1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2019 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{} 1988-2019 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) 1988-2019 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=mi3}) causes
1272 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} version 3 (@pxref{GDB/MI, ,
1273 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 9.1. @sc{gdb/mi}
1274 version 2 (@code{mi2}), included in @value{GDBN} 6.0 and version 1 (@code{mi1}),
1275 included in @value{GDBN} 5.3, are also available. Earlier @sc{gdb/mi}
1276 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 In programs using different languages, @value{GDBN} chooses the syntax
3877 to print the list of all breakpoints it sets according to the
3878 @samp{set language} value: using @samp{set language auto}
3879 (see @ref{Automatically, ,Set Language Automatically}) means to use the
3880 language of the breakpoint's function, other values mean to use
3881 the manually specified language (see @ref{Manually, ,Set Language Manually}).
3883 The syntax of the regular expression is the standard one used with tools
3884 like @file{grep}. Note that this is different from the syntax used by
3885 shells, so for instance @code{foo*} matches all functions that include
3886 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3887 @code{.*} leading and trailing the regular expression you supply, so to
3888 match only functions that begin with @code{foo}, use @code{^foo}.
3890 @cindex non-member C@t{++} functions, set breakpoint in
3891 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3892 breakpoints on overloaded functions that are not members of any special
3895 @cindex set breakpoints on all functions
3896 The @code{rbreak} command can be used to set breakpoints in
3897 @strong{all} the functions in a program, like this:
3900 (@value{GDBP}) rbreak .
3903 @item rbreak @var{file}:@var{regex}
3904 If @code{rbreak} is called with a filename qualification, it limits
3905 the search for functions matching the given regular expression to the
3906 specified @var{file}. This can be used, for example, to set breakpoints on
3907 every function in a given file:
3910 (@value{GDBP}) rbreak file.c:.
3913 The colon separating the filename qualifier from the regex may
3914 optionally be surrounded by spaces.
3916 @kindex info breakpoints
3917 @cindex @code{$_} and @code{info breakpoints}
3918 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3919 @itemx info break @r{[}@var{list}@dots{}@r{]}
3920 Print a table of all breakpoints, watchpoints, and catchpoints set and
3921 not deleted. Optional argument @var{n} means print information only
3922 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3923 For each breakpoint, following columns are printed:
3926 @item Breakpoint Numbers
3928 Breakpoint, watchpoint, or catchpoint.
3930 Whether the breakpoint is marked to be disabled or deleted when hit.
3931 @item Enabled or Disabled
3932 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3933 that are not enabled.
3935 Where the breakpoint is in your program, as a memory address. For a
3936 pending breakpoint whose address is not yet known, this field will
3937 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3938 library that has the symbol or line referred by breakpoint is loaded.
3939 See below for details. A breakpoint with several locations will
3940 have @samp{<MULTIPLE>} in this field---see below for details.
3942 Where the breakpoint is in the source for your program, as a file and
3943 line number. For a pending breakpoint, the original string passed to
3944 the breakpoint command will be listed as it cannot be resolved until
3945 the appropriate shared library is loaded in the future.
3949 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3950 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3951 @value{GDBN} on the host's side. If it is ``target'', then the condition
3952 is evaluated by the target. The @code{info break} command shows
3953 the condition on the line following the affected breakpoint, together with
3954 its condition evaluation mode in between parentheses.
3956 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3957 allowed to have a condition specified for it. The condition is not parsed for
3958 validity until a shared library is loaded that allows the pending
3959 breakpoint to resolve to a valid location.
3962 @code{info break} with a breakpoint
3963 number @var{n} as argument lists only that breakpoint. The
3964 convenience variable @code{$_} and the default examining-address for
3965 the @code{x} command are set to the address of the last breakpoint
3966 listed (@pxref{Memory, ,Examining Memory}).
3969 @code{info break} displays a count of the number of times the breakpoint
3970 has been hit. This is especially useful in conjunction with the
3971 @code{ignore} command. You can ignore a large number of breakpoint
3972 hits, look at the breakpoint info to see how many times the breakpoint
3973 was hit, and then run again, ignoring one less than that number. This
3974 will get you quickly to the last hit of that breakpoint.
3977 For a breakpoints with an enable count (xref) greater than 1,
3978 @code{info break} also displays that count.
3982 @value{GDBN} allows you to set any number of breakpoints at the same place in
3983 your program. There is nothing silly or meaningless about this. When
3984 the breakpoints are conditional, this is even useful
3985 (@pxref{Conditions, ,Break Conditions}).
3987 @cindex multiple locations, breakpoints
3988 @cindex breakpoints, multiple locations
3989 It is possible that a breakpoint corresponds to several locations
3990 in your program. Examples of this situation are:
3994 Multiple functions in the program may have the same name.
3997 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3998 instances of the function body, used in different cases.
4001 For a C@t{++} template function, a given line in the function can
4002 correspond to any number of instantiations.
4005 For an inlined function, a given source line can correspond to
4006 several places where that function is inlined.
4009 In all those cases, @value{GDBN} will insert a breakpoint at all
4010 the relevant locations.
4012 A breakpoint with multiple locations is displayed in the breakpoint
4013 table using several rows---one header row, followed by one row for
4014 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
4015 address column. The rows for individual locations contain the actual
4016 addresses for locations, and show the functions to which those
4017 locations belong. The number column for a location is of the form
4018 @var{breakpoint-number}.@var{location-number}.
4023 Num Type Disp Enb Address What
4024 1 breakpoint keep y <MULTIPLE>
4026 breakpoint already hit 1 time
4027 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
4028 1.2 y 0x080486ca in void foo<double>() at t.cc:8
4031 You cannot delete the individual locations from a breakpoint. However,
4032 each location can be individually enabled or disabled by passing
4033 @var{breakpoint-number}.@var{location-number} as argument to the
4034 @code{enable} and @code{disable} commands. It's also possible to
4035 @code{enable} and @code{disable} a range of @var{location-number}
4036 locations using a @var{breakpoint-number} and two @var{location-number}s,
4037 in increasing order, separated by a hyphen, like
4038 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
4039 in which case @value{GDBN} acts on all the locations in the range (inclusive).
4040 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
4041 all of the locations that belong to that breakpoint.
4043 @cindex pending breakpoints
4044 It's quite common to have a breakpoint inside a shared library.
4045 Shared libraries can be loaded and unloaded explicitly,
4046 and possibly repeatedly, as the program is executed. To support
4047 this use case, @value{GDBN} updates breakpoint locations whenever
4048 any shared library is loaded or unloaded. Typically, you would
4049 set a breakpoint in a shared library at the beginning of your
4050 debugging session, when the library is not loaded, and when the
4051 symbols from the library are not available. When you try to set
4052 breakpoint, @value{GDBN} will ask you if you want to set
4053 a so called @dfn{pending breakpoint}---breakpoint whose address
4054 is not yet resolved.
4056 After the program is run, whenever a new shared library is loaded,
4057 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
4058 shared library contains the symbol or line referred to by some
4059 pending breakpoint, that breakpoint is resolved and becomes an
4060 ordinary breakpoint. When a library is unloaded, all breakpoints
4061 that refer to its symbols or source lines become pending again.
4063 This logic works for breakpoints with multiple locations, too. For
4064 example, if you have a breakpoint in a C@t{++} template function, and
4065 a newly loaded shared library has an instantiation of that template,
4066 a new location is added to the list of locations for the breakpoint.
4068 Except for having unresolved address, pending breakpoints do not
4069 differ from regular breakpoints. You can set conditions or commands,
4070 enable and disable them and perform other breakpoint operations.
4072 @value{GDBN} provides some additional commands for controlling what
4073 happens when the @samp{break} command cannot resolve breakpoint
4074 address specification to an address:
4076 @kindex set breakpoint pending
4077 @kindex show breakpoint pending
4079 @item set breakpoint pending auto
4080 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4081 location, it queries you whether a pending breakpoint should be created.
4083 @item set breakpoint pending on
4084 This indicates that an unrecognized breakpoint location should automatically
4085 result in a pending breakpoint being created.
4087 @item set breakpoint pending off
4088 This indicates that pending breakpoints are not to be created. Any
4089 unrecognized breakpoint location results in an error. This setting does
4090 not affect any pending breakpoints previously created.
4092 @item show breakpoint pending
4093 Show the current behavior setting for creating pending breakpoints.
4096 The settings above only affect the @code{break} command and its
4097 variants. Once breakpoint is set, it will be automatically updated
4098 as shared libraries are loaded and unloaded.
4100 @cindex automatic hardware breakpoints
4101 For some targets, @value{GDBN} can automatically decide if hardware or
4102 software breakpoints should be used, depending on whether the
4103 breakpoint address is read-only or read-write. This applies to
4104 breakpoints set with the @code{break} command as well as to internal
4105 breakpoints set by commands like @code{next} and @code{finish}. For
4106 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4109 You can control this automatic behaviour with the following commands:
4111 @kindex set breakpoint auto-hw
4112 @kindex show breakpoint auto-hw
4114 @item set breakpoint auto-hw on
4115 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4116 will try to use the target memory map to decide if software or hardware
4117 breakpoint must be used.
4119 @item set breakpoint auto-hw off
4120 This indicates @value{GDBN} should not automatically select breakpoint
4121 type. If the target provides a memory map, @value{GDBN} will warn when
4122 trying to set software breakpoint at a read-only address.
4125 @value{GDBN} normally implements breakpoints by replacing the program code
4126 at the breakpoint address with a special instruction, which, when
4127 executed, given control to the debugger. By default, the program
4128 code is so modified only when the program is resumed. As soon as
4129 the program stops, @value{GDBN} restores the original instructions. This
4130 behaviour guards against leaving breakpoints inserted in the
4131 target should gdb abrubptly disconnect. However, with slow remote
4132 targets, inserting and removing breakpoint can reduce the performance.
4133 This behavior can be controlled with the following commands::
4135 @kindex set breakpoint always-inserted
4136 @kindex show breakpoint always-inserted
4138 @item set breakpoint always-inserted off
4139 All breakpoints, including newly added by the user, are inserted in
4140 the target only when the target is resumed. All breakpoints are
4141 removed from the target when it stops. This is the default mode.
4143 @item set breakpoint always-inserted on
4144 Causes all breakpoints to be inserted in the target at all times. If
4145 the user adds a new breakpoint, or changes an existing breakpoint, the
4146 breakpoints in the target are updated immediately. A breakpoint is
4147 removed from the target only when breakpoint itself is deleted.
4150 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4151 when a breakpoint breaks. If the condition is true, then the process being
4152 debugged stops, otherwise the process is resumed.
4154 If the target supports evaluating conditions on its end, @value{GDBN} may
4155 download the breakpoint, together with its conditions, to it.
4157 This feature can be controlled via the following commands:
4159 @kindex set breakpoint condition-evaluation
4160 @kindex show breakpoint condition-evaluation
4162 @item set breakpoint condition-evaluation host
4163 This option commands @value{GDBN} to evaluate the breakpoint
4164 conditions on the host's side. Unconditional breakpoints are sent to
4165 the target which in turn receives the triggers and reports them back to GDB
4166 for condition evaluation. This is the standard evaluation mode.
4168 @item set breakpoint condition-evaluation target
4169 This option commands @value{GDBN} to download breakpoint conditions
4170 to the target at the moment of their insertion. The target
4171 is responsible for evaluating the conditional expression and reporting
4172 breakpoint stop events back to @value{GDBN} whenever the condition
4173 is true. Due to limitations of target-side evaluation, some conditions
4174 cannot be evaluated there, e.g., conditions that depend on local data
4175 that is only known to the host. Examples include
4176 conditional expressions involving convenience variables, complex types
4177 that cannot be handled by the agent expression parser and expressions
4178 that are too long to be sent over to the target, specially when the
4179 target is a remote system. In these cases, the conditions will be
4180 evaluated by @value{GDBN}.
4182 @item set breakpoint condition-evaluation auto
4183 This is the default mode. If the target supports evaluating breakpoint
4184 conditions on its end, @value{GDBN} will download breakpoint conditions to
4185 the target (limitations mentioned previously apply). If the target does
4186 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4187 to evaluating all these conditions on the host's side.
4191 @cindex negative breakpoint numbers
4192 @cindex internal @value{GDBN} breakpoints
4193 @value{GDBN} itself sometimes sets breakpoints in your program for
4194 special purposes, such as proper handling of @code{longjmp} (in C
4195 programs). These internal breakpoints are assigned negative numbers,
4196 starting with @code{-1}; @samp{info breakpoints} does not display them.
4197 You can see these breakpoints with the @value{GDBN} maintenance command
4198 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4201 @node Set Watchpoints
4202 @subsection Setting Watchpoints
4204 @cindex setting watchpoints
4205 You can use a watchpoint to stop execution whenever the value of an
4206 expression changes, without having to predict a particular place where
4207 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4208 The expression may be as simple as the value of a single variable, or
4209 as complex as many variables combined by operators. Examples include:
4213 A reference to the value of a single variable.
4216 An address cast to an appropriate data type. For example,
4217 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4218 address (assuming an @code{int} occupies 4 bytes).
4221 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4222 expression can use any operators valid in the program's native
4223 language (@pxref{Languages}).
4226 You can set a watchpoint on an expression even if the expression can
4227 not be evaluated yet. For instance, you can set a watchpoint on
4228 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4229 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4230 the expression produces a valid value. If the expression becomes
4231 valid in some other way than changing a variable (e.g.@: if the memory
4232 pointed to by @samp{*global_ptr} becomes readable as the result of a
4233 @code{malloc} call), @value{GDBN} may not stop until the next time
4234 the expression changes.
4236 @cindex software watchpoints
4237 @cindex hardware watchpoints
4238 Depending on your system, watchpoints may be implemented in software or
4239 hardware. @value{GDBN} does software watchpointing by single-stepping your
4240 program and testing the variable's value each time, which is hundreds of
4241 times slower than normal execution. (But this may still be worth it, to
4242 catch errors where you have no clue what part of your program is the
4245 On some systems, such as most PowerPC or x86-based targets,
4246 @value{GDBN} includes support for hardware watchpoints, which do not
4247 slow down the running of your program.
4251 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4252 Set a watchpoint for an expression. @value{GDBN} will break when the
4253 expression @var{expr} is written into by the program and its value
4254 changes. The simplest (and the most popular) use of this command is
4255 to watch the value of a single variable:
4258 (@value{GDBP}) watch foo
4261 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4262 argument, @value{GDBN} breaks only when the thread identified by
4263 @var{thread-id} changes the value of @var{expr}. If any other threads
4264 change the value of @var{expr}, @value{GDBN} will not break. Note
4265 that watchpoints restricted to a single thread in this way only work
4266 with Hardware Watchpoints.
4268 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4269 (see below). The @code{-location} argument tells @value{GDBN} to
4270 instead watch the memory referred to by @var{expr}. In this case,
4271 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4272 and watch the memory at that address. The type of the result is used
4273 to determine the size of the watched memory. If the expression's
4274 result does not have an address, then @value{GDBN} will print an
4277 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4278 of masked watchpoints, if the current architecture supports this
4279 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4280 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4281 to an address to watch. The mask specifies that some bits of an address
4282 (the bits which are reset in the mask) should be ignored when matching
4283 the address accessed by the inferior against the watchpoint address.
4284 Thus, a masked watchpoint watches many addresses simultaneously---those
4285 addresses whose unmasked bits are identical to the unmasked bits in the
4286 watchpoint address. The @code{mask} argument implies @code{-location}.
4290 (@value{GDBP}) watch foo mask 0xffff00ff
4291 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4295 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4296 Set a watchpoint that will break when the value of @var{expr} is read
4300 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4301 Set a watchpoint that will break when @var{expr} is either read from
4302 or written into by the program.
4304 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4305 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4306 This command prints a list of watchpoints, using the same format as
4307 @code{info break} (@pxref{Set Breaks}).
4310 If you watch for a change in a numerically entered address you need to
4311 dereference it, as the address itself is just a constant number which will
4312 never change. @value{GDBN} refuses to create a watchpoint that watches
4313 a never-changing value:
4316 (@value{GDBP}) watch 0x600850
4317 Cannot watch constant value 0x600850.
4318 (@value{GDBP}) watch *(int *) 0x600850
4319 Watchpoint 1: *(int *) 6293584
4322 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4323 watchpoints execute very quickly, and the debugger reports a change in
4324 value at the exact instruction where the change occurs. If @value{GDBN}
4325 cannot set a hardware watchpoint, it sets a software watchpoint, which
4326 executes more slowly and reports the change in value at the next
4327 @emph{statement}, not the instruction, after the change occurs.
4329 @cindex use only software watchpoints
4330 You can force @value{GDBN} to use only software watchpoints with the
4331 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4332 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4333 the underlying system supports them. (Note that hardware-assisted
4334 watchpoints that were set @emph{before} setting
4335 @code{can-use-hw-watchpoints} to zero will still use the hardware
4336 mechanism of watching expression values.)
4339 @item set can-use-hw-watchpoints
4340 @kindex set can-use-hw-watchpoints
4341 Set whether or not to use hardware watchpoints.
4343 @item show can-use-hw-watchpoints
4344 @kindex show can-use-hw-watchpoints
4345 Show the current mode of using hardware watchpoints.
4348 For remote targets, you can restrict the number of hardware
4349 watchpoints @value{GDBN} will use, see @ref{set remote
4350 hardware-breakpoint-limit}.
4352 When you issue the @code{watch} command, @value{GDBN} reports
4355 Hardware watchpoint @var{num}: @var{expr}
4359 if it was able to set a hardware watchpoint.
4361 Currently, the @code{awatch} and @code{rwatch} commands can only set
4362 hardware watchpoints, because accesses to data that don't change the
4363 value of the watched expression cannot be detected without examining
4364 every instruction as it is being executed, and @value{GDBN} does not do
4365 that currently. If @value{GDBN} finds that it is unable to set a
4366 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4367 will print a message like this:
4370 Expression cannot be implemented with read/access watchpoint.
4373 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4374 data type of the watched expression is wider than what a hardware
4375 watchpoint on the target machine can handle. For example, some systems
4376 can only watch regions that are up to 4 bytes wide; on such systems you
4377 cannot set hardware watchpoints for an expression that yields a
4378 double-precision floating-point number (which is typically 8 bytes
4379 wide). As a work-around, it might be possible to break the large region
4380 into a series of smaller ones and watch them with separate watchpoints.
4382 If you set too many hardware watchpoints, @value{GDBN} might be unable
4383 to insert all of them when you resume the execution of your program.
4384 Since the precise number of active watchpoints is unknown until such
4385 time as the program is about to be resumed, @value{GDBN} might not be
4386 able to warn you about this when you set the watchpoints, and the
4387 warning will be printed only when the program is resumed:
4390 Hardware watchpoint @var{num}: Could not insert watchpoint
4394 If this happens, delete or disable some of the watchpoints.
4396 Watching complex expressions that reference many variables can also
4397 exhaust the resources available for hardware-assisted watchpoints.
4398 That's because @value{GDBN} needs to watch every variable in the
4399 expression with separately allocated resources.
4401 If you call a function interactively using @code{print} or @code{call},
4402 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4403 kind of breakpoint or the call completes.
4405 @value{GDBN} automatically deletes watchpoints that watch local
4406 (automatic) variables, or expressions that involve such variables, when
4407 they go out of scope, that is, when the execution leaves the block in
4408 which these variables were defined. In particular, when the program
4409 being debugged terminates, @emph{all} local variables go out of scope,
4410 and so only watchpoints that watch global variables remain set. If you
4411 rerun the program, you will need to set all such watchpoints again. One
4412 way of doing that would be to set a code breakpoint at the entry to the
4413 @code{main} function and when it breaks, set all the watchpoints.
4415 @cindex watchpoints and threads
4416 @cindex threads and watchpoints
4417 In multi-threaded programs, watchpoints will detect changes to the
4418 watched expression from every thread.
4421 @emph{Warning:} In multi-threaded programs, software watchpoints
4422 have only limited usefulness. If @value{GDBN} creates a software
4423 watchpoint, it can only watch the value of an expression @emph{in a
4424 single thread}. If you are confident that the expression can only
4425 change due to the current thread's activity (and if you are also
4426 confident that no other thread can become current), then you can use
4427 software watchpoints as usual. However, @value{GDBN} may not notice
4428 when a non-current thread's activity changes the expression. (Hardware
4429 watchpoints, in contrast, watch an expression in all threads.)
4432 @xref{set remote hardware-watchpoint-limit}.
4434 @node Set Catchpoints
4435 @subsection Setting Catchpoints
4436 @cindex catchpoints, setting
4437 @cindex exception handlers
4438 @cindex event handling
4440 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4441 kinds of program events, such as C@t{++} exceptions or the loading of a
4442 shared library. Use the @code{catch} command to set a catchpoint.
4446 @item catch @var{event}
4447 Stop when @var{event} occurs. The @var{event} can be any of the following:
4450 @item throw @r{[}@var{regexp}@r{]}
4451 @itemx rethrow @r{[}@var{regexp}@r{]}
4452 @itemx catch @r{[}@var{regexp}@r{]}
4454 @kindex catch rethrow
4456 @cindex stop on C@t{++} exceptions
4457 The throwing, re-throwing, or catching of a C@t{++} exception.
4459 If @var{regexp} is given, then only exceptions whose type matches the
4460 regular expression will be caught.
4462 @vindex $_exception@r{, convenience variable}
4463 The convenience variable @code{$_exception} is available at an
4464 exception-related catchpoint, on some systems. This holds the
4465 exception being thrown.
4467 There are currently some limitations to C@t{++} exception handling in
4472 The support for these commands is system-dependent. Currently, only
4473 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4477 The regular expression feature and the @code{$_exception} convenience
4478 variable rely on the presence of some SDT probes in @code{libstdc++}.
4479 If these probes are not present, then these features cannot be used.
4480 These probes were first available in the GCC 4.8 release, but whether
4481 or not they are available in your GCC also depends on how it was
4485 The @code{$_exception} convenience variable is only valid at the
4486 instruction at which an exception-related catchpoint is set.
4489 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4490 location in the system library which implements runtime exception
4491 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4492 (@pxref{Selection}) to get to your code.
4495 If you call a function interactively, @value{GDBN} normally returns
4496 control to you when the function has finished executing. If the call
4497 raises an exception, however, the call may bypass the mechanism that
4498 returns control to you and cause your program either to abort or to
4499 simply continue running until it hits a breakpoint, catches a signal
4500 that @value{GDBN} is listening for, or exits. This is the case even if
4501 you set a catchpoint for the exception; catchpoints on exceptions are
4502 disabled within interactive calls. @xref{Calling}, for information on
4503 controlling this with @code{set unwind-on-terminating-exception}.
4506 You cannot raise an exception interactively.
4509 You cannot install an exception handler interactively.
4512 @item exception @r{[}@var{name}@r{]}
4513 @kindex catch exception
4514 @cindex Ada exception catching
4515 @cindex catch Ada exceptions
4516 An Ada exception being raised. If an exception name is specified
4517 at the end of the command (eg @code{catch exception Program_Error}),
4518 the debugger will stop only when this specific exception is raised.
4519 Otherwise, the debugger stops execution when any Ada exception is raised.
4521 When inserting an exception catchpoint on a user-defined exception whose
4522 name is identical to one of the exceptions defined by the language, the
4523 fully qualified name must be used as the exception name. Otherwise,
4524 @value{GDBN} will assume that it should stop on the pre-defined exception
4525 rather than the user-defined one. For instance, assuming an exception
4526 called @code{Constraint_Error} is defined in package @code{Pck}, then
4527 the command to use to catch such exceptions is @kbd{catch exception
4528 Pck.Constraint_Error}.
4530 @item exception unhandled
4531 @kindex catch exception unhandled
4532 An exception that was raised but is not handled by the program.
4534 @item handlers @r{[}@var{name}@r{]}
4535 @kindex catch handlers
4536 @cindex Ada exception handlers catching
4537 @cindex catch Ada exceptions when handled
4538 An Ada exception being handled. If an exception name is
4539 specified at the end of the command
4540 (eg @kbd{catch handlers Program_Error}), the debugger will stop
4541 only when this specific exception is handled.
4542 Otherwise, the debugger stops execution when any Ada exception is handled.
4544 When inserting a handlers catchpoint on a user-defined
4545 exception whose name is identical to one of the exceptions
4546 defined by the language, the fully qualified name must be used
4547 as the exception name. Otherwise, @value{GDBN} will assume that it
4548 should stop on the pre-defined exception rather than the
4549 user-defined one. For instance, assuming an exception called
4550 @code{Constraint_Error} is defined in package @code{Pck}, then the
4551 command to use to catch such exceptions handling is
4552 @kbd{catch handlers Pck.Constraint_Error}.
4555 @kindex catch assert
4556 A failed Ada assertion.
4560 @cindex break on fork/exec
4561 A call to @code{exec}.
4563 @anchor{catch syscall}
4565 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4566 @kindex catch syscall
4567 @cindex break on a system call.
4568 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4569 syscall is a mechanism for application programs to request a service
4570 from the operating system (OS) or one of the OS system services.
4571 @value{GDBN} can catch some or all of the syscalls issued by the
4572 debuggee, and show the related information for each syscall. If no
4573 argument is specified, calls to and returns from all system calls
4576 @var{name} can be any system call name that is valid for the
4577 underlying OS. Just what syscalls are valid depends on the OS. On
4578 GNU and Unix systems, you can find the full list of valid syscall
4579 names on @file{/usr/include/asm/unistd.h}.
4581 @c For MS-Windows, the syscall names and the corresponding numbers
4582 @c can be found, e.g., on this URL:
4583 @c http://www.metasploit.com/users/opcode/syscalls.html
4584 @c but we don't support Windows syscalls yet.
4586 Normally, @value{GDBN} knows in advance which syscalls are valid for
4587 each OS, so you can use the @value{GDBN} command-line completion
4588 facilities (@pxref{Completion,, command completion}) to list the
4591 You may also specify the system call numerically. A syscall's
4592 number is the value passed to the OS's syscall dispatcher to
4593 identify the requested service. When you specify the syscall by its
4594 name, @value{GDBN} uses its database of syscalls to convert the name
4595 into the corresponding numeric code, but using the number directly
4596 may be useful if @value{GDBN}'s database does not have the complete
4597 list of syscalls on your system (e.g., because @value{GDBN} lags
4598 behind the OS upgrades).
4600 You may specify a group of related syscalls to be caught at once using
4601 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4602 instance, on some platforms @value{GDBN} allows you to catch all
4603 network related syscalls, by passing the argument @code{group:network}
4604 to @code{catch syscall}. Note that not all syscall groups are
4605 available in every system. You can use the command completion
4606 facilities (@pxref{Completion,, command completion}) to list the
4607 syscall groups available on your environment.
4609 The example below illustrates how this command works if you don't provide
4613 (@value{GDBP}) catch syscall
4614 Catchpoint 1 (syscall)
4616 Starting program: /tmp/catch-syscall
4618 Catchpoint 1 (call to syscall 'close'), \
4619 0xffffe424 in __kernel_vsyscall ()
4623 Catchpoint 1 (returned from syscall 'close'), \
4624 0xffffe424 in __kernel_vsyscall ()
4628 Here is an example of catching a system call by name:
4631 (@value{GDBP}) catch syscall chroot
4632 Catchpoint 1 (syscall 'chroot' [61])
4634 Starting program: /tmp/catch-syscall
4636 Catchpoint 1 (call to syscall 'chroot'), \
4637 0xffffe424 in __kernel_vsyscall ()
4641 Catchpoint 1 (returned from syscall 'chroot'), \
4642 0xffffe424 in __kernel_vsyscall ()
4646 An example of specifying a system call numerically. In the case
4647 below, the syscall number has a corresponding entry in the XML
4648 file, so @value{GDBN} finds its name and prints it:
4651 (@value{GDBP}) catch syscall 252
4652 Catchpoint 1 (syscall(s) 'exit_group')
4654 Starting program: /tmp/catch-syscall
4656 Catchpoint 1 (call to syscall 'exit_group'), \
4657 0xffffe424 in __kernel_vsyscall ()
4661 Program exited normally.
4665 Here is an example of catching a syscall group:
4668 (@value{GDBP}) catch syscall group:process
4669 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4670 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4671 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4673 Starting program: /tmp/catch-syscall
4675 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4676 from /lib64/ld-linux-x86-64.so.2
4682 However, there can be situations when there is no corresponding name
4683 in XML file for that syscall number. In this case, @value{GDBN} prints
4684 a warning message saying that it was not able to find the syscall name,
4685 but the catchpoint will be set anyway. See the example below:
4688 (@value{GDBP}) catch syscall 764
4689 warning: The number '764' does not represent a known syscall.
4690 Catchpoint 2 (syscall 764)
4694 If you configure @value{GDBN} using the @samp{--without-expat} option,
4695 it will not be able to display syscall names. Also, if your
4696 architecture does not have an XML file describing its system calls,
4697 you will not be able to see the syscall names. It is important to
4698 notice that these two features are used for accessing the syscall
4699 name database. In either case, you will see a warning like this:
4702 (@value{GDBP}) catch syscall
4703 warning: Could not open "syscalls/i386-linux.xml"
4704 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4705 GDB will not be able to display syscall names.
4706 Catchpoint 1 (syscall)
4710 Of course, the file name will change depending on your architecture and system.
4712 Still using the example above, you can also try to catch a syscall by its
4713 number. In this case, you would see something like:
4716 (@value{GDBP}) catch syscall 252
4717 Catchpoint 1 (syscall(s) 252)
4720 Again, in this case @value{GDBN} would not be able to display syscall's names.
4724 A call to @code{fork}.
4728 A call to @code{vfork}.
4730 @item load @r{[}@var{regexp}@r{]}
4731 @itemx unload @r{[}@var{regexp}@r{]}
4733 @kindex catch unload
4734 The loading or unloading of a shared library. If @var{regexp} is
4735 given, then the catchpoint will stop only if the regular expression
4736 matches one of the affected libraries.
4738 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4739 @kindex catch signal
4740 The delivery of a signal.
4742 With no arguments, this catchpoint will catch any signal that is not
4743 used internally by @value{GDBN}, specifically, all signals except
4744 @samp{SIGTRAP} and @samp{SIGINT}.
4746 With the argument @samp{all}, all signals, including those used by
4747 @value{GDBN}, will be caught. This argument cannot be used with other
4750 Otherwise, the arguments are a list of signal names as given to
4751 @code{handle} (@pxref{Signals}). Only signals specified in this list
4754 One reason that @code{catch signal} can be more useful than
4755 @code{handle} is that you can attach commands and conditions to the
4758 When a signal is caught by a catchpoint, the signal's @code{stop} and
4759 @code{print} settings, as specified by @code{handle}, are ignored.
4760 However, whether the signal is still delivered to the inferior depends
4761 on the @code{pass} setting; this can be changed in the catchpoint's
4766 @item tcatch @var{event}
4768 Set a catchpoint that is enabled only for one stop. The catchpoint is
4769 automatically deleted after the first time the event is caught.
4773 Use the @code{info break} command to list the current catchpoints.
4777 @subsection Deleting Breakpoints
4779 @cindex clearing breakpoints, watchpoints, catchpoints
4780 @cindex deleting breakpoints, watchpoints, catchpoints
4781 It is often necessary to eliminate a breakpoint, watchpoint, or
4782 catchpoint once it has done its job and you no longer want your program
4783 to stop there. This is called @dfn{deleting} the breakpoint. A
4784 breakpoint that has been deleted no longer exists; it is forgotten.
4786 With the @code{clear} command you can delete breakpoints according to
4787 where they are in your program. With the @code{delete} command you can
4788 delete individual breakpoints, watchpoints, or catchpoints by specifying
4789 their breakpoint numbers.
4791 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4792 automatically ignores breakpoints on the first instruction to be executed
4793 when you continue execution without changing the execution address.
4798 Delete any breakpoints at the next instruction to be executed in the
4799 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4800 the innermost frame is selected, this is a good way to delete a
4801 breakpoint where your program just stopped.
4803 @item clear @var{location}
4804 Delete any breakpoints set at the specified @var{location}.
4805 @xref{Specify Location}, for the various forms of @var{location}; the
4806 most useful ones are listed below:
4809 @item clear @var{function}
4810 @itemx clear @var{filename}:@var{function}
4811 Delete any breakpoints set at entry to the named @var{function}.
4813 @item clear @var{linenum}
4814 @itemx clear @var{filename}:@var{linenum}
4815 Delete any breakpoints set at or within the code of the specified
4816 @var{linenum} of the specified @var{filename}.
4819 @cindex delete breakpoints
4821 @kindex d @r{(@code{delete})}
4822 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4823 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4824 list specified as argument. If no argument is specified, delete all
4825 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4826 confirm off}). You can abbreviate this command as @code{d}.
4830 @subsection Disabling Breakpoints
4832 @cindex enable/disable a breakpoint
4833 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4834 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4835 it had been deleted, but remembers the information on the breakpoint so
4836 that you can @dfn{enable} it again later.
4838 You disable and enable breakpoints, watchpoints, and catchpoints with
4839 the @code{enable} and @code{disable} commands, optionally specifying
4840 one or more breakpoint numbers as arguments. Use @code{info break} to
4841 print a list of all breakpoints, watchpoints, and catchpoints if you
4842 do not know which numbers to use.
4844 Disabling and enabling a breakpoint that has multiple locations
4845 affects all of its locations.
4847 A breakpoint, watchpoint, or catchpoint can have any of several
4848 different states of enablement:
4852 Enabled. The breakpoint stops your program. A breakpoint set
4853 with the @code{break} command starts out in this state.
4855 Disabled. The breakpoint has no effect on your program.
4857 Enabled once. The breakpoint stops your program, but then becomes
4860 Enabled for a count. The breakpoint stops your program for the next
4861 N times, then becomes disabled.
4863 Enabled for deletion. The breakpoint stops your program, but
4864 immediately after it does so it is deleted permanently. A breakpoint
4865 set with the @code{tbreak} command starts out in this state.
4868 You can use the following commands to enable or disable breakpoints,
4869 watchpoints, and catchpoints:
4873 @kindex dis @r{(@code{disable})}
4874 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4875 Disable the specified breakpoints---or all breakpoints, if none are
4876 listed. A disabled breakpoint has no effect but is not forgotten. All
4877 options such as ignore-counts, conditions and commands are remembered in
4878 case the breakpoint is enabled again later. You may abbreviate
4879 @code{disable} as @code{dis}.
4882 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4883 Enable the specified breakpoints (or all defined breakpoints). They
4884 become effective once again in stopping your program.
4886 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4887 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4888 of these breakpoints immediately after stopping your program.
4890 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4891 Enable the specified breakpoints temporarily. @value{GDBN} records
4892 @var{count} with each of the specified breakpoints, and decrements a
4893 breakpoint's count when it is hit. When any count reaches 0,
4894 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4895 count (@pxref{Conditions, ,Break Conditions}), that will be
4896 decremented to 0 before @var{count} is affected.
4898 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4899 Enable the specified breakpoints to work once, then die. @value{GDBN}
4900 deletes any of these breakpoints as soon as your program stops there.
4901 Breakpoints set by the @code{tbreak} command start out in this state.
4904 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4905 @c confusing: tbreak is also initially enabled.
4906 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4907 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4908 subsequently, they become disabled or enabled only when you use one of
4909 the commands above. (The command @code{until} can set and delete a
4910 breakpoint of its own, but it does not change the state of your other
4911 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4915 @subsection Break Conditions
4916 @cindex conditional breakpoints
4917 @cindex breakpoint conditions
4919 @c FIXME what is scope of break condition expr? Context where wanted?
4920 @c in particular for a watchpoint?
4921 The simplest sort of breakpoint breaks every time your program reaches a
4922 specified place. You can also specify a @dfn{condition} for a
4923 breakpoint. A condition is just a Boolean expression in your
4924 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4925 a condition evaluates the expression each time your program reaches it,
4926 and your program stops only if the condition is @emph{true}.
4928 This is the converse of using assertions for program validation; in that
4929 situation, you want to stop when the assertion is violated---that is,
4930 when the condition is false. In C, if you want to test an assertion expressed
4931 by the condition @var{assert}, you should set the condition
4932 @samp{! @var{assert}} on the appropriate breakpoint.
4934 Conditions are also accepted for watchpoints; you may not need them,
4935 since a watchpoint is inspecting the value of an expression anyhow---but
4936 it might be simpler, say, to just set a watchpoint on a variable name,
4937 and specify a condition that tests whether the new value is an interesting
4940 Break conditions can have side effects, and may even call functions in
4941 your program. This can be useful, for example, to activate functions
4942 that log program progress, or to use your own print functions to
4943 format special data structures. The effects are completely predictable
4944 unless there is another enabled breakpoint at the same address. (In
4945 that case, @value{GDBN} might see the other breakpoint first and stop your
4946 program without checking the condition of this one.) Note that
4947 breakpoint commands are usually more convenient and flexible than break
4949 purpose of performing side effects when a breakpoint is reached
4950 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4952 Breakpoint conditions can also be evaluated on the target's side if
4953 the target supports it. Instead of evaluating the conditions locally,
4954 @value{GDBN} encodes the expression into an agent expression
4955 (@pxref{Agent Expressions}) suitable for execution on the target,
4956 independently of @value{GDBN}. Global variables become raw memory
4957 locations, locals become stack accesses, and so forth.
4959 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4960 when its condition evaluates to true. This mechanism may provide faster
4961 response times depending on the performance characteristics of the target
4962 since it does not need to keep @value{GDBN} informed about
4963 every breakpoint trigger, even those with false conditions.
4965 Break conditions can be specified when a breakpoint is set, by using
4966 @samp{if} in the arguments to the @code{break} command. @xref{Set
4967 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4968 with the @code{condition} command.
4970 You can also use the @code{if} keyword with the @code{watch} command.
4971 The @code{catch} command does not recognize the @code{if} keyword;
4972 @code{condition} is the only way to impose a further condition on a
4977 @item condition @var{bnum} @var{expression}
4978 Specify @var{expression} as the break condition for breakpoint,
4979 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4980 breakpoint @var{bnum} stops your program only if the value of
4981 @var{expression} is true (nonzero, in C). When you use
4982 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4983 syntactic correctness, and to determine whether symbols in it have
4984 referents in the context of your breakpoint. If @var{expression} uses
4985 symbols not referenced in the context of the breakpoint, @value{GDBN}
4986 prints an error message:
4989 No symbol "foo" in current context.
4994 not actually evaluate @var{expression} at the time the @code{condition}
4995 command (or a command that sets a breakpoint with a condition, like
4996 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4998 @item condition @var{bnum}
4999 Remove the condition from breakpoint number @var{bnum}. It becomes
5000 an ordinary unconditional breakpoint.
5003 @cindex ignore count (of breakpoint)
5004 A special case of a breakpoint condition is to stop only when the
5005 breakpoint has been reached a certain number of times. This is so
5006 useful that there is a special way to do it, using the @dfn{ignore
5007 count} of the breakpoint. Every breakpoint has an ignore count, which
5008 is an integer. Most of the time, the ignore count is zero, and
5009 therefore has no effect. But if your program reaches a breakpoint whose
5010 ignore count is positive, then instead of stopping, it just decrements
5011 the ignore count by one and continues. As a result, if the ignore count
5012 value is @var{n}, the breakpoint does not stop the next @var{n} times
5013 your program reaches it.
5017 @item ignore @var{bnum} @var{count}
5018 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
5019 The next @var{count} times the breakpoint is reached, your program's
5020 execution does not stop; other than to decrement the ignore count, @value{GDBN}
5023 To make the breakpoint stop the next time it is reached, specify
5026 When you use @code{continue} to resume execution of your program from a
5027 breakpoint, you can specify an ignore count directly as an argument to
5028 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
5029 Stepping,,Continuing and Stepping}.
5031 If a breakpoint has a positive ignore count and a condition, the
5032 condition is not checked. Once the ignore count reaches zero,
5033 @value{GDBN} resumes checking the condition.
5035 You could achieve the effect of the ignore count with a condition such
5036 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
5037 is decremented each time. @xref{Convenience Vars, ,Convenience
5041 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
5044 @node Break Commands
5045 @subsection Breakpoint Command Lists
5047 @cindex breakpoint commands
5048 You can give any breakpoint (or watchpoint or catchpoint) a series of
5049 commands to execute when your program stops due to that breakpoint. For
5050 example, you might want to print the values of certain expressions, or
5051 enable other breakpoints.
5055 @kindex end@r{ (breakpoint commands)}
5056 @item commands @r{[}@var{list}@dots{}@r{]}
5057 @itemx @dots{} @var{command-list} @dots{}
5059 Specify a list of commands for the given breakpoints. The commands
5060 themselves appear on the following lines. Type a line containing just
5061 @code{end} to terminate the commands.
5063 To remove all commands from a breakpoint, type @code{commands} and
5064 follow it immediately with @code{end}; that is, give no commands.
5066 With no argument, @code{commands} refers to the last breakpoint,
5067 watchpoint, or catchpoint set (not to the breakpoint most recently
5068 encountered). If the most recent breakpoints were set with a single
5069 command, then the @code{commands} will apply to all the breakpoints
5070 set by that command. This applies to breakpoints set by
5071 @code{rbreak}, and also applies when a single @code{break} command
5072 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
5076 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
5077 disabled within a @var{command-list}.
5079 You can use breakpoint commands to start your program up again. Simply
5080 use the @code{continue} command, or @code{step}, or any other command
5081 that resumes execution.
5083 Any other commands in the command list, after a command that resumes
5084 execution, are ignored. This is because any time you resume execution
5085 (even with a simple @code{next} or @code{step}), you may encounter
5086 another breakpoint---which could have its own command list, leading to
5087 ambiguities about which list to execute.
5090 If the first command you specify in a command list is @code{silent}, the
5091 usual message about stopping at a breakpoint is not printed. This may
5092 be desirable for breakpoints that are to print a specific message and
5093 then continue. If none of the remaining commands print anything, you
5094 see no sign that the breakpoint was reached. @code{silent} is
5095 meaningful only at the beginning of a breakpoint command list.
5097 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5098 print precisely controlled output, and are often useful in silent
5099 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5101 For example, here is how you could use breakpoint commands to print the
5102 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5108 printf "x is %d\n",x
5113 One application for breakpoint commands is to compensate for one bug so
5114 you can test for another. Put a breakpoint just after the erroneous line
5115 of code, give it a condition to detect the case in which something
5116 erroneous has been done, and give it commands to assign correct values
5117 to any variables that need them. End with the @code{continue} command
5118 so that your program does not stop, and start with the @code{silent}
5119 command so that no output is produced. Here is an example:
5130 @node Dynamic Printf
5131 @subsection Dynamic Printf
5133 @cindex dynamic printf
5135 The dynamic printf command @code{dprintf} combines a breakpoint with
5136 formatted printing of your program's data to give you the effect of
5137 inserting @code{printf} calls into your program on-the-fly, without
5138 having to recompile it.
5140 In its most basic form, the output goes to the GDB console. However,
5141 you can set the variable @code{dprintf-style} for alternate handling.
5142 For instance, you can ask to format the output by calling your
5143 program's @code{printf} function. This has the advantage that the
5144 characters go to the program's output device, so they can recorded in
5145 redirects to files and so forth.
5147 If you are doing remote debugging with a stub or agent, you can also
5148 ask to have the printf handled by the remote agent. In addition to
5149 ensuring that the output goes to the remote program's device along
5150 with any other output the program might produce, you can also ask that
5151 the dprintf remain active even after disconnecting from the remote
5152 target. Using the stub/agent is also more efficient, as it can do
5153 everything without needing to communicate with @value{GDBN}.
5157 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5158 Whenever execution reaches @var{location}, print the values of one or
5159 more @var{expressions} under the control of the string @var{template}.
5160 To print several values, separate them with commas.
5162 @item set dprintf-style @var{style}
5163 Set the dprintf output to be handled in one of several different
5164 styles enumerated below. A change of style affects all existing
5165 dynamic printfs immediately. (If you need individual control over the
5166 print commands, simply define normal breakpoints with
5167 explicitly-supplied command lists.)
5171 @kindex dprintf-style gdb
5172 Handle the output using the @value{GDBN} @code{printf} command.
5175 @kindex dprintf-style call
5176 Handle the output by calling a function in your program (normally
5180 @kindex dprintf-style agent
5181 Have the remote debugging agent (such as @code{gdbserver}) handle
5182 the output itself. This style is only available for agents that
5183 support running commands on the target.
5186 @item set dprintf-function @var{function}
5187 Set the function to call if the dprintf style is @code{call}. By
5188 default its value is @code{printf}. You may set it to any expression.
5189 that @value{GDBN} can evaluate to a function, as per the @code{call}
5192 @item set dprintf-channel @var{channel}
5193 Set a ``channel'' for dprintf. If set to a non-empty value,
5194 @value{GDBN} will evaluate it as an expression and pass the result as
5195 a first argument to the @code{dprintf-function}, in the manner of
5196 @code{fprintf} and similar functions. Otherwise, the dprintf format
5197 string will be the first argument, in the manner of @code{printf}.
5199 As an example, if you wanted @code{dprintf} output to go to a logfile
5200 that is a standard I/O stream assigned to the variable @code{mylog},
5201 you could do the following:
5204 (gdb) set dprintf-style call
5205 (gdb) set dprintf-function fprintf
5206 (gdb) set dprintf-channel mylog
5207 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5208 Dprintf 1 at 0x123456: file main.c, line 25.
5210 1 dprintf keep y 0x00123456 in main at main.c:25
5211 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5216 Note that the @code{info break} displays the dynamic printf commands
5217 as normal breakpoint commands; you can thus easily see the effect of
5218 the variable settings.
5220 @item set disconnected-dprintf on
5221 @itemx set disconnected-dprintf off
5222 @kindex set disconnected-dprintf
5223 Choose whether @code{dprintf} commands should continue to run if
5224 @value{GDBN} has disconnected from the target. This only applies
5225 if the @code{dprintf-style} is @code{agent}.
5227 @item show disconnected-dprintf off
5228 @kindex show disconnected-dprintf
5229 Show the current choice for disconnected @code{dprintf}.
5233 @value{GDBN} does not check the validity of function and channel,
5234 relying on you to supply values that are meaningful for the contexts
5235 in which they are being used. For instance, the function and channel
5236 may be the values of local variables, but if that is the case, then
5237 all enabled dynamic prints must be at locations within the scope of
5238 those locals. If evaluation fails, @value{GDBN} will report an error.
5240 @node Save Breakpoints
5241 @subsection How to save breakpoints to a file
5243 To save breakpoint definitions to a file use the @w{@code{save
5244 breakpoints}} command.
5247 @kindex save breakpoints
5248 @cindex save breakpoints to a file for future sessions
5249 @item save breakpoints [@var{filename}]
5250 This command saves all current breakpoint definitions together with
5251 their commands and ignore counts, into a file @file{@var{filename}}
5252 suitable for use in a later debugging session. This includes all
5253 types of breakpoints (breakpoints, watchpoints, catchpoints,
5254 tracepoints). To read the saved breakpoint definitions, use the
5255 @code{source} command (@pxref{Command Files}). Note that watchpoints
5256 with expressions involving local variables may fail to be recreated
5257 because it may not be possible to access the context where the
5258 watchpoint is valid anymore. Because the saved breakpoint definitions
5259 are simply a sequence of @value{GDBN} commands that recreate the
5260 breakpoints, you can edit the file in your favorite editing program,
5261 and remove the breakpoint definitions you're not interested in, or
5262 that can no longer be recreated.
5265 @node Static Probe Points
5266 @subsection Static Probe Points
5268 @cindex static probe point, SystemTap
5269 @cindex static probe point, DTrace
5270 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5271 for Statically Defined Tracing, and the probes are designed to have a tiny
5272 runtime code and data footprint, and no dynamic relocations.
5274 Currently, the following types of probes are supported on
5275 ELF-compatible systems:
5279 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5280 @acronym{SDT} probes@footnote{See
5281 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5282 for more information on how to add @code{SystemTap} @acronym{SDT}
5283 probes in your applications.}. @code{SystemTap} probes are usable
5284 from assembly, C and C@t{++} languages@footnote{See
5285 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5286 for a good reference on how the @acronym{SDT} probes are implemented.}.
5288 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5289 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5293 @cindex semaphores on static probe points
5294 Some @code{SystemTap} probes have an associated semaphore variable;
5295 for instance, this happens automatically if you defined your probe
5296 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5297 @value{GDBN} will automatically enable it when you specify a
5298 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5299 breakpoint at a probe's location by some other method (e.g.,
5300 @code{break file:line}), then @value{GDBN} will not automatically set
5301 the semaphore. @code{DTrace} probes do not support semaphores.
5303 You can examine the available static static probes using @code{info
5304 probes}, with optional arguments:
5308 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5309 If given, @var{type} is either @code{stap} for listing
5310 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5311 probes. If omitted all probes are listed regardless of their types.
5313 If given, @var{provider} is a regular expression used to match against provider
5314 names when selecting which probes to list. If omitted, probes by all
5315 probes from all providers are listed.
5317 If given, @var{name} is a regular expression to match against probe names
5318 when selecting which probes to list. If omitted, probe names are not
5319 considered when deciding whether to display them.
5321 If given, @var{objfile} is a regular expression used to select which
5322 object files (executable or shared libraries) to examine. If not
5323 given, all object files are considered.
5325 @item info probes all
5326 List the available static probes, from all types.
5329 @cindex enabling and disabling probes
5330 Some probe points can be enabled and/or disabled. The effect of
5331 enabling or disabling a probe depends on the type of probe being
5332 handled. Some @code{DTrace} probes can be enabled or
5333 disabled, but @code{SystemTap} probes cannot be disabled.
5335 You can enable (or disable) one or more probes using the following
5336 commands, with optional arguments:
5339 @kindex enable probes
5340 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5341 If given, @var{provider} is a regular expression used to match against
5342 provider names when selecting which probes to enable. If omitted,
5343 all probes from all providers are enabled.
5345 If given, @var{name} is a regular expression to match against probe
5346 names when selecting which probes to enable. If omitted, probe names
5347 are not considered when deciding whether to enable them.
5349 If given, @var{objfile} is a regular expression used to select which
5350 object files (executable or shared libraries) to examine. If not
5351 given, all object files are considered.
5353 @kindex disable probes
5354 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5355 See the @code{enable probes} command above for a description of the
5356 optional arguments accepted by this command.
5359 @vindex $_probe_arg@r{, convenience variable}
5360 A probe may specify up to twelve arguments. These are available at the
5361 point at which the probe is defined---that is, when the current PC is
5362 at the probe's location. The arguments are available using the
5363 convenience variables (@pxref{Convenience Vars})
5364 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5365 probes each probe argument is an integer of the appropriate size;
5366 types are not preserved. In @code{DTrace} probes types are preserved
5367 provided that they are recognized as such by @value{GDBN}; otherwise
5368 the value of the probe argument will be a long integer. The
5369 convenience variable @code{$_probe_argc} holds the number of arguments
5370 at the current probe point.
5372 These variables are always available, but attempts to access them at
5373 any location other than a probe point will cause @value{GDBN} to give
5377 @c @ifclear BARETARGET
5378 @node Error in Breakpoints
5379 @subsection ``Cannot insert breakpoints''
5381 If you request too many active hardware-assisted breakpoints and
5382 watchpoints, you will see this error message:
5384 @c FIXME: the precise wording of this message may change; the relevant
5385 @c source change is not committed yet (Sep 3, 1999).
5387 Stopped; cannot insert breakpoints.
5388 You may have requested too many hardware breakpoints and watchpoints.
5392 This message is printed when you attempt to resume the program, since
5393 only then @value{GDBN} knows exactly how many hardware breakpoints and
5394 watchpoints it needs to insert.
5396 When this message is printed, you need to disable or remove some of the
5397 hardware-assisted breakpoints and watchpoints, and then continue.
5399 @node Breakpoint-related Warnings
5400 @subsection ``Breakpoint address adjusted...''
5401 @cindex breakpoint address adjusted
5403 Some processor architectures place constraints on the addresses at
5404 which breakpoints may be placed. For architectures thus constrained,
5405 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5406 with the constraints dictated by the architecture.
5408 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5409 a VLIW architecture in which a number of RISC-like instructions may be
5410 bundled together for parallel execution. The FR-V architecture
5411 constrains the location of a breakpoint instruction within such a
5412 bundle to the instruction with the lowest address. @value{GDBN}
5413 honors this constraint by adjusting a breakpoint's address to the
5414 first in the bundle.
5416 It is not uncommon for optimized code to have bundles which contain
5417 instructions from different source statements, thus it may happen that
5418 a breakpoint's address will be adjusted from one source statement to
5419 another. Since this adjustment may significantly alter @value{GDBN}'s
5420 breakpoint related behavior from what the user expects, a warning is
5421 printed when the breakpoint is first set and also when the breakpoint
5424 A warning like the one below is printed when setting a breakpoint
5425 that's been subject to address adjustment:
5428 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5431 Such warnings are printed both for user settable and @value{GDBN}'s
5432 internal breakpoints. If you see one of these warnings, you should
5433 verify that a breakpoint set at the adjusted address will have the
5434 desired affect. If not, the breakpoint in question may be removed and
5435 other breakpoints may be set which will have the desired behavior.
5436 E.g., it may be sufficient to place the breakpoint at a later
5437 instruction. A conditional breakpoint may also be useful in some
5438 cases to prevent the breakpoint from triggering too often.
5440 @value{GDBN} will also issue a warning when stopping at one of these
5441 adjusted breakpoints:
5444 warning: Breakpoint 1 address previously adjusted from 0x00010414
5448 When this warning is encountered, it may be too late to take remedial
5449 action except in cases where the breakpoint is hit earlier or more
5450 frequently than expected.
5452 @node Continuing and Stepping
5453 @section Continuing and Stepping
5457 @cindex resuming execution
5458 @dfn{Continuing} means resuming program execution until your program
5459 completes normally. In contrast, @dfn{stepping} means executing just
5460 one more ``step'' of your program, where ``step'' may mean either one
5461 line of source code, or one machine instruction (depending on what
5462 particular command you use). Either when continuing or when stepping,
5463 your program may stop even sooner, due to a breakpoint or a signal. (If
5464 it stops due to a signal, you may want to use @code{handle}, or use
5465 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5466 or you may step into the signal's handler (@pxref{stepping and signal
5471 @kindex c @r{(@code{continue})}
5472 @kindex fg @r{(resume foreground execution)}
5473 @item continue @r{[}@var{ignore-count}@r{]}
5474 @itemx c @r{[}@var{ignore-count}@r{]}
5475 @itemx fg @r{[}@var{ignore-count}@r{]}
5476 Resume program execution, at the address where your program last stopped;
5477 any breakpoints set at that address are bypassed. The optional argument
5478 @var{ignore-count} allows you to specify a further number of times to
5479 ignore a breakpoint at this location; its effect is like that of
5480 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5482 The argument @var{ignore-count} is meaningful only when your program
5483 stopped due to a breakpoint. At other times, the argument to
5484 @code{continue} is ignored.
5486 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5487 debugged program is deemed to be the foreground program) are provided
5488 purely for convenience, and have exactly the same behavior as
5492 To resume execution at a different place, you can use @code{return}
5493 (@pxref{Returning, ,Returning from a Function}) to go back to the
5494 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5495 Different Address}) to go to an arbitrary location in your program.
5497 A typical technique for using stepping is to set a breakpoint
5498 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5499 beginning of the function or the section of your program where a problem
5500 is believed to lie, run your program until it stops at that breakpoint,
5501 and then step through the suspect area, examining the variables that are
5502 interesting, until you see the problem happen.
5506 @kindex s @r{(@code{step})}
5508 Continue running your program until control reaches a different source
5509 line, then stop it and return control to @value{GDBN}. This command is
5510 abbreviated @code{s}.
5513 @c "without debugging information" is imprecise; actually "without line
5514 @c numbers in the debugging information". (gcc -g1 has debugging info but
5515 @c not line numbers). But it seems complex to try to make that
5516 @c distinction here.
5517 @emph{Warning:} If you use the @code{step} command while control is
5518 within a function that was compiled without debugging information,
5519 execution proceeds until control reaches a function that does have
5520 debugging information. Likewise, it will not step into a function which
5521 is compiled without debugging information. To step through functions
5522 without debugging information, use the @code{stepi} command, described
5526 The @code{step} command only stops at the first instruction of a source
5527 line. This prevents the multiple stops that could otherwise occur in
5528 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5529 to stop if a function that has debugging information is called within
5530 the line. In other words, @code{step} @emph{steps inside} any functions
5531 called within the line.
5533 Also, the @code{step} command only enters a function if there is line
5534 number information for the function. Otherwise it acts like the
5535 @code{next} command. This avoids problems when using @code{cc -gl}
5536 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5537 was any debugging information about the routine.
5539 @item step @var{count}
5540 Continue running as in @code{step}, but do so @var{count} times. If a
5541 breakpoint is reached, or a signal not related to stepping occurs before
5542 @var{count} steps, stepping stops right away.
5545 @kindex n @r{(@code{next})}
5546 @item next @r{[}@var{count}@r{]}
5547 Continue to the next source line in the current (innermost) stack frame.
5548 This is similar to @code{step}, but function calls that appear within
5549 the line of code are executed without stopping. Execution stops when
5550 control reaches a different line of code at the original stack level
5551 that was executing when you gave the @code{next} command. This command
5552 is abbreviated @code{n}.
5554 An argument @var{count} is a repeat count, as for @code{step}.
5557 @c FIX ME!! Do we delete this, or is there a way it fits in with
5558 @c the following paragraph? --- Vctoria
5560 @c @code{next} within a function that lacks debugging information acts like
5561 @c @code{step}, but any function calls appearing within the code of the
5562 @c function are executed without stopping.
5564 The @code{next} command only stops at the first instruction of a
5565 source line. This prevents multiple stops that could otherwise occur in
5566 @code{switch} statements, @code{for} loops, etc.
5568 @kindex set step-mode
5570 @cindex functions without line info, and stepping
5571 @cindex stepping into functions with no line info
5572 @itemx set step-mode on
5573 The @code{set step-mode on} command causes the @code{step} command to
5574 stop at the first instruction of a function which contains no debug line
5575 information rather than stepping over it.
5577 This is useful in cases where you may be interested in inspecting the
5578 machine instructions of a function which has no symbolic info and do not
5579 want @value{GDBN} to automatically skip over this function.
5581 @item set step-mode off
5582 Causes the @code{step} command to step over any functions which contains no
5583 debug information. This is the default.
5585 @item show step-mode
5586 Show whether @value{GDBN} will stop in or step over functions without
5587 source line debug information.
5590 @kindex fin @r{(@code{finish})}
5592 Continue running until just after function in the selected stack frame
5593 returns. Print the returned value (if any). This command can be
5594 abbreviated as @code{fin}.
5596 Contrast this with the @code{return} command (@pxref{Returning,
5597 ,Returning from a Function}).
5600 @kindex u @r{(@code{until})}
5601 @cindex run until specified location
5604 Continue running until a source line past the current line, in the
5605 current stack frame, is reached. This command is used to avoid single
5606 stepping through a loop more than once. It is like the @code{next}
5607 command, except that when @code{until} encounters a jump, it
5608 automatically continues execution until the program counter is greater
5609 than the address of the jump.
5611 This means that when you reach the end of a loop after single stepping
5612 though it, @code{until} makes your program continue execution until it
5613 exits the loop. In contrast, a @code{next} command at the end of a loop
5614 simply steps back to the beginning of the loop, which forces you to step
5615 through the next iteration.
5617 @code{until} always stops your program if it attempts to exit the current
5620 @code{until} may produce somewhat counterintuitive results if the order
5621 of machine code does not match the order of the source lines. For
5622 example, in the following excerpt from a debugging session, the @code{f}
5623 (@code{frame}) command shows that execution is stopped at line
5624 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5628 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5630 (@value{GDBP}) until
5631 195 for ( ; argc > 0; NEXTARG) @{
5634 This happened because, for execution efficiency, the compiler had
5635 generated code for the loop closure test at the end, rather than the
5636 start, of the loop---even though the test in a C @code{for}-loop is
5637 written before the body of the loop. The @code{until} command appeared
5638 to step back to the beginning of the loop when it advanced to this
5639 expression; however, it has not really gone to an earlier
5640 statement---not in terms of the actual machine code.
5642 @code{until} with no argument works by means of single
5643 instruction stepping, and hence is slower than @code{until} with an
5646 @item until @var{location}
5647 @itemx u @var{location}
5648 Continue running your program until either the specified @var{location} is
5649 reached, or the current stack frame returns. The location is any of
5650 the forms described in @ref{Specify Location}.
5651 This form of the command uses temporary breakpoints, and
5652 hence is quicker than @code{until} without an argument. The specified
5653 location is actually reached only if it is in the current frame. This
5654 implies that @code{until} can be used to skip over recursive function
5655 invocations. For instance in the code below, if the current location is
5656 line @code{96}, issuing @code{until 99} will execute the program up to
5657 line @code{99} in the same invocation of factorial, i.e., after the inner
5658 invocations have returned.
5661 94 int factorial (int value)
5663 96 if (value > 1) @{
5664 97 value *= factorial (value - 1);
5671 @kindex advance @var{location}
5672 @item advance @var{location}
5673 Continue running the program up to the given @var{location}. An argument is
5674 required, which should be of one of the forms described in
5675 @ref{Specify Location}.
5676 Execution will also stop upon exit from the current stack
5677 frame. This command is similar to @code{until}, but @code{advance} will
5678 not skip over recursive function calls, and the target location doesn't
5679 have to be in the same frame as the current one.
5683 @kindex si @r{(@code{stepi})}
5685 @itemx stepi @var{arg}
5687 Execute one machine instruction, then stop and return to the debugger.
5689 It is often useful to do @samp{display/i $pc} when stepping by machine
5690 instructions. This makes @value{GDBN} automatically display the next
5691 instruction to be executed, each time your program stops. @xref{Auto
5692 Display,, Automatic Display}.
5694 An argument is a repeat count, as in @code{step}.
5698 @kindex ni @r{(@code{nexti})}
5700 @itemx nexti @var{arg}
5702 Execute one machine instruction, but if it is a function call,
5703 proceed until the function returns.
5705 An argument is a repeat count, as in @code{next}.
5709 @anchor{range stepping}
5710 @cindex range stepping
5711 @cindex target-assisted range stepping
5712 By default, and if available, @value{GDBN} makes use of
5713 target-assisted @dfn{range stepping}. In other words, whenever you
5714 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5715 tells the target to step the corresponding range of instruction
5716 addresses instead of issuing multiple single-steps. This speeds up
5717 line stepping, particularly for remote targets. Ideally, there should
5718 be no reason you would want to turn range stepping off. However, it's
5719 possible that a bug in the debug info, a bug in the remote stub (for
5720 remote targets), or even a bug in @value{GDBN} could make line
5721 stepping behave incorrectly when target-assisted range stepping is
5722 enabled. You can use the following command to turn off range stepping
5726 @kindex set range-stepping
5727 @kindex show range-stepping
5728 @item set range-stepping
5729 @itemx show range-stepping
5730 Control whether range stepping is enabled.
5732 If @code{on}, and the target supports it, @value{GDBN} tells the
5733 target to step a range of addresses itself, instead of issuing
5734 multiple single-steps. If @code{off}, @value{GDBN} always issues
5735 single-steps, even if range stepping is supported by the target. The
5736 default is @code{on}.
5740 @node Skipping Over Functions and Files
5741 @section Skipping Over Functions and Files
5742 @cindex skipping over functions and files
5744 The program you are debugging may contain some functions which are
5745 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5746 skip a function, all functions in a file or a particular function in
5747 a particular file when stepping.
5749 For example, consider the following C function:
5760 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5761 are not interested in stepping through @code{boring}. If you run @code{step}
5762 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5763 step over both @code{foo} and @code{boring}!
5765 One solution is to @code{step} into @code{boring} and use the @code{finish}
5766 command to immediately exit it. But this can become tedious if @code{boring}
5767 is called from many places.
5769 A more flexible solution is to execute @kbd{skip boring}. This instructs
5770 @value{GDBN} never to step into @code{boring}. Now when you execute
5771 @code{step} at line 103, you'll step over @code{boring} and directly into
5774 Functions may be skipped by providing either a function name, linespec
5775 (@pxref{Specify Location}), regular expression that matches the function's
5776 name, file name or a @code{glob}-style pattern that matches the file name.
5778 On Posix systems the form of the regular expression is
5779 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5780 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5781 expression is whatever is provided by the @code{regcomp} function of
5782 the underlying system.
5783 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5784 description of @code{glob}-style patterns.
5788 @item skip @r{[}@var{options}@r{]}
5789 The basic form of the @code{skip} command takes zero or more options
5790 that specify what to skip.
5791 The @var{options} argument is any useful combination of the following:
5794 @item -file @var{file}
5795 @itemx -fi @var{file}
5796 Functions in @var{file} will be skipped over when stepping.
5798 @item -gfile @var{file-glob-pattern}
5799 @itemx -gfi @var{file-glob-pattern}
5800 @cindex skipping over files via glob-style patterns
5801 Functions in files matching @var{file-glob-pattern} will be skipped
5805 (gdb) skip -gfi utils/*.c
5808 @item -function @var{linespec}
5809 @itemx -fu @var{linespec}
5810 Functions named by @var{linespec} or the function containing the line
5811 named by @var{linespec} will be skipped over when stepping.
5812 @xref{Specify Location}.
5814 @item -rfunction @var{regexp}
5815 @itemx -rfu @var{regexp}
5816 @cindex skipping over functions via regular expressions
5817 Functions whose name matches @var{regexp} will be skipped over when stepping.
5819 This form is useful for complex function names.
5820 For example, there is generally no need to step into C@t{++} @code{std::string}
5821 constructors or destructors. Plus with C@t{++} templates it can be hard to
5822 write out the full name of the function, and often it doesn't matter what
5823 the template arguments are. Specifying the function to be skipped as a
5824 regular expression makes this easier.
5827 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5830 If you want to skip every templated C@t{++} constructor and destructor
5831 in the @code{std} namespace you can do:
5834 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5838 If no options are specified, the function you're currently debugging
5841 @kindex skip function
5842 @item skip function @r{[}@var{linespec}@r{]}
5843 After running this command, the function named by @var{linespec} or the
5844 function containing the line named by @var{linespec} will be skipped over when
5845 stepping. @xref{Specify Location}.
5847 If you do not specify @var{linespec}, the function you're currently debugging
5850 (If you have a function called @code{file} that you want to skip, use
5851 @kbd{skip function file}.)
5854 @item skip file @r{[}@var{filename}@r{]}
5855 After running this command, any function whose source lives in @var{filename}
5856 will be skipped over when stepping.
5859 (gdb) skip file boring.c
5860 File boring.c will be skipped when stepping.
5863 If you do not specify @var{filename}, functions whose source lives in the file
5864 you're currently debugging will be skipped.
5867 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5868 These are the commands for managing your list of skips:
5872 @item info skip @r{[}@var{range}@r{]}
5873 Print details about the specified skip(s). If @var{range} is not specified,
5874 print a table with details about all functions and files marked for skipping.
5875 @code{info skip} prints the following information about each skip:
5879 A number identifying this skip.
5880 @item Enabled or Disabled
5881 Enabled skips are marked with @samp{y}.
5882 Disabled skips are marked with @samp{n}.
5884 If the file name is a @samp{glob} pattern this is @samp{y}.
5885 Otherwise it is @samp{n}.
5887 The name or @samp{glob} pattern of the file to be skipped.
5888 If no file is specified this is @samp{<none>}.
5890 If the function name is a @samp{regular expression} this is @samp{y}.
5891 Otherwise it is @samp{n}.
5893 The name or regular expression of the function to skip.
5894 If no function is specified this is @samp{<none>}.
5898 @item skip delete @r{[}@var{range}@r{]}
5899 Delete the specified skip(s). If @var{range} is not specified, delete all
5903 @item skip enable @r{[}@var{range}@r{]}
5904 Enable the specified skip(s). If @var{range} is not specified, enable all
5907 @kindex skip disable
5908 @item skip disable @r{[}@var{range}@r{]}
5909 Disable the specified skip(s). If @var{range} is not specified, disable all
5912 @kindex set debug skip
5913 @item set debug skip @r{[}on|off@r{]}
5914 Set whether to print the debug output about skipping files and functions.
5916 @kindex show debug skip
5917 @item show debug skip
5918 Show whether the debug output about skipping files and functions is printed.
5926 A signal is an asynchronous event that can happen in a program. The
5927 operating system defines the possible kinds of signals, and gives each
5928 kind a name and a number. For example, in Unix @code{SIGINT} is the
5929 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5930 @code{SIGSEGV} is the signal a program gets from referencing a place in
5931 memory far away from all the areas in use; @code{SIGALRM} occurs when
5932 the alarm clock timer goes off (which happens only if your program has
5933 requested an alarm).
5935 @cindex fatal signals
5936 Some signals, including @code{SIGALRM}, are a normal part of the
5937 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5938 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5939 program has not specified in advance some other way to handle the signal.
5940 @code{SIGINT} does not indicate an error in your program, but it is normally
5941 fatal so it can carry out the purpose of the interrupt: to kill the program.
5943 @value{GDBN} has the ability to detect any occurrence of a signal in your
5944 program. You can tell @value{GDBN} in advance what to do for each kind of
5947 @cindex handling signals
5948 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5949 @code{SIGALRM} be silently passed to your program
5950 (so as not to interfere with their role in the program's functioning)
5951 but to stop your program immediately whenever an error signal happens.
5952 You can change these settings with the @code{handle} command.
5955 @kindex info signals
5959 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5960 handle each one. You can use this to see the signal numbers of all
5961 the defined types of signals.
5963 @item info signals @var{sig}
5964 Similar, but print information only about the specified signal number.
5966 @code{info handle} is an alias for @code{info signals}.
5968 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5969 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5970 for details about this command.
5973 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5974 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5975 can be the number of a signal or its name (with or without the
5976 @samp{SIG} at the beginning); a list of signal numbers of the form
5977 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5978 known signals. Optional arguments @var{keywords}, described below,
5979 say what change to make.
5983 The keywords allowed by the @code{handle} command can be abbreviated.
5984 Their full names are:
5988 @value{GDBN} should not stop your program when this signal happens. It may
5989 still print a message telling you that the signal has come in.
5992 @value{GDBN} should stop your program when this signal happens. This implies
5993 the @code{print} keyword as well.
5996 @value{GDBN} should print a message when this signal happens.
5999 @value{GDBN} should not mention the occurrence of the signal at all. This
6000 implies the @code{nostop} keyword as well.
6004 @value{GDBN} should allow your program to see this signal; your program
6005 can handle the signal, or else it may terminate if the signal is fatal
6006 and not handled. @code{pass} and @code{noignore} are synonyms.
6010 @value{GDBN} should not allow your program to see this signal.
6011 @code{nopass} and @code{ignore} are synonyms.
6015 When a signal stops your program, the signal is not visible to the
6017 continue. Your program sees the signal then, if @code{pass} is in
6018 effect for the signal in question @emph{at that time}. In other words,
6019 after @value{GDBN} reports a signal, you can use the @code{handle}
6020 command with @code{pass} or @code{nopass} to control whether your
6021 program sees that signal when you continue.
6023 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
6024 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
6025 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
6028 You can also use the @code{signal} command to prevent your program from
6029 seeing a signal, or cause it to see a signal it normally would not see,
6030 or to give it any signal at any time. For example, if your program stopped
6031 due to some sort of memory reference error, you might store correct
6032 values into the erroneous variables and continue, hoping to see more
6033 execution; but your program would probably terminate immediately as
6034 a result of the fatal signal once it saw the signal. To prevent this,
6035 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
6038 @cindex stepping and signal handlers
6039 @anchor{stepping and signal handlers}
6041 @value{GDBN} optimizes for stepping the mainline code. If a signal
6042 that has @code{handle nostop} and @code{handle pass} set arrives while
6043 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
6044 in progress, @value{GDBN} lets the signal handler run and then resumes
6045 stepping the mainline code once the signal handler returns. In other
6046 words, @value{GDBN} steps over the signal handler. This prevents
6047 signals that you've specified as not interesting (with @code{handle
6048 nostop}) from changing the focus of debugging unexpectedly. Note that
6049 the signal handler itself may still hit a breakpoint, stop for another
6050 signal that has @code{handle stop} in effect, or for any other event
6051 that normally results in stopping the stepping command sooner. Also
6052 note that @value{GDBN} still informs you that the program received a
6053 signal if @code{handle print} is set.
6055 @anchor{stepping into signal handlers}
6057 If you set @code{handle pass} for a signal, and your program sets up a
6058 handler for it, then issuing a stepping command, such as @code{step}
6059 or @code{stepi}, when your program is stopped due to the signal will
6060 step @emph{into} the signal handler (if the target supports that).
6062 Likewise, if you use the @code{queue-signal} command to queue a signal
6063 to be delivered to the current thread when execution of the thread
6064 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
6065 stepping command will step into the signal handler.
6067 Here's an example, using @code{stepi} to step to the first instruction
6068 of @code{SIGUSR1}'s handler:
6071 (@value{GDBP}) handle SIGUSR1
6072 Signal Stop Print Pass to program Description
6073 SIGUSR1 Yes Yes Yes User defined signal 1
6077 Program received signal SIGUSR1, User defined signal 1.
6078 main () sigusr1.c:28
6081 sigusr1_handler () at sigusr1.c:9
6085 The same, but using @code{queue-signal} instead of waiting for the
6086 program to receive the signal first:
6091 (@value{GDBP}) queue-signal SIGUSR1
6093 sigusr1_handler () at sigusr1.c:9
6098 @cindex extra signal information
6099 @anchor{extra signal information}
6101 On some targets, @value{GDBN} can inspect extra signal information
6102 associated with the intercepted signal, before it is actually
6103 delivered to the program being debugged. This information is exported
6104 by the convenience variable @code{$_siginfo}, and consists of data
6105 that is passed by the kernel to the signal handler at the time of the
6106 receipt of a signal. The data type of the information itself is
6107 target dependent. You can see the data type using the @code{ptype
6108 $_siginfo} command. On Unix systems, it typically corresponds to the
6109 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6112 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6113 referenced address that raised a segmentation fault.
6117 (@value{GDBP}) continue
6118 Program received signal SIGSEGV, Segmentation fault.
6119 0x0000000000400766 in main ()
6121 (@value{GDBP}) ptype $_siginfo
6128 struct @{...@} _kill;
6129 struct @{...@} _timer;
6131 struct @{...@} _sigchld;
6132 struct @{...@} _sigfault;
6133 struct @{...@} _sigpoll;
6136 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6140 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6141 $1 = (void *) 0x7ffff7ff7000
6145 Depending on target support, @code{$_siginfo} may also be writable.
6147 @cindex Intel MPX boundary violations
6148 @cindex boundary violations, Intel MPX
6149 On some targets, a @code{SIGSEGV} can be caused by a boundary
6150 violation, i.e., accessing an address outside of the allowed range.
6151 In those cases @value{GDBN} may displays additional information,
6152 depending on how @value{GDBN} has been told to handle the signal.
6153 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6154 kind: "Upper" or "Lower", the memory address accessed and the
6155 bounds, while with @code{handle nostop SIGSEGV} no additional
6156 information is displayed.
6158 The usual output of a segfault is:
6160 Program received signal SIGSEGV, Segmentation fault
6161 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6162 68 value = *(p + len);
6165 While a bound violation is presented as:
6167 Program received signal SIGSEGV, Segmentation fault
6168 Upper bound violation while accessing address 0x7fffffffc3b3
6169 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6170 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6171 68 value = *(p + len);
6175 @section Stopping and Starting Multi-thread Programs
6177 @cindex stopped threads
6178 @cindex threads, stopped
6180 @cindex continuing threads
6181 @cindex threads, continuing
6183 @value{GDBN} supports debugging programs with multiple threads
6184 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6185 are two modes of controlling execution of your program within the
6186 debugger. In the default mode, referred to as @dfn{all-stop mode},
6187 when any thread in your program stops (for example, at a breakpoint
6188 or while being stepped), all other threads in the program are also stopped by
6189 @value{GDBN}. On some targets, @value{GDBN} also supports
6190 @dfn{non-stop mode}, in which other threads can continue to run freely while
6191 you examine the stopped thread in the debugger.
6194 * All-Stop Mode:: All threads stop when GDB takes control
6195 * Non-Stop Mode:: Other threads continue to execute
6196 * Background Execution:: Running your program asynchronously
6197 * Thread-Specific Breakpoints:: Controlling breakpoints
6198 * Interrupted System Calls:: GDB may interfere with system calls
6199 * Observer Mode:: GDB does not alter program behavior
6203 @subsection All-Stop Mode
6205 @cindex all-stop mode
6207 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6208 @emph{all} threads of execution stop, not just the current thread. This
6209 allows you to examine the overall state of the program, including
6210 switching between threads, without worrying that things may change
6213 Conversely, whenever you restart the program, @emph{all} threads start
6214 executing. @emph{This is true even when single-stepping} with commands
6215 like @code{step} or @code{next}.
6217 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6218 Since thread scheduling is up to your debugging target's operating
6219 system (not controlled by @value{GDBN}), other threads may
6220 execute more than one statement while the current thread completes a
6221 single step. Moreover, in general other threads stop in the middle of a
6222 statement, rather than at a clean statement boundary, when the program
6225 You might even find your program stopped in another thread after
6226 continuing or even single-stepping. This happens whenever some other
6227 thread runs into a breakpoint, a signal, or an exception before the
6228 first thread completes whatever you requested.
6230 @cindex automatic thread selection
6231 @cindex switching threads automatically
6232 @cindex threads, automatic switching
6233 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6234 signal, it automatically selects the thread where that breakpoint or
6235 signal happened. @value{GDBN} alerts you to the context switch with a
6236 message such as @samp{[Switching to Thread @var{n}]} to identify the
6239 On some OSes, you can modify @value{GDBN}'s default behavior by
6240 locking the OS scheduler to allow only a single thread to run.
6243 @item set scheduler-locking @var{mode}
6244 @cindex scheduler locking mode
6245 @cindex lock scheduler
6246 Set the scheduler locking mode. It applies to normal execution,
6247 record mode, and replay mode. If it is @code{off}, then there is no
6248 locking and any thread may run at any time. If @code{on}, then only
6249 the current thread may run when the inferior is resumed. The
6250 @code{step} mode optimizes for single-stepping; it prevents other
6251 threads from preempting the current thread while you are stepping, so
6252 that the focus of debugging does not change unexpectedly. Other
6253 threads never get a chance to run when you step, and they are
6254 completely free to run when you use commands like @samp{continue},
6255 @samp{until}, or @samp{finish}. However, unless another thread hits a
6256 breakpoint during its timeslice, @value{GDBN} does not change the
6257 current thread away from the thread that you are debugging. The
6258 @code{replay} mode behaves like @code{off} in record mode and like
6259 @code{on} in replay mode.
6261 @item show scheduler-locking
6262 Display the current scheduler locking mode.
6265 @cindex resume threads of multiple processes simultaneously
6266 By default, when you issue one of the execution commands such as
6267 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6268 threads of the current inferior to run. For example, if @value{GDBN}
6269 is attached to two inferiors, each with two threads, the
6270 @code{continue} command resumes only the two threads of the current
6271 inferior. This is useful, for example, when you debug a program that
6272 forks and you want to hold the parent stopped (so that, for instance,
6273 it doesn't run to exit), while you debug the child. In other
6274 situations, you may not be interested in inspecting the current state
6275 of any of the processes @value{GDBN} is attached to, and you may want
6276 to resume them all until some breakpoint is hit. In the latter case,
6277 you can instruct @value{GDBN} to allow all threads of all the
6278 inferiors to run with the @w{@code{set schedule-multiple}} command.
6281 @kindex set schedule-multiple
6282 @item set schedule-multiple
6283 Set the mode for allowing threads of multiple processes to be resumed
6284 when an execution command is issued. When @code{on}, all threads of
6285 all processes are allowed to run. When @code{off}, only the threads
6286 of the current process are resumed. The default is @code{off}. The
6287 @code{scheduler-locking} mode takes precedence when set to @code{on},
6288 or while you are stepping and set to @code{step}.
6290 @item show schedule-multiple
6291 Display the current mode for resuming the execution of threads of
6296 @subsection Non-Stop Mode
6298 @cindex non-stop mode
6300 @c This section is really only a place-holder, and needs to be expanded
6301 @c with more details.
6303 For some multi-threaded targets, @value{GDBN} supports an optional
6304 mode of operation in which you can examine stopped program threads in
6305 the debugger while other threads continue to execute freely. This
6306 minimizes intrusion when debugging live systems, such as programs
6307 where some threads have real-time constraints or must continue to
6308 respond to external events. This is referred to as @dfn{non-stop} mode.
6310 In non-stop mode, when a thread stops to report a debugging event,
6311 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6312 threads as well, in contrast to the all-stop mode behavior. Additionally,
6313 execution commands such as @code{continue} and @code{step} apply by default
6314 only to the current thread in non-stop mode, rather than all threads as
6315 in all-stop mode. This allows you to control threads explicitly in
6316 ways that are not possible in all-stop mode --- for example, stepping
6317 one thread while allowing others to run freely, stepping
6318 one thread while holding all others stopped, or stepping several threads
6319 independently and simultaneously.
6321 To enter non-stop mode, use this sequence of commands before you run
6322 or attach to your program:
6325 # If using the CLI, pagination breaks non-stop.
6328 # Finally, turn it on!
6332 You can use these commands to manipulate the non-stop mode setting:
6335 @kindex set non-stop
6336 @item set non-stop on
6337 Enable selection of non-stop mode.
6338 @item set non-stop off
6339 Disable selection of non-stop mode.
6340 @kindex show non-stop
6342 Show the current non-stop enablement setting.
6345 Note these commands only reflect whether non-stop mode is enabled,
6346 not whether the currently-executing program is being run in non-stop mode.
6347 In particular, the @code{set non-stop} preference is only consulted when
6348 @value{GDBN} starts or connects to the target program, and it is generally
6349 not possible to switch modes once debugging has started. Furthermore,
6350 since not all targets support non-stop mode, even when you have enabled
6351 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6354 In non-stop mode, all execution commands apply only to the current thread
6355 by default. That is, @code{continue} only continues one thread.
6356 To continue all threads, issue @code{continue -a} or @code{c -a}.
6358 You can use @value{GDBN}'s background execution commands
6359 (@pxref{Background Execution}) to run some threads in the background
6360 while you continue to examine or step others from @value{GDBN}.
6361 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6362 always executed asynchronously in non-stop mode.
6364 Suspending execution is done with the @code{interrupt} command when
6365 running in the background, or @kbd{Ctrl-c} during foreground execution.
6366 In all-stop mode, this stops the whole process;
6367 but in non-stop mode the interrupt applies only to the current thread.
6368 To stop the whole program, use @code{interrupt -a}.
6370 Other execution commands do not currently support the @code{-a} option.
6372 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6373 that thread current, as it does in all-stop mode. This is because the
6374 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6375 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6376 changed to a different thread just as you entered a command to operate on the
6377 previously current thread.
6379 @node Background Execution
6380 @subsection Background Execution
6382 @cindex foreground execution
6383 @cindex background execution
6384 @cindex asynchronous execution
6385 @cindex execution, foreground, background and asynchronous
6387 @value{GDBN}'s execution commands have two variants: the normal
6388 foreground (synchronous) behavior, and a background
6389 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6390 the program to report that some thread has stopped before prompting for
6391 another command. In background execution, @value{GDBN} immediately gives
6392 a command prompt so that you can issue other commands while your program runs.
6394 If the target doesn't support async mode, @value{GDBN} issues an error
6395 message if you attempt to use the background execution commands.
6397 @cindex @code{&}, background execution of commands
6398 To specify background execution, add a @code{&} to the command. For example,
6399 the background form of the @code{continue} command is @code{continue&}, or
6400 just @code{c&}. The execution commands that accept background execution
6406 @xref{Starting, , Starting your Program}.
6410 @xref{Attach, , Debugging an Already-running Process}.
6414 @xref{Continuing and Stepping, step}.
6418 @xref{Continuing and Stepping, stepi}.
6422 @xref{Continuing and Stepping, next}.
6426 @xref{Continuing and Stepping, nexti}.
6430 @xref{Continuing and Stepping, continue}.
6434 @xref{Continuing and Stepping, finish}.
6438 @xref{Continuing and Stepping, until}.
6442 Background execution is especially useful in conjunction with non-stop
6443 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6444 However, you can also use these commands in the normal all-stop mode with
6445 the restriction that you cannot issue another execution command until the
6446 previous one finishes. Examples of commands that are valid in all-stop
6447 mode while the program is running include @code{help} and @code{info break}.
6449 You can interrupt your program while it is running in the background by
6450 using the @code{interrupt} command.
6457 Suspend execution of the running program. In all-stop mode,
6458 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6459 only the current thread. To stop the whole program in non-stop mode,
6460 use @code{interrupt -a}.
6463 @node Thread-Specific Breakpoints
6464 @subsection Thread-Specific Breakpoints
6466 When your program has multiple threads (@pxref{Threads,, Debugging
6467 Programs with Multiple Threads}), you can choose whether to set
6468 breakpoints on all threads, or on a particular thread.
6471 @cindex breakpoints and threads
6472 @cindex thread breakpoints
6473 @kindex break @dots{} thread @var{thread-id}
6474 @item break @var{location} thread @var{thread-id}
6475 @itemx break @var{location} thread @var{thread-id} if @dots{}
6476 @var{location} specifies source lines; there are several ways of
6477 writing them (@pxref{Specify Location}), but the effect is always to
6478 specify some source line.
6480 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6481 to specify that you only want @value{GDBN} to stop the program when a
6482 particular thread reaches this breakpoint. The @var{thread-id} specifier
6483 is one of the thread identifiers assigned by @value{GDBN}, shown
6484 in the first column of the @samp{info threads} display.
6486 If you do not specify @samp{thread @var{thread-id}} when you set a
6487 breakpoint, the breakpoint applies to @emph{all} threads of your
6490 You can use the @code{thread} qualifier on conditional breakpoints as
6491 well; in this case, place @samp{thread @var{thread-id}} before or
6492 after the breakpoint condition, like this:
6495 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6500 Thread-specific breakpoints are automatically deleted when
6501 @value{GDBN} detects the corresponding thread is no longer in the
6502 thread list. For example:
6506 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6509 There are several ways for a thread to disappear, such as a regular
6510 thread exit, but also when you detach from the process with the
6511 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6512 Process}), or if @value{GDBN} loses the remote connection
6513 (@pxref{Remote Debugging}), etc. Note that with some targets,
6514 @value{GDBN} is only able to detect a thread has exited when the user
6515 explictly asks for the thread list with the @code{info threads}
6518 @node Interrupted System Calls
6519 @subsection Interrupted System Calls
6521 @cindex thread breakpoints and system calls
6522 @cindex system calls and thread breakpoints
6523 @cindex premature return from system calls
6524 There is an unfortunate side effect when using @value{GDBN} to debug
6525 multi-threaded programs. If one thread stops for a
6526 breakpoint, or for some other reason, and another thread is blocked in a
6527 system call, then the system call may return prematurely. This is a
6528 consequence of the interaction between multiple threads and the signals
6529 that @value{GDBN} uses to implement breakpoints and other events that
6532 To handle this problem, your program should check the return value of
6533 each system call and react appropriately. This is good programming
6536 For example, do not write code like this:
6542 The call to @code{sleep} will return early if a different thread stops
6543 at a breakpoint or for some other reason.
6545 Instead, write this:
6550 unslept = sleep (unslept);
6553 A system call is allowed to return early, so the system is still
6554 conforming to its specification. But @value{GDBN} does cause your
6555 multi-threaded program to behave differently than it would without
6558 Also, @value{GDBN} uses internal breakpoints in the thread library to
6559 monitor certain events such as thread creation and thread destruction.
6560 When such an event happens, a system call in another thread may return
6561 prematurely, even though your program does not appear to stop.
6564 @subsection Observer Mode
6566 If you want to build on non-stop mode and observe program behavior
6567 without any chance of disruption by @value{GDBN}, you can set
6568 variables to disable all of the debugger's attempts to modify state,
6569 whether by writing memory, inserting breakpoints, etc. These operate
6570 at a low level, intercepting operations from all commands.
6572 When all of these are set to @code{off}, then @value{GDBN} is said to
6573 be @dfn{observer mode}. As a convenience, the variable
6574 @code{observer} can be set to disable these, plus enable non-stop
6577 Note that @value{GDBN} will not prevent you from making nonsensical
6578 combinations of these settings. For instance, if you have enabled
6579 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6580 then breakpoints that work by writing trap instructions into the code
6581 stream will still not be able to be placed.
6586 @item set observer on
6587 @itemx set observer off
6588 When set to @code{on}, this disables all the permission variables
6589 below (except for @code{insert-fast-tracepoints}), plus enables
6590 non-stop debugging. Setting this to @code{off} switches back to
6591 normal debugging, though remaining in non-stop mode.
6594 Show whether observer mode is on or off.
6596 @kindex may-write-registers
6597 @item set may-write-registers on
6598 @itemx set may-write-registers off
6599 This controls whether @value{GDBN} will attempt to alter the values of
6600 registers, such as with assignment expressions in @code{print}, or the
6601 @code{jump} command. It defaults to @code{on}.
6603 @item show may-write-registers
6604 Show the current permission to write registers.
6606 @kindex may-write-memory
6607 @item set may-write-memory on
6608 @itemx set may-write-memory off
6609 This controls whether @value{GDBN} will attempt to alter the contents
6610 of memory, such as with assignment expressions in @code{print}. It
6611 defaults to @code{on}.
6613 @item show may-write-memory
6614 Show the current permission to write memory.
6616 @kindex may-insert-breakpoints
6617 @item set may-insert-breakpoints on
6618 @itemx set may-insert-breakpoints off
6619 This controls whether @value{GDBN} will attempt to insert breakpoints.
6620 This affects all breakpoints, including internal breakpoints defined
6621 by @value{GDBN}. It defaults to @code{on}.
6623 @item show may-insert-breakpoints
6624 Show the current permission to insert breakpoints.
6626 @kindex may-insert-tracepoints
6627 @item set may-insert-tracepoints on
6628 @itemx set may-insert-tracepoints off
6629 This controls whether @value{GDBN} will attempt to insert (regular)
6630 tracepoints at the beginning of a tracing experiment. It affects only
6631 non-fast tracepoints, fast tracepoints being under the control of
6632 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6634 @item show may-insert-tracepoints
6635 Show the current permission to insert tracepoints.
6637 @kindex may-insert-fast-tracepoints
6638 @item set may-insert-fast-tracepoints on
6639 @itemx set may-insert-fast-tracepoints off
6640 This controls whether @value{GDBN} will attempt to insert fast
6641 tracepoints at the beginning of a tracing experiment. It affects only
6642 fast tracepoints, regular (non-fast) tracepoints being under the
6643 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6645 @item show may-insert-fast-tracepoints
6646 Show the current permission to insert fast tracepoints.
6648 @kindex may-interrupt
6649 @item set may-interrupt on
6650 @itemx set may-interrupt off
6651 This controls whether @value{GDBN} will attempt to interrupt or stop
6652 program execution. When this variable is @code{off}, the
6653 @code{interrupt} command will have no effect, nor will
6654 @kbd{Ctrl-c}. It defaults to @code{on}.
6656 @item show may-interrupt
6657 Show the current permission to interrupt or stop the program.
6661 @node Reverse Execution
6662 @chapter Running programs backward
6663 @cindex reverse execution
6664 @cindex running programs backward
6666 When you are debugging a program, it is not unusual to realize that
6667 you have gone too far, and some event of interest has already happened.
6668 If the target environment supports it, @value{GDBN} can allow you to
6669 ``rewind'' the program by running it backward.
6671 A target environment that supports reverse execution should be able
6672 to ``undo'' the changes in machine state that have taken place as the
6673 program was executing normally. Variables, registers etc.@: should
6674 revert to their previous values. Obviously this requires a great
6675 deal of sophistication on the part of the target environment; not
6676 all target environments can support reverse execution.
6678 When a program is executed in reverse, the instructions that
6679 have most recently been executed are ``un-executed'', in reverse
6680 order. The program counter runs backward, following the previous
6681 thread of execution in reverse. As each instruction is ``un-executed'',
6682 the values of memory and/or registers that were changed by that
6683 instruction are reverted to their previous states. After executing
6684 a piece of source code in reverse, all side effects of that code
6685 should be ``undone'', and all variables should be returned to their
6686 prior values@footnote{
6687 Note that some side effects are easier to undo than others. For instance,
6688 memory and registers are relatively easy, but device I/O is hard. Some
6689 targets may be able undo things like device I/O, and some may not.
6691 The contract between @value{GDBN} and the reverse executing target
6692 requires only that the target do something reasonable when
6693 @value{GDBN} tells it to execute backwards, and then report the
6694 results back to @value{GDBN}. Whatever the target reports back to
6695 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6696 assumes that the memory and registers that the target reports are in a
6697 consistant state, but @value{GDBN} accepts whatever it is given.
6700 On some platforms, @value{GDBN} has built-in support for reverse
6701 execution, activated with the @code{record} or @code{record btrace}
6702 commands. @xref{Process Record and Replay}. Some remote targets,
6703 typically full system emulators, support reverse execution directly
6704 without requiring any special command.
6706 If you are debugging in a target environment that supports
6707 reverse execution, @value{GDBN} provides the following commands.
6710 @kindex reverse-continue
6711 @kindex rc @r{(@code{reverse-continue})}
6712 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6713 @itemx rc @r{[}@var{ignore-count}@r{]}
6714 Beginning at the point where your program last stopped, start executing
6715 in reverse. Reverse execution will stop for breakpoints and synchronous
6716 exceptions (signals), just like normal execution. Behavior of
6717 asynchronous signals depends on the target environment.
6719 @kindex reverse-step
6720 @kindex rs @r{(@code{step})}
6721 @item reverse-step @r{[}@var{count}@r{]}
6722 Run the program backward until control reaches the start of a
6723 different source line; then stop it, and return control to @value{GDBN}.
6725 Like the @code{step} command, @code{reverse-step} will only stop
6726 at the beginning of a source line. It ``un-executes'' the previously
6727 executed source line. If the previous source line included calls to
6728 debuggable functions, @code{reverse-step} will step (backward) into
6729 the called function, stopping at the beginning of the @emph{last}
6730 statement in the called function (typically a return statement).
6732 Also, as with the @code{step} command, if non-debuggable functions are
6733 called, @code{reverse-step} will run thru them backward without stopping.
6735 @kindex reverse-stepi
6736 @kindex rsi @r{(@code{reverse-stepi})}
6737 @item reverse-stepi @r{[}@var{count}@r{]}
6738 Reverse-execute one machine instruction. Note that the instruction
6739 to be reverse-executed is @emph{not} the one pointed to by the program
6740 counter, but the instruction executed prior to that one. For instance,
6741 if the last instruction was a jump, @code{reverse-stepi} will take you
6742 back from the destination of the jump to the jump instruction itself.
6744 @kindex reverse-next
6745 @kindex rn @r{(@code{reverse-next})}
6746 @item reverse-next @r{[}@var{count}@r{]}
6747 Run backward to the beginning of the previous line executed in
6748 the current (innermost) stack frame. If the line contains function
6749 calls, they will be ``un-executed'' without stopping. Starting from
6750 the first line of a function, @code{reverse-next} will take you back
6751 to the caller of that function, @emph{before} the function was called,
6752 just as the normal @code{next} command would take you from the last
6753 line of a function back to its return to its caller
6754 @footnote{Unless the code is too heavily optimized.}.
6756 @kindex reverse-nexti
6757 @kindex rni @r{(@code{reverse-nexti})}
6758 @item reverse-nexti @r{[}@var{count}@r{]}
6759 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6760 in reverse, except that called functions are ``un-executed'' atomically.
6761 That is, if the previously executed instruction was a return from
6762 another function, @code{reverse-nexti} will continue to execute
6763 in reverse until the call to that function (from the current stack
6766 @kindex reverse-finish
6767 @item reverse-finish
6768 Just as the @code{finish} command takes you to the point where the
6769 current function returns, @code{reverse-finish} takes you to the point
6770 where it was called. Instead of ending up at the end of the current
6771 function invocation, you end up at the beginning.
6773 @kindex set exec-direction
6774 @item set exec-direction
6775 Set the direction of target execution.
6776 @item set exec-direction reverse
6777 @cindex execute forward or backward in time
6778 @value{GDBN} will perform all execution commands in reverse, until the
6779 exec-direction mode is changed to ``forward''. Affected commands include
6780 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6781 command cannot be used in reverse mode.
6782 @item set exec-direction forward
6783 @value{GDBN} will perform all execution commands in the normal fashion.
6784 This is the default.
6788 @node Process Record and Replay
6789 @chapter Recording Inferior's Execution and Replaying It
6790 @cindex process record and replay
6791 @cindex recording inferior's execution and replaying it
6793 On some platforms, @value{GDBN} provides a special @dfn{process record
6794 and replay} target that can record a log of the process execution, and
6795 replay it later with both forward and reverse execution commands.
6798 When this target is in use, if the execution log includes the record
6799 for the next instruction, @value{GDBN} will debug in @dfn{replay
6800 mode}. In the replay mode, the inferior does not really execute code
6801 instructions. Instead, all the events that normally happen during
6802 code execution are taken from the execution log. While code is not
6803 really executed in replay mode, the values of registers (including the
6804 program counter register) and the memory of the inferior are still
6805 changed as they normally would. Their contents are taken from the
6809 If the record for the next instruction is not in the execution log,
6810 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6811 inferior executes normally, and @value{GDBN} records the execution log
6814 The process record and replay target supports reverse execution
6815 (@pxref{Reverse Execution}), even if the platform on which the
6816 inferior runs does not. However, the reverse execution is limited in
6817 this case by the range of the instructions recorded in the execution
6818 log. In other words, reverse execution on platforms that don't
6819 support it directly can only be done in the replay mode.
6821 When debugging in the reverse direction, @value{GDBN} will work in
6822 replay mode as long as the execution log includes the record for the
6823 previous instruction; otherwise, it will work in record mode, if the
6824 platform supports reverse execution, or stop if not.
6826 Currently, process record and replay is supported on ARM, Aarch64,
6827 Moxie, PowerPC, PowerPC64, S/390, and x86 (i386/amd64) running
6828 GNU/Linux. Process record and replay can be used both when native
6829 debugging, and when remote debugging via @code{gdbserver}.
6831 For architecture environments that support process record and replay,
6832 @value{GDBN} provides the following commands:
6835 @kindex target record
6836 @kindex target record-full
6837 @kindex target record-btrace
6840 @kindex record btrace
6841 @kindex record btrace bts
6842 @kindex record btrace pt
6848 @kindex rec btrace bts
6849 @kindex rec btrace pt
6852 @item record @var{method}
6853 This command starts the process record and replay target. The
6854 recording method can be specified as parameter. Without a parameter
6855 the command uses the @code{full} recording method. The following
6856 recording methods are available:
6860 Full record/replay recording using @value{GDBN}'s software record and
6861 replay implementation. This method allows replaying and reverse
6864 @item btrace @var{format}
6865 Hardware-supported instruction recording, supported on Intel
6866 processors. This method does not record data. Further, the data is
6867 collected in a ring buffer so old data will be overwritten when the
6868 buffer is full. It allows limited reverse execution. Variables and
6869 registers are not available during reverse execution. In remote
6870 debugging, recording continues on disconnect. Recorded data can be
6871 inspected after reconnecting. The recording may be stopped using
6874 The recording format can be specified as parameter. Without a parameter
6875 the command chooses the recording format. The following recording
6876 formats are available:
6880 @cindex branch trace store
6881 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6882 this format, the processor stores a from/to record for each executed
6883 branch in the btrace ring buffer.
6886 @cindex Intel Processor Trace
6887 Use the @dfn{Intel Processor Trace} recording format. In this
6888 format, the processor stores the execution trace in a compressed form
6889 that is afterwards decoded by @value{GDBN}.
6891 The trace can be recorded with very low overhead. The compressed
6892 trace format also allows small trace buffers to already contain a big
6893 number of instructions compared to @acronym{BTS}.
6895 Decoding the recorded execution trace, on the other hand, is more
6896 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6897 increased number of instructions to process. You should increase the
6898 buffer-size with care.
6901 Not all recording formats may be available on all processors.
6904 The process record and replay target can only debug a process that is
6905 already running. Therefore, you need first to start the process with
6906 the @kbd{run} or @kbd{start} commands, and then start the recording
6907 with the @kbd{record @var{method}} command.
6909 @cindex displaced stepping, and process record and replay
6910 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6911 will be automatically disabled when process record and replay target
6912 is started. That's because the process record and replay target
6913 doesn't support displaced stepping.
6915 @cindex non-stop mode, and process record and replay
6916 @cindex asynchronous execution, and process record and replay
6917 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6918 the asynchronous execution mode (@pxref{Background Execution}), not
6919 all recording methods are available. The @code{full} recording method
6920 does not support these two modes.
6925 Stop the process record and replay target. When process record and
6926 replay target stops, the entire execution log will be deleted and the
6927 inferior will either be terminated, or will remain in its final state.
6929 When you stop the process record and replay target in record mode (at
6930 the end of the execution log), the inferior will be stopped at the
6931 next instruction that would have been recorded. In other words, if
6932 you record for a while and then stop recording, the inferior process
6933 will be left in the same state as if the recording never happened.
6935 On the other hand, if the process record and replay target is stopped
6936 while in replay mode (that is, not at the end of the execution log,
6937 but at some earlier point), the inferior process will become ``live''
6938 at that earlier state, and it will then be possible to continue the
6939 usual ``live'' debugging of the process from that state.
6941 When the inferior process exits, or @value{GDBN} detaches from it,
6942 process record and replay target will automatically stop itself.
6946 Go to a specific location in the execution log. There are several
6947 ways to specify the location to go to:
6950 @item record goto begin
6951 @itemx record goto start
6952 Go to the beginning of the execution log.
6954 @item record goto end
6955 Go to the end of the execution log.
6957 @item record goto @var{n}
6958 Go to instruction number @var{n} in the execution log.
6962 @item record save @var{filename}
6963 Save the execution log to a file @file{@var{filename}}.
6964 Default filename is @file{gdb_record.@var{process_id}}, where
6965 @var{process_id} is the process ID of the inferior.
6967 This command may not be available for all recording methods.
6969 @kindex record restore
6970 @item record restore @var{filename}
6971 Restore the execution log from a file @file{@var{filename}}.
6972 File must have been created with @code{record save}.
6974 @kindex set record full
6975 @item set record full insn-number-max @var{limit}
6976 @itemx set record full insn-number-max unlimited
6977 Set the limit of instructions to be recorded for the @code{full}
6978 recording method. Default value is 200000.
6980 If @var{limit} is a positive number, then @value{GDBN} will start
6981 deleting instructions from the log once the number of the record
6982 instructions becomes greater than @var{limit}. For every new recorded
6983 instruction, @value{GDBN} will delete the earliest recorded
6984 instruction to keep the number of recorded instructions at the limit.
6985 (Since deleting recorded instructions loses information, @value{GDBN}
6986 lets you control what happens when the limit is reached, by means of
6987 the @code{stop-at-limit} option, described below.)
6989 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6990 delete recorded instructions from the execution log. The number of
6991 recorded instructions is limited only by the available memory.
6993 @kindex show record full
6994 @item show record full insn-number-max
6995 Show the limit of instructions to be recorded with the @code{full}
6998 @item set record full stop-at-limit
6999 Control the behavior of the @code{full} recording method when the
7000 number of recorded instructions reaches the limit. If ON (the
7001 default), @value{GDBN} will stop when the limit is reached for the
7002 first time and ask you whether you want to stop the inferior or
7003 continue running it and recording the execution log. If you decide
7004 to continue recording, each new recorded instruction will cause the
7005 oldest one to be deleted.
7007 If this option is OFF, @value{GDBN} will automatically delete the
7008 oldest record to make room for each new one, without asking.
7010 @item show record full stop-at-limit
7011 Show the current setting of @code{stop-at-limit}.
7013 @item set record full memory-query
7014 Control the behavior when @value{GDBN} is unable to record memory
7015 changes caused by an instruction for the @code{full} recording method.
7016 If ON, @value{GDBN} will query whether to stop the inferior in that
7019 If this option is OFF (the default), @value{GDBN} will automatically
7020 ignore the effect of such instructions on memory. Later, when
7021 @value{GDBN} replays this execution log, it will mark the log of this
7022 instruction as not accessible, and it will not affect the replay
7025 @item show record full memory-query
7026 Show the current setting of @code{memory-query}.
7028 @kindex set record btrace
7029 The @code{btrace} record target does not trace data. As a
7030 convenience, when replaying, @value{GDBN} reads read-only memory off
7031 the live program directly, assuming that the addresses of the
7032 read-only areas don't change. This for example makes it possible to
7033 disassemble code while replaying, but not to print variables.
7034 In some cases, being able to inspect variables might be useful.
7035 You can use the following command for that:
7037 @item set record btrace replay-memory-access
7038 Control the behavior of the @code{btrace} recording method when
7039 accessing memory during replay. If @code{read-only} (the default),
7040 @value{GDBN} will only allow accesses to read-only memory.
7041 If @code{read-write}, @value{GDBN} will allow accesses to read-only
7042 and to read-write memory. Beware that the accessed memory corresponds
7043 to the live target and not necessarily to the current replay
7046 @item set record btrace cpu @var{identifier}
7047 Set the processor to be used for enabling workarounds for processor
7048 errata when decoding the trace.
7050 Processor errata are defects in processor operation, caused by its
7051 design or manufacture. They can cause a trace not to match the
7052 specification. This, in turn, may cause trace decode to fail.
7053 @value{GDBN} can detect erroneous trace packets and correct them, thus
7054 avoiding the decoding failures. These corrections are known as
7055 @dfn{errata workarounds}, and are enabled based on the processor on
7056 which the trace was recorded.
7058 By default, @value{GDBN} attempts to detect the processor
7059 automatically, and apply the necessary workarounds for it. However,
7060 you may need to specify the processor if @value{GDBN} does not yet
7061 support it. This command allows you to do that, and also allows to
7062 disable the workarounds.
7064 The argument @var{identifier} identifies the @sc{cpu} and is of the
7065 form: @code{@var{vendor}:@var{procesor identifier}}. In addition,
7066 there are two special identifiers, @code{none} and @code{auto}
7069 The following vendor identifiers and corresponding processor
7070 identifiers are currently supported:
7072 @multitable @columnfractions .1 .9
7075 @tab @var{family}/@var{model}[/@var{stepping}]
7079 On GNU/Linux systems, the processor @var{family}, @var{model}, and
7080 @var{stepping} can be obtained from @code{/proc/cpuinfo}.
7082 If @var{identifier} is @code{auto}, enable errata workarounds for the
7083 processor on which the trace was recorded. If @var{identifier} is
7084 @code{none}, errata workarounds are disabled.
7086 For example, when using an old @value{GDBN} on a new system, decode
7087 may fail because @value{GDBN} does not support the new processor. It
7088 often suffices to specify an older processor that @value{GDBN}
7093 Active record target: record-btrace
7094 Recording format: Intel Processor Trace.
7096 Failed to configure the Intel Processor Trace decoder: unknown cpu.
7097 (gdb) set record btrace cpu intel:6/158
7099 Active record target: record-btrace
7100 Recording format: Intel Processor Trace.
7102 Recorded 84872 instructions in 3189 functions (0 gaps) for thread 1 (...).
7105 @kindex show record btrace
7106 @item show record btrace replay-memory-access
7107 Show the current setting of @code{replay-memory-access}.
7109 @item show record btrace cpu
7110 Show the processor to be used for enabling trace decode errata
7113 @kindex set record btrace bts
7114 @item set record btrace bts buffer-size @var{size}
7115 @itemx set record btrace bts buffer-size unlimited
7116 Set the requested ring buffer size for branch tracing in @acronym{BTS}
7117 format. Default is 64KB.
7119 If @var{size} is a positive number, then @value{GDBN} will try to
7120 allocate a buffer of at least @var{size} bytes for each new thread
7121 that uses the btrace recording method and the @acronym{BTS} format.
7122 The actually obtained buffer size may differ from the requested
7123 @var{size}. Use the @code{info record} command to see the actual
7124 buffer size for each thread that uses the btrace recording method and
7125 the @acronym{BTS} format.
7127 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7128 allocate a buffer of 4MB.
7130 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7131 also need longer to process the branch trace data before it can be used.
7133 @item show record btrace bts buffer-size @var{size}
7134 Show the current setting of the requested ring buffer size for branch
7135 tracing in @acronym{BTS} format.
7137 @kindex set record btrace pt
7138 @item set record btrace pt buffer-size @var{size}
7139 @itemx set record btrace pt buffer-size unlimited
7140 Set the requested ring buffer size for branch tracing in Intel
7141 Processor Trace format. Default is 16KB.
7143 If @var{size} is a positive number, then @value{GDBN} will try to
7144 allocate a buffer of at least @var{size} bytes for each new thread
7145 that uses the btrace recording method and the Intel Processor Trace
7146 format. The actually obtained buffer size may differ from the
7147 requested @var{size}. Use the @code{info record} command to see the
7148 actual buffer size for each thread.
7150 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
7151 allocate a buffer of 4MB.
7153 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
7154 also need longer to process the branch trace data before it can be used.
7156 @item show record btrace pt buffer-size @var{size}
7157 Show the current setting of the requested ring buffer size for branch
7158 tracing in Intel Processor Trace format.
7162 Show various statistics about the recording depending on the recording
7167 For the @code{full} recording method, it shows the state of process
7168 record and its in-memory execution log buffer, including:
7172 Whether in record mode or replay mode.
7174 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7176 Highest recorded instruction number.
7178 Current instruction about to be replayed (if in replay mode).
7180 Number of instructions contained in the execution log.
7182 Maximum number of instructions that may be contained in the execution log.
7186 For the @code{btrace} recording method, it shows:
7192 Number of instructions that have been recorded.
7194 Number of blocks of sequential control-flow formed by the recorded
7197 Whether in record mode or replay mode.
7200 For the @code{bts} recording format, it also shows:
7203 Size of the perf ring buffer.
7206 For the @code{pt} recording format, it also shows:
7209 Size of the perf ring buffer.
7213 @kindex record delete
7216 When record target runs in replay mode (``in the past''), delete the
7217 subsequent execution log and begin to record a new execution log starting
7218 from the current address. This means you will abandon the previously
7219 recorded ``future'' and begin recording a new ``future''.
7221 @kindex record instruction-history
7222 @kindex rec instruction-history
7223 @item record instruction-history
7224 Disassembles instructions from the recorded execution log. By
7225 default, ten instructions are disassembled. This can be changed using
7226 the @code{set record instruction-history-size} command. Instructions
7227 are printed in execution order.
7229 It can also print mixed source+disassembly if you specify the the
7230 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7231 as well as in symbolic form by specifying the @code{/r} modifier.
7233 The current position marker is printed for the instruction at the
7234 current program counter value. This instruction can appear multiple
7235 times in the trace and the current position marker will be printed
7236 every time. To omit the current position marker, specify the
7239 To better align the printed instructions when the trace contains
7240 instructions from more than one function, the function name may be
7241 omitted by specifying the @code{/f} modifier.
7243 Speculatively executed instructions are prefixed with @samp{?}. This
7244 feature is not available for all recording formats.
7246 There are several ways to specify what part of the execution log to
7250 @item record instruction-history @var{insn}
7251 Disassembles ten instructions starting from instruction number
7254 @item record instruction-history @var{insn}, +/-@var{n}
7255 Disassembles @var{n} instructions around instruction number
7256 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7257 @var{n} instructions after instruction number @var{insn}. If
7258 @var{n} is preceded with @code{-}, disassembles @var{n}
7259 instructions before instruction number @var{insn}.
7261 @item record instruction-history
7262 Disassembles ten more instructions after the last disassembly.
7264 @item record instruction-history -
7265 Disassembles ten more instructions before the last disassembly.
7267 @item record instruction-history @var{begin}, @var{end}
7268 Disassembles instructions beginning with instruction number
7269 @var{begin} until instruction number @var{end}. The instruction
7270 number @var{end} is included.
7273 This command may not be available for all recording methods.
7276 @item set record instruction-history-size @var{size}
7277 @itemx set record instruction-history-size unlimited
7278 Define how many instructions to disassemble in the @code{record
7279 instruction-history} command. The default value is 10.
7280 A @var{size} of @code{unlimited} means unlimited instructions.
7283 @item show record instruction-history-size
7284 Show how many instructions to disassemble in the @code{record
7285 instruction-history} command.
7287 @kindex record function-call-history
7288 @kindex rec function-call-history
7289 @item record function-call-history
7290 Prints the execution history at function granularity. It prints one
7291 line for each sequence of instructions that belong to the same
7292 function giving the name of that function, the source lines
7293 for this instruction sequence (if the @code{/l} modifier is
7294 specified), and the instructions numbers that form the sequence (if
7295 the @code{/i} modifier is specified). The function names are indented
7296 to reflect the call stack depth if the @code{/c} modifier is
7297 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7301 (@value{GDBP}) @b{list 1, 10}
7312 (@value{GDBP}) @b{record function-call-history /ilc}
7313 1 bar inst 1,4 at foo.c:6,8
7314 2 foo inst 5,10 at foo.c:2,3
7315 3 bar inst 11,13 at foo.c:9,10
7318 By default, ten lines are printed. This can be changed using the
7319 @code{set record function-call-history-size} command. Functions are
7320 printed in execution order. There are several ways to specify what
7324 @item record function-call-history @var{func}
7325 Prints ten functions starting from function number @var{func}.
7327 @item record function-call-history @var{func}, +/-@var{n}
7328 Prints @var{n} functions around function number @var{func}. If
7329 @var{n} is preceded with @code{+}, prints @var{n} functions after
7330 function number @var{func}. If @var{n} is preceded with @code{-},
7331 prints @var{n} functions before function number @var{func}.
7333 @item record function-call-history
7334 Prints ten more functions after the last ten-line print.
7336 @item record function-call-history -
7337 Prints ten more functions before the last ten-line print.
7339 @item record function-call-history @var{begin}, @var{end}
7340 Prints functions beginning with function number @var{begin} until
7341 function number @var{end}. The function number @var{end} is included.
7344 This command may not be available for all recording methods.
7346 @item set record function-call-history-size @var{size}
7347 @itemx set record function-call-history-size unlimited
7348 Define how many lines to print in the
7349 @code{record function-call-history} command. The default value is 10.
7350 A size of @code{unlimited} means unlimited lines.
7352 @item show record function-call-history-size
7353 Show how many lines to print in the
7354 @code{record function-call-history} command.
7359 @chapter Examining the Stack
7361 When your program has stopped, the first thing you need to know is where it
7362 stopped and how it got there.
7365 Each time your program performs a function call, information about the call
7367 That information includes the location of the call in your program,
7368 the arguments of the call,
7369 and the local variables of the function being called.
7370 The information is saved in a block of data called a @dfn{stack frame}.
7371 The stack frames are allocated in a region of memory called the @dfn{call
7374 When your program stops, the @value{GDBN} commands for examining the
7375 stack allow you to see all of this information.
7377 @cindex selected frame
7378 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7379 @value{GDBN} commands refer implicitly to the selected frame. In
7380 particular, whenever you ask @value{GDBN} for the value of a variable in
7381 your program, the value is found in the selected frame. There are
7382 special @value{GDBN} commands to select whichever frame you are
7383 interested in. @xref{Selection, ,Selecting a Frame}.
7385 When your program stops, @value{GDBN} automatically selects the
7386 currently executing frame and describes it briefly, similar to the
7387 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7390 * Frames:: Stack frames
7391 * Backtrace:: Backtraces
7392 * Selection:: Selecting a frame
7393 * Frame Info:: Information on a frame
7394 * Frame Apply:: Applying a command to several frames
7395 * Frame Filter Management:: Managing frame filters
7400 @section Stack Frames
7402 @cindex frame, definition
7404 The call stack is divided up into contiguous pieces called @dfn{stack
7405 frames}, or @dfn{frames} for short; each frame is the data associated
7406 with one call to one function. The frame contains the arguments given
7407 to the function, the function's local variables, and the address at
7408 which the function is executing.
7410 @cindex initial frame
7411 @cindex outermost frame
7412 @cindex innermost frame
7413 When your program is started, the stack has only one frame, that of the
7414 function @code{main}. This is called the @dfn{initial} frame or the
7415 @dfn{outermost} frame. Each time a function is called, a new frame is
7416 made. Each time a function returns, the frame for that function invocation
7417 is eliminated. If a function is recursive, there can be many frames for
7418 the same function. The frame for the function in which execution is
7419 actually occurring is called the @dfn{innermost} frame. This is the most
7420 recently created of all the stack frames that still exist.
7422 @cindex frame pointer
7423 Inside your program, stack frames are identified by their addresses. A
7424 stack frame consists of many bytes, each of which has its own address; each
7425 kind of computer has a convention for choosing one byte whose
7426 address serves as the address of the frame. Usually this address is kept
7427 in a register called the @dfn{frame pointer register}
7428 (@pxref{Registers, $fp}) while execution is going on in that frame.
7431 @cindex frame number
7432 @value{GDBN} labels each existing stack frame with a @dfn{level}, a
7433 number that is zero for the innermost frame, one for the frame that
7434 called it, and so on upward. These level numbers give you a way of
7435 designating stack frames in @value{GDBN} commands. The terms
7436 @dfn{frame number} and @dfn{frame level} can be used interchangeably to
7437 describe this number.
7439 @c The -fomit-frame-pointer below perennially causes hbox overflow
7440 @c underflow problems.
7441 @cindex frameless execution
7442 Some compilers provide a way to compile functions so that they operate
7443 without stack frames. (For example, the @value{NGCC} option
7445 @samp{-fomit-frame-pointer}
7447 generates functions without a frame.)
7448 This is occasionally done with heavily used library functions to save
7449 the frame setup time. @value{GDBN} has limited facilities for dealing
7450 with these function invocations. If the innermost function invocation
7451 has no stack frame, @value{GDBN} nevertheless regards it as though
7452 it had a separate frame, which is numbered zero as usual, allowing
7453 correct tracing of the function call chain. However, @value{GDBN} has
7454 no provision for frameless functions elsewhere in the stack.
7460 @cindex call stack traces
7461 A backtrace is a summary of how your program got where it is. It shows one
7462 line per frame, for many frames, starting with the currently executing
7463 frame (frame zero), followed by its caller (frame one), and on up the
7466 @anchor{backtrace-command}
7468 @kindex bt @r{(@code{backtrace})}
7469 To print a backtrace of the entire stack, use the @code{backtrace}
7470 command, or its alias @code{bt}. This command will print one line per
7471 frame for frames in the stack. By default, all stack frames are
7472 printed. You can stop the backtrace at any time by typing the system
7473 interrupt character, normally @kbd{Ctrl-c}.
7476 @item backtrace [@var{args}@dots{}]
7477 @itemx bt [@var{args}@dots{}]
7478 Print the backtrace of the entire stack. The optional @var{args} can
7479 be one of the following:
7484 Print only the innermost @var{n} frames, where @var{n} is a positive
7489 Print only the outermost @var{n} frames, where @var{n} is a positive
7493 Print the values of the local variables also. This can be combined
7494 with a number to limit the number of frames shown.
7497 Do not run Python frame filters on this backtrace. @xref{Frame
7498 Filter API}, for more information. Additionally use @ref{disable
7499 frame-filter all} to turn off all frame filters. This is only
7500 relevant when @value{GDBN} has been configured with @code{Python}
7504 A Python frame filter might decide to ``elide'' some frames. Normally
7505 such elided frames are still printed, but they are indented relative
7506 to the filtered frames that cause them to be elided. The @code{hide}
7507 option causes elided frames to not be printed at all.
7513 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7514 are additional aliases for @code{backtrace}.
7516 @cindex multiple threads, backtrace
7517 In a multi-threaded program, @value{GDBN} by default shows the
7518 backtrace only for the current thread. To display the backtrace for
7519 several or all of the threads, use the command @code{thread apply}
7520 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7521 apply all backtrace}, @value{GDBN} will display the backtrace for all
7522 the threads; this is handy when you debug a core dump of a
7523 multi-threaded program.
7525 Each line in the backtrace shows the frame number and the function name.
7526 The program counter value is also shown---unless you use @code{set
7527 print address off}. The backtrace also shows the source file name and
7528 line number, as well as the arguments to the function. The program
7529 counter value is omitted if it is at the beginning of the code for that
7532 Here is an example of a backtrace. It was made with the command
7533 @samp{bt 3}, so it shows the innermost three frames.
7537 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7539 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7540 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7542 (More stack frames follow...)
7547 The display for frame zero does not begin with a program counter
7548 value, indicating that your program has stopped at the beginning of the
7549 code for line @code{993} of @code{builtin.c}.
7552 The value of parameter @code{data} in frame 1 has been replaced by
7553 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7554 only if it is a scalar (integer, pointer, enumeration, etc). See command
7555 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7556 on how to configure the way function parameter values are printed.
7558 @cindex optimized out, in backtrace
7559 @cindex function call arguments, optimized out
7560 If your program was compiled with optimizations, some compilers will
7561 optimize away arguments passed to functions if those arguments are
7562 never used after the call. Such optimizations generate code that
7563 passes arguments through registers, but doesn't store those arguments
7564 in the stack frame. @value{GDBN} has no way of displaying such
7565 arguments in stack frames other than the innermost one. Here's what
7566 such a backtrace might look like:
7570 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7572 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7573 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7575 (More stack frames follow...)
7580 The values of arguments that were not saved in their stack frames are
7581 shown as @samp{<optimized out>}.
7583 If you need to display the values of such optimized-out arguments,
7584 either deduce that from other variables whose values depend on the one
7585 you are interested in, or recompile without optimizations.
7587 @cindex backtrace beyond @code{main} function
7588 @cindex program entry point
7589 @cindex startup code, and backtrace
7590 Most programs have a standard user entry point---a place where system
7591 libraries and startup code transition into user code. For C this is
7592 @code{main}@footnote{
7593 Note that embedded programs (the so-called ``free-standing''
7594 environment) are not required to have a @code{main} function as the
7595 entry point. They could even have multiple entry points.}.
7596 When @value{GDBN} finds the entry function in a backtrace
7597 it will terminate the backtrace, to avoid tracing into highly
7598 system-specific (and generally uninteresting) code.
7600 If you need to examine the startup code, or limit the number of levels
7601 in a backtrace, you can change this behavior:
7604 @item set backtrace past-main
7605 @itemx set backtrace past-main on
7606 @kindex set backtrace
7607 Backtraces will continue past the user entry point.
7609 @item set backtrace past-main off
7610 Backtraces will stop when they encounter the user entry point. This is the
7613 @item show backtrace past-main
7614 @kindex show backtrace
7615 Display the current user entry point backtrace policy.
7617 @item set backtrace past-entry
7618 @itemx set backtrace past-entry on
7619 Backtraces will continue past the internal entry point of an application.
7620 This entry point is encoded by the linker when the application is built,
7621 and is likely before the user entry point @code{main} (or equivalent) is called.
7623 @item set backtrace past-entry off
7624 Backtraces will stop when they encounter the internal entry point of an
7625 application. This is the default.
7627 @item show backtrace past-entry
7628 Display the current internal entry point backtrace policy.
7630 @item set backtrace limit @var{n}
7631 @itemx set backtrace limit 0
7632 @itemx set backtrace limit unlimited
7633 @cindex backtrace limit
7634 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7635 or zero means unlimited levels.
7637 @item show backtrace limit
7638 Display the current limit on backtrace levels.
7641 You can control how file names are displayed.
7644 @item set filename-display
7645 @itemx set filename-display relative
7646 @cindex filename-display
7647 Display file names relative to the compilation directory. This is the default.
7649 @item set filename-display basename
7650 Display only basename of a filename.
7652 @item set filename-display absolute
7653 Display an absolute filename.
7655 @item show filename-display
7656 Show the current way to display filenames.
7660 @section Selecting a Frame
7662 Most commands for examining the stack and other data in your program work on
7663 whichever stack frame is selected at the moment. Here are the commands for
7664 selecting a stack frame; all of them finish by printing a brief description
7665 of the stack frame just selected.
7668 @kindex frame@r{, selecting}
7669 @kindex f @r{(@code{frame})}
7670 @item frame @r{[} @var{frame-selection-spec} @r{]}
7671 @item f @r{[} @var{frame-selection-spec} @r{]}
7672 The @command{frame} command allows different stack frames to be
7673 selected. The @var{frame-selection-spec} can be any of the following:
7678 @item level @var{num}
7679 Select frame level @var{num}. Recall that frame zero is the innermost
7680 (currently executing) frame, frame one is the frame that called the
7681 innermost one, and so on. The highest level frame is usually the one
7684 As this is the most common method of navigating the frame stack, the
7685 string @command{level} can be omitted. For example, the following two
7686 commands are equivalent:
7689 (@value{GDBP}) frame 3
7690 (@value{GDBP}) frame level 3
7693 @kindex frame address
7694 @item address @var{stack-address}
7695 Select the frame with stack address @var{stack-address}. The
7696 @var{stack-address} for a frame can be seen in the output of
7697 @command{info frame}, for example:
7701 Stack level 1, frame at 0x7fffffffda30:
7702 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
7703 tail call frame, caller of frame at 0x7fffffffda30
7704 source language c++.
7705 Arglist at unknown address.
7706 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
7709 The @var{stack-address} for this frame is @code{0x7fffffffda30} as
7710 indicated by the line:
7713 Stack level 1, frame at 0x7fffffffda30:
7716 @kindex frame function
7717 @item function @var{function-name}
7718 Select the stack frame for function @var{function-name}. If there are
7719 multiple stack frames for function @var{function-name} then the inner
7720 most stack frame is selected.
7723 @item view @var{stack-address} @r{[} @var{pc-addr} @r{]}
7724 View a frame that is not part of @value{GDBN}'s backtrace. The frame
7725 viewed has stack address @var{stack-addr}, and optionally, a program
7726 counter address of @var{pc-addr}.
7728 This is useful mainly if the chaining of stack frames has been
7729 damaged by a bug, making it impossible for @value{GDBN} to assign
7730 numbers properly to all frames. In addition, this can be useful
7731 when your program has multiple stacks and switches between them.
7733 When viewing a frame outside the current backtrace using
7734 @command{frame view} then you can always return to the original
7735 stack using one of the previous stack frame selection instructions,
7736 for example @command{frame level 0}.
7742 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7743 numbers @var{n}, this advances toward the outermost frame, to higher
7744 frame numbers, to frames that have existed longer.
7747 @kindex do @r{(@code{down})}
7749 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7750 positive numbers @var{n}, this advances toward the innermost frame, to
7751 lower frame numbers, to frames that were created more recently.
7752 You may abbreviate @code{down} as @code{do}.
7755 All of these commands end by printing two lines of output describing the
7756 frame. The first line shows the frame number, the function name, the
7757 arguments, and the source file and line number of execution in that
7758 frame. The second line shows the text of that source line.
7766 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7768 10 read_input_file (argv[i]);
7772 After such a printout, the @code{list} command with no arguments
7773 prints ten lines centered on the point of execution in the frame.
7774 You can also edit the program at the point of execution with your favorite
7775 editing program by typing @code{edit}.
7776 @xref{List, ,Printing Source Lines},
7780 @kindex select-frame
7781 @item select-frame @r{[} @var{frame-selection-spec} @r{]}
7782 The @code{select-frame} command is a variant of @code{frame} that does
7783 not display the new frame after selecting it. This command is
7784 intended primarily for use in @value{GDBN} command scripts, where the
7785 output might be unnecessary and distracting. The
7786 @var{frame-selection-spec} is as for the @command{frame} command
7787 described in @ref{Selection, ,Selecting a Frame}.
7789 @kindex down-silently
7791 @item up-silently @var{n}
7792 @itemx down-silently @var{n}
7793 These two commands are variants of @code{up} and @code{down},
7794 respectively; they differ in that they do their work silently, without
7795 causing display of the new frame. They are intended primarily for use
7796 in @value{GDBN} command scripts, where the output might be unnecessary and
7801 @section Information About a Frame
7803 There are several other commands to print information about the selected
7809 When used without any argument, this command does not change which
7810 frame is selected, but prints a brief description of the currently
7811 selected stack frame. It can be abbreviated @code{f}. With an
7812 argument, this command is used to select a stack frame.
7813 @xref{Selection, ,Selecting a Frame}.
7816 @kindex info f @r{(@code{info frame})}
7819 This command prints a verbose description of the selected stack frame,
7824 the address of the frame
7826 the address of the next frame down (called by this frame)
7828 the address of the next frame up (caller of this frame)
7830 the language in which the source code corresponding to this frame is written
7832 the address of the frame's arguments
7834 the address of the frame's local variables
7836 the program counter saved in it (the address of execution in the caller frame)
7838 which registers were saved in the frame
7841 @noindent The verbose description is useful when
7842 something has gone wrong that has made the stack format fail to fit
7843 the usual conventions.
7845 @item info frame @r{[} @var{frame-selection-spec} @r{]}
7846 @itemx info f @r{[} @var{frame-selection-spec} @r{]}
7847 Print a verbose description of the frame selected by
7848 @var{frame-selection-spec}. The @var{frame-selection-spec} is the
7849 same as for the @command{frame} command (@pxref{Selection, ,Selecting
7850 a Frame}). The selected frame remains unchanged by this command.
7853 @item info args [-q]
7854 Print the arguments of the selected frame, each on a separate line.
7856 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7857 printing header information and messages explaining why no argument
7860 @item info args [-q] [-t @var{type_regexp}] [@var{regexp}]
7861 Like @kbd{info args}, but only print the arguments selected
7862 with the provided regexp(s).
7864 If @var{regexp} is provided, print only the arguments whose names
7865 match the regular expression @var{regexp}.
7867 If @var{type_regexp} is provided, print only the arguments whose
7868 types, as printed by the @code{whatis} command, match
7869 the regular expression @var{type_regexp}.
7870 If @var{type_regexp} contains space(s), it should be enclosed in
7871 quote characters. If needed, use backslash to escape the meaning
7872 of special characters or quotes.
7874 If both @var{regexp} and @var{type_regexp} are provided, an argument
7875 is printed only if its name matches @var{regexp} and its type matches
7878 @item info locals [-q]
7880 Print the local variables of the selected frame, each on a separate
7881 line. These are all variables (declared either static or automatic)
7882 accessible at the point of execution of the selected frame.
7884 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
7885 printing header information and messages explaining why no local variables
7888 @item info locals [-q] [-t @var{type_regexp}] [@var{regexp}]
7889 Like @kbd{info locals}, but only print the local variables selected
7890 with the provided regexp(s).
7892 If @var{regexp} is provided, print only the local variables whose names
7893 match the regular expression @var{regexp}.
7895 If @var{type_regexp} is provided, print only the local variables whose
7896 types, as printed by the @code{whatis} command, match
7897 the regular expression @var{type_regexp}.
7898 If @var{type_regexp} contains space(s), it should be enclosed in
7899 quote characters. If needed, use backslash to escape the meaning
7900 of special characters or quotes.
7902 If both @var{regexp} and @var{type_regexp} are provided, a local variable
7903 is printed only if its name matches @var{regexp} and its type matches
7906 The command @kbd{info locals -q -t @var{type_regexp}} can usefully be
7907 combined with the commands @kbd{frame apply} and @kbd{thread apply}.
7908 For example, your program might use Resource Acquisition Is
7909 Initialization types (RAII) such as @code{lock_something_t}: each
7910 local variable of type @code{lock_something_t} automatically places a
7911 lock that is destroyed when the variable goes out of scope. You can
7912 then list all acquired locks in your program by doing
7914 thread apply all -s frame apply all -s info locals -q -t lock_something_t
7917 or the equivalent shorter form
7919 tfaas i lo -q -t lock_something_t
7925 @section Applying a Command to Several Frames.
7927 @cindex apply command to several frames
7929 @item frame apply [all | @var{count} | @var{-count} | level @var{level}@dots{}] [@var{flag}]@dots{} @var{command}
7930 The @code{frame apply} command allows you to apply the named
7931 @var{command} to one or more frames.
7935 Specify @code{all} to apply @var{command} to all frames.
7938 Use @var{count} to apply @var{command} to the innermost @var{count}
7939 frames, where @var{count} is a positive number.
7942 Use @var{-count} to apply @var{command} to the outermost @var{count}
7943 frames, where @var{count} is a positive number.
7946 Use @code{level} to apply @var{command} to the set of frames identified
7947 by the @var{level} list. @var{level} is a frame level or a range of frame
7948 levels as @var{level1}-@var{level2}. The frame level is the number shown
7949 in the first field of the @samp{backtrace} command output.
7950 E.g., @samp{2-4 6-8 3} indicates to apply @var{command} for the frames
7951 at levels 2, 3, 4, 6, 7, 8, and then again on frame at level 3.
7957 Note that the frames on which @code{frame apply} applies a command are
7958 also influenced by the @code{set backtrace} settings such as @code{set
7959 backtrace past-main} and @code{set backtrace limit N}. See
7960 @xref{Backtrace,,Backtraces}.
7962 The @var{flag} arguments control what output to produce and how to handle
7963 errors raised when applying @var{command} to a frame. @var{flag}
7964 must start with a @code{-} directly followed by one letter in
7965 @code{qcs}. If several flags are provided, they must be given
7966 individually, such as @code{-c -q}.
7968 By default, @value{GDBN} displays some frame information before the
7969 output produced by @var{command}, and an error raised during the
7970 execution of a @var{command} will abort @code{frame apply}. The
7971 following flags can be used to fine-tune this behavior:
7975 The flag @code{-c}, which stands for @samp{continue}, causes any
7976 errors in @var{command} to be displayed, and the execution of
7977 @code{frame apply} then continues.
7979 The flag @code{-s}, which stands for @samp{silent}, causes any errors
7980 or empty output produced by a @var{command} to be silently ignored.
7981 That is, the execution continues, but the frame information and errors
7984 The flag @code{-q} (@samp{quiet}) disables printing the frame
7988 The following example shows how the flags @code{-c} and @code{-s} are
7989 working when applying the command @code{p j} to all frames, where
7990 variable @code{j} can only be successfully printed in the outermost
7991 @code{#1 main} frame.
7995 (gdb) frame apply all p j
7996 #0 some_function (i=5) at fun.c:4
7997 No symbol "j" in current context.
7998 (gdb) frame apply all -c p j
7999 #0 some_function (i=5) at fun.c:4
8000 No symbol "j" in current context.
8001 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8003 (gdb) frame apply all -s p j
8004 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8010 By default, @samp{frame apply}, prints the frame location
8011 information before the command output:
8015 (gdb) frame apply all p $sp
8016 #0 some_function (i=5) at fun.c:4
8017 $4 = (void *) 0xffffd1e0
8018 #1 0x565555fb in main (argc=1, argv=0xffffd2c4) at fun.c:11
8019 $5 = (void *) 0xffffd1f0
8024 If flag @code{-q} is given, no frame information is printed:
8027 (gdb) frame apply all -q p $sp
8028 $12 = (void *) 0xffffd1e0
8029 $13 = (void *) 0xffffd1f0
8037 @cindex apply a command to all frames (ignoring errors and empty output)
8038 @item faas @var{command}
8039 Shortcut for @code{frame apply all -s @var{command}}.
8040 Applies @var{command} on all frames, ignoring errors and empty output.
8042 It can for example be used to print a local variable or a function
8043 argument without knowing the frame where this variable or argument
8046 (@value{GDBP}) faas p some_local_var_i_do_not_remember_where_it_is
8049 Note that the command @code{tfaas @var{command}} applies @var{command}
8050 on all frames of all threads. See @xref{Threads,,Threads}.
8054 @node Frame Filter Management
8055 @section Management of Frame Filters.
8056 @cindex managing frame filters
8058 Frame filters are Python based utilities to manage and decorate the
8059 output of frames. @xref{Frame Filter API}, for further information.
8061 Managing frame filters is performed by several commands available
8062 within @value{GDBN}, detailed here.
8065 @kindex info frame-filter
8066 @item info frame-filter
8067 Print a list of installed frame filters from all dictionaries, showing
8068 their name, priority and enabled status.
8070 @kindex disable frame-filter
8071 @anchor{disable frame-filter all}
8072 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
8073 Disable a frame filter in the dictionary matching
8074 @var{filter-dictionary} and @var{filter-name}. The
8075 @var{filter-dictionary} may be @code{all}, @code{global},
8076 @code{progspace}, or the name of the object file where the frame filter
8077 dictionary resides. When @code{all} is specified, all frame filters
8078 across all dictionaries are disabled. The @var{filter-name} is the name
8079 of the frame filter and is used when @code{all} is not the option for
8080 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
8081 may be enabled again later.
8083 @kindex enable frame-filter
8084 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
8085 Enable a frame filter in the dictionary matching
8086 @var{filter-dictionary} and @var{filter-name}. The
8087 @var{filter-dictionary} may be @code{all}, @code{global},
8088 @code{progspace} or the name of the object file where the frame filter
8089 dictionary resides. When @code{all} is specified, all frame filters across
8090 all dictionaries are enabled. The @var{filter-name} is the name of the frame
8091 filter and is used when @code{all} is not the option for
8092 @var{filter-dictionary}.
8097 (gdb) info frame-filter
8099 global frame-filters:
8100 Priority Enabled Name
8101 1000 No PrimaryFunctionFilter
8104 progspace /build/test frame-filters:
8105 Priority Enabled Name
8106 100 Yes ProgspaceFilter
8108 objfile /build/test frame-filters:
8109 Priority Enabled Name
8110 999 Yes BuildProgra Filter
8112 (gdb) disable frame-filter /build/test BuildProgramFilter
8113 (gdb) info frame-filter
8115 global frame-filters:
8116 Priority Enabled Name
8117 1000 No PrimaryFunctionFilter
8120 progspace /build/test frame-filters:
8121 Priority Enabled Name
8122 100 Yes ProgspaceFilter
8124 objfile /build/test frame-filters:
8125 Priority Enabled Name
8126 999 No BuildProgramFilter
8128 (gdb) enable frame-filter global PrimaryFunctionFilter
8129 (gdb) info frame-filter
8131 global frame-filters:
8132 Priority Enabled Name
8133 1000 Yes PrimaryFunctionFilter
8136 progspace /build/test frame-filters:
8137 Priority Enabled Name
8138 100 Yes ProgspaceFilter
8140 objfile /build/test frame-filters:
8141 Priority Enabled Name
8142 999 No BuildProgramFilter
8145 @kindex set frame-filter priority
8146 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
8147 Set the @var{priority} of a frame filter in the dictionary matching
8148 @var{filter-dictionary}, and the frame filter name matching
8149 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8150 @code{progspace} or the name of the object file where the frame filter
8151 dictionary resides. The @var{priority} is an integer.
8153 @kindex show frame-filter priority
8154 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
8155 Show the @var{priority} of a frame filter in the dictionary matching
8156 @var{filter-dictionary}, and the frame filter name matching
8157 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
8158 @code{progspace} or the name of the object file where the frame filter
8164 (gdb) info frame-filter
8166 global frame-filters:
8167 Priority Enabled Name
8168 1000 Yes PrimaryFunctionFilter
8171 progspace /build/test frame-filters:
8172 Priority Enabled Name
8173 100 Yes ProgspaceFilter
8175 objfile /build/test frame-filters:
8176 Priority Enabled Name
8177 999 No BuildProgramFilter
8179 (gdb) set frame-filter priority global Reverse 50
8180 (gdb) info frame-filter
8182 global frame-filters:
8183 Priority Enabled Name
8184 1000 Yes PrimaryFunctionFilter
8187 progspace /build/test frame-filters:
8188 Priority Enabled Name
8189 100 Yes ProgspaceFilter
8191 objfile /build/test frame-filters:
8192 Priority Enabled Name
8193 999 No BuildProgramFilter
8198 @chapter Examining Source Files
8200 @value{GDBN} can print parts of your program's source, since the debugging
8201 information recorded in the program tells @value{GDBN} what source files were
8202 used to build it. When your program stops, @value{GDBN} spontaneously prints
8203 the line where it stopped. Likewise, when you select a stack frame
8204 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
8205 execution in that frame has stopped. You can print other portions of
8206 source files by explicit command.
8208 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
8209 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
8210 @value{GDBN} under @sc{gnu} Emacs}.
8213 * List:: Printing source lines
8214 * Specify Location:: How to specify code locations
8215 * Edit:: Editing source files
8216 * Search:: Searching source files
8217 * Source Path:: Specifying source directories
8218 * Machine Code:: Source and machine code
8222 @section Printing Source Lines
8225 @kindex l @r{(@code{list})}
8226 To print lines from a source file, use the @code{list} command
8227 (abbreviated @code{l}). By default, ten lines are printed.
8228 There are several ways to specify what part of the file you want to
8229 print; see @ref{Specify Location}, for the full list.
8231 Here are the forms of the @code{list} command most commonly used:
8234 @item list @var{linenum}
8235 Print lines centered around line number @var{linenum} in the
8236 current source file.
8238 @item list @var{function}
8239 Print lines centered around the beginning of function
8243 Print more lines. If the last lines printed were printed with a
8244 @code{list} command, this prints lines following the last lines
8245 printed; however, if the last line printed was a solitary line printed
8246 as part of displaying a stack frame (@pxref{Stack, ,Examining the
8247 Stack}), this prints lines centered around that line.
8250 Print lines just before the lines last printed.
8253 @cindex @code{list}, how many lines to display
8254 By default, @value{GDBN} prints ten source lines with any of these forms of
8255 the @code{list} command. You can change this using @code{set listsize}:
8258 @kindex set listsize
8259 @item set listsize @var{count}
8260 @itemx set listsize unlimited
8261 Make the @code{list} command display @var{count} source lines (unless
8262 the @code{list} argument explicitly specifies some other number).
8263 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
8265 @kindex show listsize
8267 Display the number of lines that @code{list} prints.
8270 Repeating a @code{list} command with @key{RET} discards the argument,
8271 so it is equivalent to typing just @code{list}. This is more useful
8272 than listing the same lines again. An exception is made for an
8273 argument of @samp{-}; that argument is preserved in repetition so that
8274 each repetition moves up in the source file.
8276 In general, the @code{list} command expects you to supply zero, one or two
8277 @dfn{locations}. Locations specify source lines; there are several ways
8278 of writing them (@pxref{Specify Location}), but the effect is always
8279 to specify some source line.
8281 Here is a complete description of the possible arguments for @code{list}:
8284 @item list @var{location}
8285 Print lines centered around the line specified by @var{location}.
8287 @item list @var{first},@var{last}
8288 Print lines from @var{first} to @var{last}. Both arguments are
8289 locations. When a @code{list} command has two locations, and the
8290 source file of the second location is omitted, this refers to
8291 the same source file as the first location.
8293 @item list ,@var{last}
8294 Print lines ending with @var{last}.
8296 @item list @var{first},
8297 Print lines starting with @var{first}.
8300 Print lines just after the lines last printed.
8303 Print lines just before the lines last printed.
8306 As described in the preceding table.
8309 @node Specify Location
8310 @section Specifying a Location
8311 @cindex specifying location
8313 @cindex source location
8316 * Linespec Locations:: Linespec locations
8317 * Explicit Locations:: Explicit locations
8318 * Address Locations:: Address locations
8321 Several @value{GDBN} commands accept arguments that specify a location
8322 of your program's code. Since @value{GDBN} is a source-level
8323 debugger, a location usually specifies some line in the source code.
8324 Locations may be specified using three different formats:
8325 linespec locations, explicit locations, or address locations.
8327 @node Linespec Locations
8328 @subsection Linespec Locations
8329 @cindex linespec locations
8331 A @dfn{linespec} is a colon-separated list of source location parameters such
8332 as file name, function name, etc. Here are all the different ways of
8333 specifying a linespec:
8337 Specifies the line number @var{linenum} of the current source file.
8340 @itemx +@var{offset}
8341 Specifies the line @var{offset} lines before or after the @dfn{current
8342 line}. For the @code{list} command, the current line is the last one
8343 printed; for the breakpoint commands, this is the line at which
8344 execution stopped in the currently selected @dfn{stack frame}
8345 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
8346 used as the second of the two linespecs in a @code{list} command,
8347 this specifies the line @var{offset} lines up or down from the first
8350 @item @var{filename}:@var{linenum}
8351 Specifies the line @var{linenum} in the source file @var{filename}.
8352 If @var{filename} is a relative file name, then it will match any
8353 source file name with the same trailing components. For example, if
8354 @var{filename} is @samp{gcc/expr.c}, then it will match source file
8355 name of @file{/build/trunk/gcc/expr.c}, but not
8356 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
8358 @item @var{function}
8359 Specifies the line that begins the body of the function @var{function}.
8360 For example, in C, this is the line with the open brace.
8362 By default, in C@t{++} and Ada, @var{function} is interpreted as
8363 specifying all functions named @var{function} in all scopes. For
8364 C@t{++}, this means in all namespaces and classes. For Ada, this
8365 means in all packages.
8367 For example, assuming a program with C@t{++} symbols named
8368 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8369 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
8371 Commands that accept a linespec let you override this with the
8372 @code{-qualified} option. For example, @w{@kbd{break -qualified
8373 func}} sets a breakpoint on a free-function named @code{func} ignoring
8374 any C@t{++} class methods and namespace functions called @code{func}.
8376 @xref{Explicit Locations}.
8378 @item @var{function}:@var{label}
8379 Specifies the line where @var{label} appears in @var{function}.
8381 @item @var{filename}:@var{function}
8382 Specifies the line that begins the body of the function @var{function}
8383 in the file @var{filename}. You only need the file name with a
8384 function name to avoid ambiguity when there are identically named
8385 functions in different source files.
8388 Specifies the line at which the label named @var{label} appears
8389 in the function corresponding to the currently selected stack frame.
8390 If there is no current selected stack frame (for instance, if the inferior
8391 is not running), then @value{GDBN} will not search for a label.
8393 @cindex breakpoint at static probe point
8394 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
8395 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
8396 applications to embed static probes. @xref{Static Probe Points}, for more
8397 information on finding and using static probes. This form of linespec
8398 specifies the location of such a static probe.
8400 If @var{objfile} is given, only probes coming from that shared library
8401 or executable matching @var{objfile} as a regular expression are considered.
8402 If @var{provider} is given, then only probes from that provider are considered.
8403 If several probes match the spec, @value{GDBN} will insert a breakpoint at
8404 each one of those probes.
8407 @node Explicit Locations
8408 @subsection Explicit Locations
8409 @cindex explicit locations
8411 @dfn{Explicit locations} allow the user to directly specify the source
8412 location's parameters using option-value pairs.
8414 Explicit locations are useful when several functions, labels, or
8415 file names have the same name (base name for files) in the program's
8416 sources. In these cases, explicit locations point to the source
8417 line you meant more accurately and unambiguously. Also, using
8418 explicit locations might be faster in large programs.
8420 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
8421 defined in the file named @file{foo} or the label @code{bar} in a function
8422 named @code{foo}. @value{GDBN} must search either the file system or
8423 the symbol table to know.
8425 The list of valid explicit location options is summarized in the
8429 @item -source @var{filename}
8430 The value specifies the source file name. To differentiate between
8431 files with the same base name, prepend as many directories as is necessary
8432 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8433 @value{GDBN} will use the first file it finds with the given base
8434 name. This option requires the use of either @code{-function} or @code{-line}.
8436 @item -function @var{function}
8437 The value specifies the name of a function. Operations
8438 on function locations unmodified by other options (such as @code{-label}
8439 or @code{-line}) refer to the line that begins the body of the function.
8440 In C, for example, this is the line with the open brace.
8442 By default, in C@t{++} and Ada, @var{function} is interpreted as
8443 specifying all functions named @var{function} in all scopes. For
8444 C@t{++}, this means in all namespaces and classes. For Ada, this
8445 means in all packages.
8447 For example, assuming a program with C@t{++} symbols named
8448 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8449 -function func}} and @w{@kbd{break -function B::func}} set a
8450 breakpoint on both symbols.
8452 You can use the @kbd{-qualified} flag to override this (see below).
8456 This flag makes @value{GDBN} interpret a function name specified with
8457 @kbd{-function} as a complete fully-qualified name.
8459 For example, assuming a C@t{++} program with symbols named
8460 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8461 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8463 (Note: the @kbd{-qualified} option can precede a linespec as well
8464 (@pxref{Linespec Locations}), so the particular example above could be
8465 simplified as @w{@kbd{break -qualified B::func}}.)
8467 @item -label @var{label}
8468 The value specifies the name of a label. When the function
8469 name is not specified, the label is searched in the function of the currently
8470 selected stack frame.
8472 @item -line @var{number}
8473 The value specifies a line offset for the location. The offset may either
8474 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8475 the command. When specified without any other options, the line offset is
8476 relative to the current line.
8479 Explicit location options may be abbreviated by omitting any non-unique
8480 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8482 @node Address Locations
8483 @subsection Address Locations
8484 @cindex address locations
8486 @dfn{Address locations} indicate a specific program address. They have
8487 the generalized form *@var{address}.
8489 For line-oriented commands, such as @code{list} and @code{edit}, this
8490 specifies a source line that contains @var{address}. For @code{break} and
8491 other breakpoint-oriented commands, this can be used to set breakpoints in
8492 parts of your program which do not have debugging information or
8495 Here @var{address} may be any expression valid in the current working
8496 language (@pxref{Languages, working language}) that specifies a code
8497 address. In addition, as a convenience, @value{GDBN} extends the
8498 semantics of expressions used in locations to cover several situations
8499 that frequently occur during debugging. Here are the various forms
8503 @item @var{expression}
8504 Any expression valid in the current working language.
8506 @item @var{funcaddr}
8507 An address of a function or procedure derived from its name. In C,
8508 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8509 simply the function's name @var{function} (and actually a special case
8510 of a valid expression). In Pascal and Modula-2, this is
8511 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8512 (although the Pascal form also works).
8514 This form specifies the address of the function's first instruction,
8515 before the stack frame and arguments have been set up.
8517 @item '@var{filename}':@var{funcaddr}
8518 Like @var{funcaddr} above, but also specifies the name of the source
8519 file explicitly. This is useful if the name of the function does not
8520 specify the function unambiguously, e.g., if there are several
8521 functions with identical names in different source files.
8525 @section Editing Source Files
8526 @cindex editing source files
8529 @kindex e @r{(@code{edit})}
8530 To edit the lines in a source file, use the @code{edit} command.
8531 The editing program of your choice
8532 is invoked with the current line set to
8533 the active line in the program.
8534 Alternatively, there are several ways to specify what part of the file you
8535 want to print if you want to see other parts of the program:
8538 @item edit @var{location}
8539 Edit the source file specified by @code{location}. Editing starts at
8540 that @var{location}, e.g., at the specified source line of the
8541 specified file. @xref{Specify Location}, for all the possible forms
8542 of the @var{location} argument; here are the forms of the @code{edit}
8543 command most commonly used:
8546 @item edit @var{number}
8547 Edit the current source file with @var{number} as the active line number.
8549 @item edit @var{function}
8550 Edit the file containing @var{function} at the beginning of its definition.
8555 @subsection Choosing your Editor
8556 You can customize @value{GDBN} to use any editor you want
8558 The only restriction is that your editor (say @code{ex}), recognizes the
8559 following command-line syntax:
8561 ex +@var{number} file
8563 The optional numeric value +@var{number} specifies the number of the line in
8564 the file where to start editing.}.
8565 By default, it is @file{@value{EDITOR}}, but you can change this
8566 by setting the environment variable @code{EDITOR} before using
8567 @value{GDBN}. For example, to configure @value{GDBN} to use the
8568 @code{vi} editor, you could use these commands with the @code{sh} shell:
8574 or in the @code{csh} shell,
8576 setenv EDITOR /usr/bin/vi
8581 @section Searching Source Files
8582 @cindex searching source files
8584 There are two commands for searching through the current source file for a
8589 @kindex forward-search
8590 @kindex fo @r{(@code{forward-search})}
8591 @item forward-search @var{regexp}
8592 @itemx search @var{regexp}
8593 The command @samp{forward-search @var{regexp}} checks each line,
8594 starting with the one following the last line listed, for a match for
8595 @var{regexp}. It lists the line that is found. You can use the
8596 synonym @samp{search @var{regexp}} or abbreviate the command name as
8599 @kindex reverse-search
8600 @item reverse-search @var{regexp}
8601 The command @samp{reverse-search @var{regexp}} checks each line, starting
8602 with the one before the last line listed and going backward, for a match
8603 for @var{regexp}. It lists the line that is found. You can abbreviate
8604 this command as @code{rev}.
8608 @section Specifying Source Directories
8611 @cindex directories for source files
8612 Executable programs sometimes do not record the directories of the source
8613 files from which they were compiled, just the names. Even when they do,
8614 the directories could be moved between the compilation and your debugging
8615 session. @value{GDBN} has a list of directories to search for source files;
8616 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8617 it tries all the directories in the list, in the order they are present
8618 in the list, until it finds a file with the desired name.
8620 For example, suppose an executable references the file
8621 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8622 @file{/mnt/cross}. The file is first looked up literally; if this
8623 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8624 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8625 message is printed. @value{GDBN} does not look up the parts of the
8626 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8627 Likewise, the subdirectories of the source path are not searched: if
8628 the source path is @file{/mnt/cross}, and the binary refers to
8629 @file{foo.c}, @value{GDBN} would not find it under
8630 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8632 Plain file names, relative file names with leading directories, file
8633 names containing dots, etc.@: are all treated as described above; for
8634 instance, if the source path is @file{/mnt/cross}, and the source file
8635 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8636 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8637 that---@file{/mnt/cross/foo.c}.
8639 Note that the executable search path is @emph{not} used to locate the
8642 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8643 any information it has cached about where source files are found and where
8644 each line is in the file.
8648 When you start @value{GDBN}, its source path includes only @samp{cdir}
8649 and @samp{cwd}, in that order.
8650 To add other directories, use the @code{directory} command.
8652 The search path is used to find both program source files and @value{GDBN}
8653 script files (read using the @samp{-command} option and @samp{source} command).
8655 In addition to the source path, @value{GDBN} provides a set of commands
8656 that manage a list of source path substitution rules. A @dfn{substitution
8657 rule} specifies how to rewrite source directories stored in the program's
8658 debug information in case the sources were moved to a different
8659 directory between compilation and debugging. A rule is made of
8660 two strings, the first specifying what needs to be rewritten in
8661 the path, and the second specifying how it should be rewritten.
8662 In @ref{set substitute-path}, we name these two parts @var{from} and
8663 @var{to} respectively. @value{GDBN} does a simple string replacement
8664 of @var{from} with @var{to} at the start of the directory part of the
8665 source file name, and uses that result instead of the original file
8666 name to look up the sources.
8668 Using the previous example, suppose the @file{foo-1.0} tree has been
8669 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8670 @value{GDBN} to replace @file{/usr/src} in all source path names with
8671 @file{/mnt/cross}. The first lookup will then be
8672 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8673 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8674 substitution rule, use the @code{set substitute-path} command
8675 (@pxref{set substitute-path}).
8677 To avoid unexpected substitution results, a rule is applied only if the
8678 @var{from} part of the directory name ends at a directory separator.
8679 For instance, a rule substituting @file{/usr/source} into
8680 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8681 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8682 is applied only at the beginning of the directory name, this rule will
8683 not be applied to @file{/root/usr/source/baz.c} either.
8685 In many cases, you can achieve the same result using the @code{directory}
8686 command. However, @code{set substitute-path} can be more efficient in
8687 the case where the sources are organized in a complex tree with multiple
8688 subdirectories. With the @code{directory} command, you need to add each
8689 subdirectory of your project. If you moved the entire tree while
8690 preserving its internal organization, then @code{set substitute-path}
8691 allows you to direct the debugger to all the sources with one single
8694 @code{set substitute-path} is also more than just a shortcut command.
8695 The source path is only used if the file at the original location no
8696 longer exists. On the other hand, @code{set substitute-path} modifies
8697 the debugger behavior to look at the rewritten location instead. So, if
8698 for any reason a source file that is not relevant to your executable is
8699 located at the original location, a substitution rule is the only
8700 method available to point @value{GDBN} at the new location.
8702 @cindex @samp{--with-relocated-sources}
8703 @cindex default source path substitution
8704 You can configure a default source path substitution rule by
8705 configuring @value{GDBN} with the
8706 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8707 should be the name of a directory under @value{GDBN}'s configured
8708 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8709 directory names in debug information under @var{dir} will be adjusted
8710 automatically if the installed @value{GDBN} is moved to a new
8711 location. This is useful if @value{GDBN}, libraries or executables
8712 with debug information and corresponding source code are being moved
8716 @item directory @var{dirname} @dots{}
8717 @item dir @var{dirname} @dots{}
8718 Add directory @var{dirname} to the front of the source path. Several
8719 directory names may be given to this command, separated by @samp{:}
8720 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8721 part of absolute file names) or
8722 whitespace. You may specify a directory that is already in the source
8723 path; this moves it forward, so @value{GDBN} searches it sooner.
8727 @vindex $cdir@r{, convenience variable}
8728 @vindex $cwd@r{, convenience variable}
8729 @cindex compilation directory
8730 @cindex current directory
8731 @cindex working directory
8732 @cindex directory, current
8733 @cindex directory, compilation
8734 You can use the string @samp{$cdir} to refer to the compilation
8735 directory (if one is recorded), and @samp{$cwd} to refer to the current
8736 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8737 tracks the current working directory as it changes during your @value{GDBN}
8738 session, while the latter is immediately expanded to the current
8739 directory at the time you add an entry to the source path.
8742 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8744 @c RET-repeat for @code{directory} is explicitly disabled, but since
8745 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8747 @item set directories @var{path-list}
8748 @kindex set directories
8749 Set the source path to @var{path-list}.
8750 @samp{$cdir:$cwd} are added if missing.
8752 @item show directories
8753 @kindex show directories
8754 Print the source path: show which directories it contains.
8756 @anchor{set substitute-path}
8757 @item set substitute-path @var{from} @var{to}
8758 @kindex set substitute-path
8759 Define a source path substitution rule, and add it at the end of the
8760 current list of existing substitution rules. If a rule with the same
8761 @var{from} was already defined, then the old rule is also deleted.
8763 For example, if the file @file{/foo/bar/baz.c} was moved to
8764 @file{/mnt/cross/baz.c}, then the command
8767 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8771 will tell @value{GDBN} to replace @samp{/foo/bar} with
8772 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8773 @file{baz.c} even though it was moved.
8775 In the case when more than one substitution rule have been defined,
8776 the rules are evaluated one by one in the order where they have been
8777 defined. The first one matching, if any, is selected to perform
8780 For instance, if we had entered the following commands:
8783 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8784 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8788 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8789 @file{/mnt/include/defs.h} by using the first rule. However, it would
8790 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8791 @file{/mnt/src/lib/foo.c}.
8794 @item unset substitute-path [path]
8795 @kindex unset substitute-path
8796 If a path is specified, search the current list of substitution rules
8797 for a rule that would rewrite that path. Delete that rule if found.
8798 A warning is emitted by the debugger if no rule could be found.
8800 If no path is specified, then all substitution rules are deleted.
8802 @item show substitute-path [path]
8803 @kindex show substitute-path
8804 If a path is specified, then print the source path substitution rule
8805 which would rewrite that path, if any.
8807 If no path is specified, then print all existing source path substitution
8812 If your source path is cluttered with directories that are no longer of
8813 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8814 versions of source. You can correct the situation as follows:
8818 Use @code{directory} with no argument to reset the source path to its default value.
8821 Use @code{directory} with suitable arguments to reinstall the
8822 directories you want in the source path. You can add all the
8823 directories in one command.
8827 @section Source and Machine Code
8828 @cindex source line and its code address
8830 You can use the command @code{info line} to map source lines to program
8831 addresses (and vice versa), and the command @code{disassemble} to display
8832 a range of addresses as machine instructions. You can use the command
8833 @code{set disassemble-next-line} to set whether to disassemble next
8834 source line when execution stops. When run under @sc{gnu} Emacs
8835 mode, the @code{info line} command causes the arrow to point to the
8836 line specified. Also, @code{info line} prints addresses in symbolic form as
8842 @itemx info line @var{location}
8843 Print the starting and ending addresses of the compiled code for
8844 source line @var{location}. You can specify source lines in any of
8845 the ways documented in @ref{Specify Location}. With no @var{location}
8846 information about the current source line is printed.
8849 For example, we can use @code{info line} to discover the location of
8850 the object code for the first line of function
8851 @code{m4_changequote}:
8854 (@value{GDBP}) info line m4_changequote
8855 Line 895 of "builtin.c" starts at pc 0x634c <m4_changequote> and \
8856 ends at 0x6350 <m4_changequote+4>.
8860 @cindex code address and its source line
8861 We can also inquire (using @code{*@var{addr}} as the form for
8862 @var{location}) what source line covers a particular address:
8864 (@value{GDBP}) info line *0x63ff
8865 Line 926 of "builtin.c" starts at pc 0x63e4 <m4_changequote+152> and \
8866 ends at 0x6404 <m4_changequote+184>.
8869 @cindex @code{$_} and @code{info line}
8870 @cindex @code{x} command, default address
8871 @kindex x@r{(examine), and} info line
8872 After @code{info line}, the default address for the @code{x} command
8873 is changed to the starting address of the line, so that @samp{x/i} is
8874 sufficient to begin examining the machine code (@pxref{Memory,
8875 ,Examining Memory}). Also, this address is saved as the value of the
8876 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8879 @cindex info line, repeated calls
8880 After @code{info line}, using @code{info line} again without
8881 specifying a location will display information about the next source
8886 @cindex assembly instructions
8887 @cindex instructions, assembly
8888 @cindex machine instructions
8889 @cindex listing machine instructions
8891 @itemx disassemble /m
8892 @itemx disassemble /s
8893 @itemx disassemble /r
8894 This specialized command dumps a range of memory as machine
8895 instructions. It can also print mixed source+disassembly by specifying
8896 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8897 as well as in symbolic form by specifying the @code{/r} modifier.
8898 The default memory range is the function surrounding the
8899 program counter of the selected frame. A single argument to this
8900 command is a program counter value; @value{GDBN} dumps the function
8901 surrounding this value. When two arguments are given, they should
8902 be separated by a comma, possibly surrounded by whitespace. The
8903 arguments specify a range of addresses to dump, in one of two forms:
8906 @item @var{start},@var{end}
8907 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8908 @item @var{start},+@var{length}
8909 the addresses from @var{start} (inclusive) to
8910 @code{@var{start}+@var{length}} (exclusive).
8914 When 2 arguments are specified, the name of the function is also
8915 printed (since there could be several functions in the given range).
8917 The argument(s) can be any expression yielding a numeric value, such as
8918 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8920 If the range of memory being disassembled contains current program counter,
8921 the instruction at that location is shown with a @code{=>} marker.
8924 The following example shows the disassembly of a range of addresses of
8925 HP PA-RISC 2.0 code:
8928 (@value{GDBP}) disas 0x32c4, 0x32e4
8929 Dump of assembler code from 0x32c4 to 0x32e4:
8930 0x32c4 <main+204>: addil 0,dp
8931 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8932 0x32cc <main+212>: ldil 0x3000,r31
8933 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8934 0x32d4 <main+220>: ldo 0(r31),rp
8935 0x32d8 <main+224>: addil -0x800,dp
8936 0x32dc <main+228>: ldo 0x588(r1),r26
8937 0x32e0 <main+232>: ldil 0x3000,r31
8938 End of assembler dump.
8941 Here is an example showing mixed source+assembly for Intel x86
8942 with @code{/m} or @code{/s}, when the program is stopped just after
8943 function prologue in a non-optimized function with no inline code.
8946 (@value{GDBP}) disas /m main
8947 Dump of assembler code for function main:
8949 0x08048330 <+0>: push %ebp
8950 0x08048331 <+1>: mov %esp,%ebp
8951 0x08048333 <+3>: sub $0x8,%esp
8952 0x08048336 <+6>: and $0xfffffff0,%esp
8953 0x08048339 <+9>: sub $0x10,%esp
8955 6 printf ("Hello.\n");
8956 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8957 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8961 0x08048348 <+24>: mov $0x0,%eax
8962 0x0804834d <+29>: leave
8963 0x0804834e <+30>: ret
8965 End of assembler dump.
8968 The @code{/m} option is deprecated as its output is not useful when
8969 there is either inlined code or re-ordered code.
8970 The @code{/s} option is the preferred choice.
8971 Here is an example for AMD x86-64 showing the difference between
8972 @code{/m} output and @code{/s} output.
8973 This example has one inline function defined in a header file,
8974 and the code is compiled with @samp{-O2} optimization.
8975 Note how the @code{/m} output is missing the disassembly of
8976 several instructions that are present in the @code{/s} output.
9006 (@value{GDBP}) disas /m main
9007 Dump of assembler code for function main:
9011 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9012 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9016 0x000000000040041d <+29>: xor %eax,%eax
9017 0x000000000040041f <+31>: retq
9018 0x0000000000400420 <+32>: add %eax,%eax
9019 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9021 End of assembler dump.
9022 (@value{GDBP}) disas /s main
9023 Dump of assembler code for function main:
9027 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
9031 0x0000000000400406 <+6>: test %eax,%eax
9032 0x0000000000400408 <+8>: js 0x400420 <main+32>
9037 0x000000000040040a <+10>: lea 0xa(%rax),%edx
9038 0x000000000040040d <+13>: test %eax,%eax
9039 0x000000000040040f <+15>: mov $0x1,%eax
9040 0x0000000000400414 <+20>: cmovne %edx,%eax
9044 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
9048 0x000000000040041d <+29>: xor %eax,%eax
9049 0x000000000040041f <+31>: retq
9053 0x0000000000400420 <+32>: add %eax,%eax
9054 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
9055 End of assembler dump.
9058 Here is another example showing raw instructions in hex for AMD x86-64,
9061 (gdb) disas /r 0x400281,+10
9062 Dump of assembler code from 0x400281 to 0x40028b:
9063 0x0000000000400281: 38 36 cmp %dh,(%rsi)
9064 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
9065 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
9066 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
9067 End of assembler dump.
9070 Addresses cannot be specified as a location (@pxref{Specify Location}).
9071 So, for example, if you want to disassemble function @code{bar}
9072 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
9073 and not @samp{disassemble foo.c:bar}.
9075 Some architectures have more than one commonly-used set of instruction
9076 mnemonics or other syntax.
9078 For programs that were dynamically linked and use shared libraries,
9079 instructions that call functions or branch to locations in the shared
9080 libraries might show a seemingly bogus location---it's actually a
9081 location of the relocation table. On some architectures, @value{GDBN}
9082 might be able to resolve these to actual function names.
9085 @kindex set disassembler-options
9086 @cindex disassembler options
9087 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
9088 This command controls the passing of target specific information to
9089 the disassembler. For a list of valid options, please refer to the
9090 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
9091 manual and/or the output of @kbd{objdump --help}
9092 (@pxref{objdump,,objdump,binutils,The GNU Binary Utilities}).
9093 The default value is the empty string.
9095 If it is necessary to specify more than one disassembler option, then
9096 multiple options can be placed together into a comma separated list.
9097 Currently this command is only supported on targets ARM, MIPS, PowerPC
9100 @kindex show disassembler-options
9101 @item show disassembler-options
9102 Show the current setting of the disassembler options.
9106 @kindex set disassembly-flavor
9107 @cindex Intel disassembly flavor
9108 @cindex AT&T disassembly flavor
9109 @item set disassembly-flavor @var{instruction-set}
9110 Select the instruction set to use when disassembling the
9111 program via the @code{disassemble} or @code{x/i} commands.
9113 Currently this command is only defined for the Intel x86 family. You
9114 can set @var{instruction-set} to either @code{intel} or @code{att}.
9115 The default is @code{att}, the AT&T flavor used by default by Unix
9116 assemblers for x86-based targets.
9118 @kindex show disassembly-flavor
9119 @item show disassembly-flavor
9120 Show the current setting of the disassembly flavor.
9124 @kindex set disassemble-next-line
9125 @kindex show disassemble-next-line
9126 @item set disassemble-next-line
9127 @itemx show disassemble-next-line
9128 Control whether or not @value{GDBN} will disassemble the next source
9129 line or instruction when execution stops. If ON, @value{GDBN} will
9130 display disassembly of the next source line when execution of the
9131 program being debugged stops. This is @emph{in addition} to
9132 displaying the source line itself, which @value{GDBN} always does if
9133 possible. If the next source line cannot be displayed for some reason
9134 (e.g., if @value{GDBN} cannot find the source file, or there's no line
9135 info in the debug info), @value{GDBN} will display disassembly of the
9136 next @emph{instruction} instead of showing the next source line. If
9137 AUTO, @value{GDBN} will display disassembly of next instruction only
9138 if the source line cannot be displayed. This setting causes
9139 @value{GDBN} to display some feedback when you step through a function
9140 with no line info or whose source file is unavailable. The default is
9141 OFF, which means never display the disassembly of the next line or
9147 @chapter Examining Data
9149 @cindex printing data
9150 @cindex examining data
9153 The usual way to examine data in your program is with the @code{print}
9154 command (abbreviated @code{p}), or its synonym @code{inspect}. It
9155 evaluates and prints the value of an expression of the language your
9156 program is written in (@pxref{Languages, ,Using @value{GDBN} with
9157 Different Languages}). It may also print the expression using a
9158 Python-based pretty-printer (@pxref{Pretty Printing}).
9161 @item print @var{expr}
9162 @itemx print /@var{f} @var{expr}
9163 @var{expr} is an expression (in the source language). By default the
9164 value of @var{expr} is printed in a format appropriate to its data type;
9165 you can choose a different format by specifying @samp{/@var{f}}, where
9166 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
9170 @itemx print /@var{f}
9171 @cindex reprint the last value
9172 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
9173 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
9174 conveniently inspect the same value in an alternative format.
9177 A more low-level way of examining data is with the @code{x} command.
9178 It examines data in memory at a specified address and prints it in a
9179 specified format. @xref{Memory, ,Examining Memory}.
9181 If you are interested in information about types, or about how the
9182 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
9183 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
9186 @cindex exploring hierarchical data structures
9188 Another way of examining values of expressions and type information is
9189 through the Python extension command @code{explore} (available only if
9190 the @value{GDBN} build is configured with @code{--with-python}). It
9191 offers an interactive way to start at the highest level (or, the most
9192 abstract level) of the data type of an expression (or, the data type
9193 itself) and explore all the way down to leaf scalar values/fields
9194 embedded in the higher level data types.
9197 @item explore @var{arg}
9198 @var{arg} is either an expression (in the source language), or a type
9199 visible in the current context of the program being debugged.
9202 The working of the @code{explore} command can be illustrated with an
9203 example. If a data type @code{struct ComplexStruct} is defined in your
9213 struct ComplexStruct
9215 struct SimpleStruct *ss_p;
9221 followed by variable declarations as
9224 struct SimpleStruct ss = @{ 10, 1.11 @};
9225 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
9229 then, the value of the variable @code{cs} can be explored using the
9230 @code{explore} command as follows.
9234 The value of `cs' is a struct/class of type `struct ComplexStruct' with
9235 the following fields:
9237 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
9238 arr = <Enter 1 to explore this field of type `int [10]'>
9240 Enter the field number of choice:
9244 Since the fields of @code{cs} are not scalar values, you are being
9245 prompted to chose the field you want to explore. Let's say you choose
9246 the field @code{ss_p} by entering @code{0}. Then, since this field is a
9247 pointer, you will be asked if it is pointing to a single value. From
9248 the declaration of @code{cs} above, it is indeed pointing to a single
9249 value, hence you enter @code{y}. If you enter @code{n}, then you will
9250 be asked if it were pointing to an array of values, in which case this
9251 field will be explored as if it were an array.
9254 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
9255 Continue exploring it as a pointer to a single value [y/n]: y
9256 The value of `*(cs.ss_p)' is a struct/class of type `struct
9257 SimpleStruct' with the following fields:
9259 i = 10 .. (Value of type `int')
9260 d = 1.1100000000000001 .. (Value of type `double')
9262 Press enter to return to parent value:
9266 If the field @code{arr} of @code{cs} was chosen for exploration by
9267 entering @code{1} earlier, then since it is as array, you will be
9268 prompted to enter the index of the element in the array that you want
9272 `cs.arr' is an array of `int'.
9273 Enter the index of the element you want to explore in `cs.arr': 5
9275 `(cs.arr)[5]' is a scalar value of type `int'.
9279 Press enter to return to parent value:
9282 In general, at any stage of exploration, you can go deeper towards the
9283 leaf values by responding to the prompts appropriately, or hit the
9284 return key to return to the enclosing data structure (the @i{higher}
9285 level data structure).
9287 Similar to exploring values, you can use the @code{explore} command to
9288 explore types. Instead of specifying a value (which is typically a
9289 variable name or an expression valid in the current context of the
9290 program being debugged), you specify a type name. If you consider the
9291 same example as above, your can explore the type
9292 @code{struct ComplexStruct} by passing the argument
9293 @code{struct ComplexStruct} to the @code{explore} command.
9296 (gdb) explore struct ComplexStruct
9300 By responding to the prompts appropriately in the subsequent interactive
9301 session, you can explore the type @code{struct ComplexStruct} in a
9302 manner similar to how the value @code{cs} was explored in the above
9305 The @code{explore} command also has two sub-commands,
9306 @code{explore value} and @code{explore type}. The former sub-command is
9307 a way to explicitly specify that value exploration of the argument is
9308 being invoked, while the latter is a way to explicitly specify that type
9309 exploration of the argument is being invoked.
9312 @item explore value @var{expr}
9313 @cindex explore value
9314 This sub-command of @code{explore} explores the value of the
9315 expression @var{expr} (if @var{expr} is an expression valid in the
9316 current context of the program being debugged). The behavior of this
9317 command is identical to that of the behavior of the @code{explore}
9318 command being passed the argument @var{expr}.
9320 @item explore type @var{arg}
9321 @cindex explore type
9322 This sub-command of @code{explore} explores the type of @var{arg} (if
9323 @var{arg} is a type visible in the current context of program being
9324 debugged), or the type of the value/expression @var{arg} (if @var{arg}
9325 is an expression valid in the current context of the program being
9326 debugged). If @var{arg} is a type, then the behavior of this command is
9327 identical to that of the @code{explore} command being passed the
9328 argument @var{arg}. If @var{arg} is an expression, then the behavior of
9329 this command will be identical to that of the @code{explore} command
9330 being passed the type of @var{arg} as the argument.
9334 * Expressions:: Expressions
9335 * Ambiguous Expressions:: Ambiguous Expressions
9336 * Variables:: Program variables
9337 * Arrays:: Artificial arrays
9338 * Output Formats:: Output formats
9339 * Memory:: Examining memory
9340 * Auto Display:: Automatic display
9341 * Print Settings:: Print settings
9342 * Pretty Printing:: Python pretty printing
9343 * Value History:: Value history
9344 * Convenience Vars:: Convenience variables
9345 * Convenience Funs:: Convenience functions
9346 * Registers:: Registers
9347 * Floating Point Hardware:: Floating point hardware
9348 * Vector Unit:: Vector Unit
9349 * OS Information:: Auxiliary data provided by operating system
9350 * Memory Region Attributes:: Memory region attributes
9351 * Dump/Restore Files:: Copy between memory and a file
9352 * Core File Generation:: Cause a program dump its core
9353 * Character Sets:: Debugging programs that use a different
9354 character set than GDB does
9355 * Caching Target Data:: Data caching for targets
9356 * Searching Memory:: Searching memory for a sequence of bytes
9357 * Value Sizes:: Managing memory allocated for values
9361 @section Expressions
9364 @code{print} and many other @value{GDBN} commands accept an expression and
9365 compute its value. Any kind of constant, variable or operator defined
9366 by the programming language you are using is valid in an expression in
9367 @value{GDBN}. This includes conditional expressions, function calls,
9368 casts, and string constants. It also includes preprocessor macros, if
9369 you compiled your program to include this information; see
9372 @cindex arrays in expressions
9373 @value{GDBN} supports array constants in expressions input by
9374 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
9375 you can use the command @code{print @{1, 2, 3@}} to create an array
9376 of three integers. If you pass an array to a function or assign it
9377 to a program variable, @value{GDBN} copies the array to memory that
9378 is @code{malloc}ed in the target program.
9380 Because C is so widespread, most of the expressions shown in examples in
9381 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
9382 Languages}, for information on how to use expressions in other
9385 In this section, we discuss operators that you can use in @value{GDBN}
9386 expressions regardless of your programming language.
9388 @cindex casts, in expressions
9389 Casts are supported in all languages, not just in C, because it is so
9390 useful to cast a number into a pointer in order to examine a structure
9391 at that address in memory.
9392 @c FIXME: casts supported---Mod2 true?
9394 @value{GDBN} supports these operators, in addition to those common
9395 to programming languages:
9399 @samp{@@} is a binary operator for treating parts of memory as arrays.
9400 @xref{Arrays, ,Artificial Arrays}, for more information.
9403 @samp{::} allows you to specify a variable in terms of the file or
9404 function where it is defined. @xref{Variables, ,Program Variables}.
9406 @cindex @{@var{type}@}
9407 @cindex type casting memory
9408 @cindex memory, viewing as typed object
9409 @cindex casts, to view memory
9410 @item @{@var{type}@} @var{addr}
9411 Refers to an object of type @var{type} stored at address @var{addr} in
9412 memory. The address @var{addr} may be any expression whose value is
9413 an integer or pointer (but parentheses are required around binary
9414 operators, just as in a cast). This construct is allowed regardless
9415 of what kind of data is normally supposed to reside at @var{addr}.
9418 @node Ambiguous Expressions
9419 @section Ambiguous Expressions
9420 @cindex ambiguous expressions
9422 Expressions can sometimes contain some ambiguous elements. For instance,
9423 some programming languages (notably Ada, C@t{++} and Objective-C) permit
9424 a single function name to be defined several times, for application in
9425 different contexts. This is called @dfn{overloading}. Another example
9426 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
9427 templates and is typically instantiated several times, resulting in
9428 the same function name being defined in different contexts.
9430 In some cases and depending on the language, it is possible to adjust
9431 the expression to remove the ambiguity. For instance in C@t{++}, you
9432 can specify the signature of the function you want to break on, as in
9433 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9434 qualified name of your function often makes the expression unambiguous
9437 When an ambiguity that needs to be resolved is detected, the debugger
9438 has the capability to display a menu of numbered choices for each
9439 possibility, and then waits for the selection with the prompt @samp{>}.
9440 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9441 aborts the current command. If the command in which the expression was
9442 used allows more than one choice to be selected, the next option in the
9443 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9446 For example, the following session excerpt shows an attempt to set a
9447 breakpoint at the overloaded symbol @code{String::after}.
9448 We choose three particular definitions of that function name:
9450 @c FIXME! This is likely to change to show arg type lists, at least
9453 (@value{GDBP}) b String::after
9456 [2] file:String.cc; line number:867
9457 [3] file:String.cc; line number:860
9458 [4] file:String.cc; line number:875
9459 [5] file:String.cc; line number:853
9460 [6] file:String.cc; line number:846
9461 [7] file:String.cc; line number:735
9463 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9464 Breakpoint 2 at 0xb344: file String.cc, line 875.
9465 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9466 Multiple breakpoints were set.
9467 Use the "delete" command to delete unwanted
9474 @kindex set multiple-symbols
9475 @item set multiple-symbols @var{mode}
9476 @cindex multiple-symbols menu
9478 This option allows you to adjust the debugger behavior when an expression
9481 By default, @var{mode} is set to @code{all}. If the command with which
9482 the expression is used allows more than one choice, then @value{GDBN}
9483 automatically selects all possible choices. For instance, inserting
9484 a breakpoint on a function using an ambiguous name results in a breakpoint
9485 inserted on each possible match. However, if a unique choice must be made,
9486 then @value{GDBN} uses the menu to help you disambiguate the expression.
9487 For instance, printing the address of an overloaded function will result
9488 in the use of the menu.
9490 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9491 when an ambiguity is detected.
9493 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9494 an error due to the ambiguity and the command is aborted.
9496 @kindex show multiple-symbols
9497 @item show multiple-symbols
9498 Show the current value of the @code{multiple-symbols} setting.
9502 @section Program Variables
9504 The most common kind of expression to use is the name of a variable
9507 Variables in expressions are understood in the selected stack frame
9508 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9512 global (or file-static)
9519 visible according to the scope rules of the
9520 programming language from the point of execution in that frame
9523 @noindent This means that in the function
9538 you can examine and use the variable @code{a} whenever your program is
9539 executing within the function @code{foo}, but you can only use or
9540 examine the variable @code{b} while your program is executing inside
9541 the block where @code{b} is declared.
9543 @cindex variable name conflict
9544 There is an exception: you can refer to a variable or function whose
9545 scope is a single source file even if the current execution point is not
9546 in this file. But it is possible to have more than one such variable or
9547 function with the same name (in different source files). If that
9548 happens, referring to that name has unpredictable effects. If you wish,
9549 you can specify a static variable in a particular function or file by
9550 using the colon-colon (@code{::}) notation:
9552 @cindex colon-colon, context for variables/functions
9554 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9555 @cindex @code{::}, context for variables/functions
9558 @var{file}::@var{variable}
9559 @var{function}::@var{variable}
9563 Here @var{file} or @var{function} is the name of the context for the
9564 static @var{variable}. In the case of file names, you can use quotes to
9565 make sure @value{GDBN} parses the file name as a single word---for example,
9566 to print a global value of @code{x} defined in @file{f2.c}:
9569 (@value{GDBP}) p 'f2.c'::x
9572 The @code{::} notation is normally used for referring to
9573 static variables, since you typically disambiguate uses of local variables
9574 in functions by selecting the appropriate frame and using the
9575 simple name of the variable. However, you may also use this notation
9576 to refer to local variables in frames enclosing the selected frame:
9585 process (a); /* Stop here */
9596 For example, if there is a breakpoint at the commented line,
9597 here is what you might see
9598 when the program stops after executing the call @code{bar(0)}:
9603 (@value{GDBP}) p bar::a
9606 #2 0x080483d0 in foo (a=5) at foobar.c:12
9609 (@value{GDBP}) p bar::a
9613 @cindex C@t{++} scope resolution
9614 These uses of @samp{::} are very rarely in conflict with the very
9615 similar use of the same notation in C@t{++}. When they are in
9616 conflict, the C@t{++} meaning takes precedence; however, this can be
9617 overridden by quoting the file or function name with single quotes.
9619 For example, suppose the program is stopped in a method of a class
9620 that has a field named @code{includefile}, and there is also an
9621 include file named @file{includefile} that defines a variable,
9625 (@value{GDBP}) p includefile
9627 (@value{GDBP}) p includefile::some_global
9628 A syntax error in expression, near `'.
9629 (@value{GDBP}) p 'includefile'::some_global
9633 @cindex wrong values
9634 @cindex variable values, wrong
9635 @cindex function entry/exit, wrong values of variables
9636 @cindex optimized code, wrong values of variables
9638 @emph{Warning:} Occasionally, a local variable may appear to have the
9639 wrong value at certain points in a function---just after entry to a new
9640 scope, and just before exit.
9642 You may see this problem when you are stepping by machine instructions.
9643 This is because, on most machines, it takes more than one instruction to
9644 set up a stack frame (including local variable definitions); if you are
9645 stepping by machine instructions, variables may appear to have the wrong
9646 values until the stack frame is completely built. On exit, it usually
9647 also takes more than one machine instruction to destroy a stack frame;
9648 after you begin stepping through that group of instructions, local
9649 variable definitions may be gone.
9651 This may also happen when the compiler does significant optimizations.
9652 To be sure of always seeing accurate values, turn off all optimization
9655 @cindex ``No symbol "foo" in current context''
9656 Another possible effect of compiler optimizations is to optimize
9657 unused variables out of existence, or assign variables to registers (as
9658 opposed to memory addresses). Depending on the support for such cases
9659 offered by the debug info format used by the compiler, @value{GDBN}
9660 might not be able to display values for such local variables. If that
9661 happens, @value{GDBN} will print a message like this:
9664 No symbol "foo" in current context.
9667 To solve such problems, either recompile without optimizations, or use a
9668 different debug info format, if the compiler supports several such
9669 formats. @xref{Compilation}, for more information on choosing compiler
9670 options. @xref{C, ,C and C@t{++}}, for more information about debug
9671 info formats that are best suited to C@t{++} programs.
9673 If you ask to print an object whose contents are unknown to
9674 @value{GDBN}, e.g., because its data type is not completely specified
9675 by the debug information, @value{GDBN} will say @samp{<incomplete
9676 type>}. @xref{Symbols, incomplete type}, for more about this.
9678 @cindex no debug info variables
9679 If you try to examine or use the value of a (global) variable for
9680 which @value{GDBN} has no type information, e.g., because the program
9681 includes no debug information, @value{GDBN} displays an error message.
9682 @xref{Symbols, unknown type}, for more about unknown types. If you
9683 cast the variable to its declared type, @value{GDBN} gets the
9684 variable's value using the cast-to type as the variable's type. For
9685 example, in a C program:
9688 (@value{GDBP}) p var
9689 'var' has unknown type; cast it to its declared type
9690 (@value{GDBP}) p (float) var
9694 If you append @kbd{@@entry} string to a function parameter name you get its
9695 value at the time the function got called. If the value is not available an
9696 error message is printed. Entry values are available only with some compilers.
9697 Entry values are normally also printed at the function parameter list according
9698 to @ref{set print entry-values}.
9701 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9707 (gdb) print i@@entry
9711 Strings are identified as arrays of @code{char} values without specified
9712 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9713 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9714 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9715 defines literal string type @code{"char"} as @code{char} without a sign.
9720 signed char var1[] = "A";
9723 You get during debugging
9728 $2 = @{65 'A', 0 '\0'@}
9732 @section Artificial Arrays
9734 @cindex artificial array
9736 @kindex @@@r{, referencing memory as an array}
9737 It is often useful to print out several successive objects of the
9738 same type in memory; a section of an array, or an array of
9739 dynamically determined size for which only a pointer exists in the
9742 You can do this by referring to a contiguous span of memory as an
9743 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9744 operand of @samp{@@} should be the first element of the desired array
9745 and be an individual object. The right operand should be the desired length
9746 of the array. The result is an array value whose elements are all of
9747 the type of the left argument. The first element is actually the left
9748 argument; the second element comes from bytes of memory immediately
9749 following those that hold the first element, and so on. Here is an
9750 example. If a program says
9753 int *array = (int *) malloc (len * sizeof (int));
9757 you can print the contents of @code{array} with
9763 The left operand of @samp{@@} must reside in memory. Array values made
9764 with @samp{@@} in this way behave just like other arrays in terms of
9765 subscripting, and are coerced to pointers when used in expressions.
9766 Artificial arrays most often appear in expressions via the value history
9767 (@pxref{Value History, ,Value History}), after printing one out.
9769 Another way to create an artificial array is to use a cast.
9770 This re-interprets a value as if it were an array.
9771 The value need not be in memory:
9773 (@value{GDBP}) p/x (short[2])0x12345678
9774 $1 = @{0x1234, 0x5678@}
9777 As a convenience, if you leave the array length out (as in
9778 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9779 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9781 (@value{GDBP}) p/x (short[])0x12345678
9782 $2 = @{0x1234, 0x5678@}
9785 Sometimes the artificial array mechanism is not quite enough; in
9786 moderately complex data structures, the elements of interest may not
9787 actually be adjacent---for example, if you are interested in the values
9788 of pointers in an array. One useful work-around in this situation is
9789 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9790 Variables}) as a counter in an expression that prints the first
9791 interesting value, and then repeat that expression via @key{RET}. For
9792 instance, suppose you have an array @code{dtab} of pointers to
9793 structures, and you are interested in the values of a field @code{fv}
9794 in each structure. Here is an example of what you might type:
9804 @node Output Formats
9805 @section Output Formats
9807 @cindex formatted output
9808 @cindex output formats
9809 By default, @value{GDBN} prints a value according to its data type. Sometimes
9810 this is not what you want. For example, you might want to print a number
9811 in hex, or a pointer in decimal. Or you might want to view data in memory
9812 at a certain address as a character string or as an instruction. To do
9813 these things, specify an @dfn{output format} when you print a value.
9815 The simplest use of output formats is to say how to print a value
9816 already computed. This is done by starting the arguments of the
9817 @code{print} command with a slash and a format letter. The format
9818 letters supported are:
9822 Regard the bits of the value as an integer, and print the integer in
9826 Print as integer in signed decimal.
9829 Print as integer in unsigned decimal.
9832 Print as integer in octal.
9835 Print as integer in binary. The letter @samp{t} stands for ``two''.
9836 @footnote{@samp{b} cannot be used because these format letters are also
9837 used with the @code{x} command, where @samp{b} stands for ``byte'';
9838 see @ref{Memory,,Examining Memory}.}
9841 @cindex unknown address, locating
9842 @cindex locate address
9843 Print as an address, both absolute in hexadecimal and as an offset from
9844 the nearest preceding symbol. You can use this format used to discover
9845 where (in what function) an unknown address is located:
9848 (@value{GDBP}) p/a 0x54320
9849 $3 = 0x54320 <_initialize_vx+396>
9853 The command @code{info symbol 0x54320} yields similar results.
9854 @xref{Symbols, info symbol}.
9857 Regard as an integer and print it as a character constant. This
9858 prints both the numerical value and its character representation. The
9859 character representation is replaced with the octal escape @samp{\nnn}
9860 for characters outside the 7-bit @sc{ascii} range.
9862 Without this format, @value{GDBN} displays @code{char},
9863 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9864 constants. Single-byte members of vectors are displayed as integer
9868 Regard the bits of the value as a floating point number and print
9869 using typical floating point syntax.
9872 @cindex printing strings
9873 @cindex printing byte arrays
9874 Regard as a string, if possible. With this format, pointers to single-byte
9875 data are displayed as null-terminated strings and arrays of single-byte data
9876 are displayed as fixed-length strings. Other values are displayed in their
9879 Without this format, @value{GDBN} displays pointers to and arrays of
9880 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9881 strings. Single-byte members of a vector are displayed as an integer
9885 Like @samp{x} formatting, the value is treated as an integer and
9886 printed as hexadecimal, but leading zeros are printed to pad the value
9887 to the size of the integer type.
9890 @cindex raw printing
9891 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9892 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9893 Printing}). This typically results in a higher-level display of the
9894 value's contents. The @samp{r} format bypasses any Python
9895 pretty-printer which might exist.
9898 For example, to print the program counter in hex (@pxref{Registers}), type
9905 Note that no space is required before the slash; this is because command
9906 names in @value{GDBN} cannot contain a slash.
9908 To reprint the last value in the value history with a different format,
9909 you can use the @code{print} command with just a format and no
9910 expression. For example, @samp{p/x} reprints the last value in hex.
9913 @section Examining Memory
9915 You can use the command @code{x} (for ``examine'') to examine memory in
9916 any of several formats, independently of your program's data types.
9918 @cindex examining memory
9920 @kindex x @r{(examine memory)}
9921 @item x/@var{nfu} @var{addr}
9924 Use the @code{x} command to examine memory.
9927 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9928 much memory to display and how to format it; @var{addr} is an
9929 expression giving the address where you want to start displaying memory.
9930 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9931 Several commands set convenient defaults for @var{addr}.
9934 @item @var{n}, the repeat count
9935 The repeat count is a decimal integer; the default is 1. It specifies
9936 how much memory (counting by units @var{u}) to display. If a negative
9937 number is specified, memory is examined backward from @var{addr}.
9938 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9941 @item @var{f}, the display format
9942 The display format is one of the formats used by @code{print}
9943 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9944 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9945 The default is @samp{x} (hexadecimal) initially. The default changes
9946 each time you use either @code{x} or @code{print}.
9948 @item @var{u}, the unit size
9949 The unit size is any of
9955 Halfwords (two bytes).
9957 Words (four bytes). This is the initial default.
9959 Giant words (eight bytes).
9962 Each time you specify a unit size with @code{x}, that size becomes the
9963 default unit the next time you use @code{x}. For the @samp{i} format,
9964 the unit size is ignored and is normally not written. For the @samp{s} format,
9965 the unit size defaults to @samp{b}, unless it is explicitly given.
9966 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9967 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9968 Note that the results depend on the programming language of the
9969 current compilation unit. If the language is C, the @samp{s}
9970 modifier will use the UTF-16 encoding while @samp{w} will use
9971 UTF-32. The encoding is set by the programming language and cannot
9974 @item @var{addr}, starting display address
9975 @var{addr} is the address where you want @value{GDBN} to begin displaying
9976 memory. The expression need not have a pointer value (though it may);
9977 it is always interpreted as an integer address of a byte of memory.
9978 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9979 @var{addr} is usually just after the last address examined---but several
9980 other commands also set the default address: @code{info breakpoints} (to
9981 the address of the last breakpoint listed), @code{info line} (to the
9982 starting address of a line), and @code{print} (if you use it to display
9983 a value from memory).
9986 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9987 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9988 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9989 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9990 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9992 You can also specify a negative repeat count to examine memory backward
9993 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9994 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9996 Since the letters indicating unit sizes are all distinct from the
9997 letters specifying output formats, you do not have to remember whether
9998 unit size or format comes first; either order works. The output
9999 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
10000 (However, the count @var{n} must come first; @samp{wx4} does not work.)
10002 Even though the unit size @var{u} is ignored for the formats @samp{s}
10003 and @samp{i}, you might still want to use a count @var{n}; for example,
10004 @samp{3i} specifies that you want to see three machine instructions,
10005 including any operands. For convenience, especially when used with
10006 the @code{display} command, the @samp{i} format also prints branch delay
10007 slot instructions, if any, beyond the count specified, which immediately
10008 follow the last instruction that is within the count. The command
10009 @code{disassemble} gives an alternative way of inspecting machine
10010 instructions; see @ref{Machine Code,,Source and Machine Code}.
10012 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
10013 the command displays null-terminated strings or instructions before the given
10014 address as many as the absolute value of the given number. For the @samp{i}
10015 format, we use line number information in the debug info to accurately locate
10016 instruction boundaries while disassembling backward. If line info is not
10017 available, the command stops examining memory with an error message.
10019 All the defaults for the arguments to @code{x} are designed to make it
10020 easy to continue scanning memory with minimal specifications each time
10021 you use @code{x}. For example, after you have inspected three machine
10022 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
10023 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
10024 the repeat count @var{n} is used again; the other arguments default as
10025 for successive uses of @code{x}.
10027 When examining machine instructions, the instruction at current program
10028 counter is shown with a @code{=>} marker. For example:
10031 (@value{GDBP}) x/5i $pc-6
10032 0x804837f <main+11>: mov %esp,%ebp
10033 0x8048381 <main+13>: push %ecx
10034 0x8048382 <main+14>: sub $0x4,%esp
10035 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
10036 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
10039 @cindex @code{$_}, @code{$__}, and value history
10040 The addresses and contents printed by the @code{x} command are not saved
10041 in the value history because there is often too much of them and they
10042 would get in the way. Instead, @value{GDBN} makes these values available for
10043 subsequent use in expressions as values of the convenience variables
10044 @code{$_} and @code{$__}. After an @code{x} command, the last address
10045 examined is available for use in expressions in the convenience variable
10046 @code{$_}. The contents of that address, as examined, are available in
10047 the convenience variable @code{$__}.
10049 If the @code{x} command has a repeat count, the address and contents saved
10050 are from the last memory unit printed; this is not the same as the last
10051 address printed if several units were printed on the last line of output.
10053 @anchor{addressable memory unit}
10054 @cindex addressable memory unit
10055 Most targets have an addressable memory unit size of 8 bits. This means
10056 that to each memory address are associated 8 bits of data. Some
10057 targets, however, have other addressable memory unit sizes.
10058 Within @value{GDBN} and this document, the term
10059 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
10060 when explicitly referring to a chunk of data of that size. The word
10061 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
10062 the addressable memory unit size of the target. For most systems,
10063 addressable memory unit is a synonym of byte.
10065 @cindex remote memory comparison
10066 @cindex target memory comparison
10067 @cindex verify remote memory image
10068 @cindex verify target memory image
10069 When you are debugging a program running on a remote target machine
10070 (@pxref{Remote Debugging}), you may wish to verify the program's image
10071 in the remote machine's memory against the executable file you
10072 downloaded to the target. Or, on any target, you may want to check
10073 whether the program has corrupted its own read-only sections. The
10074 @code{compare-sections} command is provided for such situations.
10077 @kindex compare-sections
10078 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
10079 Compare the data of a loadable section @var{section-name} in the
10080 executable file of the program being debugged with the same section in
10081 the target machine's memory, and report any mismatches. With no
10082 arguments, compares all loadable sections. With an argument of
10083 @code{-r}, compares all loadable read-only sections.
10085 Note: for remote targets, this command can be accelerated if the
10086 target supports computing the CRC checksum of a block of memory
10087 (@pxref{qCRC packet}).
10091 @section Automatic Display
10092 @cindex automatic display
10093 @cindex display of expressions
10095 If you find that you want to print the value of an expression frequently
10096 (to see how it changes), you might want to add it to the @dfn{automatic
10097 display list} so that @value{GDBN} prints its value each time your program stops.
10098 Each expression added to the list is given a number to identify it;
10099 to remove an expression from the list, you specify that number.
10100 The automatic display looks like this:
10104 3: bar[5] = (struct hack *) 0x3804
10108 This display shows item numbers, expressions and their current values. As with
10109 displays you request manually using @code{x} or @code{print}, you can
10110 specify the output format you prefer; in fact, @code{display} decides
10111 whether to use @code{print} or @code{x} depending your format
10112 specification---it uses @code{x} if you specify either the @samp{i}
10113 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
10117 @item display @var{expr}
10118 Add the expression @var{expr} to the list of expressions to display
10119 each time your program stops. @xref{Expressions, ,Expressions}.
10121 @code{display} does not repeat if you press @key{RET} again after using it.
10123 @item display/@var{fmt} @var{expr}
10124 For @var{fmt} specifying only a display format and not a size or
10125 count, add the expression @var{expr} to the auto-display list but
10126 arrange to display it each time in the specified format @var{fmt}.
10127 @xref{Output Formats,,Output Formats}.
10129 @item display/@var{fmt} @var{addr}
10130 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
10131 number of units, add the expression @var{addr} as a memory address to
10132 be examined each time your program stops. Examining means in effect
10133 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
10136 For example, @samp{display/i $pc} can be helpful, to see the machine
10137 instruction about to be executed each time execution stops (@samp{$pc}
10138 is a common name for the program counter; @pxref{Registers, ,Registers}).
10141 @kindex delete display
10143 @item undisplay @var{dnums}@dots{}
10144 @itemx delete display @var{dnums}@dots{}
10145 Remove items from the list of expressions to display. Specify the
10146 numbers of the displays that you want affected with the command
10147 argument @var{dnums}. It can be a single display number, one of the
10148 numbers shown in the first field of the @samp{info display} display;
10149 or it could be a range of display numbers, as in @code{2-4}.
10151 @code{undisplay} does not repeat if you press @key{RET} after using it.
10152 (Otherwise you would just get the error @samp{No display number @dots{}}.)
10154 @kindex disable display
10155 @item disable display @var{dnums}@dots{}
10156 Disable the display of item numbers @var{dnums}. A disabled display
10157 item is not printed automatically, but is not forgotten. It may be
10158 enabled again later. Specify the numbers of the displays that you
10159 want affected with the command argument @var{dnums}. It can be a
10160 single display number, one of the numbers shown in the first field of
10161 the @samp{info display} display; or it could be a range of display
10162 numbers, as in @code{2-4}.
10164 @kindex enable display
10165 @item enable display @var{dnums}@dots{}
10166 Enable display of item numbers @var{dnums}. It becomes effective once
10167 again in auto display of its expression, until you specify otherwise.
10168 Specify the numbers of the displays that you want affected with the
10169 command argument @var{dnums}. It can be a single display number, one
10170 of the numbers shown in the first field of the @samp{info display}
10171 display; or it could be a range of display numbers, as in @code{2-4}.
10174 Display the current values of the expressions on the list, just as is
10175 done when your program stops.
10177 @kindex info display
10179 Print the list of expressions previously set up to display
10180 automatically, each one with its item number, but without showing the
10181 values. This includes disabled expressions, which are marked as such.
10182 It also includes expressions which would not be displayed right now
10183 because they refer to automatic variables not currently available.
10186 @cindex display disabled out of scope
10187 If a display expression refers to local variables, then it does not make
10188 sense outside the lexical context for which it was set up. Such an
10189 expression is disabled when execution enters a context where one of its
10190 variables is not defined. For example, if you give the command
10191 @code{display last_char} while inside a function with an argument
10192 @code{last_char}, @value{GDBN} displays this argument while your program
10193 continues to stop inside that function. When it stops elsewhere---where
10194 there is no variable @code{last_char}---the display is disabled
10195 automatically. The next time your program stops where @code{last_char}
10196 is meaningful, you can enable the display expression once again.
10198 @node Print Settings
10199 @section Print Settings
10201 @cindex format options
10202 @cindex print settings
10203 @value{GDBN} provides the following ways to control how arrays, structures,
10204 and symbols are printed.
10207 These settings are useful for debugging programs in any language:
10211 @item set print address
10212 @itemx set print address on
10213 @cindex print/don't print memory addresses
10214 @value{GDBN} prints memory addresses showing the location of stack
10215 traces, structure values, pointer values, breakpoints, and so forth,
10216 even when it also displays the contents of those addresses. The default
10217 is @code{on}. For example, this is what a stack frame display looks like with
10218 @code{set print address on}:
10223 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
10225 530 if (lquote != def_lquote)
10229 @item set print address off
10230 Do not print addresses when displaying their contents. For example,
10231 this is the same stack frame displayed with @code{set print address off}:
10235 (@value{GDBP}) set print addr off
10237 #0 set_quotes (lq="<<", rq=">>") at input.c:530
10238 530 if (lquote != def_lquote)
10242 You can use @samp{set print address off} to eliminate all machine
10243 dependent displays from the @value{GDBN} interface. For example, with
10244 @code{print address off}, you should get the same text for backtraces on
10245 all machines---whether or not they involve pointer arguments.
10248 @item show print address
10249 Show whether or not addresses are to be printed.
10252 When @value{GDBN} prints a symbolic address, it normally prints the
10253 closest earlier symbol plus an offset. If that symbol does not uniquely
10254 identify the address (for example, it is a name whose scope is a single
10255 source file), you may need to clarify. One way to do this is with
10256 @code{info line}, for example @samp{info line *0x4537}. Alternately,
10257 you can set @value{GDBN} to print the source file and line number when
10258 it prints a symbolic address:
10261 @item set print symbol-filename on
10262 @cindex source file and line of a symbol
10263 @cindex symbol, source file and line
10264 Tell @value{GDBN} to print the source file name and line number of a
10265 symbol in the symbolic form of an address.
10267 @item set print symbol-filename off
10268 Do not print source file name and line number of a symbol. This is the
10271 @item show print symbol-filename
10272 Show whether or not @value{GDBN} will print the source file name and
10273 line number of a symbol in the symbolic form of an address.
10276 Another situation where it is helpful to show symbol filenames and line
10277 numbers is when disassembling code; @value{GDBN} shows you the line
10278 number and source file that corresponds to each instruction.
10280 Also, you may wish to see the symbolic form only if the address being
10281 printed is reasonably close to the closest earlier symbol:
10284 @item set print max-symbolic-offset @var{max-offset}
10285 @itemx set print max-symbolic-offset unlimited
10286 @cindex maximum value for offset of closest symbol
10287 Tell @value{GDBN} to only display the symbolic form of an address if the
10288 offset between the closest earlier symbol and the address is less than
10289 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
10290 to always print the symbolic form of an address if any symbol precedes
10291 it. Zero is equivalent to @code{unlimited}.
10293 @item show print max-symbolic-offset
10294 Ask how large the maximum offset is that @value{GDBN} prints in a
10298 @cindex wild pointer, interpreting
10299 @cindex pointer, finding referent
10300 If you have a pointer and you are not sure where it points, try
10301 @samp{set print symbol-filename on}. Then you can determine the name
10302 and source file location of the variable where it points, using
10303 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
10304 For example, here @value{GDBN} shows that a variable @code{ptt} points
10305 at another variable @code{t}, defined in @file{hi2.c}:
10308 (@value{GDBP}) set print symbol-filename on
10309 (@value{GDBP}) p/a ptt
10310 $4 = 0xe008 <t in hi2.c>
10314 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
10315 does not show the symbol name and filename of the referent, even with
10316 the appropriate @code{set print} options turned on.
10319 You can also enable @samp{/a}-like formatting all the time using
10320 @samp{set print symbol on}:
10323 @item set print symbol on
10324 Tell @value{GDBN} to print the symbol corresponding to an address, if
10327 @item set print symbol off
10328 Tell @value{GDBN} not to print the symbol corresponding to an
10329 address. In this mode, @value{GDBN} will still print the symbol
10330 corresponding to pointers to functions. This is the default.
10332 @item show print symbol
10333 Show whether @value{GDBN} will display the symbol corresponding to an
10337 Other settings control how different kinds of objects are printed:
10340 @item set print array
10341 @itemx set print array on
10342 @cindex pretty print arrays
10343 Pretty print arrays. This format is more convenient to read,
10344 but uses more space. The default is off.
10346 @item set print array off
10347 Return to compressed format for arrays.
10349 @item show print array
10350 Show whether compressed or pretty format is selected for displaying
10353 @cindex print array indexes
10354 @item set print array-indexes
10355 @itemx set print array-indexes on
10356 Print the index of each element when displaying arrays. May be more
10357 convenient to locate a given element in the array or quickly find the
10358 index of a given element in that printed array. The default is off.
10360 @item set print array-indexes off
10361 Stop printing element indexes when displaying arrays.
10363 @item show print array-indexes
10364 Show whether the index of each element is printed when displaying
10367 @item set print elements @var{number-of-elements}
10368 @itemx set print elements unlimited
10369 @cindex number of array elements to print
10370 @cindex limit on number of printed array elements
10371 Set a limit on how many elements of an array @value{GDBN} will print.
10372 If @value{GDBN} is printing a large array, it stops printing after it has
10373 printed the number of elements set by the @code{set print elements} command.
10374 This limit also applies to the display of strings.
10375 When @value{GDBN} starts, this limit is set to 200.
10376 Setting @var{number-of-elements} to @code{unlimited} or zero means
10377 that the number of elements to print is unlimited.
10379 @item show print elements
10380 Display the number of elements of a large array that @value{GDBN} will print.
10381 If the number is 0, then the printing is unlimited.
10383 @item set print frame-arguments @var{value}
10384 @kindex set print frame-arguments
10385 @cindex printing frame argument values
10386 @cindex print all frame argument values
10387 @cindex print frame argument values for scalars only
10388 @cindex do not print frame argument values
10389 This command allows to control how the values of arguments are printed
10390 when the debugger prints a frame (@pxref{Frames}). The possible
10395 The values of all arguments are printed.
10398 Print the value of an argument only if it is a scalar. The value of more
10399 complex arguments such as arrays, structures, unions, etc, is replaced
10400 by @code{@dots{}}. This is the default. Here is an example where
10401 only scalar arguments are shown:
10404 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
10409 None of the argument values are printed. Instead, the value of each argument
10410 is replaced by @code{@dots{}}. In this case, the example above now becomes:
10413 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
10418 By default, only scalar arguments are printed. This command can be used
10419 to configure the debugger to print the value of all arguments, regardless
10420 of their type. However, it is often advantageous to not print the value
10421 of more complex parameters. For instance, it reduces the amount of
10422 information printed in each frame, making the backtrace more readable.
10423 Also, it improves performance when displaying Ada frames, because
10424 the computation of large arguments can sometimes be CPU-intensive,
10425 especially in large applications. Setting @code{print frame-arguments}
10426 to @code{scalars} (the default) or @code{none} avoids this computation,
10427 thus speeding up the display of each Ada frame.
10429 @item show print frame-arguments
10430 Show how the value of arguments should be displayed when printing a frame.
10432 @item set print raw frame-arguments on
10433 Print frame arguments in raw, non pretty-printed, form.
10435 @item set print raw frame-arguments off
10436 Print frame arguments in pretty-printed form, if there is a pretty-printer
10437 for the value (@pxref{Pretty Printing}),
10438 otherwise print the value in raw form.
10439 This is the default.
10441 @item show print raw frame-arguments
10442 Show whether to print frame arguments in raw form.
10444 @anchor{set print entry-values}
10445 @item set print entry-values @var{value}
10446 @kindex set print entry-values
10447 Set printing of frame argument values at function entry. In some cases
10448 @value{GDBN} can determine the value of function argument which was passed by
10449 the function caller, even if the value was modified inside the called function
10450 and therefore is different. With optimized code, the current value could be
10451 unavailable, but the entry value may still be known.
10453 The default value is @code{default} (see below for its description). Older
10454 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10455 this feature will behave in the @code{default} setting the same way as with the
10458 This functionality is currently supported only by DWARF 2 debugging format and
10459 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10460 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10463 The @var{value} parameter can be one of the following:
10467 Print only actual parameter values, never print values from function entry
10471 #0 different (val=6)
10472 #0 lost (val=<optimized out>)
10474 #0 invalid (val=<optimized out>)
10478 Print only parameter values from function entry point. The actual parameter
10479 values are never printed.
10481 #0 equal (val@@entry=5)
10482 #0 different (val@@entry=5)
10483 #0 lost (val@@entry=5)
10484 #0 born (val@@entry=<optimized out>)
10485 #0 invalid (val@@entry=<optimized out>)
10489 Print only parameter values from function entry point. If value from function
10490 entry point is not known while the actual value is known, print the actual
10491 value for such parameter.
10493 #0 equal (val@@entry=5)
10494 #0 different (val@@entry=5)
10495 #0 lost (val@@entry=5)
10497 #0 invalid (val@@entry=<optimized out>)
10501 Print actual parameter values. If actual parameter value is not known while
10502 value from function entry point is known, print the entry point value for such
10506 #0 different (val=6)
10507 #0 lost (val@@entry=5)
10509 #0 invalid (val=<optimized out>)
10513 Always print both the actual parameter value and its value from function entry
10514 point, even if values of one or both are not available due to compiler
10517 #0 equal (val=5, val@@entry=5)
10518 #0 different (val=6, val@@entry=5)
10519 #0 lost (val=<optimized out>, val@@entry=5)
10520 #0 born (val=10, val@@entry=<optimized out>)
10521 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10525 Print the actual parameter value if it is known and also its value from
10526 function entry point if it is known. If neither is known, print for the actual
10527 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10528 values are known and identical, print the shortened
10529 @code{param=param@@entry=VALUE} notation.
10531 #0 equal (val=val@@entry=5)
10532 #0 different (val=6, val@@entry=5)
10533 #0 lost (val@@entry=5)
10535 #0 invalid (val=<optimized out>)
10539 Always print the actual parameter value. Print also its value from function
10540 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10541 if both values are known and identical, print the shortened
10542 @code{param=param@@entry=VALUE} notation.
10544 #0 equal (val=val@@entry=5)
10545 #0 different (val=6, val@@entry=5)
10546 #0 lost (val=<optimized out>, val@@entry=5)
10548 #0 invalid (val=<optimized out>)
10552 For analysis messages on possible failures of frame argument values at function
10553 entry resolution see @ref{set debug entry-values}.
10555 @item show print entry-values
10556 Show the method being used for printing of frame argument values at function
10559 @item set print repeats @var{number-of-repeats}
10560 @itemx set print repeats unlimited
10561 @cindex repeated array elements
10562 Set the threshold for suppressing display of repeated array
10563 elements. When the number of consecutive identical elements of an
10564 array exceeds the threshold, @value{GDBN} prints the string
10565 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10566 identical repetitions, instead of displaying the identical elements
10567 themselves. Setting the threshold to @code{unlimited} or zero will
10568 cause all elements to be individually printed. The default threshold
10571 @item show print repeats
10572 Display the current threshold for printing repeated identical
10575 @item set print max-depth @var{depth}
10576 @item set print max-depth unlimited
10577 @cindex printing nested structures
10578 Set the threshold after which nested structures are replaced with
10579 ellipsis, this can make visualising deeply nested structures easier.
10581 For example, given this C code
10584 typedef struct s1 @{ int a; @} s1;
10585 typedef struct s2 @{ s1 b; @} s2;
10586 typedef struct s3 @{ s2 c; @} s3;
10587 typedef struct s4 @{ s3 d; @} s4;
10589 s4 var = @{ @{ @{ @{ 3 @} @} @} @};
10592 The following table shows how different values of @var{depth} will
10593 effect how @code{var} is printed by @value{GDBN}:
10595 @multitable @columnfractions .3 .7
10596 @headitem @var{depth} setting @tab Result of @samp{p var}
10598 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
10600 @tab @code{$1 = @{...@}}
10602 @tab @code{$1 = @{d = @{...@}@}}
10604 @tab @code{$1 = @{d = @{c = @{...@}@}@}}
10606 @tab @code{$1 = @{d = @{c = @{b = @{...@}@}@}@}}
10608 @tab @code{$1 = @{d = @{c = @{b = @{a = 3@}@}@}@}}
10611 To see the contents of structures that have been hidden the user can
10612 either increase the print max-depth, or they can print the elements of
10613 the structure that are visible, for example
10616 (gdb) set print max-depth 2
10618 $1 = @{d = @{c = @{...@}@}@}
10620 $2 = @{c = @{b = @{...@}@}@}
10622 $3 = @{b = @{a = 3@}@}
10625 The pattern used to replace nested structures varies based on
10626 language, for most languages @code{@{...@}} is used, but Fortran uses
10629 @item show print max-depth
10630 Display the current threshold after which nested structures are
10631 replaces with ellipsis.
10633 @item set print null-stop
10634 @cindex @sc{null} elements in arrays
10635 Cause @value{GDBN} to stop printing the characters of an array when the first
10636 @sc{null} is encountered. This is useful when large arrays actually
10637 contain only short strings.
10638 The default is off.
10640 @item show print null-stop
10641 Show whether @value{GDBN} stops printing an array on the first
10642 @sc{null} character.
10644 @item set print pretty on
10645 @cindex print structures in indented form
10646 @cindex indentation in structure display
10647 Cause @value{GDBN} to print structures in an indented format with one member
10648 per line, like this:
10663 @item set print pretty off
10664 Cause @value{GDBN} to print structures in a compact format, like this:
10668 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10669 meat = 0x54 "Pork"@}
10674 This is the default format.
10676 @item show print pretty
10677 Show which format @value{GDBN} is using to print structures.
10679 @item set print sevenbit-strings on
10680 @cindex eight-bit characters in strings
10681 @cindex octal escapes in strings
10682 Print using only seven-bit characters; if this option is set,
10683 @value{GDBN} displays any eight-bit characters (in strings or
10684 character values) using the notation @code{\}@var{nnn}. This setting is
10685 best if you are working in English (@sc{ascii}) and you use the
10686 high-order bit of characters as a marker or ``meta'' bit.
10688 @item set print sevenbit-strings off
10689 Print full eight-bit characters. This allows the use of more
10690 international character sets, and is the default.
10692 @item show print sevenbit-strings
10693 Show whether or not @value{GDBN} is printing only seven-bit characters.
10695 @item set print union on
10696 @cindex unions in structures, printing
10697 Tell @value{GDBN} to print unions which are contained in structures
10698 and other unions. This is the default setting.
10700 @item set print union off
10701 Tell @value{GDBN} not to print unions which are contained in
10702 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10705 @item show print union
10706 Ask @value{GDBN} whether or not it will print unions which are contained in
10707 structures and other unions.
10709 For example, given the declarations
10712 typedef enum @{Tree, Bug@} Species;
10713 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10714 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10725 struct thing foo = @{Tree, @{Acorn@}@};
10729 with @code{set print union on} in effect @samp{p foo} would print
10732 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10736 and with @code{set print union off} in effect it would print
10739 $1 = @{it = Tree, form = @{...@}@}
10743 @code{set print union} affects programs written in C-like languages
10749 These settings are of interest when debugging C@t{++} programs:
10752 @cindex demangling C@t{++} names
10753 @item set print demangle
10754 @itemx set print demangle on
10755 Print C@t{++} names in their source form rather than in the encoded
10756 (``mangled'') form passed to the assembler and linker for type-safe
10757 linkage. The default is on.
10759 @item show print demangle
10760 Show whether C@t{++} names are printed in mangled or demangled form.
10762 @item set print asm-demangle
10763 @itemx set print asm-demangle on
10764 Print C@t{++} names in their source form rather than their mangled form, even
10765 in assembler code printouts such as instruction disassemblies.
10766 The default is off.
10768 @item show print asm-demangle
10769 Show whether C@t{++} names in assembly listings are printed in mangled
10772 @cindex C@t{++} symbol decoding style
10773 @cindex symbol decoding style, C@t{++}
10774 @kindex set demangle-style
10775 @item set demangle-style @var{style}
10776 Choose among several encoding schemes used by different compilers to represent
10777 C@t{++} names. If you omit @var{style}, you will see a list of possible
10778 formats. The default value is @var{auto}, which lets @value{GDBN} choose a
10779 decoding style by inspecting your program.
10781 @item show demangle-style
10782 Display the encoding style currently in use for decoding C@t{++} symbols.
10784 @item set print object
10785 @itemx set print object on
10786 @cindex derived type of an object, printing
10787 @cindex display derived types
10788 When displaying a pointer to an object, identify the @emph{actual}
10789 (derived) type of the object rather than the @emph{declared} type, using
10790 the virtual function table. Note that the virtual function table is
10791 required---this feature can only work for objects that have run-time
10792 type identification; a single virtual method in the object's declared
10793 type is sufficient. Note that this setting is also taken into account when
10794 working with variable objects via MI (@pxref{GDB/MI}).
10796 @item set print object off
10797 Display only the declared type of objects, without reference to the
10798 virtual function table. This is the default setting.
10800 @item show print object
10801 Show whether actual, or declared, object types are displayed.
10803 @item set print static-members
10804 @itemx set print static-members on
10805 @cindex static members of C@t{++} objects
10806 Print static members when displaying a C@t{++} object. The default is on.
10808 @item set print static-members off
10809 Do not print static members when displaying a C@t{++} object.
10811 @item show print static-members
10812 Show whether C@t{++} static members are printed or not.
10814 @item set print pascal_static-members
10815 @itemx set print pascal_static-members on
10816 @cindex static members of Pascal objects
10817 @cindex Pascal objects, static members display
10818 Print static members when displaying a Pascal object. The default is on.
10820 @item set print pascal_static-members off
10821 Do not print static members when displaying a Pascal object.
10823 @item show print pascal_static-members
10824 Show whether Pascal static members are printed or not.
10826 @c These don't work with HP ANSI C++ yet.
10827 @item set print vtbl
10828 @itemx set print vtbl on
10829 @cindex pretty print C@t{++} virtual function tables
10830 @cindex virtual functions (C@t{++}) display
10831 @cindex VTBL display
10832 Pretty print C@t{++} virtual function tables. The default is off.
10833 (The @code{vtbl} commands do not work on programs compiled with the HP
10834 ANSI C@t{++} compiler (@code{aCC}).)
10836 @item set print vtbl off
10837 Do not pretty print C@t{++} virtual function tables.
10839 @item show print vtbl
10840 Show whether C@t{++} virtual function tables are pretty printed, or not.
10843 @node Pretty Printing
10844 @section Pretty Printing
10846 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10847 Python code. It greatly simplifies the display of complex objects. This
10848 mechanism works for both MI and the CLI.
10851 * Pretty-Printer Introduction:: Introduction to pretty-printers
10852 * Pretty-Printer Example:: An example pretty-printer
10853 * Pretty-Printer Commands:: Pretty-printer commands
10856 @node Pretty-Printer Introduction
10857 @subsection Pretty-Printer Introduction
10859 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10860 registered for the value. If there is then @value{GDBN} invokes the
10861 pretty-printer to print the value. Otherwise the value is printed normally.
10863 Pretty-printers are normally named. This makes them easy to manage.
10864 The @samp{info pretty-printer} command will list all the installed
10865 pretty-printers with their names.
10866 If a pretty-printer can handle multiple data types, then its
10867 @dfn{subprinters} are the printers for the individual data types.
10868 Each such subprinter has its own name.
10869 The format of the name is @var{printer-name};@var{subprinter-name}.
10871 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10872 Typically they are automatically loaded and registered when the corresponding
10873 debug information is loaded, thus making them available without having to
10874 do anything special.
10876 There are three places where a pretty-printer can be registered.
10880 Pretty-printers registered globally are available when debugging
10884 Pretty-printers registered with a program space are available only
10885 when debugging that program.
10886 @xref{Progspaces In Python}, for more details on program spaces in Python.
10889 Pretty-printers registered with an objfile are loaded and unloaded
10890 with the corresponding objfile (e.g., shared library).
10891 @xref{Objfiles In Python}, for more details on objfiles in Python.
10894 @xref{Selecting Pretty-Printers}, for further information on how
10895 pretty-printers are selected,
10897 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10900 @node Pretty-Printer Example
10901 @subsection Pretty-Printer Example
10903 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10906 (@value{GDBP}) print s
10908 static npos = 4294967295,
10910 <std::allocator<char>> = @{
10911 <__gnu_cxx::new_allocator<char>> = @{
10912 <No data fields>@}, <No data fields>
10914 members of std::basic_string<char, std::char_traits<char>,
10915 std::allocator<char> >::_Alloc_hider:
10916 _M_p = 0x804a014 "abcd"
10921 With a pretty-printer for @code{std::string} only the contents are printed:
10924 (@value{GDBP}) print s
10928 @node Pretty-Printer Commands
10929 @subsection Pretty-Printer Commands
10930 @cindex pretty-printer commands
10933 @kindex info pretty-printer
10934 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10935 Print the list of installed pretty-printers.
10936 This includes disabled pretty-printers, which are marked as such.
10938 @var{object-regexp} is a regular expression matching the objects
10939 whose pretty-printers to list.
10940 Objects can be @code{global}, the program space's file
10941 (@pxref{Progspaces In Python}),
10942 and the object files within that program space (@pxref{Objfiles In Python}).
10943 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10944 looks up a printer from these three objects.
10946 @var{name-regexp} is a regular expression matching the name of the printers
10949 @kindex disable pretty-printer
10950 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10951 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10952 A disabled pretty-printer is not forgotten, it may be enabled again later.
10954 @kindex enable pretty-printer
10955 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10956 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10961 Suppose we have three pretty-printers installed: one from library1.so
10962 named @code{foo} that prints objects of type @code{foo}, and
10963 another from library2.so named @code{bar} that prints two types of objects,
10964 @code{bar1} and @code{bar2}.
10967 (gdb) info pretty-printer
10974 (gdb) info pretty-printer library2
10979 (gdb) disable pretty-printer library1
10981 2 of 3 printers enabled
10982 (gdb) info pretty-printer
10989 (gdb) disable pretty-printer library2 bar;bar1
10991 1 of 3 printers enabled
10992 (gdb) info pretty-printer library2
10999 (gdb) disable pretty-printer library2 bar
11001 0 of 3 printers enabled
11002 (gdb) info pretty-printer library2
11011 Note that for @code{bar} the entire printer can be disabled,
11012 as can each individual subprinter.
11014 @node Value History
11015 @section Value History
11017 @cindex value history
11018 @cindex history of values printed by @value{GDBN}
11019 Values printed by the @code{print} command are saved in the @value{GDBN}
11020 @dfn{value history}. This allows you to refer to them in other expressions.
11021 Values are kept until the symbol table is re-read or discarded
11022 (for example with the @code{file} or @code{symbol-file} commands).
11023 When the symbol table changes, the value history is discarded,
11024 since the values may contain pointers back to the types defined in the
11029 @cindex history number
11030 The values printed are given @dfn{history numbers} by which you can
11031 refer to them. These are successive integers starting with one.
11032 @code{print} shows you the history number assigned to a value by
11033 printing @samp{$@var{num} = } before the value; here @var{num} is the
11036 To refer to any previous value, use @samp{$} followed by the value's
11037 history number. The way @code{print} labels its output is designed to
11038 remind you of this. Just @code{$} refers to the most recent value in
11039 the history, and @code{$$} refers to the value before that.
11040 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
11041 is the value just prior to @code{$$}, @code{$$1} is equivalent to
11042 @code{$$}, and @code{$$0} is equivalent to @code{$}.
11044 For example, suppose you have just printed a pointer to a structure and
11045 want to see the contents of the structure. It suffices to type
11051 If you have a chain of structures where the component @code{next} points
11052 to the next one, you can print the contents of the next one with this:
11059 You can print successive links in the chain by repeating this
11060 command---which you can do by just typing @key{RET}.
11062 Note that the history records values, not expressions. If the value of
11063 @code{x} is 4 and you type these commands:
11071 then the value recorded in the value history by the @code{print} command
11072 remains 4 even though the value of @code{x} has changed.
11075 @kindex show values
11077 Print the last ten values in the value history, with their item numbers.
11078 This is like @samp{p@ $$9} repeated ten times, except that @code{show
11079 values} does not change the history.
11081 @item show values @var{n}
11082 Print ten history values centered on history item number @var{n}.
11084 @item show values +
11085 Print ten history values just after the values last printed. If no more
11086 values are available, @code{show values +} produces no display.
11089 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
11090 same effect as @samp{show values +}.
11092 @node Convenience Vars
11093 @section Convenience Variables
11095 @cindex convenience variables
11096 @cindex user-defined variables
11097 @value{GDBN} provides @dfn{convenience variables} that you can use within
11098 @value{GDBN} to hold on to a value and refer to it later. These variables
11099 exist entirely within @value{GDBN}; they are not part of your program, and
11100 setting a convenience variable has no direct effect on further execution
11101 of your program. That is why you can use them freely.
11103 Convenience variables are prefixed with @samp{$}. Any name preceded by
11104 @samp{$} can be used for a convenience variable, unless it is one of
11105 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
11106 (Value history references, in contrast, are @emph{numbers} preceded
11107 by @samp{$}. @xref{Value History, ,Value History}.)
11109 You can save a value in a convenience variable with an assignment
11110 expression, just as you would set a variable in your program.
11114 set $foo = *object_ptr
11118 would save in @code{$foo} the value contained in the object pointed to by
11121 Using a convenience variable for the first time creates it, but its
11122 value is @code{void} until you assign a new value. You can alter the
11123 value with another assignment at any time.
11125 Convenience variables have no fixed types. You can assign a convenience
11126 variable any type of value, including structures and arrays, even if
11127 that variable already has a value of a different type. The convenience
11128 variable, when used as an expression, has the type of its current value.
11131 @kindex show convenience
11132 @cindex show all user variables and functions
11133 @item show convenience
11134 Print a list of convenience variables used so far, and their values,
11135 as well as a list of the convenience functions.
11136 Abbreviated @code{show conv}.
11138 @kindex init-if-undefined
11139 @cindex convenience variables, initializing
11140 @item init-if-undefined $@var{variable} = @var{expression}
11141 Set a convenience variable if it has not already been set. This is useful
11142 for user-defined commands that keep some state. It is similar, in concept,
11143 to using local static variables with initializers in C (except that
11144 convenience variables are global). It can also be used to allow users to
11145 override default values used in a command script.
11147 If the variable is already defined then the expression is not evaluated so
11148 any side-effects do not occur.
11151 One of the ways to use a convenience variable is as a counter to be
11152 incremented or a pointer to be advanced. For example, to print
11153 a field from successive elements of an array of structures:
11157 print bar[$i++]->contents
11161 Repeat that command by typing @key{RET}.
11163 Some convenience variables are created automatically by @value{GDBN} and given
11164 values likely to be useful.
11167 @vindex $_@r{, convenience variable}
11169 The variable @code{$_} is automatically set by the @code{x} command to
11170 the last address examined (@pxref{Memory, ,Examining Memory}). Other
11171 commands which provide a default address for @code{x} to examine also
11172 set @code{$_} to that address; these commands include @code{info line}
11173 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
11174 except when set by the @code{x} command, in which case it is a pointer
11175 to the type of @code{$__}.
11177 @vindex $__@r{, convenience variable}
11179 The variable @code{$__} is automatically set by the @code{x} command
11180 to the value found in the last address examined. Its type is chosen
11181 to match the format in which the data was printed.
11184 @vindex $_exitcode@r{, convenience variable}
11185 When the program being debugged terminates normally, @value{GDBN}
11186 automatically sets this variable to the exit code of the program, and
11187 resets @code{$_exitsignal} to @code{void}.
11190 @vindex $_exitsignal@r{, convenience variable}
11191 When the program being debugged dies due to an uncaught signal,
11192 @value{GDBN} automatically sets this variable to that signal's number,
11193 and resets @code{$_exitcode} to @code{void}.
11195 To distinguish between whether the program being debugged has exited
11196 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
11197 @code{$_exitsignal} is not @code{void}), the convenience function
11198 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
11199 Functions}). For example, considering the following source code:
11202 #include <signal.h>
11205 main (int argc, char *argv[])
11212 A valid way of telling whether the program being debugged has exited
11213 or signalled would be:
11216 (@value{GDBP}) define has_exited_or_signalled
11217 Type commands for definition of ``has_exited_or_signalled''.
11218 End with a line saying just ``end''.
11219 >if $_isvoid ($_exitsignal)
11220 >echo The program has exited\n
11222 >echo The program has signalled\n
11228 Program terminated with signal SIGALRM, Alarm clock.
11229 The program no longer exists.
11230 (@value{GDBP}) has_exited_or_signalled
11231 The program has signalled
11234 As can be seen, @value{GDBN} correctly informs that the program being
11235 debugged has signalled, since it calls @code{raise} and raises a
11236 @code{SIGALRM} signal. If the program being debugged had not called
11237 @code{raise}, then @value{GDBN} would report a normal exit:
11240 (@value{GDBP}) has_exited_or_signalled
11241 The program has exited
11245 The variable @code{$_exception} is set to the exception object being
11246 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
11249 @itemx $_probe_arg0@dots{}$_probe_arg11
11250 Arguments to a static probe. @xref{Static Probe Points}.
11253 @vindex $_sdata@r{, inspect, convenience variable}
11254 The variable @code{$_sdata} contains extra collected static tracepoint
11255 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
11256 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
11257 if extra static tracepoint data has not been collected.
11260 @vindex $_siginfo@r{, convenience variable}
11261 The variable @code{$_siginfo} contains extra signal information
11262 (@pxref{extra signal information}). Note that @code{$_siginfo}
11263 could be empty, if the application has not yet received any signals.
11264 For example, it will be empty before you execute the @code{run} command.
11267 @vindex $_tlb@r{, convenience variable}
11268 The variable @code{$_tlb} is automatically set when debugging
11269 applications running on MS-Windows in native mode or connected to
11270 gdbserver that supports the @code{qGetTIBAddr} request.
11271 @xref{General Query Packets}.
11272 This variable contains the address of the thread information block.
11275 The number of the current inferior. @xref{Inferiors and
11276 Programs, ,Debugging Multiple Inferiors and Programs}.
11279 The thread number of the current thread. @xref{thread numbers}.
11282 The global number of the current thread. @xref{global thread numbers}.
11286 @vindex $_gdb_major@r{, convenience variable}
11287 @vindex $_gdb_minor@r{, convenience variable}
11288 The major and minor version numbers of the running @value{GDBN}.
11289 Development snapshots and pretest versions have their minor version
11290 incremented by one; thus, @value{GDBN} pretest 9.11.90 will produce
11291 the value 12 for @code{$_gdb_minor}. These variables allow you to
11292 write scripts that work with different versions of @value{GDBN}
11293 without errors caused by features unavailable in some of those
11297 @node Convenience Funs
11298 @section Convenience Functions
11300 @cindex convenience functions
11301 @value{GDBN} also supplies some @dfn{convenience functions}. These
11302 have a syntax similar to convenience variables. A convenience
11303 function can be used in an expression just like an ordinary function;
11304 however, a convenience function is implemented internally to
11307 These functions do not require @value{GDBN} to be configured with
11308 @code{Python} support, which means that they are always available.
11312 @item $_isvoid (@var{expr})
11313 @findex $_isvoid@r{, convenience function}
11314 Return one if the expression @var{expr} is @code{void}. Otherwise it
11317 A @code{void} expression is an expression where the type of the result
11318 is @code{void}. For example, you can examine a convenience variable
11319 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
11323 (@value{GDBP}) print $_exitcode
11325 (@value{GDBP}) print $_isvoid ($_exitcode)
11328 Starting program: ./a.out
11329 [Inferior 1 (process 29572) exited normally]
11330 (@value{GDBP}) print $_exitcode
11332 (@value{GDBP}) print $_isvoid ($_exitcode)
11336 In the example above, we used @code{$_isvoid} to check whether
11337 @code{$_exitcode} is @code{void} before and after the execution of the
11338 program being debugged. Before the execution there is no exit code to
11339 be examined, therefore @code{$_exitcode} is @code{void}. After the
11340 execution the program being debugged returned zero, therefore
11341 @code{$_exitcode} is zero, which means that it is not @code{void}
11344 The @code{void} expression can also be a call of a function from the
11345 program being debugged. For example, given the following function:
11354 The result of calling it inside @value{GDBN} is @code{void}:
11357 (@value{GDBP}) print foo ()
11359 (@value{GDBP}) print $_isvoid (foo ())
11361 (@value{GDBP}) set $v = foo ()
11362 (@value{GDBP}) print $v
11364 (@value{GDBP}) print $_isvoid ($v)
11370 These functions require @value{GDBN} to be configured with
11371 @code{Python} support.
11375 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
11376 @findex $_memeq@r{, convenience function}
11377 Returns one if the @var{length} bytes at the addresses given by
11378 @var{buf1} and @var{buf2} are equal.
11379 Otherwise it returns zero.
11381 @item $_regex(@var{str}, @var{regex})
11382 @findex $_regex@r{, convenience function}
11383 Returns one if the string @var{str} matches the regular expression
11384 @var{regex}. Otherwise it returns zero.
11385 The syntax of the regular expression is that specified by @code{Python}'s
11386 regular expression support.
11388 @item $_streq(@var{str1}, @var{str2})
11389 @findex $_streq@r{, convenience function}
11390 Returns one if the strings @var{str1} and @var{str2} are equal.
11391 Otherwise it returns zero.
11393 @item $_strlen(@var{str})
11394 @findex $_strlen@r{, convenience function}
11395 Returns the length of string @var{str}.
11397 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11398 @findex $_caller_is@r{, convenience function}
11399 Returns one if the calling function's name is equal to @var{name}.
11400 Otherwise it returns zero.
11402 If the optional argument @var{number_of_frames} is provided,
11403 it is the number of frames up in the stack to look.
11411 at testsuite/gdb.python/py-caller-is.c:21
11412 #1 0x00000000004005a0 in middle_func ()
11413 at testsuite/gdb.python/py-caller-is.c:27
11414 #2 0x00000000004005ab in top_func ()
11415 at testsuite/gdb.python/py-caller-is.c:33
11416 #3 0x00000000004005b6 in main ()
11417 at testsuite/gdb.python/py-caller-is.c:39
11418 (gdb) print $_caller_is ("middle_func")
11420 (gdb) print $_caller_is ("top_func", 2)
11424 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11425 @findex $_caller_matches@r{, convenience function}
11426 Returns one if the calling function's name matches the regular expression
11427 @var{regexp}. Otherwise it returns zero.
11429 If the optional argument @var{number_of_frames} is provided,
11430 it is the number of frames up in the stack to look.
11433 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
11434 @findex $_any_caller_is@r{, convenience function}
11435 Returns one if any calling function's name is equal to @var{name}.
11436 Otherwise it returns zero.
11438 If the optional argument @var{number_of_frames} is provided,
11439 it is the number of frames up in the stack to look.
11442 This function differs from @code{$_caller_is} in that this function
11443 checks all stack frames from the immediate caller to the frame specified
11444 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
11445 frame specified by @var{number_of_frames}.
11447 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
11448 @findex $_any_caller_matches@r{, convenience function}
11449 Returns one if any calling function's name matches the regular expression
11450 @var{regexp}. Otherwise it returns zero.
11452 If the optional argument @var{number_of_frames} is provided,
11453 it is the number of frames up in the stack to look.
11456 This function differs from @code{$_caller_matches} in that this function
11457 checks all stack frames from the immediate caller to the frame specified
11458 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
11459 frame specified by @var{number_of_frames}.
11461 @item $_as_string(@var{value})
11462 @findex $_as_string@r{, convenience function}
11463 Return the string representation of @var{value}.
11465 This function is useful to obtain the textual label (enumerator) of an
11466 enumeration value. For example, assuming the variable @var{node} is of
11467 an enumerated type:
11470 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
11471 Visiting node of type NODE_INTEGER
11474 @item $_cimag(@var{value})
11475 @itemx $_creal(@var{value})
11476 @findex $_cimag@r{, convenience function}
11477 @findex $_creal@r{, convenience function}
11478 Return the imaginary (@code{$_cimag}) or real (@code{$_creal}) part of
11479 the complex number @var{value}.
11481 The type of the imaginary or real part depends on the type of the
11482 complex number, e.g., using @code{$_cimag} on a @code{float complex}
11483 will return an imaginary part of type @code{float}.
11487 @value{GDBN} provides the ability to list and get help on
11488 convenience functions.
11491 @item help function
11492 @kindex help function
11493 @cindex show all convenience functions
11494 Print a list of all convenience functions.
11501 You can refer to machine register contents, in expressions, as variables
11502 with names starting with @samp{$}. The names of registers are different
11503 for each machine; use @code{info registers} to see the names used on
11507 @kindex info registers
11508 @item info registers
11509 Print the names and values of all registers except floating-point
11510 and vector registers (in the selected stack frame).
11512 @kindex info all-registers
11513 @cindex floating point registers
11514 @item info all-registers
11515 Print the names and values of all registers, including floating-point
11516 and vector registers (in the selected stack frame).
11518 @item info registers @var{reggroup} @dots{}
11519 Print the name and value of the registers in each of the specified
11520 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11521 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11523 @item info registers @var{regname} @dots{}
11524 Print the @dfn{relativized} value of each specified register @var{regname}.
11525 As discussed in detail below, register values are normally relative to
11526 the selected stack frame. The @var{regname} may be any register name valid on
11527 the machine you are using, with or without the initial @samp{$}.
11530 @anchor{standard registers}
11531 @cindex stack pointer register
11532 @cindex program counter register
11533 @cindex process status register
11534 @cindex frame pointer register
11535 @cindex standard registers
11536 @value{GDBN} has four ``standard'' register names that are available (in
11537 expressions) on most machines---whenever they do not conflict with an
11538 architecture's canonical mnemonics for registers. The register names
11539 @code{$pc} and @code{$sp} are used for the program counter register and
11540 the stack pointer. @code{$fp} is used for a register that contains a
11541 pointer to the current stack frame, and @code{$ps} is used for a
11542 register that contains the processor status. For example,
11543 you could print the program counter in hex with
11550 or print the instruction to be executed next with
11557 or add four to the stack pointer@footnote{This is a way of removing
11558 one word from the stack, on machines where stacks grow downward in
11559 memory (most machines, nowadays). This assumes that the innermost
11560 stack frame is selected; setting @code{$sp} is not allowed when other
11561 stack frames are selected. To pop entire frames off the stack,
11562 regardless of machine architecture, use @code{return};
11563 see @ref{Returning, ,Returning from a Function}.} with
11569 Whenever possible, these four standard register names are available on
11570 your machine even though the machine has different canonical mnemonics,
11571 so long as there is no conflict. The @code{info registers} command
11572 shows the canonical names. For example, on the SPARC, @code{info
11573 registers} displays the processor status register as @code{$psr} but you
11574 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11575 is an alias for the @sc{eflags} register.
11577 @value{GDBN} always considers the contents of an ordinary register as an
11578 integer when the register is examined in this way. Some machines have
11579 special registers which can hold nothing but floating point; these
11580 registers are considered to have floating point values. There is no way
11581 to refer to the contents of an ordinary register as floating point value
11582 (although you can @emph{print} it as a floating point value with
11583 @samp{print/f $@var{regname}}).
11585 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11586 means that the data format in which the register contents are saved by
11587 the operating system is not the same one that your program normally
11588 sees. For example, the registers of the 68881 floating point
11589 coprocessor are always saved in ``extended'' (raw) format, but all C
11590 programs expect to work with ``double'' (virtual) format. In such
11591 cases, @value{GDBN} normally works with the virtual format only (the format
11592 that makes sense for your program), but the @code{info registers} command
11593 prints the data in both formats.
11595 @cindex SSE registers (x86)
11596 @cindex MMX registers (x86)
11597 Some machines have special registers whose contents can be interpreted
11598 in several different ways. For example, modern x86-based machines
11599 have SSE and MMX registers that can hold several values packed
11600 together in several different formats. @value{GDBN} refers to such
11601 registers in @code{struct} notation:
11604 (@value{GDBP}) print $xmm1
11606 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11607 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11608 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11609 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11610 v4_int32 = @{0, 20657912, 11, 13@},
11611 v2_int64 = @{88725056443645952, 55834574859@},
11612 uint128 = 0x0000000d0000000b013b36f800000000
11617 To set values of such registers, you need to tell @value{GDBN} which
11618 view of the register you wish to change, as if you were assigning
11619 value to a @code{struct} member:
11622 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11625 Normally, register values are relative to the selected stack frame
11626 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11627 value that the register would contain if all stack frames farther in
11628 were exited and their saved registers restored. In order to see the
11629 true contents of hardware registers, you must select the innermost
11630 frame (with @samp{frame 0}).
11632 @cindex caller-saved registers
11633 @cindex call-clobbered registers
11634 @cindex volatile registers
11635 @cindex <not saved> values
11636 Usually ABIs reserve some registers as not needed to be saved by the
11637 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11638 registers). It may therefore not be possible for @value{GDBN} to know
11639 the value a register had before the call (in other words, in the outer
11640 frame), if the register value has since been changed by the callee.
11641 @value{GDBN} tries to deduce where the inner frame saved
11642 (``callee-saved'') registers, from the debug info, unwind info, or the
11643 machine code generated by your compiler. If some register is not
11644 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11645 its own knowledge of the ABI, or because the debug/unwind info
11646 explicitly says the register's value is undefined), @value{GDBN}
11647 displays @w{@samp{<not saved>}} as the register's value. With targets
11648 that @value{GDBN} has no knowledge of the register saving convention,
11649 if a register was not saved by the callee, then its value and location
11650 in the outer frame are assumed to be the same of the inner frame.
11651 This is usually harmless, because if the register is call-clobbered,
11652 the caller either does not care what is in the register after the
11653 call, or has code to restore the value that it does care about. Note,
11654 however, that if you change such a register in the outer frame, you
11655 may also be affecting the inner frame. Also, the more ``outer'' the
11656 frame is you're looking at, the more likely a call-clobbered
11657 register's value is to be wrong, in the sense that it doesn't actually
11658 represent the value the register had just before the call.
11660 @node Floating Point Hardware
11661 @section Floating Point Hardware
11662 @cindex floating point
11664 Depending on the configuration, @value{GDBN} may be able to give
11665 you more information about the status of the floating point hardware.
11670 Display hardware-dependent information about the floating
11671 point unit. The exact contents and layout vary depending on the
11672 floating point chip. Currently, @samp{info float} is supported on
11673 the ARM and x86 machines.
11677 @section Vector Unit
11678 @cindex vector unit
11680 Depending on the configuration, @value{GDBN} may be able to give you
11681 more information about the status of the vector unit.
11684 @kindex info vector
11686 Display information about the vector unit. The exact contents and
11687 layout vary depending on the hardware.
11690 @node OS Information
11691 @section Operating System Auxiliary Information
11692 @cindex OS information
11694 @value{GDBN} provides interfaces to useful OS facilities that can help
11695 you debug your program.
11697 @cindex auxiliary vector
11698 @cindex vector, auxiliary
11699 Some operating systems supply an @dfn{auxiliary vector} to programs at
11700 startup. This is akin to the arguments and environment that you
11701 specify for a program, but contains a system-dependent variety of
11702 binary values that tell system libraries important details about the
11703 hardware, operating system, and process. Each value's purpose is
11704 identified by an integer tag; the meanings are well-known but system-specific.
11705 Depending on the configuration and operating system facilities,
11706 @value{GDBN} may be able to show you this information. For remote
11707 targets, this functionality may further depend on the remote stub's
11708 support of the @samp{qXfer:auxv:read} packet, see
11709 @ref{qXfer auxiliary vector read}.
11714 Display the auxiliary vector of the inferior, which can be either a
11715 live process or a core dump file. @value{GDBN} prints each tag value
11716 numerically, and also shows names and text descriptions for recognized
11717 tags. Some values in the vector are numbers, some bit masks, and some
11718 pointers to strings or other data. @value{GDBN} displays each value in the
11719 most appropriate form for a recognized tag, and in hexadecimal for
11720 an unrecognized tag.
11723 On some targets, @value{GDBN} can access operating system-specific
11724 information and show it to you. The types of information available
11725 will differ depending on the type of operating system running on the
11726 target. The mechanism used to fetch the data is described in
11727 @ref{Operating System Information}. For remote targets, this
11728 functionality depends on the remote stub's support of the
11729 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11733 @item info os @var{infotype}
11735 Display OS information of the requested type.
11737 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11739 @anchor{linux info os infotypes}
11741 @kindex info os cpus
11743 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11744 the available fields from /proc/cpuinfo. For each supported architecture
11745 different fields are available. Two common entries are processor which gives
11746 CPU number and bogomips; a system constant that is calculated during
11747 kernel initialization.
11749 @kindex info os files
11751 Display the list of open file descriptors on the target. For each
11752 file descriptor, @value{GDBN} prints the identifier of the process
11753 owning the descriptor, the command of the owning process, the value
11754 of the descriptor, and the target of the descriptor.
11756 @kindex info os modules
11758 Display the list of all loaded kernel modules on the target. For each
11759 module, @value{GDBN} prints the module name, the size of the module in
11760 bytes, the number of times the module is used, the dependencies of the
11761 module, the status of the module, and the address of the loaded module
11764 @kindex info os msg
11766 Display the list of all System V message queues on the target. For each
11767 message queue, @value{GDBN} prints the message queue key, the message
11768 queue identifier, the access permissions, the current number of bytes
11769 on the queue, the current number of messages on the queue, the processes
11770 that last sent and received a message on the queue, the user and group
11771 of the owner and creator of the message queue, the times at which a
11772 message was last sent and received on the queue, and the time at which
11773 the message queue was last changed.
11775 @kindex info os processes
11777 Display the list of processes on the target. For each process,
11778 @value{GDBN} prints the process identifier, the name of the user, the
11779 command corresponding to the process, and the list of processor cores
11780 that the process is currently running on. (To understand what these
11781 properties mean, for this and the following info types, please consult
11782 the general @sc{gnu}/Linux documentation.)
11784 @kindex info os procgroups
11786 Display the list of process groups on the target. For each process,
11787 @value{GDBN} prints the identifier of the process group that it belongs
11788 to, the command corresponding to the process group leader, the process
11789 identifier, and the command line of the process. The list is sorted
11790 first by the process group identifier, then by the process identifier,
11791 so that processes belonging to the same process group are grouped together
11792 and the process group leader is listed first.
11794 @kindex info os semaphores
11796 Display the list of all System V semaphore sets on the target. For each
11797 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11798 set identifier, the access permissions, the number of semaphores in the
11799 set, the user and group of the owner and creator of the semaphore set,
11800 and the times at which the semaphore set was operated upon and changed.
11802 @kindex info os shm
11804 Display the list of all System V shared-memory regions on the target.
11805 For each shared-memory region, @value{GDBN} prints the region key,
11806 the shared-memory identifier, the access permissions, the size of the
11807 region, the process that created the region, the process that last
11808 attached to or detached from the region, the current number of live
11809 attaches to the region, and the times at which the region was last
11810 attached to, detach from, and changed.
11812 @kindex info os sockets
11814 Display the list of Internet-domain sockets on the target. For each
11815 socket, @value{GDBN} prints the address and port of the local and
11816 remote endpoints, the current state of the connection, the creator of
11817 the socket, the IP address family of the socket, and the type of the
11820 @kindex info os threads
11822 Display the list of threads running on the target. For each thread,
11823 @value{GDBN} prints the identifier of the process that the thread
11824 belongs to, the command of the process, the thread identifier, and the
11825 processor core that it is currently running on. The main thread of a
11826 process is not listed.
11830 If @var{infotype} is omitted, then list the possible values for
11831 @var{infotype} and the kind of OS information available for each
11832 @var{infotype}. If the target does not return a list of possible
11833 types, this command will report an error.
11836 @node Memory Region Attributes
11837 @section Memory Region Attributes
11838 @cindex memory region attributes
11840 @dfn{Memory region attributes} allow you to describe special handling
11841 required by regions of your target's memory. @value{GDBN} uses
11842 attributes to determine whether to allow certain types of memory
11843 accesses; whether to use specific width accesses; and whether to cache
11844 target memory. By default the description of memory regions is
11845 fetched from the target (if the current target supports this), but the
11846 user can override the fetched regions.
11848 Defined memory regions can be individually enabled and disabled. When a
11849 memory region is disabled, @value{GDBN} uses the default attributes when
11850 accessing memory in that region. Similarly, if no memory regions have
11851 been defined, @value{GDBN} uses the default attributes when accessing
11854 When a memory region is defined, it is given a number to identify it;
11855 to enable, disable, or remove a memory region, you specify that number.
11859 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11860 Define a memory region bounded by @var{lower} and @var{upper} with
11861 attributes @var{attributes}@dots{}, and add it to the list of regions
11862 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11863 case: it is treated as the target's maximum memory address.
11864 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11867 Discard any user changes to the memory regions and use target-supplied
11868 regions, if available, or no regions if the target does not support.
11871 @item delete mem @var{nums}@dots{}
11872 Remove memory regions @var{nums}@dots{} from the list of regions
11873 monitored by @value{GDBN}.
11875 @kindex disable mem
11876 @item disable mem @var{nums}@dots{}
11877 Disable monitoring of memory regions @var{nums}@dots{}.
11878 A disabled memory region is not forgotten.
11879 It may be enabled again later.
11882 @item enable mem @var{nums}@dots{}
11883 Enable monitoring of memory regions @var{nums}@dots{}.
11887 Print a table of all defined memory regions, with the following columns
11891 @item Memory Region Number
11892 @item Enabled or Disabled.
11893 Enabled memory regions are marked with @samp{y}.
11894 Disabled memory regions are marked with @samp{n}.
11897 The address defining the inclusive lower bound of the memory region.
11900 The address defining the exclusive upper bound of the memory region.
11903 The list of attributes set for this memory region.
11908 @subsection Attributes
11910 @subsubsection Memory Access Mode
11911 The access mode attributes set whether @value{GDBN} may make read or
11912 write accesses to a memory region.
11914 While these attributes prevent @value{GDBN} from performing invalid
11915 memory accesses, they do nothing to prevent the target system, I/O DMA,
11916 etc.@: from accessing memory.
11920 Memory is read only.
11922 Memory is write only.
11924 Memory is read/write. This is the default.
11927 @subsubsection Memory Access Size
11928 The access size attribute tells @value{GDBN} to use specific sized
11929 accesses in the memory region. Often memory mapped device registers
11930 require specific sized accesses. If no access size attribute is
11931 specified, @value{GDBN} may use accesses of any size.
11935 Use 8 bit memory accesses.
11937 Use 16 bit memory accesses.
11939 Use 32 bit memory accesses.
11941 Use 64 bit memory accesses.
11944 @c @subsubsection Hardware/Software Breakpoints
11945 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11946 @c will use hardware or software breakpoints for the internal breakpoints
11947 @c used by the step, next, finish, until, etc. commands.
11951 @c Always use hardware breakpoints
11952 @c @item swbreak (default)
11955 @subsubsection Data Cache
11956 The data cache attributes set whether @value{GDBN} will cache target
11957 memory. While this generally improves performance by reducing debug
11958 protocol overhead, it can lead to incorrect results because @value{GDBN}
11959 does not know about volatile variables or memory mapped device
11964 Enable @value{GDBN} to cache target memory.
11966 Disable @value{GDBN} from caching target memory. This is the default.
11969 @subsection Memory Access Checking
11970 @value{GDBN} can be instructed to refuse accesses to memory that is
11971 not explicitly described. This can be useful if accessing such
11972 regions has undesired effects for a specific target, or to provide
11973 better error checking. The following commands control this behaviour.
11976 @kindex set mem inaccessible-by-default
11977 @item set mem inaccessible-by-default [on|off]
11978 If @code{on} is specified, make @value{GDBN} treat memory not
11979 explicitly described by the memory ranges as non-existent and refuse accesses
11980 to such memory. The checks are only performed if there's at least one
11981 memory range defined. If @code{off} is specified, make @value{GDBN}
11982 treat the memory not explicitly described by the memory ranges as RAM.
11983 The default value is @code{on}.
11984 @kindex show mem inaccessible-by-default
11985 @item show mem inaccessible-by-default
11986 Show the current handling of accesses to unknown memory.
11990 @c @subsubsection Memory Write Verification
11991 @c The memory write verification attributes set whether @value{GDBN}
11992 @c will re-reads data after each write to verify the write was successful.
11996 @c @item noverify (default)
11999 @node Dump/Restore Files
12000 @section Copy Between Memory and a File
12001 @cindex dump/restore files
12002 @cindex append data to a file
12003 @cindex dump data to a file
12004 @cindex restore data from a file
12006 You can use the commands @code{dump}, @code{append}, and
12007 @code{restore} to copy data between target memory and a file. The
12008 @code{dump} and @code{append} commands write data to a file, and the
12009 @code{restore} command reads data from a file back into the inferior's
12010 memory. Files may be in binary, Motorola S-record, Intel hex,
12011 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
12012 append to binary files, and cannot read from Verilog Hex files.
12017 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12018 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
12019 Dump the contents of memory from @var{start_addr} to @var{end_addr},
12020 or the value of @var{expr}, to @var{filename} in the given format.
12022 The @var{format} parameter may be any one of:
12029 Motorola S-record format.
12031 Tektronix Hex format.
12033 Verilog Hex format.
12036 @value{GDBN} uses the same definitions of these formats as the
12037 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
12038 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
12042 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
12043 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
12044 Append the contents of memory from @var{start_addr} to @var{end_addr},
12045 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
12046 (@value{GDBN} can only append data to files in raw binary form.)
12049 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
12050 Restore the contents of file @var{filename} into memory. The
12051 @code{restore} command can automatically recognize any known @sc{bfd}
12052 file format, except for raw binary. To restore a raw binary file you
12053 must specify the optional keyword @code{binary} after the filename.
12055 If @var{bias} is non-zero, its value will be added to the addresses
12056 contained in the file. Binary files always start at address zero, so
12057 they will be restored at address @var{bias}. Other bfd files have
12058 a built-in location; they will be restored at offset @var{bias}
12059 from that location.
12061 If @var{start} and/or @var{end} are non-zero, then only data between
12062 file offset @var{start} and file offset @var{end} will be restored.
12063 These offsets are relative to the addresses in the file, before
12064 the @var{bias} argument is applied.
12068 @node Core File Generation
12069 @section How to Produce a Core File from Your Program
12070 @cindex dump core from inferior
12072 A @dfn{core file} or @dfn{core dump} is a file that records the memory
12073 image of a running process and its process status (register values
12074 etc.). Its primary use is post-mortem debugging of a program that
12075 crashed while it ran outside a debugger. A program that crashes
12076 automatically produces a core file, unless this feature is disabled by
12077 the user. @xref{Files}, for information on invoking @value{GDBN} in
12078 the post-mortem debugging mode.
12080 Occasionally, you may wish to produce a core file of the program you
12081 are debugging in order to preserve a snapshot of its state.
12082 @value{GDBN} has a special command for that.
12086 @kindex generate-core-file
12087 @item generate-core-file [@var{file}]
12088 @itemx gcore [@var{file}]
12089 Produce a core dump of the inferior process. The optional argument
12090 @var{file} specifies the file name where to put the core dump. If not
12091 specified, the file name defaults to @file{core.@var{pid}}, where
12092 @var{pid} is the inferior process ID.
12094 Note that this command is implemented only for some systems (as of
12095 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
12097 On @sc{gnu}/Linux, this command can take into account the value of the
12098 file @file{/proc/@var{pid}/coredump_filter} when generating the core
12099 dump (@pxref{set use-coredump-filter}), and by default honors the
12100 @code{VM_DONTDUMP} flag for mappings where it is present in the file
12101 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
12103 @kindex set use-coredump-filter
12104 @anchor{set use-coredump-filter}
12105 @item set use-coredump-filter on
12106 @itemx set use-coredump-filter off
12107 Enable or disable the use of the file
12108 @file{/proc/@var{pid}/coredump_filter} when generating core dump
12109 files. This file is used by the Linux kernel to decide what types of
12110 memory mappings will be dumped or ignored when generating a core dump
12111 file. @var{pid} is the process ID of a currently running process.
12113 To make use of this feature, you have to write in the
12114 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
12115 which is a bit mask representing the memory mapping types. If a bit
12116 is set in the bit mask, then the memory mappings of the corresponding
12117 types will be dumped; otherwise, they will be ignored. This
12118 configuration is inherited by child processes. For more information
12119 about the bits that can be set in the
12120 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
12121 manpage of @code{core(5)}.
12123 By default, this option is @code{on}. If this option is turned
12124 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
12125 and instead uses the same default value as the Linux kernel in order
12126 to decide which pages will be dumped in the core dump file. This
12127 value is currently @code{0x33}, which means that bits @code{0}
12128 (anonymous private mappings), @code{1} (anonymous shared mappings),
12129 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
12130 This will cause these memory mappings to be dumped automatically.
12132 @kindex set dump-excluded-mappings
12133 @anchor{set dump-excluded-mappings}
12134 @item set dump-excluded-mappings on
12135 @itemx set dump-excluded-mappings off
12136 If @code{on} is specified, @value{GDBN} will dump memory mappings
12137 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
12138 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
12140 The default value is @code{off}.
12143 @node Character Sets
12144 @section Character Sets
12145 @cindex character sets
12147 @cindex translating between character sets
12148 @cindex host character set
12149 @cindex target character set
12151 If the program you are debugging uses a different character set to
12152 represent characters and strings than the one @value{GDBN} uses itself,
12153 @value{GDBN} can automatically translate between the character sets for
12154 you. The character set @value{GDBN} uses we call the @dfn{host
12155 character set}; the one the inferior program uses we call the
12156 @dfn{target character set}.
12158 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
12159 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
12160 remote protocol (@pxref{Remote Debugging}) to debug a program
12161 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
12162 then the host character set is Latin-1, and the target character set is
12163 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
12164 target-charset EBCDIC-US}, then @value{GDBN} translates between
12165 @sc{ebcdic} and Latin 1 as you print character or string values, or use
12166 character and string literals in expressions.
12168 @value{GDBN} has no way to automatically recognize which character set
12169 the inferior program uses; you must tell it, using the @code{set
12170 target-charset} command, described below.
12172 Here are the commands for controlling @value{GDBN}'s character set
12176 @item set target-charset @var{charset}
12177 @kindex set target-charset
12178 Set the current target character set to @var{charset}. To display the
12179 list of supported target character sets, type
12180 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
12182 @item set host-charset @var{charset}
12183 @kindex set host-charset
12184 Set the current host character set to @var{charset}.
12186 By default, @value{GDBN} uses a host character set appropriate to the
12187 system it is running on; you can override that default using the
12188 @code{set host-charset} command. On some systems, @value{GDBN} cannot
12189 automatically determine the appropriate host character set. In this
12190 case, @value{GDBN} uses @samp{UTF-8}.
12192 @value{GDBN} can only use certain character sets as its host character
12193 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
12194 @value{GDBN} will list the host character sets it supports.
12196 @item set charset @var{charset}
12197 @kindex set charset
12198 Set the current host and target character sets to @var{charset}. As
12199 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
12200 @value{GDBN} will list the names of the character sets that can be used
12201 for both host and target.
12204 @kindex show charset
12205 Show the names of the current host and target character sets.
12207 @item show host-charset
12208 @kindex show host-charset
12209 Show the name of the current host character set.
12211 @item show target-charset
12212 @kindex show target-charset
12213 Show the name of the current target character set.
12215 @item set target-wide-charset @var{charset}
12216 @kindex set target-wide-charset
12217 Set the current target's wide character set to @var{charset}. This is
12218 the character set used by the target's @code{wchar_t} type. To
12219 display the list of supported wide character sets, type
12220 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
12222 @item show target-wide-charset
12223 @kindex show target-wide-charset
12224 Show the name of the current target's wide character set.
12227 Here is an example of @value{GDBN}'s character set support in action.
12228 Assume that the following source code has been placed in the file
12229 @file{charset-test.c}:
12235 = @{72, 101, 108, 108, 111, 44, 32, 119,
12236 111, 114, 108, 100, 33, 10, 0@};
12237 char ibm1047_hello[]
12238 = @{200, 133, 147, 147, 150, 107, 64, 166,
12239 150, 153, 147, 132, 90, 37, 0@};
12243 printf ("Hello, world!\n");
12247 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
12248 containing the string @samp{Hello, world!} followed by a newline,
12249 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
12251 We compile the program, and invoke the debugger on it:
12254 $ gcc -g charset-test.c -o charset-test
12255 $ gdb -nw charset-test
12256 GNU gdb 2001-12-19-cvs
12257 Copyright 2001 Free Software Foundation, Inc.
12262 We can use the @code{show charset} command to see what character sets
12263 @value{GDBN} is currently using to interpret and display characters and
12267 (@value{GDBP}) show charset
12268 The current host and target character set is `ISO-8859-1'.
12272 For the sake of printing this manual, let's use @sc{ascii} as our
12273 initial character set:
12275 (@value{GDBP}) set charset ASCII
12276 (@value{GDBP}) show charset
12277 The current host and target character set is `ASCII'.
12281 Let's assume that @sc{ascii} is indeed the correct character set for our
12282 host system --- in other words, let's assume that if @value{GDBN} prints
12283 characters using the @sc{ascii} character set, our terminal will display
12284 them properly. Since our current target character set is also
12285 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
12288 (@value{GDBP}) print ascii_hello
12289 $1 = 0x401698 "Hello, world!\n"
12290 (@value{GDBP}) print ascii_hello[0]
12295 @value{GDBN} uses the target character set for character and string
12296 literals you use in expressions:
12299 (@value{GDBP}) print '+'
12304 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
12307 @value{GDBN} relies on the user to tell it which character set the
12308 target program uses. If we print @code{ibm1047_hello} while our target
12309 character set is still @sc{ascii}, we get jibberish:
12312 (@value{GDBP}) print ibm1047_hello
12313 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
12314 (@value{GDBP}) print ibm1047_hello[0]
12319 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
12320 @value{GDBN} tells us the character sets it supports:
12323 (@value{GDBP}) set target-charset
12324 ASCII EBCDIC-US IBM1047 ISO-8859-1
12325 (@value{GDBP}) set target-charset
12328 We can select @sc{ibm1047} as our target character set, and examine the
12329 program's strings again. Now the @sc{ascii} string is wrong, but
12330 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
12331 target character set, @sc{ibm1047}, to the host character set,
12332 @sc{ascii}, and they display correctly:
12335 (@value{GDBP}) set target-charset IBM1047
12336 (@value{GDBP}) show charset
12337 The current host character set is `ASCII'.
12338 The current target character set is `IBM1047'.
12339 (@value{GDBP}) print ascii_hello
12340 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
12341 (@value{GDBP}) print ascii_hello[0]
12343 (@value{GDBP}) print ibm1047_hello
12344 $8 = 0x4016a8 "Hello, world!\n"
12345 (@value{GDBP}) print ibm1047_hello[0]
12350 As above, @value{GDBN} uses the target character set for character and
12351 string literals you use in expressions:
12354 (@value{GDBP}) print '+'
12359 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
12362 @node Caching Target Data
12363 @section Caching Data of Targets
12364 @cindex caching data of targets
12366 @value{GDBN} caches data exchanged between the debugger and a target.
12367 Each cache is associated with the address space of the inferior.
12368 @xref{Inferiors and Programs}, about inferior and address space.
12369 Such caching generally improves performance in remote debugging
12370 (@pxref{Remote Debugging}), because it reduces the overhead of the
12371 remote protocol by bundling memory reads and writes into large chunks.
12372 Unfortunately, simply caching everything would lead to incorrect results,
12373 since @value{GDBN} does not necessarily know anything about volatile
12374 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
12375 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
12377 Therefore, by default, @value{GDBN} only caches data
12378 known to be on the stack@footnote{In non-stop mode, it is moderately
12379 rare for a running thread to modify the stack of a stopped thread
12380 in a way that would interfere with a backtrace, and caching of
12381 stack reads provides a significant speed up of remote backtraces.} or
12382 in the code segment.
12383 Other regions of memory can be explicitly marked as
12384 cacheable; @pxref{Memory Region Attributes}.
12387 @kindex set remotecache
12388 @item set remotecache on
12389 @itemx set remotecache off
12390 This option no longer does anything; it exists for compatibility
12393 @kindex show remotecache
12394 @item show remotecache
12395 Show the current state of the obsolete remotecache flag.
12397 @kindex set stack-cache
12398 @item set stack-cache on
12399 @itemx set stack-cache off
12400 Enable or disable caching of stack accesses. When @code{on}, use
12401 caching. By default, this option is @code{on}.
12403 @kindex show stack-cache
12404 @item show stack-cache
12405 Show the current state of data caching for memory accesses.
12407 @kindex set code-cache
12408 @item set code-cache on
12409 @itemx set code-cache off
12410 Enable or disable caching of code segment accesses. When @code{on},
12411 use caching. By default, this option is @code{on}. This improves
12412 performance of disassembly in remote debugging.
12414 @kindex show code-cache
12415 @item show code-cache
12416 Show the current state of target memory cache for code segment
12419 @kindex info dcache
12420 @item info dcache @r{[}line@r{]}
12421 Print the information about the performance of data cache of the
12422 current inferior's address space. The information displayed
12423 includes the dcache width and depth, and for each cache line, its
12424 number, address, and how many times it was referenced. This
12425 command is useful for debugging the data cache operation.
12427 If a line number is specified, the contents of that line will be
12430 @item set dcache size @var{size}
12431 @cindex dcache size
12432 @kindex set dcache size
12433 Set maximum number of entries in dcache (dcache depth above).
12435 @item set dcache line-size @var{line-size}
12436 @cindex dcache line-size
12437 @kindex set dcache line-size
12438 Set number of bytes each dcache entry caches (dcache width above).
12439 Must be a power of 2.
12441 @item show dcache size
12442 @kindex show dcache size
12443 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
12445 @item show dcache line-size
12446 @kindex show dcache line-size
12447 Show default size of dcache lines.
12451 @node Searching Memory
12452 @section Search Memory
12453 @cindex searching memory
12455 Memory can be searched for a particular sequence of bytes with the
12456 @code{find} command.
12460 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12461 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
12462 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
12463 etc. The search begins at address @var{start_addr} and continues for either
12464 @var{len} bytes or through to @var{end_addr} inclusive.
12467 @var{s} and @var{n} are optional parameters.
12468 They may be specified in either order, apart or together.
12471 @item @var{s}, search query size
12472 The size of each search query value.
12478 halfwords (two bytes)
12482 giant words (eight bytes)
12485 All values are interpreted in the current language.
12486 This means, for example, that if the current source language is C/C@t{++}
12487 then searching for the string ``hello'' includes the trailing '\0'.
12488 The null terminator can be removed from searching by using casts,
12489 e.g.: @samp{@{char[5]@}"hello"}.
12491 If the value size is not specified, it is taken from the
12492 value's type in the current language.
12493 This is useful when one wants to specify the search
12494 pattern as a mixture of types.
12495 Note that this means, for example, that in the case of C-like languages
12496 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12497 which is typically four bytes.
12499 @item @var{n}, maximum number of finds
12500 The maximum number of matches to print. The default is to print all finds.
12503 You can use strings as search values. Quote them with double-quotes
12505 The string value is copied into the search pattern byte by byte,
12506 regardless of the endianness of the target and the size specification.
12508 The address of each match found is printed as well as a count of the
12509 number of matches found.
12511 The address of the last value found is stored in convenience variable
12513 A count of the number of matches is stored in @samp{$numfound}.
12515 For example, if stopped at the @code{printf} in this function:
12521 static char hello[] = "hello-hello";
12522 static struct @{ char c; short s; int i; @}
12523 __attribute__ ((packed)) mixed
12524 = @{ 'c', 0x1234, 0x87654321 @};
12525 printf ("%s\n", hello);
12530 you get during debugging:
12533 (gdb) find &hello[0], +sizeof(hello), "hello"
12534 0x804956d <hello.1620+6>
12536 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12537 0x8049567 <hello.1620>
12538 0x804956d <hello.1620+6>
12540 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12541 0x8049567 <hello.1620>
12542 0x804956d <hello.1620+6>
12544 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12545 0x8049567 <hello.1620>
12547 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12548 0x8049560 <mixed.1625>
12550 (gdb) print $numfound
12553 $2 = (void *) 0x8049560
12557 @section Value Sizes
12559 Whenever @value{GDBN} prints a value memory will be allocated within
12560 @value{GDBN} to hold the contents of the value. It is possible in
12561 some languages with dynamic typing systems, that an invalid program
12562 may indicate a value that is incorrectly large, this in turn may cause
12563 @value{GDBN} to try and allocate an overly large ammount of memory.
12566 @kindex set max-value-size
12567 @item set max-value-size @var{bytes}
12568 @itemx set max-value-size unlimited
12569 Set the maximum size of memory that @value{GDBN} will allocate for the
12570 contents of a value to @var{bytes}, trying to display a value that
12571 requires more memory than that will result in an error.
12573 Setting this variable does not effect values that have already been
12574 allocated within @value{GDBN}, only future allocations.
12576 There's a minimum size that @code{max-value-size} can be set to in
12577 order that @value{GDBN} can still operate correctly, this minimum is
12578 currently 16 bytes.
12580 The limit applies to the results of some subexpressions as well as to
12581 complete expressions. For example, an expression denoting a simple
12582 integer component, such as @code{x.y.z}, may fail if the size of
12583 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12584 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12585 @var{A} is an array variable with non-constant size, will generally
12586 succeed regardless of the bounds on @var{A}, as long as the component
12587 size is less than @var{bytes}.
12589 The default value of @code{max-value-size} is currently 64k.
12591 @kindex show max-value-size
12592 @item show max-value-size
12593 Show the maximum size of memory, in bytes, that @value{GDBN} will
12594 allocate for the contents of a value.
12597 @node Optimized Code
12598 @chapter Debugging Optimized Code
12599 @cindex optimized code, debugging
12600 @cindex debugging optimized code
12602 Almost all compilers support optimization. With optimization
12603 disabled, the compiler generates assembly code that corresponds
12604 directly to your source code, in a simplistic way. As the compiler
12605 applies more powerful optimizations, the generated assembly code
12606 diverges from your original source code. With help from debugging
12607 information generated by the compiler, @value{GDBN} can map from
12608 the running program back to constructs from your original source.
12610 @value{GDBN} is more accurate with optimization disabled. If you
12611 can recompile without optimization, it is easier to follow the
12612 progress of your program during debugging. But, there are many cases
12613 where you may need to debug an optimized version.
12615 When you debug a program compiled with @samp{-g -O}, remember that the
12616 optimizer has rearranged your code; the debugger shows you what is
12617 really there. Do not be too surprised when the execution path does not
12618 exactly match your source file! An extreme example: if you define a
12619 variable, but never use it, @value{GDBN} never sees that
12620 variable---because the compiler optimizes it out of existence.
12622 Some things do not work as well with @samp{-g -O} as with just
12623 @samp{-g}, particularly on machines with instruction scheduling. If in
12624 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12625 please report it to us as a bug (including a test case!).
12626 @xref{Variables}, for more information about debugging optimized code.
12629 * Inline Functions:: How @value{GDBN} presents inlining
12630 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12633 @node Inline Functions
12634 @section Inline Functions
12635 @cindex inline functions, debugging
12637 @dfn{Inlining} is an optimization that inserts a copy of the function
12638 body directly at each call site, instead of jumping to a shared
12639 routine. @value{GDBN} displays inlined functions just like
12640 non-inlined functions. They appear in backtraces. You can view their
12641 arguments and local variables, step into them with @code{step}, skip
12642 them with @code{next}, and escape from them with @code{finish}.
12643 You can check whether a function was inlined by using the
12644 @code{info frame} command.
12646 For @value{GDBN} to support inlined functions, the compiler must
12647 record information about inlining in the debug information ---
12648 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12649 other compilers do also. @value{GDBN} only supports inlined functions
12650 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12651 do not emit two required attributes (@samp{DW_AT_call_file} and
12652 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12653 function calls with earlier versions of @value{NGCC}. It instead
12654 displays the arguments and local variables of inlined functions as
12655 local variables in the caller.
12657 The body of an inlined function is directly included at its call site;
12658 unlike a non-inlined function, there are no instructions devoted to
12659 the call. @value{GDBN} still pretends that the call site and the
12660 start of the inlined function are different instructions. Stepping to
12661 the call site shows the call site, and then stepping again shows
12662 the first line of the inlined function, even though no additional
12663 instructions are executed.
12665 This makes source-level debugging much clearer; you can see both the
12666 context of the call and then the effect of the call. Only stepping by
12667 a single instruction using @code{stepi} or @code{nexti} does not do
12668 this; single instruction steps always show the inlined body.
12670 There are some ways that @value{GDBN} does not pretend that inlined
12671 function calls are the same as normal calls:
12675 Setting breakpoints at the call site of an inlined function may not
12676 work, because the call site does not contain any code. @value{GDBN}
12677 may incorrectly move the breakpoint to the next line of the enclosing
12678 function, after the call. This limitation will be removed in a future
12679 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12680 or inside the inlined function instead.
12683 @value{GDBN} cannot locate the return value of inlined calls after
12684 using the @code{finish} command. This is a limitation of compiler-generated
12685 debugging information; after @code{finish}, you can step to the next line
12686 and print a variable where your program stored the return value.
12690 @node Tail Call Frames
12691 @section Tail Call Frames
12692 @cindex tail call frames, debugging
12694 Function @code{B} can call function @code{C} in its very last statement. In
12695 unoptimized compilation the call of @code{C} is immediately followed by return
12696 instruction at the end of @code{B} code. Optimizing compiler may replace the
12697 call and return in function @code{B} into one jump to function @code{C}
12698 instead. Such use of a jump instruction is called @dfn{tail call}.
12700 During execution of function @code{C}, there will be no indication in the
12701 function call stack frames that it was tail-called from @code{B}. If function
12702 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12703 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12704 some cases @value{GDBN} can determine that @code{C} was tail-called from
12705 @code{B}, and it will then create fictitious call frame for that, with the
12706 return address set up as if @code{B} called @code{C} normally.
12708 This functionality is currently supported only by DWARF 2 debugging format and
12709 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12710 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12713 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12714 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12718 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12720 Stack level 1, frame at 0x7fffffffda30:
12721 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12722 tail call frame, caller of frame at 0x7fffffffda30
12723 source language c++.
12724 Arglist at unknown address.
12725 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12728 The detection of all the possible code path executions can find them ambiguous.
12729 There is no execution history stored (possible @ref{Reverse Execution} is never
12730 used for this purpose) and the last known caller could have reached the known
12731 callee by multiple different jump sequences. In such case @value{GDBN} still
12732 tries to show at least all the unambiguous top tail callers and all the
12733 unambiguous bottom tail calees, if any.
12736 @anchor{set debug entry-values}
12737 @item set debug entry-values
12738 @kindex set debug entry-values
12739 When set to on, enables printing of analysis messages for both frame argument
12740 values at function entry and tail calls. It will show all the possible valid
12741 tail calls code paths it has considered. It will also print the intersection
12742 of them with the final unambiguous (possibly partial or even empty) code path
12745 @item show debug entry-values
12746 @kindex show debug entry-values
12747 Show the current state of analysis messages printing for both frame argument
12748 values at function entry and tail calls.
12751 The analysis messages for tail calls can for example show why the virtual tail
12752 call frame for function @code{c} has not been recognized (due to the indirect
12753 reference by variable @code{x}):
12756 static void __attribute__((noinline, noclone)) c (void);
12757 void (*x) (void) = c;
12758 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12759 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12760 int main (void) @{ x (); return 0; @}
12762 Breakpoint 1, DW_OP_entry_value resolving cannot find
12763 DW_TAG_call_site 0x40039a in main
12765 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12768 #1 0x000000000040039a in main () at t.c:5
12771 Another possibility is an ambiguous virtual tail call frames resolution:
12775 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12776 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12777 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12778 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12779 static void __attribute__((noinline, noclone)) b (void)
12780 @{ if (i) c (); else e (); @}
12781 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12782 int main (void) @{ a (); return 0; @}
12784 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12785 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12786 tailcall: reduced: 0x4004d2(a) |
12789 #1 0x00000000004004d2 in a () at t.c:8
12790 #2 0x0000000000400395 in main () at t.c:9
12793 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12794 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12796 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12797 @ifset HAVE_MAKEINFO_CLICK
12798 @set ARROW @click{}
12799 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12800 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12802 @ifclear HAVE_MAKEINFO_CLICK
12804 @set CALLSEQ1B @value{CALLSEQ1A}
12805 @set CALLSEQ2B @value{CALLSEQ2A}
12808 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12809 The code can have possible execution paths @value{CALLSEQ1B} or
12810 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12812 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12813 has found. It then finds another possible calling sequcen - that one is
12814 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12815 printed as the @code{reduced:} calling sequence. That one could have many
12816 futher @code{compare:} and @code{reduced:} statements as long as there remain
12817 any non-ambiguous sequence entries.
12819 For the frame of function @code{b} in both cases there are different possible
12820 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12821 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12822 therefore this one is displayed to the user while the ambiguous frames are
12825 There can be also reasons why printing of frame argument values at function
12830 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12831 static void __attribute__((noinline, noclone)) a (int i);
12832 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12833 static void __attribute__((noinline, noclone)) a (int i)
12834 @{ if (i) b (i - 1); else c (0); @}
12835 int main (void) @{ a (5); return 0; @}
12838 #0 c (i=i@@entry=0) at t.c:2
12839 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12840 function "a" at 0x400420 can call itself via tail calls
12841 i=<optimized out>) at t.c:6
12842 #2 0x000000000040036e in main () at t.c:7
12845 @value{GDBN} cannot find out from the inferior state if and how many times did
12846 function @code{a} call itself (via function @code{b}) as these calls would be
12847 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12848 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12849 prints @code{<optimized out>} instead.
12852 @chapter C Preprocessor Macros
12854 Some languages, such as C and C@t{++}, provide a way to define and invoke
12855 ``preprocessor macros'' which expand into strings of tokens.
12856 @value{GDBN} can evaluate expressions containing macro invocations, show
12857 the result of macro expansion, and show a macro's definition, including
12858 where it was defined.
12860 You may need to compile your program specially to provide @value{GDBN}
12861 with information about preprocessor macros. Most compilers do not
12862 include macros in their debugging information, even when you compile
12863 with the @option{-g} flag. @xref{Compilation}.
12865 A program may define a macro at one point, remove that definition later,
12866 and then provide a different definition after that. Thus, at different
12867 points in the program, a macro may have different definitions, or have
12868 no definition at all. If there is a current stack frame, @value{GDBN}
12869 uses the macros in scope at that frame's source code line. Otherwise,
12870 @value{GDBN} uses the macros in scope at the current listing location;
12873 Whenever @value{GDBN} evaluates an expression, it always expands any
12874 macro invocations present in the expression. @value{GDBN} also provides
12875 the following commands for working with macros explicitly.
12879 @kindex macro expand
12880 @cindex macro expansion, showing the results of preprocessor
12881 @cindex preprocessor macro expansion, showing the results of
12882 @cindex expanding preprocessor macros
12883 @item macro expand @var{expression}
12884 @itemx macro exp @var{expression}
12885 Show the results of expanding all preprocessor macro invocations in
12886 @var{expression}. Since @value{GDBN} simply expands macros, but does
12887 not parse the result, @var{expression} need not be a valid expression;
12888 it can be any string of tokens.
12891 @item macro expand-once @var{expression}
12892 @itemx macro exp1 @var{expression}
12893 @cindex expand macro once
12894 @i{(This command is not yet implemented.)} Show the results of
12895 expanding those preprocessor macro invocations that appear explicitly in
12896 @var{expression}. Macro invocations appearing in that expansion are
12897 left unchanged. This command allows you to see the effect of a
12898 particular macro more clearly, without being confused by further
12899 expansions. Since @value{GDBN} simply expands macros, but does not
12900 parse the result, @var{expression} need not be a valid expression; it
12901 can be any string of tokens.
12904 @cindex macro definition, showing
12905 @cindex definition of a macro, showing
12906 @cindex macros, from debug info
12907 @item info macro [-a|-all] [--] @var{macro}
12908 Show the current definition or all definitions of the named @var{macro},
12909 and describe the source location or compiler command-line where that
12910 definition was established. The optional double dash is to signify the end of
12911 argument processing and the beginning of @var{macro} for non C-like macros where
12912 the macro may begin with a hyphen.
12914 @kindex info macros
12915 @item info macros @var{location}
12916 Show all macro definitions that are in effect at the location specified
12917 by @var{location}, and describe the source location or compiler
12918 command-line where those definitions were established.
12920 @kindex macro define
12921 @cindex user-defined macros
12922 @cindex defining macros interactively
12923 @cindex macros, user-defined
12924 @item macro define @var{macro} @var{replacement-list}
12925 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12926 Introduce a definition for a preprocessor macro named @var{macro},
12927 invocations of which are replaced by the tokens given in
12928 @var{replacement-list}. The first form of this command defines an
12929 ``object-like'' macro, which takes no arguments; the second form
12930 defines a ``function-like'' macro, which takes the arguments given in
12933 A definition introduced by this command is in scope in every
12934 expression evaluated in @value{GDBN}, until it is removed with the
12935 @code{macro undef} command, described below. The definition overrides
12936 all definitions for @var{macro} present in the program being debugged,
12937 as well as any previous user-supplied definition.
12939 @kindex macro undef
12940 @item macro undef @var{macro}
12941 Remove any user-supplied definition for the macro named @var{macro}.
12942 This command only affects definitions provided with the @code{macro
12943 define} command, described above; it cannot remove definitions present
12944 in the program being debugged.
12948 List all the macros defined using the @code{macro define} command.
12951 @cindex macros, example of debugging with
12952 Here is a transcript showing the above commands in action. First, we
12953 show our source files:
12958 #include "sample.h"
12961 #define ADD(x) (M + x)
12966 printf ("Hello, world!\n");
12968 printf ("We're so creative.\n");
12970 printf ("Goodbye, world!\n");
12977 Now, we compile the program using the @sc{gnu} C compiler,
12978 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12979 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12980 and @option{-gdwarf-4}; we recommend always choosing the most recent
12981 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12982 includes information about preprocessor macros in the debugging
12986 $ gcc -gdwarf-2 -g3 sample.c -o sample
12990 Now, we start @value{GDBN} on our sample program:
12994 GNU gdb 2002-05-06-cvs
12995 Copyright 2002 Free Software Foundation, Inc.
12996 GDB is free software, @dots{}
13000 We can expand macros and examine their definitions, even when the
13001 program is not running. @value{GDBN} uses the current listing position
13002 to decide which macro definitions are in scope:
13005 (@value{GDBP}) list main
13008 5 #define ADD(x) (M + x)
13013 10 printf ("Hello, world!\n");
13015 12 printf ("We're so creative.\n");
13016 (@value{GDBP}) info macro ADD
13017 Defined at /home/jimb/gdb/macros/play/sample.c:5
13018 #define ADD(x) (M + x)
13019 (@value{GDBP}) info macro Q
13020 Defined at /home/jimb/gdb/macros/play/sample.h:1
13021 included at /home/jimb/gdb/macros/play/sample.c:2
13023 (@value{GDBP}) macro expand ADD(1)
13024 expands to: (42 + 1)
13025 (@value{GDBP}) macro expand-once ADD(1)
13026 expands to: once (M + 1)
13030 In the example above, note that @code{macro expand-once} expands only
13031 the macro invocation explicit in the original text --- the invocation of
13032 @code{ADD} --- but does not expand the invocation of the macro @code{M},
13033 which was introduced by @code{ADD}.
13035 Once the program is running, @value{GDBN} uses the macro definitions in
13036 force at the source line of the current stack frame:
13039 (@value{GDBP}) break main
13040 Breakpoint 1 at 0x8048370: file sample.c, line 10.
13042 Starting program: /home/jimb/gdb/macros/play/sample
13044 Breakpoint 1, main () at sample.c:10
13045 10 printf ("Hello, world!\n");
13049 At line 10, the definition of the macro @code{N} at line 9 is in force:
13052 (@value{GDBP}) info macro N
13053 Defined at /home/jimb/gdb/macros/play/sample.c:9
13055 (@value{GDBP}) macro expand N Q M
13056 expands to: 28 < 42
13057 (@value{GDBP}) print N Q M
13062 As we step over directives that remove @code{N}'s definition, and then
13063 give it a new definition, @value{GDBN} finds the definition (or lack
13064 thereof) in force at each point:
13067 (@value{GDBP}) next
13069 12 printf ("We're so creative.\n");
13070 (@value{GDBP}) info macro N
13071 The symbol `N' has no definition as a C/C++ preprocessor macro
13072 at /home/jimb/gdb/macros/play/sample.c:12
13073 (@value{GDBP}) next
13075 14 printf ("Goodbye, world!\n");
13076 (@value{GDBP}) info macro N
13077 Defined at /home/jimb/gdb/macros/play/sample.c:13
13079 (@value{GDBP}) macro expand N Q M
13080 expands to: 1729 < 42
13081 (@value{GDBP}) print N Q M
13086 In addition to source files, macros can be defined on the compilation command
13087 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
13088 such a way, @value{GDBN} displays the location of their definition as line zero
13089 of the source file submitted to the compiler.
13092 (@value{GDBP}) info macro __STDC__
13093 Defined at /home/jimb/gdb/macros/play/sample.c:0
13100 @chapter Tracepoints
13101 @c This chapter is based on the documentation written by Michael
13102 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
13104 @cindex tracepoints
13105 In some applications, it is not feasible for the debugger to interrupt
13106 the program's execution long enough for the developer to learn
13107 anything helpful about its behavior. If the program's correctness
13108 depends on its real-time behavior, delays introduced by a debugger
13109 might cause the program to change its behavior drastically, or perhaps
13110 fail, even when the code itself is correct. It is useful to be able
13111 to observe the program's behavior without interrupting it.
13113 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
13114 specify locations in the program, called @dfn{tracepoints}, and
13115 arbitrary expressions to evaluate when those tracepoints are reached.
13116 Later, using the @code{tfind} command, you can examine the values
13117 those expressions had when the program hit the tracepoints. The
13118 expressions may also denote objects in memory---structures or arrays,
13119 for example---whose values @value{GDBN} should record; while visiting
13120 a particular tracepoint, you may inspect those objects as if they were
13121 in memory at that moment. However, because @value{GDBN} records these
13122 values without interacting with you, it can do so quickly and
13123 unobtrusively, hopefully not disturbing the program's behavior.
13125 The tracepoint facility is currently available only for remote
13126 targets. @xref{Targets}. In addition, your remote target must know
13127 how to collect trace data. This functionality is implemented in the
13128 remote stub; however, none of the stubs distributed with @value{GDBN}
13129 support tracepoints as of this writing. The format of the remote
13130 packets used to implement tracepoints are described in @ref{Tracepoint
13133 It is also possible to get trace data from a file, in a manner reminiscent
13134 of corefiles; you specify the filename, and use @code{tfind} to search
13135 through the file. @xref{Trace Files}, for more details.
13137 This chapter describes the tracepoint commands and features.
13140 * Set Tracepoints::
13141 * Analyze Collected Data::
13142 * Tracepoint Variables::
13146 @node Set Tracepoints
13147 @section Commands to Set Tracepoints
13149 Before running such a @dfn{trace experiment}, an arbitrary number of
13150 tracepoints can be set. A tracepoint is actually a special type of
13151 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
13152 standard breakpoint commands. For instance, as with breakpoints,
13153 tracepoint numbers are successive integers starting from one, and many
13154 of the commands associated with tracepoints take the tracepoint number
13155 as their argument, to identify which tracepoint to work on.
13157 For each tracepoint, you can specify, in advance, some arbitrary set
13158 of data that you want the target to collect in the trace buffer when
13159 it hits that tracepoint. The collected data can include registers,
13160 local variables, or global data. Later, you can use @value{GDBN}
13161 commands to examine the values these data had at the time the
13162 tracepoint was hit.
13164 Tracepoints do not support every breakpoint feature. Ignore counts on
13165 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
13166 commands when they are hit. Tracepoints may not be thread-specific
13169 @cindex fast tracepoints
13170 Some targets may support @dfn{fast tracepoints}, which are inserted in
13171 a different way (such as with a jump instead of a trap), that is
13172 faster but possibly restricted in where they may be installed.
13174 @cindex static tracepoints
13175 @cindex markers, static tracepoints
13176 @cindex probing markers, static tracepoints
13177 Regular and fast tracepoints are dynamic tracing facilities, meaning
13178 that they can be used to insert tracepoints at (almost) any location
13179 in the target. Some targets may also support controlling @dfn{static
13180 tracepoints} from @value{GDBN}. With static tracing, a set of
13181 instrumentation points, also known as @dfn{markers}, are embedded in
13182 the target program, and can be activated or deactivated by name or
13183 address. These are usually placed at locations which facilitate
13184 investigating what the target is actually doing. @value{GDBN}'s
13185 support for static tracing includes being able to list instrumentation
13186 points, and attach them with @value{GDBN} defined high level
13187 tracepoints that expose the whole range of convenience of
13188 @value{GDBN}'s tracepoints support. Namely, support for collecting
13189 registers values and values of global or local (to the instrumentation
13190 point) variables; tracepoint conditions and trace state variables.
13191 The act of installing a @value{GDBN} static tracepoint on an
13192 instrumentation point, or marker, is referred to as @dfn{probing} a
13193 static tracepoint marker.
13195 @code{gdbserver} supports tracepoints on some target systems.
13196 @xref{Server,,Tracepoints support in @code{gdbserver}}.
13198 This section describes commands to set tracepoints and associated
13199 conditions and actions.
13202 * Create and Delete Tracepoints::
13203 * Enable and Disable Tracepoints::
13204 * Tracepoint Passcounts::
13205 * Tracepoint Conditions::
13206 * Trace State Variables::
13207 * Tracepoint Actions::
13208 * Listing Tracepoints::
13209 * Listing Static Tracepoint Markers::
13210 * Starting and Stopping Trace Experiments::
13211 * Tracepoint Restrictions::
13214 @node Create and Delete Tracepoints
13215 @subsection Create and Delete Tracepoints
13218 @cindex set tracepoint
13220 @item trace @var{location}
13221 The @code{trace} command is very similar to the @code{break} command.
13222 Its argument @var{location} can be any valid location.
13223 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
13224 which is a point in the target program where the debugger will briefly stop,
13225 collect some data, and then allow the program to continue. Setting a tracepoint
13226 or changing its actions takes effect immediately if the remote stub
13227 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
13229 If remote stub doesn't support the @samp{InstallInTrace} feature, all
13230 these changes don't take effect until the next @code{tstart}
13231 command, and once a trace experiment is running, further changes will
13232 not have any effect until the next trace experiment starts. In addition,
13233 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
13234 address is not yet resolved. (This is similar to pending breakpoints.)
13235 Pending tracepoints are not downloaded to the target and not installed
13236 until they are resolved. The resolution of pending tracepoints requires
13237 @value{GDBN} support---when debugging with the remote target, and
13238 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
13239 tracing}), pending tracepoints can not be resolved (and downloaded to
13240 the remote stub) while @value{GDBN} is disconnected.
13242 Here are some examples of using the @code{trace} command:
13245 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
13247 (@value{GDBP}) @b{trace +2} // 2 lines forward
13249 (@value{GDBP}) @b{trace my_function} // first source line of function
13251 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
13253 (@value{GDBP}) @b{trace *0x2117c4} // an address
13257 You can abbreviate @code{trace} as @code{tr}.
13259 @item trace @var{location} if @var{cond}
13260 Set a tracepoint with condition @var{cond}; evaluate the expression
13261 @var{cond} each time the tracepoint is reached, and collect data only
13262 if the value is nonzero---that is, if @var{cond} evaluates as true.
13263 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
13264 information on tracepoint conditions.
13266 @item ftrace @var{location} [ if @var{cond} ]
13267 @cindex set fast tracepoint
13268 @cindex fast tracepoints, setting
13270 The @code{ftrace} command sets a fast tracepoint. For targets that
13271 support them, fast tracepoints will use a more efficient but possibly
13272 less general technique to trigger data collection, such as a jump
13273 instruction instead of a trap, or some sort of hardware support. It
13274 may not be possible to create a fast tracepoint at the desired
13275 location, in which case the command will exit with an explanatory
13278 @value{GDBN} handles arguments to @code{ftrace} exactly as for
13281 On 32-bit x86-architecture systems, fast tracepoints normally need to
13282 be placed at an instruction that is 5 bytes or longer, but can be
13283 placed at 4-byte instructions if the low 64K of memory of the target
13284 program is available to install trampolines. Some Unix-type systems,
13285 such as @sc{gnu}/Linux, exclude low addresses from the program's
13286 address space; but for instance with the Linux kernel it is possible
13287 to let @value{GDBN} use this area by doing a @command{sysctl} command
13288 to set the @code{mmap_min_addr} kernel parameter, as in
13291 sudo sysctl -w vm.mmap_min_addr=32768
13295 which sets the low address to 32K, which leaves plenty of room for
13296 trampolines. The minimum address should be set to a page boundary.
13298 @item strace @var{location} [ if @var{cond} ]
13299 @cindex set static tracepoint
13300 @cindex static tracepoints, setting
13301 @cindex probe static tracepoint marker
13303 The @code{strace} command sets a static tracepoint. For targets that
13304 support it, setting a static tracepoint probes a static
13305 instrumentation point, or marker, found at @var{location}. It may not
13306 be possible to set a static tracepoint at the desired location, in
13307 which case the command will exit with an explanatory message.
13309 @value{GDBN} handles arguments to @code{strace} exactly as for
13310 @code{trace}, with the addition that the user can also specify
13311 @code{-m @var{marker}} as @var{location}. This probes the marker
13312 identified by the @var{marker} string identifier. This identifier
13313 depends on the static tracepoint backend library your program is
13314 using. You can find all the marker identifiers in the @samp{ID} field
13315 of the @code{info static-tracepoint-markers} command output.
13316 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
13317 Markers}. For example, in the following small program using the UST
13323 trace_mark(ust, bar33, "str %s", "FOOBAZ");
13328 the marker id is composed of joining the first two arguments to the
13329 @code{trace_mark} call with a slash, which translates to:
13332 (@value{GDBP}) info static-tracepoint-markers
13333 Cnt Enb ID Address What
13334 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
13340 so you may probe the marker above with:
13343 (@value{GDBP}) strace -m ust/bar33
13346 Static tracepoints accept an extra collect action --- @code{collect
13347 $_sdata}. This collects arbitrary user data passed in the probe point
13348 call to the tracing library. In the UST example above, you'll see
13349 that the third argument to @code{trace_mark} is a printf-like format
13350 string. The user data is then the result of running that formating
13351 string against the following arguments. Note that @code{info
13352 static-tracepoint-markers} command output lists that format string in
13353 the @samp{Data:} field.
13355 You can inspect this data when analyzing the trace buffer, by printing
13356 the $_sdata variable like any other variable available to
13357 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
13360 @cindex last tracepoint number
13361 @cindex recent tracepoint number
13362 @cindex tracepoint number
13363 The convenience variable @code{$tpnum} records the tracepoint number
13364 of the most recently set tracepoint.
13366 @kindex delete tracepoint
13367 @cindex tracepoint deletion
13368 @item delete tracepoint @r{[}@var{num}@r{]}
13369 Permanently delete one or more tracepoints. With no argument, the
13370 default is to delete all tracepoints. Note that the regular
13371 @code{delete} command can remove tracepoints also.
13376 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
13378 (@value{GDBP}) @b{delete trace} // remove all tracepoints
13382 You can abbreviate this command as @code{del tr}.
13385 @node Enable and Disable Tracepoints
13386 @subsection Enable and Disable Tracepoints
13388 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
13391 @kindex disable tracepoint
13392 @item disable tracepoint @r{[}@var{num}@r{]}
13393 Disable tracepoint @var{num}, or all tracepoints if no argument
13394 @var{num} is given. A disabled tracepoint will have no effect during
13395 a trace experiment, but it is not forgotten. You can re-enable
13396 a disabled tracepoint using the @code{enable tracepoint} command.
13397 If the command is issued during a trace experiment and the debug target
13398 has support for disabling tracepoints during a trace experiment, then the
13399 change will be effective immediately. Otherwise, it will be applied to the
13400 next trace experiment.
13402 @kindex enable tracepoint
13403 @item enable tracepoint @r{[}@var{num}@r{]}
13404 Enable tracepoint @var{num}, or all tracepoints. If this command is
13405 issued during a trace experiment and the debug target supports enabling
13406 tracepoints during a trace experiment, then the enabled tracepoints will
13407 become effective immediately. Otherwise, they will become effective the
13408 next time a trace experiment is run.
13411 @node Tracepoint Passcounts
13412 @subsection Tracepoint Passcounts
13416 @cindex tracepoint pass count
13417 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
13418 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
13419 automatically stop a trace experiment. If a tracepoint's passcount is
13420 @var{n}, then the trace experiment will be automatically stopped on
13421 the @var{n}'th time that tracepoint is hit. If the tracepoint number
13422 @var{num} is not specified, the @code{passcount} command sets the
13423 passcount of the most recently defined tracepoint. If no passcount is
13424 given, the trace experiment will run until stopped explicitly by the
13430 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
13431 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
13433 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
13434 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
13435 (@value{GDBP}) @b{trace foo}
13436 (@value{GDBP}) @b{pass 3}
13437 (@value{GDBP}) @b{trace bar}
13438 (@value{GDBP}) @b{pass 2}
13439 (@value{GDBP}) @b{trace baz}
13440 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
13441 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
13442 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
13443 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
13447 @node Tracepoint Conditions
13448 @subsection Tracepoint Conditions
13449 @cindex conditional tracepoints
13450 @cindex tracepoint conditions
13452 The simplest sort of tracepoint collects data every time your program
13453 reaches a specified place. You can also specify a @dfn{condition} for
13454 a tracepoint. A condition is just a Boolean expression in your
13455 programming language (@pxref{Expressions, ,Expressions}). A
13456 tracepoint with a condition evaluates the expression each time your
13457 program reaches it, and data collection happens only if the condition
13460 Tracepoint conditions can be specified when a tracepoint is set, by
13461 using @samp{if} in the arguments to the @code{trace} command.
13462 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
13463 also be set or changed at any time with the @code{condition} command,
13464 just as with breakpoints.
13466 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
13467 the conditional expression itself. Instead, @value{GDBN} encodes the
13468 expression into an agent expression (@pxref{Agent Expressions})
13469 suitable for execution on the target, independently of @value{GDBN}.
13470 Global variables become raw memory locations, locals become stack
13471 accesses, and so forth.
13473 For instance, suppose you have a function that is usually called
13474 frequently, but should not be called after an error has occurred. You
13475 could use the following tracepoint command to collect data about calls
13476 of that function that happen while the error code is propagating
13477 through the program; an unconditional tracepoint could end up
13478 collecting thousands of useless trace frames that you would have to
13482 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
13485 @node Trace State Variables
13486 @subsection Trace State Variables
13487 @cindex trace state variables
13489 A @dfn{trace state variable} is a special type of variable that is
13490 created and managed by target-side code. The syntax is the same as
13491 that for GDB's convenience variables (a string prefixed with ``$''),
13492 but they are stored on the target. They must be created explicitly,
13493 using a @code{tvariable} command. They are always 64-bit signed
13496 Trace state variables are remembered by @value{GDBN}, and downloaded
13497 to the target along with tracepoint information when the trace
13498 experiment starts. There are no intrinsic limits on the number of
13499 trace state variables, beyond memory limitations of the target.
13501 @cindex convenience variables, and trace state variables
13502 Although trace state variables are managed by the target, you can use
13503 them in print commands and expressions as if they were convenience
13504 variables; @value{GDBN} will get the current value from the target
13505 while the trace experiment is running. Trace state variables share
13506 the same namespace as other ``$'' variables, which means that you
13507 cannot have trace state variables with names like @code{$23} or
13508 @code{$pc}, nor can you have a trace state variable and a convenience
13509 variable with the same name.
13513 @item tvariable $@var{name} [ = @var{expression} ]
13515 The @code{tvariable} command creates a new trace state variable named
13516 @code{$@var{name}}, and optionally gives it an initial value of
13517 @var{expression}. The @var{expression} is evaluated when this command is
13518 entered; the result will be converted to an integer if possible,
13519 otherwise @value{GDBN} will report an error. A subsequent
13520 @code{tvariable} command specifying the same name does not create a
13521 variable, but instead assigns the supplied initial value to the
13522 existing variable of that name, overwriting any previous initial
13523 value. The default initial value is 0.
13525 @item info tvariables
13526 @kindex info tvariables
13527 List all the trace state variables along with their initial values.
13528 Their current values may also be displayed, if the trace experiment is
13531 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13532 @kindex delete tvariable
13533 Delete the given trace state variables, or all of them if no arguments
13538 @node Tracepoint Actions
13539 @subsection Tracepoint Action Lists
13543 @cindex tracepoint actions
13544 @item actions @r{[}@var{num}@r{]}
13545 This command will prompt for a list of actions to be taken when the
13546 tracepoint is hit. If the tracepoint number @var{num} is not
13547 specified, this command sets the actions for the one that was most
13548 recently defined (so that you can define a tracepoint and then say
13549 @code{actions} without bothering about its number). You specify the
13550 actions themselves on the following lines, one action at a time, and
13551 terminate the actions list with a line containing just @code{end}. So
13552 far, the only defined actions are @code{collect}, @code{teval}, and
13553 @code{while-stepping}.
13555 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13556 Commands, ,Breakpoint Command Lists}), except that only the defined
13557 actions are allowed; any other @value{GDBN} command is rejected.
13559 @cindex remove actions from a tracepoint
13560 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13561 and follow it immediately with @samp{end}.
13564 (@value{GDBP}) @b{collect @var{data}} // collect some data
13566 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13568 (@value{GDBP}) @b{end} // signals the end of actions.
13571 In the following example, the action list begins with @code{collect}
13572 commands indicating the things to be collected when the tracepoint is
13573 hit. Then, in order to single-step and collect additional data
13574 following the tracepoint, a @code{while-stepping} command is used,
13575 followed by the list of things to be collected after each step in a
13576 sequence of single steps. The @code{while-stepping} command is
13577 terminated by its own separate @code{end} command. Lastly, the action
13578 list is terminated by an @code{end} command.
13581 (@value{GDBP}) @b{trace foo}
13582 (@value{GDBP}) @b{actions}
13583 Enter actions for tracepoint 1, one per line:
13586 > while-stepping 12
13587 > collect $pc, arr[i]
13592 @kindex collect @r{(tracepoints)}
13593 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13594 Collect values of the given expressions when the tracepoint is hit.
13595 This command accepts a comma-separated list of any valid expressions.
13596 In addition to global, static, or local variables, the following
13597 special arguments are supported:
13601 Collect all registers.
13604 Collect all function arguments.
13607 Collect all local variables.
13610 Collect the return address. This is helpful if you want to see more
13613 @emph{Note:} The return address location can not always be reliably
13614 determined up front, and the wrong address / registers may end up
13615 collected instead. On some architectures the reliability is higher
13616 for tracepoints at function entry, while on others it's the opposite.
13617 When this happens, backtracing will stop because the return address is
13618 found unavailable (unless another collect rule happened to match it).
13621 Collects the number of arguments from the static probe at which the
13622 tracepoint is located.
13623 @xref{Static Probe Points}.
13625 @item $_probe_arg@var{n}
13626 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13627 from the static probe at which the tracepoint is located.
13628 @xref{Static Probe Points}.
13631 @vindex $_sdata@r{, collect}
13632 Collect static tracepoint marker specific data. Only available for
13633 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13634 Lists}. On the UST static tracepoints library backend, an
13635 instrumentation point resembles a @code{printf} function call. The
13636 tracing library is able to collect user specified data formatted to a
13637 character string using the format provided by the programmer that
13638 instrumented the program. Other backends have similar mechanisms.
13639 Here's an example of a UST marker call:
13642 const char master_name[] = "$your_name";
13643 trace_mark(channel1, marker1, "hello %s", master_name)
13646 In this case, collecting @code{$_sdata} collects the string
13647 @samp{hello $yourname}. When analyzing the trace buffer, you can
13648 inspect @samp{$_sdata} like any other variable available to
13652 You can give several consecutive @code{collect} commands, each one
13653 with a single argument, or one @code{collect} command with several
13654 arguments separated by commas; the effect is the same.
13656 The optional @var{mods} changes the usual handling of the arguments.
13657 @code{s} requests that pointers to chars be handled as strings, in
13658 particular collecting the contents of the memory being pointed at, up
13659 to the first zero. The upper bound is by default the value of the
13660 @code{print elements} variable; if @code{s} is followed by a decimal
13661 number, that is the upper bound instead. So for instance
13662 @samp{collect/s25 mystr} collects as many as 25 characters at
13665 The command @code{info scope} (@pxref{Symbols, info scope}) is
13666 particularly useful for figuring out what data to collect.
13668 @kindex teval @r{(tracepoints)}
13669 @item teval @var{expr1}, @var{expr2}, @dots{}
13670 Evaluate the given expressions when the tracepoint is hit. This
13671 command accepts a comma-separated list of expressions. The results
13672 are discarded, so this is mainly useful for assigning values to trace
13673 state variables (@pxref{Trace State Variables}) without adding those
13674 values to the trace buffer, as would be the case if the @code{collect}
13677 @kindex while-stepping @r{(tracepoints)}
13678 @item while-stepping @var{n}
13679 Perform @var{n} single-step instruction traces after the tracepoint,
13680 collecting new data after each step. The @code{while-stepping}
13681 command is followed by the list of what to collect while stepping
13682 (followed by its own @code{end} command):
13685 > while-stepping 12
13686 > collect $regs, myglobal
13692 Note that @code{$pc} is not automatically collected by
13693 @code{while-stepping}; you need to explicitly collect that register if
13694 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13697 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13698 @kindex set default-collect
13699 @cindex default collection action
13700 This variable is a list of expressions to collect at each tracepoint
13701 hit. It is effectively an additional @code{collect} action prepended
13702 to every tracepoint action list. The expressions are parsed
13703 individually for each tracepoint, so for instance a variable named
13704 @code{xyz} may be interpreted as a global for one tracepoint, and a
13705 local for another, as appropriate to the tracepoint's location.
13707 @item show default-collect
13708 @kindex show default-collect
13709 Show the list of expressions that are collected by default at each
13714 @node Listing Tracepoints
13715 @subsection Listing Tracepoints
13718 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13719 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13720 @cindex information about tracepoints
13721 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13722 Display information about the tracepoint @var{num}. If you don't
13723 specify a tracepoint number, displays information about all the
13724 tracepoints defined so far. The format is similar to that used for
13725 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13726 command, simply restricting itself to tracepoints.
13728 A tracepoint's listing may include additional information specific to
13733 its passcount as given by the @code{passcount @var{n}} command
13736 the state about installed on target of each location
13740 (@value{GDBP}) @b{info trace}
13741 Num Type Disp Enb Address What
13742 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13744 collect globfoo, $regs
13749 2 tracepoint keep y <MULTIPLE>
13751 2.1 y 0x0804859c in func4 at change-loc.h:35
13752 installed on target
13753 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13754 installed on target
13755 2.3 y <PENDING> set_tracepoint
13756 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13757 not installed on target
13762 This command can be abbreviated @code{info tp}.
13765 @node Listing Static Tracepoint Markers
13766 @subsection Listing Static Tracepoint Markers
13769 @kindex info static-tracepoint-markers
13770 @cindex information about static tracepoint markers
13771 @item info static-tracepoint-markers
13772 Display information about all static tracepoint markers defined in the
13775 For each marker, the following columns are printed:
13779 An incrementing counter, output to help readability. This is not a
13782 The marker ID, as reported by the target.
13783 @item Enabled or Disabled
13784 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13785 that are not enabled.
13787 Where the marker is in your program, as a memory address.
13789 Where the marker is in the source for your program, as a file and line
13790 number. If the debug information included in the program does not
13791 allow @value{GDBN} to locate the source of the marker, this column
13792 will be left blank.
13796 In addition, the following information may be printed for each marker:
13800 User data passed to the tracing library by the marker call. In the
13801 UST backend, this is the format string passed as argument to the
13803 @item Static tracepoints probing the marker
13804 The list of static tracepoints attached to the marker.
13808 (@value{GDBP}) info static-tracepoint-markers
13809 Cnt ID Enb Address What
13810 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13811 Data: number1 %d number2 %d
13812 Probed by static tracepoints: #2
13813 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13819 @node Starting and Stopping Trace Experiments
13820 @subsection Starting and Stopping Trace Experiments
13823 @kindex tstart [ @var{notes} ]
13824 @cindex start a new trace experiment
13825 @cindex collected data discarded
13827 This command starts the trace experiment, and begins collecting data.
13828 It has the side effect of discarding all the data collected in the
13829 trace buffer during the previous trace experiment. If any arguments
13830 are supplied, they are taken as a note and stored with the trace
13831 experiment's state. The notes may be arbitrary text, and are
13832 especially useful with disconnected tracing in a multi-user context;
13833 the notes can explain what the trace is doing, supply user contact
13834 information, and so forth.
13836 @kindex tstop [ @var{notes} ]
13837 @cindex stop a running trace experiment
13839 This command stops the trace experiment. If any arguments are
13840 supplied, they are recorded with the experiment as a note. This is
13841 useful if you are stopping a trace started by someone else, for
13842 instance if the trace is interfering with the system's behavior and
13843 needs to be stopped quickly.
13845 @strong{Note}: a trace experiment and data collection may stop
13846 automatically if any tracepoint's passcount is reached
13847 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13850 @cindex status of trace data collection
13851 @cindex trace experiment, status of
13853 This command displays the status of the current trace data
13857 Here is an example of the commands we described so far:
13860 (@value{GDBP}) @b{trace gdb_c_test}
13861 (@value{GDBP}) @b{actions}
13862 Enter actions for tracepoint #1, one per line.
13863 > collect $regs,$locals,$args
13864 > while-stepping 11
13868 (@value{GDBP}) @b{tstart}
13869 [time passes @dots{}]
13870 (@value{GDBP}) @b{tstop}
13873 @anchor{disconnected tracing}
13874 @cindex disconnected tracing
13875 You can choose to continue running the trace experiment even if
13876 @value{GDBN} disconnects from the target, voluntarily or
13877 involuntarily. For commands such as @code{detach}, the debugger will
13878 ask what you want to do with the trace. But for unexpected
13879 terminations (@value{GDBN} crash, network outage), it would be
13880 unfortunate to lose hard-won trace data, so the variable
13881 @code{disconnected-tracing} lets you decide whether the trace should
13882 continue running without @value{GDBN}.
13885 @item set disconnected-tracing on
13886 @itemx set disconnected-tracing off
13887 @kindex set disconnected-tracing
13888 Choose whether a tracing run should continue to run if @value{GDBN}
13889 has disconnected from the target. Note that @code{detach} or
13890 @code{quit} will ask you directly what to do about a running trace no
13891 matter what this variable's setting, so the variable is mainly useful
13892 for handling unexpected situations, such as loss of the network.
13894 @item show disconnected-tracing
13895 @kindex show disconnected-tracing
13896 Show the current choice for disconnected tracing.
13900 When you reconnect to the target, the trace experiment may or may not
13901 still be running; it might have filled the trace buffer in the
13902 meantime, or stopped for one of the other reasons. If it is running,
13903 it will continue after reconnection.
13905 Upon reconnection, the target will upload information about the
13906 tracepoints in effect. @value{GDBN} will then compare that
13907 information to the set of tracepoints currently defined, and attempt
13908 to match them up, allowing for the possibility that the numbers may
13909 have changed due to creation and deletion in the meantime. If one of
13910 the target's tracepoints does not match any in @value{GDBN}, the
13911 debugger will create a new tracepoint, so that you have a number with
13912 which to specify that tracepoint. This matching-up process is
13913 necessarily heuristic, and it may result in useless tracepoints being
13914 created; you may simply delete them if they are of no use.
13916 @cindex circular trace buffer
13917 If your target agent supports a @dfn{circular trace buffer}, then you
13918 can run a trace experiment indefinitely without filling the trace
13919 buffer; when space runs out, the agent deletes already-collected trace
13920 frames, oldest first, until there is enough room to continue
13921 collecting. This is especially useful if your tracepoints are being
13922 hit too often, and your trace gets terminated prematurely because the
13923 buffer is full. To ask for a circular trace buffer, simply set
13924 @samp{circular-trace-buffer} to on. You can set this at any time,
13925 including during tracing; if the agent can do it, it will change
13926 buffer handling on the fly, otherwise it will not take effect until
13930 @item set circular-trace-buffer on
13931 @itemx set circular-trace-buffer off
13932 @kindex set circular-trace-buffer
13933 Choose whether a tracing run should use a linear or circular buffer
13934 for trace data. A linear buffer will not lose any trace data, but may
13935 fill up prematurely, while a circular buffer will discard old trace
13936 data, but it will have always room for the latest tracepoint hits.
13938 @item show circular-trace-buffer
13939 @kindex show circular-trace-buffer
13940 Show the current choice for the trace buffer. Note that this may not
13941 match the agent's current buffer handling, nor is it guaranteed to
13942 match the setting that might have been in effect during a past run,
13943 for instance if you are looking at frames from a trace file.
13948 @item set trace-buffer-size @var{n}
13949 @itemx set trace-buffer-size unlimited
13950 @kindex set trace-buffer-size
13951 Request that the target use a trace buffer of @var{n} bytes. Not all
13952 targets will honor the request; they may have a compiled-in size for
13953 the trace buffer, or some other limitation. Set to a value of
13954 @code{unlimited} or @code{-1} to let the target use whatever size it
13955 likes. This is also the default.
13957 @item show trace-buffer-size
13958 @kindex show trace-buffer-size
13959 Show the current requested size for the trace buffer. Note that this
13960 will only match the actual size if the target supports size-setting,
13961 and was able to handle the requested size. For instance, if the
13962 target can only change buffer size between runs, this variable will
13963 not reflect the change until the next run starts. Use @code{tstatus}
13964 to get a report of the actual buffer size.
13968 @item set trace-user @var{text}
13969 @kindex set trace-user
13971 @item show trace-user
13972 @kindex show trace-user
13974 @item set trace-notes @var{text}
13975 @kindex set trace-notes
13976 Set the trace run's notes.
13978 @item show trace-notes
13979 @kindex show trace-notes
13980 Show the trace run's notes.
13982 @item set trace-stop-notes @var{text}
13983 @kindex set trace-stop-notes
13984 Set the trace run's stop notes. The handling of the note is as for
13985 @code{tstop} arguments; the set command is convenient way to fix a
13986 stop note that is mistaken or incomplete.
13988 @item show trace-stop-notes
13989 @kindex show trace-stop-notes
13990 Show the trace run's stop notes.
13994 @node Tracepoint Restrictions
13995 @subsection Tracepoint Restrictions
13997 @cindex tracepoint restrictions
13998 There are a number of restrictions on the use of tracepoints. As
13999 described above, tracepoint data gathering occurs on the target
14000 without interaction from @value{GDBN}. Thus the full capabilities of
14001 the debugger are not available during data gathering, and then at data
14002 examination time, you will be limited by only having what was
14003 collected. The following items describe some common problems, but it
14004 is not exhaustive, and you may run into additional difficulties not
14010 Tracepoint expressions are intended to gather objects (lvalues). Thus
14011 the full flexibility of GDB's expression evaluator is not available.
14012 You cannot call functions, cast objects to aggregate types, access
14013 convenience variables or modify values (except by assignment to trace
14014 state variables). Some language features may implicitly call
14015 functions (for instance Objective-C fields with accessors), and therefore
14016 cannot be collected either.
14019 Collection of local variables, either individually or in bulk with
14020 @code{$locals} or @code{$args}, during @code{while-stepping} may
14021 behave erratically. The stepping action may enter a new scope (for
14022 instance by stepping into a function), or the location of the variable
14023 may change (for instance it is loaded into a register). The
14024 tracepoint data recorded uses the location information for the
14025 variables that is correct for the tracepoint location. When the
14026 tracepoint is created, it is not possible, in general, to determine
14027 where the steps of a @code{while-stepping} sequence will advance the
14028 program---particularly if a conditional branch is stepped.
14031 Collection of an incompletely-initialized or partially-destroyed object
14032 may result in something that @value{GDBN} cannot display, or displays
14033 in a misleading way.
14036 When @value{GDBN} displays a pointer to character it automatically
14037 dereferences the pointer to also display characters of the string
14038 being pointed to. However, collecting the pointer during tracing does
14039 not automatically collect the string. You need to explicitly
14040 dereference the pointer and provide size information if you want to
14041 collect not only the pointer, but the memory pointed to. For example,
14042 @code{*ptr@@50} can be used to collect the 50 element array pointed to
14046 It is not possible to collect a complete stack backtrace at a
14047 tracepoint. Instead, you may collect the registers and a few hundred
14048 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
14049 (adjust to use the name of the actual stack pointer register on your
14050 target architecture, and the amount of stack you wish to capture).
14051 Then the @code{backtrace} command will show a partial backtrace when
14052 using a trace frame. The number of stack frames that can be examined
14053 depends on the sizes of the frames in the collected stack. Note that
14054 if you ask for a block so large that it goes past the bottom of the
14055 stack, the target agent may report an error trying to read from an
14059 If you do not collect registers at a tracepoint, @value{GDBN} can
14060 infer that the value of @code{$pc} must be the same as the address of
14061 the tracepoint and use that when you are looking at a trace frame
14062 for that tracepoint. However, this cannot work if the tracepoint has
14063 multiple locations (for instance if it was set in a function that was
14064 inlined), or if it has a @code{while-stepping} loop. In those cases
14065 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
14070 @node Analyze Collected Data
14071 @section Using the Collected Data
14073 After the tracepoint experiment ends, you use @value{GDBN} commands
14074 for examining the trace data. The basic idea is that each tracepoint
14075 collects a trace @dfn{snapshot} every time it is hit and another
14076 snapshot every time it single-steps. All these snapshots are
14077 consecutively numbered from zero and go into a buffer, and you can
14078 examine them later. The way you examine them is to @dfn{focus} on a
14079 specific trace snapshot. When the remote stub is focused on a trace
14080 snapshot, it will respond to all @value{GDBN} requests for memory and
14081 registers by reading from the buffer which belongs to that snapshot,
14082 rather than from @emph{real} memory or registers of the program being
14083 debugged. This means that @strong{all} @value{GDBN} commands
14084 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
14085 behave as if we were currently debugging the program state as it was
14086 when the tracepoint occurred. Any requests for data that are not in
14087 the buffer will fail.
14090 * tfind:: How to select a trace snapshot
14091 * tdump:: How to display all data for a snapshot
14092 * save tracepoints:: How to save tracepoints for a future run
14096 @subsection @code{tfind @var{n}}
14099 @cindex select trace snapshot
14100 @cindex find trace snapshot
14101 The basic command for selecting a trace snapshot from the buffer is
14102 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
14103 counting from zero. If no argument @var{n} is given, the next
14104 snapshot is selected.
14106 Here are the various forms of using the @code{tfind} command.
14110 Find the first snapshot in the buffer. This is a synonym for
14111 @code{tfind 0} (since 0 is the number of the first snapshot).
14114 Stop debugging trace snapshots, resume @emph{live} debugging.
14117 Same as @samp{tfind none}.
14120 No argument means find the next trace snapshot or find the first
14121 one if no trace snapshot is selected.
14124 Find the previous trace snapshot before the current one. This permits
14125 retracing earlier steps.
14127 @item tfind tracepoint @var{num}
14128 Find the next snapshot associated with tracepoint @var{num}. Search
14129 proceeds forward from the last examined trace snapshot. If no
14130 argument @var{num} is given, it means find the next snapshot collected
14131 for the same tracepoint as the current snapshot.
14133 @item tfind pc @var{addr}
14134 Find the next snapshot associated with the value @var{addr} of the
14135 program counter. Search proceeds forward from the last examined trace
14136 snapshot. If no argument @var{addr} is given, it means find the next
14137 snapshot with the same value of PC as the current snapshot.
14139 @item tfind outside @var{addr1}, @var{addr2}
14140 Find the next snapshot whose PC is outside the given range of
14141 addresses (exclusive).
14143 @item tfind range @var{addr1}, @var{addr2}
14144 Find the next snapshot whose PC is between @var{addr1} and
14145 @var{addr2} (inclusive).
14147 @item tfind line @r{[}@var{file}:@r{]}@var{n}
14148 Find the next snapshot associated with the source line @var{n}. If
14149 the optional argument @var{file} is given, refer to line @var{n} in
14150 that source file. Search proceeds forward from the last examined
14151 trace snapshot. If no argument @var{n} is given, it means find the
14152 next line other than the one currently being examined; thus saying
14153 @code{tfind line} repeatedly can appear to have the same effect as
14154 stepping from line to line in a @emph{live} debugging session.
14157 The default arguments for the @code{tfind} commands are specifically
14158 designed to make it easy to scan through the trace buffer. For
14159 instance, @code{tfind} with no argument selects the next trace
14160 snapshot, and @code{tfind -} with no argument selects the previous
14161 trace snapshot. So, by giving one @code{tfind} command, and then
14162 simply hitting @key{RET} repeatedly you can examine all the trace
14163 snapshots in order. Or, by saying @code{tfind -} and then hitting
14164 @key{RET} repeatedly you can examine the snapshots in reverse order.
14165 The @code{tfind line} command with no argument selects the snapshot
14166 for the next source line executed. The @code{tfind pc} command with
14167 no argument selects the next snapshot with the same program counter
14168 (PC) as the current frame. The @code{tfind tracepoint} command with
14169 no argument selects the next trace snapshot collected by the same
14170 tracepoint as the current one.
14172 In addition to letting you scan through the trace buffer manually,
14173 these commands make it easy to construct @value{GDBN} scripts that
14174 scan through the trace buffer and print out whatever collected data
14175 you are interested in. Thus, if we want to examine the PC, FP, and SP
14176 registers from each trace frame in the buffer, we can say this:
14179 (@value{GDBP}) @b{tfind start}
14180 (@value{GDBP}) @b{while ($trace_frame != -1)}
14181 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
14182 $trace_frame, $pc, $sp, $fp
14186 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
14187 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
14188 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
14189 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
14190 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
14191 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
14192 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
14193 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
14194 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
14195 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
14196 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
14199 Or, if we want to examine the variable @code{X} at each source line in
14203 (@value{GDBP}) @b{tfind start}
14204 (@value{GDBP}) @b{while ($trace_frame != -1)}
14205 > printf "Frame %d, X == %d\n", $trace_frame, X
14215 @subsection @code{tdump}
14217 @cindex dump all data collected at tracepoint
14218 @cindex tracepoint data, display
14220 This command takes no arguments. It prints all the data collected at
14221 the current trace snapshot.
14224 (@value{GDBP}) @b{trace 444}
14225 (@value{GDBP}) @b{actions}
14226 Enter actions for tracepoint #2, one per line:
14227 > collect $regs, $locals, $args, gdb_long_test
14230 (@value{GDBP}) @b{tstart}
14232 (@value{GDBP}) @b{tfind line 444}
14233 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
14235 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
14237 (@value{GDBP}) @b{tdump}
14238 Data collected at tracepoint 2, trace frame 1:
14239 d0 0xc4aa0085 -995491707
14243 d4 0x71aea3d 119204413
14246 d7 0x380035 3670069
14247 a0 0x19e24a 1696330
14248 a1 0x3000668 50333288
14250 a3 0x322000 3284992
14251 a4 0x3000698 50333336
14252 a5 0x1ad3cc 1758156
14253 fp 0x30bf3c 0x30bf3c
14254 sp 0x30bf34 0x30bf34
14256 pc 0x20b2c8 0x20b2c8
14260 p = 0x20e5b4 "gdb-test"
14267 gdb_long_test = 17 '\021'
14272 @code{tdump} works by scanning the tracepoint's current collection
14273 actions and printing the value of each expression listed. So
14274 @code{tdump} can fail, if after a run, you change the tracepoint's
14275 actions to mention variables that were not collected during the run.
14277 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
14278 uses the collected value of @code{$pc} to distinguish between trace
14279 frames that were collected at the tracepoint hit, and frames that were
14280 collected while stepping. This allows it to correctly choose whether
14281 to display the basic list of collections, or the collections from the
14282 body of the while-stepping loop. However, if @code{$pc} was not collected,
14283 then @code{tdump} will always attempt to dump using the basic collection
14284 list, and may fail if a while-stepping frame does not include all the
14285 same data that is collected at the tracepoint hit.
14286 @c This is getting pretty arcane, example would be good.
14288 @node save tracepoints
14289 @subsection @code{save tracepoints @var{filename}}
14290 @kindex save tracepoints
14291 @kindex save-tracepoints
14292 @cindex save tracepoints for future sessions
14294 This command saves all current tracepoint definitions together with
14295 their actions and passcounts, into a file @file{@var{filename}}
14296 suitable for use in a later debugging session. To read the saved
14297 tracepoint definitions, use the @code{source} command (@pxref{Command
14298 Files}). The @w{@code{save-tracepoints}} command is a deprecated
14299 alias for @w{@code{save tracepoints}}
14301 @node Tracepoint Variables
14302 @section Convenience Variables for Tracepoints
14303 @cindex tracepoint variables
14304 @cindex convenience variables for tracepoints
14307 @vindex $trace_frame
14308 @item (int) $trace_frame
14309 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
14310 snapshot is selected.
14312 @vindex $tracepoint
14313 @item (int) $tracepoint
14314 The tracepoint for the current trace snapshot.
14316 @vindex $trace_line
14317 @item (int) $trace_line
14318 The line number for the current trace snapshot.
14320 @vindex $trace_file
14321 @item (char []) $trace_file
14322 The source file for the current trace snapshot.
14324 @vindex $trace_func
14325 @item (char []) $trace_func
14326 The name of the function containing @code{$tracepoint}.
14329 Note: @code{$trace_file} is not suitable for use in @code{printf},
14330 use @code{output} instead.
14332 Here's a simple example of using these convenience variables for
14333 stepping through all the trace snapshots and printing some of their
14334 data. Note that these are not the same as trace state variables,
14335 which are managed by the target.
14338 (@value{GDBP}) @b{tfind start}
14340 (@value{GDBP}) @b{while $trace_frame != -1}
14341 > output $trace_file
14342 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
14348 @section Using Trace Files
14349 @cindex trace files
14351 In some situations, the target running a trace experiment may no
14352 longer be available; perhaps it crashed, or the hardware was needed
14353 for a different activity. To handle these cases, you can arrange to
14354 dump the trace data into a file, and later use that file as a source
14355 of trace data, via the @code{target tfile} command.
14360 @item tsave [ -r ] @var{filename}
14361 @itemx tsave [-ctf] @var{dirname}
14362 Save the trace data to @var{filename}. By default, this command
14363 assumes that @var{filename} refers to the host filesystem, so if
14364 necessary @value{GDBN} will copy raw trace data up from the target and
14365 then save it. If the target supports it, you can also supply the
14366 optional argument @code{-r} (``remote'') to direct the target to save
14367 the data directly into @var{filename} in its own filesystem, which may be
14368 more efficient if the trace buffer is very large. (Note, however, that
14369 @code{target tfile} can only read from files accessible to the host.)
14370 By default, this command will save trace frame in tfile format.
14371 You can supply the optional argument @code{-ctf} to save data in CTF
14372 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
14373 that can be shared by multiple debugging and tracing tools. Please go to
14374 @indicateurl{http://www.efficios.com/ctf} to get more information.
14376 @kindex target tfile
14380 @item target tfile @var{filename}
14381 @itemx target ctf @var{dirname}
14382 Use the file named @var{filename} or directory named @var{dirname} as
14383 a source of trace data. Commands that examine data work as they do with
14384 a live target, but it is not possible to run any new trace experiments.
14385 @code{tstatus} will report the state of the trace run at the moment
14386 the data was saved, as well as the current trace frame you are examining.
14387 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
14391 (@value{GDBP}) target ctf ctf.ctf
14392 (@value{GDBP}) tfind
14393 Found trace frame 0, tracepoint 2
14394 39 ++a; /* set tracepoint 1 here */
14395 (@value{GDBP}) tdump
14396 Data collected at tracepoint 2, trace frame 0:
14400 c = @{"123", "456", "789", "123", "456", "789"@}
14401 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
14409 @chapter Debugging Programs That Use Overlays
14412 If your program is too large to fit completely in your target system's
14413 memory, you can sometimes use @dfn{overlays} to work around this
14414 problem. @value{GDBN} provides some support for debugging programs that
14418 * How Overlays Work:: A general explanation of overlays.
14419 * Overlay Commands:: Managing overlays in @value{GDBN}.
14420 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
14421 mapped by asking the inferior.
14422 * Overlay Sample Program:: A sample program using overlays.
14425 @node How Overlays Work
14426 @section How Overlays Work
14427 @cindex mapped overlays
14428 @cindex unmapped overlays
14429 @cindex load address, overlay's
14430 @cindex mapped address
14431 @cindex overlay area
14433 Suppose you have a computer whose instruction address space is only 64
14434 kilobytes long, but which has much more memory which can be accessed by
14435 other means: special instructions, segment registers, or memory
14436 management hardware, for example. Suppose further that you want to
14437 adapt a program which is larger than 64 kilobytes to run on this system.
14439 One solution is to identify modules of your program which are relatively
14440 independent, and need not call each other directly; call these modules
14441 @dfn{overlays}. Separate the overlays from the main program, and place
14442 their machine code in the larger memory. Place your main program in
14443 instruction memory, but leave at least enough space there to hold the
14444 largest overlay as well.
14446 Now, to call a function located in an overlay, you must first copy that
14447 overlay's machine code from the large memory into the space set aside
14448 for it in the instruction memory, and then jump to its entry point
14451 @c NB: In the below the mapped area's size is greater or equal to the
14452 @c size of all overlays. This is intentional to remind the developer
14453 @c that overlays don't necessarily need to be the same size.
14457 Data Instruction Larger
14458 Address Space Address Space Address Space
14459 +-----------+ +-----------+ +-----------+
14461 +-----------+ +-----------+ +-----------+<-- overlay 1
14462 | program | | main | .----| overlay 1 | load address
14463 | variables | | program | | +-----------+
14464 | and heap | | | | | |
14465 +-----------+ | | | +-----------+<-- overlay 2
14466 | | +-----------+ | | | load address
14467 +-----------+ | | | .-| overlay 2 |
14469 mapped --->+-----------+ | | +-----------+
14470 address | | | | | |
14471 | overlay | <-' | | |
14472 | area | <---' +-----------+<-- overlay 3
14473 | | <---. | | load address
14474 +-----------+ `--| overlay 3 |
14481 @anchor{A code overlay}A code overlay
14485 The diagram (@pxref{A code overlay}) shows a system with separate data
14486 and instruction address spaces. To map an overlay, the program copies
14487 its code from the larger address space to the instruction address space.
14488 Since the overlays shown here all use the same mapped address, only one
14489 may be mapped at a time. For a system with a single address space for
14490 data and instructions, the diagram would be similar, except that the
14491 program variables and heap would share an address space with the main
14492 program and the overlay area.
14494 An overlay loaded into instruction memory and ready for use is called a
14495 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14496 instruction memory. An overlay not present (or only partially present)
14497 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14498 is its address in the larger memory. The mapped address is also called
14499 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14500 called the @dfn{load memory address}, or @dfn{LMA}.
14502 Unfortunately, overlays are not a completely transparent way to adapt a
14503 program to limited instruction memory. They introduce a new set of
14504 global constraints you must keep in mind as you design your program:
14509 Before calling or returning to a function in an overlay, your program
14510 must make sure that overlay is actually mapped. Otherwise, the call or
14511 return will transfer control to the right address, but in the wrong
14512 overlay, and your program will probably crash.
14515 If the process of mapping an overlay is expensive on your system, you
14516 will need to choose your overlays carefully to minimize their effect on
14517 your program's performance.
14520 The executable file you load onto your system must contain each
14521 overlay's instructions, appearing at the overlay's load address, not its
14522 mapped address. However, each overlay's instructions must be relocated
14523 and its symbols defined as if the overlay were at its mapped address.
14524 You can use GNU linker scripts to specify different load and relocation
14525 addresses for pieces of your program; see @ref{Overlay Description,,,
14526 ld.info, Using ld: the GNU linker}.
14529 The procedure for loading executable files onto your system must be able
14530 to load their contents into the larger address space as well as the
14531 instruction and data spaces.
14535 The overlay system described above is rather simple, and could be
14536 improved in many ways:
14541 If your system has suitable bank switch registers or memory management
14542 hardware, you could use those facilities to make an overlay's load area
14543 contents simply appear at their mapped address in instruction space.
14544 This would probably be faster than copying the overlay to its mapped
14545 area in the usual way.
14548 If your overlays are small enough, you could set aside more than one
14549 overlay area, and have more than one overlay mapped at a time.
14552 You can use overlays to manage data, as well as instructions. In
14553 general, data overlays are even less transparent to your design than
14554 code overlays: whereas code overlays only require care when you call or
14555 return to functions, data overlays require care every time you access
14556 the data. Also, if you change the contents of a data overlay, you
14557 must copy its contents back out to its load address before you can copy a
14558 different data overlay into the same mapped area.
14563 @node Overlay Commands
14564 @section Overlay Commands
14566 To use @value{GDBN}'s overlay support, each overlay in your program must
14567 correspond to a separate section of the executable file. The section's
14568 virtual memory address and load memory address must be the overlay's
14569 mapped and load addresses. Identifying overlays with sections allows
14570 @value{GDBN} to determine the appropriate address of a function or
14571 variable, depending on whether the overlay is mapped or not.
14573 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14574 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14579 Disable @value{GDBN}'s overlay support. When overlay support is
14580 disabled, @value{GDBN} assumes that all functions and variables are
14581 always present at their mapped addresses. By default, @value{GDBN}'s
14582 overlay support is disabled.
14584 @item overlay manual
14585 @cindex manual overlay debugging
14586 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14587 relies on you to tell it which overlays are mapped, and which are not,
14588 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14589 commands described below.
14591 @item overlay map-overlay @var{overlay}
14592 @itemx overlay map @var{overlay}
14593 @cindex map an overlay
14594 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14595 be the name of the object file section containing the overlay. When an
14596 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14597 functions and variables at their mapped addresses. @value{GDBN} assumes
14598 that any other overlays whose mapped ranges overlap that of
14599 @var{overlay} are now unmapped.
14601 @item overlay unmap-overlay @var{overlay}
14602 @itemx overlay unmap @var{overlay}
14603 @cindex unmap an overlay
14604 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14605 must be the name of the object file section containing the overlay.
14606 When an overlay is unmapped, @value{GDBN} assumes it can find the
14607 overlay's functions and variables at their load addresses.
14610 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14611 consults a data structure the overlay manager maintains in the inferior
14612 to see which overlays are mapped. For details, see @ref{Automatic
14613 Overlay Debugging}.
14615 @item overlay load-target
14616 @itemx overlay load
14617 @cindex reloading the overlay table
14618 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14619 re-reads the table @value{GDBN} automatically each time the inferior
14620 stops, so this command should only be necessary if you have changed the
14621 overlay mapping yourself using @value{GDBN}. This command is only
14622 useful when using automatic overlay debugging.
14624 @item overlay list-overlays
14625 @itemx overlay list
14626 @cindex listing mapped overlays
14627 Display a list of the overlays currently mapped, along with their mapped
14628 addresses, load addresses, and sizes.
14632 Normally, when @value{GDBN} prints a code address, it includes the name
14633 of the function the address falls in:
14636 (@value{GDBP}) print main
14637 $3 = @{int ()@} 0x11a0 <main>
14640 When overlay debugging is enabled, @value{GDBN} recognizes code in
14641 unmapped overlays, and prints the names of unmapped functions with
14642 asterisks around them. For example, if @code{foo} is a function in an
14643 unmapped overlay, @value{GDBN} prints it this way:
14646 (@value{GDBP}) overlay list
14647 No sections are mapped.
14648 (@value{GDBP}) print foo
14649 $5 = @{int (int)@} 0x100000 <*foo*>
14652 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14656 (@value{GDBP}) overlay list
14657 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14658 mapped at 0x1016 - 0x104a
14659 (@value{GDBP}) print foo
14660 $6 = @{int (int)@} 0x1016 <foo>
14663 When overlay debugging is enabled, @value{GDBN} can find the correct
14664 address for functions and variables in an overlay, whether or not the
14665 overlay is mapped. This allows most @value{GDBN} commands, like
14666 @code{break} and @code{disassemble}, to work normally, even on unmapped
14667 code. However, @value{GDBN}'s breakpoint support has some limitations:
14671 @cindex breakpoints in overlays
14672 @cindex overlays, setting breakpoints in
14673 You can set breakpoints in functions in unmapped overlays, as long as
14674 @value{GDBN} can write to the overlay at its load address.
14676 @value{GDBN} can not set hardware or simulator-based breakpoints in
14677 unmapped overlays. However, if you set a breakpoint at the end of your
14678 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14679 you are using manual overlay management), @value{GDBN} will re-set its
14680 breakpoints properly.
14684 @node Automatic Overlay Debugging
14685 @section Automatic Overlay Debugging
14686 @cindex automatic overlay debugging
14688 @value{GDBN} can automatically track which overlays are mapped and which
14689 are not, given some simple co-operation from the overlay manager in the
14690 inferior. If you enable automatic overlay debugging with the
14691 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14692 looks in the inferior's memory for certain variables describing the
14693 current state of the overlays.
14695 Here are the variables your overlay manager must define to support
14696 @value{GDBN}'s automatic overlay debugging:
14700 @item @code{_ovly_table}:
14701 This variable must be an array of the following structures:
14706 /* The overlay's mapped address. */
14709 /* The size of the overlay, in bytes. */
14710 unsigned long size;
14712 /* The overlay's load address. */
14715 /* Non-zero if the overlay is currently mapped;
14717 unsigned long mapped;
14721 @item @code{_novlys}:
14722 This variable must be a four-byte signed integer, holding the total
14723 number of elements in @code{_ovly_table}.
14727 To decide whether a particular overlay is mapped or not, @value{GDBN}
14728 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14729 @code{lma} members equal the VMA and LMA of the overlay's section in the
14730 executable file. When @value{GDBN} finds a matching entry, it consults
14731 the entry's @code{mapped} member to determine whether the overlay is
14734 In addition, your overlay manager may define a function called
14735 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14736 will silently set a breakpoint there. If the overlay manager then
14737 calls this function whenever it has changed the overlay table, this
14738 will enable @value{GDBN} to accurately keep track of which overlays
14739 are in program memory, and update any breakpoints that may be set
14740 in overlays. This will allow breakpoints to work even if the
14741 overlays are kept in ROM or other non-writable memory while they
14742 are not being executed.
14744 @node Overlay Sample Program
14745 @section Overlay Sample Program
14746 @cindex overlay example program
14748 When linking a program which uses overlays, you must place the overlays
14749 at their load addresses, while relocating them to run at their mapped
14750 addresses. To do this, you must write a linker script (@pxref{Overlay
14751 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14752 since linker scripts are specific to a particular host system, target
14753 architecture, and target memory layout, this manual cannot provide
14754 portable sample code demonstrating @value{GDBN}'s overlay support.
14756 However, the @value{GDBN} source distribution does contain an overlaid
14757 program, with linker scripts for a few systems, as part of its test
14758 suite. The program consists of the following files from
14759 @file{gdb/testsuite/gdb.base}:
14763 The main program file.
14765 A simple overlay manager, used by @file{overlays.c}.
14770 Overlay modules, loaded and used by @file{overlays.c}.
14773 Linker scripts for linking the test program on the @code{d10v-elf}
14774 and @code{m32r-elf} targets.
14777 You can build the test program using the @code{d10v-elf} GCC
14778 cross-compiler like this:
14781 $ d10v-elf-gcc -g -c overlays.c
14782 $ d10v-elf-gcc -g -c ovlymgr.c
14783 $ d10v-elf-gcc -g -c foo.c
14784 $ d10v-elf-gcc -g -c bar.c
14785 $ d10v-elf-gcc -g -c baz.c
14786 $ d10v-elf-gcc -g -c grbx.c
14787 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14788 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14791 The build process is identical for any other architecture, except that
14792 you must substitute the appropriate compiler and linker script for the
14793 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14797 @chapter Using @value{GDBN} with Different Languages
14800 Although programming languages generally have common aspects, they are
14801 rarely expressed in the same manner. For instance, in ANSI C,
14802 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14803 Modula-2, it is accomplished by @code{p^}. Values can also be
14804 represented (and displayed) differently. Hex numbers in C appear as
14805 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14807 @cindex working language
14808 Language-specific information is built into @value{GDBN} for some languages,
14809 allowing you to express operations like the above in your program's
14810 native language, and allowing @value{GDBN} to output values in a manner
14811 consistent with the syntax of your program's native language. The
14812 language you use to build expressions is called the @dfn{working
14816 * Setting:: Switching between source languages
14817 * Show:: Displaying the language
14818 * Checks:: Type and range checks
14819 * Supported Languages:: Supported languages
14820 * Unsupported Languages:: Unsupported languages
14824 @section Switching Between Source Languages
14826 There are two ways to control the working language---either have @value{GDBN}
14827 set it automatically, or select it manually yourself. You can use the
14828 @code{set language} command for either purpose. On startup, @value{GDBN}
14829 defaults to setting the language automatically. The working language is
14830 used to determine how expressions you type are interpreted, how values
14833 In addition to the working language, every source file that
14834 @value{GDBN} knows about has its own working language. For some object
14835 file formats, the compiler might indicate which language a particular
14836 source file is in. However, most of the time @value{GDBN} infers the
14837 language from the name of the file. The language of a source file
14838 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14839 show each frame appropriately for its own language. There is no way to
14840 set the language of a source file from within @value{GDBN}, but you can
14841 set the language associated with a filename extension. @xref{Show, ,
14842 Displaying the Language}.
14844 This is most commonly a problem when you use a program, such
14845 as @code{cfront} or @code{f2c}, that generates C but is written in
14846 another language. In that case, make the
14847 program use @code{#line} directives in its C output; that way
14848 @value{GDBN} will know the correct language of the source code of the original
14849 program, and will display that source code, not the generated C code.
14852 * Filenames:: Filename extensions and languages.
14853 * Manually:: Setting the working language manually
14854 * Automatically:: Having @value{GDBN} infer the source language
14858 @subsection List of Filename Extensions and Languages
14860 If a source file name ends in one of the following extensions, then
14861 @value{GDBN} infers that its language is the one indicated.
14879 C@t{++} source file
14885 Objective-C source file
14889 Fortran source file
14892 Modula-2 source file
14896 Assembler source file. This actually behaves almost like C, but
14897 @value{GDBN} does not skip over function prologues when stepping.
14900 In addition, you may set the language associated with a filename
14901 extension. @xref{Show, , Displaying the Language}.
14904 @subsection Setting the Working Language
14906 If you allow @value{GDBN} to set the language automatically,
14907 expressions are interpreted the same way in your debugging session and
14910 @kindex set language
14911 If you wish, you may set the language manually. To do this, issue the
14912 command @samp{set language @var{lang}}, where @var{lang} is the name of
14913 a language, such as
14914 @code{c} or @code{modula-2}.
14915 For a list of the supported languages, type @samp{set language}.
14917 Setting the language manually prevents @value{GDBN} from updating the working
14918 language automatically. This can lead to confusion if you try
14919 to debug a program when the working language is not the same as the
14920 source language, when an expression is acceptable to both
14921 languages---but means different things. For instance, if the current
14922 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14930 might not have the effect you intended. In C, this means to add
14931 @code{b} and @code{c} and place the result in @code{a}. The result
14932 printed would be the value of @code{a}. In Modula-2, this means to compare
14933 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14935 @node Automatically
14936 @subsection Having @value{GDBN} Infer the Source Language
14938 To have @value{GDBN} set the working language automatically, use
14939 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14940 then infers the working language. That is, when your program stops in a
14941 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14942 working language to the language recorded for the function in that
14943 frame. If the language for a frame is unknown (that is, if the function
14944 or block corresponding to the frame was defined in a source file that
14945 does not have a recognized extension), the current working language is
14946 not changed, and @value{GDBN} issues a warning.
14948 This may not seem necessary for most programs, which are written
14949 entirely in one source language. However, program modules and libraries
14950 written in one source language can be used by a main program written in
14951 a different source language. Using @samp{set language auto} in this
14952 case frees you from having to set the working language manually.
14955 @section Displaying the Language
14957 The following commands help you find out which language is the
14958 working language, and also what language source files were written in.
14961 @item show language
14962 @anchor{show language}
14963 @kindex show language
14964 Display the current working language. This is the
14965 language you can use with commands such as @code{print} to
14966 build and compute expressions that may involve variables in your program.
14969 @kindex info frame@r{, show the source language}
14970 Display the source language for this frame. This language becomes the
14971 working language if you use an identifier from this frame.
14972 @xref{Frame Info, ,Information about a Frame}, to identify the other
14973 information listed here.
14976 @kindex info source@r{, show the source language}
14977 Display the source language of this source file.
14978 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14979 information listed here.
14982 In unusual circumstances, you may have source files with extensions
14983 not in the standard list. You can then set the extension associated
14984 with a language explicitly:
14987 @item set extension-language @var{ext} @var{language}
14988 @kindex set extension-language
14989 Tell @value{GDBN} that source files with extension @var{ext} are to be
14990 assumed as written in the source language @var{language}.
14992 @item info extensions
14993 @kindex info extensions
14994 List all the filename extensions and the associated languages.
14998 @section Type and Range Checking
15000 Some languages are designed to guard you against making seemingly common
15001 errors through a series of compile- and run-time checks. These include
15002 checking the type of arguments to functions and operators and making
15003 sure mathematical overflows are caught at run time. Checks such as
15004 these help to ensure a program's correctness once it has been compiled
15005 by eliminating type mismatches and providing active checks for range
15006 errors when your program is running.
15008 By default @value{GDBN} checks for these errors according to the
15009 rules of the current source language. Although @value{GDBN} does not check
15010 the statements in your program, it can check expressions entered directly
15011 into @value{GDBN} for evaluation via the @code{print} command, for example.
15014 * Type Checking:: An overview of type checking
15015 * Range Checking:: An overview of range checking
15018 @cindex type checking
15019 @cindex checks, type
15020 @node Type Checking
15021 @subsection An Overview of Type Checking
15023 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
15024 arguments to operators and functions have to be of the correct type,
15025 otherwise an error occurs. These checks prevent type mismatch
15026 errors from ever causing any run-time problems. For example,
15029 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
15031 (@value{GDBP}) print obj.my_method (0)
15034 (@value{GDBP}) print obj.my_method (0x1234)
15035 Cannot resolve method klass::my_method to any overloaded instance
15038 The second example fails because in C@t{++} the integer constant
15039 @samp{0x1234} is not type-compatible with the pointer parameter type.
15041 For the expressions you use in @value{GDBN} commands, you can tell
15042 @value{GDBN} to not enforce strict type checking or
15043 to treat any mismatches as errors and abandon the expression;
15044 When type checking is disabled, @value{GDBN} successfully evaluates
15045 expressions like the second example above.
15047 Even if type checking is off, there may be other reasons
15048 related to type that prevent @value{GDBN} from evaluating an expression.
15049 For instance, @value{GDBN} does not know how to add an @code{int} and
15050 a @code{struct foo}. These particular type errors have nothing to do
15051 with the language in use and usually arise from expressions which make
15052 little sense to evaluate anyway.
15054 @value{GDBN} provides some additional commands for controlling type checking:
15056 @kindex set check type
15057 @kindex show check type
15059 @item set check type on
15060 @itemx set check type off
15061 Set strict type checking on or off. If any type mismatches occur in
15062 evaluating an expression while type checking is on, @value{GDBN} prints a
15063 message and aborts evaluation of the expression.
15065 @item show check type
15066 Show the current setting of type checking and whether @value{GDBN}
15067 is enforcing strict type checking rules.
15070 @cindex range checking
15071 @cindex checks, range
15072 @node Range Checking
15073 @subsection An Overview of Range Checking
15075 In some languages (such as Modula-2), it is an error to exceed the
15076 bounds of a type; this is enforced with run-time checks. Such range
15077 checking is meant to ensure program correctness by making sure
15078 computations do not overflow, or indices on an array element access do
15079 not exceed the bounds of the array.
15081 For expressions you use in @value{GDBN} commands, you can tell
15082 @value{GDBN} to treat range errors in one of three ways: ignore them,
15083 always treat them as errors and abandon the expression, or issue
15084 warnings but evaluate the expression anyway.
15086 A range error can result from numerical overflow, from exceeding an
15087 array index bound, or when you type a constant that is not a member
15088 of any type. Some languages, however, do not treat overflows as an
15089 error. In many implementations of C, mathematical overflow causes the
15090 result to ``wrap around'' to lower values---for example, if @var{m} is
15091 the largest integer value, and @var{s} is the smallest, then
15094 @var{m} + 1 @result{} @var{s}
15097 This, too, is specific to individual languages, and in some cases
15098 specific to individual compilers or machines. @xref{Supported Languages, ,
15099 Supported Languages}, for further details on specific languages.
15101 @value{GDBN} provides some additional commands for controlling the range checker:
15103 @kindex set check range
15104 @kindex show check range
15106 @item set check range auto
15107 Set range checking on or off based on the current working language.
15108 @xref{Supported Languages, ,Supported Languages}, for the default settings for
15111 @item set check range on
15112 @itemx set check range off
15113 Set range checking on or off, overriding the default setting for the
15114 current working language. A warning is issued if the setting does not
15115 match the language default. If a range error occurs and range checking is on,
15116 then a message is printed and evaluation of the expression is aborted.
15118 @item set check range warn
15119 Output messages when the @value{GDBN} range checker detects a range error,
15120 but attempt to evaluate the expression anyway. Evaluating the
15121 expression may still be impossible for other reasons, such as accessing
15122 memory that the process does not own (a typical example from many Unix
15126 Show the current setting of the range checker, and whether or not it is
15127 being set automatically by @value{GDBN}.
15130 @node Supported Languages
15131 @section Supported Languages
15133 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
15134 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
15135 @c This is false ...
15136 Some @value{GDBN} features may be used in expressions regardless of the
15137 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
15138 and the @samp{@{type@}addr} construct (@pxref{Expressions,
15139 ,Expressions}) can be used with the constructs of any supported
15142 The following sections detail to what degree each source language is
15143 supported by @value{GDBN}. These sections are not meant to be language
15144 tutorials or references, but serve only as a reference guide to what the
15145 @value{GDBN} expression parser accepts, and what input and output
15146 formats should look like for different languages. There are many good
15147 books written on each of these languages; please look to these for a
15148 language reference or tutorial.
15151 * C:: C and C@t{++}
15154 * Objective-C:: Objective-C
15155 * OpenCL C:: OpenCL C
15156 * Fortran:: Fortran
15159 * Modula-2:: Modula-2
15164 @subsection C and C@t{++}
15166 @cindex C and C@t{++}
15167 @cindex expressions in C or C@t{++}
15169 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
15170 to both languages. Whenever this is the case, we discuss those languages
15174 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
15175 @cindex @sc{gnu} C@t{++}
15176 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
15177 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
15178 effectively, you must compile your C@t{++} programs with a supported
15179 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
15180 compiler (@code{aCC}).
15183 * C Operators:: C and C@t{++} operators
15184 * C Constants:: C and C@t{++} constants
15185 * C Plus Plus Expressions:: C@t{++} expressions
15186 * C Defaults:: Default settings for C and C@t{++}
15187 * C Checks:: C and C@t{++} type and range checks
15188 * Debugging C:: @value{GDBN} and C
15189 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
15190 * Decimal Floating Point:: Numbers in Decimal Floating Point format
15194 @subsubsection C and C@t{++} Operators
15196 @cindex C and C@t{++} operators
15198 Operators must be defined on values of specific types. For instance,
15199 @code{+} is defined on numbers, but not on structures. Operators are
15200 often defined on groups of types.
15202 For the purposes of C and C@t{++}, the following definitions hold:
15207 @emph{Integral types} include @code{int} with any of its storage-class
15208 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
15211 @emph{Floating-point types} include @code{float}, @code{double}, and
15212 @code{long double} (if supported by the target platform).
15215 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
15218 @emph{Scalar types} include all of the above.
15223 The following operators are supported. They are listed here
15224 in order of increasing precedence:
15228 The comma or sequencing operator. Expressions in a comma-separated list
15229 are evaluated from left to right, with the result of the entire
15230 expression being the last expression evaluated.
15233 Assignment. The value of an assignment expression is the value
15234 assigned. Defined on scalar types.
15237 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
15238 and translated to @w{@code{@var{a} = @var{a op b}}}.
15239 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
15240 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
15241 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
15244 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
15245 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
15246 should be of an integral type.
15249 Logical @sc{or}. Defined on integral types.
15252 Logical @sc{and}. Defined on integral types.
15255 Bitwise @sc{or}. Defined on integral types.
15258 Bitwise exclusive-@sc{or}. Defined on integral types.
15261 Bitwise @sc{and}. Defined on integral types.
15264 Equality and inequality. Defined on scalar types. The value of these
15265 expressions is 0 for false and non-zero for true.
15267 @item <@r{, }>@r{, }<=@r{, }>=
15268 Less than, greater than, less than or equal, greater than or equal.
15269 Defined on scalar types. The value of these expressions is 0 for false
15270 and non-zero for true.
15273 left shift, and right shift. Defined on integral types.
15276 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15279 Addition and subtraction. Defined on integral types, floating-point types and
15282 @item *@r{, }/@r{, }%
15283 Multiplication, division, and modulus. Multiplication and division are
15284 defined on integral and floating-point types. Modulus is defined on
15288 Increment and decrement. When appearing before a variable, the
15289 operation is performed before the variable is used in an expression;
15290 when appearing after it, the variable's value is used before the
15291 operation takes place.
15294 Pointer dereferencing. Defined on pointer types. Same precedence as
15298 Address operator. Defined on variables. Same precedence as @code{++}.
15300 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
15301 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
15302 to examine the address
15303 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
15307 Negative. Defined on integral and floating-point types. Same
15308 precedence as @code{++}.
15311 Logical negation. Defined on integral types. Same precedence as
15315 Bitwise complement operator. Defined on integral types. Same precedence as
15320 Structure member, and pointer-to-structure member. For convenience,
15321 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
15322 pointer based on the stored type information.
15323 Defined on @code{struct} and @code{union} data.
15326 Dereferences of pointers to members.
15329 Array indexing. @code{@var{a}[@var{i}]} is defined as
15330 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
15333 Function parameter list. Same precedence as @code{->}.
15336 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
15337 and @code{class} types.
15340 Doubled colons also represent the @value{GDBN} scope operator
15341 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
15345 If an operator is redefined in the user code, @value{GDBN} usually
15346 attempts to invoke the redefined version instead of using the operator's
15347 predefined meaning.
15350 @subsubsection C and C@t{++} Constants
15352 @cindex C and C@t{++} constants
15354 @value{GDBN} allows you to express the constants of C and C@t{++} in the
15359 Integer constants are a sequence of digits. Octal constants are
15360 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
15361 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
15362 @samp{l}, specifying that the constant should be treated as a
15366 Floating point constants are a sequence of digits, followed by a decimal
15367 point, followed by a sequence of digits, and optionally followed by an
15368 exponent. An exponent is of the form:
15369 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
15370 sequence of digits. The @samp{+} is optional for positive exponents.
15371 A floating-point constant may also end with a letter @samp{f} or
15372 @samp{F}, specifying that the constant should be treated as being of
15373 the @code{float} (as opposed to the default @code{double}) type; or with
15374 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
15378 Enumerated constants consist of enumerated identifiers, or their
15379 integral equivalents.
15382 Character constants are a single character surrounded by single quotes
15383 (@code{'}), or a number---the ordinal value of the corresponding character
15384 (usually its @sc{ascii} value). Within quotes, the single character may
15385 be represented by a letter or by @dfn{escape sequences}, which are of
15386 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
15387 of the character's ordinal value; or of the form @samp{\@var{x}}, where
15388 @samp{@var{x}} is a predefined special character---for example,
15389 @samp{\n} for newline.
15391 Wide character constants can be written by prefixing a character
15392 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
15393 form of @samp{x}. The target wide character set is used when
15394 computing the value of this constant (@pxref{Character Sets}).
15397 String constants are a sequence of character constants surrounded by
15398 double quotes (@code{"}). Any valid character constant (as described
15399 above) may appear. Double quotes within the string must be preceded by
15400 a backslash, so for instance @samp{"a\"b'c"} is a string of five
15403 Wide string constants can be written by prefixing a string constant
15404 with @samp{L}, as in C. The target wide character set is used when
15405 computing the value of this constant (@pxref{Character Sets}).
15408 Pointer constants are an integral value. You can also write pointers
15409 to constants using the C operator @samp{&}.
15412 Array constants are comma-separated lists surrounded by braces @samp{@{}
15413 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
15414 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
15415 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
15418 @node C Plus Plus Expressions
15419 @subsubsection C@t{++} Expressions
15421 @cindex expressions in C@t{++}
15422 @value{GDBN} expression handling can interpret most C@t{++} expressions.
15424 @cindex debugging C@t{++} programs
15425 @cindex C@t{++} compilers
15426 @cindex debug formats and C@t{++}
15427 @cindex @value{NGCC} and C@t{++}
15429 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
15430 the proper compiler and the proper debug format. Currently,
15431 @value{GDBN} works best when debugging C@t{++} code that is compiled
15432 with the most recent version of @value{NGCC} possible. The DWARF
15433 debugging format is preferred; @value{NGCC} defaults to this on most
15434 popular platforms. Other compilers and/or debug formats are likely to
15435 work badly or not at all when using @value{GDBN} to debug C@t{++}
15436 code. @xref{Compilation}.
15441 @cindex member functions
15443 Member function calls are allowed; you can use expressions like
15446 count = aml->GetOriginal(x, y)
15449 @vindex this@r{, inside C@t{++} member functions}
15450 @cindex namespace in C@t{++}
15452 While a member function is active (in the selected stack frame), your
15453 expressions have the same namespace available as the member function;
15454 that is, @value{GDBN} allows implicit references to the class instance
15455 pointer @code{this} following the same rules as C@t{++}. @code{using}
15456 declarations in the current scope are also respected by @value{GDBN}.
15458 @cindex call overloaded functions
15459 @cindex overloaded functions, calling
15460 @cindex type conversions in C@t{++}
15462 You can call overloaded functions; @value{GDBN} resolves the function
15463 call to the right definition, with some restrictions. @value{GDBN} does not
15464 perform overload resolution involving user-defined type conversions,
15465 calls to constructors, or instantiations of templates that do not exist
15466 in the program. It also cannot handle ellipsis argument lists or
15469 It does perform integral conversions and promotions, floating-point
15470 promotions, arithmetic conversions, pointer conversions, conversions of
15471 class objects to base classes, and standard conversions such as those of
15472 functions or arrays to pointers; it requires an exact match on the
15473 number of function arguments.
15475 Overload resolution is always performed, unless you have specified
15476 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
15477 ,@value{GDBN} Features for C@t{++}}.
15479 You must specify @code{set overload-resolution off} in order to use an
15480 explicit function signature to call an overloaded function, as in
15482 p 'foo(char,int)'('x', 13)
15485 The @value{GDBN} command-completion facility can simplify this;
15486 see @ref{Completion, ,Command Completion}.
15488 @cindex reference declarations
15490 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
15491 references; you can use them in expressions just as you do in C@t{++}
15492 source---they are automatically dereferenced.
15494 In the parameter list shown when @value{GDBN} displays a frame, the values of
15495 reference variables are not displayed (unlike other variables); this
15496 avoids clutter, since references are often used for large structures.
15497 The @emph{address} of a reference variable is always shown, unless
15498 you have specified @samp{set print address off}.
15501 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15502 expressions can use it just as expressions in your program do. Since
15503 one scope may be defined in another, you can use @code{::} repeatedly if
15504 necessary, for example in an expression like
15505 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15506 resolving name scope by reference to source files, in both C and C@t{++}
15507 debugging (@pxref{Variables, ,Program Variables}).
15510 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15515 @subsubsection C and C@t{++} Defaults
15517 @cindex C and C@t{++} defaults
15519 If you allow @value{GDBN} to set range checking automatically, it
15520 defaults to @code{off} whenever the working language changes to
15521 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15522 selects the working language.
15524 If you allow @value{GDBN} to set the language automatically, it
15525 recognizes source files whose names end with @file{.c}, @file{.C}, or
15526 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15527 these files, it sets the working language to C or C@t{++}.
15528 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15529 for further details.
15532 @subsubsection C and C@t{++} Type and Range Checks
15534 @cindex C and C@t{++} checks
15536 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15537 checking is used. However, if you turn type checking off, @value{GDBN}
15538 will allow certain non-standard conversions, such as promoting integer
15539 constants to pointers.
15541 Range checking, if turned on, is done on mathematical operations. Array
15542 indices are not checked, since they are often used to index a pointer
15543 that is not itself an array.
15546 @subsubsection @value{GDBN} and C
15548 The @code{set print union} and @code{show print union} commands apply to
15549 the @code{union} type. When set to @samp{on}, any @code{union} that is
15550 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15551 appears as @samp{@{...@}}.
15553 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15554 with pointers and a memory allocation function. @xref{Expressions,
15557 @node Debugging C Plus Plus
15558 @subsubsection @value{GDBN} Features for C@t{++}
15560 @cindex commands for C@t{++}
15562 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15563 designed specifically for use with C@t{++}. Here is a summary:
15566 @cindex break in overloaded functions
15567 @item @r{breakpoint menus}
15568 When you want a breakpoint in a function whose name is overloaded,
15569 @value{GDBN} has the capability to display a menu of possible breakpoint
15570 locations to help you specify which function definition you want.
15571 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15573 @cindex overloading in C@t{++}
15574 @item rbreak @var{regex}
15575 Setting breakpoints using regular expressions is helpful for setting
15576 breakpoints on overloaded functions that are not members of any special
15578 @xref{Set Breaks, ,Setting Breakpoints}.
15580 @cindex C@t{++} exception handling
15582 @itemx catch rethrow
15584 Debug C@t{++} exception handling using these commands. @xref{Set
15585 Catchpoints, , Setting Catchpoints}.
15587 @cindex inheritance
15588 @item ptype @var{typename}
15589 Print inheritance relationships as well as other information for type
15591 @xref{Symbols, ,Examining the Symbol Table}.
15593 @item info vtbl @var{expression}.
15594 The @code{info vtbl} command can be used to display the virtual
15595 method tables of the object computed by @var{expression}. This shows
15596 one entry per virtual table; there may be multiple virtual tables when
15597 multiple inheritance is in use.
15599 @cindex C@t{++} demangling
15600 @item demangle @var{name}
15601 Demangle @var{name}.
15602 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15604 @cindex C@t{++} symbol display
15605 @item set print demangle
15606 @itemx show print demangle
15607 @itemx set print asm-demangle
15608 @itemx show print asm-demangle
15609 Control whether C@t{++} symbols display in their source form, both when
15610 displaying code as C@t{++} source and when displaying disassemblies.
15611 @xref{Print Settings, ,Print Settings}.
15613 @item set print object
15614 @itemx show print object
15615 Choose whether to print derived (actual) or declared types of objects.
15616 @xref{Print Settings, ,Print Settings}.
15618 @item set print vtbl
15619 @itemx show print vtbl
15620 Control the format for printing virtual function tables.
15621 @xref{Print Settings, ,Print Settings}.
15622 (The @code{vtbl} commands do not work on programs compiled with the HP
15623 ANSI C@t{++} compiler (@code{aCC}).)
15625 @kindex set overload-resolution
15626 @cindex overloaded functions, overload resolution
15627 @item set overload-resolution on
15628 Enable overload resolution for C@t{++} expression evaluation. The default
15629 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15630 and searches for a function whose signature matches the argument types,
15631 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15632 Expressions, ,C@t{++} Expressions}, for details).
15633 If it cannot find a match, it emits a message.
15635 @item set overload-resolution off
15636 Disable overload resolution for C@t{++} expression evaluation. For
15637 overloaded functions that are not class member functions, @value{GDBN}
15638 chooses the first function of the specified name that it finds in the
15639 symbol table, whether or not its arguments are of the correct type. For
15640 overloaded functions that are class member functions, @value{GDBN}
15641 searches for a function whose signature @emph{exactly} matches the
15644 @kindex show overload-resolution
15645 @item show overload-resolution
15646 Show the current setting of overload resolution.
15648 @item @r{Overloaded symbol names}
15649 You can specify a particular definition of an overloaded symbol, using
15650 the same notation that is used to declare such symbols in C@t{++}: type
15651 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15652 also use the @value{GDBN} command-line word completion facilities to list the
15653 available choices, or to finish the type list for you.
15654 @xref{Completion,, Command Completion}, for details on how to do this.
15656 @item @r{Breakpoints in functions with ABI tags}
15658 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15659 correspond to changes in the ABI of a type, function, or variable that
15660 would not otherwise be reflected in a mangled name. See
15661 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15664 The ABI tags are visible in C@t{++} demangled names. For example, a
15665 function that returns a std::string:
15668 std::string function(int);
15672 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15673 tag, and @value{GDBN} displays the symbol like this:
15676 function[abi:cxx11](int)
15679 You can set a breakpoint on such functions simply as if they had no
15683 (gdb) b function(int)
15684 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15685 (gdb) info breakpoints
15686 Num Type Disp Enb Address What
15687 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15691 On the rare occasion you need to disambiguate between different ABI
15692 tags, you can do so by simply including the ABI tag in the function
15696 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15700 @node Decimal Floating Point
15701 @subsubsection Decimal Floating Point format
15702 @cindex decimal floating point format
15704 @value{GDBN} can examine, set and perform computations with numbers in
15705 decimal floating point format, which in the C language correspond to the
15706 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15707 specified by the extension to support decimal floating-point arithmetic.
15709 There are two encodings in use, depending on the architecture: BID (Binary
15710 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15711 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15714 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15715 to manipulate decimal floating point numbers, it is not possible to convert
15716 (using a cast, for example) integers wider than 32-bit to decimal float.
15718 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15719 point computations, error checking in decimal float operations ignores
15720 underflow, overflow and divide by zero exceptions.
15722 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15723 to inspect @code{_Decimal128} values stored in floating point registers.
15724 See @ref{PowerPC,,PowerPC} for more details.
15730 @value{GDBN} can be used to debug programs written in D and compiled with
15731 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15732 specific feature --- dynamic arrays.
15737 @cindex Go (programming language)
15738 @value{GDBN} can be used to debug programs written in Go and compiled with
15739 @file{gccgo} or @file{6g} compilers.
15741 Here is a summary of the Go-specific features and restrictions:
15744 @cindex current Go package
15745 @item The current Go package
15746 The name of the current package does not need to be specified when
15747 specifying global variables and functions.
15749 For example, given the program:
15753 var myglob = "Shall we?"
15759 When stopped inside @code{main} either of these work:
15763 (gdb) p main.myglob
15766 @cindex builtin Go types
15767 @item Builtin Go types
15768 The @code{string} type is recognized by @value{GDBN} and is printed
15771 @cindex builtin Go functions
15772 @item Builtin Go functions
15773 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15774 function and handles it internally.
15776 @cindex restrictions on Go expressions
15777 @item Restrictions on Go expressions
15778 All Go operators are supported except @code{&^}.
15779 The Go @code{_} ``blank identifier'' is not supported.
15780 Automatic dereferencing of pointers is not supported.
15784 @subsection Objective-C
15786 @cindex Objective-C
15787 This section provides information about some commands and command
15788 options that are useful for debugging Objective-C code. See also
15789 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15790 few more commands specific to Objective-C support.
15793 * Method Names in Commands::
15794 * The Print Command with Objective-C::
15797 @node Method Names in Commands
15798 @subsubsection Method Names in Commands
15800 The following commands have been extended to accept Objective-C method
15801 names as line specifications:
15803 @kindex clear@r{, and Objective-C}
15804 @kindex break@r{, and Objective-C}
15805 @kindex info line@r{, and Objective-C}
15806 @kindex jump@r{, and Objective-C}
15807 @kindex list@r{, and Objective-C}
15811 @item @code{info line}
15816 A fully qualified Objective-C method name is specified as
15819 -[@var{Class} @var{methodName}]
15822 where the minus sign is used to indicate an instance method and a
15823 plus sign (not shown) is used to indicate a class method. The class
15824 name @var{Class} and method name @var{methodName} are enclosed in
15825 brackets, similar to the way messages are specified in Objective-C
15826 source code. For example, to set a breakpoint at the @code{create}
15827 instance method of class @code{Fruit} in the program currently being
15831 break -[Fruit create]
15834 To list ten program lines around the @code{initialize} class method,
15838 list +[NSText initialize]
15841 In the current version of @value{GDBN}, the plus or minus sign is
15842 required. In future versions of @value{GDBN}, the plus or minus
15843 sign will be optional, but you can use it to narrow the search. It
15844 is also possible to specify just a method name:
15850 You must specify the complete method name, including any colons. If
15851 your program's source files contain more than one @code{create} method,
15852 you'll be presented with a numbered list of classes that implement that
15853 method. Indicate your choice by number, or type @samp{0} to exit if
15856 As another example, to clear a breakpoint established at the
15857 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15860 clear -[NSWindow makeKeyAndOrderFront:]
15863 @node The Print Command with Objective-C
15864 @subsubsection The Print Command With Objective-C
15865 @cindex Objective-C, print objects
15866 @kindex print-object
15867 @kindex po @r{(@code{print-object})}
15869 The print command has also been extended to accept methods. For example:
15872 print -[@var{object} hash]
15875 @cindex print an Objective-C object description
15876 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15878 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15879 and print the result. Also, an additional command has been added,
15880 @code{print-object} or @code{po} for short, which is meant to print
15881 the description of an object. However, this command may only work
15882 with certain Objective-C libraries that have a particular hook
15883 function, @code{_NSPrintForDebugger}, defined.
15886 @subsection OpenCL C
15889 This section provides information about @value{GDBN}s OpenCL C support.
15892 * OpenCL C Datatypes::
15893 * OpenCL C Expressions::
15894 * OpenCL C Operators::
15897 @node OpenCL C Datatypes
15898 @subsubsection OpenCL C Datatypes
15900 @cindex OpenCL C Datatypes
15901 @value{GDBN} supports the builtin scalar and vector datatypes specified
15902 by OpenCL 1.1. In addition the half- and double-precision floating point
15903 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15904 extensions are also known to @value{GDBN}.
15906 @node OpenCL C Expressions
15907 @subsubsection OpenCL C Expressions
15909 @cindex OpenCL C Expressions
15910 @value{GDBN} supports accesses to vector components including the access as
15911 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15912 supported by @value{GDBN} can be used as well.
15914 @node OpenCL C Operators
15915 @subsubsection OpenCL C Operators
15917 @cindex OpenCL C Operators
15918 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15922 @subsection Fortran
15923 @cindex Fortran-specific support in @value{GDBN}
15925 @value{GDBN} can be used to debug programs written in Fortran, but it
15926 currently supports only the features of Fortran 77 language.
15928 @cindex trailing underscore, in Fortran symbols
15929 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15930 among them) append an underscore to the names of variables and
15931 functions. When you debug programs compiled by those compilers, you
15932 will need to refer to variables and functions with a trailing
15936 * Fortran Operators:: Fortran operators and expressions
15937 * Fortran Defaults:: Default settings for Fortran
15938 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15941 @node Fortran Operators
15942 @subsubsection Fortran Operators and Expressions
15944 @cindex Fortran operators and expressions
15946 Operators must be defined on values of specific types. For instance,
15947 @code{+} is defined on numbers, but not on characters or other non-
15948 arithmetic types. Operators are often defined on groups of types.
15952 The exponentiation operator. It raises the first operand to the power
15956 The range operator. Normally used in the form of array(low:high) to
15957 represent a section of array.
15960 The access component operator. Normally used to access elements in derived
15961 types. Also suitable for unions. As unions aren't part of regular Fortran,
15962 this can only happen when accessing a register that uses a gdbarch-defined
15966 @node Fortran Defaults
15967 @subsubsection Fortran Defaults
15969 @cindex Fortran Defaults
15971 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15972 default uses case-insensitive matches for Fortran symbols. You can
15973 change that with the @samp{set case-insensitive} command, see
15974 @ref{Symbols}, for the details.
15976 @node Special Fortran Commands
15977 @subsubsection Special Fortran Commands
15979 @cindex Special Fortran commands
15981 @value{GDBN} has some commands to support Fortran-specific features,
15982 such as displaying common blocks.
15985 @cindex @code{COMMON} blocks, Fortran
15986 @kindex info common
15987 @item info common @r{[}@var{common-name}@r{]}
15988 This command prints the values contained in the Fortran @code{COMMON}
15989 block whose name is @var{common-name}. With no argument, the names of
15990 all @code{COMMON} blocks visible at the current program location are
15997 @cindex Pascal support in @value{GDBN}, limitations
15998 Debugging Pascal programs which use sets, subranges, file variables, or
15999 nested functions does not currently work. @value{GDBN} does not support
16000 entering expressions, printing values, or similar features using Pascal
16003 The Pascal-specific command @code{set print pascal_static-members}
16004 controls whether static members of Pascal objects are displayed.
16005 @xref{Print Settings, pascal_static-members}.
16010 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
16011 Programming Language}. Type- and value-printing, and expression
16012 parsing, are reasonably complete. However, there are a few
16013 peculiarities and holes to be aware of.
16017 Linespecs (@pxref{Specify Location}) are never relative to the current
16018 crate. Instead, they act as if there were a global namespace of
16019 crates, somewhat similar to the way @code{extern crate} behaves.
16021 That is, if @value{GDBN} is stopped at a breakpoint in a function in
16022 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
16023 to set a breakpoint in a function named @samp{f} in a crate named
16026 As a consequence of this approach, linespecs also cannot refer to
16027 items using @samp{self::} or @samp{super::}.
16030 Because @value{GDBN} implements Rust name-lookup semantics in
16031 expressions, it will sometimes prepend the current crate to a name.
16032 For example, if @value{GDBN} is stopped at a breakpoint in the crate
16033 @samp{K}, then @code{print ::x::y} will try to find the symbol
16036 However, since it is useful to be able to refer to other crates when
16037 debugging, @value{GDBN} provides the @code{extern} extension to
16038 circumvent this. To use the extension, just put @code{extern} before
16039 a path expression to refer to the otherwise unavailable ``global''
16042 In the above example, if you wanted to refer to the symbol @samp{y} in
16043 the crate @samp{x}, you would use @code{print extern x::y}.
16046 The Rust expression evaluator does not support ``statement-like''
16047 expressions such as @code{if} or @code{match}, or lambda expressions.
16050 Tuple expressions are not implemented.
16053 The Rust expression evaluator does not currently implement the
16054 @code{Drop} trait. Objects that may be created by the evaluator will
16055 never be destroyed.
16058 @value{GDBN} does not implement type inference for generics. In order
16059 to call generic functions or otherwise refer to generic items, you
16060 will have to specify the type parameters manually.
16063 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
16064 cases this does not cause any problems. However, in an expression
16065 context, completing a generic function name will give syntactically
16066 invalid results. This happens because Rust requires the @samp{::}
16067 operator between the function name and its generic arguments. For
16068 example, @value{GDBN} might provide a completion like
16069 @code{crate::f<u32>}, where the parser would require
16070 @code{crate::f::<u32>}.
16073 As of this writing, the Rust compiler (version 1.8) has a few holes in
16074 the debugging information it generates. These holes prevent certain
16075 features from being implemented by @value{GDBN}:
16079 Method calls cannot be made via traits.
16082 Operator overloading is not implemented.
16085 When debugging in a monomorphized function, you cannot use the generic
16089 The type @code{Self} is not available.
16092 @code{use} statements are not available, so some names may not be
16093 available in the crate.
16098 @subsection Modula-2
16100 @cindex Modula-2, @value{GDBN} support
16102 The extensions made to @value{GDBN} to support Modula-2 only support
16103 output from the @sc{gnu} Modula-2 compiler (which is currently being
16104 developed). Other Modula-2 compilers are not currently supported, and
16105 attempting to debug executables produced by them is most likely
16106 to give an error as @value{GDBN} reads in the executable's symbol
16109 @cindex expressions in Modula-2
16111 * M2 Operators:: Built-in operators
16112 * Built-In Func/Proc:: Built-in functions and procedures
16113 * M2 Constants:: Modula-2 constants
16114 * M2 Types:: Modula-2 types
16115 * M2 Defaults:: Default settings for Modula-2
16116 * Deviations:: Deviations from standard Modula-2
16117 * M2 Checks:: Modula-2 type and range checks
16118 * M2 Scope:: The scope operators @code{::} and @code{.}
16119 * GDB/M2:: @value{GDBN} and Modula-2
16123 @subsubsection Operators
16124 @cindex Modula-2 operators
16126 Operators must be defined on values of specific types. For instance,
16127 @code{+} is defined on numbers, but not on structures. Operators are
16128 often defined on groups of types. For the purposes of Modula-2, the
16129 following definitions hold:
16134 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
16138 @emph{Character types} consist of @code{CHAR} and its subranges.
16141 @emph{Floating-point types} consist of @code{REAL}.
16144 @emph{Pointer types} consist of anything declared as @code{POINTER TO
16148 @emph{Scalar types} consist of all of the above.
16151 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
16154 @emph{Boolean types} consist of @code{BOOLEAN}.
16158 The following operators are supported, and appear in order of
16159 increasing precedence:
16163 Function argument or array index separator.
16166 Assignment. The value of @var{var} @code{:=} @var{value} is
16170 Less than, greater than on integral, floating-point, or enumerated
16174 Less than or equal to, greater than or equal to
16175 on integral, floating-point and enumerated types, or set inclusion on
16176 set types. Same precedence as @code{<}.
16178 @item =@r{, }<>@r{, }#
16179 Equality and two ways of expressing inequality, valid on scalar types.
16180 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
16181 available for inequality, since @code{#} conflicts with the script
16185 Set membership. Defined on set types and the types of their members.
16186 Same precedence as @code{<}.
16189 Boolean disjunction. Defined on boolean types.
16192 Boolean conjunction. Defined on boolean types.
16195 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
16198 Addition and subtraction on integral and floating-point types, or union
16199 and difference on set types.
16202 Multiplication on integral and floating-point types, or set intersection
16206 Division on floating-point types, or symmetric set difference on set
16207 types. Same precedence as @code{*}.
16210 Integer division and remainder. Defined on integral types. Same
16211 precedence as @code{*}.
16214 Negative. Defined on @code{INTEGER} and @code{REAL} data.
16217 Pointer dereferencing. Defined on pointer types.
16220 Boolean negation. Defined on boolean types. Same precedence as
16224 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
16225 precedence as @code{^}.
16228 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
16231 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
16235 @value{GDBN} and Modula-2 scope operators.
16239 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
16240 treats the use of the operator @code{IN}, or the use of operators
16241 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
16242 @code{<=}, and @code{>=} on sets as an error.
16246 @node Built-In Func/Proc
16247 @subsubsection Built-in Functions and Procedures
16248 @cindex Modula-2 built-ins
16250 Modula-2 also makes available several built-in procedures and functions.
16251 In describing these, the following metavariables are used:
16256 represents an @code{ARRAY} variable.
16259 represents a @code{CHAR} constant or variable.
16262 represents a variable or constant of integral type.
16265 represents an identifier that belongs to a set. Generally used in the
16266 same function with the metavariable @var{s}. The type of @var{s} should
16267 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
16270 represents a variable or constant of integral or floating-point type.
16273 represents a variable or constant of floating-point type.
16279 represents a variable.
16282 represents a variable or constant of one of many types. See the
16283 explanation of the function for details.
16286 All Modula-2 built-in procedures also return a result, described below.
16290 Returns the absolute value of @var{n}.
16293 If @var{c} is a lower case letter, it returns its upper case
16294 equivalent, otherwise it returns its argument.
16297 Returns the character whose ordinal value is @var{i}.
16300 Decrements the value in the variable @var{v} by one. Returns the new value.
16302 @item DEC(@var{v},@var{i})
16303 Decrements the value in the variable @var{v} by @var{i}. Returns the
16306 @item EXCL(@var{m},@var{s})
16307 Removes the element @var{m} from the set @var{s}. Returns the new
16310 @item FLOAT(@var{i})
16311 Returns the floating point equivalent of the integer @var{i}.
16313 @item HIGH(@var{a})
16314 Returns the index of the last member of @var{a}.
16317 Increments the value in the variable @var{v} by one. Returns the new value.
16319 @item INC(@var{v},@var{i})
16320 Increments the value in the variable @var{v} by @var{i}. Returns the
16323 @item INCL(@var{m},@var{s})
16324 Adds the element @var{m} to the set @var{s} if it is not already
16325 there. Returns the new set.
16328 Returns the maximum value of the type @var{t}.
16331 Returns the minimum value of the type @var{t}.
16334 Returns boolean TRUE if @var{i} is an odd number.
16337 Returns the ordinal value of its argument. For example, the ordinal
16338 value of a character is its @sc{ascii} value (on machines supporting
16339 the @sc{ascii} character set). The argument @var{x} must be of an
16340 ordered type, which include integral, character and enumerated types.
16342 @item SIZE(@var{x})
16343 Returns the size of its argument. The argument @var{x} can be a
16344 variable or a type.
16346 @item TRUNC(@var{r})
16347 Returns the integral part of @var{r}.
16349 @item TSIZE(@var{x})
16350 Returns the size of its argument. The argument @var{x} can be a
16351 variable or a type.
16353 @item VAL(@var{t},@var{i})
16354 Returns the member of the type @var{t} whose ordinal value is @var{i}.
16358 @emph{Warning:} Sets and their operations are not yet supported, so
16359 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
16363 @cindex Modula-2 constants
16365 @subsubsection Constants
16367 @value{GDBN} allows you to express the constants of Modula-2 in the following
16373 Integer constants are simply a sequence of digits. When used in an
16374 expression, a constant is interpreted to be type-compatible with the
16375 rest of the expression. Hexadecimal integers are specified by a
16376 trailing @samp{H}, and octal integers by a trailing @samp{B}.
16379 Floating point constants appear as a sequence of digits, followed by a
16380 decimal point and another sequence of digits. An optional exponent can
16381 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
16382 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
16383 digits of the floating point constant must be valid decimal (base 10)
16387 Character constants consist of a single character enclosed by a pair of
16388 like quotes, either single (@code{'}) or double (@code{"}). They may
16389 also be expressed by their ordinal value (their @sc{ascii} value, usually)
16390 followed by a @samp{C}.
16393 String constants consist of a sequence of characters enclosed by a
16394 pair of like quotes, either single (@code{'}) or double (@code{"}).
16395 Escape sequences in the style of C are also allowed. @xref{C
16396 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
16400 Enumerated constants consist of an enumerated identifier.
16403 Boolean constants consist of the identifiers @code{TRUE} and
16407 Pointer constants consist of integral values only.
16410 Set constants are not yet supported.
16414 @subsubsection Modula-2 Types
16415 @cindex Modula-2 types
16417 Currently @value{GDBN} can print the following data types in Modula-2
16418 syntax: array types, record types, set types, pointer types, procedure
16419 types, enumerated types, subrange types and base types. You can also
16420 print the contents of variables declared using these type.
16421 This section gives a number of simple source code examples together with
16422 sample @value{GDBN} sessions.
16424 The first example contains the following section of code:
16433 and you can request @value{GDBN} to interrogate the type and value of
16434 @code{r} and @code{s}.
16437 (@value{GDBP}) print s
16439 (@value{GDBP}) ptype s
16441 (@value{GDBP}) print r
16443 (@value{GDBP}) ptype r
16448 Likewise if your source code declares @code{s} as:
16452 s: SET ['A'..'Z'] ;
16456 then you may query the type of @code{s} by:
16459 (@value{GDBP}) ptype s
16460 type = SET ['A'..'Z']
16464 Note that at present you cannot interactively manipulate set
16465 expressions using the debugger.
16467 The following example shows how you might declare an array in Modula-2
16468 and how you can interact with @value{GDBN} to print its type and contents:
16472 s: ARRAY [-10..10] OF CHAR ;
16476 (@value{GDBP}) ptype s
16477 ARRAY [-10..10] OF CHAR
16480 Note that the array handling is not yet complete and although the type
16481 is printed correctly, expression handling still assumes that all
16482 arrays have a lower bound of zero and not @code{-10} as in the example
16485 Here are some more type related Modula-2 examples:
16489 colour = (blue, red, yellow, green) ;
16490 t = [blue..yellow] ;
16498 The @value{GDBN} interaction shows how you can query the data type
16499 and value of a variable.
16502 (@value{GDBP}) print s
16504 (@value{GDBP}) ptype t
16505 type = [blue..yellow]
16509 In this example a Modula-2 array is declared and its contents
16510 displayed. Observe that the contents are written in the same way as
16511 their @code{C} counterparts.
16515 s: ARRAY [1..5] OF CARDINAL ;
16521 (@value{GDBP}) print s
16522 $1 = @{1, 0, 0, 0, 0@}
16523 (@value{GDBP}) ptype s
16524 type = ARRAY [1..5] OF CARDINAL
16527 The Modula-2 language interface to @value{GDBN} also understands
16528 pointer types as shown in this example:
16532 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16539 and you can request that @value{GDBN} describes the type of @code{s}.
16542 (@value{GDBP}) ptype s
16543 type = POINTER TO ARRAY [1..5] OF CARDINAL
16546 @value{GDBN} handles compound types as we can see in this example.
16547 Here we combine array types, record types, pointer types and subrange
16558 myarray = ARRAY myrange OF CARDINAL ;
16559 myrange = [-2..2] ;
16561 s: POINTER TO ARRAY myrange OF foo ;
16565 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16569 (@value{GDBP}) ptype s
16570 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16573 f3 : ARRAY [-2..2] OF CARDINAL;
16578 @subsubsection Modula-2 Defaults
16579 @cindex Modula-2 defaults
16581 If type and range checking are set automatically by @value{GDBN}, they
16582 both default to @code{on} whenever the working language changes to
16583 Modula-2. This happens regardless of whether you or @value{GDBN}
16584 selected the working language.
16586 If you allow @value{GDBN} to set the language automatically, then entering
16587 code compiled from a file whose name ends with @file{.mod} sets the
16588 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16589 Infer the Source Language}, for further details.
16592 @subsubsection Deviations from Standard Modula-2
16593 @cindex Modula-2, deviations from
16595 A few changes have been made to make Modula-2 programs easier to debug.
16596 This is done primarily via loosening its type strictness:
16600 Unlike in standard Modula-2, pointer constants can be formed by
16601 integers. This allows you to modify pointer variables during
16602 debugging. (In standard Modula-2, the actual address contained in a
16603 pointer variable is hidden from you; it can only be modified
16604 through direct assignment to another pointer variable or expression that
16605 returned a pointer.)
16608 C escape sequences can be used in strings and characters to represent
16609 non-printable characters. @value{GDBN} prints out strings with these
16610 escape sequences embedded. Single non-printable characters are
16611 printed using the @samp{CHR(@var{nnn})} format.
16614 The assignment operator (@code{:=}) returns the value of its right-hand
16618 All built-in procedures both modify @emph{and} return their argument.
16622 @subsubsection Modula-2 Type and Range Checks
16623 @cindex Modula-2 checks
16626 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16629 @c FIXME remove warning when type/range checks added
16631 @value{GDBN} considers two Modula-2 variables type equivalent if:
16635 They are of types that have been declared equivalent via a @code{TYPE
16636 @var{t1} = @var{t2}} statement
16639 They have been declared on the same line. (Note: This is true of the
16640 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16643 As long as type checking is enabled, any attempt to combine variables
16644 whose types are not equivalent is an error.
16646 Range checking is done on all mathematical operations, assignment, array
16647 index bounds, and all built-in functions and procedures.
16650 @subsubsection The Scope Operators @code{::} and @code{.}
16652 @cindex @code{.}, Modula-2 scope operator
16653 @cindex colon, doubled as scope operator
16655 @vindex colon-colon@r{, in Modula-2}
16656 @c Info cannot handle :: but TeX can.
16659 @vindex ::@r{, in Modula-2}
16662 There are a few subtle differences between the Modula-2 scope operator
16663 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16668 @var{module} . @var{id}
16669 @var{scope} :: @var{id}
16673 where @var{scope} is the name of a module or a procedure,
16674 @var{module} the name of a module, and @var{id} is any declared
16675 identifier within your program, except another module.
16677 Using the @code{::} operator makes @value{GDBN} search the scope
16678 specified by @var{scope} for the identifier @var{id}. If it is not
16679 found in the specified scope, then @value{GDBN} searches all scopes
16680 enclosing the one specified by @var{scope}.
16682 Using the @code{.} operator makes @value{GDBN} search the current scope for
16683 the identifier specified by @var{id} that was imported from the
16684 definition module specified by @var{module}. With this operator, it is
16685 an error if the identifier @var{id} was not imported from definition
16686 module @var{module}, or if @var{id} is not an identifier in
16690 @subsubsection @value{GDBN} and Modula-2
16692 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16693 Five subcommands of @code{set print} and @code{show print} apply
16694 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16695 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16696 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16697 analogue in Modula-2.
16699 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16700 with any language, is not useful with Modula-2. Its
16701 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16702 created in Modula-2 as they can in C or C@t{++}. However, because an
16703 address can be specified by an integral constant, the construct
16704 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16706 @cindex @code{#} in Modula-2
16707 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16708 interpreted as the beginning of a comment. Use @code{<>} instead.
16714 The extensions made to @value{GDBN} for Ada only support
16715 output from the @sc{gnu} Ada (GNAT) compiler.
16716 Other Ada compilers are not currently supported, and
16717 attempting to debug executables produced by them is most likely
16721 @cindex expressions in Ada
16723 * Ada Mode Intro:: General remarks on the Ada syntax
16724 and semantics supported by Ada mode
16726 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16727 * Additions to Ada:: Extensions of the Ada expression syntax.
16728 * Overloading support for Ada:: Support for expressions involving overloaded
16730 * Stopping Before Main Program:: Debugging the program during elaboration.
16731 * Ada Exceptions:: Ada Exceptions
16732 * Ada Tasks:: Listing and setting breakpoints in tasks.
16733 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16734 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16736 * Ada Settings:: New settable GDB parameters for Ada.
16737 * Ada Glitches:: Known peculiarities of Ada mode.
16740 @node Ada Mode Intro
16741 @subsubsection Introduction
16742 @cindex Ada mode, general
16744 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16745 syntax, with some extensions.
16746 The philosophy behind the design of this subset is
16750 That @value{GDBN} should provide basic literals and access to operations for
16751 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16752 leaving more sophisticated computations to subprograms written into the
16753 program (which therefore may be called from @value{GDBN}).
16756 That type safety and strict adherence to Ada language restrictions
16757 are not particularly important to the @value{GDBN} user.
16760 That brevity is important to the @value{GDBN} user.
16763 Thus, for brevity, the debugger acts as if all names declared in
16764 user-written packages are directly visible, even if they are not visible
16765 according to Ada rules, thus making it unnecessary to fully qualify most
16766 names with their packages, regardless of context. Where this causes
16767 ambiguity, @value{GDBN} asks the user's intent.
16769 The debugger will start in Ada mode if it detects an Ada main program.
16770 As for other languages, it will enter Ada mode when stopped in a program that
16771 was translated from an Ada source file.
16773 While in Ada mode, you may use `@t{--}' for comments. This is useful
16774 mostly for documenting command files. The standard @value{GDBN} comment
16775 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16776 middle (to allow based literals).
16778 @node Omissions from Ada
16779 @subsubsection Omissions from Ada
16780 @cindex Ada, omissions from
16782 Here are the notable omissions from the subset:
16786 Only a subset of the attributes are supported:
16790 @t{'First}, @t{'Last}, and @t{'Length}
16791 on array objects (not on types and subtypes).
16794 @t{'Min} and @t{'Max}.
16797 @t{'Pos} and @t{'Val}.
16803 @t{'Range} on array objects (not subtypes), but only as the right
16804 operand of the membership (@code{in}) operator.
16807 @t{'Access}, @t{'Unchecked_Access}, and
16808 @t{'Unrestricted_Access} (a GNAT extension).
16816 @code{Characters.Latin_1} are not available and
16817 concatenation is not implemented. Thus, escape characters in strings are
16818 not currently available.
16821 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16822 equality of representations. They will generally work correctly
16823 for strings and arrays whose elements have integer or enumeration types.
16824 They may not work correctly for arrays whose element
16825 types have user-defined equality, for arrays of real values
16826 (in particular, IEEE-conformant floating point, because of negative
16827 zeroes and NaNs), and for arrays whose elements contain unused bits with
16828 indeterminate values.
16831 The other component-by-component array operations (@code{and}, @code{or},
16832 @code{xor}, @code{not}, and relational tests other than equality)
16833 are not implemented.
16836 @cindex array aggregates (Ada)
16837 @cindex record aggregates (Ada)
16838 @cindex aggregates (Ada)
16839 There is limited support for array and record aggregates. They are
16840 permitted only on the right sides of assignments, as in these examples:
16843 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16844 (@value{GDBP}) set An_Array := (1, others => 0)
16845 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16846 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16847 (@value{GDBP}) set A_Record := (1, "Peter", True);
16848 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16852 discriminant's value by assigning an aggregate has an
16853 undefined effect if that discriminant is used within the record.
16854 However, you can first modify discriminants by directly assigning to
16855 them (which normally would not be allowed in Ada), and then performing an
16856 aggregate assignment. For example, given a variable @code{A_Rec}
16857 declared to have a type such as:
16860 type Rec (Len : Small_Integer := 0) is record
16862 Vals : IntArray (1 .. Len);
16866 you can assign a value with a different size of @code{Vals} with two
16870 (@value{GDBP}) set A_Rec.Len := 4
16871 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16874 As this example also illustrates, @value{GDBN} is very loose about the usual
16875 rules concerning aggregates. You may leave out some of the
16876 components of an array or record aggregate (such as the @code{Len}
16877 component in the assignment to @code{A_Rec} above); they will retain their
16878 original values upon assignment. You may freely use dynamic values as
16879 indices in component associations. You may even use overlapping or
16880 redundant component associations, although which component values are
16881 assigned in such cases is not defined.
16884 Calls to dispatching subprograms are not implemented.
16887 The overloading algorithm is much more limited (i.e., less selective)
16888 than that of real Ada. It makes only limited use of the context in
16889 which a subexpression appears to resolve its meaning, and it is much
16890 looser in its rules for allowing type matches. As a result, some
16891 function calls will be ambiguous, and the user will be asked to choose
16892 the proper resolution.
16895 The @code{new} operator is not implemented.
16898 Entry calls are not implemented.
16901 Aside from printing, arithmetic operations on the native VAX floating-point
16902 formats are not supported.
16905 It is not possible to slice a packed array.
16908 The names @code{True} and @code{False}, when not part of a qualified name,
16909 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16911 Should your program
16912 redefine these names in a package or procedure (at best a dubious practice),
16913 you will have to use fully qualified names to access their new definitions.
16916 @node Additions to Ada
16917 @subsubsection Additions to Ada
16918 @cindex Ada, deviations from
16920 As it does for other languages, @value{GDBN} makes certain generic
16921 extensions to Ada (@pxref{Expressions}):
16925 If the expression @var{E} is a variable residing in memory (typically
16926 a local variable or array element) and @var{N} is a positive integer,
16927 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16928 @var{N}-1 adjacent variables following it in memory as an array. In
16929 Ada, this operator is generally not necessary, since its prime use is
16930 in displaying parts of an array, and slicing will usually do this in
16931 Ada. However, there are occasional uses when debugging programs in
16932 which certain debugging information has been optimized away.
16935 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16936 appears in function or file @var{B}.'' When @var{B} is a file name,
16937 you must typically surround it in single quotes.
16940 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16941 @var{type} that appears at address @var{addr}.''
16944 A name starting with @samp{$} is a convenience variable
16945 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16948 In addition, @value{GDBN} provides a few other shortcuts and outright
16949 additions specific to Ada:
16953 The assignment statement is allowed as an expression, returning
16954 its right-hand operand as its value. Thus, you may enter
16957 (@value{GDBP}) set x := y + 3
16958 (@value{GDBP}) print A(tmp := y + 1)
16962 The semicolon is allowed as an ``operator,'' returning as its value
16963 the value of its right-hand operand.
16964 This allows, for example,
16965 complex conditional breaks:
16968 (@value{GDBP}) break f
16969 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16973 Rather than use catenation and symbolic character names to introduce special
16974 characters into strings, one may instead use a special bracket notation,
16975 which is also used to print strings. A sequence of characters of the form
16976 @samp{["@var{XX}"]} within a string or character literal denotes the
16977 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16978 sequence of characters @samp{["""]} also denotes a single quotation mark
16979 in strings. For example,
16981 "One line.["0a"]Next line.["0a"]"
16984 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16988 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16989 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16993 (@value{GDBP}) print 'max(x, y)
16997 When printing arrays, @value{GDBN} uses positional notation when the
16998 array has a lower bound of 1, and uses a modified named notation otherwise.
16999 For example, a one-dimensional array of three integers with a lower bound
17000 of 3 might print as
17007 That is, in contrast to valid Ada, only the first component has a @code{=>}
17011 You may abbreviate attributes in expressions with any unique,
17012 multi-character subsequence of
17013 their names (an exact match gets preference).
17014 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
17015 in place of @t{a'length}.
17018 @cindex quoting Ada internal identifiers
17019 Since Ada is case-insensitive, the debugger normally maps identifiers you type
17020 to lower case. The GNAT compiler uses upper-case characters for
17021 some of its internal identifiers, which are normally of no interest to users.
17022 For the rare occasions when you actually have to look at them,
17023 enclose them in angle brackets to avoid the lower-case mapping.
17026 (@value{GDBP}) print <JMPBUF_SAVE>[0]
17030 Printing an object of class-wide type or dereferencing an
17031 access-to-class-wide value will display all the components of the object's
17032 specific type (as indicated by its run-time tag). Likewise, component
17033 selection on such a value will operate on the specific type of the
17038 @node Overloading support for Ada
17039 @subsubsection Overloading support for Ada
17040 @cindex overloading, Ada
17042 The debugger supports limited overloading. Given a subprogram call in which
17043 the function symbol has multiple definitions, it will use the number of
17044 actual parameters and some information about their types to attempt to narrow
17045 the set of definitions. It also makes very limited use of context, preferring
17046 procedures to functions in the context of the @code{call} command, and
17047 functions to procedures elsewhere.
17049 If, after narrowing, the set of matching definitions still contains more than
17050 one definition, @value{GDBN} will display a menu to query which one it should
17054 (@value{GDBP}) print f(1)
17055 Multiple matches for f
17057 [1] foo.f (integer) return boolean at foo.adb:23
17058 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
17062 In this case, just select one menu entry either to cancel expression evaluation
17063 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
17064 instance (type the corresponding number and press @key{RET}).
17066 Here are a couple of commands to customize @value{GDBN}'s behavior in this
17071 @kindex set ada print-signatures
17072 @item set ada print-signatures
17073 Control whether parameter types and return types are displayed in overloads
17074 selection menus. It is @code{on} by default.
17075 @xref{Overloading support for Ada}.
17077 @kindex show ada print-signatures
17078 @item show ada print-signatures
17079 Show the current setting for displaying parameter types and return types in
17080 overloads selection menu.
17081 @xref{Overloading support for Ada}.
17085 @node Stopping Before Main Program
17086 @subsubsection Stopping at the Very Beginning
17088 @cindex breakpointing Ada elaboration code
17089 It is sometimes necessary to debug the program during elaboration, and
17090 before reaching the main procedure.
17091 As defined in the Ada Reference
17092 Manual, the elaboration code is invoked from a procedure called
17093 @code{adainit}. To run your program up to the beginning of
17094 elaboration, simply use the following two commands:
17095 @code{tbreak adainit} and @code{run}.
17097 @node Ada Exceptions
17098 @subsubsection Ada Exceptions
17100 A command is provided to list all Ada exceptions:
17103 @kindex info exceptions
17104 @item info exceptions
17105 @itemx info exceptions @var{regexp}
17106 The @code{info exceptions} command allows you to list all Ada exceptions
17107 defined within the program being debugged, as well as their addresses.
17108 With a regular expression, @var{regexp}, as argument, only those exceptions
17109 whose names match @var{regexp} are listed.
17112 Below is a small example, showing how the command can be used, first
17113 without argument, and next with a regular expression passed as an
17117 (@value{GDBP}) info exceptions
17118 All defined Ada exceptions:
17119 constraint_error: 0x613da0
17120 program_error: 0x613d20
17121 storage_error: 0x613ce0
17122 tasking_error: 0x613ca0
17123 const.aint_global_e: 0x613b00
17124 (@value{GDBP}) info exceptions const.aint
17125 All Ada exceptions matching regular expression "const.aint":
17126 constraint_error: 0x613da0
17127 const.aint_global_e: 0x613b00
17130 It is also possible to ask @value{GDBN} to stop your program's execution
17131 when an exception is raised. For more details, see @ref{Set Catchpoints}.
17134 @subsubsection Extensions for Ada Tasks
17135 @cindex Ada, tasking
17137 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
17138 @value{GDBN} provides the following task-related commands:
17143 This command shows a list of current Ada tasks, as in the following example:
17150 (@value{GDBP}) info tasks
17151 ID TID P-ID Pri State Name
17152 1 8088000 0 15 Child Activation Wait main_task
17153 2 80a4000 1 15 Accept Statement b
17154 3 809a800 1 15 Child Activation Wait a
17155 * 4 80ae800 3 15 Runnable c
17160 In this listing, the asterisk before the last task indicates it to be the
17161 task currently being inspected.
17165 Represents @value{GDBN}'s internal task number.
17171 The parent's task ID (@value{GDBN}'s internal task number).
17174 The base priority of the task.
17177 Current state of the task.
17181 The task has been created but has not been activated. It cannot be
17185 The task is not blocked for any reason known to Ada. (It may be waiting
17186 for a mutex, though.) It is conceptually "executing" in normal mode.
17189 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
17190 that were waiting on terminate alternatives have been awakened and have
17191 terminated themselves.
17193 @item Child Activation Wait
17194 The task is waiting for created tasks to complete activation.
17196 @item Accept Statement
17197 The task is waiting on an accept or selective wait statement.
17199 @item Waiting on entry call
17200 The task is waiting on an entry call.
17202 @item Async Select Wait
17203 The task is waiting to start the abortable part of an asynchronous
17207 The task is waiting on a select statement with only a delay
17210 @item Child Termination Wait
17211 The task is sleeping having completed a master within itself, and is
17212 waiting for the tasks dependent on that master to become terminated or
17213 waiting on a terminate Phase.
17215 @item Wait Child in Term Alt
17216 The task is sleeping waiting for tasks on terminate alternatives to
17217 finish terminating.
17219 @item Accepting RV with @var{taskno}
17220 The task is accepting a rendez-vous with the task @var{taskno}.
17224 Name of the task in the program.
17228 @kindex info task @var{taskno}
17229 @item info task @var{taskno}
17230 This command shows detailled informations on the specified task, as in
17231 the following example:
17236 (@value{GDBP}) info tasks
17237 ID TID P-ID Pri State Name
17238 1 8077880 0 15 Child Activation Wait main_task
17239 * 2 807c468 1 15 Runnable task_1
17240 (@value{GDBP}) info task 2
17241 Ada Task: 0x807c468
17245 Parent: 1 (main_task)
17251 @kindex task@r{ (Ada)}
17252 @cindex current Ada task ID
17253 This command prints the ID of the current task.
17259 (@value{GDBP}) info tasks
17260 ID TID P-ID Pri State Name
17261 1 8077870 0 15 Child Activation Wait main_task
17262 * 2 807c458 1 15 Runnable t
17263 (@value{GDBP}) task
17264 [Current task is 2]
17267 @item task @var{taskno}
17268 @cindex Ada task switching
17269 This command is like the @code{thread @var{thread-id}}
17270 command (@pxref{Threads}). It switches the context of debugging
17271 from the current task to the given task.
17277 (@value{GDBP}) info tasks
17278 ID TID P-ID Pri State Name
17279 1 8077870 0 15 Child Activation Wait main_task
17280 * 2 807c458 1 15 Runnable t
17281 (@value{GDBP}) task 1
17282 [Switching to task 1]
17283 #0 0x8067726 in pthread_cond_wait ()
17285 #0 0x8067726 in pthread_cond_wait ()
17286 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
17287 #2 0x805cb63 in system.task_primitives.operations.sleep ()
17288 #3 0x806153e in system.tasking.stages.activate_tasks ()
17289 #4 0x804aacc in un () at un.adb:5
17292 @item break @var{location} task @var{taskno}
17293 @itemx break @var{location} task @var{taskno} if @dots{}
17294 @cindex breakpoints and tasks, in Ada
17295 @cindex task breakpoints, in Ada
17296 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
17297 These commands are like the @code{break @dots{} thread @dots{}}
17298 command (@pxref{Thread Stops}). The
17299 @var{location} argument specifies source lines, as described
17300 in @ref{Specify Location}.
17302 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
17303 to specify that you only want @value{GDBN} to stop the program when a
17304 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
17305 numeric task identifiers assigned by @value{GDBN}, shown in the first
17306 column of the @samp{info tasks} display.
17308 If you do not specify @samp{task @var{taskno}} when you set a
17309 breakpoint, the breakpoint applies to @emph{all} tasks of your
17312 You can use the @code{task} qualifier on conditional breakpoints as
17313 well; in this case, place @samp{task @var{taskno}} before the
17314 breakpoint condition (before the @code{if}).
17322 (@value{GDBP}) info tasks
17323 ID TID P-ID Pri State Name
17324 1 140022020 0 15 Child Activation Wait main_task
17325 2 140045060 1 15 Accept/Select Wait t2
17326 3 140044840 1 15 Runnable t1
17327 * 4 140056040 1 15 Runnable t3
17328 (@value{GDBP}) b 15 task 2
17329 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
17330 (@value{GDBP}) cont
17335 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
17337 (@value{GDBP}) info tasks
17338 ID TID P-ID Pri State Name
17339 1 140022020 0 15 Child Activation Wait main_task
17340 * 2 140045060 1 15 Runnable t2
17341 3 140044840 1 15 Runnable t1
17342 4 140056040 1 15 Delay Sleep t3
17346 @node Ada Tasks and Core Files
17347 @subsubsection Tasking Support when Debugging Core Files
17348 @cindex Ada tasking and core file debugging
17350 When inspecting a core file, as opposed to debugging a live program,
17351 tasking support may be limited or even unavailable, depending on
17352 the platform being used.
17353 For instance, on x86-linux, the list of tasks is available, but task
17354 switching is not supported.
17356 On certain platforms, the debugger needs to perform some
17357 memory writes in order to provide Ada tasking support. When inspecting
17358 a core file, this means that the core file must be opened with read-write
17359 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
17360 Under these circumstances, you should make a backup copy of the core
17361 file before inspecting it with @value{GDBN}.
17363 @node Ravenscar Profile
17364 @subsubsection Tasking Support when using the Ravenscar Profile
17365 @cindex Ravenscar Profile
17367 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
17368 specifically designed for systems with safety-critical real-time
17372 @kindex set ravenscar task-switching on
17373 @cindex task switching with program using Ravenscar Profile
17374 @item set ravenscar task-switching on
17375 Allows task switching when debugging a program that uses the Ravenscar
17376 Profile. This is the default.
17378 @kindex set ravenscar task-switching off
17379 @item set ravenscar task-switching off
17380 Turn off task switching when debugging a program that uses the Ravenscar
17381 Profile. This is mostly intended to disable the code that adds support
17382 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
17383 the Ravenscar runtime is preventing @value{GDBN} from working properly.
17384 To be effective, this command should be run before the program is started.
17386 @kindex show ravenscar task-switching
17387 @item show ravenscar task-switching
17388 Show whether it is possible to switch from task to task in a program
17389 using the Ravenscar Profile.
17394 @subsubsection Ada Settings
17395 @cindex Ada settings
17398 @kindex set varsize-limit
17399 @item set varsize-limit @var{size}
17400 Prevent @value{GDBN} from attempting to evaluate objects whose size
17401 is above the given limit (@var{size}) when those sizes are computed
17402 from run-time quantities. This is typically the case when the object
17403 has a variable size, such as an array whose bounds are not known at
17404 compile time for example. Setting @var{size} to @code{unlimited}
17405 removes the size limitation. By default, the limit is about 65KB.
17407 The purpose of having such a limit is to prevent @value{GDBN} from
17408 trying to grab enormous chunks of virtual memory when asked to evaluate
17409 a quantity whose bounds have been corrupted or have not yet been fully
17410 initialized. The limit applies to the results of some subexpressions
17411 as well as to complete expressions. For example, an expression denoting
17412 a simple integer component, such as @code{x.y.z}, may fail if the size of
17413 @code{x.y} is variable and exceeds @code{size}. On the other hand,
17414 @value{GDBN} is sometimes clever; the expression @code{A(i)}, where
17415 @code{A} is an array variable with non-constant size, will generally
17416 succeed regardless of the bounds on @code{A}, as long as the component
17417 size is less than @var{size}.
17419 @kindex show varsize-limit
17420 @item show varsize-limit
17421 Show the limit on types whose size is determined by run-time quantities.
17425 @subsubsection Known Peculiarities of Ada Mode
17426 @cindex Ada, problems
17428 Besides the omissions listed previously (@pxref{Omissions from Ada}),
17429 we know of several problems with and limitations of Ada mode in
17431 some of which will be fixed with planned future releases of the debugger
17432 and the GNU Ada compiler.
17436 Static constants that the compiler chooses not to materialize as objects in
17437 storage are invisible to the debugger.
17440 Named parameter associations in function argument lists are ignored (the
17441 argument lists are treated as positional).
17444 Many useful library packages are currently invisible to the debugger.
17447 Fixed-point arithmetic, conversions, input, and output is carried out using
17448 floating-point arithmetic, and may give results that only approximate those on
17452 The GNAT compiler never generates the prefix @code{Standard} for any of
17453 the standard symbols defined by the Ada language. @value{GDBN} knows about
17454 this: it will strip the prefix from names when you use it, and will never
17455 look for a name you have so qualified among local symbols, nor match against
17456 symbols in other packages or subprograms. If you have
17457 defined entities anywhere in your program other than parameters and
17458 local variables whose simple names match names in @code{Standard},
17459 GNAT's lack of qualification here can cause confusion. When this happens,
17460 you can usually resolve the confusion
17461 by qualifying the problematic names with package
17462 @code{Standard} explicitly.
17465 Older versions of the compiler sometimes generate erroneous debugging
17466 information, resulting in the debugger incorrectly printing the value
17467 of affected entities. In some cases, the debugger is able to work
17468 around an issue automatically. In other cases, the debugger is able
17469 to work around the issue, but the work-around has to be specifically
17472 @kindex set ada trust-PAD-over-XVS
17473 @kindex show ada trust-PAD-over-XVS
17476 @item set ada trust-PAD-over-XVS on
17477 Configure GDB to strictly follow the GNAT encoding when computing the
17478 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
17479 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
17480 a complete description of the encoding used by the GNAT compiler).
17481 This is the default.
17483 @item set ada trust-PAD-over-XVS off
17484 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
17485 sometimes prints the wrong value for certain entities, changing @code{ada
17486 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
17487 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
17488 @code{off}, but this incurs a slight performance penalty, so it is
17489 recommended to leave this setting to @code{on} unless necessary.
17493 @cindex GNAT descriptive types
17494 @cindex GNAT encoding
17495 Internally, the debugger also relies on the compiler following a number
17496 of conventions known as the @samp{GNAT Encoding}, all documented in
17497 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
17498 how the debugging information should be generated for certain types.
17499 In particular, this convention makes use of @dfn{descriptive types},
17500 which are artificial types generated purely to help the debugger.
17502 These encodings were defined at a time when the debugging information
17503 format used was not powerful enough to describe some of the more complex
17504 types available in Ada. Since DWARF allows us to express nearly all
17505 Ada features, the long-term goal is to slowly replace these descriptive
17506 types by their pure DWARF equivalent. To facilitate that transition,
17507 a new maintenance option is available to force the debugger to ignore
17508 those descriptive types. It allows the user to quickly evaluate how
17509 well @value{GDBN} works without them.
17513 @kindex maint ada set ignore-descriptive-types
17514 @item maintenance ada set ignore-descriptive-types [on|off]
17515 Control whether the debugger should ignore descriptive types.
17516 The default is not to ignore descriptives types (@code{off}).
17518 @kindex maint ada show ignore-descriptive-types
17519 @item maintenance ada show ignore-descriptive-types
17520 Show if descriptive types are ignored by @value{GDBN}.
17524 @node Unsupported Languages
17525 @section Unsupported Languages
17527 @cindex unsupported languages
17528 @cindex minimal language
17529 In addition to the other fully-supported programming languages,
17530 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17531 It does not represent a real programming language, but provides a set
17532 of capabilities close to what the C or assembly languages provide.
17533 This should allow most simple operations to be performed while debugging
17534 an application that uses a language currently not supported by @value{GDBN}.
17536 If the language is set to @code{auto}, @value{GDBN} will automatically
17537 select this language if the current frame corresponds to an unsupported
17541 @chapter Examining the Symbol Table
17543 The commands described in this chapter allow you to inquire about the
17544 symbols (names of variables, functions and types) defined in your
17545 program. This information is inherent in the text of your program and
17546 does not change as your program executes. @value{GDBN} finds it in your
17547 program's symbol table, in the file indicated when you started @value{GDBN}
17548 (@pxref{File Options, ,Choosing Files}), or by one of the
17549 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17551 @cindex symbol names
17552 @cindex names of symbols
17553 @cindex quoting names
17554 @anchor{quoting names}
17555 Occasionally, you may need to refer to symbols that contain unusual
17556 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17557 most frequent case is in referring to static variables in other
17558 source files (@pxref{Variables,,Program Variables}). File names
17559 are recorded in object files as debugging symbols, but @value{GDBN} would
17560 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17561 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17562 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17569 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17572 @cindex case-insensitive symbol names
17573 @cindex case sensitivity in symbol names
17574 @kindex set case-sensitive
17575 @item set case-sensitive on
17576 @itemx set case-sensitive off
17577 @itemx set case-sensitive auto
17578 Normally, when @value{GDBN} looks up symbols, it matches their names
17579 with case sensitivity determined by the current source language.
17580 Occasionally, you may wish to control that. The command @code{set
17581 case-sensitive} lets you do that by specifying @code{on} for
17582 case-sensitive matches or @code{off} for case-insensitive ones. If
17583 you specify @code{auto}, case sensitivity is reset to the default
17584 suitable for the source language. The default is case-sensitive
17585 matches for all languages except for Fortran, for which the default is
17586 case-insensitive matches.
17588 @kindex show case-sensitive
17589 @item show case-sensitive
17590 This command shows the current setting of case sensitivity for symbols
17593 @kindex set print type methods
17594 @item set print type methods
17595 @itemx set print type methods on
17596 @itemx set print type methods off
17597 Normally, when @value{GDBN} prints a class, it displays any methods
17598 declared in that class. You can control this behavior either by
17599 passing the appropriate flag to @code{ptype}, or using @command{set
17600 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17601 display the methods; this is the default. Specifying @code{off} will
17602 cause @value{GDBN} to omit the methods.
17604 @kindex show print type methods
17605 @item show print type methods
17606 This command shows the current setting of method display when printing
17609 @kindex set print type nested-type-limit
17610 @item set print type nested-type-limit @var{limit}
17611 @itemx set print type nested-type-limit unlimited
17612 Set the limit of displayed nested types that the type printer will
17613 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17614 nested definitions. By default, the type printer will not show any nested
17615 types defined in classes.
17617 @kindex show print type nested-type-limit
17618 @item show print type nested-type-limit
17619 This command shows the current display limit of nested types when
17622 @kindex set print type typedefs
17623 @item set print type typedefs
17624 @itemx set print type typedefs on
17625 @itemx set print type typedefs off
17627 Normally, when @value{GDBN} prints a class, it displays any typedefs
17628 defined in that class. You can control this behavior either by
17629 passing the appropriate flag to @code{ptype}, or using @command{set
17630 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17631 display the typedef definitions; this is the default. Specifying
17632 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17633 Note that this controls whether the typedef definition itself is
17634 printed, not whether typedef names are substituted when printing other
17637 @kindex show print type typedefs
17638 @item show print type typedefs
17639 This command shows the current setting of typedef display when
17642 @kindex info address
17643 @cindex address of a symbol
17644 @item info address @var{symbol}
17645 Describe where the data for @var{symbol} is stored. For a register
17646 variable, this says which register it is kept in. For a non-register
17647 local variable, this prints the stack-frame offset at which the variable
17650 Note the contrast with @samp{print &@var{symbol}}, which does not work
17651 at all for a register variable, and for a stack local variable prints
17652 the exact address of the current instantiation of the variable.
17654 @kindex info symbol
17655 @cindex symbol from address
17656 @cindex closest symbol and offset for an address
17657 @item info symbol @var{addr}
17658 Print the name of a symbol which is stored at the address @var{addr}.
17659 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17660 nearest symbol and an offset from it:
17663 (@value{GDBP}) info symbol 0x54320
17664 _initialize_vx + 396 in section .text
17668 This is the opposite of the @code{info address} command. You can use
17669 it to find out the name of a variable or a function given its address.
17671 For dynamically linked executables, the name of executable or shared
17672 library containing the symbol is also printed:
17675 (@value{GDBP}) info symbol 0x400225
17676 _start + 5 in section .text of /tmp/a.out
17677 (@value{GDBP}) info symbol 0x2aaaac2811cf
17678 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17683 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17684 Demangle @var{name}.
17685 If @var{language} is provided it is the name of the language to demangle
17686 @var{name} in. Otherwise @var{name} is demangled in the current language.
17688 The @samp{--} option specifies the end of options,
17689 and is useful when @var{name} begins with a dash.
17691 The parameter @code{demangle-style} specifies how to interpret the kind
17692 of mangling used. @xref{Print Settings}.
17695 @item whatis[/@var{flags}] [@var{arg}]
17696 Print the data type of @var{arg}, which can be either an expression
17697 or a name of a data type. With no argument, print the data type of
17698 @code{$}, the last value in the value history.
17700 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17701 is not actually evaluated, and any side-effecting operations (such as
17702 assignments or function calls) inside it do not take place.
17704 If @var{arg} is a variable or an expression, @code{whatis} prints its
17705 literal type as it is used in the source code. If the type was
17706 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17707 the data type underlying the @code{typedef}. If the type of the
17708 variable or the expression is a compound data type, such as
17709 @code{struct} or @code{class}, @code{whatis} never prints their
17710 fields or methods. It just prints the @code{struct}/@code{class}
17711 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17712 such a compound data type, use @code{ptype}.
17714 If @var{arg} is a type name that was defined using @code{typedef},
17715 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17716 Unrolling means that @code{whatis} will show the underlying type used
17717 in the @code{typedef} declaration of @var{arg}. However, if that
17718 underlying type is also a @code{typedef}, @code{whatis} will not
17721 For C code, the type names may also have the form @samp{class
17722 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17723 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17725 @var{flags} can be used to modify how the type is displayed.
17726 Available flags are:
17730 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17731 parameters and typedefs defined in a class when printing the class'
17732 members. The @code{/r} flag disables this.
17735 Do not print methods defined in the class.
17738 Print methods defined in the class. This is the default, but the flag
17739 exists in case you change the default with @command{set print type methods}.
17742 Do not print typedefs defined in the class. Note that this controls
17743 whether the typedef definition itself is printed, not whether typedef
17744 names are substituted when printing other types.
17747 Print typedefs defined in the class. This is the default, but the flag
17748 exists in case you change the default with @command{set print type typedefs}.
17751 Print the offsets and sizes of fields in a struct, similar to what the
17752 @command{pahole} tool does. This option implies the @code{/tm} flags.
17754 For example, given the following declarations:
17790 Issuing a @kbd{ptype /o struct tuv} command would print:
17793 (@value{GDBP}) ptype /o struct tuv
17794 /* offset | size */ type = struct tuv @{
17795 /* 0 | 4 */ int a1;
17796 /* XXX 4-byte hole */
17797 /* 8 | 8 */ char *a2;
17798 /* 16 | 4 */ int a3;
17800 /* total size (bytes): 24 */
17804 Notice the format of the first column of comments. There, you can
17805 find two parts separated by the @samp{|} character: the @emph{offset},
17806 which indicates where the field is located inside the struct, in
17807 bytes, and the @emph{size} of the field. Another interesting line is
17808 the marker of a @emph{hole} in the struct, indicating that it may be
17809 possible to pack the struct and make it use less space by reorganizing
17812 It is also possible to print offsets inside an union:
17815 (@value{GDBP}) ptype /o union qwe
17816 /* offset | size */ type = union qwe @{
17817 /* 24 */ struct tuv @{
17818 /* 0 | 4 */ int a1;
17819 /* XXX 4-byte hole */
17820 /* 8 | 8 */ char *a2;
17821 /* 16 | 4 */ int a3;
17823 /* total size (bytes): 24 */
17825 /* 40 */ struct xyz @{
17826 /* 0 | 4 */ int f1;
17827 /* 4 | 1 */ char f2;
17828 /* XXX 3-byte hole */
17829 /* 8 | 8 */ void *f3;
17830 /* 16 | 24 */ struct tuv @{
17831 /* 16 | 4 */ int a1;
17832 /* XXX 4-byte hole */
17833 /* 24 | 8 */ char *a2;
17834 /* 32 | 4 */ int a3;
17836 /* total size (bytes): 24 */
17839 /* total size (bytes): 40 */
17842 /* total size (bytes): 40 */
17846 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17847 same space (because we are dealing with an union), the offset is not
17848 printed for them. However, you can still examine the offset of each
17849 of these structures' fields.
17851 Another useful scenario is printing the offsets of a struct containing
17855 (@value{GDBP}) ptype /o struct tyu
17856 /* offset | size */ type = struct tyu @{
17857 /* 0:31 | 4 */ int a1 : 1;
17858 /* 0:28 | 4 */ int a2 : 3;
17859 /* 0: 5 | 4 */ int a3 : 23;
17860 /* 3: 3 | 1 */ signed char a4 : 2;
17861 /* XXX 3-bit hole */
17862 /* XXX 4-byte hole */
17863 /* 8 | 8 */ int64_t a5;
17864 /* 16: 0 | 4 */ int a6 : 5;
17865 /* 16: 5 | 8 */ int64_t a7 : 3;
17866 "/* XXX 7-byte padding */
17868 /* total size (bytes): 24 */
17872 Note how the offset information is now extended to also include the
17873 first bit of the bitfield.
17877 @item ptype[/@var{flags}] [@var{arg}]
17878 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17879 detailed description of the type, instead of just the name of the type.
17880 @xref{Expressions, ,Expressions}.
17882 Contrary to @code{whatis}, @code{ptype} always unrolls any
17883 @code{typedef}s in its argument declaration, whether the argument is
17884 a variable, expression, or a data type. This means that @code{ptype}
17885 of a variable or an expression will not print literally its type as
17886 present in the source code---use @code{whatis} for that. @code{typedef}s at
17887 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17888 fields, methods and inner @code{class typedef}s of @code{struct}s,
17889 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17891 For example, for this variable declaration:
17894 typedef double real_t;
17895 struct complex @{ real_t real; double imag; @};
17896 typedef struct complex complex_t;
17898 real_t *real_pointer_var;
17902 the two commands give this output:
17906 (@value{GDBP}) whatis var
17908 (@value{GDBP}) ptype var
17909 type = struct complex @{
17913 (@value{GDBP}) whatis complex_t
17914 type = struct complex
17915 (@value{GDBP}) whatis struct complex
17916 type = struct complex
17917 (@value{GDBP}) ptype struct complex
17918 type = struct complex @{
17922 (@value{GDBP}) whatis real_pointer_var
17924 (@value{GDBP}) ptype real_pointer_var
17930 As with @code{whatis}, using @code{ptype} without an argument refers to
17931 the type of @code{$}, the last value in the value history.
17933 @cindex incomplete type
17934 Sometimes, programs use opaque data types or incomplete specifications
17935 of complex data structure. If the debug information included in the
17936 program does not allow @value{GDBN} to display a full declaration of
17937 the data type, it will say @samp{<incomplete type>}. For example,
17938 given these declarations:
17942 struct foo *fooptr;
17946 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17949 (@value{GDBP}) ptype foo
17950 $1 = <incomplete type>
17954 ``Incomplete type'' is C terminology for data types that are not
17955 completely specified.
17957 @cindex unknown type
17958 Othertimes, information about a variable's type is completely absent
17959 from the debug information included in the program. This most often
17960 happens when the program or library where the variable is defined
17961 includes no debug information at all. @value{GDBN} knows the variable
17962 exists from inspecting the linker/loader symbol table (e.g., the ELF
17963 dynamic symbol table), but such symbols do not contain type
17964 information. Inspecting the type of a (global) variable for which
17965 @value{GDBN} has no type information shows:
17968 (@value{GDBP}) ptype var
17969 type = <data variable, no debug info>
17972 @xref{Variables, no debug info variables}, for how to print the values
17976 @item info types @var{regexp}
17978 Print a brief description of all types whose names match the regular
17979 expression @var{regexp} (or all types in your program, if you supply
17980 no argument). Each complete typename is matched as though it were a
17981 complete line; thus, @samp{i type value} gives information on all
17982 types in your program whose names include the string @code{value}, but
17983 @samp{i type ^value$} gives information only on types whose complete
17984 name is @code{value}.
17986 In programs using different languages, @value{GDBN} chooses the syntax
17987 to print the type description according to the
17988 @samp{set language} value: using @samp{set language auto}
17989 (see @ref{Automatically, ,Set Language Automatically}) means to use the
17990 language of the type, other values mean to use
17991 the manually specified language (see @ref{Manually, ,Set Language Manually}).
17993 This command differs from @code{ptype} in two ways: first, like
17994 @code{whatis}, it does not print a detailed description; second, it
17995 lists all source files and line numbers where a type is defined.
17997 @kindex info type-printers
17998 @item info type-printers
17999 Versions of @value{GDBN} that ship with Python scripting enabled may
18000 have ``type printers'' available. When using @command{ptype} or
18001 @command{whatis}, these printers are consulted when the name of a type
18002 is needed. @xref{Type Printing API}, for more information on writing
18005 @code{info type-printers} displays all the available type printers.
18007 @kindex enable type-printer
18008 @kindex disable type-printer
18009 @item enable type-printer @var{name}@dots{}
18010 @item disable type-printer @var{name}@dots{}
18011 These commands can be used to enable or disable type printers.
18014 @cindex local variables
18015 @item info scope @var{location}
18016 List all the variables local to a particular scope. This command
18017 accepts a @var{location} argument---a function name, a source line, or
18018 an address preceded by a @samp{*}, and prints all the variables local
18019 to the scope defined by that location. (@xref{Specify Location}, for
18020 details about supported forms of @var{location}.) For example:
18023 (@value{GDBP}) @b{info scope command_line_handler}
18024 Scope for command_line_handler:
18025 Symbol rl is an argument at stack/frame offset 8, length 4.
18026 Symbol linebuffer is in static storage at address 0x150a18, length 4.
18027 Symbol linelength is in static storage at address 0x150a1c, length 4.
18028 Symbol p is a local variable in register $esi, length 4.
18029 Symbol p1 is a local variable in register $ebx, length 4.
18030 Symbol nline is a local variable in register $edx, length 4.
18031 Symbol repeat is a local variable at frame offset -8, length 4.
18035 This command is especially useful for determining what data to collect
18036 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
18039 @kindex info source
18041 Show information about the current source file---that is, the source file for
18042 the function containing the current point of execution:
18045 the name of the source file, and the directory containing it,
18047 the directory it was compiled in,
18049 its length, in lines,
18051 which programming language it is written in,
18053 if the debug information provides it, the program that compiled the file
18054 (which may include, e.g., the compiler version and command line arguments),
18056 whether the executable includes debugging information for that file, and
18057 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
18059 whether the debugging information includes information about
18060 preprocessor macros.
18064 @kindex info sources
18066 Print the names of all source files in your program for which there is
18067 debugging information, organized into two lists: files whose symbols
18068 have already been read, and files whose symbols will be read when needed.
18070 @kindex info functions
18071 @item info functions [-q]
18072 Print the names and data types of all defined functions.
18073 Similarly to @samp{info types}, this command groups its output by source
18074 files and annotates each function definition with its source line
18077 In programs using different languages, @value{GDBN} chooses the syntax
18078 to print the function name and type according to the
18079 @samp{set language} value: using @samp{set language auto}
18080 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18081 language of the function, other values mean to use
18082 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18084 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18085 printing header information and messages explaining why no functions
18088 @item info functions [-q] [-t @var{type_regexp}] [@var{regexp}]
18089 Like @samp{info functions}, but only print the names and data types
18090 of the functions selected with the provided regexp(s).
18092 If @var{regexp} is provided, print only the functions whose names
18093 match the regular expression @var{regexp}.
18094 Thus, @samp{info fun step} finds all functions whose
18095 names include @code{step}; @samp{info fun ^step} finds those whose names
18096 start with @code{step}. If a function name contains characters that
18097 conflict with the regular expression language (e.g.@:
18098 @samp{operator*()}), they may be quoted with a backslash.
18100 If @var{type_regexp} is provided, print only the functions whose
18101 types, as printed by the @code{whatis} command, match
18102 the regular expression @var{type_regexp}.
18103 If @var{type_regexp} contains space(s), it should be enclosed in
18104 quote characters. If needed, use backslash to escape the meaning
18105 of special characters or quotes.
18106 Thus, @samp{info fun -t '^int ('} finds the functions that return
18107 an integer; @samp{info fun -t '(.*int.*'} finds the functions that
18108 have an argument type containing int; @samp{info fun -t '^int (' ^step}
18109 finds the functions whose names start with @code{step} and that return
18112 If both @var{regexp} and @var{type_regexp} are provided, a function
18113 is printed only if its name matches @var{regexp} and its type matches
18117 @kindex info variables
18118 @item info variables [-q]
18119 Print the names and data types of all variables that are defined
18120 outside of functions (i.e.@: excluding local variables).
18121 The printed variables are grouped by source files and annotated with
18122 their respective source line numbers.
18124 In programs using different languages, @value{GDBN} chooses the syntax
18125 to print the variable name and type according to the
18126 @samp{set language} value: using @samp{set language auto}
18127 (see @ref{Automatically, ,Set Language Automatically}) means to use the
18128 language of the variable, other values mean to use
18129 the manually specified language (see @ref{Manually, ,Set Language Manually}).
18131 The optional flag @samp{-q}, which stands for @samp{quiet}, disables
18132 printing header information and messages explaining why no variables
18135 @item info variables [-q] [-t @var{type_regexp}] [@var{regexp}]
18136 Like @kbd{info variables}, but only print the variables selected
18137 with the provided regexp(s).
18139 If @var{regexp} is provided, print only the variables whose names
18140 match the regular expression @var{regexp}.
18142 If @var{type_regexp} is provided, print only the variables whose
18143 types, as printed by the @code{whatis} command, match
18144 the regular expression @var{type_regexp}.
18145 If @var{type_regexp} contains space(s), it should be enclosed in
18146 quote characters. If needed, use backslash to escape the meaning
18147 of special characters or quotes.
18149 If both @var{regexp} and @var{type_regexp} are provided, an argument
18150 is printed only if its name matches @var{regexp} and its type matches
18153 @kindex info classes
18154 @cindex Objective-C, classes and selectors
18156 @itemx info classes @var{regexp}
18157 Display all Objective-C classes in your program, or
18158 (with the @var{regexp} argument) all those matching a particular regular
18161 @kindex info selectors
18162 @item info selectors
18163 @itemx info selectors @var{regexp}
18164 Display all Objective-C selectors in your program, or
18165 (with the @var{regexp} argument) all those matching a particular regular
18169 This was never implemented.
18170 @kindex info methods
18172 @itemx info methods @var{regexp}
18173 The @code{info methods} command permits the user to examine all defined
18174 methods within C@t{++} program, or (with the @var{regexp} argument) a
18175 specific set of methods found in the various C@t{++} classes. Many
18176 C@t{++} classes provide a large number of methods. Thus, the output
18177 from the @code{ptype} command can be overwhelming and hard to use. The
18178 @code{info-methods} command filters the methods, printing only those
18179 which match the regular-expression @var{regexp}.
18182 @cindex opaque data types
18183 @kindex set opaque-type-resolution
18184 @item set opaque-type-resolution on
18185 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
18186 declared as a pointer to a @code{struct}, @code{class}, or
18187 @code{union}---for example, @code{struct MyType *}---that is used in one
18188 source file although the full declaration of @code{struct MyType} is in
18189 another source file. The default is on.
18191 A change in the setting of this subcommand will not take effect until
18192 the next time symbols for a file are loaded.
18194 @item set opaque-type-resolution off
18195 Tell @value{GDBN} not to resolve opaque types. In this case, the type
18196 is printed as follows:
18198 @{<no data fields>@}
18201 @kindex show opaque-type-resolution
18202 @item show opaque-type-resolution
18203 Show whether opaque types are resolved or not.
18205 @kindex set print symbol-loading
18206 @cindex print messages when symbols are loaded
18207 @item set print symbol-loading
18208 @itemx set print symbol-loading full
18209 @itemx set print symbol-loading brief
18210 @itemx set print symbol-loading off
18211 The @code{set print symbol-loading} command allows you to control the
18212 printing of messages when @value{GDBN} loads symbol information.
18213 By default a message is printed for the executable and one for each
18214 shared library, and normally this is what you want. However, when
18215 debugging apps with large numbers of shared libraries these messages
18217 When set to @code{brief} a message is printed for each executable,
18218 and when @value{GDBN} loads a collection of shared libraries at once
18219 it will only print one message regardless of the number of shared
18220 libraries. When set to @code{off} no messages are printed.
18222 @kindex show print symbol-loading
18223 @item show print symbol-loading
18224 Show whether messages will be printed when a @value{GDBN} command
18225 entered from the keyboard causes symbol information to be loaded.
18227 @kindex maint print symbols
18228 @cindex symbol dump
18229 @kindex maint print psymbols
18230 @cindex partial symbol dump
18231 @kindex maint print msymbols
18232 @cindex minimal symbol dump
18233 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
18234 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18235 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18236 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18237 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
18238 Write a dump of debugging symbol data into the file @var{filename} or
18239 the terminal if @var{filename} is unspecified.
18240 If @code{-objfile @var{objfile}} is specified, only dump symbols for
18242 If @code{-pc @var{address}} is specified, only dump symbols for the file
18243 with code at that address. Note that @var{address} may be a symbol like
18245 If @code{-source @var{source}} is specified, only dump symbols for that
18248 These commands are used to debug the @value{GDBN} symbol-reading code.
18249 These commands do not modify internal @value{GDBN} state, therefore
18250 @samp{maint print symbols} will only print symbols for already expanded symbol
18252 You can use the command @code{info sources} to find out which files these are.
18253 If you use @samp{maint print psymbols} instead, the dump shows information
18254 about symbols that @value{GDBN} only knows partially---that is, symbols
18255 defined in files that @value{GDBN} has skimmed, but not yet read completely.
18256 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
18259 @xref{Files, ,Commands to Specify Files}, for a discussion of how
18260 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
18262 @kindex maint info symtabs
18263 @kindex maint info psymtabs
18264 @cindex listing @value{GDBN}'s internal symbol tables
18265 @cindex symbol tables, listing @value{GDBN}'s internal
18266 @cindex full symbol tables, listing @value{GDBN}'s internal
18267 @cindex partial symbol tables, listing @value{GDBN}'s internal
18268 @item maint info symtabs @r{[} @var{regexp} @r{]}
18269 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
18271 List the @code{struct symtab} or @code{struct partial_symtab}
18272 structures whose names match @var{regexp}. If @var{regexp} is not
18273 given, list them all. The output includes expressions which you can
18274 copy into a @value{GDBN} debugging this one to examine a particular
18275 structure in more detail. For example:
18278 (@value{GDBP}) maint info psymtabs dwarf2read
18279 @{ objfile /home/gnu/build/gdb/gdb
18280 ((struct objfile *) 0x82e69d0)
18281 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
18282 ((struct partial_symtab *) 0x8474b10)
18285 text addresses 0x814d3c8 -- 0x8158074
18286 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
18287 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
18288 dependencies (none)
18291 (@value{GDBP}) maint info symtabs
18295 We see that there is one partial symbol table whose filename contains
18296 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
18297 and we see that @value{GDBN} has not read in any symtabs yet at all.
18298 If we set a breakpoint on a function, that will cause @value{GDBN} to
18299 read the symtab for the compilation unit containing that function:
18302 (@value{GDBP}) break dwarf2_psymtab_to_symtab
18303 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
18305 (@value{GDBP}) maint info symtabs
18306 @{ objfile /home/gnu/build/gdb/gdb
18307 ((struct objfile *) 0x82e69d0)
18308 @{ symtab /home/gnu/src/gdb/dwarf2read.c
18309 ((struct symtab *) 0x86c1f38)
18312 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
18313 linetable ((struct linetable *) 0x8370fa0)
18314 debugformat DWARF 2
18320 @kindex maint info line-table
18321 @cindex listing @value{GDBN}'s internal line tables
18322 @cindex line tables, listing @value{GDBN}'s internal
18323 @item maint info line-table @r{[} @var{regexp} @r{]}
18325 List the @code{struct linetable} from all @code{struct symtab}
18326 instances whose name matches @var{regexp}. If @var{regexp} is not
18327 given, list the @code{struct linetable} from all @code{struct symtab}.
18329 @kindex maint set symbol-cache-size
18330 @cindex symbol cache size
18331 @item maint set symbol-cache-size @var{size}
18332 Set the size of the symbol cache to @var{size}.
18333 The default size is intended to be good enough for debugging
18334 most applications. This option exists to allow for experimenting
18335 with different sizes.
18337 @kindex maint show symbol-cache-size
18338 @item maint show symbol-cache-size
18339 Show the size of the symbol cache.
18341 @kindex maint print symbol-cache
18342 @cindex symbol cache, printing its contents
18343 @item maint print symbol-cache
18344 Print the contents of the symbol cache.
18345 This is useful when debugging symbol cache issues.
18347 @kindex maint print symbol-cache-statistics
18348 @cindex symbol cache, printing usage statistics
18349 @item maint print symbol-cache-statistics
18350 Print symbol cache usage statistics.
18351 This helps determine how well the cache is being utilized.
18353 @kindex maint flush-symbol-cache
18354 @cindex symbol cache, flushing
18355 @item maint flush-symbol-cache
18356 Flush the contents of the symbol cache, all entries are removed.
18357 This command is useful when debugging the symbol cache.
18358 It is also useful when collecting performance data.
18363 @chapter Altering Execution
18365 Once you think you have found an error in your program, you might want to
18366 find out for certain whether correcting the apparent error would lead to
18367 correct results in the rest of the run. You can find the answer by
18368 experiment, using the @value{GDBN} features for altering execution of the
18371 For example, you can store new values into variables or memory
18372 locations, give your program a signal, restart it at a different
18373 address, or even return prematurely from a function.
18376 * Assignment:: Assignment to variables
18377 * Jumping:: Continuing at a different address
18378 * Signaling:: Giving your program a signal
18379 * Returning:: Returning from a function
18380 * Calling:: Calling your program's functions
18381 * Patching:: Patching your program
18382 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
18386 @section Assignment to Variables
18389 @cindex setting variables
18390 To alter the value of a variable, evaluate an assignment expression.
18391 @xref{Expressions, ,Expressions}. For example,
18398 stores the value 4 into the variable @code{x}, and then prints the
18399 value of the assignment expression (which is 4).
18400 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
18401 information on operators in supported languages.
18403 @kindex set variable
18404 @cindex variables, setting
18405 If you are not interested in seeing the value of the assignment, use the
18406 @code{set} command instead of the @code{print} command. @code{set} is
18407 really the same as @code{print} except that the expression's value is
18408 not printed and is not put in the value history (@pxref{Value History,
18409 ,Value History}). The expression is evaluated only for its effects.
18411 If the beginning of the argument string of the @code{set} command
18412 appears identical to a @code{set} subcommand, use the @code{set
18413 variable} command instead of just @code{set}. This command is identical
18414 to @code{set} except for its lack of subcommands. For example, if your
18415 program has a variable @code{width}, you get an error if you try to set
18416 a new value with just @samp{set width=13}, because @value{GDBN} has the
18417 command @code{set width}:
18420 (@value{GDBP}) whatis width
18422 (@value{GDBP}) p width
18424 (@value{GDBP}) set width=47
18425 Invalid syntax in expression.
18429 The invalid expression, of course, is @samp{=47}. In
18430 order to actually set the program's variable @code{width}, use
18433 (@value{GDBP}) set var width=47
18436 Because the @code{set} command has many subcommands that can conflict
18437 with the names of program variables, it is a good idea to use the
18438 @code{set variable} command instead of just @code{set}. For example, if
18439 your program has a variable @code{g}, you run into problems if you try
18440 to set a new value with just @samp{set g=4}, because @value{GDBN} has
18441 the command @code{set gnutarget}, abbreviated @code{set g}:
18445 (@value{GDBP}) whatis g
18449 (@value{GDBP}) set g=4
18453 The program being debugged has been started already.
18454 Start it from the beginning? (y or n) y
18455 Starting program: /home/smith/cc_progs/a.out
18456 "/home/smith/cc_progs/a.out": can't open to read symbols:
18457 Invalid bfd target.
18458 (@value{GDBP}) show g
18459 The current BFD target is "=4".
18464 The program variable @code{g} did not change, and you silently set the
18465 @code{gnutarget} to an invalid value. In order to set the variable
18469 (@value{GDBP}) set var g=4
18472 @value{GDBN} allows more implicit conversions in assignments than C; you can
18473 freely store an integer value into a pointer variable or vice versa,
18474 and you can convert any structure to any other structure that is the
18475 same length or shorter.
18476 @comment FIXME: how do structs align/pad in these conversions?
18477 @comment /doc@cygnus.com 18dec1990
18479 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
18480 construct to generate a value of specified type at a specified address
18481 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
18482 to memory location @code{0x83040} as an integer (which implies a certain size
18483 and representation in memory), and
18486 set @{int@}0x83040 = 4
18490 stores the value 4 into that memory location.
18493 @section Continuing at a Different Address
18495 Ordinarily, when you continue your program, you do so at the place where
18496 it stopped, with the @code{continue} command. You can instead continue at
18497 an address of your own choosing, with the following commands:
18501 @kindex j @r{(@code{jump})}
18502 @item jump @var{location}
18503 @itemx j @var{location}
18504 Resume execution at @var{location}. Execution stops again immediately
18505 if there is a breakpoint there. @xref{Specify Location}, for a description
18506 of the different forms of @var{location}. It is common
18507 practice to use the @code{tbreak} command in conjunction with
18508 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
18510 The @code{jump} command does not change the current stack frame, or
18511 the stack pointer, or the contents of any memory location or any
18512 register other than the program counter. If @var{location} is in
18513 a different function from the one currently executing, the results may
18514 be bizarre if the two functions expect different patterns of arguments or
18515 of local variables. For this reason, the @code{jump} command requests
18516 confirmation if the specified line is not in the function currently
18517 executing. However, even bizarre results are predictable if you are
18518 well acquainted with the machine-language code of your program.
18521 On many systems, you can get much the same effect as the @code{jump}
18522 command by storing a new value into the register @code{$pc}. The
18523 difference is that this does not start your program running; it only
18524 changes the address of where it @emph{will} run when you continue. For
18532 makes the next @code{continue} command or stepping command execute at
18533 address @code{0x485}, rather than at the address where your program stopped.
18534 @xref{Continuing and Stepping, ,Continuing and Stepping}.
18536 The most common occasion to use the @code{jump} command is to back
18537 up---perhaps with more breakpoints set---over a portion of a program
18538 that has already executed, in order to examine its execution in more
18543 @section Giving your Program a Signal
18544 @cindex deliver a signal to a program
18548 @item signal @var{signal}
18549 Resume execution where your program is stopped, but immediately give it the
18550 signal @var{signal}. The @var{signal} can be the name or the number of a
18551 signal. For example, on many systems @code{signal 2} and @code{signal
18552 SIGINT} are both ways of sending an interrupt signal.
18554 Alternatively, if @var{signal} is zero, continue execution without
18555 giving a signal. This is useful when your program stopped on account of
18556 a signal and would ordinarily see the signal when resumed with the
18557 @code{continue} command; @samp{signal 0} causes it to resume without a
18560 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
18561 delivered to the currently selected thread, not the thread that last
18562 reported a stop. This includes the situation where a thread was
18563 stopped due to a signal. So if you want to continue execution
18564 suppressing the signal that stopped a thread, you should select that
18565 same thread before issuing the @samp{signal 0} command. If you issue
18566 the @samp{signal 0} command with another thread as the selected one,
18567 @value{GDBN} detects that and asks for confirmation.
18569 Invoking the @code{signal} command is not the same as invoking the
18570 @code{kill} utility from the shell. Sending a signal with @code{kill}
18571 causes @value{GDBN} to decide what to do with the signal depending on
18572 the signal handling tables (@pxref{Signals}). The @code{signal} command
18573 passes the signal directly to your program.
18575 @code{signal} does not repeat when you press @key{RET} a second time
18576 after executing the command.
18578 @kindex queue-signal
18579 @item queue-signal @var{signal}
18580 Queue @var{signal} to be delivered immediately to the current thread
18581 when execution of the thread resumes. The @var{signal} can be the name or
18582 the number of a signal. For example, on many systems @code{signal 2} and
18583 @code{signal SIGINT} are both ways of sending an interrupt signal.
18584 The handling of the signal must be set to pass the signal to the program,
18585 otherwise @value{GDBN} will report an error.
18586 You can control the handling of signals from @value{GDBN} with the
18587 @code{handle} command (@pxref{Signals}).
18589 Alternatively, if @var{signal} is zero, any currently queued signal
18590 for the current thread is discarded and when execution resumes no signal
18591 will be delivered. This is useful when your program stopped on account
18592 of a signal and would ordinarily see the signal when resumed with the
18593 @code{continue} command.
18595 This command differs from the @code{signal} command in that the signal
18596 is just queued, execution is not resumed. And @code{queue-signal} cannot
18597 be used to pass a signal whose handling state has been set to @code{nopass}
18602 @xref{stepping into signal handlers}, for information on how stepping
18603 commands behave when the thread has a signal queued.
18606 @section Returning from a Function
18609 @cindex returning from a function
18612 @itemx return @var{expression}
18613 You can cancel execution of a function call with the @code{return}
18614 command. If you give an
18615 @var{expression} argument, its value is used as the function's return
18619 When you use @code{return}, @value{GDBN} discards the selected stack frame
18620 (and all frames within it). You can think of this as making the
18621 discarded frame return prematurely. If you wish to specify a value to
18622 be returned, give that value as the argument to @code{return}.
18624 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18625 Frame}), and any other frames inside of it, leaving its caller as the
18626 innermost remaining frame. That frame becomes selected. The
18627 specified value is stored in the registers used for returning values
18630 The @code{return} command does not resume execution; it leaves the
18631 program stopped in the state that would exist if the function had just
18632 returned. In contrast, the @code{finish} command (@pxref{Continuing
18633 and Stepping, ,Continuing and Stepping}) resumes execution until the
18634 selected stack frame returns naturally.
18636 @value{GDBN} needs to know how the @var{expression} argument should be set for
18637 the inferior. The concrete registers assignment depends on the OS ABI and the
18638 type being returned by the selected stack frame. For example it is common for
18639 OS ABI to return floating point values in FPU registers while integer values in
18640 CPU registers. Still some ABIs return even floating point values in CPU
18641 registers. Larger integer widths (such as @code{long long int}) also have
18642 specific placement rules. @value{GDBN} already knows the OS ABI from its
18643 current target so it needs to find out also the type being returned to make the
18644 assignment into the right register(s).
18646 Normally, the selected stack frame has debug info. @value{GDBN} will always
18647 use the debug info instead of the implicit type of @var{expression} when the
18648 debug info is available. For example, if you type @kbd{return -1}, and the
18649 function in the current stack frame is declared to return a @code{long long
18650 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18651 into a @code{long long int}:
18654 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18656 (@value{GDBP}) return -1
18657 Make func return now? (y or n) y
18658 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18659 43 printf ("result=%lld\n", func ());
18663 However, if the selected stack frame does not have a debug info, e.g., if the
18664 function was compiled without debug info, @value{GDBN} has to find out the type
18665 to return from user. Specifying a different type by mistake may set the value
18666 in different inferior registers than the caller code expects. For example,
18667 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18668 of a @code{long long int} result for a debug info less function (on 32-bit
18669 architectures). Therefore the user is required to specify the return type by
18670 an appropriate cast explicitly:
18673 Breakpoint 2, 0x0040050b in func ()
18674 (@value{GDBP}) return -1
18675 Return value type not available for selected stack frame.
18676 Please use an explicit cast of the value to return.
18677 (@value{GDBP}) return (long long int) -1
18678 Make selected stack frame return now? (y or n) y
18679 #0 0x00400526 in main ()
18684 @section Calling Program Functions
18687 @cindex calling functions
18688 @cindex inferior functions, calling
18689 @item print @var{expr}
18690 Evaluate the expression @var{expr} and display the resulting value.
18691 The expression may include calls to functions in the program being
18695 @item call @var{expr}
18696 Evaluate the expression @var{expr} without displaying @code{void}
18699 You can use this variant of the @code{print} command if you want to
18700 execute a function from your program that does not return anything
18701 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18702 with @code{void} returned values that @value{GDBN} will otherwise
18703 print. If the result is not void, it is printed and saved in the
18707 It is possible for the function you call via the @code{print} or
18708 @code{call} command to generate a signal (e.g., if there's a bug in
18709 the function, or if you passed it incorrect arguments). What happens
18710 in that case is controlled by the @code{set unwindonsignal} command.
18712 Similarly, with a C@t{++} program it is possible for the function you
18713 call via the @code{print} or @code{call} command to generate an
18714 exception that is not handled due to the constraints of the dummy
18715 frame. In this case, any exception that is raised in the frame, but has
18716 an out-of-frame exception handler will not be found. GDB builds a
18717 dummy-frame for the inferior function call, and the unwinder cannot
18718 seek for exception handlers outside of this dummy-frame. What happens
18719 in that case is controlled by the
18720 @code{set unwind-on-terminating-exception} command.
18723 @item set unwindonsignal
18724 @kindex set unwindonsignal
18725 @cindex unwind stack in called functions
18726 @cindex call dummy stack unwinding
18727 Set unwinding of the stack if a signal is received while in a function
18728 that @value{GDBN} called in the program being debugged. If set to on,
18729 @value{GDBN} unwinds the stack it created for the call and restores
18730 the context to what it was before the call. If set to off (the
18731 default), @value{GDBN} stops in the frame where the signal was
18734 @item show unwindonsignal
18735 @kindex show unwindonsignal
18736 Show the current setting of stack unwinding in the functions called by
18739 @item set unwind-on-terminating-exception
18740 @kindex set unwind-on-terminating-exception
18741 @cindex unwind stack in called functions with unhandled exceptions
18742 @cindex call dummy stack unwinding on unhandled exception.
18743 Set unwinding of the stack if a C@t{++} exception is raised, but left
18744 unhandled while in a function that @value{GDBN} called in the program being
18745 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18746 it created for the call and restores the context to what it was before
18747 the call. If set to off, @value{GDBN} the exception is delivered to
18748 the default C@t{++} exception handler and the inferior terminated.
18750 @item show unwind-on-terminating-exception
18751 @kindex show unwind-on-terminating-exception
18752 Show the current setting of stack unwinding in the functions called by
18755 @item set may-call-functions
18756 @kindex set may-call-functions
18757 @cindex disabling calling functions in the program
18758 @cindex calling functions in the program, disabling
18759 Set permission to call functions in the program.
18760 This controls whether @value{GDBN} will attempt to call functions in
18761 the program, such as with expressions in the @code{print} command. It
18762 defaults to @code{on}.
18764 To call a function in the program, @value{GDBN} has to temporarily
18765 modify the state of the inferior. This has potentially undesired side
18766 effects. Also, having @value{GDBN} call nested functions is likely to
18767 be erroneous and may even crash the program being debugged. You can
18768 avoid such hazards by forbidding @value{GDBN} from calling functions
18769 in the program being debugged. If calling functions in the program
18770 is forbidden, GDB will throw an error when a command (such as printing
18771 an expression) starts a function call in the program.
18773 @item show may-call-functions
18774 @kindex show may-call-functions
18775 Show permission to call functions in the program.
18779 @subsection Calling functions with no debug info
18781 @cindex no debug info functions
18782 Sometimes, a function you wish to call is missing debug information.
18783 In such case, @value{GDBN} does not know the type of the function,
18784 including the types of the function's parameters. To avoid calling
18785 the inferior function incorrectly, which could result in the called
18786 function functioning erroneously and even crash, @value{GDBN} refuses
18787 to call the function unless you tell it the type of the function.
18789 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18790 to do that. The simplest is to cast the call to the function's
18791 declared return type. For example:
18794 (@value{GDBP}) p getenv ("PATH")
18795 'getenv' has unknown return type; cast the call to its declared return type
18796 (@value{GDBP}) p (char *) getenv ("PATH")
18797 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18800 Casting the return type of a no-debug function is equivalent to
18801 casting the function to a pointer to a prototyped function that has a
18802 prototype that matches the types of the passed-in arguments, and
18803 calling that. I.e., the call above is equivalent to:
18806 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18810 and given this prototyped C or C++ function with float parameters:
18813 float multiply (float v1, float v2) @{ return v1 * v2; @}
18817 these calls are equivalent:
18820 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18821 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18824 If the function you wish to call is declared as unprototyped (i.e.@:
18825 old K&R style), you must use the cast-to-function-pointer syntax, so
18826 that @value{GDBN} knows that it needs to apply default argument
18827 promotions (promote float arguments to double). @xref{ABI, float
18828 promotion}. For example, given this unprototyped C function with
18829 float parameters, and no debug info:
18833 multiply_noproto (v1, v2)
18841 you call it like this:
18844 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18848 @section Patching Programs
18850 @cindex patching binaries
18851 @cindex writing into executables
18852 @cindex writing into corefiles
18854 By default, @value{GDBN} opens the file containing your program's
18855 executable code (or the corefile) read-only. This prevents accidental
18856 alterations to machine code; but it also prevents you from intentionally
18857 patching your program's binary.
18859 If you'd like to be able to patch the binary, you can specify that
18860 explicitly with the @code{set write} command. For example, you might
18861 want to turn on internal debugging flags, or even to make emergency
18867 @itemx set write off
18868 If you specify @samp{set write on}, @value{GDBN} opens executable and
18869 core files for both reading and writing; if you specify @kbd{set write
18870 off} (the default), @value{GDBN} opens them read-only.
18872 If you have already loaded a file, you must load it again (using the
18873 @code{exec-file} or @code{core-file} command) after changing @code{set
18874 write}, for your new setting to take effect.
18878 Display whether executable files and core files are opened for writing
18879 as well as reading.
18882 @node Compiling and Injecting Code
18883 @section Compiling and injecting code in @value{GDBN}
18884 @cindex injecting code
18885 @cindex writing into executables
18886 @cindex compiling code
18888 @value{GDBN} supports on-demand compilation and code injection into
18889 programs running under @value{GDBN}. GCC 5.0 or higher built with
18890 @file{libcc1.so} must be installed for this functionality to be enabled.
18891 This functionality is implemented with the following commands.
18894 @kindex compile code
18895 @item compile code @var{source-code}
18896 @itemx compile code -raw @var{--} @var{source-code}
18897 Compile @var{source-code} with the compiler language found as the current
18898 language in @value{GDBN} (@pxref{Languages}). If compilation and
18899 injection is not supported with the current language specified in
18900 @value{GDBN}, or the compiler does not support this feature, an error
18901 message will be printed. If @var{source-code} compiles and links
18902 successfully, @value{GDBN} will load the object-code emitted,
18903 and execute it within the context of the currently selected inferior.
18904 It is important to note that the compiled code is executed immediately.
18905 After execution, the compiled code is removed from @value{GDBN} and any
18906 new types or variables you have defined will be deleted.
18908 The command allows you to specify @var{source-code} in two ways.
18909 The simplest method is to provide a single line of code to the command.
18913 compile code printf ("hello world\n");
18916 If you specify options on the command line as well as source code, they
18917 may conflict. The @samp{--} delimiter can be used to separate options
18918 from actual source code. E.g.:
18921 compile code -r -- printf ("hello world\n");
18924 Alternatively you can enter source code as multiple lines of text. To
18925 enter this mode, invoke the @samp{compile code} command without any text
18926 following the command. This will start the multiple-line editor and
18927 allow you to type as many lines of source code as required. When you
18928 have completed typing, enter @samp{end} on its own line to exit the
18933 >printf ("hello\n");
18934 >printf ("world\n");
18938 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18939 provided @var{source-code} in a callable scope. In this case, you must
18940 specify the entry point of the code by defining a function named
18941 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18942 inferior. Using @samp{-raw} option may be needed for example when
18943 @var{source-code} requires @samp{#include} lines which may conflict with
18944 inferior symbols otherwise.
18946 @kindex compile file
18947 @item compile file @var{filename}
18948 @itemx compile file -raw @var{filename}
18949 Like @code{compile code}, but take the source code from @var{filename}.
18952 compile file /home/user/example.c
18957 @item compile print @var{expr}
18958 @itemx compile print /@var{f} @var{expr}
18959 Compile and execute @var{expr} with the compiler language found as the
18960 current language in @value{GDBN} (@pxref{Languages}). By default the
18961 value of @var{expr} is printed in a format appropriate to its data type;
18962 you can choose a different format by specifying @samp{/@var{f}}, where
18963 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18966 @item compile print
18967 @itemx compile print /@var{f}
18968 @cindex reprint the last value
18969 Alternatively you can enter the expression (source code producing it) as
18970 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18971 command without any text following the command. This will start the
18972 multiple-line editor.
18976 The process of compiling and injecting the code can be inspected using:
18979 @anchor{set debug compile}
18980 @item set debug compile
18981 @cindex compile command debugging info
18982 Turns on or off display of @value{GDBN} process of compiling and
18983 injecting the code. The default is off.
18985 @item show debug compile
18986 Displays the current state of displaying @value{GDBN} process of
18987 compiling and injecting the code.
18989 @anchor{set debug compile-cplus-types}
18990 @item set debug compile-cplus-types
18991 @cindex compile C@t{++} type conversion
18992 Turns on or off the display of C@t{++} type conversion debugging information.
18993 The default is off.
18995 @item show debug compile-cplus-types
18996 Displays the current state of displaying debugging information for
18997 C@t{++} type conversion.
19000 @subsection Compilation options for the @code{compile} command
19002 @value{GDBN} needs to specify the right compilation options for the code
19003 to be injected, in part to make its ABI compatible with the inferior
19004 and in part to make the injected code compatible with @value{GDBN}'s
19008 The options used, in increasing precedence:
19011 @item target architecture and OS options (@code{gdbarch})
19012 These options depend on target processor type and target operating
19013 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
19014 (@code{-m64}) compilation option.
19016 @item compilation options recorded in the target
19017 @value{NGCC} (since version 4.7) stores the options used for compilation
19018 into @code{DW_AT_producer} part of DWARF debugging information according
19019 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
19020 explicitly specify @code{-g} during inferior compilation otherwise
19021 @value{NGCC} produces no DWARF. This feature is only relevant for
19022 platforms where @code{-g} produces DWARF by default, otherwise one may
19023 try to enforce DWARF by using @code{-gdwarf-4}.
19025 @item compilation options set by @code{set compile-args}
19029 You can override compilation options using the following command:
19032 @item set compile-args
19033 @cindex compile command options override
19034 Set compilation options used for compiling and injecting code with the
19035 @code{compile} commands. These options override any conflicting ones
19036 from the target architecture and/or options stored during inferior
19039 @item show compile-args
19040 Displays the current state of compilation options override.
19041 This does not show all the options actually used during compilation,
19042 use @ref{set debug compile} for that.
19045 @subsection Caveats when using the @code{compile} command
19047 There are a few caveats to keep in mind when using the @code{compile}
19048 command. As the caveats are different per language, the table below
19049 highlights specific issues on a per language basis.
19052 @item C code examples and caveats
19053 When the language in @value{GDBN} is set to @samp{C}, the compiler will
19054 attempt to compile the source code with a @samp{C} compiler. The source
19055 code provided to the @code{compile} command will have much the same
19056 access to variables and types as it normally would if it were part of
19057 the program currently being debugged in @value{GDBN}.
19059 Below is a sample program that forms the basis of the examples that
19060 follow. This program has been compiled and loaded into @value{GDBN},
19061 much like any other normal debugging session.
19064 void function1 (void)
19067 printf ("function 1\n");
19070 void function2 (void)
19085 For the purposes of the examples in this section, the program above has
19086 been compiled, loaded into @value{GDBN}, stopped at the function
19087 @code{main}, and @value{GDBN} is awaiting input from the user.
19089 To access variables and types for any program in @value{GDBN}, the
19090 program must be compiled and packaged with debug information. The
19091 @code{compile} command is not an exception to this rule. Without debug
19092 information, you can still use the @code{compile} command, but you will
19093 be very limited in what variables and types you can access.
19095 So with that in mind, the example above has been compiled with debug
19096 information enabled. The @code{compile} command will have access to
19097 all variables and types (except those that may have been optimized
19098 out). Currently, as @value{GDBN} has stopped the program in the
19099 @code{main} function, the @code{compile} command would have access to
19100 the variable @code{k}. You could invoke the @code{compile} command
19101 and type some source code to set the value of @code{k}. You can also
19102 read it, or do anything with that variable you would normally do in
19103 @code{C}. Be aware that changes to inferior variables in the
19104 @code{compile} command are persistent. In the following example:
19107 compile code k = 3;
19111 the variable @code{k} is now 3. It will retain that value until
19112 something else in the example program changes it, or another
19113 @code{compile} command changes it.
19115 Normal scope and access rules apply to source code compiled and
19116 injected by the @code{compile} command. In the example, the variables
19117 @code{j} and @code{k} are not accessible yet, because the program is
19118 currently stopped in the @code{main} function, where these variables
19119 are not in scope. Therefore, the following command
19122 compile code j = 3;
19126 will result in a compilation error message.
19128 Once the program is continued, execution will bring these variables in
19129 scope, and they will become accessible; then the code you specify via
19130 the @code{compile} command will be able to access them.
19132 You can create variables and types with the @code{compile} command as
19133 part of your source code. Variables and types that are created as part
19134 of the @code{compile} command are not visible to the rest of the program for
19135 the duration of its run. This example is valid:
19138 compile code int ff = 5; printf ("ff is %d\n", ff);
19141 However, if you were to type the following into @value{GDBN} after that
19142 command has completed:
19145 compile code printf ("ff is %d\n'', ff);
19149 a compiler error would be raised as the variable @code{ff} no longer
19150 exists. Object code generated and injected by the @code{compile}
19151 command is removed when its execution ends. Caution is advised
19152 when assigning to program variables values of variables created by the
19153 code submitted to the @code{compile} command. This example is valid:
19156 compile code int ff = 5; k = ff;
19159 The value of the variable @code{ff} is assigned to @code{k}. The variable
19160 @code{k} does not require the existence of @code{ff} to maintain the value
19161 it has been assigned. However, pointers require particular care in
19162 assignment. If the source code compiled with the @code{compile} command
19163 changed the address of a pointer in the example program, perhaps to a
19164 variable created in the @code{compile} command, that pointer would point
19165 to an invalid location when the command exits. The following example
19166 would likely cause issues with your debugged program:
19169 compile code int ff = 5; p = &ff;
19172 In this example, @code{p} would point to @code{ff} when the
19173 @code{compile} command is executing the source code provided to it.
19174 However, as variables in the (example) program persist with their
19175 assigned values, the variable @code{p} would point to an invalid
19176 location when the command exists. A general rule should be followed
19177 in that you should either assign @code{NULL} to any assigned pointers,
19178 or restore a valid location to the pointer before the command exits.
19180 Similar caution must be exercised with any structs, unions, and typedefs
19181 defined in @code{compile} command. Types defined in the @code{compile}
19182 command will no longer be available in the next @code{compile} command.
19183 Therefore, if you cast a variable to a type defined in the
19184 @code{compile} command, care must be taken to ensure that any future
19185 need to resolve the type can be achieved.
19188 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
19189 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
19190 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
19191 Compilation failed.
19192 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
19196 Variables that have been optimized away by the compiler are not
19197 accessible to the code submitted to the @code{compile} command.
19198 Access to those variables will generate a compiler error which @value{GDBN}
19199 will print to the console.
19202 @subsection Compiler search for the @code{compile} command
19204 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
19205 which may not be obvious for remote targets of different architecture
19206 than where @value{GDBN} is running. Environment variable @code{PATH} on
19207 @value{GDBN} host is searched for @value{NGCC} binary matching the
19208 target architecture and operating system. This search can be overriden
19209 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
19210 taken from shell that executed @value{GDBN}, it is not the value set by
19211 @value{GDBN} command @code{set environment}). @xref{Environment}.
19214 Specifically @code{PATH} is searched for binaries matching regular expression
19215 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
19216 debugged. @var{arch} is processor name --- multiarch is supported, so for
19217 example both @code{i386} and @code{x86_64} targets look for pattern
19218 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
19219 for pattern @code{s390x?}. @var{os} is currently supported only for
19220 pattern @code{linux(-gnu)?}.
19222 On Posix hosts the compiler driver @value{GDBN} needs to find also
19223 shared library @file{libcc1.so} from the compiler. It is searched in
19224 default shared library search path (overridable with usual environment
19225 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
19226 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
19227 according to the installation of the found compiler --- as possibly
19228 specified by the @code{set compile-gcc} command.
19231 @item set compile-gcc
19232 @cindex compile command driver filename override
19233 Set compilation command used for compiling and injecting code with the
19234 @code{compile} commands. If this option is not set (it is set to
19235 an empty string), the search described above will occur --- that is the
19238 @item show compile-gcc
19239 Displays the current compile command @value{NGCC} driver filename.
19240 If set, it is the main command @command{gcc}, found usually for example
19241 under name @file{x86_64-linux-gnu-gcc}.
19245 @chapter @value{GDBN} Files
19247 @value{GDBN} needs to know the file name of the program to be debugged,
19248 both in order to read its symbol table and in order to start your
19249 program. To debug a core dump of a previous run, you must also tell
19250 @value{GDBN} the name of the core dump file.
19253 * Files:: Commands to specify files
19254 * File Caching:: Information about @value{GDBN}'s file caching
19255 * Separate Debug Files:: Debugging information in separate files
19256 * MiniDebugInfo:: Debugging information in a special section
19257 * Index Files:: Index files speed up GDB
19258 * Symbol Errors:: Errors reading symbol files
19259 * Data Files:: GDB data files
19263 @section Commands to Specify Files
19265 @cindex symbol table
19266 @cindex core dump file
19268 You may want to specify executable and core dump file names. The usual
19269 way to do this is at start-up time, using the arguments to
19270 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
19271 Out of @value{GDBN}}).
19273 Occasionally it is necessary to change to a different file during a
19274 @value{GDBN} session. Or you may run @value{GDBN} and forget to
19275 specify a file you want to use. Or you are debugging a remote target
19276 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
19277 Program}). In these situations the @value{GDBN} commands to specify
19278 new files are useful.
19281 @cindex executable file
19283 @item file @var{filename}
19284 Use @var{filename} as the program to be debugged. It is read for its
19285 symbols and for the contents of pure memory. It is also the program
19286 executed when you use the @code{run} command. If you do not specify a
19287 directory and the file is not found in the @value{GDBN} working directory,
19288 @value{GDBN} uses the environment variable @code{PATH} as a list of
19289 directories to search, just as the shell does when looking for a program
19290 to run. You can change the value of this variable, for both @value{GDBN}
19291 and your program, using the @code{path} command.
19293 @cindex unlinked object files
19294 @cindex patching object files
19295 You can load unlinked object @file{.o} files into @value{GDBN} using
19296 the @code{file} command. You will not be able to ``run'' an object
19297 file, but you can disassemble functions and inspect variables. Also,
19298 if the underlying BFD functionality supports it, you could use
19299 @kbd{gdb -write} to patch object files using this technique. Note
19300 that @value{GDBN} can neither interpret nor modify relocations in this
19301 case, so branches and some initialized variables will appear to go to
19302 the wrong place. But this feature is still handy from time to time.
19305 @code{file} with no argument makes @value{GDBN} discard any information it
19306 has on both executable file and the symbol table.
19309 @item exec-file @r{[} @var{filename} @r{]}
19310 Specify that the program to be run (but not the symbol table) is found
19311 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
19312 if necessary to locate your program. Omitting @var{filename} means to
19313 discard information on the executable file.
19315 @kindex symbol-file
19316 @item symbol-file @r{[} @var{filename} @r{[} -o @var{offset} @r{]]}
19317 Read symbol table information from file @var{filename}. @code{PATH} is
19318 searched when necessary. Use the @code{file} command to get both symbol
19319 table and program to run from the same file.
19321 If an optional @var{offset} is specified, it is added to the start
19322 address of each section in the symbol file. This is useful if the
19323 program is relocated at runtime, such as the Linux kernel with kASLR
19326 @code{symbol-file} with no argument clears out @value{GDBN} information on your
19327 program's symbol table.
19329 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
19330 some breakpoints and auto-display expressions. This is because they may
19331 contain pointers to the internal data recording symbols and data types,
19332 which are part of the old symbol table data being discarded inside
19335 @code{symbol-file} does not repeat if you press @key{RET} again after
19338 When @value{GDBN} is configured for a particular environment, it
19339 understands debugging information in whatever format is the standard
19340 generated for that environment; you may use either a @sc{gnu} compiler, or
19341 other compilers that adhere to the local conventions.
19342 Best results are usually obtained from @sc{gnu} compilers; for example,
19343 using @code{@value{NGCC}} you can generate debugging information for
19346 For most kinds of object files, with the exception of old SVR3 systems
19347 using COFF, the @code{symbol-file} command does not normally read the
19348 symbol table in full right away. Instead, it scans the symbol table
19349 quickly to find which source files and which symbols are present. The
19350 details are read later, one source file at a time, as they are needed.
19352 The purpose of this two-stage reading strategy is to make @value{GDBN}
19353 start up faster. For the most part, it is invisible except for
19354 occasional pauses while the symbol table details for a particular source
19355 file are being read. (The @code{set verbose} command can turn these
19356 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
19357 Warnings and Messages}.)
19359 We have not implemented the two-stage strategy for COFF yet. When the
19360 symbol table is stored in COFF format, @code{symbol-file} reads the
19361 symbol table data in full right away. Note that ``stabs-in-COFF''
19362 still does the two-stage strategy, since the debug info is actually
19366 @cindex reading symbols immediately
19367 @cindex symbols, reading immediately
19368 @item symbol-file @r{[} -readnow @r{]} @var{filename}
19369 @itemx file @r{[} -readnow @r{]} @var{filename}
19370 You can override the @value{GDBN} two-stage strategy for reading symbol
19371 tables by using the @samp{-readnow} option with any of the commands that
19372 load symbol table information, if you want to be sure @value{GDBN} has the
19373 entire symbol table available.
19375 @cindex @code{-readnever}, option for symbol-file command
19376 @cindex never read symbols
19377 @cindex symbols, never read
19378 @item symbol-file @r{[} -readnever @r{]} @var{filename}
19379 @itemx file @r{[} -readnever @r{]} @var{filename}
19380 You can instruct @value{GDBN} to never read the symbolic information
19381 contained in @var{filename} by using the @samp{-readnever} option.
19382 @xref{--readnever}.
19384 @c FIXME: for now no mention of directories, since this seems to be in
19385 @c flux. 13mar1992 status is that in theory GDB would look either in
19386 @c current dir or in same dir as myprog; but issues like competing
19387 @c GDB's, or clutter in system dirs, mean that in practice right now
19388 @c only current dir is used. FFish says maybe a special GDB hierarchy
19389 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
19393 @item core-file @r{[}@var{filename}@r{]}
19395 Specify the whereabouts of a core dump file to be used as the ``contents
19396 of memory''. Traditionally, core files contain only some parts of the
19397 address space of the process that generated them; @value{GDBN} can access the
19398 executable file itself for other parts.
19400 @code{core-file} with no argument specifies that no core file is
19403 Note that the core file is ignored when your program is actually running
19404 under @value{GDBN}. So, if you have been running your program and you
19405 wish to debug a core file instead, you must kill the subprocess in which
19406 the program is running. To do this, use the @code{kill} command
19407 (@pxref{Kill Process, ,Killing the Child Process}).
19409 @kindex add-symbol-file
19410 @cindex dynamic linking
19411 @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{]}
19412 The @code{add-symbol-file} command reads additional symbol table
19413 information from the file @var{filename}. You would use this command
19414 when @var{filename} has been dynamically loaded (by some other means)
19415 into the program that is running. The @var{textaddress} parameter gives
19416 the memory address at which the file's text section has been loaded.
19417 You can additionally specify the base address of other sections using
19418 an arbitrary number of @samp{-s @var{section} @var{address}} pairs.
19419 If a section is omitted, @value{GDBN} will use its default addresses
19420 as found in @var{filename}. Any @var{address} or @var{textaddress}
19421 can be given as an expression.
19423 If an optional @var{offset} is specified, it is added to the start
19424 address of each section, except those for which the address was
19425 specified explicitly.
19427 The symbol table of the file @var{filename} is added to the symbol table
19428 originally read with the @code{symbol-file} command. You can use the
19429 @code{add-symbol-file} command any number of times; the new symbol data
19430 thus read is kept in addition to the old.
19432 Changes can be reverted using the command @code{remove-symbol-file}.
19434 @cindex relocatable object files, reading symbols from
19435 @cindex object files, relocatable, reading symbols from
19436 @cindex reading symbols from relocatable object files
19437 @cindex symbols, reading from relocatable object files
19438 @cindex @file{.o} files, reading symbols from
19439 Although @var{filename} is typically a shared library file, an
19440 executable file, or some other object file which has been fully
19441 relocated for loading into a process, you can also load symbolic
19442 information from relocatable @file{.o} files, as long as:
19446 the file's symbolic information refers only to linker symbols defined in
19447 that file, not to symbols defined by other object files,
19449 every section the file's symbolic information refers to has actually
19450 been loaded into the inferior, as it appears in the file, and
19452 you can determine the address at which every section was loaded, and
19453 provide these to the @code{add-symbol-file} command.
19457 Some embedded operating systems, like Sun Chorus and VxWorks, can load
19458 relocatable files into an already running program; such systems
19459 typically make the requirements above easy to meet. However, it's
19460 important to recognize that many native systems use complex link
19461 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
19462 assembly, for example) that make the requirements difficult to meet. In
19463 general, one cannot assume that using @code{add-symbol-file} to read a
19464 relocatable object file's symbolic information will have the same effect
19465 as linking the relocatable object file into the program in the normal
19468 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
19470 @kindex remove-symbol-file
19471 @item remove-symbol-file @var{filename}
19472 @item remove-symbol-file -a @var{address}
19473 Remove a symbol file added via the @code{add-symbol-file} command. The
19474 file to remove can be identified by its @var{filename} or by an @var{address}
19475 that lies within the boundaries of this symbol file in memory. Example:
19478 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
19479 add symbol table from file "/home/user/gdb/mylib.so" at
19480 .text_addr = 0x7ffff7ff9480
19482 Reading symbols from /home/user/gdb/mylib.so...done.
19483 (gdb) remove-symbol-file -a 0x7ffff7ff9480
19484 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
19489 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
19491 @kindex add-symbol-file-from-memory
19492 @cindex @code{syscall DSO}
19493 @cindex load symbols from memory
19494 @item add-symbol-file-from-memory @var{address}
19495 Load symbols from the given @var{address} in a dynamically loaded
19496 object file whose image is mapped directly into the inferior's memory.
19497 For example, the Linux kernel maps a @code{syscall DSO} into each
19498 process's address space; this DSO provides kernel-specific code for
19499 some system calls. The argument can be any expression whose
19500 evaluation yields the address of the file's shared object file header.
19501 For this command to work, you must have used @code{symbol-file} or
19502 @code{exec-file} commands in advance.
19505 @item section @var{section} @var{addr}
19506 The @code{section} command changes the base address of the named
19507 @var{section} of the exec file to @var{addr}. This can be used if the
19508 exec file does not contain section addresses, (such as in the
19509 @code{a.out} format), or when the addresses specified in the file
19510 itself are wrong. Each section must be changed separately. The
19511 @code{info files} command, described below, lists all the sections and
19515 @kindex info target
19518 @code{info files} and @code{info target} are synonymous; both print the
19519 current target (@pxref{Targets, ,Specifying a Debugging Target}),
19520 including the names of the executable and core dump files currently in
19521 use by @value{GDBN}, and the files from which symbols were loaded. The
19522 command @code{help target} lists all possible targets rather than
19525 @kindex maint info sections
19526 @item maint info sections
19527 Another command that can give you extra information about program sections
19528 is @code{maint info sections}. In addition to the section information
19529 displayed by @code{info files}, this command displays the flags and file
19530 offset of each section in the executable and core dump files. In addition,
19531 @code{maint info sections} provides the following command options (which
19532 may be arbitrarily combined):
19536 Display sections for all loaded object files, including shared libraries.
19537 @item @var{sections}
19538 Display info only for named @var{sections}.
19539 @item @var{section-flags}
19540 Display info only for sections for which @var{section-flags} are true.
19541 The section flags that @value{GDBN} currently knows about are:
19544 Section will have space allocated in the process when loaded.
19545 Set for all sections except those containing debug information.
19547 Section will be loaded from the file into the child process memory.
19548 Set for pre-initialized code and data, clear for @code{.bss} sections.
19550 Section needs to be relocated before loading.
19552 Section cannot be modified by the child process.
19554 Section contains executable code only.
19556 Section contains data only (no executable code).
19558 Section will reside in ROM.
19560 Section contains data for constructor/destructor lists.
19562 Section is not empty.
19564 An instruction to the linker to not output the section.
19565 @item COFF_SHARED_LIBRARY
19566 A notification to the linker that the section contains
19567 COFF shared library information.
19569 Section contains common symbols.
19572 @kindex set trust-readonly-sections
19573 @cindex read-only sections
19574 @item set trust-readonly-sections on
19575 Tell @value{GDBN} that readonly sections in your object file
19576 really are read-only (i.e.@: that their contents will not change).
19577 In that case, @value{GDBN} can fetch values from these sections
19578 out of the object file, rather than from the target program.
19579 For some targets (notably embedded ones), this can be a significant
19580 enhancement to debugging performance.
19582 The default is off.
19584 @item set trust-readonly-sections off
19585 Tell @value{GDBN} not to trust readonly sections. This means that
19586 the contents of the section might change while the program is running,
19587 and must therefore be fetched from the target when needed.
19589 @item show trust-readonly-sections
19590 Show the current setting of trusting readonly sections.
19593 All file-specifying commands allow both absolute and relative file names
19594 as arguments. @value{GDBN} always converts the file name to an absolute file
19595 name and remembers it that way.
19597 @cindex shared libraries
19598 @anchor{Shared Libraries}
19599 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
19600 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
19601 DSBT (TIC6X) shared libraries.
19603 On MS-Windows @value{GDBN} must be linked with the Expat library to support
19604 shared libraries. @xref{Expat}.
19606 @value{GDBN} automatically loads symbol definitions from shared libraries
19607 when you use the @code{run} command, or when you examine a core file.
19608 (Before you issue the @code{run} command, @value{GDBN} does not understand
19609 references to a function in a shared library, however---unless you are
19610 debugging a core file).
19612 @c FIXME: some @value{GDBN} release may permit some refs to undef
19613 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
19614 @c FIXME...lib; check this from time to time when updating manual
19616 There are times, however, when you may wish to not automatically load
19617 symbol definitions from shared libraries, such as when they are
19618 particularly large or there are many of them.
19620 To control the automatic loading of shared library symbols, use the
19624 @kindex set auto-solib-add
19625 @item set auto-solib-add @var{mode}
19626 If @var{mode} is @code{on}, symbols from all shared object libraries
19627 will be loaded automatically when the inferior begins execution, you
19628 attach to an independently started inferior, or when the dynamic linker
19629 informs @value{GDBN} that a new library has been loaded. If @var{mode}
19630 is @code{off}, symbols must be loaded manually, using the
19631 @code{sharedlibrary} command. The default value is @code{on}.
19633 @cindex memory used for symbol tables
19634 If your program uses lots of shared libraries with debug info that
19635 takes large amounts of memory, you can decrease the @value{GDBN}
19636 memory footprint by preventing it from automatically loading the
19637 symbols from shared libraries. To that end, type @kbd{set
19638 auto-solib-add off} before running the inferior, then load each
19639 library whose debug symbols you do need with @kbd{sharedlibrary
19640 @var{regexp}}, where @var{regexp} is a regular expression that matches
19641 the libraries whose symbols you want to be loaded.
19643 @kindex show auto-solib-add
19644 @item show auto-solib-add
19645 Display the current autoloading mode.
19648 @cindex load shared library
19649 To explicitly load shared library symbols, use the @code{sharedlibrary}
19653 @kindex info sharedlibrary
19655 @item info share @var{regex}
19656 @itemx info sharedlibrary @var{regex}
19657 Print the names of the shared libraries which are currently loaded
19658 that match @var{regex}. If @var{regex} is omitted then print
19659 all shared libraries that are loaded.
19662 @item info dll @var{regex}
19663 This is an alias of @code{info sharedlibrary}.
19665 @kindex sharedlibrary
19667 @item sharedlibrary @var{regex}
19668 @itemx share @var{regex}
19669 Load shared object library symbols for files matching a
19670 Unix regular expression.
19671 As with files loaded automatically, it only loads shared libraries
19672 required by your program for a core file or after typing @code{run}. If
19673 @var{regex} is omitted all shared libraries required by your program are
19676 @item nosharedlibrary
19677 @kindex nosharedlibrary
19678 @cindex unload symbols from shared libraries
19679 Unload all shared object library symbols. This discards all symbols
19680 that have been loaded from all shared libraries. Symbols from shared
19681 libraries that were loaded by explicit user requests are not
19685 Sometimes you may wish that @value{GDBN} stops and gives you control
19686 when any of shared library events happen. The best way to do this is
19687 to use @code{catch load} and @code{catch unload} (@pxref{Set
19690 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19691 command for this. This command exists for historical reasons. It is
19692 less useful than setting a catchpoint, because it does not allow for
19693 conditions or commands as a catchpoint does.
19696 @item set stop-on-solib-events
19697 @kindex set stop-on-solib-events
19698 This command controls whether @value{GDBN} should give you control
19699 when the dynamic linker notifies it about some shared library event.
19700 The most common event of interest is loading or unloading of a new
19703 @item show stop-on-solib-events
19704 @kindex show stop-on-solib-events
19705 Show whether @value{GDBN} stops and gives you control when shared
19706 library events happen.
19709 Shared libraries are also supported in many cross or remote debugging
19710 configurations. @value{GDBN} needs to have access to the target's libraries;
19711 this can be accomplished either by providing copies of the libraries
19712 on the host system, or by asking @value{GDBN} to automatically retrieve the
19713 libraries from the target. If copies of the target libraries are
19714 provided, they need to be the same as the target libraries, although the
19715 copies on the target can be stripped as long as the copies on the host are
19718 @cindex where to look for shared libraries
19719 For remote debugging, you need to tell @value{GDBN} where the target
19720 libraries are, so that it can load the correct copies---otherwise, it
19721 may try to load the host's libraries. @value{GDBN} has two variables
19722 to specify the search directories for target libraries.
19725 @cindex prefix for executable and shared library file names
19726 @cindex system root, alternate
19727 @kindex set solib-absolute-prefix
19728 @kindex set sysroot
19729 @item set sysroot @var{path}
19730 Use @var{path} as the system root for the program being debugged. Any
19731 absolute shared library paths will be prefixed with @var{path}; many
19732 runtime loaders store the absolute paths to the shared library in the
19733 target program's memory. When starting processes remotely, and when
19734 attaching to already-running processes (local or remote), their
19735 executable filenames will be prefixed with @var{path} if reported to
19736 @value{GDBN} as absolute by the operating system. If you use
19737 @code{set sysroot} to find executables and shared libraries, they need
19738 to be laid out in the same way that they are on the target, with
19739 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19742 If @var{path} starts with the sequence @file{target:} and the target
19743 system is remote then @value{GDBN} will retrieve the target binaries
19744 from the remote system. This is only supported when using a remote
19745 target that supports the @code{remote get} command (@pxref{File
19746 Transfer,,Sending files to a remote system}). The part of @var{path}
19747 following the initial @file{target:} (if present) is used as system
19748 root prefix on the remote file system. If @var{path} starts with the
19749 sequence @file{remote:} this is converted to the sequence
19750 @file{target:} by @code{set sysroot}@footnote{Historically the
19751 functionality to retrieve binaries from the remote system was
19752 provided by prefixing @var{path} with @file{remote:}}. If you want
19753 to specify a local system root using a directory that happens to be
19754 named @file{target:} or @file{remote:}, you need to use some
19755 equivalent variant of the name like @file{./target:}.
19757 For targets with an MS-DOS based filesystem, such as MS-Windows and
19758 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19759 absolute file name with @var{path}. But first, on Unix hosts,
19760 @value{GDBN} converts all backslash directory separators into forward
19761 slashes, because the backslash is not a directory separator on Unix:
19764 c:\foo\bar.dll @result{} c:/foo/bar.dll
19767 Then, @value{GDBN} attempts prefixing the target file name with
19768 @var{path}, and looks for the resulting file name in the host file
19772 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19775 If that does not find the binary, @value{GDBN} tries removing
19776 the @samp{:} character from the drive spec, both for convenience, and,
19777 for the case of the host file system not supporting file names with
19781 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19784 This makes it possible to have a system root that mirrors a target
19785 with more than one drive. E.g., you may want to setup your local
19786 copies of the target system shared libraries like so (note @samp{c} vs
19790 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19791 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19792 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19796 and point the system root at @file{/path/to/sysroot}, so that
19797 @value{GDBN} can find the correct copies of both
19798 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19800 If that still does not find the binary, @value{GDBN} tries
19801 removing the whole drive spec from the target file name:
19804 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19807 This last lookup makes it possible to not care about the drive name,
19808 if you don't want or need to.
19810 The @code{set solib-absolute-prefix} command is an alias for @code{set
19813 @cindex default system root
19814 @cindex @samp{--with-sysroot}
19815 You can set the default system root by using the configure-time
19816 @samp{--with-sysroot} option. If the system root is inside
19817 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19818 @samp{--exec-prefix}), then the default system root will be updated
19819 automatically if the installed @value{GDBN} is moved to a new
19822 @kindex show sysroot
19824 Display the current executable and shared library prefix.
19826 @kindex set solib-search-path
19827 @item set solib-search-path @var{path}
19828 If this variable is set, @var{path} is a colon-separated list of
19829 directories to search for shared libraries. @samp{solib-search-path}
19830 is used after @samp{sysroot} fails to locate the library, or if the
19831 path to the library is relative instead of absolute. If you want to
19832 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19833 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19834 finding your host's libraries. @samp{sysroot} is preferred; setting
19835 it to a nonexistent directory may interfere with automatic loading
19836 of shared library symbols.
19838 @kindex show solib-search-path
19839 @item show solib-search-path
19840 Display the current shared library search path.
19842 @cindex DOS file-name semantics of file names.
19843 @kindex set target-file-system-kind (unix|dos-based|auto)
19844 @kindex show target-file-system-kind
19845 @item set target-file-system-kind @var{kind}
19846 Set assumed file system kind for target reported file names.
19848 Shared library file names as reported by the target system may not
19849 make sense as is on the system @value{GDBN} is running on. For
19850 example, when remote debugging a target that has MS-DOS based file
19851 system semantics, from a Unix host, the target may be reporting to
19852 @value{GDBN} a list of loaded shared libraries with file names such as
19853 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19854 drive letters, so the @samp{c:\} prefix is not normally understood as
19855 indicating an absolute file name, and neither is the backslash
19856 normally considered a directory separator character. In that case,
19857 the native file system would interpret this whole absolute file name
19858 as a relative file name with no directory components. This would make
19859 it impossible to point @value{GDBN} at a copy of the remote target's
19860 shared libraries on the host using @code{set sysroot}, and impractical
19861 with @code{set solib-search-path}. Setting
19862 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19863 to interpret such file names similarly to how the target would, and to
19864 map them to file names valid on @value{GDBN}'s native file system
19865 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19866 to one of the supported file system kinds. In that case, @value{GDBN}
19867 tries to determine the appropriate file system variant based on the
19868 current target's operating system (@pxref{ABI, ,Configuring the
19869 Current ABI}). The supported file system settings are:
19873 Instruct @value{GDBN} to assume the target file system is of Unix
19874 kind. Only file names starting the forward slash (@samp{/}) character
19875 are considered absolute, and the directory separator character is also
19879 Instruct @value{GDBN} to assume the target file system is DOS based.
19880 File names starting with either a forward slash, or a drive letter
19881 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19882 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19883 considered directory separators.
19886 Instruct @value{GDBN} to use the file system kind associated with the
19887 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19888 This is the default.
19892 @cindex file name canonicalization
19893 @cindex base name differences
19894 When processing file names provided by the user, @value{GDBN}
19895 frequently needs to compare them to the file names recorded in the
19896 program's debug info. Normally, @value{GDBN} compares just the
19897 @dfn{base names} of the files as strings, which is reasonably fast
19898 even for very large programs. (The base name of a file is the last
19899 portion of its name, after stripping all the leading directories.)
19900 This shortcut in comparison is based upon the assumption that files
19901 cannot have more than one base name. This is usually true, but
19902 references to files that use symlinks or similar filesystem
19903 facilities violate that assumption. If your program records files
19904 using such facilities, or if you provide file names to @value{GDBN}
19905 using symlinks etc., you can set @code{basenames-may-differ} to
19906 @code{true} to instruct @value{GDBN} to completely canonicalize each
19907 pair of file names it needs to compare. This will make file-name
19908 comparisons accurate, but at a price of a significant slowdown.
19911 @item set basenames-may-differ
19912 @kindex set basenames-may-differ
19913 Set whether a source file may have multiple base names.
19915 @item show basenames-may-differ
19916 @kindex show basenames-may-differ
19917 Show whether a source file may have multiple base names.
19921 @section File Caching
19922 @cindex caching of opened files
19923 @cindex caching of bfd objects
19925 To speed up file loading, and reduce memory usage, @value{GDBN} will
19926 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19927 BFD, bfd, The Binary File Descriptor Library}. The following commands
19928 allow visibility and control of the caching behavior.
19931 @kindex maint info bfds
19932 @item maint info bfds
19933 This prints information about each @code{bfd} object that is known to
19936 @kindex maint set bfd-sharing
19937 @kindex maint show bfd-sharing
19938 @kindex bfd caching
19939 @item maint set bfd-sharing
19940 @item maint show bfd-sharing
19941 Control whether @code{bfd} objects can be shared. When sharing is
19942 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19943 than reopening the same file. Turning sharing off does not cause
19944 already shared @code{bfd} objects to be unshared, but all future files
19945 that are opened will create a new @code{bfd} object. Similarly,
19946 re-enabling sharing does not cause multiple existing @code{bfd}
19947 objects to be collapsed into a single shared @code{bfd} object.
19949 @kindex set debug bfd-cache @var{level}
19950 @kindex bfd caching
19951 @item set debug bfd-cache @var{level}
19952 Turns on debugging of the bfd cache, setting the level to @var{level}.
19954 @kindex show debug bfd-cache
19955 @kindex bfd caching
19956 @item show debug bfd-cache
19957 Show the current debugging level of the bfd cache.
19960 @node Separate Debug Files
19961 @section Debugging Information in Separate Files
19962 @cindex separate debugging information files
19963 @cindex debugging information in separate files
19964 @cindex @file{.debug} subdirectories
19965 @cindex debugging information directory, global
19966 @cindex global debugging information directories
19967 @cindex build ID, and separate debugging files
19968 @cindex @file{.build-id} directory
19970 @value{GDBN} allows you to put a program's debugging information in a
19971 file separate from the executable itself, in a way that allows
19972 @value{GDBN} to find and load the debugging information automatically.
19973 Since debugging information can be very large---sometimes larger
19974 than the executable code itself---some systems distribute debugging
19975 information for their executables in separate files, which users can
19976 install only when they need to debug a problem.
19978 @value{GDBN} supports two ways of specifying the separate debug info
19983 The executable contains a @dfn{debug link} that specifies the name of
19984 the separate debug info file. The separate debug file's name is
19985 usually @file{@var{executable}.debug}, where @var{executable} is the
19986 name of the corresponding executable file without leading directories
19987 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19988 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19989 checksum for the debug file, which @value{GDBN} uses to validate that
19990 the executable and the debug file came from the same build.
19993 The executable contains a @dfn{build ID}, a unique bit string that is
19994 also present in the corresponding debug info file. (This is supported
19995 only on some operating systems, when using the ELF or PE file formats
19996 for binary files and the @sc{gnu} Binutils.) For more details about
19997 this feature, see the description of the @option{--build-id}
19998 command-line option in @ref{Options, , Command Line Options, ld,
19999 The GNU Linker}. The debug info file's name is not specified
20000 explicitly by the build ID, but can be computed from the build ID, see
20004 Depending on the way the debug info file is specified, @value{GDBN}
20005 uses two different methods of looking for the debug file:
20009 For the ``debug link'' method, @value{GDBN} looks up the named file in
20010 the directory of the executable file, then in a subdirectory of that
20011 directory named @file{.debug}, and finally under each one of the
20012 global debug directories, in a subdirectory whose name is identical to
20013 the leading directories of the executable's absolute file name. (On
20014 MS-Windows/MS-DOS, the drive letter of the executable's leading
20015 directories is converted to a one-letter subdirectory, i.e.@:
20016 @file{d:/usr/bin/} is converted to @file{/d/usr/bin/}, because Windows
20017 filesystems disallow colons in file names.)
20020 For the ``build ID'' method, @value{GDBN} looks in the
20021 @file{.build-id} subdirectory of each one of the global debug directories for
20022 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
20023 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
20024 are the rest of the bit string. (Real build ID strings are 32 or more
20025 hex characters, not 10.)
20028 So, for example, suppose you ask @value{GDBN} to debug
20029 @file{/usr/bin/ls}, which has a debug link that specifies the
20030 file @file{ls.debug}, and a build ID whose value in hex is
20031 @code{abcdef1234}. If the list of the global debug directories includes
20032 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
20033 debug information files, in the indicated order:
20037 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
20039 @file{/usr/bin/ls.debug}
20041 @file{/usr/bin/.debug/ls.debug}
20043 @file{/usr/lib/debug/usr/bin/ls.debug}.
20046 @anchor{debug-file-directory}
20047 Global debugging info directories default to what is set by @value{GDBN}
20048 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
20049 you can also set the global debugging info directories, and view the list
20050 @value{GDBN} is currently using.
20054 @kindex set debug-file-directory
20055 @item set debug-file-directory @var{directories}
20056 Set the directories which @value{GDBN} searches for separate debugging
20057 information files to @var{directory}. Multiple path components can be set
20058 concatenating them by a path separator.
20060 @kindex show debug-file-directory
20061 @item show debug-file-directory
20062 Show the directories @value{GDBN} searches for separate debugging
20067 @cindex @code{.gnu_debuglink} sections
20068 @cindex debug link sections
20069 A debug link is a special section of the executable file named
20070 @code{.gnu_debuglink}. The section must contain:
20074 A filename, with any leading directory components removed, followed by
20077 zero to three bytes of padding, as needed to reach the next four-byte
20078 boundary within the section, and
20080 a four-byte CRC checksum, stored in the same endianness used for the
20081 executable file itself. The checksum is computed on the debugging
20082 information file's full contents by the function given below, passing
20083 zero as the @var{crc} argument.
20086 Any executable file format can carry a debug link, as long as it can
20087 contain a section named @code{.gnu_debuglink} with the contents
20090 @cindex @code{.note.gnu.build-id} sections
20091 @cindex build ID sections
20092 The build ID is a special section in the executable file (and in other
20093 ELF binary files that @value{GDBN} may consider). This section is
20094 often named @code{.note.gnu.build-id}, but that name is not mandatory.
20095 It contains unique identification for the built files---the ID remains
20096 the same across multiple builds of the same build tree. The default
20097 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
20098 content for the build ID string. The same section with an identical
20099 value is present in the original built binary with symbols, in its
20100 stripped variant, and in the separate debugging information file.
20102 The debugging information file itself should be an ordinary
20103 executable, containing a full set of linker symbols, sections, and
20104 debugging information. The sections of the debugging information file
20105 should have the same names, addresses, and sizes as the original file,
20106 but they need not contain any data---much like a @code{.bss} section
20107 in an ordinary executable.
20109 The @sc{gnu} binary utilities (Binutils) package includes the
20110 @samp{objcopy} utility that can produce
20111 the separated executable / debugging information file pairs using the
20112 following commands:
20115 @kbd{objcopy --only-keep-debug foo foo.debug}
20120 These commands remove the debugging
20121 information from the executable file @file{foo} and place it in the file
20122 @file{foo.debug}. You can use the first, second or both methods to link the
20127 The debug link method needs the following additional command to also leave
20128 behind a debug link in @file{foo}:
20131 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
20134 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
20135 a version of the @code{strip} command such that the command @kbd{strip foo -f
20136 foo.debug} has the same functionality as the two @code{objcopy} commands and
20137 the @code{ln -s} command above, together.
20140 Build ID gets embedded into the main executable using @code{ld --build-id} or
20141 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
20142 compatibility fixes for debug files separation are present in @sc{gnu} binary
20143 utilities (Binutils) package since version 2.18.
20148 @cindex CRC algorithm definition
20149 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
20150 IEEE 802.3 using the polynomial:
20152 @c TexInfo requires naked braces for multi-digit exponents for Tex
20153 @c output, but this causes HTML output to barf. HTML has to be set using
20154 @c raw commands. So we end up having to specify this equation in 2
20159 <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>
20160 + <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
20166 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
20167 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
20171 The function is computed byte at a time, taking the least
20172 significant bit of each byte first. The initial pattern
20173 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
20174 the final result is inverted to ensure trailing zeros also affect the
20177 @emph{Note:} This is the same CRC polynomial as used in handling the
20178 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
20179 However in the case of the Remote Serial Protocol, the CRC is computed
20180 @emph{most} significant bit first, and the result is not inverted, so
20181 trailing zeros have no effect on the CRC value.
20183 To complete the description, we show below the code of the function
20184 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
20185 initially supplied @code{crc} argument means that an initial call to
20186 this function passing in zero will start computing the CRC using
20189 @kindex gnu_debuglink_crc32
20192 gnu_debuglink_crc32 (unsigned long crc,
20193 unsigned char *buf, size_t len)
20195 static const unsigned long crc32_table[256] =
20197 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
20198 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
20199 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
20200 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
20201 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
20202 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
20203 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
20204 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
20205 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
20206 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
20207 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
20208 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
20209 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
20210 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20211 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
20212 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
20213 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
20214 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
20215 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
20216 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
20217 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
20218 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
20219 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
20220 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
20221 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
20222 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
20223 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
20224 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
20225 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
20226 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
20227 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
20228 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
20229 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
20230 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
20231 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
20232 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
20233 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
20234 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
20235 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
20236 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
20237 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
20238 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
20239 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
20240 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
20241 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
20242 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
20243 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
20244 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
20245 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
20246 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
20247 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
20250 unsigned char *end;
20252 crc = ~crc & 0xffffffff;
20253 for (end = buf + len; buf < end; ++buf)
20254 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
20255 return ~crc & 0xffffffff;
20260 This computation does not apply to the ``build ID'' method.
20262 @node MiniDebugInfo
20263 @section Debugging information in a special section
20264 @cindex separate debug sections
20265 @cindex @samp{.gnu_debugdata} section
20267 Some systems ship pre-built executables and libraries that have a
20268 special @samp{.gnu_debugdata} section. This feature is called
20269 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
20270 is used to supply extra symbols for backtraces.
20272 The intent of this section is to provide extra minimal debugging
20273 information for use in simple backtraces. It is not intended to be a
20274 replacement for full separate debugging information (@pxref{Separate
20275 Debug Files}). The example below shows the intended use; however,
20276 @value{GDBN} does not currently put restrictions on what sort of
20277 debugging information might be included in the section.
20279 @value{GDBN} has support for this extension. If the section exists,
20280 then it is used provided that no other source of debugging information
20281 can be found, and that @value{GDBN} was configured with LZMA support.
20283 This section can be easily created using @command{objcopy} and other
20284 standard utilities:
20287 # Extract the dynamic symbols from the main binary, there is no need
20288 # to also have these in the normal symbol table.
20289 nm -D @var{binary} --format=posix --defined-only \
20290 | awk '@{ print $1 @}' | sort > dynsyms
20292 # Extract all the text (i.e. function) symbols from the debuginfo.
20293 # (Note that we actually also accept "D" symbols, for the benefit
20294 # of platforms like PowerPC64 that use function descriptors.)
20295 nm @var{binary} --format=posix --defined-only \
20296 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
20299 # Keep all the function symbols not already in the dynamic symbol
20301 comm -13 dynsyms funcsyms > keep_symbols
20303 # Separate full debug info into debug binary.
20304 objcopy --only-keep-debug @var{binary} debug
20306 # Copy the full debuginfo, keeping only a minimal set of symbols and
20307 # removing some unnecessary sections.
20308 objcopy -S --remove-section .gdb_index --remove-section .comment \
20309 --keep-symbols=keep_symbols debug mini_debuginfo
20311 # Drop the full debug info from the original binary.
20312 strip --strip-all -R .comment @var{binary}
20314 # Inject the compressed data into the .gnu_debugdata section of the
20317 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
20321 @section Index Files Speed Up @value{GDBN}
20322 @cindex index files
20323 @cindex @samp{.gdb_index} section
20325 When @value{GDBN} finds a symbol file, it scans the symbols in the
20326 file in order to construct an internal symbol table. This lets most
20327 @value{GDBN} operations work quickly---at the cost of a delay early
20328 on. For large programs, this delay can be quite lengthy, so
20329 @value{GDBN} provides a way to build an index, which speeds up
20332 For convenience, @value{GDBN} comes with a program,
20333 @command{gdb-add-index}, which can be used to add the index to a
20334 symbol file. It takes the symbol file as its only argument:
20337 $ gdb-add-index symfile
20340 @xref{gdb-add-index}.
20342 It is also possible to do the work manually. Here is what
20343 @command{gdb-add-index} does behind the curtains.
20345 The index is stored as a section in the symbol file. @value{GDBN} can
20346 write the index to a file, then you can put it into the symbol file
20347 using @command{objcopy}.
20349 To create an index file, use the @code{save gdb-index} command:
20352 @item save gdb-index [-dwarf-5] @var{directory}
20353 @kindex save gdb-index
20354 Create index files for all symbol files currently known by
20355 @value{GDBN}. For each known @var{symbol-file}, this command by
20356 default creates it produces a single file
20357 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
20358 the @option{-dwarf-5} option, it produces 2 files:
20359 @file{@var{symbol-file}.debug_names} and
20360 @file{@var{symbol-file}.debug_str}. The files are created in the
20361 given @var{directory}.
20364 Once you have created an index file you can merge it into your symbol
20365 file, here named @file{symfile}, using @command{objcopy}:
20368 $ objcopy --add-section .gdb_index=symfile.gdb-index \
20369 --set-section-flags .gdb_index=readonly symfile symfile
20372 Or for @code{-dwarf-5}:
20375 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
20376 $ cat symfile.debug_str >>symfile.debug_str.new
20377 $ objcopy --add-section .debug_names=symfile.gdb-index \
20378 --set-section-flags .debug_names=readonly \
20379 --update-section .debug_str=symfile.debug_str.new symfile symfile
20382 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
20383 sections that have been deprecated. Usually they are deprecated because
20384 they are missing a new feature or have performance issues.
20385 To tell @value{GDBN} to use a deprecated index section anyway
20386 specify @code{set use-deprecated-index-sections on}.
20387 The default is @code{off}.
20388 This can speed up startup, but may result in some functionality being lost.
20389 @xref{Index Section Format}.
20391 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
20392 must be done before gdb reads the file. The following will not work:
20395 $ gdb -ex "set use-deprecated-index-sections on" <program>
20398 Instead you must do, for example,
20401 $ gdb -iex "set use-deprecated-index-sections on" <program>
20404 There are currently some limitation on indices. They only work when
20405 for DWARF debugging information, not stabs. And, they do not
20406 currently work for programs using Ada.
20408 @subsection Automatic symbol index cache
20410 It is possible for @value{GDBN} to automatically save a copy of this index in a
20411 cache on disk and retrieve it from there when loading the same binary in the
20412 future. This feature can be turned on with @kbd{set index-cache on}. The
20413 following commands can be used to tweak the behavior of the index cache.
20417 @item set index-cache on
20418 @itemx set index-cache off
20419 Enable or disable the use of the symbol index cache.
20421 @item set index-cache directory @var{directory}
20422 @itemx show index-cache directory
20423 Set/show the directory where index files will be saved.
20425 The default value for this directory depends on the host platform. On
20426 most systems, the index is cached in the @file{gdb} subdirectory of
20427 the directory pointed to by the @env{XDG_CACHE_HOME} environment
20428 variable, if it is defined, else in the @file{.cache/gdb} subdirectory
20429 of your home directory. However, on some systems, the default may
20430 differ according to local convention.
20432 There is no limit on the disk space used by index cache. It is perfectly safe
20433 to delete the content of that directory to free up disk space.
20435 @item show index-cache stats
20436 Print the number of cache hits and misses since the launch of @value{GDBN}.
20440 @node Symbol Errors
20441 @section Errors Reading Symbol Files
20443 While reading a symbol file, @value{GDBN} occasionally encounters problems,
20444 such as symbol types it does not recognize, or known bugs in compiler
20445 output. By default, @value{GDBN} does not notify you of such problems, since
20446 they are relatively common and primarily of interest to people
20447 debugging compilers. If you are interested in seeing information
20448 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
20449 only one message about each such type of problem, no matter how many
20450 times the problem occurs; or you can ask @value{GDBN} to print more messages,
20451 to see how many times the problems occur, with the @code{set
20452 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
20455 The messages currently printed, and their meanings, include:
20458 @item inner block not inside outer block in @var{symbol}
20460 The symbol information shows where symbol scopes begin and end
20461 (such as at the start of a function or a block of statements). This
20462 error indicates that an inner scope block is not fully contained
20463 in its outer scope blocks.
20465 @value{GDBN} circumvents the problem by treating the inner block as if it had
20466 the same scope as the outer block. In the error message, @var{symbol}
20467 may be shown as ``@code{(don't know)}'' if the outer block is not a
20470 @item block at @var{address} out of order
20472 The symbol information for symbol scope blocks should occur in
20473 order of increasing addresses. This error indicates that it does not
20476 @value{GDBN} does not circumvent this problem, and has trouble
20477 locating symbols in the source file whose symbols it is reading. (You
20478 can often determine what source file is affected by specifying
20479 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
20482 @item bad block start address patched
20484 The symbol information for a symbol scope block has a start address
20485 smaller than the address of the preceding source line. This is known
20486 to occur in the SunOS 4.1.1 (and earlier) C compiler.
20488 @value{GDBN} circumvents the problem by treating the symbol scope block as
20489 starting on the previous source line.
20491 @item bad string table offset in symbol @var{n}
20494 Symbol number @var{n} contains a pointer into the string table which is
20495 larger than the size of the string table.
20497 @value{GDBN} circumvents the problem by considering the symbol to have the
20498 name @code{foo}, which may cause other problems if many symbols end up
20501 @item unknown symbol type @code{0x@var{nn}}
20503 The symbol information contains new data types that @value{GDBN} does
20504 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
20505 uncomprehended information, in hexadecimal.
20507 @value{GDBN} circumvents the error by ignoring this symbol information.
20508 This usually allows you to debug your program, though certain symbols
20509 are not accessible. If you encounter such a problem and feel like
20510 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
20511 on @code{complain}, then go up to the function @code{read_dbx_symtab}
20512 and examine @code{*bufp} to see the symbol.
20514 @item stub type has NULL name
20516 @value{GDBN} could not find the full definition for a struct or class.
20518 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
20519 The symbol information for a C@t{++} member function is missing some
20520 information that recent versions of the compiler should have output for
20523 @item info mismatch between compiler and debugger
20525 @value{GDBN} could not parse a type specification output by the compiler.
20530 @section GDB Data Files
20532 @cindex prefix for data files
20533 @value{GDBN} will sometimes read an auxiliary data file. These files
20534 are kept in a directory known as the @dfn{data directory}.
20536 You can set the data directory's name, and view the name @value{GDBN}
20537 is currently using.
20540 @kindex set data-directory
20541 @item set data-directory @var{directory}
20542 Set the directory which @value{GDBN} searches for auxiliary data files
20543 to @var{directory}.
20545 @kindex show data-directory
20546 @item show data-directory
20547 Show the directory @value{GDBN} searches for auxiliary data files.
20550 @cindex default data directory
20551 @cindex @samp{--with-gdb-datadir}
20552 You can set the default data directory by using the configure-time
20553 @samp{--with-gdb-datadir} option. If the data directory is inside
20554 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
20555 @samp{--exec-prefix}), then the default data directory will be updated
20556 automatically if the installed @value{GDBN} is moved to a new
20559 The data directory may also be specified with the
20560 @code{--data-directory} command line option.
20561 @xref{Mode Options}.
20564 @chapter Specifying a Debugging Target
20566 @cindex debugging target
20567 A @dfn{target} is the execution environment occupied by your program.
20569 Often, @value{GDBN} runs in the same host environment as your program;
20570 in that case, the debugging target is specified as a side effect when
20571 you use the @code{file} or @code{core} commands. When you need more
20572 flexibility---for example, running @value{GDBN} on a physically separate
20573 host, or controlling a standalone system over a serial port or a
20574 realtime system over a TCP/IP connection---you can use the @code{target}
20575 command to specify one of the target types configured for @value{GDBN}
20576 (@pxref{Target Commands, ,Commands for Managing Targets}).
20578 @cindex target architecture
20579 It is possible to build @value{GDBN} for several different @dfn{target
20580 architectures}. When @value{GDBN} is built like that, you can choose
20581 one of the available architectures with the @kbd{set architecture}
20585 @kindex set architecture
20586 @kindex show architecture
20587 @item set architecture @var{arch}
20588 This command sets the current target architecture to @var{arch}. The
20589 value of @var{arch} can be @code{"auto"}, in addition to one of the
20590 supported architectures.
20592 @item show architecture
20593 Show the current target architecture.
20595 @item set processor
20597 @kindex set processor
20598 @kindex show processor
20599 These are alias commands for, respectively, @code{set architecture}
20600 and @code{show architecture}.
20604 * Active Targets:: Active targets
20605 * Target Commands:: Commands for managing targets
20606 * Byte Order:: Choosing target byte order
20609 @node Active Targets
20610 @section Active Targets
20612 @cindex stacking targets
20613 @cindex active targets
20614 @cindex multiple targets
20616 There are multiple classes of targets such as: processes, executable files or
20617 recording sessions. Core files belong to the process class, making core file
20618 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
20619 on multiple active targets, one in each class. This allows you to (for
20620 example) start a process and inspect its activity, while still having access to
20621 the executable file after the process finishes. Or if you start process
20622 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
20623 presented a virtual layer of the recording target, while the process target
20624 remains stopped at the chronologically last point of the process execution.
20626 Use the @code{core-file} and @code{exec-file} commands to select a new core
20627 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
20628 specify as a target a process that is already running, use the @code{attach}
20629 command (@pxref{Attach, ,Debugging an Already-running Process}).
20631 @node Target Commands
20632 @section Commands for Managing Targets
20635 @item target @var{type} @var{parameters}
20636 Connects the @value{GDBN} host environment to a target machine or
20637 process. A target is typically a protocol for talking to debugging
20638 facilities. You use the argument @var{type} to specify the type or
20639 protocol of the target machine.
20641 Further @var{parameters} are interpreted by the target protocol, but
20642 typically include things like device names or host names to connect
20643 with, process numbers, and baud rates.
20645 The @code{target} command does not repeat if you press @key{RET} again
20646 after executing the command.
20648 @kindex help target
20650 Displays the names of all targets available. To display targets
20651 currently selected, use either @code{info target} or @code{info files}
20652 (@pxref{Files, ,Commands to Specify Files}).
20654 @item help target @var{name}
20655 Describe a particular target, including any parameters necessary to
20658 @kindex set gnutarget
20659 @item set gnutarget @var{args}
20660 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
20661 knows whether it is reading an @dfn{executable},
20662 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
20663 with the @code{set gnutarget} command. Unlike most @code{target} commands,
20664 with @code{gnutarget} the @code{target} refers to a program, not a machine.
20667 @emph{Warning:} To specify a file format with @code{set gnutarget},
20668 you must know the actual BFD name.
20672 @xref{Files, , Commands to Specify Files}.
20674 @kindex show gnutarget
20675 @item show gnutarget
20676 Use the @code{show gnutarget} command to display what file format
20677 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
20678 @value{GDBN} will determine the file format for each file automatically,
20679 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20682 @cindex common targets
20683 Here are some common targets (available, or not, depending on the GDB
20688 @item target exec @var{program}
20689 @cindex executable file target
20690 An executable file. @samp{target exec @var{program}} is the same as
20691 @samp{exec-file @var{program}}.
20693 @item target core @var{filename}
20694 @cindex core dump file target
20695 A core dump file. @samp{target core @var{filename}} is the same as
20696 @samp{core-file @var{filename}}.
20698 @item target remote @var{medium}
20699 @cindex remote target
20700 A remote system connected to @value{GDBN} via a serial line or network
20701 connection. This command tells @value{GDBN} to use its own remote
20702 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20704 For example, if you have a board connected to @file{/dev/ttya} on the
20705 machine running @value{GDBN}, you could say:
20708 target remote /dev/ttya
20711 @code{target remote} supports the @code{load} command. This is only
20712 useful if you have some other way of getting the stub to the target
20713 system, and you can put it somewhere in memory where it won't get
20714 clobbered by the download.
20716 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20717 @cindex built-in simulator target
20718 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20726 works; however, you cannot assume that a specific memory map, device
20727 drivers, or even basic I/O is available, although some simulators do
20728 provide these. For info about any processor-specific simulator details,
20729 see the appropriate section in @ref{Embedded Processors, ,Embedded
20732 @item target native
20733 @cindex native target
20734 Setup for local/native process debugging. Useful to make the
20735 @code{run} command spawn native processes (likewise @code{attach},
20736 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20737 (@pxref{set auto-connect-native-target}).
20741 Different targets are available on different configurations of @value{GDBN};
20742 your configuration may have more or fewer targets.
20744 Many remote targets require you to download the executable's code once
20745 you've successfully established a connection. You may wish to control
20746 various aspects of this process.
20751 @kindex set hash@r{, for remote monitors}
20752 @cindex hash mark while downloading
20753 This command controls whether a hash mark @samp{#} is displayed while
20754 downloading a file to the remote monitor. If on, a hash mark is
20755 displayed after each S-record is successfully downloaded to the
20759 @kindex show hash@r{, for remote monitors}
20760 Show the current status of displaying the hash mark.
20762 @item set debug monitor
20763 @kindex set debug monitor
20764 @cindex display remote monitor communications
20765 Enable or disable display of communications messages between
20766 @value{GDBN} and the remote monitor.
20768 @item show debug monitor
20769 @kindex show debug monitor
20770 Show the current status of displaying communications between
20771 @value{GDBN} and the remote monitor.
20776 @kindex load @var{filename} @var{offset}
20777 @item load @var{filename} @var{offset}
20779 Depending on what remote debugging facilities are configured into
20780 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20781 is meant to make @var{filename} (an executable) available for debugging
20782 on the remote system---by downloading, or dynamic linking, for example.
20783 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20784 the @code{add-symbol-file} command.
20786 If your @value{GDBN} does not have a @code{load} command, attempting to
20787 execute it gets the error message ``@code{You can't do that when your
20788 target is @dots{}}''
20790 The file is loaded at whatever address is specified in the executable.
20791 For some object file formats, you can specify the load address when you
20792 link the program; for other formats, like a.out, the object file format
20793 specifies a fixed address.
20794 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20796 It is also possible to tell @value{GDBN} to load the executable file at a
20797 specific offset described by the optional argument @var{offset}. When
20798 @var{offset} is provided, @var{filename} must also be provided.
20800 Depending on the remote side capabilities, @value{GDBN} may be able to
20801 load programs into flash memory.
20803 @code{load} does not repeat if you press @key{RET} again after using it.
20808 @kindex flash-erase
20810 @anchor{flash-erase}
20812 Erases all known flash memory regions on the target.
20817 @section Choosing Target Byte Order
20819 @cindex choosing target byte order
20820 @cindex target byte order
20822 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20823 offer the ability to run either big-endian or little-endian byte
20824 orders. Usually the executable or symbol will include a bit to
20825 designate the endian-ness, and you will not need to worry about
20826 which to use. However, you may still find it useful to adjust
20827 @value{GDBN}'s idea of processor endian-ness manually.
20831 @item set endian big
20832 Instruct @value{GDBN} to assume the target is big-endian.
20834 @item set endian little
20835 Instruct @value{GDBN} to assume the target is little-endian.
20837 @item set endian auto
20838 Instruct @value{GDBN} to use the byte order associated with the
20842 Display @value{GDBN}'s current idea of the target byte order.
20846 If the @code{set endian auto} mode is in effect and no executable has
20847 been selected, then the endianness used is the last one chosen either
20848 by one of the @code{set endian big} and @code{set endian little}
20849 commands or by inferring from the last executable used. If no
20850 endianness has been previously chosen, then the default for this mode
20851 is inferred from the target @value{GDBN} has been built for, and is
20852 @code{little} if the name of the target CPU has an @code{el} suffix
20853 and @code{big} otherwise.
20855 Note that these commands merely adjust interpretation of symbolic
20856 data on the host, and that they have absolutely no effect on the
20860 @node Remote Debugging
20861 @chapter Debugging Remote Programs
20862 @cindex remote debugging
20864 If you are trying to debug a program running on a machine that cannot run
20865 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20866 For example, you might use remote debugging on an operating system kernel,
20867 or on a small system which does not have a general purpose operating system
20868 powerful enough to run a full-featured debugger.
20870 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20871 to make this work with particular debugging targets. In addition,
20872 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20873 but not specific to any particular target system) which you can use if you
20874 write the remote stubs---the code that runs on the remote system to
20875 communicate with @value{GDBN}.
20877 Other remote targets may be available in your
20878 configuration of @value{GDBN}; use @code{help target} to list them.
20881 * Connecting:: Connecting to a remote target
20882 * File Transfer:: Sending files to a remote system
20883 * Server:: Using the gdbserver program
20884 * Remote Configuration:: Remote configuration
20885 * Remote Stub:: Implementing a remote stub
20889 @section Connecting to a Remote Target
20890 @cindex remote debugging, connecting
20891 @cindex @code{gdbserver}, connecting
20892 @cindex remote debugging, types of connections
20893 @cindex @code{gdbserver}, types of connections
20894 @cindex @code{gdbserver}, @code{target remote} mode
20895 @cindex @code{gdbserver}, @code{target extended-remote} mode
20897 This section describes how to connect to a remote target, including the
20898 types of connections and their differences, how to set up executable and
20899 symbol files on the host and target, and the commands used for
20900 connecting to and disconnecting from the remote target.
20902 @subsection Types of Remote Connections
20904 @value{GDBN} supports two types of remote connections, @code{target remote}
20905 mode and @code{target extended-remote} mode. Note that many remote targets
20906 support only @code{target remote} mode. There are several major
20907 differences between the two types of connections, enumerated here:
20911 @cindex remote debugging, detach and program exit
20912 @item Result of detach or program exit
20913 @strong{With target remote mode:} When the debugged program exits or you
20914 detach from it, @value{GDBN} disconnects from the target. When using
20915 @code{gdbserver}, @code{gdbserver} will exit.
20917 @strong{With target extended-remote mode:} When the debugged program exits or
20918 you detach from it, @value{GDBN} remains connected to the target, even
20919 though no program is running. You can rerun the program, attach to a
20920 running program, or use @code{monitor} commands specific to the target.
20922 When using @code{gdbserver} in this case, it does not exit unless it was
20923 invoked using the @option{--once} option. If the @option{--once} option
20924 was not used, you can ask @code{gdbserver} to exit using the
20925 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20927 @item Specifying the program to debug
20928 For both connection types you use the @code{file} command to specify the
20929 program on the host system. If you are using @code{gdbserver} there are
20930 some differences in how to specify the location of the program on the
20933 @strong{With target remote mode:} You must either specify the program to debug
20934 on the @code{gdbserver} command line or use the @option{--attach} option
20935 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20937 @cindex @option{--multi}, @code{gdbserver} option
20938 @strong{With target extended-remote mode:} You may specify the program to debug
20939 on the @code{gdbserver} command line, or you can load the program or attach
20940 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20942 @anchor{--multi Option in Types of Remote Connnections}
20943 You can start @code{gdbserver} without supplying an initial command to run
20944 or process ID to attach. To do this, use the @option{--multi} command line
20945 option. Then you can connect using @code{target extended-remote} and start
20946 the program you want to debug (see below for details on using the
20947 @code{run} command in this scenario). Note that the conditions under which
20948 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20949 (@code{target remote} or @code{target extended-remote}). The
20950 @option{--multi} option to @code{gdbserver} has no influence on that.
20952 @item The @code{run} command
20953 @strong{With target remote mode:} The @code{run} command is not
20954 supported. Once a connection has been established, you can use all
20955 the usual @value{GDBN} commands to examine and change data. The
20956 remote program is already running, so you can use commands like
20957 @kbd{step} and @kbd{continue}.
20959 @strong{With target extended-remote mode:} The @code{run} command is
20960 supported. The @code{run} command uses the value set by
20961 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20962 the program to run. Command line arguments are supported, except for
20963 wildcard expansion and I/O redirection (@pxref{Arguments}).
20965 If you specify the program to debug on the command line, then the
20966 @code{run} command is not required to start execution, and you can
20967 resume using commands like @kbd{step} and @kbd{continue} as with
20968 @code{target remote} mode.
20970 @anchor{Attaching in Types of Remote Connections}
20972 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20973 not supported. To attach to a running program using @code{gdbserver}, you
20974 must use the @option{--attach} option (@pxref{Running gdbserver}).
20976 @strong{With target extended-remote mode:} To attach to a running program,
20977 you may use the @code{attach} command after the connection has been
20978 established. If you are using @code{gdbserver}, you may also invoke
20979 @code{gdbserver} using the @option{--attach} option
20980 (@pxref{Running gdbserver}).
20984 @anchor{Host and target files}
20985 @subsection Host and Target Files
20986 @cindex remote debugging, symbol files
20987 @cindex symbol files, remote debugging
20989 @value{GDBN}, running on the host, needs access to symbol and debugging
20990 information for your program running on the target. This requires
20991 access to an unstripped copy of your program, and possibly any associated
20992 symbol files. Note that this section applies equally to both @code{target
20993 remote} mode and @code{target extended-remote} mode.
20995 Some remote targets (@pxref{qXfer executable filename read}, and
20996 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20997 the same connection used to communicate with @value{GDBN}. With such a
20998 target, if the remote program is unstripped, the only command you need is
20999 @code{target remote} (or @code{target extended-remote}).
21001 If the remote program is stripped, or the target does not support remote
21002 program file access, start up @value{GDBN} using the name of the local
21003 unstripped copy of your program as the first argument, or use the
21004 @code{file} command. Use @code{set sysroot} to specify the location (on
21005 the host) of target libraries (unless your @value{GDBN} was compiled with
21006 the correct sysroot using @code{--with-sysroot}). Alternatively, you
21007 may use @code{set solib-search-path} to specify how @value{GDBN} locates
21010 The symbol file and target libraries must exactly match the executable
21011 and libraries on the target, with one exception: the files on the host
21012 system should not be stripped, even if the files on the target system
21013 are. Mismatched or missing files will lead to confusing results
21014 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
21015 files may also prevent @code{gdbserver} from debugging multi-threaded
21018 @subsection Remote Connection Commands
21019 @cindex remote connection commands
21020 @value{GDBN} can communicate with the target over a serial line, a
21021 local Unix domain socket, or
21022 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
21023 each case, @value{GDBN} uses the same protocol for debugging your
21024 program; only the medium carrying the debugging packets varies. The
21025 @code{target remote} and @code{target extended-remote} commands
21026 establish a connection to the target. Both commands accept the same
21027 arguments, which indicate the medium to use:
21031 @item target remote @var{serial-device}
21032 @itemx target extended-remote @var{serial-device}
21033 @cindex serial line, @code{target remote}
21034 Use @var{serial-device} to communicate with the target. For example,
21035 to use a serial line connected to the device named @file{/dev/ttyb}:
21038 target remote /dev/ttyb
21041 If you're using a serial line, you may want to give @value{GDBN} the
21042 @samp{--baud} option, or use the @code{set serial baud} command
21043 (@pxref{Remote Configuration, set serial baud}) before the
21044 @code{target} command.
21046 @item target remote @var{local-socket}
21047 @itemx target extended-remote @var{local-socket}
21048 @cindex local socket, @code{target remote}
21049 @cindex Unix domain socket
21050 Use @var{local-socket} to communicate with the target. For example,
21051 to use a local Unix domain socket bound to the file system entry @file{/tmp/gdb-socket0}:
21054 target remote /tmp/gdb-socket0
21057 Note that this command has the same form as the command to connect
21058 to a serial line. @value{GDBN} will automatically determine which
21059 kind of file you have specified and will make the appropriate kind
21061 This feature is not available if the host system does not support
21062 Unix domain sockets.
21064 @item target remote @code{@var{host}:@var{port}}
21065 @itemx target remote @code{@var{[host]}:@var{port}}
21066 @itemx target remote @code{tcp:@var{host}:@var{port}}
21067 @itemx target remote @code{tcp:@var{[host]}:@var{port}}
21068 @itemx target remote @code{tcp4:@var{host}:@var{port}}
21069 @itemx target remote @code{tcp6:@var{host}:@var{port}}
21070 @itemx target remote @code{tcp6:@var{[host]}:@var{port}}
21071 @itemx target extended-remote @code{@var{host}:@var{port}}
21072 @itemx target extended-remote @code{@var{[host]}:@var{port}}
21073 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
21074 @itemx target extended-remote @code{tcp:@var{[host]}:@var{port}}
21075 @itemx target extended-remote @code{tcp4:@var{host}:@var{port}}
21076 @itemx target extended-remote @code{tcp6:@var{host}:@var{port}}
21077 @itemx target extended-remote @code{tcp6:@var{[host]}:@var{port}}
21078 @cindex @acronym{TCP} port, @code{target remote}
21079 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
21080 The @var{host} may be either a host name, a numeric @acronym{IPv4}
21081 address, or a numeric @acronym{IPv6} address (with or without the
21082 square brackets to separate the address from the port); @var{port}
21083 must be a decimal number. The @var{host} could be the target machine
21084 itself, if it is directly connected to the net, or it might be a
21085 terminal server which in turn has a serial line to the target.
21087 For example, to connect to port 2828 on a terminal server named
21091 target remote manyfarms:2828
21094 To connect to port 2828 on a terminal server whose address is
21095 @code{2001:0db8:85a3:0000:0000:8a2e:0370:7334}, you can either use the
21096 square bracket syntax:
21099 target remote [2001:0db8:85a3:0000:0000:8a2e:0370:7334]:2828
21103 or explicitly specify the @acronym{IPv6} protocol:
21106 target remote tcp6:2001:0db8:85a3:0000:0000:8a2e:0370:7334:2828
21109 This last example may be confusing to the reader, because there is no
21110 visible separation between the hostname and the port number.
21111 Therefore, we recommend the user to provide @acronym{IPv6} addresses
21112 using square brackets for clarity. However, it is important to
21113 mention that for @value{GDBN} there is no ambiguity: the number after
21114 the last colon is considered to be the port number.
21116 If your remote target is actually running on the same machine as your
21117 debugger session (e.g.@: a simulator for your target running on the
21118 same host), you can omit the hostname. For example, to connect to
21119 port 1234 on your local machine:
21122 target remote :1234
21126 Note that the colon is still required here.
21128 @item target remote @code{udp:@var{host}:@var{port}}
21129 @itemx target remote @code{udp:@var{[host]}:@var{port}}
21130 @itemx target remote @code{udp4:@var{host}:@var{port}}
21131 @itemx target remote @code{udp6:@var{[host]}:@var{port}}
21132 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21133 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
21134 @itemx target extended-remote @code{udp:@var{[host]}:@var{port}}
21135 @itemx target extended-remote @code{udp4:@var{host}:@var{port}}
21136 @itemx target extended-remote @code{udp6:@var{host}:@var{port}}
21137 @itemx target extended-remote @code{udp6:@var{[host]}:@var{port}}
21138 @cindex @acronym{UDP} port, @code{target remote}
21139 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
21140 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
21143 target remote udp:manyfarms:2828
21146 When using a @acronym{UDP} connection for remote debugging, you should
21147 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
21148 can silently drop packets on busy or unreliable networks, which will
21149 cause havoc with your debugging session.
21151 @item target remote | @var{command}
21152 @itemx target extended-remote | @var{command}
21153 @cindex pipe, @code{target remote} to
21154 Run @var{command} in the background and communicate with it using a
21155 pipe. The @var{command} is a shell command, to be parsed and expanded
21156 by the system's command shell, @code{/bin/sh}; it should expect remote
21157 protocol packets on its standard input, and send replies on its
21158 standard output. You could use this to run a stand-alone simulator
21159 that speaks the remote debugging protocol, to make net connections
21160 using programs like @code{ssh}, or for other similar tricks.
21162 If @var{command} closes its standard output (perhaps by exiting),
21163 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
21164 program has already exited, this will have no effect.)
21168 @cindex interrupting remote programs
21169 @cindex remote programs, interrupting
21170 Whenever @value{GDBN} is waiting for the remote program, if you type the
21171 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
21172 program. This may or may not succeed, depending in part on the hardware
21173 and the serial drivers the remote system uses. If you type the
21174 interrupt character once again, @value{GDBN} displays this prompt:
21177 Interrupted while waiting for the program.
21178 Give up (and stop debugging it)? (y or n)
21181 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
21182 the remote debugging session. (If you decide you want to try again later,
21183 you can use @kbd{target remote} again to connect once more.) If you type
21184 @kbd{n}, @value{GDBN} goes back to waiting.
21186 In @code{target extended-remote} mode, typing @kbd{n} will leave
21187 @value{GDBN} connected to the target.
21190 @kindex detach (remote)
21192 When you have finished debugging the remote program, you can use the
21193 @code{detach} command to release it from @value{GDBN} control.
21194 Detaching from the target normally resumes its execution, but the results
21195 will depend on your particular remote stub. After the @code{detach}
21196 command in @code{target remote} mode, @value{GDBN} is free to connect to
21197 another target. In @code{target extended-remote} mode, @value{GDBN} is
21198 still connected to the target.
21202 The @code{disconnect} command closes the connection to the target, and
21203 the target is generally not resumed. It will wait for @value{GDBN}
21204 (this instance or another one) to connect and continue debugging. After
21205 the @code{disconnect} command, @value{GDBN} is again free to connect to
21208 @cindex send command to remote monitor
21209 @cindex extend @value{GDBN} for remote targets
21210 @cindex add new commands for external monitor
21212 @item monitor @var{cmd}
21213 This command allows you to send arbitrary commands directly to the
21214 remote monitor. Since @value{GDBN} doesn't care about the commands it
21215 sends like this, this command is the way to extend @value{GDBN}---you
21216 can add new commands that only the external monitor will understand
21220 @node File Transfer
21221 @section Sending files to a remote system
21222 @cindex remote target, file transfer
21223 @cindex file transfer
21224 @cindex sending files to remote systems
21226 Some remote targets offer the ability to transfer files over the same
21227 connection used to communicate with @value{GDBN}. This is convenient
21228 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
21229 running @code{gdbserver} over a network interface. For other targets,
21230 e.g.@: embedded devices with only a single serial port, this may be
21231 the only way to upload or download files.
21233 Not all remote targets support these commands.
21237 @item remote put @var{hostfile} @var{targetfile}
21238 Copy file @var{hostfile} from the host system (the machine running
21239 @value{GDBN}) to @var{targetfile} on the target system.
21242 @item remote get @var{targetfile} @var{hostfile}
21243 Copy file @var{targetfile} from the target system to @var{hostfile}
21244 on the host system.
21246 @kindex remote delete
21247 @item remote delete @var{targetfile}
21248 Delete @var{targetfile} from the target system.
21253 @section Using the @code{gdbserver} Program
21256 @cindex remote connection without stubs
21257 @code{gdbserver} is a control program for Unix-like systems, which
21258 allows you to connect your program with a remote @value{GDBN} via
21259 @code{target remote} or @code{target extended-remote}---but without
21260 linking in the usual debugging stub.
21262 @code{gdbserver} is not a complete replacement for the debugging stubs,
21263 because it requires essentially the same operating-system facilities
21264 that @value{GDBN} itself does. In fact, a system that can run
21265 @code{gdbserver} to connect to a remote @value{GDBN} could also run
21266 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
21267 because it is a much smaller program than @value{GDBN} itself. It is
21268 also easier to port than all of @value{GDBN}, so you may be able to get
21269 started more quickly on a new system by using @code{gdbserver}.
21270 Finally, if you develop code for real-time systems, you may find that
21271 the tradeoffs involved in real-time operation make it more convenient to
21272 do as much development work as possible on another system, for example
21273 by cross-compiling. You can use @code{gdbserver} to make a similar
21274 choice for debugging.
21276 @value{GDBN} and @code{gdbserver} communicate via either a serial line
21277 or a TCP connection, using the standard @value{GDBN} remote serial
21281 @emph{Warning:} @code{gdbserver} does not have any built-in security.
21282 Do not run @code{gdbserver} connected to any public network; a
21283 @value{GDBN} connection to @code{gdbserver} provides access to the
21284 target system with the same privileges as the user running
21288 @anchor{Running gdbserver}
21289 @subsection Running @code{gdbserver}
21290 @cindex arguments, to @code{gdbserver}
21291 @cindex @code{gdbserver}, command-line arguments
21293 Run @code{gdbserver} on the target system. You need a copy of the
21294 program you want to debug, including any libraries it requires.
21295 @code{gdbserver} does not need your program's symbol table, so you can
21296 strip the program if necessary to save space. @value{GDBN} on the host
21297 system does all the symbol handling.
21299 To use the server, you must tell it how to communicate with @value{GDBN};
21300 the name of your program; and the arguments for your program. The usual
21304 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
21307 @var{comm} is either a device name (to use a serial line), or a TCP
21308 hostname and portnumber, or @code{-} or @code{stdio} to use
21309 stdin/stdout of @code{gdbserver}.
21310 For example, to debug Emacs with the argument
21311 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
21315 target> gdbserver /dev/com1 emacs foo.txt
21318 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
21321 To use a TCP connection instead of a serial line:
21324 target> gdbserver host:2345 emacs foo.txt
21327 The only difference from the previous example is the first argument,
21328 specifying that you are communicating with the host @value{GDBN} via
21329 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
21330 expect a TCP connection from machine @samp{host} to local TCP port 2345.
21331 (Currently, the @samp{host} part is ignored.) You can choose any number
21332 you want for the port number as long as it does not conflict with any
21333 TCP ports already in use on the target system (for example, @code{23} is
21334 reserved for @code{telnet}).@footnote{If you choose a port number that
21335 conflicts with another service, @code{gdbserver} prints an error message
21336 and exits.} You must use the same port number with the host @value{GDBN}
21337 @code{target remote} command.
21339 The @code{stdio} connection is useful when starting @code{gdbserver}
21343 (gdb) target remote | ssh -T hostname gdbserver - hello
21346 The @samp{-T} option to ssh is provided because we don't need a remote pty,
21347 and we don't want escape-character handling. Ssh does this by default when
21348 a command is provided, the flag is provided to make it explicit.
21349 You could elide it if you want to.
21351 Programs started with stdio-connected gdbserver have @file{/dev/null} for
21352 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
21353 display through a pipe connected to gdbserver.
21354 Both @code{stdout} and @code{stderr} use the same pipe.
21356 @anchor{Attaching to a program}
21357 @subsubsection Attaching to a Running Program
21358 @cindex attach to a program, @code{gdbserver}
21359 @cindex @option{--attach}, @code{gdbserver} option
21361 On some targets, @code{gdbserver} can also attach to running programs.
21362 This is accomplished via the @code{--attach} argument. The syntax is:
21365 target> gdbserver --attach @var{comm} @var{pid}
21368 @var{pid} is the process ID of a currently running process. It isn't
21369 necessary to point @code{gdbserver} at a binary for the running process.
21371 In @code{target extended-remote} mode, you can also attach using the
21372 @value{GDBN} attach command
21373 (@pxref{Attaching in Types of Remote Connections}).
21376 You can debug processes by name instead of process ID if your target has the
21377 @code{pidof} utility:
21380 target> gdbserver --attach @var{comm} `pidof @var{program}`
21383 In case more than one copy of @var{program} is running, or @var{program}
21384 has multiple threads, most versions of @code{pidof} support the
21385 @code{-s} option to only return the first process ID.
21387 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
21389 This section applies only when @code{gdbserver} is run to listen on a TCP
21392 @code{gdbserver} normally terminates after all of its debugged processes have
21393 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
21394 extended-remote}, @code{gdbserver} stays running even with no processes left.
21395 @value{GDBN} normally terminates the spawned debugged process on its exit,
21396 which normally also terminates @code{gdbserver} in the @kbd{target remote}
21397 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
21398 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
21399 stays running even in the @kbd{target remote} mode.
21401 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
21402 Such reconnecting is useful for features like @ref{disconnected tracing}. For
21403 completeness, at most one @value{GDBN} can be connected at a time.
21405 @cindex @option{--once}, @code{gdbserver} option
21406 By default, @code{gdbserver} keeps the listening TCP port open, so that
21407 subsequent connections are possible. However, if you start @code{gdbserver}
21408 with the @option{--once} option, it will stop listening for any further
21409 connection attempts after connecting to the first @value{GDBN} session. This
21410 means no further connections to @code{gdbserver} will be possible after the
21411 first one. It also means @code{gdbserver} will terminate after the first
21412 connection with remote @value{GDBN} has closed, even for unexpectedly closed
21413 connections and even in the @kbd{target extended-remote} mode. The
21414 @option{--once} option allows reusing the same port number for connecting to
21415 multiple instances of @code{gdbserver} running on the same host, since each
21416 instance closes its port after the first connection.
21418 @anchor{Other Command-Line Arguments for gdbserver}
21419 @subsubsection Other Command-Line Arguments for @code{gdbserver}
21421 You can use the @option{--multi} option to start @code{gdbserver} without
21422 specifying a program to debug or a process to attach to. Then you can
21423 attach in @code{target extended-remote} mode and run or attach to a
21424 program. For more information,
21425 @pxref{--multi Option in Types of Remote Connnections}.
21427 @cindex @option{--debug}, @code{gdbserver} option
21428 The @option{--debug} option tells @code{gdbserver} to display extra
21429 status information about the debugging process.
21430 @cindex @option{--remote-debug}, @code{gdbserver} option
21431 The @option{--remote-debug} option tells @code{gdbserver} to display
21432 remote protocol debug output.
21433 @cindex @option{--debug-file}, @code{gdbserver} option
21434 @cindex @code{gdbserver}, send all debug output to a single file
21435 The @option{--debug-file=@var{filename}} option tells @code{gdbserver} to
21436 write any debug output to the given @var{filename}. These options are intended
21437 for @code{gdbserver} development and for bug reports to the developers.
21439 @cindex @option{--debug-format}, @code{gdbserver} option
21440 The @option{--debug-format=option1[,option2,...]} option tells
21441 @code{gdbserver} to include additional information in each output.
21442 Possible options are:
21446 Turn off all extra information in debugging output.
21448 Turn on all extra information in debugging output.
21450 Include a timestamp in each line of debugging output.
21453 Options are processed in order. Thus, for example, if @option{none}
21454 appears last then no additional information is added to debugging output.
21456 @cindex @option{--wrapper}, @code{gdbserver} option
21457 The @option{--wrapper} option specifies a wrapper to launch programs
21458 for debugging. The option should be followed by the name of the
21459 wrapper, then any command-line arguments to pass to the wrapper, then
21460 @kbd{--} indicating the end of the wrapper arguments.
21462 @code{gdbserver} runs the specified wrapper program with a combined
21463 command line including the wrapper arguments, then the name of the
21464 program to debug, then any arguments to the program. The wrapper
21465 runs until it executes your program, and then @value{GDBN} gains control.
21467 You can use any program that eventually calls @code{execve} with
21468 its arguments as a wrapper. Several standard Unix utilities do
21469 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
21470 with @code{exec "$@@"} will also work.
21472 For example, you can use @code{env} to pass an environment variable to
21473 the debugged program, without setting the variable in @code{gdbserver}'s
21477 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
21480 @cindex @option{--selftest}
21481 The @option{--selftest} option runs the self tests in @code{gdbserver}:
21484 $ gdbserver --selftest
21485 Ran 2 unit tests, 0 failed
21488 These tests are disabled in release.
21489 @subsection Connecting to @code{gdbserver}
21491 The basic procedure for connecting to the remote target is:
21495 Run @value{GDBN} on the host system.
21498 Make sure you have the necessary symbol files
21499 (@pxref{Host and target files}).
21500 Load symbols for your application using the @code{file} command before you
21501 connect. Use @code{set sysroot} to locate target libraries (unless your
21502 @value{GDBN} was compiled with the correct sysroot using
21503 @code{--with-sysroot}).
21506 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
21507 For TCP connections, you must start up @code{gdbserver} prior to using
21508 the @code{target} command. Otherwise you may get an error whose
21509 text depends on the host system, but which usually looks something like
21510 @samp{Connection refused}. Don't use the @code{load}
21511 command in @value{GDBN} when using @code{target remote} mode, since the
21512 program is already on the target.
21516 @anchor{Monitor Commands for gdbserver}
21517 @subsection Monitor Commands for @code{gdbserver}
21518 @cindex monitor commands, for @code{gdbserver}
21520 During a @value{GDBN} session using @code{gdbserver}, you can use the
21521 @code{monitor} command to send special requests to @code{gdbserver}.
21522 Here are the available commands.
21526 List the available monitor commands.
21528 @item monitor set debug 0
21529 @itemx monitor set debug 1
21530 Disable or enable general debugging messages.
21532 @item monitor set remote-debug 0
21533 @itemx monitor set remote-debug 1
21534 Disable or enable specific debugging messages associated with the remote
21535 protocol (@pxref{Remote Protocol}).
21537 @item monitor set debug-file filename
21538 @itemx monitor set debug-file
21539 Send any debug output to the given file, or to stderr.
21541 @item monitor set debug-format option1@r{[},option2,...@r{]}
21542 Specify additional text to add to debugging messages.
21543 Possible options are:
21547 Turn off all extra information in debugging output.
21549 Turn on all extra information in debugging output.
21551 Include a timestamp in each line of debugging output.
21554 Options are processed in order. Thus, for example, if @option{none}
21555 appears last then no additional information is added to debugging output.
21557 @item monitor set libthread-db-search-path [PATH]
21558 @cindex gdbserver, search path for @code{libthread_db}
21559 When this command is issued, @var{path} is a colon-separated list of
21560 directories to search for @code{libthread_db} (@pxref{Threads,,set
21561 libthread-db-search-path}). If you omit @var{path},
21562 @samp{libthread-db-search-path} will be reset to its default value.
21564 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
21565 not supported in @code{gdbserver}.
21568 Tell gdbserver to exit immediately. This command should be followed by
21569 @code{disconnect} to close the debugging session. @code{gdbserver} will
21570 detach from any attached processes and kill any processes it created.
21571 Use @code{monitor exit} to terminate @code{gdbserver} at the end
21572 of a multi-process mode debug session.
21576 @subsection Tracepoints support in @code{gdbserver}
21577 @cindex tracepoints support in @code{gdbserver}
21579 On some targets, @code{gdbserver} supports tracepoints, fast
21580 tracepoints and static tracepoints.
21582 For fast or static tracepoints to work, a special library called the
21583 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
21584 This library is built and distributed as an integral part of
21585 @code{gdbserver}. In addition, support for static tracepoints
21586 requires building the in-process agent library with static tracepoints
21587 support. At present, the UST (LTTng Userspace Tracer,
21588 @url{http://lttng.org/ust}) tracing engine is supported. This support
21589 is automatically available if UST development headers are found in the
21590 standard include path when @code{gdbserver} is built, or if
21591 @code{gdbserver} was explicitly configured using @option{--with-ust}
21592 to point at such headers. You can explicitly disable the support
21593 using @option{--with-ust=no}.
21595 There are several ways to load the in-process agent in your program:
21598 @item Specifying it as dependency at link time
21600 You can link your program dynamically with the in-process agent
21601 library. On most systems, this is accomplished by adding
21602 @code{-linproctrace} to the link command.
21604 @item Using the system's preloading mechanisms
21606 You can force loading the in-process agent at startup time by using
21607 your system's support for preloading shared libraries. Many Unixes
21608 support the concept of preloading user defined libraries. In most
21609 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
21610 in the environment. See also the description of @code{gdbserver}'s
21611 @option{--wrapper} command line option.
21613 @item Using @value{GDBN} to force loading the agent at run time
21615 On some systems, you can force the inferior to load a shared library,
21616 by calling a dynamic loader function in the inferior that takes care
21617 of dynamically looking up and loading a shared library. On most Unix
21618 systems, the function is @code{dlopen}. You'll use the @code{call}
21619 command for that. For example:
21622 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
21625 Note that on most Unix systems, for the @code{dlopen} function to be
21626 available, the program needs to be linked with @code{-ldl}.
21629 On systems that have a userspace dynamic loader, like most Unix
21630 systems, when you connect to @code{gdbserver} using @code{target
21631 remote}, you'll find that the program is stopped at the dynamic
21632 loader's entry point, and no shared library has been loaded in the
21633 program's address space yet, including the in-process agent. In that
21634 case, before being able to use any of the fast or static tracepoints
21635 features, you need to let the loader run and load the shared
21636 libraries. The simplest way to do that is to run the program to the
21637 main procedure. E.g., if debugging a C or C@t{++} program, start
21638 @code{gdbserver} like so:
21641 $ gdbserver :9999 myprogram
21644 Start GDB and connect to @code{gdbserver} like so, and run to main:
21648 (@value{GDBP}) target remote myhost:9999
21649 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
21650 (@value{GDBP}) b main
21651 (@value{GDBP}) continue
21654 The in-process tracing agent library should now be loaded into the
21655 process; you can confirm it with the @code{info sharedlibrary}
21656 command, which will list @file{libinproctrace.so} as loaded in the
21657 process. You are now ready to install fast tracepoints, list static
21658 tracepoint markers, probe static tracepoints markers, and start
21661 @node Remote Configuration
21662 @section Remote Configuration
21665 @kindex show remote
21666 This section documents the configuration options available when
21667 debugging remote programs. For the options related to the File I/O
21668 extensions of the remote protocol, see @ref{system,
21669 system-call-allowed}.
21672 @item set remoteaddresssize @var{bits}
21673 @cindex address size for remote targets
21674 @cindex bits in remote address
21675 Set the maximum size of address in a memory packet to the specified
21676 number of bits. @value{GDBN} will mask off the address bits above
21677 that number, when it passes addresses to the remote target. The
21678 default value is the number of bits in the target's address.
21680 @item show remoteaddresssize
21681 Show the current value of remote address size in bits.
21683 @item set serial baud @var{n}
21684 @cindex baud rate for remote targets
21685 Set the baud rate for the remote serial I/O to @var{n} baud. The
21686 value is used to set the speed of the serial port used for debugging
21689 @item show serial baud
21690 Show the current speed of the remote connection.
21692 @item set serial parity @var{parity}
21693 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
21694 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
21696 @item show serial parity
21697 Show the current parity of the serial port.
21699 @item set remotebreak
21700 @cindex interrupt remote programs
21701 @cindex BREAK signal instead of Ctrl-C
21702 @anchor{set remotebreak}
21703 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
21704 when you type @kbd{Ctrl-c} to interrupt the program running
21705 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
21706 character instead. The default is off, since most remote systems
21707 expect to see @samp{Ctrl-C} as the interrupt signal.
21709 @item show remotebreak
21710 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
21711 interrupt the remote program.
21713 @item set remoteflow on
21714 @itemx set remoteflow off
21715 @kindex set remoteflow
21716 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
21717 on the serial port used to communicate to the remote target.
21719 @item show remoteflow
21720 @kindex show remoteflow
21721 Show the current setting of hardware flow control.
21723 @item set remotelogbase @var{base}
21724 Set the base (a.k.a.@: radix) of logging serial protocol
21725 communications to @var{base}. Supported values of @var{base} are:
21726 @code{ascii}, @code{octal}, and @code{hex}. The default is
21729 @item show remotelogbase
21730 Show the current setting of the radix for logging remote serial
21733 @item set remotelogfile @var{file}
21734 @cindex record serial communications on file
21735 Record remote serial communications on the named @var{file}. The
21736 default is not to record at all.
21738 @item show remotelogfile
21739 Show the current setting of the file name on which to record the
21740 serial communications.
21742 @item set remotetimeout @var{num}
21743 @cindex timeout for serial communications
21744 @cindex remote timeout
21745 Set the timeout limit to wait for the remote target to respond to
21746 @var{num} seconds. The default is 2 seconds.
21748 @item show remotetimeout
21749 Show the current number of seconds to wait for the remote target
21752 @cindex limit hardware breakpoints and watchpoints
21753 @cindex remote target, limit break- and watchpoints
21754 @anchor{set remote hardware-watchpoint-limit}
21755 @anchor{set remote hardware-breakpoint-limit}
21756 @item set remote hardware-watchpoint-limit @var{limit}
21757 @itemx set remote hardware-breakpoint-limit @var{limit}
21758 Restrict @value{GDBN} to using @var{limit} remote hardware watchpoints
21759 or breakpoints. The @var{limit} can be set to 0 to disable hardware
21760 watchpoints or breakpoints, and @code{unlimited} for unlimited
21761 watchpoints or breakpoints.
21763 @item show remote hardware-watchpoint-limit
21764 @itemx show remote hardware-breakpoint-limit
21765 Show the current limit for the number of hardware watchpoints or
21766 breakpoints that @value{GDBN} can use.
21768 @cindex limit hardware watchpoints length
21769 @cindex remote target, limit watchpoints length
21770 @anchor{set remote hardware-watchpoint-length-limit}
21771 @item set remote hardware-watchpoint-length-limit @var{limit}
21772 Restrict @value{GDBN} to using @var{limit} bytes for the maximum
21773 length of a remote hardware watchpoint. A @var{limit} of 0 disables
21774 hardware watchpoints and @code{unlimited} allows watchpoints of any
21777 @item show remote hardware-watchpoint-length-limit
21778 Show the current limit (in bytes) of the maximum length of
21779 a remote hardware watchpoint.
21781 @item set remote exec-file @var{filename}
21782 @itemx show remote exec-file
21783 @anchor{set remote exec-file}
21784 @cindex executable file, for remote target
21785 Select the file used for @code{run} with @code{target
21786 extended-remote}. This should be set to a filename valid on the
21787 target system. If it is not set, the target will use a default
21788 filename (e.g.@: the last program run).
21790 @item set remote interrupt-sequence
21791 @cindex interrupt remote programs
21792 @cindex select Ctrl-C, BREAK or BREAK-g
21793 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21794 @samp{BREAK-g} as the
21795 sequence to the remote target in order to interrupt the execution.
21796 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21797 is high level of serial line for some certain time.
21798 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21799 It is @code{BREAK} signal followed by character @code{g}.
21801 @item show interrupt-sequence
21802 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21803 is sent by @value{GDBN} to interrupt the remote program.
21804 @code{BREAK-g} is BREAK signal followed by @code{g} and
21805 also known as Magic SysRq g.
21807 @item set remote interrupt-on-connect
21808 @cindex send interrupt-sequence on start
21809 Specify whether interrupt-sequence is sent to remote target when
21810 @value{GDBN} connects to it. This is mostly needed when you debug
21811 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21812 which is known as Magic SysRq g in order to connect @value{GDBN}.
21814 @item show interrupt-on-connect
21815 Show whether interrupt-sequence is sent
21816 to remote target when @value{GDBN} connects to it.
21820 @item set tcp auto-retry on
21821 @cindex auto-retry, for remote TCP target
21822 Enable auto-retry for remote TCP connections. This is useful if the remote
21823 debugging agent is launched in parallel with @value{GDBN}; there is a race
21824 condition because the agent may not become ready to accept the connection
21825 before @value{GDBN} attempts to connect. When auto-retry is
21826 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21827 to establish the connection using the timeout specified by
21828 @code{set tcp connect-timeout}.
21830 @item set tcp auto-retry off
21831 Do not auto-retry failed TCP connections.
21833 @item show tcp auto-retry
21834 Show the current auto-retry setting.
21836 @item set tcp connect-timeout @var{seconds}
21837 @itemx set tcp connect-timeout unlimited
21838 @cindex connection timeout, for remote TCP target
21839 @cindex timeout, for remote target connection
21840 Set the timeout for establishing a TCP connection to the remote target to
21841 @var{seconds}. The timeout affects both polling to retry failed connections
21842 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21843 that are merely slow to complete, and represents an approximate cumulative
21844 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21845 @value{GDBN} will keep attempting to establish a connection forever,
21846 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21848 @item show tcp connect-timeout
21849 Show the current connection timeout setting.
21852 @cindex remote packets, enabling and disabling
21853 The @value{GDBN} remote protocol autodetects the packets supported by
21854 your debugging stub. If you need to override the autodetection, you
21855 can use these commands to enable or disable individual packets. Each
21856 packet can be set to @samp{on} (the remote target supports this
21857 packet), @samp{off} (the remote target does not support this packet),
21858 or @samp{auto} (detect remote target support for this packet). They
21859 all default to @samp{auto}. For more information about each packet,
21860 see @ref{Remote Protocol}.
21862 During normal use, you should not have to use any of these commands.
21863 If you do, that may be a bug in your remote debugging stub, or a bug
21864 in @value{GDBN}. You may want to report the problem to the
21865 @value{GDBN} developers.
21867 For each packet @var{name}, the command to enable or disable the
21868 packet is @code{set remote @var{name}-packet}. The available settings
21871 @multitable @columnfractions 0.28 0.32 0.25
21874 @tab Related Features
21876 @item @code{fetch-register}
21878 @tab @code{info registers}
21880 @item @code{set-register}
21884 @item @code{binary-download}
21886 @tab @code{load}, @code{set}
21888 @item @code{read-aux-vector}
21889 @tab @code{qXfer:auxv:read}
21890 @tab @code{info auxv}
21892 @item @code{symbol-lookup}
21893 @tab @code{qSymbol}
21894 @tab Detecting multiple threads
21896 @item @code{attach}
21897 @tab @code{vAttach}
21900 @item @code{verbose-resume}
21902 @tab Stepping or resuming multiple threads
21908 @item @code{software-breakpoint}
21912 @item @code{hardware-breakpoint}
21916 @item @code{write-watchpoint}
21920 @item @code{read-watchpoint}
21924 @item @code{access-watchpoint}
21928 @item @code{pid-to-exec-file}
21929 @tab @code{qXfer:exec-file:read}
21930 @tab @code{attach}, @code{run}
21932 @item @code{target-features}
21933 @tab @code{qXfer:features:read}
21934 @tab @code{set architecture}
21936 @item @code{library-info}
21937 @tab @code{qXfer:libraries:read}
21938 @tab @code{info sharedlibrary}
21940 @item @code{memory-map}
21941 @tab @code{qXfer:memory-map:read}
21942 @tab @code{info mem}
21944 @item @code{read-sdata-object}
21945 @tab @code{qXfer:sdata:read}
21946 @tab @code{print $_sdata}
21948 @item @code{read-spu-object}
21949 @tab @code{qXfer:spu:read}
21950 @tab @code{info spu}
21952 @item @code{write-spu-object}
21953 @tab @code{qXfer:spu:write}
21954 @tab @code{info spu}
21956 @item @code{read-siginfo-object}
21957 @tab @code{qXfer:siginfo:read}
21958 @tab @code{print $_siginfo}
21960 @item @code{write-siginfo-object}
21961 @tab @code{qXfer:siginfo:write}
21962 @tab @code{set $_siginfo}
21964 @item @code{threads}
21965 @tab @code{qXfer:threads:read}
21966 @tab @code{info threads}
21968 @item @code{get-thread-local-@*storage-address}
21969 @tab @code{qGetTLSAddr}
21970 @tab Displaying @code{__thread} variables
21972 @item @code{get-thread-information-block-address}
21973 @tab @code{qGetTIBAddr}
21974 @tab Display MS-Windows Thread Information Block.
21976 @item @code{search-memory}
21977 @tab @code{qSearch:memory}
21980 @item @code{supported-packets}
21981 @tab @code{qSupported}
21982 @tab Remote communications parameters
21984 @item @code{catch-syscalls}
21985 @tab @code{QCatchSyscalls}
21986 @tab @code{catch syscall}
21988 @item @code{pass-signals}
21989 @tab @code{QPassSignals}
21990 @tab @code{handle @var{signal}}
21992 @item @code{program-signals}
21993 @tab @code{QProgramSignals}
21994 @tab @code{handle @var{signal}}
21996 @item @code{hostio-close-packet}
21997 @tab @code{vFile:close}
21998 @tab @code{remote get}, @code{remote put}
22000 @item @code{hostio-open-packet}
22001 @tab @code{vFile:open}
22002 @tab @code{remote get}, @code{remote put}
22004 @item @code{hostio-pread-packet}
22005 @tab @code{vFile:pread}
22006 @tab @code{remote get}, @code{remote put}
22008 @item @code{hostio-pwrite-packet}
22009 @tab @code{vFile:pwrite}
22010 @tab @code{remote get}, @code{remote put}
22012 @item @code{hostio-unlink-packet}
22013 @tab @code{vFile:unlink}
22014 @tab @code{remote delete}
22016 @item @code{hostio-readlink-packet}
22017 @tab @code{vFile:readlink}
22020 @item @code{hostio-fstat-packet}
22021 @tab @code{vFile:fstat}
22024 @item @code{hostio-setfs-packet}
22025 @tab @code{vFile:setfs}
22028 @item @code{noack-packet}
22029 @tab @code{QStartNoAckMode}
22030 @tab Packet acknowledgment
22032 @item @code{osdata}
22033 @tab @code{qXfer:osdata:read}
22034 @tab @code{info os}
22036 @item @code{query-attached}
22037 @tab @code{qAttached}
22038 @tab Querying remote process attach state.
22040 @item @code{trace-buffer-size}
22041 @tab @code{QTBuffer:size}
22042 @tab @code{set trace-buffer-size}
22044 @item @code{trace-status}
22045 @tab @code{qTStatus}
22046 @tab @code{tstatus}
22048 @item @code{traceframe-info}
22049 @tab @code{qXfer:traceframe-info:read}
22050 @tab Traceframe info
22052 @item @code{install-in-trace}
22053 @tab @code{InstallInTrace}
22054 @tab Install tracepoint in tracing
22056 @item @code{disable-randomization}
22057 @tab @code{QDisableRandomization}
22058 @tab @code{set disable-randomization}
22060 @item @code{startup-with-shell}
22061 @tab @code{QStartupWithShell}
22062 @tab @code{set startup-with-shell}
22064 @item @code{environment-hex-encoded}
22065 @tab @code{QEnvironmentHexEncoded}
22066 @tab @code{set environment}
22068 @item @code{environment-unset}
22069 @tab @code{QEnvironmentUnset}
22070 @tab @code{unset environment}
22072 @item @code{environment-reset}
22073 @tab @code{QEnvironmentReset}
22074 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
22076 @item @code{set-working-dir}
22077 @tab @code{QSetWorkingDir}
22078 @tab @code{set cwd}
22080 @item @code{conditional-breakpoints-packet}
22081 @tab @code{Z0 and Z1}
22082 @tab @code{Support for target-side breakpoint condition evaluation}
22084 @item @code{multiprocess-extensions}
22085 @tab @code{multiprocess extensions}
22086 @tab Debug multiple processes and remote process PID awareness
22088 @item @code{swbreak-feature}
22089 @tab @code{swbreak stop reason}
22092 @item @code{hwbreak-feature}
22093 @tab @code{hwbreak stop reason}
22096 @item @code{fork-event-feature}
22097 @tab @code{fork stop reason}
22100 @item @code{vfork-event-feature}
22101 @tab @code{vfork stop reason}
22104 @item @code{exec-event-feature}
22105 @tab @code{exec stop reason}
22108 @item @code{thread-events}
22109 @tab @code{QThreadEvents}
22110 @tab Tracking thread lifetime.
22112 @item @code{no-resumed-stop-reply}
22113 @tab @code{no resumed thread left stop reply}
22114 @tab Tracking thread lifetime.
22119 @section Implementing a Remote Stub
22121 @cindex debugging stub, example
22122 @cindex remote stub, example
22123 @cindex stub example, remote debugging
22124 The stub files provided with @value{GDBN} implement the target side of the
22125 communication protocol, and the @value{GDBN} side is implemented in the
22126 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
22127 these subroutines to communicate, and ignore the details. (If you're
22128 implementing your own stub file, you can still ignore the details: start
22129 with one of the existing stub files. @file{sparc-stub.c} is the best
22130 organized, and therefore the easiest to read.)
22132 @cindex remote serial debugging, overview
22133 To debug a program running on another machine (the debugging
22134 @dfn{target} machine), you must first arrange for all the usual
22135 prerequisites for the program to run by itself. For example, for a C
22140 A startup routine to set up the C runtime environment; these usually
22141 have a name like @file{crt0}. The startup routine may be supplied by
22142 your hardware supplier, or you may have to write your own.
22145 A C subroutine library to support your program's
22146 subroutine calls, notably managing input and output.
22149 A way of getting your program to the other machine---for example, a
22150 download program. These are often supplied by the hardware
22151 manufacturer, but you may have to write your own from hardware
22155 The next step is to arrange for your program to use a serial port to
22156 communicate with the machine where @value{GDBN} is running (the @dfn{host}
22157 machine). In general terms, the scheme looks like this:
22161 @value{GDBN} already understands how to use this protocol; when everything
22162 else is set up, you can simply use the @samp{target remote} command
22163 (@pxref{Targets,,Specifying a Debugging Target}).
22165 @item On the target,
22166 you must link with your program a few special-purpose subroutines that
22167 implement the @value{GDBN} remote serial protocol. The file containing these
22168 subroutines is called a @dfn{debugging stub}.
22170 On certain remote targets, you can use an auxiliary program
22171 @code{gdbserver} instead of linking a stub into your program.
22172 @xref{Server,,Using the @code{gdbserver} Program}, for details.
22175 The debugging stub is specific to the architecture of the remote
22176 machine; for example, use @file{sparc-stub.c} to debug programs on
22179 @cindex remote serial stub list
22180 These working remote stubs are distributed with @value{GDBN}:
22185 @cindex @file{i386-stub.c}
22188 For Intel 386 and compatible architectures.
22191 @cindex @file{m68k-stub.c}
22192 @cindex Motorola 680x0
22194 For Motorola 680x0 architectures.
22197 @cindex @file{sh-stub.c}
22200 For Renesas SH architectures.
22203 @cindex @file{sparc-stub.c}
22205 For @sc{sparc} architectures.
22207 @item sparcl-stub.c
22208 @cindex @file{sparcl-stub.c}
22211 For Fujitsu @sc{sparclite} architectures.
22215 The @file{README} file in the @value{GDBN} distribution may list other
22216 recently added stubs.
22219 * Stub Contents:: What the stub can do for you
22220 * Bootstrapping:: What you must do for the stub
22221 * Debug Session:: Putting it all together
22224 @node Stub Contents
22225 @subsection What the Stub Can Do for You
22227 @cindex remote serial stub
22228 The debugging stub for your architecture supplies these three
22232 @item set_debug_traps
22233 @findex set_debug_traps
22234 @cindex remote serial stub, initialization
22235 This routine arranges for @code{handle_exception} to run when your
22236 program stops. You must call this subroutine explicitly in your
22237 program's startup code.
22239 @item handle_exception
22240 @findex handle_exception
22241 @cindex remote serial stub, main routine
22242 This is the central workhorse, but your program never calls it
22243 explicitly---the setup code arranges for @code{handle_exception} to
22244 run when a trap is triggered.
22246 @code{handle_exception} takes control when your program stops during
22247 execution (for example, on a breakpoint), and mediates communications
22248 with @value{GDBN} on the host machine. This is where the communications
22249 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
22250 representative on the target machine. It begins by sending summary
22251 information on the state of your program, then continues to execute,
22252 retrieving and transmitting any information @value{GDBN} needs, until you
22253 execute a @value{GDBN} command that makes your program resume; at that point,
22254 @code{handle_exception} returns control to your own code on the target
22258 @cindex @code{breakpoint} subroutine, remote
22259 Use this auxiliary subroutine to make your program contain a
22260 breakpoint. Depending on the particular situation, this may be the only
22261 way for @value{GDBN} to get control. For instance, if your target
22262 machine has some sort of interrupt button, you won't need to call this;
22263 pressing the interrupt button transfers control to
22264 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
22265 simply receiving characters on the serial port may also trigger a trap;
22266 again, in that situation, you don't need to call @code{breakpoint} from
22267 your own program---simply running @samp{target remote} from the host
22268 @value{GDBN} session gets control.
22270 Call @code{breakpoint} if none of these is true, or if you simply want
22271 to make certain your program stops at a predetermined point for the
22272 start of your debugging session.
22275 @node Bootstrapping
22276 @subsection What You Must Do for the Stub
22278 @cindex remote stub, support routines
22279 The debugging stubs that come with @value{GDBN} are set up for a particular
22280 chip architecture, but they have no information about the rest of your
22281 debugging target machine.
22283 First of all you need to tell the stub how to communicate with the
22287 @item int getDebugChar()
22288 @findex getDebugChar
22289 Write this subroutine to read a single character from the serial port.
22290 It may be identical to @code{getchar} for your target system; a
22291 different name is used to allow you to distinguish the two if you wish.
22293 @item void putDebugChar(int)
22294 @findex putDebugChar
22295 Write this subroutine to write a single character to the serial port.
22296 It may be identical to @code{putchar} for your target system; a
22297 different name is used to allow you to distinguish the two if you wish.
22300 @cindex control C, and remote debugging
22301 @cindex interrupting remote targets
22302 If you want @value{GDBN} to be able to stop your program while it is
22303 running, you need to use an interrupt-driven serial driver, and arrange
22304 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
22305 character). That is the character which @value{GDBN} uses to tell the
22306 remote system to stop.
22308 Getting the debugging target to return the proper status to @value{GDBN}
22309 probably requires changes to the standard stub; one quick and dirty way
22310 is to just execute a breakpoint instruction (the ``dirty'' part is that
22311 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
22313 Other routines you need to supply are:
22316 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
22317 @findex exceptionHandler
22318 Write this function to install @var{exception_address} in the exception
22319 handling tables. You need to do this because the stub does not have any
22320 way of knowing what the exception handling tables on your target system
22321 are like (for example, the processor's table might be in @sc{rom},
22322 containing entries which point to a table in @sc{ram}).
22323 The @var{exception_number} specifies the exception which should be changed;
22324 its meaning is architecture-dependent (for example, different numbers
22325 might represent divide by zero, misaligned access, etc). When this
22326 exception occurs, control should be transferred directly to
22327 @var{exception_address}, and the processor state (stack, registers,
22328 and so on) should be just as it is when a processor exception occurs. So if
22329 you want to use a jump instruction to reach @var{exception_address}, it
22330 should be a simple jump, not a jump to subroutine.
22332 For the 386, @var{exception_address} should be installed as an interrupt
22333 gate so that interrupts are masked while the handler runs. The gate
22334 should be at privilege level 0 (the most privileged level). The
22335 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
22336 help from @code{exceptionHandler}.
22338 @item void flush_i_cache()
22339 @findex flush_i_cache
22340 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
22341 instruction cache, if any, on your target machine. If there is no
22342 instruction cache, this subroutine may be a no-op.
22344 On target machines that have instruction caches, @value{GDBN} requires this
22345 function to make certain that the state of your program is stable.
22349 You must also make sure this library routine is available:
22352 @item void *memset(void *, int, int)
22354 This is the standard library function @code{memset} that sets an area of
22355 memory to a known value. If you have one of the free versions of
22356 @code{libc.a}, @code{memset} can be found there; otherwise, you must
22357 either obtain it from your hardware manufacturer, or write your own.
22360 If you do not use the GNU C compiler, you may need other standard
22361 library subroutines as well; this varies from one stub to another,
22362 but in general the stubs are likely to use any of the common library
22363 subroutines which @code{@value{NGCC}} generates as inline code.
22366 @node Debug Session
22367 @subsection Putting it All Together
22369 @cindex remote serial debugging summary
22370 In summary, when your program is ready to debug, you must follow these
22375 Make sure you have defined the supporting low-level routines
22376 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
22378 @code{getDebugChar}, @code{putDebugChar},
22379 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
22383 Insert these lines in your program's startup code, before the main
22384 procedure is called:
22391 On some machines, when a breakpoint trap is raised, the hardware
22392 automatically makes the PC point to the instruction after the
22393 breakpoint. If your machine doesn't do that, you may need to adjust
22394 @code{handle_exception} to arrange for it to return to the instruction
22395 after the breakpoint on this first invocation, so that your program
22396 doesn't keep hitting the initial breakpoint instead of making
22400 For the 680x0 stub only, you need to provide a variable called
22401 @code{exceptionHook}. Normally you just use:
22404 void (*exceptionHook)() = 0;
22408 but if before calling @code{set_debug_traps}, you set it to point to a
22409 function in your program, that function is called when
22410 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
22411 error). The function indicated by @code{exceptionHook} is called with
22412 one parameter: an @code{int} which is the exception number.
22415 Compile and link together: your program, the @value{GDBN} debugging stub for
22416 your target architecture, and the supporting subroutines.
22419 Make sure you have a serial connection between your target machine and
22420 the @value{GDBN} host, and identify the serial port on the host.
22423 @c The "remote" target now provides a `load' command, so we should
22424 @c document that. FIXME.
22425 Download your program to your target machine (or get it there by
22426 whatever means the manufacturer provides), and start it.
22429 Start @value{GDBN} on the host, and connect to the target
22430 (@pxref{Connecting,,Connecting to a Remote Target}).
22434 @node Configurations
22435 @chapter Configuration-Specific Information
22437 While nearly all @value{GDBN} commands are available for all native and
22438 cross versions of the debugger, there are some exceptions. This chapter
22439 describes things that are only available in certain configurations.
22441 There are three major categories of configurations: native
22442 configurations, where the host and target are the same, embedded
22443 operating system configurations, which are usually the same for several
22444 different processor architectures, and bare embedded processors, which
22445 are quite different from each other.
22450 * Embedded Processors::
22457 This section describes details specific to particular native
22461 * BSD libkvm Interface:: Debugging BSD kernel memory images
22462 * Process Information:: Process information
22463 * DJGPP Native:: Features specific to the DJGPP port
22464 * Cygwin Native:: Features specific to the Cygwin port
22465 * Hurd Native:: Features specific to @sc{gnu} Hurd
22466 * Darwin:: Features specific to Darwin
22467 * FreeBSD:: Features specific to FreeBSD
22470 @node BSD libkvm Interface
22471 @subsection BSD libkvm Interface
22474 @cindex kernel memory image
22475 @cindex kernel crash dump
22477 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
22478 interface that provides a uniform interface for accessing kernel virtual
22479 memory images, including live systems and crash dumps. @value{GDBN}
22480 uses this interface to allow you to debug live kernels and kernel crash
22481 dumps on many native BSD configurations. This is implemented as a
22482 special @code{kvm} debugging target. For debugging a live system, load
22483 the currently running kernel into @value{GDBN} and connect to the
22487 (@value{GDBP}) @b{target kvm}
22490 For debugging crash dumps, provide the file name of the crash dump as an
22494 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
22497 Once connected to the @code{kvm} target, the following commands are
22503 Set current context from the @dfn{Process Control Block} (PCB) address.
22506 Set current context from proc address. This command isn't available on
22507 modern FreeBSD systems.
22510 @node Process Information
22511 @subsection Process Information
22513 @cindex examine process image
22514 @cindex process info via @file{/proc}
22516 Some operating systems provide interfaces to fetch additional
22517 information about running processes beyond memory and per-thread
22518 register state. If @value{GDBN} is configured for an operating system
22519 with a supported interface, the command @code{info proc} is available
22520 to report information about the process running your program, or about
22521 any process running on your system.
22523 One supported interface is a facility called @samp{/proc} that can be
22524 used to examine the image of a running process using file-system
22525 subroutines. This facility is supported on @sc{gnu}/Linux and Solaris
22528 On FreeBSD systems, system control nodes are used to query process
22531 In addition, some systems may provide additional process information
22532 in core files. Note that a core file may include a subset of the
22533 information available from a live process. Process information is
22534 currently avaiable from cores created on @sc{gnu}/Linux and FreeBSD
22541 @itemx info proc @var{process-id}
22542 Summarize available information about a process. If a
22543 process ID is specified by @var{process-id}, display information about
22544 that process; otherwise display information about the program being
22545 debugged. The summary includes the debugged process ID, the command
22546 line used to invoke it, its current working directory, and its
22547 executable file's absolute file name.
22549 On some systems, @var{process-id} can be of the form
22550 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
22551 within a process. If the optional @var{pid} part is missing, it means
22552 a thread from the process being debugged (the leading @samp{/} still
22553 needs to be present, or else @value{GDBN} will interpret the number as
22554 a process ID rather than a thread ID).
22556 @item info proc cmdline
22557 @cindex info proc cmdline
22558 Show the original command line of the process. This command is
22559 supported on @sc{gnu}/Linux and FreeBSD.
22561 @item info proc cwd
22562 @cindex info proc cwd
22563 Show the current working directory of the process. This command is
22564 supported on @sc{gnu}/Linux and FreeBSD.
22566 @item info proc exe
22567 @cindex info proc exe
22568 Show the name of executable of the process. This command is supported
22569 on @sc{gnu}/Linux and FreeBSD.
22571 @item info proc files
22572 @cindex info proc files
22573 Show the file descriptors open by the process. For each open file
22574 descriptor, @value{GDBN} shows its number, type (file, directory,
22575 character device, socket), file pointer offset, and the name of the
22576 resource open on the descriptor. The resource name can be a file name
22577 (for files, directories, and devices) or a protocol followed by socket
22578 address (for network connections). This command is supported on
22581 This example shows the open file descriptors for a process using a
22582 tty for standard input and output as well as two network sockets:
22585 (gdb) info proc files 22136
22589 FD Type Offset Flags Name
22590 text file - r-------- /usr/bin/ssh
22591 ctty chr - rw------- /dev/pts/20
22592 cwd dir - r-------- /usr/home/john
22593 root dir - r-------- /
22594 0 chr 0x32933a4 rw------- /dev/pts/20
22595 1 chr 0x32933a4 rw------- /dev/pts/20
22596 2 chr 0x32933a4 rw------- /dev/pts/20
22597 3 socket 0x0 rw----n-- tcp4 10.0.1.2:53014 -> 10.0.1.10:22
22598 4 socket 0x0 rw------- unix stream:/tmp/ssh-FIt89oAzOn5f/agent.2456
22601 @item info proc mappings
22602 @cindex memory address space mappings
22603 Report the memory address space ranges accessible in a process. On
22604 Solaris and FreeBSD systems, each memory range includes information on
22605 whether the process has read, write, or execute access rights to each
22606 range. On @sc{gnu}/Linux and FreeBSD systems, each memory range
22607 includes the object file which is mapped to that range.
22609 @item info proc stat
22610 @itemx info proc status
22611 @cindex process detailed status information
22612 Show additional process-related information, including the user ID and
22613 group ID; virtual memory usage; the signals that are pending, blocked,
22614 and ignored; its TTY; its consumption of system and user time; its
22615 stack size; its @samp{nice} value; etc. These commands are supported
22616 on @sc{gnu}/Linux and FreeBSD.
22618 For @sc{gnu}/Linux systems, see the @samp{proc} man page for more
22619 information (type @kbd{man 5 proc} from your shell prompt).
22621 For FreeBSD systems, @code{info proc stat} is an alias for @code{info
22624 @item info proc all
22625 Show all the information about the process described under all of the
22626 above @code{info proc} subcommands.
22629 @comment These sub-options of 'info proc' were not included when
22630 @comment procfs.c was re-written. Keep their descriptions around
22631 @comment against the day when someone finds the time to put them back in.
22632 @kindex info proc times
22633 @item info proc times
22634 Starting time, user CPU time, and system CPU time for your program and
22637 @kindex info proc id
22639 Report on the process IDs related to your program: its own process ID,
22640 the ID of its parent, the process group ID, and the session ID.
22643 @item set procfs-trace
22644 @kindex set procfs-trace
22645 @cindex @code{procfs} API calls
22646 This command enables and disables tracing of @code{procfs} API calls.
22648 @item show procfs-trace
22649 @kindex show procfs-trace
22650 Show the current state of @code{procfs} API call tracing.
22652 @item set procfs-file @var{file}
22653 @kindex set procfs-file
22654 Tell @value{GDBN} to write @code{procfs} API trace to the named
22655 @var{file}. @value{GDBN} appends the trace info to the previous
22656 contents of the file. The default is to display the trace on the
22659 @item show procfs-file
22660 @kindex show procfs-file
22661 Show the file to which @code{procfs} API trace is written.
22663 @item proc-trace-entry
22664 @itemx proc-trace-exit
22665 @itemx proc-untrace-entry
22666 @itemx proc-untrace-exit
22667 @kindex proc-trace-entry
22668 @kindex proc-trace-exit
22669 @kindex proc-untrace-entry
22670 @kindex proc-untrace-exit
22671 These commands enable and disable tracing of entries into and exits
22672 from the @code{syscall} interface.
22675 @kindex info pidlist
22676 @cindex process list, QNX Neutrino
22677 For QNX Neutrino only, this command displays the list of all the
22678 processes and all the threads within each process.
22681 @kindex info meminfo
22682 @cindex mapinfo list, QNX Neutrino
22683 For QNX Neutrino only, this command displays the list of all mapinfos.
22687 @subsection Features for Debugging @sc{djgpp} Programs
22688 @cindex @sc{djgpp} debugging
22689 @cindex native @sc{djgpp} debugging
22690 @cindex MS-DOS-specific commands
22693 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
22694 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
22695 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
22696 top of real-mode DOS systems and their emulations.
22698 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
22699 defines a few commands specific to the @sc{djgpp} port. This
22700 subsection describes those commands.
22705 This is a prefix of @sc{djgpp}-specific commands which print
22706 information about the target system and important OS structures.
22709 @cindex MS-DOS system info
22710 @cindex free memory information (MS-DOS)
22711 @item info dos sysinfo
22712 This command displays assorted information about the underlying
22713 platform: the CPU type and features, the OS version and flavor, the
22714 DPMI version, and the available conventional and DPMI memory.
22719 @cindex segment descriptor tables
22720 @cindex descriptor tables display
22722 @itemx info dos ldt
22723 @itemx info dos idt
22724 These 3 commands display entries from, respectively, Global, Local,
22725 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
22726 tables are data structures which store a descriptor for each segment
22727 that is currently in use. The segment's selector is an index into a
22728 descriptor table; the table entry for that index holds the
22729 descriptor's base address and limit, and its attributes and access
22732 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
22733 segment (used for both data and the stack), and a DOS segment (which
22734 allows access to DOS/BIOS data structures and absolute addresses in
22735 conventional memory). However, the DPMI host will usually define
22736 additional segments in order to support the DPMI environment.
22738 @cindex garbled pointers
22739 These commands allow to display entries from the descriptor tables.
22740 Without an argument, all entries from the specified table are
22741 displayed. An argument, which should be an integer expression, means
22742 display a single entry whose index is given by the argument. For
22743 example, here's a convenient way to display information about the
22744 debugged program's data segment:
22747 @exdent @code{(@value{GDBP}) info dos ldt $ds}
22748 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
22752 This comes in handy when you want to see whether a pointer is outside
22753 the data segment's limit (i.e.@: @dfn{garbled}).
22755 @cindex page tables display (MS-DOS)
22757 @itemx info dos pte
22758 These two commands display entries from, respectively, the Page
22759 Directory and the Page Tables. Page Directories and Page Tables are
22760 data structures which control how virtual memory addresses are mapped
22761 into physical addresses. A Page Table includes an entry for every
22762 page of memory that is mapped into the program's address space; there
22763 may be several Page Tables, each one holding up to 4096 entries. A
22764 Page Directory has up to 4096 entries, one each for every Page Table
22765 that is currently in use.
22767 Without an argument, @kbd{info dos pde} displays the entire Page
22768 Directory, and @kbd{info dos pte} displays all the entries in all of
22769 the Page Tables. An argument, an integer expression, given to the
22770 @kbd{info dos pde} command means display only that entry from the Page
22771 Directory table. An argument given to the @kbd{info dos pte} command
22772 means display entries from a single Page Table, the one pointed to by
22773 the specified entry in the Page Directory.
22775 @cindex direct memory access (DMA) on MS-DOS
22776 These commands are useful when your program uses @dfn{DMA} (Direct
22777 Memory Access), which needs physical addresses to program the DMA
22780 These commands are supported only with some DPMI servers.
22782 @cindex physical address from linear address
22783 @item info dos address-pte @var{addr}
22784 This command displays the Page Table entry for a specified linear
22785 address. The argument @var{addr} is a linear address which should
22786 already have the appropriate segment's base address added to it,
22787 because this command accepts addresses which may belong to @emph{any}
22788 segment. For example, here's how to display the Page Table entry for
22789 the page where a variable @code{i} is stored:
22792 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
22793 @exdent @code{Page Table entry for address 0x11a00d30:}
22794 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
22798 This says that @code{i} is stored at offset @code{0xd30} from the page
22799 whose physical base address is @code{0x02698000}, and shows all the
22800 attributes of that page.
22802 Note that you must cast the addresses of variables to a @code{char *},
22803 since otherwise the value of @code{__djgpp_base_address}, the base
22804 address of all variables and functions in a @sc{djgpp} program, will
22805 be added using the rules of C pointer arithmetics: if @code{i} is
22806 declared an @code{int}, @value{GDBN} will add 4 times the value of
22807 @code{__djgpp_base_address} to the address of @code{i}.
22809 Here's another example, it displays the Page Table entry for the
22813 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22814 @exdent @code{Page Table entry for address 0x29110:}
22815 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22819 (The @code{+ 3} offset is because the transfer buffer's address is the
22820 3rd member of the @code{_go32_info_block} structure.) The output
22821 clearly shows that this DPMI server maps the addresses in conventional
22822 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22823 linear (@code{0x29110}) addresses are identical.
22825 This command is supported only with some DPMI servers.
22828 @cindex DOS serial data link, remote debugging
22829 In addition to native debugging, the DJGPP port supports remote
22830 debugging via a serial data link. The following commands are specific
22831 to remote serial debugging in the DJGPP port of @value{GDBN}.
22834 @kindex set com1base
22835 @kindex set com1irq
22836 @kindex set com2base
22837 @kindex set com2irq
22838 @kindex set com3base
22839 @kindex set com3irq
22840 @kindex set com4base
22841 @kindex set com4irq
22842 @item set com1base @var{addr}
22843 This command sets the base I/O port address of the @file{COM1} serial
22846 @item set com1irq @var{irq}
22847 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22848 for the @file{COM1} serial port.
22850 There are similar commands @samp{set com2base}, @samp{set com3irq},
22851 etc.@: for setting the port address and the @code{IRQ} lines for the
22854 @kindex show com1base
22855 @kindex show com1irq
22856 @kindex show com2base
22857 @kindex show com2irq
22858 @kindex show com3base
22859 @kindex show com3irq
22860 @kindex show com4base
22861 @kindex show com4irq
22862 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22863 display the current settings of the base address and the @code{IRQ}
22864 lines used by the COM ports.
22867 @kindex info serial
22868 @cindex DOS serial port status
22869 This command prints the status of the 4 DOS serial ports. For each
22870 port, it prints whether it's active or not, its I/O base address and
22871 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22872 counts of various errors encountered so far.
22876 @node Cygwin Native
22877 @subsection Features for Debugging MS Windows PE Executables
22878 @cindex MS Windows debugging
22879 @cindex native Cygwin debugging
22880 @cindex Cygwin-specific commands
22882 @value{GDBN} supports native debugging of MS Windows programs, including
22883 DLLs with and without symbolic debugging information.
22885 @cindex Ctrl-BREAK, MS-Windows
22886 @cindex interrupt debuggee on MS-Windows
22887 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22888 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22889 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22890 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22891 sequence, which can be used to interrupt the debuggee even if it
22894 There are various additional Cygwin-specific commands, described in
22895 this section. Working with DLLs that have no debugging symbols is
22896 described in @ref{Non-debug DLL Symbols}.
22901 This is a prefix of MS Windows-specific commands which print
22902 information about the target system and important OS structures.
22904 @item info w32 selector
22905 This command displays information returned by
22906 the Win32 API @code{GetThreadSelectorEntry} function.
22907 It takes an optional argument that is evaluated to
22908 a long value to give the information about this given selector.
22909 Without argument, this command displays information
22910 about the six segment registers.
22912 @item info w32 thread-information-block
22913 This command displays thread specific information stored in the
22914 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22915 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22917 @kindex signal-event
22918 @item signal-event @var{id}
22919 This command signals an event with user-provided @var{id}. Used to resume
22920 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22922 To use it, create or edit the following keys in
22923 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22924 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22925 (for x86_64 versions):
22929 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22930 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22931 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22933 The first @code{%ld} will be replaced by the process ID of the
22934 crashing process, the second @code{%ld} will be replaced by the ID of
22935 the event that blocks the crashing process, waiting for @value{GDBN}
22939 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22940 make the system run debugger specified by the Debugger key
22941 automatically, @code{0} will cause a dialog box with ``OK'' and
22942 ``Cancel'' buttons to appear, which allows the user to either
22943 terminate the crashing process (OK) or debug it (Cancel).
22946 @kindex set cygwin-exceptions
22947 @cindex debugging the Cygwin DLL
22948 @cindex Cygwin DLL, debugging
22949 @item set cygwin-exceptions @var{mode}
22950 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22951 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22952 @value{GDBN} will delay recognition of exceptions, and may ignore some
22953 exceptions which seem to be caused by internal Cygwin DLL
22954 ``bookkeeping''. This option is meant primarily for debugging the
22955 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22956 @value{GDBN} users with false @code{SIGSEGV} signals.
22958 @kindex show cygwin-exceptions
22959 @item show cygwin-exceptions
22960 Displays whether @value{GDBN} will break on exceptions that happen
22961 inside the Cygwin DLL itself.
22963 @kindex set new-console
22964 @item set new-console @var{mode}
22965 If @var{mode} is @code{on} the debuggee will
22966 be started in a new console on next start.
22967 If @var{mode} is @code{off}, the debuggee will
22968 be started in the same console as the debugger.
22970 @kindex show new-console
22971 @item show new-console
22972 Displays whether a new console is used
22973 when the debuggee is started.
22975 @kindex set new-group
22976 @item set new-group @var{mode}
22977 This boolean value controls whether the debuggee should
22978 start a new group or stay in the same group as the debugger.
22979 This affects the way the Windows OS handles
22982 @kindex show new-group
22983 @item show new-group
22984 Displays current value of new-group boolean.
22986 @kindex set debugevents
22987 @item set debugevents
22988 This boolean value adds debug output concerning kernel events related
22989 to the debuggee seen by the debugger. This includes events that
22990 signal thread and process creation and exit, DLL loading and
22991 unloading, console interrupts, and debugging messages produced by the
22992 Windows @code{OutputDebugString} API call.
22994 @kindex set debugexec
22995 @item set debugexec
22996 This boolean value adds debug output concerning execute events
22997 (such as resume thread) seen by the debugger.
22999 @kindex set debugexceptions
23000 @item set debugexceptions
23001 This boolean value adds debug output concerning exceptions in the
23002 debuggee seen by the debugger.
23004 @kindex set debugmemory
23005 @item set debugmemory
23006 This boolean value adds debug output concerning debuggee memory reads
23007 and writes by the debugger.
23011 This boolean values specifies whether the debuggee is called
23012 via a shell or directly (default value is on).
23016 Displays if the debuggee will be started with a shell.
23021 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
23024 @node Non-debug DLL Symbols
23025 @subsubsection Support for DLLs without Debugging Symbols
23026 @cindex DLLs with no debugging symbols
23027 @cindex Minimal symbols and DLLs
23029 Very often on windows, some of the DLLs that your program relies on do
23030 not include symbolic debugging information (for example,
23031 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
23032 symbols in a DLL, it relies on the minimal amount of symbolic
23033 information contained in the DLL's export table. This section
23034 describes working with such symbols, known internally to @value{GDBN} as
23035 ``minimal symbols''.
23037 Note that before the debugged program has started execution, no DLLs
23038 will have been loaded. The easiest way around this problem is simply to
23039 start the program --- either by setting a breakpoint or letting the
23040 program run once to completion.
23042 @subsubsection DLL Name Prefixes
23044 In keeping with the naming conventions used by the Microsoft debugging
23045 tools, DLL export symbols are made available with a prefix based on the
23046 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
23047 also entered into the symbol table, so @code{CreateFileA} is often
23048 sufficient. In some cases there will be name clashes within a program
23049 (particularly if the executable itself includes full debugging symbols)
23050 necessitating the use of the fully qualified name when referring to the
23051 contents of the DLL. Use single-quotes around the name to avoid the
23052 exclamation mark (``!'') being interpreted as a language operator.
23054 Note that the internal name of the DLL may be all upper-case, even
23055 though the file name of the DLL is lower-case, or vice-versa. Since
23056 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
23057 some confusion. If in doubt, try the @code{info functions} and
23058 @code{info variables} commands or even @code{maint print msymbols}
23059 (@pxref{Symbols}). Here's an example:
23062 (@value{GDBP}) info function CreateFileA
23063 All functions matching regular expression "CreateFileA":
23065 Non-debugging symbols:
23066 0x77e885f4 CreateFileA
23067 0x77e885f4 KERNEL32!CreateFileA
23071 (@value{GDBP}) info function !
23072 All functions matching regular expression "!":
23074 Non-debugging symbols:
23075 0x6100114c cygwin1!__assert
23076 0x61004034 cygwin1!_dll_crt0@@0
23077 0x61004240 cygwin1!dll_crt0(per_process *)
23081 @subsubsection Working with Minimal Symbols
23083 Symbols extracted from a DLL's export table do not contain very much
23084 type information. All that @value{GDBN} can do is guess whether a symbol
23085 refers to a function or variable depending on the linker section that
23086 contains the symbol. Also note that the actual contents of the memory
23087 contained in a DLL are not available unless the program is running. This
23088 means that you cannot examine the contents of a variable or disassemble
23089 a function within a DLL without a running program.
23091 Variables are generally treated as pointers and dereferenced
23092 automatically. For this reason, it is often necessary to prefix a
23093 variable name with the address-of operator (``&'') and provide explicit
23094 type information in the command. Here's an example of the type of
23098 (@value{GDBP}) print 'cygwin1!__argv'
23099 'cygwin1!__argv' has unknown type; cast it to its declared type
23103 (@value{GDBP}) x 'cygwin1!__argv'
23104 'cygwin1!__argv' has unknown type; cast it to its declared type
23107 And two possible solutions:
23110 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
23111 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
23115 (@value{GDBP}) x/2x &'cygwin1!__argv'
23116 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
23117 (@value{GDBP}) x/x 0x10021608
23118 0x10021608: 0x0022fd98
23119 (@value{GDBP}) x/s 0x0022fd98
23120 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
23123 Setting a break point within a DLL is possible even before the program
23124 starts execution. However, under these circumstances, @value{GDBN} can't
23125 examine the initial instructions of the function in order to skip the
23126 function's frame set-up code. You can work around this by using ``*&''
23127 to set the breakpoint at a raw memory address:
23130 (@value{GDBP}) break *&'python22!PyOS_Readline'
23131 Breakpoint 1 at 0x1e04eff0
23134 The author of these extensions is not entirely convinced that setting a
23135 break point within a shared DLL like @file{kernel32.dll} is completely
23139 @subsection Commands Specific to @sc{gnu} Hurd Systems
23140 @cindex @sc{gnu} Hurd debugging
23142 This subsection describes @value{GDBN} commands specific to the
23143 @sc{gnu} Hurd native debugging.
23148 @kindex set signals@r{, Hurd command}
23149 @kindex set sigs@r{, Hurd command}
23150 This command toggles the state of inferior signal interception by
23151 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
23152 affected by this command. @code{sigs} is a shorthand alias for
23157 @kindex show signals@r{, Hurd command}
23158 @kindex show sigs@r{, Hurd command}
23159 Show the current state of intercepting inferior's signals.
23161 @item set signal-thread
23162 @itemx set sigthread
23163 @kindex set signal-thread
23164 @kindex set sigthread
23165 This command tells @value{GDBN} which thread is the @code{libc} signal
23166 thread. That thread is run when a signal is delivered to a running
23167 process. @code{set sigthread} is the shorthand alias of @code{set
23170 @item show signal-thread
23171 @itemx show sigthread
23172 @kindex show signal-thread
23173 @kindex show sigthread
23174 These two commands show which thread will run when the inferior is
23175 delivered a signal.
23178 @kindex set stopped@r{, Hurd command}
23179 This commands tells @value{GDBN} that the inferior process is stopped,
23180 as with the @code{SIGSTOP} signal. The stopped process can be
23181 continued by delivering a signal to it.
23184 @kindex show stopped@r{, Hurd command}
23185 This command shows whether @value{GDBN} thinks the debuggee is
23188 @item set exceptions
23189 @kindex set exceptions@r{, Hurd command}
23190 Use this command to turn off trapping of exceptions in the inferior.
23191 When exception trapping is off, neither breakpoints nor
23192 single-stepping will work. To restore the default, set exception
23195 @item show exceptions
23196 @kindex show exceptions@r{, Hurd command}
23197 Show the current state of trapping exceptions in the inferior.
23199 @item set task pause
23200 @kindex set task@r{, Hurd commands}
23201 @cindex task attributes (@sc{gnu} Hurd)
23202 @cindex pause current task (@sc{gnu} Hurd)
23203 This command toggles task suspension when @value{GDBN} has control.
23204 Setting it to on takes effect immediately, and the task is suspended
23205 whenever @value{GDBN} gets control. Setting it to off will take
23206 effect the next time the inferior is continued. If this option is set
23207 to off, you can use @code{set thread default pause on} or @code{set
23208 thread pause on} (see below) to pause individual threads.
23210 @item show task pause
23211 @kindex show task@r{, Hurd commands}
23212 Show the current state of task suspension.
23214 @item set task detach-suspend-count
23215 @cindex task suspend count
23216 @cindex detach from task, @sc{gnu} Hurd
23217 This command sets the suspend count the task will be left with when
23218 @value{GDBN} detaches from it.
23220 @item show task detach-suspend-count
23221 Show the suspend count the task will be left with when detaching.
23223 @item set task exception-port
23224 @itemx set task excp
23225 @cindex task exception port, @sc{gnu} Hurd
23226 This command sets the task exception port to which @value{GDBN} will
23227 forward exceptions. The argument should be the value of the @dfn{send
23228 rights} of the task. @code{set task excp} is a shorthand alias.
23230 @item set noninvasive
23231 @cindex noninvasive task options
23232 This command switches @value{GDBN} to a mode that is the least
23233 invasive as far as interfering with the inferior is concerned. This
23234 is the same as using @code{set task pause}, @code{set exceptions}, and
23235 @code{set signals} to values opposite to the defaults.
23237 @item info send-rights
23238 @itemx info receive-rights
23239 @itemx info port-rights
23240 @itemx info port-sets
23241 @itemx info dead-names
23244 @cindex send rights, @sc{gnu} Hurd
23245 @cindex receive rights, @sc{gnu} Hurd
23246 @cindex port rights, @sc{gnu} Hurd
23247 @cindex port sets, @sc{gnu} Hurd
23248 @cindex dead names, @sc{gnu} Hurd
23249 These commands display information about, respectively, send rights,
23250 receive rights, port rights, port sets, and dead names of a task.
23251 There are also shorthand aliases: @code{info ports} for @code{info
23252 port-rights} and @code{info psets} for @code{info port-sets}.
23254 @item set thread pause
23255 @kindex set thread@r{, Hurd command}
23256 @cindex thread properties, @sc{gnu} Hurd
23257 @cindex pause current thread (@sc{gnu} Hurd)
23258 This command toggles current thread suspension when @value{GDBN} has
23259 control. Setting it to on takes effect immediately, and the current
23260 thread is suspended whenever @value{GDBN} gets control. Setting it to
23261 off will take effect the next time the inferior is continued.
23262 Normally, this command has no effect, since when @value{GDBN} has
23263 control, the whole task is suspended. However, if you used @code{set
23264 task pause off} (see above), this command comes in handy to suspend
23265 only the current thread.
23267 @item show thread pause
23268 @kindex show thread@r{, Hurd command}
23269 This command shows the state of current thread suspension.
23271 @item set thread run
23272 This command sets whether the current thread is allowed to run.
23274 @item show thread run
23275 Show whether the current thread is allowed to run.
23277 @item set thread detach-suspend-count
23278 @cindex thread suspend count, @sc{gnu} Hurd
23279 @cindex detach from thread, @sc{gnu} Hurd
23280 This command sets the suspend count @value{GDBN} will leave on a
23281 thread when detaching. This number is relative to the suspend count
23282 found by @value{GDBN} when it notices the thread; use @code{set thread
23283 takeover-suspend-count} to force it to an absolute value.
23285 @item show thread detach-suspend-count
23286 Show the suspend count @value{GDBN} will leave on the thread when
23289 @item set thread exception-port
23290 @itemx set thread excp
23291 Set the thread exception port to which to forward exceptions. This
23292 overrides the port set by @code{set task exception-port} (see above).
23293 @code{set thread excp} is the shorthand alias.
23295 @item set thread takeover-suspend-count
23296 Normally, @value{GDBN}'s thread suspend counts are relative to the
23297 value @value{GDBN} finds when it notices each thread. This command
23298 changes the suspend counts to be absolute instead.
23300 @item set thread default
23301 @itemx show thread default
23302 @cindex thread default settings, @sc{gnu} Hurd
23303 Each of the above @code{set thread} commands has a @code{set thread
23304 default} counterpart (e.g., @code{set thread default pause}, @code{set
23305 thread default exception-port}, etc.). The @code{thread default}
23306 variety of commands sets the default thread properties for all
23307 threads; you can then change the properties of individual threads with
23308 the non-default commands.
23315 @value{GDBN} provides the following commands specific to the Darwin target:
23318 @item set debug darwin @var{num}
23319 @kindex set debug darwin
23320 When set to a non zero value, enables debugging messages specific to
23321 the Darwin support. Higher values produce more verbose output.
23323 @item show debug darwin
23324 @kindex show debug darwin
23325 Show the current state of Darwin messages.
23327 @item set debug mach-o @var{num}
23328 @kindex set debug mach-o
23329 When set to a non zero value, enables debugging messages while
23330 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
23331 file format used on Darwin for object and executable files.) Higher
23332 values produce more verbose output. This is a command to diagnose
23333 problems internal to @value{GDBN} and should not be needed in normal
23336 @item show debug mach-o
23337 @kindex show debug mach-o
23338 Show the current state of Mach-O file messages.
23340 @item set mach-exceptions on
23341 @itemx set mach-exceptions off
23342 @kindex set mach-exceptions
23343 On Darwin, faults are first reported as a Mach exception and are then
23344 mapped to a Posix signal. Use this command to turn on trapping of
23345 Mach exceptions in the inferior. This might be sometimes useful to
23346 better understand the cause of a fault. The default is off.
23348 @item show mach-exceptions
23349 @kindex show mach-exceptions
23350 Show the current state of exceptions trapping.
23354 @subsection FreeBSD
23357 When the ABI of a system call is changed in the FreeBSD kernel, this
23358 is implemented by leaving a compatibility system call using the old
23359 ABI at the existing number and allocating a new system call number for
23360 the version using the new ABI. As a convenience, when a system call
23361 is caught by name (@pxref{catch syscall}), compatibility system calls
23364 For example, FreeBSD 12 introduced a new variant of the @code{kevent}
23365 system call and catching the @code{kevent} system call by name catches
23369 (@value{GDBP}) catch syscall kevent
23370 Catchpoint 1 (syscalls 'freebsd11_kevent' [363] 'kevent' [560])
23376 @section Embedded Operating Systems
23378 This section describes configurations involving the debugging of
23379 embedded operating systems that are available for several different
23382 @value{GDBN} includes the ability to debug programs running on
23383 various real-time operating systems.
23385 @node Embedded Processors
23386 @section Embedded Processors
23388 This section goes into details specific to particular embedded
23391 @cindex send command to simulator
23392 Whenever a specific embedded processor has a simulator, @value{GDBN}
23393 allows to send an arbitrary command to the simulator.
23396 @item sim @var{command}
23397 @kindex sim@r{, a command}
23398 Send an arbitrary @var{command} string to the simulator. Consult the
23399 documentation for the specific simulator in use for information about
23400 acceptable commands.
23405 * ARC:: Synopsys ARC
23407 * M68K:: Motorola M68K
23408 * MicroBlaze:: Xilinx MicroBlaze
23409 * MIPS Embedded:: MIPS Embedded
23410 * OpenRISC 1000:: OpenRISC 1000 (or1k)
23411 * PowerPC Embedded:: PowerPC Embedded
23414 * Super-H:: Renesas Super-H
23418 @subsection Synopsys ARC
23419 @cindex Synopsys ARC
23420 @cindex ARC specific commands
23426 @value{GDBN} provides the following ARC-specific commands:
23429 @item set debug arc
23430 @kindex set debug arc
23431 Control the level of ARC specific debug messages. Use 0 for no messages (the
23432 default), 1 for debug messages, and 2 for even more debug messages.
23434 @item show debug arc
23435 @kindex show debug arc
23436 Show the level of ARC specific debugging in operation.
23438 @item maint print arc arc-instruction @var{address}
23439 @kindex maint print arc arc-instruction
23440 Print internal disassembler information about instruction at a given address.
23447 @value{GDBN} provides the following ARM-specific commands:
23450 @item set arm disassembler
23452 This commands selects from a list of disassembly styles. The
23453 @code{"std"} style is the standard style.
23455 @item show arm disassembler
23457 Show the current disassembly style.
23459 @item set arm apcs32
23460 @cindex ARM 32-bit mode
23461 This command toggles ARM operation mode between 32-bit and 26-bit.
23463 @item show arm apcs32
23464 Display the current usage of the ARM 32-bit mode.
23466 @item set arm fpu @var{fputype}
23467 This command sets the ARM floating-point unit (FPU) type. The
23468 argument @var{fputype} can be one of these:
23472 Determine the FPU type by querying the OS ABI.
23474 Software FPU, with mixed-endian doubles on little-endian ARM
23477 GCC-compiled FPA co-processor.
23479 Software FPU with pure-endian doubles.
23485 Show the current type of the FPU.
23488 This command forces @value{GDBN} to use the specified ABI.
23491 Show the currently used ABI.
23493 @item set arm fallback-mode (arm|thumb|auto)
23494 @value{GDBN} uses the symbol table, when available, to determine
23495 whether instructions are ARM or Thumb. This command controls
23496 @value{GDBN}'s default behavior when the symbol table is not
23497 available. The default is @samp{auto}, which causes @value{GDBN} to
23498 use the current execution mode (from the @code{T} bit in the @code{CPSR}
23501 @item show arm fallback-mode
23502 Show the current fallback instruction mode.
23504 @item set arm force-mode (arm|thumb|auto)
23505 This command overrides use of the symbol table to determine whether
23506 instructions are ARM or Thumb. The default is @samp{auto}, which
23507 causes @value{GDBN} to use the symbol table and then the setting
23508 of @samp{set arm fallback-mode}.
23510 @item show arm force-mode
23511 Show the current forced instruction mode.
23513 @item set debug arm
23514 Toggle whether to display ARM-specific debugging messages from the ARM
23515 target support subsystem.
23517 @item show debug arm
23518 Show whether ARM-specific debugging messages are enabled.
23522 @item target sim @r{[}@var{simargs}@r{]} @dots{}
23523 The @value{GDBN} ARM simulator accepts the following optional arguments.
23526 @item --swi-support=@var{type}
23527 Tell the simulator which SWI interfaces to support. The argument
23528 @var{type} may be a comma separated list of the following values.
23529 The default value is @code{all}.
23544 The Motorola m68k configuration includes ColdFire support.
23547 @subsection MicroBlaze
23548 @cindex Xilinx MicroBlaze
23549 @cindex XMD, Xilinx Microprocessor Debugger
23551 The MicroBlaze is a soft-core processor supported on various Xilinx
23552 FPGAs, such as Spartan or Virtex series. Boards with these processors
23553 usually have JTAG ports which connect to a host system running the Xilinx
23554 Embedded Development Kit (EDK) or Software Development Kit (SDK).
23555 This host system is used to download the configuration bitstream to
23556 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
23557 communicates with the target board using the JTAG interface and
23558 presents a @code{gdbserver} interface to the board. By default
23559 @code{xmd} uses port @code{1234}. (While it is possible to change
23560 this default port, it requires the use of undocumented @code{xmd}
23561 commands. Contact Xilinx support if you need to do this.)
23563 Use these GDB commands to connect to the MicroBlaze target processor.
23566 @item target remote :1234
23567 Use this command to connect to the target if you are running @value{GDBN}
23568 on the same system as @code{xmd}.
23570 @item target remote @var{xmd-host}:1234
23571 Use this command to connect to the target if it is connected to @code{xmd}
23572 running on a different system named @var{xmd-host}.
23575 Use this command to download a program to the MicroBlaze target.
23577 @item set debug microblaze @var{n}
23578 Enable MicroBlaze-specific debugging messages if non-zero.
23580 @item show debug microblaze @var{n}
23581 Show MicroBlaze-specific debugging level.
23584 @node MIPS Embedded
23585 @subsection @acronym{MIPS} Embedded
23588 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
23591 @item set mipsfpu double
23592 @itemx set mipsfpu single
23593 @itemx set mipsfpu none
23594 @itemx set mipsfpu auto
23595 @itemx show mipsfpu
23596 @kindex set mipsfpu
23597 @kindex show mipsfpu
23598 @cindex @acronym{MIPS} remote floating point
23599 @cindex floating point, @acronym{MIPS} remote
23600 If your target board does not support the @acronym{MIPS} floating point
23601 coprocessor, you should use the command @samp{set mipsfpu none} (if you
23602 need this, you may wish to put the command in your @value{GDBN} init
23603 file). This tells @value{GDBN} how to find the return value of
23604 functions which return floating point values. It also allows
23605 @value{GDBN} to avoid saving the floating point registers when calling
23606 functions on the board. If you are using a floating point coprocessor
23607 with only single precision floating point support, as on the @sc{r4650}
23608 processor, use the command @samp{set mipsfpu single}. The default
23609 double precision floating point coprocessor may be selected using
23610 @samp{set mipsfpu double}.
23612 In previous versions the only choices were double precision or no
23613 floating point, so @samp{set mipsfpu on} will select double precision
23614 and @samp{set mipsfpu off} will select no floating point.
23616 As usual, you can inquire about the @code{mipsfpu} variable with
23617 @samp{show mipsfpu}.
23620 @node OpenRISC 1000
23621 @subsection OpenRISC 1000
23622 @cindex OpenRISC 1000
23625 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
23626 mainly provided as a soft-core which can run on Xilinx, Altera and other
23629 @value{GDBN} for OpenRISC supports the below commands when connecting to
23637 Runs the builtin CPU simulator which can run very basic
23638 programs but does not support most hardware functions like MMU.
23639 For more complex use cases the user is advised to run an external
23640 target, and connect using @samp{target remote}.
23642 Example: @code{target sim}
23644 @item set debug or1k
23645 Toggle whether to display OpenRISC-specific debugging messages from the
23646 OpenRISC target support subsystem.
23648 @item show debug or1k
23649 Show whether OpenRISC-specific debugging messages are enabled.
23652 @node PowerPC Embedded
23653 @subsection PowerPC Embedded
23655 @cindex DVC register
23656 @value{GDBN} supports using the DVC (Data Value Compare) register to
23657 implement in hardware simple hardware watchpoint conditions of the form:
23660 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
23661 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
23664 The DVC register will be automatically used when @value{GDBN} detects
23665 such pattern in a condition expression, and the created watchpoint uses one
23666 debug register (either the @code{exact-watchpoints} option is on and the
23667 variable is scalar, or the variable has a length of one byte). This feature
23668 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
23671 When running on PowerPC embedded processors, @value{GDBN} automatically uses
23672 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
23673 in which case watchpoints using only one debug register are created when
23674 watching variables of scalar types.
23676 You can create an artificial array to watch an arbitrary memory
23677 region using one of the following commands (@pxref{Expressions}):
23680 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
23681 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
23684 PowerPC embedded processors support masked watchpoints. See the discussion
23685 about the @code{mask} argument in @ref{Set Watchpoints}.
23687 @cindex ranged breakpoint
23688 PowerPC embedded processors support hardware accelerated
23689 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
23690 the inferior whenever it executes an instruction at any address within
23691 the range it specifies. To set a ranged breakpoint in @value{GDBN},
23692 use the @code{break-range} command.
23694 @value{GDBN} provides the following PowerPC-specific commands:
23697 @kindex break-range
23698 @item break-range @var{start-location}, @var{end-location}
23699 Set a breakpoint for an address range given by
23700 @var{start-location} and @var{end-location}, which can specify a function name,
23701 a line number, an offset of lines from the current line or from the start
23702 location, or an address of an instruction (see @ref{Specify Location},
23703 for a list of all the possible ways to specify a @var{location}.)
23704 The breakpoint will stop execution of the inferior whenever it
23705 executes an instruction at any address within the specified range,
23706 (including @var{start-location} and @var{end-location}.)
23708 @kindex set powerpc
23709 @item set powerpc soft-float
23710 @itemx show powerpc soft-float
23711 Force @value{GDBN} to use (or not use) a software floating point calling
23712 convention. By default, @value{GDBN} selects the calling convention based
23713 on the selected architecture and the provided executable file.
23715 @item set powerpc vector-abi
23716 @itemx show powerpc vector-abi
23717 Force @value{GDBN} to use the specified calling convention for vector
23718 arguments and return values. The valid options are @samp{auto};
23719 @samp{generic}, to avoid vector registers even if they are present;
23720 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
23721 registers. By default, @value{GDBN} selects the calling convention
23722 based on the selected architecture and the provided executable file.
23724 @item set powerpc exact-watchpoints
23725 @itemx show powerpc exact-watchpoints
23726 Allow @value{GDBN} to use only one debug register when watching a variable
23727 of scalar type, thus assuming that the variable is accessed through the
23728 address of its first byte.
23733 @subsection Atmel AVR
23736 When configured for debugging the Atmel AVR, @value{GDBN} supports the
23737 following AVR-specific commands:
23740 @item info io_registers
23741 @kindex info io_registers@r{, AVR}
23742 @cindex I/O registers (Atmel AVR)
23743 This command displays information about the AVR I/O registers. For
23744 each register, @value{GDBN} prints its number and value.
23751 When configured for debugging CRIS, @value{GDBN} provides the
23752 following CRIS-specific commands:
23755 @item set cris-version @var{ver}
23756 @cindex CRIS version
23757 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
23758 The CRIS version affects register names and sizes. This command is useful in
23759 case autodetection of the CRIS version fails.
23761 @item show cris-version
23762 Show the current CRIS version.
23764 @item set cris-dwarf2-cfi
23765 @cindex DWARF-2 CFI and CRIS
23766 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
23767 Change to @samp{off} when using @code{gcc-cris} whose version is below
23770 @item show cris-dwarf2-cfi
23771 Show the current state of using DWARF-2 CFI.
23773 @item set cris-mode @var{mode}
23775 Set the current CRIS mode to @var{mode}. It should only be changed when
23776 debugging in guru mode, in which case it should be set to
23777 @samp{guru} (the default is @samp{normal}).
23779 @item show cris-mode
23780 Show the current CRIS mode.
23784 @subsection Renesas Super-H
23787 For the Renesas Super-H processor, @value{GDBN} provides these
23791 @item set sh calling-convention @var{convention}
23792 @kindex set sh calling-convention
23793 Set the calling-convention used when calling functions from @value{GDBN}.
23794 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
23795 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
23796 convention. If the DWARF-2 information of the called function specifies
23797 that the function follows the Renesas calling convention, the function
23798 is called using the Renesas calling convention. If the calling convention
23799 is set to @samp{renesas}, the Renesas calling convention is always used,
23800 regardless of the DWARF-2 information. This can be used to override the
23801 default of @samp{gcc} if debug information is missing, or the compiler
23802 does not emit the DWARF-2 calling convention entry for a function.
23804 @item show sh calling-convention
23805 @kindex show sh calling-convention
23806 Show the current calling convention setting.
23811 @node Architectures
23812 @section Architectures
23814 This section describes characteristics of architectures that affect
23815 all uses of @value{GDBN} with the architecture, both native and cross.
23822 * HPPA:: HP PA architecture
23823 * SPU:: Cell Broadband Engine SPU architecture
23831 @subsection AArch64
23832 @cindex AArch64 support
23834 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23835 following special commands:
23838 @item set debug aarch64
23839 @kindex set debug aarch64
23840 This command determines whether AArch64 architecture-specific debugging
23841 messages are to be displayed.
23843 @item show debug aarch64
23844 Show whether AArch64 debugging messages are displayed.
23848 @subsubsection AArch64 SVE.
23849 @cindex AArch64 SVE.
23851 When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
23852 Extension (SVE) is present, then @value{GDBN} will provide the vector registers
23853 @code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
23854 @code{$p15}, and the @code{$ffr} register. In addition, the pseudo register
23855 @code{$vg} will be provided. This is the vector granule for the current thread
23856 and represents the number of 64-bit chunks in an SVE @code{z} register.
23858 If the vector length changes, then the @code{$vg} register will be updated,
23859 but the lengths of the @code{z} and @code{p} registers will not change. This
23860 is a known limitation of @value{GDBN} and does not affect the execution of the
23865 @subsection x86 Architecture-specific Issues
23868 @item set struct-convention @var{mode}
23869 @kindex set struct-convention
23870 @cindex struct return convention
23871 @cindex struct/union returned in registers
23872 Set the convention used by the inferior to return @code{struct}s and
23873 @code{union}s from functions to @var{mode}. Possible values of
23874 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23875 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23876 are returned on the stack, while @code{"reg"} means that a
23877 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23878 be returned in a register.
23880 @item show struct-convention
23881 @kindex show struct-convention
23882 Show the current setting of the convention to return @code{struct}s
23887 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23888 @cindex Intel Memory Protection Extensions (MPX).
23890 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23891 @footnote{The register named with capital letters represent the architecture
23892 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23893 which are the lower bound and upper bound. Bounds are effective addresses or
23894 memory locations. The upper bounds are architecturally represented in 1's
23895 complement form. A bound having lower bound = 0, and upper bound = 0
23896 (1's complement of all bits set) will allow access to the entire address space.
23898 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23899 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23900 display the upper bound performing the complement of one operation on the
23901 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23902 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23903 can also be noted that the upper bounds are inclusive.
23905 As an example, assume that the register BND0 holds bounds for a pointer having
23906 access allowed for the range between 0x32 and 0x71. The values present on
23907 bnd0raw and bnd registers are presented as follows:
23910 bnd0raw = @{0x32, 0xffffffff8e@}
23911 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23914 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23915 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23916 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23917 Python, the display includes the memory size, in bits, accessible to
23920 Bounds can also be stored in bounds tables, which are stored in
23921 application memory. These tables store bounds for pointers by specifying
23922 the bounds pointer's value along with its bounds. Evaluating and changing
23923 bounds located in bound tables is therefore interesting while investigating
23924 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23927 @item show mpx bound @var{pointer}
23928 @kindex show mpx bound
23929 Display bounds of the given @var{pointer}.
23931 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23932 @kindex set mpx bound
23933 Set the bounds of a pointer in the bound table.
23934 This command takes three parameters: @var{pointer} is the pointers
23935 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23936 for lower and upper bounds respectively.
23939 When you call an inferior function on an Intel MPX enabled program,
23940 GDB sets the inferior's bound registers to the init (disabled) state
23941 before calling the function. As a consequence, bounds checks for the
23942 pointer arguments passed to the function will always pass.
23944 This is necessary because when you call an inferior function, the
23945 program is usually in the middle of the execution of other function.
23946 Since at that point bound registers are in an arbitrary state, not
23947 clearing them would lead to random bound violations in the called
23950 You can still examine the influence of the bound registers on the
23951 execution of the called function by stopping the execution of the
23952 called function at its prologue, setting bound registers, and
23953 continuing the execution. For example:
23957 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23958 $ print upper (a, b, c, d, 1)
23959 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23961 @{lbound = 0x0, ubound = ffffffff@} : size -1
23964 At this last step the value of bnd0 can be changed for investigation of bound
23965 violations caused along the execution of the call. In order to know how to
23966 set the bound registers or bound table for the call consult the ABI.
23971 See the following section.
23974 @subsection @acronym{MIPS}
23976 @cindex stack on Alpha
23977 @cindex stack on @acronym{MIPS}
23978 @cindex Alpha stack
23979 @cindex @acronym{MIPS} stack
23980 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23981 sometimes requires @value{GDBN} to search backward in the object code to
23982 find the beginning of a function.
23984 @cindex response time, @acronym{MIPS} debugging
23985 To improve response time (especially for embedded applications, where
23986 @value{GDBN} may be restricted to a slow serial line for this search)
23987 you may want to limit the size of this search, using one of these
23991 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23992 @item set heuristic-fence-post @var{limit}
23993 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23994 search for the beginning of a function. A value of @var{0} (the
23995 default) means there is no limit. However, except for @var{0}, the
23996 larger the limit the more bytes @code{heuristic-fence-post} must search
23997 and therefore the longer it takes to run. You should only need to use
23998 this command when debugging a stripped executable.
24000 @item show heuristic-fence-post
24001 Display the current limit.
24005 These commands are available @emph{only} when @value{GDBN} is configured
24006 for debugging programs on Alpha or @acronym{MIPS} processors.
24008 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
24012 @item set mips abi @var{arg}
24013 @kindex set mips abi
24014 @cindex set ABI for @acronym{MIPS}
24015 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
24016 values of @var{arg} are:
24020 The default ABI associated with the current binary (this is the
24030 @item show mips abi
24031 @kindex show mips abi
24032 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
24034 @item set mips compression @var{arg}
24035 @kindex set mips compression
24036 @cindex code compression, @acronym{MIPS}
24037 Tell @value{GDBN} which @acronym{MIPS} compressed
24038 @acronym{ISA, Instruction Set Architecture} encoding is used by the
24039 inferior. @value{GDBN} uses this for code disassembly and other
24040 internal interpretation purposes. This setting is only referred to
24041 when no executable has been associated with the debugging session or
24042 the executable does not provide information about the encoding it uses.
24043 Otherwise this setting is automatically updated from information
24044 provided by the executable.
24046 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
24047 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
24048 executables containing @acronym{MIPS16} code frequently are not
24049 identified as such.
24051 This setting is ``sticky''; that is, it retains its value across
24052 debugging sessions until reset either explicitly with this command or
24053 implicitly from an executable.
24055 The compiler and/or assembler typically add symbol table annotations to
24056 identify functions compiled for the @acronym{MIPS16} or
24057 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
24058 are present, @value{GDBN} uses them in preference to the global
24059 compressed @acronym{ISA} encoding setting.
24061 @item show mips compression
24062 @kindex show mips compression
24063 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
24064 @value{GDBN} to debug the inferior.
24067 @itemx show mipsfpu
24068 @xref{MIPS Embedded, set mipsfpu}.
24070 @item set mips mask-address @var{arg}
24071 @kindex set mips mask-address
24072 @cindex @acronym{MIPS} addresses, masking
24073 This command determines whether the most-significant 32 bits of 64-bit
24074 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
24075 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
24076 setting, which lets @value{GDBN} determine the correct value.
24078 @item show mips mask-address
24079 @kindex show mips mask-address
24080 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
24083 @item set remote-mips64-transfers-32bit-regs
24084 @kindex set remote-mips64-transfers-32bit-regs
24085 This command controls compatibility with 64-bit @acronym{MIPS} targets that
24086 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
24087 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
24088 and 64 bits for other registers, set this option to @samp{on}.
24090 @item show remote-mips64-transfers-32bit-regs
24091 @kindex show remote-mips64-transfers-32bit-regs
24092 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
24094 @item set debug mips
24095 @kindex set debug mips
24096 This command turns on and off debugging messages for the @acronym{MIPS}-specific
24097 target code in @value{GDBN}.
24099 @item show debug mips
24100 @kindex show debug mips
24101 Show the current setting of @acronym{MIPS} debugging messages.
24107 @cindex HPPA support
24109 When @value{GDBN} is debugging the HP PA architecture, it provides the
24110 following special commands:
24113 @item set debug hppa
24114 @kindex set debug hppa
24115 This command determines whether HPPA architecture-specific debugging
24116 messages are to be displayed.
24118 @item show debug hppa
24119 Show whether HPPA debugging messages are displayed.
24121 @item maint print unwind @var{address}
24122 @kindex maint print unwind@r{, HPPA}
24123 This command displays the contents of the unwind table entry at the
24124 given @var{address}.
24130 @subsection Cell Broadband Engine SPU architecture
24131 @cindex Cell Broadband Engine
24134 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
24135 it provides the following special commands:
24138 @item info spu event
24140 Display SPU event facility status. Shows current event mask
24141 and pending event status.
24143 @item info spu signal
24144 Display SPU signal notification facility status. Shows pending
24145 signal-control word and signal notification mode of both signal
24146 notification channels.
24148 @item info spu mailbox
24149 Display SPU mailbox facility status. Shows all pending entries,
24150 in order of processing, in each of the SPU Write Outbound,
24151 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
24154 Display MFC DMA status. Shows all pending commands in the MFC
24155 DMA queue. For each entry, opcode, tag, class IDs, effective
24156 and local store addresses and transfer size are shown.
24158 @item info spu proxydma
24159 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
24160 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
24161 and local store addresses and transfer size are shown.
24165 When @value{GDBN} is debugging a combined PowerPC/SPU application
24166 on the Cell Broadband Engine, it provides in addition the following
24170 @item set spu stop-on-load @var{arg}
24172 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
24173 will give control to the user when a new SPE thread enters its @code{main}
24174 function. The default is @code{off}.
24176 @item show spu stop-on-load
24178 Show whether to stop for new SPE threads.
24180 @item set spu auto-flush-cache @var{arg}
24181 Set whether to automatically flush the software-managed cache. When set to
24182 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
24183 cache to be flushed whenever SPE execution stops. This provides a consistent
24184 view of PowerPC memory that is accessed via the cache. If an application
24185 does not use the software-managed cache, this option has no effect.
24187 @item show spu auto-flush-cache
24188 Show whether to automatically flush the software-managed cache.
24193 @subsection PowerPC
24194 @cindex PowerPC architecture
24196 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
24197 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
24198 numbers stored in the floating point registers. These values must be stored
24199 in two consecutive registers, always starting at an even register like
24200 @code{f0} or @code{f2}.
24202 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
24203 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
24204 @code{f2} and @code{f3} for @code{$dl1} and so on.
24206 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
24207 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
24210 @subsection Nios II
24211 @cindex Nios II architecture
24213 When @value{GDBN} is debugging the Nios II architecture,
24214 it provides the following special commands:
24218 @item set debug nios2
24219 @kindex set debug nios2
24220 This command turns on and off debugging messages for the Nios II
24221 target code in @value{GDBN}.
24223 @item show debug nios2
24224 @kindex show debug nios2
24225 Show the current setting of Nios II debugging messages.
24229 @subsection Sparc64
24230 @cindex Sparc64 support
24231 @cindex Application Data Integrity
24232 @subsubsection ADI Support
24234 The M7 processor supports an Application Data Integrity (ADI) feature that
24235 detects invalid data accesses. When software allocates memory and enables
24236 ADI on the allocated memory, it chooses a 4-bit version number, sets the
24237 version in the upper 4 bits of the 64-bit pointer to that data, and stores
24238 the 4-bit version in every cacheline of that data. Hardware saves the latter
24239 in spare bits in the cache and memory hierarchy. On each load and store,
24240 the processor compares the upper 4 VA (virtual address) bits to the
24241 cacheline's version. If there is a mismatch, the processor generates a
24242 version mismatch trap which can be either precise or disrupting. The trap
24243 is an error condition which the kernel delivers to the process as a SIGSEGV
24246 Note that only 64-bit applications can use ADI and need to be built with
24249 Values of the ADI version tags, which are in granularity of a
24250 cacheline (64 bytes), can be viewed or modified.
24254 @kindex adi examine
24255 @item adi (examine | x) [ / @var{n} ] @var{addr}
24257 The @code{adi examine} command displays the value of one ADI version tag per
24260 @var{n} is a decimal integer specifying the number in bytes; the default
24261 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
24262 block size, to display.
24264 @var{addr} is the address in user address space where you want @value{GDBN}
24265 to begin displaying the ADI version tags.
24267 Below is an example of displaying ADI versions of variable "shmaddr".
24270 (@value{GDBP}) adi x/100 shmaddr
24271 0xfff800010002c000: 0 0
24275 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
24277 The @code{adi assign} command is used to assign new ADI version tag
24280 @var{n} is a decimal integer specifying the number in bytes;
24281 the default is 1. It specifies how much ADI version information, at the
24282 ratio of 1:ADI block size, to modify.
24284 @var{addr} is the address in user address space where you want @value{GDBN}
24285 to begin modifying the ADI version tags.
24287 @var{tag} is the new ADI version tag.
24289 For example, do the following to modify then verify ADI versions of
24290 variable "shmaddr":
24293 (@value{GDBP}) adi a/100 shmaddr = 7
24294 (@value{GDBP}) adi x/100 shmaddr
24295 0xfff800010002c000: 7 7
24302 @cindex S12Z support
24304 When @value{GDBN} is debugging the S12Z architecture,
24305 it provides the following special command:
24308 @item maint info bdccsr
24309 @kindex maint info bdccsr@r{, S12Z}
24310 This command displays the current value of the microprocessor's
24315 @node Controlling GDB
24316 @chapter Controlling @value{GDBN}
24318 You can alter the way @value{GDBN} interacts with you by using the
24319 @code{set} command. For commands controlling how @value{GDBN} displays
24320 data, see @ref{Print Settings, ,Print Settings}. Other settings are
24325 * Editing:: Command editing
24326 * Command History:: Command history
24327 * Screen Size:: Screen size
24328 * Output Styling:: Output styling
24329 * Numbers:: Numbers
24330 * ABI:: Configuring the current ABI
24331 * Auto-loading:: Automatically loading associated files
24332 * Messages/Warnings:: Optional warnings and messages
24333 * Debugging Output:: Optional messages about internal happenings
24334 * Other Misc Settings:: Other Miscellaneous Settings
24342 @value{GDBN} indicates its readiness to read a command by printing a string
24343 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
24344 can change the prompt string with the @code{set prompt} command. For
24345 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
24346 the prompt in one of the @value{GDBN} sessions so that you can always tell
24347 which one you are talking to.
24349 @emph{Note:} @code{set prompt} does not add a space for you after the
24350 prompt you set. This allows you to set a prompt which ends in a space
24351 or a prompt that does not.
24355 @item set prompt @var{newprompt}
24356 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
24358 @kindex show prompt
24360 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
24363 Versions of @value{GDBN} that ship with Python scripting enabled have
24364 prompt extensions. The commands for interacting with these extensions
24368 @kindex set extended-prompt
24369 @item set extended-prompt @var{prompt}
24370 Set an extended prompt that allows for substitutions.
24371 @xref{gdb.prompt}, for a list of escape sequences that can be used for
24372 substitution. Any escape sequences specified as part of the prompt
24373 string are replaced with the corresponding strings each time the prompt
24379 set extended-prompt Current working directory: \w (gdb)
24382 Note that when an extended-prompt is set, it takes control of the
24383 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
24385 @kindex show extended-prompt
24386 @item show extended-prompt
24387 Prints the extended prompt. Any escape sequences specified as part of
24388 the prompt string with @code{set extended-prompt}, are replaced with the
24389 corresponding strings each time the prompt is displayed.
24393 @section Command Editing
24395 @cindex command line editing
24397 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
24398 @sc{gnu} library provides consistent behavior for programs which provide a
24399 command line interface to the user. Advantages are @sc{gnu} Emacs-style
24400 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
24401 substitution, and a storage and recall of command history across
24402 debugging sessions.
24404 You may control the behavior of command line editing in @value{GDBN} with the
24405 command @code{set}.
24408 @kindex set editing
24411 @itemx set editing on
24412 Enable command line editing (enabled by default).
24414 @item set editing off
24415 Disable command line editing.
24417 @kindex show editing
24419 Show whether command line editing is enabled.
24422 @ifset SYSTEM_READLINE
24423 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
24425 @ifclear SYSTEM_READLINE
24426 @xref{Command Line Editing},
24428 for more details about the Readline
24429 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
24430 encouraged to read that chapter.
24432 @node Command History
24433 @section Command History
24434 @cindex command history
24436 @value{GDBN} can keep track of the commands you type during your
24437 debugging sessions, so that you can be certain of precisely what
24438 happened. Use these commands to manage the @value{GDBN} command
24441 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
24442 package, to provide the history facility.
24443 @ifset SYSTEM_READLINE
24444 @xref{Using History Interactively, , , history, GNU History Library},
24446 @ifclear SYSTEM_READLINE
24447 @xref{Using History Interactively},
24449 for the detailed description of the History library.
24451 To issue a command to @value{GDBN} without affecting certain aspects of
24452 the state which is seen by users, prefix it with @samp{server }
24453 (@pxref{Server Prefix}). This
24454 means that this command will not affect the command history, nor will it
24455 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
24456 pressed on a line by itself.
24458 @cindex @code{server}, command prefix
24459 The server prefix does not affect the recording of values into the value
24460 history; to print a value without recording it into the value history,
24461 use the @code{output} command instead of the @code{print} command.
24463 Here is the description of @value{GDBN} commands related to command
24467 @cindex history substitution
24468 @cindex history file
24469 @kindex set history filename
24470 @cindex @env{GDBHISTFILE}, environment variable
24471 @item set history filename @var{fname}
24472 Set the name of the @value{GDBN} command history file to @var{fname}.
24473 This is the file where @value{GDBN} reads an initial command history
24474 list, and where it writes the command history from this session when it
24475 exits. You can access this list through history expansion or through
24476 the history command editing characters listed below. This file defaults
24477 to the value of the environment variable @code{GDBHISTFILE}, or to
24478 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
24481 @cindex save command history
24482 @kindex set history save
24483 @item set history save
24484 @itemx set history save on
24485 Record command history in a file, whose name may be specified with the
24486 @code{set history filename} command. By default, this option is disabled.
24488 @item set history save off
24489 Stop recording command history in a file.
24491 @cindex history size
24492 @kindex set history size
24493 @cindex @env{GDBHISTSIZE}, environment variable
24494 @item set history size @var{size}
24495 @itemx set history size unlimited
24496 Set the number of commands which @value{GDBN} keeps in its history list.
24497 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
24498 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
24499 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
24500 either a negative number or the empty string, then the number of commands
24501 @value{GDBN} keeps in the history list is unlimited.
24503 @cindex remove duplicate history
24504 @kindex set history remove-duplicates
24505 @item set history remove-duplicates @var{count}
24506 @itemx set history remove-duplicates unlimited
24507 Control the removal of duplicate history entries in the command history list.
24508 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
24509 history entries and remove the first entry that is a duplicate of the current
24510 entry being added to the command history list. If @var{count} is
24511 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
24512 removal of duplicate history entries is disabled.
24514 Only history entries added during the current session are considered for
24515 removal. This option is set to 0 by default.
24519 History expansion assigns special meaning to the character @kbd{!}.
24520 @ifset SYSTEM_READLINE
24521 @xref{Event Designators, , , history, GNU History Library},
24523 @ifclear SYSTEM_READLINE
24524 @xref{Event Designators},
24528 @cindex history expansion, turn on/off
24529 Since @kbd{!} is also the logical not operator in C, history expansion
24530 is off by default. If you decide to enable history expansion with the
24531 @code{set history expansion on} command, you may sometimes need to
24532 follow @kbd{!} (when it is used as logical not, in an expression) with
24533 a space or a tab to prevent it from being expanded. The readline
24534 history facilities do not attempt substitution on the strings
24535 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
24537 The commands to control history expansion are:
24540 @item set history expansion on
24541 @itemx set history expansion
24542 @kindex set history expansion
24543 Enable history expansion. History expansion is off by default.
24545 @item set history expansion off
24546 Disable history expansion.
24549 @kindex show history
24551 @itemx show history filename
24552 @itemx show history save
24553 @itemx show history size
24554 @itemx show history expansion
24555 These commands display the state of the @value{GDBN} history parameters.
24556 @code{show history} by itself displays all four states.
24561 @kindex show commands
24562 @cindex show last commands
24563 @cindex display command history
24564 @item show commands
24565 Display the last ten commands in the command history.
24567 @item show commands @var{n}
24568 Print ten commands centered on command number @var{n}.
24570 @item show commands +
24571 Print ten commands just after the commands last printed.
24575 @section Screen Size
24576 @cindex size of screen
24577 @cindex screen size
24580 @cindex pauses in output
24582 Certain commands to @value{GDBN} may produce large amounts of
24583 information output to the screen. To help you read all of it,
24584 @value{GDBN} pauses and asks you for input at the end of each page of
24585 output. Type @key{RET} when you want to see one more page of output,
24586 @kbd{q} to discard the remaining output, or @kbd{c} to continue
24587 without paging for the rest of the current command. Also, the screen
24588 width setting determines when to wrap lines of output. Depending on
24589 what is being printed, @value{GDBN} tries to break the line at a
24590 readable place, rather than simply letting it overflow onto the
24593 Normally @value{GDBN} knows the size of the screen from the terminal
24594 driver software. For example, on Unix @value{GDBN} uses the termcap data base
24595 together with the value of the @code{TERM} environment variable and the
24596 @code{stty rows} and @code{stty cols} settings. If this is not correct,
24597 you can override it with the @code{set height} and @code{set
24604 @kindex show height
24605 @item set height @var{lpp}
24606 @itemx set height unlimited
24608 @itemx set width @var{cpl}
24609 @itemx set width unlimited
24611 These @code{set} commands specify a screen height of @var{lpp} lines and
24612 a screen width of @var{cpl} characters. The associated @code{show}
24613 commands display the current settings.
24615 If you specify a height of either @code{unlimited} or zero lines,
24616 @value{GDBN} does not pause during output no matter how long the
24617 output is. This is useful if output is to a file or to an editor
24620 Likewise, you can specify @samp{set width unlimited} or @samp{set
24621 width 0} to prevent @value{GDBN} from wrapping its output.
24623 @item set pagination on
24624 @itemx set pagination off
24625 @kindex set pagination
24626 Turn the output pagination on or off; the default is on. Turning
24627 pagination off is the alternative to @code{set height unlimited}. Note that
24628 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
24629 Options, -batch}) also automatically disables pagination.
24631 @item show pagination
24632 @kindex show pagination
24633 Show the current pagination mode.
24636 @node Output Styling
24637 @section Output Styling
24643 @value{GDBN} can style its output on a capable terminal. This is
24644 enabled by default on most systems, but disabled by default when in
24645 batch mode (@pxref{Mode Options}). Various style settings are available;
24646 and styles can also be disabled entirely.
24649 @item set style enabled @samp{on|off}
24650 Enable or disable all styling. The default is host-dependent, with
24651 most hosts defaulting to @samp{on}.
24653 @item show style enabled
24654 Show the current state of styling.
24656 @item set style sources @samp{on|off}
24657 Enable or disable source code styling. This affects whether source
24658 code, such as the output of the @code{list} command, is styled. Note
24659 that source styling only works if styling in general is enabled, and
24660 if @value{GDBN} was linked with the GNU Source Highlight library. The
24661 default is @samp{on}.
24663 @item show style sources
24664 Show the current state of source code styling.
24667 Subcommands of @code{set style} control specific forms of styling.
24668 These subcommands all follow the same pattern: each style-able object
24669 can be styled with a foreground color, a background color, and an
24672 For example, the style of file names can be controlled using the
24673 @code{set style filename} group of commands:
24676 @item set style filename background @var{color}
24677 Set the background to @var{color}. Valid colors are @samp{none}
24678 (meaning the terminal's default color), @samp{black}, @samp{red},
24679 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24682 @item set style filename foreground @var{color}
24683 Set the foreground to @var{color}. Valid colors are @samp{none}
24684 (meaning the terminal's default color), @samp{black}, @samp{red},
24685 @samp{green}, @samp{yellow}, @samp{blue}, @samp{magenta}, @samp{cyan},
24688 @item set style filename intensity @var{value}
24689 Set the intensity to @var{value}. Valid intensities are @samp{normal}
24690 (the default), @samp{bold}, and @samp{dim}.
24693 The style-able objects are:
24696 Control the styling of file names. By default, this style's
24697 foreground color is green.
24700 Control the styling of function names. These are managed with the
24701 @code{set style function} family of commands. By default, this
24702 style's foreground color is yellow.
24705 Control the styling of variable names. These are managed with the
24706 @code{set style variable} family of commands. By default, this style's
24707 foreground color is cyan.
24710 Control the styling of addresses. These are managed with the
24711 @code{set style address} family of commands. By default, this style's
24712 foreground color is blue.
24717 @cindex number representation
24718 @cindex entering numbers
24720 You can always enter numbers in octal, decimal, or hexadecimal in
24721 @value{GDBN} by the usual conventions: octal numbers begin with
24722 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
24723 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
24724 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
24725 10; likewise, the default display for numbers---when no particular
24726 format is specified---is base 10. You can change the default base for
24727 both input and output with the commands described below.
24730 @kindex set input-radix
24731 @item set input-radix @var{base}
24732 Set the default base for numeric input. Supported choices
24733 for @var{base} are decimal 8, 10, or 16. The base must itself be
24734 specified either unambiguously or using the current input radix; for
24738 set input-radix 012
24739 set input-radix 10.
24740 set input-radix 0xa
24744 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
24745 leaves the input radix unchanged, no matter what it was, since
24746 @samp{10}, being without any leading or trailing signs of its base, is
24747 interpreted in the current radix. Thus, if the current radix is 16,
24748 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
24751 @kindex set output-radix
24752 @item set output-radix @var{base}
24753 Set the default base for numeric display. Supported choices
24754 for @var{base} are decimal 8, 10, or 16. The base must itself be
24755 specified either unambiguously or using the current input radix.
24757 @kindex show input-radix
24758 @item show input-radix
24759 Display the current default base for numeric input.
24761 @kindex show output-radix
24762 @item show output-radix
24763 Display the current default base for numeric display.
24765 @item set radix @r{[}@var{base}@r{]}
24769 These commands set and show the default base for both input and output
24770 of numbers. @code{set radix} sets the radix of input and output to
24771 the same base; without an argument, it resets the radix back to its
24772 default value of 10.
24777 @section Configuring the Current ABI
24779 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
24780 application automatically. However, sometimes you need to override its
24781 conclusions. Use these commands to manage @value{GDBN}'s view of the
24787 @cindex Newlib OS ABI and its influence on the longjmp handling
24789 One @value{GDBN} configuration can debug binaries for multiple operating
24790 system targets, either via remote debugging or native emulation.
24791 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
24792 but you can override its conclusion using the @code{set osabi} command.
24793 One example where this is useful is in debugging of binaries which use
24794 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
24795 not have the same identifying marks that the standard C library for your
24798 When @value{GDBN} is debugging the AArch64 architecture, it provides a
24799 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
24800 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
24801 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
24805 Show the OS ABI currently in use.
24808 With no argument, show the list of registered available OS ABI's.
24810 @item set osabi @var{abi}
24811 Set the current OS ABI to @var{abi}.
24814 @cindex float promotion
24816 Generally, the way that an argument of type @code{float} is passed to a
24817 function depends on whether the function is prototyped. For a prototyped
24818 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
24819 according to the architecture's convention for @code{float}. For unprototyped
24820 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
24821 @code{double} and then passed.
24823 Unfortunately, some forms of debug information do not reliably indicate whether
24824 a function is prototyped. If @value{GDBN} calls a function that is not marked
24825 as prototyped, it consults @kbd{set coerce-float-to-double}.
24828 @kindex set coerce-float-to-double
24829 @item set coerce-float-to-double
24830 @itemx set coerce-float-to-double on
24831 Arguments of type @code{float} will be promoted to @code{double} when passed
24832 to an unprototyped function. This is the default setting.
24834 @item set coerce-float-to-double off
24835 Arguments of type @code{float} will be passed directly to unprototyped
24838 @kindex show coerce-float-to-double
24839 @item show coerce-float-to-double
24840 Show the current setting of promoting @code{float} to @code{double}.
24844 @kindex show cp-abi
24845 @value{GDBN} needs to know the ABI used for your program's C@t{++}
24846 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
24847 used to build your application. @value{GDBN} only fully supports
24848 programs with a single C@t{++} ABI; if your program contains code using
24849 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
24850 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
24851 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
24852 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
24853 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
24854 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
24859 Show the C@t{++} ABI currently in use.
24862 With no argument, show the list of supported C@t{++} ABI's.
24864 @item set cp-abi @var{abi}
24865 @itemx set cp-abi auto
24866 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
24870 @section Automatically loading associated files
24871 @cindex auto-loading
24873 @value{GDBN} sometimes reads files with commands and settings automatically,
24874 without being explicitly told so by the user. We call this feature
24875 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
24876 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
24877 results or introduce security risks (e.g., if the file comes from untrusted
24881 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
24882 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
24884 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
24885 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
24888 There are various kinds of files @value{GDBN} can automatically load.
24889 In addition to these files, @value{GDBN} supports auto-loading code written
24890 in various extension languages. @xref{Auto-loading extensions}.
24892 Note that loading of these associated files (including the local @file{.gdbinit}
24893 file) requires accordingly configured @code{auto-load safe-path}
24894 (@pxref{Auto-loading safe path}).
24896 For these reasons, @value{GDBN} includes commands and options to let you
24897 control when to auto-load files and which files should be auto-loaded.
24900 @anchor{set auto-load off}
24901 @kindex set auto-load off
24902 @item set auto-load off
24903 Globally disable loading of all auto-loaded files.
24904 You may want to use this command with the @samp{-iex} option
24905 (@pxref{Option -init-eval-command}) such as:
24907 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
24910 Be aware that system init file (@pxref{System-wide configuration})
24911 and init files from your home directory (@pxref{Home Directory Init File})
24912 still get read (as they come from generally trusted directories).
24913 To prevent @value{GDBN} from auto-loading even those init files, use the
24914 @option{-nx} option (@pxref{Mode Options}), in addition to
24915 @code{set auto-load no}.
24917 @anchor{show auto-load}
24918 @kindex show auto-load
24919 @item show auto-load
24920 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
24924 (gdb) show auto-load
24925 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
24926 libthread-db: Auto-loading of inferior specific libthread_db is on.
24927 local-gdbinit: Auto-loading of .gdbinit script from current directory
24929 python-scripts: Auto-loading of Python scripts is on.
24930 safe-path: List of directories from which it is safe to auto-load files
24931 is $debugdir:$datadir/auto-load.
24932 scripts-directory: List of directories from which to load auto-loaded scripts
24933 is $debugdir:$datadir/auto-load.
24936 @anchor{info auto-load}
24937 @kindex info auto-load
24938 @item info auto-load
24939 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
24943 (gdb) info auto-load
24946 Yes /home/user/gdb/gdb-gdb.gdb
24947 libthread-db: No auto-loaded libthread-db.
24948 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24952 Yes /home/user/gdb/gdb-gdb.py
24956 These are @value{GDBN} control commands for the auto-loading:
24958 @multitable @columnfractions .5 .5
24959 @item @xref{set auto-load off}.
24960 @tab Disable auto-loading globally.
24961 @item @xref{show auto-load}.
24962 @tab Show setting of all kinds of files.
24963 @item @xref{info auto-load}.
24964 @tab Show state of all kinds of files.
24965 @item @xref{set auto-load gdb-scripts}.
24966 @tab Control for @value{GDBN} command scripts.
24967 @item @xref{show auto-load gdb-scripts}.
24968 @tab Show setting of @value{GDBN} command scripts.
24969 @item @xref{info auto-load gdb-scripts}.
24970 @tab Show state of @value{GDBN} command scripts.
24971 @item @xref{set auto-load python-scripts}.
24972 @tab Control for @value{GDBN} Python scripts.
24973 @item @xref{show auto-load python-scripts}.
24974 @tab Show setting of @value{GDBN} Python scripts.
24975 @item @xref{info auto-load python-scripts}.
24976 @tab Show state of @value{GDBN} Python scripts.
24977 @item @xref{set auto-load guile-scripts}.
24978 @tab Control for @value{GDBN} Guile scripts.
24979 @item @xref{show auto-load guile-scripts}.
24980 @tab Show setting of @value{GDBN} Guile scripts.
24981 @item @xref{info auto-load guile-scripts}.
24982 @tab Show state of @value{GDBN} Guile scripts.
24983 @item @xref{set auto-load scripts-directory}.
24984 @tab Control for @value{GDBN} auto-loaded scripts location.
24985 @item @xref{show auto-load scripts-directory}.
24986 @tab Show @value{GDBN} auto-loaded scripts location.
24987 @item @xref{add-auto-load-scripts-directory}.
24988 @tab Add directory for auto-loaded scripts location list.
24989 @item @xref{set auto-load local-gdbinit}.
24990 @tab Control for init file in the current directory.
24991 @item @xref{show auto-load local-gdbinit}.
24992 @tab Show setting of init file in the current directory.
24993 @item @xref{info auto-load local-gdbinit}.
24994 @tab Show state of init file in the current directory.
24995 @item @xref{set auto-load libthread-db}.
24996 @tab Control for thread debugging library.
24997 @item @xref{show auto-load libthread-db}.
24998 @tab Show setting of thread debugging library.
24999 @item @xref{info auto-load libthread-db}.
25000 @tab Show state of thread debugging library.
25001 @item @xref{set auto-load safe-path}.
25002 @tab Control directories trusted for automatic loading.
25003 @item @xref{show auto-load safe-path}.
25004 @tab Show directories trusted for automatic loading.
25005 @item @xref{add-auto-load-safe-path}.
25006 @tab Add directory trusted for automatic loading.
25009 @node Init File in the Current Directory
25010 @subsection Automatically loading init file in the current directory
25011 @cindex auto-loading init file in the current directory
25013 By default, @value{GDBN} reads and executes the canned sequences of commands
25014 from init file (if any) in the current working directory,
25015 see @ref{Init File in the Current Directory during Startup}.
25017 Note that loading of this local @file{.gdbinit} file also requires accordingly
25018 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25021 @anchor{set auto-load local-gdbinit}
25022 @kindex set auto-load local-gdbinit
25023 @item set auto-load local-gdbinit [on|off]
25024 Enable or disable the auto-loading of canned sequences of commands
25025 (@pxref{Sequences}) found in init file in the current directory.
25027 @anchor{show auto-load local-gdbinit}
25028 @kindex show auto-load local-gdbinit
25029 @item show auto-load local-gdbinit
25030 Show whether auto-loading of canned sequences of commands from init file in the
25031 current directory is enabled or disabled.
25033 @anchor{info auto-load local-gdbinit}
25034 @kindex info auto-load local-gdbinit
25035 @item info auto-load local-gdbinit
25036 Print whether canned sequences of commands from init file in the
25037 current directory have been auto-loaded.
25040 @node libthread_db.so.1 file
25041 @subsection Automatically loading thread debugging library
25042 @cindex auto-loading libthread_db.so.1
25044 This feature is currently present only on @sc{gnu}/Linux native hosts.
25046 @value{GDBN} reads in some cases thread debugging library from places specific
25047 to the inferior (@pxref{set libthread-db-search-path}).
25049 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
25050 without checking this @samp{set auto-load libthread-db} switch as system
25051 libraries have to be trusted in general. In all other cases of
25052 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
25053 auto-load libthread-db} is enabled before trying to open such thread debugging
25056 Note that loading of this debugging library also requires accordingly configured
25057 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25060 @anchor{set auto-load libthread-db}
25061 @kindex set auto-load libthread-db
25062 @item set auto-load libthread-db [on|off]
25063 Enable or disable the auto-loading of inferior specific thread debugging library.
25065 @anchor{show auto-load libthread-db}
25066 @kindex show auto-load libthread-db
25067 @item show auto-load libthread-db
25068 Show whether auto-loading of inferior specific thread debugging library is
25069 enabled or disabled.
25071 @anchor{info auto-load libthread-db}
25072 @kindex info auto-load libthread-db
25073 @item info auto-load libthread-db
25074 Print the list of all loaded inferior specific thread debugging libraries and
25075 for each such library print list of inferior @var{pid}s using it.
25078 @node Auto-loading safe path
25079 @subsection Security restriction for auto-loading
25080 @cindex auto-loading safe-path
25082 As the files of inferior can come from untrusted source (such as submitted by
25083 an application user) @value{GDBN} does not always load any files automatically.
25084 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
25085 directories trusted for loading files not explicitly requested by user.
25086 Each directory can also be a shell wildcard pattern.
25088 If the path is not set properly you will see a warning and the file will not
25093 Reading symbols from /home/user/gdb/gdb...done.
25094 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
25095 declined by your `auto-load safe-path' set
25096 to "$debugdir:$datadir/auto-load".
25097 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
25098 declined by your `auto-load safe-path' set
25099 to "$debugdir:$datadir/auto-load".
25103 To instruct @value{GDBN} to go ahead and use the init files anyway,
25104 invoke @value{GDBN} like this:
25107 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
25110 The list of trusted directories is controlled by the following commands:
25113 @anchor{set auto-load safe-path}
25114 @kindex set auto-load safe-path
25115 @item set auto-load safe-path @r{[}@var{directories}@r{]}
25116 Set the list of directories (and their subdirectories) trusted for automatic
25117 loading and execution of scripts. You can also enter a specific trusted file.
25118 Each directory can also be a shell wildcard pattern; wildcards do not match
25119 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
25120 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
25121 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
25122 its default value as specified during @value{GDBN} compilation.
25124 The list of directories uses path separator (@samp{:} on GNU and Unix
25125 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25126 to the @env{PATH} environment variable.
25128 @anchor{show auto-load safe-path}
25129 @kindex show auto-load safe-path
25130 @item show auto-load safe-path
25131 Show the list of directories trusted for automatic loading and execution of
25134 @anchor{add-auto-load-safe-path}
25135 @kindex add-auto-load-safe-path
25136 @item add-auto-load-safe-path
25137 Add an entry (or list of entries) to the list of directories trusted for
25138 automatic loading and execution of scripts. Multiple entries may be delimited
25139 by the host platform path separator in use.
25142 This variable defaults to what @code{--with-auto-load-dir} has been configured
25143 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
25144 substitution applies the same as for @ref{set auto-load scripts-directory}.
25145 The default @code{set auto-load safe-path} value can be also overriden by
25146 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
25148 Setting this variable to @file{/} disables this security protection,
25149 corresponding @value{GDBN} configuration option is
25150 @option{--without-auto-load-safe-path}.
25151 This variable is supposed to be set to the system directories writable by the
25152 system superuser only. Users can add their source directories in init files in
25153 their home directories (@pxref{Home Directory Init File}). See also deprecated
25154 init file in the current directory
25155 (@pxref{Init File in the Current Directory during Startup}).
25157 To force @value{GDBN} to load the files it declined to load in the previous
25158 example, you could use one of the following ways:
25161 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
25162 Specify this trusted directory (or a file) as additional component of the list.
25163 You have to specify also any existing directories displayed by
25164 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
25166 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
25167 Specify this directory as in the previous case but just for a single
25168 @value{GDBN} session.
25170 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
25171 Disable auto-loading safety for a single @value{GDBN} session.
25172 This assumes all the files you debug during this @value{GDBN} session will come
25173 from trusted sources.
25175 @item @kbd{./configure --without-auto-load-safe-path}
25176 During compilation of @value{GDBN} you may disable any auto-loading safety.
25177 This assumes all the files you will ever debug with this @value{GDBN} come from
25181 On the other hand you can also explicitly forbid automatic files loading which
25182 also suppresses any such warning messages:
25185 @item @kbd{gdb -iex "set auto-load no" @dots{}}
25186 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
25188 @item @file{~/.gdbinit}: @samp{set auto-load no}
25189 Disable auto-loading globally for the user
25190 (@pxref{Home Directory Init File}). While it is improbable, you could also
25191 use system init file instead (@pxref{System-wide configuration}).
25194 This setting applies to the file names as entered by user. If no entry matches
25195 @value{GDBN} tries as a last resort to also resolve all the file names into
25196 their canonical form (typically resolving symbolic links) and compare the
25197 entries again. @value{GDBN} already canonicalizes most of the filenames on its
25198 own before starting the comparison so a canonical form of directories is
25199 recommended to be entered.
25201 @node Auto-loading verbose mode
25202 @subsection Displaying files tried for auto-load
25203 @cindex auto-loading verbose mode
25205 For better visibility of all the file locations where you can place scripts to
25206 be auto-loaded with inferior --- or to protect yourself against accidental
25207 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
25208 all the files attempted to be loaded. Both existing and non-existing files may
25211 For example the list of directories from which it is safe to auto-load files
25212 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
25213 may not be too obvious while setting it up.
25216 (gdb) set debug auto-load on
25217 (gdb) file ~/src/t/true
25218 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
25219 for objfile "/tmp/true".
25220 auto-load: Updating directories of "/usr:/opt".
25221 auto-load: Using directory "/usr".
25222 auto-load: Using directory "/opt".
25223 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
25224 by your `auto-load safe-path' set to "/usr:/opt".
25228 @anchor{set debug auto-load}
25229 @kindex set debug auto-load
25230 @item set debug auto-load [on|off]
25231 Set whether to print the filenames attempted to be auto-loaded.
25233 @anchor{show debug auto-load}
25234 @kindex show debug auto-load
25235 @item show debug auto-load
25236 Show whether printing of the filenames attempted to be auto-loaded is turned
25240 @node Messages/Warnings
25241 @section Optional Warnings and Messages
25243 @cindex verbose operation
25244 @cindex optional warnings
25245 By default, @value{GDBN} is silent about its inner workings. If you are
25246 running on a slow machine, you may want to use the @code{set verbose}
25247 command. This makes @value{GDBN} tell you when it does a lengthy
25248 internal operation, so you will not think it has crashed.
25250 Currently, the messages controlled by @code{set verbose} are those
25251 which announce that the symbol table for a source file is being read;
25252 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
25255 @kindex set verbose
25256 @item set verbose on
25257 Enables @value{GDBN} output of certain informational messages.
25259 @item set verbose off
25260 Disables @value{GDBN} output of certain informational messages.
25262 @kindex show verbose
25264 Displays whether @code{set verbose} is on or off.
25267 By default, if @value{GDBN} encounters bugs in the symbol table of an
25268 object file, it is silent; but if you are debugging a compiler, you may
25269 find this information useful (@pxref{Symbol Errors, ,Errors Reading
25274 @kindex set complaints
25275 @item set complaints @var{limit}
25276 Permits @value{GDBN} to output @var{limit} complaints about each type of
25277 unusual symbols before becoming silent about the problem. Set
25278 @var{limit} to zero to suppress all complaints; set it to a large number
25279 to prevent complaints from being suppressed.
25281 @kindex show complaints
25282 @item show complaints
25283 Displays how many symbol complaints @value{GDBN} is permitted to produce.
25287 @anchor{confirmation requests}
25288 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
25289 lot of stupid questions to confirm certain commands. For example, if
25290 you try to run a program which is already running:
25294 The program being debugged has been started already.
25295 Start it from the beginning? (y or n)
25298 If you are willing to unflinchingly face the consequences of your own
25299 commands, you can disable this ``feature'':
25303 @kindex set confirm
25305 @cindex confirmation
25306 @cindex stupid questions
25307 @item set confirm off
25308 Disables confirmation requests. Note that running @value{GDBN} with
25309 the @option{--batch} option (@pxref{Mode Options, -batch}) also
25310 automatically disables confirmation requests.
25312 @item set confirm on
25313 Enables confirmation requests (the default).
25315 @kindex show confirm
25317 Displays state of confirmation requests.
25321 @cindex command tracing
25322 If you need to debug user-defined commands or sourced files you may find it
25323 useful to enable @dfn{command tracing}. In this mode each command will be
25324 printed as it is executed, prefixed with one or more @samp{+} symbols, the
25325 quantity denoting the call depth of each command.
25328 @kindex set trace-commands
25329 @cindex command scripts, debugging
25330 @item set trace-commands on
25331 Enable command tracing.
25332 @item set trace-commands off
25333 Disable command tracing.
25334 @item show trace-commands
25335 Display the current state of command tracing.
25338 @node Debugging Output
25339 @section Optional Messages about Internal Happenings
25340 @cindex optional debugging messages
25342 @value{GDBN} has commands that enable optional debugging messages from
25343 various @value{GDBN} subsystems; normally these commands are of
25344 interest to @value{GDBN} maintainers, or when reporting a bug. This
25345 section documents those commands.
25348 @kindex set exec-done-display
25349 @item set exec-done-display
25350 Turns on or off the notification of asynchronous commands'
25351 completion. When on, @value{GDBN} will print a message when an
25352 asynchronous command finishes its execution. The default is off.
25353 @kindex show exec-done-display
25354 @item show exec-done-display
25355 Displays the current setting of asynchronous command completion
25358 @cindex ARM AArch64
25359 @item set debug aarch64
25360 Turns on or off display of debugging messages related to ARM AArch64.
25361 The default is off.
25363 @item show debug aarch64
25364 Displays the current state of displaying debugging messages related to
25366 @cindex gdbarch debugging info
25367 @cindex architecture debugging info
25368 @item set debug arch
25369 Turns on or off display of gdbarch debugging info. The default is off
25370 @item show debug arch
25371 Displays the current state of displaying gdbarch debugging info.
25372 @item set debug aix-solib
25373 @cindex AIX shared library debugging
25374 Control display of debugging messages from the AIX shared library
25375 support module. The default is off.
25376 @item show debug aix-thread
25377 Show the current state of displaying AIX shared library debugging messages.
25378 @item set debug aix-thread
25379 @cindex AIX threads
25380 Display debugging messages about inner workings of the AIX thread
25382 @item show debug aix-thread
25383 Show the current state of AIX thread debugging info display.
25384 @item set debug check-physname
25386 Check the results of the ``physname'' computation. When reading DWARF
25387 debugging information for C@t{++}, @value{GDBN} attempts to compute
25388 each entity's name. @value{GDBN} can do this computation in two
25389 different ways, depending on exactly what information is present.
25390 When enabled, this setting causes @value{GDBN} to compute the names
25391 both ways and display any discrepancies.
25392 @item show debug check-physname
25393 Show the current state of ``physname'' checking.
25394 @item set debug coff-pe-read
25395 @cindex COFF/PE exported symbols
25396 Control display of debugging messages related to reading of COFF/PE
25397 exported symbols. The default is off.
25398 @item show debug coff-pe-read
25399 Displays the current state of displaying debugging messages related to
25400 reading of COFF/PE exported symbols.
25401 @item set debug dwarf-die
25403 Dump DWARF DIEs after they are read in.
25404 The value is the number of nesting levels to print.
25405 A value of zero turns off the display.
25406 @item show debug dwarf-die
25407 Show the current state of DWARF DIE debugging.
25408 @item set debug dwarf-line
25409 @cindex DWARF Line Tables
25410 Turns on or off display of debugging messages related to reading
25411 DWARF line tables. The default is 0 (off).
25412 A value of 1 provides basic information.
25413 A value greater than 1 provides more verbose information.
25414 @item show debug dwarf-line
25415 Show the current state of DWARF line table debugging.
25416 @item set debug dwarf-read
25417 @cindex DWARF Reading
25418 Turns on or off display of debugging messages related to reading
25419 DWARF debug info. The default is 0 (off).
25420 A value of 1 provides basic information.
25421 A value greater than 1 provides more verbose information.
25422 @item show debug dwarf-read
25423 Show the current state of DWARF reader debugging.
25424 @item set debug displaced
25425 @cindex displaced stepping debugging info
25426 Turns on or off display of @value{GDBN} debugging info for the
25427 displaced stepping support. The default is off.
25428 @item show debug displaced
25429 Displays the current state of displaying @value{GDBN} debugging info
25430 related to displaced stepping.
25431 @item set debug event
25432 @cindex event debugging info
25433 Turns on or off display of @value{GDBN} event debugging info. The
25435 @item show debug event
25436 Displays the current state of displaying @value{GDBN} event debugging
25438 @item set debug expression
25439 @cindex expression debugging info
25440 Turns on or off display of debugging info about @value{GDBN}
25441 expression parsing. The default is off.
25442 @item show debug expression
25443 Displays the current state of displaying debugging info about
25444 @value{GDBN} expression parsing.
25445 @item set debug fbsd-lwp
25446 @cindex FreeBSD LWP debug messages
25447 Turns on or off debugging messages from the FreeBSD LWP debug support.
25448 @item show debug fbsd-lwp
25449 Show the current state of FreeBSD LWP debugging messages.
25450 @item set debug fbsd-nat
25451 @cindex FreeBSD native target debug messages
25452 Turns on or off debugging messages from the FreeBSD native target.
25453 @item show debug fbsd-nat
25454 Show the current state of FreeBSD native target debugging messages.
25455 @item set debug frame
25456 @cindex frame debugging info
25457 Turns on or off display of @value{GDBN} frame debugging info. The
25459 @item show debug frame
25460 Displays the current state of displaying @value{GDBN} frame debugging
25462 @item set debug gnu-nat
25463 @cindex @sc{gnu}/Hurd debug messages
25464 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
25465 @item show debug gnu-nat
25466 Show the current state of @sc{gnu}/Hurd debugging messages.
25467 @item set debug infrun
25468 @cindex inferior debugging info
25469 Turns on or off display of @value{GDBN} debugging info for running the inferior.
25470 The default is off. @file{infrun.c} contains GDB's runtime state machine used
25471 for implementing operations such as single-stepping the inferior.
25472 @item show debug infrun
25473 Displays the current state of @value{GDBN} inferior debugging.
25474 @item set debug jit
25475 @cindex just-in-time compilation, debugging messages
25476 Turn on or off debugging messages from JIT debug support.
25477 @item show debug jit
25478 Displays the current state of @value{GDBN} JIT debugging.
25479 @item set debug lin-lwp
25480 @cindex @sc{gnu}/Linux LWP debug messages
25481 @cindex Linux lightweight processes
25482 Turn on or off debugging messages from the Linux LWP debug support.
25483 @item show debug lin-lwp
25484 Show the current state of Linux LWP debugging messages.
25485 @item set debug linux-namespaces
25486 @cindex @sc{gnu}/Linux namespaces debug messages
25487 Turn on or off debugging messages from the Linux namespaces debug support.
25488 @item show debug linux-namespaces
25489 Show the current state of Linux namespaces debugging messages.
25490 @item set debug mach-o
25491 @cindex Mach-O symbols processing
25492 Control display of debugging messages related to Mach-O symbols
25493 processing. The default is off.
25494 @item show debug mach-o
25495 Displays the current state of displaying debugging messages related to
25496 reading of COFF/PE exported symbols.
25497 @item set debug notification
25498 @cindex remote async notification debugging info
25499 Turn on or off debugging messages about remote async notification.
25500 The default is off.
25501 @item show debug notification
25502 Displays the current state of remote async notification debugging messages.
25503 @item set debug observer
25504 @cindex observer debugging info
25505 Turns on or off display of @value{GDBN} observer debugging. This
25506 includes info such as the notification of observable events.
25507 @item show debug observer
25508 Displays the current state of observer debugging.
25509 @item set debug overload
25510 @cindex C@t{++} overload debugging info
25511 Turns on or off display of @value{GDBN} C@t{++} overload debugging
25512 info. This includes info such as ranking of functions, etc. The default
25514 @item show debug overload
25515 Displays the current state of displaying @value{GDBN} C@t{++} overload
25517 @cindex expression parser, debugging info
25518 @cindex debug expression parser
25519 @item set debug parser
25520 Turns on or off the display of expression parser debugging output.
25521 Internally, this sets the @code{yydebug} variable in the expression
25522 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
25523 details. The default is off.
25524 @item show debug parser
25525 Show the current state of expression parser debugging.
25526 @cindex packets, reporting on stdout
25527 @cindex serial connections, debugging
25528 @cindex debug remote protocol
25529 @cindex remote protocol debugging
25530 @cindex display remote packets
25531 @item set debug remote
25532 Turns on or off display of reports on all packets sent back and forth across
25533 the serial line to the remote machine. The info is printed on the
25534 @value{GDBN} standard output stream. The default is off.
25535 @item show debug remote
25536 Displays the state of display of remote packets.
25538 @item set debug separate-debug-file
25539 Turns on or off display of debug output about separate debug file search.
25540 @item show debug separate-debug-file
25541 Displays the state of separate debug file search debug output.
25543 @item set debug serial
25544 Turns on or off display of @value{GDBN} serial debugging info. The
25546 @item show debug serial
25547 Displays the current state of displaying @value{GDBN} serial debugging
25549 @item set debug solib-frv
25550 @cindex FR-V shared-library debugging
25551 Turn on or off debugging messages for FR-V shared-library code.
25552 @item show debug solib-frv
25553 Display the current state of FR-V shared-library code debugging
25555 @item set debug symbol-lookup
25556 @cindex symbol lookup
25557 Turns on or off display of debugging messages related to symbol lookup.
25558 The default is 0 (off).
25559 A value of 1 provides basic information.
25560 A value greater than 1 provides more verbose information.
25561 @item show debug symbol-lookup
25562 Show the current state of symbol lookup debugging messages.
25563 @item set debug symfile
25564 @cindex symbol file functions
25565 Turns on or off display of debugging messages related to symbol file functions.
25566 The default is off. @xref{Files}.
25567 @item show debug symfile
25568 Show the current state of symbol file debugging messages.
25569 @item set debug symtab-create
25570 @cindex symbol table creation
25571 Turns on or off display of debugging messages related to symbol table creation.
25572 The default is 0 (off).
25573 A value of 1 provides basic information.
25574 A value greater than 1 provides more verbose information.
25575 @item show debug symtab-create
25576 Show the current state of symbol table creation debugging.
25577 @item set debug target
25578 @cindex target debugging info
25579 Turns on or off display of @value{GDBN} target debugging info. This info
25580 includes what is going on at the target level of GDB, as it happens. The
25581 default is 0. Set it to 1 to track events, and to 2 to also track the
25582 value of large memory transfers.
25583 @item show debug target
25584 Displays the current state of displaying @value{GDBN} target debugging
25586 @item set debug timestamp
25587 @cindex timestampping debugging info
25588 Turns on or off display of timestamps with @value{GDBN} debugging info.
25589 When enabled, seconds and microseconds are displayed before each debugging
25591 @item show debug timestamp
25592 Displays the current state of displaying timestamps with @value{GDBN}
25594 @item set debug varobj
25595 @cindex variable object debugging info
25596 Turns on or off display of @value{GDBN} variable object debugging
25597 info. The default is off.
25598 @item show debug varobj
25599 Displays the current state of displaying @value{GDBN} variable object
25601 @item set debug xml
25602 @cindex XML parser debugging
25603 Turn on or off debugging messages for built-in XML parsers.
25604 @item show debug xml
25605 Displays the current state of XML debugging messages.
25608 @node Other Misc Settings
25609 @section Other Miscellaneous Settings
25610 @cindex miscellaneous settings
25613 @kindex set interactive-mode
25614 @item set interactive-mode
25615 If @code{on}, forces @value{GDBN} to assume that GDB was started
25616 in a terminal. In practice, this means that @value{GDBN} should wait
25617 for the user to answer queries generated by commands entered at
25618 the command prompt. If @code{off}, forces @value{GDBN} to operate
25619 in the opposite mode, and it uses the default answers to all queries.
25620 If @code{auto} (the default), @value{GDBN} tries to determine whether
25621 its standard input is a terminal, and works in interactive-mode if it
25622 is, non-interactively otherwise.
25624 In the vast majority of cases, the debugger should be able to guess
25625 correctly which mode should be used. But this setting can be useful
25626 in certain specific cases, such as running a MinGW @value{GDBN}
25627 inside a cygwin window.
25629 @kindex show interactive-mode
25630 @item show interactive-mode
25631 Displays whether the debugger is operating in interactive mode or not.
25634 @node Extending GDB
25635 @chapter Extending @value{GDBN}
25636 @cindex extending GDB
25638 @value{GDBN} provides several mechanisms for extension.
25639 @value{GDBN} also provides the ability to automatically load
25640 extensions when it reads a file for debugging. This allows the
25641 user to automatically customize @value{GDBN} for the program
25645 * Sequences:: Canned Sequences of @value{GDBN} Commands
25646 * Python:: Extending @value{GDBN} using Python
25647 * Guile:: Extending @value{GDBN} using Guile
25648 * Auto-loading extensions:: Automatically loading extensions
25649 * Multiple Extension Languages:: Working with multiple extension languages
25650 * Aliases:: Creating new spellings of existing commands
25653 To facilitate the use of extension languages, @value{GDBN} is capable
25654 of evaluating the contents of a file. When doing so, @value{GDBN}
25655 can recognize which extension language is being used by looking at
25656 the filename extension. Files with an unrecognized filename extension
25657 are always treated as a @value{GDBN} Command Files.
25658 @xref{Command Files,, Command files}.
25660 You can control how @value{GDBN} evaluates these files with the following
25664 @kindex set script-extension
25665 @kindex show script-extension
25666 @item set script-extension off
25667 All scripts are always evaluated as @value{GDBN} Command Files.
25669 @item set script-extension soft
25670 The debugger determines the scripting language based on filename
25671 extension. If this scripting language is supported, @value{GDBN}
25672 evaluates the script using that language. Otherwise, it evaluates
25673 the file as a @value{GDBN} Command File.
25675 @item set script-extension strict
25676 The debugger determines the scripting language based on filename
25677 extension, and evaluates the script using that language. If the
25678 language is not supported, then the evaluation fails.
25680 @item show script-extension
25681 Display the current value of the @code{script-extension} option.
25686 @section Canned Sequences of Commands
25688 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
25689 Command Lists}), @value{GDBN} provides two ways to store sequences of
25690 commands for execution as a unit: user-defined commands and command
25694 * Define:: How to define your own commands
25695 * Hooks:: Hooks for user-defined commands
25696 * Command Files:: How to write scripts of commands to be stored in a file
25697 * Output:: Commands for controlled output
25698 * Auto-loading sequences:: Controlling auto-loaded command files
25702 @subsection User-defined Commands
25704 @cindex user-defined command
25705 @cindex arguments, to user-defined commands
25706 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
25707 which you assign a new name as a command. This is done with the
25708 @code{define} command. User commands may accept an unlimited number of arguments
25709 separated by whitespace. Arguments are accessed within the user command
25710 via @code{$arg0@dots{}$argN}. A trivial example:
25714 print $arg0 + $arg1 + $arg2
25719 To execute the command use:
25726 This defines the command @code{adder}, which prints the sum of
25727 its three arguments. Note the arguments are text substitutions, so they may
25728 reference variables, use complex expressions, or even perform inferior
25731 @cindex argument count in user-defined commands
25732 @cindex how many arguments (user-defined commands)
25733 In addition, @code{$argc} may be used to find out how many arguments have
25739 print $arg0 + $arg1
25742 print $arg0 + $arg1 + $arg2
25747 Combining with the @code{eval} command (@pxref{eval}) makes it easier
25748 to process a variable number of arguments:
25755 eval "set $sum = $sum + $arg%d", $i
25765 @item define @var{commandname}
25766 Define a command named @var{commandname}. If there is already a command
25767 by that name, you are asked to confirm that you want to redefine it.
25768 The argument @var{commandname} may be a bare command name consisting of letters,
25769 numbers, dashes, and underscores. It may also start with any predefined
25770 prefix command. For example, @samp{define target my-target} creates
25771 a user-defined @samp{target my-target} command.
25773 The definition of the command is made up of other @value{GDBN} command lines,
25774 which are given following the @code{define} command. The end of these
25775 commands is marked by a line containing @code{end}.
25778 @kindex end@r{ (user-defined commands)}
25779 @item document @var{commandname}
25780 Document the user-defined command @var{commandname}, so that it can be
25781 accessed by @code{help}. The command @var{commandname} must already be
25782 defined. This command reads lines of documentation just as @code{define}
25783 reads the lines of the command definition, ending with @code{end}.
25784 After the @code{document} command is finished, @code{help} on command
25785 @var{commandname} displays the documentation you have written.
25787 You may use the @code{document} command again to change the
25788 documentation of a command. Redefining the command with @code{define}
25789 does not change the documentation.
25791 @kindex dont-repeat
25792 @cindex don't repeat command
25794 Used inside a user-defined command, this tells @value{GDBN} that this
25795 command should not be repeated when the user hits @key{RET}
25796 (@pxref{Command Syntax, repeat last command}).
25798 @kindex help user-defined
25799 @item help user-defined
25800 List all user-defined commands and all python commands defined in class
25801 COMAND_USER. The first line of the documentation or docstring is
25806 @itemx show user @var{commandname}
25807 Display the @value{GDBN} commands used to define @var{commandname} (but
25808 not its documentation). If no @var{commandname} is given, display the
25809 definitions for all user-defined commands.
25810 This does not work for user-defined python commands.
25812 @cindex infinite recursion in user-defined commands
25813 @kindex show max-user-call-depth
25814 @kindex set max-user-call-depth
25815 @item show max-user-call-depth
25816 @itemx set max-user-call-depth
25817 The value of @code{max-user-call-depth} controls how many recursion
25818 levels are allowed in user-defined commands before @value{GDBN} suspects an
25819 infinite recursion and aborts the command.
25820 This does not apply to user-defined python commands.
25823 In addition to the above commands, user-defined commands frequently
25824 use control flow commands, described in @ref{Command Files}.
25826 When user-defined commands are executed, the
25827 commands of the definition are not printed. An error in any command
25828 stops execution of the user-defined command.
25830 If used interactively, commands that would ask for confirmation proceed
25831 without asking when used inside a user-defined command. Many @value{GDBN}
25832 commands that normally print messages to say what they are doing omit the
25833 messages when used in a user-defined command.
25836 @subsection User-defined Command Hooks
25837 @cindex command hooks
25838 @cindex hooks, for commands
25839 @cindex hooks, pre-command
25842 You may define @dfn{hooks}, which are a special kind of user-defined
25843 command. Whenever you run the command @samp{foo}, if the user-defined
25844 command @samp{hook-foo} exists, it is executed (with no arguments)
25845 before that command.
25847 @cindex hooks, post-command
25849 A hook may also be defined which is run after the command you executed.
25850 Whenever you run the command @samp{foo}, if the user-defined command
25851 @samp{hookpost-foo} exists, it is executed (with no arguments) after
25852 that command. Post-execution hooks may exist simultaneously with
25853 pre-execution hooks, for the same command.
25855 It is valid for a hook to call the command which it hooks. If this
25856 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
25858 @c It would be nice if hookpost could be passed a parameter indicating
25859 @c if the command it hooks executed properly or not. FIXME!
25861 @kindex stop@r{, a pseudo-command}
25862 In addition, a pseudo-command, @samp{stop} exists. Defining
25863 (@samp{hook-stop}) makes the associated commands execute every time
25864 execution stops in your program: before breakpoint commands are run,
25865 displays are printed, or the stack frame is printed.
25867 For example, to ignore @code{SIGALRM} signals while
25868 single-stepping, but treat them normally during normal execution,
25873 handle SIGALRM nopass
25877 handle SIGALRM pass
25880 define hook-continue
25881 handle SIGALRM pass
25885 As a further example, to hook at the beginning and end of the @code{echo}
25886 command, and to add extra text to the beginning and end of the message,
25894 define hookpost-echo
25898 (@value{GDBP}) echo Hello World
25899 <<<---Hello World--->>>
25904 You can define a hook for any single-word command in @value{GDBN}, but
25905 not for command aliases; you should define a hook for the basic command
25906 name, e.g.@: @code{backtrace} rather than @code{bt}.
25907 @c FIXME! So how does Joe User discover whether a command is an alias
25909 You can hook a multi-word command by adding @code{hook-} or
25910 @code{hookpost-} to the last word of the command, e.g.@:
25911 @samp{define target hook-remote} to add a hook to @samp{target remote}.
25913 If an error occurs during the execution of your hook, execution of
25914 @value{GDBN} commands stops and @value{GDBN} issues a prompt
25915 (before the command that you actually typed had a chance to run).
25917 If you try to define a hook which does not match any known command, you
25918 get a warning from the @code{define} command.
25920 @node Command Files
25921 @subsection Command Files
25923 @cindex command files
25924 @cindex scripting commands
25925 A command file for @value{GDBN} is a text file made of lines that are
25926 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
25927 also be included. An empty line in a command file does nothing; it
25928 does not mean to repeat the last command, as it would from the
25931 You can request the execution of a command file with the @code{source}
25932 command. Note that the @code{source} command is also used to evaluate
25933 scripts that are not Command Files. The exact behavior can be configured
25934 using the @code{script-extension} setting.
25935 @xref{Extending GDB,, Extending GDB}.
25939 @cindex execute commands from a file
25940 @item source [-s] [-v] @var{filename}
25941 Execute the command file @var{filename}.
25944 The lines in a command file are generally executed sequentially,
25945 unless the order of execution is changed by one of the
25946 @emph{flow-control commands} described below. The commands are not
25947 printed as they are executed. An error in any command terminates
25948 execution of the command file and control is returned to the console.
25950 @value{GDBN} first searches for @var{filename} in the current directory.
25951 If the file is not found there, and @var{filename} does not specify a
25952 directory, then @value{GDBN} also looks for the file on the source search path
25953 (specified with the @samp{directory} command);
25954 except that @file{$cdir} is not searched because the compilation directory
25955 is not relevant to scripts.
25957 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25958 on the search path even if @var{filename} specifies a directory.
25959 The search is done by appending @var{filename} to each element of the
25960 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25961 and the search path contains @file{/home/user} then @value{GDBN} will
25962 look for the script @file{/home/user/mylib/myscript}.
25963 The search is also done if @var{filename} is an absolute path.
25964 For example, if @var{filename} is @file{/tmp/myscript} and
25965 the search path contains @file{/home/user} then @value{GDBN} will
25966 look for the script @file{/home/user/tmp/myscript}.
25967 For DOS-like systems, if @var{filename} contains a drive specification,
25968 it is stripped before concatenation. For example, if @var{filename} is
25969 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25970 will look for the script @file{c:/tmp/myscript}.
25972 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25973 each command as it is executed. The option must be given before
25974 @var{filename}, and is interpreted as part of the filename anywhere else.
25976 Commands that would ask for confirmation if used interactively proceed
25977 without asking when used in a command file. Many @value{GDBN} commands that
25978 normally print messages to say what they are doing omit the messages
25979 when called from command files.
25981 @value{GDBN} also accepts command input from standard input. In this
25982 mode, normal output goes to standard output and error output goes to
25983 standard error. Errors in a command file supplied on standard input do
25984 not terminate execution of the command file---execution continues with
25988 gdb < cmds > log 2>&1
25991 (The syntax above will vary depending on the shell used.) This example
25992 will execute commands from the file @file{cmds}. All output and errors
25993 would be directed to @file{log}.
25995 Since commands stored on command files tend to be more general than
25996 commands typed interactively, they frequently need to deal with
25997 complicated situations, such as different or unexpected values of
25998 variables and symbols, changes in how the program being debugged is
25999 built, etc. @value{GDBN} provides a set of flow-control commands to
26000 deal with these complexities. Using these commands, you can write
26001 complex scripts that loop over data structures, execute commands
26002 conditionally, etc.
26009 This command allows to include in your script conditionally executed
26010 commands. The @code{if} command takes a single argument, which is an
26011 expression to evaluate. It is followed by a series of commands that
26012 are executed only if the expression is true (its value is nonzero).
26013 There can then optionally be an @code{else} line, followed by a series
26014 of commands that are only executed if the expression was false. The
26015 end of the list is marked by a line containing @code{end}.
26019 This command allows to write loops. Its syntax is similar to
26020 @code{if}: the command takes a single argument, which is an expression
26021 to evaluate, and must be followed by the commands to execute, one per
26022 line, terminated by an @code{end}. These commands are called the
26023 @dfn{body} of the loop. The commands in the body of @code{while} are
26024 executed repeatedly as long as the expression evaluates to true.
26028 This command exits the @code{while} loop in whose body it is included.
26029 Execution of the script continues after that @code{while}s @code{end}
26032 @kindex loop_continue
26033 @item loop_continue
26034 This command skips the execution of the rest of the body of commands
26035 in the @code{while} loop in whose body it is included. Execution
26036 branches to the beginning of the @code{while} loop, where it evaluates
26037 the controlling expression.
26039 @kindex end@r{ (if/else/while commands)}
26041 Terminate the block of commands that are the body of @code{if},
26042 @code{else}, or @code{while} flow-control commands.
26047 @subsection Commands for Controlled Output
26049 During the execution of a command file or a user-defined command, normal
26050 @value{GDBN} output is suppressed; the only output that appears is what is
26051 explicitly printed by the commands in the definition. This section
26052 describes three commands useful for generating exactly the output you
26057 @item echo @var{text}
26058 @c I do not consider backslash-space a standard C escape sequence
26059 @c because it is not in ANSI.
26060 Print @var{text}. Nonprinting characters can be included in
26061 @var{text} using C escape sequences, such as @samp{\n} to print a
26062 newline. @strong{No newline is printed unless you specify one.}
26063 In addition to the standard C escape sequences, a backslash followed
26064 by a space stands for a space. This is useful for displaying a
26065 string with spaces at the beginning or the end, since leading and
26066 trailing spaces are otherwise trimmed from all arguments.
26067 To print @samp{@w{ }and foo =@w{ }}, use the command
26068 @samp{echo \@w{ }and foo = \@w{ }}.
26070 A backslash at the end of @var{text} can be used, as in C, to continue
26071 the command onto subsequent lines. For example,
26074 echo This is some text\n\
26075 which is continued\n\
26076 onto several lines.\n
26079 produces the same output as
26082 echo This is some text\n
26083 echo which is continued\n
26084 echo onto several lines.\n
26088 @item output @var{expression}
26089 Print the value of @var{expression} and nothing but that value: no
26090 newlines, no @samp{$@var{nn} = }. The value is not entered in the
26091 value history either. @xref{Expressions, ,Expressions}, for more information
26094 @item output/@var{fmt} @var{expression}
26095 Print the value of @var{expression} in format @var{fmt}. You can use
26096 the same formats as for @code{print}. @xref{Output Formats,,Output
26097 Formats}, for more information.
26100 @item printf @var{template}, @var{expressions}@dots{}
26101 Print the values of one or more @var{expressions} under the control of
26102 the string @var{template}. To print several values, make
26103 @var{expressions} be a comma-separated list of individual expressions,
26104 which may be either numbers or pointers. Their values are printed as
26105 specified by @var{template}, exactly as a C program would do by
26106 executing the code below:
26109 printf (@var{template}, @var{expressions}@dots{});
26112 As in @code{C} @code{printf}, ordinary characters in @var{template}
26113 are printed verbatim, while @dfn{conversion specification} introduced
26114 by the @samp{%} character cause subsequent @var{expressions} to be
26115 evaluated, their values converted and formatted according to type and
26116 style information encoded in the conversion specifications, and then
26119 For example, you can print two values in hex like this:
26122 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
26125 @code{printf} supports all the standard @code{C} conversion
26126 specifications, including the flags and modifiers between the @samp{%}
26127 character and the conversion letter, with the following exceptions:
26131 The argument-ordering modifiers, such as @samp{2$}, are not supported.
26134 The modifier @samp{*} is not supported for specifying precision or
26138 The @samp{'} flag (for separation of digits into groups according to
26139 @code{LC_NUMERIC'}) is not supported.
26142 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
26146 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
26149 The conversion letters @samp{a} and @samp{A} are not supported.
26153 Note that the @samp{ll} type modifier is supported only if the
26154 underlying @code{C} implementation used to build @value{GDBN} supports
26155 the @code{long long int} type, and the @samp{L} type modifier is
26156 supported only if @code{long double} type is available.
26158 As in @code{C}, @code{printf} supports simple backslash-escape
26159 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
26160 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
26161 single character. Octal and hexadecimal escape sequences are not
26164 Additionally, @code{printf} supports conversion specifications for DFP
26165 (@dfn{Decimal Floating Point}) types using the following length modifiers
26166 together with a floating point specifier.
26171 @samp{H} for printing @code{Decimal32} types.
26174 @samp{D} for printing @code{Decimal64} types.
26177 @samp{DD} for printing @code{Decimal128} types.
26180 If the underlying @code{C} implementation used to build @value{GDBN} has
26181 support for the three length modifiers for DFP types, other modifiers
26182 such as width and precision will also be available for @value{GDBN} to use.
26184 In case there is no such @code{C} support, no additional modifiers will be
26185 available and the value will be printed in the standard way.
26187 Here's an example of printing DFP types using the above conversion letters:
26189 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
26194 @item eval @var{template}, @var{expressions}@dots{}
26195 Convert the values of one or more @var{expressions} under the control of
26196 the string @var{template} to a command line, and call it.
26200 @node Auto-loading sequences
26201 @subsection Controlling auto-loading native @value{GDBN} scripts
26202 @cindex native script auto-loading
26204 When a new object file is read (for example, due to the @code{file}
26205 command, or because the inferior has loaded a shared library),
26206 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
26207 @xref{Auto-loading extensions}.
26209 Auto-loading can be enabled or disabled,
26210 and the list of auto-loaded scripts can be printed.
26213 @anchor{set auto-load gdb-scripts}
26214 @kindex set auto-load gdb-scripts
26215 @item set auto-load gdb-scripts [on|off]
26216 Enable or disable the auto-loading of canned sequences of commands scripts.
26218 @anchor{show auto-load gdb-scripts}
26219 @kindex show auto-load gdb-scripts
26220 @item show auto-load gdb-scripts
26221 Show whether auto-loading of canned sequences of commands scripts is enabled or
26224 @anchor{info auto-load gdb-scripts}
26225 @kindex info auto-load gdb-scripts
26226 @cindex print list of auto-loaded canned sequences of commands scripts
26227 @item info auto-load gdb-scripts [@var{regexp}]
26228 Print the list of all canned sequences of commands scripts that @value{GDBN}
26232 If @var{regexp} is supplied only canned sequences of commands scripts with
26233 matching names are printed.
26235 @c Python docs live in a separate file.
26236 @include python.texi
26238 @c Guile docs live in a separate file.
26239 @include guile.texi
26241 @node Auto-loading extensions
26242 @section Auto-loading extensions
26243 @cindex auto-loading extensions
26245 @value{GDBN} provides two mechanisms for automatically loading extensions
26246 when a new object file is read (for example, due to the @code{file}
26247 command, or because the inferior has loaded a shared library):
26248 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
26249 section of modern file formats like ELF.
26252 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
26253 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
26254 * Which flavor to choose?::
26257 The auto-loading feature is useful for supplying application-specific
26258 debugging commands and features.
26260 Auto-loading can be enabled or disabled,
26261 and the list of auto-loaded scripts can be printed.
26262 See the @samp{auto-loading} section of each extension language
26263 for more information.
26264 For @value{GDBN} command files see @ref{Auto-loading sequences}.
26265 For Python files see @ref{Python Auto-loading}.
26267 Note that loading of this script file also requires accordingly configured
26268 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26270 @node objfile-gdbdotext file
26271 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
26272 @cindex @file{@var{objfile}-gdb.gdb}
26273 @cindex @file{@var{objfile}-gdb.py}
26274 @cindex @file{@var{objfile}-gdb.scm}
26276 When a new object file is read, @value{GDBN} looks for a file named
26277 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
26278 where @var{objfile} is the object file's name and
26279 where @var{ext} is the file extension for the extension language:
26282 @item @file{@var{objfile}-gdb.gdb}
26283 GDB's own command language
26284 @item @file{@var{objfile}-gdb.py}
26286 @item @file{@var{objfile}-gdb.scm}
26290 @var{script-name} is formed by ensuring that the file name of @var{objfile}
26291 is absolute, following all symlinks, and resolving @code{.} and @code{..}
26292 components, and appending the @file{-gdb.@var{ext}} suffix.
26293 If this file exists and is readable, @value{GDBN} will evaluate it as a
26294 script in the specified extension language.
26296 If this file does not exist, then @value{GDBN} will look for
26297 @var{script-name} file in all of the directories as specified below.
26299 Note that loading of these files requires an accordingly configured
26300 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26302 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26303 scripts normally according to its @file{.exe} filename. But if no scripts are
26304 found @value{GDBN} also tries script filenames matching the object file without
26305 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26306 is attempted on any platform. This makes the script filenames compatible
26307 between Unix and MS-Windows hosts.
26310 @anchor{set auto-load scripts-directory}
26311 @kindex set auto-load scripts-directory
26312 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26313 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26314 may be delimited by the host platform path separator in use
26315 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26317 Each entry here needs to be covered also by the security setting
26318 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26320 @anchor{with-auto-load-dir}
26321 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26322 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26323 configuration option @option{--with-auto-load-dir}.
26325 Any reference to @file{$debugdir} will get replaced by
26326 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26327 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26328 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26329 @file{$datadir} must be placed as a directory component --- either alone or
26330 delimited by @file{/} or @file{\} directory separators, depending on the host
26333 The list of directories uses path separator (@samp{:} on GNU and Unix
26334 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26335 to the @env{PATH} environment variable.
26337 @anchor{show auto-load scripts-directory}
26338 @kindex show auto-load scripts-directory
26339 @item show auto-load scripts-directory
26340 Show @value{GDBN} auto-loaded scripts location.
26342 @anchor{add-auto-load-scripts-directory}
26343 @kindex add-auto-load-scripts-directory
26344 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
26345 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
26346 Multiple entries may be delimited by the host platform path separator in use.
26349 @value{GDBN} does not track which files it has already auto-loaded this way.
26350 @value{GDBN} will load the associated script every time the corresponding
26351 @var{objfile} is opened.
26352 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
26353 is evaluated more than once.
26355 @node dotdebug_gdb_scripts section
26356 @subsection The @code{.debug_gdb_scripts} section
26357 @cindex @code{.debug_gdb_scripts} section
26359 For systems using file formats like ELF and COFF,
26360 when @value{GDBN} loads a new object file
26361 it will look for a special section named @code{.debug_gdb_scripts}.
26362 If this section exists, its contents is a list of null-terminated entries
26363 specifying scripts to load. Each entry begins with a non-null prefix byte that
26364 specifies the kind of entry, typically the extension language and whether the
26365 script is in a file or inlined in @code{.debug_gdb_scripts}.
26367 The following entries are supported:
26370 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
26371 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
26372 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
26373 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
26376 @subsubsection Script File Entries
26378 If the entry specifies a file, @value{GDBN} will look for the file first
26379 in the current directory and then along the source search path
26380 (@pxref{Source Path, ,Specifying Source Directories}),
26381 except that @file{$cdir} is not searched, since the compilation
26382 directory is not relevant to scripts.
26384 File entries can be placed in section @code{.debug_gdb_scripts} with,
26385 for example, this GCC macro for Python scripts.
26388 /* Note: The "MS" section flags are to remove duplicates. */
26389 #define DEFINE_GDB_PY_SCRIPT(script_name) \
26391 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26392 .byte 1 /* Python */\n\
26393 .asciz \"" script_name "\"\n\
26399 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
26400 Then one can reference the macro in a header or source file like this:
26403 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
26406 The script name may include directories if desired.
26408 Note that loading of this script file also requires accordingly configured
26409 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26411 If the macro invocation is put in a header, any application or library
26412 using this header will get a reference to the specified script,
26413 and with the use of @code{"MS"} attributes on the section, the linker
26414 will remove duplicates.
26416 @subsubsection Script Text Entries
26418 Script text entries allow to put the executable script in the entry
26419 itself instead of loading it from a file.
26420 The first line of the entry, everything after the prefix byte and up to
26421 the first newline (@code{0xa}) character, is the script name, and must not
26422 contain any kind of space character, e.g., spaces or tabs.
26423 The rest of the entry, up to the trailing null byte, is the script to
26424 execute in the specified language. The name needs to be unique among
26425 all script names, as @value{GDBN} executes each script only once based
26428 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
26432 #include "symcat.h"
26433 #include "gdb/section-scripts.h"
26435 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
26436 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
26437 ".ascii \"gdb.inlined-script\\n\"\n"
26438 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
26439 ".ascii \" def __init__ (self):\\n\"\n"
26440 ".ascii \" super (test_cmd, self).__init__ ("
26441 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
26442 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
26443 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
26444 ".ascii \"test_cmd ()\\n\"\n"
26450 Loading of inlined scripts requires a properly configured
26451 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26452 The path to specify in @code{auto-load safe-path} is the path of the file
26453 containing the @code{.debug_gdb_scripts} section.
26455 @node Which flavor to choose?
26456 @subsection Which flavor to choose?
26458 Given the multiple ways of auto-loading extensions, it might not always
26459 be clear which one to choose. This section provides some guidance.
26462 Benefits of the @file{-gdb.@var{ext}} way:
26466 Can be used with file formats that don't support multiple sections.
26469 Ease of finding scripts for public libraries.
26471 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26472 in the source search path.
26473 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26474 isn't a source directory in which to find the script.
26477 Doesn't require source code additions.
26481 Benefits of the @code{.debug_gdb_scripts} way:
26485 Works with static linking.
26487 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
26488 trigger their loading. When an application is statically linked the only
26489 objfile available is the executable, and it is cumbersome to attach all the
26490 scripts from all the input libraries to the executable's
26491 @file{-gdb.@var{ext}} script.
26494 Works with classes that are entirely inlined.
26496 Some classes can be entirely inlined, and thus there may not be an associated
26497 shared library to attach a @file{-gdb.@var{ext}} script to.
26500 Scripts needn't be copied out of the source tree.
26502 In some circumstances, apps can be built out of large collections of internal
26503 libraries, and the build infrastructure necessary to install the
26504 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
26505 cumbersome. It may be easier to specify the scripts in the
26506 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26507 top of the source tree to the source search path.
26510 @node Multiple Extension Languages
26511 @section Multiple Extension Languages
26513 The Guile and Python extension languages do not share any state,
26514 and generally do not interfere with each other.
26515 There are some things to be aware of, however.
26517 @subsection Python comes first
26519 Python was @value{GDBN}'s first extension language, and to avoid breaking
26520 existing behaviour Python comes first. This is generally solved by the
26521 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
26522 extension languages, and when it makes a call to an extension language,
26523 (say to pretty-print a value), it tries each in turn until an extension
26524 language indicates it has performed the request (e.g., has returned the
26525 pretty-printed form of a value).
26526 This extends to errors while performing such requests: If an error happens
26527 while, for example, trying to pretty-print an object then the error is
26528 reported and any following extension languages are not tried.
26531 @section Creating new spellings of existing commands
26532 @cindex aliases for commands
26534 It is often useful to define alternate spellings of existing commands.
26535 For example, if a new @value{GDBN} command defined in Python has
26536 a long name to type, it is handy to have an abbreviated version of it
26537 that involves less typing.
26539 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26540 of the @samp{step} command even though it is otherwise an ambiguous
26541 abbreviation of other commands like @samp{set} and @samp{show}.
26543 Aliases are also used to provide shortened or more common versions
26544 of multi-word commands. For example, @value{GDBN} provides the
26545 @samp{tty} alias of the @samp{set inferior-tty} command.
26547 You can define a new alias with the @samp{alias} command.
26552 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26556 @var{ALIAS} specifies the name of the new alias.
26557 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26560 @var{COMMAND} specifies the name of an existing command
26561 that is being aliased.
26563 The @samp{-a} option specifies that the new alias is an abbreviation
26564 of the command. Abbreviations are not shown in command
26565 lists displayed by the @samp{help} command.
26567 The @samp{--} option specifies the end of options,
26568 and is useful when @var{ALIAS} begins with a dash.
26570 Here is a simple example showing how to make an abbreviation
26571 of a command so that there is less to type.
26572 Suppose you were tired of typing @samp{disas}, the current
26573 shortest unambiguous abbreviation of the @samp{disassemble} command
26574 and you wanted an even shorter version named @samp{di}.
26575 The following will accomplish this.
26578 (gdb) alias -a di = disas
26581 Note that aliases are different from user-defined commands.
26582 With a user-defined command, you also need to write documentation
26583 for it with the @samp{document} command.
26584 An alias automatically picks up the documentation of the existing command.
26586 Here is an example where we make @samp{elms} an abbreviation of
26587 @samp{elements} in the @samp{set print elements} command.
26588 This is to show that you can make an abbreviation of any part
26592 (gdb) alias -a set print elms = set print elements
26593 (gdb) alias -a show print elms = show print elements
26594 (gdb) set p elms 20
26596 Limit on string chars or array elements to print is 200.
26599 Note that if you are defining an alias of a @samp{set} command,
26600 and you want to have an alias for the corresponding @samp{show}
26601 command, then you need to define the latter separately.
26603 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26604 @var{ALIAS}, just as they are normally.
26607 (gdb) alias -a set pr elms = set p ele
26610 Finally, here is an example showing the creation of a one word
26611 alias for a more complex command.
26612 This creates alias @samp{spe} of the command @samp{set print elements}.
26615 (gdb) alias spe = set print elements
26620 @chapter Command Interpreters
26621 @cindex command interpreters
26623 @value{GDBN} supports multiple command interpreters, and some command
26624 infrastructure to allow users or user interface writers to switch
26625 between interpreters or run commands in other interpreters.
26627 @value{GDBN} currently supports two command interpreters, the console
26628 interpreter (sometimes called the command-line interpreter or @sc{cli})
26629 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26630 describes both of these interfaces in great detail.
26632 By default, @value{GDBN} will start with the console interpreter.
26633 However, the user may choose to start @value{GDBN} with another
26634 interpreter by specifying the @option{-i} or @option{--interpreter}
26635 startup options. Defined interpreters include:
26639 @cindex console interpreter
26640 The traditional console or command-line interpreter. This is the most often
26641 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26642 @value{GDBN} will use this interpreter.
26645 @cindex mi interpreter
26646 The newest @sc{gdb/mi} interface (currently @code{mi3}). Used primarily
26647 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26648 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26652 @cindex mi3 interpreter
26653 The @sc{gdb/mi} interface introduced in @value{GDBN} 9.1.
26656 @cindex mi2 interpreter
26657 The @sc{gdb/mi} interface introduced in @value{GDBN} 6.0.
26660 @cindex mi1 interpreter
26661 The @sc{gdb/mi} interface introduced in @value{GDBN} 5.1.
26665 @cindex invoke another interpreter
26667 @kindex interpreter-exec
26668 You may execute commands in any interpreter from the current
26669 interpreter using the appropriate command. If you are running the
26670 console interpreter, simply use the @code{interpreter-exec} command:
26673 interpreter-exec mi "-data-list-register-names"
26676 @sc{gdb/mi} has a similar command, although it is only available in versions of
26677 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26679 Note that @code{interpreter-exec} only changes the interpreter for the
26680 duration of the specified command. It does not change the interpreter
26683 @cindex start a new independent interpreter
26685 Although you may only choose a single interpreter at startup, it is
26686 possible to run an independent interpreter on a specified input/output
26687 device (usually a tty).
26689 For example, consider a debugger GUI or IDE that wants to provide a
26690 @value{GDBN} console view. It may do so by embedding a terminal
26691 emulator widget in its GUI, starting @value{GDBN} in the traditional
26692 command-line mode with stdin/stdout/stderr redirected to that
26693 terminal, and then creating an MI interpreter running on a specified
26694 input/output device. The console interpreter created by @value{GDBN}
26695 at startup handles commands the user types in the terminal widget,
26696 while the GUI controls and synchronizes state with @value{GDBN} using
26697 the separate MI interpreter.
26699 To start a new secondary @dfn{user interface} running MI, use the
26700 @code{new-ui} command:
26703 @cindex new user interface
26705 new-ui @var{interpreter} @var{tty}
26708 The @var{interpreter} parameter specifies the interpreter to run.
26709 This accepts the same values as the @code{interpreter-exec} command.
26710 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
26711 @var{tty} parameter specifies the name of the bidirectional file the
26712 interpreter uses for input/output, usually the name of a
26713 pseudoterminal slave on Unix systems. For example:
26716 (@value{GDBP}) new-ui mi /dev/pts/9
26720 runs an MI interpreter on @file{/dev/pts/9}.
26723 @chapter @value{GDBN} Text User Interface
26725 @cindex Text User Interface
26728 * TUI Overview:: TUI overview
26729 * TUI Keys:: TUI key bindings
26730 * TUI Single Key Mode:: TUI single key mode
26731 * TUI Commands:: TUI-specific commands
26732 * TUI Configuration:: TUI configuration variables
26735 The @value{GDBN} Text User Interface (TUI) is a terminal
26736 interface which uses the @code{curses} library to show the source
26737 file, the assembly output, the program registers and @value{GDBN}
26738 commands in separate text windows. The TUI mode is supported only
26739 on platforms where a suitable version of the @code{curses} library
26742 The TUI mode is enabled by default when you invoke @value{GDBN} as
26743 @samp{@value{GDBP} -tui}.
26744 You can also switch in and out of TUI mode while @value{GDBN} runs by
26745 using various TUI commands and key bindings, such as @command{tui
26746 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
26747 @ref{TUI Keys, ,TUI Key Bindings}.
26750 @section TUI Overview
26752 In TUI mode, @value{GDBN} can display several text windows:
26756 This window is the @value{GDBN} command window with the @value{GDBN}
26757 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26758 managed using readline.
26761 The source window shows the source file of the program. The current
26762 line and active breakpoints are displayed in this window.
26765 The assembly window shows the disassembly output of the program.
26768 This window shows the processor registers. Registers are highlighted
26769 when their values change.
26772 The source and assembly windows show the current program position
26773 by highlighting the current line and marking it with a @samp{>} marker.
26774 Breakpoints are indicated with two markers. The first marker
26775 indicates the breakpoint type:
26779 Breakpoint which was hit at least once.
26782 Breakpoint which was never hit.
26785 Hardware breakpoint which was hit at least once.
26788 Hardware breakpoint which was never hit.
26791 The second marker indicates whether the breakpoint is enabled or not:
26795 Breakpoint is enabled.
26798 Breakpoint is disabled.
26801 The source, assembly and register windows are updated when the current
26802 thread changes, when the frame changes, or when the program counter
26805 These windows are not all visible at the same time. The command
26806 window is always visible. The others can be arranged in several
26817 source and assembly,
26820 source and registers, or
26823 assembly and registers.
26826 A status line above the command window shows the following information:
26830 Indicates the current @value{GDBN} target.
26831 (@pxref{Targets, ,Specifying a Debugging Target}).
26834 Gives the current process or thread number.
26835 When no process is being debugged, this field is set to @code{No process}.
26838 Gives the current function name for the selected frame.
26839 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26840 When there is no symbol corresponding to the current program counter,
26841 the string @code{??} is displayed.
26844 Indicates the current line number for the selected frame.
26845 When the current line number is not known, the string @code{??} is displayed.
26848 Indicates the current program counter address.
26852 @section TUI Key Bindings
26853 @cindex TUI key bindings
26855 The TUI installs several key bindings in the readline keymaps
26856 @ifset SYSTEM_READLINE
26857 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26859 @ifclear SYSTEM_READLINE
26860 (@pxref{Command Line Editing}).
26862 The following key bindings are installed for both TUI mode and the
26863 @value{GDBN} standard mode.
26872 Enter or leave the TUI mode. When leaving the TUI mode,
26873 the curses window management stops and @value{GDBN} operates using
26874 its standard mode, writing on the terminal directly. When reentering
26875 the TUI mode, control is given back to the curses windows.
26876 The screen is then refreshed.
26880 Use a TUI layout with only one window. The layout will
26881 either be @samp{source} or @samp{assembly}. When the TUI mode
26882 is not active, it will switch to the TUI mode.
26884 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26888 Use a TUI layout with at least two windows. When the current
26889 layout already has two windows, the next layout with two windows is used.
26890 When a new layout is chosen, one window will always be common to the
26891 previous layout and the new one.
26893 Think of it as the Emacs @kbd{C-x 2} binding.
26897 Change the active window. The TUI associates several key bindings
26898 (like scrolling and arrow keys) with the active window. This command
26899 gives the focus to the next TUI window.
26901 Think of it as the Emacs @kbd{C-x o} binding.
26905 Switch in and out of the TUI SingleKey mode that binds single
26906 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26909 The following key bindings only work in the TUI mode:
26914 Scroll the active window one page up.
26918 Scroll the active window one page down.
26922 Scroll the active window one line up.
26926 Scroll the active window one line down.
26930 Scroll the active window one column left.
26934 Scroll the active window one column right.
26938 Refresh the screen.
26941 Because the arrow keys scroll the active window in the TUI mode, they
26942 are not available for their normal use by readline unless the command
26943 window has the focus. When another window is active, you must use
26944 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26945 and @kbd{C-f} to control the command window.
26947 @node TUI Single Key Mode
26948 @section TUI Single Key Mode
26949 @cindex TUI single key mode
26951 The TUI also provides a @dfn{SingleKey} mode, which binds several
26952 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26953 switch into this mode, where the following key bindings are used:
26956 @kindex c @r{(SingleKey TUI key)}
26960 @kindex d @r{(SingleKey TUI key)}
26964 @kindex f @r{(SingleKey TUI key)}
26968 @kindex n @r{(SingleKey TUI key)}
26972 @kindex o @r{(SingleKey TUI key)}
26974 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26976 @kindex q @r{(SingleKey TUI key)}
26978 exit the SingleKey mode.
26980 @kindex r @r{(SingleKey TUI key)}
26984 @kindex s @r{(SingleKey TUI key)}
26988 @kindex i @r{(SingleKey TUI key)}
26990 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26992 @kindex u @r{(SingleKey TUI key)}
26996 @kindex v @r{(SingleKey TUI key)}
27000 @kindex w @r{(SingleKey TUI key)}
27005 Other keys temporarily switch to the @value{GDBN} command prompt.
27006 The key that was pressed is inserted in the editing buffer so that
27007 it is possible to type most @value{GDBN} commands without interaction
27008 with the TUI SingleKey mode. Once the command is entered the TUI
27009 SingleKey mode is restored. The only way to permanently leave
27010 this mode is by typing @kbd{q} or @kbd{C-x s}.
27014 @section TUI-specific Commands
27015 @cindex TUI commands
27017 The TUI has specific commands to control the text windows.
27018 These commands are always available, even when @value{GDBN} is not in
27019 the TUI mode. When @value{GDBN} is in the standard mode, most
27020 of these commands will automatically switch to the TUI mode.
27022 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27023 terminal, or @value{GDBN} has been started with the machine interface
27024 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27025 these commands will fail with an error, because it would not be
27026 possible or desirable to enable curses window management.
27031 Activate TUI mode. The last active TUI window layout will be used if
27032 TUI mode has prevsiouly been used in the current debugging session,
27033 otherwise a default layout is used.
27036 @kindex tui disable
27037 Disable TUI mode, returning to the console interpreter.
27041 List and give the size of all displayed windows.
27043 @item layout @var{name}
27045 Changes which TUI windows are displayed. In each layout the command
27046 window is always displayed, the @var{name} parameter controls which
27047 additional windows are displayed, and can be any of the following:
27051 Display the next layout.
27054 Display the previous layout.
27057 Display the source and command windows.
27060 Display the assembly and command windows.
27063 Display the source, assembly, and command windows.
27066 When in @code{src} layout display the register, source, and command
27067 windows. When in @code{asm} or @code{split} layout display the
27068 register, assembler, and command windows.
27071 @item focus @var{name}
27073 Changes which TUI window is currently active for scrolling. The
27074 @var{name} parameter can be any of the following:
27078 Make the next window active for scrolling.
27081 Make the previous window active for scrolling.
27084 Make the source window active for scrolling.
27087 Make the assembly window active for scrolling.
27090 Make the register window active for scrolling.
27093 Make the command window active for scrolling.
27098 Refresh the screen. This is similar to typing @kbd{C-L}.
27100 @item tui reg @var{group}
27102 Changes the register group displayed in the tui register window to
27103 @var{group}. If the register window is not currently displayed this
27104 command will cause the register window to be displayed. The list of
27105 register groups, as well as their order is target specific. The
27106 following groups are available on most targets:
27109 Repeatedly selecting this group will cause the display to cycle
27110 through all of the available register groups.
27113 Repeatedly selecting this group will cause the display to cycle
27114 through all of the available register groups in the reverse order to
27118 Display the general registers.
27120 Display the floating point registers.
27122 Display the system registers.
27124 Display the vector registers.
27126 Display all registers.
27131 Update the source window and the current execution point.
27133 @item winheight @var{name} +@var{count}
27134 @itemx winheight @var{name} -@var{count}
27136 Change the height of the window @var{name} by @var{count}
27137 lines. Positive counts increase the height, while negative counts
27138 decrease it. The @var{name} parameter can be one of @code{src} (the
27139 source window), @code{cmd} (the command window), @code{asm} (the
27140 disassembly window), or @code{regs} (the register display window).
27143 @node TUI Configuration
27144 @section TUI Configuration Variables
27145 @cindex TUI configuration variables
27147 Several configuration variables control the appearance of TUI windows.
27150 @item set tui border-kind @var{kind}
27151 @kindex set tui border-kind
27152 Select the border appearance for the source, assembly and register windows.
27153 The possible values are the following:
27156 Use a space character to draw the border.
27159 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27162 Use the Alternate Character Set to draw the border. The border is
27163 drawn using character line graphics if the terminal supports them.
27166 @item set tui border-mode @var{mode}
27167 @kindex set tui border-mode
27168 @itemx set tui active-border-mode @var{mode}
27169 @kindex set tui active-border-mode
27170 Select the display attributes for the borders of the inactive windows
27171 or the active window. The @var{mode} can be one of the following:
27174 Use normal attributes to display the border.
27180 Use reverse video mode.
27183 Use half bright mode.
27185 @item half-standout
27186 Use half bright and standout mode.
27189 Use extra bright or bold mode.
27191 @item bold-standout
27192 Use extra bright or bold and standout mode.
27195 @item set tui tab-width @var{nchars}
27196 @kindex set tui tab-width
27198 Set the width of tab stops to be @var{nchars} characters. This
27199 setting affects the display of TAB characters in the source and
27204 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27207 @cindex @sc{gnu} Emacs
27208 A special interface allows you to use @sc{gnu} Emacs to view (and
27209 edit) the source files for the program you are debugging with
27212 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27213 executable file you want to debug as an argument. This command starts
27214 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27215 created Emacs buffer.
27216 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27218 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27223 All ``terminal'' input and output goes through an Emacs buffer, called
27226 This applies both to @value{GDBN} commands and their output, and to the input
27227 and output done by the program you are debugging.
27229 This is useful because it means that you can copy the text of previous
27230 commands and input them again; you can even use parts of the output
27233 All the facilities of Emacs' Shell mode are available for interacting
27234 with your program. In particular, you can send signals the usual
27235 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27239 @value{GDBN} displays source code through Emacs.
27241 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27242 source file for that frame and puts an arrow (@samp{=>}) at the
27243 left margin of the current line. Emacs uses a separate buffer for
27244 source display, and splits the screen to show both your @value{GDBN} session
27247 Explicit @value{GDBN} @code{list} or search commands still produce output as
27248 usual, but you probably have no reason to use them from Emacs.
27251 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27252 a graphical mode, enabled by default, which provides further buffers
27253 that can control the execution and describe the state of your program.
27254 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27256 If you specify an absolute file name when prompted for the @kbd{M-x
27257 gdb} argument, then Emacs sets your current working directory to where
27258 your program resides. If you only specify the file name, then Emacs
27259 sets your current working directory to the directory associated
27260 with the previous buffer. In this case, @value{GDBN} may find your
27261 program by searching your environment's @code{PATH} variable, but on
27262 some operating systems it might not find the source. So, although the
27263 @value{GDBN} input and output session proceeds normally, the auxiliary
27264 buffer does not display the current source and line of execution.
27266 The initial working directory of @value{GDBN} is printed on the top
27267 line of the GUD buffer and this serves as a default for the commands
27268 that specify files for @value{GDBN} to operate on. @xref{Files,
27269 ,Commands to Specify Files}.
27271 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27272 need to call @value{GDBN} by a different name (for example, if you
27273 keep several configurations around, with different names) you can
27274 customize the Emacs variable @code{gud-gdb-command-name} to run the
27277 In the GUD buffer, you can use these special Emacs commands in
27278 addition to the standard Shell mode commands:
27282 Describe the features of Emacs' GUD Mode.
27285 Execute to another source line, like the @value{GDBN} @code{step} command; also
27286 update the display window to show the current file and location.
27289 Execute to next source line in this function, skipping all function
27290 calls, like the @value{GDBN} @code{next} command. Then update the display window
27291 to show the current file and location.
27294 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27295 display window accordingly.
27298 Execute until exit from the selected stack frame, like the @value{GDBN}
27299 @code{finish} command.
27302 Continue execution of your program, like the @value{GDBN} @code{continue}
27306 Go up the number of frames indicated by the numeric argument
27307 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27308 like the @value{GDBN} @code{up} command.
27311 Go down the number of frames indicated by the numeric argument, like the
27312 @value{GDBN} @code{down} command.
27315 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27316 tells @value{GDBN} to set a breakpoint on the source line point is on.
27318 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27319 separate frame which shows a backtrace when the GUD buffer is current.
27320 Move point to any frame in the stack and type @key{RET} to make it
27321 become the current frame and display the associated source in the
27322 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27323 selected frame become the current one. In graphical mode, the
27324 speedbar displays watch expressions.
27326 If you accidentally delete the source-display buffer, an easy way to get
27327 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27328 request a frame display; when you run under Emacs, this recreates
27329 the source buffer if necessary to show you the context of the current
27332 The source files displayed in Emacs are in ordinary Emacs buffers
27333 which are visiting the source files in the usual way. You can edit
27334 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27335 communicates with Emacs in terms of line numbers. If you add or
27336 delete lines from the text, the line numbers that @value{GDBN} knows cease
27337 to correspond properly with the code.
27339 A more detailed description of Emacs' interaction with @value{GDBN} is
27340 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27344 @chapter The @sc{gdb/mi} Interface
27346 @unnumberedsec Function and Purpose
27348 @cindex @sc{gdb/mi}, its purpose
27349 @sc{gdb/mi} is a line based machine oriented text interface to
27350 @value{GDBN} and is activated by specifying using the
27351 @option{--interpreter} command line option (@pxref{Mode Options}). It
27352 is specifically intended to support the development of systems which
27353 use the debugger as just one small component of a larger system.
27355 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27356 in the form of a reference manual.
27358 Note that @sc{gdb/mi} is still under construction, so some of the
27359 features described below are incomplete and subject to change
27360 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27362 @unnumberedsec Notation and Terminology
27364 @cindex notational conventions, for @sc{gdb/mi}
27365 This chapter uses the following notation:
27369 @code{|} separates two alternatives.
27372 @code{[ @var{something} ]} indicates that @var{something} is optional:
27373 it may or may not be given.
27376 @code{( @var{group} )*} means that @var{group} inside the parentheses
27377 may repeat zero or more times.
27380 @code{( @var{group} )+} means that @var{group} inside the parentheses
27381 may repeat one or more times.
27384 @code{"@var{string}"} means a literal @var{string}.
27388 @heading Dependencies
27392 * GDB/MI General Design::
27393 * GDB/MI Command Syntax::
27394 * GDB/MI Compatibility with CLI::
27395 * GDB/MI Development and Front Ends::
27396 * GDB/MI Output Records::
27397 * GDB/MI Simple Examples::
27398 * GDB/MI Command Description Format::
27399 * GDB/MI Breakpoint Commands::
27400 * GDB/MI Catchpoint Commands::
27401 * GDB/MI Program Context::
27402 * GDB/MI Thread Commands::
27403 * GDB/MI Ada Tasking Commands::
27404 * GDB/MI Program Execution::
27405 * GDB/MI Stack Manipulation::
27406 * GDB/MI Variable Objects::
27407 * GDB/MI Data Manipulation::
27408 * GDB/MI Tracepoint Commands::
27409 * GDB/MI Symbol Query::
27410 * GDB/MI File Commands::
27412 * GDB/MI Kod Commands::
27413 * GDB/MI Memory Overlay Commands::
27414 * GDB/MI Signal Handling Commands::
27416 * GDB/MI Target Manipulation::
27417 * GDB/MI File Transfer Commands::
27418 * GDB/MI Ada Exceptions Commands::
27419 * GDB/MI Support Commands::
27420 * GDB/MI Miscellaneous Commands::
27423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27424 @node GDB/MI General Design
27425 @section @sc{gdb/mi} General Design
27426 @cindex GDB/MI General Design
27428 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27429 parts---commands sent to @value{GDBN}, responses to those commands
27430 and notifications. Each command results in exactly one response,
27431 indicating either successful completion of the command, or an error.
27432 For the commands that do not resume the target, the response contains the
27433 requested information. For the commands that resume the target, the
27434 response only indicates whether the target was successfully resumed.
27435 Notifications is the mechanism for reporting changes in the state of the
27436 target, or in @value{GDBN} state, that cannot conveniently be associated with
27437 a command and reported as part of that command response.
27439 The important examples of notifications are:
27443 Exec notifications. These are used to report changes in
27444 target state---when a target is resumed, or stopped. It would not
27445 be feasible to include this information in response of resuming
27446 commands, because one resume commands can result in multiple events in
27447 different threads. Also, quite some time may pass before any event
27448 happens in the target, while a frontend needs to know whether the resuming
27449 command itself was successfully executed.
27452 Console output, and status notifications. Console output
27453 notifications are used to report output of CLI commands, as well as
27454 diagnostics for other commands. Status notifications are used to
27455 report the progress of a long-running operation. Naturally, including
27456 this information in command response would mean no output is produced
27457 until the command is finished, which is undesirable.
27460 General notifications. Commands may have various side effects on
27461 the @value{GDBN} or target state beyond their official purpose. For example,
27462 a command may change the selected thread. Although such changes can
27463 be included in command response, using notification allows for more
27464 orthogonal frontend design.
27468 There's no guarantee that whenever an MI command reports an error,
27469 @value{GDBN} or the target are in any specific state, and especially,
27470 the state is not reverted to the state before the MI command was
27471 processed. Therefore, whenever an MI command results in an error,
27472 we recommend that the frontend refreshes all the information shown in
27473 the user interface.
27477 * Context management::
27478 * Asynchronous and non-stop modes::
27482 @node Context management
27483 @subsection Context management
27485 @subsubsection Threads and Frames
27487 In most cases when @value{GDBN} accesses the target, this access is
27488 done in context of a specific thread and frame (@pxref{Frames}).
27489 Often, even when accessing global data, the target requires that a thread
27490 be specified. The CLI interface maintains the selected thread and frame,
27491 and supplies them to target on each command. This is convenient,
27492 because a command line user would not want to specify that information
27493 explicitly on each command, and because user interacts with
27494 @value{GDBN} via a single terminal, so no confusion is possible as
27495 to what thread and frame are the current ones.
27497 In the case of MI, the concept of selected thread and frame is less
27498 useful. First, a frontend can easily remember this information
27499 itself. Second, a graphical frontend can have more than one window,
27500 each one used for debugging a different thread, and the frontend might
27501 want to access additional threads for internal purposes. This
27502 increases the risk that by relying on implicitly selected thread, the
27503 frontend may be operating on a wrong one. Therefore, each MI command
27504 should explicitly specify which thread and frame to operate on. To
27505 make it possible, each MI command accepts the @samp{--thread} and
27506 @samp{--frame} options, the value to each is @value{GDBN} global
27507 identifier for thread and frame to operate on.
27509 Usually, each top-level window in a frontend allows the user to select
27510 a thread and a frame, and remembers the user selection for further
27511 operations. However, in some cases @value{GDBN} may suggest that the
27512 current thread or frame be changed. For example, when stopping on a
27513 breakpoint it is reasonable to switch to the thread where breakpoint is
27514 hit. For another example, if the user issues the CLI @samp{thread} or
27515 @samp{frame} commands via the frontend, it is desirable to change the
27516 frontend's selection to the one specified by user. @value{GDBN}
27517 communicates the suggestion to change current thread and frame using the
27518 @samp{=thread-selected} notification.
27520 Note that historically, MI shares the selected thread with CLI, so
27521 frontends used the @code{-thread-select} to execute commands in the
27522 right context. However, getting this to work right is cumbersome. The
27523 simplest way is for frontend to emit @code{-thread-select} command
27524 before every command. This doubles the number of commands that need
27525 to be sent. The alternative approach is to suppress @code{-thread-select}
27526 if the selected thread in @value{GDBN} is supposed to be identical to the
27527 thread the frontend wants to operate on. However, getting this
27528 optimization right can be tricky. In particular, if the frontend
27529 sends several commands to @value{GDBN}, and one of the commands changes the
27530 selected thread, then the behaviour of subsequent commands will
27531 change. So, a frontend should either wait for response from such
27532 problematic commands, or explicitly add @code{-thread-select} for
27533 all subsequent commands. No frontend is known to do this exactly
27534 right, so it is suggested to just always pass the @samp{--thread} and
27535 @samp{--frame} options.
27537 @subsubsection Language
27539 The execution of several commands depends on which language is selected.
27540 By default, the current language (@pxref{show language}) is used.
27541 But for commands known to be language-sensitive, it is recommended
27542 to use the @samp{--language} option. This option takes one argument,
27543 which is the name of the language to use while executing the command.
27547 -data-evaluate-expression --language c "sizeof (void*)"
27552 The valid language names are the same names accepted by the
27553 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
27554 @samp{local} or @samp{unknown}.
27556 @node Asynchronous and non-stop modes
27557 @subsection Asynchronous command execution and non-stop mode
27559 On some targets, @value{GDBN} is capable of processing MI commands
27560 even while the target is running. This is called @dfn{asynchronous
27561 command execution} (@pxref{Background Execution}). The frontend may
27562 specify a preferrence for asynchronous execution using the
27563 @code{-gdb-set mi-async 1} command, which should be emitted before
27564 either running the executable or attaching to the target. After the
27565 frontend has started the executable or attached to the target, it can
27566 find if asynchronous execution is enabled using the
27567 @code{-list-target-features} command.
27570 @item -gdb-set mi-async on
27571 @item -gdb-set mi-async off
27572 Set whether MI is in asynchronous mode.
27574 When @code{off}, which is the default, MI execution commands (e.g.,
27575 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
27576 for the program to stop before processing further commands.
27578 When @code{on}, MI execution commands are background execution
27579 commands (e.g., @code{-exec-continue} becomes the equivalent of the
27580 @code{c&} CLI command), and so @value{GDBN} is capable of processing
27581 MI commands even while the target is running.
27583 @item -gdb-show mi-async
27584 Show whether MI asynchronous mode is enabled.
27587 Note: In @value{GDBN} version 7.7 and earlier, this option was called
27588 @code{target-async} instead of @code{mi-async}, and it had the effect
27589 of both putting MI in asynchronous mode and making CLI background
27590 commands possible. CLI background commands are now always possible
27591 ``out of the box'' if the target supports them. The old spelling is
27592 kept as a deprecated alias for backwards compatibility.
27594 Even if @value{GDBN} can accept a command while target is running,
27595 many commands that access the target do not work when the target is
27596 running. Therefore, asynchronous command execution is most useful
27597 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27598 it is possible to examine the state of one thread, while other threads
27601 When a given thread is running, MI commands that try to access the
27602 target in the context of that thread may not work, or may work only on
27603 some targets. In particular, commands that try to operate on thread's
27604 stack will not work, on any target. Commands that read memory, or
27605 modify breakpoints, may work or not work, depending on the target. Note
27606 that even commands that operate on global state, such as @code{print},
27607 @code{set}, and breakpoint commands, still access the target in the
27608 context of a specific thread, so frontend should try to find a
27609 stopped thread and perform the operation on that thread (using the
27610 @samp{--thread} option).
27612 Which commands will work in the context of a running thread is
27613 highly target dependent. However, the two commands
27614 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27615 to find the state of a thread, will always work.
27617 @node Thread groups
27618 @subsection Thread groups
27619 @value{GDBN} may be used to debug several processes at the same time.
27620 On some platfroms, @value{GDBN} may support debugging of several
27621 hardware systems, each one having several cores with several different
27622 processes running on each core. This section describes the MI
27623 mechanism to support such debugging scenarios.
27625 The key observation is that regardless of the structure of the
27626 target, MI can have a global list of threads, because most commands that
27627 accept the @samp{--thread} option do not need to know what process that
27628 thread belongs to. Therefore, it is not necessary to introduce
27629 neither additional @samp{--process} option, nor an notion of the
27630 current process in the MI interface. The only strictly new feature
27631 that is required is the ability to find how the threads are grouped
27634 To allow the user to discover such grouping, and to support arbitrary
27635 hierarchy of machines/cores/processes, MI introduces the concept of a
27636 @dfn{thread group}. Thread group is a collection of threads and other
27637 thread groups. A thread group always has a string identifier, a type,
27638 and may have additional attributes specific to the type. A new
27639 command, @code{-list-thread-groups}, returns the list of top-level
27640 thread groups, which correspond to processes that @value{GDBN} is
27641 debugging at the moment. By passing an identifier of a thread group
27642 to the @code{-list-thread-groups} command, it is possible to obtain
27643 the members of specific thread group.
27645 To allow the user to easily discover processes, and other objects, he
27646 wishes to debug, a concept of @dfn{available thread group} is
27647 introduced. Available thread group is an thread group that
27648 @value{GDBN} is not debugging, but that can be attached to, using the
27649 @code{-target-attach} command. The list of available top-level thread
27650 groups can be obtained using @samp{-list-thread-groups --available}.
27651 In general, the content of a thread group may be only retrieved only
27652 after attaching to that thread group.
27654 Thread groups are related to inferiors (@pxref{Inferiors and
27655 Programs}). Each inferior corresponds to a thread group of a special
27656 type @samp{process}, and some additional operations are permitted on
27657 such thread groups.
27659 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27660 @node GDB/MI Command Syntax
27661 @section @sc{gdb/mi} Command Syntax
27664 * GDB/MI Input Syntax::
27665 * GDB/MI Output Syntax::
27668 @node GDB/MI Input Syntax
27669 @subsection @sc{gdb/mi} Input Syntax
27671 @cindex input syntax for @sc{gdb/mi}
27672 @cindex @sc{gdb/mi}, input syntax
27674 @item @var{command} @expansion{}
27675 @code{@var{cli-command} | @var{mi-command}}
27677 @item @var{cli-command} @expansion{}
27678 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27679 @var{cli-command} is any existing @value{GDBN} CLI command.
27681 @item @var{mi-command} @expansion{}
27682 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27683 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27685 @item @var{token} @expansion{}
27686 "any sequence of digits"
27688 @item @var{option} @expansion{}
27689 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27691 @item @var{parameter} @expansion{}
27692 @code{@var{non-blank-sequence} | @var{c-string}}
27694 @item @var{operation} @expansion{}
27695 @emph{any of the operations described in this chapter}
27697 @item @var{non-blank-sequence} @expansion{}
27698 @emph{anything, provided it doesn't contain special characters such as
27699 "-", @var{nl}, """ and of course " "}
27701 @item @var{c-string} @expansion{}
27702 @code{""" @var{seven-bit-iso-c-string-content} """}
27704 @item @var{nl} @expansion{}
27713 The CLI commands are still handled by the @sc{mi} interpreter; their
27714 output is described below.
27717 The @code{@var{token}}, when present, is passed back when the command
27721 Some @sc{mi} commands accept optional arguments as part of the parameter
27722 list. Each option is identified by a leading @samp{-} (dash) and may be
27723 followed by an optional argument parameter. Options occur first in the
27724 parameter list and can be delimited from normal parameters using
27725 @samp{--} (this is useful when some parameters begin with a dash).
27732 We want easy access to the existing CLI syntax (for debugging).
27735 We want it to be easy to spot a @sc{mi} operation.
27738 @node GDB/MI Output Syntax
27739 @subsection @sc{gdb/mi} Output Syntax
27741 @cindex output syntax of @sc{gdb/mi}
27742 @cindex @sc{gdb/mi}, output syntax
27743 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27744 followed, optionally, by a single result record. This result record
27745 is for the most recent command. The sequence of output records is
27746 terminated by @samp{(gdb)}.
27748 If an input command was prefixed with a @code{@var{token}} then the
27749 corresponding output for that command will also be prefixed by that same
27753 @item @var{output} @expansion{}
27754 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27756 @item @var{result-record} @expansion{}
27757 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27759 @item @var{out-of-band-record} @expansion{}
27760 @code{@var{async-record} | @var{stream-record}}
27762 @item @var{async-record} @expansion{}
27763 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27765 @item @var{exec-async-output} @expansion{}
27766 @code{[ @var{token} ] "*" @var{async-output nl}}
27768 @item @var{status-async-output} @expansion{}
27769 @code{[ @var{token} ] "+" @var{async-output nl}}
27771 @item @var{notify-async-output} @expansion{}
27772 @code{[ @var{token} ] "=" @var{async-output nl}}
27774 @item @var{async-output} @expansion{}
27775 @code{@var{async-class} ( "," @var{result} )*}
27777 @item @var{result-class} @expansion{}
27778 @code{"done" | "running" | "connected" | "error" | "exit"}
27780 @item @var{async-class} @expansion{}
27781 @code{"stopped" | @var{others}} (where @var{others} will be added
27782 depending on the needs---this is still in development).
27784 @item @var{result} @expansion{}
27785 @code{ @var{variable} "=" @var{value}}
27787 @item @var{variable} @expansion{}
27788 @code{ @var{string} }
27790 @item @var{value} @expansion{}
27791 @code{ @var{const} | @var{tuple} | @var{list} }
27793 @item @var{const} @expansion{}
27794 @code{@var{c-string}}
27796 @item @var{tuple} @expansion{}
27797 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27799 @item @var{list} @expansion{}
27800 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27801 @var{result} ( "," @var{result} )* "]" }
27803 @item @var{stream-record} @expansion{}
27804 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27806 @item @var{console-stream-output} @expansion{}
27807 @code{"~" @var{c-string nl}}
27809 @item @var{target-stream-output} @expansion{}
27810 @code{"@@" @var{c-string nl}}
27812 @item @var{log-stream-output} @expansion{}
27813 @code{"&" @var{c-string nl}}
27815 @item @var{nl} @expansion{}
27818 @item @var{token} @expansion{}
27819 @emph{any sequence of digits}.
27827 All output sequences end in a single line containing a period.
27830 The @code{@var{token}} is from the corresponding request. Note that
27831 for all async output, while the token is allowed by the grammar and
27832 may be output by future versions of @value{GDBN} for select async
27833 output messages, it is generally omitted. Frontends should treat
27834 all async output as reporting general changes in the state of the
27835 target and there should be no need to associate async output to any
27839 @cindex status output in @sc{gdb/mi}
27840 @var{status-async-output} contains on-going status information about the
27841 progress of a slow operation. It can be discarded. All status output is
27842 prefixed by @samp{+}.
27845 @cindex async output in @sc{gdb/mi}
27846 @var{exec-async-output} contains asynchronous state change on the target
27847 (stopped, started, disappeared). All async output is prefixed by
27851 @cindex notify output in @sc{gdb/mi}
27852 @var{notify-async-output} contains supplementary information that the
27853 client should handle (e.g., a new breakpoint information). All notify
27854 output is prefixed by @samp{=}.
27857 @cindex console output in @sc{gdb/mi}
27858 @var{console-stream-output} is output that should be displayed as is in the
27859 console. It is the textual response to a CLI command. All the console
27860 output is prefixed by @samp{~}.
27863 @cindex target output in @sc{gdb/mi}
27864 @var{target-stream-output} is the output produced by the target program.
27865 All the target output is prefixed by @samp{@@}.
27868 @cindex log output in @sc{gdb/mi}
27869 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27870 instance messages that should be displayed as part of an error log. All
27871 the log output is prefixed by @samp{&}.
27874 @cindex list output in @sc{gdb/mi}
27875 New @sc{gdb/mi} commands should only output @var{lists} containing
27881 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27882 details about the various output records.
27884 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27885 @node GDB/MI Compatibility with CLI
27886 @section @sc{gdb/mi} Compatibility with CLI
27888 @cindex compatibility, @sc{gdb/mi} and CLI
27889 @cindex @sc{gdb/mi}, compatibility with CLI
27891 For the developers convenience CLI commands can be entered directly,
27892 but there may be some unexpected behaviour. For example, commands
27893 that query the user will behave as if the user replied yes, breakpoint
27894 command lists are not executed and some CLI commands, such as
27895 @code{if}, @code{when} and @code{define}, prompt for further input with
27896 @samp{>}, which is not valid MI output.
27898 This feature may be removed at some stage in the future and it is
27899 recommended that front ends use the @code{-interpreter-exec} command
27900 (@pxref{-interpreter-exec}).
27902 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27903 @node GDB/MI Development and Front Ends
27904 @section @sc{gdb/mi} Development and Front Ends
27905 @cindex @sc{gdb/mi} development
27907 The application which takes the MI output and presents the state of the
27908 program being debugged to the user is called a @dfn{front end}.
27910 Since @sc{gdb/mi} is used by a variety of front ends to @value{GDBN}, changes
27911 to the MI interface may break existing usage. This section describes how the
27912 protocol changes and how to request previous version of the protocol when it
27915 Some changes in MI need not break a carefully designed front end, and
27916 for these the MI version will remain unchanged. The following is a
27917 list of changes that may occur within one level, so front ends should
27918 parse MI output in a way that can handle them:
27922 New MI commands may be added.
27925 New fields may be added to the output of any MI command.
27928 The range of values for fields with specified values, e.g.,
27929 @code{in_scope} (@pxref{-var-update}) may be extended.
27931 @c The format of field's content e.g type prefix, may change so parse it
27932 @c at your own risk. Yes, in general?
27934 @c The order of fields may change? Shouldn't really matter but it might
27935 @c resolve inconsistencies.
27938 If the changes are likely to break front ends, the MI version level
27939 will be increased by one. The new versions of the MI protocol are not compatible
27940 with the old versions. Old versions of MI remain available, allowing front ends
27941 to keep using them until they are modified to use the latest MI version.
27943 Since @code{--interpreter=mi} always points to the latest MI version, it is
27944 recommended that front ends request a specific version of MI when launching
27945 @value{GDBN} (e.g. @code{--interpreter=mi2}) to make sure they get an
27946 interpreter with the MI version they expect.
27948 The following table gives a summary of the the released versions of the MI
27949 interface: the version number, the version of GDB in which it first appeared
27950 and the breaking changes compared to the previous version.
27952 @multitable @columnfractions .05 .05 .9
27953 @headitem MI version @tab GDB version @tab Breaking changes
27970 The @code{-environment-pwd}, @code{-environment-directory} and
27971 @code{-environment-path} commands now returns values using the MI output
27972 syntax, rather than CLI output syntax.
27975 @code{-var-list-children}'s @code{children} result field is now a list, rather
27979 @code{-var-update}'s @code{changelist} result field is now a list, rather than
27991 The output of information about multi-location breakpoints has changed in the
27992 responses to the @code{-break-insert} and @code{-break-info} commands, as well
27993 as in the @code{=breakpoint-created} and @code{=breakpoint-modified} events.
27994 The multiple locations are now placed in a @code{locations} field, whose value
28000 If your front end cannot yet migrate to a more recent version of the
28001 MI protocol, you can nevertheless selectively enable specific features
28002 available in those recent MI versions, using the following commands:
28006 @item -fix-multi-location-breakpoint-output
28007 Use the output for multi-location breakpoints which was introduced by
28008 MI 3, even when using MI versions 2 or 1. This command has no
28009 effect when using MI version 3 or later.
28013 The best way to avoid unexpected changes in MI that might break your front
28014 end is to make your project known to @value{GDBN} developers and
28015 follow development on @email{gdb@@sourceware.org} and
28016 @email{gdb-patches@@sourceware.org}.
28017 @cindex mailing lists
28019 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28020 @node GDB/MI Output Records
28021 @section @sc{gdb/mi} Output Records
28024 * GDB/MI Result Records::
28025 * GDB/MI Stream Records::
28026 * GDB/MI Async Records::
28027 * GDB/MI Breakpoint Information::
28028 * GDB/MI Frame Information::
28029 * GDB/MI Thread Information::
28030 * GDB/MI Ada Exception Information::
28033 @node GDB/MI Result Records
28034 @subsection @sc{gdb/mi} Result Records
28036 @cindex result records in @sc{gdb/mi}
28037 @cindex @sc{gdb/mi}, result records
28038 In addition to a number of out-of-band notifications, the response to a
28039 @sc{gdb/mi} command includes one of the following result indications:
28043 @item "^done" [ "," @var{results} ]
28044 The synchronous operation was successful, @code{@var{results}} are the return
28049 This result record is equivalent to @samp{^done}. Historically, it
28050 was output instead of @samp{^done} if the command has resumed the
28051 target. This behaviour is maintained for backward compatibility, but
28052 all frontends should treat @samp{^done} and @samp{^running}
28053 identically and rely on the @samp{*running} output record to determine
28054 which threads are resumed.
28058 @value{GDBN} has connected to a remote target.
28060 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
28062 The operation failed. The @code{msg=@var{c-string}} variable contains
28063 the corresponding error message.
28065 If present, the @code{code=@var{c-string}} variable provides an error
28066 code on which consumers can rely on to detect the corresponding
28067 error condition. At present, only one error code is defined:
28070 @item "undefined-command"
28071 Indicates that the command causing the error does not exist.
28076 @value{GDBN} has terminated.
28080 @node GDB/MI Stream Records
28081 @subsection @sc{gdb/mi} Stream Records
28083 @cindex @sc{gdb/mi}, stream records
28084 @cindex stream records in @sc{gdb/mi}
28085 @value{GDBN} internally maintains a number of output streams: the console, the
28086 target, and the log. The output intended for each of these streams is
28087 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28089 Each stream record begins with a unique @dfn{prefix character} which
28090 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28091 Syntax}). In addition to the prefix, each stream record contains a
28092 @code{@var{string-output}}. This is either raw text (with an implicit new
28093 line) or a quoted C string (which does not contain an implicit newline).
28096 @item "~" @var{string-output}
28097 The console output stream contains text that should be displayed in the
28098 CLI console window. It contains the textual responses to CLI commands.
28100 @item "@@" @var{string-output}
28101 The target output stream contains any textual output from the running
28102 target. This is only present when GDB's event loop is truly
28103 asynchronous, which is currently only the case for remote targets.
28105 @item "&" @var{string-output}
28106 The log stream contains debugging messages being produced by @value{GDBN}'s
28110 @node GDB/MI Async Records
28111 @subsection @sc{gdb/mi} Async Records
28113 @cindex async records in @sc{gdb/mi}
28114 @cindex @sc{gdb/mi}, async records
28115 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28116 additional changes that have occurred. Those changes can either be a
28117 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28118 target activity (e.g., target stopped).
28120 The following is the list of possible async records:
28124 @item *running,thread-id="@var{thread}"
28125 The target is now running. The @var{thread} field can be the global
28126 thread ID of the the thread that is now running, and it can be
28127 @samp{all} if all threads are running. The frontend should assume
28128 that no interaction with a running thread is possible after this
28129 notification is produced. The frontend should not assume that this
28130 notification is output only once for any command. @value{GDBN} may
28131 emit this notification several times, either for different threads,
28132 because it cannot resume all threads together, or even for a single
28133 thread, if the thread must be stepped though some code before letting
28136 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28137 The target has stopped. The @var{reason} field can have one of the
28141 @item breakpoint-hit
28142 A breakpoint was reached.
28143 @item watchpoint-trigger
28144 A watchpoint was triggered.
28145 @item read-watchpoint-trigger
28146 A read watchpoint was triggered.
28147 @item access-watchpoint-trigger
28148 An access watchpoint was triggered.
28149 @item function-finished
28150 An -exec-finish or similar CLI command was accomplished.
28151 @item location-reached
28152 An -exec-until or similar CLI command was accomplished.
28153 @item watchpoint-scope
28154 A watchpoint has gone out of scope.
28155 @item end-stepping-range
28156 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28157 similar CLI command was accomplished.
28158 @item exited-signalled
28159 The inferior exited because of a signal.
28161 The inferior exited.
28162 @item exited-normally
28163 The inferior exited normally.
28164 @item signal-received
28165 A signal was received by the inferior.
28167 The inferior has stopped due to a library being loaded or unloaded.
28168 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28169 set or when a @code{catch load} or @code{catch unload} catchpoint is
28170 in use (@pxref{Set Catchpoints}).
28172 The inferior has forked. This is reported when @code{catch fork}
28173 (@pxref{Set Catchpoints}) has been used.
28175 The inferior has vforked. This is reported in when @code{catch vfork}
28176 (@pxref{Set Catchpoints}) has been used.
28177 @item syscall-entry
28178 The inferior entered a system call. This is reported when @code{catch
28179 syscall} (@pxref{Set Catchpoints}) has been used.
28180 @item syscall-return
28181 The inferior returned from a system call. This is reported when
28182 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28184 The inferior called @code{exec}. This is reported when @code{catch exec}
28185 (@pxref{Set Catchpoints}) has been used.
28188 The @var{id} field identifies the global thread ID of the thread
28189 that directly caused the stop -- for example by hitting a breakpoint.
28190 Depending on whether all-stop
28191 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28192 stop all threads, or only the thread that directly triggered the stop.
28193 If all threads are stopped, the @var{stopped} field will have the
28194 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28195 field will be a list of thread identifiers. Presently, this list will
28196 always include a single thread, but frontend should be prepared to see
28197 several threads in the list. The @var{core} field reports the
28198 processor core on which the stop event has happened. This field may be absent
28199 if such information is not available.
28201 @item =thread-group-added,id="@var{id}"
28202 @itemx =thread-group-removed,id="@var{id}"
28203 A thread group was either added or removed. The @var{id} field
28204 contains the @value{GDBN} identifier of the thread group. When a thread
28205 group is added, it generally might not be associated with a running
28206 process. When a thread group is removed, its id becomes invalid and
28207 cannot be used in any way.
28209 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28210 A thread group became associated with a running program,
28211 either because the program was just started or the thread group
28212 was attached to a program. The @var{id} field contains the
28213 @value{GDBN} identifier of the thread group. The @var{pid} field
28214 contains process identifier, specific to the operating system.
28216 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28217 A thread group is no longer associated with a running program,
28218 either because the program has exited, or because it was detached
28219 from. The @var{id} field contains the @value{GDBN} identifier of the
28220 thread group. The @var{code} field is the exit code of the inferior; it exists
28221 only when the inferior exited with some code.
28223 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28224 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28225 A thread either was created, or has exited. The @var{id} field
28226 contains the global @value{GDBN} identifier of the thread. The @var{gid}
28227 field identifies the thread group this thread belongs to.
28229 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
28230 Informs that the selected thread or frame were changed. This notification
28231 is not emitted as result of the @code{-thread-select} or
28232 @code{-stack-select-frame} commands, but is emitted whenever an MI command
28233 that is not documented to change the selected thread and frame actually
28234 changes them. In particular, invoking, directly or indirectly
28235 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
28236 will generate this notification. Changing the thread or frame from another
28237 user interface (see @ref{Interpreters}) will also generate this notification.
28239 The @var{frame} field is only present if the newly selected thread is
28240 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
28242 We suggest that in response to this notification, front ends
28243 highlight the selected thread and cause subsequent commands to apply to
28246 @item =library-loaded,...
28247 Reports that a new library file was loaded by the program. This
28248 notification has 5 fields---@var{id}, @var{target-name},
28249 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
28250 opaque identifier of the library. For remote debugging case,
28251 @var{target-name} and @var{host-name} fields give the name of the
28252 library file on the target, and on the host respectively. For native
28253 debugging, both those fields have the same value. The
28254 @var{symbols-loaded} field is emitted only for backward compatibility
28255 and should not be relied on to convey any useful information. The
28256 @var{thread-group} field, if present, specifies the id of the thread
28257 group in whose context the library was loaded. If the field is
28258 absent, it means the library was loaded in the context of all present
28259 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
28262 @item =library-unloaded,...
28263 Reports that a library was unloaded by the program. This notification
28264 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28265 the same meaning as for the @code{=library-loaded} notification.
28266 The @var{thread-group} field, if present, specifies the id of the
28267 thread group in whose context the library was unloaded. If the field is
28268 absent, it means the library was unloaded in the context of all present
28271 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28272 @itemx =traceframe-changed,end
28273 Reports that the trace frame was changed and its new number is
28274 @var{tfnum}. The number of the tracepoint associated with this trace
28275 frame is @var{tpnum}.
28277 @item =tsv-created,name=@var{name},initial=@var{initial}
28278 Reports that the new trace state variable @var{name} is created with
28279 initial value @var{initial}.
28281 @item =tsv-deleted,name=@var{name}
28282 @itemx =tsv-deleted
28283 Reports that the trace state variable @var{name} is deleted or all
28284 trace state variables are deleted.
28286 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28287 Reports that the trace state variable @var{name} is modified with
28288 the initial value @var{initial}. The current value @var{current} of
28289 trace state variable is optional and is reported if the current
28290 value of trace state variable is known.
28292 @item =breakpoint-created,bkpt=@{...@}
28293 @itemx =breakpoint-modified,bkpt=@{...@}
28294 @itemx =breakpoint-deleted,id=@var{number}
28295 Reports that a breakpoint was created, modified, or deleted,
28296 respectively. Only user-visible breakpoints are reported to the MI
28299 The @var{bkpt} argument is of the same form as returned by the various
28300 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28301 @var{number} is the ordinal number of the breakpoint.
28303 Note that if a breakpoint is emitted in the result record of a
28304 command, then it will not also be emitted in an async record.
28306 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
28307 @itemx =record-stopped,thread-group="@var{id}"
28308 Execution log recording was either started or stopped on an
28309 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28310 group corresponding to the affected inferior.
28312 The @var{method} field indicates the method used to record execution. If the
28313 method in use supports multiple recording formats, @var{format} will be present
28314 and contain the currently used format. @xref{Process Record and Replay},
28315 for existing method and format values.
28317 @item =cmd-param-changed,param=@var{param},value=@var{value}
28318 Reports that a parameter of the command @code{set @var{param}} is
28319 changed to @var{value}. In the multi-word @code{set} command,
28320 the @var{param} is the whole parameter list to @code{set} command.
28321 For example, In command @code{set check type on}, @var{param}
28322 is @code{check type} and @var{value} is @code{on}.
28324 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28325 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28326 written in an inferior. The @var{id} is the identifier of the
28327 thread group corresponding to the affected inferior. The optional
28328 @code{type="code"} part is reported if the memory written to holds
28332 @node GDB/MI Breakpoint Information
28333 @subsection @sc{gdb/mi} Breakpoint Information
28335 When @value{GDBN} reports information about a breakpoint, a
28336 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28341 The breakpoint number.
28344 The type of the breakpoint. For ordinary breakpoints this will be
28345 @samp{breakpoint}, but many values are possible.
28348 If the type of the breakpoint is @samp{catchpoint}, then this
28349 indicates the exact type of catchpoint.
28352 This is the breakpoint disposition---either @samp{del}, meaning that
28353 the breakpoint will be deleted at the next stop, or @samp{keep},
28354 meaning that the breakpoint will not be deleted.
28357 This indicates whether the breakpoint is enabled, in which case the
28358 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28359 Note that this is not the same as the field @code{enable}.
28362 The address of the breakpoint. This may be a hexidecimal number,
28363 giving the address; or the string @samp{<PENDING>}, for a pending
28364 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28365 multiple locations. This field will not be present if no address can
28366 be determined. For example, a watchpoint does not have an address.
28369 If known, the function in which the breakpoint appears.
28370 If not known, this field is not present.
28373 The name of the source file which contains this function, if known.
28374 If not known, this field is not present.
28377 The full file name of the source file which contains this function, if
28378 known. If not known, this field is not present.
28381 The line number at which this breakpoint appears, if known.
28382 If not known, this field is not present.
28385 If the source file is not known, this field may be provided. If
28386 provided, this holds the address of the breakpoint, possibly followed
28390 If this breakpoint is pending, this field is present and holds the
28391 text used to set the breakpoint, as entered by the user.
28394 Where this breakpoint's condition is evaluated, either @samp{host} or
28398 If this is a thread-specific breakpoint, then this identifies the
28399 thread in which the breakpoint can trigger.
28402 If this breakpoint is restricted to a particular Ada task, then this
28403 field will hold the task identifier.
28406 If the breakpoint is conditional, this is the condition expression.
28409 The ignore count of the breakpoint.
28412 The enable count of the breakpoint.
28414 @item traceframe-usage
28417 @item static-tracepoint-marker-string-id
28418 For a static tracepoint, the name of the static tracepoint marker.
28421 For a masked watchpoint, this is the mask.
28424 A tracepoint's pass count.
28426 @item original-location
28427 The location of the breakpoint as originally specified by the user.
28428 This field is optional.
28431 The number of times the breakpoint has been hit.
28434 This field is only given for tracepoints. This is either @samp{y},
28435 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28439 Some extra data, the exact contents of which are type-dependent.
28442 This field is present if the breakpoint has multiple locations. It is also
28443 exceptionally present if the breakpoint is enabled and has a single, disabled
28446 The value is a list of locations. The format of a location is decribed below.
28450 A location in a multi-location breakpoint is represented as a tuple with the
28456 The location number as a dotted pair, like @samp{1.2}. The first digit is the
28457 number of the parent breakpoint. The second digit is the number of the
28458 location within that breakpoint.
28461 This indicates whether the location is enabled, in which case the
28462 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28463 Note that this is not the same as the field @code{enable}.
28466 The address of this location as an hexidecimal number.
28469 If known, the function in which the location appears.
28470 If not known, this field is not present.
28473 The name of the source file which contains this location, if known.
28474 If not known, this field is not present.
28477 The full file name of the source file which contains this location, if
28478 known. If not known, this field is not present.
28481 The line number at which this location appears, if known.
28482 If not known, this field is not present.
28484 @item thread-groups
28485 The thread groups this location is in.
28489 For example, here is what the output of @code{-break-insert}
28490 (@pxref{GDB/MI Breakpoint Commands}) might be:
28493 -> -break-insert main
28494 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28495 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28496 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28501 @node GDB/MI Frame Information
28502 @subsection @sc{gdb/mi} Frame Information
28504 Response from many MI commands includes an information about stack
28505 frame. This information is a tuple that may have the following
28510 The level of the stack frame. The innermost frame has the level of
28511 zero. This field is always present.
28514 The name of the function corresponding to the frame. This field may
28515 be absent if @value{GDBN} is unable to determine the function name.
28518 The code address for the frame. This field is always present.
28521 The name of the source files that correspond to the frame's code
28522 address. This field may be absent.
28525 The source line corresponding to the frames' code address. This field
28529 The name of the binary file (either executable or shared library) the
28530 corresponds to the frame's code address. This field may be absent.
28534 @node GDB/MI Thread Information
28535 @subsection @sc{gdb/mi} Thread Information
28537 Whenever @value{GDBN} has to report an information about a thread, it
28538 uses a tuple with the following fields. The fields are always present unless
28543 The global numeric id assigned to the thread by @value{GDBN}.
28546 The target-specific string identifying the thread.
28549 Additional information about the thread provided by the target.
28550 It is supposed to be human-readable and not interpreted by the
28551 frontend. This field is optional.
28554 The name of the thread. If the user specified a name using the
28555 @code{thread name} command, then this name is given. Otherwise, if
28556 @value{GDBN} can extract the thread name from the target, then that
28557 name is given. If @value{GDBN} cannot find the thread name, then this
28561 The execution state of the thread, either @samp{stopped} or @samp{running},
28562 depending on whether the thread is presently running.
28565 The stack frame currently executing in the thread. This field is only present
28566 if the thread is stopped. Its format is documented in
28567 @ref{GDB/MI Frame Information}.
28570 The value of this field is an integer number of the processor core the
28571 thread was last seen on. This field is optional.
28574 @node GDB/MI Ada Exception Information
28575 @subsection @sc{gdb/mi} Ada Exception Information
28577 Whenever a @code{*stopped} record is emitted because the program
28578 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28579 @value{GDBN} provides the name of the exception that was raised via
28580 the @code{exception-name} field. Also, for exceptions that were raised
28581 with an exception message, @value{GDBN} provides that message via
28582 the @code{exception-message} field.
28584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28585 @node GDB/MI Simple Examples
28586 @section Simple Examples of @sc{gdb/mi} Interaction
28587 @cindex @sc{gdb/mi}, simple examples
28589 This subsection presents several simple examples of interaction using
28590 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28591 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28592 the output received from @sc{gdb/mi}.
28594 Note the line breaks shown in the examples are here only for
28595 readability, they don't appear in the real output.
28597 @subheading Setting a Breakpoint
28599 Setting a breakpoint generates synchronous output which contains detailed
28600 information of the breakpoint.
28603 -> -break-insert main
28604 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28605 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28606 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28611 @subheading Program Execution
28613 Program execution generates asynchronous records and MI gives the
28614 reason that execution stopped.
28620 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28621 frame=@{addr="0x08048564",func="main",
28622 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28623 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68",
28624 arch="i386:x86_64"@}
28629 <- *stopped,reason="exited-normally"
28633 @subheading Quitting @value{GDBN}
28635 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28643 Please note that @samp{^exit} is printed immediately, but it might
28644 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28645 performs necessary cleanups, including killing programs being debugged
28646 or disconnecting from debug hardware, so the frontend should wait till
28647 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28648 fails to exit in reasonable time.
28650 @subheading A Bad Command
28652 Here's what happens if you pass a non-existent command:
28656 <- ^error,msg="Undefined MI command: rubbish"
28661 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28662 @node GDB/MI Command Description Format
28663 @section @sc{gdb/mi} Command Description Format
28665 The remaining sections describe blocks of commands. Each block of
28666 commands is laid out in a fashion similar to this section.
28668 @subheading Motivation
28670 The motivation for this collection of commands.
28672 @subheading Introduction
28674 A brief introduction to this collection of commands as a whole.
28676 @subheading Commands
28678 For each command in the block, the following is described:
28680 @subsubheading Synopsis
28683 -command @var{args}@dots{}
28686 @subsubheading Result
28688 @subsubheading @value{GDBN} Command
28690 The corresponding @value{GDBN} CLI command(s), if any.
28692 @subsubheading Example
28694 Example(s) formatted for readability. Some of the described commands have
28695 not been implemented yet and these are labeled N.A.@: (not available).
28698 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28699 @node GDB/MI Breakpoint Commands
28700 @section @sc{gdb/mi} Breakpoint Commands
28702 @cindex breakpoint commands for @sc{gdb/mi}
28703 @cindex @sc{gdb/mi}, breakpoint commands
28704 This section documents @sc{gdb/mi} commands for manipulating
28707 @subheading The @code{-break-after} Command
28708 @findex -break-after
28710 @subsubheading Synopsis
28713 -break-after @var{number} @var{count}
28716 The breakpoint number @var{number} is not in effect until it has been
28717 hit @var{count} times. To see how this is reflected in the output of
28718 the @samp{-break-list} command, see the description of the
28719 @samp{-break-list} command below.
28721 @subsubheading @value{GDBN} Command
28723 The corresponding @value{GDBN} command is @samp{ignore}.
28725 @subsubheading Example
28730 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28731 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28732 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28740 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28741 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28742 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28743 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28744 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28745 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28746 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28747 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28748 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28749 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28754 @subheading The @code{-break-catch} Command
28755 @findex -break-catch
28758 @subheading The @code{-break-commands} Command
28759 @findex -break-commands
28761 @subsubheading Synopsis
28764 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28767 Specifies the CLI commands that should be executed when breakpoint
28768 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28769 are the commands. If no command is specified, any previously-set
28770 commands are cleared. @xref{Break Commands}. Typical use of this
28771 functionality is tracing a program, that is, printing of values of
28772 some variables whenever breakpoint is hit and then continuing.
28774 @subsubheading @value{GDBN} Command
28776 The corresponding @value{GDBN} command is @samp{commands}.
28778 @subsubheading Example
28783 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28784 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28785 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28788 -break-commands 1 "print v" "continue"
28793 @subheading The @code{-break-condition} Command
28794 @findex -break-condition
28796 @subsubheading Synopsis
28799 -break-condition @var{number} @var{expr}
28802 Breakpoint @var{number} will stop the program only if the condition in
28803 @var{expr} is true. The condition becomes part of the
28804 @samp{-break-list} output (see the description of the @samp{-break-list}
28807 @subsubheading @value{GDBN} Command
28809 The corresponding @value{GDBN} command is @samp{condition}.
28811 @subsubheading Example
28815 -break-condition 1 1
28819 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28820 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28821 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28822 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28823 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28824 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28825 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28826 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28827 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28828 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28832 @subheading The @code{-break-delete} Command
28833 @findex -break-delete
28835 @subsubheading Synopsis
28838 -break-delete ( @var{breakpoint} )+
28841 Delete the breakpoint(s) whose number(s) are specified in the argument
28842 list. This is obviously reflected in the breakpoint list.
28844 @subsubheading @value{GDBN} Command
28846 The corresponding @value{GDBN} command is @samp{delete}.
28848 @subsubheading Example
28856 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28857 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28858 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28859 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28860 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28861 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28862 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28867 @subheading The @code{-break-disable} Command
28868 @findex -break-disable
28870 @subsubheading Synopsis
28873 -break-disable ( @var{breakpoint} )+
28876 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28877 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28879 @subsubheading @value{GDBN} Command
28881 The corresponding @value{GDBN} command is @samp{disable}.
28883 @subsubheading Example
28891 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28892 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28893 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28894 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28895 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28896 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28897 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28898 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28899 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28900 line="5",thread-groups=["i1"],times="0"@}]@}
28904 @subheading The @code{-break-enable} Command
28905 @findex -break-enable
28907 @subsubheading Synopsis
28910 -break-enable ( @var{breakpoint} )+
28913 Enable (previously disabled) @var{breakpoint}(s).
28915 @subsubheading @value{GDBN} Command
28917 The corresponding @value{GDBN} command is @samp{enable}.
28919 @subsubheading Example
28927 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28928 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28929 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28930 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28931 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28932 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28933 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28934 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28935 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28936 line="5",thread-groups=["i1"],times="0"@}]@}
28940 @subheading The @code{-break-info} Command
28941 @findex -break-info
28943 @subsubheading Synopsis
28946 -break-info @var{breakpoint}
28950 Get information about a single breakpoint.
28952 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28953 Information}, for details on the format of each breakpoint in the
28956 @subsubheading @value{GDBN} Command
28958 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28960 @subsubheading Example
28963 @subheading The @code{-break-insert} Command
28964 @findex -break-insert
28965 @anchor{-break-insert}
28967 @subsubheading Synopsis
28970 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28971 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28972 [ -p @var{thread-id} ] [ @var{location} ]
28976 If specified, @var{location}, can be one of:
28979 @item linespec location
28980 A linespec location. @xref{Linespec Locations}.
28982 @item explicit location
28983 An explicit location. @sc{gdb/mi} explicit locations are
28984 analogous to the CLI's explicit locations using the option names
28985 listed below. @xref{Explicit Locations}.
28988 @item --source @var{filename}
28989 The source file name of the location. This option requires the use
28990 of either @samp{--function} or @samp{--line}.
28992 @item --function @var{function}
28993 The name of a function or method.
28995 @item --label @var{label}
28996 The name of a label.
28998 @item --line @var{lineoffset}
28999 An absolute or relative line offset from the start of the location.
29002 @item address location
29003 An address location, *@var{address}. @xref{Address Locations}.
29007 The possible optional parameters of this command are:
29011 Insert a temporary breakpoint.
29013 Insert a hardware breakpoint.
29015 If @var{location} cannot be parsed (for example if it
29016 refers to unknown files or functions), create a pending
29017 breakpoint. Without this flag, @value{GDBN} will report
29018 an error, and won't create a breakpoint, if @var{location}
29021 Create a disabled breakpoint.
29023 Create a tracepoint. @xref{Tracepoints}. When this parameter
29024 is used together with @samp{-h}, a fast tracepoint is created.
29025 @item -c @var{condition}
29026 Make the breakpoint conditional on @var{condition}.
29027 @item -i @var{ignore-count}
29028 Initialize the @var{ignore-count}.
29029 @item -p @var{thread-id}
29030 Restrict the breakpoint to the thread with the specified global
29034 @subsubheading Result
29036 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29037 resulting breakpoint.
29039 Note: this format is open to change.
29040 @c An out-of-band breakpoint instead of part of the result?
29042 @subsubheading @value{GDBN} Command
29044 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29045 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29047 @subsubheading Example
29052 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29053 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29056 -break-insert -t foo
29057 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29058 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29062 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29063 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29064 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29065 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29066 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29067 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29068 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29069 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29070 addr="0x0001072c", func="main",file="recursive2.c",
29071 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29073 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29074 addr="0x00010774",func="foo",file="recursive2.c",
29075 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29078 @c -break-insert -r foo.*
29079 @c ~int foo(int, int);
29080 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29081 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29086 @subheading The @code{-dprintf-insert} Command
29087 @findex -dprintf-insert
29089 @subsubheading Synopsis
29092 -dprintf-insert [ -t ] [ -f ] [ -d ]
29093 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29094 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29099 If supplied, @var{location} may be specified the same way as for
29100 the @code{-break-insert} command. @xref{-break-insert}.
29102 The possible optional parameters of this command are:
29106 Insert a temporary breakpoint.
29108 If @var{location} cannot be parsed (for example, if it
29109 refers to unknown files or functions), create a pending
29110 breakpoint. Without this flag, @value{GDBN} will report
29111 an error, and won't create a breakpoint, if @var{location}
29114 Create a disabled breakpoint.
29115 @item -c @var{condition}
29116 Make the breakpoint conditional on @var{condition}.
29117 @item -i @var{ignore-count}
29118 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29119 to @var{ignore-count}.
29120 @item -p @var{thread-id}
29121 Restrict the breakpoint to the thread with the specified global
29125 @subsubheading Result
29127 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29128 resulting breakpoint.
29130 @c An out-of-band breakpoint instead of part of the result?
29132 @subsubheading @value{GDBN} Command
29134 The corresponding @value{GDBN} command is @samp{dprintf}.
29136 @subsubheading Example
29140 4-dprintf-insert foo "At foo entry\n"
29141 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29142 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29143 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29144 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29145 original-location="foo"@}
29147 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29148 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29149 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29150 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29151 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29152 original-location="mi-dprintf.c:26"@}
29156 @subheading The @code{-break-list} Command
29157 @findex -break-list
29159 @subsubheading Synopsis
29165 Displays the list of inserted breakpoints, showing the following fields:
29169 number of the breakpoint
29171 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29173 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29176 is the breakpoint enabled or no: @samp{y} or @samp{n}
29178 memory location at which the breakpoint is set
29180 logical location of the breakpoint, expressed by function name, file
29182 @item Thread-groups
29183 list of thread groups to which this breakpoint applies
29185 number of times the breakpoint has been hit
29188 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29189 @code{body} field is an empty list.
29191 @subsubheading @value{GDBN} Command
29193 The corresponding @value{GDBN} command is @samp{info break}.
29195 @subsubheading Example
29200 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29201 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29202 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29203 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29204 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29205 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29206 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29207 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29208 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29210 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29211 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29212 line="13",thread-groups=["i1"],times="0"@}]@}
29216 Here's an example of the result when there are no breakpoints:
29221 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29222 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29223 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29224 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29225 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29226 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29227 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29232 @subheading The @code{-break-passcount} Command
29233 @findex -break-passcount
29235 @subsubheading Synopsis
29238 -break-passcount @var{tracepoint-number} @var{passcount}
29241 Set the passcount for tracepoint @var{tracepoint-number} to
29242 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29243 is not a tracepoint, error is emitted. This corresponds to CLI
29244 command @samp{passcount}.
29246 @subheading The @code{-break-watch} Command
29247 @findex -break-watch
29249 @subsubheading Synopsis
29252 -break-watch [ -a | -r ]
29255 Create a watchpoint. With the @samp{-a} option it will create an
29256 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
29257 read from or on a write to the memory location. With the @samp{-r}
29258 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
29259 trigger only when the memory location is accessed for reading. Without
29260 either of the options, the watchpoint created is a regular watchpoint,
29261 i.e., it will trigger when the memory location is accessed for writing.
29262 @xref{Set Watchpoints, , Setting Watchpoints}.
29264 Note that @samp{-break-list} will report a single list of watchpoints and
29265 breakpoints inserted.
29267 @subsubheading @value{GDBN} Command
29269 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
29272 @subsubheading Example
29274 Setting a watchpoint on a variable in the @code{main} function:
29279 ^done,wpt=@{number="2",exp="x"@}
29284 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29285 value=@{old="-268439212",new="55"@},
29286 frame=@{func="main",args=[],file="recursive2.c",
29287 fullname="/home/foo/bar/recursive2.c",line="5",arch="i386:x86_64"@}
29291 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29292 the program execution twice: first for the variable changing value, then
29293 for the watchpoint going out of scope.
29298 ^done,wpt=@{number="5",exp="C"@}
29303 *stopped,reason="watchpoint-trigger",
29304 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29305 frame=@{func="callee4",args=[],
29306 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29307 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29308 arch="i386:x86_64"@}
29313 *stopped,reason="watchpoint-scope",wpnum="5",
29314 frame=@{func="callee3",args=[@{name="strarg",
29315 value="0x11940 \"A string argument.\""@}],
29316 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29317 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29318 arch="i386:x86_64"@}
29322 Listing breakpoints and watchpoints, at different points in the program
29323 execution. Note that once the watchpoint goes out of scope, it is
29329 ^done,wpt=@{number="2",exp="C"@}
29332 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29333 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29334 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29335 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29336 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29337 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29338 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29339 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29340 addr="0x00010734",func="callee4",
29341 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29342 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29344 bkpt=@{number="2",type="watchpoint",disp="keep",
29345 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29350 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29351 value=@{old="-276895068",new="3"@},
29352 frame=@{func="callee4",args=[],
29353 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29354 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13",
29355 arch="i386:x86_64"@}
29358 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29359 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29360 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29361 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29362 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29363 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29364 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29365 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29366 addr="0x00010734",func="callee4",
29367 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29368 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29370 bkpt=@{number="2",type="watchpoint",disp="keep",
29371 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29375 ^done,reason="watchpoint-scope",wpnum="2",
29376 frame=@{func="callee3",args=[@{name="strarg",
29377 value="0x11940 \"A string argument.\""@}],
29378 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29379 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
29380 arch="i386:x86_64"@}
29383 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29384 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29385 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29386 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29387 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29388 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29389 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29390 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29391 addr="0x00010734",func="callee4",
29392 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29393 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29394 thread-groups=["i1"],times="1"@}]@}
29399 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29400 @node GDB/MI Catchpoint Commands
29401 @section @sc{gdb/mi} Catchpoint Commands
29403 This section documents @sc{gdb/mi} commands for manipulating
29407 * Shared Library GDB/MI Catchpoint Commands::
29408 * Ada Exception GDB/MI Catchpoint Commands::
29411 @node Shared Library GDB/MI Catchpoint Commands
29412 @subsection Shared Library @sc{gdb/mi} Catchpoints
29414 @subheading The @code{-catch-load} Command
29415 @findex -catch-load
29417 @subsubheading Synopsis
29420 -catch-load [ -t ] [ -d ] @var{regexp}
29423 Add a catchpoint for library load events. If the @samp{-t} option is used,
29424 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29425 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29426 in a disabled state. The @samp{regexp} argument is a regular
29427 expression used to match the name of the loaded library.
29430 @subsubheading @value{GDBN} Command
29432 The corresponding @value{GDBN} command is @samp{catch load}.
29434 @subsubheading Example
29437 -catch-load -t foo.so
29438 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29439 what="load of library matching foo.so",catch-type="load",times="0"@}
29444 @subheading The @code{-catch-unload} Command
29445 @findex -catch-unload
29447 @subsubheading Synopsis
29450 -catch-unload [ -t ] [ -d ] @var{regexp}
29453 Add a catchpoint for library unload events. If the @samp{-t} option is
29454 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29455 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29456 created in a disabled state. The @samp{regexp} argument is a regular
29457 expression used to match the name of the unloaded library.
29459 @subsubheading @value{GDBN} Command
29461 The corresponding @value{GDBN} command is @samp{catch unload}.
29463 @subsubheading Example
29466 -catch-unload -d bar.so
29467 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29468 what="load of library matching bar.so",catch-type="unload",times="0"@}
29472 @node Ada Exception GDB/MI Catchpoint Commands
29473 @subsection Ada Exception @sc{gdb/mi} Catchpoints
29475 The following @sc{gdb/mi} commands can be used to create catchpoints
29476 that stop the execution when Ada exceptions are being raised.
29478 @subheading The @code{-catch-assert} Command
29479 @findex -catch-assert
29481 @subsubheading Synopsis
29484 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
29487 Add a catchpoint for failed Ada assertions.
29489 The possible optional parameters for this command are:
29492 @item -c @var{condition}
29493 Make the catchpoint conditional on @var{condition}.
29495 Create a disabled catchpoint.
29497 Create a temporary catchpoint.
29500 @subsubheading @value{GDBN} Command
29502 The corresponding @value{GDBN} command is @samp{catch assert}.
29504 @subsubheading Example
29508 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
29509 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
29510 thread-groups=["i1"],times="0",
29511 original-location="__gnat_debug_raise_assert_failure"@}
29515 @subheading The @code{-catch-exception} Command
29516 @findex -catch-exception
29518 @subsubheading Synopsis
29521 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29525 Add a catchpoint stopping when Ada exceptions are raised.
29526 By default, the command stops the program when any Ada exception
29527 gets raised. But it is also possible, by using some of the
29528 optional parameters described below, to create more selective
29531 The possible optional parameters for this command are:
29534 @item -c @var{condition}
29535 Make the catchpoint conditional on @var{condition}.
29537 Create a disabled catchpoint.
29538 @item -e @var{exception-name}
29539 Only stop when @var{exception-name} is raised. This option cannot
29540 be used combined with @samp{-u}.
29542 Create a temporary catchpoint.
29544 Stop only when an unhandled exception gets raised. This option
29545 cannot be used combined with @samp{-e}.
29548 @subsubheading @value{GDBN} Command
29550 The corresponding @value{GDBN} commands are @samp{catch exception}
29551 and @samp{catch exception unhandled}.
29553 @subsubheading Example
29556 -catch-exception -e Program_Error
29557 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29558 enabled="y",addr="0x0000000000404874",
29559 what="`Program_Error' Ada exception", thread-groups=["i1"],
29560 times="0",original-location="__gnat_debug_raise_exception"@}
29564 @subheading The @code{-catch-handlers} Command
29565 @findex -catch-handlers
29567 @subsubheading Synopsis
29570 -catch-handlers [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
29574 Add a catchpoint stopping when Ada exceptions are handled.
29575 By default, the command stops the program when any Ada exception
29576 gets handled. But it is also possible, by using some of the
29577 optional parameters described below, to create more selective
29580 The possible optional parameters for this command are:
29583 @item -c @var{condition}
29584 Make the catchpoint conditional on @var{condition}.
29586 Create a disabled catchpoint.
29587 @item -e @var{exception-name}
29588 Only stop when @var{exception-name} is handled.
29590 Create a temporary catchpoint.
29593 @subsubheading @value{GDBN} Command
29595 The corresponding @value{GDBN} command is @samp{catch handlers}.
29597 @subsubheading Example
29600 -catch-handlers -e Constraint_Error
29601 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
29602 enabled="y",addr="0x0000000000402f68",
29603 what="`Constraint_Error' Ada exception handlers",thread-groups=["i1"],
29604 times="0",original-location="__gnat_begin_handler"@}
29608 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29609 @node GDB/MI Program Context
29610 @section @sc{gdb/mi} Program Context
29612 @subheading The @code{-exec-arguments} Command
29613 @findex -exec-arguments
29616 @subsubheading Synopsis
29619 -exec-arguments @var{args}
29622 Set the inferior program arguments, to be used in the next
29625 @subsubheading @value{GDBN} Command
29627 The corresponding @value{GDBN} command is @samp{set args}.
29629 @subsubheading Example
29633 -exec-arguments -v word
29640 @subheading The @code{-exec-show-arguments} Command
29641 @findex -exec-show-arguments
29643 @subsubheading Synopsis
29646 -exec-show-arguments
29649 Print the arguments of the program.
29651 @subsubheading @value{GDBN} Command
29653 The corresponding @value{GDBN} command is @samp{show args}.
29655 @subsubheading Example
29660 @subheading The @code{-environment-cd} Command
29661 @findex -environment-cd
29663 @subsubheading Synopsis
29666 -environment-cd @var{pathdir}
29669 Set @value{GDBN}'s working directory.
29671 @subsubheading @value{GDBN} Command
29673 The corresponding @value{GDBN} command is @samp{cd}.
29675 @subsubheading Example
29679 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29685 @subheading The @code{-environment-directory} Command
29686 @findex -environment-directory
29688 @subsubheading Synopsis
29691 -environment-directory [ -r ] [ @var{pathdir} ]+
29694 Add directories @var{pathdir} to beginning of search path for source files.
29695 If the @samp{-r} option is used, the search path is reset to the default
29696 search path. If directories @var{pathdir} are supplied in addition to the
29697 @samp{-r} option, the search path is first reset and then addition
29699 Multiple directories may be specified, separated by blanks. Specifying
29700 multiple directories in a single command
29701 results in the directories added to the beginning of the
29702 search path in the same order they were presented in the command.
29703 If blanks are needed as
29704 part of a directory name, double-quotes should be used around
29705 the name. In the command output, the path will show up separated
29706 by the system directory-separator character. The directory-separator
29707 character must not be used
29708 in any directory name.
29709 If no directories are specified, the current search path is displayed.
29711 @subsubheading @value{GDBN} Command
29713 The corresponding @value{GDBN} command is @samp{dir}.
29715 @subsubheading Example
29719 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29720 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29722 -environment-directory ""
29723 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29725 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29726 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29728 -environment-directory -r
29729 ^done,source-path="$cdir:$cwd"
29734 @subheading The @code{-environment-path} Command
29735 @findex -environment-path
29737 @subsubheading Synopsis
29740 -environment-path [ -r ] [ @var{pathdir} ]+
29743 Add directories @var{pathdir} to beginning of search path for object files.
29744 If the @samp{-r} option is used, the search path is reset to the original
29745 search path that existed at gdb start-up. If directories @var{pathdir} are
29746 supplied in addition to the
29747 @samp{-r} option, the search path is first reset and then addition
29749 Multiple directories may be specified, separated by blanks. Specifying
29750 multiple directories in a single command
29751 results in the directories added to the beginning of the
29752 search path in the same order they were presented in the command.
29753 If blanks are needed as
29754 part of a directory name, double-quotes should be used around
29755 the name. In the command output, the path will show up separated
29756 by the system directory-separator character. The directory-separator
29757 character must not be used
29758 in any directory name.
29759 If no directories are specified, the current path is displayed.
29762 @subsubheading @value{GDBN} Command
29764 The corresponding @value{GDBN} command is @samp{path}.
29766 @subsubheading Example
29771 ^done,path="/usr/bin"
29773 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29774 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29776 -environment-path -r /usr/local/bin
29777 ^done,path="/usr/local/bin:/usr/bin"
29782 @subheading The @code{-environment-pwd} Command
29783 @findex -environment-pwd
29785 @subsubheading Synopsis
29791 Show the current working directory.
29793 @subsubheading @value{GDBN} Command
29795 The corresponding @value{GDBN} command is @samp{pwd}.
29797 @subsubheading Example
29802 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29806 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29807 @node GDB/MI Thread Commands
29808 @section @sc{gdb/mi} Thread Commands
29811 @subheading The @code{-thread-info} Command
29812 @findex -thread-info
29814 @subsubheading Synopsis
29817 -thread-info [ @var{thread-id} ]
29820 Reports information about either a specific thread, if the
29821 @var{thread-id} parameter is present, or about all threads.
29822 @var{thread-id} is the thread's global thread ID. When printing
29823 information about all threads, also reports the global ID of the
29826 @subsubheading @value{GDBN} Command
29828 The @samp{info thread} command prints the same information
29831 @subsubheading Result
29833 The result contains the following attributes:
29837 A list of threads. The format of the elements of the list is described in
29838 @ref{GDB/MI Thread Information}.
29840 @item current-thread-id
29841 The global id of the currently selected thread. This field is omitted if there
29842 is no selected thread (for example, when the selected inferior is not running,
29843 and therefore has no threads) or if a @var{thread-id} argument was passed to
29848 @subsubheading Example
29853 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29854 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29855 args=[]@},state="running"@},
29856 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29857 frame=@{level="0",addr="0x0804891f",func="foo",
29858 args=[@{name="i",value="10"@}],
29859 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},
29860 state="running"@}],
29861 current-thread-id="1"
29865 @subheading The @code{-thread-list-ids} Command
29866 @findex -thread-list-ids
29868 @subsubheading Synopsis
29874 Produces a list of the currently known global @value{GDBN} thread ids.
29875 At the end of the list it also prints the total number of such
29878 This command is retained for historical reasons, the
29879 @code{-thread-info} command should be used instead.
29881 @subsubheading @value{GDBN} Command
29883 Part of @samp{info threads} supplies the same information.
29885 @subsubheading Example
29890 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29891 current-thread-id="1",number-of-threads="3"
29896 @subheading The @code{-thread-select} Command
29897 @findex -thread-select
29899 @subsubheading Synopsis
29902 -thread-select @var{thread-id}
29905 Make thread with global thread number @var{thread-id} the current
29906 thread. It prints the number of the new current thread, and the
29907 topmost frame for that thread.
29909 This command is deprecated in favor of explicitly using the
29910 @samp{--thread} option to each command.
29912 @subsubheading @value{GDBN} Command
29914 The corresponding @value{GDBN} command is @samp{thread}.
29916 @subsubheading Example
29923 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29924 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29928 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29929 number-of-threads="3"
29932 ^done,new-thread-id="3",
29933 frame=@{level="0",func="vprintf",
29934 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29935 @{name="arg",value="0x2"@}],file="vprintf.c",line="31",arch="i386:x86_64"@}
29939 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29940 @node GDB/MI Ada Tasking Commands
29941 @section @sc{gdb/mi} Ada Tasking Commands
29943 @subheading The @code{-ada-task-info} Command
29944 @findex -ada-task-info
29946 @subsubheading Synopsis
29949 -ada-task-info [ @var{task-id} ]
29952 Reports information about either a specific Ada task, if the
29953 @var{task-id} parameter is present, or about all Ada tasks.
29955 @subsubheading @value{GDBN} Command
29957 The @samp{info tasks} command prints the same information
29958 about all Ada tasks (@pxref{Ada Tasks}).
29960 @subsubheading Result
29962 The result is a table of Ada tasks. The following columns are
29963 defined for each Ada task:
29967 This field exists only for the current thread. It has the value @samp{*}.
29970 The identifier that @value{GDBN} uses to refer to the Ada task.
29973 The identifier that the target uses to refer to the Ada task.
29976 The global thread identifier of the thread corresponding to the Ada
29979 This field should always exist, as Ada tasks are always implemented
29980 on top of a thread. But if @value{GDBN} cannot find this corresponding
29981 thread for any reason, the field is omitted.
29984 This field exists only when the task was created by another task.
29985 In this case, it provides the ID of the parent task.
29988 The base priority of the task.
29991 The current state of the task. For a detailed description of the
29992 possible states, see @ref{Ada Tasks}.
29995 The name of the task.
29999 @subsubheading Example
30003 ^done,tasks=@{nr_rows="3",nr_cols="8",
30004 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30005 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30006 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30007 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30008 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30009 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30010 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30011 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30012 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30013 state="Child Termination Wait",name="main_task"@}]@}
30017 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30018 @node GDB/MI Program Execution
30019 @section @sc{gdb/mi} Program Execution
30021 These are the asynchronous commands which generate the out-of-band
30022 record @samp{*stopped}. Currently @value{GDBN} only really executes
30023 asynchronously with remote targets and this interaction is mimicked in
30026 @subheading The @code{-exec-continue} Command
30027 @findex -exec-continue
30029 @subsubheading Synopsis
30032 -exec-continue [--reverse] [--all|--thread-group N]
30035 Resumes the execution of the inferior program, which will continue
30036 to execute until it reaches a debugger stop event. If the
30037 @samp{--reverse} option is specified, execution resumes in reverse until
30038 it reaches a stop event. Stop events may include
30041 breakpoints or watchpoints
30043 signals or exceptions
30045 the end of the process (or its beginning under @samp{--reverse})
30047 the end or beginning of a replay log if one is being used.
30049 In all-stop mode (@pxref{All-Stop
30050 Mode}), may resume only one thread, or all threads, depending on the
30051 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30052 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30053 ignored in all-stop mode. If the @samp{--thread-group} options is
30054 specified, then all threads in that thread group are resumed.
30056 @subsubheading @value{GDBN} Command
30058 The corresponding @value{GDBN} corresponding is @samp{continue}.
30060 @subsubheading Example
30067 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30068 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30069 line="13",arch="i386:x86_64"@}
30074 @subheading The @code{-exec-finish} Command
30075 @findex -exec-finish
30077 @subsubheading Synopsis
30080 -exec-finish [--reverse]
30083 Resumes the execution of the inferior program until the current
30084 function is exited. Displays the results returned by the function.
30085 If the @samp{--reverse} option is specified, resumes the reverse
30086 execution of the inferior program until the point where current
30087 function was called.
30089 @subsubheading @value{GDBN} Command
30091 The corresponding @value{GDBN} command is @samp{finish}.
30093 @subsubheading Example
30095 Function returning @code{void}.
30102 *stopped,reason="function-finished",frame=@{func="main",args=[],
30103 file="hello.c",fullname="/home/foo/bar/hello.c",line="7",arch="i386:x86_64"@}
30107 Function returning other than @code{void}. The name of the internal
30108 @value{GDBN} variable storing the result is printed, together with the
30115 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30116 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30117 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30118 arch="i386:x86_64"@},
30119 gdb-result-var="$1",return-value="0"
30124 @subheading The @code{-exec-interrupt} Command
30125 @findex -exec-interrupt
30127 @subsubheading Synopsis
30130 -exec-interrupt [--all|--thread-group N]
30133 Interrupts the background execution of the target. Note how the token
30134 associated with the stop message is the one for the execution command
30135 that has been interrupted. The token for the interrupt itself only
30136 appears in the @samp{^done} output. If the user is trying to
30137 interrupt a non-running program, an error message will be printed.
30139 Note that when asynchronous execution is enabled, this command is
30140 asynchronous just like other execution commands. That is, first the
30141 @samp{^done} response will be printed, and the target stop will be
30142 reported after that using the @samp{*stopped} notification.
30144 In non-stop mode, only the context thread is interrupted by default.
30145 All threads (in all inferiors) will be interrupted if the
30146 @samp{--all} option is specified. If the @samp{--thread-group}
30147 option is specified, all threads in that group will be interrupted.
30149 @subsubheading @value{GDBN} Command
30151 The corresponding @value{GDBN} command is @samp{interrupt}.
30153 @subsubheading Example
30164 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30165 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30166 fullname="/home/foo/bar/try.c",line="13",arch="i386:x86_64"@}
30171 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30175 @subheading The @code{-exec-jump} Command
30178 @subsubheading Synopsis
30181 -exec-jump @var{location}
30184 Resumes execution of the inferior program at the location specified by
30185 parameter. @xref{Specify Location}, for a description of the
30186 different forms of @var{location}.
30188 @subsubheading @value{GDBN} Command
30190 The corresponding @value{GDBN} command is @samp{jump}.
30192 @subsubheading Example
30195 -exec-jump foo.c:10
30196 *running,thread-id="all"
30201 @subheading The @code{-exec-next} Command
30204 @subsubheading Synopsis
30207 -exec-next [--reverse]
30210 Resumes execution of the inferior program, stopping when the beginning
30211 of the next source line is reached.
30213 If the @samp{--reverse} option is specified, resumes reverse execution
30214 of the inferior program, stopping at the beginning of the previous
30215 source line. If you issue this command on the first line of a
30216 function, it will take you back to the caller of that function, to the
30217 source line where the function was called.
30220 @subsubheading @value{GDBN} Command
30222 The corresponding @value{GDBN} command is @samp{next}.
30224 @subsubheading Example
30230 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30235 @subheading The @code{-exec-next-instruction} Command
30236 @findex -exec-next-instruction
30238 @subsubheading Synopsis
30241 -exec-next-instruction [--reverse]
30244 Executes one machine instruction. If the instruction is a function
30245 call, continues until the function returns. If the program stops at an
30246 instruction in the middle of a source line, the address will be
30249 If the @samp{--reverse} option is specified, resumes reverse execution
30250 of the inferior program, stopping at the previous instruction. If the
30251 previously executed instruction was a return from another function,
30252 it will continue to execute in reverse until the call to that function
30253 (from the current stack frame) is reached.
30255 @subsubheading @value{GDBN} Command
30257 The corresponding @value{GDBN} command is @samp{nexti}.
30259 @subsubheading Example
30263 -exec-next-instruction
30267 *stopped,reason="end-stepping-range",
30268 addr="0x000100d4",line="5",file="hello.c"
30273 @subheading The @code{-exec-return} Command
30274 @findex -exec-return
30276 @subsubheading Synopsis
30282 Makes current function return immediately. Doesn't execute the inferior.
30283 Displays the new current frame.
30285 @subsubheading @value{GDBN} Command
30287 The corresponding @value{GDBN} command is @samp{return}.
30289 @subsubheading Example
30293 200-break-insert callee4
30294 200^done,bkpt=@{number="1",addr="0x00010734",
30295 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30300 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30301 frame=@{func="callee4",args=[],
30302 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30303 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30304 arch="i386:x86_64"@}
30310 111^done,frame=@{level="0",func="callee3",
30311 args=[@{name="strarg",
30312 value="0x11940 \"A string argument.\""@}],
30313 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30314 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18",
30315 arch="i386:x86_64"@}
30320 @subheading The @code{-exec-run} Command
30323 @subsubheading Synopsis
30326 -exec-run [ --all | --thread-group N ] [ --start ]
30329 Starts execution of the inferior from the beginning. The inferior
30330 executes until either a breakpoint is encountered or the program
30331 exits. In the latter case the output will include an exit code, if
30332 the program has exited exceptionally.
30334 When neither the @samp{--all} nor the @samp{--thread-group} option
30335 is specified, the current inferior is started. If the
30336 @samp{--thread-group} option is specified, it should refer to a thread
30337 group of type @samp{process}, and that thread group will be started.
30338 If the @samp{--all} option is specified, then all inferiors will be started.
30340 Using the @samp{--start} option instructs the debugger to stop
30341 the execution at the start of the inferior's main subprogram,
30342 following the same behavior as the @code{start} command
30343 (@pxref{Starting}).
30345 @subsubheading @value{GDBN} Command
30347 The corresponding @value{GDBN} command is @samp{run}.
30349 @subsubheading Examples
30354 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30359 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30360 frame=@{func="main",args=[],file="recursive2.c",
30361 fullname="/home/foo/bar/recursive2.c",line="4",arch="i386:x86_64"@}
30366 Program exited normally:
30374 *stopped,reason="exited-normally"
30379 Program exited exceptionally:
30387 *stopped,reason="exited",exit-code="01"
30391 Another way the program can terminate is if it receives a signal such as
30392 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
30396 *stopped,reason="exited-signalled",signal-name="SIGINT",
30397 signal-meaning="Interrupt"
30401 @c @subheading -exec-signal
30404 @subheading The @code{-exec-step} Command
30407 @subsubheading Synopsis
30410 -exec-step [--reverse]
30413 Resumes execution of the inferior program, stopping when the beginning
30414 of the next source line is reached, if the next source line is not a
30415 function call. If it is, stop at the first instruction of the called
30416 function. If the @samp{--reverse} option is specified, resumes reverse
30417 execution of the inferior program, stopping at the beginning of the
30418 previously executed source line.
30420 @subsubheading @value{GDBN} Command
30422 The corresponding @value{GDBN} command is @samp{step}.
30424 @subsubheading Example
30426 Stepping into a function:
30432 *stopped,reason="end-stepping-range",
30433 frame=@{func="foo",args=[@{name="a",value="10"@},
30434 @{name="b",value="0"@}],file="recursive2.c",
30435 fullname="/home/foo/bar/recursive2.c",line="11",arch="i386:x86_64"@}
30445 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30450 @subheading The @code{-exec-step-instruction} Command
30451 @findex -exec-step-instruction
30453 @subsubheading Synopsis
30456 -exec-step-instruction [--reverse]
30459 Resumes the inferior which executes one machine instruction. If the
30460 @samp{--reverse} option is specified, resumes reverse execution of the
30461 inferior program, stopping at the previously executed instruction.
30462 The output, once @value{GDBN} has stopped, will vary depending on
30463 whether we have stopped in the middle of a source line or not. In the
30464 former case, the address at which the program stopped will be printed
30467 @subsubheading @value{GDBN} Command
30469 The corresponding @value{GDBN} command is @samp{stepi}.
30471 @subsubheading Example
30475 -exec-step-instruction
30479 *stopped,reason="end-stepping-range",
30480 frame=@{func="foo",args=[],file="try.c",
30481 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30483 -exec-step-instruction
30487 *stopped,reason="end-stepping-range",
30488 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30489 fullname="/home/foo/bar/try.c",line="10",arch="i386:x86_64"@}
30494 @subheading The @code{-exec-until} Command
30495 @findex -exec-until
30497 @subsubheading Synopsis
30500 -exec-until [ @var{location} ]
30503 Executes the inferior until the @var{location} specified in the
30504 argument is reached. If there is no argument, the inferior executes
30505 until a source line greater than the current one is reached. The
30506 reason for stopping in this case will be @samp{location-reached}.
30508 @subsubheading @value{GDBN} Command
30510 The corresponding @value{GDBN} command is @samp{until}.
30512 @subsubheading Example
30516 -exec-until recursive2.c:6
30520 *stopped,reason="location-reached",frame=@{func="main",args=[],
30521 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6",
30522 arch="i386:x86_64"@}
30527 @subheading -file-clear
30528 Is this going away????
30531 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30532 @node GDB/MI Stack Manipulation
30533 @section @sc{gdb/mi} Stack Manipulation Commands
30535 @subheading The @code{-enable-frame-filters} Command
30536 @findex -enable-frame-filters
30539 -enable-frame-filters
30542 @value{GDBN} allows Python-based frame filters to affect the output of
30543 the MI commands relating to stack traces. As there is no way to
30544 implement this in a fully backward-compatible way, a front end must
30545 request that this functionality be enabled.
30547 Once enabled, this feature cannot be disabled.
30549 Note that if Python support has not been compiled into @value{GDBN},
30550 this command will still succeed (and do nothing).
30552 @subheading The @code{-stack-info-frame} Command
30553 @findex -stack-info-frame
30555 @subsubheading Synopsis
30561 Get info on the selected frame.
30563 @subsubheading @value{GDBN} Command
30565 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30566 (without arguments).
30568 @subsubheading Example
30573 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30574 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30575 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30576 arch="i386:x86_64"@}
30580 @subheading The @code{-stack-info-depth} Command
30581 @findex -stack-info-depth
30583 @subsubheading Synopsis
30586 -stack-info-depth [ @var{max-depth} ]
30589 Return the depth of the stack. If the integer argument @var{max-depth}
30590 is specified, do not count beyond @var{max-depth} frames.
30592 @subsubheading @value{GDBN} Command
30594 There's no equivalent @value{GDBN} command.
30596 @subsubheading Example
30598 For a stack with frame levels 0 through 11:
30605 -stack-info-depth 4
30608 -stack-info-depth 12
30611 -stack-info-depth 11
30614 -stack-info-depth 13
30619 @anchor{-stack-list-arguments}
30620 @subheading The @code{-stack-list-arguments} Command
30621 @findex -stack-list-arguments
30623 @subsubheading Synopsis
30626 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30627 [ @var{low-frame} @var{high-frame} ]
30630 Display a list of the arguments for the frames between @var{low-frame}
30631 and @var{high-frame} (inclusive). If @var{low-frame} and
30632 @var{high-frame} are not provided, list the arguments for the whole
30633 call stack. If the two arguments are equal, show the single frame
30634 at the corresponding level. It is an error if @var{low-frame} is
30635 larger than the actual number of frames. On the other hand,
30636 @var{high-frame} may be larger than the actual number of frames, in
30637 which case only existing frames will be returned.
30639 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30640 the variables; if it is 1 or @code{--all-values}, print also their
30641 values; and if it is 2 or @code{--simple-values}, print the name,
30642 type and value for simple data types, and the name and type for arrays,
30643 structures and unions. If the option @code{--no-frame-filters} is
30644 supplied, then Python frame filters will not be executed.
30646 If the @code{--skip-unavailable} option is specified, arguments that
30647 are not available are not listed. Partially available arguments
30648 are still displayed, however.
30650 Use of this command to obtain arguments in a single frame is
30651 deprecated in favor of the @samp{-stack-list-variables} command.
30653 @subsubheading @value{GDBN} Command
30655 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30656 @samp{gdb_get_args} command which partially overlaps with the
30657 functionality of @samp{-stack-list-arguments}.
30659 @subsubheading Example
30666 frame=@{level="0",addr="0x00010734",func="callee4",
30667 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30668 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30669 arch="i386:x86_64"@},
30670 frame=@{level="1",addr="0x0001076c",func="callee3",
30671 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30672 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17",
30673 arch="i386:x86_64"@},
30674 frame=@{level="2",addr="0x0001078c",func="callee2",
30675 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30676 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22",
30677 arch="i386:x86_64"@},
30678 frame=@{level="3",addr="0x000107b4",func="callee1",
30679 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30680 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27",
30681 arch="i386:x86_64"@},
30682 frame=@{level="4",addr="0x000107e0",func="main",
30683 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30684 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32",
30685 arch="i386:x86_64"@}]
30687 -stack-list-arguments 0
30690 frame=@{level="0",args=[]@},
30691 frame=@{level="1",args=[name="strarg"]@},
30692 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30693 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30694 frame=@{level="4",args=[]@}]
30696 -stack-list-arguments 1
30699 frame=@{level="0",args=[]@},
30701 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30702 frame=@{level="2",args=[
30703 @{name="intarg",value="2"@},
30704 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30705 @{frame=@{level="3",args=[
30706 @{name="intarg",value="2"@},
30707 @{name="strarg",value="0x11940 \"A string argument.\""@},
30708 @{name="fltarg",value="3.5"@}]@},
30709 frame=@{level="4",args=[]@}]
30711 -stack-list-arguments 0 2 2
30712 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30714 -stack-list-arguments 1 2 2
30715 ^done,stack-args=[frame=@{level="2",
30716 args=[@{name="intarg",value="2"@},
30717 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30721 @c @subheading -stack-list-exception-handlers
30724 @anchor{-stack-list-frames}
30725 @subheading The @code{-stack-list-frames} Command
30726 @findex -stack-list-frames
30728 @subsubheading Synopsis
30731 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
30734 List the frames currently on the stack. For each frame it displays the
30739 The frame number, 0 being the topmost frame, i.e., the innermost function.
30741 The @code{$pc} value for that frame.
30745 File name of the source file where the function lives.
30746 @item @var{fullname}
30747 The full file name of the source file where the function lives.
30749 Line number corresponding to the @code{$pc}.
30751 The shared library where this function is defined. This is only given
30752 if the frame's function is not known.
30754 Frame's architecture.
30757 If invoked without arguments, this command prints a backtrace for the
30758 whole stack. If given two integer arguments, it shows the frames whose
30759 levels are between the two arguments (inclusive). If the two arguments
30760 are equal, it shows the single frame at the corresponding level. It is
30761 an error if @var{low-frame} is larger than the actual number of
30762 frames. On the other hand, @var{high-frame} may be larger than the
30763 actual number of frames, in which case only existing frames will be
30764 returned. If the option @code{--no-frame-filters} is supplied, then
30765 Python frame filters will not be executed.
30767 @subsubheading @value{GDBN} Command
30769 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30771 @subsubheading Example
30773 Full stack backtrace:
30779 [frame=@{level="0",addr="0x0001076c",func="foo",
30780 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11",
30781 arch="i386:x86_64"@},
30782 frame=@{level="1",addr="0x000107a4",func="foo",
30783 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30784 arch="i386:x86_64"@},
30785 frame=@{level="2",addr="0x000107a4",func="foo",
30786 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30787 arch="i386:x86_64"@},
30788 frame=@{level="3",addr="0x000107a4",func="foo",
30789 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30790 arch="i386:x86_64"@},
30791 frame=@{level="4",addr="0x000107a4",func="foo",
30792 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30793 arch="i386:x86_64"@},
30794 frame=@{level="5",addr="0x000107a4",func="foo",
30795 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30796 arch="i386:x86_64"@},
30797 frame=@{level="6",addr="0x000107a4",func="foo",
30798 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30799 arch="i386:x86_64"@},
30800 frame=@{level="7",addr="0x000107a4",func="foo",
30801 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30802 arch="i386:x86_64"@},
30803 frame=@{level="8",addr="0x000107a4",func="foo",
30804 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30805 arch="i386:x86_64"@},
30806 frame=@{level="9",addr="0x000107a4",func="foo",
30807 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30808 arch="i386:x86_64"@},
30809 frame=@{level="10",addr="0x000107a4",func="foo",
30810 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30811 arch="i386:x86_64"@},
30812 frame=@{level="11",addr="0x00010738",func="main",
30813 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4",
30814 arch="i386:x86_64"@}]
30818 Show frames between @var{low_frame} and @var{high_frame}:
30822 -stack-list-frames 3 5
30824 [frame=@{level="3",addr="0x000107a4",func="foo",
30825 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30826 arch="i386:x86_64"@},
30827 frame=@{level="4",addr="0x000107a4",func="foo",
30828 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30829 arch="i386:x86_64"@},
30830 frame=@{level="5",addr="0x000107a4",func="foo",
30831 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30832 arch="i386:x86_64"@}]
30836 Show a single frame:
30840 -stack-list-frames 3 3
30842 [frame=@{level="3",addr="0x000107a4",func="foo",
30843 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14",
30844 arch="i386:x86_64"@}]
30849 @subheading The @code{-stack-list-locals} Command
30850 @findex -stack-list-locals
30851 @anchor{-stack-list-locals}
30853 @subsubheading Synopsis
30856 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30859 Display the local variable names for the selected frame. If
30860 @var{print-values} is 0 or @code{--no-values}, print only the names of
30861 the variables; if it is 1 or @code{--all-values}, print also their
30862 values; and if it is 2 or @code{--simple-values}, print the name,
30863 type and value for simple data types, and the name and type for arrays,
30864 structures and unions. In this last case, a frontend can immediately
30865 display the value of simple data types and create variable objects for
30866 other data types when the user wishes to explore their values in
30867 more detail. If the option @code{--no-frame-filters} is supplied, then
30868 Python frame filters will not be executed.
30870 If the @code{--skip-unavailable} option is specified, local variables
30871 that are not available are not listed. Partially available local
30872 variables are still displayed, however.
30874 This command is deprecated in favor of the
30875 @samp{-stack-list-variables} command.
30877 @subsubheading @value{GDBN} Command
30879 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30881 @subsubheading Example
30885 -stack-list-locals 0
30886 ^done,locals=[name="A",name="B",name="C"]
30888 -stack-list-locals --all-values
30889 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30890 @{name="C",value="@{1, 2, 3@}"@}]
30891 -stack-list-locals --simple-values
30892 ^done,locals=[@{name="A",type="int",value="1"@},
30893 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30897 @anchor{-stack-list-variables}
30898 @subheading The @code{-stack-list-variables} Command
30899 @findex -stack-list-variables
30901 @subsubheading Synopsis
30904 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
30907 Display the names of local variables and function arguments for the selected frame. If
30908 @var{print-values} is 0 or @code{--no-values}, print only the names of
30909 the variables; if it is 1 or @code{--all-values}, print also their
30910 values; and if it is 2 or @code{--simple-values}, print the name,
30911 type and value for simple data types, and the name and type for arrays,
30912 structures and unions. If the option @code{--no-frame-filters} is
30913 supplied, then Python frame filters will not be executed.
30915 If the @code{--skip-unavailable} option is specified, local variables
30916 and arguments that are not available are not listed. Partially
30917 available arguments and local variables are still displayed, however.
30919 @subsubheading Example
30923 -stack-list-variables --thread 1 --frame 0 --all-values
30924 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30929 @subheading The @code{-stack-select-frame} Command
30930 @findex -stack-select-frame
30932 @subsubheading Synopsis
30935 -stack-select-frame @var{framenum}
30938 Change the selected frame. Select a different frame @var{framenum} on
30941 This command in deprecated in favor of passing the @samp{--frame}
30942 option to every command.
30944 @subsubheading @value{GDBN} Command
30946 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30947 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30949 @subsubheading Example
30953 -stack-select-frame 2
30958 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30959 @node GDB/MI Variable Objects
30960 @section @sc{gdb/mi} Variable Objects
30964 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30966 For the implementation of a variable debugger window (locals, watched
30967 expressions, etc.), we are proposing the adaptation of the existing code
30968 used by @code{Insight}.
30970 The two main reasons for that are:
30974 It has been proven in practice (it is already on its second generation).
30977 It will shorten development time (needless to say how important it is
30981 The original interface was designed to be used by Tcl code, so it was
30982 slightly changed so it could be used through @sc{gdb/mi}. This section
30983 describes the @sc{gdb/mi} operations that will be available and gives some
30984 hints about their use.
30986 @emph{Note}: In addition to the set of operations described here, we
30987 expect the @sc{gui} implementation of a variable window to require, at
30988 least, the following operations:
30991 @item @code{-gdb-show} @code{output-radix}
30992 @item @code{-stack-list-arguments}
30993 @item @code{-stack-list-locals}
30994 @item @code{-stack-select-frame}
30999 @subheading Introduction to Variable Objects
31001 @cindex variable objects in @sc{gdb/mi}
31003 Variable objects are "object-oriented" MI interface for examining and
31004 changing values of expressions. Unlike some other MI interfaces that
31005 work with expressions, variable objects are specifically designed for
31006 simple and efficient presentation in the frontend. A variable object
31007 is identified by string name. When a variable object is created, the
31008 frontend specifies the expression for that variable object. The
31009 expression can be a simple variable, or it can be an arbitrary complex
31010 expression, and can even involve CPU registers. After creating a
31011 variable object, the frontend can invoke other variable object
31012 operations---for example to obtain or change the value of a variable
31013 object, or to change display format.
31015 Variable objects have hierarchical tree structure. Any variable object
31016 that corresponds to a composite type, such as structure in C, has
31017 a number of child variable objects, for example corresponding to each
31018 element of a structure. A child variable object can itself have
31019 children, recursively. Recursion ends when we reach
31020 leaf variable objects, which always have built-in types. Child variable
31021 objects are created only by explicit request, so if a frontend
31022 is not interested in the children of a particular variable object, no
31023 child will be created.
31025 For a leaf variable object it is possible to obtain its value as a
31026 string, or set the value from a string. String value can be also
31027 obtained for a non-leaf variable object, but it's generally a string
31028 that only indicates the type of the object, and does not list its
31029 contents. Assignment to a non-leaf variable object is not allowed.
31031 A frontend does not need to read the values of all variable objects each time
31032 the program stops. Instead, MI provides an update command that lists all
31033 variable objects whose values has changed since the last update
31034 operation. This considerably reduces the amount of data that must
31035 be transferred to the frontend. As noted above, children variable
31036 objects are created on demand, and only leaf variable objects have a
31037 real value. As result, gdb will read target memory only for leaf
31038 variables that frontend has created.
31040 The automatic update is not always desirable. For example, a frontend
31041 might want to keep a value of some expression for future reference,
31042 and never update it. For another example, fetching memory is
31043 relatively slow for embedded targets, so a frontend might want
31044 to disable automatic update for the variables that are either not
31045 visible on the screen, or ``closed''. This is possible using so
31046 called ``frozen variable objects''. Such variable objects are never
31047 implicitly updated.
31049 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31050 fixed variable object, the expression is parsed when the variable
31051 object is created, including associating identifiers to specific
31052 variables. The meaning of expression never changes. For a floating
31053 variable object the values of variables whose names appear in the
31054 expressions are re-evaluated every time in the context of the current
31055 frame. Consider this example:
31060 struct work_state state;
31067 If a fixed variable object for the @code{state} variable is created in
31068 this function, and we enter the recursive call, the variable
31069 object will report the value of @code{state} in the top-level
31070 @code{do_work} invocation. On the other hand, a floating variable
31071 object will report the value of @code{state} in the current frame.
31073 If an expression specified when creating a fixed variable object
31074 refers to a local variable, the variable object becomes bound to the
31075 thread and frame in which the variable object is created. When such
31076 variable object is updated, @value{GDBN} makes sure that the
31077 thread/frame combination the variable object is bound to still exists,
31078 and re-evaluates the variable object in context of that thread/frame.
31080 The following is the complete set of @sc{gdb/mi} operations defined to
31081 access this functionality:
31083 @multitable @columnfractions .4 .6
31084 @item @strong{Operation}
31085 @tab @strong{Description}
31087 @item @code{-enable-pretty-printing}
31088 @tab enable Python-based pretty-printing
31089 @item @code{-var-create}
31090 @tab create a variable object
31091 @item @code{-var-delete}
31092 @tab delete the variable object and/or its children
31093 @item @code{-var-set-format}
31094 @tab set the display format of this variable
31095 @item @code{-var-show-format}
31096 @tab show the display format of this variable
31097 @item @code{-var-info-num-children}
31098 @tab tells how many children this object has
31099 @item @code{-var-list-children}
31100 @tab return a list of the object's children
31101 @item @code{-var-info-type}
31102 @tab show the type of this variable object
31103 @item @code{-var-info-expression}
31104 @tab print parent-relative expression that this variable object represents
31105 @item @code{-var-info-path-expression}
31106 @tab print full expression that this variable object represents
31107 @item @code{-var-show-attributes}
31108 @tab is this variable editable? does it exist here?
31109 @item @code{-var-evaluate-expression}
31110 @tab get the value of this variable
31111 @item @code{-var-assign}
31112 @tab set the value of this variable
31113 @item @code{-var-update}
31114 @tab update the variable and its children
31115 @item @code{-var-set-frozen}
31116 @tab set frozeness attribute
31117 @item @code{-var-set-update-range}
31118 @tab set range of children to display on update
31121 In the next subsection we describe each operation in detail and suggest
31122 how it can be used.
31124 @subheading Description And Use of Operations on Variable Objects
31126 @subheading The @code{-enable-pretty-printing} Command
31127 @findex -enable-pretty-printing
31130 -enable-pretty-printing
31133 @value{GDBN} allows Python-based visualizers to affect the output of the
31134 MI variable object commands. However, because there was no way to
31135 implement this in a fully backward-compatible way, a front end must
31136 request that this functionality be enabled.
31138 Once enabled, this feature cannot be disabled.
31140 Note that if Python support has not been compiled into @value{GDBN},
31141 this command will still succeed (and do nothing).
31143 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31144 may work differently in future versions of @value{GDBN}.
31146 @subheading The @code{-var-create} Command
31147 @findex -var-create
31149 @subsubheading Synopsis
31152 -var-create @{@var{name} | "-"@}
31153 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31156 This operation creates a variable object, which allows the monitoring of
31157 a variable, the result of an expression, a memory cell or a CPU
31160 The @var{name} parameter is the string by which the object can be
31161 referenced. It must be unique. If @samp{-} is specified, the varobj
31162 system will generate a string ``varNNNNNN'' automatically. It will be
31163 unique provided that one does not specify @var{name} of that format.
31164 The command fails if a duplicate name is found.
31166 The frame under which the expression should be evaluated can be
31167 specified by @var{frame-addr}. A @samp{*} indicates that the current
31168 frame should be used. A @samp{@@} indicates that a floating variable
31169 object must be created.
31171 @var{expression} is any expression valid on the current language set (must not
31172 begin with a @samp{*}), or one of the following:
31176 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31179 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31182 @samp{$@var{regname}} --- a CPU register name
31185 @cindex dynamic varobj
31186 A varobj's contents may be provided by a Python-based pretty-printer. In this
31187 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31188 have slightly different semantics in some cases. If the
31189 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31190 will never create a dynamic varobj. This ensures backward
31191 compatibility for existing clients.
31193 @subsubheading Result
31195 This operation returns attributes of the newly-created varobj. These
31200 The name of the varobj.
31203 The number of children of the varobj. This number is not necessarily
31204 reliable for a dynamic varobj. Instead, you must examine the
31205 @samp{has_more} attribute.
31208 The varobj's scalar value. For a varobj whose type is some sort of
31209 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31210 will not be interesting.
31213 The varobj's type. This is a string representation of the type, as
31214 would be printed by the @value{GDBN} CLI. If @samp{print object}
31215 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31216 @emph{actual} (derived) type of the object is shown rather than the
31217 @emph{declared} one.
31220 If a variable object is bound to a specific thread, then this is the
31221 thread's global identifier.
31224 For a dynamic varobj, this indicates whether there appear to be any
31225 children available. For a non-dynamic varobj, this will be 0.
31228 This attribute will be present and have the value @samp{1} if the
31229 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31230 then this attribute will not be present.
31233 A dynamic varobj can supply a display hint to the front end. The
31234 value comes directly from the Python pretty-printer object's
31235 @code{display_hint} method. @xref{Pretty Printing API}.
31238 Typical output will look like this:
31241 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31242 has_more="@var{has_more}"
31246 @subheading The @code{-var-delete} Command
31247 @findex -var-delete
31249 @subsubheading Synopsis
31252 -var-delete [ -c ] @var{name}
31255 Deletes a previously created variable object and all of its children.
31256 With the @samp{-c} option, just deletes the children.
31258 Returns an error if the object @var{name} is not found.
31261 @subheading The @code{-var-set-format} Command
31262 @findex -var-set-format
31264 @subsubheading Synopsis
31267 -var-set-format @var{name} @var{format-spec}
31270 Sets the output format for the value of the object @var{name} to be
31273 @anchor{-var-set-format}
31274 The syntax for the @var{format-spec} is as follows:
31277 @var{format-spec} @expansion{}
31278 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
31281 The natural format is the default format choosen automatically
31282 based on the variable type (like decimal for an @code{int}, hex
31283 for pointers, etc.).
31285 The zero-hexadecimal format has a representation similar to hexadecimal
31286 but with padding zeroes to the left of the value. For example, a 32-bit
31287 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
31288 zero-hexadecimal format.
31290 For a variable with children, the format is set only on the
31291 variable itself, and the children are not affected.
31293 @subheading The @code{-var-show-format} Command
31294 @findex -var-show-format
31296 @subsubheading Synopsis
31299 -var-show-format @var{name}
31302 Returns the format used to display the value of the object @var{name}.
31305 @var{format} @expansion{}
31310 @subheading The @code{-var-info-num-children} Command
31311 @findex -var-info-num-children
31313 @subsubheading Synopsis
31316 -var-info-num-children @var{name}
31319 Returns the number of children of a variable object @var{name}:
31325 Note that this number is not completely reliable for a dynamic varobj.
31326 It will return the current number of children, but more children may
31330 @subheading The @code{-var-list-children} Command
31331 @findex -var-list-children
31333 @subsubheading Synopsis
31336 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31338 @anchor{-var-list-children}
31340 Return a list of the children of the specified variable object and
31341 create variable objects for them, if they do not already exist. With
31342 a single argument or if @var{print-values} has a value of 0 or
31343 @code{--no-values}, print only the names of the variables; if
31344 @var{print-values} is 1 or @code{--all-values}, also print their
31345 values; and if it is 2 or @code{--simple-values} print the name and
31346 value for simple data types and just the name for arrays, structures
31349 @var{from} and @var{to}, if specified, indicate the range of children
31350 to report. If @var{from} or @var{to} is less than zero, the range is
31351 reset and all children will be reported. Otherwise, children starting
31352 at @var{from} (zero-based) and up to and excluding @var{to} will be
31355 If a child range is requested, it will only affect the current call to
31356 @code{-var-list-children}, but not future calls to @code{-var-update}.
31357 For this, you must instead use @code{-var-set-update-range}. The
31358 intent of this approach is to enable a front end to implement any
31359 update approach it likes; for example, scrolling a view may cause the
31360 front end to request more children with @code{-var-list-children}, and
31361 then the front end could call @code{-var-set-update-range} with a
31362 different range to ensure that future updates are restricted to just
31365 For each child the following results are returned:
31370 Name of the variable object created for this child.
31373 The expression to be shown to the user by the front end to designate this child.
31374 For example this may be the name of a structure member.
31376 For a dynamic varobj, this value cannot be used to form an
31377 expression. There is no way to do this at all with a dynamic varobj.
31379 For C/C@t{++} structures there are several pseudo children returned to
31380 designate access qualifiers. For these pseudo children @var{exp} is
31381 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31382 type and value are not present.
31384 A dynamic varobj will not report the access qualifying
31385 pseudo-children, regardless of the language. This information is not
31386 available at all with a dynamic varobj.
31389 Number of children this child has. For a dynamic varobj, this will be
31393 The type of the child. If @samp{print object}
31394 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31395 @emph{actual} (derived) type of the object is shown rather than the
31396 @emph{declared} one.
31399 If values were requested, this is the value.
31402 If this variable object is associated with a thread, this is the
31403 thread's global thread id. Otherwise this result is not present.
31406 If the variable object is frozen, this variable will be present with a value of 1.
31409 A dynamic varobj can supply a display hint to the front end. The
31410 value comes directly from the Python pretty-printer object's
31411 @code{display_hint} method. @xref{Pretty Printing API}.
31414 This attribute will be present and have the value @samp{1} if the
31415 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31416 then this attribute will not be present.
31420 The result may have its own attributes:
31424 A dynamic varobj can supply a display hint to the front end. The
31425 value comes directly from the Python pretty-printer object's
31426 @code{display_hint} method. @xref{Pretty Printing API}.
31429 This is an integer attribute which is nonzero if there are children
31430 remaining after the end of the selected range.
31433 @subsubheading Example
31437 -var-list-children n
31438 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31439 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
31441 -var-list-children --all-values n
31442 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
31443 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
31447 @subheading The @code{-var-info-type} Command
31448 @findex -var-info-type
31450 @subsubheading Synopsis
31453 -var-info-type @var{name}
31456 Returns the type of the specified variable @var{name}. The type is
31457 returned as a string in the same format as it is output by the
31461 type=@var{typename}
31465 @subheading The @code{-var-info-expression} Command
31466 @findex -var-info-expression
31468 @subsubheading Synopsis
31471 -var-info-expression @var{name}
31474 Returns a string that is suitable for presenting this
31475 variable object in user interface. The string is generally
31476 not valid expression in the current language, and cannot be evaluated.
31478 For example, if @code{a} is an array, and variable object
31479 @code{A} was created for @code{a}, then we'll get this output:
31482 (gdb) -var-info-expression A.1
31483 ^done,lang="C",exp="1"
31487 Here, the value of @code{lang} is the language name, which can be
31488 found in @ref{Supported Languages}.
31490 Note that the output of the @code{-var-list-children} command also
31491 includes those expressions, so the @code{-var-info-expression} command
31494 @subheading The @code{-var-info-path-expression} Command
31495 @findex -var-info-path-expression
31497 @subsubheading Synopsis
31500 -var-info-path-expression @var{name}
31503 Returns an expression that can be evaluated in the current
31504 context and will yield the same value that a variable object has.
31505 Compare this with the @code{-var-info-expression} command, which
31506 result can be used only for UI presentation. Typical use of
31507 the @code{-var-info-path-expression} command is creating a
31508 watchpoint from a variable object.
31510 This command is currently not valid for children of a dynamic varobj,
31511 and will give an error when invoked on one.
31513 For example, suppose @code{C} is a C@t{++} class, derived from class
31514 @code{Base}, and that the @code{Base} class has a member called
31515 @code{m_size}. Assume a variable @code{c} is has the type of
31516 @code{C} and a variable object @code{C} was created for variable
31517 @code{c}. Then, we'll get this output:
31519 (gdb) -var-info-path-expression C.Base.public.m_size
31520 ^done,path_expr=((Base)c).m_size)
31523 @subheading The @code{-var-show-attributes} Command
31524 @findex -var-show-attributes
31526 @subsubheading Synopsis
31529 -var-show-attributes @var{name}
31532 List attributes of the specified variable object @var{name}:
31535 status=@var{attr} [ ( ,@var{attr} )* ]
31539 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31541 @subheading The @code{-var-evaluate-expression} Command
31542 @findex -var-evaluate-expression
31544 @subsubheading Synopsis
31547 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31550 Evaluates the expression that is represented by the specified variable
31551 object and returns its value as a string. The format of the string
31552 can be specified with the @samp{-f} option. The possible values of
31553 this option are the same as for @code{-var-set-format}
31554 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31555 the current display format will be used. The current display format
31556 can be changed using the @code{-var-set-format} command.
31562 Note that one must invoke @code{-var-list-children} for a variable
31563 before the value of a child variable can be evaluated.
31565 @subheading The @code{-var-assign} Command
31566 @findex -var-assign
31568 @subsubheading Synopsis
31571 -var-assign @var{name} @var{expression}
31574 Assigns the value of @var{expression} to the variable object specified
31575 by @var{name}. The object must be @samp{editable}. If the variable's
31576 value is altered by the assign, the variable will show up in any
31577 subsequent @code{-var-update} list.
31579 @subsubheading Example
31587 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31591 @subheading The @code{-var-update} Command
31592 @findex -var-update
31594 @subsubheading Synopsis
31597 -var-update [@var{print-values}] @{@var{name} | "*"@}
31600 Reevaluate the expressions corresponding to the variable object
31601 @var{name} and all its direct and indirect children, and return the
31602 list of variable objects whose values have changed; @var{name} must
31603 be a root variable object. Here, ``changed'' means that the result of
31604 @code{-var-evaluate-expression} before and after the
31605 @code{-var-update} is different. If @samp{*} is used as the variable
31606 object names, all existing variable objects are updated, except
31607 for frozen ones (@pxref{-var-set-frozen}). The option
31608 @var{print-values} determines whether both names and values, or just
31609 names are printed. The possible values of this option are the same
31610 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31611 recommended to use the @samp{--all-values} option, to reduce the
31612 number of MI commands needed on each program stop.
31614 With the @samp{*} parameter, if a variable object is bound to a
31615 currently running thread, it will not be updated, without any
31618 If @code{-var-set-update-range} was previously used on a varobj, then
31619 only the selected range of children will be reported.
31621 @code{-var-update} reports all the changed varobjs in a tuple named
31624 Each item in the change list is itself a tuple holding:
31628 The name of the varobj.
31631 If values were requested for this update, then this field will be
31632 present and will hold the value of the varobj.
31635 @anchor{-var-update}
31636 This field is a string which may take one of three values:
31640 The variable object's current value is valid.
31643 The variable object does not currently hold a valid value but it may
31644 hold one in the future if its associated expression comes back into
31648 The variable object no longer holds a valid value.
31649 This can occur when the executable file being debugged has changed,
31650 either through recompilation or by using the @value{GDBN} @code{file}
31651 command. The front end should normally choose to delete these variable
31655 In the future new values may be added to this list so the front should
31656 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31659 This is only present if the varobj is still valid. If the type
31660 changed, then this will be the string @samp{true}; otherwise it will
31663 When a varobj's type changes, its children are also likely to have
31664 become incorrect. Therefore, the varobj's children are automatically
31665 deleted when this attribute is @samp{true}. Also, the varobj's update
31666 range, when set using the @code{-var-set-update-range} command, is
31670 If the varobj's type changed, then this field will be present and will
31673 @item new_num_children
31674 For a dynamic varobj, if the number of children changed, or if the
31675 type changed, this will be the new number of children.
31677 The @samp{numchild} field in other varobj responses is generally not
31678 valid for a dynamic varobj -- it will show the number of children that
31679 @value{GDBN} knows about, but because dynamic varobjs lazily
31680 instantiate their children, this will not reflect the number of
31681 children which may be available.
31683 The @samp{new_num_children} attribute only reports changes to the
31684 number of children known by @value{GDBN}. This is the only way to
31685 detect whether an update has removed children (which necessarily can
31686 only happen at the end of the update range).
31689 The display hint, if any.
31692 This is an integer value, which will be 1 if there are more children
31693 available outside the varobj's update range.
31696 This attribute will be present and have the value @samp{1} if the
31697 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31698 then this attribute will not be present.
31701 If new children were added to a dynamic varobj within the selected
31702 update range (as set by @code{-var-set-update-range}), then they will
31703 be listed in this attribute.
31706 @subsubheading Example
31713 -var-update --all-values var1
31714 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31715 type_changed="false"@}]
31719 @subheading The @code{-var-set-frozen} Command
31720 @findex -var-set-frozen
31721 @anchor{-var-set-frozen}
31723 @subsubheading Synopsis
31726 -var-set-frozen @var{name} @var{flag}
31729 Set the frozenness flag on the variable object @var{name}. The
31730 @var{flag} parameter should be either @samp{1} to make the variable
31731 frozen or @samp{0} to make it unfrozen. If a variable object is
31732 frozen, then neither itself, nor any of its children, are
31733 implicitly updated by @code{-var-update} of
31734 a parent variable or by @code{-var-update *}. Only
31735 @code{-var-update} of the variable itself will update its value and
31736 values of its children. After a variable object is unfrozen, it is
31737 implicitly updated by all subsequent @code{-var-update} operations.
31738 Unfreezing a variable does not update it, only subsequent
31739 @code{-var-update} does.
31741 @subsubheading Example
31745 -var-set-frozen V 1
31750 @subheading The @code{-var-set-update-range} command
31751 @findex -var-set-update-range
31752 @anchor{-var-set-update-range}
31754 @subsubheading Synopsis
31757 -var-set-update-range @var{name} @var{from} @var{to}
31760 Set the range of children to be returned by future invocations of
31761 @code{-var-update}.
31763 @var{from} and @var{to} indicate the range of children to report. If
31764 @var{from} or @var{to} is less than zero, the range is reset and all
31765 children will be reported. Otherwise, children starting at @var{from}
31766 (zero-based) and up to and excluding @var{to} will be reported.
31768 @subsubheading Example
31772 -var-set-update-range V 1 2
31776 @subheading The @code{-var-set-visualizer} command
31777 @findex -var-set-visualizer
31778 @anchor{-var-set-visualizer}
31780 @subsubheading Synopsis
31783 -var-set-visualizer @var{name} @var{visualizer}
31786 Set a visualizer for the variable object @var{name}.
31788 @var{visualizer} is the visualizer to use. The special value
31789 @samp{None} means to disable any visualizer in use.
31791 If not @samp{None}, @var{visualizer} must be a Python expression.
31792 This expression must evaluate to a callable object which accepts a
31793 single argument. @value{GDBN} will call this object with the value of
31794 the varobj @var{name} as an argument (this is done so that the same
31795 Python pretty-printing code can be used for both the CLI and MI).
31796 When called, this object must return an object which conforms to the
31797 pretty-printing interface (@pxref{Pretty Printing API}).
31799 The pre-defined function @code{gdb.default_visualizer} may be used to
31800 select a visualizer by following the built-in process
31801 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31802 a varobj is created, and so ordinarily is not needed.
31804 This feature is only available if Python support is enabled. The MI
31805 command @code{-list-features} (@pxref{GDB/MI Support Commands})
31806 can be used to check this.
31808 @subsubheading Example
31810 Resetting the visualizer:
31814 -var-set-visualizer V None
31818 Reselecting the default (type-based) visualizer:
31822 -var-set-visualizer V gdb.default_visualizer
31826 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31827 can be used to instantiate this class for a varobj:
31831 -var-set-visualizer V "lambda val: SomeClass()"
31835 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31836 @node GDB/MI Data Manipulation
31837 @section @sc{gdb/mi} Data Manipulation
31839 @cindex data manipulation, in @sc{gdb/mi}
31840 @cindex @sc{gdb/mi}, data manipulation
31841 This section describes the @sc{gdb/mi} commands that manipulate data:
31842 examine memory and registers, evaluate expressions, etc.
31844 For details about what an addressable memory unit is,
31845 @pxref{addressable memory unit}.
31847 @c REMOVED FROM THE INTERFACE.
31848 @c @subheading -data-assign
31849 @c Change the value of a program variable. Plenty of side effects.
31850 @c @subsubheading GDB Command
31852 @c @subsubheading Example
31855 @subheading The @code{-data-disassemble} Command
31856 @findex -data-disassemble
31858 @subsubheading Synopsis
31862 [ -s @var{start-addr} -e @var{end-addr} ]
31863 | [ -a @var{addr} ]
31864 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31872 @item @var{start-addr}
31873 is the beginning address (or @code{$pc})
31874 @item @var{end-addr}
31877 is an address anywhere within (or the name of) the function to
31878 disassemble. If an address is specified, the whole function
31879 surrounding that address will be disassembled. If a name is
31880 specified, the whole function with that name will be disassembled.
31881 @item @var{filename}
31882 is the name of the file to disassemble
31883 @item @var{linenum}
31884 is the line number to disassemble around
31886 is the number of disassembly lines to be produced. If it is -1,
31887 the whole function will be disassembled, in case no @var{end-addr} is
31888 specified. If @var{end-addr} is specified as a non-zero value, and
31889 @var{lines} is lower than the number of disassembly lines between
31890 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31891 displayed; if @var{lines} is higher than the number of lines between
31892 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31897 @item 0 disassembly only
31898 @item 1 mixed source and disassembly (deprecated)
31899 @item 2 disassembly with raw opcodes
31900 @item 3 mixed source and disassembly with raw opcodes (deprecated)
31901 @item 4 mixed source and disassembly
31902 @item 5 mixed source and disassembly with raw opcodes
31905 Modes 1 and 3 are deprecated. The output is ``source centric''
31906 which hasn't proved useful in practice.
31907 @xref{Machine Code}, for a discussion of the difference between
31908 @code{/m} and @code{/s} output of the @code{disassemble} command.
31911 @subsubheading Result
31913 The result of the @code{-data-disassemble} command will be a list named
31914 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31915 used with the @code{-data-disassemble} command.
31917 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31922 The address at which this instruction was disassembled.
31925 The name of the function this instruction is within.
31928 The decimal offset in bytes from the start of @samp{func-name}.
31931 The text disassembly for this @samp{address}.
31934 This field is only present for modes 2, 3 and 5. This contains the raw opcode
31935 bytes for the @samp{inst} field.
31939 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
31940 @samp{src_and_asm_line}, each of which has the following fields:
31944 The line number within @samp{file}.
31947 The file name from the compilation unit. This might be an absolute
31948 file name or a relative file name depending on the compile command
31952 Absolute file name of @samp{file}. It is converted to a canonical form
31953 using the source file search path
31954 (@pxref{Source Path, ,Specifying Source Directories})
31955 and after resolving all the symbolic links.
31957 If the source file is not found this field will contain the path as
31958 present in the debug information.
31960 @item line_asm_insn
31961 This is a list of tuples containing the disassembly for @samp{line} in
31962 @samp{file}. The fields of each tuple are the same as for
31963 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31964 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31969 Note that whatever included in the @samp{inst} field, is not
31970 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31973 @subsubheading @value{GDBN} Command
31975 The corresponding @value{GDBN} command is @samp{disassemble}.
31977 @subsubheading Example
31979 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31983 -data-disassemble -s $pc -e "$pc + 20" -- 0
31986 @{address="0x000107c0",func-name="main",offset="4",
31987 inst="mov 2, %o0"@},
31988 @{address="0x000107c4",func-name="main",offset="8",
31989 inst="sethi %hi(0x11800), %o2"@},
31990 @{address="0x000107c8",func-name="main",offset="12",
31991 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31992 @{address="0x000107cc",func-name="main",offset="16",
31993 inst="sethi %hi(0x11800), %o2"@},
31994 @{address="0x000107d0",func-name="main",offset="20",
31995 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31999 Disassemble the whole @code{main} function. Line 32 is part of
32003 -data-disassemble -f basics.c -l 32 -- 0
32005 @{address="0x000107bc",func-name="main",offset="0",
32006 inst="save %sp, -112, %sp"@},
32007 @{address="0x000107c0",func-name="main",offset="4",
32008 inst="mov 2, %o0"@},
32009 @{address="0x000107c4",func-name="main",offset="8",
32010 inst="sethi %hi(0x11800), %o2"@},
32012 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32013 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32017 Disassemble 3 instructions from the start of @code{main}:
32021 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32023 @{address="0x000107bc",func-name="main",offset="0",
32024 inst="save %sp, -112, %sp"@},
32025 @{address="0x000107c0",func-name="main",offset="4",
32026 inst="mov 2, %o0"@},
32027 @{address="0x000107c4",func-name="main",offset="8",
32028 inst="sethi %hi(0x11800), %o2"@}]
32032 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32036 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32038 src_and_asm_line=@{line="31",
32039 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32040 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32041 line_asm_insn=[@{address="0x000107bc",
32042 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32043 src_and_asm_line=@{line="32",
32044 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32045 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32046 line_asm_insn=[@{address="0x000107c0",
32047 func-name="main",offset="4",inst="mov 2, %o0"@},
32048 @{address="0x000107c4",func-name="main",offset="8",
32049 inst="sethi %hi(0x11800), %o2"@}]@}]
32054 @subheading The @code{-data-evaluate-expression} Command
32055 @findex -data-evaluate-expression
32057 @subsubheading Synopsis
32060 -data-evaluate-expression @var{expr}
32063 Evaluate @var{expr} as an expression. The expression could contain an
32064 inferior function call. The function call will execute synchronously.
32065 If the expression contains spaces, it must be enclosed in double quotes.
32067 @subsubheading @value{GDBN} Command
32069 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32070 @samp{call}. In @code{gdbtk} only, there's a corresponding
32071 @samp{gdb_eval} command.
32073 @subsubheading Example
32075 In the following example, the numbers that precede the commands are the
32076 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32077 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32081 211-data-evaluate-expression A
32084 311-data-evaluate-expression &A
32085 311^done,value="0xefffeb7c"
32087 411-data-evaluate-expression A+3
32090 511-data-evaluate-expression "A + 3"
32096 @subheading The @code{-data-list-changed-registers} Command
32097 @findex -data-list-changed-registers
32099 @subsubheading Synopsis
32102 -data-list-changed-registers
32105 Display a list of the registers that have changed.
32107 @subsubheading @value{GDBN} Command
32109 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32110 has the corresponding command @samp{gdb_changed_register_list}.
32112 @subsubheading Example
32114 On a PPC MBX board:
32122 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32123 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32124 line="5",arch="powerpc"@}
32126 -data-list-changed-registers
32127 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32128 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32129 "24","25","26","27","28","30","31","64","65","66","67","69"]
32134 @subheading The @code{-data-list-register-names} Command
32135 @findex -data-list-register-names
32137 @subsubheading Synopsis
32140 -data-list-register-names [ ( @var{regno} )+ ]
32143 Show a list of register names for the current target. If no arguments
32144 are given, it shows a list of the names of all the registers. If
32145 integer numbers are given as arguments, it will print a list of the
32146 names of the registers corresponding to the arguments. To ensure
32147 consistency between a register name and its number, the output list may
32148 include empty register names.
32150 @subsubheading @value{GDBN} Command
32152 @value{GDBN} does not have a command which corresponds to
32153 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32154 corresponding command @samp{gdb_regnames}.
32156 @subsubheading Example
32158 For the PPC MBX board:
32161 -data-list-register-names
32162 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32163 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32164 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32165 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32166 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32167 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32168 "", "pc","ps","cr","lr","ctr","xer"]
32170 -data-list-register-names 1 2 3
32171 ^done,register-names=["r1","r2","r3"]
32175 @subheading The @code{-data-list-register-values} Command
32176 @findex -data-list-register-values
32178 @subsubheading Synopsis
32181 -data-list-register-values
32182 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32185 Display the registers' contents. The format according to which the
32186 registers' contents are to be returned is given by @var{fmt}, followed
32187 by an optional list of numbers specifying the registers to display. A
32188 missing list of numbers indicates that the contents of all the
32189 registers must be returned. The @code{--skip-unavailable} option
32190 indicates that only the available registers are to be returned.
32192 Allowed formats for @var{fmt} are:
32209 @subsubheading @value{GDBN} Command
32211 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32212 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32214 @subsubheading Example
32216 For a PPC MBX board (note: line breaks are for readability only, they
32217 don't appear in the actual output):
32221 -data-list-register-values r 64 65
32222 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32223 @{number="65",value="0x00029002"@}]
32225 -data-list-register-values x
32226 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32227 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32228 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32229 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32230 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32231 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32232 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32233 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32234 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32235 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32236 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32237 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32238 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32239 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32240 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32241 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32242 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32243 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32244 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32245 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32246 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32247 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32248 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32249 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32250 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32251 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32252 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32253 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32254 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32255 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32256 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32257 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32258 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32259 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32260 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32261 @{number="69",value="0x20002b03"@}]
32266 @subheading The @code{-data-read-memory} Command
32267 @findex -data-read-memory
32269 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32271 @subsubheading Synopsis
32274 -data-read-memory [ -o @var{byte-offset} ]
32275 @var{address} @var{word-format} @var{word-size}
32276 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32283 @item @var{address}
32284 An expression specifying the address of the first memory word to be
32285 read. Complex expressions containing embedded white space should be
32286 quoted using the C convention.
32288 @item @var{word-format}
32289 The format to be used to print the memory words. The notation is the
32290 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32293 @item @var{word-size}
32294 The size of each memory word in bytes.
32296 @item @var{nr-rows}
32297 The number of rows in the output table.
32299 @item @var{nr-cols}
32300 The number of columns in the output table.
32303 If present, indicates that each row should include an @sc{ascii} dump. The
32304 value of @var{aschar} is used as a padding character when a byte is not a
32305 member of the printable @sc{ascii} character set (printable @sc{ascii}
32306 characters are those whose code is between 32 and 126, inclusively).
32308 @item @var{byte-offset}
32309 An offset to add to the @var{address} before fetching memory.
32312 This command displays memory contents as a table of @var{nr-rows} by
32313 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32314 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32315 (returned as @samp{total-bytes}). Should less than the requested number
32316 of bytes be returned by the target, the missing words are identified
32317 using @samp{N/A}. The number of bytes read from the target is returned
32318 in @samp{nr-bytes} and the starting address used to read memory in
32321 The address of the next/previous row or page is available in
32322 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32325 @subsubheading @value{GDBN} Command
32327 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32328 @samp{gdb_get_mem} memory read command.
32330 @subsubheading Example
32332 Read six bytes of memory starting at @code{bytes+6} but then offset by
32333 @code{-6} bytes. Format as three rows of two columns. One byte per
32334 word. Display each word in hex.
32338 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32339 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32340 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32341 prev-page="0x0000138a",memory=[
32342 @{addr="0x00001390",data=["0x00","0x01"]@},
32343 @{addr="0x00001392",data=["0x02","0x03"]@},
32344 @{addr="0x00001394",data=["0x04","0x05"]@}]
32348 Read two bytes of memory starting at address @code{shorts + 64} and
32349 display as a single word formatted in decimal.
32353 5-data-read-memory shorts+64 d 2 1 1
32354 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32355 next-row="0x00001512",prev-row="0x0000150e",
32356 next-page="0x00001512",prev-page="0x0000150e",memory=[
32357 @{addr="0x00001510",data=["128"]@}]
32361 Read thirty two bytes of memory starting at @code{bytes+16} and format
32362 as eight rows of four columns. Include a string encoding with @samp{x}
32363 used as the non-printable character.
32367 4-data-read-memory bytes+16 x 1 8 4 x
32368 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32369 next-row="0x000013c0",prev-row="0x0000139c",
32370 next-page="0x000013c0",prev-page="0x00001380",memory=[
32371 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32372 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32373 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32374 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32375 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32376 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32377 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32378 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32382 @subheading The @code{-data-read-memory-bytes} Command
32383 @findex -data-read-memory-bytes
32385 @subsubheading Synopsis
32388 -data-read-memory-bytes [ -o @var{offset} ]
32389 @var{address} @var{count}
32396 @item @var{address}
32397 An expression specifying the address of the first addressable memory unit
32398 to be read. Complex expressions containing embedded white space should be
32399 quoted using the C convention.
32402 The number of addressable memory units to read. This should be an integer
32406 The offset relative to @var{address} at which to start reading. This
32407 should be an integer literal. This option is provided so that a frontend
32408 is not required to first evaluate address and then perform address
32409 arithmetics itself.
32413 This command attempts to read all accessible memory regions in the
32414 specified range. First, all regions marked as unreadable in the memory
32415 map (if one is defined) will be skipped. @xref{Memory Region
32416 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32417 regions. For each one, if reading full region results in an errors,
32418 @value{GDBN} will try to read a subset of the region.
32420 In general, every single memory unit in the region may be readable or not,
32421 and the only way to read every readable unit is to try a read at
32422 every address, which is not practical. Therefore, @value{GDBN} will
32423 attempt to read all accessible memory units at either beginning or the end
32424 of the region, using a binary division scheme. This heuristic works
32425 well for reading accross a memory map boundary. Note that if a region
32426 has a readable range that is neither at the beginning or the end,
32427 @value{GDBN} will not read it.
32429 The result record (@pxref{GDB/MI Result Records}) that is output of
32430 the command includes a field named @samp{memory} whose content is a
32431 list of tuples. Each tuple represent a successfully read memory block
32432 and has the following fields:
32436 The start address of the memory block, as hexadecimal literal.
32439 The end address of the memory block, as hexadecimal literal.
32442 The offset of the memory block, as hexadecimal literal, relative to
32443 the start address passed to @code{-data-read-memory-bytes}.
32446 The contents of the memory block, in hex.
32452 @subsubheading @value{GDBN} Command
32454 The corresponding @value{GDBN} command is @samp{x}.
32456 @subsubheading Example
32460 -data-read-memory-bytes &a 10
32461 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
32463 contents="01000000020000000300"@}]
32468 @subheading The @code{-data-write-memory-bytes} Command
32469 @findex -data-write-memory-bytes
32471 @subsubheading Synopsis
32474 -data-write-memory-bytes @var{address} @var{contents}
32475 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
32482 @item @var{address}
32483 An expression specifying the address of the first addressable memory unit
32484 to be written. Complex expressions containing embedded white space should
32485 be quoted using the C convention.
32487 @item @var{contents}
32488 The hex-encoded data to write. It is an error if @var{contents} does
32489 not represent an integral number of addressable memory units.
32492 Optional argument indicating the number of addressable memory units to be
32493 written. If @var{count} is greater than @var{contents}' length,
32494 @value{GDBN} will repeatedly write @var{contents} until it fills
32495 @var{count} memory units.
32499 @subsubheading @value{GDBN} Command
32501 There's no corresponding @value{GDBN} command.
32503 @subsubheading Example
32507 -data-write-memory-bytes &a "aabbccdd"
32514 -data-write-memory-bytes &a "aabbccdd" 16e
32519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32520 @node GDB/MI Tracepoint Commands
32521 @section @sc{gdb/mi} Tracepoint Commands
32523 The commands defined in this section implement MI support for
32524 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32526 @subheading The @code{-trace-find} Command
32527 @findex -trace-find
32529 @subsubheading Synopsis
32532 -trace-find @var{mode} [@var{parameters}@dots{}]
32535 Find a trace frame using criteria defined by @var{mode} and
32536 @var{parameters}. The following table lists permissible
32537 modes and their parameters. For details of operation, see @ref{tfind}.
32542 No parameters are required. Stops examining trace frames.
32545 An integer is required as parameter. Selects tracepoint frame with
32548 @item tracepoint-number
32549 An integer is required as parameter. Finds next
32550 trace frame that corresponds to tracepoint with the specified number.
32553 An address is required as parameter. Finds
32554 next trace frame that corresponds to any tracepoint at the specified
32557 @item pc-inside-range
32558 Two addresses are required as parameters. Finds next trace
32559 frame that corresponds to a tracepoint at an address inside the
32560 specified range. Both bounds are considered to be inside the range.
32562 @item pc-outside-range
32563 Two addresses are required as parameters. Finds
32564 next trace frame that corresponds to a tracepoint at an address outside
32565 the specified range. Both bounds are considered to be inside the range.
32568 Line specification is required as parameter. @xref{Specify Location}.
32569 Finds next trace frame that corresponds to a tracepoint at
32570 the specified location.
32574 If @samp{none} was passed as @var{mode}, the response does not
32575 have fields. Otherwise, the response may have the following fields:
32579 This field has either @samp{0} or @samp{1} as the value, depending
32580 on whether a matching tracepoint was found.
32583 The index of the found traceframe. This field is present iff
32584 the @samp{found} field has value of @samp{1}.
32587 The index of the found tracepoint. This field is present iff
32588 the @samp{found} field has value of @samp{1}.
32591 The information about the frame corresponding to the found trace
32592 frame. This field is present only if a trace frame was found.
32593 @xref{GDB/MI Frame Information}, for description of this field.
32597 @subsubheading @value{GDBN} Command
32599 The corresponding @value{GDBN} command is @samp{tfind}.
32601 @subheading -trace-define-variable
32602 @findex -trace-define-variable
32604 @subsubheading Synopsis
32607 -trace-define-variable @var{name} [ @var{value} ]
32610 Create trace variable @var{name} if it does not exist. If
32611 @var{value} is specified, sets the initial value of the specified
32612 trace variable to that value. Note that the @var{name} should start
32613 with the @samp{$} character.
32615 @subsubheading @value{GDBN} Command
32617 The corresponding @value{GDBN} command is @samp{tvariable}.
32619 @subheading The @code{-trace-frame-collected} Command
32620 @findex -trace-frame-collected
32622 @subsubheading Synopsis
32625 -trace-frame-collected
32626 [--var-print-values @var{var_pval}]
32627 [--comp-print-values @var{comp_pval}]
32628 [--registers-format @var{regformat}]
32629 [--memory-contents]
32632 This command returns the set of collected objects, register names,
32633 trace state variable names, memory ranges and computed expressions
32634 that have been collected at a particular trace frame. The optional
32635 parameters to the command affect the output format in different ways.
32636 See the output description table below for more details.
32638 The reported names can be used in the normal manner to create
32639 varobjs and inspect the objects themselves. The items returned by
32640 this command are categorized so that it is clear which is a variable,
32641 which is a register, which is a trace state variable, which is a
32642 memory range and which is a computed expression.
32644 For instance, if the actions were
32646 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
32647 collect *(int*)0xaf02bef0@@40
32651 the object collected in its entirety would be @code{myVar}. The
32652 object @code{myArray} would be partially collected, because only the
32653 element at index @code{myIndex} would be collected. The remaining
32654 objects would be computed expressions.
32656 An example output would be:
32660 -trace-frame-collected
32662 explicit-variables=[@{name="myVar",value="1"@}],
32663 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
32664 @{name="myObj.field",value="0"@},
32665 @{name="myPtr->field",value="1"@},
32666 @{name="myCount + 2",value="3"@},
32667 @{name="$tvar1 + 1",value="43970027"@}],
32668 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
32669 @{number="1",value="0x0"@},
32670 @{number="2",value="0x4"@},
32672 @{number="125",value="0x0"@}],
32673 tvars=[@{name="$tvar1",current="43970026"@}],
32674 memory=[@{address="0x0000000000602264",length="4"@},
32675 @{address="0x0000000000615bc0",length="4"@}]
32682 @item explicit-variables
32683 The set of objects that have been collected in their entirety (as
32684 opposed to collecting just a few elements of an array or a few struct
32685 members). For each object, its name and value are printed.
32686 The @code{--var-print-values} option affects how or whether the value
32687 field is output. If @var{var_pval} is 0, then print only the names;
32688 if it is 1, print also their values; and if it is 2, print the name,
32689 type and value for simple data types, and the name and type for
32690 arrays, structures and unions.
32692 @item computed-expressions
32693 The set of computed expressions that have been collected at the
32694 current trace frame. The @code{--comp-print-values} option affects
32695 this set like the @code{--var-print-values} option affects the
32696 @code{explicit-variables} set. See above.
32699 The registers that have been collected at the current trace frame.
32700 For each register collected, the name and current value are returned.
32701 The value is formatted according to the @code{--registers-format}
32702 option. See the @command{-data-list-register-values} command for a
32703 list of the allowed formats. The default is @samp{x}.
32706 The trace state variables that have been collected at the current
32707 trace frame. For each trace state variable collected, the name and
32708 current value are returned.
32711 The set of memory ranges that have been collected at the current trace
32712 frame. Its content is a list of tuples. Each tuple represents a
32713 collected memory range and has the following fields:
32717 The start address of the memory range, as hexadecimal literal.
32720 The length of the memory range, as decimal literal.
32723 The contents of the memory block, in hex. This field is only present
32724 if the @code{--memory-contents} option is specified.
32730 @subsubheading @value{GDBN} Command
32732 There is no corresponding @value{GDBN} command.
32734 @subsubheading Example
32736 @subheading -trace-list-variables
32737 @findex -trace-list-variables
32739 @subsubheading Synopsis
32742 -trace-list-variables
32745 Return a table of all defined trace variables. Each element of the
32746 table has the following fields:
32750 The name of the trace variable. This field is always present.
32753 The initial value. This is a 64-bit signed integer. This
32754 field is always present.
32757 The value the trace variable has at the moment. This is a 64-bit
32758 signed integer. This field is absent iff current value is
32759 not defined, for example if the trace was never run, or is
32764 @subsubheading @value{GDBN} Command
32766 The corresponding @value{GDBN} command is @samp{tvariables}.
32768 @subsubheading Example
32772 -trace-list-variables
32773 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32774 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32775 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32776 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32777 body=[variable=@{name="$trace_timestamp",initial="0"@}
32778 variable=@{name="$foo",initial="10",current="15"@}]@}
32782 @subheading -trace-save
32783 @findex -trace-save
32785 @subsubheading Synopsis
32788 -trace-save [ -r ] [ -ctf ] @var{filename}
32791 Saves the collected trace data to @var{filename}. Without the
32792 @samp{-r} option, the data is downloaded from the target and saved
32793 in a local file. With the @samp{-r} option the target is asked
32794 to perform the save.
32796 By default, this command will save the trace in the tfile format. You can
32797 supply the optional @samp{-ctf} argument to save it the CTF format. See
32798 @ref{Trace Files} for more information about CTF.
32800 @subsubheading @value{GDBN} Command
32802 The corresponding @value{GDBN} command is @samp{tsave}.
32805 @subheading -trace-start
32806 @findex -trace-start
32808 @subsubheading Synopsis
32814 Starts a tracing experiment. The result of this command does not
32817 @subsubheading @value{GDBN} Command
32819 The corresponding @value{GDBN} command is @samp{tstart}.
32821 @subheading -trace-status
32822 @findex -trace-status
32824 @subsubheading Synopsis
32830 Obtains the status of a tracing experiment. The result may include
32831 the following fields:
32836 May have a value of either @samp{0}, when no tracing operations are
32837 supported, @samp{1}, when all tracing operations are supported, or
32838 @samp{file} when examining trace file. In the latter case, examining
32839 of trace frame is possible but new tracing experiement cannot be
32840 started. This field is always present.
32843 May have a value of either @samp{0} or @samp{1} depending on whether
32844 tracing experiement is in progress on target. This field is present
32845 if @samp{supported} field is not @samp{0}.
32848 Report the reason why the tracing was stopped last time. This field
32849 may be absent iff tracing was never stopped on target yet. The
32850 value of @samp{request} means the tracing was stopped as result of
32851 the @code{-trace-stop} command. The value of @samp{overflow} means
32852 the tracing buffer is full. The value of @samp{disconnection} means
32853 tracing was automatically stopped when @value{GDBN} has disconnected.
32854 The value of @samp{passcount} means tracing was stopped when a
32855 tracepoint was passed a maximal number of times for that tracepoint.
32856 This field is present if @samp{supported} field is not @samp{0}.
32858 @item stopping-tracepoint
32859 The number of tracepoint whose passcount as exceeded. This field is
32860 present iff the @samp{stop-reason} field has the value of
32864 @itemx frames-created
32865 The @samp{frames} field is a count of the total number of trace frames
32866 in the trace buffer, while @samp{frames-created} is the total created
32867 during the run, including ones that were discarded, such as when a
32868 circular trace buffer filled up. Both fields are optional.
32872 These fields tell the current size of the tracing buffer and the
32873 remaining space. These fields are optional.
32876 The value of the circular trace buffer flag. @code{1} means that the
32877 trace buffer is circular and old trace frames will be discarded if
32878 necessary to make room, @code{0} means that the trace buffer is linear
32882 The value of the disconnected tracing flag. @code{1} means that
32883 tracing will continue after @value{GDBN} disconnects, @code{0} means
32884 that the trace run will stop.
32887 The filename of the trace file being examined. This field is
32888 optional, and only present when examining a trace file.
32892 @subsubheading @value{GDBN} Command
32894 The corresponding @value{GDBN} command is @samp{tstatus}.
32896 @subheading -trace-stop
32897 @findex -trace-stop
32899 @subsubheading Synopsis
32905 Stops a tracing experiment. The result of this command has the same
32906 fields as @code{-trace-status}, except that the @samp{supported} and
32907 @samp{running} fields are not output.
32909 @subsubheading @value{GDBN} Command
32911 The corresponding @value{GDBN} command is @samp{tstop}.
32914 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32915 @node GDB/MI Symbol Query
32916 @section @sc{gdb/mi} Symbol Query Commands
32920 @subheading The @code{-symbol-info-address} Command
32921 @findex -symbol-info-address
32923 @subsubheading Synopsis
32926 -symbol-info-address @var{symbol}
32929 Describe where @var{symbol} is stored.
32931 @subsubheading @value{GDBN} Command
32933 The corresponding @value{GDBN} command is @samp{info address}.
32935 @subsubheading Example
32939 @subheading The @code{-symbol-info-file} Command
32940 @findex -symbol-info-file
32942 @subsubheading Synopsis
32948 Show the file for the symbol.
32950 @subsubheading @value{GDBN} Command
32952 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32953 @samp{gdb_find_file}.
32955 @subsubheading Example
32959 @subheading The @code{-symbol-info-function} Command
32960 @findex -symbol-info-function
32962 @subsubheading Synopsis
32965 -symbol-info-function
32968 Show which function the symbol lives in.
32970 @subsubheading @value{GDBN} Command
32972 @samp{gdb_get_function} in @code{gdbtk}.
32974 @subsubheading Example
32978 @subheading The @code{-symbol-info-line} Command
32979 @findex -symbol-info-line
32981 @subsubheading Synopsis
32987 Show the core addresses of the code for a source line.
32989 @subsubheading @value{GDBN} Command
32991 The corresponding @value{GDBN} command is @samp{info line}.
32992 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32994 @subsubheading Example
32998 @subheading The @code{-symbol-info-symbol} Command
32999 @findex -symbol-info-symbol
33001 @subsubheading Synopsis
33004 -symbol-info-symbol @var{addr}
33007 Describe what symbol is at location @var{addr}.
33009 @subsubheading @value{GDBN} Command
33011 The corresponding @value{GDBN} command is @samp{info symbol}.
33013 @subsubheading Example
33017 @subheading The @code{-symbol-list-functions} Command
33018 @findex -symbol-list-functions
33020 @subsubheading Synopsis
33023 -symbol-list-functions
33026 List the functions in the executable.
33028 @subsubheading @value{GDBN} Command
33030 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33031 @samp{gdb_search} in @code{gdbtk}.
33033 @subsubheading Example
33038 @subheading The @code{-symbol-list-lines} Command
33039 @findex -symbol-list-lines
33041 @subsubheading Synopsis
33044 -symbol-list-lines @var{filename}
33047 Print the list of lines that contain code and their associated program
33048 addresses for the given source filename. The entries are sorted in
33049 ascending PC order.
33051 @subsubheading @value{GDBN} Command
33053 There is no corresponding @value{GDBN} command.
33055 @subsubheading Example
33058 -symbol-list-lines basics.c
33059 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33065 @subheading The @code{-symbol-list-types} Command
33066 @findex -symbol-list-types
33068 @subsubheading Synopsis
33074 List all the type names.
33076 @subsubheading @value{GDBN} Command
33078 The corresponding commands are @samp{info types} in @value{GDBN},
33079 @samp{gdb_search} in @code{gdbtk}.
33081 @subsubheading Example
33085 @subheading The @code{-symbol-list-variables} Command
33086 @findex -symbol-list-variables
33088 @subsubheading Synopsis
33091 -symbol-list-variables
33094 List all the global and static variable names.
33096 @subsubheading @value{GDBN} Command
33098 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33100 @subsubheading Example
33104 @subheading The @code{-symbol-locate} Command
33105 @findex -symbol-locate
33107 @subsubheading Synopsis
33113 @subsubheading @value{GDBN} Command
33115 @samp{gdb_loc} in @code{gdbtk}.
33117 @subsubheading Example
33121 @subheading The @code{-symbol-type} Command
33122 @findex -symbol-type
33124 @subsubheading Synopsis
33127 -symbol-type @var{variable}
33130 Show type of @var{variable}.
33132 @subsubheading @value{GDBN} Command
33134 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33135 @samp{gdb_obj_variable}.
33137 @subsubheading Example
33142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33143 @node GDB/MI File Commands
33144 @section @sc{gdb/mi} File Commands
33146 This section describes the GDB/MI commands to specify executable file names
33147 and to read in and obtain symbol table information.
33149 @subheading The @code{-file-exec-and-symbols} Command
33150 @findex -file-exec-and-symbols
33152 @subsubheading Synopsis
33155 -file-exec-and-symbols @var{file}
33158 Specify the executable file to be debugged. This file is the one from
33159 which the symbol table is also read. If no file is specified, the
33160 command clears the executable and symbol information. If breakpoints
33161 are set when using this command with no arguments, @value{GDBN} will produce
33162 error messages. Otherwise, no output is produced, except a completion
33165 @subsubheading @value{GDBN} Command
33167 The corresponding @value{GDBN} command is @samp{file}.
33169 @subsubheading Example
33173 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33179 @subheading The @code{-file-exec-file} Command
33180 @findex -file-exec-file
33182 @subsubheading Synopsis
33185 -file-exec-file @var{file}
33188 Specify the executable file to be debugged. Unlike
33189 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33190 from this file. If used without argument, @value{GDBN} clears the information
33191 about the executable file. No output is produced, except a completion
33194 @subsubheading @value{GDBN} Command
33196 The corresponding @value{GDBN} command is @samp{exec-file}.
33198 @subsubheading Example
33202 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33209 @subheading The @code{-file-list-exec-sections} Command
33210 @findex -file-list-exec-sections
33212 @subsubheading Synopsis
33215 -file-list-exec-sections
33218 List the sections of the current executable file.
33220 @subsubheading @value{GDBN} Command
33222 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33223 information as this command. @code{gdbtk} has a corresponding command
33224 @samp{gdb_load_info}.
33226 @subsubheading Example
33231 @subheading The @code{-file-list-exec-source-file} Command
33232 @findex -file-list-exec-source-file
33234 @subsubheading Synopsis
33237 -file-list-exec-source-file
33240 List the line number, the current source file, and the absolute path
33241 to the current source file for the current executable. The macro
33242 information field has a value of @samp{1} or @samp{0} depending on
33243 whether or not the file includes preprocessor macro information.
33245 @subsubheading @value{GDBN} Command
33247 The @value{GDBN} equivalent is @samp{info source}
33249 @subsubheading Example
33253 123-file-list-exec-source-file
33254 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33259 @subheading The @code{-file-list-exec-source-files} Command
33260 @findex -file-list-exec-source-files
33262 @subsubheading Synopsis
33265 -file-list-exec-source-files
33268 List the source files for the current executable.
33270 It will always output both the filename and fullname (absolute file
33271 name) of a source file.
33273 @subsubheading @value{GDBN} Command
33275 The @value{GDBN} equivalent is @samp{info sources}.
33276 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33278 @subsubheading Example
33281 -file-list-exec-source-files
33283 @{file=foo.c,fullname=/home/foo.c@},
33284 @{file=/home/bar.c,fullname=/home/bar.c@},
33285 @{file=gdb_could_not_find_fullpath.c@}]
33289 @subheading The @code{-file-list-shared-libraries} Command
33290 @findex -file-list-shared-libraries
33292 @subsubheading Synopsis
33295 -file-list-shared-libraries [ @var{regexp} ]
33298 List the shared libraries in the program.
33299 With a regular expression @var{regexp}, only those libraries whose
33300 names match @var{regexp} are listed.
33302 @subsubheading @value{GDBN} Command
33304 The corresponding @value{GDBN} command is @samp{info shared}. The fields
33305 have a similar meaning to the @code{=library-loaded} notification.
33306 The @code{ranges} field specifies the multiple segments belonging to this
33307 library. Each range has the following fields:
33311 The address defining the inclusive lower bound of the segment.
33313 The address defining the exclusive upper bound of the segment.
33316 @subsubheading Example
33319 -file-list-exec-source-files
33320 ^done,shared-libraries=[
33321 @{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"@}]@},
33322 @{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"@}]@}]
33328 @subheading The @code{-file-list-symbol-files} Command
33329 @findex -file-list-symbol-files
33331 @subsubheading Synopsis
33334 -file-list-symbol-files
33339 @subsubheading @value{GDBN} Command
33341 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33343 @subsubheading Example
33348 @subheading The @code{-file-symbol-file} Command
33349 @findex -file-symbol-file
33351 @subsubheading Synopsis
33354 -file-symbol-file @var{file}
33357 Read symbol table info from the specified @var{file} argument. When
33358 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33359 produced, except for a completion notification.
33361 @subsubheading @value{GDBN} Command
33363 The corresponding @value{GDBN} command is @samp{symbol-file}.
33365 @subsubheading Example
33369 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33375 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33376 @node GDB/MI Memory Overlay Commands
33377 @section @sc{gdb/mi} Memory Overlay Commands
33379 The memory overlay commands are not implemented.
33381 @c @subheading -overlay-auto
33383 @c @subheading -overlay-list-mapping-state
33385 @c @subheading -overlay-list-overlays
33387 @c @subheading -overlay-map
33389 @c @subheading -overlay-off
33391 @c @subheading -overlay-on
33393 @c @subheading -overlay-unmap
33395 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33396 @node GDB/MI Signal Handling Commands
33397 @section @sc{gdb/mi} Signal Handling Commands
33399 Signal handling commands are not implemented.
33401 @c @subheading -signal-handle
33403 @c @subheading -signal-list-handle-actions
33405 @c @subheading -signal-list-signal-types
33409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33410 @node GDB/MI Target Manipulation
33411 @section @sc{gdb/mi} Target Manipulation Commands
33414 @subheading The @code{-target-attach} Command
33415 @findex -target-attach
33417 @subsubheading Synopsis
33420 -target-attach @var{pid} | @var{gid} | @var{file}
33423 Attach to a process @var{pid} or a file @var{file} outside of
33424 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33425 group, the id previously returned by
33426 @samp{-list-thread-groups --available} must be used.
33428 @subsubheading @value{GDBN} Command
33430 The corresponding @value{GDBN} command is @samp{attach}.
33432 @subsubheading Example
33436 =thread-created,id="1"
33437 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33443 @subheading The @code{-target-compare-sections} Command
33444 @findex -target-compare-sections
33446 @subsubheading Synopsis
33449 -target-compare-sections [ @var{section} ]
33452 Compare data of section @var{section} on target to the exec file.
33453 Without the argument, all sections are compared.
33455 @subsubheading @value{GDBN} Command
33457 The @value{GDBN} equivalent is @samp{compare-sections}.
33459 @subsubheading Example
33464 @subheading The @code{-target-detach} Command
33465 @findex -target-detach
33467 @subsubheading Synopsis
33470 -target-detach [ @var{pid} | @var{gid} ]
33473 Detach from the remote target which normally resumes its execution.
33474 If either @var{pid} or @var{gid} is specified, detaches from either
33475 the specified process, or specified thread group. There's no output.
33477 @subsubheading @value{GDBN} Command
33479 The corresponding @value{GDBN} command is @samp{detach}.
33481 @subsubheading Example
33491 @subheading The @code{-target-disconnect} Command
33492 @findex -target-disconnect
33494 @subsubheading Synopsis
33500 Disconnect from the remote target. There's no output and the target is
33501 generally not resumed.
33503 @subsubheading @value{GDBN} Command
33505 The corresponding @value{GDBN} command is @samp{disconnect}.
33507 @subsubheading Example
33517 @subheading The @code{-target-download} Command
33518 @findex -target-download
33520 @subsubheading Synopsis
33526 Loads the executable onto the remote target.
33527 It prints out an update message every half second, which includes the fields:
33531 The name of the section.
33533 The size of what has been sent so far for that section.
33535 The size of the section.
33537 The total size of what was sent so far (the current and the previous sections).
33539 The size of the overall executable to download.
33543 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
33544 @sc{gdb/mi} Output Syntax}).
33546 In addition, it prints the name and size of the sections, as they are
33547 downloaded. These messages include the following fields:
33551 The name of the section.
33553 The size of the section.
33555 The size of the overall executable to download.
33559 At the end, a summary is printed.
33561 @subsubheading @value{GDBN} Command
33563 The corresponding @value{GDBN} command is @samp{load}.
33565 @subsubheading Example
33567 Note: each status message appears on a single line. Here the messages
33568 have been broken down so that they can fit onto a page.
33573 +download,@{section=".text",section-size="6668",total-size="9880"@}
33574 +download,@{section=".text",section-sent="512",section-size="6668",
33575 total-sent="512",total-size="9880"@}
33576 +download,@{section=".text",section-sent="1024",section-size="6668",
33577 total-sent="1024",total-size="9880"@}
33578 +download,@{section=".text",section-sent="1536",section-size="6668",
33579 total-sent="1536",total-size="9880"@}
33580 +download,@{section=".text",section-sent="2048",section-size="6668",
33581 total-sent="2048",total-size="9880"@}
33582 +download,@{section=".text",section-sent="2560",section-size="6668",
33583 total-sent="2560",total-size="9880"@}
33584 +download,@{section=".text",section-sent="3072",section-size="6668",
33585 total-sent="3072",total-size="9880"@}
33586 +download,@{section=".text",section-sent="3584",section-size="6668",
33587 total-sent="3584",total-size="9880"@}
33588 +download,@{section=".text",section-sent="4096",section-size="6668",
33589 total-sent="4096",total-size="9880"@}
33590 +download,@{section=".text",section-sent="4608",section-size="6668",
33591 total-sent="4608",total-size="9880"@}
33592 +download,@{section=".text",section-sent="5120",section-size="6668",
33593 total-sent="5120",total-size="9880"@}
33594 +download,@{section=".text",section-sent="5632",section-size="6668",
33595 total-sent="5632",total-size="9880"@}
33596 +download,@{section=".text",section-sent="6144",section-size="6668",
33597 total-sent="6144",total-size="9880"@}
33598 +download,@{section=".text",section-sent="6656",section-size="6668",
33599 total-sent="6656",total-size="9880"@}
33600 +download,@{section=".init",section-size="28",total-size="9880"@}
33601 +download,@{section=".fini",section-size="28",total-size="9880"@}
33602 +download,@{section=".data",section-size="3156",total-size="9880"@}
33603 +download,@{section=".data",section-sent="512",section-size="3156",
33604 total-sent="7236",total-size="9880"@}
33605 +download,@{section=".data",section-sent="1024",section-size="3156",
33606 total-sent="7748",total-size="9880"@}
33607 +download,@{section=".data",section-sent="1536",section-size="3156",
33608 total-sent="8260",total-size="9880"@}
33609 +download,@{section=".data",section-sent="2048",section-size="3156",
33610 total-sent="8772",total-size="9880"@}
33611 +download,@{section=".data",section-sent="2560",section-size="3156",
33612 total-sent="9284",total-size="9880"@}
33613 +download,@{section=".data",section-sent="3072",section-size="3156",
33614 total-sent="9796",total-size="9880"@}
33615 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
33622 @subheading The @code{-target-exec-status} Command
33623 @findex -target-exec-status
33625 @subsubheading Synopsis
33628 -target-exec-status
33631 Provide information on the state of the target (whether it is running or
33632 not, for instance).
33634 @subsubheading @value{GDBN} Command
33636 There's no equivalent @value{GDBN} command.
33638 @subsubheading Example
33642 @subheading The @code{-target-list-available-targets} Command
33643 @findex -target-list-available-targets
33645 @subsubheading Synopsis
33648 -target-list-available-targets
33651 List the possible targets to connect to.
33653 @subsubheading @value{GDBN} Command
33655 The corresponding @value{GDBN} command is @samp{help target}.
33657 @subsubheading Example
33661 @subheading The @code{-target-list-current-targets} Command
33662 @findex -target-list-current-targets
33664 @subsubheading Synopsis
33667 -target-list-current-targets
33670 Describe the current target.
33672 @subsubheading @value{GDBN} Command
33674 The corresponding information is printed by @samp{info file} (among
33677 @subsubheading Example
33681 @subheading The @code{-target-list-parameters} Command
33682 @findex -target-list-parameters
33684 @subsubheading Synopsis
33687 -target-list-parameters
33693 @subsubheading @value{GDBN} Command
33697 @subsubheading Example
33700 @subheading The @code{-target-flash-erase} Command
33701 @findex -target-flash-erase
33703 @subsubheading Synopsis
33706 -target-flash-erase
33709 Erases all known flash memory regions on the target.
33711 The corresponding @value{GDBN} command is @samp{flash-erase}.
33713 The output is a list of flash regions that have been erased, with starting
33714 addresses and memory region sizes.
33718 -target-flash-erase
33719 ^done,erased-regions=@{address="0x0",size="0x40000"@}
33723 @subheading The @code{-target-select} Command
33724 @findex -target-select
33726 @subsubheading Synopsis
33729 -target-select @var{type} @var{parameters @dots{}}
33732 Connect @value{GDBN} to the remote target. This command takes two args:
33736 The type of target, for instance @samp{remote}, etc.
33737 @item @var{parameters}
33738 Device names, host names and the like. @xref{Target Commands, ,
33739 Commands for Managing Targets}, for more details.
33742 The output is a connection notification, followed by the address at
33743 which the target program is, in the following form:
33746 ^connected,addr="@var{address}",func="@var{function name}",
33747 args=[@var{arg list}]
33750 @subsubheading @value{GDBN} Command
33752 The corresponding @value{GDBN} command is @samp{target}.
33754 @subsubheading Example
33758 -target-select remote /dev/ttya
33759 ^connected,addr="0xfe00a300",func="??",args=[]
33763 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33764 @node GDB/MI File Transfer Commands
33765 @section @sc{gdb/mi} File Transfer Commands
33768 @subheading The @code{-target-file-put} Command
33769 @findex -target-file-put
33771 @subsubheading Synopsis
33774 -target-file-put @var{hostfile} @var{targetfile}
33777 Copy file @var{hostfile} from the host system (the machine running
33778 @value{GDBN}) to @var{targetfile} on the target system.
33780 @subsubheading @value{GDBN} Command
33782 The corresponding @value{GDBN} command is @samp{remote put}.
33784 @subsubheading Example
33788 -target-file-put localfile remotefile
33794 @subheading The @code{-target-file-get} Command
33795 @findex -target-file-get
33797 @subsubheading Synopsis
33800 -target-file-get @var{targetfile} @var{hostfile}
33803 Copy file @var{targetfile} from the target system to @var{hostfile}
33804 on the host system.
33806 @subsubheading @value{GDBN} Command
33808 The corresponding @value{GDBN} command is @samp{remote get}.
33810 @subsubheading Example
33814 -target-file-get remotefile localfile
33820 @subheading The @code{-target-file-delete} Command
33821 @findex -target-file-delete
33823 @subsubheading Synopsis
33826 -target-file-delete @var{targetfile}
33829 Delete @var{targetfile} from the target system.
33831 @subsubheading @value{GDBN} Command
33833 The corresponding @value{GDBN} command is @samp{remote delete}.
33835 @subsubheading Example
33839 -target-file-delete remotefile
33845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33846 @node GDB/MI Ada Exceptions Commands
33847 @section Ada Exceptions @sc{gdb/mi} Commands
33849 @subheading The @code{-info-ada-exceptions} Command
33850 @findex -info-ada-exceptions
33852 @subsubheading Synopsis
33855 -info-ada-exceptions [ @var{regexp}]
33858 List all Ada exceptions defined within the program being debugged.
33859 With a regular expression @var{regexp}, only those exceptions whose
33860 names match @var{regexp} are listed.
33862 @subsubheading @value{GDBN} Command
33864 The corresponding @value{GDBN} command is @samp{info exceptions}.
33866 @subsubheading Result
33868 The result is a table of Ada exceptions. The following columns are
33869 defined for each exception:
33873 The name of the exception.
33876 The address of the exception.
33880 @subsubheading Example
33883 -info-ada-exceptions aint
33884 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
33885 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
33886 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
33887 body=[@{name="constraint_error",address="0x0000000000613da0"@},
33888 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
33891 @subheading Catching Ada Exceptions
33893 The commands describing how to ask @value{GDBN} to stop when a program
33894 raises an exception are described at @ref{Ada Exception GDB/MI
33895 Catchpoint Commands}.
33898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33899 @node GDB/MI Support Commands
33900 @section @sc{gdb/mi} Support Commands
33902 Since new commands and features get regularly added to @sc{gdb/mi},
33903 some commands are available to help front-ends query the debugger
33904 about support for these capabilities. Similarly, it is also possible
33905 to query @value{GDBN} about target support of certain features.
33907 @subheading The @code{-info-gdb-mi-command} Command
33908 @cindex @code{-info-gdb-mi-command}
33909 @findex -info-gdb-mi-command
33911 @subsubheading Synopsis
33914 -info-gdb-mi-command @var{cmd_name}
33917 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
33919 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
33920 is technically not part of the command name (@pxref{GDB/MI Input
33921 Syntax}), and thus should be omitted in @var{cmd_name}. However,
33922 for ease of use, this command also accepts the form with the leading
33925 @subsubheading @value{GDBN} Command
33927 There is no corresponding @value{GDBN} command.
33929 @subsubheading Result
33931 The result is a tuple. There is currently only one field:
33935 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
33936 @code{"false"} otherwise.
33940 @subsubheading Example
33942 Here is an example where the @sc{gdb/mi} command does not exist:
33945 -info-gdb-mi-command unsupported-command
33946 ^done,command=@{exists="false"@}
33950 And here is an example where the @sc{gdb/mi} command is known
33954 -info-gdb-mi-command symbol-list-lines
33955 ^done,command=@{exists="true"@}
33958 @subheading The @code{-list-features} Command
33959 @findex -list-features
33960 @cindex supported @sc{gdb/mi} features, list
33962 Returns a list of particular features of the MI protocol that
33963 this version of gdb implements. A feature can be a command,
33964 or a new field in an output of some command, or even an
33965 important bugfix. While a frontend can sometimes detect presence
33966 of a feature at runtime, it is easier to perform detection at debugger
33969 The command returns a list of strings, with each string naming an
33970 available feature. Each returned string is just a name, it does not
33971 have any internal structure. The list of possible feature names
33977 (gdb) -list-features
33978 ^done,result=["feature1","feature2"]
33981 The current list of features is:
33984 @item frozen-varobjs
33985 Indicates support for the @code{-var-set-frozen} command, as well
33986 as possible presense of the @code{frozen} field in the output
33987 of @code{-varobj-create}.
33988 @item pending-breakpoints
33989 Indicates support for the @option{-f} option to the @code{-break-insert}
33992 Indicates Python scripting support, Python-based
33993 pretty-printing commands, and possible presence of the
33994 @samp{display_hint} field in the output of @code{-var-list-children}
33996 Indicates support for the @code{-thread-info} command.
33997 @item data-read-memory-bytes
33998 Indicates support for the @code{-data-read-memory-bytes} and the
33999 @code{-data-write-memory-bytes} commands.
34000 @item breakpoint-notifications
34001 Indicates that changes to breakpoints and breakpoints created via the
34002 CLI will be announced via async records.
34003 @item ada-task-info
34004 Indicates support for the @code{-ada-task-info} command.
34005 @item language-option
34006 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
34007 option (@pxref{Context management}).
34008 @item info-gdb-mi-command
34009 Indicates support for the @code{-info-gdb-mi-command} command.
34010 @item undefined-command-error-code
34011 Indicates support for the "undefined-command" error code in error result
34012 records, produced when trying to execute an undefined @sc{gdb/mi} command
34013 (@pxref{GDB/MI Result Records}).
34014 @item exec-run-start-option
34015 Indicates that the @code{-exec-run} command supports the @option{--start}
34016 option (@pxref{GDB/MI Program Execution}).
34017 @item data-disassemble-a-option
34018 Indicates that the @code{-data-disassemble} command supports the @option{-a}
34019 option (@pxref{GDB/MI Data Manipulation}).
34022 @subheading The @code{-list-target-features} Command
34023 @findex -list-target-features
34025 Returns a list of particular features that are supported by the
34026 target. Those features affect the permitted MI commands, but
34027 unlike the features reported by the @code{-list-features} command, the
34028 features depend on which target GDB is using at the moment. Whenever
34029 a target can change, due to commands such as @code{-target-select},
34030 @code{-target-attach} or @code{-exec-run}, the list of target features
34031 may change, and the frontend should obtain it again.
34035 (gdb) -list-target-features
34036 ^done,result=["async"]
34039 The current list of features is:
34043 Indicates that the target is capable of asynchronous command
34044 execution, which means that @value{GDBN} will accept further commands
34045 while the target is running.
34048 Indicates that the target is capable of reverse execution.
34049 @xref{Reverse Execution}, for more information.
34053 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34054 @node GDB/MI Miscellaneous Commands
34055 @section Miscellaneous @sc{gdb/mi} Commands
34057 @c @subheading -gdb-complete
34059 @subheading The @code{-gdb-exit} Command
34062 @subsubheading Synopsis
34068 Exit @value{GDBN} immediately.
34070 @subsubheading @value{GDBN} Command
34072 Approximately corresponds to @samp{quit}.
34074 @subsubheading Example
34084 @subheading The @code{-exec-abort} Command
34085 @findex -exec-abort
34087 @subsubheading Synopsis
34093 Kill the inferior running program.
34095 @subsubheading @value{GDBN} Command
34097 The corresponding @value{GDBN} command is @samp{kill}.
34099 @subsubheading Example
34104 @subheading The @code{-gdb-set} Command
34107 @subsubheading Synopsis
34113 Set an internal @value{GDBN} variable.
34114 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34116 @subsubheading @value{GDBN} Command
34118 The corresponding @value{GDBN} command is @samp{set}.
34120 @subsubheading Example
34130 @subheading The @code{-gdb-show} Command
34133 @subsubheading Synopsis
34139 Show the current value of a @value{GDBN} variable.
34141 @subsubheading @value{GDBN} Command
34143 The corresponding @value{GDBN} command is @samp{show}.
34145 @subsubheading Example
34154 @c @subheading -gdb-source
34157 @subheading The @code{-gdb-version} Command
34158 @findex -gdb-version
34160 @subsubheading Synopsis
34166 Show version information for @value{GDBN}. Used mostly in testing.
34168 @subsubheading @value{GDBN} Command
34170 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34171 default shows this information when you start an interactive session.
34173 @subsubheading Example
34175 @c This example modifies the actual output from GDB to avoid overfull
34181 ~Copyright 2000 Free Software Foundation, Inc.
34182 ~GDB is free software, covered by the GNU General Public License, and
34183 ~you are welcome to change it and/or distribute copies of it under
34184 ~ certain conditions.
34185 ~Type "show copying" to see the conditions.
34186 ~There is absolutely no warranty for GDB. Type "show warranty" for
34188 ~This GDB was configured as
34189 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34194 @subheading The @code{-list-thread-groups} Command
34195 @findex -list-thread-groups
34197 @subheading Synopsis
34200 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34203 Lists thread groups (@pxref{Thread groups}). When a single thread
34204 group is passed as the argument, lists the children of that group.
34205 When several thread group are passed, lists information about those
34206 thread groups. Without any parameters, lists information about all
34207 top-level thread groups.
34209 Normally, thread groups that are being debugged are reported.
34210 With the @samp{--available} option, @value{GDBN} reports thread groups
34211 available on the target.
34213 The output of this command may have either a @samp{threads} result or
34214 a @samp{groups} result. The @samp{thread} result has a list of tuples
34215 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34216 Information}). The @samp{groups} result has a list of tuples as value,
34217 each tuple describing a thread group. If top-level groups are
34218 requested (that is, no parameter is passed), or when several groups
34219 are passed, the output always has a @samp{groups} result. The format
34220 of the @samp{group} result is described below.
34222 To reduce the number of roundtrips it's possible to list thread groups
34223 together with their children, by passing the @samp{--recurse} option
34224 and the recursion depth. Presently, only recursion depth of 1 is
34225 permitted. If this option is present, then every reported thread group
34226 will also include its children, either as @samp{group} or
34227 @samp{threads} field.
34229 In general, any combination of option and parameters is permitted, with
34230 the following caveats:
34234 When a single thread group is passed, the output will typically
34235 be the @samp{threads} result. Because threads may not contain
34236 anything, the @samp{recurse} option will be ignored.
34239 When the @samp{--available} option is passed, limited information may
34240 be available. In particular, the list of threads of a process might
34241 be inaccessible. Further, specifying specific thread groups might
34242 not give any performance advantage over listing all thread groups.
34243 The frontend should assume that @samp{-list-thread-groups --available}
34244 is always an expensive operation and cache the results.
34248 The @samp{groups} result is a list of tuples, where each tuple may
34249 have the following fields:
34253 Identifier of the thread group. This field is always present.
34254 The identifier is an opaque string; frontends should not try to
34255 convert it to an integer, even though it might look like one.
34258 The type of the thread group. At present, only @samp{process} is a
34262 The target-specific process identifier. This field is only present
34263 for thread groups of type @samp{process} and only if the process exists.
34266 The exit code of this group's last exited thread, formatted in octal.
34267 This field is only present for thread groups of type @samp{process} and
34268 only if the process is not running.
34271 The number of children this thread group has. This field may be
34272 absent for an available thread group.
34275 This field has a list of tuples as value, each tuple describing a
34276 thread. It may be present if the @samp{--recurse} option is
34277 specified, and it's actually possible to obtain the threads.
34280 This field is a list of integers, each identifying a core that one
34281 thread of the group is running on. This field may be absent if
34282 such information is not available.
34285 The name of the executable file that corresponds to this thread group.
34286 The field is only present for thread groups of type @samp{process},
34287 and only if there is a corresponding executable file.
34291 @subheading Example
34295 -list-thread-groups
34296 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34297 -list-thread-groups 17
34298 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34299 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34300 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34301 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34302 file="/tmp/a.c",fullname="/tmp/a.c",line="158",arch="i386:x86_64"@},state="running"@}]]
34303 -list-thread-groups --available
34304 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34305 -list-thread-groups --available --recurse 1
34306 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34307 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34308 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34309 -list-thread-groups --available --recurse 1 17 18
34310 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34311 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34312 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34315 @subheading The @code{-info-os} Command
34318 @subsubheading Synopsis
34321 -info-os [ @var{type} ]
34324 If no argument is supplied, the command returns a table of available
34325 operating-system-specific information types. If one of these types is
34326 supplied as an argument @var{type}, then the command returns a table
34327 of data of that type.
34329 The types of information available depend on the target operating
34332 @subsubheading @value{GDBN} Command
34334 The corresponding @value{GDBN} command is @samp{info os}.
34336 @subsubheading Example
34338 When run on a @sc{gnu}/Linux system, the output will look something
34344 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
34345 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34346 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34347 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34348 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
34350 item=@{col0="files",col1="Listing of all file descriptors",
34351 col2="File descriptors"@},
34352 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34353 col2="Kernel modules"@},
34354 item=@{col0="msg",col1="Listing of all message queues",
34355 col2="Message queues"@},
34356 item=@{col0="processes",col1="Listing of all processes",
34357 col2="Processes"@},
34358 item=@{col0="procgroups",col1="Listing of all process groups",
34359 col2="Process groups"@},
34360 item=@{col0="semaphores",col1="Listing of all semaphores",
34361 col2="Semaphores"@},
34362 item=@{col0="shm",col1="Listing of all shared-memory regions",
34363 col2="Shared-memory regions"@},
34364 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34366 item=@{col0="threads",col1="Listing of all threads",
34370 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34371 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34372 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34373 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34374 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34375 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34376 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34377 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34379 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34380 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34384 (Note that the MI output here includes a @code{"Title"} column that
34385 does not appear in command-line @code{info os}; this column is useful
34386 for MI clients that want to enumerate the types of data, such as in a
34387 popup menu, but is needless clutter on the command line, and
34388 @code{info os} omits it.)
34390 @subheading The @code{-add-inferior} Command
34391 @findex -add-inferior
34393 @subheading Synopsis
34399 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34400 inferior is not associated with any executable. Such association may
34401 be established with the @samp{-file-exec-and-symbols} command
34402 (@pxref{GDB/MI File Commands}). The command response has a single
34403 field, @samp{inferior}, whose value is the identifier of the
34404 thread group corresponding to the new inferior.
34406 @subheading Example
34411 ^done,inferior="i3"
34414 @subheading The @code{-interpreter-exec} Command
34415 @findex -interpreter-exec
34417 @subheading Synopsis
34420 -interpreter-exec @var{interpreter} @var{command}
34422 @anchor{-interpreter-exec}
34424 Execute the specified @var{command} in the given @var{interpreter}.
34426 @subheading @value{GDBN} Command
34428 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34430 @subheading Example
34434 -interpreter-exec console "break main"
34435 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34436 &"During symbol reading, bad structure-type format.\n"
34437 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34442 @subheading The @code{-inferior-tty-set} Command
34443 @findex -inferior-tty-set
34445 @subheading Synopsis
34448 -inferior-tty-set /dev/pts/1
34451 Set terminal for future runs of the program being debugged.
34453 @subheading @value{GDBN} Command
34455 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34457 @subheading Example
34461 -inferior-tty-set /dev/pts/1
34466 @subheading The @code{-inferior-tty-show} Command
34467 @findex -inferior-tty-show
34469 @subheading Synopsis
34475 Show terminal for future runs of program being debugged.
34477 @subheading @value{GDBN} Command
34479 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34481 @subheading Example
34485 -inferior-tty-set /dev/pts/1
34489 ^done,inferior_tty_terminal="/dev/pts/1"
34493 @subheading The @code{-enable-timings} Command
34494 @findex -enable-timings
34496 @subheading Synopsis
34499 -enable-timings [yes | no]
34502 Toggle the printing of the wallclock, user and system times for an MI
34503 command as a field in its output. This command is to help frontend
34504 developers optimize the performance of their code. No argument is
34505 equivalent to @samp{yes}.
34507 @subheading @value{GDBN} Command
34511 @subheading Example
34519 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34520 addr="0x080484ed",func="main",file="myprog.c",
34521 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34523 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34531 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34532 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34533 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34534 fullname="/home/nickrob/myprog.c",line="73",arch="i386:x86_64"@}
34539 @chapter @value{GDBN} Annotations
34541 This chapter describes annotations in @value{GDBN}. Annotations were
34542 designed to interface @value{GDBN} to graphical user interfaces or other
34543 similar programs which want to interact with @value{GDBN} at a
34544 relatively high level.
34546 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34550 This is Edition @value{EDITION}, @value{DATE}.
34554 * Annotations Overview:: What annotations are; the general syntax.
34555 * Server Prefix:: Issuing a command without affecting user state.
34556 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34557 * Errors:: Annotations for error messages.
34558 * Invalidation:: Some annotations describe things now invalid.
34559 * Annotations for Running::
34560 Whether the program is running, how it stopped, etc.
34561 * Source Annotations:: Annotations describing source code.
34564 @node Annotations Overview
34565 @section What is an Annotation?
34566 @cindex annotations
34568 Annotations start with a newline character, two @samp{control-z}
34569 characters, and the name of the annotation. If there is no additional
34570 information associated with this annotation, the name of the annotation
34571 is followed immediately by a newline. If there is additional
34572 information, the name of the annotation is followed by a space, the
34573 additional information, and a newline. The additional information
34574 cannot contain newline characters.
34576 Any output not beginning with a newline and two @samp{control-z}
34577 characters denotes literal output from @value{GDBN}. Currently there is
34578 no need for @value{GDBN} to output a newline followed by two
34579 @samp{control-z} characters, but if there was such a need, the
34580 annotations could be extended with an @samp{escape} annotation which
34581 means those three characters as output.
34583 The annotation @var{level}, which is specified using the
34584 @option{--annotate} command line option (@pxref{Mode Options}), controls
34585 how much information @value{GDBN} prints together with its prompt,
34586 values of expressions, source lines, and other types of output. Level 0
34587 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34588 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34589 for programs that control @value{GDBN}, and level 2 annotations have
34590 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34591 Interface, annotate, GDB's Obsolete Annotations}).
34594 @kindex set annotate
34595 @item set annotate @var{level}
34596 The @value{GDBN} command @code{set annotate} sets the level of
34597 annotations to the specified @var{level}.
34599 @item show annotate
34600 @kindex show annotate
34601 Show the current annotation level.
34604 This chapter describes level 3 annotations.
34606 A simple example of starting up @value{GDBN} with annotations is:
34609 $ @kbd{gdb --annotate=3}
34611 Copyright 2003 Free Software Foundation, Inc.
34612 GDB is free software, covered by the GNU General Public License,
34613 and you are welcome to change it and/or distribute copies of it
34614 under certain conditions.
34615 Type "show copying" to see the conditions.
34616 There is absolutely no warranty for GDB. Type "show warranty"
34618 This GDB was configured as "i386-pc-linux-gnu"
34629 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34630 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34631 denotes a @samp{control-z} character) are annotations; the rest is
34632 output from @value{GDBN}.
34634 @node Server Prefix
34635 @section The Server Prefix
34636 @cindex server prefix
34638 If you prefix a command with @samp{server } then it will not affect
34639 the command history, nor will it affect @value{GDBN}'s notion of which
34640 command to repeat if @key{RET} is pressed on a line by itself. This
34641 means that commands can be run behind a user's back by a front-end in
34642 a transparent manner.
34644 The @code{server } prefix does not affect the recording of values into
34645 the value history; to print a value without recording it into the
34646 value history, use the @code{output} command instead of the
34647 @code{print} command.
34649 Using this prefix also disables confirmation requests
34650 (@pxref{confirmation requests}).
34653 @section Annotation for @value{GDBN} Input
34655 @cindex annotations for prompts
34656 When @value{GDBN} prompts for input, it annotates this fact so it is possible
34657 to know when to send output, when the output from a given command is
34660 Different kinds of input each have a different @dfn{input type}. Each
34661 input type has three annotations: a @code{pre-} annotation, which
34662 denotes the beginning of any prompt which is being output, a plain
34663 annotation, which denotes the end of the prompt, and then a @code{post-}
34664 annotation which denotes the end of any echo which may (or may not) be
34665 associated with the input. For example, the @code{prompt} input type
34666 features the following annotations:
34674 The input types are
34677 @findex pre-prompt annotation
34678 @findex prompt annotation
34679 @findex post-prompt annotation
34681 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
34683 @findex pre-commands annotation
34684 @findex commands annotation
34685 @findex post-commands annotation
34687 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
34688 command. The annotations are repeated for each command which is input.
34690 @findex pre-overload-choice annotation
34691 @findex overload-choice annotation
34692 @findex post-overload-choice annotation
34693 @item overload-choice
34694 When @value{GDBN} wants the user to select between various overloaded functions.
34696 @findex pre-query annotation
34697 @findex query annotation
34698 @findex post-query annotation
34700 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
34702 @findex pre-prompt-for-continue annotation
34703 @findex prompt-for-continue annotation
34704 @findex post-prompt-for-continue annotation
34705 @item prompt-for-continue
34706 When @value{GDBN} is asking the user to press return to continue. Note: Don't
34707 expect this to work well; instead use @code{set height 0} to disable
34708 prompting. This is because the counting of lines is buggy in the
34709 presence of annotations.
34714 @cindex annotations for errors, warnings and interrupts
34716 @findex quit annotation
34721 This annotation occurs right before @value{GDBN} responds to an interrupt.
34723 @findex error annotation
34728 This annotation occurs right before @value{GDBN} responds to an error.
34730 Quit and error annotations indicate that any annotations which @value{GDBN} was
34731 in the middle of may end abruptly. For example, if a
34732 @code{value-history-begin} annotation is followed by a @code{error}, one
34733 cannot expect to receive the matching @code{value-history-end}. One
34734 cannot expect not to receive it either, however; an error annotation
34735 does not necessarily mean that @value{GDBN} is immediately returning all the way
34738 @findex error-begin annotation
34739 A quit or error annotation may be preceded by
34745 Any output between that and the quit or error annotation is the error
34748 Warning messages are not yet annotated.
34749 @c If we want to change that, need to fix warning(), type_error(),
34750 @c range_error(), and possibly other places.
34753 @section Invalidation Notices
34755 @cindex annotations for invalidation messages
34756 The following annotations say that certain pieces of state may have
34760 @findex frames-invalid annotation
34761 @item ^Z^Zframes-invalid
34763 The frames (for example, output from the @code{backtrace} command) may
34766 @findex breakpoints-invalid annotation
34767 @item ^Z^Zbreakpoints-invalid
34769 The breakpoints may have changed. For example, the user just added or
34770 deleted a breakpoint.
34773 @node Annotations for Running
34774 @section Running the Program
34775 @cindex annotations for running programs
34777 @findex starting annotation
34778 @findex stopping annotation
34779 When the program starts executing due to a @value{GDBN} command such as
34780 @code{step} or @code{continue},
34786 is output. When the program stops,
34792 is output. Before the @code{stopped} annotation, a variety of
34793 annotations describe how the program stopped.
34796 @findex exited annotation
34797 @item ^Z^Zexited @var{exit-status}
34798 The program exited, and @var{exit-status} is the exit status (zero for
34799 successful exit, otherwise nonzero).
34801 @findex signalled annotation
34802 @findex signal-name annotation
34803 @findex signal-name-end annotation
34804 @findex signal-string annotation
34805 @findex signal-string-end annotation
34806 @item ^Z^Zsignalled
34807 The program exited with a signal. After the @code{^Z^Zsignalled}, the
34808 annotation continues:
34814 ^Z^Zsignal-name-end
34818 ^Z^Zsignal-string-end
34823 where @var{name} is the name of the signal, such as @code{SIGILL} or
34824 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34825 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
34826 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34827 user's benefit and have no particular format.
34829 @findex signal annotation
34831 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34832 just saying that the program received the signal, not that it was
34833 terminated with it.
34835 @findex breakpoint annotation
34836 @item ^Z^Zbreakpoint @var{number}
34837 The program hit breakpoint number @var{number}.
34839 @findex watchpoint annotation
34840 @item ^Z^Zwatchpoint @var{number}
34841 The program hit watchpoint number @var{number}.
34844 @node Source Annotations
34845 @section Displaying Source
34846 @cindex annotations for source display
34848 @findex source annotation
34849 The following annotation is used instead of displaying source code:
34852 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34855 where @var{filename} is an absolute file name indicating which source
34856 file, @var{line} is the line number within that file (where 1 is the
34857 first line in the file), @var{character} is the character position
34858 within the file (where 0 is the first character in the file) (for most
34859 debug formats this will necessarily point to the beginning of a line),
34860 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34861 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34862 @var{addr} is the address in the target program associated with the
34863 source which is being displayed. The @var{addr} is in the form @samp{0x}
34864 followed by one or more lowercase hex digits (note that this does not
34865 depend on the language).
34867 @node JIT Interface
34868 @chapter JIT Compilation Interface
34869 @cindex just-in-time compilation
34870 @cindex JIT compilation interface
34872 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34873 interface. A JIT compiler is a program or library that generates native
34874 executable code at runtime and executes it, usually in order to achieve good
34875 performance while maintaining platform independence.
34877 Programs that use JIT compilation are normally difficult to debug because
34878 portions of their code are generated at runtime, instead of being loaded from
34879 object files, which is where @value{GDBN} normally finds the program's symbols
34880 and debug information. In order to debug programs that use JIT compilation,
34881 @value{GDBN} has an interface that allows the program to register in-memory
34882 symbol files with @value{GDBN} at runtime.
34884 If you are using @value{GDBN} to debug a program that uses this interface, then
34885 it should work transparently so long as you have not stripped the binary. If
34886 you are developing a JIT compiler, then the interface is documented in the rest
34887 of this chapter. At this time, the only known client of this interface is the
34890 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34891 JIT compiler communicates with @value{GDBN} by writing data into a global
34892 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34893 attaches, it reads a linked list of symbol files from the global variable to
34894 find existing code, and puts a breakpoint in the function so that it can find
34895 out about additional code.
34898 * Declarations:: Relevant C struct declarations
34899 * Registering Code:: Steps to register code
34900 * Unregistering Code:: Steps to unregister code
34901 * Custom Debug Info:: Emit debug information in a custom format
34905 @section JIT Declarations
34907 These are the relevant struct declarations that a C program should include to
34908 implement the interface:
34918 struct jit_code_entry
34920 struct jit_code_entry *next_entry;
34921 struct jit_code_entry *prev_entry;
34922 const char *symfile_addr;
34923 uint64_t symfile_size;
34926 struct jit_descriptor
34929 /* This type should be jit_actions_t, but we use uint32_t
34930 to be explicit about the bitwidth. */
34931 uint32_t action_flag;
34932 struct jit_code_entry *relevant_entry;
34933 struct jit_code_entry *first_entry;
34936 /* GDB puts a breakpoint in this function. */
34937 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34939 /* Make sure to specify the version statically, because the
34940 debugger may check the version before we can set it. */
34941 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34944 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34945 modifications to this global data properly, which can easily be done by putting
34946 a global mutex around modifications to these structures.
34948 @node Registering Code
34949 @section Registering Code
34951 To register code with @value{GDBN}, the JIT should follow this protocol:
34955 Generate an object file in memory with symbols and other desired debug
34956 information. The file must include the virtual addresses of the sections.
34959 Create a code entry for the file, which gives the start and size of the symbol
34963 Add it to the linked list in the JIT descriptor.
34966 Point the relevant_entry field of the descriptor at the entry.
34969 Set @code{action_flag} to @code{JIT_REGISTER} and call
34970 @code{__jit_debug_register_code}.
34973 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34974 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34975 new code. However, the linked list must still be maintained in order to allow
34976 @value{GDBN} to attach to a running process and still find the symbol files.
34978 @node Unregistering Code
34979 @section Unregistering Code
34981 If code is freed, then the JIT should use the following protocol:
34985 Remove the code entry corresponding to the code from the linked list.
34988 Point the @code{relevant_entry} field of the descriptor at the code entry.
34991 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34992 @code{__jit_debug_register_code}.
34995 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34996 and the JIT will leak the memory used for the associated symbol files.
34998 @node Custom Debug Info
34999 @section Custom Debug Info
35000 @cindex custom JIT debug info
35001 @cindex JIT debug info reader
35003 Generating debug information in platform-native file formats (like ELF
35004 or COFF) may be an overkill for JIT compilers; especially if all the
35005 debug info is used for is displaying a meaningful backtrace. The
35006 issue can be resolved by having the JIT writers decide on a debug info
35007 format and also provide a reader that parses the debug info generated
35008 by the JIT compiler. This section gives a brief overview on writing
35009 such a parser. More specific details can be found in the source file
35010 @file{gdb/jit-reader.in}, which is also installed as a header at
35011 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35013 The reader is implemented as a shared object (so this functionality is
35014 not available on platforms which don't allow loading shared objects at
35015 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35016 @code{jit-reader-unload} are provided, to be used to load and unload
35017 the readers from a preconfigured directory. Once loaded, the shared
35018 object is used the parse the debug information emitted by the JIT
35022 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35023 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35026 @node Using JIT Debug Info Readers
35027 @subsection Using JIT Debug Info Readers
35028 @kindex jit-reader-load
35029 @kindex jit-reader-unload
35031 Readers can be loaded and unloaded using the @code{jit-reader-load}
35032 and @code{jit-reader-unload} commands.
35035 @item jit-reader-load @var{reader}
35036 Load the JIT reader named @var{reader}, which is a shared
35037 object specified as either an absolute or a relative file name. In
35038 the latter case, @value{GDBN} will try to load the reader from a
35039 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35040 system (here @var{libdir} is the system library directory, often
35041 @file{/usr/local/lib}).
35043 Only one reader can be active at a time; trying to load a second
35044 reader when one is already loaded will result in @value{GDBN}
35045 reporting an error. A new JIT reader can be loaded by first unloading
35046 the current one using @code{jit-reader-unload} and then invoking
35047 @code{jit-reader-load}.
35049 @item jit-reader-unload
35050 Unload the currently loaded JIT reader.
35054 @node Writing JIT Debug Info Readers
35055 @subsection Writing JIT Debug Info Readers
35056 @cindex writing JIT debug info readers
35058 As mentioned, a reader is essentially a shared object conforming to a
35059 certain ABI. This ABI is described in @file{jit-reader.h}.
35061 @file{jit-reader.h} defines the structures, macros and functions
35062 required to write a reader. It is installed (along with
35063 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35064 the system include directory.
35066 Readers need to be released under a GPL compatible license. A reader
35067 can be declared as released under such a license by placing the macro
35068 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35070 The entry point for readers is the symbol @code{gdb_init_reader},
35071 which is expected to be a function with the prototype
35073 @findex gdb_init_reader
35075 extern struct gdb_reader_funcs *gdb_init_reader (void);
35078 @cindex @code{struct gdb_reader_funcs}
35080 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35081 functions. These functions are executed to read the debug info
35082 generated by the JIT compiler (@code{read}), to unwind stack frames
35083 (@code{unwind}) and to create canonical frame IDs
35084 (@code{get_Frame_id}). It also has a callback that is called when the
35085 reader is being unloaded (@code{destroy}). The struct looks like this
35088 struct gdb_reader_funcs
35090 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35091 int reader_version;
35093 /* For use by the reader. */
35096 gdb_read_debug_info *read;
35097 gdb_unwind_frame *unwind;
35098 gdb_get_frame_id *get_frame_id;
35099 gdb_destroy_reader *destroy;
35103 @cindex @code{struct gdb_symbol_callbacks}
35104 @cindex @code{struct gdb_unwind_callbacks}
35106 The callbacks are provided with another set of callbacks by
35107 @value{GDBN} to do their job. For @code{read}, these callbacks are
35108 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35109 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35110 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35111 files and new symbol tables inside those object files. @code{struct
35112 gdb_unwind_callbacks} has callbacks to read registers off the current
35113 frame and to write out the values of the registers in the previous
35114 frame. Both have a callback (@code{target_read}) to read bytes off the
35115 target's address space.
35117 @node In-Process Agent
35118 @chapter In-Process Agent
35119 @cindex debugging agent
35120 The traditional debugging model is conceptually low-speed, but works fine,
35121 because most bugs can be reproduced in debugging-mode execution. However,
35122 as multi-core or many-core processors are becoming mainstream, and
35123 multi-threaded programs become more and more popular, there should be more
35124 and more bugs that only manifest themselves at normal-mode execution, for
35125 example, thread races, because debugger's interference with the program's
35126 timing may conceal the bugs. On the other hand, in some applications,
35127 it is not feasible for the debugger to interrupt the program's execution
35128 long enough for the developer to learn anything helpful about its behavior.
35129 If the program's correctness depends on its real-time behavior, delays
35130 introduced by a debugger might cause the program to fail, even when the
35131 code itself is correct. It is useful to be able to observe the program's
35132 behavior without interrupting it.
35134 Therefore, traditional debugging model is too intrusive to reproduce
35135 some bugs. In order to reduce the interference with the program, we can
35136 reduce the number of operations performed by debugger. The
35137 @dfn{In-Process Agent}, a shared library, is running within the same
35138 process with inferior, and is able to perform some debugging operations
35139 itself. As a result, debugger is only involved when necessary, and
35140 performance of debugging can be improved accordingly. Note that
35141 interference with program can be reduced but can't be removed completely,
35142 because the in-process agent will still stop or slow down the program.
35144 The in-process agent can interpret and execute Agent Expressions
35145 (@pxref{Agent Expressions}) during performing debugging operations. The
35146 agent expressions can be used for different purposes, such as collecting
35147 data in tracepoints, and condition evaluation in breakpoints.
35149 @anchor{Control Agent}
35150 You can control whether the in-process agent is used as an aid for
35151 debugging with the following commands:
35154 @kindex set agent on
35156 Causes the in-process agent to perform some operations on behalf of the
35157 debugger. Just which operations requested by the user will be done
35158 by the in-process agent depends on the its capabilities. For example,
35159 if you request to evaluate breakpoint conditions in the in-process agent,
35160 and the in-process agent has such capability as well, then breakpoint
35161 conditions will be evaluated in the in-process agent.
35163 @kindex set agent off
35164 @item set agent off
35165 Disables execution of debugging operations by the in-process agent. All
35166 of the operations will be performed by @value{GDBN}.
35170 Display the current setting of execution of debugging operations by
35171 the in-process agent.
35175 * In-Process Agent Protocol::
35178 @node In-Process Agent Protocol
35179 @section In-Process Agent Protocol
35180 @cindex in-process agent protocol
35182 The in-process agent is able to communicate with both @value{GDBN} and
35183 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35184 used for communications between @value{GDBN} or GDBserver and the IPA.
35185 In general, @value{GDBN} or GDBserver sends commands
35186 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35187 in-process agent replies back with the return result of the command, or
35188 some other information. The data sent to in-process agent is composed
35189 of primitive data types, such as 4-byte or 8-byte type, and composite
35190 types, which are called objects (@pxref{IPA Protocol Objects}).
35193 * IPA Protocol Objects::
35194 * IPA Protocol Commands::
35197 @node IPA Protocol Objects
35198 @subsection IPA Protocol Objects
35199 @cindex ipa protocol objects
35201 The commands sent to and results received from agent may contain some
35202 complex data types called @dfn{objects}.
35204 The in-process agent is running on the same machine with @value{GDBN}
35205 or GDBserver, so it doesn't have to handle as much differences between
35206 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35207 However, there are still some differences of two ends in two processes:
35211 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35212 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35214 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35215 GDBserver is compiled with one, and in-process agent is compiled with
35219 Here are the IPA Protocol Objects:
35223 agent expression object. It represents an agent expression
35224 (@pxref{Agent Expressions}).
35225 @anchor{agent expression object}
35227 tracepoint action object. It represents a tracepoint action
35228 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35229 memory, static trace data and to evaluate expression.
35230 @anchor{tracepoint action object}
35232 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35233 @anchor{tracepoint object}
35237 The following table describes important attributes of each IPA protocol
35240 @multitable @columnfractions .30 .20 .50
35241 @headitem Name @tab Size @tab Description
35242 @item @emph{agent expression object} @tab @tab
35243 @item length @tab 4 @tab length of bytes code
35244 @item byte code @tab @var{length} @tab contents of byte code
35245 @item @emph{tracepoint action for collecting memory} @tab @tab
35246 @item 'M' @tab 1 @tab type of tracepoint action
35247 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35248 address of the lowest byte to collect, otherwise @var{addr} is the offset
35249 of @var{basereg} for memory collecting.
35250 @item len @tab 8 @tab length of memory for collecting
35251 @item basereg @tab 4 @tab the register number containing the starting
35252 memory address for collecting.
35253 @item @emph{tracepoint action for collecting registers} @tab @tab
35254 @item 'R' @tab 1 @tab type of tracepoint action
35255 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35256 @item 'L' @tab 1 @tab type of tracepoint action
35257 @item @emph{tracepoint action for expression evaluation} @tab @tab
35258 @item 'X' @tab 1 @tab type of tracepoint action
35259 @item agent expression @tab length of @tab @ref{agent expression object}
35260 @item @emph{tracepoint object} @tab @tab
35261 @item number @tab 4 @tab number of tracepoint
35262 @item address @tab 8 @tab address of tracepoint inserted on
35263 @item type @tab 4 @tab type of tracepoint
35264 @item enabled @tab 1 @tab enable or disable of tracepoint
35265 @item step_count @tab 8 @tab step
35266 @item pass_count @tab 8 @tab pass
35267 @item numactions @tab 4 @tab number of tracepoint actions
35268 @item hit count @tab 8 @tab hit count
35269 @item trace frame usage @tab 8 @tab trace frame usage
35270 @item compiled_cond @tab 8 @tab compiled condition
35271 @item orig_size @tab 8 @tab orig size
35272 @item condition @tab 4 if condition is NULL otherwise length of
35273 @ref{agent expression object}
35274 @tab zero if condition is NULL, otherwise is
35275 @ref{agent expression object}
35276 @item actions @tab variable
35277 @tab numactions number of @ref{tracepoint action object}
35280 @node IPA Protocol Commands
35281 @subsection IPA Protocol Commands
35282 @cindex ipa protocol commands
35284 The spaces in each command are delimiters to ease reading this commands
35285 specification. They don't exist in real commands.
35289 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35290 Installs a new fast tracepoint described by @var{tracepoint_object}
35291 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
35292 head of @dfn{jumppad}, which is used to jump to data collection routine
35297 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35298 @var{target_address} is address of tracepoint in the inferior.
35299 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35300 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35301 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
35302 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35309 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35310 is about to kill inferiors.
35318 @item probe_marker_at:@var{address}
35319 Asks in-process agent to probe the marker at @var{address}.
35326 @item unprobe_marker_at:@var{address}
35327 Asks in-process agent to unprobe the marker at @var{address}.
35331 @chapter Reporting Bugs in @value{GDBN}
35332 @cindex bugs in @value{GDBN}
35333 @cindex reporting bugs in @value{GDBN}
35335 Your bug reports play an essential role in making @value{GDBN} reliable.
35337 Reporting a bug may help you by bringing a solution to your problem, or it
35338 may not. But in any case the principal function of a bug report is to help
35339 the entire community by making the next version of @value{GDBN} work better. Bug
35340 reports are your contribution to the maintenance of @value{GDBN}.
35342 In order for a bug report to serve its purpose, you must include the
35343 information that enables us to fix the bug.
35346 * Bug Criteria:: Have you found a bug?
35347 * Bug Reporting:: How to report bugs
35351 @section Have You Found a Bug?
35352 @cindex bug criteria
35354 If you are not sure whether you have found a bug, here are some guidelines:
35357 @cindex fatal signal
35358 @cindex debugger crash
35359 @cindex crash of debugger
35361 If the debugger gets a fatal signal, for any input whatever, that is a
35362 @value{GDBN} bug. Reliable debuggers never crash.
35364 @cindex error on valid input
35366 If @value{GDBN} produces an error message for valid input, that is a
35367 bug. (Note that if you're cross debugging, the problem may also be
35368 somewhere in the connection to the target.)
35370 @cindex invalid input
35372 If @value{GDBN} does not produce an error message for invalid input,
35373 that is a bug. However, you should note that your idea of
35374 ``invalid input'' might be our idea of ``an extension'' or ``support
35375 for traditional practice''.
35378 If you are an experienced user of debugging tools, your suggestions
35379 for improvement of @value{GDBN} are welcome in any case.
35382 @node Bug Reporting
35383 @section How to Report Bugs
35384 @cindex bug reports
35385 @cindex @value{GDBN} bugs, reporting
35387 A number of companies and individuals offer support for @sc{gnu} products.
35388 If you obtained @value{GDBN} from a support organization, we recommend you
35389 contact that organization first.
35391 You can find contact information for many support companies and
35392 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35394 @c should add a web page ref...
35397 @ifset BUGURL_DEFAULT
35398 In any event, we also recommend that you submit bug reports for
35399 @value{GDBN}. The preferred method is to submit them directly using
35400 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35401 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35404 @strong{Do not send bug reports to @samp{info-gdb}, or to
35405 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35406 not want to receive bug reports. Those that do have arranged to receive
35409 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35410 serves as a repeater. The mailing list and the newsgroup carry exactly
35411 the same messages. Often people think of posting bug reports to the
35412 newsgroup instead of mailing them. This appears to work, but it has one
35413 problem which can be crucial: a newsgroup posting often lacks a mail
35414 path back to the sender. Thus, if we need to ask for more information,
35415 we may be unable to reach you. For this reason, it is better to send
35416 bug reports to the mailing list.
35418 @ifclear BUGURL_DEFAULT
35419 In any event, we also recommend that you submit bug reports for
35420 @value{GDBN} to @value{BUGURL}.
35424 The fundamental principle of reporting bugs usefully is this:
35425 @strong{report all the facts}. If you are not sure whether to state a
35426 fact or leave it out, state it!
35428 Often people omit facts because they think they know what causes the
35429 problem and assume that some details do not matter. Thus, you might
35430 assume that the name of the variable you use in an example does not matter.
35431 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35432 stray memory reference which happens to fetch from the location where that
35433 name is stored in memory; perhaps, if the name were different, the contents
35434 of that location would fool the debugger into doing the right thing despite
35435 the bug. Play it safe and give a specific, complete example. That is the
35436 easiest thing for you to do, and the most helpful.
35438 Keep in mind that the purpose of a bug report is to enable us to fix the
35439 bug. It may be that the bug has been reported previously, but neither
35440 you nor we can know that unless your bug report is complete and
35443 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35444 bell?'' Those bug reports are useless, and we urge everyone to
35445 @emph{refuse to respond to them} except to chide the sender to report
35448 To enable us to fix the bug, you should include all these things:
35452 The version of @value{GDBN}. @value{GDBN} announces it if you start
35453 with no arguments; you can also print it at any time using @code{show
35456 Without this, we will not know whether there is any point in looking for
35457 the bug in the current version of @value{GDBN}.
35460 The type of machine you are using, and the operating system name and
35464 The details of the @value{GDBN} build-time configuration.
35465 @value{GDBN} shows these details if you invoke it with the
35466 @option{--configuration} command-line option, or if you type
35467 @code{show configuration} at @value{GDBN}'s prompt.
35470 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35471 ``@value{GCC}--2.8.1''.
35474 What compiler (and its version) was used to compile the program you are
35475 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35476 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35477 to get this information; for other compilers, see the documentation for
35481 The command arguments you gave the compiler to compile your example and
35482 observe the bug. For example, did you use @samp{-O}? To guarantee
35483 you will not omit something important, list them all. A copy of the
35484 Makefile (or the output from make) is sufficient.
35486 If we were to try to guess the arguments, we would probably guess wrong
35487 and then we might not encounter the bug.
35490 A complete input script, and all necessary source files, that will
35494 A description of what behavior you observe that you believe is
35495 incorrect. For example, ``It gets a fatal signal.''
35497 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35498 will certainly notice it. But if the bug is incorrect output, we might
35499 not notice unless it is glaringly wrong. You might as well not give us
35500 a chance to make a mistake.
35502 Even if the problem you experience is a fatal signal, you should still
35503 say so explicitly. Suppose something strange is going on, such as, your
35504 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35505 the C library on your system. (This has happened!) Your copy might
35506 crash and ours would not. If you told us to expect a crash, then when
35507 ours fails to crash, we would know that the bug was not happening for
35508 us. If you had not told us to expect a crash, then we would not be able
35509 to draw any conclusion from our observations.
35512 @cindex recording a session script
35513 To collect all this information, you can use a session recording program
35514 such as @command{script}, which is available on many Unix systems.
35515 Just run your @value{GDBN} session inside @command{script} and then
35516 include the @file{typescript} file with your bug report.
35518 Another way to record a @value{GDBN} session is to run @value{GDBN}
35519 inside Emacs and then save the entire buffer to a file.
35522 If you wish to suggest changes to the @value{GDBN} source, send us context
35523 diffs. If you even discuss something in the @value{GDBN} source, refer to
35524 it by context, not by line number.
35526 The line numbers in our development sources will not match those in your
35527 sources. Your line numbers would convey no useful information to us.
35531 Here are some things that are not necessary:
35535 A description of the envelope of the bug.
35537 Often people who encounter a bug spend a lot of time investigating
35538 which changes to the input file will make the bug go away and which
35539 changes will not affect it.
35541 This is often time consuming and not very useful, because the way we
35542 will find the bug is by running a single example under the debugger
35543 with breakpoints, not by pure deduction from a series of examples.
35544 We recommend that you save your time for something else.
35546 Of course, if you can find a simpler example to report @emph{instead}
35547 of the original one, that is a convenience for us. Errors in the
35548 output will be easier to spot, running under the debugger will take
35549 less time, and so on.
35551 However, simplification is not vital; if you do not want to do this,
35552 report the bug anyway and send us the entire test case you used.
35555 A patch for the bug.
35557 A patch for the bug does help us if it is a good one. But do not omit
35558 the necessary information, such as the test case, on the assumption that
35559 a patch is all we need. We might see problems with your patch and decide
35560 to fix the problem another way, or we might not understand it at all.
35562 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35563 construct an example that will make the program follow a certain path
35564 through the code. If you do not send us the example, we will not be able
35565 to construct one, so we will not be able to verify that the bug is fixed.
35567 And if we cannot understand what bug you are trying to fix, or why your
35568 patch should be an improvement, we will not install it. A test case will
35569 help us to understand.
35572 A guess about what the bug is or what it depends on.
35574 Such guesses are usually wrong. Even we cannot guess right about such
35575 things without first using the debugger to find the facts.
35578 @c The readline documentation is distributed with the readline code
35579 @c and consists of the two following files:
35582 @c Use -I with makeinfo to point to the appropriate directory,
35583 @c environment var TEXINPUTS with TeX.
35584 @ifclear SYSTEM_READLINE
35585 @include rluser.texi
35586 @include hsuser.texi
35590 @appendix In Memoriam
35592 The @value{GDBN} project mourns the loss of the following long-time
35597 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35598 to Free Software in general. Outside of @value{GDBN}, he was known in
35599 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35601 @item Michael Snyder
35602 Michael was one of the Global Maintainers of the @value{GDBN} project,
35603 with contributions recorded as early as 1996, until 2011. In addition
35604 to his day to day participation, he was a large driving force behind
35605 adding Reverse Debugging to @value{GDBN}.
35608 Beyond their technical contributions to the project, they were also
35609 enjoyable members of the Free Software Community. We will miss them.
35611 @node Formatting Documentation
35612 @appendix Formatting Documentation
35614 @cindex @value{GDBN} reference card
35615 @cindex reference card
35616 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35617 for printing with PostScript or Ghostscript, in the @file{gdb}
35618 subdirectory of the main source directory@footnote{In
35619 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35620 release.}. If you can use PostScript or Ghostscript with your printer,
35621 you can print the reference card immediately with @file{refcard.ps}.
35623 The release also includes the source for the reference card. You
35624 can format it, using @TeX{}, by typing:
35630 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35631 mode on US ``letter'' size paper;
35632 that is, on a sheet 11 inches wide by 8.5 inches
35633 high. You will need to specify this form of printing as an option to
35634 your @sc{dvi} output program.
35636 @cindex documentation
35638 All the documentation for @value{GDBN} comes as part of the machine-readable
35639 distribution. The documentation is written in Texinfo format, which is
35640 a documentation system that uses a single source file to produce both
35641 on-line information and a printed manual. You can use one of the Info
35642 formatting commands to create the on-line version of the documentation
35643 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
35645 @value{GDBN} includes an already formatted copy of the on-line Info
35646 version of this manual in the @file{gdb} subdirectory. The main Info
35647 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
35648 subordinate files matching @samp{gdb.info*} in the same directory. If
35649 necessary, you can print out these files, or read them with any editor;
35650 but they are easier to read using the @code{info} subsystem in @sc{gnu}
35651 Emacs or the standalone @code{info} program, available as part of the
35652 @sc{gnu} Texinfo distribution.
35654 If you want to format these Info files yourself, you need one of the
35655 Info formatting programs, such as @code{texinfo-format-buffer} or
35658 If you have @code{makeinfo} installed, and are in the top level
35659 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
35660 version @value{GDBVN}), you can make the Info file by typing:
35667 If you want to typeset and print copies of this manual, you need @TeX{},
35668 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
35669 Texinfo definitions file.
35671 @TeX{} is a typesetting program; it does not print files directly, but
35672 produces output files called @sc{dvi} files. To print a typeset
35673 document, you need a program to print @sc{dvi} files. If your system
35674 has @TeX{} installed, chances are it has such a program. The precise
35675 command to use depends on your system; @kbd{lpr -d} is common; another
35676 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
35677 require a file name without any extension or a @samp{.dvi} extension.
35679 @TeX{} also requires a macro definitions file called
35680 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
35681 written in Texinfo format. On its own, @TeX{} cannot either read or
35682 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
35683 and is located in the @file{gdb-@var{version-number}/texinfo}
35686 If you have @TeX{} and a @sc{dvi} printer program installed, you can
35687 typeset and print this manual. First switch to the @file{gdb}
35688 subdirectory of the main source directory (for example, to
35689 @file{gdb-@value{GDBVN}/gdb}) and type:
35695 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
35697 @node Installing GDB
35698 @appendix Installing @value{GDBN}
35699 @cindex installation
35702 * Requirements:: Requirements for building @value{GDBN}
35703 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
35704 * Separate Objdir:: Compiling @value{GDBN} in another directory
35705 * Config Names:: Specifying names for hosts and targets
35706 * Configure Options:: Summary of options for configure
35707 * System-wide configuration:: Having a system-wide init file
35711 @section Requirements for Building @value{GDBN}
35712 @cindex building @value{GDBN}, requirements for
35714 Building @value{GDBN} requires various tools and packages to be available.
35715 Other packages will be used only if they are found.
35717 @heading Tools/Packages Necessary for Building @value{GDBN}
35719 @item C@t{++}11 compiler
35720 @value{GDBN} is written in C@t{++}11. It should be buildable with any
35721 recent C@t{++}11 compiler, e.g.@: GCC.
35724 @value{GDBN}'s build system relies on features only found in the GNU
35725 make program. Other variants of @code{make} will not work.
35728 @heading Tools/Packages Optional for Building @value{GDBN}
35732 @value{GDBN} can use the Expat XML parsing library. This library may be
35733 included with your operating system distribution; if it is not, you
35734 can get the latest version from @url{http://expat.sourceforge.net}.
35735 The @file{configure} script will search for this library in several
35736 standard locations; if it is installed in an unusual path, you can
35737 use the @option{--with-libexpat-prefix} option to specify its location.
35743 Remote protocol memory maps (@pxref{Memory Map Format})
35745 Target descriptions (@pxref{Target Descriptions})
35747 Remote shared library lists (@xref{Library List Format},
35748 or alternatively @pxref{Library List Format for SVR4 Targets})
35750 MS-Windows shared libraries (@pxref{Shared Libraries})
35752 Traceframe info (@pxref{Traceframe Info Format})
35754 Branch trace (@pxref{Branch Trace Format},
35755 @pxref{Branch Trace Configuration Format})
35759 @value{GDBN} can be scripted using GNU Guile. @xref{Guile}. By
35760 default, @value{GDBN} will be compiled if the Guile libraries are
35761 installed and are found by @file{configure}. You can use the
35762 @code{--with-guile} option to request Guile, and pass either the Guile
35763 version number or the file name of the relevant @code{pkg-config}
35764 program to choose a particular version of Guile.
35767 @value{GDBN}'s features related to character sets (@pxref{Character
35768 Sets}) require a functioning @code{iconv} implementation. If you are
35769 on a GNU system, then this is provided by the GNU C Library. Some
35770 other systems also provide a working @code{iconv}.
35772 If @value{GDBN} is using the @code{iconv} program which is installed
35773 in a non-standard place, you will need to tell @value{GDBN} where to
35774 find it. This is done with @option{--with-iconv-bin} which specifies
35775 the directory that contains the @code{iconv} program. This program is
35776 run in order to make a list of the available character sets.
35778 On systems without @code{iconv}, you can install GNU Libiconv. If
35779 Libiconv is installed in a standard place, @value{GDBN} will
35780 automatically use it if it is needed. If you have previously
35781 installed Libiconv in a non-standard place, you can use the
35782 @option{--with-libiconv-prefix} option to @file{configure}.
35784 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
35785 arrange to build Libiconv if a directory named @file{libiconv} appears
35786 in the top-most source directory. If Libiconv is built this way, and
35787 if the operating system does not provide a suitable @code{iconv}
35788 implementation, then the just-built library will automatically be used
35789 by @value{GDBN}. One easy way to set this up is to download GNU
35790 Libiconv, unpack it inside the top-level directory of the @value{GDBN}
35791 source tree, and then rename the directory holding the Libiconv source
35792 code to @samp{libiconv}.
35795 @value{GDBN} can support debugging sections that are compressed with
35796 the LZMA library. @xref{MiniDebugInfo}. If this library is not
35797 included with your operating system, you can find it in the xz package
35798 at @url{http://tukaani.org/xz/}. If the LZMA library is available in
35799 the usual place, then the @file{configure} script will use it
35800 automatically. If it is installed in an unusual path, you can use the
35801 @option{--with-lzma-prefix} option to specify its location.
35805 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
35806 library. This library may be included with your operating system
35807 distribution; if it is not, you can get the latest version from
35808 @url{http://www.mpfr.org}. The @file{configure} script will search
35809 for this library in several standard locations; if it is installed
35810 in an unusual path, you can use the @option{--with-libmpfr-prefix}
35811 option to specify its location.
35813 GNU MPFR is used to emulate target floating-point arithmetic during
35814 expression evaluation when the target uses different floating-point
35815 formats than the host. If GNU MPFR it is not available, @value{GDBN}
35816 will fall back to using host floating-point arithmetic.
35819 @value{GDBN} can be scripted using Python language. @xref{Python}.
35820 By default, @value{GDBN} will be compiled if the Python libraries are
35821 installed and are found by @file{configure}. You can use the
35822 @code{--with-python} option to request Python, and pass either the
35823 file name of the relevant @code{python} executable, or the name of the
35824 directory in which Python is installed, to choose a particular
35825 installation of Python.
35828 @cindex compressed debug sections
35829 @value{GDBN} will use the @samp{zlib} library, if available, to read
35830 compressed debug sections. Some linkers, such as GNU gold, are capable
35831 of producing binaries with compressed debug sections. If @value{GDBN}
35832 is compiled with @samp{zlib}, it will be able to read the debug
35833 information in such binaries.
35835 The @samp{zlib} library is likely included with your operating system
35836 distribution; if it is not, you can get the latest version from
35837 @url{http://zlib.net}.
35840 @node Running Configure
35841 @section Invoking the @value{GDBN} @file{configure} Script
35842 @cindex configuring @value{GDBN}
35843 @value{GDBN} comes with a @file{configure} script that automates the process
35844 of preparing @value{GDBN} for installation; you can then use @code{make} to
35845 build the @code{gdb} program.
35847 @c irrelevant in info file; it's as current as the code it lives with.
35848 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
35849 look at the @file{README} file in the sources; we may have improved the
35850 installation procedures since publishing this manual.}
35853 The @value{GDBN} distribution includes all the source code you need for
35854 @value{GDBN} in a single directory, whose name is usually composed by
35855 appending the version number to @samp{gdb}.
35857 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
35858 @file{gdb-@value{GDBVN}} directory. That directory contains:
35861 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
35862 script for configuring @value{GDBN} and all its supporting libraries
35864 @item gdb-@value{GDBVN}/gdb
35865 the source specific to @value{GDBN} itself
35867 @item gdb-@value{GDBVN}/bfd
35868 source for the Binary File Descriptor library
35870 @item gdb-@value{GDBVN}/include
35871 @sc{gnu} include files
35873 @item gdb-@value{GDBVN}/libiberty
35874 source for the @samp{-liberty} free software library
35876 @item gdb-@value{GDBVN}/opcodes
35877 source for the library of opcode tables and disassemblers
35879 @item gdb-@value{GDBVN}/readline
35880 source for the @sc{gnu} command-line interface
35883 There may be other subdirectories as well.
35885 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35886 from the @file{gdb-@var{version-number}} source directory, which in
35887 this example is the @file{gdb-@value{GDBVN}} directory.
35889 First switch to the @file{gdb-@var{version-number}} source directory
35890 if you are not already in it; then run @file{configure}. Pass the
35891 identifier for the platform on which @value{GDBN} will run as an
35897 cd gdb-@value{GDBVN}
35902 Running @samp{configure} and then running @code{make} builds the
35903 included supporting libraries, then @code{gdb} itself. The configured
35904 source files, and the binaries, are left in the corresponding source
35908 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35909 system does not recognize this automatically when you run a different
35910 shell, you may need to run @code{sh} on it explicitly:
35916 You should run the @file{configure} script from the top directory in the
35917 source tree, the @file{gdb-@var{version-number}} directory. If you run
35918 @file{configure} from one of the subdirectories, you will configure only
35919 that subdirectory. That is usually not what you want. In particular,
35920 if you run the first @file{configure} from the @file{gdb} subdirectory
35921 of the @file{gdb-@var{version-number}} directory, you will omit the
35922 configuration of @file{bfd}, @file{readline}, and other sibling
35923 directories of the @file{gdb} subdirectory. This leads to build errors
35924 about missing include files such as @file{bfd/bfd.h}.
35926 You can install @code{@value{GDBN}} anywhere. The best way to do this
35927 is to pass the @code{--prefix} option to @code{configure}, and then
35928 install it with @code{make install}.
35930 @node Separate Objdir
35931 @section Compiling @value{GDBN} in Another Directory
35933 If you want to run @value{GDBN} versions for several host or target machines,
35934 you need a different @code{gdb} compiled for each combination of
35935 host and target. @file{configure} is designed to make this easy by
35936 allowing you to generate each configuration in a separate subdirectory,
35937 rather than in the source directory. If your @code{make} program
35938 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35939 @code{make} in each of these directories builds the @code{gdb}
35940 program specified there.
35942 To build @code{gdb} in a separate directory, run @file{configure}
35943 with the @samp{--srcdir} option to specify where to find the source.
35944 (You also need to specify a path to find @file{configure}
35945 itself from your working directory. If the path to @file{configure}
35946 would be the same as the argument to @samp{--srcdir}, you can leave out
35947 the @samp{--srcdir} option; it is assumed.)
35949 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35950 separate directory for a Sun 4 like this:
35954 cd gdb-@value{GDBVN}
35957 ../gdb-@value{GDBVN}/configure
35962 When @file{configure} builds a configuration using a remote source
35963 directory, it creates a tree for the binaries with the same structure
35964 (and using the same names) as the tree under the source directory. In
35965 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35966 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35967 @file{gdb-sun4/gdb}.
35969 Make sure that your path to the @file{configure} script has just one
35970 instance of @file{gdb} in it. If your path to @file{configure} looks
35971 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35972 one subdirectory of @value{GDBN}, not the whole package. This leads to
35973 build errors about missing include files such as @file{bfd/bfd.h}.
35975 One popular reason to build several @value{GDBN} configurations in separate
35976 directories is to configure @value{GDBN} for cross-compiling (where
35977 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35978 programs that run on another machine---the @dfn{target}).
35979 You specify a cross-debugging target by
35980 giving the @samp{--target=@var{target}} option to @file{configure}.
35982 When you run @code{make} to build a program or library, you must run
35983 it in a configured directory---whatever directory you were in when you
35984 called @file{configure} (or one of its subdirectories).
35986 The @code{Makefile} that @file{configure} generates in each source
35987 directory also runs recursively. If you type @code{make} in a source
35988 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35989 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35990 will build all the required libraries, and then build GDB.
35992 When you have multiple hosts or targets configured in separate
35993 directories, you can run @code{make} on them in parallel (for example,
35994 if they are NFS-mounted on each of the hosts); they will not interfere
35998 @section Specifying Names for Hosts and Targets
36000 The specifications used for hosts and targets in the @file{configure}
36001 script are based on a three-part naming scheme, but some short predefined
36002 aliases are also supported. The full naming scheme encodes three pieces
36003 of information in the following pattern:
36006 @var{architecture}-@var{vendor}-@var{os}
36009 For example, you can use the alias @code{sun4} as a @var{host} argument,
36010 or as the value for @var{target} in a @code{--target=@var{target}}
36011 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36013 The @file{configure} script accompanying @value{GDBN} does not provide
36014 any query facility to list all supported host and target names or
36015 aliases. @file{configure} calls the Bourne shell script
36016 @code{config.sub} to map abbreviations to full names; you can read the
36017 script, if you wish, or you can use it to test your guesses on
36018 abbreviations---for example:
36021 % sh config.sub i386-linux
36023 % sh config.sub alpha-linux
36024 alpha-unknown-linux-gnu
36025 % sh config.sub hp9k700
36027 % sh config.sub sun4
36028 sparc-sun-sunos4.1.1
36029 % sh config.sub sun3
36030 m68k-sun-sunos4.1.1
36031 % sh config.sub i986v
36032 Invalid configuration `i986v': machine `i986v' not recognized
36036 @code{config.sub} is also distributed in the @value{GDBN} source
36037 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36039 @node Configure Options
36040 @section @file{configure} Options
36042 Here is a summary of the @file{configure} options and arguments that
36043 are most often useful for building @value{GDBN}. @file{configure}
36044 also has several other options not listed here. @inforef{Running
36045 configure scripts,,autoconf.info}, for a full
36046 explanation of @file{configure}.
36049 configure @r{[}--help@r{]}
36050 @r{[}--prefix=@var{dir}@r{]}
36051 @r{[}--exec-prefix=@var{dir}@r{]}
36052 @r{[}--srcdir=@var{dirname}@r{]}
36053 @r{[}--target=@var{target}@r{]}
36057 You may introduce options with a single @samp{-} rather than
36058 @samp{--} if you prefer; but you may abbreviate option names if you use
36063 Display a quick summary of how to invoke @file{configure}.
36065 @item --prefix=@var{dir}
36066 Configure the source to install programs and files under directory
36069 @item --exec-prefix=@var{dir}
36070 Configure the source to install programs under directory
36073 @c avoid splitting the warning from the explanation:
36075 @item --srcdir=@var{dirname}
36076 Use this option to make configurations in directories separate from the
36077 @value{GDBN} source directories. Among other things, you can use this to
36078 build (or maintain) several configurations simultaneously, in separate
36079 directories. @file{configure} writes configuration-specific files in
36080 the current directory, but arranges for them to use the source in the
36081 directory @var{dirname}. @file{configure} creates directories under
36082 the working directory in parallel to the source directories below
36085 @item --target=@var{target}
36086 Configure @value{GDBN} for cross-debugging programs running on the specified
36087 @var{target}. Without this option, @value{GDBN} is configured to debug
36088 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36090 There is no convenient way to generate a list of all available
36091 targets. Also see the @code{--enable-targets} option, below.
36094 There are many other options that are specific to @value{GDBN}. This
36095 lists just the most common ones; there are some very specialized
36096 options not described here.
36099 @item --enable-targets=@r{[}@var{target}@r{]}@dots{}
36100 @itemx --enable-targets=all
36101 Configure @value{GDBN} for cross-debugging programs running on the
36102 specified list of targets. The special value @samp{all} configures
36103 @value{GDBN} for debugging programs running on any target it supports.
36105 @item --with-gdb-datadir=@var{path}
36106 Set the @value{GDBN}-specific data directory. @value{GDBN} will look
36107 here for certain supporting files or scripts. This defaults to the
36108 @file{gdb} subdirectory of @samp{datadi} (which can be set using
36111 @item --with-relocated-sources=@var{dir}
36112 Sets up the default source path substitution rule so that directory
36113 names recorded in debug information will be automatically adjusted for
36114 any directory under @var{dir}. @var{dir} should be a subdirectory of
36115 @value{GDBN}'s configured prefix, the one mentioned in the
36116 @code{--prefix} or @code{--exec-prefix} options to configure. This
36117 option is useful if GDB is supposed to be moved to a different place
36120 @item --enable-64-bit-bfd
36121 Enable 64-bit support in BFD on 32-bit hosts.
36123 @item --disable-gdbmi
36124 Build @value{GDBN} without the GDB/MI machine interface
36128 Build @value{GDBN} with the text-mode full-screen user interface
36129 (TUI). Requires a curses library (ncurses and cursesX are also
36132 @item --with-curses
36133 Use the curses library instead of the termcap library, for text-mode
36134 terminal operations.
36136 @item --with-libunwind-ia64
36137 Use the libunwind library for unwinding function call stack on ia64
36138 target platforms. See http://www.nongnu.org/libunwind/index.html for
36141 @item --with-system-readline
36142 Use the readline library installed on the host, rather than the
36143 library supplied as part of @value{GDBN}.
36145 @item --with-system-zlib
36146 Use the zlib library installed on the host, rather than the library
36147 supplied as part of @value{GDBN}.
36150 Build @value{GDBN} with Expat, a library for XML parsing. (Done by
36151 default if libexpat is installed and found at configure time.) This
36152 library is used to read XML files supplied with @value{GDBN}. If it
36153 is unavailable, some features, such as remote protocol memory maps,
36154 target descriptions, and shared library lists, that are based on XML
36155 files, will not be available in @value{GDBN}. If your host does not
36156 have libexpat installed, you can get the latest version from
36157 `http://expat.sourceforge.net'.
36159 @item --with-libiconv-prefix@r{[}=@var{dir}@r{]}
36161 Build @value{GDBN} with GNU libiconv, a character set encoding
36162 conversion library. This is not done by default, as on GNU systems
36163 the @code{iconv} that is built in to the C library is sufficient. If
36164 your host does not have a working @code{iconv}, you can get the latest
36165 version of GNU iconv from `https://www.gnu.org/software/libiconv/'.
36167 @value{GDBN}'s build system also supports building GNU libiconv as
36168 part of the overall build. @xref{Requirements}.
36171 Build @value{GDBN} with LZMA, a compression library. (Done by default
36172 if liblzma is installed and found at configure time.) LZMA is used by
36173 @value{GDBN}'s "mini debuginfo" feature, which is only useful on
36174 platforms using the ELF object file format. If your host does not
36175 have liblzma installed, you can get the latest version from
36176 `https://tukaani.org/xz/'.
36179 Build @value{GDBN} with GNU MPFR, a library for multiple-precision
36180 floating-point computation with correct rounding. (Done by default if
36181 GNU MPFR is installed and found at configure time.) This library is
36182 used to emulate target floating-point arithmetic during expression
36183 evaluation when the target uses different floating-point formats than
36184 the host. If GNU MPFR is not available, @value{GDBN} will fall back
36185 to using host floating-point arithmetic. If your host does not have
36186 GNU MPFR installed, you can get the latest version from
36187 `http://www.mpfr.org'.
36189 @item --with-python@r{[}=@var{python}@r{]}
36190 Build @value{GDBN} with Python scripting support. (Done by default if
36191 libpython is present and found at configure time.) Python makes
36192 @value{GDBN} scripting much more powerful than the restricted CLI
36193 scripting language. If your host does not have Python installed, you
36194 can find it on `http://www.python.org/download/'. The oldest version
36195 of Python supported by GDB is 2.6. The optional argument @var{python}
36196 is used to find the Python headers and libraries. It can be either
36197 the name of a Python executable, or the name of the directory in which
36198 Python is installed.
36200 @item --with-guile[=GUILE]'
36201 Build @value{GDBN} with GNU Guile scripting support. (Done by default
36202 if libguile is present and found at configure time.) If your host
36203 does not have Guile installed, you can find it at
36204 `https://www.gnu.org/software/guile/'. The optional argument GUILE
36205 can be a version number, which will cause @code{configure} to try to
36206 use that version of Guile; or the file name of a @code{pkg-config}
36207 executable, which will be queried to find the information needed to
36208 compile and link against Guile.
36210 @item --without-included-regex
36211 Don't use the regex library included with @value{GDBN} (as part of the
36212 libiberty library). This is the default on hosts with version 2 of
36215 @item --with-sysroot=@var{dir}
36216 Use @var{dir} as the default system root directory for libraries whose
36217 file names begin with @file{/lib}' or @file{/usr/lib'}. (The value of
36218 @var{dir} can be modified at run time by using the @command{set
36219 sysroot} command.) If @var{dir} is under the @value{GDBN} configured
36220 prefix (set with @code{--prefix} or @code{--exec-prefix options}, the
36221 default system root will be automatically adjusted if and when
36222 @value{GDBN} is moved to a different location.
36224 @item --with-system-gdbinit=@var{file}
36225 Configure @value{GDBN} to automatically load a system-wide init file.
36226 @var{file} should be an absolute file name. If @var{file} is in a
36227 directory under the configured prefix, and @value{GDBN} is moved to
36228 another location after being built, the location of the system-wide
36229 init file will be adjusted accordingly.
36231 @item --enable-build-warnings
36232 When building the @value{GDBN} sources, ask the compiler to warn about
36233 any code which looks even vaguely suspicious. It passes many
36234 different warning flags, depending on the exact version of the
36235 compiler you are using.
36237 @item --enable-werror
36238 Treat compiler warnings as werrors. It adds the @code{-Werror} flag
36239 to the compiler, which will fail the compilation if the compiler
36240 outputs any warning messages.
36242 @item --enable-ubsan
36243 Enable the GCC undefined behavior sanitizer. This is disabled by
36244 default, but passing @code{--enable-ubsan=yes} or
36245 @code{--enable-ubsan=auto} to @code{configure} will enable it. The
36246 undefined behavior sanitizer checks for C@t{++} undefined behavior.
36247 It has a performance cost, so if you are looking at @value{GDBN}'s
36248 performance, you should disable it. The undefined behavior sanitizer
36249 was first introduced in GCC 4.9.
36252 @node System-wide configuration
36253 @section System-wide configuration and settings
36254 @cindex system-wide init file
36256 @value{GDBN} can be configured to have a system-wide init file;
36257 this file will be read and executed at startup (@pxref{Startup, , What
36258 @value{GDBN} does during startup}).
36260 Here is the corresponding configure option:
36263 @item --with-system-gdbinit=@var{file}
36264 Specify that the default location of the system-wide init file is
36268 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36269 it may be subject to relocation. Two possible cases:
36273 If the default location of this init file contains @file{$prefix},
36274 it will be subject to relocation. Suppose that the configure options
36275 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36276 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36277 init file is looked for as @file{$install/etc/gdbinit} instead of
36278 @file{$prefix/etc/gdbinit}.
36281 By contrast, if the default location does not contain the prefix,
36282 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36283 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36284 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36285 wherever @value{GDBN} is installed.
36288 If the configured location of the system-wide init file (as given by the
36289 @option{--with-system-gdbinit} option at configure time) is in the
36290 data-directory (as specified by @option{--with-gdb-datadir} at configure
36291 time) or in one of its subdirectories, then @value{GDBN} will look for the
36292 system-wide init file in the directory specified by the
36293 @option{--data-directory} command-line option.
36294 Note that the system-wide init file is only read once, during @value{GDBN}
36295 initialization. If the data-directory is changed after @value{GDBN} has
36296 started with the @code{set data-directory} command, the file will not be
36300 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36303 @node System-wide Configuration Scripts
36304 @subsection Installed System-wide Configuration Scripts
36305 @cindex system-wide configuration scripts
36307 The @file{system-gdbinit} directory, located inside the data-directory
36308 (as specified by @option{--with-gdb-datadir} at configure time) contains
36309 a number of scripts which can be used as system-wide init files. To
36310 automatically source those scripts at startup, @value{GDBN} should be
36311 configured with @option{--with-system-gdbinit}. Otherwise, any user
36312 should be able to source them by hand as needed.
36314 The following scripts are currently available:
36317 @item @file{elinos.py}
36319 @cindex ELinOS system-wide configuration script
36320 This script is useful when debugging a program on an ELinOS target.
36321 It takes advantage of the environment variables defined in a standard
36322 ELinOS environment in order to determine the location of the system
36323 shared libraries, and then sets the @samp{solib-absolute-prefix}
36324 and @samp{solib-search-path} variables appropriately.
36326 @item @file{wrs-linux.py}
36327 @pindex wrs-linux.py
36328 @cindex Wind River Linux system-wide configuration script
36329 This script is useful when debugging a program on a target running
36330 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36331 the host-side sysroot used by the target system.
36335 @node Maintenance Commands
36336 @appendix Maintenance Commands
36337 @cindex maintenance commands
36338 @cindex internal commands
36340 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36341 includes a number of commands intended for @value{GDBN} developers,
36342 that are not documented elsewhere in this manual. These commands are
36343 provided here for reference. (For commands that turn on debugging
36344 messages, see @ref{Debugging Output}.)
36347 @kindex maint agent
36348 @kindex maint agent-eval
36349 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36350 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36351 Translate the given @var{expression} into remote agent bytecodes.
36352 This command is useful for debugging the Agent Expression mechanism
36353 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36354 expression useful for data collection, such as by tracepoints, while
36355 @samp{maint agent-eval} produces an expression that evaluates directly
36356 to a result. For instance, a collection expression for @code{globa +
36357 globb} will include bytecodes to record four bytes of memory at each
36358 of the addresses of @code{globa} and @code{globb}, while discarding
36359 the result of the addition, while an evaluation expression will do the
36360 addition and return the sum.
36361 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36362 If not, generate remote agent bytecode for current frame PC address.
36364 @kindex maint agent-printf
36365 @item maint agent-printf @var{format},@var{expr},...
36366 Translate the given format string and list of argument expressions
36367 into remote agent bytecodes and display them as a disassembled list.
36368 This command is useful for debugging the agent version of dynamic
36369 printf (@pxref{Dynamic Printf}).
36371 @kindex maint info breakpoints
36372 @item @anchor{maint info breakpoints}maint info breakpoints
36373 Using the same format as @samp{info breakpoints}, display both the
36374 breakpoints you've set explicitly, and those @value{GDBN} is using for
36375 internal purposes. Internal breakpoints are shown with negative
36376 breakpoint numbers. The type column identifies what kind of breakpoint
36381 Normal, explicitly set breakpoint.
36384 Normal, explicitly set watchpoint.
36387 Internal breakpoint, used to handle correctly stepping through
36388 @code{longjmp} calls.
36390 @item longjmp resume
36391 Internal breakpoint at the target of a @code{longjmp}.
36394 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36397 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36400 Shared library events.
36404 @kindex maint info btrace
36405 @item maint info btrace
36406 Pint information about raw branch tracing data.
36408 @kindex maint btrace packet-history
36409 @item maint btrace packet-history
36410 Print the raw branch trace packets that are used to compute the
36411 execution history for the @samp{record btrace} command. Both the
36412 information and the format in which it is printed depend on the btrace
36417 For the BTS recording format, print a list of blocks of sequential
36418 code. For each block, the following information is printed:
36422 Newer blocks have higher numbers. The oldest block has number zero.
36423 @item Lowest @samp{PC}
36424 @item Highest @samp{PC}
36428 For the Intel Processor Trace recording format, print a list of
36429 Intel Processor Trace packets. For each packet, the following
36430 information is printed:
36433 @item Packet number
36434 Newer packets have higher numbers. The oldest packet has number zero.
36436 The packet's offset in the trace stream.
36437 @item Packet opcode and payload
36441 @kindex maint btrace clear-packet-history
36442 @item maint btrace clear-packet-history
36443 Discards the cached packet history printed by the @samp{maint btrace
36444 packet-history} command. The history will be computed again when
36447 @kindex maint btrace clear
36448 @item maint btrace clear
36449 Discard the branch trace data. The data will be fetched anew and the
36450 branch trace will be recomputed when needed.
36452 This implicitly truncates the branch trace to a single branch trace
36453 buffer. When updating branch trace incrementally, the branch trace
36454 available to @value{GDBN} may be bigger than a single branch trace
36457 @kindex maint set btrace pt skip-pad
36458 @item maint set btrace pt skip-pad
36459 @kindex maint show btrace pt skip-pad
36460 @item maint show btrace pt skip-pad
36461 Control whether @value{GDBN} will skip PAD packets when computing the
36464 @kindex set displaced-stepping
36465 @kindex show displaced-stepping
36466 @cindex displaced stepping support
36467 @cindex out-of-line single-stepping
36468 @item set displaced-stepping
36469 @itemx show displaced-stepping
36470 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36471 if the target supports it. Displaced stepping is a way to single-step
36472 over breakpoints without removing them from the inferior, by executing
36473 an out-of-line copy of the instruction that was originally at the
36474 breakpoint location. It is also known as out-of-line single-stepping.
36477 @item set displaced-stepping on
36478 If the target architecture supports it, @value{GDBN} will use
36479 displaced stepping to step over breakpoints.
36481 @item set displaced-stepping off
36482 @value{GDBN} will not use displaced stepping to step over breakpoints,
36483 even if such is supported by the target architecture.
36485 @cindex non-stop mode, and @samp{set displaced-stepping}
36486 @item set displaced-stepping auto
36487 This is the default mode. @value{GDBN} will use displaced stepping
36488 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36489 architecture supports displaced stepping.
36492 @kindex maint check-psymtabs
36493 @item maint check-psymtabs
36494 Check the consistency of currently expanded psymtabs versus symtabs.
36495 Use this to check, for example, whether a symbol is in one but not the other.
36497 @kindex maint check-symtabs
36498 @item maint check-symtabs
36499 Check the consistency of currently expanded symtabs.
36501 @kindex maint expand-symtabs
36502 @item maint expand-symtabs [@var{regexp}]
36503 Expand symbol tables.
36504 If @var{regexp} is specified, only expand symbol tables for file
36505 names matching @var{regexp}.
36507 @kindex maint set catch-demangler-crashes
36508 @kindex maint show catch-demangler-crashes
36509 @cindex demangler crashes
36510 @item maint set catch-demangler-crashes [on|off]
36511 @itemx maint show catch-demangler-crashes
36512 Control whether @value{GDBN} should attempt to catch crashes in the
36513 symbol name demangler. The default is to attempt to catch crashes.
36514 If enabled, the first time a crash is caught, a core file is created,
36515 the offending symbol is displayed and the user is presented with the
36516 option to terminate the current session.
36518 @kindex maint cplus first_component
36519 @item maint cplus first_component @var{name}
36520 Print the first C@t{++} class/namespace component of @var{name}.
36522 @kindex maint cplus namespace
36523 @item maint cplus namespace
36524 Print the list of possible C@t{++} namespaces.
36526 @kindex maint deprecate
36527 @kindex maint undeprecate
36528 @cindex deprecated commands
36529 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36530 @itemx maint undeprecate @var{command}
36531 Deprecate or undeprecate the named @var{command}. Deprecated commands
36532 cause @value{GDBN} to issue a warning when you use them. The optional
36533 argument @var{replacement} says which newer command should be used in
36534 favor of the deprecated one; if it is given, @value{GDBN} will mention
36535 the replacement as part of the warning.
36537 @kindex maint dump-me
36538 @item maint dump-me
36539 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36540 Cause a fatal signal in the debugger and force it to dump its core.
36541 This is supported only on systems which support aborting a program
36542 with the @code{SIGQUIT} signal.
36544 @kindex maint internal-error
36545 @kindex maint internal-warning
36546 @kindex maint demangler-warning
36547 @cindex demangler crashes
36548 @item maint internal-error @r{[}@var{message-text}@r{]}
36549 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36550 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
36552 Cause @value{GDBN} to call the internal function @code{internal_error},
36553 @code{internal_warning} or @code{demangler_warning} and hence behave
36554 as though an internal problem has been detected. In addition to
36555 reporting the internal problem, these functions give the user the
36556 opportunity to either quit @value{GDBN} or (for @code{internal_error}
36557 and @code{internal_warning}) create a core file of the current
36558 @value{GDBN} session.
36560 These commands take an optional parameter @var{message-text} that is
36561 used as the text of the error or warning message.
36563 Here's an example of using @code{internal-error}:
36566 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36567 @dots{}/maint.c:121: internal-error: testing, 1, 2
36568 A problem internal to GDB has been detected. Further
36569 debugging may prove unreliable.
36570 Quit this debugging session? (y or n) @kbd{n}
36571 Create a core file? (y or n) @kbd{n}
36575 @cindex @value{GDBN} internal error
36576 @cindex internal errors, control of @value{GDBN} behavior
36577 @cindex demangler crashes
36579 @kindex maint set internal-error
36580 @kindex maint show internal-error
36581 @kindex maint set internal-warning
36582 @kindex maint show internal-warning
36583 @kindex maint set demangler-warning
36584 @kindex maint show demangler-warning
36585 @item maint set internal-error @var{action} [ask|yes|no]
36586 @itemx maint show internal-error @var{action}
36587 @itemx maint set internal-warning @var{action} [ask|yes|no]
36588 @itemx maint show internal-warning @var{action}
36589 @itemx maint set demangler-warning @var{action} [ask|yes|no]
36590 @itemx maint show demangler-warning @var{action}
36591 When @value{GDBN} reports an internal problem (error or warning) it
36592 gives the user the opportunity to both quit @value{GDBN} and create a
36593 core file of the current @value{GDBN} session. These commands let you
36594 override the default behaviour for each particular @var{action},
36595 described in the table below.
36599 You can specify that @value{GDBN} should always (yes) or never (no)
36600 quit. The default is to ask the user what to do.
36603 You can specify that @value{GDBN} should always (yes) or never (no)
36604 create a core file. The default is to ask the user what to do. Note
36605 that there is no @code{corefile} option for @code{demangler-warning}:
36606 demangler warnings always create a core file and this cannot be
36610 @kindex maint packet
36611 @item maint packet @var{text}
36612 If @value{GDBN} is talking to an inferior via the serial protocol,
36613 then this command sends the string @var{text} to the inferior, and
36614 displays the response packet. @value{GDBN} supplies the initial
36615 @samp{$} character, the terminating @samp{#} character, and the
36618 @kindex maint print architecture
36619 @item maint print architecture @r{[}@var{file}@r{]}
36620 Print the entire architecture configuration. The optional argument
36621 @var{file} names the file where the output goes.
36623 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
36624 @item maint print c-tdesc
36625 Print the target description (@pxref{Target Descriptions}) as
36626 a C source file. By default, the target description is for the current
36627 target, but if the optional argument @var{file} is provided, that file
36628 is used to produce the description. The @var{file} should be an XML
36629 document, of the form described in @ref{Target Description Format}.
36630 The created source file is built into @value{GDBN} when @value{GDBN} is
36631 built again. This command is used by developers after they add or
36632 modify XML target descriptions.
36634 @kindex maint check xml-descriptions
36635 @item maint check xml-descriptions @var{dir}
36636 Check that the target descriptions dynamically created by @value{GDBN}
36637 equal the descriptions created from XML files found in @var{dir}.
36639 @anchor{maint check libthread-db}
36640 @kindex maint check libthread-db
36641 @item maint check libthread-db
36642 Run integrity checks on the current inferior's thread debugging
36643 library. This exercises all @code{libthread_db} functionality used by
36644 @value{GDBN} on GNU/Linux systems, and by extension also exercises the
36645 @code{proc_service} functions provided by @value{GDBN} that
36646 @code{libthread_db} uses. Note that parts of the test may be skipped
36647 on some platforms when debugging core files.
36649 @kindex maint print dummy-frames
36650 @item maint print dummy-frames
36651 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36654 (@value{GDBP}) @kbd{b add}
36656 (@value{GDBP}) @kbd{print add(2,3)}
36657 Breakpoint 2, add (a=2, b=3) at @dots{}
36659 The program being debugged stopped while in a function called from GDB.
36661 (@value{GDBP}) @kbd{maint print dummy-frames}
36662 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
36666 Takes an optional file parameter.
36668 @kindex maint print registers
36669 @kindex maint print raw-registers
36670 @kindex maint print cooked-registers
36671 @kindex maint print register-groups
36672 @kindex maint print remote-registers
36673 @item maint print registers @r{[}@var{file}@r{]}
36674 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36675 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36676 @itemx maint print register-groups @r{[}@var{file}@r{]}
36677 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36678 Print @value{GDBN}'s internal register data structures.
36680 The command @code{maint print raw-registers} includes the contents of
36681 the raw register cache; the command @code{maint print
36682 cooked-registers} includes the (cooked) value of all registers,
36683 including registers which aren't available on the target nor visible
36684 to user; the command @code{maint print register-groups} includes the
36685 groups that each register is a member of; and the command @code{maint
36686 print remote-registers} includes the remote target's register numbers
36687 and offsets in the `G' packets.
36689 These commands take an optional parameter, a file name to which to
36690 write the information.
36692 @kindex maint print reggroups
36693 @item maint print reggroups @r{[}@var{file}@r{]}
36694 Print @value{GDBN}'s internal register group data structures. The
36695 optional argument @var{file} tells to what file to write the
36698 The register groups info looks like this:
36701 (@value{GDBP}) @kbd{maint print reggroups}
36714 This command forces @value{GDBN} to flush its internal register cache.
36716 @kindex maint print objfiles
36717 @cindex info for known object files
36718 @item maint print objfiles @r{[}@var{regexp}@r{]}
36719 Print a dump of all known object files.
36720 If @var{regexp} is specified, only print object files whose names
36721 match @var{regexp}. For each object file, this command prints its name,
36722 address in memory, and all of its psymtabs and symtabs.
36724 @kindex maint print user-registers
36725 @cindex user registers
36726 @item maint print user-registers
36727 List all currently available @dfn{user registers}. User registers
36728 typically provide alternate names for actual hardware registers. They
36729 include the four ``standard'' registers @code{$fp}, @code{$pc},
36730 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
36731 registers can be used in expressions in the same way as the canonical
36732 register names, but only the latter are listed by the @code{info
36733 registers} and @code{maint print registers} commands.
36735 @kindex maint print section-scripts
36736 @cindex info for known .debug_gdb_scripts-loaded scripts
36737 @item maint print section-scripts [@var{regexp}]
36738 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36739 If @var{regexp} is specified, only print scripts loaded by object files
36740 matching @var{regexp}.
36741 For each script, this command prints its name as specified in the objfile,
36742 and the full path if known.
36743 @xref{dotdebug_gdb_scripts section}.
36745 @kindex maint print statistics
36746 @cindex bcache statistics
36747 @item maint print statistics
36748 This command prints, for each object file in the program, various data
36749 about that object file followed by the byte cache (@dfn{bcache})
36750 statistics for the object file. The objfile data includes the number
36751 of minimal, partial, full, and stabs symbols, the number of types
36752 defined by the objfile, the number of as yet unexpanded psym tables,
36753 the number of line tables and string tables, and the amount of memory
36754 used by the various tables. The bcache statistics include the counts,
36755 sizes, and counts of duplicates of all and unique objects, max,
36756 average, and median entry size, total memory used and its overhead and
36757 savings, and various measures of the hash table size and chain
36760 @kindex maint print target-stack
36761 @cindex target stack description
36762 @item maint print target-stack
36763 A @dfn{target} is an interface between the debugger and a particular
36764 kind of file or process. Targets can be stacked in @dfn{strata},
36765 so that more than one target can potentially respond to a request.
36766 In particular, memory accesses will walk down the stack of targets
36767 until they find a target that is interested in handling that particular
36770 This command prints a short description of each layer that was pushed on
36771 the @dfn{target stack}, starting from the top layer down to the bottom one.
36773 @kindex maint print type
36774 @cindex type chain of a data type
36775 @item maint print type @var{expr}
36776 Print the type chain for a type specified by @var{expr}. The argument
36777 can be either a type name or a symbol. If it is a symbol, the type of
36778 that symbol is described. The type chain produced by this command is
36779 a recursive definition of the data type as stored in @value{GDBN}'s
36780 data structures, including its flags and contained types.
36782 @kindex maint selftest
36784 @item maint selftest @r{[}@var{filter}@r{]}
36785 Run any self tests that were compiled in to @value{GDBN}. This will
36786 print a message showing how many tests were run, and how many failed.
36787 If a @var{filter} is passed, only the tests with @var{filter} in their
36790 @kindex maint info selftests
36792 @item maint info selftests
36793 List the selftests compiled in to @value{GDBN}.
36795 @kindex maint set dwarf always-disassemble
36796 @kindex maint show dwarf always-disassemble
36797 @item maint set dwarf always-disassemble
36798 @item maint show dwarf always-disassemble
36799 Control the behavior of @code{info address} when using DWARF debugging
36802 The default is @code{off}, which means that @value{GDBN} should try to
36803 describe a variable's location in an easily readable format. When
36804 @code{on}, @value{GDBN} will instead display the DWARF location
36805 expression in an assembly-like format. Note that some locations are
36806 too complex for @value{GDBN} to describe simply; in this case you will
36807 always see the disassembly form.
36809 Here is an example of the resulting disassembly:
36812 (gdb) info addr argc
36813 Symbol "argc" is a complex DWARF expression:
36817 For more information on these expressions, see
36818 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36820 @kindex maint set dwarf max-cache-age
36821 @kindex maint show dwarf max-cache-age
36822 @item maint set dwarf max-cache-age
36823 @itemx maint show dwarf max-cache-age
36824 Control the DWARF compilation unit cache.
36826 @cindex DWARF compilation units cache
36827 In object files with inter-compilation-unit references, such as those
36828 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
36829 reader needs to frequently refer to previously read compilation units.
36830 This setting controls how long a compilation unit will remain in the
36831 cache if it is not referenced. A higher limit means that cached
36832 compilation units will be stored in memory longer, and more total
36833 memory will be used. Setting it to zero disables caching, which will
36834 slow down @value{GDBN} startup, but reduce memory consumption.
36836 @kindex maint set dwarf unwinders
36837 @kindex maint show dwarf unwinders
36838 @item maint set dwarf unwinders
36839 @itemx maint show dwarf unwinders
36840 Control use of the DWARF frame unwinders.
36842 @cindex DWARF frame unwinders
36843 Many targets that support DWARF debugging use @value{GDBN}'s DWARF
36844 frame unwinders to build the backtrace. Many of these targets will
36845 also have a second mechanism for building the backtrace for use in
36846 cases where DWARF information is not available, this second mechanism
36847 is often an analysis of a function's prologue.
36849 In order to extend testing coverage of the second level stack
36850 unwinding mechanisms it is helpful to be able to disable the DWARF
36851 stack unwinders, this can be done with this switch.
36853 In normal use of @value{GDBN} disabling the DWARF unwinders is not
36854 advisable, there are cases that are better handled through DWARF than
36855 prologue analysis, and the debug experience is likely to be better
36856 with the DWARF frame unwinders enabled.
36858 If DWARF frame unwinders are not supported for a particular target
36859 architecture, then enabling this flag does not cause them to be used.
36860 @kindex maint set profile
36861 @kindex maint show profile
36862 @cindex profiling GDB
36863 @item maint set profile
36864 @itemx maint show profile
36865 Control profiling of @value{GDBN}.
36867 Profiling will be disabled until you use the @samp{maint set profile}
36868 command to enable it. When you enable profiling, the system will begin
36869 collecting timing and execution count data; when you disable profiling or
36870 exit @value{GDBN}, the results will be written to a log file. Remember that
36871 if you use profiling, @value{GDBN} will overwrite the profiling log file
36872 (often called @file{gmon.out}). If you have a record of important profiling
36873 data in a @file{gmon.out} file, be sure to move it to a safe location.
36875 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36876 compiled with the @samp{-pg} compiler option.
36878 @kindex maint set show-debug-regs
36879 @kindex maint show show-debug-regs
36880 @cindex hardware debug registers
36881 @item maint set show-debug-regs
36882 @itemx maint show show-debug-regs
36883 Control whether to show variables that mirror the hardware debug
36884 registers. Use @code{on} to enable, @code{off} to disable. If
36885 enabled, the debug registers values are shown when @value{GDBN} inserts or
36886 removes a hardware breakpoint or watchpoint, and when the inferior
36887 triggers a hardware-assisted breakpoint or watchpoint.
36889 @kindex maint set show-all-tib
36890 @kindex maint show show-all-tib
36891 @item maint set show-all-tib
36892 @itemx maint show show-all-tib
36893 Control whether to show all non zero areas within a 1k block starting
36894 at thread local base, when using the @samp{info w32 thread-information-block}
36897 @kindex maint set target-async
36898 @kindex maint show target-async
36899 @item maint set target-async
36900 @itemx maint show target-async
36901 This controls whether @value{GDBN} targets operate in synchronous or
36902 asynchronous mode (@pxref{Background Execution}). Normally the
36903 default is asynchronous, if it is available; but this can be changed
36904 to more easily debug problems occurring only in synchronous mode.
36906 @kindex maint set target-non-stop @var{mode} [on|off|auto]
36907 @kindex maint show target-non-stop
36908 @item maint set target-non-stop
36909 @itemx maint show target-non-stop
36911 This controls whether @value{GDBN} targets always operate in non-stop
36912 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
36913 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
36914 if supported by the target.
36917 @item maint set target-non-stop auto
36918 This is the default mode. @value{GDBN} controls the target in
36919 non-stop mode if the target supports it.
36921 @item maint set target-non-stop on
36922 @value{GDBN} controls the target in non-stop mode even if the target
36923 does not indicate support.
36925 @item maint set target-non-stop off
36926 @value{GDBN} does not control the target in non-stop mode even if the
36927 target supports it.
36930 @kindex maint set per-command
36931 @kindex maint show per-command
36932 @item maint set per-command
36933 @itemx maint show per-command
36934 @cindex resources used by commands
36936 @value{GDBN} can display the resources used by each command.
36937 This is useful in debugging performance problems.
36940 @item maint set per-command space [on|off]
36941 @itemx maint show per-command space
36942 Enable or disable the printing of the memory used by GDB for each command.
36943 If enabled, @value{GDBN} will display how much memory each command
36944 took, following the command's own output.
36945 This can also be requested by invoking @value{GDBN} with the
36946 @option{--statistics} command-line switch (@pxref{Mode Options}).
36948 @item maint set per-command time [on|off]
36949 @itemx maint show per-command time
36950 Enable or disable the printing of the execution time of @value{GDBN}
36952 If enabled, @value{GDBN} will display how much time it
36953 took to execute each command, following the command's own output.
36954 Both CPU time and wallclock time are printed.
36955 Printing both is useful when trying to determine whether the cost is
36956 CPU or, e.g., disk/network latency.
36957 Note that the CPU time printed is for @value{GDBN} only, it does not include
36958 the execution time of the inferior because there's no mechanism currently
36959 to compute how much time was spent by @value{GDBN} and how much time was
36960 spent by the program been debugged.
36961 This can also be requested by invoking @value{GDBN} with the
36962 @option{--statistics} command-line switch (@pxref{Mode Options}).
36964 @item maint set per-command symtab [on|off]
36965 @itemx maint show per-command symtab
36966 Enable or disable the printing of basic symbol table statistics
36968 If enabled, @value{GDBN} will display the following information:
36972 number of symbol tables
36974 number of primary symbol tables
36976 number of blocks in the blockvector
36980 @kindex maint set check-libthread-db
36981 @kindex maint show check-libthread-db
36982 @item maint set check-libthread-db [on|off]
36983 @itemx maint show check-libthread-db
36984 Control whether @value{GDBN} should run integrity checks on inferior
36985 specific thread debugging libraries as they are loaded. The default
36986 is not to perform such checks. If any check fails @value{GDBN} will
36987 unload the library and continue searching for a suitable candidate as
36988 described in @ref{set libthread-db-search-path}. For more information
36989 about the tests, see @ref{maint check libthread-db}.
36991 @kindex maint space
36992 @cindex memory used by commands
36993 @item maint space @var{value}
36994 An alias for @code{maint set per-command space}.
36995 A non-zero value enables it, zero disables it.
36998 @cindex time of command execution
36999 @item maint time @var{value}
37000 An alias for @code{maint set per-command time}.
37001 A non-zero value enables it, zero disables it.
37003 @kindex maint translate-address
37004 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37005 Find the symbol stored at the location specified by the address
37006 @var{addr} and an optional section name @var{section}. If found,
37007 @value{GDBN} prints the name of the closest symbol and an offset from
37008 the symbol's location to the specified address. This is similar to
37009 the @code{info address} command (@pxref{Symbols}), except that this
37010 command also allows to find symbols in other sections.
37012 If section was not specified, the section in which the symbol was found
37013 is also printed. For dynamically linked executables, the name of
37014 executable or shared library containing the symbol is printed as well.
37018 The following command is useful for non-interactive invocations of
37019 @value{GDBN}, such as in the test suite.
37022 @item set watchdog @var{nsec}
37023 @kindex set watchdog
37024 @cindex watchdog timer
37025 @cindex timeout for commands
37026 Set the maximum number of seconds @value{GDBN} will wait for the
37027 target operation to finish. If this time expires, @value{GDBN}
37028 reports and error and the command is aborted.
37030 @item show watchdog
37031 Show the current setting of the target wait timeout.
37034 @node Remote Protocol
37035 @appendix @value{GDBN} Remote Serial Protocol
37040 * Stop Reply Packets::
37041 * General Query Packets::
37042 * Architecture-Specific Protocol Details::
37043 * Tracepoint Packets::
37044 * Host I/O Packets::
37046 * Notification Packets::
37047 * Remote Non-Stop::
37048 * Packet Acknowledgment::
37050 * File-I/O Remote Protocol Extension::
37051 * Library List Format::
37052 * Library List Format for SVR4 Targets::
37053 * Memory Map Format::
37054 * Thread List Format::
37055 * Traceframe Info Format::
37056 * Branch Trace Format::
37057 * Branch Trace Configuration Format::
37063 There may be occasions when you need to know something about the
37064 protocol---for example, if there is only one serial port to your target
37065 machine, you might want your program to do something special if it
37066 recognizes a packet meant for @value{GDBN}.
37068 In the examples below, @samp{->} and @samp{<-} are used to indicate
37069 transmitted and received data, respectively.
37071 @cindex protocol, @value{GDBN} remote serial
37072 @cindex serial protocol, @value{GDBN} remote
37073 @cindex remote serial protocol
37074 All @value{GDBN} commands and responses (other than acknowledgments
37075 and notifications, see @ref{Notification Packets}) are sent as a
37076 @var{packet}. A @var{packet} is introduced with the character
37077 @samp{$}, the actual @var{packet-data}, and the terminating character
37078 @samp{#} followed by a two-digit @var{checksum}:
37081 @code{$}@var{packet-data}@code{#}@var{checksum}
37085 @cindex checksum, for @value{GDBN} remote
37087 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37088 characters between the leading @samp{$} and the trailing @samp{#} (an
37089 eight bit unsigned checksum).
37091 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37092 specification also included an optional two-digit @var{sequence-id}:
37095 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37098 @cindex sequence-id, for @value{GDBN} remote
37100 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37101 has never output @var{sequence-id}s. Stubs that handle packets added
37102 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37104 When either the host or the target machine receives a packet, the first
37105 response expected is an acknowledgment: either @samp{+} (to indicate
37106 the package was received correctly) or @samp{-} (to request
37110 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37115 The @samp{+}/@samp{-} acknowledgments can be disabled
37116 once a connection is established.
37117 @xref{Packet Acknowledgment}, for details.
37119 The host (@value{GDBN}) sends @var{command}s, and the target (the
37120 debugging stub incorporated in your program) sends a @var{response}. In
37121 the case of step and continue @var{command}s, the response is only sent
37122 when the operation has completed, and the target has again stopped all
37123 threads in all attached processes. This is the default all-stop mode
37124 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37125 execution mode; see @ref{Remote Non-Stop}, for details.
37127 @var{packet-data} consists of a sequence of characters with the
37128 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37131 @cindex remote protocol, field separator
37132 Fields within the packet should be separated using @samp{,} @samp{;} or
37133 @samp{:}. Except where otherwise noted all numbers are represented in
37134 @sc{hex} with leading zeros suppressed.
37136 Implementors should note that prior to @value{GDBN} 5.0, the character
37137 @samp{:} could not appear as the third character in a packet (as it
37138 would potentially conflict with the @var{sequence-id}).
37140 @cindex remote protocol, binary data
37141 @anchor{Binary Data}
37142 Binary data in most packets is encoded either as two hexadecimal
37143 digits per byte of binary data. This allowed the traditional remote
37144 protocol to work over connections which were only seven-bit clean.
37145 Some packets designed more recently assume an eight-bit clean
37146 connection, and use a more efficient encoding to send and receive
37149 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37150 as an escape character. Any escaped byte is transmitted as the escape
37151 character followed by the original character XORed with @code{0x20}.
37152 For example, the byte @code{0x7d} would be transmitted as the two
37153 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37154 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37155 @samp{@}}) must always be escaped. Responses sent by the stub
37156 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37157 is not interpreted as the start of a run-length encoded sequence
37160 Response @var{data} can be run-length encoded to save space.
37161 Run-length encoding replaces runs of identical characters with one
37162 instance of the repeated character, followed by a @samp{*} and a
37163 repeat count. The repeat count is itself sent encoded, to avoid
37164 binary characters in @var{data}: a value of @var{n} is sent as
37165 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37166 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37167 code 32) for a repeat count of 3. (This is because run-length
37168 encoding starts to win for counts 3 or more.) Thus, for example,
37169 @samp{0* } is a run-length encoding of ``0000'': the space character
37170 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37173 The printable characters @samp{#} and @samp{$} or with a numeric value
37174 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37175 seven repeats (@samp{$}) can be expanded using a repeat count of only
37176 five (@samp{"}). For example, @samp{00000000} can be encoded as
37179 The error response returned for some packets includes a two character
37180 error number. That number is not well defined.
37182 @cindex empty response, for unsupported packets
37183 For any @var{command} not supported by the stub, an empty response
37184 (@samp{$#00}) should be returned. That way it is possible to extend the
37185 protocol. A newer @value{GDBN} can tell if a packet is supported based
37188 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37189 commands for register access, and the @samp{m} and @samp{M} commands
37190 for memory access. Stubs that only control single-threaded targets
37191 can implement run control with the @samp{c} (continue), and @samp{s}
37192 (step) commands. Stubs that support multi-threading targets should
37193 support the @samp{vCont} command. All other commands are optional.
37198 The following table provides a complete list of all currently defined
37199 @var{command}s and their corresponding response @var{data}.
37200 @xref{File-I/O Remote Protocol Extension}, for details about the File
37201 I/O extension of the remote protocol.
37203 Each packet's description has a template showing the packet's overall
37204 syntax, followed by an explanation of the packet's meaning. We
37205 include spaces in some of the templates for clarity; these are not
37206 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37207 separate its components. For example, a template like @samp{foo
37208 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37209 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37210 @var{baz}. @value{GDBN} does not transmit a space character between the
37211 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37214 @cindex @var{thread-id}, in remote protocol
37215 @anchor{thread-id syntax}
37216 Several packets and replies include a @var{thread-id} field to identify
37217 a thread. Normally these are positive numbers with a target-specific
37218 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37219 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37222 In addition, the remote protocol supports a multiprocess feature in
37223 which the @var{thread-id} syntax is extended to optionally include both
37224 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37225 The @var{pid} (process) and @var{tid} (thread) components each have the
37226 format described above: a positive number with target-specific
37227 interpretation formatted as a big-endian hex string, literal @samp{-1}
37228 to indicate all processes or threads (respectively), or @samp{0} to
37229 indicate an arbitrary process or thread. Specifying just a process, as
37230 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37231 error to specify all processes but a specific thread, such as
37232 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37233 for those packets and replies explicitly documented to include a process
37234 ID, rather than a @var{thread-id}.
37236 The multiprocess @var{thread-id} syntax extensions are only used if both
37237 @value{GDBN} and the stub report support for the @samp{multiprocess}
37238 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37241 Note that all packet forms beginning with an upper- or lower-case
37242 letter, other than those described here, are reserved for future use.
37244 Here are the packet descriptions.
37249 @cindex @samp{!} packet
37250 @anchor{extended mode}
37251 Enable extended mode. In extended mode, the remote server is made
37252 persistent. The @samp{R} packet is used to restart the program being
37258 The remote target both supports and has enabled extended mode.
37262 @cindex @samp{?} packet
37264 Indicate the reason the target halted. The reply is the same as for
37265 step and continue. This packet has a special interpretation when the
37266 target is in non-stop mode; see @ref{Remote Non-Stop}.
37269 @xref{Stop Reply Packets}, for the reply specifications.
37271 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37272 @cindex @samp{A} packet
37273 Initialized @code{argv[]} array passed into program. @var{arglen}
37274 specifies the number of bytes in the hex encoded byte stream
37275 @var{arg}. See @code{gdbserver} for more details.
37280 The arguments were set.
37286 @cindex @samp{b} packet
37287 (Don't use this packet; its behavior is not well-defined.)
37288 Change the serial line speed to @var{baud}.
37290 JTC: @emph{When does the transport layer state change? When it's
37291 received, or after the ACK is transmitted. In either case, there are
37292 problems if the command or the acknowledgment packet is dropped.}
37294 Stan: @emph{If people really wanted to add something like this, and get
37295 it working for the first time, they ought to modify ser-unix.c to send
37296 some kind of out-of-band message to a specially-setup stub and have the
37297 switch happen "in between" packets, so that from remote protocol's point
37298 of view, nothing actually happened.}
37300 @item B @var{addr},@var{mode}
37301 @cindex @samp{B} packet
37302 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37303 breakpoint at @var{addr}.
37305 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37306 (@pxref{insert breakpoint or watchpoint packet}).
37308 @cindex @samp{bc} packet
37311 Backward continue. Execute the target system in reverse. No parameter.
37312 @xref{Reverse Execution}, for more information.
37315 @xref{Stop Reply Packets}, for the reply specifications.
37317 @cindex @samp{bs} packet
37320 Backward single step. Execute one instruction in reverse. No parameter.
37321 @xref{Reverse Execution}, for more information.
37324 @xref{Stop Reply Packets}, for the reply specifications.
37326 @item c @r{[}@var{addr}@r{]}
37327 @cindex @samp{c} packet
37328 Continue at @var{addr}, which is the address to resume. If @var{addr}
37329 is omitted, resume at current address.
37331 This packet is deprecated for multi-threading support. @xref{vCont
37335 @xref{Stop Reply Packets}, for the reply specifications.
37337 @item C @var{sig}@r{[};@var{addr}@r{]}
37338 @cindex @samp{C} packet
37339 Continue with signal @var{sig} (hex signal number). If
37340 @samp{;@var{addr}} is omitted, resume at same address.
37342 This packet is deprecated for multi-threading support. @xref{vCont
37346 @xref{Stop Reply Packets}, for the reply specifications.
37349 @cindex @samp{d} packet
37352 Don't use this packet; instead, define a general set packet
37353 (@pxref{General Query Packets}).
37357 @cindex @samp{D} packet
37358 The first form of the packet is used to detach @value{GDBN} from the
37359 remote system. It is sent to the remote target
37360 before @value{GDBN} disconnects via the @code{detach} command.
37362 The second form, including a process ID, is used when multiprocess
37363 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37364 detach only a specific process. The @var{pid} is specified as a
37365 big-endian hex string.
37375 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37376 @cindex @samp{F} packet
37377 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37378 This is part of the File-I/O protocol extension. @xref{File-I/O
37379 Remote Protocol Extension}, for the specification.
37382 @anchor{read registers packet}
37383 @cindex @samp{g} packet
37384 Read general registers.
37388 @item @var{XX@dots{}}
37389 Each byte of register data is described by two hex digits. The bytes
37390 with the register are transmitted in target byte order. The size of
37391 each register and their position within the @samp{g} packet are
37392 determined by the @value{GDBN} internal gdbarch functions
37393 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
37395 When reading registers from a trace frame (@pxref{Analyze Collected
37396 Data,,Using the Collected Data}), the stub may also return a string of
37397 literal @samp{x}'s in place of the register data digits, to indicate
37398 that the corresponding register has not been collected, thus its value
37399 is unavailable. For example, for an architecture with 4 registers of
37400 4 bytes each, the following reply indicates to @value{GDBN} that
37401 registers 0 and 2 have not been collected, while registers 1 and 3
37402 have been collected, and both have zero value:
37406 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37413 @item G @var{XX@dots{}}
37414 @cindex @samp{G} packet
37415 Write general registers. @xref{read registers packet}, for a
37416 description of the @var{XX@dots{}} data.
37426 @item H @var{op} @var{thread-id}
37427 @cindex @samp{H} packet
37428 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37429 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
37430 should be @samp{c} for step and continue operations (note that this
37431 is deprecated, supporting the @samp{vCont} command is a better
37432 option), and @samp{g} for other operations. The thread designator
37433 @var{thread-id} has the format and interpretation described in
37434 @ref{thread-id syntax}.
37445 @c 'H': How restrictive (or permissive) is the thread model. If a
37446 @c thread is selected and stopped, are other threads allowed
37447 @c to continue to execute? As I mentioned above, I think the
37448 @c semantics of each command when a thread is selected must be
37449 @c described. For example:
37451 @c 'g': If the stub supports threads and a specific thread is
37452 @c selected, returns the register block from that thread;
37453 @c otherwise returns current registers.
37455 @c 'G' If the stub supports threads and a specific thread is
37456 @c selected, sets the registers of the register block of
37457 @c that thread; otherwise sets current registers.
37459 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37460 @anchor{cycle step packet}
37461 @cindex @samp{i} packet
37462 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37463 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37464 step starting at that address.
37467 @cindex @samp{I} packet
37468 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37472 @cindex @samp{k} packet
37475 The exact effect of this packet is not specified.
37477 For a bare-metal target, it may power cycle or reset the target
37478 system. For that reason, the @samp{k} packet has no reply.
37480 For a single-process target, it may kill that process if possible.
37482 A multiple-process target may choose to kill just one process, or all
37483 that are under @value{GDBN}'s control. For more precise control, use
37484 the vKill packet (@pxref{vKill packet}).
37486 If the target system immediately closes the connection in response to
37487 @samp{k}, @value{GDBN} does not consider the lack of packet
37488 acknowledgment to be an error, and assumes the kill was successful.
37490 If connected using @kbd{target extended-remote}, and the target does
37491 not close the connection in response to a kill request, @value{GDBN}
37492 probes the target state as if a new connection was opened
37493 (@pxref{? packet}).
37495 @item m @var{addr},@var{length}
37496 @cindex @samp{m} packet
37497 Read @var{length} addressable memory units starting at address @var{addr}
37498 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
37499 any particular boundary.
37501 The stub need not use any particular size or alignment when gathering
37502 data from memory for the response; even if @var{addr} is word-aligned
37503 and @var{length} is a multiple of the word size, the stub is free to
37504 use byte accesses, or not. For this reason, this packet may not be
37505 suitable for accessing memory-mapped I/O devices.
37506 @cindex alignment of remote memory accesses
37507 @cindex size of remote memory accesses
37508 @cindex memory, alignment and size of remote accesses
37512 @item @var{XX@dots{}}
37513 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
37514 The reply may contain fewer addressable memory units than requested if the
37515 server was able to read only part of the region of memory.
37520 @item M @var{addr},@var{length}:@var{XX@dots{}}
37521 @cindex @samp{M} packet
37522 Write @var{length} addressable memory units starting at address @var{addr}
37523 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
37524 byte is transmitted as a two-digit hexadecimal number.
37531 for an error (this includes the case where only part of the data was
37536 @cindex @samp{p} packet
37537 Read the value of register @var{n}; @var{n} is in hex.
37538 @xref{read registers packet}, for a description of how the returned
37539 register value is encoded.
37543 @item @var{XX@dots{}}
37544 the register's value
37548 Indicating an unrecognized @var{query}.
37551 @item P @var{n@dots{}}=@var{r@dots{}}
37552 @anchor{write register packet}
37553 @cindex @samp{P} packet
37554 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37555 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37556 digits for each byte in the register (target byte order).
37566 @item q @var{name} @var{params}@dots{}
37567 @itemx Q @var{name} @var{params}@dots{}
37568 @cindex @samp{q} packet
37569 @cindex @samp{Q} packet
37570 General query (@samp{q}) and set (@samp{Q}). These packets are
37571 described fully in @ref{General Query Packets}.
37574 @cindex @samp{r} packet
37575 Reset the entire system.
37577 Don't use this packet; use the @samp{R} packet instead.
37580 @cindex @samp{R} packet
37581 Restart the program being debugged. The @var{XX}, while needed, is ignored.
37582 This packet is only available in extended mode (@pxref{extended mode}).
37584 The @samp{R} packet has no reply.
37586 @item s @r{[}@var{addr}@r{]}
37587 @cindex @samp{s} packet
37588 Single step, resuming at @var{addr}. If
37589 @var{addr} is omitted, resume at same address.
37591 This packet is deprecated for multi-threading support. @xref{vCont
37595 @xref{Stop Reply Packets}, for the reply specifications.
37597 @item S @var{sig}@r{[};@var{addr}@r{]}
37598 @anchor{step with signal packet}
37599 @cindex @samp{S} packet
37600 Step with signal. This is analogous to the @samp{C} packet, but
37601 requests a single-step, rather than a normal resumption of execution.
37603 This packet is deprecated for multi-threading support. @xref{vCont
37607 @xref{Stop Reply Packets}, for the reply specifications.
37609 @item t @var{addr}:@var{PP},@var{MM}
37610 @cindex @samp{t} packet
37611 Search backwards starting at address @var{addr} for a match with pattern
37612 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
37613 There must be at least 3 digits in @var{addr}.
37615 @item T @var{thread-id}
37616 @cindex @samp{T} packet
37617 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37622 thread is still alive
37628 Packets starting with @samp{v} are identified by a multi-letter name,
37629 up to the first @samp{;} or @samp{?} (or the end of the packet).
37631 @item vAttach;@var{pid}
37632 @cindex @samp{vAttach} packet
37633 Attach to a new process with the specified process ID @var{pid}.
37634 The process ID is a
37635 hexadecimal integer identifying the process. In all-stop mode, all
37636 threads in the attached process are stopped; in non-stop mode, it may be
37637 attached without being stopped if that is supported by the target.
37639 @c In non-stop mode, on a successful vAttach, the stub should set the
37640 @c current thread to a thread of the newly-attached process. After
37641 @c attaching, GDB queries for the attached process's thread ID with qC.
37642 @c Also note that, from a user perspective, whether or not the
37643 @c target is stopped on attach in non-stop mode depends on whether you
37644 @c use the foreground or background version of the attach command, not
37645 @c on what vAttach does; GDB does the right thing with respect to either
37646 @c stopping or restarting threads.
37648 This packet is only available in extended mode (@pxref{extended mode}).
37654 @item @r{Any stop packet}
37655 for success in all-stop mode (@pxref{Stop Reply Packets})
37657 for success in non-stop mode (@pxref{Remote Non-Stop})
37660 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37661 @cindex @samp{vCont} packet
37662 @anchor{vCont packet}
37663 Resume the inferior, specifying different actions for each thread.
37665 For each inferior thread, the leftmost action with a matching
37666 @var{thread-id} is applied. Threads that don't match any action
37667 remain in their current state. Thread IDs are specified using the
37668 syntax described in @ref{thread-id syntax}. If multiprocess
37669 extensions (@pxref{multiprocess extensions}) are supported, actions
37670 can be specified to match all threads in a process by using the
37671 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
37672 @var{thread-id} matches all threads. Specifying no actions is an
37675 Currently supported actions are:
37681 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37685 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37688 @item r @var{start},@var{end}
37689 Step once, and then keep stepping as long as the thread stops at
37690 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37691 The remote stub reports a stop reply when either the thread goes out
37692 of the range or is stopped due to an unrelated reason, such as hitting
37693 a breakpoint. @xref{range stepping}.
37695 If the range is empty (@var{start} == @var{end}), then the action
37696 becomes equivalent to the @samp{s} action. In other words,
37697 single-step once, and report the stop (even if the stepped instruction
37698 jumps to @var{start}).
37700 (A stop reply may be sent at any point even if the PC is still within
37701 the stepping range; for example, it is valid to implement this packet
37702 in a degenerate way as a single instruction step operation.)
37706 The optional argument @var{addr} normally associated with the
37707 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37708 not supported in @samp{vCont}.
37710 The @samp{t} action is only relevant in non-stop mode
37711 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37712 A stop reply should be generated for any affected thread not already stopped.
37713 When a thread is stopped by means of a @samp{t} action,
37714 the corresponding stop reply should indicate that the thread has stopped with
37715 signal @samp{0}, regardless of whether the target uses some other signal
37716 as an implementation detail.
37718 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
37719 @samp{r} actions for threads that are already running. Conversely,
37720 the server must ignore @samp{t} actions for threads that are already
37723 @emph{Note:} In non-stop mode, a thread is considered running until
37724 @value{GDBN} acknowleges an asynchronous stop notification for it with
37725 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
37727 The stub must support @samp{vCont} if it reports support for
37728 multiprocess extensions (@pxref{multiprocess extensions}).
37731 @xref{Stop Reply Packets}, for the reply specifications.
37734 @cindex @samp{vCont?} packet
37735 Request a list of actions supported by the @samp{vCont} packet.
37739 @item vCont@r{[};@var{action}@dots{}@r{]}
37740 The @samp{vCont} packet is supported. Each @var{action} is a supported
37741 command in the @samp{vCont} packet.
37743 The @samp{vCont} packet is not supported.
37746 @anchor{vCtrlC packet}
37748 @cindex @samp{vCtrlC} packet
37749 Interrupt remote target as if a control-C was pressed on the remote
37750 terminal. This is the equivalent to reacting to the @code{^C}
37751 (@samp{\003}, the control-C character) character in all-stop mode
37752 while the target is running, except this works in non-stop mode.
37753 @xref{interrupting remote targets}, for more info on the all-stop
37764 @item vFile:@var{operation}:@var{parameter}@dots{}
37765 @cindex @samp{vFile} packet
37766 Perform a file operation on the target system. For details,
37767 see @ref{Host I/O Packets}.
37769 @item vFlashErase:@var{addr},@var{length}
37770 @cindex @samp{vFlashErase} packet
37771 Direct the stub to erase @var{length} bytes of flash starting at
37772 @var{addr}. The region may enclose any number of flash blocks, but
37773 its start and end must fall on block boundaries, as indicated by the
37774 flash block size appearing in the memory map (@pxref{Memory Map
37775 Format}). @value{GDBN} groups flash memory programming operations
37776 together, and sends a @samp{vFlashDone} request after each group; the
37777 stub is allowed to delay erase operation until the @samp{vFlashDone}
37778 packet is received.
37788 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37789 @cindex @samp{vFlashWrite} packet
37790 Direct the stub to write data to flash address @var{addr}. The data
37791 is passed in binary form using the same encoding as for the @samp{X}
37792 packet (@pxref{Binary Data}). The memory ranges specified by
37793 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37794 not overlap, and must appear in order of increasing addresses
37795 (although @samp{vFlashErase} packets for higher addresses may already
37796 have been received; the ordering is guaranteed only between
37797 @samp{vFlashWrite} packets). If a packet writes to an address that was
37798 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37799 target-specific method, the results are unpredictable.
37807 for vFlashWrite addressing non-flash memory
37813 @cindex @samp{vFlashDone} packet
37814 Indicate to the stub that flash programming operation is finished.
37815 The stub is permitted to delay or batch the effects of a group of
37816 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37817 @samp{vFlashDone} packet is received. The contents of the affected
37818 regions of flash memory are unpredictable until the @samp{vFlashDone}
37819 request is completed.
37821 @item vKill;@var{pid}
37822 @cindex @samp{vKill} packet
37823 @anchor{vKill packet}
37824 Kill the process with the specified process ID @var{pid}, which is a
37825 hexadecimal integer identifying the process. This packet is used in
37826 preference to @samp{k} when multiprocess protocol extensions are
37827 supported; see @ref{multiprocess extensions}.
37837 @item vMustReplyEmpty
37838 @cindex @samp{vMustReplyEmpty} packet
37839 The correct reply to an unknown @samp{v} packet is to return the empty
37840 string, however, some older versions of @command{gdbserver} would
37841 incorrectly return @samp{OK} for unknown @samp{v} packets.
37843 The @samp{vMustReplyEmpty} is used as a feature test to check how
37844 @command{gdbserver} handles unknown packets, it is important that this
37845 packet be handled in the same way as other unknown @samp{v} packets.
37846 If this packet is handled differently to other unknown @samp{v}
37847 packets then it is possile that @value{GDBN} may run into problems in
37848 other areas, specifically around use of @samp{vFile:setfs:}.
37850 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37851 @cindex @samp{vRun} packet
37852 Run the program @var{filename}, passing it each @var{argument} on its
37853 command line. The file and arguments are hex-encoded strings. If
37854 @var{filename} is an empty string, the stub may use a default program
37855 (e.g.@: the last program run). The program is created in the stopped
37858 @c FIXME: What about non-stop mode?
37860 This packet is only available in extended mode (@pxref{extended mode}).
37866 @item @r{Any stop packet}
37867 for success (@pxref{Stop Reply Packets})
37871 @cindex @samp{vStopped} packet
37872 @xref{Notification Packets}.
37874 @item X @var{addr},@var{length}:@var{XX@dots{}}
37876 @cindex @samp{X} packet
37877 Write data to memory, where the data is transmitted in binary.
37878 Memory is specified by its address @var{addr} and number of addressable memory
37879 units @var{length} (@pxref{addressable memory unit});
37880 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37890 @item z @var{type},@var{addr},@var{kind}
37891 @itemx Z @var{type},@var{addr},@var{kind}
37892 @anchor{insert breakpoint or watchpoint packet}
37893 @cindex @samp{z} packet
37894 @cindex @samp{Z} packets
37895 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37896 watchpoint starting at address @var{address} of kind @var{kind}.
37898 Each breakpoint and watchpoint packet @var{type} is documented
37901 @emph{Implementation notes: A remote target shall return an empty string
37902 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37903 remote target shall support either both or neither of a given
37904 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37905 avoid potential problems with duplicate packets, the operations should
37906 be implemented in an idempotent way.}
37908 @item z0,@var{addr},@var{kind}
37909 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37910 @cindex @samp{z0} packet
37911 @cindex @samp{Z0} packet
37912 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
37913 @var{addr} of type @var{kind}.
37915 A software breakpoint is implemented by replacing the instruction at
37916 @var{addr} with a software breakpoint or trap instruction. The
37917 @var{kind} is target-specific and typically indicates the size of the
37918 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
37919 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37920 architectures have additional meanings for @var{kind}
37921 (@pxref{Architecture-Specific Protocol Details}); if no
37922 architecture-specific value is being used, it should be @samp{0}.
37923 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
37924 conditional expressions in bytecode form that should be evaluated on
37925 the target's side. These are the conditions that should be taken into
37926 consideration when deciding if the breakpoint trigger should be
37927 reported back to @value{GDBN}.
37929 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
37930 for how to best report a software breakpoint event to @value{GDBN}.
37932 The @var{cond_list} parameter is comprised of a series of expressions,
37933 concatenated without separators. Each expression has the following form:
37937 @item X @var{len},@var{expr}
37938 @var{len} is the length of the bytecode expression and @var{expr} is the
37939 actual conditional expression in bytecode form.
37943 The optional @var{cmd_list} parameter introduces commands that may be
37944 run on the target, rather than being reported back to @value{GDBN}.
37945 The parameter starts with a numeric flag @var{persist}; if the flag is
37946 nonzero, then the breakpoint may remain active and the commands
37947 continue to be run even when @value{GDBN} disconnects from the target.
37948 Following this flag is a series of expressions concatenated with no
37949 separators. Each expression has the following form:
37953 @item X @var{len},@var{expr}
37954 @var{len} is the length of the bytecode expression and @var{expr} is the
37955 actual commands expression in bytecode form.
37959 @emph{Implementation note: It is possible for a target to copy or move
37960 code that contains software breakpoints (e.g., when implementing
37961 overlays). The behavior of this packet, in the presence of such a
37962 target, is not defined.}
37974 @item z1,@var{addr},@var{kind}
37975 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37976 @cindex @samp{z1} packet
37977 @cindex @samp{Z1} packet
37978 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37979 address @var{addr}.
37981 A hardware breakpoint is implemented using a mechanism that is not
37982 dependent on being able to modify the target's memory. The
37983 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
37984 same meaning as in @samp{Z0} packets.
37986 @emph{Implementation note: A hardware breakpoint is not affected by code
37999 @item z2,@var{addr},@var{kind}
38000 @itemx Z2,@var{addr},@var{kind}
38001 @cindex @samp{z2} packet
38002 @cindex @samp{Z2} packet
38003 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38004 The number of bytes to watch is specified by @var{kind}.
38016 @item z3,@var{addr},@var{kind}
38017 @itemx Z3,@var{addr},@var{kind}
38018 @cindex @samp{z3} packet
38019 @cindex @samp{Z3} packet
38020 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38021 The number of bytes to watch is specified by @var{kind}.
38033 @item z4,@var{addr},@var{kind}
38034 @itemx Z4,@var{addr},@var{kind}
38035 @cindex @samp{z4} packet
38036 @cindex @samp{Z4} packet
38037 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38038 The number of bytes to watch is specified by @var{kind}.
38052 @node Stop Reply Packets
38053 @section Stop Reply Packets
38054 @cindex stop reply packets
38056 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38057 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38058 receive any of the below as a reply. Except for @samp{?}
38059 and @samp{vStopped}, that reply is only returned
38060 when the target halts. In the below the exact meaning of @dfn{signal
38061 number} is defined by the header @file{include/gdb/signals.h} in the
38062 @value{GDBN} source code.
38064 In non-stop mode, the server will simply reply @samp{OK} to commands
38065 such as @samp{vCont}; any stop will be the subject of a future
38066 notification. @xref{Remote Non-Stop}.
38068 As in the description of request packets, we include spaces in the
38069 reply templates for clarity; these are not part of the reply packet's
38070 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38076 The program received signal number @var{AA} (a two-digit hexadecimal
38077 number). This is equivalent to a @samp{T} response with no
38078 @var{n}:@var{r} pairs.
38080 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38081 @cindex @samp{T} packet reply
38082 The program received signal number @var{AA} (a two-digit hexadecimal
38083 number). This is equivalent to an @samp{S} response, except that the
38084 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38085 and other information directly in the stop reply packet, reducing
38086 round-trip latency. Single-step and breakpoint traps are reported
38087 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38091 If @var{n} is a hexadecimal number, it is a register number, and the
38092 corresponding @var{r} gives that register's value. The data @var{r} is a
38093 series of bytes in target byte order, with each byte given by a
38094 two-digit hex number.
38097 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38098 the stopped thread, as specified in @ref{thread-id syntax}.
38101 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38102 the core on which the stop event was detected.
38105 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38106 specific event that stopped the target. The currently defined stop
38107 reasons are listed below. The @var{aa} should be @samp{05}, the trap
38108 signal. At most one stop reason should be present.
38111 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38112 and go on to the next; this allows us to extend the protocol in the
38116 The currently defined stop reasons are:
38122 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38125 @item syscall_entry
38126 @itemx syscall_return
38127 The packet indicates a syscall entry or return, and @var{r} is the
38128 syscall number, in hex.
38130 @cindex shared library events, remote reply
38132 The packet indicates that the loaded libraries have changed.
38133 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38134 list of loaded libraries. The @var{r} part is ignored.
38136 @cindex replay log events, remote reply
38138 The packet indicates that the target cannot continue replaying
38139 logged execution events, because it has reached the end (or the
38140 beginning when executing backward) of the log. The value of @var{r}
38141 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38142 for more information.
38145 @anchor{swbreak stop reason}
38146 The packet indicates a software breakpoint instruction was executed,
38147 irrespective of whether it was @value{GDBN} that planted the
38148 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
38149 part must be left empty.
38151 On some architectures, such as x86, at the architecture level, when a
38152 breakpoint instruction executes the program counter points at the
38153 breakpoint address plus an offset. On such targets, the stub is
38154 responsible for adjusting the PC to point back at the breakpoint
38157 This packet should not be sent by default; older @value{GDBN} versions
38158 did not support it. @value{GDBN} requests it, by supplying an
38159 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38160 remote stub must also supply the appropriate @samp{qSupported} feature
38161 indicating support.
38163 This packet is required for correct non-stop mode operation.
38166 The packet indicates the target stopped for a hardware breakpoint.
38167 The @var{r} part must be left empty.
38169 The same remarks about @samp{qSupported} and non-stop mode above
38172 @cindex fork events, remote reply
38174 The packet indicates that @code{fork} was called, and @var{r}
38175 is the thread ID of the new child process. Refer to
38176 @ref{thread-id syntax} for the format of the @var{thread-id}
38177 field. This packet is only applicable to targets that support
38180 This packet should not be sent by default; older @value{GDBN} versions
38181 did not support it. @value{GDBN} requests it, by supplying an
38182 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38183 remote stub must also supply the appropriate @samp{qSupported} feature
38184 indicating support.
38186 @cindex vfork events, remote reply
38188 The packet indicates that @code{vfork} was called, and @var{r}
38189 is the thread ID of the new child process. Refer to
38190 @ref{thread-id syntax} for the format of the @var{thread-id}
38191 field. This packet is only applicable to targets that support
38194 This packet should not be sent by default; older @value{GDBN} versions
38195 did not support it. @value{GDBN} requests it, by supplying an
38196 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38197 remote stub must also supply the appropriate @samp{qSupported} feature
38198 indicating support.
38200 @cindex vforkdone events, remote reply
38202 The packet indicates that a child process created by a vfork
38203 has either called @code{exec} or terminated, so that the
38204 address spaces of the parent and child process are no longer
38205 shared. The @var{r} part is ignored. This packet is only
38206 applicable to targets that support vforkdone events.
38208 This packet should not be sent by default; older @value{GDBN} versions
38209 did not support it. @value{GDBN} requests it, by supplying an
38210 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38211 remote stub must also supply the appropriate @samp{qSupported} feature
38212 indicating support.
38214 @cindex exec events, remote reply
38216 The packet indicates that @code{execve} was called, and @var{r}
38217 is the absolute pathname of the file that was executed, in hex.
38218 This packet is only applicable to targets that support exec events.
38220 This packet should not be sent by default; older @value{GDBN} versions
38221 did not support it. @value{GDBN} requests it, by supplying an
38222 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
38223 remote stub must also supply the appropriate @samp{qSupported} feature
38224 indicating support.
38226 @cindex thread create event, remote reply
38227 @anchor{thread create event}
38229 The packet indicates that the thread was just created. The new thread
38230 is stopped until @value{GDBN} sets it running with a resumption packet
38231 (@pxref{vCont packet}). This packet should not be sent by default;
38232 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
38233 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
38234 @var{r} part is ignored.
38239 @itemx W @var{AA} ; process:@var{pid}
38240 The process exited, and @var{AA} is the exit status. This is only
38241 applicable to certain targets.
38243 The second form of the response, including the process ID of the
38244 exited process, can be used only when @value{GDBN} has reported
38245 support for multiprocess protocol extensions; see @ref{multiprocess
38246 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38250 @itemx X @var{AA} ; process:@var{pid}
38251 The process terminated with signal @var{AA}.
38253 The second form of the response, including the process ID of the
38254 terminated process, can be used only when @value{GDBN} has reported
38255 support for multiprocess protocol extensions; see @ref{multiprocess
38256 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
38259 @anchor{thread exit event}
38260 @cindex thread exit event, remote reply
38261 @item w @var{AA} ; @var{tid}
38263 The thread exited, and @var{AA} is the exit status. This response
38264 should not be sent by default; @value{GDBN} requests it with the
38265 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
38266 @var{AA} is formatted as a big-endian hex string.
38269 There are no resumed threads left in the target. In other words, even
38270 though the process is alive, the last resumed thread has exited. For
38271 example, say the target process has two threads: thread 1 and thread
38272 2. The client leaves thread 1 stopped, and resumes thread 2, which
38273 subsequently exits. At this point, even though the process is still
38274 alive, and thus no @samp{W} stop reply is sent, no thread is actually
38275 executing either. The @samp{N} stop reply thus informs the client
38276 that it can stop waiting for stop replies. This packet should not be
38277 sent by default; older @value{GDBN} versions did not support it.
38278 @value{GDBN} requests it, by supplying an appropriate
38279 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
38280 also supply the appropriate @samp{qSupported} feature indicating
38283 @item O @var{XX}@dots{}
38284 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38285 written as the program's console output. This can happen at any time
38286 while the program is running and the debugger should continue to wait
38287 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38289 @item F @var{call-id},@var{parameter}@dots{}
38290 @var{call-id} is the identifier which says which host system call should
38291 be called. This is just the name of the function. Translation into the
38292 correct system call is only applicable as it's defined in @value{GDBN}.
38293 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38296 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38297 this very system call.
38299 The target replies with this packet when it expects @value{GDBN} to
38300 call a host system call on behalf of the target. @value{GDBN} replies
38301 with an appropriate @samp{F} packet and keeps up waiting for the next
38302 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38303 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38304 Protocol Extension}, for more details.
38308 @node General Query Packets
38309 @section General Query Packets
38310 @cindex remote query requests
38312 Packets starting with @samp{q} are @dfn{general query packets};
38313 packets starting with @samp{Q} are @dfn{general set packets}. General
38314 query and set packets are a semi-unified form for retrieving and
38315 sending information to and from the stub.
38317 The initial letter of a query or set packet is followed by a name
38318 indicating what sort of thing the packet applies to. For example,
38319 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38320 definitions with the stub. These packet names follow some
38325 The name must not contain commas, colons or semicolons.
38327 Most @value{GDBN} query and set packets have a leading upper case
38330 The names of custom vendor packets should use a company prefix, in
38331 lower case, followed by a period. For example, packets designed at
38332 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38333 foos) or @samp{Qacme.bar} (for setting bars).
38336 The name of a query or set packet should be separated from any
38337 parameters by a @samp{:}; the parameters themselves should be
38338 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38339 full packet name, and check for a separator or the end of the packet,
38340 in case two packet names share a common prefix. New packets should not begin
38341 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38342 packets predate these conventions, and have arguments without any terminator
38343 for the packet name; we suspect they are in widespread use in places that
38344 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38345 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38348 Like the descriptions of the other packets, each description here
38349 has a template showing the packet's overall syntax, followed by an
38350 explanation of the packet's meaning. We include spaces in some of the
38351 templates for clarity; these are not part of the packet's syntax. No
38352 @value{GDBN} packet uses spaces to separate its components.
38354 Here are the currently defined query and set packets:
38360 Turn on or off the agent as a helper to perform some debugging operations
38361 delegated from @value{GDBN} (@pxref{Control Agent}).
38363 @item QAllow:@var{op}:@var{val}@dots{}
38364 @cindex @samp{QAllow} packet
38365 Specify which operations @value{GDBN} expects to request of the
38366 target, as a semicolon-separated list of operation name and value
38367 pairs. Possible values for @var{op} include @samp{WriteReg},
38368 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38369 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38370 indicating that @value{GDBN} will not request the operation, or 1,
38371 indicating that it may. (The target can then use this to set up its
38372 own internals optimally, for instance if the debugger never expects to
38373 insert breakpoints, it may not need to install its own trap handler.)
38376 @cindex current thread, remote request
38377 @cindex @samp{qC} packet
38378 Return the current thread ID.
38382 @item QC @var{thread-id}
38383 Where @var{thread-id} is a thread ID as documented in
38384 @ref{thread-id syntax}.
38385 @item @r{(anything else)}
38386 Any other reply implies the old thread ID.
38389 @item qCRC:@var{addr},@var{length}
38390 @cindex CRC of memory block, remote request
38391 @cindex @samp{qCRC} packet
38392 @anchor{qCRC packet}
38393 Compute the CRC checksum of a block of memory using CRC-32 defined in
38394 IEEE 802.3. The CRC is computed byte at a time, taking the most
38395 significant bit of each byte first. The initial pattern code
38396 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38398 @emph{Note:} This is the same CRC used in validating separate debug
38399 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38400 Files}). However the algorithm is slightly different. When validating
38401 separate debug files, the CRC is computed taking the @emph{least}
38402 significant bit of each byte first, and the final result is inverted to
38403 detect trailing zeros.
38408 An error (such as memory fault)
38409 @item C @var{crc32}
38410 The specified memory region's checksum is @var{crc32}.
38413 @item QDisableRandomization:@var{value}
38414 @cindex disable address space randomization, remote request
38415 @cindex @samp{QDisableRandomization} packet
38416 Some target operating systems will randomize the virtual address space
38417 of the inferior process as a security feature, but provide a feature
38418 to disable such randomization, e.g.@: to allow for a more deterministic
38419 debugging experience. On such systems, this packet with a @var{value}
38420 of 1 directs the target to disable address space randomization for
38421 processes subsequently started via @samp{vRun} packets, while a packet
38422 with a @var{value} of 0 tells the target to enable address space
38425 This packet is only available in extended mode (@pxref{extended mode}).
38430 The request succeeded.
38433 An error occurred. The error number @var{nn} is given as hex digits.
38436 An empty reply indicates that @samp{QDisableRandomization} is not supported
38440 This packet is not probed by default; the remote stub must request it,
38441 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38442 This should only be done on targets that actually support disabling
38443 address space randomization.
38445 @item QStartupWithShell:@var{value}
38446 @cindex startup with shell, remote request
38447 @cindex @samp{QStartupWithShell} packet
38448 On UNIX-like targets, it is possible to start the inferior using a
38449 shell program. This is the default behavior on both @value{GDBN} and
38450 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
38451 used to inform @command{gdbserver} whether it should start the
38452 inferior using a shell or not.
38454 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
38455 to start the inferior. If @var{value} is @samp{1},
38456 @command{gdbserver} will use a shell to start the inferior. All other
38457 values are considered an error.
38459 This packet is only available in extended mode (@pxref{extended
38465 The request succeeded.
38468 An error occurred. The error number @var{nn} is given as hex digits.
38471 This packet is not probed by default; the remote stub must request it,
38472 by supplying an appropriate @samp{qSupported} response
38473 (@pxref{qSupported}). This should only be done on targets that
38474 actually support starting the inferior using a shell.
38476 Use of this packet is controlled by the @code{set startup-with-shell}
38477 command; @pxref{set startup-with-shell}.
38479 @item QEnvironmentHexEncoded:@var{hex-value}
38480 @anchor{QEnvironmentHexEncoded}
38481 @cindex set environment variable, remote request
38482 @cindex @samp{QEnvironmentHexEncoded} packet
38483 On UNIX-like targets, it is possible to set environment variables that
38484 will be passed to the inferior during the startup process. This
38485 packet is used to inform @command{gdbserver} of an environment
38486 variable that has been defined by the user on @value{GDBN} (@pxref{set
38489 The packet is composed by @var{hex-value}, an hex encoded
38490 representation of the @var{name=value} format representing an
38491 environment variable. The name of the environment variable is
38492 represented by @var{name}, and the value to be assigned to the
38493 environment variable is represented by @var{value}. If the variable
38494 has no value (i.e., the value is @code{null}), then @var{value} will
38497 This packet is only available in extended mode (@pxref{extended
38503 The request succeeded.
38506 This packet is not probed by default; the remote stub must request it,
38507 by supplying an appropriate @samp{qSupported} response
38508 (@pxref{qSupported}). This should only be done on targets that
38509 actually support passing environment variables to the starting
38512 This packet is related to the @code{set environment} command;
38513 @pxref{set environment}.
38515 @item QEnvironmentUnset:@var{hex-value}
38516 @anchor{QEnvironmentUnset}
38517 @cindex unset environment variable, remote request
38518 @cindex @samp{QEnvironmentUnset} packet
38519 On UNIX-like targets, it is possible to unset environment variables
38520 before starting the inferior in the remote target. This packet is
38521 used to inform @command{gdbserver} of an environment variable that has
38522 been unset by the user on @value{GDBN} (@pxref{unset environment}).
38524 The packet is composed by @var{hex-value}, an hex encoded
38525 representation of the name of the environment variable to be unset.
38527 This packet is only available in extended mode (@pxref{extended
38533 The request succeeded.
38536 This packet is not probed by default; the remote stub must request it,
38537 by supplying an appropriate @samp{qSupported} response
38538 (@pxref{qSupported}). This should only be done on targets that
38539 actually support passing environment variables to the starting
38542 This packet is related to the @code{unset environment} command;
38543 @pxref{unset environment}.
38545 @item QEnvironmentReset
38546 @anchor{QEnvironmentReset}
38547 @cindex reset environment, remote request
38548 @cindex @samp{QEnvironmentReset} packet
38549 On UNIX-like targets, this packet is used to reset the state of
38550 environment variables in the remote target before starting the
38551 inferior. In this context, reset means unsetting all environment
38552 variables that were previously set by the user (i.e., were not
38553 initially present in the environment). It is sent to
38554 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
38555 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
38556 (@pxref{QEnvironmentUnset}) packets.
38558 This packet is only available in extended mode (@pxref{extended
38564 The request succeeded.
38567 This packet is not probed by default; the remote stub must request it,
38568 by supplying an appropriate @samp{qSupported} response
38569 (@pxref{qSupported}). This should only be done on targets that
38570 actually support passing environment variables to the starting
38573 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
38574 @anchor{QSetWorkingDir packet}
38575 @cindex set working directory, remote request
38576 @cindex @samp{QSetWorkingDir} packet
38577 This packet is used to inform the remote server of the intended
38578 current working directory for programs that are going to be executed.
38580 The packet is composed by @var{directory}, an hex encoded
38581 representation of the directory that the remote inferior will use as
38582 its current working directory. If @var{directory} is an empty string,
38583 the remote server should reset the inferior's current working
38584 directory to its original, empty value.
38586 This packet is only available in extended mode (@pxref{extended
38592 The request succeeded.
38596 @itemx qsThreadInfo
38597 @cindex list active threads, remote request
38598 @cindex @samp{qfThreadInfo} packet
38599 @cindex @samp{qsThreadInfo} packet
38600 Obtain a list of all active thread IDs from the target (OS). Since there
38601 may be too many active threads to fit into one reply packet, this query
38602 works iteratively: it may require more than one query/reply sequence to
38603 obtain the entire list of threads. The first query of the sequence will
38604 be the @samp{qfThreadInfo} query; subsequent queries in the
38605 sequence will be the @samp{qsThreadInfo} query.
38607 NOTE: This packet replaces the @samp{qL} query (see below).
38611 @item m @var{thread-id}
38613 @item m @var{thread-id},@var{thread-id}@dots{}
38614 a comma-separated list of thread IDs
38616 (lower case letter @samp{L}) denotes end of list.
38619 In response to each query, the target will reply with a list of one or
38620 more thread IDs, separated by commas.
38621 @value{GDBN} will respond to each reply with a request for more thread
38622 ids (using the @samp{qs} form of the query), until the target responds
38623 with @samp{l} (lower-case ell, for @dfn{last}).
38624 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38627 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
38628 initial connection with the remote target, and the very first thread ID
38629 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
38630 message. Therefore, the stub should ensure that the first thread ID in
38631 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
38633 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38634 @cindex get thread-local storage address, remote request
38635 @cindex @samp{qGetTLSAddr} packet
38636 Fetch the address associated with thread local storage specified
38637 by @var{thread-id}, @var{offset}, and @var{lm}.
38639 @var{thread-id} is the thread ID associated with the
38640 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38642 @var{offset} is the (big endian, hex encoded) offset associated with the
38643 thread local variable. (This offset is obtained from the debug
38644 information associated with the variable.)
38646 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38647 load module associated with the thread local storage. For example,
38648 a @sc{gnu}/Linux system will pass the link map address of the shared
38649 object associated with the thread local storage under consideration.
38650 Other operating environments may choose to represent the load module
38651 differently, so the precise meaning of this parameter will vary.
38655 @item @var{XX}@dots{}
38656 Hex encoded (big endian) bytes representing the address of the thread
38657 local storage requested.
38660 An error occurred. The error number @var{nn} is given as hex digits.
38663 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38666 @item qGetTIBAddr:@var{thread-id}
38667 @cindex get thread information block address
38668 @cindex @samp{qGetTIBAddr} packet
38669 Fetch address of the Windows OS specific Thread Information Block.
38671 @var{thread-id} is the thread ID associated with the thread.
38675 @item @var{XX}@dots{}
38676 Hex encoded (big endian) bytes representing the linear address of the
38677 thread information block.
38680 An error occured. This means that either the thread was not found, or the
38681 address could not be retrieved.
38684 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38687 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38688 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38689 digit) is one to indicate the first query and zero to indicate a
38690 subsequent query; @var{threadcount} (two hex digits) is the maximum
38691 number of threads the response packet can contain; and @var{nextthread}
38692 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38693 returned in the response as @var{argthread}.
38695 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38699 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38700 Where: @var{count} (two hex digits) is the number of threads being
38701 returned; @var{done} (one hex digit) is zero to indicate more threads
38702 and one indicates no further threads; @var{argthreadid} (eight hex
38703 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38704 is a sequence of thread IDs, @var{threadid} (eight hex
38705 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
38709 @cindex section offsets, remote request
38710 @cindex @samp{qOffsets} packet
38711 Get section offsets that the target used when relocating the downloaded
38716 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38717 Relocate the @code{Text} section by @var{xxx} from its original address.
38718 Relocate the @code{Data} section by @var{yyy} from its original address.
38719 If the object file format provides segment information (e.g.@: @sc{elf}
38720 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38721 segments by the supplied offsets.
38723 @emph{Note: while a @code{Bss} offset may be included in the response,
38724 @value{GDBN} ignores this and instead applies the @code{Data} offset
38725 to the @code{Bss} section.}
38727 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38728 Relocate the first segment of the object file, which conventionally
38729 contains program code, to a starting address of @var{xxx}. If
38730 @samp{DataSeg} is specified, relocate the second segment, which
38731 conventionally contains modifiable data, to a starting address of
38732 @var{yyy}. @value{GDBN} will report an error if the object file
38733 does not contain segment information, or does not contain at least
38734 as many segments as mentioned in the reply. Extra segments are
38735 kept at fixed offsets relative to the last relocated segment.
38738 @item qP @var{mode} @var{thread-id}
38739 @cindex thread information, remote request
38740 @cindex @samp{qP} packet
38741 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38742 encoded 32 bit mode; @var{thread-id} is a thread ID
38743 (@pxref{thread-id syntax}).
38745 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38748 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38752 @cindex non-stop mode, remote request
38753 @cindex @samp{QNonStop} packet
38755 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38756 @xref{Remote Non-Stop}, for more information.
38761 The request succeeded.
38764 An error occurred. The error number @var{nn} is given as hex digits.
38767 An empty reply indicates that @samp{QNonStop} is not supported by
38771 This packet is not probed by default; the remote stub must request it,
38772 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38773 Use of this packet is controlled by the @code{set non-stop} command;
38774 @pxref{Non-Stop Mode}.
38776 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
38777 @itemx QCatchSyscalls:0
38778 @cindex catch syscalls from inferior, remote request
38779 @cindex @samp{QCatchSyscalls} packet
38780 @anchor{QCatchSyscalls}
38781 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
38782 catching syscalls from the inferior process.
38784 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
38785 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
38786 is listed, every system call should be reported.
38788 Note that if a syscall not in the list is reported, @value{GDBN} will
38789 still filter the event according to its own list from all corresponding
38790 @code{catch syscall} commands. However, it is more efficient to only
38791 report the requested syscalls.
38793 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
38794 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
38796 If the inferior process execs, the state of @samp{QCatchSyscalls} is
38797 kept for the new process too. On targets where exec may affect syscall
38798 numbers, for example with exec between 32 and 64-bit processes, the
38799 client should send a new packet with the new syscall list.
38804 The request succeeded.
38807 An error occurred. @var{nn} are hex digits.
38810 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
38814 Use of this packet is controlled by the @code{set remote catch-syscalls}
38815 command (@pxref{Remote Configuration, set remote catch-syscalls}).
38816 This packet is not probed by default; the remote stub must request it,
38817 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38819 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38820 @cindex pass signals to inferior, remote request
38821 @cindex @samp{QPassSignals} packet
38822 @anchor{QPassSignals}
38823 Each listed @var{signal} should be passed directly to the inferior process.
38824 Signals are numbered identically to continue packets and stop replies
38825 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38826 strictly greater than the previous item. These signals do not need to stop
38827 the inferior, or be reported to @value{GDBN}. All other signals should be
38828 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38829 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38830 new list. This packet improves performance when using @samp{handle
38831 @var{signal} nostop noprint pass}.
38836 The request succeeded.
38839 An error occurred. The error number @var{nn} is given as hex digits.
38842 An empty reply indicates that @samp{QPassSignals} is not supported by
38846 Use of this packet is controlled by the @code{set remote pass-signals}
38847 command (@pxref{Remote Configuration, set remote pass-signals}).
38848 This packet is not probed by default; the remote stub must request it,
38849 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38851 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38852 @cindex signals the inferior may see, remote request
38853 @cindex @samp{QProgramSignals} packet
38854 @anchor{QProgramSignals}
38855 Each listed @var{signal} may be delivered to the inferior process.
38856 Others should be silently discarded.
38858 In some cases, the remote stub may need to decide whether to deliver a
38859 signal to the program or not without @value{GDBN} involvement. One
38860 example of that is while detaching --- the program's threads may have
38861 stopped for signals that haven't yet had a chance of being reported to
38862 @value{GDBN}, and so the remote stub can use the signal list specified
38863 by this packet to know whether to deliver or ignore those pending
38866 This does not influence whether to deliver a signal as requested by a
38867 resumption packet (@pxref{vCont packet}).
38869 Signals are numbered identically to continue packets and stop replies
38870 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38871 strictly greater than the previous item. Multiple
38872 @samp{QProgramSignals} packets do not combine; any earlier
38873 @samp{QProgramSignals} list is completely replaced by the new list.
38878 The request succeeded.
38881 An error occurred. The error number @var{nn} is given as hex digits.
38884 An empty reply indicates that @samp{QProgramSignals} is not supported
38888 Use of this packet is controlled by the @code{set remote program-signals}
38889 command (@pxref{Remote Configuration, set remote program-signals}).
38890 This packet is not probed by default; the remote stub must request it,
38891 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38893 @anchor{QThreadEvents}
38894 @item QThreadEvents:1
38895 @itemx QThreadEvents:0
38896 @cindex thread create/exit events, remote request
38897 @cindex @samp{QThreadEvents} packet
38899 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
38900 reporting of thread create and exit events. @xref{thread create
38901 event}, for the reply specifications. For example, this is used in
38902 non-stop mode when @value{GDBN} stops a set of threads and
38903 synchronously waits for the their corresponding stop replies. Without
38904 exit events, if one of the threads exits, @value{GDBN} would hang
38905 forever not knowing that it should no longer expect a stop for that
38906 same thread. @value{GDBN} does not enable this feature unless the
38907 stub reports that it supports it by including @samp{QThreadEvents+} in
38908 its @samp{qSupported} reply.
38913 The request succeeded.
38916 An error occurred. The error number @var{nn} is given as hex digits.
38919 An empty reply indicates that @samp{QThreadEvents} is not supported by
38923 Use of this packet is controlled by the @code{set remote thread-events}
38924 command (@pxref{Remote Configuration, set remote thread-events}).
38926 @item qRcmd,@var{command}
38927 @cindex execute remote command, remote request
38928 @cindex @samp{qRcmd} packet
38929 @var{command} (hex encoded) is passed to the local interpreter for
38930 execution. Invalid commands should be reported using the output
38931 string. Before the final result packet, the target may also respond
38932 with a number of intermediate @samp{O@var{output}} console output
38933 packets. @emph{Implementors should note that providing access to a
38934 stubs's interpreter may have security implications}.
38939 A command response with no output.
38941 A command response with the hex encoded output string @var{OUTPUT}.
38943 Indicate a badly formed request.
38945 An empty reply indicates that @samp{qRcmd} is not recognized.
38948 (Note that the @code{qRcmd} packet's name is separated from the
38949 command by a @samp{,}, not a @samp{:}, contrary to the naming
38950 conventions above. Please don't use this packet as a model for new
38953 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38954 @cindex searching memory, in remote debugging
38956 @cindex @samp{qSearch:memory} packet
38958 @cindex @samp{qSearch memory} packet
38959 @anchor{qSearch memory}
38960 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38961 Both @var{address} and @var{length} are encoded in hex;
38962 @var{search-pattern} is a sequence of bytes, also hex encoded.
38967 The pattern was not found.
38969 The pattern was found at @var{address}.
38971 A badly formed request or an error was encountered while searching memory.
38973 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38976 @item QStartNoAckMode
38977 @cindex @samp{QStartNoAckMode} packet
38978 @anchor{QStartNoAckMode}
38979 Request that the remote stub disable the normal @samp{+}/@samp{-}
38980 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38985 The stub has switched to no-acknowledgment mode.
38986 @value{GDBN} acknowledges this reponse,
38987 but neither the stub nor @value{GDBN} shall send or expect further
38988 @samp{+}/@samp{-} acknowledgments in the current connection.
38990 An empty reply indicates that the stub does not support no-acknowledgment mode.
38993 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38994 @cindex supported packets, remote query
38995 @cindex features of the remote protocol
38996 @cindex @samp{qSupported} packet
38997 @anchor{qSupported}
38998 Tell the remote stub about features supported by @value{GDBN}, and
38999 query the stub for features it supports. This packet allows
39000 @value{GDBN} and the remote stub to take advantage of each others'
39001 features. @samp{qSupported} also consolidates multiple feature probes
39002 at startup, to improve @value{GDBN} performance---a single larger
39003 packet performs better than multiple smaller probe packets on
39004 high-latency links. Some features may enable behavior which must not
39005 be on by default, e.g.@: because it would confuse older clients or
39006 stubs. Other features may describe packets which could be
39007 automatically probed for, but are not. These features must be
39008 reported before @value{GDBN} will use them. This ``default
39009 unsupported'' behavior is not appropriate for all packets, but it
39010 helps to keep the initial connection time under control with new
39011 versions of @value{GDBN} which support increasing numbers of packets.
39015 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39016 The stub supports or does not support each returned @var{stubfeature},
39017 depending on the form of each @var{stubfeature} (see below for the
39020 An empty reply indicates that @samp{qSupported} is not recognized,
39021 or that no features needed to be reported to @value{GDBN}.
39024 The allowed forms for each feature (either a @var{gdbfeature} in the
39025 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39029 @item @var{name}=@var{value}
39030 The remote protocol feature @var{name} is supported, and associated
39031 with the specified @var{value}. The format of @var{value} depends
39032 on the feature, but it must not include a semicolon.
39034 The remote protocol feature @var{name} is supported, and does not
39035 need an associated value.
39037 The remote protocol feature @var{name} is not supported.
39039 The remote protocol feature @var{name} may be supported, and
39040 @value{GDBN} should auto-detect support in some other way when it is
39041 needed. This form will not be used for @var{gdbfeature} notifications,
39042 but may be used for @var{stubfeature} responses.
39045 Whenever the stub receives a @samp{qSupported} request, the
39046 supplied set of @value{GDBN} features should override any previous
39047 request. This allows @value{GDBN} to put the stub in a known
39048 state, even if the stub had previously been communicating with
39049 a different version of @value{GDBN}.
39051 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39056 This feature indicates whether @value{GDBN} supports multiprocess
39057 extensions to the remote protocol. @value{GDBN} does not use such
39058 extensions unless the stub also reports that it supports them by
39059 including @samp{multiprocess+} in its @samp{qSupported} reply.
39060 @xref{multiprocess extensions}, for details.
39063 This feature indicates that @value{GDBN} supports the XML target
39064 description. If the stub sees @samp{xmlRegisters=} with target
39065 specific strings separated by a comma, it will report register
39069 This feature indicates whether @value{GDBN} supports the
39070 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39071 instruction reply packet}).
39074 This feature indicates whether @value{GDBN} supports the swbreak stop
39075 reason in stop replies. @xref{swbreak stop reason}, for details.
39078 This feature indicates whether @value{GDBN} supports the hwbreak stop
39079 reason in stop replies. @xref{swbreak stop reason}, for details.
39082 This feature indicates whether @value{GDBN} supports fork event
39083 extensions to the remote protocol. @value{GDBN} does not use such
39084 extensions unless the stub also reports that it supports them by
39085 including @samp{fork-events+} in its @samp{qSupported} reply.
39088 This feature indicates whether @value{GDBN} supports vfork event
39089 extensions to the remote protocol. @value{GDBN} does not use such
39090 extensions unless the stub also reports that it supports them by
39091 including @samp{vfork-events+} in its @samp{qSupported} reply.
39094 This feature indicates whether @value{GDBN} supports exec event
39095 extensions to the remote protocol. @value{GDBN} does not use such
39096 extensions unless the stub also reports that it supports them by
39097 including @samp{exec-events+} in its @samp{qSupported} reply.
39099 @item vContSupported
39100 This feature indicates whether @value{GDBN} wants to know the
39101 supported actions in the reply to @samp{vCont?} packet.
39104 Stubs should ignore any unknown values for
39105 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39106 packet supports receiving packets of unlimited length (earlier
39107 versions of @value{GDBN} may reject overly long responses). Additional values
39108 for @var{gdbfeature} may be defined in the future to let the stub take
39109 advantage of new features in @value{GDBN}, e.g.@: incompatible
39110 improvements in the remote protocol---the @samp{multiprocess} feature is
39111 an example of such a feature. The stub's reply should be independent
39112 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39113 describes all the features it supports, and then the stub replies with
39114 all the features it supports.
39116 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39117 responses, as long as each response uses one of the standard forms.
39119 Some features are flags. A stub which supports a flag feature
39120 should respond with a @samp{+} form response. Other features
39121 require values, and the stub should respond with an @samp{=}
39124 Each feature has a default value, which @value{GDBN} will use if
39125 @samp{qSupported} is not available or if the feature is not mentioned
39126 in the @samp{qSupported} response. The default values are fixed; a
39127 stub is free to omit any feature responses that match the defaults.
39129 Not all features can be probed, but for those which can, the probing
39130 mechanism is useful: in some cases, a stub's internal
39131 architecture may not allow the protocol layer to know some information
39132 about the underlying target in advance. This is especially common in
39133 stubs which may be configured for multiple targets.
39135 These are the currently defined stub features and their properties:
39137 @multitable @columnfractions 0.35 0.2 0.12 0.2
39138 @c NOTE: The first row should be @headitem, but we do not yet require
39139 @c a new enough version of Texinfo (4.7) to use @headitem.
39141 @tab Value Required
39145 @item @samp{PacketSize}
39150 @item @samp{qXfer:auxv:read}
39155 @item @samp{qXfer:btrace:read}
39160 @item @samp{qXfer:btrace-conf:read}
39165 @item @samp{qXfer:exec-file:read}
39170 @item @samp{qXfer:features:read}
39175 @item @samp{qXfer:libraries:read}
39180 @item @samp{qXfer:libraries-svr4:read}
39185 @item @samp{augmented-libraries-svr4-read}
39190 @item @samp{qXfer:memory-map:read}
39195 @item @samp{qXfer:sdata:read}
39200 @item @samp{qXfer:spu:read}
39205 @item @samp{qXfer:spu:write}
39210 @item @samp{qXfer:siginfo:read}
39215 @item @samp{qXfer:siginfo:write}
39220 @item @samp{qXfer:threads:read}
39225 @item @samp{qXfer:traceframe-info:read}
39230 @item @samp{qXfer:uib:read}
39235 @item @samp{qXfer:fdpic:read}
39240 @item @samp{Qbtrace:off}
39245 @item @samp{Qbtrace:bts}
39250 @item @samp{Qbtrace:pt}
39255 @item @samp{Qbtrace-conf:bts:size}
39260 @item @samp{Qbtrace-conf:pt:size}
39265 @item @samp{QNonStop}
39270 @item @samp{QCatchSyscalls}
39275 @item @samp{QPassSignals}
39280 @item @samp{QStartNoAckMode}
39285 @item @samp{multiprocess}
39290 @item @samp{ConditionalBreakpoints}
39295 @item @samp{ConditionalTracepoints}
39300 @item @samp{ReverseContinue}
39305 @item @samp{ReverseStep}
39310 @item @samp{TracepointSource}
39315 @item @samp{QAgent}
39320 @item @samp{QAllow}
39325 @item @samp{QDisableRandomization}
39330 @item @samp{EnableDisableTracepoints}
39335 @item @samp{QTBuffer:size}
39340 @item @samp{tracenz}
39345 @item @samp{BreakpointCommands}
39350 @item @samp{swbreak}
39355 @item @samp{hwbreak}
39360 @item @samp{fork-events}
39365 @item @samp{vfork-events}
39370 @item @samp{exec-events}
39375 @item @samp{QThreadEvents}
39380 @item @samp{no-resumed}
39387 These are the currently defined stub features, in more detail:
39390 @cindex packet size, remote protocol
39391 @item PacketSize=@var{bytes}
39392 The remote stub can accept packets up to at least @var{bytes} in
39393 length. @value{GDBN} will send packets up to this size for bulk
39394 transfers, and will never send larger packets. This is a limit on the
39395 data characters in the packet, including the frame and checksum.
39396 There is no trailing NUL byte in a remote protocol packet; if the stub
39397 stores packets in a NUL-terminated format, it should allow an extra
39398 byte in its buffer for the NUL. If this stub feature is not supported,
39399 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39401 @item qXfer:auxv:read
39402 The remote stub understands the @samp{qXfer:auxv:read} packet
39403 (@pxref{qXfer auxiliary vector read}).
39405 @item qXfer:btrace:read
39406 The remote stub understands the @samp{qXfer:btrace:read}
39407 packet (@pxref{qXfer btrace read}).
39409 @item qXfer:btrace-conf:read
39410 The remote stub understands the @samp{qXfer:btrace-conf:read}
39411 packet (@pxref{qXfer btrace-conf read}).
39413 @item qXfer:exec-file:read
39414 The remote stub understands the @samp{qXfer:exec-file:read} packet
39415 (@pxref{qXfer executable filename read}).
39417 @item qXfer:features:read
39418 The remote stub understands the @samp{qXfer:features:read} packet
39419 (@pxref{qXfer target description read}).
39421 @item qXfer:libraries:read
39422 The remote stub understands the @samp{qXfer:libraries:read} packet
39423 (@pxref{qXfer library list read}).
39425 @item qXfer:libraries-svr4:read
39426 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39427 (@pxref{qXfer svr4 library list read}).
39429 @item augmented-libraries-svr4-read
39430 The remote stub understands the augmented form of the
39431 @samp{qXfer:libraries-svr4:read} packet
39432 (@pxref{qXfer svr4 library list read}).
39434 @item qXfer:memory-map:read
39435 The remote stub understands the @samp{qXfer:memory-map:read} packet
39436 (@pxref{qXfer memory map read}).
39438 @item qXfer:sdata:read
39439 The remote stub understands the @samp{qXfer:sdata:read} packet
39440 (@pxref{qXfer sdata read}).
39442 @item qXfer:spu:read
39443 The remote stub understands the @samp{qXfer:spu:read} packet
39444 (@pxref{qXfer spu read}).
39446 @item qXfer:spu:write
39447 The remote stub understands the @samp{qXfer:spu:write} packet
39448 (@pxref{qXfer spu write}).
39450 @item qXfer:siginfo:read
39451 The remote stub understands the @samp{qXfer:siginfo:read} packet
39452 (@pxref{qXfer siginfo read}).
39454 @item qXfer:siginfo:write
39455 The remote stub understands the @samp{qXfer:siginfo:write} packet
39456 (@pxref{qXfer siginfo write}).
39458 @item qXfer:threads:read
39459 The remote stub understands the @samp{qXfer:threads:read} packet
39460 (@pxref{qXfer threads read}).
39462 @item qXfer:traceframe-info:read
39463 The remote stub understands the @samp{qXfer:traceframe-info:read}
39464 packet (@pxref{qXfer traceframe info read}).
39466 @item qXfer:uib:read
39467 The remote stub understands the @samp{qXfer:uib:read}
39468 packet (@pxref{qXfer unwind info block}).
39470 @item qXfer:fdpic:read
39471 The remote stub understands the @samp{qXfer:fdpic:read}
39472 packet (@pxref{qXfer fdpic loadmap read}).
39475 The remote stub understands the @samp{QNonStop} packet
39476 (@pxref{QNonStop}).
39478 @item QCatchSyscalls
39479 The remote stub understands the @samp{QCatchSyscalls} packet
39480 (@pxref{QCatchSyscalls}).
39483 The remote stub understands the @samp{QPassSignals} packet
39484 (@pxref{QPassSignals}).
39486 @item QStartNoAckMode
39487 The remote stub understands the @samp{QStartNoAckMode} packet and
39488 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39491 @anchor{multiprocess extensions}
39492 @cindex multiprocess extensions, in remote protocol
39493 The remote stub understands the multiprocess extensions to the remote
39494 protocol syntax. The multiprocess extensions affect the syntax of
39495 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39496 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39497 replies. Note that reporting this feature indicates support for the
39498 syntactic extensions only, not that the stub necessarily supports
39499 debugging of more than one process at a time. The stub must not use
39500 multiprocess extensions in packet replies unless @value{GDBN} has also
39501 indicated it supports them in its @samp{qSupported} request.
39503 @item qXfer:osdata:read
39504 The remote stub understands the @samp{qXfer:osdata:read} packet
39505 ((@pxref{qXfer osdata read}).
39507 @item ConditionalBreakpoints
39508 The target accepts and implements evaluation of conditional expressions
39509 defined for breakpoints. The target will only report breakpoint triggers
39510 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39512 @item ConditionalTracepoints
39513 The remote stub accepts and implements conditional expressions defined
39514 for tracepoints (@pxref{Tracepoint Conditions}).
39516 @item ReverseContinue
39517 The remote stub accepts and implements the reverse continue packet
39521 The remote stub accepts and implements the reverse step packet
39524 @item TracepointSource
39525 The remote stub understands the @samp{QTDPsrc} packet that supplies
39526 the source form of tracepoint definitions.
39529 The remote stub understands the @samp{QAgent} packet.
39532 The remote stub understands the @samp{QAllow} packet.
39534 @item QDisableRandomization
39535 The remote stub understands the @samp{QDisableRandomization} packet.
39537 @item StaticTracepoint
39538 @cindex static tracepoints, in remote protocol
39539 The remote stub supports static tracepoints.
39541 @item InstallInTrace
39542 @anchor{install tracepoint in tracing}
39543 The remote stub supports installing tracepoint in tracing.
39545 @item EnableDisableTracepoints
39546 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39547 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39548 to be enabled and disabled while a trace experiment is running.
39550 @item QTBuffer:size
39551 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39552 packet that allows to change the size of the trace buffer.
39555 @cindex string tracing, in remote protocol
39556 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39557 See @ref{Bytecode Descriptions} for details about the bytecode.
39559 @item BreakpointCommands
39560 @cindex breakpoint commands, in remote protocol
39561 The remote stub supports running a breakpoint's command list itself,
39562 rather than reporting the hit to @value{GDBN}.
39565 The remote stub understands the @samp{Qbtrace:off} packet.
39568 The remote stub understands the @samp{Qbtrace:bts} packet.
39571 The remote stub understands the @samp{Qbtrace:pt} packet.
39573 @item Qbtrace-conf:bts:size
39574 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
39576 @item Qbtrace-conf:pt:size
39577 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
39580 The remote stub reports the @samp{swbreak} stop reason for memory
39584 The remote stub reports the @samp{hwbreak} stop reason for hardware
39588 The remote stub reports the @samp{fork} stop reason for fork events.
39591 The remote stub reports the @samp{vfork} stop reason for vfork events
39592 and vforkdone events.
39595 The remote stub reports the @samp{exec} stop reason for exec events.
39597 @item vContSupported
39598 The remote stub reports the supported actions in the reply to
39599 @samp{vCont?} packet.
39601 @item QThreadEvents
39602 The remote stub understands the @samp{QThreadEvents} packet.
39605 The remote stub reports the @samp{N} stop reply.
39610 @cindex symbol lookup, remote request
39611 @cindex @samp{qSymbol} packet
39612 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39613 requests. Accept requests from the target for the values of symbols.
39618 The target does not need to look up any (more) symbols.
39619 @item qSymbol:@var{sym_name}
39620 The target requests the value of symbol @var{sym_name} (hex encoded).
39621 @value{GDBN} may provide the value by using the
39622 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39626 @item qSymbol:@var{sym_value}:@var{sym_name}
39627 Set the value of @var{sym_name} to @var{sym_value}.
39629 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39630 target has previously requested.
39632 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39633 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39639 The target does not need to look up any (more) symbols.
39640 @item qSymbol:@var{sym_name}
39641 The target requests the value of a new symbol @var{sym_name} (hex
39642 encoded). @value{GDBN} will continue to supply the values of symbols
39643 (if available), until the target ceases to request them.
39648 @itemx QTDisconnected
39655 @itemx qTMinFTPILen
39657 @xref{Tracepoint Packets}.
39659 @item qThreadExtraInfo,@var{thread-id}
39660 @cindex thread attributes info, remote request
39661 @cindex @samp{qThreadExtraInfo} packet
39662 Obtain from the target OS a printable string description of thread
39663 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
39664 for the forms of @var{thread-id}. This
39665 string may contain anything that the target OS thinks is interesting
39666 for @value{GDBN} to tell the user about the thread. The string is
39667 displayed in @value{GDBN}'s @code{info threads} display. Some
39668 examples of possible thread extra info strings are @samp{Runnable}, or
39669 @samp{Blocked on Mutex}.
39673 @item @var{XX}@dots{}
39674 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39675 comprising the printable string containing the extra information about
39676 the thread's attributes.
39679 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39680 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39681 conventions above. Please don't use this packet as a model for new
39700 @xref{Tracepoint Packets}.
39702 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39703 @cindex read special object, remote request
39704 @cindex @samp{qXfer} packet
39705 @anchor{qXfer read}
39706 Read uninterpreted bytes from the target's special data area
39707 identified by the keyword @var{object}. Request @var{length} bytes
39708 starting at @var{offset} bytes into the data. The content and
39709 encoding of @var{annex} is specific to @var{object}; it can supply
39710 additional details about what data to access.
39715 Data @var{data} (@pxref{Binary Data}) has been read from the
39716 target. There may be more data at a higher address (although
39717 it is permitted to return @samp{m} even for the last valid
39718 block of data, as long as at least one byte of data was read).
39719 It is possible for @var{data} to have fewer bytes than the @var{length} in the
39723 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39724 There is no more data to be read. It is possible for @var{data} to
39725 have fewer bytes than the @var{length} in the request.
39728 The @var{offset} in the request is at the end of the data.
39729 There is no more data to be read.
39732 The request was malformed, or @var{annex} was invalid.
39735 The offset was invalid, or there was an error encountered reading the data.
39736 The @var{nn} part is a hex-encoded @code{errno} value.
39739 An empty reply indicates the @var{object} string was not recognized by
39740 the stub, or that the object does not support reading.
39743 Here are the specific requests of this form defined so far. All the
39744 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39745 formats, listed above.
39748 @item qXfer:auxv:read::@var{offset},@var{length}
39749 @anchor{qXfer auxiliary vector read}
39750 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39751 auxiliary vector}. Note @var{annex} must be empty.
39753 This packet is not probed by default; the remote stub must request it,
39754 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39756 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39757 @anchor{qXfer btrace read}
39759 Return a description of the current branch trace.
39760 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39761 packet may have one of the following values:
39765 Returns all available branch trace.
39768 Returns all available branch trace if the branch trace changed since
39769 the last read request.
39772 Returns the new branch trace since the last read request. Adds a new
39773 block to the end of the trace that begins at zero and ends at the source
39774 location of the first branch in the trace buffer. This extra block is
39775 used to stitch traces together.
39777 If the trace buffer overflowed, returns an error indicating the overflow.
39780 This packet is not probed by default; the remote stub must request it
39781 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39783 @item qXfer:btrace-conf:read::@var{offset},@var{length}
39784 @anchor{qXfer btrace-conf read}
39786 Return a description of the current branch trace configuration.
39787 @xref{Branch Trace Configuration Format}.
39789 This packet is not probed by default; the remote stub must request it
39790 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39792 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
39793 @anchor{qXfer executable filename read}
39794 Return the full absolute name of the file that was executed to create
39795 a process running on the remote system. The annex specifies the
39796 numeric process ID of the process to query, encoded as a hexadecimal
39797 number. If the annex part is empty the remote stub should return the
39798 filename corresponding to the currently executing process.
39800 This packet is not probed by default; the remote stub must request it,
39801 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39803 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39804 @anchor{qXfer target description read}
39805 Access the @dfn{target description}. @xref{Target Descriptions}. The
39806 annex specifies which XML document to access. The main description is
39807 always loaded from the @samp{target.xml} annex.
39809 This packet is not probed by default; the remote stub must request it,
39810 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39812 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39813 @anchor{qXfer library list read}
39814 Access the target's list of loaded libraries. @xref{Library List Format}.
39815 The annex part of the generic @samp{qXfer} packet must be empty
39816 (@pxref{qXfer read}).
39818 Targets which maintain a list of libraries in the program's memory do
39819 not need to implement this packet; it is designed for platforms where
39820 the operating system manages the list of loaded libraries.
39822 This packet is not probed by default; the remote stub must request it,
39823 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39825 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39826 @anchor{qXfer svr4 library list read}
39827 Access the target's list of loaded libraries when the target is an SVR4
39828 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39829 of the generic @samp{qXfer} packet must be empty unless the remote
39830 stub indicated it supports the augmented form of this packet
39831 by supplying an appropriate @samp{qSupported} response
39832 (@pxref{qXfer read}, @ref{qSupported}).
39834 This packet is optional for better performance on SVR4 targets.
39835 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39837 This packet is not probed by default; the remote stub must request it,
39838 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39840 If the remote stub indicates it supports the augmented form of this
39841 packet then the annex part of the generic @samp{qXfer} packet may
39842 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39843 arguments. The currently supported arguments are:
39846 @item start=@var{address}
39847 A hexadecimal number specifying the address of the @samp{struct
39848 link_map} to start reading the library list from. If unset or zero
39849 then the first @samp{struct link_map} in the library list will be
39850 chosen as the starting point.
39852 @item prev=@var{address}
39853 A hexadecimal number specifying the address of the @samp{struct
39854 link_map} immediately preceding the @samp{struct link_map}
39855 specified by the @samp{start} argument. If unset or zero then
39856 the remote stub will expect that no @samp{struct link_map}
39857 exists prior to the starting point.
39861 Arguments that are not understood by the remote stub will be silently
39864 @item qXfer:memory-map:read::@var{offset},@var{length}
39865 @anchor{qXfer memory map read}
39866 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39867 annex part of the generic @samp{qXfer} packet must be empty
39868 (@pxref{qXfer read}).
39870 This packet is not probed by default; the remote stub must request it,
39871 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39873 @item qXfer:sdata:read::@var{offset},@var{length}
39874 @anchor{qXfer sdata read}
39876 Read contents of the extra collected static tracepoint marker
39877 information. The annex part of the generic @samp{qXfer} packet must
39878 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39881 This packet is not probed by default; the remote stub must request it,
39882 by supplying an appropriate @samp{qSupported} response
39883 (@pxref{qSupported}).
39885 @item qXfer:siginfo:read::@var{offset},@var{length}
39886 @anchor{qXfer siginfo read}
39887 Read contents of the extra signal information on the target
39888 system. The annex part of the generic @samp{qXfer} packet must be
39889 empty (@pxref{qXfer read}).
39891 This packet is not probed by default; the remote stub must request it,
39892 by supplying an appropriate @samp{qSupported} response
39893 (@pxref{qSupported}).
39895 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39896 @anchor{qXfer spu read}
39897 Read contents of an @code{spufs} file on the target system. The
39898 annex specifies which file to read; it must be of the form
39899 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39900 in the target process, and @var{name} identifes the @code{spufs} file
39901 in that context to be accessed.
39903 This packet is not probed by default; the remote stub must request it,
39904 by supplying an appropriate @samp{qSupported} response
39905 (@pxref{qSupported}).
39907 @item qXfer:threads:read::@var{offset},@var{length}
39908 @anchor{qXfer threads read}
39909 Access the list of threads on target. @xref{Thread List Format}. The
39910 annex part of the generic @samp{qXfer} packet must be empty
39911 (@pxref{qXfer read}).
39913 This packet is not probed by default; the remote stub must request it,
39914 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39916 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39917 @anchor{qXfer traceframe info read}
39919 Return a description of the current traceframe's contents.
39920 @xref{Traceframe Info Format}. The annex part of the generic
39921 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39923 This packet is not probed by default; the remote stub must request it,
39924 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39926 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39927 @anchor{qXfer unwind info block}
39929 Return the unwind information block for @var{pc}. This packet is used
39930 on OpenVMS/ia64 to ask the kernel unwind information.
39932 This packet is not probed by default.
39934 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39935 @anchor{qXfer fdpic loadmap read}
39936 Read contents of @code{loadmap}s on the target system. The
39937 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39938 executable @code{loadmap} or interpreter @code{loadmap} to read.
39940 This packet is not probed by default; the remote stub must request it,
39941 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39943 @item qXfer:osdata:read::@var{offset},@var{length}
39944 @anchor{qXfer osdata read}
39945 Access the target's @dfn{operating system information}.
39946 @xref{Operating System Information}.
39950 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39951 @cindex write data into object, remote request
39952 @anchor{qXfer write}
39953 Write uninterpreted bytes into the target's special data area
39954 identified by the keyword @var{object}, starting at @var{offset} bytes
39955 into the data. The binary-encoded data (@pxref{Binary Data}) to be
39956 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
39957 is specific to @var{object}; it can supply additional details about what data
39963 @var{nn} (hex encoded) is the number of bytes written.
39964 This may be fewer bytes than supplied in the request.
39967 The request was malformed, or @var{annex} was invalid.
39970 The offset was invalid, or there was an error encountered writing the data.
39971 The @var{nn} part is a hex-encoded @code{errno} value.
39974 An empty reply indicates the @var{object} string was not
39975 recognized by the stub, or that the object does not support writing.
39978 Here are the specific requests of this form defined so far. All the
39979 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39980 formats, listed above.
39983 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39984 @anchor{qXfer siginfo write}
39985 Write @var{data} to the extra signal information on the target system.
39986 The annex part of the generic @samp{qXfer} packet must be
39987 empty (@pxref{qXfer write}).
39989 This packet is not probed by default; the remote stub must request it,
39990 by supplying an appropriate @samp{qSupported} response
39991 (@pxref{qSupported}).
39993 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39994 @anchor{qXfer spu write}
39995 Write @var{data} to an @code{spufs} file on the target system. The
39996 annex specifies which file to write; it must be of the form
39997 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39998 in the target process, and @var{name} identifes the @code{spufs} file
39999 in that context to be accessed.
40001 This packet is not probed by default; the remote stub must request it,
40002 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40005 @item qXfer:@var{object}:@var{operation}:@dots{}
40006 Requests of this form may be added in the future. When a stub does
40007 not recognize the @var{object} keyword, or its support for
40008 @var{object} does not recognize the @var{operation} keyword, the stub
40009 must respond with an empty packet.
40011 @item qAttached:@var{pid}
40012 @cindex query attached, remote request
40013 @cindex @samp{qAttached} packet
40014 Return an indication of whether the remote server attached to an
40015 existing process or created a new process. When the multiprocess
40016 protocol extensions are supported (@pxref{multiprocess extensions}),
40017 @var{pid} is an integer in hexadecimal format identifying the target
40018 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40019 the query packet will be simplified as @samp{qAttached}.
40021 This query is used, for example, to know whether the remote process
40022 should be detached or killed when a @value{GDBN} session is ended with
40023 the @code{quit} command.
40028 The remote server attached to an existing process.
40030 The remote server created a new process.
40032 A badly formed request or an error was encountered.
40036 Enable branch tracing for the current thread using Branch Trace Store.
40041 Branch tracing has been enabled.
40043 A badly formed request or an error was encountered.
40047 Enable branch tracing for the current thread using Intel Processor Trace.
40052 Branch tracing has been enabled.
40054 A badly formed request or an error was encountered.
40058 Disable branch tracing for the current thread.
40063 Branch tracing has been disabled.
40065 A badly formed request or an error was encountered.
40068 @item Qbtrace-conf:bts:size=@var{value}
40069 Set the requested ring buffer size for new threads that use the
40070 btrace recording method in bts format.
40075 The ring buffer size has been set.
40077 A badly formed request or an error was encountered.
40080 @item Qbtrace-conf:pt:size=@var{value}
40081 Set the requested ring buffer size for new threads that use the
40082 btrace recording method in pt format.
40087 The ring buffer size has been set.
40089 A badly formed request or an error was encountered.
40094 @node Architecture-Specific Protocol Details
40095 @section Architecture-Specific Protocol Details
40097 This section describes how the remote protocol is applied to specific
40098 target architectures. Also see @ref{Standard Target Features}, for
40099 details of XML target descriptions for each architecture.
40102 * ARM-Specific Protocol Details::
40103 * MIPS-Specific Protocol Details::
40106 @node ARM-Specific Protocol Details
40107 @subsection @acronym{ARM}-specific Protocol Details
40110 * ARM Breakpoint Kinds::
40113 @node ARM Breakpoint Kinds
40114 @subsubsection @acronym{ARM} Breakpoint Kinds
40115 @cindex breakpoint kinds, @acronym{ARM}
40117 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40122 16-bit Thumb mode breakpoint.
40125 32-bit Thumb mode (Thumb-2) breakpoint.
40128 32-bit @acronym{ARM} mode breakpoint.
40132 @node MIPS-Specific Protocol Details
40133 @subsection @acronym{MIPS}-specific Protocol Details
40136 * MIPS Register packet Format::
40137 * MIPS Breakpoint Kinds::
40140 @node MIPS Register packet Format
40141 @subsubsection @acronym{MIPS} Register Packet Format
40142 @cindex register packet format, @acronym{MIPS}
40144 The following @code{g}/@code{G} packets have previously been defined.
40145 In the below, some thirty-two bit registers are transferred as
40146 sixty-four bits. Those registers should be zero/sign extended (which?)
40147 to fill the space allocated. Register bytes are transferred in target
40148 byte order. The two nibbles within a register byte are transferred
40149 most-significant -- least-significant.
40154 All registers are transferred as thirty-two bit quantities in the order:
40155 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40156 registers; fsr; fir; fp.
40159 All registers are transferred as sixty-four bit quantities (including
40160 thirty-two bit registers such as @code{sr}). The ordering is the same
40165 @node MIPS Breakpoint Kinds
40166 @subsubsection @acronym{MIPS} Breakpoint Kinds
40167 @cindex breakpoint kinds, @acronym{MIPS}
40169 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40174 16-bit @acronym{MIPS16} mode breakpoint.
40177 16-bit @acronym{microMIPS} mode breakpoint.
40180 32-bit standard @acronym{MIPS} mode breakpoint.
40183 32-bit @acronym{microMIPS} mode breakpoint.
40187 @node Tracepoint Packets
40188 @section Tracepoint Packets
40189 @cindex tracepoint packets
40190 @cindex packets, tracepoint
40192 Here we describe the packets @value{GDBN} uses to implement
40193 tracepoints (@pxref{Tracepoints}).
40197 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40198 @cindex @samp{QTDP} packet
40199 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40200 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40201 the tracepoint is disabled. The @var{step} gives the tracepoint's step
40202 count, and @var{pass} gives its pass count. If an @samp{F} is present,
40203 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40204 the number of bytes that the target should copy elsewhere to make room
40205 for the tracepoint. If an @samp{X} is present, it introduces a
40206 tracepoint condition, which consists of a hexadecimal length, followed
40207 by a comma and hex-encoded bytes, in a manner similar to action
40208 encodings as described below. If the trailing @samp{-} is present,
40209 further @samp{QTDP} packets will follow to specify this tracepoint's
40215 The packet was understood and carried out.
40217 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40219 The packet was not recognized.
40222 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40223 Define actions to be taken when a tracepoint is hit. The @var{n} and
40224 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40225 this tracepoint. This packet may only be sent immediately after
40226 another @samp{QTDP} packet that ended with a @samp{-}. If the
40227 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40228 specifying more actions for this tracepoint.
40230 In the series of action packets for a given tracepoint, at most one
40231 can have an @samp{S} before its first @var{action}. If such a packet
40232 is sent, it and the following packets define ``while-stepping''
40233 actions. Any prior packets define ordinary actions --- that is, those
40234 taken when the tracepoint is first hit. If no action packet has an
40235 @samp{S}, then all the packets in the series specify ordinary
40236 tracepoint actions.
40238 The @samp{@var{action}@dots{}} portion of the packet is a series of
40239 actions, concatenated without separators. Each action has one of the
40245 Collect the registers whose bits are set in @var{mask},
40246 a hexadecimal number whose @var{i}'th bit is set if register number
40247 @var{i} should be collected. (The least significant bit is numbered
40248 zero.) Note that @var{mask} may be any number of digits long; it may
40249 not fit in a 32-bit word.
40251 @item M @var{basereg},@var{offset},@var{len}
40252 Collect @var{len} bytes of memory starting at the address in register
40253 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40254 @samp{-1}, then the range has a fixed address: @var{offset} is the
40255 address of the lowest byte to collect. The @var{basereg},
40256 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40257 values (the @samp{-1} value for @var{basereg} is a special case).
40259 @item X @var{len},@var{expr}
40260 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40261 it directs. The agent expression @var{expr} is as described in
40262 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40263 two-digit hex number in the packet; @var{len} is the number of bytes
40264 in the expression (and thus one-half the number of hex digits in the
40269 Any number of actions may be packed together in a single @samp{QTDP}
40270 packet, as long as the packet does not exceed the maximum packet
40271 length (400 bytes, for many stubs). There may be only one @samp{R}
40272 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40273 actions. Any registers referred to by @samp{M} and @samp{X} actions
40274 must be collected by a preceding @samp{R} action. (The
40275 ``while-stepping'' actions are treated as if they were attached to a
40276 separate tracepoint, as far as these restrictions are concerned.)
40281 The packet was understood and carried out.
40283 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40285 The packet was not recognized.
40288 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40289 @cindex @samp{QTDPsrc} packet
40290 Specify a source string of tracepoint @var{n} at address @var{addr}.
40291 This is useful to get accurate reproduction of the tracepoints
40292 originally downloaded at the beginning of the trace run. The @var{type}
40293 is the name of the tracepoint part, such as @samp{cond} for the
40294 tracepoint's conditional expression (see below for a list of types), while
40295 @var{bytes} is the string, encoded in hexadecimal.
40297 @var{start} is the offset of the @var{bytes} within the overall source
40298 string, while @var{slen} is the total length of the source string.
40299 This is intended for handling source strings that are longer than will
40300 fit in a single packet.
40301 @c Add detailed example when this info is moved into a dedicated
40302 @c tracepoint descriptions section.
40304 The available string types are @samp{at} for the location,
40305 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40306 @value{GDBN} sends a separate packet for each command in the action
40307 list, in the same order in which the commands are stored in the list.
40309 The target does not need to do anything with source strings except
40310 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40313 Although this packet is optional, and @value{GDBN} will only send it
40314 if the target replies with @samp{TracepointSource} @xref{General
40315 Query Packets}, it makes both disconnected tracing and trace files
40316 much easier to use. Otherwise the user must be careful that the
40317 tracepoints in effect while looking at trace frames are identical to
40318 the ones in effect during the trace run; even a small discrepancy
40319 could cause @samp{tdump} not to work, or a particular trace frame not
40322 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
40323 @cindex define trace state variable, remote request
40324 @cindex @samp{QTDV} packet
40325 Create a new trace state variable, number @var{n}, with an initial
40326 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40327 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40328 the option of not using this packet for initial values of zero; the
40329 target should simply create the trace state variables as they are
40330 mentioned in expressions. The value @var{builtin} should be 1 (one)
40331 if the trace state variable is builtin and 0 (zero) if it is not builtin.
40332 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
40333 @samp{qTsV} packet had it set. The contents of @var{name} is the
40334 hex-encoded name (without the leading @samp{$}) of the trace state
40337 @item QTFrame:@var{n}
40338 @cindex @samp{QTFrame} packet
40339 Select the @var{n}'th tracepoint frame from the buffer, and use the
40340 register and memory contents recorded there to answer subsequent
40341 request packets from @value{GDBN}.
40343 A successful reply from the stub indicates that the stub has found the
40344 requested frame. The response is a series of parts, concatenated
40345 without separators, describing the frame we selected. Each part has
40346 one of the following forms:
40350 The selected frame is number @var{n} in the trace frame buffer;
40351 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40352 was no frame matching the criteria in the request packet.
40355 The selected trace frame records a hit of tracepoint number @var{t};
40356 @var{t} is a hexadecimal number.
40360 @item QTFrame:pc:@var{addr}
40361 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40362 currently selected frame whose PC is @var{addr};
40363 @var{addr} is a hexadecimal number.
40365 @item QTFrame:tdp:@var{t}
40366 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40367 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40368 is a hexadecimal number.
40370 @item QTFrame:range:@var{start}:@var{end}
40371 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40372 currently selected frame whose PC is between @var{start} (inclusive)
40373 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40376 @item QTFrame:outside:@var{start}:@var{end}
40377 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40378 frame @emph{outside} the given range of addresses (exclusive).
40381 @cindex @samp{qTMinFTPILen} packet
40382 This packet requests the minimum length of instruction at which a fast
40383 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40384 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40385 it depends on the target system being able to create trampolines in
40386 the first 64K of memory, which might or might not be possible for that
40387 system. So the reply to this packet will be 4 if it is able to
40394 The minimum instruction length is currently unknown.
40396 The minimum instruction length is @var{length}, where @var{length}
40397 is a hexadecimal number greater or equal to 1. A reply
40398 of 1 means that a fast tracepoint may be placed on any instruction
40399 regardless of size.
40401 An error has occurred.
40403 An empty reply indicates that the request is not supported by the stub.
40407 @cindex @samp{QTStart} packet
40408 Begin the tracepoint experiment. Begin collecting data from
40409 tracepoint hits in the trace frame buffer. This packet supports the
40410 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40411 instruction reply packet}).
40414 @cindex @samp{QTStop} packet
40415 End the tracepoint experiment. Stop collecting trace frames.
40417 @item QTEnable:@var{n}:@var{addr}
40419 @cindex @samp{QTEnable} packet
40420 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40421 experiment. If the tracepoint was previously disabled, then collection
40422 of data from it will resume.
40424 @item QTDisable:@var{n}:@var{addr}
40426 @cindex @samp{QTDisable} packet
40427 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40428 experiment. No more data will be collected from the tracepoint unless
40429 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40432 @cindex @samp{QTinit} packet
40433 Clear the table of tracepoints, and empty the trace frame buffer.
40435 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40436 @cindex @samp{QTro} packet
40437 Establish the given ranges of memory as ``transparent''. The stub
40438 will answer requests for these ranges from memory's current contents,
40439 if they were not collected as part of the tracepoint hit.
40441 @value{GDBN} uses this to mark read-only regions of memory, like those
40442 containing program code. Since these areas never change, they should
40443 still have the same contents they did when the tracepoint was hit, so
40444 there's no reason for the stub to refuse to provide their contents.
40446 @item QTDisconnected:@var{value}
40447 @cindex @samp{QTDisconnected} packet
40448 Set the choice to what to do with the tracing run when @value{GDBN}
40449 disconnects from the target. A @var{value} of 1 directs the target to
40450 continue the tracing run, while 0 tells the target to stop tracing if
40451 @value{GDBN} is no longer in the picture.
40454 @cindex @samp{qTStatus} packet
40455 Ask the stub if there is a trace experiment running right now.
40457 The reply has the form:
40461 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40462 @var{running} is a single digit @code{1} if the trace is presently
40463 running, or @code{0} if not. It is followed by semicolon-separated
40464 optional fields that an agent may use to report additional status.
40468 If the trace is not running, the agent may report any of several
40469 explanations as one of the optional fields:
40474 No trace has been run yet.
40476 @item tstop[:@var{text}]:0
40477 The trace was stopped by a user-originated stop command. The optional
40478 @var{text} field is a user-supplied string supplied as part of the
40479 stop command (for instance, an explanation of why the trace was
40480 stopped manually). It is hex-encoded.
40483 The trace stopped because the trace buffer filled up.
40485 @item tdisconnected:0
40486 The trace stopped because @value{GDBN} disconnected from the target.
40488 @item tpasscount:@var{tpnum}
40489 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40491 @item terror:@var{text}:@var{tpnum}
40492 The trace stopped because tracepoint @var{tpnum} had an error. The
40493 string @var{text} is available to describe the nature of the error
40494 (for instance, a divide by zero in the condition expression); it
40498 The trace stopped for some other reason.
40502 Additional optional fields supply statistical and other information.
40503 Although not required, they are extremely useful for users monitoring
40504 the progress of a trace run. If a trace has stopped, and these
40505 numbers are reported, they must reflect the state of the just-stopped
40510 @item tframes:@var{n}
40511 The number of trace frames in the buffer.
40513 @item tcreated:@var{n}
40514 The total number of trace frames created during the run. This may
40515 be larger than the trace frame count, if the buffer is circular.
40517 @item tsize:@var{n}
40518 The total size of the trace buffer, in bytes.
40520 @item tfree:@var{n}
40521 The number of bytes still unused in the buffer.
40523 @item circular:@var{n}
40524 The value of the circular trace buffer flag. @code{1} means that the
40525 trace buffer is circular and old trace frames will be discarded if
40526 necessary to make room, @code{0} means that the trace buffer is linear
40529 @item disconn:@var{n}
40530 The value of the disconnected tracing flag. @code{1} means that
40531 tracing will continue after @value{GDBN} disconnects, @code{0} means
40532 that the trace run will stop.
40536 @item qTP:@var{tp}:@var{addr}
40537 @cindex tracepoint status, remote request
40538 @cindex @samp{qTP} packet
40539 Ask the stub for the current state of tracepoint number @var{tp} at
40540 address @var{addr}.
40544 @item V@var{hits}:@var{usage}
40545 The tracepoint has been hit @var{hits} times so far during the trace
40546 run, and accounts for @var{usage} in the trace buffer. Note that
40547 @code{while-stepping} steps are not counted as separate hits, but the
40548 steps' space consumption is added into the usage number.
40552 @item qTV:@var{var}
40553 @cindex trace state variable value, remote request
40554 @cindex @samp{qTV} packet
40555 Ask the stub for the value of the trace state variable number @var{var}.
40560 The value of the variable is @var{value}. This will be the current
40561 value of the variable if the user is examining a running target, or a
40562 saved value if the variable was collected in the trace frame that the
40563 user is looking at. Note that multiple requests may result in
40564 different reply values, such as when requesting values while the
40565 program is running.
40568 The value of the variable is unknown. This would occur, for example,
40569 if the user is examining a trace frame in which the requested variable
40574 @cindex @samp{qTfP} packet
40576 @cindex @samp{qTsP} packet
40577 These packets request data about tracepoints that are being used by
40578 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40579 of data, and multiple @code{qTsP} to get additional pieces. Replies
40580 to these packets generally take the form of the @code{QTDP} packets
40581 that define tracepoints. (FIXME add detailed syntax)
40584 @cindex @samp{qTfV} packet
40586 @cindex @samp{qTsV} packet
40587 These packets request data about trace state variables that are on the
40588 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40589 and multiple @code{qTsV} to get additional variables. Replies to
40590 these packets follow the syntax of the @code{QTDV} packets that define
40591 trace state variables.
40597 @cindex @samp{qTfSTM} packet
40598 @cindex @samp{qTsSTM} packet
40599 These packets request data about static tracepoint markers that exist
40600 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40601 first piece of data, and multiple @code{qTsSTM} to get additional
40602 pieces. Replies to these packets take the following form:
40606 @item m @var{address}:@var{id}:@var{extra}
40608 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40609 a comma-separated list of markers
40611 (lower case letter @samp{L}) denotes end of list.
40613 An error occurred. The error number @var{nn} is given as hex digits.
40615 An empty reply indicates that the request is not supported by the
40619 The @var{address} is encoded in hex;
40620 @var{id} and @var{extra} are strings encoded in hex.
40622 In response to each query, the target will reply with a list of one or
40623 more markers, separated by commas. @value{GDBN} will respond to each
40624 reply with a request for more markers (using the @samp{qs} form of the
40625 query), until the target responds with @samp{l} (lower-case ell, for
40628 @item qTSTMat:@var{address}
40630 @cindex @samp{qTSTMat} packet
40631 This packets requests data about static tracepoint markers in the
40632 target program at @var{address}. Replies to this packet follow the
40633 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40634 tracepoint markers.
40636 @item QTSave:@var{filename}
40637 @cindex @samp{QTSave} packet
40638 This packet directs the target to save trace data to the file name
40639 @var{filename} in the target's filesystem. The @var{filename} is encoded
40640 as a hex string; the interpretation of the file name (relative vs
40641 absolute, wild cards, etc) is up to the target.
40643 @item qTBuffer:@var{offset},@var{len}
40644 @cindex @samp{qTBuffer} packet
40645 Return up to @var{len} bytes of the current contents of trace buffer,
40646 starting at @var{offset}. The trace buffer is treated as if it were
40647 a contiguous collection of traceframes, as per the trace file format.
40648 The reply consists as many hex-encoded bytes as the target can deliver
40649 in a packet; it is not an error to return fewer than were asked for.
40650 A reply consisting of just @code{l} indicates that no bytes are
40653 @item QTBuffer:circular:@var{value}
40654 This packet directs the target to use a circular trace buffer if
40655 @var{value} is 1, or a linear buffer if the value is 0.
40657 @item QTBuffer:size:@var{size}
40658 @anchor{QTBuffer-size}
40659 @cindex @samp{QTBuffer size} packet
40660 This packet directs the target to make the trace buffer be of size
40661 @var{size} if possible. A value of @code{-1} tells the target to
40662 use whatever size it prefers.
40664 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40665 @cindex @samp{QTNotes} packet
40666 This packet adds optional textual notes to the trace run. Allowable
40667 types include @code{user}, @code{notes}, and @code{tstop}, the
40668 @var{text} fields are arbitrary strings, hex-encoded.
40672 @subsection Relocate instruction reply packet
40673 When installing fast tracepoints in memory, the target may need to
40674 relocate the instruction currently at the tracepoint address to a
40675 different address in memory. For most instructions, a simple copy is
40676 enough, but, for example, call instructions that implicitly push the
40677 return address on the stack, and relative branches or other
40678 PC-relative instructions require offset adjustment, so that the effect
40679 of executing the instruction at a different address is the same as if
40680 it had executed in the original location.
40682 In response to several of the tracepoint packets, the target may also
40683 respond with a number of intermediate @samp{qRelocInsn} request
40684 packets before the final result packet, to have @value{GDBN} handle
40685 this relocation operation. If a packet supports this mechanism, its
40686 documentation will explicitly say so. See for example the above
40687 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40688 format of the request is:
40691 @item qRelocInsn:@var{from};@var{to}
40693 This requests @value{GDBN} to copy instruction at address @var{from}
40694 to address @var{to}, possibly adjusted so that executing the
40695 instruction at @var{to} has the same effect as executing it at
40696 @var{from}. @value{GDBN} writes the adjusted instruction to target
40697 memory starting at @var{to}.
40702 @item qRelocInsn:@var{adjusted_size}
40703 Informs the stub the relocation is complete. The @var{adjusted_size} is
40704 the length in bytes of resulting relocated instruction sequence.
40706 A badly formed request was detected, or an error was encountered while
40707 relocating the instruction.
40710 @node Host I/O Packets
40711 @section Host I/O Packets
40712 @cindex Host I/O, remote protocol
40713 @cindex file transfer, remote protocol
40715 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40716 operations on the far side of a remote link. For example, Host I/O is
40717 used to upload and download files to a remote target with its own
40718 filesystem. Host I/O uses the same constant values and data structure
40719 layout as the target-initiated File-I/O protocol. However, the
40720 Host I/O packets are structured differently. The target-initiated
40721 protocol relies on target memory to store parameters and buffers.
40722 Host I/O requests are initiated by @value{GDBN}, and the
40723 target's memory is not involved. @xref{File-I/O Remote Protocol
40724 Extension}, for more details on the target-initiated protocol.
40726 The Host I/O request packets all encode a single operation along with
40727 its arguments. They have this format:
40731 @item vFile:@var{operation}: @var{parameter}@dots{}
40732 @var{operation} is the name of the particular request; the target
40733 should compare the entire packet name up to the second colon when checking
40734 for a supported operation. The format of @var{parameter} depends on
40735 the operation. Numbers are always passed in hexadecimal. Negative
40736 numbers have an explicit minus sign (i.e.@: two's complement is not
40737 used). Strings (e.g.@: filenames) are encoded as a series of
40738 hexadecimal bytes. The last argument to a system call may be a
40739 buffer of escaped binary data (@pxref{Binary Data}).
40743 The valid responses to Host I/O packets are:
40747 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40748 @var{result} is the integer value returned by this operation, usually
40749 non-negative for success and -1 for errors. If an error has occured,
40750 @var{errno} will be included in the result specifying a
40751 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40752 operations which return data, @var{attachment} supplies the data as a
40753 binary buffer. Binary buffers in response packets are escaped in the
40754 normal way (@pxref{Binary Data}). See the individual packet
40755 documentation for the interpretation of @var{result} and
40759 An empty response indicates that this operation is not recognized.
40763 These are the supported Host I/O operations:
40766 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
40767 Open a file at @var{filename} and return a file descriptor for it, or
40768 return -1 if an error occurs. The @var{filename} is a string,
40769 @var{flags} is an integer indicating a mask of open flags
40770 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40771 of mode bits to use if the file is created (@pxref{mode_t Values}).
40772 @xref{open}, for details of the open flags and mode values.
40774 @item vFile:close: @var{fd}
40775 Close the open file corresponding to @var{fd} and return 0, or
40776 -1 if an error occurs.
40778 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40779 Read data from the open file corresponding to @var{fd}. Up to
40780 @var{count} bytes will be read from the file, starting at @var{offset}
40781 relative to the start of the file. The target may read fewer bytes;
40782 common reasons include packet size limits and an end-of-file
40783 condition. The number of bytes read is returned. Zero should only be
40784 returned for a successful read at the end of the file, or if
40785 @var{count} was zero.
40787 The data read should be returned as a binary attachment on success.
40788 If zero bytes were read, the response should include an empty binary
40789 attachment (i.e.@: a trailing semicolon). The return value is the
40790 number of target bytes read; the binary attachment may be longer if
40791 some characters were escaped.
40793 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40794 Write @var{data} (a binary buffer) to the open file corresponding
40795 to @var{fd}. Start the write at @var{offset} from the start of the
40796 file. Unlike many @code{write} system calls, there is no
40797 separate @var{count} argument; the length of @var{data} in the
40798 packet is used. @samp{vFile:write} returns the number of bytes written,
40799 which may be shorter than the length of @var{data}, or -1 if an
40802 @item vFile:fstat: @var{fd}
40803 Get information about the open file corresponding to @var{fd}.
40804 On success the information is returned as a binary attachment
40805 and the return value is the size of this attachment in bytes.
40806 If an error occurs the return value is -1. The format of the
40807 returned binary attachment is as described in @ref{struct stat}.
40809 @item vFile:unlink: @var{filename}
40810 Delete the file at @var{filename} on the target. Return 0,
40811 or -1 if an error occurs. The @var{filename} is a string.
40813 @item vFile:readlink: @var{filename}
40814 Read value of symbolic link @var{filename} on the target. Return
40815 the number of bytes read, or -1 if an error occurs.
40817 The data read should be returned as a binary attachment on success.
40818 If zero bytes were read, the response should include an empty binary
40819 attachment (i.e.@: a trailing semicolon). The return value is the
40820 number of target bytes read; the binary attachment may be longer if
40821 some characters were escaped.
40823 @item vFile:setfs: @var{pid}
40824 Select the filesystem on which @code{vFile} operations with
40825 @var{filename} arguments will operate. This is required for
40826 @value{GDBN} to be able to access files on remote targets where
40827 the remote stub does not share a common filesystem with the
40830 If @var{pid} is nonzero, select the filesystem as seen by process
40831 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
40832 the remote stub. Return 0 on success, or -1 if an error occurs.
40833 If @code{vFile:setfs:} indicates success, the selected filesystem
40834 remains selected until the next successful @code{vFile:setfs:}
40840 @section Interrupts
40841 @cindex interrupts (remote protocol)
40842 @anchor{interrupting remote targets}
40844 In all-stop mode, when a program on the remote target is running,
40845 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
40846 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
40847 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40849 The precise meaning of @code{BREAK} is defined by the transport
40850 mechanism and may, in fact, be undefined. @value{GDBN} does not
40851 currently define a @code{BREAK} mechanism for any of the network
40852 interfaces except for TCP, in which case @value{GDBN} sends the
40853 @code{telnet} BREAK sequence.
40855 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40856 transport mechanisms. It is represented by sending the single byte
40857 @code{0x03} without any of the usual packet overhead described in
40858 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40859 transmitted as part of a packet, it is considered to be packet data
40860 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40861 (@pxref{X packet}), used for binary downloads, may include an unescaped
40862 @code{0x03} as part of its packet.
40864 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40865 When Linux kernel receives this sequence from serial port,
40866 it stops execution and connects to gdb.
40868 In non-stop mode, because packet resumptions are asynchronous
40869 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
40870 command to the remote stub, even when the target is running. For that
40871 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
40872 packet}) with the usual packet framing instead of the single byte
40875 Stubs are not required to recognize these interrupt mechanisms and the
40876 precise meaning associated with receipt of the interrupt is
40877 implementation defined. If the target supports debugging of multiple
40878 threads and/or processes, it should attempt to interrupt all
40879 currently-executing threads and processes.
40880 If the stub is successful at interrupting the
40881 running program, it should send one of the stop
40882 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40883 of successfully stopping the program in all-stop mode, and a stop reply
40884 for each stopped thread in non-stop mode.
40885 Interrupts received while the
40886 program is stopped are queued and the program will be interrupted when
40887 it is resumed next time.
40889 @node Notification Packets
40890 @section Notification Packets
40891 @cindex notification packets
40892 @cindex packets, notification
40894 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40895 packets that require no acknowledgment. Both the GDB and the stub
40896 may send notifications (although the only notifications defined at
40897 present are sent by the stub). Notifications carry information
40898 without incurring the round-trip latency of an acknowledgment, and so
40899 are useful for low-impact communications where occasional packet loss
40902 A notification packet has the form @samp{% @var{data} #
40903 @var{checksum}}, where @var{data} is the content of the notification,
40904 and @var{checksum} is a checksum of @var{data}, computed and formatted
40905 as for ordinary @value{GDBN} packets. A notification's @var{data}
40906 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40907 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40908 to acknowledge the notification's receipt or to report its corruption.
40910 Every notification's @var{data} begins with a name, which contains no
40911 colon characters, followed by a colon character.
40913 Recipients should silently ignore corrupted notifications and
40914 notifications they do not understand. Recipients should restart
40915 timeout periods on receipt of a well-formed notification, whether or
40916 not they understand it.
40918 Senders should only send the notifications described here when this
40919 protocol description specifies that they are permitted. In the
40920 future, we may extend the protocol to permit existing notifications in
40921 new contexts; this rule helps older senders avoid confusing newer
40924 (Older versions of @value{GDBN} ignore bytes received until they see
40925 the @samp{$} byte that begins an ordinary packet, so new stubs may
40926 transmit notifications without fear of confusing older clients. There
40927 are no notifications defined for @value{GDBN} to send at the moment, but we
40928 assume that most older stubs would ignore them, as well.)
40930 Each notification is comprised of three parts:
40932 @item @var{name}:@var{event}
40933 The notification packet is sent by the side that initiates the
40934 exchange (currently, only the stub does that), with @var{event}
40935 carrying the specific information about the notification, and
40936 @var{name} specifying the name of the notification.
40938 The acknowledge sent by the other side, usually @value{GDBN}, to
40939 acknowledge the exchange and request the event.
40942 The purpose of an asynchronous notification mechanism is to report to
40943 @value{GDBN} that something interesting happened in the remote stub.
40945 The remote stub may send notification @var{name}:@var{event}
40946 at any time, but @value{GDBN} acknowledges the notification when
40947 appropriate. The notification event is pending before @value{GDBN}
40948 acknowledges. Only one notification at a time may be pending; if
40949 additional events occur before @value{GDBN} has acknowledged the
40950 previous notification, they must be queued by the stub for later
40951 synchronous transmission in response to @var{ack} packets from
40952 @value{GDBN}. Because the notification mechanism is unreliable,
40953 the stub is permitted to resend a notification if it believes
40954 @value{GDBN} may not have received it.
40956 Specifically, notifications may appear when @value{GDBN} is not
40957 otherwise reading input from the stub, or when @value{GDBN} is
40958 expecting to read a normal synchronous response or a
40959 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40960 Notification packets are distinct from any other communication from
40961 the stub so there is no ambiguity.
40963 After receiving a notification, @value{GDBN} shall acknowledge it by
40964 sending a @var{ack} packet as a regular, synchronous request to the
40965 stub. Such acknowledgment is not required to happen immediately, as
40966 @value{GDBN} is permitted to send other, unrelated packets to the
40967 stub first, which the stub should process normally.
40969 Upon receiving a @var{ack} packet, if the stub has other queued
40970 events to report to @value{GDBN}, it shall respond by sending a
40971 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40972 packet to solicit further responses; again, it is permitted to send
40973 other, unrelated packets as well which the stub should process
40976 If the stub receives a @var{ack} packet and there are no additional
40977 @var{event} to report, the stub shall return an @samp{OK} response.
40978 At this point, @value{GDBN} has finished processing a notification
40979 and the stub has completed sending any queued events. @value{GDBN}
40980 won't accept any new notifications until the final @samp{OK} is
40981 received . If further notification events occur, the stub shall send
40982 a new notification, @value{GDBN} shall accept the notification, and
40983 the process shall be repeated.
40985 The process of asynchronous notification can be illustrated by the
40988 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40991 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40993 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40998 The following notifications are defined:
40999 @multitable @columnfractions 0.12 0.12 0.38 0.38
41008 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41009 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41010 for information on how these notifications are acknowledged by
41012 @tab Report an asynchronous stop event in non-stop mode.
41016 @node Remote Non-Stop
41017 @section Remote Protocol Support for Non-Stop Mode
41019 @value{GDBN}'s remote protocol supports non-stop debugging of
41020 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41021 supports non-stop mode, it should report that to @value{GDBN} by including
41022 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41024 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41025 establishing a new connection with the stub. Entering non-stop mode
41026 does not alter the state of any currently-running threads, but targets
41027 must stop all threads in any already-attached processes when entering
41028 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41029 probe the target state after a mode change.
41031 In non-stop mode, when an attached process encounters an event that
41032 would otherwise be reported with a stop reply, it uses the
41033 asynchronous notification mechanism (@pxref{Notification Packets}) to
41034 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41035 in all processes are stopped when a stop reply is sent, in non-stop
41036 mode only the thread reporting the stop event is stopped. That is,
41037 when reporting a @samp{S} or @samp{T} response to indicate completion
41038 of a step operation, hitting a breakpoint, or a fault, only the
41039 affected thread is stopped; any other still-running threads continue
41040 to run. When reporting a @samp{W} or @samp{X} response, all running
41041 threads belonging to other attached processes continue to run.
41043 In non-stop mode, the target shall respond to the @samp{?} packet as
41044 follows. First, any incomplete stop reply notification/@samp{vStopped}
41045 sequence in progress is abandoned. The target must begin a new
41046 sequence reporting stop events for all stopped threads, whether or not
41047 it has previously reported those events to @value{GDBN}. The first
41048 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41049 subsequent stop replies are sent as responses to @samp{vStopped} packets
41050 using the mechanism described above. The target must not send
41051 asynchronous stop reply notifications until the sequence is complete.
41052 If all threads are running when the target receives the @samp{?} packet,
41053 or if the target is not attached to any process, it shall respond
41056 If the stub supports non-stop mode, it should also support the
41057 @samp{swbreak} stop reason if software breakpoints are supported, and
41058 the @samp{hwbreak} stop reason if hardware breakpoints are supported
41059 (@pxref{swbreak stop reason}). This is because given the asynchronous
41060 nature of non-stop mode, between the time a thread hits a breakpoint
41061 and the time the event is finally processed by @value{GDBN}, the
41062 breakpoint may have already been removed from the target. Due to
41063 this, @value{GDBN} needs to be able to tell whether a trap stop was
41064 caused by a delayed breakpoint event, which should be ignored, as
41065 opposed to a random trap signal, which should be reported to the user.
41066 Note the @samp{swbreak} feature implies that the target is responsible
41067 for adjusting the PC when a software breakpoint triggers, if
41068 necessary, such as on the x86 architecture.
41070 @node Packet Acknowledgment
41071 @section Packet Acknowledgment
41073 @cindex acknowledgment, for @value{GDBN} remote
41074 @cindex packet acknowledgment, for @value{GDBN} remote
41075 By default, when either the host or the target machine receives a packet,
41076 the first response expected is an acknowledgment: either @samp{+} (to indicate
41077 the package was received correctly) or @samp{-} (to request retransmission).
41078 This mechanism allows the @value{GDBN} remote protocol to operate over
41079 unreliable transport mechanisms, such as a serial line.
41081 In cases where the transport mechanism is itself reliable (such as a pipe or
41082 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41083 It may be desirable to disable them in that case to reduce communication
41084 overhead, or for other reasons. This can be accomplished by means of the
41085 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41087 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41088 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41089 and response format still includes the normal checksum, as described in
41090 @ref{Overview}, but the checksum may be ignored by the receiver.
41092 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41093 no-acknowledgment mode, it should report that to @value{GDBN}
41094 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41095 @pxref{qSupported}.
41096 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41097 disabled via the @code{set remote noack-packet off} command
41098 (@pxref{Remote Configuration}),
41099 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41100 Only then may the stub actually turn off packet acknowledgments.
41101 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41102 response, which can be safely ignored by the stub.
41104 Note that @code{set remote noack-packet} command only affects negotiation
41105 between @value{GDBN} and the stub when subsequent connections are made;
41106 it does not affect the protocol acknowledgment state for any current
41108 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41109 new connection is established,
41110 there is also no protocol request to re-enable the acknowledgments
41111 for the current connection, once disabled.
41116 Example sequence of a target being re-started. Notice how the restart
41117 does not get any direct output:
41122 @emph{target restarts}
41125 <- @code{T001:1234123412341234}
41129 Example sequence of a target being stepped by a single instruction:
41132 -> @code{G1445@dots{}}
41137 <- @code{T001:1234123412341234}
41141 <- @code{1455@dots{}}
41145 @node File-I/O Remote Protocol Extension
41146 @section File-I/O Remote Protocol Extension
41147 @cindex File-I/O remote protocol extension
41150 * File-I/O Overview::
41151 * Protocol Basics::
41152 * The F Request Packet::
41153 * The F Reply Packet::
41154 * The Ctrl-C Message::
41156 * List of Supported Calls::
41157 * Protocol-specific Representation of Datatypes::
41159 * File-I/O Examples::
41162 @node File-I/O Overview
41163 @subsection File-I/O Overview
41164 @cindex file-i/o overview
41166 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41167 target to use the host's file system and console I/O to perform various
41168 system calls. System calls on the target system are translated into a
41169 remote protocol packet to the host system, which then performs the needed
41170 actions and returns a response packet to the target system.
41171 This simulates file system operations even on targets that lack file systems.
41173 The protocol is defined to be independent of both the host and target systems.
41174 It uses its own internal representation of datatypes and values. Both
41175 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41176 translating the system-dependent value representations into the internal
41177 protocol representations when data is transmitted.
41179 The communication is synchronous. A system call is possible only when
41180 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41181 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41182 the target is stopped to allow deterministic access to the target's
41183 memory. Therefore File-I/O is not interruptible by target signals. On
41184 the other hand, it is possible to interrupt File-I/O by a user interrupt
41185 (@samp{Ctrl-C}) within @value{GDBN}.
41187 The target's request to perform a host system call does not finish
41188 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41189 after finishing the system call, the target returns to continuing the
41190 previous activity (continue, step). No additional continue or step
41191 request from @value{GDBN} is required.
41194 (@value{GDBP}) continue
41195 <- target requests 'system call X'
41196 target is stopped, @value{GDBN} executes system call
41197 -> @value{GDBN} returns result
41198 ... target continues, @value{GDBN} returns to wait for the target
41199 <- target hits breakpoint and sends a Txx packet
41202 The protocol only supports I/O on the console and to regular files on
41203 the host file system. Character or block special devices, pipes,
41204 named pipes, sockets or any other communication method on the host
41205 system are not supported by this protocol.
41207 File I/O is not supported in non-stop mode.
41209 @node Protocol Basics
41210 @subsection Protocol Basics
41211 @cindex protocol basics, file-i/o
41213 The File-I/O protocol uses the @code{F} packet as the request as well
41214 as reply packet. Since a File-I/O system call can only occur when
41215 @value{GDBN} is waiting for a response from the continuing or stepping target,
41216 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41217 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41218 This @code{F} packet contains all information needed to allow @value{GDBN}
41219 to call the appropriate host system call:
41223 A unique identifier for the requested system call.
41226 All parameters to the system call. Pointers are given as addresses
41227 in the target memory address space. Pointers to strings are given as
41228 pointer/length pair. Numerical values are given as they are.
41229 Numerical control flags are given in a protocol-specific representation.
41233 At this point, @value{GDBN} has to perform the following actions.
41237 If the parameters include pointer values to data needed as input to a
41238 system call, @value{GDBN} requests this data from the target with a
41239 standard @code{m} packet request. This additional communication has to be
41240 expected by the target implementation and is handled as any other @code{m}
41244 @value{GDBN} translates all value from protocol representation to host
41245 representation as needed. Datatypes are coerced into the host types.
41248 @value{GDBN} calls the system call.
41251 It then coerces datatypes back to protocol representation.
41254 If the system call is expected to return data in buffer space specified
41255 by pointer parameters to the call, the data is transmitted to the
41256 target using a @code{M} or @code{X} packet. This packet has to be expected
41257 by the target implementation and is handled as any other @code{M} or @code{X}
41262 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41263 necessary information for the target to continue. This at least contains
41270 @code{errno}, if has been changed by the system call.
41277 After having done the needed type and value coercion, the target continues
41278 the latest continue or step action.
41280 @node The F Request Packet
41281 @subsection The @code{F} Request Packet
41282 @cindex file-i/o request packet
41283 @cindex @code{F} request packet
41285 The @code{F} request packet has the following format:
41288 @item F@var{call-id},@var{parameter@dots{}}
41290 @var{call-id} is the identifier to indicate the host system call to be called.
41291 This is just the name of the function.
41293 @var{parameter@dots{}} are the parameters to the system call.
41294 Parameters are hexadecimal integer values, either the actual values in case
41295 of scalar datatypes, pointers to target buffer space in case of compound
41296 datatypes and unspecified memory areas, or pointer/length pairs in case
41297 of string parameters. These are appended to the @var{call-id} as a
41298 comma-delimited list. All values are transmitted in ASCII
41299 string representation, pointer/length pairs separated by a slash.
41305 @node The F Reply Packet
41306 @subsection The @code{F} Reply Packet
41307 @cindex file-i/o reply packet
41308 @cindex @code{F} reply packet
41310 The @code{F} reply packet has the following format:
41314 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41316 @var{retcode} is the return code of the system call as hexadecimal value.
41318 @var{errno} is the @code{errno} set by the call, in protocol-specific
41320 This parameter can be omitted if the call was successful.
41322 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41323 case, @var{errno} must be sent as well, even if the call was successful.
41324 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41331 or, if the call was interrupted before the host call has been performed:
41338 assuming 4 is the protocol-specific representation of @code{EINTR}.
41343 @node The Ctrl-C Message
41344 @subsection The @samp{Ctrl-C} Message
41345 @cindex ctrl-c message, in file-i/o protocol
41347 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41348 reply packet (@pxref{The F Reply Packet}),
41349 the target should behave as if it had
41350 gotten a break message. The meaning for the target is ``system call
41351 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41352 (as with a break message) and return to @value{GDBN} with a @code{T02}
41355 It's important for the target to know in which
41356 state the system call was interrupted. There are two possible cases:
41360 The system call hasn't been performed on the host yet.
41363 The system call on the host has been finished.
41367 These two states can be distinguished by the target by the value of the
41368 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41369 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41370 on POSIX systems. In any other case, the target may presume that the
41371 system call has been finished --- successfully or not --- and should behave
41372 as if the break message arrived right after the system call.
41374 @value{GDBN} must behave reliably. If the system call has not been called
41375 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41376 @code{errno} in the packet. If the system call on the host has been finished
41377 before the user requests a break, the full action must be finished by
41378 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41379 The @code{F} packet may only be sent when either nothing has happened
41380 or the full action has been completed.
41383 @subsection Console I/O
41384 @cindex console i/o as part of file-i/o
41386 By default and if not explicitly closed by the target system, the file
41387 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41388 on the @value{GDBN} console is handled as any other file output operation
41389 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41390 by @value{GDBN} so that after the target read request from file descriptor
41391 0 all following typing is buffered until either one of the following
41396 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41398 system call is treated as finished.
41401 The user presses @key{RET}. This is treated as end of input with a trailing
41405 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41406 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41410 If the user has typed more characters than fit in the buffer given to
41411 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41412 either another @code{read(0, @dots{})} is requested by the target, or debugging
41413 is stopped at the user's request.
41416 @node List of Supported Calls
41417 @subsection List of Supported Calls
41418 @cindex list of supported file-i/o calls
41435 @unnumberedsubsubsec open
41436 @cindex open, file-i/o system call
41441 int open(const char *pathname, int flags);
41442 int open(const char *pathname, int flags, mode_t mode);
41446 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41449 @var{flags} is the bitwise @code{OR} of the following values:
41453 If the file does not exist it will be created. The host
41454 rules apply as far as file ownership and time stamps
41458 When used with @code{O_CREAT}, if the file already exists it is
41459 an error and open() fails.
41462 If the file already exists and the open mode allows
41463 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41464 truncated to zero length.
41467 The file is opened in append mode.
41470 The file is opened for reading only.
41473 The file is opened for writing only.
41476 The file is opened for reading and writing.
41480 Other bits are silently ignored.
41484 @var{mode} is the bitwise @code{OR} of the following values:
41488 User has read permission.
41491 User has write permission.
41494 Group has read permission.
41497 Group has write permission.
41500 Others have read permission.
41503 Others have write permission.
41507 Other bits are silently ignored.
41510 @item Return value:
41511 @code{open} returns the new file descriptor or -1 if an error
41518 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41521 @var{pathname} refers to a directory.
41524 The requested access is not allowed.
41527 @var{pathname} was too long.
41530 A directory component in @var{pathname} does not exist.
41533 @var{pathname} refers to a device, pipe, named pipe or socket.
41536 @var{pathname} refers to a file on a read-only filesystem and
41537 write access was requested.
41540 @var{pathname} is an invalid pointer value.
41543 No space on device to create the file.
41546 The process already has the maximum number of files open.
41549 The limit on the total number of files open on the system
41553 The call was interrupted by the user.
41559 @unnumberedsubsubsec close
41560 @cindex close, file-i/o system call
41569 @samp{Fclose,@var{fd}}
41571 @item Return value:
41572 @code{close} returns zero on success, or -1 if an error occurred.
41578 @var{fd} isn't a valid open file descriptor.
41581 The call was interrupted by the user.
41587 @unnumberedsubsubsec read
41588 @cindex read, file-i/o system call
41593 int read(int fd, void *buf, unsigned int count);
41597 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41599 @item Return value:
41600 On success, the number of bytes read is returned.
41601 Zero indicates end of file. If count is zero, read
41602 returns zero as well. On error, -1 is returned.
41608 @var{fd} is not a valid file descriptor or is not open for
41612 @var{bufptr} is an invalid pointer value.
41615 The call was interrupted by the user.
41621 @unnumberedsubsubsec write
41622 @cindex write, file-i/o system call
41627 int write(int fd, const void *buf, unsigned int count);
41631 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41633 @item Return value:
41634 On success, the number of bytes written are returned.
41635 Zero indicates nothing was written. On error, -1
41642 @var{fd} is not a valid file descriptor or is not open for
41646 @var{bufptr} is an invalid pointer value.
41649 An attempt was made to write a file that exceeds the
41650 host-specific maximum file size allowed.
41653 No space on device to write the data.
41656 The call was interrupted by the user.
41662 @unnumberedsubsubsec lseek
41663 @cindex lseek, file-i/o system call
41668 long lseek (int fd, long offset, int flag);
41672 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41674 @var{flag} is one of:
41678 The offset is set to @var{offset} bytes.
41681 The offset is set to its current location plus @var{offset}
41685 The offset is set to the size of the file plus @var{offset}
41689 @item Return value:
41690 On success, the resulting unsigned offset in bytes from
41691 the beginning of the file is returned. Otherwise, a
41692 value of -1 is returned.
41698 @var{fd} is not a valid open file descriptor.
41701 @var{fd} is associated with the @value{GDBN} console.
41704 @var{flag} is not a proper value.
41707 The call was interrupted by the user.
41713 @unnumberedsubsubsec rename
41714 @cindex rename, file-i/o system call
41719 int rename(const char *oldpath, const char *newpath);
41723 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41725 @item Return value:
41726 On success, zero is returned. On error, -1 is returned.
41732 @var{newpath} is an existing directory, but @var{oldpath} is not a
41736 @var{newpath} is a non-empty directory.
41739 @var{oldpath} or @var{newpath} is a directory that is in use by some
41743 An attempt was made to make a directory a subdirectory
41747 A component used as a directory in @var{oldpath} or new
41748 path is not a directory. Or @var{oldpath} is a directory
41749 and @var{newpath} exists but is not a directory.
41752 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41755 No access to the file or the path of the file.
41759 @var{oldpath} or @var{newpath} was too long.
41762 A directory component in @var{oldpath} or @var{newpath} does not exist.
41765 The file is on a read-only filesystem.
41768 The device containing the file has no room for the new
41772 The call was interrupted by the user.
41778 @unnumberedsubsubsec unlink
41779 @cindex unlink, file-i/o system call
41784 int unlink(const char *pathname);
41788 @samp{Funlink,@var{pathnameptr}/@var{len}}
41790 @item Return value:
41791 On success, zero is returned. On error, -1 is returned.
41797 No access to the file or the path of the file.
41800 The system does not allow unlinking of directories.
41803 The file @var{pathname} cannot be unlinked because it's
41804 being used by another process.
41807 @var{pathnameptr} is an invalid pointer value.
41810 @var{pathname} was too long.
41813 A directory component in @var{pathname} does not exist.
41816 A component of the path is not a directory.
41819 The file is on a read-only filesystem.
41822 The call was interrupted by the user.
41828 @unnumberedsubsubsec stat/fstat
41829 @cindex fstat, file-i/o system call
41830 @cindex stat, file-i/o system call
41835 int stat(const char *pathname, struct stat *buf);
41836 int fstat(int fd, struct stat *buf);
41840 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41841 @samp{Ffstat,@var{fd},@var{bufptr}}
41843 @item Return value:
41844 On success, zero is returned. On error, -1 is returned.
41850 @var{fd} is not a valid open file.
41853 A directory component in @var{pathname} does not exist or the
41854 path is an empty string.
41857 A component of the path is not a directory.
41860 @var{pathnameptr} is an invalid pointer value.
41863 No access to the file or the path of the file.
41866 @var{pathname} was too long.
41869 The call was interrupted by the user.
41875 @unnumberedsubsubsec gettimeofday
41876 @cindex gettimeofday, file-i/o system call
41881 int gettimeofday(struct timeval *tv, void *tz);
41885 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41887 @item Return value:
41888 On success, 0 is returned, -1 otherwise.
41894 @var{tz} is a non-NULL pointer.
41897 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41903 @unnumberedsubsubsec isatty
41904 @cindex isatty, file-i/o system call
41909 int isatty(int fd);
41913 @samp{Fisatty,@var{fd}}
41915 @item Return value:
41916 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41922 The call was interrupted by the user.
41927 Note that the @code{isatty} call is treated as a special case: it returns
41928 1 to the target if the file descriptor is attached
41929 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41930 would require implementing @code{ioctl} and would be more complex than
41935 @unnumberedsubsubsec system
41936 @cindex system, file-i/o system call
41941 int system(const char *command);
41945 @samp{Fsystem,@var{commandptr}/@var{len}}
41947 @item Return value:
41948 If @var{len} is zero, the return value indicates whether a shell is
41949 available. A zero return value indicates a shell is not available.
41950 For non-zero @var{len}, the value returned is -1 on error and the
41951 return status of the command otherwise. Only the exit status of the
41952 command is returned, which is extracted from the host's @code{system}
41953 return value by calling @code{WEXITSTATUS(retval)}. In case
41954 @file{/bin/sh} could not be executed, 127 is returned.
41960 The call was interrupted by the user.
41965 @value{GDBN} takes over the full task of calling the necessary host calls
41966 to perform the @code{system} call. The return value of @code{system} on
41967 the host is simplified before it's returned
41968 to the target. Any termination signal information from the child process
41969 is discarded, and the return value consists
41970 entirely of the exit status of the called command.
41972 Due to security concerns, the @code{system} call is by default refused
41973 by @value{GDBN}. The user has to allow this call explicitly with the
41974 @code{set remote system-call-allowed 1} command.
41977 @item set remote system-call-allowed
41978 @kindex set remote system-call-allowed
41979 Control whether to allow the @code{system} calls in the File I/O
41980 protocol for the remote target. The default is zero (disabled).
41982 @item show remote system-call-allowed
41983 @kindex show remote system-call-allowed
41984 Show whether the @code{system} calls are allowed in the File I/O
41988 @node Protocol-specific Representation of Datatypes
41989 @subsection Protocol-specific Representation of Datatypes
41990 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41993 * Integral Datatypes::
41995 * Memory Transfer::
42000 @node Integral Datatypes
42001 @unnumberedsubsubsec Integral Datatypes
42002 @cindex integral datatypes, in file-i/o protocol
42004 The integral datatypes used in the system calls are @code{int},
42005 @code{unsigned int}, @code{long}, @code{unsigned long},
42006 @code{mode_t}, and @code{time_t}.
42008 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42009 implemented as 32 bit values in this protocol.
42011 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42013 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42014 in @file{limits.h}) to allow range checking on host and target.
42016 @code{time_t} datatypes are defined as seconds since the Epoch.
42018 All integral datatypes transferred as part of a memory read or write of a
42019 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42022 @node Pointer Values
42023 @unnumberedsubsubsec Pointer Values
42024 @cindex pointer values, in file-i/o protocol
42026 Pointers to target data are transmitted as they are. An exception
42027 is made for pointers to buffers for which the length isn't
42028 transmitted as part of the function call, namely strings. Strings
42029 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42036 which is a pointer to data of length 18 bytes at position 0x1aaf.
42037 The length is defined as the full string length in bytes, including
42038 the trailing null byte. For example, the string @code{"hello world"}
42039 at address 0x123456 is transmitted as
42045 @node Memory Transfer
42046 @unnumberedsubsubsec Memory Transfer
42047 @cindex memory transfer, in file-i/o protocol
42049 Structured data which is transferred using a memory read or write (for
42050 example, a @code{struct stat}) is expected to be in a protocol-specific format
42051 with all scalar multibyte datatypes being big endian. Translation to
42052 this representation needs to be done both by the target before the @code{F}
42053 packet is sent, and by @value{GDBN} before
42054 it transfers memory to the target. Transferred pointers to structured
42055 data should point to the already-coerced data at any time.
42059 @unnumberedsubsubsec struct stat
42060 @cindex struct stat, in file-i/o protocol
42062 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42063 is defined as follows:
42067 unsigned int st_dev; /* device */
42068 unsigned int st_ino; /* inode */
42069 mode_t st_mode; /* protection */
42070 unsigned int st_nlink; /* number of hard links */
42071 unsigned int st_uid; /* user ID of owner */
42072 unsigned int st_gid; /* group ID of owner */
42073 unsigned int st_rdev; /* device type (if inode device) */
42074 unsigned long st_size; /* total size, in bytes */
42075 unsigned long st_blksize; /* blocksize for filesystem I/O */
42076 unsigned long st_blocks; /* number of blocks allocated */
42077 time_t st_atime; /* time of last access */
42078 time_t st_mtime; /* time of last modification */
42079 time_t st_ctime; /* time of last change */
42083 The integral datatypes conform to the definitions given in the
42084 appropriate section (see @ref{Integral Datatypes}, for details) so this
42085 structure is of size 64 bytes.
42087 The values of several fields have a restricted meaning and/or
42093 A value of 0 represents a file, 1 the console.
42096 No valid meaning for the target. Transmitted unchanged.
42099 Valid mode bits are described in @ref{Constants}. Any other
42100 bits have currently no meaning for the target.
42105 No valid meaning for the target. Transmitted unchanged.
42110 These values have a host and file system dependent
42111 accuracy. Especially on Windows hosts, the file system may not
42112 support exact timing values.
42115 The target gets a @code{struct stat} of the above representation and is
42116 responsible for coercing it to the target representation before
42119 Note that due to size differences between the host, target, and protocol
42120 representations of @code{struct stat} members, these members could eventually
42121 get truncated on the target.
42123 @node struct timeval
42124 @unnumberedsubsubsec struct timeval
42125 @cindex struct timeval, in file-i/o protocol
42127 The buffer of type @code{struct timeval} used by the File-I/O protocol
42128 is defined as follows:
42132 time_t tv_sec; /* second */
42133 long tv_usec; /* microsecond */
42137 The integral datatypes conform to the definitions given in the
42138 appropriate section (see @ref{Integral Datatypes}, for details) so this
42139 structure is of size 8 bytes.
42142 @subsection Constants
42143 @cindex constants, in file-i/o protocol
42145 The following values are used for the constants inside of the
42146 protocol. @value{GDBN} and target are responsible for translating these
42147 values before and after the call as needed.
42158 @unnumberedsubsubsec Open Flags
42159 @cindex open flags, in file-i/o protocol
42161 All values are given in hexadecimal representation.
42173 @node mode_t Values
42174 @unnumberedsubsubsec mode_t Values
42175 @cindex mode_t values, in file-i/o protocol
42177 All values are given in octal representation.
42194 @unnumberedsubsubsec Errno Values
42195 @cindex errno values, in file-i/o protocol
42197 All values are given in decimal representation.
42222 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42223 any error value not in the list of supported error numbers.
42226 @unnumberedsubsubsec Lseek Flags
42227 @cindex lseek flags, in file-i/o protocol
42236 @unnumberedsubsubsec Limits
42237 @cindex limits, in file-i/o protocol
42239 All values are given in decimal representation.
42242 INT_MIN -2147483648
42244 UINT_MAX 4294967295
42245 LONG_MIN -9223372036854775808
42246 LONG_MAX 9223372036854775807
42247 ULONG_MAX 18446744073709551615
42250 @node File-I/O Examples
42251 @subsection File-I/O Examples
42252 @cindex file-i/o examples
42254 Example sequence of a write call, file descriptor 3, buffer is at target
42255 address 0x1234, 6 bytes should be written:
42258 <- @code{Fwrite,3,1234,6}
42259 @emph{request memory read from target}
42262 @emph{return "6 bytes written"}
42266 Example sequence of a read call, file descriptor 3, buffer is at target
42267 address 0x1234, 6 bytes should be read:
42270 <- @code{Fread,3,1234,6}
42271 @emph{request memory write to target}
42272 -> @code{X1234,6:XXXXXX}
42273 @emph{return "6 bytes read"}
42277 Example sequence of a read call, call fails on the host due to invalid
42278 file descriptor (@code{EBADF}):
42281 <- @code{Fread,3,1234,6}
42285 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42289 <- @code{Fread,3,1234,6}
42294 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42298 <- @code{Fread,3,1234,6}
42299 -> @code{X1234,6:XXXXXX}
42303 @node Library List Format
42304 @section Library List Format
42305 @cindex library list format, remote protocol
42307 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42308 same process as your application to manage libraries. In this case,
42309 @value{GDBN} can use the loader's symbol table and normal memory
42310 operations to maintain a list of shared libraries. On other
42311 platforms, the operating system manages loaded libraries.
42312 @value{GDBN} can not retrieve the list of currently loaded libraries
42313 through memory operations, so it uses the @samp{qXfer:libraries:read}
42314 packet (@pxref{qXfer library list read}) instead. The remote stub
42315 queries the target's operating system and reports which libraries
42318 The @samp{qXfer:libraries:read} packet returns an XML document which
42319 lists loaded libraries and their offsets. Each library has an
42320 associated name and one or more segment or section base addresses,
42321 which report where the library was loaded in memory.
42323 For the common case of libraries that are fully linked binaries, the
42324 library should have a list of segments. If the target supports
42325 dynamic linking of a relocatable object file, its library XML element
42326 should instead include a list of allocated sections. The segment or
42327 section bases are start addresses, not relocation offsets; they do not
42328 depend on the library's link-time base addresses.
42330 @value{GDBN} must be linked with the Expat library to support XML
42331 library lists. @xref{Expat}.
42333 A simple memory map, with one loaded library relocated by a single
42334 offset, looks like this:
42338 <library name="/lib/libc.so.6">
42339 <segment address="0x10000000"/>
42344 Another simple memory map, with one loaded library with three
42345 allocated sections (.text, .data, .bss), looks like this:
42349 <library name="sharedlib.o">
42350 <section address="0x10000000"/>
42351 <section address="0x20000000"/>
42352 <section address="0x30000000"/>
42357 The format of a library list is described by this DTD:
42360 <!-- library-list: Root element with versioning -->
42361 <!ELEMENT library-list (library)*>
42362 <!ATTLIST library-list version CDATA #FIXED "1.0">
42363 <!ELEMENT library (segment*, section*)>
42364 <!ATTLIST library name CDATA #REQUIRED>
42365 <!ELEMENT segment EMPTY>
42366 <!ATTLIST segment address CDATA #REQUIRED>
42367 <!ELEMENT section EMPTY>
42368 <!ATTLIST section address CDATA #REQUIRED>
42371 In addition, segments and section descriptors cannot be mixed within a
42372 single library element, and you must supply at least one segment or
42373 section for each library.
42375 @node Library List Format for SVR4 Targets
42376 @section Library List Format for SVR4 Targets
42377 @cindex library list format, remote protocol
42379 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42380 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42381 shared libraries. Still a special library list provided by this packet is
42382 more efficient for the @value{GDBN} remote protocol.
42384 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42385 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42386 target, the following parameters are reported:
42390 @code{name}, the absolute file name from the @code{l_name} field of
42391 @code{struct link_map}.
42393 @code{lm} with address of @code{struct link_map} used for TLS
42394 (Thread Local Storage) access.
42396 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42397 @code{struct link_map}. For prelinked libraries this is not an absolute
42398 memory address. It is a displacement of absolute memory address against
42399 address the file was prelinked to during the library load.
42401 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42404 Additionally the single @code{main-lm} attribute specifies address of
42405 @code{struct link_map} used for the main executable. This parameter is used
42406 for TLS access and its presence is optional.
42408 @value{GDBN} must be linked with the Expat library to support XML
42409 SVR4 library lists. @xref{Expat}.
42411 A simple memory map, with two loaded libraries (which do not use prelink),
42415 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42416 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42418 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42420 </library-list-svr>
42423 The format of an SVR4 library list is described by this DTD:
42426 <!-- library-list-svr4: Root element with versioning -->
42427 <!ELEMENT library-list-svr4 (library)*>
42428 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42429 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42430 <!ELEMENT library EMPTY>
42431 <!ATTLIST library name CDATA #REQUIRED>
42432 <!ATTLIST library lm CDATA #REQUIRED>
42433 <!ATTLIST library l_addr CDATA #REQUIRED>
42434 <!ATTLIST library l_ld CDATA #REQUIRED>
42437 @node Memory Map Format
42438 @section Memory Map Format
42439 @cindex memory map format
42441 To be able to write into flash memory, @value{GDBN} needs to obtain a
42442 memory map from the target. This section describes the format of the
42445 The memory map is obtained using the @samp{qXfer:memory-map:read}
42446 (@pxref{qXfer memory map read}) packet and is an XML document that
42447 lists memory regions.
42449 @value{GDBN} must be linked with the Expat library to support XML
42450 memory maps. @xref{Expat}.
42452 The top-level structure of the document is shown below:
42455 <?xml version="1.0"?>
42456 <!DOCTYPE memory-map
42457 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42458 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42464 Each region can be either:
42469 A region of RAM starting at @var{addr} and extending for @var{length}
42473 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42478 A region of read-only memory:
42481 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42486 A region of flash memory, with erasure blocks @var{blocksize}
42490 <memory type="flash" start="@var{addr}" length="@var{length}">
42491 <property name="blocksize">@var{blocksize}</property>
42497 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42498 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42499 packets to write to addresses in such ranges.
42501 The formal DTD for memory map format is given below:
42504 <!-- ................................................... -->
42505 <!-- Memory Map XML DTD ................................ -->
42506 <!-- File: memory-map.dtd .............................. -->
42507 <!-- .................................... .............. -->
42508 <!-- memory-map.dtd -->
42509 <!-- memory-map: Root element with versioning -->
42510 <!ELEMENT memory-map (memory)*>
42511 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42512 <!ELEMENT memory (property)*>
42513 <!-- memory: Specifies a memory region,
42514 and its type, or device. -->
42515 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
42516 start CDATA #REQUIRED
42517 length CDATA #REQUIRED>
42518 <!-- property: Generic attribute tag -->
42519 <!ELEMENT property (#PCDATA | property)*>
42520 <!ATTLIST property name (blocksize) #REQUIRED>
42523 @node Thread List Format
42524 @section Thread List Format
42525 @cindex thread list format
42527 To efficiently update the list of threads and their attributes,
42528 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42529 (@pxref{qXfer threads read}) and obtains the XML document with
42530 the following structure:
42533 <?xml version="1.0"?>
42535 <thread id="id" core="0" name="name">
42536 ... description ...
42541 Each @samp{thread} element must have the @samp{id} attribute that
42542 identifies the thread (@pxref{thread-id syntax}). The
42543 @samp{core} attribute, if present, specifies which processor core
42544 the thread was last executing on. The @samp{name} attribute, if
42545 present, specifies the human-readable name of the thread. The content
42546 of the of @samp{thread} element is interpreted as human-readable
42547 auxiliary information. The @samp{handle} attribute, if present,
42548 is a hex encoded representation of the thread handle.
42551 @node Traceframe Info Format
42552 @section Traceframe Info Format
42553 @cindex traceframe info format
42555 To be able to know which objects in the inferior can be examined when
42556 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42557 memory ranges, registers and trace state variables that have been
42558 collected in a traceframe.
42560 This list is obtained using the @samp{qXfer:traceframe-info:read}
42561 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42563 @value{GDBN} must be linked with the Expat library to support XML
42564 traceframe info discovery. @xref{Expat}.
42566 The top-level structure of the document is shown below:
42569 <?xml version="1.0"?>
42570 <!DOCTYPE traceframe-info
42571 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42572 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42578 Each traceframe block can be either:
42583 A region of collected memory starting at @var{addr} and extending for
42584 @var{length} bytes from there:
42587 <memory start="@var{addr}" length="@var{length}"/>
42591 A block indicating trace state variable numbered @var{number} has been
42595 <tvar id="@var{number}"/>
42600 The formal DTD for the traceframe info format is given below:
42603 <!ELEMENT traceframe-info (memory | tvar)* >
42604 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42606 <!ELEMENT memory EMPTY>
42607 <!ATTLIST memory start CDATA #REQUIRED
42608 length CDATA #REQUIRED>
42610 <!ATTLIST tvar id CDATA #REQUIRED>
42613 @node Branch Trace Format
42614 @section Branch Trace Format
42615 @cindex branch trace format
42617 In order to display the branch trace of an inferior thread,
42618 @value{GDBN} needs to obtain the list of branches. This list is
42619 represented as list of sequential code blocks that are connected via
42620 branches. The code in each block has been executed sequentially.
42622 This list is obtained using the @samp{qXfer:btrace:read}
42623 (@pxref{qXfer btrace read}) packet and is an XML document.
42625 @value{GDBN} must be linked with the Expat library to support XML
42626 traceframe info discovery. @xref{Expat}.
42628 The top-level structure of the document is shown below:
42631 <?xml version="1.0"?>
42633 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42634 "http://sourceware.org/gdb/gdb-btrace.dtd">
42643 A block of sequentially executed instructions starting at @var{begin}
42644 and ending at @var{end}:
42647 <block begin="@var{begin}" end="@var{end}"/>
42652 The formal DTD for the branch trace format is given below:
42655 <!ELEMENT btrace (block* | pt) >
42656 <!ATTLIST btrace version CDATA #FIXED "1.0">
42658 <!ELEMENT block EMPTY>
42659 <!ATTLIST block begin CDATA #REQUIRED
42660 end CDATA #REQUIRED>
42662 <!ELEMENT pt (pt-config?, raw?)>
42664 <!ELEMENT pt-config (cpu?)>
42666 <!ELEMENT cpu EMPTY>
42667 <!ATTLIST cpu vendor CDATA #REQUIRED
42668 family CDATA #REQUIRED
42669 model CDATA #REQUIRED
42670 stepping CDATA #REQUIRED>
42672 <!ELEMENT raw (#PCDATA)>
42675 @node Branch Trace Configuration Format
42676 @section Branch Trace Configuration Format
42677 @cindex branch trace configuration format
42679 For each inferior thread, @value{GDBN} can obtain the branch trace
42680 configuration using the @samp{qXfer:btrace-conf:read}
42681 (@pxref{qXfer btrace-conf read}) packet.
42683 The configuration describes the branch trace format and configuration
42684 settings for that format. The following information is described:
42688 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
42691 The size of the @acronym{BTS} ring buffer in bytes.
42694 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
42698 The size of the @acronym{Intel PT} ring buffer in bytes.
42702 @value{GDBN} must be linked with the Expat library to support XML
42703 branch trace configuration discovery. @xref{Expat}.
42705 The formal DTD for the branch trace configuration format is given below:
42708 <!ELEMENT btrace-conf (bts?, pt?)>
42709 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
42711 <!ELEMENT bts EMPTY>
42712 <!ATTLIST bts size CDATA #IMPLIED>
42714 <!ELEMENT pt EMPTY>
42715 <!ATTLIST pt size CDATA #IMPLIED>
42718 @include agentexpr.texi
42720 @node Target Descriptions
42721 @appendix Target Descriptions
42722 @cindex target descriptions
42724 One of the challenges of using @value{GDBN} to debug embedded systems
42725 is that there are so many minor variants of each processor
42726 architecture in use. It is common practice for vendors to start with
42727 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42728 and then make changes to adapt it to a particular market niche. Some
42729 architectures have hundreds of variants, available from dozens of
42730 vendors. This leads to a number of problems:
42734 With so many different customized processors, it is difficult for
42735 the @value{GDBN} maintainers to keep up with the changes.
42737 Since individual variants may have short lifetimes or limited
42738 audiences, it may not be worthwhile to carry information about every
42739 variant in the @value{GDBN} source tree.
42741 When @value{GDBN} does support the architecture of the embedded system
42742 at hand, the task of finding the correct architecture name to give the
42743 @command{set architecture} command can be error-prone.
42746 To address these problems, the @value{GDBN} remote protocol allows a
42747 target system to not only identify itself to @value{GDBN}, but to
42748 actually describe its own features. This lets @value{GDBN} support
42749 processor variants it has never seen before --- to the extent that the
42750 descriptions are accurate, and that @value{GDBN} understands them.
42752 @value{GDBN} must be linked with the Expat library to support XML
42753 target descriptions. @xref{Expat}.
42756 * Retrieving Descriptions:: How descriptions are fetched from a target.
42757 * Target Description Format:: The contents of a target description.
42758 * Predefined Target Types:: Standard types available for target
42760 * Enum Target Types:: How to define enum target types.
42761 * Standard Target Features:: Features @value{GDBN} knows about.
42764 @node Retrieving Descriptions
42765 @section Retrieving Descriptions
42767 Target descriptions can be read from the target automatically, or
42768 specified by the user manually. The default behavior is to read the
42769 description from the target. @value{GDBN} retrieves it via the remote
42770 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42771 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42772 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42773 XML document, of the form described in @ref{Target Description
42776 Alternatively, you can specify a file to read for the target description.
42777 If a file is set, the target will not be queried. The commands to
42778 specify a file are:
42781 @cindex set tdesc filename
42782 @item set tdesc filename @var{path}
42783 Read the target description from @var{path}.
42785 @cindex unset tdesc filename
42786 @item unset tdesc filename
42787 Do not read the XML target description from a file. @value{GDBN}
42788 will use the description supplied by the current target.
42790 @cindex show tdesc filename
42791 @item show tdesc filename
42792 Show the filename to read for a target description, if any.
42796 @node Target Description Format
42797 @section Target Description Format
42798 @cindex target descriptions, XML format
42800 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42801 document which complies with the Document Type Definition provided in
42802 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42803 means you can use generally available tools like @command{xmllint} to
42804 check that your feature descriptions are well-formed and valid.
42805 However, to help people unfamiliar with XML write descriptions for
42806 their targets, we also describe the grammar here.
42808 Target descriptions can identify the architecture of the remote target
42809 and (for some architectures) provide information about custom register
42810 sets. They can also identify the OS ABI of the remote target.
42811 @value{GDBN} can use this information to autoconfigure for your
42812 target, or to warn you if you connect to an unsupported target.
42814 Here is a simple target description:
42817 <target version="1.0">
42818 <architecture>i386:x86-64</architecture>
42823 This minimal description only says that the target uses
42824 the x86-64 architecture.
42826 A target description has the following overall form, with [ ] marking
42827 optional elements and @dots{} marking repeatable elements. The elements
42828 are explained further below.
42831 <?xml version="1.0"?>
42832 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42833 <target version="1.0">
42834 @r{[}@var{architecture}@r{]}
42835 @r{[}@var{osabi}@r{]}
42836 @r{[}@var{compatible}@r{]}
42837 @r{[}@var{feature}@dots{}@r{]}
42842 The description is generally insensitive to whitespace and line
42843 breaks, under the usual common-sense rules. The XML version
42844 declaration and document type declaration can generally be omitted
42845 (@value{GDBN} does not require them), but specifying them may be
42846 useful for XML validation tools. The @samp{version} attribute for
42847 @samp{<target>} may also be omitted, but we recommend
42848 including it; if future versions of @value{GDBN} use an incompatible
42849 revision of @file{gdb-target.dtd}, they will detect and report
42850 the version mismatch.
42852 @subsection Inclusion
42853 @cindex target descriptions, inclusion
42856 @cindex <xi:include>
42859 It can sometimes be valuable to split a target description up into
42860 several different annexes, either for organizational purposes, or to
42861 share files between different possible target descriptions. You can
42862 divide a description into multiple files by replacing any element of
42863 the target description with an inclusion directive of the form:
42866 <xi:include href="@var{document}"/>
42870 When @value{GDBN} encounters an element of this form, it will retrieve
42871 the named XML @var{document}, and replace the inclusion directive with
42872 the contents of that document. If the current description was read
42873 using @samp{qXfer}, then so will be the included document;
42874 @var{document} will be interpreted as the name of an annex. If the
42875 current description was read from a file, @value{GDBN} will look for
42876 @var{document} as a file in the same directory where it found the
42877 original description.
42879 @subsection Architecture
42880 @cindex <architecture>
42882 An @samp{<architecture>} element has this form:
42885 <architecture>@var{arch}</architecture>
42888 @var{arch} is one of the architectures from the set accepted by
42889 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42892 @cindex @code{<osabi>}
42894 This optional field was introduced in @value{GDBN} version 7.0.
42895 Previous versions of @value{GDBN} ignore it.
42897 An @samp{<osabi>} element has this form:
42900 <osabi>@var{abi-name}</osabi>
42903 @var{abi-name} is an OS ABI name from the same selection accepted by
42904 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42906 @subsection Compatible Architecture
42907 @cindex @code{<compatible>}
42909 This optional field was introduced in @value{GDBN} version 7.0.
42910 Previous versions of @value{GDBN} ignore it.
42912 A @samp{<compatible>} element has this form:
42915 <compatible>@var{arch}</compatible>
42918 @var{arch} is one of the architectures from the set accepted by
42919 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42921 A @samp{<compatible>} element is used to specify that the target
42922 is able to run binaries in some other than the main target architecture
42923 given by the @samp{<architecture>} element. For example, on the
42924 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42925 or @code{powerpc:common64}, but the system is able to run binaries
42926 in the @code{spu} architecture as well. The way to describe this
42927 capability with @samp{<compatible>} is as follows:
42930 <architecture>powerpc:common</architecture>
42931 <compatible>spu</compatible>
42934 @subsection Features
42937 Each @samp{<feature>} describes some logical portion of the target
42938 system. Features are currently used to describe available CPU
42939 registers and the types of their contents. A @samp{<feature>} element
42943 <feature name="@var{name}">
42944 @r{[}@var{type}@dots{}@r{]}
42950 Each feature's name should be unique within the description. The name
42951 of a feature does not matter unless @value{GDBN} has some special
42952 knowledge of the contents of that feature; if it does, the feature
42953 should have its standard name. @xref{Standard Target Features}.
42957 Any register's value is a collection of bits which @value{GDBN} must
42958 interpret. The default interpretation is a two's complement integer,
42959 but other types can be requested by name in the register description.
42960 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42961 Target Types}), and the description can define additional composite
42964 Each type element must have an @samp{id} attribute, which gives
42965 a unique (within the containing @samp{<feature>}) name to the type.
42966 Types must be defined before they are used.
42969 Some targets offer vector registers, which can be treated as arrays
42970 of scalar elements. These types are written as @samp{<vector>} elements,
42971 specifying the array element type, @var{type}, and the number of elements,
42975 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42979 If a register's value is usefully viewed in multiple ways, define it
42980 with a union type containing the useful representations. The
42981 @samp{<union>} element contains one or more @samp{<field>} elements,
42982 each of which has a @var{name} and a @var{type}:
42985 <union id="@var{id}">
42986 <field name="@var{name}" type="@var{type}"/>
42993 If a register's value is composed from several separate values, define
42994 it with either a structure type or a flags type.
42995 A flags type may only contain bitfields.
42996 A structure type may either contain only bitfields or contain no bitfields.
42997 If the value contains only bitfields, its total size in bytes must be
43000 Non-bitfield values have a @var{name} and @var{type}.
43003 <struct id="@var{id}">
43004 <field name="@var{name}" type="@var{type}"/>
43009 Both @var{name} and @var{type} values are required.
43010 No implicit padding is added.
43012 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
43015 <struct id="@var{id}" size="@var{size}">
43016 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43022 <flags id="@var{id}" size="@var{size}">
43023 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
43028 The @var{name} value is required.
43029 Bitfield values may be named with the empty string, @samp{""},
43030 in which case the field is ``filler'' and its value is not printed.
43031 Not all bits need to be specified, so ``filler'' fields are optional.
43033 The @var{start} and @var{end} values are required, and @var{type}
43035 The field's @var{start} must be less than or equal to its @var{end},
43036 and zero represents the least significant bit.
43038 The default value of @var{type} is @code{bool} for single bit fields,
43039 and an unsigned integer otherwise.
43041 Which to choose? Structures or flags?
43043 Registers defined with @samp{flags} have these advantages over
43044 defining them with @samp{struct}:
43048 Arithmetic may be performed on them as if they were integers.
43050 They are printed in a more readable fashion.
43053 Registers defined with @samp{struct} have one advantage over
43054 defining them with @samp{flags}:
43058 One can fetch individual fields like in @samp{C}.
43061 (gdb) print $my_struct_reg.field3
43067 @subsection Registers
43070 Each register is represented as an element with this form:
43073 <reg name="@var{name}"
43074 bitsize="@var{size}"
43075 @r{[}regnum="@var{num}"@r{]}
43076 @r{[}save-restore="@var{save-restore}"@r{]}
43077 @r{[}type="@var{type}"@r{]}
43078 @r{[}group="@var{group}"@r{]}/>
43082 The components are as follows:
43087 The register's name; it must be unique within the target description.
43090 The register's size, in bits.
43093 The register's number. If omitted, a register's number is one greater
43094 than that of the previous register (either in the current feature or in
43095 a preceding feature); the first register in the target description
43096 defaults to zero. This register number is used to read or write
43097 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43098 packets, and registers appear in the @code{g} and @code{G} packets
43099 in order of increasing register number.
43102 Whether the register should be preserved across inferior function
43103 calls; this must be either @code{yes} or @code{no}. The default is
43104 @code{yes}, which is appropriate for most registers except for
43105 some system control registers; this is not related to the target's
43109 The type of the register. It may be a predefined type, a type
43110 defined in the current feature, or one of the special types @code{int}
43111 and @code{float}. @code{int} is an integer type of the correct size
43112 for @var{bitsize}, and @code{float} is a floating point type (in the
43113 architecture's normal floating point format) of the correct size for
43114 @var{bitsize}. The default is @code{int}.
43117 The register group to which this register belongs. It can be one of the
43118 standard register groups @code{general}, @code{float}, @code{vector} or an
43119 arbitrary string. Group names should be limited to alphanumeric characters.
43120 If a group name is made up of multiple words the words may be separated by
43121 hyphens; e.g.@: @code{special-group} or @code{ultra-special-group}. If no
43122 @var{group} is specified, @value{GDBN} will not display the register in
43123 @code{info registers}.
43127 @node Predefined Target Types
43128 @section Predefined Target Types
43129 @cindex target descriptions, predefined types
43131 Type definitions in the self-description can build up composite types
43132 from basic building blocks, but can not define fundamental types. Instead,
43133 standard identifiers are provided by @value{GDBN} for the fundamental
43134 types. The currently supported types are:
43139 Boolean type, occupying a single bit.
43147 Signed integer types holding the specified number of bits.
43155 Unsigned integer types holding the specified number of bits.
43159 Pointers to unspecified code and data. The program counter and
43160 any dedicated return address register may be marked as code
43161 pointers; printing a code pointer converts it into a symbolic
43162 address. The stack pointer and any dedicated address registers
43163 may be marked as data pointers.
43166 Single precision IEEE floating point.
43169 Double precision IEEE floating point.
43172 The 12-byte extended precision format used by ARM FPA registers.
43175 The 10-byte extended precision format used by x87 registers.
43178 32bit @sc{eflags} register used by x86.
43181 32bit @sc{mxcsr} register used by x86.
43185 @node Enum Target Types
43186 @section Enum Target Types
43187 @cindex target descriptions, enum types
43189 Enum target types are useful in @samp{struct} and @samp{flags}
43190 register descriptions. @xref{Target Description Format}.
43192 Enum types have a name, size and a list of name/value pairs.
43195 <enum id="@var{id}" size="@var{size}">
43196 <evalue name="@var{name}" value="@var{value}"/>
43201 Enums must be defined before they are used.
43204 <enum id="levels_type" size="4">
43205 <evalue name="low" value="0"/>
43206 <evalue name="high" value="1"/>
43208 <flags id="flags_type" size="4">
43209 <field name="X" start="0"/>
43210 <field name="LEVEL" start="1" end="1" type="levels_type"/>
43212 <reg name="flags" bitsize="32" type="flags_type"/>
43215 Given that description, a value of 3 for the @samp{flags} register
43216 would be printed as:
43219 (gdb) info register flags
43220 flags 0x3 [ X LEVEL=high ]
43223 @node Standard Target Features
43224 @section Standard Target Features
43225 @cindex target descriptions, standard features
43227 A target description must contain either no registers or all the
43228 target's registers. If the description contains no registers, then
43229 @value{GDBN} will assume a default register layout, selected based on
43230 the architecture. If the description contains any registers, the
43231 default layout will not be used; the standard registers must be
43232 described in the target description, in such a way that @value{GDBN}
43233 can recognize them.
43235 This is accomplished by giving specific names to feature elements
43236 which contain standard registers. @value{GDBN} will look for features
43237 with those names and verify that they contain the expected registers;
43238 if any known feature is missing required registers, or if any required
43239 feature is missing, @value{GDBN} will reject the target
43240 description. You can add additional registers to any of the
43241 standard features --- @value{GDBN} will display them just as if
43242 they were added to an unrecognized feature.
43244 This section lists the known features and their expected contents.
43245 Sample XML documents for these features are included in the
43246 @value{GDBN} source tree, in the directory @file{gdb/features}.
43248 Names recognized by @value{GDBN} should include the name of the
43249 company or organization which selected the name, and the overall
43250 architecture to which the feature applies; so e.g.@: the feature
43251 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43253 The names of registers are not case sensitive for the purpose
43254 of recognizing standard features, but @value{GDBN} will only display
43255 registers using the capitalization used in the description.
43258 * AArch64 Features::
43262 * MicroBlaze Features::
43266 * Nios II Features::
43267 * OpenRISC 1000 Features::
43268 * PowerPC Features::
43269 * RISC-V Features::
43270 * S/390 and System z Features::
43276 @node AArch64 Features
43277 @subsection AArch64 Features
43278 @cindex target descriptions, AArch64 features
43280 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43281 targets. It should contain registers @samp{x0} through @samp{x30},
43282 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43284 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43285 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43288 The @samp{org.gnu.gdb.aarch64.sve} feature is optional. If present,
43289 it should contain registers @samp{z0} through @samp{z31}, @samp{p0}
43290 through @samp{p15}, @samp{ffr} and @samp{vg}.
43292 The @samp{org.gnu.gdb.aarch64.pauth} feature is optional. If present,
43293 it should contain registers @samp{pauth_dmask} and @samp{pauth_cmask}.
43296 @subsection ARC Features
43297 @cindex target descriptions, ARC Features
43299 ARC processors are highly configurable, so even core registers and their number
43300 are not completely predetermined. In addition flags and PC registers which are
43301 important to @value{GDBN} are not ``core'' registers in ARC. It is required
43302 that one of the core registers features is present.
43303 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
43305 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
43306 targets with a normal register file. It should contain registers @samp{r0}
43307 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43308 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
43309 and any of extension core registers @samp{r32} through @samp{r59/acch}.
43310 @samp{ilink} and extension core registers are not available to read/write, when
43311 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
43313 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
43314 ARC HS targets with a reduced register file. It should contain registers
43315 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
43316 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
43317 This feature may contain register @samp{ilink} and any of extension core
43318 registers @samp{r32} through @samp{r59/acch}.
43320 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
43321 targets with a normal register file. It should contain registers @samp{r0}
43322 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
43323 @samp{lp_count} and @samp{pcl}. This feature may contain registers
43324 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
43325 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
43326 registers are not available when debugging GNU/Linux applications. The only
43327 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
43328 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
43329 ARC v2, but @samp{ilink2} is optional on ARCompact.
43331 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
43332 targets. It should contain registers @samp{pc} and @samp{status32}.
43335 @subsection ARM Features
43336 @cindex target descriptions, ARM features
43338 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43340 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43341 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43343 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43344 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43345 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43348 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43349 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43351 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43352 it should contain at least registers @samp{wR0} through @samp{wR15} and
43353 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43354 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43356 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43357 should contain at least registers @samp{d0} through @samp{d15}. If
43358 they are present, @samp{d16} through @samp{d31} should also be included.
43359 @value{GDBN} will synthesize the single-precision registers from
43360 halves of the double-precision registers.
43362 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43363 need to contain registers; it instructs @value{GDBN} to display the
43364 VFP double-precision registers as vectors and to synthesize the
43365 quad-precision registers from pairs of double-precision registers.
43366 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43367 be present and include 32 double-precision registers.
43369 @node i386 Features
43370 @subsection i386 Features
43371 @cindex target descriptions, i386 features
43373 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43374 targets. It should describe the following registers:
43378 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43380 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43382 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43383 @samp{fs}, @samp{gs}
43385 @samp{st0} through @samp{st7}
43387 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43388 @samp{foseg}, @samp{fooff} and @samp{fop}
43391 The register sets may be different, depending on the target.
43393 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43394 describe registers:
43398 @samp{xmm0} through @samp{xmm7} for i386
43400 @samp{xmm0} through @samp{xmm15} for amd64
43405 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43406 @samp{org.gnu.gdb.i386.sse} feature. It should
43407 describe the upper 128 bits of @sc{ymm} registers:
43411 @samp{ymm0h} through @samp{ymm7h} for i386
43413 @samp{ymm0h} through @samp{ymm15h} for amd64
43416 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
43417 Memory Protection Extension (MPX). It should describe the following registers:
43421 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43423 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43426 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43427 describe a single register, @samp{orig_eax}.
43429 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
43430 describe two system registers: @samp{fs_base} and @samp{gs_base}.
43432 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
43433 @samp{org.gnu.gdb.i386.avx} feature. It should
43434 describe additional @sc{xmm} registers:
43438 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
43441 It should describe the upper 128 bits of additional @sc{ymm} registers:
43445 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
43449 describe the upper 256 bits of @sc{zmm} registers:
43453 @samp{zmm0h} through @samp{zmm7h} for i386.
43455 @samp{zmm0h} through @samp{zmm15h} for amd64.
43459 describe the additional @sc{zmm} registers:
43463 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
43466 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
43467 describe a single register, @samp{pkru}. It is a 32-bit register
43468 valid for i386 and amd64.
43470 @node MicroBlaze Features
43471 @subsection MicroBlaze Features
43472 @cindex target descriptions, MicroBlaze features
43474 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
43475 targets. It should contain registers @samp{r0} through @samp{r31},
43476 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
43477 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
43478 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
43480 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
43481 If present, it should contain registers @samp{rshr} and @samp{rslr}
43483 @node MIPS Features
43484 @subsection @acronym{MIPS} Features
43485 @cindex target descriptions, @acronym{MIPS} features
43487 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43488 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43489 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43492 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43493 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43494 registers. They may be 32-bit or 64-bit depending on the target.
43496 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43497 it may be optional in a future version of @value{GDBN}. It should
43498 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43499 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43501 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43502 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43503 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43504 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43506 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43507 contain a single register, @samp{restart}, which is used by the
43508 Linux kernel to control restartable syscalls.
43510 @node M68K Features
43511 @subsection M68K Features
43512 @cindex target descriptions, M68K features
43515 @item @samp{org.gnu.gdb.m68k.core}
43516 @itemx @samp{org.gnu.gdb.coldfire.core}
43517 @itemx @samp{org.gnu.gdb.fido.core}
43518 One of those features must be always present.
43519 The feature that is present determines which flavor of m68k is
43520 used. The feature that is present should contain registers
43521 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43522 @samp{sp}, @samp{ps} and @samp{pc}.
43524 @item @samp{org.gnu.gdb.coldfire.fp}
43525 This feature is optional. If present, it should contain registers
43526 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43530 @node NDS32 Features
43531 @subsection NDS32 Features
43532 @cindex target descriptions, NDS32 features
43534 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
43535 targets. It should contain at least registers @samp{r0} through
43536 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
43539 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
43540 it should contain 64-bit double-precision floating-point registers
43541 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
43542 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
43544 @emph{Note:} The first sixteen 64-bit double-precision floating-point
43545 registers are overlapped with the thirty-two 32-bit single-precision
43546 floating-point registers. The 32-bit single-precision registers, if
43547 not being listed explicitly, will be synthesized from halves of the
43548 overlapping 64-bit double-precision registers. Listing 32-bit
43549 single-precision registers explicitly is deprecated, and the
43550 support to it could be totally removed some day.
43552 @node Nios II Features
43553 @subsection Nios II Features
43554 @cindex target descriptions, Nios II features
43556 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43557 targets. It should contain the 32 core registers (@samp{zero},
43558 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43559 @samp{pc}, and the 16 control registers (@samp{status} through
43562 @node OpenRISC 1000 Features
43563 @subsection Openrisc 1000 Features
43564 @cindex target descriptions, OpenRISC 1000 features
43566 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
43567 targets. It should contain the 32 general purpose registers (@samp{r0}
43568 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
43570 @node PowerPC Features
43571 @subsection PowerPC Features
43572 @cindex target descriptions, PowerPC features
43574 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43575 targets. It should contain registers @samp{r0} through @samp{r31},
43576 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43577 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43579 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43580 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43582 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43583 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr}, and
43584 @samp{vrsave}. @value{GDBN} will define pseudo-registers @samp{v0}
43585 through @samp{v31} as aliases for the corresponding @samp{vrX}
43588 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43589 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN} will
43590 combine these registers with the floating point registers (@samp{f0}
43591 through @samp{f31}) and the altivec registers (@samp{vr0} through
43592 @samp{vr31}) to present the 128-bit wide registers @samp{vs0} through
43593 @samp{vs63}, the set of vector-scalar registers for POWER7.
43594 Therefore, this feature requires both @samp{org.gnu.gdb.power.fpu} and
43595 @samp{org.gnu.gdb.power.altivec}.
43597 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43598 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43599 @samp{spefscr}. SPE targets should provide 32-bit registers in
43600 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43601 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43602 these to present registers @samp{ev0} through @samp{ev31} to the
43605 The @samp{org.gnu.gdb.power.ppr} feature is optional. It should
43606 contain the 64-bit register @samp{ppr}.
43608 The @samp{org.gnu.gdb.power.dscr} feature is optional. It should
43609 contain the 64-bit register @samp{dscr}.
43611 The @samp{org.gnu.gdb.power.tar} feature is optional. It should
43612 contain the 64-bit register @samp{tar}.
43614 The @samp{org.gnu.gdb.power.ebb} feature is optional. It should
43615 contain registers @samp{bescr}, @samp{ebbhr} and @samp{ebbrr}, all
43618 The @samp{org.gnu.gdb.power.linux.pmu} feature is optional. It should
43619 contain registers @samp{mmcr0}, @samp{mmcr2}, @samp{siar}, @samp{sdar}
43620 and @samp{sier}, all 64-bit wide. This is the subset of the isa 2.07
43621 server PMU registers provided by @sc{gnu}/Linux.
43623 The @samp{org.gnu.gdb.power.htm.spr} feature is optional. It should
43624 contain registers @samp{tfhar}, @samp{texasr} and @samp{tfiar}, all
43627 The @samp{org.gnu.gdb.power.htm.core} feature is optional. It should
43628 contain the checkpointed general-purpose registers @samp{cr0} through
43629 @samp{cr31}, as well as the checkpointed registers @samp{clr} and
43630 @samp{cctr}. These registers may all be either 32-bit or 64-bit
43631 depending on the target. It should also contain the checkpointed
43632 registers @samp{ccr} and @samp{cxer}, which should both be 32-bit
43635 The @samp{org.gnu.gdb.power.htm.fpu} feature is optional. It should
43636 contain the checkpointed 64-bit floating-point registers @samp{cf0}
43637 through @samp{cf31}, as well as the checkpointed 64-bit register
43640 The @samp{org.gnu.gdb.power.htm.altivec} feature is optional. It
43641 should contain the checkpointed altivec registers @samp{cvr0} through
43642 @samp{cvr31}, all 128-bit wide. It should also contain the
43643 checkpointed registers @samp{cvscr} and @samp{cvrsave}, both 32-bit
43646 The @samp{org.gnu.gdb.power.htm.vsx} feature is optional. It should
43647 contain registers @samp{cvs0h} through @samp{cvs31h}. @value{GDBN}
43648 will combine these registers with the checkpointed floating point
43649 registers (@samp{cf0} through @samp{cf31}) and the checkpointed
43650 altivec registers (@samp{cvr0} through @samp{cvr31}) to present the
43651 128-bit wide checkpointed vector-scalar registers @samp{cvs0} through
43652 @samp{cvs63}. Therefore, this feature requires both
43653 @samp{org.gnu.gdb.power.htm.altivec} and
43654 @samp{org.gnu.gdb.power.htm.fpu}.
43656 The @samp{org.gnu.gdb.power.htm.ppr} feature is optional. It should
43657 contain the 64-bit checkpointed register @samp{cppr}.
43659 The @samp{org.gnu.gdb.power.htm.dscr} feature is optional. It should
43660 contain the 64-bit checkpointed register @samp{cdscr}.
43662 The @samp{org.gnu.gdb.power.htm.tar} feature is optional. It should
43663 contain the 64-bit checkpointed register @samp{ctar}.
43666 @node RISC-V Features
43667 @subsection RISC-V Features
43668 @cindex target descriptions, RISC-V Features
43670 The @samp{org.gnu.gdb.riscv.cpu} feature is required for RISC-V
43671 targets. It should contain the registers @samp{x0} through
43672 @samp{x31}, and @samp{pc}. Either the architectural names (@samp{x0},
43673 @samp{x1}, etc) can be used, or the ABI names (@samp{zero}, @samp{ra},
43676 The @samp{org.gnu.gdb.riscv.fpu} feature is optional. If present, it
43677 should contain registers @samp{f0} through @samp{f31}, @samp{fflags},
43678 @samp{frm}, and @samp{fcsr}. As with the cpu feature, either the
43679 architectural register names, or the ABI names can be used.
43681 The @samp{org.gnu.gdb.riscv.virtual} feature is optional. If present,
43682 it should contain registers that are not backed by real registers on
43683 the target, but are instead virtual, where the register value is
43684 derived from other target state. In many ways these are like
43685 @value{GDBN}s pseudo-registers, except implemented by the target.
43686 Currently the only register expected in this set is the one byte
43687 @samp{priv} register that contains the target's privilege level in the
43688 least significant two bits.
43690 The @samp{org.gnu.gdb.riscv.csr} feature is optional. If present, it
43691 should contain all of the target's standard CSRs. Standard CSRs are
43692 those defined in the RISC-V specification documents. There is some
43693 overlap between this feature and the fpu feature; the @samp{fflags},
43694 @samp{frm}, and @samp{fcsr} registers could be in either feature. The
43695 expectation is that these registers will be in the fpu feature if the
43696 target has floating point hardware, but can be moved into the csr
43697 feature if the target has the floating point control registers, but no
43698 other floating point hardware.
43700 @node S/390 and System z Features
43701 @subsection S/390 and System z Features
43702 @cindex target descriptions, S/390 features
43703 @cindex target descriptions, System z features
43705 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43706 System z targets. It should contain the PSW and the 16 general
43707 registers. In particular, System z targets should provide the 64-bit
43708 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43709 S/390 targets should provide the 32-bit versions of these registers.
43710 A System z target that runs in 31-bit addressing mode should provide
43711 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43712 register's upper halves @samp{r0h} through @samp{r15h}, and their
43713 lower halves @samp{r0l} through @samp{r15l}.
43715 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43716 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43719 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43720 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43722 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43723 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43724 targets and 32-bit otherwise. In addition, the feature may contain
43725 the @samp{last_break} register, whose width depends on the addressing
43726 mode, as well as the @samp{system_call} register, which is always
43729 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43730 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43731 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43733 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
43734 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
43735 combined by @value{GDBN} with the floating point registers @samp{f0}
43736 through @samp{f15} to present the 128-bit wide vector registers
43737 @samp{v0} through @samp{v15}. In addition, this feature should
43738 contain the 128-bit wide vector registers @samp{v16} through
43741 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
43742 the 64-bit wide guarded-storage-control registers @samp{gsd},
43743 @samp{gssm}, and @samp{gsepla}.
43745 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
43746 the 64-bit wide guarded-storage broadcast control registers
43747 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
43749 @node Sparc Features
43750 @subsection Sparc Features
43751 @cindex target descriptions, sparc32 features
43752 @cindex target descriptions, sparc64 features
43753 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
43754 targets. It should describe the following registers:
43758 @samp{g0} through @samp{g7}
43760 @samp{o0} through @samp{o7}
43762 @samp{l0} through @samp{l7}
43764 @samp{i0} through @samp{i7}
43767 They may be 32-bit or 64-bit depending on the target.
43769 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
43770 targets. It should describe the following registers:
43774 @samp{f0} through @samp{f31}
43776 @samp{f32} through @samp{f62} for sparc64
43779 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
43780 targets. It should describe the following registers:
43784 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
43785 @samp{fsr}, and @samp{csr} for sparc32
43787 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
43791 @node TIC6x Features
43792 @subsection TMS320C6x Features
43793 @cindex target descriptions, TIC6x features
43794 @cindex target descriptions, TMS320C6x features
43795 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43796 targets. It should contain registers @samp{A0} through @samp{A15},
43797 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43799 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43800 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43801 through @samp{B31}.
43803 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43804 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43806 @node Operating System Information
43807 @appendix Operating System Information
43808 @cindex operating system information
43814 Users of @value{GDBN} often wish to obtain information about the state of
43815 the operating system running on the target---for example the list of
43816 processes, or the list of open files. This section describes the
43817 mechanism that makes it possible. This mechanism is similar to the
43818 target features mechanism (@pxref{Target Descriptions}), but focuses
43819 on a different aspect of target.
43821 Operating system information is retrived from the target via the
43822 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43823 read}). The object name in the request should be @samp{osdata}, and
43824 the @var{annex} identifies the data to be fetched.
43827 @appendixsection Process list
43828 @cindex operating system information, process list
43830 When requesting the process list, the @var{annex} field in the
43831 @samp{qXfer} request should be @samp{processes}. The returned data is
43832 an XML document. The formal syntax of this document is defined in
43833 @file{gdb/features/osdata.dtd}.
43835 An example document is:
43838 <?xml version="1.0"?>
43839 <!DOCTYPE target SYSTEM "osdata.dtd">
43840 <osdata type="processes">
43842 <column name="pid">1</column>
43843 <column name="user">root</column>
43844 <column name="command">/sbin/init</column>
43845 <column name="cores">1,2,3</column>
43850 Each item should include a column whose name is @samp{pid}. The value
43851 of that column should identify the process on the target. The
43852 @samp{user} and @samp{command} columns are optional, and will be
43853 displayed by @value{GDBN}. The @samp{cores} column, if present,
43854 should contain a comma-separated list of cores that this process
43855 is running on. Target may provide additional columns,
43856 which @value{GDBN} currently ignores.
43858 @node Trace File Format
43859 @appendix Trace File Format
43860 @cindex trace file format
43862 The trace file comes in three parts: a header, a textual description
43863 section, and a trace frame section with binary data.
43865 The header has the form @code{\x7fTRACE0\n}. The first byte is
43866 @code{0x7f} so as to indicate that the file contains binary data,
43867 while the @code{0} is a version number that may have different values
43870 The description section consists of multiple lines of @sc{ascii} text
43871 separated by newline characters (@code{0xa}). The lines may include a
43872 variety of optional descriptive or context-setting information, such
43873 as tracepoint definitions or register set size. @value{GDBN} will
43874 ignore any line that it does not recognize. An empty line marks the end
43879 Specifies the size of a register block in bytes. This is equal to the
43880 size of a @code{g} packet payload in the remote protocol. @var{size}
43881 is an ascii decimal number. There should be only one such line in
43882 a single trace file.
43884 @item status @var{status}
43885 Trace status. @var{status} has the same format as a @code{qTStatus}
43886 remote packet reply. There should be only one such line in a single trace
43889 @item tp @var{payload}
43890 Tracepoint definition. The @var{payload} has the same format as
43891 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
43892 may take multiple lines of definition, corresponding to the multiple
43895 @item tsv @var{payload}
43896 Trace state variable definition. The @var{payload} has the same format as
43897 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
43898 may take multiple lines of definition, corresponding to the multiple
43901 @item tdesc @var{payload}
43902 Target description in XML format. The @var{payload} is a single line of
43903 the XML file. All such lines should be concatenated together to get
43904 the original XML file. This file is in the same format as @code{qXfer}
43905 @code{features} payload, and corresponds to the main @code{target.xml}
43906 file. Includes are not allowed.
43910 The trace frame section consists of a number of consecutive frames.
43911 Each frame begins with a two-byte tracepoint number, followed by a
43912 four-byte size giving the amount of data in the frame. The data in
43913 the frame consists of a number of blocks, each introduced by a
43914 character indicating its type (at least register, memory, and trace
43915 state variable). The data in this section is raw binary, not a
43916 hexadecimal or other encoding; its endianness matches the target's
43919 @c FIXME bi-arch may require endianness/arch info in description section
43922 @item R @var{bytes}
43923 Register block. The number and ordering of bytes matches that of a
43924 @code{g} packet in the remote protocol. Note that these are the
43925 actual bytes, in target order, not a hexadecimal encoding.
43927 @item M @var{address} @var{length} @var{bytes}...
43928 Memory block. This is a contiguous block of memory, at the 8-byte
43929 address @var{address}, with a 2-byte length @var{length}, followed by
43930 @var{length} bytes.
43932 @item V @var{number} @var{value}
43933 Trace state variable block. This records the 8-byte signed value
43934 @var{value} of trace state variable numbered @var{number}.
43938 Future enhancements of the trace file format may include additional types
43941 @node Index Section Format
43942 @appendix @code{.gdb_index} section format
43943 @cindex .gdb_index section format
43944 @cindex index section format
43946 This section documents the index section that is created by @code{save
43947 gdb-index} (@pxref{Index Files}). The index section is
43948 DWARF-specific; some knowledge of DWARF is assumed in this
43951 The mapped index file format is designed to be directly
43952 @code{mmap}able on any architecture. In most cases, a datum is
43953 represented using a little-endian 32-bit integer value, called an
43954 @code{offset_type}. Big endian machines must byte-swap the values
43955 before using them. Exceptions to this rule are noted. The data is
43956 laid out such that alignment is always respected.
43958 A mapped index consists of several areas, laid out in order.
43962 The file header. This is a sequence of values, of @code{offset_type}
43963 unless otherwise noted:
43967 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43968 Version 4 uses a different hashing function from versions 5 and 6.
43969 Version 6 includes symbols for inlined functions, whereas versions 4
43970 and 5 do not. Version 7 adds attributes to the CU indices in the
43971 symbol table. Version 8 specifies that symbols from DWARF type units
43972 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43973 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43975 @value{GDBN} will only read version 4, 5, or 6 indices
43976 by specifying @code{set use-deprecated-index-sections on}.
43977 GDB has a workaround for potentially broken version 7 indices so it is
43978 currently not flagged as deprecated.
43981 The offset, from the start of the file, of the CU list.
43984 The offset, from the start of the file, of the types CU list. Note
43985 that this area can be empty, in which case this offset will be equal
43986 to the next offset.
43989 The offset, from the start of the file, of the address area.
43992 The offset, from the start of the file, of the symbol table.
43995 The offset, from the start of the file, of the constant pool.
43999 The CU list. This is a sequence of pairs of 64-bit little-endian
44000 values, sorted by the CU offset. The first element in each pair is
44001 the offset of a CU in the @code{.debug_info} section. The second
44002 element in each pair is the length of that CU. References to a CU
44003 elsewhere in the map are done using a CU index, which is just the
44004 0-based index into this table. Note that if there are type CUs, then
44005 conceptually CUs and type CUs form a single list for the purposes of
44009 The types CU list. This is a sequence of triplets of 64-bit
44010 little-endian values. In a triplet, the first value is the CU offset,
44011 the second value is the type offset in the CU, and the third value is
44012 the type signature. The types CU list is not sorted.
44015 The address area. The address area consists of a sequence of address
44016 entries. Each address entry has three elements:
44020 The low address. This is a 64-bit little-endian value.
44023 The high address. This is a 64-bit little-endian value. Like
44024 @code{DW_AT_high_pc}, the value is one byte beyond the end.
44027 The CU index. This is an @code{offset_type} value.
44031 The symbol table. This is an open-addressed hash table. The size of
44032 the hash table is always a power of 2.
44034 Each slot in the hash table consists of a pair of @code{offset_type}
44035 values. The first value is the offset of the symbol's name in the
44036 constant pool. The second value is the offset of the CU vector in the
44039 If both values are 0, then this slot in the hash table is empty. This
44040 is ok because while 0 is a valid constant pool index, it cannot be a
44041 valid index for both a string and a CU vector.
44043 The hash value for a table entry is computed by applying an
44044 iterative hash function to the symbol's name. Starting with an
44045 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
44046 the string is incorporated into the hash using the formula depending on the
44051 The formula is @code{r = r * 67 + c - 113}.
44053 @item Versions 5 to 7
44054 The formula is @code{r = r * 67 + tolower (c) - 113}.
44057 The terminating @samp{\0} is not incorporated into the hash.
44059 The step size used in the hash table is computed via
44060 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
44061 value, and @samp{size} is the size of the hash table. The step size
44062 is used to find the next candidate slot when handling a hash
44065 The names of C@t{++} symbols in the hash table are canonicalized. We
44066 don't currently have a simple description of the canonicalization
44067 algorithm; if you intend to create new index sections, you must read
44071 The constant pool. This is simply a bunch of bytes. It is organized
44072 so that alignment is correct: CU vectors are stored first, followed by
44075 A CU vector in the constant pool is a sequence of @code{offset_type}
44076 values. The first value is the number of CU indices in the vector.
44077 Each subsequent value is the index and symbol attributes of a CU in
44078 the CU list. This element in the hash table is used to indicate which
44079 CUs define the symbol and how the symbol is used.
44080 See below for the format of each CU index+attributes entry.
44082 A string in the constant pool is zero-terminated.
44085 Attributes were added to CU index values in @code{.gdb_index} version 7.
44086 If a symbol has multiple uses within a CU then there is one
44087 CU index+attributes value for each use.
44089 The format of each CU index+attributes entry is as follows
44095 This is the index of the CU in the CU list.
44097 These bits are reserved for future purposes and must be zero.
44099 The kind of the symbol in the CU.
44103 This value is reserved and should not be used.
44104 By reserving zero the full @code{offset_type} value is backwards compatible
44105 with previous versions of the index.
44107 The symbol is a type.
44109 The symbol is a variable or an enum value.
44111 The symbol is a function.
44113 Any other kind of symbol.
44115 These values are reserved.
44119 This bit is zero if the value is global and one if it is static.
44121 The determination of whether a symbol is global or static is complicated.
44122 The authorative reference is the file @file{dwarf2read.c} in
44123 @value{GDBN} sources.
44127 This pseudo-code describes the computation of a symbol's kind and
44128 global/static attributes in the index.
44131 is_external = get_attribute (die, DW_AT_external);
44132 language = get_attribute (cu_die, DW_AT_language);
44135 case DW_TAG_typedef:
44136 case DW_TAG_base_type:
44137 case DW_TAG_subrange_type:
44141 case DW_TAG_enumerator:
44143 is_static = language != CPLUS;
44145 case DW_TAG_subprogram:
44147 is_static = ! (is_external || language == ADA);
44149 case DW_TAG_constant:
44151 is_static = ! is_external;
44153 case DW_TAG_variable:
44155 is_static = ! is_external;
44157 case DW_TAG_namespace:
44161 case DW_TAG_class_type:
44162 case DW_TAG_interface_type:
44163 case DW_TAG_structure_type:
44164 case DW_TAG_union_type:
44165 case DW_TAG_enumeration_type:
44167 is_static = language != CPLUS;
44175 @appendix Manual pages
44179 * gdb man:: The GNU Debugger man page
44180 * gdbserver man:: Remote Server for the GNU Debugger man page
44181 * gcore man:: Generate a core file of a running program
44182 * gdbinit man:: gdbinit scripts
44183 * gdb-add-index man:: Add index files to speed up GDB
44189 @c man title gdb The GNU Debugger
44191 @c man begin SYNOPSIS gdb
44192 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
44193 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
44194 [@option{-b}@w{ }@var{bps}]
44195 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
44196 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
44197 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
44198 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
44199 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
44202 @c man begin DESCRIPTION gdb
44203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
44204 going on ``inside'' another program while it executes -- or what another
44205 program was doing at the moment it crashed.
44207 @value{GDBN} can do four main kinds of things (plus other things in support of
44208 these) to help you catch bugs in the act:
44212 Start your program, specifying anything that might affect its behavior.
44215 Make your program stop on specified conditions.
44218 Examine what has happened, when your program has stopped.
44221 Change things in your program, so you can experiment with correcting the
44222 effects of one bug and go on to learn about another.
44225 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
44228 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
44229 commands from the terminal until you tell it to exit with the @value{GDBN}
44230 command @code{quit}. You can get online help from @value{GDBN} itself
44231 by using the command @code{help}.
44233 You can run @code{gdb} with no arguments or options; but the most
44234 usual way to start @value{GDBN} is with one argument or two, specifying an
44235 executable program as the argument:
44241 You can also start with both an executable program and a core file specified:
44247 You can, instead, specify a process ID as a second argument, if you want
44248 to debug a running process:
44256 would attach @value{GDBN} to process @code{1234} (unless you also have a file
44257 named @file{1234}; @value{GDBN} does check for a core file first).
44258 With option @option{-p} you can omit the @var{program} filename.
44260 Here are some of the most frequently needed @value{GDBN} commands:
44262 @c pod2man highlights the right hand side of the @item lines.
44264 @item break [@var{file}:]@var{function}
44265 Set a breakpoint at @var{function} (in @var{file}).
44267 @item run [@var{arglist}]
44268 Start your program (with @var{arglist}, if specified).
44271 Backtrace: display the program stack.
44273 @item print @var{expr}
44274 Display the value of an expression.
44277 Continue running your program (after stopping, e.g. at a breakpoint).
44280 Execute next program line (after stopping); step @emph{over} any
44281 function calls in the line.
44283 @item edit [@var{file}:]@var{function}
44284 look at the program line where it is presently stopped.
44286 @item list [@var{file}:]@var{function}
44287 type the text of the program in the vicinity of where it is presently stopped.
44290 Execute next program line (after stopping); step @emph{into} any
44291 function calls in the line.
44293 @item help [@var{name}]
44294 Show information about @value{GDBN} command @var{name}, or general information
44295 about using @value{GDBN}.
44298 Exit from @value{GDBN}.
44302 For full details on @value{GDBN},
44303 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44304 by Richard M. Stallman and Roland H. Pesch. The same text is available online
44305 as the @code{gdb} entry in the @code{info} program.
44309 @c man begin OPTIONS gdb
44310 Any arguments other than options specify an executable
44311 file and core file (or process ID); that is, the first argument
44312 encountered with no
44313 associated option flag is equivalent to a @option{-se} option, and the second,
44314 if any, is equivalent to a @option{-c} option if it's the name of a file.
44316 both long and short forms; both are shown here. The long forms are also
44317 recognized if you truncate them, so long as enough of the option is
44318 present to be unambiguous. (If you prefer, you can flag option
44319 arguments with @option{+} rather than @option{-}, though we illustrate the
44320 more usual convention.)
44322 All the options and command line arguments you give are processed
44323 in sequential order. The order makes a difference when the @option{-x}
44329 List all options, with brief explanations.
44331 @item -symbols=@var{file}
44332 @itemx -s @var{file}
44333 Read symbol table from file @var{file}.
44336 Enable writing into executable and core files.
44338 @item -exec=@var{file}
44339 @itemx -e @var{file}
44340 Use file @var{file} as the executable file to execute when
44341 appropriate, and for examining pure data in conjunction with a core
44344 @item -se=@var{file}
44345 Read symbol table from file @var{file} and use it as the executable
44348 @item -core=@var{file}
44349 @itemx -c @var{file}
44350 Use file @var{file} as a core dump to examine.
44352 @item -command=@var{file}
44353 @itemx -x @var{file}
44354 Execute @value{GDBN} commands from file @var{file}.
44356 @item -ex @var{command}
44357 Execute given @value{GDBN} @var{command}.
44359 @item -directory=@var{directory}
44360 @itemx -d @var{directory}
44361 Add @var{directory} to the path to search for source files.
44364 Do not execute commands from @file{~/.gdbinit}.
44368 Do not execute commands from any @file{.gdbinit} initialization files.
44372 ``Quiet''. Do not print the introductory and copyright messages. These
44373 messages are also suppressed in batch mode.
44376 Run in batch mode. Exit with status @code{0} after processing all the command
44377 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44378 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44379 commands in the command files.
44381 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44382 download and run a program on another computer; in order to make this
44383 more useful, the message
44386 Program exited normally.
44390 (which is ordinarily issued whenever a program running under @value{GDBN} control
44391 terminates) is not issued when running in batch mode.
44393 @item -cd=@var{directory}
44394 Run @value{GDBN} using @var{directory} as its working directory,
44395 instead of the current directory.
44399 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44400 @value{GDBN} to output the full file name and line number in a standard,
44401 recognizable fashion each time a stack frame is displayed (which
44402 includes each time the program stops). This recognizable format looks
44403 like two @samp{\032} characters, followed by the file name, line number
44404 and character position separated by colons, and a newline. The
44405 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44406 characters as a signal to display the source code for the frame.
44409 Set the line speed (baud rate or bits per second) of any serial
44410 interface used by @value{GDBN} for remote debugging.
44412 @item -tty=@var{device}
44413 Run using @var{device} for your program's standard input and output.
44417 @c man begin SEEALSO gdb
44419 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44420 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44421 documentation are properly installed at your site, the command
44428 should give you access to the complete manual.
44430 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44431 Richard M. Stallman and Roland H. Pesch, July 1991.
44435 @node gdbserver man
44436 @heading gdbserver man
44438 @c man title gdbserver Remote Server for the GNU Debugger
44440 @c man begin SYNOPSIS gdbserver
44441 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44443 gdbserver --attach @var{comm} @var{pid}
44445 gdbserver --multi @var{comm}
44449 @c man begin DESCRIPTION gdbserver
44450 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44451 than the one which is running the program being debugged.
44454 @subheading Usage (server (target) side)
44457 Usage (server (target) side):
44460 First, you need to have a copy of the program you want to debug put onto
44461 the target system. The program can be stripped to save space if needed, as
44462 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44463 the @value{GDBN} running on the host system.
44465 To use the server, you log on to the target system, and run the @command{gdbserver}
44466 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44467 your program, and (c) its arguments. The general syntax is:
44470 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44473 For example, using a serial port, you might say:
44477 @c @file would wrap it as F</dev/com1>.
44478 target> gdbserver /dev/com1 emacs foo.txt
44481 target> gdbserver @file{/dev/com1} emacs foo.txt
44485 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44486 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44487 waits patiently for the host @value{GDBN} to communicate with it.
44489 To use a TCP connection, you could say:
44492 target> gdbserver host:2345 emacs foo.txt
44495 This says pretty much the same thing as the last example, except that we are
44496 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44497 that we are expecting to see a TCP connection from @code{host} to local TCP port
44498 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44499 want for the port number as long as it does not conflict with any existing TCP
44500 ports on the target system. This same port number must be used in the host
44501 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44502 you chose a port number that conflicts with another service, @command{gdbserver} will
44503 print an error message and exit.
44505 @command{gdbserver} can also attach to running programs.
44506 This is accomplished via the @option{--attach} argument. The syntax is:
44509 target> gdbserver --attach @var{comm} @var{pid}
44512 @var{pid} is the process ID of a currently running process. It isn't
44513 necessary to point @command{gdbserver} at a binary for the running process.
44515 To start @code{gdbserver} without supplying an initial command to run
44516 or process ID to attach, use the @option{--multi} command line option.
44517 In such case you should connect using @kbd{target extended-remote} to start
44518 the program you want to debug.
44521 target> gdbserver --multi @var{comm}
44525 @subheading Usage (host side)
44531 You need an unstripped copy of the target program on your host system, since
44532 @value{GDBN} needs to examine its symbol tables and such. Start up @value{GDBN} as you normally
44533 would, with the target program as the first argument. (You may need to use the
44534 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44535 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44536 new command you need to know about is @code{target remote}
44537 (or @code{target extended-remote}). Its argument is either
44538 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44539 descriptor. For example:
44543 @c @file would wrap it as F</dev/ttyb>.
44544 (gdb) target remote /dev/ttyb
44547 (gdb) target remote @file{/dev/ttyb}
44552 communicates with the server via serial line @file{/dev/ttyb}, and:
44555 (gdb) target remote the-target:2345
44559 communicates via a TCP connection to port 2345 on host `the-target', where
44560 you previously started up @command{gdbserver} with the same port number. Note that for
44561 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44562 command, otherwise you may get an error that looks something like
44563 `Connection refused'.
44565 @command{gdbserver} can also debug multiple inferiors at once,
44568 the @value{GDBN} manual in node @code{Inferiors and Programs}
44569 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44572 @ref{Inferiors and Programs}.
44574 In such case use the @code{extended-remote} @value{GDBN} command variant:
44577 (gdb) target extended-remote the-target:2345
44580 The @command{gdbserver} option @option{--multi} may or may not be used in such
44584 @c man begin OPTIONS gdbserver
44585 There are three different modes for invoking @command{gdbserver}:
44590 Debug a specific program specified by its program name:
44593 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44596 The @var{comm} parameter specifies how should the server communicate
44597 with @value{GDBN}; it is either a device name (to use a serial line),
44598 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44599 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44600 debug in @var{prog}. Any remaining arguments will be passed to the
44601 program verbatim. When the program exits, @value{GDBN} will close the
44602 connection, and @code{gdbserver} will exit.
44605 Debug a specific program by specifying the process ID of a running
44609 gdbserver --attach @var{comm} @var{pid}
44612 The @var{comm} parameter is as described above. Supply the process ID
44613 of a running program in @var{pid}; @value{GDBN} will do everything
44614 else. Like with the previous mode, when the process @var{pid} exits,
44615 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44618 Multi-process mode -- debug more than one program/process:
44621 gdbserver --multi @var{comm}
44624 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44625 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44626 close the connection when a process being debugged exits, so you can
44627 debug several processes in the same session.
44630 In each of the modes you may specify these options:
44635 List all options, with brief explanations.
44638 This option causes @command{gdbserver} to print its version number and exit.
44641 @command{gdbserver} will attach to a running program. The syntax is:
44644 target> gdbserver --attach @var{comm} @var{pid}
44647 @var{pid} is the process ID of a currently running process. It isn't
44648 necessary to point @command{gdbserver} at a binary for the running process.
44651 To start @code{gdbserver} without supplying an initial command to run
44652 or process ID to attach, use this command line option.
44653 Then you can connect using @kbd{target extended-remote} and start
44654 the program you want to debug. The syntax is:
44657 target> gdbserver --multi @var{comm}
44661 Instruct @code{gdbserver} to display extra status information about the debugging
44663 This option is intended for @code{gdbserver} development and for bug reports to
44666 @item --remote-debug
44667 Instruct @code{gdbserver} to display remote protocol debug output.
44668 This option is intended for @code{gdbserver} development and for bug reports to
44671 @item --debug-file=@var{filename}
44672 Instruct @code{gdbserver} to send any debug output to the given @var{filename}.
44673 This option is intended for @code{gdbserver} development and for bug reports to
44676 @item --debug-format=option1@r{[},option2,...@r{]}
44677 Instruct @code{gdbserver} to include extra information in each line
44678 of debugging output.
44679 @xref{Other Command-Line Arguments for gdbserver}.
44682 Specify a wrapper to launch programs
44683 for debugging. The option should be followed by the name of the
44684 wrapper, then any command-line arguments to pass to the wrapper, then
44685 @kbd{--} indicating the end of the wrapper arguments.
44688 By default, @command{gdbserver} keeps the listening TCP port open, so that
44689 additional connections are possible. However, if you start @code{gdbserver}
44690 with the @option{--once} option, it will stop listening for any further
44691 connection attempts after connecting to the first @value{GDBN} session.
44693 @c --disable-packet is not documented for users.
44695 @c --disable-randomization and --no-disable-randomization are superseded by
44696 @c QDisableRandomization.
44701 @c man begin SEEALSO gdbserver
44703 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44704 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44705 documentation are properly installed at your site, the command
44711 should give you access to the complete manual.
44713 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44714 Richard M. Stallman and Roland H. Pesch, July 1991.
44721 @c man title gcore Generate a core file of a running program
44724 @c man begin SYNOPSIS gcore
44725 gcore [-a] [-o @var{prefix}] @var{pid1} [@var{pid2}...@var{pidN}]
44729 @c man begin DESCRIPTION gcore
44730 Generate core dumps of one or more running programs with process IDs
44731 @var{pid1}, @var{pid2}, etc. A core file produced by @command{gcore}
44732 is equivalent to one produced by the kernel when the process crashes
44733 (and when @kbd{ulimit -c} was used to set up an appropriate core dump
44734 limit). However, unlike after a crash, after @command{gcore} finishes
44735 its job the program remains running without any change.
44738 @c man begin OPTIONS gcore
44741 Dump all memory mappings. The actual effect of this option depends on
44742 the Operating System. On @sc{gnu}/Linux, it will disable
44743 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
44744 enable @code{dump-excluded-mappings} (@pxref{set
44745 dump-excluded-mappings}).
44747 @item -o @var{prefix}
44748 The optional argument @var{prefix} specifies the prefix to be used
44749 when composing the file names of the core dumps. The file name is
44750 composed as @file{@var{prefix}.@var{pid}}, where @var{pid} is the
44751 process ID of the running program being analyzed by @command{gcore}.
44752 If not specified, @var{prefix} defaults to @var{gcore}.
44756 @c man begin SEEALSO gcore
44758 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44759 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44760 documentation are properly installed at your site, the command
44767 should give you access to the complete manual.
44769 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44770 Richard M. Stallman and Roland H. Pesch, July 1991.
44777 @c man title gdbinit GDB initialization scripts
44780 @c man begin SYNOPSIS gdbinit
44781 @ifset SYSTEM_GDBINIT
44782 @value{SYSTEM_GDBINIT}
44791 @c man begin DESCRIPTION gdbinit
44792 These files contain @value{GDBN} commands to automatically execute during
44793 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44796 the @value{GDBN} manual in node @code{Sequences}
44797 -- shell command @code{info -f gdb -n Sequences}.
44803 Please read more in
44805 the @value{GDBN} manual in node @code{Startup}
44806 -- shell command @code{info -f gdb -n Startup}.
44813 @ifset SYSTEM_GDBINIT
44814 @item @value{SYSTEM_GDBINIT}
44816 @ifclear SYSTEM_GDBINIT
44817 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44819 System-wide initialization file. It is executed unless user specified
44820 @value{GDBN} option @code{-nx} or @code{-n}.
44823 the @value{GDBN} manual in node @code{System-wide configuration}
44824 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44827 @ref{System-wide configuration}.
44831 User initialization file. It is executed unless user specified
44832 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44835 Initialization file for current directory. It may need to be enabled with
44836 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44839 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44840 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44843 @ref{Init File in the Current Directory}.
44848 @c man begin SEEALSO gdbinit
44850 gdb(1), @code{info -f gdb -n Startup}
44852 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44853 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44854 documentation are properly installed at your site, the command
44860 should give you access to the complete manual.
44862 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44863 Richard M. Stallman and Roland H. Pesch, July 1991.
44867 @node gdb-add-index man
44868 @heading gdb-add-index
44869 @pindex gdb-add-index
44870 @anchor{gdb-add-index}
44872 @c man title gdb-add-index Add index files to speed up GDB
44874 @c man begin SYNOPSIS gdb-add-index
44875 gdb-add-index @var{filename}
44878 @c man begin DESCRIPTION gdb-add-index
44879 When @value{GDBN} finds a symbol file, it scans the symbols in the
44880 file in order to construct an internal symbol table. This lets most
44881 @value{GDBN} operations work quickly--at the cost of a delay early on.
44882 For large programs, this delay can be quite lengthy, so @value{GDBN}
44883 provides a way to build an index, which speeds up startup.
44885 To determine whether a file contains such an index, use the command
44886 @kbd{readelf -S filename}: the index is stored in a section named
44887 @code{.gdb_index}. The index file can only be produced on systems
44888 which use ELF binaries and DWARF debug information (i.e., sections
44889 named @code{.debug_*}).
44891 @command{gdb-add-index} uses @value{GDBN} and @command{objdump} found
44892 in the @env{PATH} environment variable. If you want to use different
44893 versions of these programs, you can specify them through the
44894 @env{GDB} and @env{OBJDUMP} environment variables.
44898 the @value{GDBN} manual in node @code{Index Files}
44899 -- shell command @kbd{info -f gdb -n "Index Files"}.
44906 @c man begin SEEALSO gdb-add-index
44908 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44909 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44910 documentation are properly installed at your site, the command
44916 should give you access to the complete manual.
44918 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44919 Richard M. Stallman and Roland H. Pesch, July 1991.
44925 @node GNU Free Documentation License
44926 @appendix GNU Free Documentation License
44929 @node Concept Index
44930 @unnumbered Concept Index
44934 @node Command and Variable Index
44935 @unnumbered Command, Variable, and Function Index
44940 % I think something like @@colophon should be in texinfo. In the
44942 \long\def\colophon{\hbox to0pt{}\vfill
44943 \centerline{The body of this manual is set in}
44944 \centerline{\fontname\tenrm,}
44945 \centerline{with headings in {\bf\fontname\tenbf}}
44946 \centerline{and examples in {\tt\fontname\tentt}.}
44947 \centerline{{\it\fontname\tenit\/},}
44948 \centerline{{\bf\fontname\tenbf}, and}
44949 \centerline{{\sl\fontname\tensl\/}}
44950 \centerline{are used for emphasis.}\vfill}
44952 % Blame: doc@@cygnus.com, 1991.