex thread identifier (GDB)
2994 For debugging purposes, @value{GDBN} associates its own thread number
2995 ---always a single integer---with each thread of an inferior. This
2996 number is unique between all threads of an inferior, but not unique
2997 between threads of different inferiors.
2999 @cindex qualified thread ID
3000 You can refer to a given thread in an inferior using the qualified
3001 @var{inferior-num}.@var{thread-num} syntax, also known as
3002 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
3003 number and @var{thread-num} being the thread number of the given
3004 inferior. For example, thread @code{2.3} refers to thread number 3 of
3005 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
3006 then @value{GDBN} infers you're referring to a thread of the current
3009 Until you create a second inferior, @value{GDBN} does not show the
3010 @var{inferior-num} part of thread IDs, even though you can always use
3011 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3012 of inferior 1, the initial inferior.
3014 @anchor{thread ID lists}
3015 @cindex thread ID lists
3016 Some commands accept a space-separated @dfn{thread ID list} as
3017 argument. A list element can be:
3021 A thread ID as shown in the first field of the @samp{info threads}
3022 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3026 A range of thread numbers, again with or without an inferior
3027 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3028 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3031 All threads of an inferior, specified with a star wildcard, with or
3032 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3033 @samp{1.*}) or @code{*}. The former refers to all threads of the
3034 given inferior, and the latter form without an inferior qualifier
3035 refers to all threads of the current inferior.
3039 For example, if the current inferior is 1, and inferior 7 has one
3040 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3041 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3042 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3043 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3047 @anchor{global thread numbers}
3048 @cindex global thread number
3049 @cindex global thread identifier (GDB)
3050 In addition to a @emph{per-inferior} number, each thread is also
3051 assigned a unique @emph{global} number, also known as @dfn{global
3052 thread ID}, a single integer. Unlike the thread number component of
3053 the thread ID, no two threads have the same global ID, even when
3054 you're debugging multiple inferiors.
3056 From @value{GDBN}'s perspective, a process always has at least one
3057 thread. In other words, @value{GDBN} assigns a thread number to the
3058 program's ``main thread'' even if the program is not multi-threaded.
3060 @vindex $_thread@r{, convenience variable}
3061 @vindex $_gthread@r{, convenience variable}
3062 The debugger convenience variables @samp{$_thread} and
3063 @samp{$_gthread} contain, respectively, the per-inferior thread number
3064 and the global thread number of the current thread. You may find this
3065 useful in writing breakpoint conditional expressions, command scripts,
3066 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3067 general information on convenience variables.
3069 If @value{GDBN} detects the program is multi-threaded, it augments the
3070 usual message about stopping at a breakpoint with the ID and name of
3071 the thread that hit the breakpoint.
3074 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3077 Likewise when the program receives a signal:
3080 Thread 1 "main" received signal SIGINT, Interrupt.
3084 @kindex info threads
3085 @item info threads @r{[}@var{thread-id-list}@r{]}
3087 Display information about one or more threads. With no arguments
3088 displays information about all threads. You can specify the list of
3089 threads that you want to display using the thread ID list syntax
3090 (@pxref{thread ID lists}).
3092 @value{GDBN} displays for each thread (in this order):
3096 the per-inferior thread number assigned by @value{GDBN}
3099 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3100 option was specified
3103 the target system's thread identifier (@var{systag})
3106 the thread's name, if one is known. A thread can either be named by
3107 the user (see @code{thread name}, below), or, in some cases, by the
3111 the current stack frame summary for that thread
3115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3116 indicates the current thread.
3120 @c end table here to get a little more width for example
3123 (@value{GDBP}) info threads
3125 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3126 2 process 35 thread 23 0x34e5 in sigpause ()
3127 3 process 35 thread 27 0x34e5 in sigpause ()
3131 If you're debugging multiple inferiors, @value{GDBN} displays thread
3132 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3133 Otherwise, only @var{thread-num} is shown.
3135 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3136 indicating each thread's global thread ID:
3139 (@value{GDBP}) info threads
3140 Id GId Target Id Frame
3141 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3142 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3143 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3144 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3147 On Solaris, you can display more information about user threads with a
3148 Solaris-specific command:
3151 @item maint info sol-threads
3152 @kindex maint info sol-threads
3153 @cindex thread info (Solaris)
3154 Display info on Solaris user threads.
3158 @kindex thread @var{thread-id}
3159 @item thread @var{thread-id}
3160 Make thread ID @var{thread-id} the current thread. The command
3161 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3162 the first field of the @samp{info threads} display, with or without an
3163 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3165 @value{GDBN} responds by displaying the system identifier of the
3166 thread you selected, and its current stack frame summary:
3169 (@value{GDBP}) thread 2
3170 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3171 #0 some_function (ignore=0x0) at example.c:8
3172 8 printf ("hello\n");
3176 As with the @samp{[New @dots{}]} message, the form of the text after
3177 @samp{Switching to} depends on your system's conventions for identifying
3180 @kindex thread apply
3181 @cindex apply command to several threads
3182 @item thread apply [@var{thread-id-list} | all [-ascending]] [@var{flag}]@dots{} @var{command}
3183 The @code{thread apply} command allows you to apply the named
3184 @var{command} to one or more threads. Specify the threads that you
3185 want affected using the thread ID list syntax (@pxref{thread ID
3186 lists}), or specify @code{all} to apply to all threads. To apply a
3187 command to all threads in descending order, type @kbd{thread apply all
3188 @var{command}}. To apply a command to all threads in ascending order,
3189 type @kbd{thread apply all -ascending @var{command}}.
3191 The @var{flag} arguments control what output to produce and how to handle
3192 errors raised when applying @var{command} to a thread. @var{flag}
3193 must start with a @code{-} directly followed by one letter in
3194 @code{qcs}. If several flags are provided, they must be given
3195 individually, such as @code{-c -q}.
3197 By default, @value{GDBN} displays some thread information before the
3198 output produced by @var{command}, and an error raised during the
3199 execution of a @var{command} will abort @code{thread apply}. The
3200 following flags can be used to fine-tune this behavior:
3204 The flag @code{-c}, which stands for @samp{continue}, causes any
3205 errors in @var{command} to be displayed, and the execution of
3206 @code{thread apply} then continues.
3208 The flag @code{-s}, which stands for @samp{silent}, causes any errors
3209 or empty output produced by a @var{command} to be silently ignored.
3210 That is, the execution continues, but the thread information and errors
3213 The flag @code{-q} (@samp{quiet}) disables printing the thread
3217 Flags @code{-c} and @code{-s} cannot be used together.
3220 @cindex apply command to all threads (ignoring errors and empty output)
3221 @item taas @var{command}
3222 Shortcut for @code{thread apply all -s @var{command}}.
3223 Applies @var{command} on all threads, ignoring errors and empty output.
3226 @cindex apply a command to all frames of all threads (ignoring errors and empty output)
3227 @item tfaas @var{command}
3228 Shortcut for @code{thread apply all -s frame apply all -s @var{command}}.
3229 Applies @var{command} on all frames of all threads, ignoring errors
3230 and empty output. Note that the flag @code{-s} is specified twice:
3231 The first @code{-s} ensures that @code{thread apply} only shows the thread
3232 information of the threads for which @code{frame apply} produces
3233 some output. The second @code{-s} is needed to ensure that @code{frame
3234 apply} shows the frame information of a frame only if the
3235 @var{command} successfully produced some output.
3237 It can for example be used to print a local variable or a function
3238 argument without knowing the thread or frame where this variable or argument
3241 (@value{GDBP}) tfaas p some_local_var_i_do_not_remember_where_it_is
3246 @cindex name a thread
3247 @item thread name [@var{name}]
3248 This command assigns a name to the current thread. If no argument is
3249 given, any existing user-specified name is removed. The thread name
3250 appears in the @samp{info threads} display.
3252 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3253 determine the name of the thread as given by the OS. On these
3254 systems, a name specified with @samp{thread name} will override the
3255 system-give name, and removing the user-specified name will cause
3256 @value{GDBN} to once again display the system-specified name.
3259 @cindex search for a thread
3260 @item thread find [@var{regexp}]
3261 Search for and display thread ids whose name or @var{systag}
3262 matches the supplied regular expression.
3264 As well as being the complement to the @samp{thread name} command,
3265 this command also allows you to identify a thread by its target
3266 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3270 (@value{GDBN}) thread find 26688
3271 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3272 (@value{GDBN}) info thread 4
3274 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3277 @kindex set print thread-events
3278 @cindex print messages on thread start and exit
3279 @item set print thread-events
3280 @itemx set print thread-events on
3281 @itemx set print thread-events off
3282 The @code{set print thread-events} command allows you to enable or
3283 disable printing of messages when @value{GDBN} notices that new threads have
3284 started or that threads have exited. By default, these messages will
3285 be printed if detection of these events is supported by the target.
3286 Note that these messages cannot be disabled on all targets.
3288 @kindex show print thread-events
3289 @item show print thread-events
3290 Show whether messages will be printed when @value{GDBN} detects that threads
3291 have started and exited.
3294 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3295 more information about how @value{GDBN} behaves when you stop and start
3296 programs with multiple threads.
3298 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3299 watchpoints in programs with multiple threads.
3301 @anchor{set libthread-db-search-path}
3303 @kindex set libthread-db-search-path
3304 @cindex search path for @code{libthread_db}
3305 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3306 If this variable is set, @var{path} is a colon-separated list of
3307 directories @value{GDBN} will use to search for @code{libthread_db}.
3308 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3309 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3310 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3313 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3314 @code{libthread_db} library to obtain information about threads in the
3315 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3316 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3317 specific thread debugging library loading is enabled
3318 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3320 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3321 refers to the default system directories that are
3322 normally searched for loading shared libraries. The @samp{$sdir} entry
3323 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3324 (@pxref{libthread_db.so.1 file}).
3326 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3327 refers to the directory from which @code{libpthread}
3328 was loaded in the inferior process.
3330 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3331 @value{GDBN} attempts to initialize it with the current inferior process.
3332 If this initialization fails (which could happen because of a version
3333 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3334 will unload @code{libthread_db}, and continue with the next directory.
3335 If none of @code{libthread_db} libraries initialize successfully,
3336 @value{GDBN} will issue a warning and thread debugging will be disabled.
3338 Setting @code{libthread-db-search-path} is currently implemented
3339 only on some platforms.
3341 @kindex show libthread-db-search-path
3342 @item show libthread-db-search-path
3343 Display current libthread_db search path.
3345 @kindex set debug libthread-db
3346 @kindex show debug libthread-db
3347 @cindex debugging @code{libthread_db}
3348 @item set debug libthread-db
3349 @itemx show debug libthread-db
3350 Turns on or off display of @code{libthread_db}-related events.
3351 Use @code{1} to enable, @code{0} to disable.
3355 @section Debugging Forks
3357 @cindex fork, debugging programs which call
3358 @cindex multiple processes
3359 @cindex processes, multiple
3360 On most systems, @value{GDBN} has no special support for debugging
3361 programs which create additional processes using the @code{fork}
3362 function. When a program forks, @value{GDBN} will continue to debug the
3363 parent process and the child process will run unimpeded. If you have
3364 set a breakpoint in any code which the child then executes, the child
3365 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3366 will cause it to terminate.
3368 However, if you want to debug the child process there is a workaround
3369 which isn't too painful. Put a call to @code{sleep} in the code which
3370 the child process executes after the fork. It may be useful to sleep
3371 only if a certain environment variable is set, or a certain file exists,
3372 so that the delay need not occur when you don't want to run @value{GDBN}
3373 on the child. While the child is sleeping, use the @code{ps} program to
3374 get its process ID. Then tell @value{GDBN} (a new invocation of
3375 @value{GDBN} if you are also debugging the parent process) to attach to
3376 the child process (@pxref{Attach}). From that point on you can debug
3377 the child process just like any other process which you attached to.
3379 On some systems, @value{GDBN} provides support for debugging programs
3380 that create additional processes using the @code{fork} or @code{vfork}
3381 functions. On @sc{gnu}/Linux platforms, this feature is supported
3382 with kernel version 2.5.46 and later.
3384 The fork debugging commands are supported in native mode and when
3385 connected to @code{gdbserver} in either @code{target remote} mode or
3386 @code{target extended-remote} mode.
3388 By default, when a program forks, @value{GDBN} will continue to debug
3389 the parent process and the child process will run unimpeded.
3391 If you want to follow the child process instead of the parent process,
3392 use the command @w{@code{set follow-fork-mode}}.
3395 @kindex set follow-fork-mode
3396 @item set follow-fork-mode @var{mode}
3397 Set the debugger response to a program call of @code{fork} or
3398 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3399 process. The @var{mode} argument can be:
3403 The original process is debugged after a fork. The child process runs
3404 unimpeded. This is the default.
3407 The new process is debugged after a fork. The parent process runs
3412 @kindex show follow-fork-mode
3413 @item show follow-fork-mode
3414 Display the current debugger response to a @code{fork} or @code{vfork} call.
3417 @cindex debugging multiple processes
3418 On Linux, if you want to debug both the parent and child processes, use the
3419 command @w{@code{set detach-on-fork}}.
3422 @kindex set detach-on-fork
3423 @item set detach-on-fork @var{mode}
3424 Tells gdb whether to detach one of the processes after a fork, or
3425 retain debugger control over them both.
3429 The child process (or parent process, depending on the value of
3430 @code{follow-fork-mode}) will be detached and allowed to run
3431 independently. This is the default.
3434 Both processes will be held under the control of @value{GDBN}.
3435 One process (child or parent, depending on the value of
3436 @code{follow-fork-mode}) is debugged as usual, while the other
3441 @kindex show detach-on-fork
3442 @item show detach-on-fork
3443 Show whether detach-on-fork mode is on/off.
3446 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3447 will retain control of all forked processes (including nested forks).
3448 You can list the forked processes under the control of @value{GDBN} by
3449 using the @w{@code{info inferiors}} command, and switch from one fork
3450 to another by using the @code{inferior} command (@pxref{Inferiors and
3451 Programs, ,Debugging Multiple Inferiors and Programs}).
3453 To quit debugging one of the forked processes, you can either detach
3454 from it by using the @w{@code{detach inferiors}} command (allowing it
3455 to run independently), or kill it using the @w{@code{kill inferiors}}
3456 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3459 If you ask to debug a child process and a @code{vfork} is followed by an
3460 @code{exec}, @value{GDBN} executes the new target up to the first
3461 breakpoint in the new target. If you have a breakpoint set on
3462 @code{main} in your original program, the breakpoint will also be set on
3463 the child process's @code{main}.
3465 On some systems, when a child process is spawned by @code{vfork}, you
3466 cannot debug the child or parent until an @code{exec} call completes.
3468 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3469 call executes, the new target restarts. To restart the parent
3470 process, use the @code{file} command with the parent executable name
3471 as its argument. By default, after an @code{exec} call executes,
3472 @value{GDBN} discards the symbols of the previous executable image.
3473 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3477 @kindex set follow-exec-mode
3478 @item set follow-exec-mode @var{mode}
3480 Set debugger response to a program call of @code{exec}. An
3481 @code{exec} call replaces the program image of a process.
3483 @code{follow-exec-mode} can be:
3487 @value{GDBN} creates a new inferior and rebinds the process to this
3488 new inferior. The program the process was running before the
3489 @code{exec} call can be restarted afterwards by restarting the
3495 (@value{GDBP}) info inferiors
3497 Id Description Executable
3500 process 12020 is executing new program: prog2
3501 Program exited normally.
3502 (@value{GDBP}) info inferiors
3503 Id Description Executable
3509 @value{GDBN} keeps the process bound to the same inferior. The new
3510 executable image replaces the previous executable loaded in the
3511 inferior. Restarting the inferior after the @code{exec} call, with
3512 e.g., the @code{run} command, restarts the executable the process was
3513 running after the @code{exec} call. This is the default mode.
3518 (@value{GDBP}) info inferiors
3519 Id Description Executable
3522 process 12020 is executing new program: prog2
3523 Program exited normally.
3524 (@value{GDBP}) info inferiors
3525 Id Description Executable
3532 @code{follow-exec-mode} is supported in native mode and
3533 @code{target extended-remote} mode.
3535 You can use the @code{catch} command to make @value{GDBN} stop whenever
3536 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3537 Catchpoints, ,Setting Catchpoints}.
3539 @node Checkpoint/Restart
3540 @section Setting a @emph{Bookmark} to Return to Later
3545 @cindex snapshot of a process
3546 @cindex rewind program state
3548 On certain operating systems@footnote{Currently, only
3549 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3550 program's state, called a @dfn{checkpoint}, and come back to it
3553 Returning to a checkpoint effectively undoes everything that has
3554 happened in the program since the @code{checkpoint} was saved. This
3555 includes changes in memory, registers, and even (within some limits)
3556 system state. Effectively, it is like going back in time to the
3557 moment when the checkpoint was saved.
3559 Thus, if you're stepping thru a program and you think you're
3560 getting close to the point where things go wrong, you can save
3561 a checkpoint. Then, if you accidentally go too far and miss
3562 the critical statement, instead of having to restart your program
3563 from the beginning, you can just go back to the checkpoint and
3564 start again from there.
3566 This can be especially useful if it takes a lot of time or
3567 steps to reach the point where you think the bug occurs.
3569 To use the @code{checkpoint}/@code{restart} method of debugging:
3574 Save a snapshot of the debugged program's current execution state.
3575 The @code{checkpoint} command takes no arguments, but each checkpoint
3576 is assigned a small integer id, similar to a breakpoint id.
3578 @kindex info checkpoints
3579 @item info checkpoints
3580 List the checkpoints that have been saved in the current debugging
3581 session. For each checkpoint, the following information will be
3588 @item Source line, or label
3591 @kindex restart @var{checkpoint-id}
3592 @item restart @var{checkpoint-id}
3593 Restore the program state that was saved as checkpoint number
3594 @var{checkpoint-id}. All program variables, registers, stack frames
3595 etc.@: will be returned to the values that they had when the checkpoint
3596 was saved. In essence, gdb will ``wind back the clock'' to the point
3597 in time when the checkpoint was saved.
3599 Note that breakpoints, @value{GDBN} variables, command history etc.
3600 are not affected by restoring a checkpoint. In general, a checkpoint
3601 only restores things that reside in the program being debugged, not in
3604 @kindex delete checkpoint @var{checkpoint-id}
3605 @item delete checkpoint @var{checkpoint-id}
3606 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3610 Returning to a previously saved checkpoint will restore the user state
3611 of the program being debugged, plus a significant subset of the system
3612 (OS) state, including file pointers. It won't ``un-write'' data from
3613 a file, but it will rewind the file pointer to the previous location,
3614 so that the previously written data can be overwritten. For files
3615 opened in read mode, the pointer will also be restored so that the
3616 previously read data can be read again.
3618 Of course, characters that have been sent to a printer (or other
3619 external device) cannot be ``snatched back'', and characters received
3620 from eg.@: a serial device can be removed from internal program buffers,
3621 but they cannot be ``pushed back'' into the serial pipeline, ready to
3622 be received again. Similarly, the actual contents of files that have
3623 been changed cannot be restored (at this time).
3625 However, within those constraints, you actually can ``rewind'' your
3626 program to a previously saved point in time, and begin debugging it
3627 again --- and you can change the course of events so as to debug a
3628 different execution path this time.
3630 @cindex checkpoints and process id
3631 Finally, there is one bit of internal program state that will be
3632 different when you return to a checkpoint --- the program's process
3633 id. Each checkpoint will have a unique process id (or @var{pid}),
3634 and each will be different from the program's original @var{pid}.
3635 If your program has saved a local copy of its process id, this could
3636 potentially pose a problem.
3638 @subsection A Non-obvious Benefit of Using Checkpoints
3640 On some systems such as @sc{gnu}/Linux, address space randomization
3641 is performed on new processes for security reasons. This makes it
3642 difficult or impossible to set a breakpoint, or watchpoint, on an
3643 absolute address if you have to restart the program, since the
3644 absolute location of a symbol will change from one execution to the
3647 A checkpoint, however, is an @emph{identical} copy of a process.
3648 Therefore if you create a checkpoint at (eg.@:) the start of main,
3649 and simply return to that checkpoint instead of restarting the
3650 process, you can avoid the effects of address randomization and
3651 your symbols will all stay in the same place.
3654 @chapter Stopping and Continuing
3656 The principal purposes of using a debugger are so that you can stop your
3657 program before it terminates; or so that, if your program runs into
3658 trouble, you can investigate and find out why.
3660 Inside @value{GDBN}, your program may stop for any of several reasons,
3661 such as a signal, a breakpoint, or reaching a new line after a
3662 @value{GDBN} command such as @code{step}. You may then examine and
3663 change variables, set new breakpoints or remove old ones, and then
3664 continue execution. Usually, the messages shown by @value{GDBN} provide
3665 ample explanation of the status of your program---but you can also
3666 explicitly request this information at any time.
3669 @kindex info program
3671 Display information about the status of your program: whether it is
3672 running or not, what process it is, and why it stopped.
3676 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3677 * Continuing and Stepping:: Resuming execution
3678 * Skipping Over Functions and Files::
3679 Skipping over functions and files
3681 * Thread Stops:: Stopping and starting multi-thread programs
3685 @section Breakpoints, Watchpoints, and Catchpoints
3688 A @dfn{breakpoint} makes your program stop whenever a certain point in
3689 the program is reached. For each breakpoint, you can add conditions to
3690 control in finer detail whether your program stops. You can set
3691 breakpoints with the @code{break} command and its variants (@pxref{Set
3692 Breaks, ,Setting Breakpoints}), to specify the place where your program
3693 should stop by line number, function name or exact address in the
3696 On some systems, you can set breakpoints in shared libraries before
3697 the executable is run.
3700 @cindex data breakpoints
3701 @cindex memory tracing
3702 @cindex breakpoint on memory address
3703 @cindex breakpoint on variable modification
3704 A @dfn{watchpoint} is a special breakpoint that stops your program
3705 when the value of an expression changes. The expression may be a value
3706 of a variable, or it could involve values of one or more variables
3707 combined by operators, such as @samp{a + b}. This is sometimes called
3708 @dfn{data breakpoints}. You must use a different command to set
3709 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3710 from that, you can manage a watchpoint like any other breakpoint: you
3711 enable, disable, and delete both breakpoints and watchpoints using the
3714 You can arrange to have values from your program displayed automatically
3715 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3719 @cindex breakpoint on events
3720 A @dfn{catchpoint} is another special breakpoint that stops your program
3721 when a certain kind of event occurs, such as the throwing of a C@t{++}
3722 exception or the loading of a library. As with watchpoints, you use a
3723 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3724 Catchpoints}), but aside from that, you can manage a catchpoint like any
3725 other breakpoint. (To stop when your program receives a signal, use the
3726 @code{handle} command; see @ref{Signals, ,Signals}.)
3728 @cindex breakpoint numbers
3729 @cindex numbers for breakpoints
3730 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3731 catchpoint when you create it; these numbers are successive integers
3732 starting with one. In many of the commands for controlling various
3733 features of breakpoints you use the breakpoint number to say which
3734 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3735 @dfn{disabled}; if disabled, it has no effect on your program until you
3738 @cindex breakpoint ranges
3739 @cindex breakpoint lists
3740 @cindex ranges of breakpoints
3741 @cindex lists of breakpoints
3742 Some @value{GDBN} commands accept a space-separated list of breakpoints
3743 on which to operate. A list element can be either a single breakpoint number,
3744 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3745 When a breakpoint list is given to a command, all breakpoints in that list
3749 * Set Breaks:: Setting breakpoints
3750 * Set Watchpoints:: Setting watchpoints
3751 * Set Catchpoints:: Setting catchpoints
3752 * Delete Breaks:: Deleting breakpoints
3753 * Disabling:: Disabling breakpoints
3754 * Conditions:: Break conditions
3755 * Break Commands:: Breakpoint command lists
3756 * Dynamic Printf:: Dynamic printf
3757 * Save Breakpoints:: How to save breakpoints in a file
3758 * Static Probe Points:: Listing static probe points
3759 * Error in Breakpoints:: ``Cannot insert breakpoints''
3760 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3764 @subsection Setting Breakpoints
3766 @c FIXME LMB what does GDB do if no code on line of breakpt?
3767 @c consider in particular declaration with/without initialization.
3769 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3772 @kindex b @r{(@code{break})}
3773 @vindex $bpnum@r{, convenience variable}
3774 @cindex latest breakpoint
3775 Breakpoints are set with the @code{break} command (abbreviated
3776 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3777 number of the breakpoint you've set most recently; see @ref{Convenience
3778 Vars,, Convenience Variables}, for a discussion of what you can do with
3779 convenience variables.
3782 @item break @var{location}
3783 Set a breakpoint at the given @var{location}, which can specify a
3784 function name, a line number, or an address of an instruction.
3785 (@xref{Specify Location}, for a list of all the possible ways to
3786 specify a @var{location}.) The breakpoint will stop your program just
3787 before it executes any of the code in the specified @var{location}.
3789 When using source languages that permit overloading of symbols, such as
3790 C@t{++}, a function name may refer to more than one possible place to break.
3791 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3794 It is also possible to insert a breakpoint that will stop the program
3795 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3796 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3799 When called without any arguments, @code{break} sets a breakpoint at
3800 the next instruction to be executed in the selected stack frame
3801 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3802 innermost, this makes your program stop as soon as control
3803 returns to that frame. This is similar to the effect of a
3804 @code{finish} command in the frame inside the selected frame---except
3805 that @code{finish} does not leave an active breakpoint. If you use
3806 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3807 the next time it reaches the current location; this may be useful
3810 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3811 least one instruction has been executed. If it did not do this, you
3812 would be unable to proceed past a breakpoint without first disabling the
3813 breakpoint. This rule applies whether or not the breakpoint already
3814 existed when your program stopped.
3816 @item break @dots{} if @var{cond}
3817 Set a breakpoint with condition @var{cond}; evaluate the expression
3818 @var{cond} each time the breakpoint is reached, and stop only if the
3819 value is nonzero---that is, if @var{cond} evaluates as true.
3820 @samp{@dots{}} stands for one of the possible arguments described
3821 above (or no argument) specifying where to break. @xref{Conditions,
3822 ,Break Conditions}, for more information on breakpoint conditions.
3825 @item tbreak @var{args}
3826 Set a breakpoint enabled only for one stop. The @var{args} are the
3827 same as for the @code{break} command, and the breakpoint is set in the same
3828 way, but the breakpoint is automatically deleted after the first time your
3829 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3832 @cindex hardware breakpoints
3833 @item hbreak @var{args}
3834 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3835 @code{break} command and the breakpoint is set in the same way, but the
3836 breakpoint requires hardware support and some target hardware may not
3837 have this support. The main purpose of this is EPROM/ROM code
3838 debugging, so you can set a breakpoint at an instruction without
3839 changing the instruction. This can be used with the new trap-generation
3840 provided by SPARClite DSU and most x86-based targets. These targets
3841 will generate traps when a program accesses some data or instruction
3842 address that is assigned to the debug registers. However the hardware
3843 breakpoint registers can take a limited number of breakpoints. For
3844 example, on the DSU, only two data breakpoints can be set at a time, and
3845 @value{GDBN} will reject this command if more than two are used. Delete
3846 or disable unused hardware breakpoints before setting new ones
3847 (@pxref{Disabling, ,Disabling Breakpoints}).
3848 @xref{Conditions, ,Break Conditions}.
3849 For remote targets, you can restrict the number of hardware
3850 breakpoints @value{GDBN} will use, see @ref{set remote
3851 hardware-breakpoint-limit}.
3854 @item thbreak @var{args}
3855 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3856 are the same as for the @code{hbreak} command and the breakpoint is set in
3857 the same way. However, like the @code{tbreak} command,
3858 the breakpoint is automatically deleted after the
3859 first time your program stops there. Also, like the @code{hbreak}
3860 command, the breakpoint requires hardware support and some target hardware
3861 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3862 See also @ref{Conditions, ,Break Conditions}.
3865 @cindex regular expression
3866 @cindex breakpoints at functions matching a regexp
3867 @cindex set breakpoints in many functions
3868 @item rbreak @var{regex}
3869 Set breakpoints on all functions matching the regular expression
3870 @var{regex}. This command sets an unconditional breakpoint on all
3871 matches, printing a list of all breakpoints it set. Once these
3872 breakpoints are set, they are treated just like the breakpoints set with
3873 the @code{break} command. You can delete them, disable them, or make
3874 them conditional the same way as any other breakpoint.
3876 The syntax of the regular expression is the standard one used with tools
3877 like @file{grep}. Note that this is different from the syntax used by
3878 shells, so for instance @code{foo*} matches all functions that include
3879 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3880 @code{.*} leading and trailing the regular expression you supply, so to
3881 match only functions that begin with @code{foo}, use @code{^foo}.
3883 @cindex non-member C@t{++} functions, set breakpoint in
3884 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3885 breakpoints on overloaded functions that are not members of any special
3888 @cindex set breakpoints on all functions
3889 The @code{rbreak} command can be used to set breakpoints in
3890 @strong{all} the functions in a program, like this:
3893 (@value{GDBP}) rbreak .
3896 @item rbreak @var{file}:@var{regex}
3897 If @code{rbreak} is called with a filename qualification, it limits
3898 the search for functions matching the given regular expression to the
3899 specified @var{file}. This can be used, for example, to set breakpoints on
3900 every function in a given file:
3903 (@value{GDBP}) rbreak file.c:.
3906 The colon separating the filename qualifier from the regex may
3907 optionally be surrounded by spaces.
3909 @kindex info breakpoints
3910 @cindex @code{$_} and @code{info breakpoints}
3911 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3912 @itemx info break @r{[}@var{list}@dots{}@r{]}
3913 Print a table of all breakpoints, watchpoints, and catchpoints set and
3914 not deleted. Optional argument @var{n} means print information only
3915 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3916 For each breakpoint, following columns are printed:
3919 @item Breakpoint Numbers
3921 Breakpoint, watchpoint, or catchpoint.
3923 Whether the breakpoint is marked to be disabled or deleted when hit.
3924 @item Enabled or Disabled
3925 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3926 that are not enabled.
3928 Where the breakpoint is in your program, as a memory address. For a
3929 pending breakpoint whose address is not yet known, this field will
3930 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3931 library that has the symbol or line referred by breakpoint is loaded.
3932 See below for details. A breakpoint with several locations will
3933 have @samp{<MULTIPLE>} in this field---see below for details.
3935 Where the breakpoint is in the source for your program, as a file and
3936 line number. For a pending breakpoint, the original string passed to
3937 the breakpoint command will be listed as it cannot be resolved until
3938 the appropriate shared library is loaded in the future.
3942 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3943 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3944 @value{GDBN} on the host's side. If it is ``target'', then the condition
3945 is evaluated by the target. The @code{info break} command shows
3946 the condition on the line following the affected breakpoint, together with
3947 its condition evaluation mode in between parentheses.
3949 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3950 allowed to have a condition specified for it. The condition is not parsed for
3951 validity until a shared library is loaded that allows the pending
3952 breakpoint to resolve to a valid location.
3955 @code{info break} with a breakpoint
3956 number @var{n} as argument lists only that breakpoint. The
3957 convenience variable @code{$_} and the default examining-address for
3958 the @code{x} command are set to the address of the last breakpoint
3959 listed (@pxref{Memory, ,Examining Memory}).
3962 @code{info break} displays a count of the number of times the breakpoint
3963 has been hit. This is especially useful in conjunction with the
3964 @code{ignore} command. You can ignore a large number of breakpoint
3965 hits, look at the breakpoint info to see how many times the breakpoint
3966 was hit, and then run again, ignoring one less than that number. This
3967 will get you quickly to the last hit of that breakpoint.
3970 For a breakpoints with an enable count (xref) greater than 1,
3971 @code{info break} also displays that count.
3975 @value{GDBN} allows you to set any number of breakpoints at the same place in
3976 your program. There is nothing silly or meaningless about this. When
3977 the breakpoints are conditional, this is even useful
3978 (@pxref{Conditions, ,Break Conditions}).
3980 @cindex multiple locations, breakpoints
3981 @cindex breakpoints, multiple locations
3982 It is possible that a breakpoint corresponds to several locations
3983 in your program. Examples of this situation are:
3987 Multiple functions in the program may have the same name.
3990 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3991 instances of the function body, used in different cases.
3994 For a C@t{++} template function, a given line in the function can
3995 correspond to any number of instantiations.
3998 For an inlined function, a given source line can correspond to
3999 several places where that function is inlined.
4002 In all those cases, @value{GDBN} will insert a breakpoint at all
4003 the relevant locations.
4005 A breakpoint with multiple locations is displayed in the breakpoint
4006 table using several rows---one header row, followed by one row for
4007 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4008 address column. The rows for individual locations contain the actual
4009 addresses for locations, and show the functions to which those
4010 locations belong. The number column for a location is of the form
4011 @var{breakpoint-number}.@var{location-number}.
4016 Num Type Disp Enb Address What
4017 1 breakpoint keep y <MULTIPLE>
4019 breakpoint already hit 1 time
4020 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4021 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4024 You cannot delete the individual locations from a breakpoint. However,
4025 each location can be individually enabled or disabled by passing
4026 @var{breakpoint-number}.@var{location-number} as argument to the
4027 @code{enable} and @code{disable} commands. It's also possible to
4028 @code{enable} and @code{disable} a range of @var{location-number}
4029 locations using a @var{breakpoint-number} and two @var{location-number}s,
4030 in increasing order, separated by a hyphen, like
4031 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4032 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4033 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4034 all of the locations that belong to that breakpoint.
4036 @cindex pending breakpoints
4037 It's quite common to have a breakpoint inside a shared library.
4038 Shared libraries can be loaded and unloaded explicitly,
4039 and possibly repeatedly, as the program is executed. To support
4040 this use case, @value{GDBN} updates breakpoint locations whenever
4041 any shared library is loaded or unloaded. Typically, you would
4042 set a breakpoint in a shared library at the beginning of your
4043 debugging session, when the library is not loaded, and when the
4044 symbols from the library are not available. When you try to set
4045 breakpoint, @value{GDBN} will ask you if you want to set
4046 a so called @dfn{pending breakpoint}---breakpoint whose address
4047 is not yet resolved.
4049 After the program is run, whenever a new shared library is loaded,
4050 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4051 shared library contains the symbol or line referred to by some
4052 pending breakpoint, that breakpoint is resolved and becomes an
4053 ordinary breakpoint. When a library is unloaded, all breakpoints
4054 that refer to its symbols or source lines become pending again.
4056 This logic works for breakpoints with multiple locations, too. For
4057 example, if you have a breakpoint in a C@t{++} template function, and
4058 a newly loaded shared library has an instantiation of that template,
4059 a new location is added to the list of locations for the breakpoint.
4061 Except for having unresolved address, pending breakpoints do not
4062 differ from regular breakpoints. You can set conditions or commands,
4063 enable and disable them and perform other breakpoint operations.
4065 @value{GDBN} provides some additional commands for controlling what
4066 happens when the @samp{break} command cannot resolve breakpoint
4067 address specification to an address:
4069 @kindex set breakpoint pending
4070 @kindex show breakpoint pending
4072 @item set breakpoint pending auto
4073 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4074 location, it queries you whether a pending breakpoint should be created.
4076 @item set breakpoint pending on
4077 This indicates that an unrecognized breakpoint location should automatically
4078 result in a pending breakpoint being created.
4080 @item set breakpoint pending off
4081 This indicates that pending breakpoints are not to be created. Any
4082 unrecognized breakpoint location results in an error. This setting does
4083 not affect any pending breakpoints previously created.
4085 @item show breakpoint pending
4086 Show the current behavior setting for creating pending breakpoints.
4089 The settings above only affect the @code{break} command and its
4090 variants. Once breakpoint is set, it will be automatically updated
4091 as shared libraries are loaded and unloaded.
4093 @cindex automatic hardware breakpoints
4094 For some targets, @value{GDBN} can automatically decide if hardware or
4095 software breakpoints should be used, depending on whether the
4096 breakpoint address is read-only or read-write. This applies to
4097 breakpoints set with the @code{break} command as well as to internal
4098 breakpoints set by commands like @code{next} and @code{finish}. For
4099 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4102 You can control this automatic behaviour with the following commands:
4104 @kindex set breakpoint auto-hw
4105 @kindex show breakpoint auto-hw
4107 @item set breakpoint auto-hw on
4108 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4109 will try to use the target memory map to decide if software or hardware
4110 breakpoint must be used.
4112 @item set breakpoint auto-hw off
4113 This indicates @value{GDBN} should not automatically select breakpoint
4114 type. If the target provides a memory map, @value{GDBN} will warn when
4115 trying to set software breakpoint at a read-only address.
4118 @value{GDBN} normally implements breakpoints by replacing the program code
4119 at the breakpoint address with a special instruction, which, when
4120 executed, given control to the debugger. By default, the program
4121 code is so modified only when the program is resumed. As soon as
4122 the program stops, @value{GDBN} restores the original instructions. This
4123 behaviour guards against leaving breakpoints inserted in the
4124 target should gdb abrubptly disconnect. However, with slow remote
4125 targets, inserting and removing breakpoint can reduce the performance.
4126 This behavior can be controlled with the following commands::
4128 @kindex set breakpoint always-inserted
4129 @kindex show breakpoint always-inserted
4131 @item set breakpoint always-inserted off
4132 All breakpoints, including newly added by the user, are inserted in
4133 the target only when the target is resumed. All breakpoints are
4134 removed from the target when it stops. This is the default mode.
4136 @item set breakpoint always-inserted on
4137 Causes all breakpoints to be inserted in the target at all times. If
4138 the user adds a new breakpoint, or changes an existing breakpoint, the
4139 breakpoints in the target are updated immediately. A breakpoint is
4140 removed from the target only when breakpoint itself is deleted.
4143 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4144 when a breakpoint breaks. If the condition is true, then the process being
4145 debugged stops, otherwise the process is resumed.
4147 If the target supports evaluating conditions on its end, @value{GDBN} may
4148 download the breakpoint, together with its conditions, to it.
4150 This feature can be controlled via the following commands:
4152 @kindex set breakpoint condition-evaluation
4153 @kindex show breakpoint condition-evaluation
4155 @item set breakpoint condition-evaluation host
4156 This option commands @value{GDBN} to evaluate the breakpoint
4157 conditions on the host's side. Unconditional breakpoints are sent to
4158 the target which in turn receives the triggers and reports them back to GDB
4159 for condition evaluation. This is the standard evaluation mode.
4161 @item set breakpoint condition-evaluation target
4162 This option commands @value{GDBN} to download breakpoint conditions
4163 to the target at the moment of their insertion. The target
4164 is responsible for evaluating the conditional expression and reporting
4165 breakpoint stop events back to @value{GDBN} whenever the condition
4166 is true. Due to limitations of target-side evaluation, some conditions
4167 cannot be evaluated there, e.g., conditions that depend on local data
4168 that is only known to the host. Examples include
4169 conditional expressions involving convenience variables, complex types
4170 that cannot be handled by the agent expression parser and expressions
4171 that are too long to be sent over to the target, specially when the
4172 target is a remote system. In these cases, the conditions will be
4173 evaluated by @value{GDBN}.
4175 @item set breakpoint condition-evaluation auto
4176 This is the default mode. If the target supports evaluating breakpoint
4177 conditions on its end, @value{GDBN} will download breakpoint conditions to
4178 the target (limitations mentioned previously apply). If the target does
4179 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4180 to evaluating all these conditions on the host's side.
4184 @cindex negative breakpoint numbers
4185 @cindex internal @value{GDBN} breakpoints
4186 @value{GDBN} itself sometimes sets breakpoints in your program for
4187 special purposes, such as proper handling of @code{longjmp} (in C
4188 programs). These internal breakpoints are assigned negative numbers,
4189 starting with @code{-1}; @samp{info breakpoints} does not display them.
4190 You can see these breakpoints with the @value{GDBN} maintenance command
4191 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4194 @node Set Watchpoints
4195 @subsection Setting Watchpoints
4197 @cindex setting watchpoints
4198 You can use a watchpoint to stop execution whenever the value of an
4199 expression changes, without having to predict a particular place where
4200 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4201 The expression may be as simple as the value of a single variable, or
4202 as complex as many variables combined by operators. Examples include:
4206 A reference to the value of a single variable.
4209 An address cast to an appropriate data type. For example,
4210 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4211 address (assuming an @code{int} occupies 4 bytes).
4214 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4215 expression can use any operators valid in the program's native
4216 language (@pxref{Languages}).
4219 You can set a watchpoint on an expression even if the expression can
4220 not be evaluated yet. For instance, you can set a watchpoint on
4221 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4222 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4223 the expression produces a valid value. If the expression becomes
4224 valid in some other way than changing a variable (e.g.@: if the memory
4225 pointed to by @samp{*global_ptr} becomes readable as the result of a
4226 @code{malloc} call), @value{GDBN} may not stop until the next time
4227 the expression changes.
4229 @cindex software watchpoints
4230 @cindex hardware watchpoints
4231 Depending on your system, watchpoints may be implemented in software or
4232 hardware. @value{GDBN} does software watchpointing by single-stepping your
4233 program and testing the variable's value each time, which is hundreds of
4234 times slower than normal execution. (But this may still be worth it, to
4235 catch errors where you have no clue what part of your program is the
4238 On some systems, such as most PowerPC or x86-based targets,
4239 @value{GDBN} includes support for hardware watchpoints, which do not
4240 slow down the running of your program.
4244 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4245 Set a watchpoint for an expression. @value{GDBN} will break when the
4246 expression @var{expr} is written into by the program and its value
4247 changes. The simplest (and the most popular) use of this command is
4248 to watch the value of a single variable:
4251 (@value{GDBP}) watch foo
4254 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4255 argument, @value{GDBN} breaks only when the thread identified by
4256 @var{thread-id} changes the value of @var{expr}. If any other threads
4257 change the value of @var{expr}, @value{GDBN} will not break. Note
4258 that watchpoints restricted to a single thread in this way only work
4259 with Hardware Watchpoints.
4261 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4262 (see below). The @code{-location} argument tells @value{GDBN} to
4263 instead watch the memory referred to by @var{expr}. In this case,
4264 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4265 and watch the memory at that address. The type of the result is used
4266 to determine the size of the watched memory. If the expression's
4267 result does not have an address, then @value{GDBN} will print an
4270 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4271 of masked watchpoints, if the current architecture supports this
4272 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4273 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4274 to an address to watch. The mask specifies that some bits of an address
4275 (the bits which are reset in the mask) should be ignored when matching
4276 the address accessed by the inferior against the watchpoint address.
4277 Thus, a masked watchpoint watches many addresses simultaneously---those
4278 addresses whose unmasked bits are identical to the unmasked bits in the
4279 watchpoint address. The @code{mask} argument implies @code{-location}.
4283 (@value{GDBP}) watch foo mask 0xffff00ff
4284 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4288 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4289 Set a watchpoint that will break when the value of @var{expr} is read
4293 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4294 Set a watchpoint that will break when @var{expr} is either read from
4295 or written into by the program.
4297 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4298 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4299 This command prints a list of watchpoints, using the same format as
4300 @code{info break} (@pxref{Set Breaks}).
4303 If you watch for a change in a numerically entered address you need to
4304 dereference it, as the address itself is just a constant number which will
4305 never change. @value{GDBN} refuses to create a watchpoint that watches
4306 a never-changing value:
4309 (@value{GDBP}) watch 0x600850
4310 Cannot watch constant value 0x600850.
4311 (@value{GDBP}) watch *(int *) 0x600850
4312 Watchpoint 1: *(int *) 6293584
4315 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4316 watchpoints execute very quickly, and the debugger reports a change in
4317 value at the exact instruction where the change occurs. If @value{GDBN}
4318 cannot set a hardware watchpoint, it sets a software watchpoint, which
4319 executes more slowly and reports the change in value at the next
4320 @emph{statement}, not the instruction, after the change occurs.
4322 @cindex use only software watchpoints
4323 You can force @value{GDBN} to use only software watchpoints with the
4324 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4325 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4326 the underlying system supports them. (Note that hardware-assisted
4327 watchpoints that were set @emph{before} setting
4328 @code{can-use-hw-watchpoints} to zero will still use the hardware
4329 mechanism of watching expression values.)
4332 @item set can-use-hw-watchpoints
4333 @kindex set can-use-hw-watchpoints
4334 Set whether or not to use hardware watchpoints.
4336 @item show can-use-hw-watchpoints
4337 @kindex show can-use-hw-watchpoints
4338 Show the current mode of using hardware watchpoints.
4341 For remote targets, you can restrict the number of hardware
4342 watchpoints @value{GDBN} will use, see @ref{set remote
4343 hardware-breakpoint-limit}.
4345 When you issue the @code{watch} command, @value{GDBN} reports
4348 Hardware watchpoint @var{num}: @var{expr}
4352 if it was able to set a hardware watchpoint.
4354 Currently, the @code{awatch} and @code{rwatch} commands can only set
4355 hardware watchpoints, because accesses to data that don't change the
4356 value of the watched expression cannot be detected without examining
4357 every instruction as it is being executed, and @value{GDBN} does not do
4358 that currently. If @value{GDBN} finds that it is unable to set a
4359 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4360 will print a message like this:
4363 Expression cannot be implemented with read/access watchpoint.
4366 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4367 data type of the watched expression is wider than what a hardware
4368 watchpoint on the target machine can handle. For example, some systems
4369 can only watch regions that are up to 4 bytes wide; on such systems you
4370 cannot set hardware watchpoints for an expression that yields a
4371 double-precision floating-point number (which is typically 8 bytes
4372 wide). As a work-around, it might be possible to break the large region
4373 into a series of smaller ones and watch them with separate watchpoints.
4375 If you set too many hardware watchpoints, @value{GDBN} might be unable
4376 to insert all of them when you resume the execution of your program.
4377 Since the precise number of active watchpoints is unknown until such
4378 time as the program is about to be resumed, @value{GDBN} might not be
4379 able to warn you about this when you set the watchpoints, and the
4380 warning will be printed only when the program is resumed:
4383 Hardware watchpoint @var{num}: Could not insert watchpoint
4387 If this happens, delete or disable some of the watchpoints.
4389 Watching complex expressions that reference many variables can also
4390 exhaust the resources available for hardware-assisted watchpoints.
4391 That's because @value{GDBN} needs to watch every variable in the
4392 expression with separately allocated resources.
4394 If you call a function interactively using @code{print} or @code{call},
4395 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4396 kind of breakpoint or the call completes.
4398 @value{GDBN} automatically deletes watchpoints that watch local
4399 (automatic) variables, or expressions that involve such variables, when
4400 they go out of scope, that is, when the execution leaves the block in
4401 which these variables were defined. In particular, when the program
4402 being debugged terminates, @emph{all} local variables go out of scope,
4403 and so only watchpoints that watch global variables remain set. If you
4404 rerun the program, you will need to set all such watchpoints again. One
4405 way of doing that would be to set a code breakpoint at the entry to the
4406 @code{main} function and when it breaks, set all the watchpoints.
4408 @cindex watchpoints and threads
4409 @cindex threads and watchpoints
4410 In multi-threaded programs, watchpoints will detect changes to the
4411 watched expression from every thread.
4414 @emph{Warning:} In multi-threaded programs, software watchpoints
4415 have only limited usefulness. If @value{GDBN} creates a software
4416 watchpoint, it can only watch the value of an expression @emph{in a
4417 single thread}. If you are confident that the expression can only
4418 change due to the current thread's activity (and if you are also
4419 confident that no other thread can become current), then you can use
4420 software watchpoints as usual. However, @value{GDBN} may not notice
4421 when a non-current thread's activity changes the expression. (Hardware
4422 watchpoints, in contrast, watch an expression in all threads.)
4425 @xref{set remote hardware-watchpoint-limit}.
4427 @node Set Catchpoints
4428 @subsection Setting Catchpoints
4429 @cindex catchpoints, setting
4430 @cindex exception handlers
4431 @cindex event handling
4433 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4434 kinds of program events, such as C@t{++} exceptions or the loading of a
4435 shared library. Use the @code{catch} command to set a catchpoint.
4439 @item catch @var{event}
4440 Stop when @var{event} occurs. The @var{event} can be any of the following:
4443 @item throw @r{[}@var{regexp}@r{]}
4444 @itemx rethrow @r{[}@var{regexp}@r{]}
4445 @itemx catch @r{[}@var{regexp}@r{]}
4447 @kindex catch rethrow
4449 @cindex stop on C@t{++} exceptions
4450 The throwing, re-throwing, or catching of a C@t{++} exception.
4452 If @var{regexp} is given, then only exceptions whose type matches the
4453 regular expression will be caught.
4455 @vindex $_exception@r{, convenience variable}
4456 The convenience variable @code{$_exception} is available at an
4457 exception-related catchpoint, on some systems. This holds the
4458 exception being thrown.
4460 There are currently some limitations to C@t{++} exception handling in
4465 The support for these commands is system-dependent. Currently, only
4466 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4470 The regular expression feature and the @code{$_exception} convenience
4471 variable rely on the presence of some SDT probes in @code{libstdc++}.
4472 If these probes are not present, then these features cannot be used.
4473 These probes were first available in the GCC 4.8 release, but whether
4474 or not they are available in your GCC also depends on how it was
4478 The @code{$_exception} convenience variable is only valid at the
4479 instruction at which an exception-related catchpoint is set.
4482 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4483 location in the system library which implements runtime exception
4484 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4485 (@pxref{Selection}) to get to your code.
4488 If you call a function interactively, @value{GDBN} normally returns
4489 control to you when the function has finished executing. If the call
4490 raises an exception, however, the call may bypass the mechanism that
4491 returns control to you and cause your program either to abort or to
4492 simply continue running until it hits a breakpoint, catches a signal
4493 that @value{GDBN} is listening for, or exits. This is the case even if
4494 you set a catchpoint for the exception; catchpoints on exceptions are
4495 disabled within interactive calls. @xref{Calling}, for information on
4496 controlling this with @code{set unwind-on-terminating-exception}.
4499 You cannot raise an exception interactively.
4502 You cannot install an exception handler interactively.
4506 @kindex catch exception
4507 @cindex Ada exception catching
4508 @cindex catch Ada exceptions
4509 An Ada exception being raised. If an exception name is specified
4510 at the end of the command (eg @code{catch exception Program_Error}),
4511 the debugger will stop only when this specific exception is raised.
4512 Otherwise, the debugger stops execution when any Ada exception is raised.
4514 When inserting an exception catchpoint on a user-defined exception whose
4515 name is identical to one of the exceptions defined by the language, the
4516 fully qualified name must be used as the exception name. Otherwise,
4517 @value{GDBN} will assume that it should stop on the pre-defined exception
4518 rather than the user-defined one. For instance, assuming an exception
4519 called @code{Constraint_Error} is defined in package @code{Pck}, then
4520 the command to use to catch such exceptions is @kbd{catch exception
4521 Pck.Constraint_Error}.
4524 @kindex catch handlers
4525 @cindex Ada exception handlers catching
4526 @cindex catch Ada exceptions when handled
4527 An Ada exception being handled. If an exception name is
4528 specified at the end of the command
4529 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4530 only when this specific exception is handled.
4531 Otherwise, the debugger stops execution when any Ada exception is handled.
4533 When inserting a handlers catchpoint on a user-defined
4534 exception whose name is identical to one of the exceptions
4535 defined by the language, the fully qualified name must be used
4536 as the exception name. Otherwise, @value{GDBN} will assume that it
4537 should stop on the pre-defined exception rather than the
4538 user-defined one. For instance, assuming an exception called
4539 @code{Constraint_Error} is defined in package @code{Pck}, then the
4540 command to use to catch such exceptions handling is
4541 @kbd{catch handlers Pck.Constraint_Error}.
4543 @item exception unhandled
4544 @kindex catch exception unhandled
4545 An exception that was raised but is not handled by the program.
4548 @kindex catch assert
4549 A failed Ada assertion.
4553 @cindex break on fork/exec
4554 A call to @code{exec}.
4557 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4558 @kindex catch syscall
4559 @cindex break on a system call.
4560 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4561 syscall is a mechanism for application programs to request a service
4562 from the operating system (OS) or one of the OS system services.
4563 @value{GDBN} can catch some or all of the syscalls issued by the
4564 debuggee, and show the related information for each syscall. If no
4565 argument is specified, calls to and returns from all system calls
4568 @var{name} can be any system call name that is valid for the
4569 underlying OS. Just what syscalls are valid depends on the OS. On
4570 GNU and Unix systems, you can find the full list of valid syscall
4571 names on @file{/usr/include/asm/unistd.h}.
4573 @c For MS-Windows, the syscall names and the corresponding numbers
4574 @c can be found, e.g., on this URL:
4575 @c http://www.metasploit.com/users/opcode/syscalls.html
4576 @c but we don't support Windows syscalls yet.
4578 Normally, @value{GDBN} knows in advance which syscalls are valid for
4579 each OS, so you can use the @value{GDBN} command-line completion
4580 facilities (@pxref{Completion,, command completion}) to list the
4583 You may also specify the system call numerically. A syscall's
4584 number is the value passed to the OS's syscall dispatcher to
4585 identify the requested service. When you specify the syscall by its
4586 name, @value{GDBN} uses its database of syscalls to convert the name
4587 into the corresponding numeric code, but using the number directly
4588 may be useful if @value{GDBN}'s database does not have the complete
4589 list of syscalls on your system (e.g., because @value{GDBN} lags
4590 behind the OS upgrades).
4592 You may specify a group of related syscalls to be caught at once using
4593 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4594 instance, on some platforms @value{GDBN} allows you to catch all
4595 network related syscalls, by passing the argument @code{group:network}
4596 to @code{catch syscall}. Note that not all syscall groups are
4597 available in every system. You can use the command completion
4598 facilities (@pxref{Completion,, command completion}) to list the
4599 syscall groups available on your environment.
4601 The example below illustrates how this command works if you don't provide
4605 (@value{GDBP}) catch syscall
4606 Catchpoint 1 (syscall)
4608 Starting program: /tmp/catch-syscall
4610 Catchpoint 1 (call to syscall 'close'), \
4611 0xffffe424 in __kernel_vsyscall ()
4615 Catchpoint 1 (returned from syscall 'close'), \
4616 0xffffe424 in __kernel_vsyscall ()
4620 Here is an example of catching a system call by name:
4623 (@value{GDBP}) catch syscall chroot
4624 Catchpoint 1 (syscall 'chroot' [61])
4626 Starting program: /tmp/catch-syscall
4628 Catchpoint 1 (call to syscall 'chroot'), \
4629 0xffffe424 in __kernel_vsyscall ()
4633 Catchpoint 1 (returned from syscall 'chroot'), \
4634 0xffffe424 in __kernel_vsyscall ()
4638 An example of specifying a system call numerically. In the case
4639 below, the syscall number has a corresponding entry in the XML
4640 file, so @value{GDBN} finds its name and prints it:
4643 (@value{GDBP}) catch syscall 252
4644 Catchpoint 1 (syscall(s) 'exit_group')
4646 Starting program: /tmp/catch-syscall
4648 Catchpoint 1 (call to syscall 'exit_group'), \
4649 0xffffe424 in __kernel_vsyscall ()
4653 Program exited normally.
4657 Here is an example of catching a syscall group:
4660 (@value{GDBP}) catch syscall group:process
4661 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4662 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4663 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4665 Starting program: /tmp/catch-syscall
4667 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4668 from /lib64/ld-linux-x86-64.so.2
4674 However, there can be situations when there is no corresponding name
4675 in XML file for that syscall number. In this case, @value{GDBN} prints
4676 a warning message saying that it was not able to find the syscall name,
4677 but the catchpoint will be set anyway. See the example below:
4680 (@value{GDBP}) catch syscall 764
4681 warning: The number '764' does not represent a known syscall.
4682 Catchpoint 2 (syscall 764)
4686 If you configure @value{GDBN} using the @samp{--without-expat} option,
4687 it will not be able to display syscall names. Also, if your
4688 architecture does not have an XML file describing its system calls,
4689 you will not be able to see the syscall names. It is important to
4690 notice that these two features are used for accessing the syscall
4691 name database. In either case, you will see a warning like this:
4694 (@value{GDBP}) catch syscall
4695 warning: Could not open "syscalls/i386-linux.xml"
4696 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4697 GDB will not be able to display syscall names.
4698 Catchpoint 1 (syscall)
4702 Of course, the file name will change depending on your architecture and system.
4704 Still using the example above, you can also try to catch a syscall by its
4705 number. In this case, you would see something like:
4708 (@value{GDBP}) catch syscall 252
4709 Catchpoint 1 (syscall(s) 252)
4712 Again, in this case @value{GDBN} would not be able to display syscall's names.
4716 A call to @code{fork}.
4720 A call to @code{vfork}.
4722 @item load @r{[}regexp@r{]}
4723 @itemx unload @r{[}regexp@r{]}
4725 @kindex catch unload
4726 The loading or unloading of a shared library. If @var{regexp} is
4727 given, then the catchpoint will stop only if the regular expression
4728 matches one of the affected libraries.
4730 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4731 @kindex catch signal
4732 The delivery of a signal.
4734 With no arguments, this catchpoint will catch any signal that is not
4735 used internally by @value{GDBN}, specifically, all signals except
4736 @samp{SIGTRAP} and @samp{SIGINT}.
4738 With the argument @samp{all}, all signals, including those used by
4739 @value{GDBN}, will be caught. This argument cannot be used with other
4742 Otherwise, the arguments are a list of signal names as given to
4743 @code{handle} (@pxref{Signals}). Only signals specified in this list
4746 One reason that @code{catch signal} can be more useful than
4747 @code{handle} is that you can attach commands and conditions to the
4750 When a signal is caught by a catchpoint, the signal's @code{stop} and
4751 @code{print} settings, as specified by @code{handle}, are ignored.
4752 However, whether the signal is still delivered to the inferior depends
4753 on the @code{pass} setting; this can be changed in the catchpoint's
4758 @item tcatch @var{event}
4760 Set a catchpoint that is enabled only for one stop. The catchpoint is
4761 automatically deleted after the first time the event is caught.
4765 Use the @code{info break} command to list the current catchpoints.
4769 @subsection Deleting Breakpoints
4771 @cindex clearing breakpoints, watchpoints, catchpoints
4772 @cindex deleting breakpoints, watchpoints, catchpoints
4773 It is often necessary to eliminate a breakpoint, watchpoint, or
4774 catchpoint once it has done its job and you no longer want your program
4775 to stop there. This is called @dfn{deleting} the breakpoint. A
4776 breakpoint that has been deleted no longer exists; it is forgotten.
4778 With the @code{clear} command you can delete breakpoints according to
4779 where they are in your program. With the @code{delete} command you can
4780 delete individual breakpoints, watchpoints, or catchpoints by specifying
4781 their breakpoint numbers.
4783 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4784 automatically ignores breakpoints on the first instruction to be executed
4785 when you continue execution without changing the execution address.
4790 Delete any breakpoints at the next instruction to be executed in the
4791 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4792 the innermost frame is selected, this is a good way to delete a
4793 breakpoint where your program just stopped.
4795 @item clear @var{location}
4796 Delete any breakpoints set at the specified @var{location}.
4797 @xref{Specify Location}, for the various forms of @var{location}; the
4798 most useful ones are listed below:
4801 @item clear @var{function}
4802 @itemx clear @var{filename}:@var{function}
4803 Delete any breakpoints set at entry to the named @var{function}.
4805 @item clear @var{linenum}
4806 @itemx clear @var{filename}:@var{linenum}
4807 Delete any breakpoints set at or within the code of the specified
4808 @var{linenum} of the specified @var{filename}.
4811 @cindex delete breakpoints
4813 @kindex d @r{(@code{delete})}
4814 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4815 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4816 list specified as argument. If no argument is specified, delete all
4817 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4818 confirm off}). You can abbreviate this command as @code{d}.
4822 @subsection Disabling Breakpoints
4824 @cindex enable/disable a breakpoint
4825 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4826 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4827 it had been deleted, but remembers the information on the breakpoint so
4828 that you can @dfn{enable} it again later.
4830 You disable and enable breakpoints, watchpoints, and catchpoints with
4831 the @code{enable} and @code{disable} commands, optionally specifying
4832 one or more breakpoint numbers as arguments. Use @code{info break} to
4833 print a list of all breakpoints, watchpoints, and catchpoints if you
4834 do not know which numbers to use.
4836 Disabling and enabling a breakpoint that has multiple locations
4837 affects all of its locations.
4839 A breakpoint, watchpoint, or catchpoint can have any of several
4840 different states of enablement:
4844 Enabled. The breakpoint stops your program. A breakpoint set
4845 with the @code{break} command starts out in this state.
4847 Disabled. The breakpoint has no effect on your program.
4849 Enabled once. The breakpoint stops your program, but then becomes
4852 Enabled for a count. The breakpoint stops your program for the next
4853 N times, then becomes disabled.
4855 Enabled for deletion. The breakpoint stops your program, but
4856 immediately after it does so it is deleted permanently. A breakpoint
4857 set with the @code{tbreak} command starts out in this state.
4860 You can use the following commands to enable or disable breakpoints,
4861 watchpoints, and catchpoints:
4865 @kindex dis @r{(@code{disable})}
4866 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4867 Disable the specified breakpoints---or all breakpoints, if none are
4868 listed. A disabled breakpoint has no effect but is not forgotten. All
4869 options such as ignore-counts, conditions and commands are remembered in
4870 case the breakpoint is enabled again later. You may abbreviate
4871 @code{disable} as @code{dis}.
4874 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4875 Enable the specified breakpoints (or all defined breakpoints). They
4876 become effective once again in stopping your program.
4878 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4879 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4880 of these breakpoints immediately after stopping your program.
4882 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4883 Enable the specified breakpoints temporarily. @value{GDBN} records
4884 @var{count} with each of the specified breakpoints, and decrements a
4885 breakpoint's count when it is hit. When any count reaches 0,
4886 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4887 count (@pxref{Conditions, ,Break Conditions}), that will be
4888 decremented to 0 before @var{count} is affected.
4890 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4891 Enable the specified breakpoints to work once, then die. @value{GDBN}
4892 deletes any of these breakpoints as soon as your program stops there.
4893 Breakpoints set by the @code{tbreak} command start out in this state.
4896 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4897 @c confusing: tbreak is also initially enabled.
4898 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4899 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4900 subsequently, they become disabled or enabled only when you use one of
4901 the commands above. (The command @code{until} can set and delete a
4902 breakpoint of its own, but it does not change the state of your other
4903 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4907 @subsection Break Conditions
4908 @cindex conditional breakpoints
4909 @cindex breakpoint conditions
4911 @c FIXME what is scope of break condition expr? Context where wanted?
4912 @c in particular for a watchpoint?
4913 The simplest sort of breakpoint breaks every time your program reaches a
4914 specified place. You can also specify a @dfn{condition} for a
4915 breakpoint. A condition is just a Boolean expression in your
4916 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4917 a condition evaluates the expression each time your program reaches it,
4918 and your program stops only if the condition is @emph{true}.
4920 This is the converse of using assertions for program validation; in that
4921 situation, you want to stop when the assertion is violated---that is,
4922 when the condition is false. In C, if you want to test an assertion expressed
4923 by the condition @var{assert}, you should set the condition
4924 @samp{! @var{assert}} on the appropriate breakpoint.
4926 Conditions are also accepted for watchpoints; you may not need them,
4927 since a watchpoint is inspecting the value of an expression anyhow---but
4928 it might be simpler, say, to just set a watchpoint on a variable name,
4929 and specify a condition that tests whether the new value is an interesting
4932 Break conditions can have side effects, and may even call functions in
4933 your program. This can be useful, for example, to activate functions
4934 that log program progress, or to use your own print functions to
4935 format special data structures. The effects are completely predictable
4936 unless there is another enabled breakpoint at the same address. (In
4937 that case, @value{GDBN} might see the other breakpoint first and stop your
4938 program without checking the condition of this one.) Note that
4939 breakpoint commands are usually more convenient and flexible than break
4941 purpose of performing side effects when a breakpoint is reached
4942 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4944 Breakpoint conditions can also be evaluated on the target's side if
4945 the target supports it. Instead of evaluating the conditions locally,
4946 @value{GDBN} encodes the expression into an agent expression
4947 (@pxref{Agent Expressions}) suitable for execution on the target,
4948 independently of @value{GDBN}. Global variables become raw memory
4949 locations, locals become stack accesses, and so forth.
4951 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4952 when its condition evaluates to true. This mechanism may provide faster
4953 response times depending on the performance characteristics of the target
4954 since it does not need to keep @value{GDBN} informed about
4955 every breakpoint trigger, even those with false conditions.
4957 Break conditions can be specified when a breakpoint is set, by using
4958 @samp{if} in the arguments to the @code{break} command. @xref{Set
4959 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4960 with the @code{condition} command.
4962 You can also use the @code{if} keyword with the @code{watch} command.
4963 The @code{catch} command does not recognize the @code{if} keyword;
4964 @code{condition} is the only way to impose a further condition on a
4969 @item condition @var{bnum} @var{expression}
4970 Specify @var{expression} as the break condition for breakpoint,
4971 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4972 breakpoint @var{bnum} stops your program only if the value of
4973 @var{expression} is true (nonzero, in C). When you use
4974 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4975 syntactic correctness, and to determine whether symbols in it have
4976 referents in the context of your breakpoint. If @var{expression} uses
4977 symbols not referenced in the context of the breakpoint, @value{GDBN}
4978 prints an error message:
4981 No symbol "foo" in current context.
4986 not actually evaluate @var{expression} at the time the @code{condition}
4987 command (or a command that sets a breakpoint with a condition, like
4988 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4990 @item condition @var{bnum}
4991 Remove the condition from breakpoint number @var{bnum}. It becomes
4992 an ordinary unconditional breakpoint.
4995 @cindex ignore count (of breakpoint)
4996 A special case of a breakpoint condition is to stop only when the
4997 breakpoint has been reached a certain number of times. This is so
4998 useful that there is a special way to do it, using the @dfn{ignore
4999 count} of the breakpoint. Every breakpoint has an ignore count, which
5000 is an integer. Most of the time, the ignore count is zero, and
5001 therefore has no effect. But if your program reaches a breakpoint whose
5002 ignore count is positive, then instead of stopping, it just decrements
5003 the ignore count by one and continues. As a result, if the ignore count
5004 value is @var{n}, the breakpoint does not stop the next @var{n} times
5005 your program reaches it.
5009 @item ignore @var{bnum} @var{count}
5010 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5011 The next @var{count} times the breakpoint is reached, your program's
5012 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5015 To make the breakpoint stop the next time it is reached, specify
5018 When you use @code{continue} to resume execution of your program from a
5019 breakpoint, you can specify an ignore count directly as an argument to
5020 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5021 Stepping,,Continuing and Stepping}.
5023 If a breakpoint has a positive ignore count and a condition, the
5024 condition is not checked. Once the ignore count reaches zero,
5025 @value{GDBN} resumes checking the condition.
5027 You could achieve the effect of the ignore count with a condition such
5028 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5029 is decremented each time. @xref{Convenience Vars, ,Convenience
5033 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5036 @node Break Commands
5037 @subsection Breakpoint Command Lists
5039 @cindex breakpoint commands
5040 You can give any breakpoint (or watchpoint or catchpoint) a series of
5041 commands to execute when your program stops due to that breakpoint. For
5042 example, you might want to print the values of certain expressions, or
5043 enable other breakpoints.
5047 @kindex end@r{ (breakpoint commands)}
5048 @item commands @r{[}@var{list}@dots{}@r{]}
5049 @itemx @dots{} @var{command-list} @dots{}
5051 Specify a list of commands for the given breakpoints. The commands
5052 themselves appear on the following lines. Type a line containing just
5053 @code{end} to terminate the commands.
5055 To remove all commands from a breakpoint, type @code{commands} and
5056 follow it immediately with @code{end}; that is, give no commands.
5058 With no argument, @code{commands} refers to the last breakpoint,
5059 watchpoint, or catchpoint set (not to the breakpoint most recently
5060 encountered). If the most recent breakpoints were set with a single
5061 command, then the @code{commands} will apply to all the breakpoints
5062 set by that command. This applies to breakpoints set by
5063 @code{rbreak}, and also applies when a single @code{break} command
5064 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5068 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5069 disabled within a @var{command-list}.
5071 You can use breakpoint commands to start your program up again. Simply
5072 use the @code{continue} command, or @code{step}, or any other command
5073 that resumes execution.
5075 Any other commands in the command list, after a command that resumes
5076 execution, are ignored. This is because any time you resume execution
5077 (even with a simple @code{next} or @code{step}), you may encounter
5078 another breakpoint---which could have its own command list, leading to
5079 ambiguities about which list to execute.
5082 If the first command you specify in a command list is @code{silent}, the
5083 usual message about stopping at a breakpoint is not printed. This may
5084 be desirable for breakpoints that are to print a specific message and
5085 then continue. If none of the remaining commands print anything, you
5086 see no sign that the breakpoint was reached. @code{silent} is
5087 meaningful only at the beginning of a breakpoint command list.
5089 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5090 print precisely controlled output, and are often useful in silent
5091 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5093 For example, here is how you could use breakpoint commands to print the
5094 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5100 printf "x is %d\n",x
5105 One application for breakpoint commands is to compensate for one bug so
5106 you can test for another. Put a breakpoint just after the erroneous line
5107 of code, give it a condition to detect the case in which something
5108 erroneous has been done, and give it commands to assign correct values
5109 to any variables that need them. End with the @code{continue} command
5110 so that your program does not stop, and start with the @code{silent}
5111 command so that no output is produced. Here is an example:
5122 @node Dynamic Printf
5123 @subsection Dynamic Printf
5125 @cindex dynamic printf
5127 The dynamic printf command @code{dprintf} combines a breakpoint with
5128 formatted printing of your program's data to give you the effect of
5129 inserting @code{printf} calls into your program on-the-fly, without
5130 having to recompile it.
5132 In its most basic form, the output goes to the GDB console. However,
5133 you can set the variable @code{dprintf-style} for alternate handling.
5134 For instance, you can ask to format the output by calling your
5135 program's @code{printf} function. This has the advantage that the
5136 characters go to the program's output device, so they can recorded in
5137 redirects to files and so forth.
5139 If you are doing remote debugging with a stub or agent, you can also
5140 ask to have the printf handled by the remote agent. In addition to
5141 ensuring that the output goes to the remote program's device along
5142 with any other output the program might produce, you can also ask that
5143 the dprintf remain active even after disconnecting from the remote
5144 target. Using the stub/agent is also more efficient, as it can do
5145 everything without needing to communicate with @value{GDBN}.
5149 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5150 Whenever execution reaches @var{location}, print the values of one or
5151 more @var{expressions} under the control of the string @var{template}.
5152 To print several values, separate them with commas.
5154 @item set dprintf-style @var{style}
5155 Set the dprintf output to be handled in one of several different
5156 styles enumerated below. A change of style affects all existing
5157 dynamic printfs immediately. (If you need individual control over the
5158 print commands, simply define normal breakpoints with
5159 explicitly-supplied command lists.)
5163 @kindex dprintf-style gdb
5164 Handle the output using the @value{GDBN} @code{printf} command.
5167 @kindex dprintf-style call
5168 Handle the output by calling a function in your program (normally
5172 @kindex dprintf-style agent
5173 Have the remote debugging agent (such as @code{gdbserver}) handle
5174 the output itself. This style is only available for agents that
5175 support running commands on the target.
5178 @item set dprintf-function @var{function}
5179 Set the function to call if the dprintf style is @code{call}. By
5180 default its value is @code{printf}. You may set it to any expression.
5181 that @value{GDBN} can evaluate to a function, as per the @code{call}
5184 @item set dprintf-channel @var{channel}
5185 Set a ``channel'' for dprintf. If set to a non-empty value,
5186 @value{GDBN} will evaluate it as an expression and pass the result as
5187 a first argument to the @code{dprintf-function}, in the manner of
5188 @code{fprintf} and similar functions. Otherwise, the dprintf format
5189 string will be the first argument, in the manner of @code{printf}.
5191 As an example, if you wanted @code{dprintf} output to go to a logfile
5192 that is a standard I/O stream assigned to the variable @code{mylog},
5193 you could do the following:
5196 (gdb) set dprintf-style call
5197 (gdb) set dprintf-function fprintf
5198 (gdb) set dprintf-channel mylog
5199 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5200 Dprintf 1 at 0x123456: file main.c, line 25.
5202 1 dprintf keep y 0x00123456 in main at main.c:25
5203 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5208 Note that the @code{info break} displays the dynamic printf commands
5209 as normal breakpoint commands; you can thus easily see the effect of
5210 the variable settings.
5212 @item set disconnected-dprintf on
5213 @itemx set disconnected-dprintf off
5214 @kindex set disconnected-dprintf
5215 Choose whether @code{dprintf} commands should continue to run if
5216 @value{GDBN} has disconnected from the target. This only applies
5217 if the @code{dprintf-style} is @code{agent}.
5219 @item show disconnected-dprintf off
5220 @kindex show disconnected-dprintf
5221 Show the current choice for disconnected @code{dprintf}.
5225 @value{GDBN} does not check the validity of function and channel,
5226 relying on you to supply values that are meaningful for the contexts
5227 in which they are being used. For instance, the function and channel
5228 may be the values of local variables, but if that is the case, then
5229 all enabled dynamic prints must be at locations within the scope of
5230 those locals. If evaluation fails, @value{GDBN} will report an error.
5232 @node Save Breakpoints
5233 @subsection How to save breakpoints to a file
5235 To save breakpoint definitions to a file use the @w{@code{save
5236 breakpoints}} command.
5239 @kindex save breakpoints
5240 @cindex save breakpoints to a file for future sessions
5241 @item save breakpoints [@var{filename}]
5242 This command saves all current breakpoint definitions together with
5243 their commands and ignore counts, into a file @file{@var{filename}}
5244 suitable for use in a later debugging session. This includes all
5245 types of breakpoints (breakpoints, watchpoints, catchpoints,
5246 tracepoints). To read the saved breakpoint definitions, use the
5247 @code{source} command (@pxref{Command Files}). Note that watchpoints
5248 with expressions involving local variables may fail to be recreated
5249 because it may not be possible to access the context where the
5250 watchpoint is valid anymore. Because the saved breakpoint definitions
5251 are simply a sequence of @value{GDBN} commands that recreate the
5252 breakpoints, you can edit the file in your favorite editing program,
5253 and remove the breakpoint definitions you're not interested in, or
5254 that can no longer be recreated.
5257 @node Static Probe Points
5258 @subsection Static Probe Points
5260 @cindex static probe point, SystemTap
5261 @cindex static probe point, DTrace
5262 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5263 for Statically Defined Tracing, and the probes are designed to have a tiny
5264 runtime code and data footprint, and no dynamic relocations.
5266 Currently, the following types of probes are supported on
5267 ELF-compatible systems:
5271 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5272 @acronym{SDT} probes@footnote{See
5273 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5274 for more information on how to add @code{SystemTap} @acronym{SDT}
5275 probes in your applications.}. @code{SystemTap} probes are usable
5276 from assembly, C and C@t{++} languages@footnote{See
5277 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5278 for a good reference on how the @acronym{SDT} probes are implemented.}.
5280 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5281 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5285 @cindex semaphores on static probe points
5286 Some @code{SystemTap} probes have an associated semaphore variable;
5287 for instance, this happens automatically if you defined your probe
5288 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5289 @value{GDBN} will automatically enable it when you specify a
5290 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5291 breakpoint at a probe's location by some other method (e.g.,
5292 @code{break file:line}), then @value{GDBN} will not automatically set
5293 the semaphore. @code{DTrace} probes do not support semaphores.
5295 You can examine the available static static probes using @code{info
5296 probes}, with optional arguments:
5300 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5301 If given, @var{type} is either @code{stap} for listing
5302 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5303 probes. If omitted all probes are listed regardless of their types.
5305 If given, @var{provider} is a regular expression used to match against provider
5306 names when selecting which probes to list. If omitted, probes by all
5307 probes from all providers are listed.
5309 If given, @var{name} is a regular expression to match against probe names
5310 when selecting which probes to list. If omitted, probe names are not
5311 considered when deciding whether to display them.
5313 If given, @var{objfile} is a regular expression used to select which
5314 object files (executable or shared libraries) to examine. If not
5315 given, all object files are considered.
5317 @item info probes all
5318 List the available static probes, from all types.
5321 @cindex enabling and disabling probes
5322 Some probe points can be enabled and/or disabled. The effect of
5323 enabling or disabling a probe depends on the type of probe being
5324 handled. Some @code{DTrace} probes can be enabled or
5325 disabled, but @code{SystemTap} probes cannot be disabled.
5327 You can enable (or disable) one or more probes using the following
5328 commands, with optional arguments:
5331 @kindex enable probes
5332 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5333 If given, @var{provider} is a regular expression used to match against
5334 provider names when selecting which probes to enable. If omitted,
5335 all probes from all providers are enabled.
5337 If given, @var{name} is a regular expression to match against probe
5338 names when selecting which probes to enable. If omitted, probe names
5339 are not considered when deciding whether to enable them.
5341 If given, @var{objfile} is a regular expression used to select which
5342 object files (executable or shared libraries) to examine. If not
5343 given, all object files are considered.
5345 @kindex disable probes
5346 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5347 See the @code{enable probes} command above for a description of the
5348 optional arguments accepted by this command.
5351 @vindex $_probe_arg@r{, convenience variable}
5352 A probe may specify up to twelve arguments. These are available at the
5353 point at which the probe is defined---that is, when the current PC is
5354 at the probe's location. The arguments are available using the
5355 convenience variables (@pxref{Convenience Vars})
5356 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5357 probes each probe argument is an integer of the appropriate size;
5358 types are not preserved. In @code{DTrace} probes types are preserved
5359 provided that they are recognized as such by @value{GDBN}; otherwise
5360 the value of the probe argument will be a long integer. The
5361 convenience variable @code{$_probe_argc} holds the number of arguments
5362 at the current probe point.
5364 These variables are always available, but attempts to access them at
5365 any location other than a probe point will cause @value{GDBN} to give
5369 @c @ifclear BARETARGET
5370 @node Error in Breakpoints
5371 @subsection ``Cannot insert breakpoints''
5373 If you request too many active hardware-assisted breakpoints and
5374 watchpoints, you will see this error message:
5376 @c FIXME: the precise wording of this message may change; the relevant
5377 @c source change is not committed yet (Sep 3, 1999).
5379 Stopped; cannot insert breakpoints.
5380 You may have requested too many hardware breakpoints and watchpoints.
5384 This message is printed when you attempt to resume the program, since
5385 only then @value{GDBN} knows exactly how many hardware breakpoints and
5386 watchpoints it needs to insert.
5388 When this message is printed, you need to disable or remove some of the
5389 hardware-assisted breakpoints and watchpoints, and then continue.
5391 @node Breakpoint-related Warnings
5392 @subsection ``Breakpoint address adjusted...''
5393 @cindex breakpoint address adjusted
5395 Some processor architectures place constraints on the addresses at
5396 which breakpoints may be placed. For architectures thus constrained,
5397 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5398 with the constraints dictated by the architecture.
5400 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5401 a VLIW architecture in which a number of RISC-like instructions may be
5402 bundled together for parallel execution. The FR-V architecture
5403 constrains the location of a breakpoint instruction within such a
5404 bundle to the instruction with the lowest address. @value{GDBN}
5405 honors this constraint by adjusting a breakpoint's address to the
5406 first in the bundle.
5408 It is not uncommon for optimized code to have bundles which contain
5409 instructions from different source statements, thus it may happen that
5410 a breakpoint's address will be adjusted from one source statement to
5411 another. Since this adjustment may significantly alter @value{GDBN}'s
5412 breakpoint related behavior from what the user expects, a warning is
5413 printed when the breakpoint is first set and also when the breakpoint
5416 A warning like the one below is printed when setting a breakpoint
5417 that's been subject to address adjustment:
5420 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5423 Such warnings are printed both for user settable and @value{GDBN}'s
5424 internal breakpoints. If you see one of these warnings, you should
5425 verify that a breakpoint set at the adjusted address will have the
5426 desired affect. If not, the breakpoint in question may be removed and
5427 other breakpoints may be set which will have the desired behavior.
5428 E.g., it may be sufficient to place the breakpoint at a later
5429 instruction. A conditional breakpoint may also be useful in some
5430 cases to prevent the breakpoint from triggering too often.
5432 @value{GDBN} will also issue a warning when stopping at one of these
5433 adjusted breakpoints:
5436 warning: Breakpoint 1 address previously adjusted from 0x00010414
5440 When this warning is encountered, it may be too late to take remedial
5441 action except in cases where the breakpoint is hit earlier or more
5442 frequently than expected.
5444 @node Continuing and Stepping
5445 @section Continuing and Stepping
5449 @cindex resuming execution
5450 @dfn{Continuing} means resuming program execution until your program
5451 completes normally. In contrast, @dfn{stepping} means executing just
5452 one more ``step'' of your program, where ``step'' may mean either one
5453 line of source code, or one machine instruction (depending on what
5454 particular command you use). Either when continuing or when stepping,
5455 your program may stop even sooner, due to a breakpoint or a signal. (If
5456 it stops due to a signal, you may want to use @code{handle}, or use
5457 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5458 or you may step into the signal's handler (@pxref{stepping and signal
5463 @kindex c @r{(@code{continue})}
5464 @kindex fg @r{(resume foreground execution)}
5465 @item continue @r{[}@var{ignore-count}@r{]}
5466 @itemx c @r{[}@var{ignore-count}@r{]}
5467 @itemx fg @r{[}@var{ignore-count}@r{]}
5468 Resume program execution, at the address where your program last stopped;
5469 any breakpoints set at that address are bypassed. The optional argument
5470 @var{ignore-count} allows you to specify a further number of times to
5471 ignore a breakpoint at this location; its effect is like that of
5472 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5474 The argument @var{ignore-count} is meaningful only when your program
5475 stopped due to a breakpoint. At other times, the argument to
5476 @code{continue} is ignored.
5478 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5479 debugged program is deemed to be the foreground program) are provided
5480 purely for convenience, and have exactly the same behavior as
5484 To resume execution at a different place, you can use @code{return}
5485 (@pxref{Returning, ,Returning from a Function}) to go back to the
5486 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5487 Different Address}) to go to an arbitrary location in your program.
5489 A typical technique for using stepping is to set a breakpoint
5490 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5491 beginning of the function or the section of your program where a problem
5492 is believed to lie, run your program until it stops at that breakpoint,
5493 and then step through the suspect area, examining the variables that are
5494 interesting, until you see the problem happen.
5498 @kindex s @r{(@code{step})}
5500 Continue running your program until control reaches a different source
5501 line, then stop it and return control to @value{GDBN}. This command is
5502 abbreviated @code{s}.
5505 @c "without debugging information" is imprecise; actually "without line
5506 @c numbers in the debugging information". (gcc -g1 has debugging info but
5507 @c not line numbers). But it seems complex to try to make that
5508 @c distinction here.
5509 @emph{Warning:} If you use the @code{step} command while control is
5510 within a function that was compiled without debugging information,
5511 execution proceeds until control reaches a function that does have
5512 debugging information. Likewise, it will not step into a function which
5513 is compiled without debugging information. To step through functions
5514 without debugging information, use the @code{stepi} command, described
5518 The @code{step} command only stops at the first instruction of a source
5519 line. This prevents the multiple stops that could otherwise occur in
5520 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5521 to stop if a function that has debugging information is called within
5522 the line. In other words, @code{step} @emph{steps inside} any functions
5523 called within the line.
5525 Also, the @code{step} command only enters a function if there is line
5526 number information for the function. Otherwise it acts like the
5527 @code{next} command. This avoids problems when using @code{cc -gl}
5528 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5529 was any debugging information about the routine.
5531 @item step @var{count}
5532 Continue running as in @code{step}, but do so @var{count} times. If a
5533 breakpoint is reached, or a signal not related to stepping occurs before
5534 @var{count} steps, stepping stops right away.
5537 @kindex n @r{(@code{next})}
5538 @item next @r{[}@var{count}@r{]}
5539 Continue to the next source line in the current (innermost) stack frame.
5540 This is similar to @code{step}, but function calls that appear within
5541 the line of code are executed without stopping. Execution stops when
5542 control reaches a different line of code at the original stack level
5543 that was executing when you gave the @code{next} command. This command
5544 is abbreviated @code{n}.
5546 An argument @var{count} is a repeat count, as for @code{step}.
5549 @c FIX ME!! Do we delete this, or is there a way it fits in with
5550 @c the following paragraph? --- Vctoria
5552 @c @code{next} within a function that lacks debugging information acts like
5553 @c @code{step}, but any function calls appearing within the code of the
5554 @c function are executed without stopping.
5556 The @code{next} command only stops at the first instruction of a
5557 source line. This prevents multiple stops that could otherwise occur in
5558 @code{switch} statements, @code{for} loops, etc.
5560 @kindex set step-mode
5562 @cindex functions without line info, and stepping
5563 @cindex stepping into functions with no line info
5564 @itemx set step-mode on
5565 The @code{set step-mode on} command causes the @code{step} command to
5566 stop at the first instruction of a function which contains no debug line
5567 information rather than stepping over it.
5569 This is useful in cases where you may be interested in inspecting the
5570 machine instructions of a function which has no symbolic info and do not
5571 want @value{GDBN} to automatically skip over this function.
5573 @item set step-mode off
5574 Causes the @code{step} command to step over any functions which contains no
5575 debug information. This is the default.
5577 @item show step-mode
5578 Show whether @value{GDBN} will stop in or step over functions without
5579 source line debug information.
5582 @kindex fin @r{(@code{finish})}
5584 Continue running until just after function in the selected stack frame
5585 returns. Print the returned value (if any). This command can be
5586 abbreviated as @code{fin}.
5588 Contrast this with the @code{return} command (@pxref{Returning,
5589 ,Returning from a Function}).
5592 @kindex u @r{(@code{until})}
5593 @cindex run until specified location
5596 Continue running until a source line past the current line, in the
5597 current stack frame, is reached. This command is used to avoid single
5598 stepping through a loop more than once. It is like the @code{next}
5599 command, except that when @code{until} encounters a jump, it
5600 automatically continues execution until the program counter is greater
5601 than the address of the jump.
5603 This means that when you reach the end of a loop after single stepping
5604 though it, @code{until} makes your program continue execution until it
5605 exits the loop. In contrast, a @code{next} command at the end of a loop
5606 simply steps back to the beginning of the loop, which forces you to step
5607 through the next iteration.
5609 @code{until} always stops your program if it attempts to exit the current
5612 @code{until} may produce somewhat counterintuitive results if the order
5613 of machine code does not match the order of the source lines. For
5614 example, in the following excerpt from a debugging session, the @code{f}
5615 (@code{frame}) command shows that execution is stopped at line
5616 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5620 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5622 (@value{GDBP}) until
5623 195 for ( ; argc > 0; NEXTARG) @{
5626 This happened because, for execution efficiency, the compiler had
5627 generated code for the loop closure test at the end, rather than the
5628 start, of the loop---even though the test in a C @code{for}-loop is
5629 written before the body of the loop. The @code{until} command appeared
5630 to step back to the beginning of the loop when it advanced to this
5631 expression; however, it has not really gone to an earlier
5632 statement---not in terms of the actual machine code.
5634 @code{until} with no argument works by means of single
5635 instruction stepping, and hence is slower than @code{until} with an
5638 @item until @var{location}
5639 @itemx u @var{location}
5640 Continue running your program until either the specified @var{location} is
5641 reached, or the current stack frame returns. The location is any of
5642 the forms described in @ref{Specify Location}.
5643 This form of the command uses temporary breakpoints, and
5644 hence is quicker than @code{until} without an argument. The specified
5645 location is actually reached only if it is in the current frame. This
5646 implies that @code{until} can be used to skip over recursive function
5647 invocations. For instance in the code below, if the current location is
5648 line @code{96}, issuing @code{until 99} will execute the program up to
5649 line @code{99} in the same invocation of factorial, i.e., after the inner
5650 invocations have returned.
5653 94 int factorial (int value)
5655 96 if (value > 1) @{
5656 97 value *= factorial (value - 1);
5663 @kindex advance @var{location}
5664 @item advance @var{location}
5665 Continue running the program up to the given @var{location}. An argument is
5666 required, which should be of one of the forms described in
5667 @ref{Specify Location}.
5668 Execution will also stop upon exit from the current stack
5669 frame. This command is similar to @code{until}, but @code{advance} will
5670 not skip over recursive function calls, and the target location doesn't
5671 have to be in the same frame as the current one.
5675 @kindex si @r{(@code{stepi})}
5677 @itemx stepi @var{arg}
5679 Execute one machine instruction, then stop and return to the debugger.
5681 It is often useful to do @samp{display/i $pc} when stepping by machine
5682 instructions. This makes @value{GDBN} automatically display the next
5683 instruction to be executed, each time your program stops. @xref{Auto
5684 Display,, Automatic Display}.
5686 An argument is a repeat count, as in @code{step}.
5690 @kindex ni @r{(@code{nexti})}
5692 @itemx nexti @var{arg}
5694 Execute one machine instruction, but if it is a function call,
5695 proceed until the function returns.
5697 An argument is a repeat count, as in @code{next}.
5701 @anchor{range stepping}
5702 @cindex range stepping
5703 @cindex target-assisted range stepping
5704 By default, and if available, @value{GDBN} makes use of
5705 target-assisted @dfn{range stepping}. In other words, whenever you
5706 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5707 tells the target to step the corresponding range of instruction
5708 addresses instead of issuing multiple single-steps. This speeds up
5709 line stepping, particularly for remote targets. Ideally, there should
5710 be no reason you would want to turn range stepping off. However, it's
5711 possible that a bug in the debug info, a bug in the remote stub (for
5712 remote targets), or even a bug in @value{GDBN} could make line
5713 stepping behave incorrectly when target-assisted range stepping is
5714 enabled. You can use the following command to turn off range stepping
5718 @kindex set range-stepping
5719 @kindex show range-stepping
5720 @item set range-stepping
5721 @itemx show range-stepping
5722 Control whether range stepping is enabled.
5724 If @code{on}, and the target supports it, @value{GDBN} tells the
5725 target to step a range of addresses itself, instead of issuing
5726 multiple single-steps. If @code{off}, @value{GDBN} always issues
5727 single-steps, even if range stepping is supported by the target. The
5728 default is @code{on}.
5732 @node Skipping Over Functions and Files
5733 @section Skipping Over Functions and Files
5734 @cindex skipping over functions and files
5736 The program you are debugging may contain some functions which are
5737 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5738 skip a function, all functions in a file or a particular function in
5739 a particular file when stepping.
5741 For example, consider the following C function:
5752 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5753 are not interested in stepping through @code{boring}. If you run @code{step}
5754 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5755 step over both @code{foo} and @code{boring}!
5757 One solution is to @code{step} into @code{boring} and use the @code{finish}
5758 command to immediately exit it. But this can become tedious if @code{boring}
5759 is called from many places.
5761 A more flexible solution is to execute @kbd{skip boring}. This instructs
5762 @value{GDBN} never to step into @code{boring}. Now when you execute
5763 @code{step} at line 103, you'll step over @code{boring} and directly into
5766 Functions may be skipped by providing either a function name, linespec
5767 (@pxref{Specify Location}), regular expression that matches the function's
5768 name, file name or a @code{glob}-style pattern that matches the file name.
5770 On Posix systems the form of the regular expression is
5771 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5772 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5773 expression is whatever is provided by the @code{regcomp} function of
5774 the underlying system.
5775 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5776 description of @code{glob}-style patterns.
5780 @item skip @r{[}@var{options}@r{]}
5781 The basic form of the @code{skip} command takes zero or more options
5782 that specify what to skip.
5783 The @var{options} argument is any useful combination of the following:
5786 @item -file @var{file}
5787 @itemx -fi @var{file}
5788 Functions in @var{file} will be skipped over when stepping.
5790 @item -gfile @var{file-glob-pattern}
5791 @itemx -gfi @var{file-glob-pattern}
5792 @cindex skipping over files via glob-style patterns
5793 Functions in files matching @var{file-glob-pattern} will be skipped
5797 (gdb) skip -gfi utils/*.c
5800 @item -function @var{linespec}
5801 @itemx -fu @var{linespec}
5802 Functions named by @var{linespec} or the function containing the line
5803 named by @var{linespec} will be skipped over when stepping.
5804 @xref{Specify Location}.
5806 @item -rfunction @var{regexp}
5807 @itemx -rfu @var{regexp}
5808 @cindex skipping over functions via regular expressions
5809 Functions whose name matches @var{regexp} will be skipped over when stepping.
5811 This form is useful for complex function names.
5812 For example, there is generally no need to step into C@t{++} @code{std::string}
5813 constructors or destructors. Plus with C@t{++} templates it can be hard to
5814 write out the full name of the function, and often it doesn't matter what
5815 the template arguments are. Specifying the function to be skipped as a
5816 regular expression makes this easier.
5819 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5822 If you want to skip every templated C@t{++} constructor and destructor
5823 in the @code{std} namespace you can do:
5826 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5830 If no options are specified, the function you're currently debugging
5833 @kindex skip function
5834 @item skip function @r{[}@var{linespec}@r{]}
5835 After running this command, the function named by @var{linespec} or the
5836 function containing the line named by @var{linespec} will be skipped over when
5837 stepping. @xref{Specify Location}.
5839 If you do not specify @var{linespec}, the function you're currently debugging
5842 (If you have a function called @code{file} that you want to skip, use
5843 @kbd{skip function file}.)
5846 @item skip file @r{[}@var{filename}@r{]}
5847 After running this command, any function whose source lives in @var{filename}
5848 will be skipped over when stepping.
5851 (gdb) skip file boring.c
5852 File boring.c will be skipped when stepping.
5855 If you do not specify @var{filename}, functions whose source lives in the file
5856 you're currently debugging will be skipped.
5859 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5860 These are the commands for managing your list of skips:
5864 @item info skip @r{[}@var{range}@r{]}
5865 Print details about the specified skip(s). If @var{range} is not specified,
5866 print a table with details about all functions and files marked for skipping.
5867 @code{info skip} prints the following information about each skip:
5871 A number identifying this skip.
5872 @item Enabled or Disabled
5873 Enabled skips are marked with @samp{y}.
5874 Disabled skips are marked with @samp{n}.
5876 If the file name is a @samp{glob} pattern this is @samp{y}.
5877 Otherwise it is @samp{n}.
5879 The name or @samp{glob} pattern of the file to be skipped.
5880 If no file is specified this is @samp{<none>}.
5882 If the function name is a @samp{regular expression} this is @samp{y}.
5883 Otherwise it is @samp{n}.
5885 The name or regular expression of the function to skip.
5886 If no function is specified this is @samp{<none>}.
5890 @item skip delete @r{[}@var{range}@r{]}
5891 Delete the specified skip(s). If @var{range} is not specified, delete all
5895 @item skip enable @r{[}@var{range}@r{]}
5896 Enable the specified skip(s). If @var{range} is not specified, enable all
5899 @kindex skip disable
5900 @item skip disable @r{[}@var{range}@r{]}
5901 Disable the specified skip(s). If @var{range} is not specified, disable all
5904 @kindex set debug skip
5905 @item set debug skip @r{[}on|off@r{]}
5906 Set whether to print the debug output about skipping files and functions.
5908 @kindex show debug skip
5909 @item show debug skip
5910 Show whether the debug output about skipping files and functions is printed.
5918 A signal is an asynchronous event that can happen in a program. The
5919 operating system defines the possible kinds of signals, and gives each
5920 kind a name and a number. For example, in Unix @code{SIGINT} is the
5921 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5922 @code{SIGSEGV} is the signal a program gets from referencing a place in
5923 memory far away from all the areas in use; @code{SIGALRM} occurs when
5924 the alarm clock timer goes off (which happens only if your program has
5925 requested an alarm).
5927 @cindex fatal signals
5928 Some signals, including @code{SIGALRM}, are a normal part of the
5929 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5930 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5931 program has not specified in advance some other way to handle the signal.
5932 @code{SIGINT} does not indicate an error in your program, but it is normally
5933 fatal so it can carry out the purpose of the interrupt: to kill the program.
5935 @value{GDBN} has the ability to detect any occurrence of a signal in your
5936 program. You can tell @value{GDBN} in advance what to do for each kind of
5939 @cindex handling signals
5940 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5941 @code{SIGALRM} be silently passed to your program
5942 (so as not to interfere with their role in the program's functioning)
5943 but to stop your program immediately whenever an error signal happens.
5944 You can change these settings with the @code{handle} command.
5947 @kindex info signals
5951 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5952 handle each one. You can use this to see the signal numbers of all
5953 the defined types of signals.
5955 @item info signals @var{sig}
5956 Similar, but print information only about the specified signal number.
5958 @code{info handle} is an alias for @code{info signals}.
5960 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5961 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5962 for details about this command.
5965 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5966 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5967 can be the number of a signal or its name (with or without the
5968 @samp{SIG} at the beginning); a list of signal numbers of the form
5969 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5970 known signals. Optional arguments @var{keywords}, described below,
5971 say what change to make.
5975 The keywords allowed by the @code{handle} command can be abbreviated.
5976 Their full names are:
5980 @value{GDBN} should not stop your program when this signal happens. It may
5981 still print a message telling you that the signal has come in.
5984 @value{GDBN} should stop your program when this signal happens. This implies
5985 the @code{print} keyword as well.
5988 @value{GDBN} should print a message when this signal happens.
5991 @value{GDBN} should not mention the occurrence of the signal at all. This
5992 implies the @code{nostop} keyword as well.
5996 @value{GDBN} should allow your program to see this signal; your program
5997 can handle the signal, or else it may terminate if the signal is fatal
5998 and not handled. @code{pass} and @code{noignore} are synonyms.
6002 @value{GDBN} should not allow your program to see this signal.
6003 @code{nopass} and @code{ignore} are synonyms.
6007 When a signal stops your program, the signal is not visible to the
6009 continue. Your program sees the signal then, if @code{pass} is in
6010 effect for the signal in question @emph{at that time}. In other words,
6011 after @value{GDBN} reports a signal, you can use the @code{handle}
6012 command with @code{pass} or @code{nopass} to control whether your
6013 program sees that signal when you continue.
6015 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6016 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6017 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6020 You can also use the @code{signal} command to prevent your program from
6021 seeing a signal, or cause it to see a signal it normally would not see,
6022 or to give it any signal at any time. For example, if your program stopped
6023 due to some sort of memory reference error, you might store correct
6024 values into the erroneous variables and continue, hoping to see more
6025 execution; but your program would probably terminate immediately as
6026 a result of the fatal signal once it saw the signal. To prevent this,
6027 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6030 @cindex stepping and signal handlers
6031 @anchor{stepping and signal handlers}
6033 @value{GDBN} optimizes for stepping the mainline code. If a signal
6034 that has @code{handle nostop} and @code{handle pass} set arrives while
6035 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6036 in progress, @value{GDBN} lets the signal handler run and then resumes
6037 stepping the mainline code once the signal handler returns. In other
6038 words, @value{GDBN} steps over the signal handler. This prevents
6039 signals that you've specified as not interesting (with @code{handle
6040 nostop}) from changing the focus of debugging unexpectedly. Note that
6041 the signal handler itself may still hit a breakpoint, stop for another
6042 signal that has @code{handle stop} in effect, or for any other event
6043 that normally results in stopping the stepping command sooner. Also
6044 note that @value{GDBN} still informs you that the program received a
6045 signal if @code{handle print} is set.
6047 @anchor{stepping into signal handlers}
6049 If you set @code{handle pass} for a signal, and your program sets up a
6050 handler for it, then issuing a stepping command, such as @code{step}
6051 or @code{stepi}, when your program is stopped due to the signal will
6052 step @emph{into} the signal handler (if the target supports that).
6054 Likewise, if you use the @code{queue-signal} command to queue a signal
6055 to be delivered to the current thread when execution of the thread
6056 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6057 stepping command will step into the signal handler.
6059 Here's an example, using @code{stepi} to step to the first instruction
6060 of @code{SIGUSR1}'s handler:
6063 (@value{GDBP}) handle SIGUSR1
6064 Signal Stop Print Pass to program Description
6065 SIGUSR1 Yes Yes Yes User defined signal 1
6069 Program received signal SIGUSR1, User defined signal 1.
6070 main () sigusr1.c:28
6073 sigusr1_handler () at sigusr1.c:9
6077 The same, but using @code{queue-signal} instead of waiting for the
6078 program to receive the signal first:
6083 (@value{GDBP}) queue-signal SIGUSR1
6085 sigusr1_handler () at sigusr1.c:9
6090 @cindex extra signal information
6091 @anchor{extra signal information}
6093 On some targets, @value{GDBN} can inspect extra signal information
6094 associated with the intercepted signal, before it is actually
6095 delivered to the program being debugged. This information is exported
6096 by the convenience variable @code{$_siginfo}, and consists of data
6097 that is passed by the kernel to the signal handler at the time of the
6098 receipt of a signal. The data type of the information itself is
6099 target dependent. You can see the data type using the @code{ptype
6100 $_siginfo} command. On Unix systems, it typically corresponds to the
6101 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6104 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6105 referenced address that raised a segmentation fault.
6109 (@value{GDBP}) continue
6110 Program received signal SIGSEGV, Segmentation fault.
6111 0x0000000000400766 in main ()
6113 (@value{GDBP}) ptype $_siginfo
6120 struct @{...@} _kill;
6121 struct @{...@} _timer;
6123 struct @{...@} _sigchld;
6124 struct @{...@} _sigfault;
6125 struct @{...@} _sigpoll;
6128 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6132 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6133 $1 = (void *) 0x7ffff7ff7000
6137 Depending on target support, @code{$_siginfo} may also be writable.
6139 @cindex Intel MPX boundary violations
6140 @cindex boundary violations, Intel MPX
6141 On some targets, a @code{SIGSEGV} can be caused by a boundary
6142 violation, i.e., accessing an address outside of the allowed range.
6143 In those cases @value{GDBN} may displays additional information,
6144 depending on how @value{GDBN} has been told to handle the signal.
6145 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6146 kind: "Upper" or "Lower", the memory address accessed and the
6147 bounds, while with @code{handle nostop SIGSEGV} no additional
6148 information is displayed.
6150 The usual output of a segfault is:
6152 Program received signal SIGSEGV, Segmentation fault
6153 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6154 68 value = *(p + len);
6157 While a bound violation is presented as:
6159 Program received signal SIGSEGV, Segmentation fault
6160 Upper bound violation while accessing address 0x7fffffffc3b3
6161 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6162 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6163 68 value = *(p + len);
6167 @section Stopping and Starting Multi-thread Programs
6169 @cindex stopped threads
6170 @cindex threads, stopped
6172 @cindex continuing threads
6173 @cindex threads, continuing
6175 @value{GDBN} supports debugging programs with multiple threads
6176 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6177 are two modes of controlling execution of your program within the
6178 debugger. In the default mode, referred to as @dfn{all-stop mode},
6179 when any thread in your program stops (for example, at a breakpoint
6180 or while being stepped), all other threads in the program are also stopped by
6181 @value{GDBN}. On some targets, @value{GDBN} also supports
6182 @dfn{non-stop mode}, in which other threads can continue to run freely while
6183 you examine the stopped thread in the debugger.
6186 * All-Stop Mode:: All threads stop when GDB takes control
6187 * Non-Stop Mode:: Other threads continue to execute
6188 * Background Execution:: Running your program asynchronously
6189 * Thread-Specific Breakpoints:: Controlling breakpoints
6190 * Interrupted System Calls:: GDB may interfere with system calls
6191 * Observer Mode:: GDB does not alter program behavior
6195 @subsection All-Stop Mode
6197 @cindex all-stop mode
6199 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6200 @emph{all} threads of execution stop, not just the current thread. This
6201 allows you to examine the overall state of the program, including
6202 switching between threads, without worrying that things may change
6205 Conversely, whenever you restart the program, @emph{all} threads start
6206 executing. @emph{This is true even when single-stepping} with commands
6207 like @code{step} or @code{next}.
6209 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6210 Since thread scheduling is up to your debugging target's operating
6211 system (not controlled by @value{GDBN}), other threads may
6212 execute more than one statement while the current thread completes a
6213 single step. Moreover, in general other threads stop in the middle of a
6214 statement, rather than at a clean statement boundary, when the program
6217 You might even find your program stopped in another thread after
6218 continuing or even single-stepping. This happens whenever some other
6219 thread runs into a breakpoint, a signal, or an exception before the
6220 first thread completes whatever you requested.
6222 @cindex automatic thread selection
6223 @cindex switching threads automatically
6224 @cindex threads, automatic switching
6225 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6226 signal, it automatically selects the thread where that breakpoint or
6227 signal happened. @value{GDBN} alerts you to the context switch with a
6228 message such as @samp{[Switching to Thread @var{n}]} to identify the
6231 On some OSes, you can modify @value{GDBN}'s default behavior by
6232 locking the OS scheduler to allow only a single thread to run.
6235 @item set scheduler-locking @var{mode}
6236 @cindex scheduler locking mode
6237 @cindex lock scheduler
6238 Set the scheduler locking mode. It applies to normal execution,
6239 record mode, and replay mode. If it is @code{off}, then there is no
6240 locking and any thread may run at any time. If @code{on}, then only
6241 the current thread may run when the inferior is resumed. The
6242 @code{step} mode optimizes for single-stepping; it prevents other
6243 threads from preempting the current thread while you are stepping, so
6244 that the focus of debugging does not change unexpectedly. Other
6245 threads never get a chance to run when you step, and they are
6246 completely free to run when you use commands like @samp{continue},
6247 @samp{until}, or @samp{finish}. However, unless another thread hits a
6248 breakpoint during its timeslice, @value{GDBN} does not change the
6249 current thread away from the thread that you are debugging. The
6250 @code{replay} mode behaves like @code{off} in record mode and like
6251 @code{on} in replay mode.
6253 @item show scheduler-locking
6254 Display the current scheduler locking mode.
6257 @cindex resume threads of multiple processes simultaneously
6258 By default, when you issue one of the execution commands such as
6259 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6260 threads of the current inferior to run. For example, if @value{GDBN}
6261 is attached to two inferiors, each with two threads, the
6262 @code{continue} command resumes only the two threads of the current
6263 inferior. This is useful, for example, when you debug a program that
6264 forks and you want to hold the parent stopped (so that, for instance,
6265 it doesn't run to exit), while you debug the child. In other
6266 situations, you may not be interested in inspecting the current state
6267 of any of the processes @value{GDBN} is attached to, and you may want
6268 to resume them all until some breakpoint is hit. In the latter case,
6269 you can instruct @value{GDBN} to allow all threads of all the
6270 inferiors to run with the @w{@code{set schedule-multiple}} command.
6273 @kindex set schedule-multiple
6274 @item set schedule-multiple
6275 Set the mode for allowing threads of multiple processes to be resumed
6276 when an execution command is issued. When @code{on}, all threads of
6277 all processes are allowed to run. When @code{off}, only the threads
6278 of the current process are resumed. The default is @code{off}. The
6279 @code{scheduler-locking} mode takes precedence when set to @code{on},
6280 or while you are stepping and set to @code{step}.
6282 @item show schedule-multiple
6283 Display the current mode for resuming the execution of threads of
6288 @subsection Non-Stop Mode
6290 @cindex non-stop mode
6292 @c This section is really only a place-holder, and needs to be expanded
6293 @c with more details.
6295 For some multi-threaded targets, @value{GDBN} supports an optional
6296 mode of operation in which you can examine stopped program threads in
6297 the debugger while other threads continue to execute freely. This
6298 minimizes intrusion when debugging live systems, such as programs
6299 where some threads have real-time constraints or must continue to
6300 respond to external events. This is referred to as @dfn{non-stop} mode.
6302 In non-stop mode, when a thread stops to report a debugging event,
6303 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6304 threads as well, in contrast to the all-stop mode behavior. Additionally,
6305 execution commands such as @code{continue} and @code{step} apply by default
6306 only to the current thread in non-stop mode, rather than all threads as
6307 in all-stop mode. This allows you to control threads explicitly in
6308 ways that are not possible in all-stop mode --- for example, stepping
6309 one thread while allowing others to run freely, stepping
6310 one thread while holding all others stopped, or stepping several threads
6311 independently and simultaneously.
6313 To enter non-stop mode, use this sequence of commands before you run
6314 or attach to your program:
6317 # If using the CLI, pagination breaks non-stop.
6320 # Finally, turn it on!
6324 You can use these commands to manipulate the non-stop mode setting:
6327 @kindex set non-stop
6328 @item set non-stop on
6329 Enable selection of non-stop mode.
6330 @item set non-stop off
6331 Disable selection of non-stop mode.
6332 @kindex show non-stop
6334 Show the current non-stop enablement setting.
6337 Note these commands only reflect whether non-stop mode is enabled,
6338 not whether the currently-executing program is being run in non-stop mode.
6339 In particular, the @code{set non-stop} preference is only consulted when
6340 @value{GDBN} starts or connects to the target program, and it is generally
6341 not possible to switch modes once debugging has started. Furthermore,
6342 since not all targets support non-stop mode, even when you have enabled
6343 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6346 In non-stop mode, all execution commands apply only to the current thread
6347 by default. That is, @code{continue} only continues one thread.
6348 To continue all threads, issue @code{continue -a} or @code{c -a}.
6350 You can use @value{GDBN}'s background execution commands
6351 (@pxref{Background Execution}) to run some threads in the background
6352 while you continue to examine or step others from @value{GDBN}.
6353 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6354 always executed asynchronously in non-stop mode.
6356 Suspending execution is done with the @code{interrupt} command when
6357 running in the background, or @kbd{Ctrl-c} during foreground execution.
6358 In all-stop mode, this stops the whole process;
6359 but in non-stop mode the interrupt applies only to the current thread.
6360 To stop the whole program, use @code{interrupt -a}.
6362 Other execution commands do not currently support the @code{-a} option.
6364 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6365 that thread current, as it does in all-stop mode. This is because the
6366 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6367 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6368 changed to a different thread just as you entered a command to operate on the
6369 previously current thread.
6371 @node Background Execution
6372 @subsection Background Execution
6374 @cindex foreground execution
6375 @cindex background execution
6376 @cindex asynchronous execution
6377 @cindex execution, foreground, background and asynchronous
6379 @value{GDBN}'s execution commands have two variants: the normal
6380 foreground (synchronous) behavior, and a background
6381 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6382 the program to report that some thread has stopped before prompting for
6383 another command. In background execution, @value{GDBN} immediately gives
6384 a command prompt so that you can issue other commands while your program runs.
6386 If the target doesn't support async mode, @value{GDBN} issues an error
6387 message if you attempt to use the background execution commands.
6389 @cindex @code{&}, background execution of commands
6390 To specify background execution, add a @code{&} to the command. For example,
6391 the background form of the @code{continue} command is @code{continue&}, or
6392 just @code{c&}. The execution commands that accept background execution
6398 @xref{Starting, , Starting your Program}.
6402 @xref{Attach, , Debugging an Already-running Process}.
6406 @xref{Continuing and Stepping, step}.
6410 @xref{Continuing and Stepping, stepi}.
6414 @xref{Continuing and Stepping, next}.
6418 @xref{Continuing and Stepping, nexti}.
6422 @xref{Continuing and Stepping, continue}.
6426 @xref{Continuing and Stepping, finish}.
6430 @xref{Continuing and Stepping, until}.
6434 Background execution is especially useful in conjunction with non-stop
6435 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6436 However, you can also use these commands in the normal all-stop mode with
6437 the restriction that you cannot issue another execution command until the
6438 previous one finishes. Examples of commands that are valid in all-stop
6439 mode while the program is running include @code{help} and @code{info break}.
6441 You can interrupt your program while it is running in the background by
6442 using the @code{interrupt} command.
6449 Suspend execution of the running program. In all-stop mode,
6450 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6451 only the current thread. To stop the whole program in non-stop mode,
6452 use @code{interrupt -a}.
6455 @node Thread-Specific Breakpoints
6456 @subsection Thread-Specific Breakpoints
6458 When your program has multiple threads (@pxref{Threads,, Debugging
6459 Programs with Multiple Threads}), you can choose whether to set
6460 breakpoints on all threads, or on a particular thread.
6463 @cindex breakpoints and threads
6464 @cindex thread breakpoints
6465 @kindex break @dots{} thread @var{thread-id}
6466 @item break @var{location} thread @var{thread-id}
6467 @itemx break @var{location} thread @var{thread-id} if @dots{}
6468 @var{location} specifies source lines; there are several ways of
6469 writing them (@pxref{Specify Location}), but the effect is always to
6470 specify some source line.
6472 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6473 to specify that you only want @value{GDBN} to stop the program when a
6474 particular thread reaches this breakpoint. The @var{thread-id} specifier
6475 is one of the thread identifiers assigned by @value{GDBN}, shown
6476 in the first column of the @samp{info threads} display.
6478 If you do not specify @samp{thread @var{thread-id}} when you set a
6479 breakpoint, the breakpoint applies to @emph{all} threads of your
6482 You can use the @code{thread} qualifier on conditional breakpoints as
6483 well; in this case, place @samp{thread @var{thread-id}} before or
6484 after the breakpoint condition, like this:
6487 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6492 Thread-specific breakpoints are automatically deleted when
6493 @value{GDBN} detects the corresponding thread is no longer in the
6494 thread list. For example:
6498 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6501 There are several ways for a thread to disappear, such as a regular
6502 thread exit, but also when you detach from the process with the
6503 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6504 Process}), or if @value{GDBN} loses the remote connection
6505 (@pxref{Remote Debugging}), etc. Note that with some targets,
6506 @value{GDBN} is only able to detect a thread has exited when the user
6507 explictly asks for the thread list with the @code{info threads}
6510 @node Interrupted System Calls
6511 @subsection Interrupted System Calls
6513 @cindex thread breakpoints and system calls
6514 @cindex system calls and thread breakpoints
6515 @cindex premature return from system calls
6516 There is an unfortunate side effect when using @value{GDBN} to debug
6517 multi-threaded programs. If one thread stops for a
6518 breakpoint, or for some other reason, and another thread is blocked in a
6519 system call, then the system call may return prematurely. This is a
6520 consequence of the interaction between multiple threads and the signals
6521 that @value{GDBN} uses to implement breakpoints and other events that
6524 To handle this problem, your program should check the return value of
6525 each system call and react appropriately. This is good programming
6528 For example, do not write code like this:
6534 The call to @code{sleep} will return early if a different thread stops
6535 at a breakpoint or for some other reason.
6537 Instead, write this:
6542 unslept = sleep (unslept);
6545 A system call is allowed to return early, so the system is still
6546 conforming to its specification. But @value{GDBN} does cause your
6547 multi-threaded program to behave differently than it would without
6550 Also, @value{GDBN} uses internal breakpoints in the thread library to
6551 monitor certain events such as thread creation and thread destruction.
6552 When such an event happens, a system call in another thread may return
6553 prematurely, even though your program does not appear to stop.
6556 @subsection Observer Mode
6558 If you want to build on non-stop mode and observe program behavior
6559 without any chance of disruption by @value{GDBN}, you can set
6560 variables to disable all of the debugger's attempts to modify state,
6561 whether by writing memory, inserting breakpoints, etc. These operate
6562 at a low level, intercepting operations from all commands.
6564 When all of these are set to @code{off}, then @value{GDBN} is said to
6565 be @dfn{observer mode}. As a convenience, the variable
6566 @code{observer} can be set to disable these, plus enable non-stop
6569 Note that @value{GDBN} will not prevent you from making nonsensical
6570 combinations of these settings. For instance, if you have enabled
6571 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6572 then breakpoints that work by writing trap instructions into the code
6573 stream will still not be able to be placed.
6578 @item set observer on
6579 @itemx set observer off
6580 When set to @code{on}, this disables all the permission variables
6581 below (except for @code{insert-fast-tracepoints}), plus enables
6582 non-stop debugging. Setting this to @code{off} switches back to
6583 normal debugging, though remaining in non-stop mode.
6586 Show whether observer mode is on or off.
6588 @kindex may-write-registers
6589 @item set may-write-registers on
6590 @itemx set may-write-registers off
6591 This controls whether @value{GDBN} will attempt to alter the values of
6592 registers, such as with assignment expressions in @code{print}, or the
6593 @code{jump} command. It defaults to @code{on}.
6595 @item show may-write-registers
6596 Show the current permission to write registers.
6598 @kindex may-write-memory
6599 @item set may-write-memory on
6600 @itemx set may-write-memory off
6601 This controls whether @value{GDBN} will attempt to alter the contents
6602 of memory, such as with assignment expressions in @code{print}. It
6603 defaults to @code{on}.
6605 @item show may-write-memory
6606 Show the current permission to write memory.
6608 @kindex may-insert-breakpoints
6609 @item set may-insert-breakpoints on
6610 @itemx set may-insert-breakpoints off
6611 This controls whether @value{GDBN} will attempt to insert breakpoints.
6612 This affects all breakpoints, including internal breakpoints defined
6613 by @value{GDBN}. It defaults to @code{on}.
6615 @item show may-insert-breakpoints
6616 Show the current permission to insert breakpoints.
6618 @kindex may-insert-tracepoints
6619 @item set may-insert-tracepoints on
6620 @itemx set may-insert-tracepoints off
6621 This controls whether @value{GDBN} will attempt to insert (regular)
6622 tracepoints at the beginning of a tracing experiment. It affects only
6623 non-fast tracepoints, fast tracepoints being under the control of
6624 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6626 @item show may-insert-tracepoints
6627 Show the current permission to insert tracepoints.
6629 @kindex may-insert-fast-tracepoints
6630 @item set may-insert-fast-tracepoints on
6631 @itemx set may-insert-fast-tracepoints off
6632 This controls whether @value{GDBN} will attempt to insert fast
6633 tracepoints at the beginning of a tracing experiment. It affects only
6634 fast tracepoints, regular (non-fast) tracepoints being under the
6635 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6637 @item show may-insert-fast-tracepoints
6638 Show the current permission to insert fast tracepoints.
6640 @kindex may-interrupt
6641 @item set may-interrupt on
6642 @itemx set may-interrupt off
6643 This controls whether @value{GDBN} will attempt to interrupt or stop
6644 program execution. When this variable is @code{off}, the
6645 @code{interrupt} command will have no effect, nor will
6646 @kbd{Ctrl-c}. It defaults to @code{on}.
6648 @item show may-interrupt
6649 Show the current permission to interrupt or stop the program.
6653 @node Reverse Execution
6654 @chapter Running programs backward
6655 @cindex reverse execution
6656 @cindex running programs backward
6658 When you are debugging a program, it is not unusual to realize that
6659 you have gone too far, and some event of interest has already happened.
6660 If the target environment supports it, @value{GDBN} can allow you to
6661 ``rewind'' the program by running it backward.
6663 A target environment that supports reverse execution should be able
6664 to ``undo'' the changes in machine state that have taken place as the
6665 program was executing normally. Variables, registers etc.@: should
6666 revert to their previous values. Obviously this requires a great
6667 deal of sophistication on the part of the target environment; not
6668 all target environments can support reverse execution.
6670 When a program is executed in reverse, the instructions that
6671 have most recently been executed are ``un-executed'', in reverse
6672 order. The program counter runs backward, following the previous
6673 thread of execution in reverse. As each instruction is ``un-executed'',
6674 the values of memory and/or registers that were changed by that
6675 instruction are reverted to their previous states. After executing
6676 a piece of source code in reverse, all side effects of that code
6677 should be ``undone'', and all variables should be returned to their
6678 prior values@footnote{
6679 Note that some side effects are easier to undo than others. For instance,
6680 memory and registers are relatively easy, but device I/O is hard. Some
6681 targets may be able undo things like device I/O, and some may not.
6683 The contract between @value{GDBN} and the reverse executing target
6684 requires only that the target do something reasonable when
6685 @value{GDBN} tells it to execute backwards, and then report the
6686 results back to @value{GDBN}. Whatever the target reports back to
6687 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6688 assumes that the memory and registers that the target reports are in a
6689 consistant state, but @value{GDBN} accepts whatever it is given.
6692 If you are debugging in a target environment that supports
6693 reverse execution, @value{GDBN} provides the following commands.
6696 @kindex reverse-continue
6697 @kindex rc @r{(@code{reverse-continue})}
6698 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6699 @itemx rc @r{[}@var{ignore-count}@r{]}
6700 Beginning at the point where your program last stopped, start executing
6701 in reverse. Reverse execution will stop for breakpoints and synchronous
6702 exceptions (signals), just like normal execution. Behavior of
6703 asynchronous signals depends on the target environment.
6705 @kindex reverse-step
6706 @kindex rs @r{(@code{step})}
6707 @item reverse-step @r{[}@var{count}@r{]}
6708 Run the program backward until control reaches the start of a
6709 different source line; then stop it, and return control to @value{GDBN}.
6711 Like the @code{step} command, @code{reverse-step} will only stop
6712 at the beginning of a source line. It ``un-executes'' the previously
6713 executed source line. If the previous source line included calls to
6714 debuggable functions, @code{reverse-step} will step (backward) into
6715 the called function, stopping at the beginning of the @emph{last}
6716 statement in the called function (typically a return statement).
6718 Also, as with the @code{step} command, if non-debuggable functions are
6719 called, @code{reverse-step} will run thru them backward without stopping.
6721 @kindex reverse-stepi
6722 @kindex rsi @r{(@code{reverse-stepi})}
6723 @item reverse-stepi @r{[}@var{count}@r{]}
6724 Reverse-execute one machine instruction. Note that the instruction
6725 to be reverse-executed is @emph{not} the one pointed to by the program
6726 counter, but the instruction executed prior to that one. For instance,
6727 if the last instruction was a jump, @code{reverse-stepi} will take you
6728 back from the destination of the jump to the jump instruction itself.
6730 @kindex reverse-next
6731 @kindex rn @r{(@code{reverse-next})}
6732 @item reverse-next @r{[}@var{count}@r{]}
6733 Run backward to the beginning of the previous line executed in
6734 the current (innermost) stack frame. If the line contains function
6735 calls, they will be ``un-executed'' without stopping. Starting from
6736 the first line of a function, @code{reverse-next} will take you back
6737 to the caller of that function, @emph{before} the function was called,
6738 just as the normal @code{next} command would take you from the last
6739 line of a function back to its return to its caller
6740 @footnote{Unless the code is too heavily optimized.}.
6742 @kindex reverse-nexti
6743 @kindex rni @r{(@code{reverse-nexti})}
6744 @item reverse-nexti @r{[}@var{count}@r{]}
6745 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6746 in reverse, except that called functions are ``un-executed'' atomically.
6747 That is, if the previously executed instruction was a return from
6748 another function, @code{reverse-nexti} will continue to execute
6749 in reverse until the call to that function (from the current stack
6752 @kindex reverse-finish
6753 @item reverse-finish
6754 Just as the @code{finish} command takes you to the point where the
6755 current function returns, @code{reverse-finish} takes you to the point
6756 where it was called. Instead of ending up at the end of the current
6757 function invocation, you end up at the beginning.
6759 @kindex set exec-direction
6760 @item set exec-direction
6761 Set the direction of target execution.
6762 @item set exec-direction reverse
6763 @cindex execute forward or backward in time
6764 @value{GDBN} will perform all execution commands in reverse, until the
6765 exec-direction mode is changed to ``forward''. Affected commands include
6766 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6767 command cannot be used in reverse mode.
6768 @item set exec-direction forward
6769 @value{GDBN} will perform all execution commands in the normal fashion.
6770 This is the default.
6774 @node Process Record and Replay
6775 @chapter Recording Inferior's Execution and Replaying It
6776 @cindex process record and replay
6777 @cindex recording inferior's execution and replaying it
6779 On some platforms, @value{GDBN} provides a special @dfn{process record
6780 and replay} target that can record a log of the process execution, and
6781 replay it later with both forward and reverse execution commands.
6784 When this target is in use, if the execution log includes the record
6785 for the next instruction, @value{GDBN} will debug in @dfn{replay
6786 mode}. In the replay mode, the inferior does not really execute code
6787 instructions. Instead, all the events that normally happen during
6788 code execution are taken from the execution log. While code is not
6789 really executed in replay mode, the values of registers (including the
6790 program counter register) and the memory of the inferior are still
6791 changed as they normally would. Their contents are taken from the
6795 If the record for the next instruction is not in the execution log,
6796 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6797 inferior executes normally, and @value{GDBN} records the execution log
6800 The process record and replay target supports reverse execution
6801 (@pxref{Reverse Execution}), even if the platform on which the
6802 inferior runs does not. However, the reverse execution is limited in
6803 this case by the range of the instructions recorded in the execution
6804 log. In other words, reverse execution on platforms that don't
6805 support it directly can only be done in the replay mode.
6807 When debugging in the reverse direction, @value{GDBN} will work in
6808 replay mode as long as the execution log includes the record for the
6809 previous instruction; otherwise, it will work in record mode, if the
6810 platform supports reverse execution, or stop if not.
6812 For architecture environments that support process record and replay,
6813 @value{GDBN} provides the following commands:
6816 @kindex target record
6817 @kindex target record-full
6818 @kindex target record-btrace
6821 @kindex record btrace
6822 @kindex record btrace bts
6823 @kindex record btrace pt
6829 @kindex rec btrace bts
6830 @kindex rec btrace pt
6833 @item record @var{method}
6834 This command starts the process record and replay target. The
6835 recording method can be specified as parameter. Without a parameter
6836 the command uses the @code{full} recording method. The following
6837 recording methods are available:
6841 Full record/replay recording using @value{GDBN}'s software record and
6842 replay implementation. This method allows replaying and reverse
6845 @item btrace @var{format}
6846 Hardware-supported instruction recording. This method does not record
6847 data. Further, the data is collected in a ring buffer so old data will
6848 be overwritten when the buffer is full. It allows limited reverse
6849 execution. Variables and registers are not available during reverse
6850 execution. In remote debugging, recording continues on disconnect.
6851 Recorded data can be inspected after reconnecting. The recording may
6852 be stopped using @code{record stop}.
6854 The recording format can be specified as parameter. Without a parameter
6855 the command chooses the recording format. The following recording
6856 formats are available:
6860 @cindex branch trace store
6861 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6862 this format, the processor stores a from/to record for each executed
6863 branch in the btrace ring buffer.
6866 @cindex Intel Processor Trace
6867 Use the @dfn{Intel Processor Trace} recording format. In this
6868 format, the processor stores the execution trace in a compressed form
6869 that is afterwards decoded by @value{GDBN}.
6871 The trace can be recorded with very low overhead. The compressed
6872 trace format also allows small trace buffers to already contain a big
6873 number of instructions compared to @acronym{BTS}.
6875 Decoding the recorded execution trace, on the other hand, is more
6876 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6877 increased number of instructions to process. You should increase the
6878 buffer-size with care.
6881 Not all recording formats may be available on all processors.
6884 The process record and replay target can only debug a process that is
6885 already running. Therefore, you need first to start the process with
6886 the @kbd{run} or @kbd{start} commands, and then start the recording
6887 with the @kbd{record @var{method}} command.
6889 @cindex displaced stepping, and process record and replay
6890 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6891 will be automatically disabled when process record and replay target
6892 is started. That's because the process record and replay target
6893 doesn't support displaced stepping.
6895 @cindex non-stop mode, and process record and replay
6896 @cindex asynchronous execution, and process record and replay
6897 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6898 the asynchronous execution mode (@pxref{Background Execution}), not
6899 all recording methods are available. The @code{full} recording method
6900 does not support these two modes.
6905 Stop the process record and replay target. When process record and
6906 replay target stops, the entire execution log will be deleted and the
6907 inferior will either be terminated, or will remain in its final state.
6909 When you stop the process record and replay target in record mode (at
6910 the end of the execution log), the inferior will be stopped at the
6911 next instruction that would have been recorded. In other words, if
6912 you record for a while and then stop recording, the inferior process
6913 will be left in the same state as if the recording never happened.
6915 On the other hand, if the process record and replay target is stopped
6916 while in replay mode (that is, not at the end of the execution log,
6917 but at some earlier point), the inferior process will become ``live''
6918 at that earlier state, and it will then be possible to continue the
6919 usual ``live'' debugging of the process from that state.
6921 When the inferior process exits, or @value{GDBN} detaches from it,
6922 process record and replay target will automatically stop itself.
6926 Go to a specific location in the execution log. There are several
6927 ways to specify the location to go to:
6930 @item record goto begin
6931 @itemx record goto start
6932 Go to the beginning of the execution log.
6934 @item record goto end
6935 Go to the end of the execution log.
6937 @item record goto @var{n}
6938 Go to instruction number @var{n} in the execution log.
6942 @item record save @var{filename}
6943 Save the execution log to a file @file{@var{filename}}.
6944 Default filename is @file{gdb_record.@var{process_id}}, where
6945 @var{process_id} is the process ID of the inferior.
6947 This command may not be available for all recording methods.
6949 @kindex record restore
6950 @item record restore @var{filename}
6951 Restore the execution log from a file @file{@var{filename}}.
6952 File must have been created with @code{record save}.
6954 @kindex set record full
6955 @item set record full insn-number-max @var{limit}
6956 @itemx set record full insn-number-max unlimited
6957 Set the limit of instructions to be recorded for the @code{full}
6958 recording method. Default value is 200000.
6960 If @var{limit} is a positive number, then @value{GDBN} will start
6961 deleting instructions from the log once the number of the record
6962 instructions becomes greater than @var{limit}. For every new recorded
6963 instruction, @value{GDBN} will delete the earliest recorded
6964 instruction to keep the number of recorded instructions at the limit.
6965 (Since deleting recorded instructions loses information, @value{GDBN}
6966 lets you control what happens when the limit is reached, by means of
6967 the @code{stop-at-limit} option, described below.)
6969 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6970 delete recorded instructions from the execution log. The number of
6971 recorded instructions is limited only by the available memory.
6973 @kindex show record full
6974 @item show record full insn-number-max
6975 Show the limit of instructions to be recorded with the @code{full}
6978 @item set record full stop-at-limit
6979 Control the behavior of the @code{full} recording method when the
6980 number of recorded instructions reaches the limit. If ON (the
6981 default), @value{GDBN} will stop when the limit is reached for the
6982 first time and ask you whether you want to stop the inferior or
6983 continue running it and recording the execution log. If you decide
6984 to continue recording, each new recorded instruction will cause the
6985 oldest one to be deleted.
6987 If this option is OFF, @value{GDBN} will automatically delete the
6988 oldest record to make room for each new one, without asking.
6990 @item show record full stop-at-limit
6991 Show the current setting of @code{stop-at-limit}.
6993 @item set record full memory-query
6994 Control the behavior when @value{GDBN} is unable to record memory
6995 changes caused by an instruction for the @code{full} recording method.
6996 If ON, @value{GDBN} will query whether to stop the inferior in that
6999 If this option is OFF (the default), @value{GDBN} will automatically
7000 ignore the effect of such instructions on memory. Later, when
7001 @value{GDBN} replays this execution log, it will mark the log of this
7002 instruction as not accessible, and it will not affect the replay
7005 @item show record full memory-query
7006 Show the current setting of @code{memory-query}.
7008 @kindex set record btrace
7009 The @code{btrace} record target does not trace data. As a
7010 convenience, when replaying, @value{GDBN} reads read-only memory off
7011 the live program directly, assuming that the addresses of the
7012 read-only areas don't change. This for example makes it possible to
7013 disassemble code while replaying, but not to print variables.
7014 In some cases, being able to inspect variables might be useful.
7015 You can use the following command for that:
7017 @item set record btrace replay-memory-access
7018 Control the behavior of the @code{btrace} recording method when
7019 accessing memory during replay. If @code{read-only} (the default),
7020 @value{GDBN} will only allow accesses to read-only memory.
7021 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7022 and to read-write memory. Beware that the accessed memory corresponds
7023 to the live target and not necessarily to the current replay
7026 @item set record btrace cpu @var{identifier}
7027 Set the processor to be used for enabling workarounds for processor
7028 errata when decoding the trace.
7030 Processor errata are defects in processor operation, caused by its
7031 design or manufacture. They can cause a trace not to match the
7032 specification. This, in turn, may cause trace decode to fail.
7033 @value{GDBN} can detect erroneous trace packets and correct them, thus
7034 avoiding the decoding failures. These corrections are known as
7035 @dfn{errata workarounds}, and are enabled based on the processor on
7036 which the trace was recorded.
7038 By default, @value{GDBN} attempts to detect the processor
7039 automatically, and apply the necessary workarounds for it. However,
7040 you may need to specify the processor if @value{GDBN} does not yet
7041 support it. This command allows you to do that, and also allows to
7042 disable the workarounds.
7044 The argument @var{identifier} identifies the @sc{cpu} and is of the
7045 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7046 there are two special identifiers, @code{none} and @code{auto}
7049 The following vendor identifiers and corresponding processor
7050 identifiers are currently supported:
7052 @multitable @columnfractions .1 .9
7055 @tab @var{family}/@var{model}[/@var{stepping}]
7059 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7060 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7062 If @var{identifier} is @code{auto}, enable errata workarounds for the
7063 processor on which the trace was recorded. If @var{identifier} is
7064 @code{none}, errata workarounds are disabled.
7066 For example, when using an old @value{GDBN} on a new system, decode
7067 may fail because @value{GDBN} does not support the new processor. It
7068 often suffices to specify an older processor that @value{GDBN}
7073 Active record target: record-btrace
7074 Recording format: Intel Processor Trace.
7076 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7077 (gdb) set record btrace cpu intel:6/158
7079 Active record target: record-btrace
7080 Recording format: Intel Processor Trace.
7082 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7085 @kindex show record btrace
7086 @item show record btrace replay-memory-access
7087 Show the current setting of @code{replay-memory-access}.
7089 @item show record btrace cpu
7090 Show the processor to be used for enabling trace decode errata
7093 @kindex set record btrace bts
7094 @item set record btrace bts buffer-size @var{size}
7095 @itemx set record btrace bts buffer-size unlimited
7096 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7097 format. Default is 64KB.
7099 If @var{size} is a positive number, then @value{GDBN} will try to
7100 allocate a buffer of at least @var{size} bytes for each new thread
7101 that uses the btrace recording method and the @acronym{BTS} format.
7102 The actually obtained buffer size may differ from the requested
7103 @var{size}. Use the @code{info record} command to see the actual
7104 buffer size for each thread that uses the btrace recording method and
7105 the @acronym{BTS} format.
7107 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7108 allocate a buffer of 4MB.
7110 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7111 also need longer to process the branch trace data before it can be used.
7113 @item show record btrace bts buffer-size @var{size}
7114 Show the current setting of the requested ring buffer size for branch
7115 tracing in @acronym{BTS} format.
7117 @kindex set record btrace pt
7118 @item set record btrace pt buffer-size @var{size}
7119 @itemx set record btrace pt buffer-size unlimited
7120 Set the requested ring buffer size for branch tracing in Intel
7121 Processor Trace format. Default is 16KB.
7123 If @var{size} is a positive number, then @value{GDBN} will try to
7124 allocate a buffer of at least @var{size} bytes for each new thread
7125 that uses the btrace recording method and the Intel Processor Trace
7126 format. The actually obtained buffer size may differ from the
7127 requested @var{size}. Use the @code{info record} command to see the
7128 actual buffer size for each thread.
7130 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7131 allocate a buffer of 4MB.
7133 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7134 also need longer to process the branch trace data before it can be used.
7136 @item show record btrace pt buffer-size @var{size}
7137 Show the current setting of the requested ring buffer size for branch
7138 tracing in Intel Processor Trace format.
7142 Show various statistics about the recording depending on the recording
7147 For the @code{full} recording method, it shows the state of process
7148 record and its in-memory execution log buffer, including:
7152 Whether in record mode or replay mode.
7154 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7156 Highest recorded instruction number.
7158 Current instruction about to be replayed (if in replay mode).
7160 Number of instructions contained in the execution log.
7162 Maximum number of instructions that may be contained in the execution log.
7166 For the @code{btrace} recording method, it shows:
7172 Number of instructions that have been recorded.
7174 Number of blocks of sequential control-flow formed by the recorded
7177 Whether in record mode or replay mode.
7180 For the @code{bts} recording format, it also shows:
7183 Size of the perf ring buffer.
7186 For the @code{pt} recording format, it also shows:
7189 Size of the perf ring buffer.
7193 @kindex record delete
7196 When record target runs in replay mode (``in the past''), delete the
7197 subsequent execution log and begin to record a new execution log starting
7198 from the current address. This means you will abandon the previously
7199 recorded ``future'' and begin recording a new ``future''.
7201 @kindex record instruction-history
7202 @kindex rec instruction-history
7203 @item record instruction-history
7204 Disassembles instructions from the recorded execution log. By
7205 default, ten instructions are disassembled. This can be changed using
7206 the @code{set record instruction-history-size} command. Instructions
7207 are printed in execution order.
7209 It can also print mixed source+disassembly if you specify the the
7210 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7211 as well as in symbolic form by specifying the @code{/r} modifier.
7213 The current position marker is printed for the instruction at the
7214 current program counter value. This instruction can appear multiple
7215 times in the trace and the current position marker will be printed
7216 every time. To omit the current position marker, specify the
7219 To better align the printed instructions when the trace contains
7220 instructions from more than one function, the function name may be
7221 omitted by specifying the @code{/f} modifier.
7223 Speculatively executed instructions are prefixed with @samp{?}. This
7224 feature is not available for all recording formats.
7226 There are several ways to specify what part of the execution log to
7230 @item record instruction-history @var{insn}
7231 Disassembles ten instructions starting from instruction number
7234 @item record instruction-history @var{insn}, +/-@var{n}
7235 Disassembles @var{n} instructions around instruction number
7236 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7237 @var{n} instructions after instruction number @var{insn}. If
7238 @var{n} is preceded with @code{-}, disassembles @var{n}
7239 instructions before instruction number @var{insn}.
7241 @item record instruction-history
7242 Disassembles ten more instructions after the last disassembly.
7244 @item record instruction-history -
7245 Disassembles ten more instructions before the last disassembly.
7247 @item record instruction-history @var{begin}, @var{end}
7248 Disassembles instructions beginning with instruction number
7249 @var{begin} until instruction number @var{end}. The instruction
7250 number @var{end} is included.
7253 This command may not be available for all recording methods.
7256 @item set record instruction-history-size @var{size}
7257 @itemx set record instruction-history-size unlimited
7258 Define how many instructions to disassemble in the @code{record
7259 instruction-history} command. The default value is 10.
7260 A @var{size} of @code{unlimited} means unlimited instructions.
7263 @item show record instruction-history-size
7264 Show how many instructions to disassemble in the @code{record
7265 instruction-history} command.
7267 @kindex record function-call-history
7268 @kindex rec function-call-history
7269 @item record function-call-history
7270 Prints the execution history at function granularity. It prints one
7271 line for each sequence of instructions that belong to the same
7272 function giving the name of that function, the source lines
7273 for this instruction sequence (if the @code{/l} modifier is
7274 specified), and the instructions numbers that form the sequence (if
7275 the @code{/i} modifier is specified). The function names are indented
7276 to reflect the call stack depth if the @code{/c} modifier is
7277 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7281 (@value{GDBP}) @b{list 1, 10}
7292 (@value{GDBP}) @b{record function-call-history /ilc}
7293 1 bar inst 1,4 at foo.c:6,8
7294 2 foo inst 5,10 at foo.c:2,3
7295 3 bar inst 11,13 at foo.c:9,10
7298 By default, ten lines are printed. This can be changed using the
7299 @code{set record function-call-history-size} command. Functions are
7300 printed in execution order. There are several ways to specify what
7304 @item record function-call-history @var{func}
7305 Prints ten functions starting from function number @var{func}.
7307 @item record function-call-history @var{func}, +/-@var{n}
7308 Prints @var{n} functions around function number @var{func}. If
7309 @var{n} is preceded with @code{+}, prints @var{n} functions after
7310 function number @var{func}. If @var{n} is preceded with @code{-},
7311 prints @var{n} functions before function number @var{func}.
7313 @item record function-call-history
7314 Prints ten more functions after the last ten-line print.
7316 @item record function-call-history -
7317 Prints ten more functions before the last ten-line print.
7319 @item record function-call-history @var{begin}, @var{end}
7320 Prints functions beginning with function number @var{begin} until
7321 function number @var{end}. The function number @var{end} is included.
7324 This command may not be available for all recording methods.
7326 @item set record function-call-history-size @var{size}
7327 @itemx set record function-call-history-size unlimited
7328 Define how many lines to print in the
7329 @code{record function-call-history} command. The default value is 10.
7330 A size of @code{unlimited} means unlimited lines.
7332 @item show record function-call-history-size
7333 Show how many lines to print in the
7334 @code{record function-call-history} command.
7339 @chapter Examining the Stack
7341 When your program has stopped, the first thing you need to know is where it
7342 stopped and how it got there.
7345 Each time your program performs a function call, information about the call
7347 That information includes the location of the call in your program,
7348 the arguments of the call,
7349 and the local variables of the function being called.
7350 The information is saved in a block of data called a @dfn{stack frame}.
7351 The stack frames are allocated in a region of memory called the @dfn{call
7354 When your program stops, the @value{GDBN} commands for examining the
7355 stack allow you to see all of this information.
7357 @cindex selected frame
7358 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7359 @value{GDBN} commands refer implicitly to the selected frame. In
7360 particular, whenever you ask @value{GDBN} for the value of a variable in
7361 your program, the value is found in the selected frame. There are
7362 special @value{GDBN} commands to select whichever frame you are
7363 interested in. @xref{Selection, ,Selecting a Frame}.
7365 When your program stops, @value{GDBN} automatically selects the
7366 currently executing frame and describes it briefly, similar to the
7367 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7370 * Frames:: Stack frames
7371 * Backtrace:: Backtraces
7372 * Selection:: Selecting a frame
7373 * Frame Info:: Information on a frame
7374 * Frame Apply:: Applying a command to several frames
7375 * Frame Filter Management:: Managing frame filters
7380 @section Stack Frames
7382 @cindex frame, definition
7384 The call stack is divided up into contiguous pieces called @dfn{stack
7385 frames}, or @dfn{frames} for short; each frame is the data associated
7386 with one call to one function. The frame contains the arguments given
7387 to the function, the function's local variables, and the address at
7388 which the function is executing.
7390 @cindex initial frame
7391 @cindex outermost frame
7392 @cindex innermost frame
7393 When your program is started, the stack has only one frame, that of the
7394 function @code{main}. This is called the @dfn{initial} frame or the
7395 @dfn{outermost} frame. Each time a function is called, a new frame is
7396 made. Each time a function returns, the frame for that function invocation
7397 is eliminated. If a function is recursive, there can be many frames for
7398 the same function. The frame for the function in which execution is
7399 actually occurring is called the @dfn{innermost} frame. This is the most
7400 recently created of all the stack frames that still exist.
7402 @cindex frame pointer
7403 Inside your program, stack frames are identified by their addresses. A
7404 stack frame consists of many bytes, each of which has its own address; each
7405 kind of computer has a convention for choosing one byte whose
7406 address serves as the address of the frame. Usually this address is kept
7407 in a register called the @dfn{frame pointer register}
7408 (@pxref{Registers, $fp}) while execution is going on in that frame.
7411 @cindex frame number
7412 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7413 number that is zero for the innermost frame, one for the frame that
7414 called it, and so on upward. These level numbers give you a way of
7415 designating stack frames in @value{GDBN} commands. The terms
7416 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7417 describe this number.
7419 @c The -fomit-frame-pointer below perennially causes hbox overflow
7420 @c underflow problems.
7421 @cindex frameless execution
7422 Some compilers provide a way to compile functions so that they operate
7423 without stack frames. (For example, the @value{NGCC} option
7425 @samp{-fomit-frame-pointer}
7427 generates functions without a frame.)
7428 This is occasionally done with heavily used library functions to save
7429 the frame setup time. @value{GDBN} has limited facilities for dealing
7430 with these function invocations. If the innermost function invocation
7431 has no stack frame, @value{GDBN} nevertheless regards it as though
7432 it had a separate frame, which is numbered zero as usual, allowing
7433 correct tracing of the function call chain. However, @value{GDBN} has
7434 no provision for frameless functions elsewhere in the stack.
7440 @cindex call stack traces
7441 A backtrace is a summary of how your program got where it is. It shows one
7442 line per frame, for many frames, starting with the currently executing
7443 frame (frame zero), followed by its caller (frame one), and on up the
7446 @anchor{backtrace-command}
7448 @kindex bt @r{(@code{backtrace})}
7449 To print a backtrace of the entire stack, use the @code{backtrace}
7450 command, or its alias @code{bt}. This command will print one line per
7451 frame for frames in the stack. By default, all stack frames are
7452 printed. You can stop the backtrace at any time by typing the system
7453 interrupt character, normally @kbd{Ctrl-c}.
7456 @item backtrace [@var{args}@dots{}]
7457 @itemx bt [@var{args}@dots{}]
7458 Print the backtrace of the entire stack. The optional @var{args} can
7459 be one of the following:
7464 Print only the innermost @var{n} frames, where @var{n} is a positive
7469 Print only the outermost @var{n} frames, where @var{n} is a positive
7473 Print the values of the local variables also. This can be combined
7474 with a number to limit the number of frames shown.
7477 Do not run Python frame filters on this backtrace. @xref{Frame
7478 Filter API}, for more information. Additionally use @ref{disable
7479 frame-filter all} to turn off all frame filters. This is only
7480 relevant when @value{GDBN} has been configured with @code{Python}
7484 A Python frame filter might decide to ``elide'' some frames. Normally
7485 such elided frames are still printed, but they are indented relative
7486 to the filtered frames that cause them to be elided. The @code{hide}
7487 option causes elided frames to not be printed at all.
7493 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7494 are additional aliases for @code{backtrace}.
7496 @cindex multiple threads, backtrace
7497 In a multi-threaded program, @value{GDBN} by default shows the
7498 backtrace only for the current thread. To display the backtrace for
7499 several or all of the threads, use the command @code{thread apply}
7500 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7501 apply all backtrace}, @value{GDBN} will display the backtrace for all
7502 the threads; this is handy when you debug a core dump of a
7503 multi-threaded program.
7505 Each line in the backtrace shows the frame number and the function name.
7506 The program counter value is also shown---unless you use @code{set
7507 print address off}. The backtrace also shows the source file name and
7508 line number, as well as the arguments to the function. The program
7509 counter value is omitted if it is at the beginning of the code for that
7512 Here is an example of a backtrace. It was made with the command
7513 @samp{bt 3}, so it shows the innermost three frames.
7517 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7519 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7520 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7522 (More stack frames follow...)
7527 The display for frame zero does not begin with a program counter
7528 value, indicating that your program has stopped at the beginning of the
7529 code for line @code{993} of @code{builtin.c}.
7532 The value of parameter @code{data} in frame 1 has been replaced by
7533 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7534 only if it is a scalar (integer, pointer, enumeration, etc). See command
7535 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7536 on how to configure the way function parameter values are printed.
7538 @cindex optimized out, in backtrace
7539 @cindex function call arguments, optimized out
7540 If your program was compiled with optimizations, some compilers will
7541 optimize away arguments passed to functions if those arguments are
7542 never used after the call. Such optimizations generate code that
7543 passes arguments through registers, but doesn't store those arguments
7544 in the stack frame. @value{GDBN} has no way of displaying such
7545 arguments in stack frames other than the innermost one. Here's what
7546 such a backtrace might look like:
7550 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7552 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7553 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7555 (More stack frames follow...)
7560 The values of arguments that were not saved in their stack frames are
7561 shown as @samp{<optimized out>}.
7563 If you need to display the values of such optimized-out arguments,
7564 either deduce that from other variables whose values depend on the one
7565 you are interested in, or recompile without optimizations.
7567 @cindex backtrace beyond @code{main} function
7568 @cindex program entry point
7569 @cindex startup code, and backtrace
7570 Most programs have a standard user entry point---a place where system
7571 libraries and startup code transition into user code. For C this is
7572 @code{main}@footnote{
7573 Note that embedded programs (the so-called ``free-standing''
7574 environment) are not required to have a @code{main} function as the
7575 entry point. They could even have multiple entry points.}.
7576 When @value{GDBN} finds the entry function in a backtrace
7577 it will terminate the backtrace, to avoid tracing into highly
7578 system-specific (and generally uninteresting) code.
7580 If you need to examine the startup code, or limit the number of levels
7581 in a backtrace, you can change this behavior:
7584 @item set backtrace past-main
7585 @itemx set backtrace past-main on
7586 @kindex set backtrace
7587 Backtraces will continue past the user entry point.
7589 @item set backtrace past-main off
7590 Backtraces will stop when they encounter the user entry point. This is the
7593 @item show backtrace past-main
7594 @kindex show backtrace
7595 Display the current user entry point backtrace policy.
7597 @item set backtrace past-entry
7598 @itemx set backtrace past-entry on
7599 Backtraces will continue past the internal entry point of an application.
7600 This entry point is encoded by the linker when the application is built,
7601 and is likely before the user entry point @code{main} (or equivalent) is called.
7603 @item set backtrace past-entry off
7604 Backtraces will stop when they encounter the internal entry point of an
7605 application. This is the default.
7607 @item show backtrace past-entry
7608 Display the current internal entry point backtrace policy.
7610 @item set backtrace limit @var{n}
7611 @itemx set backtrace limit 0
7612 @itemx set backtrace limit unlimited
7613 @cindex backtrace limit
7614 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7615 or zero means unlimited levels.
7617 @item show backtrace limit
7618 Display the current limit on backtrace levels.
7621 You can control how file names are displayed.
7624 @item set filename-display
7625 @itemx set filename-display relative
7626 @cindex filename-display
7627 Display file names relative to the compilation directory. This is the default.
7629 @item set filename-display basename
7630 Display only basename of a filename.
7632 @item set filename-display absolute
7633 Display an absolute filename.
7635 @item show filename-display
7636 Show the current way to display filenames.
7640 @section Selecting a Frame
7642 Most commands for examining the stack and other data in your program work on
7643 whichever stack frame is selected at the moment. Here are the commands for
7644 selecting a stack frame; all of them finish by printing a brief description
7645 of the stack frame just selected.
7648 @kindex frame@r{, selecting}
7649 @kindex f @r{(@code{frame})}
7650 @item frame @r{[} @var{frame-selection-spec} @r{]}
7651 @item f @r{[} @var{frame-selection-spec} @r{]}
7652 The @command{frame} command allows different stack frames to be
7653 selected. The @var{frame-selection-spec} can be any of the following:
7658 @item level @var{num}
7659 Select frame level @var{num}. Recall that frame zero is the innermost
7660 (currently executing) frame, frame one is the frame that called the
7661 innermost one, and so on. The highest level frame is usually the one
7664 As this is the most common method of navigating the frame stack, the
7665 string @command{level} can be omitted. For example, the following two
7666 commands are equivalent:
7669 (@value{GDBP}) frame 3
7670 (@value{GDBP}) frame level 3
7673 @kindex frame address
7674 @item address @var{stack-address}
7675 Select the frame with stack address @var{stack-address}. The
7676 @var{stack-address} for a frame can be seen in the output of
7677 @command{info frame}, for example:
7681 Stack level 1, frame at 0x7fffffffda30:
7682 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7683 tail call frame, caller of frame at 0x7fffffffda30
7684 source language c++.
7685 Arglist at unknown address.
7686 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7689 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7690 indicated by the line:
7693 Stack level 1, frame at 0x7fffffffda30:
7696 @kindex frame function
7697 @item function @var{function-name}
7698 Select the stack frame for function @var{function-name}. If there are
7699 multiple stack frames for function @var{function-name} then the inner
7700 most stack frame is selected.
7703 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7704 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7705 viewed has stack address @var{stack-addr}, and optionally, a program
7706 counter address of @var{pc-addr}.
7708 This is useful mainly if the chaining of stack frames has been
7709 damaged by a bug, making it impossible for @value{GDBN} to assign
7710 numbers properly to all frames. In addition, this can be useful
7711 when your program has multiple stacks and switches between them.
7713 When viewing a frame outside the current backtrace using
7714 @command{frame view} then you can always return to the original
7715 stack using one of the previous stack frame selection instructions,
7716 for example @command{frame level 0}.
7722 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7723 numbers @var{n}, this advances toward the outermost frame, to higher
7724 frame numbers, to frames that have existed longer.
7727 @kindex do @r{(@code{down})}
7729 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7730 positive numbers @var{n}, this advances toward the innermost frame, to
7731 lower frame numbers, to frames that were created more recently.
7732 You may abbreviate @code{down} as @code{do}.
7735 All of these commands end by printing two lines of output describing the
7736 frame. The first line shows the frame number, the function name, the
7737 arguments, and the source file and line number of execution in that
7738 frame. The second line shows the text of that source line.
7746 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7748 10 read_input_file (argv[i]);
7752 After such a printout, the @code{list} command with no arguments
7753 prints ten lines centered on the point of execution in the frame.
7754 You can also edit the program at the point of execution with your favorite
7755 editing program by typing @code{edit}.
7756 @xref{List, ,Printing Source Lines},
7760 @kindex select-frame
7761 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7762 The @code{select-frame} command is a variant of @code{frame} that does
7763 not display the new frame after selecting it. This command is
7764 intended primarily for use in @value{GDBN} command scripts, where the
7765 output might be unnecessary and distracting. The
7766 @var{frame-selection-spec} is as for the @command{frame} command
7767 described in @ref{Selection, ,Selecting a Frame}.
7769 @kindex down-silently
7771 @item up-silently @var{n}
7772 @itemx down-silently @var{n}
7773 These two commands are variants of @code{up} and @code{down},
7774 respectively; they differ in that they do their work silently, without
7775 causing display of the new frame. They are intended primarily for use
7776 in @value{GDBN} command scripts, where the output might be unnecessary and
7781 @section Information About a Frame
7783 There are several other commands to print information about the selected
7789 When used without any argument, this command does not change which
7790 frame is selected, but prints a brief description of the currently
7791 selected stack frame. It can be abbreviated @code{f}. With an
7792 argument, this command is used to select a stack frame.
7793 @xref{Selection, ,Selecting a Frame}.
7796 @kindex info f @r{(@code{info frame})}
7799 This command prints a verbose description of the selected stack frame,
7804 the address of the frame
7806 the address of the next frame down (called by this frame)
7808 the address of the next frame up (caller of this frame)
7810 the language in which the source code corresponding to this frame is written
7812 the address of the frame's arguments
7814 the address of the frame's local variables
7816 the program counter saved in it (the address of execution in the caller frame)
7818 which registers were saved in the frame
7821 @noindent The verbose description is useful when
7822 something has gone wrong that has made the stack format fail to fit
7823 the usual conventions.
7825 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7826 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7827 Print a verbose description of the frame selected by
7828 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7829 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7830 a Frame}). The selected frame remains unchanged by this command.
7833 @item info args [-q]
7834 Print the arguments of the selected frame, each on a separate line.
7836 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7837 printing header information and messages explaining why no argument
7840 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7841 Like @kbd{info args}, but only print the arguments selected
7842 with the provided regexp(s).
7844 If @var{regexp} is provided, print only the arguments whose names
7845 match the regular expression @var{regexp}.
7847 If @var{type_regexp} is provided, print only the arguments whose
7848 types, as printed by the @code{whatis} command, match
7849 the regular expression @var{type_regexp}.
7850 If @var{type_regexp} contains space(s), it should be enclosed in
7851 quote characters. If needed, use backslash to escape the meaning
7852 of special characters or quotes.
7854 If both @var{regexp} and @var{type_regexp} are provided, an argument
7855 is printed only if its name matches @var{regexp} and its type matches
7858 @item info locals [-q]
7860 Print the local variables of the selected frame, each on a separate
7861 line. These are all variables (declared either static or automatic)
7862 accessible at the point of execution of the selected frame.
7864 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7865 printing header information and messages explaining why no local variables
7868 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7869 Like @kbd{info locals}, but only print the local variables selected
7870 with the provided regexp(s).
7872 If @var{regexp} is provided, print only the local variables whose names
7873 match the regular expression @var{regexp}.
7875 If @var{type_regexp} is provided, print only the local variables whose
7876 types, as printed by the @code{whatis} command, match
7877 the regular expression @var{type_regexp}.
7878 If @var{type_regexp} contains space(s), it should be enclosed in
7879 quote characters. If needed, use backslash to escape the meaning
7880 of special characters or quotes.
7882 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7883 is printed only if its name matches @var{regexp} and its type matches
7886 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7887 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7888 For example, your program might use Resource Acquisition Is
7889 Initialization types (RAII) such as @code{lock_something_t}: each
7890 local variable of type @code{lock_something_t} automatically places a
7891 lock that is destroyed when the variable goes out of scope. You can
7892 then list all acquired locks in your program by doing
7894 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7897 or the equivalent shorter form
7899 tfaas i lo -q -t lock_something_t
7905 @section Applying a Command to Several Frames.
7907 @cindex apply command to several frames
7909 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7910 The @code{frame apply} command allows you to apply the named
7911 @var{command} to one or more frames.
7915 Specify @code{all} to apply @var{command} to all frames.
7918 Use @var{count} to apply @var{command} to the innermost @var{count}
7919 frames, where @var{count} is a positive number.
7922 Use @var{-count} to apply @var{command} to the outermost @var{count}
7923 frames, where @var{count} is a positive number.
7926 Use @code{level} to apply @var{command} to the set of frames identified
7927 by the @var{level} list. @var{level} is a frame level or a range of frame
7928 levels as @var{level1}-@var{level2}. The frame level is the number shown
7929 in the first field of the @samp{backtrace} command output.
7930 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7931 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7937 Note that the frames on which @code{frame apply} applies a command are
7938 also influenced by the @code{set backtrace} settings such as @code{set
7939 backtrace past-main} and @code{set backtrace limit N}. See
7940 @xref{Backtrace,,Backtraces}.
7942 The @var{flag} arguments control what output to produce and how to handle
7943 errors raised when applying @var{command} to a frame. @var{flag}
7944 must start with a @code{-} directly followed by one letter in
7945 @code{qcs}. If several flags are provided, they must be given
7946 individually, such as @code{-c -q}.
7948 By default, @value{GDBN} displays some frame information before the
7949 output produced by @var{command}, and an error raised during the
7950 execution of a @var{command} will abort @code{frame apply}. The
7951 following flags can be used to fine-tune this behavior:
7955 The flag @code{-c}, which stands for @samp{continue}, causes any
7956 errors in @var{command} to be displayed, and the execution of
7957 @code{frame apply} then continues.
7959 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7960 or empty output produced by a @var{command} to be silently ignored.
7961 That is, the execution continues, but the frame information and errors
7964 The flag @code{-q} (@samp{quiet}) disables printing the frame
7968 The following example shows how the flags @code{-c} and @code{-s} are
7969 working when applying the command @code{p j} to all frames, where
7970 variable @code{j} can only be successfully printed in the outermost
7971 @code{#1 main} frame.
7975 (gdb) frame apply all p j
7976 #0 some_function (i=5) at fun.c:4
7977 No symbol "j" in current context.
7978 (gdb) frame apply all -c p j
7979 #0 some_function (i=5) at fun.c:4
7980 No symbol "j" in current context.
7981 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7983 (gdb) frame apply all -s p j
7984 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7990 By default, @samp{frame apply}, prints the frame location
7991 information before the command output:
7995 (gdb) frame apply all p $sp
7996 #0 some_function (i=5) at fun.c:4
7997 $4 = (void *) 0xffffd1e0
7998 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
7999 $5 = (void *) 0xffffd1f0
8004 If flag @code{-q} is given, no frame information is printed:
8007 (gdb) frame apply all -q p $sp
8008 $12 = (void *) 0xffffd1e0
8009 $13 = (void *) 0xffffd1f0
8017 @cindex apply a command to all frames (ignoring errors and empty output)
8018 @item faas @var{command}
8019 Shortcut for @code{frame apply all -s @var{command}}.
8020 Applies @var{command} on all frames, ignoring errors and empty output.
8022 It can for example be used to print a local variable or a function
8023 argument without knowing the frame where this variable or argument
8026 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8029 Note that the command @code{tfaas @var{command}} applies @var{command}
8030 on all frames of all threads. See @xref{Threads,,Threads}.
8034 @node Frame Filter Management
8035 @section Management of Frame Filters.
8036 @cindex managing frame filters
8038 Frame filters are Python based utilities to manage and decorate the
8039 output of frames. @xref{Frame Filter API}, for further information.
8041 Managing frame filters is performed by several commands available
8042 within @value{GDBN}, detailed here.
8045 @kindex info frame-filter
8046 @item info frame-filter
8047 Print a list of installed frame filters from all dictionaries, showing
8048 their name, priority and enabled status.
8050 @kindex disable frame-filter
8051 @anchor{disable frame-filter all}
8052 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8053 Disable a frame filter in the dictionary matching
8054 @var{filter-dictionary} and @var{filter-name}. The
8055 @var{filter-dictionary} may be @code{all}, @code{global},
8056 @code{progspace}, or the name of the object file where the frame filter
8057 dictionary resides. When @code{all} is specified, all frame filters
8058 across all dictionaries are disabled. The @var{filter-name} is the name
8059 of the frame filter and is used when @code{all} is not the option for
8060 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8061 may be enabled again later.
8063 @kindex enable frame-filter
8064 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8065 Enable a frame filter in the dictionary matching
8066 @var{filter-dictionary} and @var{filter-name}. The
8067 @var{filter-dictionary} may be @code{all}, @code{global},
8068 @code{progspace} or the name of the object file where the frame filter
8069 dictionary resides. When @code{all} is specified, all frame filters across
8070 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8071 filter and is used when @code{all} is not the option for
8072 @var{filter-dictionary}.
8077 (gdb) info frame-filter
8079 global frame-filters:
8080 Priority Enabled Name
8081 1000 No PrimaryFunctionFilter
8084 progspace /build/test frame-filters:
8085 Priority Enabled Name
8086 100 Yes ProgspaceFilter
8088 objfile /build/test frame-filters:
8089 Priority Enabled Name
8090 999 Yes BuildProgra Filter
8092 (gdb) disable frame-filter /build/test BuildProgramFilter
8093 (gdb) info frame-filter
8095 global frame-filters:
8096 Priority Enabled Name
8097 1000 No PrimaryFunctionFilter
8100 progspace /build/test frame-filters:
8101 Priority Enabled Name
8102 100 Yes ProgspaceFilter
8104 objfile /build/test frame-filters:
8105 Priority Enabled Name
8106 999 No BuildProgramFilter
8108 (gdb) enable frame-filter global PrimaryFunctionFilter
8109 (gdb) info frame-filter
8111 global frame-filters:
8112 Priority Enabled Name
8113 1000 Yes PrimaryFunctionFilter
8116 progspace /build/test frame-filters:
8117 Priority Enabled Name
8118 100 Yes ProgspaceFilter
8120 objfile /build/test frame-filters:
8121 Priority Enabled Name
8122 999 No BuildProgramFilter
8125 @kindex set frame-filter priority
8126 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8127 Set the @var{priority} of a frame filter in the dictionary matching
8128 @var{filter-dictionary}, and the frame filter name matching
8129 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8130 @code{progspace} or the name of the object file where the frame filter
8131 dictionary resides. The @var{priority} is an integer.
8133 @kindex show frame-filter priority
8134 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8135 Show the @var{priority} of a frame filter in the dictionary matching
8136 @var{filter-dictionary}, and the frame filter name matching
8137 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8138 @code{progspace} or the name of the object file where the frame filter
8144 (gdb) info frame-filter
8146 global frame-filters:
8147 Priority Enabled Name
8148 1000 Yes PrimaryFunctionFilter
8151 progspace /build/test frame-filters:
8152 Priority Enabled Name
8153 100 Yes ProgspaceFilter
8155 objfile /build/test frame-filters:
8156 Priority Enabled Name
8157 999 No BuildProgramFilter
8159 (gdb) set frame-filter priority global Reverse 50
8160 (gdb) info frame-filter
8162 global frame-filters:
8163 Priority Enabled Name
8164 1000 Yes PrimaryFunctionFilter
8167 progspace /build/test frame-filters:
8168 Priority Enabled Name
8169 100 Yes ProgspaceFilter
8171 objfile /build/test frame-filters:
8172 Priority Enabled Name
8173 999 No BuildProgramFilter
8178 @chapter Examining Source Files
8180 @value{GDBN} can print parts of your program's source, since the debugging
8181 information recorded in the program tells @value{GDBN} what source files were
8182 used to build it. When your program stops, @value{GDBN} spontaneously prints
8183 the line where it stopped. Likewise, when you select a stack frame
8184 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8185 execution in that frame has stopped. You can print other portions of
8186 source files by explicit command.
8188 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8189 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8190 @value{GDBN} under @sc{gnu} Emacs}.
8193 * List:: Printing source lines
8194 * Specify Location:: How to specify code locations
8195 * Edit:: Editing source files
8196 * Search:: Searching source files
8197 * Source Path:: Specifying source directories
8198 * Machine Code:: Source and machine code
8202 @section Printing Source Lines
8205 @kindex l @r{(@code{list})}
8206 To print lines from a source file, use the @code{list} command
8207 (abbreviated @code{l}). By default, ten lines are printed.
8208 There are several ways to specify what part of the file you want to
8209 print; see @ref{Specify Location}, for the full list.
8211 Here are the forms of the @code{list} command most commonly used:
8214 @item list @var{linenum}
8215 Print lines centered around line number @var{linenum} in the
8216 current source file.
8218 @item list @var{function}
8219 Print lines centered around the beginning of function
8223 Print more lines. If the last lines printed were printed with a
8224 @code{list} command, this prints lines following the last lines
8225 printed; however, if the last line printed was a solitary line printed
8226 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8227 Stack}), this prints lines centered around that line.
8230 Print lines just before the lines last printed.
8233 @cindex @code{list}, how many lines to display
8234 By default, @value{GDBN} prints ten source lines with any of these forms of
8235 the @code{list} command. You can change this using @code{set listsize}:
8238 @kindex set listsize
8239 @item set listsize @var{count}
8240 @itemx set listsize unlimited
8241 Make the @code{list} command display @var{count} source lines (unless
8242 the @code{list} argument explicitly specifies some other number).
8243 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8245 @kindex show listsize
8247 Display the number of lines that @code{list} prints.
8250 Repeating a @code{list} command with @key{RET} discards the argument,
8251 so it is equivalent to typing just @code{list}. This is more useful
8252 than listing the same lines again. An exception is made for an
8253 argument of @samp{-}; that argument is preserved in repetition so that
8254 each repetition moves up in the source file.
8256 In general, the @code{list} command expects you to supply zero, one or two
8257 @dfn{locations}. Locations specify source lines; there are several ways
8258 of writing them (@pxref{Specify Location}), but the effect is always
8259 to specify some source line.
8261 Here is a complete description of the possible arguments for @code{list}:
8264 @item list @var{location}
8265 Print lines centered around the line specified by @var{location}.
8267 @item list @var{first},@var{last}
8268 Print lines from @var{first} to @var{last}. Both arguments are
8269 locations. When a @code{list} command has two locations, and the
8270 source file of the second location is omitted, this refers to
8271 the same source file as the first location.
8273 @item list ,@var{last}
8274 Print lines ending with @var{last}.
8276 @item list @var{first},
8277 Print lines starting with @var{first}.
8280 Print lines just after the lines last printed.
8283 Print lines just before the lines last printed.
8286 As described in the preceding table.
8289 @node Specify Location
8290 @section Specifying a Location
8291 @cindex specifying location
8293 @cindex source location
8296 * Linespec Locations:: Linespec locations
8297 * Explicit Locations:: Explicit locations
8298 * Address Locations:: Address locations
8301 Several @value{GDBN} commands accept arguments that specify a location
8302 of your program's code. Since @value{GDBN} is a source-level
8303 debugger, a location usually specifies some line in the source code.
8304 Locations may be specified using three different formats:
8305 linespec locations, explicit locations, or address locations.
8307 @node Linespec Locations
8308 @subsection Linespec Locations
8309 @cindex linespec locations
8311 A @dfn{linespec} is a colon-separated list of source location parameters such
8312 as file name, function name, etc. Here are all the different ways of
8313 specifying a linespec:
8317 Specifies the line number @var{linenum} of the current source file.
8320 @itemx +@var{offset}
8321 Specifies the line @var{offset} lines before or after the @dfn{current
8322 line}. For the @code{list} command, the current line is the last one
8323 printed; for the breakpoint commands, this is the line at which
8324 execution stopped in the currently selected @dfn{stack frame}
8325 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8326 used as the second of the two linespecs in a @code{list} command,
8327 this specifies the line @var{offset} lines up or down from the first
8330 @item @var{filename}:@var{linenum}
8331 Specifies the line @var{linenum} in the source file @var{filename}.
8332 If @var{filename} is a relative file name, then it will match any
8333 source file name with the same trailing components. For example, if
8334 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8335 name of @file{/build/trunk/gcc/expr.c}, but not
8336 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8338 @item @var{function}
8339 Specifies the line that begins the body of the function @var{function}.
8340 For example, in C, this is the line with the open brace.
8342 By default, in C@t{++} and Ada, @var{function} is interpreted as
8343 specifying all functions named @var{function} in all scopes. For
8344 C@t{++}, this means in all namespaces and classes. For Ada, this
8345 means in all packages.
8347 For example, assuming a program with C@t{++} symbols named
8348 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8349 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8351 Commands that accept a linespec let you override this with the
8352 @code{-qualified} option. For example, @w{@kbd{break -qualified
8353 func}} sets a breakpoint on a free-function named @code{func} ignoring
8354 any C@t{++} class methods and namespace functions called @code{func}.
8356 @xref{Explicit Locations}.
8358 @item @var{function}:@var{label}
8359 Specifies the line where @var{label} appears in @var{function}.
8361 @item @var{filename}:@var{function}
8362 Specifies the line that begins the body of the function @var{function}
8363 in the file @var{filename}. You only need the file name with a
8364 function name to avoid ambiguity when there are identically named
8365 functions in different source files.
8368 Specifies the line at which the label named @var{label} appears
8369 in the function corresponding to the currently selected stack frame.
8370 If there is no current selected stack frame (for instance, if the inferior
8371 is not running), then @value{GDBN} will not search for a label.
8373 @cindex breakpoint at static probe point
8374 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8375 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8376 applications to embed static probes. @xref{Static Probe Points}, for more
8377 information on finding and using static probes. This form of linespec
8378 specifies the location of such a static probe.
8380 If @var{objfile} is given, only probes coming from that shared library
8381 or executable matching @var{objfile} as a regular expression are considered.
8382 If @var{provider} is given, then only probes from that provider are considered.
8383 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8384 each one of those probes.
8387 @node Explicit Locations
8388 @subsection Explicit Locations
8389 @cindex explicit locations
8391 @dfn{Explicit locations} allow the user to directly specify the source
8392 location's parameters using option-value pairs.
8394 Explicit locations are useful when several functions, labels, or
8395 file names have the same name (base name for files) in the program's
8396 sources. In these cases, explicit locations point to the source
8397 line you meant more accurately and unambiguously. Also, using
8398 explicit locations might be faster in large programs.
8400 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8401 defined in the file named @file{foo} or the label @code{bar} in a function
8402 named @code{foo}. @value{GDBN} must search either the file system or
8403 the symbol table to know.
8405 The list of valid explicit location options is summarized in the
8409 @item -source @var{filename}
8410 The value specifies the source file name. To differentiate between
8411 files with the same base name, prepend as many directories as is necessary
8412 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8413 @value{GDBN} will use the first file it finds with the given base
8414 name. This option requires the use of either @code{-function} or @code{-line}.
8416 @item -function @var{function}
8417 The value specifies the name of a function. Operations
8418 on function locations unmodified by other options (such as @code{-label}
8419 or @code{-line}) refer to the line that begins the body of the function.
8420 In C, for example, this is the line with the open brace.
8422 By default, in C@t{++} and Ada, @var{function} is interpreted as
8423 specifying all functions named @var{function} in all scopes. For
8424 C@t{++}, this means in all namespaces and classes. For Ada, this
8425 means in all packages.
8427 For example, assuming a program with C@t{++} symbols named
8428 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8429 -function func}} and @w{@kbd{break -function B::func}} set a
8430 breakpoint on both symbols.
8432 You can use the @kbd{-qualified} flag to override this (see below).
8436 This flag makes @value{GDBN} interpret a function name specified with
8437 @kbd{-function} as a complete fully-qualified name.
8439 For example, assuming a C@t{++} program with symbols named
8440 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8441 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8443 (Note: the @kbd{-qualified} option can precede a linespec as well
8444 (@pxref{Linespec Locations}), so the particular example above could be
8445 simplified as @w{@kbd{break -qualified B::func}}.)
8447 @item -label @var{label}
8448 The value specifies the name of a label. When the function
8449 name is not specified, the label is searched in the function of the currently
8450 selected stack frame.
8452 @item -line @var{number}
8453 The value specifies a line offset for the location. The offset may either
8454 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8455 the command. When specified without any other options, the line offset is
8456 relative to the current line.
8459 Explicit location options may be abbreviated by omitting any non-unique
8460 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8462 @node Address Locations
8463 @subsection Address Locations
8464 @cindex address locations
8466 @dfn{Address locations} indicate a specific program address. They have
8467 the generalized form *@var{address}.
8469 For line-oriented commands, such as @code{list} and @code{edit}, this
8470 specifies a source line that contains @var{address}. For @code{break} and
8471 other breakpoint-oriented commands, this can be used to set breakpoints in
8472 parts of your program which do not have debugging information or
8475 Here @var{address} may be any expression valid in the current working
8476 language (@pxref{Languages, working language}) that specifies a code
8477 address. In addition, as a convenience, @value{GDBN} extends the
8478 semantics of expressions used in locations to cover several situations
8479 that frequently occur during debugging. Here are the various forms
8483 @item @var{expression}
8484 Any expression valid in the current working language.
8486 @item @var{funcaddr}
8487 An address of a function or procedure derived from its name. In C,
8488 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8489 simply the function's name @var{function} (and actually a special case
8490 of a valid expression). In Pascal and Modula-2, this is
8491 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8492 (although the Pascal form also works).
8494 This form specifies the address of the function's first instruction,
8495 before the stack frame and arguments have been set up.
8497 @item '@var{filename}':@var{funcaddr}
8498 Like @var{funcaddr} above, but also specifies the name of the source
8499 file explicitly. This is useful if the name of the function does not
8500 specify the function unambiguously, e.g., if there are several
8501 functions with identical names in different source files.
8505 @section Editing Source Files
8506 @cindex editing source files
8509 @kindex e @r{(@code{edit})}
8510 To edit the lines in a source file, use the @code{edit} command.
8511 The editing program of your choice
8512 is invoked with the current line set to
8513 the active line in the program.
8514 Alternatively, there are several ways to specify what part of the file you
8515 want to print if you want to see other parts of the program:
8518 @item edit @var{location}
8519 Edit the source file specified by @code{location}. Editing starts at
8520 that @var{location}, e.g., at the specified source line of the
8521 specified file. @xref{Specify Location}, for all the possible forms
8522 of the @var{location} argument; here are the forms of the @code{edit}
8523 command most commonly used:
8526 @item edit @var{number}
8527 Edit the current source file with @var{number} as the active line number.
8529 @item edit @var{function}
8530 Edit the file containing @var{function} at the beginning of its definition.
8535 @subsection Choosing your Editor
8536 You can customize @value{GDBN} to use any editor you want
8538 The only restriction is that your editor (say @code{ex}), recognizes the
8539 following command-line syntax:
8541 ex +@var{number} file
8543 The optional numeric value +@var{number} specifies the number of the line in
8544 the file where to start editing.}.
8545 By default, it is @file{@value{EDITOR}}, but you can change this
8546 by setting the environment variable @code{EDITOR} before using
8547 @value{GDBN}. For example, to configure @value{GDBN} to use the
8548 @code{vi} editor, you could use these commands with the @code{sh} shell:
8554 or in the @code{csh} shell,
8556 setenv EDITOR /usr/bin/vi
8561 @section Searching Source Files
8562 @cindex searching source files
8564 There are two commands for searching through the current source file for a
8569 @kindex forward-search
8570 @kindex fo @r{(@code{forward-search})}
8571 @item forward-search @var{regexp}
8572 @itemx search @var{regexp}
8573 The command @samp{forward-search @var{regexp}} checks each line,
8574 starting with the one following the last line listed, for a match for
8575 @var{regexp}. It lists the line that is found. You can use the
8576 synonym @samp{search @var{regexp}} or abbreviate the command name as
8579 @kindex reverse-search
8580 @item reverse-search @var{regexp}
8581 The command @samp{reverse-search @var{regexp}} checks each line, starting
8582 with the one before the last line listed and going backward, for a match
8583 for @var{regexp}. It lists the line that is found. You can abbreviate
8584 this command as @code{rev}.
8588 @section Specifying Source Directories
8591 @cindex directories for source files
8592 Executable programs sometimes do not record the directories of the source
8593 files from which they were compiled, just the names. Even when they do,
8594 the directories could be moved between the compilation and your debugging
8595 session. @value{GDBN} has a list of directories to search for source files;
8596 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8597 it tries all the directories in the list, in the order they are present
8598 in the list, until it finds a file with the desired name.
8600 For example, suppose an executable references the file
8601 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8602 @file{/mnt/cross}. The file is first looked up literally; if this
8603 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8604 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8605 message is printed. @value{GDBN} does not look up the parts of the
8606 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8607 Likewise, the subdirectories of the source path are not searched: if
8608 the source path is @file{/mnt/cross}, and the binary refers to
8609 @file{foo.c}, @value{GDBN} would not find it under
8610 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8612 Plain file names, relative file names with leading directories, file
8613 names containing dots, etc.@: are all treated as described above; for
8614 instance, if the source path is @file{/mnt/cross}, and the source file
8615 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8616 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8617 that---@file{/mnt/cross/foo.c}.
8619 Note that the executable search path is @emph{not} used to locate the
8622 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8623 any information it has cached about where source files are found and where
8624 each line is in the file.
8628 When you start @value{GDBN}, its source path includes only @samp{cdir}
8629 and @samp{cwd}, in that order.
8630 To add other directories, use the @code{directory} command.
8632 The search path is used to find both program source files and @value{GDBN}
8633 script files (read using the @samp{-command} option and @samp{source} command).
8635 In addition to the source path, @value{GDBN} provides a set of commands
8636 that manage a list of source path substitution rules. A @dfn{substitution
8637 rule} specifies how to rewrite source directories stored in the program's
8638 debug information in case the sources were moved to a different
8639 directory between compilation and debugging. A rule is made of
8640 two strings, the first specifying what needs to be rewritten in
8641 the path, and the second specifying how it should be rewritten.
8642 In @ref{set substitute-path}, we name these two parts @var{from} and
8643 @var{to} respectively. @value{GDBN} does a simple string replacement
8644 of @var{from} with @var{to} at the start of the directory part of the
8645 source file name, and uses that result instead of the original file
8646 name to look up the sources.
8648 Using the previous example, suppose the @file{foo-1.0} tree has been
8649 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8650 @value{GDBN} to replace @file{/usr/src} in all source path names with
8651 @file{/mnt/cross}. The first lookup will then be
8652 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8653 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8654 substitution rule, use the @code{set substitute-path} command
8655 (@pxref{set substitute-path}).
8657 To avoid unexpected substitution results, a rule is applied only if the
8658 @var{from} part of the directory name ends at a directory separator.
8659 For instance, a rule substituting @file{/usr/source} into
8660 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8661 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8662 is applied only at the beginning of the directory name, this rule will
8663 not be applied to @file{/root/usr/source/baz.c} either.
8665 In many cases, you can achieve the same result using the @code{directory}
8666 command. However, @code{set substitute-path} can be more efficient in
8667 the case where the sources are organized in a complex tree with multiple
8668 subdirectories. With the @code{directory} command, you need to add each
8669 subdirectory of your project. If you moved the entire tree while
8670 preserving its internal organization, then @code{set substitute-path}
8671 allows you to direct the debugger to all the sources with one single
8674 @code{set substitute-path} is also more than just a shortcut command.
8675 The source path is only used if the file at the original location no
8676 longer exists. On the other hand, @code{set substitute-path} modifies
8677 the debugger behavior to look at the rewritten location instead. So, if
8678 for any reason a source file that is not relevant to your executable is
8679 located at the original location, a substitution rule is the only
8680 method available to point @value{GDBN} at the new location.
8682 @cindex @samp{--with-relocated-sources}
8683 @cindex default source path substitution
8684 You can configure a default source path substitution rule by
8685 configuring @value{GDBN} with the
8686 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8687 should be the name of a directory under @value{GDBN}'s configured
8688 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8689 directory names in debug information under @var{dir} will be adjusted
8690 automatically if the installed @value{GDBN} is moved to a new
8691 location. This is useful if @value{GDBN}, libraries or executables
8692 with debug information and corresponding source code are being moved
8696 @item directory @var{dirname} @dots{}
8697 @item dir @var{dirname} @dots{}
8698 Add directory @var{dirname} to the front of the source path. Several
8699 directory names may be given to this command, separated by @samp{:}
8700 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8701 part of absolute file names) or
8702 whitespace. You may specify a directory that is already in the source
8703 path; this moves it forward, so @value{GDBN} searches it sooner.
8707 @vindex $cdir@r{, convenience variable}
8708 @vindex $cwd@r{, convenience variable}
8709 @cindex compilation directory
8710 @cindex current directory
8711 @cindex working directory
8712 @cindex directory, current
8713 @cindex directory, compilation
8714 You can use the string @samp{$cdir} to refer to the compilation
8715 directory (if one is recorded), and @samp{$cwd} to refer to the current
8716 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8717 tracks the current working directory as it changes during your @value{GDBN}
8718 session, while the latter is immediately expanded to the current
8719 directory at the time you add an entry to the source path.
8722 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8724 @c RET-repeat for @code{directory} is explicitly disabled, but since
8725 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8727 @item set directories @var{path-list}
8728 @kindex set directories
8729 Set the source path to @var{path-list}.
8730 @samp{$cdir:$cwd} are added if missing.
8732 @item show directories
8733 @kindex show directories
8734 Print the source path: show which directories it contains.
8736 @anchor{set substitute-path}
8737 @item set substitute-path @var{from} @var{to}
8738 @kindex set substitute-path
8739 Define a source path substitution rule, and add it at the end of the
8740 current list of existing substitution rules. If a rule with the same
8741 @var{from} was already defined, then the old rule is also deleted.
8743 For example, if the file @file{/foo/bar/baz.c} was moved to
8744 @file{/mnt/cross/baz.c}, then the command
8747 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8751 will tell @value{GDBN} to replace @samp{/foo/bar} with
8752 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8753 @file{baz.c} even though it was moved.
8755 In the case when more than one substitution rule have been defined,
8756 the rules are evaluated one by one in the order where they have been
8757 defined. The first one matching, if any, is selected to perform
8760 For instance, if we had entered the following commands:
8763 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8764 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8768 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8769 @file{/mnt/include/defs.h} by using the first rule. However, it would
8770 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8771 @file{/mnt/src/lib/foo.c}.
8774 @item unset substitute-path [path]
8775 @kindex unset substitute-path
8776 If a path is specified, search the current list of substitution rules
8777 for a rule that would rewrite that path. Delete that rule if found.
8778 A warning is emitted by the debugger if no rule could be found.
8780 If no path is specified, then all substitution rules are deleted.
8782 @item show substitute-path [path]
8783 @kindex show substitute-path
8784 If a path is specified, then print the source path substitution rule
8785 which would rewrite that path, if any.
8787 If no path is specified, then print all existing source path substitution
8792 If your source path is cluttered with directories that are no longer of
8793 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8794 versions of source. You can correct the situation as follows:
8798 Use @code{directory} with no argument to reset the source path to its default value.
8801 Use @code{directory} with suitable arguments to reinstall the
8802 directories you want in the source path. You can add all the
8803 directories in one command.
8807 @section Source and Machine Code
8808 @cindex source line and its code address
8810 You can use the command @code{info line} to map source lines to program
8811 addresses (and vice versa), and the command @code{disassemble} to display
8812 a range of addresses as machine instructions. You can use the command
8813 @code{set disassemble-next-line} to set whether to disassemble next
8814 source line when execution stops. When run under @sc{gnu} Emacs
8815 mode, the @code{info line} command causes the arrow to point to the
8816 line specified. Also, @code{info line} prints addresses in symbolic form as
8822 @itemx info line @var{location}
8823 Print the starting and ending addresses of the compiled code for
8824 source line @var{location}. You can specify source lines in any of
8825 the ways documented in @ref{Specify Location}. With no @var{location}
8826 information about the current source line is printed.
8829 For example, we can use @code{info line} to discover the location of
8830 the object code for the first line of function
8831 @code{m4_changequote}:
8834 (@value{GDBP}) info line m4_changequote
8835 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8836 ends at 0x6350 <m4_changequote+4>.
8840 @cindex code address and its source line
8841 We can also inquire (using @code{*@var{addr}} as the form for
8842 @var{location}) what source line covers a particular address:
8844 (@value{GDBP}) info line *0x63ff
8845 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8846 ends at 0x6404 <m4_changequote+184>.
8849 @cindex @code{$_} and @code{info line}
8850 @cindex @code{x} command, default address
8851 @kindex x@r{(examine), and} info line
8852 After @code{info line}, the default address for the @code{x} command
8853 is changed to the starting address of the line, so that @samp{x/i} is
8854 sufficient to begin examining the machine code (@pxref{Memory,
8855 ,Examining Memory}). Also, this address is saved as the value of the
8856 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8859 @cindex info line, repeated calls
8860 After @code{info line}, using @code{info line} again without
8861 specifying a location will display information about the next source
8866 @cindex assembly instructions
8867 @cindex instructions, assembly
8868 @cindex machine instructions
8869 @cindex listing machine instructions
8871 @itemx disassemble /m
8872 @itemx disassemble /s
8873 @itemx disassemble /r
8874 This specialized command dumps a range of memory as machine
8875 instructions. It can also print mixed source+disassembly by specifying
8876 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8877 as well as in symbolic form by specifying the @code{/r} modifier.
8878 The default memory range is the function surrounding the
8879 program counter of the selected frame. A single argument to this
8880 command is a program counter value; @value{GDBN} dumps the function
8881 surrounding this value. When two arguments are given, they should
8882 be separated by a comma, possibly surrounded by whitespace. The
8883 arguments specify a range of addresses to dump, in one of two forms:
8886 @item @var{start},@var{end}
8887 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8888 @item @var{start},+@var{length}
8889 the addresses from @var{start} (inclusive) to
8890 @code{@var{start}+@var{length}} (exclusive).
8894 When 2 arguments are specified, the name of the function is also
8895 printed (since there could be several functions in the given range).
8897 The argument(s) can be any expression yielding a numeric value, such as
8898 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8900 If the range of memory being disassembled contains current program counter,
8901 the instruction at that location is shown with a @code{=>} marker.
8904 The following example shows the disassembly of a range of addresses of
8905 HP PA-RISC 2.0 code:
8908 (@value{GDBP}) disas 0x32c4, 0x32e4
8909 Dump of assembler code from 0x32c4 to 0x32e4:
8910 0x32c4 <main+204>: addil 0,dp
8911 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8912 0x32cc <main+212>: ldil 0x3000,r31
8913 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8914 0x32d4 <main+220>: ldo 0(r31),rp
8915 0x32d8 <main+224>: addil -0x800,dp
8916 0x32dc <main+228>: ldo 0x588(r1),r26
8917 0x32e0 <main+232>: ldil 0x3000,r31
8918 End of assembler dump.
8921 Here is an example showing mixed source+assembly for Intel x86
8922 with @code{/m} or @code{/s}, when the program is stopped just after
8923 function prologue in a non-optimized function with no inline code.
8926 (@value{GDBP}) disas /m main
8927 Dump of assembler code for function main:
8929 0x08048330 <+0>: push %ebp
8930 0x08048331 <+1>: mov %esp,%ebp
8931 0x08048333 <+3>: sub $0x8,%esp
8932 0x08048336 <+6>: and $0xfffffff0,%esp
8933 0x08048339 <+9>: sub $0x10,%esp
8935 6 printf ("Hello.\n");
8936 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8937 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8941 0x08048348 <+24>: mov $0x0,%eax
8942 0x0804834d <+29>: leave
8943 0x0804834e <+30>: ret
8945 End of assembler dump.
8948 The @code{/m} option is deprecated as its output is not useful when
8949 there is either inlined code or re-ordered code.
8950 The @code{/s} option is the preferred choice.
8951 Here is an example for AMD x86-64 showing the difference between
8952 @code{/m} output and @code{/s} output.
8953 This example has one inline function defined in a header file,
8954 and the code is compiled with @samp{-O2} optimization.
8955 Note how the @code{/m} output is missing the disassembly of
8956 several instructions that are present in the @code{/s} output.
8986 (@value{GDBP}) disas /m main
8987 Dump of assembler code for function main:
8991 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8992 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8996 0x000000000040041d <+29>: xor %eax,%eax
8997 0x000000000040041f <+31>: retq
8998 0x0000000000400420 <+32>: add %eax,%eax
8999 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9001 End of assembler dump.
9002 (@value{GDBP}) disas /s main
9003 Dump of assembler code for function main:
9007 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9011 0x0000000000400406 <+6>: test %eax,%eax
9012 0x0000000000400408 <+8>: js 0x400420 <main+32>
9017 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9018 0x000000000040040d <+13>: test %eax,%eax
9019 0x000000000040040f <+15>: mov $0x1,%eax
9020 0x0000000000400414 <+20>: cmovne %edx,%eax
9024 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9028 0x000000000040041d <+29>: xor %eax,%eax
9029 0x000000000040041f <+31>: retq
9033 0x0000000000400420 <+32>: add %eax,%eax
9034 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9035 End of assembler dump.
9038 Here is another example showing raw instructions in hex for AMD x86-64,
9041 (gdb) disas /r 0x400281,+10
9042 Dump of assembler code from 0x400281 to 0x40028b:
9043 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9044 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9045 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9046 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9047 End of assembler dump.
9050 Addresses cannot be specified as a location (@pxref{Specify Location}).
9051 So, for example, if you want to disassemble function @code{bar}
9052 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9053 and not @samp{disassemble foo.c:bar}.
9055 Some architectures have more than one commonly-used set of instruction
9056 mnemonics or other syntax.
9058 For programs that were dynamically linked and use shared libraries,
9059 instructions that call functions or branch to locations in the shared
9060 libraries might show a seemingly bogus location---it's actually a
9061 location of the relocation table. On some architectures, @value{GDBN}
9062 might be able to resolve these to actual function names.
9065 @kindex set disassembler-options
9066 @cindex disassembler options
9067 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9068 This command controls the passing of target specific information to
9069 the disassembler. For a list of valid options, please refer to the
9070 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9071 manual and/or the output of @kbd{objdump --help}
9072 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9073 The default value is the empty string.
9075 If it is necessary to specify more than one disassembler option, then
9076 multiple options can be placed together into a comma separated list.
9077 Currently this command is only supported on targets ARM, MIPS, PowerPC
9080 @kindex show disassembler-options
9081 @item show disassembler-options
9082 Show the current setting of the disassembler options.
9086 @kindex set disassembly-flavor
9087 @cindex Intel disassembly flavor
9088 @cindex AT&T disassembly flavor
9089 @item set disassembly-flavor @var{instruction-set}
9090 Select the instruction set to use when disassembling the
9091 program via the @code{disassemble} or @code{x/i} commands.
9093 Currently this command is only defined for the Intel x86 family. You
9094 can set @var{instruction-set} to either @code{intel} or @code{att}.
9095 The default is @code{att}, the AT&T flavor used by default by Unix
9096 assemblers for x86-based targets.
9098 @kindex show disassembly-flavor
9099 @item show disassembly-flavor
9100 Show the current setting of the disassembly flavor.
9104 @kindex set disassemble-next-line
9105 @kindex show disassemble-next-line
9106 @item set disassemble-next-line
9107 @itemx show disassemble-next-line
9108 Control whether or not @value{GDBN} will disassemble the next source
9109 line or instruction when execution stops. If ON, @value{GDBN} will
9110 display disassembly of the next source line when execution of the
9111 program being debugged stops. This is @emph{in addition} to
9112 displaying the source line itself, which @value{GDBN} always does if
9113 possible. If the next source line cannot be displayed for some reason
9114 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9115 info in the debug info), @value{GDBN} will display disassembly of the
9116 next @emph{instruction} instead of showing the next source line. If
9117 AUTO, @value{GDBN} will display disassembly of next instruction only
9118 if the source line cannot be displayed. This setting causes
9119 @value{GDBN} to display some feedback when you step through a function
9120 with no line info or whose source file is unavailable. The default is
9121 OFF, which means never display the disassembly of the next line or
9127 @chapter Examining Data
9129 @cindex printing data
9130 @cindex examining data
9133 The usual way to examine data in your program is with the @code{print}
9134 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9135 evaluates and prints the value of an expression of the language your
9136 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9137 Different Languages}). It may also print the expression using a
9138 Python-based pretty-printer (@pxref{Pretty Printing}).
9141 @item print @var{expr}
9142 @itemx print /@var{f} @var{expr}
9143 @var{expr} is an expression (in the source language). By default the
9144 value of @var{expr} is printed in a format appropriate to its data type;
9145 you can choose a different format by specifying @samp{/@var{f}}, where
9146 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9150 @itemx print /@var{f}
9151 @cindex reprint the last value
9152 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9153 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9154 conveniently inspect the same value in an alternative format.
9157 A more low-level way of examining data is with the @code{x} command.
9158 It examines data in memory at a specified address and prints it in a
9159 specified format. @xref{Memory, ,Examining Memory}.
9161 If you are interested in information about types, or about how the
9162 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9163 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9166 @cindex exploring hierarchical data structures
9168 Another way of examining values of expressions and type information is
9169 through the Python extension command @code{explore} (available only if
9170 the @value{GDBN} build is configured with @code{--with-python}). It
9171 offers an interactive way to start at the highest level (or, the most
9172 abstract level) of the data type of an expression (or, the data type
9173 itself) and explore all the way down to leaf scalar values/fields
9174 embedded in the higher level data types.
9177 @item explore @var{arg}
9178 @var{arg} is either an expression (in the source language), or a type
9179 visible in the current context of the program being debugged.
9182 The working of the @code{explore} command can be illustrated with an
9183 example. If a data type @code{struct ComplexStruct} is defined in your
9193 struct ComplexStruct
9195 struct SimpleStruct *ss_p;
9201 followed by variable declarations as
9204 struct SimpleStruct ss = @{ 10, 1.11 @};
9205 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9209 then, the value of the variable @code{cs} can be explored using the
9210 @code{explore} command as follows.
9214 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9215 the following fields:
9217 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9218 arr = <Enter 1 to explore this field of type `int [10]'>
9220 Enter the field number of choice:
9224 Since the fields of @code{cs} are not scalar values, you are being
9225 prompted to chose the field you want to explore. Let's say you choose
9226 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9227 pointer, you will be asked if it is pointing to a single value. From
9228 the declaration of @code{cs} above, it is indeed pointing to a single
9229 value, hence you enter @code{y}. If you enter @code{n}, then you will
9230 be asked if it were pointing to an array of values, in which case this
9231 field will be explored as if it were an array.
9234 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9235 Continue exploring it as a pointer to a single value [y/n]: y
9236 The value of `*(cs.ss_p)' is a struct/class of type `struct
9237 SimpleStruct' with the following fields:
9239 i = 10 .. (Value of type `int')
9240 d = 1.1100000000000001 .. (Value of type `double')
9242 Press enter to return to parent value:
9246 If the field @code{arr} of @code{cs} was chosen for exploration by
9247 entering @code{1} earlier, then since it is as array, you will be
9248 prompted to enter the index of the element in the array that you want
9252 `cs.arr' is an array of `int'.
9253 Enter the index of the element you want to explore in `cs.arr': 5
9255 `(cs.arr)[5]' is a scalar value of type `int'.
9259 Press enter to return to parent value:
9262 In general, at any stage of exploration, you can go deeper towards the
9263 leaf values by responding to the prompts appropriately, or hit the
9264 return key to return to the enclosing data structure (the @i{higher}
9265 level data structure).
9267 Similar to exploring values, you can use the @code{explore} command to
9268 explore types. Instead of specifying a value (which is typically a
9269 variable name or an expression valid in the current context of the
9270 program being debugged), you specify a type name. If you consider the
9271 same example as above, your can explore the type
9272 @code{struct ComplexStruct} by passing the argument
9273 @code{struct ComplexStruct} to the @code{explore} command.
9276 (gdb) explore struct ComplexStruct
9280 By responding to the prompts appropriately in the subsequent interactive
9281 session, you can explore the type @code{struct ComplexStruct} in a
9282 manner similar to how the value @code{cs} was explored in the above
9285 The @code{explore} command also has two sub-commands,
9286 @code{explore value} and @code{explore type}. The former sub-command is
9287 a way to explicitly specify that value exploration of the argument is
9288 being invoked, while the latter is a way to explicitly specify that type
9289 exploration of the argument is being invoked.
9292 @item explore value @var{expr}
9293 @cindex explore value
9294 This sub-command of @code{explore} explores the value of the
9295 expression @var{expr} (if @var{expr} is an expression valid in the
9296 current context of the program being debugged). The behavior of this
9297 command is identical to that of the behavior of the @code{explore}
9298 command being passed the argument @var{expr}.
9300 @item explore type @var{arg}
9301 @cindex explore type
9302 This sub-command of @code{explore} explores the type of @var{arg} (if
9303 @var{arg} is a type visible in the current context of program being
9304 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9305 is an expression valid in the current context of the program being
9306 debugged). If @var{arg} is a type, then the behavior of this command is
9307 identical to that of the @code{explore} command being passed the
9308 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9309 this command will be identical to that of the @code{explore} command
9310 being passed the type of @var{arg} as the argument.
9314 * Expressions:: Expressions
9315 * Ambiguous Expressions:: Ambiguous Expressions
9316 * Variables:: Program variables
9317 * Arrays:: Artificial arrays
9318 * Output Formats:: Output formats
9319 * Memory:: Examining memory
9320 * Auto Display:: Automatic display
9321 * Print Settings:: Print settings
9322 * Pretty Printing:: Python pretty printing
9323 * Value History:: Value history
9324 * Convenience Vars:: Convenience variables
9325 * Convenience Funs:: Convenience functions
9326 * Registers:: Registers
9327 * Floating Point Hardware:: Floating point hardware
9328 * Vector Unit:: Vector Unit
9329 * OS Information:: Auxiliary data provided by operating system
9330 * Memory Region Attributes:: Memory region attributes
9331 * Dump/Restore Files:: Copy between memory and a file
9332 * Core File Generation:: Cause a program dump its core
9333 * Character Sets:: Debugging programs that use a different
9334 character set than GDB does
9335 * Caching Target Data:: Data caching for targets
9336 * Searching Memory:: Searching memory for a sequence of bytes
9337 * Value Sizes:: Managing memory allocated for values
9341 @section Expressions
9344 @code{print} and many other @value{GDBN} commands accept an expression and
9345 compute its value. Any kind of constant, variable or operator defined
9346 by the programming language you are using is valid in an expression in
9347 @value{GDBN}. This includes conditional expressions, function calls,
9348 casts, and string constants. It also includes preprocessor macros, if
9349 you compiled your program to include this information; see
9352 @cindex arrays in expressions
9353 @value{GDBN} supports array constants in expressions input by
9354 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9355 you can use the command @code{print @{1, 2, 3@}} to create an array
9356 of three integers. If you pass an array to a function or assign it
9357 to a program variable, @value{GDBN} copies the array to memory that
9358 is @code{malloc}ed in the target program.
9360 Because C is so widespread, most of the expressions shown in examples in
9361 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9362 Languages}, for information on how to use expressions in other
9365 In this section, we discuss operators that you can use in @value{GDBN}
9366 expressions regardless of your programming language.
9368 @cindex casts, in expressions
9369 Casts are supported in all languages, not just in C, because it is so
9370 useful to cast a number into a pointer in order to examine a structure
9371 at that address in memory.
9372 @c FIXME: casts supported---Mod2 true?
9374 @value{GDBN} supports these operators, in addition to those common
9375 to programming languages:
9379 @samp{@@} is a binary operator for treating parts of memory as arrays.
9380 @xref{Arrays, ,Artificial Arrays}, for more information.
9383 @samp{::} allows you to specify a variable in terms of the file or
9384 function where it is defined. @xref{Variables, ,Program Variables}.
9386 @cindex @{@var{type}@}
9387 @cindex type casting memory
9388 @cindex memory, viewing as typed object
9389 @cindex casts, to view memory
9390 @item @{@var{type}@} @var{addr}
9391 Refers to an object of type @var{type} stored at address @var{addr} in
9392 memory. The address @var{addr} may be any expression whose value is
9393 an integer or pointer (but parentheses are required around binary
9394 operators, just as in a cast). This construct is allowed regardless
9395 of what kind of data is normally supposed to reside at @var{addr}.
9398 @node Ambiguous Expressions
9399 @section Ambiguous Expressions
9400 @cindex ambiguous expressions
9402 Expressions can sometimes contain some ambiguous elements. For instance,
9403 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9404 a single function name to be defined several times, for application in
9405 different contexts. This is called @dfn{overloading}. Another example
9406 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9407 templates and is typically instantiated several times, resulting in
9408 the same function name being defined in different contexts.
9410 In some cases and depending on the language, it is possible to adjust
9411 the expression to remove the ambiguity. For instance in C@t{++}, you
9412 can specify the signature of the function you want to break on, as in
9413 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9414 qualified name of your function often makes the expression unambiguous
9417 When an ambiguity that needs to be resolved is detected, the debugger
9418 has the capability to display a menu of numbered choices for each
9419 possibility, and then waits for the selection with the prompt @samp{>}.
9420 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9421 aborts the current command. If the command in which the expression was
9422 used allows more than one choice to be selected, the next option in the
9423 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9426 For example, the following session excerpt shows an attempt to set a
9427 breakpoint at the overloaded symbol @code{String::after}.
9428 We choose three particular definitions of that function name:
9430 @c FIXME! This is likely to change to show arg type lists, at least
9433 (@value{GDBP}) b String::after
9436 [2] file:String.cc; line number:867
9437 [3] file:String.cc; line number:860
9438 [4] file:String.cc; line number:875
9439 [5] file:String.cc; line number:853
9440 [6] file:String.cc; line number:846
9441 [7] file:String.cc; line number:735
9443 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9444 Breakpoint 2 at 0xb344: file String.cc, line 875.
9445 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9446 Multiple breakpoints were set.
9447 Use the "delete" command to delete unwanted
9454 @kindex set multiple-symbols
9455 @item set multiple-symbols @var{mode}
9456 @cindex multiple-symbols menu
9458 This option allows you to adjust the debugger behavior when an expression
9461 By default, @var{mode} is set to @code{all}. If the command with which
9462 the expression is used allows more than one choice, then @value{GDBN}
9463 automatically selects all possible choices. For instance, inserting
9464 a breakpoint on a function using an ambiguous name results in a breakpoint
9465 inserted on each possible match. However, if a unique choice must be made,
9466 then @value{GDBN} uses the menu to help you disambiguate the expression.
9467 For instance, printing the address of an overloaded function will result
9468 in the use of the menu.
9470 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9471 when an ambiguity is detected.
9473 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9474 an error due to the ambiguity and the command is aborted.
9476 @kindex show multiple-symbols
9477 @item show multiple-symbols
9478 Show the current value of the @code{multiple-symbols} setting.
9482 @section Program Variables
9484 The most common kind of expression to use is the name of a variable
9487 Variables in expressions are understood in the selected stack frame
9488 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9492 global (or file-static)
9499 visible according to the scope rules of the
9500 programming language from the point of execution in that frame
9503 @noindent This means that in the function
9518 you can examine and use the variable @code{a} whenever your program is
9519 executing within the function @code{foo}, but you can only use or
9520 examine the variable @code{b} while your program is executing inside
9521 the block where @code{b} is declared.
9523 @cindex variable name conflict
9524 There is an exception: you can refer to a variable or function whose
9525 scope is a single source file even if the current execution point is not
9526 in this file. But it is possible to have more than one such variable or
9527 function with the same name (in different source files). If that
9528 happens, referring to that name has unpredictable effects. If you wish,
9529 you can specify a static variable in a particular function or file by
9530 using the colon-colon (@code{::}) notation:
9532 @cindex colon-colon, context for variables/functions
9534 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9535 @cindex @code{::}, context for variables/functions
9538 @var{file}::@var{variable}
9539 @var{function}::@var{variable}
9543 Here @var{file} or @var{function} is the name of the context for the
9544 static @var{variable}. In the case of file names, you can use quotes to
9545 make sure @value{GDBN} parses the file name as a single word---for example,
9546 to print a global value of @code{x} defined in @file{f2.c}:
9549 (@value{GDBP}) p 'f2.c'::x
9552 The @code{::} notation is normally used for referring to
9553 static variables, since you typically disambiguate uses of local variables
9554 in functions by selecting the appropriate frame and using the
9555 simple name of the variable. However, you may also use this notation
9556 to refer to local variables in frames enclosing the selected frame:
9565 process (a); /* Stop here */
9576 For example, if there is a breakpoint at the commented line,
9577 here is what you might see
9578 when the program stops after executing the call @code{bar(0)}:
9583 (@value{GDBP}) p bar::a
9586 #2 0x080483d0 in foo (a=5) at foobar.c:12
9589 (@value{GDBP}) p bar::a
9593 @cindex C@t{++} scope resolution
9594 These uses of @samp{::} are very rarely in conflict with the very
9595 similar use of the same notation in C@t{++}. When they are in
9596 conflict, the C@t{++} meaning takes precedence; however, this can be
9597 overridden by quoting the file or function name with single quotes.
9599 For example, suppose the program is stopped in a method of a class
9600 that has a field named @code{includefile}, and there is also an
9601 include file named @file{includefile} that defines a variable,
9605 (@value{GDBP}) p includefile
9607 (@value{GDBP}) p includefile::some_global
9608 A syntax error in expression, near `'.
9609 (@value{GDBP}) p 'includefile'::some_global
9613 @cindex wrong values
9614 @cindex variable values, wrong
9615 @cindex function entry/exit, wrong values of variables
9616 @cindex optimized code, wrong values of variables
9618 @emph{Warning:} Occasionally, a local variable may appear to have the
9619 wrong value at certain points in a function---just after entry to a new
9620 scope, and just before exit.
9622 You may see this problem when you are stepping by machine instructions.
9623 This is because, on most machines, it takes more than one instruction to
9624 set up a stack frame (including local variable definitions); if you are
9625 stepping by machine instructions, variables may appear to have the wrong
9626 values until the stack frame is completely built. On exit, it usually
9627 also takes more than one machine instruction to destroy a stack frame;
9628 after you begin stepping through that group of instructions, local
9629 variable definitions may be gone.
9631 This may also happen when the compiler does significant optimizations.
9632 To be sure of always seeing accurate values, turn off all optimization
9635 @cindex ``No symbol "foo" in current context''
9636 Another possible effect of compiler optimizations is to optimize
9637 unused variables out of existence, or assign variables to registers (as
9638 opposed to memory addresses). Depending on the support for such cases
9639 offered by the debug info format used by the compiler, @value{GDBN}
9640 might not be able to display values for such local variables. If that
9641 happens, @value{GDBN} will print a message like this:
9644 No symbol "foo" in current context.
9647 To solve such problems, either recompile without optimizations, or use a
9648 different debug info format, if the compiler supports several such
9649 formats. @xref{Compilation}, for more information on choosing compiler
9650 options. @xref{C, ,C and C@t{++}}, for more information about debug
9651 info formats that are best suited to C@t{++} programs.
9653 If you ask to print an object whose contents are unknown to
9654 @value{GDBN}, e.g., because its data type is not completely specified
9655 by the debug information, @value{GDBN} will say @samp{<incomplete
9656 type>}. @xref{Symbols, incomplete type}, for more about this.
9658 @cindex no debug info variables
9659 If you try to examine or use the value of a (global) variable for
9660 which @value{GDBN} has no type information, e.g., because the program
9661 includes no debug information, @value{GDBN} displays an error message.
9662 @xref{Symbols, unknown type}, for more about unknown types. If you
9663 cast the variable to its declared type, @value{GDBN} gets the
9664 variable's value using the cast-to type as the variable's type. For
9665 example, in a C program:
9668 (@value{GDBP}) p var
9669 'var' has unknown type; cast it to its declared type
9670 (@value{GDBP}) p (float) var
9674 If you append @kbd{@@entry} string to a function parameter name you get its
9675 value at the time the function got called. If the value is not available an
9676 error message is printed. Entry values are available only with some compilers.
9677 Entry values are normally also printed at the function parameter list according
9678 to @ref{set print entry-values}.
9681 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9687 (gdb) print i@@entry
9691 Strings are identified as arrays of @code{char} values without specified
9692 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9693 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9694 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9695 defines literal string type @code{"char"} as @code{char} without a sign.
9700 signed char var1[] = "A";
9703 You get during debugging
9708 $2 = @{65 'A', 0 '\0'@}
9712 @section Artificial Arrays
9714 @cindex artificial array
9716 @kindex @@@r{, referencing memory as an array}
9717 It is often useful to print out several successive objects of the
9718 same type in memory; a section of an array, or an array of
9719 dynamically determined size for which only a pointer exists in the
9722 You can do this by referring to a contiguous span of memory as an
9723 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9724 operand of @samp{@@} should be the first element of the desired array
9725 and be an individual object. The right operand should be the desired length
9726 of the array. The result is an array value whose elements are all of
9727 the type of the left argument. The first element is actually the left
9728 argument; the second element comes from bytes of memory immediately
9729 following those that hold the first element, and so on. Here is an
9730 example. If a program says
9733 int *array = (int *) malloc (len * sizeof (int));
9737 you can print the contents of @code{array} with
9743 The left operand of @samp{@@} must reside in memory. Array values made
9744 with @samp{@@} in this way behave just like other arrays in terms of
9745 subscripting, and are coerced to pointers when used in expressions.
9746 Artificial arrays most often appear in expressions via the value history
9747 (@pxref{Value History, ,Value History}), after printing one out.
9749 Another way to create an artificial array is to use a cast.
9750 This re-interprets a value as if it were an array.
9751 The value need not be in memory:
9753 (@value{GDBP}) p/x (short[2])0x12345678
9754 $1 = @{0x1234, 0x5678@}
9757 As a convenience, if you leave the array length out (as in
9758 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9759 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9761 (@value{GDBP}) p/x (short[])0x12345678
9762 $2 = @{0x1234, 0x5678@}
9765 Sometimes the artificial array mechanism is not quite enough; in
9766 moderately complex data structures, the elements of interest may not
9767 actually be adjacent---for example, if you are interested in the values
9768 of pointers in an array. One useful work-around in this situation is
9769 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9770 Variables}) as a counter in an expression that prints the first
9771 interesting value, and then repeat that expression via @key{RET}. For
9772 instance, suppose you have an array @code{dtab} of pointers to
9773 structures, and you are interested in the values of a field @code{fv}
9774 in each structure. Here is an example of what you might type:
9784 @node Output Formats
9785 @section Output Formats
9787 @cindex formatted output
9788 @cindex output formats
9789 By default, @value{GDBN} prints a value according to its data type. Sometimes
9790 this is not what you want. For example, you might want to print a number
9791 in hex, or a pointer in decimal. Or you might want to view data in memory
9792 at a certain address as a character string or as an instruction. To do
9793 these things, specify an @dfn{output format} when you print a value.
9795 The simplest use of output formats is to say how to print a value
9796 already computed. This is done by starting the arguments of the
9797 @code{print} command with a slash and a format letter. The format
9798 letters supported are:
9802 Regard the bits of the value as an integer, and print the integer in
9806 Print as integer in signed decimal.
9809 Print as integer in unsigned decimal.
9812 Print as integer in octal.
9815 Print as integer in binary. The letter @samp{t} stands for ``two''.
9816 @footnote{@samp{b} cannot be used because these format letters are also
9817 used with the @code{x} command, where @samp{b} stands for ``byte'';
9818 see @ref{Memory,,Examining Memory}.}
9821 @cindex unknown address, locating
9822 @cindex locate address
9823 Print as an address, both absolute in hexadecimal and as an offset from
9824 the nearest preceding symbol. You can use this format used to discover
9825 where (in what function) an unknown address is located:
9828 (@value{GDBP}) p/a 0x54320
9829 $3 = 0x54320 <_initialize_vx+396>
9833 The command @code{info symbol 0x54320} yields similar results.
9834 @xref{Symbols, info symbol}.
9837 Regard as an integer and print it as a character constant. This
9838 prints both the numerical value and its character representation. The
9839 character representation is replaced with the octal escape @samp{\nnn}
9840 for characters outside the 7-bit @sc{ascii} range.
9842 Without this format, @value{GDBN} displays @code{char},
9843 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9844 constants. Single-byte members of vectors are displayed as integer
9848 Regard the bits of the value as a floating point number and print
9849 using typical floating point syntax.
9852 @cindex printing strings
9853 @cindex printing byte arrays
9854 Regard as a string, if possible. With this format, pointers to single-byte
9855 data are displayed as null-terminated strings and arrays of single-byte data
9856 are displayed as fixed-length strings. Other values are displayed in their
9859 Without this format, @value{GDBN} displays pointers to and arrays of
9860 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9861 strings. Single-byte members of a vector are displayed as an integer
9865 Like @samp{x} formatting, the value is treated as an integer and
9866 printed as hexadecimal, but leading zeros are printed to pad the value
9867 to the size of the integer type.
9870 @cindex raw printing
9871 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9872 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9873 Printing}). This typically results in a higher-level display of the
9874 value's contents. The @samp{r} format bypasses any Python
9875 pretty-printer which might exist.
9878 For example, to print the program counter in hex (@pxref{Registers}), type
9885 Note that no space is required before the slash; this is because command
9886 names in @value{GDBN} cannot contain a slash.
9888 To reprint the last value in the value history with a different format,
9889 you can use the @code{print} command with just a format and no
9890 expression. For example, @samp{p/x} reprints the last value in hex.
9893 @section Examining Memory
9895 You can use the command @code{x} (for ``examine'') to examine memory in
9896 any of several formats, independently of your program's data types.
9898 @cindex examining memory
9900 @kindex x @r{(examine memory)}
9901 @item x/@var{nfu} @var{addr}
9904 Use the @code{x} command to examine memory.
9907 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9908 much memory to display and how to format it; @var{addr} is an
9909 expression giving the address where you want to start displaying memory.
9910 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9911 Several commands set convenient defaults for @var{addr}.
9914 @item @var{n}, the repeat count
9915 The repeat count is a decimal integer; the default is 1. It specifies
9916 how much memory (counting by units @var{u}) to display. If a negative
9917 number is specified, memory is examined backward from @var{addr}.
9918 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9921 @item @var{f}, the display format
9922 The display format is one of the formats used by @code{print}
9923 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9924 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9925 The default is @samp{x} (hexadecimal) initially. The default changes
9926 each time you use either @code{x} or @code{print}.
9928 @item @var{u}, the unit size
9929 The unit size is any of
9935 Halfwords (two bytes).
9937 Words (four bytes). This is the initial default.
9939 Giant words (eight bytes).
9942 Each time you specify a unit size with @code{x}, that size becomes the
9943 default unit the next time you use @code{x}. For the @samp{i} format,
9944 the unit size is ignored and is normally not written. For the @samp{s} format,
9945 the unit size defaults to @samp{b}, unless it is explicitly given.
9946 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9947 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9948 Note that the results depend on the programming language of the
9949 current compilation unit. If the language is C, the @samp{s}
9950 modifier will use the UTF-16 encoding while @samp{w} will use
9951 UTF-32. The encoding is set by the programming language and cannot
9954 @item @var{addr}, starting display address
9955 @var{addr} is the address where you want @value{GDBN} to begin displaying
9956 memory. The expression need not have a pointer value (though it may);
9957 it is always interpreted as an integer address of a byte of memory.
9958 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9959 @var{addr} is usually just after the last address examined---but several
9960 other commands also set the default address: @code{info breakpoints} (to
9961 the address of the last breakpoint listed), @code{info line} (to the
9962 starting address of a line), and @code{print} (if you use it to display
9963 a value from memory).
9966 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9967 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9968 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9969 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9970 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9972 You can also specify a negative repeat count to examine memory backward
9973 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9974 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9976 Since the letters indicating unit sizes are all distinct from the
9977 letters specifying output formats, you do not have to remember whether
9978 unit size or format comes first; either order works. The output
9979 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9980 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9982 Even though the unit size @var{u} is ignored for the formats @samp{s}
9983 and @samp{i}, you might still want to use a count @var{n}; for example,
9984 @samp{3i} specifies that you want to see three machine instructions,
9985 including any operands. For convenience, especially when used with
9986 the @code{display} command, the @samp{i} format also prints branch delay
9987 slot instructions, if any, beyond the count specified, which immediately
9988 follow the last instruction that is within the count. The command
9989 @code{disassemble} gives an alternative way of inspecting machine
9990 instructions; see @ref{Machine Code,,Source and Machine Code}.
9992 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9993 the command displays null-terminated strings or instructions before the given
9994 address as many as the absolute value of the given number. For the @samp{i}
9995 format, we use line number information in the debug info to accurately locate
9996 instruction boundaries while disassembling backward. If line info is not
9997 available, the command stops examining memory with an error message.
9999 All the defaults for the arguments to @code{x} are designed to make it
10000 easy to continue scanning memory with minimal specifications each time
10001 you use @code{x}. For example, after you have inspected three machine
10002 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10003 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10004 the repeat count @var{n} is used again; the other arguments default as
10005 for successive uses of @code{x}.
10007 When examining machine instructions, the instruction at current program
10008 counter is shown with a @code{=>} marker. For example:
10011 (@value{GDBP}) x/5i $pc-6
10012 0x804837f <main+11>: mov %esp,%ebp
10013 0x8048381 <main+13>: push %ecx
10014 0x8048382 <main+14>: sub $0x4,%esp
10015 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10016 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10019 @cindex @code{$_}, @code{$__}, and value history
10020 The addresses and contents printed by the @code{x} command are not saved
10021 in the value history because there is often too much of them and they
10022 would get in the way. Instead, @value{GDBN} makes these values available for
10023 subsequent use in expressions as values of the convenience variables
10024 @code{$_} and @code{$__}. After an @code{x} command, the last address
10025 examined is available for use in expressions in the convenience variable
10026 @code{$_}. The contents of that address, as examined, are available in
10027 the convenience variable @code{$__}.
10029 If the @code{x} command has a repeat count, the address and contents saved
10030 are from the last memory unit printed; this is not the same as the last
10031 address printed if several units were printed on the last line of output.
10033 @anchor{addressable memory unit}
10034 @cindex addressable memory unit
10035 Most targets have an addressable memory unit size of 8 bits. This means
10036 that to each memory address are associated 8 bits of data. Some
10037 targets, however, have other addressable memory unit sizes.
10038 Within @value{GDBN} and this document, the term
10039 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10040 when explicitly referring to a chunk of data of that size. The word
10041 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10042 the addressable memory unit size of the target. For most systems,
10043 addressable memory unit is a synonym of byte.
10045 @cindex remote memory comparison
10046 @cindex target memory comparison
10047 @cindex verify remote memory image
10048 @cindex verify target memory image
10049 When you are debugging a program running on a remote target machine
10050 (@pxref{Remote Debugging}), you may wish to verify the program's image
10051 in the remote machine's memory against the executable file you
10052 downloaded to the target. Or, on any target, you may want to check
10053 whether the program has corrupted its own read-only sections. The
10054 @code{compare-sections} command is provided for such situations.
10057 @kindex compare-sections
10058 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10059 Compare the data of a loadable section @var{section-name} in the
10060 executable file of the program being debugged with the same section in
10061 the target machine's memory, and report any mismatches. With no
10062 arguments, compares all loadable sections. With an argument of
10063 @code{-r}, compares all loadable read-only sections.
10065 Note: for remote targets, this command can be accelerated if the
10066 target supports computing the CRC checksum of a block of memory
10067 (@pxref{qCRC packet}).
10071 @section Automatic Display
10072 @cindex automatic display
10073 @cindex display of expressions
10075 If you find that you want to print the value of an expression frequently
10076 (to see how it changes), you might want to add it to the @dfn{automatic
10077 display list} so that @value{GDBN} prints its value each time your program stops.
10078 Each expression added to the list is given a number to identify it;
10079 to remove an expression from the list, you specify that number.
10080 The automatic display looks like this:
10084 3: bar[5] = (struct hack *) 0x3804
10088 This display shows item numbers, expressions and their current values. As with
10089 displays you request manually using @code{x} or @code{print}, you can
10090 specify the output format you prefer; in fact, @code{display} decides
10091 whether to use @code{print} or @code{x} depending your format
10092 specification---it uses @code{x} if you specify either the @samp{i}
10093 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10097 @item display @var{expr}
10098 Add the expression @var{expr} to the list of expressions to display
10099 each time your program stops. @xref{Expressions, ,Expressions}.
10101 @code{display} does not repeat if you press @key{RET} again after using it.
10103 @item display/@var{fmt} @var{expr}
10104 For @var{fmt} specifying only a display format and not a size or
10105 count, add the expression @var{expr} to the auto-display list but
10106 arrange to display it each time in the specified format @var{fmt}.
10107 @xref{Output Formats,,Output Formats}.
10109 @item display/@var{fmt} @var{addr}
10110 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10111 number of units, add the expression @var{addr} as a memory address to
10112 be examined each time your program stops. Examining means in effect
10113 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10116 For example, @samp{display/i $pc} can be helpful, to see the machine
10117 instruction about to be executed each time execution stops (@samp{$pc}
10118 is a common name for the program counter; @pxref{Registers, ,Registers}).
10121 @kindex delete display
10123 @item undisplay @var{dnums}@dots{}
10124 @itemx delete display @var{dnums}@dots{}
10125 Remove items from the list of expressions to display. Specify the
10126 numbers of the displays that you want affected with the command
10127 argument @var{dnums}. It can be a single display number, one of the
10128 numbers shown in the first field of the @samp{info display} display;
10129 or it could be a range of display numbers, as in @code{2-4}.
10131 @code{undisplay} does not repeat if you press @key{RET} after using it.
10132 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10134 @kindex disable display
10135 @item disable display @var{dnums}@dots{}
10136 Disable the display of item numbers @var{dnums}. A disabled display
10137 item is not printed automatically, but is not forgotten. It may be
10138 enabled again later. Specify the numbers of the displays that you
10139 want affected with the command argument @var{dnums}. It can be a
10140 single display number, one of the numbers shown in the first field of
10141 the @samp{info display} display; or it could be a range of display
10142 numbers, as in @code{2-4}.
10144 @kindex enable display
10145 @item enable display @var{dnums}@dots{}
10146 Enable display of item numbers @var{dnums}. It becomes effective once
10147 again in auto display of its expression, until you specify otherwise.
10148 Specify the numbers of the displays that you want affected with the
10149 command argument @var{dnums}. It can be a single display number, one
10150 of the numbers shown in the first field of the @samp{info display}
10151 display; or it could be a range of display numbers, as in @code{2-4}.
10154 Display the current values of the expressions on the list, just as is
10155 done when your program stops.
10157 @kindex info display
10159 Print the list of expressions previously set up to display
10160 automatically, each one with its item number, but without showing the
10161 values. This includes disabled expressions, which are marked as such.
10162 It also includes expressions which would not be displayed right now
10163 because they refer to automatic variables not currently available.
10166 @cindex display disabled out of scope
10167 If a display expression refers to local variables, then it does not make
10168 sense outside the lexical context for which it was set up. Such an
10169 expression is disabled when execution enters a context where one of its
10170 variables is not defined. For example, if you give the command
10171 @code{display last_char} while inside a function with an argument
10172 @code{last_char}, @value{GDBN} displays this argument while your program
10173 continues to stop inside that function. When it stops elsewhere---where
10174 there is no variable @code{last_char}---the display is disabled
10175 automatically. The next time your program stops where @code{last_char}
10176 is meaningful, you can enable the display expression once again.
10178 @node Print Settings
10179 @section Print Settings
10181 @cindex format options
10182 @cindex print settings
10183 @value{GDBN} provides the following ways to control how arrays, structures,
10184 and symbols are printed.
10187 These settings are useful for debugging programs in any language:
10191 @item set print address
10192 @itemx set print address on
10193 @cindex print/don't print memory addresses
10194 @value{GDBN} prints memory addresses showing the location of stack
10195 traces, structure values, pointer values, breakpoints, and so forth,
10196 even when it also displays the contents of those addresses. The default
10197 is @code{on}. For example, this is what a stack frame display looks like with
10198 @code{set print address on}:
10203 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10205 530 if (lquote != def_lquote)
10209 @item set print address off
10210 Do not print addresses when displaying their contents. For example,
10211 this is the same stack frame displayed with @code{set print address off}:
10215 (@value{GDBP}) set print addr off
10217 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10218 530 if (lquote != def_lquote)
10222 You can use @samp{set print address off} to eliminate all machine
10223 dependent displays from the @value{GDBN} interface. For example, with
10224 @code{print address off}, you should get the same text for backtraces on
10225 all machines---whether or not they involve pointer arguments.
10228 @item show print address
10229 Show whether or not addresses are to be printed.
10232 When @value{GDBN} prints a symbolic address, it normally prints the
10233 closest earlier symbol plus an offset. If that symbol does not uniquely
10234 identify the address (for example, it is a name whose scope is a single
10235 source file), you may need to clarify. One way to do this is with
10236 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10237 you can set @value{GDBN} to print the source file and line number when
10238 it prints a symbolic address:
10241 @item set print symbol-filename on
10242 @cindex source file and line of a symbol
10243 @cindex symbol, source file and line
10244 Tell @value{GDBN} to print the source file name and line number of a
10245 symbol in the symbolic form of an address.
10247 @item set print symbol-filename off
10248 Do not print source file name and line number of a symbol. This is the
10251 @item show print symbol-filename
10252 Show whether or not @value{GDBN} will print the source file name and
10253 line number of a symbol in the symbolic form of an address.
10256 Another situation where it is helpful to show symbol filenames and line
10257 numbers is when disassembling code; @value{GDBN} shows you the line
10258 number and source file that corresponds to each instruction.
10260 Also, you may wish to see the symbolic form only if the address being
10261 printed is reasonably close to the closest earlier symbol:
10264 @item set print max-symbolic-offset @var{max-offset}
10265 @itemx set print max-symbolic-offset unlimited
10266 @cindex maximum value for offset of closest symbol
10267 Tell @value{GDBN} to only display the symbolic form of an address if the
10268 offset between the closest earlier symbol and the address is less than
10269 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10270 to always print the symbolic form of an address if any symbol precedes
10271 it. Zero is equivalent to @code{unlimited}.
10273 @item show print max-symbolic-offset
10274 Ask how large the maximum offset is that @value{GDBN} prints in a
10278 @cindex wild pointer, interpreting
10279 @cindex pointer, finding referent
10280 If you have a pointer and you are not sure where it points, try
10281 @samp{set print symbol-filename on}. Then you can determine the name
10282 and source file location of the variable where it points, using
10283 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10284 For example, here @value{GDBN} shows that a variable @code{ptt} points
10285 at another variable @code{t}, defined in @file{hi2.c}:
10288 (@value{GDBP}) set print symbol-filename on
10289 (@value{GDBP}) p/a ptt
10290 $4 = 0xe008 <t in hi2.c>
10294 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10295 does not show the symbol name and filename of the referent, even with
10296 the appropriate @code{set print} options turned on.
10299 You can also enable @samp{/a}-like formatting all the time using
10300 @samp{set print symbol on}:
10303 @item set print symbol on
10304 Tell @value{GDBN} to print the symbol corresponding to an address, if
10307 @item set print symbol off
10308 Tell @value{GDBN} not to print the symbol corresponding to an
10309 address. In this mode, @value{GDBN} will still print the symbol
10310 corresponding to pointers to functions. This is the default.
10312 @item show print symbol
10313 Show whether @value{GDBN} will display the symbol corresponding to an
10317 Other settings control how different kinds of objects are printed:
10320 @item set print array
10321 @itemx set print array on
10322 @cindex pretty print arrays
10323 Pretty print arrays. This format is more convenient to read,
10324 but uses more space. The default is off.
10326 @item set print array off
10327 Return to compressed format for arrays.
10329 @item show print array
10330 Show whether compressed or pretty format is selected for displaying
10333 @cindex print array indexes
10334 @item set print array-indexes
10335 @itemx set print array-indexes on
10336 Print the index of each element when displaying arrays. May be more
10337 convenient to locate a given element in the array or quickly find the
10338 index of a given element in that printed array. The default is off.
10340 @item set print array-indexes off
10341 Stop printing element indexes when displaying arrays.
10343 @item show print array-indexes
10344 Show whether the index of each element is printed when displaying
10347 @item set print elements @var{number-of-elements}
10348 @itemx set print elements unlimited
10349 @cindex number of array elements to print
10350 @cindex limit on number of printed array elements
10351 Set a limit on how many elements of an array @value{GDBN} will print.
10352 If @value{GDBN} is printing a large array, it stops printing after it has
10353 printed the number of elements set by the @code{set print elements} command.
10354 This limit also applies to the display of strings.
10355 When @value{GDBN} starts, this limit is set to 200.
10356 Setting @var{number-of-elements} to @code{unlimited} or zero means
10357 that the number of elements to print is unlimited.
10359 @item show print elements
10360 Display the number of elements of a large array that @value{GDBN} will print.
10361 If the number is 0, then the printing is unlimited.
10363 @item set print frame-arguments @var{value}
10364 @kindex set print frame-arguments
10365 @cindex printing frame argument values
10366 @cindex print all frame argument values
10367 @cindex print frame argument values for scalars only
10368 @cindex do not print frame argument values
10369 This command allows to control how the values of arguments are printed
10370 when the debugger prints a frame (@pxref{Frames}). The possible
10375 The values of all arguments are printed.
10378 Print the value of an argument only if it is a scalar. The value of more
10379 complex arguments such as arrays, structures, unions, etc, is replaced
10380 by @code{@dots{}}. This is the default. Here is an example where
10381 only scalar arguments are shown:
10384 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10389 None of the argument values are printed. Instead, the value of each argument
10390 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10393 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10398 By default, only scalar arguments are printed. This command can be used
10399 to configure the debugger to print the value of all arguments, regardless
10400 of their type. However, it is often advantageous to not print the value
10401 of more complex parameters. For instance, it reduces the amount of
10402 information printed in each frame, making the backtrace more readable.
10403 Also, it improves performance when displaying Ada frames, because
10404 the computation of large arguments can sometimes be CPU-intensive,
10405 especially in large applications. Setting @code{print frame-arguments}
10406 to @code{scalars} (the default) or @code{none} avoids this computation,
10407 thus speeding up the display of each Ada frame.
10409 @item show print frame-arguments
10410 Show how the value of arguments should be displayed when printing a frame.
10412 @item set print raw frame-arguments on
10413 Print frame arguments in raw, non pretty-printed, form.
10415 @item set print raw frame-arguments off
10416 Print frame arguments in pretty-printed form, if there is a pretty-printer
10417 for the value (@pxref{Pretty Printing}),
10418 otherwise print the value in raw form.
10419 This is the default.
10421 @item show print raw frame-arguments
10422 Show whether to print frame arguments in raw form.
10424 @anchor{set print entry-values}
10425 @item set print entry-values @var{value}
10426 @kindex set print entry-values
10427 Set printing of frame argument values at function entry. In some cases
10428 @value{GDBN} can determine the value of function argument which was passed by
10429 the function caller, even if the value was modified inside the called function
10430 and therefore is different. With optimized code, the current value could be
10431 unavailable, but the entry value may still be known.
10433 The default value is @code{default} (see below for its description). Older
10434 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10435 this feature will behave in the @code{default} setting the same way as with the
10438 This functionality is currently supported only by DWARF 2 debugging format and
10439 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10440 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10443 The @var{value} parameter can be one of the following:
10447 Print only actual parameter values, never print values from function entry
10451 #0 different (val=6)
10452 #0 lost (val=<optimized out>)
10454 #0 invalid (val=<optimized out>)
10458 Print only parameter values from function entry point. The actual parameter
10459 values are never printed.
10461 #0 equal (val@@entry=5)
10462 #0 different (val@@entry=5)
10463 #0 lost (val@@entry=5)
10464 #0 born (val@@entry=<optimized out>)
10465 #0 invalid (val@@entry=<optimized out>)
10469 Print only parameter values from function entry point. If value from function
10470 entry point is not known while the actual value is known, print the actual
10471 value for such parameter.
10473 #0 equal (val@@entry=5)
10474 #0 different (val@@entry=5)
10475 #0 lost (val@@entry=5)
10477 #0 invalid (val@@entry=<optimized out>)
10481 Print actual parameter values. If actual parameter value is not known while
10482 value from function entry point is known, print the entry point value for such
10486 #0 different (val=6)
10487 #0 lost (val@@entry=5)
10489 #0 invalid (val=<optimized out>)
10493 Always print both the actual parameter value and its value from function entry
10494 point, even if values of one or both are not available due to compiler
10497 #0 equal (val=5, val@@entry=5)
10498 #0 different (val=6, val@@entry=5)
10499 #0 lost (val=<optimized out>, val@@entry=5)
10500 #0 born (val=10, val@@entry=<optimized out>)
10501 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10505 Print the actual parameter value if it is known and also its value from
10506 function entry point if it is known. If neither is known, print for the actual
10507 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10508 values are known and identical, print the shortened
10509 @code{param=param@@entry=VALUE} notation.
10511 #0 equal (val=val@@entry=5)
10512 #0 different (val=6, val@@entry=5)
10513 #0 lost (val@@entry=5)
10515 #0 invalid (val=<optimized out>)
10519 Always print the actual parameter value. Print also its value from function
10520 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10521 if both values are known and identical, print the shortened
10522 @code{param=param@@entry=VALUE} notation.
10524 #0 equal (val=val@@entry=5)
10525 #0 different (val=6, val@@entry=5)
10526 #0 lost (val=<optimized out>, val@@entry=5)
10528 #0 invalid (val=<optimized out>)
10532 For analysis messages on possible failures of frame argument values at function
10533 entry resolution see @ref{set debug entry-values}.
10535 @item show print entry-values
10536 Show the method being used for printing of frame argument values at function
10539 @item set print repeats @var{number-of-repeats}
10540 @itemx set print repeats unlimited
10541 @cindex repeated array elements
10542 Set the threshold for suppressing display of repeated array
10543 elements. When the number of consecutive identical elements of an
10544 array exceeds the threshold, @value{GDBN} prints the string
10545 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10546 identical repetitions, instead of displaying the identical elements
10547 themselves. Setting the threshold to @code{unlimited} or zero will
10548 cause all elements to be individually printed. The default threshold
10551 @item show print repeats
10552 Display the current threshold for printing repeated identical
10555 @item set print null-stop
10556 @cindex @sc{null} elements in arrays
10557 Cause @value{GDBN} to stop printing the characters of an array when the first
10558 @sc{null} is encountered. This is useful when large arrays actually
10559 contain only short strings.
10560 The default is off.
10562 @item show print null-stop
10563 Show whether @value{GDBN} stops printing an array on the first
10564 @sc{null} character.
10566 @item set print pretty on
10567 @cindex print structures in indented form
10568 @cindex indentation in structure display
10569 Cause @value{GDBN} to print structures in an indented format with one member
10570 per line, like this:
10585 @item set print pretty off
10586 Cause @value{GDBN} to print structures in a compact format, like this:
10590 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10591 meat = 0x54 "Pork"@}
10596 This is the default format.
10598 @item show print pretty
10599 Show which format @value{GDBN} is using to print structures.
10601 @item set print sevenbit-strings on
10602 @cindex eight-bit characters in strings
10603 @cindex octal escapes in strings
10604 Print using only seven-bit characters; if this option is set,
10605 @value{GDBN} displays any eight-bit characters (in strings or
10606 character values) using the notation @code{\}@var{nnn}. This setting is
10607 best if you are working in English (@sc{ascii}) and you use the
10608 high-order bit of characters as a marker or ``meta'' bit.
10610 @item set print sevenbit-strings off
10611 Print full eight-bit characters. This allows the use of more
10612 international character sets, and is the default.
10614 @item show print sevenbit-strings
10615 Show whether or not @value{GDBN} is printing only seven-bit characters.
10617 @item set print union on
10618 @cindex unions in structures, printing
10619 Tell @value{GDBN} to print unions which are contained in structures
10620 and other unions. This is the default setting.
10622 @item set print union off
10623 Tell @value{GDBN} not to print unions which are contained in
10624 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10627 @item show print union
10628 Ask @value{GDBN} whether or not it will print unions which are contained in
10629 structures and other unions.
10631 For example, given the declarations
10634 typedef enum @{Tree, Bug@} Species;
10635 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10636 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10647 struct thing foo = @{Tree, @{Acorn@}@};
10651 with @code{set print union on} in effect @samp{p foo} would print
10654 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10658 and with @code{set print union off} in effect it would print
10661 $1 = @{it = Tree, form = @{...@}@}
10665 @code{set print union} affects programs written in C-like languages
10671 These settings are of interest when debugging C@t{++} programs:
10674 @cindex demangling C@t{++} names
10675 @item set print demangle
10676 @itemx set print demangle on
10677 Print C@t{++} names in their source form rather than in the encoded
10678 (``mangled'') form passed to the assembler and linker for type-safe
10679 linkage. The default is on.
10681 @item show print demangle
10682 Show whether C@t{++} names are printed in mangled or demangled form.
10684 @item set print asm-demangle
10685 @itemx set print asm-demangle on
10686 Print C@t{++} names in their source form rather than their mangled form, even
10687 in assembler code printouts such as instruction disassemblies.
10688 The default is off.
10690 @item show print asm-demangle
10691 Show whether C@t{++} names in assembly listings are printed in mangled
10694 @cindex C@t{++} symbol decoding style
10695 @cindex symbol decoding style, C@t{++}
10696 @kindex set demangle-style
10697 @item set demangle-style @var{style}
10698 Choose among several encoding schemes used by different compilers to
10699 represent C@t{++} names. The choices for @var{style} are currently:
10703 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10704 This is the default.
10707 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10710 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10713 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10716 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10717 @strong{Warning:} this setting alone is not sufficient to allow
10718 debugging @code{cfront}-generated executables. @value{GDBN} would
10719 require further enhancement to permit that.
10722 If you omit @var{style}, you will see a list of possible formats.
10724 @item show demangle-style
10725 Display the encoding style currently in use for decoding C@t{++} symbols.
10727 @item set print object
10728 @itemx set print object on
10729 @cindex derived type of an object, printing
10730 @cindex display derived types
10731 When displaying a pointer to an object, identify the @emph{actual}
10732 (derived) type of the object rather than the @emph{declared} type, using
10733 the virtual function table. Note that the virtual function table is
10734 required---this feature can only work for objects that have run-time
10735 type identification; a single virtual method in the object's declared
10736 type is sufficient. Note that this setting is also taken into account when
10737 working with variable objects via MI (@pxref{GDB/MI}).
10739 @item set print object off
10740 Display only the declared type of objects, without reference to the
10741 virtual function table. This is the default setting.
10743 @item show print object
10744 Show whether actual, or declared, object types are displayed.
10746 @item set print static-members
10747 @itemx set print static-members on
10748 @cindex static members of C@t{++} objects
10749 Print static members when displaying a C@t{++} object. The default is on.
10751 @item set print static-members off
10752 Do not print static members when displaying a C@t{++} object.
10754 @item show print static-members
10755 Show whether C@t{++} static members are printed or not.
10757 @item set print pascal_static-members
10758 @itemx set print pascal_static-members on
10759 @cindex static members of Pascal objects
10760 @cindex Pascal objects, static members display
10761 Print static members when displaying a Pascal object. The default is on.
10763 @item set print pascal_static-members off
10764 Do not print static members when displaying a Pascal object.
10766 @item show print pascal_static-members
10767 Show whether Pascal static members are printed or not.
10769 @c These don't work with HP ANSI C++ yet.
10770 @item set print vtbl
10771 @itemx set print vtbl on
10772 @cindex pretty print C@t{++} virtual function tables
10773 @cindex virtual functions (C@t{++}) display
10774 @cindex VTBL display
10775 Pretty print C@t{++} virtual function tables. The default is off.
10776 (The @code{vtbl} commands do not work on programs compiled with the HP
10777 ANSI C@t{++} compiler (@code{aCC}).)
10779 @item set print vtbl off
10780 Do not pretty print C@t{++} virtual function tables.
10782 @item show print vtbl
10783 Show whether C@t{++} virtual function tables are pretty printed, or not.
10786 @node Pretty Printing
10787 @section Pretty Printing
10789 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10790 Python code. It greatly simplifies the display of complex objects. This
10791 mechanism works for both MI and the CLI.
10794 * Pretty-Printer Introduction:: Introduction to pretty-printers
10795 * Pretty-Printer Example:: An example pretty-printer
10796 * Pretty-Printer Commands:: Pretty-printer commands
10799 @node Pretty-Printer Introduction
10800 @subsection Pretty-Printer Introduction
10802 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10803 registered for the value. If there is then @value{GDBN} invokes the
10804 pretty-printer to print the value. Otherwise the value is printed normally.
10806 Pretty-printers are normally named. This makes them easy to manage.
10807 The @samp{info pretty-printer} command will list all the installed
10808 pretty-printers with their names.
10809 If a pretty-printer can handle multiple data types, then its
10810 @dfn{subprinters} are the printers for the individual data types.
10811 Each such subprinter has its own name.
10812 The format of the name is @var{printer-name};@var{subprinter-name}.
10814 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10815 Typically they are automatically loaded and registered when the corresponding
10816 debug information is loaded, thus making them available without having to
10817 do anything special.
10819 There are three places where a pretty-printer can be registered.
10823 Pretty-printers registered globally are available when debugging
10827 Pretty-printers registered with a program space are available only
10828 when debugging that program.
10829 @xref{Progspaces In Python}, for more details on program spaces in Python.
10832 Pretty-printers registered with an objfile are loaded and unloaded
10833 with the corresponding objfile (e.g., shared library).
10834 @xref{Objfiles In Python}, for more details on objfiles in Python.
10837 @xref{Selecting Pretty-Printers}, for further information on how
10838 pretty-printers are selected,
10840 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10843 @node Pretty-Printer Example
10844 @subsection Pretty-Printer Example
10846 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10849 (@value{GDBP}) print s
10851 static npos = 4294967295,
10853 <std::allocator<char>> = @{
10854 <__gnu_cxx::new_allocator<char>> = @{
10855 <No data fields>@}, <No data fields>
10857 members of std::basic_string<char, std::char_traits<char>,
10858 std::allocator<char> >::_Alloc_hider:
10859 _M_p = 0x804a014 "abcd"
10864 With a pretty-printer for @code{std::string} only the contents are printed:
10867 (@value{GDBP}) print s
10871 @node Pretty-Printer Commands
10872 @subsection Pretty-Printer Commands
10873 @cindex pretty-printer commands
10876 @kindex info pretty-printer
10877 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10878 Print the list of installed pretty-printers.
10879 This includes disabled pretty-printers, which are marked as such.
10881 @var{object-regexp} is a regular expression matching the objects
10882 whose pretty-printers to list.
10883 Objects can be @code{global}, the program space's file
10884 (@pxref{Progspaces In Python}),
10885 and the object files within that program space (@pxref{Objfiles In Python}).
10886 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10887 looks up a printer from these three objects.
10889 @var{name-regexp} is a regular expression matching the name of the printers
10892 @kindex disable pretty-printer
10893 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10894 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10895 A disabled pretty-printer is not forgotten, it may be enabled again later.
10897 @kindex enable pretty-printer
10898 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10899 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10904 Suppose we have three pretty-printers installed: one from library1.so
10905 named @code{foo} that prints objects of type @code{foo}, and
10906 another from library2.so named @code{bar} that prints two types of objects,
10907 @code{bar1} and @code{bar2}.
10910 (gdb) info pretty-printer
10917 (gdb) info pretty-printer library2
10922 (gdb) disable pretty-printer library1
10924 2 of 3 printers enabled
10925 (gdb) info pretty-printer
10932 (gdb) disable pretty-printer library2 bar;bar1
10934 1 of 3 printers enabled
10935 (gdb) info pretty-printer library2
10942 (gdb) disable pretty-printer library2 bar
10944 0 of 3 printers enabled
10945 (gdb) info pretty-printer library2
10954 Note that for @code{bar} the entire printer can be disabled,
10955 as can each individual subprinter.
10957 @node Value History
10958 @section Value History
10960 @cindex value history
10961 @cindex history of values printed by @value{GDBN}
10962 Values printed by the @code{print} command are saved in the @value{GDBN}
10963 @dfn{value history}. This allows you to refer to them in other expressions.
10964 Values are kept until the symbol table is re-read or discarded
10965 (for example with the @code{file} or @code{symbol-file} commands).
10966 When the symbol table changes, the value history is discarded,
10967 since the values may contain pointers back to the types defined in the
10972 @cindex history number
10973 The values printed are given @dfn{history numbers} by which you can
10974 refer to them. These are successive integers starting with one.
10975 @code{print} shows you the history number assigned to a value by
10976 printing @samp{$@var{num} = } before the value; here @var{num} is the
10979 To refer to any previous value, use @samp{$} followed by the value's
10980 history number. The way @code{print} labels its output is designed to
10981 remind you of this. Just @code{$} refers to the most recent value in
10982 the history, and @code{$$} refers to the value before that.
10983 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10984 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10985 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10987 For example, suppose you have just printed a pointer to a structure and
10988 want to see the contents of the structure. It suffices to type
10994 If you have a chain of structures where the component @code{next} points
10995 to the next one, you can print the contents of the next one with this:
11002 You can print successive links in the chain by repeating this
11003 command---which you can do by just typing @key{RET}.
11005 Note that the history records values, not expressions. If the value of
11006 @code{x} is 4 and you type these commands:
11014 then the value recorded in the value history by the @code{print} command
11015 remains 4 even though the value of @code{x} has changed.
11018 @kindex show values
11020 Print the last ten values in the value history, with their item numbers.
11021 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11022 values} does not change the history.
11024 @item show values @var{n}
11025 Print ten history values centered on history item number @var{n}.
11027 @item show values +
11028 Print ten history values just after the values last printed. If no more
11029 values are available, @code{show values +} produces no display.
11032 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11033 same effect as @samp{show values +}.
11035 @node Convenience Vars
11036 @section Convenience Variables
11038 @cindex convenience variables
11039 @cindex user-defined variables
11040 @value{GDBN} provides @dfn{convenience variables} that you can use within
11041 @value{GDBN} to hold on to a value and refer to it later. These variables
11042 exist entirely within @value{GDBN}; they are not part of your program, and
11043 setting a convenience variable has no direct effect on further execution
11044 of your program. That is why you can use them freely.
11046 Convenience variables are prefixed with @samp{$}. Any name preceded by
11047 @samp{$} can be used for a convenience variable, unless it is one of
11048 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11049 (Value history references, in contrast, are @emph{numbers} preceded
11050 by @samp{$}. @xref{Value History, ,Value History}.)
11052 You can save a value in a convenience variable with an assignment
11053 expression, just as you would set a variable in your program.
11057 set $foo = *object_ptr
11061 would save in @code{$foo} the value contained in the object pointed to by
11064 Using a convenience variable for the first time creates it, but its
11065 value is @code{void} until you assign a new value. You can alter the
11066 value with another assignment at any time.
11068 Convenience variables have no fixed types. You can assign a convenience
11069 variable any type of value, including structures and arrays, even if
11070 that variable already has a value of a different type. The convenience
11071 variable, when used as an expression, has the type of its current value.
11074 @kindex show convenience
11075 @cindex show all user variables and functions
11076 @item show convenience
11077 Print a list of convenience variables used so far, and their values,
11078 as well as a list of the convenience functions.
11079 Abbreviated @code{show conv}.
11081 @kindex init-if-undefined
11082 @cindex convenience variables, initializing
11083 @item init-if-undefined $@var{variable} = @var{expression}
11084 Set a convenience variable if it has not already been set. This is useful
11085 for user-defined commands that keep some state. It is similar, in concept,
11086 to using local static variables with initializers in C (except that
11087 convenience variables are global). It can also be used to allow users to
11088 override default values used in a command script.
11090 If the variable is already defined then the expression is not evaluated so
11091 any side-effects do not occur.
11094 One of the ways to use a convenience variable is as a counter to be
11095 incremented or a pointer to be advanced. For example, to print
11096 a field from successive elements of an array of structures:
11100 print bar[$i++]->contents
11104 Repeat that command by typing @key{RET}.
11106 Some convenience variables are created automatically by @value{GDBN} and given
11107 values likely to be useful.
11110 @vindex $_@r{, convenience variable}
11112 The variable @code{$_} is automatically set by the @code{x} command to
11113 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11114 commands which provide a default address for @code{x} to examine also
11115 set @code{$_} to that address; these commands include @code{info line}
11116 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11117 except when set by the @code{x} command, in which case it is a pointer
11118 to the type of @code{$__}.
11120 @vindex $__@r{, convenience variable}
11122 The variable @code{$__} is automatically set by the @code{x} command
11123 to the value found in the last address examined. Its type is chosen
11124 to match the format in which the data was printed.
11127 @vindex $_exitcode@r{, convenience variable}
11128 When the program being debugged terminates normally, @value{GDBN}
11129 automatically sets this variable to the exit code of the program, and
11130 resets @code{$_exitsignal} to @code{void}.
11133 @vindex $_exitsignal@r{, convenience variable}
11134 When the program being debugged dies due to an uncaught signal,
11135 @value{GDBN} automatically sets this variable to that signal's number,
11136 and resets @code{$_exitcode} to @code{void}.
11138 To distinguish between whether the program being debugged has exited
11139 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11140 @code{$_exitsignal} is not @code{void}), the convenience function
11141 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11142 Functions}). For example, considering the following source code:
11145 #include <signal.h>
11148 main (int argc, char *argv[])
11155 A valid way of telling whether the program being debugged has exited
11156 or signalled would be:
11159 (@value{GDBP}) define has_exited_or_signalled
11160 Type commands for definition of ``has_exited_or_signalled''.
11161 End with a line saying just ``end''.
11162 >if $_isvoid ($_exitsignal)
11163 >echo The program has exited\n
11165 >echo The program has signalled\n
11171 Program terminated with signal SIGALRM, Alarm clock.
11172 The program no longer exists.
11173 (@value{GDBP}) has_exited_or_signalled
11174 The program has signalled
11177 As can be seen, @value{GDBN} correctly informs that the program being
11178 debugged has signalled, since it calls @code{raise} and raises a
11179 @code{SIGALRM} signal. If the program being debugged had not called
11180 @code{raise}, then @value{GDBN} would report a normal exit:
11183 (@value{GDBP}) has_exited_or_signalled
11184 The program has exited
11188 The variable @code{$_exception} is set to the exception object being
11189 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11192 @itemx $_probe_arg0@dots{}$_probe_arg11
11193 Arguments to a static probe. @xref{Static Probe Points}.
11196 @vindex $_sdata@r{, inspect, convenience variable}
11197 The variable @code{$_sdata} contains extra collected static tracepoint
11198 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11199 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11200 if extra static tracepoint data has not been collected.
11203 @vindex $_siginfo@r{, convenience variable}
11204 The variable @code{$_siginfo} contains extra signal information
11205 (@pxref{extra signal information}). Note that @code{$_siginfo}
11206 could be empty, if the application has not yet received any signals.
11207 For example, it will be empty before you execute the @code{run} command.
11210 @vindex $_tlb@r{, convenience variable}
11211 The variable @code{$_tlb} is automatically set when debugging
11212 applications running on MS-Windows in native mode or connected to
11213 gdbserver that supports the @code{qGetTIBAddr} request.
11214 @xref{General Query Packets}.
11215 This variable contains the address of the thread information block.
11218 The number of the current inferior. @xref{Inferiors and
11219 Programs, ,Debugging Multiple Inferiors and Programs}.
11222 The thread number of the current thread. @xref{thread numbers}.
11225 The global number of the current thread. @xref{global thread numbers}.
11229 @node Convenience Funs
11230 @section Convenience Functions
11232 @cindex convenience functions
11233 @value{GDBN} also supplies some @dfn{convenience functions}. These
11234 have a syntax similar to convenience variables. A convenience
11235 function can be used in an expression just like an ordinary function;
11236 however, a convenience function is implemented internally to
11239 These functions do not require @value{GDBN} to be configured with
11240 @code{Python} support, which means that they are always available.
11244 @item $_isvoid (@var{expr})
11245 @findex $_isvoid@r{, convenience function}
11246 Return one if the expression @var{expr} is @code{void}. Otherwise it
11249 A @code{void} expression is an expression where the type of the result
11250 is @code{void}. For example, you can examine a convenience variable
11251 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11255 (@value{GDBP}) print $_exitcode
11257 (@value{GDBP}) print $_isvoid ($_exitcode)
11260 Starting program: ./a.out
11261 [Inferior 1 (process 29572) exited normally]
11262 (@value{GDBP}) print $_exitcode
11264 (@value{GDBP}) print $_isvoid ($_exitcode)
11268 In the example above, we used @code{$_isvoid} to check whether
11269 @code{$_exitcode} is @code{void} before and after the execution of the
11270 program being debugged. Before the execution there is no exit code to
11271 be examined, therefore @code{$_exitcode} is @code{void}. After the
11272 execution the program being debugged returned zero, therefore
11273 @code{$_exitcode} is zero, which means that it is not @code{void}
11276 The @code{void} expression can also be a call of a function from the
11277 program being debugged. For example, given the following function:
11286 The result of calling it inside @value{GDBN} is @code{void}:
11289 (@value{GDBP}) print foo ()
11291 (@value{GDBP}) print $_isvoid (foo ())
11293 (@value{GDBP}) set $v = foo ()
11294 (@value{GDBP}) print $v
11296 (@value{GDBP}) print $_isvoid ($v)
11302 These functions require @value{GDBN} to be configured with
11303 @code{Python} support.
11307 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11308 @findex $_memeq@r{, convenience function}
11309 Returns one if the @var{length} bytes at the addresses given by
11310 @var{buf1} and @var{buf2} are equal.
11311 Otherwise it returns zero.
11313 @item $_regex(@var{str}, @var{regex})
11314 @findex $_regex@r{, convenience function}
11315 Returns one if the string @var{str} matches the regular expression
11316 @var{regex}. Otherwise it returns zero.
11317 The syntax of the regular expression is that specified by @code{Python}'s
11318 regular expression support.
11320 @item $_streq(@var{str1}, @var{str2})
11321 @findex $_streq@r{, convenience function}
11322 Returns one if the strings @var{str1} and @var{str2} are equal.
11323 Otherwise it returns zero.
11325 @item $_strlen(@var{str})
11326 @findex $_strlen@r{, convenience function}
11327 Returns the length of string @var{str}.
11329 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11330 @findex $_caller_is@r{, convenience function}
11331 Returns one if the calling function's name is equal to @var{name}.
11332 Otherwise it returns zero.
11334 If the optional argument @var{number_of_frames} is provided,
11335 it is the number of frames up in the stack to look.
11343 at testsuite/gdb.python/py-caller-is.c:21
11344 #1 0x00000000004005a0 in middle_func ()
11345 at testsuite/gdb.python/py-caller-is.c:27
11346 #2 0x00000000004005ab in top_func ()
11347 at testsuite/gdb.python/py-caller-is.c:33
11348 #3 0x00000000004005b6 in main ()
11349 at testsuite/gdb.python/py-caller-is.c:39
11350 (gdb) print $_caller_is ("middle_func")
11352 (gdb) print $_caller_is ("top_func", 2)
11356 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11357 @findex $_caller_matches@r{, convenience function}
11358 Returns one if the calling function's name matches the regular expression
11359 @var{regexp}. Otherwise it returns zero.
11361 If the optional argument @var{number_of_frames} is provided,
11362 it is the number of frames up in the stack to look.
11365 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11366 @findex $_any_caller_is@r{, convenience function}
11367 Returns one if any calling function's name is equal to @var{name}.
11368 Otherwise it returns zero.
11370 If the optional argument @var{number_of_frames} is provided,
11371 it is the number of frames up in the stack to look.
11374 This function differs from @code{$_caller_is} in that this function
11375 checks all stack frames from the immediate caller to the frame specified
11376 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11377 frame specified by @var{number_of_frames}.
11379 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11380 @findex $_any_caller_matches@r{, convenience function}
11381 Returns one if any calling function's name matches the regular expression
11382 @var{regexp}. Otherwise it returns zero.
11384 If the optional argument @var{number_of_frames} is provided,
11385 it is the number of frames up in the stack to look.
11388 This function differs from @code{$_caller_matches} in that this function
11389 checks all stack frames from the immediate caller to the frame specified
11390 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11391 frame specified by @var{number_of_frames}.
11393 @item $_as_string(@var{value})
11394 @findex $_as_string@r{, convenience function}
11395 Return the string representation of @var{value}.
11397 This function is useful to obtain the textual label (enumerator) of an
11398 enumeration value. For example, assuming the variable @var{node} is of
11399 an enumerated type:
11402 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11403 Visiting node of type NODE_INTEGER
11408 @value{GDBN} provides the ability to list and get help on
11409 convenience functions.
11412 @item help function
11413 @kindex help function
11414 @cindex show all convenience functions
11415 Print a list of all convenience functions.
11422 You can refer to machine register contents, in expressions, as variables
11423 with names starting with @samp{$}. The names of registers are different
11424 for each machine; use @code{info registers} to see the names used on
11428 @kindex info registers
11429 @item info registers
11430 Print the names and values of all registers except floating-point
11431 and vector registers (in the selected stack frame).
11433 @kindex info all-registers
11434 @cindex floating point registers
11435 @item info all-registers
11436 Print the names and values of all registers, including floating-point
11437 and vector registers (in the selected stack frame).
11439 @item info registers @var{reggroup} @dots{}
11440 Print the name and value of the registers in each of the specified
11441 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11442 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11444 @item info registers @var{regname} @dots{}
11445 Print the @dfn{relativized} value of each specified register @var{regname}.
11446 As discussed in detail below, register values are normally relative to
11447 the selected stack frame. The @var{regname} may be any register name valid on
11448 the machine you are using, with or without the initial @samp{$}.
11451 @anchor{standard registers}
11452 @cindex stack pointer register
11453 @cindex program counter register
11454 @cindex process status register
11455 @cindex frame pointer register
11456 @cindex standard registers
11457 @value{GDBN} has four ``standard'' register names that are available (in
11458 expressions) on most machines---whenever they do not conflict with an
11459 architecture's canonical mnemonics for registers. The register names
11460 @code{$pc} and @code{$sp} are used for the program counter register and
11461 the stack pointer. @code{$fp} is used for a register that contains a
11462 pointer to the current stack frame, and @code{$ps} is used for a
11463 register that contains the processor status. For example,
11464 you could print the program counter in hex with
11471 or print the instruction to be executed next with
11478 or add four to the stack pointer@footnote{This is a way of removing
11479 one word from the stack, on machines where stacks grow downward in
11480 memory (most machines, nowadays). This assumes that the innermost
11481 stack frame is selected; setting @code{$sp} is not allowed when other
11482 stack frames are selected. To pop entire frames off the stack,
11483 regardless of machine architecture, use @code{return};
11484 see @ref{Returning, ,Returning from a Function}.} with
11490 Whenever possible, these four standard register names are available on
11491 your machine even though the machine has different canonical mnemonics,
11492 so long as there is no conflict. The @code{info registers} command
11493 shows the canonical names. For example, on the SPARC, @code{info
11494 registers} displays the processor status register as @code{$psr} but you
11495 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11496 is an alias for the @sc{eflags} register.
11498 @value{GDBN} always considers the contents of an ordinary register as an
11499 integer when the register is examined in this way. Some machines have
11500 special registers which can hold nothing but floating point; these
11501 registers are considered to have floating point values. There is no way
11502 to refer to the contents of an ordinary register as floating point value
11503 (although you can @emph{print} it as a floating point value with
11504 @samp{print/f $@var{regname}}).
11506 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11507 means that the data format in which the register contents are saved by
11508 the operating system is not the same one that your program normally
11509 sees. For example, the registers of the 68881 floating point
11510 coprocessor are always saved in ``extended'' (raw) format, but all C
11511 programs expect to work with ``double'' (virtual) format. In such
11512 cases, @value{GDBN} normally works with the virtual format only (the format
11513 that makes sense for your program), but the @code{info registers} command
11514 prints the data in both formats.
11516 @cindex SSE registers (x86)
11517 @cindex MMX registers (x86)
11518 Some machines have special registers whose contents can be interpreted
11519 in several different ways. For example, modern x86-based machines
11520 have SSE and MMX registers that can hold several values packed
11521 together in several different formats. @value{GDBN} refers to such
11522 registers in @code{struct} notation:
11525 (@value{GDBP}) print $xmm1
11527 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11528 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11529 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11530 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11531 v4_int32 = @{0, 20657912, 11, 13@},
11532 v2_int64 = @{88725056443645952, 55834574859@},
11533 uint128 = 0x0000000d0000000b013b36f800000000
11538 To set values of such registers, you need to tell @value{GDBN} which
11539 view of the register you wish to change, as if you were assigning
11540 value to a @code{struct} member:
11543 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11546 Normally, register values are relative to the selected stack frame
11547 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11548 value that the register would contain if all stack frames farther in
11549 were exited and their saved registers restored. In order to see the
11550 true contents of hardware registers, you must select the innermost
11551 frame (with @samp{frame 0}).
11553 @cindex caller-saved registers
11554 @cindex call-clobbered registers
11555 @cindex volatile registers
11556 @cindex <not saved> values
11557 Usually ABIs reserve some registers as not needed to be saved by the
11558 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11559 registers). It may therefore not be possible for @value{GDBN} to know
11560 the value a register had before the call (in other words, in the outer
11561 frame), if the register value has since been changed by the callee.
11562 @value{GDBN} tries to deduce where the inner frame saved
11563 (``callee-saved'') registers, from the debug info, unwind info, or the
11564 machine code generated by your compiler. If some register is not
11565 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11566 its own knowledge of the ABI, or because the debug/unwind info
11567 explicitly says the register's value is undefined), @value{GDBN}
11568 displays @w{@samp{<not saved>}} as the register's value. With targets
11569 that @value{GDBN} has no knowledge of the register saving convention,
11570 if a register was not saved by the callee, then its value and location
11571 in the outer frame are assumed to be the same of the inner frame.
11572 This is usually harmless, because if the register is call-clobbered,
11573 the caller either does not care what is in the register after the
11574 call, or has code to restore the value that it does care about. Note,
11575 however, that if you change such a register in the outer frame, you
11576 may also be affecting the inner frame. Also, the more ``outer'' the
11577 frame is you're looking at, the more likely a call-clobbered
11578 register's value is to be wrong, in the sense that it doesn't actually
11579 represent the value the register had just before the call.
11581 @node Floating Point Hardware
11582 @section Floating Point Hardware
11583 @cindex floating point
11585 Depending on the configuration, @value{GDBN} may be able to give
11586 you more information about the status of the floating point hardware.
11591 Display hardware-dependent information about the floating
11592 point unit. The exact contents and layout vary depending on the
11593 floating point chip. Currently, @samp{info float} is supported on
11594 the ARM and x86 machines.
11598 @section Vector Unit
11599 @cindex vector unit
11601 Depending on the configuration, @value{GDBN} may be able to give you
11602 more information about the status of the vector unit.
11605 @kindex info vector
11607 Display information about the vector unit. The exact contents and
11608 layout vary depending on the hardware.
11611 @node OS Information
11612 @section Operating System Auxiliary Information
11613 @cindex OS information
11615 @value{GDBN} provides interfaces to useful OS facilities that can help
11616 you debug your program.
11618 @cindex auxiliary vector
11619 @cindex vector, auxiliary
11620 Some operating systems supply an @dfn{auxiliary vector} to programs at
11621 startup. This is akin to the arguments and environment that you
11622 specify for a program, but contains a system-dependent variety of
11623 binary values that tell system libraries important details about the
11624 hardware, operating system, and process. Each value's purpose is
11625 identified by an integer tag; the meanings are well-known but system-specific.
11626 Depending on the configuration and operating system facilities,
11627 @value{GDBN} may be able to show you this information. For remote
11628 targets, this functionality may further depend on the remote stub's
11629 support of the @samp{qXfer:auxv:read} packet, see
11630 @ref{qXfer auxiliary vector read}.
11635 Display the auxiliary vector of the inferior, which can be either a
11636 live process or a core dump file. @value{GDBN} prints each tag value
11637 numerically, and also shows names and text descriptions for recognized
11638 tags. Some values in the vector are numbers, some bit masks, and some
11639 pointers to strings or other data. @value{GDBN} displays each value in the
11640 most appropriate form for a recognized tag, and in hexadecimal for
11641 an unrecognized tag.
11644 On some targets, @value{GDBN} can access operating system-specific
11645 information and show it to you. The types of information available
11646 will differ depending on the type of operating system running on the
11647 target. The mechanism used to fetch the data is described in
11648 @ref{Operating System Information}. For remote targets, this
11649 functionality depends on the remote stub's support of the
11650 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11654 @item info os @var{infotype}
11656 Display OS information of the requested type.
11658 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11660 @anchor{linux info os infotypes}
11662 @kindex info os cpus
11664 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11665 the available fields from /proc/cpuinfo. For each supported architecture
11666 different fields are available. Two common entries are processor which gives
11667 CPU number and bogomips; a system constant that is calculated during
11668 kernel initialization.
11670 @kindex info os files
11672 Display the list of open file descriptors on the target. For each
11673 file descriptor, @value{GDBN} prints the identifier of the process
11674 owning the descriptor, the command of the owning process, the value
11675 of the descriptor, and the target of the descriptor.
11677 @kindex info os modules
11679 Display the list of all loaded kernel modules on the target. For each
11680 module, @value{GDBN} prints the module name, the size of the module in
11681 bytes, the number of times the module is used, the dependencies of the
11682 module, the status of the module, and the address of the loaded module
11685 @kindex info os msg
11687 Display the list of all System V message queues on the target. For each
11688 message queue, @value{GDBN} prints the message queue key, the message
11689 queue identifier, the access permissions, the current number of bytes
11690 on the queue, the current number of messages on the queue, the processes
11691 that last sent and received a message on the queue, the user and group
11692 of the owner and creator of the message queue, the times at which a
11693 message was last sent and received on the queue, and the time at which
11694 the message queue was last changed.
11696 @kindex info os processes
11698 Display the list of processes on the target. For each process,
11699 @value{GDBN} prints the process identifier, the name of the user, the
11700 command corresponding to the process, and the list of processor cores
11701 that the process is currently running on. (To understand what these
11702 properties mean, for this and the following info types, please consult
11703 the general @sc{gnu}/Linux documentation.)
11705 @kindex info os procgroups
11707 Display the list of process groups on the target. For each process,
11708 @value{GDBN} prints the identifier of the process group that it belongs
11709 to, the command corresponding to the process group leader, the process
11710 identifier, and the command line of the process. The list is sorted
11711 first by the process group identifier, then by the process identifier,
11712 so that processes belonging to the same process group are grouped together
11713 and the process group leader is listed first.
11715 @kindex info os semaphores
11717 Display the list of all System V semaphore sets on the target. For each
11718 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11719 set identifier, the access permissions, the number of semaphores in the
11720 set, the user and group of the owner and creator of the semaphore set,
11721 and the times at which the semaphore set was operated upon and changed.
11723 @kindex info os shm
11725 Display the list of all System V shared-memory regions on the target.
11726 For each shared-memory region, @value{GDBN} prints the region key,
11727 the shared-memory identifier, the access permissions, the size of the
11728 region, the process that created the region, the process that last
11729 attached to or detached from the region, the current number of live
11730 attaches to the region, and the times at which the region was last
11731 attached to, detach from, and changed.
11733 @kindex info os sockets
11735 Display the list of Internet-domain sockets on the target. For each
11736 socket, @value{GDBN} prints the address and port of the local and
11737 remote endpoints, the current state of the connection, the creator of
11738 the socket, the IP address family of the socket, and the type of the
11741 @kindex info os threads
11743 Display the list of threads running on the target. For each thread,
11744 @value{GDBN} prints the identifier of the process that the thread
11745 belongs to, the command of the process, the thread identifier, and the
11746 processor core that it is currently running on. The main thread of a
11747 process is not listed.
11751 If @var{infotype} is omitted, then list the possible values for
11752 @var{infotype} and the kind of OS information available for each
11753 @var{infotype}. If the target does not return a list of possible
11754 types, this command will report an error.
11757 @node Memory Region Attributes
11758 @section Memory Region Attributes
11759 @cindex memory region attributes
11761 @dfn{Memory region attributes} allow you to describe special handling
11762 required by regions of your target's memory. @value{GDBN} uses
11763 attributes to determine whether to allow certain types of memory
11764 accesses; whether to use specific width accesses; and whether to cache
11765 target memory. By default the description of memory regions is
11766 fetched from the target (if the current target supports this), but the
11767 user can override the fetched regions.
11769 Defined memory regions can be individually enabled and disabled. When a
11770 memory region is disabled, @value{GDBN} uses the default attributes when
11771 accessing memory in that region. Similarly, if no memory regions have
11772 been defined, @value{GDBN} uses the default attributes when accessing
11775 When a memory region is defined, it is given a number to identify it;
11776 to enable, disable, or remove a memory region, you specify that number.
11780 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11781 Define a memory region bounded by @var{lower} and @var{upper} with
11782 attributes @var{attributes}@dots{}, and add it to the list of regions
11783 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11784 case: it is treated as the target's maximum memory address.
11785 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11788 Discard any user changes to the memory regions and use target-supplied
11789 regions, if available, or no regions if the target does not support.
11792 @item delete mem @var{nums}@dots{}
11793 Remove memory regions @var{nums}@dots{} from the list of regions
11794 monitored by @value{GDBN}.
11796 @kindex disable mem
11797 @item disable mem @var{nums}@dots{}
11798 Disable monitoring of memory regions @var{nums}@dots{}.
11799 A disabled memory region is not forgotten.
11800 It may be enabled again later.
11803 @item enable mem @var{nums}@dots{}
11804 Enable monitoring of memory regions @var{nums}@dots{}.
11808 Print a table of all defined memory regions, with the following columns
11812 @item Memory Region Number
11813 @item Enabled or Disabled.
11814 Enabled memory regions are marked with @samp{y}.
11815 Disabled memory regions are marked with @samp{n}.
11818 The address defining the inclusive lower bound of the memory region.
11821 The address defining the exclusive upper bound of the memory region.
11824 The list of attributes set for this memory region.
11829 @subsection Attributes
11831 @subsubsection Memory Access Mode
11832 The access mode attributes set whether @value{GDBN} may make read or
11833 write accesses to a memory region.
11835 While these attributes prevent @value{GDBN} from performing invalid
11836 memory accesses, they do nothing to prevent the target system, I/O DMA,
11837 etc.@: from accessing memory.
11841 Memory is read only.
11843 Memory is write only.
11845 Memory is read/write. This is the default.
11848 @subsubsection Memory Access Size
11849 The access size attribute tells @value{GDBN} to use specific sized
11850 accesses in the memory region. Often memory mapped device registers
11851 require specific sized accesses. If no access size attribute is
11852 specified, @value{GDBN} may use accesses of any size.
11856 Use 8 bit memory accesses.
11858 Use 16 bit memory accesses.
11860 Use 32 bit memory accesses.
11862 Use 64 bit memory accesses.
11865 @c @subsubsection Hardware/Software Breakpoints
11866 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11867 @c will use hardware or software breakpoints for the internal breakpoints
11868 @c used by the step, next, finish, until, etc. commands.
11872 @c Always use hardware breakpoints
11873 @c @item swbreak (default)
11876 @subsubsection Data Cache
11877 The data cache attributes set whether @value{GDBN} will cache target
11878 memory. While this generally improves performance by reducing debug
11879 protocol overhead, it can lead to incorrect results because @value{GDBN}
11880 does not know about volatile variables or memory mapped device
11885 Enable @value{GDBN} to cache target memory.
11887 Disable @value{GDBN} from caching target memory. This is the default.
11890 @subsection Memory Access Checking
11891 @value{GDBN} can be instructed to refuse accesses to memory that is
11892 not explicitly described. This can be useful if accessing such
11893 regions has undesired effects for a specific target, or to provide
11894 better error checking. The following commands control this behaviour.
11897 @kindex set mem inaccessible-by-default
11898 @item set mem inaccessible-by-default [on|off]
11899 If @code{on} is specified, make @value{GDBN} treat memory not
11900 explicitly described by the memory ranges as non-existent and refuse accesses
11901 to such memory. The checks are only performed if there's at least one
11902 memory range defined. If @code{off} is specified, make @value{GDBN}
11903 treat the memory not explicitly described by the memory ranges as RAM.
11904 The default value is @code{on}.
11905 @kindex show mem inaccessible-by-default
11906 @item show mem inaccessible-by-default
11907 Show the current handling of accesses to unknown memory.
11911 @c @subsubsection Memory Write Verification
11912 @c The memory write verification attributes set whether @value{GDBN}
11913 @c will re-reads data after each write to verify the write was successful.
11917 @c @item noverify (default)
11920 @node Dump/Restore Files
11921 @section Copy Between Memory and a File
11922 @cindex dump/restore files
11923 @cindex append data to a file
11924 @cindex dump data to a file
11925 @cindex restore data from a file
11927 You can use the commands @code{dump}, @code{append}, and
11928 @code{restore} to copy data between target memory and a file. The
11929 @code{dump} and @code{append} commands write data to a file, and the
11930 @code{restore} command reads data from a file back into the inferior's
11931 memory. Files may be in binary, Motorola S-record, Intel hex,
11932 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11933 append to binary files, and cannot read from Verilog Hex files.
11938 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11939 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11940 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11941 or the value of @var{expr}, to @var{filename} in the given format.
11943 The @var{format} parameter may be any one of:
11950 Motorola S-record format.
11952 Tektronix Hex format.
11954 Verilog Hex format.
11957 @value{GDBN} uses the same definitions of these formats as the
11958 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11959 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11963 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11964 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11965 Append the contents of memory from @var{start_addr} to @var{end_addr},
11966 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11967 (@value{GDBN} can only append data to files in raw binary form.)
11970 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11971 Restore the contents of file @var{filename} into memory. The
11972 @code{restore} command can automatically recognize any known @sc{bfd}
11973 file format, except for raw binary. To restore a raw binary file you
11974 must specify the optional keyword @code{binary} after the filename.
11976 If @var{bias} is non-zero, its value will be added to the addresses
11977 contained in the file. Binary files always start at address zero, so
11978 they will be restored at address @var{bias}. Other bfd files have
11979 a built-in location; they will be restored at offset @var{bias}
11980 from that location.
11982 If @var{start} and/or @var{end} are non-zero, then only data between
11983 file offset @var{start} and file offset @var{end} will be restored.
11984 These offsets are relative to the addresses in the file, before
11985 the @var{bias} argument is applied.
11989 @node Core File Generation
11990 @section How to Produce a Core File from Your Program
11991 @cindex dump core from inferior
11993 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11994 image of a running process and its process status (register values
11995 etc.). Its primary use is post-mortem debugging of a program that
11996 crashed while it ran outside a debugger. A program that crashes
11997 automatically produces a core file, unless this feature is disabled by
11998 the user. @xref{Files}, for information on invoking @value{GDBN} in
11999 the post-mortem debugging mode.
12001 Occasionally, you may wish to produce a core file of the program you
12002 are debugging in order to preserve a snapshot of its state.
12003 @value{GDBN} has a special command for that.
12007 @kindex generate-core-file
12008 @item generate-core-file [@var{file}]
12009 @itemx gcore [@var{file}]
12010 Produce a core dump of the inferior process. The optional argument
12011 @var{file} specifies the file name where to put the core dump. If not
12012 specified, the file name defaults to @file{core.@var{pid}}, where
12013 @var{pid} is the inferior process ID.
12015 Note that this command is implemented only for some systems (as of
12016 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12018 On @sc{gnu}/Linux, this command can take into account the value of the
12019 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12020 dump (@pxref{set use-coredump-filter}), and by default honors the
12021 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12022 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12024 @kindex set use-coredump-filter
12025 @anchor{set use-coredump-filter}
12026 @item set use-coredump-filter on
12027 @itemx set use-coredump-filter off
12028 Enable or disable the use of the file
12029 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12030 files. This file is used by the Linux kernel to decide what types of
12031 memory mappings will be dumped or ignored when generating a core dump
12032 file. @var{pid} is the process ID of a currently running process.
12034 To make use of this feature, you have to write in the
12035 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12036 which is a bit mask representing the memory mapping types. If a bit
12037 is set in the bit mask, then the memory mappings of the corresponding
12038 types will be dumped; otherwise, they will be ignored. This
12039 configuration is inherited by child processes. For more information
12040 about the bits that can be set in the
12041 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12042 manpage of @code{core(5)}.
12044 By default, this option is @code{on}. If this option is turned
12045 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12046 and instead uses the same default value as the Linux kernel in order
12047 to decide which pages will be dumped in the core dump file. This
12048 value is currently @code{0x33}, which means that bits @code{0}
12049 (anonymous private mappings), @code{1} (anonymous shared mappings),
12050 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12051 This will cause these memory mappings to be dumped automatically.
12053 @kindex set dump-excluded-mappings
12054 @anchor{set dump-excluded-mappings}
12055 @item set dump-excluded-mappings on
12056 @itemx set dump-excluded-mappings off
12057 If @code{on} is specified, @value{GDBN} will dump memory mappings
12058 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12059 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12061 The default value is @code{off}.
12064 @node Character Sets
12065 @section Character Sets
12066 @cindex character sets
12068 @cindex translating between character sets
12069 @cindex host character set
12070 @cindex target character set
12072 If the program you are debugging uses a different character set to
12073 represent characters and strings than the one @value{GDBN} uses itself,
12074 @value{GDBN} can automatically translate between the character sets for
12075 you. The character set @value{GDBN} uses we call the @dfn{host
12076 character set}; the one the inferior program uses we call the
12077 @dfn{target character set}.
12079 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12080 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12081 remote protocol (@pxref{Remote Debugging}) to debug a program
12082 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12083 then the host character set is Latin-1, and the target character set is
12084 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12085 target-charset EBCDIC-US}, then @value{GDBN} translates between
12086 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12087 character and string literals in expressions.
12089 @value{GDBN} has no way to automatically recognize which character set
12090 the inferior program uses; you must tell it, using the @code{set
12091 target-charset} command, described below.
12093 Here are the commands for controlling @value{GDBN}'s character set
12097 @item set target-charset @var{charset}
12098 @kindex set target-charset
12099 Set the current target character set to @var{charset}. To display the
12100 list of supported target character sets, type
12101 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12103 @item set host-charset @var{charset}
12104 @kindex set host-charset
12105 Set the current host character set to @var{charset}.
12107 By default, @value{GDBN} uses a host character set appropriate to the
12108 system it is running on; you can override that default using the
12109 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12110 automatically determine the appropriate host character set. In this
12111 case, @value{GDBN} uses @samp{UTF-8}.
12113 @value{GDBN} can only use certain character sets as its host character
12114 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12115 @value{GDBN} will list the host character sets it supports.
12117 @item set charset @var{charset}
12118 @kindex set charset
12119 Set the current host and target character sets to @var{charset}. As
12120 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12121 @value{GDBN} will list the names of the character sets that can be used
12122 for both host and target.
12125 @kindex show charset
12126 Show the names of the current host and target character sets.
12128 @item show host-charset
12129 @kindex show host-charset
12130 Show the name of the current host character set.
12132 @item show target-charset
12133 @kindex show target-charset
12134 Show the name of the current target character set.
12136 @item set target-wide-charset @var{charset}
12137 @kindex set target-wide-charset
12138 Set the current target's wide character set to @var{charset}. This is
12139 the character set used by the target's @code{wchar_t} type. To
12140 display the list of supported wide character sets, type
12141 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12143 @item show target-wide-charset
12144 @kindex show target-wide-charset
12145 Show the name of the current target's wide character set.
12148 Here is an example of @value{GDBN}'s character set support in action.
12149 Assume that the following source code has been placed in the file
12150 @file{charset-test.c}:
12156 = @{72, 101, 108, 108, 111, 44, 32, 119,
12157 111, 114, 108, 100, 33, 10, 0@};
12158 char ibm1047_hello[]
12159 = @{200, 133, 147, 147, 150, 107, 64, 166,
12160 150, 153, 147, 132, 90, 37, 0@};
12164 printf ("Hello, world!\n");
12168 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12169 containing the string @samp{Hello, world!} followed by a newline,
12170 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12172 We compile the program, and invoke the debugger on it:
12175 $ gcc -g charset-test.c -o charset-test
12176 $ gdb -nw charset-test
12177 GNU gdb 2001-12-19-cvs
12178 Copyright 2001 Free Software Foundation, Inc.
12183 We can use the @code{show charset} command to see what character sets
12184 @value{GDBN} is currently using to interpret and display characters and
12188 (@value{GDBP}) show charset
12189 The current host and target character set is `ISO-8859-1'.
12193 For the sake of printing this manual, let's use @sc{ascii} as our
12194 initial character set:
12196 (@value{GDBP}) set charset ASCII
12197 (@value{GDBP}) show charset
12198 The current host and target character set is `ASCII'.
12202 Let's assume that @sc{ascii} is indeed the correct character set for our
12203 host system --- in other words, let's assume that if @value{GDBN} prints
12204 characters using the @sc{ascii} character set, our terminal will display
12205 them properly. Since our current target character set is also
12206 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12209 (@value{GDBP}) print ascii_hello
12210 $1 = 0x401698 "Hello, world!\n"
12211 (@value{GDBP}) print ascii_hello[0]
12216 @value{GDBN} uses the target character set for character and string
12217 literals you use in expressions:
12220 (@value{GDBP}) print '+'
12225 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12228 @value{GDBN} relies on the user to tell it which character set the
12229 target program uses. If we print @code{ibm1047_hello} while our target
12230 character set is still @sc{ascii}, we get jibberish:
12233 (@value{GDBP}) print ibm1047_hello
12234 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12235 (@value{GDBP}) print ibm1047_hello[0]
12240 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12241 @value{GDBN} tells us the character sets it supports:
12244 (@value{GDBP}) set target-charset
12245 ASCII EBCDIC-US IBM1047 ISO-8859-1
12246 (@value{GDBP}) set target-charset
12249 We can select @sc{ibm1047} as our target character set, and examine the
12250 program's strings again. Now the @sc{ascii} string is wrong, but
12251 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12252 target character set, @sc{ibm1047}, to the host character set,
12253 @sc{ascii}, and they display correctly:
12256 (@value{GDBP}) set target-charset IBM1047
12257 (@value{GDBP}) show charset
12258 The current host character set is `ASCII'.
12259 The current target character set is `IBM1047'.
12260 (@value{GDBP}) print ascii_hello
12261 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12262 (@value{GDBP}) print ascii_hello[0]
12264 (@value{GDBP}) print ibm1047_hello
12265 $8 = 0x4016a8 "Hello, world!\n"
12266 (@value{GDBP}) print ibm1047_hello[0]
12271 As above, @value{GDBN} uses the target character set for character and
12272 string literals you use in expressions:
12275 (@value{GDBP}) print '+'
12280 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12283 @node Caching Target Data
12284 @section Caching Data of Targets
12285 @cindex caching data of targets
12287 @value{GDBN} caches data exchanged between the debugger and a target.
12288 Each cache is associated with the address space of the inferior.
12289 @xref{Inferiors and Programs}, about inferior and address space.
12290 Such caching generally improves performance in remote debugging
12291 (@pxref{Remote Debugging}), because it reduces the overhead of the
12292 remote protocol by bundling memory reads and writes into large chunks.
12293 Unfortunately, simply caching everything would lead to incorrect results,
12294 since @value{GDBN} does not necessarily know anything about volatile
12295 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12296 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12298 Therefore, by default, @value{GDBN} only caches data
12299 known to be on the stack@footnote{In non-stop mode, it is moderately
12300 rare for a running thread to modify the stack of a stopped thread
12301 in a way that would interfere with a backtrace, and caching of
12302 stack reads provides a significant speed up of remote backtraces.} or
12303 in the code segment.
12304 Other regions of memory can be explicitly marked as
12305 cacheable; @pxref{Memory Region Attributes}.
12308 @kindex set remotecache
12309 @item set remotecache on
12310 @itemx set remotecache off
12311 This option no longer does anything; it exists for compatibility
12314 @kindex show remotecache
12315 @item show remotecache
12316 Show the current state of the obsolete remotecache flag.
12318 @kindex set stack-cache
12319 @item set stack-cache on
12320 @itemx set stack-cache off
12321 Enable or disable caching of stack accesses. When @code{on}, use
12322 caching. By default, this option is @code{on}.
12324 @kindex show stack-cache
12325 @item show stack-cache
12326 Show the current state of data caching for memory accesses.
12328 @kindex set code-cache
12329 @item set code-cache on
12330 @itemx set code-cache off
12331 Enable or disable caching of code segment accesses. When @code{on},
12332 use caching. By default, this option is @code{on}. This improves
12333 performance of disassembly in remote debugging.
12335 @kindex show code-cache
12336 @item show code-cache
12337 Show the current state of target memory cache for code segment
12340 @kindex info dcache
12341 @item info dcache @r{[}line@r{]}
12342 Print the information about the performance of data cache of the
12343 current inferior's address space. The information displayed
12344 includes the dcache width and depth, and for each cache line, its
12345 number, address, and how many times it was referenced. This
12346 command is useful for debugging the data cache operation.
12348 If a line number is specified, the contents of that line will be
12351 @item set dcache size @var{size}
12352 @cindex dcache size
12353 @kindex set dcache size
12354 Set maximum number of entries in dcache (dcache depth above).
12356 @item set dcache line-size @var{line-size}
12357 @cindex dcache line-size
12358 @kindex set dcache line-size
12359 Set number of bytes each dcache entry caches (dcache width above).
12360 Must be a power of 2.
12362 @item show dcache size
12363 @kindex show dcache size
12364 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12366 @item show dcache line-size
12367 @kindex show dcache line-size
12368 Show default size of dcache lines.
12372 @node Searching Memory
12373 @section Search Memory
12374 @cindex searching memory
12376 Memory can be searched for a particular sequence of bytes with the
12377 @code{find} command.
12381 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12382 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12383 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12384 etc. The search begins at address @var{start_addr} and continues for either
12385 @var{len} bytes or through to @var{end_addr} inclusive.
12388 @var{s} and @var{n} are optional parameters.
12389 They may be specified in either order, apart or together.
12392 @item @var{s}, search query size
12393 The size of each search query value.
12399 halfwords (two bytes)
12403 giant words (eight bytes)
12406 All values are interpreted in the current language.
12407 This means, for example, that if the current source language is C/C@t{++}
12408 then searching for the string ``hello'' includes the trailing '\0'.
12409 The null terminator can be removed from searching by using casts,
12410 e.g.: @samp{@{char[5]@}"hello"}.
12412 If the value size is not specified, it is taken from the
12413 value's type in the current language.
12414 This is useful when one wants to specify the search
12415 pattern as a mixture of types.
12416 Note that this means, for example, that in the case of C-like languages
12417 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12418 which is typically four bytes.
12420 @item @var{n}, maximum number of finds
12421 The maximum number of matches to print. The default is to print all finds.
12424 You can use strings as search values. Quote them with double-quotes
12426 The string value is copied into the search pattern byte by byte,
12427 regardless of the endianness of the target and the size specification.
12429 The address of each match found is printed as well as a count of the
12430 number of matches found.
12432 The address of the last value found is stored in convenience variable
12434 A count of the number of matches is stored in @samp{$numfound}.
12436 For example, if stopped at the @code{printf} in this function:
12442 static char hello[] = "hello-hello";
12443 static struct @{ char c; short s; int i; @}
12444 __attribute__ ((packed)) mixed
12445 = @{ 'c', 0x1234, 0x87654321 @};
12446 printf ("%s\n", hello);
12451 you get during debugging:
12454 (gdb) find &hello[0], +sizeof(hello), "hello"
12455 0x804956d <hello.1620+6>
12457 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12458 0x8049567 <hello.1620>
12459 0x804956d <hello.1620+6>
12461 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12462 0x8049567 <hello.1620>
12463 0x804956d <hello.1620+6>
12465 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12466 0x8049567 <hello.1620>
12468 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12469 0x8049560 <mixed.1625>
12471 (gdb) print $numfound
12474 $2 = (void *) 0x8049560
12478 @section Value Sizes
12480 Whenever @value{GDBN} prints a value memory will be allocated within
12481 @value{GDBN} to hold the contents of the value. It is possible in
12482 some languages with dynamic typing systems, that an invalid program
12483 may indicate a value that is incorrectly large, this in turn may cause
12484 @value{GDBN} to try and allocate an overly large ammount of memory.
12487 @kindex set max-value-size
12488 @item set max-value-size @var{bytes}
12489 @itemx set max-value-size unlimited
12490 Set the maximum size of memory that @value{GDBN} will allocate for the
12491 contents of a value to @var{bytes}, trying to display a value that
12492 requires more memory than that will result in an error.
12494 Setting this variable does not effect values that have already been
12495 allocated within @value{GDBN}, only future allocations.
12497 There's a minimum size that @code{max-value-size} can be set to in
12498 order that @value{GDBN} can still operate correctly, this minimum is
12499 currently 16 bytes.
12501 The limit applies to the results of some subexpressions as well as to
12502 complete expressions. For example, an expression denoting a simple
12503 integer component, such as @code{x.y.z}, may fail if the size of
12504 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12505 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12506 @var{A} is an array variable with non-constant size, will generally
12507 succeed regardless of the bounds on @var{A}, as long as the component
12508 size is less than @var{bytes}.
12510 The default value of @code{max-value-size} is currently 64k.
12512 @kindex show max-value-size
12513 @item show max-value-size
12514 Show the maximum size of memory, in bytes, that @value{GDBN} will
12515 allocate for the contents of a value.
12518 @node Optimized Code
12519 @chapter Debugging Optimized Code
12520 @cindex optimized code, debugging
12521 @cindex debugging optimized code
12523 Almost all compilers support optimization. With optimization
12524 disabled, the compiler generates assembly code that corresponds
12525 directly to your source code, in a simplistic way. As the compiler
12526 applies more powerful optimizations, the generated assembly code
12527 diverges from your original source code. With help from debugging
12528 information generated by the compiler, @value{GDBN} can map from
12529 the running program back to constructs from your original source.
12531 @value{GDBN} is more accurate with optimization disabled. If you
12532 can recompile without optimization, it is easier to follow the
12533 progress of your program during debugging. But, there are many cases
12534 where you may need to debug an optimized version.
12536 When you debug a program compiled with @samp{-g -O}, remember that the
12537 optimizer has rearranged your code; the debugger shows you what is
12538 really there. Do not be too surprised when the execution path does not
12539 exactly match your source file! An extreme example: if you define a
12540 variable, but never use it, @value{GDBN} never sees that
12541 variable---because the compiler optimizes it out of existence.
12543 Some things do not work as well with @samp{-g -O} as with just
12544 @samp{-g}, particularly on machines with instruction scheduling. If in
12545 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12546 please report it to us as a bug (including a test case!).
12547 @xref{Variables}, for more information about debugging optimized code.
12550 * Inline Functions:: How @value{GDBN} presents inlining
12551 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12554 @node Inline Functions
12555 @section Inline Functions
12556 @cindex inline functions, debugging
12558 @dfn{Inlining} is an optimization that inserts a copy of the function
12559 body directly at each call site, instead of jumping to a shared
12560 routine. @value{GDBN} displays inlined functions just like
12561 non-inlined functions. They appear in backtraces. You can view their
12562 arguments and local variables, step into them with @code{step}, skip
12563 them with @code{next}, and escape from them with @code{finish}.
12564 You can check whether a function was inlined by using the
12565 @code{info frame} command.
12567 For @value{GDBN} to support inlined functions, the compiler must
12568 record information about inlining in the debug information ---
12569 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12570 other compilers do also. @value{GDBN} only supports inlined functions
12571 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12572 do not emit two required attributes (@samp{DW_AT_call_file} and
12573 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12574 function calls with earlier versions of @value{NGCC}. It instead
12575 displays the arguments and local variables of inlined functions as
12576 local variables in the caller.
12578 The body of an inlined function is directly included at its call site;
12579 unlike a non-inlined function, there are no instructions devoted to
12580 the call. @value{GDBN} still pretends that the call site and the
12581 start of the inlined function are different instructions. Stepping to
12582 the call site shows the call site, and then stepping again shows
12583 the first line of the inlined function, even though no additional
12584 instructions are executed.
12586 This makes source-level debugging much clearer; you can see both the
12587 context of the call and then the effect of the call. Only stepping by
12588 a single instruction using @code{stepi} or @code{nexti} does not do
12589 this; single instruction steps always show the inlined body.
12591 There are some ways that @value{GDBN} does not pretend that inlined
12592 function calls are the same as normal calls:
12596 Setting breakpoints at the call site of an inlined function may not
12597 work, because the call site does not contain any code. @value{GDBN}
12598 may incorrectly move the breakpoint to the next line of the enclosing
12599 function, after the call. This limitation will be removed in a future
12600 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12601 or inside the inlined function instead.
12604 @value{GDBN} cannot locate the return value of inlined calls after
12605 using the @code{finish} command. This is a limitation of compiler-generated
12606 debugging information; after @code{finish}, you can step to the next line
12607 and print a variable where your program stored the return value.
12611 @node Tail Call Frames
12612 @section Tail Call Frames
12613 @cindex tail call frames, debugging
12615 Function @code{B} can call function @code{C} in its very last statement. In
12616 unoptimized compilation the call of @code{C} is immediately followed by return
12617 instruction at the end of @code{B} code. Optimizing compiler may replace the
12618 call and return in function @code{B} into one jump to function @code{C}
12619 instead. Such use of a jump instruction is called @dfn{tail call}.
12621 During execution of function @code{C}, there will be no indication in the
12622 function call stack frames that it was tail-called from @code{B}. If function
12623 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12624 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12625 some cases @value{GDBN} can determine that @code{C} was tail-called from
12626 @code{B}, and it will then create fictitious call frame for that, with the
12627 return address set up as if @code{B} called @code{C} normally.
12629 This functionality is currently supported only by DWARF 2 debugging format and
12630 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12631 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12634 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12635 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12639 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12641 Stack level 1, frame at 0x7fffffffda30:
12642 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12643 tail call frame, caller of frame at 0x7fffffffda30
12644 source language c++.
12645 Arglist at unknown address.
12646 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12649 The detection of all the possible code path executions can find them ambiguous.
12650 There is no execution history stored (possible @ref{Reverse Execution} is never
12651 used for this purpose) and the last known caller could have reached the known
12652 callee by multiple different jump sequences. In such case @value{GDBN} still
12653 tries to show at least all the unambiguous top tail callers and all the
12654 unambiguous bottom tail calees, if any.
12657 @anchor{set debug entry-values}
12658 @item set debug entry-values
12659 @kindex set debug entry-values
12660 When set to on, enables printing of analysis messages for both frame argument
12661 values at function entry and tail calls. It will show all the possible valid
12662 tail calls code paths it has considered. It will also print the intersection
12663 of them with the final unambiguous (possibly partial or even empty) code path
12666 @item show debug entry-values
12667 @kindex show debug entry-values
12668 Show the current state of analysis messages printing for both frame argument
12669 values at function entry and tail calls.
12672 The analysis messages for tail calls can for example show why the virtual tail
12673 call frame for function @code{c} has not been recognized (due to the indirect
12674 reference by variable @code{x}):
12677 static void __attribute__((noinline, noclone)) c (void);
12678 void (*x) (void) = c;
12679 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12680 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12681 int main (void) @{ x (); return 0; @}
12683 Breakpoint 1, DW_OP_entry_value resolving cannot find
12684 DW_TAG_call_site 0x40039a in main
12686 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12689 #1 0x000000000040039a in main () at t.c:5
12692 Another possibility is an ambiguous virtual tail call frames resolution:
12696 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12697 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12698 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12699 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12700 static void __attribute__((noinline, noclone)) b (void)
12701 @{ if (i) c (); else e (); @}
12702 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12703 int main (void) @{ a (); return 0; @}
12705 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12706 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12707 tailcall: reduced: 0x4004d2(a) |
12710 #1 0x00000000004004d2 in a () at t.c:8
12711 #2 0x0000000000400395 in main () at t.c:9
12714 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12715 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12717 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12718 @ifset HAVE_MAKEINFO_CLICK
12719 @set ARROW @click{}
12720 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12721 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12723 @ifclear HAVE_MAKEINFO_CLICK
12725 @set CALLSEQ1B @value{CALLSEQ1A}
12726 @set CALLSEQ2B @value{CALLSEQ2A}
12729 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12730 The code can have possible execution paths @value{CALLSEQ1B} or
12731 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12733 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12734 has found. It then finds another possible calling sequcen - that one is
12735 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12736 printed as the @code{reduced:} calling sequence. That one could have many
12737 futher @code{compare:} and @code{reduced:} statements as long as there remain
12738 any non-ambiguous sequence entries.
12740 For the frame of function @code{b} in both cases there are different possible
12741 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12742 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12743 therefore this one is displayed to the user while the ambiguous frames are
12746 There can be also reasons why printing of frame argument values at function
12751 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12752 static void __attribute__((noinline, noclone)) a (int i);
12753 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12754 static void __attribute__((noinline, noclone)) a (int i)
12755 @{ if (i) b (i - 1); else c (0); @}
12756 int main (void) @{ a (5); return 0; @}
12759 #0 c (i=i@@entry=0) at t.c:2
12760 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12761 function "a" at 0x400420 can call itself via tail calls
12762 i=<optimized out>) at t.c:6
12763 #2 0x000000000040036e in main () at t.c:7
12766 @value{GDBN} cannot find out from the inferior state if and how many times did
12767 function @code{a} call itself (via function @code{b}) as these calls would be
12768 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12769 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12770 prints @code{<optimized out>} instead.
12773 @chapter C Preprocessor Macros
12775 Some languages, such as C and C@t{++}, provide a way to define and invoke
12776 ``preprocessor macros'' which expand into strings of tokens.
12777 @value{GDBN} can evaluate expressions containing macro invocations, show
12778 the result of macro expansion, and show a macro's definition, including
12779 where it was defined.
12781 You may need to compile your program specially to provide @value{GDBN}
12782 with information about preprocessor macros. Most compilers do not
12783 include macros in their debugging information, even when you compile
12784 with the @option{-g} flag. @xref{Compilation}.
12786 A program may define a macro at one point, remove that definition later,
12787 and then provide a different definition after that. Thus, at different
12788 points in the program, a macro may have different definitions, or have
12789 no definition at all. If there is a current stack frame, @value{GDBN}
12790 uses the macros in scope at that frame's source code line. Otherwise,
12791 @value{GDBN} uses the macros in scope at the current listing location;
12794 Whenever @value{GDBN} evaluates an expression, it always expands any
12795 macro invocations present in the expression. @value{GDBN} also provides
12796 the following commands for working with macros explicitly.
12800 @kindex macro expand
12801 @cindex macro expansion, showing the results of preprocessor
12802 @cindex preprocessor macro expansion, showing the results of
12803 @cindex expanding preprocessor macros
12804 @item macro expand @var{expression}
12805 @itemx macro exp @var{expression}
12806 Show the results of expanding all preprocessor macro invocations in
12807 @var{expression}. Since @value{GDBN} simply expands macros, but does
12808 not parse the result, @var{expression} need not be a valid expression;
12809 it can be any string of tokens.
12812 @item macro expand-once @var{expression}
12813 @itemx macro exp1 @var{expression}
12814 @cindex expand macro once
12815 @i{(This command is not yet implemented.)} Show the results of
12816 expanding those preprocessor macro invocations that appear explicitly in
12817 @var{expression}. Macro invocations appearing in that expansion are
12818 left unchanged. This command allows you to see the effect of a
12819 particular macro more clearly, without being confused by further
12820 expansions. Since @value{GDBN} simply expands macros, but does not
12821 parse the result, @var{expression} need not be a valid expression; it
12822 can be any string of tokens.
12825 @cindex macro definition, showing
12826 @cindex definition of a macro, showing
12827 @cindex macros, from debug info
12828 @item info macro [-a|-all] [--] @var{macro}
12829 Show the current definition or all definitions of the named @var{macro},
12830 and describe the source location or compiler command-line where that
12831 definition was established. The optional double dash is to signify the end of
12832 argument processing and the beginning of @var{macro} for non C-like macros where
12833 the macro may begin with a hyphen.
12835 @kindex info macros
12836 @item info macros @var{location}
12837 Show all macro definitions that are in effect at the location specified
12838 by @var{location}, and describe the source location or compiler
12839 command-line where those definitions were established.
12841 @kindex macro define
12842 @cindex user-defined macros
12843 @cindex defining macros interactively
12844 @cindex macros, user-defined
12845 @item macro define @var{macro} @var{replacement-list}
12846 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12847 Introduce a definition for a preprocessor macro named @var{macro},
12848 invocations of which are replaced by the tokens given in
12849 @var{replacement-list}. The first form of this command defines an
12850 ``object-like'' macro, which takes no arguments; the second form
12851 defines a ``function-like'' macro, which takes the arguments given in
12854 A definition introduced by this command is in scope in every
12855 expression evaluated in @value{GDBN}, until it is removed with the
12856 @code{macro undef} command, described below. The definition overrides
12857 all definitions for @var{macro} present in the program being debugged,
12858 as well as any previous user-supplied definition.
12860 @kindex macro undef
12861 @item macro undef @var{macro}
12862 Remove any user-supplied definition for the macro named @var{macro}.
12863 This command only affects definitions provided with the @code{macro
12864 define} command, described above; it cannot remove definitions present
12865 in the program being debugged.
12869 List all the macros defined using the @code{macro define} command.
12872 @cindex macros, example of debugging with
12873 Here is a transcript showing the above commands in action. First, we
12874 show our source files:
12879 #include "sample.h"
12882 #define ADD(x) (M + x)
12887 printf ("Hello, world!\n");
12889 printf ("We're so creative.\n");
12891 printf ("Goodbye, world!\n");
12898 Now, we compile the program using the @sc{gnu} C compiler,
12899 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12900 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12901 and @option{-gdwarf-4}; we recommend always choosing the most recent
12902 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12903 includes information about preprocessor macros in the debugging
12907 $ gcc -gdwarf-2 -g3 sample.c -o sample
12911 Now, we start @value{GDBN} on our sample program:
12915 GNU gdb 2002-05-06-cvs
12916 Copyright 2002 Free Software Foundation, Inc.
12917 GDB is free software, @dots{}
12921 We can expand macros and examine their definitions, even when the
12922 program is not running. @value{GDBN} uses the current listing position
12923 to decide which macro definitions are in scope:
12926 (@value{GDBP}) list main
12929 5 #define ADD(x) (M + x)
12934 10 printf ("Hello, world!\n");
12936 12 printf ("We're so creative.\n");
12937 (@value{GDBP}) info macro ADD
12938 Defined at /home/jimb/gdb/macros/play/sample.c:5
12939 #define ADD(x) (M + x)
12940 (@value{GDBP}) info macro Q
12941 Defined at /home/jimb/gdb/macros/play/sample.h:1
12942 included at /home/jimb/gdb/macros/play/sample.c:2
12944 (@value{GDBP}) macro expand ADD(1)
12945 expands to: (42 + 1)
12946 (@value{GDBP}) macro expand-once ADD(1)
12947 expands to: once (M + 1)
12951 In the example above, note that @code{macro expand-once} expands only
12952 the macro invocation explicit in the original text --- the invocation of
12953 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12954 which was introduced by @code{ADD}.
12956 Once the program is running, @value{GDBN} uses the macro definitions in
12957 force at the source line of the current stack frame:
12960 (@value{GDBP}) break main
12961 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12963 Starting program: /home/jimb/gdb/macros/play/sample
12965 Breakpoint 1, main () at sample.c:10
12966 10 printf ("Hello, world!\n");
12970 At line 10, the definition of the macro @code{N} at line 9 is in force:
12973 (@value{GDBP}) info macro N
12974 Defined at /home/jimb/gdb/macros/play/sample.c:9
12976 (@value{GDBP}) macro expand N Q M
12977 expands to: 28 < 42
12978 (@value{GDBP}) print N Q M
12983 As we step over directives that remove @code{N}'s definition, and then
12984 give it a new definition, @value{GDBN} finds the definition (or lack
12985 thereof) in force at each point:
12988 (@value{GDBP}) next
12990 12 printf ("We're so creative.\n");
12991 (@value{GDBP}) info macro N
12992 The symbol `N' has no definition as a C/C++ preprocessor macro
12993 at /home/jimb/gdb/macros/play/sample.c:12
12994 (@value{GDBP}) next
12996 14 printf ("Goodbye, world!\n");
12997 (@value{GDBP}) info macro N
12998 Defined at /home/jimb/gdb/macros/play/sample.c:13
13000 (@value{GDBP}) macro expand N Q M
13001 expands to: 1729 < 42
13002 (@value{GDBP}) print N Q M
13007 In addition to source files, macros can be defined on the compilation command
13008 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13009 such a way, @value{GDBN} displays the location of their definition as line zero
13010 of the source file submitted to the compiler.
13013 (@value{GDBP}) info macro __STDC__
13014 Defined at /home/jimb/gdb/macros/play/sample.c:0
13021 @chapter Tracepoints
13022 @c This chapter is based on the documentation written by Michael
13023 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13025 @cindex tracepoints
13026 In some applications, it is not feasible for the debugger to interrupt
13027 the program's execution long enough for the developer to learn
13028 anything helpful about its behavior. If the program's correctness
13029 depends on its real-time behavior, delays introduced by a debugger
13030 might cause the program to change its behavior drastically, or perhaps
13031 fail, even when the code itself is correct. It is useful to be able
13032 to observe the program's behavior without interrupting it.
13034 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13035 specify locations in the program, called @dfn{tracepoints}, and
13036 arbitrary expressions to evaluate when those tracepoints are reached.
13037 Later, using the @code{tfind} command, you can examine the values
13038 those expressions had when the program hit the tracepoints. The
13039 expressions may also denote objects in memory---structures or arrays,
13040 for example---whose values @value{GDBN} should record; while visiting
13041 a particular tracepoint, you may inspect those objects as if they were
13042 in memory at that moment. However, because @value{GDBN} records these
13043 values without interacting with you, it can do so quickly and
13044 unobtrusively, hopefully not disturbing the program's behavior.
13046 The tracepoint facility is currently available only for remote
13047 targets. @xref{Targets}. In addition, your remote target must know
13048 how to collect trace data. This functionality is implemented in the
13049 remote stub; however, none of the stubs distributed with @value{GDBN}
13050 support tracepoints as of this writing. The format of the remote
13051 packets used to implement tracepoints are described in @ref{Tracepoint
13054 It is also possible to get trace data from a file, in a manner reminiscent
13055 of corefiles; you specify the filename, and use @code{tfind} to search
13056 through the file. @xref{Trace Files}, for more details.
13058 This chapter describes the tracepoint commands and features.
13061 * Set Tracepoints::
13062 * Analyze Collected Data::
13063 * Tracepoint Variables::
13067 @node Set Tracepoints
13068 @section Commands to Set Tracepoints
13070 Before running such a @dfn{trace experiment}, an arbitrary number of
13071 tracepoints can be set. A tracepoint is actually a special type of
13072 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13073 standard breakpoint commands. For instance, as with breakpoints,
13074 tracepoint numbers are successive integers starting from one, and many
13075 of the commands associated with tracepoints take the tracepoint number
13076 as their argument, to identify which tracepoint to work on.
13078 For each tracepoint, you can specify, in advance, some arbitrary set
13079 of data that you want the target to collect in the trace buffer when
13080 it hits that tracepoint. The collected data can include registers,
13081 local variables, or global data. Later, you can use @value{GDBN}
13082 commands to examine the values these data had at the time the
13083 tracepoint was hit.
13085 Tracepoints do not support every breakpoint feature. Ignore counts on
13086 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13087 commands when they are hit. Tracepoints may not be thread-specific
13090 @cindex fast tracepoints
13091 Some targets may support @dfn{fast tracepoints}, which are inserted in
13092 a different way (such as with a jump instead of a trap), that is
13093 faster but possibly restricted in where they may be installed.
13095 @cindex static tracepoints
13096 @cindex markers, static tracepoints
13097 @cindex probing markers, static tracepoints
13098 Regular and fast tracepoints are dynamic tracing facilities, meaning
13099 that they can be used to insert tracepoints at (almost) any location
13100 in the target. Some targets may also support controlling @dfn{static
13101 tracepoints} from @value{GDBN}. With static tracing, a set of
13102 instrumentation points, also known as @dfn{markers}, are embedded in
13103 the target program, and can be activated or deactivated by name or
13104 address. These are usually placed at locations which facilitate
13105 investigating what the target is actually doing. @value{GDBN}'s
13106 support for static tracing includes being able to list instrumentation
13107 points, and attach them with @value{GDBN} defined high level
13108 tracepoints that expose the whole range of convenience of
13109 @value{GDBN}'s tracepoints support. Namely, support for collecting
13110 registers values and values of global or local (to the instrumentation
13111 point) variables; tracepoint conditions and trace state variables.
13112 The act of installing a @value{GDBN} static tracepoint on an
13113 instrumentation point, or marker, is referred to as @dfn{probing} a
13114 static tracepoint marker.
13116 @code{gdbserver} supports tracepoints on some target systems.
13117 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13119 This section describes commands to set tracepoints and associated
13120 conditions and actions.
13123 * Create and Delete Tracepoints::
13124 * Enable and Disable Tracepoints::
13125 * Tracepoint Passcounts::
13126 * Tracepoint Conditions::
13127 * Trace State Variables::
13128 * Tracepoint Actions::
13129 * Listing Tracepoints::
13130 * Listing Static Tracepoint Markers::
13131 * Starting and Stopping Trace Experiments::
13132 * Tracepoint Restrictions::
13135 @node Create and Delete Tracepoints
13136 @subsection Create and Delete Tracepoints
13139 @cindex set tracepoint
13141 @item trace @var{location}
13142 The @code{trace} command is very similar to the @code{break} command.
13143 Its argument @var{location} can be any valid location.
13144 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13145 which is a point in the target program where the debugger will briefly stop,
13146 collect some data, and then allow the program to continue. Setting a tracepoint
13147 or changing its actions takes effect immediately if the remote stub
13148 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13150 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13151 these changes don't take effect until the next @code{tstart}
13152 command, and once a trace experiment is running, further changes will
13153 not have any effect until the next trace experiment starts. In addition,
13154 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13155 address is not yet resolved. (This is similar to pending breakpoints.)
13156 Pending tracepoints are not downloaded to the target and not installed
13157 until they are resolved. The resolution of pending tracepoints requires
13158 @value{GDBN} support---when debugging with the remote target, and
13159 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13160 tracing}), pending tracepoints can not be resolved (and downloaded to
13161 the remote stub) while @value{GDBN} is disconnected.
13163 Here are some examples of using the @code{trace} command:
13166 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13168 (@value{GDBP}) @b{trace +2} // 2 lines forward
13170 (@value{GDBP}) @b{trace my_function} // first source line of function
13172 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13174 (@value{GDBP}) @b{trace *0x2117c4} // an address
13178 You can abbreviate @code{trace} as @code{tr}.
13180 @item trace @var{location} if @var{cond}
13181 Set a tracepoint with condition @var{cond}; evaluate the expression
13182 @var{cond} each time the tracepoint is reached, and collect data only
13183 if the value is nonzero---that is, if @var{cond} evaluates as true.
13184 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13185 information on tracepoint conditions.
13187 @item ftrace @var{location} [ if @var{cond} ]
13188 @cindex set fast tracepoint
13189 @cindex fast tracepoints, setting
13191 The @code{ftrace} command sets a fast tracepoint. For targets that
13192 support them, fast tracepoints will use a more efficient but possibly
13193 less general technique to trigger data collection, such as a jump
13194 instruction instead of a trap, or some sort of hardware support. It
13195 may not be possible to create a fast tracepoint at the desired
13196 location, in which case the command will exit with an explanatory
13199 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13202 On 32-bit x86-architecture systems, fast tracepoints normally need to
13203 be placed at an instruction that is 5 bytes or longer, but can be
13204 placed at 4-byte instructions if the low 64K of memory of the target
13205 program is available to install trampolines. Some Unix-type systems,
13206 such as @sc{gnu}/Linux, exclude low addresses from the program's
13207 address space; but for instance with the Linux kernel it is possible
13208 to let @value{GDBN} use this area by doing a @command{sysctl} command
13209 to set the @code{mmap_min_addr} kernel parameter, as in
13212 sudo sysctl -w vm.mmap_min_addr=32768
13216 which sets the low address to 32K, which leaves plenty of room for
13217 trampolines. The minimum address should be set to a page boundary.
13219 @item strace @var{location} [ if @var{cond} ]
13220 @cindex set static tracepoint
13221 @cindex static tracepoints, setting
13222 @cindex probe static tracepoint marker
13224 The @code{strace} command sets a static tracepoint. For targets that
13225 support it, setting a static tracepoint probes a static
13226 instrumentation point, or marker, found at @var{location}. It may not
13227 be possible to set a static tracepoint at the desired location, in
13228 which case the command will exit with an explanatory message.
13230 @value{GDBN} handles arguments to @code{strace} exactly as for
13231 @code{trace}, with the addition that the user can also specify
13232 @code{-m @var{marker}} as @var{location}. This probes the marker
13233 identified by the @var{marker} string identifier. This identifier
13234 depends on the static tracepoint backend library your program is
13235 using. You can find all the marker identifiers in the @samp{ID} field
13236 of the @code{info static-tracepoint-markers} command output.
13237 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13238 Markers}. For example, in the following small program using the UST
13244 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13249 the marker id is composed of joining the first two arguments to the
13250 @code{trace_mark} call with a slash, which translates to:
13253 (@value{GDBP}) info static-tracepoint-markers
13254 Cnt Enb ID Address What
13255 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13261 so you may probe the marker above with:
13264 (@value{GDBP}) strace -m ust/bar33
13267 Static tracepoints accept an extra collect action --- @code{collect
13268 $_sdata}. This collects arbitrary user data passed in the probe point
13269 call to the tracing library. In the UST example above, you'll see
13270 that the third argument to @code{trace_mark} is a printf-like format
13271 string. The user data is then the result of running that formating
13272 string against the following arguments. Note that @code{info
13273 static-tracepoint-markers} command output lists that format string in
13274 the @samp{Data:} field.
13276 You can inspect this data when analyzing the trace buffer, by printing
13277 the $_sdata variable like any other variable available to
13278 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13281 @cindex last tracepoint number
13282 @cindex recent tracepoint number
13283 @cindex tracepoint number
13284 The convenience variable @code{$tpnum} records the tracepoint number
13285 of the most recently set tracepoint.
13287 @kindex delete tracepoint
13288 @cindex tracepoint deletion
13289 @item delete tracepoint @r{[}@var{num}@r{]}
13290 Permanently delete one or more tracepoints. With no argument, the
13291 default is to delete all tracepoints. Note that the regular
13292 @code{delete} command can remove tracepoints also.
13297 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13299 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13303 You can abbreviate this command as @code{del tr}.
13306 @node Enable and Disable Tracepoints
13307 @subsection Enable and Disable Tracepoints
13309 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13312 @kindex disable tracepoint
13313 @item disable tracepoint @r{[}@var{num}@r{]}
13314 Disable tracepoint @var{num}, or all tracepoints if no argument
13315 @var{num} is given. A disabled tracepoint will have no effect during
13316 a trace experiment, but it is not forgotten. You can re-enable
13317 a disabled tracepoint using the @code{enable tracepoint} command.
13318 If the command is issued during a trace experiment and the debug target
13319 has support for disabling tracepoints during a trace experiment, then the
13320 change will be effective immediately. Otherwise, it will be applied to the
13321 next trace experiment.
13323 @kindex enable tracepoint
13324 @item enable tracepoint @r{[}@var{num}@r{]}
13325 Enable tracepoint @var{num}, or all tracepoints. If this command is
13326 issued during a trace experiment and the debug target supports enabling
13327 tracepoints during a trace experiment, then the enabled tracepoints will
13328 become effective immediately. Otherwise, they will become effective the
13329 next time a trace experiment is run.
13332 @node Tracepoint Passcounts
13333 @subsection Tracepoint Passcounts
13337 @cindex tracepoint pass count
13338 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13339 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13340 automatically stop a trace experiment. If a tracepoint's passcount is
13341 @var{n}, then the trace experiment will be automatically stopped on
13342 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13343 @var{num} is not specified, the @code{passcount} command sets the
13344 passcount of the most recently defined tracepoint. If no passcount is
13345 given, the trace experiment will run until stopped explicitly by the
13351 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13352 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13354 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13355 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13356 (@value{GDBP}) @b{trace foo}
13357 (@value{GDBP}) @b{pass 3}
13358 (@value{GDBP}) @b{trace bar}
13359 (@value{GDBP}) @b{pass 2}
13360 (@value{GDBP}) @b{trace baz}
13361 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13362 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13363 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13364 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13368 @node Tracepoint Conditions
13369 @subsection Tracepoint Conditions
13370 @cindex conditional tracepoints
13371 @cindex tracepoint conditions
13373 The simplest sort of tracepoint collects data every time your program
13374 reaches a specified place. You can also specify a @dfn{condition} for
13375 a tracepoint. A condition is just a Boolean expression in your
13376 programming language (@pxref{Expressions, ,Expressions}). A
13377 tracepoint with a condition evaluates the expression each time your
13378 program reaches it, and data collection happens only if the condition
13381 Tracepoint conditions can be specified when a tracepoint is set, by
13382 using @samp{if} in the arguments to the @code{trace} command.
13383 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13384 also be set or changed at any time with the @code{condition} command,
13385 just as with breakpoints.
13387 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13388 the conditional expression itself. Instead, @value{GDBN} encodes the
13389 expression into an agent expression (@pxref{Agent Expressions})
13390 suitable for execution on the target, independently of @value{GDBN}.
13391 Global variables become raw memory locations, locals become stack
13392 accesses, and so forth.
13394 For instance, suppose you have a function that is usually called
13395 frequently, but should not be called after an error has occurred. You
13396 could use the following tracepoint command to collect data about calls
13397 of that function that happen while the error code is propagating
13398 through the program; an unconditional tracepoint could end up
13399 collecting thousands of useless trace frames that you would have to
13403 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13406 @node Trace State Variables
13407 @subsection Trace State Variables
13408 @cindex trace state variables
13410 A @dfn{trace state variable} is a special type of variable that is
13411 created and managed by target-side code. The syntax is the same as
13412 that for GDB's convenience variables (a string prefixed with ``$''),
13413 but they are stored on the target. They must be created explicitly,
13414 using a @code{tvariable} command. They are always 64-bit signed
13417 Trace state variables are remembered by @value{GDBN}, and downloaded
13418 to the target along with tracepoint information when the trace
13419 experiment starts. There are no intrinsic limits on the number of
13420 trace state variables, beyond memory limitations of the target.
13422 @cindex convenience variables, and trace state variables
13423 Although trace state variables are managed by the target, you can use
13424 them in print commands and expressions as if they were convenience
13425 variables; @value{GDBN} will get the current value from the target
13426 while the trace experiment is running. Trace state variables share
13427 the same namespace as other ``$'' variables, which means that you
13428 cannot have trace state variables with names like @code{$23} or
13429 @code{$pc}, nor can you have a trace state variable and a convenience
13430 variable with the same name.
13434 @item tvariable $@var{name} [ = @var{expression} ]
13436 The @code{tvariable} command creates a new trace state variable named
13437 @code{$@var{name}}, and optionally gives it an initial value of
13438 @var{expression}. The @var{expression} is evaluated when this command is
13439 entered; the result will be converted to an integer if possible,
13440 otherwise @value{GDBN} will report an error. A subsequent
13441 @code{tvariable} command specifying the same name does not create a
13442 variable, but instead assigns the supplied initial value to the
13443 existing variable of that name, overwriting any previous initial
13444 value. The default initial value is 0.
13446 @item info tvariables
13447 @kindex info tvariables
13448 List all the trace state variables along with their initial values.
13449 Their current values may also be displayed, if the trace experiment is
13452 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13453 @kindex delete tvariable
13454 Delete the given trace state variables, or all of them if no arguments
13459 @node Tracepoint Actions
13460 @subsection Tracepoint Action Lists
13464 @cindex tracepoint actions
13465 @item actions @r{[}@var{num}@r{]}
13466 This command will prompt for a list of actions to be taken when the
13467 tracepoint is hit. If the tracepoint number @var{num} is not
13468 specified, this command sets the actions for the one that was most
13469 recently defined (so that you can define a tracepoint and then say
13470 @code{actions} without bothering about its number). You specify the
13471 actions themselves on the following lines, one action at a time, and
13472 terminate the actions list with a line containing just @code{end}. So
13473 far, the only defined actions are @code{collect}, @code{teval}, and
13474 @code{while-stepping}.
13476 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13477 Commands, ,Breakpoint Command Lists}), except that only the defined
13478 actions are allowed; any other @value{GDBN} command is rejected.
13480 @cindex remove actions from a tracepoint
13481 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13482 and follow it immediately with @samp{end}.
13485 (@value{GDBP}) @b{collect @var{data}} // collect some data
13487 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13489 (@value{GDBP}) @b{end} // signals the end of actions.
13492 In the following example, the action list begins with @code{collect}
13493 commands indicating the things to be collected when the tracepoint is
13494 hit. Then, in order to single-step and collect additional data
13495 following the tracepoint, a @code{while-stepping} command is used,
13496 followed by the list of things to be collected after each step in a
13497 sequence of single steps. The @code{while-stepping} command is
13498 terminated by its own separate @code{end} command. Lastly, the action
13499 list is terminated by an @code{end} command.
13502 (@value{GDBP}) @b{trace foo}
13503 (@value{GDBP}) @b{actions}
13504 Enter actions for tracepoint 1, one per line:
13507 > while-stepping 12
13508 > collect $pc, arr[i]
13513 @kindex collect @r{(tracepoints)}
13514 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13515 Collect values of the given expressions when the tracepoint is hit.
13516 This command accepts a comma-separated list of any valid expressions.
13517 In addition to global, static, or local variables, the following
13518 special arguments are supported:
13522 Collect all registers.
13525 Collect all function arguments.
13528 Collect all local variables.
13531 Collect the return address. This is helpful if you want to see more
13534 @emph{Note:} The return address location can not always be reliably
13535 determined up front, and the wrong address / registers may end up
13536 collected instead. On some architectures the reliability is higher
13537 for tracepoints at function entry, while on others it's the opposite.
13538 When this happens, backtracing will stop because the return address is
13539 found unavailable (unless another collect rule happened to match it).
13542 Collects the number of arguments from the static probe at which the
13543 tracepoint is located.
13544 @xref{Static Probe Points}.
13546 @item $_probe_arg@var{n}
13547 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13548 from the static probe at which the tracepoint is located.
13549 @xref{Static Probe Points}.
13552 @vindex $_sdata@r{, collect}
13553 Collect static tracepoint marker specific data. Only available for
13554 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13555 Lists}. On the UST static tracepoints library backend, an
13556 instrumentation point resembles a @code{printf} function call. The
13557 tracing library is able to collect user specified data formatted to a
13558 character string using the format provided by the programmer that
13559 instrumented the program. Other backends have similar mechanisms.
13560 Here's an example of a UST marker call:
13563 const char master_name[] = "$your_name";
13564 trace_mark(channel1, marker1, "hello %s", master_name)
13567 In this case, collecting @code{$_sdata} collects the string
13568 @samp{hello $yourname}. When analyzing the trace buffer, you can
13569 inspect @samp{$_sdata} like any other variable available to
13573 You can give several consecutive @code{collect} commands, each one
13574 with a single argument, or one @code{collect} command with several
13575 arguments separated by commas; the effect is the same.
13577 The optional @var{mods} changes the usual handling of the arguments.
13578 @code{s} requests that pointers to chars be handled as strings, in
13579 particular collecting the contents of the memory being pointed at, up
13580 to the first zero. The upper bound is by default the value of the
13581 @code{print elements} variable; if @code{s} is followed by a decimal
13582 number, that is the upper bound instead. So for instance
13583 @samp{collect/s25 mystr} collects as many as 25 characters at
13586 The command @code{info scope} (@pxref{Symbols, info scope}) is
13587 particularly useful for figuring out what data to collect.
13589 @kindex teval @r{(tracepoints)}
13590 @item teval @var{expr1}, @var{expr2}, @dots{}
13591 Evaluate the given expressions when the tracepoint is hit. This
13592 command accepts a comma-separated list of expressions. The results
13593 are discarded, so this is mainly useful for assigning values to trace
13594 state variables (@pxref{Trace State Variables}) without adding those
13595 values to the trace buffer, as would be the case if the @code{collect}
13598 @kindex while-stepping @r{(tracepoints)}
13599 @item while-stepping @var{n}
13600 Perform @var{n} single-step instruction traces after the tracepoint,
13601 collecting new data after each step. The @code{while-stepping}
13602 command is followed by the list of what to collect while stepping
13603 (followed by its own @code{end} command):
13606 > while-stepping 12
13607 > collect $regs, myglobal
13613 Note that @code{$pc} is not automatically collected by
13614 @code{while-stepping}; you need to explicitly collect that register if
13615 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13618 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13619 @kindex set default-collect
13620 @cindex default collection action
13621 This variable is a list of expressions to collect at each tracepoint
13622 hit. It is effectively an additional @code{collect} action prepended
13623 to every tracepoint action list. The expressions are parsed
13624 individually for each tracepoint, so for instance a variable named
13625 @code{xyz} may be interpreted as a global for one tracepoint, and a
13626 local for another, as appropriate to the tracepoint's location.
13628 @item show default-collect
13629 @kindex show default-collect
13630 Show the list of expressions that are collected by default at each
13635 @node Listing Tracepoints
13636 @subsection Listing Tracepoints
13639 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13640 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13641 @cindex information about tracepoints
13642 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13643 Display information about the tracepoint @var{num}. If you don't
13644 specify a tracepoint number, displays information about all the
13645 tracepoints defined so far. The format is similar to that used for
13646 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13647 command, simply restricting itself to tracepoints.
13649 A tracepoint's listing may include additional information specific to
13654 its passcount as given by the @code{passcount @var{n}} command
13657 the state about installed on target of each location
13661 (@value{GDBP}) @b{info trace}
13662 Num Type Disp Enb Address What
13663 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13665 collect globfoo, $regs
13670 2 tracepoint keep y <MULTIPLE>
13672 2.1 y 0x0804859c in func4 at change-loc.h:35
13673 installed on target
13674 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13675 installed on target
13676 2.3 y <PENDING> set_tracepoint
13677 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13678 not installed on target
13683 This command can be abbreviated @code{info tp}.
13686 @node Listing Static Tracepoint Markers
13687 @subsection Listing Static Tracepoint Markers
13690 @kindex info static-tracepoint-markers
13691 @cindex information about static tracepoint markers
13692 @item info static-tracepoint-markers
13693 Display information about all static tracepoint markers defined in the
13696 For each marker, the following columns are printed:
13700 An incrementing counter, output to help readability. This is not a
13703 The marker ID, as reported by the target.
13704 @item Enabled or Disabled
13705 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13706 that are not enabled.
13708 Where the marker is in your program, as a memory address.
13710 Where the marker is in the source for your program, as a file and line
13711 number. If the debug information included in the program does not
13712 allow @value{GDBN} to locate the source of the marker, this column
13713 will be left blank.
13717 In addition, the following information may be printed for each marker:
13721 User data passed to the tracing library by the marker call. In the
13722 UST backend, this is the format string passed as argument to the
13724 @item Static tracepoints probing the marker
13725 The list of static tracepoints attached to the marker.
13729 (@value{GDBP}) info static-tracepoint-markers
13730 Cnt ID Enb Address What
13731 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13732 Data: number1 %d number2 %d
13733 Probed by static tracepoints: #2
13734 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13740 @node Starting and Stopping Trace Experiments
13741 @subsection Starting and Stopping Trace Experiments
13744 @kindex tstart [ @var{notes} ]
13745 @cindex start a new trace experiment
13746 @cindex collected data discarded
13748 This command starts the trace experiment, and begins collecting data.
13749 It has the side effect of discarding all the data collected in the
13750 trace buffer during the previous trace experiment. If any arguments
13751 are supplied, they are taken as a note and stored with the trace
13752 experiment's state. The notes may be arbitrary text, and are
13753 especially useful with disconnected tracing in a multi-user context;
13754 the notes can explain what the trace is doing, supply user contact
13755 information, and so forth.
13757 @kindex tstop [ @var{notes} ]
13758 @cindex stop a running trace experiment
13760 This command stops the trace experiment. If any arguments are
13761 supplied, they are recorded with the experiment as a note. This is
13762 useful if you are stopping a trace started by someone else, for
13763 instance if the trace is interfering with the system's behavior and
13764 needs to be stopped quickly.
13766 @strong{Note}: a trace experiment and data collection may stop
13767 automatically if any tracepoint's passcount is reached
13768 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13771 @cindex status of trace data collection
13772 @cindex trace experiment, status of
13774 This command displays the status of the current trace data
13778 Here is an example of the commands we described so far:
13781 (@value{GDBP}) @b{trace gdb_c_test}
13782 (@value{GDBP}) @b{actions}
13783 Enter actions for tracepoint #1, one per line.
13784 > collect $regs,$locals,$args
13785 > while-stepping 11
13789 (@value{GDBP}) @b{tstart}
13790 [time passes @dots{}]
13791 (@value{GDBP}) @b{tstop}
13794 @anchor{disconnected tracing}
13795 @cindex disconnected tracing
13796 You can choose to continue running the trace experiment even if
13797 @value{GDBN} disconnects from the target, voluntarily or
13798 involuntarily. For commands such as @code{detach}, the debugger will
13799 ask what you want to do with the trace. But for unexpected
13800 terminations (@value{GDBN} crash, network outage), it would be
13801 unfortunate to lose hard-won trace data, so the variable
13802 @code{disconnected-tracing} lets you decide whether the trace should
13803 continue running without @value{GDBN}.
13806 @item set disconnected-tracing on
13807 @itemx set disconnected-tracing off
13808 @kindex set disconnected-tracing
13809 Choose whether a tracing run should continue to run if @value{GDBN}
13810 has disconnected from the target. Note that @code{detach} or
13811 @code{quit} will ask you directly what to do about a running trace no
13812 matter what this variable's setting, so the variable is mainly useful
13813 for handling unexpected situations, such as loss of the network.
13815 @item show disconnected-tracing
13816 @kindex show disconnected-tracing
13817 Show the current choice for disconnected tracing.
13821 When you reconnect to the target, the trace experiment may or may not
13822 still be running; it might have filled the trace buffer in the
13823 meantime, or stopped for one of the other reasons. If it is running,
13824 it will continue after reconnection.
13826 Upon reconnection, the target will upload information about the
13827 tracepoints in effect. @value{GDBN} will then compare that
13828 information to the set of tracepoints currently defined, and attempt
13829 to match them up, allowing for the possibility that the numbers may
13830 have changed due to creation and deletion in the meantime. If one of
13831 the target's tracepoints does not match any in @value{GDBN}, the
13832 debugger will create a new tracepoint, so that you have a number with
13833 which to specify that tracepoint. This matching-up process is
13834 necessarily heuristic, and it may result in useless tracepoints being
13835 created; you may simply delete them if they are of no use.
13837 @cindex circular trace buffer
13838 If your target agent supports a @dfn{circular trace buffer}, then you
13839 can run a trace experiment indefinitely without filling the trace
13840 buffer; when space runs out, the agent deletes already-collected trace
13841 frames, oldest first, until there is enough room to continue
13842 collecting. This is especially useful if your tracepoints are being
13843 hit too often, and your trace gets terminated prematurely because the
13844 buffer is full. To ask for a circular trace buffer, simply set
13845 @samp{circular-trace-buffer} to on. You can set this at any time,
13846 including during tracing; if the agent can do it, it will change
13847 buffer handling on the fly, otherwise it will not take effect until
13851 @item set circular-trace-buffer on
13852 @itemx set circular-trace-buffer off
13853 @kindex set circular-trace-buffer
13854 Choose whether a tracing run should use a linear or circular buffer
13855 for trace data. A linear buffer will not lose any trace data, but may
13856 fill up prematurely, while a circular buffer will discard old trace
13857 data, but it will have always room for the latest tracepoint hits.
13859 @item show circular-trace-buffer
13860 @kindex show circular-trace-buffer
13861 Show the current choice for the trace buffer. Note that this may not
13862 match the agent's current buffer handling, nor is it guaranteed to
13863 match the setting that might have been in effect during a past run,
13864 for instance if you are looking at frames from a trace file.
13869 @item set trace-buffer-size @var{n}
13870 @itemx set trace-buffer-size unlimited
13871 @kindex set trace-buffer-size
13872 Request that the target use a trace buffer of @var{n} bytes. Not all
13873 targets will honor the request; they may have a compiled-in size for
13874 the trace buffer, or some other limitation. Set to a value of
13875 @code{unlimited} or @code{-1} to let the target use whatever size it
13876 likes. This is also the default.
13878 @item show trace-buffer-size
13879 @kindex show trace-buffer-size
13880 Show the current requested size for the trace buffer. Note that this
13881 will only match the actual size if the target supports size-setting,
13882 and was able to handle the requested size. For instance, if the
13883 target can only change buffer size between runs, this variable will
13884 not reflect the change until the next run starts. Use @code{tstatus}
13885 to get a report of the actual buffer size.
13889 @item set trace-user @var{text}
13890 @kindex set trace-user
13892 @item show trace-user
13893 @kindex show trace-user
13895 @item set trace-notes @var{text}
13896 @kindex set trace-notes
13897 Set the trace run's notes.
13899 @item show trace-notes
13900 @kindex show trace-notes
13901 Show the trace run's notes.
13903 @item set trace-stop-notes @var{text}
13904 @kindex set trace-stop-notes
13905 Set the trace run's stop notes. The handling of the note is as for
13906 @code{tstop} arguments; the set command is convenient way to fix a
13907 stop note that is mistaken or incomplete.
13909 @item show trace-stop-notes
13910 @kindex show trace-stop-notes
13911 Show the trace run's stop notes.
13915 @node Tracepoint Restrictions
13916 @subsection Tracepoint Restrictions
13918 @cindex tracepoint restrictions
13919 There are a number of restrictions on the use of tracepoints. As
13920 described above, tracepoint data gathering occurs on the target
13921 without interaction from @value{GDBN}. Thus the full capabilities of
13922 the debugger are not available during data gathering, and then at data
13923 examination time, you will be limited by only having what was
13924 collected. The following items describe some common problems, but it
13925 is not exhaustive, and you may run into additional difficulties not
13931 Tracepoint expressions are intended to gather objects (lvalues). Thus
13932 the full flexibility of GDB's expression evaluator is not available.
13933 You cannot call functions, cast objects to aggregate types, access
13934 convenience variables or modify values (except by assignment to trace
13935 state variables). Some language features may implicitly call
13936 functions (for instance Objective-C fields with accessors), and therefore
13937 cannot be collected either.
13940 Collection of local variables, either individually or in bulk with
13941 @code{$locals} or @code{$args}, during @code{while-stepping} may
13942 behave erratically. The stepping action may enter a new scope (for
13943 instance by stepping into a function), or the location of the variable
13944 may change (for instance it is loaded into a register). The
13945 tracepoint data recorded uses the location information for the
13946 variables that is correct for the tracepoint location. When the
13947 tracepoint is created, it is not possible, in general, to determine
13948 where the steps of a @code{while-stepping} sequence will advance the
13949 program---particularly if a conditional branch is stepped.
13952 Collection of an incompletely-initialized or partially-destroyed object
13953 may result in something that @value{GDBN} cannot display, or displays
13954 in a misleading way.
13957 When @value{GDBN} displays a pointer to character it automatically
13958 dereferences the pointer to also display characters of the string
13959 being pointed to. However, collecting the pointer during tracing does
13960 not automatically collect the string. You need to explicitly
13961 dereference the pointer and provide size information if you want to
13962 collect not only the pointer, but the memory pointed to. For example,
13963 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13967 It is not possible to collect a complete stack backtrace at a
13968 tracepoint. Instead, you may collect the registers and a few hundred
13969 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13970 (adjust to use the name of the actual stack pointer register on your
13971 target architecture, and the amount of stack you wish to capture).
13972 Then the @code{backtrace} command will show a partial backtrace when
13973 using a trace frame. The number of stack frames that can be examined
13974 depends on the sizes of the frames in the collected stack. Note that
13975 if you ask for a block so large that it goes past the bottom of the
13976 stack, the target agent may report an error trying to read from an
13980 If you do not collect registers at a tracepoint, @value{GDBN} can
13981 infer that the value of @code{$pc} must be the same as the address of
13982 the tracepoint and use that when you are looking at a trace frame
13983 for that tracepoint. However, this cannot work if the tracepoint has
13984 multiple locations (for instance if it was set in a function that was
13985 inlined), or if it has a @code{while-stepping} loop. In those cases
13986 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13991 @node Analyze Collected Data
13992 @section Using the Collected Data
13994 After the tracepoint experiment ends, you use @value{GDBN} commands
13995 for examining the trace data. The basic idea is that each tracepoint
13996 collects a trace @dfn{snapshot} every time it is hit and another
13997 snapshot every time it single-steps. All these snapshots are
13998 consecutively numbered from zero and go into a buffer, and you can
13999 examine them later. The way you examine them is to @dfn{focus} on a
14000 specific trace snapshot. When the remote stub is focused on a trace
14001 snapshot, it will respond to all @value{GDBN} requests for memory and
14002 registers by reading from the buffer which belongs to that snapshot,
14003 rather than from @emph{real} memory or registers of the program being
14004 debugged. This means that @strong{all} @value{GDBN} commands
14005 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14006 behave as if we were currently debugging the program state as it was
14007 when the tracepoint occurred. Any requests for data that are not in
14008 the buffer will fail.
14011 * tfind:: How to select a trace snapshot
14012 * tdump:: How to display all data for a snapshot
14013 * save tracepoints:: How to save tracepoints for a future run
14017 @subsection @code{tfind @var{n}}
14020 @cindex select trace snapshot
14021 @cindex find trace snapshot
14022 The basic command for selecting a trace snapshot from the buffer is
14023 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14024 counting from zero. If no argument @var{n} is given, the next
14025 snapshot is selected.
14027 Here are the various forms of using the @code{tfind} command.
14031 Find the first snapshot in the buffer. This is a synonym for
14032 @code{tfind 0} (since 0 is the number of the first snapshot).
14035 Stop debugging trace snapshots, resume @emph{live} debugging.
14038 Same as @samp{tfind none}.
14041 No argument means find the next trace snapshot or find the first
14042 one if no trace snapshot is selected.
14045 Find the previous trace snapshot before the current one. This permits
14046 retracing earlier steps.
14048 @item tfind tracepoint @var{num}
14049 Find the next snapshot associated with tracepoint @var{num}. Search
14050 proceeds forward from the last examined trace snapshot. If no
14051 argument @var{num} is given, it means find the next snapshot collected
14052 for the same tracepoint as the current snapshot.
14054 @item tfind pc @var{addr}
14055 Find the next snapshot associated with the value @var{addr} of the
14056 program counter. Search proceeds forward from the last examined trace
14057 snapshot. If no argument @var{addr} is given, it means find the next
14058 snapshot with the same value of PC as the current snapshot.
14060 @item tfind outside @var{addr1}, @var{addr2}
14061 Find the next snapshot whose PC is outside the given range of
14062 addresses (exclusive).
14064 @item tfind range @var{addr1}, @var{addr2}
14065 Find the next snapshot whose PC is between @var{addr1} and
14066 @var{addr2} (inclusive).
14068 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14069 Find the next snapshot associated with the source line @var{n}. If
14070 the optional argument @var{file} is given, refer to line @var{n} in
14071 that source file. Search proceeds forward from the last examined
14072 trace snapshot. If no argument @var{n} is given, it means find the
14073 next line other than the one currently being examined; thus saying
14074 @code{tfind line} repeatedly can appear to have the same effect as
14075 stepping from line to line in a @emph{live} debugging session.
14078 The default arguments for the @code{tfind} commands are specifically
14079 designed to make it easy to scan through the trace buffer. For
14080 instance, @code{tfind} with no argument selects the next trace
14081 snapshot, and @code{tfind -} with no argument selects the previous
14082 trace snapshot. So, by giving one @code{tfind} command, and then
14083 simply hitting @key{RET} repeatedly you can examine all the trace
14084 snapshots in order. Or, by saying @code{tfind -} and then hitting
14085 @key{RET} repeatedly you can examine the snapshots in reverse order.
14086 The @code{tfind line} command with no argument selects the snapshot
14087 for the next source line executed. The @code{tfind pc} command with
14088 no argument selects the next snapshot with the same program counter
14089 (PC) as the current frame. The @code{tfind tracepoint} command with
14090 no argument selects the next trace snapshot collected by the same
14091 tracepoint as the current one.
14093 In addition to letting you scan through the trace buffer manually,
14094 these commands make it easy to construct @value{GDBN} scripts that
14095 scan through the trace buffer and print out whatever collected data
14096 you are interested in. Thus, if we want to examine the PC, FP, and SP
14097 registers from each trace frame in the buffer, we can say this:
14100 (@value{GDBP}) @b{tfind start}
14101 (@value{GDBP}) @b{while ($trace_frame != -1)}
14102 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14103 $trace_frame, $pc, $sp, $fp
14107 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14108 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14109 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14110 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14111 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14112 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14113 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14114 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14115 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14116 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14117 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14120 Or, if we want to examine the variable @code{X} at each source line in
14124 (@value{GDBP}) @b{tfind start}
14125 (@value{GDBP}) @b{while ($trace_frame != -1)}
14126 > printf "Frame %d, X == %d\n", $trace_frame, X
14136 @subsection @code{tdump}
14138 @cindex dump all data collected at tracepoint
14139 @cindex tracepoint data, display
14141 This command takes no arguments. It prints all the data collected at
14142 the current trace snapshot.
14145 (@value{GDBP}) @b{trace 444}
14146 (@value{GDBP}) @b{actions}
14147 Enter actions for tracepoint #2, one per line:
14148 > collect $regs, $locals, $args, gdb_long_test
14151 (@value{GDBP}) @b{tstart}
14153 (@value{GDBP}) @b{tfind line 444}
14154 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14156 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14158 (@value{GDBP}) @b{tdump}
14159 Data collected at tracepoint 2, trace frame 1:
14160 d0 0xc4aa0085 -995491707
14164 d4 0x71aea3d 119204413
14167 d7 0x380035 3670069
14168 a0 0x19e24a 1696330
14169 a1 0x3000668 50333288
14171 a3 0x322000 3284992
14172 a4 0x3000698 50333336
14173 a5 0x1ad3cc 1758156
14174 fp 0x30bf3c 0x30bf3c
14175 sp 0x30bf34 0x30bf34
14177 pc 0x20b2c8 0x20b2c8
14181 p = 0x20e5b4 "gdb-test"
14188 gdb_long_test = 17 '\021'
14193 @code{tdump} works by scanning the tracepoint's current collection
14194 actions and printing the value of each expression listed. So
14195 @code{tdump} can fail, if after a run, you change the tracepoint's
14196 actions to mention variables that were not collected during the run.
14198 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14199 uses the collected value of @code{$pc} to distinguish between trace
14200 frames that were collected at the tracepoint hit, and frames that were
14201 collected while stepping. This allows it to correctly choose whether
14202 to display the basic list of collections, or the collections from the
14203 body of the while-stepping loop. However, if @code{$pc} was not collected,
14204 then @code{tdump} will always attempt to dump using the basic collection
14205 list, and may fail if a while-stepping frame does not include all the
14206 same data that is collected at the tracepoint hit.
14207 @c This is getting pretty arcane, example would be good.
14209 @node save tracepoints
14210 @subsection @code{save tracepoints @var{filename}}
14211 @kindex save tracepoints
14212 @kindex save-tracepoints
14213 @cindex save tracepoints for future sessions
14215 This command saves all current tracepoint definitions together with
14216 their actions and passcounts, into a file @file{@var{filename}}
14217 suitable for use in a later debugging session. To read the saved
14218 tracepoint definitions, use the @code{source} command (@pxref{Command
14219 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14220 alias for @w{@code{save tracepoints}}
14222 @node Tracepoint Variables
14223 @section Convenience Variables for Tracepoints
14224 @cindex tracepoint variables
14225 @cindex convenience variables for tracepoints
14228 @vindex $trace_frame
14229 @item (int) $trace_frame
14230 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14231 snapshot is selected.
14233 @vindex $tracepoint
14234 @item (int) $tracepoint
14235 The tracepoint for the current trace snapshot.
14237 @vindex $trace_line
14238 @item (int) $trace_line
14239 The line number for the current trace snapshot.
14241 @vindex $trace_file
14242 @item (char []) $trace_file
14243 The source file for the current trace snapshot.
14245 @vindex $trace_func
14246 @item (char []) $trace_func
14247 The name of the function containing @code{$tracepoint}.
14250 Note: @code{$trace_file} is not suitable for use in @code{printf},
14251 use @code{output} instead.
14253 Here's a simple example of using these convenience variables for
14254 stepping through all the trace snapshots and printing some of their
14255 data. Note that these are not the same as trace state variables,
14256 which are managed by the target.
14259 (@value{GDBP}) @b{tfind start}
14261 (@value{GDBP}) @b{while $trace_frame != -1}
14262 > output $trace_file
14263 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14269 @section Using Trace Files
14270 @cindex trace files
14272 In some situations, the target running a trace experiment may no
14273 longer be available; perhaps it crashed, or the hardware was needed
14274 for a different activity. To handle these cases, you can arrange to
14275 dump the trace data into a file, and later use that file as a source
14276 of trace data, via the @code{target tfile} command.
14281 @item tsave [ -r ] @var{filename}
14282 @itemx tsave [-ctf] @var{dirname}
14283 Save the trace data to @var{filename}. By default, this command
14284 assumes that @var{filename} refers to the host filesystem, so if
14285 necessary @value{GDBN} will copy raw trace data up from the target and
14286 then save it. If the target supports it, you can also supply the
14287 optional argument @code{-r} (``remote'') to direct the target to save
14288 the data directly into @var{filename} in its own filesystem, which may be
14289 more efficient if the trace buffer is very large. (Note, however, that
14290 @code{target tfile} can only read from files accessible to the host.)
14291 By default, this command will save trace frame in tfile format.
14292 You can supply the optional argument @code{-ctf} to save data in CTF
14293 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14294 that can be shared by multiple debugging and tracing tools. Please go to
14295 @indicateurl{http://www.efficios.com/ctf} to get more information.
14297 @kindex target tfile
14301 @item target tfile @var{filename}
14302 @itemx target ctf @var{dirname}
14303 Use the file named @var{filename} or directory named @var{dirname} as
14304 a source of trace data. Commands that examine data work as they do with
14305 a live target, but it is not possible to run any new trace experiments.
14306 @code{tstatus} will report the state of the trace run at the moment
14307 the data was saved, as well as the current trace frame you are examining.
14308 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14312 (@value{GDBP}) target ctf ctf.ctf
14313 (@value{GDBP}) tfind
14314 Found trace frame 0, tracepoint 2
14315 39 ++a; /* set tracepoint 1 here */
14316 (@value{GDBP}) tdump
14317 Data collected at tracepoint 2, trace frame 0:
14321 c = @{"123", "456", "789", "123", "456", "789"@}
14322 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14330 @chapter Debugging Programs That Use Overlays
14333 If your program is too large to fit completely in your target system's
14334 memory, you can sometimes use @dfn{overlays} to work around this
14335 problem. @value{GDBN} provides some support for debugging programs that
14339 * How Overlays Work:: A general explanation of overlays.
14340 * Overlay Commands:: Managing overlays in @value{GDBN}.
14341 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14342 mapped by asking the inferior.
14343 * Overlay Sample Program:: A sample program using overlays.
14346 @node How Overlays Work
14347 @section How Overlays Work
14348 @cindex mapped overlays
14349 @cindex unmapped overlays
14350 @cindex load address, overlay's
14351 @cindex mapped address
14352 @cindex overlay area
14354 Suppose you have a computer whose instruction address space is only 64
14355 kilobytes long, but which has much more memory which can be accessed by
14356 other means: special instructions, segment registers, or memory
14357 management hardware, for example. Suppose further that you want to
14358 adapt a program which is larger than 64 kilobytes to run on this system.
14360 One solution is to identify modules of your program which are relatively
14361 independent, and need not call each other directly; call these modules
14362 @dfn{overlays}. Separate the overlays from the main program, and place
14363 their machine code in the larger memory. Place your main program in
14364 instruction memory, but leave at least enough space there to hold the
14365 largest overlay as well.
14367 Now, to call a function located in an overlay, you must first copy that
14368 overlay's machine code from the large memory into the space set aside
14369 for it in the instruction memory, and then jump to its entry point
14372 @c NB: In the below the mapped area's size is greater or equal to the
14373 @c size of all overlays. This is intentional to remind the developer
14374 @c that overlays don't necessarily need to be the same size.
14378 Data Instruction Larger
14379 Address Space Address Space Address Space
14380 +-----------+ +-----------+ +-----------+
14382 +-----------+ +-----------+ +-----------+<-- overlay 1
14383 | program | | main | .----| overlay 1 | load address
14384 | variables | | program | | +-----------+
14385 | and heap | | | | | |
14386 +-----------+ | | | +-----------+<-- overlay 2
14387 | | +-----------+ | | | load address
14388 +-----------+ | | | .-| overlay 2 |
14390 mapped --->+-----------+ | | +-----------+
14391 address | | | | | |
14392 | overlay | <-' | | |
14393 | area | <---' +-----------+<-- overlay 3
14394 | | <---. | | load address
14395 +-----------+ `--| overlay 3 |
14402 @anchor{A code overlay}A code overlay
14406 The diagram (@pxref{A code overlay}) shows a system with separate data
14407 and instruction address spaces. To map an overlay, the program copies
14408 its code from the larger address space to the instruction address space.
14409 Since the overlays shown here all use the same mapped address, only one
14410 may be mapped at a time. For a system with a single address space for
14411 data and instructions, the diagram would be similar, except that the
14412 program variables and heap would share an address space with the main
14413 program and the overlay area.
14415 An overlay loaded into instruction memory and ready for use is called a
14416 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14417 instruction memory. An overlay not present (or only partially present)
14418 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14419 is its address in the larger memory. The mapped address is also called
14420 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14421 called the @dfn{load memory address}, or @dfn{LMA}.
14423 Unfortunately, overlays are not a completely transparent way to adapt a
14424 program to limited instruction memory. They introduce a new set of
14425 global constraints you must keep in mind as you design your program:
14430 Before calling or returning to a function in an overlay, your program
14431 must make sure that overlay is actually mapped. Otherwise, the call or
14432 return will transfer control to the right address, but in the wrong
14433 overlay, and your program will probably crash.
14436 If the process of mapping an overlay is expensive on your system, you
14437 will need to choose your overlays carefully to minimize their effect on
14438 your program's performance.
14441 The executable file you load onto your system must contain each
14442 overlay's instructions, appearing at the overlay's load address, not its
14443 mapped address. However, each overlay's instructions must be relocated
14444 and its symbols defined as if the overlay were at its mapped address.
14445 You can use GNU linker scripts to specify different load and relocation
14446 addresses for pieces of your program; see @ref{Overlay Description,,,
14447 ld.info, Using ld: the GNU linker}.
14450 The procedure for loading executable files onto your system must be able
14451 to load their contents into the larger address space as well as the
14452 instruction and data spaces.
14456 The overlay system described above is rather simple, and could be
14457 improved in many ways:
14462 If your system has suitable bank switch registers or memory management
14463 hardware, you could use those facilities to make an overlay's load area
14464 contents simply appear at their mapped address in instruction space.
14465 This would probably be faster than copying the overlay to its mapped
14466 area in the usual way.
14469 If your overlays are small enough, you could set aside more than one
14470 overlay area, and have more than one overlay mapped at a time.
14473 You can use overlays to manage data, as well as instructions. In
14474 general, data overlays are even less transparent to your design than
14475 code overlays: whereas code overlays only require care when you call or
14476 return to functions, data overlays require care every time you access
14477 the data. Also, if you change the contents of a data overlay, you
14478 must copy its contents back out to its load address before you can copy a
14479 different data overlay into the same mapped area.
14484 @node Overlay Commands
14485 @section Overlay Commands
14487 To use @value{GDBN}'s overlay support, each overlay in your program must
14488 correspond to a separate section of the executable file. The section's
14489 virtual memory address and load memory address must be the overlay's
14490 mapped and load addresses. Identifying overlays with sections allows
14491 @value{GDBN} to determine the appropriate address of a function or
14492 variable, depending on whether the overlay is mapped or not.
14494 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14495 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14500 Disable @value{GDBN}'s overlay support. When overlay support is
14501 disabled, @value{GDBN} assumes that all functions and variables are
14502 always present at their mapped addresses. By default, @value{GDBN}'s
14503 overlay support is disabled.
14505 @item overlay manual
14506 @cindex manual overlay debugging
14507 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14508 relies on you to tell it which overlays are mapped, and which are not,
14509 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14510 commands described below.
14512 @item overlay map-overlay @var{overlay}
14513 @itemx overlay map @var{overlay}
14514 @cindex map an overlay
14515 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14516 be the name of the object file section containing the overlay. When an
14517 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14518 functions and variables at their mapped addresses. @value{GDBN} assumes
14519 that any other overlays whose mapped ranges overlap that of
14520 @var{overlay} are now unmapped.
14522 @item overlay unmap-overlay @var{overlay}
14523 @itemx overlay unmap @var{overlay}
14524 @cindex unmap an overlay
14525 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14526 must be the name of the object file section containing the overlay.
14527 When an overlay is unmapped, @value{GDBN} assumes it can find the
14528 overlay's functions and variables at their load addresses.
14531 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14532 consults a data structure the overlay manager maintains in the inferior
14533 to see which overlays are mapped. For details, see @ref{Automatic
14534 Overlay Debugging}.
14536 @item overlay load-target
14537 @itemx overlay load
14538 @cindex reloading the overlay table
14539 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14540 re-reads the table @value{GDBN} automatically each time the inferior
14541 stops, so this command should only be necessary if you have changed the
14542 overlay mapping yourself using @value{GDBN}. This command is only
14543 useful when using automatic overlay debugging.
14545 @item overlay list-overlays
14546 @itemx overlay list
14547 @cindex listing mapped overlays
14548 Display a list of the overlays currently mapped, along with their mapped
14549 addresses, load addresses, and sizes.
14553 Normally, when @value{GDBN} prints a code address, it includes the name
14554 of the function the address falls in:
14557 (@value{GDBP}) print main
14558 $3 = @{int ()@} 0x11a0 <main>
14561 When overlay debugging is enabled, @value{GDBN} recognizes code in
14562 unmapped overlays, and prints the names of unmapped functions with
14563 asterisks around them. For example, if @code{foo} is a function in an
14564 unmapped overlay, @value{GDBN} prints it this way:
14567 (@value{GDBP}) overlay list
14568 No sections are mapped.
14569 (@value{GDBP}) print foo
14570 $5 = @{int (int)@} 0x100000 <*foo*>
14573 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14577 (@value{GDBP}) overlay list
14578 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14579 mapped at 0x1016 - 0x104a
14580 (@value{GDBP}) print foo
14581 $6 = @{int (int)@} 0x1016 <foo>
14584 When overlay debugging is enabled, @value{GDBN} can find the correct
14585 address for functions and variables in an overlay, whether or not the
14586 overlay is mapped. This allows most @value{GDBN} commands, like
14587 @code{break} and @code{disassemble}, to work normally, even on unmapped
14588 code. However, @value{GDBN}'s breakpoint support has some limitations:
14592 @cindex breakpoints in overlays
14593 @cindex overlays, setting breakpoints in
14594 You can set breakpoints in functions in unmapped overlays, as long as
14595 @value{GDBN} can write to the overlay at its load address.
14597 @value{GDBN} can not set hardware or simulator-based breakpoints in
14598 unmapped overlays. However, if you set a breakpoint at the end of your
14599 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14600 you are using manual overlay management), @value{GDBN} will re-set its
14601 breakpoints properly.
14605 @node Automatic Overlay Debugging
14606 @section Automatic Overlay Debugging
14607 @cindex automatic overlay debugging
14609 @value{GDBN} can automatically track which overlays are mapped and which
14610 are not, given some simple co-operation from the overlay manager in the
14611 inferior. If you enable automatic overlay debugging with the
14612 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14613 looks in the inferior's memory for certain variables describing the
14614 current state of the overlays.
14616 Here are the variables your overlay manager must define to support
14617 @value{GDBN}'s automatic overlay debugging:
14621 @item @code{_ovly_table}:
14622 This variable must be an array of the following structures:
14627 /* The overlay's mapped address. */
14630 /* The size of the overlay, in bytes. */
14631 unsigned long size;
14633 /* The overlay's load address. */
14636 /* Non-zero if the overlay is currently mapped;
14638 unsigned long mapped;
14642 @item @code{_novlys}:
14643 This variable must be a four-byte signed integer, holding the total
14644 number of elements in @code{_ovly_table}.
14648 To decide whether a particular overlay is mapped or not, @value{GDBN}
14649 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14650 @code{lma} members equal the VMA and LMA of the overlay's section in the
14651 executable file. When @value{GDBN} finds a matching entry, it consults
14652 the entry's @code{mapped} member to determine whether the overlay is
14655 In addition, your overlay manager may define a function called
14656 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14657 will silently set a breakpoint there. If the overlay manager then
14658 calls this function whenever it has changed the overlay table, this
14659 will enable @value{GDBN} to accurately keep track of which overlays
14660 are in program memory, and update any breakpoints that may be set
14661 in overlays. This will allow breakpoints to work even if the
14662 overlays are kept in ROM or other non-writable memory while they
14663 are not being executed.
14665 @node Overlay Sample Program
14666 @section Overlay Sample Program
14667 @cindex overlay example program
14669 When linking a program which uses overlays, you must place the overlays
14670 at their load addresses, while relocating them to run at their mapped
14671 addresses. To do this, you must write a linker script (@pxref{Overlay
14672 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14673 since linker scripts are specific to a particular host system, target
14674 architecture, and target memory layout, this manual cannot provide
14675 portable sample code demonstrating @value{GDBN}'s overlay support.
14677 However, the @value{GDBN} source distribution does contain an overlaid
14678 program, with linker scripts for a few systems, as part of its test
14679 suite. The program consists of the following files from
14680 @file{gdb/testsuite/gdb.base}:
14684 The main program file.
14686 A simple overlay manager, used by @file{overlays.c}.
14691 Overlay modules, loaded and used by @file{overlays.c}.
14694 Linker scripts for linking the test program on the @code{d10v-elf}
14695 and @code{m32r-elf} targets.
14698 You can build the test program using the @code{d10v-elf} GCC
14699 cross-compiler like this:
14702 $ d10v-elf-gcc -g -c overlays.c
14703 $ d10v-elf-gcc -g -c ovlymgr.c
14704 $ d10v-elf-gcc -g -c foo.c
14705 $ d10v-elf-gcc -g -c bar.c
14706 $ d10v-elf-gcc -g -c baz.c
14707 $ d10v-elf-gcc -g -c grbx.c
14708 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14709 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14712 The build process is identical for any other architecture, except that
14713 you must substitute the appropriate compiler and linker script for the
14714 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14718 @chapter Using @value{GDBN} with Different Languages
14721 Although programming languages generally have common aspects, they are
14722 rarely expressed in the same manner. For instance, in ANSI C,
14723 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14724 Modula-2, it is accomplished by @code{p^}. Values can also be
14725 represented (and displayed) differently. Hex numbers in C appear as
14726 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14728 @cindex working language
14729 Language-specific information is built into @value{GDBN} for some languages,
14730 allowing you to express operations like the above in your program's
14731 native language, and allowing @value{GDBN} to output values in a manner
14732 consistent with the syntax of your program's native language. The
14733 language you use to build expressions is called the @dfn{working
14737 * Setting:: Switching between source languages
14738 * Show:: Displaying the language
14739 * Checks:: Type and range checks
14740 * Supported Languages:: Supported languages
14741 * Unsupported Languages:: Unsupported languages
14745 @section Switching Between Source Languages
14747 There are two ways to control the working language---either have @value{GDBN}
14748 set it automatically, or select it manually yourself. You can use the
14749 @code{set language} command for either purpose. On startup, @value{GDBN}
14750 defaults to setting the language automatically. The working language is
14751 used to determine how expressions you type are interpreted, how values
14754 In addition to the working language, every source file that
14755 @value{GDBN} knows about has its own working language. For some object
14756 file formats, the compiler might indicate which language a particular
14757 source file is in. However, most of the time @value{GDBN} infers the
14758 language from the name of the file. The language of a source file
14759 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14760 show each frame appropriately for its own language. There is no way to
14761 set the language of a source file from within @value{GDBN}, but you can
14762 set the language associated with a filename extension. @xref{Show, ,
14763 Displaying the Language}.
14765 This is most commonly a problem when you use a program, such
14766 as @code{cfront} or @code{f2c}, that generates C but is written in
14767 another language. In that case, make the
14768 program use @code{#line} directives in its C output; that way
14769 @value{GDBN} will know the correct language of the source code of the original
14770 program, and will display that source code, not the generated C code.
14773 * Filenames:: Filename extensions and languages.
14774 * Manually:: Setting the working language manually
14775 * Automatically:: Having @value{GDBN} infer the source language
14779 @subsection List of Filename Extensions and Languages
14781 If a source file name ends in one of the following extensions, then
14782 @value{GDBN} infers that its language is the one indicated.
14800 C@t{++} source file
14806 Objective-C source file
14810 Fortran source file
14813 Modula-2 source file
14817 Assembler source file. This actually behaves almost like C, but
14818 @value{GDBN} does not skip over function prologues when stepping.
14821 In addition, you may set the language associated with a filename
14822 extension. @xref{Show, , Displaying the Language}.
14825 @subsection Setting the Working Language
14827 If you allow @value{GDBN} to set the language automatically,
14828 expressions are interpreted the same way in your debugging session and
14831 @kindex set language
14832 If you wish, you may set the language manually. To do this, issue the
14833 command @samp{set language @var{lang}}, where @var{lang} is the name of
14834 a language, such as
14835 @code{c} or @code{modula-2}.
14836 For a list of the supported languages, type @samp{set language}.
14838 Setting the language manually prevents @value{GDBN} from updating the working
14839 language automatically. This can lead to confusion if you try
14840 to debug a program when the working language is not the same as the
14841 source language, when an expression is acceptable to both
14842 languages---but means different things. For instance, if the current
14843 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14851 might not have the effect you intended. In C, this means to add
14852 @code{b} and @code{c} and place the result in @code{a}. The result
14853 printed would be the value of @code{a}. In Modula-2, this means to compare
14854 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14856 @node Automatically
14857 @subsection Having @value{GDBN} Infer the Source Language
14859 To have @value{GDBN} set the working language automatically, use
14860 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14861 then infers the working language. That is, when your program stops in a
14862 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14863 working language to the language recorded for the function in that
14864 frame. If the language for a frame is unknown (that is, if the function
14865 or block corresponding to the frame was defined in a source file that
14866 does not have a recognized extension), the current working language is
14867 not changed, and @value{GDBN} issues a warning.
14869 This may not seem necessary for most programs, which are written
14870 entirely in one source language. However, program modules and libraries
14871 written in one source language can be used by a main program written in
14872 a different source language. Using @samp{set language auto} in this
14873 case frees you from having to set the working language manually.
14876 @section Displaying the Language
14878 The following commands help you find out which language is the
14879 working language, and also what language source files were written in.
14882 @item show language
14883 @anchor{show language}
14884 @kindex show language
14885 Display the current working language. This is the
14886 language you can use with commands such as @code{print} to
14887 build and compute expressions that may involve variables in your program.
14890 @kindex info frame@r{, show the source language}
14891 Display the source language for this frame. This language becomes the
14892 working language if you use an identifier from this frame.
14893 @xref{Frame Info, ,Information about a Frame}, to identify the other
14894 information listed here.
14897 @kindex info source@r{, show the source language}
14898 Display the source language of this source file.
14899 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14900 information listed here.
14903 In unusual circumstances, you may have source files with extensions
14904 not in the standard list. You can then set the extension associated
14905 with a language explicitly:
14908 @item set extension-language @var{ext} @var{language}
14909 @kindex set extension-language
14910 Tell @value{GDBN} that source files with extension @var{ext} are to be
14911 assumed as written in the source language @var{language}.
14913 @item info extensions
14914 @kindex info extensions
14915 List all the filename extensions and the associated languages.
14919 @section Type and Range Checking
14921 Some languages are designed to guard you against making seemingly common
14922 errors through a series of compile- and run-time checks. These include
14923 checking the type of arguments to functions and operators and making
14924 sure mathematical overflows are caught at run time. Checks such as
14925 these help to ensure a program's correctness once it has been compiled
14926 by eliminating type mismatches and providing active checks for range
14927 errors when your program is running.
14929 By default @value{GDBN} checks for these errors according to the
14930 rules of the current source language. Although @value{GDBN} does not check
14931 the statements in your program, it can check expressions entered directly
14932 into @value{GDBN} for evaluation via the @code{print} command, for example.
14935 * Type Checking:: An overview of type checking
14936 * Range Checking:: An overview of range checking
14939 @cindex type checking
14940 @cindex checks, type
14941 @node Type Checking
14942 @subsection An Overview of Type Checking
14944 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14945 arguments to operators and functions have to be of the correct type,
14946 otherwise an error occurs. These checks prevent type mismatch
14947 errors from ever causing any run-time problems. For example,
14950 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14952 (@value{GDBP}) print obj.my_method (0)
14955 (@value{GDBP}) print obj.my_method (0x1234)
14956 Cannot resolve method klass::my_method to any overloaded instance
14959 The second example fails because in C@t{++} the integer constant
14960 @samp{0x1234} is not type-compatible with the pointer parameter type.
14962 For the expressions you use in @value{GDBN} commands, you can tell
14963 @value{GDBN} to not enforce strict type checking or
14964 to treat any mismatches as errors and abandon the expression;
14965 When type checking is disabled, @value{GDBN} successfully evaluates
14966 expressions like the second example above.
14968 Even if type checking is off, there may be other reasons
14969 related to type that prevent @value{GDBN} from evaluating an expression.
14970 For instance, @value{GDBN} does not know how to add an @code{int} and
14971 a @code{struct foo}. These particular type errors have nothing to do
14972 with the language in use and usually arise from expressions which make
14973 little sense to evaluate anyway.
14975 @value{GDBN} provides some additional commands for controlling type checking:
14977 @kindex set check type
14978 @kindex show check type
14980 @item set check type on
14981 @itemx set check type off
14982 Set strict type checking on or off. If any type mismatches occur in
14983 evaluating an expression while type checking is on, @value{GDBN} prints a
14984 message and aborts evaluation of the expression.
14986 @item show check type
14987 Show the current setting of type checking and whether @value{GDBN}
14988 is enforcing strict type checking rules.
14991 @cindex range checking
14992 @cindex checks, range
14993 @node Range Checking
14994 @subsection An Overview of Range Checking
14996 In some languages (such as Modula-2), it is an error to exceed the
14997 bounds of a type; this is enforced with run-time checks. Such range
14998 checking is meant to ensure program correctness by making sure
14999 computations do not overflow, or indices on an array element access do
15000 not exceed the bounds of the array.
15002 For expressions you use in @value{GDBN} commands, you can tell
15003 @value{GDBN} to treat range errors in one of three ways: ignore them,
15004 always treat them as errors and abandon the expression, or issue
15005 warnings but evaluate the expression anyway.
15007 A range error can result from numerical overflow, from exceeding an
15008 array index bound, or when you type a constant that is not a member
15009 of any type. Some languages, however, do not treat overflows as an
15010 error. In many implementations of C, mathematical overflow causes the
15011 result to ``wrap around'' to lower values---for example, if @var{m} is
15012 the largest integer value, and @var{s} is the smallest, then
15015 @var{m} + 1 @result{} @var{s}
15018 This, too, is specific to individual languages, and in some cases
15019 specific to individual compilers or machines. @xref{Supported Languages, ,
15020 Supported Languages}, for further details on specific languages.
15022 @value{GDBN} provides some additional commands for controlling the range checker:
15024 @kindex set check range
15025 @kindex show check range
15027 @item set check range auto
15028 Set range checking on or off based on the current working language.
15029 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15032 @item set check range on
15033 @itemx set check range off
15034 Set range checking on or off, overriding the default setting for the
15035 current working language. A warning is issued if the setting does not
15036 match the language default. If a range error occurs and range checking is on,
15037 then a message is printed and evaluation of the expression is aborted.
15039 @item set check range warn
15040 Output messages when the @value{GDBN} range checker detects a range error,
15041 but attempt to evaluate the expression anyway. Evaluating the
15042 expression may still be impossible for other reasons, such as accessing
15043 memory that the process does not own (a typical example from many Unix
15047 Show the current setting of the range checker, and whether or not it is
15048 being set automatically by @value{GDBN}.
15051 @node Supported Languages
15052 @section Supported Languages
15054 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15055 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15056 @c This is false ...
15057 Some @value{GDBN} features may be used in expressions regardless of the
15058 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15059 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15060 ,Expressions}) can be used with the constructs of any supported
15063 The following sections detail to what degree each source language is
15064 supported by @value{GDBN}. These sections are not meant to be language
15065 tutorials or references, but serve only as a reference guide to what the
15066 @value{GDBN} expression parser accepts, and what input and output
15067 formats should look like for different languages. There are many good
15068 books written on each of these languages; please look to these for a
15069 language reference or tutorial.
15072 * C:: C and C@t{++}
15075 * Objective-C:: Objective-C
15076 * OpenCL C:: OpenCL C
15077 * Fortran:: Fortran
15080 * Modula-2:: Modula-2
15085 @subsection C and C@t{++}
15087 @cindex C and C@t{++}
15088 @cindex expressions in C or C@t{++}
15090 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15091 to both languages. Whenever this is the case, we discuss those languages
15095 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15096 @cindex @sc{gnu} C@t{++}
15097 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15098 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15099 effectively, you must compile your C@t{++} programs with a supported
15100 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15101 compiler (@code{aCC}).
15104 * C Operators:: C and C@t{++} operators
15105 * C Constants:: C and C@t{++} constants
15106 * C Plus Plus Expressions:: C@t{++} expressions
15107 * C Defaults:: Default settings for C and C@t{++}
15108 * C Checks:: C and C@t{++} type and range checks
15109 * Debugging C:: @value{GDBN} and C
15110 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15111 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15115 @subsubsection C and C@t{++} Operators
15117 @cindex C and C@t{++} operators
15119 Operators must be defined on values of specific types. For instance,
15120 @code{+} is defined on numbers, but not on structures. Operators are
15121 often defined on groups of types.
15123 For the purposes of C and C@t{++}, the following definitions hold:
15128 @emph{Integral types} include @code{int} with any of its storage-class
15129 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15132 @emph{Floating-point types} include @code{float}, @code{double}, and
15133 @code{long double} (if supported by the target platform).
15136 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15139 @emph{Scalar types} include all of the above.
15144 The following operators are supported. They are listed here
15145 in order of increasing precedence:
15149 The comma or sequencing operator. Expressions in a comma-separated list
15150 are evaluated from left to right, with the result of the entire
15151 expression being the last expression evaluated.
15154 Assignment. The value of an assignment expression is the value
15155 assigned. Defined on scalar types.
15158 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15159 and translated to @w{@code{@var{a} = @var{a op b}}}.
15160 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15161 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15162 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15165 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15166 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15167 should be of an integral type.
15170 Logical @sc{or}. Defined on integral types.
15173 Logical @sc{and}. Defined on integral types.
15176 Bitwise @sc{or}. Defined on integral types.
15179 Bitwise exclusive-@sc{or}. Defined on integral types.
15182 Bitwise @sc{and}. Defined on integral types.
15185 Equality and inequality. Defined on scalar types. The value of these
15186 expressions is 0 for false and non-zero for true.
15188 @item <@r{, }>@r{, }<=@r{, }>=
15189 Less than, greater than, less than or equal, greater than or equal.
15190 Defined on scalar types. The value of these expressions is 0 for false
15191 and non-zero for true.
15194 left shift, and right shift. Defined on integral types.
15197 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15200 Addition and subtraction. Defined on integral types, floating-point types and
15203 @item *@r{, }/@r{, }%
15204 Multiplication, division, and modulus. Multiplication and division are
15205 defined on integral and floating-point types. Modulus is defined on
15209 Increment and decrement. When appearing before a variable, the
15210 operation is performed before the variable is used in an expression;
15211 when appearing after it, the variable's value is used before the
15212 operation takes place.
15215 Pointer dereferencing. Defined on pointer types. Same precedence as
15219 Address operator. Defined on variables. Same precedence as @code{++}.
15221 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15222 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15223 to examine the address
15224 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15228 Negative. Defined on integral and floating-point types. Same
15229 precedence as @code{++}.
15232 Logical negation. Defined on integral types. Same precedence as
15236 Bitwise complement operator. Defined on integral types. Same precedence as
15241 Structure member, and pointer-to-structure member. For convenience,
15242 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15243 pointer based on the stored type information.
15244 Defined on @code{struct} and @code{union} data.
15247 Dereferences of pointers to members.
15250 Array indexing. @code{@var{a}[@var{i}]} is defined as
15251 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15254 Function parameter list. Same precedence as @code{->}.
15257 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15258 and @code{class} types.
15261 Doubled colons also represent the @value{GDBN} scope operator
15262 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15266 If an operator is redefined in the user code, @value{GDBN} usually
15267 attempts to invoke the redefined version instead of using the operator's
15268 predefined meaning.
15271 @subsubsection C and C@t{++} Constants
15273 @cindex C and C@t{++} constants
15275 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15280 Integer constants are a sequence of digits. Octal constants are
15281 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15282 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15283 @samp{l}, specifying that the constant should be treated as a
15287 Floating point constants are a sequence of digits, followed by a decimal
15288 point, followed by a sequence of digits, and optionally followed by an
15289 exponent. An exponent is of the form:
15290 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15291 sequence of digits. The @samp{+} is optional for positive exponents.
15292 A floating-point constant may also end with a letter @samp{f} or
15293 @samp{F}, specifying that the constant should be treated as being of
15294 the @code{float} (as opposed to the default @code{double}) type; or with
15295 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15299 Enumerated constants consist of enumerated identifiers, or their
15300 integral equivalents.
15303 Character constants are a single character surrounded by single quotes
15304 (@code{'}), or a number---the ordinal value of the corresponding character
15305 (usually its @sc{ascii} value). Within quotes, the single character may
15306 be represented by a letter or by @dfn{escape sequences}, which are of
15307 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15308 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15309 @samp{@var{x}} is a predefined special character---for example,
15310 @samp{\n} for newline.
15312 Wide character constants can be written by prefixing a character
15313 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15314 form of @samp{x}. The target wide character set is used when
15315 computing the value of this constant (@pxref{Character Sets}).
15318 String constants are a sequence of character constants surrounded by
15319 double quotes (@code{"}). Any valid character constant (as described
15320 above) may appear. Double quotes within the string must be preceded by
15321 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15324 Wide string constants can be written by prefixing a string constant
15325 with @samp{L}, as in C. The target wide character set is used when
15326 computing the value of this constant (@pxref{Character Sets}).
15329 Pointer constants are an integral value. You can also write pointers
15330 to constants using the C operator @samp{&}.
15333 Array constants are comma-separated lists surrounded by braces @samp{@{}
15334 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15335 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15336 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15339 @node C Plus Plus Expressions
15340 @subsubsection C@t{++} Expressions
15342 @cindex expressions in C@t{++}
15343 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15345 @cindex debugging C@t{++} programs
15346 @cindex C@t{++} compilers
15347 @cindex debug formats and C@t{++}
15348 @cindex @value{NGCC} and C@t{++}
15350 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15351 the proper compiler and the proper debug format. Currently,
15352 @value{GDBN} works best when debugging C@t{++} code that is compiled
15353 with the most recent version of @value{NGCC} possible. The DWARF
15354 debugging format is preferred; @value{NGCC} defaults to this on most
15355 popular platforms. Other compilers and/or debug formats are likely to
15356 work badly or not at all when using @value{GDBN} to debug C@t{++}
15357 code. @xref{Compilation}.
15362 @cindex member functions
15364 Member function calls are allowed; you can use expressions like
15367 count = aml->GetOriginal(x, y)
15370 @vindex this@r{, inside C@t{++} member functions}
15371 @cindex namespace in C@t{++}
15373 While a member function is active (in the selected stack frame), your
15374 expressions have the same namespace available as the member function;
15375 that is, @value{GDBN} allows implicit references to the class instance
15376 pointer @code{this} following the same rules as C@t{++}. @code{using}
15377 declarations in the current scope are also respected by @value{GDBN}.
15379 @cindex call overloaded functions
15380 @cindex overloaded functions, calling
15381 @cindex type conversions in C@t{++}
15383 You can call overloaded functions; @value{GDBN} resolves the function
15384 call to the right definition, with some restrictions. @value{GDBN} does not
15385 perform overload resolution involving user-defined type conversions,
15386 calls to constructors, or instantiations of templates that do not exist
15387 in the program. It also cannot handle ellipsis argument lists or
15390 It does perform integral conversions and promotions, floating-point
15391 promotions, arithmetic conversions, pointer conversions, conversions of
15392 class objects to base classes, and standard conversions such as those of
15393 functions or arrays to pointers; it requires an exact match on the
15394 number of function arguments.
15396 Overload resolution is always performed, unless you have specified
15397 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15398 ,@value{GDBN} Features for C@t{++}}.
15400 You must specify @code{set overload-resolution off} in order to use an
15401 explicit function signature to call an overloaded function, as in
15403 p 'foo(char,int)'('x', 13)
15406 The @value{GDBN} command-completion facility can simplify this;
15407 see @ref{Completion, ,Command Completion}.
15409 @cindex reference declarations
15411 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15412 references; you can use them in expressions just as you do in C@t{++}
15413 source---they are automatically dereferenced.
15415 In the parameter list shown when @value{GDBN} displays a frame, the values of
15416 reference variables are not displayed (unlike other variables); this
15417 avoids clutter, since references are often used for large structures.
15418 The @emph{address} of a reference variable is always shown, unless
15419 you have specified @samp{set print address off}.
15422 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15423 expressions can use it just as expressions in your program do. Since
15424 one scope may be defined in another, you can use @code{::} repeatedly if
15425 necessary, for example in an expression like
15426 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15427 resolving name scope by reference to source files, in both C and C@t{++}
15428 debugging (@pxref{Variables, ,Program Variables}).
15431 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15436 @subsubsection C and C@t{++} Defaults
15438 @cindex C and C@t{++} defaults
15440 If you allow @value{GDBN} to set range checking automatically, it
15441 defaults to @code{off} whenever the working language changes to
15442 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15443 selects the working language.
15445 If you allow @value{GDBN} to set the language automatically, it
15446 recognizes source files whose names end with @file{.c}, @file{.C}, or
15447 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15448 these files, it sets the working language to C or C@t{++}.
15449 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15450 for further details.
15453 @subsubsection C and C@t{++} Type and Range Checks
15455 @cindex C and C@t{++} checks
15457 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15458 checking is used. However, if you turn type checking off, @value{GDBN}
15459 will allow certain non-standard conversions, such as promoting integer
15460 constants to pointers.
15462 Range checking, if turned on, is done on mathematical operations. Array
15463 indices are not checked, since they are often used to index a pointer
15464 that is not itself an array.
15467 @subsubsection @value{GDBN} and C
15469 The @code{set print union} and @code{show print union} commands apply to
15470 the @code{union} type. When set to @samp{on}, any @code{union} that is
15471 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15472 appears as @samp{@{...@}}.
15474 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15475 with pointers and a memory allocation function. @xref{Expressions,
15478 @node Debugging C Plus Plus
15479 @subsubsection @value{GDBN} Features for C@t{++}
15481 @cindex commands for C@t{++}
15483 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15484 designed specifically for use with C@t{++}. Here is a summary:
15487 @cindex break in overloaded functions
15488 @item @r{breakpoint menus}
15489 When you want a breakpoint in a function whose name is overloaded,
15490 @value{GDBN} has the capability to display a menu of possible breakpoint
15491 locations to help you specify which function definition you want.
15492 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15494 @cindex overloading in C@t{++}
15495 @item rbreak @var{regex}
15496 Setting breakpoints using regular expressions is helpful for setting
15497 breakpoints on overloaded functions that are not members of any special
15499 @xref{Set Breaks, ,Setting Breakpoints}.
15501 @cindex C@t{++} exception handling
15503 @itemx catch rethrow
15505 Debug C@t{++} exception handling using these commands. @xref{Set
15506 Catchpoints, , Setting Catchpoints}.
15508 @cindex inheritance
15509 @item ptype @var{typename}
15510 Print inheritance relationships as well as other information for type
15512 @xref{Symbols, ,Examining the Symbol Table}.
15514 @item info vtbl @var{expression}.
15515 The @code{info vtbl} command can be used to display the virtual
15516 method tables of the object computed by @var{expression}. This shows
15517 one entry per virtual table; there may be multiple virtual tables when
15518 multiple inheritance is in use.
15520 @cindex C@t{++} demangling
15521 @item demangle @var{name}
15522 Demangle @var{name}.
15523 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15525 @cindex C@t{++} symbol display
15526 @item set print demangle
15527 @itemx show print demangle
15528 @itemx set print asm-demangle
15529 @itemx show print asm-demangle
15530 Control whether C@t{++} symbols display in their source form, both when
15531 displaying code as C@t{++} source and when displaying disassemblies.
15532 @xref{Print Settings, ,Print Settings}.
15534 @item set print object
15535 @itemx show print object
15536 Choose whether to print derived (actual) or declared types of objects.
15537 @xref{Print Settings, ,Print Settings}.
15539 @item set print vtbl
15540 @itemx show print vtbl
15541 Control the format for printing virtual function tables.
15542 @xref{Print Settings, ,Print Settings}.
15543 (The @code{vtbl} commands do not work on programs compiled with the HP
15544 ANSI C@t{++} compiler (@code{aCC}).)
15546 @kindex set overload-resolution
15547 @cindex overloaded functions, overload resolution
15548 @item set overload-resolution on
15549 Enable overload resolution for C@t{++} expression evaluation. The default
15550 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15551 and searches for a function whose signature matches the argument types,
15552 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15553 Expressions, ,C@t{++} Expressions}, for details).
15554 If it cannot find a match, it emits a message.
15556 @item set overload-resolution off
15557 Disable overload resolution for C@t{++} expression evaluation. For
15558 overloaded functions that are not class member functions, @value{GDBN}
15559 chooses the first function of the specified name that it finds in the
15560 symbol table, whether or not its arguments are of the correct type. For
15561 overloaded functions that are class member functions, @value{GDBN}
15562 searches for a function whose signature @emph{exactly} matches the
15565 @kindex show overload-resolution
15566 @item show overload-resolution
15567 Show the current setting of overload resolution.
15569 @item @r{Overloaded symbol names}
15570 You can specify a particular definition of an overloaded symbol, using
15571 the same notation that is used to declare such symbols in C@t{++}: type
15572 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15573 also use the @value{GDBN} command-line word completion facilities to list the
15574 available choices, or to finish the type list for you.
15575 @xref{Completion,, Command Completion}, for details on how to do this.
15577 @item @r{Breakpoints in functions with ABI tags}
15579 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15580 correspond to changes in the ABI of a type, function, or variable that
15581 would not otherwise be reflected in a mangled name. See
15582 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15585 The ABI tags are visible in C@t{++} demangled names. For example, a
15586 function that returns a std::string:
15589 std::string function(int);
15593 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15594 tag, and @value{GDBN} displays the symbol like this:
15597 function[abi:cxx11](int)
15600 You can set a breakpoint on such functions simply as if they had no
15604 (gdb) b function(int)
15605 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15606 (gdb) info breakpoints
15607 Num Type Disp Enb Address What
15608 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15612 On the rare occasion you need to disambiguate between different ABI
15613 tags, you can do so by simply including the ABI tag in the function
15617 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15621 @node Decimal Floating Point
15622 @subsubsection Decimal Floating Point format
15623 @cindex decimal floating point format
15625 @value{GDBN} can examine, set and perform computations with numbers in
15626 decimal floating point format, which in the C language correspond to the
15627 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15628 specified by the extension to support decimal floating-point arithmetic.
15630 There are two encodings in use, depending on the architecture: BID (Binary
15631 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15632 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15635 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15636 to manipulate decimal floating point numbers, it is not possible to convert
15637 (using a cast, for example) integers wider than 32-bit to decimal float.
15639 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15640 point computations, error checking in decimal float operations ignores
15641 underflow, overflow and divide by zero exceptions.
15643 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15644 to inspect @code{_Decimal128} values stored in floating point registers.
15645 See @ref{PowerPC,,PowerPC} for more details.
15651 @value{GDBN} can be used to debug programs written in D and compiled with
15652 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15653 specific feature --- dynamic arrays.
15658 @cindex Go (programming language)
15659 @value{GDBN} can be used to debug programs written in Go and compiled with
15660 @file{gccgo} or @file{6g} compilers.
15662 Here is a summary of the Go-specific features and restrictions:
15665 @cindex current Go package
15666 @item The current Go package
15667 The name of the current package does not need to be specified when
15668 specifying global variables and functions.
15670 For example, given the program:
15674 var myglob = "Shall we?"
15680 When stopped inside @code{main} either of these work:
15684 (gdb) p main.myglob
15687 @cindex builtin Go types
15688 @item Builtin Go types
15689 The @code{string} type is recognized by @value{GDBN} and is printed
15692 @cindex builtin Go functions
15693 @item Builtin Go functions
15694 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15695 function and handles it internally.
15697 @cindex restrictions on Go expressions
15698 @item Restrictions on Go expressions
15699 All Go operators are supported except @code{&^}.
15700 The Go @code{_} ``blank identifier'' is not supported.
15701 Automatic dereferencing of pointers is not supported.
15705 @subsection Objective-C
15707 @cindex Objective-C
15708 This section provides information about some commands and command
15709 options that are useful for debugging Objective-C code. See also
15710 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15711 few more commands specific to Objective-C support.
15714 * Method Names in Commands::
15715 * The Print Command with Objective-C::
15718 @node Method Names in Commands
15719 @subsubsection Method Names in Commands
15721 The following commands have been extended to accept Objective-C method
15722 names as line specifications:
15724 @kindex clear@r{, and Objective-C}
15725 @kindex break@r{, and Objective-C}
15726 @kindex info line@r{, and Objective-C}
15727 @kindex jump@r{, and Objective-C}
15728 @kindex list@r{, and Objective-C}
15732 @item @code{info line}
15737 A fully qualified Objective-C method name is specified as
15740 -[@var{Class} @var{methodName}]
15743 where the minus sign is used to indicate an instance method and a
15744 plus sign (not shown) is used to indicate a class method. The class
15745 name @var{Class} and method name @var{methodName} are enclosed in
15746 brackets, similar to the way messages are specified in Objective-C
15747 source code. For example, to set a breakpoint at the @code{create}
15748 instance method of class @code{Fruit} in the program currently being
15752 break -[Fruit create]
15755 To list ten program lines around the @code{initialize} class method,
15759 list +[NSText initialize]
15762 In the current version of @value{GDBN}, the plus or minus sign is
15763 required. In future versions of @value{GDBN}, the plus or minus
15764 sign will be optional, but you can use it to narrow the search. It
15765 is also possible to specify just a method name:
15771 You must specify the complete method name, including any colons. If
15772 your program's source files contain more than one @code{create} method,
15773 you'll be presented with a numbered list of classes that implement that
15774 method. Indicate your choice by number, or type @samp{0} to exit if
15777 As another example, to clear a breakpoint established at the
15778 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15781 clear -[NSWindow makeKeyAndOrderFront:]
15784 @node The Print Command with Objective-C
15785 @subsubsection The Print Command With Objective-C
15786 @cindex Objective-C, print objects
15787 @kindex print-object
15788 @kindex po @r{(@code{print-object})}
15790 The print command has also been extended to accept methods. For example:
15793 print -[@var{object} hash]
15796 @cindex print an Objective-C object description
15797 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15799 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15800 and print the result. Also, an additional command has been added,
15801 @code{print-object} or @code{po} for short, which is meant to print
15802 the description of an object. However, this command may only work
15803 with certain Objective-C libraries that have a particular hook
15804 function, @code{_NSPrintForDebugger}, defined.
15807 @subsection OpenCL C
15810 This section provides information about @value{GDBN}s OpenCL C support.
15813 * OpenCL C Datatypes::
15814 * OpenCL C Expressions::
15815 * OpenCL C Operators::
15818 @node OpenCL C Datatypes
15819 @subsubsection OpenCL C Datatypes
15821 @cindex OpenCL C Datatypes
15822 @value{GDBN} supports the builtin scalar and vector datatypes specified
15823 by OpenCL 1.1. In addition the half- and double-precision floating point
15824 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15825 extensions are also known to @value{GDBN}.
15827 @node OpenCL C Expressions
15828 @subsubsection OpenCL C Expressions
15830 @cindex OpenCL C Expressions
15831 @value{GDBN} supports accesses to vector components including the access as
15832 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15833 supported by @value{GDBN} can be used as well.
15835 @node OpenCL C Operators
15836 @subsubsection OpenCL C Operators
15838 @cindex OpenCL C Operators
15839 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15843 @subsection Fortran
15844 @cindex Fortran-specific support in @value{GDBN}
15846 @value{GDBN} can be used to debug programs written in Fortran, but it
15847 currently supports only the features of Fortran 77 language.
15849 @cindex trailing underscore, in Fortran symbols
15850 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15851 among them) append an underscore to the names of variables and
15852 functions. When you debug programs compiled by those compilers, you
15853 will need to refer to variables and functions with a trailing
15857 * Fortran Operators:: Fortran operators and expressions
15858 * Fortran Defaults:: Default settings for Fortran
15859 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15862 @node Fortran Operators
15863 @subsubsection Fortran Operators and Expressions
15865 @cindex Fortran operators and expressions
15867 Operators must be defined on values of specific types. For instance,
15868 @code{+} is defined on numbers, but not on characters or other non-
15869 arithmetic types. Operators are often defined on groups of types.
15873 The exponentiation operator. It raises the first operand to the power
15877 The range operator. Normally used in the form of array(low:high) to
15878 represent a section of array.
15881 The access component operator. Normally used to access elements in derived
15882 types. Also suitable for unions. As unions aren't part of regular Fortran,
15883 this can only happen when accessing a register that uses a gdbarch-defined
15887 @node Fortran Defaults
15888 @subsubsection Fortran Defaults
15890 @cindex Fortran Defaults
15892 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15893 default uses case-insensitive matches for Fortran symbols. You can
15894 change that with the @samp{set case-insensitive} command, see
15895 @ref{Symbols}, for the details.
15897 @node Special Fortran Commands
15898 @subsubsection Special Fortran Commands
15900 @cindex Special Fortran commands
15902 @value{GDBN} has some commands to support Fortran-specific features,
15903 such as displaying common blocks.
15906 @cindex @code{COMMON} blocks, Fortran
15907 @kindex info common
15908 @item info common @r{[}@var{common-name}@r{]}
15909 This command prints the values contained in the Fortran @code{COMMON}
15910 block whose name is @var{common-name}. With no argument, the names of
15911 all @code{COMMON} blocks visible at the current program location are
15918 @cindex Pascal support in @value{GDBN}, limitations
15919 Debugging Pascal programs which use sets, subranges, file variables, or
15920 nested functions does not currently work. @value{GDBN} does not support
15921 entering expressions, printing values, or similar features using Pascal
15924 The Pascal-specific command @code{set print pascal_static-members}
15925 controls whether static members of Pascal objects are displayed.
15926 @xref{Print Settings, pascal_static-members}.
15931 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15932 Programming Language}. Type- and value-printing, and expression
15933 parsing, are reasonably complete. However, there are a few
15934 peculiarities and holes to be aware of.
15938 Linespecs (@pxref{Specify Location}) are never relative to the current
15939 crate. Instead, they act as if there were a global namespace of
15940 crates, somewhat similar to the way @code{extern crate} behaves.
15942 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15943 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15944 to set a breakpoint in a function named @samp{f} in a crate named
15947 As a consequence of this approach, linespecs also cannot refer to
15948 items using @samp{self::} or @samp{super::}.
15951 Because @value{GDBN} implements Rust name-lookup semantics in
15952 expressions, it will sometimes prepend the current crate to a name.
15953 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15954 @samp{K}, then @code{print ::x::y} will try to find the symbol
15957 However, since it is useful to be able to refer to other crates when
15958 debugging, @value{GDBN} provides the @code{extern} extension to
15959 circumvent this. To use the extension, just put @code{extern} before
15960 a path expression to refer to the otherwise unavailable ``global''
15963 In the above example, if you wanted to refer to the symbol @samp{y} in
15964 the crate @samp{x}, you would use @code{print extern x::y}.
15967 The Rust expression evaluator does not support ``statement-like''
15968 expressions such as @code{if} or @code{match}, or lambda expressions.
15971 Tuple expressions are not implemented.
15974 The Rust expression evaluator does not currently implement the
15975 @code{Drop} trait. Objects that may be created by the evaluator will
15976 never be destroyed.
15979 @value{GDBN} does not implement type inference for generics. In order
15980 to call generic functions or otherwise refer to generic items, you
15981 will have to specify the type parameters manually.
15984 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15985 cases this does not cause any problems. However, in an expression
15986 context, completing a generic function name will give syntactically
15987 invalid results. This happens because Rust requires the @samp{::}
15988 operator between the function name and its generic arguments. For
15989 example, @value{GDBN} might provide a completion like
15990 @code{crate::f<u32>}, where the parser would require
15991 @code{crate::f::<u32>}.
15994 As of this writing, the Rust compiler (version 1.8) has a few holes in
15995 the debugging information it generates. These holes prevent certain
15996 features from being implemented by @value{GDBN}:
16000 Method calls cannot be made via traits.
16003 Operator overloading is not implemented.
16006 When debugging in a monomorphized function, you cannot use the generic
16010 The type @code{Self} is not available.
16013 @code{use} statements are not available, so some names may not be
16014 available in the crate.
16019 @subsection Modula-2
16021 @cindex Modula-2, @value{GDBN} support
16023 The extensions made to @value{GDBN} to support Modula-2 only support
16024 output from the @sc{gnu} Modula-2 compiler (which is currently being
16025 developed). Other Modula-2 compilers are not currently supported, and
16026 attempting to debug executables produced by them is most likely
16027 to give an error as @value{GDBN} reads in the executable's symbol
16030 @cindex expressions in Modula-2
16032 * M2 Operators:: Built-in operators
16033 * Built-In Func/Proc:: Built-in functions and procedures
16034 * M2 Constants:: Modula-2 constants
16035 * M2 Types:: Modula-2 types
16036 * M2 Defaults:: Default settings for Modula-2
16037 * Deviations:: Deviations from standard Modula-2
16038 * M2 Checks:: Modula-2 type and range checks
16039 * M2 Scope:: The scope operators @code{::} and @code{.}
16040 * GDB/M2:: @value{GDBN} and Modula-2
16044 @subsubsection Operators
16045 @cindex Modula-2 operators
16047 Operators must be defined on values of specific types. For instance,
16048 @code{+} is defined on numbers, but not on structures. Operators are
16049 often defined on groups of types. For the purposes of Modula-2, the
16050 following definitions hold:
16055 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16059 @emph{Character types} consist of @code{CHAR} and its subranges.
16062 @emph{Floating-point types} consist of @code{REAL}.
16065 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16069 @emph{Scalar types} consist of all of the above.
16072 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16075 @emph{Boolean types} consist of @code{BOOLEAN}.
16079 The following operators are supported, and appear in order of
16080 increasing precedence:
16084 Function argument or array index separator.
16087 Assignment. The value of @var{var} @code{:=} @var{value} is
16091 Less than, greater than on integral, floating-point, or enumerated
16095 Less than or equal to, greater than or equal to
16096 on integral, floating-point and enumerated types, or set inclusion on
16097 set types. Same precedence as @code{<}.
16099 @item =@r{, }<>@r{, }#
16100 Equality and two ways of expressing inequality, valid on scalar types.
16101 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16102 available for inequality, since @code{#} conflicts with the script
16106 Set membership. Defined on set types and the types of their members.
16107 Same precedence as @code{<}.
16110 Boolean disjunction. Defined on boolean types.
16113 Boolean conjunction. Defined on boolean types.
16116 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16119 Addition and subtraction on integral and floating-point types, or union
16120 and difference on set types.
16123 Multiplication on integral and floating-point types, or set intersection
16127 Division on floating-point types, or symmetric set difference on set
16128 types. Same precedence as @code{*}.
16131 Integer division and remainder. Defined on integral types. Same
16132 precedence as @code{*}.
16135 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16138 Pointer dereferencing. Defined on pointer types.
16141 Boolean negation. Defined on boolean types. Same precedence as
16145 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16146 precedence as @code{^}.
16149 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16152 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16156 @value{GDBN} and Modula-2 scope operators.
16160 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16161 treats the use of the operator @code{IN}, or the use of operators
16162 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16163 @code{<=}, and @code{>=} on sets as an error.
16167 @node Built-In Func/Proc
16168 @subsubsection Built-in Functions and Procedures
16169 @cindex Modula-2 built-ins
16171 Modula-2 also makes available several built-in procedures and functions.
16172 In describing these, the following metavariables are used:
16177 represents an @code{ARRAY} variable.
16180 represents a @code{CHAR} constant or variable.
16183 represents a variable or constant of integral type.
16186 represents an identifier that belongs to a set. Generally used in the
16187 same function with the metavariable @var{s}. The type of @var{s} should
16188 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16191 represents a variable or constant of integral or floating-point type.
16194 represents a variable or constant of floating-point type.
16200 represents a variable.
16203 represents a variable or constant of one of many types. See the
16204 explanation of the function for details.
16207 All Modula-2 built-in procedures also return a result, described below.
16211 Returns the absolute value of @var{n}.
16214 If @var{c} is a lower case letter, it returns its upper case
16215 equivalent, otherwise it returns its argument.
16218 Returns the character whose ordinal value is @var{i}.
16221 Decrements the value in the variable @var{v} by one. Returns the new value.
16223 @item DEC(@var{v},@var{i})
16224 Decrements the value in the variable @var{v} by @var{i}. Returns the
16227 @item EXCL(@var{m},@var{s})
16228 Removes the element @var{m} from the set @var{s}. Returns the new
16231 @item FLOAT(@var{i})
16232 Returns the floating point equivalent of the integer @var{i}.
16234 @item HIGH(@var{a})
16235 Returns the index of the last member of @var{a}.
16238 Increments the value in the variable @var{v} by one. Returns the new value.
16240 @item INC(@var{v},@var{i})
16241 Increments the value in the variable @var{v} by @var{i}. Returns the
16244 @item INCL(@var{m},@var{s})
16245 Adds the element @var{m} to the set @var{s} if it is not already
16246 there. Returns the new set.
16249 Returns the maximum value of the type @var{t}.
16252 Returns the minimum value of the type @var{t}.
16255 Returns boolean TRUE if @var{i} is an odd number.
16258 Returns the ordinal value of its argument. For example, the ordinal
16259 value of a character is its @sc{ascii} value (on machines supporting
16260 the @sc{ascii} character set). The argument @var{x} must be of an
16261 ordered type, which include integral, character and enumerated types.
16263 @item SIZE(@var{x})
16264 Returns the size of its argument. The argument @var{x} can be a
16265 variable or a type.
16267 @item TRUNC(@var{r})
16268 Returns the integral part of @var{r}.
16270 @item TSIZE(@var{x})
16271 Returns the size of its argument. The argument @var{x} can be a
16272 variable or a type.
16274 @item VAL(@var{t},@var{i})
16275 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16279 @emph{Warning:} Sets and their operations are not yet supported, so
16280 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16284 @cindex Modula-2 constants
16286 @subsubsection Constants
16288 @value{GDBN} allows you to express the constants of Modula-2 in the following
16294 Integer constants are simply a sequence of digits. When used in an
16295 expression, a constant is interpreted to be type-compatible with the
16296 rest of the expression. Hexadecimal integers are specified by a
16297 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16300 Floating point constants appear as a sequence of digits, followed by a
16301 decimal point and another sequence of digits. An optional exponent can
16302 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16303 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16304 digits of the floating point constant must be valid decimal (base 10)
16308 Character constants consist of a single character enclosed by a pair of
16309 like quotes, either single (@code{'}) or double (@code{"}). They may
16310 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16311 followed by a @samp{C}.
16314 String constants consist of a sequence of characters enclosed by a
16315 pair of like quotes, either single (@code{'}) or double (@code{"}).
16316 Escape sequences in the style of C are also allowed. @xref{C
16317 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16321 Enumerated constants consist of an enumerated identifier.
16324 Boolean constants consist of the identifiers @code{TRUE} and
16328 Pointer constants consist of integral values only.
16331 Set constants are not yet supported.
16335 @subsubsection Modula-2 Types
16336 @cindex Modula-2 types
16338 Currently @value{GDBN} can print the following data types in Modula-2
16339 syntax: array types, record types, set types, pointer types, procedure
16340 types, enumerated types, subrange types and base types. You can also
16341 print the contents of variables declared using these type.
16342 This section gives a number of simple source code examples together with
16343 sample @value{GDBN} sessions.
16345 The first example contains the following section of code:
16354 and you can request @value{GDBN} to interrogate the type and value of
16355 @code{r} and @code{s}.
16358 (@value{GDBP}) print s
16360 (@value{GDBP}) ptype s
16362 (@value{GDBP}) print r
16364 (@value{GDBP}) ptype r
16369 Likewise if your source code declares @code{s} as:
16373 s: SET ['A'..'Z'] ;
16377 then you may query the type of @code{s} by:
16380 (@value{GDBP}) ptype s
16381 type = SET ['A'..'Z']
16385 Note that at present you cannot interactively manipulate set
16386 expressions using the debugger.
16388 The following example shows how you might declare an array in Modula-2
16389 and how you can interact with @value{GDBN} to print its type and contents:
16393 s: ARRAY [-10..10] OF CHAR ;
16397 (@value{GDBP}) ptype s
16398 ARRAY [-10..10] OF CHAR
16401 Note that the array handling is not yet complete and although the type
16402 is printed correctly, expression handling still assumes that all
16403 arrays have a lower bound of zero and not @code{-10} as in the example
16406 Here are some more type related Modula-2 examples:
16410 colour = (blue, red, yellow, green) ;
16411 t = [blue..yellow] ;
16419 The @value{GDBN} interaction shows how you can query the data type
16420 and value of a variable.
16423 (@value{GDBP}) print s
16425 (@value{GDBP}) ptype t
16426 type = [blue..yellow]
16430 In this example a Modula-2 array is declared and its contents
16431 displayed. Observe that the contents are written in the same way as
16432 their @code{C} counterparts.
16436 s: ARRAY [1..5] OF CARDINAL ;
16442 (@value{GDBP}) print s
16443 $1 = @{1, 0, 0, 0, 0@}
16444 (@value{GDBP}) ptype s
16445 type = ARRAY [1..5] OF CARDINAL
16448 The Modula-2 language interface to @value{GDBN} also understands
16449 pointer types as shown in this example:
16453 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16460 and you can request that @value{GDBN} describes the type of @code{s}.
16463 (@value{GDBP}) ptype s
16464 type = POINTER TO ARRAY [1..5] OF CARDINAL
16467 @value{GDBN} handles compound types as we can see in this example.
16468 Here we combine array types, record types, pointer types and subrange
16479 myarray = ARRAY myrange OF CARDINAL ;
16480 myrange = [-2..2] ;
16482 s: POINTER TO ARRAY myrange OF foo ;
16486 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16490 (@value{GDBP}) ptype s
16491 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16494 f3 : ARRAY [-2..2] OF CARDINAL;
16499 @subsubsection Modula-2 Defaults
16500 @cindex Modula-2 defaults
16502 If type and range checking are set automatically by @value{GDBN}, they
16503 both default to @code{on} whenever the working language changes to
16504 Modula-2. This happens regardless of whether you or @value{GDBN}
16505 selected the working language.
16507 If you allow @value{GDBN} to set the language automatically, then entering
16508 code compiled from a file whose name ends with @file{.mod} sets the
16509 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16510 Infer the Source Language}, for further details.
16513 @subsubsection Deviations from Standard Modula-2
16514 @cindex Modula-2, deviations from
16516 A few changes have been made to make Modula-2 programs easier to debug.
16517 This is done primarily via loosening its type strictness:
16521 Unlike in standard Modula-2, pointer constants can be formed by
16522 integers. This allows you to modify pointer variables during
16523 debugging. (In standard Modula-2, the actual address contained in a
16524 pointer variable is hidden from you; it can only be modified
16525 through direct assignment to another pointer variable or expression that
16526 returned a pointer.)
16529 C escape sequences can be used in strings and characters to represent
16530 non-printable characters. @value{GDBN} prints out strings with these
16531 escape sequences embedded. Single non-printable characters are
16532 printed using the @samp{CHR(@var{nnn})} format.
16535 The assignment operator (@code{:=}) returns the value of its right-hand
16539 All built-in procedures both modify @emph{and} return their argument.
16543 @subsubsection Modula-2 Type and Range Checks
16544 @cindex Modula-2 checks
16547 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16550 @c FIXME remove warning when type/range checks added
16552 @value{GDBN} considers two Modula-2 variables type equivalent if:
16556 They are of types that have been declared equivalent via a @code{TYPE
16557 @var{t1} = @var{t2}} statement
16560 They have been declared on the same line. (Note: This is true of the
16561 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16564 As long as type checking is enabled, any attempt to combine variables
16565 whose types are not equivalent is an error.
16567 Range checking is done on all mathematical operations, assignment, array
16568 index bounds, and all built-in functions and procedures.
16571 @subsubsection The Scope Operators @code{::} and @code{.}
16573 @cindex @code{.}, Modula-2 scope operator
16574 @cindex colon, doubled as scope operator
16576 @vindex colon-colon@r{, in Modula-2}
16577 @c Info cannot handle :: but TeX can.
16580 @vindex ::@r{, in Modula-2}
16583 There are a few subtle differences between the Modula-2 scope operator
16584 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16589 @var{module} . @var{id}
16590 @var{scope} :: @var{id}
16594 where @var{scope} is the name of a module or a procedure,
16595 @var{module} the name of a module, and @var{id} is any declared
16596 identifier within your program, except another module.
16598 Using the @code{::} operator makes @value{GDBN} search the scope
16599 specified by @var{scope} for the identifier @var{id}. If it is not
16600 found in the specified scope, then @value{GDBN} searches all scopes
16601 enclosing the one specified by @var{scope}.
16603 Using the @code{.} operator makes @value{GDBN} search the current scope for
16604 the identifier specified by @var{id} that was imported from the
16605 definition module specified by @var{module}. With this operator, it is
16606 an error if the identifier @var{id} was not imported from definition
16607 module @var{module}, or if @var{id} is not an identifier in
16611 @subsubsection @value{GDBN} and Modula-2
16613 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16614 Five subcommands of @code{set print} and @code{show print} apply
16615 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16616 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16617 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16618 analogue in Modula-2.
16620 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16621 with any language, is not useful with Modula-2. Its
16622 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16623 created in Modula-2 as they can in C or C@t{++}. However, because an
16624 address can be specified by an integral constant, the construct
16625 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16627 @cindex @code{#} in Modula-2
16628 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16629 interpreted as the beginning of a comment. Use @code{<>} instead.
16635 The extensions made to @value{GDBN} for Ada only support
16636 output from the @sc{gnu} Ada (GNAT) compiler.
16637 Other Ada compilers are not currently supported, and
16638 attempting to debug executables produced by them is most likely
16642 @cindex expressions in Ada
16644 * Ada Mode Intro:: General remarks on the Ada syntax
16645 and semantics supported by Ada mode
16647 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16648 * Additions to Ada:: Extensions of the Ada expression syntax.
16649 * Overloading support for Ada:: Support for expressions involving overloaded
16651 * Stopping Before Main Program:: Debugging the program during elaboration.
16652 * Ada Exceptions:: Ada Exceptions
16653 * Ada Tasks:: Listing and setting breakpoints in tasks.
16654 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16655 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16657 * Ada Settings:: New settable GDB parameters for Ada.
16658 * Ada Glitches:: Known peculiarities of Ada mode.
16661 @node Ada Mode Intro
16662 @subsubsection Introduction
16663 @cindex Ada mode, general
16665 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16666 syntax, with some extensions.
16667 The philosophy behind the design of this subset is
16671 That @value{GDBN} should provide basic literals and access to operations for
16672 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16673 leaving more sophisticated computations to subprograms written into the
16674 program (which therefore may be called from @value{GDBN}).
16677 That type safety and strict adherence to Ada language restrictions
16678 are not particularly important to the @value{GDBN} user.
16681 That brevity is important to the @value{GDBN} user.
16684 Thus, for brevity, the debugger acts as if all names declared in
16685 user-written packages are directly visible, even if they are not visible
16686 according to Ada rules, thus making it unnecessary to fully qualify most
16687 names with their packages, regardless of context. Where this causes
16688 ambiguity, @value{GDBN} asks the user's intent.
16690 The debugger will start in Ada mode if it detects an Ada main program.
16691 As for other languages, it will enter Ada mode when stopped in a program that
16692 was translated from an Ada source file.
16694 While in Ada mode, you may use `@t{--}' for comments. This is useful
16695 mostly for documenting command files. The standard @value{GDBN} comment
16696 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16697 middle (to allow based literals).
16699 @node Omissions from Ada
16700 @subsubsection Omissions from Ada
16701 @cindex Ada, omissions from
16703 Here are the notable omissions from the subset:
16707 Only a subset of the attributes are supported:
16711 @t{'First}, @t{'Last}, and @t{'Length}
16712 on array objects (not on types and subtypes).
16715 @t{'Min} and @t{'Max}.
16718 @t{'Pos} and @t{'Val}.
16724 @t{'Range} on array objects (not subtypes), but only as the right
16725 operand of the membership (@code{in}) operator.
16728 @t{'Access}, @t{'Unchecked_Access}, and
16729 @t{'Unrestricted_Access} (a GNAT extension).
16737 @code{Characters.Latin_1} are not available and
16738 concatenation is not implemented. Thus, escape characters in strings are
16739 not currently available.
16742 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16743 equality of representations. They will generally work correctly
16744 for strings and arrays whose elements have integer or enumeration types.
16745 They may not work correctly for arrays whose element
16746 types have user-defined equality, for arrays of real values
16747 (in particular, IEEE-conformant floating point, because of negative
16748 zeroes and NaNs), and for arrays whose elements contain unused bits with
16749 indeterminate values.
16752 The other component-by-component array operations (@code{and}, @code{or},
16753 @code{xor}, @code{not}, and relational tests other than equality)
16754 are not implemented.
16757 @cindex array aggregates (Ada)
16758 @cindex record aggregates (Ada)
16759 @cindex aggregates (Ada)
16760 There is limited support for array and record aggregates. They are
16761 permitted only on the right sides of assignments, as in these examples:
16764 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16765 (@value{GDBP}) set An_Array := (1, others => 0)
16766 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16767 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16768 (@value{GDBP}) set A_Record := (1, "Peter", True);
16769 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16773 discriminant's value by assigning an aggregate has an
16774 undefined effect if that discriminant is used within the record.
16775 However, you can first modify discriminants by directly assigning to
16776 them (which normally would not be allowed in Ada), and then performing an
16777 aggregate assignment. For example, given a variable @code{A_Rec}
16778 declared to have a type such as:
16781 type Rec (Len : Small_Integer := 0) is record
16783 Vals : IntArray (1 .. Len);
16787 you can assign a value with a different size of @code{Vals} with two
16791 (@value{GDBP}) set A_Rec.Len := 4
16792 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16795 As this example also illustrates, @value{GDBN} is very loose about the usual
16796 rules concerning aggregates. You may leave out some of the
16797 components of an array or record aggregate (such as the @code{Len}
16798 component in the assignment to @code{A_Rec} above); they will retain their
16799 original values upon assignment. You may freely use dynamic values as
16800 indices in component associations. You may even use overlapping or
16801 redundant component associations, although which component values are
16802 assigned in such cases is not defined.
16805 Calls to dispatching subprograms are not implemented.
16808 The overloading algorithm is much more limited (i.e., less selective)
16809 than that of real Ada. It makes only limited use of the context in
16810 which a subexpression appears to resolve its meaning, and it is much
16811 looser in its rules for allowing type matches. As a result, some
16812 function calls will be ambiguous, and the user will be asked to choose
16813 the proper resolution.
16816 The @code{new} operator is not implemented.
16819 Entry calls are not implemented.
16822 Aside from printing, arithmetic operations on the native VAX floating-point
16823 formats are not supported.
16826 It is not possible to slice a packed array.
16829 The names @code{True} and @code{False}, when not part of a qualified name,
16830 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16832 Should your program
16833 redefine these names in a package or procedure (at best a dubious practice),
16834 you will have to use fully qualified names to access their new definitions.
16837 @node Additions to Ada
16838 @subsubsection Additions to Ada
16839 @cindex Ada, deviations from
16841 As it does for other languages, @value{GDBN} makes certain generic
16842 extensions to Ada (@pxref{Expressions}):
16846 If the expression @var{E} is a variable residing in memory (typically
16847 a local variable or array element) and @var{N} is a positive integer,
16848 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16849 @var{N}-1 adjacent variables following it in memory as an array. In
16850 Ada, this operator is generally not necessary, since its prime use is
16851 in displaying parts of an array, and slicing will usually do this in
16852 Ada. However, there are occasional uses when debugging programs in
16853 which certain debugging information has been optimized away.
16856 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16857 appears in function or file @var{B}.'' When @var{B} is a file name,
16858 you must typically surround it in single quotes.
16861 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16862 @var{type} that appears at address @var{addr}.''
16865 A name starting with @samp{$} is a convenience variable
16866 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16869 In addition, @value{GDBN} provides a few other shortcuts and outright
16870 additions specific to Ada:
16874 The assignment statement is allowed as an expression, returning
16875 its right-hand operand as its value. Thus, you may enter
16878 (@value{GDBP}) set x := y + 3
16879 (@value{GDBP}) print A(tmp := y + 1)
16883 The semicolon is allowed as an ``operator,'' returning as its value
16884 the value of its right-hand operand.
16885 This allows, for example,
16886 complex conditional breaks:
16889 (@value{GDBP}) break f
16890 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16894 Rather than use catenation and symbolic character names to introduce special
16895 characters into strings, one may instead use a special bracket notation,
16896 which is also used to print strings. A sequence of characters of the form
16897 @samp{["@var{XX}"]} within a string or character literal denotes the
16898 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16899 sequence of characters @samp{["""]} also denotes a single quotation mark
16900 in strings. For example,
16902 "One line.["0a"]Next line.["0a"]"
16905 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16909 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16910 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16914 (@value{GDBP}) print 'max(x, y)
16918 When printing arrays, @value{GDBN} uses positional notation when the
16919 array has a lower bound of 1, and uses a modified named notation otherwise.
16920 For example, a one-dimensional array of three integers with a lower bound
16921 of 3 might print as
16928 That is, in contrast to valid Ada, only the first component has a @code{=>}
16932 You may abbreviate attributes in expressions with any unique,
16933 multi-character subsequence of
16934 their names (an exact match gets preference).
16935 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16936 in place of @t{a'length}.
16939 @cindex quoting Ada internal identifiers
16940 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16941 to lower case. The GNAT compiler uses upper-case characters for
16942 some of its internal identifiers, which are normally of no interest to users.
16943 For the rare occasions when you actually have to look at them,
16944 enclose them in angle brackets to avoid the lower-case mapping.
16947 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16951 Printing an object of class-wide type or dereferencing an
16952 access-to-class-wide value will display all the components of the object's
16953 specific type (as indicated by its run-time tag). Likewise, component
16954 selection on such a value will operate on the specific type of the
16959 @node Overloading support for Ada
16960 @subsubsection Overloading support for Ada
16961 @cindex overloading, Ada
16963 The debugger supports limited overloading. Given a subprogram call in which
16964 the function symbol has multiple definitions, it will use the number of
16965 actual parameters and some information about their types to attempt to narrow
16966 the set of definitions. It also makes very limited use of context, preferring
16967 procedures to functions in the context of the @code{call} command, and
16968 functions to procedures elsewhere.
16970 If, after narrowing, the set of matching definitions still contains more than
16971 one definition, @value{GDBN} will display a menu to query which one it should
16975 (@value{GDBP}) print f(1)
16976 Multiple matches for f
16978 [1] foo.f (integer) return boolean at foo.adb:23
16979 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16983 In this case, just select one menu entry either to cancel expression evaluation
16984 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16985 instance (type the corresponding number and press @key{RET}).
16987 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16992 @kindex set ada print-signatures
16993 @item set ada print-signatures
16994 Control whether parameter types and return types are displayed in overloads
16995 selection menus. It is @code{on} by default.
16996 @xref{Overloading support for Ada}.
16998 @kindex show ada print-signatures
16999 @item show ada print-signatures
17000 Show the current setting for displaying parameter types and return types in
17001 overloads selection menu.
17002 @xref{Overloading support for Ada}.
17006 @node Stopping Before Main Program
17007 @subsubsection Stopping at the Very Beginning
17009 @cindex breakpointing Ada elaboration code
17010 It is sometimes necessary to debug the program during elaboration, and
17011 before reaching the main procedure.
17012 As defined in the Ada Reference
17013 Manual, the elaboration code is invoked from a procedure called
17014 @code{adainit}. To run your program up to the beginning of
17015 elaboration, simply use the following two commands:
17016 @code{tbreak adainit} and @code{run}.
17018 @node Ada Exceptions
17019 @subsubsection Ada Exceptions
17021 A command is provided to list all Ada exceptions:
17024 @kindex info exceptions
17025 @item info exceptions
17026 @itemx info exceptions @var{regexp}
17027 The @code{info exceptions} command allows you to list all Ada exceptions
17028 defined within the program being debugged, as well as their addresses.
17029 With a regular expression, @var{regexp}, as argument, only those exceptions
17030 whose names match @var{regexp} are listed.
17033 Below is a small example, showing how the command can be used, first
17034 without argument, and next with a regular expression passed as an
17038 (@value{GDBP}) info exceptions
17039 All defined Ada exceptions:
17040 constraint_error: 0x613da0
17041 program_error: 0x613d20
17042 storage_error: 0x613ce0
17043 tasking_error: 0x613ca0
17044 const.aint_global_e: 0x613b00
17045 (@value{GDBP}) info exceptions const.aint
17046 All Ada exceptions matching regular expression "const.aint":
17047 constraint_error: 0x613da0
17048 const.aint_global_e: 0x613b00
17051 It is also possible to ask @value{GDBN} to stop your program's execution
17052 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17055 @subsubsection Extensions for Ada Tasks
17056 @cindex Ada, tasking
17058 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17059 @value{GDBN} provides the following task-related commands:
17064 This command shows a list of current Ada tasks, as in the following example:
17071 (@value{GDBP}) info tasks
17072 ID TID P-ID Pri State Name
17073 1 8088000 0 15 Child Activation Wait main_task
17074 2 80a4000 1 15 Accept Statement b
17075 3 809a800 1 15 Child Activation Wait a
17076 * 4 80ae800 3 15 Runnable c
17081 In this listing, the asterisk before the last task indicates it to be the
17082 task currently being inspected.
17086 Represents @value{GDBN}'s internal task number.
17092 The parent's task ID (@value{GDBN}'s internal task number).
17095 The base priority of the task.
17098 Current state of the task.
17102 The task has been created but has not been activated. It cannot be
17106 The task is not blocked for any reason known to Ada. (It may be waiting
17107 for a mutex, though.) It is conceptually "executing" in normal mode.
17110 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17111 that were waiting on terminate alternatives have been awakened and have
17112 terminated themselves.
17114 @item Child Activation Wait
17115 The task is waiting for created tasks to complete activation.
17117 @item Accept Statement
17118 The task is waiting on an accept or selective wait statement.
17120 @item Waiting on entry call
17121 The task is waiting on an entry call.
17123 @item Async Select Wait
17124 The task is waiting to start the abortable part of an asynchronous
17128 The task is waiting on a select statement with only a delay
17131 @item Child Termination Wait
17132 The task is sleeping having completed a master within itself, and is
17133 waiting for the tasks dependent on that master to become terminated or
17134 waiting on a terminate Phase.
17136 @item Wait Child in Term Alt
17137 The task is sleeping waiting for tasks on terminate alternatives to
17138 finish terminating.
17140 @item Accepting RV with @var{taskno}
17141 The task is accepting a rendez-vous with the task @var{taskno}.
17145 Name of the task in the program.
17149 @kindex info task @var{taskno}
17150 @item info task @var{taskno}
17151 This command shows detailled informations on the specified task, as in
17152 the following example:
17157 (@value{GDBP}) info tasks
17158 ID TID P-ID Pri State Name
17159 1 8077880 0 15 Child Activation Wait main_task
17160 * 2 807c468 1 15 Runnable task_1
17161 (@value{GDBP}) info task 2
17162 Ada Task: 0x807c468
17165 Parent: 1 (main_task)
17171 @kindex task@r{ (Ada)}
17172 @cindex current Ada task ID
17173 This command prints the ID of the current task.
17179 (@value{GDBP}) info tasks
17180 ID TID P-ID Pri State Name
17181 1 8077870 0 15 Child Activation Wait main_task
17182 * 2 807c458 1 15 Runnable t
17183 (@value{GDBP}) task
17184 [Current task is 2]
17187 @item task @var{taskno}
17188 @cindex Ada task switching
17189 This command is like the @code{thread @var{thread-id}}
17190 command (@pxref{Threads}). It switches the context of debugging
17191 from the current task to the given task.
17197 (@value{GDBP}) info tasks
17198 ID TID P-ID Pri State Name
17199 1 8077870 0 15 Child Activation Wait main_task
17200 * 2 807c458 1 15 Runnable t
17201 (@value{GDBP}) task 1
17202 [Switching to task 1]
17203 #0 0x8067726 in pthread_cond_wait ()
17205 #0 0x8067726 in pthread_cond_wait ()
17206 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17207 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17208 #3 0x806153e in system.tasking.stages.activate_tasks ()
17209 #4 0x804aacc in un () at un.adb:5
17212 @item break @var{location} task @var{taskno}
17213 @itemx break @var{location} task @var{taskno} if @dots{}
17214 @cindex breakpoints and tasks, in Ada
17215 @cindex task breakpoints, in Ada
17216 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17217 These commands are like the @code{break @dots{} thread @dots{}}
17218 command (@pxref{Thread Stops}). The
17219 @var{location} argument specifies source lines, as described
17220 in @ref{Specify Location}.
17222 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17223 to specify that you only want @value{GDBN} to stop the program when a
17224 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17225 numeric task identifiers assigned by @value{GDBN}, shown in the first
17226 column of the @samp{info tasks} display.
17228 If you do not specify @samp{task @var{taskno}} when you set a
17229 breakpoint, the breakpoint applies to @emph{all} tasks of your
17232 You can use the @code{task} qualifier on conditional breakpoints as
17233 well; in this case, place @samp{task @var{taskno}} before the
17234 breakpoint condition (before the @code{if}).
17242 (@value{GDBP}) info tasks
17243 ID TID P-ID Pri State Name
17244 1 140022020 0 15 Child Activation Wait main_task
17245 2 140045060 1 15 Accept/Select Wait t2
17246 3 140044840 1 15 Runnable t1
17247 * 4 140056040 1 15 Runnable t3
17248 (@value{GDBP}) b 15 task 2
17249 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17250 (@value{GDBP}) cont
17255 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17257 (@value{GDBP}) info tasks
17258 ID TID P-ID Pri State Name
17259 1 140022020 0 15 Child Activation Wait main_task
17260 * 2 140045060 1 15 Runnable t2
17261 3 140044840 1 15 Runnable t1
17262 4 140056040 1 15 Delay Sleep t3
17266 @node Ada Tasks and Core Files
17267 @subsubsection Tasking Support when Debugging Core Files
17268 @cindex Ada tasking and core file debugging
17270 When inspecting a core file, as opposed to debugging a live program,
17271 tasking support may be limited or even unavailable, depending on
17272 the platform being used.
17273 For instance, on x86-linux, the list of tasks is available, but task
17274 switching is not supported.
17276 On certain platforms, the debugger needs to perform some
17277 memory writes in order to provide Ada tasking support. When inspecting
17278 a core file, this means that the core file must be opened with read-write
17279 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17280 Under these circumstances, you should make a backup copy of the core
17281 file before inspecting it with @value{GDBN}.
17283 @node Ravenscar Profile
17284 @subsubsection Tasking Support when using the Ravenscar Profile
17285 @cindex Ravenscar Profile
17287 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17288 specifically designed for systems with safety-critical real-time
17292 @kindex set ravenscar task-switching on
17293 @cindex task switching with program using Ravenscar Profile
17294 @item set ravenscar task-switching on
17295 Allows task switching when debugging a program that uses the Ravenscar
17296 Profile. This is the default.
17298 @kindex set ravenscar task-switching off
17299 @item set ravenscar task-switching off
17300 Turn off task switching when debugging a program that uses the Ravenscar
17301 Profile. This is mostly intended to disable the code that adds support
17302 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17303 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17304 To be effective, this command should be run before the program is started.
17306 @kindex show ravenscar task-switching
17307 @item show ravenscar task-switching
17308 Show whether it is possible to switch from task to task in a program
17309 using the Ravenscar Profile.
17314 @subsubsection Ada Settings
17315 @cindex Ada settings
17318 @kindex set varsize-limit
17319 @item set varsize-limit @var{size}
17320 Prevent @value{GDBN} from attempting to evaluate objects whose size
17321 is above the given limit (@var{size}) when those sizes are computed
17322 from run-time quantities. This is typically the case when the object
17323 has a variable size, such as an array whose bounds are not known at
17324 compile time for example. Setting @var{size} to @code{unlimited}
17325 removes the size limitation. By default, the limit is about 65KB.
17327 The purpose of having such a limit is to prevent @value{GDBN} from
17328 trying to grab enormous chunks of virtual memory when asked to evaluate
17329 a quantity whose bounds have been corrupted or have not yet been fully
17330 initialized. The limit applies to the results of some subexpressions
17331 as well as to complete expressions. For example, an expression denoting
17332 a simple integer component, such as @code{x.y.z}, may fail if the size of
17333 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17334 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17335 @code{A} is an array variable with non-constant size, will generally
17336 succeed regardless of the bounds on @code{A}, as long as the component
17337 size is less than @var{size}.
17339 @kindex show varsize-limit
17340 @item show varsize-limit
17341 Show the limit on types whose size is determined by run-time quantities.
17345 @subsubsection Known Peculiarities of Ada Mode
17346 @cindex Ada, problems
17348 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17349 we know of several problems with and limitations of Ada mode in
17351 some of which will be fixed with planned future releases of the debugger
17352 and the GNU Ada compiler.
17356 Static constants that the compiler chooses not to materialize as objects in
17357 storage are invisible to the debugger.
17360 Named parameter associations in function argument lists are ignored (the
17361 argument lists are treated as positional).
17364 Many useful library packages are currently invisible to the debugger.
17367 Fixed-point arithmetic, conversions, input, and output is carried out using
17368 floating-point arithmetic, and may give results that only approximate those on
17372 The GNAT compiler never generates the prefix @code{Standard} for any of
17373 the standard symbols defined by the Ada language. @value{GDBN} knows about
17374 this: it will strip the prefix from names when you use it, and will never
17375 look for a name you have so qualified among local symbols, nor match against
17376 symbols in other packages or subprograms. If you have
17377 defined entities anywhere in your program other than parameters and
17378 local variables whose simple names match names in @code{Standard},
17379 GNAT's lack of qualification here can cause confusion. When this happens,
17380 you can usually resolve the confusion
17381 by qualifying the problematic names with package
17382 @code{Standard} explicitly.
17385 Older versions of the compiler sometimes generate erroneous debugging
17386 information, resulting in the debugger incorrectly printing the value
17387 of affected entities. In some cases, the debugger is able to work
17388 around an issue automatically. In other cases, the debugger is able
17389 to work around the issue, but the work-around has to be specifically
17392 @kindex set ada trust-PAD-over-XVS
17393 @kindex show ada trust-PAD-over-XVS
17396 @item set ada trust-PAD-over-XVS on
17397 Configure GDB to strictly follow the GNAT encoding when computing the
17398 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17399 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17400 a complete description of the encoding used by the GNAT compiler).
17401 This is the default.
17403 @item set ada trust-PAD-over-XVS off
17404 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17405 sometimes prints the wrong value for certain entities, changing @code{ada
17406 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17407 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17408 @code{off}, but this incurs a slight performance penalty, so it is
17409 recommended to leave this setting to @code{on} unless necessary.
17413 @cindex GNAT descriptive types
17414 @cindex GNAT encoding
17415 Internally, the debugger also relies on the compiler following a number
17416 of conventions known as the @samp{GNAT Encoding}, all documented in
17417 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17418 how the debugging information should be generated for certain types.
17419 In particular, this convention makes use of @dfn{descriptive types},
17420 which are artificial types generated purely to help the debugger.
17422 These encodings were defined at a time when the debugging information
17423 format used was not powerful enough to describe some of the more complex
17424 types available in Ada. Since DWARF allows us to express nearly all
17425 Ada features, the long-term goal is to slowly replace these descriptive
17426 types by their pure DWARF equivalent. To facilitate that transition,
17427 a new maintenance option is available to force the debugger to ignore
17428 those descriptive types. It allows the user to quickly evaluate how
17429 well @value{GDBN} works without them.
17433 @kindex maint ada set ignore-descriptive-types
17434 @item maintenance ada set ignore-descriptive-types [on|off]
17435 Control whether the debugger should ignore descriptive types.
17436 The default is not to ignore descriptives types (@code{off}).
17438 @kindex maint ada show ignore-descriptive-types
17439 @item maintenance ada show ignore-descriptive-types
17440 Show if descriptive types are ignored by @value{GDBN}.
17444 @node Unsupported Languages
17445 @section Unsupported Languages
17447 @cindex unsupported languages
17448 @cindex minimal language
17449 In addition to the other fully-supported programming languages,
17450 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17451 It does not represent a real programming language, but provides a set
17452 of capabilities close to what the C or assembly languages provide.
17453 This should allow most simple operations to be performed while debugging
17454 an application that uses a language currently not supported by @value{GDBN}.
17456 If the language is set to @code{auto}, @value{GDBN} will automatically
17457 select this language if the current frame corresponds to an unsupported
17461 @chapter Examining the Symbol Table
17463 The commands described in this chapter allow you to inquire about the
17464 symbols (names of variables, functions and types) defined in your
17465 program. This information is inherent in the text of your program and
17466 does not change as your program executes. @value{GDBN} finds it in your
17467 program's symbol table, in the file indicated when you started @value{GDBN}
17468 (@pxref{File Options, ,Choosing Files}), or by one of the
17469 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17471 @cindex symbol names
17472 @cindex names of symbols
17473 @cindex quoting names
17474 @anchor{quoting names}
17475 Occasionally, you may need to refer to symbols that contain unusual
17476 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17477 most frequent case is in referring to static variables in other
17478 source files (@pxref{Variables,,Program Variables}). File names
17479 are recorded in object files as debugging symbols, but @value{GDBN} would
17480 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17481 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17482 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17489 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17492 @cindex case-insensitive symbol names
17493 @cindex case sensitivity in symbol names
17494 @kindex set case-sensitive
17495 @item set case-sensitive on
17496 @itemx set case-sensitive off
17497 @itemx set case-sensitive auto
17498 Normally, when @value{GDBN} looks up symbols, it matches their names
17499 with case sensitivity determined by the current source language.
17500 Occasionally, you may wish to control that. The command @code{set
17501 case-sensitive} lets you do that by specifying @code{on} for
17502 case-sensitive matches or @code{off} for case-insensitive ones. If
17503 you specify @code{auto}, case sensitivity is reset to the default
17504 suitable for the source language. The default is case-sensitive
17505 matches for all languages except for Fortran, for which the default is
17506 case-insensitive matches.
17508 @kindex show case-sensitive
17509 @item show case-sensitive
17510 This command shows the current setting of case sensitivity for symbols
17513 @kindex set print type methods
17514 @item set print type methods
17515 @itemx set print type methods on
17516 @itemx set print type methods off
17517 Normally, when @value{GDBN} prints a class, it displays any methods
17518 declared in that class. You can control this behavior either by
17519 passing the appropriate flag to @code{ptype}, or using @command{set
17520 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17521 display the methods; this is the default. Specifying @code{off} will
17522 cause @value{GDBN} to omit the methods.
17524 @kindex show print type methods
17525 @item show print type methods
17526 This command shows the current setting of method display when printing
17529 @kindex set print type nested-type-limit
17530 @item set print type nested-type-limit @var{limit}
17531 @itemx set print type nested-type-limit unlimited
17532 Set the limit of displayed nested types that the type printer will
17533 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17534 nested definitions. By default, the type printer will not show any nested
17535 types defined in classes.
17537 @kindex show print type nested-type-limit
17538 @item show print type nested-type-limit
17539 This command shows the current display limit of nested types when
17542 @kindex set print type typedefs
17543 @item set print type typedefs
17544 @itemx set print type typedefs on
17545 @itemx set print type typedefs off
17547 Normally, when @value{GDBN} prints a class, it displays any typedefs
17548 defined in that class. You can control this behavior either by
17549 passing the appropriate flag to @code{ptype}, or using @command{set
17550 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17551 display the typedef definitions; this is the default. Specifying
17552 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17553 Note that this controls whether the typedef definition itself is
17554 printed, not whether typedef names are substituted when printing other
17557 @kindex show print type typedefs
17558 @item show print type typedefs
17559 This command shows the current setting of typedef display when
17562 @kindex info address
17563 @cindex address of a symbol
17564 @item info address @var{symbol}
17565 Describe where the data for @var{symbol} is stored. For a register
17566 variable, this says which register it is kept in. For a non-register
17567 local variable, this prints the stack-frame offset at which the variable
17570 Note the contrast with @samp{print &@var{symbol}}, which does not work
17571 at all for a register variable, and for a stack local variable prints
17572 the exact address of the current instantiation of the variable.
17574 @kindex info symbol
17575 @cindex symbol from address
17576 @cindex closest symbol and offset for an address
17577 @item info symbol @var{addr}
17578 Print the name of a symbol which is stored at the address @var{addr}.
17579 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17580 nearest symbol and an offset from it:
17583 (@value{GDBP}) info symbol 0x54320
17584 _initialize_vx + 396 in section .text
17588 This is the opposite of the @code{info address} command. You can use
17589 it to find out the name of a variable or a function given its address.
17591 For dynamically linked executables, the name of executable or shared
17592 library containing the symbol is also printed:
17595 (@value{GDBP}) info symbol 0x400225
17596 _start + 5 in section .text of /tmp/a.out
17597 (@value{GDBP}) info symbol 0x2aaaac2811cf
17598 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17603 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17604 Demangle @var{name}.
17605 If @var{language} is provided it is the name of the language to demangle
17606 @var{name} in. Otherwise @var{name} is demangled in the current language.
17608 The @samp{--} option specifies the end of options,
17609 and is useful when @var{name} begins with a dash.
17611 The parameter @code{demangle-style} specifies how to interpret the kind
17612 of mangling used. @xref{Print Settings}.
17615 @item whatis[/@var{flags}] [@var{arg}]
17616 Print the data type of @var{arg}, which can be either an expression
17617 or a name of a data type. With no argument, print the data type of
17618 @code{$}, the last value in the value history.
17620 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17621 is not actually evaluated, and any side-effecting operations (such as
17622 assignments or function calls) inside it do not take place.
17624 If @var{arg} is a variable or an expression, @code{whatis} prints its
17625 literal type as it is used in the source code. If the type was
17626 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17627 the data type underlying the @code{typedef}. If the type of the
17628 variable or the expression is a compound data type, such as
17629 @code{struct} or @code{class}, @code{whatis} never prints their
17630 fields or methods. It just prints the @code{struct}/@code{class}
17631 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17632 such a compound data type, use @code{ptype}.
17634 If @var{arg} is a type name that was defined using @code{typedef},
17635 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17636 Unrolling means that @code{whatis} will show the underlying type used
17637 in the @code{typedef} declaration of @var{arg}. However, if that
17638 underlying type is also a @code{typedef}, @code{whatis} will not
17641 For C code, the type names may also have the form @samp{class
17642 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17643 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17645 @var{flags} can be used to modify how the type is displayed.
17646 Available flags are:
17650 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17651 parameters and typedefs defined in a class when printing the class'
17652 members. The @code{/r} flag disables this.
17655 Do not print methods defined in the class.
17658 Print methods defined in the class. This is the default, but the flag
17659 exists in case you change the default with @command{set print type methods}.
17662 Do not print typedefs defined in the class. Note that this controls
17663 whether the typedef definition itself is printed, not whether typedef
17664 names are substituted when printing other types.
17667 Print typedefs defined in the class. This is the default, but the flag
17668 exists in case you change the default with @command{set print type typedefs}.
17671 Print the offsets and sizes of fields in a struct, similar to what the
17672 @command{pahole} tool does. This option implies the @code{/tm} flags.
17674 For example, given the following declarations:
17710 Issuing a @kbd{ptype /o struct tuv} command would print:
17713 (@value{GDBP}) ptype /o struct tuv
17714 /* offset | size */ type = struct tuv @{
17715 /* 0 | 4 */ int a1;
17716 /* XXX 4-byte hole */
17717 /* 8 | 8 */ char *a2;
17718 /* 16 | 4 */ int a3;
17720 /* total size (bytes): 24 */
17724 Notice the format of the first column of comments. There, you can
17725 find two parts separated by the @samp{|} character: the @emph{offset},
17726 which indicates where the field is located inside the struct, in
17727 bytes, and the @emph{size} of the field. Another interesting line is
17728 the marker of a @emph{hole} in the struct, indicating that it may be
17729 possible to pack the struct and make it use less space by reorganizing
17732 It is also possible to print offsets inside an union:
17735 (@value{GDBP}) ptype /o union qwe
17736 /* offset | size */ type = union qwe @{
17737 /* 24 */ struct tuv @{
17738 /* 0 | 4 */ int a1;
17739 /* XXX 4-byte hole */
17740 /* 8 | 8 */ char *a2;
17741 /* 16 | 4 */ int a3;
17743 /* total size (bytes): 24 */
17745 /* 40 */ struct xyz @{
17746 /* 0 | 4 */ int f1;
17747 /* 4 | 1 */ char f2;
17748 /* XXX 3-byte hole */
17749 /* 8 | 8 */ void *f3;
17750 /* 16 | 24 */ struct tuv @{
17751 /* 16 | 4 */ int a1;
17752 /* XXX 4-byte hole */
17753 /* 24 | 8 */ char *a2;
17754 /* 32 | 4 */ int a3;
17756 /* total size (bytes): 24 */
17759 /* total size (bytes): 40 */
17762 /* total size (bytes): 40 */
17766 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17767 same space (because we are dealing with an union), the offset is not
17768 printed for them. However, you can still examine the offset of each
17769 of these structures' fields.
17771 Another useful scenario is printing the offsets of a struct containing
17775 (@value{GDBP}) ptype /o struct tyu
17776 /* offset | size */ type = struct tyu @{
17777 /* 0:31 | 4 */ int a1 : 1;
17778 /* 0:28 | 4 */ int a2 : 3;
17779 /* 0: 5 | 4 */ int a3 : 23;
17780 /* 3: 3 | 1 */ signed char a4 : 2;
17781 /* XXX 3-bit hole */
17782 /* XXX 4-byte hole */
17783 /* 8 | 8 */ int64_t a5;
17784 /* 16:27 | 4 */ int a6 : 5;
17785 /* 16:56 | 8 */ int64_t a7 : 3;
17787 /* total size (bytes): 24 */
17791 Note how the offset information is now extended to also include how
17792 many bits are left to be used in each bitfield.
17796 @item ptype[/@var{flags}] [@var{arg}]
17797 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17798 detailed description of the type, instead of just the name of the type.
17799 @xref{Expressions, ,Expressions}.
17801 Contrary to @code{whatis}, @code{ptype} always unrolls any
17802 @code{typedef}s in its argument declaration, whether the argument is
17803 a variable, expression, or a data type. This means that @code{ptype}
17804 of a variable or an expression will not print literally its type as
17805 present in the source code---use @code{whatis} for that. @code{typedef}s at
17806 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17807 fields, methods and inner @code{class typedef}s of @code{struct}s,
17808 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17810 For example, for this variable declaration:
17813 typedef double real_t;
17814 struct complex @{ real_t real; double imag; @};
17815 typedef struct complex complex_t;
17817 real_t *real_pointer_var;
17821 the two commands give this output:
17825 (@value{GDBP}) whatis var
17827 (@value{GDBP}) ptype var
17828 type = struct complex @{
17832 (@value{GDBP}) whatis complex_t
17833 type = struct complex
17834 (@value{GDBP}) whatis struct complex
17835 type = struct complex
17836 (@value{GDBP}) ptype struct complex
17837 type = struct complex @{
17841 (@value{GDBP}) whatis real_pointer_var
17843 (@value{GDBP}) ptype real_pointer_var
17849 As with @code{whatis}, using @code{ptype} without an argument refers to
17850 the type of @code{$}, the last value in the value history.
17852 @cindex incomplete type
17853 Sometimes, programs use opaque data types or incomplete specifications
17854 of complex data structure. If the debug information included in the
17855 program does not allow @value{GDBN} to display a full declaration of
17856 the data type, it will say @samp{<incomplete type>}. For example,
17857 given these declarations:
17861 struct foo *fooptr;
17865 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17868 (@value{GDBP}) ptype foo
17869 $1 = <incomplete type>
17873 ``Incomplete type'' is C terminology for data types that are not
17874 completely specified.
17876 @cindex unknown type
17877 Othertimes, information about a variable's type is completely absent
17878 from the debug information included in the program. This most often
17879 happens when the program or library where the variable is defined
17880 includes no debug information at all. @value{GDBN} knows the variable
17881 exists from inspecting the linker/loader symbol table (e.g., the ELF
17882 dynamic symbol table), but such symbols do not contain type
17883 information. Inspecting the type of a (global) variable for which
17884 @value{GDBN} has no type information shows:
17887 (@value{GDBP}) ptype var
17888 type = <data variable, no debug info>
17891 @xref{Variables, no debug info variables}, for how to print the values
17895 @item info types @var{regexp}
17897 Print a brief description of all types whose names match the regular
17898 expression @var{regexp} (or all types in your program, if you supply
17899 no argument). Each complete typename is matched as though it were a
17900 complete line; thus, @samp{i type value} gives information on all
17901 types in your program whose names include the string @code{value}, but
17902 @samp{i type ^value$} gives information only on types whose complete
17903 name is @code{value}.
17905 This command differs from @code{ptype} in two ways: first, like
17906 @code{whatis}, it does not print a detailed description; second, it
17907 lists all source files and line numbers where a type is defined.
17909 @kindex info type-printers
17910 @item info type-printers
17911 Versions of @value{GDBN} that ship with Python scripting enabled may
17912 have ``type printers'' available. When using @command{ptype} or
17913 @command{whatis}, these printers are consulted when the name of a type
17914 is needed. @xref{Type Printing API}, for more information on writing
17917 @code{info type-printers} displays all the available type printers.
17919 @kindex enable type-printer
17920 @kindex disable type-printer
17921 @item enable type-printer @var{name}@dots{}
17922 @item disable type-printer @var{name}@dots{}
17923 These commands can be used to enable or disable type printers.
17926 @cindex local variables
17927 @item info scope @var{location}
17928 List all the variables local to a particular scope. This command
17929 accepts a @var{location} argument---a function name, a source line, or
17930 an address preceded by a @samp{*}, and prints all the variables local
17931 to the scope defined by that location. (@xref{Specify Location}, for
17932 details about supported forms of @var{location}.) For example:
17935 (@value{GDBP}) @b{info scope command_line_handler}
17936 Scope for command_line_handler:
17937 Symbol rl is an argument at stack/frame offset 8, length 4.
17938 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17939 Symbol linelength is in static storage at address 0x150a1c, length 4.
17940 Symbol p is a local variable in register $esi, length 4.
17941 Symbol p1 is a local variable in register $ebx, length 4.
17942 Symbol nline is a local variable in register $edx, length 4.
17943 Symbol repeat is a local variable at frame offset -8, length 4.
17947 This command is especially useful for determining what data to collect
17948 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17951 @kindex info source
17953 Show information about the current source file---that is, the source file for
17954 the function containing the current point of execution:
17957 the name of the source file, and the directory containing it,
17959 the directory it was compiled in,
17961 its length, in lines,
17963 which programming language it is written in,
17965 if the debug information provides it, the program that compiled the file
17966 (which may include, e.g., the compiler version and command line arguments),
17968 whether the executable includes debugging information for that file, and
17969 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17971 whether the debugging information includes information about
17972 preprocessor macros.
17976 @kindex info sources
17978 Print the names of all source files in your program for which there is
17979 debugging information, organized into two lists: files whose symbols
17980 have already been read, and files whose symbols will be read when needed.
17982 @kindex info functions
17983 @item info functions [-q]
17984 Print the names and data types of all defined functions.
17985 Similarly to @samp{info types}, this command groups its output by source
17986 files and annotates each function definition with its source line
17989 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
17990 printing header information and messages explaining why no functions
17993 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
17994 Like @samp{info functions}, but only print the names and data types
17995 of the functions selected with the provided regexp(s).
17997 If @var{regexp} is provided, print only the functions whose names
17998 match the regular expression @var{regexp}.
17999 Thus, @samp{info fun step} finds all functions whose
18000 names include @code{step}; @samp{info fun ^step} finds those whose names
18001 start with @code{step}. If a function name contains characters that
18002 conflict with the regular expression language (e.g.@:
18003 @samp{operator*()}), they may be quoted with a backslash.
18005 If @var{type_regexp} is provided, print only the functions whose
18006 types, as printed by the @code{whatis} command, match
18007 the regular expression @var{type_regexp}.
18008 If @var{type_regexp} contains space(s), it should be enclosed in
18009 quote characters. If needed, use backslash to escape the meaning
18010 of special characters or quotes.
18011 Thus, @samp{info fun -t '^int ('} finds the functions that return
18012 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18013 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18014 finds the functions whose names start with @code{step} and that return
18017 If both @var{regexp} and @var{type_regexp} are provided, a function
18018 is printed only if its name matches @var{regexp} and its type matches
18022 @kindex info variables
18023 @item info variables [-q]
18024 Print the names and data types of all variables that are defined
18025 outside of functions (i.e.@: excluding local variables).
18026 The printed variables are grouped by source files and annotated with
18027 their respective source line numbers.
18029 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18030 printing header information and messages explaining why no variables
18033 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18034 Like @kbd{info variables}, but only print the variables selected
18035 with the provided regexp(s).
18037 If @var{regexp} is provided, print only the variables whose names
18038 match the regular expression @var{regexp}.
18040 If @var{type_regexp} is provided, print only the variables whose
18041 types, as printed by the @code{whatis} command, match
18042 the regular expression @var{type_regexp}.
18043 If @var{type_regexp} contains space(s), it should be enclosed in
18044 quote characters. If needed, use backslash to escape the meaning
18045 of special characters or quotes.
18047 If both @var{regexp} and @var{type_regexp} are provided, an argument
18048 is printed only if its name matches @var{regexp} and its type matches
18051 @kindex info classes
18052 @cindex Objective-C, classes and selectors
18054 @itemx info classes @var{regexp}
18055 Display all Objective-C classes in your program, or
18056 (with the @var{regexp} argument) all those matching a particular regular
18059 @kindex info selectors
18060 @item info selectors
18061 @itemx info selectors @var{regexp}
18062 Display all Objective-C selectors in your program, or
18063 (with the @var{regexp} argument) all those matching a particular regular
18067 This was never implemented.
18068 @kindex info methods
18070 @itemx info methods @var{regexp}
18071 The @code{info methods} command permits the user to examine all defined
18072 methods within C@t{++} program, or (with the @var{regexp} argument) a
18073 specific set of methods found in the various C@t{++} classes. Many
18074 C@t{++} classes provide a large number of methods. Thus, the output
18075 from the @code{ptype} command can be overwhelming and hard to use. The
18076 @code{info-methods} command filters the methods, printing only those
18077 which match the regular-expression @var{regexp}.
18080 @cindex opaque data types
18081 @kindex set opaque-type-resolution
18082 @item set opaque-type-resolution on
18083 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18084 declared as a pointer to a @code{struct}, @code{class}, or
18085 @code{union}---for example, @code{struct MyType *}---that is used in one
18086 source file although the full declaration of @code{struct MyType} is in
18087 another source file. The default is on.
18089 A change in the setting of this subcommand will not take effect until
18090 the next time symbols for a file are loaded.
18092 @item set opaque-type-resolution off
18093 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18094 is printed as follows:
18096 @{<no data fields>@}
18099 @kindex show opaque-type-resolution
18100 @item show opaque-type-resolution
18101 Show whether opaque types are resolved or not.
18103 @kindex set print symbol-loading
18104 @cindex print messages when symbols are loaded
18105 @item set print symbol-loading
18106 @itemx set print symbol-loading full
18107 @itemx set print symbol-loading brief
18108 @itemx set print symbol-loading off
18109 The @code{set print symbol-loading} command allows you to control the
18110 printing of messages when @value{GDBN} loads symbol information.
18111 By default a message is printed for the executable and one for each
18112 shared library, and normally this is what you want. However, when
18113 debugging apps with large numbers of shared libraries these messages
18115 When set to @code{brief} a message is printed for each executable,
18116 and when @value{GDBN} loads a collection of shared libraries at once
18117 it will only print one message regardless of the number of shared
18118 libraries. When set to @code{off} no messages are printed.
18120 @kindex show print symbol-loading
18121 @item show print symbol-loading
18122 Show whether messages will be printed when a @value{GDBN} command
18123 entered from the keyboard causes symbol information to be loaded.
18125 @kindex maint print symbols
18126 @cindex symbol dump
18127 @kindex maint print psymbols
18128 @cindex partial symbol dump
18129 @kindex maint print msymbols
18130 @cindex minimal symbol dump
18131 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18132 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18133 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18134 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18135 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18136 Write a dump of debugging symbol data into the file @var{filename} or
18137 the terminal if @var{filename} is unspecified.
18138 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18140 If @code{-pc @var{address}} is specified, only dump symbols for the file
18141 with code at that address. Note that @var{address} may be a symbol like
18143 If @code{-source @var{source}} is specified, only dump symbols for that
18146 These commands are used to debug the @value{GDBN} symbol-reading code.
18147 These commands do not modify internal @value{GDBN} state, therefore
18148 @samp{maint print symbols} will only print symbols for already expanded symbol
18150 You can use the command @code{info sources} to find out which files these are.
18151 If you use @samp{maint print psymbols} instead, the dump shows information
18152 about symbols that @value{GDBN} only knows partially---that is, symbols
18153 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18154 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18157 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18158 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18160 @kindex maint info symtabs
18161 @kindex maint info psymtabs
18162 @cindex listing @value{GDBN}'s internal symbol tables
18163 @cindex symbol tables, listing @value{GDBN}'s internal
18164 @cindex full symbol tables, listing @value{GDBN}'s internal
18165 @cindex partial symbol tables, listing @value{GDBN}'s internal
18166 @item maint info symtabs @r{[} @var{regexp} @r{]}
18167 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18169 List the @code{struct symtab} or @code{struct partial_symtab}
18170 structures whose names match @var{regexp}. If @var{regexp} is not
18171 given, list them all. The output includes expressions which you can
18172 copy into a @value{GDBN} debugging this one to examine a particular
18173 structure in more detail. For example:
18176 (@value{GDBP}) maint info psymtabs dwarf2read
18177 @{ objfile /home/gnu/build/gdb/gdb
18178 ((struct objfile *) 0x82e69d0)
18179 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18180 ((struct partial_symtab *) 0x8474b10)
18183 text addresses 0x814d3c8 -- 0x8158074
18184 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18185 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18186 dependencies (none)
18189 (@value{GDBP}) maint info symtabs
18193 We see that there is one partial symbol table whose filename contains
18194 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18195 and we see that @value{GDBN} has not read in any symtabs yet at all.
18196 If we set a breakpoint on a function, that will cause @value{GDBN} to
18197 read the symtab for the compilation unit containing that function:
18200 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18201 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18203 (@value{GDBP}) maint info symtabs
18204 @{ objfile /home/gnu/build/gdb/gdb
18205 ((struct objfile *) 0x82e69d0)
18206 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18207 ((struct symtab *) 0x86c1f38)
18210 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18211 linetable ((struct linetable *) 0x8370fa0)
18212 debugformat DWARF 2
18218 @kindex maint info line-table
18219 @cindex listing @value{GDBN}'s internal line tables
18220 @cindex line tables, listing @value{GDBN}'s internal
18221 @item maint info line-table @r{[} @var{regexp} @r{]}
18223 List the @code{struct linetable} from all @code{struct symtab}
18224 instances whose name matches @var{regexp}. If @var{regexp} is not
18225 given, list the @code{struct linetable} from all @code{struct symtab}.
18227 @kindex maint set symbol-cache-size
18228 @cindex symbol cache size
18229 @item maint set symbol-cache-size @var{size}
18230 Set the size of the symbol cache to @var{size}.
18231 The default size is intended to be good enough for debugging
18232 most applications. This option exists to allow for experimenting
18233 with different sizes.
18235 @kindex maint show symbol-cache-size
18236 @item maint show symbol-cache-size
18237 Show the size of the symbol cache.
18239 @kindex maint print symbol-cache
18240 @cindex symbol cache, printing its contents
18241 @item maint print symbol-cache
18242 Print the contents of the symbol cache.
18243 This is useful when debugging symbol cache issues.
18245 @kindex maint print symbol-cache-statistics
18246 @cindex symbol cache, printing usage statistics
18247 @item maint print symbol-cache-statistics
18248 Print symbol cache usage statistics.
18249 This helps determine how well the cache is being utilized.
18251 @kindex maint flush-symbol-cache
18252 @cindex symbol cache, flushing
18253 @item maint flush-symbol-cache
18254 Flush the contents of the symbol cache, all entries are removed.
18255 This command is useful when debugging the symbol cache.
18256 It is also useful when collecting performance data.
18261 @chapter Altering Execution
18263 Once you think you have found an error in your program, you might want to
18264 find out for certain whether correcting the apparent error would lead to
18265 correct results in the rest of the run. You can find the answer by
18266 experiment, using the @value{GDBN} features for altering execution of the
18269 For example, you can store new values into variables or memory
18270 locations, give your program a signal, restart it at a different
18271 address, or even return prematurely from a function.
18274 * Assignment:: Assignment to variables
18275 * Jumping:: Continuing at a different address
18276 * Signaling:: Giving your program a signal
18277 * Returning:: Returning from a function
18278 * Calling:: Calling your program's functions
18279 * Patching:: Patching your program
18280 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18284 @section Assignment to Variables
18287 @cindex setting variables
18288 To alter the value of a variable, evaluate an assignment expression.
18289 @xref{Expressions, ,Expressions}. For example,
18296 stores the value 4 into the variable @code{x}, and then prints the
18297 value of the assignment expression (which is 4).
18298 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18299 information on operators in supported languages.
18301 @kindex set variable
18302 @cindex variables, setting
18303 If you are not interested in seeing the value of the assignment, use the
18304 @code{set} command instead of the @code{print} command. @code{set} is
18305 really the same as @code{print} except that the expression's value is
18306 not printed and is not put in the value history (@pxref{Value History,
18307 ,Value History}). The expression is evaluated only for its effects.
18309 If the beginning of the argument string of the @code{set} command
18310 appears identical to a @code{set} subcommand, use the @code{set
18311 variable} command instead of just @code{set}. This command is identical
18312 to @code{set} except for its lack of subcommands. For example, if your
18313 program has a variable @code{width}, you get an error if you try to set
18314 a new value with just @samp{set width=13}, because @value{GDBN} has the
18315 command @code{set width}:
18318 (@value{GDBP}) whatis width
18320 (@value{GDBP}) p width
18322 (@value{GDBP}) set width=47
18323 Invalid syntax in expression.
18327 The invalid expression, of course, is @samp{=47}. In
18328 order to actually set the program's variable @code{width}, use
18331 (@value{GDBP}) set var width=47
18334 Because the @code{set} command has many subcommands that can conflict
18335 with the names of program variables, it is a good idea to use the
18336 @code{set variable} command instead of just @code{set}. For example, if
18337 your program has a variable @code{g}, you run into problems if you try
18338 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18339 the command @code{set gnutarget}, abbreviated @code{set g}:
18343 (@value{GDBP}) whatis g
18347 (@value{GDBP}) set g=4
18351 The program being debugged has been started already.
18352 Start it from the beginning? (y or n) y
18353 Starting program: /home/smith/cc_progs/a.out
18354 "/home/smith/cc_progs/a.out": can't open to read symbols:
18355 Invalid bfd target.
18356 (@value{GDBP}) show g
18357 The current BFD target is "=4".
18362 The program variable @code{g} did not change, and you silently set the
18363 @code{gnutarget} to an invalid value. In order to set the variable
18367 (@value{GDBP}) set var g=4
18370 @value{GDBN} allows more implicit conversions in assignments than C; you can
18371 freely store an integer value into a pointer variable or vice versa,
18372 and you can convert any structure to any other structure that is the
18373 same length or shorter.
18374 @comment FIXME: how do structs align/pad in these conversions?
18375 @comment /doc@cygnus.com 18dec1990
18377 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18378 construct to generate a value of specified type at a specified address
18379 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18380 to memory location @code{0x83040} as an integer (which implies a certain size
18381 and representation in memory), and
18384 set @{int@}0x83040 = 4
18388 stores the value 4 into that memory location.
18391 @section Continuing at a Different Address
18393 Ordinarily, when you continue your program, you do so at the place where
18394 it stopped, with the @code{continue} command. You can instead continue at
18395 an address of your own choosing, with the following commands:
18399 @kindex j @r{(@code{jump})}
18400 @item jump @var{location}
18401 @itemx j @var{location}
18402 Resume execution at @var{location}. Execution stops again immediately
18403 if there is a breakpoint there. @xref{Specify Location}, for a description
18404 of the different forms of @var{location}. It is common
18405 practice to use the @code{tbreak} command in conjunction with
18406 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18408 The @code{jump} command does not change the current stack frame, or
18409 the stack pointer, or the contents of any memory location or any
18410 register other than the program counter. If @var{location} is in
18411 a different function from the one currently executing, the results may
18412 be bizarre if the two functions expect different patterns of arguments or
18413 of local variables. For this reason, the @code{jump} command requests
18414 confirmation if the specified line is not in the function currently
18415 executing. However, even bizarre results are predictable if you are
18416 well acquainted with the machine-language code of your program.
18419 On many systems, you can get much the same effect as the @code{jump}
18420 command by storing a new value into the register @code{$pc}. The
18421 difference is that this does not start your program running; it only
18422 changes the address of where it @emph{will} run when you continue. For
18430 makes the next @code{continue} command or stepping command execute at
18431 address @code{0x485}, rather than at the address where your program stopped.
18432 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18434 The most common occasion to use the @code{jump} command is to back
18435 up---perhaps with more breakpoints set---over a portion of a program
18436 that has already executed, in order to examine its execution in more
18441 @section Giving your Program a Signal
18442 @cindex deliver a signal to a program
18446 @item signal @var{signal}
18447 Resume execution where your program is stopped, but immediately give it the
18448 signal @var{signal}. The @var{signal} can be the name or the number of a
18449 signal. For example, on many systems @code{signal 2} and @code{signal
18450 SIGINT} are both ways of sending an interrupt signal.
18452 Alternatively, if @var{signal} is zero, continue execution without
18453 giving a signal. This is useful when your program stopped on account of
18454 a signal and would ordinarily see the signal when resumed with the
18455 @code{continue} command; @samp{signal 0} causes it to resume without a
18458 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18459 delivered to the currently selected thread, not the thread that last
18460 reported a stop. This includes the situation where a thread was
18461 stopped due to a signal. So if you want to continue execution
18462 suppressing the signal that stopped a thread, you should select that
18463 same thread before issuing the @samp{signal 0} command. If you issue
18464 the @samp{signal 0} command with another thread as the selected one,
18465 @value{GDBN} detects that and asks for confirmation.
18467 Invoking the @code{signal} command is not the same as invoking the
18468 @code{kill} utility from the shell. Sending a signal with @code{kill}
18469 causes @value{GDBN} to decide what to do with the signal depending on
18470 the signal handling tables (@pxref{Signals}). The @code{signal} command
18471 passes the signal directly to your program.
18473 @code{signal} does not repeat when you press @key{RET} a second time
18474 after executing the command.
18476 @kindex queue-signal
18477 @item queue-signal @var{signal}
18478 Queue @var{signal} to be delivered immediately to the current thread
18479 when execution of the thread resumes. The @var{signal} can be the name or
18480 the number of a signal. For example, on many systems @code{signal 2} and
18481 @code{signal SIGINT} are both ways of sending an interrupt signal.
18482 The handling of the signal must be set to pass the signal to the program,
18483 otherwise @value{GDBN} will report an error.
18484 You can control the handling of signals from @value{GDBN} with the
18485 @code{handle} command (@pxref{Signals}).
18487 Alternatively, if @var{signal} is zero, any currently queued signal
18488 for the current thread is discarded and when execution resumes no signal
18489 will be delivered. This is useful when your program stopped on account
18490 of a signal and would ordinarily see the signal when resumed with the
18491 @code{continue} command.
18493 This command differs from the @code{signal} command in that the signal
18494 is just queued, execution is not resumed. And @code{queue-signal} cannot
18495 be used to pass a signal whose handling state has been set to @code{nopass}
18500 @xref{stepping into signal handlers}, for information on how stepping
18501 commands behave when the thread has a signal queued.
18504 @section Returning from a Function
18507 @cindex returning from a function
18510 @itemx return @var{expression}
18511 You can cancel execution of a function call with the @code{return}
18512 command. If you give an
18513 @var{expression} argument, its value is used as the function's return
18517 When you use @code{return}, @value{GDBN} discards the selected stack frame
18518 (and all frames within it). You can think of this as making the
18519 discarded frame return prematurely. If you wish to specify a value to
18520 be returned, give that value as the argument to @code{return}.
18522 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18523 Frame}), and any other frames inside of it, leaving its caller as the
18524 innermost remaining frame. That frame becomes selected. The
18525 specified value is stored in the registers used for returning values
18528 The @code{return} command does not resume execution; it leaves the
18529 program stopped in the state that would exist if the function had just
18530 returned. In contrast, the @code{finish} command (@pxref{Continuing
18531 and Stepping, ,Continuing and Stepping}) resumes execution until the
18532 selected stack frame returns naturally.
18534 @value{GDBN} needs to know how the @var{expression} argument should be set for
18535 the inferior. The concrete registers assignment depends on the OS ABI and the
18536 type being returned by the selected stack frame. For example it is common for
18537 OS ABI to return floating point values in FPU registers while integer values in
18538 CPU registers. Still some ABIs return even floating point values in CPU
18539 registers. Larger integer widths (such as @code{long long int}) also have
18540 specific placement rules. @value{GDBN} already knows the OS ABI from its
18541 current target so it needs to find out also the type being returned to make the
18542 assignment into the right register(s).
18544 Normally, the selected stack frame has debug info. @value{GDBN} will always
18545 use the debug info instead of the implicit type of @var{expression} when the
18546 debug info is available. For example, if you type @kbd{return -1}, and the
18547 function in the current stack frame is declared to return a @code{long long
18548 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18549 into a @code{long long int}:
18552 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18554 (@value{GDBP}) return -1
18555 Make func return now? (y or n) y
18556 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18557 43 printf ("result=%lld\n", func ());
18561 However, if the selected stack frame does not have a debug info, e.g., if the
18562 function was compiled without debug info, @value{GDBN} has to find out the type
18563 to return from user. Specifying a different type by mistake may set the value
18564 in different inferior registers than the caller code expects. For example,
18565 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18566 of a @code{long long int} result for a debug info less function (on 32-bit
18567 architectures). Therefore the user is required to specify the return type by
18568 an appropriate cast explicitly:
18571 Breakpoint 2, 0x0040050b in func ()
18572 (@value{GDBP}) return -1
18573 Return value type not available for selected stack frame.
18574 Please use an explicit cast of the value to return.
18575 (@value{GDBP}) return (long long int) -1
18576 Make selected stack frame return now? (y or n) y
18577 #0 0x00400526 in main ()
18582 @section Calling Program Functions
18585 @cindex calling functions
18586 @cindex inferior functions, calling
18587 @item print @var{expr}
18588 Evaluate the expression @var{expr} and display the resulting value.
18589 The expression may include calls to functions in the program being
18593 @item call @var{expr}
18594 Evaluate the expression @var{expr} without displaying @code{void}
18597 You can use this variant of the @code{print} command if you want to
18598 execute a function from your program that does not return anything
18599 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18600 with @code{void} returned values that @value{GDBN} will otherwise
18601 print. If the result is not void, it is printed and saved in the
18605 It is possible for the function you call via the @code{print} or
18606 @code{call} command to generate a signal (e.g., if there's a bug in
18607 the function, or if you passed it incorrect arguments). What happens
18608 in that case is controlled by the @code{set unwindonsignal} command.
18610 Similarly, with a C@t{++} program it is possible for the function you
18611 call via the @code{print} or @code{call} command to generate an
18612 exception that is not handled due to the constraints of the dummy
18613 frame. In this case, any exception that is raised in the frame, but has
18614 an out-of-frame exception handler will not be found. GDB builds a
18615 dummy-frame for the inferior function call, and the unwinder cannot
18616 seek for exception handlers outside of this dummy-frame. What happens
18617 in that case is controlled by the
18618 @code{set unwind-on-terminating-exception} command.
18621 @item set unwindonsignal
18622 @kindex set unwindonsignal
18623 @cindex unwind stack in called functions
18624 @cindex call dummy stack unwinding
18625 Set unwinding of the stack if a signal is received while in a function
18626 that @value{GDBN} called in the program being debugged. If set to on,
18627 @value{GDBN} unwinds the stack it created for the call and restores
18628 the context to what it was before the call. If set to off (the
18629 default), @value{GDBN} stops in the frame where the signal was
18632 @item show unwindonsignal
18633 @kindex show unwindonsignal
18634 Show the current setting of stack unwinding in the functions called by
18637 @item set unwind-on-terminating-exception
18638 @kindex set unwind-on-terminating-exception
18639 @cindex unwind stack in called functions with unhandled exceptions
18640 @cindex call dummy stack unwinding on unhandled exception.
18641 Set unwinding of the stack if a C@t{++} exception is raised, but left
18642 unhandled while in a function that @value{GDBN} called in the program being
18643 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18644 it created for the call and restores the context to what it was before
18645 the call. If set to off, @value{GDBN} the exception is delivered to
18646 the default C@t{++} exception handler and the inferior terminated.
18648 @item show unwind-on-terminating-exception
18649 @kindex show unwind-on-terminating-exception
18650 Show the current setting of stack unwinding in the functions called by
18655 @subsection Calling functions with no debug info
18657 @cindex no debug info functions
18658 Sometimes, a function you wish to call is missing debug information.
18659 In such case, @value{GDBN} does not know the type of the function,
18660 including the types of the function's parameters. To avoid calling
18661 the inferior function incorrectly, which could result in the called
18662 function functioning erroneously and even crash, @value{GDBN} refuses
18663 to call the function unless you tell it the type of the function.
18665 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18666 to do that. The simplest is to cast the call to the function's
18667 declared return type. For example:
18670 (@value{GDBP}) p getenv ("PATH")
18671 'getenv' has unknown return type; cast the call to its declared return type
18672 (@value{GDBP}) p (char *) getenv ("PATH")
18673 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18676 Casting the return type of a no-debug function is equivalent to
18677 casting the function to a pointer to a prototyped function that has a
18678 prototype that matches the types of the passed-in arguments, and
18679 calling that. I.e., the call above is equivalent to:
18682 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18686 and given this prototyped C or C++ function with float parameters:
18689 float multiply (float v1, float v2) @{ return v1 * v2; @}
18693 these calls are equivalent:
18696 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18697 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18700 If the function you wish to call is declared as unprototyped (i.e.@:
18701 old K&R style), you must use the cast-to-function-pointer syntax, so
18702 that @value{GDBN} knows that it needs to apply default argument
18703 promotions (promote float arguments to double). @xref{ABI, float
18704 promotion}. For example, given this unprototyped C function with
18705 float parameters, and no debug info:
18709 multiply_noproto (v1, v2)
18717 you call it like this:
18720 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18724 @section Patching Programs
18726 @cindex patching binaries
18727 @cindex writing into executables
18728 @cindex writing into corefiles
18730 By default, @value{GDBN} opens the file containing your program's
18731 executable code (or the corefile) read-only. This prevents accidental
18732 alterations to machine code; but it also prevents you from intentionally
18733 patching your program's binary.
18735 If you'd like to be able to patch the binary, you can specify that
18736 explicitly with the @code{set write} command. For example, you might
18737 want to turn on internal debugging flags, or even to make emergency
18743 @itemx set write off
18744 If you specify @samp{set write on}, @value{GDBN} opens executable and
18745 core files for both reading and writing; if you specify @kbd{set write
18746 off} (the default), @value{GDBN} opens them read-only.
18748 If you have already loaded a file, you must load it again (using the
18749 @code{exec-file} or @code{core-file} command) after changing @code{set
18750 write}, for your new setting to take effect.
18754 Display whether executable files and core files are opened for writing
18755 as well as reading.
18758 @node Compiling and Injecting Code
18759 @section Compiling and injecting code in @value{GDBN}
18760 @cindex injecting code
18761 @cindex writing into executables
18762 @cindex compiling code
18764 @value{GDBN} supports on-demand compilation and code injection into
18765 programs running under @value{GDBN}. GCC 5.0 or higher built with
18766 @file{libcc1.so} must be installed for this functionality to be enabled.
18767 This functionality is implemented with the following commands.
18770 @kindex compile code
18771 @item compile code @var{source-code}
18772 @itemx compile code -raw @var{--} @var{source-code}
18773 Compile @var{source-code} with the compiler language found as the current
18774 language in @value{GDBN} (@pxref{Languages}). If compilation and
18775 injection is not supported with the current language specified in
18776 @value{GDBN}, or the compiler does not support this feature, an error
18777 message will be printed. If @var{source-code} compiles and links
18778 successfully, @value{GDBN} will load the object-code emitted,
18779 and execute it within the context of the currently selected inferior.
18780 It is important to note that the compiled code is executed immediately.
18781 After execution, the compiled code is removed from @value{GDBN} and any
18782 new types or variables you have defined will be deleted.
18784 The command allows you to specify @var{source-code} in two ways.
18785 The simplest method is to provide a single line of code to the command.
18789 compile code printf ("hello world\n");
18792 If you specify options on the command line as well as source code, they
18793 may conflict. The @samp{--} delimiter can be used to separate options
18794 from actual source code. E.g.:
18797 compile code -r -- printf ("hello world\n");
18800 Alternatively you can enter source code as multiple lines of text. To
18801 enter this mode, invoke the @samp{compile code} command without any text
18802 following the command. This will start the multiple-line editor and
18803 allow you to type as many lines of source code as required. When you
18804 have completed typing, enter @samp{end} on its own line to exit the
18809 >printf ("hello\n");
18810 >printf ("world\n");
18814 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18815 provided @var{source-code} in a callable scope. In this case, you must
18816 specify the entry point of the code by defining a function named
18817 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18818 inferior. Using @samp{-raw} option may be needed for example when
18819 @var{source-code} requires @samp{#include} lines which may conflict with
18820 inferior symbols otherwise.
18822 @kindex compile file
18823 @item compile file @var{filename}
18824 @itemx compile file -raw @var{filename}
18825 Like @code{compile code}, but take the source code from @var{filename}.
18828 compile file /home/user/example.c
18833 @item compile print @var{expr}
18834 @itemx compile print /@var{f} @var{expr}
18835 Compile and execute @var{expr} with the compiler language found as the
18836 current language in @value{GDBN} (@pxref{Languages}). By default the
18837 value of @var{expr} is printed in a format appropriate to its data type;
18838 you can choose a different format by specifying @samp{/@var{f}}, where
18839 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18842 @item compile print
18843 @itemx compile print /@var{f}
18844 @cindex reprint the last value
18845 Alternatively you can enter the expression (source code producing it) as
18846 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18847 command without any text following the command. This will start the
18848 multiple-line editor.
18852 The process of compiling and injecting the code can be inspected using:
18855 @anchor{set debug compile}
18856 @item set debug compile
18857 @cindex compile command debugging info
18858 Turns on or off display of @value{GDBN} process of compiling and
18859 injecting the code. The default is off.
18861 @item show debug compile
18862 Displays the current state of displaying @value{GDBN} process of
18863 compiling and injecting the code.
18865 @anchor{set debug compile-cplus-types}
18866 @item set debug compile-cplus-types
18867 @cindex compile C@t{++} type conversion
18868 Turns on or off the display of C@t{++} type conversion debugging information.
18869 The default is off.
18871 @item show debug compile-cplus-types
18872 Displays the current state of displaying debugging information for
18873 C@t{++} type conversion.
18876 @subsection Compilation options for the @code{compile} command
18878 @value{GDBN} needs to specify the right compilation options for the code
18879 to be injected, in part to make its ABI compatible with the inferior
18880 and in part to make the injected code compatible with @value{GDBN}'s
18884 The options used, in increasing precedence:
18887 @item target architecture and OS options (@code{gdbarch})
18888 These options depend on target processor type and target operating
18889 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18890 (@code{-m64}) compilation option.
18892 @item compilation options recorded in the target
18893 @value{NGCC} (since version 4.7) stores the options used for compilation
18894 into @code{DW_AT_producer} part of DWARF debugging information according
18895 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18896 explicitly specify @code{-g} during inferior compilation otherwise
18897 @value{NGCC} produces no DWARF. This feature is only relevant for
18898 platforms where @code{-g} produces DWARF by default, otherwise one may
18899 try to enforce DWARF by using @code{-gdwarf-4}.
18901 @item compilation options set by @code{set compile-args}
18905 You can override compilation options using the following command:
18908 @item set compile-args
18909 @cindex compile command options override
18910 Set compilation options used for compiling and injecting code with the
18911 @code{compile} commands. These options override any conflicting ones
18912 from the target architecture and/or options stored during inferior
18915 @item show compile-args
18916 Displays the current state of compilation options override.
18917 This does not show all the options actually used during compilation,
18918 use @ref{set debug compile} for that.
18921 @subsection Caveats when using the @code{compile} command
18923 There are a few caveats to keep in mind when using the @code{compile}
18924 command. As the caveats are different per language, the table below
18925 highlights specific issues on a per language basis.
18928 @item C code examples and caveats
18929 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18930 attempt to compile the source code with a @samp{C} compiler. The source
18931 code provided to the @code{compile} command will have much the same
18932 access to variables and types as it normally would if it were part of
18933 the program currently being debugged in @value{GDBN}.
18935 Below is a sample program that forms the basis of the examples that
18936 follow. This program has been compiled and loaded into @value{GDBN},
18937 much like any other normal debugging session.
18940 void function1 (void)
18943 printf ("function 1\n");
18946 void function2 (void)
18961 For the purposes of the examples in this section, the program above has
18962 been compiled, loaded into @value{GDBN}, stopped at the function
18963 @code{main}, and @value{GDBN} is awaiting input from the user.
18965 To access variables and types for any program in @value{GDBN}, the
18966 program must be compiled and packaged with debug information. The
18967 @code{compile} command is not an exception to this rule. Without debug
18968 information, you can still use the @code{compile} command, but you will
18969 be very limited in what variables and types you can access.
18971 So with that in mind, the example above has been compiled with debug
18972 information enabled. The @code{compile} command will have access to
18973 all variables and types (except those that may have been optimized
18974 out). Currently, as @value{GDBN} has stopped the program in the
18975 @code{main} function, the @code{compile} command would have access to
18976 the variable @code{k}. You could invoke the @code{compile} command
18977 and type some source code to set the value of @code{k}. You can also
18978 read it, or do anything with that variable you would normally do in
18979 @code{C}. Be aware that changes to inferior variables in the
18980 @code{compile} command are persistent. In the following example:
18983 compile code k = 3;
18987 the variable @code{k} is now 3. It will retain that value until
18988 something else in the example program changes it, or another
18989 @code{compile} command changes it.
18991 Normal scope and access rules apply to source code compiled and
18992 injected by the @code{compile} command. In the example, the variables
18993 @code{j} and @code{k} are not accessible yet, because the program is
18994 currently stopped in the @code{main} function, where these variables
18995 are not in scope. Therefore, the following command
18998 compile code j = 3;
19002 will result in a compilation error message.
19004 Once the program is continued, execution will bring these variables in
19005 scope, and they will become accessible; then the code you specify via
19006 the @code{compile} command will be able to access them.
19008 You can create variables and types with the @code{compile} command as
19009 part of your source code. Variables and types that are created as part
19010 of the @code{compile} command are not visible to the rest of the program for
19011 the duration of its run. This example is valid:
19014 compile code int ff = 5; printf ("ff is %d\n", ff);
19017 However, if you were to type the following into @value{GDBN} after that
19018 command has completed:
19021 compile code printf ("ff is %d\n'', ff);
19025 a compiler error would be raised as the variable @code{ff} no longer
19026 exists. Object code generated and injected by the @code{compile}
19027 command is removed when its execution ends. Caution is advised
19028 when assigning to program variables values of variables created by the
19029 code submitted to the @code{compile} command. This example is valid:
19032 compile code int ff = 5; k = ff;
19035 The value of the variable @code{ff} is assigned to @code{k}. The variable
19036 @code{k} does not require the existence of @code{ff} to maintain the value
19037 it has been assigned. However, pointers require particular care in
19038 assignment. If the source code compiled with the @code{compile} command
19039 changed the address of a pointer in the example program, perhaps to a
19040 variable created in the @code{compile} command, that pointer would point
19041 to an invalid location when the command exits. The following example
19042 would likely cause issues with your debugged program:
19045 compile code int ff = 5; p = &ff;
19048 In this example, @code{p} would point to @code{ff} when the
19049 @code{compile} command is executing the source code provided to it.
19050 However, as variables in the (example) program persist with their
19051 assigned values, the variable @code{p} would point to an invalid
19052 location when the command exists. A general rule should be followed
19053 in that you should either assign @code{NULL} to any assigned pointers,
19054 or restore a valid location to the pointer before the command exits.
19056 Similar caution must be exercised with any structs, unions, and typedefs
19057 defined in @code{compile} command. Types defined in the @code{compile}
19058 command will no longer be available in the next @code{compile} command.
19059 Therefore, if you cast a variable to a type defined in the
19060 @code{compile} command, care must be taken to ensure that any future
19061 need to resolve the type can be achieved.
19064 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19065 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19066 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19067 Compilation failed.
19068 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19072 Variables that have been optimized away by the compiler are not
19073 accessible to the code submitted to the @code{compile} command.
19074 Access to those variables will generate a compiler error which @value{GDBN}
19075 will print to the console.
19078 @subsection Compiler search for the @code{compile} command
19080 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19081 which may not be obvious for remote targets of different architecture
19082 than where @value{GDBN} is running. Environment variable @code{PATH} on
19083 @value{GDBN} host is searched for @value{NGCC} binary matching the
19084 target architecture and operating system. This search can be overriden
19085 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19086 taken from shell that executed @value{GDBN}, it is not the value set by
19087 @value{GDBN} command @code{set environment}). @xref{Environment}.
19090 Specifically @code{PATH} is searched for binaries matching regular expression
19091 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19092 debugged. @var{arch} is processor name --- multiarch is supported, so for
19093 example both @code{i386} and @code{x86_64} targets look for pattern
19094 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19095 for pattern @code{s390x?}. @var{os} is currently supported only for
19096 pattern @code{linux(-gnu)?}.
19098 On Posix hosts the compiler driver @value{GDBN} needs to find also
19099 shared library @file{libcc1.so} from the compiler. It is searched in
19100 default shared library search path (overridable with usual environment
19101 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19102 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19103 according to the installation of the found compiler --- as possibly
19104 specified by the @code{set compile-gcc} command.
19107 @item set compile-gcc
19108 @cindex compile command driver filename override
19109 Set compilation command used for compiling and injecting code with the
19110 @code{compile} commands. If this option is not set (it is set to
19111 an empty string), the search described above will occur --- that is the
19114 @item show compile-gcc
19115 Displays the current compile command @value{NGCC} driver filename.
19116 If set, it is the main command @command{gcc}, found usually for example
19117 under name @file{x86_64-linux-gnu-gcc}.
19121 @chapter @value{GDBN} Files
19123 @value{GDBN} needs to know the file name of the program to be debugged,
19124 both in order to read its symbol table and in order to start your
19125 program. To debug a core dump of a previous run, you must also tell
19126 @value{GDBN} the name of the core dump file.
19129 * Files:: Commands to specify files
19130 * File Caching:: Information about @value{GDBN}'s file caching
19131 * Separate Debug Files:: Debugging information in separate files
19132 * MiniDebugInfo:: Debugging information in a special section
19133 * Index Files:: Index files speed up GDB
19134 * Symbol Errors:: Errors reading symbol files
19135 * Data Files:: GDB data files
19139 @section Commands to Specify Files
19141 @cindex symbol table
19142 @cindex core dump file
19144 You may want to specify executable and core dump file names. The usual
19145 way to do this is at start-up time, using the arguments to
19146 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19147 Out of @value{GDBN}}).
19149 Occasionally it is necessary to change to a different file during a
19150 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19151 specify a file you want to use. Or you are debugging a remote target
19152 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19153 Program}). In these situations the @value{GDBN} commands to specify
19154 new files are useful.
19157 @cindex executable file
19159 @item file @var{filename}
19160 Use @var{filename} as the program to be debugged. It is read for its
19161 symbols and for the contents of pure memory. It is also the program
19162 executed when you use the @code{run} command. If you do not specify a
19163 directory and the file is not found in the @value{GDBN} working directory,
19164 @value{GDBN} uses the environment variable @code{PATH} as a list of
19165 directories to search, just as the shell does when looking for a program
19166 to run. You can change the value of this variable, for both @value{GDBN}
19167 and your program, using the @code{path} command.
19169 @cindex unlinked object files
19170 @cindex patching object files
19171 You can load unlinked object @file{.o} files into @value{GDBN} using
19172 the @code{file} command. You will not be able to ``run'' an object
19173 file, but you can disassemble functions and inspect variables. Also,
19174 if the underlying BFD functionality supports it, you could use
19175 @kbd{gdb -write} to patch object files using this technique. Note
19176 that @value{GDBN} can neither interpret nor modify relocations in this
19177 case, so branches and some initialized variables will appear to go to
19178 the wrong place. But this feature is still handy from time to time.
19181 @code{file} with no argument makes @value{GDBN} discard any information it
19182 has on both executable file and the symbol table.
19185 @item exec-file @r{[} @var{filename} @r{]}
19186 Specify that the program to be run (but not the symbol table) is found
19187 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19188 if necessary to locate your program. Omitting @var{filename} means to
19189 discard information on the executable file.
19191 @kindex symbol-file
19192 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19193 Read symbol table information from file @var{filename}. @code{PATH} is
19194 searched when necessary. Use the @code{file} command to get both symbol
19195 table and program to run from the same file.
19197 If an optional @var{offset} is specified, it is added to the start
19198 address of each section in the symbol file. This is useful if the
19199 program is relocated at runtime, such as the Linux kernel with kASLR
19202 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19203 program's symbol table.
19205 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19206 some breakpoints and auto-display expressions. This is because they may
19207 contain pointers to the internal data recording symbols and data types,
19208 which are part of the old symbol table data being discarded inside
19211 @code{symbol-file} does not repeat if you press @key{RET} again after
19214 When @value{GDBN} is configured for a particular environment, it
19215 understands debugging information in whatever format is the standard
19216 generated for that environment; you may use either a @sc{gnu} compiler, or
19217 other compilers that adhere to the local conventions.
19218 Best results are usually obtained from @sc{gnu} compilers; for example,
19219 using @code{@value{NGCC}} you can generate debugging information for
19222 For most kinds of object files, with the exception of old SVR3 systems
19223 using COFF, the @code{symbol-file} command does not normally read the
19224 symbol table in full right away. Instead, it scans the symbol table
19225 quickly to find which source files and which symbols are present. The
19226 details are read later, one source file at a time, as they are needed.
19228 The purpose of this two-stage reading strategy is to make @value{GDBN}
19229 start up faster. For the most part, it is invisible except for
19230 occasional pauses while the symbol table details for a particular source
19231 file are being read. (The @code{set verbose} command can turn these
19232 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19233 Warnings and Messages}.)
19235 We have not implemented the two-stage strategy for COFF yet. When the
19236 symbol table is stored in COFF format, @code{symbol-file} reads the
19237 symbol table data in full right away. Note that ``stabs-in-COFF''
19238 still does the two-stage strategy, since the debug info is actually
19242 @cindex reading symbols immediately
19243 @cindex symbols, reading immediately
19244 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19245 @itemx file @r{[} -readnow @r{]} @var{filename}
19246 You can override the @value{GDBN} two-stage strategy for reading symbol
19247 tables by using the @samp{-readnow} option with any of the commands that
19248 load symbol table information, if you want to be sure @value{GDBN} has the
19249 entire symbol table available.
19251 @cindex @code{-readnever}, option for symbol-file command
19252 @cindex never read symbols
19253 @cindex symbols, never read
19254 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19255 @itemx file @r{[} -readnever @r{]} @var{filename}
19256 You can instruct @value{GDBN} to never read the symbolic information
19257 contained in @var{filename} by using the @samp{-readnever} option.
19258 @xref{--readnever}.
19260 @c FIXME: for now no mention of directories, since this seems to be in
19261 @c flux. 13mar1992 status is that in theory GDB would look either in
19262 @c current dir or in same dir as myprog; but issues like competing
19263 @c GDB's, or clutter in system dirs, mean that in practice right now
19264 @c only current dir is used. FFish says maybe a special GDB hierarchy
19265 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19269 @item core-file @r{[}@var{filename}@r{]}
19271 Specify the whereabouts of a core dump file to be used as the ``contents
19272 of memory''. Traditionally, core files contain only some parts of the
19273 address space of the process that generated them; @value{GDBN} can access the
19274 executable file itself for other parts.
19276 @code{core-file} with no argument specifies that no core file is
19279 Note that the core file is ignored when your program is actually running
19280 under @value{GDBN}. So, if you have been running your program and you
19281 wish to debug a core file instead, you must kill the subprocess in which
19282 the program is running. To do this, use the @code{kill} command
19283 (@pxref{Kill Process, ,Killing the Child Process}).
19285 @kindex add-symbol-file
19286 @cindex dynamic linking
19287 @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{]}
19288 The @code{add-symbol-file} command reads additional symbol table
19289 information from the file @var{filename}. You would use this command
19290 when @var{filename} has been dynamically loaded (by some other means)
19291 into the program that is running. The @var{textaddress} parameter gives
19292 the memory address at which the file's text section has been loaded.
19293 You can additionally specify the base address of other sections using
19294 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19295 If a section is omitted, @value{GDBN} will use its default addresses
19296 as found in @var{filename}. Any @var{address} or @var{textaddress}
19297 can be given as an expression.
19299 If an optional @var{offset} is specified, it is added to the start
19300 address of each section, except those for which the address was
19301 specified explicitly.
19303 The symbol table of the file @var{filename} is added to the symbol table
19304 originally read with the @code{symbol-file} command. You can use the
19305 @code{add-symbol-file} command any number of times; the new symbol data
19306 thus read is kept in addition to the old.
19308 Changes can be reverted using the command @code{remove-symbol-file}.
19310 @cindex relocatable object files, reading symbols from
19311 @cindex object files, relocatable, reading symbols from
19312 @cindex reading symbols from relocatable object files
19313 @cindex symbols, reading from relocatable object files
19314 @cindex @file{.o} files, reading symbols from
19315 Although @var{filename} is typically a shared library file, an
19316 executable file, or some other object file which has been fully
19317 relocated for loading into a process, you can also load symbolic
19318 information from relocatable @file{.o} files, as long as:
19322 the file's symbolic information refers only to linker symbols defined in
19323 that file, not to symbols defined by other object files,
19325 every section the file's symbolic information refers to has actually
19326 been loaded into the inferior, as it appears in the file, and
19328 you can determine the address at which every section was loaded, and
19329 provide these to the @code{add-symbol-file} command.
19333 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19334 relocatable files into an already running program; such systems
19335 typically make the requirements above easy to meet. However, it's
19336 important to recognize that many native systems use complex link
19337 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19338 assembly, for example) that make the requirements difficult to meet. In
19339 general, one cannot assume that using @code{add-symbol-file} to read a
19340 relocatable object file's symbolic information will have the same effect
19341 as linking the relocatable object file into the program in the normal
19344 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19346 @kindex remove-symbol-file
19347 @item remove-symbol-file @var{filename}
19348 @item remove-symbol-file -a @var{address}
19349 Remove a symbol file added via the @code{add-symbol-file} command. The
19350 file to remove can be identified by its @var{filename} or by an @var{address}
19351 that lies within the boundaries of this symbol file in memory. Example:
19354 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19355 add symbol table from file "/home/user/gdb/mylib.so" at
19356 .text_addr = 0x7ffff7ff9480
19358 Reading symbols from /home/user/gdb/mylib.so...done.
19359 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19360 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19365 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19367 @kindex add-symbol-file-from-memory
19368 @cindex @code{syscall DSO}
19369 @cindex load symbols from memory
19370 @item add-symbol-file-from-memory @var{address}
19371 Load symbols from the given @var{address} in a dynamically loaded
19372 object file whose image is mapped directly into the inferior's memory.
19373 For example, the Linux kernel maps a @code{syscall DSO} into each
19374 process's address space; this DSO provides kernel-specific code for
19375 some system calls. The argument can be any expression whose
19376 evaluation yields the address of the file's shared object file header.
19377 For this command to work, you must have used @code{symbol-file} or
19378 @code{exec-file} commands in advance.
19381 @item section @var{section} @var{addr}
19382 The @code{section} command changes the base address of the named
19383 @var{section} of the exec file to @var{addr}. This can be used if the
19384 exec file does not contain section addresses, (such as in the
19385 @code{a.out} format), or when the addresses specified in the file
19386 itself are wrong. Each section must be changed separately. The
19387 @code{info files} command, described below, lists all the sections and
19391 @kindex info target
19394 @code{info files} and @code{info target} are synonymous; both print the
19395 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19396 including the names of the executable and core dump files currently in
19397 use by @value{GDBN}, and the files from which symbols were loaded. The
19398 command @code{help target} lists all possible targets rather than
19401 @kindex maint info sections
19402 @item maint info sections
19403 Another command that can give you extra information about program sections
19404 is @code{maint info sections}. In addition to the section information
19405 displayed by @code{info files}, this command displays the flags and file
19406 offset of each section in the executable and core dump files. In addition,
19407 @code{maint info sections} provides the following command options (which
19408 may be arbitrarily combined):
19412 Display sections for all loaded object files, including shared libraries.
19413 @item @var{sections}
19414 Display info only for named @var{sections}.
19415 @item @var{section-flags}
19416 Display info only for sections for which @var{section-flags} are true.
19417 The section flags that @value{GDBN} currently knows about are:
19420 Section will have space allocated in the process when loaded.
19421 Set for all sections except those containing debug information.
19423 Section will be loaded from the file into the child process memory.
19424 Set for pre-initialized code and data, clear for @code{.bss} sections.
19426 Section needs to be relocated before loading.
19428 Section cannot be modified by the child process.
19430 Section contains executable code only.
19432 Section contains data only (no executable code).
19434 Section will reside in ROM.
19436 Section contains data for constructor/destructor lists.
19438 Section is not empty.
19440 An instruction to the linker to not output the section.
19441 @item COFF_SHARED_LIBRARY
19442 A notification to the linker that the section contains
19443 COFF shared library information.
19445 Section contains common symbols.
19448 @kindex set trust-readonly-sections
19449 @cindex read-only sections
19450 @item set trust-readonly-sections on
19451 Tell @value{GDBN} that readonly sections in your object file
19452 really are read-only (i.e.@: that their contents will not change).
19453 In that case, @value{GDBN} can fetch values from these sections
19454 out of the object file, rather than from the target program.
19455 For some targets (notably embedded ones), this can be a significant
19456 enhancement to debugging performance.
19458 The default is off.
19460 @item set trust-readonly-sections off
19461 Tell @value{GDBN} not to trust readonly sections. This means that
19462 the contents of the section might change while the program is running,
19463 and must therefore be fetched from the target when needed.
19465 @item show trust-readonly-sections
19466 Show the current setting of trusting readonly sections.
19469 All file-specifying commands allow both absolute and relative file names
19470 as arguments. @value{GDBN} always converts the file name to an absolute file
19471 name and remembers it that way.
19473 @cindex shared libraries
19474 @anchor{Shared Libraries}
19475 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19476 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19477 DSBT (TIC6X) shared libraries.
19479 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19480 shared libraries. @xref{Expat}.
19482 @value{GDBN} automatically loads symbol definitions from shared libraries
19483 when you use the @code{run} command, or when you examine a core file.
19484 (Before you issue the @code{run} command, @value{GDBN} does not understand
19485 references to a function in a shared library, however---unless you are
19486 debugging a core file).
19488 @c FIXME: some @value{GDBN} release may permit some refs to undef
19489 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19490 @c FIXME...lib; check this from time to time when updating manual
19492 There are times, however, when you may wish to not automatically load
19493 symbol definitions from shared libraries, such as when they are
19494 particularly large or there are many of them.
19496 To control the automatic loading of shared library symbols, use the
19500 @kindex set auto-solib-add
19501 @item set auto-solib-add @var{mode}
19502 If @var{mode} is @code{on}, symbols from all shared object libraries
19503 will be loaded automatically when the inferior begins execution, you
19504 attach to an independently started inferior, or when the dynamic linker
19505 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19506 is @code{off}, symbols must be loaded manually, using the
19507 @code{sharedlibrary} command. The default value is @code{on}.
19509 @cindex memory used for symbol tables
19510 If your program uses lots of shared libraries with debug info that
19511 takes large amounts of memory, you can decrease the @value{GDBN}
19512 memory footprint by preventing it from automatically loading the
19513 symbols from shared libraries. To that end, type @kbd{set
19514 auto-solib-add off} before running the inferior, then load each
19515 library whose debug symbols you do need with @kbd{sharedlibrary
19516 @var{regexp}}, where @var{regexp} is a regular expression that matches
19517 the libraries whose symbols you want to be loaded.
19519 @kindex show auto-solib-add
19520 @item show auto-solib-add
19521 Display the current autoloading mode.
19524 @cindex load shared library
19525 To explicitly load shared library symbols, use the @code{sharedlibrary}
19529 @kindex info sharedlibrary
19531 @item info share @var{regex}
19532 @itemx info sharedlibrary @var{regex}
19533 Print the names of the shared libraries which are currently loaded
19534 that match @var{regex}. If @var{regex} is omitted then print
19535 all shared libraries that are loaded.
19538 @item info dll @var{regex}
19539 This is an alias of @code{info sharedlibrary}.
19541 @kindex sharedlibrary
19543 @item sharedlibrary @var{regex}
19544 @itemx share @var{regex}
19545 Load shared object library symbols for files matching a
19546 Unix regular expression.
19547 As with files loaded automatically, it only loads shared libraries
19548 required by your program for a core file or after typing @code{run}. If
19549 @var{regex} is omitted all shared libraries required by your program are
19552 @item nosharedlibrary
19553 @kindex nosharedlibrary
19554 @cindex unload symbols from shared libraries
19555 Unload all shared object library symbols. This discards all symbols
19556 that have been loaded from all shared libraries. Symbols from shared
19557 libraries that were loaded by explicit user requests are not
19561 Sometimes you may wish that @value{GDBN} stops and gives you control
19562 when any of shared library events happen. The best way to do this is
19563 to use @code{catch load} and @code{catch unload} (@pxref{Set
19566 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19567 command for this. This command exists for historical reasons. It is
19568 less useful than setting a catchpoint, because it does not allow for
19569 conditions or commands as a catchpoint does.
19572 @item set stop-on-solib-events
19573 @kindex set stop-on-solib-events
19574 This command controls whether @value{GDBN} should give you control
19575 when the dynamic linker notifies it about some shared library event.
19576 The most common event of interest is loading or unloading of a new
19579 @item show stop-on-solib-events
19580 @kindex show stop-on-solib-events
19581 Show whether @value{GDBN} stops and gives you control when shared
19582 library events happen.
19585 Shared libraries are also supported in many cross or remote debugging
19586 configurations. @value{GDBN} needs to have access to the target's libraries;
19587 this can be accomplished either by providing copies of the libraries
19588 on the host system, or by asking @value{GDBN} to automatically retrieve the
19589 libraries from the target. If copies of the target libraries are
19590 provided, they need to be the same as the target libraries, although the
19591 copies on the target can be stripped as long as the copies on the host are
19594 @cindex where to look for shared libraries
19595 For remote debugging, you need to tell @value{GDBN} where the target
19596 libraries are, so that it can load the correct copies---otherwise, it
19597 may try to load the host's libraries. @value{GDBN} has two variables
19598 to specify the search directories for target libraries.
19601 @cindex prefix for executable and shared library file names
19602 @cindex system root, alternate
19603 @kindex set solib-absolute-prefix
19604 @kindex set sysroot
19605 @item set sysroot @var{path}
19606 Use @var{path} as the system root for the program being debugged. Any
19607 absolute shared library paths will be prefixed with @var{path}; many
19608 runtime loaders store the absolute paths to the shared library in the
19609 target program's memory. When starting processes remotely, and when
19610 attaching to already-running processes (local or remote), their
19611 executable filenames will be prefixed with @var{path} if reported to
19612 @value{GDBN} as absolute by the operating system. If you use
19613 @code{set sysroot} to find executables and shared libraries, they need
19614 to be laid out in the same way that they are on the target, with
19615 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19618 If @var{path} starts with the sequence @file{target:} and the target
19619 system is remote then @value{GDBN} will retrieve the target binaries
19620 from the remote system. This is only supported when using a remote
19621 target that supports the @code{remote get} command (@pxref{File
19622 Transfer,,Sending files to a remote system}). The part of @var{path}
19623 following the initial @file{target:} (if present) is used as system
19624 root prefix on the remote file system. If @var{path} starts with the
19625 sequence @file{remote:} this is converted to the sequence
19626 @file{target:} by @code{set sysroot}@footnote{Historically the
19627 functionality to retrieve binaries from the remote system was
19628 provided by prefixing @var{path} with @file{remote:}}. If you want
19629 to specify a local system root using a directory that happens to be
19630 named @file{target:} or @file{remote:}, you need to use some
19631 equivalent variant of the name like @file{./target:}.
19633 For targets with an MS-DOS based filesystem, such as MS-Windows and
19634 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19635 absolute file name with @var{path}. But first, on Unix hosts,
19636 @value{GDBN} converts all backslash directory separators into forward
19637 slashes, because the backslash is not a directory separator on Unix:
19640 c:\foo\bar.dll @result{} c:/foo/bar.dll
19643 Then, @value{GDBN} attempts prefixing the target file name with
19644 @var{path}, and looks for the resulting file name in the host file
19648 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19651 If that does not find the binary, @value{GDBN} tries removing
19652 the @samp{:} character from the drive spec, both for convenience, and,
19653 for the case of the host file system not supporting file names with
19657 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19660 This makes it possible to have a system root that mirrors a target
19661 with more than one drive. E.g., you may want to setup your local
19662 copies of the target system shared libraries like so (note @samp{c} vs
19666 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19667 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19668 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19672 and point the system root at @file{/path/to/sysroot}, so that
19673 @value{GDBN} can find the correct copies of both
19674 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19676 If that still does not find the binary, @value{GDBN} tries
19677 removing the whole drive spec from the target file name:
19680 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19683 This last lookup makes it possible to not care about the drive name,
19684 if you don't want or need to.
19686 The @code{set solib-absolute-prefix} command is an alias for @code{set
19689 @cindex default system root
19690 @cindex @samp{--with-sysroot}
19691 You can set the default system root by using the configure-time
19692 @samp{--with-sysroot} option. If the system root is inside
19693 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19694 @samp{--exec-prefix}), then the default system root will be updated
19695 automatically if the installed @value{GDBN} is moved to a new
19698 @kindex show sysroot
19700 Display the current executable and shared library prefix.
19702 @kindex set solib-search-path
19703 @item set solib-search-path @var{path}
19704 If this variable is set, @var{path} is a colon-separated list of
19705 directories to search for shared libraries. @samp{solib-search-path}
19706 is used after @samp{sysroot} fails to locate the library, or if the
19707 path to the library is relative instead of absolute. If you want to
19708 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19709 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19710 finding your host's libraries. @samp{sysroot} is preferred; setting
19711 it to a nonexistent directory may interfere with automatic loading
19712 of shared library symbols.
19714 @kindex show solib-search-path
19715 @item show solib-search-path
19716 Display the current shared library search path.
19718 @cindex DOS file-name semantics of file names.
19719 @kindex set target-file-system-kind (unix|dos-based|auto)
19720 @kindex show target-file-system-kind
19721 @item set target-file-system-kind @var{kind}
19722 Set assumed file system kind for target reported file names.
19724 Shared library file names as reported by the target system may not
19725 make sense as is on the system @value{GDBN} is running on. For
19726 example, when remote debugging a target that has MS-DOS based file
19727 system semantics, from a Unix host, the target may be reporting to
19728 @value{GDBN} a list of loaded shared libraries with file names such as
19729 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19730 drive letters, so the @samp{c:\} prefix is not normally understood as
19731 indicating an absolute file name, and neither is the backslash
19732 normally considered a directory separator character. In that case,
19733 the native file system would interpret this whole absolute file name
19734 as a relative file name with no directory components. This would make
19735 it impossible to point @value{GDBN} at a copy of the remote target's
19736 shared libraries on the host using @code{set sysroot}, and impractical
19737 with @code{set solib-search-path}. Setting
19738 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19739 to interpret such file names similarly to how the target would, and to
19740 map them to file names valid on @value{GDBN}'s native file system
19741 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19742 to one of the supported file system kinds. In that case, @value{GDBN}
19743 tries to determine the appropriate file system variant based on the
19744 current target's operating system (@pxref{ABI, ,Configuring the
19745 Current ABI}). The supported file system settings are:
19749 Instruct @value{GDBN} to assume the target file system is of Unix
19750 kind. Only file names starting the forward slash (@samp{/}) character
19751 are considered absolute, and the directory separator character is also
19755 Instruct @value{GDBN} to assume the target file system is DOS based.
19756 File names starting with either a forward slash, or a drive letter
19757 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19758 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19759 considered directory separators.
19762 Instruct @value{GDBN} to use the file system kind associated with the
19763 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19764 This is the default.
19768 @cindex file name canonicalization
19769 @cindex base name differences
19770 When processing file names provided by the user, @value{GDBN}
19771 frequently needs to compare them to the file names recorded in the
19772 program's debug info. Normally, @value{GDBN} compares just the
19773 @dfn{base names} of the files as strings, which is reasonably fast
19774 even for very large programs. (The base name of a file is the last
19775 portion of its name, after stripping all the leading directories.)
19776 This shortcut in comparison is based upon the assumption that files
19777 cannot have more than one base name. This is usually true, but
19778 references to files that use symlinks or similar filesystem
19779 facilities violate that assumption. If your program records files
19780 using such facilities, or if you provide file names to @value{GDBN}
19781 using symlinks etc., you can set @code{basenames-may-differ} to
19782 @code{true} to instruct @value{GDBN} to completely canonicalize each
19783 pair of file names it needs to compare. This will make file-name
19784 comparisons accurate, but at a price of a significant slowdown.
19787 @item set basenames-may-differ
19788 @kindex set basenames-may-differ
19789 Set whether a source file may have multiple base names.
19791 @item show basenames-may-differ
19792 @kindex show basenames-may-differ
19793 Show whether a source file may have multiple base names.
19797 @section File Caching
19798 @cindex caching of opened files
19799 @cindex caching of bfd objects
19801 To speed up file loading, and reduce memory usage, @value{GDBN} will
19802 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19803 BFD, bfd, The Binary File Descriptor Library}. The following commands
19804 allow visibility and control of the caching behavior.
19807 @kindex maint info bfds
19808 @item maint info bfds
19809 This prints information about each @code{bfd} object that is known to
19812 @kindex maint set bfd-sharing
19813 @kindex maint show bfd-sharing
19814 @kindex bfd caching
19815 @item maint set bfd-sharing
19816 @item maint show bfd-sharing
19817 Control whether @code{bfd} objects can be shared. When sharing is
19818 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19819 than reopening the same file. Turning sharing off does not cause
19820 already shared @code{bfd} objects to be unshared, but all future files
19821 that are opened will create a new @code{bfd} object. Similarly,
19822 re-enabling sharing does not cause multiple existing @code{bfd}
19823 objects to be collapsed into a single shared @code{bfd} object.
19825 @kindex set debug bfd-cache @var{level}
19826 @kindex bfd caching
19827 @item set debug bfd-cache @var{level}
19828 Turns on debugging of the bfd cache, setting the level to @var{level}.
19830 @kindex show debug bfd-cache
19831 @kindex bfd caching
19832 @item show debug bfd-cache
19833 Show the current debugging level of the bfd cache.
19836 @node Separate Debug Files
19837 @section Debugging Information in Separate Files
19838 @cindex separate debugging information files
19839 @cindex debugging information in separate files
19840 @cindex @file{.debug} subdirectories
19841 @cindex debugging information directory, global
19842 @cindex global debugging information directories
19843 @cindex build ID, and separate debugging files
19844 @cindex @file{.build-id} directory
19846 @value{GDBN} allows you to put a program's debugging information in a
19847 file separate from the executable itself, in a way that allows
19848 @value{GDBN} to find and load the debugging information automatically.
19849 Since debugging information can be very large---sometimes larger
19850 than the executable code itself---some systems distribute debugging
19851 information for their executables in separate files, which users can
19852 install only when they need to debug a problem.
19854 @value{GDBN} supports two ways of specifying the separate debug info
19859 The executable contains a @dfn{debug link} that specifies the name of
19860 the separate debug info file. The separate debug file's name is
19861 usually @file{@var{executable}.debug}, where @var{executable} is the
19862 name of the corresponding executable file without leading directories
19863 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19864 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19865 checksum for the debug file, which @value{GDBN} uses to validate that
19866 the executable and the debug file came from the same build.
19869 The executable contains a @dfn{build ID}, a unique bit string that is
19870 also present in the corresponding debug info file. (This is supported
19871 only on some operating systems, when using the ELF or PE file formats
19872 for binary files and the @sc{gnu} Binutils.) For more details about
19873 this feature, see the description of the @option{--build-id}
19874 command-line option in @ref{Options, , Command Line Options, ld,
19875 The GNU Linker}. The debug info file's name is not specified
19876 explicitly by the build ID, but can be computed from the build ID, see
19880 Depending on the way the debug info file is specified, @value{GDBN}
19881 uses two different methods of looking for the debug file:
19885 For the ``debug link'' method, @value{GDBN} looks up the named file in
19886 the directory of the executable file, then in a subdirectory of that
19887 directory named @file{.debug}, and finally under each one of the global debug
19888 directories, in a subdirectory whose name is identical to the leading
19889 directories of the executable's absolute file name.
19892 For the ``build ID'' method, @value{GDBN} looks in the
19893 @file{.build-id} subdirectory of each one of the global debug directories for
19894 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19895 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19896 are the rest of the bit string. (Real build ID strings are 32 or more
19897 hex characters, not 10.)
19900 So, for example, suppose you ask @value{GDBN} to debug
19901 @file{/usr/bin/ls}, which has a debug link that specifies the
19902 file @file{ls.debug}, and a build ID whose value in hex is
19903 @code{abcdef1234}. If the list of the global debug directories includes
19904 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19905 debug information files, in the indicated order:
19909 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19911 @file{/usr/bin/ls.debug}
19913 @file{/usr/bin/.debug/ls.debug}
19915 @file{/usr/lib/debug/usr/bin/ls.debug}.
19918 @anchor{debug-file-directory}
19919 Global debugging info directories default to what is set by @value{GDBN}
19920 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19921 you can also set the global debugging info directories, and view the list
19922 @value{GDBN} is currently using.
19926 @kindex set debug-file-directory
19927 @item set debug-file-directory @var{directories}
19928 Set the directories which @value{GDBN} searches for separate debugging
19929 information files to @var{directory}. Multiple path components can be set
19930 concatenating them by a path separator.
19932 @kindex show debug-file-directory
19933 @item show debug-file-directory
19934 Show the directories @value{GDBN} searches for separate debugging
19939 @cindex @code{.gnu_debuglink} sections
19940 @cindex debug link sections
19941 A debug link is a special section of the executable file named
19942 @code{.gnu_debuglink}. The section must contain:
19946 A filename, with any leading directory components removed, followed by
19949 zero to three bytes of padding, as needed to reach the next four-byte
19950 boundary within the section, and
19952 a four-byte CRC checksum, stored in the same endianness used for the
19953 executable file itself. The checksum is computed on the debugging
19954 information file's full contents by the function given below, passing
19955 zero as the @var{crc} argument.
19958 Any executable file format can carry a debug link, as long as it can
19959 contain a section named @code{.gnu_debuglink} with the contents
19962 @cindex @code{.note.gnu.build-id} sections
19963 @cindex build ID sections
19964 The build ID is a special section in the executable file (and in other
19965 ELF binary files that @value{GDBN} may consider). This section is
19966 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19967 It contains unique identification for the built files---the ID remains
19968 the same across multiple builds of the same build tree. The default
19969 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19970 content for the build ID string. The same section with an identical
19971 value is present in the original built binary with symbols, in its
19972 stripped variant, and in the separate debugging information file.
19974 The debugging information file itself should be an ordinary
19975 executable, containing a full set of linker symbols, sections, and
19976 debugging information. The sections of the debugging information file
19977 should have the same names, addresses, and sizes as the original file,
19978 but they need not contain any data---much like a @code{.bss} section
19979 in an ordinary executable.
19981 The @sc{gnu} binary utilities (Binutils) package includes the
19982 @samp{objcopy} utility that can produce
19983 the separated executable / debugging information file pairs using the
19984 following commands:
19987 @kbd{objcopy --only-keep-debug foo foo.debug}
19992 These commands remove the debugging
19993 information from the executable file @file{foo} and place it in the file
19994 @file{foo.debug}. You can use the first, second or both methods to link the
19999 The debug link method needs the following additional command to also leave
20000 behind a debug link in @file{foo}:
20003 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20006 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20007 a version of the @code{strip} command such that the command @kbd{strip foo -f
20008 foo.debug} has the same functionality as the two @code{objcopy} commands and
20009 the @code{ln -s} command above, together.
20012 Build ID gets embedded into the main executable using @code{ld --build-id} or
20013 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20014 compatibility fixes for debug files separation are present in @sc{gnu} binary
20015 utilities (Binutils) package since version 2.18.
20020 @cindex CRC algorithm definition
20021 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20022 IEEE 802.3 using the polynomial:
20024 @c TexInfo requires naked braces for multi-digit exponents for Tex
20025 @c output, but this causes HTML output to barf. HTML has to be set using
20026 @c raw commands. So we end up having to specify this equation in 2
20031 <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>
20032 + <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
20038 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20039 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20043 The function is computed byte at a time, taking the least
20044 significant bit of each byte first. The initial pattern
20045 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20046 the final result is inverted to ensure trailing zeros also affect the
20049 @emph{Note:} This is the same CRC polynomial as used in handling the
20050 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20051 However in the case of the Remote Serial Protocol, the CRC is computed
20052 @emph{most} significant bit first, and the result is not inverted, so
20053 trailing zeros have no effect on the CRC value.
20055 To complete the description, we show below the code of the function
20056 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20057 initially supplied @code{crc} argument means that an initial call to
20058 this function passing in zero will start computing the CRC using
20061 @kindex gnu_debuglink_crc32
20064 gnu_debuglink_crc32 (unsigned long crc,
20065 unsigned char *buf, size_t len)
20067 static const unsigned long crc32_table[256] =
20069 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20070 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20071 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20072 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20073 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20074 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20075 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20076 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20077 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20078 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20079 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20080 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20081 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20082 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20083 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20084 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20085 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20086 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20087 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20088 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20089 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20090 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20091 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20092 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20093 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20094 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20095 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20096 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20097 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20098 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20099 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20100 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20101 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20102 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20103 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20104 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20105 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20106 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20107 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20108 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20109 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20110 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20111 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20112 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20113 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20114 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20115 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20116 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20117 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20118 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20119 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20122 unsigned char *end;
20124 crc = ~crc & 0xffffffff;
20125 for (end = buf + len; buf < end; ++buf)
20126 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20127 return ~crc & 0xffffffff;
20132 This computation does not apply to the ``build ID'' method.
20134 @node MiniDebugInfo
20135 @section Debugging information in a special section
20136 @cindex separate debug sections
20137 @cindex @samp{.gnu_debugdata} section
20139 Some systems ship pre-built executables and libraries that have a
20140 special @samp{.gnu_debugdata} section. This feature is called
20141 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20142 is used to supply extra symbols for backtraces.
20144 The intent of this section is to provide extra minimal debugging
20145 information for use in simple backtraces. It is not intended to be a
20146 replacement for full separate debugging information (@pxref{Separate
20147 Debug Files}). The example below shows the intended use; however,
20148 @value{GDBN} does not currently put restrictions on what sort of
20149 debugging information might be included in the section.
20151 @value{GDBN} has support for this extension. If the section exists,
20152 then it is used provided that no other source of debugging information
20153 can be found, and that @value{GDBN} was configured with LZMA support.
20155 This section can be easily created using @command{objcopy} and other
20156 standard utilities:
20159 # Extract the dynamic symbols from the main binary, there is no need
20160 # to also have these in the normal symbol table.
20161 nm -D @var{binary} --format=posix --defined-only \
20162 | awk '@{ print $1 @}' | sort > dynsyms
20164 # Extract all the text (i.e. function) symbols from the debuginfo.
20165 # (Note that we actually also accept "D" symbols, for the benefit
20166 # of platforms like PowerPC64 that use function descriptors.)
20167 nm @var{binary} --format=posix --defined-only \
20168 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20171 # Keep all the function symbols not already in the dynamic symbol
20173 comm -13 dynsyms funcsyms > keep_symbols
20175 # Separate full debug info into debug binary.
20176 objcopy --only-keep-debug @var{binary} debug
20178 # Copy the full debuginfo, keeping only a minimal set of symbols and
20179 # removing some unnecessary sections.
20180 objcopy -S --remove-section .gdb_index --remove-section .comment \
20181 --keep-symbols=keep_symbols debug mini_debuginfo
20183 # Drop the full debug info from the original binary.
20184 strip --strip-all -R .comment @var{binary}
20186 # Inject the compressed data into the .gnu_debugdata section of the
20189 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20193 @section Index Files Speed Up @value{GDBN}
20194 @cindex index files
20195 @cindex @samp{.gdb_index} section
20197 When @value{GDBN} finds a symbol file, it scans the symbols in the
20198 file in order to construct an internal symbol table. This lets most
20199 @value{GDBN} operations work quickly---at the cost of a delay early
20200 on. For large programs, this delay can be quite lengthy, so
20201 @value{GDBN} provides a way to build an index, which speeds up
20204 For convenience, @value{GDBN} comes with a program,
20205 @command{gdb-add-index}, which can be used to add the index to a
20206 symbol file. It takes the symbol file as its only argument:
20209 $ gdb-add-index symfile
20212 @xref{gdb-add-index}.
20214 It is also possible to do the work manually. Here is what
20215 @command{gdb-add-index} does behind the curtains.
20217 The index is stored as a section in the symbol file. @value{GDBN} can
20218 write the index to a file, then you can put it into the symbol file
20219 using @command{objcopy}.
20221 To create an index file, use the @code{save gdb-index} command:
20224 @item save gdb-index [-dwarf-5] @var{directory}
20225 @kindex save gdb-index
20226 Create index files for all symbol files currently known by
20227 @value{GDBN}. For each known @var{symbol-file}, this command by
20228 default creates it produces a single file
20229 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20230 the @option{-dwarf-5} option, it produces 2 files:
20231 @file{@var{symbol-file}.debug_names} and
20232 @file{@var{symbol-file}.debug_str}. The files are created in the
20233 given @var{directory}.
20236 Once you have created an index file you can merge it into your symbol
20237 file, here named @file{symfile}, using @command{objcopy}:
20240 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20241 --set-section-flags .gdb_index=readonly symfile symfile
20244 Or for @code{-dwarf-5}:
20247 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20248 $ cat symfile.debug_str >>symfile.debug_str.new
20249 $ objcopy --add-section .debug_names=symfile.gdb-index \
20250 --set-section-flags .debug_names=readonly \
20251 --update-section .debug_str=symfile.debug_str.new symfile symfile
20254 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20255 sections that have been deprecated. Usually they are deprecated because
20256 they are missing a new feature or have performance issues.
20257 To tell @value{GDBN} to use a deprecated index section anyway
20258 specify @code{set use-deprecated-index-sections on}.
20259 The default is @code{off}.
20260 This can speed up startup, but may result in some functionality being lost.
20261 @xref{Index Section Format}.
20263 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20264 must be done before gdb reads the file. The following will not work:
20267 $ gdb -ex "set use-deprecated-index-sections on" <program>
20270 Instead you must do, for example,
20273 $ gdb -iex "set use-deprecated-index-sections on" <program>
20276 There are currently some limitation on indices. They only work when
20277 for DWARF debugging information, not stabs. And, they do not
20278 currently work for programs using Ada.
20280 @subsection Automatic symbol index cache
20282 It is possible for @value{GDBN} to automatically save a copy of this index in a
20283 cache on disk and retrieve it from there when loading the same binary in the
20284 future. This feature can be turned on with @kbd{set index-cache on}. The
20285 following commands can be used to tweak the behavior of the index cache.
20289 @item set index-cache on
20290 @itemx set index-cache off
20291 Enable or disable the use of the symbol index cache.
20293 @item set index-cache directory @var{directory}
20294 @itemx show index-cache directory
20295 Set/show the directory where index files will be saved.
20297 The default value for this directory depends on the host platform. On
20298 most systems, the index is cached in the @file{gdb} subdirectory of
20299 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20300 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20301 of your home directory. However, on some systems, the default may
20302 differ according to local convention.
20304 There is no limit on the disk space used by index cache. It is perfectly safe
20305 to delete the content of that directory to free up disk space.
20307 @item show index-cache stats
20308 Print the number of cache hits and misses since the launch of @value{GDBN}.
20312 @node Symbol Errors
20313 @section Errors Reading Symbol Files
20315 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20316 such as symbol types it does not recognize, or known bugs in compiler
20317 output. By default, @value{GDBN} does not notify you of such problems, since
20318 they are relatively common and primarily of interest to people
20319 debugging compilers. If you are interested in seeing information
20320 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20321 only one message about each such type of problem, no matter how many
20322 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20323 to see how many times the problems occur, with the @code{set
20324 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20327 The messages currently printed, and their meanings, include:
20330 @item inner block not inside outer block in @var{symbol}
20332 The symbol information shows where symbol scopes begin and end
20333 (such as at the start of a function or a block of statements). This
20334 error indicates that an inner scope block is not fully contained
20335 in its outer scope blocks.
20337 @value{GDBN} circumvents the problem by treating the inner block as if it had
20338 the same scope as the outer block. In the error message, @var{symbol}
20339 may be shown as ``@code{(don't know)}'' if the outer block is not a
20342 @item block at @var{address} out of order
20344 The symbol information for symbol scope blocks should occur in
20345 order of increasing addresses. This error indicates that it does not
20348 @value{GDBN} does not circumvent this problem, and has trouble
20349 locating symbols in the source file whose symbols it is reading. (You
20350 can often determine what source file is affected by specifying
20351 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20354 @item bad block start address patched
20356 The symbol information for a symbol scope block has a start address
20357 smaller than the address of the preceding source line. This is known
20358 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20360 @value{GDBN} circumvents the problem by treating the symbol scope block as
20361 starting on the previous source line.
20363 @item bad string table offset in symbol @var{n}
20366 Symbol number @var{n} contains a pointer into the string table which is
20367 larger than the size of the string table.
20369 @value{GDBN} circumvents the problem by considering the symbol to have the
20370 name @code{foo}, which may cause other problems if many symbols end up
20373 @item unknown symbol type @code{0x@var{nn}}
20375 The symbol information contains new data types that @value{GDBN} does
20376 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20377 uncomprehended information, in hexadecimal.
20379 @value{GDBN} circumvents the error by ignoring this symbol information.
20380 This usually allows you to debug your program, though certain symbols
20381 are not accessible. If you encounter such a problem and feel like
20382 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20383 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20384 and examine @code{*bufp} to see the symbol.
20386 @item stub type has NULL name
20388 @value{GDBN} could not find the full definition for a struct or class.
20390 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20391 The symbol information for a C@t{++} member function is missing some
20392 information that recent versions of the compiler should have output for
20395 @item info mismatch between compiler and debugger
20397 @value{GDBN} could not parse a type specification output by the compiler.
20402 @section GDB Data Files
20404 @cindex prefix for data files
20405 @value{GDBN} will sometimes read an auxiliary data file. These files
20406 are kept in a directory known as the @dfn{data directory}.
20408 You can set the data directory's name, and view the name @value{GDBN}
20409 is currently using.
20412 @kindex set data-directory
20413 @item set data-directory @var{directory}
20414 Set the directory which @value{GDBN} searches for auxiliary data files
20415 to @var{directory}.
20417 @kindex show data-directory
20418 @item show data-directory
20419 Show the directory @value{GDBN} searches for auxiliary data files.
20422 @cindex default data directory
20423 @cindex @samp{--with-gdb-datadir}
20424 You can set the default data directory by using the configure-time
20425 @samp{--with-gdb-datadir} option. If the data directory is inside
20426 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20427 @samp{--exec-prefix}), then the default data directory will be updated
20428 automatically if the installed @value{GDBN} is moved to a new
20431 The data directory may also be specified with the
20432 @code{--data-directory} command line option.
20433 @xref{Mode Options}.
20436 @chapter Specifying a Debugging Target
20438 @cindex debugging target
20439 A @dfn{target} is the execution environment occupied by your program.
20441 Often, @value{GDBN} runs in the same host environment as your program;
20442 in that case, the debugging target is specified as a side effect when
20443 you use the @code{file} or @code{core} commands. When you need more
20444 flexibility---for example, running @value{GDBN} on a physically separate
20445 host, or controlling a standalone system over a serial port or a
20446 realtime system over a TCP/IP connection---you can use the @code{target}
20447 command to specify one of the target types configured for @value{GDBN}
20448 (@pxref{Target Commands, ,Commands for Managing Targets}).
20450 @cindex target architecture
20451 It is possible to build @value{GDBN} for several different @dfn{target
20452 architectures}. When @value{GDBN} is built like that, you can choose
20453 one of the available architectures with the @kbd{set architecture}
20457 @kindex set architecture
20458 @kindex show architecture
20459 @item set architecture @var{arch}
20460 This command sets the current target architecture to @var{arch}. The
20461 value of @var{arch} can be @code{"auto"}, in addition to one of the
20462 supported architectures.
20464 @item show architecture
20465 Show the current target architecture.
20467 @item set processor
20469 @kindex set processor
20470 @kindex show processor
20471 These are alias commands for, respectively, @code{set architecture}
20472 and @code{show architecture}.
20476 * Active Targets:: Active targets
20477 * Target Commands:: Commands for managing targets
20478 * Byte Order:: Choosing target byte order
20481 @node Active Targets
20482 @section Active Targets
20484 @cindex stacking targets
20485 @cindex active targets
20486 @cindex multiple targets
20488 There are multiple classes of targets such as: processes, executable files or
20489 recording sessions. Core files belong to the process class, making core file
20490 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20491 on multiple active targets, one in each class. This allows you to (for
20492 example) start a process and inspect its activity, while still having access to
20493 the executable file after the process finishes. Or if you start process
20494 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20495 presented a virtual layer of the recording target, while the process target
20496 remains stopped at the chronologically last point of the process execution.
20498 Use the @code{core-file} and @code{exec-file} commands to select a new core
20499 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20500 specify as a target a process that is already running, use the @code{attach}
20501 command (@pxref{Attach, ,Debugging an Already-running Process}).
20503 @node Target Commands
20504 @section Commands for Managing Targets
20507 @item target @var{type} @var{parameters}
20508 Connects the @value{GDBN} host environment to a target machine or
20509 process. A target is typically a protocol for talking to debugging
20510 facilities. You use the argument @var{type} to specify the type or
20511 protocol of the target machine.
20513 Further @var{parameters} are interpreted by the target protocol, but
20514 typically include things like device names or host names to connect
20515 with, process numbers, and baud rates.
20517 The @code{target} command does not repeat if you press @key{RET} again
20518 after executing the command.
20520 @kindex help target
20522 Displays the names of all targets available. To display targets
20523 currently selected, use either @code{info target} or @code{info files}
20524 (@pxref{Files, ,Commands to Specify Files}).
20526 @item help target @var{name}
20527 Describe a particular target, including any parameters necessary to
20530 @kindex set gnutarget
20531 @item set gnutarget @var{args}
20532 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20533 knows whether it is reading an @dfn{executable},
20534 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20535 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20536 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20539 @emph{Warning:} To specify a file format with @code{set gnutarget},
20540 you must know the actual BFD name.
20544 @xref{Files, , Commands to Specify Files}.
20546 @kindex show gnutarget
20547 @item show gnutarget
20548 Use the @code{show gnutarget} command to display what file format
20549 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20550 @value{GDBN} will determine the file format for each file automatically,
20551 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20554 @cindex common targets
20555 Here are some common targets (available, or not, depending on the GDB
20560 @item target exec @var{program}
20561 @cindex executable file target
20562 An executable file. @samp{target exec @var{program}} is the same as
20563 @samp{exec-file @var{program}}.
20565 @item target core @var{filename}
20566 @cindex core dump file target
20567 A core dump file. @samp{target core @var{filename}} is the same as
20568 @samp{core-file @var{filename}}.
20570 @item target remote @var{medium}
20571 @cindex remote target
20572 A remote system connected to @value{GDBN} via a serial line or network
20573 connection. This command tells @value{GDBN} to use its own remote
20574 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20576 For example, if you have a board connected to @file{/dev/ttya} on the
20577 machine running @value{GDBN}, you could say:
20580 target remote /dev/ttya
20583 @code{target remote} supports the @code{load} command. This is only
20584 useful if you have some other way of getting the stub to the target
20585 system, and you can put it somewhere in memory where it won't get
20586 clobbered by the download.
20588 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20589 @cindex built-in simulator target
20590 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20598 works; however, you cannot assume that a specific memory map, device
20599 drivers, or even basic I/O is available, although some simulators do
20600 provide these. For info about any processor-specific simulator details,
20601 see the appropriate section in @ref{Embedded Processors, ,Embedded
20604 @item target native
20605 @cindex native target
20606 Setup for local/native process debugging. Useful to make the
20607 @code{run} command spawn native processes (likewise @code{attach},
20608 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20609 (@pxref{set auto-connect-native-target}).
20613 Different targets are available on different configurations of @value{GDBN};
20614 your configuration may have more or fewer targets.
20616 Many remote targets require you to download the executable's code once
20617 you've successfully established a connection. You may wish to control
20618 various aspects of this process.
20623 @kindex set hash@r{, for remote monitors}
20624 @cindex hash mark while downloading
20625 This command controls whether a hash mark @samp{#} is displayed while
20626 downloading a file to the remote monitor. If on, a hash mark is
20627 displayed after each S-record is successfully downloaded to the
20631 @kindex show hash@r{, for remote monitors}
20632 Show the current status of displaying the hash mark.
20634 @item set debug monitor
20635 @kindex set debug monitor
20636 @cindex display remote monitor communications
20637 Enable or disable display of communications messages between
20638 @value{GDBN} and the remote monitor.
20640 @item show debug monitor
20641 @kindex show debug monitor
20642 Show the current status of displaying communications between
20643 @value{GDBN} and the remote monitor.
20648 @kindex load @var{filename} @var{offset}
20649 @item load @var{filename} @var{offset}
20651 Depending on what remote debugging facilities are configured into
20652 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20653 is meant to make @var{filename} (an executable) available for debugging
20654 on the remote system---by downloading, or dynamic linking, for example.
20655 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20656 the @code{add-symbol-file} command.
20658 If your @value{GDBN} does not have a @code{load} command, attempting to
20659 execute it gets the error message ``@code{You can't do that when your
20660 target is @dots{}}''
20662 The file is loaded at whatever address is specified in the executable.
20663 For some object file formats, you can specify the load address when you
20664 link the program; for other formats, like a.out, the object file format
20665 specifies a fixed address.
20666 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20668 It is also possible to tell @value{GDBN} to load the executable file at a
20669 specific offset described by the optional argument @var{offset}. When
20670 @var{offset} is provided, @var{filename} must also be provided.
20672 Depending on the remote side capabilities, @value{GDBN} may be able to
20673 load programs into flash memory.
20675 @code{load} does not repeat if you press @key{RET} again after using it.
20680 @kindex flash-erase
20682 @anchor{flash-erase}
20684 Erases all known flash memory regions on the target.
20689 @section Choosing Target Byte Order
20691 @cindex choosing target byte order
20692 @cindex target byte order
20694 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20695 offer the ability to run either big-endian or little-endian byte
20696 orders. Usually the executable or symbol will include a bit to
20697 designate the endian-ness, and you will not need to worry about
20698 which to use. However, you may still find it useful to adjust
20699 @value{GDBN}'s idea of processor endian-ness manually.
20703 @item set endian big
20704 Instruct @value{GDBN} to assume the target is big-endian.
20706 @item set endian little
20707 Instruct @value{GDBN} to assume the target is little-endian.
20709 @item set endian auto
20710 Instruct @value{GDBN} to use the byte order associated with the
20714 Display @value{GDBN}'s current idea of the target byte order.
20718 If the @code{set endian auto} mode is in effect and no executable has
20719 been selected, then the endianness used is the last one chosen either
20720 by one of the @code{set endian big} and @code{set endian little}
20721 commands or by inferring from the last executable used. If no
20722 endianness has been previously chosen, then the default for this mode
20723 is inferred from the target @value{GDBN} has been built for, and is
20724 @code{little} if the name of the target CPU has an @code{el} suffix
20725 and @code{big} otherwise.
20727 Note that these commands merely adjust interpretation of symbolic
20728 data on the host, and that they have absolutely no effect on the
20732 @node Remote Debugging
20733 @chapter Debugging Remote Programs
20734 @cindex remote debugging
20736 If you are trying to debug a program running on a machine that cannot run
20737 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20738 For example, you might use remote debugging on an operating system kernel,
20739 or on a small system which does not have a general purpose operating system
20740 powerful enough to run a full-featured debugger.
20742 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20743 to make this work with particular debugging targets. In addition,
20744 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20745 but not specific to any particular target system) which you can use if you
20746 write the remote stubs---the code that runs on the remote system to
20747 communicate with @value{GDBN}.
20749 Other remote targets may be available in your
20750 configuration of @value{GDBN}; use @code{help target} to list them.
20753 * Connecting:: Connecting to a remote target
20754 * File Transfer:: Sending files to a remote system
20755 * Server:: Using the gdbserver program
20756 * Remote Configuration:: Remote configuration
20757 * Remote Stub:: Implementing a remote stub
20761 @section Connecting to a Remote Target
20762 @cindex remote debugging, connecting
20763 @cindex @code{gdbserver}, connecting
20764 @cindex remote debugging, types of connections
20765 @cindex @code{gdbserver}, types of connections
20766 @cindex @code{gdbserver}, @code{target remote} mode
20767 @cindex @code{gdbserver}, @code{target extended-remote} mode
20769 This section describes how to connect to a remote target, including the
20770 types of connections and their differences, how to set up executable and
20771 symbol files on the host and target, and the commands used for
20772 connecting to and disconnecting from the remote target.
20774 @subsection Types of Remote Connections
20776 @value{GDBN} supports two types of remote connections, @code{target remote}
20777 mode and @code{target extended-remote} mode. Note that many remote targets
20778 support only @code{target remote} mode. There are several major
20779 differences between the two types of connections, enumerated here:
20783 @cindex remote debugging, detach and program exit
20784 @item Result of detach or program exit
20785 @strong{With target remote mode:} When the debugged program exits or you
20786 detach from it, @value{GDBN} disconnects from the target. When using
20787 @code{gdbserver}, @code{gdbserver} will exit.
20789 @strong{With target extended-remote mode:} When the debugged program exits or
20790 you detach from it, @value{GDBN} remains connected to the target, even
20791 though no program is running. You can rerun the program, attach to a
20792 running program, or use @code{monitor} commands specific to the target.
20794 When using @code{gdbserver} in this case, it does not exit unless it was
20795 invoked using the @option{--once} option. If the @option{--once} option
20796 was not used, you can ask @code{gdbserver} to exit using the
20797 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20799 @item Specifying the program to debug
20800 For both connection types you use the @code{file} command to specify the
20801 program on the host system. If you are using @code{gdbserver} there are
20802 some differences in how to specify the location of the program on the
20805 @strong{With target remote mode:} You must either specify the program to debug
20806 on the @code{gdbserver} command line or use the @option{--attach} option
20807 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20809 @cindex @option{--multi}, @code{gdbserver} option
20810 @strong{With target extended-remote mode:} You may specify the program to debug
20811 on the @code{gdbserver} command line, or you can load the program or attach
20812 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20814 @anchor{--multi Option in Types of Remote Connnections}
20815 You can start @code{gdbserver} without supplying an initial command to run
20816 or process ID to attach. To do this, use the @option{--multi} command line
20817 option. Then you can connect using @code{target extended-remote} and start
20818 the program you want to debug (see below for details on using the
20819 @code{run} command in this scenario). Note that the conditions under which
20820 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20821 (@code{target remote} or @code{target extended-remote}). The
20822 @option{--multi} option to @code{gdbserver} has no influence on that.
20824 @item The @code{run} command
20825 @strong{With target remote mode:} The @code{run} command is not
20826 supported. Once a connection has been established, you can use all
20827 the usual @value{GDBN} commands to examine and change data. The
20828 remote program is already running, so you can use commands like
20829 @kbd{step} and @kbd{continue}.
20831 @strong{With target extended-remote mode:} The @code{run} command is
20832 supported. The @code{run} command uses the value set by
20833 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20834 the program to run. Command line arguments are supported, except for
20835 wildcard expansion and I/O redirection (@pxref{Arguments}).
20837 If you specify the program to debug on the command line, then the
20838 @code{run} command is not required to start execution, and you can
20839 resume using commands like @kbd{step} and @kbd{continue} as with
20840 @code{target remote} mode.
20842 @anchor{Attaching in Types of Remote Connections}
20844 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20845 not supported. To attach to a running program using @code{gdbserver}, you
20846 must use the @option{--attach} option (@pxref{Running gdbserver}).
20848 @strong{With target extended-remote mode:} To attach to a running program,
20849 you may use the @code{attach} command after the connection has been
20850 established. If you are using @code{gdbserver}, you may also invoke
20851 @code{gdbserver} using the @option{--attach} option
20852 (@pxref{Running gdbserver}).
20856 @anchor{Host and target files}
20857 @subsection Host and Target Files
20858 @cindex remote debugging, symbol files
20859 @cindex symbol files, remote debugging
20861 @value{GDBN}, running on the host, needs access to symbol and debugging
20862 information for your program running on the target. This requires
20863 access to an unstripped copy of your program, and possibly any associated
20864 symbol files. Note that this section applies equally to both @code{target
20865 remote} mode and @code{target extended-remote} mode.
20867 Some remote targets (@pxref{qXfer executable filename read}, and
20868 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20869 the same connection used to communicate with @value{GDBN}. With such a
20870 target, if the remote program is unstripped, the only command you need is
20871 @code{target remote} (or @code{target extended-remote}).
20873 If the remote program is stripped, or the target does not support remote
20874 program file access, start up @value{GDBN} using the name of the local
20875 unstripped copy of your program as the first argument, or use the
20876 @code{file} command. Use @code{set sysroot} to specify the location (on
20877 the host) of target libraries (unless your @value{GDBN} was compiled with
20878 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20879 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20882 The symbol file and target libraries must exactly match the executable
20883 and libraries on the target, with one exception: the files on the host
20884 system should not be stripped, even if the files on the target system
20885 are. Mismatched or missing files will lead to confusing results
20886 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20887 files may also prevent @code{gdbserver} from debugging multi-threaded
20890 @subsection Remote Connection Commands
20891 @cindex remote connection commands
20892 @value{GDBN} can communicate with the target over a serial line, a
20893 local Unix domain socket, or
20894 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20895 each case, @value{GDBN} uses the same protocol for debugging your
20896 program; only the medium carrying the debugging packets varies. The
20897 @code{target remote} and @code{target extended-remote} commands
20898 establish a connection to the target. Both commands accept the same
20899 arguments, which indicate the medium to use:
20903 @item target remote @var{serial-device}
20904 @itemx target extended-remote @var{serial-device}
20905 @cindex serial line, @code{target remote}
20906 Use @var{serial-device} to communicate with the target. For example,
20907 to use a serial line connected to the device named @file{/dev/ttyb}:
20910 target remote /dev/ttyb
20913 If you're using a serial line, you may want to give @value{GDBN} the
20914 @samp{--baud} option, or use the @code{set serial baud} command
20915 (@pxref{Remote Configuration, set serial baud}) before the
20916 @code{target} command.
20918 @item target remote @var{local-socket}
20919 @itemx target extended-remote @var{local-socket}
20920 @cindex local socket, @code{target remote}
20921 @cindex Unix domain socket
20922 Use @var{local-socket} to communicate with the target. For example,
20923 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
20926 target remote /tmp/gdb-socket0
20929 Note that this command has the same form as the command to connect
20930 to a serial line. @value{GDBN} will automatically determine which
20931 kind of file you have specified and will make the appropriate kind
20933 The above command is identical to the command:
20936 target remote unix::/tmp/gdb-socket1
20940 See below for the explanation of this syntax.
20942 This feature is not available if the host system does not support
20943 Unix domain sockets.
20945 @item target remote @code{@var{host}:@var{port}}
20946 @itemx target remote @code{@var{[host]}:@var{port}}
20947 @itemx target remote @code{tcp:@var{host}:@var{port}}
20948 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
20949 @itemx target remote @code{tcp4:@var{host}:@var{port}}
20950 @itemx target remote @code{tcp6:@var{host}:@var{port}}
20951 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
20952 @itemx target remote @code{unix::@var{local-socket}}
20953 @itemx target extended-remote @code{@var{host}:@var{port}}
20954 @itemx target extended-remote @code{@var{[host]}:@var{port}}
20955 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20956 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
20957 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
20958 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
20959 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
20960 @itemx target extended-remote @code{unix::@var{local-socket}}
20961 @cindex @acronym{TCP} port, @code{target remote}
20962 Debug using a @acronym{TCP} connection to @var{port} on @var{host}
20963 or using the Unix domain socket @var{local-socket} on the local machine.
20964 The @var{host} may be either a host name, a numeric @acronym{IPv4}
20965 address, or a numeric @acronym{IPv6} address (with or without the
20966 square brackets to separate the address from the port); @var{port}
20967 must be a decimal number. The @var{host} could be the target machine
20968 itself, if it is directly connected to the net, or it might be a
20969 terminal server which in turn has a serial line to the target.
20971 For example, to connect to port 2828 on a terminal server named
20975 target remote manyfarms:2828
20978 To connect to port 2828 on a terminal server whose address is
20979 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
20980 square bracket syntax:
20983 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
20987 or explicitly specify the @acronym{IPv6} protocol:
20990 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
20993 This last example may be confusing to the reader, because there is no
20994 visible separation between the hostname and the port number.
20995 Therefore, we recommend the user to provide @acronym{IPv6} addresses
20996 using square brackets for clarity. However, it is important to
20997 mention that for @value{GDBN} there is no ambiguity: the number after
20998 the last colon is considered to be the port number.
21000 If your remote target is actually running on the same machine as your
21001 debugger session (e.g.@: a simulator for your target running on the
21002 same host), you can omit the hostname. For example, to connect to
21003 port 1234 on your local machine:
21006 target remote :1234
21010 Note that the colon is still required here.
21011 Alternatively you can use a Unix domain socket:
21014 target remote unix::/tmp/gdb-socket1
21018 This has the advantage that it'll not fail if the port number is already
21022 @item target remote @code{udp:@var{host}:@var{port}}
21023 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21024 @itemx target remote @code{udp4:@var{host}:@var{port}}
21025 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21026 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21027 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21028 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21029 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21030 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21031 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21032 @cindex @acronym{UDP} port, @code{target remote}
21033 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21034 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21037 target remote udp:manyfarms:2828
21040 When using a @acronym{UDP} connection for remote debugging, you should
21041 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21042 can silently drop packets on busy or unreliable networks, which will
21043 cause havoc with your debugging session.
21045 @item target remote | @var{command}
21046 @itemx target extended-remote | @var{command}
21047 @cindex pipe, @code{target remote} to
21048 Run @var{command} in the background and communicate with it using a
21049 pipe. The @var{command} is a shell command, to be parsed and expanded
21050 by the system's command shell, @code{/bin/sh}; it should expect remote
21051 protocol packets on its standard input, and send replies on its
21052 standard output. You could use this to run a stand-alone simulator
21053 that speaks the remote debugging protocol, to make net connections
21054 using programs like @code{ssh}, or for other similar tricks.
21056 If @var{command} closes its standard output (perhaps by exiting),
21057 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21058 program has already exited, this will have no effect.)
21062 @cindex interrupting remote programs
21063 @cindex remote programs, interrupting
21064 Whenever @value{GDBN} is waiting for the remote program, if you type the
21065 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21066 program. This may or may not succeed, depending in part on the hardware
21067 and the serial drivers the remote system uses. If you type the
21068 interrupt character once again, @value{GDBN} displays this prompt:
21071 Interrupted while waiting for the program.
21072 Give up (and stop debugging it)? (y or n)
21075 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21076 the remote debugging session. (If you decide you want to try again later,
21077 you can use @kbd{target remote} again to connect once more.) If you type
21078 @kbd{n}, @value{GDBN} goes back to waiting.
21080 In @code{target extended-remote} mode, typing @kbd{n} will leave
21081 @value{GDBN} connected to the target.
21084 @kindex detach (remote)
21086 When you have finished debugging the remote program, you can use the
21087 @code{detach} command to release it from @value{GDBN} control.
21088 Detaching from the target normally resumes its execution, but the results
21089 will depend on your particular remote stub. After the @code{detach}
21090 command in @code{target remote} mode, @value{GDBN} is free to connect to
21091 another target. In @code{target extended-remote} mode, @value{GDBN} is
21092 still connected to the target.
21096 The @code{disconnect} command closes the connection to the target, and
21097 the target is generally not resumed. It will wait for @value{GDBN}
21098 (this instance or another one) to connect and continue debugging. After
21099 the @code{disconnect} command, @value{GDBN} is again free to connect to
21102 @cindex send command to remote monitor
21103 @cindex extend @value{GDBN} for remote targets
21104 @cindex add new commands for external monitor
21106 @item monitor @var{cmd}
21107 This command allows you to send arbitrary commands directly to the
21108 remote monitor. Since @value{GDBN} doesn't care about the commands it
21109 sends like this, this command is the way to extend @value{GDBN}---you
21110 can add new commands that only the external monitor will understand
21114 @node File Transfer
21115 @section Sending files to a remote system
21116 @cindex remote target, file transfer
21117 @cindex file transfer
21118 @cindex sending files to remote systems
21120 Some remote targets offer the ability to transfer files over the same
21121 connection used to communicate with @value{GDBN}. This is convenient
21122 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21123 running @code{gdbserver} over a network interface. For other targets,
21124 e.g.@: embedded devices with only a single serial port, this may be
21125 the only way to upload or download files.
21127 Not all remote targets support these commands.
21131 @item remote put @var{hostfile} @var{targetfile}
21132 Copy file @var{hostfile} from the host system (the machine running
21133 @value{GDBN}) to @var{targetfile} on the target system.
21136 @item remote get @var{targetfile} @var{hostfile}
21137 Copy file @var{targetfile} from the target system to @var{hostfile}
21138 on the host system.
21140 @kindex remote delete
21141 @item remote delete @var{targetfile}
21142 Delete @var{targetfile} from the target system.
21147 @section Using the @code{gdbserver} Program
21150 @cindex remote connection without stubs
21151 @code{gdbserver} is a control program for Unix-like systems, which
21152 allows you to connect your program with a remote @value{GDBN} via
21153 @code{target remote} or @code{target extended-remote}---but without
21154 linking in the usual debugging stub.
21156 @code{gdbserver} is not a complete replacement for the debugging stubs,
21157 because it requires essentially the same operating-system facilities
21158 that @value{GDBN} itself does. In fact, a system that can run
21159 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21160 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21161 because it is a much smaller program than @value{GDBN} itself. It is
21162 also easier to port than all of @value{GDBN}, so you may be able to get
21163 started more quickly on a new system by using @code{gdbserver}.
21164 Finally, if you develop code for real-time systems, you may find that
21165 the tradeoffs involved in real-time operation make it more convenient to
21166 do as much development work as possible on another system, for example
21167 by cross-compiling. You can use @code{gdbserver} to make a similar
21168 choice for debugging.
21170 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21171 or a TCP connection, using the standard @value{GDBN} remote serial
21175 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21176 Do not run @code{gdbserver} connected to any public network; a
21177 @value{GDBN} connection to @code{gdbserver} provides access to the
21178 target system with the same privileges as the user running
21182 @anchor{Running gdbserver}
21183 @subsection Running @code{gdbserver}
21184 @cindex arguments, to @code{gdbserver}
21185 @cindex @code{gdbserver}, command-line arguments
21187 Run @code{gdbserver} on the target system. You need a copy of the
21188 program you want to debug, including any libraries it requires.
21189 @code{gdbserver} does not need your program's symbol table, so you can
21190 strip the program if necessary to save space. @value{GDBN} on the host
21191 system does all the symbol handling.
21193 To use the server, you must tell it how to communicate with @value{GDBN};
21194 the name of your program; and the arguments for your program. The usual
21198 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21201 @var{comm} is either a device name (to use a serial line), or a TCP
21202 hostname and portnumber, or @code{-} or @code{stdio} to use
21203 stdin/stdout of @code{gdbserver}.
21204 For example, to debug Emacs with the argument
21205 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21209 target> gdbserver /dev/com1 emacs foo.txt
21212 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21215 To use a TCP connection instead of a serial line:
21218 target> gdbserver host:2345 emacs foo.txt
21221 The only difference from the previous example is the first argument,
21222 specifying that you are communicating with the host @value{GDBN} via
21223 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21224 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21225 (Currently, the @samp{host} part is ignored.) You can choose any number
21226 you want for the port number as long as it does not conflict with any
21227 TCP ports already in use on the target system (for example, @code{23} is
21228 reserved for @code{telnet}).@footnote{If you choose a port number that
21229 conflicts with another service, @code{gdbserver} prints an error message
21230 and exits.} You must use the same port number with the host @value{GDBN}
21231 @code{target remote} command.
21233 The @code{stdio} connection is useful when starting @code{gdbserver}
21237 (gdb) target remote | ssh -T hostname gdbserver - hello
21240 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21241 and we don't want escape-character handling. Ssh does this by default when
21242 a command is provided, the flag is provided to make it explicit.
21243 You could elide it if you want to.
21245 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21246 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21247 display through a pipe connected to gdbserver.
21248 Both @code{stdout} and @code{stderr} use the same pipe.
21250 @anchor{Attaching to a program}
21251 @subsubsection Attaching to a Running Program
21252 @cindex attach to a program, @code{gdbserver}
21253 @cindex @option{--attach}, @code{gdbserver} option
21255 On some targets, @code{gdbserver} can also attach to running programs.
21256 This is accomplished via the @code{--attach} argument. The syntax is:
21259 target> gdbserver --attach @var{comm} @var{pid}
21262 @var{pid} is the process ID of a currently running process. It isn't
21263 necessary to point @code{gdbserver} at a binary for the running process.
21265 In @code{target extended-remote} mode, you can also attach using the
21266 @value{GDBN} attach command
21267 (@pxref{Attaching in Types of Remote Connections}).
21270 You can debug processes by name instead of process ID if your target has the
21271 @code{pidof} utility:
21274 target> gdbserver --attach @var{comm} `pidof @var{program}`
21277 In case more than one copy of @var{program} is running, or @var{program}
21278 has multiple threads, most versions of @code{pidof} support the
21279 @code{-s} option to only return the first process ID.
21281 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21283 This section applies only when @code{gdbserver} is run to listen on a TCP
21286 @code{gdbserver} normally terminates after all of its debugged processes have
21287 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21288 extended-remote}, @code{gdbserver} stays running even with no processes left.
21289 @value{GDBN} normally terminates the spawned debugged process on its exit,
21290 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21291 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21292 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21293 stays running even in the @kbd{target remote} mode.
21295 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21296 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21297 completeness, at most one @value{GDBN} can be connected at a time.
21299 @cindex @option{--once}, @code{gdbserver} option
21300 By default, @code{gdbserver} keeps the listening TCP port open, so that
21301 subsequent connections are possible. However, if you start @code{gdbserver}
21302 with the @option{--once} option, it will stop listening for any further
21303 connection attempts after connecting to the first @value{GDBN} session. This
21304 means no further connections to @code{gdbserver} will be possible after the
21305 first one. It also means @code{gdbserver} will terminate after the first
21306 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21307 connections and even in the @kbd{target extended-remote} mode. The
21308 @option{--once} option allows reusing the same port number for connecting to
21309 multiple instances of @code{gdbserver} running on the same host, since each
21310 instance closes its port after the first connection.
21312 @anchor{Other Command-Line Arguments for gdbserver}
21313 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21315 You can use the @option{--multi} option to start @code{gdbserver} without
21316 specifying a program to debug or a process to attach to. Then you can
21317 attach in @code{target extended-remote} mode and run or attach to a
21318 program. For more information,
21319 @pxref{--multi Option in Types of Remote Connnections}.
21321 @cindex @option{--debug}, @code{gdbserver} option
21322 The @option{--debug} option tells @code{gdbserver} to display extra
21323 status information about the debugging process.
21324 @cindex @option{--remote-debug}, @code{gdbserver} option
21325 The @option{--remote-debug} option tells @code{gdbserver} to display
21326 remote protocol debug output. These options are intended for
21327 @code{gdbserver} development and for bug reports to the developers.
21329 @cindex @option{--debug-format}, @code{gdbserver} option
21330 The @option{--debug-format=option1[,option2,...]} option tells
21331 @code{gdbserver} to include additional information in each output.
21332 Possible options are:
21336 Turn off all extra information in debugging output.
21338 Turn on all extra information in debugging output.
21340 Include a timestamp in each line of debugging output.
21343 Options are processed in order. Thus, for example, if @option{none}
21344 appears last then no additional information is added to debugging output.
21346 @cindex @option{--wrapper}, @code{gdbserver} option
21347 The @option{--wrapper} option specifies a wrapper to launch programs
21348 for debugging. The option should be followed by the name of the
21349 wrapper, then any command-line arguments to pass to the wrapper, then
21350 @kbd{--} indicating the end of the wrapper arguments.
21352 @code{gdbserver} runs the specified wrapper program with a combined
21353 command line including the wrapper arguments, then the name of the
21354 program to debug, then any arguments to the program. The wrapper
21355 runs until it executes your program, and then @value{GDBN} gains control.
21357 You can use any program that eventually calls @code{execve} with
21358 its arguments as a wrapper. Several standard Unix utilities do
21359 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21360 with @code{exec "$@@"} will also work.
21362 For example, you can use @code{env} to pass an environment variable to
21363 the debugged program, without setting the variable in @code{gdbserver}'s
21367 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21370 @cindex @option{--selftest}
21371 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21374 $ gdbserver --selftest
21375 Ran 2 unit tests, 0 failed
21378 These tests are disabled in release.
21379 @subsection Connecting to @code{gdbserver}
21381 The basic procedure for connecting to the remote target is:
21385 Run @value{GDBN} on the host system.
21388 Make sure you have the necessary symbol files
21389 (@pxref{Host and target files}).
21390 Load symbols for your application using the @code{file} command before you
21391 connect. Use @code{set sysroot} to locate target libraries (unless your
21392 @value{GDBN} was compiled with the correct sysroot using
21393 @code{--with-sysroot}).
21396 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21397 For TCP connections, you must start up @code{gdbserver} prior to using
21398 the @code{target} command. Otherwise you may get an error whose
21399 text depends on the host system, but which usually looks something like
21400 @samp{Connection refused}. Don't use the @code{load}
21401 command in @value{GDBN} when using @code{target remote} mode, since the
21402 program is already on the target.
21406 @anchor{Monitor Commands for gdbserver}
21407 @subsection Monitor Commands for @code{gdbserver}
21408 @cindex monitor commands, for @code{gdbserver}
21410 During a @value{GDBN} session using @code{gdbserver}, you can use the
21411 @code{monitor} command to send special requests to @code{gdbserver}.
21412 Here are the available commands.
21416 List the available monitor commands.
21418 @item monitor set debug 0
21419 @itemx monitor set debug 1
21420 Disable or enable general debugging messages.
21422 @item monitor set remote-debug 0
21423 @itemx monitor set remote-debug 1
21424 Disable or enable specific debugging messages associated with the remote
21425 protocol (@pxref{Remote Protocol}).
21427 @item monitor set debug-format option1@r{[},option2,...@r{]}
21428 Specify additional text to add to debugging messages.
21429 Possible options are:
21433 Turn off all extra information in debugging output.
21435 Turn on all extra information in debugging output.
21437 Include a timestamp in each line of debugging output.
21440 Options are processed in order. Thus, for example, if @option{none}
21441 appears last then no additional information is added to debugging output.
21443 @item monitor set libthread-db-search-path [PATH]
21444 @cindex gdbserver, search path for @code{libthread_db}
21445 When this command is issued, @var{path} is a colon-separated list of
21446 directories to search for @code{libthread_db} (@pxref{Threads,,set
21447 libthread-db-search-path}). If you omit @var{path},
21448 @samp{libthread-db-search-path} will be reset to its default value.
21450 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21451 not supported in @code{gdbserver}.
21454 Tell gdbserver to exit immediately. This command should be followed by
21455 @code{disconnect} to close the debugging session. @code{gdbserver} will
21456 detach from any attached processes and kill any processes it created.
21457 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21458 of a multi-process mode debug session.
21462 @subsection Tracepoints support in @code{gdbserver}
21463 @cindex tracepoints support in @code{gdbserver}
21465 On some targets, @code{gdbserver} supports tracepoints, fast
21466 tracepoints and static tracepoints.
21468 For fast or static tracepoints to work, a special library called the
21469 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21470 This library is built and distributed as an integral part of
21471 @code{gdbserver}. In addition, support for static tracepoints
21472 requires building the in-process agent library with static tracepoints
21473 support. At present, the UST (LTTng Userspace Tracer,
21474 @url{http://lttng.org/ust}) tracing engine is supported. This support
21475 is automatically available if UST development headers are found in the
21476 standard include path when @code{gdbserver} is built, or if
21477 @code{gdbserver} was explicitly configured using @option{--with-ust}
21478 to point at such headers. You can explicitly disable the support
21479 using @option{--with-ust=no}.
21481 There are several ways to load the in-process agent in your program:
21484 @item Specifying it as dependency at link time
21486 You can link your program dynamically with the in-process agent
21487 library. On most systems, this is accomplished by adding
21488 @code{-linproctrace} to the link command.
21490 @item Using the system's preloading mechanisms
21492 You can force loading the in-process agent at startup time by using
21493 your system's support for preloading shared libraries. Many Unixes
21494 support the concept of preloading user defined libraries. In most
21495 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21496 in the environment. See also the description of @code{gdbserver}'s
21497 @option{--wrapper} command line option.
21499 @item Using @value{GDBN} to force loading the agent at run time
21501 On some systems, you can force the inferior to load a shared library,
21502 by calling a dynamic loader function in the inferior that takes care
21503 of dynamically looking up and loading a shared library. On most Unix
21504 systems, the function is @code{dlopen}. You'll use the @code{call}
21505 command for that. For example:
21508 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21511 Note that on most Unix systems, for the @code{dlopen} function to be
21512 available, the program needs to be linked with @code{-ldl}.
21515 On systems that have a userspace dynamic loader, like most Unix
21516 systems, when you connect to @code{gdbserver} using @code{target
21517 remote}, you'll find that the program is stopped at the dynamic
21518 loader's entry point, and no shared library has been loaded in the
21519 program's address space yet, including the in-process agent. In that
21520 case, before being able to use any of the fast or static tracepoints
21521 features, you need to let the loader run and load the shared
21522 libraries. The simplest way to do that is to run the program to the
21523 main procedure. E.g., if debugging a C or C@t{++} program, start
21524 @code{gdbserver} like so:
21527 $ gdbserver :9999 myprogram
21530 Start GDB and connect to @code{gdbserver} like so, and run to main:
21534 (@value{GDBP}) target remote myhost:9999
21535 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21536 (@value{GDBP}) b main
21537 (@value{GDBP}) continue
21540 The in-process tracing agent library should now be loaded into the
21541 process; you can confirm it with the @code{info sharedlibrary}
21542 command, which will list @file{libinproctrace.so} as loaded in the
21543 process. You are now ready to install fast tracepoints, list static
21544 tracepoint markers, probe static tracepoints markers, and start
21547 @node Remote Configuration
21548 @section Remote Configuration
21551 @kindex show remote
21552 This section documents the configuration options available when
21553 debugging remote programs. For the options related to the File I/O
21554 extensions of the remote protocol, see @ref{system,
21555 system-call-allowed}.
21558 @item set remoteaddresssize @var{bits}
21559 @cindex address size for remote targets
21560 @cindex bits in remote address
21561 Set the maximum size of address in a memory packet to the specified
21562 number of bits. @value{GDBN} will mask off the address bits above
21563 that number, when it passes addresses to the remote target. The
21564 default value is the number of bits in the target's address.
21566 @item show remoteaddresssize
21567 Show the current value of remote address size in bits.
21569 @item set serial baud @var{n}
21570 @cindex baud rate for remote targets
21571 Set the baud rate for the remote serial I/O to @var{n} baud. The
21572 value is used to set the speed of the serial port used for debugging
21575 @item show serial baud
21576 Show the current speed of the remote connection.
21578 @item set serial parity @var{parity}
21579 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21580 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21582 @item show serial parity
21583 Show the current parity of the serial port.
21585 @item set remotebreak
21586 @cindex interrupt remote programs
21587 @cindex BREAK signal instead of Ctrl-C
21588 @anchor{set remotebreak}
21589 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21590 when you type @kbd{Ctrl-c} to interrupt the program running
21591 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21592 character instead. The default is off, since most remote systems
21593 expect to see @samp{Ctrl-C} as the interrupt signal.
21595 @item show remotebreak
21596 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21597 interrupt the remote program.
21599 @item set remoteflow on
21600 @itemx set remoteflow off
21601 @kindex set remoteflow
21602 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21603 on the serial port used to communicate to the remote target.
21605 @item show remoteflow
21606 @kindex show remoteflow
21607 Show the current setting of hardware flow control.
21609 @item set remotelogbase @var{base}
21610 Set the base (a.k.a.@: radix) of logging serial protocol
21611 communications to @var{base}. Supported values of @var{base} are:
21612 @code{ascii}, @code{octal}, and @code{hex}. The default is
21615 @item show remotelogbase
21616 Show the current setting of the radix for logging remote serial
21619 @item set remotelogfile @var{file}
21620 @cindex record serial communications on file
21621 Record remote serial communications on the named @var{file}. The
21622 default is not to record at all.
21624 @item show remotelogfile.
21625 Show the current setting of the file name on which to record the
21626 serial communications.
21628 @item set remotetimeout @var{num}
21629 @cindex timeout for serial communications
21630 @cindex remote timeout
21631 Set the timeout limit to wait for the remote target to respond to
21632 @var{num} seconds. The default is 2 seconds.
21634 @item show remotetimeout
21635 Show the current number of seconds to wait for the remote target
21638 @cindex limit hardware breakpoints and watchpoints
21639 @cindex remote target, limit break- and watchpoints
21640 @anchor{set remote hardware-watchpoint-limit}
21641 @anchor{set remote hardware-breakpoint-limit}
21642 @item set remote hardware-watchpoint-limit @var{limit}
21643 @itemx set remote hardware-breakpoint-limit @var{limit}
21644 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21645 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21646 watchpoints or breakpoints, and @code{unlimited} for unlimited
21647 watchpoints or breakpoints.
21649 @item show remote hardware-watchpoint-limit
21650 @itemx show remote hardware-breakpoint-limit
21651 Show the current limit for the number of hardware watchpoints or
21652 breakpoints that @value{GDBN} can use.
21654 @cindex limit hardware watchpoints length
21655 @cindex remote target, limit watchpoints length
21656 @anchor{set remote hardware-watchpoint-length-limit}
21657 @item set remote hardware-watchpoint-length-limit @var{limit}
21658 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21659 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21660 hardware watchpoints and @code{unlimited} allows watchpoints of any
21663 @item show remote hardware-watchpoint-length-limit
21664 Show the current limit (in bytes) of the maximum length of
21665 a remote hardware watchpoint.
21667 @item set remote exec-file @var{filename}
21668 @itemx show remote exec-file
21669 @anchor{set remote exec-file}
21670 @cindex executable file, for remote target
21671 Select the file used for @code{run} with @code{target
21672 extended-remote}. This should be set to a filename valid on the
21673 target system. If it is not set, the target will use a default
21674 filename (e.g.@: the last program run).
21676 @item set remote interrupt-sequence
21677 @cindex interrupt remote programs
21678 @cindex select Ctrl-C, BREAK or BREAK-g
21679 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21680 @samp{BREAK-g} as the
21681 sequence to the remote target in order to interrupt the execution.
21682 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21683 is high level of serial line for some certain time.
21684 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21685 It is @code{BREAK} signal followed by character @code{g}.
21687 @item show interrupt-sequence
21688 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21689 is sent by @value{GDBN} to interrupt the remote program.
21690 @code{BREAK-g} is BREAK signal followed by @code{g} and
21691 also known as Magic SysRq g.
21693 @item set remote interrupt-on-connect
21694 @cindex send interrupt-sequence on start
21695 Specify whether interrupt-sequence is sent to remote target when
21696 @value{GDBN} connects to it. This is mostly needed when you debug
21697 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21698 which is known as Magic SysRq g in order to connect @value{GDBN}.
21700 @item show interrupt-on-connect
21701 Show whether interrupt-sequence is sent
21702 to remote target when @value{GDBN} connects to it.
21706 @item set tcp auto-retry on
21707 @cindex auto-retry, for remote TCP target
21708 Enable auto-retry for remote TCP connections. This is useful if the remote
21709 debugging agent is launched in parallel with @value{GDBN}; there is a race
21710 condition because the agent may not become ready to accept the connection
21711 before @value{GDBN} attempts to connect. When auto-retry is
21712 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21713 to establish the connection using the timeout specified by
21714 @code{set tcp connect-timeout}.
21716 @item set tcp auto-retry off
21717 Do not auto-retry failed TCP connections.
21719 @item show tcp auto-retry
21720 Show the current auto-retry setting.
21722 @item set tcp connect-timeout @var{seconds}
21723 @itemx set tcp connect-timeout unlimited
21724 @cindex connection timeout, for remote TCP target
21725 @cindex timeout, for remote target connection
21726 Set the timeout for establishing a TCP connection to the remote target to
21727 @var{seconds}. The timeout affects both polling to retry failed connections
21728 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21729 that are merely slow to complete, and represents an approximate cumulative
21730 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21731 @value{GDBN} will keep attempting to establish a connection forever,
21732 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21734 @item show tcp connect-timeout
21735 Show the current connection timeout setting.
21738 @cindex remote packets, enabling and disabling
21739 The @value{GDBN} remote protocol autodetects the packets supported by
21740 your debugging stub. If you need to override the autodetection, you
21741 can use these commands to enable or disable individual packets. Each
21742 packet can be set to @samp{on} (the remote target supports this
21743 packet), @samp{off} (the remote target does not support this packet),
21744 or @samp{auto} (detect remote target support for this packet). They
21745 all default to @samp{auto}. For more information about each packet,
21746 see @ref{Remote Protocol}.
21748 During normal use, you should not have to use any of these commands.
21749 If you do, that may be a bug in your remote debugging stub, or a bug
21750 in @value{GDBN}. You may want to report the problem to the
21751 @value{GDBN} developers.
21753 For each packet @var{name}, the command to enable or disable the
21754 packet is @code{set remote @var{name}-packet}. The available settings
21757 @multitable @columnfractions 0.28 0.32 0.25
21760 @tab Related Features
21762 @item @code{fetch-register}
21764 @tab @code{info registers}
21766 @item @code{set-register}
21770 @item @code{binary-download}
21772 @tab @code{load}, @code{set}
21774 @item @code{read-aux-vector}
21775 @tab @code{qXfer:auxv:read}
21776 @tab @code{info auxv}
21778 @item @code{symbol-lookup}
21779 @tab @code{qSymbol}
21780 @tab Detecting multiple threads
21782 @item @code{attach}
21783 @tab @code{vAttach}
21786 @item @code{verbose-resume}
21788 @tab Stepping or resuming multiple threads
21794 @item @code{software-breakpoint}
21798 @item @code{hardware-breakpoint}
21802 @item @code{write-watchpoint}
21806 @item @code{read-watchpoint}
21810 @item @code{access-watchpoint}
21814 @item @code{pid-to-exec-file}
21815 @tab @code{qXfer:exec-file:read}
21816 @tab @code{attach}, @code{run}
21818 @item @code{target-features}
21819 @tab @code{qXfer:features:read}
21820 @tab @code{set architecture}
21822 @item @code{library-info}
21823 @tab @code{qXfer:libraries:read}
21824 @tab @code{info sharedlibrary}
21826 @item @code{memory-map}
21827 @tab @code{qXfer:memory-map:read}
21828 @tab @code{info mem}
21830 @item @code{read-sdata-object}
21831 @tab @code{qXfer:sdata:read}
21832 @tab @code{print $_sdata}
21834 @item @code{read-spu-object}
21835 @tab @code{qXfer:spu:read}
21836 @tab @code{info spu}
21838 @item @code{write-spu-object}
21839 @tab @code{qXfer:spu:write}
21840 @tab @code{info spu}
21842 @item @code{read-siginfo-object}
21843 @tab @code{qXfer:siginfo:read}
21844 @tab @code{print $_siginfo}
21846 @item @code{write-siginfo-object}
21847 @tab @code{qXfer:siginfo:write}
21848 @tab @code{set $_siginfo}
21850 @item @code{threads}
21851 @tab @code{qXfer:threads:read}
21852 @tab @code{info threads}
21854 @item @code{get-thread-local-@*storage-address}
21855 @tab @code{qGetTLSAddr}
21856 @tab Displaying @code{__thread} variables
21858 @item @code{get-thread-information-block-address}
21859 @tab @code{qGetTIBAddr}
21860 @tab Display MS-Windows Thread Information Block.
21862 @item @code{search-memory}
21863 @tab @code{qSearch:memory}
21866 @item @code{supported-packets}
21867 @tab @code{qSupported}
21868 @tab Remote communications parameters
21870 @item @code{catch-syscalls}
21871 @tab @code{QCatchSyscalls}
21872 @tab @code{catch syscall}
21874 @item @code{pass-signals}
21875 @tab @code{QPassSignals}
21876 @tab @code{handle @var{signal}}
21878 @item @code{program-signals}
21879 @tab @code{QProgramSignals}
21880 @tab @code{handle @var{signal}}
21882 @item @code{hostio-close-packet}
21883 @tab @code{vFile:close}
21884 @tab @code{remote get}, @code{remote put}
21886 @item @code{hostio-open-packet}
21887 @tab @code{vFile:open}
21888 @tab @code{remote get}, @code{remote put}
21890 @item @code{hostio-pread-packet}
21891 @tab @code{vFile:pread}
21892 @tab @code{remote get}, @code{remote put}
21894 @item @code{hostio-pwrite-packet}
21895 @tab @code{vFile:pwrite}
21896 @tab @code{remote get}, @code{remote put}
21898 @item @code{hostio-unlink-packet}
21899 @tab @code{vFile:unlink}
21900 @tab @code{remote delete}
21902 @item @code{hostio-readlink-packet}
21903 @tab @code{vFile:readlink}
21906 @item @code{hostio-fstat-packet}
21907 @tab @code{vFile:fstat}
21910 @item @code{hostio-setfs-packet}
21911 @tab @code{vFile:setfs}
21914 @item @code{noack-packet}
21915 @tab @code{QStartNoAckMode}
21916 @tab Packet acknowledgment
21918 @item @code{osdata}
21919 @tab @code{qXfer:osdata:read}
21920 @tab @code{info os}
21922 @item @code{query-attached}
21923 @tab @code{qAttached}
21924 @tab Querying remote process attach state.
21926 @item @code{trace-buffer-size}
21927 @tab @code{QTBuffer:size}
21928 @tab @code{set trace-buffer-size}
21930 @item @code{trace-status}
21931 @tab @code{qTStatus}
21932 @tab @code{tstatus}
21934 @item @code{traceframe-info}
21935 @tab @code{qXfer:traceframe-info:read}
21936 @tab Traceframe info
21938 @item @code{install-in-trace}
21939 @tab @code{InstallInTrace}
21940 @tab Install tracepoint in tracing
21942 @item @code{disable-randomization}
21943 @tab @code{QDisableRandomization}
21944 @tab @code{set disable-randomization}
21946 @item @code{startup-with-shell}
21947 @tab @code{QStartupWithShell}
21948 @tab @code{set startup-with-shell}
21950 @item @code{environment-hex-encoded}
21951 @tab @code{QEnvironmentHexEncoded}
21952 @tab @code{set environment}
21954 @item @code{environment-unset}
21955 @tab @code{QEnvironmentUnset}
21956 @tab @code{unset environment}
21958 @item @code{environment-reset}
21959 @tab @code{QEnvironmentReset}
21960 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21962 @item @code{set-working-dir}
21963 @tab @code{QSetWorkingDir}
21964 @tab @code{set cwd}
21966 @item @code{conditional-breakpoints-packet}
21967 @tab @code{Z0 and Z1}
21968 @tab @code{Support for target-side breakpoint condition evaluation}
21970 @item @code{multiprocess-extensions}
21971 @tab @code{multiprocess extensions}
21972 @tab Debug multiple processes and remote process PID awareness
21974 @item @code{swbreak-feature}
21975 @tab @code{swbreak stop reason}
21978 @item @code{hwbreak-feature}
21979 @tab @code{hwbreak stop reason}
21982 @item @code{fork-event-feature}
21983 @tab @code{fork stop reason}
21986 @item @code{vfork-event-feature}
21987 @tab @code{vfork stop reason}
21990 @item @code{exec-event-feature}
21991 @tab @code{exec stop reason}
21994 @item @code{thread-events}
21995 @tab @code{QThreadEvents}
21996 @tab Tracking thread lifetime.
21998 @item @code{no-resumed-stop-reply}
21999 @tab @code{no resumed thread left stop reply}
22000 @tab Tracking thread lifetime.
22005 @section Implementing a Remote Stub
22007 @cindex debugging stub, example
22008 @cindex remote stub, example
22009 @cindex stub example, remote debugging
22010 The stub files provided with @value{GDBN} implement the target side of the
22011 communication protocol, and the @value{GDBN} side is implemented in the
22012 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22013 these subroutines to communicate, and ignore the details. (If you're
22014 implementing your own stub file, you can still ignore the details: start
22015 with one of the existing stub files. @file{sparc-stub.c} is the best
22016 organized, and therefore the easiest to read.)
22018 @cindex remote serial debugging, overview
22019 To debug a program running on another machine (the debugging
22020 @dfn{target} machine), you must first arrange for all the usual
22021 prerequisites for the program to run by itself. For example, for a C
22026 A startup routine to set up the C runtime environment; these usually
22027 have a name like @file{crt0}. The startup routine may be supplied by
22028 your hardware supplier, or you may have to write your own.
22031 A C subroutine library to support your program's
22032 subroutine calls, notably managing input and output.
22035 A way of getting your program to the other machine---for example, a
22036 download program. These are often supplied by the hardware
22037 manufacturer, but you may have to write your own from hardware
22041 The next step is to arrange for your program to use a serial port to
22042 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22043 machine). In general terms, the scheme looks like this:
22047 @value{GDBN} already understands how to use this protocol; when everything
22048 else is set up, you can simply use the @samp{target remote} command
22049 (@pxref{Targets,,Specifying a Debugging Target}).
22051 @item On the target,
22052 you must link with your program a few special-purpose subroutines that
22053 implement the @value{GDBN} remote serial protocol. The file containing these
22054 subroutines is called a @dfn{debugging stub}.
22056 On certain remote targets, you can use an auxiliary program
22057 @code{gdbserver} instead of linking a stub into your program.
22058 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22061 The debugging stub is specific to the architecture of the remote
22062 machine; for example, use @file{sparc-stub.c} to debug programs on
22065 @cindex remote serial stub list
22066 These working remote stubs are distributed with @value{GDBN}:
22071 @cindex @file{i386-stub.c}
22074 For Intel 386 and compatible architectures.
22077 @cindex @file{m68k-stub.c}
22078 @cindex Motorola 680x0
22080 For Motorola 680x0 architectures.
22083 @cindex @file{sh-stub.c}
22086 For Renesas SH architectures.
22089 @cindex @file{sparc-stub.c}
22091 For @sc{sparc} architectures.
22093 @item sparcl-stub.c
22094 @cindex @file{sparcl-stub.c}
22097 For Fujitsu @sc{sparclite} architectures.
22101 The @file{README} file in the @value{GDBN} distribution may list other
22102 recently added stubs.
22105 * Stub Contents:: What the stub can do for you
22106 * Bootstrapping:: What you must do for the stub
22107 * Debug Session:: Putting it all together
22110 @node Stub Contents
22111 @subsection What the Stub Can Do for You
22113 @cindex remote serial stub
22114 The debugging stub for your architecture supplies these three
22118 @item set_debug_traps
22119 @findex set_debug_traps
22120 @cindex remote serial stub, initialization
22121 This routine arranges for @code{handle_exception} to run when your
22122 program stops. You must call this subroutine explicitly in your
22123 program's startup code.
22125 @item handle_exception
22126 @findex handle_exception
22127 @cindex remote serial stub, main routine
22128 This is the central workhorse, but your program never calls it
22129 explicitly---the setup code arranges for @code{handle_exception} to
22130 run when a trap is triggered.
22132 @code{handle_exception} takes control when your program stops during
22133 execution (for example, on a breakpoint), and mediates communications
22134 with @value{GDBN} on the host machine. This is where the communications
22135 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22136 representative on the target machine. It begins by sending summary
22137 information on the state of your program, then continues to execute,
22138 retrieving and transmitting any information @value{GDBN} needs, until you
22139 execute a @value{GDBN} command that makes your program resume; at that point,
22140 @code{handle_exception} returns control to your own code on the target
22144 @cindex @code{breakpoint} subroutine, remote
22145 Use this auxiliary subroutine to make your program contain a
22146 breakpoint. Depending on the particular situation, this may be the only
22147 way for @value{GDBN} to get control. For instance, if your target
22148 machine has some sort of interrupt button, you won't need to call this;
22149 pressing the interrupt button transfers control to
22150 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22151 simply receiving characters on the serial port may also trigger a trap;
22152 again, in that situation, you don't need to call @code{breakpoint} from
22153 your own program---simply running @samp{target remote} from the host
22154 @value{GDBN} session gets control.
22156 Call @code{breakpoint} if none of these is true, or if you simply want
22157 to make certain your program stops at a predetermined point for the
22158 start of your debugging session.
22161 @node Bootstrapping
22162 @subsection What You Must Do for the Stub
22164 @cindex remote stub, support routines
22165 The debugging stubs that come with @value{GDBN} are set up for a particular
22166 chip architecture, but they have no information about the rest of your
22167 debugging target machine.
22169 First of all you need to tell the stub how to communicate with the
22173 @item int getDebugChar()
22174 @findex getDebugChar
22175 Write this subroutine to read a single character from the serial port.
22176 It may be identical to @code{getchar} for your target system; a
22177 different name is used to allow you to distinguish the two if you wish.
22179 @item void putDebugChar(int)
22180 @findex putDebugChar
22181 Write this subroutine to write a single character to the serial port.
22182 It may be identical to @code{putchar} for your target system; a
22183 different name is used to allow you to distinguish the two if you wish.
22186 @cindex control C, and remote debugging
22187 @cindex interrupting remote targets
22188 If you want @value{GDBN} to be able to stop your program while it is
22189 running, you need to use an interrupt-driven serial driver, and arrange
22190 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22191 character). That is the character which @value{GDBN} uses to tell the
22192 remote system to stop.
22194 Getting the debugging target to return the proper status to @value{GDBN}
22195 probably requires changes to the standard stub; one quick and dirty way
22196 is to just execute a breakpoint instruction (the ``dirty'' part is that
22197 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22199 Other routines you need to supply are:
22202 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22203 @findex exceptionHandler
22204 Write this function to install @var{exception_address} in the exception
22205 handling tables. You need to do this because the stub does not have any
22206 way of knowing what the exception handling tables on your target system
22207 are like (for example, the processor's table might be in @sc{rom},
22208 containing entries which point to a table in @sc{ram}).
22209 The @var{exception_number} specifies the exception which should be changed;
22210 its meaning is architecture-dependent (for example, different numbers
22211 might represent divide by zero, misaligned access, etc). When this
22212 exception occurs, control should be transferred directly to
22213 @var{exception_address}, and the processor state (stack, registers,
22214 and so on) should be just as it is when a processor exception occurs. So if
22215 you want to use a jump instruction to reach @var{exception_address}, it
22216 should be a simple jump, not a jump to subroutine.
22218 For the 386, @var{exception_address} should be installed as an interrupt
22219 gate so that interrupts are masked while the handler runs. The gate
22220 should be at privilege level 0 (the most privileged level). The
22221 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22222 help from @code{exceptionHandler}.
22224 @item void flush_i_cache()
22225 @findex flush_i_cache
22226 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22227 instruction cache, if any, on your target machine. If there is no
22228 instruction cache, this subroutine may be a no-op.
22230 On target machines that have instruction caches, @value{GDBN} requires this
22231 function to make certain that the state of your program is stable.
22235 You must also make sure this library routine is available:
22238 @item void *memset(void *, int, int)
22240 This is the standard library function @code{memset} that sets an area of
22241 memory to a known value. If you have one of the free versions of
22242 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22243 either obtain it from your hardware manufacturer, or write your own.
22246 If you do not use the GNU C compiler, you may need other standard
22247 library subroutines as well; this varies from one stub to another,
22248 but in general the stubs are likely to use any of the common library
22249 subroutines which @code{@value{NGCC}} generates as inline code.
22252 @node Debug Session
22253 @subsection Putting it All Together
22255 @cindex remote serial debugging summary
22256 In summary, when your program is ready to debug, you must follow these
22261 Make sure you have defined the supporting low-level routines
22262 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22264 @code{getDebugChar}, @code{putDebugChar},
22265 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22269 Insert these lines in your program's startup code, before the main
22270 procedure is called:
22277 On some machines, when a breakpoint trap is raised, the hardware
22278 automatically makes the PC point to the instruction after the
22279 breakpoint. If your machine doesn't do that, you may need to adjust
22280 @code{handle_exception} to arrange for it to return to the instruction
22281 after the breakpoint on this first invocation, so that your program
22282 doesn't keep hitting the initial breakpoint instead of making
22286 For the 680x0 stub only, you need to provide a variable called
22287 @code{exceptionHook}. Normally you just use:
22290 void (*exceptionHook)() = 0;
22294 but if before calling @code{set_debug_traps}, you set it to point to a
22295 function in your program, that function is called when
22296 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22297 error). The function indicated by @code{exceptionHook} is called with
22298 one parameter: an @code{int} which is the exception number.
22301 Compile and link together: your program, the @value{GDBN} debugging stub for
22302 your target architecture, and the supporting subroutines.
22305 Make sure you have a serial connection between your target machine and
22306 the @value{GDBN} host, and identify the serial port on the host.
22309 @c The "remote" target now provides a `load' command, so we should
22310 @c document that. FIXME.
22311 Download your program to your target machine (or get it there by
22312 whatever means the manufacturer provides), and start it.
22315 Start @value{GDBN} on the host, and connect to the target
22316 (@pxref{Connecting,,Connecting to a Remote Target}).
22320 @node Configurations
22321 @chapter Configuration-Specific Information
22323 While nearly all @value{GDBN} commands are available for all native and
22324 cross versions of the debugger, there are some exceptions. This chapter
22325 describes things that are only available in certain configurations.
22327 There are three major categories of configurations: native
22328 configurations, where the host and target are the same, embedded
22329 operating system configurations, which are usually the same for several
22330 different processor architectures, and bare embedded processors, which
22331 are quite different from each other.
22336 * Embedded Processors::
22343 This section describes details specific to particular native
22347 * BSD libkvm Interface:: Debugging BSD kernel memory images
22348 * Process Information:: Process information
22349 * DJGPP Native:: Features specific to the DJGPP port
22350 * Cygwin Native:: Features specific to the Cygwin port
22351 * Hurd Native:: Features specific to @sc{gnu} Hurd
22352 * Darwin:: Features specific to Darwin
22355 @node BSD libkvm Interface
22356 @subsection BSD libkvm Interface
22359 @cindex kernel memory image
22360 @cindex kernel crash dump
22362 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22363 interface that provides a uniform interface for accessing kernel virtual
22364 memory images, including live systems and crash dumps. @value{GDBN}
22365 uses this interface to allow you to debug live kernels and kernel crash
22366 dumps on many native BSD configurations. This is implemented as a
22367 special @code{kvm} debugging target. For debugging a live system, load
22368 the currently running kernel into @value{GDBN} and connect to the
22372 (@value{GDBP}) @b{target kvm}
22375 For debugging crash dumps, provide the file name of the crash dump as an
22379 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22382 Once connected to the @code{kvm} target, the following commands are
22388 Set current context from the @dfn{Process Control Block} (PCB) address.
22391 Set current context from proc address. This command isn't available on
22392 modern FreeBSD systems.
22395 @node Process Information
22396 @subsection Process Information
22398 @cindex examine process image
22399 @cindex process info via @file{/proc}
22401 Some operating systems provide interfaces to fetch additional
22402 information about running processes beyond memory and per-thread
22403 register state. If @value{GDBN} is configured for an operating system
22404 with a supported interface, the command @code{info proc} is available
22405 to report information about the process running your program, or about
22406 any process running on your system.
22408 One supported interface is a facility called @samp{/proc} that can be
22409 used to examine the image of a running process using file-system
22410 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22413 On FreeBSD systems, system control nodes are used to query process
22416 In addition, some systems may provide additional process information
22417 in core files. Note that a core file may include a subset of the
22418 information available from a live process. Process information is
22419 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22426 @itemx info proc @var{process-id}
22427 Summarize available information about a process. If a
22428 process ID is specified by @var{process-id}, display information about
22429 that process; otherwise display information about the program being
22430 debugged. The summary includes the debugged process ID, the command
22431 line used to invoke it, its current working directory, and its
22432 executable file's absolute file name.
22434 On some systems, @var{process-id} can be of the form
22435 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22436 within a process. If the optional @var{pid} part is missing, it means
22437 a thread from the process being debugged (the leading @samp{/} still
22438 needs to be present, or else @value{GDBN} will interpret the number as
22439 a process ID rather than a thread ID).
22441 @item info proc cmdline
22442 @cindex info proc cmdline
22443 Show the original command line of the process. This command is
22444 supported on @sc{gnu}/Linux and FreeBSD.
22446 @item info proc cwd
22447 @cindex info proc cwd
22448 Show the current working directory of the process. This command is
22449 supported on @sc{gnu}/Linux and FreeBSD.
22451 @item info proc exe
22452 @cindex info proc exe
22453 Show the name of executable of the process. This command is supported
22454 on @sc{gnu}/Linux and FreeBSD.
22456 @item info proc files
22457 @cindex info proc files
22458 Show the file descriptors open by the process. For each open file
22459 descriptor, @value{GDBN} shows its number, type (file, directory,
22460 character device, socket), file pointer offset, and the name of the
22461 resource open on the descriptor. The resource name can be a file name
22462 (for files, directories, and devices) or a protocol followed by socket
22463 address (for network connections). This command is supported on
22466 This example shows the open file descriptors for a process using a
22467 tty for standard input and output as well as two network sockets:
22470 (gdb) info proc files 22136
22474 FD Type Offset Flags Name
22475 text file - r-------- /usr/bin/ssh
22476 ctty chr - rw------- /dev/pts/20
22477 cwd dir - r-------- /usr/home/john
22478 root dir - r-------- /
22479 0 chr 0x32933a4 rw------- /dev/pts/20
22480 1 chr 0x32933a4 rw------- /dev/pts/20
22481 2 chr 0x32933a4 rw------- /dev/pts/20
22482 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22483 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22486 @item info proc mappings
22487 @cindex memory address space mappings
22488 Report the memory address space ranges accessible in a process. On
22489 Solaris and FreeBSD systems, each memory range includes information on
22490 whether the process has read, write, or execute access rights to each
22491 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22492 includes the object file which is mapped to that range.
22494 @item info proc stat
22495 @itemx info proc status
22496 @cindex process detailed status information
22497 Show additional process-related information, including the user ID and
22498 group ID; virtual memory usage; the signals that are pending, blocked,
22499 and ignored; its TTY; its consumption of system and user time; its
22500 stack size; its @samp{nice} value; etc. These commands are supported
22501 on @sc{gnu}/Linux and FreeBSD.
22503 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22504 information (type @kbd{man 5 proc} from your shell prompt).
22506 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22509 @item info proc all
22510 Show all the information about the process described under all of the
22511 above @code{info proc} subcommands.
22514 @comment These sub-options of 'info proc' were not included when
22515 @comment procfs.c was re-written. Keep their descriptions around
22516 @comment against the day when someone finds the time to put them back in.
22517 @kindex info proc times
22518 @item info proc times
22519 Starting time, user CPU time, and system CPU time for your program and
22522 @kindex info proc id
22524 Report on the process IDs related to your program: its own process ID,
22525 the ID of its parent, the process group ID, and the session ID.
22528 @item set procfs-trace
22529 @kindex set procfs-trace
22530 @cindex @code{procfs} API calls
22531 This command enables and disables tracing of @code{procfs} API calls.
22533 @item show procfs-trace
22534 @kindex show procfs-trace
22535 Show the current state of @code{procfs} API call tracing.
22537 @item set procfs-file @var{file}
22538 @kindex set procfs-file
22539 Tell @value{GDBN} to write @code{procfs} API trace to the named
22540 @var{file}. @value{GDBN} appends the trace info to the previous
22541 contents of the file. The default is to display the trace on the
22544 @item show procfs-file
22545 @kindex show procfs-file
22546 Show the file to which @code{procfs} API trace is written.
22548 @item proc-trace-entry
22549 @itemx proc-trace-exit
22550 @itemx proc-untrace-entry
22551 @itemx proc-untrace-exit
22552 @kindex proc-trace-entry
22553 @kindex proc-trace-exit
22554 @kindex proc-untrace-entry
22555 @kindex proc-untrace-exit
22556 These commands enable and disable tracing of entries into and exits
22557 from the @code{syscall} interface.
22560 @kindex info pidlist
22561 @cindex process list, QNX Neutrino
22562 For QNX Neutrino only, this command displays the list of all the
22563 processes and all the threads within each process.
22566 @kindex info meminfo
22567 @cindex mapinfo list, QNX Neutrino
22568 For QNX Neutrino only, this command displays the list of all mapinfos.
22572 @subsection Features for Debugging @sc{djgpp} Programs
22573 @cindex @sc{djgpp} debugging
22574 @cindex native @sc{djgpp} debugging
22575 @cindex MS-DOS-specific commands
22578 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22579 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22580 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22581 top of real-mode DOS systems and their emulations.
22583 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22584 defines a few commands specific to the @sc{djgpp} port. This
22585 subsection describes those commands.
22590 This is a prefix of @sc{djgpp}-specific commands which print
22591 information about the target system and important OS structures.
22594 @cindex MS-DOS system info
22595 @cindex free memory information (MS-DOS)
22596 @item info dos sysinfo
22597 This command displays assorted information about the underlying
22598 platform: the CPU type and features, the OS version and flavor, the
22599 DPMI version, and the available conventional and DPMI memory.
22604 @cindex segment descriptor tables
22605 @cindex descriptor tables display
22607 @itemx info dos ldt
22608 @itemx info dos idt
22609 These 3 commands display entries from, respectively, Global, Local,
22610 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22611 tables are data structures which store a descriptor for each segment
22612 that is currently in use. The segment's selector is an index into a
22613 descriptor table; the table entry for that index holds the
22614 descriptor's base address and limit, and its attributes and access
22617 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22618 segment (used for both data and the stack), and a DOS segment (which
22619 allows access to DOS/BIOS data structures and absolute addresses in
22620 conventional memory). However, the DPMI host will usually define
22621 additional segments in order to support the DPMI environment.
22623 @cindex garbled pointers
22624 These commands allow to display entries from the descriptor tables.
22625 Without an argument, all entries from the specified table are
22626 displayed. An argument, which should be an integer expression, means
22627 display a single entry whose index is given by the argument. For
22628 example, here's a convenient way to display information about the
22629 debugged program's data segment:
22632 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22633 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22637 This comes in handy when you want to see whether a pointer is outside
22638 the data segment's limit (i.e.@: @dfn{garbled}).
22640 @cindex page tables display (MS-DOS)
22642 @itemx info dos pte
22643 These two commands display entries from, respectively, the Page
22644 Directory and the Page Tables. Page Directories and Page Tables are
22645 data structures which control how virtual memory addresses are mapped
22646 into physical addresses. A Page Table includes an entry for every
22647 page of memory that is mapped into the program's address space; there
22648 may be several Page Tables, each one holding up to 4096 entries. A
22649 Page Directory has up to 4096 entries, one each for every Page Table
22650 that is currently in use.
22652 Without an argument, @kbd{info dos pde} displays the entire Page
22653 Directory, and @kbd{info dos pte} displays all the entries in all of
22654 the Page Tables. An argument, an integer expression, given to the
22655 @kbd{info dos pde} command means display only that entry from the Page
22656 Directory table. An argument given to the @kbd{info dos pte} command
22657 means display entries from a single Page Table, the one pointed to by
22658 the specified entry in the Page Directory.
22660 @cindex direct memory access (DMA) on MS-DOS
22661 These commands are useful when your program uses @dfn{DMA} (Direct
22662 Memory Access), which needs physical addresses to program the DMA
22665 These commands are supported only with some DPMI servers.
22667 @cindex physical address from linear address
22668 @item info dos address-pte @var{addr}
22669 This command displays the Page Table entry for a specified linear
22670 address. The argument @var{addr} is a linear address which should
22671 already have the appropriate segment's base address added to it,
22672 because this command accepts addresses which may belong to @emph{any}
22673 segment. For example, here's how to display the Page Table entry for
22674 the page where a variable @code{i} is stored:
22677 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22678 @exdent @code{Page Table entry for address 0x11a00d30:}
22679 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22683 This says that @code{i} is stored at offset @code{0xd30} from the page
22684 whose physical base address is @code{0x02698000}, and shows all the
22685 attributes of that page.
22687 Note that you must cast the addresses of variables to a @code{char *},
22688 since otherwise the value of @code{__djgpp_base_address}, the base
22689 address of all variables and functions in a @sc{djgpp} program, will
22690 be added using the rules of C pointer arithmetics: if @code{i} is
22691 declared an @code{int}, @value{GDBN} will add 4 times the value of
22692 @code{__djgpp_base_address} to the address of @code{i}.
22694 Here's another example, it displays the Page Table entry for the
22698 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22699 @exdent @code{Page Table entry for address 0x29110:}
22700 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22704 (The @code{+ 3} offset is because the transfer buffer's address is the
22705 3rd member of the @code{_go32_info_block} structure.) The output
22706 clearly shows that this DPMI server maps the addresses in conventional
22707 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22708 linear (@code{0x29110}) addresses are identical.
22710 This command is supported only with some DPMI servers.
22713 @cindex DOS serial data link, remote debugging
22714 In addition to native debugging, the DJGPP port supports remote
22715 debugging via a serial data link. The following commands are specific
22716 to remote serial debugging in the DJGPP port of @value{GDBN}.
22719 @kindex set com1base
22720 @kindex set com1irq
22721 @kindex set com2base
22722 @kindex set com2irq
22723 @kindex set com3base
22724 @kindex set com3irq
22725 @kindex set com4base
22726 @kindex set com4irq
22727 @item set com1base @var{addr}
22728 This command sets the base I/O port address of the @file{COM1} serial
22731 @item set com1irq @var{irq}
22732 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22733 for the @file{COM1} serial port.
22735 There are similar commands @samp{set com2base}, @samp{set com3irq},
22736 etc.@: for setting the port address and the @code{IRQ} lines for the
22739 @kindex show com1base
22740 @kindex show com1irq
22741 @kindex show com2base
22742 @kindex show com2irq
22743 @kindex show com3base
22744 @kindex show com3irq
22745 @kindex show com4base
22746 @kindex show com4irq
22747 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22748 display the current settings of the base address and the @code{IRQ}
22749 lines used by the COM ports.
22752 @kindex info serial
22753 @cindex DOS serial port status
22754 This command prints the status of the 4 DOS serial ports. For each
22755 port, it prints whether it's active or not, its I/O base address and
22756 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22757 counts of various errors encountered so far.
22761 @node Cygwin Native
22762 @subsection Features for Debugging MS Windows PE Executables
22763 @cindex MS Windows debugging
22764 @cindex native Cygwin debugging
22765 @cindex Cygwin-specific commands
22767 @value{GDBN} supports native debugging of MS Windows programs, including
22768 DLLs with and without symbolic debugging information.
22770 @cindex Ctrl-BREAK, MS-Windows
22771 @cindex interrupt debuggee on MS-Windows
22772 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22773 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22774 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22775 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22776 sequence, which can be used to interrupt the debuggee even if it
22779 There are various additional Cygwin-specific commands, described in
22780 this section. Working with DLLs that have no debugging symbols is
22781 described in @ref{Non-debug DLL Symbols}.
22786 This is a prefix of MS Windows-specific commands which print
22787 information about the target system and important OS structures.
22789 @item info w32 selector
22790 This command displays information returned by
22791 the Win32 API @code{GetThreadSelectorEntry} function.
22792 It takes an optional argument that is evaluated to
22793 a long value to give the information about this given selector.
22794 Without argument, this command displays information
22795 about the six segment registers.
22797 @item info w32 thread-information-block
22798 This command displays thread specific information stored in the
22799 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22800 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22802 @kindex signal-event
22803 @item signal-event @var{id}
22804 This command signals an event with user-provided @var{id}. Used to resume
22805 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22807 To use it, create or edit the following keys in
22808 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22809 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22810 (for x86_64 versions):
22814 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22815 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22816 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22818 The first @code{%ld} will be replaced by the process ID of the
22819 crashing process, the second @code{%ld} will be replaced by the ID of
22820 the event that blocks the crashing process, waiting for @value{GDBN}
22824 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22825 make the system run debugger specified by the Debugger key
22826 automatically, @code{0} will cause a dialog box with ``OK'' and
22827 ``Cancel'' buttons to appear, which allows the user to either
22828 terminate the crashing process (OK) or debug it (Cancel).
22831 @kindex set cygwin-exceptions
22832 @cindex debugging the Cygwin DLL
22833 @cindex Cygwin DLL, debugging
22834 @item set cygwin-exceptions @var{mode}
22835 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22836 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22837 @value{GDBN} will delay recognition of exceptions, and may ignore some
22838 exceptions which seem to be caused by internal Cygwin DLL
22839 ``bookkeeping''. This option is meant primarily for debugging the
22840 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22841 @value{GDBN} users with false @code{SIGSEGV} signals.
22843 @kindex show cygwin-exceptions
22844 @item show cygwin-exceptions
22845 Displays whether @value{GDBN} will break on exceptions that happen
22846 inside the Cygwin DLL itself.
22848 @kindex set new-console
22849 @item set new-console @var{mode}
22850 If @var{mode} is @code{on} the debuggee will
22851 be started in a new console on next start.
22852 If @var{mode} is @code{off}, the debuggee will
22853 be started in the same console as the debugger.
22855 @kindex show new-console
22856 @item show new-console
22857 Displays whether a new console is used
22858 when the debuggee is started.
22860 @kindex set new-group
22861 @item set new-group @var{mode}
22862 This boolean value controls whether the debuggee should
22863 start a new group or stay in the same group as the debugger.
22864 This affects the way the Windows OS handles
22867 @kindex show new-group
22868 @item show new-group
22869 Displays current value of new-group boolean.
22871 @kindex set debugevents
22872 @item set debugevents
22873 This boolean value adds debug output concerning kernel events related
22874 to the debuggee seen by the debugger. This includes events that
22875 signal thread and process creation and exit, DLL loading and
22876 unloading, console interrupts, and debugging messages produced by the
22877 Windows @code{OutputDebugString} API call.
22879 @kindex set debugexec
22880 @item set debugexec
22881 This boolean value adds debug output concerning execute events
22882 (such as resume thread) seen by the debugger.
22884 @kindex set debugexceptions
22885 @item set debugexceptions
22886 This boolean value adds debug output concerning exceptions in the
22887 debuggee seen by the debugger.
22889 @kindex set debugmemory
22890 @item set debugmemory
22891 This boolean value adds debug output concerning debuggee memory reads
22892 and writes by the debugger.
22896 This boolean values specifies whether the debuggee is called
22897 via a shell or directly (default value is on).
22901 Displays if the debuggee will be started with a shell.
22906 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22909 @node Non-debug DLL Symbols
22910 @subsubsection Support for DLLs without Debugging Symbols
22911 @cindex DLLs with no debugging symbols
22912 @cindex Minimal symbols and DLLs
22914 Very often on windows, some of the DLLs that your program relies on do
22915 not include symbolic debugging information (for example,
22916 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22917 symbols in a DLL, it relies on the minimal amount of symbolic
22918 information contained in the DLL's export table. This section
22919 describes working with such symbols, known internally to @value{GDBN} as
22920 ``minimal symbols''.
22922 Note that before the debugged program has started execution, no DLLs
22923 will have been loaded. The easiest way around this problem is simply to
22924 start the program --- either by setting a breakpoint or letting the
22925 program run once to completion.
22927 @subsubsection DLL Name Prefixes
22929 In keeping with the naming conventions used by the Microsoft debugging
22930 tools, DLL export symbols are made available with a prefix based on the
22931 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22932 also entered into the symbol table, so @code{CreateFileA} is often
22933 sufficient. In some cases there will be name clashes within a program
22934 (particularly if the executable itself includes full debugging symbols)
22935 necessitating the use of the fully qualified name when referring to the
22936 contents of the DLL. Use single-quotes around the name to avoid the
22937 exclamation mark (``!'') being interpreted as a language operator.
22939 Note that the internal name of the DLL may be all upper-case, even
22940 though the file name of the DLL is lower-case, or vice-versa. Since
22941 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22942 some confusion. If in doubt, try the @code{info functions} and
22943 @code{info variables} commands or even @code{maint print msymbols}
22944 (@pxref{Symbols}). Here's an example:
22947 (@value{GDBP}) info function CreateFileA
22948 All functions matching regular expression "CreateFileA":
22950 Non-debugging symbols:
22951 0x77e885f4 CreateFileA
22952 0x77e885f4 KERNEL32!CreateFileA
22956 (@value{GDBP}) info function !
22957 All functions matching regular expression "!":
22959 Non-debugging symbols:
22960 0x6100114c cygwin1!__assert
22961 0x61004034 cygwin1!_dll_crt0@@0
22962 0x61004240 cygwin1!dll_crt0(per_process *)
22966 @subsubsection Working with Minimal Symbols
22968 Symbols extracted from a DLL's export table do not contain very much
22969 type information. All that @value{GDBN} can do is guess whether a symbol
22970 refers to a function or variable depending on the linker section that
22971 contains the symbol. Also note that the actual contents of the memory
22972 contained in a DLL are not available unless the program is running. This
22973 means that you cannot examine the contents of a variable or disassemble
22974 a function within a DLL without a running program.
22976 Variables are generally treated as pointers and dereferenced
22977 automatically. For this reason, it is often necessary to prefix a
22978 variable name with the address-of operator (``&'') and provide explicit
22979 type information in the command. Here's an example of the type of
22983 (@value{GDBP}) print 'cygwin1!__argv'
22984 'cygwin1!__argv' has unknown type; cast it to its declared type
22988 (@value{GDBP}) x 'cygwin1!__argv'
22989 'cygwin1!__argv' has unknown type; cast it to its declared type
22992 And two possible solutions:
22995 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22996 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23000 (@value{GDBP}) x/2x &'cygwin1!__argv'
23001 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23002 (@value{GDBP}) x/x 0x10021608
23003 0x10021608: 0x0022fd98
23004 (@value{GDBP}) x/s 0x0022fd98
23005 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23008 Setting a break point within a DLL is possible even before the program
23009 starts execution. However, under these circumstances, @value{GDBN} can't
23010 examine the initial instructions of the function in order to skip the
23011 function's frame set-up code. You can work around this by using ``*&''
23012 to set the breakpoint at a raw memory address:
23015 (@value{GDBP}) break *&'python22!PyOS_Readline'
23016 Breakpoint 1 at 0x1e04eff0
23019 The author of these extensions is not entirely convinced that setting a
23020 break point within a shared DLL like @file{kernel32.dll} is completely
23024 @subsection Commands Specific to @sc{gnu} Hurd Systems
23025 @cindex @sc{gnu} Hurd debugging
23027 This subsection describes @value{GDBN} commands specific to the
23028 @sc{gnu} Hurd native debugging.
23033 @kindex set signals@r{, Hurd command}
23034 @kindex set sigs@r{, Hurd command}
23035 This command toggles the state of inferior signal interception by
23036 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23037 affected by this command. @code{sigs} is a shorthand alias for
23042 @kindex show signals@r{, Hurd command}
23043 @kindex show sigs@r{, Hurd command}
23044 Show the current state of intercepting inferior's signals.
23046 @item set signal-thread
23047 @itemx set sigthread
23048 @kindex set signal-thread
23049 @kindex set sigthread
23050 This command tells @value{GDBN} which thread is the @code{libc} signal
23051 thread. That thread is run when a signal is delivered to a running
23052 process. @code{set sigthread} is the shorthand alias of @code{set
23055 @item show signal-thread
23056 @itemx show sigthread
23057 @kindex show signal-thread
23058 @kindex show sigthread
23059 These two commands show which thread will run when the inferior is
23060 delivered a signal.
23063 @kindex set stopped@r{, Hurd command}
23064 This commands tells @value{GDBN} that the inferior process is stopped,
23065 as with the @code{SIGSTOP} signal. The stopped process can be
23066 continued by delivering a signal to it.
23069 @kindex show stopped@r{, Hurd command}
23070 This command shows whether @value{GDBN} thinks the debuggee is
23073 @item set exceptions
23074 @kindex set exceptions@r{, Hurd command}
23075 Use this command to turn off trapping of exceptions in the inferior.
23076 When exception trapping is off, neither breakpoints nor
23077 single-stepping will work. To restore the default, set exception
23080 @item show exceptions
23081 @kindex show exceptions@r{, Hurd command}
23082 Show the current state of trapping exceptions in the inferior.
23084 @item set task pause
23085 @kindex set task@r{, Hurd commands}
23086 @cindex task attributes (@sc{gnu} Hurd)
23087 @cindex pause current task (@sc{gnu} Hurd)
23088 This command toggles task suspension when @value{GDBN} has control.
23089 Setting it to on takes effect immediately, and the task is suspended
23090 whenever @value{GDBN} gets control. Setting it to off will take
23091 effect the next time the inferior is continued. If this option is set
23092 to off, you can use @code{set thread default pause on} or @code{set
23093 thread pause on} (see below) to pause individual threads.
23095 @item show task pause
23096 @kindex show task@r{, Hurd commands}
23097 Show the current state of task suspension.
23099 @item set task detach-suspend-count
23100 @cindex task suspend count
23101 @cindex detach from task, @sc{gnu} Hurd
23102 This command sets the suspend count the task will be left with when
23103 @value{GDBN} detaches from it.
23105 @item show task detach-suspend-count
23106 Show the suspend count the task will be left with when detaching.
23108 @item set task exception-port
23109 @itemx set task excp
23110 @cindex task exception port, @sc{gnu} Hurd
23111 This command sets the task exception port to which @value{GDBN} will
23112 forward exceptions. The argument should be the value of the @dfn{send
23113 rights} of the task. @code{set task excp} is a shorthand alias.
23115 @item set noninvasive
23116 @cindex noninvasive task options
23117 This command switches @value{GDBN} to a mode that is the least
23118 invasive as far as interfering with the inferior is concerned. This
23119 is the same as using @code{set task pause}, @code{set exceptions}, and
23120 @code{set signals} to values opposite to the defaults.
23122 @item info send-rights
23123 @itemx info receive-rights
23124 @itemx info port-rights
23125 @itemx info port-sets
23126 @itemx info dead-names
23129 @cindex send rights, @sc{gnu} Hurd
23130 @cindex receive rights, @sc{gnu} Hurd
23131 @cindex port rights, @sc{gnu} Hurd
23132 @cindex port sets, @sc{gnu} Hurd
23133 @cindex dead names, @sc{gnu} Hurd
23134 These commands display information about, respectively, send rights,
23135 receive rights, port rights, port sets, and dead names of a task.
23136 There are also shorthand aliases: @code{info ports} for @code{info
23137 port-rights} and @code{info psets} for @code{info port-sets}.
23139 @item set thread pause
23140 @kindex set thread@r{, Hurd command}
23141 @cindex thread properties, @sc{gnu} Hurd
23142 @cindex pause current thread (@sc{gnu} Hurd)
23143 This command toggles current thread suspension when @value{GDBN} has
23144 control. Setting it to on takes effect immediately, and the current
23145 thread is suspended whenever @value{GDBN} gets control. Setting it to
23146 off will take effect the next time the inferior is continued.
23147 Normally, this command has no effect, since when @value{GDBN} has
23148 control, the whole task is suspended. However, if you used @code{set
23149 task pause off} (see above), this command comes in handy to suspend
23150 only the current thread.
23152 @item show thread pause
23153 @kindex show thread@r{, Hurd command}
23154 This command shows the state of current thread suspension.
23156 @item set thread run
23157 This command sets whether the current thread is allowed to run.
23159 @item show thread run
23160 Show whether the current thread is allowed to run.
23162 @item set thread detach-suspend-count
23163 @cindex thread suspend count, @sc{gnu} Hurd
23164 @cindex detach from thread, @sc{gnu} Hurd
23165 This command sets the suspend count @value{GDBN} will leave on a
23166 thread when detaching. This number is relative to the suspend count
23167 found by @value{GDBN} when it notices the thread; use @code{set thread
23168 takeover-suspend-count} to force it to an absolute value.
23170 @item show thread detach-suspend-count
23171 Show the suspend count @value{GDBN} will leave on the thread when
23174 @item set thread exception-port
23175 @itemx set thread excp
23176 Set the thread exception port to which to forward exceptions. This
23177 overrides the port set by @code{set task exception-port} (see above).
23178 @code{set thread excp} is the shorthand alias.
23180 @item set thread takeover-suspend-count
23181 Normally, @value{GDBN}'s thread suspend counts are relative to the
23182 value @value{GDBN} finds when it notices each thread. This command
23183 changes the suspend counts to be absolute instead.
23185 @item set thread default
23186 @itemx show thread default
23187 @cindex thread default settings, @sc{gnu} Hurd
23188 Each of the above @code{set thread} commands has a @code{set thread
23189 default} counterpart (e.g., @code{set thread default pause}, @code{set
23190 thread default exception-port}, etc.). The @code{thread default}
23191 variety of commands sets the default thread properties for all
23192 threads; you can then change the properties of individual threads with
23193 the non-default commands.
23200 @value{GDBN} provides the following commands specific to the Darwin target:
23203 @item set debug darwin @var{num}
23204 @kindex set debug darwin
23205 When set to a non zero value, enables debugging messages specific to
23206 the Darwin support. Higher values produce more verbose output.
23208 @item show debug darwin
23209 @kindex show debug darwin
23210 Show the current state of Darwin messages.
23212 @item set debug mach-o @var{num}
23213 @kindex set debug mach-o
23214 When set to a non zero value, enables debugging messages while
23215 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23216 file format used on Darwin for object and executable files.) Higher
23217 values produce more verbose output. This is a command to diagnose
23218 problems internal to @value{GDBN} and should not be needed in normal
23221 @item show debug mach-o
23222 @kindex show debug mach-o
23223 Show the current state of Mach-O file messages.
23225 @item set mach-exceptions on
23226 @itemx set mach-exceptions off
23227 @kindex set mach-exceptions
23228 On Darwin, faults are first reported as a Mach exception and are then
23229 mapped to a Posix signal. Use this command to turn on trapping of
23230 Mach exceptions in the inferior. This might be sometimes useful to
23231 better understand the cause of a fault. The default is off.
23233 @item show mach-exceptions
23234 @kindex show mach-exceptions
23235 Show the current state of exceptions trapping.
23240 @section Embedded Operating Systems
23242 This section describes configurations involving the debugging of
23243 embedded operating systems that are available for several different
23246 @value{GDBN} includes the ability to debug programs running on
23247 various real-time operating systems.
23249 @node Embedded Processors
23250 @section Embedded Processors
23252 This section goes into details specific to particular embedded
23255 @cindex send command to simulator
23256 Whenever a specific embedded processor has a simulator, @value{GDBN}
23257 allows to send an arbitrary command to the simulator.
23260 @item sim @var{command}
23261 @kindex sim@r{, a command}
23262 Send an arbitrary @var{command} string to the simulator. Consult the
23263 documentation for the specific simulator in use for information about
23264 acceptable commands.
23269 * ARC:: Synopsys ARC
23271 * M68K:: Motorola M68K
23272 * MicroBlaze:: Xilinx MicroBlaze
23273 * MIPS Embedded:: MIPS Embedded
23274 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23275 * PowerPC Embedded:: PowerPC Embedded
23278 * Super-H:: Renesas Super-H
23282 @subsection Synopsys ARC
23283 @cindex Synopsys ARC
23284 @cindex ARC specific commands
23290 @value{GDBN} provides the following ARC-specific commands:
23293 @item set debug arc
23294 @kindex set debug arc
23295 Control the level of ARC specific debug messages. Use 0 for no messages (the
23296 default), 1 for debug messages, and 2 for even more debug messages.
23298 @item show debug arc
23299 @kindex show debug arc
23300 Show the level of ARC specific debugging in operation.
23302 @item maint print arc arc-instruction @var{address}
23303 @kindex maint print arc arc-instruction
23304 Print internal disassembler information about instruction at a given address.
23311 @value{GDBN} provides the following ARM-specific commands:
23314 @item set arm disassembler
23316 This commands selects from a list of disassembly styles. The
23317 @code{"std"} style is the standard style.
23319 @item show arm disassembler
23321 Show the current disassembly style.
23323 @item set arm apcs32
23324 @cindex ARM 32-bit mode
23325 This command toggles ARM operation mode between 32-bit and 26-bit.
23327 @item show arm apcs32
23328 Display the current usage of the ARM 32-bit mode.
23330 @item set arm fpu @var{fputype}
23331 This command sets the ARM floating-point unit (FPU) type. The
23332 argument @var{fputype} can be one of these:
23336 Determine the FPU type by querying the OS ABI.
23338 Software FPU, with mixed-endian doubles on little-endian ARM
23341 GCC-compiled FPA co-processor.
23343 Software FPU with pure-endian doubles.
23349 Show the current type of the FPU.
23352 This command forces @value{GDBN} to use the specified ABI.
23355 Show the currently used ABI.
23357 @item set arm fallback-mode (arm|thumb|auto)
23358 @value{GDBN} uses the symbol table, when available, to determine
23359 whether instructions are ARM or Thumb. This command controls
23360 @value{GDBN}'s default behavior when the symbol table is not
23361 available. The default is @samp{auto}, which causes @value{GDBN} to
23362 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23365 @item show arm fallback-mode
23366 Show the current fallback instruction mode.
23368 @item set arm force-mode (arm|thumb|auto)
23369 This command overrides use of the symbol table to determine whether
23370 instructions are ARM or Thumb. The default is @samp{auto}, which
23371 causes @value{GDBN} to use the symbol table and then the setting
23372 of @samp{set arm fallback-mode}.
23374 @item show arm force-mode
23375 Show the current forced instruction mode.
23377 @item set debug arm
23378 Toggle whether to display ARM-specific debugging messages from the ARM
23379 target support subsystem.
23381 @item show debug arm
23382 Show whether ARM-specific debugging messages are enabled.
23386 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23387 The @value{GDBN} ARM simulator accepts the following optional arguments.
23390 @item --swi-support=@var{type}
23391 Tell the simulator which SWI interfaces to support. The argument
23392 @var{type} may be a comma separated list of the following values.
23393 The default value is @code{all}.
23408 The Motorola m68k configuration includes ColdFire support.
23411 @subsection MicroBlaze
23412 @cindex Xilinx MicroBlaze
23413 @cindex XMD, Xilinx Microprocessor Debugger
23415 The MicroBlaze is a soft-core processor supported on various Xilinx
23416 FPGAs, such as Spartan or Virtex series. Boards with these processors
23417 usually have JTAG ports which connect to a host system running the Xilinx
23418 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23419 This host system is used to download the configuration bitstream to
23420 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23421 communicates with the target board using the JTAG interface and
23422 presents a @code{gdbserver} interface to the board. By default
23423 @code{xmd} uses port @code{1234}. (While it is possible to change
23424 this default port, it requires the use of undocumented @code{xmd}
23425 commands. Contact Xilinx support if you need to do this.)
23427 Use these GDB commands to connect to the MicroBlaze target processor.
23430 @item target remote :1234
23431 Use this command to connect to the target if you are running @value{GDBN}
23432 on the same system as @code{xmd}.
23434 @item target remote @var{xmd-host}:1234
23435 Use this command to connect to the target if it is connected to @code{xmd}
23436 running on a different system named @var{xmd-host}.
23439 Use this command to download a program to the MicroBlaze target.
23441 @item set debug microblaze @var{n}
23442 Enable MicroBlaze-specific debugging messages if non-zero.
23444 @item show debug microblaze @var{n}
23445 Show MicroBlaze-specific debugging level.
23448 @node MIPS Embedded
23449 @subsection @acronym{MIPS} Embedded
23452 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23455 @item set mipsfpu double
23456 @itemx set mipsfpu single
23457 @itemx set mipsfpu none
23458 @itemx set mipsfpu auto
23459 @itemx show mipsfpu
23460 @kindex set mipsfpu
23461 @kindex show mipsfpu
23462 @cindex @acronym{MIPS} remote floating point
23463 @cindex floating point, @acronym{MIPS} remote
23464 If your target board does not support the @acronym{MIPS} floating point
23465 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23466 need this, you may wish to put the command in your @value{GDBN} init
23467 file). This tells @value{GDBN} how to find the return value of
23468 functions which return floating point values. It also allows
23469 @value{GDBN} to avoid saving the floating point registers when calling
23470 functions on the board. If you are using a floating point coprocessor
23471 with only single precision floating point support, as on the @sc{r4650}
23472 processor, use the command @samp{set mipsfpu single}. The default
23473 double precision floating point coprocessor may be selected using
23474 @samp{set mipsfpu double}.
23476 In previous versions the only choices were double precision or no
23477 floating point, so @samp{set mipsfpu on} will select double precision
23478 and @samp{set mipsfpu off} will select no floating point.
23480 As usual, you can inquire about the @code{mipsfpu} variable with
23481 @samp{show mipsfpu}.
23484 @node OpenRISC 1000
23485 @subsection OpenRISC 1000
23486 @cindex OpenRISC 1000
23489 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23490 mainly provided as a soft-core which can run on Xilinx, Altera and other
23493 @value{GDBN} for OpenRISC supports the below commands when connecting to
23501 Runs the builtin CPU simulator which can run very basic
23502 programs but does not support most hardware functions like MMU.
23503 For more complex use cases the user is advised to run an external
23504 target, and connect using @samp{target remote}.
23506 Example: @code{target sim}
23508 @item set debug or1k
23509 Toggle whether to display OpenRISC-specific debugging messages from the
23510 OpenRISC target support subsystem.
23512 @item show debug or1k
23513 Show whether OpenRISC-specific debugging messages are enabled.
23516 @node PowerPC Embedded
23517 @subsection PowerPC Embedded
23519 @cindex DVC register
23520 @value{GDBN} supports using the DVC (Data Value Compare) register to
23521 implement in hardware simple hardware watchpoint conditions of the form:
23524 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23525 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23528 The DVC register will be automatically used when @value{GDBN} detects
23529 such pattern in a condition expression, and the created watchpoint uses one
23530 debug register (either the @code{exact-watchpoints} option is on and the
23531 variable is scalar, or the variable has a length of one byte). This feature
23532 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23535 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23536 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23537 in which case watchpoints using only one debug register are created when
23538 watching variables of scalar types.
23540 You can create an artificial array to watch an arbitrary memory
23541 region using one of the following commands (@pxref{Expressions}):
23544 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23545 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23548 PowerPC embedded processors support masked watchpoints. See the discussion
23549 about the @code{mask} argument in @ref{Set Watchpoints}.
23551 @cindex ranged breakpoint
23552 PowerPC embedded processors support hardware accelerated
23553 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23554 the inferior whenever it executes an instruction at any address within
23555 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23556 use the @code{break-range} command.
23558 @value{GDBN} provides the following PowerPC-specific commands:
23561 @kindex break-range
23562 @item break-range @var{start-location}, @var{end-location}
23563 Set a breakpoint for an address range given by
23564 @var{start-location} and @var{end-location}, which can specify a function name,
23565 a line number, an offset of lines from the current line or from the start
23566 location, or an address of an instruction (see @ref{Specify Location},
23567 for a list of all the possible ways to specify a @var{location}.)
23568 The breakpoint will stop execution of the inferior whenever it
23569 executes an instruction at any address within the specified range,
23570 (including @var{start-location} and @var{end-location}.)
23572 @kindex set powerpc
23573 @item set powerpc soft-float
23574 @itemx show powerpc soft-float
23575 Force @value{GDBN} to use (or not use) a software floating point calling
23576 convention. By default, @value{GDBN} selects the calling convention based
23577 on the selected architecture and the provided executable file.
23579 @item set powerpc vector-abi
23580 @itemx show powerpc vector-abi
23581 Force @value{GDBN} to use the specified calling convention for vector
23582 arguments and return values. The valid options are @samp{auto};
23583 @samp{generic}, to avoid vector registers even if they are present;
23584 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23585 registers. By default, @value{GDBN} selects the calling convention
23586 based on the selected architecture and the provided executable file.
23588 @item set powerpc exact-watchpoints
23589 @itemx show powerpc exact-watchpoints
23590 Allow @value{GDBN} to use only one debug register when watching a variable
23591 of scalar type, thus assuming that the variable is accessed through the
23592 address of its first byte.
23597 @subsection Atmel AVR
23600 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23601 following AVR-specific commands:
23604 @item info io_registers
23605 @kindex info io_registers@r{, AVR}
23606 @cindex I/O registers (Atmel AVR)
23607 This command displays information about the AVR I/O registers. For
23608 each register, @value{GDBN} prints its number and value.
23615 When configured for debugging CRIS, @value{GDBN} provides the
23616 following CRIS-specific commands:
23619 @item set cris-version @var{ver}
23620 @cindex CRIS version
23621 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23622 The CRIS version affects register names and sizes. This command is useful in
23623 case autodetection of the CRIS version fails.
23625 @item show cris-version
23626 Show the current CRIS version.
23628 @item set cris-dwarf2-cfi
23629 @cindex DWARF-2 CFI and CRIS
23630 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23631 Change to @samp{off} when using @code{gcc-cris} whose version is below
23634 @item show cris-dwarf2-cfi
23635 Show the current state of using DWARF-2 CFI.
23637 @item set cris-mode @var{mode}
23639 Set the current CRIS mode to @var{mode}. It should only be changed when
23640 debugging in guru mode, in which case it should be set to
23641 @samp{guru} (the default is @samp{normal}).
23643 @item show cris-mode
23644 Show the current CRIS mode.
23648 @subsection Renesas Super-H
23651 For the Renesas Super-H processor, @value{GDBN} provides these
23655 @item set sh calling-convention @var{convention}
23656 @kindex set sh calling-convention
23657 Set the calling-convention used when calling functions from @value{GDBN}.
23658 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23659 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23660 convention. If the DWARF-2 information of the called function specifies
23661 that the function follows the Renesas calling convention, the function
23662 is called using the Renesas calling convention. If the calling convention
23663 is set to @samp{renesas}, the Renesas calling convention is always used,
23664 regardless of the DWARF-2 information. This can be used to override the
23665 default of @samp{gcc} if debug information is missing, or the compiler
23666 does not emit the DWARF-2 calling convention entry for a function.
23668 @item show sh calling-convention
23669 @kindex show sh calling-convention
23670 Show the current calling convention setting.
23675 @node Architectures
23676 @section Architectures
23678 This section describes characteristics of architectures that affect
23679 all uses of @value{GDBN} with the architecture, both native and cross.
23686 * HPPA:: HP PA architecture
23687 * SPU:: Cell Broadband Engine SPU architecture
23695 @subsection AArch64
23696 @cindex AArch64 support
23698 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23699 following special commands:
23702 @item set debug aarch64
23703 @kindex set debug aarch64
23704 This command determines whether AArch64 architecture-specific debugging
23705 messages are to be displayed.
23707 @item show debug aarch64
23708 Show whether AArch64 debugging messages are displayed.
23712 @subsubsection AArch64 SVE.
23713 @cindex AArch64 SVE.
23715 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23716 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23717 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23718 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23719 @code{$vg} will be provided. This is the vector granule for the current thread
23720 and represents the number of 64-bit chunks in an SVE @code{z} register.
23722 If the vector length changes, then the @code{$vg} register will be updated,
23723 but the lengths of the @code{z} and @code{p} registers will not change. This
23724 is a known limitation of @value{GDBN} and does not affect the execution of the
23729 @subsection x86 Architecture-specific Issues
23732 @item set struct-convention @var{mode}
23733 @kindex set struct-convention
23734 @cindex struct return convention
23735 @cindex struct/union returned in registers
23736 Set the convention used by the inferior to return @code{struct}s and
23737 @code{union}s from functions to @var{mode}. Possible values of
23738 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23739 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23740 are returned on the stack, while @code{"reg"} means that a
23741 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23742 be returned in a register.
23744 @item show struct-convention
23745 @kindex show struct-convention
23746 Show the current setting of the convention to return @code{struct}s
23751 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23752 @cindex Intel Memory Protection Extensions (MPX).
23754 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23755 @footnote{The register named with capital letters represent the architecture
23756 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23757 which are the lower bound and upper bound. Bounds are effective addresses or
23758 memory locations. The upper bounds are architecturally represented in 1's
23759 complement form. A bound having lower bound = 0, and upper bound = 0
23760 (1's complement of all bits set) will allow access to the entire address space.
23762 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23763 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23764 display the upper bound performing the complement of one operation on the
23765 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23766 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23767 can also be noted that the upper bounds are inclusive.
23769 As an example, assume that the register BND0 holds bounds for a pointer having
23770 access allowed for the range between 0x32 and 0x71. The values present on
23771 bnd0raw and bnd registers are presented as follows:
23774 bnd0raw = @{0x32, 0xffffffff8e@}
23775 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23778 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23779 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23780 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23781 Python, the display includes the memory size, in bits, accessible to
23784 Bounds can also be stored in bounds tables, which are stored in
23785 application memory. These tables store bounds for pointers by specifying
23786 the bounds pointer's value along with its bounds. Evaluating and changing
23787 bounds located in bound tables is therefore interesting while investigating
23788 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23791 @item show mpx bound @var{pointer}
23792 @kindex show mpx bound
23793 Display bounds of the given @var{pointer}.
23795 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23796 @kindex set mpx bound
23797 Set the bounds of a pointer in the bound table.
23798 This command takes three parameters: @var{pointer} is the pointers
23799 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23800 for lower and upper bounds respectively.
23803 When you call an inferior function on an Intel MPX enabled program,
23804 GDB sets the inferior's bound registers to the init (disabled) state
23805 before calling the function. As a consequence, bounds checks for the
23806 pointer arguments passed to the function will always pass.
23808 This is necessary because when you call an inferior function, the
23809 program is usually in the middle of the execution of other function.
23810 Since at that point bound registers are in an arbitrary state, not
23811 clearing them would lead to random bound violations in the called
23814 You can still examine the influence of the bound registers on the
23815 execution of the called function by stopping the execution of the
23816 called function at its prologue, setting bound registers, and
23817 continuing the execution. For example:
23821 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23822 $ print upper (a, b, c, d, 1)
23823 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23825 @{lbound = 0x0, ubound = ffffffff@} : size -1
23828 At this last step the value of bnd0 can be changed for investigation of bound
23829 violations caused along the execution of the call. In order to know how to
23830 set the bound registers or bound table for the call consult the ABI.
23835 See the following section.
23838 @subsection @acronym{MIPS}
23840 @cindex stack on Alpha
23841 @cindex stack on @acronym{MIPS}
23842 @cindex Alpha stack
23843 @cindex @acronym{MIPS} stack
23844 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23845 sometimes requires @value{GDBN} to search backward in the object code to
23846 find the beginning of a function.
23848 @cindex response time, @acronym{MIPS} debugging
23849 To improve response time (especially for embedded applications, where
23850 @value{GDBN} may be restricted to a slow serial line for this search)
23851 you may want to limit the size of this search, using one of these
23855 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23856 @item set heuristic-fence-post @var{limit}
23857 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23858 search for the beginning of a function. A value of @var{0} (the
23859 default) means there is no limit. However, except for @var{0}, the
23860 larger the limit the more bytes @code{heuristic-fence-post} must search
23861 and therefore the longer it takes to run. You should only need to use
23862 this command when debugging a stripped executable.
23864 @item show heuristic-fence-post
23865 Display the current limit.
23869 These commands are available @emph{only} when @value{GDBN} is configured
23870 for debugging programs on Alpha or @acronym{MIPS} processors.
23872 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23876 @item set mips abi @var{arg}
23877 @kindex set mips abi
23878 @cindex set ABI for @acronym{MIPS}
23879 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23880 values of @var{arg} are:
23884 The default ABI associated with the current binary (this is the
23894 @item show mips abi
23895 @kindex show mips abi
23896 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23898 @item set mips compression @var{arg}
23899 @kindex set mips compression
23900 @cindex code compression, @acronym{MIPS}
23901 Tell @value{GDBN} which @acronym{MIPS} compressed
23902 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23903 inferior. @value{GDBN} uses this for code disassembly and other
23904 internal interpretation purposes. This setting is only referred to
23905 when no executable has been associated with the debugging session or
23906 the executable does not provide information about the encoding it uses.
23907 Otherwise this setting is automatically updated from information
23908 provided by the executable.
23910 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23911 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23912 executables containing @acronym{MIPS16} code frequently are not
23913 identified as such.
23915 This setting is ``sticky''; that is, it retains its value across
23916 debugging sessions until reset either explicitly with this command or
23917 implicitly from an executable.
23919 The compiler and/or assembler typically add symbol table annotations to
23920 identify functions compiled for the @acronym{MIPS16} or
23921 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23922 are present, @value{GDBN} uses them in preference to the global
23923 compressed @acronym{ISA} encoding setting.
23925 @item show mips compression
23926 @kindex show mips compression
23927 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23928 @value{GDBN} to debug the inferior.
23931 @itemx show mipsfpu
23932 @xref{MIPS Embedded, set mipsfpu}.
23934 @item set mips mask-address @var{arg}
23935 @kindex set mips mask-address
23936 @cindex @acronym{MIPS} addresses, masking
23937 This command determines whether the most-significant 32 bits of 64-bit
23938 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23939 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23940 setting, which lets @value{GDBN} determine the correct value.
23942 @item show mips mask-address
23943 @kindex show mips mask-address
23944 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23947 @item set remote-mips64-transfers-32bit-regs
23948 @kindex set remote-mips64-transfers-32bit-regs
23949 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23950 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23951 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23952 and 64 bits for other registers, set this option to @samp{on}.
23954 @item show remote-mips64-transfers-32bit-regs
23955 @kindex show remote-mips64-transfers-32bit-regs
23956 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23958 @item set debug mips
23959 @kindex set debug mips
23960 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23961 target code in @value{GDBN}.
23963 @item show debug mips
23964 @kindex show debug mips
23965 Show the current setting of @acronym{MIPS} debugging messages.
23971 @cindex HPPA support
23973 When @value{GDBN} is debugging the HP PA architecture, it provides the
23974 following special commands:
23977 @item set debug hppa
23978 @kindex set debug hppa
23979 This command determines whether HPPA architecture-specific debugging
23980 messages are to be displayed.
23982 @item show debug hppa
23983 Show whether HPPA debugging messages are displayed.
23985 @item maint print unwind @var{address}
23986 @kindex maint print unwind@r{, HPPA}
23987 This command displays the contents of the unwind table entry at the
23988 given @var{address}.
23994 @subsection Cell Broadband Engine SPU architecture
23995 @cindex Cell Broadband Engine
23998 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23999 it provides the following special commands:
24002 @item info spu event
24004 Display SPU event facility status. Shows current event mask
24005 and pending event status.
24007 @item info spu signal
24008 Display SPU signal notification facility status. Shows pending
24009 signal-control word and signal notification mode of both signal
24010 notification channels.
24012 @item info spu mailbox
24013 Display SPU mailbox facility status. Shows all pending entries,
24014 in order of processing, in each of the SPU Write Outbound,
24015 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24018 Display MFC DMA status. Shows all pending commands in the MFC
24019 DMA queue. For each entry, opcode, tag, class IDs, effective
24020 and local store addresses and transfer size are shown.
24022 @item info spu proxydma
24023 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24024 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24025 and local store addresses and transfer size are shown.
24029 When @value{GDBN} is debugging a combined PowerPC/SPU application
24030 on the Cell Broadband Engine, it provides in addition the following
24034 @item set spu stop-on-load @var{arg}
24036 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24037 will give control to the user when a new SPE thread enters its @code{main}
24038 function. The default is @code{off}.
24040 @item show spu stop-on-load
24042 Show whether to stop for new SPE threads.
24044 @item set spu auto-flush-cache @var{arg}
24045 Set whether to automatically flush the software-managed cache. When set to
24046 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24047 cache to be flushed whenever SPE execution stops. This provides a consistent
24048 view of PowerPC memory that is accessed via the cache. If an application
24049 does not use the software-managed cache, this option has no effect.
24051 @item show spu auto-flush-cache
24052 Show whether to automatically flush the software-managed cache.
24057 @subsection PowerPC
24058 @cindex PowerPC architecture
24060 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24061 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24062 numbers stored in the floating point registers. These values must be stored
24063 in two consecutive registers, always starting at an even register like
24064 @code{f0} or @code{f2}.
24066 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24067 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24068 @code{f2} and @code{f3} for @code{$dl1} and so on.
24070 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24071 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24074 @subsection Nios II
24075 @cindex Nios II architecture
24077 When @value{GDBN} is debugging the Nios II architecture,
24078 it provides the following special commands:
24082 @item set debug nios2
24083 @kindex set debug nios2
24084 This command turns on and off debugging messages for the Nios II
24085 target code in @value{GDBN}.
24087 @item show debug nios2
24088 @kindex show debug nios2
24089 Show the current setting of Nios II debugging messages.
24093 @subsection Sparc64
24094 @cindex Sparc64 support
24095 @cindex Application Data Integrity
24096 @subsubsection ADI Support
24098 The M7 processor supports an Application Data Integrity (ADI) feature that
24099 detects invalid data accesses. When software allocates memory and enables
24100 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24101 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24102 the 4-bit version in every cacheline of that data. Hardware saves the latter
24103 in spare bits in the cache and memory hierarchy. On each load and store,
24104 the processor compares the upper 4 VA (virtual address) bits to the
24105 cacheline's version. If there is a mismatch, the processor generates a
24106 version mismatch trap which can be either precise or disrupting. The trap
24107 is an error condition which the kernel delivers to the process as a SIGSEGV
24110 Note that only 64-bit applications can use ADI and need to be built with
24113 Values of the ADI version tags, which are in granularity of a
24114 cacheline (64 bytes), can be viewed or modified.
24118 @kindex adi examine
24119 @item adi (examine | x) [ / @var{n} ] @var{addr}
24121 The @code{adi examine} command displays the value of one ADI version tag per
24124 @var{n} is a decimal integer specifying the number in bytes; the default
24125 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24126 block size, to display.
24128 @var{addr} is the address in user address space where you want @value{GDBN}
24129 to begin displaying the ADI version tags.
24131 Below is an example of displaying ADI versions of variable "shmaddr".
24134 (@value{GDBP}) adi x/100 shmaddr
24135 0xfff800010002c000: 0 0
24139 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24141 The @code{adi assign} command is used to assign new ADI version tag
24144 @var{n} is a decimal integer specifying the number in bytes;
24145 the default is 1. It specifies how much ADI version information, at the
24146 ratio of 1:ADI block size, to modify.
24148 @var{addr} is the address in user address space where you want @value{GDBN}
24149 to begin modifying the ADI version tags.
24151 @var{tag} is the new ADI version tag.
24153 For example, do the following to modify then verify ADI versions of
24154 variable "shmaddr":
24157 (@value{GDBP}) adi a/100 shmaddr = 7
24158 (@value{GDBP}) adi x/100 shmaddr
24159 0xfff800010002c000: 7 7
24166 @cindex S12Z support
24168 When @value{GDBN} is debugging the S12Z architecture,
24169 it provides the following special command:
24172 @item maint info bdccsr
24173 @kindex maint info bdccsr@r{, S12Z}
24174 This command displays the current value of the microprocessor's
24179 @node Controlling GDB
24180 @chapter Controlling @value{GDBN}
24182 You can alter the way @value{GDBN} interacts with you by using the
24183 @code{set} command. For commands controlling how @value{GDBN} displays
24184 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24189 * Editing:: Command editing
24190 * Command History:: Command history
24191 * Screen Size:: Screen size
24192 * Numbers:: Numbers
24193 * ABI:: Configuring the current ABI
24194 * Auto-loading:: Automatically loading associated files
24195 * Messages/Warnings:: Optional warnings and messages
24196 * Debugging Output:: Optional messages about internal happenings
24197 * Other Misc Settings:: Other Miscellaneous Settings
24205 @value{GDBN} indicates its readiness to read a command by printing a string
24206 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24207 can change the prompt string with the @code{set prompt} command. For
24208 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24209 the prompt in one of the @value{GDBN} sessions so that you can always tell
24210 which one you are talking to.
24212 @emph{Note:} @code{set prompt} does not add a space for you after the
24213 prompt you set. This allows you to set a prompt which ends in a space
24214 or a prompt that does not.
24218 @item set prompt @var{newprompt}
24219 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24221 @kindex show prompt
24223 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24226 Versions of @value{GDBN} that ship with Python scripting enabled have
24227 prompt extensions. The commands for interacting with these extensions
24231 @kindex set extended-prompt
24232 @item set extended-prompt @var{prompt}
24233 Set an extended prompt that allows for substitutions.
24234 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24235 substitution. Any escape sequences specified as part of the prompt
24236 string are replaced with the corresponding strings each time the prompt
24242 set extended-prompt Current working directory: \w (gdb)
24245 Note that when an extended-prompt is set, it takes control of the
24246 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24248 @kindex show extended-prompt
24249 @item show extended-prompt
24250 Prints the extended prompt. Any escape sequences specified as part of
24251 the prompt string with @code{set extended-prompt}, are replaced with the
24252 corresponding strings each time the prompt is displayed.
24256 @section Command Editing
24258 @cindex command line editing
24260 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24261 @sc{gnu} library provides consistent behavior for programs which provide a
24262 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24263 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24264 substitution, and a storage and recall of command history across
24265 debugging sessions.
24267 You may control the behavior of command line editing in @value{GDBN} with the
24268 command @code{set}.
24271 @kindex set editing
24274 @itemx set editing on
24275 Enable command line editing (enabled by default).
24277 @item set editing off
24278 Disable command line editing.
24280 @kindex show editing
24282 Show whether command line editing is enabled.
24285 @ifset SYSTEM_READLINE
24286 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24288 @ifclear SYSTEM_READLINE
24289 @xref{Command Line Editing},
24291 for more details about the Readline
24292 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24293 encouraged to read that chapter.
24295 @node Command History
24296 @section Command History
24297 @cindex command history
24299 @value{GDBN} can keep track of the commands you type during your
24300 debugging sessions, so that you can be certain of precisely what
24301 happened. Use these commands to manage the @value{GDBN} command
24304 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24305 package, to provide the history facility.
24306 @ifset SYSTEM_READLINE
24307 @xref{Using History Interactively, , , history, GNU History Library},
24309 @ifclear SYSTEM_READLINE
24310 @xref{Using History Interactively},
24312 for the detailed description of the History library.
24314 To issue a command to @value{GDBN} without affecting certain aspects of
24315 the state which is seen by users, prefix it with @samp{server }
24316 (@pxref{Server Prefix}). This
24317 means that this command will not affect the command history, nor will it
24318 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24319 pressed on a line by itself.
24321 @cindex @code{server}, command prefix
24322 The server prefix does not affect the recording of values into the value
24323 history; to print a value without recording it into the value history,
24324 use the @code{output} command instead of the @code{print} command.
24326 Here is the description of @value{GDBN} commands related to command
24330 @cindex history substitution
24331 @cindex history file
24332 @kindex set history filename
24333 @cindex @env{GDBHISTFILE}, environment variable
24334 @item set history filename @var{fname}
24335 Set the name of the @value{GDBN} command history file to @var{fname}.
24336 This is the file where @value{GDBN} reads an initial command history
24337 list, and where it writes the command history from this session when it
24338 exits. You can access this list through history expansion or through
24339 the history command editing characters listed below. This file defaults
24340 to the value of the environment variable @code{GDBHISTFILE}, or to
24341 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24344 @cindex save command history
24345 @kindex set history save
24346 @item set history save
24347 @itemx set history save on
24348 Record command history in a file, whose name may be specified with the
24349 @code{set history filename} command. By default, this option is disabled.
24351 @item set history save off
24352 Stop recording command history in a file.
24354 @cindex history size
24355 @kindex set history size
24356 @cindex @env{GDBHISTSIZE}, environment variable
24357 @item set history size @var{size}
24358 @itemx set history size unlimited
24359 Set the number of commands which @value{GDBN} keeps in its history list.
24360 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24361 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24362 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24363 either a negative number or the empty string, then the number of commands
24364 @value{GDBN} keeps in the history list is unlimited.
24366 @cindex remove duplicate history
24367 @kindex set history remove-duplicates
24368 @item set history remove-duplicates @var{count}
24369 @itemx set history remove-duplicates unlimited
24370 Control the removal of duplicate history entries in the command history list.
24371 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24372 history entries and remove the first entry that is a duplicate of the current
24373 entry being added to the command history list. If @var{count} is
24374 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24375 removal of duplicate history entries is disabled.
24377 Only history entries added during the current session are considered for
24378 removal. This option is set to 0 by default.
24382 History expansion assigns special meaning to the character @kbd{!}.
24383 @ifset SYSTEM_READLINE
24384 @xref{Event Designators, , , history, GNU History Library},
24386 @ifclear SYSTEM_READLINE
24387 @xref{Event Designators},
24391 @cindex history expansion, turn on/off
24392 Since @kbd{!} is also the logical not operator in C, history expansion
24393 is off by default. If you decide to enable history expansion with the
24394 @code{set history expansion on} command, you may sometimes need to
24395 follow @kbd{!} (when it is used as logical not, in an expression) with
24396 a space or a tab to prevent it from being expanded. The readline
24397 history facilities do not attempt substitution on the strings
24398 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24400 The commands to control history expansion are:
24403 @item set history expansion on
24404 @itemx set history expansion
24405 @kindex set history expansion
24406 Enable history expansion. History expansion is off by default.
24408 @item set history expansion off
24409 Disable history expansion.
24412 @kindex show history
24414 @itemx show history filename
24415 @itemx show history save
24416 @itemx show history size
24417 @itemx show history expansion
24418 These commands display the state of the @value{GDBN} history parameters.
24419 @code{show history} by itself displays all four states.
24424 @kindex show commands
24425 @cindex show last commands
24426 @cindex display command history
24427 @item show commands
24428 Display the last ten commands in the command history.
24430 @item show commands @var{n}
24431 Print ten commands centered on command number @var{n}.
24433 @item show commands +
24434 Print ten commands just after the commands last printed.
24438 @section Screen Size
24439 @cindex size of screen
24440 @cindex screen size
24443 @cindex pauses in output
24445 Certain commands to @value{GDBN} may produce large amounts of
24446 information output to the screen. To help you read all of it,
24447 @value{GDBN} pauses and asks you for input at the end of each page of
24448 output. Type @key{RET} when you want to see one more page of output,
24449 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24450 without paging for the rest of the current command. Also, the screen
24451 width setting determines when to wrap lines of output. Depending on
24452 what is being printed, @value{GDBN} tries to break the line at a
24453 readable place, rather than simply letting it overflow onto the
24456 Normally @value{GDBN} knows the size of the screen from the terminal
24457 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24458 together with the value of the @code{TERM} environment variable and the
24459 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24460 you can override it with the @code{set height} and @code{set
24467 @kindex show height
24468 @item set height @var{lpp}
24469 @itemx set height unlimited
24471 @itemx set width @var{cpl}
24472 @itemx set width unlimited
24474 These @code{set} commands specify a screen height of @var{lpp} lines and
24475 a screen width of @var{cpl} characters. The associated @code{show}
24476 commands display the current settings.
24478 If you specify a height of either @code{unlimited} or zero lines,
24479 @value{GDBN} does not pause during output no matter how long the
24480 output is. This is useful if output is to a file or to an editor
24483 Likewise, you can specify @samp{set width unlimited} or @samp{set
24484 width 0} to prevent @value{GDBN} from wrapping its output.
24486 @item set pagination on
24487 @itemx set pagination off
24488 @kindex set pagination
24489 Turn the output pagination on or off; the default is on. Turning
24490 pagination off is the alternative to @code{set height unlimited}. Note that
24491 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24492 Options, -batch}) also automatically disables pagination.
24494 @item show pagination
24495 @kindex show pagination
24496 Show the current pagination mode.
24501 @cindex number representation
24502 @cindex entering numbers
24504 You can always enter numbers in octal, decimal, or hexadecimal in
24505 @value{GDBN} by the usual conventions: octal numbers begin with
24506 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24507 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24508 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24509 10; likewise, the default display for numbers---when no particular
24510 format is specified---is base 10. You can change the default base for
24511 both input and output with the commands described below.
24514 @kindex set input-radix
24515 @item set input-radix @var{base}
24516 Set the default base for numeric input. Supported choices
24517 for @var{base} are decimal 8, 10, or 16. The base must itself be
24518 specified either unambiguously or using the current input radix; for
24522 set input-radix 012
24523 set input-radix 10.
24524 set input-radix 0xa
24528 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24529 leaves the input radix unchanged, no matter what it was, since
24530 @samp{10}, being without any leading or trailing signs of its base, is
24531 interpreted in the current radix. Thus, if the current radix is 16,
24532 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24535 @kindex set output-radix
24536 @item set output-radix @var{base}
24537 Set the default base for numeric display. Supported choices
24538 for @var{base} are decimal 8, 10, or 16. The base must itself be
24539 specified either unambiguously or using the current input radix.
24541 @kindex show input-radix
24542 @item show input-radix
24543 Display the current default base for numeric input.
24545 @kindex show output-radix
24546 @item show output-radix
24547 Display the current default base for numeric display.
24549 @item set radix @r{[}@var{base}@r{]}
24553 These commands set and show the default base for both input and output
24554 of numbers. @code{set radix} sets the radix of input and output to
24555 the same base; without an argument, it resets the radix back to its
24556 default value of 10.
24561 @section Configuring the Current ABI
24563 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24564 application automatically. However, sometimes you need to override its
24565 conclusions. Use these commands to manage @value{GDBN}'s view of the
24571 @cindex Newlib OS ABI and its influence on the longjmp handling
24573 One @value{GDBN} configuration can debug binaries for multiple operating
24574 system targets, either via remote debugging or native emulation.
24575 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24576 but you can override its conclusion using the @code{set osabi} command.
24577 One example where this is useful is in debugging of binaries which use
24578 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24579 not have the same identifying marks that the standard C library for your
24582 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24583 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24584 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24585 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24589 Show the OS ABI currently in use.
24592 With no argument, show the list of registered available OS ABI's.
24594 @item set osabi @var{abi}
24595 Set the current OS ABI to @var{abi}.
24598 @cindex float promotion
24600 Generally, the way that an argument of type @code{float} is passed to a
24601 function depends on whether the function is prototyped. For a prototyped
24602 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24603 according to the architecture's convention for @code{float}. For unprototyped
24604 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24605 @code{double} and then passed.
24607 Unfortunately, some forms of debug information do not reliably indicate whether
24608 a function is prototyped. If @value{GDBN} calls a function that is not marked
24609 as prototyped, it consults @kbd{set coerce-float-to-double}.
24612 @kindex set coerce-float-to-double
24613 @item set coerce-float-to-double
24614 @itemx set coerce-float-to-double on
24615 Arguments of type @code{float} will be promoted to @code{double} when passed
24616 to an unprototyped function. This is the default setting.
24618 @item set coerce-float-to-double off
24619 Arguments of type @code{float} will be passed directly to unprototyped
24622 @kindex show coerce-float-to-double
24623 @item show coerce-float-to-double
24624 Show the current setting of promoting @code{float} to @code{double}.
24628 @kindex show cp-abi
24629 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24630 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24631 used to build your application. @value{GDBN} only fully supports
24632 programs with a single C@t{++} ABI; if your program contains code using
24633 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24634 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24635 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24636 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24637 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24638 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24643 Show the C@t{++} ABI currently in use.
24646 With no argument, show the list of supported C@t{++} ABI's.
24648 @item set cp-abi @var{abi}
24649 @itemx set cp-abi auto
24650 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24654 @section Automatically loading associated files
24655 @cindex auto-loading
24657 @value{GDBN} sometimes reads files with commands and settings automatically,
24658 without being explicitly told so by the user. We call this feature
24659 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24660 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24661 results or introduce security risks (e.g., if the file comes from untrusted
24665 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24666 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24668 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24669 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24672 There are various kinds of files @value{GDBN} can automatically load.
24673 In addition to these files, @value{GDBN} supports auto-loading code written
24674 in various extension languages. @xref{Auto-loading extensions}.
24676 Note that loading of these associated files (including the local @file{.gdbinit}
24677 file) requires accordingly configured @code{auto-load safe-path}
24678 (@pxref{Auto-loading safe path}).
24680 For these reasons, @value{GDBN} includes commands and options to let you
24681 control when to auto-load files and which files should be auto-loaded.
24684 @anchor{set auto-load off}
24685 @kindex set auto-load off
24686 @item set auto-load off
24687 Globally disable loading of all auto-loaded files.
24688 You may want to use this command with the @samp{-iex} option
24689 (@pxref{Option -init-eval-command}) such as:
24691 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24694 Be aware that system init file (@pxref{System-wide configuration})
24695 and init files from your home directory (@pxref{Home Directory Init File})
24696 still get read (as they come from generally trusted directories).
24697 To prevent @value{GDBN} from auto-loading even those init files, use the
24698 @option{-nx} option (@pxref{Mode Options}), in addition to
24699 @code{set auto-load no}.
24701 @anchor{show auto-load}
24702 @kindex show auto-load
24703 @item show auto-load
24704 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24708 (gdb) show auto-load
24709 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24710 libthread-db: Auto-loading of inferior specific libthread_db is on.
24711 local-gdbinit: Auto-loading of .gdbinit script from current directory
24713 python-scripts: Auto-loading of Python scripts is on.
24714 safe-path: List of directories from which it is safe to auto-load files
24715 is $debugdir:$datadir/auto-load.
24716 scripts-directory: List of directories from which to load auto-loaded scripts
24717 is $debugdir:$datadir/auto-load.
24720 @anchor{info auto-load}
24721 @kindex info auto-load
24722 @item info auto-load
24723 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24727 (gdb) info auto-load
24730 Yes /home/user/gdb/gdb-gdb.gdb
24731 libthread-db: No auto-loaded libthread-db.
24732 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24736 Yes /home/user/gdb/gdb-gdb.py
24740 These are @value{GDBN} control commands for the auto-loading:
24742 @multitable @columnfractions .5 .5
24743 @item @xref{set auto-load off}.
24744 @tab Disable auto-loading globally.
24745 @item @xref{show auto-load}.
24746 @tab Show setting of all kinds of files.
24747 @item @xref{info auto-load}.
24748 @tab Show state of all kinds of files.
24749 @item @xref{set auto-load gdb-scripts}.
24750 @tab Control for @value{GDBN} command scripts.
24751 @item @xref{show auto-load gdb-scripts}.
24752 @tab Show setting of @value{GDBN} command scripts.
24753 @item @xref{info auto-load gdb-scripts}.
24754 @tab Show state of @value{GDBN} command scripts.
24755 @item @xref{set auto-load python-scripts}.
24756 @tab Control for @value{GDBN} Python scripts.
24757 @item @xref{show auto-load python-scripts}.
24758 @tab Show setting of @value{GDBN} Python scripts.
24759 @item @xref{info auto-load python-scripts}.
24760 @tab Show state of @value{GDBN} Python scripts.
24761 @item @xref{set auto-load guile-scripts}.
24762 @tab Control for @value{GDBN} Guile scripts.
24763 @item @xref{show auto-load guile-scripts}.
24764 @tab Show setting of @value{GDBN} Guile scripts.
24765 @item @xref{info auto-load guile-scripts}.
24766 @tab Show state of @value{GDBN} Guile scripts.
24767 @item @xref{set auto-load scripts-directory}.
24768 @tab Control for @value{GDBN} auto-loaded scripts location.
24769 @item @xref{show auto-load scripts-directory}.
24770 @tab Show @value{GDBN} auto-loaded scripts location.
24771 @item @xref{add-auto-load-scripts-directory}.
24772 @tab Add directory for auto-loaded scripts location list.
24773 @item @xref{set auto-load local-gdbinit}.
24774 @tab Control for init file in the current directory.
24775 @item @xref{show auto-load local-gdbinit}.
24776 @tab Show setting of init file in the current directory.
24777 @item @xref{info auto-load local-gdbinit}.
24778 @tab Show state of init file in the current directory.
24779 @item @xref{set auto-load libthread-db}.
24780 @tab Control for thread debugging library.
24781 @item @xref{show auto-load libthread-db}.
24782 @tab Show setting of thread debugging library.
24783 @item @xref{info auto-load libthread-db}.
24784 @tab Show state of thread debugging library.
24785 @item @xref{set auto-load safe-path}.
24786 @tab Control directories trusted for automatic loading.
24787 @item @xref{show auto-load safe-path}.
24788 @tab Show directories trusted for automatic loading.
24789 @item @xref{add-auto-load-safe-path}.
24790 @tab Add directory trusted for automatic loading.
24793 @node Init File in the Current Directory
24794 @subsection Automatically loading init file in the current directory
24795 @cindex auto-loading init file in the current directory
24797 By default, @value{GDBN} reads and executes the canned sequences of commands
24798 from init file (if any) in the current working directory,
24799 see @ref{Init File in the Current Directory during Startup}.
24801 Note that loading of this local @file{.gdbinit} file also requires accordingly
24802 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24805 @anchor{set auto-load local-gdbinit}
24806 @kindex set auto-load local-gdbinit
24807 @item set auto-load local-gdbinit [on|off]
24808 Enable or disable the auto-loading of canned sequences of commands
24809 (@pxref{Sequences}) found in init file in the current directory.
24811 @anchor{show auto-load local-gdbinit}
24812 @kindex show auto-load local-gdbinit
24813 @item show auto-load local-gdbinit
24814 Show whether auto-loading of canned sequences of commands from init file in the
24815 current directory is enabled or disabled.
24817 @anchor{info auto-load local-gdbinit}
24818 @kindex info auto-load local-gdbinit
24819 @item info auto-load local-gdbinit
24820 Print whether canned sequences of commands from init file in the
24821 current directory have been auto-loaded.
24824 @node libthread_db.so.1 file
24825 @subsection Automatically loading thread debugging library
24826 @cindex auto-loading libthread_db.so.1
24828 This feature is currently present only on @sc{gnu}/Linux native hosts.
24830 @value{GDBN} reads in some cases thread debugging library from places specific
24831 to the inferior (@pxref{set libthread-db-search-path}).
24833 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24834 without checking this @samp{set auto-load libthread-db} switch as system
24835 libraries have to be trusted in general. In all other cases of
24836 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24837 auto-load libthread-db} is enabled before trying to open such thread debugging
24840 Note that loading of this debugging library also requires accordingly configured
24841 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24844 @anchor{set auto-load libthread-db}
24845 @kindex set auto-load libthread-db
24846 @item set auto-load libthread-db [on|off]
24847 Enable or disable the auto-loading of inferior specific thread debugging library.
24849 @anchor{show auto-load libthread-db}
24850 @kindex show auto-load libthread-db
24851 @item show auto-load libthread-db
24852 Show whether auto-loading of inferior specific thread debugging library is
24853 enabled or disabled.
24855 @anchor{info auto-load libthread-db}
24856 @kindex info auto-load libthread-db
24857 @item info auto-load libthread-db
24858 Print the list of all loaded inferior specific thread debugging libraries and
24859 for each such library print list of inferior @var{pid}s using it.
24862 @node Auto-loading safe path
24863 @subsection Security restriction for auto-loading
24864 @cindex auto-loading safe-path
24866 As the files of inferior can come from untrusted source (such as submitted by
24867 an application user) @value{GDBN} does not always load any files automatically.
24868 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24869 directories trusted for loading files not explicitly requested by user.
24870 Each directory can also be a shell wildcard pattern.
24872 If the path is not set properly you will see a warning and the file will not
24877 Reading symbols from /home/user/gdb/gdb...done.
24878 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24879 declined by your `auto-load safe-path' set
24880 to "$debugdir:$datadir/auto-load".
24881 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24882 declined by your `auto-load safe-path' set
24883 to "$debugdir:$datadir/auto-load".
24887 To instruct @value{GDBN} to go ahead and use the init files anyway,
24888 invoke @value{GDBN} like this:
24891 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24894 The list of trusted directories is controlled by the following commands:
24897 @anchor{set auto-load safe-path}
24898 @kindex set auto-load safe-path
24899 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24900 Set the list of directories (and their subdirectories) trusted for automatic
24901 loading and execution of scripts. You can also enter a specific trusted file.
24902 Each directory can also be a shell wildcard pattern; wildcards do not match
24903 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24904 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24905 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24906 its default value as specified during @value{GDBN} compilation.
24908 The list of directories uses path separator (@samp{:} on GNU and Unix
24909 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24910 to the @env{PATH} environment variable.
24912 @anchor{show auto-load safe-path}
24913 @kindex show auto-load safe-path
24914 @item show auto-load safe-path
24915 Show the list of directories trusted for automatic loading and execution of
24918 @anchor{add-auto-load-safe-path}
24919 @kindex add-auto-load-safe-path
24920 @item add-auto-load-safe-path
24921 Add an entry (or list of entries) to the list of directories trusted for
24922 automatic loading and execution of scripts. Multiple entries may be delimited
24923 by the host platform path separator in use.
24926 This variable defaults to what @code{--with-auto-load-dir} has been configured
24927 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24928 substitution applies the same as for @ref{set auto-load scripts-directory}.
24929 The default @code{set auto-load safe-path} value can be also overriden by
24930 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24932 Setting this variable to @file{/} disables this security protection,
24933 corresponding @value{GDBN} configuration option is
24934 @option{--without-auto-load-safe-path}.
24935 This variable is supposed to be set to the system directories writable by the
24936 system superuser only. Users can add their source directories in init files in
24937 their home directories (@pxref{Home Directory Init File}). See also deprecated
24938 init file in the current directory
24939 (@pxref{Init File in the Current Directory during Startup}).
24941 To force @value{GDBN} to load the files it declined to load in the previous
24942 example, you could use one of the following ways:
24945 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24946 Specify this trusted directory (or a file) as additional component of the list.
24947 You have to specify also any existing directories displayed by
24948 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24950 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24951 Specify this directory as in the previous case but just for a single
24952 @value{GDBN} session.
24954 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24955 Disable auto-loading safety for a single @value{GDBN} session.
24956 This assumes all the files you debug during this @value{GDBN} session will come
24957 from trusted sources.
24959 @item @kbd{./configure --without-auto-load-safe-path}
24960 During compilation of @value{GDBN} you may disable any auto-loading safety.
24961 This assumes all the files you will ever debug with this @value{GDBN} come from
24965 On the other hand you can also explicitly forbid automatic files loading which
24966 also suppresses any such warning messages:
24969 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24970 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24972 @item @file{~/.gdbinit}: @samp{set auto-load no}
24973 Disable auto-loading globally for the user
24974 (@pxref{Home Directory Init File}). While it is improbable, you could also
24975 use system init file instead (@pxref{System-wide configuration}).
24978 This setting applies to the file names as entered by user. If no entry matches
24979 @value{GDBN} tries as a last resort to also resolve all the file names into
24980 their canonical form (typically resolving symbolic links) and compare the
24981 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24982 own before starting the comparison so a canonical form of directories is
24983 recommended to be entered.
24985 @node Auto-loading verbose mode
24986 @subsection Displaying files tried for auto-load
24987 @cindex auto-loading verbose mode
24989 For better visibility of all the file locations where you can place scripts to
24990 be auto-loaded with inferior --- or to protect yourself against accidental
24991 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24992 all the files attempted to be loaded. Both existing and non-existing files may
24995 For example the list of directories from which it is safe to auto-load files
24996 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24997 may not be too obvious while setting it up.
25000 (gdb) set debug auto-load on
25001 (gdb) file ~/src/t/true
25002 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25003 for objfile "/tmp/true".
25004 auto-load: Updating directories of "/usr:/opt".
25005 auto-load: Using directory "/usr".
25006 auto-load: Using directory "/opt".
25007 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25008 by your `auto-load safe-path' set to "/usr:/opt".
25012 @anchor{set debug auto-load}
25013 @kindex set debug auto-load
25014 @item set debug auto-load [on|off]
25015 Set whether to print the filenames attempted to be auto-loaded.
25017 @anchor{show debug auto-load}
25018 @kindex show debug auto-load
25019 @item show debug auto-load
25020 Show whether printing of the filenames attempted to be auto-loaded is turned
25024 @node Messages/Warnings
25025 @section Optional Warnings and Messages
25027 @cindex verbose operation
25028 @cindex optional warnings
25029 By default, @value{GDBN} is silent about its inner workings. If you are
25030 running on a slow machine, you may want to use the @code{set verbose}
25031 command. This makes @value{GDBN} tell you when it does a lengthy
25032 internal operation, so you will not think it has crashed.
25034 Currently, the messages controlled by @code{set verbose} are those
25035 which announce that the symbol table for a source file is being read;
25036 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25039 @kindex set verbose
25040 @item set verbose on
25041 Enables @value{GDBN} output of certain informational messages.
25043 @item set verbose off
25044 Disables @value{GDBN} output of certain informational messages.
25046 @kindex show verbose
25048 Displays whether @code{set verbose} is on or off.
25051 By default, if @value{GDBN} encounters bugs in the symbol table of an
25052 object file, it is silent; but if you are debugging a compiler, you may
25053 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25058 @kindex set complaints
25059 @item set complaints @var{limit}
25060 Permits @value{GDBN} to output @var{limit} complaints about each type of
25061 unusual symbols before becoming silent about the problem. Set
25062 @var{limit} to zero to suppress all complaints; set it to a large number
25063 to prevent complaints from being suppressed.
25065 @kindex show complaints
25066 @item show complaints
25067 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25071 @anchor{confirmation requests}
25072 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25073 lot of stupid questions to confirm certain commands. For example, if
25074 you try to run a program which is already running:
25078 The program being debugged has been started already.
25079 Start it from the beginning? (y or n)
25082 If you are willing to unflinchingly face the consequences of your own
25083 commands, you can disable this ``feature'':
25087 @kindex set confirm
25089 @cindex confirmation
25090 @cindex stupid questions
25091 @item set confirm off
25092 Disables confirmation requests. Note that running @value{GDBN} with
25093 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25094 automatically disables confirmation requests.
25096 @item set confirm on
25097 Enables confirmation requests (the default).
25099 @kindex show confirm
25101 Displays state of confirmation requests.
25105 @cindex command tracing
25106 If you need to debug user-defined commands or sourced files you may find it
25107 useful to enable @dfn{command tracing}. In this mode each command will be
25108 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25109 quantity denoting the call depth of each command.
25112 @kindex set trace-commands
25113 @cindex command scripts, debugging
25114 @item set trace-commands on
25115 Enable command tracing.
25116 @item set trace-commands off
25117 Disable command tracing.
25118 @item show trace-commands
25119 Display the current state of command tracing.
25122 @node Debugging Output
25123 @section Optional Messages about Internal Happenings
25124 @cindex optional debugging messages
25126 @value{GDBN} has commands that enable optional debugging messages from
25127 various @value{GDBN} subsystems; normally these commands are of
25128 interest to @value{GDBN} maintainers, or when reporting a bug. This
25129 section documents those commands.
25132 @kindex set exec-done-display
25133 @item set exec-done-display
25134 Turns on or off the notification of asynchronous commands'
25135 completion. When on, @value{GDBN} will print a message when an
25136 asynchronous command finishes its execution. The default is off.
25137 @kindex show exec-done-display
25138 @item show exec-done-display
25139 Displays the current setting of asynchronous command completion
25142 @cindex ARM AArch64
25143 @item set debug aarch64
25144 Turns on or off display of debugging messages related to ARM AArch64.
25145 The default is off.
25147 @item show debug aarch64
25148 Displays the current state of displaying debugging messages related to
25150 @cindex gdbarch debugging info
25151 @cindex architecture debugging info
25152 @item set debug arch
25153 Turns on or off display of gdbarch debugging info. The default is off
25154 @item show debug arch
25155 Displays the current state of displaying gdbarch debugging info.
25156 @item set debug aix-solib
25157 @cindex AIX shared library debugging
25158 Control display of debugging messages from the AIX shared library
25159 support module. The default is off.
25160 @item show debug aix-thread
25161 Show the current state of displaying AIX shared library debugging messages.
25162 @item set debug aix-thread
25163 @cindex AIX threads
25164 Display debugging messages about inner workings of the AIX thread
25166 @item show debug aix-thread
25167 Show the current state of AIX thread debugging info display.
25168 @item set debug check-physname
25170 Check the results of the ``physname'' computation. When reading DWARF
25171 debugging information for C@t{++}, @value{GDBN} attempts to compute
25172 each entity's name. @value{GDBN} can do this computation in two
25173 different ways, depending on exactly what information is present.
25174 When enabled, this setting causes @value{GDBN} to compute the names
25175 both ways and display any discrepancies.
25176 @item show debug check-physname
25177 Show the current state of ``physname'' checking.
25178 @item set debug coff-pe-read
25179 @cindex COFF/PE exported symbols
25180 Control display of debugging messages related to reading of COFF/PE
25181 exported symbols. The default is off.
25182 @item show debug coff-pe-read
25183 Displays the current state of displaying debugging messages related to
25184 reading of COFF/PE exported symbols.
25185 @item set debug dwarf-die
25187 Dump DWARF DIEs after they are read in.
25188 The value is the number of nesting levels to print.
25189 A value of zero turns off the display.
25190 @item show debug dwarf-die
25191 Show the current state of DWARF DIE debugging.
25192 @item set debug dwarf-line
25193 @cindex DWARF Line Tables
25194 Turns on or off display of debugging messages related to reading
25195 DWARF line tables. The default is 0 (off).
25196 A value of 1 provides basic information.
25197 A value greater than 1 provides more verbose information.
25198 @item show debug dwarf-line
25199 Show the current state of DWARF line table debugging.
25200 @item set debug dwarf-read
25201 @cindex DWARF Reading
25202 Turns on or off display of debugging messages related to reading
25203 DWARF debug info. The default is 0 (off).
25204 A value of 1 provides basic information.
25205 A value greater than 1 provides more verbose information.
25206 @item show debug dwarf-read
25207 Show the current state of DWARF reader debugging.
25208 @item set debug displaced
25209 @cindex displaced stepping debugging info
25210 Turns on or off display of @value{GDBN} debugging info for the
25211 displaced stepping support. The default is off.
25212 @item show debug displaced
25213 Displays the current state of displaying @value{GDBN} debugging info
25214 related to displaced stepping.
25215 @item set debug event
25216 @cindex event debugging info
25217 Turns on or off display of @value{GDBN} event debugging info. The
25219 @item show debug event
25220 Displays the current state of displaying @value{GDBN} event debugging
25222 @item set debug expression
25223 @cindex expression debugging info
25224 Turns on or off display of debugging info about @value{GDBN}
25225 expression parsing. The default is off.
25226 @item show debug expression
25227 Displays the current state of displaying debugging info about
25228 @value{GDBN} expression parsing.
25229 @item set debug fbsd-lwp
25230 @cindex FreeBSD LWP debug messages
25231 Turns on or off debugging messages from the FreeBSD LWP debug support.
25232 @item show debug fbsd-lwp
25233 Show the current state of FreeBSD LWP debugging messages.
25234 @item set debug fbsd-nat
25235 @cindex FreeBSD native target debug messages
25236 Turns on or off debugging messages from the FreeBSD native target.
25237 @item show debug fbsd-nat
25238 Show the current state of FreeBSD native target debugging messages.
25239 @item set debug frame
25240 @cindex frame debugging info
25241 Turns on or off display of @value{GDBN} frame debugging info. The
25243 @item show debug frame
25244 Displays the current state of displaying @value{GDBN} frame debugging
25246 @item set debug gnu-nat
25247 @cindex @sc{gnu}/Hurd debug messages
25248 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25249 @item show debug gnu-nat
25250 Show the current state of @sc{gnu}/Hurd debugging messages.
25251 @item set debug infrun
25252 @cindex inferior debugging info
25253 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25254 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25255 for implementing operations such as single-stepping the inferior.
25256 @item show debug infrun
25257 Displays the current state of @value{GDBN} inferior debugging.
25258 @item set debug jit
25259 @cindex just-in-time compilation, debugging messages
25260 Turn on or off debugging messages from JIT debug support.
25261 @item show debug jit
25262 Displays the current state of @value{GDBN} JIT debugging.
25263 @item set debug lin-lwp
25264 @cindex @sc{gnu}/Linux LWP debug messages
25265 @cindex Linux lightweight processes
25266 Turn on or off debugging messages from the Linux LWP debug support.
25267 @item show debug lin-lwp
25268 Show the current state of Linux LWP debugging messages.
25269 @item set debug linux-namespaces
25270 @cindex @sc{gnu}/Linux namespaces debug messages
25271 Turn on or off debugging messages from the Linux namespaces debug support.
25272 @item show debug linux-namespaces
25273 Show the current state of Linux namespaces debugging messages.
25274 @item set debug mach-o
25275 @cindex Mach-O symbols processing
25276 Control display of debugging messages related to Mach-O symbols
25277 processing. The default is off.
25278 @item show debug mach-o
25279 Displays the current state of displaying debugging messages related to
25280 reading of COFF/PE exported symbols.
25281 @item set debug notification
25282 @cindex remote async notification debugging info
25283 Turn on or off debugging messages about remote async notification.
25284 The default is off.
25285 @item show debug notification
25286 Displays the current state of remote async notification debugging messages.
25287 @item set debug observer
25288 @cindex observer debugging info
25289 Turns on or off display of @value{GDBN} observer debugging. This
25290 includes info such as the notification of observable events.
25291 @item show debug observer
25292 Displays the current state of observer debugging.
25293 @item set debug overload
25294 @cindex C@t{++} overload debugging info
25295 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25296 info. This includes info such as ranking of functions, etc. The default
25298 @item show debug overload
25299 Displays the current state of displaying @value{GDBN} C@t{++} overload
25301 @cindex expression parser, debugging info
25302 @cindex debug expression parser
25303 @item set debug parser
25304 Turns on or off the display of expression parser debugging output.
25305 Internally, this sets the @code{yydebug} variable in the expression
25306 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25307 details. The default is off.
25308 @item show debug parser
25309 Show the current state of expression parser debugging.
25310 @cindex packets, reporting on stdout
25311 @cindex serial connections, debugging
25312 @cindex debug remote protocol
25313 @cindex remote protocol debugging
25314 @cindex display remote packets
25315 @item set debug remote
25316 Turns on or off display of reports on all packets sent back and forth across
25317 the serial line to the remote machine. The info is printed on the
25318 @value{GDBN} standard output stream. The default is off.
25319 @item show debug remote
25320 Displays the state of display of remote packets.
25322 @item set debug separate-debug-file
25323 Turns on or off display of debug output about separate debug file search.
25324 @item show debug separate-debug-file
25325 Displays the state of separate debug file search debug output.
25327 @item set debug serial
25328 Turns on or off display of @value{GDBN} serial debugging info. The
25330 @item show debug serial
25331 Displays the current state of displaying @value{GDBN} serial debugging
25333 @item set debug solib-frv
25334 @cindex FR-V shared-library debugging
25335 Turn on or off debugging messages for FR-V shared-library code.
25336 @item show debug solib-frv
25337 Display the current state of FR-V shared-library code debugging
25339 @item set debug symbol-lookup
25340 @cindex symbol lookup
25341 Turns on or off display of debugging messages related to symbol lookup.
25342 The default is 0 (off).
25343 A value of 1 provides basic information.
25344 A value greater than 1 provides more verbose information.
25345 @item show debug symbol-lookup
25346 Show the current state of symbol lookup debugging messages.
25347 @item set debug symfile
25348 @cindex symbol file functions
25349 Turns on or off display of debugging messages related to symbol file functions.
25350 The default is off. @xref{Files}.
25351 @item show debug symfile
25352 Show the current state of symbol file debugging messages.
25353 @item set debug symtab-create
25354 @cindex symbol table creation
25355 Turns on or off display of debugging messages related to symbol table creation.
25356 The default is 0 (off).
25357 A value of 1 provides basic information.
25358 A value greater than 1 provides more verbose information.
25359 @item show debug symtab-create
25360 Show the current state of symbol table creation debugging.
25361 @item set debug target
25362 @cindex target debugging info
25363 Turns on or off display of @value{GDBN} target debugging info. This info
25364 includes what is going on at the target level of GDB, as it happens. The
25365 default is 0. Set it to 1 to track events, and to 2 to also track the
25366 value of large memory transfers.
25367 @item show debug target
25368 Displays the current state of displaying @value{GDBN} target debugging
25370 @item set debug timestamp
25371 @cindex timestampping debugging info
25372 Turns on or off display of timestamps with @value{GDBN} debugging info.
25373 When enabled, seconds and microseconds are displayed before each debugging
25375 @item show debug timestamp
25376 Displays the current state of displaying timestamps with @value{GDBN}
25378 @item set debug varobj
25379 @cindex variable object debugging info
25380 Turns on or off display of @value{GDBN} variable object debugging
25381 info. The default is off.
25382 @item show debug varobj
25383 Displays the current state of displaying @value{GDBN} variable object
25385 @item set debug xml
25386 @cindex XML parser debugging
25387 Turn on or off debugging messages for built-in XML parsers.
25388 @item show debug xml
25389 Displays the current state of XML debugging messages.
25392 @node Other Misc Settings
25393 @section Other Miscellaneous Settings
25394 @cindex miscellaneous settings
25397 @kindex set interactive-mode
25398 @item set interactive-mode
25399 If @code{on}, forces @value{GDBN} to assume that GDB was started
25400 in a terminal. In practice, this means that @value{GDBN} should wait
25401 for the user to answer queries generated by commands entered at
25402 the command prompt. If @code{off}, forces @value{GDBN} to operate
25403 in the opposite mode, and it uses the default answers to all queries.
25404 If @code{auto} (the default), @value{GDBN} tries to determine whether
25405 its standard input is a terminal, and works in interactive-mode if it
25406 is, non-interactively otherwise.
25408 In the vast majority of cases, the debugger should be able to guess
25409 correctly which mode should be used. But this setting can be useful
25410 in certain specific cases, such as running a MinGW @value{GDBN}
25411 inside a cygwin window.
25413 @kindex show interactive-mode
25414 @item show interactive-mode
25415 Displays whether the debugger is operating in interactive mode or not.
25418 @node Extending GDB
25419 @chapter Extending @value{GDBN}
25420 @cindex extending GDB
25422 @value{GDBN} provides several mechanisms for extension.
25423 @value{GDBN} also provides the ability to automatically load
25424 extensions when it reads a file for debugging. This allows the
25425 user to automatically customize @value{GDBN} for the program
25429 * Sequences:: Canned Sequences of @value{GDBN} Commands
25430 * Python:: Extending @value{GDBN} using Python
25431 * Guile:: Extending @value{GDBN} using Guile
25432 * Auto-loading extensions:: Automatically loading extensions
25433 * Multiple Extension Languages:: Working with multiple extension languages
25434 * Aliases:: Creating new spellings of existing commands
25437 To facilitate the use of extension languages, @value{GDBN} is capable
25438 of evaluating the contents of a file. When doing so, @value{GDBN}
25439 can recognize which extension language is being used by looking at
25440 the filename extension. Files with an unrecognized filename extension
25441 are always treated as a @value{GDBN} Command Files.
25442 @xref{Command Files,, Command files}.
25444 You can control how @value{GDBN} evaluates these files with the following
25448 @kindex set script-extension
25449 @kindex show script-extension
25450 @item set script-extension off
25451 All scripts are always evaluated as @value{GDBN} Command Files.
25453 @item set script-extension soft
25454 The debugger determines the scripting language based on filename
25455 extension. If this scripting language is supported, @value{GDBN}
25456 evaluates the script using that language. Otherwise, it evaluates
25457 the file as a @value{GDBN} Command File.
25459 @item set script-extension strict
25460 The debugger determines the scripting language based on filename
25461 extension, and evaluates the script using that language. If the
25462 language is not supported, then the evaluation fails.
25464 @item show script-extension
25465 Display the current value of the @code{script-extension} option.
25470 @section Canned Sequences of Commands
25472 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25473 Command Lists}), @value{GDBN} provides two ways to store sequences of
25474 commands for execution as a unit: user-defined commands and command
25478 * Define:: How to define your own commands
25479 * Hooks:: Hooks for user-defined commands
25480 * Command Files:: How to write scripts of commands to be stored in a file
25481 * Output:: Commands for controlled output
25482 * Auto-loading sequences:: Controlling auto-loaded command files
25486 @subsection User-defined Commands
25488 @cindex user-defined command
25489 @cindex arguments, to user-defined commands
25490 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25491 which you assign a new name as a command. This is done with the
25492 @code{define} command. User commands may accept an unlimited number of arguments
25493 separated by whitespace. Arguments are accessed within the user command
25494 via @code{$arg0@dots{}$argN}. A trivial example:
25498 print $arg0 + $arg1 + $arg2
25503 To execute the command use:
25510 This defines the command @code{adder}, which prints the sum of
25511 its three arguments. Note the arguments are text substitutions, so they may
25512 reference variables, use complex expressions, or even perform inferior
25515 @cindex argument count in user-defined commands
25516 @cindex how many arguments (user-defined commands)
25517 In addition, @code{$argc} may be used to find out how many arguments have
25523 print $arg0 + $arg1
25526 print $arg0 + $arg1 + $arg2
25531 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25532 to process a variable number of arguments:
25539 eval "set $sum = $sum + $arg%d", $i
25549 @item define @var{commandname}
25550 Define a command named @var{commandname}. If there is already a command
25551 by that name, you are asked to confirm that you want to redefine it.
25552 The argument @var{commandname} may be a bare command name consisting of letters,
25553 numbers, dashes, and underscores. It may also start with any predefined
25554 prefix command. For example, @samp{define target my-target} creates
25555 a user-defined @samp{target my-target} command.
25557 The definition of the command is made up of other @value{GDBN} command lines,
25558 which are given following the @code{define} command. The end of these
25559 commands is marked by a line containing @code{end}.
25562 @kindex end@r{ (user-defined commands)}
25563 @item document @var{commandname}
25564 Document the user-defined command @var{commandname}, so that it can be
25565 accessed by @code{help}. The command @var{commandname} must already be
25566 defined. This command reads lines of documentation just as @code{define}
25567 reads the lines of the command definition, ending with @code{end}.
25568 After the @code{document} command is finished, @code{help} on command
25569 @var{commandname} displays the documentation you have written.
25571 You may use the @code{document} command again to change the
25572 documentation of a command. Redefining the command with @code{define}
25573 does not change the documentation.
25575 @kindex dont-repeat
25576 @cindex don't repeat command
25578 Used inside a user-defined command, this tells @value{GDBN} that this
25579 command should not be repeated when the user hits @key{RET}
25580 (@pxref{Command Syntax, repeat last command}).
25582 @kindex help user-defined
25583 @item help user-defined
25584 List all user-defined commands and all python commands defined in class
25585 COMAND_USER. The first line of the documentation or docstring is
25590 @itemx show user @var{commandname}
25591 Display the @value{GDBN} commands used to define @var{commandname} (but
25592 not its documentation). If no @var{commandname} is given, display the
25593 definitions for all user-defined commands.
25594 This does not work for user-defined python commands.
25596 @cindex infinite recursion in user-defined commands
25597 @kindex show max-user-call-depth
25598 @kindex set max-user-call-depth
25599 @item show max-user-call-depth
25600 @itemx set max-user-call-depth
25601 The value of @code{max-user-call-depth} controls how many recursion
25602 levels are allowed in user-defined commands before @value{GDBN} suspects an
25603 infinite recursion and aborts the command.
25604 This does not apply to user-defined python commands.
25607 In addition to the above commands, user-defined commands frequently
25608 use control flow commands, described in @ref{Command Files}.
25610 When user-defined commands are executed, the
25611 commands of the definition are not printed. An error in any command
25612 stops execution of the user-defined command.
25614 If used interactively, commands that would ask for confirmation proceed
25615 without asking when used inside a user-defined command. Many @value{GDBN}
25616 commands that normally print messages to say what they are doing omit the
25617 messages when used in a user-defined command.
25620 @subsection User-defined Command Hooks
25621 @cindex command hooks
25622 @cindex hooks, for commands
25623 @cindex hooks, pre-command
25626 You may define @dfn{hooks}, which are a special kind of user-defined
25627 command. Whenever you run the command @samp{foo}, if the user-defined
25628 command @samp{hook-foo} exists, it is executed (with no arguments)
25629 before that command.
25631 @cindex hooks, post-command
25633 A hook may also be defined which is run after the command you executed.
25634 Whenever you run the command @samp{foo}, if the user-defined command
25635 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25636 that command. Post-execution hooks may exist simultaneously with
25637 pre-execution hooks, for the same command.
25639 It is valid for a hook to call the command which it hooks. If this
25640 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25642 @c It would be nice if hookpost could be passed a parameter indicating
25643 @c if the command it hooks executed properly or not. FIXME!
25645 @kindex stop@r{, a pseudo-command}
25646 In addition, a pseudo-command, @samp{stop} exists. Defining
25647 (@samp{hook-stop}) makes the associated commands execute every time
25648 execution stops in your program: before breakpoint commands are run,
25649 displays are printed, or the stack frame is printed.
25651 For example, to ignore @code{SIGALRM} signals while
25652 single-stepping, but treat them normally during normal execution,
25657 handle SIGALRM nopass
25661 handle SIGALRM pass
25664 define hook-continue
25665 handle SIGALRM pass
25669 As a further example, to hook at the beginning and end of the @code{echo}
25670 command, and to add extra text to the beginning and end of the message,
25678 define hookpost-echo
25682 (@value{GDBP}) echo Hello World
25683 <<<---Hello World--->>>
25688 You can define a hook for any single-word command in @value{GDBN}, but
25689 not for command aliases; you should define a hook for the basic command
25690 name, e.g.@: @code{backtrace} rather than @code{bt}.
25691 @c FIXME! So how does Joe User discover whether a command is an alias
25693 You can hook a multi-word command by adding @code{hook-} or
25694 @code{hookpost-} to the last word of the command, e.g.@:
25695 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25697 If an error occurs during the execution of your hook, execution of
25698 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25699 (before the command that you actually typed had a chance to run).
25701 If you try to define a hook which does not match any known command, you
25702 get a warning from the @code{define} command.
25704 @node Command Files
25705 @subsection Command Files
25707 @cindex command files
25708 @cindex scripting commands
25709 A command file for @value{GDBN} is a text file made of lines that are
25710 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25711 also be included. An empty line in a command file does nothing; it
25712 does not mean to repeat the last command, as it would from the
25715 You can request the execution of a command file with the @code{source}
25716 command. Note that the @code{source} command is also used to evaluate
25717 scripts that are not Command Files. The exact behavior can be configured
25718 using the @code{script-extension} setting.
25719 @xref{Extending GDB,, Extending GDB}.
25723 @cindex execute commands from a file
25724 @item source [-s] [-v] @var{filename}
25725 Execute the command file @var{filename}.
25728 The lines in a command file are generally executed sequentially,
25729 unless the order of execution is changed by one of the
25730 @emph{flow-control commands} described below. The commands are not
25731 printed as they are executed. An error in any command terminates
25732 execution of the command file and control is returned to the console.
25734 @value{GDBN} first searches for @var{filename} in the current directory.
25735 If the file is not found there, and @var{filename} does not specify a
25736 directory, then @value{GDBN} also looks for the file on the source search path
25737 (specified with the @samp{directory} command);
25738 except that @file{$cdir} is not searched because the compilation directory
25739 is not relevant to scripts.
25741 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25742 on the search path even if @var{filename} specifies a directory.
25743 The search is done by appending @var{filename} to each element of the
25744 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25745 and the search path contains @file{/home/user} then @value{GDBN} will
25746 look for the script @file{/home/user/mylib/myscript}.
25747 The search is also done if @var{filename} is an absolute path.
25748 For example, if @var{filename} is @file{/tmp/myscript} and
25749 the search path contains @file{/home/user} then @value{GDBN} will
25750 look for the script @file{/home/user/tmp/myscript}.
25751 For DOS-like systems, if @var{filename} contains a drive specification,
25752 it is stripped before concatenation. For example, if @var{filename} is
25753 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25754 will look for the script @file{c:/tmp/myscript}.
25756 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25757 each command as it is executed. The option must be given before
25758 @var{filename}, and is interpreted as part of the filename anywhere else.
25760 Commands that would ask for confirmation if used interactively proceed
25761 without asking when used in a command file. Many @value{GDBN} commands that
25762 normally print messages to say what they are doing omit the messages
25763 when called from command files.
25765 @value{GDBN} also accepts command input from standard input. In this
25766 mode, normal output goes to standard output and error output goes to
25767 standard error. Errors in a command file supplied on standard input do
25768 not terminate execution of the command file---execution continues with
25772 gdb < cmds > log 2>&1
25775 (The syntax above will vary depending on the shell used.) This example
25776 will execute commands from the file @file{cmds}. All output and errors
25777 would be directed to @file{log}.
25779 Since commands stored on command files tend to be more general than
25780 commands typed interactively, they frequently need to deal with
25781 complicated situations, such as different or unexpected values of
25782 variables and symbols, changes in how the program being debugged is
25783 built, etc. @value{GDBN} provides a set of flow-control commands to
25784 deal with these complexities. Using these commands, you can write
25785 complex scripts that loop over data structures, execute commands
25786 conditionally, etc.
25793 This command allows to include in your script conditionally executed
25794 commands. The @code{if} command takes a single argument, which is an
25795 expression to evaluate. It is followed by a series of commands that
25796 are executed only if the expression is true (its value is nonzero).
25797 There can then optionally be an @code{else} line, followed by a series
25798 of commands that are only executed if the expression was false. The
25799 end of the list is marked by a line containing @code{end}.
25803 This command allows to write loops. Its syntax is similar to
25804 @code{if}: the command takes a single argument, which is an expression
25805 to evaluate, and must be followed by the commands to execute, one per
25806 line, terminated by an @code{end}. These commands are called the
25807 @dfn{body} of the loop. The commands in the body of @code{while} are
25808 executed repeatedly as long as the expression evaluates to true.
25812 This command exits the @code{while} loop in whose body it is included.
25813 Execution of the script continues after that @code{while}s @code{end}
25816 @kindex loop_continue
25817 @item loop_continue
25818 This command skips the execution of the rest of the body of commands
25819 in the @code{while} loop in whose body it is included. Execution
25820 branches to the beginning of the @code{while} loop, where it evaluates
25821 the controlling expression.
25823 @kindex end@r{ (if/else/while commands)}
25825 Terminate the block of commands that are the body of @code{if},
25826 @code{else}, or @code{while} flow-control commands.
25831 @subsection Commands for Controlled Output
25833 During the execution of a command file or a user-defined command, normal
25834 @value{GDBN} output is suppressed; the only output that appears is what is
25835 explicitly printed by the commands in the definition. This section
25836 describes three commands useful for generating exactly the output you
25841 @item echo @var{text}
25842 @c I do not consider backslash-space a standard C escape sequence
25843 @c because it is not in ANSI.
25844 Print @var{text}. Nonprinting characters can be included in
25845 @var{text} using C escape sequences, such as @samp{\n} to print a
25846 newline. @strong{No newline is printed unless you specify one.}
25847 In addition to the standard C escape sequences, a backslash followed
25848 by a space stands for a space. This is useful for displaying a
25849 string with spaces at the beginning or the end, since leading and
25850 trailing spaces are otherwise trimmed from all arguments.
25851 To print @samp{@w{ }and foo =@w{ }}, use the command
25852 @samp{echo \@w{ }and foo = \@w{ }}.
25854 A backslash at the end of @var{text} can be used, as in C, to continue
25855 the command onto subsequent lines. For example,
25858 echo This is some text\n\
25859 which is continued\n\
25860 onto several lines.\n
25863 produces the same output as
25866 echo This is some text\n
25867 echo which is continued\n
25868 echo onto several lines.\n
25872 @item output @var{expression}
25873 Print the value of @var{expression} and nothing but that value: no
25874 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25875 value history either. @xref{Expressions, ,Expressions}, for more information
25878 @item output/@var{fmt} @var{expression}
25879 Print the value of @var{expression} in format @var{fmt}. You can use
25880 the same formats as for @code{print}. @xref{Output Formats,,Output
25881 Formats}, for more information.
25884 @item printf @var{template}, @var{expressions}@dots{}
25885 Print the values of one or more @var{expressions} under the control of
25886 the string @var{template}. To print several values, make
25887 @var{expressions} be a comma-separated list of individual expressions,
25888 which may be either numbers or pointers. Their values are printed as
25889 specified by @var{template}, exactly as a C program would do by
25890 executing the code below:
25893 printf (@var{template}, @var{expressions}@dots{});
25896 As in @code{C} @code{printf}, ordinary characters in @var{template}
25897 are printed verbatim, while @dfn{conversion specification} introduced
25898 by the @samp{%} character cause subsequent @var{expressions} to be
25899 evaluated, their values converted and formatted according to type and
25900 style information encoded in the conversion specifications, and then
25903 For example, you can print two values in hex like this:
25906 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25909 @code{printf} supports all the standard @code{C} conversion
25910 specifications, including the flags and modifiers between the @samp{%}
25911 character and the conversion letter, with the following exceptions:
25915 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25918 The modifier @samp{*} is not supported for specifying precision or
25922 The @samp{'} flag (for separation of digits into groups according to
25923 @code{LC_NUMERIC'}) is not supported.
25926 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25930 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25933 The conversion letters @samp{a} and @samp{A} are not supported.
25937 Note that the @samp{ll} type modifier is supported only if the
25938 underlying @code{C} implementation used to build @value{GDBN} supports
25939 the @code{long long int} type, and the @samp{L} type modifier is
25940 supported only if @code{long double} type is available.
25942 As in @code{C}, @code{printf} supports simple backslash-escape
25943 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25944 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25945 single character. Octal and hexadecimal escape sequences are not
25948 Additionally, @code{printf} supports conversion specifications for DFP
25949 (@dfn{Decimal Floating Point}) types using the following length modifiers
25950 together with a floating point specifier.
25955 @samp{H} for printing @code{Decimal32} types.
25958 @samp{D} for printing @code{Decimal64} types.
25961 @samp{DD} for printing @code{Decimal128} types.
25964 If the underlying @code{C} implementation used to build @value{GDBN} has
25965 support for the three length modifiers for DFP types, other modifiers
25966 such as width and precision will also be available for @value{GDBN} to use.
25968 In case there is no such @code{C} support, no additional modifiers will be
25969 available and the value will be printed in the standard way.
25971 Here's an example of printing DFP types using the above conversion letters:
25973 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25978 @item eval @var{template}, @var{expressions}@dots{}
25979 Convert the values of one or more @var{expressions} under the control of
25980 the string @var{template} to a command line, and call it.
25984 @node Auto-loading sequences
25985 @subsection Controlling auto-loading native @value{GDBN} scripts
25986 @cindex native script auto-loading
25988 When a new object file is read (for example, due to the @code{file}
25989 command, or because the inferior has loaded a shared library),
25990 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25991 @xref{Auto-loading extensions}.
25993 Auto-loading can be enabled or disabled,
25994 and the list of auto-loaded scripts can be printed.
25997 @anchor{set auto-load gdb-scripts}
25998 @kindex set auto-load gdb-scripts
25999 @item set auto-load gdb-scripts [on|off]
26000 Enable or disable the auto-loading of canned sequences of commands scripts.
26002 @anchor{show auto-load gdb-scripts}
26003 @kindex show auto-load gdb-scripts
26004 @item show auto-load gdb-scripts
26005 Show whether auto-loading of canned sequences of commands scripts is enabled or
26008 @anchor{info auto-load gdb-scripts}
26009 @kindex info auto-load gdb-scripts
26010 @cindex print list of auto-loaded canned sequences of commands scripts
26011 @item info auto-load gdb-scripts [@var{regexp}]
26012 Print the list of all canned sequences of commands scripts that @value{GDBN}
26016 If @var{regexp} is supplied only canned sequences of commands scripts with
26017 matching names are printed.
26019 @c Python docs live in a separate file.
26020 @include python.texi
26022 @c Guile docs live in a separate file.
26023 @include guile.texi
26025 @node Auto-loading extensions
26026 @section Auto-loading extensions
26027 @cindex auto-loading extensions
26029 @value{GDBN} provides two mechanisms for automatically loading extensions
26030 when a new object file is read (for example, due to the @code{file}
26031 command, or because the inferior has loaded a shared library):
26032 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26033 section of modern file formats like ELF.
26036 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26037 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26038 * Which flavor to choose?::
26041 The auto-loading feature is useful for supplying application-specific
26042 debugging commands and features.
26044 Auto-loading can be enabled or disabled,
26045 and the list of auto-loaded scripts can be printed.
26046 See the @samp{auto-loading} section of each extension language
26047 for more information.
26048 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26049 For Python files see @ref{Python Auto-loading}.
26051 Note that loading of this script file also requires accordingly configured
26052 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26054 @node objfile-gdbdotext file
26055 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26056 @cindex @file{@var{objfile}-gdb.gdb}
26057 @cindex @file{@var{objfile}-gdb.py}
26058 @cindex @file{@var{objfile}-gdb.scm}
26060 When a new object file is read, @value{GDBN} looks for a file named
26061 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26062 where @var{objfile} is the object file's name and
26063 where @var{ext} is the file extension for the extension language:
26066 @item @file{@var{objfile}-gdb.gdb}
26067 GDB's own command language
26068 @item @file{@var{objfile}-gdb.py}
26070 @item @file{@var{objfile}-gdb.scm}
26074 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26075 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26076 components, and appending the @file{-gdb.@var{ext}} suffix.
26077 If this file exists and is readable, @value{GDBN} will evaluate it as a
26078 script in the specified extension language.
26080 If this file does not exist, then @value{GDBN} will look for
26081 @var{script-name} file in all of the directories as specified below.
26083 Note that loading of these files requires an accordingly configured
26084 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26086 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26087 scripts normally according to its @file{.exe} filename. But if no scripts are
26088 found @value{GDBN} also tries script filenames matching the object file without
26089 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26090 is attempted on any platform. This makes the script filenames compatible
26091 between Unix and MS-Windows hosts.
26094 @anchor{set auto-load scripts-directory}
26095 @kindex set auto-load scripts-directory
26096 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26097 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26098 may be delimited by the host platform path separator in use
26099 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26101 Each entry here needs to be covered also by the security setting
26102 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26104 @anchor{with-auto-load-dir}
26105 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26106 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26107 configuration option @option{--with-auto-load-dir}.
26109 Any reference to @file{$debugdir} will get replaced by
26110 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26111 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26112 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26113 @file{$datadir} must be placed as a directory component --- either alone or
26114 delimited by @file{/} or @file{\} directory separators, depending on the host
26117 The list of directories uses path separator (@samp{:} on GNU and Unix
26118 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26119 to the @env{PATH} environment variable.
26121 @anchor{show auto-load scripts-directory}
26122 @kindex show auto-load scripts-directory
26123 @item show auto-load scripts-directory
26124 Show @value{GDBN} auto-loaded scripts location.
26126 @anchor{add-auto-load-scripts-directory}
26127 @kindex add-auto-load-scripts-directory
26128 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26129 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26130 Multiple entries may be delimited by the host platform path separator in use.
26133 @value{GDBN} does not track which files it has already auto-loaded this way.
26134 @value{GDBN} will load the associated script every time the corresponding
26135 @var{objfile} is opened.
26136 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26137 is evaluated more than once.
26139 @node dotdebug_gdb_scripts section
26140 @subsection The @code{.debug_gdb_scripts} section
26141 @cindex @code{.debug_gdb_scripts} section
26143 For systems using file formats like ELF and COFF,
26144 when @value{GDBN} loads a new object file
26145 it will look for a special section named @code{.debug_gdb_scripts}.
26146 If this section exists, its contents is a list of null-terminated entries
26147 specifying scripts to load. Each entry begins with a non-null prefix byte that
26148 specifies the kind of entry, typically the extension language and whether the
26149 script is in a file or inlined in @code{.debug_gdb_scripts}.
26151 The following entries are supported:
26154 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26155 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26156 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26157 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26160 @subsubsection Script File Entries
26162 If the entry specifies a file, @value{GDBN} will look for the file first
26163 in the current directory and then along the source search path
26164 (@pxref{Source Path, ,Specifying Source Directories}),
26165 except that @file{$cdir} is not searched, since the compilation
26166 directory is not relevant to scripts.
26168 File entries can be placed in section @code{.debug_gdb_scripts} with,
26169 for example, this GCC macro for Python scripts.
26172 /* Note: The "MS" section flags are to remove duplicates. */
26173 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26175 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26176 .byte 1 /* Python */\n\
26177 .asciz \"" script_name "\"\n\
26183 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26184 Then one can reference the macro in a header or source file like this:
26187 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26190 The script name may include directories if desired.
26192 Note that loading of this script file also requires accordingly configured
26193 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26195 If the macro invocation is put in a header, any application or library
26196 using this header will get a reference to the specified script,
26197 and with the use of @code{"MS"} attributes on the section, the linker
26198 will remove duplicates.
26200 @subsubsection Script Text Entries
26202 Script text entries allow to put the executable script in the entry
26203 itself instead of loading it from a file.
26204 The first line of the entry, everything after the prefix byte and up to
26205 the first newline (@code{0xa}) character, is the script name, and must not
26206 contain any kind of space character, e.g., spaces or tabs.
26207 The rest of the entry, up to the trailing null byte, is the script to
26208 execute in the specified language. The name needs to be unique among
26209 all script names, as @value{GDBN} executes each script only once based
26212 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26216 #include "symcat.h"
26217 #include "gdb/section-scripts.h"
26219 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26220 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26221 ".ascii \"gdb.inlined-script\\n\"\n"
26222 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26223 ".ascii \" def __init__ (self):\\n\"\n"
26224 ".ascii \" super (test_cmd, self).__init__ ("
26225 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26226 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26227 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26228 ".ascii \"test_cmd ()\\n\"\n"
26234 Loading of inlined scripts requires a properly configured
26235 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26236 The path to specify in @code{auto-load safe-path} is the path of the file
26237 containing the @code{.debug_gdb_scripts} section.
26239 @node Which flavor to choose?
26240 @subsection Which flavor to choose?
26242 Given the multiple ways of auto-loading extensions, it might not always
26243 be clear which one to choose. This section provides some guidance.
26246 Benefits of the @file{-gdb.@var{ext}} way:
26250 Can be used with file formats that don't support multiple sections.
26253 Ease of finding scripts for public libraries.
26255 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26256 in the source search path.
26257 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26258 isn't a source directory in which to find the script.
26261 Doesn't require source code additions.
26265 Benefits of the @code{.debug_gdb_scripts} way:
26269 Works with static linking.
26271 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26272 trigger their loading. When an application is statically linked the only
26273 objfile available is the executable, and it is cumbersome to attach all the
26274 scripts from all the input libraries to the executable's
26275 @file{-gdb.@var{ext}} script.
26278 Works with classes that are entirely inlined.
26280 Some classes can be entirely inlined, and thus there may not be an associated
26281 shared library to attach a @file{-gdb.@var{ext}} script to.
26284 Scripts needn't be copied out of the source tree.
26286 In some circumstances, apps can be built out of large collections of internal
26287 libraries, and the build infrastructure necessary to install the
26288 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26289 cumbersome. It may be easier to specify the scripts in the
26290 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26291 top of the source tree to the source search path.
26294 @node Multiple Extension Languages
26295 @section Multiple Extension Languages
26297 The Guile and Python extension languages do not share any state,
26298 and generally do not interfere with each other.
26299 There are some things to be aware of, however.
26301 @subsection Python comes first
26303 Python was @value{GDBN}'s first extension language, and to avoid breaking
26304 existing behaviour Python comes first. This is generally solved by the
26305 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26306 extension languages, and when it makes a call to an extension language,
26307 (say to pretty-print a value), it tries each in turn until an extension
26308 language indicates it has performed the request (e.g., has returned the
26309 pretty-printed form of a value).
26310 This extends to errors while performing such requests: If an error happens
26311 while, for example, trying to pretty-print an object then the error is
26312 reported and any following extension languages are not tried.
26315 @section Creating new spellings of existing commands
26316 @cindex aliases for commands
26318 It is often useful to define alternate spellings of existing commands.
26319 For example, if a new @value{GDBN} command defined in Python has
26320 a long name to type, it is handy to have an abbreviated version of it
26321 that involves less typing.
26323 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26324 of the @samp{step} command even though it is otherwise an ambiguous
26325 abbreviation of other commands like @samp{set} and @samp{show}.
26327 Aliases are also used to provide shortened or more common versions
26328 of multi-word commands. For example, @value{GDBN} provides the
26329 @samp{tty} alias of the @samp{set inferior-tty} command.
26331 You can define a new alias with the @samp{alias} command.
26336 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26340 @var{ALIAS} specifies the name of the new alias.
26341 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26344 @var{COMMAND} specifies the name of an existing command
26345 that is being aliased.
26347 The @samp{-a} option specifies that the new alias is an abbreviation
26348 of the command. Abbreviations are not shown in command
26349 lists displayed by the @samp{help} command.
26351 The @samp{--} option specifies the end of options,
26352 and is useful when @var{ALIAS} begins with a dash.
26354 Here is a simple example showing how to make an abbreviation
26355 of a command so that there is less to type.
26356 Suppose you were tired of typing @samp{disas}, the current
26357 shortest unambiguous abbreviation of the @samp{disassemble} command
26358 and you wanted an even shorter version named @samp{di}.
26359 The following will accomplish this.
26362 (gdb) alias -a di = disas
26365 Note that aliases are different from user-defined commands.
26366 With a user-defined command, you also need to write documentation
26367 for it with the @samp{document} command.
26368 An alias automatically picks up the documentation of the existing command.
26370 Here is an example where we make @samp{elms} an abbreviation of
26371 @samp{elements} in the @samp{set print elements} command.
26372 This is to show that you can make an abbreviation of any part
26376 (gdb) alias -a set print elms = set print elements
26377 (gdb) alias -a show print elms = show print elements
26378 (gdb) set p elms 20
26380 Limit on string chars or array elements to print is 200.
26383 Note that if you are defining an alias of a @samp{set} command,
26384 and you want to have an alias for the corresponding @samp{show}
26385 command, then you need to define the latter separately.
26387 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26388 @var{ALIAS}, just as they are normally.
26391 (gdb) alias -a set pr elms = set p ele
26394 Finally, here is an example showing the creation of a one word
26395 alias for a more complex command.
26396 This creates alias @samp{spe} of the command @samp{set print elements}.
26399 (gdb) alias spe = set print elements
26404 @chapter Command Interpreters
26405 @cindex command interpreters
26407 @value{GDBN} supports multiple command interpreters, and some command
26408 infrastructure to allow users or user interface writers to switch
26409 between interpreters or run commands in other interpreters.
26411 @value{GDBN} currently supports two command interpreters, the console
26412 interpreter (sometimes called the command-line interpreter or @sc{cli})
26413 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26414 describes both of these interfaces in great detail.
26416 By default, @value{GDBN} will start with the console interpreter.
26417 However, the user may choose to start @value{GDBN} with another
26418 interpreter by specifying the @option{-i} or @option{--interpreter}
26419 startup options. Defined interpreters include:
26423 @cindex console interpreter
26424 The traditional console or command-line interpreter. This is the most often
26425 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26426 @value{GDBN} will use this interpreter.
26429 @cindex mi interpreter
26430 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26431 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26432 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26436 @cindex mi2 interpreter
26437 The current @sc{gdb/mi} interface.
26440 @cindex mi1 interpreter
26441 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26445 @cindex invoke another interpreter
26447 @kindex interpreter-exec
26448 You may execute commands in any interpreter from the current
26449 interpreter using the appropriate command. If you are running the
26450 console interpreter, simply use the @code{interpreter-exec} command:
26453 interpreter-exec mi "-data-list-register-names"
26456 @sc{gdb/mi} has a similar command, although it is only available in versions of
26457 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26459 Note that @code{interpreter-exec} only changes the interpreter for the
26460 duration of the specified command. It does not change the interpreter
26463 @cindex start a new independent interpreter
26465 Although you may only choose a single interpreter at startup, it is
26466 possible to run an independent interpreter on a specified input/output
26467 device (usually a tty).
26469 For example, consider a debugger GUI or IDE that wants to provide a
26470 @value{GDBN} console view. It may do so by embedding a terminal
26471 emulator widget in its GUI, starting @value{GDBN} in the traditional
26472 command-line mode with stdin/stdout/stderr redirected to that
26473 terminal, and then creating an MI interpreter running on a specified
26474 input/output device. The console interpreter created by @value{GDBN}
26475 at startup handles commands the user types in the terminal widget,
26476 while the GUI controls and synchronizes state with @value{GDBN} using
26477 the separate MI interpreter.
26479 To start a new secondary @dfn{user interface} running MI, use the
26480 @code{new-ui} command:
26483 @cindex new user interface
26485 new-ui @var{interpreter} @var{tty}
26488 The @var{interpreter} parameter specifies the interpreter to run.
26489 This accepts the same values as the @code{interpreter-exec} command.
26490 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26491 @var{tty} parameter specifies the name of the bidirectional file the
26492 interpreter uses for input/output, usually the name of a
26493 pseudoterminal slave on Unix systems. For example:
26496 (@value{GDBP}) new-ui mi /dev/pts/9
26500 runs an MI interpreter on @file{/dev/pts/9}.
26503 @chapter @value{GDBN} Text User Interface
26505 @cindex Text User Interface
26508 * TUI Overview:: TUI overview
26509 * TUI Keys:: TUI key bindings
26510 * TUI Single Key Mode:: TUI single key mode
26511 * TUI Commands:: TUI-specific commands
26512 * TUI Configuration:: TUI configuration variables
26515 The @value{GDBN} Text User Interface (TUI) is a terminal
26516 interface which uses the @code{curses} library to show the source
26517 file, the assembly output, the program registers and @value{GDBN}
26518 commands in separate text windows. The TUI mode is supported only
26519 on platforms where a suitable version of the @code{curses} library
26522 The TUI mode is enabled by default when you invoke @value{GDBN} as
26523 @samp{@value{GDBP} -tui}.
26524 You can also switch in and out of TUI mode while @value{GDBN} runs by
26525 using various TUI commands and key bindings, such as @command{tui
26526 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26527 @ref{TUI Keys, ,TUI Key Bindings}.
26530 @section TUI Overview
26532 In TUI mode, @value{GDBN} can display several text windows:
26536 This window is the @value{GDBN} command window with the @value{GDBN}
26537 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26538 managed using readline.
26541 The source window shows the source file of the program. The current
26542 line and active breakpoints are displayed in this window.
26545 The assembly window shows the disassembly output of the program.
26548 This window shows the processor registers. Registers are highlighted
26549 when their values change.
26552 The source and assembly windows show the current program position
26553 by highlighting the current line and marking it with a @samp{>} marker.
26554 Breakpoints are indicated with two markers. The first marker
26555 indicates the breakpoint type:
26559 Breakpoint which was hit at least once.
26562 Breakpoint which was never hit.
26565 Hardware breakpoint which was hit at least once.
26568 Hardware breakpoint which was never hit.
26571 The second marker indicates whether the breakpoint is enabled or not:
26575 Breakpoint is enabled.
26578 Breakpoint is disabled.
26581 The source, assembly and register windows are updated when the current
26582 thread changes, when the frame changes, or when the program counter
26585 These windows are not all visible at the same time. The command
26586 window is always visible. The others can be arranged in several
26597 source and assembly,
26600 source and registers, or
26603 assembly and registers.
26606 A status line above the command window shows the following information:
26610 Indicates the current @value{GDBN} target.
26611 (@pxref{Targets, ,Specifying a Debugging Target}).
26614 Gives the current process or thread number.
26615 When no process is being debugged, this field is set to @code{No process}.
26618 Gives the current function name for the selected frame.
26619 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26620 When there is no symbol corresponding to the current program counter,
26621 the string @code{??} is displayed.
26624 Indicates the current line number for the selected frame.
26625 When the current line number is not known, the string @code{??} is displayed.
26628 Indicates the current program counter address.
26632 @section TUI Key Bindings
26633 @cindex TUI key bindings
26635 The TUI installs several key bindings in the readline keymaps
26636 @ifset SYSTEM_READLINE
26637 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26639 @ifclear SYSTEM_READLINE
26640 (@pxref{Command Line Editing}).
26642 The following key bindings are installed for both TUI mode and the
26643 @value{GDBN} standard mode.
26652 Enter or leave the TUI mode. When leaving the TUI mode,
26653 the curses window management stops and @value{GDBN} operates using
26654 its standard mode, writing on the terminal directly. When reentering
26655 the TUI mode, control is given back to the curses windows.
26656 The screen is then refreshed.
26660 Use a TUI layout with only one window. The layout will
26661 either be @samp{source} or @samp{assembly}. When the TUI mode
26662 is not active, it will switch to the TUI mode.
26664 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26668 Use a TUI layout with at least two windows. When the current
26669 layout already has two windows, the next layout with two windows is used.
26670 When a new layout is chosen, one window will always be common to the
26671 previous layout and the new one.
26673 Think of it as the Emacs @kbd{C-x 2} binding.
26677 Change the active window. The TUI associates several key bindings
26678 (like scrolling and arrow keys) with the active window. This command
26679 gives the focus to the next TUI window.
26681 Think of it as the Emacs @kbd{C-x o} binding.
26685 Switch in and out of the TUI SingleKey mode that binds single
26686 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26689 The following key bindings only work in the TUI mode:
26694 Scroll the active window one page up.
26698 Scroll the active window one page down.
26702 Scroll the active window one line up.
26706 Scroll the active window one line down.
26710 Scroll the active window one column left.
26714 Scroll the active window one column right.
26718 Refresh the screen.
26721 Because the arrow keys scroll the active window in the TUI mode, they
26722 are not available for their normal use by readline unless the command
26723 window has the focus. When another window is active, you must use
26724 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26725 and @kbd{C-f} to control the command window.
26727 @node TUI Single Key Mode
26728 @section TUI Single Key Mode
26729 @cindex TUI single key mode
26731 The TUI also provides a @dfn{SingleKey} mode, which binds several
26732 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26733 switch into this mode, where the following key bindings are used:
26736 @kindex c @r{(SingleKey TUI key)}
26740 @kindex d @r{(SingleKey TUI key)}
26744 @kindex f @r{(SingleKey TUI key)}
26748 @kindex n @r{(SingleKey TUI key)}
26752 @kindex o @r{(SingleKey TUI key)}
26754 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26756 @kindex q @r{(SingleKey TUI key)}
26758 exit the SingleKey mode.
26760 @kindex r @r{(SingleKey TUI key)}
26764 @kindex s @r{(SingleKey TUI key)}
26768 @kindex i @r{(SingleKey TUI key)}
26770 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26772 @kindex u @r{(SingleKey TUI key)}
26776 @kindex v @r{(SingleKey TUI key)}
26780 @kindex w @r{(SingleKey TUI key)}
26785 Other keys temporarily switch to the @value{GDBN} command prompt.
26786 The key that was pressed is inserted in the editing buffer so that
26787 it is possible to type most @value{GDBN} commands without interaction
26788 with the TUI SingleKey mode. Once the command is entered the TUI
26789 SingleKey mode is restored. The only way to permanently leave
26790 this mode is by typing @kbd{q} or @kbd{C-x s}.
26794 @section TUI-specific Commands
26795 @cindex TUI commands
26797 The TUI has specific commands to control the text windows.
26798 These commands are always available, even when @value{GDBN} is not in
26799 the TUI mode. When @value{GDBN} is in the standard mode, most
26800 of these commands will automatically switch to the TUI mode.
26802 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26803 terminal, or @value{GDBN} has been started with the machine interface
26804 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26805 these commands will fail with an error, because it would not be
26806 possible or desirable to enable curses window management.
26811 Activate TUI mode. The last active TUI window layout will be used if
26812 TUI mode has prevsiouly been used in the current debugging session,
26813 otherwise a default layout is used.
26816 @kindex tui disable
26817 Disable TUI mode, returning to the console interpreter.
26821 List and give the size of all displayed windows.
26823 @item layout @var{name}
26825 Changes which TUI windows are displayed. In each layout the command
26826 window is always displayed, the @var{name} parameter controls which
26827 additional windows are displayed, and can be any of the following:
26831 Display the next layout.
26834 Display the previous layout.
26837 Display the source and command windows.
26840 Display the assembly and command windows.
26843 Display the source, assembly, and command windows.
26846 When in @code{src} layout display the register, source, and command
26847 windows. When in @code{asm} or @code{split} layout display the
26848 register, assembler, and command windows.
26851 @item focus @var{name}
26853 Changes which TUI window is currently active for scrolling. The
26854 @var{name} parameter can be any of the following:
26858 Make the next window active for scrolling.
26861 Make the previous window active for scrolling.
26864 Make the source window active for scrolling.
26867 Make the assembly window active for scrolling.
26870 Make the register window active for scrolling.
26873 Make the command window active for scrolling.
26878 Refresh the screen. This is similar to typing @kbd{C-L}.
26880 @item tui reg @var{group}
26882 Changes the register group displayed in the tui register window to
26883 @var{group}. If the register window is not currently displayed this
26884 command will cause the register window to be displayed. The list of
26885 register groups, as well as their order is target specific. The
26886 following groups are available on most targets:
26889 Repeatedly selecting this group will cause the display to cycle
26890 through all of the available register groups.
26893 Repeatedly selecting this group will cause the display to cycle
26894 through all of the available register groups in the reverse order to
26898 Display the general registers.
26900 Display the floating point registers.
26902 Display the system registers.
26904 Display the vector registers.
26906 Display all registers.
26911 Update the source window and the current execution point.
26913 @item winheight @var{name} +@var{count}
26914 @itemx winheight @var{name} -@var{count}
26916 Change the height of the window @var{name} by @var{count}
26917 lines. Positive counts increase the height, while negative counts
26918 decrease it. The @var{name} parameter can be one of @code{src} (the
26919 source window), @code{cmd} (the command window), @code{asm} (the
26920 disassembly window), or @code{regs} (the register display window).
26923 @node TUI Configuration
26924 @section TUI Configuration Variables
26925 @cindex TUI configuration variables
26927 Several configuration variables control the appearance of TUI windows.
26930 @item set tui border-kind @var{kind}
26931 @kindex set tui border-kind
26932 Select the border appearance for the source, assembly and register windows.
26933 The possible values are the following:
26936 Use a space character to draw the border.
26939 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26942 Use the Alternate Character Set to draw the border. The border is
26943 drawn using character line graphics if the terminal supports them.
26946 @item set tui border-mode @var{mode}
26947 @kindex set tui border-mode
26948 @itemx set tui active-border-mode @var{mode}
26949 @kindex set tui active-border-mode
26950 Select the display attributes for the borders of the inactive windows
26951 or the active window. The @var{mode} can be one of the following:
26954 Use normal attributes to display the border.
26960 Use reverse video mode.
26963 Use half bright mode.
26965 @item half-standout
26966 Use half bright and standout mode.
26969 Use extra bright or bold mode.
26971 @item bold-standout
26972 Use extra bright or bold and standout mode.
26975 @item set tui tab-width @var{nchars}
26976 @kindex set tui tab-width
26978 Set the width of tab stops to be @var{nchars} characters. This
26979 setting affects the display of TAB characters in the source and
26984 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26987 @cindex @sc{gnu} Emacs
26988 A special interface allows you to use @sc{gnu} Emacs to view (and
26989 edit) the source files for the program you are debugging with
26992 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26993 executable file you want to debug as an argument. This command starts
26994 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26995 created Emacs buffer.
26996 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26998 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27003 All ``terminal'' input and output goes through an Emacs buffer, called
27006 This applies both to @value{GDBN} commands and their output, and to the input
27007 and output done by the program you are debugging.
27009 This is useful because it means that you can copy the text of previous
27010 commands and input them again; you can even use parts of the output
27013 All the facilities of Emacs' Shell mode are available for interacting
27014 with your program. In particular, you can send signals the usual
27015 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27019 @value{GDBN} displays source code through Emacs.
27021 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27022 source file for that frame and puts an arrow (@samp{=>}) at the
27023 left margin of the current line. Emacs uses a separate buffer for
27024 source display, and splits the screen to show both your @value{GDBN} session
27027 Explicit @value{GDBN} @code{list} or search commands still produce output as
27028 usual, but you probably have no reason to use them from Emacs.
27031 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27032 a graphical mode, enabled by default, which provides further buffers
27033 that can control the execution and describe the state of your program.
27034 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27036 If you specify an absolute file name when prompted for the @kbd{M-x
27037 gdb} argument, then Emacs sets your current working directory to where
27038 your program resides. If you only specify the file name, then Emacs
27039 sets your current working directory to the directory associated
27040 with the previous buffer. In this case, @value{GDBN} may find your
27041 program by searching your environment's @code{PATH} variable, but on
27042 some operating systems it might not find the source. So, although the
27043 @value{GDBN} input and output session proceeds normally, the auxiliary
27044 buffer does not display the current source and line of execution.
27046 The initial working directory of @value{GDBN} is printed on the top
27047 line of the GUD buffer and this serves as a default for the commands
27048 that specify files for @value{GDBN} to operate on. @xref{Files,
27049 ,Commands to Specify Files}.
27051 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27052 need to call @value{GDBN} by a different name (for example, if you
27053 keep several configurations around, with different names) you can
27054 customize the Emacs variable @code{gud-gdb-command-name} to run the
27057 In the GUD buffer, you can use these special Emacs commands in
27058 addition to the standard Shell mode commands:
27062 Describe the features of Emacs' GUD Mode.
27065 Execute to another source line, like the @value{GDBN} @code{step} command; also
27066 update the display window to show the current file and location.
27069 Execute to next source line in this function, skipping all function
27070 calls, like the @value{GDBN} @code{next} command. Then update the display window
27071 to show the current file and location.
27074 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27075 display window accordingly.
27078 Execute until exit from the selected stack frame, like the @value{GDBN}
27079 @code{finish} command.
27082 Continue execution of your program, like the @value{GDBN} @code{continue}
27086 Go up the number of frames indicated by the numeric argument
27087 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27088 like the @value{GDBN} @code{up} command.
27091 Go down the number of frames indicated by the numeric argument, like the
27092 @value{GDBN} @code{down} command.
27095 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27096 tells @value{GDBN} to set a breakpoint on the source line point is on.
27098 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27099 separate frame which shows a backtrace when the GUD buffer is current.
27100 Move point to any frame in the stack and type @key{RET} to make it
27101 become the current frame and display the associated source in the
27102 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27103 selected frame become the current one. In graphical mode, the
27104 speedbar displays watch expressions.
27106 If you accidentally delete the source-display buffer, an easy way to get
27107 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27108 request a frame display; when you run under Emacs, this recreates
27109 the source buffer if necessary to show you the context of the current
27112 The source files displayed in Emacs are in ordinary Emacs buffers
27113 which are visiting the source files in the usual way. You can edit
27114 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27115 communicates with Emacs in terms of line numbers. If you add or
27116 delete lines from the text, the line numbers that @value{GDBN} knows cease
27117 to correspond properly with the code.
27119 A more detailed description of Emacs' interaction with @value{GDBN} is
27120 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27124 @chapter The @sc{gdb/mi} Interface
27126 @unnumberedsec Function and Purpose
27128 @cindex @sc{gdb/mi}, its purpose
27129 @sc{gdb/mi} is a line based machine oriented text interface to
27130 @value{GDBN} and is activated by specifying using the
27131 @option{--interpreter} command line option (@pxref{Mode Options}). It
27132 is specifically intended to support the development of systems which
27133 use the debugger as just one small component of a larger system.
27135 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27136 in the form of a reference manual.
27138 Note that @sc{gdb/mi} is still under construction, so some of the
27139 features described below are incomplete and subject to change
27140 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27142 @unnumberedsec Notation and Terminology
27144 @cindex notational conventions, for @sc{gdb/mi}
27145 This chapter uses the following notation:
27149 @code{|} separates two alternatives.
27152 @code{[ @var{something} ]} indicates that @var{something} is optional:
27153 it may or may not be given.
27156 @code{( @var{group} )*} means that @var{group} inside the parentheses
27157 may repeat zero or more times.
27160 @code{( @var{group} )+} means that @var{group} inside the parentheses
27161 may repeat one or more times.
27164 @code{"@var{string}"} means a literal @var{string}.
27168 @heading Dependencies
27172 * GDB/MI General Design::
27173 * GDB/MI Command Syntax::
27174 * GDB/MI Compatibility with CLI::
27175 * GDB/MI Development and Front Ends::
27176 * GDB/MI Output Records::
27177 * GDB/MI Simple Examples::
27178 * GDB/MI Command Description Format::
27179 * GDB/MI Breakpoint Commands::
27180 * GDB/MI Catchpoint Commands::
27181 * GDB/MI Program Context::
27182 * GDB/MI Thread Commands::
27183 * GDB/MI Ada Tasking Commands::
27184 * GDB/MI Program Execution::
27185 * GDB/MI Stack Manipulation::
27186 * GDB/MI Variable Objects::
27187 * GDB/MI Data Manipulation::
27188 * GDB/MI Tracepoint Commands::
27189 * GDB/MI Symbol Query::
27190 * GDB/MI File Commands::
27192 * GDB/MI Kod Commands::
27193 * GDB/MI Memory Overlay Commands::
27194 * GDB/MI Signal Handling Commands::
27196 * GDB/MI Target Manipulation::
27197 * GDB/MI File Transfer Commands::
27198 * GDB/MI Ada Exceptions Commands::
27199 * GDB/MI Support Commands::
27200 * GDB/MI Miscellaneous Commands::
27203 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27204 @node GDB/MI General Design
27205 @section @sc{gdb/mi} General Design
27206 @cindex GDB/MI General Design
27208 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27209 parts---commands sent to @value{GDBN}, responses to those commands
27210 and notifications. Each command results in exactly one response,
27211 indicating either successful completion of the command, or an error.
27212 For the commands that do not resume the target, the response contains the
27213 requested information. For the commands that resume the target, the
27214 response only indicates whether the target was successfully resumed.
27215 Notifications is the mechanism for reporting changes in the state of the
27216 target, or in @value{GDBN} state, that cannot conveniently be associated with
27217 a command and reported as part of that command response.
27219 The important examples of notifications are:
27223 Exec notifications. These are used to report changes in
27224 target state---when a target is resumed, or stopped. It would not
27225 be feasible to include this information in response of resuming
27226 commands, because one resume commands can result in multiple events in
27227 different threads. Also, quite some time may pass before any event
27228 happens in the target, while a frontend needs to know whether the resuming
27229 command itself was successfully executed.
27232 Console output, and status notifications. Console output
27233 notifications are used to report output of CLI commands, as well as
27234 diagnostics for other commands. Status notifications are used to
27235 report the progress of a long-running operation. Naturally, including
27236 this information in command response would mean no output is produced
27237 until the command is finished, which is undesirable.
27240 General notifications. Commands may have various side effects on
27241 the @value{GDBN} or target state beyond their official purpose. For example,
27242 a command may change the selected thread. Although such changes can
27243 be included in command response, using notification allows for more
27244 orthogonal frontend design.
27248 There's no guarantee that whenever an MI command reports an error,
27249 @value{GDBN} or the target are in any specific state, and especially,
27250 the state is not reverted to the state before the MI command was
27251 processed. Therefore, whenever an MI command results in an error,
27252 we recommend that the frontend refreshes all the information shown in
27253 the user interface.
27257 * Context management::
27258 * Asynchronous and non-stop modes::
27262 @node Context management
27263 @subsection Context management
27265 @subsubsection Threads and Frames
27267 In most cases when @value{GDBN} accesses the target, this access is
27268 done in context of a specific thread and frame (@pxref{Frames}).
27269 Often, even when accessing global data, the target requires that a thread
27270 be specified. The CLI interface maintains the selected thread and frame,
27271 and supplies them to target on each command. This is convenient,
27272 because a command line user would not want to specify that information
27273 explicitly on each command, and because user interacts with
27274 @value{GDBN} via a single terminal, so no confusion is possible as
27275 to what thread and frame are the current ones.
27277 In the case of MI, the concept of selected thread and frame is less
27278 useful. First, a frontend can easily remember this information
27279 itself. Second, a graphical frontend can have more than one window,
27280 each one used for debugging a different thread, and the frontend might
27281 want to access additional threads for internal purposes. This
27282 increases the risk that by relying on implicitly selected thread, the
27283 frontend may be operating on a wrong one. Therefore, each MI command
27284 should explicitly specify which thread and frame to operate on. To
27285 make it possible, each MI command accepts the @samp{--thread} and
27286 @samp{--frame} options, the value to each is @value{GDBN} global
27287 identifier for thread and frame to operate on.
27289 Usually, each top-level window in a frontend allows the user to select
27290 a thread and a frame, and remembers the user selection for further
27291 operations. However, in some cases @value{GDBN} may suggest that the
27292 current thread or frame be changed. For example, when stopping on a
27293 breakpoint it is reasonable to switch to the thread where breakpoint is
27294 hit. For another example, if the user issues the CLI @samp{thread} or
27295 @samp{frame} commands via the frontend, it is desirable to change the
27296 frontend's selection to the one specified by user. @value{GDBN}
27297 communicates the suggestion to change current thread and frame using the
27298 @samp{=thread-selected} notification.
27300 Note that historically, MI shares the selected thread with CLI, so
27301 frontends used the @code{-thread-select} to execute commands in the
27302 right context. However, getting this to work right is cumbersome. The
27303 simplest way is for frontend to emit @code{-thread-select} command
27304 before every command. This doubles the number of commands that need
27305 to be sent. The alternative approach is to suppress @code{-thread-select}
27306 if the selected thread in @value{GDBN} is supposed to be identical to the
27307 thread the frontend wants to operate on. However, getting this
27308 optimization right can be tricky. In particular, if the frontend
27309 sends several commands to @value{GDBN}, and one of the commands changes the
27310 selected thread, then the behaviour of subsequent commands will
27311 change. So, a frontend should either wait for response from such
27312 problematic commands, or explicitly add @code{-thread-select} for
27313 all subsequent commands. No frontend is known to do this exactly
27314 right, so it is suggested to just always pass the @samp{--thread} and
27315 @samp{--frame} options.
27317 @subsubsection Language
27319 The execution of several commands depends on which language is selected.
27320 By default, the current language (@pxref{show language}) is used.
27321 But for commands known to be language-sensitive, it is recommended
27322 to use the @samp{--language} option. This option takes one argument,
27323 which is the name of the language to use while executing the command.
27327 -data-evaluate-expression --language c "sizeof (void*)"
27332 The valid language names are the same names accepted by the
27333 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27334 @samp{local} or @samp{unknown}.
27336 @node Asynchronous and non-stop modes
27337 @subsection Asynchronous command execution and non-stop mode
27339 On some targets, @value{GDBN} is capable of processing MI commands
27340 even while the target is running. This is called @dfn{asynchronous
27341 command execution} (@pxref{Background Execution}). The frontend may
27342 specify a preferrence for asynchronous execution using the
27343 @code{-gdb-set mi-async 1} command, which should be emitted before
27344 either running the executable or attaching to the target. After the
27345 frontend has started the executable or attached to the target, it can
27346 find if asynchronous execution is enabled using the
27347 @code{-list-target-features} command.
27350 @item -gdb-set mi-async on
27351 @item -gdb-set mi-async off
27352 Set whether MI is in asynchronous mode.
27354 When @code{off}, which is the default, MI execution commands (e.g.,
27355 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27356 for the program to stop before processing further commands.
27358 When @code{on}, MI execution commands are background execution
27359 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27360 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27361 MI commands even while the target is running.
27363 @item -gdb-show mi-async
27364 Show whether MI asynchronous mode is enabled.
27367 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27368 @code{target-async} instead of @code{mi-async}, and it had the effect
27369 of both putting MI in asynchronous mode and making CLI background
27370 commands possible. CLI background commands are now always possible
27371 ``out of the box'' if the target supports them. The old spelling is
27372 kept as a deprecated alias for backwards compatibility.
27374 Even if @value{GDBN} can accept a command while target is running,
27375 many commands that access the target do not work when the target is
27376 running. Therefore, asynchronous command execution is most useful
27377 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27378 it is possible to examine the state of one thread, while other threads
27381 When a given thread is running, MI commands that try to access the
27382 target in the context of that thread may not work, or may work only on
27383 some targets. In particular, commands that try to operate on thread's
27384 stack will not work, on any target. Commands that read memory, or
27385 modify breakpoints, may work or not work, depending on the target. Note
27386 that even commands that operate on global state, such as @code{print},
27387 @code{set}, and breakpoint commands, still access the target in the
27388 context of a specific thread, so frontend should try to find a
27389 stopped thread and perform the operation on that thread (using the
27390 @samp{--thread} option).
27392 Which commands will work in the context of a running thread is
27393 highly target dependent. However, the two commands
27394 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27395 to find the state of a thread, will always work.
27397 @node Thread groups
27398 @subsection Thread groups
27399 @value{GDBN} may be used to debug several processes at the same time.
27400 On some platfroms, @value{GDBN} may support debugging of several
27401 hardware systems, each one having several cores with several different
27402 processes running on each core. This section describes the MI
27403 mechanism to support such debugging scenarios.
27405 The key observation is that regardless of the structure of the
27406 target, MI can have a global list of threads, because most commands that
27407 accept the @samp{--thread} option do not need to know what process that
27408 thread belongs to. Therefore, it is not necessary to introduce
27409 neither additional @samp{--process} option, nor an notion of the
27410 current process in the MI interface. The only strictly new feature
27411 that is required is the ability to find how the threads are grouped
27414 To allow the user to discover such grouping, and to support arbitrary
27415 hierarchy of machines/cores/processes, MI introduces the concept of a
27416 @dfn{thread group}. Thread group is a collection of threads and other
27417 thread groups. A thread group always has a string identifier, a type,
27418 and may have additional attributes specific to the type. A new
27419 command, @code{-list-thread-groups}, returns the list of top-level
27420 thread groups, which correspond to processes that @value{GDBN} is
27421 debugging at the moment. By passing an identifier of a thread group
27422 to the @code{-list-thread-groups} command, it is possible to obtain
27423 the members of specific thread group.
27425 To allow the user to easily discover processes, and other objects, he
27426 wishes to debug, a concept of @dfn{available thread group} is
27427 introduced. Available thread group is an thread group that
27428 @value{GDBN} is not debugging, but that can be attached to, using the
27429 @code{-target-attach} command. The list of available top-level thread
27430 groups can be obtained using @samp{-list-thread-groups --available}.
27431 In general, the content of a thread group may be only retrieved only
27432 after attaching to that thread group.
27434 Thread groups are related to inferiors (@pxref{Inferiors and
27435 Programs}). Each inferior corresponds to a thread group of a special
27436 type @samp{process}, and some additional operations are permitted on
27437 such thread groups.
27439 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27440 @node GDB/MI Command Syntax
27441 @section @sc{gdb/mi} Command Syntax
27444 * GDB/MI Input Syntax::
27445 * GDB/MI Output Syntax::
27448 @node GDB/MI Input Syntax
27449 @subsection @sc{gdb/mi} Input Syntax
27451 @cindex input syntax for @sc{gdb/mi}
27452 @cindex @sc{gdb/mi}, input syntax
27454 @item @var{command} @expansion{}
27455 @code{@var{cli-command} | @var{mi-command}}
27457 @item @var{cli-command} @expansion{}
27458 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27459 @var{cli-command} is any existing @value{GDBN} CLI command.
27461 @item @var{mi-command} @expansion{}
27462 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27463 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27465 @item @var{token} @expansion{}
27466 "any sequence of digits"
27468 @item @var{option} @expansion{}
27469 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27471 @item @var{parameter} @expansion{}
27472 @code{@var{non-blank-sequence} | @var{c-string}}
27474 @item @var{operation} @expansion{}
27475 @emph{any of the operations described in this chapter}
27477 @item @var{non-blank-sequence} @expansion{}
27478 @emph{anything, provided it doesn't contain special characters such as
27479 "-", @var{nl}, """ and of course " "}
27481 @item @var{c-string} @expansion{}
27482 @code{""" @var{seven-bit-iso-c-string-content} """}
27484 @item @var{nl} @expansion{}
27493 The CLI commands are still handled by the @sc{mi} interpreter; their
27494 output is described below.
27497 The @code{@var{token}}, when present, is passed back when the command
27501 Some @sc{mi} commands accept optional arguments as part of the parameter
27502 list. Each option is identified by a leading @samp{-} (dash) and may be
27503 followed by an optional argument parameter. Options occur first in the
27504 parameter list and can be delimited from normal parameters using
27505 @samp{--} (this is useful when some parameters begin with a dash).
27512 We want easy access to the existing CLI syntax (for debugging).
27515 We want it to be easy to spot a @sc{mi} operation.
27518 @node GDB/MI Output Syntax
27519 @subsection @sc{gdb/mi} Output Syntax
27521 @cindex output syntax of @sc{gdb/mi}
27522 @cindex @sc{gdb/mi}, output syntax
27523 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27524 followed, optionally, by a single result record. This result record
27525 is for the most recent command. The sequence of output records is
27526 terminated by @samp{(gdb)}.
27528 If an input command was prefixed with a @code{@var{token}} then the
27529 corresponding output for that command will also be prefixed by that same
27533 @item @var{output} @expansion{}
27534 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27536 @item @var{result-record} @expansion{}
27537 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27539 @item @var{out-of-band-record} @expansion{}
27540 @code{@var{async-record} | @var{stream-record}}
27542 @item @var{async-record} @expansion{}
27543 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27545 @item @var{exec-async-output} @expansion{}
27546 @code{[ @var{token} ] "*" @var{async-output nl}}
27548 @item @var{status-async-output} @expansion{}
27549 @code{[ @var{token} ] "+" @var{async-output nl}}
27551 @item @var{notify-async-output} @expansion{}
27552 @code{[ @var{token} ] "=" @var{async-output nl}}
27554 @item @var{async-output} @expansion{}
27555 @code{@var{async-class} ( "," @var{result} )*}
27557 @item @var{result-class} @expansion{}
27558 @code{"done" | "running" | "connected" | "error" | "exit"}
27560 @item @var{async-class} @expansion{}
27561 @code{"stopped" | @var{others}} (where @var{others} will be added
27562 depending on the needs---this is still in development).
27564 @item @var{result} @expansion{}
27565 @code{ @var{variable} "=" @var{value}}
27567 @item @var{variable} @expansion{}
27568 @code{ @var{string} }
27570 @item @var{value} @expansion{}
27571 @code{ @var{const} | @var{tuple} | @var{list} }
27573 @item @var{const} @expansion{}
27574 @code{@var{c-string}}
27576 @item @var{tuple} @expansion{}
27577 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27579 @item @var{list} @expansion{}
27580 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27581 @var{result} ( "," @var{result} )* "]" }
27583 @item @var{stream-record} @expansion{}
27584 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27586 @item @var{console-stream-output} @expansion{}
27587 @code{"~" @var{c-string nl}}
27589 @item @var{target-stream-output} @expansion{}
27590 @code{"@@" @var{c-string nl}}
27592 @item @var{log-stream-output} @expansion{}
27593 @code{"&" @var{c-string nl}}
27595 @item @var{nl} @expansion{}
27598 @item @var{token} @expansion{}
27599 @emph{any sequence of digits}.
27607 All output sequences end in a single line containing a period.
27610 The @code{@var{token}} is from the corresponding request. Note that
27611 for all async output, while the token is allowed by the grammar and
27612 may be output by future versions of @value{GDBN} for select async
27613 output messages, it is generally omitted. Frontends should treat
27614 all async output as reporting general changes in the state of the
27615 target and there should be no need to associate async output to any
27619 @cindex status output in @sc{gdb/mi}
27620 @var{status-async-output} contains on-going status information about the
27621 progress of a slow operation. It can be discarded. All status output is
27622 prefixed by @samp{+}.
27625 @cindex async output in @sc{gdb/mi}
27626 @var{exec-async-output} contains asynchronous state change on the target
27627 (stopped, started, disappeared). All async output is prefixed by
27631 @cindex notify output in @sc{gdb/mi}
27632 @var{notify-async-output} contains supplementary information that the
27633 client should handle (e.g., a new breakpoint information). All notify
27634 output is prefixed by @samp{=}.
27637 @cindex console output in @sc{gdb/mi}
27638 @var{console-stream-output} is output that should be displayed as is in the
27639 console. It is the textual response to a CLI command. All the console
27640 output is prefixed by @samp{~}.
27643 @cindex target output in @sc{gdb/mi}
27644 @var{target-stream-output} is the output produced by the target program.
27645 All the target output is prefixed by @samp{@@}.
27648 @cindex log output in @sc{gdb/mi}
27649 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27650 instance messages that should be displayed as part of an error log. All
27651 the log output is prefixed by @samp{&}.
27654 @cindex list output in @sc{gdb/mi}
27655 New @sc{gdb/mi} commands should only output @var{lists} containing
27661 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27662 details about the various output records.
27664 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27665 @node GDB/MI Compatibility with CLI
27666 @section @sc{gdb/mi} Compatibility with CLI
27668 @cindex compatibility, @sc{gdb/mi} and CLI
27669 @cindex @sc{gdb/mi}, compatibility with CLI
27671 For the developers convenience CLI commands can be entered directly,
27672 but there may be some unexpected behaviour. For example, commands
27673 that query the user will behave as if the user replied yes, breakpoint
27674 command lists are not executed and some CLI commands, such as
27675 @code{if}, @code{when} and @code{define}, prompt for further input with
27676 @samp{>}, which is not valid MI output.
27678 This feature may be removed at some stage in the future and it is
27679 recommended that front ends use the @code{-interpreter-exec} command
27680 (@pxref{-interpreter-exec}).
27682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27683 @node GDB/MI Development and Front Ends
27684 @section @sc{gdb/mi} Development and Front Ends
27685 @cindex @sc{gdb/mi} development
27687 The application which takes the MI output and presents the state of the
27688 program being debugged to the user is called a @dfn{front end}.
27690 Although @sc{gdb/mi} is still incomplete, it is currently being used
27691 by a variety of front ends to @value{GDBN}. This makes it difficult
27692 to introduce new functionality without breaking existing usage. This
27693 section tries to minimize the problems by describing how the protocol
27696 Some changes in MI need not break a carefully designed front end, and
27697 for these the MI version will remain unchanged. The following is a
27698 list of changes that may occur within one level, so front ends should
27699 parse MI output in a way that can handle them:
27703 New MI commands may be added.
27706 New fields may be added to the output of any MI command.
27709 The range of values for fields with specified values, e.g.,
27710 @code{in_scope} (@pxref{-var-update}) may be extended.
27712 @c The format of field's content e.g type prefix, may change so parse it
27713 @c at your own risk. Yes, in general?
27715 @c The order of fields may change? Shouldn't really matter but it might
27716 @c resolve inconsistencies.
27719 If the changes are likely to break front ends, the MI version level
27720 will be increased by one. This will allow the front end to parse the
27721 output according to the MI version. Apart from mi0, new versions of
27722 @value{GDBN} will not support old versions of MI and it will be the
27723 responsibility of the front end to work with the new one.
27725 @c Starting with mi3, add a new command -mi-version that prints the MI
27728 The best way to avoid unexpected changes in MI that might break your front
27729 end is to make your project known to @value{GDBN} developers and
27730 follow development on @email{gdb@@sourceware.org} and
27731 @email{gdb-patches@@sourceware.org}.
27732 @cindex mailing lists
27734 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27735 @node GDB/MI Output Records
27736 @section @sc{gdb/mi} Output Records
27739 * GDB/MI Result Records::
27740 * GDB/MI Stream Records::
27741 * GDB/MI Async Records::
27742 * GDB/MI Breakpoint Information::
27743 * GDB/MI Frame Information::
27744 * GDB/MI Thread Information::
27745 * GDB/MI Ada Exception Information::
27748 @node GDB/MI Result Records
27749 @subsection @sc{gdb/mi} Result Records
27751 @cindex result records in @sc{gdb/mi}
27752 @cindex @sc{gdb/mi}, result records
27753 In addition to a number of out-of-band notifications, the response to a
27754 @sc{gdb/mi} command includes one of the following result indications:
27758 @item "^done" [ "," @var{results} ]
27759 The synchronous operation was successful, @code{@var{results}} are the return
27764 This result record is equivalent to @samp{^done}. Historically, it
27765 was output instead of @samp{^done} if the command has resumed the
27766 target. This behaviour is maintained for backward compatibility, but
27767 all frontends should treat @samp{^done} and @samp{^running}
27768 identically and rely on the @samp{*running} output record to determine
27769 which threads are resumed.
27773 @value{GDBN} has connected to a remote target.
27775 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27777 The operation failed. The @code{msg=@var{c-string}} variable contains
27778 the corresponding error message.
27780 If present, the @code{code=@var{c-string}} variable provides an error
27781 code on which consumers can rely on to detect the corresponding
27782 error condition. At present, only one error code is defined:
27785 @item "undefined-command"
27786 Indicates that the command causing the error does not exist.
27791 @value{GDBN} has terminated.
27795 @node GDB/MI Stream Records
27796 @subsection @sc{gdb/mi} Stream Records
27798 @cindex @sc{gdb/mi}, stream records
27799 @cindex stream records in @sc{gdb/mi}
27800 @value{GDBN} internally maintains a number of output streams: the console, the
27801 target, and the log. The output intended for each of these streams is
27802 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27804 Each stream record begins with a unique @dfn{prefix character} which
27805 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27806 Syntax}). In addition to the prefix, each stream record contains a
27807 @code{@var{string-output}}. This is either raw text (with an implicit new
27808 line) or a quoted C string (which does not contain an implicit newline).
27811 @item "~" @var{string-output}
27812 The console output stream contains text that should be displayed in the
27813 CLI console window. It contains the textual responses to CLI commands.
27815 @item "@@" @var{string-output}
27816 The target output stream contains any textual output from the running
27817 target. This is only present when GDB's event loop is truly
27818 asynchronous, which is currently only the case for remote targets.
27820 @item "&" @var{string-output}
27821 The log stream contains debugging messages being produced by @value{GDBN}'s
27825 @node GDB/MI Async Records
27826 @subsection @sc{gdb/mi} Async Records
27828 @cindex async records in @sc{gdb/mi}
27829 @cindex @sc{gdb/mi}, async records
27830 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27831 additional changes that have occurred. Those changes can either be a
27832 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27833 target activity (e.g., target stopped).
27835 The following is the list of possible async records:
27839 @item *running,thread-id="@var{thread}"
27840 The target is now running. The @var{thread} field can be the global
27841 thread ID of the the thread that is now running, and it can be
27842 @samp{all} if all threads are running. The frontend should assume
27843 that no interaction with a running thread is possible after this
27844 notification is produced. The frontend should not assume that this
27845 notification is output only once for any command. @value{GDBN} may
27846 emit this notification several times, either for different threads,
27847 because it cannot resume all threads together, or even for a single
27848 thread, if the thread must be stepped though some code before letting
27851 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27852 The target has stopped. The @var{reason} field can have one of the
27856 @item breakpoint-hit
27857 A breakpoint was reached.
27858 @item watchpoint-trigger
27859 A watchpoint was triggered.
27860 @item read-watchpoint-trigger
27861 A read watchpoint was triggered.
27862 @item access-watchpoint-trigger
27863 An access watchpoint was triggered.
27864 @item function-finished
27865 An -exec-finish or similar CLI command was accomplished.
27866 @item location-reached
27867 An -exec-until or similar CLI command was accomplished.
27868 @item watchpoint-scope
27869 A watchpoint has gone out of scope.
27870 @item end-stepping-range
27871 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27872 similar CLI command was accomplished.
27873 @item exited-signalled
27874 The inferior exited because of a signal.
27876 The inferior exited.
27877 @item exited-normally
27878 The inferior exited normally.
27879 @item signal-received
27880 A signal was received by the inferior.
27882 The inferior has stopped due to a library being loaded or unloaded.
27883 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27884 set or when a @code{catch load} or @code{catch unload} catchpoint is
27885 in use (@pxref{Set Catchpoints}).
27887 The inferior has forked. This is reported when @code{catch fork}
27888 (@pxref{Set Catchpoints}) has been used.
27890 The inferior has vforked. This is reported in when @code{catch vfork}
27891 (@pxref{Set Catchpoints}) has been used.
27892 @item syscall-entry
27893 The inferior entered a system call. This is reported when @code{catch
27894 syscall} (@pxref{Set Catchpoints}) has been used.
27895 @item syscall-return
27896 The inferior returned from a system call. This is reported when
27897 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27899 The inferior called @code{exec}. This is reported when @code{catch exec}
27900 (@pxref{Set Catchpoints}) has been used.
27903 The @var{id} field identifies the global thread ID of the thread
27904 that directly caused the stop -- for example by hitting a breakpoint.
27905 Depending on whether all-stop
27906 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27907 stop all threads, or only the thread that directly triggered the stop.
27908 If all threads are stopped, the @var{stopped} field will have the
27909 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27910 field will be a list of thread identifiers. Presently, this list will
27911 always include a single thread, but frontend should be prepared to see
27912 several threads in the list. The @var{core} field reports the
27913 processor core on which the stop event has happened. This field may be absent
27914 if such information is not available.
27916 @item =thread-group-added,id="@var{id}"
27917 @itemx =thread-group-removed,id="@var{id}"
27918 A thread group was either added or removed. The @var{id} field
27919 contains the @value{GDBN} identifier of the thread group. When a thread
27920 group is added, it generally might not be associated with a running
27921 process. When a thread group is removed, its id becomes invalid and
27922 cannot be used in any way.
27924 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27925 A thread group became associated with a running program,
27926 either because the program was just started or the thread group
27927 was attached to a program. The @var{id} field contains the
27928 @value{GDBN} identifier of the thread group. The @var{pid} field
27929 contains process identifier, specific to the operating system.
27931 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27932 A thread group is no longer associated with a running program,
27933 either because the program has exited, or because it was detached
27934 from. The @var{id} field contains the @value{GDBN} identifier of the
27935 thread group. The @var{code} field is the exit code of the inferior; it exists
27936 only when the inferior exited with some code.
27938 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27939 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27940 A thread either was created, or has exited. The @var{id} field
27941 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27942 field identifies the thread group this thread belongs to.
27944 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27945 Informs that the selected thread or frame were changed. This notification
27946 is not emitted as result of the @code{-thread-select} or
27947 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27948 that is not documented to change the selected thread and frame actually
27949 changes them. In particular, invoking, directly or indirectly
27950 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27951 will generate this notification. Changing the thread or frame from another
27952 user interface (see @ref{Interpreters}) will also generate this notification.
27954 The @var{frame} field is only present if the newly selected thread is
27955 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27957 We suggest that in response to this notification, front ends
27958 highlight the selected thread and cause subsequent commands to apply to
27961 @item =library-loaded,...
27962 Reports that a new library file was loaded by the program. This
27963 notification has 5 fields---@var{id}, @var{target-name},
27964 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27965 opaque identifier of the library. For remote debugging case,
27966 @var{target-name} and @var{host-name} fields give the name of the
27967 library file on the target, and on the host respectively. For native
27968 debugging, both those fields have the same value. The
27969 @var{symbols-loaded} field is emitted only for backward compatibility
27970 and should not be relied on to convey any useful information. The
27971 @var{thread-group} field, if present, specifies the id of the thread
27972 group in whose context the library was loaded. If the field is
27973 absent, it means the library was loaded in the context of all present
27974 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27977 @item =library-unloaded,...
27978 Reports that a library was unloaded by the program. This notification
27979 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27980 the same meaning as for the @code{=library-loaded} notification.
27981 The @var{thread-group} field, if present, specifies the id of the
27982 thread group in whose context the library was unloaded. If the field is
27983 absent, it means the library was unloaded in the context of all present
27986 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27987 @itemx =traceframe-changed,end
27988 Reports that the trace frame was changed and its new number is
27989 @var{tfnum}. The number of the tracepoint associated with this trace
27990 frame is @var{tpnum}.
27992 @item =tsv-created,name=@var{name},initial=@var{initial}
27993 Reports that the new trace state variable @var{name} is created with
27994 initial value @var{initial}.
27996 @item =tsv-deleted,name=@var{name}
27997 @itemx =tsv-deleted
27998 Reports that the trace state variable @var{name} is deleted or all
27999 trace state variables are deleted.
28001 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28002 Reports that the trace state variable @var{name} is modified with
28003 the initial value @var{initial}. The current value @var{current} of
28004 trace state variable is optional and is reported if the current
28005 value of trace state variable is known.
28007 @item =breakpoint-created,bkpt=@{...@}
28008 @itemx =breakpoint-modified,bkpt=@{...@}
28009 @itemx =breakpoint-deleted,id=@var{number}
28010 Reports that a breakpoint was created, modified, or deleted,
28011 respectively. Only user-visible breakpoints are reported to the MI
28014 The @var{bkpt} argument is of the same form as returned by the various
28015 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28016 @var{number} is the ordinal number of the breakpoint.
28018 Note that if a breakpoint is emitted in the result record of a
28019 command, then it will not also be emitted in an async record.
28021 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28022 @itemx =record-stopped,thread-group="@var{id}"
28023 Execution log recording was either started or stopped on an
28024 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28025 group corresponding to the affected inferior.
28027 The @var{method} field indicates the method used to record execution. If the
28028 method in use supports multiple recording formats, @var{format} will be present
28029 and contain the currently used format. @xref{Process Record and Replay},
28030 for existing method and format values.
28032 @item =cmd-param-changed,param=@var{param},value=@var{value}
28033 Reports that a parameter of the command @code{set @var{param}} is
28034 changed to @var{value}. In the multi-word @code{set} command,
28035 the @var{param} is the whole parameter list to @code{set} command.
28036 For example, In command @code{set check type on}, @var{param}
28037 is @code{check type} and @var{value} is @code{on}.
28039 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28040 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28041 written in an inferior. The @var{id} is the identifier of the
28042 thread group corresponding to the affected inferior. The optional
28043 @code{type="code"} part is reported if the memory written to holds
28047 @node GDB/MI Breakpoint Information
28048 @subsection @sc{gdb/mi} Breakpoint Information
28050 When @value{GDBN} reports information about a breakpoint, a
28051 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28056 The breakpoint number. For a breakpoint that represents one location
28057 of a multi-location breakpoint, this will be a dotted pair, like
28061 The type of the breakpoint. For ordinary breakpoints this will be
28062 @samp{breakpoint}, but many values are possible.
28065 If the type of the breakpoint is @samp{catchpoint}, then this
28066 indicates the exact type of catchpoint.
28069 This is the breakpoint disposition---either @samp{del}, meaning that
28070 the breakpoint will be deleted at the next stop, or @samp{keep},
28071 meaning that the breakpoint will not be deleted.
28074 This indicates whether the breakpoint is enabled, in which case the
28075 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28076 Note that this is not the same as the field @code{enable}.
28079 The address of the breakpoint. This may be a hexidecimal number,
28080 giving the address; or the string @samp{<PENDING>}, for a pending
28081 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28082 multiple locations. This field will not be present if no address can
28083 be determined. For example, a watchpoint does not have an address.
28086 If known, the function in which the breakpoint appears.
28087 If not known, this field is not present.
28090 The name of the source file which contains this function, if known.
28091 If not known, this field is not present.
28094 The full file name of the source file which contains this function, if
28095 known. If not known, this field is not present.
28098 The line number at which this breakpoint appears, if known.
28099 If not known, this field is not present.
28102 If the source file is not known, this field may be provided. If
28103 provided, this holds the address of the breakpoint, possibly followed
28107 If this breakpoint is pending, this field is present and holds the
28108 text used to set the breakpoint, as entered by the user.
28111 Where this breakpoint's condition is evaluated, either @samp{host} or
28115 If this is a thread-specific breakpoint, then this identifies the
28116 thread in which the breakpoint can trigger.
28119 If this breakpoint is restricted to a particular Ada task, then this
28120 field will hold the task identifier.
28123 If the breakpoint is conditional, this is the condition expression.
28126 The ignore count of the breakpoint.
28129 The enable count of the breakpoint.
28131 @item traceframe-usage
28134 @item static-tracepoint-marker-string-id
28135 For a static tracepoint, the name of the static tracepoint marker.
28138 For a masked watchpoint, this is the mask.
28141 A tracepoint's pass count.
28143 @item original-location
28144 The location of the breakpoint as originally specified by the user.
28145 This field is optional.
28148 The number of times the breakpoint has been hit.
28151 This field is only given for tracepoints. This is either @samp{y},
28152 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28156 Some extra data, the exact contents of which are type-dependent.
28160 For example, here is what the output of @code{-break-insert}
28161 (@pxref{GDB/MI Breakpoint Commands}) might be:
28164 -> -break-insert main
28165 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28166 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28167 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28172 @node GDB/MI Frame Information
28173 @subsection @sc{gdb/mi} Frame Information
28175 Response from many MI commands includes an information about stack
28176 frame. This information is a tuple that may have the following
28181 The level of the stack frame. The innermost frame has the level of
28182 zero. This field is always present.
28185 The name of the function corresponding to the frame. This field may
28186 be absent if @value{GDBN} is unable to determine the function name.
28189 The code address for the frame. This field is always present.
28192 The name of the source files that correspond to the frame's code
28193 address. This field may be absent.
28196 The source line corresponding to the frames' code address. This field
28200 The name of the binary file (either executable or shared library) the
28201 corresponds to the frame's code address. This field may be absent.
28205 @node GDB/MI Thread Information
28206 @subsection @sc{gdb/mi} Thread Information
28208 Whenever @value{GDBN} has to report an information about a thread, it
28209 uses a tuple with the following fields. The fields are always present unless
28214 The global numeric id assigned to the thread by @value{GDBN}.
28217 The target-specific string identifying the thread.
28220 Additional information about the thread provided by the target.
28221 It is supposed to be human-readable and not interpreted by the
28222 frontend. This field is optional.
28225 The name of the thread. If the user specified a name using the
28226 @code{thread name} command, then this name is given. Otherwise, if
28227 @value{GDBN} can extract the thread name from the target, then that
28228 name is given. If @value{GDBN} cannot find the thread name, then this
28232 The execution state of the thread, either @samp{stopped} or @samp{running},
28233 depending on whether the thread is presently running.
28236 The stack frame currently executing in the thread. This field is only present
28237 if the thread is stopped. Its format is documented in
28238 @ref{GDB/MI Frame Information}.
28241 The value of this field is an integer number of the processor core the
28242 thread was last seen on. This field is optional.
28245 @node GDB/MI Ada Exception Information
28246 @subsection @sc{gdb/mi} Ada Exception Information
28248 Whenever a @code{*stopped} record is emitted because the program
28249 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28250 @value{GDBN} provides the name of the exception that was raised via
28251 the @code{exception-name} field. Also, for exceptions that were raised
28252 with an exception message, @value{GDBN} provides that message via
28253 the @code{exception-message} field.
28255 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28256 @node GDB/MI Simple Examples
28257 @section Simple Examples of @sc{gdb/mi} Interaction
28258 @cindex @sc{gdb/mi}, simple examples
28260 This subsection presents several simple examples of interaction using
28261 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28262 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28263 the output received from @sc{gdb/mi}.
28265 Note the line breaks shown in the examples are here only for
28266 readability, they don't appear in the real output.
28268 @subheading Setting a Breakpoint
28270 Setting a breakpoint generates synchronous output which contains detailed
28271 information of the breakpoint.
28274 -> -break-insert main
28275 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28276 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28277 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28282 @subheading Program Execution
28284 Program execution generates asynchronous records and MI gives the
28285 reason that execution stopped.
28291 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28292 frame=@{addr="0x08048564",func="main",
28293 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28294 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28295 arch="i386:x86_64"@}
28300 <- *stopped,reason="exited-normally"
28304 @subheading Quitting @value{GDBN}
28306 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28314 Please note that @samp{^exit} is printed immediately, but it might
28315 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28316 performs necessary cleanups, including killing programs being debugged
28317 or disconnecting from debug hardware, so the frontend should wait till
28318 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28319 fails to exit in reasonable time.
28321 @subheading A Bad Command
28323 Here's what happens if you pass a non-existent command:
28327 <- ^error,msg="Undefined MI command: rubbish"
28332 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28333 @node GDB/MI Command Description Format
28334 @section @sc{gdb/mi} Command Description Format
28336 The remaining sections describe blocks of commands. Each block of
28337 commands is laid out in a fashion similar to this section.
28339 @subheading Motivation
28341 The motivation for this collection of commands.
28343 @subheading Introduction
28345 A brief introduction to this collection of commands as a whole.
28347 @subheading Commands
28349 For each command in the block, the following is described:
28351 @subsubheading Synopsis
28354 -command @var{args}@dots{}
28357 @subsubheading Result
28359 @subsubheading @value{GDBN} Command
28361 The corresponding @value{GDBN} CLI command(s), if any.
28363 @subsubheading Example
28365 Example(s) formatted for readability. Some of the described commands have
28366 not been implemented yet and these are labeled N.A.@: (not available).
28369 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28370 @node GDB/MI Breakpoint Commands
28371 @section @sc{gdb/mi} Breakpoint Commands
28373 @cindex breakpoint commands for @sc{gdb/mi}
28374 @cindex @sc{gdb/mi}, breakpoint commands
28375 This section documents @sc{gdb/mi} commands for manipulating
28378 @subheading The @code{-break-after} Command
28379 @findex -break-after
28381 @subsubheading Synopsis
28384 -break-after @var{number} @var{count}
28387 The breakpoint number @var{number} is not in effect until it has been
28388 hit @var{count} times. To see how this is reflected in the output of
28389 the @samp{-break-list} command, see the description of the
28390 @samp{-break-list} command below.
28392 @subsubheading @value{GDBN} Command
28394 The corresponding @value{GDBN} command is @samp{ignore}.
28396 @subsubheading Example
28401 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28402 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28403 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28411 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28412 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28413 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28414 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28415 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28416 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28417 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28418 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28419 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28420 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28425 @subheading The @code{-break-catch} Command
28426 @findex -break-catch
28429 @subheading The @code{-break-commands} Command
28430 @findex -break-commands
28432 @subsubheading Synopsis
28435 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28438 Specifies the CLI commands that should be executed when breakpoint
28439 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28440 are the commands. If no command is specified, any previously-set
28441 commands are cleared. @xref{Break Commands}. Typical use of this
28442 functionality is tracing a program, that is, printing of values of
28443 some variables whenever breakpoint is hit and then continuing.
28445 @subsubheading @value{GDBN} Command
28447 The corresponding @value{GDBN} command is @samp{commands}.
28449 @subsubheading Example
28454 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28455 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28456 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28459 -break-commands 1 "print v" "continue"
28464 @subheading The @code{-break-condition} Command
28465 @findex -break-condition
28467 @subsubheading Synopsis
28470 -break-condition @var{number} @var{expr}
28473 Breakpoint @var{number} will stop the program only if the condition in
28474 @var{expr} is true. The condition becomes part of the
28475 @samp{-break-list} output (see the description of the @samp{-break-list}
28478 @subsubheading @value{GDBN} Command
28480 The corresponding @value{GDBN} command is @samp{condition}.
28482 @subsubheading Example
28486 -break-condition 1 1
28490 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28491 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28492 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28493 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28494 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28495 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28496 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28497 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28498 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28499 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28503 @subheading The @code{-break-delete} Command
28504 @findex -break-delete
28506 @subsubheading Synopsis
28509 -break-delete ( @var{breakpoint} )+
28512 Delete the breakpoint(s) whose number(s) are specified in the argument
28513 list. This is obviously reflected in the breakpoint list.
28515 @subsubheading @value{GDBN} Command
28517 The corresponding @value{GDBN} command is @samp{delete}.
28519 @subsubheading Example
28527 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28528 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28529 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28530 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28531 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28532 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28533 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28538 @subheading The @code{-break-disable} Command
28539 @findex -break-disable
28541 @subsubheading Synopsis
28544 -break-disable ( @var{breakpoint} )+
28547 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28548 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28550 @subsubheading @value{GDBN} Command
28552 The corresponding @value{GDBN} command is @samp{disable}.
28554 @subsubheading Example
28562 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28563 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28564 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28565 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28566 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28567 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28568 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28569 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28570 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28571 line="5",thread-groups=["i1"],times="0"@}]@}
28575 @subheading The @code{-break-enable} Command
28576 @findex -break-enable
28578 @subsubheading Synopsis
28581 -break-enable ( @var{breakpoint} )+
28584 Enable (previously disabled) @var{breakpoint}(s).
28586 @subsubheading @value{GDBN} Command
28588 The corresponding @value{GDBN} command is @samp{enable}.
28590 @subsubheading Example
28598 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28599 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28600 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28601 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28602 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28603 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28604 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28605 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28606 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28607 line="5",thread-groups=["i1"],times="0"@}]@}
28611 @subheading The @code{-break-info} Command
28612 @findex -break-info
28614 @subsubheading Synopsis
28617 -break-info @var{breakpoint}
28621 Get information about a single breakpoint.
28623 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28624 Information}, for details on the format of each breakpoint in the
28627 @subsubheading @value{GDBN} Command
28629 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28631 @subsubheading Example
28634 @subheading The @code{-break-insert} Command
28635 @findex -break-insert
28636 @anchor{-break-insert}
28638 @subsubheading Synopsis
28641 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28642 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28643 [ -p @var{thread-id} ] [ @var{location} ]
28647 If specified, @var{location}, can be one of:
28650 @item linespec location
28651 A linespec location. @xref{Linespec Locations}.
28653 @item explicit location
28654 An explicit location. @sc{gdb/mi} explicit locations are
28655 analogous to the CLI's explicit locations using the option names
28656 listed below. @xref{Explicit Locations}.
28659 @item --source @var{filename}
28660 The source file name of the location. This option requires the use
28661 of either @samp{--function} or @samp{--line}.
28663 @item --function @var{function}
28664 The name of a function or method.
28666 @item --label @var{label}
28667 The name of a label.
28669 @item --line @var{lineoffset}
28670 An absolute or relative line offset from the start of the location.
28673 @item address location
28674 An address location, *@var{address}. @xref{Address Locations}.
28678 The possible optional parameters of this command are:
28682 Insert a temporary breakpoint.
28684 Insert a hardware breakpoint.
28686 If @var{location} cannot be parsed (for example if it
28687 refers to unknown files or functions), create a pending
28688 breakpoint. Without this flag, @value{GDBN} will report
28689 an error, and won't create a breakpoint, if @var{location}
28692 Create a disabled breakpoint.
28694 Create a tracepoint. @xref{Tracepoints}. When this parameter
28695 is used together with @samp{-h}, a fast tracepoint is created.
28696 @item -c @var{condition}
28697 Make the breakpoint conditional on @var{condition}.
28698 @item -i @var{ignore-count}
28699 Initialize the @var{ignore-count}.
28700 @item -p @var{thread-id}
28701 Restrict the breakpoint to the thread with the specified global
28705 @subsubheading Result
28707 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28708 resulting breakpoint.
28710 Note: this format is open to change.
28711 @c An out-of-band breakpoint instead of part of the result?
28713 @subsubheading @value{GDBN} Command
28715 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28716 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28718 @subsubheading Example
28723 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28724 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28727 -break-insert -t foo
28728 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28729 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28733 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28734 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28735 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28736 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28737 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28738 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28739 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28740 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28741 addr="0x0001072c", func="main",file="recursive2.c",
28742 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28744 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28745 addr="0x00010774",func="foo",file="recursive2.c",
28746 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28749 @c -break-insert -r foo.*
28750 @c ~int foo(int, int);
28751 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28752 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28757 @subheading The @code{-dprintf-insert} Command
28758 @findex -dprintf-insert
28760 @subsubheading Synopsis
28763 -dprintf-insert [ -t ] [ -f ] [ -d ]
28764 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28765 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28770 If supplied, @var{location} may be specified the same way as for
28771 the @code{-break-insert} command. @xref{-break-insert}.
28773 The possible optional parameters of this command are:
28777 Insert a temporary breakpoint.
28779 If @var{location} cannot be parsed (for example, if it
28780 refers to unknown files or functions), create a pending
28781 breakpoint. Without this flag, @value{GDBN} will report
28782 an error, and won't create a breakpoint, if @var{location}
28785 Create a disabled breakpoint.
28786 @item -c @var{condition}
28787 Make the breakpoint conditional on @var{condition}.
28788 @item -i @var{ignore-count}
28789 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28790 to @var{ignore-count}.
28791 @item -p @var{thread-id}
28792 Restrict the breakpoint to the thread with the specified global
28796 @subsubheading Result
28798 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28799 resulting breakpoint.
28801 @c An out-of-band breakpoint instead of part of the result?
28803 @subsubheading @value{GDBN} Command
28805 The corresponding @value{GDBN} command is @samp{dprintf}.
28807 @subsubheading Example
28811 4-dprintf-insert foo "At foo entry\n"
28812 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28813 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28814 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28815 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28816 original-location="foo"@}
28818 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28819 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28820 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28821 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28822 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28823 original-location="mi-dprintf.c:26"@}
28827 @subheading The @code{-break-list} Command
28828 @findex -break-list
28830 @subsubheading Synopsis
28836 Displays the list of inserted breakpoints, showing the following fields:
28840 number of the breakpoint
28842 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28844 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28847 is the breakpoint enabled or no: @samp{y} or @samp{n}
28849 memory location at which the breakpoint is set
28851 logical location of the breakpoint, expressed by function name, file
28853 @item Thread-groups
28854 list of thread groups to which this breakpoint applies
28856 number of times the breakpoint has been hit
28859 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28860 @code{body} field is an empty list.
28862 @subsubheading @value{GDBN} Command
28864 The corresponding @value{GDBN} command is @samp{info break}.
28866 @subsubheading Example
28871 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28872 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28873 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28874 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28875 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28876 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28877 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28878 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28879 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28881 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28882 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28883 line="13",thread-groups=["i1"],times="0"@}]@}
28887 Here's an example of the result when there are no breakpoints:
28892 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28893 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28894 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28895 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28896 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28897 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28898 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28903 @subheading The @code{-break-passcount} Command
28904 @findex -break-passcount
28906 @subsubheading Synopsis
28909 -break-passcount @var{tracepoint-number} @var{passcount}
28912 Set the passcount for tracepoint @var{tracepoint-number} to
28913 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28914 is not a tracepoint, error is emitted. This corresponds to CLI
28915 command @samp{passcount}.
28917 @subheading The @code{-break-watch} Command
28918 @findex -break-watch
28920 @subsubheading Synopsis
28923 -break-watch [ -a | -r ]
28926 Create a watchpoint. With the @samp{-a} option it will create an
28927 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28928 read from or on a write to the memory location. With the @samp{-r}
28929 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28930 trigger only when the memory location is accessed for reading. Without
28931 either of the options, the watchpoint created is a regular watchpoint,
28932 i.e., it will trigger when the memory location is accessed for writing.
28933 @xref{Set Watchpoints, , Setting Watchpoints}.
28935 Note that @samp{-break-list} will report a single list of watchpoints and
28936 breakpoints inserted.
28938 @subsubheading @value{GDBN} Command
28940 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28943 @subsubheading Example
28945 Setting a watchpoint on a variable in the @code{main} function:
28950 ^done,wpt=@{number="2",exp="x"@}
28955 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28956 value=@{old="-268439212",new="55"@},
28957 frame=@{func="main",args=[],file="recursive2.c",
28958 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
28962 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28963 the program execution twice: first for the variable changing value, then
28964 for the watchpoint going out of scope.
28969 ^done,wpt=@{number="5",exp="C"@}
28974 *stopped,reason="watchpoint-trigger",
28975 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28976 frame=@{func="callee4",args=[],
28977 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28978 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
28979 arch="i386:x86_64"@}
28984 *stopped,reason="watchpoint-scope",wpnum="5",
28985 frame=@{func="callee3",args=[@{name="strarg",
28986 value="0x11940 \"A string argument.\""@}],
28987 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28988 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
28989 arch="i386:x86_64"@}
28993 Listing breakpoints and watchpoints, at different points in the program
28994 execution. Note that once the watchpoint goes out of scope, it is
29000 ^done,wpt=@{number="2",exp="C"@}
29003 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29004 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29005 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29006 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29007 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29008 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29009 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29010 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29011 addr="0x00010734",func="callee4",
29012 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29013 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29015 bkpt=@{number="2",type="watchpoint",disp="keep",
29016 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29021 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29022 value=@{old="-276895068",new="3"@},
29023 frame=@{func="callee4",args=[],
29024 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29025 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29026 arch="i386:x86_64"@}
29029 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29030 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29031 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29032 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29033 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29034 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29035 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29036 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29037 addr="0x00010734",func="callee4",
29038 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29039 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29041 bkpt=@{number="2",type="watchpoint",disp="keep",
29042 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29046 ^done,reason="watchpoint-scope",wpnum="2",
29047 frame=@{func="callee3",args=[@{name="strarg",
29048 value="0x11940 \"A string argument.\""@}],
29049 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29050 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29051 arch="i386:x86_64"@}
29054 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29061 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29062 addr="0x00010734",func="callee4",
29063 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29064 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29065 thread-groups=["i1"],times="1"@}]@}
29070 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29071 @node GDB/MI Catchpoint Commands
29072 @section @sc{gdb/mi} Catchpoint Commands
29074 This section documents @sc{gdb/mi} commands for manipulating
29078 * Shared Library GDB/MI Catchpoint Commands::
29079 * Ada Exception GDB/MI Catchpoint Commands::
29082 @node Shared Library GDB/MI Catchpoint Commands
29083 @subsection Shared Library @sc{gdb/mi} Catchpoints
29085 @subheading The @code{-catch-load} Command
29086 @findex -catch-load
29088 @subsubheading Synopsis
29091 -catch-load [ -t ] [ -d ] @var{regexp}
29094 Add a catchpoint for library load events. If the @samp{-t} option is used,
29095 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29096 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29097 in a disabled state. The @samp{regexp} argument is a regular
29098 expression used to match the name of the loaded library.
29101 @subsubheading @value{GDBN} Command
29103 The corresponding @value{GDBN} command is @samp{catch load}.
29105 @subsubheading Example
29108 -catch-load -t foo.so
29109 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29110 what="load of library matching foo.so",catch-type="load",times="0"@}
29115 @subheading The @code{-catch-unload} Command
29116 @findex -catch-unload
29118 @subsubheading Synopsis
29121 -catch-unload [ -t ] [ -d ] @var{regexp}
29124 Add a catchpoint for library unload events. If the @samp{-t} option is
29125 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29126 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29127 created in a disabled state. The @samp{regexp} argument is a regular
29128 expression used to match the name of the unloaded library.
29130 @subsubheading @value{GDBN} Command
29132 The corresponding @value{GDBN} command is @samp{catch unload}.
29134 @subsubheading Example
29137 -catch-unload -d bar.so
29138 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29139 what="load of library matching bar.so",catch-type="unload",times="0"@}
29143 @node Ada Exception GDB/MI Catchpoint Commands
29144 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29146 The following @sc{gdb/mi} commands can be used to create catchpoints
29147 that stop the execution when Ada exceptions are being raised.
29149 @subheading The @code{-catch-assert} Command
29150 @findex -catch-assert
29152 @subsubheading Synopsis
29155 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29158 Add a catchpoint for failed Ada assertions.
29160 The possible optional parameters for this command are:
29163 @item -c @var{condition}
29164 Make the catchpoint conditional on @var{condition}.
29166 Create a disabled catchpoint.
29168 Create a temporary catchpoint.
29171 @subsubheading @value{GDBN} Command
29173 The corresponding @value{GDBN} command is @samp{catch assert}.
29175 @subsubheading Example
29179 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29180 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29181 thread-groups=["i1"],times="0",
29182 original-location="__gnat_debug_raise_assert_failure"@}
29186 @subheading The @code{-catch-exception} Command
29187 @findex -catch-exception
29189 @subsubheading Synopsis
29192 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29196 Add a catchpoint stopping when Ada exceptions are raised.
29197 By default, the command stops the program when any Ada exception
29198 gets raised. But it is also possible, by using some of the
29199 optional parameters described below, to create more selective
29202 The possible optional parameters for this command are:
29205 @item -c @var{condition}
29206 Make the catchpoint conditional on @var{condition}.
29208 Create a disabled catchpoint.
29209 @item -e @var{exception-name}
29210 Only stop when @var{exception-name} is raised. This option cannot
29211 be used combined with @samp{-u}.
29213 Create a temporary catchpoint.
29215 Stop only when an unhandled exception gets raised. This option
29216 cannot be used combined with @samp{-e}.
29219 @subsubheading @value{GDBN} Command
29221 The corresponding @value{GDBN} commands are @samp{catch exception}
29222 and @samp{catch exception unhandled}.
29224 @subsubheading Example
29227 -catch-exception -e Program_Error
29228 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29229 enabled="y",addr="0x0000000000404874",
29230 what="`Program_Error' Ada exception", thread-groups=["i1"],
29231 times="0",original-location="__gnat_debug_raise_exception"@}
29235 @subheading The @code{-catch-handlers} Command
29236 @findex -catch-handlers
29238 @subsubheading Synopsis
29241 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29245 Add a catchpoint stopping when Ada exceptions are handled.
29246 By default, the command stops the program when any Ada exception
29247 gets handled. But it is also possible, by using some of the
29248 optional parameters described below, to create more selective
29251 The possible optional parameters for this command are:
29254 @item -c @var{condition}
29255 Make the catchpoint conditional on @var{condition}.
29257 Create a disabled catchpoint.
29258 @item -e @var{exception-name}
29259 Only stop when @var{exception-name} is handled.
29261 Create a temporary catchpoint.
29264 @subsubheading @value{GDBN} Command
29266 The corresponding @value{GDBN} command is @samp{catch handlers}.
29268 @subsubheading Example
29271 -catch-handlers -e Constraint_Error
29272 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29273 enabled="y",addr="0x0000000000402f68",
29274 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29275 times="0",original-location="__gnat_begin_handler"@}
29279 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29280 @node GDB/MI Program Context
29281 @section @sc{gdb/mi} Program Context
29283 @subheading The @code{-exec-arguments} Command
29284 @findex -exec-arguments
29287 @subsubheading Synopsis
29290 -exec-arguments @var{args}
29293 Set the inferior program arguments, to be used in the next
29296 @subsubheading @value{GDBN} Command
29298 The corresponding @value{GDBN} command is @samp{set args}.
29300 @subsubheading Example
29304 -exec-arguments -v word
29311 @subheading The @code{-exec-show-arguments} Command
29312 @findex -exec-show-arguments
29314 @subsubheading Synopsis
29317 -exec-show-arguments
29320 Print the arguments of the program.
29322 @subsubheading @value{GDBN} Command
29324 The corresponding @value{GDBN} command is @samp{show args}.
29326 @subsubheading Example
29331 @subheading The @code{-environment-cd} Command
29332 @findex -environment-cd
29334 @subsubheading Synopsis
29337 -environment-cd @var{pathdir}
29340 Set @value{GDBN}'s working directory.
29342 @subsubheading @value{GDBN} Command
29344 The corresponding @value{GDBN} command is @samp{cd}.
29346 @subsubheading Example
29350 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29356 @subheading The @code{-environment-directory} Command
29357 @findex -environment-directory
29359 @subsubheading Synopsis
29362 -environment-directory [ -r ] [ @var{pathdir} ]+
29365 Add directories @var{pathdir} to beginning of search path for source files.
29366 If the @samp{-r} option is used, the search path is reset to the default
29367 search path. If directories @var{pathdir} are supplied in addition to the
29368 @samp{-r} option, the search path is first reset and then addition
29370 Multiple directories may be specified, separated by blanks. Specifying
29371 multiple directories in a single command
29372 results in the directories added to the beginning of the
29373 search path in the same order they were presented in the command.
29374 If blanks are needed as
29375 part of a directory name, double-quotes should be used around
29376 the name. In the command output, the path will show up separated
29377 by the system directory-separator character. The directory-separator
29378 character must not be used
29379 in any directory name.
29380 If no directories are specified, the current search path is displayed.
29382 @subsubheading @value{GDBN} Command
29384 The corresponding @value{GDBN} command is @samp{dir}.
29386 @subsubheading Example
29390 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29391 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29393 -environment-directory ""
29394 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29396 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29397 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29399 -environment-directory -r
29400 ^done,source-path="$cdir:$cwd"
29405 @subheading The @code{-environment-path} Command
29406 @findex -environment-path
29408 @subsubheading Synopsis
29411 -environment-path [ -r ] [ @var{pathdir} ]+
29414 Add directories @var{pathdir} to beginning of search path for object files.
29415 If the @samp{-r} option is used, the search path is reset to the original
29416 search path that existed at gdb start-up. If directories @var{pathdir} are
29417 supplied in addition to the
29418 @samp{-r} option, the search path is first reset and then addition
29420 Multiple directories may be specified, separated by blanks. Specifying
29421 multiple directories in a single command
29422 results in the directories added to the beginning of the
29423 search path in the same order they were presented in the command.
29424 If blanks are needed as
29425 part of a directory name, double-quotes should be used around
29426 the name. In the command output, the path will show up separated
29427 by the system directory-separator character. The directory-separator
29428 character must not be used
29429 in any directory name.
29430 If no directories are specified, the current path is displayed.
29433 @subsubheading @value{GDBN} Command
29435 The corresponding @value{GDBN} command is @samp{path}.
29437 @subsubheading Example
29442 ^done,path="/usr/bin"
29444 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29445 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29447 -environment-path -r /usr/local/bin
29448 ^done,path="/usr/local/bin:/usr/bin"
29453 @subheading The @code{-environment-pwd} Command
29454 @findex -environment-pwd
29456 @subsubheading Synopsis
29462 Show the current working directory.
29464 @subsubheading @value{GDBN} Command
29466 The corresponding @value{GDBN} command is @samp{pwd}.
29468 @subsubheading Example
29473 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29477 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29478 @node GDB/MI Thread Commands
29479 @section @sc{gdb/mi} Thread Commands
29482 @subheading The @code{-thread-info} Command
29483 @findex -thread-info
29485 @subsubheading Synopsis
29488 -thread-info [ @var{thread-id} ]
29491 Reports information about either a specific thread, if the
29492 @var{thread-id} parameter is present, or about all threads.
29493 @var{thread-id} is the thread's global thread ID. When printing
29494 information about all threads, also reports the global ID of the
29497 @subsubheading @value{GDBN} Command
29499 The @samp{info thread} command prints the same information
29502 @subsubheading Result
29504 The result contains the following attributes:
29508 A list of threads. The format of the elements of the list is described in
29509 @ref{GDB/MI Thread Information}.
29511 @item current-thread-id
29512 The global id of the currently selected thread. This field is omitted if there
29513 is no selected thread (for example, when the selected inferior is not running,
29514 and therefore has no threads) or if a @var{thread-id} argument was passed to
29519 @subsubheading Example
29524 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29525 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29526 args=[]@},state="running"@},
29527 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29528 frame=@{level="0",addr="0x0804891f",func="foo",
29529 args=[@{name="i",value="10"@}],
29530 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29531 state="running"@}],
29532 current-thread-id="1"
29536 @subheading The @code{-thread-list-ids} Command
29537 @findex -thread-list-ids
29539 @subsubheading Synopsis
29545 Produces a list of the currently known global @value{GDBN} thread ids.
29546 At the end of the list it also prints the total number of such
29549 This command is retained for historical reasons, the
29550 @code{-thread-info} command should be used instead.
29552 @subsubheading @value{GDBN} Command
29554 Part of @samp{info threads} supplies the same information.
29556 @subsubheading Example
29561 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29562 current-thread-id="1",number-of-threads="3"
29567 @subheading The @code{-thread-select} Command
29568 @findex -thread-select
29570 @subsubheading Synopsis
29573 -thread-select @var{thread-id}
29576 Make thread with global thread number @var{thread-id} the current
29577 thread. It prints the number of the new current thread, and the
29578 topmost frame for that thread.
29580 This command is deprecated in favor of explicitly using the
29581 @samp{--thread} option to each command.
29583 @subsubheading @value{GDBN} Command
29585 The corresponding @value{GDBN} command is @samp{thread}.
29587 @subsubheading Example
29594 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29595 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29599 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29600 number-of-threads="3"
29603 ^done,new-thread-id="3",
29604 frame=@{level="0",func="vprintf",
29605 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29606 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29611 @node GDB/MI Ada Tasking Commands
29612 @section @sc{gdb/mi} Ada Tasking Commands
29614 @subheading The @code{-ada-task-info} Command
29615 @findex -ada-task-info
29617 @subsubheading Synopsis
29620 -ada-task-info [ @var{task-id} ]
29623 Reports information about either a specific Ada task, if the
29624 @var{task-id} parameter is present, or about all Ada tasks.
29626 @subsubheading @value{GDBN} Command
29628 The @samp{info tasks} command prints the same information
29629 about all Ada tasks (@pxref{Ada Tasks}).
29631 @subsubheading Result
29633 The result is a table of Ada tasks. The following columns are
29634 defined for each Ada task:
29638 This field exists only for the current thread. It has the value @samp{*}.
29641 The identifier that @value{GDBN} uses to refer to the Ada task.
29644 The identifier that the target uses to refer to the Ada task.
29647 The global thread identifier of the thread corresponding to the Ada
29650 This field should always exist, as Ada tasks are always implemented
29651 on top of a thread. But if @value{GDBN} cannot find this corresponding
29652 thread for any reason, the field is omitted.
29655 This field exists only when the task was created by another task.
29656 In this case, it provides the ID of the parent task.
29659 The base priority of the task.
29662 The current state of the task. For a detailed description of the
29663 possible states, see @ref{Ada Tasks}.
29666 The name of the task.
29670 @subsubheading Example
29674 ^done,tasks=@{nr_rows="3",nr_cols="8",
29675 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29676 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29677 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29678 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29679 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29680 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29681 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29682 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29683 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29684 state="Child Termination Wait",name="main_task"@}]@}
29688 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29689 @node GDB/MI Program Execution
29690 @section @sc{gdb/mi} Program Execution
29692 These are the asynchronous commands which generate the out-of-band
29693 record @samp{*stopped}. Currently @value{GDBN} only really executes
29694 asynchronously with remote targets and this interaction is mimicked in
29697 @subheading The @code{-exec-continue} Command
29698 @findex -exec-continue
29700 @subsubheading Synopsis
29703 -exec-continue [--reverse] [--all|--thread-group N]
29706 Resumes the execution of the inferior program, which will continue
29707 to execute until it reaches a debugger stop event. If the
29708 @samp{--reverse} option is specified, execution resumes in reverse until
29709 it reaches a stop event. Stop events may include
29712 breakpoints or watchpoints
29714 signals or exceptions
29716 the end of the process (or its beginning under @samp{--reverse})
29718 the end or beginning of a replay log if one is being used.
29720 In all-stop mode (@pxref{All-Stop
29721 Mode}), may resume only one thread, or all threads, depending on the
29722 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29723 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29724 ignored in all-stop mode. If the @samp{--thread-group} options is
29725 specified, then all threads in that thread group are resumed.
29727 @subsubheading @value{GDBN} Command
29729 The corresponding @value{GDBN} corresponding is @samp{continue}.
29731 @subsubheading Example
29738 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29739 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29740 line="13",arch="i386:x86_64"@}
29745 @subheading The @code{-exec-finish} Command
29746 @findex -exec-finish
29748 @subsubheading Synopsis
29751 -exec-finish [--reverse]
29754 Resumes the execution of the inferior program until the current
29755 function is exited. Displays the results returned by the function.
29756 If the @samp{--reverse} option is specified, resumes the reverse
29757 execution of the inferior program until the point where current
29758 function was called.
29760 @subsubheading @value{GDBN} Command
29762 The corresponding @value{GDBN} command is @samp{finish}.
29764 @subsubheading Example
29766 Function returning @code{void}.
29773 *stopped,reason="function-finished",frame=@{func="main",args=[],
29774 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
29778 Function returning other than @code{void}. The name of the internal
29779 @value{GDBN} variable storing the result is printed, together with the
29786 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29787 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29788 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
29789 arch="i386:x86_64"@},
29790 gdb-result-var="$1",return-value="0"
29795 @subheading The @code{-exec-interrupt} Command
29796 @findex -exec-interrupt
29798 @subsubheading Synopsis
29801 -exec-interrupt [--all|--thread-group N]
29804 Interrupts the background execution of the target. Note how the token
29805 associated with the stop message is the one for the execution command
29806 that has been interrupted. The token for the interrupt itself only
29807 appears in the @samp{^done} output. If the user is trying to
29808 interrupt a non-running program, an error message will be printed.
29810 Note that when asynchronous execution is enabled, this command is
29811 asynchronous just like other execution commands. That is, first the
29812 @samp{^done} response will be printed, and the target stop will be
29813 reported after that using the @samp{*stopped} notification.
29815 In non-stop mode, only the context thread is interrupted by default.
29816 All threads (in all inferiors) will be interrupted if the
29817 @samp{--all} option is specified. If the @samp{--thread-group}
29818 option is specified, all threads in that group will be interrupted.
29820 @subsubheading @value{GDBN} Command
29822 The corresponding @value{GDBN} command is @samp{interrupt}.
29824 @subsubheading Example
29835 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29836 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29837 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
29842 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29846 @subheading The @code{-exec-jump} Command
29849 @subsubheading Synopsis
29852 -exec-jump @var{location}
29855 Resumes execution of the inferior program at the location specified by
29856 parameter. @xref{Specify Location}, for a description of the
29857 different forms of @var{location}.
29859 @subsubheading @value{GDBN} Command
29861 The corresponding @value{GDBN} command is @samp{jump}.
29863 @subsubheading Example
29866 -exec-jump foo.c:10
29867 *running,thread-id="all"
29872 @subheading The @code{-exec-next} Command
29875 @subsubheading Synopsis
29878 -exec-next [--reverse]
29881 Resumes execution of the inferior program, stopping when the beginning
29882 of the next source line is reached.
29884 If the @samp{--reverse} option is specified, resumes reverse execution
29885 of the inferior program, stopping at the beginning of the previous
29886 source line. If you issue this command on the first line of a
29887 function, it will take you back to the caller of that function, to the
29888 source line where the function was called.
29891 @subsubheading @value{GDBN} Command
29893 The corresponding @value{GDBN} command is @samp{next}.
29895 @subsubheading Example
29901 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29906 @subheading The @code{-exec-next-instruction} Command
29907 @findex -exec-next-instruction
29909 @subsubheading Synopsis
29912 -exec-next-instruction [--reverse]
29915 Executes one machine instruction. If the instruction is a function
29916 call, continues until the function returns. If the program stops at an
29917 instruction in the middle of a source line, the address will be
29920 If the @samp{--reverse} option is specified, resumes reverse execution
29921 of the inferior program, stopping at the previous instruction. If the
29922 previously executed instruction was a return from another function,
29923 it will continue to execute in reverse until the call to that function
29924 (from the current stack frame) is reached.
29926 @subsubheading @value{GDBN} Command
29928 The corresponding @value{GDBN} command is @samp{nexti}.
29930 @subsubheading Example
29934 -exec-next-instruction
29938 *stopped,reason="end-stepping-range",
29939 addr="0x000100d4",line="5",file="hello.c"
29944 @subheading The @code{-exec-return} Command
29945 @findex -exec-return
29947 @subsubheading Synopsis
29953 Makes current function return immediately. Doesn't execute the inferior.
29954 Displays the new current frame.
29956 @subsubheading @value{GDBN} Command
29958 The corresponding @value{GDBN} command is @samp{return}.
29960 @subsubheading Example
29964 200-break-insert callee4
29965 200^done,bkpt=@{number="1",addr="0x00010734",
29966 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29971 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29972 frame=@{func="callee4",args=[],
29973 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29974 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29975 arch="i386:x86_64"@}
29981 111^done,frame=@{level="0",func="callee3",
29982 args=[@{name="strarg",
29983 value="0x11940 \"A string argument.\""@}],
29984 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29985 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29986 arch="i386:x86_64"@}
29991 @subheading The @code{-exec-run} Command
29994 @subsubheading Synopsis
29997 -exec-run [ --all | --thread-group N ] [ --start ]
30000 Starts execution of the inferior from the beginning. The inferior
30001 executes until either a breakpoint is encountered or the program
30002 exits. In the latter case the output will include an exit code, if
30003 the program has exited exceptionally.
30005 When neither the @samp{--all} nor the @samp{--thread-group} option
30006 is specified, the current inferior is started. If the
30007 @samp{--thread-group} option is specified, it should refer to a thread
30008 group of type @samp{process}, and that thread group will be started.
30009 If the @samp{--all} option is specified, then all inferiors will be started.
30011 Using the @samp{--start} option instructs the debugger to stop
30012 the execution at the start of the inferior's main subprogram,
30013 following the same behavior as the @code{start} command
30014 (@pxref{Starting}).
30016 @subsubheading @value{GDBN} Command
30018 The corresponding @value{GDBN} command is @samp{run}.
30020 @subsubheading Examples
30025 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30030 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30031 frame=@{func="main",args=[],file="recursive2.c",
30032 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30037 Program exited normally:
30045 *stopped,reason="exited-normally"
30050 Program exited exceptionally:
30058 *stopped,reason="exited",exit-code="01"
30062 Another way the program can terminate is if it receives a signal such as
30063 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30067 *stopped,reason="exited-signalled",signal-name="SIGINT",
30068 signal-meaning="Interrupt"
30072 @c @subheading -exec-signal
30075 @subheading The @code{-exec-step} Command
30078 @subsubheading Synopsis
30081 -exec-step [--reverse]
30084 Resumes execution of the inferior program, stopping when the beginning
30085 of the next source line is reached, if the next source line is not a
30086 function call. If it is, stop at the first instruction of the called
30087 function. If the @samp{--reverse} option is specified, resumes reverse
30088 execution of the inferior program, stopping at the beginning of the
30089 previously executed source line.
30091 @subsubheading @value{GDBN} Command
30093 The corresponding @value{GDBN} command is @samp{step}.
30095 @subsubheading Example
30097 Stepping into a function:
30103 *stopped,reason="end-stepping-range",
30104 frame=@{func="foo",args=[@{name="a",value="10"@},
30105 @{name="b",value="0"@}],file="recursive2.c",
30106 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30116 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30121 @subheading The @code{-exec-step-instruction} Command
30122 @findex -exec-step-instruction
30124 @subsubheading Synopsis
30127 -exec-step-instruction [--reverse]
30130 Resumes the inferior which executes one machine instruction. If the
30131 @samp{--reverse} option is specified, resumes reverse execution of the
30132 inferior program, stopping at the previously executed instruction.
30133 The output, once @value{GDBN} has stopped, will vary depending on
30134 whether we have stopped in the middle of a source line or not. In the
30135 former case, the address at which the program stopped will be printed
30138 @subsubheading @value{GDBN} Command
30140 The corresponding @value{GDBN} command is @samp{stepi}.
30142 @subsubheading Example
30146 -exec-step-instruction
30150 *stopped,reason="end-stepping-range",
30151 frame=@{func="foo",args=[],file="try.c",
30152 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30154 -exec-step-instruction
30158 *stopped,reason="end-stepping-range",
30159 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30160 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30165 @subheading The @code{-exec-until} Command
30166 @findex -exec-until
30168 @subsubheading Synopsis
30171 -exec-until [ @var{location} ]
30174 Executes the inferior until the @var{location} specified in the
30175 argument is reached. If there is no argument, the inferior executes
30176 until a source line greater than the current one is reached. The
30177 reason for stopping in this case will be @samp{location-reached}.
30179 @subsubheading @value{GDBN} Command
30181 The corresponding @value{GDBN} command is @samp{until}.
30183 @subsubheading Example
30187 -exec-until recursive2.c:6
30191 *stopped,reason="location-reached",frame=@{func="main",args=[],
30192 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30193 arch="i386:x86_64"@}
30198 @subheading -file-clear
30199 Is this going away????
30202 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30203 @node GDB/MI Stack Manipulation
30204 @section @sc{gdb/mi} Stack Manipulation Commands
30206 @subheading The @code{-enable-frame-filters} Command
30207 @findex -enable-frame-filters
30210 -enable-frame-filters
30213 @value{GDBN} allows Python-based frame filters to affect the output of
30214 the MI commands relating to stack traces. As there is no way to
30215 implement this in a fully backward-compatible way, a front end must
30216 request that this functionality be enabled.
30218 Once enabled, this feature cannot be disabled.
30220 Note that if Python support has not been compiled into @value{GDBN},
30221 this command will still succeed (and do nothing).
30223 @subheading The @code{-stack-info-frame} Command
30224 @findex -stack-info-frame
30226 @subsubheading Synopsis
30232 Get info on the selected frame.
30234 @subsubheading @value{GDBN} Command
30236 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30237 (without arguments).
30239 @subsubheading Example
30244 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30245 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30246 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30247 arch="i386:x86_64"@}
30251 @subheading The @code{-stack-info-depth} Command
30252 @findex -stack-info-depth
30254 @subsubheading Synopsis
30257 -stack-info-depth [ @var{max-depth} ]
30260 Return the depth of the stack. If the integer argument @var{max-depth}
30261 is specified, do not count beyond @var{max-depth} frames.
30263 @subsubheading @value{GDBN} Command
30265 There's no equivalent @value{GDBN} command.
30267 @subsubheading Example
30269 For a stack with frame levels 0 through 11:
30276 -stack-info-depth 4
30279 -stack-info-depth 12
30282 -stack-info-depth 11
30285 -stack-info-depth 13
30290 @anchor{-stack-list-arguments}
30291 @subheading The @code{-stack-list-arguments} Command
30292 @findex -stack-list-arguments
30294 @subsubheading Synopsis
30297 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30298 [ @var{low-frame} @var{high-frame} ]
30301 Display a list of the arguments for the frames between @var{low-frame}
30302 and @var{high-frame} (inclusive). If @var{low-frame} and
30303 @var{high-frame} are not provided, list the arguments for the whole
30304 call stack. If the two arguments are equal, show the single frame
30305 at the corresponding level. It is an error if @var{low-frame} is
30306 larger than the actual number of frames. On the other hand,
30307 @var{high-frame} may be larger than the actual number of frames, in
30308 which case only existing frames will be returned.
30310 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30311 the variables; if it is 1 or @code{--all-values}, print also their
30312 values; and if it is 2 or @code{--simple-values}, print the name,
30313 type and value for simple data types, and the name and type for arrays,
30314 structures and unions. If the option @code{--no-frame-filters} is
30315 supplied, then Python frame filters will not be executed.
30317 If the @code{--skip-unavailable} option is specified, arguments that
30318 are not available are not listed. Partially available arguments
30319 are still displayed, however.
30321 Use of this command to obtain arguments in a single frame is
30322 deprecated in favor of the @samp{-stack-list-variables} command.
30324 @subsubheading @value{GDBN} Command
30326 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30327 @samp{gdb_get_args} command which partially overlaps with the
30328 functionality of @samp{-stack-list-arguments}.
30330 @subsubheading Example
30337 frame=@{level="0",addr="0x00010734",func="callee4",
30338 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30339 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30340 arch="i386:x86_64"@},
30341 frame=@{level="1",addr="0x0001076c",func="callee3",
30342 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30343 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30344 arch="i386:x86_64"@},
30345 frame=@{level="2",addr="0x0001078c",func="callee2",
30346 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30347 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30348 arch="i386:x86_64"@},
30349 frame=@{level="3",addr="0x000107b4",func="callee1",
30350 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30351 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30352 arch="i386:x86_64"@},
30353 frame=@{level="4",addr="0x000107e0",func="main",
30354 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30355 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30356 arch="i386:x86_64"@}]
30358 -stack-list-arguments 0
30361 frame=@{level="0",args=[]@},
30362 frame=@{level="1",args=[name="strarg"]@},
30363 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30364 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30365 frame=@{level="4",args=[]@}]
30367 -stack-list-arguments 1
30370 frame=@{level="0",args=[]@},
30372 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30373 frame=@{level="2",args=[
30374 @{name="intarg",value="2"@},
30375 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30376 @{frame=@{level="3",args=[
30377 @{name="intarg",value="2"@},
30378 @{name="strarg",value="0x11940 \"A string argument.\""@},
30379 @{name="fltarg",value="3.5"@}]@},
30380 frame=@{level="4",args=[]@}]
30382 -stack-list-arguments 0 2 2
30383 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30385 -stack-list-arguments 1 2 2
30386 ^done,stack-args=[frame=@{level="2",
30387 args=[@{name="intarg",value="2"@},
30388 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30392 @c @subheading -stack-list-exception-handlers
30395 @anchor{-stack-list-frames}
30396 @subheading The @code{-stack-list-frames} Command
30397 @findex -stack-list-frames
30399 @subsubheading Synopsis
30402 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30405 List the frames currently on the stack. For each frame it displays the
30410 The frame number, 0 being the topmost frame, i.e., the innermost function.
30412 The @code{$pc} value for that frame.
30416 File name of the source file where the function lives.
30417 @item @var{fullname}
30418 The full file name of the source file where the function lives.
30420 Line number corresponding to the @code{$pc}.
30422 The shared library where this function is defined. This is only given
30423 if the frame's function is not known.
30425 Frame's architecture.
30428 If invoked without arguments, this command prints a backtrace for the
30429 whole stack. If given two integer arguments, it shows the frames whose
30430 levels are between the two arguments (inclusive). If the two arguments
30431 are equal, it shows the single frame at the corresponding level. It is
30432 an error if @var{low-frame} is larger than the actual number of
30433 frames. On the other hand, @var{high-frame} may be larger than the
30434 actual number of frames, in which case only existing frames will be
30435 returned. If the option @code{--no-frame-filters} is supplied, then
30436 Python frame filters will not be executed.
30438 @subsubheading @value{GDBN} Command
30440 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30442 @subsubheading Example
30444 Full stack backtrace:
30450 [frame=@{level="0",addr="0x0001076c",func="foo",
30451 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30452 arch="i386:x86_64"@},
30453 frame=@{level="1",addr="0x000107a4",func="foo",
30454 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30455 arch="i386:x86_64"@},
30456 frame=@{level="2",addr="0x000107a4",func="foo",
30457 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30458 arch="i386:x86_64"@},
30459 frame=@{level="3",addr="0x000107a4",func="foo",
30460 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30461 arch="i386:x86_64"@},
30462 frame=@{level="4",addr="0x000107a4",func="foo",
30463 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30464 arch="i386:x86_64"@},
30465 frame=@{level="5",addr="0x000107a4",func="foo",
30466 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30467 arch="i386:x86_64"@},
30468 frame=@{level="6",addr="0x000107a4",func="foo",
30469 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30470 arch="i386:x86_64"@},
30471 frame=@{level="7",addr="0x000107a4",func="foo",
30472 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30473 arch="i386:x86_64"@},
30474 frame=@{level="8",addr="0x000107a4",func="foo",
30475 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30476 arch="i386:x86_64"@},
30477 frame=@{level="9",addr="0x000107a4",func="foo",
30478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30479 arch="i386:x86_64"@},
30480 frame=@{level="10",addr="0x000107a4",func="foo",
30481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30482 arch="i386:x86_64"@},
30483 frame=@{level="11",addr="0x00010738",func="main",
30484 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30485 arch="i386:x86_64"@}]
30489 Show frames between @var{low_frame} and @var{high_frame}:
30493 -stack-list-frames 3 5
30495 [frame=@{level="3",addr="0x000107a4",func="foo",
30496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30497 arch="i386:x86_64"@},
30498 frame=@{level="4",addr="0x000107a4",func="foo",
30499 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30500 arch="i386:x86_64"@},
30501 frame=@{level="5",addr="0x000107a4",func="foo",
30502 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30503 arch="i386:x86_64"@}]
30507 Show a single frame:
30511 -stack-list-frames 3 3
30513 [frame=@{level="3",addr="0x000107a4",func="foo",
30514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30515 arch="i386:x86_64"@}]
30520 @subheading The @code{-stack-list-locals} Command
30521 @findex -stack-list-locals
30522 @anchor{-stack-list-locals}
30524 @subsubheading Synopsis
30527 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30530 Display the local variable names for the selected frame. If
30531 @var{print-values} is 0 or @code{--no-values}, print only the names of
30532 the variables; if it is 1 or @code{--all-values}, print also their
30533 values; and if it is 2 or @code{--simple-values}, print the name,
30534 type and value for simple data types, and the name and type for arrays,
30535 structures and unions. In this last case, a frontend can immediately
30536 display the value of simple data types and create variable objects for
30537 other data types when the user wishes to explore their values in
30538 more detail. If the option @code{--no-frame-filters} is supplied, then
30539 Python frame filters will not be executed.
30541 If the @code{--skip-unavailable} option is specified, local variables
30542 that are not available are not listed. Partially available local
30543 variables are still displayed, however.
30545 This command is deprecated in favor of the
30546 @samp{-stack-list-variables} command.
30548 @subsubheading @value{GDBN} Command
30550 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30552 @subsubheading Example
30556 -stack-list-locals 0
30557 ^done,locals=[name="A",name="B",name="C"]
30559 -stack-list-locals --all-values
30560 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30561 @{name="C",value="@{1, 2, 3@}"@}]
30562 -stack-list-locals --simple-values
30563 ^done,locals=[@{name="A",type="int",value="1"@},
30564 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30568 @anchor{-stack-list-variables}
30569 @subheading The @code{-stack-list-variables} Command
30570 @findex -stack-list-variables
30572 @subsubheading Synopsis
30575 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30578 Display the names of local variables and function arguments for the selected frame. If
30579 @var{print-values} is 0 or @code{--no-values}, print only the names of
30580 the variables; if it is 1 or @code{--all-values}, print also their
30581 values; and if it is 2 or @code{--simple-values}, print the name,
30582 type and value for simple data types, and the name and type for arrays,
30583 structures and unions. If the option @code{--no-frame-filters} is
30584 supplied, then Python frame filters will not be executed.
30586 If the @code{--skip-unavailable} option is specified, local variables
30587 and arguments that are not available are not listed. Partially
30588 available arguments and local variables are still displayed, however.
30590 @subsubheading Example
30594 -stack-list-variables --thread 1 --frame 0 --all-values
30595 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30600 @subheading The @code{-stack-select-frame} Command
30601 @findex -stack-select-frame
30603 @subsubheading Synopsis
30606 -stack-select-frame @var{framenum}
30609 Change the selected frame. Select a different frame @var{framenum} on
30612 This command in deprecated in favor of passing the @samp{--frame}
30613 option to every command.
30615 @subsubheading @value{GDBN} Command
30617 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30618 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30620 @subsubheading Example
30624 -stack-select-frame 2
30629 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30630 @node GDB/MI Variable Objects
30631 @section @sc{gdb/mi} Variable Objects
30635 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30637 For the implementation of a variable debugger window (locals, watched
30638 expressions, etc.), we are proposing the adaptation of the existing code
30639 used by @code{Insight}.
30641 The two main reasons for that are:
30645 It has been proven in practice (it is already on its second generation).
30648 It will shorten development time (needless to say how important it is
30652 The original interface was designed to be used by Tcl code, so it was
30653 slightly changed so it could be used through @sc{gdb/mi}. This section
30654 describes the @sc{gdb/mi} operations that will be available and gives some
30655 hints about their use.
30657 @emph{Note}: In addition to the set of operations described here, we
30658 expect the @sc{gui} implementation of a variable window to require, at
30659 least, the following operations:
30662 @item @code{-gdb-show} @code{output-radix}
30663 @item @code{-stack-list-arguments}
30664 @item @code{-stack-list-locals}
30665 @item @code{-stack-select-frame}
30670 @subheading Introduction to Variable Objects
30672 @cindex variable objects in @sc{gdb/mi}
30674 Variable objects are "object-oriented" MI interface for examining and
30675 changing values of expressions. Unlike some other MI interfaces that
30676 work with expressions, variable objects are specifically designed for
30677 simple and efficient presentation in the frontend. A variable object
30678 is identified by string name. When a variable object is created, the
30679 frontend specifies the expression for that variable object. The
30680 expression can be a simple variable, or it can be an arbitrary complex
30681 expression, and can even involve CPU registers. After creating a
30682 variable object, the frontend can invoke other variable object
30683 operations---for example to obtain or change the value of a variable
30684 object, or to change display format.
30686 Variable objects have hierarchical tree structure. Any variable object
30687 that corresponds to a composite type, such as structure in C, has
30688 a number of child variable objects, for example corresponding to each
30689 element of a structure. A child variable object can itself have
30690 children, recursively. Recursion ends when we reach
30691 leaf variable objects, which always have built-in types. Child variable
30692 objects are created only by explicit request, so if a frontend
30693 is not interested in the children of a particular variable object, no
30694 child will be created.
30696 For a leaf variable object it is possible to obtain its value as a
30697 string, or set the value from a string. String value can be also
30698 obtained for a non-leaf variable object, but it's generally a string
30699 that only indicates the type of the object, and does not list its
30700 contents. Assignment to a non-leaf variable object is not allowed.
30702 A frontend does not need to read the values of all variable objects each time
30703 the program stops. Instead, MI provides an update command that lists all
30704 variable objects whose values has changed since the last update
30705 operation. This considerably reduces the amount of data that must
30706 be transferred to the frontend. As noted above, children variable
30707 objects are created on demand, and only leaf variable objects have a
30708 real value. As result, gdb will read target memory only for leaf
30709 variables that frontend has created.
30711 The automatic update is not always desirable. For example, a frontend
30712 might want to keep a value of some expression for future reference,
30713 and never update it. For another example, fetching memory is
30714 relatively slow for embedded targets, so a frontend might want
30715 to disable automatic update for the variables that are either not
30716 visible on the screen, or ``closed''. This is possible using so
30717 called ``frozen variable objects''. Such variable objects are never
30718 implicitly updated.
30720 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30721 fixed variable object, the expression is parsed when the variable
30722 object is created, including associating identifiers to specific
30723 variables. The meaning of expression never changes. For a floating
30724 variable object the values of variables whose names appear in the
30725 expressions are re-evaluated every time in the context of the current
30726 frame. Consider this example:
30731 struct work_state state;
30738 If a fixed variable object for the @code{state} variable is created in
30739 this function, and we enter the recursive call, the variable
30740 object will report the value of @code{state} in the top-level
30741 @code{do_work} invocation. On the other hand, a floating variable
30742 object will report the value of @code{state} in the current frame.
30744 If an expression specified when creating a fixed variable object
30745 refers to a local variable, the variable object becomes bound to the
30746 thread and frame in which the variable object is created. When such
30747 variable object is updated, @value{GDBN} makes sure that the
30748 thread/frame combination the variable object is bound to still exists,
30749 and re-evaluates the variable object in context of that thread/frame.
30751 The following is the complete set of @sc{gdb/mi} operations defined to
30752 access this functionality:
30754 @multitable @columnfractions .4 .6
30755 @item @strong{Operation}
30756 @tab @strong{Description}
30758 @item @code{-enable-pretty-printing}
30759 @tab enable Python-based pretty-printing
30760 @item @code{-var-create}
30761 @tab create a variable object
30762 @item @code{-var-delete}
30763 @tab delete the variable object and/or its children
30764 @item @code{-var-set-format}
30765 @tab set the display format of this variable
30766 @item @code{-var-show-format}
30767 @tab show the display format of this variable
30768 @item @code{-var-info-num-children}
30769 @tab tells how many children this object has
30770 @item @code{-var-list-children}
30771 @tab return a list of the object's children
30772 @item @code{-var-info-type}
30773 @tab show the type of this variable object
30774 @item @code{-var-info-expression}
30775 @tab print parent-relative expression that this variable object represents
30776 @item @code{-var-info-path-expression}
30777 @tab print full expression that this variable object represents
30778 @item @code{-var-show-attributes}
30779 @tab is this variable editable? does it exist here?
30780 @item @code{-var-evaluate-expression}
30781 @tab get the value of this variable
30782 @item @code{-var-assign}
30783 @tab set the value of this variable
30784 @item @code{-var-update}
30785 @tab update the variable and its children
30786 @item @code{-var-set-frozen}
30787 @tab set frozeness attribute
30788 @item @code{-var-set-update-range}
30789 @tab set range of children to display on update
30792 In the next subsection we describe each operation in detail and suggest
30793 how it can be used.
30795 @subheading Description And Use of Operations on Variable Objects
30797 @subheading The @code{-enable-pretty-printing} Command
30798 @findex -enable-pretty-printing
30801 -enable-pretty-printing
30804 @value{GDBN} allows Python-based visualizers to affect the output of the
30805 MI variable object commands. However, because there was no way to
30806 implement this in a fully backward-compatible way, a front end must
30807 request that this functionality be enabled.
30809 Once enabled, this feature cannot be disabled.
30811 Note that if Python support has not been compiled into @value{GDBN},
30812 this command will still succeed (and do nothing).
30814 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30815 may work differently in future versions of @value{GDBN}.
30817 @subheading The @code{-var-create} Command
30818 @findex -var-create
30820 @subsubheading Synopsis
30823 -var-create @{@var{name} | "-"@}
30824 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30827 This operation creates a variable object, which allows the monitoring of
30828 a variable, the result of an expression, a memory cell or a CPU
30831 The @var{name} parameter is the string by which the object can be
30832 referenced. It must be unique. If @samp{-} is specified, the varobj
30833 system will generate a string ``varNNNNNN'' automatically. It will be
30834 unique provided that one does not specify @var{name} of that format.
30835 The command fails if a duplicate name is found.
30837 The frame under which the expression should be evaluated can be
30838 specified by @var{frame-addr}. A @samp{*} indicates that the current
30839 frame should be used. A @samp{@@} indicates that a floating variable
30840 object must be created.
30842 @var{expression} is any expression valid on the current language set (must not
30843 begin with a @samp{*}), or one of the following:
30847 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30850 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30853 @samp{$@var{regname}} --- a CPU register name
30856 @cindex dynamic varobj
30857 A varobj's contents may be provided by a Python-based pretty-printer. In this
30858 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30859 have slightly different semantics in some cases. If the
30860 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30861 will never create a dynamic varobj. This ensures backward
30862 compatibility for existing clients.
30864 @subsubheading Result
30866 This operation returns attributes of the newly-created varobj. These
30871 The name of the varobj.
30874 The number of children of the varobj. This number is not necessarily
30875 reliable for a dynamic varobj. Instead, you must examine the
30876 @samp{has_more} attribute.
30879 The varobj's scalar value. For a varobj whose type is some sort of
30880 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30881 will not be interesting.
30884 The varobj's type. This is a string representation of the type, as
30885 would be printed by the @value{GDBN} CLI. If @samp{print object}
30886 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30887 @emph{actual} (derived) type of the object is shown rather than the
30888 @emph{declared} one.
30891 If a variable object is bound to a specific thread, then this is the
30892 thread's global identifier.
30895 For a dynamic varobj, this indicates whether there appear to be any
30896 children available. For a non-dynamic varobj, this will be 0.
30899 This attribute will be present and have the value @samp{1} if the
30900 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30901 then this attribute will not be present.
30904 A dynamic varobj can supply a display hint to the front end. The
30905 value comes directly from the Python pretty-printer object's
30906 @code{display_hint} method. @xref{Pretty Printing API}.
30909 Typical output will look like this:
30912 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30913 has_more="@var{has_more}"
30917 @subheading The @code{-var-delete} Command
30918 @findex -var-delete
30920 @subsubheading Synopsis
30923 -var-delete [ -c ] @var{name}
30926 Deletes a previously created variable object and all of its children.
30927 With the @samp{-c} option, just deletes the children.
30929 Returns an error if the object @var{name} is not found.
30932 @subheading The @code{-var-set-format} Command
30933 @findex -var-set-format
30935 @subsubheading Synopsis
30938 -var-set-format @var{name} @var{format-spec}
30941 Sets the output format for the value of the object @var{name} to be
30944 @anchor{-var-set-format}
30945 The syntax for the @var{format-spec} is as follows:
30948 @var{format-spec} @expansion{}
30949 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30952 The natural format is the default format choosen automatically
30953 based on the variable type (like decimal for an @code{int}, hex
30954 for pointers, etc.).
30956 The zero-hexadecimal format has a representation similar to hexadecimal
30957 but with padding zeroes to the left of the value. For example, a 32-bit
30958 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30959 zero-hexadecimal format.
30961 For a variable with children, the format is set only on the
30962 variable itself, and the children are not affected.
30964 @subheading The @code{-var-show-format} Command
30965 @findex -var-show-format
30967 @subsubheading Synopsis
30970 -var-show-format @var{name}
30973 Returns the format used to display the value of the object @var{name}.
30976 @var{format} @expansion{}
30981 @subheading The @code{-var-info-num-children} Command
30982 @findex -var-info-num-children
30984 @subsubheading Synopsis
30987 -var-info-num-children @var{name}
30990 Returns the number of children of a variable object @var{name}:
30996 Note that this number is not completely reliable for a dynamic varobj.
30997 It will return the current number of children, but more children may
31001 @subheading The @code{-var-list-children} Command
31002 @findex -var-list-children
31004 @subsubheading Synopsis
31007 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31009 @anchor{-var-list-children}
31011 Return a list of the children of the specified variable object and
31012 create variable objects for them, if they do not already exist. With
31013 a single argument or if @var{print-values} has a value of 0 or
31014 @code{--no-values}, print only the names of the variables; if
31015 @var{print-values} is 1 or @code{--all-values}, also print their
31016 values; and if it is 2 or @code{--simple-values} print the name and
31017 value for simple data types and just the name for arrays, structures
31020 @var{from} and @var{to}, if specified, indicate the range of children
31021 to report. If @var{from} or @var{to} is less than zero, the range is
31022 reset and all children will be reported. Otherwise, children starting
31023 at @var{from} (zero-based) and up to and excluding @var{to} will be
31026 If a child range is requested, it will only affect the current call to
31027 @code{-var-list-children}, but not future calls to @code{-var-update}.
31028 For this, you must instead use @code{-var-set-update-range}. The
31029 intent of this approach is to enable a front end to implement any
31030 update approach it likes; for example, scrolling a view may cause the
31031 front end to request more children with @code{-var-list-children}, and
31032 then the front end could call @code{-var-set-update-range} with a
31033 different range to ensure that future updates are restricted to just
31036 For each child the following results are returned:
31041 Name of the variable object created for this child.
31044 The expression to be shown to the user by the front end to designate this child.
31045 For example this may be the name of a structure member.
31047 For a dynamic varobj, this value cannot be used to form an
31048 expression. There is no way to do this at all with a dynamic varobj.
31050 For C/C@t{++} structures there are several pseudo children returned to
31051 designate access qualifiers. For these pseudo children @var{exp} is
31052 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31053 type and value are not present.
31055 A dynamic varobj will not report the access qualifying
31056 pseudo-children, regardless of the language. This information is not
31057 available at all with a dynamic varobj.
31060 Number of children this child has. For a dynamic varobj, this will be
31064 The type of the child. If @samp{print object}
31065 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31066 @emph{actual} (derived) type of the object is shown rather than the
31067 @emph{declared} one.
31070 If values were requested, this is the value.
31073 If this variable object is associated with a thread, this is the
31074 thread's global thread id. Otherwise this result is not present.
31077 If the variable object is frozen, this variable will be present with a value of 1.
31080 A dynamic varobj can supply a display hint to the front end. The
31081 value comes directly from the Python pretty-printer object's
31082 @code{display_hint} method. @xref{Pretty Printing API}.
31085 This attribute will be present and have the value @samp{1} if the
31086 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31087 then this attribute will not be present.
31091 The result may have its own attributes:
31095 A dynamic varobj can supply a display hint to the front end. The
31096 value comes directly from the Python pretty-printer object's
31097 @code{display_hint} method. @xref{Pretty Printing API}.
31100 This is an integer attribute which is nonzero if there are children
31101 remaining after the end of the selected range.
31104 @subsubheading Example
31108 -var-list-children n
31109 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31110 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31112 -var-list-children --all-values n
31113 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31114 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31118 @subheading The @code{-var-info-type} Command
31119 @findex -var-info-type
31121 @subsubheading Synopsis
31124 -var-info-type @var{name}
31127 Returns the type of the specified variable @var{name}. The type is
31128 returned as a string in the same format as it is output by the
31132 type=@var{typename}
31136 @subheading The @code{-var-info-expression} Command
31137 @findex -var-info-expression
31139 @subsubheading Synopsis
31142 -var-info-expression @var{name}
31145 Returns a string that is suitable for presenting this
31146 variable object in user interface. The string is generally
31147 not valid expression in the current language, and cannot be evaluated.
31149 For example, if @code{a} is an array, and variable object
31150 @code{A} was created for @code{a}, then we'll get this output:
31153 (gdb) -var-info-expression A.1
31154 ^done,lang="C",exp="1"
31158 Here, the value of @code{lang} is the language name, which can be
31159 found in @ref{Supported Languages}.
31161 Note that the output of the @code{-var-list-children} command also
31162 includes those expressions, so the @code{-var-info-expression} command
31165 @subheading The @code{-var-info-path-expression} Command
31166 @findex -var-info-path-expression
31168 @subsubheading Synopsis
31171 -var-info-path-expression @var{name}
31174 Returns an expression that can be evaluated in the current
31175 context and will yield the same value that a variable object has.
31176 Compare this with the @code{-var-info-expression} command, which
31177 result can be used only for UI presentation. Typical use of
31178 the @code{-var-info-path-expression} command is creating a
31179 watchpoint from a variable object.
31181 This command is currently not valid for children of a dynamic varobj,
31182 and will give an error when invoked on one.
31184 For example, suppose @code{C} is a C@t{++} class, derived from class
31185 @code{Base}, and that the @code{Base} class has a member called
31186 @code{m_size}. Assume a variable @code{c} is has the type of
31187 @code{C} and a variable object @code{C} was created for variable
31188 @code{c}. Then, we'll get this output:
31190 (gdb) -var-info-path-expression C.Base.public.m_size
31191 ^done,path_expr=((Base)c).m_size)
31194 @subheading The @code{-var-show-attributes} Command
31195 @findex -var-show-attributes
31197 @subsubheading Synopsis
31200 -var-show-attributes @var{name}
31203 List attributes of the specified variable object @var{name}:
31206 status=@var{attr} [ ( ,@var{attr} )* ]
31210 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31212 @subheading The @code{-var-evaluate-expression} Command
31213 @findex -var-evaluate-expression
31215 @subsubheading Synopsis
31218 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31221 Evaluates the expression that is represented by the specified variable
31222 object and returns its value as a string. The format of the string
31223 can be specified with the @samp{-f} option. The possible values of
31224 this option are the same as for @code{-var-set-format}
31225 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31226 the current display format will be used. The current display format
31227 can be changed using the @code{-var-set-format} command.
31233 Note that one must invoke @code{-var-list-children} for a variable
31234 before the value of a child variable can be evaluated.
31236 @subheading The @code{-var-assign} Command
31237 @findex -var-assign
31239 @subsubheading Synopsis
31242 -var-assign @var{name} @var{expression}
31245 Assigns the value of @var{expression} to the variable object specified
31246 by @var{name}. The object must be @samp{editable}. If the variable's
31247 value is altered by the assign, the variable will show up in any
31248 subsequent @code{-var-update} list.
31250 @subsubheading Example
31258 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31262 @subheading The @code{-var-update} Command
31263 @findex -var-update
31265 @subsubheading Synopsis
31268 -var-update [@var{print-values}] @{@var{name} | "*"@}
31271 Reevaluate the expressions corresponding to the variable object
31272 @var{name} and all its direct and indirect children, and return the
31273 list of variable objects whose values have changed; @var{name} must
31274 be a root variable object. Here, ``changed'' means that the result of
31275 @code{-var-evaluate-expression} before and after the
31276 @code{-var-update} is different. If @samp{*} is used as the variable
31277 object names, all existing variable objects are updated, except
31278 for frozen ones (@pxref{-var-set-frozen}). The option
31279 @var{print-values} determines whether both names and values, or just
31280 names are printed. The possible values of this option are the same
31281 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31282 recommended to use the @samp{--all-values} option, to reduce the
31283 number of MI commands needed on each program stop.
31285 With the @samp{*} parameter, if a variable object is bound to a
31286 currently running thread, it will not be updated, without any
31289 If @code{-var-set-update-range} was previously used on a varobj, then
31290 only the selected range of children will be reported.
31292 @code{-var-update} reports all the changed varobjs in a tuple named
31295 Each item in the change list is itself a tuple holding:
31299 The name of the varobj.
31302 If values were requested for this update, then this field will be
31303 present and will hold the value of the varobj.
31306 @anchor{-var-update}
31307 This field is a string which may take one of three values:
31311 The variable object's current value is valid.
31314 The variable object does not currently hold a valid value but it may
31315 hold one in the future if its associated expression comes back into
31319 The variable object no longer holds a valid value.
31320 This can occur when the executable file being debugged has changed,
31321 either through recompilation or by using the @value{GDBN} @code{file}
31322 command. The front end should normally choose to delete these variable
31326 In the future new values may be added to this list so the front should
31327 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31330 This is only present if the varobj is still valid. If the type
31331 changed, then this will be the string @samp{true}; otherwise it will
31334 When a varobj's type changes, its children are also likely to have
31335 become incorrect. Therefore, the varobj's children are automatically
31336 deleted when this attribute is @samp{true}. Also, the varobj's update
31337 range, when set using the @code{-var-set-update-range} command, is
31341 If the varobj's type changed, then this field will be present and will
31344 @item new_num_children
31345 For a dynamic varobj, if the number of children changed, or if the
31346 type changed, this will be the new number of children.
31348 The @samp{numchild} field in other varobj responses is generally not
31349 valid for a dynamic varobj -- it will show the number of children that
31350 @value{GDBN} knows about, but because dynamic varobjs lazily
31351 instantiate their children, this will not reflect the number of
31352 children which may be available.
31354 The @samp{new_num_children} attribute only reports changes to the
31355 number of children known by @value{GDBN}. This is the only way to
31356 detect whether an update has removed children (which necessarily can
31357 only happen at the end of the update range).
31360 The display hint, if any.
31363 This is an integer value, which will be 1 if there are more children
31364 available outside the varobj's update range.
31367 This attribute will be present and have the value @samp{1} if the
31368 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31369 then this attribute will not be present.
31372 If new children were added to a dynamic varobj within the selected
31373 update range (as set by @code{-var-set-update-range}), then they will
31374 be listed in this attribute.
31377 @subsubheading Example
31384 -var-update --all-values var1
31385 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31386 type_changed="false"@}]
31390 @subheading The @code{-var-set-frozen} Command
31391 @findex -var-set-frozen
31392 @anchor{-var-set-frozen}
31394 @subsubheading Synopsis
31397 -var-set-frozen @var{name} @var{flag}
31400 Set the frozenness flag on the variable object @var{name}. The
31401 @var{flag} parameter should be either @samp{1} to make the variable
31402 frozen or @samp{0} to make it unfrozen. If a variable object is
31403 frozen, then neither itself, nor any of its children, are
31404 implicitly updated by @code{-var-update} of
31405 a parent variable or by @code{-var-update *}. Only
31406 @code{-var-update} of the variable itself will update its value and
31407 values of its children. After a variable object is unfrozen, it is
31408 implicitly updated by all subsequent @code{-var-update} operations.
31409 Unfreezing a variable does not update it, only subsequent
31410 @code{-var-update} does.
31412 @subsubheading Example
31416 -var-set-frozen V 1
31421 @subheading The @code{-var-set-update-range} command
31422 @findex -var-set-update-range
31423 @anchor{-var-set-update-range}
31425 @subsubheading Synopsis
31428 -var-set-update-range @var{name} @var{from} @var{to}
31431 Set the range of children to be returned by future invocations of
31432 @code{-var-update}.
31434 @var{from} and @var{to} indicate the range of children to report. If
31435 @var{from} or @var{to} is less than zero, the range is reset and all
31436 children will be reported. Otherwise, children starting at @var{from}
31437 (zero-based) and up to and excluding @var{to} will be reported.
31439 @subsubheading Example
31443 -var-set-update-range V 1 2
31447 @subheading The @code{-var-set-visualizer} command
31448 @findex -var-set-visualizer
31449 @anchor{-var-set-visualizer}
31451 @subsubheading Synopsis
31454 -var-set-visualizer @var{name} @var{visualizer}
31457 Set a visualizer for the variable object @var{name}.
31459 @var{visualizer} is the visualizer to use. The special value
31460 @samp{None} means to disable any visualizer in use.
31462 If not @samp{None}, @var{visualizer} must be a Python expression.
31463 This expression must evaluate to a callable object which accepts a
31464 single argument. @value{GDBN} will call this object with the value of
31465 the varobj @var{name} as an argument (this is done so that the same
31466 Python pretty-printing code can be used for both the CLI and MI).
31467 When called, this object must return an object which conforms to the
31468 pretty-printing interface (@pxref{Pretty Printing API}).
31470 The pre-defined function @code{gdb.default_visualizer} may be used to
31471 select a visualizer by following the built-in process
31472 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31473 a varobj is created, and so ordinarily is not needed.
31475 This feature is only available if Python support is enabled. The MI
31476 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31477 can be used to check this.
31479 @subsubheading Example
31481 Resetting the visualizer:
31485 -var-set-visualizer V None
31489 Reselecting the default (type-based) visualizer:
31493 -var-set-visualizer V gdb.default_visualizer
31497 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31498 can be used to instantiate this class for a varobj:
31502 -var-set-visualizer V "lambda val: SomeClass()"
31506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31507 @node GDB/MI Data Manipulation
31508 @section @sc{gdb/mi} Data Manipulation
31510 @cindex data manipulation, in @sc{gdb/mi}
31511 @cindex @sc{gdb/mi}, data manipulation
31512 This section describes the @sc{gdb/mi} commands that manipulate data:
31513 examine memory and registers, evaluate expressions, etc.
31515 For details about what an addressable memory unit is,
31516 @pxref{addressable memory unit}.
31518 @c REMOVED FROM THE INTERFACE.
31519 @c @subheading -data-assign
31520 @c Change the value of a program variable. Plenty of side effects.
31521 @c @subsubheading GDB Command
31523 @c @subsubheading Example
31526 @subheading The @code{-data-disassemble} Command
31527 @findex -data-disassemble
31529 @subsubheading Synopsis
31533 [ -s @var{start-addr} -e @var{end-addr} ]
31534 | [ -a @var{addr} ]
31535 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31543 @item @var{start-addr}
31544 is the beginning address (or @code{$pc})
31545 @item @var{end-addr}
31548 is an address anywhere within (or the name of) the function to
31549 disassemble. If an address is specified, the whole function
31550 surrounding that address will be disassembled. If a name is
31551 specified, the whole function with that name will be disassembled.
31552 @item @var{filename}
31553 is the name of the file to disassemble
31554 @item @var{linenum}
31555 is the line number to disassemble around
31557 is the number of disassembly lines to be produced. If it is -1,
31558 the whole function will be disassembled, in case no @var{end-addr} is
31559 specified. If @var{end-addr} is specified as a non-zero value, and
31560 @var{lines} is lower than the number of disassembly lines between
31561 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31562 displayed; if @var{lines} is higher than the number of lines between
31563 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31568 @item 0 disassembly only
31569 @item 1 mixed source and disassembly (deprecated)
31570 @item 2 disassembly with raw opcodes
31571 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31572 @item 4 mixed source and disassembly
31573 @item 5 mixed source and disassembly with raw opcodes
31576 Modes 1 and 3 are deprecated. The output is ``source centric''
31577 which hasn't proved useful in practice.
31578 @xref{Machine Code}, for a discussion of the difference between
31579 @code{/m} and @code{/s} output of the @code{disassemble} command.
31582 @subsubheading Result
31584 The result of the @code{-data-disassemble} command will be a list named
31585 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31586 used with the @code{-data-disassemble} command.
31588 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31593 The address at which this instruction was disassembled.
31596 The name of the function this instruction is within.
31599 The decimal offset in bytes from the start of @samp{func-name}.
31602 The text disassembly for this @samp{address}.
31605 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31606 bytes for the @samp{inst} field.
31610 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31611 @samp{src_and_asm_line}, each of which has the following fields:
31615 The line number within @samp{file}.
31618 The file name from the compilation unit. This might be an absolute
31619 file name or a relative file name depending on the compile command
31623 Absolute file name of @samp{file}. It is converted to a canonical form
31624 using the source file search path
31625 (@pxref{Source Path, ,Specifying Source Directories})
31626 and after resolving all the symbolic links.
31628 If the source file is not found this field will contain the path as
31629 present in the debug information.
31631 @item line_asm_insn
31632 This is a list of tuples containing the disassembly for @samp{line} in
31633 @samp{file}. The fields of each tuple are the same as for
31634 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31635 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31640 Note that whatever included in the @samp{inst} field, is not
31641 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31644 @subsubheading @value{GDBN} Command
31646 The corresponding @value{GDBN} command is @samp{disassemble}.
31648 @subsubheading Example
31650 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31654 -data-disassemble -s $pc -e "$pc + 20" -- 0
31657 @{address="0x000107c0",func-name="main",offset="4",
31658 inst="mov 2, %o0"@},
31659 @{address="0x000107c4",func-name="main",offset="8",
31660 inst="sethi %hi(0x11800), %o2"@},
31661 @{address="0x000107c8",func-name="main",offset="12",
31662 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31663 @{address="0x000107cc",func-name="main",offset="16",
31664 inst="sethi %hi(0x11800), %o2"@},
31665 @{address="0x000107d0",func-name="main",offset="20",
31666 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31670 Disassemble the whole @code{main} function. Line 32 is part of
31674 -data-disassemble -f basics.c -l 32 -- 0
31676 @{address="0x000107bc",func-name="main",offset="0",
31677 inst="save %sp, -112, %sp"@},
31678 @{address="0x000107c0",func-name="main",offset="4",
31679 inst="mov 2, %o0"@},
31680 @{address="0x000107c4",func-name="main",offset="8",
31681 inst="sethi %hi(0x11800), %o2"@},
31683 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31684 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31688 Disassemble 3 instructions from the start of @code{main}:
31692 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31694 @{address="0x000107bc",func-name="main",offset="0",
31695 inst="save %sp, -112, %sp"@},
31696 @{address="0x000107c0",func-name="main",offset="4",
31697 inst="mov 2, %o0"@},
31698 @{address="0x000107c4",func-name="main",offset="8",
31699 inst="sethi %hi(0x11800), %o2"@}]
31703 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31707 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31709 src_and_asm_line=@{line="31",
31710 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31711 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31712 line_asm_insn=[@{address="0x000107bc",
31713 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31714 src_and_asm_line=@{line="32",
31715 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31716 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31717 line_asm_insn=[@{address="0x000107c0",
31718 func-name="main",offset="4",inst="mov 2, %o0"@},
31719 @{address="0x000107c4",func-name="main",offset="8",
31720 inst="sethi %hi(0x11800), %o2"@}]@}]
31725 @subheading The @code{-data-evaluate-expression} Command
31726 @findex -data-evaluate-expression
31728 @subsubheading Synopsis
31731 -data-evaluate-expression @var{expr}
31734 Evaluate @var{expr} as an expression. The expression could contain an
31735 inferior function call. The function call will execute synchronously.
31736 If the expression contains spaces, it must be enclosed in double quotes.
31738 @subsubheading @value{GDBN} Command
31740 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31741 @samp{call}. In @code{gdbtk} only, there's a corresponding
31742 @samp{gdb_eval} command.
31744 @subsubheading Example
31746 In the following example, the numbers that precede the commands are the
31747 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31748 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31752 211-data-evaluate-expression A
31755 311-data-evaluate-expression &A
31756 311^done,value="0xefffeb7c"
31758 411-data-evaluate-expression A+3
31761 511-data-evaluate-expression "A + 3"
31767 @subheading The @code{-data-list-changed-registers} Command
31768 @findex -data-list-changed-registers
31770 @subsubheading Synopsis
31773 -data-list-changed-registers
31776 Display a list of the registers that have changed.
31778 @subsubheading @value{GDBN} Command
31780 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31781 has the corresponding command @samp{gdb_changed_register_list}.
31783 @subsubheading Example
31785 On a PPC MBX board:
31793 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31794 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31795 line="5",arch="powerpc"@}
31797 -data-list-changed-registers
31798 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31799 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31800 "24","25","26","27","28","30","31","64","65","66","67","69"]
31805 @subheading The @code{-data-list-register-names} Command
31806 @findex -data-list-register-names
31808 @subsubheading Synopsis
31811 -data-list-register-names [ ( @var{regno} )+ ]
31814 Show a list of register names for the current target. If no arguments
31815 are given, it shows a list of the names of all the registers. If
31816 integer numbers are given as arguments, it will print a list of the
31817 names of the registers corresponding to the arguments. To ensure
31818 consistency between a register name and its number, the output list may
31819 include empty register names.
31821 @subsubheading @value{GDBN} Command
31823 @value{GDBN} does not have a command which corresponds to
31824 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31825 corresponding command @samp{gdb_regnames}.
31827 @subsubheading Example
31829 For the PPC MBX board:
31832 -data-list-register-names
31833 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31834 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31835 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31836 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31837 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31838 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31839 "", "pc","ps","cr","lr","ctr","xer"]
31841 -data-list-register-names 1 2 3
31842 ^done,register-names=["r1","r2","r3"]
31846 @subheading The @code{-data-list-register-values} Command
31847 @findex -data-list-register-values
31849 @subsubheading Synopsis
31852 -data-list-register-values
31853 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31856 Display the registers' contents. The format according to which the
31857 registers' contents are to be returned is given by @var{fmt}, followed
31858 by an optional list of numbers specifying the registers to display. A
31859 missing list of numbers indicates that the contents of all the
31860 registers must be returned. The @code{--skip-unavailable} option
31861 indicates that only the available registers are to be returned.
31863 Allowed formats for @var{fmt} are:
31880 @subsubheading @value{GDBN} Command
31882 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31883 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31885 @subsubheading Example
31887 For a PPC MBX board (note: line breaks are for readability only, they
31888 don't appear in the actual output):
31892 -data-list-register-values r 64 65
31893 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31894 @{number="65",value="0x00029002"@}]
31896 -data-list-register-values x
31897 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31898 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31899 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31900 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31901 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31902 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31903 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31904 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31905 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31906 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31907 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31908 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31909 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31910 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31911 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31912 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31913 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31914 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31915 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31916 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31917 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31918 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31919 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31920 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31921 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31922 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31923 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31924 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31925 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31926 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31927 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31928 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31929 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31930 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31931 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31932 @{number="69",value="0x20002b03"@}]
31937 @subheading The @code{-data-read-memory} Command
31938 @findex -data-read-memory
31940 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31942 @subsubheading Synopsis
31945 -data-read-memory [ -o @var{byte-offset} ]
31946 @var{address} @var{word-format} @var{word-size}
31947 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31954 @item @var{address}
31955 An expression specifying the address of the first memory word to be
31956 read. Complex expressions containing embedded white space should be
31957 quoted using the C convention.
31959 @item @var{word-format}
31960 The format to be used to print the memory words. The notation is the
31961 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31964 @item @var{word-size}
31965 The size of each memory word in bytes.
31967 @item @var{nr-rows}
31968 The number of rows in the output table.
31970 @item @var{nr-cols}
31971 The number of columns in the output table.
31974 If present, indicates that each row should include an @sc{ascii} dump. The
31975 value of @var{aschar} is used as a padding character when a byte is not a
31976 member of the printable @sc{ascii} character set (printable @sc{ascii}
31977 characters are those whose code is between 32 and 126, inclusively).
31979 @item @var{byte-offset}
31980 An offset to add to the @var{address} before fetching memory.
31983 This command displays memory contents as a table of @var{nr-rows} by
31984 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31985 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31986 (returned as @samp{total-bytes}). Should less than the requested number
31987 of bytes be returned by the target, the missing words are identified
31988 using @samp{N/A}. The number of bytes read from the target is returned
31989 in @samp{nr-bytes} and the starting address used to read memory in
31992 The address of the next/previous row or page is available in
31993 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31996 @subsubheading @value{GDBN} Command
31998 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31999 @samp{gdb_get_mem} memory read command.
32001 @subsubheading Example
32003 Read six bytes of memory starting at @code{bytes+6} but then offset by
32004 @code{-6} bytes. Format as three rows of two columns. One byte per
32005 word. Display each word in hex.
32009 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32010 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32011 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32012 prev-page="0x0000138a",memory=[
32013 @{addr="0x00001390",data=["0x00","0x01"]@},
32014 @{addr="0x00001392",data=["0x02","0x03"]@},
32015 @{addr="0x00001394",data=["0x04","0x05"]@}]
32019 Read two bytes of memory starting at address @code{shorts + 64} and
32020 display as a single word formatted in decimal.
32024 5-data-read-memory shorts+64 d 2 1 1
32025 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32026 next-row="0x00001512",prev-row="0x0000150e",
32027 next-page="0x00001512",prev-page="0x0000150e",memory=[
32028 @{addr="0x00001510",data=["128"]@}]
32032 Read thirty two bytes of memory starting at @code{bytes+16} and format
32033 as eight rows of four columns. Include a string encoding with @samp{x}
32034 used as the non-printable character.
32038 4-data-read-memory bytes+16 x 1 8 4 x
32039 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32040 next-row="0x000013c0",prev-row="0x0000139c",
32041 next-page="0x000013c0",prev-page="0x00001380",memory=[
32042 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32043 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32044 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32045 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32046 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32047 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32048 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32049 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32053 @subheading The @code{-data-read-memory-bytes} Command
32054 @findex -data-read-memory-bytes
32056 @subsubheading Synopsis
32059 -data-read-memory-bytes [ -o @var{offset} ]
32060 @var{address} @var{count}
32067 @item @var{address}
32068 An expression specifying the address of the first addressable memory unit
32069 to be read. Complex expressions containing embedded white space should be
32070 quoted using the C convention.
32073 The number of addressable memory units to read. This should be an integer
32077 The offset relative to @var{address} at which to start reading. This
32078 should be an integer literal. This option is provided so that a frontend
32079 is not required to first evaluate address and then perform address
32080 arithmetics itself.
32084 This command attempts to read all accessible memory regions in the
32085 specified range. First, all regions marked as unreadable in the memory
32086 map (if one is defined) will be skipped. @xref{Memory Region
32087 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32088 regions. For each one, if reading full region results in an errors,
32089 @value{GDBN} will try to read a subset of the region.
32091 In general, every single memory unit in the region may be readable or not,
32092 and the only way to read every readable unit is to try a read at
32093 every address, which is not practical. Therefore, @value{GDBN} will
32094 attempt to read all accessible memory units at either beginning or the end
32095 of the region, using a binary division scheme. This heuristic works
32096 well for reading accross a memory map boundary. Note that if a region
32097 has a readable range that is neither at the beginning or the end,
32098 @value{GDBN} will not read it.
32100 The result record (@pxref{GDB/MI Result Records}) that is output of
32101 the command includes a field named @samp{memory} whose content is a
32102 list of tuples. Each tuple represent a successfully read memory block
32103 and has the following fields:
32107 The start address of the memory block, as hexadecimal literal.
32110 The end address of the memory block, as hexadecimal literal.
32113 The offset of the memory block, as hexadecimal literal, relative to
32114 the start address passed to @code{-data-read-memory-bytes}.
32117 The contents of the memory block, in hex.
32123 @subsubheading @value{GDBN} Command
32125 The corresponding @value{GDBN} command is @samp{x}.
32127 @subsubheading Example
32131 -data-read-memory-bytes &a 10
32132 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32134 contents="01000000020000000300"@}]
32139 @subheading The @code{-data-write-memory-bytes} Command
32140 @findex -data-write-memory-bytes
32142 @subsubheading Synopsis
32145 -data-write-memory-bytes @var{address} @var{contents}
32146 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32153 @item @var{address}
32154 An expression specifying the address of the first addressable memory unit
32155 to be written. Complex expressions containing embedded white space should
32156 be quoted using the C convention.
32158 @item @var{contents}
32159 The hex-encoded data to write. It is an error if @var{contents} does
32160 not represent an integral number of addressable memory units.
32163 Optional argument indicating the number of addressable memory units to be
32164 written. If @var{count} is greater than @var{contents}' length,
32165 @value{GDBN} will repeatedly write @var{contents} until it fills
32166 @var{count} memory units.
32170 @subsubheading @value{GDBN} Command
32172 There's no corresponding @value{GDBN} command.
32174 @subsubheading Example
32178 -data-write-memory-bytes &a "aabbccdd"
32185 -data-write-memory-bytes &a "aabbccdd" 16e
32190 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32191 @node GDB/MI Tracepoint Commands
32192 @section @sc{gdb/mi} Tracepoint Commands
32194 The commands defined in this section implement MI support for
32195 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32197 @subheading The @code{-trace-find} Command
32198 @findex -trace-find
32200 @subsubheading Synopsis
32203 -trace-find @var{mode} [@var{parameters}@dots{}]
32206 Find a trace frame using criteria defined by @var{mode} and
32207 @var{parameters}. The following table lists permissible
32208 modes and their parameters. For details of operation, see @ref{tfind}.
32213 No parameters are required. Stops examining trace frames.
32216 An integer is required as parameter. Selects tracepoint frame with
32219 @item tracepoint-number
32220 An integer is required as parameter. Finds next
32221 trace frame that corresponds to tracepoint with the specified number.
32224 An address is required as parameter. Finds
32225 next trace frame that corresponds to any tracepoint at the specified
32228 @item pc-inside-range
32229 Two addresses are required as parameters. Finds next trace
32230 frame that corresponds to a tracepoint at an address inside the
32231 specified range. Both bounds are considered to be inside the range.
32233 @item pc-outside-range
32234 Two addresses are required as parameters. Finds
32235 next trace frame that corresponds to a tracepoint at an address outside
32236 the specified range. Both bounds are considered to be inside the range.
32239 Line specification is required as parameter. @xref{Specify Location}.
32240 Finds next trace frame that corresponds to a tracepoint at
32241 the specified location.
32245 If @samp{none} was passed as @var{mode}, the response does not
32246 have fields. Otherwise, the response may have the following fields:
32250 This field has either @samp{0} or @samp{1} as the value, depending
32251 on whether a matching tracepoint was found.
32254 The index of the found traceframe. This field is present iff
32255 the @samp{found} field has value of @samp{1}.
32258 The index of the found tracepoint. This field is present iff
32259 the @samp{found} field has value of @samp{1}.
32262 The information about the frame corresponding to the found trace
32263 frame. This field is present only if a trace frame was found.
32264 @xref{GDB/MI Frame Information}, for description of this field.
32268 @subsubheading @value{GDBN} Command
32270 The corresponding @value{GDBN} command is @samp{tfind}.
32272 @subheading -trace-define-variable
32273 @findex -trace-define-variable
32275 @subsubheading Synopsis
32278 -trace-define-variable @var{name} [ @var{value} ]
32281 Create trace variable @var{name} if it does not exist. If
32282 @var{value} is specified, sets the initial value of the specified
32283 trace variable to that value. Note that the @var{name} should start
32284 with the @samp{$} character.
32286 @subsubheading @value{GDBN} Command
32288 The corresponding @value{GDBN} command is @samp{tvariable}.
32290 @subheading The @code{-trace-frame-collected} Command
32291 @findex -trace-frame-collected
32293 @subsubheading Synopsis
32296 -trace-frame-collected
32297 [--var-print-values @var{var_pval}]
32298 [--comp-print-values @var{comp_pval}]
32299 [--registers-format @var{regformat}]
32300 [--memory-contents]
32303 This command returns the set of collected objects, register names,
32304 trace state variable names, memory ranges and computed expressions
32305 that have been collected at a particular trace frame. The optional
32306 parameters to the command affect the output format in different ways.
32307 See the output description table below for more details.
32309 The reported names can be used in the normal manner to create
32310 varobjs and inspect the objects themselves. The items returned by
32311 this command are categorized so that it is clear which is a variable,
32312 which is a register, which is a trace state variable, which is a
32313 memory range and which is a computed expression.
32315 For instance, if the actions were
32317 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32318 collect *(int*)0xaf02bef0@@40
32322 the object collected in its entirety would be @code{myVar}. The
32323 object @code{myArray} would be partially collected, because only the
32324 element at index @code{myIndex} would be collected. The remaining
32325 objects would be computed expressions.
32327 An example output would be:
32331 -trace-frame-collected
32333 explicit-variables=[@{name="myVar",value="1"@}],
32334 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32335 @{name="myObj.field",value="0"@},
32336 @{name="myPtr->field",value="1"@},
32337 @{name="myCount + 2",value="3"@},
32338 @{name="$tvar1 + 1",value="43970027"@}],
32339 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32340 @{number="1",value="0x0"@},
32341 @{number="2",value="0x4"@},
32343 @{number="125",value="0x0"@}],
32344 tvars=[@{name="$tvar1",current="43970026"@}],
32345 memory=[@{address="0x0000000000602264",length="4"@},
32346 @{address="0x0000000000615bc0",length="4"@}]
32353 @item explicit-variables
32354 The set of objects that have been collected in their entirety (as
32355 opposed to collecting just a few elements of an array or a few struct
32356 members). For each object, its name and value are printed.
32357 The @code{--var-print-values} option affects how or whether the value
32358 field is output. If @var{var_pval} is 0, then print only the names;
32359 if it is 1, print also their values; and if it is 2, print the name,
32360 type and value for simple data types, and the name and type for
32361 arrays, structures and unions.
32363 @item computed-expressions
32364 The set of computed expressions that have been collected at the
32365 current trace frame. The @code{--comp-print-values} option affects
32366 this set like the @code{--var-print-values} option affects the
32367 @code{explicit-variables} set. See above.
32370 The registers that have been collected at the current trace frame.
32371 For each register collected, the name and current value are returned.
32372 The value is formatted according to the @code{--registers-format}
32373 option. See the @command{-data-list-register-values} command for a
32374 list of the allowed formats. The default is @samp{x}.
32377 The trace state variables that have been collected at the current
32378 trace frame. For each trace state variable collected, the name and
32379 current value are returned.
32382 The set of memory ranges that have been collected at the current trace
32383 frame. Its content is a list of tuples. Each tuple represents a
32384 collected memory range and has the following fields:
32388 The start address of the memory range, as hexadecimal literal.
32391 The length of the memory range, as decimal literal.
32394 The contents of the memory block, in hex. This field is only present
32395 if the @code{--memory-contents} option is specified.
32401 @subsubheading @value{GDBN} Command
32403 There is no corresponding @value{GDBN} command.
32405 @subsubheading Example
32407 @subheading -trace-list-variables
32408 @findex -trace-list-variables
32410 @subsubheading Synopsis
32413 -trace-list-variables
32416 Return a table of all defined trace variables. Each element of the
32417 table has the following fields:
32421 The name of the trace variable. This field is always present.
32424 The initial value. This is a 64-bit signed integer. This
32425 field is always present.
32428 The value the trace variable has at the moment. This is a 64-bit
32429 signed integer. This field is absent iff current value is
32430 not defined, for example if the trace was never run, or is
32435 @subsubheading @value{GDBN} Command
32437 The corresponding @value{GDBN} command is @samp{tvariables}.
32439 @subsubheading Example
32443 -trace-list-variables
32444 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32445 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32446 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32447 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32448 body=[variable=@{name="$trace_timestamp",initial="0"@}
32449 variable=@{name="$foo",initial="10",current="15"@}]@}
32453 @subheading -trace-save
32454 @findex -trace-save
32456 @subsubheading Synopsis
32459 -trace-save [ -r ] [ -ctf ] @var{filename}
32462 Saves the collected trace data to @var{filename}. Without the
32463 @samp{-r} option, the data is downloaded from the target and saved
32464 in a local file. With the @samp{-r} option the target is asked
32465 to perform the save.
32467 By default, this command will save the trace in the tfile format. You can
32468 supply the optional @samp{-ctf} argument to save it the CTF format. See
32469 @ref{Trace Files} for more information about CTF.
32471 @subsubheading @value{GDBN} Command
32473 The corresponding @value{GDBN} command is @samp{tsave}.
32476 @subheading -trace-start
32477 @findex -trace-start
32479 @subsubheading Synopsis
32485 Starts a tracing experiment. The result of this command does not
32488 @subsubheading @value{GDBN} Command
32490 The corresponding @value{GDBN} command is @samp{tstart}.
32492 @subheading -trace-status
32493 @findex -trace-status
32495 @subsubheading Synopsis
32501 Obtains the status of a tracing experiment. The result may include
32502 the following fields:
32507 May have a value of either @samp{0}, when no tracing operations are
32508 supported, @samp{1}, when all tracing operations are supported, or
32509 @samp{file} when examining trace file. In the latter case, examining
32510 of trace frame is possible but new tracing experiement cannot be
32511 started. This field is always present.
32514 May have a value of either @samp{0} or @samp{1} depending on whether
32515 tracing experiement is in progress on target. This field is present
32516 if @samp{supported} field is not @samp{0}.
32519 Report the reason why the tracing was stopped last time. This field
32520 may be absent iff tracing was never stopped on target yet. The
32521 value of @samp{request} means the tracing was stopped as result of
32522 the @code{-trace-stop} command. The value of @samp{overflow} means
32523 the tracing buffer is full. The value of @samp{disconnection} means
32524 tracing was automatically stopped when @value{GDBN} has disconnected.
32525 The value of @samp{passcount} means tracing was stopped when a
32526 tracepoint was passed a maximal number of times for that tracepoint.
32527 This field is present if @samp{supported} field is not @samp{0}.
32529 @item stopping-tracepoint
32530 The number of tracepoint whose passcount as exceeded. This field is
32531 present iff the @samp{stop-reason} field has the value of
32535 @itemx frames-created
32536 The @samp{frames} field is a count of the total number of trace frames
32537 in the trace buffer, while @samp{frames-created} is the total created
32538 during the run, including ones that were discarded, such as when a
32539 circular trace buffer filled up. Both fields are optional.
32543 These fields tell the current size of the tracing buffer and the
32544 remaining space. These fields are optional.
32547 The value of the circular trace buffer flag. @code{1} means that the
32548 trace buffer is circular and old trace frames will be discarded if
32549 necessary to make room, @code{0} means that the trace buffer is linear
32553 The value of the disconnected tracing flag. @code{1} means that
32554 tracing will continue after @value{GDBN} disconnects, @code{0} means
32555 that the trace run will stop.
32558 The filename of the trace file being examined. This field is
32559 optional, and only present when examining a trace file.
32563 @subsubheading @value{GDBN} Command
32565 The corresponding @value{GDBN} command is @samp{tstatus}.
32567 @subheading -trace-stop
32568 @findex -trace-stop
32570 @subsubheading Synopsis
32576 Stops a tracing experiment. The result of this command has the same
32577 fields as @code{-trace-status}, except that the @samp{supported} and
32578 @samp{running} fields are not output.
32580 @subsubheading @value{GDBN} Command
32582 The corresponding @value{GDBN} command is @samp{tstop}.
32585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32586 @node GDB/MI Symbol Query
32587 @section @sc{gdb/mi} Symbol Query Commands
32591 @subheading The @code{-symbol-info-address} Command
32592 @findex -symbol-info-address
32594 @subsubheading Synopsis
32597 -symbol-info-address @var{symbol}
32600 Describe where @var{symbol} is stored.
32602 @subsubheading @value{GDBN} Command
32604 The corresponding @value{GDBN} command is @samp{info address}.
32606 @subsubheading Example
32610 @subheading The @code{-symbol-info-file} Command
32611 @findex -symbol-info-file
32613 @subsubheading Synopsis
32619 Show the file for the symbol.
32621 @subsubheading @value{GDBN} Command
32623 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32624 @samp{gdb_find_file}.
32626 @subsubheading Example
32630 @subheading The @code{-symbol-info-function} Command
32631 @findex -symbol-info-function
32633 @subsubheading Synopsis
32636 -symbol-info-function
32639 Show which function the symbol lives in.
32641 @subsubheading @value{GDBN} Command
32643 @samp{gdb_get_function} in @code{gdbtk}.
32645 @subsubheading Example
32649 @subheading The @code{-symbol-info-line} Command
32650 @findex -symbol-info-line
32652 @subsubheading Synopsis
32658 Show the core addresses of the code for a source line.
32660 @subsubheading @value{GDBN} Command
32662 The corresponding @value{GDBN} command is @samp{info line}.
32663 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32665 @subsubheading Example
32669 @subheading The @code{-symbol-info-symbol} Command
32670 @findex -symbol-info-symbol
32672 @subsubheading Synopsis
32675 -symbol-info-symbol @var{addr}
32678 Describe what symbol is at location @var{addr}.
32680 @subsubheading @value{GDBN} Command
32682 The corresponding @value{GDBN} command is @samp{info symbol}.
32684 @subsubheading Example
32688 @subheading The @code{-symbol-list-functions} Command
32689 @findex -symbol-list-functions
32691 @subsubheading Synopsis
32694 -symbol-list-functions
32697 List the functions in the executable.
32699 @subsubheading @value{GDBN} Command
32701 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32702 @samp{gdb_search} in @code{gdbtk}.
32704 @subsubheading Example
32709 @subheading The @code{-symbol-list-lines} Command
32710 @findex -symbol-list-lines
32712 @subsubheading Synopsis
32715 -symbol-list-lines @var{filename}
32718 Print the list of lines that contain code and their associated program
32719 addresses for the given source filename. The entries are sorted in
32720 ascending PC order.
32722 @subsubheading @value{GDBN} Command
32724 There is no corresponding @value{GDBN} command.
32726 @subsubheading Example
32729 -symbol-list-lines basics.c
32730 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32736 @subheading The @code{-symbol-list-types} Command
32737 @findex -symbol-list-types
32739 @subsubheading Synopsis
32745 List all the type names.
32747 @subsubheading @value{GDBN} Command
32749 The corresponding commands are @samp{info types} in @value{GDBN},
32750 @samp{gdb_search} in @code{gdbtk}.
32752 @subsubheading Example
32756 @subheading The @code{-symbol-list-variables} Command
32757 @findex -symbol-list-variables
32759 @subsubheading Synopsis
32762 -symbol-list-variables
32765 List all the global and static variable names.
32767 @subsubheading @value{GDBN} Command
32769 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32771 @subsubheading Example
32775 @subheading The @code{-symbol-locate} Command
32776 @findex -symbol-locate
32778 @subsubheading Synopsis
32784 @subsubheading @value{GDBN} Command
32786 @samp{gdb_loc} in @code{gdbtk}.
32788 @subsubheading Example
32792 @subheading The @code{-symbol-type} Command
32793 @findex -symbol-type
32795 @subsubheading Synopsis
32798 -symbol-type @var{variable}
32801 Show type of @var{variable}.
32803 @subsubheading @value{GDBN} Command
32805 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32806 @samp{gdb_obj_variable}.
32808 @subsubheading Example
32813 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32814 @node GDB/MI File Commands
32815 @section @sc{gdb/mi} File Commands
32817 This section describes the GDB/MI commands to specify executable file names
32818 and to read in and obtain symbol table information.
32820 @subheading The @code{-file-exec-and-symbols} Command
32821 @findex -file-exec-and-symbols
32823 @subsubheading Synopsis
32826 -file-exec-and-symbols @var{file}
32829 Specify the executable file to be debugged. This file is the one from
32830 which the symbol table is also read. If no file is specified, the
32831 command clears the executable and symbol information. If breakpoints
32832 are set when using this command with no arguments, @value{GDBN} will produce
32833 error messages. Otherwise, no output is produced, except a completion
32836 @subsubheading @value{GDBN} Command
32838 The corresponding @value{GDBN} command is @samp{file}.
32840 @subsubheading Example
32844 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32850 @subheading The @code{-file-exec-file} Command
32851 @findex -file-exec-file
32853 @subsubheading Synopsis
32856 -file-exec-file @var{file}
32859 Specify the executable file to be debugged. Unlike
32860 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32861 from this file. If used without argument, @value{GDBN} clears the information
32862 about the executable file. No output is produced, except a completion
32865 @subsubheading @value{GDBN} Command
32867 The corresponding @value{GDBN} command is @samp{exec-file}.
32869 @subsubheading Example
32873 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32880 @subheading The @code{-file-list-exec-sections} Command
32881 @findex -file-list-exec-sections
32883 @subsubheading Synopsis
32886 -file-list-exec-sections
32889 List the sections of the current executable file.
32891 @subsubheading @value{GDBN} Command
32893 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32894 information as this command. @code{gdbtk} has a corresponding command
32895 @samp{gdb_load_info}.
32897 @subsubheading Example
32902 @subheading The @code{-file-list-exec-source-file} Command
32903 @findex -file-list-exec-source-file
32905 @subsubheading Synopsis
32908 -file-list-exec-source-file
32911 List the line number, the current source file, and the absolute path
32912 to the current source file for the current executable. The macro
32913 information field has a value of @samp{1} or @samp{0} depending on
32914 whether or not the file includes preprocessor macro information.
32916 @subsubheading @value{GDBN} Command
32918 The @value{GDBN} equivalent is @samp{info source}
32920 @subsubheading Example
32924 123-file-list-exec-source-file
32925 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32930 @subheading The @code{-file-list-exec-source-files} Command
32931 @findex -file-list-exec-source-files
32933 @subsubheading Synopsis
32936 -file-list-exec-source-files
32939 List the source files for the current executable.
32941 It will always output both the filename and fullname (absolute file
32942 name) of a source file.
32944 @subsubheading @value{GDBN} Command
32946 The @value{GDBN} equivalent is @samp{info sources}.
32947 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32949 @subsubheading Example
32952 -file-list-exec-source-files
32954 @{file=foo.c,fullname=/home/foo.c@},
32955 @{file=/home/bar.c,fullname=/home/bar.c@},
32956 @{file=gdb_could_not_find_fullpath.c@}]
32960 @subheading The @code{-file-list-shared-libraries} Command
32961 @findex -file-list-shared-libraries
32963 @subsubheading Synopsis
32966 -file-list-shared-libraries [ @var{regexp} ]
32969 List the shared libraries in the program.
32970 With a regular expression @var{regexp}, only those libraries whose
32971 names match @var{regexp} are listed.
32973 @subsubheading @value{GDBN} Command
32975 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32976 have a similar meaning to the @code{=library-loaded} notification.
32977 The @code{ranges} field specifies the multiple segments belonging to this
32978 library. Each range has the following fields:
32982 The address defining the inclusive lower bound of the segment.
32984 The address defining the exclusive upper bound of the segment.
32987 @subsubheading Example
32990 -file-list-exec-source-files
32991 ^done,shared-libraries=[
32992 @{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"@}]@},
32993 @{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"@}]@}]
32999 @subheading The @code{-file-list-symbol-files} Command
33000 @findex -file-list-symbol-files
33002 @subsubheading Synopsis
33005 -file-list-symbol-files
33010 @subsubheading @value{GDBN} Command
33012 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33014 @subsubheading Example
33019 @subheading The @code{-file-symbol-file} Command
33020 @findex -file-symbol-file
33022 @subsubheading Synopsis
33025 -file-symbol-file @var{file}
33028 Read symbol table info from the specified @var{file} argument. When
33029 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33030 produced, except for a completion notification.
33032 @subsubheading @value{GDBN} Command
33034 The corresponding @value{GDBN} command is @samp{symbol-file}.
33036 @subsubheading Example
33040 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33046 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33047 @node GDB/MI Memory Overlay Commands
33048 @section @sc{gdb/mi} Memory Overlay Commands
33050 The memory overlay commands are not implemented.
33052 @c @subheading -overlay-auto
33054 @c @subheading -overlay-list-mapping-state
33056 @c @subheading -overlay-list-overlays
33058 @c @subheading -overlay-map
33060 @c @subheading -overlay-off
33062 @c @subheading -overlay-on
33064 @c @subheading -overlay-unmap
33066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33067 @node GDB/MI Signal Handling Commands
33068 @section @sc{gdb/mi} Signal Handling Commands
33070 Signal handling commands are not implemented.
33072 @c @subheading -signal-handle
33074 @c @subheading -signal-list-handle-actions
33076 @c @subheading -signal-list-signal-types
33080 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33081 @node GDB/MI Target Manipulation
33082 @section @sc{gdb/mi} Target Manipulation Commands
33085 @subheading The @code{-target-attach} Command
33086 @findex -target-attach
33088 @subsubheading Synopsis
33091 -target-attach @var{pid} | @var{gid} | @var{file}
33094 Attach to a process @var{pid} or a file @var{file} outside of
33095 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33096 group, the id previously returned by
33097 @samp{-list-thread-groups --available} must be used.
33099 @subsubheading @value{GDBN} Command
33101 The corresponding @value{GDBN} command is @samp{attach}.
33103 @subsubheading Example
33107 =thread-created,id="1"
33108 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33114 @subheading The @code{-target-compare-sections} Command
33115 @findex -target-compare-sections
33117 @subsubheading Synopsis
33120 -target-compare-sections [ @var{section} ]
33123 Compare data of section @var{section} on target to the exec file.
33124 Without the argument, all sections are compared.
33126 @subsubheading @value{GDBN} Command
33128 The @value{GDBN} equivalent is @samp{compare-sections}.
33130 @subsubheading Example
33135 @subheading The @code{-target-detach} Command
33136 @findex -target-detach
33138 @subsubheading Synopsis
33141 -target-detach [ @var{pid} | @var{gid} ]
33144 Detach from the remote target which normally resumes its execution.
33145 If either @var{pid} or @var{gid} is specified, detaches from either
33146 the specified process, or specified thread group. There's no output.
33148 @subsubheading @value{GDBN} Command
33150 The corresponding @value{GDBN} command is @samp{detach}.
33152 @subsubheading Example
33162 @subheading The @code{-target-disconnect} Command
33163 @findex -target-disconnect
33165 @subsubheading Synopsis
33171 Disconnect from the remote target. There's no output and the target is
33172 generally not resumed.
33174 @subsubheading @value{GDBN} Command
33176 The corresponding @value{GDBN} command is @samp{disconnect}.
33178 @subsubheading Example
33188 @subheading The @code{-target-download} Command
33189 @findex -target-download
33191 @subsubheading Synopsis
33197 Loads the executable onto the remote target.
33198 It prints out an update message every half second, which includes the fields:
33202 The name of the section.
33204 The size of what has been sent so far for that section.
33206 The size of the section.
33208 The total size of what was sent so far (the current and the previous sections).
33210 The size of the overall executable to download.
33214 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33215 @sc{gdb/mi} Output Syntax}).
33217 In addition, it prints the name and size of the sections, as they are
33218 downloaded. These messages include the following fields:
33222 The name of the section.
33224 The size of the section.
33226 The size of the overall executable to download.
33230 At the end, a summary is printed.
33232 @subsubheading @value{GDBN} Command
33234 The corresponding @value{GDBN} command is @samp{load}.
33236 @subsubheading Example
33238 Note: each status message appears on a single line. Here the messages
33239 have been broken down so that they can fit onto a page.
33244 +download,@{section=".text",section-size="6668",total-size="9880"@}
33245 +download,@{section=".text",section-sent="512",section-size="6668",
33246 total-sent="512",total-size="9880"@}
33247 +download,@{section=".text",section-sent="1024",section-size="6668",
33248 total-sent="1024",total-size="9880"@}
33249 +download,@{section=".text",section-sent="1536",section-size="6668",
33250 total-sent="1536",total-size="9880"@}
33251 +download,@{section=".text",section-sent="2048",section-size="6668",
33252 total-sent="2048",total-size="9880"@}
33253 +download,@{section=".text",section-sent="2560",section-size="6668",
33254 total-sent="2560",total-size="9880"@}
33255 +download,@{section=".text",section-sent="3072",section-size="6668",
33256 total-sent="3072",total-size="9880"@}
33257 +download,@{section=".text",section-sent="3584",section-size="6668",
33258 total-sent="3584",total-size="9880"@}
33259 +download,@{section=".text",section-sent="4096",section-size="6668",
33260 total-sent="4096",total-size="9880"@}
33261 +download,@{section=".text",section-sent="4608",section-size="6668",
33262 total-sent="4608",total-size="9880"@}
33263 +download,@{section=".text",section-sent="5120",section-size="6668",
33264 total-sent="5120",total-size="9880"@}
33265 +download,@{section=".text",section-sent="5632",section-size="6668",
33266 total-sent="5632",total-size="9880"@}
33267 +download,@{section=".text",section-sent="6144",section-size="6668",
33268 total-sent="6144",total-size="9880"@}
33269 +download,@{section=".text",section-sent="6656",section-size="6668",
33270 total-sent="6656",total-size="9880"@}
33271 +download,@{section=".init",section-size="28",total-size="9880"@}
33272 +download,@{section=".fini",section-size="28",total-size="9880"@}
33273 +download,@{section=".data",section-size="3156",total-size="9880"@}
33274 +download,@{section=".data",section-sent="512",section-size="3156",
33275 total-sent="7236",total-size="9880"@}
33276 +download,@{section=".data",section-sent="1024",section-size="3156",
33277 total-sent="7748",total-size="9880"@}
33278 +download,@{section=".data",section-sent="1536",section-size="3156",
33279 total-sent="8260",total-size="9880"@}
33280 +download,@{section=".data",section-sent="2048",section-size="3156",
33281 total-sent="8772",total-size="9880"@}
33282 +download,@{section=".data",section-sent="2560",section-size="3156",
33283 total-sent="9284",total-size="9880"@}
33284 +download,@{section=".data",section-sent="3072",section-size="3156",
33285 total-sent="9796",total-size="9880"@}
33286 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33293 @subheading The @code{-target-exec-status} Command
33294 @findex -target-exec-status
33296 @subsubheading Synopsis
33299 -target-exec-status
33302 Provide information on the state of the target (whether it is running or
33303 not, for instance).
33305 @subsubheading @value{GDBN} Command
33307 There's no equivalent @value{GDBN} command.
33309 @subsubheading Example
33313 @subheading The @code{-target-list-available-targets} Command
33314 @findex -target-list-available-targets
33316 @subsubheading Synopsis
33319 -target-list-available-targets
33322 List the possible targets to connect to.
33324 @subsubheading @value{GDBN} Command
33326 The corresponding @value{GDBN} command is @samp{help target}.
33328 @subsubheading Example
33332 @subheading The @code{-target-list-current-targets} Command
33333 @findex -target-list-current-targets
33335 @subsubheading Synopsis
33338 -target-list-current-targets
33341 Describe the current target.
33343 @subsubheading @value{GDBN} Command
33345 The corresponding information is printed by @samp{info file} (among
33348 @subsubheading Example
33352 @subheading The @code{-target-list-parameters} Command
33353 @findex -target-list-parameters
33355 @subsubheading Synopsis
33358 -target-list-parameters
33364 @subsubheading @value{GDBN} Command
33368 @subsubheading Example
33371 @subheading The @code{-target-flash-erase} Command
33372 @findex -target-flash-erase
33374 @subsubheading Synopsis
33377 -target-flash-erase
33380 Erases all known flash memory regions on the target.
33382 The corresponding @value{GDBN} command is @samp{flash-erase}.
33384 The output is a list of flash regions that have been erased, with starting
33385 addresses and memory region sizes.
33389 -target-flash-erase
33390 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33394 @subheading The @code{-target-select} Command
33395 @findex -target-select
33397 @subsubheading Synopsis
33400 -target-select @var{type} @var{parameters @dots{}}
33403 Connect @value{GDBN} to the remote target. This command takes two args:
33407 The type of target, for instance @samp{remote}, etc.
33408 @item @var{parameters}
33409 Device names, host names and the like. @xref{Target Commands, ,
33410 Commands for Managing Targets}, for more details.
33413 The output is a connection notification, followed by the address at
33414 which the target program is, in the following form:
33417 ^connected,addr="@var{address}",func="@var{function name}",
33418 args=[@var{arg list}]
33421 @subsubheading @value{GDBN} Command
33423 The corresponding @value{GDBN} command is @samp{target}.
33425 @subsubheading Example
33429 -target-select remote /dev/ttya
33430 ^connected,addr="0xfe00a300",func="??",args=[]
33434 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33435 @node GDB/MI File Transfer Commands
33436 @section @sc{gdb/mi} File Transfer Commands
33439 @subheading The @code{-target-file-put} Command
33440 @findex -target-file-put
33442 @subsubheading Synopsis
33445 -target-file-put @var{hostfile} @var{targetfile}
33448 Copy file @var{hostfile} from the host system (the machine running
33449 @value{GDBN}) to @var{targetfile} on the target system.
33451 @subsubheading @value{GDBN} Command
33453 The corresponding @value{GDBN} command is @samp{remote put}.
33455 @subsubheading Example
33459 -target-file-put localfile remotefile
33465 @subheading The @code{-target-file-get} Command
33466 @findex -target-file-get
33468 @subsubheading Synopsis
33471 -target-file-get @var{targetfile} @var{hostfile}
33474 Copy file @var{targetfile} from the target system to @var{hostfile}
33475 on the host system.
33477 @subsubheading @value{GDBN} Command
33479 The corresponding @value{GDBN} command is @samp{remote get}.
33481 @subsubheading Example
33485 -target-file-get remotefile localfile
33491 @subheading The @code{-target-file-delete} Command
33492 @findex -target-file-delete
33494 @subsubheading Synopsis
33497 -target-file-delete @var{targetfile}
33500 Delete @var{targetfile} from the target system.
33502 @subsubheading @value{GDBN} Command
33504 The corresponding @value{GDBN} command is @samp{remote delete}.
33506 @subsubheading Example
33510 -target-file-delete remotefile
33516 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33517 @node GDB/MI Ada Exceptions Commands
33518 @section Ada Exceptions @sc{gdb/mi} Commands
33520 @subheading The @code{-info-ada-exceptions} Command
33521 @findex -info-ada-exceptions
33523 @subsubheading Synopsis
33526 -info-ada-exceptions [ @var{regexp}]
33529 List all Ada exceptions defined within the program being debugged.
33530 With a regular expression @var{regexp}, only those exceptions whose
33531 names match @var{regexp} are listed.
33533 @subsubheading @value{GDBN} Command
33535 The corresponding @value{GDBN} command is @samp{info exceptions}.
33537 @subsubheading Result
33539 The result is a table of Ada exceptions. The following columns are
33540 defined for each exception:
33544 The name of the exception.
33547 The address of the exception.
33551 @subsubheading Example
33554 -info-ada-exceptions aint
33555 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33556 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33557 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33558 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33559 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33562 @subheading Catching Ada Exceptions
33564 The commands describing how to ask @value{GDBN} to stop when a program
33565 raises an exception are described at @ref{Ada Exception GDB/MI
33566 Catchpoint Commands}.
33569 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33570 @node GDB/MI Support Commands
33571 @section @sc{gdb/mi} Support Commands
33573 Since new commands and features get regularly added to @sc{gdb/mi},
33574 some commands are available to help front-ends query the debugger
33575 about support for these capabilities. Similarly, it is also possible
33576 to query @value{GDBN} about target support of certain features.
33578 @subheading The @code{-info-gdb-mi-command} Command
33579 @cindex @code{-info-gdb-mi-command}
33580 @findex -info-gdb-mi-command
33582 @subsubheading Synopsis
33585 -info-gdb-mi-command @var{cmd_name}
33588 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33590 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33591 is technically not part of the command name (@pxref{GDB/MI Input
33592 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33593 for ease of use, this command also accepts the form with the leading
33596 @subsubheading @value{GDBN} Command
33598 There is no corresponding @value{GDBN} command.
33600 @subsubheading Result
33602 The result is a tuple. There is currently only one field:
33606 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33607 @code{"false"} otherwise.
33611 @subsubheading Example
33613 Here is an example where the @sc{gdb/mi} command does not exist:
33616 -info-gdb-mi-command unsupported-command
33617 ^done,command=@{exists="false"@}
33621 And here is an example where the @sc{gdb/mi} command is known
33625 -info-gdb-mi-command symbol-list-lines
33626 ^done,command=@{exists="true"@}
33629 @subheading The @code{-list-features} Command
33630 @findex -list-features
33631 @cindex supported @sc{gdb/mi} features, list
33633 Returns a list of particular features of the MI protocol that
33634 this version of gdb implements. A feature can be a command,
33635 or a new field in an output of some command, or even an
33636 important bugfix. While a frontend can sometimes detect presence
33637 of a feature at runtime, it is easier to perform detection at debugger
33640 The command returns a list of strings, with each string naming an
33641 available feature. Each returned string is just a name, it does not
33642 have any internal structure. The list of possible feature names
33648 (gdb) -list-features
33649 ^done,result=["feature1","feature2"]
33652 The current list of features is:
33655 @item frozen-varobjs
33656 Indicates support for the @code{-var-set-frozen} command, as well
33657 as possible presense of the @code{frozen} field in the output
33658 of @code{-varobj-create}.
33659 @item pending-breakpoints
33660 Indicates support for the @option{-f} option to the @code{-break-insert}
33663 Indicates Python scripting support, Python-based
33664 pretty-printing commands, and possible presence of the
33665 @samp{display_hint} field in the output of @code{-var-list-children}
33667 Indicates support for the @code{-thread-info} command.
33668 @item data-read-memory-bytes
33669 Indicates support for the @code{-data-read-memory-bytes} and the
33670 @code{-data-write-memory-bytes} commands.
33671 @item breakpoint-notifications
33672 Indicates that changes to breakpoints and breakpoints created via the
33673 CLI will be announced via async records.
33674 @item ada-task-info
33675 Indicates support for the @code{-ada-task-info} command.
33676 @item language-option
33677 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
33678 option (@pxref{Context management}).
33679 @item info-gdb-mi-command
33680 Indicates support for the @code{-info-gdb-mi-command} command.
33681 @item undefined-command-error-code
33682 Indicates support for the "undefined-command" error code in error result
33683 records, produced when trying to execute an undefined @sc{gdb/mi} command
33684 (@pxref{GDB/MI Result Records}).
33685 @item exec-run-start-option
33686 Indicates that the @code{-exec-run} command supports the @option{--start}
33687 option (@pxref{GDB/MI Program Execution}).
33688 @item data-disassemble-a-option
33689 Indicates that the @code{-data-disassemble} command supports the @option{-a}
33690 option (@pxref{GDB/MI Data Manipulation}).
33693 @subheading The @code{-list-target-features} Command
33694 @findex -list-target-features
33696 Returns a list of particular features that are supported by the
33697 target. Those features affect the permitted MI commands, but
33698 unlike the features reported by the @code{-list-features} command, the
33699 features depend on which target GDB is using at the moment. Whenever
33700 a target can change, due to commands such as @code{-target-select},
33701 @code{-target-attach} or @code{-exec-run}, the list of target features
33702 may change, and the frontend should obtain it again.
33706 (gdb) -list-target-features
33707 ^done,result=["async"]
33710 The current list of features is:
33714 Indicates that the target is capable of asynchronous command
33715 execution, which means that @value{GDBN} will accept further commands
33716 while the target is running.
33719 Indicates that the target is capable of reverse execution.
33720 @xref{Reverse Execution}, for more information.
33724 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33725 @node GDB/MI Miscellaneous Commands
33726 @section Miscellaneous @sc{gdb/mi} Commands
33728 @c @subheading -gdb-complete
33730 @subheading The @code{-gdb-exit} Command
33733 @subsubheading Synopsis
33739 Exit @value{GDBN} immediately.
33741 @subsubheading @value{GDBN} Command
33743 Approximately corresponds to @samp{quit}.
33745 @subsubheading Example
33755 @subheading The @code{-exec-abort} Command
33756 @findex -exec-abort
33758 @subsubheading Synopsis
33764 Kill the inferior running program.
33766 @subsubheading @value{GDBN} Command
33768 The corresponding @value{GDBN} command is @samp{kill}.
33770 @subsubheading Example
33775 @subheading The @code{-gdb-set} Command
33778 @subsubheading Synopsis
33784 Set an internal @value{GDBN} variable.
33785 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33787 @subsubheading @value{GDBN} Command
33789 The corresponding @value{GDBN} command is @samp{set}.
33791 @subsubheading Example
33801 @subheading The @code{-gdb-show} Command
33804 @subsubheading Synopsis
33810 Show the current value of a @value{GDBN} variable.
33812 @subsubheading @value{GDBN} Command
33814 The corresponding @value{GDBN} command is @samp{show}.
33816 @subsubheading Example
33825 @c @subheading -gdb-source
33828 @subheading The @code{-gdb-version} Command
33829 @findex -gdb-version
33831 @subsubheading Synopsis
33837 Show version information for @value{GDBN}. Used mostly in testing.
33839 @subsubheading @value{GDBN} Command
33841 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33842 default shows this information when you start an interactive session.
33844 @subsubheading Example
33846 @c This example modifies the actual output from GDB to avoid overfull
33852 ~Copyright 2000 Free Software Foundation, Inc.
33853 ~GDB is free software, covered by the GNU General Public License, and
33854 ~you are welcome to change it and/or distribute copies of it under
33855 ~ certain conditions.
33856 ~Type "show copying" to see the conditions.
33857 ~There is absolutely no warranty for GDB. Type "show warranty" for
33859 ~This GDB was configured as
33860 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33865 @subheading The @code{-list-thread-groups} Command
33866 @findex -list-thread-groups
33868 @subheading Synopsis
33871 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33874 Lists thread groups (@pxref{Thread groups}). When a single thread
33875 group is passed as the argument, lists the children of that group.
33876 When several thread group are passed, lists information about those
33877 thread groups. Without any parameters, lists information about all
33878 top-level thread groups.
33880 Normally, thread groups that are being debugged are reported.
33881 With the @samp{--available} option, @value{GDBN} reports thread groups
33882 available on the target.
33884 The output of this command may have either a @samp{threads} result or
33885 a @samp{groups} result. The @samp{thread} result has a list of tuples
33886 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33887 Information}). The @samp{groups} result has a list of tuples as value,
33888 each tuple describing a thread group. If top-level groups are
33889 requested (that is, no parameter is passed), or when several groups
33890 are passed, the output always has a @samp{groups} result. The format
33891 of the @samp{group} result is described below.
33893 To reduce the number of roundtrips it's possible to list thread groups
33894 together with their children, by passing the @samp{--recurse} option
33895 and the recursion depth. Presently, only recursion depth of 1 is
33896 permitted. If this option is present, then every reported thread group
33897 will also include its children, either as @samp{group} or
33898 @samp{threads} field.
33900 In general, any combination of option and parameters is permitted, with
33901 the following caveats:
33905 When a single thread group is passed, the output will typically
33906 be the @samp{threads} result. Because threads may not contain
33907 anything, the @samp{recurse} option will be ignored.
33910 When the @samp{--available} option is passed, limited information may
33911 be available. In particular, the list of threads of a process might
33912 be inaccessible. Further, specifying specific thread groups might
33913 not give any performance advantage over listing all thread groups.
33914 The frontend should assume that @samp{-list-thread-groups --available}
33915 is always an expensive operation and cache the results.
33919 The @samp{groups} result is a list of tuples, where each tuple may
33920 have the following fields:
33924 Identifier of the thread group. This field is always present.
33925 The identifier is an opaque string; frontends should not try to
33926 convert it to an integer, even though it might look like one.
33929 The type of the thread group. At present, only @samp{process} is a
33933 The target-specific process identifier. This field is only present
33934 for thread groups of type @samp{process} and only if the process exists.
33937 The exit code of this group's last exited thread, formatted in octal.
33938 This field is only present for thread groups of type @samp{process} and
33939 only if the process is not running.
33942 The number of children this thread group has. This field may be
33943 absent for an available thread group.
33946 This field has a list of tuples as value, each tuple describing a
33947 thread. It may be present if the @samp{--recurse} option is
33948 specified, and it's actually possible to obtain the threads.
33951 This field is a list of integers, each identifying a core that one
33952 thread of the group is running on. This field may be absent if
33953 such information is not available.
33956 The name of the executable file that corresponds to this thread group.
33957 The field is only present for thread groups of type @samp{process},
33958 and only if there is a corresponding executable file.
33962 @subheading Example
33966 -list-thread-groups
33967 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33968 -list-thread-groups 17
33969 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33970 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33971 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33972 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33973 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
33974 -list-thread-groups --available
33975 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33976 -list-thread-groups --available --recurse 1
33977 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33978 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33979 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33980 -list-thread-groups --available --recurse 1 17 18
33981 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33982 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33983 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33986 @subheading The @code{-info-os} Command
33989 @subsubheading Synopsis
33992 -info-os [ @var{type} ]
33995 If no argument is supplied, the command returns a table of available
33996 operating-system-specific information types. If one of these types is
33997 supplied as an argument @var{type}, then the command returns a table
33998 of data of that type.
34000 The types of information available depend on the target operating
34003 @subsubheading @value{GDBN} Command
34005 The corresponding @value{GDBN} command is @samp{info os}.
34007 @subsubheading Example
34009 When run on a @sc{gnu}/Linux system, the output will look something
34015 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34016 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34017 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34018 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34019 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34021 item=@{col0="files",col1="Listing of all file descriptors",
34022 col2="File descriptors"@},
34023 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34024 col2="Kernel modules"@},
34025 item=@{col0="msg",col1="Listing of all message queues",
34026 col2="Message queues"@},
34027 item=@{col0="processes",col1="Listing of all processes",
34028 col2="Processes"@},
34029 item=@{col0="procgroups",col1="Listing of all process groups",
34030 col2="Process groups"@},
34031 item=@{col0="semaphores",col1="Listing of all semaphores",
34032 col2="Semaphores"@},
34033 item=@{col0="shm",col1="Listing of all shared-memory regions",
34034 col2="Shared-memory regions"@},
34035 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34037 item=@{col0="threads",col1="Listing of all threads",
34041 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34042 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34043 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34044 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34045 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34046 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34047 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34048 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34050 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34051 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34055 (Note that the MI output here includes a @code{"Title"} column that
34056 does not appear in command-line @code{info os}; this column is useful
34057 for MI clients that want to enumerate the types of data, such as in a
34058 popup menu, but is needless clutter on the command line, and
34059 @code{info os} omits it.)
34061 @subheading The @code{-add-inferior} Command
34062 @findex -add-inferior
34064 @subheading Synopsis
34070 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34071 inferior is not associated with any executable. Such association may
34072 be established with the @samp{-file-exec-and-symbols} command
34073 (@pxref{GDB/MI File Commands}). The command response has a single
34074 field, @samp{inferior}, whose value is the identifier of the
34075 thread group corresponding to the new inferior.
34077 @subheading Example
34082 ^done,inferior="i3"
34085 @subheading The @code{-interpreter-exec} Command
34086 @findex -interpreter-exec
34088 @subheading Synopsis
34091 -interpreter-exec @var{interpreter} @var{command}
34093 @anchor{-interpreter-exec}
34095 Execute the specified @var{command} in the given @var{interpreter}.
34097 @subheading @value{GDBN} Command
34099 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34101 @subheading Example
34105 -interpreter-exec console "break main"
34106 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34107 &"During symbol reading, bad structure-type format.\n"
34108 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34113 @subheading The @code{-inferior-tty-set} Command
34114 @findex -inferior-tty-set
34116 @subheading Synopsis
34119 -inferior-tty-set /dev/pts/1
34122 Set terminal for future runs of the program being debugged.
34124 @subheading @value{GDBN} Command
34126 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34128 @subheading Example
34132 -inferior-tty-set /dev/pts/1
34137 @subheading The @code{-inferior-tty-show} Command
34138 @findex -inferior-tty-show
34140 @subheading Synopsis
34146 Show terminal for future runs of program being debugged.
34148 @subheading @value{GDBN} Command
34150 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34152 @subheading Example
34156 -inferior-tty-set /dev/pts/1
34160 ^done,inferior_tty_terminal="/dev/pts/1"
34164 @subheading The @code{-enable-timings} Command
34165 @findex -enable-timings
34167 @subheading Synopsis
34170 -enable-timings [yes | no]
34173 Toggle the printing of the wallclock, user and system times for an MI
34174 command as a field in its output. This command is to help frontend
34175 developers optimize the performance of their code. No argument is
34176 equivalent to @samp{yes}.
34178 @subheading @value{GDBN} Command
34182 @subheading Example
34190 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34191 addr="0x080484ed",func="main",file="myprog.c",
34192 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34194 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34202 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34203 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34204 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34205 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34210 @chapter @value{GDBN} Annotations
34212 This chapter describes annotations in @value{GDBN}. Annotations were
34213 designed to interface @value{GDBN} to graphical user interfaces or other
34214 similar programs which want to interact with @value{GDBN} at a
34215 relatively high level.
34217 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34221 This is Edition @value{EDITION}, @value{DATE}.
34225 * Annotations Overview:: What annotations are; the general syntax.
34226 * Server Prefix:: Issuing a command without affecting user state.
34227 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34228 * Errors:: Annotations for error messages.
34229 * Invalidation:: Some annotations describe things now invalid.
34230 * Annotations for Running::
34231 Whether the program is running, how it stopped, etc.
34232 * Source Annotations:: Annotations describing source code.
34235 @node Annotations Overview
34236 @section What is an Annotation?
34237 @cindex annotations
34239 Annotations start with a newline character, two @samp{control-z}
34240 characters, and the name of the annotation. If there is no additional
34241 information associated with this annotation, the name of the annotation
34242 is followed immediately by a newline. If there is additional
34243 information, the name of the annotation is followed by a space, the
34244 additional information, and a newline. The additional information
34245 cannot contain newline characters.
34247 Any output not beginning with a newline and two @samp{control-z}
34248 characters denotes literal output from @value{GDBN}. Currently there is
34249 no need for @value{GDBN} to output a newline followed by two
34250 @samp{control-z} characters, but if there was such a need, the
34251 annotations could be extended with an @samp{escape} annotation which
34252 means those three characters as output.
34254 The annotation @var{level}, which is specified using the
34255 @option{--annotate} command line option (@pxref{Mode Options}), controls
34256 how much information @value{GDBN} prints together with its prompt,
34257 values of expressions, source lines, and other types of output. Level 0
34258 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34259 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34260 for programs that control @value{GDBN}, and level 2 annotations have
34261 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34262 Interface, annotate, GDB's Obsolete Annotations}).
34265 @kindex set annotate
34266 @item set annotate @var{level}
34267 The @value{GDBN} command @code{set annotate} sets the level of
34268 annotations to the specified @var{level}.
34270 @item show annotate
34271 @kindex show annotate
34272 Show the current annotation level.
34275 This chapter describes level 3 annotations.
34277 A simple example of starting up @value{GDBN} with annotations is:
34280 $ @kbd{gdb --annotate=3}
34282 Copyright 2003 Free Software Foundation, Inc.
34283 GDB is free software, covered by the GNU General Public License,
34284 and you are welcome to change it and/or distribute copies of it
34285 under certain conditions.
34286 Type "show copying" to see the conditions.
34287 There is absolutely no warranty for GDB. Type "show warranty"
34289 This GDB was configured as "i386-pc-linux-gnu"
34300 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34301 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34302 denotes a @samp{control-z} character) are annotations; the rest is
34303 output from @value{GDBN}.
34305 @node Server Prefix
34306 @section The Server Prefix
34307 @cindex server prefix
34309 If you prefix a command with @samp{server } then it will not affect
34310 the command history, nor will it affect @value{GDBN}'s notion of which
34311 command to repeat if @key{RET} is pressed on a line by itself. This
34312 means that commands can be run behind a user's back by a front-end in
34313 a transparent manner.
34315 The @code{server } prefix does not affect the recording of values into
34316 the value history; to print a value without recording it into the
34317 value history, use the @code{output} command instead of the
34318 @code{print} command.
34320 Using this prefix also disables confirmation requests
34321 (@pxref{confirmation requests}).
34324 @section Annotation for @value{GDBN} Input
34326 @cindex annotations for prompts
34327 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34328 to know when to send output, when the output from a given command is
34331 Different kinds of input each have a different @dfn{input type}. Each
34332 input type has three annotations: a @code{pre-} annotation, which
34333 denotes the beginning of any prompt which is being output, a plain
34334 annotation, which denotes the end of the prompt, and then a @code{post-}
34335 annotation which denotes the end of any echo which may (or may not) be
34336 associated with the input. For example, the @code{prompt} input type
34337 features the following annotations:
34345 The input types are
34348 @findex pre-prompt annotation
34349 @findex prompt annotation
34350 @findex post-prompt annotation
34352 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34354 @findex pre-commands annotation
34355 @findex commands annotation
34356 @findex post-commands annotation
34358 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34359 command. The annotations are repeated for each command which is input.
34361 @findex pre-overload-choice annotation
34362 @findex overload-choice annotation
34363 @findex post-overload-choice annotation
34364 @item overload-choice
34365 When @value{GDBN} wants the user to select between various overloaded functions.
34367 @findex pre-query annotation
34368 @findex query annotation
34369 @findex post-query annotation
34371 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34373 @findex pre-prompt-for-continue annotation
34374 @findex prompt-for-continue annotation
34375 @findex post-prompt-for-continue annotation
34376 @item prompt-for-continue
34377 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34378 expect this to work well; instead use @code{set height 0} to disable
34379 prompting. This is because the counting of lines is buggy in the
34380 presence of annotations.
34385 @cindex annotations for errors, warnings and interrupts
34387 @findex quit annotation
34392 This annotation occurs right before @value{GDBN} responds to an interrupt.
34394 @findex error annotation
34399 This annotation occurs right before @value{GDBN} responds to an error.
34401 Quit and error annotations indicate that any annotations which @value{GDBN} was
34402 in the middle of may end abruptly. For example, if a
34403 @code{value-history-begin} annotation is followed by a @code{error}, one
34404 cannot expect to receive the matching @code{value-history-end}. One
34405 cannot expect not to receive it either, however; an error annotation
34406 does not necessarily mean that @value{GDBN} is immediately returning all the way
34409 @findex error-begin annotation
34410 A quit or error annotation may be preceded by
34416 Any output between that and the quit or error annotation is the error
34419 Warning messages are not yet annotated.
34420 @c If we want to change that, need to fix warning(), type_error(),
34421 @c range_error(), and possibly other places.
34424 @section Invalidation Notices
34426 @cindex annotations for invalidation messages
34427 The following annotations say that certain pieces of state may have
34431 @findex frames-invalid annotation
34432 @item ^Z^Zframes-invalid
34434 The frames (for example, output from the @code{backtrace} command) may
34437 @findex breakpoints-invalid annotation
34438 @item ^Z^Zbreakpoints-invalid
34440 The breakpoints may have changed. For example, the user just added or
34441 deleted a breakpoint.
34444 @node Annotations for Running
34445 @section Running the Program
34446 @cindex annotations for running programs
34448 @findex starting annotation
34449 @findex stopping annotation
34450 When the program starts executing due to a @value{GDBN} command such as
34451 @code{step} or @code{continue},
34457 is output. When the program stops,
34463 is output. Before the @code{stopped} annotation, a variety of
34464 annotations describe how the program stopped.
34467 @findex exited annotation
34468 @item ^Z^Zexited @var{exit-status}
34469 The program exited, and @var{exit-status} is the exit status (zero for
34470 successful exit, otherwise nonzero).
34472 @findex signalled annotation
34473 @findex signal-name annotation
34474 @findex signal-name-end annotation
34475 @findex signal-string annotation
34476 @findex signal-string-end annotation
34477 @item ^Z^Zsignalled
34478 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34479 annotation continues:
34485 ^Z^Zsignal-name-end
34489 ^Z^Zsignal-string-end
34494 where @var{name} is the name of the signal, such as @code{SIGILL} or
34495 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34496 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34497 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34498 user's benefit and have no particular format.
34500 @findex signal annotation
34502 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34503 just saying that the program received the signal, not that it was
34504 terminated with it.
34506 @findex breakpoint annotation
34507 @item ^Z^Zbreakpoint @var{number}
34508 The program hit breakpoint number @var{number}.
34510 @findex watchpoint annotation
34511 @item ^Z^Zwatchpoint @var{number}
34512 The program hit watchpoint number @var{number}.
34515 @node Source Annotations
34516 @section Displaying Source
34517 @cindex annotations for source display
34519 @findex source annotation
34520 The following annotation is used instead of displaying source code:
34523 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34526 where @var{filename} is an absolute file name indicating which source
34527 file, @var{line} is the line number within that file (where 1 is the
34528 first line in the file), @var{character} is the character position
34529 within the file (where 0 is the first character in the file) (for most
34530 debug formats this will necessarily point to the beginning of a line),
34531 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34532 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34533 @var{addr} is the address in the target program associated with the
34534 source which is being displayed. The @var{addr} is in the form @samp{0x}
34535 followed by one or more lowercase hex digits (note that this does not
34536 depend on the language).
34538 @node JIT Interface
34539 @chapter JIT Compilation Interface
34540 @cindex just-in-time compilation
34541 @cindex JIT compilation interface
34543 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34544 interface. A JIT compiler is a program or library that generates native
34545 executable code at runtime and executes it, usually in order to achieve good
34546 performance while maintaining platform independence.
34548 Programs that use JIT compilation are normally difficult to debug because
34549 portions of their code are generated at runtime, instead of being loaded from
34550 object files, which is where @value{GDBN} normally finds the program's symbols
34551 and debug information. In order to debug programs that use JIT compilation,
34552 @value{GDBN} has an interface that allows the program to register in-memory
34553 symbol files with @value{GDBN} at runtime.
34555 If you are using @value{GDBN} to debug a program that uses this interface, then
34556 it should work transparently so long as you have not stripped the binary. If
34557 you are developing a JIT compiler, then the interface is documented in the rest
34558 of this chapter. At this time, the only known client of this interface is the
34561 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34562 JIT compiler communicates with @value{GDBN} by writing data into a global
34563 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34564 attaches, it reads a linked list of symbol files from the global variable to
34565 find existing code, and puts a breakpoint in the function so that it can find
34566 out about additional code.
34569 * Declarations:: Relevant C struct declarations
34570 * Registering Code:: Steps to register code
34571 * Unregistering Code:: Steps to unregister code
34572 * Custom Debug Info:: Emit debug information in a custom format
34576 @section JIT Declarations
34578 These are the relevant struct declarations that a C program should include to
34579 implement the interface:
34589 struct jit_code_entry
34591 struct jit_code_entry *next_entry;
34592 struct jit_code_entry *prev_entry;
34593 const char *symfile_addr;
34594 uint64_t symfile_size;
34597 struct jit_descriptor
34600 /* This type should be jit_actions_t, but we use uint32_t
34601 to be explicit about the bitwidth. */
34602 uint32_t action_flag;
34603 struct jit_code_entry *relevant_entry;
34604 struct jit_code_entry *first_entry;
34607 /* GDB puts a breakpoint in this function. */
34608 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34610 /* Make sure to specify the version statically, because the
34611 debugger may check the version before we can set it. */
34612 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34615 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34616 modifications to this global data properly, which can easily be done by putting
34617 a global mutex around modifications to these structures.
34619 @node Registering Code
34620 @section Registering Code
34622 To register code with @value{GDBN}, the JIT should follow this protocol:
34626 Generate an object file in memory with symbols and other desired debug
34627 information. The file must include the virtual addresses of the sections.
34630 Create a code entry for the file, which gives the start and size of the symbol
34634 Add it to the linked list in the JIT descriptor.
34637 Point the relevant_entry field of the descriptor at the entry.
34640 Set @code{action_flag} to @code{JIT_REGISTER} and call
34641 @code{__jit_debug_register_code}.
34644 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34645 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34646 new code. However, the linked list must still be maintained in order to allow
34647 @value{GDBN} to attach to a running process and still find the symbol files.
34649 @node Unregistering Code
34650 @section Unregistering Code
34652 If code is freed, then the JIT should use the following protocol:
34656 Remove the code entry corresponding to the code from the linked list.
34659 Point the @code{relevant_entry} field of the descriptor at the code entry.
34662 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34663 @code{__jit_debug_register_code}.
34666 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34667 and the JIT will leak the memory used for the associated symbol files.
34669 @node Custom Debug Info
34670 @section Custom Debug Info
34671 @cindex custom JIT debug info
34672 @cindex JIT debug info reader
34674 Generating debug information in platform-native file formats (like ELF
34675 or COFF) may be an overkill for JIT compilers; especially if all the
34676 debug info is used for is displaying a meaningful backtrace. The
34677 issue can be resolved by having the JIT writers decide on a debug info
34678 format and also provide a reader that parses the debug info generated
34679 by the JIT compiler. This section gives a brief overview on writing
34680 such a parser. More specific details can be found in the source file
34681 @file{gdb/jit-reader.in}, which is also installed as a header at
34682 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34684 The reader is implemented as a shared object (so this functionality is
34685 not available on platforms which don't allow loading shared objects at
34686 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34687 @code{jit-reader-unload} are provided, to be used to load and unload
34688 the readers from a preconfigured directory. Once loaded, the shared
34689 object is used the parse the debug information emitted by the JIT
34693 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34694 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34697 @node Using JIT Debug Info Readers
34698 @subsection Using JIT Debug Info Readers
34699 @kindex jit-reader-load
34700 @kindex jit-reader-unload
34702 Readers can be loaded and unloaded using the @code{jit-reader-load}
34703 and @code{jit-reader-unload} commands.
34706 @item jit-reader-load @var{reader}
34707 Load the JIT reader named @var{reader}, which is a shared
34708 object specified as either an absolute or a relative file name. In
34709 the latter case, @value{GDBN} will try to load the reader from a
34710 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34711 system (here @var{libdir} is the system library directory, often
34712 @file{/usr/local/lib}).
34714 Only one reader can be active at a time; trying to load a second
34715 reader when one is already loaded will result in @value{GDBN}
34716 reporting an error. A new JIT reader can be loaded by first unloading
34717 the current one using @code{jit-reader-unload} and then invoking
34718 @code{jit-reader-load}.
34720 @item jit-reader-unload
34721 Unload the currently loaded JIT reader.
34725 @node Writing JIT Debug Info Readers
34726 @subsection Writing JIT Debug Info Readers
34727 @cindex writing JIT debug info readers
34729 As mentioned, a reader is essentially a shared object conforming to a
34730 certain ABI. This ABI is described in @file{jit-reader.h}.
34732 @file{jit-reader.h} defines the structures, macros and functions
34733 required to write a reader. It is installed (along with
34734 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34735 the system include directory.
34737 Readers need to be released under a GPL compatible license. A reader
34738 can be declared as released under such a license by placing the macro
34739 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34741 The entry point for readers is the symbol @code{gdb_init_reader},
34742 which is expected to be a function with the prototype
34744 @findex gdb_init_reader
34746 extern struct gdb_reader_funcs *gdb_init_reader (void);
34749 @cindex @code{struct gdb_reader_funcs}
34751 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34752 functions. These functions are executed to read the debug info
34753 generated by the JIT compiler (@code{read}), to unwind stack frames
34754 (@code{unwind}) and to create canonical frame IDs
34755 (@code{get_Frame_id}). It also has a callback that is called when the
34756 reader is being unloaded (@code{destroy}). The struct looks like this
34759 struct gdb_reader_funcs
34761 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34762 int reader_version;
34764 /* For use by the reader. */
34767 gdb_read_debug_info *read;
34768 gdb_unwind_frame *unwind;
34769 gdb_get_frame_id *get_frame_id;
34770 gdb_destroy_reader *destroy;
34774 @cindex @code{struct gdb_symbol_callbacks}
34775 @cindex @code{struct gdb_unwind_callbacks}
34777 The callbacks are provided with another set of callbacks by
34778 @value{GDBN} to do their job. For @code{read}, these callbacks are
34779 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34780 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34781 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34782 files and new symbol tables inside those object files. @code{struct
34783 gdb_unwind_callbacks} has callbacks to read registers off the current
34784 frame and to write out the values of the registers in the previous
34785 frame. Both have a callback (@code{target_read}) to read bytes off the
34786 target's address space.
34788 @node In-Process Agent
34789 @chapter In-Process Agent
34790 @cindex debugging agent
34791 The traditional debugging model is conceptually low-speed, but works fine,
34792 because most bugs can be reproduced in debugging-mode execution. However,
34793 as multi-core or many-core processors are becoming mainstream, and
34794 multi-threaded programs become more and more popular, there should be more
34795 and more bugs that only manifest themselves at normal-mode execution, for
34796 example, thread races, because debugger's interference with the program's
34797 timing may conceal the bugs. On the other hand, in some applications,
34798 it is not feasible for the debugger to interrupt the program's execution
34799 long enough for the developer to learn anything helpful about its behavior.
34800 If the program's correctness depends on its real-time behavior, delays
34801 introduced by a debugger might cause the program to fail, even when the
34802 code itself is correct. It is useful to be able to observe the program's
34803 behavior without interrupting it.
34805 Therefore, traditional debugging model is too intrusive to reproduce
34806 some bugs. In order to reduce the interference with the program, we can
34807 reduce the number of operations performed by debugger. The
34808 @dfn{In-Process Agent}, a shared library, is running within the same
34809 process with inferior, and is able to perform some debugging operations
34810 itself. As a result, debugger is only involved when necessary, and
34811 performance of debugging can be improved accordingly. Note that
34812 interference with program can be reduced but can't be removed completely,
34813 because the in-process agent will still stop or slow down the program.
34815 The in-process agent can interpret and execute Agent Expressions
34816 (@pxref{Agent Expressions}) during performing debugging operations. The
34817 agent expressions can be used for different purposes, such as collecting
34818 data in tracepoints, and condition evaluation in breakpoints.
34820 @anchor{Control Agent}
34821 You can control whether the in-process agent is used as an aid for
34822 debugging with the following commands:
34825 @kindex set agent on
34827 Causes the in-process agent to perform some operations on behalf of the
34828 debugger. Just which operations requested by the user will be done
34829 by the in-process agent depends on the its capabilities. For example,
34830 if you request to evaluate breakpoint conditions in the in-process agent,
34831 and the in-process agent has such capability as well, then breakpoint
34832 conditions will be evaluated in the in-process agent.
34834 @kindex set agent off
34835 @item set agent off
34836 Disables execution of debugging operations by the in-process agent. All
34837 of the operations will be performed by @value{GDBN}.
34841 Display the current setting of execution of debugging operations by
34842 the in-process agent.
34846 * In-Process Agent Protocol::
34849 @node In-Process Agent Protocol
34850 @section In-Process Agent Protocol
34851 @cindex in-process agent protocol
34853 The in-process agent is able to communicate with both @value{GDBN} and
34854 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34855 used for communications between @value{GDBN} or GDBserver and the IPA.
34856 In general, @value{GDBN} or GDBserver sends commands
34857 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34858 in-process agent replies back with the return result of the command, or
34859 some other information. The data sent to in-process agent is composed
34860 of primitive data types, such as 4-byte or 8-byte type, and composite
34861 types, which are called objects (@pxref{IPA Protocol Objects}).
34864 * IPA Protocol Objects::
34865 * IPA Protocol Commands::
34868 @node IPA Protocol Objects
34869 @subsection IPA Protocol Objects
34870 @cindex ipa protocol objects
34872 The commands sent to and results received from agent may contain some
34873 complex data types called @dfn{objects}.
34875 The in-process agent is running on the same machine with @value{GDBN}
34876 or GDBserver, so it doesn't have to handle as much differences between
34877 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34878 However, there are still some differences of two ends in two processes:
34882 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34883 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34885 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34886 GDBserver is compiled with one, and in-process agent is compiled with
34890 Here are the IPA Protocol Objects:
34894 agent expression object. It represents an agent expression
34895 (@pxref{Agent Expressions}).
34896 @anchor{agent expression object}
34898 tracepoint action object. It represents a tracepoint action
34899 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34900 memory, static trace data and to evaluate expression.
34901 @anchor{tracepoint action object}
34903 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34904 @anchor{tracepoint object}
34908 The following table describes important attributes of each IPA protocol
34911 @multitable @columnfractions .30 .20 .50
34912 @headitem Name @tab Size @tab Description
34913 @item @emph{agent expression object} @tab @tab
34914 @item length @tab 4 @tab length of bytes code
34915 @item byte code @tab @var{length} @tab contents of byte code
34916 @item @emph{tracepoint action for collecting memory} @tab @tab
34917 @item 'M' @tab 1 @tab type of tracepoint action
34918 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34919 address of the lowest byte to collect, otherwise @var{addr} is the offset
34920 of @var{basereg} for memory collecting.
34921 @item len @tab 8 @tab length of memory for collecting
34922 @item basereg @tab 4 @tab the register number containing the starting
34923 memory address for collecting.
34924 @item @emph{tracepoint action for collecting registers} @tab @tab
34925 @item 'R' @tab 1 @tab type of tracepoint action
34926 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34927 @item 'L' @tab 1 @tab type of tracepoint action
34928 @item @emph{tracepoint action for expression evaluation} @tab @tab
34929 @item 'X' @tab 1 @tab type of tracepoint action
34930 @item agent expression @tab length of @tab @ref{agent expression object}
34931 @item @emph{tracepoint object} @tab @tab
34932 @item number @tab 4 @tab number of tracepoint
34933 @item address @tab 8 @tab address of tracepoint inserted on
34934 @item type @tab 4 @tab type of tracepoint
34935 @item enabled @tab 1 @tab enable or disable of tracepoint
34936 @item step_count @tab 8 @tab step
34937 @item pass_count @tab 8 @tab pass
34938 @item numactions @tab 4 @tab number of tracepoint actions
34939 @item hit count @tab 8 @tab hit count
34940 @item trace frame usage @tab 8 @tab trace frame usage
34941 @item compiled_cond @tab 8 @tab compiled condition
34942 @item orig_size @tab 8 @tab orig size
34943 @item condition @tab 4 if condition is NULL otherwise length of
34944 @ref{agent expression object}
34945 @tab zero if condition is NULL, otherwise is
34946 @ref{agent expression object}
34947 @item actions @tab variable
34948 @tab numactions number of @ref{tracepoint action object}
34951 @node IPA Protocol Commands
34952 @subsection IPA Protocol Commands
34953 @cindex ipa protocol commands
34955 The spaces in each command are delimiters to ease reading this commands
34956 specification. They don't exist in real commands.
34960 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34961 Installs a new fast tracepoint described by @var{tracepoint_object}
34962 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34963 head of @dfn{jumppad}, which is used to jump to data collection routine
34968 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34969 @var{target_address} is address of tracepoint in the inferior.
34970 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34971 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34972 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34973 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34980 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34981 is about to kill inferiors.
34989 @item probe_marker_at:@var{address}
34990 Asks in-process agent to probe the marker at @var{address}.
34997 @item unprobe_marker_at:@var{address}
34998 Asks in-process agent to unprobe the marker at @var{address}.
35002 @chapter Reporting Bugs in @value{GDBN}
35003 @cindex bugs in @value{GDBN}
35004 @cindex reporting bugs in @value{GDBN}
35006 Your bug reports play an essential role in making @value{GDBN} reliable.
35008 Reporting a bug may help you by bringing a solution to your problem, or it
35009 may not. But in any case the principal function of a bug report is to help
35010 the entire community by making the next version of @value{GDBN} work better. Bug
35011 reports are your contribution to the maintenance of @value{GDBN}.
35013 In order for a bug report to serve its purpose, you must include the
35014 information that enables us to fix the bug.
35017 * Bug Criteria:: Have you found a bug?
35018 * Bug Reporting:: How to report bugs
35022 @section Have You Found a Bug?
35023 @cindex bug criteria
35025 If you are not sure whether you have found a bug, here are some guidelines:
35028 @cindex fatal signal
35029 @cindex debugger crash
35030 @cindex crash of debugger
35032 If the debugger gets a fatal signal, for any input whatever, that is a
35033 @value{GDBN} bug. Reliable debuggers never crash.
35035 @cindex error on valid input
35037 If @value{GDBN} produces an error message for valid input, that is a
35038 bug. (Note that if you're cross debugging, the problem may also be
35039 somewhere in the connection to the target.)
35041 @cindex invalid input
35043 If @value{GDBN} does not produce an error message for invalid input,
35044 that is a bug. However, you should note that your idea of
35045 ``invalid input'' might be our idea of ``an extension'' or ``support
35046 for traditional practice''.
35049 If you are an experienced user of debugging tools, your suggestions
35050 for improvement of @value{GDBN} are welcome in any case.
35053 @node Bug Reporting
35054 @section How to Report Bugs
35055 @cindex bug reports
35056 @cindex @value{GDBN} bugs, reporting
35058 A number of companies and individuals offer support for @sc{gnu} products.
35059 If you obtained @value{GDBN} from a support organization, we recommend you
35060 contact that organization first.
35062 You can find contact information for many support companies and
35063 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35065 @c should add a web page ref...
35068 @ifset BUGURL_DEFAULT
35069 In any event, we also recommend that you submit bug reports for
35070 @value{GDBN}. The preferred method is to submit them directly using
35071 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35072 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35075 @strong{Do not send bug reports to @samp{info-gdb}, or to
35076 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35077 not want to receive bug reports. Those that do have arranged to receive
35080 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35081 serves as a repeater. The mailing list and the newsgroup carry exactly
35082 the same messages. Often people think of posting bug reports to the
35083 newsgroup instead of mailing them. This appears to work, but it has one
35084 problem which can be crucial: a newsgroup posting often lacks a mail
35085 path back to the sender. Thus, if we need to ask for more information,
35086 we may be unable to reach you. For this reason, it is better to send
35087 bug reports to the mailing list.
35089 @ifclear BUGURL_DEFAULT
35090 In any event, we also recommend that you submit bug reports for
35091 @value{GDBN} to @value{BUGURL}.
35095 The fundamental principle of reporting bugs usefully is this:
35096 @strong{report all the facts}. If you are not sure whether to state a
35097 fact or leave it out, state it!
35099 Often people omit facts because they think they know what causes the
35100 problem and assume that some details do not matter. Thus, you might
35101 assume that the name of the variable you use in an example does not matter.
35102 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35103 stray memory reference which happens to fetch from the location where that
35104 name is stored in memory; perhaps, if the name were different, the contents
35105 of that location would fool the debugger into doing the right thing despite
35106 the bug. Play it safe and give a specific, complete example. That is the
35107 easiest thing for you to do, and the most helpful.
35109 Keep in mind that the purpose of a bug report is to enable us to fix the
35110 bug. It may be that the bug has been reported previously, but neither
35111 you nor we can know that unless your bug report is complete and
35114 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35115 bell?'' Those bug reports are useless, and we urge everyone to
35116 @emph{refuse to respond to them} except to chide the sender to report
35119 To enable us to fix the bug, you should include all these things:
35123 The version of @value{GDBN}. @value{GDBN} announces it if you start
35124 with no arguments; you can also print it at any time using @code{show
35127 Without this, we will not know whether there is any point in looking for
35128 the bug in the current version of @value{GDBN}.
35131 The type of machine you are using, and the operating system name and
35135 The details of the @value{GDBN} build-time configuration.
35136 @value{GDBN} shows these details if you invoke it with the
35137 @option{--configuration} command-line option, or if you type
35138 @code{show configuration} at @value{GDBN}'s prompt.
35141 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35142 ``@value{GCC}--2.8.1''.
35145 What compiler (and its version) was used to compile the program you are
35146 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35147 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35148 to get this information; for other compilers, see the documentation for
35152 The command arguments you gave the compiler to compile your example and
35153 observe the bug. For example, did you use @samp{-O}? To guarantee
35154 you will not omit something important, list them all. A copy of the
35155 Makefile (or the output from make) is sufficient.
35157 If we were to try to guess the arguments, we would probably guess wrong
35158 and then we might not encounter the bug.
35161 A complete input script, and all necessary source files, that will
35165 A description of what behavior you observe that you believe is
35166 incorrect. For example, ``It gets a fatal signal.''
35168 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35169 will certainly notice it. But if the bug is incorrect output, we might
35170 not notice unless it is glaringly wrong. You might as well not give us
35171 a chance to make a mistake.
35173 Even if the problem you experience is a fatal signal, you should still
35174 say so explicitly. Suppose something strange is going on, such as, your
35175 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35176 the C library on your system. (This has happened!) Your copy might
35177 crash and ours would not. If you told us to expect a crash, then when
35178 ours fails to crash, we would know that the bug was not happening for
35179 us. If you had not told us to expect a crash, then we would not be able
35180 to draw any conclusion from our observations.
35183 @cindex recording a session script
35184 To collect all this information, you can use a session recording program
35185 such as @command{script}, which is available on many Unix systems.
35186 Just run your @value{GDBN} session inside @command{script} and then
35187 include the @file{typescript} file with your bug report.
35189 Another way to record a @value{GDBN} session is to run @value{GDBN}
35190 inside Emacs and then save the entire buffer to a file.
35193 If you wish to suggest changes to the @value{GDBN} source, send us context
35194 diffs. If you even discuss something in the @value{GDBN} source, refer to
35195 it by context, not by line number.
35197 The line numbers in our development sources will not match those in your
35198 sources. Your line numbers would convey no useful information to us.
35202 Here are some things that are not necessary:
35206 A description of the envelope of the bug.
35208 Often people who encounter a bug spend a lot of time investigating
35209 which changes to the input file will make the bug go away and which
35210 changes will not affect it.
35212 This is often time consuming and not very useful, because the way we
35213 will find the bug is by running a single example under the debugger
35214 with breakpoints, not by pure deduction from a series of examples.
35215 We recommend that you save your time for something else.
35217 Of course, if you can find a simpler example to report @emph{instead}
35218 of the original one, that is a convenience for us. Errors in the
35219 output will be easier to spot, running under the debugger will take
35220 less time, and so on.
35222 However, simplification is not vital; if you do not want to do this,
35223 report the bug anyway and send us the entire test case you used.
35226 A patch for the bug.
35228 A patch for the bug does help us if it is a good one. But do not omit
35229 the necessary information, such as the test case, on the assumption that
35230 a patch is all we need. We might see problems with your patch and decide
35231 to fix the problem another way, or we might not understand it at all.
35233 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35234 construct an example that will make the program follow a certain path
35235 through the code. If you do not send us the example, we will not be able
35236 to construct one, so we will not be able to verify that the bug is fixed.
35238 And if we cannot understand what bug you are trying to fix, or why your
35239 patch should be an improvement, we will not install it. A test case will
35240 help us to understand.
35243 A guess about what the bug is or what it depends on.
35245 Such guesses are usually wrong. Even we cannot guess right about such
35246 things without first using the debugger to find the facts.
35249 @c The readline documentation is distributed with the readline code
35250 @c and consists of the two following files:
35253 @c Use -I with makeinfo to point to the appropriate directory,
35254 @c environment var TEXINPUTS with TeX.
35255 @ifclear SYSTEM_READLINE
35256 @include rluser.texi
35257 @include hsuser.texi
35261 @appendix In Memoriam
35263 The @value{GDBN} project mourns the loss of the following long-time
35268 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35269 to Free Software in general. Outside of @value{GDBN}, he was known in
35270 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35272 @item Michael Snyder
35273 Michael was one of the Global Maintainers of the @value{GDBN} project,
35274 with contributions recorded as early as 1996, until 2011. In addition
35275 to his day to day participation, he was a large driving force behind
35276 adding Reverse Debugging to @value{GDBN}.
35279 Beyond their technical contributions to the project, they were also
35280 enjoyable members of the Free Software Community. We will miss them.
35282 @node Formatting Documentation
35283 @appendix Formatting Documentation
35285 @cindex @value{GDBN} reference card
35286 @cindex reference card
35287 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35288 for printing with PostScript or Ghostscript, in the @file{gdb}
35289 subdirectory of the main source directory@footnote{In
35290 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35291 release.}. If you can use PostScript or Ghostscript with your printer,
35292 you can print the reference card immediately with @file{refcard.ps}.
35294 The release also includes the source for the reference card. You
35295 can format it, using @TeX{}, by typing:
35301 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35302 mode on US ``letter'' size paper;
35303 that is, on a sheet 11 inches wide by 8.5 inches
35304 high. You will need to specify this form of printing as an option to
35305 your @sc{dvi} output program.
35307 @cindex documentation
35309 All the documentation for @value{GDBN} comes as part of the machine-readable
35310 distribution. The documentation is written in Texinfo format, which is
35311 a documentation system that uses a single source file to produce both
35312 on-line information and a printed manual. You can use one of the Info
35313 formatting commands to create the on-line version of the documentation
35314 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35316 @value{GDBN} includes an already formatted copy of the on-line Info
35317 version of this manual in the @file{gdb} subdirectory. The main Info
35318 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35319 subordinate files matching @samp{gdb.info*} in the same directory. If
35320 necessary, you can print out these files, or read them with any editor;
35321 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35322 Emacs or the standalone @code{info} program, available as part of the
35323 @sc{gnu} Texinfo distribution.
35325 If you want to format these Info files yourself, you need one of the
35326 Info formatting programs, such as @code{texinfo-format-buffer} or
35329 If you have @code{makeinfo} installed, and are in the top level
35330 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35331 version @value{GDBVN}), you can make the Info file by typing:
35338 If you want to typeset and print copies of this manual, you need @TeX{},
35339 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35340 Texinfo definitions file.
35342 @TeX{} is a typesetting program; it does not print files directly, but
35343 produces output files called @sc{dvi} files. To print a typeset
35344 document, you need a program to print @sc{dvi} files. If your system
35345 has @TeX{} installed, chances are it has such a program. The precise
35346 command to use depends on your system; @kbd{lpr -d} is common; another
35347 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35348 require a file name without any extension or a @samp{.dvi} extension.
35350 @TeX{} also requires a macro definitions file called
35351 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35352 written in Texinfo format. On its own, @TeX{} cannot either read or
35353 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35354 and is located in the @file{gdb-@var{version-number}/texinfo}
35357 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35358 typeset and print this manual. First switch to the @file{gdb}
35359 subdirectory of the main source directory (for example, to
35360 @file{gdb-@value{GDBVN}/gdb}) and type:
35366 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35368 @node Installing GDB
35369 @appendix Installing @value{GDBN}
35370 @cindex installation
35373 * Requirements:: Requirements for building @value{GDBN}
35374 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35375 * Separate Objdir:: Compiling @value{GDBN} in another directory
35376 * Config Names:: Specifying names for hosts and targets
35377 * Configure Options:: Summary of options for configure
35378 * System-wide configuration:: Having a system-wide init file
35382 @section Requirements for Building @value{GDBN}
35383 @cindex building @value{GDBN}, requirements for
35385 Building @value{GDBN} requires various tools and packages to be available.
35386 Other packages will be used only if they are found.
35388 @heading Tools/Packages Necessary for Building @value{GDBN}
35390 @item C@t{++}11 compiler
35391 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35392 recent C@t{++}11 compiler, e.g.@: GCC.
35395 @value{GDBN}'s build system relies on features only found in the GNU
35396 make program. Other variants of @code{make} will not work.
35399 @heading Tools/Packages Optional for Building @value{GDBN}
35403 @value{GDBN} can use the Expat XML parsing library. This library may be
35404 included with your operating system distribution; if it is not, you
35405 can get the latest version from @url{http://expat.sourceforge.net}.
35406 The @file{configure} script will search for this library in several
35407 standard locations; if it is installed in an unusual path, you can
35408 use the @option{--with-libexpat-prefix} option to specify its location.
35414 Remote protocol memory maps (@pxref{Memory Map Format})
35416 Target descriptions (@pxref{Target Descriptions})
35418 Remote shared library lists (@xref{Library List Format},
35419 or alternatively @pxref{Library List Format for SVR4 Targets})
35421 MS-Windows shared libraries (@pxref{Shared Libraries})
35423 Traceframe info (@pxref{Traceframe Info Format})
35425 Branch trace (@pxref{Branch Trace Format},
35426 @pxref{Branch Trace Configuration Format})
35430 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35431 default, @value{GDBN} will be compiled if the Guile libraries are
35432 installed and are found by @file{configure}. You can use the
35433 @code{--with-guile} option to request Guile, and pass either the Guile
35434 version number or the file name of the relevant @code{pkg-config}
35435 program to choose a particular version of Guile.
35438 @value{GDBN}'s features related to character sets (@pxref{Character
35439 Sets}) require a functioning @code{iconv} implementation. If you are
35440 on a GNU system, then this is provided by the GNU C Library. Some
35441 other systems also provide a working @code{iconv}.
35443 If @value{GDBN} is using the @code{iconv} program which is installed
35444 in a non-standard place, you will need to tell @value{GDBN} where to
35445 find it. This is done with @option{--with-iconv-bin} which specifies
35446 the directory that contains the @code{iconv} program. This program is
35447 run in order to make a list of the available character sets.
35449 On systems without @code{iconv}, you can install GNU Libiconv. If
35450 Libiconv is installed in a standard place, @value{GDBN} will
35451 automatically use it if it is needed. If you have previously
35452 installed Libiconv in a non-standard place, you can use the
35453 @option{--with-libiconv-prefix} option to @file{configure}.
35455 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35456 arrange to build Libiconv if a directory named @file{libiconv} appears
35457 in the top-most source directory. If Libiconv is built this way, and
35458 if the operating system does not provide a suitable @code{iconv}
35459 implementation, then the just-built library will automatically be used
35460 by @value{GDBN}. One easy way to set this up is to download GNU
35461 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35462 source tree, and then rename the directory holding the Libiconv source
35463 code to @samp{libiconv}.
35466 @value{GDBN} can support debugging sections that are compressed with
35467 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35468 included with your operating system, you can find it in the xz package
35469 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35470 the usual place, then the @file{configure} script will use it
35471 automatically. If it is installed in an unusual path, you can use the
35472 @option{--with-lzma-prefix} option to specify its location.
35476 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35477 library. This library may be included with your operating system
35478 distribution; if it is not, you can get the latest version from
35479 @url{http://www.mpfr.org}. The @file{configure} script will search
35480 for this library in several standard locations; if it is installed
35481 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35482 option to specify its location.
35484 GNU MPFR is used to emulate target floating-point arithmetic during
35485 expression evaluation when the target uses different floating-point
35486 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35487 will fall back to using host floating-point arithmetic.
35490 @value{GDBN} can be scripted using Python language. @xref{Python}.
35491 By default, @value{GDBN} will be compiled if the Python libraries are
35492 installed and are found by @file{configure}. You can use the
35493 @code{--with-python} option to request Python, and pass either the
35494 file name of the relevant @code{python} executable, or the name of the
35495 directory in which Python is installed, to choose a particular
35496 installation of Python.
35499 @cindex compressed debug sections
35500 @value{GDBN} will use the @samp{zlib} library, if available, to read
35501 compressed debug sections. Some linkers, such as GNU gold, are capable
35502 of producing binaries with compressed debug sections. If @value{GDBN}
35503 is compiled with @samp{zlib}, it will be able to read the debug
35504 information in such binaries.
35506 The @samp{zlib} library is likely included with your operating system
35507 distribution; if it is not, you can get the latest version from
35508 @url{http://zlib.net}.
35511 @node Running Configure
35512 @section Invoking the @value{GDBN} @file{configure} Script
35513 @cindex configuring @value{GDBN}
35514 @value{GDBN} comes with a @file{configure} script that automates the process
35515 of preparing @value{GDBN} for installation; you can then use @code{make} to
35516 build the @code{gdb} program.
35518 @c irrelevant in info file; it's as current as the code it lives with.
35519 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35520 look at the @file{README} file in the sources; we may have improved the
35521 installation procedures since publishing this manual.}
35524 The @value{GDBN} distribution includes all the source code you need for
35525 @value{GDBN} in a single directory, whose name is usually composed by
35526 appending the version number to @samp{gdb}.
35528 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35529 @file{gdb-@value{GDBVN}} directory. That directory contains:
35532 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35533 script for configuring @value{GDBN} and all its supporting libraries
35535 @item gdb-@value{GDBVN}/gdb
35536 the source specific to @value{GDBN} itself
35538 @item gdb-@value{GDBVN}/bfd
35539 source for the Binary File Descriptor library
35541 @item gdb-@value{GDBVN}/include
35542 @sc{gnu} include files
35544 @item gdb-@value{GDBVN}/libiberty
35545 source for the @samp{-liberty} free software library
35547 @item gdb-@value{GDBVN}/opcodes
35548 source for the library of opcode tables and disassemblers
35550 @item gdb-@value{GDBVN}/readline
35551 source for the @sc{gnu} command-line interface
35554 There may be other subdirectories as well.
35556 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35557 from the @file{gdb-@var{version-number}} source directory, which in
35558 this example is the @file{gdb-@value{GDBVN}} directory.
35560 First switch to the @file{gdb-@var{version-number}} source directory
35561 if you are not already in it; then run @file{configure}. Pass the
35562 identifier for the platform on which @value{GDBN} will run as an
35568 cd gdb-@value{GDBVN}
35573 Running @samp{configure} and then running @code{make} builds the
35574 included supporting libraries, then @code{gdb} itself. The configured
35575 source files, and the binaries, are left in the corresponding source
35579 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35580 system does not recognize this automatically when you run a different
35581 shell, you may need to run @code{sh} on it explicitly:
35587 You should run the @file{configure} script from the top directory in the
35588 source tree, the @file{gdb-@var{version-number}} directory. If you run
35589 @file{configure} from one of the subdirectories, you will configure only
35590 that subdirectory. That is usually not what you want. In particular,
35591 if you run the first @file{configure} from the @file{gdb} subdirectory
35592 of the @file{gdb-@var{version-number}} directory, you will omit the
35593 configuration of @file{bfd}, @file{readline}, and other sibling
35594 directories of the @file{gdb} subdirectory. This leads to build errors
35595 about missing include files such as @file{bfd/bfd.h}.
35597 You can install @code{@value{GDBN}} anywhere. The best way to do this
35598 is to pass the @code{--prefix} option to @code{configure}, and then
35599 install it with @code{make install}.
35601 @node Separate Objdir
35602 @section Compiling @value{GDBN} in Another Directory
35604 If you want to run @value{GDBN} versions for several host or target machines,
35605 you need a different @code{gdb} compiled for each combination of
35606 host and target. @file{configure} is designed to make this easy by
35607 allowing you to generate each configuration in a separate subdirectory,
35608 rather than in the source directory. If your @code{make} program
35609 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35610 @code{make} in each of these directories builds the @code{gdb}
35611 program specified there.
35613 To build @code{gdb} in a separate directory, run @file{configure}
35614 with the @samp{--srcdir} option to specify where to find the source.
35615 (You also need to specify a path to find @file{configure}
35616 itself from your working directory. If the path to @file{configure}
35617 would be the same as the argument to @samp{--srcdir}, you can leave out
35618 the @samp{--srcdir} option; it is assumed.)
35620 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35621 separate directory for a Sun 4 like this:
35625 cd gdb-@value{GDBVN}
35628 ../gdb-@value{GDBVN}/configure
35633 When @file{configure} builds a configuration using a remote source
35634 directory, it creates a tree for the binaries with the same structure
35635 (and using the same names) as the tree under the source directory. In
35636 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35637 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35638 @file{gdb-sun4/gdb}.
35640 Make sure that your path to the @file{configure} script has just one
35641 instance of @file{gdb} in it. If your path to @file{configure} looks
35642 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35643 one subdirectory of @value{GDBN}, not the whole package. This leads to
35644 build errors about missing include files such as @file{bfd/bfd.h}.
35646 One popular reason to build several @value{GDBN} configurations in separate
35647 directories is to configure @value{GDBN} for cross-compiling (where
35648 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35649 programs that run on another machine---the @dfn{target}).
35650 You specify a cross-debugging target by
35651 giving the @samp{--target=@var{target}} option to @file{configure}.
35653 When you run @code{make} to build a program or library, you must run
35654 it in a configured directory---whatever directory you were in when you
35655 called @file{configure} (or one of its subdirectories).
35657 The @code{Makefile} that @file{configure} generates in each source
35658 directory also runs recursively. If you type @code{make} in a source
35659 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35660 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35661 will build all the required libraries, and then build GDB.
35663 When you have multiple hosts or targets configured in separate
35664 directories, you can run @code{make} on them in parallel (for example,
35665 if they are NFS-mounted on each of the hosts); they will not interfere
35669 @section Specifying Names for Hosts and Targets
35671 The specifications used for hosts and targets in the @file{configure}
35672 script are based on a three-part naming scheme, but some short predefined
35673 aliases are also supported. The full naming scheme encodes three pieces
35674 of information in the following pattern:
35677 @var{architecture}-@var{vendor}-@var{os}
35680 For example, you can use the alias @code{sun4} as a @var{host} argument,
35681 or as the value for @var{target} in a @code{--target=@var{target}}
35682 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35684 The @file{configure} script accompanying @value{GDBN} does not provide
35685 any query facility to list all supported host and target names or
35686 aliases. @file{configure} calls the Bourne shell script
35687 @code{config.sub} to map abbreviations to full names; you can read the
35688 script, if you wish, or you can use it to test your guesses on
35689 abbreviations---for example:
35692 % sh config.sub i386-linux
35694 % sh config.sub alpha-linux
35695 alpha-unknown-linux-gnu
35696 % sh config.sub hp9k700
35698 % sh config.sub sun4
35699 sparc-sun-sunos4.1.1
35700 % sh config.sub sun3
35701 m68k-sun-sunos4.1.1
35702 % sh config.sub i986v
35703 Invalid configuration `i986v': machine `i986v' not recognized
35707 @code{config.sub} is also distributed in the @value{GDBN} source
35708 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35710 @node Configure Options
35711 @section @file{configure} Options
35713 Here is a summary of the @file{configure} options and arguments that
35714 are most often useful for building @value{GDBN}. @file{configure}
35715 also has several other options not listed here. @inforef{Running
35716 configure scripts,,autoconf.info}, for a full
35717 explanation of @file{configure}.
35720 configure @r{[}--help@r{]}
35721 @r{[}--prefix=@var{dir}@r{]}
35722 @r{[}--exec-prefix=@var{dir}@r{]}
35723 @r{[}--srcdir=@var{dirname}@r{]}
35724 @r{[}--target=@var{target}@r{]}
35728 You may introduce options with a single @samp{-} rather than
35729 @samp{--} if you prefer; but you may abbreviate option names if you use
35734 Display a quick summary of how to invoke @file{configure}.
35736 @item --prefix=@var{dir}
35737 Configure the source to install programs and files under directory
35740 @item --exec-prefix=@var{dir}
35741 Configure the source to install programs under directory
35744 @c avoid splitting the warning from the explanation:
35746 @item --srcdir=@var{dirname}
35747 Use this option to make configurations in directories separate from the
35748 @value{GDBN} source directories. Among other things, you can use this to
35749 build (or maintain) several configurations simultaneously, in separate
35750 directories. @file{configure} writes configuration-specific files in
35751 the current directory, but arranges for them to use the source in the
35752 directory @var{dirname}. @file{configure} creates directories under
35753 the working directory in parallel to the source directories below
35756 @item --target=@var{target}
35757 Configure @value{GDBN} for cross-debugging programs running on the specified
35758 @var{target}. Without this option, @value{GDBN} is configured to debug
35759 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35761 There is no convenient way to generate a list of all available
35762 targets. Also see the @code{--enable-targets} option, below.
35765 There are many other options that are specific to @value{GDBN}. This
35766 lists just the most common ones; there are some very specialized
35767 options not described here.
35770 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
35771 @itemx --enable-targets=all
35772 Configure @value{GDBN} for cross-debugging programs running on the
35773 specified list of targets. The special value @samp{all} configures
35774 @value{GDBN} for debugging programs running on any target it supports.
35776 @item --with-gdb-datadir=@var{path}
35777 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
35778 here for certain supporting files or scripts. This defaults to the
35779 @file{gdb} subdirectory of @samp{datadi} (which can be set using
35782 @item --with-relocated-sources=@var{dir}
35783 Sets up the default source path substitution rule so that directory
35784 names recorded in debug information will be automatically adjusted for
35785 any directory under @var{dir}. @var{dir} should be a subdirectory of
35786 @value{GDBN}'s configured prefix, the one mentioned in the
35787 @code{--prefix} or @code{--exec-prefix} options to configure. This
35788 option is useful if GDB is supposed to be moved to a different place
35791 @item --enable-64-bit-bfd
35792 Enable 64-bit support in BFD on 32-bit hosts.
35794 @item --disable-gdbmi
35795 Build @value{GDBN} without the GDB/MI machine interface
35799 Build @value{GDBN} with the text-mode full-screen user interface
35800 (TUI). Requires a curses library (ncurses and cursesX are also
35803 @item --with-curses
35804 Use the curses library instead of the termcap library, for text-mode
35805 terminal operations.
35807 @item --with-libunwind-ia64
35808 Use the libunwind library for unwinding function call stack on ia64
35809 target platforms. See http://www.nongnu.org/libunwind/index.html for
35812 @item --with-system-readline
35813 Use the readline library installed on the host, rather than the
35814 library supplied as part of @value{GDBN}.
35816 @item --with-system-zlib
35817 Use the zlib library installed on the host, rather than the library
35818 supplied as part of @value{GDBN}.
35821 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
35822 default if libexpat is installed and found at configure time.) This
35823 library is used to read XML files supplied with @value{GDBN}. If it
35824 is unavailable, some features, such as remote protocol memory maps,
35825 target descriptions, and shared library lists, that are based on XML
35826 files, will not be available in @value{GDBN}. If your host does not
35827 have libexpat installed, you can get the latest version from
35828 `http://expat.sourceforge.net'.
35830 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
35832 Build @value{GDBN} with GNU libiconv, a character set encoding
35833 conversion library. This is not done by default, as on GNU systems
35834 the @code{iconv} that is built in to the C library is sufficient. If
35835 your host does not have a working @code{iconv}, you can get the latest
35836 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
35838 @value{GDBN}'s build system also supports building GNU libiconv as
35839 part of the overall build. @xref{Requirements}.
35842 Build @value{GDBN} with LZMA, a compression library. (Done by default
35843 if liblzma is installed and found at configure time.) LZMA is used by
35844 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
35845 platforms using the ELF object file format. If your host does not
35846 have liblzma installed, you can get the latest version from
35847 `https://tukaani.org/xz/'.
35850 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
35851 floating-point computation with correct rounding. (Done by default if
35852 GNU MPFR is installed and found at configure time.) This library is
35853 used to emulate target floating-point arithmetic during expression
35854 evaluation when the target uses different floating-point formats than
35855 the host. If GNU MPFR is not available, @value{GDBN} will fall back
35856 to using host floating-point arithmetic. If your host does not have
35857 GNU MPFR installed, you can get the latest version from
35858 `http://www.mpfr.org'.
35860 @item --with-python@r{[}=@var{python}@r{]}
35861 Build @value{GDBN} with Python scripting support. (Done by default if
35862 libpython is present and found at configure time.) Python makes
35863 @value{GDBN} scripting much more powerful than the restricted CLI
35864 scripting language. If your host does not have Python installed, you
35865 can find it on `http://www.python.org/download/'. The oldest version
35866 of Python supported by GDB is 2.4. The optional argument @var{python}
35867 is used to find the Python headers and libraries. It can be either
35868 the name of a Python executable, or the name of the directory in which
35869 Python is installed.
35871 @item --with-guile[=GUILE]'
35872 Build @value{GDBN} with GNU Guile scripting support. (Done by default
35873 if libguile is present and found at configure time.) If your host
35874 does not have Guile installed, you can find it at
35875 `https://www.gnu.org/software/guile/'. The optional argument GUILE
35876 can be a version number, which will cause @code{configure} to try to
35877 use that version of Guile; or the file name of a @code{pkg-config}
35878 executable, which will be queried to find the information needed to
35879 compile and link against Guile.
35881 @item --without-included-regex
35882 Don't use the regex library included with @value{GDBN} (as part of the
35883 libiberty library). This is the default on hosts with version 2 of
35886 @item --with-sysroot=@var{dir}
35887 Use @var{dir} as the default system root directory for libraries whose
35888 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
35889 @var{dir} can be modified at run time by using the @command{set
35890 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
35891 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
35892 default system root will be automatically adjusted if and when
35893 @value{GDBN} is moved to a different location.
35895 @item --with-system-gdbinit=@var{file}
35896 Configure @value{GDBN} to automatically load a system-wide init file.
35897 @var{file} should be an absolute file name. If @var{file} is in a
35898 directory under the configured prefix, and @value{GDBN} is moved to
35899 another location after being built, the location of the system-wide
35900 init file will be adjusted accordingly.
35902 @item --enable-build-warnings
35903 When building the @value{GDBN} sources, ask the compiler to warn about
35904 any code which looks even vaguely suspicious. It passes many
35905 different warning flags, depending on the exact version of the
35906 compiler you are using.
35908 @item --enable-werror
35909 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
35910 to the compiler, which will fail the compilation if the compiler
35911 outputs any warning messages.
35913 @item --enable-ubsan
35914 Enable the GCC undefined behavior sanitizer. This is disabled by
35915 default, but passing @code{--enable-ubsan=yes} or
35916 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
35917 undefined behavior sanitizer checks for C@t{++} undefined behavior.
35918 It has a performance cost, so if you are looking at @value{GDBN}'s
35919 performance, you should disable it. The undefined behavior sanitizer
35920 was first introduced in GCC 4.9.
35923 @node System-wide configuration
35924 @section System-wide configuration and settings
35925 @cindex system-wide init file
35927 @value{GDBN} can be configured to have a system-wide init file;
35928 this file will be read and executed at startup (@pxref{Startup, , What
35929 @value{GDBN} does during startup}).
35931 Here is the corresponding configure option:
35934 @item --with-system-gdbinit=@var{file}
35935 Specify that the default location of the system-wide init file is
35939 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35940 it may be subject to relocation. Two possible cases:
35944 If the default location of this init file contains @file{$prefix},
35945 it will be subject to relocation. Suppose that the configure options
35946 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35947 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35948 init file is looked for as @file{$install/etc/gdbinit} instead of
35949 @file{$prefix/etc/gdbinit}.
35952 By contrast, if the default location does not contain the prefix,
35953 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35954 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35955 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35956 wherever @value{GDBN} is installed.
35959 If the configured location of the system-wide init file (as given by the
35960 @option{--with-system-gdbinit} option at configure time) is in the
35961 data-directory (as specified by @option{--with-gdb-datadir} at configure
35962 time) or in one of its subdirectories, then @value{GDBN} will look for the
35963 system-wide init file in the directory specified by the
35964 @option{--data-directory} command-line option.
35965 Note that the system-wide init file is only read once, during @value{GDBN}
35966 initialization. If the data-directory is changed after @value{GDBN} has
35967 started with the @code{set data-directory} command, the file will not be
35971 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
35974 @node System-wide Configuration Scripts
35975 @subsection Installed System-wide Configuration Scripts
35976 @cindex system-wide configuration scripts
35978 The @file{system-gdbinit} directory, located inside the data-directory
35979 (as specified by @option{--with-gdb-datadir} at configure time) contains
35980 a number of scripts which can be used as system-wide init files. To
35981 automatically source those scripts at startup, @value{GDBN} should be
35982 configured with @option{--with-system-gdbinit}. Otherwise, any user
35983 should be able to source them by hand as needed.
35985 The following scripts are currently available:
35988 @item @file{elinos.py}
35990 @cindex ELinOS system-wide configuration script
35991 This script is useful when debugging a program on an ELinOS target.
35992 It takes advantage of the environment variables defined in a standard
35993 ELinOS environment in order to determine the location of the system
35994 shared libraries, and then sets the @samp{solib-absolute-prefix}
35995 and @samp{solib-search-path} variables appropriately.
35997 @item @file{wrs-linux.py}
35998 @pindex wrs-linux.py
35999 @cindex Wind River Linux system-wide configuration script
36000 This script is useful when debugging a program on a target running
36001 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36002 the host-side sysroot used by the target system.
36006 @node Maintenance Commands
36007 @appendix Maintenance Commands
36008 @cindex maintenance commands
36009 @cindex internal commands
36011 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36012 includes a number of commands intended for @value{GDBN} developers,
36013 that are not documented elsewhere in this manual. These commands are
36014 provided here for reference. (For commands that turn on debugging
36015 messages, see @ref{Debugging Output}.)
36018 @kindex maint agent
36019 @kindex maint agent-eval
36020 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36021 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36022 Translate the given @var{expression} into remote agent bytecodes.
36023 This command is useful for debugging the Agent Expression mechanism
36024 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36025 expression useful for data collection, such as by tracepoints, while
36026 @samp{maint agent-eval} produces an expression that evaluates directly
36027 to a result. For instance, a collection expression for @code{globa +
36028 globb} will include bytecodes to record four bytes of memory at each
36029 of the addresses of @code{globa} and @code{globb}, while discarding
36030 the result of the addition, while an evaluation expression will do the
36031 addition and return the sum.
36032 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36033 If not, generate remote agent bytecode for current frame PC address.
36035 @kindex maint agent-printf
36036 @item maint agent-printf @var{format},@var{expr},...
36037 Translate the given format string and list of argument expressions
36038 into remote agent bytecodes and display them as a disassembled list.
36039 This command is useful for debugging the agent version of dynamic
36040 printf (@pxref{Dynamic Printf}).
36042 @kindex maint info breakpoints
36043 @item @anchor{maint info breakpoints}maint info breakpoints
36044 Using the same format as @samp{info breakpoints}, display both the
36045 breakpoints you've set explicitly, and those @value{GDBN} is using for
36046 internal purposes. Internal breakpoints are shown with negative
36047 breakpoint numbers. The type column identifies what kind of breakpoint
36052 Normal, explicitly set breakpoint.
36055 Normal, explicitly set watchpoint.
36058 Internal breakpoint, used to handle correctly stepping through
36059 @code{longjmp} calls.
36061 @item longjmp resume
36062 Internal breakpoint at the target of a @code{longjmp}.
36065 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36068 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36071 Shared library events.
36075 @kindex maint info btrace
36076 @item maint info btrace
36077 Pint information about raw branch tracing data.
36079 @kindex maint btrace packet-history
36080 @item maint btrace packet-history
36081 Print the raw branch trace packets that are used to compute the
36082 execution history for the @samp{record btrace} command. Both the
36083 information and the format in which it is printed depend on the btrace
36088 For the BTS recording format, print a list of blocks of sequential
36089 code. For each block, the following information is printed:
36093 Newer blocks have higher numbers. The oldest block has number zero.
36094 @item Lowest @samp{PC}
36095 @item Highest @samp{PC}
36099 For the Intel Processor Trace recording format, print a list of
36100 Intel Processor Trace packets. For each packet, the following
36101 information is printed:
36104 @item Packet number
36105 Newer packets have higher numbers. The oldest packet has number zero.
36107 The packet's offset in the trace stream.
36108 @item Packet opcode and payload
36112 @kindex maint btrace clear-packet-history
36113 @item maint btrace clear-packet-history
36114 Discards the cached packet history printed by the @samp{maint btrace
36115 packet-history} command. The history will be computed again when
36118 @kindex maint btrace clear
36119 @item maint btrace clear
36120 Discard the branch trace data. The data will be fetched anew and the
36121 branch trace will be recomputed when needed.
36123 This implicitly truncates the branch trace to a single branch trace
36124 buffer. When updating branch trace incrementally, the branch trace
36125 available to @value{GDBN} may be bigger than a single branch trace
36128 @kindex maint set btrace pt skip-pad
36129 @item maint set btrace pt skip-pad
36130 @kindex maint show btrace pt skip-pad
36131 @item maint show btrace pt skip-pad
36132 Control whether @value{GDBN} will skip PAD packets when computing the
36135 @kindex set displaced-stepping
36136 @kindex show displaced-stepping
36137 @cindex displaced stepping support
36138 @cindex out-of-line single-stepping
36139 @item set displaced-stepping
36140 @itemx show displaced-stepping
36141 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36142 if the target supports it. Displaced stepping is a way to single-step
36143 over breakpoints without removing them from the inferior, by executing
36144 an out-of-line copy of the instruction that was originally at the
36145 breakpoint location. It is also known as out-of-line single-stepping.
36148 @item set displaced-stepping on
36149 If the target architecture supports it, @value{GDBN} will use
36150 displaced stepping to step over breakpoints.
36152 @item set displaced-stepping off
36153 @value{GDBN} will not use displaced stepping to step over breakpoints,
36154 even if such is supported by the target architecture.
36156 @cindex non-stop mode, and @samp{set displaced-stepping}
36157 @item set displaced-stepping auto
36158 This is the default mode. @value{GDBN} will use displaced stepping
36159 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36160 architecture supports displaced stepping.
36163 @kindex maint check-psymtabs
36164 @item maint check-psymtabs
36165 Check the consistency of currently expanded psymtabs versus symtabs.
36166 Use this to check, for example, whether a symbol is in one but not the other.
36168 @kindex maint check-symtabs
36169 @item maint check-symtabs
36170 Check the consistency of currently expanded symtabs.
36172 @kindex maint expand-symtabs
36173 @item maint expand-symtabs [@var{regexp}]
36174 Expand symbol tables.
36175 If @var{regexp} is specified, only expand symbol tables for file
36176 names matching @var{regexp}.
36178 @kindex maint set catch-demangler-crashes
36179 @kindex maint show catch-demangler-crashes
36180 @cindex demangler crashes
36181 @item maint set catch-demangler-crashes [on|off]
36182 @itemx maint show catch-demangler-crashes
36183 Control whether @value{GDBN} should attempt to catch crashes in the
36184 symbol name demangler. The default is to attempt to catch crashes.
36185 If enabled, the first time a crash is caught, a core file is created,
36186 the offending symbol is displayed and the user is presented with the
36187 option to terminate the current session.
36189 @kindex maint cplus first_component
36190 @item maint cplus first_component @var{name}
36191 Print the first C@t{++} class/namespace component of @var{name}.
36193 @kindex maint cplus namespace
36194 @item maint cplus namespace
36195 Print the list of possible C@t{++} namespaces.
36197 @kindex maint deprecate
36198 @kindex maint undeprecate
36199 @cindex deprecated commands
36200 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36201 @itemx maint undeprecate @var{command}
36202 Deprecate or undeprecate the named @var{command}. Deprecated commands
36203 cause @value{GDBN} to issue a warning when you use them. The optional
36204 argument @var{replacement} says which newer command should be used in
36205 favor of the deprecated one; if it is given, @value{GDBN} will mention
36206 the replacement as part of the warning.
36208 @kindex maint dump-me
36209 @item maint dump-me
36210 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36211 Cause a fatal signal in the debugger and force it to dump its core.
36212 This is supported only on systems which support aborting a program
36213 with the @code{SIGQUIT} signal.
36215 @kindex maint internal-error
36216 @kindex maint internal-warning
36217 @kindex maint demangler-warning
36218 @cindex demangler crashes
36219 @item maint internal-error @r{[}@var{message-text}@r{]}
36220 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36221 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36223 Cause @value{GDBN} to call the internal function @code{internal_error},
36224 @code{internal_warning} or @code{demangler_warning} and hence behave
36225 as though an internal problem has been detected. In addition to
36226 reporting the internal problem, these functions give the user the
36227 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36228 and @code{internal_warning}) create a core file of the current
36229 @value{GDBN} session.
36231 These commands take an optional parameter @var{message-text} that is
36232 used as the text of the error or warning message.
36234 Here's an example of using @code{internal-error}:
36237 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36238 @dots{}/maint.c:121: internal-error: testing, 1, 2
36239 A problem internal to GDB has been detected. Further
36240 debugging may prove unreliable.
36241 Quit this debugging session? (y or n) @kbd{n}
36242 Create a core file? (y or n) @kbd{n}
36246 @cindex @value{GDBN} internal error
36247 @cindex internal errors, control of @value{GDBN} behavior
36248 @cindex demangler crashes
36250 @kindex maint set internal-error
36251 @kindex maint show internal-error
36252 @kindex maint set internal-warning
36253 @kindex maint show internal-warning
36254 @kindex maint set demangler-warning
36255 @kindex maint show demangler-warning
36256 @item maint set internal-error @var{action} [ask|yes|no]
36257 @itemx maint show internal-error @var{action}
36258 @itemx maint set internal-warning @var{action} [ask|yes|no]
36259 @itemx maint show internal-warning @var{action}
36260 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36261 @itemx maint show demangler-warning @var{action}
36262 When @value{GDBN} reports an internal problem (error or warning) it
36263 gives the user the opportunity to both quit @value{GDBN} and create a
36264 core file of the current @value{GDBN} session. These commands let you
36265 override the default behaviour for each particular @var{action},
36266 described in the table below.
36270 You can specify that @value{GDBN} should always (yes) or never (no)
36271 quit. The default is to ask the user what to do.
36274 You can specify that @value{GDBN} should always (yes) or never (no)
36275 create a core file. The default is to ask the user what to do. Note
36276 that there is no @code{corefile} option for @code{demangler-warning}:
36277 demangler warnings always create a core file and this cannot be
36281 @kindex maint packet
36282 @item maint packet @var{text}
36283 If @value{GDBN} is talking to an inferior via the serial protocol,
36284 then this command sends the string @var{text} to the inferior, and
36285 displays the response packet. @value{GDBN} supplies the initial
36286 @samp{$} character, the terminating @samp{#} character, and the
36289 @kindex maint print architecture
36290 @item maint print architecture @r{[}@var{file}@r{]}
36291 Print the entire architecture configuration. The optional argument
36292 @var{file} names the file where the output goes.
36294 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36295 @item maint print c-tdesc
36296 Print the target description (@pxref{Target Descriptions}) as
36297 a C source file. By default, the target description is for the current
36298 target, but if the optional argument @var{file} is provided, that file
36299 is used to produce the description. The @var{file} should be an XML
36300 document, of the form described in @ref{Target Description Format}.
36301 The created source file is built into @value{GDBN} when @value{GDBN} is
36302 built again. This command is used by developers after they add or
36303 modify XML target descriptions.
36305 @kindex maint check xml-descriptions
36306 @item maint check xml-descriptions @var{dir}
36307 Check that the target descriptions dynamically created by @value{GDBN}
36308 equal the descriptions created from XML files found in @var{dir}.
36310 @anchor{maint check libthread-db}
36311 @kindex maint check libthread-db
36312 @item maint check libthread-db
36313 Run integrity checks on the current inferior's thread debugging
36314 library. This exercises all @code{libthread_db} functionality used by
36315 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36316 @code{proc_service} functions provided by @value{GDBN} that
36317 @code{libthread_db} uses. Note that parts of the test may be skipped
36318 on some platforms when debugging core files.
36320 @kindex maint print dummy-frames
36321 @item maint print dummy-frames
36322 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36325 (@value{GDBP}) @kbd{b add}
36327 (@value{GDBP}) @kbd{print add(2,3)}
36328 Breakpoint 2, add (a=2, b=3) at @dots{}
36330 The program being debugged stopped while in a function called from GDB.
36332 (@value{GDBP}) @kbd{maint print dummy-frames}
36333 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36337 Takes an optional file parameter.
36339 @kindex maint print registers
36340 @kindex maint print raw-registers
36341 @kindex maint print cooked-registers
36342 @kindex maint print register-groups
36343 @kindex maint print remote-registers
36344 @item maint print registers @r{[}@var{file}@r{]}
36345 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36346 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36347 @itemx maint print register-groups @r{[}@var{file}@r{]}
36348 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36349 Print @value{GDBN}'s internal register data structures.
36351 The command @code{maint print raw-registers} includes the contents of
36352 the raw register cache; the command @code{maint print
36353 cooked-registers} includes the (cooked) value of all registers,
36354 including registers which aren't available on the target nor visible
36355 to user; the command @code{maint print register-groups} includes the
36356 groups that each register is a member of; and the command @code{maint
36357 print remote-registers} includes the remote target's register numbers
36358 and offsets in the `G' packets.
36360 These commands take an optional parameter, a file name to which to
36361 write the information.
36363 @kindex maint print reggroups
36364 @item maint print reggroups @r{[}@var{file}@r{]}
36365 Print @value{GDBN}'s internal register group data structures. The
36366 optional argument @var{file} tells to what file to write the
36369 The register groups info looks like this:
36372 (@value{GDBP}) @kbd{maint print reggroups}
36385 This command forces @value{GDBN} to flush its internal register cache.
36387 @kindex maint print objfiles
36388 @cindex info for known object files
36389 @item maint print objfiles @r{[}@var{regexp}@r{]}
36390 Print a dump of all known object files.
36391 If @var{regexp} is specified, only print object files whose names
36392 match @var{regexp}. For each object file, this command prints its name,
36393 address in memory, and all of its psymtabs and symtabs.
36395 @kindex maint print user-registers
36396 @cindex user registers
36397 @item maint print user-registers
36398 List all currently available @dfn{user registers}. User registers
36399 typically provide alternate names for actual hardware registers. They
36400 include the four ``standard'' registers @code{$fp}, @code{$pc},
36401 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36402 registers can be used in expressions in the same way as the canonical
36403 register names, but only the latter are listed by the @code{info
36404 registers} and @code{maint print registers} commands.
36406 @kindex maint print section-scripts
36407 @cindex info for known .debug_gdb_scripts-loaded scripts
36408 @item maint print section-scripts [@var{regexp}]
36409 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36410 If @var{regexp} is specified, only print scripts loaded by object files
36411 matching @var{regexp}.
36412 For each script, this command prints its name as specified in the objfile,
36413 and the full path if known.
36414 @xref{dotdebug_gdb_scripts section}.
36416 @kindex maint print statistics
36417 @cindex bcache statistics
36418 @item maint print statistics
36419 This command prints, for each object file in the program, various data
36420 about that object file followed by the byte cache (@dfn{bcache})
36421 statistics for the object file. The objfile data includes the number
36422 of minimal, partial, full, and stabs symbols, the number of types
36423 defined by the objfile, the number of as yet unexpanded psym tables,
36424 the number of line tables and string tables, and the amount of memory
36425 used by the various tables. The bcache statistics include the counts,
36426 sizes, and counts of duplicates of all and unique objects, max,
36427 average, and median entry size, total memory used and its overhead and
36428 savings, and various measures of the hash table size and chain
36431 @kindex maint print target-stack
36432 @cindex target stack description
36433 @item maint print target-stack
36434 A @dfn{target} is an interface between the debugger and a particular
36435 kind of file or process. Targets can be stacked in @dfn{strata},
36436 so that more than one target can potentially respond to a request.
36437 In particular, memory accesses will walk down the stack of targets
36438 until they find a target that is interested in handling that particular
36441 This command prints a short description of each layer that was pushed on
36442 the @dfn{target stack}, starting from the top layer down to the bottom one.
36444 @kindex maint print type
36445 @cindex type chain of a data type
36446 @item maint print type @var{expr}
36447 Print the type chain for a type specified by @var{expr}. The argument
36448 can be either a type name or a symbol. If it is a symbol, the type of
36449 that symbol is described. The type chain produced by this command is
36450 a recursive definition of the data type as stored in @value{GDBN}'s
36451 data structures, including its flags and contained types.
36453 @kindex maint selftest
36455 @item maint selftest @r{[}@var{filter}@r{]}
36456 Run any self tests that were compiled in to @value{GDBN}. This will
36457 print a message showing how many tests were run, and how many failed.
36458 If a @var{filter} is passed, only the tests with @var{filter} in their
36461 @kindex "maint info selftests"
36463 @item maint info selftests
36464 List the selftests compiled in to @value{GDBN}.
36466 @kindex maint set dwarf always-disassemble
36467 @kindex maint show dwarf always-disassemble
36468 @item maint set dwarf always-disassemble
36469 @item maint show dwarf always-disassemble
36470 Control the behavior of @code{info address} when using DWARF debugging
36473 The default is @code{off}, which means that @value{GDBN} should try to
36474 describe a variable's location in an easily readable format. When
36475 @code{on}, @value{GDBN} will instead display the DWARF location
36476 expression in an assembly-like format. Note that some locations are
36477 too complex for @value{GDBN} to describe simply; in this case you will
36478 always see the disassembly form.
36480 Here is an example of the resulting disassembly:
36483 (gdb) info addr argc
36484 Symbol "argc" is a complex DWARF expression:
36488 For more information on these expressions, see
36489 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36491 @kindex maint set dwarf max-cache-age
36492 @kindex maint show dwarf max-cache-age
36493 @item maint set dwarf max-cache-age
36494 @itemx maint show dwarf max-cache-age
36495 Control the DWARF compilation unit cache.
36497 @cindex DWARF compilation units cache
36498 In object files with inter-compilation-unit references, such as those
36499 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36500 reader needs to frequently refer to previously read compilation units.
36501 This setting controls how long a compilation unit will remain in the
36502 cache if it is not referenced. A higher limit means that cached
36503 compilation units will be stored in memory longer, and more total
36504 memory will be used. Setting it to zero disables caching, which will
36505 slow down @value{GDBN} startup, but reduce memory consumption.
36507 @kindex maint set dwarf unwinders
36508 @kindex maint show dwarf unwinders
36509 @item maint set dwarf unwinders
36510 @itemx maint show dwarf unwinders
36511 Control use of the DWARF frame unwinders.
36513 @cindex DWARF frame unwinders
36514 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36515 frame unwinders to build the backtrace. Many of these targets will
36516 also have a second mechanism for building the backtrace for use in
36517 cases where DWARF information is not available, this second mechanism
36518 is often an analysis of a function's prologue.
36520 In order to extend testing coverage of the second level stack
36521 unwinding mechanisms it is helpful to be able to disable the DWARF
36522 stack unwinders, this can be done with this switch.
36524 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36525 advisable, there are cases that are better handled through DWARF than
36526 prologue analysis, and the debug experience is likely to be better
36527 with the DWARF frame unwinders enabled.
36529 If DWARF frame unwinders are not supported for a particular target
36530 architecture, then enabling this flag does not cause them to be used.
36531 @kindex maint set profile
36532 @kindex maint show profile
36533 @cindex profiling GDB
36534 @item maint set profile
36535 @itemx maint show profile
36536 Control profiling of @value{GDBN}.
36538 Profiling will be disabled until you use the @samp{maint set profile}
36539 command to enable it. When you enable profiling, the system will begin
36540 collecting timing and execution count data; when you disable profiling or
36541 exit @value{GDBN}, the results will be written to a log file. Remember that
36542 if you use profiling, @value{GDBN} will overwrite the profiling log file
36543 (often called @file{gmon.out}). If you have a record of important profiling
36544 data in a @file{gmon.out} file, be sure to move it to a safe location.
36546 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36547 compiled with the @samp{-pg} compiler option.
36549 @kindex maint set show-debug-regs
36550 @kindex maint show show-debug-regs
36551 @cindex hardware debug registers
36552 @item maint set show-debug-regs
36553 @itemx maint show show-debug-regs
36554 Control whether to show variables that mirror the hardware debug
36555 registers. Use @code{on} to enable, @code{off} to disable. If
36556 enabled, the debug registers values are shown when @value{GDBN} inserts or
36557 removes a hardware breakpoint or watchpoint, and when the inferior
36558 triggers a hardware-assisted breakpoint or watchpoint.
36560 @kindex maint set show-all-tib
36561 @kindex maint show show-all-tib
36562 @item maint set show-all-tib
36563 @itemx maint show show-all-tib
36564 Control whether to show all non zero areas within a 1k block starting
36565 at thread local base, when using the @samp{info w32 thread-information-block}
36568 @kindex maint set target-async
36569 @kindex maint show target-async
36570 @item maint set target-async
36571 @itemx maint show target-async
36572 This controls whether @value{GDBN} targets operate in synchronous or
36573 asynchronous mode (@pxref{Background Execution}). Normally the
36574 default is asynchronous, if it is available; but this can be changed
36575 to more easily debug problems occurring only in synchronous mode.
36577 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36578 @kindex maint show target-non-stop
36579 @item maint set target-non-stop
36580 @itemx maint show target-non-stop
36582 This controls whether @value{GDBN} targets always operate in non-stop
36583 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36584 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36585 if supported by the target.
36588 @item maint set target-non-stop auto
36589 This is the default mode. @value{GDBN} controls the target in
36590 non-stop mode if the target supports it.
36592 @item maint set target-non-stop on
36593 @value{GDBN} controls the target in non-stop mode even if the target
36594 does not indicate support.
36596 @item maint set target-non-stop off
36597 @value{GDBN} does not control the target in non-stop mode even if the
36598 target supports it.
36601 @kindex maint set per-command
36602 @kindex maint show per-command
36603 @item maint set per-command
36604 @itemx maint show per-command
36605 @cindex resources used by commands
36607 @value{GDBN} can display the resources used by each command.
36608 This is useful in debugging performance problems.
36611 @item maint set per-command space [on|off]
36612 @itemx maint show per-command space
36613 Enable or disable the printing of the memory used by GDB for each command.
36614 If enabled, @value{GDBN} will display how much memory each command
36615 took, following the command's own output.
36616 This can also be requested by invoking @value{GDBN} with the
36617 @option{--statistics} command-line switch (@pxref{Mode Options}).
36619 @item maint set per-command time [on|off]
36620 @itemx maint show per-command time
36621 Enable or disable the printing of the execution time of @value{GDBN}
36623 If enabled, @value{GDBN} will display how much time it
36624 took to execute each command, following the command's own output.
36625 Both CPU time and wallclock time are printed.
36626 Printing both is useful when trying to determine whether the cost is
36627 CPU or, e.g., disk/network latency.
36628 Note that the CPU time printed is for @value{GDBN} only, it does not include
36629 the execution time of the inferior because there's no mechanism currently
36630 to compute how much time was spent by @value{GDBN} and how much time was
36631 spent by the program been debugged.
36632 This can also be requested by invoking @value{GDBN} with the
36633 @option{--statistics} command-line switch (@pxref{Mode Options}).
36635 @item maint set per-command symtab [on|off]
36636 @itemx maint show per-command symtab
36637 Enable or disable the printing of basic symbol table statistics
36639 If enabled, @value{GDBN} will display the following information:
36643 number of symbol tables
36645 number of primary symbol tables
36647 number of blocks in the blockvector
36651 @kindex maint set check-libthread-db
36652 @kindex maint show check-libthread-db
36653 @item maint set check-libthread-db [on|off]
36654 @itemx maint show check-libthread-db
36655 Control whether @value{GDBN} should run integrity checks on inferior
36656 specific thread debugging libraries as they are loaded. The default
36657 is not to perform such checks. If any check fails @value{GDBN} will
36658 unload the library and continue searching for a suitable candidate as
36659 described in @ref{set libthread-db-search-path}. For more information
36660 about the tests, see @ref{maint check libthread-db}.
36662 @kindex maint space
36663 @cindex memory used by commands
36664 @item maint space @var{value}
36665 An alias for @code{maint set per-command space}.
36666 A non-zero value enables it, zero disables it.
36669 @cindex time of command execution
36670 @item maint time @var{value}
36671 An alias for @code{maint set per-command time}.
36672 A non-zero value enables it, zero disables it.
36674 @kindex maint translate-address
36675 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
36676 Find the symbol stored at the location specified by the address
36677 @var{addr} and an optional section name @var{section}. If found,
36678 @value{GDBN} prints the name of the closest symbol and an offset from
36679 the symbol's location to the specified address. This is similar to
36680 the @code{info address} command (@pxref{Symbols}), except that this
36681 command also allows to find symbols in other sections.
36683 If section was not specified, the section in which the symbol was found
36684 is also printed. For dynamically linked executables, the name of
36685 executable or shared library containing the symbol is printed as well.
36689 The following command is useful for non-interactive invocations of
36690 @value{GDBN}, such as in the test suite.
36693 @item set watchdog @var{nsec}
36694 @kindex set watchdog
36695 @cindex watchdog timer
36696 @cindex timeout for commands
36697 Set the maximum number of seconds @value{GDBN} will wait for the
36698 target operation to finish. If this time expires, @value{GDBN}
36699 reports and error and the command is aborted.
36701 @item show watchdog
36702 Show the current setting of the target wait timeout.
36705 @node Remote Protocol
36706 @appendix @value{GDBN} Remote Serial Protocol
36711 * Stop Reply Packets::
36712 * General Query Packets::
36713 * Architecture-Specific Protocol Details::
36714 * Tracepoint Packets::
36715 * Host I/O Packets::
36717 * Notification Packets::
36718 * Remote Non-Stop::
36719 * Packet Acknowledgment::
36721 * File-I/O Remote Protocol Extension::
36722 * Library List Format::
36723 * Library List Format for SVR4 Targets::
36724 * Memory Map Format::
36725 * Thread List Format::
36726 * Traceframe Info Format::
36727 * Branch Trace Format::
36728 * Branch Trace Configuration Format::
36734 There may be occasions when you need to know something about the
36735 protocol---for example, if there is only one serial port to your target
36736 machine, you might want your program to do something special if it
36737 recognizes a packet meant for @value{GDBN}.
36739 In the examples below, @samp{->} and @samp{<-} are used to indicate
36740 transmitted and received data, respectively.
36742 @cindex protocol, @value{GDBN} remote serial
36743 @cindex serial protocol, @value{GDBN} remote
36744 @cindex remote serial protocol
36745 All @value{GDBN} commands and responses (other than acknowledgments
36746 and notifications, see @ref{Notification Packets}) are sent as a
36747 @var{packet}. A @var{packet} is introduced with the character
36748 @samp{$}, the actual @var{packet-data}, and the terminating character
36749 @samp{#} followed by a two-digit @var{checksum}:
36752 @code{$}@var{packet-data}@code{#}@var{checksum}
36756 @cindex checksum, for @value{GDBN} remote
36758 The two-digit @var{checksum} is computed as the modulo 256 sum of all
36759 characters between the leading @samp{$} and the trailing @samp{#} (an
36760 eight bit unsigned checksum).
36762 Implementors should note that prior to @value{GDBN} 5.0 the protocol
36763 specification also included an optional two-digit @var{sequence-id}:
36766 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
36769 @cindex sequence-id, for @value{GDBN} remote
36771 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
36772 has never output @var{sequence-id}s. Stubs that handle packets added
36773 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
36775 When either the host or the target machine receives a packet, the first
36776 response expected is an acknowledgment: either @samp{+} (to indicate
36777 the package was received correctly) or @samp{-} (to request
36781 -> @code{$}@var{packet-data}@code{#}@var{checksum}
36786 The @samp{+}/@samp{-} acknowledgments can be disabled
36787 once a connection is established.
36788 @xref{Packet Acknowledgment}, for details.
36790 The host (@value{GDBN}) sends @var{command}s, and the target (the
36791 debugging stub incorporated in your program) sends a @var{response}. In
36792 the case of step and continue @var{command}s, the response is only sent
36793 when the operation has completed, and the target has again stopped all
36794 threads in all attached processes. This is the default all-stop mode
36795 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
36796 execution mode; see @ref{Remote Non-Stop}, for details.
36798 @var{packet-data} consists of a sequence of characters with the
36799 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
36802 @cindex remote protocol, field separator
36803 Fields within the packet should be separated using @samp{,} @samp{;} or
36804 @samp{:}. Except where otherwise noted all numbers are represented in
36805 @sc{hex} with leading zeros suppressed.
36807 Implementors should note that prior to @value{GDBN} 5.0, the character
36808 @samp{:} could not appear as the third character in a packet (as it
36809 would potentially conflict with the @var{sequence-id}).
36811 @cindex remote protocol, binary data
36812 @anchor{Binary Data}
36813 Binary data in most packets is encoded either as two hexadecimal
36814 digits per byte of binary data. This allowed the traditional remote
36815 protocol to work over connections which were only seven-bit clean.
36816 Some packets designed more recently assume an eight-bit clean
36817 connection, and use a more efficient encoding to send and receive
36820 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
36821 as an escape character. Any escaped byte is transmitted as the escape
36822 character followed by the original character XORed with @code{0x20}.
36823 For example, the byte @code{0x7d} would be transmitted as the two
36824 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
36825 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
36826 @samp{@}}) must always be escaped. Responses sent by the stub
36827 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
36828 is not interpreted as the start of a run-length encoded sequence
36831 Response @var{data} can be run-length encoded to save space.
36832 Run-length encoding replaces runs of identical characters with one
36833 instance of the repeated character, followed by a @samp{*} and a
36834 repeat count. The repeat count is itself sent encoded, to avoid
36835 binary characters in @var{data}: a value of @var{n} is sent as
36836 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
36837 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
36838 code 32) for a repeat count of 3. (This is because run-length
36839 encoding starts to win for counts 3 or more.) Thus, for example,
36840 @samp{0* } is a run-length encoding of ``0000'': the space character
36841 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
36844 The printable characters @samp{#} and @samp{$} or with a numeric value
36845 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
36846 seven repeats (@samp{$}) can be expanded using a repeat count of only
36847 five (@samp{"}). For example, @samp{00000000} can be encoded as
36850 The error response returned for some packets includes a two character
36851 error number. That number is not well defined.
36853 @cindex empty response, for unsupported packets
36854 For any @var{command} not supported by the stub, an empty response
36855 (@samp{$#00}) should be returned. That way it is possible to extend the
36856 protocol. A newer @value{GDBN} can tell if a packet is supported based
36859 At a minimum, a stub is required to support the @samp{g} and @samp{G}
36860 commands for register access, and the @samp{m} and @samp{M} commands
36861 for memory access. Stubs that only control single-threaded targets
36862 can implement run control with the @samp{c} (continue), and @samp{s}
36863 (step) commands. Stubs that support multi-threading targets should
36864 support the @samp{vCont} command. All other commands are optional.
36869 The following table provides a complete list of all currently defined
36870 @var{command}s and their corresponding response @var{data}.
36871 @xref{File-I/O Remote Protocol Extension}, for details about the File
36872 I/O extension of the remote protocol.
36874 Each packet's description has a template showing the packet's overall
36875 syntax, followed by an explanation of the packet's meaning. We
36876 include spaces in some of the templates for clarity; these are not
36877 part of the packet's syntax. No @value{GDBN} packet uses spaces to
36878 separate its components. For example, a template like @samp{foo
36879 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
36880 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
36881 @var{baz}. @value{GDBN} does not transmit a space character between the
36882 @samp{foo} and the @var{bar}, or between the @var{bar} and the
36885 @cindex @var{thread-id}, in remote protocol
36886 @anchor{thread-id syntax}
36887 Several packets and replies include a @var{thread-id} field to identify
36888 a thread. Normally these are positive numbers with a target-specific
36889 interpretation, formatted as big-endian hex strings. A @var{thread-id}
36890 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
36893 In addition, the remote protocol supports a multiprocess feature in
36894 which the @var{thread-id} syntax is extended to optionally include both
36895 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
36896 The @var{pid} (process) and @var{tid} (thread) components each have the
36897 format described above: a positive number with target-specific
36898 interpretation formatted as a big-endian hex string, literal @samp{-1}
36899 to indicate all processes or threads (respectively), or @samp{0} to
36900 indicate an arbitrary process or thread. Specifying just a process, as
36901 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
36902 error to specify all processes but a specific thread, such as
36903 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
36904 for those packets and replies explicitly documented to include a process
36905 ID, rather than a @var{thread-id}.
36907 The multiprocess @var{thread-id} syntax extensions are only used if both
36908 @value{GDBN} and the stub report support for the @samp{multiprocess}
36909 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
36912 Note that all packet forms beginning with an upper- or lower-case
36913 letter, other than those described here, are reserved for future use.
36915 Here are the packet descriptions.
36920 @cindex @samp{!} packet
36921 @anchor{extended mode}
36922 Enable extended mode. In extended mode, the remote server is made
36923 persistent. The @samp{R} packet is used to restart the program being
36929 The remote target both supports and has enabled extended mode.
36933 @cindex @samp{?} packet
36935 Indicate the reason the target halted. The reply is the same as for
36936 step and continue. This packet has a special interpretation when the
36937 target is in non-stop mode; see @ref{Remote Non-Stop}.
36940 @xref{Stop Reply Packets}, for the reply specifications.
36942 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36943 @cindex @samp{A} packet
36944 Initialized @code{argv[]} array passed into program. @var{arglen}
36945 specifies the number of bytes in the hex encoded byte stream
36946 @var{arg}. See @code{gdbserver} for more details.
36951 The arguments were set.
36957 @cindex @samp{b} packet
36958 (Don't use this packet; its behavior is not well-defined.)
36959 Change the serial line speed to @var{baud}.
36961 JTC: @emph{When does the transport layer state change? When it's
36962 received, or after the ACK is transmitted. In either case, there are
36963 problems if the command or the acknowledgment packet is dropped.}
36965 Stan: @emph{If people really wanted to add something like this, and get
36966 it working for the first time, they ought to modify ser-unix.c to send
36967 some kind of out-of-band message to a specially-setup stub and have the
36968 switch happen "in between" packets, so that from remote protocol's point
36969 of view, nothing actually happened.}
36971 @item B @var{addr},@var{mode}
36972 @cindex @samp{B} packet
36973 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36974 breakpoint at @var{addr}.
36976 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36977 (@pxref{insert breakpoint or watchpoint packet}).
36979 @cindex @samp{bc} packet
36982 Backward continue. Execute the target system in reverse. No parameter.
36983 @xref{Reverse Execution}, for more information.
36986 @xref{Stop Reply Packets}, for the reply specifications.
36988 @cindex @samp{bs} packet
36991 Backward single step. Execute one instruction in reverse. No parameter.
36992 @xref{Reverse Execution}, for more information.
36995 @xref{Stop Reply Packets}, for the reply specifications.
36997 @item c @r{[}@var{addr}@r{]}
36998 @cindex @samp{c} packet
36999 Continue at @var{addr}, which is the address to resume. If @var{addr}
37000 is omitted, resume at current address.
37002 This packet is deprecated for multi-threading support. @xref{vCont
37006 @xref{Stop Reply Packets}, for the reply specifications.
37008 @item C @var{sig}@r{[};@var{addr}@r{]}
37009 @cindex @samp{C} packet
37010 Continue with signal @var{sig} (hex signal number). If
37011 @samp{;@var{addr}} is omitted, resume at same address.
37013 This packet is deprecated for multi-threading support. @xref{vCont
37017 @xref{Stop Reply Packets}, for the reply specifications.
37020 @cindex @samp{d} packet
37023 Don't use this packet; instead, define a general set packet
37024 (@pxref{General Query Packets}).
37028 @cindex @samp{D} packet
37029 The first form of the packet is used to detach @value{GDBN} from the
37030 remote system. It is sent to the remote target
37031 before @value{GDBN} disconnects via the @code{detach} command.
37033 The second form, including a process ID, is used when multiprocess
37034 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37035 detach only a specific process. The @var{pid} is specified as a
37036 big-endian hex string.
37046 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37047 @cindex @samp{F} packet
37048 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37049 This is part of the File-I/O protocol extension. @xref{File-I/O
37050 Remote Protocol Extension}, for the specification.
37053 @anchor{read registers packet}
37054 @cindex @samp{g} packet
37055 Read general registers.
37059 @item @var{XX@dots{}}
37060 Each byte of register data is described by two hex digits. The bytes
37061 with the register are transmitted in target byte order. The size of
37062 each register and their position within the @samp{g} packet are
37063 determined by the @value{GDBN} internal gdbarch functions
37064 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37066 When reading registers from a trace frame (@pxref{Analyze Collected
37067 Data,,Using the Collected Data}), the stub may also return a string of
37068 literal @samp{x}'s in place of the register data digits, to indicate
37069 that the corresponding register has not been collected, thus its value
37070 is unavailable. For example, for an architecture with 4 registers of
37071 4 bytes each, the following reply indicates to @value{GDBN} that
37072 registers 0 and 2 have not been collected, while registers 1 and 3
37073 have been collected, and both have zero value:
37077 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37084 @item G @var{XX@dots{}}
37085 @cindex @samp{G} packet
37086 Write general registers. @xref{read registers packet}, for a
37087 description of the @var{XX@dots{}} data.
37097 @item H @var{op} @var{thread-id}
37098 @cindex @samp{H} packet
37099 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37100 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37101 should be @samp{c} for step and continue operations (note that this
37102 is deprecated, supporting the @samp{vCont} command is a better
37103 option), and @samp{g} for other operations. The thread designator
37104 @var{thread-id} has the format and interpretation described in
37105 @ref{thread-id syntax}.
37116 @c 'H': How restrictive (or permissive) is the thread model. If a
37117 @c thread is selected and stopped, are other threads allowed
37118 @c to continue to execute? As I mentioned above, I think the
37119 @c semantics of each command when a thread is selected must be
37120 @c described. For example:
37122 @c 'g': If the stub supports threads and a specific thread is
37123 @c selected, returns the register block from that thread;
37124 @c otherwise returns current registers.
37126 @c 'G' If the stub supports threads and a specific thread is
37127 @c selected, sets the registers of the register block of
37128 @c that thread; otherwise sets current registers.
37130 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37131 @anchor{cycle step packet}
37132 @cindex @samp{i} packet
37133 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37134 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37135 step starting at that address.
37138 @cindex @samp{I} packet
37139 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37143 @cindex @samp{k} packet
37146 The exact effect of this packet is not specified.
37148 For a bare-metal target, it may power cycle or reset the target
37149 system. For that reason, the @samp{k} packet has no reply.
37151 For a single-process target, it may kill that process if possible.
37153 A multiple-process target may choose to kill just one process, or all
37154 that are under @value{GDBN}'s control. For more precise control, use
37155 the vKill packet (@pxref{vKill packet}).
37157 If the target system immediately closes the connection in response to
37158 @samp{k}, @value{GDBN} does not consider the lack of packet
37159 acknowledgment to be an error, and assumes the kill was successful.
37161 If connected using @kbd{target extended-remote}, and the target does
37162 not close the connection in response to a kill request, @value{GDBN}
37163 probes the target state as if a new connection was opened
37164 (@pxref{? packet}).
37166 @item m @var{addr},@var{length}
37167 @cindex @samp{m} packet
37168 Read @var{length} addressable memory units starting at address @var{addr}
37169 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37170 any particular boundary.
37172 The stub need not use any particular size or alignment when gathering
37173 data from memory for the response; even if @var{addr} is word-aligned
37174 and @var{length} is a multiple of the word size, the stub is free to
37175 use byte accesses, or not. For this reason, this packet may not be
37176 suitable for accessing memory-mapped I/O devices.
37177 @cindex alignment of remote memory accesses
37178 @cindex size of remote memory accesses
37179 @cindex memory, alignment and size of remote accesses
37183 @item @var{XX@dots{}}
37184 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37185 The reply may contain fewer addressable memory units than requested if the
37186 server was able to read only part of the region of memory.
37191 @item M @var{addr},@var{length}:@var{XX@dots{}}
37192 @cindex @samp{M} packet
37193 Write @var{length} addressable memory units starting at address @var{addr}
37194 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37195 byte is transmitted as a two-digit hexadecimal number.
37202 for an error (this includes the case where only part of the data was
37207 @cindex @samp{p} packet
37208 Read the value of register @var{n}; @var{n} is in hex.
37209 @xref{read registers packet}, for a description of how the returned
37210 register value is encoded.
37214 @item @var{XX@dots{}}
37215 the register's value
37219 Indicating an unrecognized @var{query}.
37222 @item P @var{n@dots{}}=@var{r@dots{}}
37223 @anchor{write register packet}
37224 @cindex @samp{P} packet
37225 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37226 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37227 digits for each byte in the register (target byte order).
37237 @item q @var{name} @var{params}@dots{}
37238 @itemx Q @var{name} @var{params}@dots{}
37239 @cindex @samp{q} packet
37240 @cindex @samp{Q} packet
37241 General query (@samp{q}) and set (@samp{Q}). These packets are
37242 described fully in @ref{General Query Packets}.
37245 @cindex @samp{r} packet
37246 Reset the entire system.
37248 Don't use this packet; use the @samp{R} packet instead.
37251 @cindex @samp{R} packet
37252 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37253 This packet is only available in extended mode (@pxref{extended mode}).
37255 The @samp{R} packet has no reply.
37257 @item s @r{[}@var{addr}@r{]}
37258 @cindex @samp{s} packet
37259 Single step, resuming at @var{addr}. If
37260 @var{addr} is omitted, resume at same address.
37262 This packet is deprecated for multi-threading support. @xref{vCont
37266 @xref{Stop Reply Packets}, for the reply specifications.
37268 @item S @var{sig}@r{[};@var{addr}@r{]}
37269 @anchor{step with signal packet}
37270 @cindex @samp{S} packet
37271 Step with signal. This is analogous to the @samp{C} packet, but
37272 requests a single-step, rather than a normal resumption of execution.
37274 This packet is deprecated for multi-threading support. @xref{vCont
37278 @xref{Stop Reply Packets}, for the reply specifications.
37280 @item t @var{addr}:@var{PP},@var{MM}
37281 @cindex @samp{t} packet
37282 Search backwards starting at address @var{addr} for a match with pattern
37283 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37284 There must be at least 3 digits in @var{addr}.
37286 @item T @var{thread-id}
37287 @cindex @samp{T} packet
37288 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37293 thread is still alive
37299 Packets starting with @samp{v} are identified by a multi-letter name,
37300 up to the first @samp{;} or @samp{?} (or the end of the packet).
37302 @item vAttach;@var{pid}
37303 @cindex @samp{vAttach} packet
37304 Attach to a new process with the specified process ID @var{pid}.
37305 The process ID is a
37306 hexadecimal integer identifying the process. In all-stop mode, all
37307 threads in the attached process are stopped; in non-stop mode, it may be
37308 attached without being stopped if that is supported by the target.
37310 @c In non-stop mode, on a successful vAttach, the stub should set the
37311 @c current thread to a thread of the newly-attached process. After
37312 @c attaching, GDB queries for the attached process's thread ID with qC.
37313 @c Also note that, from a user perspective, whether or not the
37314 @c target is stopped on attach in non-stop mode depends on whether you
37315 @c use the foreground or background version of the attach command, not
37316 @c on what vAttach does; GDB does the right thing with respect to either
37317 @c stopping or restarting threads.
37319 This packet is only available in extended mode (@pxref{extended mode}).
37325 @item @r{Any stop packet}
37326 for success in all-stop mode (@pxref{Stop Reply Packets})
37328 for success in non-stop mode (@pxref{Remote Non-Stop})
37331 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37332 @cindex @samp{vCont} packet
37333 @anchor{vCont packet}
37334 Resume the inferior, specifying different actions for each thread.
37336 For each inferior thread, the leftmost action with a matching
37337 @var{thread-id} is applied. Threads that don't match any action
37338 remain in their current state. Thread IDs are specified using the
37339 syntax described in @ref{thread-id syntax}. If multiprocess
37340 extensions (@pxref{multiprocess extensions}) are supported, actions
37341 can be specified to match all threads in a process by using the
37342 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37343 @var{thread-id} matches all threads. Specifying no actions is an
37346 Currently supported actions are:
37352 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37356 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37359 @item r @var{start},@var{end}
37360 Step once, and then keep stepping as long as the thread stops at
37361 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37362 The remote stub reports a stop reply when either the thread goes out
37363 of the range or is stopped due to an unrelated reason, such as hitting
37364 a breakpoint. @xref{range stepping}.
37366 If the range is empty (@var{start} == @var{end}), then the action
37367 becomes equivalent to the @samp{s} action. In other words,
37368 single-step once, and report the stop (even if the stepped instruction
37369 jumps to @var{start}).
37371 (A stop reply may be sent at any point even if the PC is still within
37372 the stepping range; for example, it is valid to implement this packet
37373 in a degenerate way as a single instruction step operation.)
37377 The optional argument @var{addr} normally associated with the
37378 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37379 not supported in @samp{vCont}.
37381 The @samp{t} action is only relevant in non-stop mode
37382 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37383 A stop reply should be generated for any affected thread not already stopped.
37384 When a thread is stopped by means of a @samp{t} action,
37385 the corresponding stop reply should indicate that the thread has stopped with
37386 signal @samp{0}, regardless of whether the target uses some other signal
37387 as an implementation detail.
37389 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37390 @samp{r} actions for threads that are already running. Conversely,
37391 the server must ignore @samp{t} actions for threads that are already
37394 @emph{Note:} In non-stop mode, a thread is considered running until
37395 @value{GDBN} acknowleges an asynchronous stop notification for it with
37396 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37398 The stub must support @samp{vCont} if it reports support for
37399 multiprocess extensions (@pxref{multiprocess extensions}).
37402 @xref{Stop Reply Packets}, for the reply specifications.
37405 @cindex @samp{vCont?} packet
37406 Request a list of actions supported by the @samp{vCont} packet.
37410 @item vCont@r{[};@var{action}@dots{}@r{]}
37411 The @samp{vCont} packet is supported. Each @var{action} is a supported
37412 command in the @samp{vCont} packet.
37414 The @samp{vCont} packet is not supported.
37417 @anchor{vCtrlC packet}
37419 @cindex @samp{vCtrlC} packet
37420 Interrupt remote target as if a control-C was pressed on the remote
37421 terminal. This is the equivalent to reacting to the @code{^C}
37422 (@samp{\003}, the control-C character) character in all-stop mode
37423 while the target is running, except this works in non-stop mode.
37424 @xref{interrupting remote targets}, for more info on the all-stop
37435 @item vFile:@var{operation}:@var{parameter}@dots{}
37436 @cindex @samp{vFile} packet
37437 Perform a file operation on the target system. For details,
37438 see @ref{Host I/O Packets}.
37440 @item vFlashErase:@var{addr},@var{length}
37441 @cindex @samp{vFlashErase} packet
37442 Direct the stub to erase @var{length} bytes of flash starting at
37443 @var{addr}. The region may enclose any number of flash blocks, but
37444 its start and end must fall on block boundaries, as indicated by the
37445 flash block size appearing in the memory map (@pxref{Memory Map
37446 Format}). @value{GDBN} groups flash memory programming operations
37447 together, and sends a @samp{vFlashDone} request after each group; the
37448 stub is allowed to delay erase operation until the @samp{vFlashDone}
37449 packet is received.
37459 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37460 @cindex @samp{vFlashWrite} packet
37461 Direct the stub to write data to flash address @var{addr}. The data
37462 is passed in binary form using the same encoding as for the @samp{X}
37463 packet (@pxref{Binary Data}). The memory ranges specified by
37464 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37465 not overlap, and must appear in order of increasing addresses
37466 (although @samp{vFlashErase} packets for higher addresses may already
37467 have been received; the ordering is guaranteed only between
37468 @samp{vFlashWrite} packets). If a packet writes to an address that was
37469 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37470 target-specific method, the results are unpredictable.
37478 for vFlashWrite addressing non-flash memory
37484 @cindex @samp{vFlashDone} packet
37485 Indicate to the stub that flash programming operation is finished.
37486 The stub is permitted to delay or batch the effects of a group of
37487 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37488 @samp{vFlashDone} packet is received. The contents of the affected
37489 regions of flash memory are unpredictable until the @samp{vFlashDone}
37490 request is completed.
37492 @item vKill;@var{pid}
37493 @cindex @samp{vKill} packet
37494 @anchor{vKill packet}
37495 Kill the process with the specified process ID @var{pid}, which is a
37496 hexadecimal integer identifying the process. This packet is used in
37497 preference to @samp{k} when multiprocess protocol extensions are
37498 supported; see @ref{multiprocess extensions}.
37508 @item vMustReplyEmpty
37509 @cindex @samp{vMustReplyEmpty} packet
37510 The correct reply to an unknown @samp{v} packet is to return the empty
37511 string, however, some older versions of @command{gdbserver} would
37512 incorrectly return @samp{OK} for unknown @samp{v} packets.
37514 The @samp{vMustReplyEmpty} is used as a feature test to check how
37515 @command{gdbserver} handles unknown packets, it is important that this
37516 packet be handled in the same way as other unknown @samp{v} packets.
37517 If this packet is handled differently to other unknown @samp{v}
37518 packets then it is possile that @value{GDBN} may run into problems in
37519 other areas, specifically around use of @samp{vFile:setfs:}.
37521 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37522 @cindex @samp{vRun} packet
37523 Run the program @var{filename}, passing it each @var{argument} on its
37524 command line. The file and arguments are hex-encoded strings. If
37525 @var{filename} is an empty string, the stub may use a default program
37526 (e.g.@: the last program run). The program is created in the stopped
37529 @c FIXME: What about non-stop mode?
37531 This packet is only available in extended mode (@pxref{extended mode}).
37537 @item @r{Any stop packet}
37538 for success (@pxref{Stop Reply Packets})
37542 @cindex @samp{vStopped} packet
37543 @xref{Notification Packets}.
37545 @item X @var{addr},@var{length}:@var{XX@dots{}}
37547 @cindex @samp{X} packet
37548 Write data to memory, where the data is transmitted in binary.
37549 Memory is specified by its address @var{addr} and number of addressable memory
37550 units @var{length} (@pxref{addressable memory unit});
37551 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37561 @item z @var{type},@var{addr},@var{kind}
37562 @itemx Z @var{type},@var{addr},@var{kind}
37563 @anchor{insert breakpoint or watchpoint packet}
37564 @cindex @samp{z} packet
37565 @cindex @samp{Z} packets
37566 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37567 watchpoint starting at address @var{address} of kind @var{kind}.
37569 Each breakpoint and watchpoint packet @var{type} is documented
37572 @emph{Implementation notes: A remote target shall return an empty string
37573 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37574 remote target shall support either both or neither of a given
37575 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37576 avoid potential problems with duplicate packets, the operations should
37577 be implemented in an idempotent way.}
37579 @item z0,@var{addr},@var{kind}
37580 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37581 @cindex @samp{z0} packet
37582 @cindex @samp{Z0} packet
37583 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37584 @var{addr} of type @var{kind}.
37586 A software breakpoint is implemented by replacing the instruction at
37587 @var{addr} with a software breakpoint or trap instruction. The
37588 @var{kind} is target-specific and typically indicates the size of the
37589 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37590 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37591 architectures have additional meanings for @var{kind}
37592 (@pxref{Architecture-Specific Protocol Details}); if no
37593 architecture-specific value is being used, it should be @samp{0}.
37594 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37595 conditional expressions in bytecode form that should be evaluated on
37596 the target's side. These are the conditions that should be taken into
37597 consideration when deciding if the breakpoint trigger should be
37598 reported back to @value{GDBN}.
37600 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37601 for how to best report a software breakpoint event to @value{GDBN}.
37603 The @var{cond_list} parameter is comprised of a series of expressions,
37604 concatenated without separators. Each expression has the following form:
37608 @item X @var{len},@var{expr}
37609 @var{len} is the length of the bytecode expression and @var{expr} is the
37610 actual conditional expression in bytecode form.
37614 The optional @var{cmd_list} parameter introduces commands that may be
37615 run on the target, rather than being reported back to @value{GDBN}.
37616 The parameter starts with a numeric flag @var{persist}; if the flag is
37617 nonzero, then the breakpoint may remain active and the commands
37618 continue to be run even when @value{GDBN} disconnects from the target.
37619 Following this flag is a series of expressions concatenated with no
37620 separators. Each expression has the following form:
37624 @item X @var{len},@var{expr}
37625 @var{len} is the length of the bytecode expression and @var{expr} is the
37626 actual commands expression in bytecode form.
37630 @emph{Implementation note: It is possible for a target to copy or move
37631 code that contains software breakpoints (e.g., when implementing
37632 overlays). The behavior of this packet, in the presence of such a
37633 target, is not defined.}
37645 @item z1,@var{addr},@var{kind}
37646 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37647 @cindex @samp{z1} packet
37648 @cindex @samp{Z1} packet
37649 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37650 address @var{addr}.
37652 A hardware breakpoint is implemented using a mechanism that is not
37653 dependent on being able to modify the target's memory. The
37654 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37655 same meaning as in @samp{Z0} packets.
37657 @emph{Implementation note: A hardware breakpoint is not affected by code
37670 @item z2,@var{addr},@var{kind}
37671 @itemx Z2,@var{addr},@var{kind}
37672 @cindex @samp{z2} packet
37673 @cindex @samp{Z2} packet
37674 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37675 The number of bytes to watch is specified by @var{kind}.
37687 @item z3,@var{addr},@var{kind}
37688 @itemx Z3,@var{addr},@var{kind}
37689 @cindex @samp{z3} packet
37690 @cindex @samp{Z3} packet
37691 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37692 The number of bytes to watch is specified by @var{kind}.
37704 @item z4,@var{addr},@var{kind}
37705 @itemx Z4,@var{addr},@var{kind}
37706 @cindex @samp{z4} packet
37707 @cindex @samp{Z4} packet
37708 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37709 The number of bytes to watch is specified by @var{kind}.
37723 @node Stop Reply Packets
37724 @section Stop Reply Packets
37725 @cindex stop reply packets
37727 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37728 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
37729 receive any of the below as a reply. Except for @samp{?}
37730 and @samp{vStopped}, that reply is only returned
37731 when the target halts. In the below the exact meaning of @dfn{signal
37732 number} is defined by the header @file{include/gdb/signals.h} in the
37733 @value{GDBN} source code.
37735 In non-stop mode, the server will simply reply @samp{OK} to commands
37736 such as @samp{vCont}; any stop will be the subject of a future
37737 notification. @xref{Remote Non-Stop}.
37739 As in the description of request packets, we include spaces in the
37740 reply templates for clarity; these are not part of the reply packet's
37741 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
37747 The program received signal number @var{AA} (a two-digit hexadecimal
37748 number). This is equivalent to a @samp{T} response with no
37749 @var{n}:@var{r} pairs.
37751 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
37752 @cindex @samp{T} packet reply
37753 The program received signal number @var{AA} (a two-digit hexadecimal
37754 number). This is equivalent to an @samp{S} response, except that the
37755 @samp{@var{n}:@var{r}} pairs can carry values of important registers
37756 and other information directly in the stop reply packet, reducing
37757 round-trip latency. Single-step and breakpoint traps are reported
37758 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
37762 If @var{n} is a hexadecimal number, it is a register number, and the
37763 corresponding @var{r} gives that register's value. The data @var{r} is a
37764 series of bytes in target byte order, with each byte given by a
37765 two-digit hex number.
37768 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
37769 the stopped thread, as specified in @ref{thread-id syntax}.
37772 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
37773 the core on which the stop event was detected.
37776 If @var{n} is a recognized @dfn{stop reason}, it describes a more
37777 specific event that stopped the target. The currently defined stop
37778 reasons are listed below. The @var{aa} should be @samp{05}, the trap
37779 signal. At most one stop reason should be present.
37782 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
37783 and go on to the next; this allows us to extend the protocol in the
37787 The currently defined stop reasons are:
37793 The packet indicates a watchpoint hit, and @var{r} is the data address, in
37796 @item syscall_entry
37797 @itemx syscall_return
37798 The packet indicates a syscall entry or return, and @var{r} is the
37799 syscall number, in hex.
37801 @cindex shared library events, remote reply
37803 The packet indicates that the loaded libraries have changed.
37804 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
37805 list of loaded libraries. The @var{r} part is ignored.
37807 @cindex replay log events, remote reply
37809 The packet indicates that the target cannot continue replaying
37810 logged execution events, because it has reached the end (or the
37811 beginning when executing backward) of the log. The value of @var{r}
37812 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
37813 for more information.
37816 @anchor{swbreak stop reason}
37817 The packet indicates a software breakpoint instruction was executed,
37818 irrespective of whether it was @value{GDBN} that planted the
37819 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
37820 part must be left empty.
37822 On some architectures, such as x86, at the architecture level, when a
37823 breakpoint instruction executes the program counter points at the
37824 breakpoint address plus an offset. On such targets, the stub is
37825 responsible for adjusting the PC to point back at the breakpoint
37828 This packet should not be sent by default; older @value{GDBN} versions
37829 did not support it. @value{GDBN} requests it, by supplying an
37830 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37831 remote stub must also supply the appropriate @samp{qSupported} feature
37832 indicating support.
37834 This packet is required for correct non-stop mode operation.
37837 The packet indicates the target stopped for a hardware breakpoint.
37838 The @var{r} part must be left empty.
37840 The same remarks about @samp{qSupported} and non-stop mode above
37843 @cindex fork events, remote reply
37845 The packet indicates that @code{fork} was called, and @var{r}
37846 is the thread ID of the new child process. Refer to
37847 @ref{thread-id syntax} for the format of the @var{thread-id}
37848 field. This packet is only applicable to targets that support
37851 This packet should not be sent by default; older @value{GDBN} versions
37852 did not support it. @value{GDBN} requests it, by supplying an
37853 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37854 remote stub must also supply the appropriate @samp{qSupported} feature
37855 indicating support.
37857 @cindex vfork events, remote reply
37859 The packet indicates that @code{vfork} was called, and @var{r}
37860 is the thread ID of the new child process. Refer to
37861 @ref{thread-id syntax} for the format of the @var{thread-id}
37862 field. This packet is only applicable to targets that support
37865 This packet should not be sent by default; older @value{GDBN} versions
37866 did not support it. @value{GDBN} requests it, by supplying an
37867 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37868 remote stub must also supply the appropriate @samp{qSupported} feature
37869 indicating support.
37871 @cindex vforkdone events, remote reply
37873 The packet indicates that a child process created by a vfork
37874 has either called @code{exec} or terminated, so that the
37875 address spaces of the parent and child process are no longer
37876 shared. The @var{r} part is ignored. This packet is only
37877 applicable to targets that support vforkdone events.
37879 This packet should not be sent by default; older @value{GDBN} versions
37880 did not support it. @value{GDBN} requests it, by supplying an
37881 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37882 remote stub must also supply the appropriate @samp{qSupported} feature
37883 indicating support.
37885 @cindex exec events, remote reply
37887 The packet indicates that @code{execve} was called, and @var{r}
37888 is the absolute pathname of the file that was executed, in hex.
37889 This packet is only applicable to targets that support exec events.
37891 This packet should not be sent by default; older @value{GDBN} versions
37892 did not support it. @value{GDBN} requests it, by supplying an
37893 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
37894 remote stub must also supply the appropriate @samp{qSupported} feature
37895 indicating support.
37897 @cindex thread create event, remote reply
37898 @anchor{thread create event}
37900 The packet indicates that the thread was just created. The new thread
37901 is stopped until @value{GDBN} sets it running with a resumption packet
37902 (@pxref{vCont packet}). This packet should not be sent by default;
37903 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
37904 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
37905 @var{r} part is ignored.
37910 @itemx W @var{AA} ; process:@var{pid}
37911 The process exited, and @var{AA} is the exit status. This is only
37912 applicable to certain targets.
37914 The second form of the response, including the process ID of the
37915 exited process, can be used only when @value{GDBN} has reported
37916 support for multiprocess protocol extensions; see @ref{multiprocess
37917 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37921 @itemx X @var{AA} ; process:@var{pid}
37922 The process terminated with signal @var{AA}.
37924 The second form of the response, including the process ID of the
37925 terminated process, can be used only when @value{GDBN} has reported
37926 support for multiprocess protocol extensions; see @ref{multiprocess
37927 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
37930 @anchor{thread exit event}
37931 @cindex thread exit event, remote reply
37932 @item w @var{AA} ; @var{tid}
37934 The thread exited, and @var{AA} is the exit status. This response
37935 should not be sent by default; @value{GDBN} requests it with the
37936 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
37937 @var{AA} is formatted as a big-endian hex string.
37940 There are no resumed threads left in the target. In other words, even
37941 though the process is alive, the last resumed thread has exited. For
37942 example, say the target process has two threads: thread 1 and thread
37943 2. The client leaves thread 1 stopped, and resumes thread 2, which
37944 subsequently exits. At this point, even though the process is still
37945 alive, and thus no @samp{W} stop reply is sent, no thread is actually
37946 executing either. The @samp{N} stop reply thus informs the client
37947 that it can stop waiting for stop replies. This packet should not be
37948 sent by default; older @value{GDBN} versions did not support it.
37949 @value{GDBN} requests it, by supplying an appropriate
37950 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
37951 also supply the appropriate @samp{qSupported} feature indicating
37954 @item O @var{XX}@dots{}
37955 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
37956 written as the program's console output. This can happen at any time
37957 while the program is running and the debugger should continue to wait
37958 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
37960 @item F @var{call-id},@var{parameter}@dots{}
37961 @var{call-id} is the identifier which says which host system call should
37962 be called. This is just the name of the function. Translation into the
37963 correct system call is only applicable as it's defined in @value{GDBN}.
37964 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
37967 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
37968 this very system call.
37970 The target replies with this packet when it expects @value{GDBN} to
37971 call a host system call on behalf of the target. @value{GDBN} replies
37972 with an appropriate @samp{F} packet and keeps up waiting for the next
37973 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
37974 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
37975 Protocol Extension}, for more details.
37979 @node General Query Packets
37980 @section General Query Packets
37981 @cindex remote query requests
37983 Packets starting with @samp{q} are @dfn{general query packets};
37984 packets starting with @samp{Q} are @dfn{general set packets}. General
37985 query and set packets are a semi-unified form for retrieving and
37986 sending information to and from the stub.
37988 The initial letter of a query or set packet is followed by a name
37989 indicating what sort of thing the packet applies to. For example,
37990 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
37991 definitions with the stub. These packet names follow some
37996 The name must not contain commas, colons or semicolons.
37998 Most @value{GDBN} query and set packets have a leading upper case
38001 The names of custom vendor packets should use a company prefix, in
38002 lower case, followed by a period. For example, packets designed at
38003 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38004 foos) or @samp{Qacme.bar} (for setting bars).
38007 The name of a query or set packet should be separated from any
38008 parameters by a @samp{:}; the parameters themselves should be
38009 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38010 full packet name, and check for a separator or the end of the packet,
38011 in case two packet names share a common prefix. New packets should not begin
38012 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38013 packets predate these conventions, and have arguments without any terminator
38014 for the packet name; we suspect they are in widespread use in places that
38015 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38016 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38019 Like the descriptions of the other packets, each description here
38020 has a template showing the packet's overall syntax, followed by an
38021 explanation of the packet's meaning. We include spaces in some of the
38022 templates for clarity; these are not part of the packet's syntax. No
38023 @value{GDBN} packet uses spaces to separate its components.
38025 Here are the currently defined query and set packets:
38031 Turn on or off the agent as a helper to perform some debugging operations
38032 delegated from @value{GDBN} (@pxref{Control Agent}).
38034 @item QAllow:@var{op}:@var{val}@dots{}
38035 @cindex @samp{QAllow} packet
38036 Specify which operations @value{GDBN} expects to request of the
38037 target, as a semicolon-separated list of operation name and value
38038 pairs. Possible values for @var{op} include @samp{WriteReg},
38039 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38040 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38041 indicating that @value{GDBN} will not request the operation, or 1,
38042 indicating that it may. (The target can then use this to set up its
38043 own internals optimally, for instance if the debugger never expects to
38044 insert breakpoints, it may not need to install its own trap handler.)
38047 @cindex current thread, remote request
38048 @cindex @samp{qC} packet
38049 Return the current thread ID.
38053 @item QC @var{thread-id}
38054 Where @var{thread-id} is a thread ID as documented in
38055 @ref{thread-id syntax}.
38056 @item @r{(anything else)}
38057 Any other reply implies the old thread ID.
38060 @item qCRC:@var{addr},@var{length}
38061 @cindex CRC of memory block, remote request
38062 @cindex @samp{qCRC} packet
38063 @anchor{qCRC packet}
38064 Compute the CRC checksum of a block of memory using CRC-32 defined in
38065 IEEE 802.3. The CRC is computed byte at a time, taking the most
38066 significant bit of each byte first. The initial pattern code
38067 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38069 @emph{Note:} This is the same CRC used in validating separate debug
38070 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38071 Files}). However the algorithm is slightly different. When validating
38072 separate debug files, the CRC is computed taking the @emph{least}
38073 significant bit of each byte first, and the final result is inverted to
38074 detect trailing zeros.
38079 An error (such as memory fault)
38080 @item C @var{crc32}
38081 The specified memory region's checksum is @var{crc32}.
38084 @item QDisableRandomization:@var{value}
38085 @cindex disable address space randomization, remote request
38086 @cindex @samp{QDisableRandomization} packet
38087 Some target operating systems will randomize the virtual address space
38088 of the inferior process as a security feature, but provide a feature
38089 to disable such randomization, e.g.@: to allow for a more deterministic
38090 debugging experience. On such systems, this packet with a @var{value}
38091 of 1 directs the target to disable address space randomization for
38092 processes subsequently started via @samp{vRun} packets, while a packet
38093 with a @var{value} of 0 tells the target to enable address space
38096 This packet is only available in extended mode (@pxref{extended mode}).
38101 The request succeeded.
38104 An error occurred. The error number @var{nn} is given as hex digits.
38107 An empty reply indicates that @samp{QDisableRandomization} is not supported
38111 This packet is not probed by default; the remote stub must request it,
38112 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38113 This should only be done on targets that actually support disabling
38114 address space randomization.
38116 @item QStartupWithShell:@var{value}
38117 @cindex startup with shell, remote request
38118 @cindex @samp{QStartupWithShell} packet
38119 On UNIX-like targets, it is possible to start the inferior using a
38120 shell program. This is the default behavior on both @value{GDBN} and
38121 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38122 used to inform @command{gdbserver} whether it should start the
38123 inferior using a shell or not.
38125 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38126 to start the inferior. If @var{value} is @samp{1},
38127 @command{gdbserver} will use a shell to start the inferior. All other
38128 values are considered an error.
38130 This packet is only available in extended mode (@pxref{extended
38136 The request succeeded.
38139 An error occurred. The error number @var{nn} is given as hex digits.
38142 This packet is not probed by default; the remote stub must request it,
38143 by supplying an appropriate @samp{qSupported} response
38144 (@pxref{qSupported}). This should only be done on targets that
38145 actually support starting the inferior using a shell.
38147 Use of this packet is controlled by the @code{set startup-with-shell}
38148 command; @pxref{set startup-with-shell}.
38150 @item QEnvironmentHexEncoded:@var{hex-value}
38151 @anchor{QEnvironmentHexEncoded}
38152 @cindex set environment variable, remote request
38153 @cindex @samp{QEnvironmentHexEncoded} packet
38154 On UNIX-like targets, it is possible to set environment variables that
38155 will be passed to the inferior during the startup process. This
38156 packet is used to inform @command{gdbserver} of an environment
38157 variable that has been defined by the user on @value{GDBN} (@pxref{set
38160 The packet is composed by @var{hex-value}, an hex encoded
38161 representation of the @var{name=value} format representing an
38162 environment variable. The name of the environment variable is
38163 represented by @var{name}, and the value to be assigned to the
38164 environment variable is represented by @var{value}. If the variable
38165 has no value (i.e., the value is @code{null}), then @var{value} will
38168 This packet is only available in extended mode (@pxref{extended
38174 The request succeeded.
38177 This packet is not probed by default; the remote stub must request it,
38178 by supplying an appropriate @samp{qSupported} response
38179 (@pxref{qSupported}). This should only be done on targets that
38180 actually support passing environment variables to the starting
38183 This packet is related to the @code{set environment} command;
38184 @pxref{set environment}.
38186 @item QEnvironmentUnset:@var{hex-value}
38187 @anchor{QEnvironmentUnset}
38188 @cindex unset environment variable, remote request
38189 @cindex @samp{QEnvironmentUnset} packet
38190 On UNIX-like targets, it is possible to unset environment variables
38191 before starting the inferior in the remote target. This packet is
38192 used to inform @command{gdbserver} of an environment variable that has
38193 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38195 The packet is composed by @var{hex-value}, an hex encoded
38196 representation of the name of the environment variable to be unset.
38198 This packet is only available in extended mode (@pxref{extended
38204 The request succeeded.
38207 This packet is not probed by default; the remote stub must request it,
38208 by supplying an appropriate @samp{qSupported} response
38209 (@pxref{qSupported}). This should only be done on targets that
38210 actually support passing environment variables to the starting
38213 This packet is related to the @code{unset environment} command;
38214 @pxref{unset environment}.
38216 @item QEnvironmentReset
38217 @anchor{QEnvironmentReset}
38218 @cindex reset environment, remote request
38219 @cindex @samp{QEnvironmentReset} packet
38220 On UNIX-like targets, this packet is used to reset the state of
38221 environment variables in the remote target before starting the
38222 inferior. In this context, reset means unsetting all environment
38223 variables that were previously set by the user (i.e., were not
38224 initially present in the environment). It is sent to
38225 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38226 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38227 (@pxref{QEnvironmentUnset}) packets.
38229 This packet is only available in extended mode (@pxref{extended
38235 The request succeeded.
38238 This packet is not probed by default; the remote stub must request it,
38239 by supplying an appropriate @samp{qSupported} response
38240 (@pxref{qSupported}). This should only be done on targets that
38241 actually support passing environment variables to the starting
38244 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38245 @anchor{QSetWorkingDir packet}
38246 @cindex set working directory, remote request
38247 @cindex @samp{QSetWorkingDir} packet
38248 This packet is used to inform the remote server of the intended
38249 current working directory for programs that are going to be executed.
38251 The packet is composed by @var{directory}, an hex encoded
38252 representation of the directory that the remote inferior will use as
38253 its current working directory. If @var{directory} is an empty string,
38254 the remote server should reset the inferior's current working
38255 directory to its original, empty value.
38257 This packet is only available in extended mode (@pxref{extended
38263 The request succeeded.
38267 @itemx qsThreadInfo
38268 @cindex list active threads, remote request
38269 @cindex @samp{qfThreadInfo} packet
38270 @cindex @samp{qsThreadInfo} packet
38271 Obtain a list of all active thread IDs from the target (OS). Since there
38272 may be too many active threads to fit into one reply packet, this query
38273 works iteratively: it may require more than one query/reply sequence to
38274 obtain the entire list of threads. The first query of the sequence will
38275 be the @samp{qfThreadInfo} query; subsequent queries in the
38276 sequence will be the @samp{qsThreadInfo} query.
38278 NOTE: This packet replaces the @samp{qL} query (see below).
38282 @item m @var{thread-id}
38284 @item m @var{thread-id},@var{thread-id}@dots{}
38285 a comma-separated list of thread IDs
38287 (lower case letter @samp{L}) denotes end of list.
38290 In response to each query, the target will reply with a list of one or
38291 more thread IDs, separated by commas.
38292 @value{GDBN} will respond to each reply with a request for more thread
38293 ids (using the @samp{qs} form of the query), until the target responds
38294 with @samp{l} (lower-case ell, for @dfn{last}).
38295 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38298 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38299 initial connection with the remote target, and the very first thread ID
38300 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38301 message. Therefore, the stub should ensure that the first thread ID in
38302 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38304 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38305 @cindex get thread-local storage address, remote request
38306 @cindex @samp{qGetTLSAddr} packet
38307 Fetch the address associated with thread local storage specified
38308 by @var{thread-id}, @var{offset}, and @var{lm}.
38310 @var{thread-id} is the thread ID associated with the
38311 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38313 @var{offset} is the (big endian, hex encoded) offset associated with the
38314 thread local variable. (This offset is obtained from the debug
38315 information associated with the variable.)
38317 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38318 load module associated with the thread local storage. For example,
38319 a @sc{gnu}/Linux system will pass the link map address of the shared
38320 object associated with the thread local storage under consideration.
38321 Other operating environments may choose to represent the load module
38322 differently, so the precise meaning of this parameter will vary.
38326 @item @var{XX}@dots{}
38327 Hex encoded (big endian) bytes representing the address of the thread
38328 local storage requested.
38331 An error occurred. The error number @var{nn} is given as hex digits.
38334 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38337 @item qGetTIBAddr:@var{thread-id}
38338 @cindex get thread information block address
38339 @cindex @samp{qGetTIBAddr} packet
38340 Fetch address of the Windows OS specific Thread Information Block.
38342 @var{thread-id} is the thread ID associated with the thread.
38346 @item @var{XX}@dots{}
38347 Hex encoded (big endian) bytes representing the linear address of the
38348 thread information block.
38351 An error occured. This means that either the thread was not found, or the
38352 address could not be retrieved.
38355 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38358 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38359 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38360 digit) is one to indicate the first query and zero to indicate a
38361 subsequent query; @var{threadcount} (two hex digits) is the maximum
38362 number of threads the response packet can contain; and @var{nextthread}
38363 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38364 returned in the response as @var{argthread}.
38366 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38370 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38371 Where: @var{count} (two hex digits) is the number of threads being
38372 returned; @var{done} (one hex digit) is zero to indicate more threads
38373 and one indicates no further threads; @var{argthreadid} (eight hex
38374 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38375 is a sequence of thread IDs, @var{threadid} (eight hex
38376 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38380 @cindex section offsets, remote request
38381 @cindex @samp{qOffsets} packet
38382 Get section offsets that the target used when relocating the downloaded
38387 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38388 Relocate the @code{Text} section by @var{xxx} from its original address.
38389 Relocate the @code{Data} section by @var{yyy} from its original address.
38390 If the object file format provides segment information (e.g.@: @sc{elf}
38391 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38392 segments by the supplied offsets.
38394 @emph{Note: while a @code{Bss} offset may be included in the response,
38395 @value{GDBN} ignores this and instead applies the @code{Data} offset
38396 to the @code{Bss} section.}
38398 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38399 Relocate the first segment of the object file, which conventionally
38400 contains program code, to a starting address of @var{xxx}. If
38401 @samp{DataSeg} is specified, relocate the second segment, which
38402 conventionally contains modifiable data, to a starting address of
38403 @var{yyy}. @value{GDBN} will report an error if the object file
38404 does not contain segment information, or does not contain at least
38405 as many segments as mentioned in the reply. Extra segments are
38406 kept at fixed offsets relative to the last relocated segment.
38409 @item qP @var{mode} @var{thread-id}
38410 @cindex thread information, remote request
38411 @cindex @samp{qP} packet
38412 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38413 encoded 32 bit mode; @var{thread-id} is a thread ID
38414 (@pxref{thread-id syntax}).
38416 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38419 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38423 @cindex non-stop mode, remote request
38424 @cindex @samp{QNonStop} packet
38426 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38427 @xref{Remote Non-Stop}, for more information.
38432 The request succeeded.
38435 An error occurred. The error number @var{nn} is given as hex digits.
38438 An empty reply indicates that @samp{QNonStop} is not supported by
38442 This packet is not probed by default; the remote stub must request it,
38443 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38444 Use of this packet is controlled by the @code{set non-stop} command;
38445 @pxref{Non-Stop Mode}.
38447 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38448 @itemx QCatchSyscalls:0
38449 @cindex catch syscalls from inferior, remote request
38450 @cindex @samp{QCatchSyscalls} packet
38451 @anchor{QCatchSyscalls}
38452 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38453 catching syscalls from the inferior process.
38455 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38456 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38457 is listed, every system call should be reported.
38459 Note that if a syscall not in the list is reported, @value{GDBN} will
38460 still filter the event according to its own list from all corresponding
38461 @code{catch syscall} commands. However, it is more efficient to only
38462 report the requested syscalls.
38464 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38465 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38467 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38468 kept for the new process too. On targets where exec may affect syscall
38469 numbers, for example with exec between 32 and 64-bit processes, the
38470 client should send a new packet with the new syscall list.
38475 The request succeeded.
38478 An error occurred. @var{nn} are hex digits.
38481 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38485 Use of this packet is controlled by the @code{set remote catch-syscalls}
38486 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38487 This packet is not probed by default; the remote stub must request it,
38488 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38490 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38491 @cindex pass signals to inferior, remote request
38492 @cindex @samp{QPassSignals} packet
38493 @anchor{QPassSignals}
38494 Each listed @var{signal} should be passed directly to the inferior process.
38495 Signals are numbered identically to continue packets and stop replies
38496 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38497 strictly greater than the previous item. These signals do not need to stop
38498 the inferior, or be reported to @value{GDBN}. All other signals should be
38499 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38500 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38501 new list. This packet improves performance when using @samp{handle
38502 @var{signal} nostop noprint pass}.
38507 The request succeeded.
38510 An error occurred. The error number @var{nn} is given as hex digits.
38513 An empty reply indicates that @samp{QPassSignals} is not supported by
38517 Use of this packet is controlled by the @code{set remote pass-signals}
38518 command (@pxref{Remote Configuration, set remote pass-signals}).
38519 This packet is not probed by default; the remote stub must request it,
38520 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38522 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38523 @cindex signals the inferior may see, remote request
38524 @cindex @samp{QProgramSignals} packet
38525 @anchor{QProgramSignals}
38526 Each listed @var{signal} may be delivered to the inferior process.
38527 Others should be silently discarded.
38529 In some cases, the remote stub may need to decide whether to deliver a
38530 signal to the program or not without @value{GDBN} involvement. One
38531 example of that is while detaching --- the program's threads may have
38532 stopped for signals that haven't yet had a chance of being reported to
38533 @value{GDBN}, and so the remote stub can use the signal list specified
38534 by this packet to know whether to deliver or ignore those pending
38537 This does not influence whether to deliver a signal as requested by a
38538 resumption packet (@pxref{vCont packet}).
38540 Signals are numbered identically to continue packets and stop replies
38541 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38542 strictly greater than the previous item. Multiple
38543 @samp{QProgramSignals} packets do not combine; any earlier
38544 @samp{QProgramSignals} list is completely replaced by the new list.
38549 The request succeeded.
38552 An error occurred. The error number @var{nn} is given as hex digits.
38555 An empty reply indicates that @samp{QProgramSignals} is not supported
38559 Use of this packet is controlled by the @code{set remote program-signals}
38560 command (@pxref{Remote Configuration, set remote program-signals}).
38561 This packet is not probed by default; the remote stub must request it,
38562 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38564 @anchor{QThreadEvents}
38565 @item QThreadEvents:1
38566 @itemx QThreadEvents:0
38567 @cindex thread create/exit events, remote request
38568 @cindex @samp{QThreadEvents} packet
38570 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38571 reporting of thread create and exit events. @xref{thread create
38572 event}, for the reply specifications. For example, this is used in
38573 non-stop mode when @value{GDBN} stops a set of threads and
38574 synchronously waits for the their corresponding stop replies. Without
38575 exit events, if one of the threads exits, @value{GDBN} would hang
38576 forever not knowing that it should no longer expect a stop for that
38577 same thread. @value{GDBN} does not enable this feature unless the
38578 stub reports that it supports it by including @samp{QThreadEvents+} in
38579 its @samp{qSupported} reply.
38584 The request succeeded.
38587 An error occurred. The error number @var{nn} is given as hex digits.
38590 An empty reply indicates that @samp{QThreadEvents} is not supported by
38594 Use of this packet is controlled by the @code{set remote thread-events}
38595 command (@pxref{Remote Configuration, set remote thread-events}).
38597 @item qRcmd,@var{command}
38598 @cindex execute remote command, remote request
38599 @cindex @samp{qRcmd} packet
38600 @var{command} (hex encoded) is passed to the local interpreter for
38601 execution. Invalid commands should be reported using the output
38602 string. Before the final result packet, the target may also respond
38603 with a number of intermediate @samp{O@var{output}} console output
38604 packets. @emph{Implementors should note that providing access to a
38605 stubs's interpreter may have security implications}.
38610 A command response with no output.
38612 A command response with the hex encoded output string @var{OUTPUT}.
38614 Indicate a badly formed request.
38616 An empty reply indicates that @samp{qRcmd} is not recognized.
38619 (Note that the @code{qRcmd} packet's name is separated from the
38620 command by a @samp{,}, not a @samp{:}, contrary to the naming
38621 conventions above. Please don't use this packet as a model for new
38624 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38625 @cindex searching memory, in remote debugging
38627 @cindex @samp{qSearch:memory} packet
38629 @cindex @samp{qSearch memory} packet
38630 @anchor{qSearch memory}
38631 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38632 Both @var{address} and @var{length} are encoded in hex;
38633 @var{search-pattern} is a sequence of bytes, also hex encoded.
38638 The pattern was not found.
38640 The pattern was found at @var{address}.
38642 A badly formed request or an error was encountered while searching memory.
38644 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38647 @item QStartNoAckMode
38648 @cindex @samp{QStartNoAckMode} packet
38649 @anchor{QStartNoAckMode}
38650 Request that the remote stub disable the normal @samp{+}/@samp{-}
38651 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38656 The stub has switched to no-acknowledgment mode.
38657 @value{GDBN} acknowledges this reponse,
38658 but neither the stub nor @value{GDBN} shall send or expect further
38659 @samp{+}/@samp{-} acknowledgments in the current connection.
38661 An empty reply indicates that the stub does not support no-acknowledgment mode.
38664 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38665 @cindex supported packets, remote query
38666 @cindex features of the remote protocol
38667 @cindex @samp{qSupported} packet
38668 @anchor{qSupported}
38669 Tell the remote stub about features supported by @value{GDBN}, and
38670 query the stub for features it supports. This packet allows
38671 @value{GDBN} and the remote stub to take advantage of each others'
38672 features. @samp{qSupported} also consolidates multiple feature probes
38673 at startup, to improve @value{GDBN} performance---a single larger
38674 packet performs better than multiple smaller probe packets on
38675 high-latency links. Some features may enable behavior which must not
38676 be on by default, e.g.@: because it would confuse older clients or
38677 stubs. Other features may describe packets which could be
38678 automatically probed for, but are not. These features must be
38679 reported before @value{GDBN} will use them. This ``default
38680 unsupported'' behavior is not appropriate for all packets, but it
38681 helps to keep the initial connection time under control with new
38682 versions of @value{GDBN} which support increasing numbers of packets.
38686 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38687 The stub supports or does not support each returned @var{stubfeature},
38688 depending on the form of each @var{stubfeature} (see below for the
38691 An empty reply indicates that @samp{qSupported} is not recognized,
38692 or that no features needed to be reported to @value{GDBN}.
38695 The allowed forms for each feature (either a @var{gdbfeature} in the
38696 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38700 @item @var{name}=@var{value}
38701 The remote protocol feature @var{name} is supported, and associated
38702 with the specified @var{value}. The format of @var{value} depends
38703 on the feature, but it must not include a semicolon.
38705 The remote protocol feature @var{name} is supported, and does not
38706 need an associated value.
38708 The remote protocol feature @var{name} is not supported.
38710 The remote protocol feature @var{name} may be supported, and
38711 @value{GDBN} should auto-detect support in some other way when it is
38712 needed. This form will not be used for @var{gdbfeature} notifications,
38713 but may be used for @var{stubfeature} responses.
38716 Whenever the stub receives a @samp{qSupported} request, the
38717 supplied set of @value{GDBN} features should override any previous
38718 request. This allows @value{GDBN} to put the stub in a known
38719 state, even if the stub had previously been communicating with
38720 a different version of @value{GDBN}.
38722 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38727 This feature indicates whether @value{GDBN} supports multiprocess
38728 extensions to the remote protocol. @value{GDBN} does not use such
38729 extensions unless the stub also reports that it supports them by
38730 including @samp{multiprocess+} in its @samp{qSupported} reply.
38731 @xref{multiprocess extensions}, for details.
38734 This feature indicates that @value{GDBN} supports the XML target
38735 description. If the stub sees @samp{xmlRegisters=} with target
38736 specific strings separated by a comma, it will report register
38740 This feature indicates whether @value{GDBN} supports the
38741 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38742 instruction reply packet}).
38745 This feature indicates whether @value{GDBN} supports the swbreak stop
38746 reason in stop replies. @xref{swbreak stop reason}, for details.
38749 This feature indicates whether @value{GDBN} supports the hwbreak stop
38750 reason in stop replies. @xref{swbreak stop reason}, for details.
38753 This feature indicates whether @value{GDBN} supports fork event
38754 extensions to the remote protocol. @value{GDBN} does not use such
38755 extensions unless the stub also reports that it supports them by
38756 including @samp{fork-events+} in its @samp{qSupported} reply.
38759 This feature indicates whether @value{GDBN} supports vfork event
38760 extensions to the remote protocol. @value{GDBN} does not use such
38761 extensions unless the stub also reports that it supports them by
38762 including @samp{vfork-events+} in its @samp{qSupported} reply.
38765 This feature indicates whether @value{GDBN} supports exec event
38766 extensions to the remote protocol. @value{GDBN} does not use such
38767 extensions unless the stub also reports that it supports them by
38768 including @samp{exec-events+} in its @samp{qSupported} reply.
38770 @item vContSupported
38771 This feature indicates whether @value{GDBN} wants to know the
38772 supported actions in the reply to @samp{vCont?} packet.
38775 Stubs should ignore any unknown values for
38776 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38777 packet supports receiving packets of unlimited length (earlier
38778 versions of @value{GDBN} may reject overly long responses). Additional values
38779 for @var{gdbfeature} may be defined in the future to let the stub take
38780 advantage of new features in @value{GDBN}, e.g.@: incompatible
38781 improvements in the remote protocol---the @samp{multiprocess} feature is
38782 an example of such a feature. The stub's reply should be independent
38783 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38784 describes all the features it supports, and then the stub replies with
38785 all the features it supports.
38787 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38788 responses, as long as each response uses one of the standard forms.
38790 Some features are flags. A stub which supports a flag feature
38791 should respond with a @samp{+} form response. Other features
38792 require values, and the stub should respond with an @samp{=}
38795 Each feature has a default value, which @value{GDBN} will use if
38796 @samp{qSupported} is not available or if the feature is not mentioned
38797 in the @samp{qSupported} response. The default values are fixed; a
38798 stub is free to omit any feature responses that match the defaults.
38800 Not all features can be probed, but for those which can, the probing
38801 mechanism is useful: in some cases, a stub's internal
38802 architecture may not allow the protocol layer to know some information
38803 about the underlying target in advance. This is especially common in
38804 stubs which may be configured for multiple targets.
38806 These are the currently defined stub features and their properties:
38808 @multitable @columnfractions 0.35 0.2 0.12 0.2
38809 @c NOTE: The first row should be @headitem, but we do not yet require
38810 @c a new enough version of Texinfo (4.7) to use @headitem.
38812 @tab Value Required
38816 @item @samp{PacketSize}
38821 @item @samp{qXfer:auxv:read}
38826 @item @samp{qXfer:btrace:read}
38831 @item @samp{qXfer:btrace-conf:read}
38836 @item @samp{qXfer:exec-file:read}
38841 @item @samp{qXfer:features:read}
38846 @item @samp{qXfer:libraries:read}
38851 @item @samp{qXfer:libraries-svr4:read}
38856 @item @samp{augmented-libraries-svr4-read}
38861 @item @samp{qXfer:memory-map:read}
38866 @item @samp{qXfer:sdata:read}
38871 @item @samp{qXfer:spu:read}
38876 @item @samp{qXfer:spu:write}
38881 @item @samp{qXfer:siginfo:read}
38886 @item @samp{qXfer:siginfo:write}
38891 @item @samp{qXfer:threads:read}
38896 @item @samp{qXfer:traceframe-info:read}
38901 @item @samp{qXfer:uib:read}
38906 @item @samp{qXfer:fdpic:read}
38911 @item @samp{Qbtrace:off}
38916 @item @samp{Qbtrace:bts}
38921 @item @samp{Qbtrace:pt}
38926 @item @samp{Qbtrace-conf:bts:size}
38931 @item @samp{Qbtrace-conf:pt:size}
38936 @item @samp{QNonStop}
38941 @item @samp{QCatchSyscalls}
38946 @item @samp{QPassSignals}
38951 @item @samp{QStartNoAckMode}
38956 @item @samp{multiprocess}
38961 @item @samp{ConditionalBreakpoints}
38966 @item @samp{ConditionalTracepoints}
38971 @item @samp{ReverseContinue}
38976 @item @samp{ReverseStep}
38981 @item @samp{TracepointSource}
38986 @item @samp{QAgent}
38991 @item @samp{QAllow}
38996 @item @samp{QDisableRandomization}
39001 @item @samp{EnableDisableTracepoints}
39006 @item @samp{QTBuffer:size}
39011 @item @samp{tracenz}
39016 @item @samp{BreakpointCommands}
39021 @item @samp{swbreak}
39026 @item @samp{hwbreak}
39031 @item @samp{fork-events}
39036 @item @samp{vfork-events}
39041 @item @samp{exec-events}
39046 @item @samp{QThreadEvents}
39051 @item @samp{no-resumed}
39058 These are the currently defined stub features, in more detail:
39061 @cindex packet size, remote protocol
39062 @item PacketSize=@var{bytes}
39063 The remote stub can accept packets up to at least @var{bytes} in
39064 length. @value{GDBN} will send packets up to this size for bulk
39065 transfers, and will never send larger packets. This is a limit on the
39066 data characters in the packet, including the frame and checksum.
39067 There is no trailing NUL byte in a remote protocol packet; if the stub
39068 stores packets in a NUL-terminated format, it should allow an extra
39069 byte in its buffer for the NUL. If this stub feature is not supported,
39070 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39072 @item qXfer:auxv:read
39073 The remote stub understands the @samp{qXfer:auxv:read} packet
39074 (@pxref{qXfer auxiliary vector read}).
39076 @item qXfer:btrace:read
39077 The remote stub understands the @samp{qXfer:btrace:read}
39078 packet (@pxref{qXfer btrace read}).
39080 @item qXfer:btrace-conf:read
39081 The remote stub understands the @samp{qXfer:btrace-conf:read}
39082 packet (@pxref{qXfer btrace-conf read}).
39084 @item qXfer:exec-file:read
39085 The remote stub understands the @samp{qXfer:exec-file:read} packet
39086 (@pxref{qXfer executable filename read}).
39088 @item qXfer:features:read
39089 The remote stub understands the @samp{qXfer:features:read} packet
39090 (@pxref{qXfer target description read}).
39092 @item qXfer:libraries:read
39093 The remote stub understands the @samp{qXfer:libraries:read} packet
39094 (@pxref{qXfer library list read}).
39096 @item qXfer:libraries-svr4:read
39097 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39098 (@pxref{qXfer svr4 library list read}).
39100 @item augmented-libraries-svr4-read
39101 The remote stub understands the augmented form of the
39102 @samp{qXfer:libraries-svr4:read} packet
39103 (@pxref{qXfer svr4 library list read}).
39105 @item qXfer:memory-map:read
39106 The remote stub understands the @samp{qXfer:memory-map:read} packet
39107 (@pxref{qXfer memory map read}).
39109 @item qXfer:sdata:read
39110 The remote stub understands the @samp{qXfer:sdata:read} packet
39111 (@pxref{qXfer sdata read}).
39113 @item qXfer:spu:read
39114 The remote stub understands the @samp{qXfer:spu:read} packet
39115 (@pxref{qXfer spu read}).
39117 @item qXfer:spu:write
39118 The remote stub understands the @samp{qXfer:spu:write} packet
39119 (@pxref{qXfer spu write}).
39121 @item qXfer:siginfo:read
39122 The remote stub understands the @samp{qXfer:siginfo:read} packet
39123 (@pxref{qXfer siginfo read}).
39125 @item qXfer:siginfo:write
39126 The remote stub understands the @samp{qXfer:siginfo:write} packet
39127 (@pxref{qXfer siginfo write}).
39129 @item qXfer:threads:read
39130 The remote stub understands the @samp{qXfer:threads:read} packet
39131 (@pxref{qXfer threads read}).
39133 @item qXfer:traceframe-info:read
39134 The remote stub understands the @samp{qXfer:traceframe-info:read}
39135 packet (@pxref{qXfer traceframe info read}).
39137 @item qXfer:uib:read
39138 The remote stub understands the @samp{qXfer:uib:read}
39139 packet (@pxref{qXfer unwind info block}).
39141 @item qXfer:fdpic:read
39142 The remote stub understands the @samp{qXfer:fdpic:read}
39143 packet (@pxref{qXfer fdpic loadmap read}).
39146 The remote stub understands the @samp{QNonStop} packet
39147 (@pxref{QNonStop}).
39149 @item QCatchSyscalls
39150 The remote stub understands the @samp{QCatchSyscalls} packet
39151 (@pxref{QCatchSyscalls}).
39154 The remote stub understands the @samp{QPassSignals} packet
39155 (@pxref{QPassSignals}).
39157 @item QStartNoAckMode
39158 The remote stub understands the @samp{QStartNoAckMode} packet and
39159 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39162 @anchor{multiprocess extensions}
39163 @cindex multiprocess extensions, in remote protocol
39164 The remote stub understands the multiprocess extensions to the remote
39165 protocol syntax. The multiprocess extensions affect the syntax of
39166 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39167 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39168 replies. Note that reporting this feature indicates support for the
39169 syntactic extensions only, not that the stub necessarily supports
39170 debugging of more than one process at a time. The stub must not use
39171 multiprocess extensions in packet replies unless @value{GDBN} has also
39172 indicated it supports them in its @samp{qSupported} request.
39174 @item qXfer:osdata:read
39175 The remote stub understands the @samp{qXfer:osdata:read} packet
39176 ((@pxref{qXfer osdata read}).
39178 @item ConditionalBreakpoints
39179 The target accepts and implements evaluation of conditional expressions
39180 defined for breakpoints. The target will only report breakpoint triggers
39181 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39183 @item ConditionalTracepoints
39184 The remote stub accepts and implements conditional expressions defined
39185 for tracepoints (@pxref{Tracepoint Conditions}).
39187 @item ReverseContinue
39188 The remote stub accepts and implements the reverse continue packet
39192 The remote stub accepts and implements the reverse step packet
39195 @item TracepointSource
39196 The remote stub understands the @samp{QTDPsrc} packet that supplies
39197 the source form of tracepoint definitions.
39200 The remote stub understands the @samp{QAgent} packet.
39203 The remote stub understands the @samp{QAllow} packet.
39205 @item QDisableRandomization
39206 The remote stub understands the @samp{QDisableRandomization} packet.
39208 @item StaticTracepoint
39209 @cindex static tracepoints, in remote protocol
39210 The remote stub supports static tracepoints.
39212 @item InstallInTrace
39213 @anchor{install tracepoint in tracing}
39214 The remote stub supports installing tracepoint in tracing.
39216 @item EnableDisableTracepoints
39217 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39218 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39219 to be enabled and disabled while a trace experiment is running.
39221 @item QTBuffer:size
39222 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39223 packet that allows to change the size of the trace buffer.
39226 @cindex string tracing, in remote protocol
39227 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39228 See @ref{Bytecode Descriptions} for details about the bytecode.
39230 @item BreakpointCommands
39231 @cindex breakpoint commands, in remote protocol
39232 The remote stub supports running a breakpoint's command list itself,
39233 rather than reporting the hit to @value{GDBN}.
39236 The remote stub understands the @samp{Qbtrace:off} packet.
39239 The remote stub understands the @samp{Qbtrace:bts} packet.
39242 The remote stub understands the @samp{Qbtrace:pt} packet.
39244 @item Qbtrace-conf:bts:size
39245 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39247 @item Qbtrace-conf:pt:size
39248 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39251 The remote stub reports the @samp{swbreak} stop reason for memory
39255 The remote stub reports the @samp{hwbreak} stop reason for hardware
39259 The remote stub reports the @samp{fork} stop reason for fork events.
39262 The remote stub reports the @samp{vfork} stop reason for vfork events
39263 and vforkdone events.
39266 The remote stub reports the @samp{exec} stop reason for exec events.
39268 @item vContSupported
39269 The remote stub reports the supported actions in the reply to
39270 @samp{vCont?} packet.
39272 @item QThreadEvents
39273 The remote stub understands the @samp{QThreadEvents} packet.
39276 The remote stub reports the @samp{N} stop reply.
39281 @cindex symbol lookup, remote request
39282 @cindex @samp{qSymbol} packet
39283 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39284 requests. Accept requests from the target for the values of symbols.
39289 The target does not need to look up any (more) symbols.
39290 @item qSymbol:@var{sym_name}
39291 The target requests the value of symbol @var{sym_name} (hex encoded).
39292 @value{GDBN} may provide the value by using the
39293 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39297 @item qSymbol:@var{sym_value}:@var{sym_name}
39298 Set the value of @var{sym_name} to @var{sym_value}.
39300 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39301 target has previously requested.
39303 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39304 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39310 The target does not need to look up any (more) symbols.
39311 @item qSymbol:@var{sym_name}
39312 The target requests the value of a new symbol @var{sym_name} (hex
39313 encoded). @value{GDBN} will continue to supply the values of symbols
39314 (if available), until the target ceases to request them.
39319 @itemx QTDisconnected
39326 @itemx qTMinFTPILen
39328 @xref{Tracepoint Packets}.
39330 @item qThreadExtraInfo,@var{thread-id}
39331 @cindex thread attributes info, remote request
39332 @cindex @samp{qThreadExtraInfo} packet
39333 Obtain from the target OS a printable string description of thread
39334 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39335 for the forms of @var{thread-id}. This
39336 string may contain anything that the target OS thinks is interesting
39337 for @value{GDBN} to tell the user about the thread. The string is
39338 displayed in @value{GDBN}'s @code{info threads} display. Some
39339 examples of possible thread extra info strings are @samp{Runnable}, or
39340 @samp{Blocked on Mutex}.
39344 @item @var{XX}@dots{}
39345 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39346 comprising the printable string containing the extra information about
39347 the thread's attributes.
39350 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39351 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39352 conventions above. Please don't use this packet as a model for new
39371 @xref{Tracepoint Packets}.
39373 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39374 @cindex read special object, remote request
39375 @cindex @samp{qXfer} packet
39376 @anchor{qXfer read}
39377 Read uninterpreted bytes from the target's special data area
39378 identified by the keyword @var{object}. Request @var{length} bytes
39379 starting at @var{offset} bytes into the data. The content and
39380 encoding of @var{annex} is specific to @var{object}; it can supply
39381 additional details about what data to access.
39386 Data @var{data} (@pxref{Binary Data}) has been read from the
39387 target. There may be more data at a higher address (although
39388 it is permitted to return @samp{m} even for the last valid
39389 block of data, as long as at least one byte of data was read).
39390 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39394 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39395 There is no more data to be read. It is possible for @var{data} to
39396 have fewer bytes than the @var{length} in the request.
39399 The @var{offset} in the request is at the end of the data.
39400 There is no more data to be read.
39403 The request was malformed, or @var{annex} was invalid.
39406 The offset was invalid, or there was an error encountered reading the data.
39407 The @var{nn} part is a hex-encoded @code{errno} value.
39410 An empty reply indicates the @var{object} string was not recognized by
39411 the stub, or that the object does not support reading.
39414 Here are the specific requests of this form defined so far. All the
39415 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39416 formats, listed above.
39419 @item qXfer:auxv:read::@var{offset},@var{length}
39420 @anchor{qXfer auxiliary vector read}
39421 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39422 auxiliary vector}. Note @var{annex} must be empty.
39424 This packet is not probed by default; the remote stub must request it,
39425 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39427 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39428 @anchor{qXfer btrace read}
39430 Return a description of the current branch trace.
39431 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39432 packet may have one of the following values:
39436 Returns all available branch trace.
39439 Returns all available branch trace if the branch trace changed since
39440 the last read request.
39443 Returns the new branch trace since the last read request. Adds a new
39444 block to the end of the trace that begins at zero and ends at the source
39445 location of the first branch in the trace buffer. This extra block is
39446 used to stitch traces together.
39448 If the trace buffer overflowed, returns an error indicating the overflow.
39451 This packet is not probed by default; the remote stub must request it
39452 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39454 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39455 @anchor{qXfer btrace-conf read}
39457 Return a description of the current branch trace configuration.
39458 @xref{Branch Trace Configuration Format}.
39460 This packet is not probed by default; the remote stub must request it
39461 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39463 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39464 @anchor{qXfer executable filename read}
39465 Return the full absolute name of the file that was executed to create
39466 a process running on the remote system. The annex specifies the
39467 numeric process ID of the process to query, encoded as a hexadecimal
39468 number. If the annex part is empty the remote stub should return the
39469 filename corresponding to the currently executing process.
39471 This packet is not probed by default; the remote stub must request it,
39472 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39474 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39475 @anchor{qXfer target description read}
39476 Access the @dfn{target description}. @xref{Target Descriptions}. The
39477 annex specifies which XML document to access. The main description is
39478 always loaded from the @samp{target.xml} annex.
39480 This packet is not probed by default; the remote stub must request it,
39481 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39483 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39484 @anchor{qXfer library list read}
39485 Access the target's list of loaded libraries. @xref{Library List Format}.
39486 The annex part of the generic @samp{qXfer} packet must be empty
39487 (@pxref{qXfer read}).
39489 Targets which maintain a list of libraries in the program's memory do
39490 not need to implement this packet; it is designed for platforms where
39491 the operating system manages the list of loaded libraries.
39493 This packet is not probed by default; the remote stub must request it,
39494 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39496 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39497 @anchor{qXfer svr4 library list read}
39498 Access the target's list of loaded libraries when the target is an SVR4
39499 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39500 of the generic @samp{qXfer} packet must be empty unless the remote
39501 stub indicated it supports the augmented form of this packet
39502 by supplying an appropriate @samp{qSupported} response
39503 (@pxref{qXfer read}, @ref{qSupported}).
39505 This packet is optional for better performance on SVR4 targets.
39506 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39508 This packet is not probed by default; the remote stub must request it,
39509 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39511 If the remote stub indicates it supports the augmented form of this
39512 packet then the annex part of the generic @samp{qXfer} packet may
39513 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39514 arguments. The currently supported arguments are:
39517 @item start=@var{address}
39518 A hexadecimal number specifying the address of the @samp{struct
39519 link_map} to start reading the library list from. If unset or zero
39520 then the first @samp{struct link_map} in the library list will be
39521 chosen as the starting point.
39523 @item prev=@var{address}
39524 A hexadecimal number specifying the address of the @samp{struct
39525 link_map} immediately preceding the @samp{struct link_map}
39526 specified by the @samp{start} argument. If unset or zero then
39527 the remote stub will expect that no @samp{struct link_map}
39528 exists prior to the starting point.
39532 Arguments that are not understood by the remote stub will be silently
39535 @item qXfer:memory-map:read::@var{offset},@var{length}
39536 @anchor{qXfer memory map read}
39537 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39538 annex part of the generic @samp{qXfer} packet must be empty
39539 (@pxref{qXfer read}).
39541 This packet is not probed by default; the remote stub must request it,
39542 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39544 @item qXfer:sdata:read::@var{offset},@var{length}
39545 @anchor{qXfer sdata read}
39547 Read contents of the extra collected static tracepoint marker
39548 information. The annex part of the generic @samp{qXfer} packet must
39549 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39552 This packet is not probed by default; the remote stub must request it,
39553 by supplying an appropriate @samp{qSupported} response
39554 (@pxref{qSupported}).
39556 @item qXfer:siginfo:read::@var{offset},@var{length}
39557 @anchor{qXfer siginfo read}
39558 Read contents of the extra signal information on the target
39559 system. The annex part of the generic @samp{qXfer} packet must be
39560 empty (@pxref{qXfer read}).
39562 This packet is not probed by default; the remote stub must request it,
39563 by supplying an appropriate @samp{qSupported} response
39564 (@pxref{qSupported}).
39566 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39567 @anchor{qXfer spu read}
39568 Read contents of an @code{spufs} file on the target system. The
39569 annex specifies which file to read; it must be of the form
39570 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39571 in the target process, and @var{name} identifes the @code{spufs} file
39572 in that context to be accessed.
39574 This packet is not probed by default; the remote stub must request it,
39575 by supplying an appropriate @samp{qSupported} response
39576 (@pxref{qSupported}).
39578 @item qXfer:threads:read::@var{offset},@var{length}
39579 @anchor{qXfer threads read}
39580 Access the list of threads on target. @xref{Thread List Format}. The
39581 annex part of the generic @samp{qXfer} packet must be empty
39582 (@pxref{qXfer read}).
39584 This packet is not probed by default; the remote stub must request it,
39585 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39587 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39588 @anchor{qXfer traceframe info read}
39590 Return a description of the current traceframe's contents.
39591 @xref{Traceframe Info Format}. The annex part of the generic
39592 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39594 This packet is not probed by default; the remote stub must request it,
39595 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39597 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39598 @anchor{qXfer unwind info block}
39600 Return the unwind information block for @var{pc}. This packet is used
39601 on OpenVMS/ia64 to ask the kernel unwind information.
39603 This packet is not probed by default.
39605 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39606 @anchor{qXfer fdpic loadmap read}
39607 Read contents of @code{loadmap}s on the target system. The
39608 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39609 executable @code{loadmap} or interpreter @code{loadmap} to read.
39611 This packet is not probed by default; the remote stub must request it,
39612 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39614 @item qXfer:osdata:read::@var{offset},@var{length}
39615 @anchor{qXfer osdata read}
39616 Access the target's @dfn{operating system information}.
39617 @xref{Operating System Information}.
39621 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39622 @cindex write data into object, remote request
39623 @anchor{qXfer write}
39624 Write uninterpreted bytes into the target's special data area
39625 identified by the keyword @var{object}, starting at @var{offset} bytes
39626 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39627 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39628 is specific to @var{object}; it can supply additional details about what data
39634 @var{nn} (hex encoded) is the number of bytes written.
39635 This may be fewer bytes than supplied in the request.
39638 The request was malformed, or @var{annex} was invalid.
39641 The offset was invalid, or there was an error encountered writing the data.
39642 The @var{nn} part is a hex-encoded @code{errno} value.
39645 An empty reply indicates the @var{object} string was not
39646 recognized by the stub, or that the object does not support writing.
39649 Here are the specific requests of this form defined so far. All the
39650 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39651 formats, listed above.
39654 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39655 @anchor{qXfer siginfo write}
39656 Write @var{data} to the extra signal information on the target system.
39657 The annex part of the generic @samp{qXfer} packet must be
39658 empty (@pxref{qXfer write}).
39660 This packet is not probed by default; the remote stub must request it,
39661 by supplying an appropriate @samp{qSupported} response
39662 (@pxref{qSupported}).
39664 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39665 @anchor{qXfer spu write}
39666 Write @var{data} to an @code{spufs} file on the target system. The
39667 annex specifies which file to write; it must be of the form
39668 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39669 in the target process, and @var{name} identifes the @code{spufs} file
39670 in that context to be accessed.
39672 This packet is not probed by default; the remote stub must request it,
39673 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39676 @item qXfer:@var{object}:@var{operation}:@dots{}
39677 Requests of this form may be added in the future. When a stub does
39678 not recognize the @var{object} keyword, or its support for
39679 @var{object} does not recognize the @var{operation} keyword, the stub
39680 must respond with an empty packet.
39682 @item qAttached:@var{pid}
39683 @cindex query attached, remote request
39684 @cindex @samp{qAttached} packet
39685 Return an indication of whether the remote server attached to an
39686 existing process or created a new process. When the multiprocess
39687 protocol extensions are supported (@pxref{multiprocess extensions}),
39688 @var{pid} is an integer in hexadecimal format identifying the target
39689 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39690 the query packet will be simplified as @samp{qAttached}.
39692 This query is used, for example, to know whether the remote process
39693 should be detached or killed when a @value{GDBN} session is ended with
39694 the @code{quit} command.
39699 The remote server attached to an existing process.
39701 The remote server created a new process.
39703 A badly formed request or an error was encountered.
39707 Enable branch tracing for the current thread using Branch Trace Store.
39712 Branch tracing has been enabled.
39714 A badly formed request or an error was encountered.
39718 Enable branch tracing for the current thread using Intel Processor Trace.
39723 Branch tracing has been enabled.
39725 A badly formed request or an error was encountered.
39729 Disable branch tracing for the current thread.
39734 Branch tracing has been disabled.
39736 A badly formed request or an error was encountered.
39739 @item Qbtrace-conf:bts:size=@var{value}
39740 Set the requested ring buffer size for new threads that use the
39741 btrace recording method in bts format.
39746 The ring buffer size has been set.
39748 A badly formed request or an error was encountered.
39751 @item Qbtrace-conf:pt:size=@var{value}
39752 Set the requested ring buffer size for new threads that use the
39753 btrace recording method in pt format.
39758 The ring buffer size has been set.
39760 A badly formed request or an error was encountered.
39765 @node Architecture-Specific Protocol Details
39766 @section Architecture-Specific Protocol Details
39768 This section describes how the remote protocol is applied to specific
39769 target architectures. Also see @ref{Standard Target Features}, for
39770 details of XML target descriptions for each architecture.
39773 * ARM-Specific Protocol Details::
39774 * MIPS-Specific Protocol Details::
39777 @node ARM-Specific Protocol Details
39778 @subsection @acronym{ARM}-specific Protocol Details
39781 * ARM Breakpoint Kinds::
39784 @node ARM Breakpoint Kinds
39785 @subsubsection @acronym{ARM} Breakpoint Kinds
39786 @cindex breakpoint kinds, @acronym{ARM}
39788 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39793 16-bit Thumb mode breakpoint.
39796 32-bit Thumb mode (Thumb-2) breakpoint.
39799 32-bit @acronym{ARM} mode breakpoint.
39803 @node MIPS-Specific Protocol Details
39804 @subsection @acronym{MIPS}-specific Protocol Details
39807 * MIPS Register packet Format::
39808 * MIPS Breakpoint Kinds::
39811 @node MIPS Register packet Format
39812 @subsubsection @acronym{MIPS} Register Packet Format
39813 @cindex register packet format, @acronym{MIPS}
39815 The following @code{g}/@code{G} packets have previously been defined.
39816 In the below, some thirty-two bit registers are transferred as
39817 sixty-four bits. Those registers should be zero/sign extended (which?)
39818 to fill the space allocated. Register bytes are transferred in target
39819 byte order. The two nibbles within a register byte are transferred
39820 most-significant -- least-significant.
39825 All registers are transferred as thirty-two bit quantities in the order:
39826 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39827 registers; fsr; fir; fp.
39830 All registers are transferred as sixty-four bit quantities (including
39831 thirty-two bit registers such as @code{sr}). The ordering is the same
39836 @node MIPS Breakpoint Kinds
39837 @subsubsection @acronym{MIPS} Breakpoint Kinds
39838 @cindex breakpoint kinds, @acronym{MIPS}
39840 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39845 16-bit @acronym{MIPS16} mode breakpoint.
39848 16-bit @acronym{microMIPS} mode breakpoint.
39851 32-bit standard @acronym{MIPS} mode breakpoint.
39854 32-bit @acronym{microMIPS} mode breakpoint.
39858 @node Tracepoint Packets
39859 @section Tracepoint Packets
39860 @cindex tracepoint packets
39861 @cindex packets, tracepoint
39863 Here we describe the packets @value{GDBN} uses to implement
39864 tracepoints (@pxref{Tracepoints}).
39868 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39869 @cindex @samp{QTDP} packet
39870 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39871 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39872 the tracepoint is disabled. The @var{step} gives the tracepoint's step
39873 count, and @var{pass} gives its pass count. If an @samp{F} is present,
39874 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39875 the number of bytes that the target should copy elsewhere to make room
39876 for the tracepoint. If an @samp{X} is present, it introduces a
39877 tracepoint condition, which consists of a hexadecimal length, followed
39878 by a comma and hex-encoded bytes, in a manner similar to action
39879 encodings as described below. If the trailing @samp{-} is present,
39880 further @samp{QTDP} packets will follow to specify this tracepoint's
39886 The packet was understood and carried out.
39888 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39890 The packet was not recognized.
39893 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39894 Define actions to be taken when a tracepoint is hit. The @var{n} and
39895 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39896 this tracepoint. This packet may only be sent immediately after
39897 another @samp{QTDP} packet that ended with a @samp{-}. If the
39898 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39899 specifying more actions for this tracepoint.
39901 In the series of action packets for a given tracepoint, at most one
39902 can have an @samp{S} before its first @var{action}. If such a packet
39903 is sent, it and the following packets define ``while-stepping''
39904 actions. Any prior packets define ordinary actions --- that is, those
39905 taken when the tracepoint is first hit. If no action packet has an
39906 @samp{S}, then all the packets in the series specify ordinary
39907 tracepoint actions.
39909 The @samp{@var{action}@dots{}} portion of the packet is a series of
39910 actions, concatenated without separators. Each action has one of the
39916 Collect the registers whose bits are set in @var{mask},
39917 a hexadecimal number whose @var{i}'th bit is set if register number
39918 @var{i} should be collected. (The least significant bit is numbered
39919 zero.) Note that @var{mask} may be any number of digits long; it may
39920 not fit in a 32-bit word.
39922 @item M @var{basereg},@var{offset},@var{len}
39923 Collect @var{len} bytes of memory starting at the address in register
39924 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39925 @samp{-1}, then the range has a fixed address: @var{offset} is the
39926 address of the lowest byte to collect. The @var{basereg},
39927 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39928 values (the @samp{-1} value for @var{basereg} is a special case).
39930 @item X @var{len},@var{expr}
39931 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39932 it directs. The agent expression @var{expr} is as described in
39933 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39934 two-digit hex number in the packet; @var{len} is the number of bytes
39935 in the expression (and thus one-half the number of hex digits in the
39940 Any number of actions may be packed together in a single @samp{QTDP}
39941 packet, as long as the packet does not exceed the maximum packet
39942 length (400 bytes, for many stubs). There may be only one @samp{R}
39943 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39944 actions. Any registers referred to by @samp{M} and @samp{X} actions
39945 must be collected by a preceding @samp{R} action. (The
39946 ``while-stepping'' actions are treated as if they were attached to a
39947 separate tracepoint, as far as these restrictions are concerned.)
39952 The packet was understood and carried out.
39954 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39956 The packet was not recognized.
39959 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39960 @cindex @samp{QTDPsrc} packet
39961 Specify a source string of tracepoint @var{n} at address @var{addr}.
39962 This is useful to get accurate reproduction of the tracepoints
39963 originally downloaded at the beginning of the trace run. The @var{type}
39964 is the name of the tracepoint part, such as @samp{cond} for the
39965 tracepoint's conditional expression (see below for a list of types), while
39966 @var{bytes} is the string, encoded in hexadecimal.
39968 @var{start} is the offset of the @var{bytes} within the overall source
39969 string, while @var{slen} is the total length of the source string.
39970 This is intended for handling source strings that are longer than will
39971 fit in a single packet.
39972 @c Add detailed example when this info is moved into a dedicated
39973 @c tracepoint descriptions section.
39975 The available string types are @samp{at} for the location,
39976 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39977 @value{GDBN} sends a separate packet for each command in the action
39978 list, in the same order in which the commands are stored in the list.
39980 The target does not need to do anything with source strings except
39981 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39984 Although this packet is optional, and @value{GDBN} will only send it
39985 if the target replies with @samp{TracepointSource} @xref{General
39986 Query Packets}, it makes both disconnected tracing and trace files
39987 much easier to use. Otherwise the user must be careful that the
39988 tracepoints in effect while looking at trace frames are identical to
39989 the ones in effect during the trace run; even a small discrepancy
39990 could cause @samp{tdump} not to work, or a particular trace frame not
39993 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
39994 @cindex define trace state variable, remote request
39995 @cindex @samp{QTDV} packet
39996 Create a new trace state variable, number @var{n}, with an initial
39997 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39998 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39999 the option of not using this packet for initial values of zero; the
40000 target should simply create the trace state variables as they are
40001 mentioned in expressions. The value @var{builtin} should be 1 (one)
40002 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40003 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40004 @samp{qTsV} packet had it set. The contents of @var{name} is the
40005 hex-encoded name (without the leading @samp{$}) of the trace state
40008 @item QTFrame:@var{n}
40009 @cindex @samp{QTFrame} packet
40010 Select the @var{n}'th tracepoint frame from the buffer, and use the
40011 register and memory contents recorded there to answer subsequent
40012 request packets from @value{GDBN}.
40014 A successful reply from the stub indicates that the stub has found the
40015 requested frame. The response is a series of parts, concatenated
40016 without separators, describing the frame we selected. Each part has
40017 one of the following forms:
40021 The selected frame is number @var{n} in the trace frame buffer;
40022 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40023 was no frame matching the criteria in the request packet.
40026 The selected trace frame records a hit of tracepoint number @var{t};
40027 @var{t} is a hexadecimal number.
40031 @item QTFrame:pc:@var{addr}
40032 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40033 currently selected frame whose PC is @var{addr};
40034 @var{addr} is a hexadecimal number.
40036 @item QTFrame:tdp:@var{t}
40037 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40038 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40039 is a hexadecimal number.
40041 @item QTFrame:range:@var{start}:@var{end}
40042 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40043 currently selected frame whose PC is between @var{start} (inclusive)
40044 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40047 @item QTFrame:outside:@var{start}:@var{end}
40048 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40049 frame @emph{outside} the given range of addresses (exclusive).
40052 @cindex @samp{qTMinFTPILen} packet
40053 This packet requests the minimum length of instruction at which a fast
40054 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40055 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40056 it depends on the target system being able to create trampolines in
40057 the first 64K of memory, which might or might not be possible for that
40058 system. So the reply to this packet will be 4 if it is able to
40065 The minimum instruction length is currently unknown.
40067 The minimum instruction length is @var{length}, where @var{length}
40068 is a hexadecimal number greater or equal to 1. A reply
40069 of 1 means that a fast tracepoint may be placed on any instruction
40070 regardless of size.
40072 An error has occurred.
40074 An empty reply indicates that the request is not supported by the stub.
40078 @cindex @samp{QTStart} packet
40079 Begin the tracepoint experiment. Begin collecting data from
40080 tracepoint hits in the trace frame buffer. This packet supports the
40081 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40082 instruction reply packet}).
40085 @cindex @samp{QTStop} packet
40086 End the tracepoint experiment. Stop collecting trace frames.
40088 @item QTEnable:@var{n}:@var{addr}
40090 @cindex @samp{QTEnable} packet
40091 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40092 experiment. If the tracepoint was previously disabled, then collection
40093 of data from it will resume.
40095 @item QTDisable:@var{n}:@var{addr}
40097 @cindex @samp{QTDisable} packet
40098 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40099 experiment. No more data will be collected from the tracepoint unless
40100 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40103 @cindex @samp{QTinit} packet
40104 Clear the table of tracepoints, and empty the trace frame buffer.
40106 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40107 @cindex @samp{QTro} packet
40108 Establish the given ranges of memory as ``transparent''. The stub
40109 will answer requests for these ranges from memory's current contents,
40110 if they were not collected as part of the tracepoint hit.
40112 @value{GDBN} uses this to mark read-only regions of memory, like those
40113 containing program code. Since these areas never change, they should
40114 still have the same contents they did when the tracepoint was hit, so
40115 there's no reason for the stub to refuse to provide their contents.
40117 @item QTDisconnected:@var{value}
40118 @cindex @samp{QTDisconnected} packet
40119 Set the choice to what to do with the tracing run when @value{GDBN}
40120 disconnects from the target. A @var{value} of 1 directs the target to
40121 continue the tracing run, while 0 tells the target to stop tracing if
40122 @value{GDBN} is no longer in the picture.
40125 @cindex @samp{qTStatus} packet
40126 Ask the stub if there is a trace experiment running right now.
40128 The reply has the form:
40132 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40133 @var{running} is a single digit @code{1} if the trace is presently
40134 running, or @code{0} if not. It is followed by semicolon-separated
40135 optional fields that an agent may use to report additional status.
40139 If the trace is not running, the agent may report any of several
40140 explanations as one of the optional fields:
40145 No trace has been run yet.
40147 @item tstop[:@var{text}]:0
40148 The trace was stopped by a user-originated stop command. The optional
40149 @var{text} field is a user-supplied string supplied as part of the
40150 stop command (for instance, an explanation of why the trace was
40151 stopped manually). It is hex-encoded.
40154 The trace stopped because the trace buffer filled up.
40156 @item tdisconnected:0
40157 The trace stopped because @value{GDBN} disconnected from the target.
40159 @item tpasscount:@var{tpnum}
40160 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40162 @item terror:@var{text}:@var{tpnum}
40163 The trace stopped because tracepoint @var{tpnum} had an error. The
40164 string @var{text} is available to describe the nature of the error
40165 (for instance, a divide by zero in the condition expression); it
40169 The trace stopped for some other reason.
40173 Additional optional fields supply statistical and other information.
40174 Although not required, they are extremely useful for users monitoring
40175 the progress of a trace run. If a trace has stopped, and these
40176 numbers are reported, they must reflect the state of the just-stopped
40181 @item tframes:@var{n}
40182 The number of trace frames in the buffer.
40184 @item tcreated:@var{n}
40185 The total number of trace frames created during the run. This may
40186 be larger than the trace frame count, if the buffer is circular.
40188 @item tsize:@var{n}
40189 The total size of the trace buffer, in bytes.
40191 @item tfree:@var{n}
40192 The number of bytes still unused in the buffer.
40194 @item circular:@var{n}
40195 The value of the circular trace buffer flag. @code{1} means that the
40196 trace buffer is circular and old trace frames will be discarded if
40197 necessary to make room, @code{0} means that the trace buffer is linear
40200 @item disconn:@var{n}
40201 The value of the disconnected tracing flag. @code{1} means that
40202 tracing will continue after @value{GDBN} disconnects, @code{0} means
40203 that the trace run will stop.
40207 @item qTP:@var{tp}:@var{addr}
40208 @cindex tracepoint status, remote request
40209 @cindex @samp{qTP} packet
40210 Ask the stub for the current state of tracepoint number @var{tp} at
40211 address @var{addr}.
40215 @item V@var{hits}:@var{usage}
40216 The tracepoint has been hit @var{hits} times so far during the trace
40217 run, and accounts for @var{usage} in the trace buffer. Note that
40218 @code{while-stepping} steps are not counted as separate hits, but the
40219 steps' space consumption is added into the usage number.
40223 @item qTV:@var{var}
40224 @cindex trace state variable value, remote request
40225 @cindex @samp{qTV} packet
40226 Ask the stub for the value of the trace state variable number @var{var}.
40231 The value of the variable is @var{value}. This will be the current
40232 value of the variable if the user is examining a running target, or a
40233 saved value if the variable was collected in the trace frame that the
40234 user is looking at. Note that multiple requests may result in
40235 different reply values, such as when requesting values while the
40236 program is running.
40239 The value of the variable is unknown. This would occur, for example,
40240 if the user is examining a trace frame in which the requested variable
40245 @cindex @samp{qTfP} packet
40247 @cindex @samp{qTsP} packet
40248 These packets request data about tracepoints that are being used by
40249 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40250 of data, and multiple @code{qTsP} to get additional pieces. Replies
40251 to these packets generally take the form of the @code{QTDP} packets
40252 that define tracepoints. (FIXME add detailed syntax)
40255 @cindex @samp{qTfV} packet
40257 @cindex @samp{qTsV} packet
40258 These packets request data about trace state variables that are on the
40259 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40260 and multiple @code{qTsV} to get additional variables. Replies to
40261 these packets follow the syntax of the @code{QTDV} packets that define
40262 trace state variables.
40268 @cindex @samp{qTfSTM} packet
40269 @cindex @samp{qTsSTM} packet
40270 These packets request data about static tracepoint markers that exist
40271 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40272 first piece of data, and multiple @code{qTsSTM} to get additional
40273 pieces. Replies to these packets take the following form:
40277 @item m @var{address}:@var{id}:@var{extra}
40279 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40280 a comma-separated list of markers
40282 (lower case letter @samp{L}) denotes end of list.
40284 An error occurred. The error number @var{nn} is given as hex digits.
40286 An empty reply indicates that the request is not supported by the
40290 The @var{address} is encoded in hex;
40291 @var{id} and @var{extra} are strings encoded in hex.
40293 In response to each query, the target will reply with a list of one or
40294 more markers, separated by commas. @value{GDBN} will respond to each
40295 reply with a request for more markers (using the @samp{qs} form of the
40296 query), until the target responds with @samp{l} (lower-case ell, for
40299 @item qTSTMat:@var{address}
40301 @cindex @samp{qTSTMat} packet
40302 This packets requests data about static tracepoint markers in the
40303 target program at @var{address}. Replies to this packet follow the
40304 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40305 tracepoint markers.
40307 @item QTSave:@var{filename}
40308 @cindex @samp{QTSave} packet
40309 This packet directs the target to save trace data to the file name
40310 @var{filename} in the target's filesystem. The @var{filename} is encoded
40311 as a hex string; the interpretation of the file name (relative vs
40312 absolute, wild cards, etc) is up to the target.
40314 @item qTBuffer:@var{offset},@var{len}
40315 @cindex @samp{qTBuffer} packet
40316 Return up to @var{len} bytes of the current contents of trace buffer,
40317 starting at @var{offset}. The trace buffer is treated as if it were
40318 a contiguous collection of traceframes, as per the trace file format.
40319 The reply consists as many hex-encoded bytes as the target can deliver
40320 in a packet; it is not an error to return fewer than were asked for.
40321 A reply consisting of just @code{l} indicates that no bytes are
40324 @item QTBuffer:circular:@var{value}
40325 This packet directs the target to use a circular trace buffer if
40326 @var{value} is 1, or a linear buffer if the value is 0.
40328 @item QTBuffer:size:@var{size}
40329 @anchor{QTBuffer-size}
40330 @cindex @samp{QTBuffer size} packet
40331 This packet directs the target to make the trace buffer be of size
40332 @var{size} if possible. A value of @code{-1} tells the target to
40333 use whatever size it prefers.
40335 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40336 @cindex @samp{QTNotes} packet
40337 This packet adds optional textual notes to the trace run. Allowable
40338 types include @code{user}, @code{notes}, and @code{tstop}, the
40339 @var{text} fields are arbitrary strings, hex-encoded.
40343 @subsection Relocate instruction reply packet
40344 When installing fast tracepoints in memory, the target may need to
40345 relocate the instruction currently at the tracepoint address to a
40346 different address in memory. For most instructions, a simple copy is
40347 enough, but, for example, call instructions that implicitly push the
40348 return address on the stack, and relative branches or other
40349 PC-relative instructions require offset adjustment, so that the effect
40350 of executing the instruction at a different address is the same as if
40351 it had executed in the original location.
40353 In response to several of the tracepoint packets, the target may also
40354 respond with a number of intermediate @samp{qRelocInsn} request
40355 packets before the final result packet, to have @value{GDBN} handle
40356 this relocation operation. If a packet supports this mechanism, its
40357 documentation will explicitly say so. See for example the above
40358 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40359 format of the request is:
40362 @item qRelocInsn:@var{from};@var{to}
40364 This requests @value{GDBN} to copy instruction at address @var{from}
40365 to address @var{to}, possibly adjusted so that executing the
40366 instruction at @var{to} has the same effect as executing it at
40367 @var{from}. @value{GDBN} writes the adjusted instruction to target
40368 memory starting at @var{to}.
40373 @item qRelocInsn:@var{adjusted_size}
40374 Informs the stub the relocation is complete. The @var{adjusted_size} is
40375 the length in bytes of resulting relocated instruction sequence.
40377 A badly formed request was detected, or an error was encountered while
40378 relocating the instruction.
40381 @node Host I/O Packets
40382 @section Host I/O Packets
40383 @cindex Host I/O, remote protocol
40384 @cindex file transfer, remote protocol
40386 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40387 operations on the far side of a remote link. For example, Host I/O is
40388 used to upload and download files to a remote target with its own
40389 filesystem. Host I/O uses the same constant values and data structure
40390 layout as the target-initiated File-I/O protocol. However, the
40391 Host I/O packets are structured differently. The target-initiated
40392 protocol relies on target memory to store parameters and buffers.
40393 Host I/O requests are initiated by @value{GDBN}, and the
40394 target's memory is not involved. @xref{File-I/O Remote Protocol
40395 Extension}, for more details on the target-initiated protocol.
40397 The Host I/O request packets all encode a single operation along with
40398 its arguments. They have this format:
40402 @item vFile:@var{operation}: @var{parameter}@dots{}
40403 @var{operation} is the name of the particular request; the target
40404 should compare the entire packet name up to the second colon when checking
40405 for a supported operation. The format of @var{parameter} depends on
40406 the operation. Numbers are always passed in hexadecimal. Negative
40407 numbers have an explicit minus sign (i.e.@: two's complement is not
40408 used). Strings (e.g.@: filenames) are encoded as a series of
40409 hexadecimal bytes. The last argument to a system call may be a
40410 buffer of escaped binary data (@pxref{Binary Data}).
40414 The valid responses to Host I/O packets are:
40418 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40419 @var{result} is the integer value returned by this operation, usually
40420 non-negative for success and -1 for errors. If an error has occured,
40421 @var{errno} will be included in the result specifying a
40422 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40423 operations which return data, @var{attachment} supplies the data as a
40424 binary buffer. Binary buffers in response packets are escaped in the
40425 normal way (@pxref{Binary Data}). See the individual packet
40426 documentation for the interpretation of @var{result} and
40430 An empty response indicates that this operation is not recognized.
40434 These are the supported Host I/O operations:
40437 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40438 Open a file at @var{filename} and return a file descriptor for it, or
40439 return -1 if an error occurs. The @var{filename} is a string,
40440 @var{flags} is an integer indicating a mask of open flags
40441 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40442 of mode bits to use if the file is created (@pxref{mode_t Values}).
40443 @xref{open}, for details of the open flags and mode values.
40445 @item vFile:close: @var{fd}
40446 Close the open file corresponding to @var{fd} and return 0, or
40447 -1 if an error occurs.
40449 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40450 Read data from the open file corresponding to @var{fd}. Up to
40451 @var{count} bytes will be read from the file, starting at @var{offset}
40452 relative to the start of the file. The target may read fewer bytes;
40453 common reasons include packet size limits and an end-of-file
40454 condition. The number of bytes read is returned. Zero should only be
40455 returned for a successful read at the end of the file, or if
40456 @var{count} was zero.
40458 The data read should be returned as a binary attachment on success.
40459 If zero bytes were read, the response should include an empty binary
40460 attachment (i.e.@: a trailing semicolon). The return value is the
40461 number of target bytes read; the binary attachment may be longer if
40462 some characters were escaped.
40464 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40465 Write @var{data} (a binary buffer) to the open file corresponding
40466 to @var{fd}. Start the write at @var{offset} from the start of the
40467 file. Unlike many @code{write} system calls, there is no
40468 separate @var{count} argument; the length of @var{data} in the
40469 packet is used. @samp{vFile:write} returns the number of bytes written,
40470 which may be shorter than the length of @var{data}, or -1 if an
40473 @item vFile:fstat: @var{fd}
40474 Get information about the open file corresponding to @var{fd}.
40475 On success the information is returned as a binary attachment
40476 and the return value is the size of this attachment in bytes.
40477 If an error occurs the return value is -1. The format of the
40478 returned binary attachment is as described in @ref{struct stat}.
40480 @item vFile:unlink: @var{filename}
40481 Delete the file at @var{filename} on the target. Return 0,
40482 or -1 if an error occurs. The @var{filename} is a string.
40484 @item vFile:readlink: @var{filename}
40485 Read value of symbolic link @var{filename} on the target. Return
40486 the number of bytes read, or -1 if an error occurs.
40488 The data read should be returned as a binary attachment on success.
40489 If zero bytes were read, the response should include an empty binary
40490 attachment (i.e.@: a trailing semicolon). The return value is the
40491 number of target bytes read; the binary attachment may be longer if
40492 some characters were escaped.
40494 @item vFile:setfs: @var{pid}
40495 Select the filesystem on which @code{vFile} operations with
40496 @var{filename} arguments will operate. This is required for
40497 @value{GDBN} to be able to access files on remote targets where
40498 the remote stub does not share a common filesystem with the
40501 If @var{pid} is nonzero, select the filesystem as seen by process
40502 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40503 the remote stub. Return 0 on success, or -1 if an error occurs.
40504 If @code{vFile:setfs:} indicates success, the selected filesystem
40505 remains selected until the next successful @code{vFile:setfs:}
40511 @section Interrupts
40512 @cindex interrupts (remote protocol)
40513 @anchor{interrupting remote targets}
40515 In all-stop mode, when a program on the remote target is running,
40516 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40517 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40518 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40520 The precise meaning of @code{BREAK} is defined by the transport
40521 mechanism and may, in fact, be undefined. @value{GDBN} does not
40522 currently define a @code{BREAK} mechanism for any of the network
40523 interfaces except for TCP, in which case @value{GDBN} sends the
40524 @code{telnet} BREAK sequence.
40526 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40527 transport mechanisms. It is represented by sending the single byte
40528 @code{0x03} without any of the usual packet overhead described in
40529 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40530 transmitted as part of a packet, it is considered to be packet data
40531 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40532 (@pxref{X packet}), used for binary downloads, may include an unescaped
40533 @code{0x03} as part of its packet.
40535 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40536 When Linux kernel receives this sequence from serial port,
40537 it stops execution and connects to gdb.
40539 In non-stop mode, because packet resumptions are asynchronous
40540 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40541 command to the remote stub, even when the target is running. For that
40542 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40543 packet}) with the usual packet framing instead of the single byte
40546 Stubs are not required to recognize these interrupt mechanisms and the
40547 precise meaning associated with receipt of the interrupt is
40548 implementation defined. If the target supports debugging of multiple
40549 threads and/or processes, it should attempt to interrupt all
40550 currently-executing threads and processes.
40551 If the stub is successful at interrupting the
40552 running program, it should send one of the stop
40553 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40554 of successfully stopping the program in all-stop mode, and a stop reply
40555 for each stopped thread in non-stop mode.
40556 Interrupts received while the
40557 program is stopped are queued and the program will be interrupted when
40558 it is resumed next time.
40560 @node Notification Packets
40561 @section Notification Packets
40562 @cindex notification packets
40563 @cindex packets, notification
40565 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40566 packets that require no acknowledgment. Both the GDB and the stub
40567 may send notifications (although the only notifications defined at
40568 present are sent by the stub). Notifications carry information
40569 without incurring the round-trip latency of an acknowledgment, and so
40570 are useful for low-impact communications where occasional packet loss
40573 A notification packet has the form @samp{% @var{data} #
40574 @var{checksum}}, where @var{data} is the content of the notification,
40575 and @var{checksum} is a checksum of @var{data}, computed and formatted
40576 as for ordinary @value{GDBN} packets. A notification's @var{data}
40577 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40578 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40579 to acknowledge the notification's receipt or to report its corruption.
40581 Every notification's @var{data} begins with a name, which contains no
40582 colon characters, followed by a colon character.
40584 Recipients should silently ignore corrupted notifications and
40585 notifications they do not understand. Recipients should restart
40586 timeout periods on receipt of a well-formed notification, whether or
40587 not they understand it.
40589 Senders should only send the notifications described here when this
40590 protocol description specifies that they are permitted. In the
40591 future, we may extend the protocol to permit existing notifications in
40592 new contexts; this rule helps older senders avoid confusing newer
40595 (Older versions of @value{GDBN} ignore bytes received until they see
40596 the @samp{$} byte that begins an ordinary packet, so new stubs may
40597 transmit notifications without fear of confusing older clients. There
40598 are no notifications defined for @value{GDBN} to send at the moment, but we
40599 assume that most older stubs would ignore them, as well.)
40601 Each notification is comprised of three parts:
40603 @item @var{name}:@var{event}
40604 The notification packet is sent by the side that initiates the
40605 exchange (currently, only the stub does that), with @var{event}
40606 carrying the specific information about the notification, and
40607 @var{name} specifying the name of the notification.
40609 The acknowledge sent by the other side, usually @value{GDBN}, to
40610 acknowledge the exchange and request the event.
40613 The purpose of an asynchronous notification mechanism is to report to
40614 @value{GDBN} that something interesting happened in the remote stub.
40616 The remote stub may send notification @var{name}:@var{event}
40617 at any time, but @value{GDBN} acknowledges the notification when
40618 appropriate. The notification event is pending before @value{GDBN}
40619 acknowledges. Only one notification at a time may be pending; if
40620 additional events occur before @value{GDBN} has acknowledged the
40621 previous notification, they must be queued by the stub for later
40622 synchronous transmission in response to @var{ack} packets from
40623 @value{GDBN}. Because the notification mechanism is unreliable,
40624 the stub is permitted to resend a notification if it believes
40625 @value{GDBN} may not have received it.
40627 Specifically, notifications may appear when @value{GDBN} is not
40628 otherwise reading input from the stub, or when @value{GDBN} is
40629 expecting to read a normal synchronous response or a
40630 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40631 Notification packets are distinct from any other communication from
40632 the stub so there is no ambiguity.
40634 After receiving a notification, @value{GDBN} shall acknowledge it by
40635 sending a @var{ack} packet as a regular, synchronous request to the
40636 stub. Such acknowledgment is not required to happen immediately, as
40637 @value{GDBN} is permitted to send other, unrelated packets to the
40638 stub first, which the stub should process normally.
40640 Upon receiving a @var{ack} packet, if the stub has other queued
40641 events to report to @value{GDBN}, it shall respond by sending a
40642 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40643 packet to solicit further responses; again, it is permitted to send
40644 other, unrelated packets as well which the stub should process
40647 If the stub receives a @var{ack} packet and there are no additional
40648 @var{event} to report, the stub shall return an @samp{OK} response.
40649 At this point, @value{GDBN} has finished processing a notification
40650 and the stub has completed sending any queued events. @value{GDBN}
40651 won't accept any new notifications until the final @samp{OK} is
40652 received . If further notification events occur, the stub shall send
40653 a new notification, @value{GDBN} shall accept the notification, and
40654 the process shall be repeated.
40656 The process of asynchronous notification can be illustrated by the
40659 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40662 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40664 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40669 The following notifications are defined:
40670 @multitable @columnfractions 0.12 0.12 0.38 0.38
40679 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40680 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40681 for information on how these notifications are acknowledged by
40683 @tab Report an asynchronous stop event in non-stop mode.
40687 @node Remote Non-Stop
40688 @section Remote Protocol Support for Non-Stop Mode
40690 @value{GDBN}'s remote protocol supports non-stop debugging of
40691 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40692 supports non-stop mode, it should report that to @value{GDBN} by including
40693 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40695 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40696 establishing a new connection with the stub. Entering non-stop mode
40697 does not alter the state of any currently-running threads, but targets
40698 must stop all threads in any already-attached processes when entering
40699 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40700 probe the target state after a mode change.
40702 In non-stop mode, when an attached process encounters an event that
40703 would otherwise be reported with a stop reply, it uses the
40704 asynchronous notification mechanism (@pxref{Notification Packets}) to
40705 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40706 in all processes are stopped when a stop reply is sent, in non-stop
40707 mode only the thread reporting the stop event is stopped. That is,
40708 when reporting a @samp{S} or @samp{T} response to indicate completion
40709 of a step operation, hitting a breakpoint, or a fault, only the
40710 affected thread is stopped; any other still-running threads continue
40711 to run. When reporting a @samp{W} or @samp{X} response, all running
40712 threads belonging to other attached processes continue to run.
40714 In non-stop mode, the target shall respond to the @samp{?} packet as
40715 follows. First, any incomplete stop reply notification/@samp{vStopped}
40716 sequence in progress is abandoned. The target must begin a new
40717 sequence reporting stop events for all stopped threads, whether or not
40718 it has previously reported those events to @value{GDBN}. The first
40719 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40720 subsequent stop replies are sent as responses to @samp{vStopped} packets
40721 using the mechanism described above. The target must not send
40722 asynchronous stop reply notifications until the sequence is complete.
40723 If all threads are running when the target receives the @samp{?} packet,
40724 or if the target is not attached to any process, it shall respond
40727 If the stub supports non-stop mode, it should also support the
40728 @samp{swbreak} stop reason if software breakpoints are supported, and
40729 the @samp{hwbreak} stop reason if hardware breakpoints are supported
40730 (@pxref{swbreak stop reason}). This is because given the asynchronous
40731 nature of non-stop mode, between the time a thread hits a breakpoint
40732 and the time the event is finally processed by @value{GDBN}, the
40733 breakpoint may have already been removed from the target. Due to
40734 this, @value{GDBN} needs to be able to tell whether a trap stop was
40735 caused by a delayed breakpoint event, which should be ignored, as
40736 opposed to a random trap signal, which should be reported to the user.
40737 Note the @samp{swbreak} feature implies that the target is responsible
40738 for adjusting the PC when a software breakpoint triggers, if
40739 necessary, such as on the x86 architecture.
40741 @node Packet Acknowledgment
40742 @section Packet Acknowledgment
40744 @cindex acknowledgment, for @value{GDBN} remote
40745 @cindex packet acknowledgment, for @value{GDBN} remote
40746 By default, when either the host or the target machine receives a packet,
40747 the first response expected is an acknowledgment: either @samp{+} (to indicate
40748 the package was received correctly) or @samp{-} (to request retransmission).
40749 This mechanism allows the @value{GDBN} remote protocol to operate over
40750 unreliable transport mechanisms, such as a serial line.
40752 In cases where the transport mechanism is itself reliable (such as a pipe or
40753 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40754 It may be desirable to disable them in that case to reduce communication
40755 overhead, or for other reasons. This can be accomplished by means of the
40756 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40758 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40759 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40760 and response format still includes the normal checksum, as described in
40761 @ref{Overview}, but the checksum may be ignored by the receiver.
40763 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40764 no-acknowledgment mode, it should report that to @value{GDBN}
40765 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40766 @pxref{qSupported}.
40767 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40768 disabled via the @code{set remote noack-packet off} command
40769 (@pxref{Remote Configuration}),
40770 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40771 Only then may the stub actually turn off packet acknowledgments.
40772 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40773 response, which can be safely ignored by the stub.
40775 Note that @code{set remote noack-packet} command only affects negotiation
40776 between @value{GDBN} and the stub when subsequent connections are made;
40777 it does not affect the protocol acknowledgment state for any current
40779 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40780 new connection is established,
40781 there is also no protocol request to re-enable the acknowledgments
40782 for the current connection, once disabled.
40787 Example sequence of a target being re-started. Notice how the restart
40788 does not get any direct output:
40793 @emph{target restarts}
40796 <- @code{T001:1234123412341234}
40800 Example sequence of a target being stepped by a single instruction:
40803 -> @code{G1445@dots{}}
40808 <- @code{T001:1234123412341234}
40812 <- @code{1455@dots{}}
40816 @node File-I/O Remote Protocol Extension
40817 @section File-I/O Remote Protocol Extension
40818 @cindex File-I/O remote protocol extension
40821 * File-I/O Overview::
40822 * Protocol Basics::
40823 * The F Request Packet::
40824 * The F Reply Packet::
40825 * The Ctrl-C Message::
40827 * List of Supported Calls::
40828 * Protocol-specific Representation of Datatypes::
40830 * File-I/O Examples::
40833 @node File-I/O Overview
40834 @subsection File-I/O Overview
40835 @cindex file-i/o overview
40837 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40838 target to use the host's file system and console I/O to perform various
40839 system calls. System calls on the target system are translated into a
40840 remote protocol packet to the host system, which then performs the needed
40841 actions and returns a response packet to the target system.
40842 This simulates file system operations even on targets that lack file systems.
40844 The protocol is defined to be independent of both the host and target systems.
40845 It uses its own internal representation of datatypes and values. Both
40846 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40847 translating the system-dependent value representations into the internal
40848 protocol representations when data is transmitted.
40850 The communication is synchronous. A system call is possible only when
40851 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40852 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40853 the target is stopped to allow deterministic access to the target's
40854 memory. Therefore File-I/O is not interruptible by target signals. On
40855 the other hand, it is possible to interrupt File-I/O by a user interrupt
40856 (@samp{Ctrl-C}) within @value{GDBN}.
40858 The target's request to perform a host system call does not finish
40859 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40860 after finishing the system call, the target returns to continuing the
40861 previous activity (continue, step). No additional continue or step
40862 request from @value{GDBN} is required.
40865 (@value{GDBP}) continue
40866 <- target requests 'system call X'
40867 target is stopped, @value{GDBN} executes system call
40868 -> @value{GDBN} returns result
40869 ... target continues, @value{GDBN} returns to wait for the target
40870 <- target hits breakpoint and sends a Txx packet
40873 The protocol only supports I/O on the console and to regular files on
40874 the host file system. Character or block special devices, pipes,
40875 named pipes, sockets or any other communication method on the host
40876 system are not supported by this protocol.
40878 File I/O is not supported in non-stop mode.
40880 @node Protocol Basics
40881 @subsection Protocol Basics
40882 @cindex protocol basics, file-i/o
40884 The File-I/O protocol uses the @code{F} packet as the request as well
40885 as reply packet. Since a File-I/O system call can only occur when
40886 @value{GDBN} is waiting for a response from the continuing or stepping target,
40887 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40888 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40889 This @code{F} packet contains all information needed to allow @value{GDBN}
40890 to call the appropriate host system call:
40894 A unique identifier for the requested system call.
40897 All parameters to the system call. Pointers are given as addresses
40898 in the target memory address space. Pointers to strings are given as
40899 pointer/length pair. Numerical values are given as they are.
40900 Numerical control flags are given in a protocol-specific representation.
40904 At this point, @value{GDBN} has to perform the following actions.
40908 If the parameters include pointer values to data needed as input to a
40909 system call, @value{GDBN} requests this data from the target with a
40910 standard @code{m} packet request. This additional communication has to be
40911 expected by the target implementation and is handled as any other @code{m}
40915 @value{GDBN} translates all value from protocol representation to host
40916 representation as needed. Datatypes are coerced into the host types.
40919 @value{GDBN} calls the system call.
40922 It then coerces datatypes back to protocol representation.
40925 If the system call is expected to return data in buffer space specified
40926 by pointer parameters to the call, the data is transmitted to the
40927 target using a @code{M} or @code{X} packet. This packet has to be expected
40928 by the target implementation and is handled as any other @code{M} or @code{X}
40933 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40934 necessary information for the target to continue. This at least contains
40941 @code{errno}, if has been changed by the system call.
40948 After having done the needed type and value coercion, the target continues
40949 the latest continue or step action.
40951 @node The F Request Packet
40952 @subsection The @code{F} Request Packet
40953 @cindex file-i/o request packet
40954 @cindex @code{F} request packet
40956 The @code{F} request packet has the following format:
40959 @item F@var{call-id},@var{parameter@dots{}}
40961 @var{call-id} is the identifier to indicate the host system call to be called.
40962 This is just the name of the function.
40964 @var{parameter@dots{}} are the parameters to the system call.
40965 Parameters are hexadecimal integer values, either the actual values in case
40966 of scalar datatypes, pointers to target buffer space in case of compound
40967 datatypes and unspecified memory areas, or pointer/length pairs in case
40968 of string parameters. These are appended to the @var{call-id} as a
40969 comma-delimited list. All values are transmitted in ASCII
40970 string representation, pointer/length pairs separated by a slash.
40976 @node The F Reply Packet
40977 @subsection The @code{F} Reply Packet
40978 @cindex file-i/o reply packet
40979 @cindex @code{F} reply packet
40981 The @code{F} reply packet has the following format:
40985 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40987 @var{retcode} is the return code of the system call as hexadecimal value.
40989 @var{errno} is the @code{errno} set by the call, in protocol-specific
40991 This parameter can be omitted if the call was successful.
40993 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40994 case, @var{errno} must be sent as well, even if the call was successful.
40995 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41002 or, if the call was interrupted before the host call has been performed:
41009 assuming 4 is the protocol-specific representation of @code{EINTR}.
41014 @node The Ctrl-C Message
41015 @subsection The @samp{Ctrl-C} Message
41016 @cindex ctrl-c message, in file-i/o protocol
41018 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41019 reply packet (@pxref{The F Reply Packet}),
41020 the target should behave as if it had
41021 gotten a break message. The meaning for the target is ``system call
41022 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41023 (as with a break message) and return to @value{GDBN} with a @code{T02}
41026 It's important for the target to know in which
41027 state the system call was interrupted. There are two possible cases:
41031 The system call hasn't been performed on the host yet.
41034 The system call on the host has been finished.
41038 These two states can be distinguished by the target by the value of the
41039 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41040 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41041 on POSIX systems. In any other case, the target may presume that the
41042 system call has been finished --- successfully or not --- and should behave
41043 as if the break message arrived right after the system call.
41045 @value{GDBN} must behave reliably. If the system call has not been called
41046 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41047 @code{errno} in the packet. If the system call on the host has been finished
41048 before the user requests a break, the full action must be finished by
41049 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41050 The @code{F} packet may only be sent when either nothing has happened
41051 or the full action has been completed.
41054 @subsection Console I/O
41055 @cindex console i/o as part of file-i/o
41057 By default and if not explicitly closed by the target system, the file
41058 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41059 on the @value{GDBN} console is handled as any other file output operation
41060 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41061 by @value{GDBN} so that after the target read request from file descriptor
41062 0 all following typing is buffered until either one of the following
41067 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41069 system call is treated as finished.
41072 The user presses @key{RET}. This is treated as end of input with a trailing
41076 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41077 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41081 If the user has typed more characters than fit in the buffer given to
41082 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41083 either another @code{read(0, @dots{})} is requested by the target, or debugging
41084 is stopped at the user's request.
41087 @node List of Supported Calls
41088 @subsection List of Supported Calls
41089 @cindex list of supported file-i/o calls
41106 @unnumberedsubsubsec open
41107 @cindex open, file-i/o system call
41112 int open(const char *pathname, int flags);
41113 int open(const char *pathname, int flags, mode_t mode);
41117 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41120 @var{flags} is the bitwise @code{OR} of the following values:
41124 If the file does not exist it will be created. The host
41125 rules apply as far as file ownership and time stamps
41129 When used with @code{O_CREAT}, if the file already exists it is
41130 an error and open() fails.
41133 If the file already exists and the open mode allows
41134 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41135 truncated to zero length.
41138 The file is opened in append mode.
41141 The file is opened for reading only.
41144 The file is opened for writing only.
41147 The file is opened for reading and writing.
41151 Other bits are silently ignored.
41155 @var{mode} is the bitwise @code{OR} of the following values:
41159 User has read permission.
41162 User has write permission.
41165 Group has read permission.
41168 Group has write permission.
41171 Others have read permission.
41174 Others have write permission.
41178 Other bits are silently ignored.
41181 @item Return value:
41182 @code{open} returns the new file descriptor or -1 if an error
41189 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41192 @var{pathname} refers to a directory.
41195 The requested access is not allowed.
41198 @var{pathname} was too long.
41201 A directory component in @var{pathname} does not exist.
41204 @var{pathname} refers to a device, pipe, named pipe or socket.
41207 @var{pathname} refers to a file on a read-only filesystem and
41208 write access was requested.
41211 @var{pathname} is an invalid pointer value.
41214 No space on device to create the file.
41217 The process already has the maximum number of files open.
41220 The limit on the total number of files open on the system
41224 The call was interrupted by the user.
41230 @unnumberedsubsubsec close
41231 @cindex close, file-i/o system call
41240 @samp{Fclose,@var{fd}}
41242 @item Return value:
41243 @code{close} returns zero on success, or -1 if an error occurred.
41249 @var{fd} isn't a valid open file descriptor.
41252 The call was interrupted by the user.
41258 @unnumberedsubsubsec read
41259 @cindex read, file-i/o system call
41264 int read(int fd, void *buf, unsigned int count);
41268 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41270 @item Return value:
41271 On success, the number of bytes read is returned.
41272 Zero indicates end of file. If count is zero, read
41273 returns zero as well. On error, -1 is returned.
41279 @var{fd} is not a valid file descriptor or is not open for
41283 @var{bufptr} is an invalid pointer value.
41286 The call was interrupted by the user.
41292 @unnumberedsubsubsec write
41293 @cindex write, file-i/o system call
41298 int write(int fd, const void *buf, unsigned int count);
41302 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41304 @item Return value:
41305 On success, the number of bytes written are returned.
41306 Zero indicates nothing was written. On error, -1
41313 @var{fd} is not a valid file descriptor or is not open for
41317 @var{bufptr} is an invalid pointer value.
41320 An attempt was made to write a file that exceeds the
41321 host-specific maximum file size allowed.
41324 No space on device to write the data.
41327 The call was interrupted by the user.
41333 @unnumberedsubsubsec lseek
41334 @cindex lseek, file-i/o system call
41339 long lseek (int fd, long offset, int flag);
41343 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41345 @var{flag} is one of:
41349 The offset is set to @var{offset} bytes.
41352 The offset is set to its current location plus @var{offset}
41356 The offset is set to the size of the file plus @var{offset}
41360 @item Return value:
41361 On success, the resulting unsigned offset in bytes from
41362 the beginning of the file is returned. Otherwise, a
41363 value of -1 is returned.
41369 @var{fd} is not a valid open file descriptor.
41372 @var{fd} is associated with the @value{GDBN} console.
41375 @var{flag} is not a proper value.
41378 The call was interrupted by the user.
41384 @unnumberedsubsubsec rename
41385 @cindex rename, file-i/o system call
41390 int rename(const char *oldpath, const char *newpath);
41394 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41396 @item Return value:
41397 On success, zero is returned. On error, -1 is returned.
41403 @var{newpath} is an existing directory, but @var{oldpath} is not a
41407 @var{newpath} is a non-empty directory.
41410 @var{oldpath} or @var{newpath} is a directory that is in use by some
41414 An attempt was made to make a directory a subdirectory
41418 A component used as a directory in @var{oldpath} or new
41419 path is not a directory. Or @var{oldpath} is a directory
41420 and @var{newpath} exists but is not a directory.
41423 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41426 No access to the file or the path of the file.
41430 @var{oldpath} or @var{newpath} was too long.
41433 A directory component in @var{oldpath} or @var{newpath} does not exist.
41436 The file is on a read-only filesystem.
41439 The device containing the file has no room for the new
41443 The call was interrupted by the user.
41449 @unnumberedsubsubsec unlink
41450 @cindex unlink, file-i/o system call
41455 int unlink(const char *pathname);
41459 @samp{Funlink,@var{pathnameptr}/@var{len}}
41461 @item Return value:
41462 On success, zero is returned. On error, -1 is returned.
41468 No access to the file or the path of the file.
41471 The system does not allow unlinking of directories.
41474 The file @var{pathname} cannot be unlinked because it's
41475 being used by another process.
41478 @var{pathnameptr} is an invalid pointer value.
41481 @var{pathname} was too long.
41484 A directory component in @var{pathname} does not exist.
41487 A component of the path is not a directory.
41490 The file is on a read-only filesystem.
41493 The call was interrupted by the user.
41499 @unnumberedsubsubsec stat/fstat
41500 @cindex fstat, file-i/o system call
41501 @cindex stat, file-i/o system call
41506 int stat(const char *pathname, struct stat *buf);
41507 int fstat(int fd, struct stat *buf);
41511 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41512 @samp{Ffstat,@var{fd},@var{bufptr}}
41514 @item Return value:
41515 On success, zero is returned. On error, -1 is returned.
41521 @var{fd} is not a valid open file.
41524 A directory component in @var{pathname} does not exist or the
41525 path is an empty string.
41528 A component of the path is not a directory.
41531 @var{pathnameptr} is an invalid pointer value.
41534 No access to the file or the path of the file.
41537 @var{pathname} was too long.
41540 The call was interrupted by the user.
41546 @unnumberedsubsubsec gettimeofday
41547 @cindex gettimeofday, file-i/o system call
41552 int gettimeofday(struct timeval *tv, void *tz);
41556 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41558 @item Return value:
41559 On success, 0 is returned, -1 otherwise.
41565 @var{tz} is a non-NULL pointer.
41568 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41574 @unnumberedsubsubsec isatty
41575 @cindex isatty, file-i/o system call
41580 int isatty(int fd);
41584 @samp{Fisatty,@var{fd}}
41586 @item Return value:
41587 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41593 The call was interrupted by the user.
41598 Note that the @code{isatty} call is treated as a special case: it returns
41599 1 to the target if the file descriptor is attached
41600 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41601 would require implementing @code{ioctl} and would be more complex than
41606 @unnumberedsubsubsec system
41607 @cindex system, file-i/o system call
41612 int system(const char *command);
41616 @samp{Fsystem,@var{commandptr}/@var{len}}
41618 @item Return value:
41619 If @var{len} is zero, the return value indicates whether a shell is
41620 available. A zero return value indicates a shell is not available.
41621 For non-zero @var{len}, the value returned is -1 on error and the
41622 return status of the command otherwise. Only the exit status of the
41623 command is returned, which is extracted from the host's @code{system}
41624 return value by calling @code{WEXITSTATUS(retval)}. In case
41625 @file{/bin/sh} could not be executed, 127 is returned.
41631 The call was interrupted by the user.
41636 @value{GDBN} takes over the full task of calling the necessary host calls
41637 to perform the @code{system} call. The return value of @code{system} on
41638 the host is simplified before it's returned
41639 to the target. Any termination signal information from the child process
41640 is discarded, and the return value consists
41641 entirely of the exit status of the called command.
41643 Due to security concerns, the @code{system} call is by default refused
41644 by @value{GDBN}. The user has to allow this call explicitly with the
41645 @code{set remote system-call-allowed 1} command.
41648 @item set remote system-call-allowed
41649 @kindex set remote system-call-allowed
41650 Control whether to allow the @code{system} calls in the File I/O
41651 protocol for the remote target. The default is zero (disabled).
41653 @item show remote system-call-allowed
41654 @kindex show remote system-call-allowed
41655 Show whether the @code{system} calls are allowed in the File I/O
41659 @node Protocol-specific Representation of Datatypes
41660 @subsection Protocol-specific Representation of Datatypes
41661 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41664 * Integral Datatypes::
41666 * Memory Transfer::
41671 @node Integral Datatypes
41672 @unnumberedsubsubsec Integral Datatypes
41673 @cindex integral datatypes, in file-i/o protocol
41675 The integral datatypes used in the system calls are @code{int},
41676 @code{unsigned int}, @code{long}, @code{unsigned long},
41677 @code{mode_t}, and @code{time_t}.
41679 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41680 implemented as 32 bit values in this protocol.
41682 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41684 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41685 in @file{limits.h}) to allow range checking on host and target.
41687 @code{time_t} datatypes are defined as seconds since the Epoch.
41689 All integral datatypes transferred as part of a memory read or write of a
41690 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41693 @node Pointer Values
41694 @unnumberedsubsubsec Pointer Values
41695 @cindex pointer values, in file-i/o protocol
41697 Pointers to target data are transmitted as they are. An exception
41698 is made for pointers to buffers for which the length isn't
41699 transmitted as part of the function call, namely strings. Strings
41700 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41707 which is a pointer to data of length 18 bytes at position 0x1aaf.
41708 The length is defined as the full string length in bytes, including
41709 the trailing null byte. For example, the string @code{"hello world"}
41710 at address 0x123456 is transmitted as
41716 @node Memory Transfer
41717 @unnumberedsubsubsec Memory Transfer
41718 @cindex memory transfer, in file-i/o protocol
41720 Structured data which is transferred using a memory read or write (for
41721 example, a @code{struct stat}) is expected to be in a protocol-specific format
41722 with all scalar multibyte datatypes being big endian. Translation to
41723 this representation needs to be done both by the target before the @code{F}
41724 packet is sent, and by @value{GDBN} before
41725 it transfers memory to the target. Transferred pointers to structured
41726 data should point to the already-coerced data at any time.
41730 @unnumberedsubsubsec struct stat
41731 @cindex struct stat, in file-i/o protocol
41733 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41734 is defined as follows:
41738 unsigned int st_dev; /* device */
41739 unsigned int st_ino; /* inode */
41740 mode_t st_mode; /* protection */
41741 unsigned int st_nlink; /* number of hard links */
41742 unsigned int st_uid; /* user ID of owner */
41743 unsigned int st_gid; /* group ID of owner */
41744 unsigned int st_rdev; /* device type (if inode device) */
41745 unsigned long st_size; /* total size, in bytes */
41746 unsigned long st_blksize; /* blocksize for filesystem I/O */
41747 unsigned long st_blocks; /* number of blocks allocated */
41748 time_t st_atime; /* time of last access */
41749 time_t st_mtime; /* time of last modification */
41750 time_t st_ctime; /* time of last change */
41754 The integral datatypes conform to the definitions given in the
41755 appropriate section (see @ref{Integral Datatypes}, for details) so this
41756 structure is of size 64 bytes.
41758 The values of several fields have a restricted meaning and/or
41764 A value of 0 represents a file, 1 the console.
41767 No valid meaning for the target. Transmitted unchanged.
41770 Valid mode bits are described in @ref{Constants}. Any other
41771 bits have currently no meaning for the target.
41776 No valid meaning for the target. Transmitted unchanged.
41781 These values have a host and file system dependent
41782 accuracy. Especially on Windows hosts, the file system may not
41783 support exact timing values.
41786 The target gets a @code{struct stat} of the above representation and is
41787 responsible for coercing it to the target representation before
41790 Note that due to size differences between the host, target, and protocol
41791 representations of @code{struct stat} members, these members could eventually
41792 get truncated on the target.
41794 @node struct timeval
41795 @unnumberedsubsubsec struct timeval
41796 @cindex struct timeval, in file-i/o protocol
41798 The buffer of type @code{struct timeval} used by the File-I/O protocol
41799 is defined as follows:
41803 time_t tv_sec; /* second */
41804 long tv_usec; /* microsecond */
41808 The integral datatypes conform to the definitions given in the
41809 appropriate section (see @ref{Integral Datatypes}, for details) so this
41810 structure is of size 8 bytes.
41813 @subsection Constants
41814 @cindex constants, in file-i/o protocol
41816 The following values are used for the constants inside of the
41817 protocol. @value{GDBN} and target are responsible for translating these
41818 values before and after the call as needed.
41829 @unnumberedsubsubsec Open Flags
41830 @cindex open flags, in file-i/o protocol
41832 All values are given in hexadecimal representation.
41844 @node mode_t Values
41845 @unnumberedsubsubsec mode_t Values
41846 @cindex mode_t values, in file-i/o protocol
41848 All values are given in octal representation.
41865 @unnumberedsubsubsec Errno Values
41866 @cindex errno values, in file-i/o protocol
41868 All values are given in decimal representation.
41893 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41894 any error value not in the list of supported error numbers.
41897 @unnumberedsubsubsec Lseek Flags
41898 @cindex lseek flags, in file-i/o protocol
41907 @unnumberedsubsubsec Limits
41908 @cindex limits, in file-i/o protocol
41910 All values are given in decimal representation.
41913 INT_MIN -2147483648
41915 UINT_MAX 4294967295
41916 LONG_MIN -9223372036854775808
41917 LONG_MAX 9223372036854775807
41918 ULONG_MAX 18446744073709551615
41921 @node File-I/O Examples
41922 @subsection File-I/O Examples
41923 @cindex file-i/o examples
41925 Example sequence of a write call, file descriptor 3, buffer is at target
41926 address 0x1234, 6 bytes should be written:
41929 <- @code{Fwrite,3,1234,6}
41930 @emph{request memory read from target}
41933 @emph{return "6 bytes written"}
41937 Example sequence of a read call, file descriptor 3, buffer is at target
41938 address 0x1234, 6 bytes should be read:
41941 <- @code{Fread,3,1234,6}
41942 @emph{request memory write to target}
41943 -> @code{X1234,6:XXXXXX}
41944 @emph{return "6 bytes read"}
41948 Example sequence of a read call, call fails on the host due to invalid
41949 file descriptor (@code{EBADF}):
41952 <- @code{Fread,3,1234,6}
41956 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41960 <- @code{Fread,3,1234,6}
41965 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41969 <- @code{Fread,3,1234,6}
41970 -> @code{X1234,6:XXXXXX}
41974 @node Library List Format
41975 @section Library List Format
41976 @cindex library list format, remote protocol
41978 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41979 same process as your application to manage libraries. In this case,
41980 @value{GDBN} can use the loader's symbol table and normal memory
41981 operations to maintain a list of shared libraries. On other
41982 platforms, the operating system manages loaded libraries.
41983 @value{GDBN} can not retrieve the list of currently loaded libraries
41984 through memory operations, so it uses the @samp{qXfer:libraries:read}
41985 packet (@pxref{qXfer library list read}) instead. The remote stub
41986 queries the target's operating system and reports which libraries
41989 The @samp{qXfer:libraries:read} packet returns an XML document which
41990 lists loaded libraries and their offsets. Each library has an
41991 associated name and one or more segment or section base addresses,
41992 which report where the library was loaded in memory.
41994 For the common case of libraries that are fully linked binaries, the
41995 library should have a list of segments. If the target supports
41996 dynamic linking of a relocatable object file, its library XML element
41997 should instead include a list of allocated sections. The segment or
41998 section bases are start addresses, not relocation offsets; they do not
41999 depend on the library's link-time base addresses.
42001 @value{GDBN} must be linked with the Expat library to support XML
42002 library lists. @xref{Expat}.
42004 A simple memory map, with one loaded library relocated by a single
42005 offset, looks like this:
42009 <library name="/lib/libc.so.6">
42010 <segment address="0x10000000"/>
42015 Another simple memory map, with one loaded library with three
42016 allocated sections (.text, .data, .bss), looks like this:
42020 <library name="sharedlib.o">
42021 <section address="0x10000000"/>
42022 <section address="0x20000000"/>
42023 <section address="0x30000000"/>
42028 The format of a library list is described by this DTD:
42031 <!-- library-list: Root element with versioning -->
42032 <!ELEMENT library-list (library)*>
42033 <!ATTLIST library-list version CDATA #FIXED "1.0">
42034 <!ELEMENT library (segment*, section*)>
42035 <!ATTLIST library name CDATA #REQUIRED>
42036 <!ELEMENT segment EMPTY>
42037 <!ATTLIST segment address CDATA #REQUIRED>
42038 <!ELEMENT section EMPTY>
42039 <!ATTLIST section address CDATA #REQUIRED>
42042 In addition, segments and section descriptors cannot be mixed within a
42043 single library element, and you must supply at least one segment or
42044 section for each library.
42046 @node Library List Format for SVR4 Targets
42047 @section Library List Format for SVR4 Targets
42048 @cindex library list format, remote protocol
42050 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42051 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42052 shared libraries. Still a special library list provided by this packet is
42053 more efficient for the @value{GDBN} remote protocol.
42055 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42056 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42057 target, the following parameters are reported:
42061 @code{name}, the absolute file name from the @code{l_name} field of
42062 @code{struct link_map}.
42064 @code{lm} with address of @code{struct link_map} used for TLS
42065 (Thread Local Storage) access.
42067 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42068 @code{struct link_map}. For prelinked libraries this is not an absolute
42069 memory address. It is a displacement of absolute memory address against
42070 address the file was prelinked to during the library load.
42072 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42075 Additionally the single @code{main-lm} attribute specifies address of
42076 @code{struct link_map} used for the main executable. This parameter is used
42077 for TLS access and its presence is optional.
42079 @value{GDBN} must be linked with the Expat library to support XML
42080 SVR4 library lists. @xref{Expat}.
42082 A simple memory map, with two loaded libraries (which do not use prelink),
42086 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42087 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42089 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42091 </library-list-svr>
42094 The format of an SVR4 library list is described by this DTD:
42097 <!-- library-list-svr4: Root element with versioning -->
42098 <!ELEMENT library-list-svr4 (library)*>
42099 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42100 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42101 <!ELEMENT library EMPTY>
42102 <!ATTLIST library name CDATA #REQUIRED>
42103 <!ATTLIST library lm CDATA #REQUIRED>
42104 <!ATTLIST library l_addr CDATA #REQUIRED>
42105 <!ATTLIST library l_ld CDATA #REQUIRED>
42108 @node Memory Map Format
42109 @section Memory Map Format
42110 @cindex memory map format
42112 To be able to write into flash memory, @value{GDBN} needs to obtain a
42113 memory map from the target. This section describes the format of the
42116 The memory map is obtained using the @samp{qXfer:memory-map:read}
42117 (@pxref{qXfer memory map read}) packet and is an XML document that
42118 lists memory regions.
42120 @value{GDBN} must be linked with the Expat library to support XML
42121 memory maps. @xref{Expat}.
42123 The top-level structure of the document is shown below:
42126 <?xml version="1.0"?>
42127 <!DOCTYPE memory-map
42128 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42129 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42135 Each region can be either:
42140 A region of RAM starting at @var{addr} and extending for @var{length}
42144 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42149 A region of read-only memory:
42152 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42157 A region of flash memory, with erasure blocks @var{blocksize}
42161 <memory type="flash" start="@var{addr}" length="@var{length}">
42162 <property name="blocksize">@var{blocksize}</property>
42168 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42169 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42170 packets to write to addresses in such ranges.
42172 The formal DTD for memory map format is given below:
42175 <!-- ................................................... -->
42176 <!-- Memory Map XML DTD ................................ -->
42177 <!-- File: memory-map.dtd .............................. -->
42178 <!-- .................................... .............. -->
42179 <!-- memory-map.dtd -->
42180 <!-- memory-map: Root element with versioning -->
42181 <!ELEMENT memory-map (memory)*>
42182 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42183 <!ELEMENT memory (property)*>
42184 <!-- memory: Specifies a memory region,
42185 and its type, or device. -->
42186 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42187 start CDATA #REQUIRED
42188 length CDATA #REQUIRED>
42189 <!-- property: Generic attribute tag -->
42190 <!ELEMENT property (#PCDATA | property)*>
42191 <!ATTLIST property name (blocksize) #REQUIRED>
42194 @node Thread List Format
42195 @section Thread List Format
42196 @cindex thread list format
42198 To efficiently update the list of threads and their attributes,
42199 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42200 (@pxref{qXfer threads read}) and obtains the XML document with
42201 the following structure:
42204 <?xml version="1.0"?>
42206 <thread id="id" core="0" name="name">
42207 ... description ...
42212 Each @samp{thread} element must have the @samp{id} attribute that
42213 identifies the thread (@pxref{thread-id syntax}). The
42214 @samp{core} attribute, if present, specifies which processor core
42215 the thread was last executing on. The @samp{name} attribute, if
42216 present, specifies the human-readable name of the thread. The content
42217 of the of @samp{thread} element is interpreted as human-readable
42218 auxiliary information. The @samp{handle} attribute, if present,
42219 is a hex encoded representation of the thread handle.
42222 @node Traceframe Info Format
42223 @section Traceframe Info Format
42224 @cindex traceframe info format
42226 To be able to know which objects in the inferior can be examined when
42227 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42228 memory ranges, registers and trace state variables that have been
42229 collected in a traceframe.
42231 This list is obtained using the @samp{qXfer:traceframe-info:read}
42232 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42234 @value{GDBN} must be linked with the Expat library to support XML
42235 traceframe info discovery. @xref{Expat}.
42237 The top-level structure of the document is shown below:
42240 <?xml version="1.0"?>
42241 <!DOCTYPE traceframe-info
42242 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42243 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42249 Each traceframe block can be either:
42254 A region of collected memory starting at @var{addr} and extending for
42255 @var{length} bytes from there:
42258 <memory start="@var{addr}" length="@var{length}"/>
42262 A block indicating trace state variable numbered @var{number} has been
42266 <tvar id="@var{number}"/>
42271 The formal DTD for the traceframe info format is given below:
42274 <!ELEMENT traceframe-info (memory | tvar)* >
42275 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42277 <!ELEMENT memory EMPTY>
42278 <!ATTLIST memory start CDATA #REQUIRED
42279 length CDATA #REQUIRED>
42281 <!ATTLIST tvar id CDATA #REQUIRED>
42284 @node Branch Trace Format
42285 @section Branch Trace Format
42286 @cindex branch trace format
42288 In order to display the branch trace of an inferior thread,
42289 @value{GDBN} needs to obtain the list of branches. This list is
42290 represented as list of sequential code blocks that are connected via
42291 branches. The code in each block has been executed sequentially.
42293 This list is obtained using the @samp{qXfer:btrace:read}
42294 (@pxref{qXfer btrace read}) packet and is an XML document.
42296 @value{GDBN} must be linked with the Expat library to support XML
42297 traceframe info discovery. @xref{Expat}.
42299 The top-level structure of the document is shown below:
42302 <?xml version="1.0"?>
42304 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42305 "http://sourceware.org/gdb/gdb-btrace.dtd">
42314 A block of sequentially executed instructions starting at @var{begin}
42315 and ending at @var{end}:
42318 <block begin="@var{begin}" end="@var{end}"/>
42323 The formal DTD for the branch trace format is given below:
42326 <!ELEMENT btrace (block* | pt) >
42327 <!ATTLIST btrace version CDATA #FIXED "1.0">
42329 <!ELEMENT block EMPTY>
42330 <!ATTLIST block begin CDATA #REQUIRED
42331 end CDATA #REQUIRED>
42333 <!ELEMENT pt (pt-config?, raw?)>
42335 <!ELEMENT pt-config (cpu?)>
42337 <!ELEMENT cpu EMPTY>
42338 <!ATTLIST cpu vendor CDATA #REQUIRED
42339 family CDATA #REQUIRED
42340 model CDATA #REQUIRED
42341 stepping CDATA #REQUIRED>
42343 <!ELEMENT raw (#PCDATA)>
42346 @node Branch Trace Configuration Format
42347 @section Branch Trace Configuration Format
42348 @cindex branch trace configuration format
42350 For each inferior thread, @value{GDBN} can obtain the branch trace
42351 configuration using the @samp{qXfer:btrace-conf:read}
42352 (@pxref{qXfer btrace-conf read}) packet.
42354 The configuration describes the branch trace format and configuration
42355 settings for that format. The following information is described:
42359 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42362 The size of the @acronym{BTS} ring buffer in bytes.
42365 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42369 The size of the @acronym{Intel PT} ring buffer in bytes.
42373 @value{GDBN} must be linked with the Expat library to support XML
42374 branch trace configuration discovery. @xref{Expat}.
42376 The formal DTD for the branch trace configuration format is given below:
42379 <!ELEMENT btrace-conf (bts?, pt?)>
42380 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42382 <!ELEMENT bts EMPTY>
42383 <!ATTLIST bts size CDATA #IMPLIED>
42385 <!ELEMENT pt EMPTY>
42386 <!ATTLIST pt size CDATA #IMPLIED>
42389 @include agentexpr.texi
42391 @node Target Descriptions
42392 @appendix Target Descriptions
42393 @cindex target descriptions
42395 One of the challenges of using @value{GDBN} to debug embedded systems
42396 is that there are so many minor variants of each processor
42397 architecture in use. It is common practice for vendors to start with
42398 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42399 and then make changes to adapt it to a particular market niche. Some
42400 architectures have hundreds of variants, available from dozens of
42401 vendors. This leads to a number of problems:
42405 With so many different customized processors, it is difficult for
42406 the @value{GDBN} maintainers to keep up with the changes.
42408 Since individual variants may have short lifetimes or limited
42409 audiences, it may not be worthwhile to carry information about every
42410 variant in the @value{GDBN} source tree.
42412 When @value{GDBN} does support the architecture of the embedded system
42413 at hand, the task of finding the correct architecture name to give the
42414 @command{set architecture} command can be error-prone.
42417 To address these problems, the @value{GDBN} remote protocol allows a
42418 target system to not only identify itself to @value{GDBN}, but to
42419 actually describe its own features. This lets @value{GDBN} support
42420 processor variants it has never seen before --- to the extent that the
42421 descriptions are accurate, and that @value{GDBN} understands them.
42423 @value{GDBN} must be linked with the Expat library to support XML
42424 target descriptions. @xref{Expat}.
42427 * Retrieving Descriptions:: How descriptions are fetched from a target.
42428 * Target Description Format:: The contents of a target description.
42429 * Predefined Target Types:: Standard types available for target
42431 * Enum Target Types:: How to define enum target types.
42432 * Standard Target Features:: Features @value{GDBN} knows about.
42435 @node Retrieving Descriptions
42436 @section Retrieving Descriptions
42438 Target descriptions can be read from the target automatically, or
42439 specified by the user manually. The default behavior is to read the
42440 description from the target. @value{GDBN} retrieves it via the remote
42441 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42442 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42443 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42444 XML document, of the form described in @ref{Target Description
42447 Alternatively, you can specify a file to read for the target description.
42448 If a file is set, the target will not be queried. The commands to
42449 specify a file are:
42452 @cindex set tdesc filename
42453 @item set tdesc filename @var{path}
42454 Read the target description from @var{path}.
42456 @cindex unset tdesc filename
42457 @item unset tdesc filename
42458 Do not read the XML target description from a file. @value{GDBN}
42459 will use the description supplied by the current target.
42461 @cindex show tdesc filename
42462 @item show tdesc filename
42463 Show the filename to read for a target description, if any.
42467 @node Target Description Format
42468 @section Target Description Format
42469 @cindex target descriptions, XML format
42471 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42472 document which complies with the Document Type Definition provided in
42473 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42474 means you can use generally available tools like @command{xmllint} to
42475 check that your feature descriptions are well-formed and valid.
42476 However, to help people unfamiliar with XML write descriptions for
42477 their targets, we also describe the grammar here.
42479 Target descriptions can identify the architecture of the remote target
42480 and (for some architectures) provide information about custom register
42481 sets. They can also identify the OS ABI of the remote target.
42482 @value{GDBN} can use this information to autoconfigure for your
42483 target, or to warn you if you connect to an unsupported target.
42485 Here is a simple target description:
42488 <target version="1.0">
42489 <architecture>i386:x86-64</architecture>
42494 This minimal description only says that the target uses
42495 the x86-64 architecture.
42497 A target description has the following overall form, with [ ] marking
42498 optional elements and @dots{} marking repeatable elements. The elements
42499 are explained further below.
42502 <?xml version="1.0"?>
42503 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42504 <target version="1.0">
42505 @r{[}@var{architecture}@r{]}
42506 @r{[}@var{osabi}@r{]}
42507 @r{[}@var{compatible}@r{]}
42508 @r{[}@var{feature}@dots{}@r{]}
42513 The description is generally insensitive to whitespace and line
42514 breaks, under the usual common-sense rules. The XML version
42515 declaration and document type declaration can generally be omitted
42516 (@value{GDBN} does not require them), but specifying them may be
42517 useful for XML validation tools. The @samp{version} attribute for
42518 @samp{<target>} may also be omitted, but we recommend
42519 including it; if future versions of @value{GDBN} use an incompatible
42520 revision of @file{gdb-target.dtd}, they will detect and report
42521 the version mismatch.
42523 @subsection Inclusion
42524 @cindex target descriptions, inclusion
42527 @cindex <xi:include>
42530 It can sometimes be valuable to split a target description up into
42531 several different annexes, either for organizational purposes, or to
42532 share files between different possible target descriptions. You can
42533 divide a description into multiple files by replacing any element of
42534 the target description with an inclusion directive of the form:
42537 <xi:include href="@var{document}"/>
42541 When @value{GDBN} encounters an element of this form, it will retrieve
42542 the named XML @var{document}, and replace the inclusion directive with
42543 the contents of that document. If the current description was read
42544 using @samp{qXfer}, then so will be the included document;
42545 @var{document} will be interpreted as the name of an annex. If the
42546 current description was read from a file, @value{GDBN} will look for
42547 @var{document} as a file in the same directory where it found the
42548 original description.
42550 @subsection Architecture
42551 @cindex <architecture>
42553 An @samp{<architecture>} element has this form:
42556 <architecture>@var{arch}</architecture>
42559 @var{arch} is one of the architectures from the set accepted by
42560 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42563 @cindex @code{<osabi>}
42565 This optional field was introduced in @value{GDBN} version 7.0.
42566 Previous versions of @value{GDBN} ignore it.
42568 An @samp{<osabi>} element has this form:
42571 <osabi>@var{abi-name}</osabi>
42574 @var{abi-name} is an OS ABI name from the same selection accepted by
42575 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42577 @subsection Compatible Architecture
42578 @cindex @code{<compatible>}
42580 This optional field was introduced in @value{GDBN} version 7.0.
42581 Previous versions of @value{GDBN} ignore it.
42583 A @samp{<compatible>} element has this form:
42586 <compatible>@var{arch}</compatible>
42589 @var{arch} is one of the architectures from the set accepted by
42590 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42592 A @samp{<compatible>} element is used to specify that the target
42593 is able to run binaries in some other than the main target architecture
42594 given by the @samp{<architecture>} element. For example, on the
42595 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42596 or @code{powerpc:common64}, but the system is able to run binaries
42597 in the @code{spu} architecture as well. The way to describe this
42598 capability with @samp{<compatible>} is as follows:
42601 <architecture>powerpc:common</architecture>
42602 <compatible>spu</compatible>
42605 @subsection Features
42608 Each @samp{<feature>} describes some logical portion of the target
42609 system. Features are currently used to describe available CPU
42610 registers and the types of their contents. A @samp{<feature>} element
42614 <feature name="@var{name}">
42615 @r{[}@var{type}@dots{}@r{]}
42621 Each feature's name should be unique within the description. The name
42622 of a feature does not matter unless @value{GDBN} has some special
42623 knowledge of the contents of that feature; if it does, the feature
42624 should have its standard name. @xref{Standard Target Features}.
42628 Any register's value is a collection of bits which @value{GDBN} must
42629 interpret. The default interpretation is a two's complement integer,
42630 but other types can be requested by name in the register description.
42631 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42632 Target Types}), and the description can define additional composite
42635 Each type element must have an @samp{id} attribute, which gives
42636 a unique (within the containing @samp{<feature>}) name to the type.
42637 Types must be defined before they are used.
42640 Some targets offer vector registers, which can be treated as arrays
42641 of scalar elements. These types are written as @samp{<vector>} elements,
42642 specifying the array element type, @var{type}, and the number of elements,
42646 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42650 If a register's value is usefully viewed in multiple ways, define it
42651 with a union type containing the useful representations. The
42652 @samp{<union>} element contains one or more @samp{<field>} elements,
42653 each of which has a @var{name} and a @var{type}:
42656 <union id="@var{id}">
42657 <field name="@var{name}" type="@var{type}"/>
42664 If a register's value is composed from several separate values, define
42665 it with either a structure type or a flags type.
42666 A flags type may only contain bitfields.
42667 A structure type may either contain only bitfields or contain no bitfields.
42668 If the value contains only bitfields, its total size in bytes must be
42671 Non-bitfield values have a @var{name} and @var{type}.
42674 <struct id="@var{id}">
42675 <field name="@var{name}" type="@var{type}"/>
42680 Both @var{name} and @var{type} values are required.
42681 No implicit padding is added.
42683 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
42686 <struct id="@var{id}" size="@var{size}">
42687 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42693 <flags id="@var{id}" size="@var{size}">
42694 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
42699 The @var{name} value is required.
42700 Bitfield values may be named with the empty string, @samp{""},
42701 in which case the field is ``filler'' and its value is not printed.
42702 Not all bits need to be specified, so ``filler'' fields are optional.
42704 The @var{start} and @var{end} values are required, and @var{type}
42706 The field's @var{start} must be less than or equal to its @var{end},
42707 and zero represents the least significant bit.
42709 The default value of @var{type} is @code{bool} for single bit fields,
42710 and an unsigned integer otherwise.
42712 Which to choose? Structures or flags?
42714 Registers defined with @samp{flags} have these advantages over
42715 defining them with @samp{struct}:
42719 Arithmetic may be performed on them as if they were integers.
42721 They are printed in a more readable fashion.
42724 Registers defined with @samp{struct} have one advantage over
42725 defining them with @samp{flags}:
42729 One can fetch individual fields like in @samp{C}.
42732 (gdb) print $my_struct_reg.field3
42738 @subsection Registers
42741 Each register is represented as an element with this form:
42744 <reg name="@var{name}"
42745 bitsize="@var{size}"
42746 @r{[}regnum="@var{num}"@r{]}
42747 @r{[}save-restore="@var{save-restore}"@r{]}
42748 @r{[}type="@var{type}"@r{]}
42749 @r{[}group="@var{group}"@r{]}/>
42753 The components are as follows:
42758 The register's name; it must be unique within the target description.
42761 The register's size, in bits.
42764 The register's number. If omitted, a register's number is one greater
42765 than that of the previous register (either in the current feature or in
42766 a preceding feature); the first register in the target description
42767 defaults to zero. This register number is used to read or write
42768 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42769 packets, and registers appear in the @code{g} and @code{G} packets
42770 in order of increasing register number.
42773 Whether the register should be preserved across inferior function
42774 calls; this must be either @code{yes} or @code{no}. The default is
42775 @code{yes}, which is appropriate for most registers except for
42776 some system control registers; this is not related to the target's
42780 The type of the register. It may be a predefined type, a type
42781 defined in the current feature, or one of the special types @code{int}
42782 and @code{float}. @code{int} is an integer type of the correct size
42783 for @var{bitsize}, and @code{float} is a floating point type (in the
42784 architecture's normal floating point format) of the correct size for
42785 @var{bitsize}. The default is @code{int}.
42788 The register group to which this register belongs. It can be one of the
42789 standard register groups @code{general}, @code{float}, @code{vector} or an
42790 arbitrary string. Group names should be limited to alphanumeric characters.
42791 If a group name is made up of multiple words the words may be separated by
42792 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
42793 @var{group} is specified, @value{GDBN} will not display the register in
42794 @code{info registers}.
42798 @node Predefined Target Types
42799 @section Predefined Target Types
42800 @cindex target descriptions, predefined types
42802 Type definitions in the self-description can build up composite types
42803 from basic building blocks, but can not define fundamental types. Instead,
42804 standard identifiers are provided by @value{GDBN} for the fundamental
42805 types. The currently supported types are:
42810 Boolean type, occupying a single bit.
42818 Signed integer types holding the specified number of bits.
42826 Unsigned integer types holding the specified number of bits.
42830 Pointers to unspecified code and data. The program counter and
42831 any dedicated return address register may be marked as code
42832 pointers; printing a code pointer converts it into a symbolic
42833 address. The stack pointer and any dedicated address registers
42834 may be marked as data pointers.
42837 Single precision IEEE floating point.
42840 Double precision IEEE floating point.
42843 The 12-byte extended precision format used by ARM FPA registers.
42846 The 10-byte extended precision format used by x87 registers.
42849 32bit @sc{eflags} register used by x86.
42852 32bit @sc{mxcsr} register used by x86.
42856 @node Enum Target Types
42857 @section Enum Target Types
42858 @cindex target descriptions, enum types
42860 Enum target types are useful in @samp{struct} and @samp{flags}
42861 register descriptions. @xref{Target Description Format}.
42863 Enum types have a name, size and a list of name/value pairs.
42866 <enum id="@var{id}" size="@var{size}">
42867 <evalue name="@var{name}" value="@var{value}"/>
42872 Enums must be defined before they are used.
42875 <enum id="levels_type" size="4">
42876 <evalue name="low" value="0"/>
42877 <evalue name="high" value="1"/>
42879 <flags id="flags_type" size="4">
42880 <field name="X" start="0"/>
42881 <field name="LEVEL" start="1" end="1" type="levels_type"/>
42883 <reg name="flags" bitsize="32" type="flags_type"/>
42886 Given that description, a value of 3 for the @samp{flags} register
42887 would be printed as:
42890 (gdb) info register flags
42891 flags 0x3 [ X LEVEL=high ]
42894 @node Standard Target Features
42895 @section Standard Target Features
42896 @cindex target descriptions, standard features
42898 A target description must contain either no registers or all the
42899 target's registers. If the description contains no registers, then
42900 @value{GDBN} will assume a default register layout, selected based on
42901 the architecture. If the description contains any registers, the
42902 default layout will not be used; the standard registers must be
42903 described in the target description, in such a way that @value{GDBN}
42904 can recognize them.
42906 This is accomplished by giving specific names to feature elements
42907 which contain standard registers. @value{GDBN} will look for features
42908 with those names and verify that they contain the expected registers;
42909 if any known feature is missing required registers, or if any required
42910 feature is missing, @value{GDBN} will reject the target
42911 description. You can add additional registers to any of the
42912 standard features --- @value{GDBN} will display them just as if
42913 they were added to an unrecognized feature.
42915 This section lists the known features and their expected contents.
42916 Sample XML documents for these features are included in the
42917 @value{GDBN} source tree, in the directory @file{gdb/features}.
42919 Names recognized by @value{GDBN} should include the name of the
42920 company or organization which selected the name, and the overall
42921 architecture to which the feature applies; so e.g.@: the feature
42922 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42924 The names of registers are not case sensitive for the purpose
42925 of recognizing standard features, but @value{GDBN} will only display
42926 registers using the capitalization used in the description.
42929 * AArch64 Features::
42933 * MicroBlaze Features::
42937 * Nios II Features::
42938 * OpenRISC 1000 Features::
42939 * PowerPC Features::
42940 * S/390 and System z Features::
42946 @node AArch64 Features
42947 @subsection AArch64 Features
42948 @cindex target descriptions, AArch64 features
42950 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42951 targets. It should contain registers @samp{x0} through @samp{x30},
42952 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42954 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42955 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42958 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
42959 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
42960 through @samp{p15}, @samp{ffr} and @samp{vg}.
42963 @subsection ARC Features
42964 @cindex target descriptions, ARC Features
42966 ARC processors are highly configurable, so even core registers and their number
42967 are not completely predetermined. In addition flags and PC registers which are
42968 important to @value{GDBN} are not ``core'' registers in ARC. It is required
42969 that one of the core registers features is present.
42970 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
42972 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
42973 targets with a normal register file. It should contain registers @samp{r0}
42974 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42975 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
42976 and any of extension core registers @samp{r32} through @samp{r59/acch}.
42977 @samp{ilink} and extension core registers are not available to read/write, when
42978 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
42980 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
42981 ARC HS targets with a reduced register file. It should contain registers
42982 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
42983 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
42984 This feature may contain register @samp{ilink} and any of extension core
42985 registers @samp{r32} through @samp{r59/acch}.
42987 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
42988 targets with a normal register file. It should contain registers @samp{r0}
42989 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
42990 @samp{lp_count} and @samp{pcl}. This feature may contain registers
42991 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
42992 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
42993 registers are not available when debugging GNU/Linux applications. The only
42994 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
42995 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
42996 ARC v2, but @samp{ilink2} is optional on ARCompact.
42998 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
42999 targets. It should contain registers @samp{pc} and @samp{status32}.
43002 @subsection ARM Features
43003 @cindex target descriptions, ARM features
43005 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43007 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43008 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43010 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43011 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43012 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43015 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43016 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43018 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43019 it should contain at least registers @samp{wR0} through @samp{wR15} and
43020 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43021 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43023 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43024 should contain at least registers @samp{d0} through @samp{d15}. If
43025 they are present, @samp{d16} through @samp{d31} should also be included.
43026 @value{GDBN} will synthesize the single-precision registers from
43027 halves of the double-precision registers.
43029 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43030 need to contain registers; it instructs @value{GDBN} to display the
43031 VFP double-precision registers as vectors and to synthesize the
43032 quad-precision registers from pairs of double-precision registers.
43033 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43034 be present and include 32 double-precision registers.
43036 @node i386 Features
43037 @subsection i386 Features
43038 @cindex target descriptions, i386 features
43040 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43041 targets. It should describe the following registers:
43045 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43047 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43049 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43050 @samp{fs}, @samp{gs}
43052 @samp{st0} through @samp{st7}
43054 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43055 @samp{foseg}, @samp{fooff} and @samp{fop}
43058 The register sets may be different, depending on the target.
43060 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43061 describe registers:
43065 @samp{xmm0} through @samp{xmm7} for i386
43067 @samp{xmm0} through @samp{xmm15} for amd64
43072 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43073 @samp{org.gnu.gdb.i386.sse} feature. It should
43074 describe the upper 128 bits of @sc{ymm} registers:
43078 @samp{ymm0h} through @samp{ymm7h} for i386
43080 @samp{ymm0h} through @samp{ymm15h} for amd64
43083 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43084 Memory Protection Extension (MPX). It should describe the following registers:
43088 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43090 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43093 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43094 describe a single register, @samp{orig_eax}.
43096 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43097 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43099 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43100 @samp{org.gnu.gdb.i386.avx} feature. It should
43101 describe additional @sc{xmm} registers:
43105 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43108 It should describe the upper 128 bits of additional @sc{ymm} registers:
43112 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43116 describe the upper 256 bits of @sc{zmm} registers:
43120 @samp{zmm0h} through @samp{zmm7h} for i386.
43122 @samp{zmm0h} through @samp{zmm15h} for amd64.
43126 describe the additional @sc{zmm} registers:
43130 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43133 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43134 describe a single register, @samp{pkru}. It is a 32-bit register
43135 valid for i386 and amd64.
43137 @node MicroBlaze Features
43138 @subsection MicroBlaze Features
43139 @cindex target descriptions, MicroBlaze features
43141 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43142 targets. It should contain registers @samp{r0} through @samp{r31},
43143 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43144 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43145 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43147 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43148 If present, it should contain registers @samp{rshr} and @samp{rslr}
43150 @node MIPS Features
43151 @subsection @acronym{MIPS} Features
43152 @cindex target descriptions, @acronym{MIPS} features
43154 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43155 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43156 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43159 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43160 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43161 registers. They may be 32-bit or 64-bit depending on the target.
43163 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43164 it may be optional in a future version of @value{GDBN}. It should
43165 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43166 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43168 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43169 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43170 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43171 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43173 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43174 contain a single register, @samp{restart}, which is used by the
43175 Linux kernel to control restartable syscalls.
43177 @node M68K Features
43178 @subsection M68K Features
43179 @cindex target descriptions, M68K features
43182 @item @samp{org.gnu.gdb.m68k.core}
43183 @itemx @samp{org.gnu.gdb.coldfire.core}
43184 @itemx @samp{org.gnu.gdb.fido.core}
43185 One of those features must be always present.
43186 The feature that is present determines which flavor of m68k is
43187 used. The feature that is present should contain registers
43188 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43189 @samp{sp}, @samp{ps} and @samp{pc}.
43191 @item @samp{org.gnu.gdb.coldfire.fp}
43192 This feature is optional. If present, it should contain registers
43193 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43197 @node NDS32 Features
43198 @subsection NDS32 Features
43199 @cindex target descriptions, NDS32 features
43201 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43202 targets. It should contain at least registers @samp{r0} through
43203 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43206 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43207 it should contain 64-bit double-precision floating-point registers
43208 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43209 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43211 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43212 registers are overlapped with the thirty-two 32-bit single-precision
43213 floating-point registers. The 32-bit single-precision registers, if
43214 not being listed explicitly, will be synthesized from halves of the
43215 overlapping 64-bit double-precision registers. Listing 32-bit
43216 single-precision registers explicitly is deprecated, and the
43217 support to it could be totally removed some day.
43219 @node Nios II Features
43220 @subsection Nios II Features
43221 @cindex target descriptions, Nios II features
43223 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43224 targets. It should contain the 32 core registers (@samp{zero},
43225 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43226 @samp{pc}, and the 16 control registers (@samp{status} through
43229 @node OpenRISC 1000 Features
43230 @subsection Openrisc 1000 Features
43231 @cindex target descriptions, OpenRISC 1000 features
43233 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43234 targets. It should contain the 32 general purpose registers (@samp{r0}
43235 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43237 @node PowerPC Features
43238 @subsection PowerPC Features
43239 @cindex target descriptions, PowerPC features
43241 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43242 targets. It should contain registers @samp{r0} through @samp{r31},
43243 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43244 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43246 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43247 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43249 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43250 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43253 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43254 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43255 will combine these registers with the floating point registers
43256 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43257 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43258 through @samp{vs63}, the set of vector registers for POWER7.
43260 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43261 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43262 @samp{spefscr}. SPE targets should provide 32-bit registers in
43263 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43264 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43265 these to present registers @samp{ev0} through @samp{ev31} to the
43268 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43269 contain the 64-bit register @samp{ppr}.
43271 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43272 contain the 64-bit register @samp{dscr}.
43274 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43275 contain the 64-bit register @samp{tar}.
43277 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43278 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43281 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43282 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43283 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43284 server PMU registers provided by @sc{gnu}/Linux.
43286 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43287 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43290 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43291 contain the checkpointed general-purpose registers @samp{cr0} through
43292 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43293 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43294 depending on the target. It should also contain the checkpointed
43295 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43298 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43299 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43300 through @samp{cf31}, as well as the checkpointed 64-bit register
43303 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43304 should contain the checkpointed altivec registers @samp{cvr0} through
43305 @samp{cvr31}, all 128-bit wide. It should also contain the
43306 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43309 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43310 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43311 will combine these registers with the checkpointed floating point
43312 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43313 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43314 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43315 @samp{cvs63}. Therefore, this feature requires both
43316 @samp{org.gnu.gdb.power.htm.altivec} and
43317 @samp{org.gnu.gdb.power.htm.fpu}.
43319 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43320 contain the 64-bit checkpointed register @samp{cppr}.
43322 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43323 contain the 64-bit checkpointed register @samp{cdscr}.
43325 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43326 contain the 64-bit checkpointed register @samp{ctar}.
43328 @node S/390 and System z Features
43329 @subsection S/390 and System z Features
43330 @cindex target descriptions, S/390 features
43331 @cindex target descriptions, System z features
43333 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43334 System z targets. It should contain the PSW and the 16 general
43335 registers. In particular, System z targets should provide the 64-bit
43336 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43337 S/390 targets should provide the 32-bit versions of these registers.
43338 A System z target that runs in 31-bit addressing mode should provide
43339 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43340 register's upper halves @samp{r0h} through @samp{r15h}, and their
43341 lower halves @samp{r0l} through @samp{r15l}.
43343 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43344 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43347 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43348 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43350 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43351 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43352 targets and 32-bit otherwise. In addition, the feature may contain
43353 the @samp{last_break} register, whose width depends on the addressing
43354 mode, as well as the @samp{system_call} register, which is always
43357 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43358 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43359 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43361 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43362 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43363 combined by @value{GDBN} with the floating point registers @samp{f0}
43364 through @samp{f15} to present the 128-bit wide vector registers
43365 @samp{v0} through @samp{v15}. In addition, this feature should
43366 contain the 128-bit wide vector registers @samp{v16} through
43369 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43370 the 64-bit wide guarded-storage-control registers @samp{gsd},
43371 @samp{gssm}, and @samp{gsepla}.
43373 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43374 the 64-bit wide guarded-storage broadcast control registers
43375 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43377 @node Sparc Features
43378 @subsection Sparc Features
43379 @cindex target descriptions, sparc32 features
43380 @cindex target descriptions, sparc64 features
43381 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43382 targets. It should describe the following registers:
43386 @samp{g0} through @samp{g7}
43388 @samp{o0} through @samp{o7}
43390 @samp{l0} through @samp{l7}
43392 @samp{i0} through @samp{i7}
43395 They may be 32-bit or 64-bit depending on the target.
43397 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43398 targets. It should describe the following registers:
43402 @samp{f0} through @samp{f31}
43404 @samp{f32} through @samp{f62} for sparc64
43407 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43408 targets. It should describe the following registers:
43412 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43413 @samp{fsr}, and @samp{csr} for sparc32
43415 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43419 @node TIC6x Features
43420 @subsection TMS320C6x Features
43421 @cindex target descriptions, TIC6x features
43422 @cindex target descriptions, TMS320C6x features
43423 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43424 targets. It should contain registers @samp{A0} through @samp{A15},
43425 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43427 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43428 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43429 through @samp{B31}.
43431 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43432 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43434 @node Operating System Information
43435 @appendix Operating System Information
43436 @cindex operating system information
43442 Users of @value{GDBN} often wish to obtain information about the state of
43443 the operating system running on the target---for example the list of
43444 processes, or the list of open files. This section describes the
43445 mechanism that makes it possible. This mechanism is similar to the
43446 target features mechanism (@pxref{Target Descriptions}), but focuses
43447 on a different aspect of target.
43449 Operating system information is retrived from the target via the
43450 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43451 read}). The object name in the request should be @samp{osdata}, and
43452 the @var{annex} identifies the data to be fetched.
43455 @appendixsection Process list
43456 @cindex operating system information, process list
43458 When requesting the process list, the @var{annex} field in the
43459 @samp{qXfer} request should be @samp{processes}. The returned data is
43460 an XML document. The formal syntax of this document is defined in
43461 @file{gdb/features/osdata.dtd}.
43463 An example document is:
43466 <?xml version="1.0"?>
43467 <!DOCTYPE target SYSTEM "osdata.dtd">
43468 <osdata type="processes">
43470 <column name="pid">1</column>
43471 <column name="user">root</column>
43472 <column name="command">/sbin/init</column>
43473 <column name="cores">1,2,3</column>
43478 Each item should include a column whose name is @samp{pid}. The value
43479 of that column should identify the process on the target. The
43480 @samp{user} and @samp{command} columns are optional, and will be
43481 displayed by @value{GDBN}. The @samp{cores} column, if present,
43482 should contain a comma-separated list of cores that this process
43483 is running on. Target may provide additional columns,
43484 which @value{GDBN} currently ignores.
43486 @node Trace File Format
43487 @appendix Trace File Format
43488 @cindex trace file format
43490 The trace file comes in three parts: a header, a textual description
43491 section, and a trace frame section with binary data.
43493 The header has the form @code{\x7fTRACE0\n}. The first byte is
43494 @code{0x7f} so as to indicate that the file contains binary data,
43495 while the @code{0} is a version number that may have different values
43498 The description section consists of multiple lines of @sc{ascii} text
43499 separated by newline characters (@code{0xa}). The lines may include a
43500 variety of optional descriptive or context-setting information, such
43501 as tracepoint definitions or register set size. @value{GDBN} will
43502 ignore any line that it does not recognize. An empty line marks the end
43507 Specifies the size of a register block in bytes. This is equal to the
43508 size of a @code{g} packet payload in the remote protocol. @var{size}
43509 is an ascii decimal number. There should be only one such line in
43510 a single trace file.
43512 @item status @var{status}
43513 Trace status. @var{status} has the same format as a @code{qTStatus}
43514 remote packet reply. There should be only one such line in a single trace
43517 @item tp @var{payload}
43518 Tracepoint definition. The @var{payload} has the same format as
43519 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43520 may take multiple lines of definition, corresponding to the multiple
43523 @item tsv @var{payload}
43524 Trace state variable definition. The @var{payload} has the same format as
43525 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43526 may take multiple lines of definition, corresponding to the multiple
43529 @item tdesc @var{payload}
43530 Target description in XML format. The @var{payload} is a single line of
43531 the XML file. All such lines should be concatenated together to get
43532 the original XML file. This file is in the same format as @code{qXfer}
43533 @code{features} payload, and corresponds to the main @code{target.xml}
43534 file. Includes are not allowed.
43538 The trace frame section consists of a number of consecutive frames.
43539 Each frame begins with a two-byte tracepoint number, followed by a
43540 four-byte size giving the amount of data in the frame. The data in
43541 the frame consists of a number of blocks, each introduced by a
43542 character indicating its type (at least register, memory, and trace
43543 state variable). The data in this section is raw binary, not a
43544 hexadecimal or other encoding; its endianness matches the target's
43547 @c FIXME bi-arch may require endianness/arch info in description section
43550 @item R @var{bytes}
43551 Register block. The number and ordering of bytes matches that of a
43552 @code{g} packet in the remote protocol. Note that these are the
43553 actual bytes, in target order, not a hexadecimal encoding.
43555 @item M @var{address} @var{length} @var{bytes}...
43556 Memory block. This is a contiguous block of memory, at the 8-byte
43557 address @var{address}, with a 2-byte length @var{length}, followed by
43558 @var{length} bytes.
43560 @item V @var{number} @var{value}
43561 Trace state variable block. This records the 8-byte signed value
43562 @var{value} of trace state variable numbered @var{number}.
43566 Future enhancements of the trace file format may include additional types
43569 @node Index Section Format
43570 @appendix @code{.gdb_index} section format
43571 @cindex .gdb_index section format
43572 @cindex index section format
43574 This section documents the index section that is created by @code{save
43575 gdb-index} (@pxref{Index Files}). The index section is
43576 DWARF-specific; some knowledge of DWARF is assumed in this
43579 The mapped index file format is designed to be directly
43580 @code{mmap}able on any architecture. In most cases, a datum is
43581 represented using a little-endian 32-bit integer value, called an
43582 @code{offset_type}. Big endian machines must byte-swap the values
43583 before using them. Exceptions to this rule are noted. The data is
43584 laid out such that alignment is always respected.
43586 A mapped index consists of several areas, laid out in order.
43590 The file header. This is a sequence of values, of @code{offset_type}
43591 unless otherwise noted:
43595 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43596 Version 4 uses a different hashing function from versions 5 and 6.
43597 Version 6 includes symbols for inlined functions, whereas versions 4
43598 and 5 do not. Version 7 adds attributes to the CU indices in the
43599 symbol table. Version 8 specifies that symbols from DWARF type units
43600 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43601 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43603 @value{GDBN} will only read version 4, 5, or 6 indices
43604 by specifying @code{set use-deprecated-index-sections on}.
43605 GDB has a workaround for potentially broken version 7 indices so it is
43606 currently not flagged as deprecated.
43609 The offset, from the start of the file, of the CU list.
43612 The offset, from the start of the file, of the types CU list. Note
43613 that this area can be empty, in which case this offset will be equal
43614 to the next offset.
43617 The offset, from the start of the file, of the address area.
43620 The offset, from the start of the file, of the symbol table.
43623 The offset, from the start of the file, of the constant pool.
43627 The CU list. This is a sequence of pairs of 64-bit little-endian
43628 values, sorted by the CU offset. The first element in each pair is
43629 the offset of a CU in the @code{.debug_info} section. The second
43630 element in each pair is the length of that CU. References to a CU
43631 elsewhere in the map are done using a CU index, which is just the
43632 0-based index into this table. Note that if there are type CUs, then
43633 conceptually CUs and type CUs form a single list for the purposes of
43637 The types CU list. This is a sequence of triplets of 64-bit
43638 little-endian values. In a triplet, the first value is the CU offset,
43639 the second value is the type offset in the CU, and the third value is
43640 the type signature. The types CU list is not sorted.
43643 The address area. The address area consists of a sequence of address
43644 entries. Each address entry has three elements:
43648 The low address. This is a 64-bit little-endian value.
43651 The high address. This is a 64-bit little-endian value. Like
43652 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43655 The CU index. This is an @code{offset_type} value.
43659 The symbol table. This is an open-addressed hash table. The size of
43660 the hash table is always a power of 2.
43662 Each slot in the hash table consists of a pair of @code{offset_type}
43663 values. The first value is the offset of the symbol's name in the
43664 constant pool. The second value is the offset of the CU vector in the
43667 If both values are 0, then this slot in the hash table is empty. This
43668 is ok because while 0 is a valid constant pool index, it cannot be a
43669 valid index for both a string and a CU vector.
43671 The hash value for a table entry is computed by applying an
43672 iterative hash function to the symbol's name. Starting with an
43673 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43674 the string is incorporated into the hash using the formula depending on the
43679 The formula is @code{r = r * 67 + c - 113}.
43681 @item Versions 5 to 7
43682 The formula is @code{r = r * 67 + tolower (c) - 113}.
43685 The terminating @samp{\0} is not incorporated into the hash.
43687 The step size used in the hash table is computed via
43688 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43689 value, and @samp{size} is the size of the hash table. The step size
43690 is used to find the next candidate slot when handling a hash
43693 The names of C@t{++} symbols in the hash table are canonicalized. We
43694 don't currently have a simple description of the canonicalization
43695 algorithm; if you intend to create new index sections, you must read
43699 The constant pool. This is simply a bunch of bytes. It is organized
43700 so that alignment is correct: CU vectors are stored first, followed by
43703 A CU vector in the constant pool is a sequence of @code{offset_type}
43704 values. The first value is the number of CU indices in the vector.
43705 Each subsequent value is the index and symbol attributes of a CU in
43706 the CU list. This element in the hash table is used to indicate which
43707 CUs define the symbol and how the symbol is used.
43708 See below for the format of each CU index+attributes entry.
43710 A string in the constant pool is zero-terminated.
43713 Attributes were added to CU index values in @code{.gdb_index} version 7.
43714 If a symbol has multiple uses within a CU then there is one
43715 CU index+attributes value for each use.
43717 The format of each CU index+attributes entry is as follows
43723 This is the index of the CU in the CU list.
43725 These bits are reserved for future purposes and must be zero.
43727 The kind of the symbol in the CU.
43731 This value is reserved and should not be used.
43732 By reserving zero the full @code{offset_type} value is backwards compatible
43733 with previous versions of the index.
43735 The symbol is a type.
43737 The symbol is a variable or an enum value.
43739 The symbol is a function.
43741 Any other kind of symbol.
43743 These values are reserved.
43747 This bit is zero if the value is global and one if it is static.
43749 The determination of whether a symbol is global or static is complicated.
43750 The authorative reference is the file @file{dwarf2read.c} in
43751 @value{GDBN} sources.
43755 This pseudo-code describes the computation of a symbol's kind and
43756 global/static attributes in the index.
43759 is_external = get_attribute (die, DW_AT_external);
43760 language = get_attribute (cu_die, DW_AT_language);
43763 case DW_TAG_typedef:
43764 case DW_TAG_base_type:
43765 case DW_TAG_subrange_type:
43769 case DW_TAG_enumerator:
43771 is_static = language != CPLUS;
43773 case DW_TAG_subprogram:
43775 is_static = ! (is_external || language == ADA);
43777 case DW_TAG_constant:
43779 is_static = ! is_external;
43781 case DW_TAG_variable:
43783 is_static = ! is_external;
43785 case DW_TAG_namespace:
43789 case DW_TAG_class_type:
43790 case DW_TAG_interface_type:
43791 case DW_TAG_structure_type:
43792 case DW_TAG_union_type:
43793 case DW_TAG_enumeration_type:
43795 is_static = language != CPLUS;
43803 @appendix Manual pages
43807 * gdb man:: The GNU Debugger man page
43808 * gdbserver man:: Remote Server for the GNU Debugger man page
43809 * gcore man:: Generate a core file of a running program
43810 * gdbinit man:: gdbinit scripts
43811 * gdb-add-index man:: Add index files to speed up GDB
43817 @c man title gdb The GNU Debugger
43819 @c man begin SYNOPSIS gdb
43820 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43821 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43822 [@option{-b}@w{ }@var{bps}]
43823 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43824 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43825 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43826 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43827 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43830 @c man begin DESCRIPTION gdb
43831 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43832 going on ``inside'' another program while it executes -- or what another
43833 program was doing at the moment it crashed.
43835 @value{GDBN} can do four main kinds of things (plus other things in support of
43836 these) to help you catch bugs in the act:
43840 Start your program, specifying anything that might affect its behavior.
43843 Make your program stop on specified conditions.
43846 Examine what has happened, when your program has stopped.
43849 Change things in your program, so you can experiment with correcting the
43850 effects of one bug and go on to learn about another.
43853 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43856 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43857 commands from the terminal until you tell it to exit with the @value{GDBN}
43858 command @code{quit}. You can get online help from @value{GDBN} itself
43859 by using the command @code{help}.
43861 You can run @code{gdb} with no arguments or options; but the most
43862 usual way to start @value{GDBN} is with one argument or two, specifying an
43863 executable program as the argument:
43869 You can also start with both an executable program and a core file specified:
43875 You can, instead, specify a process ID as a second argument, if you want
43876 to debug a running process:
43884 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43885 named @file{1234}; @value{GDBN} does check for a core file first).
43886 With option @option{-p} you can omit the @var{program} filename.
43888 Here are some of the most frequently needed @value{GDBN} commands:
43890 @c pod2man highlights the right hand side of the @item lines.
43892 @item break [@var{file}:]@var{function}
43893 Set a breakpoint at @var{function} (in @var{file}).
43895 @item run [@var{arglist}]
43896 Start your program (with @var{arglist}, if specified).
43899 Backtrace: display the program stack.
43901 @item print @var{expr}
43902 Display the value of an expression.
43905 Continue running your program (after stopping, e.g. at a breakpoint).
43908 Execute next program line (after stopping); step @emph{over} any
43909 function calls in the line.
43911 @item edit [@var{file}:]@var{function}
43912 look at the program line where it is presently stopped.
43914 @item list [@var{file}:]@var{function}
43915 type the text of the program in the vicinity of where it is presently stopped.
43918 Execute next program line (after stopping); step @emph{into} any
43919 function calls in the line.
43921 @item help [@var{name}]
43922 Show information about @value{GDBN} command @var{name}, or general information
43923 about using @value{GDBN}.
43926 Exit from @value{GDBN}.
43930 For full details on @value{GDBN},
43931 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43932 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43933 as the @code{gdb} entry in the @code{info} program.
43937 @c man begin OPTIONS gdb
43938 Any arguments other than options specify an executable
43939 file and core file (or process ID); that is, the first argument
43940 encountered with no
43941 associated option flag is equivalent to a @option{-se} option, and the second,
43942 if any, is equivalent to a @option{-c} option if it's the name of a file.
43944 both long and short forms; both are shown here. The long forms are also
43945 recognized if you truncate them, so long as enough of the option is
43946 present to be unambiguous. (If you prefer, you can flag option
43947 arguments with @option{+} rather than @option{-}, though we illustrate the
43948 more usual convention.)
43950 All the options and command line arguments you give are processed
43951 in sequential order. The order makes a difference when the @option{-x}
43957 List all options, with brief explanations.
43959 @item -symbols=@var{file}
43960 @itemx -s @var{file}
43961 Read symbol table from file @var{file}.
43964 Enable writing into executable and core files.
43966 @item -exec=@var{file}
43967 @itemx -e @var{file}
43968 Use file @var{file} as the executable file to execute when
43969 appropriate, and for examining pure data in conjunction with a core
43972 @item -se=@var{file}
43973 Read symbol table from file @var{file} and use it as the executable
43976 @item -core=@var{file}
43977 @itemx -c @var{file}
43978 Use file @var{file} as a core dump to examine.
43980 @item -command=@var{file}
43981 @itemx -x @var{file}
43982 Execute @value{GDBN} commands from file @var{file}.
43984 @item -ex @var{command}
43985 Execute given @value{GDBN} @var{command}.
43987 @item -directory=@var{directory}
43988 @itemx -d @var{directory}
43989 Add @var{directory} to the path to search for source files.
43992 Do not execute commands from @file{~/.gdbinit}.
43996 Do not execute commands from any @file{.gdbinit} initialization files.
44000 ``Quiet''. Do not print the introductory and copyright messages. These
44001 messages are also suppressed in batch mode.
44004 Run in batch mode. Exit with status @code{0} after processing all the command
44005 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44006 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44007 commands in the command files.
44009 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44010 download and run a program on another computer; in order to make this
44011 more useful, the message
44014 Program exited normally.
44018 (which is ordinarily issued whenever a program running under @value{GDBN} control
44019 terminates) is not issued when running in batch mode.
44021 @item -cd=@var{directory}
44022 Run @value{GDBN} using @var{directory} as its working directory,
44023 instead of the current directory.
44027 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44028 @value{GDBN} to output the full file name and line number in a standard,
44029 recognizable fashion each time a stack frame is displayed (which
44030 includes each time the program stops). This recognizable format looks
44031 like two @samp{\032} characters, followed by the file name, line number
44032 and character position separated by colons, and a newline. The
44033 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44034 characters as a signal to display the source code for the frame.
44037 Set the line speed (baud rate or bits per second) of any serial
44038 interface used by @value{GDBN} for remote debugging.
44040 @item -tty=@var{device}
44041 Run using @var{device} for your program's standard input and output.
44045 @c man begin SEEALSO gdb
44047 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44048 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44049 documentation are properly installed at your site, the command
44056 should give you access to the complete manual.
44058 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44059 Richard M. Stallman and Roland H. Pesch, July 1991.
44063 @node gdbserver man
44064 @heading gdbserver man
44066 @c man title gdbserver Remote Server for the GNU Debugger
44068 @c man begin SYNOPSIS gdbserver
44069 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44071 gdbserver --attach @var{comm} @var{pid}
44073 gdbserver --multi @var{comm}
44077 @c man begin DESCRIPTION gdbserver
44078 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44079 than the one which is running the program being debugged.
44082 @subheading Usage (server (target) side)
44085 Usage (server (target) side):
44088 First, you need to have a copy of the program you want to debug put onto
44089 the target system. The program can be stripped to save space if needed, as
44090 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44091 the @value{GDBN} running on the host system.
44093 To use the server, you log on to the target system, and run the @command{gdbserver}
44094 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44095 your program, and (c) its arguments. The general syntax is:
44098 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44101 For example, using a serial port, you might say:
44105 @c @file would wrap it as F</dev/com1>.
44106 target> gdbserver /dev/com1 emacs foo.txt
44109 target> gdbserver @file{/dev/com1} emacs foo.txt
44113 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44114 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44115 waits patiently for the host @value{GDBN} to communicate with it.
44117 To use a TCP connection, you could say:
44120 target> gdbserver host:2345 emacs foo.txt
44123 This says pretty much the same thing as the last example, except that we are
44124 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44125 that we are expecting to see a TCP connection from @code{host} to local TCP port
44126 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44127 want for the port number as long as it does not conflict with any existing TCP
44128 ports on the target system. This same port number must be used in the host
44129 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44130 you chose a port number that conflicts with another service, @command{gdbserver} will
44131 print an error message and exit.
44133 @command{gdbserver} can also attach to running programs.
44134 This is accomplished via the @option{--attach} argument. The syntax is:
44137 target> gdbserver --attach @var{comm} @var{pid}
44140 @var{pid} is the process ID of a currently running process. It isn't
44141 necessary to point @command{gdbserver} at a binary for the running process.
44143 To start @code{gdbserver} without supplying an initial command to run
44144 or process ID to attach, use the @option{--multi} command line option.
44145 In such case you should connect using @kbd{target extended-remote} to start
44146 the program you want to debug.
44149 target> gdbserver --multi @var{comm}
44153 @subheading Usage (host side)
44159 You need an unstripped copy of the target program on your host system, since
44160 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44161 would, with the target program as the first argument. (You may need to use the
44162 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44163 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44164 new command you need to know about is @code{target remote}
44165 (or @code{target extended-remote}). Its argument is either
44166 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44167 descriptor. For example:
44171 @c @file would wrap it as F</dev/ttyb>.
44172 (gdb) target remote /dev/ttyb
44175 (gdb) target remote @file{/dev/ttyb}
44180 communicates with the server via serial line @file{/dev/ttyb}, and:
44183 (gdb) target remote the-target:2345
44187 communicates via a TCP connection to port 2345 on host `the-target', where
44188 you previously started up @command{gdbserver} with the same port number. Note that for
44189 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44190 command, otherwise you may get an error that looks something like
44191 `Connection refused'.
44193 @command{gdbserver} can also debug multiple inferiors at once,
44196 the @value{GDBN} manual in node @code{Inferiors and Programs}
44197 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44200 @ref{Inferiors and Programs}.
44202 In such case use the @code{extended-remote} @value{GDBN} command variant:
44205 (gdb) target extended-remote the-target:2345
44208 The @command{gdbserver} option @option{--multi} may or may not be used in such
44212 @c man begin OPTIONS gdbserver
44213 There are three different modes for invoking @command{gdbserver}:
44218 Debug a specific program specified by its program name:
44221 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44224 The @var{comm} parameter specifies how should the server communicate
44225 with @value{GDBN}; it is either a device name (to use a serial line),
44226 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44227 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44228 debug in @var{prog}. Any remaining arguments will be passed to the
44229 program verbatim. When the program exits, @value{GDBN} will close the
44230 connection, and @code{gdbserver} will exit.
44233 Debug a specific program by specifying the process ID of a running
44237 gdbserver --attach @var{comm} @var{pid}
44240 The @var{comm} parameter is as described above. Supply the process ID
44241 of a running program in @var{pid}; @value{GDBN} will do everything
44242 else. Like with the previous mode, when the process @var{pid} exits,
44243 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44246 Multi-process mode -- debug more than one program/process:
44249 gdbserver --multi @var{comm}
44252 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44253 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44254 close the connection when a process being debugged exits, so you can
44255 debug several processes in the same session.
44258 In each of the modes you may specify these options:
44263 List all options, with brief explanations.
44266 This option causes @command{gdbserver} to print its version number and exit.
44269 @command{gdbserver} will attach to a running program. The syntax is:
44272 target> gdbserver --attach @var{comm} @var{pid}
44275 @var{pid} is the process ID of a currently running process. It isn't
44276 necessary to point @command{gdbserver} at a binary for the running process.
44279 To start @code{gdbserver} without supplying an initial command to run
44280 or process ID to attach, use this command line option.
44281 Then you can connect using @kbd{target extended-remote} and start
44282 the program you want to debug. The syntax is:
44285 target> gdbserver --multi @var{comm}
44289 Instruct @code{gdbserver} to display extra status information about the debugging
44291 This option is intended for @code{gdbserver} development and for bug reports to
44294 @item --remote-debug
44295 Instruct @code{gdbserver} to display remote protocol debug output.
44296 This option is intended for @code{gdbserver} development and for bug reports to
44299 @item --debug-format=option1@r{[},option2,...@r{]}
44300 Instruct @code{gdbserver} to include extra information in each line
44301 of debugging output.
44302 @xref{Other Command-Line Arguments for gdbserver}.
44305 Specify a wrapper to launch programs
44306 for debugging. The option should be followed by the name of the
44307 wrapper, then any command-line arguments to pass to the wrapper, then
44308 @kbd{--} indicating the end of the wrapper arguments.
44311 By default, @command{gdbserver} keeps the listening TCP port open, so that
44312 additional connections are possible. However, if you start @code{gdbserver}
44313 with the @option{--once} option, it will stop listening for any further
44314 connection attempts after connecting to the first @value{GDBN} session.
44316 @c --disable-packet is not documented for users.
44318 @c --disable-randomization and --no-disable-randomization are superseded by
44319 @c QDisableRandomization.
44324 @c man begin SEEALSO gdbserver
44326 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44327 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44328 documentation are properly installed at your site, the command
44334 should give you access to the complete manual.
44336 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44337 Richard M. Stallman and Roland H. Pesch, July 1991.
44344 @c man title gcore Generate a core file of a running program
44347 @c man begin SYNOPSIS gcore
44348 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44352 @c man begin DESCRIPTION gcore
44353 Generate core dumps of one or more running programs with process IDs
44354 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44355 is equivalent to one produced by the kernel when the process crashes
44356 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44357 limit). However, unlike after a crash, after @command{gcore} finishes
44358 its job the program remains running without any change.
44361 @c man begin OPTIONS gcore
44364 Dump all memory mappings. The actual effect of this option depends on
44365 the Operating System. On @sc{gnu}/Linux, it will disable
44366 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44367 enable @code{dump-excluded-mappings} (@pxref{set
44368 dump-excluded-mappings}).
44370 @item -o @var{prefix}
44371 The optional argument @var{prefix} specifies the prefix to be used
44372 when composing the file names of the core dumps. The file name is
44373 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44374 process ID of the running program being analyzed by @command{gcore}.
44375 If not specified, @var{prefix} defaults to @var{gcore}.
44379 @c man begin SEEALSO gcore
44381 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44382 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44383 documentation are properly installed at your site, the command
44390 should give you access to the complete manual.
44392 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44393 Richard M. Stallman and Roland H. Pesch, July 1991.
44400 @c man title gdbinit GDB initialization scripts
44403 @c man begin SYNOPSIS gdbinit
44404 @ifset SYSTEM_GDBINIT
44405 @value{SYSTEM_GDBINIT}
44414 @c man begin DESCRIPTION gdbinit
44415 These files contain @value{GDBN} commands to automatically execute during
44416 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44419 the @value{GDBN} manual in node @code{Sequences}
44420 -- shell command @code{info -f gdb -n Sequences}.
44426 Please read more in
44428 the @value{GDBN} manual in node @code{Startup}
44429 -- shell command @code{info -f gdb -n Startup}.
44436 @ifset SYSTEM_GDBINIT
44437 @item @value{SYSTEM_GDBINIT}
44439 @ifclear SYSTEM_GDBINIT
44440 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44442 System-wide initialization file. It is executed unless user specified
44443 @value{GDBN} option @code{-nx} or @code{-n}.
44446 the @value{GDBN} manual in node @code{System-wide configuration}
44447 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44450 @ref{System-wide configuration}.
44454 User initialization file. It is executed unless user specified
44455 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44458 Initialization file for current directory. It may need to be enabled with
44459 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44462 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44463 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44466 @ref{Init File in the Current Directory}.
44471 @c man begin SEEALSO gdbinit
44473 gdb(1), @code{info -f gdb -n Startup}
44475 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44476 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44477 documentation are properly installed at your site, the command
44483 should give you access to the complete manual.
44485 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44486 Richard M. Stallman and Roland H. Pesch, July 1991.
44490 @node gdb-add-index man
44491 @heading gdb-add-index
44492 @pindex gdb-add-index
44493 @anchor{gdb-add-index}
44495 @c man title gdb-add-index Add index files to speed up GDB
44497 @c man begin SYNOPSIS gdb-add-index
44498 gdb-add-index @var{filename}
44501 @c man begin DESCRIPTION gdb-add-index
44502 When @value{GDBN} finds a symbol file, it scans the symbols in the
44503 file in order to construct an internal symbol table. This lets most
44504 @value{GDBN} operations work quickly--at the cost of a delay early on.
44505 For large programs, this delay can be quite lengthy, so @value{GDBN}
44506 provides a way to build an index, which speeds up startup.
44508 To determine whether a file contains such an index, use the command
44509 @kbd{readelf -S filename}: the index is stored in a section named
44510 @code{.gdb_index}. The index file can only be produced on systems
44511 which use ELF binaries and DWARF debug information (i.e., sections
44512 named @code{.debug_*}).
44514 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44515 in the @env{PATH} environment variable. If you want to use different
44516 versions of these programs, you can specify them through the
44517 @env{GDB} and @env{OBJDUMP} environment variables.
44521 the @value{GDBN} manual in node @code{Index Files}
44522 -- shell command @kbd{info -f gdb -n "Index Files"}.
44529 @c man begin SEEALSO gdb-add-index
44531 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44532 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44533 documentation are properly installed at your site, the command
44539 should give you access to the complete manual.
44541 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44542 Richard M. Stallman and Roland H. Pesch, July 1991.
44548 @node GNU Free Documentation License
44549 @appendix GNU Free Documentation License
44552 @node Concept Index
44553 @unnumbered Concept Index
44557 @node Command and Variable Index
44558 @unnumbered Command, Variable, and Function Index
44563 % I think something like @@colophon should be in texinfo. In the
44565 \long\def\colophon{\hbox to0pt{}\vfill
44566 \centerline{The body of this manual is set in}
44567 \centerline{\fontname\tenrm,}
44568 \centerline{with headings in {\bf\fontname\tenbf}}
44569 \centerline{and examples in {\tt\fontname\tentt}.}
44570 \centerline{{\it\fontname\tenit\/},}
44571 \centerline{{\bf\fontname\tenbf}, and}
44572 \centerline{{\sl\fontname\tensl\/}}
44573 \centerline{are used for emphasis.}\vfill}
44575 % Blame: doc@@cygnus.com, 1991.