1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2017 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{} 1988-2017 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) 1988-2017 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.
550 @chapter A Sample @value{GDBN} Session
552 You can use this manual at your leisure to read all about @value{GDBN}.
553 However, a handful of commands are enough to get started using the
554 debugger. This chapter illustrates those commands.
557 In this sample session, we emphasize user input like this: @b{input},
558 to make it easier to pick out from the surrounding output.
561 @c FIXME: this example may not be appropriate for some configs, where
562 @c FIXME...primary interest is in remote use.
564 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
565 processor) exhibits the following bug: sometimes, when we change its
566 quote strings from the default, the commands used to capture one macro
567 definition within another stop working. In the following short @code{m4}
568 session, we define a macro @code{foo} which expands to @code{0000}; we
569 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
570 same thing. However, when we change the open quote string to
571 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
572 procedure fails to define a new synonym @code{baz}:
581 @b{define(bar,defn(`foo'))}
585 @b{changequote(<QUOTE>,<UNQUOTE>)}
587 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
590 m4: End of input: 0: fatal error: EOF in string
594 Let us use @value{GDBN} to try to see what is going on.
597 $ @b{@value{GDBP} m4}
598 @c FIXME: this falsifies the exact text played out, to permit smallbook
599 @c FIXME... format to come out better.
600 @value{GDBN} is free software and you are welcome to distribute copies
601 of it under certain conditions; type "show copying" to see
603 There is absolutely no warranty for @value{GDBN}; type "show warranty"
606 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
611 @value{GDBN} reads only enough symbol data to know where to find the
612 rest when needed; as a result, the first prompt comes up very quickly.
613 We now tell @value{GDBN} to use a narrower display width than usual, so
614 that examples fit in this manual.
617 (@value{GDBP}) @b{set width 70}
621 We need to see how the @code{m4} built-in @code{changequote} works.
622 Having looked at the source, we know the relevant subroutine is
623 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
624 @code{break} command.
627 (@value{GDBP}) @b{break m4_changequote}
628 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
632 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
633 control; as long as control does not reach the @code{m4_changequote}
634 subroutine, the program runs as usual:
637 (@value{GDBP}) @b{run}
638 Starting program: /work/Editorial/gdb/gnu/m4/m4
646 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
647 suspends execution of @code{m4}, displaying information about the
648 context where it stops.
651 @b{changequote(<QUOTE>,<UNQUOTE>)}
653 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
655 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
659 Now we use the command @code{n} (@code{next}) to advance execution to
660 the next line of the current function.
664 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
669 @code{set_quotes} looks like a promising subroutine. We can go into it
670 by using the command @code{s} (@code{step}) instead of @code{next}.
671 @code{step} goes to the next line to be executed in @emph{any}
672 subroutine, so it steps into @code{set_quotes}.
676 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 530 if (lquote != def_lquote)
682 The display that shows the subroutine where @code{m4} is now
683 suspended (and its arguments) is called a stack frame display. It
684 shows a summary of the stack. We can use the @code{backtrace}
685 command (which can also be spelled @code{bt}), to see where we are
686 in the stack as a whole: the @code{backtrace} command displays a
687 stack frame for each active subroutine.
690 (@value{GDBP}) @b{bt}
691 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
693 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
695 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
696 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
698 #4 0x79dc in expand_input () at macro.c:40
699 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
703 We step through a few more lines to see what happens. The first two
704 times, we can use @samp{s}; the next two times we use @code{n} to avoid
705 falling into the @code{xstrdup} subroutine.
709 0x3b5c 532 if (rquote != def_rquote)
711 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
712 def_lquote : xstrdup(lq);
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
721 The last line displayed looks a little odd; we can examine the variables
722 @code{lquote} and @code{rquote} to see if they are in fact the new left
723 and right quotes we specified. We use the command @code{p}
724 (@code{print}) to see their values.
727 (@value{GDBP}) @b{p lquote}
728 $1 = 0x35d40 "<QUOTE>"
729 (@value{GDBP}) @b{p rquote}
730 $2 = 0x35d50 "<UNQUOTE>"
734 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
735 To look at some context, we can display ten lines of source
736 surrounding the current line with the @code{l} (@code{list}) command.
742 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
744 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
747 538 len_lquote = strlen(rquote);
748 539 len_rquote = strlen(lquote);
755 Let us step past the two lines that set @code{len_lquote} and
756 @code{len_rquote}, and then examine the values of those variables.
760 539 len_rquote = strlen(lquote);
763 (@value{GDBP}) @b{p len_lquote}
765 (@value{GDBP}) @b{p len_rquote}
770 That certainly looks wrong, assuming @code{len_lquote} and
771 @code{len_rquote} are meant to be the lengths of @code{lquote} and
772 @code{rquote} respectively. We can set them to better values using
773 the @code{p} command, since it can print the value of
774 any expression---and that expression can include subroutine calls and
778 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
780 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
785 Is that enough to fix the problem of using the new quotes with the
786 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
787 executing with the @code{c} (@code{continue}) command, and then try the
788 example that caused trouble initially:
794 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
801 Success! The new quotes now work just as well as the default ones. The
802 problem seems to have been just the two typos defining the wrong
803 lengths. We allow @code{m4} exit by giving it an EOF as input:
807 Program exited normally.
811 The message @samp{Program exited normally.} is from @value{GDBN}; it
812 indicates @code{m4} has finished executing. We can end our @value{GDBN}
813 session with the @value{GDBN} @code{quit} command.
816 (@value{GDBP}) @b{quit}
820 @chapter Getting In and Out of @value{GDBN}
822 This chapter discusses how to start @value{GDBN}, and how to get out of it.
826 type @samp{@value{GDBP}} to start @value{GDBN}.
828 type @kbd{quit} or @kbd{Ctrl-d} to exit.
832 * Invoking GDB:: How to start @value{GDBN}
833 * Quitting GDB:: How to quit @value{GDBN}
834 * Shell Commands:: How to use shell commands inside @value{GDBN}
835 * Logging Output:: How to log @value{GDBN}'s output to a file
839 @section Invoking @value{GDBN}
841 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
842 @value{GDBN} reads commands from the terminal until you tell it to exit.
844 You can also run @code{@value{GDBP}} with a variety of arguments and options,
845 to specify more of your debugging environment at the outset.
847 The command-line options described here are designed
848 to cover a variety of situations; in some environments, some of these
849 options may effectively be unavailable.
851 The most usual way to start @value{GDBN} is with one argument,
852 specifying an executable program:
855 @value{GDBP} @var{program}
859 You can also start with both an executable program and a core file
863 @value{GDBP} @var{program} @var{core}
866 You can, instead, specify a process ID as a second argument, if you want
867 to debug a running process:
870 @value{GDBP} @var{program} 1234
874 would attach @value{GDBN} to process @code{1234} (unless you also have a file
875 named @file{1234}; @value{GDBN} does check for a core file first).
877 Taking advantage of the second command-line argument requires a fairly
878 complete operating system; when you use @value{GDBN} as a remote
879 debugger attached to a bare board, there may not be any notion of
880 ``process'', and there is often no way to get a core dump. @value{GDBN}
881 will warn you if it is unable to attach or to read core dumps.
883 You can optionally have @code{@value{GDBP}} pass any arguments after the
884 executable file to the inferior using @code{--args}. This option stops
887 @value{GDBP} --args gcc -O2 -c foo.c
889 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
890 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
892 You can run @code{@value{GDBP}} without printing the front material, which describes
893 @value{GDBN}'s non-warranty, by specifying @code{--silent}
894 (or @code{-q}/@code{--quiet}):
897 @value{GDBP} --silent
901 You can further control how @value{GDBN} starts up by using command-line
902 options. @value{GDBN} itself can remind you of the options available.
912 to display all available options and briefly describe their use
913 (@samp{@value{GDBP} -h} is a shorter equivalent).
915 All options and command line arguments you give are processed
916 in sequential order. The order makes a difference when the
917 @samp{-x} option is used.
921 * File Options:: Choosing files
922 * Mode Options:: Choosing modes
923 * Startup:: What @value{GDBN} does during startup
927 @subsection Choosing Files
929 When @value{GDBN} starts, it reads any arguments other than options as
930 specifying an executable file and core file (or process ID). This is
931 the same as if the arguments were specified by the @samp{-se} and
932 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
933 first argument that does not have an associated option flag as
934 equivalent to the @samp{-se} option followed by that argument; and the
935 second argument that does not have an associated option flag, if any, as
936 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
937 If the second argument begins with a decimal digit, @value{GDBN} will
938 first attempt to attach to it as a process, and if that fails, attempt
939 to open it as a corefile. If you have a corefile whose name begins with
940 a digit, you can prevent @value{GDBN} from treating it as a pid by
941 prefixing it with @file{./}, e.g.@: @file{./12345}.
943 If @value{GDBN} has not been configured to included core file support,
944 such as for most embedded targets, then it will complain about a second
945 argument and ignore it.
947 Many options have both long and short forms; both are shown in the
948 following list. @value{GDBN} also recognizes the long forms if you truncate
949 them, so long as enough of the option is present to be unambiguous.
950 (If you prefer, you can flag option arguments with @samp{--} rather
951 than @samp{-}, though we illustrate the more usual convention.)
953 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
954 @c way, both those who look for -foo and --foo in the index, will find
958 @item -symbols @var{file}
960 @cindex @code{--symbols}
962 Read symbol table from file @var{file}.
964 @item -exec @var{file}
966 @cindex @code{--exec}
968 Use file @var{file} as the executable file to execute when appropriate,
969 and for examining pure data in conjunction with a core dump.
973 Read symbol table from file @var{file} and use it as the executable
976 @item -core @var{file}
978 @cindex @code{--core}
980 Use file @var{file} as a core dump to examine.
982 @item -pid @var{number}
983 @itemx -p @var{number}
986 Connect to process ID @var{number}, as with the @code{attach} command.
988 @item -command @var{file}
990 @cindex @code{--command}
992 Execute commands from file @var{file}. The contents of this file is
993 evaluated exactly as the @code{source} command would.
994 @xref{Command Files,, Command files}.
996 @item -eval-command @var{command}
997 @itemx -ex @var{command}
998 @cindex @code{--eval-command}
1000 Execute a single @value{GDBN} command.
1002 This option may be used multiple times to call multiple commands. It may
1003 also be interleaved with @samp{-command} as required.
1006 @value{GDBP} -ex 'target sim' -ex 'load' \
1007 -x setbreakpoints -ex 'run' a.out
1010 @item -init-command @var{file}
1011 @itemx -ix @var{file}
1012 @cindex @code{--init-command}
1014 Execute commands from file @var{file} before loading the inferior (but
1015 after loading gdbinit files).
1018 @item -init-eval-command @var{command}
1019 @itemx -iex @var{command}
1020 @cindex @code{--init-eval-command}
1022 Execute a single @value{GDBN} command before loading the inferior (but
1023 after loading gdbinit files).
1026 @item -directory @var{directory}
1027 @itemx -d @var{directory}
1028 @cindex @code{--directory}
1030 Add @var{directory} to the path to search for source and script files.
1034 @cindex @code{--readnow}
1036 Read each symbol file's entire symbol table immediately, rather than
1037 the default, which is to read it incrementally as it is needed.
1038 This makes startup slower, but makes future operations faster.
1043 @subsection Choosing Modes
1045 You can run @value{GDBN} in various alternative modes---for example, in
1046 batch mode or quiet mode.
1054 Do not execute commands found in any initialization file.
1055 There are three init files, loaded in the following order:
1058 @item @file{system.gdbinit}
1059 This is the system-wide init file.
1060 Its location is specified with the @code{--with-system-gdbinit}
1061 configure option (@pxref{System-wide configuration}).
1062 It is loaded first when @value{GDBN} starts, before command line options
1063 have been processed.
1064 @item @file{~/.gdbinit}
1065 This is the init file in your home directory.
1066 It is loaded next, after @file{system.gdbinit}, and before
1067 command options have been processed.
1068 @item @file{./.gdbinit}
1069 This is the init file in the current directory.
1070 It is loaded last, after command line options other than @code{-x} and
1071 @code{-ex} have been processed. Command line options @code{-x} and
1072 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1075 For further documentation on startup processing, @xref{Startup}.
1076 For documentation on how to write command files,
1077 @xref{Command Files,,Command Files}.
1082 Do not execute commands found in @file{~/.gdbinit}, the init file
1083 in your home directory.
1089 @cindex @code{--quiet}
1090 @cindex @code{--silent}
1092 ``Quiet''. Do not print the introductory and copyright messages. These
1093 messages are also suppressed in batch mode.
1096 @cindex @code{--batch}
1097 Run in batch mode. Exit with status @code{0} after processing all the
1098 command files specified with @samp{-x} (and all commands from
1099 initialization files, if not inhibited with @samp{-n}). Exit with
1100 nonzero status if an error occurs in executing the @value{GDBN} commands
1101 in the command files. Batch mode also disables pagination, sets unlimited
1102 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1103 off} were in effect (@pxref{Messages/Warnings}).
1105 Batch mode may be useful for running @value{GDBN} as a filter, for
1106 example to download and run a program on another computer; in order to
1107 make this more useful, the message
1110 Program exited normally.
1114 (which is ordinarily issued whenever a program running under
1115 @value{GDBN} control terminates) is not issued when running in batch
1119 @cindex @code{--batch-silent}
1120 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1121 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1122 unaffected). This is much quieter than @samp{-silent} and would be useless
1123 for an interactive session.
1125 This is particularly useful when using targets that give @samp{Loading section}
1126 messages, for example.
1128 Note that targets that give their output via @value{GDBN}, as opposed to
1129 writing directly to @code{stdout}, will also be made silent.
1131 @item -return-child-result
1132 @cindex @code{--return-child-result}
1133 The return code from @value{GDBN} will be the return code from the child
1134 process (the process being debugged), with the following exceptions:
1138 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1139 internal error. In this case the exit code is the same as it would have been
1140 without @samp{-return-child-result}.
1142 The user quits with an explicit value. E.g., @samp{quit 1}.
1144 The child process never runs, or is not allowed to terminate, in which case
1145 the exit code will be -1.
1148 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1149 when @value{GDBN} is being used as a remote program loader or simulator
1154 @cindex @code{--nowindows}
1156 ``No windows''. If @value{GDBN} comes with a graphical user interface
1157 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1158 interface. If no GUI is available, this option has no effect.
1162 @cindex @code{--windows}
1164 If @value{GDBN} includes a GUI, then this option requires it to be
1167 @item -cd @var{directory}
1169 Run @value{GDBN} using @var{directory} as its working directory,
1170 instead of the current directory.
1172 @item -data-directory @var{directory}
1173 @itemx -D @var{directory}
1174 @cindex @code{--data-directory}
1176 Run @value{GDBN} using @var{directory} as its data directory.
1177 The data directory is where @value{GDBN} searches for its
1178 auxiliary files. @xref{Data Files}.
1182 @cindex @code{--fullname}
1184 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1185 subprocess. It tells @value{GDBN} to output the full file name and line
1186 number in a standard, recognizable fashion each time a stack frame is
1187 displayed (which includes each time your program stops). This
1188 recognizable format looks like two @samp{\032} characters, followed by
1189 the file name, line number and character position separated by colons,
1190 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1191 @samp{\032} characters as a signal to display the source code for the
1194 @item -annotate @var{level}
1195 @cindex @code{--annotate}
1196 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1197 effect is identical to using @samp{set annotate @var{level}}
1198 (@pxref{Annotations}). The annotation @var{level} controls how much
1199 information @value{GDBN} prints together with its prompt, values of
1200 expressions, source lines, and other types of output. Level 0 is the
1201 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1202 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1203 that control @value{GDBN}, and level 2 has been deprecated.
1205 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1209 @cindex @code{--args}
1210 Change interpretation of command line so that arguments following the
1211 executable file are passed as command line arguments to the inferior.
1212 This option stops option processing.
1214 @item -baud @var{bps}
1216 @cindex @code{--baud}
1218 Set the line speed (baud rate or bits per second) of any serial
1219 interface used by @value{GDBN} for remote debugging.
1221 @item -l @var{timeout}
1223 Set the timeout (in seconds) of any communication used by @value{GDBN}
1224 for remote debugging.
1226 @item -tty @var{device}
1227 @itemx -t @var{device}
1228 @cindex @code{--tty}
1230 Run using @var{device} for your program's standard input and output.
1231 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1233 @c resolve the situation of these eventually
1235 @cindex @code{--tui}
1236 Activate the @dfn{Text User Interface} when starting. The Text User
1237 Interface manages several text windows on the terminal, showing
1238 source, assembly, registers and @value{GDBN} command outputs
1239 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1240 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1241 Using @value{GDBN} under @sc{gnu} Emacs}).
1243 @item -interpreter @var{interp}
1244 @cindex @code{--interpreter}
1245 Use the interpreter @var{interp} for interface with the controlling
1246 program or device. This option is meant to be set by programs which
1247 communicate with @value{GDBN} using it as a back end.
1248 @xref{Interpreters, , Command Interpreters}.
1250 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1251 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1252 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1253 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1254 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1255 @sc{gdb/mi} interfaces are no longer supported.
1258 @cindex @code{--write}
1259 Open the executable and core files for both reading and writing. This
1260 is equivalent to the @samp{set write on} command inside @value{GDBN}
1264 @cindex @code{--statistics}
1265 This option causes @value{GDBN} to print statistics about time and
1266 memory usage after it completes each command and returns to the prompt.
1269 @cindex @code{--version}
1270 This option causes @value{GDBN} to print its version number and
1271 no-warranty blurb, and exit.
1273 @item -configuration
1274 @cindex @code{--configuration}
1275 This option causes @value{GDBN} to print details about its build-time
1276 configuration parameters, and then exit. These details can be
1277 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1282 @subsection What @value{GDBN} Does During Startup
1283 @cindex @value{GDBN} startup
1285 Here's the description of what @value{GDBN} does during session startup:
1289 Sets up the command interpreter as specified by the command line
1290 (@pxref{Mode Options, interpreter}).
1294 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1295 used when building @value{GDBN}; @pxref{System-wide configuration,
1296 ,System-wide configuration and settings}) and executes all the commands in
1299 @anchor{Home Directory Init File}
1301 Reads the init file (if any) in your home directory@footnote{On
1302 DOS/Windows systems, the home directory is the one pointed to by the
1303 @code{HOME} environment variable.} and executes all the commands in
1306 @anchor{Option -init-eval-command}
1308 Executes commands and command files specified by the @samp{-iex} and
1309 @samp{-ix} options in their specified order. Usually you should use the
1310 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1311 settings before @value{GDBN} init files get executed and before inferior
1315 Processes command line options and operands.
1317 @anchor{Init File in the Current Directory during Startup}
1319 Reads and executes the commands from init file (if any) in the current
1320 working directory as long as @samp{set auto-load local-gdbinit} is set to
1321 @samp{on} (@pxref{Init File in the Current Directory}).
1322 This is only done if the current directory is
1323 different from your home directory. Thus, you can have more than one
1324 init file, one generic in your home directory, and another, specific
1325 to the program you are debugging, in the directory where you invoke
1329 If the command line specified a program to debug, or a process to
1330 attach to, or a core file, @value{GDBN} loads any auto-loaded
1331 scripts provided for the program or for its loaded shared libraries.
1332 @xref{Auto-loading}.
1334 If you wish to disable the auto-loading during startup,
1335 you must do something like the following:
1338 $ gdb -iex "set auto-load python-scripts off" myprogram
1341 Option @samp{-ex} does not work because the auto-loading is then turned
1345 Executes commands and command files specified by the @samp{-ex} and
1346 @samp{-x} options in their specified order. @xref{Command Files}, for
1347 more details about @value{GDBN} command files.
1350 Reads the command history recorded in the @dfn{history file}.
1351 @xref{Command History}, for more details about the command history and the
1352 files where @value{GDBN} records it.
1355 Init files use the same syntax as @dfn{command files} (@pxref{Command
1356 Files}) and are processed by @value{GDBN} in the same way. The init
1357 file in your home directory can set options (such as @samp{set
1358 complaints}) that affect subsequent processing of command line options
1359 and operands. Init files are not executed if you use the @samp{-nx}
1360 option (@pxref{Mode Options, ,Choosing Modes}).
1362 To display the list of init files loaded by gdb at startup, you
1363 can use @kbd{gdb --help}.
1365 @cindex init file name
1366 @cindex @file{.gdbinit}
1367 @cindex @file{gdb.ini}
1368 The @value{GDBN} init files are normally called @file{.gdbinit}.
1369 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1370 the limitations of file names imposed by DOS filesystems. The Windows
1371 port of @value{GDBN} uses the standard name, but if it finds a
1372 @file{gdb.ini} file in your home directory, it warns you about that
1373 and suggests to rename the file to the standard name.
1377 @section Quitting @value{GDBN}
1378 @cindex exiting @value{GDBN}
1379 @cindex leaving @value{GDBN}
1382 @kindex quit @r{[}@var{expression}@r{]}
1383 @kindex q @r{(@code{quit})}
1384 @item quit @r{[}@var{expression}@r{]}
1386 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1387 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1388 do not supply @var{expression}, @value{GDBN} will terminate normally;
1389 otherwise it will terminate using the result of @var{expression} as the
1394 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1395 terminates the action of any @value{GDBN} command that is in progress and
1396 returns to @value{GDBN} command level. It is safe to type the interrupt
1397 character at any time because @value{GDBN} does not allow it to take effect
1398 until a time when it is safe.
1400 If you have been using @value{GDBN} to control an attached process or
1401 device, you can release it with the @code{detach} command
1402 (@pxref{Attach, ,Debugging an Already-running Process}).
1404 @node Shell Commands
1405 @section Shell Commands
1407 If you need to execute occasional shell commands during your
1408 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1409 just use the @code{shell} command.
1414 @cindex shell escape
1415 @item shell @var{command-string}
1416 @itemx !@var{command-string}
1417 Invoke a standard shell to execute @var{command-string}.
1418 Note that no space is needed between @code{!} and @var{command-string}.
1419 If it exists, the environment variable @code{SHELL} determines which
1420 shell to run. Otherwise @value{GDBN} uses the default shell
1421 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1424 The utility @code{make} is often needed in development environments.
1425 You do not have to use the @code{shell} command for this purpose in
1430 @cindex calling make
1431 @item make @var{make-args}
1432 Execute the @code{make} program with the specified
1433 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1436 @node Logging Output
1437 @section Logging Output
1438 @cindex logging @value{GDBN} output
1439 @cindex save @value{GDBN} output to a file
1441 You may want to save the output of @value{GDBN} commands to a file.
1442 There are several commands to control @value{GDBN}'s logging.
1446 @item set logging on
1448 @item set logging off
1450 @cindex logging file name
1451 @item set logging file @var{file}
1452 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1453 @item set logging overwrite [on|off]
1454 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1455 you want @code{set logging on} to overwrite the logfile instead.
1456 @item set logging redirect [on|off]
1457 By default, @value{GDBN} output will go to both the terminal and the logfile.
1458 Set @code{redirect} if you want output to go only to the log file.
1459 @kindex show logging
1461 Show the current values of the logging settings.
1465 @chapter @value{GDBN} Commands
1467 You can abbreviate a @value{GDBN} command to the first few letters of the command
1468 name, if that abbreviation is unambiguous; and you can repeat certain
1469 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1470 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1471 show you the alternatives available, if there is more than one possibility).
1474 * Command Syntax:: How to give commands to @value{GDBN}
1475 * Completion:: Command completion
1476 * Help:: How to ask @value{GDBN} for help
1479 @node Command Syntax
1480 @section Command Syntax
1482 A @value{GDBN} command is a single line of input. There is no limit on
1483 how long it can be. It starts with a command name, which is followed by
1484 arguments whose meaning depends on the command name. For example, the
1485 command @code{step} accepts an argument which is the number of times to
1486 step, as in @samp{step 5}. You can also use the @code{step} command
1487 with no arguments. Some commands do not allow any arguments.
1489 @cindex abbreviation
1490 @value{GDBN} command names may always be truncated if that abbreviation is
1491 unambiguous. Other possible command abbreviations are listed in the
1492 documentation for individual commands. In some cases, even ambiguous
1493 abbreviations are allowed; for example, @code{s} is specially defined as
1494 equivalent to @code{step} even though there are other commands whose
1495 names start with @code{s}. You can test abbreviations by using them as
1496 arguments to the @code{help} command.
1498 @cindex repeating commands
1499 @kindex RET @r{(repeat last command)}
1500 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1501 repeat the previous command. Certain commands (for example, @code{run})
1502 will not repeat this way; these are commands whose unintentional
1503 repetition might cause trouble and which you are unlikely to want to
1504 repeat. User-defined commands can disable this feature; see
1505 @ref{Define, dont-repeat}.
1507 The @code{list} and @code{x} commands, when you repeat them with
1508 @key{RET}, construct new arguments rather than repeating
1509 exactly as typed. This permits easy scanning of source or memory.
1511 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1512 output, in a way similar to the common utility @code{more}
1513 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1514 @key{RET} too many in this situation, @value{GDBN} disables command
1515 repetition after any command that generates this sort of display.
1517 @kindex # @r{(a comment)}
1519 Any text from a @kbd{#} to the end of the line is a comment; it does
1520 nothing. This is useful mainly in command files (@pxref{Command
1521 Files,,Command Files}).
1523 @cindex repeating command sequences
1524 @kindex Ctrl-o @r{(operate-and-get-next)}
1525 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1526 commands. This command accepts the current line, like @key{RET}, and
1527 then fetches the next line relative to the current line from the history
1531 @section Command Completion
1534 @cindex word completion
1535 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1536 only one possibility; it can also show you what the valid possibilities
1537 are for the next word in a command, at any time. This works for @value{GDBN}
1538 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1540 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1541 of a word. If there is only one possibility, @value{GDBN} fills in the
1542 word, and waits for you to finish the command (or press @key{RET} to
1543 enter it). For example, if you type
1545 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1546 @c complete accuracy in these examples; space introduced for clarity.
1547 @c If texinfo enhancements make it unnecessary, it would be nice to
1548 @c replace " @key" by "@key" in the following...
1550 (@value{GDBP}) info bre @key{TAB}
1554 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1555 the only @code{info} subcommand beginning with @samp{bre}:
1558 (@value{GDBP}) info breakpoints
1562 You can either press @key{RET} at this point, to run the @code{info
1563 breakpoints} command, or backspace and enter something else, if
1564 @samp{breakpoints} does not look like the command you expected. (If you
1565 were sure you wanted @code{info breakpoints} in the first place, you
1566 might as well just type @key{RET} immediately after @samp{info bre},
1567 to exploit command abbreviations rather than command completion).
1569 If there is more than one possibility for the next word when you press
1570 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1571 characters and try again, or just press @key{TAB} a second time;
1572 @value{GDBN} displays all the possible completions for that word. For
1573 example, you might want to set a breakpoint on a subroutine whose name
1574 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1575 just sounds the bell. Typing @key{TAB} again displays all the
1576 function names in your program that begin with those characters, for
1580 (@value{GDBP}) b make_ @key{TAB}
1581 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1582 make_a_section_from_file make_environ
1583 make_abs_section make_function_type
1584 make_blockvector make_pointer_type
1585 make_cleanup make_reference_type
1586 make_command make_symbol_completion_list
1587 (@value{GDBP}) b make_
1591 After displaying the available possibilities, @value{GDBN} copies your
1592 partial input (@samp{b make_} in the example) so you can finish the
1595 If you just want to see the list of alternatives in the first place, you
1596 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1597 means @kbd{@key{META} ?}. You can type this either by holding down a
1598 key designated as the @key{META} shift on your keyboard (if there is
1599 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1601 If the number of possible completions is large, @value{GDBN} will
1602 print as much of the list as it has collected, as well as a message
1603 indicating that the list may be truncated.
1606 (@value{GDBP}) b m@key{TAB}@key{TAB}
1608 <... the rest of the possible completions ...>
1609 *** List may be truncated, max-completions reached. ***
1614 This behavior can be controlled with the following commands:
1617 @kindex set max-completions
1618 @item set max-completions @var{limit}
1619 @itemx set max-completions unlimited
1620 Set the maximum number of completion candidates. @value{GDBN} will
1621 stop looking for more completions once it collects this many candidates.
1622 This is useful when completing on things like function names as collecting
1623 all the possible candidates can be time consuming.
1624 The default value is 200. A value of zero disables tab-completion.
1625 Note that setting either no limit or a very large limit can make
1627 @kindex show max-completions
1628 @item show max-completions
1629 Show the maximum number of candidates that @value{GDBN} will collect and show
1633 @cindex quotes in commands
1634 @cindex completion of quoted strings
1635 Sometimes the string you need, while logically a ``word'', may contain
1636 parentheses or other characters that @value{GDBN} normally excludes from
1637 its notion of a word. To permit word completion to work in this
1638 situation, you may enclose words in @code{'} (single quote marks) in
1639 @value{GDBN} commands.
1641 The most likely situation where you might need this is in typing the
1642 name of a C@t{++} function. This is because C@t{++} allows function
1643 overloading (multiple definitions of the same function, distinguished
1644 by argument type). For example, when you want to set a breakpoint you
1645 may need to distinguish whether you mean the version of @code{name}
1646 that takes an @code{int} parameter, @code{name(int)}, or the version
1647 that takes a @code{float} parameter, @code{name(float)}. To use the
1648 word-completion facilities in this situation, type a single quote
1649 @code{'} at the beginning of the function name. This alerts
1650 @value{GDBN} that it may need to consider more information than usual
1651 when you press @key{TAB} or @kbd{M-?} to request word completion:
1654 (@value{GDBP}) b 'bubble( @kbd{M-?}
1655 bubble(double,double) bubble(int,int)
1656 (@value{GDBP}) b 'bubble(
1659 In some cases, @value{GDBN} can tell that completing a name requires using
1660 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1661 completing as much as it can) if you do not type the quote in the first
1665 (@value{GDBP}) b bub @key{TAB}
1666 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1667 (@value{GDBP}) b 'bubble(
1671 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1672 you have not yet started typing the argument list when you ask for
1673 completion on an overloaded symbol.
1675 For more information about overloaded functions, see @ref{C Plus Plus
1676 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1677 overload-resolution off} to disable overload resolution;
1678 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1680 @cindex completion of structure field names
1681 @cindex structure field name completion
1682 @cindex completion of union field names
1683 @cindex union field name completion
1684 When completing in an expression which looks up a field in a
1685 structure, @value{GDBN} also tries@footnote{The completer can be
1686 confused by certain kinds of invalid expressions. Also, it only
1687 examines the static type of the expression, not the dynamic type.} to
1688 limit completions to the field names available in the type of the
1692 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1693 magic to_fputs to_rewind
1694 to_data to_isatty to_write
1695 to_delete to_put to_write_async_safe
1700 This is because the @code{gdb_stdout} is a variable of the type
1701 @code{struct ui_file} that is defined in @value{GDBN} sources as
1708 ui_file_flush_ftype *to_flush;
1709 ui_file_write_ftype *to_write;
1710 ui_file_write_async_safe_ftype *to_write_async_safe;
1711 ui_file_fputs_ftype *to_fputs;
1712 ui_file_read_ftype *to_read;
1713 ui_file_delete_ftype *to_delete;
1714 ui_file_isatty_ftype *to_isatty;
1715 ui_file_rewind_ftype *to_rewind;
1716 ui_file_put_ftype *to_put;
1723 @section Getting Help
1724 @cindex online documentation
1727 You can always ask @value{GDBN} itself for information on its commands,
1728 using the command @code{help}.
1731 @kindex h @r{(@code{help})}
1734 You can use @code{help} (abbreviated @code{h}) with no arguments to
1735 display a short list of named classes of commands:
1739 List of classes of commands:
1741 aliases -- Aliases of other commands
1742 breakpoints -- Making program stop at certain points
1743 data -- Examining data
1744 files -- Specifying and examining files
1745 internals -- Maintenance commands
1746 obscure -- Obscure features
1747 running -- Running the program
1748 stack -- Examining the stack
1749 status -- Status inquiries
1750 support -- Support facilities
1751 tracepoints -- Tracing of program execution without
1752 stopping the program
1753 user-defined -- User-defined commands
1755 Type "help" followed by a class name for a list of
1756 commands in that class.
1757 Type "help" followed by command name for full
1759 Command name abbreviations are allowed if unambiguous.
1762 @c the above line break eliminates huge line overfull...
1764 @item help @var{class}
1765 Using one of the general help classes as an argument, you can get a
1766 list of the individual commands in that class. For example, here is the
1767 help display for the class @code{status}:
1770 (@value{GDBP}) help status
1775 @c Line break in "show" line falsifies real output, but needed
1776 @c to fit in smallbook page size.
1777 info -- Generic command for showing things
1778 about the program being debugged
1779 show -- Generic command for showing things
1782 Type "help" followed by command name for full
1784 Command name abbreviations are allowed if unambiguous.
1788 @item help @var{command}
1789 With a command name as @code{help} argument, @value{GDBN} displays a
1790 short paragraph on how to use that command.
1793 @item apropos @var{args}
1794 The @code{apropos} command searches through all of the @value{GDBN}
1795 commands, and their documentation, for the regular expression specified in
1796 @var{args}. It prints out all matches found. For example:
1807 alias -- Define a new command that is an alias of an existing command
1808 aliases -- Aliases of other commands
1809 d -- Delete some breakpoints or auto-display expressions
1810 del -- Delete some breakpoints or auto-display expressions
1811 delete -- Delete some breakpoints or auto-display expressions
1816 @item complete @var{args}
1817 The @code{complete @var{args}} command lists all the possible completions
1818 for the beginning of a command. Use @var{args} to specify the beginning of the
1819 command you want completed. For example:
1825 @noindent results in:
1836 @noindent This is intended for use by @sc{gnu} Emacs.
1839 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1840 and @code{show} to inquire about the state of your program, or the state
1841 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1842 manual introduces each of them in the appropriate context. The listings
1843 under @code{info} and under @code{show} in the Command, Variable, and
1844 Function Index point to all the sub-commands. @xref{Command and Variable
1850 @kindex i @r{(@code{info})}
1852 This command (abbreviated @code{i}) is for describing the state of your
1853 program. For example, you can show the arguments passed to a function
1854 with @code{info args}, list the registers currently in use with @code{info
1855 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1856 You can get a complete list of the @code{info} sub-commands with
1857 @w{@code{help info}}.
1861 You can assign the result of an expression to an environment variable with
1862 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1863 @code{set prompt $}.
1867 In contrast to @code{info}, @code{show} is for describing the state of
1868 @value{GDBN} itself.
1869 You can change most of the things you can @code{show}, by using the
1870 related command @code{set}; for example, you can control what number
1871 system is used for displays with @code{set radix}, or simply inquire
1872 which is currently in use with @code{show radix}.
1875 To display all the settable parameters and their current
1876 values, you can use @code{show} with no arguments; you may also use
1877 @code{info set}. Both commands produce the same display.
1878 @c FIXME: "info set" violates the rule that "info" is for state of
1879 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1880 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1884 Here are several miscellaneous @code{show} subcommands, all of which are
1885 exceptional in lacking corresponding @code{set} commands:
1888 @kindex show version
1889 @cindex @value{GDBN} version number
1891 Show what version of @value{GDBN} is running. You should include this
1892 information in @value{GDBN} bug-reports. If multiple versions of
1893 @value{GDBN} are in use at your site, you may need to determine which
1894 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1895 commands are introduced, and old ones may wither away. Also, many
1896 system vendors ship variant versions of @value{GDBN}, and there are
1897 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1898 The version number is the same as the one announced when you start
1901 @kindex show copying
1902 @kindex info copying
1903 @cindex display @value{GDBN} copyright
1906 Display information about permission for copying @value{GDBN}.
1908 @kindex show warranty
1909 @kindex info warranty
1911 @itemx info warranty
1912 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1913 if your version of @value{GDBN} comes with one.
1915 @kindex show configuration
1916 @item show configuration
1917 Display detailed information about the way @value{GDBN} was configured
1918 when it was built. This displays the optional arguments passed to the
1919 @file{configure} script and also configuration parameters detected
1920 automatically by @command{configure}. When reporting a @value{GDBN}
1921 bug (@pxref{GDB Bugs}), it is important to include this information in
1927 @chapter Running Programs Under @value{GDBN}
1929 When you run a program under @value{GDBN}, you must first generate
1930 debugging information when you compile it.
1932 You may start @value{GDBN} with its arguments, if any, in an environment
1933 of your choice. If you are doing native debugging, you may redirect
1934 your program's input and output, debug an already running process, or
1935 kill a child process.
1938 * Compilation:: Compiling for debugging
1939 * Starting:: Starting your program
1940 * Arguments:: Your program's arguments
1941 * Environment:: Your program's environment
1943 * Working Directory:: Your program's working directory
1944 * Input/Output:: Your program's input and output
1945 * Attach:: Debugging an already-running process
1946 * Kill Process:: Killing the child process
1948 * Inferiors and Programs:: Debugging multiple inferiors and programs
1949 * Threads:: Debugging programs with multiple threads
1950 * Forks:: Debugging forks
1951 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1955 @section Compiling for Debugging
1957 In order to debug a program effectively, you need to generate
1958 debugging information when you compile it. This debugging information
1959 is stored in the object file; it describes the data type of each
1960 variable or function and the correspondence between source line numbers
1961 and addresses in the executable code.
1963 To request debugging information, specify the @samp{-g} option when you run
1966 Programs that are to be shipped to your customers are compiled with
1967 optimizations, using the @samp{-O} compiler option. However, some
1968 compilers are unable to handle the @samp{-g} and @samp{-O} options
1969 together. Using those compilers, you cannot generate optimized
1970 executables containing debugging information.
1972 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1973 without @samp{-O}, making it possible to debug optimized code. We
1974 recommend that you @emph{always} use @samp{-g} whenever you compile a
1975 program. You may think your program is correct, but there is no sense
1976 in pushing your luck. For more information, see @ref{Optimized Code}.
1978 Older versions of the @sc{gnu} C compiler permitted a variant option
1979 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1980 format; if your @sc{gnu} C compiler has this option, do not use it.
1982 @value{GDBN} knows about preprocessor macros and can show you their
1983 expansion (@pxref{Macros}). Most compilers do not include information
1984 about preprocessor macros in the debugging information if you specify
1985 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1986 the @sc{gnu} C compiler, provides macro information if you are using
1987 the DWARF debugging format, and specify the option @option{-g3}.
1989 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1990 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1991 information on @value{NGCC} options affecting debug information.
1993 You will have the best debugging experience if you use the latest
1994 version of the DWARF debugging format that your compiler supports.
1995 DWARF is currently the most expressive and best supported debugging
1996 format in @value{GDBN}.
2000 @section Starting your Program
2006 @kindex r @r{(@code{run})}
2009 Use the @code{run} command to start your program under @value{GDBN}.
2010 You must first specify the program name with an argument to
2011 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2012 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2013 command (@pxref{Files, ,Commands to Specify Files}).
2017 If you are running your program in an execution environment that
2018 supports processes, @code{run} creates an inferior process and makes
2019 that process run your program. In some environments without processes,
2020 @code{run} jumps to the start of your program. Other targets,
2021 like @samp{remote}, are always running. If you get an error
2022 message like this one:
2025 The "remote" target does not support "run".
2026 Try "help target" or "continue".
2030 then use @code{continue} to run your program. You may need @code{load}
2031 first (@pxref{load}).
2033 The execution of a program is affected by certain information it
2034 receives from its superior. @value{GDBN} provides ways to specify this
2035 information, which you must do @emph{before} starting your program. (You
2036 can change it after starting your program, but such changes only affect
2037 your program the next time you start it.) This information may be
2038 divided into four categories:
2041 @item The @emph{arguments.}
2042 Specify the arguments to give your program as the arguments of the
2043 @code{run} command. If a shell is available on your target, the shell
2044 is used to pass the arguments, so that you may use normal conventions
2045 (such as wildcard expansion or variable substitution) in describing
2047 In Unix systems, you can control which shell is used with the
2048 @code{SHELL} environment variable. If you do not define @code{SHELL},
2049 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2050 use of any shell with the @code{set startup-with-shell} command (see
2053 @item The @emph{environment.}
2054 Your program normally inherits its environment from @value{GDBN}, but you can
2055 use the @value{GDBN} commands @code{set environment} and @code{unset
2056 environment} to change parts of the environment that affect
2057 your program. @xref{Environment, ,Your Program's Environment}.
2059 @item The @emph{working directory.}
2060 Your program inherits its working directory from @value{GDBN}. You can set
2061 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2062 @xref{Working Directory, ,Your Program's Working Directory}.
2064 @item The @emph{standard input and output.}
2065 Your program normally uses the same device for standard input and
2066 standard output as @value{GDBN} is using. You can redirect input and output
2067 in the @code{run} command line, or you can use the @code{tty} command to
2068 set a different device for your program.
2069 @xref{Input/Output, ,Your Program's Input and Output}.
2072 @emph{Warning:} While input and output redirection work, you cannot use
2073 pipes to pass the output of the program you are debugging to another
2074 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2078 When you issue the @code{run} command, your program begins to execute
2079 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2080 of how to arrange for your program to stop. Once your program has
2081 stopped, you may call functions in your program, using the @code{print}
2082 or @code{call} commands. @xref{Data, ,Examining Data}.
2084 If the modification time of your symbol file has changed since the last
2085 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2086 table, and reads it again. When it does this, @value{GDBN} tries to retain
2087 your current breakpoints.
2092 @cindex run to main procedure
2093 The name of the main procedure can vary from language to language.
2094 With C or C@t{++}, the main procedure name is always @code{main}, but
2095 other languages such as Ada do not require a specific name for their
2096 main procedure. The debugger provides a convenient way to start the
2097 execution of the program and to stop at the beginning of the main
2098 procedure, depending on the language used.
2100 The @samp{start} command does the equivalent of setting a temporary
2101 breakpoint at the beginning of the main procedure and then invoking
2102 the @samp{run} command.
2104 @cindex elaboration phase
2105 Some programs contain an @dfn{elaboration} phase where some startup code is
2106 executed before the main procedure is called. This depends on the
2107 languages used to write your program. In C@t{++}, for instance,
2108 constructors for static and global objects are executed before
2109 @code{main} is called. It is therefore possible that the debugger stops
2110 before reaching the main procedure. However, the temporary breakpoint
2111 will remain to halt execution.
2113 Specify the arguments to give to your program as arguments to the
2114 @samp{start} command. These arguments will be given verbatim to the
2115 underlying @samp{run} command. Note that the same arguments will be
2116 reused if no argument is provided during subsequent calls to
2117 @samp{start} or @samp{run}.
2119 It is sometimes necessary to debug the program during elaboration. In
2120 these cases, using the @code{start} command would stop the execution of
2121 your program too late, as the program would have already completed the
2122 elaboration phase. Under these circumstances, insert breakpoints in your
2123 elaboration code before running your program.
2125 @anchor{set exec-wrapper}
2126 @kindex set exec-wrapper
2127 @item set exec-wrapper @var{wrapper}
2128 @itemx show exec-wrapper
2129 @itemx unset exec-wrapper
2130 When @samp{exec-wrapper} is set, the specified wrapper is used to
2131 launch programs for debugging. @value{GDBN} starts your program
2132 with a shell command of the form @kbd{exec @var{wrapper}
2133 @var{program}}. Quoting is added to @var{program} and its
2134 arguments, but not to @var{wrapper}, so you should add quotes if
2135 appropriate for your shell. The wrapper runs until it executes
2136 your program, and then @value{GDBN} takes control.
2138 You can use any program that eventually calls @code{execve} with
2139 its arguments as a wrapper. Several standard Unix utilities do
2140 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2141 with @code{exec "$@@"} will also work.
2143 For example, you can use @code{env} to pass an environment variable to
2144 the debugged program, without setting the variable in your shell's
2148 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2152 This command is available when debugging locally on most targets, excluding
2153 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2155 @kindex set startup-with-shell
2156 @item set startup-with-shell
2157 @itemx set startup-with-shell on
2158 @itemx set startup-with-shell off
2159 @itemx show set startup-with-shell
2160 On Unix systems, by default, if a shell is available on your target,
2161 @value{GDBN}) uses it to start your program. Arguments of the
2162 @code{run} command are passed to the shell, which does variable
2163 substitution, expands wildcard characters and performs redirection of
2164 I/O. In some circumstances, it may be useful to disable such use of a
2165 shell, for example, when debugging the shell itself or diagnosing
2166 startup failures such as:
2170 Starting program: ./a.out
2171 During startup program terminated with signal SIGSEGV, Segmentation fault.
2175 which indicates the shell or the wrapper specified with
2176 @samp{exec-wrapper} crashed, not your program. Most often, this is
2177 caused by something odd in your shell's non-interactive mode
2178 initialization file---such as @file{.cshrc} for C-shell,
2179 $@file{.zshenv} for the Z shell, or the file specified in the
2180 @samp{BASH_ENV} environment variable for BASH.
2182 @anchor{set auto-connect-native-target}
2183 @kindex set auto-connect-native-target
2184 @item set auto-connect-native-target
2185 @itemx set auto-connect-native-target on
2186 @itemx set auto-connect-native-target off
2187 @itemx show auto-connect-native-target
2189 By default, if not connected to any target yet (e.g., with
2190 @code{target remote}), the @code{run} command starts your program as a
2191 native process under @value{GDBN}, on your local machine. If you're
2192 sure you don't want to debug programs on your local machine, you can
2193 tell @value{GDBN} to not connect to the native target automatically
2194 with the @code{set auto-connect-native-target off} command.
2196 If @code{on}, which is the default, and if @value{GDBN} is not
2197 connected to a target already, the @code{run} command automaticaly
2198 connects to the native target, if one is available.
2200 If @code{off}, and if @value{GDBN} is not connected to a target
2201 already, the @code{run} command fails with an error:
2205 Don't know how to run. Try "help target".
2208 If @value{GDBN} is already connected to a target, @value{GDBN} always
2209 uses it with the @code{run} command.
2211 In any case, you can explicitly connect to the native target with the
2212 @code{target native} command. For example,
2215 (@value{GDBP}) set auto-connect-native-target off
2217 Don't know how to run. Try "help target".
2218 (@value{GDBP}) target native
2220 Starting program: ./a.out
2221 [Inferior 1 (process 10421) exited normally]
2224 In case you connected explicitly to the @code{native} target,
2225 @value{GDBN} remains connected even if all inferiors exit, ready for
2226 the next @code{run} command. Use the @code{disconnect} command to
2229 Examples of other commands that likewise respect the
2230 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2231 proc}, @code{info os}.
2233 @kindex set disable-randomization
2234 @item set disable-randomization
2235 @itemx set disable-randomization on
2236 This option (enabled by default in @value{GDBN}) will turn off the native
2237 randomization of the virtual address space of the started program. This option
2238 is useful for multiple debugging sessions to make the execution better
2239 reproducible and memory addresses reusable across debugging sessions.
2241 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2242 On @sc{gnu}/Linux you can get the same behavior using
2245 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2248 @item set disable-randomization off
2249 Leave the behavior of the started executable unchanged. Some bugs rear their
2250 ugly heads only when the program is loaded at certain addresses. If your bug
2251 disappears when you run the program under @value{GDBN}, that might be because
2252 @value{GDBN} by default disables the address randomization on platforms, such
2253 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2254 disable-randomization off} to try to reproduce such elusive bugs.
2256 On targets where it is available, virtual address space randomization
2257 protects the programs against certain kinds of security attacks. In these
2258 cases the attacker needs to know the exact location of a concrete executable
2259 code. Randomizing its location makes it impossible to inject jumps misusing
2260 a code at its expected addresses.
2262 Prelinking shared libraries provides a startup performance advantage but it
2263 makes addresses in these libraries predictable for privileged processes by
2264 having just unprivileged access at the target system. Reading the shared
2265 library binary gives enough information for assembling the malicious code
2266 misusing it. Still even a prelinked shared library can get loaded at a new
2267 random address just requiring the regular relocation process during the
2268 startup. Shared libraries not already prelinked are always loaded at
2269 a randomly chosen address.
2271 Position independent executables (PIE) contain position independent code
2272 similar to the shared libraries and therefore such executables get loaded at
2273 a randomly chosen address upon startup. PIE executables always load even
2274 already prelinked shared libraries at a random address. You can build such
2275 executable using @command{gcc -fPIE -pie}.
2277 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2278 (as long as the randomization is enabled).
2280 @item show disable-randomization
2281 Show the current setting of the explicit disable of the native randomization of
2282 the virtual address space of the started program.
2287 @section Your Program's Arguments
2289 @cindex arguments (to your program)
2290 The arguments to your program can be specified by the arguments of the
2292 They are passed to a shell, which expands wildcard characters and
2293 performs redirection of I/O, and thence to your program. Your
2294 @code{SHELL} environment variable (if it exists) specifies what shell
2295 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2296 the default shell (@file{/bin/sh} on Unix).
2298 On non-Unix systems, the program is usually invoked directly by
2299 @value{GDBN}, which emulates I/O redirection via the appropriate system
2300 calls, and the wildcard characters are expanded by the startup code of
2301 the program, not by the shell.
2303 @code{run} with no arguments uses the same arguments used by the previous
2304 @code{run}, or those set by the @code{set args} command.
2309 Specify the arguments to be used the next time your program is run. If
2310 @code{set args} has no arguments, @code{run} executes your program
2311 with no arguments. Once you have run your program with arguments,
2312 using @code{set args} before the next @code{run} is the only way to run
2313 it again without arguments.
2317 Show the arguments to give your program when it is started.
2321 @section Your Program's Environment
2323 @cindex environment (of your program)
2324 The @dfn{environment} consists of a set of environment variables and
2325 their values. Environment variables conventionally record such things as
2326 your user name, your home directory, your terminal type, and your search
2327 path for programs to run. Usually you set up environment variables with
2328 the shell and they are inherited by all the other programs you run. When
2329 debugging, it can be useful to try running your program with a modified
2330 environment without having to start @value{GDBN} over again.
2334 @item path @var{directory}
2335 Add @var{directory} to the front of the @code{PATH} environment variable
2336 (the search path for executables) that will be passed to your program.
2337 The value of @code{PATH} used by @value{GDBN} does not change.
2338 You may specify several directory names, separated by whitespace or by a
2339 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2340 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2341 is moved to the front, so it is searched sooner.
2343 You can use the string @samp{$cwd} to refer to whatever is the current
2344 working directory at the time @value{GDBN} searches the path. If you
2345 use @samp{.} instead, it refers to the directory where you executed the
2346 @code{path} command. @value{GDBN} replaces @samp{.} in the
2347 @var{directory} argument (with the current path) before adding
2348 @var{directory} to the search path.
2349 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2350 @c document that, since repeating it would be a no-op.
2354 Display the list of search paths for executables (the @code{PATH}
2355 environment variable).
2357 @kindex show environment
2358 @item show environment @r{[}@var{varname}@r{]}
2359 Print the value of environment variable @var{varname} to be given to
2360 your program when it starts. If you do not supply @var{varname},
2361 print the names and values of all environment variables to be given to
2362 your program. You can abbreviate @code{environment} as @code{env}.
2364 @kindex set environment
2365 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2366 Set environment variable @var{varname} to @var{value}. The value
2367 changes for your program (and the shell @value{GDBN} uses to launch
2368 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2369 values of environment variables are just strings, and any
2370 interpretation is supplied by your program itself. The @var{value}
2371 parameter is optional; if it is eliminated, the variable is set to a
2373 @c "any string" here does not include leading, trailing
2374 @c blanks. Gnu asks: does anyone care?
2376 For example, this command:
2383 tells the debugged program, when subsequently run, that its user is named
2384 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2385 are not actually required.)
2387 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2388 which also inherits the environment set with @code{set environment}.
2389 If necessary, you can avoid that by using the @samp{env} program as a
2390 wrapper instead of using @code{set environment}. @xref{set
2391 exec-wrapper}, for an example doing just that.
2393 @kindex unset environment
2394 @item unset environment @var{varname}
2395 Remove variable @var{varname} from the environment to be passed to your
2396 program. This is different from @samp{set env @var{varname} =};
2397 @code{unset environment} removes the variable from the environment,
2398 rather than assigning it an empty value.
2401 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2402 the shell indicated by your @code{SHELL} environment variable if it
2403 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2404 names a shell that runs an initialization file when started
2405 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2406 for the Z shell, or the file specified in the @samp{BASH_ENV}
2407 environment variable for BASH---any variables you set in that file
2408 affect your program. You may wish to move setting of environment
2409 variables to files that are only run when you sign on, such as
2410 @file{.login} or @file{.profile}.
2412 @node Working Directory
2413 @section Your Program's Working Directory
2415 @cindex working directory (of your program)
2416 Each time you start your program with @code{run}, it inherits its
2417 working directory from the current working directory of @value{GDBN}.
2418 The @value{GDBN} working directory is initially whatever it inherited
2419 from its parent process (typically the shell), but you can specify a new
2420 working directory in @value{GDBN} with the @code{cd} command.
2422 The @value{GDBN} working directory also serves as a default for the commands
2423 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2428 @cindex change working directory
2429 @item cd @r{[}@var{directory}@r{]}
2430 Set the @value{GDBN} working directory to @var{directory}. If not
2431 given, @var{directory} uses @file{'~'}.
2435 Print the @value{GDBN} working directory.
2438 It is generally impossible to find the current working directory of
2439 the process being debugged (since a program can change its directory
2440 during its run). If you work on a system where @value{GDBN} is
2441 configured with the @file{/proc} support, you can use the @code{info
2442 proc} command (@pxref{SVR4 Process Information}) to find out the
2443 current working directory of the debuggee.
2446 @section Your Program's Input and Output
2451 By default, the program you run under @value{GDBN} does input and output to
2452 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2453 to its own terminal modes to interact with you, but it records the terminal
2454 modes your program was using and switches back to them when you continue
2455 running your program.
2458 @kindex info terminal
2460 Displays information recorded by @value{GDBN} about the terminal modes your
2464 You can redirect your program's input and/or output using shell
2465 redirection with the @code{run} command. For example,
2472 starts your program, diverting its output to the file @file{outfile}.
2475 @cindex controlling terminal
2476 Another way to specify where your program should do input and output is
2477 with the @code{tty} command. This command accepts a file name as
2478 argument, and causes this file to be the default for future @code{run}
2479 commands. It also resets the controlling terminal for the child
2480 process, for future @code{run} commands. For example,
2487 directs that processes started with subsequent @code{run} commands
2488 default to do input and output on the terminal @file{/dev/ttyb} and have
2489 that as their controlling terminal.
2491 An explicit redirection in @code{run} overrides the @code{tty} command's
2492 effect on the input/output device, but not its effect on the controlling
2495 When you use the @code{tty} command or redirect input in the @code{run}
2496 command, only the input @emph{for your program} is affected. The input
2497 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2498 for @code{set inferior-tty}.
2500 @cindex inferior tty
2501 @cindex set inferior controlling terminal
2502 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2503 display the name of the terminal that will be used for future runs of your
2507 @item set inferior-tty [ @var{tty} ]
2508 @kindex set inferior-tty
2509 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2510 restores the default behavior, which is to use the same terminal as
2513 @item show inferior-tty
2514 @kindex show inferior-tty
2515 Show the current tty for the program being debugged.
2519 @section Debugging an Already-running Process
2524 @item attach @var{process-id}
2525 This command attaches to a running process---one that was started
2526 outside @value{GDBN}. (@code{info files} shows your active
2527 targets.) The command takes as argument a process ID. The usual way to
2528 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2529 or with the @samp{jobs -l} shell command.
2531 @code{attach} does not repeat if you press @key{RET} a second time after
2532 executing the command.
2535 To use @code{attach}, your program must be running in an environment
2536 which supports processes; for example, @code{attach} does not work for
2537 programs on bare-board targets that lack an operating system. You must
2538 also have permission to send the process a signal.
2540 When you use @code{attach}, the debugger finds the program running in
2541 the process first by looking in the current working directory, then (if
2542 the program is not found) by using the source file search path
2543 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2544 the @code{file} command to load the program. @xref{Files, ,Commands to
2547 The first thing @value{GDBN} does after arranging to debug the specified
2548 process is to stop it. You can examine and modify an attached process
2549 with all the @value{GDBN} commands that are ordinarily available when
2550 you start processes with @code{run}. You can insert breakpoints; you
2551 can step and continue; you can modify storage. If you would rather the
2552 process continue running, you may use the @code{continue} command after
2553 attaching @value{GDBN} to the process.
2558 When you have finished debugging the attached process, you can use the
2559 @code{detach} command to release it from @value{GDBN} control. Detaching
2560 the process continues its execution. After the @code{detach} command,
2561 that process and @value{GDBN} become completely independent once more, and you
2562 are ready to @code{attach} another process or start one with @code{run}.
2563 @code{detach} does not repeat if you press @key{RET} again after
2564 executing the command.
2567 If you exit @value{GDBN} while you have an attached process, you detach
2568 that process. If you use the @code{run} command, you kill that process.
2569 By default, @value{GDBN} asks for confirmation if you try to do either of these
2570 things; you can control whether or not you need to confirm by using the
2571 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2575 @section Killing the Child Process
2580 Kill the child process in which your program is running under @value{GDBN}.
2583 This command is useful if you wish to debug a core dump instead of a
2584 running process. @value{GDBN} ignores any core dump file while your program
2587 On some operating systems, a program cannot be executed outside @value{GDBN}
2588 while you have breakpoints set on it inside @value{GDBN}. You can use the
2589 @code{kill} command in this situation to permit running your program
2590 outside the debugger.
2592 The @code{kill} command is also useful if you wish to recompile and
2593 relink your program, since on many systems it is impossible to modify an
2594 executable file while it is running in a process. In this case, when you
2595 next type @code{run}, @value{GDBN} notices that the file has changed, and
2596 reads the symbol table again (while trying to preserve your current
2597 breakpoint settings).
2599 @node Inferiors and Programs
2600 @section Debugging Multiple Inferiors and Programs
2602 @value{GDBN} lets you run and debug multiple programs in a single
2603 session. In addition, @value{GDBN} on some systems may let you run
2604 several programs simultaneously (otherwise you have to exit from one
2605 before starting another). In the most general case, you can have
2606 multiple threads of execution in each of multiple processes, launched
2607 from multiple executables.
2610 @value{GDBN} represents the state of each program execution with an
2611 object called an @dfn{inferior}. An inferior typically corresponds to
2612 a process, but is more general and applies also to targets that do not
2613 have processes. Inferiors may be created before a process runs, and
2614 may be retained after a process exits. Inferiors have unique
2615 identifiers that are different from process ids. Usually each
2616 inferior will also have its own distinct address space, although some
2617 embedded targets may have several inferiors running in different parts
2618 of a single address space. Each inferior may in turn have multiple
2619 threads running in it.
2621 To find out what inferiors exist at any moment, use @w{@code{info
2625 @kindex info inferiors
2626 @item info inferiors
2627 Print a list of all inferiors currently being managed by @value{GDBN}.
2629 @value{GDBN} displays for each inferior (in this order):
2633 the inferior number assigned by @value{GDBN}
2636 the target system's inferior identifier
2639 the name of the executable the inferior is running.
2644 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2645 indicates the current inferior.
2649 @c end table here to get a little more width for example
2652 (@value{GDBP}) info inferiors
2653 Num Description Executable
2654 2 process 2307 hello
2655 * 1 process 3401 goodbye
2658 To switch focus between inferiors, use the @code{inferior} command:
2661 @kindex inferior @var{infno}
2662 @item inferior @var{infno}
2663 Make inferior number @var{infno} the current inferior. The argument
2664 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2665 in the first field of the @samp{info inferiors} display.
2668 @vindex $_inferior@r{, convenience variable}
2669 The debugger convenience variable @samp{$_inferior} contains the
2670 number of the current inferior. You may find this useful in writing
2671 breakpoint conditional expressions, command scripts, and so forth.
2672 @xref{Convenience Vars,, Convenience Variables}, for general
2673 information on convenience variables.
2675 You can get multiple executables into a debugging session via the
2676 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2677 systems @value{GDBN} can add inferiors to the debug session
2678 automatically by following calls to @code{fork} and @code{exec}. To
2679 remove inferiors from the debugging session use the
2680 @w{@code{remove-inferiors}} command.
2683 @kindex add-inferior
2684 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2685 Adds @var{n} inferiors to be run using @var{executable} as the
2686 executable; @var{n} defaults to 1. If no executable is specified,
2687 the inferiors begins empty, with no program. You can still assign or
2688 change the program assigned to the inferior at any time by using the
2689 @code{file} command with the executable name as its argument.
2691 @kindex clone-inferior
2692 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2693 Adds @var{n} inferiors ready to execute the same program as inferior
2694 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2695 number of the current inferior. This is a convenient command when you
2696 want to run another instance of the inferior you are debugging.
2699 (@value{GDBP}) info inferiors
2700 Num Description Executable
2701 * 1 process 29964 helloworld
2702 (@value{GDBP}) clone-inferior
2705 (@value{GDBP}) info inferiors
2706 Num Description Executable
2708 * 1 process 29964 helloworld
2711 You can now simply switch focus to inferior 2 and run it.
2713 @kindex remove-inferiors
2714 @item remove-inferiors @var{infno}@dots{}
2715 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2716 possible to remove an inferior that is running with this command. For
2717 those, use the @code{kill} or @code{detach} command first.
2721 To quit debugging one of the running inferiors that is not the current
2722 inferior, you can either detach from it by using the @w{@code{detach
2723 inferior}} command (allowing it to run independently), or kill it
2724 using the @w{@code{kill inferiors}} command:
2727 @kindex detach inferiors @var{infno}@dots{}
2728 @item detach inferior @var{infno}@dots{}
2729 Detach from the inferior or inferiors identified by @value{GDBN}
2730 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2731 still stays on the list of inferiors shown by @code{info inferiors},
2732 but its Description will show @samp{<null>}.
2734 @kindex kill inferiors @var{infno}@dots{}
2735 @item kill inferiors @var{infno}@dots{}
2736 Kill the inferior or inferiors identified by @value{GDBN} inferior
2737 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2738 stays on the list of inferiors shown by @code{info inferiors}, but its
2739 Description will show @samp{<null>}.
2742 After the successful completion of a command such as @code{detach},
2743 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2744 a normal process exit, the inferior is still valid and listed with
2745 @code{info inferiors}, ready to be restarted.
2748 To be notified when inferiors are started or exit under @value{GDBN}'s
2749 control use @w{@code{set print inferior-events}}:
2752 @kindex set print inferior-events
2753 @cindex print messages on inferior start and exit
2754 @item set print inferior-events
2755 @itemx set print inferior-events on
2756 @itemx set print inferior-events off
2757 The @code{set print inferior-events} command allows you to enable or
2758 disable printing of messages when @value{GDBN} notices that new
2759 inferiors have started or that inferiors have exited or have been
2760 detached. By default, these messages will not be printed.
2762 @kindex show print inferior-events
2763 @item show print inferior-events
2764 Show whether messages will be printed when @value{GDBN} detects that
2765 inferiors have started, exited or have been detached.
2768 Many commands will work the same with multiple programs as with a
2769 single program: e.g., @code{print myglobal} will simply display the
2770 value of @code{myglobal} in the current inferior.
2773 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2774 get more info about the relationship of inferiors, programs, address
2775 spaces in a debug session. You can do that with the @w{@code{maint
2776 info program-spaces}} command.
2779 @kindex maint info program-spaces
2780 @item maint info program-spaces
2781 Print a list of all program spaces currently being managed by
2784 @value{GDBN} displays for each program space (in this order):
2788 the program space number assigned by @value{GDBN}
2791 the name of the executable loaded into the program space, with e.g.,
2792 the @code{file} command.
2797 An asterisk @samp{*} preceding the @value{GDBN} program space number
2798 indicates the current program space.
2800 In addition, below each program space line, @value{GDBN} prints extra
2801 information that isn't suitable to display in tabular form. For
2802 example, the list of inferiors bound to the program space.
2805 (@value{GDBP}) maint info program-spaces
2809 Bound inferiors: ID 1 (process 21561)
2812 Here we can see that no inferior is running the program @code{hello},
2813 while @code{process 21561} is running the program @code{goodbye}. On
2814 some targets, it is possible that multiple inferiors are bound to the
2815 same program space. The most common example is that of debugging both
2816 the parent and child processes of a @code{vfork} call. For example,
2819 (@value{GDBP}) maint info program-spaces
2822 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2825 Here, both inferior 2 and inferior 1 are running in the same program
2826 space as a result of inferior 1 having executed a @code{vfork} call.
2830 @section Debugging Programs with Multiple Threads
2832 @cindex threads of execution
2833 @cindex multiple threads
2834 @cindex switching threads
2835 In some operating systems, such as GNU/Linux and Solaris, a single program
2836 may have more than one @dfn{thread} of execution. The precise semantics
2837 of threads differ from one operating system to another, but in general
2838 the threads of a single program are akin to multiple processes---except
2839 that they share one address space (that is, they can all examine and
2840 modify the same variables). On the other hand, each thread has its own
2841 registers and execution stack, and perhaps private memory.
2843 @value{GDBN} provides these facilities for debugging multi-thread
2847 @item automatic notification of new threads
2848 @item @samp{thread @var{thread-id}}, a command to switch among threads
2849 @item @samp{info threads}, a command to inquire about existing threads
2850 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2851 a command to apply a command to a list of threads
2852 @item thread-specific breakpoints
2853 @item @samp{set print thread-events}, which controls printing of
2854 messages on thread start and exit.
2855 @item @samp{set libthread-db-search-path @var{path}}, which lets
2856 the user specify which @code{libthread_db} to use if the default choice
2857 isn't compatible with the program.
2860 @cindex focus of debugging
2861 @cindex current thread
2862 The @value{GDBN} thread debugging facility allows you to observe all
2863 threads while your program runs---but whenever @value{GDBN} takes
2864 control, one thread in particular is always the focus of debugging.
2865 This thread is called the @dfn{current thread}. Debugging commands show
2866 program information from the perspective of the current thread.
2868 @cindex @code{New} @var{systag} message
2869 @cindex thread identifier (system)
2870 @c FIXME-implementors!! It would be more helpful if the [New...] message
2871 @c included GDB's numeric thread handle, so you could just go to that
2872 @c thread without first checking `info threads'.
2873 Whenever @value{GDBN} detects a new thread in your program, it displays
2874 the target system's identification for the thread with a message in the
2875 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2876 whose form varies depending on the particular system. For example, on
2877 @sc{gnu}/Linux, you might see
2880 [New Thread 0x41e02940 (LWP 25582)]
2884 when @value{GDBN} notices a new thread. In contrast, on other systems,
2885 the @var{systag} is simply something like @samp{process 368}, with no
2888 @c FIXME!! (1) Does the [New...] message appear even for the very first
2889 @c thread of a program, or does it only appear for the
2890 @c second---i.e.@: when it becomes obvious we have a multithread
2892 @c (2) *Is* there necessarily a first thread always? Or do some
2893 @c multithread systems permit starting a program with multiple
2894 @c threads ab initio?
2896 @anchor{thread numbers}
2897 @cindex thread number, per inferior
2898 @cindex thread identifier (GDB)
2899 For debugging purposes, @value{GDBN} associates its own thread number
2900 ---always a single integer---with each thread of an inferior. This
2901 number is unique between all threads of an inferior, but not unique
2902 between threads of different inferiors.
2904 @cindex qualified thread ID
2905 You can refer to a given thread in an inferior using the qualified
2906 @var{inferior-num}.@var{thread-num} syntax, also known as
2907 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2908 number and @var{thread-num} being the thread number of the given
2909 inferior. For example, thread @code{2.3} refers to thread number 3 of
2910 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2911 then @value{GDBN} infers you're referring to a thread of the current
2914 Until you create a second inferior, @value{GDBN} does not show the
2915 @var{inferior-num} part of thread IDs, even though you can always use
2916 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2917 of inferior 1, the initial inferior.
2919 @anchor{thread ID lists}
2920 @cindex thread ID lists
2921 Some commands accept a space-separated @dfn{thread ID list} as
2922 argument. A list element can be:
2926 A thread ID as shown in the first field of the @samp{info threads}
2927 display, with or without an inferior qualifier. E.g., @samp{2.1} or
2931 A range of thread numbers, again with or without an inferior
2932 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
2933 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
2936 All threads of an inferior, specified with a star wildcard, with or
2937 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
2938 @samp{1.*}) or @code{*}. The former refers to all threads of the
2939 given inferior, and the latter form without an inferior qualifier
2940 refers to all threads of the current inferior.
2944 For example, if the current inferior is 1, and inferior 7 has one
2945 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
2946 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
2947 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
2948 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
2952 @anchor{global thread numbers}
2953 @cindex global thread number
2954 @cindex global thread identifier (GDB)
2955 In addition to a @emph{per-inferior} number, each thread is also
2956 assigned a unique @emph{global} number, also known as @dfn{global
2957 thread ID}, a single integer. Unlike the thread number component of
2958 the thread ID, no two threads have the same global ID, even when
2959 you're debugging multiple inferiors.
2961 From @value{GDBN}'s perspective, a process always has at least one
2962 thread. In other words, @value{GDBN} assigns a thread number to the
2963 program's ``main thread'' even if the program is not multi-threaded.
2965 @vindex $_thread@r{, convenience variable}
2966 @vindex $_gthread@r{, convenience variable}
2967 The debugger convenience variables @samp{$_thread} and
2968 @samp{$_gthread} contain, respectively, the per-inferior thread number
2969 and the global thread number of the current thread. You may find this
2970 useful in writing breakpoint conditional expressions, command scripts,
2971 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2972 general information on convenience variables.
2974 If @value{GDBN} detects the program is multi-threaded, it augments the
2975 usual message about stopping at a breakpoint with the ID and name of
2976 the thread that hit the breakpoint.
2979 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
2982 Likewise when the program receives a signal:
2985 Thread 1 "main" received signal SIGINT, Interrupt.
2989 @kindex info threads
2990 @item info threads @r{[}@var{thread-id-list}@r{]}
2992 Display information about one or more threads. With no arguments
2993 displays information about all threads. You can specify the list of
2994 threads that you want to display using the thread ID list syntax
2995 (@pxref{thread ID lists}).
2997 @value{GDBN} displays for each thread (in this order):
3001 the per-inferior thread number assigned by @value{GDBN}
3004 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3005 option was specified
3008 the target system's thread identifier (@var{systag})
3011 the thread's name, if one is known. A thread can either be named by
3012 the user (see @code{thread name}, below), or, in some cases, by the
3016 the current stack frame summary for that thread
3020 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3021 indicates the current thread.
3025 @c end table here to get a little more width for example
3028 (@value{GDBP}) info threads
3030 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3031 2 process 35 thread 23 0x34e5 in sigpause ()
3032 3 process 35 thread 27 0x34e5 in sigpause ()
3036 If you're debugging multiple inferiors, @value{GDBN} displays thread
3037 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3038 Otherwise, only @var{thread-num} is shown.
3040 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3041 indicating each thread's global thread ID:
3044 (@value{GDBP}) info threads
3045 Id GId Target Id Frame
3046 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3047 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3048 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3049 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3052 On Solaris, you can display more information about user threads with a
3053 Solaris-specific command:
3056 @item maint info sol-threads
3057 @kindex maint info sol-threads
3058 @cindex thread info (Solaris)
3059 Display info on Solaris user threads.
3063 @kindex thread @var{thread-id}
3064 @item thread @var{thread-id}
3065 Make thread ID @var{thread-id} the current thread. The command
3066 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3067 the first field of the @samp{info threads} display, with or without an
3068 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3070 @value{GDBN} responds by displaying the system identifier of the
3071 thread you selected, and its current stack frame summary:
3074 (@value{GDBP}) thread 2
3075 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3076 #0 some_function (ignore=0x0) at example.c:8
3077 8 printf ("hello\n");
3081 As with the @samp{[New @dots{}]} message, the form of the text after
3082 @samp{Switching to} depends on your system's conventions for identifying
3085 @kindex thread apply
3086 @cindex apply command to several threads
3087 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3088 The @code{thread apply} command allows you to apply the named
3089 @var{command} to one or more threads. Specify the threads that you
3090 want affected using the thread ID list syntax (@pxref{thread ID
3091 lists}), or specify @code{all} to apply to all threads. To apply a
3092 command to all threads in descending order, type @kbd{thread apply all
3093 @var{command}}. To apply a command to all threads in ascending order,
3094 type @kbd{thread apply all -ascending @var{command}}.
3098 @cindex name a thread
3099 @item thread name [@var{name}]
3100 This command assigns a name to the current thread. If no argument is
3101 given, any existing user-specified name is removed. The thread name
3102 appears in the @samp{info threads} display.
3104 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3105 determine the name of the thread as given by the OS. On these
3106 systems, a name specified with @samp{thread name} will override the
3107 system-give name, and removing the user-specified name will cause
3108 @value{GDBN} to once again display the system-specified name.
3111 @cindex search for a thread
3112 @item thread find [@var{regexp}]
3113 Search for and display thread ids whose name or @var{systag}
3114 matches the supplied regular expression.
3116 As well as being the complement to the @samp{thread name} command,
3117 this command also allows you to identify a thread by its target
3118 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3122 (@value{GDBN}) thread find 26688
3123 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3124 (@value{GDBN}) info thread 4
3126 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3129 @kindex set print thread-events
3130 @cindex print messages on thread start and exit
3131 @item set print thread-events
3132 @itemx set print thread-events on
3133 @itemx set print thread-events off
3134 The @code{set print thread-events} command allows you to enable or
3135 disable printing of messages when @value{GDBN} notices that new threads have
3136 started or that threads have exited. By default, these messages will
3137 be printed if detection of these events is supported by the target.
3138 Note that these messages cannot be disabled on all targets.
3140 @kindex show print thread-events
3141 @item show print thread-events
3142 Show whether messages will be printed when @value{GDBN} detects that threads
3143 have started and exited.
3146 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3147 more information about how @value{GDBN} behaves when you stop and start
3148 programs with multiple threads.
3150 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3151 watchpoints in programs with multiple threads.
3153 @anchor{set libthread-db-search-path}
3155 @kindex set libthread-db-search-path
3156 @cindex search path for @code{libthread_db}
3157 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3158 If this variable is set, @var{path} is a colon-separated list of
3159 directories @value{GDBN} will use to search for @code{libthread_db}.
3160 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3161 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3162 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3165 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3166 @code{libthread_db} library to obtain information about threads in the
3167 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3168 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3169 specific thread debugging library loading is enabled
3170 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3172 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3173 refers to the default system directories that are
3174 normally searched for loading shared libraries. The @samp{$sdir} entry
3175 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3176 (@pxref{libthread_db.so.1 file}).
3178 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3179 refers to the directory from which @code{libpthread}
3180 was loaded in the inferior process.
3182 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3183 @value{GDBN} attempts to initialize it with the current inferior process.
3184 If this initialization fails (which could happen because of a version
3185 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3186 will unload @code{libthread_db}, and continue with the next directory.
3187 If none of @code{libthread_db} libraries initialize successfully,
3188 @value{GDBN} will issue a warning and thread debugging will be disabled.
3190 Setting @code{libthread-db-search-path} is currently implemented
3191 only on some platforms.
3193 @kindex show libthread-db-search-path
3194 @item show libthread-db-search-path
3195 Display current libthread_db search path.
3197 @kindex set debug libthread-db
3198 @kindex show debug libthread-db
3199 @cindex debugging @code{libthread_db}
3200 @item set debug libthread-db
3201 @itemx show debug libthread-db
3202 Turns on or off display of @code{libthread_db}-related events.
3203 Use @code{1} to enable, @code{0} to disable.
3207 @section Debugging Forks
3209 @cindex fork, debugging programs which call
3210 @cindex multiple processes
3211 @cindex processes, multiple
3212 On most systems, @value{GDBN} has no special support for debugging
3213 programs which create additional processes using the @code{fork}
3214 function. When a program forks, @value{GDBN} will continue to debug the
3215 parent process and the child process will run unimpeded. If you have
3216 set a breakpoint in any code which the child then executes, the child
3217 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3218 will cause it to terminate.
3220 However, if you want to debug the child process there is a workaround
3221 which isn't too painful. Put a call to @code{sleep} in the code which
3222 the child process executes after the fork. It may be useful to sleep
3223 only if a certain environment variable is set, or a certain file exists,
3224 so that the delay need not occur when you don't want to run @value{GDBN}
3225 on the child. While the child is sleeping, use the @code{ps} program to
3226 get its process ID. Then tell @value{GDBN} (a new invocation of
3227 @value{GDBN} if you are also debugging the parent process) to attach to
3228 the child process (@pxref{Attach}). From that point on you can debug
3229 the child process just like any other process which you attached to.
3231 On some systems, @value{GDBN} provides support for debugging programs
3232 that create additional processes using the @code{fork} or @code{vfork}
3233 functions. On @sc{gnu}/Linux platforms, this feature is supported
3234 with kernel version 2.5.46 and later.
3236 The fork debugging commands are supported in native mode and when
3237 connected to @code{gdbserver} in either @code{target remote} mode or
3238 @code{target extended-remote} mode.
3240 By default, when a program forks, @value{GDBN} will continue to debug
3241 the parent process and the child process will run unimpeded.
3243 If you want to follow the child process instead of the parent process,
3244 use the command @w{@code{set follow-fork-mode}}.
3247 @kindex set follow-fork-mode
3248 @item set follow-fork-mode @var{mode}
3249 Set the debugger response to a program call of @code{fork} or
3250 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3251 process. The @var{mode} argument can be:
3255 The original process is debugged after a fork. The child process runs
3256 unimpeded. This is the default.
3259 The new process is debugged after a fork. The parent process runs
3264 @kindex show follow-fork-mode
3265 @item show follow-fork-mode
3266 Display the current debugger response to a @code{fork} or @code{vfork} call.
3269 @cindex debugging multiple processes
3270 On Linux, if you want to debug both the parent and child processes, use the
3271 command @w{@code{set detach-on-fork}}.
3274 @kindex set detach-on-fork
3275 @item set detach-on-fork @var{mode}
3276 Tells gdb whether to detach one of the processes after a fork, or
3277 retain debugger control over them both.
3281 The child process (or parent process, depending on the value of
3282 @code{follow-fork-mode}) will be detached and allowed to run
3283 independently. This is the default.
3286 Both processes will be held under the control of @value{GDBN}.
3287 One process (child or parent, depending on the value of
3288 @code{follow-fork-mode}) is debugged as usual, while the other
3293 @kindex show detach-on-fork
3294 @item show detach-on-fork
3295 Show whether detach-on-fork mode is on/off.
3298 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3299 will retain control of all forked processes (including nested forks).
3300 You can list the forked processes under the control of @value{GDBN} by
3301 using the @w{@code{info inferiors}} command, and switch from one fork
3302 to another by using the @code{inferior} command (@pxref{Inferiors and
3303 Programs, ,Debugging Multiple Inferiors and Programs}).
3305 To quit debugging one of the forked processes, you can either detach
3306 from it by using the @w{@code{detach inferiors}} command (allowing it
3307 to run independently), or kill it using the @w{@code{kill inferiors}}
3308 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3311 If you ask to debug a child process and a @code{vfork} is followed by an
3312 @code{exec}, @value{GDBN} executes the new target up to the first
3313 breakpoint in the new target. If you have a breakpoint set on
3314 @code{main} in your original program, the breakpoint will also be set on
3315 the child process's @code{main}.
3317 On some systems, when a child process is spawned by @code{vfork}, you
3318 cannot debug the child or parent until an @code{exec} call completes.
3320 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3321 call executes, the new target restarts. To restart the parent
3322 process, use the @code{file} command with the parent executable name
3323 as its argument. By default, after an @code{exec} call executes,
3324 @value{GDBN} discards the symbols of the previous executable image.
3325 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3329 @kindex set follow-exec-mode
3330 @item set follow-exec-mode @var{mode}
3332 Set debugger response to a program call of @code{exec}. An
3333 @code{exec} call replaces the program image of a process.
3335 @code{follow-exec-mode} can be:
3339 @value{GDBN} creates a new inferior and rebinds the process to this
3340 new inferior. The program the process was running before the
3341 @code{exec} call can be restarted afterwards by restarting the
3347 (@value{GDBP}) info inferiors
3349 Id Description Executable
3352 process 12020 is executing new program: prog2
3353 Program exited normally.
3354 (@value{GDBP}) info inferiors
3355 Id Description Executable
3361 @value{GDBN} keeps the process bound to the same inferior. The new
3362 executable image replaces the previous executable loaded in the
3363 inferior. Restarting the inferior after the @code{exec} call, with
3364 e.g., the @code{run} command, restarts the executable the process was
3365 running after the @code{exec} call. This is the default mode.
3370 (@value{GDBP}) info inferiors
3371 Id Description Executable
3374 process 12020 is executing new program: prog2
3375 Program exited normally.
3376 (@value{GDBP}) info inferiors
3377 Id Description Executable
3384 @code{follow-exec-mode} is supported in native mode and
3385 @code{target extended-remote} mode.
3387 You can use the @code{catch} command to make @value{GDBN} stop whenever
3388 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3389 Catchpoints, ,Setting Catchpoints}.
3391 @node Checkpoint/Restart
3392 @section Setting a @emph{Bookmark} to Return to Later
3397 @cindex snapshot of a process
3398 @cindex rewind program state
3400 On certain operating systems@footnote{Currently, only
3401 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3402 program's state, called a @dfn{checkpoint}, and come back to it
3405 Returning to a checkpoint effectively undoes everything that has
3406 happened in the program since the @code{checkpoint} was saved. This
3407 includes changes in memory, registers, and even (within some limits)
3408 system state. Effectively, it is like going back in time to the
3409 moment when the checkpoint was saved.
3411 Thus, if you're stepping thru a program and you think you're
3412 getting close to the point where things go wrong, you can save
3413 a checkpoint. Then, if you accidentally go too far and miss
3414 the critical statement, instead of having to restart your program
3415 from the beginning, you can just go back to the checkpoint and
3416 start again from there.
3418 This can be especially useful if it takes a lot of time or
3419 steps to reach the point where you think the bug occurs.
3421 To use the @code{checkpoint}/@code{restart} method of debugging:
3426 Save a snapshot of the debugged program's current execution state.
3427 The @code{checkpoint} command takes no arguments, but each checkpoint
3428 is assigned a small integer id, similar to a breakpoint id.
3430 @kindex info checkpoints
3431 @item info checkpoints
3432 List the checkpoints that have been saved in the current debugging
3433 session. For each checkpoint, the following information will be
3440 @item Source line, or label
3443 @kindex restart @var{checkpoint-id}
3444 @item restart @var{checkpoint-id}
3445 Restore the program state that was saved as checkpoint number
3446 @var{checkpoint-id}. All program variables, registers, stack frames
3447 etc.@: will be returned to the values that they had when the checkpoint
3448 was saved. In essence, gdb will ``wind back the clock'' to the point
3449 in time when the checkpoint was saved.
3451 Note that breakpoints, @value{GDBN} variables, command history etc.
3452 are not affected by restoring a checkpoint. In general, a checkpoint
3453 only restores things that reside in the program being debugged, not in
3456 @kindex delete checkpoint @var{checkpoint-id}
3457 @item delete checkpoint @var{checkpoint-id}
3458 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3462 Returning to a previously saved checkpoint will restore the user state
3463 of the program being debugged, plus a significant subset of the system
3464 (OS) state, including file pointers. It won't ``un-write'' data from
3465 a file, but it will rewind the file pointer to the previous location,
3466 so that the previously written data can be overwritten. For files
3467 opened in read mode, the pointer will also be restored so that the
3468 previously read data can be read again.
3470 Of course, characters that have been sent to a printer (or other
3471 external device) cannot be ``snatched back'', and characters received
3472 from eg.@: a serial device can be removed from internal program buffers,
3473 but they cannot be ``pushed back'' into the serial pipeline, ready to
3474 be received again. Similarly, the actual contents of files that have
3475 been changed cannot be restored (at this time).
3477 However, within those constraints, you actually can ``rewind'' your
3478 program to a previously saved point in time, and begin debugging it
3479 again --- and you can change the course of events so as to debug a
3480 different execution path this time.
3482 @cindex checkpoints and process id
3483 Finally, there is one bit of internal program state that will be
3484 different when you return to a checkpoint --- the program's process
3485 id. Each checkpoint will have a unique process id (or @var{pid}),
3486 and each will be different from the program's original @var{pid}.
3487 If your program has saved a local copy of its process id, this could
3488 potentially pose a problem.
3490 @subsection A Non-obvious Benefit of Using Checkpoints
3492 On some systems such as @sc{gnu}/Linux, address space randomization
3493 is performed on new processes for security reasons. This makes it
3494 difficult or impossible to set a breakpoint, or watchpoint, on an
3495 absolute address if you have to restart the program, since the
3496 absolute location of a symbol will change from one execution to the
3499 A checkpoint, however, is an @emph{identical} copy of a process.
3500 Therefore if you create a checkpoint at (eg.@:) the start of main,
3501 and simply return to that checkpoint instead of restarting the
3502 process, you can avoid the effects of address randomization and
3503 your symbols will all stay in the same place.
3506 @chapter Stopping and Continuing
3508 The principal purposes of using a debugger are so that you can stop your
3509 program before it terminates; or so that, if your program runs into
3510 trouble, you can investigate and find out why.
3512 Inside @value{GDBN}, your program may stop for any of several reasons,
3513 such as a signal, a breakpoint, or reaching a new line after a
3514 @value{GDBN} command such as @code{step}. You may then examine and
3515 change variables, set new breakpoints or remove old ones, and then
3516 continue execution. Usually, the messages shown by @value{GDBN} provide
3517 ample explanation of the status of your program---but you can also
3518 explicitly request this information at any time.
3521 @kindex info program
3523 Display information about the status of your program: whether it is
3524 running or not, what process it is, and why it stopped.
3528 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3529 * Continuing and Stepping:: Resuming execution
3530 * Skipping Over Functions and Files::
3531 Skipping over functions and files
3533 * Thread Stops:: Stopping and starting multi-thread programs
3537 @section Breakpoints, Watchpoints, and Catchpoints
3540 A @dfn{breakpoint} makes your program stop whenever a certain point in
3541 the program is reached. For each breakpoint, you can add conditions to
3542 control in finer detail whether your program stops. You can set
3543 breakpoints with the @code{break} command and its variants (@pxref{Set
3544 Breaks, ,Setting Breakpoints}), to specify the place where your program
3545 should stop by line number, function name or exact address in the
3548 On some systems, you can set breakpoints in shared libraries before
3549 the executable is run.
3552 @cindex data breakpoints
3553 @cindex memory tracing
3554 @cindex breakpoint on memory address
3555 @cindex breakpoint on variable modification
3556 A @dfn{watchpoint} is a special breakpoint that stops your program
3557 when the value of an expression changes. The expression may be a value
3558 of a variable, or it could involve values of one or more variables
3559 combined by operators, such as @samp{a + b}. This is sometimes called
3560 @dfn{data breakpoints}. You must use a different command to set
3561 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3562 from that, you can manage a watchpoint like any other breakpoint: you
3563 enable, disable, and delete both breakpoints and watchpoints using the
3566 You can arrange to have values from your program displayed automatically
3567 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3571 @cindex breakpoint on events
3572 A @dfn{catchpoint} is another special breakpoint that stops your program
3573 when a certain kind of event occurs, such as the throwing of a C@t{++}
3574 exception or the loading of a library. As with watchpoints, you use a
3575 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3576 Catchpoints}), but aside from that, you can manage a catchpoint like any
3577 other breakpoint. (To stop when your program receives a signal, use the
3578 @code{handle} command; see @ref{Signals, ,Signals}.)
3580 @cindex breakpoint numbers
3581 @cindex numbers for breakpoints
3582 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3583 catchpoint when you create it; these numbers are successive integers
3584 starting with one. In many of the commands for controlling various
3585 features of breakpoints you use the breakpoint number to say which
3586 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3587 @dfn{disabled}; if disabled, it has no effect on your program until you
3590 @cindex breakpoint ranges
3591 @cindex breakpoint lists
3592 @cindex ranges of breakpoints
3593 @cindex lists of breakpoints
3594 Some @value{GDBN} commands accept a space-separated list of breakpoints
3595 on which to operate. A list element can be either a single breakpoint number,
3596 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3597 When a breakpoint list is given to a command, all breakpoints in that list
3601 * Set Breaks:: Setting breakpoints
3602 * Set Watchpoints:: Setting watchpoints
3603 * Set Catchpoints:: Setting catchpoints
3604 * Delete Breaks:: Deleting breakpoints
3605 * Disabling:: Disabling breakpoints
3606 * Conditions:: Break conditions
3607 * Break Commands:: Breakpoint command lists
3608 * Dynamic Printf:: Dynamic printf
3609 * Save Breakpoints:: How to save breakpoints in a file
3610 * Static Probe Points:: Listing static probe points
3611 * Error in Breakpoints:: ``Cannot insert breakpoints''
3612 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3616 @subsection Setting Breakpoints
3618 @c FIXME LMB what does GDB do if no code on line of breakpt?
3619 @c consider in particular declaration with/without initialization.
3621 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3624 @kindex b @r{(@code{break})}
3625 @vindex $bpnum@r{, convenience variable}
3626 @cindex latest breakpoint
3627 Breakpoints are set with the @code{break} command (abbreviated
3628 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3629 number of the breakpoint you've set most recently; see @ref{Convenience
3630 Vars,, Convenience Variables}, for a discussion of what you can do with
3631 convenience variables.
3634 @item break @var{location}
3635 Set a breakpoint at the given @var{location}, which can specify a
3636 function name, a line number, or an address of an instruction.
3637 (@xref{Specify Location}, for a list of all the possible ways to
3638 specify a @var{location}.) The breakpoint will stop your program just
3639 before it executes any of the code in the specified @var{location}.
3641 When using source languages that permit overloading of symbols, such as
3642 C@t{++}, a function name may refer to more than one possible place to break.
3643 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3646 It is also possible to insert a breakpoint that will stop the program
3647 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3648 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3651 When called without any arguments, @code{break} sets a breakpoint at
3652 the next instruction to be executed in the selected stack frame
3653 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3654 innermost, this makes your program stop as soon as control
3655 returns to that frame. This is similar to the effect of a
3656 @code{finish} command in the frame inside the selected frame---except
3657 that @code{finish} does not leave an active breakpoint. If you use
3658 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3659 the next time it reaches the current location; this may be useful
3662 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3663 least one instruction has been executed. If it did not do this, you
3664 would be unable to proceed past a breakpoint without first disabling the
3665 breakpoint. This rule applies whether or not the breakpoint already
3666 existed when your program stopped.
3668 @item break @dots{} if @var{cond}
3669 Set a breakpoint with condition @var{cond}; evaluate the expression
3670 @var{cond} each time the breakpoint is reached, and stop only if the
3671 value is nonzero---that is, if @var{cond} evaluates as true.
3672 @samp{@dots{}} stands for one of the possible arguments described
3673 above (or no argument) specifying where to break. @xref{Conditions,
3674 ,Break Conditions}, for more information on breakpoint conditions.
3677 @item tbreak @var{args}
3678 Set a breakpoint enabled only for one stop. The @var{args} are the
3679 same as for the @code{break} command, and the breakpoint is set in the same
3680 way, but the breakpoint is automatically deleted after the first time your
3681 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3684 @cindex hardware breakpoints
3685 @item hbreak @var{args}
3686 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3687 @code{break} command and the breakpoint is set in the same way, but the
3688 breakpoint requires hardware support and some target hardware may not
3689 have this support. The main purpose of this is EPROM/ROM code
3690 debugging, so you can set a breakpoint at an instruction without
3691 changing the instruction. This can be used with the new trap-generation
3692 provided by SPARClite DSU and most x86-based targets. These targets
3693 will generate traps when a program accesses some data or instruction
3694 address that is assigned to the debug registers. However the hardware
3695 breakpoint registers can take a limited number of breakpoints. For
3696 example, on the DSU, only two data breakpoints can be set at a time, and
3697 @value{GDBN} will reject this command if more than two are used. Delete
3698 or disable unused hardware breakpoints before setting new ones
3699 (@pxref{Disabling, ,Disabling Breakpoints}).
3700 @xref{Conditions, ,Break Conditions}.
3701 For remote targets, you can restrict the number of hardware
3702 breakpoints @value{GDBN} will use, see @ref{set remote
3703 hardware-breakpoint-limit}.
3706 @item thbreak @var{args}
3707 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3708 are the same as for the @code{hbreak} command and the breakpoint is set in
3709 the same way. However, like the @code{tbreak} command,
3710 the breakpoint is automatically deleted after the
3711 first time your program stops there. Also, like the @code{hbreak}
3712 command, the breakpoint requires hardware support and some target hardware
3713 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3714 See also @ref{Conditions, ,Break Conditions}.
3717 @cindex regular expression
3718 @cindex breakpoints at functions matching a regexp
3719 @cindex set breakpoints in many functions
3720 @item rbreak @var{regex}
3721 Set breakpoints on all functions matching the regular expression
3722 @var{regex}. This command sets an unconditional breakpoint on all
3723 matches, printing a list of all breakpoints it set. Once these
3724 breakpoints are set, they are treated just like the breakpoints set with
3725 the @code{break} command. You can delete them, disable them, or make
3726 them conditional the same way as any other breakpoint.
3728 The syntax of the regular expression is the standard one used with tools
3729 like @file{grep}. Note that this is different from the syntax used by
3730 shells, so for instance @code{foo*} matches all functions that include
3731 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3732 @code{.*} leading and trailing the regular expression you supply, so to
3733 match only functions that begin with @code{foo}, use @code{^foo}.
3735 @cindex non-member C@t{++} functions, set breakpoint in
3736 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3737 breakpoints on overloaded functions that are not members of any special
3740 @cindex set breakpoints on all functions
3741 The @code{rbreak} command can be used to set breakpoints in
3742 @strong{all} the functions in a program, like this:
3745 (@value{GDBP}) rbreak .
3748 @item rbreak @var{file}:@var{regex}
3749 If @code{rbreak} is called with a filename qualification, it limits
3750 the search for functions matching the given regular expression to the
3751 specified @var{file}. This can be used, for example, to set breakpoints on
3752 every function in a given file:
3755 (@value{GDBP}) rbreak file.c:.
3758 The colon separating the filename qualifier from the regex may
3759 optionally be surrounded by spaces.
3761 @kindex info breakpoints
3762 @cindex @code{$_} and @code{info breakpoints}
3763 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3764 @itemx info break @r{[}@var{list}@dots{}@r{]}
3765 Print a table of all breakpoints, watchpoints, and catchpoints set and
3766 not deleted. Optional argument @var{n} means print information only
3767 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3768 For each breakpoint, following columns are printed:
3771 @item Breakpoint Numbers
3773 Breakpoint, watchpoint, or catchpoint.
3775 Whether the breakpoint is marked to be disabled or deleted when hit.
3776 @item Enabled or Disabled
3777 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3778 that are not enabled.
3780 Where the breakpoint is in your program, as a memory address. For a
3781 pending breakpoint whose address is not yet known, this field will
3782 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3783 library that has the symbol or line referred by breakpoint is loaded.
3784 See below for details. A breakpoint with several locations will
3785 have @samp{<MULTIPLE>} in this field---see below for details.
3787 Where the breakpoint is in the source for your program, as a file and
3788 line number. For a pending breakpoint, the original string passed to
3789 the breakpoint command will be listed as it cannot be resolved until
3790 the appropriate shared library is loaded in the future.
3794 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3795 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3796 @value{GDBN} on the host's side. If it is ``target'', then the condition
3797 is evaluated by the target. The @code{info break} command shows
3798 the condition on the line following the affected breakpoint, together with
3799 its condition evaluation mode in between parentheses.
3801 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3802 allowed to have a condition specified for it. The condition is not parsed for
3803 validity until a shared library is loaded that allows the pending
3804 breakpoint to resolve to a valid location.
3807 @code{info break} with a breakpoint
3808 number @var{n} as argument lists only that breakpoint. The
3809 convenience variable @code{$_} and the default examining-address for
3810 the @code{x} command are set to the address of the last breakpoint
3811 listed (@pxref{Memory, ,Examining Memory}).
3814 @code{info break} displays a count of the number of times the breakpoint
3815 has been hit. This is especially useful in conjunction with the
3816 @code{ignore} command. You can ignore a large number of breakpoint
3817 hits, look at the breakpoint info to see how many times the breakpoint
3818 was hit, and then run again, ignoring one less than that number. This
3819 will get you quickly to the last hit of that breakpoint.
3822 For a breakpoints with an enable count (xref) greater than 1,
3823 @code{info break} also displays that count.
3827 @value{GDBN} allows you to set any number of breakpoints at the same place in
3828 your program. There is nothing silly or meaningless about this. When
3829 the breakpoints are conditional, this is even useful
3830 (@pxref{Conditions, ,Break Conditions}).
3832 @cindex multiple locations, breakpoints
3833 @cindex breakpoints, multiple locations
3834 It is possible that a breakpoint corresponds to several locations
3835 in your program. Examples of this situation are:
3839 Multiple functions in the program may have the same name.
3842 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3843 instances of the function body, used in different cases.
3846 For a C@t{++} template function, a given line in the function can
3847 correspond to any number of instantiations.
3850 For an inlined function, a given source line can correspond to
3851 several places where that function is inlined.
3854 In all those cases, @value{GDBN} will insert a breakpoint at all
3855 the relevant locations.
3857 A breakpoint with multiple locations is displayed in the breakpoint
3858 table using several rows---one header row, followed by one row for
3859 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3860 address column. The rows for individual locations contain the actual
3861 addresses for locations, and show the functions to which those
3862 locations belong. The number column for a location is of the form
3863 @var{breakpoint-number}.@var{location-number}.
3868 Num Type Disp Enb Address What
3869 1 breakpoint keep y <MULTIPLE>
3871 breakpoint already hit 1 time
3872 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3873 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3876 Each location can be individually enabled or disabled by passing
3877 @var{breakpoint-number}.@var{location-number} as argument to the
3878 @code{enable} and @code{disable} commands. Note that you cannot
3879 delete the individual locations from the list, you can only delete the
3880 entire list of locations that belong to their parent breakpoint (with
3881 the @kbd{delete @var{num}} command, where @var{num} is the number of
3882 the parent breakpoint, 1 in the above example). Disabling or enabling
3883 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3884 that belong to that breakpoint.
3886 @cindex pending breakpoints
3887 It's quite common to have a breakpoint inside a shared library.
3888 Shared libraries can be loaded and unloaded explicitly,
3889 and possibly repeatedly, as the program is executed. To support
3890 this use case, @value{GDBN} updates breakpoint locations whenever
3891 any shared library is loaded or unloaded. Typically, you would
3892 set a breakpoint in a shared library at the beginning of your
3893 debugging session, when the library is not loaded, and when the
3894 symbols from the library are not available. When you try to set
3895 breakpoint, @value{GDBN} will ask you if you want to set
3896 a so called @dfn{pending breakpoint}---breakpoint whose address
3897 is not yet resolved.
3899 After the program is run, whenever a new shared library is loaded,
3900 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3901 shared library contains the symbol or line referred to by some
3902 pending breakpoint, that breakpoint is resolved and becomes an
3903 ordinary breakpoint. When a library is unloaded, all breakpoints
3904 that refer to its symbols or source lines become pending again.
3906 This logic works for breakpoints with multiple locations, too. For
3907 example, if you have a breakpoint in a C@t{++} template function, and
3908 a newly loaded shared library has an instantiation of that template,
3909 a new location is added to the list of locations for the breakpoint.
3911 Except for having unresolved address, pending breakpoints do not
3912 differ from regular breakpoints. You can set conditions or commands,
3913 enable and disable them and perform other breakpoint operations.
3915 @value{GDBN} provides some additional commands for controlling what
3916 happens when the @samp{break} command cannot resolve breakpoint
3917 address specification to an address:
3919 @kindex set breakpoint pending
3920 @kindex show breakpoint pending
3922 @item set breakpoint pending auto
3923 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3924 location, it queries you whether a pending breakpoint should be created.
3926 @item set breakpoint pending on
3927 This indicates that an unrecognized breakpoint location should automatically
3928 result in a pending breakpoint being created.
3930 @item set breakpoint pending off
3931 This indicates that pending breakpoints are not to be created. Any
3932 unrecognized breakpoint location results in an error. This setting does
3933 not affect any pending breakpoints previously created.
3935 @item show breakpoint pending
3936 Show the current behavior setting for creating pending breakpoints.
3939 The settings above only affect the @code{break} command and its
3940 variants. Once breakpoint is set, it will be automatically updated
3941 as shared libraries are loaded and unloaded.
3943 @cindex automatic hardware breakpoints
3944 For some targets, @value{GDBN} can automatically decide if hardware or
3945 software breakpoints should be used, depending on whether the
3946 breakpoint address is read-only or read-write. This applies to
3947 breakpoints set with the @code{break} command as well as to internal
3948 breakpoints set by commands like @code{next} and @code{finish}. For
3949 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3952 You can control this automatic behaviour with the following commands:
3954 @kindex set breakpoint auto-hw
3955 @kindex show breakpoint auto-hw
3957 @item set breakpoint auto-hw on
3958 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3959 will try to use the target memory map to decide if software or hardware
3960 breakpoint must be used.
3962 @item set breakpoint auto-hw off
3963 This indicates @value{GDBN} should not automatically select breakpoint
3964 type. If the target provides a memory map, @value{GDBN} will warn when
3965 trying to set software breakpoint at a read-only address.
3968 @value{GDBN} normally implements breakpoints by replacing the program code
3969 at the breakpoint address with a special instruction, which, when
3970 executed, given control to the debugger. By default, the program
3971 code is so modified only when the program is resumed. As soon as
3972 the program stops, @value{GDBN} restores the original instructions. This
3973 behaviour guards against leaving breakpoints inserted in the
3974 target should gdb abrubptly disconnect. However, with slow remote
3975 targets, inserting and removing breakpoint can reduce the performance.
3976 This behavior can be controlled with the following commands::
3978 @kindex set breakpoint always-inserted
3979 @kindex show breakpoint always-inserted
3981 @item set breakpoint always-inserted off
3982 All breakpoints, including newly added by the user, are inserted in
3983 the target only when the target is resumed. All breakpoints are
3984 removed from the target when it stops. This is the default mode.
3986 @item set breakpoint always-inserted on
3987 Causes all breakpoints to be inserted in the target at all times. If
3988 the user adds a new breakpoint, or changes an existing breakpoint, the
3989 breakpoints in the target are updated immediately. A breakpoint is
3990 removed from the target only when breakpoint itself is deleted.
3993 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3994 when a breakpoint breaks. If the condition is true, then the process being
3995 debugged stops, otherwise the process is resumed.
3997 If the target supports evaluating conditions on its end, @value{GDBN} may
3998 download the breakpoint, together with its conditions, to it.
4000 This feature can be controlled via the following commands:
4002 @kindex set breakpoint condition-evaluation
4003 @kindex show breakpoint condition-evaluation
4005 @item set breakpoint condition-evaluation host
4006 This option commands @value{GDBN} to evaluate the breakpoint
4007 conditions on the host's side. Unconditional breakpoints are sent to
4008 the target which in turn receives the triggers and reports them back to GDB
4009 for condition evaluation. This is the standard evaluation mode.
4011 @item set breakpoint condition-evaluation target
4012 This option commands @value{GDBN} to download breakpoint conditions
4013 to the target at the moment of their insertion. The target
4014 is responsible for evaluating the conditional expression and reporting
4015 breakpoint stop events back to @value{GDBN} whenever the condition
4016 is true. Due to limitations of target-side evaluation, some conditions
4017 cannot be evaluated there, e.g., conditions that depend on local data
4018 that is only known to the host. Examples include
4019 conditional expressions involving convenience variables, complex types
4020 that cannot be handled by the agent expression parser and expressions
4021 that are too long to be sent over to the target, specially when the
4022 target is a remote system. In these cases, the conditions will be
4023 evaluated by @value{GDBN}.
4025 @item set breakpoint condition-evaluation auto
4026 This is the default mode. If the target supports evaluating breakpoint
4027 conditions on its end, @value{GDBN} will download breakpoint conditions to
4028 the target (limitations mentioned previously apply). If the target does
4029 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4030 to evaluating all these conditions on the host's side.
4034 @cindex negative breakpoint numbers
4035 @cindex internal @value{GDBN} breakpoints
4036 @value{GDBN} itself sometimes sets breakpoints in your program for
4037 special purposes, such as proper handling of @code{longjmp} (in C
4038 programs). These internal breakpoints are assigned negative numbers,
4039 starting with @code{-1}; @samp{info breakpoints} does not display them.
4040 You can see these breakpoints with the @value{GDBN} maintenance command
4041 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4044 @node Set Watchpoints
4045 @subsection Setting Watchpoints
4047 @cindex setting watchpoints
4048 You can use a watchpoint to stop execution whenever the value of an
4049 expression changes, without having to predict a particular place where
4050 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4051 The expression may be as simple as the value of a single variable, or
4052 as complex as many variables combined by operators. Examples include:
4056 A reference to the value of a single variable.
4059 An address cast to an appropriate data type. For example,
4060 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4061 address (assuming an @code{int} occupies 4 bytes).
4064 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4065 expression can use any operators valid in the program's native
4066 language (@pxref{Languages}).
4069 You can set a watchpoint on an expression even if the expression can
4070 not be evaluated yet. For instance, you can set a watchpoint on
4071 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4072 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4073 the expression produces a valid value. If the expression becomes
4074 valid in some other way than changing a variable (e.g.@: if the memory
4075 pointed to by @samp{*global_ptr} becomes readable as the result of a
4076 @code{malloc} call), @value{GDBN} may not stop until the next time
4077 the expression changes.
4079 @cindex software watchpoints
4080 @cindex hardware watchpoints
4081 Depending on your system, watchpoints may be implemented in software or
4082 hardware. @value{GDBN} does software watchpointing by single-stepping your
4083 program and testing the variable's value each time, which is hundreds of
4084 times slower than normal execution. (But this may still be worth it, to
4085 catch errors where you have no clue what part of your program is the
4088 On some systems, such as most PowerPC or x86-based targets,
4089 @value{GDBN} includes support for hardware watchpoints, which do not
4090 slow down the running of your program.
4094 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4095 Set a watchpoint for an expression. @value{GDBN} will break when the
4096 expression @var{expr} is written into by the program and its value
4097 changes. The simplest (and the most popular) use of this command is
4098 to watch the value of a single variable:
4101 (@value{GDBP}) watch foo
4104 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4105 argument, @value{GDBN} breaks only when the thread identified by
4106 @var{thread-id} changes the value of @var{expr}. If any other threads
4107 change the value of @var{expr}, @value{GDBN} will not break. Note
4108 that watchpoints restricted to a single thread in this way only work
4109 with Hardware Watchpoints.
4111 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4112 (see below). The @code{-location} argument tells @value{GDBN} to
4113 instead watch the memory referred to by @var{expr}. In this case,
4114 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4115 and watch the memory at that address. The type of the result is used
4116 to determine the size of the watched memory. If the expression's
4117 result does not have an address, then @value{GDBN} will print an
4120 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4121 of masked watchpoints, if the current architecture supports this
4122 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4123 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4124 to an address to watch. The mask specifies that some bits of an address
4125 (the bits which are reset in the mask) should be ignored when matching
4126 the address accessed by the inferior against the watchpoint address.
4127 Thus, a masked watchpoint watches many addresses simultaneously---those
4128 addresses whose unmasked bits are identical to the unmasked bits in the
4129 watchpoint address. The @code{mask} argument implies @code{-location}.
4133 (@value{GDBP}) watch foo mask 0xffff00ff
4134 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4138 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4139 Set a watchpoint that will break when the value of @var{expr} is read
4143 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4144 Set a watchpoint that will break when @var{expr} is either read from
4145 or written into by the program.
4147 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4148 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4149 This command prints a list of watchpoints, using the same format as
4150 @code{info break} (@pxref{Set Breaks}).
4153 If you watch for a change in a numerically entered address you need to
4154 dereference it, as the address itself is just a constant number which will
4155 never change. @value{GDBN} refuses to create a watchpoint that watches
4156 a never-changing value:
4159 (@value{GDBP}) watch 0x600850
4160 Cannot watch constant value 0x600850.
4161 (@value{GDBP}) watch *(int *) 0x600850
4162 Watchpoint 1: *(int *) 6293584
4165 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4166 watchpoints execute very quickly, and the debugger reports a change in
4167 value at the exact instruction where the change occurs. If @value{GDBN}
4168 cannot set a hardware watchpoint, it sets a software watchpoint, which
4169 executes more slowly and reports the change in value at the next
4170 @emph{statement}, not the instruction, after the change occurs.
4172 @cindex use only software watchpoints
4173 You can force @value{GDBN} to use only software watchpoints with the
4174 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4175 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4176 the underlying system supports them. (Note that hardware-assisted
4177 watchpoints that were set @emph{before} setting
4178 @code{can-use-hw-watchpoints} to zero will still use the hardware
4179 mechanism of watching expression values.)
4182 @item set can-use-hw-watchpoints
4183 @kindex set can-use-hw-watchpoints
4184 Set whether or not to use hardware watchpoints.
4186 @item show can-use-hw-watchpoints
4187 @kindex show can-use-hw-watchpoints
4188 Show the current mode of using hardware watchpoints.
4191 For remote targets, you can restrict the number of hardware
4192 watchpoints @value{GDBN} will use, see @ref{set remote
4193 hardware-breakpoint-limit}.
4195 When you issue the @code{watch} command, @value{GDBN} reports
4198 Hardware watchpoint @var{num}: @var{expr}
4202 if it was able to set a hardware watchpoint.
4204 Currently, the @code{awatch} and @code{rwatch} commands can only set
4205 hardware watchpoints, because accesses to data that don't change the
4206 value of the watched expression cannot be detected without examining
4207 every instruction as it is being executed, and @value{GDBN} does not do
4208 that currently. If @value{GDBN} finds that it is unable to set a
4209 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4210 will print a message like this:
4213 Expression cannot be implemented with read/access watchpoint.
4216 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4217 data type of the watched expression is wider than what a hardware
4218 watchpoint on the target machine can handle. For example, some systems
4219 can only watch regions that are up to 4 bytes wide; on such systems you
4220 cannot set hardware watchpoints for an expression that yields a
4221 double-precision floating-point number (which is typically 8 bytes
4222 wide). As a work-around, it might be possible to break the large region
4223 into a series of smaller ones and watch them with separate watchpoints.
4225 If you set too many hardware watchpoints, @value{GDBN} might be unable
4226 to insert all of them when you resume the execution of your program.
4227 Since the precise number of active watchpoints is unknown until such
4228 time as the program is about to be resumed, @value{GDBN} might not be
4229 able to warn you about this when you set the watchpoints, and the
4230 warning will be printed only when the program is resumed:
4233 Hardware watchpoint @var{num}: Could not insert watchpoint
4237 If this happens, delete or disable some of the watchpoints.
4239 Watching complex expressions that reference many variables can also
4240 exhaust the resources available for hardware-assisted watchpoints.
4241 That's because @value{GDBN} needs to watch every variable in the
4242 expression with separately allocated resources.
4244 If you call a function interactively using @code{print} or @code{call},
4245 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4246 kind of breakpoint or the call completes.
4248 @value{GDBN} automatically deletes watchpoints that watch local
4249 (automatic) variables, or expressions that involve such variables, when
4250 they go out of scope, that is, when the execution leaves the block in
4251 which these variables were defined. In particular, when the program
4252 being debugged terminates, @emph{all} local variables go out of scope,
4253 and so only watchpoints that watch global variables remain set. If you
4254 rerun the program, you will need to set all such watchpoints again. One
4255 way of doing that would be to set a code breakpoint at the entry to the
4256 @code{main} function and when it breaks, set all the watchpoints.
4258 @cindex watchpoints and threads
4259 @cindex threads and watchpoints
4260 In multi-threaded programs, watchpoints will detect changes to the
4261 watched expression from every thread.
4264 @emph{Warning:} In multi-threaded programs, software watchpoints
4265 have only limited usefulness. If @value{GDBN} creates a software
4266 watchpoint, it can only watch the value of an expression @emph{in a
4267 single thread}. If you are confident that the expression can only
4268 change due to the current thread's activity (and if you are also
4269 confident that no other thread can become current), then you can use
4270 software watchpoints as usual. However, @value{GDBN} may not notice
4271 when a non-current thread's activity changes the expression. (Hardware
4272 watchpoints, in contrast, watch an expression in all threads.)
4275 @xref{set remote hardware-watchpoint-limit}.
4277 @node Set Catchpoints
4278 @subsection Setting Catchpoints
4279 @cindex catchpoints, setting
4280 @cindex exception handlers
4281 @cindex event handling
4283 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4284 kinds of program events, such as C@t{++} exceptions or the loading of a
4285 shared library. Use the @code{catch} command to set a catchpoint.
4289 @item catch @var{event}
4290 Stop when @var{event} occurs. The @var{event} can be any of the following:
4293 @item throw @r{[}@var{regexp}@r{]}
4294 @itemx rethrow @r{[}@var{regexp}@r{]}
4295 @itemx catch @r{[}@var{regexp}@r{]}
4297 @kindex catch rethrow
4299 @cindex stop on C@t{++} exceptions
4300 The throwing, re-throwing, or catching of a C@t{++} exception.
4302 If @var{regexp} is given, then only exceptions whose type matches the
4303 regular expression will be caught.
4305 @vindex $_exception@r{, convenience variable}
4306 The convenience variable @code{$_exception} is available at an
4307 exception-related catchpoint, on some systems. This holds the
4308 exception being thrown.
4310 There are currently some limitations to C@t{++} exception handling in
4315 The support for these commands is system-dependent. Currently, only
4316 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4320 The regular expression feature and the @code{$_exception} convenience
4321 variable rely on the presence of some SDT probes in @code{libstdc++}.
4322 If these probes are not present, then these features cannot be used.
4323 These probes were first available in the GCC 4.8 release, but whether
4324 or not they are available in your GCC also depends on how it was
4328 The @code{$_exception} convenience variable is only valid at the
4329 instruction at which an exception-related catchpoint is set.
4332 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4333 location in the system library which implements runtime exception
4334 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4335 (@pxref{Selection}) to get to your code.
4338 If you call a function interactively, @value{GDBN} normally returns
4339 control to you when the function has finished executing. If the call
4340 raises an exception, however, the call may bypass the mechanism that
4341 returns control to you and cause your program either to abort or to
4342 simply continue running until it hits a breakpoint, catches a signal
4343 that @value{GDBN} is listening for, or exits. This is the case even if
4344 you set a catchpoint for the exception; catchpoints on exceptions are
4345 disabled within interactive calls. @xref{Calling}, for information on
4346 controlling this with @code{set unwind-on-terminating-exception}.
4349 You cannot raise an exception interactively.
4352 You cannot install an exception handler interactively.
4356 @kindex catch exception
4357 @cindex Ada exception catching
4358 @cindex catch Ada exceptions
4359 An Ada exception being raised. If an exception name is specified
4360 at the end of the command (eg @code{catch exception Program_Error}),
4361 the debugger will stop only when this specific exception is raised.
4362 Otherwise, the debugger stops execution when any Ada exception is raised.
4364 When inserting an exception catchpoint on a user-defined exception whose
4365 name is identical to one of the exceptions defined by the language, the
4366 fully qualified name must be used as the exception name. Otherwise,
4367 @value{GDBN} will assume that it should stop on the pre-defined exception
4368 rather than the user-defined one. For instance, assuming an exception
4369 called @code{Constraint_Error} is defined in package @code{Pck}, then
4370 the command to use to catch such exceptions is @kbd{catch exception
4371 Pck.Constraint_Error}.
4373 @item exception unhandled
4374 @kindex catch exception unhandled
4375 An exception that was raised but is not handled by the program.
4378 @kindex catch assert
4379 A failed Ada assertion.
4383 @cindex break on fork/exec
4384 A call to @code{exec}.
4387 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4388 @kindex catch syscall
4389 @cindex break on a system call.
4390 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4391 syscall is a mechanism for application programs to request a service
4392 from the operating system (OS) or one of the OS system services.
4393 @value{GDBN} can catch some or all of the syscalls issued by the
4394 debuggee, and show the related information for each syscall. If no
4395 argument is specified, calls to and returns from all system calls
4398 @var{name} can be any system call name that is valid for the
4399 underlying OS. Just what syscalls are valid depends on the OS. On
4400 GNU and Unix systems, you can find the full list of valid syscall
4401 names on @file{/usr/include/asm/unistd.h}.
4403 @c For MS-Windows, the syscall names and the corresponding numbers
4404 @c can be found, e.g., on this URL:
4405 @c http://www.metasploit.com/users/opcode/syscalls.html
4406 @c but we don't support Windows syscalls yet.
4408 Normally, @value{GDBN} knows in advance which syscalls are valid for
4409 each OS, so you can use the @value{GDBN} command-line completion
4410 facilities (@pxref{Completion,, command completion}) to list the
4413 You may also specify the system call numerically. A syscall's
4414 number is the value passed to the OS's syscall dispatcher to
4415 identify the requested service. When you specify the syscall by its
4416 name, @value{GDBN} uses its database of syscalls to convert the name
4417 into the corresponding numeric code, but using the number directly
4418 may be useful if @value{GDBN}'s database does not have the complete
4419 list of syscalls on your system (e.g., because @value{GDBN} lags
4420 behind the OS upgrades).
4422 You may specify a group of related syscalls to be caught at once using
4423 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4424 instance, on some platforms @value{GDBN} allows you to catch all
4425 network related syscalls, by passing the argument @code{group:network}
4426 to @code{catch syscall}. Note that not all syscall groups are
4427 available in every system. You can use the command completion
4428 facilities (@pxref{Completion,, command completion}) to list the
4429 syscall groups available on your environment.
4431 The example below illustrates how this command works if you don't provide
4435 (@value{GDBP}) catch syscall
4436 Catchpoint 1 (syscall)
4438 Starting program: /tmp/catch-syscall
4440 Catchpoint 1 (call to syscall 'close'), \
4441 0xffffe424 in __kernel_vsyscall ()
4445 Catchpoint 1 (returned from syscall 'close'), \
4446 0xffffe424 in __kernel_vsyscall ()
4450 Here is an example of catching a system call by name:
4453 (@value{GDBP}) catch syscall chroot
4454 Catchpoint 1 (syscall 'chroot' [61])
4456 Starting program: /tmp/catch-syscall
4458 Catchpoint 1 (call to syscall 'chroot'), \
4459 0xffffe424 in __kernel_vsyscall ()
4463 Catchpoint 1 (returned from syscall 'chroot'), \
4464 0xffffe424 in __kernel_vsyscall ()
4468 An example of specifying a system call numerically. In the case
4469 below, the syscall number has a corresponding entry in the XML
4470 file, so @value{GDBN} finds its name and prints it:
4473 (@value{GDBP}) catch syscall 252
4474 Catchpoint 1 (syscall(s) 'exit_group')
4476 Starting program: /tmp/catch-syscall
4478 Catchpoint 1 (call to syscall 'exit_group'), \
4479 0xffffe424 in __kernel_vsyscall ()
4483 Program exited normally.
4487 Here is an example of catching a syscall group:
4490 (@value{GDBP}) catch syscall group:process
4491 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4492 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4493 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4495 Starting program: /tmp/catch-syscall
4497 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4498 from /lib64/ld-linux-x86-64.so.2
4504 However, there can be situations when there is no corresponding name
4505 in XML file for that syscall number. In this case, @value{GDBN} prints
4506 a warning message saying that it was not able to find the syscall name,
4507 but the catchpoint will be set anyway. See the example below:
4510 (@value{GDBP}) catch syscall 764
4511 warning: The number '764' does not represent a known syscall.
4512 Catchpoint 2 (syscall 764)
4516 If you configure @value{GDBN} using the @samp{--without-expat} option,
4517 it will not be able to display syscall names. Also, if your
4518 architecture does not have an XML file describing its system calls,
4519 you will not be able to see the syscall names. It is important to
4520 notice that these two features are used for accessing the syscall
4521 name database. In either case, you will see a warning like this:
4524 (@value{GDBP}) catch syscall
4525 warning: Could not open "syscalls/i386-linux.xml"
4526 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4527 GDB will not be able to display syscall names.
4528 Catchpoint 1 (syscall)
4532 Of course, the file name will change depending on your architecture and system.
4534 Still using the example above, you can also try to catch a syscall by its
4535 number. In this case, you would see something like:
4538 (@value{GDBP}) catch syscall 252
4539 Catchpoint 1 (syscall(s) 252)
4542 Again, in this case @value{GDBN} would not be able to display syscall's names.
4546 A call to @code{fork}.
4550 A call to @code{vfork}.
4552 @item load @r{[}regexp@r{]}
4553 @itemx unload @r{[}regexp@r{]}
4555 @kindex catch unload
4556 The loading or unloading of a shared library. If @var{regexp} is
4557 given, then the catchpoint will stop only if the regular expression
4558 matches one of the affected libraries.
4560 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4561 @kindex catch signal
4562 The delivery of a signal.
4564 With no arguments, this catchpoint will catch any signal that is not
4565 used internally by @value{GDBN}, specifically, all signals except
4566 @samp{SIGTRAP} and @samp{SIGINT}.
4568 With the argument @samp{all}, all signals, including those used by
4569 @value{GDBN}, will be caught. This argument cannot be used with other
4572 Otherwise, the arguments are a list of signal names as given to
4573 @code{handle} (@pxref{Signals}). Only signals specified in this list
4576 One reason that @code{catch signal} can be more useful than
4577 @code{handle} is that you can attach commands and conditions to the
4580 When a signal is caught by a catchpoint, the signal's @code{stop} and
4581 @code{print} settings, as specified by @code{handle}, are ignored.
4582 However, whether the signal is still delivered to the inferior depends
4583 on the @code{pass} setting; this can be changed in the catchpoint's
4588 @item tcatch @var{event}
4590 Set a catchpoint that is enabled only for one stop. The catchpoint is
4591 automatically deleted after the first time the event is caught.
4595 Use the @code{info break} command to list the current catchpoints.
4599 @subsection Deleting Breakpoints
4601 @cindex clearing breakpoints, watchpoints, catchpoints
4602 @cindex deleting breakpoints, watchpoints, catchpoints
4603 It is often necessary to eliminate a breakpoint, watchpoint, or
4604 catchpoint once it has done its job and you no longer want your program
4605 to stop there. This is called @dfn{deleting} the breakpoint. A
4606 breakpoint that has been deleted no longer exists; it is forgotten.
4608 With the @code{clear} command you can delete breakpoints according to
4609 where they are in your program. With the @code{delete} command you can
4610 delete individual breakpoints, watchpoints, or catchpoints by specifying
4611 their breakpoint numbers.
4613 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4614 automatically ignores breakpoints on the first instruction to be executed
4615 when you continue execution without changing the execution address.
4620 Delete any breakpoints at the next instruction to be executed in the
4621 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4622 the innermost frame is selected, this is a good way to delete a
4623 breakpoint where your program just stopped.
4625 @item clear @var{location}
4626 Delete any breakpoints set at the specified @var{location}.
4627 @xref{Specify Location}, for the various forms of @var{location}; the
4628 most useful ones are listed below:
4631 @item clear @var{function}
4632 @itemx clear @var{filename}:@var{function}
4633 Delete any breakpoints set at entry to the named @var{function}.
4635 @item clear @var{linenum}
4636 @itemx clear @var{filename}:@var{linenum}
4637 Delete any breakpoints set at or within the code of the specified
4638 @var{linenum} of the specified @var{filename}.
4641 @cindex delete breakpoints
4643 @kindex d @r{(@code{delete})}
4644 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4645 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4646 list specified as argument. If no argument is specified, delete all
4647 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4648 confirm off}). You can abbreviate this command as @code{d}.
4652 @subsection Disabling Breakpoints
4654 @cindex enable/disable a breakpoint
4655 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4656 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4657 it had been deleted, but remembers the information on the breakpoint so
4658 that you can @dfn{enable} it again later.
4660 You disable and enable breakpoints, watchpoints, and catchpoints with
4661 the @code{enable} and @code{disable} commands, optionally specifying
4662 one or more breakpoint numbers as arguments. Use @code{info break} to
4663 print a list of all breakpoints, watchpoints, and catchpoints if you
4664 do not know which numbers to use.
4666 Disabling and enabling a breakpoint that has multiple locations
4667 affects all of its locations.
4669 A breakpoint, watchpoint, or catchpoint can have any of several
4670 different states of enablement:
4674 Enabled. The breakpoint stops your program. A breakpoint set
4675 with the @code{break} command starts out in this state.
4677 Disabled. The breakpoint has no effect on your program.
4679 Enabled once. The breakpoint stops your program, but then becomes
4682 Enabled for a count. The breakpoint stops your program for the next
4683 N times, then becomes disabled.
4685 Enabled for deletion. The breakpoint stops your program, but
4686 immediately after it does so it is deleted permanently. A breakpoint
4687 set with the @code{tbreak} command starts out in this state.
4690 You can use the following commands to enable or disable breakpoints,
4691 watchpoints, and catchpoints:
4695 @kindex dis @r{(@code{disable})}
4696 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4697 Disable the specified breakpoints---or all breakpoints, if none are
4698 listed. A disabled breakpoint has no effect but is not forgotten. All
4699 options such as ignore-counts, conditions and commands are remembered in
4700 case the breakpoint is enabled again later. You may abbreviate
4701 @code{disable} as @code{dis}.
4704 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4705 Enable the specified breakpoints (or all defined breakpoints). They
4706 become effective once again in stopping your program.
4708 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4709 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4710 of these breakpoints immediately after stopping your program.
4712 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4713 Enable the specified breakpoints temporarily. @value{GDBN} records
4714 @var{count} with each of the specified breakpoints, and decrements a
4715 breakpoint's count when it is hit. When any count reaches 0,
4716 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4717 count (@pxref{Conditions, ,Break Conditions}), that will be
4718 decremented to 0 before @var{count} is affected.
4720 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4721 Enable the specified breakpoints to work once, then die. @value{GDBN}
4722 deletes any of these breakpoints as soon as your program stops there.
4723 Breakpoints set by the @code{tbreak} command start out in this state.
4726 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4727 @c confusing: tbreak is also initially enabled.
4728 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4729 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4730 subsequently, they become disabled or enabled only when you use one of
4731 the commands above. (The command @code{until} can set and delete a
4732 breakpoint of its own, but it does not change the state of your other
4733 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4737 @subsection Break Conditions
4738 @cindex conditional breakpoints
4739 @cindex breakpoint conditions
4741 @c FIXME what is scope of break condition expr? Context where wanted?
4742 @c in particular for a watchpoint?
4743 The simplest sort of breakpoint breaks every time your program reaches a
4744 specified place. You can also specify a @dfn{condition} for a
4745 breakpoint. A condition is just a Boolean expression in your
4746 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4747 a condition evaluates the expression each time your program reaches it,
4748 and your program stops only if the condition is @emph{true}.
4750 This is the converse of using assertions for program validation; in that
4751 situation, you want to stop when the assertion is violated---that is,
4752 when the condition is false. In C, if you want to test an assertion expressed
4753 by the condition @var{assert}, you should set the condition
4754 @samp{! @var{assert}} on the appropriate breakpoint.
4756 Conditions are also accepted for watchpoints; you may not need them,
4757 since a watchpoint is inspecting the value of an expression anyhow---but
4758 it might be simpler, say, to just set a watchpoint on a variable name,
4759 and specify a condition that tests whether the new value is an interesting
4762 Break conditions can have side effects, and may even call functions in
4763 your program. This can be useful, for example, to activate functions
4764 that log program progress, or to use your own print functions to
4765 format special data structures. The effects are completely predictable
4766 unless there is another enabled breakpoint at the same address. (In
4767 that case, @value{GDBN} might see the other breakpoint first and stop your
4768 program without checking the condition of this one.) Note that
4769 breakpoint commands are usually more convenient and flexible than break
4771 purpose of performing side effects when a breakpoint is reached
4772 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4774 Breakpoint conditions can also be evaluated on the target's side if
4775 the target supports it. Instead of evaluating the conditions locally,
4776 @value{GDBN} encodes the expression into an agent expression
4777 (@pxref{Agent Expressions}) suitable for execution on the target,
4778 independently of @value{GDBN}. Global variables become raw memory
4779 locations, locals become stack accesses, and so forth.
4781 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4782 when its condition evaluates to true. This mechanism may provide faster
4783 response times depending on the performance characteristics of the target
4784 since it does not need to keep @value{GDBN} informed about
4785 every breakpoint trigger, even those with false conditions.
4787 Break conditions can be specified when a breakpoint is set, by using
4788 @samp{if} in the arguments to the @code{break} command. @xref{Set
4789 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4790 with the @code{condition} command.
4792 You can also use the @code{if} keyword with the @code{watch} command.
4793 The @code{catch} command does not recognize the @code{if} keyword;
4794 @code{condition} is the only way to impose a further condition on a
4799 @item condition @var{bnum} @var{expression}
4800 Specify @var{expression} as the break condition for breakpoint,
4801 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4802 breakpoint @var{bnum} stops your program only if the value of
4803 @var{expression} is true (nonzero, in C). When you use
4804 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4805 syntactic correctness, and to determine whether symbols in it have
4806 referents in the context of your breakpoint. If @var{expression} uses
4807 symbols not referenced in the context of the breakpoint, @value{GDBN}
4808 prints an error message:
4811 No symbol "foo" in current context.
4816 not actually evaluate @var{expression} at the time the @code{condition}
4817 command (or a command that sets a breakpoint with a condition, like
4818 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4820 @item condition @var{bnum}
4821 Remove the condition from breakpoint number @var{bnum}. It becomes
4822 an ordinary unconditional breakpoint.
4825 @cindex ignore count (of breakpoint)
4826 A special case of a breakpoint condition is to stop only when the
4827 breakpoint has been reached a certain number of times. This is so
4828 useful that there is a special way to do it, using the @dfn{ignore
4829 count} of the breakpoint. Every breakpoint has an ignore count, which
4830 is an integer. Most of the time, the ignore count is zero, and
4831 therefore has no effect. But if your program reaches a breakpoint whose
4832 ignore count is positive, then instead of stopping, it just decrements
4833 the ignore count by one and continues. As a result, if the ignore count
4834 value is @var{n}, the breakpoint does not stop the next @var{n} times
4835 your program reaches it.
4839 @item ignore @var{bnum} @var{count}
4840 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4841 The next @var{count} times the breakpoint is reached, your program's
4842 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4845 To make the breakpoint stop the next time it is reached, specify
4848 When you use @code{continue} to resume execution of your program from a
4849 breakpoint, you can specify an ignore count directly as an argument to
4850 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4851 Stepping,,Continuing and Stepping}.
4853 If a breakpoint has a positive ignore count and a condition, the
4854 condition is not checked. Once the ignore count reaches zero,
4855 @value{GDBN} resumes checking the condition.
4857 You could achieve the effect of the ignore count with a condition such
4858 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4859 is decremented each time. @xref{Convenience Vars, ,Convenience
4863 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4866 @node Break Commands
4867 @subsection Breakpoint Command Lists
4869 @cindex breakpoint commands
4870 You can give any breakpoint (or watchpoint or catchpoint) a series of
4871 commands to execute when your program stops due to that breakpoint. For
4872 example, you might want to print the values of certain expressions, or
4873 enable other breakpoints.
4877 @kindex end@r{ (breakpoint commands)}
4878 @item commands @r{[}@var{list}@dots{}@r{]}
4879 @itemx @dots{} @var{command-list} @dots{}
4881 Specify a list of commands for the given breakpoints. The commands
4882 themselves appear on the following lines. Type a line containing just
4883 @code{end} to terminate the commands.
4885 To remove all commands from a breakpoint, type @code{commands} and
4886 follow it immediately with @code{end}; that is, give no commands.
4888 With no argument, @code{commands} refers to the last breakpoint,
4889 watchpoint, or catchpoint set (not to the breakpoint most recently
4890 encountered). If the most recent breakpoints were set with a single
4891 command, then the @code{commands} will apply to all the breakpoints
4892 set by that command. This applies to breakpoints set by
4893 @code{rbreak}, and also applies when a single @code{break} command
4894 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4898 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4899 disabled within a @var{command-list}.
4901 You can use breakpoint commands to start your program up again. Simply
4902 use the @code{continue} command, or @code{step}, or any other command
4903 that resumes execution.
4905 Any other commands in the command list, after a command that resumes
4906 execution, are ignored. This is because any time you resume execution
4907 (even with a simple @code{next} or @code{step}), you may encounter
4908 another breakpoint---which could have its own command list, leading to
4909 ambiguities about which list to execute.
4912 If the first command you specify in a command list is @code{silent}, the
4913 usual message about stopping at a breakpoint is not printed. This may
4914 be desirable for breakpoints that are to print a specific message and
4915 then continue. If none of the remaining commands print anything, you
4916 see no sign that the breakpoint was reached. @code{silent} is
4917 meaningful only at the beginning of a breakpoint command list.
4919 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4920 print precisely controlled output, and are often useful in silent
4921 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4923 For example, here is how you could use breakpoint commands to print the
4924 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4930 printf "x is %d\n",x
4935 One application for breakpoint commands is to compensate for one bug so
4936 you can test for another. Put a breakpoint just after the erroneous line
4937 of code, give it a condition to detect the case in which something
4938 erroneous has been done, and give it commands to assign correct values
4939 to any variables that need them. End with the @code{continue} command
4940 so that your program does not stop, and start with the @code{silent}
4941 command so that no output is produced. Here is an example:
4952 @node Dynamic Printf
4953 @subsection Dynamic Printf
4955 @cindex dynamic printf
4957 The dynamic printf command @code{dprintf} combines a breakpoint with
4958 formatted printing of your program's data to give you the effect of
4959 inserting @code{printf} calls into your program on-the-fly, without
4960 having to recompile it.
4962 In its most basic form, the output goes to the GDB console. However,
4963 you can set the variable @code{dprintf-style} for alternate handling.
4964 For instance, you can ask to format the output by calling your
4965 program's @code{printf} function. This has the advantage that the
4966 characters go to the program's output device, so they can recorded in
4967 redirects to files and so forth.
4969 If you are doing remote debugging with a stub or agent, you can also
4970 ask to have the printf handled by the remote agent. In addition to
4971 ensuring that the output goes to the remote program's device along
4972 with any other output the program might produce, you can also ask that
4973 the dprintf remain active even after disconnecting from the remote
4974 target. Using the stub/agent is also more efficient, as it can do
4975 everything without needing to communicate with @value{GDBN}.
4979 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4980 Whenever execution reaches @var{location}, print the values of one or
4981 more @var{expressions} under the control of the string @var{template}.
4982 To print several values, separate them with commas.
4984 @item set dprintf-style @var{style}
4985 Set the dprintf output to be handled in one of several different
4986 styles enumerated below. A change of style affects all existing
4987 dynamic printfs immediately. (If you need individual control over the
4988 print commands, simply define normal breakpoints with
4989 explicitly-supplied command lists.)
4993 @kindex dprintf-style gdb
4994 Handle the output using the @value{GDBN} @code{printf} command.
4997 @kindex dprintf-style call
4998 Handle the output by calling a function in your program (normally
5002 @kindex dprintf-style agent
5003 Have the remote debugging agent (such as @code{gdbserver}) handle
5004 the output itself. This style is only available for agents that
5005 support running commands on the target.
5008 @item set dprintf-function @var{function}
5009 Set the function to call if the dprintf style is @code{call}. By
5010 default its value is @code{printf}. You may set it to any expression.
5011 that @value{GDBN} can evaluate to a function, as per the @code{call}
5014 @item set dprintf-channel @var{channel}
5015 Set a ``channel'' for dprintf. If set to a non-empty value,
5016 @value{GDBN} will evaluate it as an expression and pass the result as
5017 a first argument to the @code{dprintf-function}, in the manner of
5018 @code{fprintf} and similar functions. Otherwise, the dprintf format
5019 string will be the first argument, in the manner of @code{printf}.
5021 As an example, if you wanted @code{dprintf} output to go to a logfile
5022 that is a standard I/O stream assigned to the variable @code{mylog},
5023 you could do the following:
5026 (gdb) set dprintf-style call
5027 (gdb) set dprintf-function fprintf
5028 (gdb) set dprintf-channel mylog
5029 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5030 Dprintf 1 at 0x123456: file main.c, line 25.
5032 1 dprintf keep y 0x00123456 in main at main.c:25
5033 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5038 Note that the @code{info break} displays the dynamic printf commands
5039 as normal breakpoint commands; you can thus easily see the effect of
5040 the variable settings.
5042 @item set disconnected-dprintf on
5043 @itemx set disconnected-dprintf off
5044 @kindex set disconnected-dprintf
5045 Choose whether @code{dprintf} commands should continue to run if
5046 @value{GDBN} has disconnected from the target. This only applies
5047 if the @code{dprintf-style} is @code{agent}.
5049 @item show disconnected-dprintf off
5050 @kindex show disconnected-dprintf
5051 Show the current choice for disconnected @code{dprintf}.
5055 @value{GDBN} does not check the validity of function and channel,
5056 relying on you to supply values that are meaningful for the contexts
5057 in which they are being used. For instance, the function and channel
5058 may be the values of local variables, but if that is the case, then
5059 all enabled dynamic prints must be at locations within the scope of
5060 those locals. If evaluation fails, @value{GDBN} will report an error.
5062 @node Save Breakpoints
5063 @subsection How to save breakpoints to a file
5065 To save breakpoint definitions to a file use the @w{@code{save
5066 breakpoints}} command.
5069 @kindex save breakpoints
5070 @cindex save breakpoints to a file for future sessions
5071 @item save breakpoints [@var{filename}]
5072 This command saves all current breakpoint definitions together with
5073 their commands and ignore counts, into a file @file{@var{filename}}
5074 suitable for use in a later debugging session. This includes all
5075 types of breakpoints (breakpoints, watchpoints, catchpoints,
5076 tracepoints). To read the saved breakpoint definitions, use the
5077 @code{source} command (@pxref{Command Files}). Note that watchpoints
5078 with expressions involving local variables may fail to be recreated
5079 because it may not be possible to access the context where the
5080 watchpoint is valid anymore. Because the saved breakpoint definitions
5081 are simply a sequence of @value{GDBN} commands that recreate the
5082 breakpoints, you can edit the file in your favorite editing program,
5083 and remove the breakpoint definitions you're not interested in, or
5084 that can no longer be recreated.
5087 @node Static Probe Points
5088 @subsection Static Probe Points
5090 @cindex static probe point, SystemTap
5091 @cindex static probe point, DTrace
5092 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5093 for Statically Defined Tracing, and the probes are designed to have a tiny
5094 runtime code and data footprint, and no dynamic relocations.
5096 Currently, the following types of probes are supported on
5097 ELF-compatible systems:
5101 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5102 @acronym{SDT} probes@footnote{See
5103 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5104 for more information on how to add @code{SystemTap} @acronym{SDT}
5105 probes in your applications.}. @code{SystemTap} probes are usable
5106 from assembly, C and C@t{++} languages@footnote{See
5107 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5108 for a good reference on how the @acronym{SDT} probes are implemented.}.
5110 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5111 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5115 @cindex semaphores on static probe points
5116 Some @code{SystemTap} probes have an associated semaphore variable;
5117 for instance, this happens automatically if you defined your probe
5118 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5119 @value{GDBN} will automatically enable it when you specify a
5120 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5121 breakpoint at a probe's location by some other method (e.g.,
5122 @code{break file:line}), then @value{GDBN} will not automatically set
5123 the semaphore. @code{DTrace} probes do not support semaphores.
5125 You can examine the available static static probes using @code{info
5126 probes}, with optional arguments:
5130 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5131 If given, @var{type} is either @code{stap} for listing
5132 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5133 probes. If omitted all probes are listed regardless of their types.
5135 If given, @var{provider} is a regular expression used to match against provider
5136 names when selecting which probes to list. If omitted, probes by all
5137 probes from all providers are listed.
5139 If given, @var{name} is a regular expression to match against probe names
5140 when selecting which probes to list. If omitted, probe names are not
5141 considered when deciding whether to display them.
5143 If given, @var{objfile} is a regular expression used to select which
5144 object files (executable or shared libraries) to examine. If not
5145 given, all object files are considered.
5147 @item info probes all
5148 List the available static probes, from all types.
5151 @cindex enabling and disabling probes
5152 Some probe points can be enabled and/or disabled. The effect of
5153 enabling or disabling a probe depends on the type of probe being
5154 handled. Some @code{DTrace} probes can be enabled or
5155 disabled, but @code{SystemTap} probes cannot be disabled.
5157 You can enable (or disable) one or more probes using the following
5158 commands, with optional arguments:
5161 @kindex enable probes
5162 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5163 If given, @var{provider} is a regular expression used to match against
5164 provider names when selecting which probes to enable. If omitted,
5165 all probes from all providers are enabled.
5167 If given, @var{name} is a regular expression to match against probe
5168 names when selecting which probes to enable. If omitted, probe names
5169 are not considered when deciding whether to enable them.
5171 If given, @var{objfile} is a regular expression used to select which
5172 object files (executable or shared libraries) to examine. If not
5173 given, all object files are considered.
5175 @kindex disable probes
5176 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5177 See the @code{enable probes} command above for a description of the
5178 optional arguments accepted by this command.
5181 @vindex $_probe_arg@r{, convenience variable}
5182 A probe may specify up to twelve arguments. These are available at the
5183 point at which the probe is defined---that is, when the current PC is
5184 at the probe's location. The arguments are available using the
5185 convenience variables (@pxref{Convenience Vars})
5186 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5187 probes each probe argument is an integer of the appropriate size;
5188 types are not preserved. In @code{DTrace} probes types are preserved
5189 provided that they are recognized as such by @value{GDBN}; otherwise
5190 the value of the probe argument will be a long integer. The
5191 convenience variable @code{$_probe_argc} holds the number of arguments
5192 at the current probe point.
5194 These variables are always available, but attempts to access them at
5195 any location other than a probe point will cause @value{GDBN} to give
5199 @c @ifclear BARETARGET
5200 @node Error in Breakpoints
5201 @subsection ``Cannot insert breakpoints''
5203 If you request too many active hardware-assisted breakpoints and
5204 watchpoints, you will see this error message:
5206 @c FIXME: the precise wording of this message may change; the relevant
5207 @c source change is not committed yet (Sep 3, 1999).
5209 Stopped; cannot insert breakpoints.
5210 You may have requested too many hardware breakpoints and watchpoints.
5214 This message is printed when you attempt to resume the program, since
5215 only then @value{GDBN} knows exactly how many hardware breakpoints and
5216 watchpoints it needs to insert.
5218 When this message is printed, you need to disable or remove some of the
5219 hardware-assisted breakpoints and watchpoints, and then continue.
5221 @node Breakpoint-related Warnings
5222 @subsection ``Breakpoint address adjusted...''
5223 @cindex breakpoint address adjusted
5225 Some processor architectures place constraints on the addresses at
5226 which breakpoints may be placed. For architectures thus constrained,
5227 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5228 with the constraints dictated by the architecture.
5230 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5231 a VLIW architecture in which a number of RISC-like instructions may be
5232 bundled together for parallel execution. The FR-V architecture
5233 constrains the location of a breakpoint instruction within such a
5234 bundle to the instruction with the lowest address. @value{GDBN}
5235 honors this constraint by adjusting a breakpoint's address to the
5236 first in the bundle.
5238 It is not uncommon for optimized code to have bundles which contain
5239 instructions from different source statements, thus it may happen that
5240 a breakpoint's address will be adjusted from one source statement to
5241 another. Since this adjustment may significantly alter @value{GDBN}'s
5242 breakpoint related behavior from what the user expects, a warning is
5243 printed when the breakpoint is first set and also when the breakpoint
5246 A warning like the one below is printed when setting a breakpoint
5247 that's been subject to address adjustment:
5250 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5253 Such warnings are printed both for user settable and @value{GDBN}'s
5254 internal breakpoints. If you see one of these warnings, you should
5255 verify that a breakpoint set at the adjusted address will have the
5256 desired affect. If not, the breakpoint in question may be removed and
5257 other breakpoints may be set which will have the desired behavior.
5258 E.g., it may be sufficient to place the breakpoint at a later
5259 instruction. A conditional breakpoint may also be useful in some
5260 cases to prevent the breakpoint from triggering too often.
5262 @value{GDBN} will also issue a warning when stopping at one of these
5263 adjusted breakpoints:
5266 warning: Breakpoint 1 address previously adjusted from 0x00010414
5270 When this warning is encountered, it may be too late to take remedial
5271 action except in cases where the breakpoint is hit earlier or more
5272 frequently than expected.
5274 @node Continuing and Stepping
5275 @section Continuing and Stepping
5279 @cindex resuming execution
5280 @dfn{Continuing} means resuming program execution until your program
5281 completes normally. In contrast, @dfn{stepping} means executing just
5282 one more ``step'' of your program, where ``step'' may mean either one
5283 line of source code, or one machine instruction (depending on what
5284 particular command you use). Either when continuing or when stepping,
5285 your program may stop even sooner, due to a breakpoint or a signal. (If
5286 it stops due to a signal, you may want to use @code{handle}, or use
5287 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5288 or you may step into the signal's handler (@pxref{stepping and signal
5293 @kindex c @r{(@code{continue})}
5294 @kindex fg @r{(resume foreground execution)}
5295 @item continue @r{[}@var{ignore-count}@r{]}
5296 @itemx c @r{[}@var{ignore-count}@r{]}
5297 @itemx fg @r{[}@var{ignore-count}@r{]}
5298 Resume program execution, at the address where your program last stopped;
5299 any breakpoints set at that address are bypassed. The optional argument
5300 @var{ignore-count} allows you to specify a further number of times to
5301 ignore a breakpoint at this location; its effect is like that of
5302 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5304 The argument @var{ignore-count} is meaningful only when your program
5305 stopped due to a breakpoint. At other times, the argument to
5306 @code{continue} is ignored.
5308 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5309 debugged program is deemed to be the foreground program) are provided
5310 purely for convenience, and have exactly the same behavior as
5314 To resume execution at a different place, you can use @code{return}
5315 (@pxref{Returning, ,Returning from a Function}) to go back to the
5316 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5317 Different Address}) to go to an arbitrary location in your program.
5319 A typical technique for using stepping is to set a breakpoint
5320 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5321 beginning of the function or the section of your program where a problem
5322 is believed to lie, run your program until it stops at that breakpoint,
5323 and then step through the suspect area, examining the variables that are
5324 interesting, until you see the problem happen.
5328 @kindex s @r{(@code{step})}
5330 Continue running your program until control reaches a different source
5331 line, then stop it and return control to @value{GDBN}. This command is
5332 abbreviated @code{s}.
5335 @c "without debugging information" is imprecise; actually "without line
5336 @c numbers in the debugging information". (gcc -g1 has debugging info but
5337 @c not line numbers). But it seems complex to try to make that
5338 @c distinction here.
5339 @emph{Warning:} If you use the @code{step} command while control is
5340 within a function that was compiled without debugging information,
5341 execution proceeds until control reaches a function that does have
5342 debugging information. Likewise, it will not step into a function which
5343 is compiled without debugging information. To step through functions
5344 without debugging information, use the @code{stepi} command, described
5348 The @code{step} command only stops at the first instruction of a source
5349 line. This prevents the multiple stops that could otherwise occur in
5350 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5351 to stop if a function that has debugging information is called within
5352 the line. In other words, @code{step} @emph{steps inside} any functions
5353 called within the line.
5355 Also, the @code{step} command only enters a function if there is line
5356 number information for the function. Otherwise it acts like the
5357 @code{next} command. This avoids problems when using @code{cc -gl}
5358 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5359 was any debugging information about the routine.
5361 @item step @var{count}
5362 Continue running as in @code{step}, but do so @var{count} times. If a
5363 breakpoint is reached, or a signal not related to stepping occurs before
5364 @var{count} steps, stepping stops right away.
5367 @kindex n @r{(@code{next})}
5368 @item next @r{[}@var{count}@r{]}
5369 Continue to the next source line in the current (innermost) stack frame.
5370 This is similar to @code{step}, but function calls that appear within
5371 the line of code are executed without stopping. Execution stops when
5372 control reaches a different line of code at the original stack level
5373 that was executing when you gave the @code{next} command. This command
5374 is abbreviated @code{n}.
5376 An argument @var{count} is a repeat count, as for @code{step}.
5379 @c FIX ME!! Do we delete this, or is there a way it fits in with
5380 @c the following paragraph? --- Vctoria
5382 @c @code{next} within a function that lacks debugging information acts like
5383 @c @code{step}, but any function calls appearing within the code of the
5384 @c function are executed without stopping.
5386 The @code{next} command only stops at the first instruction of a
5387 source line. This prevents multiple stops that could otherwise occur in
5388 @code{switch} statements, @code{for} loops, etc.
5390 @kindex set step-mode
5392 @cindex functions without line info, and stepping
5393 @cindex stepping into functions with no line info
5394 @itemx set step-mode on
5395 The @code{set step-mode on} command causes the @code{step} command to
5396 stop at the first instruction of a function which contains no debug line
5397 information rather than stepping over it.
5399 This is useful in cases where you may be interested in inspecting the
5400 machine instructions of a function which has no symbolic info and do not
5401 want @value{GDBN} to automatically skip over this function.
5403 @item set step-mode off
5404 Causes the @code{step} command to step over any functions which contains no
5405 debug information. This is the default.
5407 @item show step-mode
5408 Show whether @value{GDBN} will stop in or step over functions without
5409 source line debug information.
5412 @kindex fin @r{(@code{finish})}
5414 Continue running until just after function in the selected stack frame
5415 returns. Print the returned value (if any). This command can be
5416 abbreviated as @code{fin}.
5418 Contrast this with the @code{return} command (@pxref{Returning,
5419 ,Returning from a Function}).
5422 @kindex u @r{(@code{until})}
5423 @cindex run until specified location
5426 Continue running until a source line past the current line, in the
5427 current stack frame, is reached. This command is used to avoid single
5428 stepping through a loop more than once. It is like the @code{next}
5429 command, except that when @code{until} encounters a jump, it
5430 automatically continues execution until the program counter is greater
5431 than the address of the jump.
5433 This means that when you reach the end of a loop after single stepping
5434 though it, @code{until} makes your program continue execution until it
5435 exits the loop. In contrast, a @code{next} command at the end of a loop
5436 simply steps back to the beginning of the loop, which forces you to step
5437 through the next iteration.
5439 @code{until} always stops your program if it attempts to exit the current
5442 @code{until} may produce somewhat counterintuitive results if the order
5443 of machine code does not match the order of the source lines. For
5444 example, in the following excerpt from a debugging session, the @code{f}
5445 (@code{frame}) command shows that execution is stopped at line
5446 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5450 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5452 (@value{GDBP}) until
5453 195 for ( ; argc > 0; NEXTARG) @{
5456 This happened because, for execution efficiency, the compiler had
5457 generated code for the loop closure test at the end, rather than the
5458 start, of the loop---even though the test in a C @code{for}-loop is
5459 written before the body of the loop. The @code{until} command appeared
5460 to step back to the beginning of the loop when it advanced to this
5461 expression; however, it has not really gone to an earlier
5462 statement---not in terms of the actual machine code.
5464 @code{until} with no argument works by means of single
5465 instruction stepping, and hence is slower than @code{until} with an
5468 @item until @var{location}
5469 @itemx u @var{location}
5470 Continue running your program until either the specified @var{location} is
5471 reached, or the current stack frame returns. The location is any of
5472 the forms described in @ref{Specify Location}.
5473 This form of the command uses temporary breakpoints, and
5474 hence is quicker than @code{until} without an argument. The specified
5475 location is actually reached only if it is in the current frame. This
5476 implies that @code{until} can be used to skip over recursive function
5477 invocations. For instance in the code below, if the current location is
5478 line @code{96}, issuing @code{until 99} will execute the program up to
5479 line @code{99} in the same invocation of factorial, i.e., after the inner
5480 invocations have returned.
5483 94 int factorial (int value)
5485 96 if (value > 1) @{
5486 97 value *= factorial (value - 1);
5493 @kindex advance @var{location}
5494 @item advance @var{location}
5495 Continue running the program up to the given @var{location}. An argument is
5496 required, which should be of one of the forms described in
5497 @ref{Specify Location}.
5498 Execution will also stop upon exit from the current stack
5499 frame. This command is similar to @code{until}, but @code{advance} will
5500 not skip over recursive function calls, and the target location doesn't
5501 have to be in the same frame as the current one.
5505 @kindex si @r{(@code{stepi})}
5507 @itemx stepi @var{arg}
5509 Execute one machine instruction, then stop and return to the debugger.
5511 It is often useful to do @samp{display/i $pc} when stepping by machine
5512 instructions. This makes @value{GDBN} automatically display the next
5513 instruction to be executed, each time your program stops. @xref{Auto
5514 Display,, Automatic Display}.
5516 An argument is a repeat count, as in @code{step}.
5520 @kindex ni @r{(@code{nexti})}
5522 @itemx nexti @var{arg}
5524 Execute one machine instruction, but if it is a function call,
5525 proceed until the function returns.
5527 An argument is a repeat count, as in @code{next}.
5531 @anchor{range stepping}
5532 @cindex range stepping
5533 @cindex target-assisted range stepping
5534 By default, and if available, @value{GDBN} makes use of
5535 target-assisted @dfn{range stepping}. In other words, whenever you
5536 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5537 tells the target to step the corresponding range of instruction
5538 addresses instead of issuing multiple single-steps. This speeds up
5539 line stepping, particularly for remote targets. Ideally, there should
5540 be no reason you would want to turn range stepping off. However, it's
5541 possible that a bug in the debug info, a bug in the remote stub (for
5542 remote targets), or even a bug in @value{GDBN} could make line
5543 stepping behave incorrectly when target-assisted range stepping is
5544 enabled. You can use the following command to turn off range stepping
5548 @kindex set range-stepping
5549 @kindex show range-stepping
5550 @item set range-stepping
5551 @itemx show range-stepping
5552 Control whether range stepping is enabled.
5554 If @code{on}, and the target supports it, @value{GDBN} tells the
5555 target to step a range of addresses itself, instead of issuing
5556 multiple single-steps. If @code{off}, @value{GDBN} always issues
5557 single-steps, even if range stepping is supported by the target. The
5558 default is @code{on}.
5562 @node Skipping Over Functions and Files
5563 @section Skipping Over Functions and Files
5564 @cindex skipping over functions and files
5566 The program you are debugging may contain some functions which are
5567 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5568 skip a function, all functions in a file or a particular function in
5569 a particular file when stepping.
5571 For example, consider the following C function:
5582 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5583 are not interested in stepping through @code{boring}. If you run @code{step}
5584 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5585 step over both @code{foo} and @code{boring}!
5587 One solution is to @code{step} into @code{boring} and use the @code{finish}
5588 command to immediately exit it. But this can become tedious if @code{boring}
5589 is called from many places.
5591 A more flexible solution is to execute @kbd{skip boring}. This instructs
5592 @value{GDBN} never to step into @code{boring}. Now when you execute
5593 @code{step} at line 103, you'll step over @code{boring} and directly into
5596 Functions may be skipped by providing either a function name, linespec
5597 (@pxref{Specify Location}), regular expression that matches the function's
5598 name, file name or a @code{glob}-style pattern that matches the file name.
5600 On Posix systems the form of the regular expression is
5601 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5602 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5603 expression is whatever is provided by the @code{regcomp} function of
5604 the underlying system.
5605 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5606 description of @code{glob}-style patterns.
5610 @item skip @r{[}@var{options}@r{]}
5611 The basic form of the @code{skip} command takes zero or more options
5612 that specify what to skip.
5613 The @var{options} argument is any useful combination of the following:
5616 @item -file @var{file}
5617 @itemx -fi @var{file}
5618 Functions in @var{file} will be skipped over when stepping.
5620 @item -gfile @var{file-glob-pattern}
5621 @itemx -gfi @var{file-glob-pattern}
5622 @cindex skipping over files via glob-style patterns
5623 Functions in files matching @var{file-glob-pattern} will be skipped
5627 (gdb) skip -gfi utils/*.c
5630 @item -function @var{linespec}
5631 @itemx -fu @var{linespec}
5632 Functions named by @var{linespec} or the function containing the line
5633 named by @var{linespec} will be skipped over when stepping.
5634 @xref{Specify Location}.
5636 @item -rfunction @var{regexp}
5637 @itemx -rfu @var{regexp}
5638 @cindex skipping over functions via regular expressions
5639 Functions whose name matches @var{regexp} will be skipped over when stepping.
5641 This form is useful for complex function names.
5642 For example, there is generally no need to step into C@t{++} @code{std::string}
5643 constructors or destructors. Plus with C@t{++} templates it can be hard to
5644 write out the full name of the function, and often it doesn't matter what
5645 the template arguments are. Specifying the function to be skipped as a
5646 regular expression makes this easier.
5649 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5652 If you want to skip every templated C@t{++} constructor and destructor
5653 in the @code{std} namespace you can do:
5656 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5660 If no options are specified, the function you're currently debugging
5663 @kindex skip function
5664 @item skip function @r{[}@var{linespec}@r{]}
5665 After running this command, the function named by @var{linespec} or the
5666 function containing the line named by @var{linespec} will be skipped over when
5667 stepping. @xref{Specify Location}.
5669 If you do not specify @var{linespec}, the function you're currently debugging
5672 (If you have a function called @code{file} that you want to skip, use
5673 @kbd{skip function file}.)
5676 @item skip file @r{[}@var{filename}@r{]}
5677 After running this command, any function whose source lives in @var{filename}
5678 will be skipped over when stepping.
5681 (gdb) skip file boring.c
5682 File boring.c will be skipped when stepping.
5685 If you do not specify @var{filename}, functions whose source lives in the file
5686 you're currently debugging will be skipped.
5689 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5690 These are the commands for managing your list of skips:
5694 @item info skip @r{[}@var{range}@r{]}
5695 Print details about the specified skip(s). If @var{range} is not specified,
5696 print a table with details about all functions and files marked for skipping.
5697 @code{info skip} prints the following information about each skip:
5701 A number identifying this skip.
5702 @item Enabled or Disabled
5703 Enabled skips are marked with @samp{y}.
5704 Disabled skips are marked with @samp{n}.
5706 If the file name is a @samp{glob} pattern this is @samp{y}.
5707 Otherwise it is @samp{n}.
5709 The name or @samp{glob} pattern of the file to be skipped.
5710 If no file is specified this is @samp{<none>}.
5712 If the function name is a @samp{regular expression} this is @samp{y}.
5713 Otherwise it is @samp{n}.
5715 The name or regular expression of the function to skip.
5716 If no function is specified this is @samp{<none>}.
5720 @item skip delete @r{[}@var{range}@r{]}
5721 Delete the specified skip(s). If @var{range} is not specified, delete all
5725 @item skip enable @r{[}@var{range}@r{]}
5726 Enable the specified skip(s). If @var{range} is not specified, enable all
5729 @kindex skip disable
5730 @item skip disable @r{[}@var{range}@r{]}
5731 Disable the specified skip(s). If @var{range} is not specified, disable all
5740 A signal is an asynchronous event that can happen in a program. The
5741 operating system defines the possible kinds of signals, and gives each
5742 kind a name and a number. For example, in Unix @code{SIGINT} is the
5743 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5744 @code{SIGSEGV} is the signal a program gets from referencing a place in
5745 memory far away from all the areas in use; @code{SIGALRM} occurs when
5746 the alarm clock timer goes off (which happens only if your program has
5747 requested an alarm).
5749 @cindex fatal signals
5750 Some signals, including @code{SIGALRM}, are a normal part of the
5751 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5752 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5753 program has not specified in advance some other way to handle the signal.
5754 @code{SIGINT} does not indicate an error in your program, but it is normally
5755 fatal so it can carry out the purpose of the interrupt: to kill the program.
5757 @value{GDBN} has the ability to detect any occurrence of a signal in your
5758 program. You can tell @value{GDBN} in advance what to do for each kind of
5761 @cindex handling signals
5762 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5763 @code{SIGALRM} be silently passed to your program
5764 (so as not to interfere with their role in the program's functioning)
5765 but to stop your program immediately whenever an error signal happens.
5766 You can change these settings with the @code{handle} command.
5769 @kindex info signals
5773 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5774 handle each one. You can use this to see the signal numbers of all
5775 the defined types of signals.
5777 @item info signals @var{sig}
5778 Similar, but print information only about the specified signal number.
5780 @code{info handle} is an alias for @code{info signals}.
5782 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5783 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5784 for details about this command.
5787 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5788 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5789 can be the number of a signal or its name (with or without the
5790 @samp{SIG} at the beginning); a list of signal numbers of the form
5791 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5792 known signals. Optional arguments @var{keywords}, described below,
5793 say what change to make.
5797 The keywords allowed by the @code{handle} command can be abbreviated.
5798 Their full names are:
5802 @value{GDBN} should not stop your program when this signal happens. It may
5803 still print a message telling you that the signal has come in.
5806 @value{GDBN} should stop your program when this signal happens. This implies
5807 the @code{print} keyword as well.
5810 @value{GDBN} should print a message when this signal happens.
5813 @value{GDBN} should not mention the occurrence of the signal at all. This
5814 implies the @code{nostop} keyword as well.
5818 @value{GDBN} should allow your program to see this signal; your program
5819 can handle the signal, or else it may terminate if the signal is fatal
5820 and not handled. @code{pass} and @code{noignore} are synonyms.
5824 @value{GDBN} should not allow your program to see this signal.
5825 @code{nopass} and @code{ignore} are synonyms.
5829 When a signal stops your program, the signal is not visible to the
5831 continue. Your program sees the signal then, if @code{pass} is in
5832 effect for the signal in question @emph{at that time}. In other words,
5833 after @value{GDBN} reports a signal, you can use the @code{handle}
5834 command with @code{pass} or @code{nopass} to control whether your
5835 program sees that signal when you continue.
5837 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5838 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5839 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5842 You can also use the @code{signal} command to prevent your program from
5843 seeing a signal, or cause it to see a signal it normally would not see,
5844 or to give it any signal at any time. For example, if your program stopped
5845 due to some sort of memory reference error, you might store correct
5846 values into the erroneous variables and continue, hoping to see more
5847 execution; but your program would probably terminate immediately as
5848 a result of the fatal signal once it saw the signal. To prevent this,
5849 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5852 @cindex stepping and signal handlers
5853 @anchor{stepping and signal handlers}
5855 @value{GDBN} optimizes for stepping the mainline code. If a signal
5856 that has @code{handle nostop} and @code{handle pass} set arrives while
5857 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5858 in progress, @value{GDBN} lets the signal handler run and then resumes
5859 stepping the mainline code once the signal handler returns. In other
5860 words, @value{GDBN} steps over the signal handler. This prevents
5861 signals that you've specified as not interesting (with @code{handle
5862 nostop}) from changing the focus of debugging unexpectedly. Note that
5863 the signal handler itself may still hit a breakpoint, stop for another
5864 signal that has @code{handle stop} in effect, or for any other event
5865 that normally results in stopping the stepping command sooner. Also
5866 note that @value{GDBN} still informs you that the program received a
5867 signal if @code{handle print} is set.
5869 @anchor{stepping into signal handlers}
5871 If you set @code{handle pass} for a signal, and your program sets up a
5872 handler for it, then issuing a stepping command, such as @code{step}
5873 or @code{stepi}, when your program is stopped due to the signal will
5874 step @emph{into} the signal handler (if the target supports that).
5876 Likewise, if you use the @code{queue-signal} command to queue a signal
5877 to be delivered to the current thread when execution of the thread
5878 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5879 stepping command will step into the signal handler.
5881 Here's an example, using @code{stepi} to step to the first instruction
5882 of @code{SIGUSR1}'s handler:
5885 (@value{GDBP}) handle SIGUSR1
5886 Signal Stop Print Pass to program Description
5887 SIGUSR1 Yes Yes Yes User defined signal 1
5891 Program received signal SIGUSR1, User defined signal 1.
5892 main () sigusr1.c:28
5895 sigusr1_handler () at sigusr1.c:9
5899 The same, but using @code{queue-signal} instead of waiting for the
5900 program to receive the signal first:
5905 (@value{GDBP}) queue-signal SIGUSR1
5907 sigusr1_handler () at sigusr1.c:9
5912 @cindex extra signal information
5913 @anchor{extra signal information}
5915 On some targets, @value{GDBN} can inspect extra signal information
5916 associated with the intercepted signal, before it is actually
5917 delivered to the program being debugged. This information is exported
5918 by the convenience variable @code{$_siginfo}, and consists of data
5919 that is passed by the kernel to the signal handler at the time of the
5920 receipt of a signal. The data type of the information itself is
5921 target dependent. You can see the data type using the @code{ptype
5922 $_siginfo} command. On Unix systems, it typically corresponds to the
5923 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5926 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5927 referenced address that raised a segmentation fault.
5931 (@value{GDBP}) continue
5932 Program received signal SIGSEGV, Segmentation fault.
5933 0x0000000000400766 in main ()
5935 (@value{GDBP}) ptype $_siginfo
5942 struct @{...@} _kill;
5943 struct @{...@} _timer;
5945 struct @{...@} _sigchld;
5946 struct @{...@} _sigfault;
5947 struct @{...@} _sigpoll;
5950 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5954 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5955 $1 = (void *) 0x7ffff7ff7000
5959 Depending on target support, @code{$_siginfo} may also be writable.
5961 @cindex Intel MPX boundary violations
5962 @cindex boundary violations, Intel MPX
5963 On some targets, a @code{SIGSEGV} can be caused by a boundary
5964 violation, i.e., accessing an address outside of the allowed range.
5965 In those cases @value{GDBN} may displays additional information,
5966 depending on how @value{GDBN} has been told to handle the signal.
5967 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
5968 kind: "Upper" or "Lower", the memory address accessed and the
5969 bounds, while with @code{handle nostop SIGSEGV} no additional
5970 information is displayed.
5972 The usual output of a segfault is:
5974 Program received signal SIGSEGV, Segmentation fault
5975 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5976 68 value = *(p + len);
5979 While a bound violation is presented as:
5981 Program received signal SIGSEGV, Segmentation fault
5982 Upper bound violation while accessing address 0x7fffffffc3b3
5983 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
5984 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
5985 68 value = *(p + len);
5989 @section Stopping and Starting Multi-thread Programs
5991 @cindex stopped threads
5992 @cindex threads, stopped
5994 @cindex continuing threads
5995 @cindex threads, continuing
5997 @value{GDBN} supports debugging programs with multiple threads
5998 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5999 are two modes of controlling execution of your program within the
6000 debugger. In the default mode, referred to as @dfn{all-stop mode},
6001 when any thread in your program stops (for example, at a breakpoint
6002 or while being stepped), all other threads in the program are also stopped by
6003 @value{GDBN}. On some targets, @value{GDBN} also supports
6004 @dfn{non-stop mode}, in which other threads can continue to run freely while
6005 you examine the stopped thread in the debugger.
6008 * All-Stop Mode:: All threads stop when GDB takes control
6009 * Non-Stop Mode:: Other threads continue to execute
6010 * Background Execution:: Running your program asynchronously
6011 * Thread-Specific Breakpoints:: Controlling breakpoints
6012 * Interrupted System Calls:: GDB may interfere with system calls
6013 * Observer Mode:: GDB does not alter program behavior
6017 @subsection All-Stop Mode
6019 @cindex all-stop mode
6021 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6022 @emph{all} threads of execution stop, not just the current thread. This
6023 allows you to examine the overall state of the program, including
6024 switching between threads, without worrying that things may change
6027 Conversely, whenever you restart the program, @emph{all} threads start
6028 executing. @emph{This is true even when single-stepping} with commands
6029 like @code{step} or @code{next}.
6031 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6032 Since thread scheduling is up to your debugging target's operating
6033 system (not controlled by @value{GDBN}), other threads may
6034 execute more than one statement while the current thread completes a
6035 single step. Moreover, in general other threads stop in the middle of a
6036 statement, rather than at a clean statement boundary, when the program
6039 You might even find your program stopped in another thread after
6040 continuing or even single-stepping. This happens whenever some other
6041 thread runs into a breakpoint, a signal, or an exception before the
6042 first thread completes whatever you requested.
6044 @cindex automatic thread selection
6045 @cindex switching threads automatically
6046 @cindex threads, automatic switching
6047 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6048 signal, it automatically selects the thread where that breakpoint or
6049 signal happened. @value{GDBN} alerts you to the context switch with a
6050 message such as @samp{[Switching to Thread @var{n}]} to identify the
6053 On some OSes, you can modify @value{GDBN}'s default behavior by
6054 locking the OS scheduler to allow only a single thread to run.
6057 @item set scheduler-locking @var{mode}
6058 @cindex scheduler locking mode
6059 @cindex lock scheduler
6060 Set the scheduler locking mode. It applies to normal execution,
6061 record mode, and replay mode. If it is @code{off}, then there is no
6062 locking and any thread may run at any time. If @code{on}, then only
6063 the current thread may run when the inferior is resumed. The
6064 @code{step} mode optimizes for single-stepping; it prevents other
6065 threads from preempting the current thread while you are stepping, so
6066 that the focus of debugging does not change unexpectedly. Other
6067 threads never get a chance to run when you step, and they are
6068 completely free to run when you use commands like @samp{continue},
6069 @samp{until}, or @samp{finish}. However, unless another thread hits a
6070 breakpoint during its timeslice, @value{GDBN} does not change the
6071 current thread away from the thread that you are debugging. The
6072 @code{replay} mode behaves like @code{off} in record mode and like
6073 @code{on} in replay mode.
6075 @item show scheduler-locking
6076 Display the current scheduler locking mode.
6079 @cindex resume threads of multiple processes simultaneously
6080 By default, when you issue one of the execution commands such as
6081 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6082 threads of the current inferior to run. For example, if @value{GDBN}
6083 is attached to two inferiors, each with two threads, the
6084 @code{continue} command resumes only the two threads of the current
6085 inferior. This is useful, for example, when you debug a program that
6086 forks and you want to hold the parent stopped (so that, for instance,
6087 it doesn't run to exit), while you debug the child. In other
6088 situations, you may not be interested in inspecting the current state
6089 of any of the processes @value{GDBN} is attached to, and you may want
6090 to resume them all until some breakpoint is hit. In the latter case,
6091 you can instruct @value{GDBN} to allow all threads of all the
6092 inferiors to run with the @w{@code{set schedule-multiple}} command.
6095 @kindex set schedule-multiple
6096 @item set schedule-multiple
6097 Set the mode for allowing threads of multiple processes to be resumed
6098 when an execution command is issued. When @code{on}, all threads of
6099 all processes are allowed to run. When @code{off}, only the threads
6100 of the current process are resumed. The default is @code{off}. The
6101 @code{scheduler-locking} mode takes precedence when set to @code{on},
6102 or while you are stepping and set to @code{step}.
6104 @item show schedule-multiple
6105 Display the current mode for resuming the execution of threads of
6110 @subsection Non-Stop Mode
6112 @cindex non-stop mode
6114 @c This section is really only a place-holder, and needs to be expanded
6115 @c with more details.
6117 For some multi-threaded targets, @value{GDBN} supports an optional
6118 mode of operation in which you can examine stopped program threads in
6119 the debugger while other threads continue to execute freely. This
6120 minimizes intrusion when debugging live systems, such as programs
6121 where some threads have real-time constraints or must continue to
6122 respond to external events. This is referred to as @dfn{non-stop} mode.
6124 In non-stop mode, when a thread stops to report a debugging event,
6125 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6126 threads as well, in contrast to the all-stop mode behavior. Additionally,
6127 execution commands such as @code{continue} and @code{step} apply by default
6128 only to the current thread in non-stop mode, rather than all threads as
6129 in all-stop mode. This allows you to control threads explicitly in
6130 ways that are not possible in all-stop mode --- for example, stepping
6131 one thread while allowing others to run freely, stepping
6132 one thread while holding all others stopped, or stepping several threads
6133 independently and simultaneously.
6135 To enter non-stop mode, use this sequence of commands before you run
6136 or attach to your program:
6139 # If using the CLI, pagination breaks non-stop.
6142 # Finally, turn it on!
6146 You can use these commands to manipulate the non-stop mode setting:
6149 @kindex set non-stop
6150 @item set non-stop on
6151 Enable selection of non-stop mode.
6152 @item set non-stop off
6153 Disable selection of non-stop mode.
6154 @kindex show non-stop
6156 Show the current non-stop enablement setting.
6159 Note these commands only reflect whether non-stop mode is enabled,
6160 not whether the currently-executing program is being run in non-stop mode.
6161 In particular, the @code{set non-stop} preference is only consulted when
6162 @value{GDBN} starts or connects to the target program, and it is generally
6163 not possible to switch modes once debugging has started. Furthermore,
6164 since not all targets support non-stop mode, even when you have enabled
6165 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6168 In non-stop mode, all execution commands apply only to the current thread
6169 by default. That is, @code{continue} only continues one thread.
6170 To continue all threads, issue @code{continue -a} or @code{c -a}.
6172 You can use @value{GDBN}'s background execution commands
6173 (@pxref{Background Execution}) to run some threads in the background
6174 while you continue to examine or step others from @value{GDBN}.
6175 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6176 always executed asynchronously in non-stop mode.
6178 Suspending execution is done with the @code{interrupt} command when
6179 running in the background, or @kbd{Ctrl-c} during foreground execution.
6180 In all-stop mode, this stops the whole process;
6181 but in non-stop mode the interrupt applies only to the current thread.
6182 To stop the whole program, use @code{interrupt -a}.
6184 Other execution commands do not currently support the @code{-a} option.
6186 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6187 that thread current, as it does in all-stop mode. This is because the
6188 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6189 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6190 changed to a different thread just as you entered a command to operate on the
6191 previously current thread.
6193 @node Background Execution
6194 @subsection Background Execution
6196 @cindex foreground execution
6197 @cindex background execution
6198 @cindex asynchronous execution
6199 @cindex execution, foreground, background and asynchronous
6201 @value{GDBN}'s execution commands have two variants: the normal
6202 foreground (synchronous) behavior, and a background
6203 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6204 the program to report that some thread has stopped before prompting for
6205 another command. In background execution, @value{GDBN} immediately gives
6206 a command prompt so that you can issue other commands while your program runs.
6208 If the target doesn't support async mode, @value{GDBN} issues an error
6209 message if you attempt to use the background execution commands.
6211 To specify background execution, add a @code{&} to the command. For example,
6212 the background form of the @code{continue} command is @code{continue&}, or
6213 just @code{c&}. The execution commands that accept background execution
6219 @xref{Starting, , Starting your Program}.
6223 @xref{Attach, , Debugging an Already-running Process}.
6227 @xref{Continuing and Stepping, step}.
6231 @xref{Continuing and Stepping, stepi}.
6235 @xref{Continuing and Stepping, next}.
6239 @xref{Continuing and Stepping, nexti}.
6243 @xref{Continuing and Stepping, continue}.
6247 @xref{Continuing and Stepping, finish}.
6251 @xref{Continuing and Stepping, until}.
6255 Background execution is especially useful in conjunction with non-stop
6256 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6257 However, you can also use these commands in the normal all-stop mode with
6258 the restriction that you cannot issue another execution command until the
6259 previous one finishes. Examples of commands that are valid in all-stop
6260 mode while the program is running include @code{help} and @code{info break}.
6262 You can interrupt your program while it is running in the background by
6263 using the @code{interrupt} command.
6270 Suspend execution of the running program. In all-stop mode,
6271 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6272 only the current thread. To stop the whole program in non-stop mode,
6273 use @code{interrupt -a}.
6276 @node Thread-Specific Breakpoints
6277 @subsection Thread-Specific Breakpoints
6279 When your program has multiple threads (@pxref{Threads,, Debugging
6280 Programs with Multiple Threads}), you can choose whether to set
6281 breakpoints on all threads, or on a particular thread.
6284 @cindex breakpoints and threads
6285 @cindex thread breakpoints
6286 @kindex break @dots{} thread @var{thread-id}
6287 @item break @var{location} thread @var{thread-id}
6288 @itemx break @var{location} thread @var{thread-id} if @dots{}
6289 @var{location} specifies source lines; there are several ways of
6290 writing them (@pxref{Specify Location}), but the effect is always to
6291 specify some source line.
6293 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6294 to specify that you only want @value{GDBN} to stop the program when a
6295 particular thread reaches this breakpoint. The @var{thread-id} specifier
6296 is one of the thread identifiers assigned by @value{GDBN}, shown
6297 in the first column of the @samp{info threads} display.
6299 If you do not specify @samp{thread @var{thread-id}} when you set a
6300 breakpoint, the breakpoint applies to @emph{all} threads of your
6303 You can use the @code{thread} qualifier on conditional breakpoints as
6304 well; in this case, place @samp{thread @var{thread-id}} before or
6305 after the breakpoint condition, like this:
6308 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6313 Thread-specific breakpoints are automatically deleted when
6314 @value{GDBN} detects the corresponding thread is no longer in the
6315 thread list. For example:
6319 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6322 There are several ways for a thread to disappear, such as a regular
6323 thread exit, but also when you detach from the process with the
6324 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6325 Process}), or if @value{GDBN} loses the remote connection
6326 (@pxref{Remote Debugging}), etc. Note that with some targets,
6327 @value{GDBN} is only able to detect a thread has exited when the user
6328 explictly asks for the thread list with the @code{info threads}
6331 @node Interrupted System Calls
6332 @subsection Interrupted System Calls
6334 @cindex thread breakpoints and system calls
6335 @cindex system calls and thread breakpoints
6336 @cindex premature return from system calls
6337 There is an unfortunate side effect when using @value{GDBN} to debug
6338 multi-threaded programs. If one thread stops for a
6339 breakpoint, or for some other reason, and another thread is blocked in a
6340 system call, then the system call may return prematurely. This is a
6341 consequence of the interaction between multiple threads and the signals
6342 that @value{GDBN} uses to implement breakpoints and other events that
6345 To handle this problem, your program should check the return value of
6346 each system call and react appropriately. This is good programming
6349 For example, do not write code like this:
6355 The call to @code{sleep} will return early if a different thread stops
6356 at a breakpoint or for some other reason.
6358 Instead, write this:
6363 unslept = sleep (unslept);
6366 A system call is allowed to return early, so the system is still
6367 conforming to its specification. But @value{GDBN} does cause your
6368 multi-threaded program to behave differently than it would without
6371 Also, @value{GDBN} uses internal breakpoints in the thread library to
6372 monitor certain events such as thread creation and thread destruction.
6373 When such an event happens, a system call in another thread may return
6374 prematurely, even though your program does not appear to stop.
6377 @subsection Observer Mode
6379 If you want to build on non-stop mode and observe program behavior
6380 without any chance of disruption by @value{GDBN}, you can set
6381 variables to disable all of the debugger's attempts to modify state,
6382 whether by writing memory, inserting breakpoints, etc. These operate
6383 at a low level, intercepting operations from all commands.
6385 When all of these are set to @code{off}, then @value{GDBN} is said to
6386 be @dfn{observer mode}. As a convenience, the variable
6387 @code{observer} can be set to disable these, plus enable non-stop
6390 Note that @value{GDBN} will not prevent you from making nonsensical
6391 combinations of these settings. For instance, if you have enabled
6392 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6393 then breakpoints that work by writing trap instructions into the code
6394 stream will still not be able to be placed.
6399 @item set observer on
6400 @itemx set observer off
6401 When set to @code{on}, this disables all the permission variables
6402 below (except for @code{insert-fast-tracepoints}), plus enables
6403 non-stop debugging. Setting this to @code{off} switches back to
6404 normal debugging, though remaining in non-stop mode.
6407 Show whether observer mode is on or off.
6409 @kindex may-write-registers
6410 @item set may-write-registers on
6411 @itemx set may-write-registers off
6412 This controls whether @value{GDBN} will attempt to alter the values of
6413 registers, such as with assignment expressions in @code{print}, or the
6414 @code{jump} command. It defaults to @code{on}.
6416 @item show may-write-registers
6417 Show the current permission to write registers.
6419 @kindex may-write-memory
6420 @item set may-write-memory on
6421 @itemx set may-write-memory off
6422 This controls whether @value{GDBN} will attempt to alter the contents
6423 of memory, such as with assignment expressions in @code{print}. It
6424 defaults to @code{on}.
6426 @item show may-write-memory
6427 Show the current permission to write memory.
6429 @kindex may-insert-breakpoints
6430 @item set may-insert-breakpoints on
6431 @itemx set may-insert-breakpoints off
6432 This controls whether @value{GDBN} will attempt to insert breakpoints.
6433 This affects all breakpoints, including internal breakpoints defined
6434 by @value{GDBN}. It defaults to @code{on}.
6436 @item show may-insert-breakpoints
6437 Show the current permission to insert breakpoints.
6439 @kindex may-insert-tracepoints
6440 @item set may-insert-tracepoints on
6441 @itemx set may-insert-tracepoints off
6442 This controls whether @value{GDBN} will attempt to insert (regular)
6443 tracepoints at the beginning of a tracing experiment. It affects only
6444 non-fast tracepoints, fast tracepoints being under the control of
6445 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6447 @item show may-insert-tracepoints
6448 Show the current permission to insert tracepoints.
6450 @kindex may-insert-fast-tracepoints
6451 @item set may-insert-fast-tracepoints on
6452 @itemx set may-insert-fast-tracepoints off
6453 This controls whether @value{GDBN} will attempt to insert fast
6454 tracepoints at the beginning of a tracing experiment. It affects only
6455 fast tracepoints, regular (non-fast) tracepoints being under the
6456 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6458 @item show may-insert-fast-tracepoints
6459 Show the current permission to insert fast tracepoints.
6461 @kindex may-interrupt
6462 @item set may-interrupt on
6463 @itemx set may-interrupt off
6464 This controls whether @value{GDBN} will attempt to interrupt or stop
6465 program execution. When this variable is @code{off}, the
6466 @code{interrupt} command will have no effect, nor will
6467 @kbd{Ctrl-c}. It defaults to @code{on}.
6469 @item show may-interrupt
6470 Show the current permission to interrupt or stop the program.
6474 @node Reverse Execution
6475 @chapter Running programs backward
6476 @cindex reverse execution
6477 @cindex running programs backward
6479 When you are debugging a program, it is not unusual to realize that
6480 you have gone too far, and some event of interest has already happened.
6481 If the target environment supports it, @value{GDBN} can allow you to
6482 ``rewind'' the program by running it backward.
6484 A target environment that supports reverse execution should be able
6485 to ``undo'' the changes in machine state that have taken place as the
6486 program was executing normally. Variables, registers etc.@: should
6487 revert to their previous values. Obviously this requires a great
6488 deal of sophistication on the part of the target environment; not
6489 all target environments can support reverse execution.
6491 When a program is executed in reverse, the instructions that
6492 have most recently been executed are ``un-executed'', in reverse
6493 order. The program counter runs backward, following the previous
6494 thread of execution in reverse. As each instruction is ``un-executed'',
6495 the values of memory and/or registers that were changed by that
6496 instruction are reverted to their previous states. After executing
6497 a piece of source code in reverse, all side effects of that code
6498 should be ``undone'', and all variables should be returned to their
6499 prior values@footnote{
6500 Note that some side effects are easier to undo than others. For instance,
6501 memory and registers are relatively easy, but device I/O is hard. Some
6502 targets may be able undo things like device I/O, and some may not.
6504 The contract between @value{GDBN} and the reverse executing target
6505 requires only that the target do something reasonable when
6506 @value{GDBN} tells it to execute backwards, and then report the
6507 results back to @value{GDBN}. Whatever the target reports back to
6508 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6509 assumes that the memory and registers that the target reports are in a
6510 consistant state, but @value{GDBN} accepts whatever it is given.
6513 If you are debugging in a target environment that supports
6514 reverse execution, @value{GDBN} provides the following commands.
6517 @kindex reverse-continue
6518 @kindex rc @r{(@code{reverse-continue})}
6519 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6520 @itemx rc @r{[}@var{ignore-count}@r{]}
6521 Beginning at the point where your program last stopped, start executing
6522 in reverse. Reverse execution will stop for breakpoints and synchronous
6523 exceptions (signals), just like normal execution. Behavior of
6524 asynchronous signals depends on the target environment.
6526 @kindex reverse-step
6527 @kindex rs @r{(@code{step})}
6528 @item reverse-step @r{[}@var{count}@r{]}
6529 Run the program backward until control reaches the start of a
6530 different source line; then stop it, and return control to @value{GDBN}.
6532 Like the @code{step} command, @code{reverse-step} will only stop
6533 at the beginning of a source line. It ``un-executes'' the previously
6534 executed source line. If the previous source line included calls to
6535 debuggable functions, @code{reverse-step} will step (backward) into
6536 the called function, stopping at the beginning of the @emph{last}
6537 statement in the called function (typically a return statement).
6539 Also, as with the @code{step} command, if non-debuggable functions are
6540 called, @code{reverse-step} will run thru them backward without stopping.
6542 @kindex reverse-stepi
6543 @kindex rsi @r{(@code{reverse-stepi})}
6544 @item reverse-stepi @r{[}@var{count}@r{]}
6545 Reverse-execute one machine instruction. Note that the instruction
6546 to be reverse-executed is @emph{not} the one pointed to by the program
6547 counter, but the instruction executed prior to that one. For instance,
6548 if the last instruction was a jump, @code{reverse-stepi} will take you
6549 back from the destination of the jump to the jump instruction itself.
6551 @kindex reverse-next
6552 @kindex rn @r{(@code{reverse-next})}
6553 @item reverse-next @r{[}@var{count}@r{]}
6554 Run backward to the beginning of the previous line executed in
6555 the current (innermost) stack frame. If the line contains function
6556 calls, they will be ``un-executed'' without stopping. Starting from
6557 the first line of a function, @code{reverse-next} will take you back
6558 to the caller of that function, @emph{before} the function was called,
6559 just as the normal @code{next} command would take you from the last
6560 line of a function back to its return to its caller
6561 @footnote{Unless the code is too heavily optimized.}.
6563 @kindex reverse-nexti
6564 @kindex rni @r{(@code{reverse-nexti})}
6565 @item reverse-nexti @r{[}@var{count}@r{]}
6566 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6567 in reverse, except that called functions are ``un-executed'' atomically.
6568 That is, if the previously executed instruction was a return from
6569 another function, @code{reverse-nexti} will continue to execute
6570 in reverse until the call to that function (from the current stack
6573 @kindex reverse-finish
6574 @item reverse-finish
6575 Just as the @code{finish} command takes you to the point where the
6576 current function returns, @code{reverse-finish} takes you to the point
6577 where it was called. Instead of ending up at the end of the current
6578 function invocation, you end up at the beginning.
6580 @kindex set exec-direction
6581 @item set exec-direction
6582 Set the direction of target execution.
6583 @item set exec-direction reverse
6584 @cindex execute forward or backward in time
6585 @value{GDBN} will perform all execution commands in reverse, until the
6586 exec-direction mode is changed to ``forward''. Affected commands include
6587 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6588 command cannot be used in reverse mode.
6589 @item set exec-direction forward
6590 @value{GDBN} will perform all execution commands in the normal fashion.
6591 This is the default.
6595 @node Process Record and Replay
6596 @chapter Recording Inferior's Execution and Replaying It
6597 @cindex process record and replay
6598 @cindex recording inferior's execution and replaying it
6600 On some platforms, @value{GDBN} provides a special @dfn{process record
6601 and replay} target that can record a log of the process execution, and
6602 replay it later with both forward and reverse execution commands.
6605 When this target is in use, if the execution log includes the record
6606 for the next instruction, @value{GDBN} will debug in @dfn{replay
6607 mode}. In the replay mode, the inferior does not really execute code
6608 instructions. Instead, all the events that normally happen during
6609 code execution are taken from the execution log. While code is not
6610 really executed in replay mode, the values of registers (including the
6611 program counter register) and the memory of the inferior are still
6612 changed as they normally would. Their contents are taken from the
6616 If the record for the next instruction is not in the execution log,
6617 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6618 inferior executes normally, and @value{GDBN} records the execution log
6621 The process record and replay target supports reverse execution
6622 (@pxref{Reverse Execution}), even if the platform on which the
6623 inferior runs does not. However, the reverse execution is limited in
6624 this case by the range of the instructions recorded in the execution
6625 log. In other words, reverse execution on platforms that don't
6626 support it directly can only be done in the replay mode.
6628 When debugging in the reverse direction, @value{GDBN} will work in
6629 replay mode as long as the execution log includes the record for the
6630 previous instruction; otherwise, it will work in record mode, if the
6631 platform supports reverse execution, or stop if not.
6633 For architecture environments that support process record and replay,
6634 @value{GDBN} provides the following commands:
6637 @kindex target record
6638 @kindex target record-full
6639 @kindex target record-btrace
6642 @kindex record btrace
6643 @kindex record btrace bts
6644 @kindex record btrace pt
6650 @kindex rec btrace bts
6651 @kindex rec btrace pt
6654 @item record @var{method}
6655 This command starts the process record and replay target. The
6656 recording method can be specified as parameter. Without a parameter
6657 the command uses the @code{full} recording method. The following
6658 recording methods are available:
6662 Full record/replay recording using @value{GDBN}'s software record and
6663 replay implementation. This method allows replaying and reverse
6666 @item btrace @var{format}
6667 Hardware-supported instruction recording. This method does not record
6668 data. Further, the data is collected in a ring buffer so old data will
6669 be overwritten when the buffer is full. It allows limited reverse
6670 execution. Variables and registers are not available during reverse
6671 execution. In remote debugging, recording continues on disconnect.
6672 Recorded data can be inspected after reconnecting. The recording may
6673 be stopped using @code{record stop}.
6675 The recording format can be specified as parameter. Without a parameter
6676 the command chooses the recording format. The following recording
6677 formats are available:
6681 @cindex branch trace store
6682 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6683 this format, the processor stores a from/to record for each executed
6684 branch in the btrace ring buffer.
6687 @cindex Intel Processor Trace
6688 Use the @dfn{Intel Processor Trace} recording format. In this
6689 format, the processor stores the execution trace in a compressed form
6690 that is afterwards decoded by @value{GDBN}.
6692 The trace can be recorded with very low overhead. The compressed
6693 trace format also allows small trace buffers to already contain a big
6694 number of instructions compared to @acronym{BTS}.
6696 Decoding the recorded execution trace, on the other hand, is more
6697 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6698 increased number of instructions to process. You should increase the
6699 buffer-size with care.
6702 Not all recording formats may be available on all processors.
6705 The process record and replay target can only debug a process that is
6706 already running. Therefore, you need first to start the process with
6707 the @kbd{run} or @kbd{start} commands, and then start the recording
6708 with the @kbd{record @var{method}} command.
6710 @cindex displaced stepping, and process record and replay
6711 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6712 will be automatically disabled when process record and replay target
6713 is started. That's because the process record and replay target
6714 doesn't support displaced stepping.
6716 @cindex non-stop mode, and process record and replay
6717 @cindex asynchronous execution, and process record and replay
6718 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6719 the asynchronous execution mode (@pxref{Background Execution}), not
6720 all recording methods are available. The @code{full} recording method
6721 does not support these two modes.
6726 Stop the process record and replay target. When process record and
6727 replay target stops, the entire execution log will be deleted and the
6728 inferior will either be terminated, or will remain in its final state.
6730 When you stop the process record and replay target in record mode (at
6731 the end of the execution log), the inferior will be stopped at the
6732 next instruction that would have been recorded. In other words, if
6733 you record for a while and then stop recording, the inferior process
6734 will be left in the same state as if the recording never happened.
6736 On the other hand, if the process record and replay target is stopped
6737 while in replay mode (that is, not at the end of the execution log,
6738 but at some earlier point), the inferior process will become ``live''
6739 at that earlier state, and it will then be possible to continue the
6740 usual ``live'' debugging of the process from that state.
6742 When the inferior process exits, or @value{GDBN} detaches from it,
6743 process record and replay target will automatically stop itself.
6747 Go to a specific location in the execution log. There are several
6748 ways to specify the location to go to:
6751 @item record goto begin
6752 @itemx record goto start
6753 Go to the beginning of the execution log.
6755 @item record goto end
6756 Go to the end of the execution log.
6758 @item record goto @var{n}
6759 Go to instruction number @var{n} in the execution log.
6763 @item record save @var{filename}
6764 Save the execution log to a file @file{@var{filename}}.
6765 Default filename is @file{gdb_record.@var{process_id}}, where
6766 @var{process_id} is the process ID of the inferior.
6768 This command may not be available for all recording methods.
6770 @kindex record restore
6771 @item record restore @var{filename}
6772 Restore the execution log from a file @file{@var{filename}}.
6773 File must have been created with @code{record save}.
6775 @kindex set record full
6776 @item set record full insn-number-max @var{limit}
6777 @itemx set record full insn-number-max unlimited
6778 Set the limit of instructions to be recorded for the @code{full}
6779 recording method. Default value is 200000.
6781 If @var{limit} is a positive number, then @value{GDBN} will start
6782 deleting instructions from the log once the number of the record
6783 instructions becomes greater than @var{limit}. For every new recorded
6784 instruction, @value{GDBN} will delete the earliest recorded
6785 instruction to keep the number of recorded instructions at the limit.
6786 (Since deleting recorded instructions loses information, @value{GDBN}
6787 lets you control what happens when the limit is reached, by means of
6788 the @code{stop-at-limit} option, described below.)
6790 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6791 delete recorded instructions from the execution log. The number of
6792 recorded instructions is limited only by the available memory.
6794 @kindex show record full
6795 @item show record full insn-number-max
6796 Show the limit of instructions to be recorded with the @code{full}
6799 @item set record full stop-at-limit
6800 Control the behavior of the @code{full} recording method when the
6801 number of recorded instructions reaches the limit. If ON (the
6802 default), @value{GDBN} will stop when the limit is reached for the
6803 first time and ask you whether you want to stop the inferior or
6804 continue running it and recording the execution log. If you decide
6805 to continue recording, each new recorded instruction will cause the
6806 oldest one to be deleted.
6808 If this option is OFF, @value{GDBN} will automatically delete the
6809 oldest record to make room for each new one, without asking.
6811 @item show record full stop-at-limit
6812 Show the current setting of @code{stop-at-limit}.
6814 @item set record full memory-query
6815 Control the behavior when @value{GDBN} is unable to record memory
6816 changes caused by an instruction for the @code{full} recording method.
6817 If ON, @value{GDBN} will query whether to stop the inferior in that
6820 If this option is OFF (the default), @value{GDBN} will automatically
6821 ignore the effect of such instructions on memory. Later, when
6822 @value{GDBN} replays this execution log, it will mark the log of this
6823 instruction as not accessible, and it will not affect the replay
6826 @item show record full memory-query
6827 Show the current setting of @code{memory-query}.
6829 @kindex set record btrace
6830 The @code{btrace} record target does not trace data. As a
6831 convenience, when replaying, @value{GDBN} reads read-only memory off
6832 the live program directly, assuming that the addresses of the
6833 read-only areas don't change. This for example makes it possible to
6834 disassemble code while replaying, but not to print variables.
6835 In some cases, being able to inspect variables might be useful.
6836 You can use the following command for that:
6838 @item set record btrace replay-memory-access
6839 Control the behavior of the @code{btrace} recording method when
6840 accessing memory during replay. If @code{read-only} (the default),
6841 @value{GDBN} will only allow accesses to read-only memory.
6842 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6843 and to read-write memory. Beware that the accessed memory corresponds
6844 to the live target and not necessarily to the current replay
6847 @kindex show record btrace
6848 @item show record btrace replay-memory-access
6849 Show the current setting of @code{replay-memory-access}.
6851 @kindex set record btrace bts
6852 @item set record btrace bts buffer-size @var{size}
6853 @itemx set record btrace bts buffer-size unlimited
6854 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6855 format. Default is 64KB.
6857 If @var{size} is a positive number, then @value{GDBN} will try to
6858 allocate a buffer of at least @var{size} bytes for each new thread
6859 that uses the btrace recording method and the @acronym{BTS} format.
6860 The actually obtained buffer size may differ from the requested
6861 @var{size}. Use the @code{info record} command to see the actual
6862 buffer size for each thread that uses the btrace recording method and
6863 the @acronym{BTS} format.
6865 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6866 allocate a buffer of 4MB.
6868 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6869 also need longer to process the branch trace data before it can be used.
6871 @item show record btrace bts buffer-size @var{size}
6872 Show the current setting of the requested ring buffer size for branch
6873 tracing in @acronym{BTS} format.
6875 @kindex set record btrace pt
6876 @item set record btrace pt buffer-size @var{size}
6877 @itemx set record btrace pt buffer-size unlimited
6878 Set the requested ring buffer size for branch tracing in Intel
6879 Processor Trace format. Default is 16KB.
6881 If @var{size} is a positive number, then @value{GDBN} will try to
6882 allocate a buffer of at least @var{size} bytes for each new thread
6883 that uses the btrace recording method and the Intel Processor Trace
6884 format. The actually obtained buffer size may differ from the
6885 requested @var{size}. Use the @code{info record} command to see the
6886 actual buffer size for each thread.
6888 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6889 allocate a buffer of 4MB.
6891 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6892 also need longer to process the branch trace data before it can be used.
6894 @item show record btrace pt buffer-size @var{size}
6895 Show the current setting of the requested ring buffer size for branch
6896 tracing in Intel Processor Trace format.
6900 Show various statistics about the recording depending on the recording
6905 For the @code{full} recording method, it shows the state of process
6906 record and its in-memory execution log buffer, including:
6910 Whether in record mode or replay mode.
6912 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6914 Highest recorded instruction number.
6916 Current instruction about to be replayed (if in replay mode).
6918 Number of instructions contained in the execution log.
6920 Maximum number of instructions that may be contained in the execution log.
6924 For the @code{btrace} recording method, it shows:
6930 Number of instructions that have been recorded.
6932 Number of blocks of sequential control-flow formed by the recorded
6935 Whether in record mode or replay mode.
6938 For the @code{bts} recording format, it also shows:
6941 Size of the perf ring buffer.
6944 For the @code{pt} recording format, it also shows:
6947 Size of the perf ring buffer.
6951 @kindex record delete
6954 When record target runs in replay mode (``in the past''), delete the
6955 subsequent execution log and begin to record a new execution log starting
6956 from the current address. This means you will abandon the previously
6957 recorded ``future'' and begin recording a new ``future''.
6959 @kindex record instruction-history
6960 @kindex rec instruction-history
6961 @item record instruction-history
6962 Disassembles instructions from the recorded execution log. By
6963 default, ten instructions are disassembled. This can be changed using
6964 the @code{set record instruction-history-size} command. Instructions
6965 are printed in execution order.
6967 It can also print mixed source+disassembly if you specify the the
6968 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6969 as well as in symbolic form by specifying the @code{/r} modifier.
6971 The current position marker is printed for the instruction at the
6972 current program counter value. This instruction can appear multiple
6973 times in the trace and the current position marker will be printed
6974 every time. To omit the current position marker, specify the
6977 To better align the printed instructions when the trace contains
6978 instructions from more than one function, the function name may be
6979 omitted by specifying the @code{/f} modifier.
6981 Speculatively executed instructions are prefixed with @samp{?}. This
6982 feature is not available for all recording formats.
6984 There are several ways to specify what part of the execution log to
6988 @item record instruction-history @var{insn}
6989 Disassembles ten instructions starting from instruction number
6992 @item record instruction-history @var{insn}, +/-@var{n}
6993 Disassembles @var{n} instructions around instruction number
6994 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6995 @var{n} instructions after instruction number @var{insn}. If
6996 @var{n} is preceded with @code{-}, disassembles @var{n}
6997 instructions before instruction number @var{insn}.
6999 @item record instruction-history
7000 Disassembles ten more instructions after the last disassembly.
7002 @item record instruction-history -
7003 Disassembles ten more instructions before the last disassembly.
7005 @item record instruction-history @var{begin}, @var{end}
7006 Disassembles instructions beginning with instruction number
7007 @var{begin} until instruction number @var{end}. The instruction
7008 number @var{end} is included.
7011 This command may not be available for all recording methods.
7014 @item set record instruction-history-size @var{size}
7015 @itemx set record instruction-history-size unlimited
7016 Define how many instructions to disassemble in the @code{record
7017 instruction-history} command. The default value is 10.
7018 A @var{size} of @code{unlimited} means unlimited instructions.
7021 @item show record instruction-history-size
7022 Show how many instructions to disassemble in the @code{record
7023 instruction-history} command.
7025 @kindex record function-call-history
7026 @kindex rec function-call-history
7027 @item record function-call-history
7028 Prints the execution history at function granularity. It prints one
7029 line for each sequence of instructions that belong to the same
7030 function giving the name of that function, the source lines
7031 for this instruction sequence (if the @code{/l} modifier is
7032 specified), and the instructions numbers that form the sequence (if
7033 the @code{/i} modifier is specified). The function names are indented
7034 to reflect the call stack depth if the @code{/c} modifier is
7035 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7039 (@value{GDBP}) @b{list 1, 10}
7050 (@value{GDBP}) @b{record function-call-history /ilc}
7051 1 bar inst 1,4 at foo.c:6,8
7052 2 foo inst 5,10 at foo.c:2,3
7053 3 bar inst 11,13 at foo.c:9,10
7056 By default, ten lines are printed. This can be changed using the
7057 @code{set record function-call-history-size} command. Functions are
7058 printed in execution order. There are several ways to specify what
7062 @item record function-call-history @var{func}
7063 Prints ten functions starting from function number @var{func}.
7065 @item record function-call-history @var{func}, +/-@var{n}
7066 Prints @var{n} functions around function number @var{func}. If
7067 @var{n} is preceded with @code{+}, prints @var{n} functions after
7068 function number @var{func}. If @var{n} is preceded with @code{-},
7069 prints @var{n} functions before function number @var{func}.
7071 @item record function-call-history
7072 Prints ten more functions after the last ten-line print.
7074 @item record function-call-history -
7075 Prints ten more functions before the last ten-line print.
7077 @item record function-call-history @var{begin}, @var{end}
7078 Prints functions beginning with function number @var{begin} until
7079 function number @var{end}. The function number @var{end} is included.
7082 This command may not be available for all recording methods.
7084 @item set record function-call-history-size @var{size}
7085 @itemx set record function-call-history-size unlimited
7086 Define how many lines to print in the
7087 @code{record function-call-history} command. The default value is 10.
7088 A size of @code{unlimited} means unlimited lines.
7090 @item show record function-call-history-size
7091 Show how many lines to print in the
7092 @code{record function-call-history} command.
7097 @chapter Examining the Stack
7099 When your program has stopped, the first thing you need to know is where it
7100 stopped and how it got there.
7103 Each time your program performs a function call, information about the call
7105 That information includes the location of the call in your program,
7106 the arguments of the call,
7107 and the local variables of the function being called.
7108 The information is saved in a block of data called a @dfn{stack frame}.
7109 The stack frames are allocated in a region of memory called the @dfn{call
7112 When your program stops, the @value{GDBN} commands for examining the
7113 stack allow you to see all of this information.
7115 @cindex selected frame
7116 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7117 @value{GDBN} commands refer implicitly to the selected frame. In
7118 particular, whenever you ask @value{GDBN} for the value of a variable in
7119 your program, the value is found in the selected frame. There are
7120 special @value{GDBN} commands to select whichever frame you are
7121 interested in. @xref{Selection, ,Selecting a Frame}.
7123 When your program stops, @value{GDBN} automatically selects the
7124 currently executing frame and describes it briefly, similar to the
7125 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7128 * Frames:: Stack frames
7129 * Backtrace:: Backtraces
7130 * Selection:: Selecting a frame
7131 * Frame Info:: Information on a frame
7132 * Frame Filter Management:: Managing frame filters
7137 @section Stack Frames
7139 @cindex frame, definition
7141 The call stack is divided up into contiguous pieces called @dfn{stack
7142 frames}, or @dfn{frames} for short; each frame is the data associated
7143 with one call to one function. The frame contains the arguments given
7144 to the function, the function's local variables, and the address at
7145 which the function is executing.
7147 @cindex initial frame
7148 @cindex outermost frame
7149 @cindex innermost frame
7150 When your program is started, the stack has only one frame, that of the
7151 function @code{main}. This is called the @dfn{initial} frame or the
7152 @dfn{outermost} frame. Each time a function is called, a new frame is
7153 made. Each time a function returns, the frame for that function invocation
7154 is eliminated. If a function is recursive, there can be many frames for
7155 the same function. The frame for the function in which execution is
7156 actually occurring is called the @dfn{innermost} frame. This is the most
7157 recently created of all the stack frames that still exist.
7159 @cindex frame pointer
7160 Inside your program, stack frames are identified by their addresses. A
7161 stack frame consists of many bytes, each of which has its own address; each
7162 kind of computer has a convention for choosing one byte whose
7163 address serves as the address of the frame. Usually this address is kept
7164 in a register called the @dfn{frame pointer register}
7165 (@pxref{Registers, $fp}) while execution is going on in that frame.
7167 @cindex frame number
7168 @value{GDBN} assigns numbers to all existing stack frames, starting with
7169 zero for the innermost frame, one for the frame that called it,
7170 and so on upward. These numbers do not really exist in your program;
7171 they are assigned by @value{GDBN} to give you a way of designating stack
7172 frames in @value{GDBN} commands.
7174 @c The -fomit-frame-pointer below perennially causes hbox overflow
7175 @c underflow problems.
7176 @cindex frameless execution
7177 Some compilers provide a way to compile functions so that they operate
7178 without stack frames. (For example, the @value{NGCC} option
7180 @samp{-fomit-frame-pointer}
7182 generates functions without a frame.)
7183 This is occasionally done with heavily used library functions to save
7184 the frame setup time. @value{GDBN} has limited facilities for dealing
7185 with these function invocations. If the innermost function invocation
7186 has no stack frame, @value{GDBN} nevertheless regards it as though
7187 it had a separate frame, which is numbered zero as usual, allowing
7188 correct tracing of the function call chain. However, @value{GDBN} has
7189 no provision for frameless functions elsewhere in the stack.
7195 @cindex call stack traces
7196 A backtrace is a summary of how your program got where it is. It shows one
7197 line per frame, for many frames, starting with the currently executing
7198 frame (frame zero), followed by its caller (frame one), and on up the
7201 @anchor{backtrace-command}
7204 @kindex bt @r{(@code{backtrace})}
7207 Print a backtrace of the entire stack: one line per frame for all
7208 frames in the stack.
7210 You can stop the backtrace at any time by typing the system interrupt
7211 character, normally @kbd{Ctrl-c}.
7213 @item backtrace @var{n}
7215 Similar, but print only the innermost @var{n} frames.
7217 @item backtrace -@var{n}
7219 Similar, but print only the outermost @var{n} frames.
7221 @item backtrace full
7223 @itemx bt full @var{n}
7224 @itemx bt full -@var{n}
7225 Print the values of the local variables also. As described above,
7226 @var{n} specifies the number of frames to print.
7228 @item backtrace no-filters
7229 @itemx bt no-filters
7230 @itemx bt no-filters @var{n}
7231 @itemx bt no-filters -@var{n}
7232 @itemx bt no-filters full
7233 @itemx bt no-filters full @var{n}
7234 @itemx bt no-filters full -@var{n}
7235 Do not run Python frame filters on this backtrace. @xref{Frame
7236 Filter API}, for more information. Additionally use @ref{disable
7237 frame-filter all} to turn off all frame filters. This is only
7238 relevant when @value{GDBN} has been configured with @code{Python}
7244 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7245 are additional aliases for @code{backtrace}.
7247 @cindex multiple threads, backtrace
7248 In a multi-threaded program, @value{GDBN} by default shows the
7249 backtrace only for the current thread. To display the backtrace for
7250 several or all of the threads, use the command @code{thread apply}
7251 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7252 apply all backtrace}, @value{GDBN} will display the backtrace for all
7253 the threads; this is handy when you debug a core dump of a
7254 multi-threaded program.
7256 Each line in the backtrace shows the frame number and the function name.
7257 The program counter value is also shown---unless you use @code{set
7258 print address off}. The backtrace also shows the source file name and
7259 line number, as well as the arguments to the function. The program
7260 counter value is omitted if it is at the beginning of the code for that
7263 Here is an example of a backtrace. It was made with the command
7264 @samp{bt 3}, so it shows the innermost three frames.
7268 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7270 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7271 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7273 (More stack frames follow...)
7278 The display for frame zero does not begin with a program counter
7279 value, indicating that your program has stopped at the beginning of the
7280 code for line @code{993} of @code{builtin.c}.
7283 The value of parameter @code{data} in frame 1 has been replaced by
7284 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7285 only if it is a scalar (integer, pointer, enumeration, etc). See command
7286 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7287 on how to configure the way function parameter values are printed.
7289 @cindex optimized out, in backtrace
7290 @cindex function call arguments, optimized out
7291 If your program was compiled with optimizations, some compilers will
7292 optimize away arguments passed to functions if those arguments are
7293 never used after the call. Such optimizations generate code that
7294 passes arguments through registers, but doesn't store those arguments
7295 in the stack frame. @value{GDBN} has no way of displaying such
7296 arguments in stack frames other than the innermost one. Here's what
7297 such a backtrace might look like:
7301 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7303 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7304 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7306 (More stack frames follow...)
7311 The values of arguments that were not saved in their stack frames are
7312 shown as @samp{<optimized out>}.
7314 If you need to display the values of such optimized-out arguments,
7315 either deduce that from other variables whose values depend on the one
7316 you are interested in, or recompile without optimizations.
7318 @cindex backtrace beyond @code{main} function
7319 @cindex program entry point
7320 @cindex startup code, and backtrace
7321 Most programs have a standard user entry point---a place where system
7322 libraries and startup code transition into user code. For C this is
7323 @code{main}@footnote{
7324 Note that embedded programs (the so-called ``free-standing''
7325 environment) are not required to have a @code{main} function as the
7326 entry point. They could even have multiple entry points.}.
7327 When @value{GDBN} finds the entry function in a backtrace
7328 it will terminate the backtrace, to avoid tracing into highly
7329 system-specific (and generally uninteresting) code.
7331 If you need to examine the startup code, or limit the number of levels
7332 in a backtrace, you can change this behavior:
7335 @item set backtrace past-main
7336 @itemx set backtrace past-main on
7337 @kindex set backtrace
7338 Backtraces will continue past the user entry point.
7340 @item set backtrace past-main off
7341 Backtraces will stop when they encounter the user entry point. This is the
7344 @item show backtrace past-main
7345 @kindex show backtrace
7346 Display the current user entry point backtrace policy.
7348 @item set backtrace past-entry
7349 @itemx set backtrace past-entry on
7350 Backtraces will continue past the internal entry point of an application.
7351 This entry point is encoded by the linker when the application is built,
7352 and is likely before the user entry point @code{main} (or equivalent) is called.
7354 @item set backtrace past-entry off
7355 Backtraces will stop when they encounter the internal entry point of an
7356 application. This is the default.
7358 @item show backtrace past-entry
7359 Display the current internal entry point backtrace policy.
7361 @item set backtrace limit @var{n}
7362 @itemx set backtrace limit 0
7363 @itemx set backtrace limit unlimited
7364 @cindex backtrace limit
7365 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7366 or zero means unlimited levels.
7368 @item show backtrace limit
7369 Display the current limit on backtrace levels.
7372 You can control how file names are displayed.
7375 @item set filename-display
7376 @itemx set filename-display relative
7377 @cindex filename-display
7378 Display file names relative to the compilation directory. This is the default.
7380 @item set filename-display basename
7381 Display only basename of a filename.
7383 @item set filename-display absolute
7384 Display an absolute filename.
7386 @item show filename-display
7387 Show the current way to display filenames.
7391 @section Selecting a Frame
7393 Most commands for examining the stack and other data in your program work on
7394 whichever stack frame is selected at the moment. Here are the commands for
7395 selecting a stack frame; all of them finish by printing a brief description
7396 of the stack frame just selected.
7399 @kindex frame@r{, selecting}
7400 @kindex f @r{(@code{frame})}
7403 Select frame number @var{n}. Recall that frame zero is the innermost
7404 (currently executing) frame, frame one is the frame that called the
7405 innermost one, and so on. The highest-numbered frame is the one for
7408 @item frame @var{stack-addr} [ @var{pc-addr} ]
7409 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7410 Select the frame at address @var{stack-addr}. This is useful mainly if the
7411 chaining of stack frames has been damaged by a bug, making it
7412 impossible for @value{GDBN} to assign numbers properly to all frames. In
7413 addition, this can be useful when your program has multiple stacks and
7414 switches between them. The optional @var{pc-addr} can also be given to
7415 specify the value of PC for the stack frame.
7419 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7420 numbers @var{n}, this advances toward the outermost frame, to higher
7421 frame numbers, to frames that have existed longer.
7424 @kindex do @r{(@code{down})}
7426 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7427 positive numbers @var{n}, this advances toward the innermost frame, to
7428 lower frame numbers, to frames that were created more recently.
7429 You may abbreviate @code{down} as @code{do}.
7432 All of these commands end by printing two lines of output describing the
7433 frame. The first line shows the frame number, the function name, the
7434 arguments, and the source file and line number of execution in that
7435 frame. The second line shows the text of that source line.
7443 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7445 10 read_input_file (argv[i]);
7449 After such a printout, the @code{list} command with no arguments
7450 prints ten lines centered on the point of execution in the frame.
7451 You can also edit the program at the point of execution with your favorite
7452 editing program by typing @code{edit}.
7453 @xref{List, ,Printing Source Lines},
7457 @kindex select-frame
7459 The @code{select-frame} command is a variant of @code{frame} that does
7460 not display the new frame after selecting it. This command is
7461 intended primarily for use in @value{GDBN} command scripts, where the
7462 output might be unnecessary and distracting.
7464 @kindex down-silently
7466 @item up-silently @var{n}
7467 @itemx down-silently @var{n}
7468 These two commands are variants of @code{up} and @code{down},
7469 respectively; they differ in that they do their work silently, without
7470 causing display of the new frame. They are intended primarily for use
7471 in @value{GDBN} command scripts, where the output might be unnecessary and
7476 @section Information About a Frame
7478 There are several other commands to print information about the selected
7484 When used without any argument, this command does not change which
7485 frame is selected, but prints a brief description of the currently
7486 selected stack frame. It can be abbreviated @code{f}. With an
7487 argument, this command is used to select a stack frame.
7488 @xref{Selection, ,Selecting a Frame}.
7491 @kindex info f @r{(@code{info frame})}
7494 This command prints a verbose description of the selected stack frame,
7499 the address of the frame
7501 the address of the next frame down (called by this frame)
7503 the address of the next frame up (caller of this frame)
7505 the language in which the source code corresponding to this frame is written
7507 the address of the frame's arguments
7509 the address of the frame's local variables
7511 the program counter saved in it (the address of execution in the caller frame)
7513 which registers were saved in the frame
7516 @noindent The verbose description is useful when
7517 something has gone wrong that has made the stack format fail to fit
7518 the usual conventions.
7520 @item info frame @var{addr}
7521 @itemx info f @var{addr}
7522 Print a verbose description of the frame at address @var{addr}, without
7523 selecting that frame. The selected frame remains unchanged by this
7524 command. This requires the same kind of address (more than one for some
7525 architectures) that you specify in the @code{frame} command.
7526 @xref{Selection, ,Selecting a Frame}.
7530 Print the arguments of the selected frame, each on a separate line.
7534 Print the local variables of the selected frame, each on a separate
7535 line. These are all variables (declared either static or automatic)
7536 accessible at the point of execution of the selected frame.
7540 @node Frame Filter Management
7541 @section Management of Frame Filters.
7542 @cindex managing frame filters
7544 Frame filters are Python based utilities to manage and decorate the
7545 output of frames. @xref{Frame Filter API}, for further information.
7547 Managing frame filters is performed by several commands available
7548 within @value{GDBN}, detailed here.
7551 @kindex info frame-filter
7552 @item info frame-filter
7553 Print a list of installed frame filters from all dictionaries, showing
7554 their name, priority and enabled status.
7556 @kindex disable frame-filter
7557 @anchor{disable frame-filter all}
7558 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7559 Disable a frame filter in the dictionary matching
7560 @var{filter-dictionary} and @var{filter-name}. The
7561 @var{filter-dictionary} may be @code{all}, @code{global},
7562 @code{progspace}, or the name of the object file where the frame filter
7563 dictionary resides. When @code{all} is specified, all frame filters
7564 across all dictionaries are disabled. The @var{filter-name} is the name
7565 of the frame filter and is used when @code{all} is not the option for
7566 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7567 may be enabled again later.
7569 @kindex enable frame-filter
7570 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7571 Enable a frame filter in the dictionary matching
7572 @var{filter-dictionary} and @var{filter-name}. The
7573 @var{filter-dictionary} may be @code{all}, @code{global},
7574 @code{progspace} or the name of the object file where the frame filter
7575 dictionary resides. When @code{all} is specified, all frame filters across
7576 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7577 filter and is used when @code{all} is not the option for
7578 @var{filter-dictionary}.
7583 (gdb) info frame-filter
7585 global frame-filters:
7586 Priority Enabled Name
7587 1000 No PrimaryFunctionFilter
7590 progspace /build/test frame-filters:
7591 Priority Enabled Name
7592 100 Yes ProgspaceFilter
7594 objfile /build/test frame-filters:
7595 Priority Enabled Name
7596 999 Yes BuildProgra Filter
7598 (gdb) disable frame-filter /build/test BuildProgramFilter
7599 (gdb) info frame-filter
7601 global frame-filters:
7602 Priority Enabled Name
7603 1000 No PrimaryFunctionFilter
7606 progspace /build/test frame-filters:
7607 Priority Enabled Name
7608 100 Yes ProgspaceFilter
7610 objfile /build/test frame-filters:
7611 Priority Enabled Name
7612 999 No BuildProgramFilter
7614 (gdb) enable frame-filter global PrimaryFunctionFilter
7615 (gdb) info frame-filter
7617 global frame-filters:
7618 Priority Enabled Name
7619 1000 Yes PrimaryFunctionFilter
7622 progspace /build/test frame-filters:
7623 Priority Enabled Name
7624 100 Yes ProgspaceFilter
7626 objfile /build/test frame-filters:
7627 Priority Enabled Name
7628 999 No BuildProgramFilter
7631 @kindex set frame-filter priority
7632 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7633 Set the @var{priority} of a frame filter in the dictionary matching
7634 @var{filter-dictionary}, and the frame filter name matching
7635 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7636 @code{progspace} or the name of the object file where the frame filter
7637 dictionary resides. The @var{priority} is an integer.
7639 @kindex show frame-filter priority
7640 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7641 Show the @var{priority} of a frame filter in the dictionary matching
7642 @var{filter-dictionary}, and the frame filter name matching
7643 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7644 @code{progspace} or the name of the object file where the frame filter
7650 (gdb) info frame-filter
7652 global frame-filters:
7653 Priority Enabled Name
7654 1000 Yes PrimaryFunctionFilter
7657 progspace /build/test frame-filters:
7658 Priority Enabled Name
7659 100 Yes ProgspaceFilter
7661 objfile /build/test frame-filters:
7662 Priority Enabled Name
7663 999 No BuildProgramFilter
7665 (gdb) set frame-filter priority global Reverse 50
7666 (gdb) info frame-filter
7668 global frame-filters:
7669 Priority Enabled Name
7670 1000 Yes PrimaryFunctionFilter
7673 progspace /build/test frame-filters:
7674 Priority Enabled Name
7675 100 Yes ProgspaceFilter
7677 objfile /build/test frame-filters:
7678 Priority Enabled Name
7679 999 No BuildProgramFilter
7684 @chapter Examining Source Files
7686 @value{GDBN} can print parts of your program's source, since the debugging
7687 information recorded in the program tells @value{GDBN} what source files were
7688 used to build it. When your program stops, @value{GDBN} spontaneously prints
7689 the line where it stopped. Likewise, when you select a stack frame
7690 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7691 execution in that frame has stopped. You can print other portions of
7692 source files by explicit command.
7694 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7695 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7696 @value{GDBN} under @sc{gnu} Emacs}.
7699 * List:: Printing source lines
7700 * Specify Location:: How to specify code locations
7701 * Edit:: Editing source files
7702 * Search:: Searching source files
7703 * Source Path:: Specifying source directories
7704 * Machine Code:: Source and machine code
7708 @section Printing Source Lines
7711 @kindex l @r{(@code{list})}
7712 To print lines from a source file, use the @code{list} command
7713 (abbreviated @code{l}). By default, ten lines are printed.
7714 There are several ways to specify what part of the file you want to
7715 print; see @ref{Specify Location}, for the full list.
7717 Here are the forms of the @code{list} command most commonly used:
7720 @item list @var{linenum}
7721 Print lines centered around line number @var{linenum} in the
7722 current source file.
7724 @item list @var{function}
7725 Print lines centered around the beginning of function
7729 Print more lines. If the last lines printed were printed with a
7730 @code{list} command, this prints lines following the last lines
7731 printed; however, if the last line printed was a solitary line printed
7732 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7733 Stack}), this prints lines centered around that line.
7736 Print lines just before the lines last printed.
7739 @cindex @code{list}, how many lines to display
7740 By default, @value{GDBN} prints ten source lines with any of these forms of
7741 the @code{list} command. You can change this using @code{set listsize}:
7744 @kindex set listsize
7745 @item set listsize @var{count}
7746 @itemx set listsize unlimited
7747 Make the @code{list} command display @var{count} source lines (unless
7748 the @code{list} argument explicitly specifies some other number).
7749 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7751 @kindex show listsize
7753 Display the number of lines that @code{list} prints.
7756 Repeating a @code{list} command with @key{RET} discards the argument,
7757 so it is equivalent to typing just @code{list}. This is more useful
7758 than listing the same lines again. An exception is made for an
7759 argument of @samp{-}; that argument is preserved in repetition so that
7760 each repetition moves up in the source file.
7762 In general, the @code{list} command expects you to supply zero, one or two
7763 @dfn{locations}. Locations specify source lines; there are several ways
7764 of writing them (@pxref{Specify Location}), but the effect is always
7765 to specify some source line.
7767 Here is a complete description of the possible arguments for @code{list}:
7770 @item list @var{location}
7771 Print lines centered around the line specified by @var{location}.
7773 @item list @var{first},@var{last}
7774 Print lines from @var{first} to @var{last}. Both arguments are
7775 locations. When a @code{list} command has two locations, and the
7776 source file of the second location is omitted, this refers to
7777 the same source file as the first location.
7779 @item list ,@var{last}
7780 Print lines ending with @var{last}.
7782 @item list @var{first},
7783 Print lines starting with @var{first}.
7786 Print lines just after the lines last printed.
7789 Print lines just before the lines last printed.
7792 As described in the preceding table.
7795 @node Specify Location
7796 @section Specifying a Location
7797 @cindex specifying location
7799 @cindex source location
7802 * Linespec Locations:: Linespec locations
7803 * Explicit Locations:: Explicit locations
7804 * Address Locations:: Address locations
7807 Several @value{GDBN} commands accept arguments that specify a location
7808 of your program's code. Since @value{GDBN} is a source-level
7809 debugger, a location usually specifies some line in the source code.
7810 Locations may be specified using three different formats:
7811 linespec locations, explicit locations, or address locations.
7813 @node Linespec Locations
7814 @subsection Linespec Locations
7815 @cindex linespec locations
7817 A @dfn{linespec} is a colon-separated list of source location parameters such
7818 as file name, function name, etc. Here are all the different ways of
7819 specifying a linespec:
7823 Specifies the line number @var{linenum} of the current source file.
7826 @itemx +@var{offset}
7827 Specifies the line @var{offset} lines before or after the @dfn{current
7828 line}. For the @code{list} command, the current line is the last one
7829 printed; for the breakpoint commands, this is the line at which
7830 execution stopped in the currently selected @dfn{stack frame}
7831 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7832 used as the second of the two linespecs in a @code{list} command,
7833 this specifies the line @var{offset} lines up or down from the first
7836 @item @var{filename}:@var{linenum}
7837 Specifies the line @var{linenum} in the source file @var{filename}.
7838 If @var{filename} is a relative file name, then it will match any
7839 source file name with the same trailing components. For example, if
7840 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7841 name of @file{/build/trunk/gcc/expr.c}, but not
7842 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7844 @item @var{function}
7845 Specifies the line that begins the body of the function @var{function}.
7846 For example, in C, this is the line with the open brace.
7848 @item @var{function}:@var{label}
7849 Specifies the line where @var{label} appears in @var{function}.
7851 @item @var{filename}:@var{function}
7852 Specifies the line that begins the body of the function @var{function}
7853 in the file @var{filename}. You only need the file name with a
7854 function name to avoid ambiguity when there are identically named
7855 functions in different source files.
7858 Specifies the line at which the label named @var{label} appears
7859 in the function corresponding to the currently selected stack frame.
7860 If there is no current selected stack frame (for instance, if the inferior
7861 is not running), then @value{GDBN} will not search for a label.
7863 @cindex breakpoint at static probe point
7864 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7865 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7866 applications to embed static probes. @xref{Static Probe Points}, for more
7867 information on finding and using static probes. This form of linespec
7868 specifies the location of such a static probe.
7870 If @var{objfile} is given, only probes coming from that shared library
7871 or executable matching @var{objfile} as a regular expression are considered.
7872 If @var{provider} is given, then only probes from that provider are considered.
7873 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7874 each one of those probes.
7877 @node Explicit Locations
7878 @subsection Explicit Locations
7879 @cindex explicit locations
7881 @dfn{Explicit locations} allow the user to directly specify the source
7882 location's parameters using option-value pairs.
7884 Explicit locations are useful when several functions, labels, or
7885 file names have the same name (base name for files) in the program's
7886 sources. In these cases, explicit locations point to the source
7887 line you meant more accurately and unambiguously. Also, using
7888 explicit locations might be faster in large programs.
7890 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7891 defined in the file named @file{foo} or the label @code{bar} in a function
7892 named @code{foo}. @value{GDBN} must search either the file system or
7893 the symbol table to know.
7895 The list of valid explicit location options is summarized in the
7899 @item -source @var{filename}
7900 The value specifies the source file name. To differentiate between
7901 files with the same base name, prepend as many directories as is necessary
7902 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7903 @value{GDBN} will use the first file it finds with the given base
7904 name. This option requires the use of either @code{-function} or @code{-line}.
7906 @item -function @var{function}
7907 The value specifies the name of a function. Operations
7908 on function locations unmodified by other options (such as @code{-label}
7909 or @code{-line}) refer to the line that begins the body of the function.
7910 In C, for example, this is the line with the open brace.
7912 @item -label @var{label}
7913 The value specifies the name of a label. When the function
7914 name is not specified, the label is searched in the function of the currently
7915 selected stack frame.
7917 @item -line @var{number}
7918 The value specifies a line offset for the location. The offset may either
7919 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7920 the command. When specified without any other options, the line offset is
7921 relative to the current line.
7924 Explicit location options may be abbreviated by omitting any non-unique
7925 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7927 @node Address Locations
7928 @subsection Address Locations
7929 @cindex address locations
7931 @dfn{Address locations} indicate a specific program address. They have
7932 the generalized form *@var{address}.
7934 For line-oriented commands, such as @code{list} and @code{edit}, this
7935 specifies a source line that contains @var{address}. For @code{break} and
7936 other breakpoint-oriented commands, this can be used to set breakpoints in
7937 parts of your program which do not have debugging information or
7940 Here @var{address} may be any expression valid in the current working
7941 language (@pxref{Languages, working language}) that specifies a code
7942 address. In addition, as a convenience, @value{GDBN} extends the
7943 semantics of expressions used in locations to cover several situations
7944 that frequently occur during debugging. Here are the various forms
7948 @item @var{expression}
7949 Any expression valid in the current working language.
7951 @item @var{funcaddr}
7952 An address of a function or procedure derived from its name. In C,
7953 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
7954 simply the function's name @var{function} (and actually a special case
7955 of a valid expression). In Pascal and Modula-2, this is
7956 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7957 (although the Pascal form also works).
7959 This form specifies the address of the function's first instruction,
7960 before the stack frame and arguments have been set up.
7962 @item '@var{filename}':@var{funcaddr}
7963 Like @var{funcaddr} above, but also specifies the name of the source
7964 file explicitly. This is useful if the name of the function does not
7965 specify the function unambiguously, e.g., if there are several
7966 functions with identical names in different source files.
7970 @section Editing Source Files
7971 @cindex editing source files
7974 @kindex e @r{(@code{edit})}
7975 To edit the lines in a source file, use the @code{edit} command.
7976 The editing program of your choice
7977 is invoked with the current line set to
7978 the active line in the program.
7979 Alternatively, there are several ways to specify what part of the file you
7980 want to print if you want to see other parts of the program:
7983 @item edit @var{location}
7984 Edit the source file specified by @code{location}. Editing starts at
7985 that @var{location}, e.g., at the specified source line of the
7986 specified file. @xref{Specify Location}, for all the possible forms
7987 of the @var{location} argument; here are the forms of the @code{edit}
7988 command most commonly used:
7991 @item edit @var{number}
7992 Edit the current source file with @var{number} as the active line number.
7994 @item edit @var{function}
7995 Edit the file containing @var{function} at the beginning of its definition.
8000 @subsection Choosing your Editor
8001 You can customize @value{GDBN} to use any editor you want
8003 The only restriction is that your editor (say @code{ex}), recognizes the
8004 following command-line syntax:
8006 ex +@var{number} file
8008 The optional numeric value +@var{number} specifies the number of the line in
8009 the file where to start editing.}.
8010 By default, it is @file{@value{EDITOR}}, but you can change this
8011 by setting the environment variable @code{EDITOR} before using
8012 @value{GDBN}. For example, to configure @value{GDBN} to use the
8013 @code{vi} editor, you could use these commands with the @code{sh} shell:
8019 or in the @code{csh} shell,
8021 setenv EDITOR /usr/bin/vi
8026 @section Searching Source Files
8027 @cindex searching source files
8029 There are two commands for searching through the current source file for a
8034 @kindex forward-search
8035 @kindex fo @r{(@code{forward-search})}
8036 @item forward-search @var{regexp}
8037 @itemx search @var{regexp}
8038 The command @samp{forward-search @var{regexp}} checks each line,
8039 starting with the one following the last line listed, for a match for
8040 @var{regexp}. It lists the line that is found. You can use the
8041 synonym @samp{search @var{regexp}} or abbreviate the command name as
8044 @kindex reverse-search
8045 @item reverse-search @var{regexp}
8046 The command @samp{reverse-search @var{regexp}} checks each line, starting
8047 with the one before the last line listed and going backward, for a match
8048 for @var{regexp}. It lists the line that is found. You can abbreviate
8049 this command as @code{rev}.
8053 @section Specifying Source Directories
8056 @cindex directories for source files
8057 Executable programs sometimes do not record the directories of the source
8058 files from which they were compiled, just the names. Even when they do,
8059 the directories could be moved between the compilation and your debugging
8060 session. @value{GDBN} has a list of directories to search for source files;
8061 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8062 it tries all the directories in the list, in the order they are present
8063 in the list, until it finds a file with the desired name.
8065 For example, suppose an executable references the file
8066 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8067 @file{/mnt/cross}. The file is first looked up literally; if this
8068 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8069 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8070 message is printed. @value{GDBN} does not look up the parts of the
8071 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8072 Likewise, the subdirectories of the source path are not searched: if
8073 the source path is @file{/mnt/cross}, and the binary refers to
8074 @file{foo.c}, @value{GDBN} would not find it under
8075 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8077 Plain file names, relative file names with leading directories, file
8078 names containing dots, etc.@: are all treated as described above; for
8079 instance, if the source path is @file{/mnt/cross}, and the source file
8080 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8081 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8082 that---@file{/mnt/cross/foo.c}.
8084 Note that the executable search path is @emph{not} used to locate the
8087 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8088 any information it has cached about where source files are found and where
8089 each line is in the file.
8093 When you start @value{GDBN}, its source path includes only @samp{cdir}
8094 and @samp{cwd}, in that order.
8095 To add other directories, use the @code{directory} command.
8097 The search path is used to find both program source files and @value{GDBN}
8098 script files (read using the @samp{-command} option and @samp{source} command).
8100 In addition to the source path, @value{GDBN} provides a set of commands
8101 that manage a list of source path substitution rules. A @dfn{substitution
8102 rule} specifies how to rewrite source directories stored in the program's
8103 debug information in case the sources were moved to a different
8104 directory between compilation and debugging. A rule is made of
8105 two strings, the first specifying what needs to be rewritten in
8106 the path, and the second specifying how it should be rewritten.
8107 In @ref{set substitute-path}, we name these two parts @var{from} and
8108 @var{to} respectively. @value{GDBN} does a simple string replacement
8109 of @var{from} with @var{to} at the start of the directory part of the
8110 source file name, and uses that result instead of the original file
8111 name to look up the sources.
8113 Using the previous example, suppose the @file{foo-1.0} tree has been
8114 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8115 @value{GDBN} to replace @file{/usr/src} in all source path names with
8116 @file{/mnt/cross}. The first lookup will then be
8117 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8118 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8119 substitution rule, use the @code{set substitute-path} command
8120 (@pxref{set substitute-path}).
8122 To avoid unexpected substitution results, a rule is applied only if the
8123 @var{from} part of the directory name ends at a directory separator.
8124 For instance, a rule substituting @file{/usr/source} into
8125 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8126 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8127 is applied only at the beginning of the directory name, this rule will
8128 not be applied to @file{/root/usr/source/baz.c} either.
8130 In many cases, you can achieve the same result using the @code{directory}
8131 command. However, @code{set substitute-path} can be more efficient in
8132 the case where the sources are organized in a complex tree with multiple
8133 subdirectories. With the @code{directory} command, you need to add each
8134 subdirectory of your project. If you moved the entire tree while
8135 preserving its internal organization, then @code{set substitute-path}
8136 allows you to direct the debugger to all the sources with one single
8139 @code{set substitute-path} is also more than just a shortcut command.
8140 The source path is only used if the file at the original location no
8141 longer exists. On the other hand, @code{set substitute-path} modifies
8142 the debugger behavior to look at the rewritten location instead. So, if
8143 for any reason a source file that is not relevant to your executable is
8144 located at the original location, a substitution rule is the only
8145 method available to point @value{GDBN} at the new location.
8147 @cindex @samp{--with-relocated-sources}
8148 @cindex default source path substitution
8149 You can configure a default source path substitution rule by
8150 configuring @value{GDBN} with the
8151 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8152 should be the name of a directory under @value{GDBN}'s configured
8153 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8154 directory names in debug information under @var{dir} will be adjusted
8155 automatically if the installed @value{GDBN} is moved to a new
8156 location. This is useful if @value{GDBN}, libraries or executables
8157 with debug information and corresponding source code are being moved
8161 @item directory @var{dirname} @dots{}
8162 @item dir @var{dirname} @dots{}
8163 Add directory @var{dirname} to the front of the source path. Several
8164 directory names may be given to this command, separated by @samp{:}
8165 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8166 part of absolute file names) or
8167 whitespace. You may specify a directory that is already in the source
8168 path; this moves it forward, so @value{GDBN} searches it sooner.
8172 @vindex $cdir@r{, convenience variable}
8173 @vindex $cwd@r{, convenience variable}
8174 @cindex compilation directory
8175 @cindex current directory
8176 @cindex working directory
8177 @cindex directory, current
8178 @cindex directory, compilation
8179 You can use the string @samp{$cdir} to refer to the compilation
8180 directory (if one is recorded), and @samp{$cwd} to refer to the current
8181 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8182 tracks the current working directory as it changes during your @value{GDBN}
8183 session, while the latter is immediately expanded to the current
8184 directory at the time you add an entry to the source path.
8187 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8189 @c RET-repeat for @code{directory} is explicitly disabled, but since
8190 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8192 @item set directories @var{path-list}
8193 @kindex set directories
8194 Set the source path to @var{path-list}.
8195 @samp{$cdir:$cwd} are added if missing.
8197 @item show directories
8198 @kindex show directories
8199 Print the source path: show which directories it contains.
8201 @anchor{set substitute-path}
8202 @item set substitute-path @var{from} @var{to}
8203 @kindex set substitute-path
8204 Define a source path substitution rule, and add it at the end of the
8205 current list of existing substitution rules. If a rule with the same
8206 @var{from} was already defined, then the old rule is also deleted.
8208 For example, if the file @file{/foo/bar/baz.c} was moved to
8209 @file{/mnt/cross/baz.c}, then the command
8212 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8216 will tell @value{GDBN} to replace @samp{/foo/bar} with
8217 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8218 @file{baz.c} even though it was moved.
8220 In the case when more than one substitution rule have been defined,
8221 the rules are evaluated one by one in the order where they have been
8222 defined. The first one matching, if any, is selected to perform
8225 For instance, if we had entered the following commands:
8228 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8229 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8233 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8234 @file{/mnt/include/defs.h} by using the first rule. However, it would
8235 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8236 @file{/mnt/src/lib/foo.c}.
8239 @item unset substitute-path [path]
8240 @kindex unset substitute-path
8241 If a path is specified, search the current list of substitution rules
8242 for a rule that would rewrite that path. Delete that rule if found.
8243 A warning is emitted by the debugger if no rule could be found.
8245 If no path is specified, then all substitution rules are deleted.
8247 @item show substitute-path [path]
8248 @kindex show substitute-path
8249 If a path is specified, then print the source path substitution rule
8250 which would rewrite that path, if any.
8252 If no path is specified, then print all existing source path substitution
8257 If your source path is cluttered with directories that are no longer of
8258 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8259 versions of source. You can correct the situation as follows:
8263 Use @code{directory} with no argument to reset the source path to its default value.
8266 Use @code{directory} with suitable arguments to reinstall the
8267 directories you want in the source path. You can add all the
8268 directories in one command.
8272 @section Source and Machine Code
8273 @cindex source line and its code address
8275 You can use the command @code{info line} to map source lines to program
8276 addresses (and vice versa), and the command @code{disassemble} to display
8277 a range of addresses as machine instructions. You can use the command
8278 @code{set disassemble-next-line} to set whether to disassemble next
8279 source line when execution stops. When run under @sc{gnu} Emacs
8280 mode, the @code{info line} command causes the arrow to point to the
8281 line specified. Also, @code{info line} prints addresses in symbolic form as
8286 @item info line @var{location}
8287 Print the starting and ending addresses of the compiled code for
8288 source line @var{location}. You can specify source lines in any of
8289 the ways documented in @ref{Specify Location}.
8292 For example, we can use @code{info line} to discover the location of
8293 the object code for the first line of function
8294 @code{m4_changequote}:
8296 @c FIXME: I think this example should also show the addresses in
8297 @c symbolic form, as they usually would be displayed.
8299 (@value{GDBP}) info line m4_changequote
8300 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8304 @cindex code address and its source line
8305 We can also inquire (using @code{*@var{addr}} as the form for
8306 @var{location}) what source line covers a particular address:
8308 (@value{GDBP}) info line *0x63ff
8309 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8312 @cindex @code{$_} and @code{info line}
8313 @cindex @code{x} command, default address
8314 @kindex x@r{(examine), and} info line
8315 After @code{info line}, the default address for the @code{x} command
8316 is changed to the starting address of the line, so that @samp{x/i} is
8317 sufficient to begin examining the machine code (@pxref{Memory,
8318 ,Examining Memory}). Also, this address is saved as the value of the
8319 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8324 @cindex assembly instructions
8325 @cindex instructions, assembly
8326 @cindex machine instructions
8327 @cindex listing machine instructions
8329 @itemx disassemble /m
8330 @itemx disassemble /s
8331 @itemx disassemble /r
8332 This specialized command dumps a range of memory as machine
8333 instructions. It can also print mixed source+disassembly by specifying
8334 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8335 as well as in symbolic form by specifying the @code{/r} modifier.
8336 The default memory range is the function surrounding the
8337 program counter of the selected frame. A single argument to this
8338 command is a program counter value; @value{GDBN} dumps the function
8339 surrounding this value. When two arguments are given, they should
8340 be separated by a comma, possibly surrounded by whitespace. The
8341 arguments specify a range of addresses to dump, in one of two forms:
8344 @item @var{start},@var{end}
8345 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8346 @item @var{start},+@var{length}
8347 the addresses from @var{start} (inclusive) to
8348 @code{@var{start}+@var{length}} (exclusive).
8352 When 2 arguments are specified, the name of the function is also
8353 printed (since there could be several functions in the given range).
8355 The argument(s) can be any expression yielding a numeric value, such as
8356 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8358 If the range of memory being disassembled contains current program counter,
8359 the instruction at that location is shown with a @code{=>} marker.
8362 The following example shows the disassembly of a range of addresses of
8363 HP PA-RISC 2.0 code:
8366 (@value{GDBP}) disas 0x32c4, 0x32e4
8367 Dump of assembler code from 0x32c4 to 0x32e4:
8368 0x32c4 <main+204>: addil 0,dp
8369 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8370 0x32cc <main+212>: ldil 0x3000,r31
8371 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8372 0x32d4 <main+220>: ldo 0(r31),rp
8373 0x32d8 <main+224>: addil -0x800,dp
8374 0x32dc <main+228>: ldo 0x588(r1),r26
8375 0x32e0 <main+232>: ldil 0x3000,r31
8376 End of assembler dump.
8379 Here is an example showing mixed source+assembly for Intel x86
8380 with @code{/m} or @code{/s}, when the program is stopped just after
8381 function prologue in a non-optimized function with no inline code.
8384 (@value{GDBP}) disas /m main
8385 Dump of assembler code for function main:
8387 0x08048330 <+0>: push %ebp
8388 0x08048331 <+1>: mov %esp,%ebp
8389 0x08048333 <+3>: sub $0x8,%esp
8390 0x08048336 <+6>: and $0xfffffff0,%esp
8391 0x08048339 <+9>: sub $0x10,%esp
8393 6 printf ("Hello.\n");
8394 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8395 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8399 0x08048348 <+24>: mov $0x0,%eax
8400 0x0804834d <+29>: leave
8401 0x0804834e <+30>: ret
8403 End of assembler dump.
8406 The @code{/m} option is deprecated as its output is not useful when
8407 there is either inlined code or re-ordered code.
8408 The @code{/s} option is the preferred choice.
8409 Here is an example for AMD x86-64 showing the difference between
8410 @code{/m} output and @code{/s} output.
8411 This example has one inline function defined in a header file,
8412 and the code is compiled with @samp{-O2} optimization.
8413 Note how the @code{/m} output is missing the disassembly of
8414 several instructions that are present in the @code{/s} output.
8444 (@value{GDBP}) disas /m main
8445 Dump of assembler code for function main:
8449 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8450 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8454 0x000000000040041d <+29>: xor %eax,%eax
8455 0x000000000040041f <+31>: retq
8456 0x0000000000400420 <+32>: add %eax,%eax
8457 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8459 End of assembler dump.
8460 (@value{GDBP}) disas /s main
8461 Dump of assembler code for function main:
8465 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8469 0x0000000000400406 <+6>: test %eax,%eax
8470 0x0000000000400408 <+8>: js 0x400420 <main+32>
8475 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8476 0x000000000040040d <+13>: test %eax,%eax
8477 0x000000000040040f <+15>: mov $0x1,%eax
8478 0x0000000000400414 <+20>: cmovne %edx,%eax
8482 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8486 0x000000000040041d <+29>: xor %eax,%eax
8487 0x000000000040041f <+31>: retq
8491 0x0000000000400420 <+32>: add %eax,%eax
8492 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8493 End of assembler dump.
8496 Here is another example showing raw instructions in hex for AMD x86-64,
8499 (gdb) disas /r 0x400281,+10
8500 Dump of assembler code from 0x400281 to 0x40028b:
8501 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8502 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8503 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8504 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8505 End of assembler dump.
8508 Addresses cannot be specified as a location (@pxref{Specify Location}).
8509 So, for example, if you want to disassemble function @code{bar}
8510 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8511 and not @samp{disassemble foo.c:bar}.
8513 Some architectures have more than one commonly-used set of instruction
8514 mnemonics or other syntax.
8516 For programs that were dynamically linked and use shared libraries,
8517 instructions that call functions or branch to locations in the shared
8518 libraries might show a seemingly bogus location---it's actually a
8519 location of the relocation table. On some architectures, @value{GDBN}
8520 might be able to resolve these to actual function names.
8523 @kindex set disassembly-flavor
8524 @cindex Intel disassembly flavor
8525 @cindex AT&T disassembly flavor
8526 @item set disassembly-flavor @var{instruction-set}
8527 Select the instruction set to use when disassembling the
8528 program via the @code{disassemble} or @code{x/i} commands.
8530 Currently this command is only defined for the Intel x86 family. You
8531 can set @var{instruction-set} to either @code{intel} or @code{att}.
8532 The default is @code{att}, the AT&T flavor used by default by Unix
8533 assemblers for x86-based targets.
8535 @kindex show disassembly-flavor
8536 @item show disassembly-flavor
8537 Show the current setting of the disassembly flavor.
8541 @kindex set disassemble-next-line
8542 @kindex show disassemble-next-line
8543 @item set disassemble-next-line
8544 @itemx show disassemble-next-line
8545 Control whether or not @value{GDBN} will disassemble the next source
8546 line or instruction when execution stops. If ON, @value{GDBN} will
8547 display disassembly of the next source line when execution of the
8548 program being debugged stops. This is @emph{in addition} to
8549 displaying the source line itself, which @value{GDBN} always does if
8550 possible. If the next source line cannot be displayed for some reason
8551 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8552 info in the debug info), @value{GDBN} will display disassembly of the
8553 next @emph{instruction} instead of showing the next source line. If
8554 AUTO, @value{GDBN} will display disassembly of next instruction only
8555 if the source line cannot be displayed. This setting causes
8556 @value{GDBN} to display some feedback when you step through a function
8557 with no line info or whose source file is unavailable. The default is
8558 OFF, which means never display the disassembly of the next line or
8564 @chapter Examining Data
8566 @cindex printing data
8567 @cindex examining data
8570 The usual way to examine data in your program is with the @code{print}
8571 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8572 evaluates and prints the value of an expression of the language your
8573 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8574 Different Languages}). It may also print the expression using a
8575 Python-based pretty-printer (@pxref{Pretty Printing}).
8578 @item print @var{expr}
8579 @itemx print /@var{f} @var{expr}
8580 @var{expr} is an expression (in the source language). By default the
8581 value of @var{expr} is printed in a format appropriate to its data type;
8582 you can choose a different format by specifying @samp{/@var{f}}, where
8583 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8587 @itemx print /@var{f}
8588 @cindex reprint the last value
8589 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8590 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8591 conveniently inspect the same value in an alternative format.
8594 A more low-level way of examining data is with the @code{x} command.
8595 It examines data in memory at a specified address and prints it in a
8596 specified format. @xref{Memory, ,Examining Memory}.
8598 If you are interested in information about types, or about how the
8599 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8600 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8603 @cindex exploring hierarchical data structures
8605 Another way of examining values of expressions and type information is
8606 through the Python extension command @code{explore} (available only if
8607 the @value{GDBN} build is configured with @code{--with-python}). It
8608 offers an interactive way to start at the highest level (or, the most
8609 abstract level) of the data type of an expression (or, the data type
8610 itself) and explore all the way down to leaf scalar values/fields
8611 embedded in the higher level data types.
8614 @item explore @var{arg}
8615 @var{arg} is either an expression (in the source language), or a type
8616 visible in the current context of the program being debugged.
8619 The working of the @code{explore} command can be illustrated with an
8620 example. If a data type @code{struct ComplexStruct} is defined in your
8630 struct ComplexStruct
8632 struct SimpleStruct *ss_p;
8638 followed by variable declarations as
8641 struct SimpleStruct ss = @{ 10, 1.11 @};
8642 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8646 then, the value of the variable @code{cs} can be explored using the
8647 @code{explore} command as follows.
8651 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8652 the following fields:
8654 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8655 arr = <Enter 1 to explore this field of type `int [10]'>
8657 Enter the field number of choice:
8661 Since the fields of @code{cs} are not scalar values, you are being
8662 prompted to chose the field you want to explore. Let's say you choose
8663 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8664 pointer, you will be asked if it is pointing to a single value. From
8665 the declaration of @code{cs} above, it is indeed pointing to a single
8666 value, hence you enter @code{y}. If you enter @code{n}, then you will
8667 be asked if it were pointing to an array of values, in which case this
8668 field will be explored as if it were an array.
8671 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8672 Continue exploring it as a pointer to a single value [y/n]: y
8673 The value of `*(cs.ss_p)' is a struct/class of type `struct
8674 SimpleStruct' with the following fields:
8676 i = 10 .. (Value of type `int')
8677 d = 1.1100000000000001 .. (Value of type `double')
8679 Press enter to return to parent value:
8683 If the field @code{arr} of @code{cs} was chosen for exploration by
8684 entering @code{1} earlier, then since it is as array, you will be
8685 prompted to enter the index of the element in the array that you want
8689 `cs.arr' is an array of `int'.
8690 Enter the index of the element you want to explore in `cs.arr': 5
8692 `(cs.arr)[5]' is a scalar value of type `int'.
8696 Press enter to return to parent value:
8699 In general, at any stage of exploration, you can go deeper towards the
8700 leaf values by responding to the prompts appropriately, or hit the
8701 return key to return to the enclosing data structure (the @i{higher}
8702 level data structure).
8704 Similar to exploring values, you can use the @code{explore} command to
8705 explore types. Instead of specifying a value (which is typically a
8706 variable name or an expression valid in the current context of the
8707 program being debugged), you specify a type name. If you consider the
8708 same example as above, your can explore the type
8709 @code{struct ComplexStruct} by passing the argument
8710 @code{struct ComplexStruct} to the @code{explore} command.
8713 (gdb) explore struct ComplexStruct
8717 By responding to the prompts appropriately in the subsequent interactive
8718 session, you can explore the type @code{struct ComplexStruct} in a
8719 manner similar to how the value @code{cs} was explored in the above
8722 The @code{explore} command also has two sub-commands,
8723 @code{explore value} and @code{explore type}. The former sub-command is
8724 a way to explicitly specify that value exploration of the argument is
8725 being invoked, while the latter is a way to explicitly specify that type
8726 exploration of the argument is being invoked.
8729 @item explore value @var{expr}
8730 @cindex explore value
8731 This sub-command of @code{explore} explores the value of the
8732 expression @var{expr} (if @var{expr} is an expression valid in the
8733 current context of the program being debugged). The behavior of this
8734 command is identical to that of the behavior of the @code{explore}
8735 command being passed the argument @var{expr}.
8737 @item explore type @var{arg}
8738 @cindex explore type
8739 This sub-command of @code{explore} explores the type of @var{arg} (if
8740 @var{arg} is a type visible in the current context of program being
8741 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8742 is an expression valid in the current context of the program being
8743 debugged). If @var{arg} is a type, then the behavior of this command is
8744 identical to that of the @code{explore} command being passed the
8745 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8746 this command will be identical to that of the @code{explore} command
8747 being passed the type of @var{arg} as the argument.
8751 * Expressions:: Expressions
8752 * Ambiguous Expressions:: Ambiguous Expressions
8753 * Variables:: Program variables
8754 * Arrays:: Artificial arrays
8755 * Output Formats:: Output formats
8756 * Memory:: Examining memory
8757 * Auto Display:: Automatic display
8758 * Print Settings:: Print settings
8759 * Pretty Printing:: Python pretty printing
8760 * Value History:: Value history
8761 * Convenience Vars:: Convenience variables
8762 * Convenience Funs:: Convenience functions
8763 * Registers:: Registers
8764 * Floating Point Hardware:: Floating point hardware
8765 * Vector Unit:: Vector Unit
8766 * OS Information:: Auxiliary data provided by operating system
8767 * Memory Region Attributes:: Memory region attributes
8768 * Dump/Restore Files:: Copy between memory and a file
8769 * Core File Generation:: Cause a program dump its core
8770 * Character Sets:: Debugging programs that use a different
8771 character set than GDB does
8772 * Caching Target Data:: Data caching for targets
8773 * Searching Memory:: Searching memory for a sequence of bytes
8774 * Value Sizes:: Managing memory allocated for values
8778 @section Expressions
8781 @code{print} and many other @value{GDBN} commands accept an expression and
8782 compute its value. Any kind of constant, variable or operator defined
8783 by the programming language you are using is valid in an expression in
8784 @value{GDBN}. This includes conditional expressions, function calls,
8785 casts, and string constants. It also includes preprocessor macros, if
8786 you compiled your program to include this information; see
8789 @cindex arrays in expressions
8790 @value{GDBN} supports array constants in expressions input by
8791 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8792 you can use the command @code{print @{1, 2, 3@}} to create an array
8793 of three integers. If you pass an array to a function or assign it
8794 to a program variable, @value{GDBN} copies the array to memory that
8795 is @code{malloc}ed in the target program.
8797 Because C is so widespread, most of the expressions shown in examples in
8798 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8799 Languages}, for information on how to use expressions in other
8802 In this section, we discuss operators that you can use in @value{GDBN}
8803 expressions regardless of your programming language.
8805 @cindex casts, in expressions
8806 Casts are supported in all languages, not just in C, because it is so
8807 useful to cast a number into a pointer in order to examine a structure
8808 at that address in memory.
8809 @c FIXME: casts supported---Mod2 true?
8811 @value{GDBN} supports these operators, in addition to those common
8812 to programming languages:
8816 @samp{@@} is a binary operator for treating parts of memory as arrays.
8817 @xref{Arrays, ,Artificial Arrays}, for more information.
8820 @samp{::} allows you to specify a variable in terms of the file or
8821 function where it is defined. @xref{Variables, ,Program Variables}.
8823 @cindex @{@var{type}@}
8824 @cindex type casting memory
8825 @cindex memory, viewing as typed object
8826 @cindex casts, to view memory
8827 @item @{@var{type}@} @var{addr}
8828 Refers to an object of type @var{type} stored at address @var{addr} in
8829 memory. The address @var{addr} may be any expression whose value is
8830 an integer or pointer (but parentheses are required around binary
8831 operators, just as in a cast). This construct is allowed regardless
8832 of what kind of data is normally supposed to reside at @var{addr}.
8835 @node Ambiguous Expressions
8836 @section Ambiguous Expressions
8837 @cindex ambiguous expressions
8839 Expressions can sometimes contain some ambiguous elements. For instance,
8840 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8841 a single function name to be defined several times, for application in
8842 different contexts. This is called @dfn{overloading}. Another example
8843 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8844 templates and is typically instantiated several times, resulting in
8845 the same function name being defined in different contexts.
8847 In some cases and depending on the language, it is possible to adjust
8848 the expression to remove the ambiguity. For instance in C@t{++}, you
8849 can specify the signature of the function you want to break on, as in
8850 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8851 qualified name of your function often makes the expression unambiguous
8854 When an ambiguity that needs to be resolved is detected, the debugger
8855 has the capability to display a menu of numbered choices for each
8856 possibility, and then waits for the selection with the prompt @samp{>}.
8857 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8858 aborts the current command. If the command in which the expression was
8859 used allows more than one choice to be selected, the next option in the
8860 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8863 For example, the following session excerpt shows an attempt to set a
8864 breakpoint at the overloaded symbol @code{String::after}.
8865 We choose three particular definitions of that function name:
8867 @c FIXME! This is likely to change to show arg type lists, at least
8870 (@value{GDBP}) b String::after
8873 [2] file:String.cc; line number:867
8874 [3] file:String.cc; line number:860
8875 [4] file:String.cc; line number:875
8876 [5] file:String.cc; line number:853
8877 [6] file:String.cc; line number:846
8878 [7] file:String.cc; line number:735
8880 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8881 Breakpoint 2 at 0xb344: file String.cc, line 875.
8882 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8883 Multiple breakpoints were set.
8884 Use the "delete" command to delete unwanted
8891 @kindex set multiple-symbols
8892 @item set multiple-symbols @var{mode}
8893 @cindex multiple-symbols menu
8895 This option allows you to adjust the debugger behavior when an expression
8898 By default, @var{mode} is set to @code{all}. If the command with which
8899 the expression is used allows more than one choice, then @value{GDBN}
8900 automatically selects all possible choices. For instance, inserting
8901 a breakpoint on a function using an ambiguous name results in a breakpoint
8902 inserted on each possible match. However, if a unique choice must be made,
8903 then @value{GDBN} uses the menu to help you disambiguate the expression.
8904 For instance, printing the address of an overloaded function will result
8905 in the use of the menu.
8907 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8908 when an ambiguity is detected.
8910 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8911 an error due to the ambiguity and the command is aborted.
8913 @kindex show multiple-symbols
8914 @item show multiple-symbols
8915 Show the current value of the @code{multiple-symbols} setting.
8919 @section Program Variables
8921 The most common kind of expression to use is the name of a variable
8924 Variables in expressions are understood in the selected stack frame
8925 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8929 global (or file-static)
8936 visible according to the scope rules of the
8937 programming language from the point of execution in that frame
8940 @noindent This means that in the function
8955 you can examine and use the variable @code{a} whenever your program is
8956 executing within the function @code{foo}, but you can only use or
8957 examine the variable @code{b} while your program is executing inside
8958 the block where @code{b} is declared.
8960 @cindex variable name conflict
8961 There is an exception: you can refer to a variable or function whose
8962 scope is a single source file even if the current execution point is not
8963 in this file. But it is possible to have more than one such variable or
8964 function with the same name (in different source files). If that
8965 happens, referring to that name has unpredictable effects. If you wish,
8966 you can specify a static variable in a particular function or file by
8967 using the colon-colon (@code{::}) notation:
8969 @cindex colon-colon, context for variables/functions
8971 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8972 @cindex @code{::}, context for variables/functions
8975 @var{file}::@var{variable}
8976 @var{function}::@var{variable}
8980 Here @var{file} or @var{function} is the name of the context for the
8981 static @var{variable}. In the case of file names, you can use quotes to
8982 make sure @value{GDBN} parses the file name as a single word---for example,
8983 to print a global value of @code{x} defined in @file{f2.c}:
8986 (@value{GDBP}) p 'f2.c'::x
8989 The @code{::} notation is normally used for referring to
8990 static variables, since you typically disambiguate uses of local variables
8991 in functions by selecting the appropriate frame and using the
8992 simple name of the variable. However, you may also use this notation
8993 to refer to local variables in frames enclosing the selected frame:
9002 process (a); /* Stop here */
9013 For example, if there is a breakpoint at the commented line,
9014 here is what you might see
9015 when the program stops after executing the call @code{bar(0)}:
9020 (@value{GDBP}) p bar::a
9023 #2 0x080483d0 in foo (a=5) at foobar.c:12
9026 (@value{GDBP}) p bar::a
9030 @cindex C@t{++} scope resolution
9031 These uses of @samp{::} are very rarely in conflict with the very
9032 similar use of the same notation in C@t{++}. When they are in
9033 conflict, the C@t{++} meaning takes precedence; however, this can be
9034 overridden by quoting the file or function name with single quotes.
9036 For example, suppose the program is stopped in a method of a class
9037 that has a field named @code{includefile}, and there is also an
9038 include file named @file{includefile} that defines a variable,
9042 (@value{GDBP}) p includefile
9044 (@value{GDBP}) p includefile::some_global
9045 A syntax error in expression, near `'.
9046 (@value{GDBP}) p 'includefile'::some_global
9050 @cindex wrong values
9051 @cindex variable values, wrong
9052 @cindex function entry/exit, wrong values of variables
9053 @cindex optimized code, wrong values of variables
9055 @emph{Warning:} Occasionally, a local variable may appear to have the
9056 wrong value at certain points in a function---just after entry to a new
9057 scope, and just before exit.
9059 You may see this problem when you are stepping by machine instructions.
9060 This is because, on most machines, it takes more than one instruction to
9061 set up a stack frame (including local variable definitions); if you are
9062 stepping by machine instructions, variables may appear to have the wrong
9063 values until the stack frame is completely built. On exit, it usually
9064 also takes more than one machine instruction to destroy a stack frame;
9065 after you begin stepping through that group of instructions, local
9066 variable definitions may be gone.
9068 This may also happen when the compiler does significant optimizations.
9069 To be sure of always seeing accurate values, turn off all optimization
9072 @cindex ``No symbol "foo" in current context''
9073 Another possible effect of compiler optimizations is to optimize
9074 unused variables out of existence, or assign variables to registers (as
9075 opposed to memory addresses). Depending on the support for such cases
9076 offered by the debug info format used by the compiler, @value{GDBN}
9077 might not be able to display values for such local variables. If that
9078 happens, @value{GDBN} will print a message like this:
9081 No symbol "foo" in current context.
9084 To solve such problems, either recompile without optimizations, or use a
9085 different debug info format, if the compiler supports several such
9086 formats. @xref{Compilation}, for more information on choosing compiler
9087 options. @xref{C, ,C and C@t{++}}, for more information about debug
9088 info formats that are best suited to C@t{++} programs.
9090 If you ask to print an object whose contents are unknown to
9091 @value{GDBN}, e.g., because its data type is not completely specified
9092 by the debug information, @value{GDBN} will say @samp{<incomplete
9093 type>}. @xref{Symbols, incomplete type}, for more about this.
9095 If you append @kbd{@@entry} string to a function parameter name you get its
9096 value at the time the function got called. If the value is not available an
9097 error message is printed. Entry values are available only with some compilers.
9098 Entry values are normally also printed at the function parameter list according
9099 to @ref{set print entry-values}.
9102 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9108 (gdb) print i@@entry
9112 Strings are identified as arrays of @code{char} values without specified
9113 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9114 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9115 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9116 defines literal string type @code{"char"} as @code{char} without a sign.
9121 signed char var1[] = "A";
9124 You get during debugging
9129 $2 = @{65 'A', 0 '\0'@}
9133 @section Artificial Arrays
9135 @cindex artificial array
9137 @kindex @@@r{, referencing memory as an array}
9138 It is often useful to print out several successive objects of the
9139 same type in memory; a section of an array, or an array of
9140 dynamically determined size for which only a pointer exists in the
9143 You can do this by referring to a contiguous span of memory as an
9144 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9145 operand of @samp{@@} should be the first element of the desired array
9146 and be an individual object. The right operand should be the desired length
9147 of the array. The result is an array value whose elements are all of
9148 the type of the left argument. The first element is actually the left
9149 argument; the second element comes from bytes of memory immediately
9150 following those that hold the first element, and so on. Here is an
9151 example. If a program says
9154 int *array = (int *) malloc (len * sizeof (int));
9158 you can print the contents of @code{array} with
9164 The left operand of @samp{@@} must reside in memory. Array values made
9165 with @samp{@@} in this way behave just like other arrays in terms of
9166 subscripting, and are coerced to pointers when used in expressions.
9167 Artificial arrays most often appear in expressions via the value history
9168 (@pxref{Value History, ,Value History}), after printing one out.
9170 Another way to create an artificial array is to use a cast.
9171 This re-interprets a value as if it were an array.
9172 The value need not be in memory:
9174 (@value{GDBP}) p/x (short[2])0x12345678
9175 $1 = @{0x1234, 0x5678@}
9178 As a convenience, if you leave the array length out (as in
9179 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9180 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9182 (@value{GDBP}) p/x (short[])0x12345678
9183 $2 = @{0x1234, 0x5678@}
9186 Sometimes the artificial array mechanism is not quite enough; in
9187 moderately complex data structures, the elements of interest may not
9188 actually be adjacent---for example, if you are interested in the values
9189 of pointers in an array. One useful work-around in this situation is
9190 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9191 Variables}) as a counter in an expression that prints the first
9192 interesting value, and then repeat that expression via @key{RET}. For
9193 instance, suppose you have an array @code{dtab} of pointers to
9194 structures, and you are interested in the values of a field @code{fv}
9195 in each structure. Here is an example of what you might type:
9205 @node Output Formats
9206 @section Output Formats
9208 @cindex formatted output
9209 @cindex output formats
9210 By default, @value{GDBN} prints a value according to its data type. Sometimes
9211 this is not what you want. For example, you might want to print a number
9212 in hex, or a pointer in decimal. Or you might want to view data in memory
9213 at a certain address as a character string or as an instruction. To do
9214 these things, specify an @dfn{output format} when you print a value.
9216 The simplest use of output formats is to say how to print a value
9217 already computed. This is done by starting the arguments of the
9218 @code{print} command with a slash and a format letter. The format
9219 letters supported are:
9223 Regard the bits of the value as an integer, and print the integer in
9227 Print as integer in signed decimal.
9230 Print as integer in unsigned decimal.
9233 Print as integer in octal.
9236 Print as integer in binary. The letter @samp{t} stands for ``two''.
9237 @footnote{@samp{b} cannot be used because these format letters are also
9238 used with the @code{x} command, where @samp{b} stands for ``byte'';
9239 see @ref{Memory,,Examining Memory}.}
9242 @cindex unknown address, locating
9243 @cindex locate address
9244 Print as an address, both absolute in hexadecimal and as an offset from
9245 the nearest preceding symbol. You can use this format used to discover
9246 where (in what function) an unknown address is located:
9249 (@value{GDBP}) p/a 0x54320
9250 $3 = 0x54320 <_initialize_vx+396>
9254 The command @code{info symbol 0x54320} yields similar results.
9255 @xref{Symbols, info symbol}.
9258 Regard as an integer and print it as a character constant. This
9259 prints both the numerical value and its character representation. The
9260 character representation is replaced with the octal escape @samp{\nnn}
9261 for characters outside the 7-bit @sc{ascii} range.
9263 Without this format, @value{GDBN} displays @code{char},
9264 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9265 constants. Single-byte members of vectors are displayed as integer
9269 Regard the bits of the value as a floating point number and print
9270 using typical floating point syntax.
9273 @cindex printing strings
9274 @cindex printing byte arrays
9275 Regard as a string, if possible. With this format, pointers to single-byte
9276 data are displayed as null-terminated strings and arrays of single-byte data
9277 are displayed as fixed-length strings. Other values are displayed in their
9280 Without this format, @value{GDBN} displays pointers to and arrays of
9281 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9282 strings. Single-byte members of a vector are displayed as an integer
9286 Like @samp{x} formatting, the value is treated as an integer and
9287 printed as hexadecimal, but leading zeros are printed to pad the value
9288 to the size of the integer type.
9291 @cindex raw printing
9292 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9293 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9294 Printing}). This typically results in a higher-level display of the
9295 value's contents. The @samp{r} format bypasses any Python
9296 pretty-printer which might exist.
9299 For example, to print the program counter in hex (@pxref{Registers}), type
9306 Note that no space is required before the slash; this is because command
9307 names in @value{GDBN} cannot contain a slash.
9309 To reprint the last value in the value history with a different format,
9310 you can use the @code{print} command with just a format and no
9311 expression. For example, @samp{p/x} reprints the last value in hex.
9314 @section Examining Memory
9316 You can use the command @code{x} (for ``examine'') to examine memory in
9317 any of several formats, independently of your program's data types.
9319 @cindex examining memory
9321 @kindex x @r{(examine memory)}
9322 @item x/@var{nfu} @var{addr}
9325 Use the @code{x} command to examine memory.
9328 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9329 much memory to display and how to format it; @var{addr} is an
9330 expression giving the address where you want to start displaying memory.
9331 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9332 Several commands set convenient defaults for @var{addr}.
9335 @item @var{n}, the repeat count
9336 The repeat count is a decimal integer; the default is 1. It specifies
9337 how much memory (counting by units @var{u}) to display. If a negative
9338 number is specified, memory is examined backward from @var{addr}.
9339 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9342 @item @var{f}, the display format
9343 The display format is one of the formats used by @code{print}
9344 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9345 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9346 The default is @samp{x} (hexadecimal) initially. The default changes
9347 each time you use either @code{x} or @code{print}.
9349 @item @var{u}, the unit size
9350 The unit size is any of
9356 Halfwords (two bytes).
9358 Words (four bytes). This is the initial default.
9360 Giant words (eight bytes).
9363 Each time you specify a unit size with @code{x}, that size becomes the
9364 default unit the next time you use @code{x}. For the @samp{i} format,
9365 the unit size is ignored and is normally not written. For the @samp{s} format,
9366 the unit size defaults to @samp{b}, unless it is explicitly given.
9367 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9368 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9369 Note that the results depend on the programming language of the
9370 current compilation unit. If the language is C, the @samp{s}
9371 modifier will use the UTF-16 encoding while @samp{w} will use
9372 UTF-32. The encoding is set by the programming language and cannot
9375 @item @var{addr}, starting display address
9376 @var{addr} is the address where you want @value{GDBN} to begin displaying
9377 memory. The expression need not have a pointer value (though it may);
9378 it is always interpreted as an integer address of a byte of memory.
9379 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9380 @var{addr} is usually just after the last address examined---but several
9381 other commands also set the default address: @code{info breakpoints} (to
9382 the address of the last breakpoint listed), @code{info line} (to the
9383 starting address of a line), and @code{print} (if you use it to display
9384 a value from memory).
9387 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9388 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9389 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9390 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9391 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9393 You can also specify a negative repeat count to examine memory backward
9394 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9395 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9397 Since the letters indicating unit sizes are all distinct from the
9398 letters specifying output formats, you do not have to remember whether
9399 unit size or format comes first; either order works. The output
9400 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9401 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9403 Even though the unit size @var{u} is ignored for the formats @samp{s}
9404 and @samp{i}, you might still want to use a count @var{n}; for example,
9405 @samp{3i} specifies that you want to see three machine instructions,
9406 including any operands. For convenience, especially when used with
9407 the @code{display} command, the @samp{i} format also prints branch delay
9408 slot instructions, if any, beyond the count specified, which immediately
9409 follow the last instruction that is within the count. The command
9410 @code{disassemble} gives an alternative way of inspecting machine
9411 instructions; see @ref{Machine Code,,Source and Machine Code}.
9413 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9414 the command displays null-terminated strings or instructions before the given
9415 address as many as the absolute value of the given number. For the @samp{i}
9416 format, we use line number information in the debug info to accurately locate
9417 instruction boundaries while disassembling backward. If line info is not
9418 available, the command stops examining memory with an error message.
9420 All the defaults for the arguments to @code{x} are designed to make it
9421 easy to continue scanning memory with minimal specifications each time
9422 you use @code{x}. For example, after you have inspected three machine
9423 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9424 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9425 the repeat count @var{n} is used again; the other arguments default as
9426 for successive uses of @code{x}.
9428 When examining machine instructions, the instruction at current program
9429 counter is shown with a @code{=>} marker. For example:
9432 (@value{GDBP}) x/5i $pc-6
9433 0x804837f <main+11>: mov %esp,%ebp
9434 0x8048381 <main+13>: push %ecx
9435 0x8048382 <main+14>: sub $0x4,%esp
9436 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9437 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9440 @cindex @code{$_}, @code{$__}, and value history
9441 The addresses and contents printed by the @code{x} command are not saved
9442 in the value history because there is often too much of them and they
9443 would get in the way. Instead, @value{GDBN} makes these values available for
9444 subsequent use in expressions as values of the convenience variables
9445 @code{$_} and @code{$__}. After an @code{x} command, the last address
9446 examined is available for use in expressions in the convenience variable
9447 @code{$_}. The contents of that address, as examined, are available in
9448 the convenience variable @code{$__}.
9450 If the @code{x} command has a repeat count, the address and contents saved
9451 are from the last memory unit printed; this is not the same as the last
9452 address printed if several units were printed on the last line of output.
9454 @anchor{addressable memory unit}
9455 @cindex addressable memory unit
9456 Most targets have an addressable memory unit size of 8 bits. This means
9457 that to each memory address are associated 8 bits of data. Some
9458 targets, however, have other addressable memory unit sizes.
9459 Within @value{GDBN} and this document, the term
9460 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9461 when explicitly referring to a chunk of data of that size. The word
9462 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9463 the addressable memory unit size of the target. For most systems,
9464 addressable memory unit is a synonym of byte.
9466 @cindex remote memory comparison
9467 @cindex target memory comparison
9468 @cindex verify remote memory image
9469 @cindex verify target memory image
9470 When you are debugging a program running on a remote target machine
9471 (@pxref{Remote Debugging}), you may wish to verify the program's image
9472 in the remote machine's memory against the executable file you
9473 downloaded to the target. Or, on any target, you may want to check
9474 whether the program has corrupted its own read-only sections. The
9475 @code{compare-sections} command is provided for such situations.
9478 @kindex compare-sections
9479 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9480 Compare the data of a loadable section @var{section-name} in the
9481 executable file of the program being debugged with the same section in
9482 the target machine's memory, and report any mismatches. With no
9483 arguments, compares all loadable sections. With an argument of
9484 @code{-r}, compares all loadable read-only sections.
9486 Note: for remote targets, this command can be accelerated if the
9487 target supports computing the CRC checksum of a block of memory
9488 (@pxref{qCRC packet}).
9492 @section Automatic Display
9493 @cindex automatic display
9494 @cindex display of expressions
9496 If you find that you want to print the value of an expression frequently
9497 (to see how it changes), you might want to add it to the @dfn{automatic
9498 display list} so that @value{GDBN} prints its value each time your program stops.
9499 Each expression added to the list is given a number to identify it;
9500 to remove an expression from the list, you specify that number.
9501 The automatic display looks like this:
9505 3: bar[5] = (struct hack *) 0x3804
9509 This display shows item numbers, expressions and their current values. As with
9510 displays you request manually using @code{x} or @code{print}, you can
9511 specify the output format you prefer; in fact, @code{display} decides
9512 whether to use @code{print} or @code{x} depending your format
9513 specification---it uses @code{x} if you specify either the @samp{i}
9514 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9518 @item display @var{expr}
9519 Add the expression @var{expr} to the list of expressions to display
9520 each time your program stops. @xref{Expressions, ,Expressions}.
9522 @code{display} does not repeat if you press @key{RET} again after using it.
9524 @item display/@var{fmt} @var{expr}
9525 For @var{fmt} specifying only a display format and not a size or
9526 count, add the expression @var{expr} to the auto-display list but
9527 arrange to display it each time in the specified format @var{fmt}.
9528 @xref{Output Formats,,Output Formats}.
9530 @item display/@var{fmt} @var{addr}
9531 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9532 number of units, add the expression @var{addr} as a memory address to
9533 be examined each time your program stops. Examining means in effect
9534 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9537 For example, @samp{display/i $pc} can be helpful, to see the machine
9538 instruction about to be executed each time execution stops (@samp{$pc}
9539 is a common name for the program counter; @pxref{Registers, ,Registers}).
9542 @kindex delete display
9544 @item undisplay @var{dnums}@dots{}
9545 @itemx delete display @var{dnums}@dots{}
9546 Remove items from the list of expressions to display. Specify the
9547 numbers of the displays that you want affected with the command
9548 argument @var{dnums}. It can be a single display number, one of the
9549 numbers shown in the first field of the @samp{info display} display;
9550 or it could be a range of display numbers, as in @code{2-4}.
9552 @code{undisplay} does not repeat if you press @key{RET} after using it.
9553 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9555 @kindex disable display
9556 @item disable display @var{dnums}@dots{}
9557 Disable the display of item numbers @var{dnums}. A disabled display
9558 item is not printed automatically, but is not forgotten. It may be
9559 enabled again later. Specify the numbers of the displays that you
9560 want affected with the command argument @var{dnums}. It can be a
9561 single display number, one of the numbers shown in the first field of
9562 the @samp{info display} display; or it could be a range of display
9563 numbers, as in @code{2-4}.
9565 @kindex enable display
9566 @item enable display @var{dnums}@dots{}
9567 Enable display of item numbers @var{dnums}. It becomes effective once
9568 again in auto display of its expression, until you specify otherwise.
9569 Specify the numbers of the displays that you want affected with the
9570 command argument @var{dnums}. It can be a single display number, one
9571 of the numbers shown in the first field of the @samp{info display}
9572 display; or it could be a range of display numbers, as in @code{2-4}.
9575 Display the current values of the expressions on the list, just as is
9576 done when your program stops.
9578 @kindex info display
9580 Print the list of expressions previously set up to display
9581 automatically, each one with its item number, but without showing the
9582 values. This includes disabled expressions, which are marked as such.
9583 It also includes expressions which would not be displayed right now
9584 because they refer to automatic variables not currently available.
9587 @cindex display disabled out of scope
9588 If a display expression refers to local variables, then it does not make
9589 sense outside the lexical context for which it was set up. Such an
9590 expression is disabled when execution enters a context where one of its
9591 variables is not defined. For example, if you give the command
9592 @code{display last_char} while inside a function with an argument
9593 @code{last_char}, @value{GDBN} displays this argument while your program
9594 continues to stop inside that function. When it stops elsewhere---where
9595 there is no variable @code{last_char}---the display is disabled
9596 automatically. The next time your program stops where @code{last_char}
9597 is meaningful, you can enable the display expression once again.
9599 @node Print Settings
9600 @section Print Settings
9602 @cindex format options
9603 @cindex print settings
9604 @value{GDBN} provides the following ways to control how arrays, structures,
9605 and symbols are printed.
9608 These settings are useful for debugging programs in any language:
9612 @item set print address
9613 @itemx set print address on
9614 @cindex print/don't print memory addresses
9615 @value{GDBN} prints memory addresses showing the location of stack
9616 traces, structure values, pointer values, breakpoints, and so forth,
9617 even when it also displays the contents of those addresses. The default
9618 is @code{on}. For example, this is what a stack frame display looks like with
9619 @code{set print address on}:
9624 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9626 530 if (lquote != def_lquote)
9630 @item set print address off
9631 Do not print addresses when displaying their contents. For example,
9632 this is the same stack frame displayed with @code{set print address off}:
9636 (@value{GDBP}) set print addr off
9638 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9639 530 if (lquote != def_lquote)
9643 You can use @samp{set print address off} to eliminate all machine
9644 dependent displays from the @value{GDBN} interface. For example, with
9645 @code{print address off}, you should get the same text for backtraces on
9646 all machines---whether or not they involve pointer arguments.
9649 @item show print address
9650 Show whether or not addresses are to be printed.
9653 When @value{GDBN} prints a symbolic address, it normally prints the
9654 closest earlier symbol plus an offset. If that symbol does not uniquely
9655 identify the address (for example, it is a name whose scope is a single
9656 source file), you may need to clarify. One way to do this is with
9657 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9658 you can set @value{GDBN} to print the source file and line number when
9659 it prints a symbolic address:
9662 @item set print symbol-filename on
9663 @cindex source file and line of a symbol
9664 @cindex symbol, source file and line
9665 Tell @value{GDBN} to print the source file name and line number of a
9666 symbol in the symbolic form of an address.
9668 @item set print symbol-filename off
9669 Do not print source file name and line number of a symbol. This is the
9672 @item show print symbol-filename
9673 Show whether or not @value{GDBN} will print the source file name and
9674 line number of a symbol in the symbolic form of an address.
9677 Another situation where it is helpful to show symbol filenames and line
9678 numbers is when disassembling code; @value{GDBN} shows you the line
9679 number and source file that corresponds to each instruction.
9681 Also, you may wish to see the symbolic form only if the address being
9682 printed is reasonably close to the closest earlier symbol:
9685 @item set print max-symbolic-offset @var{max-offset}
9686 @itemx set print max-symbolic-offset unlimited
9687 @cindex maximum value for offset of closest symbol
9688 Tell @value{GDBN} to only display the symbolic form of an address if the
9689 offset between the closest earlier symbol and the address is less than
9690 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9691 to always print the symbolic form of an address if any symbol precedes
9692 it. Zero is equivalent to @code{unlimited}.
9694 @item show print max-symbolic-offset
9695 Ask how large the maximum offset is that @value{GDBN} prints in a
9699 @cindex wild pointer, interpreting
9700 @cindex pointer, finding referent
9701 If you have a pointer and you are not sure where it points, try
9702 @samp{set print symbol-filename on}. Then you can determine the name
9703 and source file location of the variable where it points, using
9704 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9705 For example, here @value{GDBN} shows that a variable @code{ptt} points
9706 at another variable @code{t}, defined in @file{hi2.c}:
9709 (@value{GDBP}) set print symbol-filename on
9710 (@value{GDBP}) p/a ptt
9711 $4 = 0xe008 <t in hi2.c>
9715 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9716 does not show the symbol name and filename of the referent, even with
9717 the appropriate @code{set print} options turned on.
9720 You can also enable @samp{/a}-like formatting all the time using
9721 @samp{set print symbol on}:
9724 @item set print symbol on
9725 Tell @value{GDBN} to print the symbol corresponding to an address, if
9728 @item set print symbol off
9729 Tell @value{GDBN} not to print the symbol corresponding to an
9730 address. In this mode, @value{GDBN} will still print the symbol
9731 corresponding to pointers to functions. This is the default.
9733 @item show print symbol
9734 Show whether @value{GDBN} will display the symbol corresponding to an
9738 Other settings control how different kinds of objects are printed:
9741 @item set print array
9742 @itemx set print array on
9743 @cindex pretty print arrays
9744 Pretty print arrays. This format is more convenient to read,
9745 but uses more space. The default is off.
9747 @item set print array off
9748 Return to compressed format for arrays.
9750 @item show print array
9751 Show whether compressed or pretty format is selected for displaying
9754 @cindex print array indexes
9755 @item set print array-indexes
9756 @itemx set print array-indexes on
9757 Print the index of each element when displaying arrays. May be more
9758 convenient to locate a given element in the array or quickly find the
9759 index of a given element in that printed array. The default is off.
9761 @item set print array-indexes off
9762 Stop printing element indexes when displaying arrays.
9764 @item show print array-indexes
9765 Show whether the index of each element is printed when displaying
9768 @item set print elements @var{number-of-elements}
9769 @itemx set print elements unlimited
9770 @cindex number of array elements to print
9771 @cindex limit on number of printed array elements
9772 Set a limit on how many elements of an array @value{GDBN} will print.
9773 If @value{GDBN} is printing a large array, it stops printing after it has
9774 printed the number of elements set by the @code{set print elements} command.
9775 This limit also applies to the display of strings.
9776 When @value{GDBN} starts, this limit is set to 200.
9777 Setting @var{number-of-elements} to @code{unlimited} or zero means
9778 that the number of elements to print is unlimited.
9780 @item show print elements
9781 Display the number of elements of a large array that @value{GDBN} will print.
9782 If the number is 0, then the printing is unlimited.
9784 @item set print frame-arguments @var{value}
9785 @kindex set print frame-arguments
9786 @cindex printing frame argument values
9787 @cindex print all frame argument values
9788 @cindex print frame argument values for scalars only
9789 @cindex do not print frame argument values
9790 This command allows to control how the values of arguments are printed
9791 when the debugger prints a frame (@pxref{Frames}). The possible
9796 The values of all arguments are printed.
9799 Print the value of an argument only if it is a scalar. The value of more
9800 complex arguments such as arrays, structures, unions, etc, is replaced
9801 by @code{@dots{}}. This is the default. Here is an example where
9802 only scalar arguments are shown:
9805 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9810 None of the argument values are printed. Instead, the value of each argument
9811 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9814 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9819 By default, only scalar arguments are printed. This command can be used
9820 to configure the debugger to print the value of all arguments, regardless
9821 of their type. However, it is often advantageous to not print the value
9822 of more complex parameters. For instance, it reduces the amount of
9823 information printed in each frame, making the backtrace more readable.
9824 Also, it improves performance when displaying Ada frames, because
9825 the computation of large arguments can sometimes be CPU-intensive,
9826 especially in large applications. Setting @code{print frame-arguments}
9827 to @code{scalars} (the default) or @code{none} avoids this computation,
9828 thus speeding up the display of each Ada frame.
9830 @item show print frame-arguments
9831 Show how the value of arguments should be displayed when printing a frame.
9833 @item set print raw frame-arguments on
9834 Print frame arguments in raw, non pretty-printed, form.
9836 @item set print raw frame-arguments off
9837 Print frame arguments in pretty-printed form, if there is a pretty-printer
9838 for the value (@pxref{Pretty Printing}),
9839 otherwise print the value in raw form.
9840 This is the default.
9842 @item show print raw frame-arguments
9843 Show whether to print frame arguments in raw form.
9845 @anchor{set print entry-values}
9846 @item set print entry-values @var{value}
9847 @kindex set print entry-values
9848 Set printing of frame argument values at function entry. In some cases
9849 @value{GDBN} can determine the value of function argument which was passed by
9850 the function caller, even if the value was modified inside the called function
9851 and therefore is different. With optimized code, the current value could be
9852 unavailable, but the entry value may still be known.
9854 The default value is @code{default} (see below for its description). Older
9855 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9856 this feature will behave in the @code{default} setting the same way as with the
9859 This functionality is currently supported only by DWARF 2 debugging format and
9860 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9861 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9864 The @var{value} parameter can be one of the following:
9868 Print only actual parameter values, never print values from function entry
9872 #0 different (val=6)
9873 #0 lost (val=<optimized out>)
9875 #0 invalid (val=<optimized out>)
9879 Print only parameter values from function entry point. The actual parameter
9880 values are never printed.
9882 #0 equal (val@@entry=5)
9883 #0 different (val@@entry=5)
9884 #0 lost (val@@entry=5)
9885 #0 born (val@@entry=<optimized out>)
9886 #0 invalid (val@@entry=<optimized out>)
9890 Print only parameter values from function entry point. If value from function
9891 entry point is not known while the actual value is known, print the actual
9892 value for such parameter.
9894 #0 equal (val@@entry=5)
9895 #0 different (val@@entry=5)
9896 #0 lost (val@@entry=5)
9898 #0 invalid (val@@entry=<optimized out>)
9902 Print actual parameter values. If actual parameter value is not known while
9903 value from function entry point is known, print the entry point value for such
9907 #0 different (val=6)
9908 #0 lost (val@@entry=5)
9910 #0 invalid (val=<optimized out>)
9914 Always print both the actual parameter value and its value from function entry
9915 point, even if values of one or both are not available due to compiler
9918 #0 equal (val=5, val@@entry=5)
9919 #0 different (val=6, val@@entry=5)
9920 #0 lost (val=<optimized out>, val@@entry=5)
9921 #0 born (val=10, val@@entry=<optimized out>)
9922 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9926 Print the actual parameter value if it is known and also its value from
9927 function entry point if it is known. If neither is known, print for the actual
9928 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9929 values are known and identical, print the shortened
9930 @code{param=param@@entry=VALUE} notation.
9932 #0 equal (val=val@@entry=5)
9933 #0 different (val=6, val@@entry=5)
9934 #0 lost (val@@entry=5)
9936 #0 invalid (val=<optimized out>)
9940 Always print the actual parameter value. Print also its value from function
9941 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9942 if both values are known and identical, print the shortened
9943 @code{param=param@@entry=VALUE} notation.
9945 #0 equal (val=val@@entry=5)
9946 #0 different (val=6, val@@entry=5)
9947 #0 lost (val=<optimized out>, val@@entry=5)
9949 #0 invalid (val=<optimized out>)
9953 For analysis messages on possible failures of frame argument values at function
9954 entry resolution see @ref{set debug entry-values}.
9956 @item show print entry-values
9957 Show the method being used for printing of frame argument values at function
9960 @item set print repeats @var{number-of-repeats}
9961 @itemx set print repeats unlimited
9962 @cindex repeated array elements
9963 Set the threshold for suppressing display of repeated array
9964 elements. When the number of consecutive identical elements of an
9965 array exceeds the threshold, @value{GDBN} prints the string
9966 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9967 identical repetitions, instead of displaying the identical elements
9968 themselves. Setting the threshold to @code{unlimited} or zero will
9969 cause all elements to be individually printed. The default threshold
9972 @item show print repeats
9973 Display the current threshold for printing repeated identical
9976 @item set print null-stop
9977 @cindex @sc{null} elements in arrays
9978 Cause @value{GDBN} to stop printing the characters of an array when the first
9979 @sc{null} is encountered. This is useful when large arrays actually
9980 contain only short strings.
9983 @item show print null-stop
9984 Show whether @value{GDBN} stops printing an array on the first
9985 @sc{null} character.
9987 @item set print pretty on
9988 @cindex print structures in indented form
9989 @cindex indentation in structure display
9990 Cause @value{GDBN} to print structures in an indented format with one member
9991 per line, like this:
10006 @item set print pretty off
10007 Cause @value{GDBN} to print structures in a compact format, like this:
10011 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10012 meat = 0x54 "Pork"@}
10017 This is the default format.
10019 @item show print pretty
10020 Show which format @value{GDBN} is using to print structures.
10022 @item set print sevenbit-strings on
10023 @cindex eight-bit characters in strings
10024 @cindex octal escapes in strings
10025 Print using only seven-bit characters; if this option is set,
10026 @value{GDBN} displays any eight-bit characters (in strings or
10027 character values) using the notation @code{\}@var{nnn}. This setting is
10028 best if you are working in English (@sc{ascii}) and you use the
10029 high-order bit of characters as a marker or ``meta'' bit.
10031 @item set print sevenbit-strings off
10032 Print full eight-bit characters. This allows the use of more
10033 international character sets, and is the default.
10035 @item show print sevenbit-strings
10036 Show whether or not @value{GDBN} is printing only seven-bit characters.
10038 @item set print union on
10039 @cindex unions in structures, printing
10040 Tell @value{GDBN} to print unions which are contained in structures
10041 and other unions. This is the default setting.
10043 @item set print union off
10044 Tell @value{GDBN} not to print unions which are contained in
10045 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10048 @item show print union
10049 Ask @value{GDBN} whether or not it will print unions which are contained in
10050 structures and other unions.
10052 For example, given the declarations
10055 typedef enum @{Tree, Bug@} Species;
10056 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10057 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10068 struct thing foo = @{Tree, @{Acorn@}@};
10072 with @code{set print union on} in effect @samp{p foo} would print
10075 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10079 and with @code{set print union off} in effect it would print
10082 $1 = @{it = Tree, form = @{...@}@}
10086 @code{set print union} affects programs written in C-like languages
10092 These settings are of interest when debugging C@t{++} programs:
10095 @cindex demangling C@t{++} names
10096 @item set print demangle
10097 @itemx set print demangle on
10098 Print C@t{++} names in their source form rather than in the encoded
10099 (``mangled'') form passed to the assembler and linker for type-safe
10100 linkage. The default is on.
10102 @item show print demangle
10103 Show whether C@t{++} names are printed in mangled or demangled form.
10105 @item set print asm-demangle
10106 @itemx set print asm-demangle on
10107 Print C@t{++} names in their source form rather than their mangled form, even
10108 in assembler code printouts such as instruction disassemblies.
10109 The default is off.
10111 @item show print asm-demangle
10112 Show whether C@t{++} names in assembly listings are printed in mangled
10115 @cindex C@t{++} symbol decoding style
10116 @cindex symbol decoding style, C@t{++}
10117 @kindex set demangle-style
10118 @item set demangle-style @var{style}
10119 Choose among several encoding schemes used by different compilers to
10120 represent C@t{++} names. The choices for @var{style} are currently:
10124 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10125 This is the default.
10128 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10131 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10134 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10137 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10138 @strong{Warning:} this setting alone is not sufficient to allow
10139 debugging @code{cfront}-generated executables. @value{GDBN} would
10140 require further enhancement to permit that.
10143 If you omit @var{style}, you will see a list of possible formats.
10145 @item show demangle-style
10146 Display the encoding style currently in use for decoding C@t{++} symbols.
10148 @item set print object
10149 @itemx set print object on
10150 @cindex derived type of an object, printing
10151 @cindex display derived types
10152 When displaying a pointer to an object, identify the @emph{actual}
10153 (derived) type of the object rather than the @emph{declared} type, using
10154 the virtual function table. Note that the virtual function table is
10155 required---this feature can only work for objects that have run-time
10156 type identification; a single virtual method in the object's declared
10157 type is sufficient. Note that this setting is also taken into account when
10158 working with variable objects via MI (@pxref{GDB/MI}).
10160 @item set print object off
10161 Display only the declared type of objects, without reference to the
10162 virtual function table. This is the default setting.
10164 @item show print object
10165 Show whether actual, or declared, object types are displayed.
10167 @item set print static-members
10168 @itemx set print static-members on
10169 @cindex static members of C@t{++} objects
10170 Print static members when displaying a C@t{++} object. The default is on.
10172 @item set print static-members off
10173 Do not print static members when displaying a C@t{++} object.
10175 @item show print static-members
10176 Show whether C@t{++} static members are printed or not.
10178 @item set print pascal_static-members
10179 @itemx set print pascal_static-members on
10180 @cindex static members of Pascal objects
10181 @cindex Pascal objects, static members display
10182 Print static members when displaying a Pascal object. The default is on.
10184 @item set print pascal_static-members off
10185 Do not print static members when displaying a Pascal object.
10187 @item show print pascal_static-members
10188 Show whether Pascal static members are printed or not.
10190 @c These don't work with HP ANSI C++ yet.
10191 @item set print vtbl
10192 @itemx set print vtbl on
10193 @cindex pretty print C@t{++} virtual function tables
10194 @cindex virtual functions (C@t{++}) display
10195 @cindex VTBL display
10196 Pretty print C@t{++} virtual function tables. The default is off.
10197 (The @code{vtbl} commands do not work on programs compiled with the HP
10198 ANSI C@t{++} compiler (@code{aCC}).)
10200 @item set print vtbl off
10201 Do not pretty print C@t{++} virtual function tables.
10203 @item show print vtbl
10204 Show whether C@t{++} virtual function tables are pretty printed, or not.
10207 @node Pretty Printing
10208 @section Pretty Printing
10210 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10211 Python code. It greatly simplifies the display of complex objects. This
10212 mechanism works for both MI and the CLI.
10215 * Pretty-Printer Introduction:: Introduction to pretty-printers
10216 * Pretty-Printer Example:: An example pretty-printer
10217 * Pretty-Printer Commands:: Pretty-printer commands
10220 @node Pretty-Printer Introduction
10221 @subsection Pretty-Printer Introduction
10223 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10224 registered for the value. If there is then @value{GDBN} invokes the
10225 pretty-printer to print the value. Otherwise the value is printed normally.
10227 Pretty-printers are normally named. This makes them easy to manage.
10228 The @samp{info pretty-printer} command will list all the installed
10229 pretty-printers with their names.
10230 If a pretty-printer can handle multiple data types, then its
10231 @dfn{subprinters} are the printers for the individual data types.
10232 Each such subprinter has its own name.
10233 The format of the name is @var{printer-name};@var{subprinter-name}.
10235 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10236 Typically they are automatically loaded and registered when the corresponding
10237 debug information is loaded, thus making them available without having to
10238 do anything special.
10240 There are three places where a pretty-printer can be registered.
10244 Pretty-printers registered globally are available when debugging
10248 Pretty-printers registered with a program space are available only
10249 when debugging that program.
10250 @xref{Progspaces In Python}, for more details on program spaces in Python.
10253 Pretty-printers registered with an objfile are loaded and unloaded
10254 with the corresponding objfile (e.g., shared library).
10255 @xref{Objfiles In Python}, for more details on objfiles in Python.
10258 @xref{Selecting Pretty-Printers}, for further information on how
10259 pretty-printers are selected,
10261 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10264 @node Pretty-Printer Example
10265 @subsection Pretty-Printer Example
10267 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10270 (@value{GDBP}) print s
10272 static npos = 4294967295,
10274 <std::allocator<char>> = @{
10275 <__gnu_cxx::new_allocator<char>> = @{
10276 <No data fields>@}, <No data fields>
10278 members of std::basic_string<char, std::char_traits<char>,
10279 std::allocator<char> >::_Alloc_hider:
10280 _M_p = 0x804a014 "abcd"
10285 With a pretty-printer for @code{std::string} only the contents are printed:
10288 (@value{GDBP}) print s
10292 @node Pretty-Printer Commands
10293 @subsection Pretty-Printer Commands
10294 @cindex pretty-printer commands
10297 @kindex info pretty-printer
10298 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10299 Print the list of installed pretty-printers.
10300 This includes disabled pretty-printers, which are marked as such.
10302 @var{object-regexp} is a regular expression matching the objects
10303 whose pretty-printers to list.
10304 Objects can be @code{global}, the program space's file
10305 (@pxref{Progspaces In Python}),
10306 and the object files within that program space (@pxref{Objfiles In Python}).
10307 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10308 looks up a printer from these three objects.
10310 @var{name-regexp} is a regular expression matching the name of the printers
10313 @kindex disable pretty-printer
10314 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10315 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10316 A disabled pretty-printer is not forgotten, it may be enabled again later.
10318 @kindex enable pretty-printer
10319 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10320 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10325 Suppose we have three pretty-printers installed: one from library1.so
10326 named @code{foo} that prints objects of type @code{foo}, and
10327 another from library2.so named @code{bar} that prints two types of objects,
10328 @code{bar1} and @code{bar2}.
10331 (gdb) info pretty-printer
10338 (gdb) info pretty-printer library2
10343 (gdb) disable pretty-printer library1
10345 2 of 3 printers enabled
10346 (gdb) info pretty-printer
10353 (gdb) disable pretty-printer library2 bar:bar1
10355 1 of 3 printers enabled
10356 (gdb) info pretty-printer library2
10363 (gdb) disable pretty-printer library2 bar
10365 0 of 3 printers enabled
10366 (gdb) info pretty-printer library2
10375 Note that for @code{bar} the entire printer can be disabled,
10376 as can each individual subprinter.
10378 @node Value History
10379 @section Value History
10381 @cindex value history
10382 @cindex history of values printed by @value{GDBN}
10383 Values printed by the @code{print} command are saved in the @value{GDBN}
10384 @dfn{value history}. This allows you to refer to them in other expressions.
10385 Values are kept until the symbol table is re-read or discarded
10386 (for example with the @code{file} or @code{symbol-file} commands).
10387 When the symbol table changes, the value history is discarded,
10388 since the values may contain pointers back to the types defined in the
10393 @cindex history number
10394 The values printed are given @dfn{history numbers} by which you can
10395 refer to them. These are successive integers starting with one.
10396 @code{print} shows you the history number assigned to a value by
10397 printing @samp{$@var{num} = } before the value; here @var{num} is the
10400 To refer to any previous value, use @samp{$} followed by the value's
10401 history number. The way @code{print} labels its output is designed to
10402 remind you of this. Just @code{$} refers to the most recent value in
10403 the history, and @code{$$} refers to the value before that.
10404 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10405 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10406 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10408 For example, suppose you have just printed a pointer to a structure and
10409 want to see the contents of the structure. It suffices to type
10415 If you have a chain of structures where the component @code{next} points
10416 to the next one, you can print the contents of the next one with this:
10423 You can print successive links in the chain by repeating this
10424 command---which you can do by just typing @key{RET}.
10426 Note that the history records values, not expressions. If the value of
10427 @code{x} is 4 and you type these commands:
10435 then the value recorded in the value history by the @code{print} command
10436 remains 4 even though the value of @code{x} has changed.
10439 @kindex show values
10441 Print the last ten values in the value history, with their item numbers.
10442 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10443 values} does not change the history.
10445 @item show values @var{n}
10446 Print ten history values centered on history item number @var{n}.
10448 @item show values +
10449 Print ten history values just after the values last printed. If no more
10450 values are available, @code{show values +} produces no display.
10453 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10454 same effect as @samp{show values +}.
10456 @node Convenience Vars
10457 @section Convenience Variables
10459 @cindex convenience variables
10460 @cindex user-defined variables
10461 @value{GDBN} provides @dfn{convenience variables} that you can use within
10462 @value{GDBN} to hold on to a value and refer to it later. These variables
10463 exist entirely within @value{GDBN}; they are not part of your program, and
10464 setting a convenience variable has no direct effect on further execution
10465 of your program. That is why you can use them freely.
10467 Convenience variables are prefixed with @samp{$}. Any name preceded by
10468 @samp{$} can be used for a convenience variable, unless it is one of
10469 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10470 (Value history references, in contrast, are @emph{numbers} preceded
10471 by @samp{$}. @xref{Value History, ,Value History}.)
10473 You can save a value in a convenience variable with an assignment
10474 expression, just as you would set a variable in your program.
10478 set $foo = *object_ptr
10482 would save in @code{$foo} the value contained in the object pointed to by
10485 Using a convenience variable for the first time creates it, but its
10486 value is @code{void} until you assign a new value. You can alter the
10487 value with another assignment at any time.
10489 Convenience variables have no fixed types. You can assign a convenience
10490 variable any type of value, including structures and arrays, even if
10491 that variable already has a value of a different type. The convenience
10492 variable, when used as an expression, has the type of its current value.
10495 @kindex show convenience
10496 @cindex show all user variables and functions
10497 @item show convenience
10498 Print a list of convenience variables used so far, and their values,
10499 as well as a list of the convenience functions.
10500 Abbreviated @code{show conv}.
10502 @kindex init-if-undefined
10503 @cindex convenience variables, initializing
10504 @item init-if-undefined $@var{variable} = @var{expression}
10505 Set a convenience variable if it has not already been set. This is useful
10506 for user-defined commands that keep some state. It is similar, in concept,
10507 to using local static variables with initializers in C (except that
10508 convenience variables are global). It can also be used to allow users to
10509 override default values used in a command script.
10511 If the variable is already defined then the expression is not evaluated so
10512 any side-effects do not occur.
10515 One of the ways to use a convenience variable is as a counter to be
10516 incremented or a pointer to be advanced. For example, to print
10517 a field from successive elements of an array of structures:
10521 print bar[$i++]->contents
10525 Repeat that command by typing @key{RET}.
10527 Some convenience variables are created automatically by @value{GDBN} and given
10528 values likely to be useful.
10531 @vindex $_@r{, convenience variable}
10533 The variable @code{$_} is automatically set by the @code{x} command to
10534 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10535 commands which provide a default address for @code{x} to examine also
10536 set @code{$_} to that address; these commands include @code{info line}
10537 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10538 except when set by the @code{x} command, in which case it is a pointer
10539 to the type of @code{$__}.
10541 @vindex $__@r{, convenience variable}
10543 The variable @code{$__} is automatically set by the @code{x} command
10544 to the value found in the last address examined. Its type is chosen
10545 to match the format in which the data was printed.
10548 @vindex $_exitcode@r{, convenience variable}
10549 When the program being debugged terminates normally, @value{GDBN}
10550 automatically sets this variable to the exit code of the program, and
10551 resets @code{$_exitsignal} to @code{void}.
10554 @vindex $_exitsignal@r{, convenience variable}
10555 When the program being debugged dies due to an uncaught signal,
10556 @value{GDBN} automatically sets this variable to that signal's number,
10557 and resets @code{$_exitcode} to @code{void}.
10559 To distinguish between whether the program being debugged has exited
10560 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10561 @code{$_exitsignal} is not @code{void}), the convenience function
10562 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10563 Functions}). For example, considering the following source code:
10566 #include <signal.h>
10569 main (int argc, char *argv[])
10576 A valid way of telling whether the program being debugged has exited
10577 or signalled would be:
10580 (@value{GDBP}) define has_exited_or_signalled
10581 Type commands for definition of ``has_exited_or_signalled''.
10582 End with a line saying just ``end''.
10583 >if $_isvoid ($_exitsignal)
10584 >echo The program has exited\n
10586 >echo The program has signalled\n
10592 Program terminated with signal SIGALRM, Alarm clock.
10593 The program no longer exists.
10594 (@value{GDBP}) has_exited_or_signalled
10595 The program has signalled
10598 As can be seen, @value{GDBN} correctly informs that the program being
10599 debugged has signalled, since it calls @code{raise} and raises a
10600 @code{SIGALRM} signal. If the program being debugged had not called
10601 @code{raise}, then @value{GDBN} would report a normal exit:
10604 (@value{GDBP}) has_exited_or_signalled
10605 The program has exited
10609 The variable @code{$_exception} is set to the exception object being
10610 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10613 @itemx $_probe_arg0@dots{}$_probe_arg11
10614 Arguments to a static probe. @xref{Static Probe Points}.
10617 @vindex $_sdata@r{, inspect, convenience variable}
10618 The variable @code{$_sdata} contains extra collected static tracepoint
10619 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10620 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10621 if extra static tracepoint data has not been collected.
10624 @vindex $_siginfo@r{, convenience variable}
10625 The variable @code{$_siginfo} contains extra signal information
10626 (@pxref{extra signal information}). Note that @code{$_siginfo}
10627 could be empty, if the application has not yet received any signals.
10628 For example, it will be empty before you execute the @code{run} command.
10631 @vindex $_tlb@r{, convenience variable}
10632 The variable @code{$_tlb} is automatically set when debugging
10633 applications running on MS-Windows in native mode or connected to
10634 gdbserver that supports the @code{qGetTIBAddr} request.
10635 @xref{General Query Packets}.
10636 This variable contains the address of the thread information block.
10639 The number of the current inferior. @xref{Inferiors and
10640 Programs, ,Debugging Multiple Inferiors and Programs}.
10643 The thread number of the current thread. @xref{thread numbers}.
10646 The global number of the current thread. @xref{global thread numbers}.
10650 @node Convenience Funs
10651 @section Convenience Functions
10653 @cindex convenience functions
10654 @value{GDBN} also supplies some @dfn{convenience functions}. These
10655 have a syntax similar to convenience variables. A convenience
10656 function can be used in an expression just like an ordinary function;
10657 however, a convenience function is implemented internally to
10660 These functions do not require @value{GDBN} to be configured with
10661 @code{Python} support, which means that they are always available.
10665 @item $_isvoid (@var{expr})
10666 @findex $_isvoid@r{, convenience function}
10667 Return one if the expression @var{expr} is @code{void}. Otherwise it
10670 A @code{void} expression is an expression where the type of the result
10671 is @code{void}. For example, you can examine a convenience variable
10672 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10676 (@value{GDBP}) print $_exitcode
10678 (@value{GDBP}) print $_isvoid ($_exitcode)
10681 Starting program: ./a.out
10682 [Inferior 1 (process 29572) exited normally]
10683 (@value{GDBP}) print $_exitcode
10685 (@value{GDBP}) print $_isvoid ($_exitcode)
10689 In the example above, we used @code{$_isvoid} to check whether
10690 @code{$_exitcode} is @code{void} before and after the execution of the
10691 program being debugged. Before the execution there is no exit code to
10692 be examined, therefore @code{$_exitcode} is @code{void}. After the
10693 execution the program being debugged returned zero, therefore
10694 @code{$_exitcode} is zero, which means that it is not @code{void}
10697 The @code{void} expression can also be a call of a function from the
10698 program being debugged. For example, given the following function:
10707 The result of calling it inside @value{GDBN} is @code{void}:
10710 (@value{GDBP}) print foo ()
10712 (@value{GDBP}) print $_isvoid (foo ())
10714 (@value{GDBP}) set $v = foo ()
10715 (@value{GDBP}) print $v
10717 (@value{GDBP}) print $_isvoid ($v)
10723 These functions require @value{GDBN} to be configured with
10724 @code{Python} support.
10728 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10729 @findex $_memeq@r{, convenience function}
10730 Returns one if the @var{length} bytes at the addresses given by
10731 @var{buf1} and @var{buf2} are equal.
10732 Otherwise it returns zero.
10734 @item $_regex(@var{str}, @var{regex})
10735 @findex $_regex@r{, convenience function}
10736 Returns one if the string @var{str} matches the regular expression
10737 @var{regex}. Otherwise it returns zero.
10738 The syntax of the regular expression is that specified by @code{Python}'s
10739 regular expression support.
10741 @item $_streq(@var{str1}, @var{str2})
10742 @findex $_streq@r{, convenience function}
10743 Returns one if the strings @var{str1} and @var{str2} are equal.
10744 Otherwise it returns zero.
10746 @item $_strlen(@var{str})
10747 @findex $_strlen@r{, convenience function}
10748 Returns the length of string @var{str}.
10750 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10751 @findex $_caller_is@r{, convenience function}
10752 Returns one if the calling function's name is equal to @var{name}.
10753 Otherwise it returns zero.
10755 If the optional argument @var{number_of_frames} is provided,
10756 it is the number of frames up in the stack to look.
10764 at testsuite/gdb.python/py-caller-is.c:21
10765 #1 0x00000000004005a0 in middle_func ()
10766 at testsuite/gdb.python/py-caller-is.c:27
10767 #2 0x00000000004005ab in top_func ()
10768 at testsuite/gdb.python/py-caller-is.c:33
10769 #3 0x00000000004005b6 in main ()
10770 at testsuite/gdb.python/py-caller-is.c:39
10771 (gdb) print $_caller_is ("middle_func")
10773 (gdb) print $_caller_is ("top_func", 2)
10777 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10778 @findex $_caller_matches@r{, convenience function}
10779 Returns one if the calling function's name matches the regular expression
10780 @var{regexp}. Otherwise it returns zero.
10782 If the optional argument @var{number_of_frames} is provided,
10783 it is the number of frames up in the stack to look.
10786 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10787 @findex $_any_caller_is@r{, convenience function}
10788 Returns one if any calling function's name is equal to @var{name}.
10789 Otherwise it returns zero.
10791 If the optional argument @var{number_of_frames} is provided,
10792 it is the number of frames up in the stack to look.
10795 This function differs from @code{$_caller_is} in that this function
10796 checks all stack frames from the immediate caller to the frame specified
10797 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10798 frame specified by @var{number_of_frames}.
10800 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10801 @findex $_any_caller_matches@r{, convenience function}
10802 Returns one if any calling function's name matches the regular expression
10803 @var{regexp}. Otherwise it returns zero.
10805 If the optional argument @var{number_of_frames} is provided,
10806 it is the number of frames up in the stack to look.
10809 This function differs from @code{$_caller_matches} in that this function
10810 checks all stack frames from the immediate caller to the frame specified
10811 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10812 frame specified by @var{number_of_frames}.
10814 @item $_as_string(@var{value})
10815 @findex $_as_string@r{, convenience function}
10816 Return the string representation of @var{value}.
10818 This function is useful to obtain the textual label (enumerator) of an
10819 enumeration value. For example, assuming the variable @var{node} is of
10820 an enumerated type:
10823 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10824 Visiting node of type NODE_INTEGER
10829 @value{GDBN} provides the ability to list and get help on
10830 convenience functions.
10833 @item help function
10834 @kindex help function
10835 @cindex show all convenience functions
10836 Print a list of all convenience functions.
10843 You can refer to machine register contents, in expressions, as variables
10844 with names starting with @samp{$}. The names of registers are different
10845 for each machine; use @code{info registers} to see the names used on
10849 @kindex info registers
10850 @item info registers
10851 Print the names and values of all registers except floating-point
10852 and vector registers (in the selected stack frame).
10854 @kindex info all-registers
10855 @cindex floating point registers
10856 @item info all-registers
10857 Print the names and values of all registers, including floating-point
10858 and vector registers (in the selected stack frame).
10860 @item info registers @var{regname} @dots{}
10861 Print the @dfn{relativized} value of each specified register @var{regname}.
10862 As discussed in detail below, register values are normally relative to
10863 the selected stack frame. The @var{regname} may be any register name valid on
10864 the machine you are using, with or without the initial @samp{$}.
10867 @anchor{standard registers}
10868 @cindex stack pointer register
10869 @cindex program counter register
10870 @cindex process status register
10871 @cindex frame pointer register
10872 @cindex standard registers
10873 @value{GDBN} has four ``standard'' register names that are available (in
10874 expressions) on most machines---whenever they do not conflict with an
10875 architecture's canonical mnemonics for registers. The register names
10876 @code{$pc} and @code{$sp} are used for the program counter register and
10877 the stack pointer. @code{$fp} is used for a register that contains a
10878 pointer to the current stack frame, and @code{$ps} is used for a
10879 register that contains the processor status. For example,
10880 you could print the program counter in hex with
10887 or print the instruction to be executed next with
10894 or add four to the stack pointer@footnote{This is a way of removing
10895 one word from the stack, on machines where stacks grow downward in
10896 memory (most machines, nowadays). This assumes that the innermost
10897 stack frame is selected; setting @code{$sp} is not allowed when other
10898 stack frames are selected. To pop entire frames off the stack,
10899 regardless of machine architecture, use @code{return};
10900 see @ref{Returning, ,Returning from a Function}.} with
10906 Whenever possible, these four standard register names are available on
10907 your machine even though the machine has different canonical mnemonics,
10908 so long as there is no conflict. The @code{info registers} command
10909 shows the canonical names. For example, on the SPARC, @code{info
10910 registers} displays the processor status register as @code{$psr} but you
10911 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10912 is an alias for the @sc{eflags} register.
10914 @value{GDBN} always considers the contents of an ordinary register as an
10915 integer when the register is examined in this way. Some machines have
10916 special registers which can hold nothing but floating point; these
10917 registers are considered to have floating point values. There is no way
10918 to refer to the contents of an ordinary register as floating point value
10919 (although you can @emph{print} it as a floating point value with
10920 @samp{print/f $@var{regname}}).
10922 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10923 means that the data format in which the register contents are saved by
10924 the operating system is not the same one that your program normally
10925 sees. For example, the registers of the 68881 floating point
10926 coprocessor are always saved in ``extended'' (raw) format, but all C
10927 programs expect to work with ``double'' (virtual) format. In such
10928 cases, @value{GDBN} normally works with the virtual format only (the format
10929 that makes sense for your program), but the @code{info registers} command
10930 prints the data in both formats.
10932 @cindex SSE registers (x86)
10933 @cindex MMX registers (x86)
10934 Some machines have special registers whose contents can be interpreted
10935 in several different ways. For example, modern x86-based machines
10936 have SSE and MMX registers that can hold several values packed
10937 together in several different formats. @value{GDBN} refers to such
10938 registers in @code{struct} notation:
10941 (@value{GDBP}) print $xmm1
10943 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10944 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10945 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10946 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10947 v4_int32 = @{0, 20657912, 11, 13@},
10948 v2_int64 = @{88725056443645952, 55834574859@},
10949 uint128 = 0x0000000d0000000b013b36f800000000
10954 To set values of such registers, you need to tell @value{GDBN} which
10955 view of the register you wish to change, as if you were assigning
10956 value to a @code{struct} member:
10959 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10962 Normally, register values are relative to the selected stack frame
10963 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10964 value that the register would contain if all stack frames farther in
10965 were exited and their saved registers restored. In order to see the
10966 true contents of hardware registers, you must select the innermost
10967 frame (with @samp{frame 0}).
10969 @cindex caller-saved registers
10970 @cindex call-clobbered registers
10971 @cindex volatile registers
10972 @cindex <not saved> values
10973 Usually ABIs reserve some registers as not needed to be saved by the
10974 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10975 registers). It may therefore not be possible for @value{GDBN} to know
10976 the value a register had before the call (in other words, in the outer
10977 frame), if the register value has since been changed by the callee.
10978 @value{GDBN} tries to deduce where the inner frame saved
10979 (``callee-saved'') registers, from the debug info, unwind info, or the
10980 machine code generated by your compiler. If some register is not
10981 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10982 its own knowledge of the ABI, or because the debug/unwind info
10983 explicitly says the register's value is undefined), @value{GDBN}
10984 displays @w{@samp{<not saved>}} as the register's value. With targets
10985 that @value{GDBN} has no knowledge of the register saving convention,
10986 if a register was not saved by the callee, then its value and location
10987 in the outer frame are assumed to be the same of the inner frame.
10988 This is usually harmless, because if the register is call-clobbered,
10989 the caller either does not care what is in the register after the
10990 call, or has code to restore the value that it does care about. Note,
10991 however, that if you change such a register in the outer frame, you
10992 may also be affecting the inner frame. Also, the more ``outer'' the
10993 frame is you're looking at, the more likely a call-clobbered
10994 register's value is to be wrong, in the sense that it doesn't actually
10995 represent the value the register had just before the call.
10997 @node Floating Point Hardware
10998 @section Floating Point Hardware
10999 @cindex floating point
11001 Depending on the configuration, @value{GDBN} may be able to give
11002 you more information about the status of the floating point hardware.
11007 Display hardware-dependent information about the floating
11008 point unit. The exact contents and layout vary depending on the
11009 floating point chip. Currently, @samp{info float} is supported on
11010 the ARM and x86 machines.
11014 @section Vector Unit
11015 @cindex vector unit
11017 Depending on the configuration, @value{GDBN} may be able to give you
11018 more information about the status of the vector unit.
11021 @kindex info vector
11023 Display information about the vector unit. The exact contents and
11024 layout vary depending on the hardware.
11027 @node OS Information
11028 @section Operating System Auxiliary Information
11029 @cindex OS information
11031 @value{GDBN} provides interfaces to useful OS facilities that can help
11032 you debug your program.
11034 @cindex auxiliary vector
11035 @cindex vector, auxiliary
11036 Some operating systems supply an @dfn{auxiliary vector} to programs at
11037 startup. This is akin to the arguments and environment that you
11038 specify for a program, but contains a system-dependent variety of
11039 binary values that tell system libraries important details about the
11040 hardware, operating system, and process. Each value's purpose is
11041 identified by an integer tag; the meanings are well-known but system-specific.
11042 Depending on the configuration and operating system facilities,
11043 @value{GDBN} may be able to show you this information. For remote
11044 targets, this functionality may further depend on the remote stub's
11045 support of the @samp{qXfer:auxv:read} packet, see
11046 @ref{qXfer auxiliary vector read}.
11051 Display the auxiliary vector of the inferior, which can be either a
11052 live process or a core dump file. @value{GDBN} prints each tag value
11053 numerically, and also shows names and text descriptions for recognized
11054 tags. Some values in the vector are numbers, some bit masks, and some
11055 pointers to strings or other data. @value{GDBN} displays each value in the
11056 most appropriate form for a recognized tag, and in hexadecimal for
11057 an unrecognized tag.
11060 On some targets, @value{GDBN} can access operating system-specific
11061 information and show it to you. The types of information available
11062 will differ depending on the type of operating system running on the
11063 target. The mechanism used to fetch the data is described in
11064 @ref{Operating System Information}. For remote targets, this
11065 functionality depends on the remote stub's support of the
11066 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11070 @item info os @var{infotype}
11072 Display OS information of the requested type.
11074 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11076 @anchor{linux info os infotypes}
11078 @kindex info os cpus
11080 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11081 the available fields from /proc/cpuinfo. For each supported architecture
11082 different fields are available. Two common entries are processor which gives
11083 CPU number and bogomips; a system constant that is calculated during
11084 kernel initialization.
11086 @kindex info os files
11088 Display the list of open file descriptors on the target. For each
11089 file descriptor, @value{GDBN} prints the identifier of the process
11090 owning the descriptor, the command of the owning process, the value
11091 of the descriptor, and the target of the descriptor.
11093 @kindex info os modules
11095 Display the list of all loaded kernel modules on the target. For each
11096 module, @value{GDBN} prints the module name, the size of the module in
11097 bytes, the number of times the module is used, the dependencies of the
11098 module, the status of the module, and the address of the loaded module
11101 @kindex info os msg
11103 Display the list of all System V message queues on the target. For each
11104 message queue, @value{GDBN} prints the message queue key, the message
11105 queue identifier, the access permissions, the current number of bytes
11106 on the queue, the current number of messages on the queue, the processes
11107 that last sent and received a message on the queue, the user and group
11108 of the owner and creator of the message queue, the times at which a
11109 message was last sent and received on the queue, and the time at which
11110 the message queue was last changed.
11112 @kindex info os processes
11114 Display the list of processes on the target. For each process,
11115 @value{GDBN} prints the process identifier, the name of the user, the
11116 command corresponding to the process, and the list of processor cores
11117 that the process is currently running on. (To understand what these
11118 properties mean, for this and the following info types, please consult
11119 the general @sc{gnu}/Linux documentation.)
11121 @kindex info os procgroups
11123 Display the list of process groups on the target. For each process,
11124 @value{GDBN} prints the identifier of the process group that it belongs
11125 to, the command corresponding to the process group leader, the process
11126 identifier, and the command line of the process. The list is sorted
11127 first by the process group identifier, then by the process identifier,
11128 so that processes belonging to the same process group are grouped together
11129 and the process group leader is listed first.
11131 @kindex info os semaphores
11133 Display the list of all System V semaphore sets on the target. For each
11134 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11135 set identifier, the access permissions, the number of semaphores in the
11136 set, the user and group of the owner and creator of the semaphore set,
11137 and the times at which the semaphore set was operated upon and changed.
11139 @kindex info os shm
11141 Display the list of all System V shared-memory regions on the target.
11142 For each shared-memory region, @value{GDBN} prints the region key,
11143 the shared-memory identifier, the access permissions, the size of the
11144 region, the process that created the region, the process that last
11145 attached to or detached from the region, the current number of live
11146 attaches to the region, and the times at which the region was last
11147 attached to, detach from, and changed.
11149 @kindex info os sockets
11151 Display the list of Internet-domain sockets on the target. For each
11152 socket, @value{GDBN} prints the address and port of the local and
11153 remote endpoints, the current state of the connection, the creator of
11154 the socket, the IP address family of the socket, and the type of the
11157 @kindex info os threads
11159 Display the list of threads running on the target. For each thread,
11160 @value{GDBN} prints the identifier of the process that the thread
11161 belongs to, the command of the process, the thread identifier, and the
11162 processor core that it is currently running on. The main thread of a
11163 process is not listed.
11167 If @var{infotype} is omitted, then list the possible values for
11168 @var{infotype} and the kind of OS information available for each
11169 @var{infotype}. If the target does not return a list of possible
11170 types, this command will report an error.
11173 @node Memory Region Attributes
11174 @section Memory Region Attributes
11175 @cindex memory region attributes
11177 @dfn{Memory region attributes} allow you to describe special handling
11178 required by regions of your target's memory. @value{GDBN} uses
11179 attributes to determine whether to allow certain types of memory
11180 accesses; whether to use specific width accesses; and whether to cache
11181 target memory. By default the description of memory regions is
11182 fetched from the target (if the current target supports this), but the
11183 user can override the fetched regions.
11185 Defined memory regions can be individually enabled and disabled. When a
11186 memory region is disabled, @value{GDBN} uses the default attributes when
11187 accessing memory in that region. Similarly, if no memory regions have
11188 been defined, @value{GDBN} uses the default attributes when accessing
11191 When a memory region is defined, it is given a number to identify it;
11192 to enable, disable, or remove a memory region, you specify that number.
11196 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11197 Define a memory region bounded by @var{lower} and @var{upper} with
11198 attributes @var{attributes}@dots{}, and add it to the list of regions
11199 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11200 case: it is treated as the target's maximum memory address.
11201 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11204 Discard any user changes to the memory regions and use target-supplied
11205 regions, if available, or no regions if the target does not support.
11208 @item delete mem @var{nums}@dots{}
11209 Remove memory regions @var{nums}@dots{} from the list of regions
11210 monitored by @value{GDBN}.
11212 @kindex disable mem
11213 @item disable mem @var{nums}@dots{}
11214 Disable monitoring of memory regions @var{nums}@dots{}.
11215 A disabled memory region is not forgotten.
11216 It may be enabled again later.
11219 @item enable mem @var{nums}@dots{}
11220 Enable monitoring of memory regions @var{nums}@dots{}.
11224 Print a table of all defined memory regions, with the following columns
11228 @item Memory Region Number
11229 @item Enabled or Disabled.
11230 Enabled memory regions are marked with @samp{y}.
11231 Disabled memory regions are marked with @samp{n}.
11234 The address defining the inclusive lower bound of the memory region.
11237 The address defining the exclusive upper bound of the memory region.
11240 The list of attributes set for this memory region.
11245 @subsection Attributes
11247 @subsubsection Memory Access Mode
11248 The access mode attributes set whether @value{GDBN} may make read or
11249 write accesses to a memory region.
11251 While these attributes prevent @value{GDBN} from performing invalid
11252 memory accesses, they do nothing to prevent the target system, I/O DMA,
11253 etc.@: from accessing memory.
11257 Memory is read only.
11259 Memory is write only.
11261 Memory is read/write. This is the default.
11264 @subsubsection Memory Access Size
11265 The access size attribute tells @value{GDBN} to use specific sized
11266 accesses in the memory region. Often memory mapped device registers
11267 require specific sized accesses. If no access size attribute is
11268 specified, @value{GDBN} may use accesses of any size.
11272 Use 8 bit memory accesses.
11274 Use 16 bit memory accesses.
11276 Use 32 bit memory accesses.
11278 Use 64 bit memory accesses.
11281 @c @subsubsection Hardware/Software Breakpoints
11282 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11283 @c will use hardware or software breakpoints for the internal breakpoints
11284 @c used by the step, next, finish, until, etc. commands.
11288 @c Always use hardware breakpoints
11289 @c @item swbreak (default)
11292 @subsubsection Data Cache
11293 The data cache attributes set whether @value{GDBN} will cache target
11294 memory. While this generally improves performance by reducing debug
11295 protocol overhead, it can lead to incorrect results because @value{GDBN}
11296 does not know about volatile variables or memory mapped device
11301 Enable @value{GDBN} to cache target memory.
11303 Disable @value{GDBN} from caching target memory. This is the default.
11306 @subsection Memory Access Checking
11307 @value{GDBN} can be instructed to refuse accesses to memory that is
11308 not explicitly described. This can be useful if accessing such
11309 regions has undesired effects for a specific target, or to provide
11310 better error checking. The following commands control this behaviour.
11313 @kindex set mem inaccessible-by-default
11314 @item set mem inaccessible-by-default [on|off]
11315 If @code{on} is specified, make @value{GDBN} treat memory not
11316 explicitly described by the memory ranges as non-existent and refuse accesses
11317 to such memory. The checks are only performed if there's at least one
11318 memory range defined. If @code{off} is specified, make @value{GDBN}
11319 treat the memory not explicitly described by the memory ranges as RAM.
11320 The default value is @code{on}.
11321 @kindex show mem inaccessible-by-default
11322 @item show mem inaccessible-by-default
11323 Show the current handling of accesses to unknown memory.
11327 @c @subsubsection Memory Write Verification
11328 @c The memory write verification attributes set whether @value{GDBN}
11329 @c will re-reads data after each write to verify the write was successful.
11333 @c @item noverify (default)
11336 @node Dump/Restore Files
11337 @section Copy Between Memory and a File
11338 @cindex dump/restore files
11339 @cindex append data to a file
11340 @cindex dump data to a file
11341 @cindex restore data from a file
11343 You can use the commands @code{dump}, @code{append}, and
11344 @code{restore} to copy data between target memory and a file. The
11345 @code{dump} and @code{append} commands write data to a file, and the
11346 @code{restore} command reads data from a file back into the inferior's
11347 memory. Files may be in binary, Motorola S-record, Intel hex,
11348 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11349 append to binary files, and cannot read from Verilog Hex files.
11354 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11355 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11356 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11357 or the value of @var{expr}, to @var{filename} in the given format.
11359 The @var{format} parameter may be any one of:
11366 Motorola S-record format.
11368 Tektronix Hex format.
11370 Verilog Hex format.
11373 @value{GDBN} uses the same definitions of these formats as the
11374 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11375 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11379 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11380 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11381 Append the contents of memory from @var{start_addr} to @var{end_addr},
11382 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11383 (@value{GDBN} can only append data to files in raw binary form.)
11386 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11387 Restore the contents of file @var{filename} into memory. The
11388 @code{restore} command can automatically recognize any known @sc{bfd}
11389 file format, except for raw binary. To restore a raw binary file you
11390 must specify the optional keyword @code{binary} after the filename.
11392 If @var{bias} is non-zero, its value will be added to the addresses
11393 contained in the file. Binary files always start at address zero, so
11394 they will be restored at address @var{bias}. Other bfd files have
11395 a built-in location; they will be restored at offset @var{bias}
11396 from that location.
11398 If @var{start} and/or @var{end} are non-zero, then only data between
11399 file offset @var{start} and file offset @var{end} will be restored.
11400 These offsets are relative to the addresses in the file, before
11401 the @var{bias} argument is applied.
11405 @node Core File Generation
11406 @section How to Produce a Core File from Your Program
11407 @cindex dump core from inferior
11409 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11410 image of a running process and its process status (register values
11411 etc.). Its primary use is post-mortem debugging of a program that
11412 crashed while it ran outside a debugger. A program that crashes
11413 automatically produces a core file, unless this feature is disabled by
11414 the user. @xref{Files}, for information on invoking @value{GDBN} in
11415 the post-mortem debugging mode.
11417 Occasionally, you may wish to produce a core file of the program you
11418 are debugging in order to preserve a snapshot of its state.
11419 @value{GDBN} has a special command for that.
11423 @kindex generate-core-file
11424 @item generate-core-file [@var{file}]
11425 @itemx gcore [@var{file}]
11426 Produce a core dump of the inferior process. The optional argument
11427 @var{file} specifies the file name where to put the core dump. If not
11428 specified, the file name defaults to @file{core.@var{pid}}, where
11429 @var{pid} is the inferior process ID.
11431 Note that this command is implemented only for some systems (as of
11432 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11434 On @sc{gnu}/Linux, this command can take into account the value of the
11435 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11436 dump (@pxref{set use-coredump-filter}).
11438 @kindex set use-coredump-filter
11439 @anchor{set use-coredump-filter}
11440 @item set use-coredump-filter on
11441 @itemx set use-coredump-filter off
11442 Enable or disable the use of the file
11443 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11444 files. This file is used by the Linux kernel to decide what types of
11445 memory mappings will be dumped or ignored when generating a core dump
11446 file. @var{pid} is the process ID of a currently running process.
11448 To make use of this feature, you have to write in the
11449 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11450 which is a bit mask representing the memory mapping types. If a bit
11451 is set in the bit mask, then the memory mappings of the corresponding
11452 types will be dumped; otherwise, they will be ignored. This
11453 configuration is inherited by child processes. For more information
11454 about the bits that can be set in the
11455 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11456 manpage of @code{core(5)}.
11458 By default, this option is @code{on}. If this option is turned
11459 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11460 and instead uses the same default value as the Linux kernel in order
11461 to decide which pages will be dumped in the core dump file. This
11462 value is currently @code{0x33}, which means that bits @code{0}
11463 (anonymous private mappings), @code{1} (anonymous shared mappings),
11464 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11465 This will cause these memory mappings to be dumped automatically.
11468 @node Character Sets
11469 @section Character Sets
11470 @cindex character sets
11472 @cindex translating between character sets
11473 @cindex host character set
11474 @cindex target character set
11476 If the program you are debugging uses a different character set to
11477 represent characters and strings than the one @value{GDBN} uses itself,
11478 @value{GDBN} can automatically translate between the character sets for
11479 you. The character set @value{GDBN} uses we call the @dfn{host
11480 character set}; the one the inferior program uses we call the
11481 @dfn{target character set}.
11483 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11484 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11485 remote protocol (@pxref{Remote Debugging}) to debug a program
11486 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11487 then the host character set is Latin-1, and the target character set is
11488 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11489 target-charset EBCDIC-US}, then @value{GDBN} translates between
11490 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11491 character and string literals in expressions.
11493 @value{GDBN} has no way to automatically recognize which character set
11494 the inferior program uses; you must tell it, using the @code{set
11495 target-charset} command, described below.
11497 Here are the commands for controlling @value{GDBN}'s character set
11501 @item set target-charset @var{charset}
11502 @kindex set target-charset
11503 Set the current target character set to @var{charset}. To display the
11504 list of supported target character sets, type
11505 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11507 @item set host-charset @var{charset}
11508 @kindex set host-charset
11509 Set the current host character set to @var{charset}.
11511 By default, @value{GDBN} uses a host character set appropriate to the
11512 system it is running on; you can override that default using the
11513 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11514 automatically determine the appropriate host character set. In this
11515 case, @value{GDBN} uses @samp{UTF-8}.
11517 @value{GDBN} can only use certain character sets as its host character
11518 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11519 @value{GDBN} will list the host character sets it supports.
11521 @item set charset @var{charset}
11522 @kindex set charset
11523 Set the current host and target character sets to @var{charset}. As
11524 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11525 @value{GDBN} will list the names of the character sets that can be used
11526 for both host and target.
11529 @kindex show charset
11530 Show the names of the current host and target character sets.
11532 @item show host-charset
11533 @kindex show host-charset
11534 Show the name of the current host character set.
11536 @item show target-charset
11537 @kindex show target-charset
11538 Show the name of the current target character set.
11540 @item set target-wide-charset @var{charset}
11541 @kindex set target-wide-charset
11542 Set the current target's wide character set to @var{charset}. This is
11543 the character set used by the target's @code{wchar_t} type. To
11544 display the list of supported wide character sets, type
11545 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11547 @item show target-wide-charset
11548 @kindex show target-wide-charset
11549 Show the name of the current target's wide character set.
11552 Here is an example of @value{GDBN}'s character set support in action.
11553 Assume that the following source code has been placed in the file
11554 @file{charset-test.c}:
11560 = @{72, 101, 108, 108, 111, 44, 32, 119,
11561 111, 114, 108, 100, 33, 10, 0@};
11562 char ibm1047_hello[]
11563 = @{200, 133, 147, 147, 150, 107, 64, 166,
11564 150, 153, 147, 132, 90, 37, 0@};
11568 printf ("Hello, world!\n");
11572 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11573 containing the string @samp{Hello, world!} followed by a newline,
11574 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11576 We compile the program, and invoke the debugger on it:
11579 $ gcc -g charset-test.c -o charset-test
11580 $ gdb -nw charset-test
11581 GNU gdb 2001-12-19-cvs
11582 Copyright 2001 Free Software Foundation, Inc.
11587 We can use the @code{show charset} command to see what character sets
11588 @value{GDBN} is currently using to interpret and display characters and
11592 (@value{GDBP}) show charset
11593 The current host and target character set is `ISO-8859-1'.
11597 For the sake of printing this manual, let's use @sc{ascii} as our
11598 initial character set:
11600 (@value{GDBP}) set charset ASCII
11601 (@value{GDBP}) show charset
11602 The current host and target character set is `ASCII'.
11606 Let's assume that @sc{ascii} is indeed the correct character set for our
11607 host system --- in other words, let's assume that if @value{GDBN} prints
11608 characters using the @sc{ascii} character set, our terminal will display
11609 them properly. Since our current target character set is also
11610 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11613 (@value{GDBP}) print ascii_hello
11614 $1 = 0x401698 "Hello, world!\n"
11615 (@value{GDBP}) print ascii_hello[0]
11620 @value{GDBN} uses the target character set for character and string
11621 literals you use in expressions:
11624 (@value{GDBP}) print '+'
11629 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11632 @value{GDBN} relies on the user to tell it which character set the
11633 target program uses. If we print @code{ibm1047_hello} while our target
11634 character set is still @sc{ascii}, we get jibberish:
11637 (@value{GDBP}) print ibm1047_hello
11638 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11639 (@value{GDBP}) print ibm1047_hello[0]
11644 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11645 @value{GDBN} tells us the character sets it supports:
11648 (@value{GDBP}) set target-charset
11649 ASCII EBCDIC-US IBM1047 ISO-8859-1
11650 (@value{GDBP}) set target-charset
11653 We can select @sc{ibm1047} as our target character set, and examine the
11654 program's strings again. Now the @sc{ascii} string is wrong, but
11655 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11656 target character set, @sc{ibm1047}, to the host character set,
11657 @sc{ascii}, and they display correctly:
11660 (@value{GDBP}) set target-charset IBM1047
11661 (@value{GDBP}) show charset
11662 The current host character set is `ASCII'.
11663 The current target character set is `IBM1047'.
11664 (@value{GDBP}) print ascii_hello
11665 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11666 (@value{GDBP}) print ascii_hello[0]
11668 (@value{GDBP}) print ibm1047_hello
11669 $8 = 0x4016a8 "Hello, world!\n"
11670 (@value{GDBP}) print ibm1047_hello[0]
11675 As above, @value{GDBN} uses the target character set for character and
11676 string literals you use in expressions:
11679 (@value{GDBP}) print '+'
11684 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11687 @node Caching Target Data
11688 @section Caching Data of Targets
11689 @cindex caching data of targets
11691 @value{GDBN} caches data exchanged between the debugger and a target.
11692 Each cache is associated with the address space of the inferior.
11693 @xref{Inferiors and Programs}, about inferior and address space.
11694 Such caching generally improves performance in remote debugging
11695 (@pxref{Remote Debugging}), because it reduces the overhead of the
11696 remote protocol by bundling memory reads and writes into large chunks.
11697 Unfortunately, simply caching everything would lead to incorrect results,
11698 since @value{GDBN} does not necessarily know anything about volatile
11699 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11700 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11702 Therefore, by default, @value{GDBN} only caches data
11703 known to be on the stack@footnote{In non-stop mode, it is moderately
11704 rare for a running thread to modify the stack of a stopped thread
11705 in a way that would interfere with a backtrace, and caching of
11706 stack reads provides a significant speed up of remote backtraces.} or
11707 in the code segment.
11708 Other regions of memory can be explicitly marked as
11709 cacheable; @pxref{Memory Region Attributes}.
11712 @kindex set remotecache
11713 @item set remotecache on
11714 @itemx set remotecache off
11715 This option no longer does anything; it exists for compatibility
11718 @kindex show remotecache
11719 @item show remotecache
11720 Show the current state of the obsolete remotecache flag.
11722 @kindex set stack-cache
11723 @item set stack-cache on
11724 @itemx set stack-cache off
11725 Enable or disable caching of stack accesses. When @code{on}, use
11726 caching. By default, this option is @code{on}.
11728 @kindex show stack-cache
11729 @item show stack-cache
11730 Show the current state of data caching for memory accesses.
11732 @kindex set code-cache
11733 @item set code-cache on
11734 @itemx set code-cache off
11735 Enable or disable caching of code segment accesses. When @code{on},
11736 use caching. By default, this option is @code{on}. This improves
11737 performance of disassembly in remote debugging.
11739 @kindex show code-cache
11740 @item show code-cache
11741 Show the current state of target memory cache for code segment
11744 @kindex info dcache
11745 @item info dcache @r{[}line@r{]}
11746 Print the information about the performance of data cache of the
11747 current inferior's address space. The information displayed
11748 includes the dcache width and depth, and for each cache line, its
11749 number, address, and how many times it was referenced. This
11750 command is useful for debugging the data cache operation.
11752 If a line number is specified, the contents of that line will be
11755 @item set dcache size @var{size}
11756 @cindex dcache size
11757 @kindex set dcache size
11758 Set maximum number of entries in dcache (dcache depth above).
11760 @item set dcache line-size @var{line-size}
11761 @cindex dcache line-size
11762 @kindex set dcache line-size
11763 Set number of bytes each dcache entry caches (dcache width above).
11764 Must be a power of 2.
11766 @item show dcache size
11767 @kindex show dcache size
11768 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11770 @item show dcache line-size
11771 @kindex show dcache line-size
11772 Show default size of dcache lines.
11776 @node Searching Memory
11777 @section Search Memory
11778 @cindex searching memory
11780 Memory can be searched for a particular sequence of bytes with the
11781 @code{find} command.
11785 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11786 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11787 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11788 etc. The search begins at address @var{start_addr} and continues for either
11789 @var{len} bytes or through to @var{end_addr} inclusive.
11792 @var{s} and @var{n} are optional parameters.
11793 They may be specified in either order, apart or together.
11796 @item @var{s}, search query size
11797 The size of each search query value.
11803 halfwords (two bytes)
11807 giant words (eight bytes)
11810 All values are interpreted in the current language.
11811 This means, for example, that if the current source language is C/C@t{++}
11812 then searching for the string ``hello'' includes the trailing '\0'.
11814 If the value size is not specified, it is taken from the
11815 value's type in the current language.
11816 This is useful when one wants to specify the search
11817 pattern as a mixture of types.
11818 Note that this means, for example, that in the case of C-like languages
11819 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11820 which is typically four bytes.
11822 @item @var{n}, maximum number of finds
11823 The maximum number of matches to print. The default is to print all finds.
11826 You can use strings as search values. Quote them with double-quotes
11828 The string value is copied into the search pattern byte by byte,
11829 regardless of the endianness of the target and the size specification.
11831 The address of each match found is printed as well as a count of the
11832 number of matches found.
11834 The address of the last value found is stored in convenience variable
11836 A count of the number of matches is stored in @samp{$numfound}.
11838 For example, if stopped at the @code{printf} in this function:
11844 static char hello[] = "hello-hello";
11845 static struct @{ char c; short s; int i; @}
11846 __attribute__ ((packed)) mixed
11847 = @{ 'c', 0x1234, 0x87654321 @};
11848 printf ("%s\n", hello);
11853 you get during debugging:
11856 (gdb) find &hello[0], +sizeof(hello), "hello"
11857 0x804956d <hello.1620+6>
11859 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11860 0x8049567 <hello.1620>
11861 0x804956d <hello.1620+6>
11863 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11864 0x8049567 <hello.1620>
11866 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11867 0x8049560 <mixed.1625>
11869 (gdb) print $numfound
11872 $2 = (void *) 0x8049560
11876 @section Value Sizes
11878 Whenever @value{GDBN} prints a value memory will be allocated within
11879 @value{GDBN} to hold the contents of the value. It is possible in
11880 some languages with dynamic typing systems, that an invalid program
11881 may indicate a value that is incorrectly large, this in turn may cause
11882 @value{GDBN} to try and allocate an overly large ammount of memory.
11885 @kindex set max-value-size
11886 @item set max-value-size @var{bytes}
11887 @itemx set max-value-size unlimited
11888 Set the maximum size of memory that @value{GDBN} will allocate for the
11889 contents of a value to @var{bytes}, trying to display a value that
11890 requires more memory than that will result in an error.
11892 Setting this variable does not effect values that have already been
11893 allocated within @value{GDBN}, only future allocations.
11895 There's a minimum size that @code{max-value-size} can be set to in
11896 order that @value{GDBN} can still operate correctly, this minimum is
11897 currently 16 bytes.
11899 The limit applies to the results of some subexpressions as well as to
11900 complete expressions. For example, an expression denoting a simple
11901 integer component, such as @code{x.y.z}, may fail if the size of
11902 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
11903 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
11904 @var{A} is an array variable with non-constant size, will generally
11905 succeed regardless of the bounds on @var{A}, as long as the component
11906 size is less than @var{bytes}.
11908 The default value of @code{max-value-size} is currently 64k.
11910 @kindex show max-value-size
11911 @item show max-value-size
11912 Show the maximum size of memory, in bytes, that @value{GDBN} will
11913 allocate for the contents of a value.
11916 @node Optimized Code
11917 @chapter Debugging Optimized Code
11918 @cindex optimized code, debugging
11919 @cindex debugging optimized code
11921 Almost all compilers support optimization. With optimization
11922 disabled, the compiler generates assembly code that corresponds
11923 directly to your source code, in a simplistic way. As the compiler
11924 applies more powerful optimizations, the generated assembly code
11925 diverges from your original source code. With help from debugging
11926 information generated by the compiler, @value{GDBN} can map from
11927 the running program back to constructs from your original source.
11929 @value{GDBN} is more accurate with optimization disabled. If you
11930 can recompile without optimization, it is easier to follow the
11931 progress of your program during debugging. But, there are many cases
11932 where you may need to debug an optimized version.
11934 When you debug a program compiled with @samp{-g -O}, remember that the
11935 optimizer has rearranged your code; the debugger shows you what is
11936 really there. Do not be too surprised when the execution path does not
11937 exactly match your source file! An extreme example: if you define a
11938 variable, but never use it, @value{GDBN} never sees that
11939 variable---because the compiler optimizes it out of existence.
11941 Some things do not work as well with @samp{-g -O} as with just
11942 @samp{-g}, particularly on machines with instruction scheduling. If in
11943 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11944 please report it to us as a bug (including a test case!).
11945 @xref{Variables}, for more information about debugging optimized code.
11948 * Inline Functions:: How @value{GDBN} presents inlining
11949 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11952 @node Inline Functions
11953 @section Inline Functions
11954 @cindex inline functions, debugging
11956 @dfn{Inlining} is an optimization that inserts a copy of the function
11957 body directly at each call site, instead of jumping to a shared
11958 routine. @value{GDBN} displays inlined functions just like
11959 non-inlined functions. They appear in backtraces. You can view their
11960 arguments and local variables, step into them with @code{step}, skip
11961 them with @code{next}, and escape from them with @code{finish}.
11962 You can check whether a function was inlined by using the
11963 @code{info frame} command.
11965 For @value{GDBN} to support inlined functions, the compiler must
11966 record information about inlining in the debug information ---
11967 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11968 other compilers do also. @value{GDBN} only supports inlined functions
11969 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11970 do not emit two required attributes (@samp{DW_AT_call_file} and
11971 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11972 function calls with earlier versions of @value{NGCC}. It instead
11973 displays the arguments and local variables of inlined functions as
11974 local variables in the caller.
11976 The body of an inlined function is directly included at its call site;
11977 unlike a non-inlined function, there are no instructions devoted to
11978 the call. @value{GDBN} still pretends that the call site and the
11979 start of the inlined function are different instructions. Stepping to
11980 the call site shows the call site, and then stepping again shows
11981 the first line of the inlined function, even though no additional
11982 instructions are executed.
11984 This makes source-level debugging much clearer; you can see both the
11985 context of the call and then the effect of the call. Only stepping by
11986 a single instruction using @code{stepi} or @code{nexti} does not do
11987 this; single instruction steps always show the inlined body.
11989 There are some ways that @value{GDBN} does not pretend that inlined
11990 function calls are the same as normal calls:
11994 Setting breakpoints at the call site of an inlined function may not
11995 work, because the call site does not contain any code. @value{GDBN}
11996 may incorrectly move the breakpoint to the next line of the enclosing
11997 function, after the call. This limitation will be removed in a future
11998 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11999 or inside the inlined function instead.
12002 @value{GDBN} cannot locate the return value of inlined calls after
12003 using the @code{finish} command. This is a limitation of compiler-generated
12004 debugging information; after @code{finish}, you can step to the next line
12005 and print a variable where your program stored the return value.
12009 @node Tail Call Frames
12010 @section Tail Call Frames
12011 @cindex tail call frames, debugging
12013 Function @code{B} can call function @code{C} in its very last statement. In
12014 unoptimized compilation the call of @code{C} is immediately followed by return
12015 instruction at the end of @code{B} code. Optimizing compiler may replace the
12016 call and return in function @code{B} into one jump to function @code{C}
12017 instead. Such use of a jump instruction is called @dfn{tail call}.
12019 During execution of function @code{C}, there will be no indication in the
12020 function call stack frames that it was tail-called from @code{B}. If function
12021 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12022 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12023 some cases @value{GDBN} can determine that @code{C} was tail-called from
12024 @code{B}, and it will then create fictitious call frame for that, with the
12025 return address set up as if @code{B} called @code{C} normally.
12027 This functionality is currently supported only by DWARF 2 debugging format and
12028 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
12029 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12032 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12033 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12037 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12039 Stack level 1, frame at 0x7fffffffda30:
12040 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12041 tail call frame, caller of frame at 0x7fffffffda30
12042 source language c++.
12043 Arglist at unknown address.
12044 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12047 The detection of all the possible code path executions can find them ambiguous.
12048 There is no execution history stored (possible @ref{Reverse Execution} is never
12049 used for this purpose) and the last known caller could have reached the known
12050 callee by multiple different jump sequences. In such case @value{GDBN} still
12051 tries to show at least all the unambiguous top tail callers and all the
12052 unambiguous bottom tail calees, if any.
12055 @anchor{set debug entry-values}
12056 @item set debug entry-values
12057 @kindex set debug entry-values
12058 When set to on, enables printing of analysis messages for both frame argument
12059 values at function entry and tail calls. It will show all the possible valid
12060 tail calls code paths it has considered. It will also print the intersection
12061 of them with the final unambiguous (possibly partial or even empty) code path
12064 @item show debug entry-values
12065 @kindex show debug entry-values
12066 Show the current state of analysis messages printing for both frame argument
12067 values at function entry and tail calls.
12070 The analysis messages for tail calls can for example show why the virtual tail
12071 call frame for function @code{c} has not been recognized (due to the indirect
12072 reference by variable @code{x}):
12075 static void __attribute__((noinline, noclone)) c (void);
12076 void (*x) (void) = c;
12077 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12078 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12079 int main (void) @{ x (); return 0; @}
12081 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
12082 DW_TAG_GNU_call_site 0x40039a in main
12084 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12087 #1 0x000000000040039a in main () at t.c:5
12090 Another possibility is an ambiguous virtual tail call frames resolution:
12094 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12095 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12096 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12097 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12098 static void __attribute__((noinline, noclone)) b (void)
12099 @{ if (i) c (); else e (); @}
12100 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12101 int main (void) @{ a (); return 0; @}
12103 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12104 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12105 tailcall: reduced: 0x4004d2(a) |
12108 #1 0x00000000004004d2 in a () at t.c:8
12109 #2 0x0000000000400395 in main () at t.c:9
12112 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12113 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12115 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12116 @ifset HAVE_MAKEINFO_CLICK
12117 @set ARROW @click{}
12118 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12119 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12121 @ifclear HAVE_MAKEINFO_CLICK
12123 @set CALLSEQ1B @value{CALLSEQ1A}
12124 @set CALLSEQ2B @value{CALLSEQ2A}
12127 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12128 The code can have possible execution paths @value{CALLSEQ1B} or
12129 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12131 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12132 has found. It then finds another possible calling sequcen - that one is
12133 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12134 printed as the @code{reduced:} calling sequence. That one could have many
12135 futher @code{compare:} and @code{reduced:} statements as long as there remain
12136 any non-ambiguous sequence entries.
12138 For the frame of function @code{b} in both cases there are different possible
12139 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12140 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12141 therefore this one is displayed to the user while the ambiguous frames are
12144 There can be also reasons why printing of frame argument values at function
12149 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12150 static void __attribute__((noinline, noclone)) a (int i);
12151 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12152 static void __attribute__((noinline, noclone)) a (int i)
12153 @{ if (i) b (i - 1); else c (0); @}
12154 int main (void) @{ a (5); return 0; @}
12157 #0 c (i=i@@entry=0) at t.c:2
12158 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
12159 function "a" at 0x400420 can call itself via tail calls
12160 i=<optimized out>) at t.c:6
12161 #2 0x000000000040036e in main () at t.c:7
12164 @value{GDBN} cannot find out from the inferior state if and how many times did
12165 function @code{a} call itself (via function @code{b}) as these calls would be
12166 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12167 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12168 prints @code{<optimized out>} instead.
12171 @chapter C Preprocessor Macros
12173 Some languages, such as C and C@t{++}, provide a way to define and invoke
12174 ``preprocessor macros'' which expand into strings of tokens.
12175 @value{GDBN} can evaluate expressions containing macro invocations, show
12176 the result of macro expansion, and show a macro's definition, including
12177 where it was defined.
12179 You may need to compile your program specially to provide @value{GDBN}
12180 with information about preprocessor macros. Most compilers do not
12181 include macros in their debugging information, even when you compile
12182 with the @option{-g} flag. @xref{Compilation}.
12184 A program may define a macro at one point, remove that definition later,
12185 and then provide a different definition after that. Thus, at different
12186 points in the program, a macro may have different definitions, or have
12187 no definition at all. If there is a current stack frame, @value{GDBN}
12188 uses the macros in scope at that frame's source code line. Otherwise,
12189 @value{GDBN} uses the macros in scope at the current listing location;
12192 Whenever @value{GDBN} evaluates an expression, it always expands any
12193 macro invocations present in the expression. @value{GDBN} also provides
12194 the following commands for working with macros explicitly.
12198 @kindex macro expand
12199 @cindex macro expansion, showing the results of preprocessor
12200 @cindex preprocessor macro expansion, showing the results of
12201 @cindex expanding preprocessor macros
12202 @item macro expand @var{expression}
12203 @itemx macro exp @var{expression}
12204 Show the results of expanding all preprocessor macro invocations in
12205 @var{expression}. Since @value{GDBN} simply expands macros, but does
12206 not parse the result, @var{expression} need not be a valid expression;
12207 it can be any string of tokens.
12210 @item macro expand-once @var{expression}
12211 @itemx macro exp1 @var{expression}
12212 @cindex expand macro once
12213 @i{(This command is not yet implemented.)} Show the results of
12214 expanding those preprocessor macro invocations that appear explicitly in
12215 @var{expression}. Macro invocations appearing in that expansion are
12216 left unchanged. This command allows you to see the effect of a
12217 particular macro more clearly, without being confused by further
12218 expansions. Since @value{GDBN} simply expands macros, but does not
12219 parse the result, @var{expression} need not be a valid expression; it
12220 can be any string of tokens.
12223 @cindex macro definition, showing
12224 @cindex definition of a macro, showing
12225 @cindex macros, from debug info
12226 @item info macro [-a|-all] [--] @var{macro}
12227 Show the current definition or all definitions of the named @var{macro},
12228 and describe the source location or compiler command-line where that
12229 definition was established. The optional double dash is to signify the end of
12230 argument processing and the beginning of @var{macro} for non C-like macros where
12231 the macro may begin with a hyphen.
12233 @kindex info macros
12234 @item info macros @var{location}
12235 Show all macro definitions that are in effect at the location specified
12236 by @var{location}, and describe the source location or compiler
12237 command-line where those definitions were established.
12239 @kindex macro define
12240 @cindex user-defined macros
12241 @cindex defining macros interactively
12242 @cindex macros, user-defined
12243 @item macro define @var{macro} @var{replacement-list}
12244 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12245 Introduce a definition for a preprocessor macro named @var{macro},
12246 invocations of which are replaced by the tokens given in
12247 @var{replacement-list}. The first form of this command defines an
12248 ``object-like'' macro, which takes no arguments; the second form
12249 defines a ``function-like'' macro, which takes the arguments given in
12252 A definition introduced by this command is in scope in every
12253 expression evaluated in @value{GDBN}, until it is removed with the
12254 @code{macro undef} command, described below. The definition overrides
12255 all definitions for @var{macro} present in the program being debugged,
12256 as well as any previous user-supplied definition.
12258 @kindex macro undef
12259 @item macro undef @var{macro}
12260 Remove any user-supplied definition for the macro named @var{macro}.
12261 This command only affects definitions provided with the @code{macro
12262 define} command, described above; it cannot remove definitions present
12263 in the program being debugged.
12267 List all the macros defined using the @code{macro define} command.
12270 @cindex macros, example of debugging with
12271 Here is a transcript showing the above commands in action. First, we
12272 show our source files:
12277 #include "sample.h"
12280 #define ADD(x) (M + x)
12285 printf ("Hello, world!\n");
12287 printf ("We're so creative.\n");
12289 printf ("Goodbye, world!\n");
12296 Now, we compile the program using the @sc{gnu} C compiler,
12297 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12298 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12299 and @option{-gdwarf-4}; we recommend always choosing the most recent
12300 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12301 includes information about preprocessor macros in the debugging
12305 $ gcc -gdwarf-2 -g3 sample.c -o sample
12309 Now, we start @value{GDBN} on our sample program:
12313 GNU gdb 2002-05-06-cvs
12314 Copyright 2002 Free Software Foundation, Inc.
12315 GDB is free software, @dots{}
12319 We can expand macros and examine their definitions, even when the
12320 program is not running. @value{GDBN} uses the current listing position
12321 to decide which macro definitions are in scope:
12324 (@value{GDBP}) list main
12327 5 #define ADD(x) (M + x)
12332 10 printf ("Hello, world!\n");
12334 12 printf ("We're so creative.\n");
12335 (@value{GDBP}) info macro ADD
12336 Defined at /home/jimb/gdb/macros/play/sample.c:5
12337 #define ADD(x) (M + x)
12338 (@value{GDBP}) info macro Q
12339 Defined at /home/jimb/gdb/macros/play/sample.h:1
12340 included at /home/jimb/gdb/macros/play/sample.c:2
12342 (@value{GDBP}) macro expand ADD(1)
12343 expands to: (42 + 1)
12344 (@value{GDBP}) macro expand-once ADD(1)
12345 expands to: once (M + 1)
12349 In the example above, note that @code{macro expand-once} expands only
12350 the macro invocation explicit in the original text --- the invocation of
12351 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12352 which was introduced by @code{ADD}.
12354 Once the program is running, @value{GDBN} uses the macro definitions in
12355 force at the source line of the current stack frame:
12358 (@value{GDBP}) break main
12359 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12361 Starting program: /home/jimb/gdb/macros/play/sample
12363 Breakpoint 1, main () at sample.c:10
12364 10 printf ("Hello, world!\n");
12368 At line 10, the definition of the macro @code{N} at line 9 is in force:
12371 (@value{GDBP}) info macro N
12372 Defined at /home/jimb/gdb/macros/play/sample.c:9
12374 (@value{GDBP}) macro expand N Q M
12375 expands to: 28 < 42
12376 (@value{GDBP}) print N Q M
12381 As we step over directives that remove @code{N}'s definition, and then
12382 give it a new definition, @value{GDBN} finds the definition (or lack
12383 thereof) in force at each point:
12386 (@value{GDBP}) next
12388 12 printf ("We're so creative.\n");
12389 (@value{GDBP}) info macro N
12390 The symbol `N' has no definition as a C/C++ preprocessor macro
12391 at /home/jimb/gdb/macros/play/sample.c:12
12392 (@value{GDBP}) next
12394 14 printf ("Goodbye, world!\n");
12395 (@value{GDBP}) info macro N
12396 Defined at /home/jimb/gdb/macros/play/sample.c:13
12398 (@value{GDBP}) macro expand N Q M
12399 expands to: 1729 < 42
12400 (@value{GDBP}) print N Q M
12405 In addition to source files, macros can be defined on the compilation command
12406 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12407 such a way, @value{GDBN} displays the location of their definition as line zero
12408 of the source file submitted to the compiler.
12411 (@value{GDBP}) info macro __STDC__
12412 Defined at /home/jimb/gdb/macros/play/sample.c:0
12419 @chapter Tracepoints
12420 @c This chapter is based on the documentation written by Michael
12421 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12423 @cindex tracepoints
12424 In some applications, it is not feasible for the debugger to interrupt
12425 the program's execution long enough for the developer to learn
12426 anything helpful about its behavior. If the program's correctness
12427 depends on its real-time behavior, delays introduced by a debugger
12428 might cause the program to change its behavior drastically, or perhaps
12429 fail, even when the code itself is correct. It is useful to be able
12430 to observe the program's behavior without interrupting it.
12432 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12433 specify locations in the program, called @dfn{tracepoints}, and
12434 arbitrary expressions to evaluate when those tracepoints are reached.
12435 Later, using the @code{tfind} command, you can examine the values
12436 those expressions had when the program hit the tracepoints. The
12437 expressions may also denote objects in memory---structures or arrays,
12438 for example---whose values @value{GDBN} should record; while visiting
12439 a particular tracepoint, you may inspect those objects as if they were
12440 in memory at that moment. However, because @value{GDBN} records these
12441 values without interacting with you, it can do so quickly and
12442 unobtrusively, hopefully not disturbing the program's behavior.
12444 The tracepoint facility is currently available only for remote
12445 targets. @xref{Targets}. In addition, your remote target must know
12446 how to collect trace data. This functionality is implemented in the
12447 remote stub; however, none of the stubs distributed with @value{GDBN}
12448 support tracepoints as of this writing. The format of the remote
12449 packets used to implement tracepoints are described in @ref{Tracepoint
12452 It is also possible to get trace data from a file, in a manner reminiscent
12453 of corefiles; you specify the filename, and use @code{tfind} to search
12454 through the file. @xref{Trace Files}, for more details.
12456 This chapter describes the tracepoint commands and features.
12459 * Set Tracepoints::
12460 * Analyze Collected Data::
12461 * Tracepoint Variables::
12465 @node Set Tracepoints
12466 @section Commands to Set Tracepoints
12468 Before running such a @dfn{trace experiment}, an arbitrary number of
12469 tracepoints can be set. A tracepoint is actually a special type of
12470 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12471 standard breakpoint commands. For instance, as with breakpoints,
12472 tracepoint numbers are successive integers starting from one, and many
12473 of the commands associated with tracepoints take the tracepoint number
12474 as their argument, to identify which tracepoint to work on.
12476 For each tracepoint, you can specify, in advance, some arbitrary set
12477 of data that you want the target to collect in the trace buffer when
12478 it hits that tracepoint. The collected data can include registers,
12479 local variables, or global data. Later, you can use @value{GDBN}
12480 commands to examine the values these data had at the time the
12481 tracepoint was hit.
12483 Tracepoints do not support every breakpoint feature. Ignore counts on
12484 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12485 commands when they are hit. Tracepoints may not be thread-specific
12488 @cindex fast tracepoints
12489 Some targets may support @dfn{fast tracepoints}, which are inserted in
12490 a different way (such as with a jump instead of a trap), that is
12491 faster but possibly restricted in where they may be installed.
12493 @cindex static tracepoints
12494 @cindex markers, static tracepoints
12495 @cindex probing markers, static tracepoints
12496 Regular and fast tracepoints are dynamic tracing facilities, meaning
12497 that they can be used to insert tracepoints at (almost) any location
12498 in the target. Some targets may also support controlling @dfn{static
12499 tracepoints} from @value{GDBN}. With static tracing, a set of
12500 instrumentation points, also known as @dfn{markers}, are embedded in
12501 the target program, and can be activated or deactivated by name or
12502 address. These are usually placed at locations which facilitate
12503 investigating what the target is actually doing. @value{GDBN}'s
12504 support for static tracing includes being able to list instrumentation
12505 points, and attach them with @value{GDBN} defined high level
12506 tracepoints that expose the whole range of convenience of
12507 @value{GDBN}'s tracepoints support. Namely, support for collecting
12508 registers values and values of global or local (to the instrumentation
12509 point) variables; tracepoint conditions and trace state variables.
12510 The act of installing a @value{GDBN} static tracepoint on an
12511 instrumentation point, or marker, is referred to as @dfn{probing} a
12512 static tracepoint marker.
12514 @code{gdbserver} supports tracepoints on some target systems.
12515 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12517 This section describes commands to set tracepoints and associated
12518 conditions and actions.
12521 * Create and Delete Tracepoints::
12522 * Enable and Disable Tracepoints::
12523 * Tracepoint Passcounts::
12524 * Tracepoint Conditions::
12525 * Trace State Variables::
12526 * Tracepoint Actions::
12527 * Listing Tracepoints::
12528 * Listing Static Tracepoint Markers::
12529 * Starting and Stopping Trace Experiments::
12530 * Tracepoint Restrictions::
12533 @node Create and Delete Tracepoints
12534 @subsection Create and Delete Tracepoints
12537 @cindex set tracepoint
12539 @item trace @var{location}
12540 The @code{trace} command is very similar to the @code{break} command.
12541 Its argument @var{location} can be any valid location.
12542 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12543 which is a point in the target program where the debugger will briefly stop,
12544 collect some data, and then allow the program to continue. Setting a tracepoint
12545 or changing its actions takes effect immediately if the remote stub
12546 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12548 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12549 these changes don't take effect until the next @code{tstart}
12550 command, and once a trace experiment is running, further changes will
12551 not have any effect until the next trace experiment starts. In addition,
12552 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12553 address is not yet resolved. (This is similar to pending breakpoints.)
12554 Pending tracepoints are not downloaded to the target and not installed
12555 until they are resolved. The resolution of pending tracepoints requires
12556 @value{GDBN} support---when debugging with the remote target, and
12557 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12558 tracing}), pending tracepoints can not be resolved (and downloaded to
12559 the remote stub) while @value{GDBN} is disconnected.
12561 Here are some examples of using the @code{trace} command:
12564 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12566 (@value{GDBP}) @b{trace +2} // 2 lines forward
12568 (@value{GDBP}) @b{trace my_function} // first source line of function
12570 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12572 (@value{GDBP}) @b{trace *0x2117c4} // an address
12576 You can abbreviate @code{trace} as @code{tr}.
12578 @item trace @var{location} if @var{cond}
12579 Set a tracepoint with condition @var{cond}; evaluate the expression
12580 @var{cond} each time the tracepoint is reached, and collect data only
12581 if the value is nonzero---that is, if @var{cond} evaluates as true.
12582 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12583 information on tracepoint conditions.
12585 @item ftrace @var{location} [ if @var{cond} ]
12586 @cindex set fast tracepoint
12587 @cindex fast tracepoints, setting
12589 The @code{ftrace} command sets a fast tracepoint. For targets that
12590 support them, fast tracepoints will use a more efficient but possibly
12591 less general technique to trigger data collection, such as a jump
12592 instruction instead of a trap, or some sort of hardware support. It
12593 may not be possible to create a fast tracepoint at the desired
12594 location, in which case the command will exit with an explanatory
12597 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12600 On 32-bit x86-architecture systems, fast tracepoints normally need to
12601 be placed at an instruction that is 5 bytes or longer, but can be
12602 placed at 4-byte instructions if the low 64K of memory of the target
12603 program is available to install trampolines. Some Unix-type systems,
12604 such as @sc{gnu}/Linux, exclude low addresses from the program's
12605 address space; but for instance with the Linux kernel it is possible
12606 to let @value{GDBN} use this area by doing a @command{sysctl} command
12607 to set the @code{mmap_min_addr} kernel parameter, as in
12610 sudo sysctl -w vm.mmap_min_addr=32768
12614 which sets the low address to 32K, which leaves plenty of room for
12615 trampolines. The minimum address should be set to a page boundary.
12617 @item strace @var{location} [ if @var{cond} ]
12618 @cindex set static tracepoint
12619 @cindex static tracepoints, setting
12620 @cindex probe static tracepoint marker
12622 The @code{strace} command sets a static tracepoint. For targets that
12623 support it, setting a static tracepoint probes a static
12624 instrumentation point, or marker, found at @var{location}. It may not
12625 be possible to set a static tracepoint at the desired location, in
12626 which case the command will exit with an explanatory message.
12628 @value{GDBN} handles arguments to @code{strace} exactly as for
12629 @code{trace}, with the addition that the user can also specify
12630 @code{-m @var{marker}} as @var{location}. This probes the marker
12631 identified by the @var{marker} string identifier. This identifier
12632 depends on the static tracepoint backend library your program is
12633 using. You can find all the marker identifiers in the @samp{ID} field
12634 of the @code{info static-tracepoint-markers} command output.
12635 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12636 Markers}. For example, in the following small program using the UST
12642 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12647 the marker id is composed of joining the first two arguments to the
12648 @code{trace_mark} call with a slash, which translates to:
12651 (@value{GDBP}) info static-tracepoint-markers
12652 Cnt Enb ID Address What
12653 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12659 so you may probe the marker above with:
12662 (@value{GDBP}) strace -m ust/bar33
12665 Static tracepoints accept an extra collect action --- @code{collect
12666 $_sdata}. This collects arbitrary user data passed in the probe point
12667 call to the tracing library. In the UST example above, you'll see
12668 that the third argument to @code{trace_mark} is a printf-like format
12669 string. The user data is then the result of running that formating
12670 string against the following arguments. Note that @code{info
12671 static-tracepoint-markers} command output lists that format string in
12672 the @samp{Data:} field.
12674 You can inspect this data when analyzing the trace buffer, by printing
12675 the $_sdata variable like any other variable available to
12676 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12679 @cindex last tracepoint number
12680 @cindex recent tracepoint number
12681 @cindex tracepoint number
12682 The convenience variable @code{$tpnum} records the tracepoint number
12683 of the most recently set tracepoint.
12685 @kindex delete tracepoint
12686 @cindex tracepoint deletion
12687 @item delete tracepoint @r{[}@var{num}@r{]}
12688 Permanently delete one or more tracepoints. With no argument, the
12689 default is to delete all tracepoints. Note that the regular
12690 @code{delete} command can remove tracepoints also.
12695 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12697 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12701 You can abbreviate this command as @code{del tr}.
12704 @node Enable and Disable Tracepoints
12705 @subsection Enable and Disable Tracepoints
12707 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12710 @kindex disable tracepoint
12711 @item disable tracepoint @r{[}@var{num}@r{]}
12712 Disable tracepoint @var{num}, or all tracepoints if no argument
12713 @var{num} is given. A disabled tracepoint will have no effect during
12714 a trace experiment, but it is not forgotten. You can re-enable
12715 a disabled tracepoint using the @code{enable tracepoint} command.
12716 If the command is issued during a trace experiment and the debug target
12717 has support for disabling tracepoints during a trace experiment, then the
12718 change will be effective immediately. Otherwise, it will be applied to the
12719 next trace experiment.
12721 @kindex enable tracepoint
12722 @item enable tracepoint @r{[}@var{num}@r{]}
12723 Enable tracepoint @var{num}, or all tracepoints. If this command is
12724 issued during a trace experiment and the debug target supports enabling
12725 tracepoints during a trace experiment, then the enabled tracepoints will
12726 become effective immediately. Otherwise, they will become effective the
12727 next time a trace experiment is run.
12730 @node Tracepoint Passcounts
12731 @subsection Tracepoint Passcounts
12735 @cindex tracepoint pass count
12736 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12737 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12738 automatically stop a trace experiment. If a tracepoint's passcount is
12739 @var{n}, then the trace experiment will be automatically stopped on
12740 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12741 @var{num} is not specified, the @code{passcount} command sets the
12742 passcount of the most recently defined tracepoint. If no passcount is
12743 given, the trace experiment will run until stopped explicitly by the
12749 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12750 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12752 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12753 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12754 (@value{GDBP}) @b{trace foo}
12755 (@value{GDBP}) @b{pass 3}
12756 (@value{GDBP}) @b{trace bar}
12757 (@value{GDBP}) @b{pass 2}
12758 (@value{GDBP}) @b{trace baz}
12759 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12760 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12761 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12762 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12766 @node Tracepoint Conditions
12767 @subsection Tracepoint Conditions
12768 @cindex conditional tracepoints
12769 @cindex tracepoint conditions
12771 The simplest sort of tracepoint collects data every time your program
12772 reaches a specified place. You can also specify a @dfn{condition} for
12773 a tracepoint. A condition is just a Boolean expression in your
12774 programming language (@pxref{Expressions, ,Expressions}). A
12775 tracepoint with a condition evaluates the expression each time your
12776 program reaches it, and data collection happens only if the condition
12779 Tracepoint conditions can be specified when a tracepoint is set, by
12780 using @samp{if} in the arguments to the @code{trace} command.
12781 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12782 also be set or changed at any time with the @code{condition} command,
12783 just as with breakpoints.
12785 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12786 the conditional expression itself. Instead, @value{GDBN} encodes the
12787 expression into an agent expression (@pxref{Agent Expressions})
12788 suitable for execution on the target, independently of @value{GDBN}.
12789 Global variables become raw memory locations, locals become stack
12790 accesses, and so forth.
12792 For instance, suppose you have a function that is usually called
12793 frequently, but should not be called after an error has occurred. You
12794 could use the following tracepoint command to collect data about calls
12795 of that function that happen while the error code is propagating
12796 through the program; an unconditional tracepoint could end up
12797 collecting thousands of useless trace frames that you would have to
12801 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12804 @node Trace State Variables
12805 @subsection Trace State Variables
12806 @cindex trace state variables
12808 A @dfn{trace state variable} is a special type of variable that is
12809 created and managed by target-side code. The syntax is the same as
12810 that for GDB's convenience variables (a string prefixed with ``$''),
12811 but they are stored on the target. They must be created explicitly,
12812 using a @code{tvariable} command. They are always 64-bit signed
12815 Trace state variables are remembered by @value{GDBN}, and downloaded
12816 to the target along with tracepoint information when the trace
12817 experiment starts. There are no intrinsic limits on the number of
12818 trace state variables, beyond memory limitations of the target.
12820 @cindex convenience variables, and trace state variables
12821 Although trace state variables are managed by the target, you can use
12822 them in print commands and expressions as if they were convenience
12823 variables; @value{GDBN} will get the current value from the target
12824 while the trace experiment is running. Trace state variables share
12825 the same namespace as other ``$'' variables, which means that you
12826 cannot have trace state variables with names like @code{$23} or
12827 @code{$pc}, nor can you have a trace state variable and a convenience
12828 variable with the same name.
12832 @item tvariable $@var{name} [ = @var{expression} ]
12834 The @code{tvariable} command creates a new trace state variable named
12835 @code{$@var{name}}, and optionally gives it an initial value of
12836 @var{expression}. The @var{expression} is evaluated when this command is
12837 entered; the result will be converted to an integer if possible,
12838 otherwise @value{GDBN} will report an error. A subsequent
12839 @code{tvariable} command specifying the same name does not create a
12840 variable, but instead assigns the supplied initial value to the
12841 existing variable of that name, overwriting any previous initial
12842 value. The default initial value is 0.
12844 @item info tvariables
12845 @kindex info tvariables
12846 List all the trace state variables along with their initial values.
12847 Their current values may also be displayed, if the trace experiment is
12850 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12851 @kindex delete tvariable
12852 Delete the given trace state variables, or all of them if no arguments
12857 @node Tracepoint Actions
12858 @subsection Tracepoint Action Lists
12862 @cindex tracepoint actions
12863 @item actions @r{[}@var{num}@r{]}
12864 This command will prompt for a list of actions to be taken when the
12865 tracepoint is hit. If the tracepoint number @var{num} is not
12866 specified, this command sets the actions for the one that was most
12867 recently defined (so that you can define a tracepoint and then say
12868 @code{actions} without bothering about its number). You specify the
12869 actions themselves on the following lines, one action at a time, and
12870 terminate the actions list with a line containing just @code{end}. So
12871 far, the only defined actions are @code{collect}, @code{teval}, and
12872 @code{while-stepping}.
12874 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12875 Commands, ,Breakpoint Command Lists}), except that only the defined
12876 actions are allowed; any other @value{GDBN} command is rejected.
12878 @cindex remove actions from a tracepoint
12879 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12880 and follow it immediately with @samp{end}.
12883 (@value{GDBP}) @b{collect @var{data}} // collect some data
12885 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12887 (@value{GDBP}) @b{end} // signals the end of actions.
12890 In the following example, the action list begins with @code{collect}
12891 commands indicating the things to be collected when the tracepoint is
12892 hit. Then, in order to single-step and collect additional data
12893 following the tracepoint, a @code{while-stepping} command is used,
12894 followed by the list of things to be collected after each step in a
12895 sequence of single steps. The @code{while-stepping} command is
12896 terminated by its own separate @code{end} command. Lastly, the action
12897 list is terminated by an @code{end} command.
12900 (@value{GDBP}) @b{trace foo}
12901 (@value{GDBP}) @b{actions}
12902 Enter actions for tracepoint 1, one per line:
12905 > while-stepping 12
12906 > collect $pc, arr[i]
12911 @kindex collect @r{(tracepoints)}
12912 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12913 Collect values of the given expressions when the tracepoint is hit.
12914 This command accepts a comma-separated list of any valid expressions.
12915 In addition to global, static, or local variables, the following
12916 special arguments are supported:
12920 Collect all registers.
12923 Collect all function arguments.
12926 Collect all local variables.
12929 Collect the return address. This is helpful if you want to see more
12932 @emph{Note:} The return address location can not always be reliably
12933 determined up front, and the wrong address / registers may end up
12934 collected instead. On some architectures the reliability is higher
12935 for tracepoints at function entry, while on others it's the opposite.
12936 When this happens, backtracing will stop because the return address is
12937 found unavailable (unless another collect rule happened to match it).
12940 Collects the number of arguments from the static probe at which the
12941 tracepoint is located.
12942 @xref{Static Probe Points}.
12944 @item $_probe_arg@var{n}
12945 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12946 from the static probe at which the tracepoint is located.
12947 @xref{Static Probe Points}.
12950 @vindex $_sdata@r{, collect}
12951 Collect static tracepoint marker specific data. Only available for
12952 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12953 Lists}. On the UST static tracepoints library backend, an
12954 instrumentation point resembles a @code{printf} function call. The
12955 tracing library is able to collect user specified data formatted to a
12956 character string using the format provided by the programmer that
12957 instrumented the program. Other backends have similar mechanisms.
12958 Here's an example of a UST marker call:
12961 const char master_name[] = "$your_name";
12962 trace_mark(channel1, marker1, "hello %s", master_name)
12965 In this case, collecting @code{$_sdata} collects the string
12966 @samp{hello $yourname}. When analyzing the trace buffer, you can
12967 inspect @samp{$_sdata} like any other variable available to
12971 You can give several consecutive @code{collect} commands, each one
12972 with a single argument, or one @code{collect} command with several
12973 arguments separated by commas; the effect is the same.
12975 The optional @var{mods} changes the usual handling of the arguments.
12976 @code{s} requests that pointers to chars be handled as strings, in
12977 particular collecting the contents of the memory being pointed at, up
12978 to the first zero. The upper bound is by default the value of the
12979 @code{print elements} variable; if @code{s} is followed by a decimal
12980 number, that is the upper bound instead. So for instance
12981 @samp{collect/s25 mystr} collects as many as 25 characters at
12984 The command @code{info scope} (@pxref{Symbols, info scope}) is
12985 particularly useful for figuring out what data to collect.
12987 @kindex teval @r{(tracepoints)}
12988 @item teval @var{expr1}, @var{expr2}, @dots{}
12989 Evaluate the given expressions when the tracepoint is hit. This
12990 command accepts a comma-separated list of expressions. The results
12991 are discarded, so this is mainly useful for assigning values to trace
12992 state variables (@pxref{Trace State Variables}) without adding those
12993 values to the trace buffer, as would be the case if the @code{collect}
12996 @kindex while-stepping @r{(tracepoints)}
12997 @item while-stepping @var{n}
12998 Perform @var{n} single-step instruction traces after the tracepoint,
12999 collecting new data after each step. The @code{while-stepping}
13000 command is followed by the list of what to collect while stepping
13001 (followed by its own @code{end} command):
13004 > while-stepping 12
13005 > collect $regs, myglobal
13011 Note that @code{$pc} is not automatically collected by
13012 @code{while-stepping}; you need to explicitly collect that register if
13013 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13016 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13017 @kindex set default-collect
13018 @cindex default collection action
13019 This variable is a list of expressions to collect at each tracepoint
13020 hit. It is effectively an additional @code{collect} action prepended
13021 to every tracepoint action list. The expressions are parsed
13022 individually for each tracepoint, so for instance a variable named
13023 @code{xyz} may be interpreted as a global for one tracepoint, and a
13024 local for another, as appropriate to the tracepoint's location.
13026 @item show default-collect
13027 @kindex show default-collect
13028 Show the list of expressions that are collected by default at each
13033 @node Listing Tracepoints
13034 @subsection Listing Tracepoints
13037 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13038 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13039 @cindex information about tracepoints
13040 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13041 Display information about the tracepoint @var{num}. If you don't
13042 specify a tracepoint number, displays information about all the
13043 tracepoints defined so far. The format is similar to that used for
13044 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13045 command, simply restricting itself to tracepoints.
13047 A tracepoint's listing may include additional information specific to
13052 its passcount as given by the @code{passcount @var{n}} command
13055 the state about installed on target of each location
13059 (@value{GDBP}) @b{info trace}
13060 Num Type Disp Enb Address What
13061 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13063 collect globfoo, $regs
13068 2 tracepoint keep y <MULTIPLE>
13070 2.1 y 0x0804859c in func4 at change-loc.h:35
13071 installed on target
13072 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13073 installed on target
13074 2.3 y <PENDING> set_tracepoint
13075 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13076 not installed on target
13081 This command can be abbreviated @code{info tp}.
13084 @node Listing Static Tracepoint Markers
13085 @subsection Listing Static Tracepoint Markers
13088 @kindex info static-tracepoint-markers
13089 @cindex information about static tracepoint markers
13090 @item info static-tracepoint-markers
13091 Display information about all static tracepoint markers defined in the
13094 For each marker, the following columns are printed:
13098 An incrementing counter, output to help readability. This is not a
13101 The marker ID, as reported by the target.
13102 @item Enabled or Disabled
13103 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13104 that are not enabled.
13106 Where the marker is in your program, as a memory address.
13108 Where the marker is in the source for your program, as a file and line
13109 number. If the debug information included in the program does not
13110 allow @value{GDBN} to locate the source of the marker, this column
13111 will be left blank.
13115 In addition, the following information may be printed for each marker:
13119 User data passed to the tracing library by the marker call. In the
13120 UST backend, this is the format string passed as argument to the
13122 @item Static tracepoints probing the marker
13123 The list of static tracepoints attached to the marker.
13127 (@value{GDBP}) info static-tracepoint-markers
13128 Cnt ID Enb Address What
13129 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13130 Data: number1 %d number2 %d
13131 Probed by static tracepoints: #2
13132 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13138 @node Starting and Stopping Trace Experiments
13139 @subsection Starting and Stopping Trace Experiments
13142 @kindex tstart [ @var{notes} ]
13143 @cindex start a new trace experiment
13144 @cindex collected data discarded
13146 This command starts the trace experiment, and begins collecting data.
13147 It has the side effect of discarding all the data collected in the
13148 trace buffer during the previous trace experiment. If any arguments
13149 are supplied, they are taken as a note and stored with the trace
13150 experiment's state. The notes may be arbitrary text, and are
13151 especially useful with disconnected tracing in a multi-user context;
13152 the notes can explain what the trace is doing, supply user contact
13153 information, and so forth.
13155 @kindex tstop [ @var{notes} ]
13156 @cindex stop a running trace experiment
13158 This command stops the trace experiment. If any arguments are
13159 supplied, they are recorded with the experiment as a note. This is
13160 useful if you are stopping a trace started by someone else, for
13161 instance if the trace is interfering with the system's behavior and
13162 needs to be stopped quickly.
13164 @strong{Note}: a trace experiment and data collection may stop
13165 automatically if any tracepoint's passcount is reached
13166 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13169 @cindex status of trace data collection
13170 @cindex trace experiment, status of
13172 This command displays the status of the current trace data
13176 Here is an example of the commands we described so far:
13179 (@value{GDBP}) @b{trace gdb_c_test}
13180 (@value{GDBP}) @b{actions}
13181 Enter actions for tracepoint #1, one per line.
13182 > collect $regs,$locals,$args
13183 > while-stepping 11
13187 (@value{GDBP}) @b{tstart}
13188 [time passes @dots{}]
13189 (@value{GDBP}) @b{tstop}
13192 @anchor{disconnected tracing}
13193 @cindex disconnected tracing
13194 You can choose to continue running the trace experiment even if
13195 @value{GDBN} disconnects from the target, voluntarily or
13196 involuntarily. For commands such as @code{detach}, the debugger will
13197 ask what you want to do with the trace. But for unexpected
13198 terminations (@value{GDBN} crash, network outage), it would be
13199 unfortunate to lose hard-won trace data, so the variable
13200 @code{disconnected-tracing} lets you decide whether the trace should
13201 continue running without @value{GDBN}.
13204 @item set disconnected-tracing on
13205 @itemx set disconnected-tracing off
13206 @kindex set disconnected-tracing
13207 Choose whether a tracing run should continue to run if @value{GDBN}
13208 has disconnected from the target. Note that @code{detach} or
13209 @code{quit} will ask you directly what to do about a running trace no
13210 matter what this variable's setting, so the variable is mainly useful
13211 for handling unexpected situations, such as loss of the network.
13213 @item show disconnected-tracing
13214 @kindex show disconnected-tracing
13215 Show the current choice for disconnected tracing.
13219 When you reconnect to the target, the trace experiment may or may not
13220 still be running; it might have filled the trace buffer in the
13221 meantime, or stopped for one of the other reasons. If it is running,
13222 it will continue after reconnection.
13224 Upon reconnection, the target will upload information about the
13225 tracepoints in effect. @value{GDBN} will then compare that
13226 information to the set of tracepoints currently defined, and attempt
13227 to match them up, allowing for the possibility that the numbers may
13228 have changed due to creation and deletion in the meantime. If one of
13229 the target's tracepoints does not match any in @value{GDBN}, the
13230 debugger will create a new tracepoint, so that you have a number with
13231 which to specify that tracepoint. This matching-up process is
13232 necessarily heuristic, and it may result in useless tracepoints being
13233 created; you may simply delete them if they are of no use.
13235 @cindex circular trace buffer
13236 If your target agent supports a @dfn{circular trace buffer}, then you
13237 can run a trace experiment indefinitely without filling the trace
13238 buffer; when space runs out, the agent deletes already-collected trace
13239 frames, oldest first, until there is enough room to continue
13240 collecting. This is especially useful if your tracepoints are being
13241 hit too often, and your trace gets terminated prematurely because the
13242 buffer is full. To ask for a circular trace buffer, simply set
13243 @samp{circular-trace-buffer} to on. You can set this at any time,
13244 including during tracing; if the agent can do it, it will change
13245 buffer handling on the fly, otherwise it will not take effect until
13249 @item set circular-trace-buffer on
13250 @itemx set circular-trace-buffer off
13251 @kindex set circular-trace-buffer
13252 Choose whether a tracing run should use a linear or circular buffer
13253 for trace data. A linear buffer will not lose any trace data, but may
13254 fill up prematurely, while a circular buffer will discard old trace
13255 data, but it will have always room for the latest tracepoint hits.
13257 @item show circular-trace-buffer
13258 @kindex show circular-trace-buffer
13259 Show the current choice for the trace buffer. Note that this may not
13260 match the agent's current buffer handling, nor is it guaranteed to
13261 match the setting that might have been in effect during a past run,
13262 for instance if you are looking at frames from a trace file.
13267 @item set trace-buffer-size @var{n}
13268 @itemx set trace-buffer-size unlimited
13269 @kindex set trace-buffer-size
13270 Request that the target use a trace buffer of @var{n} bytes. Not all
13271 targets will honor the request; they may have a compiled-in size for
13272 the trace buffer, or some other limitation. Set to a value of
13273 @code{unlimited} or @code{-1} to let the target use whatever size it
13274 likes. This is also the default.
13276 @item show trace-buffer-size
13277 @kindex show trace-buffer-size
13278 Show the current requested size for the trace buffer. Note that this
13279 will only match the actual size if the target supports size-setting,
13280 and was able to handle the requested size. For instance, if the
13281 target can only change buffer size between runs, this variable will
13282 not reflect the change until the next run starts. Use @code{tstatus}
13283 to get a report of the actual buffer size.
13287 @item set trace-user @var{text}
13288 @kindex set trace-user
13290 @item show trace-user
13291 @kindex show trace-user
13293 @item set trace-notes @var{text}
13294 @kindex set trace-notes
13295 Set the trace run's notes.
13297 @item show trace-notes
13298 @kindex show trace-notes
13299 Show the trace run's notes.
13301 @item set trace-stop-notes @var{text}
13302 @kindex set trace-stop-notes
13303 Set the trace run's stop notes. The handling of the note is as for
13304 @code{tstop} arguments; the set command is convenient way to fix a
13305 stop note that is mistaken or incomplete.
13307 @item show trace-stop-notes
13308 @kindex show trace-stop-notes
13309 Show the trace run's stop notes.
13313 @node Tracepoint Restrictions
13314 @subsection Tracepoint Restrictions
13316 @cindex tracepoint restrictions
13317 There are a number of restrictions on the use of tracepoints. As
13318 described above, tracepoint data gathering occurs on the target
13319 without interaction from @value{GDBN}. Thus the full capabilities of
13320 the debugger are not available during data gathering, and then at data
13321 examination time, you will be limited by only having what was
13322 collected. The following items describe some common problems, but it
13323 is not exhaustive, and you may run into additional difficulties not
13329 Tracepoint expressions are intended to gather objects (lvalues). Thus
13330 the full flexibility of GDB's expression evaluator is not available.
13331 You cannot call functions, cast objects to aggregate types, access
13332 convenience variables or modify values (except by assignment to trace
13333 state variables). Some language features may implicitly call
13334 functions (for instance Objective-C fields with accessors), and therefore
13335 cannot be collected either.
13338 Collection of local variables, either individually or in bulk with
13339 @code{$locals} or @code{$args}, during @code{while-stepping} may
13340 behave erratically. The stepping action may enter a new scope (for
13341 instance by stepping into a function), or the location of the variable
13342 may change (for instance it is loaded into a register). The
13343 tracepoint data recorded uses the location information for the
13344 variables that is correct for the tracepoint location. When the
13345 tracepoint is created, it is not possible, in general, to determine
13346 where the steps of a @code{while-stepping} sequence will advance the
13347 program---particularly if a conditional branch is stepped.
13350 Collection of an incompletely-initialized or partially-destroyed object
13351 may result in something that @value{GDBN} cannot display, or displays
13352 in a misleading way.
13355 When @value{GDBN} displays a pointer to character it automatically
13356 dereferences the pointer to also display characters of the string
13357 being pointed to. However, collecting the pointer during tracing does
13358 not automatically collect the string. You need to explicitly
13359 dereference the pointer and provide size information if you want to
13360 collect not only the pointer, but the memory pointed to. For example,
13361 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13365 It is not possible to collect a complete stack backtrace at a
13366 tracepoint. Instead, you may collect the registers and a few hundred
13367 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13368 (adjust to use the name of the actual stack pointer register on your
13369 target architecture, and the amount of stack you wish to capture).
13370 Then the @code{backtrace} command will show a partial backtrace when
13371 using a trace frame. The number of stack frames that can be examined
13372 depends on the sizes of the frames in the collected stack. Note that
13373 if you ask for a block so large that it goes past the bottom of the
13374 stack, the target agent may report an error trying to read from an
13378 If you do not collect registers at a tracepoint, @value{GDBN} can
13379 infer that the value of @code{$pc} must be the same as the address of
13380 the tracepoint and use that when you are looking at a trace frame
13381 for that tracepoint. However, this cannot work if the tracepoint has
13382 multiple locations (for instance if it was set in a function that was
13383 inlined), or if it has a @code{while-stepping} loop. In those cases
13384 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13389 @node Analyze Collected Data
13390 @section Using the Collected Data
13392 After the tracepoint experiment ends, you use @value{GDBN} commands
13393 for examining the trace data. The basic idea is that each tracepoint
13394 collects a trace @dfn{snapshot} every time it is hit and another
13395 snapshot every time it single-steps. All these snapshots are
13396 consecutively numbered from zero and go into a buffer, and you can
13397 examine them later. The way you examine them is to @dfn{focus} on a
13398 specific trace snapshot. When the remote stub is focused on a trace
13399 snapshot, it will respond to all @value{GDBN} requests for memory and
13400 registers by reading from the buffer which belongs to that snapshot,
13401 rather than from @emph{real} memory or registers of the program being
13402 debugged. This means that @strong{all} @value{GDBN} commands
13403 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13404 behave as if we were currently debugging the program state as it was
13405 when the tracepoint occurred. Any requests for data that are not in
13406 the buffer will fail.
13409 * tfind:: How to select a trace snapshot
13410 * tdump:: How to display all data for a snapshot
13411 * save tracepoints:: How to save tracepoints for a future run
13415 @subsection @code{tfind @var{n}}
13418 @cindex select trace snapshot
13419 @cindex find trace snapshot
13420 The basic command for selecting a trace snapshot from the buffer is
13421 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13422 counting from zero. If no argument @var{n} is given, the next
13423 snapshot is selected.
13425 Here are the various forms of using the @code{tfind} command.
13429 Find the first snapshot in the buffer. This is a synonym for
13430 @code{tfind 0} (since 0 is the number of the first snapshot).
13433 Stop debugging trace snapshots, resume @emph{live} debugging.
13436 Same as @samp{tfind none}.
13439 No argument means find the next trace snapshot or find the first
13440 one if no trace snapshot is selected.
13443 Find the previous trace snapshot before the current one. This permits
13444 retracing earlier steps.
13446 @item tfind tracepoint @var{num}
13447 Find the next snapshot associated with tracepoint @var{num}. Search
13448 proceeds forward from the last examined trace snapshot. If no
13449 argument @var{num} is given, it means find the next snapshot collected
13450 for the same tracepoint as the current snapshot.
13452 @item tfind pc @var{addr}
13453 Find the next snapshot associated with the value @var{addr} of the
13454 program counter. Search proceeds forward from the last examined trace
13455 snapshot. If no argument @var{addr} is given, it means find the next
13456 snapshot with the same value of PC as the current snapshot.
13458 @item tfind outside @var{addr1}, @var{addr2}
13459 Find the next snapshot whose PC is outside the given range of
13460 addresses (exclusive).
13462 @item tfind range @var{addr1}, @var{addr2}
13463 Find the next snapshot whose PC is between @var{addr1} and
13464 @var{addr2} (inclusive).
13466 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13467 Find the next snapshot associated with the source line @var{n}. If
13468 the optional argument @var{file} is given, refer to line @var{n} in
13469 that source file. Search proceeds forward from the last examined
13470 trace snapshot. If no argument @var{n} is given, it means find the
13471 next line other than the one currently being examined; thus saying
13472 @code{tfind line} repeatedly can appear to have the same effect as
13473 stepping from line to line in a @emph{live} debugging session.
13476 The default arguments for the @code{tfind} commands are specifically
13477 designed to make it easy to scan through the trace buffer. For
13478 instance, @code{tfind} with no argument selects the next trace
13479 snapshot, and @code{tfind -} with no argument selects the previous
13480 trace snapshot. So, by giving one @code{tfind} command, and then
13481 simply hitting @key{RET} repeatedly you can examine all the trace
13482 snapshots in order. Or, by saying @code{tfind -} and then hitting
13483 @key{RET} repeatedly you can examine the snapshots in reverse order.
13484 The @code{tfind line} command with no argument selects the snapshot
13485 for the next source line executed. The @code{tfind pc} command with
13486 no argument selects the next snapshot with the same program counter
13487 (PC) as the current frame. The @code{tfind tracepoint} command with
13488 no argument selects the next trace snapshot collected by the same
13489 tracepoint as the current one.
13491 In addition to letting you scan through the trace buffer manually,
13492 these commands make it easy to construct @value{GDBN} scripts that
13493 scan through the trace buffer and print out whatever collected data
13494 you are interested in. Thus, if we want to examine the PC, FP, and SP
13495 registers from each trace frame in the buffer, we can say this:
13498 (@value{GDBP}) @b{tfind start}
13499 (@value{GDBP}) @b{while ($trace_frame != -1)}
13500 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13501 $trace_frame, $pc, $sp, $fp
13505 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13506 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13507 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13508 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13509 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13510 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13511 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13512 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13513 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13514 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13515 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13518 Or, if we want to examine the variable @code{X} at each source line in
13522 (@value{GDBP}) @b{tfind start}
13523 (@value{GDBP}) @b{while ($trace_frame != -1)}
13524 > printf "Frame %d, X == %d\n", $trace_frame, X
13534 @subsection @code{tdump}
13536 @cindex dump all data collected at tracepoint
13537 @cindex tracepoint data, display
13539 This command takes no arguments. It prints all the data collected at
13540 the current trace snapshot.
13543 (@value{GDBP}) @b{trace 444}
13544 (@value{GDBP}) @b{actions}
13545 Enter actions for tracepoint #2, one per line:
13546 > collect $regs, $locals, $args, gdb_long_test
13549 (@value{GDBP}) @b{tstart}
13551 (@value{GDBP}) @b{tfind line 444}
13552 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13554 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13556 (@value{GDBP}) @b{tdump}
13557 Data collected at tracepoint 2, trace frame 1:
13558 d0 0xc4aa0085 -995491707
13562 d4 0x71aea3d 119204413
13565 d7 0x380035 3670069
13566 a0 0x19e24a 1696330
13567 a1 0x3000668 50333288
13569 a3 0x322000 3284992
13570 a4 0x3000698 50333336
13571 a5 0x1ad3cc 1758156
13572 fp 0x30bf3c 0x30bf3c
13573 sp 0x30bf34 0x30bf34
13575 pc 0x20b2c8 0x20b2c8
13579 p = 0x20e5b4 "gdb-test"
13586 gdb_long_test = 17 '\021'
13591 @code{tdump} works by scanning the tracepoint's current collection
13592 actions and printing the value of each expression listed. So
13593 @code{tdump} can fail, if after a run, you change the tracepoint's
13594 actions to mention variables that were not collected during the run.
13596 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13597 uses the collected value of @code{$pc} to distinguish between trace
13598 frames that were collected at the tracepoint hit, and frames that were
13599 collected while stepping. This allows it to correctly choose whether
13600 to display the basic list of collections, or the collections from the
13601 body of the while-stepping loop. However, if @code{$pc} was not collected,
13602 then @code{tdump} will always attempt to dump using the basic collection
13603 list, and may fail if a while-stepping frame does not include all the
13604 same data that is collected at the tracepoint hit.
13605 @c This is getting pretty arcane, example would be good.
13607 @node save tracepoints
13608 @subsection @code{save tracepoints @var{filename}}
13609 @kindex save tracepoints
13610 @kindex save-tracepoints
13611 @cindex save tracepoints for future sessions
13613 This command saves all current tracepoint definitions together with
13614 their actions and passcounts, into a file @file{@var{filename}}
13615 suitable for use in a later debugging session. To read the saved
13616 tracepoint definitions, use the @code{source} command (@pxref{Command
13617 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13618 alias for @w{@code{save tracepoints}}
13620 @node Tracepoint Variables
13621 @section Convenience Variables for Tracepoints
13622 @cindex tracepoint variables
13623 @cindex convenience variables for tracepoints
13626 @vindex $trace_frame
13627 @item (int) $trace_frame
13628 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13629 snapshot is selected.
13631 @vindex $tracepoint
13632 @item (int) $tracepoint
13633 The tracepoint for the current trace snapshot.
13635 @vindex $trace_line
13636 @item (int) $trace_line
13637 The line number for the current trace snapshot.
13639 @vindex $trace_file
13640 @item (char []) $trace_file
13641 The source file for the current trace snapshot.
13643 @vindex $trace_func
13644 @item (char []) $trace_func
13645 The name of the function containing @code{$tracepoint}.
13648 Note: @code{$trace_file} is not suitable for use in @code{printf},
13649 use @code{output} instead.
13651 Here's a simple example of using these convenience variables for
13652 stepping through all the trace snapshots and printing some of their
13653 data. Note that these are not the same as trace state variables,
13654 which are managed by the target.
13657 (@value{GDBP}) @b{tfind start}
13659 (@value{GDBP}) @b{while $trace_frame != -1}
13660 > output $trace_file
13661 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13667 @section Using Trace Files
13668 @cindex trace files
13670 In some situations, the target running a trace experiment may no
13671 longer be available; perhaps it crashed, or the hardware was needed
13672 for a different activity. To handle these cases, you can arrange to
13673 dump the trace data into a file, and later use that file as a source
13674 of trace data, via the @code{target tfile} command.
13679 @item tsave [ -r ] @var{filename}
13680 @itemx tsave [-ctf] @var{dirname}
13681 Save the trace data to @var{filename}. By default, this command
13682 assumes that @var{filename} refers to the host filesystem, so if
13683 necessary @value{GDBN} will copy raw trace data up from the target and
13684 then save it. If the target supports it, you can also supply the
13685 optional argument @code{-r} (``remote'') to direct the target to save
13686 the data directly into @var{filename} in its own filesystem, which may be
13687 more efficient if the trace buffer is very large. (Note, however, that
13688 @code{target tfile} can only read from files accessible to the host.)
13689 By default, this command will save trace frame in tfile format.
13690 You can supply the optional argument @code{-ctf} to save data in CTF
13691 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13692 that can be shared by multiple debugging and tracing tools. Please go to
13693 @indicateurl{http://www.efficios.com/ctf} to get more information.
13695 @kindex target tfile
13699 @item target tfile @var{filename}
13700 @itemx target ctf @var{dirname}
13701 Use the file named @var{filename} or directory named @var{dirname} as
13702 a source of trace data. Commands that examine data work as they do with
13703 a live target, but it is not possible to run any new trace experiments.
13704 @code{tstatus} will report the state of the trace run at the moment
13705 the data was saved, as well as the current trace frame you are examining.
13706 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13710 (@value{GDBP}) target ctf ctf.ctf
13711 (@value{GDBP}) tfind
13712 Found trace frame 0, tracepoint 2
13713 39 ++a; /* set tracepoint 1 here */
13714 (@value{GDBP}) tdump
13715 Data collected at tracepoint 2, trace frame 0:
13719 c = @{"123", "456", "789", "123", "456", "789"@}
13720 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13728 @chapter Debugging Programs That Use Overlays
13731 If your program is too large to fit completely in your target system's
13732 memory, you can sometimes use @dfn{overlays} to work around this
13733 problem. @value{GDBN} provides some support for debugging programs that
13737 * How Overlays Work:: A general explanation of overlays.
13738 * Overlay Commands:: Managing overlays in @value{GDBN}.
13739 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13740 mapped by asking the inferior.
13741 * Overlay Sample Program:: A sample program using overlays.
13744 @node How Overlays Work
13745 @section How Overlays Work
13746 @cindex mapped overlays
13747 @cindex unmapped overlays
13748 @cindex load address, overlay's
13749 @cindex mapped address
13750 @cindex overlay area
13752 Suppose you have a computer whose instruction address space is only 64
13753 kilobytes long, but which has much more memory which can be accessed by
13754 other means: special instructions, segment registers, or memory
13755 management hardware, for example. Suppose further that you want to
13756 adapt a program which is larger than 64 kilobytes to run on this system.
13758 One solution is to identify modules of your program which are relatively
13759 independent, and need not call each other directly; call these modules
13760 @dfn{overlays}. Separate the overlays from the main program, and place
13761 their machine code in the larger memory. Place your main program in
13762 instruction memory, but leave at least enough space there to hold the
13763 largest overlay as well.
13765 Now, to call a function located in an overlay, you must first copy that
13766 overlay's machine code from the large memory into the space set aside
13767 for it in the instruction memory, and then jump to its entry point
13770 @c NB: In the below the mapped area's size is greater or equal to the
13771 @c size of all overlays. This is intentional to remind the developer
13772 @c that overlays don't necessarily need to be the same size.
13776 Data Instruction Larger
13777 Address Space Address Space Address Space
13778 +-----------+ +-----------+ +-----------+
13780 +-----------+ +-----------+ +-----------+<-- overlay 1
13781 | program | | main | .----| overlay 1 | load address
13782 | variables | | program | | +-----------+
13783 | and heap | | | | | |
13784 +-----------+ | | | +-----------+<-- overlay 2
13785 | | +-----------+ | | | load address
13786 +-----------+ | | | .-| overlay 2 |
13788 mapped --->+-----------+ | | +-----------+
13789 address | | | | | |
13790 | overlay | <-' | | |
13791 | area | <---' +-----------+<-- overlay 3
13792 | | <---. | | load address
13793 +-----------+ `--| overlay 3 |
13800 @anchor{A code overlay}A code overlay
13804 The diagram (@pxref{A code overlay}) shows a system with separate data
13805 and instruction address spaces. To map an overlay, the program copies
13806 its code from the larger address space to the instruction address space.
13807 Since the overlays shown here all use the same mapped address, only one
13808 may be mapped at a time. For a system with a single address space for
13809 data and instructions, the diagram would be similar, except that the
13810 program variables and heap would share an address space with the main
13811 program and the overlay area.
13813 An overlay loaded into instruction memory and ready for use is called a
13814 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13815 instruction memory. An overlay not present (or only partially present)
13816 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13817 is its address in the larger memory. The mapped address is also called
13818 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13819 called the @dfn{load memory address}, or @dfn{LMA}.
13821 Unfortunately, overlays are not a completely transparent way to adapt a
13822 program to limited instruction memory. They introduce a new set of
13823 global constraints you must keep in mind as you design your program:
13828 Before calling or returning to a function in an overlay, your program
13829 must make sure that overlay is actually mapped. Otherwise, the call or
13830 return will transfer control to the right address, but in the wrong
13831 overlay, and your program will probably crash.
13834 If the process of mapping an overlay is expensive on your system, you
13835 will need to choose your overlays carefully to minimize their effect on
13836 your program's performance.
13839 The executable file you load onto your system must contain each
13840 overlay's instructions, appearing at the overlay's load address, not its
13841 mapped address. However, each overlay's instructions must be relocated
13842 and its symbols defined as if the overlay were at its mapped address.
13843 You can use GNU linker scripts to specify different load and relocation
13844 addresses for pieces of your program; see @ref{Overlay Description,,,
13845 ld.info, Using ld: the GNU linker}.
13848 The procedure for loading executable files onto your system must be able
13849 to load their contents into the larger address space as well as the
13850 instruction and data spaces.
13854 The overlay system described above is rather simple, and could be
13855 improved in many ways:
13860 If your system has suitable bank switch registers or memory management
13861 hardware, you could use those facilities to make an overlay's load area
13862 contents simply appear at their mapped address in instruction space.
13863 This would probably be faster than copying the overlay to its mapped
13864 area in the usual way.
13867 If your overlays are small enough, you could set aside more than one
13868 overlay area, and have more than one overlay mapped at a time.
13871 You can use overlays to manage data, as well as instructions. In
13872 general, data overlays are even less transparent to your design than
13873 code overlays: whereas code overlays only require care when you call or
13874 return to functions, data overlays require care every time you access
13875 the data. Also, if you change the contents of a data overlay, you
13876 must copy its contents back out to its load address before you can copy a
13877 different data overlay into the same mapped area.
13882 @node Overlay Commands
13883 @section Overlay Commands
13885 To use @value{GDBN}'s overlay support, each overlay in your program must
13886 correspond to a separate section of the executable file. The section's
13887 virtual memory address and load memory address must be the overlay's
13888 mapped and load addresses. Identifying overlays with sections allows
13889 @value{GDBN} to determine the appropriate address of a function or
13890 variable, depending on whether the overlay is mapped or not.
13892 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13893 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13898 Disable @value{GDBN}'s overlay support. When overlay support is
13899 disabled, @value{GDBN} assumes that all functions and variables are
13900 always present at their mapped addresses. By default, @value{GDBN}'s
13901 overlay support is disabled.
13903 @item overlay manual
13904 @cindex manual overlay debugging
13905 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13906 relies on you to tell it which overlays are mapped, and which are not,
13907 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13908 commands described below.
13910 @item overlay map-overlay @var{overlay}
13911 @itemx overlay map @var{overlay}
13912 @cindex map an overlay
13913 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13914 be the name of the object file section containing the overlay. When an
13915 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13916 functions and variables at their mapped addresses. @value{GDBN} assumes
13917 that any other overlays whose mapped ranges overlap that of
13918 @var{overlay} are now unmapped.
13920 @item overlay unmap-overlay @var{overlay}
13921 @itemx overlay unmap @var{overlay}
13922 @cindex unmap an overlay
13923 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13924 must be the name of the object file section containing the overlay.
13925 When an overlay is unmapped, @value{GDBN} assumes it can find the
13926 overlay's functions and variables at their load addresses.
13929 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13930 consults a data structure the overlay manager maintains in the inferior
13931 to see which overlays are mapped. For details, see @ref{Automatic
13932 Overlay Debugging}.
13934 @item overlay load-target
13935 @itemx overlay load
13936 @cindex reloading the overlay table
13937 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13938 re-reads the table @value{GDBN} automatically each time the inferior
13939 stops, so this command should only be necessary if you have changed the
13940 overlay mapping yourself using @value{GDBN}. This command is only
13941 useful when using automatic overlay debugging.
13943 @item overlay list-overlays
13944 @itemx overlay list
13945 @cindex listing mapped overlays
13946 Display a list of the overlays currently mapped, along with their mapped
13947 addresses, load addresses, and sizes.
13951 Normally, when @value{GDBN} prints a code address, it includes the name
13952 of the function the address falls in:
13955 (@value{GDBP}) print main
13956 $3 = @{int ()@} 0x11a0 <main>
13959 When overlay debugging is enabled, @value{GDBN} recognizes code in
13960 unmapped overlays, and prints the names of unmapped functions with
13961 asterisks around them. For example, if @code{foo} is a function in an
13962 unmapped overlay, @value{GDBN} prints it this way:
13965 (@value{GDBP}) overlay list
13966 No sections are mapped.
13967 (@value{GDBP}) print foo
13968 $5 = @{int (int)@} 0x100000 <*foo*>
13971 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13975 (@value{GDBP}) overlay list
13976 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13977 mapped at 0x1016 - 0x104a
13978 (@value{GDBP}) print foo
13979 $6 = @{int (int)@} 0x1016 <foo>
13982 When overlay debugging is enabled, @value{GDBN} can find the correct
13983 address for functions and variables in an overlay, whether or not the
13984 overlay is mapped. This allows most @value{GDBN} commands, like
13985 @code{break} and @code{disassemble}, to work normally, even on unmapped
13986 code. However, @value{GDBN}'s breakpoint support has some limitations:
13990 @cindex breakpoints in overlays
13991 @cindex overlays, setting breakpoints in
13992 You can set breakpoints in functions in unmapped overlays, as long as
13993 @value{GDBN} can write to the overlay at its load address.
13995 @value{GDBN} can not set hardware or simulator-based breakpoints in
13996 unmapped overlays. However, if you set a breakpoint at the end of your
13997 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13998 you are using manual overlay management), @value{GDBN} will re-set its
13999 breakpoints properly.
14003 @node Automatic Overlay Debugging
14004 @section Automatic Overlay Debugging
14005 @cindex automatic overlay debugging
14007 @value{GDBN} can automatically track which overlays are mapped and which
14008 are not, given some simple co-operation from the overlay manager in the
14009 inferior. If you enable automatic overlay debugging with the
14010 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14011 looks in the inferior's memory for certain variables describing the
14012 current state of the overlays.
14014 Here are the variables your overlay manager must define to support
14015 @value{GDBN}'s automatic overlay debugging:
14019 @item @code{_ovly_table}:
14020 This variable must be an array of the following structures:
14025 /* The overlay's mapped address. */
14028 /* The size of the overlay, in bytes. */
14029 unsigned long size;
14031 /* The overlay's load address. */
14034 /* Non-zero if the overlay is currently mapped;
14036 unsigned long mapped;
14040 @item @code{_novlys}:
14041 This variable must be a four-byte signed integer, holding the total
14042 number of elements in @code{_ovly_table}.
14046 To decide whether a particular overlay is mapped or not, @value{GDBN}
14047 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14048 @code{lma} members equal the VMA and LMA of the overlay's section in the
14049 executable file. When @value{GDBN} finds a matching entry, it consults
14050 the entry's @code{mapped} member to determine whether the overlay is
14053 In addition, your overlay manager may define a function called
14054 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14055 will silently set a breakpoint there. If the overlay manager then
14056 calls this function whenever it has changed the overlay table, this
14057 will enable @value{GDBN} to accurately keep track of which overlays
14058 are in program memory, and update any breakpoints that may be set
14059 in overlays. This will allow breakpoints to work even if the
14060 overlays are kept in ROM or other non-writable memory while they
14061 are not being executed.
14063 @node Overlay Sample Program
14064 @section Overlay Sample Program
14065 @cindex overlay example program
14067 When linking a program which uses overlays, you must place the overlays
14068 at their load addresses, while relocating them to run at their mapped
14069 addresses. To do this, you must write a linker script (@pxref{Overlay
14070 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14071 since linker scripts are specific to a particular host system, target
14072 architecture, and target memory layout, this manual cannot provide
14073 portable sample code demonstrating @value{GDBN}'s overlay support.
14075 However, the @value{GDBN} source distribution does contain an overlaid
14076 program, with linker scripts for a few systems, as part of its test
14077 suite. The program consists of the following files from
14078 @file{gdb/testsuite/gdb.base}:
14082 The main program file.
14084 A simple overlay manager, used by @file{overlays.c}.
14089 Overlay modules, loaded and used by @file{overlays.c}.
14092 Linker scripts for linking the test program on the @code{d10v-elf}
14093 and @code{m32r-elf} targets.
14096 You can build the test program using the @code{d10v-elf} GCC
14097 cross-compiler like this:
14100 $ d10v-elf-gcc -g -c overlays.c
14101 $ d10v-elf-gcc -g -c ovlymgr.c
14102 $ d10v-elf-gcc -g -c foo.c
14103 $ d10v-elf-gcc -g -c bar.c
14104 $ d10v-elf-gcc -g -c baz.c
14105 $ d10v-elf-gcc -g -c grbx.c
14106 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14107 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14110 The build process is identical for any other architecture, except that
14111 you must substitute the appropriate compiler and linker script for the
14112 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14116 @chapter Using @value{GDBN} with Different Languages
14119 Although programming languages generally have common aspects, they are
14120 rarely expressed in the same manner. For instance, in ANSI C,
14121 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14122 Modula-2, it is accomplished by @code{p^}. Values can also be
14123 represented (and displayed) differently. Hex numbers in C appear as
14124 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14126 @cindex working language
14127 Language-specific information is built into @value{GDBN} for some languages,
14128 allowing you to express operations like the above in your program's
14129 native language, and allowing @value{GDBN} to output values in a manner
14130 consistent with the syntax of your program's native language. The
14131 language you use to build expressions is called the @dfn{working
14135 * Setting:: Switching between source languages
14136 * Show:: Displaying the language
14137 * Checks:: Type and range checks
14138 * Supported Languages:: Supported languages
14139 * Unsupported Languages:: Unsupported languages
14143 @section Switching Between Source Languages
14145 There are two ways to control the working language---either have @value{GDBN}
14146 set it automatically, or select it manually yourself. You can use the
14147 @code{set language} command for either purpose. On startup, @value{GDBN}
14148 defaults to setting the language automatically. The working language is
14149 used to determine how expressions you type are interpreted, how values
14152 In addition to the working language, every source file that
14153 @value{GDBN} knows about has its own working language. For some object
14154 file formats, the compiler might indicate which language a particular
14155 source file is in. However, most of the time @value{GDBN} infers the
14156 language from the name of the file. The language of a source file
14157 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14158 show each frame appropriately for its own language. There is no way to
14159 set the language of a source file from within @value{GDBN}, but you can
14160 set the language associated with a filename extension. @xref{Show, ,
14161 Displaying the Language}.
14163 This is most commonly a problem when you use a program, such
14164 as @code{cfront} or @code{f2c}, that generates C but is written in
14165 another language. In that case, make the
14166 program use @code{#line} directives in its C output; that way
14167 @value{GDBN} will know the correct language of the source code of the original
14168 program, and will display that source code, not the generated C code.
14171 * Filenames:: Filename extensions and languages.
14172 * Manually:: Setting the working language manually
14173 * Automatically:: Having @value{GDBN} infer the source language
14177 @subsection List of Filename Extensions and Languages
14179 If a source file name ends in one of the following extensions, then
14180 @value{GDBN} infers that its language is the one indicated.
14198 C@t{++} source file
14204 Objective-C source file
14208 Fortran source file
14211 Modula-2 source file
14215 Assembler source file. This actually behaves almost like C, but
14216 @value{GDBN} does not skip over function prologues when stepping.
14219 In addition, you may set the language associated with a filename
14220 extension. @xref{Show, , Displaying the Language}.
14223 @subsection Setting the Working Language
14225 If you allow @value{GDBN} to set the language automatically,
14226 expressions are interpreted the same way in your debugging session and
14229 @kindex set language
14230 If you wish, you may set the language manually. To do this, issue the
14231 command @samp{set language @var{lang}}, where @var{lang} is the name of
14232 a language, such as
14233 @code{c} or @code{modula-2}.
14234 For a list of the supported languages, type @samp{set language}.
14236 Setting the language manually prevents @value{GDBN} from updating the working
14237 language automatically. This can lead to confusion if you try
14238 to debug a program when the working language is not the same as the
14239 source language, when an expression is acceptable to both
14240 languages---but means different things. For instance, if the current
14241 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14249 might not have the effect you intended. In C, this means to add
14250 @code{b} and @code{c} and place the result in @code{a}. The result
14251 printed would be the value of @code{a}. In Modula-2, this means to compare
14252 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14254 @node Automatically
14255 @subsection Having @value{GDBN} Infer the Source Language
14257 To have @value{GDBN} set the working language automatically, use
14258 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14259 then infers the working language. That is, when your program stops in a
14260 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14261 working language to the language recorded for the function in that
14262 frame. If the language for a frame is unknown (that is, if the function
14263 or block corresponding to the frame was defined in a source file that
14264 does not have a recognized extension), the current working language is
14265 not changed, and @value{GDBN} issues a warning.
14267 This may not seem necessary for most programs, which are written
14268 entirely in one source language. However, program modules and libraries
14269 written in one source language can be used by a main program written in
14270 a different source language. Using @samp{set language auto} in this
14271 case frees you from having to set the working language manually.
14274 @section Displaying the Language
14276 The following commands help you find out which language is the
14277 working language, and also what language source files were written in.
14280 @item show language
14281 @anchor{show language}
14282 @kindex show language
14283 Display the current working language. This is the
14284 language you can use with commands such as @code{print} to
14285 build and compute expressions that may involve variables in your program.
14288 @kindex info frame@r{, show the source language}
14289 Display the source language for this frame. This language becomes the
14290 working language if you use an identifier from this frame.
14291 @xref{Frame Info, ,Information about a Frame}, to identify the other
14292 information listed here.
14295 @kindex info source@r{, show the source language}
14296 Display the source language of this source file.
14297 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14298 information listed here.
14301 In unusual circumstances, you may have source files with extensions
14302 not in the standard list. You can then set the extension associated
14303 with a language explicitly:
14306 @item set extension-language @var{ext} @var{language}
14307 @kindex set extension-language
14308 Tell @value{GDBN} that source files with extension @var{ext} are to be
14309 assumed as written in the source language @var{language}.
14311 @item info extensions
14312 @kindex info extensions
14313 List all the filename extensions and the associated languages.
14317 @section Type and Range Checking
14319 Some languages are designed to guard you against making seemingly common
14320 errors through a series of compile- and run-time checks. These include
14321 checking the type of arguments to functions and operators and making
14322 sure mathematical overflows are caught at run time. Checks such as
14323 these help to ensure a program's correctness once it has been compiled
14324 by eliminating type mismatches and providing active checks for range
14325 errors when your program is running.
14327 By default @value{GDBN} checks for these errors according to the
14328 rules of the current source language. Although @value{GDBN} does not check
14329 the statements in your program, it can check expressions entered directly
14330 into @value{GDBN} for evaluation via the @code{print} command, for example.
14333 * Type Checking:: An overview of type checking
14334 * Range Checking:: An overview of range checking
14337 @cindex type checking
14338 @cindex checks, type
14339 @node Type Checking
14340 @subsection An Overview of Type Checking
14342 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14343 arguments to operators and functions have to be of the correct type,
14344 otherwise an error occurs. These checks prevent type mismatch
14345 errors from ever causing any run-time problems. For example,
14348 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14350 (@value{GDBP}) print obj.my_method (0)
14353 (@value{GDBP}) print obj.my_method (0x1234)
14354 Cannot resolve method klass::my_method to any overloaded instance
14357 The second example fails because in C@t{++} the integer constant
14358 @samp{0x1234} is not type-compatible with the pointer parameter type.
14360 For the expressions you use in @value{GDBN} commands, you can tell
14361 @value{GDBN} to not enforce strict type checking or
14362 to treat any mismatches as errors and abandon the expression;
14363 When type checking is disabled, @value{GDBN} successfully evaluates
14364 expressions like the second example above.
14366 Even if type checking is off, there may be other reasons
14367 related to type that prevent @value{GDBN} from evaluating an expression.
14368 For instance, @value{GDBN} does not know how to add an @code{int} and
14369 a @code{struct foo}. These particular type errors have nothing to do
14370 with the language in use and usually arise from expressions which make
14371 little sense to evaluate anyway.
14373 @value{GDBN} provides some additional commands for controlling type checking:
14375 @kindex set check type
14376 @kindex show check type
14378 @item set check type on
14379 @itemx set check type off
14380 Set strict type checking on or off. If any type mismatches occur in
14381 evaluating an expression while type checking is on, @value{GDBN} prints a
14382 message and aborts evaluation of the expression.
14384 @item show check type
14385 Show the current setting of type checking and whether @value{GDBN}
14386 is enforcing strict type checking rules.
14389 @cindex range checking
14390 @cindex checks, range
14391 @node Range Checking
14392 @subsection An Overview of Range Checking
14394 In some languages (such as Modula-2), it is an error to exceed the
14395 bounds of a type; this is enforced with run-time checks. Such range
14396 checking is meant to ensure program correctness by making sure
14397 computations do not overflow, or indices on an array element access do
14398 not exceed the bounds of the array.
14400 For expressions you use in @value{GDBN} commands, you can tell
14401 @value{GDBN} to treat range errors in one of three ways: ignore them,
14402 always treat them as errors and abandon the expression, or issue
14403 warnings but evaluate the expression anyway.
14405 A range error can result from numerical overflow, from exceeding an
14406 array index bound, or when you type a constant that is not a member
14407 of any type. Some languages, however, do not treat overflows as an
14408 error. In many implementations of C, mathematical overflow causes the
14409 result to ``wrap around'' to lower values---for example, if @var{m} is
14410 the largest integer value, and @var{s} is the smallest, then
14413 @var{m} + 1 @result{} @var{s}
14416 This, too, is specific to individual languages, and in some cases
14417 specific to individual compilers or machines. @xref{Supported Languages, ,
14418 Supported Languages}, for further details on specific languages.
14420 @value{GDBN} provides some additional commands for controlling the range checker:
14422 @kindex set check range
14423 @kindex show check range
14425 @item set check range auto
14426 Set range checking on or off based on the current working language.
14427 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14430 @item set check range on
14431 @itemx set check range off
14432 Set range checking on or off, overriding the default setting for the
14433 current working language. A warning is issued if the setting does not
14434 match the language default. If a range error occurs and range checking is on,
14435 then a message is printed and evaluation of the expression is aborted.
14437 @item set check range warn
14438 Output messages when the @value{GDBN} range checker detects a range error,
14439 but attempt to evaluate the expression anyway. Evaluating the
14440 expression may still be impossible for other reasons, such as accessing
14441 memory that the process does not own (a typical example from many Unix
14445 Show the current setting of the range checker, and whether or not it is
14446 being set automatically by @value{GDBN}.
14449 @node Supported Languages
14450 @section Supported Languages
14452 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14453 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14454 @c This is false ...
14455 Some @value{GDBN} features may be used in expressions regardless of the
14456 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14457 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14458 ,Expressions}) can be used with the constructs of any supported
14461 The following sections detail to what degree each source language is
14462 supported by @value{GDBN}. These sections are not meant to be language
14463 tutorials or references, but serve only as a reference guide to what the
14464 @value{GDBN} expression parser accepts, and what input and output
14465 formats should look like for different languages. There are many good
14466 books written on each of these languages; please look to these for a
14467 language reference or tutorial.
14470 * C:: C and C@t{++}
14473 * Objective-C:: Objective-C
14474 * OpenCL C:: OpenCL C
14475 * Fortran:: Fortran
14478 * Modula-2:: Modula-2
14483 @subsection C and C@t{++}
14485 @cindex C and C@t{++}
14486 @cindex expressions in C or C@t{++}
14488 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14489 to both languages. Whenever this is the case, we discuss those languages
14493 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14494 @cindex @sc{gnu} C@t{++}
14495 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14496 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14497 effectively, you must compile your C@t{++} programs with a supported
14498 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14499 compiler (@code{aCC}).
14502 * C Operators:: C and C@t{++} operators
14503 * C Constants:: C and C@t{++} constants
14504 * C Plus Plus Expressions:: C@t{++} expressions
14505 * C Defaults:: Default settings for C and C@t{++}
14506 * C Checks:: C and C@t{++} type and range checks
14507 * Debugging C:: @value{GDBN} and C
14508 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14509 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14513 @subsubsection C and C@t{++} Operators
14515 @cindex C and C@t{++} operators
14517 Operators must be defined on values of specific types. For instance,
14518 @code{+} is defined on numbers, but not on structures. Operators are
14519 often defined on groups of types.
14521 For the purposes of C and C@t{++}, the following definitions hold:
14526 @emph{Integral types} include @code{int} with any of its storage-class
14527 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14530 @emph{Floating-point types} include @code{float}, @code{double}, and
14531 @code{long double} (if supported by the target platform).
14534 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14537 @emph{Scalar types} include all of the above.
14542 The following operators are supported. They are listed here
14543 in order of increasing precedence:
14547 The comma or sequencing operator. Expressions in a comma-separated list
14548 are evaluated from left to right, with the result of the entire
14549 expression being the last expression evaluated.
14552 Assignment. The value of an assignment expression is the value
14553 assigned. Defined on scalar types.
14556 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14557 and translated to @w{@code{@var{a} = @var{a op b}}}.
14558 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14559 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14560 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14563 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14564 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14565 should be of an integral type.
14568 Logical @sc{or}. Defined on integral types.
14571 Logical @sc{and}. Defined on integral types.
14574 Bitwise @sc{or}. Defined on integral types.
14577 Bitwise exclusive-@sc{or}. Defined on integral types.
14580 Bitwise @sc{and}. Defined on integral types.
14583 Equality and inequality. Defined on scalar types. The value of these
14584 expressions is 0 for false and non-zero for true.
14586 @item <@r{, }>@r{, }<=@r{, }>=
14587 Less than, greater than, less than or equal, greater than or equal.
14588 Defined on scalar types. The value of these expressions is 0 for false
14589 and non-zero for true.
14592 left shift, and right shift. Defined on integral types.
14595 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14598 Addition and subtraction. Defined on integral types, floating-point types and
14601 @item *@r{, }/@r{, }%
14602 Multiplication, division, and modulus. Multiplication and division are
14603 defined on integral and floating-point types. Modulus is defined on
14607 Increment and decrement. When appearing before a variable, the
14608 operation is performed before the variable is used in an expression;
14609 when appearing after it, the variable's value is used before the
14610 operation takes place.
14613 Pointer dereferencing. Defined on pointer types. Same precedence as
14617 Address operator. Defined on variables. Same precedence as @code{++}.
14619 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14620 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14621 to examine the address
14622 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14626 Negative. Defined on integral and floating-point types. Same
14627 precedence as @code{++}.
14630 Logical negation. Defined on integral types. Same precedence as
14634 Bitwise complement operator. Defined on integral types. Same precedence as
14639 Structure member, and pointer-to-structure member. For convenience,
14640 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14641 pointer based on the stored type information.
14642 Defined on @code{struct} and @code{union} data.
14645 Dereferences of pointers to members.
14648 Array indexing. @code{@var{a}[@var{i}]} is defined as
14649 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14652 Function parameter list. Same precedence as @code{->}.
14655 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14656 and @code{class} types.
14659 Doubled colons also represent the @value{GDBN} scope operator
14660 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14664 If an operator is redefined in the user code, @value{GDBN} usually
14665 attempts to invoke the redefined version instead of using the operator's
14666 predefined meaning.
14669 @subsubsection C and C@t{++} Constants
14671 @cindex C and C@t{++} constants
14673 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14678 Integer constants are a sequence of digits. Octal constants are
14679 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14680 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14681 @samp{l}, specifying that the constant should be treated as a
14685 Floating point constants are a sequence of digits, followed by a decimal
14686 point, followed by a sequence of digits, and optionally followed by an
14687 exponent. An exponent is of the form:
14688 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14689 sequence of digits. The @samp{+} is optional for positive exponents.
14690 A floating-point constant may also end with a letter @samp{f} or
14691 @samp{F}, specifying that the constant should be treated as being of
14692 the @code{float} (as opposed to the default @code{double}) type; or with
14693 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14697 Enumerated constants consist of enumerated identifiers, or their
14698 integral equivalents.
14701 Character constants are a single character surrounded by single quotes
14702 (@code{'}), or a number---the ordinal value of the corresponding character
14703 (usually its @sc{ascii} value). Within quotes, the single character may
14704 be represented by a letter or by @dfn{escape sequences}, which are of
14705 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14706 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14707 @samp{@var{x}} is a predefined special character---for example,
14708 @samp{\n} for newline.
14710 Wide character constants can be written by prefixing a character
14711 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14712 form of @samp{x}. The target wide character set is used when
14713 computing the value of this constant (@pxref{Character Sets}).
14716 String constants are a sequence of character constants surrounded by
14717 double quotes (@code{"}). Any valid character constant (as described
14718 above) may appear. Double quotes within the string must be preceded by
14719 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14722 Wide string constants can be written by prefixing a string constant
14723 with @samp{L}, as in C. The target wide character set is used when
14724 computing the value of this constant (@pxref{Character Sets}).
14727 Pointer constants are an integral value. You can also write pointers
14728 to constants using the C operator @samp{&}.
14731 Array constants are comma-separated lists surrounded by braces @samp{@{}
14732 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14733 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14734 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14737 @node C Plus Plus Expressions
14738 @subsubsection C@t{++} Expressions
14740 @cindex expressions in C@t{++}
14741 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14743 @cindex debugging C@t{++} programs
14744 @cindex C@t{++} compilers
14745 @cindex debug formats and C@t{++}
14746 @cindex @value{NGCC} and C@t{++}
14748 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14749 the proper compiler and the proper debug format. Currently,
14750 @value{GDBN} works best when debugging C@t{++} code that is compiled
14751 with the most recent version of @value{NGCC} possible. The DWARF
14752 debugging format is preferred; @value{NGCC} defaults to this on most
14753 popular platforms. Other compilers and/or debug formats are likely to
14754 work badly or not at all when using @value{GDBN} to debug C@t{++}
14755 code. @xref{Compilation}.
14760 @cindex member functions
14762 Member function calls are allowed; you can use expressions like
14765 count = aml->GetOriginal(x, y)
14768 @vindex this@r{, inside C@t{++} member functions}
14769 @cindex namespace in C@t{++}
14771 While a member function is active (in the selected stack frame), your
14772 expressions have the same namespace available as the member function;
14773 that is, @value{GDBN} allows implicit references to the class instance
14774 pointer @code{this} following the same rules as C@t{++}. @code{using}
14775 declarations in the current scope are also respected by @value{GDBN}.
14777 @cindex call overloaded functions
14778 @cindex overloaded functions, calling
14779 @cindex type conversions in C@t{++}
14781 You can call overloaded functions; @value{GDBN} resolves the function
14782 call to the right definition, with some restrictions. @value{GDBN} does not
14783 perform overload resolution involving user-defined type conversions,
14784 calls to constructors, or instantiations of templates that do not exist
14785 in the program. It also cannot handle ellipsis argument lists or
14788 It does perform integral conversions and promotions, floating-point
14789 promotions, arithmetic conversions, pointer conversions, conversions of
14790 class objects to base classes, and standard conversions such as those of
14791 functions or arrays to pointers; it requires an exact match on the
14792 number of function arguments.
14794 Overload resolution is always performed, unless you have specified
14795 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14796 ,@value{GDBN} Features for C@t{++}}.
14798 You must specify @code{set overload-resolution off} in order to use an
14799 explicit function signature to call an overloaded function, as in
14801 p 'foo(char,int)'('x', 13)
14804 The @value{GDBN} command-completion facility can simplify this;
14805 see @ref{Completion, ,Command Completion}.
14807 @cindex reference declarations
14809 @value{GDBN} understands variables declared as C@t{++} references; you can use
14810 them in expressions just as you do in C@t{++} source---they are automatically
14813 In the parameter list shown when @value{GDBN} displays a frame, the values of
14814 reference variables are not displayed (unlike other variables); this
14815 avoids clutter, since references are often used for large structures.
14816 The @emph{address} of a reference variable is always shown, unless
14817 you have specified @samp{set print address off}.
14820 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14821 expressions can use it just as expressions in your program do. Since
14822 one scope may be defined in another, you can use @code{::} repeatedly if
14823 necessary, for example in an expression like
14824 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14825 resolving name scope by reference to source files, in both C and C@t{++}
14826 debugging (@pxref{Variables, ,Program Variables}).
14829 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14834 @subsubsection C and C@t{++} Defaults
14836 @cindex C and C@t{++} defaults
14838 If you allow @value{GDBN} to set range checking automatically, it
14839 defaults to @code{off} whenever the working language changes to
14840 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14841 selects the working language.
14843 If you allow @value{GDBN} to set the language automatically, it
14844 recognizes source files whose names end with @file{.c}, @file{.C}, or
14845 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14846 these files, it sets the working language to C or C@t{++}.
14847 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14848 for further details.
14851 @subsubsection C and C@t{++} Type and Range Checks
14853 @cindex C and C@t{++} checks
14855 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14856 checking is used. However, if you turn type checking off, @value{GDBN}
14857 will allow certain non-standard conversions, such as promoting integer
14858 constants to pointers.
14860 Range checking, if turned on, is done on mathematical operations. Array
14861 indices are not checked, since they are often used to index a pointer
14862 that is not itself an array.
14865 @subsubsection @value{GDBN} and C
14867 The @code{set print union} and @code{show print union} commands apply to
14868 the @code{union} type. When set to @samp{on}, any @code{union} that is
14869 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14870 appears as @samp{@{...@}}.
14872 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14873 with pointers and a memory allocation function. @xref{Expressions,
14876 @node Debugging C Plus Plus
14877 @subsubsection @value{GDBN} Features for C@t{++}
14879 @cindex commands for C@t{++}
14881 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14882 designed specifically for use with C@t{++}. Here is a summary:
14885 @cindex break in overloaded functions
14886 @item @r{breakpoint menus}
14887 When you want a breakpoint in a function whose name is overloaded,
14888 @value{GDBN} has the capability to display a menu of possible breakpoint
14889 locations to help you specify which function definition you want.
14890 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14892 @cindex overloading in C@t{++}
14893 @item rbreak @var{regex}
14894 Setting breakpoints using regular expressions is helpful for setting
14895 breakpoints on overloaded functions that are not members of any special
14897 @xref{Set Breaks, ,Setting Breakpoints}.
14899 @cindex C@t{++} exception handling
14901 @itemx catch rethrow
14903 Debug C@t{++} exception handling using these commands. @xref{Set
14904 Catchpoints, , Setting Catchpoints}.
14906 @cindex inheritance
14907 @item ptype @var{typename}
14908 Print inheritance relationships as well as other information for type
14910 @xref{Symbols, ,Examining the Symbol Table}.
14912 @item info vtbl @var{expression}.
14913 The @code{info vtbl} command can be used to display the virtual
14914 method tables of the object computed by @var{expression}. This shows
14915 one entry per virtual table; there may be multiple virtual tables when
14916 multiple inheritance is in use.
14918 @cindex C@t{++} demangling
14919 @item demangle @var{name}
14920 Demangle @var{name}.
14921 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14923 @cindex C@t{++} symbol display
14924 @item set print demangle
14925 @itemx show print demangle
14926 @itemx set print asm-demangle
14927 @itemx show print asm-demangle
14928 Control whether C@t{++} symbols display in their source form, both when
14929 displaying code as C@t{++} source and when displaying disassemblies.
14930 @xref{Print Settings, ,Print Settings}.
14932 @item set print object
14933 @itemx show print object
14934 Choose whether to print derived (actual) or declared types of objects.
14935 @xref{Print Settings, ,Print Settings}.
14937 @item set print vtbl
14938 @itemx show print vtbl
14939 Control the format for printing virtual function tables.
14940 @xref{Print Settings, ,Print Settings}.
14941 (The @code{vtbl} commands do not work on programs compiled with the HP
14942 ANSI C@t{++} compiler (@code{aCC}).)
14944 @kindex set overload-resolution
14945 @cindex overloaded functions, overload resolution
14946 @item set overload-resolution on
14947 Enable overload resolution for C@t{++} expression evaluation. The default
14948 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14949 and searches for a function whose signature matches the argument types,
14950 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14951 Expressions, ,C@t{++} Expressions}, for details).
14952 If it cannot find a match, it emits a message.
14954 @item set overload-resolution off
14955 Disable overload resolution for C@t{++} expression evaluation. For
14956 overloaded functions that are not class member functions, @value{GDBN}
14957 chooses the first function of the specified name that it finds in the
14958 symbol table, whether or not its arguments are of the correct type. For
14959 overloaded functions that are class member functions, @value{GDBN}
14960 searches for a function whose signature @emph{exactly} matches the
14963 @kindex show overload-resolution
14964 @item show overload-resolution
14965 Show the current setting of overload resolution.
14967 @item @r{Overloaded symbol names}
14968 You can specify a particular definition of an overloaded symbol, using
14969 the same notation that is used to declare such symbols in C@t{++}: type
14970 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14971 also use the @value{GDBN} command-line word completion facilities to list the
14972 available choices, or to finish the type list for you.
14973 @xref{Completion,, Command Completion}, for details on how to do this.
14976 @node Decimal Floating Point
14977 @subsubsection Decimal Floating Point format
14978 @cindex decimal floating point format
14980 @value{GDBN} can examine, set and perform computations with numbers in
14981 decimal floating point format, which in the C language correspond to the
14982 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14983 specified by the extension to support decimal floating-point arithmetic.
14985 There are two encodings in use, depending on the architecture: BID (Binary
14986 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14987 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14990 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14991 to manipulate decimal floating point numbers, it is not possible to convert
14992 (using a cast, for example) integers wider than 32-bit to decimal float.
14994 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14995 point computations, error checking in decimal float operations ignores
14996 underflow, overflow and divide by zero exceptions.
14998 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14999 to inspect @code{_Decimal128} values stored in floating point registers.
15000 See @ref{PowerPC,,PowerPC} for more details.
15006 @value{GDBN} can be used to debug programs written in D and compiled with
15007 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15008 specific feature --- dynamic arrays.
15013 @cindex Go (programming language)
15014 @value{GDBN} can be used to debug programs written in Go and compiled with
15015 @file{gccgo} or @file{6g} compilers.
15017 Here is a summary of the Go-specific features and restrictions:
15020 @cindex current Go package
15021 @item The current Go package
15022 The name of the current package does not need to be specified when
15023 specifying global variables and functions.
15025 For example, given the program:
15029 var myglob = "Shall we?"
15035 When stopped inside @code{main} either of these work:
15039 (gdb) p main.myglob
15042 @cindex builtin Go types
15043 @item Builtin Go types
15044 The @code{string} type is recognized by @value{GDBN} and is printed
15047 @cindex builtin Go functions
15048 @item Builtin Go functions
15049 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15050 function and handles it internally.
15052 @cindex restrictions on Go expressions
15053 @item Restrictions on Go expressions
15054 All Go operators are supported except @code{&^}.
15055 The Go @code{_} ``blank identifier'' is not supported.
15056 Automatic dereferencing of pointers is not supported.
15060 @subsection Objective-C
15062 @cindex Objective-C
15063 This section provides information about some commands and command
15064 options that are useful for debugging Objective-C code. See also
15065 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15066 few more commands specific to Objective-C support.
15069 * Method Names in Commands::
15070 * The Print Command with Objective-C::
15073 @node Method Names in Commands
15074 @subsubsection Method Names in Commands
15076 The following commands have been extended to accept Objective-C method
15077 names as line specifications:
15079 @kindex clear@r{, and Objective-C}
15080 @kindex break@r{, and Objective-C}
15081 @kindex info line@r{, and Objective-C}
15082 @kindex jump@r{, and Objective-C}
15083 @kindex list@r{, and Objective-C}
15087 @item @code{info line}
15092 A fully qualified Objective-C method name is specified as
15095 -[@var{Class} @var{methodName}]
15098 where the minus sign is used to indicate an instance method and a
15099 plus sign (not shown) is used to indicate a class method. The class
15100 name @var{Class} and method name @var{methodName} are enclosed in
15101 brackets, similar to the way messages are specified in Objective-C
15102 source code. For example, to set a breakpoint at the @code{create}
15103 instance method of class @code{Fruit} in the program currently being
15107 break -[Fruit create]
15110 To list ten program lines around the @code{initialize} class method,
15114 list +[NSText initialize]
15117 In the current version of @value{GDBN}, the plus or minus sign is
15118 required. In future versions of @value{GDBN}, the plus or minus
15119 sign will be optional, but you can use it to narrow the search. It
15120 is also possible to specify just a method name:
15126 You must specify the complete method name, including any colons. If
15127 your program's source files contain more than one @code{create} method,
15128 you'll be presented with a numbered list of classes that implement that
15129 method. Indicate your choice by number, or type @samp{0} to exit if
15132 As another example, to clear a breakpoint established at the
15133 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15136 clear -[NSWindow makeKeyAndOrderFront:]
15139 @node The Print Command with Objective-C
15140 @subsubsection The Print Command With Objective-C
15141 @cindex Objective-C, print objects
15142 @kindex print-object
15143 @kindex po @r{(@code{print-object})}
15145 The print command has also been extended to accept methods. For example:
15148 print -[@var{object} hash]
15151 @cindex print an Objective-C object description
15152 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15154 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15155 and print the result. Also, an additional command has been added,
15156 @code{print-object} or @code{po} for short, which is meant to print
15157 the description of an object. However, this command may only work
15158 with certain Objective-C libraries that have a particular hook
15159 function, @code{_NSPrintForDebugger}, defined.
15162 @subsection OpenCL C
15165 This section provides information about @value{GDBN}s OpenCL C support.
15168 * OpenCL C Datatypes::
15169 * OpenCL C Expressions::
15170 * OpenCL C Operators::
15173 @node OpenCL C Datatypes
15174 @subsubsection OpenCL C Datatypes
15176 @cindex OpenCL C Datatypes
15177 @value{GDBN} supports the builtin scalar and vector datatypes specified
15178 by OpenCL 1.1. In addition the half- and double-precision floating point
15179 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15180 extensions are also known to @value{GDBN}.
15182 @node OpenCL C Expressions
15183 @subsubsection OpenCL C Expressions
15185 @cindex OpenCL C Expressions
15186 @value{GDBN} supports accesses to vector components including the access as
15187 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15188 supported by @value{GDBN} can be used as well.
15190 @node OpenCL C Operators
15191 @subsubsection OpenCL C Operators
15193 @cindex OpenCL C Operators
15194 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15198 @subsection Fortran
15199 @cindex Fortran-specific support in @value{GDBN}
15201 @value{GDBN} can be used to debug programs written in Fortran, but it
15202 currently supports only the features of Fortran 77 language.
15204 @cindex trailing underscore, in Fortran symbols
15205 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15206 among them) append an underscore to the names of variables and
15207 functions. When you debug programs compiled by those compilers, you
15208 will need to refer to variables and functions with a trailing
15212 * Fortran Operators:: Fortran operators and expressions
15213 * Fortran Defaults:: Default settings for Fortran
15214 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15217 @node Fortran Operators
15218 @subsubsection Fortran Operators and Expressions
15220 @cindex Fortran operators and expressions
15222 Operators must be defined on values of specific types. For instance,
15223 @code{+} is defined on numbers, but not on characters or other non-
15224 arithmetic types. Operators are often defined on groups of types.
15228 The exponentiation operator. It raises the first operand to the power
15232 The range operator. Normally used in the form of array(low:high) to
15233 represent a section of array.
15236 The access component operator. Normally used to access elements in derived
15237 types. Also suitable for unions. As unions aren't part of regular Fortran,
15238 this can only happen when accessing a register that uses a gdbarch-defined
15242 @node Fortran Defaults
15243 @subsubsection Fortran Defaults
15245 @cindex Fortran Defaults
15247 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15248 default uses case-insensitive matches for Fortran symbols. You can
15249 change that with the @samp{set case-insensitive} command, see
15250 @ref{Symbols}, for the details.
15252 @node Special Fortran Commands
15253 @subsubsection Special Fortran Commands
15255 @cindex Special Fortran commands
15257 @value{GDBN} has some commands to support Fortran-specific features,
15258 such as displaying common blocks.
15261 @cindex @code{COMMON} blocks, Fortran
15262 @kindex info common
15263 @item info common @r{[}@var{common-name}@r{]}
15264 This command prints the values contained in the Fortran @code{COMMON}
15265 block whose name is @var{common-name}. With no argument, the names of
15266 all @code{COMMON} blocks visible at the current program location are
15273 @cindex Pascal support in @value{GDBN}, limitations
15274 Debugging Pascal programs which use sets, subranges, file variables, or
15275 nested functions does not currently work. @value{GDBN} does not support
15276 entering expressions, printing values, or similar features using Pascal
15279 The Pascal-specific command @code{set print pascal_static-members}
15280 controls whether static members of Pascal objects are displayed.
15281 @xref{Print Settings, pascal_static-members}.
15286 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15287 Programming Language}. Type- and value-printing, and expression
15288 parsing, are reasonably complete. However, there are a few
15289 peculiarities and holes to be aware of.
15293 Linespecs (@pxref{Specify Location}) are never relative to the current
15294 crate. Instead, they act as if there were a global namespace of
15295 crates, somewhat similar to the way @code{extern crate} behaves.
15297 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15298 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15299 to set a breakpoint in a function named @samp{f} in a crate named
15302 As a consequence of this approach, linespecs also cannot refer to
15303 items using @samp{self::} or @samp{super::}.
15306 Because @value{GDBN} implements Rust name-lookup semantics in
15307 expressions, it will sometimes prepend the current crate to a name.
15308 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15309 @samp{K}, then @code{print ::x::y} will try to find the symbol
15312 However, since it is useful to be able to refer to other crates when
15313 debugging, @value{GDBN} provides the @code{extern} extension to
15314 circumvent this. To use the extension, just put @code{extern} before
15315 a path expression to refer to the otherwise unavailable ``global''
15318 In the above example, if you wanted to refer to the symbol @samp{y} in
15319 the crate @samp{x}, you would use @code{print extern x::y}.
15322 The Rust expression evaluator does not support ``statement-like''
15323 expressions such as @code{if} or @code{match}, or lambda expressions.
15326 Tuple expressions are not implemented.
15329 The Rust expression evaluator does not currently implement the
15330 @code{Drop} trait. Objects that may be created by the evaluator will
15331 never be destroyed.
15334 @value{GDBN} does not implement type inference for generics. In order
15335 to call generic functions or otherwise refer to generic items, you
15336 will have to specify the type parameters manually.
15339 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15340 cases this does not cause any problems. However, in an expression
15341 context, completing a generic function name will give syntactically
15342 invalid results. This happens because Rust requires the @samp{::}
15343 operator between the function name and its generic arguments. For
15344 example, @value{GDBN} might provide a completion like
15345 @code{crate::f<u32>}, where the parser would require
15346 @code{crate::f::<u32>}.
15349 As of this writing, the Rust compiler (version 1.8) has a few holes in
15350 the debugging information it generates. These holes prevent certain
15351 features from being implemented by @value{GDBN}:
15355 Method calls cannot be made via traits.
15358 Trait objects cannot be created or inspected.
15361 Operator overloading is not implemented.
15364 When debugging in a monomorphized function, you cannot use the generic
15368 The type @code{Self} is not available.
15371 @code{use} statements are not available, so some names may not be
15372 available in the crate.
15377 @subsection Modula-2
15379 @cindex Modula-2, @value{GDBN} support
15381 The extensions made to @value{GDBN} to support Modula-2 only support
15382 output from the @sc{gnu} Modula-2 compiler (which is currently being
15383 developed). Other Modula-2 compilers are not currently supported, and
15384 attempting to debug executables produced by them is most likely
15385 to give an error as @value{GDBN} reads in the executable's symbol
15388 @cindex expressions in Modula-2
15390 * M2 Operators:: Built-in operators
15391 * Built-In Func/Proc:: Built-in functions and procedures
15392 * M2 Constants:: Modula-2 constants
15393 * M2 Types:: Modula-2 types
15394 * M2 Defaults:: Default settings for Modula-2
15395 * Deviations:: Deviations from standard Modula-2
15396 * M2 Checks:: Modula-2 type and range checks
15397 * M2 Scope:: The scope operators @code{::} and @code{.}
15398 * GDB/M2:: @value{GDBN} and Modula-2
15402 @subsubsection Operators
15403 @cindex Modula-2 operators
15405 Operators must be defined on values of specific types. For instance,
15406 @code{+} is defined on numbers, but not on structures. Operators are
15407 often defined on groups of types. For the purposes of Modula-2, the
15408 following definitions hold:
15413 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15417 @emph{Character types} consist of @code{CHAR} and its subranges.
15420 @emph{Floating-point types} consist of @code{REAL}.
15423 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15427 @emph{Scalar types} consist of all of the above.
15430 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15433 @emph{Boolean types} consist of @code{BOOLEAN}.
15437 The following operators are supported, and appear in order of
15438 increasing precedence:
15442 Function argument or array index separator.
15445 Assignment. The value of @var{var} @code{:=} @var{value} is
15449 Less than, greater than on integral, floating-point, or enumerated
15453 Less than or equal to, greater than or equal to
15454 on integral, floating-point and enumerated types, or set inclusion on
15455 set types. Same precedence as @code{<}.
15457 @item =@r{, }<>@r{, }#
15458 Equality and two ways of expressing inequality, valid on scalar types.
15459 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15460 available for inequality, since @code{#} conflicts with the script
15464 Set membership. Defined on set types and the types of their members.
15465 Same precedence as @code{<}.
15468 Boolean disjunction. Defined on boolean types.
15471 Boolean conjunction. Defined on boolean types.
15474 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15477 Addition and subtraction on integral and floating-point types, or union
15478 and difference on set types.
15481 Multiplication on integral and floating-point types, or set intersection
15485 Division on floating-point types, or symmetric set difference on set
15486 types. Same precedence as @code{*}.
15489 Integer division and remainder. Defined on integral types. Same
15490 precedence as @code{*}.
15493 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15496 Pointer dereferencing. Defined on pointer types.
15499 Boolean negation. Defined on boolean types. Same precedence as
15503 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15504 precedence as @code{^}.
15507 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15510 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15514 @value{GDBN} and Modula-2 scope operators.
15518 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15519 treats the use of the operator @code{IN}, or the use of operators
15520 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15521 @code{<=}, and @code{>=} on sets as an error.
15525 @node Built-In Func/Proc
15526 @subsubsection Built-in Functions and Procedures
15527 @cindex Modula-2 built-ins
15529 Modula-2 also makes available several built-in procedures and functions.
15530 In describing these, the following metavariables are used:
15535 represents an @code{ARRAY} variable.
15538 represents a @code{CHAR} constant or variable.
15541 represents a variable or constant of integral type.
15544 represents an identifier that belongs to a set. Generally used in the
15545 same function with the metavariable @var{s}. The type of @var{s} should
15546 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15549 represents a variable or constant of integral or floating-point type.
15552 represents a variable or constant of floating-point type.
15558 represents a variable.
15561 represents a variable or constant of one of many types. See the
15562 explanation of the function for details.
15565 All Modula-2 built-in procedures also return a result, described below.
15569 Returns the absolute value of @var{n}.
15572 If @var{c} is a lower case letter, it returns its upper case
15573 equivalent, otherwise it returns its argument.
15576 Returns the character whose ordinal value is @var{i}.
15579 Decrements the value in the variable @var{v} by one. Returns the new value.
15581 @item DEC(@var{v},@var{i})
15582 Decrements the value in the variable @var{v} by @var{i}. Returns the
15585 @item EXCL(@var{m},@var{s})
15586 Removes the element @var{m} from the set @var{s}. Returns the new
15589 @item FLOAT(@var{i})
15590 Returns the floating point equivalent of the integer @var{i}.
15592 @item HIGH(@var{a})
15593 Returns the index of the last member of @var{a}.
15596 Increments the value in the variable @var{v} by one. Returns the new value.
15598 @item INC(@var{v},@var{i})
15599 Increments the value in the variable @var{v} by @var{i}. Returns the
15602 @item INCL(@var{m},@var{s})
15603 Adds the element @var{m} to the set @var{s} if it is not already
15604 there. Returns the new set.
15607 Returns the maximum value of the type @var{t}.
15610 Returns the minimum value of the type @var{t}.
15613 Returns boolean TRUE if @var{i} is an odd number.
15616 Returns the ordinal value of its argument. For example, the ordinal
15617 value of a character is its @sc{ascii} value (on machines supporting
15618 the @sc{ascii} character set). The argument @var{x} must be of an
15619 ordered type, which include integral, character and enumerated types.
15621 @item SIZE(@var{x})
15622 Returns the size of its argument. The argument @var{x} can be a
15623 variable or a type.
15625 @item TRUNC(@var{r})
15626 Returns the integral part of @var{r}.
15628 @item TSIZE(@var{x})
15629 Returns the size of its argument. The argument @var{x} can be a
15630 variable or a type.
15632 @item VAL(@var{t},@var{i})
15633 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15637 @emph{Warning:} Sets and their operations are not yet supported, so
15638 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15642 @cindex Modula-2 constants
15644 @subsubsection Constants
15646 @value{GDBN} allows you to express the constants of Modula-2 in the following
15652 Integer constants are simply a sequence of digits. When used in an
15653 expression, a constant is interpreted to be type-compatible with the
15654 rest of the expression. Hexadecimal integers are specified by a
15655 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15658 Floating point constants appear as a sequence of digits, followed by a
15659 decimal point and another sequence of digits. An optional exponent can
15660 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15661 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15662 digits of the floating point constant must be valid decimal (base 10)
15666 Character constants consist of a single character enclosed by a pair of
15667 like quotes, either single (@code{'}) or double (@code{"}). They may
15668 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15669 followed by a @samp{C}.
15672 String constants consist of a sequence of characters enclosed by a
15673 pair of like quotes, either single (@code{'}) or double (@code{"}).
15674 Escape sequences in the style of C are also allowed. @xref{C
15675 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15679 Enumerated constants consist of an enumerated identifier.
15682 Boolean constants consist of the identifiers @code{TRUE} and
15686 Pointer constants consist of integral values only.
15689 Set constants are not yet supported.
15693 @subsubsection Modula-2 Types
15694 @cindex Modula-2 types
15696 Currently @value{GDBN} can print the following data types in Modula-2
15697 syntax: array types, record types, set types, pointer types, procedure
15698 types, enumerated types, subrange types and base types. You can also
15699 print the contents of variables declared using these type.
15700 This section gives a number of simple source code examples together with
15701 sample @value{GDBN} sessions.
15703 The first example contains the following section of code:
15712 and you can request @value{GDBN} to interrogate the type and value of
15713 @code{r} and @code{s}.
15716 (@value{GDBP}) print s
15718 (@value{GDBP}) ptype s
15720 (@value{GDBP}) print r
15722 (@value{GDBP}) ptype r
15727 Likewise if your source code declares @code{s} as:
15731 s: SET ['A'..'Z'] ;
15735 then you may query the type of @code{s} by:
15738 (@value{GDBP}) ptype s
15739 type = SET ['A'..'Z']
15743 Note that at present you cannot interactively manipulate set
15744 expressions using the debugger.
15746 The following example shows how you might declare an array in Modula-2
15747 and how you can interact with @value{GDBN} to print its type and contents:
15751 s: ARRAY [-10..10] OF CHAR ;
15755 (@value{GDBP}) ptype s
15756 ARRAY [-10..10] OF CHAR
15759 Note that the array handling is not yet complete and although the type
15760 is printed correctly, expression handling still assumes that all
15761 arrays have a lower bound of zero and not @code{-10} as in the example
15764 Here are some more type related Modula-2 examples:
15768 colour = (blue, red, yellow, green) ;
15769 t = [blue..yellow] ;
15777 The @value{GDBN} interaction shows how you can query the data type
15778 and value of a variable.
15781 (@value{GDBP}) print s
15783 (@value{GDBP}) ptype t
15784 type = [blue..yellow]
15788 In this example a Modula-2 array is declared and its contents
15789 displayed. Observe that the contents are written in the same way as
15790 their @code{C} counterparts.
15794 s: ARRAY [1..5] OF CARDINAL ;
15800 (@value{GDBP}) print s
15801 $1 = @{1, 0, 0, 0, 0@}
15802 (@value{GDBP}) ptype s
15803 type = ARRAY [1..5] OF CARDINAL
15806 The Modula-2 language interface to @value{GDBN} also understands
15807 pointer types as shown in this example:
15811 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15818 and you can request that @value{GDBN} describes the type of @code{s}.
15821 (@value{GDBP}) ptype s
15822 type = POINTER TO ARRAY [1..5] OF CARDINAL
15825 @value{GDBN} handles compound types as we can see in this example.
15826 Here we combine array types, record types, pointer types and subrange
15837 myarray = ARRAY myrange OF CARDINAL ;
15838 myrange = [-2..2] ;
15840 s: POINTER TO ARRAY myrange OF foo ;
15844 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15848 (@value{GDBP}) ptype s
15849 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15852 f3 : ARRAY [-2..2] OF CARDINAL;
15857 @subsubsection Modula-2 Defaults
15858 @cindex Modula-2 defaults
15860 If type and range checking are set automatically by @value{GDBN}, they
15861 both default to @code{on} whenever the working language changes to
15862 Modula-2. This happens regardless of whether you or @value{GDBN}
15863 selected the working language.
15865 If you allow @value{GDBN} to set the language automatically, then entering
15866 code compiled from a file whose name ends with @file{.mod} sets the
15867 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15868 Infer the Source Language}, for further details.
15871 @subsubsection Deviations from Standard Modula-2
15872 @cindex Modula-2, deviations from
15874 A few changes have been made to make Modula-2 programs easier to debug.
15875 This is done primarily via loosening its type strictness:
15879 Unlike in standard Modula-2, pointer constants can be formed by
15880 integers. This allows you to modify pointer variables during
15881 debugging. (In standard Modula-2, the actual address contained in a
15882 pointer variable is hidden from you; it can only be modified
15883 through direct assignment to another pointer variable or expression that
15884 returned a pointer.)
15887 C escape sequences can be used in strings and characters to represent
15888 non-printable characters. @value{GDBN} prints out strings with these
15889 escape sequences embedded. Single non-printable characters are
15890 printed using the @samp{CHR(@var{nnn})} format.
15893 The assignment operator (@code{:=}) returns the value of its right-hand
15897 All built-in procedures both modify @emph{and} return their argument.
15901 @subsubsection Modula-2 Type and Range Checks
15902 @cindex Modula-2 checks
15905 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15908 @c FIXME remove warning when type/range checks added
15910 @value{GDBN} considers two Modula-2 variables type equivalent if:
15914 They are of types that have been declared equivalent via a @code{TYPE
15915 @var{t1} = @var{t2}} statement
15918 They have been declared on the same line. (Note: This is true of the
15919 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15922 As long as type checking is enabled, any attempt to combine variables
15923 whose types are not equivalent is an error.
15925 Range checking is done on all mathematical operations, assignment, array
15926 index bounds, and all built-in functions and procedures.
15929 @subsubsection The Scope Operators @code{::} and @code{.}
15931 @cindex @code{.}, Modula-2 scope operator
15932 @cindex colon, doubled as scope operator
15934 @vindex colon-colon@r{, in Modula-2}
15935 @c Info cannot handle :: but TeX can.
15938 @vindex ::@r{, in Modula-2}
15941 There are a few subtle differences between the Modula-2 scope operator
15942 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15947 @var{module} . @var{id}
15948 @var{scope} :: @var{id}
15952 where @var{scope} is the name of a module or a procedure,
15953 @var{module} the name of a module, and @var{id} is any declared
15954 identifier within your program, except another module.
15956 Using the @code{::} operator makes @value{GDBN} search the scope
15957 specified by @var{scope} for the identifier @var{id}. If it is not
15958 found in the specified scope, then @value{GDBN} searches all scopes
15959 enclosing the one specified by @var{scope}.
15961 Using the @code{.} operator makes @value{GDBN} search the current scope for
15962 the identifier specified by @var{id} that was imported from the
15963 definition module specified by @var{module}. With this operator, it is
15964 an error if the identifier @var{id} was not imported from definition
15965 module @var{module}, or if @var{id} is not an identifier in
15969 @subsubsection @value{GDBN} and Modula-2
15971 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15972 Five subcommands of @code{set print} and @code{show print} apply
15973 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15974 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15975 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15976 analogue in Modula-2.
15978 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15979 with any language, is not useful with Modula-2. Its
15980 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15981 created in Modula-2 as they can in C or C@t{++}. However, because an
15982 address can be specified by an integral constant, the construct
15983 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15985 @cindex @code{#} in Modula-2
15986 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15987 interpreted as the beginning of a comment. Use @code{<>} instead.
15993 The extensions made to @value{GDBN} for Ada only support
15994 output from the @sc{gnu} Ada (GNAT) compiler.
15995 Other Ada compilers are not currently supported, and
15996 attempting to debug executables produced by them is most likely
16000 @cindex expressions in Ada
16002 * Ada Mode Intro:: General remarks on the Ada syntax
16003 and semantics supported by Ada mode
16005 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16006 * Additions to Ada:: Extensions of the Ada expression syntax.
16007 * Overloading support for Ada:: Support for expressions involving overloaded
16009 * Stopping Before Main Program:: Debugging the program during elaboration.
16010 * Ada Exceptions:: Ada Exceptions
16011 * Ada Tasks:: Listing and setting breakpoints in tasks.
16012 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16013 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16015 * Ada Glitches:: Known peculiarities of Ada mode.
16018 @node Ada Mode Intro
16019 @subsubsection Introduction
16020 @cindex Ada mode, general
16022 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16023 syntax, with some extensions.
16024 The philosophy behind the design of this subset is
16028 That @value{GDBN} should provide basic literals and access to operations for
16029 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16030 leaving more sophisticated computations to subprograms written into the
16031 program (which therefore may be called from @value{GDBN}).
16034 That type safety and strict adherence to Ada language restrictions
16035 are not particularly important to the @value{GDBN} user.
16038 That brevity is important to the @value{GDBN} user.
16041 Thus, for brevity, the debugger acts as if all names declared in
16042 user-written packages are directly visible, even if they are not visible
16043 according to Ada rules, thus making it unnecessary to fully qualify most
16044 names with their packages, regardless of context. Where this causes
16045 ambiguity, @value{GDBN} asks the user's intent.
16047 The debugger will start in Ada mode if it detects an Ada main program.
16048 As for other languages, it will enter Ada mode when stopped in a program that
16049 was translated from an Ada source file.
16051 While in Ada mode, you may use `@t{--}' for comments. This is useful
16052 mostly for documenting command files. The standard @value{GDBN} comment
16053 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16054 middle (to allow based literals).
16056 @node Omissions from Ada
16057 @subsubsection Omissions from Ada
16058 @cindex Ada, omissions from
16060 Here are the notable omissions from the subset:
16064 Only a subset of the attributes are supported:
16068 @t{'First}, @t{'Last}, and @t{'Length}
16069 on array objects (not on types and subtypes).
16072 @t{'Min} and @t{'Max}.
16075 @t{'Pos} and @t{'Val}.
16081 @t{'Range} on array objects (not subtypes), but only as the right
16082 operand of the membership (@code{in}) operator.
16085 @t{'Access}, @t{'Unchecked_Access}, and
16086 @t{'Unrestricted_Access} (a GNAT extension).
16094 @code{Characters.Latin_1} are not available and
16095 concatenation is not implemented. Thus, escape characters in strings are
16096 not currently available.
16099 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16100 equality of representations. They will generally work correctly
16101 for strings and arrays whose elements have integer or enumeration types.
16102 They may not work correctly for arrays whose element
16103 types have user-defined equality, for arrays of real values
16104 (in particular, IEEE-conformant floating point, because of negative
16105 zeroes and NaNs), and for arrays whose elements contain unused bits with
16106 indeterminate values.
16109 The other component-by-component array operations (@code{and}, @code{or},
16110 @code{xor}, @code{not}, and relational tests other than equality)
16111 are not implemented.
16114 @cindex array aggregates (Ada)
16115 @cindex record aggregates (Ada)
16116 @cindex aggregates (Ada)
16117 There is limited support for array and record aggregates. They are
16118 permitted only on the right sides of assignments, as in these examples:
16121 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16122 (@value{GDBP}) set An_Array := (1, others => 0)
16123 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16124 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16125 (@value{GDBP}) set A_Record := (1, "Peter", True);
16126 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16130 discriminant's value by assigning an aggregate has an
16131 undefined effect if that discriminant is used within the record.
16132 However, you can first modify discriminants by directly assigning to
16133 them (which normally would not be allowed in Ada), and then performing an
16134 aggregate assignment. For example, given a variable @code{A_Rec}
16135 declared to have a type such as:
16138 type Rec (Len : Small_Integer := 0) is record
16140 Vals : IntArray (1 .. Len);
16144 you can assign a value with a different size of @code{Vals} with two
16148 (@value{GDBP}) set A_Rec.Len := 4
16149 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16152 As this example also illustrates, @value{GDBN} is very loose about the usual
16153 rules concerning aggregates. You may leave out some of the
16154 components of an array or record aggregate (such as the @code{Len}
16155 component in the assignment to @code{A_Rec} above); they will retain their
16156 original values upon assignment. You may freely use dynamic values as
16157 indices in component associations. You may even use overlapping or
16158 redundant component associations, although which component values are
16159 assigned in such cases is not defined.
16162 Calls to dispatching subprograms are not implemented.
16165 The overloading algorithm is much more limited (i.e., less selective)
16166 than that of real Ada. It makes only limited use of the context in
16167 which a subexpression appears to resolve its meaning, and it is much
16168 looser in its rules for allowing type matches. As a result, some
16169 function calls will be ambiguous, and the user will be asked to choose
16170 the proper resolution.
16173 The @code{new} operator is not implemented.
16176 Entry calls are not implemented.
16179 Aside from printing, arithmetic operations on the native VAX floating-point
16180 formats are not supported.
16183 It is not possible to slice a packed array.
16186 The names @code{True} and @code{False}, when not part of a qualified name,
16187 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16189 Should your program
16190 redefine these names in a package or procedure (at best a dubious practice),
16191 you will have to use fully qualified names to access their new definitions.
16194 @node Additions to Ada
16195 @subsubsection Additions to Ada
16196 @cindex Ada, deviations from
16198 As it does for other languages, @value{GDBN} makes certain generic
16199 extensions to Ada (@pxref{Expressions}):
16203 If the expression @var{E} is a variable residing in memory (typically
16204 a local variable or array element) and @var{N} is a positive integer,
16205 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16206 @var{N}-1 adjacent variables following it in memory as an array. In
16207 Ada, this operator is generally not necessary, since its prime use is
16208 in displaying parts of an array, and slicing will usually do this in
16209 Ada. However, there are occasional uses when debugging programs in
16210 which certain debugging information has been optimized away.
16213 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16214 appears in function or file @var{B}.'' When @var{B} is a file name,
16215 you must typically surround it in single quotes.
16218 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16219 @var{type} that appears at address @var{addr}.''
16222 A name starting with @samp{$} is a convenience variable
16223 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16226 In addition, @value{GDBN} provides a few other shortcuts and outright
16227 additions specific to Ada:
16231 The assignment statement is allowed as an expression, returning
16232 its right-hand operand as its value. Thus, you may enter
16235 (@value{GDBP}) set x := y + 3
16236 (@value{GDBP}) print A(tmp := y + 1)
16240 The semicolon is allowed as an ``operator,'' returning as its value
16241 the value of its right-hand operand.
16242 This allows, for example,
16243 complex conditional breaks:
16246 (@value{GDBP}) break f
16247 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16251 Rather than use catenation and symbolic character names to introduce special
16252 characters into strings, one may instead use a special bracket notation,
16253 which is also used to print strings. A sequence of characters of the form
16254 @samp{["@var{XX}"]} within a string or character literal denotes the
16255 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16256 sequence of characters @samp{["""]} also denotes a single quotation mark
16257 in strings. For example,
16259 "One line.["0a"]Next line.["0a"]"
16262 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16266 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16267 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16271 (@value{GDBP}) print 'max(x, y)
16275 When printing arrays, @value{GDBN} uses positional notation when the
16276 array has a lower bound of 1, and uses a modified named notation otherwise.
16277 For example, a one-dimensional array of three integers with a lower bound
16278 of 3 might print as
16285 That is, in contrast to valid Ada, only the first component has a @code{=>}
16289 You may abbreviate attributes in expressions with any unique,
16290 multi-character subsequence of
16291 their names (an exact match gets preference).
16292 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16293 in place of @t{a'length}.
16296 @cindex quoting Ada internal identifiers
16297 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16298 to lower case. The GNAT compiler uses upper-case characters for
16299 some of its internal identifiers, which are normally of no interest to users.
16300 For the rare occasions when you actually have to look at them,
16301 enclose them in angle brackets to avoid the lower-case mapping.
16304 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16308 Printing an object of class-wide type or dereferencing an
16309 access-to-class-wide value will display all the components of the object's
16310 specific type (as indicated by its run-time tag). Likewise, component
16311 selection on such a value will operate on the specific type of the
16316 @node Overloading support for Ada
16317 @subsubsection Overloading support for Ada
16318 @cindex overloading, Ada
16320 The debugger supports limited overloading. Given a subprogram call in which
16321 the function symbol has multiple definitions, it will use the number of
16322 actual parameters and some information about their types to attempt to narrow
16323 the set of definitions. It also makes very limited use of context, preferring
16324 procedures to functions in the context of the @code{call} command, and
16325 functions to procedures elsewhere.
16327 If, after narrowing, the set of matching definitions still contains more than
16328 one definition, @value{GDBN} will display a menu to query which one it should
16332 (@value{GDBP}) print f(1)
16333 Multiple matches for f
16335 [1] foo.f (integer) return boolean at foo.adb:23
16336 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16340 In this case, just select one menu entry either to cancel expression evaluation
16341 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16342 instance (type the corresponding number and press @key{RET}).
16344 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16349 @kindex set ada print-signatures
16350 @item set ada print-signatures
16351 Control whether parameter types and return types are displayed in overloads
16352 selection menus. It is @code{on} by default.
16353 @xref{Overloading support for Ada}.
16355 @kindex show ada print-signatures
16356 @item show ada print-signatures
16357 Show the current setting for displaying parameter types and return types in
16358 overloads selection menu.
16359 @xref{Overloading support for Ada}.
16363 @node Stopping Before Main Program
16364 @subsubsection Stopping at the Very Beginning
16366 @cindex breakpointing Ada elaboration code
16367 It is sometimes necessary to debug the program during elaboration, and
16368 before reaching the main procedure.
16369 As defined in the Ada Reference
16370 Manual, the elaboration code is invoked from a procedure called
16371 @code{adainit}. To run your program up to the beginning of
16372 elaboration, simply use the following two commands:
16373 @code{tbreak adainit} and @code{run}.
16375 @node Ada Exceptions
16376 @subsubsection Ada Exceptions
16378 A command is provided to list all Ada exceptions:
16381 @kindex info exceptions
16382 @item info exceptions
16383 @itemx info exceptions @var{regexp}
16384 The @code{info exceptions} command allows you to list all Ada exceptions
16385 defined within the program being debugged, as well as their addresses.
16386 With a regular expression, @var{regexp}, as argument, only those exceptions
16387 whose names match @var{regexp} are listed.
16390 Below is a small example, showing how the command can be used, first
16391 without argument, and next with a regular expression passed as an
16395 (@value{GDBP}) info exceptions
16396 All defined Ada exceptions:
16397 constraint_error: 0x613da0
16398 program_error: 0x613d20
16399 storage_error: 0x613ce0
16400 tasking_error: 0x613ca0
16401 const.aint_global_e: 0x613b00
16402 (@value{GDBP}) info exceptions const.aint
16403 All Ada exceptions matching regular expression "const.aint":
16404 constraint_error: 0x613da0
16405 const.aint_global_e: 0x613b00
16408 It is also possible to ask @value{GDBN} to stop your program's execution
16409 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16412 @subsubsection Extensions for Ada Tasks
16413 @cindex Ada, tasking
16415 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16416 @value{GDBN} provides the following task-related commands:
16421 This command shows a list of current Ada tasks, as in the following example:
16428 (@value{GDBP}) info tasks
16429 ID TID P-ID Pri State Name
16430 1 8088000 0 15 Child Activation Wait main_task
16431 2 80a4000 1 15 Accept Statement b
16432 3 809a800 1 15 Child Activation Wait a
16433 * 4 80ae800 3 15 Runnable c
16438 In this listing, the asterisk before the last task indicates it to be the
16439 task currently being inspected.
16443 Represents @value{GDBN}'s internal task number.
16449 The parent's task ID (@value{GDBN}'s internal task number).
16452 The base priority of the task.
16455 Current state of the task.
16459 The task has been created but has not been activated. It cannot be
16463 The task is not blocked for any reason known to Ada. (It may be waiting
16464 for a mutex, though.) It is conceptually "executing" in normal mode.
16467 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16468 that were waiting on terminate alternatives have been awakened and have
16469 terminated themselves.
16471 @item Child Activation Wait
16472 The task is waiting for created tasks to complete activation.
16474 @item Accept Statement
16475 The task is waiting on an accept or selective wait statement.
16477 @item Waiting on entry call
16478 The task is waiting on an entry call.
16480 @item Async Select Wait
16481 The task is waiting to start the abortable part of an asynchronous
16485 The task is waiting on a select statement with only a delay
16488 @item Child Termination Wait
16489 The task is sleeping having completed a master within itself, and is
16490 waiting for the tasks dependent on that master to become terminated or
16491 waiting on a terminate Phase.
16493 @item Wait Child in Term Alt
16494 The task is sleeping waiting for tasks on terminate alternatives to
16495 finish terminating.
16497 @item Accepting RV with @var{taskno}
16498 The task is accepting a rendez-vous with the task @var{taskno}.
16502 Name of the task in the program.
16506 @kindex info task @var{taskno}
16507 @item info task @var{taskno}
16508 This command shows detailled informations on the specified task, as in
16509 the following example:
16514 (@value{GDBP}) info tasks
16515 ID TID P-ID Pri State Name
16516 1 8077880 0 15 Child Activation Wait main_task
16517 * 2 807c468 1 15 Runnable task_1
16518 (@value{GDBP}) info task 2
16519 Ada Task: 0x807c468
16522 Parent: 1 (main_task)
16528 @kindex task@r{ (Ada)}
16529 @cindex current Ada task ID
16530 This command prints the ID of the current task.
16536 (@value{GDBP}) info tasks
16537 ID TID P-ID Pri State Name
16538 1 8077870 0 15 Child Activation Wait main_task
16539 * 2 807c458 1 15 Runnable t
16540 (@value{GDBP}) task
16541 [Current task is 2]
16544 @item task @var{taskno}
16545 @cindex Ada task switching
16546 This command is like the @code{thread @var{thread-id}}
16547 command (@pxref{Threads}). It switches the context of debugging
16548 from the current task to the given task.
16554 (@value{GDBP}) info tasks
16555 ID TID P-ID Pri State Name
16556 1 8077870 0 15 Child Activation Wait main_task
16557 * 2 807c458 1 15 Runnable t
16558 (@value{GDBP}) task 1
16559 [Switching to task 1]
16560 #0 0x8067726 in pthread_cond_wait ()
16562 #0 0x8067726 in pthread_cond_wait ()
16563 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16564 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16565 #3 0x806153e in system.tasking.stages.activate_tasks ()
16566 #4 0x804aacc in un () at un.adb:5
16569 @item break @var{location} task @var{taskno}
16570 @itemx break @var{location} task @var{taskno} if @dots{}
16571 @cindex breakpoints and tasks, in Ada
16572 @cindex task breakpoints, in Ada
16573 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16574 These commands are like the @code{break @dots{} thread @dots{}}
16575 command (@pxref{Thread Stops}). The
16576 @var{location} argument specifies source lines, as described
16577 in @ref{Specify Location}.
16579 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16580 to specify that you only want @value{GDBN} to stop the program when a
16581 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16582 numeric task identifiers assigned by @value{GDBN}, shown in the first
16583 column of the @samp{info tasks} display.
16585 If you do not specify @samp{task @var{taskno}} when you set a
16586 breakpoint, the breakpoint applies to @emph{all} tasks of your
16589 You can use the @code{task} qualifier on conditional breakpoints as
16590 well; in this case, place @samp{task @var{taskno}} before the
16591 breakpoint condition (before the @code{if}).
16599 (@value{GDBP}) info tasks
16600 ID TID P-ID Pri State Name
16601 1 140022020 0 15 Child Activation Wait main_task
16602 2 140045060 1 15 Accept/Select Wait t2
16603 3 140044840 1 15 Runnable t1
16604 * 4 140056040 1 15 Runnable t3
16605 (@value{GDBP}) b 15 task 2
16606 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16607 (@value{GDBP}) cont
16612 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16614 (@value{GDBP}) info tasks
16615 ID TID P-ID Pri State Name
16616 1 140022020 0 15 Child Activation Wait main_task
16617 * 2 140045060 1 15 Runnable t2
16618 3 140044840 1 15 Runnable t1
16619 4 140056040 1 15 Delay Sleep t3
16623 @node Ada Tasks and Core Files
16624 @subsubsection Tasking Support when Debugging Core Files
16625 @cindex Ada tasking and core file debugging
16627 When inspecting a core file, as opposed to debugging a live program,
16628 tasking support may be limited or even unavailable, depending on
16629 the platform being used.
16630 For instance, on x86-linux, the list of tasks is available, but task
16631 switching is not supported.
16633 On certain platforms, the debugger needs to perform some
16634 memory writes in order to provide Ada tasking support. When inspecting
16635 a core file, this means that the core file must be opened with read-write
16636 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16637 Under these circumstances, you should make a backup copy of the core
16638 file before inspecting it with @value{GDBN}.
16640 @node Ravenscar Profile
16641 @subsubsection Tasking Support when using the Ravenscar Profile
16642 @cindex Ravenscar Profile
16644 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16645 specifically designed for systems with safety-critical real-time
16649 @kindex set ravenscar task-switching on
16650 @cindex task switching with program using Ravenscar Profile
16651 @item set ravenscar task-switching on
16652 Allows task switching when debugging a program that uses the Ravenscar
16653 Profile. This is the default.
16655 @kindex set ravenscar task-switching off
16656 @item set ravenscar task-switching off
16657 Turn off task switching when debugging a program that uses the Ravenscar
16658 Profile. This is mostly intended to disable the code that adds support
16659 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16660 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16661 To be effective, this command should be run before the program is started.
16663 @kindex show ravenscar task-switching
16664 @item show ravenscar task-switching
16665 Show whether it is possible to switch from task to task in a program
16666 using the Ravenscar Profile.
16671 @subsubsection Known Peculiarities of Ada Mode
16672 @cindex Ada, problems
16674 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16675 we know of several problems with and limitations of Ada mode in
16677 some of which will be fixed with planned future releases of the debugger
16678 and the GNU Ada compiler.
16682 Static constants that the compiler chooses not to materialize as objects in
16683 storage are invisible to the debugger.
16686 Named parameter associations in function argument lists are ignored (the
16687 argument lists are treated as positional).
16690 Many useful library packages are currently invisible to the debugger.
16693 Fixed-point arithmetic, conversions, input, and output is carried out using
16694 floating-point arithmetic, and may give results that only approximate those on
16698 The GNAT compiler never generates the prefix @code{Standard} for any of
16699 the standard symbols defined by the Ada language. @value{GDBN} knows about
16700 this: it will strip the prefix from names when you use it, and will never
16701 look for a name you have so qualified among local symbols, nor match against
16702 symbols in other packages or subprograms. If you have
16703 defined entities anywhere in your program other than parameters and
16704 local variables whose simple names match names in @code{Standard},
16705 GNAT's lack of qualification here can cause confusion. When this happens,
16706 you can usually resolve the confusion
16707 by qualifying the problematic names with package
16708 @code{Standard} explicitly.
16711 Older versions of the compiler sometimes generate erroneous debugging
16712 information, resulting in the debugger incorrectly printing the value
16713 of affected entities. In some cases, the debugger is able to work
16714 around an issue automatically. In other cases, the debugger is able
16715 to work around the issue, but the work-around has to be specifically
16718 @kindex set ada trust-PAD-over-XVS
16719 @kindex show ada trust-PAD-over-XVS
16722 @item set ada trust-PAD-over-XVS on
16723 Configure GDB to strictly follow the GNAT encoding when computing the
16724 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16725 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16726 a complete description of the encoding used by the GNAT compiler).
16727 This is the default.
16729 @item set ada trust-PAD-over-XVS off
16730 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16731 sometimes prints the wrong value for certain entities, changing @code{ada
16732 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16733 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16734 @code{off}, but this incurs a slight performance penalty, so it is
16735 recommended to leave this setting to @code{on} unless necessary.
16739 @cindex GNAT descriptive types
16740 @cindex GNAT encoding
16741 Internally, the debugger also relies on the compiler following a number
16742 of conventions known as the @samp{GNAT Encoding}, all documented in
16743 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16744 how the debugging information should be generated for certain types.
16745 In particular, this convention makes use of @dfn{descriptive types},
16746 which are artificial types generated purely to help the debugger.
16748 These encodings were defined at a time when the debugging information
16749 format used was not powerful enough to describe some of the more complex
16750 types available in Ada. Since DWARF allows us to express nearly all
16751 Ada features, the long-term goal is to slowly replace these descriptive
16752 types by their pure DWARF equivalent. To facilitate that transition,
16753 a new maintenance option is available to force the debugger to ignore
16754 those descriptive types. It allows the user to quickly evaluate how
16755 well @value{GDBN} works without them.
16759 @kindex maint ada set ignore-descriptive-types
16760 @item maintenance ada set ignore-descriptive-types [on|off]
16761 Control whether the debugger should ignore descriptive types.
16762 The default is not to ignore descriptives types (@code{off}).
16764 @kindex maint ada show ignore-descriptive-types
16765 @item maintenance ada show ignore-descriptive-types
16766 Show if descriptive types are ignored by @value{GDBN}.
16770 @node Unsupported Languages
16771 @section Unsupported Languages
16773 @cindex unsupported languages
16774 @cindex minimal language
16775 In addition to the other fully-supported programming languages,
16776 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16777 It does not represent a real programming language, but provides a set
16778 of capabilities close to what the C or assembly languages provide.
16779 This should allow most simple operations to be performed while debugging
16780 an application that uses a language currently not supported by @value{GDBN}.
16782 If the language is set to @code{auto}, @value{GDBN} will automatically
16783 select this language if the current frame corresponds to an unsupported
16787 @chapter Examining the Symbol Table
16789 The commands described in this chapter allow you to inquire about the
16790 symbols (names of variables, functions and types) defined in your
16791 program. This information is inherent in the text of your program and
16792 does not change as your program executes. @value{GDBN} finds it in your
16793 program's symbol table, in the file indicated when you started @value{GDBN}
16794 (@pxref{File Options, ,Choosing Files}), or by one of the
16795 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16797 @cindex symbol names
16798 @cindex names of symbols
16799 @cindex quoting names
16800 Occasionally, you may need to refer to symbols that contain unusual
16801 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16802 most frequent case is in referring to static variables in other
16803 source files (@pxref{Variables,,Program Variables}). File names
16804 are recorded in object files as debugging symbols, but @value{GDBN} would
16805 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16806 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16807 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16814 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16817 @cindex case-insensitive symbol names
16818 @cindex case sensitivity in symbol names
16819 @kindex set case-sensitive
16820 @item set case-sensitive on
16821 @itemx set case-sensitive off
16822 @itemx set case-sensitive auto
16823 Normally, when @value{GDBN} looks up symbols, it matches their names
16824 with case sensitivity determined by the current source language.
16825 Occasionally, you may wish to control that. The command @code{set
16826 case-sensitive} lets you do that by specifying @code{on} for
16827 case-sensitive matches or @code{off} for case-insensitive ones. If
16828 you specify @code{auto}, case sensitivity is reset to the default
16829 suitable for the source language. The default is case-sensitive
16830 matches for all languages except for Fortran, for which the default is
16831 case-insensitive matches.
16833 @kindex show case-sensitive
16834 @item show case-sensitive
16835 This command shows the current setting of case sensitivity for symbols
16838 @kindex set print type methods
16839 @item set print type methods
16840 @itemx set print type methods on
16841 @itemx set print type methods off
16842 Normally, when @value{GDBN} prints a class, it displays any methods
16843 declared in that class. You can control this behavior either by
16844 passing the appropriate flag to @code{ptype}, or using @command{set
16845 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16846 display the methods; this is the default. Specifying @code{off} will
16847 cause @value{GDBN} to omit the methods.
16849 @kindex show print type methods
16850 @item show print type methods
16851 This command shows the current setting of method display when printing
16854 @kindex set print type typedefs
16855 @item set print type typedefs
16856 @itemx set print type typedefs on
16857 @itemx set print type typedefs off
16859 Normally, when @value{GDBN} prints a class, it displays any typedefs
16860 defined in that class. You can control this behavior either by
16861 passing the appropriate flag to @code{ptype}, or using @command{set
16862 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16863 display the typedef definitions; this is the default. Specifying
16864 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16865 Note that this controls whether the typedef definition itself is
16866 printed, not whether typedef names are substituted when printing other
16869 @kindex show print type typedefs
16870 @item show print type typedefs
16871 This command shows the current setting of typedef display when
16874 @kindex info address
16875 @cindex address of a symbol
16876 @item info address @var{symbol}
16877 Describe where the data for @var{symbol} is stored. For a register
16878 variable, this says which register it is kept in. For a non-register
16879 local variable, this prints the stack-frame offset at which the variable
16882 Note the contrast with @samp{print &@var{symbol}}, which does not work
16883 at all for a register variable, and for a stack local variable prints
16884 the exact address of the current instantiation of the variable.
16886 @kindex info symbol
16887 @cindex symbol from address
16888 @cindex closest symbol and offset for an address
16889 @item info symbol @var{addr}
16890 Print the name of a symbol which is stored at the address @var{addr}.
16891 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16892 nearest symbol and an offset from it:
16895 (@value{GDBP}) info symbol 0x54320
16896 _initialize_vx + 396 in section .text
16900 This is the opposite of the @code{info address} command. You can use
16901 it to find out the name of a variable or a function given its address.
16903 For dynamically linked executables, the name of executable or shared
16904 library containing the symbol is also printed:
16907 (@value{GDBP}) info symbol 0x400225
16908 _start + 5 in section .text of /tmp/a.out
16909 (@value{GDBP}) info symbol 0x2aaaac2811cf
16910 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16915 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16916 Demangle @var{name}.
16917 If @var{language} is provided it is the name of the language to demangle
16918 @var{name} in. Otherwise @var{name} is demangled in the current language.
16920 The @samp{--} option specifies the end of options,
16921 and is useful when @var{name} begins with a dash.
16923 The parameter @code{demangle-style} specifies how to interpret the kind
16924 of mangling used. @xref{Print Settings}.
16927 @item whatis[/@var{flags}] [@var{arg}]
16928 Print the data type of @var{arg}, which can be either an expression
16929 or a name of a data type. With no argument, print the data type of
16930 @code{$}, the last value in the value history.
16932 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16933 is not actually evaluated, and any side-effecting operations (such as
16934 assignments or function calls) inside it do not take place.
16936 If @var{arg} is a variable or an expression, @code{whatis} prints its
16937 literal type as it is used in the source code. If the type was
16938 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16939 the data type underlying the @code{typedef}. If the type of the
16940 variable or the expression is a compound data type, such as
16941 @code{struct} or @code{class}, @code{whatis} never prints their
16942 fields or methods. It just prints the @code{struct}/@code{class}
16943 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16944 such a compound data type, use @code{ptype}.
16946 If @var{arg} is a type name that was defined using @code{typedef},
16947 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16948 Unrolling means that @code{whatis} will show the underlying type used
16949 in the @code{typedef} declaration of @var{arg}. However, if that
16950 underlying type is also a @code{typedef}, @code{whatis} will not
16953 For C code, the type names may also have the form @samp{class
16954 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16955 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16957 @var{flags} can be used to modify how the type is displayed.
16958 Available flags are:
16962 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16963 parameters and typedefs defined in a class when printing the class'
16964 members. The @code{/r} flag disables this.
16967 Do not print methods defined in the class.
16970 Print methods defined in the class. This is the default, but the flag
16971 exists in case you change the default with @command{set print type methods}.
16974 Do not print typedefs defined in the class. Note that this controls
16975 whether the typedef definition itself is printed, not whether typedef
16976 names are substituted when printing other types.
16979 Print typedefs defined in the class. This is the default, but the flag
16980 exists in case you change the default with @command{set print type typedefs}.
16984 @item ptype[/@var{flags}] [@var{arg}]
16985 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16986 detailed description of the type, instead of just the name of the type.
16987 @xref{Expressions, ,Expressions}.
16989 Contrary to @code{whatis}, @code{ptype} always unrolls any
16990 @code{typedef}s in its argument declaration, whether the argument is
16991 a variable, expression, or a data type. This means that @code{ptype}
16992 of a variable or an expression will not print literally its type as
16993 present in the source code---use @code{whatis} for that. @code{typedef}s at
16994 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16995 fields, methods and inner @code{class typedef}s of @code{struct}s,
16996 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16998 For example, for this variable declaration:
17001 typedef double real_t;
17002 struct complex @{ real_t real; double imag; @};
17003 typedef struct complex complex_t;
17005 real_t *real_pointer_var;
17009 the two commands give this output:
17013 (@value{GDBP}) whatis var
17015 (@value{GDBP}) ptype var
17016 type = struct complex @{
17020 (@value{GDBP}) whatis complex_t
17021 type = struct complex
17022 (@value{GDBP}) whatis struct complex
17023 type = struct complex
17024 (@value{GDBP}) ptype struct complex
17025 type = struct complex @{
17029 (@value{GDBP}) whatis real_pointer_var
17031 (@value{GDBP}) ptype real_pointer_var
17037 As with @code{whatis}, using @code{ptype} without an argument refers to
17038 the type of @code{$}, the last value in the value history.
17040 @cindex incomplete type
17041 Sometimes, programs use opaque data types or incomplete specifications
17042 of complex data structure. If the debug information included in the
17043 program does not allow @value{GDBN} to display a full declaration of
17044 the data type, it will say @samp{<incomplete type>}. For example,
17045 given these declarations:
17049 struct foo *fooptr;
17053 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17056 (@value{GDBP}) ptype foo
17057 $1 = <incomplete type>
17061 ``Incomplete type'' is C terminology for data types that are not
17062 completely specified.
17065 @item info types @var{regexp}
17067 Print a brief description of all types whose names match the regular
17068 expression @var{regexp} (or all types in your program, if you supply
17069 no argument). Each complete typename is matched as though it were a
17070 complete line; thus, @samp{i type value} gives information on all
17071 types in your program whose names include the string @code{value}, but
17072 @samp{i type ^value$} gives information only on types whose complete
17073 name is @code{value}.
17075 This command differs from @code{ptype} in two ways: first, like
17076 @code{whatis}, it does not print a detailed description; second, it
17077 lists all source files where a type is defined.
17079 @kindex info type-printers
17080 @item info type-printers
17081 Versions of @value{GDBN} that ship with Python scripting enabled may
17082 have ``type printers'' available. When using @command{ptype} or
17083 @command{whatis}, these printers are consulted when the name of a type
17084 is needed. @xref{Type Printing API}, for more information on writing
17087 @code{info type-printers} displays all the available type printers.
17089 @kindex enable type-printer
17090 @kindex disable type-printer
17091 @item enable type-printer @var{name}@dots{}
17092 @item disable type-printer @var{name}@dots{}
17093 These commands can be used to enable or disable type printers.
17096 @cindex local variables
17097 @item info scope @var{location}
17098 List all the variables local to a particular scope. This command
17099 accepts a @var{location} argument---a function name, a source line, or
17100 an address preceded by a @samp{*}, and prints all the variables local
17101 to the scope defined by that location. (@xref{Specify Location}, for
17102 details about supported forms of @var{location}.) For example:
17105 (@value{GDBP}) @b{info scope command_line_handler}
17106 Scope for command_line_handler:
17107 Symbol rl is an argument at stack/frame offset 8, length 4.
17108 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17109 Symbol linelength is in static storage at address 0x150a1c, length 4.
17110 Symbol p is a local variable in register $esi, length 4.
17111 Symbol p1 is a local variable in register $ebx, length 4.
17112 Symbol nline is a local variable in register $edx, length 4.
17113 Symbol repeat is a local variable at frame offset -8, length 4.
17117 This command is especially useful for determining what data to collect
17118 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17121 @kindex info source
17123 Show information about the current source file---that is, the source file for
17124 the function containing the current point of execution:
17127 the name of the source file, and the directory containing it,
17129 the directory it was compiled in,
17131 its length, in lines,
17133 which programming language it is written in,
17135 if the debug information provides it, the program that compiled the file
17136 (which may include, e.g., the compiler version and command line arguments),
17138 whether the executable includes debugging information for that file, and
17139 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17141 whether the debugging information includes information about
17142 preprocessor macros.
17146 @kindex info sources
17148 Print the names of all source files in your program for which there is
17149 debugging information, organized into two lists: files whose symbols
17150 have already been read, and files whose symbols will be read when needed.
17152 @kindex info functions
17153 @item info functions
17154 Print the names and data types of all defined functions.
17156 @item info functions @var{regexp}
17157 Print the names and data types of all defined functions
17158 whose names contain a match for regular expression @var{regexp}.
17159 Thus, @samp{info fun step} finds all functions whose names
17160 include @code{step}; @samp{info fun ^step} finds those whose names
17161 start with @code{step}. If a function name contains characters
17162 that conflict with the regular expression language (e.g.@:
17163 @samp{operator*()}), they may be quoted with a backslash.
17165 @kindex info variables
17166 @item info variables
17167 Print the names and data types of all variables that are defined
17168 outside of functions (i.e.@: excluding local variables).
17170 @item info variables @var{regexp}
17171 Print the names and data types of all variables (except for local
17172 variables) whose names contain a match for regular expression
17175 @kindex info classes
17176 @cindex Objective-C, classes and selectors
17178 @itemx info classes @var{regexp}
17179 Display all Objective-C classes in your program, or
17180 (with the @var{regexp} argument) all those matching a particular regular
17183 @kindex info selectors
17184 @item info selectors
17185 @itemx info selectors @var{regexp}
17186 Display all Objective-C selectors in your program, or
17187 (with the @var{regexp} argument) all those matching a particular regular
17191 This was never implemented.
17192 @kindex info methods
17194 @itemx info methods @var{regexp}
17195 The @code{info methods} command permits the user to examine all defined
17196 methods within C@t{++} program, or (with the @var{regexp} argument) a
17197 specific set of methods found in the various C@t{++} classes. Many
17198 C@t{++} classes provide a large number of methods. Thus, the output
17199 from the @code{ptype} command can be overwhelming and hard to use. The
17200 @code{info-methods} command filters the methods, printing only those
17201 which match the regular-expression @var{regexp}.
17204 @cindex opaque data types
17205 @kindex set opaque-type-resolution
17206 @item set opaque-type-resolution on
17207 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17208 declared as a pointer to a @code{struct}, @code{class}, or
17209 @code{union}---for example, @code{struct MyType *}---that is used in one
17210 source file although the full declaration of @code{struct MyType} is in
17211 another source file. The default is on.
17213 A change in the setting of this subcommand will not take effect until
17214 the next time symbols for a file are loaded.
17216 @item set opaque-type-resolution off
17217 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17218 is printed as follows:
17220 @{<no data fields>@}
17223 @kindex show opaque-type-resolution
17224 @item show opaque-type-resolution
17225 Show whether opaque types are resolved or not.
17227 @kindex set print symbol-loading
17228 @cindex print messages when symbols are loaded
17229 @item set print symbol-loading
17230 @itemx set print symbol-loading full
17231 @itemx set print symbol-loading brief
17232 @itemx set print symbol-loading off
17233 The @code{set print symbol-loading} command allows you to control the
17234 printing of messages when @value{GDBN} loads symbol information.
17235 By default a message is printed for the executable and one for each
17236 shared library, and normally this is what you want. However, when
17237 debugging apps with large numbers of shared libraries these messages
17239 When set to @code{brief} a message is printed for each executable,
17240 and when @value{GDBN} loads a collection of shared libraries at once
17241 it will only print one message regardless of the number of shared
17242 libraries. When set to @code{off} no messages are printed.
17244 @kindex show print symbol-loading
17245 @item show print symbol-loading
17246 Show whether messages will be printed when a @value{GDBN} command
17247 entered from the keyboard causes symbol information to be loaded.
17249 @kindex maint print symbols
17250 @cindex symbol dump
17251 @kindex maint print psymbols
17252 @cindex partial symbol dump
17253 @kindex maint print msymbols
17254 @cindex minimal symbol dump
17255 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17256 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17257 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17258 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17259 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17260 Write a dump of debugging symbol data into the file @var{filename} or
17261 the terminal if @var{filename} is unspecified.
17262 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17264 If @code{-pc @var{address}} is specified, only dump symbols for the file
17265 with code at that address. Note that @var{address} may be a symbol like
17267 If @code{-source @var{source}} is specified, only dump symbols for that
17270 These commands are used to debug the @value{GDBN} symbol-reading code.
17271 These commands do not modify internal @value{GDBN} state, therefore
17272 @samp{maint print symbols} will only print symbols for already expanded symbol
17274 You can use the command @code{info sources} to find out which files these are.
17275 If you use @samp{maint print psymbols} instead, the dump shows information
17276 about symbols that @value{GDBN} only knows partially---that is, symbols
17277 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17278 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17281 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17282 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17284 @kindex maint info symtabs
17285 @kindex maint info psymtabs
17286 @cindex listing @value{GDBN}'s internal symbol tables
17287 @cindex symbol tables, listing @value{GDBN}'s internal
17288 @cindex full symbol tables, listing @value{GDBN}'s internal
17289 @cindex partial symbol tables, listing @value{GDBN}'s internal
17290 @item maint info symtabs @r{[} @var{regexp} @r{]}
17291 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17293 List the @code{struct symtab} or @code{struct partial_symtab}
17294 structures whose names match @var{regexp}. If @var{regexp} is not
17295 given, list them all. The output includes expressions which you can
17296 copy into a @value{GDBN} debugging this one to examine a particular
17297 structure in more detail. For example:
17300 (@value{GDBP}) maint info psymtabs dwarf2read
17301 @{ objfile /home/gnu/build/gdb/gdb
17302 ((struct objfile *) 0x82e69d0)
17303 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17304 ((struct partial_symtab *) 0x8474b10)
17307 text addresses 0x814d3c8 -- 0x8158074
17308 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17309 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17310 dependencies (none)
17313 (@value{GDBP}) maint info symtabs
17317 We see that there is one partial symbol table whose filename contains
17318 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17319 and we see that @value{GDBN} has not read in any symtabs yet at all.
17320 If we set a breakpoint on a function, that will cause @value{GDBN} to
17321 read the symtab for the compilation unit containing that function:
17324 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17325 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17327 (@value{GDBP}) maint info symtabs
17328 @{ objfile /home/gnu/build/gdb/gdb
17329 ((struct objfile *) 0x82e69d0)
17330 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17331 ((struct symtab *) 0x86c1f38)
17334 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17335 linetable ((struct linetable *) 0x8370fa0)
17336 debugformat DWARF 2
17342 @kindex maint info line-table
17343 @cindex listing @value{GDBN}'s internal line tables
17344 @cindex line tables, listing @value{GDBN}'s internal
17345 @item maint info line-table @r{[} @var{regexp} @r{]}
17347 List the @code{struct linetable} from all @code{struct symtab}
17348 instances whose name matches @var{regexp}. If @var{regexp} is not
17349 given, list the @code{struct linetable} from all @code{struct symtab}.
17351 @kindex maint set symbol-cache-size
17352 @cindex symbol cache size
17353 @item maint set symbol-cache-size @var{size}
17354 Set the size of the symbol cache to @var{size}.
17355 The default size is intended to be good enough for debugging
17356 most applications. This option exists to allow for experimenting
17357 with different sizes.
17359 @kindex maint show symbol-cache-size
17360 @item maint show symbol-cache-size
17361 Show the size of the symbol cache.
17363 @kindex maint print symbol-cache
17364 @cindex symbol cache, printing its contents
17365 @item maint print symbol-cache
17366 Print the contents of the symbol cache.
17367 This is useful when debugging symbol cache issues.
17369 @kindex maint print symbol-cache-statistics
17370 @cindex symbol cache, printing usage statistics
17371 @item maint print symbol-cache-statistics
17372 Print symbol cache usage statistics.
17373 This helps determine how well the cache is being utilized.
17375 @kindex maint flush-symbol-cache
17376 @cindex symbol cache, flushing
17377 @item maint flush-symbol-cache
17378 Flush the contents of the symbol cache, all entries are removed.
17379 This command is useful when debugging the symbol cache.
17380 It is also useful when collecting performance data.
17385 @chapter Altering Execution
17387 Once you think you have found an error in your program, you might want to
17388 find out for certain whether correcting the apparent error would lead to
17389 correct results in the rest of the run. You can find the answer by
17390 experiment, using the @value{GDBN} features for altering execution of the
17393 For example, you can store new values into variables or memory
17394 locations, give your program a signal, restart it at a different
17395 address, or even return prematurely from a function.
17398 * Assignment:: Assignment to variables
17399 * Jumping:: Continuing at a different address
17400 * Signaling:: Giving your program a signal
17401 * Returning:: Returning from a function
17402 * Calling:: Calling your program's functions
17403 * Patching:: Patching your program
17404 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17408 @section Assignment to Variables
17411 @cindex setting variables
17412 To alter the value of a variable, evaluate an assignment expression.
17413 @xref{Expressions, ,Expressions}. For example,
17420 stores the value 4 into the variable @code{x}, and then prints the
17421 value of the assignment expression (which is 4).
17422 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17423 information on operators in supported languages.
17425 @kindex set variable
17426 @cindex variables, setting
17427 If you are not interested in seeing the value of the assignment, use the
17428 @code{set} command instead of the @code{print} command. @code{set} is
17429 really the same as @code{print} except that the expression's value is
17430 not printed and is not put in the value history (@pxref{Value History,
17431 ,Value History}). The expression is evaluated only for its effects.
17433 If the beginning of the argument string of the @code{set} command
17434 appears identical to a @code{set} subcommand, use the @code{set
17435 variable} command instead of just @code{set}. This command is identical
17436 to @code{set} except for its lack of subcommands. For example, if your
17437 program has a variable @code{width}, you get an error if you try to set
17438 a new value with just @samp{set width=13}, because @value{GDBN} has the
17439 command @code{set width}:
17442 (@value{GDBP}) whatis width
17444 (@value{GDBP}) p width
17446 (@value{GDBP}) set width=47
17447 Invalid syntax in expression.
17451 The invalid expression, of course, is @samp{=47}. In
17452 order to actually set the program's variable @code{width}, use
17455 (@value{GDBP}) set var width=47
17458 Because the @code{set} command has many subcommands that can conflict
17459 with the names of program variables, it is a good idea to use the
17460 @code{set variable} command instead of just @code{set}. For example, if
17461 your program has a variable @code{g}, you run into problems if you try
17462 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17463 the command @code{set gnutarget}, abbreviated @code{set g}:
17467 (@value{GDBP}) whatis g
17471 (@value{GDBP}) set g=4
17475 The program being debugged has been started already.
17476 Start it from the beginning? (y or n) y
17477 Starting program: /home/smith/cc_progs/a.out
17478 "/home/smith/cc_progs/a.out": can't open to read symbols:
17479 Invalid bfd target.
17480 (@value{GDBP}) show g
17481 The current BFD target is "=4".
17486 The program variable @code{g} did not change, and you silently set the
17487 @code{gnutarget} to an invalid value. In order to set the variable
17491 (@value{GDBP}) set var g=4
17494 @value{GDBN} allows more implicit conversions in assignments than C; you can
17495 freely store an integer value into a pointer variable or vice versa,
17496 and you can convert any structure to any other structure that is the
17497 same length or shorter.
17498 @comment FIXME: how do structs align/pad in these conversions?
17499 @comment /doc@cygnus.com 18dec1990
17501 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17502 construct to generate a value of specified type at a specified address
17503 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17504 to memory location @code{0x83040} as an integer (which implies a certain size
17505 and representation in memory), and
17508 set @{int@}0x83040 = 4
17512 stores the value 4 into that memory location.
17515 @section Continuing at a Different Address
17517 Ordinarily, when you continue your program, you do so at the place where
17518 it stopped, with the @code{continue} command. You can instead continue at
17519 an address of your own choosing, with the following commands:
17523 @kindex j @r{(@code{jump})}
17524 @item jump @var{location}
17525 @itemx j @var{location}
17526 Resume execution at @var{location}. Execution stops again immediately
17527 if there is a breakpoint there. @xref{Specify Location}, for a description
17528 of the different forms of @var{location}. It is common
17529 practice to use the @code{tbreak} command in conjunction with
17530 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17532 The @code{jump} command does not change the current stack frame, or
17533 the stack pointer, or the contents of any memory location or any
17534 register other than the program counter. If @var{location} is in
17535 a different function from the one currently executing, the results may
17536 be bizarre if the two functions expect different patterns of arguments or
17537 of local variables. For this reason, the @code{jump} command requests
17538 confirmation if the specified line is not in the function currently
17539 executing. However, even bizarre results are predictable if you are
17540 well acquainted with the machine-language code of your program.
17543 On many systems, you can get much the same effect as the @code{jump}
17544 command by storing a new value into the register @code{$pc}. The
17545 difference is that this does not start your program running; it only
17546 changes the address of where it @emph{will} run when you continue. For
17554 makes the next @code{continue} command or stepping command execute at
17555 address @code{0x485}, rather than at the address where your program stopped.
17556 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17558 The most common occasion to use the @code{jump} command is to back
17559 up---perhaps with more breakpoints set---over a portion of a program
17560 that has already executed, in order to examine its execution in more
17565 @section Giving your Program a Signal
17566 @cindex deliver a signal to a program
17570 @item signal @var{signal}
17571 Resume execution where your program is stopped, but immediately give it the
17572 signal @var{signal}. The @var{signal} can be the name or the number of a
17573 signal. For example, on many systems @code{signal 2} and @code{signal
17574 SIGINT} are both ways of sending an interrupt signal.
17576 Alternatively, if @var{signal} is zero, continue execution without
17577 giving a signal. This is useful when your program stopped on account of
17578 a signal and would ordinarily see the signal when resumed with the
17579 @code{continue} command; @samp{signal 0} causes it to resume without a
17582 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17583 delivered to the currently selected thread, not the thread that last
17584 reported a stop. This includes the situation where a thread was
17585 stopped due to a signal. So if you want to continue execution
17586 suppressing the signal that stopped a thread, you should select that
17587 same thread before issuing the @samp{signal 0} command. If you issue
17588 the @samp{signal 0} command with another thread as the selected one,
17589 @value{GDBN} detects that and asks for confirmation.
17591 Invoking the @code{signal} command is not the same as invoking the
17592 @code{kill} utility from the shell. Sending a signal with @code{kill}
17593 causes @value{GDBN} to decide what to do with the signal depending on
17594 the signal handling tables (@pxref{Signals}). The @code{signal} command
17595 passes the signal directly to your program.
17597 @code{signal} does not repeat when you press @key{RET} a second time
17598 after executing the command.
17600 @kindex queue-signal
17601 @item queue-signal @var{signal}
17602 Queue @var{signal} to be delivered immediately to the current thread
17603 when execution of the thread resumes. The @var{signal} can be the name or
17604 the number of a signal. For example, on many systems @code{signal 2} and
17605 @code{signal SIGINT} are both ways of sending an interrupt signal.
17606 The handling of the signal must be set to pass the signal to the program,
17607 otherwise @value{GDBN} will report an error.
17608 You can control the handling of signals from @value{GDBN} with the
17609 @code{handle} command (@pxref{Signals}).
17611 Alternatively, if @var{signal} is zero, any currently queued signal
17612 for the current thread is discarded and when execution resumes no signal
17613 will be delivered. This is useful when your program stopped on account
17614 of a signal and would ordinarily see the signal when resumed with the
17615 @code{continue} command.
17617 This command differs from the @code{signal} command in that the signal
17618 is just queued, execution is not resumed. And @code{queue-signal} cannot
17619 be used to pass a signal whose handling state has been set to @code{nopass}
17624 @xref{stepping into signal handlers}, for information on how stepping
17625 commands behave when the thread has a signal queued.
17628 @section Returning from a Function
17631 @cindex returning from a function
17634 @itemx return @var{expression}
17635 You can cancel execution of a function call with the @code{return}
17636 command. If you give an
17637 @var{expression} argument, its value is used as the function's return
17641 When you use @code{return}, @value{GDBN} discards the selected stack frame
17642 (and all frames within it). You can think of this as making the
17643 discarded frame return prematurely. If you wish to specify a value to
17644 be returned, give that value as the argument to @code{return}.
17646 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17647 Frame}), and any other frames inside of it, leaving its caller as the
17648 innermost remaining frame. That frame becomes selected. The
17649 specified value is stored in the registers used for returning values
17652 The @code{return} command does not resume execution; it leaves the
17653 program stopped in the state that would exist if the function had just
17654 returned. In contrast, the @code{finish} command (@pxref{Continuing
17655 and Stepping, ,Continuing and Stepping}) resumes execution until the
17656 selected stack frame returns naturally.
17658 @value{GDBN} needs to know how the @var{expression} argument should be set for
17659 the inferior. The concrete registers assignment depends on the OS ABI and the
17660 type being returned by the selected stack frame. For example it is common for
17661 OS ABI to return floating point values in FPU registers while integer values in
17662 CPU registers. Still some ABIs return even floating point values in CPU
17663 registers. Larger integer widths (such as @code{long long int}) also have
17664 specific placement rules. @value{GDBN} already knows the OS ABI from its
17665 current target so it needs to find out also the type being returned to make the
17666 assignment into the right register(s).
17668 Normally, the selected stack frame has debug info. @value{GDBN} will always
17669 use the debug info instead of the implicit type of @var{expression} when the
17670 debug info is available. For example, if you type @kbd{return -1}, and the
17671 function in the current stack frame is declared to return a @code{long long
17672 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17673 into a @code{long long int}:
17676 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17678 (@value{GDBP}) return -1
17679 Make func return now? (y or n) y
17680 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17681 43 printf ("result=%lld\n", func ());
17685 However, if the selected stack frame does not have a debug info, e.g., if the
17686 function was compiled without debug info, @value{GDBN} has to find out the type
17687 to return from user. Specifying a different type by mistake may set the value
17688 in different inferior registers than the caller code expects. For example,
17689 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17690 of a @code{long long int} result for a debug info less function (on 32-bit
17691 architectures). Therefore the user is required to specify the return type by
17692 an appropriate cast explicitly:
17695 Breakpoint 2, 0x0040050b in func ()
17696 (@value{GDBP}) return -1
17697 Return value type not available for selected stack frame.
17698 Please use an explicit cast of the value to return.
17699 (@value{GDBP}) return (long long int) -1
17700 Make selected stack frame return now? (y or n) y
17701 #0 0x00400526 in main ()
17706 @section Calling Program Functions
17709 @cindex calling functions
17710 @cindex inferior functions, calling
17711 @item print @var{expr}
17712 Evaluate the expression @var{expr} and display the resulting value.
17713 The expression may include calls to functions in the program being
17717 @item call @var{expr}
17718 Evaluate the expression @var{expr} without displaying @code{void}
17721 You can use this variant of the @code{print} command if you want to
17722 execute a function from your program that does not return anything
17723 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17724 with @code{void} returned values that @value{GDBN} will otherwise
17725 print. If the result is not void, it is printed and saved in the
17729 It is possible for the function you call via the @code{print} or
17730 @code{call} command to generate a signal (e.g., if there's a bug in
17731 the function, or if you passed it incorrect arguments). What happens
17732 in that case is controlled by the @code{set unwindonsignal} command.
17734 Similarly, with a C@t{++} program it is possible for the function you
17735 call via the @code{print} or @code{call} command to generate an
17736 exception that is not handled due to the constraints of the dummy
17737 frame. In this case, any exception that is raised in the frame, but has
17738 an out-of-frame exception handler will not be found. GDB builds a
17739 dummy-frame for the inferior function call, and the unwinder cannot
17740 seek for exception handlers outside of this dummy-frame. What happens
17741 in that case is controlled by the
17742 @code{set unwind-on-terminating-exception} command.
17745 @item set unwindonsignal
17746 @kindex set unwindonsignal
17747 @cindex unwind stack in called functions
17748 @cindex call dummy stack unwinding
17749 Set unwinding of the stack if a signal is received while in a function
17750 that @value{GDBN} called in the program being debugged. If set to on,
17751 @value{GDBN} unwinds the stack it created for the call and restores
17752 the context to what it was before the call. If set to off (the
17753 default), @value{GDBN} stops in the frame where the signal was
17756 @item show unwindonsignal
17757 @kindex show unwindonsignal
17758 Show the current setting of stack unwinding in the functions called by
17761 @item set unwind-on-terminating-exception
17762 @kindex set unwind-on-terminating-exception
17763 @cindex unwind stack in called functions with unhandled exceptions
17764 @cindex call dummy stack unwinding on unhandled exception.
17765 Set unwinding of the stack if a C@t{++} exception is raised, but left
17766 unhandled while in a function that @value{GDBN} called in the program being
17767 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17768 it created for the call and restores the context to what it was before
17769 the call. If set to off, @value{GDBN} the exception is delivered to
17770 the default C@t{++} exception handler and the inferior terminated.
17772 @item show unwind-on-terminating-exception
17773 @kindex show unwind-on-terminating-exception
17774 Show the current setting of stack unwinding in the functions called by
17779 @cindex weak alias functions
17780 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17781 for another function. In such case, @value{GDBN} might not pick up
17782 the type information, including the types of the function arguments,
17783 which causes @value{GDBN} to call the inferior function incorrectly.
17784 As a result, the called function will function erroneously and may
17785 even crash. A solution to that is to use the name of the aliased
17789 @section Patching Programs
17791 @cindex patching binaries
17792 @cindex writing into executables
17793 @cindex writing into corefiles
17795 By default, @value{GDBN} opens the file containing your program's
17796 executable code (or the corefile) read-only. This prevents accidental
17797 alterations to machine code; but it also prevents you from intentionally
17798 patching your program's binary.
17800 If you'd like to be able to patch the binary, you can specify that
17801 explicitly with the @code{set write} command. For example, you might
17802 want to turn on internal debugging flags, or even to make emergency
17808 @itemx set write off
17809 If you specify @samp{set write on}, @value{GDBN} opens executable and
17810 core files for both reading and writing; if you specify @kbd{set write
17811 off} (the default), @value{GDBN} opens them read-only.
17813 If you have already loaded a file, you must load it again (using the
17814 @code{exec-file} or @code{core-file} command) after changing @code{set
17815 write}, for your new setting to take effect.
17819 Display whether executable files and core files are opened for writing
17820 as well as reading.
17823 @node Compiling and Injecting Code
17824 @section Compiling and injecting code in @value{GDBN}
17825 @cindex injecting code
17826 @cindex writing into executables
17827 @cindex compiling code
17829 @value{GDBN} supports on-demand compilation and code injection into
17830 programs running under @value{GDBN}. GCC 5.0 or higher built with
17831 @file{libcc1.so} must be installed for this functionality to be enabled.
17832 This functionality is implemented with the following commands.
17835 @kindex compile code
17836 @item compile code @var{source-code}
17837 @itemx compile code -raw @var{--} @var{source-code}
17838 Compile @var{source-code} with the compiler language found as the current
17839 language in @value{GDBN} (@pxref{Languages}). If compilation and
17840 injection is not supported with the current language specified in
17841 @value{GDBN}, or the compiler does not support this feature, an error
17842 message will be printed. If @var{source-code} compiles and links
17843 successfully, @value{GDBN} will load the object-code emitted,
17844 and execute it within the context of the currently selected inferior.
17845 It is important to note that the compiled code is executed immediately.
17846 After execution, the compiled code is removed from @value{GDBN} and any
17847 new types or variables you have defined will be deleted.
17849 The command allows you to specify @var{source-code} in two ways.
17850 The simplest method is to provide a single line of code to the command.
17854 compile code printf ("hello world\n");
17857 If you specify options on the command line as well as source code, they
17858 may conflict. The @samp{--} delimiter can be used to separate options
17859 from actual source code. E.g.:
17862 compile code -r -- printf ("hello world\n");
17865 Alternatively you can enter source code as multiple lines of text. To
17866 enter this mode, invoke the @samp{compile code} command without any text
17867 following the command. This will start the multiple-line editor and
17868 allow you to type as many lines of source code as required. When you
17869 have completed typing, enter @samp{end} on its own line to exit the
17874 >printf ("hello\n");
17875 >printf ("world\n");
17879 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17880 provided @var{source-code} in a callable scope. In this case, you must
17881 specify the entry point of the code by defining a function named
17882 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17883 inferior. Using @samp{-raw} option may be needed for example when
17884 @var{source-code} requires @samp{#include} lines which may conflict with
17885 inferior symbols otherwise.
17887 @kindex compile file
17888 @item compile file @var{filename}
17889 @itemx compile file -raw @var{filename}
17890 Like @code{compile code}, but take the source code from @var{filename}.
17893 compile file /home/user/example.c
17898 @item compile print @var{expr}
17899 @itemx compile print /@var{f} @var{expr}
17900 Compile and execute @var{expr} with the compiler language found as the
17901 current language in @value{GDBN} (@pxref{Languages}). By default the
17902 value of @var{expr} is printed in a format appropriate to its data type;
17903 you can choose a different format by specifying @samp{/@var{f}}, where
17904 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17907 @item compile print
17908 @itemx compile print /@var{f}
17909 @cindex reprint the last value
17910 Alternatively you can enter the expression (source code producing it) as
17911 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17912 command without any text following the command. This will start the
17913 multiple-line editor.
17917 The process of compiling and injecting the code can be inspected using:
17920 @anchor{set debug compile}
17921 @item set debug compile
17922 @cindex compile command debugging info
17923 Turns on or off display of @value{GDBN} process of compiling and
17924 injecting the code. The default is off.
17926 @item show debug compile
17927 Displays the current state of displaying @value{GDBN} process of
17928 compiling and injecting the code.
17931 @subsection Compilation options for the @code{compile} command
17933 @value{GDBN} needs to specify the right compilation options for the code
17934 to be injected, in part to make its ABI compatible with the inferior
17935 and in part to make the injected code compatible with @value{GDBN}'s
17939 The options used, in increasing precedence:
17942 @item target architecture and OS options (@code{gdbarch})
17943 These options depend on target processor type and target operating
17944 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17945 (@code{-m64}) compilation option.
17947 @item compilation options recorded in the target
17948 @value{NGCC} (since version 4.7) stores the options used for compilation
17949 into @code{DW_AT_producer} part of DWARF debugging information according
17950 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17951 explicitly specify @code{-g} during inferior compilation otherwise
17952 @value{NGCC} produces no DWARF. This feature is only relevant for
17953 platforms where @code{-g} produces DWARF by default, otherwise one may
17954 try to enforce DWARF by using @code{-gdwarf-4}.
17956 @item compilation options set by @code{set compile-args}
17960 You can override compilation options using the following command:
17963 @item set compile-args
17964 @cindex compile command options override
17965 Set compilation options used for compiling and injecting code with the
17966 @code{compile} commands. These options override any conflicting ones
17967 from the target architecture and/or options stored during inferior
17970 @item show compile-args
17971 Displays the current state of compilation options override.
17972 This does not show all the options actually used during compilation,
17973 use @ref{set debug compile} for that.
17976 @subsection Caveats when using the @code{compile} command
17978 There are a few caveats to keep in mind when using the @code{compile}
17979 command. As the caveats are different per language, the table below
17980 highlights specific issues on a per language basis.
17983 @item C code examples and caveats
17984 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17985 attempt to compile the source code with a @samp{C} compiler. The source
17986 code provided to the @code{compile} command will have much the same
17987 access to variables and types as it normally would if it were part of
17988 the program currently being debugged in @value{GDBN}.
17990 Below is a sample program that forms the basis of the examples that
17991 follow. This program has been compiled and loaded into @value{GDBN},
17992 much like any other normal debugging session.
17995 void function1 (void)
17998 printf ("function 1\n");
18001 void function2 (void)
18016 For the purposes of the examples in this section, the program above has
18017 been compiled, loaded into @value{GDBN}, stopped at the function
18018 @code{main}, and @value{GDBN} is awaiting input from the user.
18020 To access variables and types for any program in @value{GDBN}, the
18021 program must be compiled and packaged with debug information. The
18022 @code{compile} command is not an exception to this rule. Without debug
18023 information, you can still use the @code{compile} command, but you will
18024 be very limited in what variables and types you can access.
18026 So with that in mind, the example above has been compiled with debug
18027 information enabled. The @code{compile} command will have access to
18028 all variables and types (except those that may have been optimized
18029 out). Currently, as @value{GDBN} has stopped the program in the
18030 @code{main} function, the @code{compile} command would have access to
18031 the variable @code{k}. You could invoke the @code{compile} command
18032 and type some source code to set the value of @code{k}. You can also
18033 read it, or do anything with that variable you would normally do in
18034 @code{C}. Be aware that changes to inferior variables in the
18035 @code{compile} command are persistent. In the following example:
18038 compile code k = 3;
18042 the variable @code{k} is now 3. It will retain that value until
18043 something else in the example program changes it, or another
18044 @code{compile} command changes it.
18046 Normal scope and access rules apply to source code compiled and
18047 injected by the @code{compile} command. In the example, the variables
18048 @code{j} and @code{k} are not accessible yet, because the program is
18049 currently stopped in the @code{main} function, where these variables
18050 are not in scope. Therefore, the following command
18053 compile code j = 3;
18057 will result in a compilation error message.
18059 Once the program is continued, execution will bring these variables in
18060 scope, and they will become accessible; then the code you specify via
18061 the @code{compile} command will be able to access them.
18063 You can create variables and types with the @code{compile} command as
18064 part of your source code. Variables and types that are created as part
18065 of the @code{compile} command are not visible to the rest of the program for
18066 the duration of its run. This example is valid:
18069 compile code int ff = 5; printf ("ff is %d\n", ff);
18072 However, if you were to type the following into @value{GDBN} after that
18073 command has completed:
18076 compile code printf ("ff is %d\n'', ff);
18080 a compiler error would be raised as the variable @code{ff} no longer
18081 exists. Object code generated and injected by the @code{compile}
18082 command is removed when its execution ends. Caution is advised
18083 when assigning to program variables values of variables created by the
18084 code submitted to the @code{compile} command. This example is valid:
18087 compile code int ff = 5; k = ff;
18090 The value of the variable @code{ff} is assigned to @code{k}. The variable
18091 @code{k} does not require the existence of @code{ff} to maintain the value
18092 it has been assigned. However, pointers require particular care in
18093 assignment. If the source code compiled with the @code{compile} command
18094 changed the address of a pointer in the example program, perhaps to a
18095 variable created in the @code{compile} command, that pointer would point
18096 to an invalid location when the command exits. The following example
18097 would likely cause issues with your debugged program:
18100 compile code int ff = 5; p = &ff;
18103 In this example, @code{p} would point to @code{ff} when the
18104 @code{compile} command is executing the source code provided to it.
18105 However, as variables in the (example) program persist with their
18106 assigned values, the variable @code{p} would point to an invalid
18107 location when the command exists. A general rule should be followed
18108 in that you should either assign @code{NULL} to any assigned pointers,
18109 or restore a valid location to the pointer before the command exits.
18111 Similar caution must be exercised with any structs, unions, and typedefs
18112 defined in @code{compile} command. Types defined in the @code{compile}
18113 command will no longer be available in the next @code{compile} command.
18114 Therefore, if you cast a variable to a type defined in the
18115 @code{compile} command, care must be taken to ensure that any future
18116 need to resolve the type can be achieved.
18119 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18120 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18121 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18122 Compilation failed.
18123 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18127 Variables that have been optimized away by the compiler are not
18128 accessible to the code submitted to the @code{compile} command.
18129 Access to those variables will generate a compiler error which @value{GDBN}
18130 will print to the console.
18133 @subsection Compiler search for the @code{compile} command
18135 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
18136 may not be obvious for remote targets of different architecture than where
18137 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
18138 shell that executed @value{GDBN}, not the one set by @value{GDBN}
18139 command @code{set environment}). @xref{Environment}. @code{PATH} on
18140 @value{GDBN} host is searched for @value{NGCC} binary matching the
18141 target architecture and operating system.
18143 Specifically @code{PATH} is searched for binaries matching regular expression
18144 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18145 debugged. @var{arch} is processor name --- multiarch is supported, so for
18146 example both @code{i386} and @code{x86_64} targets look for pattern
18147 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18148 for pattern @code{s390x?}. @var{os} is currently supported only for
18149 pattern @code{linux(-gnu)?}.
18152 @chapter @value{GDBN} Files
18154 @value{GDBN} needs to know the file name of the program to be debugged,
18155 both in order to read its symbol table and in order to start your
18156 program. To debug a core dump of a previous run, you must also tell
18157 @value{GDBN} the name of the core dump file.
18160 * Files:: Commands to specify files
18161 * File Caching:: Information about @value{GDBN}'s file caching
18162 * Separate Debug Files:: Debugging information in separate files
18163 * MiniDebugInfo:: Debugging information in a special section
18164 * Index Files:: Index files speed up GDB
18165 * Symbol Errors:: Errors reading symbol files
18166 * Data Files:: GDB data files
18170 @section Commands to Specify Files
18172 @cindex symbol table
18173 @cindex core dump file
18175 You may want to specify executable and core dump file names. The usual
18176 way to do this is at start-up time, using the arguments to
18177 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18178 Out of @value{GDBN}}).
18180 Occasionally it is necessary to change to a different file during a
18181 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18182 specify a file you want to use. Or you are debugging a remote target
18183 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18184 Program}). In these situations the @value{GDBN} commands to specify
18185 new files are useful.
18188 @cindex executable file
18190 @item file @var{filename}
18191 Use @var{filename} as the program to be debugged. It is read for its
18192 symbols and for the contents of pure memory. It is also the program
18193 executed when you use the @code{run} command. If you do not specify a
18194 directory and the file is not found in the @value{GDBN} working directory,
18195 @value{GDBN} uses the environment variable @code{PATH} as a list of
18196 directories to search, just as the shell does when looking for a program
18197 to run. You can change the value of this variable, for both @value{GDBN}
18198 and your program, using the @code{path} command.
18200 @cindex unlinked object files
18201 @cindex patching object files
18202 You can load unlinked object @file{.o} files into @value{GDBN} using
18203 the @code{file} command. You will not be able to ``run'' an object
18204 file, but you can disassemble functions and inspect variables. Also,
18205 if the underlying BFD functionality supports it, you could use
18206 @kbd{gdb -write} to patch object files using this technique. Note
18207 that @value{GDBN} can neither interpret nor modify relocations in this
18208 case, so branches and some initialized variables will appear to go to
18209 the wrong place. But this feature is still handy from time to time.
18212 @code{file} with no argument makes @value{GDBN} discard any information it
18213 has on both executable file and the symbol table.
18216 @item exec-file @r{[} @var{filename} @r{]}
18217 Specify that the program to be run (but not the symbol table) is found
18218 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18219 if necessary to locate your program. Omitting @var{filename} means to
18220 discard information on the executable file.
18222 @kindex symbol-file
18223 @item symbol-file @r{[} @var{filename} @r{]}
18224 Read symbol table information from file @var{filename}. @code{PATH} is
18225 searched when necessary. Use the @code{file} command to get both symbol
18226 table and program to run from the same file.
18228 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18229 program's symbol table.
18231 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18232 some breakpoints and auto-display expressions. This is because they may
18233 contain pointers to the internal data recording symbols and data types,
18234 which are part of the old symbol table data being discarded inside
18237 @code{symbol-file} does not repeat if you press @key{RET} again after
18240 When @value{GDBN} is configured for a particular environment, it
18241 understands debugging information in whatever format is the standard
18242 generated for that environment; you may use either a @sc{gnu} compiler, or
18243 other compilers that adhere to the local conventions.
18244 Best results are usually obtained from @sc{gnu} compilers; for example,
18245 using @code{@value{NGCC}} you can generate debugging information for
18248 For most kinds of object files, with the exception of old SVR3 systems
18249 using COFF, the @code{symbol-file} command does not normally read the
18250 symbol table in full right away. Instead, it scans the symbol table
18251 quickly to find which source files and which symbols are present. The
18252 details are read later, one source file at a time, as they are needed.
18254 The purpose of this two-stage reading strategy is to make @value{GDBN}
18255 start up faster. For the most part, it is invisible except for
18256 occasional pauses while the symbol table details for a particular source
18257 file are being read. (The @code{set verbose} command can turn these
18258 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18259 Warnings and Messages}.)
18261 We have not implemented the two-stage strategy for COFF yet. When the
18262 symbol table is stored in COFF format, @code{symbol-file} reads the
18263 symbol table data in full right away. Note that ``stabs-in-COFF''
18264 still does the two-stage strategy, since the debug info is actually
18268 @cindex reading symbols immediately
18269 @cindex symbols, reading immediately
18270 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18271 @itemx file @r{[} -readnow @r{]} @var{filename}
18272 You can override the @value{GDBN} two-stage strategy for reading symbol
18273 tables by using the @samp{-readnow} option with any of the commands that
18274 load symbol table information, if you want to be sure @value{GDBN} has the
18275 entire symbol table available.
18277 @c FIXME: for now no mention of directories, since this seems to be in
18278 @c flux. 13mar1992 status is that in theory GDB would look either in
18279 @c current dir or in same dir as myprog; but issues like competing
18280 @c GDB's, or clutter in system dirs, mean that in practice right now
18281 @c only current dir is used. FFish says maybe a special GDB hierarchy
18282 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18286 @item core-file @r{[}@var{filename}@r{]}
18288 Specify the whereabouts of a core dump file to be used as the ``contents
18289 of memory''. Traditionally, core files contain only some parts of the
18290 address space of the process that generated them; @value{GDBN} can access the
18291 executable file itself for other parts.
18293 @code{core-file} with no argument specifies that no core file is
18296 Note that the core file is ignored when your program is actually running
18297 under @value{GDBN}. So, if you have been running your program and you
18298 wish to debug a core file instead, you must kill the subprocess in which
18299 the program is running. To do this, use the @code{kill} command
18300 (@pxref{Kill Process, ,Killing the Child Process}).
18302 @kindex add-symbol-file
18303 @cindex dynamic linking
18304 @item add-symbol-file @var{filename} @var{address}
18305 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
18306 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18307 The @code{add-symbol-file} command reads additional symbol table
18308 information from the file @var{filename}. You would use this command
18309 when @var{filename} has been dynamically loaded (by some other means)
18310 into the program that is running. The @var{address} should give the memory
18311 address at which the file has been loaded; @value{GDBN} cannot figure
18312 this out for itself. You can additionally specify an arbitrary number
18313 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18314 section name and base address for that section. You can specify any
18315 @var{address} as an expression.
18317 The symbol table of the file @var{filename} is added to the symbol table
18318 originally read with the @code{symbol-file} command. You can use the
18319 @code{add-symbol-file} command any number of times; the new symbol data
18320 thus read is kept in addition to the old.
18322 Changes can be reverted using the command @code{remove-symbol-file}.
18324 @cindex relocatable object files, reading symbols from
18325 @cindex object files, relocatable, reading symbols from
18326 @cindex reading symbols from relocatable object files
18327 @cindex symbols, reading from relocatable object files
18328 @cindex @file{.o} files, reading symbols from
18329 Although @var{filename} is typically a shared library file, an
18330 executable file, or some other object file which has been fully
18331 relocated for loading into a process, you can also load symbolic
18332 information from relocatable @file{.o} files, as long as:
18336 the file's symbolic information refers only to linker symbols defined in
18337 that file, not to symbols defined by other object files,
18339 every section the file's symbolic information refers to has actually
18340 been loaded into the inferior, as it appears in the file, and
18342 you can determine the address at which every section was loaded, and
18343 provide these to the @code{add-symbol-file} command.
18347 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18348 relocatable files into an already running program; such systems
18349 typically make the requirements above easy to meet. However, it's
18350 important to recognize that many native systems use complex link
18351 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18352 assembly, for example) that make the requirements difficult to meet. In
18353 general, one cannot assume that using @code{add-symbol-file} to read a
18354 relocatable object file's symbolic information will have the same effect
18355 as linking the relocatable object file into the program in the normal
18358 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18360 @kindex remove-symbol-file
18361 @item remove-symbol-file @var{filename}
18362 @item remove-symbol-file -a @var{address}
18363 Remove a symbol file added via the @code{add-symbol-file} command. The
18364 file to remove can be identified by its @var{filename} or by an @var{address}
18365 that lies within the boundaries of this symbol file in memory. Example:
18368 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18369 add symbol table from file "/home/user/gdb/mylib.so" at
18370 .text_addr = 0x7ffff7ff9480
18372 Reading symbols from /home/user/gdb/mylib.so...done.
18373 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18374 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18379 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18381 @kindex add-symbol-file-from-memory
18382 @cindex @code{syscall DSO}
18383 @cindex load symbols from memory
18384 @item add-symbol-file-from-memory @var{address}
18385 Load symbols from the given @var{address} in a dynamically loaded
18386 object file whose image is mapped directly into the inferior's memory.
18387 For example, the Linux kernel maps a @code{syscall DSO} into each
18388 process's address space; this DSO provides kernel-specific code for
18389 some system calls. The argument can be any expression whose
18390 evaluation yields the address of the file's shared object file header.
18391 For this command to work, you must have used @code{symbol-file} or
18392 @code{exec-file} commands in advance.
18395 @item section @var{section} @var{addr}
18396 The @code{section} command changes the base address of the named
18397 @var{section} of the exec file to @var{addr}. This can be used if the
18398 exec file does not contain section addresses, (such as in the
18399 @code{a.out} format), or when the addresses specified in the file
18400 itself are wrong. Each section must be changed separately. The
18401 @code{info files} command, described below, lists all the sections and
18405 @kindex info target
18408 @code{info files} and @code{info target} are synonymous; both print the
18409 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18410 including the names of the executable and core dump files currently in
18411 use by @value{GDBN}, and the files from which symbols were loaded. The
18412 command @code{help target} lists all possible targets rather than
18415 @kindex maint info sections
18416 @item maint info sections
18417 Another command that can give you extra information about program sections
18418 is @code{maint info sections}. In addition to the section information
18419 displayed by @code{info files}, this command displays the flags and file
18420 offset of each section in the executable and core dump files. In addition,
18421 @code{maint info sections} provides the following command options (which
18422 may be arbitrarily combined):
18426 Display sections for all loaded object files, including shared libraries.
18427 @item @var{sections}
18428 Display info only for named @var{sections}.
18429 @item @var{section-flags}
18430 Display info only for sections for which @var{section-flags} are true.
18431 The section flags that @value{GDBN} currently knows about are:
18434 Section will have space allocated in the process when loaded.
18435 Set for all sections except those containing debug information.
18437 Section will be loaded from the file into the child process memory.
18438 Set for pre-initialized code and data, clear for @code{.bss} sections.
18440 Section needs to be relocated before loading.
18442 Section cannot be modified by the child process.
18444 Section contains executable code only.
18446 Section contains data only (no executable code).
18448 Section will reside in ROM.
18450 Section contains data for constructor/destructor lists.
18452 Section is not empty.
18454 An instruction to the linker to not output the section.
18455 @item COFF_SHARED_LIBRARY
18456 A notification to the linker that the section contains
18457 COFF shared library information.
18459 Section contains common symbols.
18462 @kindex set trust-readonly-sections
18463 @cindex read-only sections
18464 @item set trust-readonly-sections on
18465 Tell @value{GDBN} that readonly sections in your object file
18466 really are read-only (i.e.@: that their contents will not change).
18467 In that case, @value{GDBN} can fetch values from these sections
18468 out of the object file, rather than from the target program.
18469 For some targets (notably embedded ones), this can be a significant
18470 enhancement to debugging performance.
18472 The default is off.
18474 @item set trust-readonly-sections off
18475 Tell @value{GDBN} not to trust readonly sections. This means that
18476 the contents of the section might change while the program is running,
18477 and must therefore be fetched from the target when needed.
18479 @item show trust-readonly-sections
18480 Show the current setting of trusting readonly sections.
18483 All file-specifying commands allow both absolute and relative file names
18484 as arguments. @value{GDBN} always converts the file name to an absolute file
18485 name and remembers it that way.
18487 @cindex shared libraries
18488 @anchor{Shared Libraries}
18489 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18490 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18491 DSBT (TIC6X) shared libraries.
18493 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18494 shared libraries. @xref{Expat}.
18496 @value{GDBN} automatically loads symbol definitions from shared libraries
18497 when you use the @code{run} command, or when you examine a core file.
18498 (Before you issue the @code{run} command, @value{GDBN} does not understand
18499 references to a function in a shared library, however---unless you are
18500 debugging a core file).
18502 @c FIXME: some @value{GDBN} release may permit some refs to undef
18503 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18504 @c FIXME...lib; check this from time to time when updating manual
18506 There are times, however, when you may wish to not automatically load
18507 symbol definitions from shared libraries, such as when they are
18508 particularly large or there are many of them.
18510 To control the automatic loading of shared library symbols, use the
18514 @kindex set auto-solib-add
18515 @item set auto-solib-add @var{mode}
18516 If @var{mode} is @code{on}, symbols from all shared object libraries
18517 will be loaded automatically when the inferior begins execution, you
18518 attach to an independently started inferior, or when the dynamic linker
18519 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18520 is @code{off}, symbols must be loaded manually, using the
18521 @code{sharedlibrary} command. The default value is @code{on}.
18523 @cindex memory used for symbol tables
18524 If your program uses lots of shared libraries with debug info that
18525 takes large amounts of memory, you can decrease the @value{GDBN}
18526 memory footprint by preventing it from automatically loading the
18527 symbols from shared libraries. To that end, type @kbd{set
18528 auto-solib-add off} before running the inferior, then load each
18529 library whose debug symbols you do need with @kbd{sharedlibrary
18530 @var{regexp}}, where @var{regexp} is a regular expression that matches
18531 the libraries whose symbols you want to be loaded.
18533 @kindex show auto-solib-add
18534 @item show auto-solib-add
18535 Display the current autoloading mode.
18538 @cindex load shared library
18539 To explicitly load shared library symbols, use the @code{sharedlibrary}
18543 @kindex info sharedlibrary
18545 @item info share @var{regex}
18546 @itemx info sharedlibrary @var{regex}
18547 Print the names of the shared libraries which are currently loaded
18548 that match @var{regex}. If @var{regex} is omitted then print
18549 all shared libraries that are loaded.
18552 @item info dll @var{regex}
18553 This is an alias of @code{info sharedlibrary}.
18555 @kindex sharedlibrary
18557 @item sharedlibrary @var{regex}
18558 @itemx share @var{regex}
18559 Load shared object library symbols for files matching a
18560 Unix regular expression.
18561 As with files loaded automatically, it only loads shared libraries
18562 required by your program for a core file or after typing @code{run}. If
18563 @var{regex} is omitted all shared libraries required by your program are
18566 @item nosharedlibrary
18567 @kindex nosharedlibrary
18568 @cindex unload symbols from shared libraries
18569 Unload all shared object library symbols. This discards all symbols
18570 that have been loaded from all shared libraries. Symbols from shared
18571 libraries that were loaded by explicit user requests are not
18575 Sometimes you may wish that @value{GDBN} stops and gives you control
18576 when any of shared library events happen. The best way to do this is
18577 to use @code{catch load} and @code{catch unload} (@pxref{Set
18580 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18581 command for this. This command exists for historical reasons. It is
18582 less useful than setting a catchpoint, because it does not allow for
18583 conditions or commands as a catchpoint does.
18586 @item set stop-on-solib-events
18587 @kindex set stop-on-solib-events
18588 This command controls whether @value{GDBN} should give you control
18589 when the dynamic linker notifies it about some shared library event.
18590 The most common event of interest is loading or unloading of a new
18593 @item show stop-on-solib-events
18594 @kindex show stop-on-solib-events
18595 Show whether @value{GDBN} stops and gives you control when shared
18596 library events happen.
18599 Shared libraries are also supported in many cross or remote debugging
18600 configurations. @value{GDBN} needs to have access to the target's libraries;
18601 this can be accomplished either by providing copies of the libraries
18602 on the host system, or by asking @value{GDBN} to automatically retrieve the
18603 libraries from the target. If copies of the target libraries are
18604 provided, they need to be the same as the target libraries, although the
18605 copies on the target can be stripped as long as the copies on the host are
18608 @cindex where to look for shared libraries
18609 For remote debugging, you need to tell @value{GDBN} where the target
18610 libraries are, so that it can load the correct copies---otherwise, it
18611 may try to load the host's libraries. @value{GDBN} has two variables
18612 to specify the search directories for target libraries.
18615 @cindex prefix for executable and shared library file names
18616 @cindex system root, alternate
18617 @kindex set solib-absolute-prefix
18618 @kindex set sysroot
18619 @item set sysroot @var{path}
18620 Use @var{path} as the system root for the program being debugged. Any
18621 absolute shared library paths will be prefixed with @var{path}; many
18622 runtime loaders store the absolute paths to the shared library in the
18623 target program's memory. When starting processes remotely, and when
18624 attaching to already-running processes (local or remote), their
18625 executable filenames will be prefixed with @var{path} if reported to
18626 @value{GDBN} as absolute by the operating system. If you use
18627 @code{set sysroot} to find executables and shared libraries, they need
18628 to be laid out in the same way that they are on the target, with
18629 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18632 If @var{path} starts with the sequence @file{target:} and the target
18633 system is remote then @value{GDBN} will retrieve the target binaries
18634 from the remote system. This is only supported when using a remote
18635 target that supports the @code{remote get} command (@pxref{File
18636 Transfer,,Sending files to a remote system}). The part of @var{path}
18637 following the initial @file{target:} (if present) is used as system
18638 root prefix on the remote file system. If @var{path} starts with the
18639 sequence @file{remote:} this is converted to the sequence
18640 @file{target:} by @code{set sysroot}@footnote{Historically the
18641 functionality to retrieve binaries from the remote system was
18642 provided by prefixing @var{path} with @file{remote:}}. If you want
18643 to specify a local system root using a directory that happens to be
18644 named @file{target:} or @file{remote:}, you need to use some
18645 equivalent variant of the name like @file{./target:}.
18647 For targets with an MS-DOS based filesystem, such as MS-Windows and
18648 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18649 absolute file name with @var{path}. But first, on Unix hosts,
18650 @value{GDBN} converts all backslash directory separators into forward
18651 slashes, because the backslash is not a directory separator on Unix:
18654 c:\foo\bar.dll @result{} c:/foo/bar.dll
18657 Then, @value{GDBN} attempts prefixing the target file name with
18658 @var{path}, and looks for the resulting file name in the host file
18662 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18665 If that does not find the binary, @value{GDBN} tries removing
18666 the @samp{:} character from the drive spec, both for convenience, and,
18667 for the case of the host file system not supporting file names with
18671 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18674 This makes it possible to have a system root that mirrors a target
18675 with more than one drive. E.g., you may want to setup your local
18676 copies of the target system shared libraries like so (note @samp{c} vs
18680 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18681 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18682 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18686 and point the system root at @file{/path/to/sysroot}, so that
18687 @value{GDBN} can find the correct copies of both
18688 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18690 If that still does not find the binary, @value{GDBN} tries
18691 removing the whole drive spec from the target file name:
18694 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18697 This last lookup makes it possible to not care about the drive name,
18698 if you don't want or need to.
18700 The @code{set solib-absolute-prefix} command is an alias for @code{set
18703 @cindex default system root
18704 @cindex @samp{--with-sysroot}
18705 You can set the default system root by using the configure-time
18706 @samp{--with-sysroot} option. If the system root is inside
18707 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18708 @samp{--exec-prefix}), then the default system root will be updated
18709 automatically if the installed @value{GDBN} is moved to a new
18712 @kindex show sysroot
18714 Display the current executable and shared library prefix.
18716 @kindex set solib-search-path
18717 @item set solib-search-path @var{path}
18718 If this variable is set, @var{path} is a colon-separated list of
18719 directories to search for shared libraries. @samp{solib-search-path}
18720 is used after @samp{sysroot} fails to locate the library, or if the
18721 path to the library is relative instead of absolute. If you want to
18722 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18723 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18724 finding your host's libraries. @samp{sysroot} is preferred; setting
18725 it to a nonexistent directory may interfere with automatic loading
18726 of shared library symbols.
18728 @kindex show solib-search-path
18729 @item show solib-search-path
18730 Display the current shared library search path.
18732 @cindex DOS file-name semantics of file names.
18733 @kindex set target-file-system-kind (unix|dos-based|auto)
18734 @kindex show target-file-system-kind
18735 @item set target-file-system-kind @var{kind}
18736 Set assumed file system kind for target reported file names.
18738 Shared library file names as reported by the target system may not
18739 make sense as is on the system @value{GDBN} is running on. For
18740 example, when remote debugging a target that has MS-DOS based file
18741 system semantics, from a Unix host, the target may be reporting to
18742 @value{GDBN} a list of loaded shared libraries with file names such as
18743 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18744 drive letters, so the @samp{c:\} prefix is not normally understood as
18745 indicating an absolute file name, and neither is the backslash
18746 normally considered a directory separator character. In that case,
18747 the native file system would interpret this whole absolute file name
18748 as a relative file name with no directory components. This would make
18749 it impossible to point @value{GDBN} at a copy of the remote target's
18750 shared libraries on the host using @code{set sysroot}, and impractical
18751 with @code{set solib-search-path}. Setting
18752 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18753 to interpret such file names similarly to how the target would, and to
18754 map them to file names valid on @value{GDBN}'s native file system
18755 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18756 to one of the supported file system kinds. In that case, @value{GDBN}
18757 tries to determine the appropriate file system variant based on the
18758 current target's operating system (@pxref{ABI, ,Configuring the
18759 Current ABI}). The supported file system settings are:
18763 Instruct @value{GDBN} to assume the target file system is of Unix
18764 kind. Only file names starting the forward slash (@samp{/}) character
18765 are considered absolute, and the directory separator character is also
18769 Instruct @value{GDBN} to assume the target file system is DOS based.
18770 File names starting with either a forward slash, or a drive letter
18771 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18772 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18773 considered directory separators.
18776 Instruct @value{GDBN} to use the file system kind associated with the
18777 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18778 This is the default.
18782 @cindex file name canonicalization
18783 @cindex base name differences
18784 When processing file names provided by the user, @value{GDBN}
18785 frequently needs to compare them to the file names recorded in the
18786 program's debug info. Normally, @value{GDBN} compares just the
18787 @dfn{base names} of the files as strings, which is reasonably fast
18788 even for very large programs. (The base name of a file is the last
18789 portion of its name, after stripping all the leading directories.)
18790 This shortcut in comparison is based upon the assumption that files
18791 cannot have more than one base name. This is usually true, but
18792 references to files that use symlinks or similar filesystem
18793 facilities violate that assumption. If your program records files
18794 using such facilities, or if you provide file names to @value{GDBN}
18795 using symlinks etc., you can set @code{basenames-may-differ} to
18796 @code{true} to instruct @value{GDBN} to completely canonicalize each
18797 pair of file names it needs to compare. This will make file-name
18798 comparisons accurate, but at a price of a significant slowdown.
18801 @item set basenames-may-differ
18802 @kindex set basenames-may-differ
18803 Set whether a source file may have multiple base names.
18805 @item show basenames-may-differ
18806 @kindex show basenames-may-differ
18807 Show whether a source file may have multiple base names.
18811 @section File Caching
18812 @cindex caching of opened files
18813 @cindex caching of bfd objects
18815 To speed up file loading, and reduce memory usage, @value{GDBN} will
18816 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18817 BFD, bfd, The Binary File Descriptor Library}. The following commands
18818 allow visibility and control of the caching behavior.
18821 @kindex maint info bfds
18822 @item maint info bfds
18823 This prints information about each @code{bfd} object that is known to
18826 @kindex maint set bfd-sharing
18827 @kindex maint show bfd-sharing
18828 @kindex bfd caching
18829 @item maint set bfd-sharing
18830 @item maint show bfd-sharing
18831 Control whether @code{bfd} objects can be shared. When sharing is
18832 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18833 than reopening the same file. Turning sharing off does not cause
18834 already shared @code{bfd} objects to be unshared, but all future files
18835 that are opened will create a new @code{bfd} object. Similarly,
18836 re-enabling sharing does not cause multiple existing @code{bfd}
18837 objects to be collapsed into a single shared @code{bfd} object.
18839 @kindex set debug bfd-cache @var{level}
18840 @kindex bfd caching
18841 @item set debug bfd-cache @var{level}
18842 Turns on debugging of the bfd cache, setting the level to @var{level}.
18844 @kindex show debug bfd-cache
18845 @kindex bfd caching
18846 @item show debug bfd-cache
18847 Show the current debugging level of the bfd cache.
18850 @node Separate Debug Files
18851 @section Debugging Information in Separate Files
18852 @cindex separate debugging information files
18853 @cindex debugging information in separate files
18854 @cindex @file{.debug} subdirectories
18855 @cindex debugging information directory, global
18856 @cindex global debugging information directories
18857 @cindex build ID, and separate debugging files
18858 @cindex @file{.build-id} directory
18860 @value{GDBN} allows you to put a program's debugging information in a
18861 file separate from the executable itself, in a way that allows
18862 @value{GDBN} to find and load the debugging information automatically.
18863 Since debugging information can be very large---sometimes larger
18864 than the executable code itself---some systems distribute debugging
18865 information for their executables in separate files, which users can
18866 install only when they need to debug a problem.
18868 @value{GDBN} supports two ways of specifying the separate debug info
18873 The executable contains a @dfn{debug link} that specifies the name of
18874 the separate debug info file. The separate debug file's name is
18875 usually @file{@var{executable}.debug}, where @var{executable} is the
18876 name of the corresponding executable file without leading directories
18877 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18878 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18879 checksum for the debug file, which @value{GDBN} uses to validate that
18880 the executable and the debug file came from the same build.
18883 The executable contains a @dfn{build ID}, a unique bit string that is
18884 also present in the corresponding debug info file. (This is supported
18885 only on some operating systems, when using the ELF or PE file formats
18886 for binary files and the @sc{gnu} Binutils.) For more details about
18887 this feature, see the description of the @option{--build-id}
18888 command-line option in @ref{Options, , Command Line Options, ld.info,
18889 The GNU Linker}. The debug info file's name is not specified
18890 explicitly by the build ID, but can be computed from the build ID, see
18894 Depending on the way the debug info file is specified, @value{GDBN}
18895 uses two different methods of looking for the debug file:
18899 For the ``debug link'' method, @value{GDBN} looks up the named file in
18900 the directory of the executable file, then in a subdirectory of that
18901 directory named @file{.debug}, and finally under each one of the global debug
18902 directories, in a subdirectory whose name is identical to the leading
18903 directories of the executable's absolute file name.
18906 For the ``build ID'' method, @value{GDBN} looks in the
18907 @file{.build-id} subdirectory of each one of the global debug directories for
18908 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18909 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18910 are the rest of the bit string. (Real build ID strings are 32 or more
18911 hex characters, not 10.)
18914 So, for example, suppose you ask @value{GDBN} to debug
18915 @file{/usr/bin/ls}, which has a debug link that specifies the
18916 file @file{ls.debug}, and a build ID whose value in hex is
18917 @code{abcdef1234}. If the list of the global debug directories includes
18918 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18919 debug information files, in the indicated order:
18923 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18925 @file{/usr/bin/ls.debug}
18927 @file{/usr/bin/.debug/ls.debug}
18929 @file{/usr/lib/debug/usr/bin/ls.debug}.
18932 @anchor{debug-file-directory}
18933 Global debugging info directories default to what is set by @value{GDBN}
18934 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18935 you can also set the global debugging info directories, and view the list
18936 @value{GDBN} is currently using.
18940 @kindex set debug-file-directory
18941 @item set debug-file-directory @var{directories}
18942 Set the directories which @value{GDBN} searches for separate debugging
18943 information files to @var{directory}. Multiple path components can be set
18944 concatenating them by a path separator.
18946 @kindex show debug-file-directory
18947 @item show debug-file-directory
18948 Show the directories @value{GDBN} searches for separate debugging
18953 @cindex @code{.gnu_debuglink} sections
18954 @cindex debug link sections
18955 A debug link is a special section of the executable file named
18956 @code{.gnu_debuglink}. The section must contain:
18960 A filename, with any leading directory components removed, followed by
18963 zero to three bytes of padding, as needed to reach the next four-byte
18964 boundary within the section, and
18966 a four-byte CRC checksum, stored in the same endianness used for the
18967 executable file itself. The checksum is computed on the debugging
18968 information file's full contents by the function given below, passing
18969 zero as the @var{crc} argument.
18972 Any executable file format can carry a debug link, as long as it can
18973 contain a section named @code{.gnu_debuglink} with the contents
18976 @cindex @code{.note.gnu.build-id} sections
18977 @cindex build ID sections
18978 The build ID is a special section in the executable file (and in other
18979 ELF binary files that @value{GDBN} may consider). This section is
18980 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18981 It contains unique identification for the built files---the ID remains
18982 the same across multiple builds of the same build tree. The default
18983 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18984 content for the build ID string. The same section with an identical
18985 value is present in the original built binary with symbols, in its
18986 stripped variant, and in the separate debugging information file.
18988 The debugging information file itself should be an ordinary
18989 executable, containing a full set of linker symbols, sections, and
18990 debugging information. The sections of the debugging information file
18991 should have the same names, addresses, and sizes as the original file,
18992 but they need not contain any data---much like a @code{.bss} section
18993 in an ordinary executable.
18995 The @sc{gnu} binary utilities (Binutils) package includes the
18996 @samp{objcopy} utility that can produce
18997 the separated executable / debugging information file pairs using the
18998 following commands:
19001 @kbd{objcopy --only-keep-debug foo foo.debug}
19006 These commands remove the debugging
19007 information from the executable file @file{foo} and place it in the file
19008 @file{foo.debug}. You can use the first, second or both methods to link the
19013 The debug link method needs the following additional command to also leave
19014 behind a debug link in @file{foo}:
19017 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19020 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19021 a version of the @code{strip} command such that the command @kbd{strip foo -f
19022 foo.debug} has the same functionality as the two @code{objcopy} commands and
19023 the @code{ln -s} command above, together.
19026 Build ID gets embedded into the main executable using @code{ld --build-id} or
19027 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19028 compatibility fixes for debug files separation are present in @sc{gnu} binary
19029 utilities (Binutils) package since version 2.18.
19034 @cindex CRC algorithm definition
19035 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19036 IEEE 802.3 using the polynomial:
19038 @c TexInfo requires naked braces for multi-digit exponents for Tex
19039 @c output, but this causes HTML output to barf. HTML has to be set using
19040 @c raw commands. So we end up having to specify this equation in 2
19045 <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>
19046 + <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
19052 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19053 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19057 The function is computed byte at a time, taking the least
19058 significant bit of each byte first. The initial pattern
19059 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19060 the final result is inverted to ensure trailing zeros also affect the
19063 @emph{Note:} This is the same CRC polynomial as used in handling the
19064 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19065 However in the case of the Remote Serial Protocol, the CRC is computed
19066 @emph{most} significant bit first, and the result is not inverted, so
19067 trailing zeros have no effect on the CRC value.
19069 To complete the description, we show below the code of the function
19070 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19071 initially supplied @code{crc} argument means that an initial call to
19072 this function passing in zero will start computing the CRC using
19075 @kindex gnu_debuglink_crc32
19078 gnu_debuglink_crc32 (unsigned long crc,
19079 unsigned char *buf, size_t len)
19081 static const unsigned long crc32_table[256] =
19083 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19084 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19085 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19086 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19087 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19088 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19089 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19090 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19091 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19092 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19093 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19094 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19095 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19096 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19097 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19098 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19099 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19100 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19101 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19102 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19103 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19104 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19105 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19106 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19107 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19108 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19109 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19110 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19111 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19112 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19113 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19114 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19115 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19116 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19117 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19118 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19119 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19120 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19121 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19122 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19123 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19124 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19125 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19126 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19127 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19128 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19129 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19130 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19131 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19132 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19133 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19136 unsigned char *end;
19138 crc = ~crc & 0xffffffff;
19139 for (end = buf + len; buf < end; ++buf)
19140 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19141 return ~crc & 0xffffffff;
19146 This computation does not apply to the ``build ID'' method.
19148 @node MiniDebugInfo
19149 @section Debugging information in a special section
19150 @cindex separate debug sections
19151 @cindex @samp{.gnu_debugdata} section
19153 Some systems ship pre-built executables and libraries that have a
19154 special @samp{.gnu_debugdata} section. This feature is called
19155 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19156 is used to supply extra symbols for backtraces.
19158 The intent of this section is to provide extra minimal debugging
19159 information for use in simple backtraces. It is not intended to be a
19160 replacement for full separate debugging information (@pxref{Separate
19161 Debug Files}). The example below shows the intended use; however,
19162 @value{GDBN} does not currently put restrictions on what sort of
19163 debugging information might be included in the section.
19165 @value{GDBN} has support for this extension. If the section exists,
19166 then it is used provided that no other source of debugging information
19167 can be found, and that @value{GDBN} was configured with LZMA support.
19169 This section can be easily created using @command{objcopy} and other
19170 standard utilities:
19173 # Extract the dynamic symbols from the main binary, there is no need
19174 # to also have these in the normal symbol table.
19175 nm -D @var{binary} --format=posix --defined-only \
19176 | awk '@{ print $1 @}' | sort > dynsyms
19178 # Extract all the text (i.e. function) symbols from the debuginfo.
19179 # (Note that we actually also accept "D" symbols, for the benefit
19180 # of platforms like PowerPC64 that use function descriptors.)
19181 nm @var{binary} --format=posix --defined-only \
19182 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19185 # Keep all the function symbols not already in the dynamic symbol
19187 comm -13 dynsyms funcsyms > keep_symbols
19189 # Separate full debug info into debug binary.
19190 objcopy --only-keep-debug @var{binary} debug
19192 # Copy the full debuginfo, keeping only a minimal set of symbols and
19193 # removing some unnecessary sections.
19194 objcopy -S --remove-section .gdb_index --remove-section .comment \
19195 --keep-symbols=keep_symbols debug mini_debuginfo
19197 # Drop the full debug info from the original binary.
19198 strip --strip-all -R .comment @var{binary}
19200 # Inject the compressed data into the .gnu_debugdata section of the
19203 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19207 @section Index Files Speed Up @value{GDBN}
19208 @cindex index files
19209 @cindex @samp{.gdb_index} section
19211 When @value{GDBN} finds a symbol file, it scans the symbols in the
19212 file in order to construct an internal symbol table. This lets most
19213 @value{GDBN} operations work quickly---at the cost of a delay early
19214 on. For large programs, this delay can be quite lengthy, so
19215 @value{GDBN} provides a way to build an index, which speeds up
19218 The index is stored as a section in the symbol file. @value{GDBN} can
19219 write the index to a file, then you can put it into the symbol file
19220 using @command{objcopy}.
19222 To create an index file, use the @code{save gdb-index} command:
19225 @item save gdb-index @var{directory}
19226 @kindex save gdb-index
19227 Create an index file for each symbol file currently known by
19228 @value{GDBN}. Each file is named after its corresponding symbol file,
19229 with @samp{.gdb-index} appended, and is written into the given
19233 Once you have created an index file you can merge it into your symbol
19234 file, here named @file{symfile}, using @command{objcopy}:
19237 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19238 --set-section-flags .gdb_index=readonly symfile symfile
19241 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19242 sections that have been deprecated. Usually they are deprecated because
19243 they are missing a new feature or have performance issues.
19244 To tell @value{GDBN} to use a deprecated index section anyway
19245 specify @code{set use-deprecated-index-sections on}.
19246 The default is @code{off}.
19247 This can speed up startup, but may result in some functionality being lost.
19248 @xref{Index Section Format}.
19250 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19251 must be done before gdb reads the file. The following will not work:
19254 $ gdb -ex "set use-deprecated-index-sections on" <program>
19257 Instead you must do, for example,
19260 $ gdb -iex "set use-deprecated-index-sections on" <program>
19263 There are currently some limitation on indices. They only work when
19264 for DWARF debugging information, not stabs. And, they do not
19265 currently work for programs using Ada.
19267 @node Symbol Errors
19268 @section Errors Reading Symbol Files
19270 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19271 such as symbol types it does not recognize, or known bugs in compiler
19272 output. By default, @value{GDBN} does not notify you of such problems, since
19273 they are relatively common and primarily of interest to people
19274 debugging compilers. If you are interested in seeing information
19275 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19276 only one message about each such type of problem, no matter how many
19277 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19278 to see how many times the problems occur, with the @code{set
19279 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19282 The messages currently printed, and their meanings, include:
19285 @item inner block not inside outer block in @var{symbol}
19287 The symbol information shows where symbol scopes begin and end
19288 (such as at the start of a function or a block of statements). This
19289 error indicates that an inner scope block is not fully contained
19290 in its outer scope blocks.
19292 @value{GDBN} circumvents the problem by treating the inner block as if it had
19293 the same scope as the outer block. In the error message, @var{symbol}
19294 may be shown as ``@code{(don't know)}'' if the outer block is not a
19297 @item block at @var{address} out of order
19299 The symbol information for symbol scope blocks should occur in
19300 order of increasing addresses. This error indicates that it does not
19303 @value{GDBN} does not circumvent this problem, and has trouble
19304 locating symbols in the source file whose symbols it is reading. (You
19305 can often determine what source file is affected by specifying
19306 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19309 @item bad block start address patched
19311 The symbol information for a symbol scope block has a start address
19312 smaller than the address of the preceding source line. This is known
19313 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19315 @value{GDBN} circumvents the problem by treating the symbol scope block as
19316 starting on the previous source line.
19318 @item bad string table offset in symbol @var{n}
19321 Symbol number @var{n} contains a pointer into the string table which is
19322 larger than the size of the string table.
19324 @value{GDBN} circumvents the problem by considering the symbol to have the
19325 name @code{foo}, which may cause other problems if many symbols end up
19328 @item unknown symbol type @code{0x@var{nn}}
19330 The symbol information contains new data types that @value{GDBN} does
19331 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19332 uncomprehended information, in hexadecimal.
19334 @value{GDBN} circumvents the error by ignoring this symbol information.
19335 This usually allows you to debug your program, though certain symbols
19336 are not accessible. If you encounter such a problem and feel like
19337 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19338 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19339 and examine @code{*bufp} to see the symbol.
19341 @item stub type has NULL name
19343 @value{GDBN} could not find the full definition for a struct or class.
19345 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19346 The symbol information for a C@t{++} member function is missing some
19347 information that recent versions of the compiler should have output for
19350 @item info mismatch between compiler and debugger
19352 @value{GDBN} could not parse a type specification output by the compiler.
19357 @section GDB Data Files
19359 @cindex prefix for data files
19360 @value{GDBN} will sometimes read an auxiliary data file. These files
19361 are kept in a directory known as the @dfn{data directory}.
19363 You can set the data directory's name, and view the name @value{GDBN}
19364 is currently using.
19367 @kindex set data-directory
19368 @item set data-directory @var{directory}
19369 Set the directory which @value{GDBN} searches for auxiliary data files
19370 to @var{directory}.
19372 @kindex show data-directory
19373 @item show data-directory
19374 Show the directory @value{GDBN} searches for auxiliary data files.
19377 @cindex default data directory
19378 @cindex @samp{--with-gdb-datadir}
19379 You can set the default data directory by using the configure-time
19380 @samp{--with-gdb-datadir} option. If the data directory is inside
19381 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19382 @samp{--exec-prefix}), then the default data directory will be updated
19383 automatically if the installed @value{GDBN} is moved to a new
19386 The data directory may also be specified with the
19387 @code{--data-directory} command line option.
19388 @xref{Mode Options}.
19391 @chapter Specifying a Debugging Target
19393 @cindex debugging target
19394 A @dfn{target} is the execution environment occupied by your program.
19396 Often, @value{GDBN} runs in the same host environment as your program;
19397 in that case, the debugging target is specified as a side effect when
19398 you use the @code{file} or @code{core} commands. When you need more
19399 flexibility---for example, running @value{GDBN} on a physically separate
19400 host, or controlling a standalone system over a serial port or a
19401 realtime system over a TCP/IP connection---you can use the @code{target}
19402 command to specify one of the target types configured for @value{GDBN}
19403 (@pxref{Target Commands, ,Commands for Managing Targets}).
19405 @cindex target architecture
19406 It is possible to build @value{GDBN} for several different @dfn{target
19407 architectures}. When @value{GDBN} is built like that, you can choose
19408 one of the available architectures with the @kbd{set architecture}
19412 @kindex set architecture
19413 @kindex show architecture
19414 @item set architecture @var{arch}
19415 This command sets the current target architecture to @var{arch}. The
19416 value of @var{arch} can be @code{"auto"}, in addition to one of the
19417 supported architectures.
19419 @item show architecture
19420 Show the current target architecture.
19422 @item set processor
19424 @kindex set processor
19425 @kindex show processor
19426 These are alias commands for, respectively, @code{set architecture}
19427 and @code{show architecture}.
19431 * Active Targets:: Active targets
19432 * Target Commands:: Commands for managing targets
19433 * Byte Order:: Choosing target byte order
19436 @node Active Targets
19437 @section Active Targets
19439 @cindex stacking targets
19440 @cindex active targets
19441 @cindex multiple targets
19443 There are multiple classes of targets such as: processes, executable files or
19444 recording sessions. Core files belong to the process class, making core file
19445 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19446 on multiple active targets, one in each class. This allows you to (for
19447 example) start a process and inspect its activity, while still having access to
19448 the executable file after the process finishes. Or if you start process
19449 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19450 presented a virtual layer of the recording target, while the process target
19451 remains stopped at the chronologically last point of the process execution.
19453 Use the @code{core-file} and @code{exec-file} commands to select a new core
19454 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19455 specify as a target a process that is already running, use the @code{attach}
19456 command (@pxref{Attach, ,Debugging an Already-running Process}).
19458 @node Target Commands
19459 @section Commands for Managing Targets
19462 @item target @var{type} @var{parameters}
19463 Connects the @value{GDBN} host environment to a target machine or
19464 process. A target is typically a protocol for talking to debugging
19465 facilities. You use the argument @var{type} to specify the type or
19466 protocol of the target machine.
19468 Further @var{parameters} are interpreted by the target protocol, but
19469 typically include things like device names or host names to connect
19470 with, process numbers, and baud rates.
19472 The @code{target} command does not repeat if you press @key{RET} again
19473 after executing the command.
19475 @kindex help target
19477 Displays the names of all targets available. To display targets
19478 currently selected, use either @code{info target} or @code{info files}
19479 (@pxref{Files, ,Commands to Specify Files}).
19481 @item help target @var{name}
19482 Describe a particular target, including any parameters necessary to
19485 @kindex set gnutarget
19486 @item set gnutarget @var{args}
19487 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19488 knows whether it is reading an @dfn{executable},
19489 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19490 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19491 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19494 @emph{Warning:} To specify a file format with @code{set gnutarget},
19495 you must know the actual BFD name.
19499 @xref{Files, , Commands to Specify Files}.
19501 @kindex show gnutarget
19502 @item show gnutarget
19503 Use the @code{show gnutarget} command to display what file format
19504 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19505 @value{GDBN} will determine the file format for each file automatically,
19506 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19509 @cindex common targets
19510 Here are some common targets (available, or not, depending on the GDB
19515 @item target exec @var{program}
19516 @cindex executable file target
19517 An executable file. @samp{target exec @var{program}} is the same as
19518 @samp{exec-file @var{program}}.
19520 @item target core @var{filename}
19521 @cindex core dump file target
19522 A core dump file. @samp{target core @var{filename}} is the same as
19523 @samp{core-file @var{filename}}.
19525 @item target remote @var{medium}
19526 @cindex remote target
19527 A remote system connected to @value{GDBN} via a serial line or network
19528 connection. This command tells @value{GDBN} to use its own remote
19529 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19531 For example, if you have a board connected to @file{/dev/ttya} on the
19532 machine running @value{GDBN}, you could say:
19535 target remote /dev/ttya
19538 @code{target remote} supports the @code{load} command. This is only
19539 useful if you have some other way of getting the stub to the target
19540 system, and you can put it somewhere in memory where it won't get
19541 clobbered by the download.
19543 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19544 @cindex built-in simulator target
19545 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19553 works; however, you cannot assume that a specific memory map, device
19554 drivers, or even basic I/O is available, although some simulators do
19555 provide these. For info about any processor-specific simulator details,
19556 see the appropriate section in @ref{Embedded Processors, ,Embedded
19559 @item target native
19560 @cindex native target
19561 Setup for local/native process debugging. Useful to make the
19562 @code{run} command spawn native processes (likewise @code{attach},
19563 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19564 (@pxref{set auto-connect-native-target}).
19568 Different targets are available on different configurations of @value{GDBN};
19569 your configuration may have more or fewer targets.
19571 Many remote targets require you to download the executable's code once
19572 you've successfully established a connection. You may wish to control
19573 various aspects of this process.
19578 @kindex set hash@r{, for remote monitors}
19579 @cindex hash mark while downloading
19580 This command controls whether a hash mark @samp{#} is displayed while
19581 downloading a file to the remote monitor. If on, a hash mark is
19582 displayed after each S-record is successfully downloaded to the
19586 @kindex show hash@r{, for remote monitors}
19587 Show the current status of displaying the hash mark.
19589 @item set debug monitor
19590 @kindex set debug monitor
19591 @cindex display remote monitor communications
19592 Enable or disable display of communications messages between
19593 @value{GDBN} and the remote monitor.
19595 @item show debug monitor
19596 @kindex show debug monitor
19597 Show the current status of displaying communications between
19598 @value{GDBN} and the remote monitor.
19603 @kindex load @var{filename}
19604 @item load @var{filename}
19606 Depending on what remote debugging facilities are configured into
19607 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19608 is meant to make @var{filename} (an executable) available for debugging
19609 on the remote system---by downloading, or dynamic linking, for example.
19610 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19611 the @code{add-symbol-file} command.
19613 If your @value{GDBN} does not have a @code{load} command, attempting to
19614 execute it gets the error message ``@code{You can't do that when your
19615 target is @dots{}}''
19617 The file is loaded at whatever address is specified in the executable.
19618 For some object file formats, you can specify the load address when you
19619 link the program; for other formats, like a.out, the object file format
19620 specifies a fixed address.
19621 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19623 Depending on the remote side capabilities, @value{GDBN} may be able to
19624 load programs into flash memory.
19626 @code{load} does not repeat if you press @key{RET} again after using it.
19631 @kindex flash-erase
19633 @anchor{flash-erase}
19635 Erases all known flash memory regions on the target.
19640 @section Choosing Target Byte Order
19642 @cindex choosing target byte order
19643 @cindex target byte order
19645 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19646 offer the ability to run either big-endian or little-endian byte
19647 orders. Usually the executable or symbol will include a bit to
19648 designate the endian-ness, and you will not need to worry about
19649 which to use. However, you may still find it useful to adjust
19650 @value{GDBN}'s idea of processor endian-ness manually.
19654 @item set endian big
19655 Instruct @value{GDBN} to assume the target is big-endian.
19657 @item set endian little
19658 Instruct @value{GDBN} to assume the target is little-endian.
19660 @item set endian auto
19661 Instruct @value{GDBN} to use the byte order associated with the
19665 Display @value{GDBN}'s current idea of the target byte order.
19669 Note that these commands merely adjust interpretation of symbolic
19670 data on the host, and that they have absolutely no effect on the
19674 @node Remote Debugging
19675 @chapter Debugging Remote Programs
19676 @cindex remote debugging
19678 If you are trying to debug a program running on a machine that cannot run
19679 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19680 For example, you might use remote debugging on an operating system kernel,
19681 or on a small system which does not have a general purpose operating system
19682 powerful enough to run a full-featured debugger.
19684 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19685 to make this work with particular debugging targets. In addition,
19686 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19687 but not specific to any particular target system) which you can use if you
19688 write the remote stubs---the code that runs on the remote system to
19689 communicate with @value{GDBN}.
19691 Other remote targets may be available in your
19692 configuration of @value{GDBN}; use @code{help target} to list them.
19695 * Connecting:: Connecting to a remote target
19696 * File Transfer:: Sending files to a remote system
19697 * Server:: Using the gdbserver program
19698 * Remote Configuration:: Remote configuration
19699 * Remote Stub:: Implementing a remote stub
19703 @section Connecting to a Remote Target
19704 @cindex remote debugging, connecting
19705 @cindex @code{gdbserver}, connecting
19706 @cindex remote debugging, types of connections
19707 @cindex @code{gdbserver}, types of connections
19708 @cindex @code{gdbserver}, @code{target remote} mode
19709 @cindex @code{gdbserver}, @code{target extended-remote} mode
19711 This section describes how to connect to a remote target, including the
19712 types of connections and their differences, how to set up executable and
19713 symbol files on the host and target, and the commands used for
19714 connecting to and disconnecting from the remote target.
19716 @subsection Types of Remote Connections
19718 @value{GDBN} supports two types of remote connections, @code{target remote}
19719 mode and @code{target extended-remote} mode. Note that many remote targets
19720 support only @code{target remote} mode. There are several major
19721 differences between the two types of connections, enumerated here:
19725 @cindex remote debugging, detach and program exit
19726 @item Result of detach or program exit
19727 @strong{With target remote mode:} When the debugged program exits or you
19728 detach from it, @value{GDBN} disconnects from the target. When using
19729 @code{gdbserver}, @code{gdbserver} will exit.
19731 @strong{With target extended-remote mode:} When the debugged program exits or
19732 you detach from it, @value{GDBN} remains connected to the target, even
19733 though no program is running. You can rerun the program, attach to a
19734 running program, or use @code{monitor} commands specific to the target.
19736 When using @code{gdbserver} in this case, it does not exit unless it was
19737 invoked using the @option{--once} option. If the @option{--once} option
19738 was not used, you can ask @code{gdbserver} to exit using the
19739 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19741 @item Specifying the program to debug
19742 For both connection types you use the @code{file} command to specify the
19743 program on the host system. If you are using @code{gdbserver} there are
19744 some differences in how to specify the location of the program on the
19747 @strong{With target remote mode:} You must either specify the program to debug
19748 on the @code{gdbserver} command line or use the @option{--attach} option
19749 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19751 @cindex @option{--multi}, @code{gdbserver} option
19752 @strong{With target extended-remote mode:} You may specify the program to debug
19753 on the @code{gdbserver} command line, or you can load the program or attach
19754 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19756 @anchor{--multi Option in Types of Remote Connnections}
19757 You can start @code{gdbserver} without supplying an initial command to run
19758 or process ID to attach. To do this, use the @option{--multi} command line
19759 option. Then you can connect using @code{target extended-remote} and start
19760 the program you want to debug (see below for details on using the
19761 @code{run} command in this scenario). Note that the conditions under which
19762 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19763 (@code{target remote} or @code{target extended-remote}). The
19764 @option{--multi} option to @code{gdbserver} has no influence on that.
19766 @item The @code{run} command
19767 @strong{With target remote mode:} The @code{run} command is not
19768 supported. Once a connection has been established, you can use all
19769 the usual @value{GDBN} commands to examine and change data. The
19770 remote program is already running, so you can use commands like
19771 @kbd{step} and @kbd{continue}.
19773 @strong{With target extended-remote mode:} The @code{run} command is
19774 supported. The @code{run} command uses the value set by
19775 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19776 the program to run. Command line arguments are supported, except for
19777 wildcard expansion and I/O redirection (@pxref{Arguments}).
19779 If you specify the program to debug on the command line, then the
19780 @code{run} command is not required to start execution, and you can
19781 resume using commands like @kbd{step} and @kbd{continue} as with
19782 @code{target remote} mode.
19784 @anchor{Attaching in Types of Remote Connections}
19786 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19787 not supported. To attach to a running program using @code{gdbserver}, you
19788 must use the @option{--attach} option (@pxref{Running gdbserver}).
19790 @strong{With target extended-remote mode:} To attach to a running program,
19791 you may use the @code{attach} command after the connection has been
19792 established. If you are using @code{gdbserver}, you may also invoke
19793 @code{gdbserver} using the @option{--attach} option
19794 (@pxref{Running gdbserver}).
19798 @anchor{Host and target files}
19799 @subsection Host and Target Files
19800 @cindex remote debugging, symbol files
19801 @cindex symbol files, remote debugging
19803 @value{GDBN}, running on the host, needs access to symbol and debugging
19804 information for your program running on the target. This requires
19805 access to an unstripped copy of your program, and possibly any associated
19806 symbol files. Note that this section applies equally to both @code{target
19807 remote} mode and @code{target extended-remote} mode.
19809 Some remote targets (@pxref{qXfer executable filename read}, and
19810 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19811 the same connection used to communicate with @value{GDBN}. With such a
19812 target, if the remote program is unstripped, the only command you need is
19813 @code{target remote} (or @code{target extended-remote}).
19815 If the remote program is stripped, or the target does not support remote
19816 program file access, start up @value{GDBN} using the name of the local
19817 unstripped copy of your program as the first argument, or use the
19818 @code{file} command. Use @code{set sysroot} to specify the location (on
19819 the host) of target libraries (unless your @value{GDBN} was compiled with
19820 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19821 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19824 The symbol file and target libraries must exactly match the executable
19825 and libraries on the target, with one exception: the files on the host
19826 system should not be stripped, even if the files on the target system
19827 are. Mismatched or missing files will lead to confusing results
19828 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19829 files may also prevent @code{gdbserver} from debugging multi-threaded
19832 @subsection Remote Connection Commands
19833 @cindex remote connection commands
19834 @value{GDBN} can communicate with the target over a serial line, or
19835 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19836 each case, @value{GDBN} uses the same protocol for debugging your
19837 program; only the medium carrying the debugging packets varies. The
19838 @code{target remote} and @code{target extended-remote} commands
19839 establish a connection to the target. Both commands accept the same
19840 arguments, which indicate the medium to use:
19844 @item target remote @var{serial-device}
19845 @itemx target extended-remote @var{serial-device}
19846 @cindex serial line, @code{target remote}
19847 Use @var{serial-device} to communicate with the target. For example,
19848 to use a serial line connected to the device named @file{/dev/ttyb}:
19851 target remote /dev/ttyb
19854 If you're using a serial line, you may want to give @value{GDBN} the
19855 @samp{--baud} option, or use the @code{set serial baud} command
19856 (@pxref{Remote Configuration, set serial baud}) before the
19857 @code{target} command.
19859 @item target remote @code{@var{host}:@var{port}}
19860 @itemx target remote @code{tcp:@var{host}:@var{port}}
19861 @itemx target extended-remote @code{@var{host}:@var{port}}
19862 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19863 @cindex @acronym{TCP} port, @code{target remote}
19864 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19865 The @var{host} may be either a host name or a numeric @acronym{IP}
19866 address; @var{port} must be a decimal number. The @var{host} could be
19867 the target machine itself, if it is directly connected to the net, or
19868 it might be a terminal server which in turn has a serial line to the
19871 For example, to connect to port 2828 on a terminal server named
19875 target remote manyfarms:2828
19878 If your remote target is actually running on the same machine as your
19879 debugger session (e.g.@: a simulator for your target running on the
19880 same host), you can omit the hostname. For example, to connect to
19881 port 1234 on your local machine:
19884 target remote :1234
19888 Note that the colon is still required here.
19890 @item target remote @code{udp:@var{host}:@var{port}}
19891 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19892 @cindex @acronym{UDP} port, @code{target remote}
19893 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19894 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19897 target remote udp:manyfarms:2828
19900 When using a @acronym{UDP} connection for remote debugging, you should
19901 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19902 can silently drop packets on busy or unreliable networks, which will
19903 cause havoc with your debugging session.
19905 @item target remote | @var{command}
19906 @itemx target extended-remote | @var{command}
19907 @cindex pipe, @code{target remote} to
19908 Run @var{command} in the background and communicate with it using a
19909 pipe. The @var{command} is a shell command, to be parsed and expanded
19910 by the system's command shell, @code{/bin/sh}; it should expect remote
19911 protocol packets on its standard input, and send replies on its
19912 standard output. You could use this to run a stand-alone simulator
19913 that speaks the remote debugging protocol, to make net connections
19914 using programs like @code{ssh}, or for other similar tricks.
19916 If @var{command} closes its standard output (perhaps by exiting),
19917 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19918 program has already exited, this will have no effect.)
19922 @cindex interrupting remote programs
19923 @cindex remote programs, interrupting
19924 Whenever @value{GDBN} is waiting for the remote program, if you type the
19925 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19926 program. This may or may not succeed, depending in part on the hardware
19927 and the serial drivers the remote system uses. If you type the
19928 interrupt character once again, @value{GDBN} displays this prompt:
19931 Interrupted while waiting for the program.
19932 Give up (and stop debugging it)? (y or n)
19935 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19936 the remote debugging session. (If you decide you want to try again later,
19937 you can use @kbd{target remote} again to connect once more.) If you type
19938 @kbd{n}, @value{GDBN} goes back to waiting.
19940 In @code{target extended-remote} mode, typing @kbd{n} will leave
19941 @value{GDBN} connected to the target.
19944 @kindex detach (remote)
19946 When you have finished debugging the remote program, you can use the
19947 @code{detach} command to release it from @value{GDBN} control.
19948 Detaching from the target normally resumes its execution, but the results
19949 will depend on your particular remote stub. After the @code{detach}
19950 command in @code{target remote} mode, @value{GDBN} is free to connect to
19951 another target. In @code{target extended-remote} mode, @value{GDBN} is
19952 still connected to the target.
19956 The @code{disconnect} command closes the connection to the target, and
19957 the target is generally not resumed. It will wait for @value{GDBN}
19958 (this instance or another one) to connect and continue debugging. After
19959 the @code{disconnect} command, @value{GDBN} is again free to connect to
19962 @cindex send command to remote monitor
19963 @cindex extend @value{GDBN} for remote targets
19964 @cindex add new commands for external monitor
19966 @item monitor @var{cmd}
19967 This command allows you to send arbitrary commands directly to the
19968 remote monitor. Since @value{GDBN} doesn't care about the commands it
19969 sends like this, this command is the way to extend @value{GDBN}---you
19970 can add new commands that only the external monitor will understand
19974 @node File Transfer
19975 @section Sending files to a remote system
19976 @cindex remote target, file transfer
19977 @cindex file transfer
19978 @cindex sending files to remote systems
19980 Some remote targets offer the ability to transfer files over the same
19981 connection used to communicate with @value{GDBN}. This is convenient
19982 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19983 running @code{gdbserver} over a network interface. For other targets,
19984 e.g.@: embedded devices with only a single serial port, this may be
19985 the only way to upload or download files.
19987 Not all remote targets support these commands.
19991 @item remote put @var{hostfile} @var{targetfile}
19992 Copy file @var{hostfile} from the host system (the machine running
19993 @value{GDBN}) to @var{targetfile} on the target system.
19996 @item remote get @var{targetfile} @var{hostfile}
19997 Copy file @var{targetfile} from the target system to @var{hostfile}
19998 on the host system.
20000 @kindex remote delete
20001 @item remote delete @var{targetfile}
20002 Delete @var{targetfile} from the target system.
20007 @section Using the @code{gdbserver} Program
20010 @cindex remote connection without stubs
20011 @code{gdbserver} is a control program for Unix-like systems, which
20012 allows you to connect your program with a remote @value{GDBN} via
20013 @code{target remote} or @code{target extended-remote}---but without
20014 linking in the usual debugging stub.
20016 @code{gdbserver} is not a complete replacement for the debugging stubs,
20017 because it requires essentially the same operating-system facilities
20018 that @value{GDBN} itself does. In fact, a system that can run
20019 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20020 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20021 because it is a much smaller program than @value{GDBN} itself. It is
20022 also easier to port than all of @value{GDBN}, so you may be able to get
20023 started more quickly on a new system by using @code{gdbserver}.
20024 Finally, if you develop code for real-time systems, you may find that
20025 the tradeoffs involved in real-time operation make it more convenient to
20026 do as much development work as possible on another system, for example
20027 by cross-compiling. You can use @code{gdbserver} to make a similar
20028 choice for debugging.
20030 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20031 or a TCP connection, using the standard @value{GDBN} remote serial
20035 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20036 Do not run @code{gdbserver} connected to any public network; a
20037 @value{GDBN} connection to @code{gdbserver} provides access to the
20038 target system with the same privileges as the user running
20042 @anchor{Running gdbserver}
20043 @subsection Running @code{gdbserver}
20044 @cindex arguments, to @code{gdbserver}
20045 @cindex @code{gdbserver}, command-line arguments
20047 Run @code{gdbserver} on the target system. You need a copy of the
20048 program you want to debug, including any libraries it requires.
20049 @code{gdbserver} does not need your program's symbol table, so you can
20050 strip the program if necessary to save space. @value{GDBN} on the host
20051 system does all the symbol handling.
20053 To use the server, you must tell it how to communicate with @value{GDBN};
20054 the name of your program; and the arguments for your program. The usual
20058 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20061 @var{comm} is either a device name (to use a serial line), or a TCP
20062 hostname and portnumber, or @code{-} or @code{stdio} to use
20063 stdin/stdout of @code{gdbserver}.
20064 For example, to debug Emacs with the argument
20065 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20069 target> gdbserver /dev/com1 emacs foo.txt
20072 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20075 To use a TCP connection instead of a serial line:
20078 target> gdbserver host:2345 emacs foo.txt
20081 The only difference from the previous example is the first argument,
20082 specifying that you are communicating with the host @value{GDBN} via
20083 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20084 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20085 (Currently, the @samp{host} part is ignored.) You can choose any number
20086 you want for the port number as long as it does not conflict with any
20087 TCP ports already in use on the target system (for example, @code{23} is
20088 reserved for @code{telnet}).@footnote{If you choose a port number that
20089 conflicts with another service, @code{gdbserver} prints an error message
20090 and exits.} You must use the same port number with the host @value{GDBN}
20091 @code{target remote} command.
20093 The @code{stdio} connection is useful when starting @code{gdbserver}
20097 (gdb) target remote | ssh -T hostname gdbserver - hello
20100 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20101 and we don't want escape-character handling. Ssh does this by default when
20102 a command is provided, the flag is provided to make it explicit.
20103 You could elide it if you want to.
20105 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20106 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20107 display through a pipe connected to gdbserver.
20108 Both @code{stdout} and @code{stderr} use the same pipe.
20110 @anchor{Attaching to a program}
20111 @subsubsection Attaching to a Running Program
20112 @cindex attach to a program, @code{gdbserver}
20113 @cindex @option{--attach}, @code{gdbserver} option
20115 On some targets, @code{gdbserver} can also attach to running programs.
20116 This is accomplished via the @code{--attach} argument. The syntax is:
20119 target> gdbserver --attach @var{comm} @var{pid}
20122 @var{pid} is the process ID of a currently running process. It isn't
20123 necessary to point @code{gdbserver} at a binary for the running process.
20125 In @code{target extended-remote} mode, you can also attach using the
20126 @value{GDBN} attach command
20127 (@pxref{Attaching in Types of Remote Connections}).
20130 You can debug processes by name instead of process ID if your target has the
20131 @code{pidof} utility:
20134 target> gdbserver --attach @var{comm} `pidof @var{program}`
20137 In case more than one copy of @var{program} is running, or @var{program}
20138 has multiple threads, most versions of @code{pidof} support the
20139 @code{-s} option to only return the first process ID.
20141 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20143 This section applies only when @code{gdbserver} is run to listen on a TCP
20146 @code{gdbserver} normally terminates after all of its debugged processes have
20147 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20148 extended-remote}, @code{gdbserver} stays running even with no processes left.
20149 @value{GDBN} normally terminates the spawned debugged process on its exit,
20150 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20151 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20152 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20153 stays running even in the @kbd{target remote} mode.
20155 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20156 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20157 completeness, at most one @value{GDBN} can be connected at a time.
20159 @cindex @option{--once}, @code{gdbserver} option
20160 By default, @code{gdbserver} keeps the listening TCP port open, so that
20161 subsequent connections are possible. However, if you start @code{gdbserver}
20162 with the @option{--once} option, it will stop listening for any further
20163 connection attempts after connecting to the first @value{GDBN} session. This
20164 means no further connections to @code{gdbserver} will be possible after the
20165 first one. It also means @code{gdbserver} will terminate after the first
20166 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20167 connections and even in the @kbd{target extended-remote} mode. The
20168 @option{--once} option allows reusing the same port number for connecting to
20169 multiple instances of @code{gdbserver} running on the same host, since each
20170 instance closes its port after the first connection.
20172 @anchor{Other Command-Line Arguments for gdbserver}
20173 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20175 You can use the @option{--multi} option to start @code{gdbserver} without
20176 specifying a program to debug or a process to attach to. Then you can
20177 attach in @code{target extended-remote} mode and run or attach to a
20178 program. For more information,
20179 @pxref{--multi Option in Types of Remote Connnections}.
20181 @cindex @option{--debug}, @code{gdbserver} option
20182 The @option{--debug} option tells @code{gdbserver} to display extra
20183 status information about the debugging process.
20184 @cindex @option{--remote-debug}, @code{gdbserver} option
20185 The @option{--remote-debug} option tells @code{gdbserver} to display
20186 remote protocol debug output. These options are intended for
20187 @code{gdbserver} development and for bug reports to the developers.
20189 @cindex @option{--debug-format}, @code{gdbserver} option
20190 The @option{--debug-format=option1[,option2,...]} option tells
20191 @code{gdbserver} to include additional information in each output.
20192 Possible options are:
20196 Turn off all extra information in debugging output.
20198 Turn on all extra information in debugging output.
20200 Include a timestamp in each line of debugging output.
20203 Options are processed in order. Thus, for example, if @option{none}
20204 appears last then no additional information is added to debugging output.
20206 @cindex @option{--wrapper}, @code{gdbserver} option
20207 The @option{--wrapper} option specifies a wrapper to launch programs
20208 for debugging. The option should be followed by the name of the
20209 wrapper, then any command-line arguments to pass to the wrapper, then
20210 @kbd{--} indicating the end of the wrapper arguments.
20212 @code{gdbserver} runs the specified wrapper program with a combined
20213 command line including the wrapper arguments, then the name of the
20214 program to debug, then any arguments to the program. The wrapper
20215 runs until it executes your program, and then @value{GDBN} gains control.
20217 You can use any program that eventually calls @code{execve} with
20218 its arguments as a wrapper. Several standard Unix utilities do
20219 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20220 with @code{exec "$@@"} will also work.
20222 For example, you can use @code{env} to pass an environment variable to
20223 the debugged program, without setting the variable in @code{gdbserver}'s
20227 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20230 @subsection Connecting to @code{gdbserver}
20232 The basic procedure for connecting to the remote target is:
20236 Run @value{GDBN} on the host system.
20239 Make sure you have the necessary symbol files
20240 (@pxref{Host and target files}).
20241 Load symbols for your application using the @code{file} command before you
20242 connect. Use @code{set sysroot} to locate target libraries (unless your
20243 @value{GDBN} was compiled with the correct sysroot using
20244 @code{--with-sysroot}).
20247 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20248 For TCP connections, you must start up @code{gdbserver} prior to using
20249 the @code{target} command. Otherwise you may get an error whose
20250 text depends on the host system, but which usually looks something like
20251 @samp{Connection refused}. Don't use the @code{load}
20252 command in @value{GDBN} when using @code{target remote} mode, since the
20253 program is already on the target.
20257 @anchor{Monitor Commands for gdbserver}
20258 @subsection Monitor Commands for @code{gdbserver}
20259 @cindex monitor commands, for @code{gdbserver}
20261 During a @value{GDBN} session using @code{gdbserver}, you can use the
20262 @code{monitor} command to send special requests to @code{gdbserver}.
20263 Here are the available commands.
20267 List the available monitor commands.
20269 @item monitor set debug 0
20270 @itemx monitor set debug 1
20271 Disable or enable general debugging messages.
20273 @item monitor set remote-debug 0
20274 @itemx monitor set remote-debug 1
20275 Disable or enable specific debugging messages associated with the remote
20276 protocol (@pxref{Remote Protocol}).
20278 @item monitor set debug-format option1@r{[},option2,...@r{]}
20279 Specify additional text to add to debugging messages.
20280 Possible options are:
20284 Turn off all extra information in debugging output.
20286 Turn on all extra information in debugging output.
20288 Include a timestamp in each line of debugging output.
20291 Options are processed in order. Thus, for example, if @option{none}
20292 appears last then no additional information is added to debugging output.
20294 @item monitor set libthread-db-search-path [PATH]
20295 @cindex gdbserver, search path for @code{libthread_db}
20296 When this command is issued, @var{path} is a colon-separated list of
20297 directories to search for @code{libthread_db} (@pxref{Threads,,set
20298 libthread-db-search-path}). If you omit @var{path},
20299 @samp{libthread-db-search-path} will be reset to its default value.
20301 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20302 not supported in @code{gdbserver}.
20305 Tell gdbserver to exit immediately. This command should be followed by
20306 @code{disconnect} to close the debugging session. @code{gdbserver} will
20307 detach from any attached processes and kill any processes it created.
20308 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20309 of a multi-process mode debug session.
20313 @subsection Tracepoints support in @code{gdbserver}
20314 @cindex tracepoints support in @code{gdbserver}
20316 On some targets, @code{gdbserver} supports tracepoints, fast
20317 tracepoints and static tracepoints.
20319 For fast or static tracepoints to work, a special library called the
20320 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20321 This library is built and distributed as an integral part of
20322 @code{gdbserver}. In addition, support for static tracepoints
20323 requires building the in-process agent library with static tracepoints
20324 support. At present, the UST (LTTng Userspace Tracer,
20325 @url{http://lttng.org/ust}) tracing engine is supported. This support
20326 is automatically available if UST development headers are found in the
20327 standard include path when @code{gdbserver} is built, or if
20328 @code{gdbserver} was explicitly configured using @option{--with-ust}
20329 to point at such headers. You can explicitly disable the support
20330 using @option{--with-ust=no}.
20332 There are several ways to load the in-process agent in your program:
20335 @item Specifying it as dependency at link time
20337 You can link your program dynamically with the in-process agent
20338 library. On most systems, this is accomplished by adding
20339 @code{-linproctrace} to the link command.
20341 @item Using the system's preloading mechanisms
20343 You can force loading the in-process agent at startup time by using
20344 your system's support for preloading shared libraries. Many Unixes
20345 support the concept of preloading user defined libraries. In most
20346 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20347 in the environment. See also the description of @code{gdbserver}'s
20348 @option{--wrapper} command line option.
20350 @item Using @value{GDBN} to force loading the agent at run time
20352 On some systems, you can force the inferior to load a shared library,
20353 by calling a dynamic loader function in the inferior that takes care
20354 of dynamically looking up and loading a shared library. On most Unix
20355 systems, the function is @code{dlopen}. You'll use the @code{call}
20356 command for that. For example:
20359 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20362 Note that on most Unix systems, for the @code{dlopen} function to be
20363 available, the program needs to be linked with @code{-ldl}.
20366 On systems that have a userspace dynamic loader, like most Unix
20367 systems, when you connect to @code{gdbserver} using @code{target
20368 remote}, you'll find that the program is stopped at the dynamic
20369 loader's entry point, and no shared library has been loaded in the
20370 program's address space yet, including the in-process agent. In that
20371 case, before being able to use any of the fast or static tracepoints
20372 features, you need to let the loader run and load the shared
20373 libraries. The simplest way to do that is to run the program to the
20374 main procedure. E.g., if debugging a C or C@t{++} program, start
20375 @code{gdbserver} like so:
20378 $ gdbserver :9999 myprogram
20381 Start GDB and connect to @code{gdbserver} like so, and run to main:
20385 (@value{GDBP}) target remote myhost:9999
20386 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20387 (@value{GDBP}) b main
20388 (@value{GDBP}) continue
20391 The in-process tracing agent library should now be loaded into the
20392 process; you can confirm it with the @code{info sharedlibrary}
20393 command, which will list @file{libinproctrace.so} as loaded in the
20394 process. You are now ready to install fast tracepoints, list static
20395 tracepoint markers, probe static tracepoints markers, and start
20398 @node Remote Configuration
20399 @section Remote Configuration
20402 @kindex show remote
20403 This section documents the configuration options available when
20404 debugging remote programs. For the options related to the File I/O
20405 extensions of the remote protocol, see @ref{system,
20406 system-call-allowed}.
20409 @item set remoteaddresssize @var{bits}
20410 @cindex address size for remote targets
20411 @cindex bits in remote address
20412 Set the maximum size of address in a memory packet to the specified
20413 number of bits. @value{GDBN} will mask off the address bits above
20414 that number, when it passes addresses to the remote target. The
20415 default value is the number of bits in the target's address.
20417 @item show remoteaddresssize
20418 Show the current value of remote address size in bits.
20420 @item set serial baud @var{n}
20421 @cindex baud rate for remote targets
20422 Set the baud rate for the remote serial I/O to @var{n} baud. The
20423 value is used to set the speed of the serial port used for debugging
20426 @item show serial baud
20427 Show the current speed of the remote connection.
20429 @item set serial parity @var{parity}
20430 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20431 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20433 @item show serial parity
20434 Show the current parity of the serial port.
20436 @item set remotebreak
20437 @cindex interrupt remote programs
20438 @cindex BREAK signal instead of Ctrl-C
20439 @anchor{set remotebreak}
20440 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20441 when you type @kbd{Ctrl-c} to interrupt the program running
20442 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20443 character instead. The default is off, since most remote systems
20444 expect to see @samp{Ctrl-C} as the interrupt signal.
20446 @item show remotebreak
20447 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20448 interrupt the remote program.
20450 @item set remoteflow on
20451 @itemx set remoteflow off
20452 @kindex set remoteflow
20453 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20454 on the serial port used to communicate to the remote target.
20456 @item show remoteflow
20457 @kindex show remoteflow
20458 Show the current setting of hardware flow control.
20460 @item set remotelogbase @var{base}
20461 Set the base (a.k.a.@: radix) of logging serial protocol
20462 communications to @var{base}. Supported values of @var{base} are:
20463 @code{ascii}, @code{octal}, and @code{hex}. The default is
20466 @item show remotelogbase
20467 Show the current setting of the radix for logging remote serial
20470 @item set remotelogfile @var{file}
20471 @cindex record serial communications on file
20472 Record remote serial communications on the named @var{file}. The
20473 default is not to record at all.
20475 @item show remotelogfile.
20476 Show the current setting of the file name on which to record the
20477 serial communications.
20479 @item set remotetimeout @var{num}
20480 @cindex timeout for serial communications
20481 @cindex remote timeout
20482 Set the timeout limit to wait for the remote target to respond to
20483 @var{num} seconds. The default is 2 seconds.
20485 @item show remotetimeout
20486 Show the current number of seconds to wait for the remote target
20489 @cindex limit hardware breakpoints and watchpoints
20490 @cindex remote target, limit break- and watchpoints
20491 @anchor{set remote hardware-watchpoint-limit}
20492 @anchor{set remote hardware-breakpoint-limit}
20493 @item set remote hardware-watchpoint-limit @var{limit}
20494 @itemx set remote hardware-breakpoint-limit @var{limit}
20495 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20496 watchpoints. A limit of -1, the default, is treated as unlimited.
20498 @cindex limit hardware watchpoints length
20499 @cindex remote target, limit watchpoints length
20500 @anchor{set remote hardware-watchpoint-length-limit}
20501 @item set remote hardware-watchpoint-length-limit @var{limit}
20502 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20503 a remote hardware watchpoint. A limit of -1, the default, is treated
20506 @item show remote hardware-watchpoint-length-limit
20507 Show the current limit (in bytes) of the maximum length of
20508 a remote hardware watchpoint.
20510 @item set remote exec-file @var{filename}
20511 @itemx show remote exec-file
20512 @anchor{set remote exec-file}
20513 @cindex executable file, for remote target
20514 Select the file used for @code{run} with @code{target
20515 extended-remote}. This should be set to a filename valid on the
20516 target system. If it is not set, the target will use a default
20517 filename (e.g.@: the last program run).
20519 @item set remote interrupt-sequence
20520 @cindex interrupt remote programs
20521 @cindex select Ctrl-C, BREAK or BREAK-g
20522 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20523 @samp{BREAK-g} as the
20524 sequence to the remote target in order to interrupt the execution.
20525 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20526 is high level of serial line for some certain time.
20527 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20528 It is @code{BREAK} signal followed by character @code{g}.
20530 @item show interrupt-sequence
20531 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20532 is sent by @value{GDBN} to interrupt the remote program.
20533 @code{BREAK-g} is BREAK signal followed by @code{g} and
20534 also known as Magic SysRq g.
20536 @item set remote interrupt-on-connect
20537 @cindex send interrupt-sequence on start
20538 Specify whether interrupt-sequence is sent to remote target when
20539 @value{GDBN} connects to it. This is mostly needed when you debug
20540 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20541 which is known as Magic SysRq g in order to connect @value{GDBN}.
20543 @item show interrupt-on-connect
20544 Show whether interrupt-sequence is sent
20545 to remote target when @value{GDBN} connects to it.
20549 @item set tcp auto-retry on
20550 @cindex auto-retry, for remote TCP target
20551 Enable auto-retry for remote TCP connections. This is useful if the remote
20552 debugging agent is launched in parallel with @value{GDBN}; there is a race
20553 condition because the agent may not become ready to accept the connection
20554 before @value{GDBN} attempts to connect. When auto-retry is
20555 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20556 to establish the connection using the timeout specified by
20557 @code{set tcp connect-timeout}.
20559 @item set tcp auto-retry off
20560 Do not auto-retry failed TCP connections.
20562 @item show tcp auto-retry
20563 Show the current auto-retry setting.
20565 @item set tcp connect-timeout @var{seconds}
20566 @itemx set tcp connect-timeout unlimited
20567 @cindex connection timeout, for remote TCP target
20568 @cindex timeout, for remote target connection
20569 Set the timeout for establishing a TCP connection to the remote target to
20570 @var{seconds}. The timeout affects both polling to retry failed connections
20571 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20572 that are merely slow to complete, and represents an approximate cumulative
20573 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20574 @value{GDBN} will keep attempting to establish a connection forever,
20575 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20577 @item show tcp connect-timeout
20578 Show the current connection timeout setting.
20581 @cindex remote packets, enabling and disabling
20582 The @value{GDBN} remote protocol autodetects the packets supported by
20583 your debugging stub. If you need to override the autodetection, you
20584 can use these commands to enable or disable individual packets. Each
20585 packet can be set to @samp{on} (the remote target supports this
20586 packet), @samp{off} (the remote target does not support this packet),
20587 or @samp{auto} (detect remote target support for this packet). They
20588 all default to @samp{auto}. For more information about each packet,
20589 see @ref{Remote Protocol}.
20591 During normal use, you should not have to use any of these commands.
20592 If you do, that may be a bug in your remote debugging stub, or a bug
20593 in @value{GDBN}. You may want to report the problem to the
20594 @value{GDBN} developers.
20596 For each packet @var{name}, the command to enable or disable the
20597 packet is @code{set remote @var{name}-packet}. The available settings
20600 @multitable @columnfractions 0.28 0.32 0.25
20603 @tab Related Features
20605 @item @code{fetch-register}
20607 @tab @code{info registers}
20609 @item @code{set-register}
20613 @item @code{binary-download}
20615 @tab @code{load}, @code{set}
20617 @item @code{read-aux-vector}
20618 @tab @code{qXfer:auxv:read}
20619 @tab @code{info auxv}
20621 @item @code{symbol-lookup}
20622 @tab @code{qSymbol}
20623 @tab Detecting multiple threads
20625 @item @code{attach}
20626 @tab @code{vAttach}
20629 @item @code{verbose-resume}
20631 @tab Stepping or resuming multiple threads
20637 @item @code{software-breakpoint}
20641 @item @code{hardware-breakpoint}
20645 @item @code{write-watchpoint}
20649 @item @code{read-watchpoint}
20653 @item @code{access-watchpoint}
20657 @item @code{pid-to-exec-file}
20658 @tab @code{qXfer:exec-file:read}
20659 @tab @code{attach}, @code{run}
20661 @item @code{target-features}
20662 @tab @code{qXfer:features:read}
20663 @tab @code{set architecture}
20665 @item @code{library-info}
20666 @tab @code{qXfer:libraries:read}
20667 @tab @code{info sharedlibrary}
20669 @item @code{memory-map}
20670 @tab @code{qXfer:memory-map:read}
20671 @tab @code{info mem}
20673 @item @code{read-sdata-object}
20674 @tab @code{qXfer:sdata:read}
20675 @tab @code{print $_sdata}
20677 @item @code{read-spu-object}
20678 @tab @code{qXfer:spu:read}
20679 @tab @code{info spu}
20681 @item @code{write-spu-object}
20682 @tab @code{qXfer:spu:write}
20683 @tab @code{info spu}
20685 @item @code{read-siginfo-object}
20686 @tab @code{qXfer:siginfo:read}
20687 @tab @code{print $_siginfo}
20689 @item @code{write-siginfo-object}
20690 @tab @code{qXfer:siginfo:write}
20691 @tab @code{set $_siginfo}
20693 @item @code{threads}
20694 @tab @code{qXfer:threads:read}
20695 @tab @code{info threads}
20697 @item @code{get-thread-local-@*storage-address}
20698 @tab @code{qGetTLSAddr}
20699 @tab Displaying @code{__thread} variables
20701 @item @code{get-thread-information-block-address}
20702 @tab @code{qGetTIBAddr}
20703 @tab Display MS-Windows Thread Information Block.
20705 @item @code{search-memory}
20706 @tab @code{qSearch:memory}
20709 @item @code{supported-packets}
20710 @tab @code{qSupported}
20711 @tab Remote communications parameters
20713 @item @code{catch-syscalls}
20714 @tab @code{QCatchSyscalls}
20715 @tab @code{catch syscall}
20717 @item @code{pass-signals}
20718 @tab @code{QPassSignals}
20719 @tab @code{handle @var{signal}}
20721 @item @code{program-signals}
20722 @tab @code{QProgramSignals}
20723 @tab @code{handle @var{signal}}
20725 @item @code{hostio-close-packet}
20726 @tab @code{vFile:close}
20727 @tab @code{remote get}, @code{remote put}
20729 @item @code{hostio-open-packet}
20730 @tab @code{vFile:open}
20731 @tab @code{remote get}, @code{remote put}
20733 @item @code{hostio-pread-packet}
20734 @tab @code{vFile:pread}
20735 @tab @code{remote get}, @code{remote put}
20737 @item @code{hostio-pwrite-packet}
20738 @tab @code{vFile:pwrite}
20739 @tab @code{remote get}, @code{remote put}
20741 @item @code{hostio-unlink-packet}
20742 @tab @code{vFile:unlink}
20743 @tab @code{remote delete}
20745 @item @code{hostio-readlink-packet}
20746 @tab @code{vFile:readlink}
20749 @item @code{hostio-fstat-packet}
20750 @tab @code{vFile:fstat}
20753 @item @code{hostio-setfs-packet}
20754 @tab @code{vFile:setfs}
20757 @item @code{noack-packet}
20758 @tab @code{QStartNoAckMode}
20759 @tab Packet acknowledgment
20761 @item @code{osdata}
20762 @tab @code{qXfer:osdata:read}
20763 @tab @code{info os}
20765 @item @code{query-attached}
20766 @tab @code{qAttached}
20767 @tab Querying remote process attach state.
20769 @item @code{trace-buffer-size}
20770 @tab @code{QTBuffer:size}
20771 @tab @code{set trace-buffer-size}
20773 @item @code{trace-status}
20774 @tab @code{qTStatus}
20775 @tab @code{tstatus}
20777 @item @code{traceframe-info}
20778 @tab @code{qXfer:traceframe-info:read}
20779 @tab Traceframe info
20781 @item @code{install-in-trace}
20782 @tab @code{InstallInTrace}
20783 @tab Install tracepoint in tracing
20785 @item @code{disable-randomization}
20786 @tab @code{QDisableRandomization}
20787 @tab @code{set disable-randomization}
20789 @item @code{conditional-breakpoints-packet}
20790 @tab @code{Z0 and Z1}
20791 @tab @code{Support for target-side breakpoint condition evaluation}
20793 @item @code{multiprocess-extensions}
20794 @tab @code{multiprocess extensions}
20795 @tab Debug multiple processes and remote process PID awareness
20797 @item @code{swbreak-feature}
20798 @tab @code{swbreak stop reason}
20801 @item @code{hwbreak-feature}
20802 @tab @code{hwbreak stop reason}
20805 @item @code{fork-event-feature}
20806 @tab @code{fork stop reason}
20809 @item @code{vfork-event-feature}
20810 @tab @code{vfork stop reason}
20813 @item @code{exec-event-feature}
20814 @tab @code{exec stop reason}
20817 @item @code{thread-events}
20818 @tab @code{QThreadEvents}
20819 @tab Tracking thread lifetime.
20821 @item @code{no-resumed-stop-reply}
20822 @tab @code{no resumed thread left stop reply}
20823 @tab Tracking thread lifetime.
20828 @section Implementing a Remote Stub
20830 @cindex debugging stub, example
20831 @cindex remote stub, example
20832 @cindex stub example, remote debugging
20833 The stub files provided with @value{GDBN} implement the target side of the
20834 communication protocol, and the @value{GDBN} side is implemented in the
20835 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20836 these subroutines to communicate, and ignore the details. (If you're
20837 implementing your own stub file, you can still ignore the details: start
20838 with one of the existing stub files. @file{sparc-stub.c} is the best
20839 organized, and therefore the easiest to read.)
20841 @cindex remote serial debugging, overview
20842 To debug a program running on another machine (the debugging
20843 @dfn{target} machine), you must first arrange for all the usual
20844 prerequisites for the program to run by itself. For example, for a C
20849 A startup routine to set up the C runtime environment; these usually
20850 have a name like @file{crt0}. The startup routine may be supplied by
20851 your hardware supplier, or you may have to write your own.
20854 A C subroutine library to support your program's
20855 subroutine calls, notably managing input and output.
20858 A way of getting your program to the other machine---for example, a
20859 download program. These are often supplied by the hardware
20860 manufacturer, but you may have to write your own from hardware
20864 The next step is to arrange for your program to use a serial port to
20865 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20866 machine). In general terms, the scheme looks like this:
20870 @value{GDBN} already understands how to use this protocol; when everything
20871 else is set up, you can simply use the @samp{target remote} command
20872 (@pxref{Targets,,Specifying a Debugging Target}).
20874 @item On the target,
20875 you must link with your program a few special-purpose subroutines that
20876 implement the @value{GDBN} remote serial protocol. The file containing these
20877 subroutines is called a @dfn{debugging stub}.
20879 On certain remote targets, you can use an auxiliary program
20880 @code{gdbserver} instead of linking a stub into your program.
20881 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20884 The debugging stub is specific to the architecture of the remote
20885 machine; for example, use @file{sparc-stub.c} to debug programs on
20888 @cindex remote serial stub list
20889 These working remote stubs are distributed with @value{GDBN}:
20894 @cindex @file{i386-stub.c}
20897 For Intel 386 and compatible architectures.
20900 @cindex @file{m68k-stub.c}
20901 @cindex Motorola 680x0
20903 For Motorola 680x0 architectures.
20906 @cindex @file{sh-stub.c}
20909 For Renesas SH architectures.
20912 @cindex @file{sparc-stub.c}
20914 For @sc{sparc} architectures.
20916 @item sparcl-stub.c
20917 @cindex @file{sparcl-stub.c}
20920 For Fujitsu @sc{sparclite} architectures.
20924 The @file{README} file in the @value{GDBN} distribution may list other
20925 recently added stubs.
20928 * Stub Contents:: What the stub can do for you
20929 * Bootstrapping:: What you must do for the stub
20930 * Debug Session:: Putting it all together
20933 @node Stub Contents
20934 @subsection What the Stub Can Do for You
20936 @cindex remote serial stub
20937 The debugging stub for your architecture supplies these three
20941 @item set_debug_traps
20942 @findex set_debug_traps
20943 @cindex remote serial stub, initialization
20944 This routine arranges for @code{handle_exception} to run when your
20945 program stops. You must call this subroutine explicitly in your
20946 program's startup code.
20948 @item handle_exception
20949 @findex handle_exception
20950 @cindex remote serial stub, main routine
20951 This is the central workhorse, but your program never calls it
20952 explicitly---the setup code arranges for @code{handle_exception} to
20953 run when a trap is triggered.
20955 @code{handle_exception} takes control when your program stops during
20956 execution (for example, on a breakpoint), and mediates communications
20957 with @value{GDBN} on the host machine. This is where the communications
20958 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20959 representative on the target machine. It begins by sending summary
20960 information on the state of your program, then continues to execute,
20961 retrieving and transmitting any information @value{GDBN} needs, until you
20962 execute a @value{GDBN} command that makes your program resume; at that point,
20963 @code{handle_exception} returns control to your own code on the target
20967 @cindex @code{breakpoint} subroutine, remote
20968 Use this auxiliary subroutine to make your program contain a
20969 breakpoint. Depending on the particular situation, this may be the only
20970 way for @value{GDBN} to get control. For instance, if your target
20971 machine has some sort of interrupt button, you won't need to call this;
20972 pressing the interrupt button transfers control to
20973 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20974 simply receiving characters on the serial port may also trigger a trap;
20975 again, in that situation, you don't need to call @code{breakpoint} from
20976 your own program---simply running @samp{target remote} from the host
20977 @value{GDBN} session gets control.
20979 Call @code{breakpoint} if none of these is true, or if you simply want
20980 to make certain your program stops at a predetermined point for the
20981 start of your debugging session.
20984 @node Bootstrapping
20985 @subsection What You Must Do for the Stub
20987 @cindex remote stub, support routines
20988 The debugging stubs that come with @value{GDBN} are set up for a particular
20989 chip architecture, but they have no information about the rest of your
20990 debugging target machine.
20992 First of all you need to tell the stub how to communicate with the
20996 @item int getDebugChar()
20997 @findex getDebugChar
20998 Write this subroutine to read a single character from the serial port.
20999 It may be identical to @code{getchar} for your target system; a
21000 different name is used to allow you to distinguish the two if you wish.
21002 @item void putDebugChar(int)
21003 @findex putDebugChar
21004 Write this subroutine to write a single character to the serial port.
21005 It may be identical to @code{putchar} for your target system; a
21006 different name is used to allow you to distinguish the two if you wish.
21009 @cindex control C, and remote debugging
21010 @cindex interrupting remote targets
21011 If you want @value{GDBN} to be able to stop your program while it is
21012 running, you need to use an interrupt-driven serial driver, and arrange
21013 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21014 character). That is the character which @value{GDBN} uses to tell the
21015 remote system to stop.
21017 Getting the debugging target to return the proper status to @value{GDBN}
21018 probably requires changes to the standard stub; one quick and dirty way
21019 is to just execute a breakpoint instruction (the ``dirty'' part is that
21020 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21022 Other routines you need to supply are:
21025 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21026 @findex exceptionHandler
21027 Write this function to install @var{exception_address} in the exception
21028 handling tables. You need to do this because the stub does not have any
21029 way of knowing what the exception handling tables on your target system
21030 are like (for example, the processor's table might be in @sc{rom},
21031 containing entries which point to a table in @sc{ram}).
21032 The @var{exception_number} specifies the exception which should be changed;
21033 its meaning is architecture-dependent (for example, different numbers
21034 might represent divide by zero, misaligned access, etc). When this
21035 exception occurs, control should be transferred directly to
21036 @var{exception_address}, and the processor state (stack, registers,
21037 and so on) should be just as it is when a processor exception occurs. So if
21038 you want to use a jump instruction to reach @var{exception_address}, it
21039 should be a simple jump, not a jump to subroutine.
21041 For the 386, @var{exception_address} should be installed as an interrupt
21042 gate so that interrupts are masked while the handler runs. The gate
21043 should be at privilege level 0 (the most privileged level). The
21044 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21045 help from @code{exceptionHandler}.
21047 @item void flush_i_cache()
21048 @findex flush_i_cache
21049 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21050 instruction cache, if any, on your target machine. If there is no
21051 instruction cache, this subroutine may be a no-op.
21053 On target machines that have instruction caches, @value{GDBN} requires this
21054 function to make certain that the state of your program is stable.
21058 You must also make sure this library routine is available:
21061 @item void *memset(void *, int, int)
21063 This is the standard library function @code{memset} that sets an area of
21064 memory to a known value. If you have one of the free versions of
21065 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21066 either obtain it from your hardware manufacturer, or write your own.
21069 If you do not use the GNU C compiler, you may need other standard
21070 library subroutines as well; this varies from one stub to another,
21071 but in general the stubs are likely to use any of the common library
21072 subroutines which @code{@value{NGCC}} generates as inline code.
21075 @node Debug Session
21076 @subsection Putting it All Together
21078 @cindex remote serial debugging summary
21079 In summary, when your program is ready to debug, you must follow these
21084 Make sure you have defined the supporting low-level routines
21085 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21087 @code{getDebugChar}, @code{putDebugChar},
21088 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21092 Insert these lines in your program's startup code, before the main
21093 procedure is called:
21100 On some machines, when a breakpoint trap is raised, the hardware
21101 automatically makes the PC point to the instruction after the
21102 breakpoint. If your machine doesn't do that, you may need to adjust
21103 @code{handle_exception} to arrange for it to return to the instruction
21104 after the breakpoint on this first invocation, so that your program
21105 doesn't keep hitting the initial breakpoint instead of making
21109 For the 680x0 stub only, you need to provide a variable called
21110 @code{exceptionHook}. Normally you just use:
21113 void (*exceptionHook)() = 0;
21117 but if before calling @code{set_debug_traps}, you set it to point to a
21118 function in your program, that function is called when
21119 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21120 error). The function indicated by @code{exceptionHook} is called with
21121 one parameter: an @code{int} which is the exception number.
21124 Compile and link together: your program, the @value{GDBN} debugging stub for
21125 your target architecture, and the supporting subroutines.
21128 Make sure you have a serial connection between your target machine and
21129 the @value{GDBN} host, and identify the serial port on the host.
21132 @c The "remote" target now provides a `load' command, so we should
21133 @c document that. FIXME.
21134 Download your program to your target machine (or get it there by
21135 whatever means the manufacturer provides), and start it.
21138 Start @value{GDBN} on the host, and connect to the target
21139 (@pxref{Connecting,,Connecting to a Remote Target}).
21143 @node Configurations
21144 @chapter Configuration-Specific Information
21146 While nearly all @value{GDBN} commands are available for all native and
21147 cross versions of the debugger, there are some exceptions. This chapter
21148 describes things that are only available in certain configurations.
21150 There are three major categories of configurations: native
21151 configurations, where the host and target are the same, embedded
21152 operating system configurations, which are usually the same for several
21153 different processor architectures, and bare embedded processors, which
21154 are quite different from each other.
21159 * Embedded Processors::
21166 This section describes details specific to particular native
21170 * BSD libkvm Interface:: Debugging BSD kernel memory images
21171 * SVR4 Process Information:: SVR4 process information
21172 * DJGPP Native:: Features specific to the DJGPP port
21173 * Cygwin Native:: Features specific to the Cygwin port
21174 * Hurd Native:: Features specific to @sc{gnu} Hurd
21175 * Darwin:: Features specific to Darwin
21178 @node BSD libkvm Interface
21179 @subsection BSD libkvm Interface
21182 @cindex kernel memory image
21183 @cindex kernel crash dump
21185 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21186 interface that provides a uniform interface for accessing kernel virtual
21187 memory images, including live systems and crash dumps. @value{GDBN}
21188 uses this interface to allow you to debug live kernels and kernel crash
21189 dumps on many native BSD configurations. This is implemented as a
21190 special @code{kvm} debugging target. For debugging a live system, load
21191 the currently running kernel into @value{GDBN} and connect to the
21195 (@value{GDBP}) @b{target kvm}
21198 For debugging crash dumps, provide the file name of the crash dump as an
21202 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21205 Once connected to the @code{kvm} target, the following commands are
21211 Set current context from the @dfn{Process Control Block} (PCB) address.
21214 Set current context from proc address. This command isn't available on
21215 modern FreeBSD systems.
21218 @node SVR4 Process Information
21219 @subsection SVR4 Process Information
21221 @cindex examine process image
21222 @cindex process info via @file{/proc}
21224 Many versions of SVR4 and compatible systems provide a facility called
21225 @samp{/proc} that can be used to examine the image of a running
21226 process using file-system subroutines.
21228 If @value{GDBN} is configured for an operating system with this
21229 facility, the command @code{info proc} is available to report
21230 information about the process running your program, or about any
21231 process running on your system. This includes, as of this writing,
21232 @sc{gnu}/Linux and Solaris, for example.
21234 This command may also work on core files that were created on a system
21235 that has the @samp{/proc} facility.
21241 @itemx info proc @var{process-id}
21242 Summarize available information about any running process. If a
21243 process ID is specified by @var{process-id}, display information about
21244 that process; otherwise display information about the program being
21245 debugged. The summary includes the debugged process ID, the command
21246 line used to invoke it, its current working directory, and its
21247 executable file's absolute file name.
21249 On some systems, @var{process-id} can be of the form
21250 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21251 within a process. If the optional @var{pid} part is missing, it means
21252 a thread from the process being debugged (the leading @samp{/} still
21253 needs to be present, or else @value{GDBN} will interpret the number as
21254 a process ID rather than a thread ID).
21256 @item info proc cmdline
21257 @cindex info proc cmdline
21258 Show the original command line of the process. This command is
21259 specific to @sc{gnu}/Linux.
21261 @item info proc cwd
21262 @cindex info proc cwd
21263 Show the current working directory of the process. This command is
21264 specific to @sc{gnu}/Linux.
21266 @item info proc exe
21267 @cindex info proc exe
21268 Show the name of executable of the process. This command is specific
21271 @item info proc mappings
21272 @cindex memory address space mappings
21273 Report the memory address space ranges accessible in the program, with
21274 information on whether the process has read, write, or execute access
21275 rights to each range. On @sc{gnu}/Linux systems, each memory range
21276 includes the object file which is mapped to that range, instead of the
21277 memory access rights to that range.
21279 @item info proc stat
21280 @itemx info proc status
21281 @cindex process detailed status information
21282 These subcommands are specific to @sc{gnu}/Linux systems. They show
21283 the process-related information, including the user ID and group ID;
21284 how many threads are there in the process; its virtual memory usage;
21285 the signals that are pending, blocked, and ignored; its TTY; its
21286 consumption of system and user time; its stack size; its @samp{nice}
21287 value; etc. For more information, see the @samp{proc} man page
21288 (type @kbd{man 5 proc} from your shell prompt).
21290 @item info proc all
21291 Show all the information about the process described under all of the
21292 above @code{info proc} subcommands.
21295 @comment These sub-options of 'info proc' were not included when
21296 @comment procfs.c was re-written. Keep their descriptions around
21297 @comment against the day when someone finds the time to put them back in.
21298 @kindex info proc times
21299 @item info proc times
21300 Starting time, user CPU time, and system CPU time for your program and
21303 @kindex info proc id
21305 Report on the process IDs related to your program: its own process ID,
21306 the ID of its parent, the process group ID, and the session ID.
21309 @item set procfs-trace
21310 @kindex set procfs-trace
21311 @cindex @code{procfs} API calls
21312 This command enables and disables tracing of @code{procfs} API calls.
21314 @item show procfs-trace
21315 @kindex show procfs-trace
21316 Show the current state of @code{procfs} API call tracing.
21318 @item set procfs-file @var{file}
21319 @kindex set procfs-file
21320 Tell @value{GDBN} to write @code{procfs} API trace to the named
21321 @var{file}. @value{GDBN} appends the trace info to the previous
21322 contents of the file. The default is to display the trace on the
21325 @item show procfs-file
21326 @kindex show procfs-file
21327 Show the file to which @code{procfs} API trace is written.
21329 @item proc-trace-entry
21330 @itemx proc-trace-exit
21331 @itemx proc-untrace-entry
21332 @itemx proc-untrace-exit
21333 @kindex proc-trace-entry
21334 @kindex proc-trace-exit
21335 @kindex proc-untrace-entry
21336 @kindex proc-untrace-exit
21337 These commands enable and disable tracing of entries into and exits
21338 from the @code{syscall} interface.
21341 @kindex info pidlist
21342 @cindex process list, QNX Neutrino
21343 For QNX Neutrino only, this command displays the list of all the
21344 processes and all the threads within each process.
21347 @kindex info meminfo
21348 @cindex mapinfo list, QNX Neutrino
21349 For QNX Neutrino only, this command displays the list of all mapinfos.
21353 @subsection Features for Debugging @sc{djgpp} Programs
21354 @cindex @sc{djgpp} debugging
21355 @cindex native @sc{djgpp} debugging
21356 @cindex MS-DOS-specific commands
21359 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21360 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21361 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21362 top of real-mode DOS systems and their emulations.
21364 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21365 defines a few commands specific to the @sc{djgpp} port. This
21366 subsection describes those commands.
21371 This is a prefix of @sc{djgpp}-specific commands which print
21372 information about the target system and important OS structures.
21375 @cindex MS-DOS system info
21376 @cindex free memory information (MS-DOS)
21377 @item info dos sysinfo
21378 This command displays assorted information about the underlying
21379 platform: the CPU type and features, the OS version and flavor, the
21380 DPMI version, and the available conventional and DPMI memory.
21385 @cindex segment descriptor tables
21386 @cindex descriptor tables display
21388 @itemx info dos ldt
21389 @itemx info dos idt
21390 These 3 commands display entries from, respectively, Global, Local,
21391 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21392 tables are data structures which store a descriptor for each segment
21393 that is currently in use. The segment's selector is an index into a
21394 descriptor table; the table entry for that index holds the
21395 descriptor's base address and limit, and its attributes and access
21398 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21399 segment (used for both data and the stack), and a DOS segment (which
21400 allows access to DOS/BIOS data structures and absolute addresses in
21401 conventional memory). However, the DPMI host will usually define
21402 additional segments in order to support the DPMI environment.
21404 @cindex garbled pointers
21405 These commands allow to display entries from the descriptor tables.
21406 Without an argument, all entries from the specified table are
21407 displayed. An argument, which should be an integer expression, means
21408 display a single entry whose index is given by the argument. For
21409 example, here's a convenient way to display information about the
21410 debugged program's data segment:
21413 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21414 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21418 This comes in handy when you want to see whether a pointer is outside
21419 the data segment's limit (i.e.@: @dfn{garbled}).
21421 @cindex page tables display (MS-DOS)
21423 @itemx info dos pte
21424 These two commands display entries from, respectively, the Page
21425 Directory and the Page Tables. Page Directories and Page Tables are
21426 data structures which control how virtual memory addresses are mapped
21427 into physical addresses. A Page Table includes an entry for every
21428 page of memory that is mapped into the program's address space; there
21429 may be several Page Tables, each one holding up to 4096 entries. A
21430 Page Directory has up to 4096 entries, one each for every Page Table
21431 that is currently in use.
21433 Without an argument, @kbd{info dos pde} displays the entire Page
21434 Directory, and @kbd{info dos pte} displays all the entries in all of
21435 the Page Tables. An argument, an integer expression, given to the
21436 @kbd{info dos pde} command means display only that entry from the Page
21437 Directory table. An argument given to the @kbd{info dos pte} command
21438 means display entries from a single Page Table, the one pointed to by
21439 the specified entry in the Page Directory.
21441 @cindex direct memory access (DMA) on MS-DOS
21442 These commands are useful when your program uses @dfn{DMA} (Direct
21443 Memory Access), which needs physical addresses to program the DMA
21446 These commands are supported only with some DPMI servers.
21448 @cindex physical address from linear address
21449 @item info dos address-pte @var{addr}
21450 This command displays the Page Table entry for a specified linear
21451 address. The argument @var{addr} is a linear address which should
21452 already have the appropriate segment's base address added to it,
21453 because this command accepts addresses which may belong to @emph{any}
21454 segment. For example, here's how to display the Page Table entry for
21455 the page where a variable @code{i} is stored:
21458 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21459 @exdent @code{Page Table entry for address 0x11a00d30:}
21460 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21464 This says that @code{i} is stored at offset @code{0xd30} from the page
21465 whose physical base address is @code{0x02698000}, and shows all the
21466 attributes of that page.
21468 Note that you must cast the addresses of variables to a @code{char *},
21469 since otherwise the value of @code{__djgpp_base_address}, the base
21470 address of all variables and functions in a @sc{djgpp} program, will
21471 be added using the rules of C pointer arithmetics: if @code{i} is
21472 declared an @code{int}, @value{GDBN} will add 4 times the value of
21473 @code{__djgpp_base_address} to the address of @code{i}.
21475 Here's another example, it displays the Page Table entry for the
21479 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21480 @exdent @code{Page Table entry for address 0x29110:}
21481 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21485 (The @code{+ 3} offset is because the transfer buffer's address is the
21486 3rd member of the @code{_go32_info_block} structure.) The output
21487 clearly shows that this DPMI server maps the addresses in conventional
21488 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21489 linear (@code{0x29110}) addresses are identical.
21491 This command is supported only with some DPMI servers.
21494 @cindex DOS serial data link, remote debugging
21495 In addition to native debugging, the DJGPP port supports remote
21496 debugging via a serial data link. The following commands are specific
21497 to remote serial debugging in the DJGPP port of @value{GDBN}.
21500 @kindex set com1base
21501 @kindex set com1irq
21502 @kindex set com2base
21503 @kindex set com2irq
21504 @kindex set com3base
21505 @kindex set com3irq
21506 @kindex set com4base
21507 @kindex set com4irq
21508 @item set com1base @var{addr}
21509 This command sets the base I/O port address of the @file{COM1} serial
21512 @item set com1irq @var{irq}
21513 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21514 for the @file{COM1} serial port.
21516 There are similar commands @samp{set com2base}, @samp{set com3irq},
21517 etc.@: for setting the port address and the @code{IRQ} lines for the
21520 @kindex show com1base
21521 @kindex show com1irq
21522 @kindex show com2base
21523 @kindex show com2irq
21524 @kindex show com3base
21525 @kindex show com3irq
21526 @kindex show com4base
21527 @kindex show com4irq
21528 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21529 display the current settings of the base address and the @code{IRQ}
21530 lines used by the COM ports.
21533 @kindex info serial
21534 @cindex DOS serial port status
21535 This command prints the status of the 4 DOS serial ports. For each
21536 port, it prints whether it's active or not, its I/O base address and
21537 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21538 counts of various errors encountered so far.
21542 @node Cygwin Native
21543 @subsection Features for Debugging MS Windows PE Executables
21544 @cindex MS Windows debugging
21545 @cindex native Cygwin debugging
21546 @cindex Cygwin-specific commands
21548 @value{GDBN} supports native debugging of MS Windows programs, including
21549 DLLs with and without symbolic debugging information.
21551 @cindex Ctrl-BREAK, MS-Windows
21552 @cindex interrupt debuggee on MS-Windows
21553 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21554 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21555 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21556 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21557 sequence, which can be used to interrupt the debuggee even if it
21560 There are various additional Cygwin-specific commands, described in
21561 this section. Working with DLLs that have no debugging symbols is
21562 described in @ref{Non-debug DLL Symbols}.
21567 This is a prefix of MS Windows-specific commands which print
21568 information about the target system and important OS structures.
21570 @item info w32 selector
21571 This command displays information returned by
21572 the Win32 API @code{GetThreadSelectorEntry} function.
21573 It takes an optional argument that is evaluated to
21574 a long value to give the information about this given selector.
21575 Without argument, this command displays information
21576 about the six segment registers.
21578 @item info w32 thread-information-block
21579 This command displays thread specific information stored in the
21580 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21581 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21583 @kindex signal-event
21584 @item signal-event @var{id}
21585 This command signals an event with user-provided @var{id}. Used to resume
21586 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
21588 To use it, create or edit the following keys in
21589 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
21590 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
21591 (for x86_64 versions):
21595 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
21596 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
21597 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
21599 The first @code{%ld} will be replaced by the process ID of the
21600 crashing process, the second @code{%ld} will be replaced by the ID of
21601 the event that blocks the crashing process, waiting for @value{GDBN}
21605 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
21606 make the system run debugger specified by the Debugger key
21607 automatically, @code{0} will cause a dialog box with ``OK'' and
21608 ``Cancel'' buttons to appear, which allows the user to either
21609 terminate the crashing process (OK) or debug it (Cancel).
21612 @kindex set cygwin-exceptions
21613 @cindex debugging the Cygwin DLL
21614 @cindex Cygwin DLL, debugging
21615 @item set cygwin-exceptions @var{mode}
21616 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21617 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21618 @value{GDBN} will delay recognition of exceptions, and may ignore some
21619 exceptions which seem to be caused by internal Cygwin DLL
21620 ``bookkeeping''. This option is meant primarily for debugging the
21621 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21622 @value{GDBN} users with false @code{SIGSEGV} signals.
21624 @kindex show cygwin-exceptions
21625 @item show cygwin-exceptions
21626 Displays whether @value{GDBN} will break on exceptions that happen
21627 inside the Cygwin DLL itself.
21629 @kindex set new-console
21630 @item set new-console @var{mode}
21631 If @var{mode} is @code{on} the debuggee will
21632 be started in a new console on next start.
21633 If @var{mode} is @code{off}, the debuggee will
21634 be started in the same console as the debugger.
21636 @kindex show new-console
21637 @item show new-console
21638 Displays whether a new console is used
21639 when the debuggee is started.
21641 @kindex set new-group
21642 @item set new-group @var{mode}
21643 This boolean value controls whether the debuggee should
21644 start a new group or stay in the same group as the debugger.
21645 This affects the way the Windows OS handles
21648 @kindex show new-group
21649 @item show new-group
21650 Displays current value of new-group boolean.
21652 @kindex set debugevents
21653 @item set debugevents
21654 This boolean value adds debug output concerning kernel events related
21655 to the debuggee seen by the debugger. This includes events that
21656 signal thread and process creation and exit, DLL loading and
21657 unloading, console interrupts, and debugging messages produced by the
21658 Windows @code{OutputDebugString} API call.
21660 @kindex set debugexec
21661 @item set debugexec
21662 This boolean value adds debug output concerning execute events
21663 (such as resume thread) seen by the debugger.
21665 @kindex set debugexceptions
21666 @item set debugexceptions
21667 This boolean value adds debug output concerning exceptions in the
21668 debuggee seen by the debugger.
21670 @kindex set debugmemory
21671 @item set debugmemory
21672 This boolean value adds debug output concerning debuggee memory reads
21673 and writes by the debugger.
21677 This boolean values specifies whether the debuggee is called
21678 via a shell or directly (default value is on).
21682 Displays if the debuggee will be started with a shell.
21687 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21690 @node Non-debug DLL Symbols
21691 @subsubsection Support for DLLs without Debugging Symbols
21692 @cindex DLLs with no debugging symbols
21693 @cindex Minimal symbols and DLLs
21695 Very often on windows, some of the DLLs that your program relies on do
21696 not include symbolic debugging information (for example,
21697 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21698 symbols in a DLL, it relies on the minimal amount of symbolic
21699 information contained in the DLL's export table. This section
21700 describes working with such symbols, known internally to @value{GDBN} as
21701 ``minimal symbols''.
21703 Note that before the debugged program has started execution, no DLLs
21704 will have been loaded. The easiest way around this problem is simply to
21705 start the program --- either by setting a breakpoint or letting the
21706 program run once to completion.
21708 @subsubsection DLL Name Prefixes
21710 In keeping with the naming conventions used by the Microsoft debugging
21711 tools, DLL export symbols are made available with a prefix based on the
21712 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21713 also entered into the symbol table, so @code{CreateFileA} is often
21714 sufficient. In some cases there will be name clashes within a program
21715 (particularly if the executable itself includes full debugging symbols)
21716 necessitating the use of the fully qualified name when referring to the
21717 contents of the DLL. Use single-quotes around the name to avoid the
21718 exclamation mark (``!'') being interpreted as a language operator.
21720 Note that the internal name of the DLL may be all upper-case, even
21721 though the file name of the DLL is lower-case, or vice-versa. Since
21722 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21723 some confusion. If in doubt, try the @code{info functions} and
21724 @code{info variables} commands or even @code{maint print msymbols}
21725 (@pxref{Symbols}). Here's an example:
21728 (@value{GDBP}) info function CreateFileA
21729 All functions matching regular expression "CreateFileA":
21731 Non-debugging symbols:
21732 0x77e885f4 CreateFileA
21733 0x77e885f4 KERNEL32!CreateFileA
21737 (@value{GDBP}) info function !
21738 All functions matching regular expression "!":
21740 Non-debugging symbols:
21741 0x6100114c cygwin1!__assert
21742 0x61004034 cygwin1!_dll_crt0@@0
21743 0x61004240 cygwin1!dll_crt0(per_process *)
21747 @subsubsection Working with Minimal Symbols
21749 Symbols extracted from a DLL's export table do not contain very much
21750 type information. All that @value{GDBN} can do is guess whether a symbol
21751 refers to a function or variable depending on the linker section that
21752 contains the symbol. Also note that the actual contents of the memory
21753 contained in a DLL are not available unless the program is running. This
21754 means that you cannot examine the contents of a variable or disassemble
21755 a function within a DLL without a running program.
21757 Variables are generally treated as pointers and dereferenced
21758 automatically. For this reason, it is often necessary to prefix a
21759 variable name with the address-of operator (``&'') and provide explicit
21760 type information in the command. Here's an example of the type of
21764 (@value{GDBP}) print 'cygwin1!__argv'
21769 (@value{GDBP}) x 'cygwin1!__argv'
21770 0x10021610: "\230y\""
21773 And two possible solutions:
21776 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21777 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21781 (@value{GDBP}) x/2x &'cygwin1!__argv'
21782 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21783 (@value{GDBP}) x/x 0x10021608
21784 0x10021608: 0x0022fd98
21785 (@value{GDBP}) x/s 0x0022fd98
21786 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21789 Setting a break point within a DLL is possible even before the program
21790 starts execution. However, under these circumstances, @value{GDBN} can't
21791 examine the initial instructions of the function in order to skip the
21792 function's frame set-up code. You can work around this by using ``*&''
21793 to set the breakpoint at a raw memory address:
21796 (@value{GDBP}) break *&'python22!PyOS_Readline'
21797 Breakpoint 1 at 0x1e04eff0
21800 The author of these extensions is not entirely convinced that setting a
21801 break point within a shared DLL like @file{kernel32.dll} is completely
21805 @subsection Commands Specific to @sc{gnu} Hurd Systems
21806 @cindex @sc{gnu} Hurd debugging
21808 This subsection describes @value{GDBN} commands specific to the
21809 @sc{gnu} Hurd native debugging.
21814 @kindex set signals@r{, Hurd command}
21815 @kindex set sigs@r{, Hurd command}
21816 This command toggles the state of inferior signal interception by
21817 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21818 affected by this command. @code{sigs} is a shorthand alias for
21823 @kindex show signals@r{, Hurd command}
21824 @kindex show sigs@r{, Hurd command}
21825 Show the current state of intercepting inferior's signals.
21827 @item set signal-thread
21828 @itemx set sigthread
21829 @kindex set signal-thread
21830 @kindex set sigthread
21831 This command tells @value{GDBN} which thread is the @code{libc} signal
21832 thread. That thread is run when a signal is delivered to a running
21833 process. @code{set sigthread} is the shorthand alias of @code{set
21836 @item show signal-thread
21837 @itemx show sigthread
21838 @kindex show signal-thread
21839 @kindex show sigthread
21840 These two commands show which thread will run when the inferior is
21841 delivered a signal.
21844 @kindex set stopped@r{, Hurd command}
21845 This commands tells @value{GDBN} that the inferior process is stopped,
21846 as with the @code{SIGSTOP} signal. The stopped process can be
21847 continued by delivering a signal to it.
21850 @kindex show stopped@r{, Hurd command}
21851 This command shows whether @value{GDBN} thinks the debuggee is
21854 @item set exceptions
21855 @kindex set exceptions@r{, Hurd command}
21856 Use this command to turn off trapping of exceptions in the inferior.
21857 When exception trapping is off, neither breakpoints nor
21858 single-stepping will work. To restore the default, set exception
21861 @item show exceptions
21862 @kindex show exceptions@r{, Hurd command}
21863 Show the current state of trapping exceptions in the inferior.
21865 @item set task pause
21866 @kindex set task@r{, Hurd commands}
21867 @cindex task attributes (@sc{gnu} Hurd)
21868 @cindex pause current task (@sc{gnu} Hurd)
21869 This command toggles task suspension when @value{GDBN} has control.
21870 Setting it to on takes effect immediately, and the task is suspended
21871 whenever @value{GDBN} gets control. Setting it to off will take
21872 effect the next time the inferior is continued. If this option is set
21873 to off, you can use @code{set thread default pause on} or @code{set
21874 thread pause on} (see below) to pause individual threads.
21876 @item show task pause
21877 @kindex show task@r{, Hurd commands}
21878 Show the current state of task suspension.
21880 @item set task detach-suspend-count
21881 @cindex task suspend count
21882 @cindex detach from task, @sc{gnu} Hurd
21883 This command sets the suspend count the task will be left with when
21884 @value{GDBN} detaches from it.
21886 @item show task detach-suspend-count
21887 Show the suspend count the task will be left with when detaching.
21889 @item set task exception-port
21890 @itemx set task excp
21891 @cindex task exception port, @sc{gnu} Hurd
21892 This command sets the task exception port to which @value{GDBN} will
21893 forward exceptions. The argument should be the value of the @dfn{send
21894 rights} of the task. @code{set task excp} is a shorthand alias.
21896 @item set noninvasive
21897 @cindex noninvasive task options
21898 This command switches @value{GDBN} to a mode that is the least
21899 invasive as far as interfering with the inferior is concerned. This
21900 is the same as using @code{set task pause}, @code{set exceptions}, and
21901 @code{set signals} to values opposite to the defaults.
21903 @item info send-rights
21904 @itemx info receive-rights
21905 @itemx info port-rights
21906 @itemx info port-sets
21907 @itemx info dead-names
21910 @cindex send rights, @sc{gnu} Hurd
21911 @cindex receive rights, @sc{gnu} Hurd
21912 @cindex port rights, @sc{gnu} Hurd
21913 @cindex port sets, @sc{gnu} Hurd
21914 @cindex dead names, @sc{gnu} Hurd
21915 These commands display information about, respectively, send rights,
21916 receive rights, port rights, port sets, and dead names of a task.
21917 There are also shorthand aliases: @code{info ports} for @code{info
21918 port-rights} and @code{info psets} for @code{info port-sets}.
21920 @item set thread pause
21921 @kindex set thread@r{, Hurd command}
21922 @cindex thread properties, @sc{gnu} Hurd
21923 @cindex pause current thread (@sc{gnu} Hurd)
21924 This command toggles current thread suspension when @value{GDBN} has
21925 control. Setting it to on takes effect immediately, and the current
21926 thread is suspended whenever @value{GDBN} gets control. Setting it to
21927 off will take effect the next time the inferior is continued.
21928 Normally, this command has no effect, since when @value{GDBN} has
21929 control, the whole task is suspended. However, if you used @code{set
21930 task pause off} (see above), this command comes in handy to suspend
21931 only the current thread.
21933 @item show thread pause
21934 @kindex show thread@r{, Hurd command}
21935 This command shows the state of current thread suspension.
21937 @item set thread run
21938 This command sets whether the current thread is allowed to run.
21940 @item show thread run
21941 Show whether the current thread is allowed to run.
21943 @item set thread detach-suspend-count
21944 @cindex thread suspend count, @sc{gnu} Hurd
21945 @cindex detach from thread, @sc{gnu} Hurd
21946 This command sets the suspend count @value{GDBN} will leave on a
21947 thread when detaching. This number is relative to the suspend count
21948 found by @value{GDBN} when it notices the thread; use @code{set thread
21949 takeover-suspend-count} to force it to an absolute value.
21951 @item show thread detach-suspend-count
21952 Show the suspend count @value{GDBN} will leave on the thread when
21955 @item set thread exception-port
21956 @itemx set thread excp
21957 Set the thread exception port to which to forward exceptions. This
21958 overrides the port set by @code{set task exception-port} (see above).
21959 @code{set thread excp} is the shorthand alias.
21961 @item set thread takeover-suspend-count
21962 Normally, @value{GDBN}'s thread suspend counts are relative to the
21963 value @value{GDBN} finds when it notices each thread. This command
21964 changes the suspend counts to be absolute instead.
21966 @item set thread default
21967 @itemx show thread default
21968 @cindex thread default settings, @sc{gnu} Hurd
21969 Each of the above @code{set thread} commands has a @code{set thread
21970 default} counterpart (e.g., @code{set thread default pause}, @code{set
21971 thread default exception-port}, etc.). The @code{thread default}
21972 variety of commands sets the default thread properties for all
21973 threads; you can then change the properties of individual threads with
21974 the non-default commands.
21981 @value{GDBN} provides the following commands specific to the Darwin target:
21984 @item set debug darwin @var{num}
21985 @kindex set debug darwin
21986 When set to a non zero value, enables debugging messages specific to
21987 the Darwin support. Higher values produce more verbose output.
21989 @item show debug darwin
21990 @kindex show debug darwin
21991 Show the current state of Darwin messages.
21993 @item set debug mach-o @var{num}
21994 @kindex set debug mach-o
21995 When set to a non zero value, enables debugging messages while
21996 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21997 file format used on Darwin for object and executable files.) Higher
21998 values produce more verbose output. This is a command to diagnose
21999 problems internal to @value{GDBN} and should not be needed in normal
22002 @item show debug mach-o
22003 @kindex show debug mach-o
22004 Show the current state of Mach-O file messages.
22006 @item set mach-exceptions on
22007 @itemx set mach-exceptions off
22008 @kindex set mach-exceptions
22009 On Darwin, faults are first reported as a Mach exception and are then
22010 mapped to a Posix signal. Use this command to turn on trapping of
22011 Mach exceptions in the inferior. This might be sometimes useful to
22012 better understand the cause of a fault. The default is off.
22014 @item show mach-exceptions
22015 @kindex show mach-exceptions
22016 Show the current state of exceptions trapping.
22021 @section Embedded Operating Systems
22023 This section describes configurations involving the debugging of
22024 embedded operating systems that are available for several different
22027 @value{GDBN} includes the ability to debug programs running on
22028 various real-time operating systems.
22030 @node Embedded Processors
22031 @section Embedded Processors
22033 This section goes into details specific to particular embedded
22036 @cindex send command to simulator
22037 Whenever a specific embedded processor has a simulator, @value{GDBN}
22038 allows to send an arbitrary command to the simulator.
22041 @item sim @var{command}
22042 @kindex sim@r{, a command}
22043 Send an arbitrary @var{command} string to the simulator. Consult the
22044 documentation for the specific simulator in use for information about
22045 acceptable commands.
22050 * ARC:: Synopsys ARC
22052 * M68K:: Motorola M68K
22053 * MicroBlaze:: Xilinx MicroBlaze
22054 * MIPS Embedded:: MIPS Embedded
22055 * PowerPC Embedded:: PowerPC Embedded
22058 * Super-H:: Renesas Super-H
22062 @subsection Synopsys ARC
22063 @cindex Synopsys ARC
22064 @cindex ARC specific commands
22070 @value{GDBN} provides the following ARC-specific commands:
22073 @item set debug arc
22074 @kindex set debug arc
22075 Control the level of ARC specific debug messages. Use 0 for no messages (the
22076 default) and 1 for debug messages. At present higher values offer no further
22079 @item show debug arc
22080 @kindex show debug arc
22081 Show the level of ARC specific debugging in operation.
22088 @value{GDBN} provides the following ARM-specific commands:
22091 @item set arm disassembler
22093 This commands selects from a list of disassembly styles. The
22094 @code{"std"} style is the standard style.
22096 @item show arm disassembler
22098 Show the current disassembly style.
22100 @item set arm apcs32
22101 @cindex ARM 32-bit mode
22102 This command toggles ARM operation mode between 32-bit and 26-bit.
22104 @item show arm apcs32
22105 Display the current usage of the ARM 32-bit mode.
22107 @item set arm fpu @var{fputype}
22108 This command sets the ARM floating-point unit (FPU) type. The
22109 argument @var{fputype} can be one of these:
22113 Determine the FPU type by querying the OS ABI.
22115 Software FPU, with mixed-endian doubles on little-endian ARM
22118 GCC-compiled FPA co-processor.
22120 Software FPU with pure-endian doubles.
22126 Show the current type of the FPU.
22129 This command forces @value{GDBN} to use the specified ABI.
22132 Show the currently used ABI.
22134 @item set arm fallback-mode (arm|thumb|auto)
22135 @value{GDBN} uses the symbol table, when available, to determine
22136 whether instructions are ARM or Thumb. This command controls
22137 @value{GDBN}'s default behavior when the symbol table is not
22138 available. The default is @samp{auto}, which causes @value{GDBN} to
22139 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22142 @item show arm fallback-mode
22143 Show the current fallback instruction mode.
22145 @item set arm force-mode (arm|thumb|auto)
22146 This command overrides use of the symbol table to determine whether
22147 instructions are ARM or Thumb. The default is @samp{auto}, which
22148 causes @value{GDBN} to use the symbol table and then the setting
22149 of @samp{set arm fallback-mode}.
22151 @item show arm force-mode
22152 Show the current forced instruction mode.
22154 @item set debug arm
22155 Toggle whether to display ARM-specific debugging messages from the ARM
22156 target support subsystem.
22158 @item show debug arm
22159 Show whether ARM-specific debugging messages are enabled.
22163 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22164 The @value{GDBN} ARM simulator accepts the following optional arguments.
22167 @item --swi-support=@var{type}
22168 Tell the simulator which SWI interfaces to support. The argument
22169 @var{type} may be a comma separated list of the following values.
22170 The default value is @code{all}.
22185 The Motorola m68k configuration includes ColdFire support.
22188 @subsection MicroBlaze
22189 @cindex Xilinx MicroBlaze
22190 @cindex XMD, Xilinx Microprocessor Debugger
22192 The MicroBlaze is a soft-core processor supported on various Xilinx
22193 FPGAs, such as Spartan or Virtex series. Boards with these processors
22194 usually have JTAG ports which connect to a host system running the Xilinx
22195 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22196 This host system is used to download the configuration bitstream to
22197 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22198 communicates with the target board using the JTAG interface and
22199 presents a @code{gdbserver} interface to the board. By default
22200 @code{xmd} uses port @code{1234}. (While it is possible to change
22201 this default port, it requires the use of undocumented @code{xmd}
22202 commands. Contact Xilinx support if you need to do this.)
22204 Use these GDB commands to connect to the MicroBlaze target processor.
22207 @item target remote :1234
22208 Use this command to connect to the target if you are running @value{GDBN}
22209 on the same system as @code{xmd}.
22211 @item target remote @var{xmd-host}:1234
22212 Use this command to connect to the target if it is connected to @code{xmd}
22213 running on a different system named @var{xmd-host}.
22216 Use this command to download a program to the MicroBlaze target.
22218 @item set debug microblaze @var{n}
22219 Enable MicroBlaze-specific debugging messages if non-zero.
22221 @item show debug microblaze @var{n}
22222 Show MicroBlaze-specific debugging level.
22225 @node MIPS Embedded
22226 @subsection @acronym{MIPS} Embedded
22229 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22232 @item set mipsfpu double
22233 @itemx set mipsfpu single
22234 @itemx set mipsfpu none
22235 @itemx set mipsfpu auto
22236 @itemx show mipsfpu
22237 @kindex set mipsfpu
22238 @kindex show mipsfpu
22239 @cindex @acronym{MIPS} remote floating point
22240 @cindex floating point, @acronym{MIPS} remote
22241 If your target board does not support the @acronym{MIPS} floating point
22242 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22243 need this, you may wish to put the command in your @value{GDBN} init
22244 file). This tells @value{GDBN} how to find the return value of
22245 functions which return floating point values. It also allows
22246 @value{GDBN} to avoid saving the floating point registers when calling
22247 functions on the board. If you are using a floating point coprocessor
22248 with only single precision floating point support, as on the @sc{r4650}
22249 processor, use the command @samp{set mipsfpu single}. The default
22250 double precision floating point coprocessor may be selected using
22251 @samp{set mipsfpu double}.
22253 In previous versions the only choices were double precision or no
22254 floating point, so @samp{set mipsfpu on} will select double precision
22255 and @samp{set mipsfpu off} will select no floating point.
22257 As usual, you can inquire about the @code{mipsfpu} variable with
22258 @samp{show mipsfpu}.
22261 @node PowerPC Embedded
22262 @subsection PowerPC Embedded
22264 @cindex DVC register
22265 @value{GDBN} supports using the DVC (Data Value Compare) register to
22266 implement in hardware simple hardware watchpoint conditions of the form:
22269 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22270 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22273 The DVC register will be automatically used when @value{GDBN} detects
22274 such pattern in a condition expression, and the created watchpoint uses one
22275 debug register (either the @code{exact-watchpoints} option is on and the
22276 variable is scalar, or the variable has a length of one byte). This feature
22277 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22280 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22281 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22282 in which case watchpoints using only one debug register are created when
22283 watching variables of scalar types.
22285 You can create an artificial array to watch an arbitrary memory
22286 region using one of the following commands (@pxref{Expressions}):
22289 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22290 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22293 PowerPC embedded processors support masked watchpoints. See the discussion
22294 about the @code{mask} argument in @ref{Set Watchpoints}.
22296 @cindex ranged breakpoint
22297 PowerPC embedded processors support hardware accelerated
22298 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22299 the inferior whenever it executes an instruction at any address within
22300 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22301 use the @code{break-range} command.
22303 @value{GDBN} provides the following PowerPC-specific commands:
22306 @kindex break-range
22307 @item break-range @var{start-location}, @var{end-location}
22308 Set a breakpoint for an address range given by
22309 @var{start-location} and @var{end-location}, which can specify a function name,
22310 a line number, an offset of lines from the current line or from the start
22311 location, or an address of an instruction (see @ref{Specify Location},
22312 for a list of all the possible ways to specify a @var{location}.)
22313 The breakpoint will stop execution of the inferior whenever it
22314 executes an instruction at any address within the specified range,
22315 (including @var{start-location} and @var{end-location}.)
22317 @kindex set powerpc
22318 @item set powerpc soft-float
22319 @itemx show powerpc soft-float
22320 Force @value{GDBN} to use (or not use) a software floating point calling
22321 convention. By default, @value{GDBN} selects the calling convention based
22322 on the selected architecture and the provided executable file.
22324 @item set powerpc vector-abi
22325 @itemx show powerpc vector-abi
22326 Force @value{GDBN} to use the specified calling convention for vector
22327 arguments and return values. The valid options are @samp{auto};
22328 @samp{generic}, to avoid vector registers even if they are present;
22329 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22330 registers. By default, @value{GDBN} selects the calling convention
22331 based on the selected architecture and the provided executable file.
22333 @item set powerpc exact-watchpoints
22334 @itemx show powerpc exact-watchpoints
22335 Allow @value{GDBN} to use only one debug register when watching a variable
22336 of scalar type, thus assuming that the variable is accessed through the
22337 address of its first byte.
22342 @subsection Atmel AVR
22345 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22346 following AVR-specific commands:
22349 @item info io_registers
22350 @kindex info io_registers@r{, AVR}
22351 @cindex I/O registers (Atmel AVR)
22352 This command displays information about the AVR I/O registers. For
22353 each register, @value{GDBN} prints its number and value.
22360 When configured for debugging CRIS, @value{GDBN} provides the
22361 following CRIS-specific commands:
22364 @item set cris-version @var{ver}
22365 @cindex CRIS version
22366 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22367 The CRIS version affects register names and sizes. This command is useful in
22368 case autodetection of the CRIS version fails.
22370 @item show cris-version
22371 Show the current CRIS version.
22373 @item set cris-dwarf2-cfi
22374 @cindex DWARF-2 CFI and CRIS
22375 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22376 Change to @samp{off} when using @code{gcc-cris} whose version is below
22379 @item show cris-dwarf2-cfi
22380 Show the current state of using DWARF-2 CFI.
22382 @item set cris-mode @var{mode}
22384 Set the current CRIS mode to @var{mode}. It should only be changed when
22385 debugging in guru mode, in which case it should be set to
22386 @samp{guru} (the default is @samp{normal}).
22388 @item show cris-mode
22389 Show the current CRIS mode.
22393 @subsection Renesas Super-H
22396 For the Renesas Super-H processor, @value{GDBN} provides these
22400 @item set sh calling-convention @var{convention}
22401 @kindex set sh calling-convention
22402 Set the calling-convention used when calling functions from @value{GDBN}.
22403 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22404 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22405 convention. If the DWARF-2 information of the called function specifies
22406 that the function follows the Renesas calling convention, the function
22407 is called using the Renesas calling convention. If the calling convention
22408 is set to @samp{renesas}, the Renesas calling convention is always used,
22409 regardless of the DWARF-2 information. This can be used to override the
22410 default of @samp{gcc} if debug information is missing, or the compiler
22411 does not emit the DWARF-2 calling convention entry for a function.
22413 @item show sh calling-convention
22414 @kindex show sh calling-convention
22415 Show the current calling convention setting.
22420 @node Architectures
22421 @section Architectures
22423 This section describes characteristics of architectures that affect
22424 all uses of @value{GDBN} with the architecture, both native and cross.
22431 * HPPA:: HP PA architecture
22432 * SPU:: Cell Broadband Engine SPU architecture
22438 @subsection AArch64
22439 @cindex AArch64 support
22441 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22442 following special commands:
22445 @item set debug aarch64
22446 @kindex set debug aarch64
22447 This command determines whether AArch64 architecture-specific debugging
22448 messages are to be displayed.
22450 @item show debug aarch64
22451 Show whether AArch64 debugging messages are displayed.
22456 @subsection x86 Architecture-specific Issues
22459 @item set struct-convention @var{mode}
22460 @kindex set struct-convention
22461 @cindex struct return convention
22462 @cindex struct/union returned in registers
22463 Set the convention used by the inferior to return @code{struct}s and
22464 @code{union}s from functions to @var{mode}. Possible values of
22465 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22466 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22467 are returned on the stack, while @code{"reg"} means that a
22468 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22469 be returned in a register.
22471 @item show struct-convention
22472 @kindex show struct-convention
22473 Show the current setting of the convention to return @code{struct}s
22478 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22479 @cindex Intel Memory Protection Extensions (MPX).
22481 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22482 @footnote{The register named with capital letters represent the architecture
22483 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22484 which are the lower bound and upper bound. Bounds are effective addresses or
22485 memory locations. The upper bounds are architecturally represented in 1's
22486 complement form. A bound having lower bound = 0, and upper bound = 0
22487 (1's complement of all bits set) will allow access to the entire address space.
22489 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22490 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22491 display the upper bound performing the complement of one operation on the
22492 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22493 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22494 can also be noted that the upper bounds are inclusive.
22496 As an example, assume that the register BND0 holds bounds for a pointer having
22497 access allowed for the range between 0x32 and 0x71. The values present on
22498 bnd0raw and bnd registers are presented as follows:
22501 bnd0raw = @{0x32, 0xffffffff8e@}
22502 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22505 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22506 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22507 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22508 Python, the display includes the memory size, in bits, accessible to
22511 Bounds can also be stored in bounds tables, which are stored in
22512 application memory. These tables store bounds for pointers by specifying
22513 the bounds pointer's value along with its bounds. Evaluating and changing
22514 bounds located in bound tables is therefore interesting while investigating
22515 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22518 @item show mpx bound @var{pointer}
22519 @kindex show mpx bound
22520 Display bounds of the given @var{pointer}.
22522 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22523 @kindex set mpx bound
22524 Set the bounds of a pointer in the bound table.
22525 This command takes three parameters: @var{pointer} is the pointers
22526 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22527 for lower and upper bounds respectively.
22533 See the following section.
22536 @subsection @acronym{MIPS}
22538 @cindex stack on Alpha
22539 @cindex stack on @acronym{MIPS}
22540 @cindex Alpha stack
22541 @cindex @acronym{MIPS} stack
22542 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22543 sometimes requires @value{GDBN} to search backward in the object code to
22544 find the beginning of a function.
22546 @cindex response time, @acronym{MIPS} debugging
22547 To improve response time (especially for embedded applications, where
22548 @value{GDBN} may be restricted to a slow serial line for this search)
22549 you may want to limit the size of this search, using one of these
22553 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22554 @item set heuristic-fence-post @var{limit}
22555 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22556 search for the beginning of a function. A value of @var{0} (the
22557 default) means there is no limit. However, except for @var{0}, the
22558 larger the limit the more bytes @code{heuristic-fence-post} must search
22559 and therefore the longer it takes to run. You should only need to use
22560 this command when debugging a stripped executable.
22562 @item show heuristic-fence-post
22563 Display the current limit.
22567 These commands are available @emph{only} when @value{GDBN} is configured
22568 for debugging programs on Alpha or @acronym{MIPS} processors.
22570 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22574 @item set mips abi @var{arg}
22575 @kindex set mips abi
22576 @cindex set ABI for @acronym{MIPS}
22577 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22578 values of @var{arg} are:
22582 The default ABI associated with the current binary (this is the
22592 @item show mips abi
22593 @kindex show mips abi
22594 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22596 @item set mips compression @var{arg}
22597 @kindex set mips compression
22598 @cindex code compression, @acronym{MIPS}
22599 Tell @value{GDBN} which @acronym{MIPS} compressed
22600 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22601 inferior. @value{GDBN} uses this for code disassembly and other
22602 internal interpretation purposes. This setting is only referred to
22603 when no executable has been associated with the debugging session or
22604 the executable does not provide information about the encoding it uses.
22605 Otherwise this setting is automatically updated from information
22606 provided by the executable.
22608 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22609 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22610 executables containing @acronym{MIPS16} code frequently are not
22611 identified as such.
22613 This setting is ``sticky''; that is, it retains its value across
22614 debugging sessions until reset either explicitly with this command or
22615 implicitly from an executable.
22617 The compiler and/or assembler typically add symbol table annotations to
22618 identify functions compiled for the @acronym{MIPS16} or
22619 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22620 are present, @value{GDBN} uses them in preference to the global
22621 compressed @acronym{ISA} encoding setting.
22623 @item show mips compression
22624 @kindex show mips compression
22625 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22626 @value{GDBN} to debug the inferior.
22629 @itemx show mipsfpu
22630 @xref{MIPS Embedded, set mipsfpu}.
22632 @item set mips mask-address @var{arg}
22633 @kindex set mips mask-address
22634 @cindex @acronym{MIPS} addresses, masking
22635 This command determines whether the most-significant 32 bits of 64-bit
22636 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22637 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22638 setting, which lets @value{GDBN} determine the correct value.
22640 @item show mips mask-address
22641 @kindex show mips mask-address
22642 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22645 @item set remote-mips64-transfers-32bit-regs
22646 @kindex set remote-mips64-transfers-32bit-regs
22647 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22648 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22649 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22650 and 64 bits for other registers, set this option to @samp{on}.
22652 @item show remote-mips64-transfers-32bit-regs
22653 @kindex show remote-mips64-transfers-32bit-regs
22654 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22656 @item set debug mips
22657 @kindex set debug mips
22658 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22659 target code in @value{GDBN}.
22661 @item show debug mips
22662 @kindex show debug mips
22663 Show the current setting of @acronym{MIPS} debugging messages.
22669 @cindex HPPA support
22671 When @value{GDBN} is debugging the HP PA architecture, it provides the
22672 following special commands:
22675 @item set debug hppa
22676 @kindex set debug hppa
22677 This command determines whether HPPA architecture-specific debugging
22678 messages are to be displayed.
22680 @item show debug hppa
22681 Show whether HPPA debugging messages are displayed.
22683 @item maint print unwind @var{address}
22684 @kindex maint print unwind@r{, HPPA}
22685 This command displays the contents of the unwind table entry at the
22686 given @var{address}.
22692 @subsection Cell Broadband Engine SPU architecture
22693 @cindex Cell Broadband Engine
22696 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22697 it provides the following special commands:
22700 @item info spu event
22702 Display SPU event facility status. Shows current event mask
22703 and pending event status.
22705 @item info spu signal
22706 Display SPU signal notification facility status. Shows pending
22707 signal-control word and signal notification mode of both signal
22708 notification channels.
22710 @item info spu mailbox
22711 Display SPU mailbox facility status. Shows all pending entries,
22712 in order of processing, in each of the SPU Write Outbound,
22713 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22716 Display MFC DMA status. Shows all pending commands in the MFC
22717 DMA queue. For each entry, opcode, tag, class IDs, effective
22718 and local store addresses and transfer size are shown.
22720 @item info spu proxydma
22721 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22722 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22723 and local store addresses and transfer size are shown.
22727 When @value{GDBN} is debugging a combined PowerPC/SPU application
22728 on the Cell Broadband Engine, it provides in addition the following
22732 @item set spu stop-on-load @var{arg}
22734 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22735 will give control to the user when a new SPE thread enters its @code{main}
22736 function. The default is @code{off}.
22738 @item show spu stop-on-load
22740 Show whether to stop for new SPE threads.
22742 @item set spu auto-flush-cache @var{arg}
22743 Set whether to automatically flush the software-managed cache. When set to
22744 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22745 cache to be flushed whenever SPE execution stops. This provides a consistent
22746 view of PowerPC memory that is accessed via the cache. If an application
22747 does not use the software-managed cache, this option has no effect.
22749 @item show spu auto-flush-cache
22750 Show whether to automatically flush the software-managed cache.
22755 @subsection PowerPC
22756 @cindex PowerPC architecture
22758 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22759 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22760 numbers stored in the floating point registers. These values must be stored
22761 in two consecutive registers, always starting at an even register like
22762 @code{f0} or @code{f2}.
22764 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22765 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22766 @code{f2} and @code{f3} for @code{$dl1} and so on.
22768 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22769 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22772 @subsection Nios II
22773 @cindex Nios II architecture
22775 When @value{GDBN} is debugging the Nios II architecture,
22776 it provides the following special commands:
22780 @item set debug nios2
22781 @kindex set debug nios2
22782 This command turns on and off debugging messages for the Nios II
22783 target code in @value{GDBN}.
22785 @item show debug nios2
22786 @kindex show debug nios2
22787 Show the current setting of Nios II debugging messages.
22790 @node Controlling GDB
22791 @chapter Controlling @value{GDBN}
22793 You can alter the way @value{GDBN} interacts with you by using the
22794 @code{set} command. For commands controlling how @value{GDBN} displays
22795 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22800 * Editing:: Command editing
22801 * Command History:: Command history
22802 * Screen Size:: Screen size
22803 * Numbers:: Numbers
22804 * ABI:: Configuring the current ABI
22805 * Auto-loading:: Automatically loading associated files
22806 * Messages/Warnings:: Optional warnings and messages
22807 * Debugging Output:: Optional messages about internal happenings
22808 * Other Misc Settings:: Other Miscellaneous Settings
22816 @value{GDBN} indicates its readiness to read a command by printing a string
22817 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22818 can change the prompt string with the @code{set prompt} command. For
22819 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22820 the prompt in one of the @value{GDBN} sessions so that you can always tell
22821 which one you are talking to.
22823 @emph{Note:} @code{set prompt} does not add a space for you after the
22824 prompt you set. This allows you to set a prompt which ends in a space
22825 or a prompt that does not.
22829 @item set prompt @var{newprompt}
22830 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22832 @kindex show prompt
22834 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22837 Versions of @value{GDBN} that ship with Python scripting enabled have
22838 prompt extensions. The commands for interacting with these extensions
22842 @kindex set extended-prompt
22843 @item set extended-prompt @var{prompt}
22844 Set an extended prompt that allows for substitutions.
22845 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22846 substitution. Any escape sequences specified as part of the prompt
22847 string are replaced with the corresponding strings each time the prompt
22853 set extended-prompt Current working directory: \w (gdb)
22856 Note that when an extended-prompt is set, it takes control of the
22857 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22859 @kindex show extended-prompt
22860 @item show extended-prompt
22861 Prints the extended prompt. Any escape sequences specified as part of
22862 the prompt string with @code{set extended-prompt}, are replaced with the
22863 corresponding strings each time the prompt is displayed.
22867 @section Command Editing
22869 @cindex command line editing
22871 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22872 @sc{gnu} library provides consistent behavior for programs which provide a
22873 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22874 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22875 substitution, and a storage and recall of command history across
22876 debugging sessions.
22878 You may control the behavior of command line editing in @value{GDBN} with the
22879 command @code{set}.
22882 @kindex set editing
22885 @itemx set editing on
22886 Enable command line editing (enabled by default).
22888 @item set editing off
22889 Disable command line editing.
22891 @kindex show editing
22893 Show whether command line editing is enabled.
22896 @ifset SYSTEM_READLINE
22897 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22899 @ifclear SYSTEM_READLINE
22900 @xref{Command Line Editing},
22902 for more details about the Readline
22903 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22904 encouraged to read that chapter.
22906 @node Command History
22907 @section Command History
22908 @cindex command history
22910 @value{GDBN} can keep track of the commands you type during your
22911 debugging sessions, so that you can be certain of precisely what
22912 happened. Use these commands to manage the @value{GDBN} command
22915 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22916 package, to provide the history facility.
22917 @ifset SYSTEM_READLINE
22918 @xref{Using History Interactively, , , history, GNU History Library},
22920 @ifclear SYSTEM_READLINE
22921 @xref{Using History Interactively},
22923 for the detailed description of the History library.
22925 To issue a command to @value{GDBN} without affecting certain aspects of
22926 the state which is seen by users, prefix it with @samp{server }
22927 (@pxref{Server Prefix}). This
22928 means that this command will not affect the command history, nor will it
22929 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22930 pressed on a line by itself.
22932 @cindex @code{server}, command prefix
22933 The server prefix does not affect the recording of values into the value
22934 history; to print a value without recording it into the value history,
22935 use the @code{output} command instead of the @code{print} command.
22937 Here is the description of @value{GDBN} commands related to command
22941 @cindex history substitution
22942 @cindex history file
22943 @kindex set history filename
22944 @cindex @env{GDBHISTFILE}, environment variable
22945 @item set history filename @var{fname}
22946 Set the name of the @value{GDBN} command history file to @var{fname}.
22947 This is the file where @value{GDBN} reads an initial command history
22948 list, and where it writes the command history from this session when it
22949 exits. You can access this list through history expansion or through
22950 the history command editing characters listed below. This file defaults
22951 to the value of the environment variable @code{GDBHISTFILE}, or to
22952 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22955 @cindex save command history
22956 @kindex set history save
22957 @item set history save
22958 @itemx set history save on
22959 Record command history in a file, whose name may be specified with the
22960 @code{set history filename} command. By default, this option is disabled.
22962 @item set history save off
22963 Stop recording command history in a file.
22965 @cindex history size
22966 @kindex set history size
22967 @cindex @env{GDBHISTSIZE}, environment variable
22968 @item set history size @var{size}
22969 @itemx set history size unlimited
22970 Set the number of commands which @value{GDBN} keeps in its history list.
22971 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22972 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22973 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22974 either a negative number or the empty string, then the number of commands
22975 @value{GDBN} keeps in the history list is unlimited.
22977 @cindex remove duplicate history
22978 @kindex set history remove-duplicates
22979 @item set history remove-duplicates @var{count}
22980 @itemx set history remove-duplicates unlimited
22981 Control the removal of duplicate history entries in the command history list.
22982 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22983 history entries and remove the first entry that is a duplicate of the current
22984 entry being added to the command history list. If @var{count} is
22985 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22986 removal of duplicate history entries is disabled.
22988 Only history entries added during the current session are considered for
22989 removal. This option is set to 0 by default.
22993 History expansion assigns special meaning to the character @kbd{!}.
22994 @ifset SYSTEM_READLINE
22995 @xref{Event Designators, , , history, GNU History Library},
22997 @ifclear SYSTEM_READLINE
22998 @xref{Event Designators},
23002 @cindex history expansion, turn on/off
23003 Since @kbd{!} is also the logical not operator in C, history expansion
23004 is off by default. If you decide to enable history expansion with the
23005 @code{set history expansion on} command, you may sometimes need to
23006 follow @kbd{!} (when it is used as logical not, in an expression) with
23007 a space or a tab to prevent it from being expanded. The readline
23008 history facilities do not attempt substitution on the strings
23009 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23011 The commands to control history expansion are:
23014 @item set history expansion on
23015 @itemx set history expansion
23016 @kindex set history expansion
23017 Enable history expansion. History expansion is off by default.
23019 @item set history expansion off
23020 Disable history expansion.
23023 @kindex show history
23025 @itemx show history filename
23026 @itemx show history save
23027 @itemx show history size
23028 @itemx show history expansion
23029 These commands display the state of the @value{GDBN} history parameters.
23030 @code{show history} by itself displays all four states.
23035 @kindex show commands
23036 @cindex show last commands
23037 @cindex display command history
23038 @item show commands
23039 Display the last ten commands in the command history.
23041 @item show commands @var{n}
23042 Print ten commands centered on command number @var{n}.
23044 @item show commands +
23045 Print ten commands just after the commands last printed.
23049 @section Screen Size
23050 @cindex size of screen
23051 @cindex screen size
23054 @cindex pauses in output
23056 Certain commands to @value{GDBN} may produce large amounts of
23057 information output to the screen. To help you read all of it,
23058 @value{GDBN} pauses and asks you for input at the end of each page of
23059 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23060 to discard the remaining output. Also, the screen width setting
23061 determines when to wrap lines of output. Depending on what is being
23062 printed, @value{GDBN} tries to break the line at a readable place,
23063 rather than simply letting it overflow onto the following line.
23065 Normally @value{GDBN} knows the size of the screen from the terminal
23066 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23067 together with the value of the @code{TERM} environment variable and the
23068 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23069 you can override it with the @code{set height} and @code{set
23076 @kindex show height
23077 @item set height @var{lpp}
23078 @itemx set height unlimited
23080 @itemx set width @var{cpl}
23081 @itemx set width unlimited
23083 These @code{set} commands specify a screen height of @var{lpp} lines and
23084 a screen width of @var{cpl} characters. The associated @code{show}
23085 commands display the current settings.
23087 If you specify a height of either @code{unlimited} or zero lines,
23088 @value{GDBN} does not pause during output no matter how long the
23089 output is. This is useful if output is to a file or to an editor
23092 Likewise, you can specify @samp{set width unlimited} or @samp{set
23093 width 0} to prevent @value{GDBN} from wrapping its output.
23095 @item set pagination on
23096 @itemx set pagination off
23097 @kindex set pagination
23098 Turn the output pagination on or off; the default is on. Turning
23099 pagination off is the alternative to @code{set height unlimited}. Note that
23100 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23101 Options, -batch}) also automatically disables pagination.
23103 @item show pagination
23104 @kindex show pagination
23105 Show the current pagination mode.
23110 @cindex number representation
23111 @cindex entering numbers
23113 You can always enter numbers in octal, decimal, or hexadecimal in
23114 @value{GDBN} by the usual conventions: octal numbers begin with
23115 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23116 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23117 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23118 10; likewise, the default display for numbers---when no particular
23119 format is specified---is base 10. You can change the default base for
23120 both input and output with the commands described below.
23123 @kindex set input-radix
23124 @item set input-radix @var{base}
23125 Set the default base for numeric input. Supported choices
23126 for @var{base} are decimal 8, 10, or 16. The base must itself be
23127 specified either unambiguously or using the current input radix; for
23131 set input-radix 012
23132 set input-radix 10.
23133 set input-radix 0xa
23137 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23138 leaves the input radix unchanged, no matter what it was, since
23139 @samp{10}, being without any leading or trailing signs of its base, is
23140 interpreted in the current radix. Thus, if the current radix is 16,
23141 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23144 @kindex set output-radix
23145 @item set output-radix @var{base}
23146 Set the default base for numeric display. Supported choices
23147 for @var{base} are decimal 8, 10, or 16. The base must itself be
23148 specified either unambiguously or using the current input radix.
23150 @kindex show input-radix
23151 @item show input-radix
23152 Display the current default base for numeric input.
23154 @kindex show output-radix
23155 @item show output-radix
23156 Display the current default base for numeric display.
23158 @item set radix @r{[}@var{base}@r{]}
23162 These commands set and show the default base for both input and output
23163 of numbers. @code{set radix} sets the radix of input and output to
23164 the same base; without an argument, it resets the radix back to its
23165 default value of 10.
23170 @section Configuring the Current ABI
23172 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23173 application automatically. However, sometimes you need to override its
23174 conclusions. Use these commands to manage @value{GDBN}'s view of the
23180 @cindex Newlib OS ABI and its influence on the longjmp handling
23182 One @value{GDBN} configuration can debug binaries for multiple operating
23183 system targets, either via remote debugging or native emulation.
23184 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23185 but you can override its conclusion using the @code{set osabi} command.
23186 One example where this is useful is in debugging of binaries which use
23187 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23188 not have the same identifying marks that the standard C library for your
23191 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23192 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23193 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23194 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23198 Show the OS ABI currently in use.
23201 With no argument, show the list of registered available OS ABI's.
23203 @item set osabi @var{abi}
23204 Set the current OS ABI to @var{abi}.
23207 @cindex float promotion
23209 Generally, the way that an argument of type @code{float} is passed to a
23210 function depends on whether the function is prototyped. For a prototyped
23211 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23212 according to the architecture's convention for @code{float}. For unprototyped
23213 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23214 @code{double} and then passed.
23216 Unfortunately, some forms of debug information do not reliably indicate whether
23217 a function is prototyped. If @value{GDBN} calls a function that is not marked
23218 as prototyped, it consults @kbd{set coerce-float-to-double}.
23221 @kindex set coerce-float-to-double
23222 @item set coerce-float-to-double
23223 @itemx set coerce-float-to-double on
23224 Arguments of type @code{float} will be promoted to @code{double} when passed
23225 to an unprototyped function. This is the default setting.
23227 @item set coerce-float-to-double off
23228 Arguments of type @code{float} will be passed directly to unprototyped
23231 @kindex show coerce-float-to-double
23232 @item show coerce-float-to-double
23233 Show the current setting of promoting @code{float} to @code{double}.
23237 @kindex show cp-abi
23238 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23239 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23240 used to build your application. @value{GDBN} only fully supports
23241 programs with a single C@t{++} ABI; if your program contains code using
23242 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23243 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23244 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23245 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23246 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23247 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23252 Show the C@t{++} ABI currently in use.
23255 With no argument, show the list of supported C@t{++} ABI's.
23257 @item set cp-abi @var{abi}
23258 @itemx set cp-abi auto
23259 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23263 @section Automatically loading associated files
23264 @cindex auto-loading
23266 @value{GDBN} sometimes reads files with commands and settings automatically,
23267 without being explicitly told so by the user. We call this feature
23268 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23269 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23270 results or introduce security risks (e.g., if the file comes from untrusted
23274 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23275 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23277 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23278 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23281 There are various kinds of files @value{GDBN} can automatically load.
23282 In addition to these files, @value{GDBN} supports auto-loading code written
23283 in various extension languages. @xref{Auto-loading extensions}.
23285 Note that loading of these associated files (including the local @file{.gdbinit}
23286 file) requires accordingly configured @code{auto-load safe-path}
23287 (@pxref{Auto-loading safe path}).
23289 For these reasons, @value{GDBN} includes commands and options to let you
23290 control when to auto-load files and which files should be auto-loaded.
23293 @anchor{set auto-load off}
23294 @kindex set auto-load off
23295 @item set auto-load off
23296 Globally disable loading of all auto-loaded files.
23297 You may want to use this command with the @samp{-iex} option
23298 (@pxref{Option -init-eval-command}) such as:
23300 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23303 Be aware that system init file (@pxref{System-wide configuration})
23304 and init files from your home directory (@pxref{Home Directory Init File})
23305 still get read (as they come from generally trusted directories).
23306 To prevent @value{GDBN} from auto-loading even those init files, use the
23307 @option{-nx} option (@pxref{Mode Options}), in addition to
23308 @code{set auto-load no}.
23310 @anchor{show auto-load}
23311 @kindex show auto-load
23312 @item show auto-load
23313 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23317 (gdb) show auto-load
23318 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23319 libthread-db: Auto-loading of inferior specific libthread_db is on.
23320 local-gdbinit: Auto-loading of .gdbinit script from current directory
23322 python-scripts: Auto-loading of Python scripts is on.
23323 safe-path: List of directories from which it is safe to auto-load files
23324 is $debugdir:$datadir/auto-load.
23325 scripts-directory: List of directories from which to load auto-loaded scripts
23326 is $debugdir:$datadir/auto-load.
23329 @anchor{info auto-load}
23330 @kindex info auto-load
23331 @item info auto-load
23332 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23336 (gdb) info auto-load
23339 Yes /home/user/gdb/gdb-gdb.gdb
23340 libthread-db: No auto-loaded libthread-db.
23341 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23345 Yes /home/user/gdb/gdb-gdb.py
23349 These are @value{GDBN} control commands for the auto-loading:
23351 @multitable @columnfractions .5 .5
23352 @item @xref{set auto-load off}.
23353 @tab Disable auto-loading globally.
23354 @item @xref{show auto-load}.
23355 @tab Show setting of all kinds of files.
23356 @item @xref{info auto-load}.
23357 @tab Show state of all kinds of files.
23358 @item @xref{set auto-load gdb-scripts}.
23359 @tab Control for @value{GDBN} command scripts.
23360 @item @xref{show auto-load gdb-scripts}.
23361 @tab Show setting of @value{GDBN} command scripts.
23362 @item @xref{info auto-load gdb-scripts}.
23363 @tab Show state of @value{GDBN} command scripts.
23364 @item @xref{set auto-load python-scripts}.
23365 @tab Control for @value{GDBN} Python scripts.
23366 @item @xref{show auto-load python-scripts}.
23367 @tab Show setting of @value{GDBN} Python scripts.
23368 @item @xref{info auto-load python-scripts}.
23369 @tab Show state of @value{GDBN} Python scripts.
23370 @item @xref{set auto-load guile-scripts}.
23371 @tab Control for @value{GDBN} Guile scripts.
23372 @item @xref{show auto-load guile-scripts}.
23373 @tab Show setting of @value{GDBN} Guile scripts.
23374 @item @xref{info auto-load guile-scripts}.
23375 @tab Show state of @value{GDBN} Guile scripts.
23376 @item @xref{set auto-load scripts-directory}.
23377 @tab Control for @value{GDBN} auto-loaded scripts location.
23378 @item @xref{show auto-load scripts-directory}.
23379 @tab Show @value{GDBN} auto-loaded scripts location.
23380 @item @xref{add-auto-load-scripts-directory}.
23381 @tab Add directory for auto-loaded scripts location list.
23382 @item @xref{set auto-load local-gdbinit}.
23383 @tab Control for init file in the current directory.
23384 @item @xref{show auto-load local-gdbinit}.
23385 @tab Show setting of init file in the current directory.
23386 @item @xref{info auto-load local-gdbinit}.
23387 @tab Show state of init file in the current directory.
23388 @item @xref{set auto-load libthread-db}.
23389 @tab Control for thread debugging library.
23390 @item @xref{show auto-load libthread-db}.
23391 @tab Show setting of thread debugging library.
23392 @item @xref{info auto-load libthread-db}.
23393 @tab Show state of thread debugging library.
23394 @item @xref{set auto-load safe-path}.
23395 @tab Control directories trusted for automatic loading.
23396 @item @xref{show auto-load safe-path}.
23397 @tab Show directories trusted for automatic loading.
23398 @item @xref{add-auto-load-safe-path}.
23399 @tab Add directory trusted for automatic loading.
23402 @node Init File in the Current Directory
23403 @subsection Automatically loading init file in the current directory
23404 @cindex auto-loading init file in the current directory
23406 By default, @value{GDBN} reads and executes the canned sequences of commands
23407 from init file (if any) in the current working directory,
23408 see @ref{Init File in the Current Directory during Startup}.
23410 Note that loading of this local @file{.gdbinit} file also requires accordingly
23411 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23414 @anchor{set auto-load local-gdbinit}
23415 @kindex set auto-load local-gdbinit
23416 @item set auto-load local-gdbinit [on|off]
23417 Enable or disable the auto-loading of canned sequences of commands
23418 (@pxref{Sequences}) found in init file in the current directory.
23420 @anchor{show auto-load local-gdbinit}
23421 @kindex show auto-load local-gdbinit
23422 @item show auto-load local-gdbinit
23423 Show whether auto-loading of canned sequences of commands from init file in the
23424 current directory is enabled or disabled.
23426 @anchor{info auto-load local-gdbinit}
23427 @kindex info auto-load local-gdbinit
23428 @item info auto-load local-gdbinit
23429 Print whether canned sequences of commands from init file in the
23430 current directory have been auto-loaded.
23433 @node libthread_db.so.1 file
23434 @subsection Automatically loading thread debugging library
23435 @cindex auto-loading libthread_db.so.1
23437 This feature is currently present only on @sc{gnu}/Linux native hosts.
23439 @value{GDBN} reads in some cases thread debugging library from places specific
23440 to the inferior (@pxref{set libthread-db-search-path}).
23442 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23443 without checking this @samp{set auto-load libthread-db} switch as system
23444 libraries have to be trusted in general. In all other cases of
23445 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23446 auto-load libthread-db} is enabled before trying to open such thread debugging
23449 Note that loading of this debugging library also requires accordingly configured
23450 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23453 @anchor{set auto-load libthread-db}
23454 @kindex set auto-load libthread-db
23455 @item set auto-load libthread-db [on|off]
23456 Enable or disable the auto-loading of inferior specific thread debugging library.
23458 @anchor{show auto-load libthread-db}
23459 @kindex show auto-load libthread-db
23460 @item show auto-load libthread-db
23461 Show whether auto-loading of inferior specific thread debugging library is
23462 enabled or disabled.
23464 @anchor{info auto-load libthread-db}
23465 @kindex info auto-load libthread-db
23466 @item info auto-load libthread-db
23467 Print the list of all loaded inferior specific thread debugging libraries and
23468 for each such library print list of inferior @var{pid}s using it.
23471 @node Auto-loading safe path
23472 @subsection Security restriction for auto-loading
23473 @cindex auto-loading safe-path
23475 As the files of inferior can come from untrusted source (such as submitted by
23476 an application user) @value{GDBN} does not always load any files automatically.
23477 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23478 directories trusted for loading files not explicitly requested by user.
23479 Each directory can also be a shell wildcard pattern.
23481 If the path is not set properly you will see a warning and the file will not
23486 Reading symbols from /home/user/gdb/gdb...done.
23487 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23488 declined by your `auto-load safe-path' set
23489 to "$debugdir:$datadir/auto-load".
23490 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23491 declined by your `auto-load safe-path' set
23492 to "$debugdir:$datadir/auto-load".
23496 To instruct @value{GDBN} to go ahead and use the init files anyway,
23497 invoke @value{GDBN} like this:
23500 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23503 The list of trusted directories is controlled by the following commands:
23506 @anchor{set auto-load safe-path}
23507 @kindex set auto-load safe-path
23508 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23509 Set the list of directories (and their subdirectories) trusted for automatic
23510 loading and execution of scripts. You can also enter a specific trusted file.
23511 Each directory can also be a shell wildcard pattern; wildcards do not match
23512 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23513 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23514 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23515 its default value as specified during @value{GDBN} compilation.
23517 The list of directories uses path separator (@samp{:} on GNU and Unix
23518 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23519 to the @env{PATH} environment variable.
23521 @anchor{show auto-load safe-path}
23522 @kindex show auto-load safe-path
23523 @item show auto-load safe-path
23524 Show the list of directories trusted for automatic loading and execution of
23527 @anchor{add-auto-load-safe-path}
23528 @kindex add-auto-load-safe-path
23529 @item add-auto-load-safe-path
23530 Add an entry (or list of entries) to the list of directories trusted for
23531 automatic loading and execution of scripts. Multiple entries may be delimited
23532 by the host platform path separator in use.
23535 This variable defaults to what @code{--with-auto-load-dir} has been configured
23536 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23537 substitution applies the same as for @ref{set auto-load scripts-directory}.
23538 The default @code{set auto-load safe-path} value can be also overriden by
23539 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23541 Setting this variable to @file{/} disables this security protection,
23542 corresponding @value{GDBN} configuration option is
23543 @option{--without-auto-load-safe-path}.
23544 This variable is supposed to be set to the system directories writable by the
23545 system superuser only. Users can add their source directories in init files in
23546 their home directories (@pxref{Home Directory Init File}). See also deprecated
23547 init file in the current directory
23548 (@pxref{Init File in the Current Directory during Startup}).
23550 To force @value{GDBN} to load the files it declined to load in the previous
23551 example, you could use one of the following ways:
23554 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23555 Specify this trusted directory (or a file) as additional component of the list.
23556 You have to specify also any existing directories displayed by
23557 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23559 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23560 Specify this directory as in the previous case but just for a single
23561 @value{GDBN} session.
23563 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23564 Disable auto-loading safety for a single @value{GDBN} session.
23565 This assumes all the files you debug during this @value{GDBN} session will come
23566 from trusted sources.
23568 @item @kbd{./configure --without-auto-load-safe-path}
23569 During compilation of @value{GDBN} you may disable any auto-loading safety.
23570 This assumes all the files you will ever debug with this @value{GDBN} come from
23574 On the other hand you can also explicitly forbid automatic files loading which
23575 also suppresses any such warning messages:
23578 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23579 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23581 @item @file{~/.gdbinit}: @samp{set auto-load no}
23582 Disable auto-loading globally for the user
23583 (@pxref{Home Directory Init File}). While it is improbable, you could also
23584 use system init file instead (@pxref{System-wide configuration}).
23587 This setting applies to the file names as entered by user. If no entry matches
23588 @value{GDBN} tries as a last resort to also resolve all the file names into
23589 their canonical form (typically resolving symbolic links) and compare the
23590 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23591 own before starting the comparison so a canonical form of directories is
23592 recommended to be entered.
23594 @node Auto-loading verbose mode
23595 @subsection Displaying files tried for auto-load
23596 @cindex auto-loading verbose mode
23598 For better visibility of all the file locations where you can place scripts to
23599 be auto-loaded with inferior --- or to protect yourself against accidental
23600 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23601 all the files attempted to be loaded. Both existing and non-existing files may
23604 For example the list of directories from which it is safe to auto-load files
23605 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23606 may not be too obvious while setting it up.
23609 (gdb) set debug auto-load on
23610 (gdb) file ~/src/t/true
23611 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23612 for objfile "/tmp/true".
23613 auto-load: Updating directories of "/usr:/opt".
23614 auto-load: Using directory "/usr".
23615 auto-load: Using directory "/opt".
23616 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23617 by your `auto-load safe-path' set to "/usr:/opt".
23621 @anchor{set debug auto-load}
23622 @kindex set debug auto-load
23623 @item set debug auto-load [on|off]
23624 Set whether to print the filenames attempted to be auto-loaded.
23626 @anchor{show debug auto-load}
23627 @kindex show debug auto-load
23628 @item show debug auto-load
23629 Show whether printing of the filenames attempted to be auto-loaded is turned
23633 @node Messages/Warnings
23634 @section Optional Warnings and Messages
23636 @cindex verbose operation
23637 @cindex optional warnings
23638 By default, @value{GDBN} is silent about its inner workings. If you are
23639 running on a slow machine, you may want to use the @code{set verbose}
23640 command. This makes @value{GDBN} tell you when it does a lengthy
23641 internal operation, so you will not think it has crashed.
23643 Currently, the messages controlled by @code{set verbose} are those
23644 which announce that the symbol table for a source file is being read;
23645 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23648 @kindex set verbose
23649 @item set verbose on
23650 Enables @value{GDBN} output of certain informational messages.
23652 @item set verbose off
23653 Disables @value{GDBN} output of certain informational messages.
23655 @kindex show verbose
23657 Displays whether @code{set verbose} is on or off.
23660 By default, if @value{GDBN} encounters bugs in the symbol table of an
23661 object file, it is silent; but if you are debugging a compiler, you may
23662 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23667 @kindex set complaints
23668 @item set complaints @var{limit}
23669 Permits @value{GDBN} to output @var{limit} complaints about each type of
23670 unusual symbols before becoming silent about the problem. Set
23671 @var{limit} to zero to suppress all complaints; set it to a large number
23672 to prevent complaints from being suppressed.
23674 @kindex show complaints
23675 @item show complaints
23676 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23680 @anchor{confirmation requests}
23681 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23682 lot of stupid questions to confirm certain commands. For example, if
23683 you try to run a program which is already running:
23687 The program being debugged has been started already.
23688 Start it from the beginning? (y or n)
23691 If you are willing to unflinchingly face the consequences of your own
23692 commands, you can disable this ``feature'':
23696 @kindex set confirm
23698 @cindex confirmation
23699 @cindex stupid questions
23700 @item set confirm off
23701 Disables confirmation requests. Note that running @value{GDBN} with
23702 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23703 automatically disables confirmation requests.
23705 @item set confirm on
23706 Enables confirmation requests (the default).
23708 @kindex show confirm
23710 Displays state of confirmation requests.
23714 @cindex command tracing
23715 If you need to debug user-defined commands or sourced files you may find it
23716 useful to enable @dfn{command tracing}. In this mode each command will be
23717 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23718 quantity denoting the call depth of each command.
23721 @kindex set trace-commands
23722 @cindex command scripts, debugging
23723 @item set trace-commands on
23724 Enable command tracing.
23725 @item set trace-commands off
23726 Disable command tracing.
23727 @item show trace-commands
23728 Display the current state of command tracing.
23731 @node Debugging Output
23732 @section Optional Messages about Internal Happenings
23733 @cindex optional debugging messages
23735 @value{GDBN} has commands that enable optional debugging messages from
23736 various @value{GDBN} subsystems; normally these commands are of
23737 interest to @value{GDBN} maintainers, or when reporting a bug. This
23738 section documents those commands.
23741 @kindex set exec-done-display
23742 @item set exec-done-display
23743 Turns on or off the notification of asynchronous commands'
23744 completion. When on, @value{GDBN} will print a message when an
23745 asynchronous command finishes its execution. The default is off.
23746 @kindex show exec-done-display
23747 @item show exec-done-display
23748 Displays the current setting of asynchronous command completion
23751 @cindex ARM AArch64
23752 @item set debug aarch64
23753 Turns on or off display of debugging messages related to ARM AArch64.
23754 The default is off.
23756 @item show debug aarch64
23757 Displays the current state of displaying debugging messages related to
23759 @cindex gdbarch debugging info
23760 @cindex architecture debugging info
23761 @item set debug arch
23762 Turns on or off display of gdbarch debugging info. The default is off
23763 @item show debug arch
23764 Displays the current state of displaying gdbarch debugging info.
23765 @item set debug aix-solib
23766 @cindex AIX shared library debugging
23767 Control display of debugging messages from the AIX shared library
23768 support module. The default is off.
23769 @item show debug aix-thread
23770 Show the current state of displaying AIX shared library debugging messages.
23771 @item set debug aix-thread
23772 @cindex AIX threads
23773 Display debugging messages about inner workings of the AIX thread
23775 @item show debug aix-thread
23776 Show the current state of AIX thread debugging info display.
23777 @item set debug check-physname
23779 Check the results of the ``physname'' computation. When reading DWARF
23780 debugging information for C@t{++}, @value{GDBN} attempts to compute
23781 each entity's name. @value{GDBN} can do this computation in two
23782 different ways, depending on exactly what information is present.
23783 When enabled, this setting causes @value{GDBN} to compute the names
23784 both ways and display any discrepancies.
23785 @item show debug check-physname
23786 Show the current state of ``physname'' checking.
23787 @item set debug coff-pe-read
23788 @cindex COFF/PE exported symbols
23789 Control display of debugging messages related to reading of COFF/PE
23790 exported symbols. The default is off.
23791 @item show debug coff-pe-read
23792 Displays the current state of displaying debugging messages related to
23793 reading of COFF/PE exported symbols.
23794 @item set debug dwarf-die
23796 Dump DWARF DIEs after they are read in.
23797 The value is the number of nesting levels to print.
23798 A value of zero turns off the display.
23799 @item show debug dwarf-die
23800 Show the current state of DWARF DIE debugging.
23801 @item set debug dwarf-line
23802 @cindex DWARF Line Tables
23803 Turns on or off display of debugging messages related to reading
23804 DWARF line tables. The default is 0 (off).
23805 A value of 1 provides basic information.
23806 A value greater than 1 provides more verbose information.
23807 @item show debug dwarf-line
23808 Show the current state of DWARF line table debugging.
23809 @item set debug dwarf-read
23810 @cindex DWARF Reading
23811 Turns on or off display of debugging messages related to reading
23812 DWARF debug info. The default is 0 (off).
23813 A value of 1 provides basic information.
23814 A value greater than 1 provides more verbose information.
23815 @item show debug dwarf-read
23816 Show the current state of DWARF reader debugging.
23817 @item set debug displaced
23818 @cindex displaced stepping debugging info
23819 Turns on or off display of @value{GDBN} debugging info for the
23820 displaced stepping support. The default is off.
23821 @item show debug displaced
23822 Displays the current state of displaying @value{GDBN} debugging info
23823 related to displaced stepping.
23824 @item set debug event
23825 @cindex event debugging info
23826 Turns on or off display of @value{GDBN} event debugging info. The
23828 @item show debug event
23829 Displays the current state of displaying @value{GDBN} event debugging
23831 @item set debug expression
23832 @cindex expression debugging info
23833 Turns on or off display of debugging info about @value{GDBN}
23834 expression parsing. The default is off.
23835 @item show debug expression
23836 Displays the current state of displaying debugging info about
23837 @value{GDBN} expression parsing.
23838 @item set debug fbsd-lwp
23839 @cindex FreeBSD LWP debug messages
23840 Turns on or off debugging messages from the FreeBSD LWP debug support.
23841 @item show debug fbsd-lwp
23842 Show the current state of FreeBSD LWP debugging messages.
23843 @item set debug frame
23844 @cindex frame debugging info
23845 Turns on or off display of @value{GDBN} frame debugging info. The
23847 @item show debug frame
23848 Displays the current state of displaying @value{GDBN} frame debugging
23850 @item set debug gnu-nat
23851 @cindex @sc{gnu}/Hurd debug messages
23852 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
23853 @item show debug gnu-nat
23854 Show the current state of @sc{gnu}/Hurd debugging messages.
23855 @item set debug infrun
23856 @cindex inferior debugging info
23857 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23858 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23859 for implementing operations such as single-stepping the inferior.
23860 @item show debug infrun
23861 Displays the current state of @value{GDBN} inferior debugging.
23862 @item set debug jit
23863 @cindex just-in-time compilation, debugging messages
23864 Turn on or off debugging messages from JIT debug support.
23865 @item show debug jit
23866 Displays the current state of @value{GDBN} JIT debugging.
23867 @item set debug lin-lwp
23868 @cindex @sc{gnu}/Linux LWP debug messages
23869 @cindex Linux lightweight processes
23870 Turn on or off debugging messages from the Linux LWP debug support.
23871 @item show debug lin-lwp
23872 Show the current state of Linux LWP debugging messages.
23873 @item set debug linux-namespaces
23874 @cindex @sc{gnu}/Linux namespaces debug messages
23875 Turn on or off debugging messages from the Linux namespaces debug support.
23876 @item show debug linux-namespaces
23877 Show the current state of Linux namespaces debugging messages.
23878 @item set debug mach-o
23879 @cindex Mach-O symbols processing
23880 Control display of debugging messages related to Mach-O symbols
23881 processing. The default is off.
23882 @item show debug mach-o
23883 Displays the current state of displaying debugging messages related to
23884 reading of COFF/PE exported symbols.
23885 @item set debug notification
23886 @cindex remote async notification debugging info
23887 Turn on or off debugging messages about remote async notification.
23888 The default is off.
23889 @item show debug notification
23890 Displays the current state of remote async notification debugging messages.
23891 @item set debug observer
23892 @cindex observer debugging info
23893 Turns on or off display of @value{GDBN} observer debugging. This
23894 includes info such as the notification of observable events.
23895 @item show debug observer
23896 Displays the current state of observer debugging.
23897 @item set debug overload
23898 @cindex C@t{++} overload debugging info
23899 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23900 info. This includes info such as ranking of functions, etc. The default
23902 @item show debug overload
23903 Displays the current state of displaying @value{GDBN} C@t{++} overload
23905 @cindex expression parser, debugging info
23906 @cindex debug expression parser
23907 @item set debug parser
23908 Turns on or off the display of expression parser debugging output.
23909 Internally, this sets the @code{yydebug} variable in the expression
23910 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23911 details. The default is off.
23912 @item show debug parser
23913 Show the current state of expression parser debugging.
23914 @cindex packets, reporting on stdout
23915 @cindex serial connections, debugging
23916 @cindex debug remote protocol
23917 @cindex remote protocol debugging
23918 @cindex display remote packets
23919 @item set debug remote
23920 Turns on or off display of reports on all packets sent back and forth across
23921 the serial line to the remote machine. The info is printed on the
23922 @value{GDBN} standard output stream. The default is off.
23923 @item show debug remote
23924 Displays the state of display of remote packets.
23925 @item set debug serial
23926 Turns on or off display of @value{GDBN} serial debugging info. The
23928 @item show debug serial
23929 Displays the current state of displaying @value{GDBN} serial debugging
23931 @item set debug solib-frv
23932 @cindex FR-V shared-library debugging
23933 Turn on or off debugging messages for FR-V shared-library code.
23934 @item show debug solib-frv
23935 Display the current state of FR-V shared-library code debugging
23937 @item set debug symbol-lookup
23938 @cindex symbol lookup
23939 Turns on or off display of debugging messages related to symbol lookup.
23940 The default is 0 (off).
23941 A value of 1 provides basic information.
23942 A value greater than 1 provides more verbose information.
23943 @item show debug symbol-lookup
23944 Show the current state of symbol lookup debugging messages.
23945 @item set debug symfile
23946 @cindex symbol file functions
23947 Turns on or off display of debugging messages related to symbol file functions.
23948 The default is off. @xref{Files}.
23949 @item show debug symfile
23950 Show the current state of symbol file debugging messages.
23951 @item set debug symtab-create
23952 @cindex symbol table creation
23953 Turns on or off display of debugging messages related to symbol table creation.
23954 The default is 0 (off).
23955 A value of 1 provides basic information.
23956 A value greater than 1 provides more verbose information.
23957 @item show debug symtab-create
23958 Show the current state of symbol table creation debugging.
23959 @item set debug target
23960 @cindex target debugging info
23961 Turns on or off display of @value{GDBN} target debugging info. This info
23962 includes what is going on at the target level of GDB, as it happens. The
23963 default is 0. Set it to 1 to track events, and to 2 to also track the
23964 value of large memory transfers.
23965 @item show debug target
23966 Displays the current state of displaying @value{GDBN} target debugging
23968 @item set debug timestamp
23969 @cindex timestampping debugging info
23970 Turns on or off display of timestamps with @value{GDBN} debugging info.
23971 When enabled, seconds and microseconds are displayed before each debugging
23973 @item show debug timestamp
23974 Displays the current state of displaying timestamps with @value{GDBN}
23976 @item set debug varobj
23977 @cindex variable object debugging info
23978 Turns on or off display of @value{GDBN} variable object debugging
23979 info. The default is off.
23980 @item show debug varobj
23981 Displays the current state of displaying @value{GDBN} variable object
23983 @item set debug xml
23984 @cindex XML parser debugging
23985 Turn on or off debugging messages for built-in XML parsers.
23986 @item show debug xml
23987 Displays the current state of XML debugging messages.
23990 @node Other Misc Settings
23991 @section Other Miscellaneous Settings
23992 @cindex miscellaneous settings
23995 @kindex set interactive-mode
23996 @item set interactive-mode
23997 If @code{on}, forces @value{GDBN} to assume that GDB was started
23998 in a terminal. In practice, this means that @value{GDBN} should wait
23999 for the user to answer queries generated by commands entered at
24000 the command prompt. If @code{off}, forces @value{GDBN} to operate
24001 in the opposite mode, and it uses the default answers to all queries.
24002 If @code{auto} (the default), @value{GDBN} tries to determine whether
24003 its standard input is a terminal, and works in interactive-mode if it
24004 is, non-interactively otherwise.
24006 In the vast majority of cases, the debugger should be able to guess
24007 correctly which mode should be used. But this setting can be useful
24008 in certain specific cases, such as running a MinGW @value{GDBN}
24009 inside a cygwin window.
24011 @kindex show interactive-mode
24012 @item show interactive-mode
24013 Displays whether the debugger is operating in interactive mode or not.
24016 @node Extending GDB
24017 @chapter Extending @value{GDBN}
24018 @cindex extending GDB
24020 @value{GDBN} provides several mechanisms for extension.
24021 @value{GDBN} also provides the ability to automatically load
24022 extensions when it reads a file for debugging. This allows the
24023 user to automatically customize @value{GDBN} for the program
24027 * Sequences:: Canned Sequences of @value{GDBN} Commands
24028 * Python:: Extending @value{GDBN} using Python
24029 * Guile:: Extending @value{GDBN} using Guile
24030 * Auto-loading extensions:: Automatically loading extensions
24031 * Multiple Extension Languages:: Working with multiple extension languages
24032 * Aliases:: Creating new spellings of existing commands
24035 To facilitate the use of extension languages, @value{GDBN} is capable
24036 of evaluating the contents of a file. When doing so, @value{GDBN}
24037 can recognize which extension language is being used by looking at
24038 the filename extension. Files with an unrecognized filename extension
24039 are always treated as a @value{GDBN} Command Files.
24040 @xref{Command Files,, Command files}.
24042 You can control how @value{GDBN} evaluates these files with the following
24046 @kindex set script-extension
24047 @kindex show script-extension
24048 @item set script-extension off
24049 All scripts are always evaluated as @value{GDBN} Command Files.
24051 @item set script-extension soft
24052 The debugger determines the scripting language based on filename
24053 extension. If this scripting language is supported, @value{GDBN}
24054 evaluates the script using that language. Otherwise, it evaluates
24055 the file as a @value{GDBN} Command File.
24057 @item set script-extension strict
24058 The debugger determines the scripting language based on filename
24059 extension, and evaluates the script using that language. If the
24060 language is not supported, then the evaluation fails.
24062 @item show script-extension
24063 Display the current value of the @code{script-extension} option.
24068 @section Canned Sequences of Commands
24070 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24071 Command Lists}), @value{GDBN} provides two ways to store sequences of
24072 commands for execution as a unit: user-defined commands and command
24076 * Define:: How to define your own commands
24077 * Hooks:: Hooks for user-defined commands
24078 * Command Files:: How to write scripts of commands to be stored in a file
24079 * Output:: Commands for controlled output
24080 * Auto-loading sequences:: Controlling auto-loaded command files
24084 @subsection User-defined Commands
24086 @cindex user-defined command
24087 @cindex arguments, to user-defined commands
24088 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24089 which you assign a new name as a command. This is done with the
24090 @code{define} command. User commands may accept an unlimited number of arguments
24091 separated by whitespace. Arguments are accessed within the user command
24092 via @code{$arg0@dots{}$argN}. A trivial example:
24096 print $arg0 + $arg1 + $arg2
24101 To execute the command use:
24108 This defines the command @code{adder}, which prints the sum of
24109 its three arguments. Note the arguments are text substitutions, so they may
24110 reference variables, use complex expressions, or even perform inferior
24113 @cindex argument count in user-defined commands
24114 @cindex how many arguments (user-defined commands)
24115 In addition, @code{$argc} may be used to find out how many arguments have
24121 print $arg0 + $arg1
24124 print $arg0 + $arg1 + $arg2
24129 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24130 to process a variable number of arguments:
24137 eval "set $sum = $sum + $arg%d", $i
24147 @item define @var{commandname}
24148 Define a command named @var{commandname}. If there is already a command
24149 by that name, you are asked to confirm that you want to redefine it.
24150 The argument @var{commandname} may be a bare command name consisting of letters,
24151 numbers, dashes, and underscores. It may also start with any predefined
24152 prefix command. For example, @samp{define target my-target} creates
24153 a user-defined @samp{target my-target} command.
24155 The definition of the command is made up of other @value{GDBN} command lines,
24156 which are given following the @code{define} command. The end of these
24157 commands is marked by a line containing @code{end}.
24160 @kindex end@r{ (user-defined commands)}
24161 @item document @var{commandname}
24162 Document the user-defined command @var{commandname}, so that it can be
24163 accessed by @code{help}. The command @var{commandname} must already be
24164 defined. This command reads lines of documentation just as @code{define}
24165 reads the lines of the command definition, ending with @code{end}.
24166 After the @code{document} command is finished, @code{help} on command
24167 @var{commandname} displays the documentation you have written.
24169 You may use the @code{document} command again to change the
24170 documentation of a command. Redefining the command with @code{define}
24171 does not change the documentation.
24173 @kindex dont-repeat
24174 @cindex don't repeat command
24176 Used inside a user-defined command, this tells @value{GDBN} that this
24177 command should not be repeated when the user hits @key{RET}
24178 (@pxref{Command Syntax, repeat last command}).
24180 @kindex help user-defined
24181 @item help user-defined
24182 List all user-defined commands and all python commands defined in class
24183 COMAND_USER. The first line of the documentation or docstring is
24188 @itemx show user @var{commandname}
24189 Display the @value{GDBN} commands used to define @var{commandname} (but
24190 not its documentation). If no @var{commandname} is given, display the
24191 definitions for all user-defined commands.
24192 This does not work for user-defined python commands.
24194 @cindex infinite recursion in user-defined commands
24195 @kindex show max-user-call-depth
24196 @kindex set max-user-call-depth
24197 @item show max-user-call-depth
24198 @itemx set max-user-call-depth
24199 The value of @code{max-user-call-depth} controls how many recursion
24200 levels are allowed in user-defined commands before @value{GDBN} suspects an
24201 infinite recursion and aborts the command.
24202 This does not apply to user-defined python commands.
24205 In addition to the above commands, user-defined commands frequently
24206 use control flow commands, described in @ref{Command Files}.
24208 When user-defined commands are executed, the
24209 commands of the definition are not printed. An error in any command
24210 stops execution of the user-defined command.
24212 If used interactively, commands that would ask for confirmation proceed
24213 without asking when used inside a user-defined command. Many @value{GDBN}
24214 commands that normally print messages to say what they are doing omit the
24215 messages when used in a user-defined command.
24218 @subsection User-defined Command Hooks
24219 @cindex command hooks
24220 @cindex hooks, for commands
24221 @cindex hooks, pre-command
24224 You may define @dfn{hooks}, which are a special kind of user-defined
24225 command. Whenever you run the command @samp{foo}, if the user-defined
24226 command @samp{hook-foo} exists, it is executed (with no arguments)
24227 before that command.
24229 @cindex hooks, post-command
24231 A hook may also be defined which is run after the command you executed.
24232 Whenever you run the command @samp{foo}, if the user-defined command
24233 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24234 that command. Post-execution hooks may exist simultaneously with
24235 pre-execution hooks, for the same command.
24237 It is valid for a hook to call the command which it hooks. If this
24238 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24240 @c It would be nice if hookpost could be passed a parameter indicating
24241 @c if the command it hooks executed properly or not. FIXME!
24243 @kindex stop@r{, a pseudo-command}
24244 In addition, a pseudo-command, @samp{stop} exists. Defining
24245 (@samp{hook-stop}) makes the associated commands execute every time
24246 execution stops in your program: before breakpoint commands are run,
24247 displays are printed, or the stack frame is printed.
24249 For example, to ignore @code{SIGALRM} signals while
24250 single-stepping, but treat them normally during normal execution,
24255 handle SIGALRM nopass
24259 handle SIGALRM pass
24262 define hook-continue
24263 handle SIGALRM pass
24267 As a further example, to hook at the beginning and end of the @code{echo}
24268 command, and to add extra text to the beginning and end of the message,
24276 define hookpost-echo
24280 (@value{GDBP}) echo Hello World
24281 <<<---Hello World--->>>
24286 You can define a hook for any single-word command in @value{GDBN}, but
24287 not for command aliases; you should define a hook for the basic command
24288 name, e.g.@: @code{backtrace} rather than @code{bt}.
24289 @c FIXME! So how does Joe User discover whether a command is an alias
24291 You can hook a multi-word command by adding @code{hook-} or
24292 @code{hookpost-} to the last word of the command, e.g.@:
24293 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24295 If an error occurs during the execution of your hook, execution of
24296 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24297 (before the command that you actually typed had a chance to run).
24299 If you try to define a hook which does not match any known command, you
24300 get a warning from the @code{define} command.
24302 @node Command Files
24303 @subsection Command Files
24305 @cindex command files
24306 @cindex scripting commands
24307 A command file for @value{GDBN} is a text file made of lines that are
24308 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24309 also be included. An empty line in a command file does nothing; it
24310 does not mean to repeat the last command, as it would from the
24313 You can request the execution of a command file with the @code{source}
24314 command. Note that the @code{source} command is also used to evaluate
24315 scripts that are not Command Files. The exact behavior can be configured
24316 using the @code{script-extension} setting.
24317 @xref{Extending GDB,, Extending GDB}.
24321 @cindex execute commands from a file
24322 @item source [-s] [-v] @var{filename}
24323 Execute the command file @var{filename}.
24326 The lines in a command file are generally executed sequentially,
24327 unless the order of execution is changed by one of the
24328 @emph{flow-control commands} described below. The commands are not
24329 printed as they are executed. An error in any command terminates
24330 execution of the command file and control is returned to the console.
24332 @value{GDBN} first searches for @var{filename} in the current directory.
24333 If the file is not found there, and @var{filename} does not specify a
24334 directory, then @value{GDBN} also looks for the file on the source search path
24335 (specified with the @samp{directory} command);
24336 except that @file{$cdir} is not searched because the compilation directory
24337 is not relevant to scripts.
24339 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24340 on the search path even if @var{filename} specifies a directory.
24341 The search is done by appending @var{filename} to each element of the
24342 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24343 and the search path contains @file{/home/user} then @value{GDBN} will
24344 look for the script @file{/home/user/mylib/myscript}.
24345 The search is also done if @var{filename} is an absolute path.
24346 For example, if @var{filename} is @file{/tmp/myscript} and
24347 the search path contains @file{/home/user} then @value{GDBN} will
24348 look for the script @file{/home/user/tmp/myscript}.
24349 For DOS-like systems, if @var{filename} contains a drive specification,
24350 it is stripped before concatenation. For example, if @var{filename} is
24351 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24352 will look for the script @file{c:/tmp/myscript}.
24354 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24355 each command as it is executed. The option must be given before
24356 @var{filename}, and is interpreted as part of the filename anywhere else.
24358 Commands that would ask for confirmation if used interactively proceed
24359 without asking when used in a command file. Many @value{GDBN} commands that
24360 normally print messages to say what they are doing omit the messages
24361 when called from command files.
24363 @value{GDBN} also accepts command input from standard input. In this
24364 mode, normal output goes to standard output and error output goes to
24365 standard error. Errors in a command file supplied on standard input do
24366 not terminate execution of the command file---execution continues with
24370 gdb < cmds > log 2>&1
24373 (The syntax above will vary depending on the shell used.) This example
24374 will execute commands from the file @file{cmds}. All output and errors
24375 would be directed to @file{log}.
24377 Since commands stored on command files tend to be more general than
24378 commands typed interactively, they frequently need to deal with
24379 complicated situations, such as different or unexpected values of
24380 variables and symbols, changes in how the program being debugged is
24381 built, etc. @value{GDBN} provides a set of flow-control commands to
24382 deal with these complexities. Using these commands, you can write
24383 complex scripts that loop over data structures, execute commands
24384 conditionally, etc.
24391 This command allows to include in your script conditionally executed
24392 commands. The @code{if} command takes a single argument, which is an
24393 expression to evaluate. It is followed by a series of commands that
24394 are executed only if the expression is true (its value is nonzero).
24395 There can then optionally be an @code{else} line, followed by a series
24396 of commands that are only executed if the expression was false. The
24397 end of the list is marked by a line containing @code{end}.
24401 This command allows to write loops. Its syntax is similar to
24402 @code{if}: the command takes a single argument, which is an expression
24403 to evaluate, and must be followed by the commands to execute, one per
24404 line, terminated by an @code{end}. These commands are called the
24405 @dfn{body} of the loop. The commands in the body of @code{while} are
24406 executed repeatedly as long as the expression evaluates to true.
24410 This command exits the @code{while} loop in whose body it is included.
24411 Execution of the script continues after that @code{while}s @code{end}
24414 @kindex loop_continue
24415 @item loop_continue
24416 This command skips the execution of the rest of the body of commands
24417 in the @code{while} loop in whose body it is included. Execution
24418 branches to the beginning of the @code{while} loop, where it evaluates
24419 the controlling expression.
24421 @kindex end@r{ (if/else/while commands)}
24423 Terminate the block of commands that are the body of @code{if},
24424 @code{else}, or @code{while} flow-control commands.
24429 @subsection Commands for Controlled Output
24431 During the execution of a command file or a user-defined command, normal
24432 @value{GDBN} output is suppressed; the only output that appears is what is
24433 explicitly printed by the commands in the definition. This section
24434 describes three commands useful for generating exactly the output you
24439 @item echo @var{text}
24440 @c I do not consider backslash-space a standard C escape sequence
24441 @c because it is not in ANSI.
24442 Print @var{text}. Nonprinting characters can be included in
24443 @var{text} using C escape sequences, such as @samp{\n} to print a
24444 newline. @strong{No newline is printed unless you specify one.}
24445 In addition to the standard C escape sequences, a backslash followed
24446 by a space stands for a space. This is useful for displaying a
24447 string with spaces at the beginning or the end, since leading and
24448 trailing spaces are otherwise trimmed from all arguments.
24449 To print @samp{@w{ }and foo =@w{ }}, use the command
24450 @samp{echo \@w{ }and foo = \@w{ }}.
24452 A backslash at the end of @var{text} can be used, as in C, to continue
24453 the command onto subsequent lines. For example,
24456 echo This is some text\n\
24457 which is continued\n\
24458 onto several lines.\n
24461 produces the same output as
24464 echo This is some text\n
24465 echo which is continued\n
24466 echo onto several lines.\n
24470 @item output @var{expression}
24471 Print the value of @var{expression} and nothing but that value: no
24472 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24473 value history either. @xref{Expressions, ,Expressions}, for more information
24476 @item output/@var{fmt} @var{expression}
24477 Print the value of @var{expression} in format @var{fmt}. You can use
24478 the same formats as for @code{print}. @xref{Output Formats,,Output
24479 Formats}, for more information.
24482 @item printf @var{template}, @var{expressions}@dots{}
24483 Print the values of one or more @var{expressions} under the control of
24484 the string @var{template}. To print several values, make
24485 @var{expressions} be a comma-separated list of individual expressions,
24486 which may be either numbers or pointers. Their values are printed as
24487 specified by @var{template}, exactly as a C program would do by
24488 executing the code below:
24491 printf (@var{template}, @var{expressions}@dots{});
24494 As in @code{C} @code{printf}, ordinary characters in @var{template}
24495 are printed verbatim, while @dfn{conversion specification} introduced
24496 by the @samp{%} character cause subsequent @var{expressions} to be
24497 evaluated, their values converted and formatted according to type and
24498 style information encoded in the conversion specifications, and then
24501 For example, you can print two values in hex like this:
24504 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24507 @code{printf} supports all the standard @code{C} conversion
24508 specifications, including the flags and modifiers between the @samp{%}
24509 character and the conversion letter, with the following exceptions:
24513 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24516 The modifier @samp{*} is not supported for specifying precision or
24520 The @samp{'} flag (for separation of digits into groups according to
24521 @code{LC_NUMERIC'}) is not supported.
24524 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24528 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24531 The conversion letters @samp{a} and @samp{A} are not supported.
24535 Note that the @samp{ll} type modifier is supported only if the
24536 underlying @code{C} implementation used to build @value{GDBN} supports
24537 the @code{long long int} type, and the @samp{L} type modifier is
24538 supported only if @code{long double} type is available.
24540 As in @code{C}, @code{printf} supports simple backslash-escape
24541 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24542 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24543 single character. Octal and hexadecimal escape sequences are not
24546 Additionally, @code{printf} supports conversion specifications for DFP
24547 (@dfn{Decimal Floating Point}) types using the following length modifiers
24548 together with a floating point specifier.
24553 @samp{H} for printing @code{Decimal32} types.
24556 @samp{D} for printing @code{Decimal64} types.
24559 @samp{DD} for printing @code{Decimal128} types.
24562 If the underlying @code{C} implementation used to build @value{GDBN} has
24563 support for the three length modifiers for DFP types, other modifiers
24564 such as width and precision will also be available for @value{GDBN} to use.
24566 In case there is no such @code{C} support, no additional modifiers will be
24567 available and the value will be printed in the standard way.
24569 Here's an example of printing DFP types using the above conversion letters:
24571 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24576 @item eval @var{template}, @var{expressions}@dots{}
24577 Convert the values of one or more @var{expressions} under the control of
24578 the string @var{template} to a command line, and call it.
24582 @node Auto-loading sequences
24583 @subsection Controlling auto-loading native @value{GDBN} scripts
24584 @cindex native script auto-loading
24586 When a new object file is read (for example, due to the @code{file}
24587 command, or because the inferior has loaded a shared library),
24588 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24589 @xref{Auto-loading extensions}.
24591 Auto-loading can be enabled or disabled,
24592 and the list of auto-loaded scripts can be printed.
24595 @anchor{set auto-load gdb-scripts}
24596 @kindex set auto-load gdb-scripts
24597 @item set auto-load gdb-scripts [on|off]
24598 Enable or disable the auto-loading of canned sequences of commands scripts.
24600 @anchor{show auto-load gdb-scripts}
24601 @kindex show auto-load gdb-scripts
24602 @item show auto-load gdb-scripts
24603 Show whether auto-loading of canned sequences of commands scripts is enabled or
24606 @anchor{info auto-load gdb-scripts}
24607 @kindex info auto-load gdb-scripts
24608 @cindex print list of auto-loaded canned sequences of commands scripts
24609 @item info auto-load gdb-scripts [@var{regexp}]
24610 Print the list of all canned sequences of commands scripts that @value{GDBN}
24614 If @var{regexp} is supplied only canned sequences of commands scripts with
24615 matching names are printed.
24617 @c Python docs live in a separate file.
24618 @include python.texi
24620 @c Guile docs live in a separate file.
24621 @include guile.texi
24623 @node Auto-loading extensions
24624 @section Auto-loading extensions
24625 @cindex auto-loading extensions
24627 @value{GDBN} provides two mechanisms for automatically loading extensions
24628 when a new object file is read (for example, due to the @code{file}
24629 command, or because the inferior has loaded a shared library):
24630 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24631 section of modern file formats like ELF.
24634 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24635 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24636 * Which flavor to choose?::
24639 The auto-loading feature is useful for supplying application-specific
24640 debugging commands and features.
24642 Auto-loading can be enabled or disabled,
24643 and the list of auto-loaded scripts can be printed.
24644 See the @samp{auto-loading} section of each extension language
24645 for more information.
24646 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24647 For Python files see @ref{Python Auto-loading}.
24649 Note that loading of this script file also requires accordingly configured
24650 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24652 @node objfile-gdbdotext file
24653 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24654 @cindex @file{@var{objfile}-gdb.gdb}
24655 @cindex @file{@var{objfile}-gdb.py}
24656 @cindex @file{@var{objfile}-gdb.scm}
24658 When a new object file is read, @value{GDBN} looks for a file named
24659 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24660 where @var{objfile} is the object file's name and
24661 where @var{ext} is the file extension for the extension language:
24664 @item @file{@var{objfile}-gdb.gdb}
24665 GDB's own command language
24666 @item @file{@var{objfile}-gdb.py}
24668 @item @file{@var{objfile}-gdb.scm}
24672 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24673 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24674 components, and appending the @file{-gdb.@var{ext}} suffix.
24675 If this file exists and is readable, @value{GDBN} will evaluate it as a
24676 script in the specified extension language.
24678 If this file does not exist, then @value{GDBN} will look for
24679 @var{script-name} file in all of the directories as specified below.
24681 Note that loading of these files requires an accordingly configured
24682 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24684 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24685 scripts normally according to its @file{.exe} filename. But if no scripts are
24686 found @value{GDBN} also tries script filenames matching the object file without
24687 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24688 is attempted on any platform. This makes the script filenames compatible
24689 between Unix and MS-Windows hosts.
24692 @anchor{set auto-load scripts-directory}
24693 @kindex set auto-load scripts-directory
24694 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24695 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24696 may be delimited by the host platform path separator in use
24697 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24699 Each entry here needs to be covered also by the security setting
24700 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24702 @anchor{with-auto-load-dir}
24703 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24704 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24705 configuration option @option{--with-auto-load-dir}.
24707 Any reference to @file{$debugdir} will get replaced by
24708 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24709 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24710 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24711 @file{$datadir} must be placed as a directory component --- either alone or
24712 delimited by @file{/} or @file{\} directory separators, depending on the host
24715 The list of directories uses path separator (@samp{:} on GNU and Unix
24716 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24717 to the @env{PATH} environment variable.
24719 @anchor{show auto-load scripts-directory}
24720 @kindex show auto-load scripts-directory
24721 @item show auto-load scripts-directory
24722 Show @value{GDBN} auto-loaded scripts location.
24724 @anchor{add-auto-load-scripts-directory}
24725 @kindex add-auto-load-scripts-directory
24726 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24727 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24728 Multiple entries may be delimited by the host platform path separator in use.
24731 @value{GDBN} does not track which files it has already auto-loaded this way.
24732 @value{GDBN} will load the associated script every time the corresponding
24733 @var{objfile} is opened.
24734 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24735 is evaluated more than once.
24737 @node dotdebug_gdb_scripts section
24738 @subsection The @code{.debug_gdb_scripts} section
24739 @cindex @code{.debug_gdb_scripts} section
24741 For systems using file formats like ELF and COFF,
24742 when @value{GDBN} loads a new object file
24743 it will look for a special section named @code{.debug_gdb_scripts}.
24744 If this section exists, its contents is a list of null-terminated entries
24745 specifying scripts to load. Each entry begins with a non-null prefix byte that
24746 specifies the kind of entry, typically the extension language and whether the
24747 script is in a file or inlined in @code{.debug_gdb_scripts}.
24749 The following entries are supported:
24752 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24753 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24754 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24755 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24758 @subsubsection Script File Entries
24760 If the entry specifies a file, @value{GDBN} will look for the file first
24761 in the current directory and then along the source search path
24762 (@pxref{Source Path, ,Specifying Source Directories}),
24763 except that @file{$cdir} is not searched, since the compilation
24764 directory is not relevant to scripts.
24766 File entries can be placed in section @code{.debug_gdb_scripts} with,
24767 for example, this GCC macro for Python scripts.
24770 /* Note: The "MS" section flags are to remove duplicates. */
24771 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24773 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24774 .byte 1 /* Python */\n\
24775 .asciz \"" script_name "\"\n\
24781 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24782 Then one can reference the macro in a header or source file like this:
24785 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24788 The script name may include directories if desired.
24790 Note that loading of this script file also requires accordingly configured
24791 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24793 If the macro invocation is put in a header, any application or library
24794 using this header will get a reference to the specified script,
24795 and with the use of @code{"MS"} attributes on the section, the linker
24796 will remove duplicates.
24798 @subsubsection Script Text Entries
24800 Script text entries allow to put the executable script in the entry
24801 itself instead of loading it from a file.
24802 The first line of the entry, everything after the prefix byte and up to
24803 the first newline (@code{0xa}) character, is the script name, and must not
24804 contain any kind of space character, e.g., spaces or tabs.
24805 The rest of the entry, up to the trailing null byte, is the script to
24806 execute in the specified language. The name needs to be unique among
24807 all script names, as @value{GDBN} executes each script only once based
24810 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24814 #include "symcat.h"
24815 #include "gdb/section-scripts.h"
24817 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24818 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24819 ".ascii \"gdb.inlined-script\\n\"\n"
24820 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24821 ".ascii \" def __init__ (self):\\n\"\n"
24822 ".ascii \" super (test_cmd, self).__init__ ("
24823 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24824 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24825 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24826 ".ascii \"test_cmd ()\\n\"\n"
24832 Loading of inlined scripts requires a properly configured
24833 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24834 The path to specify in @code{auto-load safe-path} is the path of the file
24835 containing the @code{.debug_gdb_scripts} section.
24837 @node Which flavor to choose?
24838 @subsection Which flavor to choose?
24840 Given the multiple ways of auto-loading extensions, it might not always
24841 be clear which one to choose. This section provides some guidance.
24844 Benefits of the @file{-gdb.@var{ext}} way:
24848 Can be used with file formats that don't support multiple sections.
24851 Ease of finding scripts for public libraries.
24853 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24854 in the source search path.
24855 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24856 isn't a source directory in which to find the script.
24859 Doesn't require source code additions.
24863 Benefits of the @code{.debug_gdb_scripts} way:
24867 Works with static linking.
24869 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24870 trigger their loading. When an application is statically linked the only
24871 objfile available is the executable, and it is cumbersome to attach all the
24872 scripts from all the input libraries to the executable's
24873 @file{-gdb.@var{ext}} script.
24876 Works with classes that are entirely inlined.
24878 Some classes can be entirely inlined, and thus there may not be an associated
24879 shared library to attach a @file{-gdb.@var{ext}} script to.
24882 Scripts needn't be copied out of the source tree.
24884 In some circumstances, apps can be built out of large collections of internal
24885 libraries, and the build infrastructure necessary to install the
24886 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24887 cumbersome. It may be easier to specify the scripts in the
24888 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24889 top of the source tree to the source search path.
24892 @node Multiple Extension Languages
24893 @section Multiple Extension Languages
24895 The Guile and Python extension languages do not share any state,
24896 and generally do not interfere with each other.
24897 There are some things to be aware of, however.
24899 @subsection Python comes first
24901 Python was @value{GDBN}'s first extension language, and to avoid breaking
24902 existing behaviour Python comes first. This is generally solved by the
24903 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24904 extension languages, and when it makes a call to an extension language,
24905 (say to pretty-print a value), it tries each in turn until an extension
24906 language indicates it has performed the request (e.g., has returned the
24907 pretty-printed form of a value).
24908 This extends to errors while performing such requests: If an error happens
24909 while, for example, trying to pretty-print an object then the error is
24910 reported and any following extension languages are not tried.
24913 @section Creating new spellings of existing commands
24914 @cindex aliases for commands
24916 It is often useful to define alternate spellings of existing commands.
24917 For example, if a new @value{GDBN} command defined in Python has
24918 a long name to type, it is handy to have an abbreviated version of it
24919 that involves less typing.
24921 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24922 of the @samp{step} command even though it is otherwise an ambiguous
24923 abbreviation of other commands like @samp{set} and @samp{show}.
24925 Aliases are also used to provide shortened or more common versions
24926 of multi-word commands. For example, @value{GDBN} provides the
24927 @samp{tty} alias of the @samp{set inferior-tty} command.
24929 You can define a new alias with the @samp{alias} command.
24934 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24938 @var{ALIAS} specifies the name of the new alias.
24939 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24942 @var{COMMAND} specifies the name of an existing command
24943 that is being aliased.
24945 The @samp{-a} option specifies that the new alias is an abbreviation
24946 of the command. Abbreviations are not shown in command
24947 lists displayed by the @samp{help} command.
24949 The @samp{--} option specifies the end of options,
24950 and is useful when @var{ALIAS} begins with a dash.
24952 Here is a simple example showing how to make an abbreviation
24953 of a command so that there is less to type.
24954 Suppose you were tired of typing @samp{disas}, the current
24955 shortest unambiguous abbreviation of the @samp{disassemble} command
24956 and you wanted an even shorter version named @samp{di}.
24957 The following will accomplish this.
24960 (gdb) alias -a di = disas
24963 Note that aliases are different from user-defined commands.
24964 With a user-defined command, you also need to write documentation
24965 for it with the @samp{document} command.
24966 An alias automatically picks up the documentation of the existing command.
24968 Here is an example where we make @samp{elms} an abbreviation of
24969 @samp{elements} in the @samp{set print elements} command.
24970 This is to show that you can make an abbreviation of any part
24974 (gdb) alias -a set print elms = set print elements
24975 (gdb) alias -a show print elms = show print elements
24976 (gdb) set p elms 20
24978 Limit on string chars or array elements to print is 200.
24981 Note that if you are defining an alias of a @samp{set} command,
24982 and you want to have an alias for the corresponding @samp{show}
24983 command, then you need to define the latter separately.
24985 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24986 @var{ALIAS}, just as they are normally.
24989 (gdb) alias -a set pr elms = set p ele
24992 Finally, here is an example showing the creation of a one word
24993 alias for a more complex command.
24994 This creates alias @samp{spe} of the command @samp{set print elements}.
24997 (gdb) alias spe = set print elements
25002 @chapter Command Interpreters
25003 @cindex command interpreters
25005 @value{GDBN} supports multiple command interpreters, and some command
25006 infrastructure to allow users or user interface writers to switch
25007 between interpreters or run commands in other interpreters.
25009 @value{GDBN} currently supports two command interpreters, the console
25010 interpreter (sometimes called the command-line interpreter or @sc{cli})
25011 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25012 describes both of these interfaces in great detail.
25014 By default, @value{GDBN} will start with the console interpreter.
25015 However, the user may choose to start @value{GDBN} with another
25016 interpreter by specifying the @option{-i} or @option{--interpreter}
25017 startup options. Defined interpreters include:
25021 @cindex console interpreter
25022 The traditional console or command-line interpreter. This is the most often
25023 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25024 @value{GDBN} will use this interpreter.
25027 @cindex mi interpreter
25028 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25029 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25030 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25034 @cindex mi2 interpreter
25035 The current @sc{gdb/mi} interface.
25038 @cindex mi1 interpreter
25039 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25043 @cindex invoke another interpreter
25045 @kindex interpreter-exec
25046 You may execute commands in any interpreter from the current
25047 interpreter using the appropriate command. If you are running the
25048 console interpreter, simply use the @code{interpreter-exec} command:
25051 interpreter-exec mi "-data-list-register-names"
25054 @sc{gdb/mi} has a similar command, although it is only available in versions of
25055 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25057 Note that @code{interpreter-exec} only changes the interpreter for the
25058 duration of the specified command. It does not change the interpreter
25061 @cindex start a new independent interpreter
25063 Although you may only choose a single interpreter at startup, it is
25064 possible to run an independent interpreter on a specified input/output
25065 device (usually a tty).
25067 For example, consider a debugger GUI or IDE that wants to provide a
25068 @value{GDBN} console view. It may do so by embedding a terminal
25069 emulator widget in its GUI, starting @value{GDBN} in the traditional
25070 command-line mode with stdin/stdout/stderr redirected to that
25071 terminal, and then creating an MI interpreter running on a specified
25072 input/output device. The console interpreter created by @value{GDBN}
25073 at startup handles commands the user types in the terminal widget,
25074 while the GUI controls and synchronizes state with @value{GDBN} using
25075 the separate MI interpreter.
25077 To start a new secondary @dfn{user interface} running MI, use the
25078 @code{new-ui} command:
25081 @cindex new user interface
25083 new-ui @var{interpreter} @var{tty}
25086 The @var{interpreter} parameter specifies the interpreter to run.
25087 This accepts the same values as the @code{interpreter-exec} command.
25088 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25089 @var{tty} parameter specifies the name of the bidirectional file the
25090 interpreter uses for input/output, usually the name of a
25091 pseudoterminal slave on Unix systems. For example:
25094 (@value{GDBP}) new-ui mi /dev/pts/9
25098 runs an MI interpreter on @file{/dev/pts/9}.
25101 @chapter @value{GDBN} Text User Interface
25103 @cindex Text User Interface
25106 * TUI Overview:: TUI overview
25107 * TUI Keys:: TUI key bindings
25108 * TUI Single Key Mode:: TUI single key mode
25109 * TUI Commands:: TUI-specific commands
25110 * TUI Configuration:: TUI configuration variables
25113 The @value{GDBN} Text User Interface (TUI) is a terminal
25114 interface which uses the @code{curses} library to show the source
25115 file, the assembly output, the program registers and @value{GDBN}
25116 commands in separate text windows. The TUI mode is supported only
25117 on platforms where a suitable version of the @code{curses} library
25120 The TUI mode is enabled by default when you invoke @value{GDBN} as
25121 @samp{@value{GDBP} -tui}.
25122 You can also switch in and out of TUI mode while @value{GDBN} runs by
25123 using various TUI commands and key bindings, such as @command{tui
25124 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25125 @ref{TUI Keys, ,TUI Key Bindings}.
25128 @section TUI Overview
25130 In TUI mode, @value{GDBN} can display several text windows:
25134 This window is the @value{GDBN} command window with the @value{GDBN}
25135 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25136 managed using readline.
25139 The source window shows the source file of the program. The current
25140 line and active breakpoints are displayed in this window.
25143 The assembly window shows the disassembly output of the program.
25146 This window shows the processor registers. Registers are highlighted
25147 when their values change.
25150 The source and assembly windows show the current program position
25151 by highlighting the current line and marking it with a @samp{>} marker.
25152 Breakpoints are indicated with two markers. The first marker
25153 indicates the breakpoint type:
25157 Breakpoint which was hit at least once.
25160 Breakpoint which was never hit.
25163 Hardware breakpoint which was hit at least once.
25166 Hardware breakpoint which was never hit.
25169 The second marker indicates whether the breakpoint is enabled or not:
25173 Breakpoint is enabled.
25176 Breakpoint is disabled.
25179 The source, assembly and register windows are updated when the current
25180 thread changes, when the frame changes, or when the program counter
25183 These windows are not all visible at the same time. The command
25184 window is always visible. The others can be arranged in several
25195 source and assembly,
25198 source and registers, or
25201 assembly and registers.
25204 A status line above the command window shows the following information:
25208 Indicates the current @value{GDBN} target.
25209 (@pxref{Targets, ,Specifying a Debugging Target}).
25212 Gives the current process or thread number.
25213 When no process is being debugged, this field is set to @code{No process}.
25216 Gives the current function name for the selected frame.
25217 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25218 When there is no symbol corresponding to the current program counter,
25219 the string @code{??} is displayed.
25222 Indicates the current line number for the selected frame.
25223 When the current line number is not known, the string @code{??} is displayed.
25226 Indicates the current program counter address.
25230 @section TUI Key Bindings
25231 @cindex TUI key bindings
25233 The TUI installs several key bindings in the readline keymaps
25234 @ifset SYSTEM_READLINE
25235 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25237 @ifclear SYSTEM_READLINE
25238 (@pxref{Command Line Editing}).
25240 The following key bindings are installed for both TUI mode and the
25241 @value{GDBN} standard mode.
25250 Enter or leave the TUI mode. When leaving the TUI mode,
25251 the curses window management stops and @value{GDBN} operates using
25252 its standard mode, writing on the terminal directly. When reentering
25253 the TUI mode, control is given back to the curses windows.
25254 The screen is then refreshed.
25258 Use a TUI layout with only one window. The layout will
25259 either be @samp{source} or @samp{assembly}. When the TUI mode
25260 is not active, it will switch to the TUI mode.
25262 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25266 Use a TUI layout with at least two windows. When the current
25267 layout already has two windows, the next layout with two windows is used.
25268 When a new layout is chosen, one window will always be common to the
25269 previous layout and the new one.
25271 Think of it as the Emacs @kbd{C-x 2} binding.
25275 Change the active window. The TUI associates several key bindings
25276 (like scrolling and arrow keys) with the active window. This command
25277 gives the focus to the next TUI window.
25279 Think of it as the Emacs @kbd{C-x o} binding.
25283 Switch in and out of the TUI SingleKey mode that binds single
25284 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25287 The following key bindings only work in the TUI mode:
25292 Scroll the active window one page up.
25296 Scroll the active window one page down.
25300 Scroll the active window one line up.
25304 Scroll the active window one line down.
25308 Scroll the active window one column left.
25312 Scroll the active window one column right.
25316 Refresh the screen.
25319 Because the arrow keys scroll the active window in the TUI mode, they
25320 are not available for their normal use by readline unless the command
25321 window has the focus. When another window is active, you must use
25322 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25323 and @kbd{C-f} to control the command window.
25325 @node TUI Single Key Mode
25326 @section TUI Single Key Mode
25327 @cindex TUI single key mode
25329 The TUI also provides a @dfn{SingleKey} mode, which binds several
25330 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25331 switch into this mode, where the following key bindings are used:
25334 @kindex c @r{(SingleKey TUI key)}
25338 @kindex d @r{(SingleKey TUI key)}
25342 @kindex f @r{(SingleKey TUI key)}
25346 @kindex n @r{(SingleKey TUI key)}
25350 @kindex q @r{(SingleKey TUI key)}
25352 exit the SingleKey mode.
25354 @kindex r @r{(SingleKey TUI key)}
25358 @kindex s @r{(SingleKey TUI key)}
25362 @kindex u @r{(SingleKey TUI key)}
25366 @kindex v @r{(SingleKey TUI key)}
25370 @kindex w @r{(SingleKey TUI key)}
25375 Other keys temporarily switch to the @value{GDBN} command prompt.
25376 The key that was pressed is inserted in the editing buffer so that
25377 it is possible to type most @value{GDBN} commands without interaction
25378 with the TUI SingleKey mode. Once the command is entered the TUI
25379 SingleKey mode is restored. The only way to permanently leave
25380 this mode is by typing @kbd{q} or @kbd{C-x s}.
25384 @section TUI-specific Commands
25385 @cindex TUI commands
25387 The TUI has specific commands to control the text windows.
25388 These commands are always available, even when @value{GDBN} is not in
25389 the TUI mode. When @value{GDBN} is in the standard mode, most
25390 of these commands will automatically switch to the TUI mode.
25392 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25393 terminal, or @value{GDBN} has been started with the machine interface
25394 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25395 these commands will fail with an error, because it would not be
25396 possible or desirable to enable curses window management.
25401 Activate TUI mode. The last active TUI window layout will be used if
25402 TUI mode has prevsiouly been used in the current debugging session,
25403 otherwise a default layout is used.
25406 @kindex tui disable
25407 Disable TUI mode, returning to the console interpreter.
25411 List and give the size of all displayed windows.
25413 @item layout @var{name}
25415 Changes which TUI windows are displayed. In each layout the command
25416 window is always displayed, the @var{name} parameter controls which
25417 additional windows are displayed, and can be any of the following:
25421 Display the next layout.
25424 Display the previous layout.
25427 Display the source and command windows.
25430 Display the assembly and command windows.
25433 Display the source, assembly, and command windows.
25436 When in @code{src} layout display the register, source, and command
25437 windows. When in @code{asm} or @code{split} layout display the
25438 register, assembler, and command windows.
25441 @item focus @var{name}
25443 Changes which TUI window is currently active for scrolling. The
25444 @var{name} parameter can be any of the following:
25448 Make the next window active for scrolling.
25451 Make the previous window active for scrolling.
25454 Make the source window active for scrolling.
25457 Make the assembly window active for scrolling.
25460 Make the register window active for scrolling.
25463 Make the command window active for scrolling.
25468 Refresh the screen. This is similar to typing @kbd{C-L}.
25470 @item tui reg @var{group}
25472 Changes the register group displayed in the tui register window to
25473 @var{group}. If the register window is not currently displayed this
25474 command will cause the register window to be displayed. The list of
25475 register groups, as well as their order is target specific. The
25476 following groups are available on most targets:
25479 Repeatedly selecting this group will cause the display to cycle
25480 through all of the available register groups.
25483 Repeatedly selecting this group will cause the display to cycle
25484 through all of the available register groups in the reverse order to
25488 Display the general registers.
25490 Display the floating point registers.
25492 Display the system registers.
25494 Display the vector registers.
25496 Display all registers.
25501 Update the source window and the current execution point.
25503 @item winheight @var{name} +@var{count}
25504 @itemx winheight @var{name} -@var{count}
25506 Change the height of the window @var{name} by @var{count}
25507 lines. Positive counts increase the height, while negative counts
25508 decrease it. The @var{name} parameter can be one of @code{src} (the
25509 source window), @code{cmd} (the command window), @code{asm} (the
25510 disassembly window), or @code{regs} (the register display window).
25512 @item tabset @var{nchars}
25514 Set the width of tab stops to be @var{nchars} characters. This
25515 setting affects the display of TAB characters in the source and
25519 @node TUI Configuration
25520 @section TUI Configuration Variables
25521 @cindex TUI configuration variables
25523 Several configuration variables control the appearance of TUI windows.
25526 @item set tui border-kind @var{kind}
25527 @kindex set tui border-kind
25528 Select the border appearance for the source, assembly and register windows.
25529 The possible values are the following:
25532 Use a space character to draw the border.
25535 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25538 Use the Alternate Character Set to draw the border. The border is
25539 drawn using character line graphics if the terminal supports them.
25542 @item set tui border-mode @var{mode}
25543 @kindex set tui border-mode
25544 @itemx set tui active-border-mode @var{mode}
25545 @kindex set tui active-border-mode
25546 Select the display attributes for the borders of the inactive windows
25547 or the active window. The @var{mode} can be one of the following:
25550 Use normal attributes to display the border.
25556 Use reverse video mode.
25559 Use half bright mode.
25561 @item half-standout
25562 Use half bright and standout mode.
25565 Use extra bright or bold mode.
25567 @item bold-standout
25568 Use extra bright or bold and standout mode.
25573 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25576 @cindex @sc{gnu} Emacs
25577 A special interface allows you to use @sc{gnu} Emacs to view (and
25578 edit) the source files for the program you are debugging with
25581 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25582 executable file you want to debug as an argument. This command starts
25583 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25584 created Emacs buffer.
25585 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25587 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25592 All ``terminal'' input and output goes through an Emacs buffer, called
25595 This applies both to @value{GDBN} commands and their output, and to the input
25596 and output done by the program you are debugging.
25598 This is useful because it means that you can copy the text of previous
25599 commands and input them again; you can even use parts of the output
25602 All the facilities of Emacs' Shell mode are available for interacting
25603 with your program. In particular, you can send signals the usual
25604 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25608 @value{GDBN} displays source code through Emacs.
25610 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25611 source file for that frame and puts an arrow (@samp{=>}) at the
25612 left margin of the current line. Emacs uses a separate buffer for
25613 source display, and splits the screen to show both your @value{GDBN} session
25616 Explicit @value{GDBN} @code{list} or search commands still produce output as
25617 usual, but you probably have no reason to use them from Emacs.
25620 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25621 a graphical mode, enabled by default, which provides further buffers
25622 that can control the execution and describe the state of your program.
25623 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25625 If you specify an absolute file name when prompted for the @kbd{M-x
25626 gdb} argument, then Emacs sets your current working directory to where
25627 your program resides. If you only specify the file name, then Emacs
25628 sets your current working directory to the directory associated
25629 with the previous buffer. In this case, @value{GDBN} may find your
25630 program by searching your environment's @code{PATH} variable, but on
25631 some operating systems it might not find the source. So, although the
25632 @value{GDBN} input and output session proceeds normally, the auxiliary
25633 buffer does not display the current source and line of execution.
25635 The initial working directory of @value{GDBN} is printed on the top
25636 line of the GUD buffer and this serves as a default for the commands
25637 that specify files for @value{GDBN} to operate on. @xref{Files,
25638 ,Commands to Specify Files}.
25640 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25641 need to call @value{GDBN} by a different name (for example, if you
25642 keep several configurations around, with different names) you can
25643 customize the Emacs variable @code{gud-gdb-command-name} to run the
25646 In the GUD buffer, you can use these special Emacs commands in
25647 addition to the standard Shell mode commands:
25651 Describe the features of Emacs' GUD Mode.
25654 Execute to another source line, like the @value{GDBN} @code{step} command; also
25655 update the display window to show the current file and location.
25658 Execute to next source line in this function, skipping all function
25659 calls, like the @value{GDBN} @code{next} command. Then update the display window
25660 to show the current file and location.
25663 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25664 display window accordingly.
25667 Execute until exit from the selected stack frame, like the @value{GDBN}
25668 @code{finish} command.
25671 Continue execution of your program, like the @value{GDBN} @code{continue}
25675 Go up the number of frames indicated by the numeric argument
25676 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25677 like the @value{GDBN} @code{up} command.
25680 Go down the number of frames indicated by the numeric argument, like the
25681 @value{GDBN} @code{down} command.
25684 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25685 tells @value{GDBN} to set a breakpoint on the source line point is on.
25687 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25688 separate frame which shows a backtrace when the GUD buffer is current.
25689 Move point to any frame in the stack and type @key{RET} to make it
25690 become the current frame and display the associated source in the
25691 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25692 selected frame become the current one. In graphical mode, the
25693 speedbar displays watch expressions.
25695 If you accidentally delete the source-display buffer, an easy way to get
25696 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25697 request a frame display; when you run under Emacs, this recreates
25698 the source buffer if necessary to show you the context of the current
25701 The source files displayed in Emacs are in ordinary Emacs buffers
25702 which are visiting the source files in the usual way. You can edit
25703 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25704 communicates with Emacs in terms of line numbers. If you add or
25705 delete lines from the text, the line numbers that @value{GDBN} knows cease
25706 to correspond properly with the code.
25708 A more detailed description of Emacs' interaction with @value{GDBN} is
25709 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25713 @chapter The @sc{gdb/mi} Interface
25715 @unnumberedsec Function and Purpose
25717 @cindex @sc{gdb/mi}, its purpose
25718 @sc{gdb/mi} is a line based machine oriented text interface to
25719 @value{GDBN} and is activated by specifying using the
25720 @option{--interpreter} command line option (@pxref{Mode Options}). It
25721 is specifically intended to support the development of systems which
25722 use the debugger as just one small component of a larger system.
25724 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25725 in the form of a reference manual.
25727 Note that @sc{gdb/mi} is still under construction, so some of the
25728 features described below are incomplete and subject to change
25729 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25731 @unnumberedsec Notation and Terminology
25733 @cindex notational conventions, for @sc{gdb/mi}
25734 This chapter uses the following notation:
25738 @code{|} separates two alternatives.
25741 @code{[ @var{something} ]} indicates that @var{something} is optional:
25742 it may or may not be given.
25745 @code{( @var{group} )*} means that @var{group} inside the parentheses
25746 may repeat zero or more times.
25749 @code{( @var{group} )+} means that @var{group} inside the parentheses
25750 may repeat one or more times.
25753 @code{"@var{string}"} means a literal @var{string}.
25757 @heading Dependencies
25761 * GDB/MI General Design::
25762 * GDB/MI Command Syntax::
25763 * GDB/MI Compatibility with CLI::
25764 * GDB/MI Development and Front Ends::
25765 * GDB/MI Output Records::
25766 * GDB/MI Simple Examples::
25767 * GDB/MI Command Description Format::
25768 * GDB/MI Breakpoint Commands::
25769 * GDB/MI Catchpoint Commands::
25770 * GDB/MI Program Context::
25771 * GDB/MI Thread Commands::
25772 * GDB/MI Ada Tasking Commands::
25773 * GDB/MI Program Execution::
25774 * GDB/MI Stack Manipulation::
25775 * GDB/MI Variable Objects::
25776 * GDB/MI Data Manipulation::
25777 * GDB/MI Tracepoint Commands::
25778 * GDB/MI Symbol Query::
25779 * GDB/MI File Commands::
25781 * GDB/MI Kod Commands::
25782 * GDB/MI Memory Overlay Commands::
25783 * GDB/MI Signal Handling Commands::
25785 * GDB/MI Target Manipulation::
25786 * GDB/MI File Transfer Commands::
25787 * GDB/MI Ada Exceptions Commands::
25788 * GDB/MI Support Commands::
25789 * GDB/MI Miscellaneous Commands::
25792 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25793 @node GDB/MI General Design
25794 @section @sc{gdb/mi} General Design
25795 @cindex GDB/MI General Design
25797 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25798 parts---commands sent to @value{GDBN}, responses to those commands
25799 and notifications. Each command results in exactly one response,
25800 indicating either successful completion of the command, or an error.
25801 For the commands that do not resume the target, the response contains the
25802 requested information. For the commands that resume the target, the
25803 response only indicates whether the target was successfully resumed.
25804 Notifications is the mechanism for reporting changes in the state of the
25805 target, or in @value{GDBN} state, that cannot conveniently be associated with
25806 a command and reported as part of that command response.
25808 The important examples of notifications are:
25812 Exec notifications. These are used to report changes in
25813 target state---when a target is resumed, or stopped. It would not
25814 be feasible to include this information in response of resuming
25815 commands, because one resume commands can result in multiple events in
25816 different threads. Also, quite some time may pass before any event
25817 happens in the target, while a frontend needs to know whether the resuming
25818 command itself was successfully executed.
25821 Console output, and status notifications. Console output
25822 notifications are used to report output of CLI commands, as well as
25823 diagnostics for other commands. Status notifications are used to
25824 report the progress of a long-running operation. Naturally, including
25825 this information in command response would mean no output is produced
25826 until the command is finished, which is undesirable.
25829 General notifications. Commands may have various side effects on
25830 the @value{GDBN} or target state beyond their official purpose. For example,
25831 a command may change the selected thread. Although such changes can
25832 be included in command response, using notification allows for more
25833 orthogonal frontend design.
25837 There's no guarantee that whenever an MI command reports an error,
25838 @value{GDBN} or the target are in any specific state, and especially,
25839 the state is not reverted to the state before the MI command was
25840 processed. Therefore, whenever an MI command results in an error,
25841 we recommend that the frontend refreshes all the information shown in
25842 the user interface.
25846 * Context management::
25847 * Asynchronous and non-stop modes::
25851 @node Context management
25852 @subsection Context management
25854 @subsubsection Threads and Frames
25856 In most cases when @value{GDBN} accesses the target, this access is
25857 done in context of a specific thread and frame (@pxref{Frames}).
25858 Often, even when accessing global data, the target requires that a thread
25859 be specified. The CLI interface maintains the selected thread and frame,
25860 and supplies them to target on each command. This is convenient,
25861 because a command line user would not want to specify that information
25862 explicitly on each command, and because user interacts with
25863 @value{GDBN} via a single terminal, so no confusion is possible as
25864 to what thread and frame are the current ones.
25866 In the case of MI, the concept of selected thread and frame is less
25867 useful. First, a frontend can easily remember this information
25868 itself. Second, a graphical frontend can have more than one window,
25869 each one used for debugging a different thread, and the frontend might
25870 want to access additional threads for internal purposes. This
25871 increases the risk that by relying on implicitly selected thread, the
25872 frontend may be operating on a wrong one. Therefore, each MI command
25873 should explicitly specify which thread and frame to operate on. To
25874 make it possible, each MI command accepts the @samp{--thread} and
25875 @samp{--frame} options, the value to each is @value{GDBN} global
25876 identifier for thread and frame to operate on.
25878 Usually, each top-level window in a frontend allows the user to select
25879 a thread and a frame, and remembers the user selection for further
25880 operations. However, in some cases @value{GDBN} may suggest that the
25881 current thread or frame be changed. For example, when stopping on a
25882 breakpoint it is reasonable to switch to the thread where breakpoint is
25883 hit. For another example, if the user issues the CLI @samp{thread} or
25884 @samp{frame} commands via the frontend, it is desirable to change the
25885 frontend's selection to the one specified by user. @value{GDBN}
25886 communicates the suggestion to change current thread and frame using the
25887 @samp{=thread-selected} notification.
25889 Note that historically, MI shares the selected thread with CLI, so
25890 frontends used the @code{-thread-select} to execute commands in the
25891 right context. However, getting this to work right is cumbersome. The
25892 simplest way is for frontend to emit @code{-thread-select} command
25893 before every command. This doubles the number of commands that need
25894 to be sent. The alternative approach is to suppress @code{-thread-select}
25895 if the selected thread in @value{GDBN} is supposed to be identical to the
25896 thread the frontend wants to operate on. However, getting this
25897 optimization right can be tricky. In particular, if the frontend
25898 sends several commands to @value{GDBN}, and one of the commands changes the
25899 selected thread, then the behaviour of subsequent commands will
25900 change. So, a frontend should either wait for response from such
25901 problematic commands, or explicitly add @code{-thread-select} for
25902 all subsequent commands. No frontend is known to do this exactly
25903 right, so it is suggested to just always pass the @samp{--thread} and
25904 @samp{--frame} options.
25906 @subsubsection Language
25908 The execution of several commands depends on which language is selected.
25909 By default, the current language (@pxref{show language}) is used.
25910 But for commands known to be language-sensitive, it is recommended
25911 to use the @samp{--language} option. This option takes one argument,
25912 which is the name of the language to use while executing the command.
25916 -data-evaluate-expression --language c "sizeof (void*)"
25921 The valid language names are the same names accepted by the
25922 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25923 @samp{local} or @samp{unknown}.
25925 @node Asynchronous and non-stop modes
25926 @subsection Asynchronous command execution and non-stop mode
25928 On some targets, @value{GDBN} is capable of processing MI commands
25929 even while the target is running. This is called @dfn{asynchronous
25930 command execution} (@pxref{Background Execution}). The frontend may
25931 specify a preferrence for asynchronous execution using the
25932 @code{-gdb-set mi-async 1} command, which should be emitted before
25933 either running the executable or attaching to the target. After the
25934 frontend has started the executable or attached to the target, it can
25935 find if asynchronous execution is enabled using the
25936 @code{-list-target-features} command.
25939 @item -gdb-set mi-async on
25940 @item -gdb-set mi-async off
25941 Set whether MI is in asynchronous mode.
25943 When @code{off}, which is the default, MI execution commands (e.g.,
25944 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25945 for the program to stop before processing further commands.
25947 When @code{on}, MI execution commands are background execution
25948 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25949 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25950 MI commands even while the target is running.
25952 @item -gdb-show mi-async
25953 Show whether MI asynchronous mode is enabled.
25956 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25957 @code{target-async} instead of @code{mi-async}, and it had the effect
25958 of both putting MI in asynchronous mode and making CLI background
25959 commands possible. CLI background commands are now always possible
25960 ``out of the box'' if the target supports them. The old spelling is
25961 kept as a deprecated alias for backwards compatibility.
25963 Even if @value{GDBN} can accept a command while target is running,
25964 many commands that access the target do not work when the target is
25965 running. Therefore, asynchronous command execution is most useful
25966 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25967 it is possible to examine the state of one thread, while other threads
25970 When a given thread is running, MI commands that try to access the
25971 target in the context of that thread may not work, or may work only on
25972 some targets. In particular, commands that try to operate on thread's
25973 stack will not work, on any target. Commands that read memory, or
25974 modify breakpoints, may work or not work, depending on the target. Note
25975 that even commands that operate on global state, such as @code{print},
25976 @code{set}, and breakpoint commands, still access the target in the
25977 context of a specific thread, so frontend should try to find a
25978 stopped thread and perform the operation on that thread (using the
25979 @samp{--thread} option).
25981 Which commands will work in the context of a running thread is
25982 highly target dependent. However, the two commands
25983 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25984 to find the state of a thread, will always work.
25986 @node Thread groups
25987 @subsection Thread groups
25988 @value{GDBN} may be used to debug several processes at the same time.
25989 On some platfroms, @value{GDBN} may support debugging of several
25990 hardware systems, each one having several cores with several different
25991 processes running on each core. This section describes the MI
25992 mechanism to support such debugging scenarios.
25994 The key observation is that regardless of the structure of the
25995 target, MI can have a global list of threads, because most commands that
25996 accept the @samp{--thread} option do not need to know what process that
25997 thread belongs to. Therefore, it is not necessary to introduce
25998 neither additional @samp{--process} option, nor an notion of the
25999 current process in the MI interface. The only strictly new feature
26000 that is required is the ability to find how the threads are grouped
26003 To allow the user to discover such grouping, and to support arbitrary
26004 hierarchy of machines/cores/processes, MI introduces the concept of a
26005 @dfn{thread group}. Thread group is a collection of threads and other
26006 thread groups. A thread group always has a string identifier, a type,
26007 and may have additional attributes specific to the type. A new
26008 command, @code{-list-thread-groups}, returns the list of top-level
26009 thread groups, which correspond to processes that @value{GDBN} is
26010 debugging at the moment. By passing an identifier of a thread group
26011 to the @code{-list-thread-groups} command, it is possible to obtain
26012 the members of specific thread group.
26014 To allow the user to easily discover processes, and other objects, he
26015 wishes to debug, a concept of @dfn{available thread group} is
26016 introduced. Available thread group is an thread group that
26017 @value{GDBN} is not debugging, but that can be attached to, using the
26018 @code{-target-attach} command. The list of available top-level thread
26019 groups can be obtained using @samp{-list-thread-groups --available}.
26020 In general, the content of a thread group may be only retrieved only
26021 after attaching to that thread group.
26023 Thread groups are related to inferiors (@pxref{Inferiors and
26024 Programs}). Each inferior corresponds to a thread group of a special
26025 type @samp{process}, and some additional operations are permitted on
26026 such thread groups.
26028 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26029 @node GDB/MI Command Syntax
26030 @section @sc{gdb/mi} Command Syntax
26033 * GDB/MI Input Syntax::
26034 * GDB/MI Output Syntax::
26037 @node GDB/MI Input Syntax
26038 @subsection @sc{gdb/mi} Input Syntax
26040 @cindex input syntax for @sc{gdb/mi}
26041 @cindex @sc{gdb/mi}, input syntax
26043 @item @var{command} @expansion{}
26044 @code{@var{cli-command} | @var{mi-command}}
26046 @item @var{cli-command} @expansion{}
26047 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26048 @var{cli-command} is any existing @value{GDBN} CLI command.
26050 @item @var{mi-command} @expansion{}
26051 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26052 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26054 @item @var{token} @expansion{}
26055 "any sequence of digits"
26057 @item @var{option} @expansion{}
26058 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26060 @item @var{parameter} @expansion{}
26061 @code{@var{non-blank-sequence} | @var{c-string}}
26063 @item @var{operation} @expansion{}
26064 @emph{any of the operations described in this chapter}
26066 @item @var{non-blank-sequence} @expansion{}
26067 @emph{anything, provided it doesn't contain special characters such as
26068 "-", @var{nl}, """ and of course " "}
26070 @item @var{c-string} @expansion{}
26071 @code{""" @var{seven-bit-iso-c-string-content} """}
26073 @item @var{nl} @expansion{}
26082 The CLI commands are still handled by the @sc{mi} interpreter; their
26083 output is described below.
26086 The @code{@var{token}}, when present, is passed back when the command
26090 Some @sc{mi} commands accept optional arguments as part of the parameter
26091 list. Each option is identified by a leading @samp{-} (dash) and may be
26092 followed by an optional argument parameter. Options occur first in the
26093 parameter list and can be delimited from normal parameters using
26094 @samp{--} (this is useful when some parameters begin with a dash).
26101 We want easy access to the existing CLI syntax (for debugging).
26104 We want it to be easy to spot a @sc{mi} operation.
26107 @node GDB/MI Output Syntax
26108 @subsection @sc{gdb/mi} Output Syntax
26110 @cindex output syntax of @sc{gdb/mi}
26111 @cindex @sc{gdb/mi}, output syntax
26112 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26113 followed, optionally, by a single result record. This result record
26114 is for the most recent command. The sequence of output records is
26115 terminated by @samp{(gdb)}.
26117 If an input command was prefixed with a @code{@var{token}} then the
26118 corresponding output for that command will also be prefixed by that same
26122 @item @var{output} @expansion{}
26123 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26125 @item @var{result-record} @expansion{}
26126 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26128 @item @var{out-of-band-record} @expansion{}
26129 @code{@var{async-record} | @var{stream-record}}
26131 @item @var{async-record} @expansion{}
26132 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26134 @item @var{exec-async-output} @expansion{}
26135 @code{[ @var{token} ] "*" @var{async-output nl}}
26137 @item @var{status-async-output} @expansion{}
26138 @code{[ @var{token} ] "+" @var{async-output nl}}
26140 @item @var{notify-async-output} @expansion{}
26141 @code{[ @var{token} ] "=" @var{async-output nl}}
26143 @item @var{async-output} @expansion{}
26144 @code{@var{async-class} ( "," @var{result} )*}
26146 @item @var{result-class} @expansion{}
26147 @code{"done" | "running" | "connected" | "error" | "exit"}
26149 @item @var{async-class} @expansion{}
26150 @code{"stopped" | @var{others}} (where @var{others} will be added
26151 depending on the needs---this is still in development).
26153 @item @var{result} @expansion{}
26154 @code{ @var{variable} "=" @var{value}}
26156 @item @var{variable} @expansion{}
26157 @code{ @var{string} }
26159 @item @var{value} @expansion{}
26160 @code{ @var{const} | @var{tuple} | @var{list} }
26162 @item @var{const} @expansion{}
26163 @code{@var{c-string}}
26165 @item @var{tuple} @expansion{}
26166 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26168 @item @var{list} @expansion{}
26169 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26170 @var{result} ( "," @var{result} )* "]" }
26172 @item @var{stream-record} @expansion{}
26173 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26175 @item @var{console-stream-output} @expansion{}
26176 @code{"~" @var{c-string nl}}
26178 @item @var{target-stream-output} @expansion{}
26179 @code{"@@" @var{c-string nl}}
26181 @item @var{log-stream-output} @expansion{}
26182 @code{"&" @var{c-string nl}}
26184 @item @var{nl} @expansion{}
26187 @item @var{token} @expansion{}
26188 @emph{any sequence of digits}.
26196 All output sequences end in a single line containing a period.
26199 The @code{@var{token}} is from the corresponding request. Note that
26200 for all async output, while the token is allowed by the grammar and
26201 may be output by future versions of @value{GDBN} for select async
26202 output messages, it is generally omitted. Frontends should treat
26203 all async output as reporting general changes in the state of the
26204 target and there should be no need to associate async output to any
26208 @cindex status output in @sc{gdb/mi}
26209 @var{status-async-output} contains on-going status information about the
26210 progress of a slow operation. It can be discarded. All status output is
26211 prefixed by @samp{+}.
26214 @cindex async output in @sc{gdb/mi}
26215 @var{exec-async-output} contains asynchronous state change on the target
26216 (stopped, started, disappeared). All async output is prefixed by
26220 @cindex notify output in @sc{gdb/mi}
26221 @var{notify-async-output} contains supplementary information that the
26222 client should handle (e.g., a new breakpoint information). All notify
26223 output is prefixed by @samp{=}.
26226 @cindex console output in @sc{gdb/mi}
26227 @var{console-stream-output} is output that should be displayed as is in the
26228 console. It is the textual response to a CLI command. All the console
26229 output is prefixed by @samp{~}.
26232 @cindex target output in @sc{gdb/mi}
26233 @var{target-stream-output} is the output produced by the target program.
26234 All the target output is prefixed by @samp{@@}.
26237 @cindex log output in @sc{gdb/mi}
26238 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26239 instance messages that should be displayed as part of an error log. All
26240 the log output is prefixed by @samp{&}.
26243 @cindex list output in @sc{gdb/mi}
26244 New @sc{gdb/mi} commands should only output @var{lists} containing
26250 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26251 details about the various output records.
26253 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26254 @node GDB/MI Compatibility with CLI
26255 @section @sc{gdb/mi} Compatibility with CLI
26257 @cindex compatibility, @sc{gdb/mi} and CLI
26258 @cindex @sc{gdb/mi}, compatibility with CLI
26260 For the developers convenience CLI commands can be entered directly,
26261 but there may be some unexpected behaviour. For example, commands
26262 that query the user will behave as if the user replied yes, breakpoint
26263 command lists are not executed and some CLI commands, such as
26264 @code{if}, @code{when} and @code{define}, prompt for further input with
26265 @samp{>}, which is not valid MI output.
26267 This feature may be removed at some stage in the future and it is
26268 recommended that front ends use the @code{-interpreter-exec} command
26269 (@pxref{-interpreter-exec}).
26271 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26272 @node GDB/MI Development and Front Ends
26273 @section @sc{gdb/mi} Development and Front Ends
26274 @cindex @sc{gdb/mi} development
26276 The application which takes the MI output and presents the state of the
26277 program being debugged to the user is called a @dfn{front end}.
26279 Although @sc{gdb/mi} is still incomplete, it is currently being used
26280 by a variety of front ends to @value{GDBN}. This makes it difficult
26281 to introduce new functionality without breaking existing usage. This
26282 section tries to minimize the problems by describing how the protocol
26285 Some changes in MI need not break a carefully designed front end, and
26286 for these the MI version will remain unchanged. The following is a
26287 list of changes that may occur within one level, so front ends should
26288 parse MI output in a way that can handle them:
26292 New MI commands may be added.
26295 New fields may be added to the output of any MI command.
26298 The range of values for fields with specified values, e.g.,
26299 @code{in_scope} (@pxref{-var-update}) may be extended.
26301 @c The format of field's content e.g type prefix, may change so parse it
26302 @c at your own risk. Yes, in general?
26304 @c The order of fields may change? Shouldn't really matter but it might
26305 @c resolve inconsistencies.
26308 If the changes are likely to break front ends, the MI version level
26309 will be increased by one. This will allow the front end to parse the
26310 output according to the MI version. Apart from mi0, new versions of
26311 @value{GDBN} will not support old versions of MI and it will be the
26312 responsibility of the front end to work with the new one.
26314 @c Starting with mi3, add a new command -mi-version that prints the MI
26317 The best way to avoid unexpected changes in MI that might break your front
26318 end is to make your project known to @value{GDBN} developers and
26319 follow development on @email{gdb@@sourceware.org} and
26320 @email{gdb-patches@@sourceware.org}.
26321 @cindex mailing lists
26323 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26324 @node GDB/MI Output Records
26325 @section @sc{gdb/mi} Output Records
26328 * GDB/MI Result Records::
26329 * GDB/MI Stream Records::
26330 * GDB/MI Async Records::
26331 * GDB/MI Breakpoint Information::
26332 * GDB/MI Frame Information::
26333 * GDB/MI Thread Information::
26334 * GDB/MI Ada Exception Information::
26337 @node GDB/MI Result Records
26338 @subsection @sc{gdb/mi} Result Records
26340 @cindex result records in @sc{gdb/mi}
26341 @cindex @sc{gdb/mi}, result records
26342 In addition to a number of out-of-band notifications, the response to a
26343 @sc{gdb/mi} command includes one of the following result indications:
26347 @item "^done" [ "," @var{results} ]
26348 The synchronous operation was successful, @code{@var{results}} are the return
26353 This result record is equivalent to @samp{^done}. Historically, it
26354 was output instead of @samp{^done} if the command has resumed the
26355 target. This behaviour is maintained for backward compatibility, but
26356 all frontends should treat @samp{^done} and @samp{^running}
26357 identically and rely on the @samp{*running} output record to determine
26358 which threads are resumed.
26362 @value{GDBN} has connected to a remote target.
26364 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26366 The operation failed. The @code{msg=@var{c-string}} variable contains
26367 the corresponding error message.
26369 If present, the @code{code=@var{c-string}} variable provides an error
26370 code on which consumers can rely on to detect the corresponding
26371 error condition. At present, only one error code is defined:
26374 @item "undefined-command"
26375 Indicates that the command causing the error does not exist.
26380 @value{GDBN} has terminated.
26384 @node GDB/MI Stream Records
26385 @subsection @sc{gdb/mi} Stream Records
26387 @cindex @sc{gdb/mi}, stream records
26388 @cindex stream records in @sc{gdb/mi}
26389 @value{GDBN} internally maintains a number of output streams: the console, the
26390 target, and the log. The output intended for each of these streams is
26391 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26393 Each stream record begins with a unique @dfn{prefix character} which
26394 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26395 Syntax}). In addition to the prefix, each stream record contains a
26396 @code{@var{string-output}}. This is either raw text (with an implicit new
26397 line) or a quoted C string (which does not contain an implicit newline).
26400 @item "~" @var{string-output}
26401 The console output stream contains text that should be displayed in the
26402 CLI console window. It contains the textual responses to CLI commands.
26404 @item "@@" @var{string-output}
26405 The target output stream contains any textual output from the running
26406 target. This is only present when GDB's event loop is truly
26407 asynchronous, which is currently only the case for remote targets.
26409 @item "&" @var{string-output}
26410 The log stream contains debugging messages being produced by @value{GDBN}'s
26414 @node GDB/MI Async Records
26415 @subsection @sc{gdb/mi} Async Records
26417 @cindex async records in @sc{gdb/mi}
26418 @cindex @sc{gdb/mi}, async records
26419 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26420 additional changes that have occurred. Those changes can either be a
26421 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26422 target activity (e.g., target stopped).
26424 The following is the list of possible async records:
26428 @item *running,thread-id="@var{thread}"
26429 The target is now running. The @var{thread} field can be the global
26430 thread ID of the the thread that is now running, and it can be
26431 @samp{all} if all threads are running. The frontend should assume
26432 that no interaction with a running thread is possible after this
26433 notification is produced. The frontend should not assume that this
26434 notification is output only once for any command. @value{GDBN} may
26435 emit this notification several times, either for different threads,
26436 because it cannot resume all threads together, or even for a single
26437 thread, if the thread must be stepped though some code before letting
26440 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26441 The target has stopped. The @var{reason} field can have one of the
26445 @item breakpoint-hit
26446 A breakpoint was reached.
26447 @item watchpoint-trigger
26448 A watchpoint was triggered.
26449 @item read-watchpoint-trigger
26450 A read watchpoint was triggered.
26451 @item access-watchpoint-trigger
26452 An access watchpoint was triggered.
26453 @item function-finished
26454 An -exec-finish or similar CLI command was accomplished.
26455 @item location-reached
26456 An -exec-until or similar CLI command was accomplished.
26457 @item watchpoint-scope
26458 A watchpoint has gone out of scope.
26459 @item end-stepping-range
26460 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26461 similar CLI command was accomplished.
26462 @item exited-signalled
26463 The inferior exited because of a signal.
26465 The inferior exited.
26466 @item exited-normally
26467 The inferior exited normally.
26468 @item signal-received
26469 A signal was received by the inferior.
26471 The inferior has stopped due to a library being loaded or unloaded.
26472 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26473 set or when a @code{catch load} or @code{catch unload} catchpoint is
26474 in use (@pxref{Set Catchpoints}).
26476 The inferior has forked. This is reported when @code{catch fork}
26477 (@pxref{Set Catchpoints}) has been used.
26479 The inferior has vforked. This is reported in when @code{catch vfork}
26480 (@pxref{Set Catchpoints}) has been used.
26481 @item syscall-entry
26482 The inferior entered a system call. This is reported when @code{catch
26483 syscall} (@pxref{Set Catchpoints}) has been used.
26484 @item syscall-return
26485 The inferior returned from a system call. This is reported when
26486 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26488 The inferior called @code{exec}. This is reported when @code{catch exec}
26489 (@pxref{Set Catchpoints}) has been used.
26492 The @var{id} field identifies the global thread ID of the thread
26493 that directly caused the stop -- for example by hitting a breakpoint.
26494 Depending on whether all-stop
26495 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26496 stop all threads, or only the thread that directly triggered the stop.
26497 If all threads are stopped, the @var{stopped} field will have the
26498 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26499 field will be a list of thread identifiers. Presently, this list will
26500 always include a single thread, but frontend should be prepared to see
26501 several threads in the list. The @var{core} field reports the
26502 processor core on which the stop event has happened. This field may be absent
26503 if such information is not available.
26505 @item =thread-group-added,id="@var{id}"
26506 @itemx =thread-group-removed,id="@var{id}"
26507 A thread group was either added or removed. The @var{id} field
26508 contains the @value{GDBN} identifier of the thread group. When a thread
26509 group is added, it generally might not be associated with a running
26510 process. When a thread group is removed, its id becomes invalid and
26511 cannot be used in any way.
26513 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26514 A thread group became associated with a running program,
26515 either because the program was just started or the thread group
26516 was attached to a program. The @var{id} field contains the
26517 @value{GDBN} identifier of the thread group. The @var{pid} field
26518 contains process identifier, specific to the operating system.
26520 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26521 A thread group is no longer associated with a running program,
26522 either because the program has exited, or because it was detached
26523 from. The @var{id} field contains the @value{GDBN} identifier of the
26524 thread group. The @var{code} field is the exit code of the inferior; it exists
26525 only when the inferior exited with some code.
26527 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26528 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26529 A thread either was created, or has exited. The @var{id} field
26530 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26531 field identifies the thread group this thread belongs to.
26533 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
26534 Informs that the selected thread or frame were changed. This notification
26535 is not emitted as result of the @code{-thread-select} or
26536 @code{-stack-select-frame} commands, but is emitted whenever an MI command
26537 that is not documented to change the selected thread and frame actually
26538 changes them. In particular, invoking, directly or indirectly
26539 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
26540 will generate this notification. Changing the thread or frame from another
26541 user interface (see @ref{Interpreters}) will also generate this notification.
26543 The @var{frame} field is only present if the newly selected thread is
26544 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
26546 We suggest that in response to this notification, front ends
26547 highlight the selected thread and cause subsequent commands to apply to
26550 @item =library-loaded,...
26551 Reports that a new library file was loaded by the program. This
26552 notification has 4 fields---@var{id}, @var{target-name},
26553 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26554 opaque identifier of the library. For remote debugging case,
26555 @var{target-name} and @var{host-name} fields give the name of the
26556 library file on the target, and on the host respectively. For native
26557 debugging, both those fields have the same value. The
26558 @var{symbols-loaded} field is emitted only for backward compatibility
26559 and should not be relied on to convey any useful information. The
26560 @var{thread-group} field, if present, specifies the id of the thread
26561 group in whose context the library was loaded. If the field is
26562 absent, it means the library was loaded in the context of all present
26565 @item =library-unloaded,...
26566 Reports that a library was unloaded by the program. This notification
26567 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26568 the same meaning as for the @code{=library-loaded} notification.
26569 The @var{thread-group} field, if present, specifies the id of the
26570 thread group in whose context the library was unloaded. If the field is
26571 absent, it means the library was unloaded in the context of all present
26574 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26575 @itemx =traceframe-changed,end
26576 Reports that the trace frame was changed and its new number is
26577 @var{tfnum}. The number of the tracepoint associated with this trace
26578 frame is @var{tpnum}.
26580 @item =tsv-created,name=@var{name},initial=@var{initial}
26581 Reports that the new trace state variable @var{name} is created with
26582 initial value @var{initial}.
26584 @item =tsv-deleted,name=@var{name}
26585 @itemx =tsv-deleted
26586 Reports that the trace state variable @var{name} is deleted or all
26587 trace state variables are deleted.
26589 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26590 Reports that the trace state variable @var{name} is modified with
26591 the initial value @var{initial}. The current value @var{current} of
26592 trace state variable is optional and is reported if the current
26593 value of trace state variable is known.
26595 @item =breakpoint-created,bkpt=@{...@}
26596 @itemx =breakpoint-modified,bkpt=@{...@}
26597 @itemx =breakpoint-deleted,id=@var{number}
26598 Reports that a breakpoint was created, modified, or deleted,
26599 respectively. Only user-visible breakpoints are reported to the MI
26602 The @var{bkpt} argument is of the same form as returned by the various
26603 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26604 @var{number} is the ordinal number of the breakpoint.
26606 Note that if a breakpoint is emitted in the result record of a
26607 command, then it will not also be emitted in an async record.
26609 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
26610 @itemx =record-stopped,thread-group="@var{id}"
26611 Execution log recording was either started or stopped on an
26612 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26613 group corresponding to the affected inferior.
26615 The @var{method} field indicates the method used to record execution. If the
26616 method in use supports multiple recording formats, @var{format} will be present
26617 and contain the currently used format. @xref{Process Record and Replay},
26618 for existing method and format values.
26620 @item =cmd-param-changed,param=@var{param},value=@var{value}
26621 Reports that a parameter of the command @code{set @var{param}} is
26622 changed to @var{value}. In the multi-word @code{set} command,
26623 the @var{param} is the whole parameter list to @code{set} command.
26624 For example, In command @code{set check type on}, @var{param}
26625 is @code{check type} and @var{value} is @code{on}.
26627 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26628 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26629 written in an inferior. The @var{id} is the identifier of the
26630 thread group corresponding to the affected inferior. The optional
26631 @code{type="code"} part is reported if the memory written to holds
26635 @node GDB/MI Breakpoint Information
26636 @subsection @sc{gdb/mi} Breakpoint Information
26638 When @value{GDBN} reports information about a breakpoint, a
26639 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26644 The breakpoint number. For a breakpoint that represents one location
26645 of a multi-location breakpoint, this will be a dotted pair, like
26649 The type of the breakpoint. For ordinary breakpoints this will be
26650 @samp{breakpoint}, but many values are possible.
26653 If the type of the breakpoint is @samp{catchpoint}, then this
26654 indicates the exact type of catchpoint.
26657 This is the breakpoint disposition---either @samp{del}, meaning that
26658 the breakpoint will be deleted at the next stop, or @samp{keep},
26659 meaning that the breakpoint will not be deleted.
26662 This indicates whether the breakpoint is enabled, in which case the
26663 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26664 Note that this is not the same as the field @code{enable}.
26667 The address of the breakpoint. This may be a hexidecimal number,
26668 giving the address; or the string @samp{<PENDING>}, for a pending
26669 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26670 multiple locations. This field will not be present if no address can
26671 be determined. For example, a watchpoint does not have an address.
26674 If known, the function in which the breakpoint appears.
26675 If not known, this field is not present.
26678 The name of the source file which contains this function, if known.
26679 If not known, this field is not present.
26682 The full file name of the source file which contains this function, if
26683 known. If not known, this field is not present.
26686 The line number at which this breakpoint appears, if known.
26687 If not known, this field is not present.
26690 If the source file is not known, this field may be provided. If
26691 provided, this holds the address of the breakpoint, possibly followed
26695 If this breakpoint is pending, this field is present and holds the
26696 text used to set the breakpoint, as entered by the user.
26699 Where this breakpoint's condition is evaluated, either @samp{host} or
26703 If this is a thread-specific breakpoint, then this identifies the
26704 thread in which the breakpoint can trigger.
26707 If this breakpoint is restricted to a particular Ada task, then this
26708 field will hold the task identifier.
26711 If the breakpoint is conditional, this is the condition expression.
26714 The ignore count of the breakpoint.
26717 The enable count of the breakpoint.
26719 @item traceframe-usage
26722 @item static-tracepoint-marker-string-id
26723 For a static tracepoint, the name of the static tracepoint marker.
26726 For a masked watchpoint, this is the mask.
26729 A tracepoint's pass count.
26731 @item original-location
26732 The location of the breakpoint as originally specified by the user.
26733 This field is optional.
26736 The number of times the breakpoint has been hit.
26739 This field is only given for tracepoints. This is either @samp{y},
26740 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26744 Some extra data, the exact contents of which are type-dependent.
26748 For example, here is what the output of @code{-break-insert}
26749 (@pxref{GDB/MI Breakpoint Commands}) might be:
26752 -> -break-insert main
26753 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26754 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26755 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26760 @node GDB/MI Frame Information
26761 @subsection @sc{gdb/mi} Frame Information
26763 Response from many MI commands includes an information about stack
26764 frame. This information is a tuple that may have the following
26769 The level of the stack frame. The innermost frame has the level of
26770 zero. This field is always present.
26773 The name of the function corresponding to the frame. This field may
26774 be absent if @value{GDBN} is unable to determine the function name.
26777 The code address for the frame. This field is always present.
26780 The name of the source files that correspond to the frame's code
26781 address. This field may be absent.
26784 The source line corresponding to the frames' code address. This field
26788 The name of the binary file (either executable or shared library) the
26789 corresponds to the frame's code address. This field may be absent.
26793 @node GDB/MI Thread Information
26794 @subsection @sc{gdb/mi} Thread Information
26796 Whenever @value{GDBN} has to report an information about a thread, it
26797 uses a tuple with the following fields:
26801 The global numeric id assigned to the thread by @value{GDBN}. This field is
26805 Target-specific string identifying the thread. This field is always present.
26808 Additional information about the thread provided by the target.
26809 It is supposed to be human-readable and not interpreted by the
26810 frontend. This field is optional.
26813 Either @samp{stopped} or @samp{running}, depending on whether the
26814 thread is presently running. This field is always present.
26817 The value of this field is an integer number of the processor core the
26818 thread was last seen on. This field is optional.
26821 @node GDB/MI Ada Exception Information
26822 @subsection @sc{gdb/mi} Ada Exception Information
26824 Whenever a @code{*stopped} record is emitted because the program
26825 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26826 @value{GDBN} provides the name of the exception that was raised via
26827 the @code{exception-name} field.
26829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26830 @node GDB/MI Simple Examples
26831 @section Simple Examples of @sc{gdb/mi} Interaction
26832 @cindex @sc{gdb/mi}, simple examples
26834 This subsection presents several simple examples of interaction using
26835 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26836 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26837 the output received from @sc{gdb/mi}.
26839 Note the line breaks shown in the examples are here only for
26840 readability, they don't appear in the real output.
26842 @subheading Setting a Breakpoint
26844 Setting a breakpoint generates synchronous output which contains detailed
26845 information of the breakpoint.
26848 -> -break-insert main
26849 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26850 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26851 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26856 @subheading Program Execution
26858 Program execution generates asynchronous records and MI gives the
26859 reason that execution stopped.
26865 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26866 frame=@{addr="0x08048564",func="main",
26867 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26868 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26873 <- *stopped,reason="exited-normally"
26877 @subheading Quitting @value{GDBN}
26879 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26887 Please note that @samp{^exit} is printed immediately, but it might
26888 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26889 performs necessary cleanups, including killing programs being debugged
26890 or disconnecting from debug hardware, so the frontend should wait till
26891 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26892 fails to exit in reasonable time.
26894 @subheading A Bad Command
26896 Here's what happens if you pass a non-existent command:
26900 <- ^error,msg="Undefined MI command: rubbish"
26905 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26906 @node GDB/MI Command Description Format
26907 @section @sc{gdb/mi} Command Description Format
26909 The remaining sections describe blocks of commands. Each block of
26910 commands is laid out in a fashion similar to this section.
26912 @subheading Motivation
26914 The motivation for this collection of commands.
26916 @subheading Introduction
26918 A brief introduction to this collection of commands as a whole.
26920 @subheading Commands
26922 For each command in the block, the following is described:
26924 @subsubheading Synopsis
26927 -command @var{args}@dots{}
26930 @subsubheading Result
26932 @subsubheading @value{GDBN} Command
26934 The corresponding @value{GDBN} CLI command(s), if any.
26936 @subsubheading Example
26938 Example(s) formatted for readability. Some of the described commands have
26939 not been implemented yet and these are labeled N.A.@: (not available).
26942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26943 @node GDB/MI Breakpoint Commands
26944 @section @sc{gdb/mi} Breakpoint Commands
26946 @cindex breakpoint commands for @sc{gdb/mi}
26947 @cindex @sc{gdb/mi}, breakpoint commands
26948 This section documents @sc{gdb/mi} commands for manipulating
26951 @subheading The @code{-break-after} Command
26952 @findex -break-after
26954 @subsubheading Synopsis
26957 -break-after @var{number} @var{count}
26960 The breakpoint number @var{number} is not in effect until it has been
26961 hit @var{count} times. To see how this is reflected in the output of
26962 the @samp{-break-list} command, see the description of the
26963 @samp{-break-list} command below.
26965 @subsubheading @value{GDBN} Command
26967 The corresponding @value{GDBN} command is @samp{ignore}.
26969 @subsubheading Example
26974 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26975 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26976 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26984 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26985 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26986 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26987 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26988 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26989 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26990 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26991 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26992 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26993 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26998 @subheading The @code{-break-catch} Command
26999 @findex -break-catch
27002 @subheading The @code{-break-commands} Command
27003 @findex -break-commands
27005 @subsubheading Synopsis
27008 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27011 Specifies the CLI commands that should be executed when breakpoint
27012 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27013 are the commands. If no command is specified, any previously-set
27014 commands are cleared. @xref{Break Commands}. Typical use of this
27015 functionality is tracing a program, that is, printing of values of
27016 some variables whenever breakpoint is hit and then continuing.
27018 @subsubheading @value{GDBN} Command
27020 The corresponding @value{GDBN} command is @samp{commands}.
27022 @subsubheading Example
27027 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27028 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27029 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27032 -break-commands 1 "print v" "continue"
27037 @subheading The @code{-break-condition} Command
27038 @findex -break-condition
27040 @subsubheading Synopsis
27043 -break-condition @var{number} @var{expr}
27046 Breakpoint @var{number} will stop the program only if the condition in
27047 @var{expr} is true. The condition becomes part of the
27048 @samp{-break-list} output (see the description of the @samp{-break-list}
27051 @subsubheading @value{GDBN} Command
27053 The corresponding @value{GDBN} command is @samp{condition}.
27055 @subsubheading Example
27059 -break-condition 1 1
27063 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27064 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27065 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27066 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27067 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27068 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27069 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27070 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27071 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27072 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27076 @subheading The @code{-break-delete} Command
27077 @findex -break-delete
27079 @subsubheading Synopsis
27082 -break-delete ( @var{breakpoint} )+
27085 Delete the breakpoint(s) whose number(s) are specified in the argument
27086 list. This is obviously reflected in the breakpoint list.
27088 @subsubheading @value{GDBN} Command
27090 The corresponding @value{GDBN} command is @samp{delete}.
27092 @subsubheading Example
27100 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27101 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27102 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27103 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27104 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27105 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27106 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27111 @subheading The @code{-break-disable} Command
27112 @findex -break-disable
27114 @subsubheading Synopsis
27117 -break-disable ( @var{breakpoint} )+
27120 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27121 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27123 @subsubheading @value{GDBN} Command
27125 The corresponding @value{GDBN} command is @samp{disable}.
27127 @subsubheading Example
27135 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27136 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27137 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27138 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27139 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27140 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27141 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27142 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27143 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27144 line="5",thread-groups=["i1"],times="0"@}]@}
27148 @subheading The @code{-break-enable} Command
27149 @findex -break-enable
27151 @subsubheading Synopsis
27154 -break-enable ( @var{breakpoint} )+
27157 Enable (previously disabled) @var{breakpoint}(s).
27159 @subsubheading @value{GDBN} Command
27161 The corresponding @value{GDBN} command is @samp{enable}.
27163 @subsubheading Example
27171 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27172 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27173 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27174 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27175 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27176 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27177 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27178 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27179 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27180 line="5",thread-groups=["i1"],times="0"@}]@}
27184 @subheading The @code{-break-info} Command
27185 @findex -break-info
27187 @subsubheading Synopsis
27190 -break-info @var{breakpoint}
27194 Get information about a single breakpoint.
27196 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27197 Information}, for details on the format of each breakpoint in the
27200 @subsubheading @value{GDBN} Command
27202 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27204 @subsubheading Example
27207 @subheading The @code{-break-insert} Command
27208 @findex -break-insert
27209 @anchor{-break-insert}
27211 @subsubheading Synopsis
27214 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27215 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27216 [ -p @var{thread-id} ] [ @var{location} ]
27220 If specified, @var{location}, can be one of:
27223 @item linespec location
27224 A linespec location. @xref{Linespec Locations}.
27226 @item explicit location
27227 An explicit location. @sc{gdb/mi} explicit locations are
27228 analogous to the CLI's explicit locations using the option names
27229 listed below. @xref{Explicit Locations}.
27232 @item --source @var{filename}
27233 The source file name of the location. This option requires the use
27234 of either @samp{--function} or @samp{--line}.
27236 @item --function @var{function}
27237 The name of a function or method.
27239 @item --label @var{label}
27240 The name of a label.
27242 @item --line @var{lineoffset}
27243 An absolute or relative line offset from the start of the location.
27246 @item address location
27247 An address location, *@var{address}. @xref{Address Locations}.
27251 The possible optional parameters of this command are:
27255 Insert a temporary breakpoint.
27257 Insert a hardware breakpoint.
27259 If @var{location} cannot be parsed (for example if it
27260 refers to unknown files or functions), create a pending
27261 breakpoint. Without this flag, @value{GDBN} will report
27262 an error, and won't create a breakpoint, if @var{location}
27265 Create a disabled breakpoint.
27267 Create a tracepoint. @xref{Tracepoints}. When this parameter
27268 is used together with @samp{-h}, a fast tracepoint is created.
27269 @item -c @var{condition}
27270 Make the breakpoint conditional on @var{condition}.
27271 @item -i @var{ignore-count}
27272 Initialize the @var{ignore-count}.
27273 @item -p @var{thread-id}
27274 Restrict the breakpoint to the thread with the specified global
27278 @subsubheading Result
27280 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27281 resulting breakpoint.
27283 Note: this format is open to change.
27284 @c An out-of-band breakpoint instead of part of the result?
27286 @subsubheading @value{GDBN} Command
27288 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27289 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27291 @subsubheading Example
27296 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27297 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27300 -break-insert -t foo
27301 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27302 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27306 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27307 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27308 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27309 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27310 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27311 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27312 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27313 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27314 addr="0x0001072c", func="main",file="recursive2.c",
27315 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
27317 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27318 addr="0x00010774",func="foo",file="recursive2.c",
27319 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27322 @c -break-insert -r foo.*
27323 @c ~int foo(int, int);
27324 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27325 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
27330 @subheading The @code{-dprintf-insert} Command
27331 @findex -dprintf-insert
27333 @subsubheading Synopsis
27336 -dprintf-insert [ -t ] [ -f ] [ -d ]
27337 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27338 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27343 If supplied, @var{location} may be specified the same way as for
27344 the @code{-break-insert} command. @xref{-break-insert}.
27346 The possible optional parameters of this command are:
27350 Insert a temporary breakpoint.
27352 If @var{location} cannot be parsed (for example, if it
27353 refers to unknown files or functions), create a pending
27354 breakpoint. Without this flag, @value{GDBN} will report
27355 an error, and won't create a breakpoint, if @var{location}
27358 Create a disabled breakpoint.
27359 @item -c @var{condition}
27360 Make the breakpoint conditional on @var{condition}.
27361 @item -i @var{ignore-count}
27362 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27363 to @var{ignore-count}.
27364 @item -p @var{thread-id}
27365 Restrict the breakpoint to the thread with the specified global
27369 @subsubheading Result
27371 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27372 resulting breakpoint.
27374 @c An out-of-band breakpoint instead of part of the result?
27376 @subsubheading @value{GDBN} Command
27378 The corresponding @value{GDBN} command is @samp{dprintf}.
27380 @subsubheading Example
27384 4-dprintf-insert foo "At foo entry\n"
27385 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27386 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27387 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27388 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27389 original-location="foo"@}
27391 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27392 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27393 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27394 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27395 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27396 original-location="mi-dprintf.c:26"@}
27400 @subheading The @code{-break-list} Command
27401 @findex -break-list
27403 @subsubheading Synopsis
27409 Displays the list of inserted breakpoints, showing the following fields:
27413 number of the breakpoint
27415 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27417 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27420 is the breakpoint enabled or no: @samp{y} or @samp{n}
27422 memory location at which the breakpoint is set
27424 logical location of the breakpoint, expressed by function name, file
27426 @item Thread-groups
27427 list of thread groups to which this breakpoint applies
27429 number of times the breakpoint has been hit
27432 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27433 @code{body} field is an empty list.
27435 @subsubheading @value{GDBN} Command
27437 The corresponding @value{GDBN} command is @samp{info break}.
27439 @subsubheading Example
27444 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27445 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27446 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27447 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27448 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27449 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27450 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27451 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27452 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27454 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27455 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27456 line="13",thread-groups=["i1"],times="0"@}]@}
27460 Here's an example of the result when there are no breakpoints:
27465 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27466 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27467 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27468 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27469 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27470 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27471 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27476 @subheading The @code{-break-passcount} Command
27477 @findex -break-passcount
27479 @subsubheading Synopsis
27482 -break-passcount @var{tracepoint-number} @var{passcount}
27485 Set the passcount for tracepoint @var{tracepoint-number} to
27486 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27487 is not a tracepoint, error is emitted. This corresponds to CLI
27488 command @samp{passcount}.
27490 @subheading The @code{-break-watch} Command
27491 @findex -break-watch
27493 @subsubheading Synopsis
27496 -break-watch [ -a | -r ]
27499 Create a watchpoint. With the @samp{-a} option it will create an
27500 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27501 read from or on a write to the memory location. With the @samp{-r}
27502 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27503 trigger only when the memory location is accessed for reading. Without
27504 either of the options, the watchpoint created is a regular watchpoint,
27505 i.e., it will trigger when the memory location is accessed for writing.
27506 @xref{Set Watchpoints, , Setting Watchpoints}.
27508 Note that @samp{-break-list} will report a single list of watchpoints and
27509 breakpoints inserted.
27511 @subsubheading @value{GDBN} Command
27513 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27516 @subsubheading Example
27518 Setting a watchpoint on a variable in the @code{main} function:
27523 ^done,wpt=@{number="2",exp="x"@}
27528 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27529 value=@{old="-268439212",new="55"@},
27530 frame=@{func="main",args=[],file="recursive2.c",
27531 fullname="/home/foo/bar/recursive2.c",line="5"@}
27535 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27536 the program execution twice: first for the variable changing value, then
27537 for the watchpoint going out of scope.
27542 ^done,wpt=@{number="5",exp="C"@}
27547 *stopped,reason="watchpoint-trigger",
27548 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27549 frame=@{func="callee4",args=[],
27550 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27551 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27556 *stopped,reason="watchpoint-scope",wpnum="5",
27557 frame=@{func="callee3",args=[@{name="strarg",
27558 value="0x11940 \"A string argument.\""@}],
27559 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27560 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27564 Listing breakpoints and watchpoints, at different points in the program
27565 execution. Note that once the watchpoint goes out of scope, it is
27571 ^done,wpt=@{number="2",exp="C"@}
27574 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27575 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27576 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27577 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27578 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27579 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27580 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27581 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27582 addr="0x00010734",func="callee4",
27583 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27584 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27586 bkpt=@{number="2",type="watchpoint",disp="keep",
27587 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27592 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27593 value=@{old="-276895068",new="3"@},
27594 frame=@{func="callee4",args=[],
27595 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27596 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27599 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27600 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27601 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27602 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27603 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27604 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27605 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27606 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27607 addr="0x00010734",func="callee4",
27608 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27609 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27611 bkpt=@{number="2",type="watchpoint",disp="keep",
27612 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27616 ^done,reason="watchpoint-scope",wpnum="2",
27617 frame=@{func="callee3",args=[@{name="strarg",
27618 value="0x11940 \"A string argument.\""@}],
27619 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27620 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27623 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27624 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27625 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27626 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27627 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27628 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27629 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27630 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27631 addr="0x00010734",func="callee4",
27632 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27633 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27634 thread-groups=["i1"],times="1"@}]@}
27639 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27640 @node GDB/MI Catchpoint Commands
27641 @section @sc{gdb/mi} Catchpoint Commands
27643 This section documents @sc{gdb/mi} commands for manipulating
27647 * Shared Library GDB/MI Catchpoint Commands::
27648 * Ada Exception GDB/MI Catchpoint Commands::
27651 @node Shared Library GDB/MI Catchpoint Commands
27652 @subsection Shared Library @sc{gdb/mi} Catchpoints
27654 @subheading The @code{-catch-load} Command
27655 @findex -catch-load
27657 @subsubheading Synopsis
27660 -catch-load [ -t ] [ -d ] @var{regexp}
27663 Add a catchpoint for library load events. If the @samp{-t} option is used,
27664 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27665 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27666 in a disabled state. The @samp{regexp} argument is a regular
27667 expression used to match the name of the loaded library.
27670 @subsubheading @value{GDBN} Command
27672 The corresponding @value{GDBN} command is @samp{catch load}.
27674 @subsubheading Example
27677 -catch-load -t foo.so
27678 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27679 what="load of library matching foo.so",catch-type="load",times="0"@}
27684 @subheading The @code{-catch-unload} Command
27685 @findex -catch-unload
27687 @subsubheading Synopsis
27690 -catch-unload [ -t ] [ -d ] @var{regexp}
27693 Add a catchpoint for library unload events. If the @samp{-t} option is
27694 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27695 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27696 created in a disabled state. The @samp{regexp} argument is a regular
27697 expression used to match the name of the unloaded library.
27699 @subsubheading @value{GDBN} Command
27701 The corresponding @value{GDBN} command is @samp{catch unload}.
27703 @subsubheading Example
27706 -catch-unload -d bar.so
27707 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27708 what="load of library matching bar.so",catch-type="unload",times="0"@}
27712 @node Ada Exception GDB/MI Catchpoint Commands
27713 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27715 The following @sc{gdb/mi} commands can be used to create catchpoints
27716 that stop the execution when Ada exceptions are being raised.
27718 @subheading The @code{-catch-assert} Command
27719 @findex -catch-assert
27721 @subsubheading Synopsis
27724 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27727 Add a catchpoint for failed Ada assertions.
27729 The possible optional parameters for this command are:
27732 @item -c @var{condition}
27733 Make the catchpoint conditional on @var{condition}.
27735 Create a disabled catchpoint.
27737 Create a temporary catchpoint.
27740 @subsubheading @value{GDBN} Command
27742 The corresponding @value{GDBN} command is @samp{catch assert}.
27744 @subsubheading Example
27748 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27749 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27750 thread-groups=["i1"],times="0",
27751 original-location="__gnat_debug_raise_assert_failure"@}
27755 @subheading The @code{-catch-exception} Command
27756 @findex -catch-exception
27758 @subsubheading Synopsis
27761 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27765 Add a catchpoint stopping when Ada exceptions are raised.
27766 By default, the command stops the program when any Ada exception
27767 gets raised. But it is also possible, by using some of the
27768 optional parameters described below, to create more selective
27771 The possible optional parameters for this command are:
27774 @item -c @var{condition}
27775 Make the catchpoint conditional on @var{condition}.
27777 Create a disabled catchpoint.
27778 @item -e @var{exception-name}
27779 Only stop when @var{exception-name} is raised. This option cannot
27780 be used combined with @samp{-u}.
27782 Create a temporary catchpoint.
27784 Stop only when an unhandled exception gets raised. This option
27785 cannot be used combined with @samp{-e}.
27788 @subsubheading @value{GDBN} Command
27790 The corresponding @value{GDBN} commands are @samp{catch exception}
27791 and @samp{catch exception unhandled}.
27793 @subsubheading Example
27796 -catch-exception -e Program_Error
27797 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27798 enabled="y",addr="0x0000000000404874",
27799 what="`Program_Error' Ada exception", thread-groups=["i1"],
27800 times="0",original-location="__gnat_debug_raise_exception"@}
27804 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27805 @node GDB/MI Program Context
27806 @section @sc{gdb/mi} Program Context
27808 @subheading The @code{-exec-arguments} Command
27809 @findex -exec-arguments
27812 @subsubheading Synopsis
27815 -exec-arguments @var{args}
27818 Set the inferior program arguments, to be used in the next
27821 @subsubheading @value{GDBN} Command
27823 The corresponding @value{GDBN} command is @samp{set args}.
27825 @subsubheading Example
27829 -exec-arguments -v word
27836 @subheading The @code{-exec-show-arguments} Command
27837 @findex -exec-show-arguments
27839 @subsubheading Synopsis
27842 -exec-show-arguments
27845 Print the arguments of the program.
27847 @subsubheading @value{GDBN} Command
27849 The corresponding @value{GDBN} command is @samp{show args}.
27851 @subsubheading Example
27856 @subheading The @code{-environment-cd} Command
27857 @findex -environment-cd
27859 @subsubheading Synopsis
27862 -environment-cd @var{pathdir}
27865 Set @value{GDBN}'s working directory.
27867 @subsubheading @value{GDBN} Command
27869 The corresponding @value{GDBN} command is @samp{cd}.
27871 @subsubheading Example
27875 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27881 @subheading The @code{-environment-directory} Command
27882 @findex -environment-directory
27884 @subsubheading Synopsis
27887 -environment-directory [ -r ] [ @var{pathdir} ]+
27890 Add directories @var{pathdir} to beginning of search path for source files.
27891 If the @samp{-r} option is used, the search path is reset to the default
27892 search path. If directories @var{pathdir} are supplied in addition to the
27893 @samp{-r} option, the search path is first reset and then addition
27895 Multiple directories may be specified, separated by blanks. Specifying
27896 multiple directories in a single command
27897 results in the directories added to the beginning of the
27898 search path in the same order they were presented in the command.
27899 If blanks are needed as
27900 part of a directory name, double-quotes should be used around
27901 the name. In the command output, the path will show up separated
27902 by the system directory-separator character. The directory-separator
27903 character must not be used
27904 in any directory name.
27905 If no directories are specified, the current search path is displayed.
27907 @subsubheading @value{GDBN} Command
27909 The corresponding @value{GDBN} command is @samp{dir}.
27911 @subsubheading Example
27915 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27916 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27918 -environment-directory ""
27919 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27921 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27922 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27924 -environment-directory -r
27925 ^done,source-path="$cdir:$cwd"
27930 @subheading The @code{-environment-path} Command
27931 @findex -environment-path
27933 @subsubheading Synopsis
27936 -environment-path [ -r ] [ @var{pathdir} ]+
27939 Add directories @var{pathdir} to beginning of search path for object files.
27940 If the @samp{-r} option is used, the search path is reset to the original
27941 search path that existed at gdb start-up. If directories @var{pathdir} are
27942 supplied in addition to the
27943 @samp{-r} option, the search path is first reset and then addition
27945 Multiple directories may be specified, separated by blanks. Specifying
27946 multiple directories in a single command
27947 results in the directories added to the beginning of the
27948 search path in the same order they were presented in the command.
27949 If blanks are needed as
27950 part of a directory name, double-quotes should be used around
27951 the name. In the command output, the path will show up separated
27952 by the system directory-separator character. The directory-separator
27953 character must not be used
27954 in any directory name.
27955 If no directories are specified, the current path is displayed.
27958 @subsubheading @value{GDBN} Command
27960 The corresponding @value{GDBN} command is @samp{path}.
27962 @subsubheading Example
27967 ^done,path="/usr/bin"
27969 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27970 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27972 -environment-path -r /usr/local/bin
27973 ^done,path="/usr/local/bin:/usr/bin"
27978 @subheading The @code{-environment-pwd} Command
27979 @findex -environment-pwd
27981 @subsubheading Synopsis
27987 Show the current working directory.
27989 @subsubheading @value{GDBN} Command
27991 The corresponding @value{GDBN} command is @samp{pwd}.
27993 @subsubheading Example
27998 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28002 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28003 @node GDB/MI Thread Commands
28004 @section @sc{gdb/mi} Thread Commands
28007 @subheading The @code{-thread-info} Command
28008 @findex -thread-info
28010 @subsubheading Synopsis
28013 -thread-info [ @var{thread-id} ]
28016 Reports information about either a specific thread, if the
28017 @var{thread-id} parameter is present, or about all threads.
28018 @var{thread-id} is the thread's global thread ID. When printing
28019 information about all threads, also reports the global ID of the
28022 @subsubheading @value{GDBN} Command
28024 The @samp{info thread} command prints the same information
28027 @subsubheading Result
28029 The result is a list of threads. The following attributes are
28030 defined for a given thread:
28034 This field exists only for the current thread. It has the value @samp{*}.
28037 The global identifier that @value{GDBN} uses to refer to the thread.
28040 The identifier that the target uses to refer to the thread.
28043 Extra information about the thread, in a target-specific format. This
28047 The name of the thread. If the user specified a name using the
28048 @code{thread name} command, then this name is given. Otherwise, if
28049 @value{GDBN} can extract the thread name from the target, then that
28050 name is given. If @value{GDBN} cannot find the thread name, then this
28054 The stack frame currently executing in the thread.
28057 The thread's state. The @samp{state} field may have the following
28062 The thread is stopped. Frame information is available for stopped
28066 The thread is running. There's no frame information for running
28072 If @value{GDBN} can find the CPU core on which this thread is running,
28073 then this field is the core identifier. This field is optional.
28077 @subsubheading Example
28082 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28083 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28084 args=[]@},state="running"@},
28085 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28086 frame=@{level="0",addr="0x0804891f",func="foo",
28087 args=[@{name="i",value="10"@}],
28088 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28089 state="running"@}],
28090 current-thread-id="1"
28094 @subheading The @code{-thread-list-ids} Command
28095 @findex -thread-list-ids
28097 @subsubheading Synopsis
28103 Produces a list of the currently known global @value{GDBN} thread ids.
28104 At the end of the list it also prints the total number of such
28107 This command is retained for historical reasons, the
28108 @code{-thread-info} command should be used instead.
28110 @subsubheading @value{GDBN} Command
28112 Part of @samp{info threads} supplies the same information.
28114 @subsubheading Example
28119 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28120 current-thread-id="1",number-of-threads="3"
28125 @subheading The @code{-thread-select} Command
28126 @findex -thread-select
28128 @subsubheading Synopsis
28131 -thread-select @var{thread-id}
28134 Make thread with global thread number @var{thread-id} the current
28135 thread. It prints the number of the new current thread, and the
28136 topmost frame for that thread.
28138 This command is deprecated in favor of explicitly using the
28139 @samp{--thread} option to each command.
28141 @subsubheading @value{GDBN} Command
28143 The corresponding @value{GDBN} command is @samp{thread}.
28145 @subsubheading Example
28152 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28153 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28157 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28158 number-of-threads="3"
28161 ^done,new-thread-id="3",
28162 frame=@{level="0",func="vprintf",
28163 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28164 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28168 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28169 @node GDB/MI Ada Tasking Commands
28170 @section @sc{gdb/mi} Ada Tasking Commands
28172 @subheading The @code{-ada-task-info} Command
28173 @findex -ada-task-info
28175 @subsubheading Synopsis
28178 -ada-task-info [ @var{task-id} ]
28181 Reports information about either a specific Ada task, if the
28182 @var{task-id} parameter is present, or about all Ada tasks.
28184 @subsubheading @value{GDBN} Command
28186 The @samp{info tasks} command prints the same information
28187 about all Ada tasks (@pxref{Ada Tasks}).
28189 @subsubheading Result
28191 The result is a table of Ada tasks. The following columns are
28192 defined for each Ada task:
28196 This field exists only for the current thread. It has the value @samp{*}.
28199 The identifier that @value{GDBN} uses to refer to the Ada task.
28202 The identifier that the target uses to refer to the Ada task.
28205 The global thread identifier of the thread corresponding to the Ada
28208 This field should always exist, as Ada tasks are always implemented
28209 on top of a thread. But if @value{GDBN} cannot find this corresponding
28210 thread for any reason, the field is omitted.
28213 This field exists only when the task was created by another task.
28214 In this case, it provides the ID of the parent task.
28217 The base priority of the task.
28220 The current state of the task. For a detailed description of the
28221 possible states, see @ref{Ada Tasks}.
28224 The name of the task.
28228 @subsubheading Example
28232 ^done,tasks=@{nr_rows="3",nr_cols="8",
28233 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28234 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28235 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28236 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28237 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28238 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28239 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28240 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28241 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28242 state="Child Termination Wait",name="main_task"@}]@}
28246 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28247 @node GDB/MI Program Execution
28248 @section @sc{gdb/mi} Program Execution
28250 These are the asynchronous commands which generate the out-of-band
28251 record @samp{*stopped}. Currently @value{GDBN} only really executes
28252 asynchronously with remote targets and this interaction is mimicked in
28255 @subheading The @code{-exec-continue} Command
28256 @findex -exec-continue
28258 @subsubheading Synopsis
28261 -exec-continue [--reverse] [--all|--thread-group N]
28264 Resumes the execution of the inferior program, which will continue
28265 to execute until it reaches a debugger stop event. If the
28266 @samp{--reverse} option is specified, execution resumes in reverse until
28267 it reaches a stop event. Stop events may include
28270 breakpoints or watchpoints
28272 signals or exceptions
28274 the end of the process (or its beginning under @samp{--reverse})
28276 the end or beginning of a replay log if one is being used.
28278 In all-stop mode (@pxref{All-Stop
28279 Mode}), may resume only one thread, or all threads, depending on the
28280 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28281 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28282 ignored in all-stop mode. If the @samp{--thread-group} options is
28283 specified, then all threads in that thread group are resumed.
28285 @subsubheading @value{GDBN} Command
28287 The corresponding @value{GDBN} corresponding is @samp{continue}.
28289 @subsubheading Example
28296 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28297 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28303 @subheading The @code{-exec-finish} Command
28304 @findex -exec-finish
28306 @subsubheading Synopsis
28309 -exec-finish [--reverse]
28312 Resumes the execution of the inferior program until the current
28313 function is exited. Displays the results returned by the function.
28314 If the @samp{--reverse} option is specified, resumes the reverse
28315 execution of the inferior program until the point where current
28316 function was called.
28318 @subsubheading @value{GDBN} Command
28320 The corresponding @value{GDBN} command is @samp{finish}.
28322 @subsubheading Example
28324 Function returning @code{void}.
28331 *stopped,reason="function-finished",frame=@{func="main",args=[],
28332 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28336 Function returning other than @code{void}. The name of the internal
28337 @value{GDBN} variable storing the result is printed, together with the
28344 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28345 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28346 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28347 gdb-result-var="$1",return-value="0"
28352 @subheading The @code{-exec-interrupt} Command
28353 @findex -exec-interrupt
28355 @subsubheading Synopsis
28358 -exec-interrupt [--all|--thread-group N]
28361 Interrupts the background execution of the target. Note how the token
28362 associated with the stop message is the one for the execution command
28363 that has been interrupted. The token for the interrupt itself only
28364 appears in the @samp{^done} output. If the user is trying to
28365 interrupt a non-running program, an error message will be printed.
28367 Note that when asynchronous execution is enabled, this command is
28368 asynchronous just like other execution commands. That is, first the
28369 @samp{^done} response will be printed, and the target stop will be
28370 reported after that using the @samp{*stopped} notification.
28372 In non-stop mode, only the context thread is interrupted by default.
28373 All threads (in all inferiors) will be interrupted if the
28374 @samp{--all} option is specified. If the @samp{--thread-group}
28375 option is specified, all threads in that group will be interrupted.
28377 @subsubheading @value{GDBN} Command
28379 The corresponding @value{GDBN} command is @samp{interrupt}.
28381 @subsubheading Example
28392 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28393 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28394 fullname="/home/foo/bar/try.c",line="13"@}
28399 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28403 @subheading The @code{-exec-jump} Command
28406 @subsubheading Synopsis
28409 -exec-jump @var{location}
28412 Resumes execution of the inferior program at the location specified by
28413 parameter. @xref{Specify Location}, for a description of the
28414 different forms of @var{location}.
28416 @subsubheading @value{GDBN} Command
28418 The corresponding @value{GDBN} command is @samp{jump}.
28420 @subsubheading Example
28423 -exec-jump foo.c:10
28424 *running,thread-id="all"
28429 @subheading The @code{-exec-next} Command
28432 @subsubheading Synopsis
28435 -exec-next [--reverse]
28438 Resumes execution of the inferior program, stopping when the beginning
28439 of the next source line is reached.
28441 If the @samp{--reverse} option is specified, resumes reverse execution
28442 of the inferior program, stopping at the beginning of the previous
28443 source line. If you issue this command on the first line of a
28444 function, it will take you back to the caller of that function, to the
28445 source line where the function was called.
28448 @subsubheading @value{GDBN} Command
28450 The corresponding @value{GDBN} command is @samp{next}.
28452 @subsubheading Example
28458 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28463 @subheading The @code{-exec-next-instruction} Command
28464 @findex -exec-next-instruction
28466 @subsubheading Synopsis
28469 -exec-next-instruction [--reverse]
28472 Executes one machine instruction. If the instruction is a function
28473 call, continues until the function returns. If the program stops at an
28474 instruction in the middle of a source line, the address will be
28477 If the @samp{--reverse} option is specified, resumes reverse execution
28478 of the inferior program, stopping at the previous instruction. If the
28479 previously executed instruction was a return from another function,
28480 it will continue to execute in reverse until the call to that function
28481 (from the current stack frame) is reached.
28483 @subsubheading @value{GDBN} Command
28485 The corresponding @value{GDBN} command is @samp{nexti}.
28487 @subsubheading Example
28491 -exec-next-instruction
28495 *stopped,reason="end-stepping-range",
28496 addr="0x000100d4",line="5",file="hello.c"
28501 @subheading The @code{-exec-return} Command
28502 @findex -exec-return
28504 @subsubheading Synopsis
28510 Makes current function return immediately. Doesn't execute the inferior.
28511 Displays the new current frame.
28513 @subsubheading @value{GDBN} Command
28515 The corresponding @value{GDBN} command is @samp{return}.
28517 @subsubheading Example
28521 200-break-insert callee4
28522 200^done,bkpt=@{number="1",addr="0x00010734",
28523 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28528 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28529 frame=@{func="callee4",args=[],
28530 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28531 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28537 111^done,frame=@{level="0",func="callee3",
28538 args=[@{name="strarg",
28539 value="0x11940 \"A string argument.\""@}],
28540 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28541 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28546 @subheading The @code{-exec-run} Command
28549 @subsubheading Synopsis
28552 -exec-run [ --all | --thread-group N ] [ --start ]
28555 Starts execution of the inferior from the beginning. The inferior
28556 executes until either a breakpoint is encountered or the program
28557 exits. In the latter case the output will include an exit code, if
28558 the program has exited exceptionally.
28560 When neither the @samp{--all} nor the @samp{--thread-group} option
28561 is specified, the current inferior is started. If the
28562 @samp{--thread-group} option is specified, it should refer to a thread
28563 group of type @samp{process}, and that thread group will be started.
28564 If the @samp{--all} option is specified, then all inferiors will be started.
28566 Using the @samp{--start} option instructs the debugger to stop
28567 the execution at the start of the inferior's main subprogram,
28568 following the same behavior as the @code{start} command
28569 (@pxref{Starting}).
28571 @subsubheading @value{GDBN} Command
28573 The corresponding @value{GDBN} command is @samp{run}.
28575 @subsubheading Examples
28580 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28585 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28586 frame=@{func="main",args=[],file="recursive2.c",
28587 fullname="/home/foo/bar/recursive2.c",line="4"@}
28592 Program exited normally:
28600 *stopped,reason="exited-normally"
28605 Program exited exceptionally:
28613 *stopped,reason="exited",exit-code="01"
28617 Another way the program can terminate is if it receives a signal such as
28618 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28622 *stopped,reason="exited-signalled",signal-name="SIGINT",
28623 signal-meaning="Interrupt"
28627 @c @subheading -exec-signal
28630 @subheading The @code{-exec-step} Command
28633 @subsubheading Synopsis
28636 -exec-step [--reverse]
28639 Resumes execution of the inferior program, stopping when the beginning
28640 of the next source line is reached, if the next source line is not a
28641 function call. If it is, stop at the first instruction of the called
28642 function. If the @samp{--reverse} option is specified, resumes reverse
28643 execution of the inferior program, stopping at the beginning of the
28644 previously executed source line.
28646 @subsubheading @value{GDBN} Command
28648 The corresponding @value{GDBN} command is @samp{step}.
28650 @subsubheading Example
28652 Stepping into a function:
28658 *stopped,reason="end-stepping-range",
28659 frame=@{func="foo",args=[@{name="a",value="10"@},
28660 @{name="b",value="0"@}],file="recursive2.c",
28661 fullname="/home/foo/bar/recursive2.c",line="11"@}
28671 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28676 @subheading The @code{-exec-step-instruction} Command
28677 @findex -exec-step-instruction
28679 @subsubheading Synopsis
28682 -exec-step-instruction [--reverse]
28685 Resumes the inferior which executes one machine instruction. If the
28686 @samp{--reverse} option is specified, resumes reverse execution of the
28687 inferior program, stopping at the previously executed instruction.
28688 The output, once @value{GDBN} has stopped, will vary depending on
28689 whether we have stopped in the middle of a source line or not. In the
28690 former case, the address at which the program stopped will be printed
28693 @subsubheading @value{GDBN} Command
28695 The corresponding @value{GDBN} command is @samp{stepi}.
28697 @subsubheading Example
28701 -exec-step-instruction
28705 *stopped,reason="end-stepping-range",
28706 frame=@{func="foo",args=[],file="try.c",
28707 fullname="/home/foo/bar/try.c",line="10"@}
28709 -exec-step-instruction
28713 *stopped,reason="end-stepping-range",
28714 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28715 fullname="/home/foo/bar/try.c",line="10"@}
28720 @subheading The @code{-exec-until} Command
28721 @findex -exec-until
28723 @subsubheading Synopsis
28726 -exec-until [ @var{location} ]
28729 Executes the inferior until the @var{location} specified in the
28730 argument is reached. If there is no argument, the inferior executes
28731 until a source line greater than the current one is reached. The
28732 reason for stopping in this case will be @samp{location-reached}.
28734 @subsubheading @value{GDBN} Command
28736 The corresponding @value{GDBN} command is @samp{until}.
28738 @subsubheading Example
28742 -exec-until recursive2.c:6
28746 *stopped,reason="location-reached",frame=@{func="main",args=[],
28747 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28752 @subheading -file-clear
28753 Is this going away????
28756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28757 @node GDB/MI Stack Manipulation
28758 @section @sc{gdb/mi} Stack Manipulation Commands
28760 @subheading The @code{-enable-frame-filters} Command
28761 @findex -enable-frame-filters
28764 -enable-frame-filters
28767 @value{GDBN} allows Python-based frame filters to affect the output of
28768 the MI commands relating to stack traces. As there is no way to
28769 implement this in a fully backward-compatible way, a front end must
28770 request that this functionality be enabled.
28772 Once enabled, this feature cannot be disabled.
28774 Note that if Python support has not been compiled into @value{GDBN},
28775 this command will still succeed (and do nothing).
28777 @subheading The @code{-stack-info-frame} Command
28778 @findex -stack-info-frame
28780 @subsubheading Synopsis
28786 Get info on the selected frame.
28788 @subsubheading @value{GDBN} Command
28790 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28791 (without arguments).
28793 @subsubheading Example
28798 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28799 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28800 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28804 @subheading The @code{-stack-info-depth} Command
28805 @findex -stack-info-depth
28807 @subsubheading Synopsis
28810 -stack-info-depth [ @var{max-depth} ]
28813 Return the depth of the stack. If the integer argument @var{max-depth}
28814 is specified, do not count beyond @var{max-depth} frames.
28816 @subsubheading @value{GDBN} Command
28818 There's no equivalent @value{GDBN} command.
28820 @subsubheading Example
28822 For a stack with frame levels 0 through 11:
28829 -stack-info-depth 4
28832 -stack-info-depth 12
28835 -stack-info-depth 11
28838 -stack-info-depth 13
28843 @anchor{-stack-list-arguments}
28844 @subheading The @code{-stack-list-arguments} Command
28845 @findex -stack-list-arguments
28847 @subsubheading Synopsis
28850 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28851 [ @var{low-frame} @var{high-frame} ]
28854 Display a list of the arguments for the frames between @var{low-frame}
28855 and @var{high-frame} (inclusive). If @var{low-frame} and
28856 @var{high-frame} are not provided, list the arguments for the whole
28857 call stack. If the two arguments are equal, show the single frame
28858 at the corresponding level. It is an error if @var{low-frame} is
28859 larger than the actual number of frames. On the other hand,
28860 @var{high-frame} may be larger than the actual number of frames, in
28861 which case only existing frames will be returned.
28863 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28864 the variables; if it is 1 or @code{--all-values}, print also their
28865 values; and if it is 2 or @code{--simple-values}, print the name,
28866 type and value for simple data types, and the name and type for arrays,
28867 structures and unions. If the option @code{--no-frame-filters} is
28868 supplied, then Python frame filters will not be executed.
28870 If the @code{--skip-unavailable} option is specified, arguments that
28871 are not available are not listed. Partially available arguments
28872 are still displayed, however.
28874 Use of this command to obtain arguments in a single frame is
28875 deprecated in favor of the @samp{-stack-list-variables} command.
28877 @subsubheading @value{GDBN} Command
28879 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28880 @samp{gdb_get_args} command which partially overlaps with the
28881 functionality of @samp{-stack-list-arguments}.
28883 @subsubheading Example
28890 frame=@{level="0",addr="0x00010734",func="callee4",
28891 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28892 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28893 frame=@{level="1",addr="0x0001076c",func="callee3",
28894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28895 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28896 frame=@{level="2",addr="0x0001078c",func="callee2",
28897 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28898 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28899 frame=@{level="3",addr="0x000107b4",func="callee1",
28900 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28901 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28902 frame=@{level="4",addr="0x000107e0",func="main",
28903 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28904 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28906 -stack-list-arguments 0
28909 frame=@{level="0",args=[]@},
28910 frame=@{level="1",args=[name="strarg"]@},
28911 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28912 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28913 frame=@{level="4",args=[]@}]
28915 -stack-list-arguments 1
28918 frame=@{level="0",args=[]@},
28920 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28921 frame=@{level="2",args=[
28922 @{name="intarg",value="2"@},
28923 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28924 @{frame=@{level="3",args=[
28925 @{name="intarg",value="2"@},
28926 @{name="strarg",value="0x11940 \"A string argument.\""@},
28927 @{name="fltarg",value="3.5"@}]@},
28928 frame=@{level="4",args=[]@}]
28930 -stack-list-arguments 0 2 2
28931 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28933 -stack-list-arguments 1 2 2
28934 ^done,stack-args=[frame=@{level="2",
28935 args=[@{name="intarg",value="2"@},
28936 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28940 @c @subheading -stack-list-exception-handlers
28943 @anchor{-stack-list-frames}
28944 @subheading The @code{-stack-list-frames} Command
28945 @findex -stack-list-frames
28947 @subsubheading Synopsis
28950 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28953 List the frames currently on the stack. For each frame it displays the
28958 The frame number, 0 being the topmost frame, i.e., the innermost function.
28960 The @code{$pc} value for that frame.
28964 File name of the source file where the function lives.
28965 @item @var{fullname}
28966 The full file name of the source file where the function lives.
28968 Line number corresponding to the @code{$pc}.
28970 The shared library where this function is defined. This is only given
28971 if the frame's function is not known.
28974 If invoked without arguments, this command prints a backtrace for the
28975 whole stack. If given two integer arguments, it shows the frames whose
28976 levels are between the two arguments (inclusive). If the two arguments
28977 are equal, it shows the single frame at the corresponding level. It is
28978 an error if @var{low-frame} is larger than the actual number of
28979 frames. On the other hand, @var{high-frame} may be larger than the
28980 actual number of frames, in which case only existing frames will be
28981 returned. If the option @code{--no-frame-filters} is supplied, then
28982 Python frame filters will not be executed.
28984 @subsubheading @value{GDBN} Command
28986 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28988 @subsubheading Example
28990 Full stack backtrace:
28996 [frame=@{level="0",addr="0x0001076c",func="foo",
28997 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28998 frame=@{level="1",addr="0x000107a4",func="foo",
28999 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29000 frame=@{level="2",addr="0x000107a4",func="foo",
29001 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29002 frame=@{level="3",addr="0x000107a4",func="foo",
29003 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29004 frame=@{level="4",addr="0x000107a4",func="foo",
29005 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29006 frame=@{level="5",addr="0x000107a4",func="foo",
29007 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29008 frame=@{level="6",addr="0x000107a4",func="foo",
29009 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29010 frame=@{level="7",addr="0x000107a4",func="foo",
29011 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29012 frame=@{level="8",addr="0x000107a4",func="foo",
29013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29014 frame=@{level="9",addr="0x000107a4",func="foo",
29015 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29016 frame=@{level="10",addr="0x000107a4",func="foo",
29017 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29018 frame=@{level="11",addr="0x00010738",func="main",
29019 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29023 Show frames between @var{low_frame} and @var{high_frame}:
29027 -stack-list-frames 3 5
29029 [frame=@{level="3",addr="0x000107a4",func="foo",
29030 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29031 frame=@{level="4",addr="0x000107a4",func="foo",
29032 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29033 frame=@{level="5",addr="0x000107a4",func="foo",
29034 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29038 Show a single frame:
29042 -stack-list-frames 3 3
29044 [frame=@{level="3",addr="0x000107a4",func="foo",
29045 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29050 @subheading The @code{-stack-list-locals} Command
29051 @findex -stack-list-locals
29052 @anchor{-stack-list-locals}
29054 @subsubheading Synopsis
29057 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29060 Display the local variable names for the selected frame. If
29061 @var{print-values} is 0 or @code{--no-values}, print only the names of
29062 the variables; if it is 1 or @code{--all-values}, print also their
29063 values; and if it is 2 or @code{--simple-values}, print the name,
29064 type and value for simple data types, and the name and type for arrays,
29065 structures and unions. In this last case, a frontend can immediately
29066 display the value of simple data types and create variable objects for
29067 other data types when the user wishes to explore their values in
29068 more detail. If the option @code{--no-frame-filters} is supplied, then
29069 Python frame filters will not be executed.
29071 If the @code{--skip-unavailable} option is specified, local variables
29072 that are not available are not listed. Partially available local
29073 variables are still displayed, however.
29075 This command is deprecated in favor of the
29076 @samp{-stack-list-variables} command.
29078 @subsubheading @value{GDBN} Command
29080 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29082 @subsubheading Example
29086 -stack-list-locals 0
29087 ^done,locals=[name="A",name="B",name="C"]
29089 -stack-list-locals --all-values
29090 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29091 @{name="C",value="@{1, 2, 3@}"@}]
29092 -stack-list-locals --simple-values
29093 ^done,locals=[@{name="A",type="int",value="1"@},
29094 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29098 @anchor{-stack-list-variables}
29099 @subheading The @code{-stack-list-variables} Command
29100 @findex -stack-list-variables
29102 @subsubheading Synopsis
29105 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29108 Display the names of local variables and function arguments for the selected frame. If
29109 @var{print-values} is 0 or @code{--no-values}, print only the names of
29110 the variables; if it is 1 or @code{--all-values}, print also their
29111 values; and if it is 2 or @code{--simple-values}, print the name,
29112 type and value for simple data types, and the name and type for arrays,
29113 structures and unions. If the option @code{--no-frame-filters} is
29114 supplied, then Python frame filters will not be executed.
29116 If the @code{--skip-unavailable} option is specified, local variables
29117 and arguments that are not available are not listed. Partially
29118 available arguments and local variables are still displayed, however.
29120 @subsubheading Example
29124 -stack-list-variables --thread 1 --frame 0 --all-values
29125 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29130 @subheading The @code{-stack-select-frame} Command
29131 @findex -stack-select-frame
29133 @subsubheading Synopsis
29136 -stack-select-frame @var{framenum}
29139 Change the selected frame. Select a different frame @var{framenum} on
29142 This command in deprecated in favor of passing the @samp{--frame}
29143 option to every command.
29145 @subsubheading @value{GDBN} Command
29147 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29148 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29150 @subsubheading Example
29154 -stack-select-frame 2
29159 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29160 @node GDB/MI Variable Objects
29161 @section @sc{gdb/mi} Variable Objects
29165 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29167 For the implementation of a variable debugger window (locals, watched
29168 expressions, etc.), we are proposing the adaptation of the existing code
29169 used by @code{Insight}.
29171 The two main reasons for that are:
29175 It has been proven in practice (it is already on its second generation).
29178 It will shorten development time (needless to say how important it is
29182 The original interface was designed to be used by Tcl code, so it was
29183 slightly changed so it could be used through @sc{gdb/mi}. This section
29184 describes the @sc{gdb/mi} operations that will be available and gives some
29185 hints about their use.
29187 @emph{Note}: In addition to the set of operations described here, we
29188 expect the @sc{gui} implementation of a variable window to require, at
29189 least, the following operations:
29192 @item @code{-gdb-show} @code{output-radix}
29193 @item @code{-stack-list-arguments}
29194 @item @code{-stack-list-locals}
29195 @item @code{-stack-select-frame}
29200 @subheading Introduction to Variable Objects
29202 @cindex variable objects in @sc{gdb/mi}
29204 Variable objects are "object-oriented" MI interface for examining and
29205 changing values of expressions. Unlike some other MI interfaces that
29206 work with expressions, variable objects are specifically designed for
29207 simple and efficient presentation in the frontend. A variable object
29208 is identified by string name. When a variable object is created, the
29209 frontend specifies the expression for that variable object. The
29210 expression can be a simple variable, or it can be an arbitrary complex
29211 expression, and can even involve CPU registers. After creating a
29212 variable object, the frontend can invoke other variable object
29213 operations---for example to obtain or change the value of a variable
29214 object, or to change display format.
29216 Variable objects have hierarchical tree structure. Any variable object
29217 that corresponds to a composite type, such as structure in C, has
29218 a number of child variable objects, for example corresponding to each
29219 element of a structure. A child variable object can itself have
29220 children, recursively. Recursion ends when we reach
29221 leaf variable objects, which always have built-in types. Child variable
29222 objects are created only by explicit request, so if a frontend
29223 is not interested in the children of a particular variable object, no
29224 child will be created.
29226 For a leaf variable object it is possible to obtain its value as a
29227 string, or set the value from a string. String value can be also
29228 obtained for a non-leaf variable object, but it's generally a string
29229 that only indicates the type of the object, and does not list its
29230 contents. Assignment to a non-leaf variable object is not allowed.
29232 A frontend does not need to read the values of all variable objects each time
29233 the program stops. Instead, MI provides an update command that lists all
29234 variable objects whose values has changed since the last update
29235 operation. This considerably reduces the amount of data that must
29236 be transferred to the frontend. As noted above, children variable
29237 objects are created on demand, and only leaf variable objects have a
29238 real value. As result, gdb will read target memory only for leaf
29239 variables that frontend has created.
29241 The automatic update is not always desirable. For example, a frontend
29242 might want to keep a value of some expression for future reference,
29243 and never update it. For another example, fetching memory is
29244 relatively slow for embedded targets, so a frontend might want
29245 to disable automatic update for the variables that are either not
29246 visible on the screen, or ``closed''. This is possible using so
29247 called ``frozen variable objects''. Such variable objects are never
29248 implicitly updated.
29250 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29251 fixed variable object, the expression is parsed when the variable
29252 object is created, including associating identifiers to specific
29253 variables. The meaning of expression never changes. For a floating
29254 variable object the values of variables whose names appear in the
29255 expressions are re-evaluated every time in the context of the current
29256 frame. Consider this example:
29261 struct work_state state;
29268 If a fixed variable object for the @code{state} variable is created in
29269 this function, and we enter the recursive call, the variable
29270 object will report the value of @code{state} in the top-level
29271 @code{do_work} invocation. On the other hand, a floating variable
29272 object will report the value of @code{state} in the current frame.
29274 If an expression specified when creating a fixed variable object
29275 refers to a local variable, the variable object becomes bound to the
29276 thread and frame in which the variable object is created. When such
29277 variable object is updated, @value{GDBN} makes sure that the
29278 thread/frame combination the variable object is bound to still exists,
29279 and re-evaluates the variable object in context of that thread/frame.
29281 The following is the complete set of @sc{gdb/mi} operations defined to
29282 access this functionality:
29284 @multitable @columnfractions .4 .6
29285 @item @strong{Operation}
29286 @tab @strong{Description}
29288 @item @code{-enable-pretty-printing}
29289 @tab enable Python-based pretty-printing
29290 @item @code{-var-create}
29291 @tab create a variable object
29292 @item @code{-var-delete}
29293 @tab delete the variable object and/or its children
29294 @item @code{-var-set-format}
29295 @tab set the display format of this variable
29296 @item @code{-var-show-format}
29297 @tab show the display format of this variable
29298 @item @code{-var-info-num-children}
29299 @tab tells how many children this object has
29300 @item @code{-var-list-children}
29301 @tab return a list of the object's children
29302 @item @code{-var-info-type}
29303 @tab show the type of this variable object
29304 @item @code{-var-info-expression}
29305 @tab print parent-relative expression that this variable object represents
29306 @item @code{-var-info-path-expression}
29307 @tab print full expression that this variable object represents
29308 @item @code{-var-show-attributes}
29309 @tab is this variable editable? does it exist here?
29310 @item @code{-var-evaluate-expression}
29311 @tab get the value of this variable
29312 @item @code{-var-assign}
29313 @tab set the value of this variable
29314 @item @code{-var-update}
29315 @tab update the variable and its children
29316 @item @code{-var-set-frozen}
29317 @tab set frozeness attribute
29318 @item @code{-var-set-update-range}
29319 @tab set range of children to display on update
29322 In the next subsection we describe each operation in detail and suggest
29323 how it can be used.
29325 @subheading Description And Use of Operations on Variable Objects
29327 @subheading The @code{-enable-pretty-printing} Command
29328 @findex -enable-pretty-printing
29331 -enable-pretty-printing
29334 @value{GDBN} allows Python-based visualizers to affect the output of the
29335 MI variable object commands. However, because there was no way to
29336 implement this in a fully backward-compatible way, a front end must
29337 request that this functionality be enabled.
29339 Once enabled, this feature cannot be disabled.
29341 Note that if Python support has not been compiled into @value{GDBN},
29342 this command will still succeed (and do nothing).
29344 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29345 may work differently in future versions of @value{GDBN}.
29347 @subheading The @code{-var-create} Command
29348 @findex -var-create
29350 @subsubheading Synopsis
29353 -var-create @{@var{name} | "-"@}
29354 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29357 This operation creates a variable object, which allows the monitoring of
29358 a variable, the result of an expression, a memory cell or a CPU
29361 The @var{name} parameter is the string by which the object can be
29362 referenced. It must be unique. If @samp{-} is specified, the varobj
29363 system will generate a string ``varNNNNNN'' automatically. It will be
29364 unique provided that one does not specify @var{name} of that format.
29365 The command fails if a duplicate name is found.
29367 The frame under which the expression should be evaluated can be
29368 specified by @var{frame-addr}. A @samp{*} indicates that the current
29369 frame should be used. A @samp{@@} indicates that a floating variable
29370 object must be created.
29372 @var{expression} is any expression valid on the current language set (must not
29373 begin with a @samp{*}), or one of the following:
29377 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29380 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29383 @samp{$@var{regname}} --- a CPU register name
29386 @cindex dynamic varobj
29387 A varobj's contents may be provided by a Python-based pretty-printer. In this
29388 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29389 have slightly different semantics in some cases. If the
29390 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29391 will never create a dynamic varobj. This ensures backward
29392 compatibility for existing clients.
29394 @subsubheading Result
29396 This operation returns attributes of the newly-created varobj. These
29401 The name of the varobj.
29404 The number of children of the varobj. This number is not necessarily
29405 reliable for a dynamic varobj. Instead, you must examine the
29406 @samp{has_more} attribute.
29409 The varobj's scalar value. For a varobj whose type is some sort of
29410 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29411 will not be interesting.
29414 The varobj's type. This is a string representation of the type, as
29415 would be printed by the @value{GDBN} CLI. If @samp{print object}
29416 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29417 @emph{actual} (derived) type of the object is shown rather than the
29418 @emph{declared} one.
29421 If a variable object is bound to a specific thread, then this is the
29422 thread's global identifier.
29425 For a dynamic varobj, this indicates whether there appear to be any
29426 children available. For a non-dynamic varobj, this will be 0.
29429 This attribute will be present and have the value @samp{1} if the
29430 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29431 then this attribute will not be present.
29434 A dynamic varobj can supply a display hint to the front end. The
29435 value comes directly from the Python pretty-printer object's
29436 @code{display_hint} method. @xref{Pretty Printing API}.
29439 Typical output will look like this:
29442 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29443 has_more="@var{has_more}"
29447 @subheading The @code{-var-delete} Command
29448 @findex -var-delete
29450 @subsubheading Synopsis
29453 -var-delete [ -c ] @var{name}
29456 Deletes a previously created variable object and all of its children.
29457 With the @samp{-c} option, just deletes the children.
29459 Returns an error if the object @var{name} is not found.
29462 @subheading The @code{-var-set-format} Command
29463 @findex -var-set-format
29465 @subsubheading Synopsis
29468 -var-set-format @var{name} @var{format-spec}
29471 Sets the output format for the value of the object @var{name} to be
29474 @anchor{-var-set-format}
29475 The syntax for the @var{format-spec} is as follows:
29478 @var{format-spec} @expansion{}
29479 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29482 The natural format is the default format choosen automatically
29483 based on the variable type (like decimal for an @code{int}, hex
29484 for pointers, etc.).
29486 The zero-hexadecimal format has a representation similar to hexadecimal
29487 but with padding zeroes to the left of the value. For example, a 32-bit
29488 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29489 zero-hexadecimal format.
29491 For a variable with children, the format is set only on the
29492 variable itself, and the children are not affected.
29494 @subheading The @code{-var-show-format} Command
29495 @findex -var-show-format
29497 @subsubheading Synopsis
29500 -var-show-format @var{name}
29503 Returns the format used to display the value of the object @var{name}.
29506 @var{format} @expansion{}
29511 @subheading The @code{-var-info-num-children} Command
29512 @findex -var-info-num-children
29514 @subsubheading Synopsis
29517 -var-info-num-children @var{name}
29520 Returns the number of children of a variable object @var{name}:
29526 Note that this number is not completely reliable for a dynamic varobj.
29527 It will return the current number of children, but more children may
29531 @subheading The @code{-var-list-children} Command
29532 @findex -var-list-children
29534 @subsubheading Synopsis
29537 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29539 @anchor{-var-list-children}
29541 Return a list of the children of the specified variable object and
29542 create variable objects for them, if they do not already exist. With
29543 a single argument or if @var{print-values} has a value of 0 or
29544 @code{--no-values}, print only the names of the variables; if
29545 @var{print-values} is 1 or @code{--all-values}, also print their
29546 values; and if it is 2 or @code{--simple-values} print the name and
29547 value for simple data types and just the name for arrays, structures
29550 @var{from} and @var{to}, if specified, indicate the range of children
29551 to report. If @var{from} or @var{to} is less than zero, the range is
29552 reset and all children will be reported. Otherwise, children starting
29553 at @var{from} (zero-based) and up to and excluding @var{to} will be
29556 If a child range is requested, it will only affect the current call to
29557 @code{-var-list-children}, but not future calls to @code{-var-update}.
29558 For this, you must instead use @code{-var-set-update-range}. The
29559 intent of this approach is to enable a front end to implement any
29560 update approach it likes; for example, scrolling a view may cause the
29561 front end to request more children with @code{-var-list-children}, and
29562 then the front end could call @code{-var-set-update-range} with a
29563 different range to ensure that future updates are restricted to just
29566 For each child the following results are returned:
29571 Name of the variable object created for this child.
29574 The expression to be shown to the user by the front end to designate this child.
29575 For example this may be the name of a structure member.
29577 For a dynamic varobj, this value cannot be used to form an
29578 expression. There is no way to do this at all with a dynamic varobj.
29580 For C/C@t{++} structures there are several pseudo children returned to
29581 designate access qualifiers. For these pseudo children @var{exp} is
29582 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29583 type and value are not present.
29585 A dynamic varobj will not report the access qualifying
29586 pseudo-children, regardless of the language. This information is not
29587 available at all with a dynamic varobj.
29590 Number of children this child has. For a dynamic varobj, this will be
29594 The type of the child. If @samp{print object}
29595 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29596 @emph{actual} (derived) type of the object is shown rather than the
29597 @emph{declared} one.
29600 If values were requested, this is the value.
29603 If this variable object is associated with a thread, this is the
29604 thread's global thread id. Otherwise this result is not present.
29607 If the variable object is frozen, this variable will be present with a value of 1.
29610 A dynamic varobj can supply a display hint to the front end. The
29611 value comes directly from the Python pretty-printer object's
29612 @code{display_hint} method. @xref{Pretty Printing API}.
29615 This attribute will be present and have the value @samp{1} if the
29616 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29617 then this attribute will not be present.
29621 The result may have its own attributes:
29625 A dynamic varobj can supply a display hint to the front end. The
29626 value comes directly from the Python pretty-printer object's
29627 @code{display_hint} method. @xref{Pretty Printing API}.
29630 This is an integer attribute which is nonzero if there are children
29631 remaining after the end of the selected range.
29634 @subsubheading Example
29638 -var-list-children n
29639 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29640 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29642 -var-list-children --all-values n
29643 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29644 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29648 @subheading The @code{-var-info-type} Command
29649 @findex -var-info-type
29651 @subsubheading Synopsis
29654 -var-info-type @var{name}
29657 Returns the type of the specified variable @var{name}. The type is
29658 returned as a string in the same format as it is output by the
29662 type=@var{typename}
29666 @subheading The @code{-var-info-expression} Command
29667 @findex -var-info-expression
29669 @subsubheading Synopsis
29672 -var-info-expression @var{name}
29675 Returns a string that is suitable for presenting this
29676 variable object in user interface. The string is generally
29677 not valid expression in the current language, and cannot be evaluated.
29679 For example, if @code{a} is an array, and variable object
29680 @code{A} was created for @code{a}, then we'll get this output:
29683 (gdb) -var-info-expression A.1
29684 ^done,lang="C",exp="1"
29688 Here, the value of @code{lang} is the language name, which can be
29689 found in @ref{Supported Languages}.
29691 Note that the output of the @code{-var-list-children} command also
29692 includes those expressions, so the @code{-var-info-expression} command
29695 @subheading The @code{-var-info-path-expression} Command
29696 @findex -var-info-path-expression
29698 @subsubheading Synopsis
29701 -var-info-path-expression @var{name}
29704 Returns an expression that can be evaluated in the current
29705 context and will yield the same value that a variable object has.
29706 Compare this with the @code{-var-info-expression} command, which
29707 result can be used only for UI presentation. Typical use of
29708 the @code{-var-info-path-expression} command is creating a
29709 watchpoint from a variable object.
29711 This command is currently not valid for children of a dynamic varobj,
29712 and will give an error when invoked on one.
29714 For example, suppose @code{C} is a C@t{++} class, derived from class
29715 @code{Base}, and that the @code{Base} class has a member called
29716 @code{m_size}. Assume a variable @code{c} is has the type of
29717 @code{C} and a variable object @code{C} was created for variable
29718 @code{c}. Then, we'll get this output:
29720 (gdb) -var-info-path-expression C.Base.public.m_size
29721 ^done,path_expr=((Base)c).m_size)
29724 @subheading The @code{-var-show-attributes} Command
29725 @findex -var-show-attributes
29727 @subsubheading Synopsis
29730 -var-show-attributes @var{name}
29733 List attributes of the specified variable object @var{name}:
29736 status=@var{attr} [ ( ,@var{attr} )* ]
29740 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29742 @subheading The @code{-var-evaluate-expression} Command
29743 @findex -var-evaluate-expression
29745 @subsubheading Synopsis
29748 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29751 Evaluates the expression that is represented by the specified variable
29752 object and returns its value as a string. The format of the string
29753 can be specified with the @samp{-f} option. The possible values of
29754 this option are the same as for @code{-var-set-format}
29755 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29756 the current display format will be used. The current display format
29757 can be changed using the @code{-var-set-format} command.
29763 Note that one must invoke @code{-var-list-children} for a variable
29764 before the value of a child variable can be evaluated.
29766 @subheading The @code{-var-assign} Command
29767 @findex -var-assign
29769 @subsubheading Synopsis
29772 -var-assign @var{name} @var{expression}
29775 Assigns the value of @var{expression} to the variable object specified
29776 by @var{name}. The object must be @samp{editable}. If the variable's
29777 value is altered by the assign, the variable will show up in any
29778 subsequent @code{-var-update} list.
29780 @subsubheading Example
29788 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29792 @subheading The @code{-var-update} Command
29793 @findex -var-update
29795 @subsubheading Synopsis
29798 -var-update [@var{print-values}] @{@var{name} | "*"@}
29801 Reevaluate the expressions corresponding to the variable object
29802 @var{name} and all its direct and indirect children, and return the
29803 list of variable objects whose values have changed; @var{name} must
29804 be a root variable object. Here, ``changed'' means that the result of
29805 @code{-var-evaluate-expression} before and after the
29806 @code{-var-update} is different. If @samp{*} is used as the variable
29807 object names, all existing variable objects are updated, except
29808 for frozen ones (@pxref{-var-set-frozen}). The option
29809 @var{print-values} determines whether both names and values, or just
29810 names are printed. The possible values of this option are the same
29811 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29812 recommended to use the @samp{--all-values} option, to reduce the
29813 number of MI commands needed on each program stop.
29815 With the @samp{*} parameter, if a variable object is bound to a
29816 currently running thread, it will not be updated, without any
29819 If @code{-var-set-update-range} was previously used on a varobj, then
29820 only the selected range of children will be reported.
29822 @code{-var-update} reports all the changed varobjs in a tuple named
29825 Each item in the change list is itself a tuple holding:
29829 The name of the varobj.
29832 If values were requested for this update, then this field will be
29833 present and will hold the value of the varobj.
29836 @anchor{-var-update}
29837 This field is a string which may take one of three values:
29841 The variable object's current value is valid.
29844 The variable object does not currently hold a valid value but it may
29845 hold one in the future if its associated expression comes back into
29849 The variable object no longer holds a valid value.
29850 This can occur when the executable file being debugged has changed,
29851 either through recompilation or by using the @value{GDBN} @code{file}
29852 command. The front end should normally choose to delete these variable
29856 In the future new values may be added to this list so the front should
29857 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29860 This is only present if the varobj is still valid. If the type
29861 changed, then this will be the string @samp{true}; otherwise it will
29864 When a varobj's type changes, its children are also likely to have
29865 become incorrect. Therefore, the varobj's children are automatically
29866 deleted when this attribute is @samp{true}. Also, the varobj's update
29867 range, when set using the @code{-var-set-update-range} command, is
29871 If the varobj's type changed, then this field will be present and will
29874 @item new_num_children
29875 For a dynamic varobj, if the number of children changed, or if the
29876 type changed, this will be the new number of children.
29878 The @samp{numchild} field in other varobj responses is generally not
29879 valid for a dynamic varobj -- it will show the number of children that
29880 @value{GDBN} knows about, but because dynamic varobjs lazily
29881 instantiate their children, this will not reflect the number of
29882 children which may be available.
29884 The @samp{new_num_children} attribute only reports changes to the
29885 number of children known by @value{GDBN}. This is the only way to
29886 detect whether an update has removed children (which necessarily can
29887 only happen at the end of the update range).
29890 The display hint, if any.
29893 This is an integer value, which will be 1 if there are more children
29894 available outside the varobj's update range.
29897 This attribute will be present and have the value @samp{1} if the
29898 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29899 then this attribute will not be present.
29902 If new children were added to a dynamic varobj within the selected
29903 update range (as set by @code{-var-set-update-range}), then they will
29904 be listed in this attribute.
29907 @subsubheading Example
29914 -var-update --all-values var1
29915 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29916 type_changed="false"@}]
29920 @subheading The @code{-var-set-frozen} Command
29921 @findex -var-set-frozen
29922 @anchor{-var-set-frozen}
29924 @subsubheading Synopsis
29927 -var-set-frozen @var{name} @var{flag}
29930 Set the frozenness flag on the variable object @var{name}. The
29931 @var{flag} parameter should be either @samp{1} to make the variable
29932 frozen or @samp{0} to make it unfrozen. If a variable object is
29933 frozen, then neither itself, nor any of its children, are
29934 implicitly updated by @code{-var-update} of
29935 a parent variable or by @code{-var-update *}. Only
29936 @code{-var-update} of the variable itself will update its value and
29937 values of its children. After a variable object is unfrozen, it is
29938 implicitly updated by all subsequent @code{-var-update} operations.
29939 Unfreezing a variable does not update it, only subsequent
29940 @code{-var-update} does.
29942 @subsubheading Example
29946 -var-set-frozen V 1
29951 @subheading The @code{-var-set-update-range} command
29952 @findex -var-set-update-range
29953 @anchor{-var-set-update-range}
29955 @subsubheading Synopsis
29958 -var-set-update-range @var{name} @var{from} @var{to}
29961 Set the range of children to be returned by future invocations of
29962 @code{-var-update}.
29964 @var{from} and @var{to} indicate the range of children to report. If
29965 @var{from} or @var{to} is less than zero, the range is reset and all
29966 children will be reported. Otherwise, children starting at @var{from}
29967 (zero-based) and up to and excluding @var{to} will be reported.
29969 @subsubheading Example
29973 -var-set-update-range V 1 2
29977 @subheading The @code{-var-set-visualizer} command
29978 @findex -var-set-visualizer
29979 @anchor{-var-set-visualizer}
29981 @subsubheading Synopsis
29984 -var-set-visualizer @var{name} @var{visualizer}
29987 Set a visualizer for the variable object @var{name}.
29989 @var{visualizer} is the visualizer to use. The special value
29990 @samp{None} means to disable any visualizer in use.
29992 If not @samp{None}, @var{visualizer} must be a Python expression.
29993 This expression must evaluate to a callable object which accepts a
29994 single argument. @value{GDBN} will call this object with the value of
29995 the varobj @var{name} as an argument (this is done so that the same
29996 Python pretty-printing code can be used for both the CLI and MI).
29997 When called, this object must return an object which conforms to the
29998 pretty-printing interface (@pxref{Pretty Printing API}).
30000 The pre-defined function @code{gdb.default_visualizer} may be used to
30001 select a visualizer by following the built-in process
30002 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30003 a varobj is created, and so ordinarily is not needed.
30005 This feature is only available if Python support is enabled. The MI
30006 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30007 can be used to check this.
30009 @subsubheading Example
30011 Resetting the visualizer:
30015 -var-set-visualizer V None
30019 Reselecting the default (type-based) visualizer:
30023 -var-set-visualizer V gdb.default_visualizer
30027 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30028 can be used to instantiate this class for a varobj:
30032 -var-set-visualizer V "lambda val: SomeClass()"
30036 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30037 @node GDB/MI Data Manipulation
30038 @section @sc{gdb/mi} Data Manipulation
30040 @cindex data manipulation, in @sc{gdb/mi}
30041 @cindex @sc{gdb/mi}, data manipulation
30042 This section describes the @sc{gdb/mi} commands that manipulate data:
30043 examine memory and registers, evaluate expressions, etc.
30045 For details about what an addressable memory unit is,
30046 @pxref{addressable memory unit}.
30048 @c REMOVED FROM THE INTERFACE.
30049 @c @subheading -data-assign
30050 @c Change the value of a program variable. Plenty of side effects.
30051 @c @subsubheading GDB Command
30053 @c @subsubheading Example
30056 @subheading The @code{-data-disassemble} Command
30057 @findex -data-disassemble
30059 @subsubheading Synopsis
30063 [ -s @var{start-addr} -e @var{end-addr} ]
30064 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30072 @item @var{start-addr}
30073 is the beginning address (or @code{$pc})
30074 @item @var{end-addr}
30076 @item @var{filename}
30077 is the name of the file to disassemble
30078 @item @var{linenum}
30079 is the line number to disassemble around
30081 is the number of disassembly lines to be produced. If it is -1,
30082 the whole function will be disassembled, in case no @var{end-addr} is
30083 specified. If @var{end-addr} is specified as a non-zero value, and
30084 @var{lines} is lower than the number of disassembly lines between
30085 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30086 displayed; if @var{lines} is higher than the number of lines between
30087 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30092 @item 0 disassembly only
30093 @item 1 mixed source and disassembly (deprecated)
30094 @item 2 disassembly with raw opcodes
30095 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30096 @item 4 mixed source and disassembly
30097 @item 5 mixed source and disassembly with raw opcodes
30100 Modes 1 and 3 are deprecated. The output is ``source centric''
30101 which hasn't proved useful in practice.
30102 @xref{Machine Code}, for a discussion of the difference between
30103 @code{/m} and @code{/s} output of the @code{disassemble} command.
30106 @subsubheading Result
30108 The result of the @code{-data-disassemble} command will be a list named
30109 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30110 used with the @code{-data-disassemble} command.
30112 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30117 The address at which this instruction was disassembled.
30120 The name of the function this instruction is within.
30123 The decimal offset in bytes from the start of @samp{func-name}.
30126 The text disassembly for this @samp{address}.
30129 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30130 bytes for the @samp{inst} field.
30134 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30135 @samp{src_and_asm_line}, each of which has the following fields:
30139 The line number within @samp{file}.
30142 The file name from the compilation unit. This might be an absolute
30143 file name or a relative file name depending on the compile command
30147 Absolute file name of @samp{file}. It is converted to a canonical form
30148 using the source file search path
30149 (@pxref{Source Path, ,Specifying Source Directories})
30150 and after resolving all the symbolic links.
30152 If the source file is not found this field will contain the path as
30153 present in the debug information.
30155 @item line_asm_insn
30156 This is a list of tuples containing the disassembly for @samp{line} in
30157 @samp{file}. The fields of each tuple are the same as for
30158 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30159 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30164 Note that whatever included in the @samp{inst} field, is not
30165 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30168 @subsubheading @value{GDBN} Command
30170 The corresponding @value{GDBN} command is @samp{disassemble}.
30172 @subsubheading Example
30174 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30178 -data-disassemble -s $pc -e "$pc + 20" -- 0
30181 @{address="0x000107c0",func-name="main",offset="4",
30182 inst="mov 2, %o0"@},
30183 @{address="0x000107c4",func-name="main",offset="8",
30184 inst="sethi %hi(0x11800), %o2"@},
30185 @{address="0x000107c8",func-name="main",offset="12",
30186 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30187 @{address="0x000107cc",func-name="main",offset="16",
30188 inst="sethi %hi(0x11800), %o2"@},
30189 @{address="0x000107d0",func-name="main",offset="20",
30190 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30194 Disassemble the whole @code{main} function. Line 32 is part of
30198 -data-disassemble -f basics.c -l 32 -- 0
30200 @{address="0x000107bc",func-name="main",offset="0",
30201 inst="save %sp, -112, %sp"@},
30202 @{address="0x000107c0",func-name="main",offset="4",
30203 inst="mov 2, %o0"@},
30204 @{address="0x000107c4",func-name="main",offset="8",
30205 inst="sethi %hi(0x11800), %o2"@},
30207 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30208 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30212 Disassemble 3 instructions from the start of @code{main}:
30216 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30218 @{address="0x000107bc",func-name="main",offset="0",
30219 inst="save %sp, -112, %sp"@},
30220 @{address="0x000107c0",func-name="main",offset="4",
30221 inst="mov 2, %o0"@},
30222 @{address="0x000107c4",func-name="main",offset="8",
30223 inst="sethi %hi(0x11800), %o2"@}]
30227 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30231 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30233 src_and_asm_line=@{line="31",
30234 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30235 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30236 line_asm_insn=[@{address="0x000107bc",
30237 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30238 src_and_asm_line=@{line="32",
30239 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30240 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30241 line_asm_insn=[@{address="0x000107c0",
30242 func-name="main",offset="4",inst="mov 2, %o0"@},
30243 @{address="0x000107c4",func-name="main",offset="8",
30244 inst="sethi %hi(0x11800), %o2"@}]@}]
30249 @subheading The @code{-data-evaluate-expression} Command
30250 @findex -data-evaluate-expression
30252 @subsubheading Synopsis
30255 -data-evaluate-expression @var{expr}
30258 Evaluate @var{expr} as an expression. The expression could contain an
30259 inferior function call. The function call will execute synchronously.
30260 If the expression contains spaces, it must be enclosed in double quotes.
30262 @subsubheading @value{GDBN} Command
30264 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30265 @samp{call}. In @code{gdbtk} only, there's a corresponding
30266 @samp{gdb_eval} command.
30268 @subsubheading Example
30270 In the following example, the numbers that precede the commands are the
30271 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30272 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30276 211-data-evaluate-expression A
30279 311-data-evaluate-expression &A
30280 311^done,value="0xefffeb7c"
30282 411-data-evaluate-expression A+3
30285 511-data-evaluate-expression "A + 3"
30291 @subheading The @code{-data-list-changed-registers} Command
30292 @findex -data-list-changed-registers
30294 @subsubheading Synopsis
30297 -data-list-changed-registers
30300 Display a list of the registers that have changed.
30302 @subsubheading @value{GDBN} Command
30304 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30305 has the corresponding command @samp{gdb_changed_register_list}.
30307 @subsubheading Example
30309 On a PPC MBX board:
30317 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30318 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30321 -data-list-changed-registers
30322 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30323 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30324 "24","25","26","27","28","30","31","64","65","66","67","69"]
30329 @subheading The @code{-data-list-register-names} Command
30330 @findex -data-list-register-names
30332 @subsubheading Synopsis
30335 -data-list-register-names [ ( @var{regno} )+ ]
30338 Show a list of register names for the current target. If no arguments
30339 are given, it shows a list of the names of all the registers. If
30340 integer numbers are given as arguments, it will print a list of the
30341 names of the registers corresponding to the arguments. To ensure
30342 consistency between a register name and its number, the output list may
30343 include empty register names.
30345 @subsubheading @value{GDBN} Command
30347 @value{GDBN} does not have a command which corresponds to
30348 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30349 corresponding command @samp{gdb_regnames}.
30351 @subsubheading Example
30353 For the PPC MBX board:
30356 -data-list-register-names
30357 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30358 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30359 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30360 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30361 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30362 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30363 "", "pc","ps","cr","lr","ctr","xer"]
30365 -data-list-register-names 1 2 3
30366 ^done,register-names=["r1","r2","r3"]
30370 @subheading The @code{-data-list-register-values} Command
30371 @findex -data-list-register-values
30373 @subsubheading Synopsis
30376 -data-list-register-values
30377 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30380 Display the registers' contents. The format according to which the
30381 registers' contents are to be returned is given by @var{fmt}, followed
30382 by an optional list of numbers specifying the registers to display. A
30383 missing list of numbers indicates that the contents of all the
30384 registers must be returned. The @code{--skip-unavailable} option
30385 indicates that only the available registers are to be returned.
30387 Allowed formats for @var{fmt} are:
30404 @subsubheading @value{GDBN} Command
30406 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30407 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30409 @subsubheading Example
30411 For a PPC MBX board (note: line breaks are for readability only, they
30412 don't appear in the actual output):
30416 -data-list-register-values r 64 65
30417 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30418 @{number="65",value="0x00029002"@}]
30420 -data-list-register-values x
30421 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30422 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30423 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30424 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30425 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30426 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30427 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30428 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30429 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30430 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30431 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30432 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30433 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30434 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30435 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30436 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30437 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30438 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30439 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30440 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30441 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30442 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30443 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30444 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30445 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30446 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30447 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30448 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30449 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30450 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30451 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30452 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30453 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30454 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30455 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30456 @{number="69",value="0x20002b03"@}]
30461 @subheading The @code{-data-read-memory} Command
30462 @findex -data-read-memory
30464 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30466 @subsubheading Synopsis
30469 -data-read-memory [ -o @var{byte-offset} ]
30470 @var{address} @var{word-format} @var{word-size}
30471 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30478 @item @var{address}
30479 An expression specifying the address of the first memory word to be
30480 read. Complex expressions containing embedded white space should be
30481 quoted using the C convention.
30483 @item @var{word-format}
30484 The format to be used to print the memory words. The notation is the
30485 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30488 @item @var{word-size}
30489 The size of each memory word in bytes.
30491 @item @var{nr-rows}
30492 The number of rows in the output table.
30494 @item @var{nr-cols}
30495 The number of columns in the output table.
30498 If present, indicates that each row should include an @sc{ascii} dump. The
30499 value of @var{aschar} is used as a padding character when a byte is not a
30500 member of the printable @sc{ascii} character set (printable @sc{ascii}
30501 characters are those whose code is between 32 and 126, inclusively).
30503 @item @var{byte-offset}
30504 An offset to add to the @var{address} before fetching memory.
30507 This command displays memory contents as a table of @var{nr-rows} by
30508 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30509 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30510 (returned as @samp{total-bytes}). Should less than the requested number
30511 of bytes be returned by the target, the missing words are identified
30512 using @samp{N/A}. The number of bytes read from the target is returned
30513 in @samp{nr-bytes} and the starting address used to read memory in
30516 The address of the next/previous row or page is available in
30517 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30520 @subsubheading @value{GDBN} Command
30522 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30523 @samp{gdb_get_mem} memory read command.
30525 @subsubheading Example
30527 Read six bytes of memory starting at @code{bytes+6} but then offset by
30528 @code{-6} bytes. Format as three rows of two columns. One byte per
30529 word. Display each word in hex.
30533 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30534 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30535 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30536 prev-page="0x0000138a",memory=[
30537 @{addr="0x00001390",data=["0x00","0x01"]@},
30538 @{addr="0x00001392",data=["0x02","0x03"]@},
30539 @{addr="0x00001394",data=["0x04","0x05"]@}]
30543 Read two bytes of memory starting at address @code{shorts + 64} and
30544 display as a single word formatted in decimal.
30548 5-data-read-memory shorts+64 d 2 1 1
30549 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30550 next-row="0x00001512",prev-row="0x0000150e",
30551 next-page="0x00001512",prev-page="0x0000150e",memory=[
30552 @{addr="0x00001510",data=["128"]@}]
30556 Read thirty two bytes of memory starting at @code{bytes+16} and format
30557 as eight rows of four columns. Include a string encoding with @samp{x}
30558 used as the non-printable character.
30562 4-data-read-memory bytes+16 x 1 8 4 x
30563 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30564 next-row="0x000013c0",prev-row="0x0000139c",
30565 next-page="0x000013c0",prev-page="0x00001380",memory=[
30566 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30567 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30568 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30569 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30570 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30571 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30572 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30573 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30577 @subheading The @code{-data-read-memory-bytes} Command
30578 @findex -data-read-memory-bytes
30580 @subsubheading Synopsis
30583 -data-read-memory-bytes [ -o @var{offset} ]
30584 @var{address} @var{count}
30591 @item @var{address}
30592 An expression specifying the address of the first addressable memory unit
30593 to be read. Complex expressions containing embedded white space should be
30594 quoted using the C convention.
30597 The number of addressable memory units to read. This should be an integer
30601 The offset relative to @var{address} at which to start reading. This
30602 should be an integer literal. This option is provided so that a frontend
30603 is not required to first evaluate address and then perform address
30604 arithmetics itself.
30608 This command attempts to read all accessible memory regions in the
30609 specified range. First, all regions marked as unreadable in the memory
30610 map (if one is defined) will be skipped. @xref{Memory Region
30611 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30612 regions. For each one, if reading full region results in an errors,
30613 @value{GDBN} will try to read a subset of the region.
30615 In general, every single memory unit in the region may be readable or not,
30616 and the only way to read every readable unit is to try a read at
30617 every address, which is not practical. Therefore, @value{GDBN} will
30618 attempt to read all accessible memory units at either beginning or the end
30619 of the region, using a binary division scheme. This heuristic works
30620 well for reading accross a memory map boundary. Note that if a region
30621 has a readable range that is neither at the beginning or the end,
30622 @value{GDBN} will not read it.
30624 The result record (@pxref{GDB/MI Result Records}) that is output of
30625 the command includes a field named @samp{memory} whose content is a
30626 list of tuples. Each tuple represent a successfully read memory block
30627 and has the following fields:
30631 The start address of the memory block, as hexadecimal literal.
30634 The end address of the memory block, as hexadecimal literal.
30637 The offset of the memory block, as hexadecimal literal, relative to
30638 the start address passed to @code{-data-read-memory-bytes}.
30641 The contents of the memory block, in hex.
30647 @subsubheading @value{GDBN} Command
30649 The corresponding @value{GDBN} command is @samp{x}.
30651 @subsubheading Example
30655 -data-read-memory-bytes &a 10
30656 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30658 contents="01000000020000000300"@}]
30663 @subheading The @code{-data-write-memory-bytes} Command
30664 @findex -data-write-memory-bytes
30666 @subsubheading Synopsis
30669 -data-write-memory-bytes @var{address} @var{contents}
30670 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30677 @item @var{address}
30678 An expression specifying the address of the first addressable memory unit
30679 to be written. Complex expressions containing embedded white space should
30680 be quoted using the C convention.
30682 @item @var{contents}
30683 The hex-encoded data to write. It is an error if @var{contents} does
30684 not represent an integral number of addressable memory units.
30687 Optional argument indicating the number of addressable memory units to be
30688 written. If @var{count} is greater than @var{contents}' length,
30689 @value{GDBN} will repeatedly write @var{contents} until it fills
30690 @var{count} memory units.
30694 @subsubheading @value{GDBN} Command
30696 There's no corresponding @value{GDBN} command.
30698 @subsubheading Example
30702 -data-write-memory-bytes &a "aabbccdd"
30709 -data-write-memory-bytes &a "aabbccdd" 16e
30714 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30715 @node GDB/MI Tracepoint Commands
30716 @section @sc{gdb/mi} Tracepoint Commands
30718 The commands defined in this section implement MI support for
30719 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30721 @subheading The @code{-trace-find} Command
30722 @findex -trace-find
30724 @subsubheading Synopsis
30727 -trace-find @var{mode} [@var{parameters}@dots{}]
30730 Find a trace frame using criteria defined by @var{mode} and
30731 @var{parameters}. The following table lists permissible
30732 modes and their parameters. For details of operation, see @ref{tfind}.
30737 No parameters are required. Stops examining trace frames.
30740 An integer is required as parameter. Selects tracepoint frame with
30743 @item tracepoint-number
30744 An integer is required as parameter. Finds next
30745 trace frame that corresponds to tracepoint with the specified number.
30748 An address is required as parameter. Finds
30749 next trace frame that corresponds to any tracepoint at the specified
30752 @item pc-inside-range
30753 Two addresses are required as parameters. Finds next trace
30754 frame that corresponds to a tracepoint at an address inside the
30755 specified range. Both bounds are considered to be inside the range.
30757 @item pc-outside-range
30758 Two addresses are required as parameters. Finds
30759 next trace frame that corresponds to a tracepoint at an address outside
30760 the specified range. Both bounds are considered to be inside the range.
30763 Line specification is required as parameter. @xref{Specify Location}.
30764 Finds next trace frame that corresponds to a tracepoint at
30765 the specified location.
30769 If @samp{none} was passed as @var{mode}, the response does not
30770 have fields. Otherwise, the response may have the following fields:
30774 This field has either @samp{0} or @samp{1} as the value, depending
30775 on whether a matching tracepoint was found.
30778 The index of the found traceframe. This field is present iff
30779 the @samp{found} field has value of @samp{1}.
30782 The index of the found tracepoint. This field is present iff
30783 the @samp{found} field has value of @samp{1}.
30786 The information about the frame corresponding to the found trace
30787 frame. This field is present only if a trace frame was found.
30788 @xref{GDB/MI Frame Information}, for description of this field.
30792 @subsubheading @value{GDBN} Command
30794 The corresponding @value{GDBN} command is @samp{tfind}.
30796 @subheading -trace-define-variable
30797 @findex -trace-define-variable
30799 @subsubheading Synopsis
30802 -trace-define-variable @var{name} [ @var{value} ]
30805 Create trace variable @var{name} if it does not exist. If
30806 @var{value} is specified, sets the initial value of the specified
30807 trace variable to that value. Note that the @var{name} should start
30808 with the @samp{$} character.
30810 @subsubheading @value{GDBN} Command
30812 The corresponding @value{GDBN} command is @samp{tvariable}.
30814 @subheading The @code{-trace-frame-collected} Command
30815 @findex -trace-frame-collected
30817 @subsubheading Synopsis
30820 -trace-frame-collected
30821 [--var-print-values @var{var_pval}]
30822 [--comp-print-values @var{comp_pval}]
30823 [--registers-format @var{regformat}]
30824 [--memory-contents]
30827 This command returns the set of collected objects, register names,
30828 trace state variable names, memory ranges and computed expressions
30829 that have been collected at a particular trace frame. The optional
30830 parameters to the command affect the output format in different ways.
30831 See the output description table below for more details.
30833 The reported names can be used in the normal manner to create
30834 varobjs and inspect the objects themselves. The items returned by
30835 this command are categorized so that it is clear which is a variable,
30836 which is a register, which is a trace state variable, which is a
30837 memory range and which is a computed expression.
30839 For instance, if the actions were
30841 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30842 collect *(int*)0xaf02bef0@@40
30846 the object collected in its entirety would be @code{myVar}. The
30847 object @code{myArray} would be partially collected, because only the
30848 element at index @code{myIndex} would be collected. The remaining
30849 objects would be computed expressions.
30851 An example output would be:
30855 -trace-frame-collected
30857 explicit-variables=[@{name="myVar",value="1"@}],
30858 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30859 @{name="myObj.field",value="0"@},
30860 @{name="myPtr->field",value="1"@},
30861 @{name="myCount + 2",value="3"@},
30862 @{name="$tvar1 + 1",value="43970027"@}],
30863 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30864 @{number="1",value="0x0"@},
30865 @{number="2",value="0x4"@},
30867 @{number="125",value="0x0"@}],
30868 tvars=[@{name="$tvar1",current="43970026"@}],
30869 memory=[@{address="0x0000000000602264",length="4"@},
30870 @{address="0x0000000000615bc0",length="4"@}]
30877 @item explicit-variables
30878 The set of objects that have been collected in their entirety (as
30879 opposed to collecting just a few elements of an array or a few struct
30880 members). For each object, its name and value are printed.
30881 The @code{--var-print-values} option affects how or whether the value
30882 field is output. If @var{var_pval} is 0, then print only the names;
30883 if it is 1, print also their values; and if it is 2, print the name,
30884 type and value for simple data types, and the name and type for
30885 arrays, structures and unions.
30887 @item computed-expressions
30888 The set of computed expressions that have been collected at the
30889 current trace frame. The @code{--comp-print-values} option affects
30890 this set like the @code{--var-print-values} option affects the
30891 @code{explicit-variables} set. See above.
30894 The registers that have been collected at the current trace frame.
30895 For each register collected, the name and current value are returned.
30896 The value is formatted according to the @code{--registers-format}
30897 option. See the @command{-data-list-register-values} command for a
30898 list of the allowed formats. The default is @samp{x}.
30901 The trace state variables that have been collected at the current
30902 trace frame. For each trace state variable collected, the name and
30903 current value are returned.
30906 The set of memory ranges that have been collected at the current trace
30907 frame. Its content is a list of tuples. Each tuple represents a
30908 collected memory range and has the following fields:
30912 The start address of the memory range, as hexadecimal literal.
30915 The length of the memory range, as decimal literal.
30918 The contents of the memory block, in hex. This field is only present
30919 if the @code{--memory-contents} option is specified.
30925 @subsubheading @value{GDBN} Command
30927 There is no corresponding @value{GDBN} command.
30929 @subsubheading Example
30931 @subheading -trace-list-variables
30932 @findex -trace-list-variables
30934 @subsubheading Synopsis
30937 -trace-list-variables
30940 Return a table of all defined trace variables. Each element of the
30941 table has the following fields:
30945 The name of the trace variable. This field is always present.
30948 The initial value. This is a 64-bit signed integer. This
30949 field is always present.
30952 The value the trace variable has at the moment. This is a 64-bit
30953 signed integer. This field is absent iff current value is
30954 not defined, for example if the trace was never run, or is
30959 @subsubheading @value{GDBN} Command
30961 The corresponding @value{GDBN} command is @samp{tvariables}.
30963 @subsubheading Example
30967 -trace-list-variables
30968 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30969 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30970 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30971 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30972 body=[variable=@{name="$trace_timestamp",initial="0"@}
30973 variable=@{name="$foo",initial="10",current="15"@}]@}
30977 @subheading -trace-save
30978 @findex -trace-save
30980 @subsubheading Synopsis
30983 -trace-save [ -r ] [ -ctf ] @var{filename}
30986 Saves the collected trace data to @var{filename}. Without the
30987 @samp{-r} option, the data is downloaded from the target and saved
30988 in a local file. With the @samp{-r} option the target is asked
30989 to perform the save.
30991 By default, this command will save the trace in the tfile format. You can
30992 supply the optional @samp{-ctf} argument to save it the CTF format. See
30993 @ref{Trace Files} for more information about CTF.
30995 @subsubheading @value{GDBN} Command
30997 The corresponding @value{GDBN} command is @samp{tsave}.
31000 @subheading -trace-start
31001 @findex -trace-start
31003 @subsubheading Synopsis
31009 Starts a tracing experiment. The result of this command does not
31012 @subsubheading @value{GDBN} Command
31014 The corresponding @value{GDBN} command is @samp{tstart}.
31016 @subheading -trace-status
31017 @findex -trace-status
31019 @subsubheading Synopsis
31025 Obtains the status of a tracing experiment. The result may include
31026 the following fields:
31031 May have a value of either @samp{0}, when no tracing operations are
31032 supported, @samp{1}, when all tracing operations are supported, or
31033 @samp{file} when examining trace file. In the latter case, examining
31034 of trace frame is possible but new tracing experiement cannot be
31035 started. This field is always present.
31038 May have a value of either @samp{0} or @samp{1} depending on whether
31039 tracing experiement is in progress on target. This field is present
31040 if @samp{supported} field is not @samp{0}.
31043 Report the reason why the tracing was stopped last time. This field
31044 may be absent iff tracing was never stopped on target yet. The
31045 value of @samp{request} means the tracing was stopped as result of
31046 the @code{-trace-stop} command. The value of @samp{overflow} means
31047 the tracing buffer is full. The value of @samp{disconnection} means
31048 tracing was automatically stopped when @value{GDBN} has disconnected.
31049 The value of @samp{passcount} means tracing was stopped when a
31050 tracepoint was passed a maximal number of times for that tracepoint.
31051 This field is present if @samp{supported} field is not @samp{0}.
31053 @item stopping-tracepoint
31054 The number of tracepoint whose passcount as exceeded. This field is
31055 present iff the @samp{stop-reason} field has the value of
31059 @itemx frames-created
31060 The @samp{frames} field is a count of the total number of trace frames
31061 in the trace buffer, while @samp{frames-created} is the total created
31062 during the run, including ones that were discarded, such as when a
31063 circular trace buffer filled up. Both fields are optional.
31067 These fields tell the current size of the tracing buffer and the
31068 remaining space. These fields are optional.
31071 The value of the circular trace buffer flag. @code{1} means that the
31072 trace buffer is circular and old trace frames will be discarded if
31073 necessary to make room, @code{0} means that the trace buffer is linear
31077 The value of the disconnected tracing flag. @code{1} means that
31078 tracing will continue after @value{GDBN} disconnects, @code{0} means
31079 that the trace run will stop.
31082 The filename of the trace file being examined. This field is
31083 optional, and only present when examining a trace file.
31087 @subsubheading @value{GDBN} Command
31089 The corresponding @value{GDBN} command is @samp{tstatus}.
31091 @subheading -trace-stop
31092 @findex -trace-stop
31094 @subsubheading Synopsis
31100 Stops a tracing experiment. The result of this command has the same
31101 fields as @code{-trace-status}, except that the @samp{supported} and
31102 @samp{running} fields are not output.
31104 @subsubheading @value{GDBN} Command
31106 The corresponding @value{GDBN} command is @samp{tstop}.
31109 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31110 @node GDB/MI Symbol Query
31111 @section @sc{gdb/mi} Symbol Query Commands
31115 @subheading The @code{-symbol-info-address} Command
31116 @findex -symbol-info-address
31118 @subsubheading Synopsis
31121 -symbol-info-address @var{symbol}
31124 Describe where @var{symbol} is stored.
31126 @subsubheading @value{GDBN} Command
31128 The corresponding @value{GDBN} command is @samp{info address}.
31130 @subsubheading Example
31134 @subheading The @code{-symbol-info-file} Command
31135 @findex -symbol-info-file
31137 @subsubheading Synopsis
31143 Show the file for the symbol.
31145 @subsubheading @value{GDBN} Command
31147 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31148 @samp{gdb_find_file}.
31150 @subsubheading Example
31154 @subheading The @code{-symbol-info-function} Command
31155 @findex -symbol-info-function
31157 @subsubheading Synopsis
31160 -symbol-info-function
31163 Show which function the symbol lives in.
31165 @subsubheading @value{GDBN} Command
31167 @samp{gdb_get_function} in @code{gdbtk}.
31169 @subsubheading Example
31173 @subheading The @code{-symbol-info-line} Command
31174 @findex -symbol-info-line
31176 @subsubheading Synopsis
31182 Show the core addresses of the code for a source line.
31184 @subsubheading @value{GDBN} Command
31186 The corresponding @value{GDBN} command is @samp{info line}.
31187 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31189 @subsubheading Example
31193 @subheading The @code{-symbol-info-symbol} Command
31194 @findex -symbol-info-symbol
31196 @subsubheading Synopsis
31199 -symbol-info-symbol @var{addr}
31202 Describe what symbol is at location @var{addr}.
31204 @subsubheading @value{GDBN} Command
31206 The corresponding @value{GDBN} command is @samp{info symbol}.
31208 @subsubheading Example
31212 @subheading The @code{-symbol-list-functions} Command
31213 @findex -symbol-list-functions
31215 @subsubheading Synopsis
31218 -symbol-list-functions
31221 List the functions in the executable.
31223 @subsubheading @value{GDBN} Command
31225 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31226 @samp{gdb_search} in @code{gdbtk}.
31228 @subsubheading Example
31233 @subheading The @code{-symbol-list-lines} Command
31234 @findex -symbol-list-lines
31236 @subsubheading Synopsis
31239 -symbol-list-lines @var{filename}
31242 Print the list of lines that contain code and their associated program
31243 addresses for the given source filename. The entries are sorted in
31244 ascending PC order.
31246 @subsubheading @value{GDBN} Command
31248 There is no corresponding @value{GDBN} command.
31250 @subsubheading Example
31253 -symbol-list-lines basics.c
31254 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31260 @subheading The @code{-symbol-list-types} Command
31261 @findex -symbol-list-types
31263 @subsubheading Synopsis
31269 List all the type names.
31271 @subsubheading @value{GDBN} Command
31273 The corresponding commands are @samp{info types} in @value{GDBN},
31274 @samp{gdb_search} in @code{gdbtk}.
31276 @subsubheading Example
31280 @subheading The @code{-symbol-list-variables} Command
31281 @findex -symbol-list-variables
31283 @subsubheading Synopsis
31286 -symbol-list-variables
31289 List all the global and static variable names.
31291 @subsubheading @value{GDBN} Command
31293 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31295 @subsubheading Example
31299 @subheading The @code{-symbol-locate} Command
31300 @findex -symbol-locate
31302 @subsubheading Synopsis
31308 @subsubheading @value{GDBN} Command
31310 @samp{gdb_loc} in @code{gdbtk}.
31312 @subsubheading Example
31316 @subheading The @code{-symbol-type} Command
31317 @findex -symbol-type
31319 @subsubheading Synopsis
31322 -symbol-type @var{variable}
31325 Show type of @var{variable}.
31327 @subsubheading @value{GDBN} Command
31329 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31330 @samp{gdb_obj_variable}.
31332 @subsubheading Example
31337 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31338 @node GDB/MI File Commands
31339 @section @sc{gdb/mi} File Commands
31341 This section describes the GDB/MI commands to specify executable file names
31342 and to read in and obtain symbol table information.
31344 @subheading The @code{-file-exec-and-symbols} Command
31345 @findex -file-exec-and-symbols
31347 @subsubheading Synopsis
31350 -file-exec-and-symbols @var{file}
31353 Specify the executable file to be debugged. This file is the one from
31354 which the symbol table is also read. If no file is specified, the
31355 command clears the executable and symbol information. If breakpoints
31356 are set when using this command with no arguments, @value{GDBN} will produce
31357 error messages. Otherwise, no output is produced, except a completion
31360 @subsubheading @value{GDBN} Command
31362 The corresponding @value{GDBN} command is @samp{file}.
31364 @subsubheading Example
31368 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31374 @subheading The @code{-file-exec-file} Command
31375 @findex -file-exec-file
31377 @subsubheading Synopsis
31380 -file-exec-file @var{file}
31383 Specify the executable file to be debugged. Unlike
31384 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31385 from this file. If used without argument, @value{GDBN} clears the information
31386 about the executable file. No output is produced, except a completion
31389 @subsubheading @value{GDBN} Command
31391 The corresponding @value{GDBN} command is @samp{exec-file}.
31393 @subsubheading Example
31397 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31404 @subheading The @code{-file-list-exec-sections} Command
31405 @findex -file-list-exec-sections
31407 @subsubheading Synopsis
31410 -file-list-exec-sections
31413 List the sections of the current executable file.
31415 @subsubheading @value{GDBN} Command
31417 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31418 information as this command. @code{gdbtk} has a corresponding command
31419 @samp{gdb_load_info}.
31421 @subsubheading Example
31426 @subheading The @code{-file-list-exec-source-file} Command
31427 @findex -file-list-exec-source-file
31429 @subsubheading Synopsis
31432 -file-list-exec-source-file
31435 List the line number, the current source file, and the absolute path
31436 to the current source file for the current executable. The macro
31437 information field has a value of @samp{1} or @samp{0} depending on
31438 whether or not the file includes preprocessor macro information.
31440 @subsubheading @value{GDBN} Command
31442 The @value{GDBN} equivalent is @samp{info source}
31444 @subsubheading Example
31448 123-file-list-exec-source-file
31449 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31454 @subheading The @code{-file-list-exec-source-files} Command
31455 @findex -file-list-exec-source-files
31457 @subsubheading Synopsis
31460 -file-list-exec-source-files
31463 List the source files for the current executable.
31465 It will always output both the filename and fullname (absolute file
31466 name) of a source file.
31468 @subsubheading @value{GDBN} Command
31470 The @value{GDBN} equivalent is @samp{info sources}.
31471 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31473 @subsubheading Example
31476 -file-list-exec-source-files
31478 @{file=foo.c,fullname=/home/foo.c@},
31479 @{file=/home/bar.c,fullname=/home/bar.c@},
31480 @{file=gdb_could_not_find_fullpath.c@}]
31485 @subheading The @code{-file-list-shared-libraries} Command
31486 @findex -file-list-shared-libraries
31488 @subsubheading Synopsis
31491 -file-list-shared-libraries
31494 List the shared libraries in the program.
31496 @subsubheading @value{GDBN} Command
31498 The corresponding @value{GDBN} command is @samp{info shared}.
31500 @subsubheading Example
31504 @subheading The @code{-file-list-symbol-files} Command
31505 @findex -file-list-symbol-files
31507 @subsubheading Synopsis
31510 -file-list-symbol-files
31515 @subsubheading @value{GDBN} Command
31517 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31519 @subsubheading Example
31524 @subheading The @code{-file-symbol-file} Command
31525 @findex -file-symbol-file
31527 @subsubheading Synopsis
31530 -file-symbol-file @var{file}
31533 Read symbol table info from the specified @var{file} argument. When
31534 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31535 produced, except for a completion notification.
31537 @subsubheading @value{GDBN} Command
31539 The corresponding @value{GDBN} command is @samp{symbol-file}.
31541 @subsubheading Example
31545 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31551 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31552 @node GDB/MI Memory Overlay Commands
31553 @section @sc{gdb/mi} Memory Overlay Commands
31555 The memory overlay commands are not implemented.
31557 @c @subheading -overlay-auto
31559 @c @subheading -overlay-list-mapping-state
31561 @c @subheading -overlay-list-overlays
31563 @c @subheading -overlay-map
31565 @c @subheading -overlay-off
31567 @c @subheading -overlay-on
31569 @c @subheading -overlay-unmap
31571 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31572 @node GDB/MI Signal Handling Commands
31573 @section @sc{gdb/mi} Signal Handling Commands
31575 Signal handling commands are not implemented.
31577 @c @subheading -signal-handle
31579 @c @subheading -signal-list-handle-actions
31581 @c @subheading -signal-list-signal-types
31585 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31586 @node GDB/MI Target Manipulation
31587 @section @sc{gdb/mi} Target Manipulation Commands
31590 @subheading The @code{-target-attach} Command
31591 @findex -target-attach
31593 @subsubheading Synopsis
31596 -target-attach @var{pid} | @var{gid} | @var{file}
31599 Attach to a process @var{pid} or a file @var{file} outside of
31600 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31601 group, the id previously returned by
31602 @samp{-list-thread-groups --available} must be used.
31604 @subsubheading @value{GDBN} Command
31606 The corresponding @value{GDBN} command is @samp{attach}.
31608 @subsubheading Example
31612 =thread-created,id="1"
31613 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31619 @subheading The @code{-target-compare-sections} Command
31620 @findex -target-compare-sections
31622 @subsubheading Synopsis
31625 -target-compare-sections [ @var{section} ]
31628 Compare data of section @var{section} on target to the exec file.
31629 Without the argument, all sections are compared.
31631 @subsubheading @value{GDBN} Command
31633 The @value{GDBN} equivalent is @samp{compare-sections}.
31635 @subsubheading Example
31640 @subheading The @code{-target-detach} Command
31641 @findex -target-detach
31643 @subsubheading Synopsis
31646 -target-detach [ @var{pid} | @var{gid} ]
31649 Detach from the remote target which normally resumes its execution.
31650 If either @var{pid} or @var{gid} is specified, detaches from either
31651 the specified process, or specified thread group. There's no output.
31653 @subsubheading @value{GDBN} Command
31655 The corresponding @value{GDBN} command is @samp{detach}.
31657 @subsubheading Example
31667 @subheading The @code{-target-disconnect} Command
31668 @findex -target-disconnect
31670 @subsubheading Synopsis
31676 Disconnect from the remote target. There's no output and the target is
31677 generally not resumed.
31679 @subsubheading @value{GDBN} Command
31681 The corresponding @value{GDBN} command is @samp{disconnect}.
31683 @subsubheading Example
31693 @subheading The @code{-target-download} Command
31694 @findex -target-download
31696 @subsubheading Synopsis
31702 Loads the executable onto the remote target.
31703 It prints out an update message every half second, which includes the fields:
31707 The name of the section.
31709 The size of what has been sent so far for that section.
31711 The size of the section.
31713 The total size of what was sent so far (the current and the previous sections).
31715 The size of the overall executable to download.
31719 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31720 @sc{gdb/mi} Output Syntax}).
31722 In addition, it prints the name and size of the sections, as they are
31723 downloaded. These messages include the following fields:
31727 The name of the section.
31729 The size of the section.
31731 The size of the overall executable to download.
31735 At the end, a summary is printed.
31737 @subsubheading @value{GDBN} Command
31739 The corresponding @value{GDBN} command is @samp{load}.
31741 @subsubheading Example
31743 Note: each status message appears on a single line. Here the messages
31744 have been broken down so that they can fit onto a page.
31749 +download,@{section=".text",section-size="6668",total-size="9880"@}
31750 +download,@{section=".text",section-sent="512",section-size="6668",
31751 total-sent="512",total-size="9880"@}
31752 +download,@{section=".text",section-sent="1024",section-size="6668",
31753 total-sent="1024",total-size="9880"@}
31754 +download,@{section=".text",section-sent="1536",section-size="6668",
31755 total-sent="1536",total-size="9880"@}
31756 +download,@{section=".text",section-sent="2048",section-size="6668",
31757 total-sent="2048",total-size="9880"@}
31758 +download,@{section=".text",section-sent="2560",section-size="6668",
31759 total-sent="2560",total-size="9880"@}
31760 +download,@{section=".text",section-sent="3072",section-size="6668",
31761 total-sent="3072",total-size="9880"@}
31762 +download,@{section=".text",section-sent="3584",section-size="6668",
31763 total-sent="3584",total-size="9880"@}
31764 +download,@{section=".text",section-sent="4096",section-size="6668",
31765 total-sent="4096",total-size="9880"@}
31766 +download,@{section=".text",section-sent="4608",section-size="6668",
31767 total-sent="4608",total-size="9880"@}
31768 +download,@{section=".text",section-sent="5120",section-size="6668",
31769 total-sent="5120",total-size="9880"@}
31770 +download,@{section=".text",section-sent="5632",section-size="6668",
31771 total-sent="5632",total-size="9880"@}
31772 +download,@{section=".text",section-sent="6144",section-size="6668",
31773 total-sent="6144",total-size="9880"@}
31774 +download,@{section=".text",section-sent="6656",section-size="6668",
31775 total-sent="6656",total-size="9880"@}
31776 +download,@{section=".init",section-size="28",total-size="9880"@}
31777 +download,@{section=".fini",section-size="28",total-size="9880"@}
31778 +download,@{section=".data",section-size="3156",total-size="9880"@}
31779 +download,@{section=".data",section-sent="512",section-size="3156",
31780 total-sent="7236",total-size="9880"@}
31781 +download,@{section=".data",section-sent="1024",section-size="3156",
31782 total-sent="7748",total-size="9880"@}
31783 +download,@{section=".data",section-sent="1536",section-size="3156",
31784 total-sent="8260",total-size="9880"@}
31785 +download,@{section=".data",section-sent="2048",section-size="3156",
31786 total-sent="8772",total-size="9880"@}
31787 +download,@{section=".data",section-sent="2560",section-size="3156",
31788 total-sent="9284",total-size="9880"@}
31789 +download,@{section=".data",section-sent="3072",section-size="3156",
31790 total-sent="9796",total-size="9880"@}
31791 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31798 @subheading The @code{-target-exec-status} Command
31799 @findex -target-exec-status
31801 @subsubheading Synopsis
31804 -target-exec-status
31807 Provide information on the state of the target (whether it is running or
31808 not, for instance).
31810 @subsubheading @value{GDBN} Command
31812 There's no equivalent @value{GDBN} command.
31814 @subsubheading Example
31818 @subheading The @code{-target-list-available-targets} Command
31819 @findex -target-list-available-targets
31821 @subsubheading Synopsis
31824 -target-list-available-targets
31827 List the possible targets to connect to.
31829 @subsubheading @value{GDBN} Command
31831 The corresponding @value{GDBN} command is @samp{help target}.
31833 @subsubheading Example
31837 @subheading The @code{-target-list-current-targets} Command
31838 @findex -target-list-current-targets
31840 @subsubheading Synopsis
31843 -target-list-current-targets
31846 Describe the current target.
31848 @subsubheading @value{GDBN} Command
31850 The corresponding information is printed by @samp{info file} (among
31853 @subsubheading Example
31857 @subheading The @code{-target-list-parameters} Command
31858 @findex -target-list-parameters
31860 @subsubheading Synopsis
31863 -target-list-parameters
31869 @subsubheading @value{GDBN} Command
31873 @subsubheading Example
31876 @subheading The @code{-target-flash-erase} Command
31877 @findex -target-flash-erase
31879 @subsubheading Synopsis
31882 -target-flash-erase
31885 Erases all known flash memory regions on the target.
31887 The corresponding @value{GDBN} command is @samp{flash-erase}.
31889 The output is a list of flash regions that have been erased, with starting
31890 addresses and memory region sizes.
31894 -target-flash-erase
31895 ^done,erased-regions=@{address="0x0",size="0x40000"@}
31899 @subheading The @code{-target-select} Command
31900 @findex -target-select
31902 @subsubheading Synopsis
31905 -target-select @var{type} @var{parameters @dots{}}
31908 Connect @value{GDBN} to the remote target. This command takes two args:
31912 The type of target, for instance @samp{remote}, etc.
31913 @item @var{parameters}
31914 Device names, host names and the like. @xref{Target Commands, ,
31915 Commands for Managing Targets}, for more details.
31918 The output is a connection notification, followed by the address at
31919 which the target program is, in the following form:
31922 ^connected,addr="@var{address}",func="@var{function name}",
31923 args=[@var{arg list}]
31926 @subsubheading @value{GDBN} Command
31928 The corresponding @value{GDBN} command is @samp{target}.
31930 @subsubheading Example
31934 -target-select remote /dev/ttya
31935 ^connected,addr="0xfe00a300",func="??",args=[]
31939 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31940 @node GDB/MI File Transfer Commands
31941 @section @sc{gdb/mi} File Transfer Commands
31944 @subheading The @code{-target-file-put} Command
31945 @findex -target-file-put
31947 @subsubheading Synopsis
31950 -target-file-put @var{hostfile} @var{targetfile}
31953 Copy file @var{hostfile} from the host system (the machine running
31954 @value{GDBN}) to @var{targetfile} on the target system.
31956 @subsubheading @value{GDBN} Command
31958 The corresponding @value{GDBN} command is @samp{remote put}.
31960 @subsubheading Example
31964 -target-file-put localfile remotefile
31970 @subheading The @code{-target-file-get} Command
31971 @findex -target-file-get
31973 @subsubheading Synopsis
31976 -target-file-get @var{targetfile} @var{hostfile}
31979 Copy file @var{targetfile} from the target system to @var{hostfile}
31980 on the host system.
31982 @subsubheading @value{GDBN} Command
31984 The corresponding @value{GDBN} command is @samp{remote get}.
31986 @subsubheading Example
31990 -target-file-get remotefile localfile
31996 @subheading The @code{-target-file-delete} Command
31997 @findex -target-file-delete
31999 @subsubheading Synopsis
32002 -target-file-delete @var{targetfile}
32005 Delete @var{targetfile} from the target system.
32007 @subsubheading @value{GDBN} Command
32009 The corresponding @value{GDBN} command is @samp{remote delete}.
32011 @subsubheading Example
32015 -target-file-delete remotefile
32021 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32022 @node GDB/MI Ada Exceptions Commands
32023 @section Ada Exceptions @sc{gdb/mi} Commands
32025 @subheading The @code{-info-ada-exceptions} Command
32026 @findex -info-ada-exceptions
32028 @subsubheading Synopsis
32031 -info-ada-exceptions [ @var{regexp}]
32034 List all Ada exceptions defined within the program being debugged.
32035 With a regular expression @var{regexp}, only those exceptions whose
32036 names match @var{regexp} are listed.
32038 @subsubheading @value{GDBN} Command
32040 The corresponding @value{GDBN} command is @samp{info exceptions}.
32042 @subsubheading Result
32044 The result is a table of Ada exceptions. The following columns are
32045 defined for each exception:
32049 The name of the exception.
32052 The address of the exception.
32056 @subsubheading Example
32059 -info-ada-exceptions aint
32060 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32061 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32062 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32063 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32064 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32067 @subheading Catching Ada Exceptions
32069 The commands describing how to ask @value{GDBN} to stop when a program
32070 raises an exception are described at @ref{Ada Exception GDB/MI
32071 Catchpoint Commands}.
32074 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32075 @node GDB/MI Support Commands
32076 @section @sc{gdb/mi} Support Commands
32078 Since new commands and features get regularly added to @sc{gdb/mi},
32079 some commands are available to help front-ends query the debugger
32080 about support for these capabilities. Similarly, it is also possible
32081 to query @value{GDBN} about target support of certain features.
32083 @subheading The @code{-info-gdb-mi-command} Command
32084 @cindex @code{-info-gdb-mi-command}
32085 @findex -info-gdb-mi-command
32087 @subsubheading Synopsis
32090 -info-gdb-mi-command @var{cmd_name}
32093 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32095 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32096 is technically not part of the command name (@pxref{GDB/MI Input
32097 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32098 for ease of use, this command also accepts the form with the leading
32101 @subsubheading @value{GDBN} Command
32103 There is no corresponding @value{GDBN} command.
32105 @subsubheading Result
32107 The result is a tuple. There is currently only one field:
32111 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32112 @code{"false"} otherwise.
32116 @subsubheading Example
32118 Here is an example where the @sc{gdb/mi} command does not exist:
32121 -info-gdb-mi-command unsupported-command
32122 ^done,command=@{exists="false"@}
32126 And here is an example where the @sc{gdb/mi} command is known
32130 -info-gdb-mi-command symbol-list-lines
32131 ^done,command=@{exists="true"@}
32134 @subheading The @code{-list-features} Command
32135 @findex -list-features
32136 @cindex supported @sc{gdb/mi} features, list
32138 Returns a list of particular features of the MI protocol that
32139 this version of gdb implements. A feature can be a command,
32140 or a new field in an output of some command, or even an
32141 important bugfix. While a frontend can sometimes detect presence
32142 of a feature at runtime, it is easier to perform detection at debugger
32145 The command returns a list of strings, with each string naming an
32146 available feature. Each returned string is just a name, it does not
32147 have any internal structure. The list of possible feature names
32153 (gdb) -list-features
32154 ^done,result=["feature1","feature2"]
32157 The current list of features is:
32160 @item frozen-varobjs
32161 Indicates support for the @code{-var-set-frozen} command, as well
32162 as possible presense of the @code{frozen} field in the output
32163 of @code{-varobj-create}.
32164 @item pending-breakpoints
32165 Indicates support for the @option{-f} option to the @code{-break-insert}
32168 Indicates Python scripting support, Python-based
32169 pretty-printing commands, and possible presence of the
32170 @samp{display_hint} field in the output of @code{-var-list-children}
32172 Indicates support for the @code{-thread-info} command.
32173 @item data-read-memory-bytes
32174 Indicates support for the @code{-data-read-memory-bytes} and the
32175 @code{-data-write-memory-bytes} commands.
32176 @item breakpoint-notifications
32177 Indicates that changes to breakpoints and breakpoints created via the
32178 CLI will be announced via async records.
32179 @item ada-task-info
32180 Indicates support for the @code{-ada-task-info} command.
32181 @item language-option
32182 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32183 option (@pxref{Context management}).
32184 @item info-gdb-mi-command
32185 Indicates support for the @code{-info-gdb-mi-command} command.
32186 @item undefined-command-error-code
32187 Indicates support for the "undefined-command" error code in error result
32188 records, produced when trying to execute an undefined @sc{gdb/mi} command
32189 (@pxref{GDB/MI Result Records}).
32190 @item exec-run-start-option
32191 Indicates that the @code{-exec-run} command supports the @option{--start}
32192 option (@pxref{GDB/MI Program Execution}).
32195 @subheading The @code{-list-target-features} Command
32196 @findex -list-target-features
32198 Returns a list of particular features that are supported by the
32199 target. Those features affect the permitted MI commands, but
32200 unlike the features reported by the @code{-list-features} command, the
32201 features depend on which target GDB is using at the moment. Whenever
32202 a target can change, due to commands such as @code{-target-select},
32203 @code{-target-attach} or @code{-exec-run}, the list of target features
32204 may change, and the frontend should obtain it again.
32208 (gdb) -list-target-features
32209 ^done,result=["async"]
32212 The current list of features is:
32216 Indicates that the target is capable of asynchronous command
32217 execution, which means that @value{GDBN} will accept further commands
32218 while the target is running.
32221 Indicates that the target is capable of reverse execution.
32222 @xref{Reverse Execution}, for more information.
32226 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32227 @node GDB/MI Miscellaneous Commands
32228 @section Miscellaneous @sc{gdb/mi} Commands
32230 @c @subheading -gdb-complete
32232 @subheading The @code{-gdb-exit} Command
32235 @subsubheading Synopsis
32241 Exit @value{GDBN} immediately.
32243 @subsubheading @value{GDBN} Command
32245 Approximately corresponds to @samp{quit}.
32247 @subsubheading Example
32257 @subheading The @code{-exec-abort} Command
32258 @findex -exec-abort
32260 @subsubheading Synopsis
32266 Kill the inferior running program.
32268 @subsubheading @value{GDBN} Command
32270 The corresponding @value{GDBN} command is @samp{kill}.
32272 @subsubheading Example
32277 @subheading The @code{-gdb-set} Command
32280 @subsubheading Synopsis
32286 Set an internal @value{GDBN} variable.
32287 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32289 @subsubheading @value{GDBN} Command
32291 The corresponding @value{GDBN} command is @samp{set}.
32293 @subsubheading Example
32303 @subheading The @code{-gdb-show} Command
32306 @subsubheading Synopsis
32312 Show the current value of a @value{GDBN} variable.
32314 @subsubheading @value{GDBN} Command
32316 The corresponding @value{GDBN} command is @samp{show}.
32318 @subsubheading Example
32327 @c @subheading -gdb-source
32330 @subheading The @code{-gdb-version} Command
32331 @findex -gdb-version
32333 @subsubheading Synopsis
32339 Show version information for @value{GDBN}. Used mostly in testing.
32341 @subsubheading @value{GDBN} Command
32343 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
32344 default shows this information when you start an interactive session.
32346 @subsubheading Example
32348 @c This example modifies the actual output from GDB to avoid overfull
32354 ~Copyright 2000 Free Software Foundation, Inc.
32355 ~GDB is free software, covered by the GNU General Public License, and
32356 ~you are welcome to change it and/or distribute copies of it under
32357 ~ certain conditions.
32358 ~Type "show copying" to see the conditions.
32359 ~There is absolutely no warranty for GDB. Type "show warranty" for
32361 ~This GDB was configured as
32362 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32367 @subheading The @code{-list-thread-groups} Command
32368 @findex -list-thread-groups
32370 @subheading Synopsis
32373 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32376 Lists thread groups (@pxref{Thread groups}). When a single thread
32377 group is passed as the argument, lists the children of that group.
32378 When several thread group are passed, lists information about those
32379 thread groups. Without any parameters, lists information about all
32380 top-level thread groups.
32382 Normally, thread groups that are being debugged are reported.
32383 With the @samp{--available} option, @value{GDBN} reports thread groups
32384 available on the target.
32386 The output of this command may have either a @samp{threads} result or
32387 a @samp{groups} result. The @samp{thread} result has a list of tuples
32388 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32389 Information}). The @samp{groups} result has a list of tuples as value,
32390 each tuple describing a thread group. If top-level groups are
32391 requested (that is, no parameter is passed), or when several groups
32392 are passed, the output always has a @samp{groups} result. The format
32393 of the @samp{group} result is described below.
32395 To reduce the number of roundtrips it's possible to list thread groups
32396 together with their children, by passing the @samp{--recurse} option
32397 and the recursion depth. Presently, only recursion depth of 1 is
32398 permitted. If this option is present, then every reported thread group
32399 will also include its children, either as @samp{group} or
32400 @samp{threads} field.
32402 In general, any combination of option and parameters is permitted, with
32403 the following caveats:
32407 When a single thread group is passed, the output will typically
32408 be the @samp{threads} result. Because threads may not contain
32409 anything, the @samp{recurse} option will be ignored.
32412 When the @samp{--available} option is passed, limited information may
32413 be available. In particular, the list of threads of a process might
32414 be inaccessible. Further, specifying specific thread groups might
32415 not give any performance advantage over listing all thread groups.
32416 The frontend should assume that @samp{-list-thread-groups --available}
32417 is always an expensive operation and cache the results.
32421 The @samp{groups} result is a list of tuples, where each tuple may
32422 have the following fields:
32426 Identifier of the thread group. This field is always present.
32427 The identifier is an opaque string; frontends should not try to
32428 convert it to an integer, even though it might look like one.
32431 The type of the thread group. At present, only @samp{process} is a
32435 The target-specific process identifier. This field is only present
32436 for thread groups of type @samp{process} and only if the process exists.
32439 The exit code of this group's last exited thread, formatted in octal.
32440 This field is only present for thread groups of type @samp{process} and
32441 only if the process is not running.
32444 The number of children this thread group has. This field may be
32445 absent for an available thread group.
32448 This field has a list of tuples as value, each tuple describing a
32449 thread. It may be present if the @samp{--recurse} option is
32450 specified, and it's actually possible to obtain the threads.
32453 This field is a list of integers, each identifying a core that one
32454 thread of the group is running on. This field may be absent if
32455 such information is not available.
32458 The name of the executable file that corresponds to this thread group.
32459 The field is only present for thread groups of type @samp{process},
32460 and only if there is a corresponding executable file.
32464 @subheading Example
32468 -list-thread-groups
32469 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32470 -list-thread-groups 17
32471 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32472 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32473 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32474 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32475 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32476 -list-thread-groups --available
32477 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32478 -list-thread-groups --available --recurse 1
32479 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32480 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32481 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32482 -list-thread-groups --available --recurse 1 17 18
32483 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32484 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32485 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32488 @subheading The @code{-info-os} Command
32491 @subsubheading Synopsis
32494 -info-os [ @var{type} ]
32497 If no argument is supplied, the command returns a table of available
32498 operating-system-specific information types. If one of these types is
32499 supplied as an argument @var{type}, then the command returns a table
32500 of data of that type.
32502 The types of information available depend on the target operating
32505 @subsubheading @value{GDBN} Command
32507 The corresponding @value{GDBN} command is @samp{info os}.
32509 @subsubheading Example
32511 When run on a @sc{gnu}/Linux system, the output will look something
32517 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32518 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32519 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32520 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32521 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32523 item=@{col0="files",col1="Listing of all file descriptors",
32524 col2="File descriptors"@},
32525 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32526 col2="Kernel modules"@},
32527 item=@{col0="msg",col1="Listing of all message queues",
32528 col2="Message queues"@},
32529 item=@{col0="processes",col1="Listing of all processes",
32530 col2="Processes"@},
32531 item=@{col0="procgroups",col1="Listing of all process groups",
32532 col2="Process groups"@},
32533 item=@{col0="semaphores",col1="Listing of all semaphores",
32534 col2="Semaphores"@},
32535 item=@{col0="shm",col1="Listing of all shared-memory regions",
32536 col2="Shared-memory regions"@},
32537 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32539 item=@{col0="threads",col1="Listing of all threads",
32543 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32544 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32545 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32546 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32547 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32548 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32549 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32550 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32552 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32553 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32557 (Note that the MI output here includes a @code{"Title"} column that
32558 does not appear in command-line @code{info os}; this column is useful
32559 for MI clients that want to enumerate the types of data, such as in a
32560 popup menu, but is needless clutter on the command line, and
32561 @code{info os} omits it.)
32563 @subheading The @code{-add-inferior} Command
32564 @findex -add-inferior
32566 @subheading Synopsis
32572 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32573 inferior is not associated with any executable. Such association may
32574 be established with the @samp{-file-exec-and-symbols} command
32575 (@pxref{GDB/MI File Commands}). The command response has a single
32576 field, @samp{inferior}, whose value is the identifier of the
32577 thread group corresponding to the new inferior.
32579 @subheading Example
32584 ^done,inferior="i3"
32587 @subheading The @code{-interpreter-exec} Command
32588 @findex -interpreter-exec
32590 @subheading Synopsis
32593 -interpreter-exec @var{interpreter} @var{command}
32595 @anchor{-interpreter-exec}
32597 Execute the specified @var{command} in the given @var{interpreter}.
32599 @subheading @value{GDBN} Command
32601 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32603 @subheading Example
32607 -interpreter-exec console "break main"
32608 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32609 &"During symbol reading, bad structure-type format.\n"
32610 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32615 @subheading The @code{-inferior-tty-set} Command
32616 @findex -inferior-tty-set
32618 @subheading Synopsis
32621 -inferior-tty-set /dev/pts/1
32624 Set terminal for future runs of the program being debugged.
32626 @subheading @value{GDBN} Command
32628 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32630 @subheading Example
32634 -inferior-tty-set /dev/pts/1
32639 @subheading The @code{-inferior-tty-show} Command
32640 @findex -inferior-tty-show
32642 @subheading Synopsis
32648 Show terminal for future runs of program being debugged.
32650 @subheading @value{GDBN} Command
32652 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32654 @subheading Example
32658 -inferior-tty-set /dev/pts/1
32662 ^done,inferior_tty_terminal="/dev/pts/1"
32666 @subheading The @code{-enable-timings} Command
32667 @findex -enable-timings
32669 @subheading Synopsis
32672 -enable-timings [yes | no]
32675 Toggle the printing of the wallclock, user and system times for an MI
32676 command as a field in its output. This command is to help frontend
32677 developers optimize the performance of their code. No argument is
32678 equivalent to @samp{yes}.
32680 @subheading @value{GDBN} Command
32684 @subheading Example
32692 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32693 addr="0x080484ed",func="main",file="myprog.c",
32694 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32696 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32704 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32705 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32706 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32707 fullname="/home/nickrob/myprog.c",line="73"@}
32712 @chapter @value{GDBN} Annotations
32714 This chapter describes annotations in @value{GDBN}. Annotations were
32715 designed to interface @value{GDBN} to graphical user interfaces or other
32716 similar programs which want to interact with @value{GDBN} at a
32717 relatively high level.
32719 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32723 This is Edition @value{EDITION}, @value{DATE}.
32727 * Annotations Overview:: What annotations are; the general syntax.
32728 * Server Prefix:: Issuing a command without affecting user state.
32729 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32730 * Errors:: Annotations for error messages.
32731 * Invalidation:: Some annotations describe things now invalid.
32732 * Annotations for Running::
32733 Whether the program is running, how it stopped, etc.
32734 * Source Annotations:: Annotations describing source code.
32737 @node Annotations Overview
32738 @section What is an Annotation?
32739 @cindex annotations
32741 Annotations start with a newline character, two @samp{control-z}
32742 characters, and the name of the annotation. If there is no additional
32743 information associated with this annotation, the name of the annotation
32744 is followed immediately by a newline. If there is additional
32745 information, the name of the annotation is followed by a space, the
32746 additional information, and a newline. The additional information
32747 cannot contain newline characters.
32749 Any output not beginning with a newline and two @samp{control-z}
32750 characters denotes literal output from @value{GDBN}. Currently there is
32751 no need for @value{GDBN} to output a newline followed by two
32752 @samp{control-z} characters, but if there was such a need, the
32753 annotations could be extended with an @samp{escape} annotation which
32754 means those three characters as output.
32756 The annotation @var{level}, which is specified using the
32757 @option{--annotate} command line option (@pxref{Mode Options}), controls
32758 how much information @value{GDBN} prints together with its prompt,
32759 values of expressions, source lines, and other types of output. Level 0
32760 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32761 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32762 for programs that control @value{GDBN}, and level 2 annotations have
32763 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32764 Interface, annotate, GDB's Obsolete Annotations}).
32767 @kindex set annotate
32768 @item set annotate @var{level}
32769 The @value{GDBN} command @code{set annotate} sets the level of
32770 annotations to the specified @var{level}.
32772 @item show annotate
32773 @kindex show annotate
32774 Show the current annotation level.
32777 This chapter describes level 3 annotations.
32779 A simple example of starting up @value{GDBN} with annotations is:
32782 $ @kbd{gdb --annotate=3}
32784 Copyright 2003 Free Software Foundation, Inc.
32785 GDB is free software, covered by the GNU General Public License,
32786 and you are welcome to change it and/or distribute copies of it
32787 under certain conditions.
32788 Type "show copying" to see the conditions.
32789 There is absolutely no warranty for GDB. Type "show warranty"
32791 This GDB was configured as "i386-pc-linux-gnu"
32802 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32803 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32804 denotes a @samp{control-z} character) are annotations; the rest is
32805 output from @value{GDBN}.
32807 @node Server Prefix
32808 @section The Server Prefix
32809 @cindex server prefix
32811 If you prefix a command with @samp{server } then it will not affect
32812 the command history, nor will it affect @value{GDBN}'s notion of which
32813 command to repeat if @key{RET} is pressed on a line by itself. This
32814 means that commands can be run behind a user's back by a front-end in
32815 a transparent manner.
32817 The @code{server } prefix does not affect the recording of values into
32818 the value history; to print a value without recording it into the
32819 value history, use the @code{output} command instead of the
32820 @code{print} command.
32822 Using this prefix also disables confirmation requests
32823 (@pxref{confirmation requests}).
32826 @section Annotation for @value{GDBN} Input
32828 @cindex annotations for prompts
32829 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32830 to know when to send output, when the output from a given command is
32833 Different kinds of input each have a different @dfn{input type}. Each
32834 input type has three annotations: a @code{pre-} annotation, which
32835 denotes the beginning of any prompt which is being output, a plain
32836 annotation, which denotes the end of the prompt, and then a @code{post-}
32837 annotation which denotes the end of any echo which may (or may not) be
32838 associated with the input. For example, the @code{prompt} input type
32839 features the following annotations:
32847 The input types are
32850 @findex pre-prompt annotation
32851 @findex prompt annotation
32852 @findex post-prompt annotation
32854 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32856 @findex pre-commands annotation
32857 @findex commands annotation
32858 @findex post-commands annotation
32860 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32861 command. The annotations are repeated for each command which is input.
32863 @findex pre-overload-choice annotation
32864 @findex overload-choice annotation
32865 @findex post-overload-choice annotation
32866 @item overload-choice
32867 When @value{GDBN} wants the user to select between various overloaded functions.
32869 @findex pre-query annotation
32870 @findex query annotation
32871 @findex post-query annotation
32873 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32875 @findex pre-prompt-for-continue annotation
32876 @findex prompt-for-continue annotation
32877 @findex post-prompt-for-continue annotation
32878 @item prompt-for-continue
32879 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32880 expect this to work well; instead use @code{set height 0} to disable
32881 prompting. This is because the counting of lines is buggy in the
32882 presence of annotations.
32887 @cindex annotations for errors, warnings and interrupts
32889 @findex quit annotation
32894 This annotation occurs right before @value{GDBN} responds to an interrupt.
32896 @findex error annotation
32901 This annotation occurs right before @value{GDBN} responds to an error.
32903 Quit and error annotations indicate that any annotations which @value{GDBN} was
32904 in the middle of may end abruptly. For example, if a
32905 @code{value-history-begin} annotation is followed by a @code{error}, one
32906 cannot expect to receive the matching @code{value-history-end}. One
32907 cannot expect not to receive it either, however; an error annotation
32908 does not necessarily mean that @value{GDBN} is immediately returning all the way
32911 @findex error-begin annotation
32912 A quit or error annotation may be preceded by
32918 Any output between that and the quit or error annotation is the error
32921 Warning messages are not yet annotated.
32922 @c If we want to change that, need to fix warning(), type_error(),
32923 @c range_error(), and possibly other places.
32926 @section Invalidation Notices
32928 @cindex annotations for invalidation messages
32929 The following annotations say that certain pieces of state may have
32933 @findex frames-invalid annotation
32934 @item ^Z^Zframes-invalid
32936 The frames (for example, output from the @code{backtrace} command) may
32939 @findex breakpoints-invalid annotation
32940 @item ^Z^Zbreakpoints-invalid
32942 The breakpoints may have changed. For example, the user just added or
32943 deleted a breakpoint.
32946 @node Annotations for Running
32947 @section Running the Program
32948 @cindex annotations for running programs
32950 @findex starting annotation
32951 @findex stopping annotation
32952 When the program starts executing due to a @value{GDBN} command such as
32953 @code{step} or @code{continue},
32959 is output. When the program stops,
32965 is output. Before the @code{stopped} annotation, a variety of
32966 annotations describe how the program stopped.
32969 @findex exited annotation
32970 @item ^Z^Zexited @var{exit-status}
32971 The program exited, and @var{exit-status} is the exit status (zero for
32972 successful exit, otherwise nonzero).
32974 @findex signalled annotation
32975 @findex signal-name annotation
32976 @findex signal-name-end annotation
32977 @findex signal-string annotation
32978 @findex signal-string-end annotation
32979 @item ^Z^Zsignalled
32980 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32981 annotation continues:
32987 ^Z^Zsignal-name-end
32991 ^Z^Zsignal-string-end
32996 where @var{name} is the name of the signal, such as @code{SIGILL} or
32997 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32998 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32999 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33000 user's benefit and have no particular format.
33002 @findex signal annotation
33004 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33005 just saying that the program received the signal, not that it was
33006 terminated with it.
33008 @findex breakpoint annotation
33009 @item ^Z^Zbreakpoint @var{number}
33010 The program hit breakpoint number @var{number}.
33012 @findex watchpoint annotation
33013 @item ^Z^Zwatchpoint @var{number}
33014 The program hit watchpoint number @var{number}.
33017 @node Source Annotations
33018 @section Displaying Source
33019 @cindex annotations for source display
33021 @findex source annotation
33022 The following annotation is used instead of displaying source code:
33025 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33028 where @var{filename} is an absolute file name indicating which source
33029 file, @var{line} is the line number within that file (where 1 is the
33030 first line in the file), @var{character} is the character position
33031 within the file (where 0 is the first character in the file) (for most
33032 debug formats this will necessarily point to the beginning of a line),
33033 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33034 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33035 @var{addr} is the address in the target program associated with the
33036 source which is being displayed. The @var{addr} is in the form @samp{0x}
33037 followed by one or more lowercase hex digits (note that this does not
33038 depend on the language).
33040 @node JIT Interface
33041 @chapter JIT Compilation Interface
33042 @cindex just-in-time compilation
33043 @cindex JIT compilation interface
33045 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33046 interface. A JIT compiler is a program or library that generates native
33047 executable code at runtime and executes it, usually in order to achieve good
33048 performance while maintaining platform independence.
33050 Programs that use JIT compilation are normally difficult to debug because
33051 portions of their code are generated at runtime, instead of being loaded from
33052 object files, which is where @value{GDBN} normally finds the program's symbols
33053 and debug information. In order to debug programs that use JIT compilation,
33054 @value{GDBN} has an interface that allows the program to register in-memory
33055 symbol files with @value{GDBN} at runtime.
33057 If you are using @value{GDBN} to debug a program that uses this interface, then
33058 it should work transparently so long as you have not stripped the binary. If
33059 you are developing a JIT compiler, then the interface is documented in the rest
33060 of this chapter. At this time, the only known client of this interface is the
33063 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33064 JIT compiler communicates with @value{GDBN} by writing data into a global
33065 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33066 attaches, it reads a linked list of symbol files from the global variable to
33067 find existing code, and puts a breakpoint in the function so that it can find
33068 out about additional code.
33071 * Declarations:: Relevant C struct declarations
33072 * Registering Code:: Steps to register code
33073 * Unregistering Code:: Steps to unregister code
33074 * Custom Debug Info:: Emit debug information in a custom format
33078 @section JIT Declarations
33080 These are the relevant struct declarations that a C program should include to
33081 implement the interface:
33091 struct jit_code_entry
33093 struct jit_code_entry *next_entry;
33094 struct jit_code_entry *prev_entry;
33095 const char *symfile_addr;
33096 uint64_t symfile_size;
33099 struct jit_descriptor
33102 /* This type should be jit_actions_t, but we use uint32_t
33103 to be explicit about the bitwidth. */
33104 uint32_t action_flag;
33105 struct jit_code_entry *relevant_entry;
33106 struct jit_code_entry *first_entry;
33109 /* GDB puts a breakpoint in this function. */
33110 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33112 /* Make sure to specify the version statically, because the
33113 debugger may check the version before we can set it. */
33114 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33117 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33118 modifications to this global data properly, which can easily be done by putting
33119 a global mutex around modifications to these structures.
33121 @node Registering Code
33122 @section Registering Code
33124 To register code with @value{GDBN}, the JIT should follow this protocol:
33128 Generate an object file in memory with symbols and other desired debug
33129 information. The file must include the virtual addresses of the sections.
33132 Create a code entry for the file, which gives the start and size of the symbol
33136 Add it to the linked list in the JIT descriptor.
33139 Point the relevant_entry field of the descriptor at the entry.
33142 Set @code{action_flag} to @code{JIT_REGISTER} and call
33143 @code{__jit_debug_register_code}.
33146 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33147 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33148 new code. However, the linked list must still be maintained in order to allow
33149 @value{GDBN} to attach to a running process and still find the symbol files.
33151 @node Unregistering Code
33152 @section Unregistering Code
33154 If code is freed, then the JIT should use the following protocol:
33158 Remove the code entry corresponding to the code from the linked list.
33161 Point the @code{relevant_entry} field of the descriptor at the code entry.
33164 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33165 @code{__jit_debug_register_code}.
33168 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33169 and the JIT will leak the memory used for the associated symbol files.
33171 @node Custom Debug Info
33172 @section Custom Debug Info
33173 @cindex custom JIT debug info
33174 @cindex JIT debug info reader
33176 Generating debug information in platform-native file formats (like ELF
33177 or COFF) may be an overkill for JIT compilers; especially if all the
33178 debug info is used for is displaying a meaningful backtrace. The
33179 issue can be resolved by having the JIT writers decide on a debug info
33180 format and also provide a reader that parses the debug info generated
33181 by the JIT compiler. This section gives a brief overview on writing
33182 such a parser. More specific details can be found in the source file
33183 @file{gdb/jit-reader.in}, which is also installed as a header at
33184 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33186 The reader is implemented as a shared object (so this functionality is
33187 not available on platforms which don't allow loading shared objects at
33188 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33189 @code{jit-reader-unload} are provided, to be used to load and unload
33190 the readers from a preconfigured directory. Once loaded, the shared
33191 object is used the parse the debug information emitted by the JIT
33195 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33196 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33199 @node Using JIT Debug Info Readers
33200 @subsection Using JIT Debug Info Readers
33201 @kindex jit-reader-load
33202 @kindex jit-reader-unload
33204 Readers can be loaded and unloaded using the @code{jit-reader-load}
33205 and @code{jit-reader-unload} commands.
33208 @item jit-reader-load @var{reader}
33209 Load the JIT reader named @var{reader}, which is a shared
33210 object specified as either an absolute or a relative file name. In
33211 the latter case, @value{GDBN} will try to load the reader from a
33212 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33213 system (here @var{libdir} is the system library directory, often
33214 @file{/usr/local/lib}).
33216 Only one reader can be active at a time; trying to load a second
33217 reader when one is already loaded will result in @value{GDBN}
33218 reporting an error. A new JIT reader can be loaded by first unloading
33219 the current one using @code{jit-reader-unload} and then invoking
33220 @code{jit-reader-load}.
33222 @item jit-reader-unload
33223 Unload the currently loaded JIT reader.
33227 @node Writing JIT Debug Info Readers
33228 @subsection Writing JIT Debug Info Readers
33229 @cindex writing JIT debug info readers
33231 As mentioned, a reader is essentially a shared object conforming to a
33232 certain ABI. This ABI is described in @file{jit-reader.h}.
33234 @file{jit-reader.h} defines the structures, macros and functions
33235 required to write a reader. It is installed (along with
33236 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33237 the system include directory.
33239 Readers need to be released under a GPL compatible license. A reader
33240 can be declared as released under such a license by placing the macro
33241 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33243 The entry point for readers is the symbol @code{gdb_init_reader},
33244 which is expected to be a function with the prototype
33246 @findex gdb_init_reader
33248 extern struct gdb_reader_funcs *gdb_init_reader (void);
33251 @cindex @code{struct gdb_reader_funcs}
33253 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33254 functions. These functions are executed to read the debug info
33255 generated by the JIT compiler (@code{read}), to unwind stack frames
33256 (@code{unwind}) and to create canonical frame IDs
33257 (@code{get_Frame_id}). It also has a callback that is called when the
33258 reader is being unloaded (@code{destroy}). The struct looks like this
33261 struct gdb_reader_funcs
33263 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33264 int reader_version;
33266 /* For use by the reader. */
33269 gdb_read_debug_info *read;
33270 gdb_unwind_frame *unwind;
33271 gdb_get_frame_id *get_frame_id;
33272 gdb_destroy_reader *destroy;
33276 @cindex @code{struct gdb_symbol_callbacks}
33277 @cindex @code{struct gdb_unwind_callbacks}
33279 The callbacks are provided with another set of callbacks by
33280 @value{GDBN} to do their job. For @code{read}, these callbacks are
33281 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33282 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33283 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33284 files and new symbol tables inside those object files. @code{struct
33285 gdb_unwind_callbacks} has callbacks to read registers off the current
33286 frame and to write out the values of the registers in the previous
33287 frame. Both have a callback (@code{target_read}) to read bytes off the
33288 target's address space.
33290 @node In-Process Agent
33291 @chapter In-Process Agent
33292 @cindex debugging agent
33293 The traditional debugging model is conceptually low-speed, but works fine,
33294 because most bugs can be reproduced in debugging-mode execution. However,
33295 as multi-core or many-core processors are becoming mainstream, and
33296 multi-threaded programs become more and more popular, there should be more
33297 and more bugs that only manifest themselves at normal-mode execution, for
33298 example, thread races, because debugger's interference with the program's
33299 timing may conceal the bugs. On the other hand, in some applications,
33300 it is not feasible for the debugger to interrupt the program's execution
33301 long enough for the developer to learn anything helpful about its behavior.
33302 If the program's correctness depends on its real-time behavior, delays
33303 introduced by a debugger might cause the program to fail, even when the
33304 code itself is correct. It is useful to be able to observe the program's
33305 behavior without interrupting it.
33307 Therefore, traditional debugging model is too intrusive to reproduce
33308 some bugs. In order to reduce the interference with the program, we can
33309 reduce the number of operations performed by debugger. The
33310 @dfn{In-Process Agent}, a shared library, is running within the same
33311 process with inferior, and is able to perform some debugging operations
33312 itself. As a result, debugger is only involved when necessary, and
33313 performance of debugging can be improved accordingly. Note that
33314 interference with program can be reduced but can't be removed completely,
33315 because the in-process agent will still stop or slow down the program.
33317 The in-process agent can interpret and execute Agent Expressions
33318 (@pxref{Agent Expressions}) during performing debugging operations. The
33319 agent expressions can be used for different purposes, such as collecting
33320 data in tracepoints, and condition evaluation in breakpoints.
33322 @anchor{Control Agent}
33323 You can control whether the in-process agent is used as an aid for
33324 debugging with the following commands:
33327 @kindex set agent on
33329 Causes the in-process agent to perform some operations on behalf of the
33330 debugger. Just which operations requested by the user will be done
33331 by the in-process agent depends on the its capabilities. For example,
33332 if you request to evaluate breakpoint conditions in the in-process agent,
33333 and the in-process agent has such capability as well, then breakpoint
33334 conditions will be evaluated in the in-process agent.
33336 @kindex set agent off
33337 @item set agent off
33338 Disables execution of debugging operations by the in-process agent. All
33339 of the operations will be performed by @value{GDBN}.
33343 Display the current setting of execution of debugging operations by
33344 the in-process agent.
33348 * In-Process Agent Protocol::
33351 @node In-Process Agent Protocol
33352 @section In-Process Agent Protocol
33353 @cindex in-process agent protocol
33355 The in-process agent is able to communicate with both @value{GDBN} and
33356 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
33357 used for communications between @value{GDBN} or GDBserver and the IPA.
33358 In general, @value{GDBN} or GDBserver sends commands
33359 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
33360 in-process agent replies back with the return result of the command, or
33361 some other information. The data sent to in-process agent is composed
33362 of primitive data types, such as 4-byte or 8-byte type, and composite
33363 types, which are called objects (@pxref{IPA Protocol Objects}).
33366 * IPA Protocol Objects::
33367 * IPA Protocol Commands::
33370 @node IPA Protocol Objects
33371 @subsection IPA Protocol Objects
33372 @cindex ipa protocol objects
33374 The commands sent to and results received from agent may contain some
33375 complex data types called @dfn{objects}.
33377 The in-process agent is running on the same machine with @value{GDBN}
33378 or GDBserver, so it doesn't have to handle as much differences between
33379 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33380 However, there are still some differences of two ends in two processes:
33384 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33385 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33387 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33388 GDBserver is compiled with one, and in-process agent is compiled with
33392 Here are the IPA Protocol Objects:
33396 agent expression object. It represents an agent expression
33397 (@pxref{Agent Expressions}).
33398 @anchor{agent expression object}
33400 tracepoint action object. It represents a tracepoint action
33401 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33402 memory, static trace data and to evaluate expression.
33403 @anchor{tracepoint action object}
33405 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33406 @anchor{tracepoint object}
33410 The following table describes important attributes of each IPA protocol
33413 @multitable @columnfractions .30 .20 .50
33414 @headitem Name @tab Size @tab Description
33415 @item @emph{agent expression object} @tab @tab
33416 @item length @tab 4 @tab length of bytes code
33417 @item byte code @tab @var{length} @tab contents of byte code
33418 @item @emph{tracepoint action for collecting memory} @tab @tab
33419 @item 'M' @tab 1 @tab type of tracepoint action
33420 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33421 address of the lowest byte to collect, otherwise @var{addr} is the offset
33422 of @var{basereg} for memory collecting.
33423 @item len @tab 8 @tab length of memory for collecting
33424 @item basereg @tab 4 @tab the register number containing the starting
33425 memory address for collecting.
33426 @item @emph{tracepoint action for collecting registers} @tab @tab
33427 @item 'R' @tab 1 @tab type of tracepoint action
33428 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33429 @item 'L' @tab 1 @tab type of tracepoint action
33430 @item @emph{tracepoint action for expression evaluation} @tab @tab
33431 @item 'X' @tab 1 @tab type of tracepoint action
33432 @item agent expression @tab length of @tab @ref{agent expression object}
33433 @item @emph{tracepoint object} @tab @tab
33434 @item number @tab 4 @tab number of tracepoint
33435 @item address @tab 8 @tab address of tracepoint inserted on
33436 @item type @tab 4 @tab type of tracepoint
33437 @item enabled @tab 1 @tab enable or disable of tracepoint
33438 @item step_count @tab 8 @tab step
33439 @item pass_count @tab 8 @tab pass
33440 @item numactions @tab 4 @tab number of tracepoint actions
33441 @item hit count @tab 8 @tab hit count
33442 @item trace frame usage @tab 8 @tab trace frame usage
33443 @item compiled_cond @tab 8 @tab compiled condition
33444 @item orig_size @tab 8 @tab orig size
33445 @item condition @tab 4 if condition is NULL otherwise length of
33446 @ref{agent expression object}
33447 @tab zero if condition is NULL, otherwise is
33448 @ref{agent expression object}
33449 @item actions @tab variable
33450 @tab numactions number of @ref{tracepoint action object}
33453 @node IPA Protocol Commands
33454 @subsection IPA Protocol Commands
33455 @cindex ipa protocol commands
33457 The spaces in each command are delimiters to ease reading this commands
33458 specification. They don't exist in real commands.
33462 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33463 Installs a new fast tracepoint described by @var{tracepoint_object}
33464 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33465 head of @dfn{jumppad}, which is used to jump to data collection routine
33470 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33471 @var{target_address} is address of tracepoint in the inferior.
33472 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33473 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33474 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33475 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33482 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33483 is about to kill inferiors.
33491 @item probe_marker_at:@var{address}
33492 Asks in-process agent to probe the marker at @var{address}.
33499 @item unprobe_marker_at:@var{address}
33500 Asks in-process agent to unprobe the marker at @var{address}.
33504 @chapter Reporting Bugs in @value{GDBN}
33505 @cindex bugs in @value{GDBN}
33506 @cindex reporting bugs in @value{GDBN}
33508 Your bug reports play an essential role in making @value{GDBN} reliable.
33510 Reporting a bug may help you by bringing a solution to your problem, or it
33511 may not. But in any case the principal function of a bug report is to help
33512 the entire community by making the next version of @value{GDBN} work better. Bug
33513 reports are your contribution to the maintenance of @value{GDBN}.
33515 In order for a bug report to serve its purpose, you must include the
33516 information that enables us to fix the bug.
33519 * Bug Criteria:: Have you found a bug?
33520 * Bug Reporting:: How to report bugs
33524 @section Have You Found a Bug?
33525 @cindex bug criteria
33527 If you are not sure whether you have found a bug, here are some guidelines:
33530 @cindex fatal signal
33531 @cindex debugger crash
33532 @cindex crash of debugger
33534 If the debugger gets a fatal signal, for any input whatever, that is a
33535 @value{GDBN} bug. Reliable debuggers never crash.
33537 @cindex error on valid input
33539 If @value{GDBN} produces an error message for valid input, that is a
33540 bug. (Note that if you're cross debugging, the problem may also be
33541 somewhere in the connection to the target.)
33543 @cindex invalid input
33545 If @value{GDBN} does not produce an error message for invalid input,
33546 that is a bug. However, you should note that your idea of
33547 ``invalid input'' might be our idea of ``an extension'' or ``support
33548 for traditional practice''.
33551 If you are an experienced user of debugging tools, your suggestions
33552 for improvement of @value{GDBN} are welcome in any case.
33555 @node Bug Reporting
33556 @section How to Report Bugs
33557 @cindex bug reports
33558 @cindex @value{GDBN} bugs, reporting
33560 A number of companies and individuals offer support for @sc{gnu} products.
33561 If you obtained @value{GDBN} from a support organization, we recommend you
33562 contact that organization first.
33564 You can find contact information for many support companies and
33565 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33567 @c should add a web page ref...
33570 @ifset BUGURL_DEFAULT
33571 In any event, we also recommend that you submit bug reports for
33572 @value{GDBN}. The preferred method is to submit them directly using
33573 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33574 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33577 @strong{Do not send bug reports to @samp{info-gdb}, or to
33578 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33579 not want to receive bug reports. Those that do have arranged to receive
33582 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33583 serves as a repeater. The mailing list and the newsgroup carry exactly
33584 the same messages. Often people think of posting bug reports to the
33585 newsgroup instead of mailing them. This appears to work, but it has one
33586 problem which can be crucial: a newsgroup posting often lacks a mail
33587 path back to the sender. Thus, if we need to ask for more information,
33588 we may be unable to reach you. For this reason, it is better to send
33589 bug reports to the mailing list.
33591 @ifclear BUGURL_DEFAULT
33592 In any event, we also recommend that you submit bug reports for
33593 @value{GDBN} to @value{BUGURL}.
33597 The fundamental principle of reporting bugs usefully is this:
33598 @strong{report all the facts}. If you are not sure whether to state a
33599 fact or leave it out, state it!
33601 Often people omit facts because they think they know what causes the
33602 problem and assume that some details do not matter. Thus, you might
33603 assume that the name of the variable you use in an example does not matter.
33604 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33605 stray memory reference which happens to fetch from the location where that
33606 name is stored in memory; perhaps, if the name were different, the contents
33607 of that location would fool the debugger into doing the right thing despite
33608 the bug. Play it safe and give a specific, complete example. That is the
33609 easiest thing for you to do, and the most helpful.
33611 Keep in mind that the purpose of a bug report is to enable us to fix the
33612 bug. It may be that the bug has been reported previously, but neither
33613 you nor we can know that unless your bug report is complete and
33616 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33617 bell?'' Those bug reports are useless, and we urge everyone to
33618 @emph{refuse to respond to them} except to chide the sender to report
33621 To enable us to fix the bug, you should include all these things:
33625 The version of @value{GDBN}. @value{GDBN} announces it if you start
33626 with no arguments; you can also print it at any time using @code{show
33629 Without this, we will not know whether there is any point in looking for
33630 the bug in the current version of @value{GDBN}.
33633 The type of machine you are using, and the operating system name and
33637 The details of the @value{GDBN} build-time configuration.
33638 @value{GDBN} shows these details if you invoke it with the
33639 @option{--configuration} command-line option, or if you type
33640 @code{show configuration} at @value{GDBN}'s prompt.
33643 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33644 ``@value{GCC}--2.8.1''.
33647 What compiler (and its version) was used to compile the program you are
33648 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33649 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33650 to get this information; for other compilers, see the documentation for
33654 The command arguments you gave the compiler to compile your example and
33655 observe the bug. For example, did you use @samp{-O}? To guarantee
33656 you will not omit something important, list them all. A copy of the
33657 Makefile (or the output from make) is sufficient.
33659 If we were to try to guess the arguments, we would probably guess wrong
33660 and then we might not encounter the bug.
33663 A complete input script, and all necessary source files, that will
33667 A description of what behavior you observe that you believe is
33668 incorrect. For example, ``It gets a fatal signal.''
33670 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33671 will certainly notice it. But if the bug is incorrect output, we might
33672 not notice unless it is glaringly wrong. You might as well not give us
33673 a chance to make a mistake.
33675 Even if the problem you experience is a fatal signal, you should still
33676 say so explicitly. Suppose something strange is going on, such as, your
33677 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33678 the C library on your system. (This has happened!) Your copy might
33679 crash and ours would not. If you told us to expect a crash, then when
33680 ours fails to crash, we would know that the bug was not happening for
33681 us. If you had not told us to expect a crash, then we would not be able
33682 to draw any conclusion from our observations.
33685 @cindex recording a session script
33686 To collect all this information, you can use a session recording program
33687 such as @command{script}, which is available on many Unix systems.
33688 Just run your @value{GDBN} session inside @command{script} and then
33689 include the @file{typescript} file with your bug report.
33691 Another way to record a @value{GDBN} session is to run @value{GDBN}
33692 inside Emacs and then save the entire buffer to a file.
33695 If you wish to suggest changes to the @value{GDBN} source, send us context
33696 diffs. If you even discuss something in the @value{GDBN} source, refer to
33697 it by context, not by line number.
33699 The line numbers in our development sources will not match those in your
33700 sources. Your line numbers would convey no useful information to us.
33704 Here are some things that are not necessary:
33708 A description of the envelope of the bug.
33710 Often people who encounter a bug spend a lot of time investigating
33711 which changes to the input file will make the bug go away and which
33712 changes will not affect it.
33714 This is often time consuming and not very useful, because the way we
33715 will find the bug is by running a single example under the debugger
33716 with breakpoints, not by pure deduction from a series of examples.
33717 We recommend that you save your time for something else.
33719 Of course, if you can find a simpler example to report @emph{instead}
33720 of the original one, that is a convenience for us. Errors in the
33721 output will be easier to spot, running under the debugger will take
33722 less time, and so on.
33724 However, simplification is not vital; if you do not want to do this,
33725 report the bug anyway and send us the entire test case you used.
33728 A patch for the bug.
33730 A patch for the bug does help us if it is a good one. But do not omit
33731 the necessary information, such as the test case, on the assumption that
33732 a patch is all we need. We might see problems with your patch and decide
33733 to fix the problem another way, or we might not understand it at all.
33735 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33736 construct an example that will make the program follow a certain path
33737 through the code. If you do not send us the example, we will not be able
33738 to construct one, so we will not be able to verify that the bug is fixed.
33740 And if we cannot understand what bug you are trying to fix, or why your
33741 patch should be an improvement, we will not install it. A test case will
33742 help us to understand.
33745 A guess about what the bug is or what it depends on.
33747 Such guesses are usually wrong. Even we cannot guess right about such
33748 things without first using the debugger to find the facts.
33751 @c The readline documentation is distributed with the readline code
33752 @c and consists of the two following files:
33755 @c Use -I with makeinfo to point to the appropriate directory,
33756 @c environment var TEXINPUTS with TeX.
33757 @ifclear SYSTEM_READLINE
33758 @include rluser.texi
33759 @include hsuser.texi
33763 @appendix In Memoriam
33765 The @value{GDBN} project mourns the loss of the following long-time
33770 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33771 to Free Software in general. Outside of @value{GDBN}, he was known in
33772 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33774 @item Michael Snyder
33775 Michael was one of the Global Maintainers of the @value{GDBN} project,
33776 with contributions recorded as early as 1996, until 2011. In addition
33777 to his day to day participation, he was a large driving force behind
33778 adding Reverse Debugging to @value{GDBN}.
33781 Beyond their technical contributions to the project, they were also
33782 enjoyable members of the Free Software Community. We will miss them.
33784 @node Formatting Documentation
33785 @appendix Formatting Documentation
33787 @cindex @value{GDBN} reference card
33788 @cindex reference card
33789 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33790 for printing with PostScript or Ghostscript, in the @file{gdb}
33791 subdirectory of the main source directory@footnote{In
33792 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33793 release.}. If you can use PostScript or Ghostscript with your printer,
33794 you can print the reference card immediately with @file{refcard.ps}.
33796 The release also includes the source for the reference card. You
33797 can format it, using @TeX{}, by typing:
33803 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33804 mode on US ``letter'' size paper;
33805 that is, on a sheet 11 inches wide by 8.5 inches
33806 high. You will need to specify this form of printing as an option to
33807 your @sc{dvi} output program.
33809 @cindex documentation
33811 All the documentation for @value{GDBN} comes as part of the machine-readable
33812 distribution. The documentation is written in Texinfo format, which is
33813 a documentation system that uses a single source file to produce both
33814 on-line information and a printed manual. You can use one of the Info
33815 formatting commands to create the on-line version of the documentation
33816 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33818 @value{GDBN} includes an already formatted copy of the on-line Info
33819 version of this manual in the @file{gdb} subdirectory. The main Info
33820 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33821 subordinate files matching @samp{gdb.info*} in the same directory. If
33822 necessary, you can print out these files, or read them with any editor;
33823 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33824 Emacs or the standalone @code{info} program, available as part of the
33825 @sc{gnu} Texinfo distribution.
33827 If you want to format these Info files yourself, you need one of the
33828 Info formatting programs, such as @code{texinfo-format-buffer} or
33831 If you have @code{makeinfo} installed, and are in the top level
33832 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33833 version @value{GDBVN}), you can make the Info file by typing:
33840 If you want to typeset and print copies of this manual, you need @TeX{},
33841 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33842 Texinfo definitions file.
33844 @TeX{} is a typesetting program; it does not print files directly, but
33845 produces output files called @sc{dvi} files. To print a typeset
33846 document, you need a program to print @sc{dvi} files. If your system
33847 has @TeX{} installed, chances are it has such a program. The precise
33848 command to use depends on your system; @kbd{lpr -d} is common; another
33849 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33850 require a file name without any extension or a @samp{.dvi} extension.
33852 @TeX{} also requires a macro definitions file called
33853 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33854 written in Texinfo format. On its own, @TeX{} cannot either read or
33855 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33856 and is located in the @file{gdb-@var{version-number}/texinfo}
33859 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33860 typeset and print this manual. First switch to the @file{gdb}
33861 subdirectory of the main source directory (for example, to
33862 @file{gdb-@value{GDBVN}/gdb}) and type:
33868 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33870 @node Installing GDB
33871 @appendix Installing @value{GDBN}
33872 @cindex installation
33875 * Requirements:: Requirements for building @value{GDBN}
33876 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33877 * Separate Objdir:: Compiling @value{GDBN} in another directory
33878 * Config Names:: Specifying names for hosts and targets
33879 * Configure Options:: Summary of options for configure
33880 * System-wide configuration:: Having a system-wide init file
33884 @section Requirements for Building @value{GDBN}
33885 @cindex building @value{GDBN}, requirements for
33887 Building @value{GDBN} requires various tools and packages to be available.
33888 Other packages will be used only if they are found.
33890 @heading Tools/Packages Necessary for Building @value{GDBN}
33892 @item ISO C90 compiler
33893 @value{GDBN} is written in ISO C90. It should be buildable with any
33894 working C90 compiler, e.g.@: GCC.
33898 @heading Tools/Packages Optional for Building @value{GDBN}
33902 @value{GDBN} can use the Expat XML parsing library. This library may be
33903 included with your operating system distribution; if it is not, you
33904 can get the latest version from @url{http://expat.sourceforge.net}.
33905 The @file{configure} script will search for this library in several
33906 standard locations; if it is installed in an unusual path, you can
33907 use the @option{--with-libexpat-prefix} option to specify its location.
33913 Remote protocol memory maps (@pxref{Memory Map Format})
33915 Target descriptions (@pxref{Target Descriptions})
33917 Remote shared library lists (@xref{Library List Format},
33918 or alternatively @pxref{Library List Format for SVR4 Targets})
33920 MS-Windows shared libraries (@pxref{Shared Libraries})
33922 Traceframe info (@pxref{Traceframe Info Format})
33924 Branch trace (@pxref{Branch Trace Format},
33925 @pxref{Branch Trace Configuration Format})
33929 @cindex compressed debug sections
33930 @value{GDBN} will use the @samp{zlib} library, if available, to read
33931 compressed debug sections. Some linkers, such as GNU gold, are capable
33932 of producing binaries with compressed debug sections. If @value{GDBN}
33933 is compiled with @samp{zlib}, it will be able to read the debug
33934 information in such binaries.
33936 The @samp{zlib} library is likely included with your operating system
33937 distribution; if it is not, you can get the latest version from
33938 @url{http://zlib.net}.
33941 @value{GDBN}'s features related to character sets (@pxref{Character
33942 Sets}) require a functioning @code{iconv} implementation. If you are
33943 on a GNU system, then this is provided by the GNU C Library. Some
33944 other systems also provide a working @code{iconv}.
33946 If @value{GDBN} is using the @code{iconv} program which is installed
33947 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33948 This is done with @option{--with-iconv-bin} which specifies the
33949 directory that contains the @code{iconv} program.
33951 On systems without @code{iconv}, you can install GNU Libiconv. If you
33952 have previously installed Libiconv, you can use the
33953 @option{--with-libiconv-prefix} option to configure.
33955 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33956 arrange to build Libiconv if a directory named @file{libiconv} appears
33957 in the top-most source directory. If Libiconv is built this way, and
33958 if the operating system does not provide a suitable @code{iconv}
33959 implementation, then the just-built library will automatically be used
33960 by @value{GDBN}. One easy way to set this up is to download GNU
33961 Libiconv, unpack it, and then rename the directory holding the
33962 Libiconv source code to @samp{libiconv}.
33965 @node Running Configure
33966 @section Invoking the @value{GDBN} @file{configure} Script
33967 @cindex configuring @value{GDBN}
33968 @value{GDBN} comes with a @file{configure} script that automates the process
33969 of preparing @value{GDBN} for installation; you can then use @code{make} to
33970 build the @code{gdb} program.
33972 @c irrelevant in info file; it's as current as the code it lives with.
33973 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33974 look at the @file{README} file in the sources; we may have improved the
33975 installation procedures since publishing this manual.}
33978 The @value{GDBN} distribution includes all the source code you need for
33979 @value{GDBN} in a single directory, whose name is usually composed by
33980 appending the version number to @samp{gdb}.
33982 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33983 @file{gdb-@value{GDBVN}} directory. That directory contains:
33986 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33987 script for configuring @value{GDBN} and all its supporting libraries
33989 @item gdb-@value{GDBVN}/gdb
33990 the source specific to @value{GDBN} itself
33992 @item gdb-@value{GDBVN}/bfd
33993 source for the Binary File Descriptor library
33995 @item gdb-@value{GDBVN}/include
33996 @sc{gnu} include files
33998 @item gdb-@value{GDBVN}/libiberty
33999 source for the @samp{-liberty} free software library
34001 @item gdb-@value{GDBVN}/opcodes
34002 source for the library of opcode tables and disassemblers
34004 @item gdb-@value{GDBVN}/readline
34005 source for the @sc{gnu} command-line interface
34007 @item gdb-@value{GDBVN}/glob
34008 source for the @sc{gnu} filename pattern-matching subroutine
34010 @item gdb-@value{GDBVN}/mmalloc
34011 source for the @sc{gnu} memory-mapped malloc package
34014 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34015 from the @file{gdb-@var{version-number}} source directory, which in
34016 this example is the @file{gdb-@value{GDBVN}} directory.
34018 First switch to the @file{gdb-@var{version-number}} source directory
34019 if you are not already in it; then run @file{configure}. Pass the
34020 identifier for the platform on which @value{GDBN} will run as an
34026 cd gdb-@value{GDBVN}
34027 ./configure @var{host}
34032 where @var{host} is an identifier such as @samp{sun4} or
34033 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34034 (You can often leave off @var{host}; @file{configure} tries to guess the
34035 correct value by examining your system.)
34037 Running @samp{configure @var{host}} and then running @code{make} builds the
34038 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34039 libraries, then @code{gdb} itself. The configured source files, and the
34040 binaries, are left in the corresponding source directories.
34043 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34044 system does not recognize this automatically when you run a different
34045 shell, you may need to run @code{sh} on it explicitly:
34048 sh configure @var{host}
34051 If you run @file{configure} from a directory that contains source
34052 directories for multiple libraries or programs, such as the
34053 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34055 creates configuration files for every directory level underneath (unless
34056 you tell it not to, with the @samp{--norecursion} option).
34058 You should run the @file{configure} script from the top directory in the
34059 source tree, the @file{gdb-@var{version-number}} directory. If you run
34060 @file{configure} from one of the subdirectories, you will configure only
34061 that subdirectory. That is usually not what you want. In particular,
34062 if you run the first @file{configure} from the @file{gdb} subdirectory
34063 of the @file{gdb-@var{version-number}} directory, you will omit the
34064 configuration of @file{bfd}, @file{readline}, and other sibling
34065 directories of the @file{gdb} subdirectory. This leads to build errors
34066 about missing include files such as @file{bfd/bfd.h}.
34068 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34069 However, you should make sure that the shell on your path (named by
34070 the @samp{SHELL} environment variable) is publicly readable. Remember
34071 that @value{GDBN} uses the shell to start your program---some systems refuse to
34072 let @value{GDBN} debug child processes whose programs are not readable.
34074 @node Separate Objdir
34075 @section Compiling @value{GDBN} in Another Directory
34077 If you want to run @value{GDBN} versions for several host or target machines,
34078 you need a different @code{gdb} compiled for each combination of
34079 host and target. @file{configure} is designed to make this easy by
34080 allowing you to generate each configuration in a separate subdirectory,
34081 rather than in the source directory. If your @code{make} program
34082 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34083 @code{make} in each of these directories builds the @code{gdb}
34084 program specified there.
34086 To build @code{gdb} in a separate directory, run @file{configure}
34087 with the @samp{--srcdir} option to specify where to find the source.
34088 (You also need to specify a path to find @file{configure}
34089 itself from your working directory. If the path to @file{configure}
34090 would be the same as the argument to @samp{--srcdir}, you can leave out
34091 the @samp{--srcdir} option; it is assumed.)
34093 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34094 separate directory for a Sun 4 like this:
34098 cd gdb-@value{GDBVN}
34101 ../gdb-@value{GDBVN}/configure sun4
34106 When @file{configure} builds a configuration using a remote source
34107 directory, it creates a tree for the binaries with the same structure
34108 (and using the same names) as the tree under the source directory. In
34109 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34110 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34111 @file{gdb-sun4/gdb}.
34113 Make sure that your path to the @file{configure} script has just one
34114 instance of @file{gdb} in it. If your path to @file{configure} looks
34115 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34116 one subdirectory of @value{GDBN}, not the whole package. This leads to
34117 build errors about missing include files such as @file{bfd/bfd.h}.
34119 One popular reason to build several @value{GDBN} configurations in separate
34120 directories is to configure @value{GDBN} for cross-compiling (where
34121 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34122 programs that run on another machine---the @dfn{target}).
34123 You specify a cross-debugging target by
34124 giving the @samp{--target=@var{target}} option to @file{configure}.
34126 When you run @code{make} to build a program or library, you must run
34127 it in a configured directory---whatever directory you were in when you
34128 called @file{configure} (or one of its subdirectories).
34130 The @code{Makefile} that @file{configure} generates in each source
34131 directory also runs recursively. If you type @code{make} in a source
34132 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34133 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34134 will build all the required libraries, and then build GDB.
34136 When you have multiple hosts or targets configured in separate
34137 directories, you can run @code{make} on them in parallel (for example,
34138 if they are NFS-mounted on each of the hosts); they will not interfere
34142 @section Specifying Names for Hosts and Targets
34144 The specifications used for hosts and targets in the @file{configure}
34145 script are based on a three-part naming scheme, but some short predefined
34146 aliases are also supported. The full naming scheme encodes three pieces
34147 of information in the following pattern:
34150 @var{architecture}-@var{vendor}-@var{os}
34153 For example, you can use the alias @code{sun4} as a @var{host} argument,
34154 or as the value for @var{target} in a @code{--target=@var{target}}
34155 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34157 The @file{configure} script accompanying @value{GDBN} does not provide
34158 any query facility to list all supported host and target names or
34159 aliases. @file{configure} calls the Bourne shell script
34160 @code{config.sub} to map abbreviations to full names; you can read the
34161 script, if you wish, or you can use it to test your guesses on
34162 abbreviations---for example:
34165 % sh config.sub i386-linux
34167 % sh config.sub alpha-linux
34168 alpha-unknown-linux-gnu
34169 % sh config.sub hp9k700
34171 % sh config.sub sun4
34172 sparc-sun-sunos4.1.1
34173 % sh config.sub sun3
34174 m68k-sun-sunos4.1.1
34175 % sh config.sub i986v
34176 Invalid configuration `i986v': machine `i986v' not recognized
34180 @code{config.sub} is also distributed in the @value{GDBN} source
34181 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34183 @node Configure Options
34184 @section @file{configure} Options
34186 Here is a summary of the @file{configure} options and arguments that
34187 are most often useful for building @value{GDBN}. @file{configure} also has
34188 several other options not listed here. @inforef{What Configure
34189 Does,,configure.info}, for a full explanation of @file{configure}.
34192 configure @r{[}--help@r{]}
34193 @r{[}--prefix=@var{dir}@r{]}
34194 @r{[}--exec-prefix=@var{dir}@r{]}
34195 @r{[}--srcdir=@var{dirname}@r{]}
34196 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34197 @r{[}--target=@var{target}@r{]}
34202 You may introduce options with a single @samp{-} rather than
34203 @samp{--} if you prefer; but you may abbreviate option names if you use
34208 Display a quick summary of how to invoke @file{configure}.
34210 @item --prefix=@var{dir}
34211 Configure the source to install programs and files under directory
34214 @item --exec-prefix=@var{dir}
34215 Configure the source to install programs under directory
34218 @c avoid splitting the warning from the explanation:
34220 @item --srcdir=@var{dirname}
34221 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34222 @code{make} that implements the @code{VPATH} feature.}@*
34223 Use this option to make configurations in directories separate from the
34224 @value{GDBN} source directories. Among other things, you can use this to
34225 build (or maintain) several configurations simultaneously, in separate
34226 directories. @file{configure} writes configuration-specific files in
34227 the current directory, but arranges for them to use the source in the
34228 directory @var{dirname}. @file{configure} creates directories under
34229 the working directory in parallel to the source directories below
34232 @item --norecursion
34233 Configure only the directory level where @file{configure} is executed; do not
34234 propagate configuration to subdirectories.
34236 @item --target=@var{target}
34237 Configure @value{GDBN} for cross-debugging programs running on the specified
34238 @var{target}. Without this option, @value{GDBN} is configured to debug
34239 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34241 There is no convenient way to generate a list of all available targets.
34243 @item @var{host} @dots{}
34244 Configure @value{GDBN} to run on the specified @var{host}.
34246 There is no convenient way to generate a list of all available hosts.
34249 There are many other options available as well, but they are generally
34250 needed for special purposes only.
34252 @node System-wide configuration
34253 @section System-wide configuration and settings
34254 @cindex system-wide init file
34256 @value{GDBN} can be configured to have a system-wide init file;
34257 this file will be read and executed at startup (@pxref{Startup, , What
34258 @value{GDBN} does during startup}).
34260 Here is the corresponding configure option:
34263 @item --with-system-gdbinit=@var{file}
34264 Specify that the default location of the system-wide init file is
34268 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34269 it may be subject to relocation. Two possible cases:
34273 If the default location of this init file contains @file{$prefix},
34274 it will be subject to relocation. Suppose that the configure options
34275 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34276 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34277 init file is looked for as @file{$install/etc/gdbinit} instead of
34278 @file{$prefix/etc/gdbinit}.
34281 By contrast, if the default location does not contain the prefix,
34282 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34283 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34284 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34285 wherever @value{GDBN} is installed.
34288 If the configured location of the system-wide init file (as given by the
34289 @option{--with-system-gdbinit} option at configure time) is in the
34290 data-directory (as specified by @option{--with-gdb-datadir} at configure
34291 time) or in one of its subdirectories, then @value{GDBN} will look for the
34292 system-wide init file in the directory specified by the
34293 @option{--data-directory} command-line option.
34294 Note that the system-wide init file is only read once, during @value{GDBN}
34295 initialization. If the data-directory is changed after @value{GDBN} has
34296 started with the @code{set data-directory} command, the file will not be
34300 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34303 @node System-wide Configuration Scripts
34304 @subsection Installed System-wide Configuration Scripts
34305 @cindex system-wide configuration scripts
34307 The @file{system-gdbinit} directory, located inside the data-directory
34308 (as specified by @option{--with-gdb-datadir} at configure time) contains
34309 a number of scripts which can be used as system-wide init files. To
34310 automatically source those scripts at startup, @value{GDBN} should be
34311 configured with @option{--with-system-gdbinit}. Otherwise, any user
34312 should be able to source them by hand as needed.
34314 The following scripts are currently available:
34317 @item @file{elinos.py}
34319 @cindex ELinOS system-wide configuration script
34320 This script is useful when debugging a program on an ELinOS target.
34321 It takes advantage of the environment variables defined in a standard
34322 ELinOS environment in order to determine the location of the system
34323 shared libraries, and then sets the @samp{solib-absolute-prefix}
34324 and @samp{solib-search-path} variables appropriately.
34326 @item @file{wrs-linux.py}
34327 @pindex wrs-linux.py
34328 @cindex Wind River Linux system-wide configuration script
34329 This script is useful when debugging a program on a target running
34330 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
34331 the host-side sysroot used by the target system.
34335 @node Maintenance Commands
34336 @appendix Maintenance Commands
34337 @cindex maintenance commands
34338 @cindex internal commands
34340 In addition to commands intended for @value{GDBN} users, @value{GDBN}
34341 includes a number of commands intended for @value{GDBN} developers,
34342 that are not documented elsewhere in this manual. These commands are
34343 provided here for reference. (For commands that turn on debugging
34344 messages, see @ref{Debugging Output}.)
34347 @kindex maint agent
34348 @kindex maint agent-eval
34349 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34350 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
34351 Translate the given @var{expression} into remote agent bytecodes.
34352 This command is useful for debugging the Agent Expression mechanism
34353 (@pxref{Agent Expressions}). The @samp{agent} version produces an
34354 expression useful for data collection, such as by tracepoints, while
34355 @samp{maint agent-eval} produces an expression that evaluates directly
34356 to a result. For instance, a collection expression for @code{globa +
34357 globb} will include bytecodes to record four bytes of memory at each
34358 of the addresses of @code{globa} and @code{globb}, while discarding
34359 the result of the addition, while an evaluation expression will do the
34360 addition and return the sum.
34361 If @code{-at} is given, generate remote agent bytecode for @var{location}.
34362 If not, generate remote agent bytecode for current frame PC address.
34364 @kindex maint agent-printf
34365 @item maint agent-printf @var{format},@var{expr},...
34366 Translate the given format string and list of argument expressions
34367 into remote agent bytecodes and display them as a disassembled list.
34368 This command is useful for debugging the agent version of dynamic
34369 printf (@pxref{Dynamic Printf}).
34371 @kindex maint info breakpoints
34372 @item @anchor{maint info breakpoints}maint info breakpoints
34373 Using the same format as @samp{info breakpoints}, display both the
34374 breakpoints you've set explicitly, and those @value{GDBN} is using for
34375 internal purposes. Internal breakpoints are shown with negative
34376 breakpoint numbers. The type column identifies what kind of breakpoint
34381 Normal, explicitly set breakpoint.
34384 Normal, explicitly set watchpoint.
34387 Internal breakpoint, used to handle correctly stepping through
34388 @code{longjmp} calls.
34390 @item longjmp resume
34391 Internal breakpoint at the target of a @code{longjmp}.
34394 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34397 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34400 Shared library events.
34404 @kindex maint info btrace
34405 @item maint info btrace
34406 Pint information about raw branch tracing data.
34408 @kindex maint btrace packet-history
34409 @item maint btrace packet-history
34410 Print the raw branch trace packets that are used to compute the
34411 execution history for the @samp{record btrace} command. Both the
34412 information and the format in which it is printed depend on the btrace
34417 For the BTS recording format, print a list of blocks of sequential
34418 code. For each block, the following information is printed:
34422 Newer blocks have higher numbers. The oldest block has number zero.
34423 @item Lowest @samp{PC}
34424 @item Highest @samp{PC}
34428 For the Intel Processor Trace recording format, print a list of
34429 Intel Processor Trace packets. For each packet, the following
34430 information is printed:
34433 @item Packet number
34434 Newer packets have higher numbers. The oldest packet has number zero.
34436 The packet's offset in the trace stream.
34437 @item Packet opcode and payload
34441 @kindex maint btrace clear-packet-history
34442 @item maint btrace clear-packet-history
34443 Discards the cached packet history printed by the @samp{maint btrace
34444 packet-history} command. The history will be computed again when
34447 @kindex maint btrace clear
34448 @item maint btrace clear
34449 Discard the branch trace data. The data will be fetched anew and the
34450 branch trace will be recomputed when needed.
34452 This implicitly truncates the branch trace to a single branch trace
34453 buffer. When updating branch trace incrementally, the branch trace
34454 available to @value{GDBN} may be bigger than a single branch trace
34457 @kindex maint set btrace pt skip-pad
34458 @item maint set btrace pt skip-pad
34459 @kindex maint show btrace pt skip-pad
34460 @item maint show btrace pt skip-pad
34461 Control whether @value{GDBN} will skip PAD packets when computing the
34464 @kindex set displaced-stepping
34465 @kindex show displaced-stepping
34466 @cindex displaced stepping support
34467 @cindex out-of-line single-stepping
34468 @item set displaced-stepping
34469 @itemx show displaced-stepping
34470 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34471 if the target supports it. Displaced stepping is a way to single-step
34472 over breakpoints without removing them from the inferior, by executing
34473 an out-of-line copy of the instruction that was originally at the
34474 breakpoint location. It is also known as out-of-line single-stepping.
34477 @item set displaced-stepping on
34478 If the target architecture supports it, @value{GDBN} will use
34479 displaced stepping to step over breakpoints.
34481 @item set displaced-stepping off
34482 @value{GDBN} will not use displaced stepping to step over breakpoints,
34483 even if such is supported by the target architecture.
34485 @cindex non-stop mode, and @samp{set displaced-stepping}
34486 @item set displaced-stepping auto
34487 This is the default mode. @value{GDBN} will use displaced stepping
34488 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34489 architecture supports displaced stepping.
34492 @kindex maint check-psymtabs
34493 @item maint check-psymtabs
34494 Check the consistency of currently expanded psymtabs versus symtabs.
34495 Use this to check, for example, whether a symbol is in one but not the other.
34497 @kindex maint check-symtabs
34498 @item maint check-symtabs
34499 Check the consistency of currently expanded symtabs.
34501 @kindex maint expand-symtabs
34502 @item maint expand-symtabs [@var{regexp}]
34503 Expand symbol tables.
34504 If @var{regexp} is specified, only expand symbol tables for file
34505 names matching @var{regexp}.
34507 @kindex maint set catch-demangler-crashes
34508 @kindex maint show catch-demangler-crashes
34509 @cindex demangler crashes
34510 @item maint set catch-demangler-crashes [on|off]
34511 @itemx maint show catch-demangler-crashes
34512 Control whether @value{GDBN} should attempt to catch crashes in the
34513 symbol name demangler. The default is to attempt to catch crashes.
34514 If enabled, the first time a crash is caught, a core file is created,
34515 the offending symbol is displayed and the user is presented with the
34516 option to terminate the current session.
34518 @kindex maint cplus first_component
34519 @item maint cplus first_component @var{name}
34520 Print the first C@t{++} class/namespace component of @var{name}.
34522 @kindex maint cplus namespace
34523 @item maint cplus namespace
34524 Print the list of possible C@t{++} namespaces.
34526 @kindex maint deprecate
34527 @kindex maint undeprecate
34528 @cindex deprecated commands
34529 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34530 @itemx maint undeprecate @var{command}
34531 Deprecate or undeprecate the named @var{command}. Deprecated commands
34532 cause @value{GDBN} to issue a warning when you use them. The optional
34533 argument @var{replacement} says which newer command should be used in
34534 favor of the deprecated one; if it is given, @value{GDBN} will mention
34535 the replacement as part of the warning.
34537 @kindex maint dump-me
34538 @item maint dump-me
34539 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34540 Cause a fatal signal in the debugger and force it to dump its core.
34541 This is supported only on systems which support aborting a program
34542 with the @code{SIGQUIT} signal.
34544 @kindex maint internal-error
34545 @kindex maint internal-warning
34546 @kindex maint demangler-warning
34547 @cindex demangler crashes
34548 @item maint internal-error @r{[}@var{message-text}@r{]}
34549 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34550 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34552 Cause @value{GDBN} to call the internal function @code{internal_error},
34553 @code{internal_warning} or @code{demangler_warning} and hence behave
34554 as though an internal problem has been detected. In addition to
34555 reporting the internal problem, these functions give the user the
34556 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34557 and @code{internal_warning}) create a core file of the current
34558 @value{GDBN} session.
34560 These commands take an optional parameter @var{message-text} that is
34561 used as the text of the error or warning message.
34563 Here's an example of using @code{internal-error}:
34566 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34567 @dots{}/maint.c:121: internal-error: testing, 1, 2
34568 A problem internal to GDB has been detected. Further
34569 debugging may prove unreliable.
34570 Quit this debugging session? (y or n) @kbd{n}
34571 Create a core file? (y or n) @kbd{n}
34575 @cindex @value{GDBN} internal error
34576 @cindex internal errors, control of @value{GDBN} behavior
34577 @cindex demangler crashes
34579 @kindex maint set internal-error
34580 @kindex maint show internal-error
34581 @kindex maint set internal-warning
34582 @kindex maint show internal-warning
34583 @kindex maint set demangler-warning
34584 @kindex maint show demangler-warning
34585 @item maint set internal-error @var{action} [ask|yes|no]
34586 @itemx maint show internal-error @var{action}
34587 @itemx maint set internal-warning @var{action} [ask|yes|no]
34588 @itemx maint show internal-warning @var{action}
34589 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34590 @itemx maint show demangler-warning @var{action}
34591 When @value{GDBN} reports an internal problem (error or warning) it
34592 gives the user the opportunity to both quit @value{GDBN} and create a
34593 core file of the current @value{GDBN} session. These commands let you
34594 override the default behaviour for each particular @var{action},
34595 described in the table below.
34599 You can specify that @value{GDBN} should always (yes) or never (no)
34600 quit. The default is to ask the user what to do.
34603 You can specify that @value{GDBN} should always (yes) or never (no)
34604 create a core file. The default is to ask the user what to do. Note
34605 that there is no @code{corefile} option for @code{demangler-warning}:
34606 demangler warnings always create a core file and this cannot be
34610 @kindex maint packet
34611 @item maint packet @var{text}
34612 If @value{GDBN} is talking to an inferior via the serial protocol,
34613 then this command sends the string @var{text} to the inferior, and
34614 displays the response packet. @value{GDBN} supplies the initial
34615 @samp{$} character, the terminating @samp{#} character, and the
34618 @kindex maint print architecture
34619 @item maint print architecture @r{[}@var{file}@r{]}
34620 Print the entire architecture configuration. The optional argument
34621 @var{file} names the file where the output goes.
34623 @kindex maint print c-tdesc
34624 @item maint print c-tdesc
34625 Print the current target description (@pxref{Target Descriptions}) as
34626 a C source file. The created source file can be used in @value{GDBN}
34627 when an XML parser is not available to parse the description.
34629 @kindex maint print dummy-frames
34630 @item maint print dummy-frames
34631 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34634 (@value{GDBP}) @kbd{b add}
34636 (@value{GDBP}) @kbd{print add(2,3)}
34637 Breakpoint 2, add (a=2, b=3) at @dots{}
34639 The program being debugged stopped while in a function called from GDB.
34641 (@value{GDBP}) @kbd{maint print dummy-frames}
34642 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34646 Takes an optional file parameter.
34648 @kindex maint print registers
34649 @kindex maint print raw-registers
34650 @kindex maint print cooked-registers
34651 @kindex maint print register-groups
34652 @kindex maint print remote-registers
34653 @item maint print registers @r{[}@var{file}@r{]}
34654 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34655 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34656 @itemx maint print register-groups @r{[}@var{file}@r{]}
34657 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34658 Print @value{GDBN}'s internal register data structures.
34660 The command @code{maint print raw-registers} includes the contents of
34661 the raw register cache; the command @code{maint print
34662 cooked-registers} includes the (cooked) value of all registers,
34663 including registers which aren't available on the target nor visible
34664 to user; the command @code{maint print register-groups} includes the
34665 groups that each register is a member of; and the command @code{maint
34666 print remote-registers} includes the remote target's register numbers
34667 and offsets in the `G' packets.
34669 These commands take an optional parameter, a file name to which to
34670 write the information.
34672 @kindex maint print reggroups
34673 @item maint print reggroups @r{[}@var{file}@r{]}
34674 Print @value{GDBN}'s internal register group data structures. The
34675 optional argument @var{file} tells to what file to write the
34678 The register groups info looks like this:
34681 (@value{GDBP}) @kbd{maint print reggroups}
34694 This command forces @value{GDBN} to flush its internal register cache.
34696 @kindex maint print objfiles
34697 @cindex info for known object files
34698 @item maint print objfiles @r{[}@var{regexp}@r{]}
34699 Print a dump of all known object files.
34700 If @var{regexp} is specified, only print object files whose names
34701 match @var{regexp}. For each object file, this command prints its name,
34702 address in memory, and all of its psymtabs and symtabs.
34704 @kindex maint print user-registers
34705 @cindex user registers
34706 @item maint print user-registers
34707 List all currently available @dfn{user registers}. User registers
34708 typically provide alternate names for actual hardware registers. They
34709 include the four ``standard'' registers @code{$fp}, @code{$pc},
34710 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34711 registers can be used in expressions in the same way as the canonical
34712 register names, but only the latter are listed by the @code{info
34713 registers} and @code{maint print registers} commands.
34715 @kindex maint print section-scripts
34716 @cindex info for known .debug_gdb_scripts-loaded scripts
34717 @item maint print section-scripts [@var{regexp}]
34718 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34719 If @var{regexp} is specified, only print scripts loaded by object files
34720 matching @var{regexp}.
34721 For each script, this command prints its name as specified in the objfile,
34722 and the full path if known.
34723 @xref{dotdebug_gdb_scripts section}.
34725 @kindex maint print statistics
34726 @cindex bcache statistics
34727 @item maint print statistics
34728 This command prints, for each object file in the program, various data
34729 about that object file followed by the byte cache (@dfn{bcache})
34730 statistics for the object file. The objfile data includes the number
34731 of minimal, partial, full, and stabs symbols, the number of types
34732 defined by the objfile, the number of as yet unexpanded psym tables,
34733 the number of line tables and string tables, and the amount of memory
34734 used by the various tables. The bcache statistics include the counts,
34735 sizes, and counts of duplicates of all and unique objects, max,
34736 average, and median entry size, total memory used and its overhead and
34737 savings, and various measures of the hash table size and chain
34740 @kindex maint print target-stack
34741 @cindex target stack description
34742 @item maint print target-stack
34743 A @dfn{target} is an interface between the debugger and a particular
34744 kind of file or process. Targets can be stacked in @dfn{strata},
34745 so that more than one target can potentially respond to a request.
34746 In particular, memory accesses will walk down the stack of targets
34747 until they find a target that is interested in handling that particular
34750 This command prints a short description of each layer that was pushed on
34751 the @dfn{target stack}, starting from the top layer down to the bottom one.
34753 @kindex maint print type
34754 @cindex type chain of a data type
34755 @item maint print type @var{expr}
34756 Print the type chain for a type specified by @var{expr}. The argument
34757 can be either a type name or a symbol. If it is a symbol, the type of
34758 that symbol is described. The type chain produced by this command is
34759 a recursive definition of the data type as stored in @value{GDBN}'s
34760 data structures, including its flags and contained types.
34762 @kindex maint selftest
34764 Run any self tests that were compiled in to @value{GDBN}. This will
34765 print a message showing how many tests were run, and how many failed.
34767 @kindex maint set dwarf always-disassemble
34768 @kindex maint show dwarf always-disassemble
34769 @item maint set dwarf always-disassemble
34770 @item maint show dwarf always-disassemble
34771 Control the behavior of @code{info address} when using DWARF debugging
34774 The default is @code{off}, which means that @value{GDBN} should try to
34775 describe a variable's location in an easily readable format. When
34776 @code{on}, @value{GDBN} will instead display the DWARF location
34777 expression in an assembly-like format. Note that some locations are
34778 too complex for @value{GDBN} to describe simply; in this case you will
34779 always see the disassembly form.
34781 Here is an example of the resulting disassembly:
34784 (gdb) info addr argc
34785 Symbol "argc" is a complex DWARF expression:
34789 For more information on these expressions, see
34790 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34792 @kindex maint set dwarf max-cache-age
34793 @kindex maint show dwarf max-cache-age
34794 @item maint set dwarf max-cache-age
34795 @itemx maint show dwarf max-cache-age
34796 Control the DWARF compilation unit cache.
34798 @cindex DWARF compilation units cache
34799 In object files with inter-compilation-unit references, such as those
34800 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34801 reader needs to frequently refer to previously read compilation units.
34802 This setting controls how long a compilation unit will remain in the
34803 cache if it is not referenced. A higher limit means that cached
34804 compilation units will be stored in memory longer, and more total
34805 memory will be used. Setting it to zero disables caching, which will
34806 slow down @value{GDBN} startup, but reduce memory consumption.
34808 @kindex maint set profile
34809 @kindex maint show profile
34810 @cindex profiling GDB
34811 @item maint set profile
34812 @itemx maint show profile
34813 Control profiling of @value{GDBN}.
34815 Profiling will be disabled until you use the @samp{maint set profile}
34816 command to enable it. When you enable profiling, the system will begin
34817 collecting timing and execution count data; when you disable profiling or
34818 exit @value{GDBN}, the results will be written to a log file. Remember that
34819 if you use profiling, @value{GDBN} will overwrite the profiling log file
34820 (often called @file{gmon.out}). If you have a record of important profiling
34821 data in a @file{gmon.out} file, be sure to move it to a safe location.
34823 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34824 compiled with the @samp{-pg} compiler option.
34826 @kindex maint set show-debug-regs
34827 @kindex maint show show-debug-regs
34828 @cindex hardware debug registers
34829 @item maint set show-debug-regs
34830 @itemx maint show show-debug-regs
34831 Control whether to show variables that mirror the hardware debug
34832 registers. Use @code{on} to enable, @code{off} to disable. If
34833 enabled, the debug registers values are shown when @value{GDBN} inserts or
34834 removes a hardware breakpoint or watchpoint, and when the inferior
34835 triggers a hardware-assisted breakpoint or watchpoint.
34837 @kindex maint set show-all-tib
34838 @kindex maint show show-all-tib
34839 @item maint set show-all-tib
34840 @itemx maint show show-all-tib
34841 Control whether to show all non zero areas within a 1k block starting
34842 at thread local base, when using the @samp{info w32 thread-information-block}
34845 @kindex maint set target-async
34846 @kindex maint show target-async
34847 @item maint set target-async
34848 @itemx maint show target-async
34849 This controls whether @value{GDBN} targets operate in synchronous or
34850 asynchronous mode (@pxref{Background Execution}). Normally the
34851 default is asynchronous, if it is available; but this can be changed
34852 to more easily debug problems occurring only in synchronous mode.
34854 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34855 @kindex maint show target-non-stop
34856 @item maint set target-non-stop
34857 @itemx maint show target-non-stop
34859 This controls whether @value{GDBN} targets always operate in non-stop
34860 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34861 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34862 if supported by the target.
34865 @item maint set target-non-stop auto
34866 This is the default mode. @value{GDBN} controls the target in
34867 non-stop mode if the target supports it.
34869 @item maint set target-non-stop on
34870 @value{GDBN} controls the target in non-stop mode even if the target
34871 does not indicate support.
34873 @item maint set target-non-stop off
34874 @value{GDBN} does not control the target in non-stop mode even if the
34875 target supports it.
34878 @kindex maint set per-command
34879 @kindex maint show per-command
34880 @item maint set per-command
34881 @itemx maint show per-command
34882 @cindex resources used by commands
34884 @value{GDBN} can display the resources used by each command.
34885 This is useful in debugging performance problems.
34888 @item maint set per-command space [on|off]
34889 @itemx maint show per-command space
34890 Enable or disable the printing of the memory used by GDB for each command.
34891 If enabled, @value{GDBN} will display how much memory each command
34892 took, following the command's own output.
34893 This can also be requested by invoking @value{GDBN} with the
34894 @option{--statistics} command-line switch (@pxref{Mode Options}).
34896 @item maint set per-command time [on|off]
34897 @itemx maint show per-command time
34898 Enable or disable the printing of the execution time of @value{GDBN}
34900 If enabled, @value{GDBN} will display how much time it
34901 took to execute each command, following the command's own output.
34902 Both CPU time and wallclock time are printed.
34903 Printing both is useful when trying to determine whether the cost is
34904 CPU or, e.g., disk/network latency.
34905 Note that the CPU time printed is for @value{GDBN} only, it does not include
34906 the execution time of the inferior because there's no mechanism currently
34907 to compute how much time was spent by @value{GDBN} and how much time was
34908 spent by the program been debugged.
34909 This can also be requested by invoking @value{GDBN} with the
34910 @option{--statistics} command-line switch (@pxref{Mode Options}).
34912 @item maint set per-command symtab [on|off]
34913 @itemx maint show per-command symtab
34914 Enable or disable the printing of basic symbol table statistics
34916 If enabled, @value{GDBN} will display the following information:
34920 number of symbol tables
34922 number of primary symbol tables
34924 number of blocks in the blockvector
34928 @kindex maint space
34929 @cindex memory used by commands
34930 @item maint space @var{value}
34931 An alias for @code{maint set per-command space}.
34932 A non-zero value enables it, zero disables it.
34935 @cindex time of command execution
34936 @item maint time @var{value}
34937 An alias for @code{maint set per-command time}.
34938 A non-zero value enables it, zero disables it.
34940 @kindex maint translate-address
34941 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34942 Find the symbol stored at the location specified by the address
34943 @var{addr} and an optional section name @var{section}. If found,
34944 @value{GDBN} prints the name of the closest symbol and an offset from
34945 the symbol's location to the specified address. This is similar to
34946 the @code{info address} command (@pxref{Symbols}), except that this
34947 command also allows to find symbols in other sections.
34949 If section was not specified, the section in which the symbol was found
34950 is also printed. For dynamically linked executables, the name of
34951 executable or shared library containing the symbol is printed as well.
34955 The following command is useful for non-interactive invocations of
34956 @value{GDBN}, such as in the test suite.
34959 @item set watchdog @var{nsec}
34960 @kindex set watchdog
34961 @cindex watchdog timer
34962 @cindex timeout for commands
34963 Set the maximum number of seconds @value{GDBN} will wait for the
34964 target operation to finish. If this time expires, @value{GDBN}
34965 reports and error and the command is aborted.
34967 @item show watchdog
34968 Show the current setting of the target wait timeout.
34971 @node Remote Protocol
34972 @appendix @value{GDBN} Remote Serial Protocol
34977 * Stop Reply Packets::
34978 * General Query Packets::
34979 * Architecture-Specific Protocol Details::
34980 * Tracepoint Packets::
34981 * Host I/O Packets::
34983 * Notification Packets::
34984 * Remote Non-Stop::
34985 * Packet Acknowledgment::
34987 * File-I/O Remote Protocol Extension::
34988 * Library List Format::
34989 * Library List Format for SVR4 Targets::
34990 * Memory Map Format::
34991 * Thread List Format::
34992 * Traceframe Info Format::
34993 * Branch Trace Format::
34994 * Branch Trace Configuration Format::
35000 There may be occasions when you need to know something about the
35001 protocol---for example, if there is only one serial port to your target
35002 machine, you might want your program to do something special if it
35003 recognizes a packet meant for @value{GDBN}.
35005 In the examples below, @samp{->} and @samp{<-} are used to indicate
35006 transmitted and received data, respectively.
35008 @cindex protocol, @value{GDBN} remote serial
35009 @cindex serial protocol, @value{GDBN} remote
35010 @cindex remote serial protocol
35011 All @value{GDBN} commands and responses (other than acknowledgments
35012 and notifications, see @ref{Notification Packets}) are sent as a
35013 @var{packet}. A @var{packet} is introduced with the character
35014 @samp{$}, the actual @var{packet-data}, and the terminating character
35015 @samp{#} followed by a two-digit @var{checksum}:
35018 @code{$}@var{packet-data}@code{#}@var{checksum}
35022 @cindex checksum, for @value{GDBN} remote
35024 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35025 characters between the leading @samp{$} and the trailing @samp{#} (an
35026 eight bit unsigned checksum).
35028 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35029 specification also included an optional two-digit @var{sequence-id}:
35032 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35035 @cindex sequence-id, for @value{GDBN} remote
35037 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35038 has never output @var{sequence-id}s. Stubs that handle packets added
35039 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35041 When either the host or the target machine receives a packet, the first
35042 response expected is an acknowledgment: either @samp{+} (to indicate
35043 the package was received correctly) or @samp{-} (to request
35047 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35052 The @samp{+}/@samp{-} acknowledgments can be disabled
35053 once a connection is established.
35054 @xref{Packet Acknowledgment}, for details.
35056 The host (@value{GDBN}) sends @var{command}s, and the target (the
35057 debugging stub incorporated in your program) sends a @var{response}. In
35058 the case of step and continue @var{command}s, the response is only sent
35059 when the operation has completed, and the target has again stopped all
35060 threads in all attached processes. This is the default all-stop mode
35061 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35062 execution mode; see @ref{Remote Non-Stop}, for details.
35064 @var{packet-data} consists of a sequence of characters with the
35065 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35068 @cindex remote protocol, field separator
35069 Fields within the packet should be separated using @samp{,} @samp{;} or
35070 @samp{:}. Except where otherwise noted all numbers are represented in
35071 @sc{hex} with leading zeros suppressed.
35073 Implementors should note that prior to @value{GDBN} 5.0, the character
35074 @samp{:} could not appear as the third character in a packet (as it
35075 would potentially conflict with the @var{sequence-id}).
35077 @cindex remote protocol, binary data
35078 @anchor{Binary Data}
35079 Binary data in most packets is encoded either as two hexadecimal
35080 digits per byte of binary data. This allowed the traditional remote
35081 protocol to work over connections which were only seven-bit clean.
35082 Some packets designed more recently assume an eight-bit clean
35083 connection, and use a more efficient encoding to send and receive
35086 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35087 as an escape character. Any escaped byte is transmitted as the escape
35088 character followed by the original character XORed with @code{0x20}.
35089 For example, the byte @code{0x7d} would be transmitted as the two
35090 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35091 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35092 @samp{@}}) must always be escaped. Responses sent by the stub
35093 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35094 is not interpreted as the start of a run-length encoded sequence
35097 Response @var{data} can be run-length encoded to save space.
35098 Run-length encoding replaces runs of identical characters with one
35099 instance of the repeated character, followed by a @samp{*} and a
35100 repeat count. The repeat count is itself sent encoded, to avoid
35101 binary characters in @var{data}: a value of @var{n} is sent as
35102 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35103 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35104 code 32) for a repeat count of 3. (This is because run-length
35105 encoding starts to win for counts 3 or more.) Thus, for example,
35106 @samp{0* } is a run-length encoding of ``0000'': the space character
35107 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35110 The printable characters @samp{#} and @samp{$} or with a numeric value
35111 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35112 seven repeats (@samp{$}) can be expanded using a repeat count of only
35113 five (@samp{"}). For example, @samp{00000000} can be encoded as
35116 The error response returned for some packets includes a two character
35117 error number. That number is not well defined.
35119 @cindex empty response, for unsupported packets
35120 For any @var{command} not supported by the stub, an empty response
35121 (@samp{$#00}) should be returned. That way it is possible to extend the
35122 protocol. A newer @value{GDBN} can tell if a packet is supported based
35125 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35126 commands for register access, and the @samp{m} and @samp{M} commands
35127 for memory access. Stubs that only control single-threaded targets
35128 can implement run control with the @samp{c} (continue), and @samp{s}
35129 (step) commands. Stubs that support multi-threading targets should
35130 support the @samp{vCont} command. All other commands are optional.
35135 The following table provides a complete list of all currently defined
35136 @var{command}s and their corresponding response @var{data}.
35137 @xref{File-I/O Remote Protocol Extension}, for details about the File
35138 I/O extension of the remote protocol.
35140 Each packet's description has a template showing the packet's overall
35141 syntax, followed by an explanation of the packet's meaning. We
35142 include spaces in some of the templates for clarity; these are not
35143 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35144 separate its components. For example, a template like @samp{foo
35145 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35146 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35147 @var{baz}. @value{GDBN} does not transmit a space character between the
35148 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35151 @cindex @var{thread-id}, in remote protocol
35152 @anchor{thread-id syntax}
35153 Several packets and replies include a @var{thread-id} field to identify
35154 a thread. Normally these are positive numbers with a target-specific
35155 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35156 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35159 In addition, the remote protocol supports a multiprocess feature in
35160 which the @var{thread-id} syntax is extended to optionally include both
35161 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35162 The @var{pid} (process) and @var{tid} (thread) components each have the
35163 format described above: a positive number with target-specific
35164 interpretation formatted as a big-endian hex string, literal @samp{-1}
35165 to indicate all processes or threads (respectively), or @samp{0} to
35166 indicate an arbitrary process or thread. Specifying just a process, as
35167 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35168 error to specify all processes but a specific thread, such as
35169 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35170 for those packets and replies explicitly documented to include a process
35171 ID, rather than a @var{thread-id}.
35173 The multiprocess @var{thread-id} syntax extensions are only used if both
35174 @value{GDBN} and the stub report support for the @samp{multiprocess}
35175 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35178 Note that all packet forms beginning with an upper- or lower-case
35179 letter, other than those described here, are reserved for future use.
35181 Here are the packet descriptions.
35186 @cindex @samp{!} packet
35187 @anchor{extended mode}
35188 Enable extended mode. In extended mode, the remote server is made
35189 persistent. The @samp{R} packet is used to restart the program being
35195 The remote target both supports and has enabled extended mode.
35199 @cindex @samp{?} packet
35201 Indicate the reason the target halted. The reply is the same as for
35202 step and continue. This packet has a special interpretation when the
35203 target is in non-stop mode; see @ref{Remote Non-Stop}.
35206 @xref{Stop Reply Packets}, for the reply specifications.
35208 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35209 @cindex @samp{A} packet
35210 Initialized @code{argv[]} array passed into program. @var{arglen}
35211 specifies the number of bytes in the hex encoded byte stream
35212 @var{arg}. See @code{gdbserver} for more details.
35217 The arguments were set.
35223 @cindex @samp{b} packet
35224 (Don't use this packet; its behavior is not well-defined.)
35225 Change the serial line speed to @var{baud}.
35227 JTC: @emph{When does the transport layer state change? When it's
35228 received, or after the ACK is transmitted. In either case, there are
35229 problems if the command or the acknowledgment packet is dropped.}
35231 Stan: @emph{If people really wanted to add something like this, and get
35232 it working for the first time, they ought to modify ser-unix.c to send
35233 some kind of out-of-band message to a specially-setup stub and have the
35234 switch happen "in between" packets, so that from remote protocol's point
35235 of view, nothing actually happened.}
35237 @item B @var{addr},@var{mode}
35238 @cindex @samp{B} packet
35239 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35240 breakpoint at @var{addr}.
35242 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35243 (@pxref{insert breakpoint or watchpoint packet}).
35245 @cindex @samp{bc} packet
35248 Backward continue. Execute the target system in reverse. No parameter.
35249 @xref{Reverse Execution}, for more information.
35252 @xref{Stop Reply Packets}, for the reply specifications.
35254 @cindex @samp{bs} packet
35257 Backward single step. Execute one instruction in reverse. No parameter.
35258 @xref{Reverse Execution}, for more information.
35261 @xref{Stop Reply Packets}, for the reply specifications.
35263 @item c @r{[}@var{addr}@r{]}
35264 @cindex @samp{c} packet
35265 Continue at @var{addr}, which is the address to resume. If @var{addr}
35266 is omitted, resume at current address.
35268 This packet is deprecated for multi-threading support. @xref{vCont
35272 @xref{Stop Reply Packets}, for the reply specifications.
35274 @item C @var{sig}@r{[};@var{addr}@r{]}
35275 @cindex @samp{C} packet
35276 Continue with signal @var{sig} (hex signal number). If
35277 @samp{;@var{addr}} is omitted, resume at same address.
35279 This packet is deprecated for multi-threading support. @xref{vCont
35283 @xref{Stop Reply Packets}, for the reply specifications.
35286 @cindex @samp{d} packet
35289 Don't use this packet; instead, define a general set packet
35290 (@pxref{General Query Packets}).
35294 @cindex @samp{D} packet
35295 The first form of the packet is used to detach @value{GDBN} from the
35296 remote system. It is sent to the remote target
35297 before @value{GDBN} disconnects via the @code{detach} command.
35299 The second form, including a process ID, is used when multiprocess
35300 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35301 detach only a specific process. The @var{pid} is specified as a
35302 big-endian hex string.
35312 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35313 @cindex @samp{F} packet
35314 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35315 This is part of the File-I/O protocol extension. @xref{File-I/O
35316 Remote Protocol Extension}, for the specification.
35319 @anchor{read registers packet}
35320 @cindex @samp{g} packet
35321 Read general registers.
35325 @item @var{XX@dots{}}
35326 Each byte of register data is described by two hex digits. The bytes
35327 with the register are transmitted in target byte order. The size of
35328 each register and their position within the @samp{g} packet are
35329 determined by the @value{GDBN} internal gdbarch functions
35330 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
35332 When reading registers from a trace frame (@pxref{Analyze Collected
35333 Data,,Using the Collected Data}), the stub may also return a string of
35334 literal @samp{x}'s in place of the register data digits, to indicate
35335 that the corresponding register has not been collected, thus its value
35336 is unavailable. For example, for an architecture with 4 registers of
35337 4 bytes each, the following reply indicates to @value{GDBN} that
35338 registers 0 and 2 have not been collected, while registers 1 and 3
35339 have been collected, and both have zero value:
35343 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35350 @item G @var{XX@dots{}}
35351 @cindex @samp{G} packet
35352 Write general registers. @xref{read registers packet}, for a
35353 description of the @var{XX@dots{}} data.
35363 @item H @var{op} @var{thread-id}
35364 @cindex @samp{H} packet
35365 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35366 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
35367 should be @samp{c} for step and continue operations (note that this
35368 is deprecated, supporting the @samp{vCont} command is a better
35369 option), and @samp{g} for other operations. The thread designator
35370 @var{thread-id} has the format and interpretation described in
35371 @ref{thread-id syntax}.
35382 @c 'H': How restrictive (or permissive) is the thread model. If a
35383 @c thread is selected and stopped, are other threads allowed
35384 @c to continue to execute? As I mentioned above, I think the
35385 @c semantics of each command when a thread is selected must be
35386 @c described. For example:
35388 @c 'g': If the stub supports threads and a specific thread is
35389 @c selected, returns the register block from that thread;
35390 @c otherwise returns current registers.
35392 @c 'G' If the stub supports threads and a specific thread is
35393 @c selected, sets the registers of the register block of
35394 @c that thread; otherwise sets current registers.
35396 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35397 @anchor{cycle step packet}
35398 @cindex @samp{i} packet
35399 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35400 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35401 step starting at that address.
35404 @cindex @samp{I} packet
35405 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35409 @cindex @samp{k} packet
35412 The exact effect of this packet is not specified.
35414 For a bare-metal target, it may power cycle or reset the target
35415 system. For that reason, the @samp{k} packet has no reply.
35417 For a single-process target, it may kill that process if possible.
35419 A multiple-process target may choose to kill just one process, or all
35420 that are under @value{GDBN}'s control. For more precise control, use
35421 the vKill packet (@pxref{vKill packet}).
35423 If the target system immediately closes the connection in response to
35424 @samp{k}, @value{GDBN} does not consider the lack of packet
35425 acknowledgment to be an error, and assumes the kill was successful.
35427 If connected using @kbd{target extended-remote}, and the target does
35428 not close the connection in response to a kill request, @value{GDBN}
35429 probes the target state as if a new connection was opened
35430 (@pxref{? packet}).
35432 @item m @var{addr},@var{length}
35433 @cindex @samp{m} packet
35434 Read @var{length} addressable memory units starting at address @var{addr}
35435 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35436 any particular boundary.
35438 The stub need not use any particular size or alignment when gathering
35439 data from memory for the response; even if @var{addr} is word-aligned
35440 and @var{length} is a multiple of the word size, the stub is free to
35441 use byte accesses, or not. For this reason, this packet may not be
35442 suitable for accessing memory-mapped I/O devices.
35443 @cindex alignment of remote memory accesses
35444 @cindex size of remote memory accesses
35445 @cindex memory, alignment and size of remote accesses
35449 @item @var{XX@dots{}}
35450 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35451 The reply may contain fewer addressable memory units than requested if the
35452 server was able to read only part of the region of memory.
35457 @item M @var{addr},@var{length}:@var{XX@dots{}}
35458 @cindex @samp{M} packet
35459 Write @var{length} addressable memory units starting at address @var{addr}
35460 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35461 byte is transmitted as a two-digit hexadecimal number.
35468 for an error (this includes the case where only part of the data was
35473 @cindex @samp{p} packet
35474 Read the value of register @var{n}; @var{n} is in hex.
35475 @xref{read registers packet}, for a description of how the returned
35476 register value is encoded.
35480 @item @var{XX@dots{}}
35481 the register's value
35485 Indicating an unrecognized @var{query}.
35488 @item P @var{n@dots{}}=@var{r@dots{}}
35489 @anchor{write register packet}
35490 @cindex @samp{P} packet
35491 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35492 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35493 digits for each byte in the register (target byte order).
35503 @item q @var{name} @var{params}@dots{}
35504 @itemx Q @var{name} @var{params}@dots{}
35505 @cindex @samp{q} packet
35506 @cindex @samp{Q} packet
35507 General query (@samp{q}) and set (@samp{Q}). These packets are
35508 described fully in @ref{General Query Packets}.
35511 @cindex @samp{r} packet
35512 Reset the entire system.
35514 Don't use this packet; use the @samp{R} packet instead.
35517 @cindex @samp{R} packet
35518 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35519 This packet is only available in extended mode (@pxref{extended mode}).
35521 The @samp{R} packet has no reply.
35523 @item s @r{[}@var{addr}@r{]}
35524 @cindex @samp{s} packet
35525 Single step, resuming at @var{addr}. If
35526 @var{addr} is omitted, resume at same address.
35528 This packet is deprecated for multi-threading support. @xref{vCont
35532 @xref{Stop Reply Packets}, for the reply specifications.
35534 @item S @var{sig}@r{[};@var{addr}@r{]}
35535 @anchor{step with signal packet}
35536 @cindex @samp{S} packet
35537 Step with signal. This is analogous to the @samp{C} packet, but
35538 requests a single-step, rather than a normal resumption of execution.
35540 This packet is deprecated for multi-threading support. @xref{vCont
35544 @xref{Stop Reply Packets}, for the reply specifications.
35546 @item t @var{addr}:@var{PP},@var{MM}
35547 @cindex @samp{t} packet
35548 Search backwards starting at address @var{addr} for a match with pattern
35549 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35550 There must be at least 3 digits in @var{addr}.
35552 @item T @var{thread-id}
35553 @cindex @samp{T} packet
35554 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35559 thread is still alive
35565 Packets starting with @samp{v} are identified by a multi-letter name,
35566 up to the first @samp{;} or @samp{?} (or the end of the packet).
35568 @item vAttach;@var{pid}
35569 @cindex @samp{vAttach} packet
35570 Attach to a new process with the specified process ID @var{pid}.
35571 The process ID is a
35572 hexadecimal integer identifying the process. In all-stop mode, all
35573 threads in the attached process are stopped; in non-stop mode, it may be
35574 attached without being stopped if that is supported by the target.
35576 @c In non-stop mode, on a successful vAttach, the stub should set the
35577 @c current thread to a thread of the newly-attached process. After
35578 @c attaching, GDB queries for the attached process's thread ID with qC.
35579 @c Also note that, from a user perspective, whether or not the
35580 @c target is stopped on attach in non-stop mode depends on whether you
35581 @c use the foreground or background version of the attach command, not
35582 @c on what vAttach does; GDB does the right thing with respect to either
35583 @c stopping or restarting threads.
35585 This packet is only available in extended mode (@pxref{extended mode}).
35591 @item @r{Any stop packet}
35592 for success in all-stop mode (@pxref{Stop Reply Packets})
35594 for success in non-stop mode (@pxref{Remote Non-Stop})
35597 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35598 @cindex @samp{vCont} packet
35599 @anchor{vCont packet}
35600 Resume the inferior, specifying different actions for each thread.
35602 For each inferior thread, the leftmost action with a matching
35603 @var{thread-id} is applied. Threads that don't match any action
35604 remain in their current state. Thread IDs are specified using the
35605 syntax described in @ref{thread-id syntax}. If multiprocess
35606 extensions (@pxref{multiprocess extensions}) are supported, actions
35607 can be specified to match all threads in a process by using the
35608 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
35609 @var{thread-id} matches all threads. Specifying no actions is an
35612 Currently supported actions are:
35618 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35622 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35625 @item r @var{start},@var{end}
35626 Step once, and then keep stepping as long as the thread stops at
35627 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35628 The remote stub reports a stop reply when either the thread goes out
35629 of the range or is stopped due to an unrelated reason, such as hitting
35630 a breakpoint. @xref{range stepping}.
35632 If the range is empty (@var{start} == @var{end}), then the action
35633 becomes equivalent to the @samp{s} action. In other words,
35634 single-step once, and report the stop (even if the stepped instruction
35635 jumps to @var{start}).
35637 (A stop reply may be sent at any point even if the PC is still within
35638 the stepping range; for example, it is valid to implement this packet
35639 in a degenerate way as a single instruction step operation.)
35643 The optional argument @var{addr} normally associated with the
35644 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35645 not supported in @samp{vCont}.
35647 The @samp{t} action is only relevant in non-stop mode
35648 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35649 A stop reply should be generated for any affected thread not already stopped.
35650 When a thread is stopped by means of a @samp{t} action,
35651 the corresponding stop reply should indicate that the thread has stopped with
35652 signal @samp{0}, regardless of whether the target uses some other signal
35653 as an implementation detail.
35655 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
35656 @samp{r} actions for threads that are already running. Conversely,
35657 the server must ignore @samp{t} actions for threads that are already
35660 @emph{Note:} In non-stop mode, a thread is considered running until
35661 @value{GDBN} acknowleges an asynchronous stop notification for it with
35662 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
35664 The stub must support @samp{vCont} if it reports support for
35665 multiprocess extensions (@pxref{multiprocess extensions}).
35668 @xref{Stop Reply Packets}, for the reply specifications.
35671 @cindex @samp{vCont?} packet
35672 Request a list of actions supported by the @samp{vCont} packet.
35676 @item vCont@r{[};@var{action}@dots{}@r{]}
35677 The @samp{vCont} packet is supported. Each @var{action} is a supported
35678 command in the @samp{vCont} packet.
35680 The @samp{vCont} packet is not supported.
35683 @anchor{vCtrlC packet}
35685 @cindex @samp{vCtrlC} packet
35686 Interrupt remote target as if a control-C was pressed on the remote
35687 terminal. This is the equivalent to reacting to the @code{^C}
35688 (@samp{\003}, the control-C character) character in all-stop mode
35689 while the target is running, except this works in non-stop mode.
35690 @xref{interrupting remote targets}, for more info on the all-stop
35701 @item vFile:@var{operation}:@var{parameter}@dots{}
35702 @cindex @samp{vFile} packet
35703 Perform a file operation on the target system. For details,
35704 see @ref{Host I/O Packets}.
35706 @item vFlashErase:@var{addr},@var{length}
35707 @cindex @samp{vFlashErase} packet
35708 Direct the stub to erase @var{length} bytes of flash starting at
35709 @var{addr}. The region may enclose any number of flash blocks, but
35710 its start and end must fall on block boundaries, as indicated by the
35711 flash block size appearing in the memory map (@pxref{Memory Map
35712 Format}). @value{GDBN} groups flash memory programming operations
35713 together, and sends a @samp{vFlashDone} request after each group; the
35714 stub is allowed to delay erase operation until the @samp{vFlashDone}
35715 packet is received.
35725 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35726 @cindex @samp{vFlashWrite} packet
35727 Direct the stub to write data to flash address @var{addr}. The data
35728 is passed in binary form using the same encoding as for the @samp{X}
35729 packet (@pxref{Binary Data}). The memory ranges specified by
35730 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35731 not overlap, and must appear in order of increasing addresses
35732 (although @samp{vFlashErase} packets for higher addresses may already
35733 have been received; the ordering is guaranteed only between
35734 @samp{vFlashWrite} packets). If a packet writes to an address that was
35735 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35736 target-specific method, the results are unpredictable.
35744 for vFlashWrite addressing non-flash memory
35750 @cindex @samp{vFlashDone} packet
35751 Indicate to the stub that flash programming operation is finished.
35752 The stub is permitted to delay or batch the effects of a group of
35753 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35754 @samp{vFlashDone} packet is received. The contents of the affected
35755 regions of flash memory are unpredictable until the @samp{vFlashDone}
35756 request is completed.
35758 @item vKill;@var{pid}
35759 @cindex @samp{vKill} packet
35760 @anchor{vKill packet}
35761 Kill the process with the specified process ID @var{pid}, which is a
35762 hexadecimal integer identifying the process. This packet is used in
35763 preference to @samp{k} when multiprocess protocol extensions are
35764 supported; see @ref{multiprocess extensions}.
35774 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35775 @cindex @samp{vRun} packet
35776 Run the program @var{filename}, passing it each @var{argument} on its
35777 command line. The file and arguments are hex-encoded strings. If
35778 @var{filename} is an empty string, the stub may use a default program
35779 (e.g.@: the last program run). The program is created in the stopped
35782 @c FIXME: What about non-stop mode?
35784 This packet is only available in extended mode (@pxref{extended mode}).
35790 @item @r{Any stop packet}
35791 for success (@pxref{Stop Reply Packets})
35795 @cindex @samp{vStopped} packet
35796 @xref{Notification Packets}.
35798 @item X @var{addr},@var{length}:@var{XX@dots{}}
35800 @cindex @samp{X} packet
35801 Write data to memory, where the data is transmitted in binary.
35802 Memory is specified by its address @var{addr} and number of addressable memory
35803 units @var{length} (@pxref{addressable memory unit});
35804 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35814 @item z @var{type},@var{addr},@var{kind}
35815 @itemx Z @var{type},@var{addr},@var{kind}
35816 @anchor{insert breakpoint or watchpoint packet}
35817 @cindex @samp{z} packet
35818 @cindex @samp{Z} packets
35819 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35820 watchpoint starting at address @var{address} of kind @var{kind}.
35822 Each breakpoint and watchpoint packet @var{type} is documented
35825 @emph{Implementation notes: A remote target shall return an empty string
35826 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35827 remote target shall support either both or neither of a given
35828 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35829 avoid potential problems with duplicate packets, the operations should
35830 be implemented in an idempotent way.}
35832 @item z0,@var{addr},@var{kind}
35833 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35834 @cindex @samp{z0} packet
35835 @cindex @samp{Z0} packet
35836 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
35837 @var{addr} of type @var{kind}.
35839 A software breakpoint is implemented by replacing the instruction at
35840 @var{addr} with a software breakpoint or trap instruction. The
35841 @var{kind} is target-specific and typically indicates the size of the
35842 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
35843 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35844 architectures have additional meanings for @var{kind}
35845 (@pxref{Architecture-Specific Protocol Details}); if no
35846 architecture-specific value is being used, it should be @samp{0}.
35847 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
35848 conditional expressions in bytecode form that should be evaluated on
35849 the target's side. These are the conditions that should be taken into
35850 consideration when deciding if the breakpoint trigger should be
35851 reported back to @value{GDBN}.
35853 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35854 for how to best report a software breakpoint event to @value{GDBN}.
35856 The @var{cond_list} parameter is comprised of a series of expressions,
35857 concatenated without separators. Each expression has the following form:
35861 @item X @var{len},@var{expr}
35862 @var{len} is the length of the bytecode expression and @var{expr} is the
35863 actual conditional expression in bytecode form.
35867 The optional @var{cmd_list} parameter introduces commands that may be
35868 run on the target, rather than being reported back to @value{GDBN}.
35869 The parameter starts with a numeric flag @var{persist}; if the flag is
35870 nonzero, then the breakpoint may remain active and the commands
35871 continue to be run even when @value{GDBN} disconnects from the target.
35872 Following this flag is a series of expressions concatenated with no
35873 separators. Each expression has the following form:
35877 @item X @var{len},@var{expr}
35878 @var{len} is the length of the bytecode expression and @var{expr} is the
35879 actual conditional expression in bytecode form.
35883 @emph{Implementation note: It is possible for a target to copy or move
35884 code that contains software breakpoints (e.g., when implementing
35885 overlays). The behavior of this packet, in the presence of such a
35886 target, is not defined.}
35898 @item z1,@var{addr},@var{kind}
35899 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35900 @cindex @samp{z1} packet
35901 @cindex @samp{Z1} packet
35902 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35903 address @var{addr}.
35905 A hardware breakpoint is implemented using a mechanism that is not
35906 dependent on being able to modify the target's memory. The
35907 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
35908 same meaning as in @samp{Z0} packets.
35910 @emph{Implementation note: A hardware breakpoint is not affected by code
35923 @item z2,@var{addr},@var{kind}
35924 @itemx Z2,@var{addr},@var{kind}
35925 @cindex @samp{z2} packet
35926 @cindex @samp{Z2} packet
35927 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35928 The number of bytes to watch is specified by @var{kind}.
35940 @item z3,@var{addr},@var{kind}
35941 @itemx Z3,@var{addr},@var{kind}
35942 @cindex @samp{z3} packet
35943 @cindex @samp{Z3} packet
35944 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35945 The number of bytes to watch is specified by @var{kind}.
35957 @item z4,@var{addr},@var{kind}
35958 @itemx Z4,@var{addr},@var{kind}
35959 @cindex @samp{z4} packet
35960 @cindex @samp{Z4} packet
35961 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35962 The number of bytes to watch is specified by @var{kind}.
35976 @node Stop Reply Packets
35977 @section Stop Reply Packets
35978 @cindex stop reply packets
35980 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35981 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35982 receive any of the below as a reply. Except for @samp{?}
35983 and @samp{vStopped}, that reply is only returned
35984 when the target halts. In the below the exact meaning of @dfn{signal
35985 number} is defined by the header @file{include/gdb/signals.h} in the
35986 @value{GDBN} source code.
35988 In non-stop mode, the server will simply reply @samp{OK} to commands
35989 such as @samp{vCont}; any stop will be the subject of a future
35990 notification. @xref{Remote Non-Stop}.
35992 As in the description of request packets, we include spaces in the
35993 reply templates for clarity; these are not part of the reply packet's
35994 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36000 The program received signal number @var{AA} (a two-digit hexadecimal
36001 number). This is equivalent to a @samp{T} response with no
36002 @var{n}:@var{r} pairs.
36004 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36005 @cindex @samp{T} packet reply
36006 The program received signal number @var{AA} (a two-digit hexadecimal
36007 number). This is equivalent to an @samp{S} response, except that the
36008 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36009 and other information directly in the stop reply packet, reducing
36010 round-trip latency. Single-step and breakpoint traps are reported
36011 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36015 If @var{n} is a hexadecimal number, it is a register number, and the
36016 corresponding @var{r} gives that register's value. The data @var{r} is a
36017 series of bytes in target byte order, with each byte given by a
36018 two-digit hex number.
36021 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36022 the stopped thread, as specified in @ref{thread-id syntax}.
36025 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36026 the core on which the stop event was detected.
36029 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36030 specific event that stopped the target. The currently defined stop
36031 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36032 signal. At most one stop reason should be present.
36035 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36036 and go on to the next; this allows us to extend the protocol in the
36040 The currently defined stop reasons are:
36046 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36049 @item syscall_entry
36050 @itemx syscall_return
36051 The packet indicates a syscall entry or return, and @var{r} is the
36052 syscall number, in hex.
36054 @cindex shared library events, remote reply
36056 The packet indicates that the loaded libraries have changed.
36057 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36058 list of loaded libraries. The @var{r} part is ignored.
36060 @cindex replay log events, remote reply
36062 The packet indicates that the target cannot continue replaying
36063 logged execution events, because it has reached the end (or the
36064 beginning when executing backward) of the log. The value of @var{r}
36065 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36066 for more information.
36069 @anchor{swbreak stop reason}
36070 The packet indicates a software breakpoint instruction was executed,
36071 irrespective of whether it was @value{GDBN} that planted the
36072 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36073 part must be left empty.
36075 On some architectures, such as x86, at the architecture level, when a
36076 breakpoint instruction executes the program counter points at the
36077 breakpoint address plus an offset. On such targets, the stub is
36078 responsible for adjusting the PC to point back at the breakpoint
36081 This packet should not be sent by default; older @value{GDBN} versions
36082 did not support it. @value{GDBN} requests it, by supplying an
36083 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36084 remote stub must also supply the appropriate @samp{qSupported} feature
36085 indicating support.
36087 This packet is required for correct non-stop mode operation.
36090 The packet indicates the target stopped for a hardware breakpoint.
36091 The @var{r} part must be left empty.
36093 The same remarks about @samp{qSupported} and non-stop mode above
36096 @cindex fork events, remote reply
36098 The packet indicates that @code{fork} was called, and @var{r}
36099 is the thread ID of the new child process. Refer to
36100 @ref{thread-id syntax} for the format of the @var{thread-id}
36101 field. This packet is only applicable to targets that support
36104 This packet should not be sent by default; older @value{GDBN} versions
36105 did not support it. @value{GDBN} requests it, by supplying an
36106 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36107 remote stub must also supply the appropriate @samp{qSupported} feature
36108 indicating support.
36110 @cindex vfork events, remote reply
36112 The packet indicates that @code{vfork} was called, and @var{r}
36113 is the thread ID of the new child process. Refer to
36114 @ref{thread-id syntax} for the format of the @var{thread-id}
36115 field. This packet is only applicable to targets that support
36118 This packet should not be sent by default; older @value{GDBN} versions
36119 did not support it. @value{GDBN} requests it, by supplying an
36120 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36121 remote stub must also supply the appropriate @samp{qSupported} feature
36122 indicating support.
36124 @cindex vforkdone events, remote reply
36126 The packet indicates that a child process created by a vfork
36127 has either called @code{exec} or terminated, so that the
36128 address spaces of the parent and child process are no longer
36129 shared. The @var{r} part is ignored. This packet is only
36130 applicable to targets that support vforkdone events.
36132 This packet should not be sent by default; older @value{GDBN} versions
36133 did not support it. @value{GDBN} requests it, by supplying an
36134 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36135 remote stub must also supply the appropriate @samp{qSupported} feature
36136 indicating support.
36138 @cindex exec events, remote reply
36140 The packet indicates that @code{execve} was called, and @var{r}
36141 is the absolute pathname of the file that was executed, in hex.
36142 This packet is only applicable to targets that support exec events.
36144 This packet should not be sent by default; older @value{GDBN} versions
36145 did not support it. @value{GDBN} requests it, by supplying an
36146 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36147 remote stub must also supply the appropriate @samp{qSupported} feature
36148 indicating support.
36150 @cindex thread create event, remote reply
36151 @anchor{thread create event}
36153 The packet indicates that the thread was just created. The new thread
36154 is stopped until @value{GDBN} sets it running with a resumption packet
36155 (@pxref{vCont packet}). This packet should not be sent by default;
36156 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36157 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36158 @var{r} part is ignored.
36163 @itemx W @var{AA} ; process:@var{pid}
36164 The process exited, and @var{AA} is the exit status. This is only
36165 applicable to certain targets.
36167 The second form of the response, including the process ID of the
36168 exited process, can be used only when @value{GDBN} has reported
36169 support for multiprocess protocol extensions; see @ref{multiprocess
36170 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36174 @itemx X @var{AA} ; process:@var{pid}
36175 The process terminated with signal @var{AA}.
36177 The second form of the response, including the process ID of the
36178 terminated process, can be used only when @value{GDBN} has reported
36179 support for multiprocess protocol extensions; see @ref{multiprocess
36180 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36183 @anchor{thread exit event}
36184 @cindex thread exit event, remote reply
36185 @item w @var{AA} ; @var{tid}
36187 The thread exited, and @var{AA} is the exit status. This response
36188 should not be sent by default; @value{GDBN} requests it with the
36189 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36190 @var{AA} is formatted as a big-endian hex string.
36193 There are no resumed threads left in the target. In other words, even
36194 though the process is alive, the last resumed thread has exited. For
36195 example, say the target process has two threads: thread 1 and thread
36196 2. The client leaves thread 1 stopped, and resumes thread 2, which
36197 subsequently exits. At this point, even though the process is still
36198 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36199 executing either. The @samp{N} stop reply thus informs the client
36200 that it can stop waiting for stop replies. This packet should not be
36201 sent by default; older @value{GDBN} versions did not support it.
36202 @value{GDBN} requests it, by supplying an appropriate
36203 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36204 also supply the appropriate @samp{qSupported} feature indicating
36207 @item O @var{XX}@dots{}
36208 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36209 written as the program's console output. This can happen at any time
36210 while the program is running and the debugger should continue to wait
36211 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36213 @item F @var{call-id},@var{parameter}@dots{}
36214 @var{call-id} is the identifier which says which host system call should
36215 be called. This is just the name of the function. Translation into the
36216 correct system call is only applicable as it's defined in @value{GDBN}.
36217 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36220 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36221 this very system call.
36223 The target replies with this packet when it expects @value{GDBN} to
36224 call a host system call on behalf of the target. @value{GDBN} replies
36225 with an appropriate @samp{F} packet and keeps up waiting for the next
36226 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36227 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36228 Protocol Extension}, for more details.
36232 @node General Query Packets
36233 @section General Query Packets
36234 @cindex remote query requests
36236 Packets starting with @samp{q} are @dfn{general query packets};
36237 packets starting with @samp{Q} are @dfn{general set packets}. General
36238 query and set packets are a semi-unified form for retrieving and
36239 sending information to and from the stub.
36241 The initial letter of a query or set packet is followed by a name
36242 indicating what sort of thing the packet applies to. For example,
36243 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36244 definitions with the stub. These packet names follow some
36249 The name must not contain commas, colons or semicolons.
36251 Most @value{GDBN} query and set packets have a leading upper case
36254 The names of custom vendor packets should use a company prefix, in
36255 lower case, followed by a period. For example, packets designed at
36256 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36257 foos) or @samp{Qacme.bar} (for setting bars).
36260 The name of a query or set packet should be separated from any
36261 parameters by a @samp{:}; the parameters themselves should be
36262 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36263 full packet name, and check for a separator or the end of the packet,
36264 in case two packet names share a common prefix. New packets should not begin
36265 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36266 packets predate these conventions, and have arguments without any terminator
36267 for the packet name; we suspect they are in widespread use in places that
36268 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36269 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36272 Like the descriptions of the other packets, each description here
36273 has a template showing the packet's overall syntax, followed by an
36274 explanation of the packet's meaning. We include spaces in some of the
36275 templates for clarity; these are not part of the packet's syntax. No
36276 @value{GDBN} packet uses spaces to separate its components.
36278 Here are the currently defined query and set packets:
36284 Turn on or off the agent as a helper to perform some debugging operations
36285 delegated from @value{GDBN} (@pxref{Control Agent}).
36287 @item QAllow:@var{op}:@var{val}@dots{}
36288 @cindex @samp{QAllow} packet
36289 Specify which operations @value{GDBN} expects to request of the
36290 target, as a semicolon-separated list of operation name and value
36291 pairs. Possible values for @var{op} include @samp{WriteReg},
36292 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36293 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36294 indicating that @value{GDBN} will not request the operation, or 1,
36295 indicating that it may. (The target can then use this to set up its
36296 own internals optimally, for instance if the debugger never expects to
36297 insert breakpoints, it may not need to install its own trap handler.)
36300 @cindex current thread, remote request
36301 @cindex @samp{qC} packet
36302 Return the current thread ID.
36306 @item QC @var{thread-id}
36307 Where @var{thread-id} is a thread ID as documented in
36308 @ref{thread-id syntax}.
36309 @item @r{(anything else)}
36310 Any other reply implies the old thread ID.
36313 @item qCRC:@var{addr},@var{length}
36314 @cindex CRC of memory block, remote request
36315 @cindex @samp{qCRC} packet
36316 @anchor{qCRC packet}
36317 Compute the CRC checksum of a block of memory using CRC-32 defined in
36318 IEEE 802.3. The CRC is computed byte at a time, taking the most
36319 significant bit of each byte first. The initial pattern code
36320 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36322 @emph{Note:} This is the same CRC used in validating separate debug
36323 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36324 Files}). However the algorithm is slightly different. When validating
36325 separate debug files, the CRC is computed taking the @emph{least}
36326 significant bit of each byte first, and the final result is inverted to
36327 detect trailing zeros.
36332 An error (such as memory fault)
36333 @item C @var{crc32}
36334 The specified memory region's checksum is @var{crc32}.
36337 @item QDisableRandomization:@var{value}
36338 @cindex disable address space randomization, remote request
36339 @cindex @samp{QDisableRandomization} packet
36340 Some target operating systems will randomize the virtual address space
36341 of the inferior process as a security feature, but provide a feature
36342 to disable such randomization, e.g.@: to allow for a more deterministic
36343 debugging experience. On such systems, this packet with a @var{value}
36344 of 1 directs the target to disable address space randomization for
36345 processes subsequently started via @samp{vRun} packets, while a packet
36346 with a @var{value} of 0 tells the target to enable address space
36349 This packet is only available in extended mode (@pxref{extended mode}).
36354 The request succeeded.
36357 An error occurred. The error number @var{nn} is given as hex digits.
36360 An empty reply indicates that @samp{QDisableRandomization} is not supported
36364 This packet is not probed by default; the remote stub must request it,
36365 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36366 This should only be done on targets that actually support disabling
36367 address space randomization.
36370 @itemx qsThreadInfo
36371 @cindex list active threads, remote request
36372 @cindex @samp{qfThreadInfo} packet
36373 @cindex @samp{qsThreadInfo} packet
36374 Obtain a list of all active thread IDs from the target (OS). Since there
36375 may be too many active threads to fit into one reply packet, this query
36376 works iteratively: it may require more than one query/reply sequence to
36377 obtain the entire list of threads. The first query of the sequence will
36378 be the @samp{qfThreadInfo} query; subsequent queries in the
36379 sequence will be the @samp{qsThreadInfo} query.
36381 NOTE: This packet replaces the @samp{qL} query (see below).
36385 @item m @var{thread-id}
36387 @item m @var{thread-id},@var{thread-id}@dots{}
36388 a comma-separated list of thread IDs
36390 (lower case letter @samp{L}) denotes end of list.
36393 In response to each query, the target will reply with a list of one or
36394 more thread IDs, separated by commas.
36395 @value{GDBN} will respond to each reply with a request for more thread
36396 ids (using the @samp{qs} form of the query), until the target responds
36397 with @samp{l} (lower-case ell, for @dfn{last}).
36398 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36401 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36402 initial connection with the remote target, and the very first thread ID
36403 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36404 message. Therefore, the stub should ensure that the first thread ID in
36405 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36407 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36408 @cindex get thread-local storage address, remote request
36409 @cindex @samp{qGetTLSAddr} packet
36410 Fetch the address associated with thread local storage specified
36411 by @var{thread-id}, @var{offset}, and @var{lm}.
36413 @var{thread-id} is the thread ID associated with the
36414 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36416 @var{offset} is the (big endian, hex encoded) offset associated with the
36417 thread local variable. (This offset is obtained from the debug
36418 information associated with the variable.)
36420 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36421 load module associated with the thread local storage. For example,
36422 a @sc{gnu}/Linux system will pass the link map address of the shared
36423 object associated with the thread local storage under consideration.
36424 Other operating environments may choose to represent the load module
36425 differently, so the precise meaning of this parameter will vary.
36429 @item @var{XX}@dots{}
36430 Hex encoded (big endian) bytes representing the address of the thread
36431 local storage requested.
36434 An error occurred. The error number @var{nn} is given as hex digits.
36437 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36440 @item qGetTIBAddr:@var{thread-id}
36441 @cindex get thread information block address
36442 @cindex @samp{qGetTIBAddr} packet
36443 Fetch address of the Windows OS specific Thread Information Block.
36445 @var{thread-id} is the thread ID associated with the thread.
36449 @item @var{XX}@dots{}
36450 Hex encoded (big endian) bytes representing the linear address of the
36451 thread information block.
36454 An error occured. This means that either the thread was not found, or the
36455 address could not be retrieved.
36458 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36461 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36462 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36463 digit) is one to indicate the first query and zero to indicate a
36464 subsequent query; @var{threadcount} (two hex digits) is the maximum
36465 number of threads the response packet can contain; and @var{nextthread}
36466 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36467 returned in the response as @var{argthread}.
36469 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36473 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36474 Where: @var{count} (two hex digits) is the number of threads being
36475 returned; @var{done} (one hex digit) is zero to indicate more threads
36476 and one indicates no further threads; @var{argthreadid} (eight hex
36477 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36478 is a sequence of thread IDs, @var{threadid} (eight hex
36479 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36483 @cindex section offsets, remote request
36484 @cindex @samp{qOffsets} packet
36485 Get section offsets that the target used when relocating the downloaded
36490 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36491 Relocate the @code{Text} section by @var{xxx} from its original address.
36492 Relocate the @code{Data} section by @var{yyy} from its original address.
36493 If the object file format provides segment information (e.g.@: @sc{elf}
36494 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36495 segments by the supplied offsets.
36497 @emph{Note: while a @code{Bss} offset may be included in the response,
36498 @value{GDBN} ignores this and instead applies the @code{Data} offset
36499 to the @code{Bss} section.}
36501 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36502 Relocate the first segment of the object file, which conventionally
36503 contains program code, to a starting address of @var{xxx}. If
36504 @samp{DataSeg} is specified, relocate the second segment, which
36505 conventionally contains modifiable data, to a starting address of
36506 @var{yyy}. @value{GDBN} will report an error if the object file
36507 does not contain segment information, or does not contain at least
36508 as many segments as mentioned in the reply. Extra segments are
36509 kept at fixed offsets relative to the last relocated segment.
36512 @item qP @var{mode} @var{thread-id}
36513 @cindex thread information, remote request
36514 @cindex @samp{qP} packet
36515 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36516 encoded 32 bit mode; @var{thread-id} is a thread ID
36517 (@pxref{thread-id syntax}).
36519 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36522 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36526 @cindex non-stop mode, remote request
36527 @cindex @samp{QNonStop} packet
36529 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36530 @xref{Remote Non-Stop}, for more information.
36535 The request succeeded.
36538 An error occurred. The error number @var{nn} is given as hex digits.
36541 An empty reply indicates that @samp{QNonStop} is not supported by
36545 This packet is not probed by default; the remote stub must request it,
36546 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36547 Use of this packet is controlled by the @code{set non-stop} command;
36548 @pxref{Non-Stop Mode}.
36550 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36551 @itemx QCatchSyscalls:0
36552 @cindex catch syscalls from inferior, remote request
36553 @cindex @samp{QCatchSyscalls} packet
36554 @anchor{QCatchSyscalls}
36555 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36556 catching syscalls from the inferior process.
36558 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36559 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36560 is listed, every system call should be reported.
36562 Note that if a syscall not in the list is reported, @value{GDBN} will
36563 still filter the event according to its own list from all corresponding
36564 @code{catch syscall} commands. However, it is more efficient to only
36565 report the requested syscalls.
36567 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36568 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36570 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36571 kept for the new process too. On targets where exec may affect syscall
36572 numbers, for example with exec between 32 and 64-bit processes, the
36573 client should send a new packet with the new syscall list.
36578 The request succeeded.
36581 An error occurred. @var{nn} are hex digits.
36584 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36588 Use of this packet is controlled by the @code{set remote catch-syscalls}
36589 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36590 This packet is not probed by default; the remote stub must request it,
36591 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36593 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36594 @cindex pass signals to inferior, remote request
36595 @cindex @samp{QPassSignals} packet
36596 @anchor{QPassSignals}
36597 Each listed @var{signal} should be passed directly to the inferior process.
36598 Signals are numbered identically to continue packets and stop replies
36599 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36600 strictly greater than the previous item. These signals do not need to stop
36601 the inferior, or be reported to @value{GDBN}. All other signals should be
36602 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36603 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36604 new list. This packet improves performance when using @samp{handle
36605 @var{signal} nostop noprint pass}.
36610 The request succeeded.
36613 An error occurred. The error number @var{nn} is given as hex digits.
36616 An empty reply indicates that @samp{QPassSignals} is not supported by
36620 Use of this packet is controlled by the @code{set remote pass-signals}
36621 command (@pxref{Remote Configuration, set remote pass-signals}).
36622 This packet is not probed by default; the remote stub must request it,
36623 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36625 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36626 @cindex signals the inferior may see, remote request
36627 @cindex @samp{QProgramSignals} packet
36628 @anchor{QProgramSignals}
36629 Each listed @var{signal} may be delivered to the inferior process.
36630 Others should be silently discarded.
36632 In some cases, the remote stub may need to decide whether to deliver a
36633 signal to the program or not without @value{GDBN} involvement. One
36634 example of that is while detaching --- the program's threads may have
36635 stopped for signals that haven't yet had a chance of being reported to
36636 @value{GDBN}, and so the remote stub can use the signal list specified
36637 by this packet to know whether to deliver or ignore those pending
36640 This does not influence whether to deliver a signal as requested by a
36641 resumption packet (@pxref{vCont packet}).
36643 Signals are numbered identically to continue packets and stop replies
36644 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36645 strictly greater than the previous item. Multiple
36646 @samp{QProgramSignals} packets do not combine; any earlier
36647 @samp{QProgramSignals} list is completely replaced by the new list.
36652 The request succeeded.
36655 An error occurred. The error number @var{nn} is given as hex digits.
36658 An empty reply indicates that @samp{QProgramSignals} is not supported
36662 Use of this packet is controlled by the @code{set remote program-signals}
36663 command (@pxref{Remote Configuration, set remote program-signals}).
36664 This packet is not probed by default; the remote stub must request it,
36665 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36667 @anchor{QThreadEvents}
36668 @item QThreadEvents:1
36669 @itemx QThreadEvents:0
36670 @cindex thread create/exit events, remote request
36671 @cindex @samp{QThreadEvents} packet
36673 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36674 reporting of thread create and exit events. @xref{thread create
36675 event}, for the reply specifications. For example, this is used in
36676 non-stop mode when @value{GDBN} stops a set of threads and
36677 synchronously waits for the their corresponding stop replies. Without
36678 exit events, if one of the threads exits, @value{GDBN} would hang
36679 forever not knowing that it should no longer expect a stop for that
36680 same thread. @value{GDBN} does not enable this feature unless the
36681 stub reports that it supports it by including @samp{QThreadEvents+} in
36682 its @samp{qSupported} reply.
36687 The request succeeded.
36690 An error occurred. The error number @var{nn} is given as hex digits.
36693 An empty reply indicates that @samp{QThreadEvents} is not supported by
36697 Use of this packet is controlled by the @code{set remote thread-events}
36698 command (@pxref{Remote Configuration, set remote thread-events}).
36700 @item qRcmd,@var{command}
36701 @cindex execute remote command, remote request
36702 @cindex @samp{qRcmd} packet
36703 @var{command} (hex encoded) is passed to the local interpreter for
36704 execution. Invalid commands should be reported using the output
36705 string. Before the final result packet, the target may also respond
36706 with a number of intermediate @samp{O@var{output}} console output
36707 packets. @emph{Implementors should note that providing access to a
36708 stubs's interpreter may have security implications}.
36713 A command response with no output.
36715 A command response with the hex encoded output string @var{OUTPUT}.
36717 Indicate a badly formed request.
36719 An empty reply indicates that @samp{qRcmd} is not recognized.
36722 (Note that the @code{qRcmd} packet's name is separated from the
36723 command by a @samp{,}, not a @samp{:}, contrary to the naming
36724 conventions above. Please don't use this packet as a model for new
36727 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36728 @cindex searching memory, in remote debugging
36730 @cindex @samp{qSearch:memory} packet
36732 @cindex @samp{qSearch memory} packet
36733 @anchor{qSearch memory}
36734 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36735 Both @var{address} and @var{length} are encoded in hex;
36736 @var{search-pattern} is a sequence of bytes, also hex encoded.
36741 The pattern was not found.
36743 The pattern was found at @var{address}.
36745 A badly formed request or an error was encountered while searching memory.
36747 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36750 @item QStartNoAckMode
36751 @cindex @samp{QStartNoAckMode} packet
36752 @anchor{QStartNoAckMode}
36753 Request that the remote stub disable the normal @samp{+}/@samp{-}
36754 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36759 The stub has switched to no-acknowledgment mode.
36760 @value{GDBN} acknowledges this reponse,
36761 but neither the stub nor @value{GDBN} shall send or expect further
36762 @samp{+}/@samp{-} acknowledgments in the current connection.
36764 An empty reply indicates that the stub does not support no-acknowledgment mode.
36767 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36768 @cindex supported packets, remote query
36769 @cindex features of the remote protocol
36770 @cindex @samp{qSupported} packet
36771 @anchor{qSupported}
36772 Tell the remote stub about features supported by @value{GDBN}, and
36773 query the stub for features it supports. This packet allows
36774 @value{GDBN} and the remote stub to take advantage of each others'
36775 features. @samp{qSupported} also consolidates multiple feature probes
36776 at startup, to improve @value{GDBN} performance---a single larger
36777 packet performs better than multiple smaller probe packets on
36778 high-latency links. Some features may enable behavior which must not
36779 be on by default, e.g.@: because it would confuse older clients or
36780 stubs. Other features may describe packets which could be
36781 automatically probed for, but are not. These features must be
36782 reported before @value{GDBN} will use them. This ``default
36783 unsupported'' behavior is not appropriate for all packets, but it
36784 helps to keep the initial connection time under control with new
36785 versions of @value{GDBN} which support increasing numbers of packets.
36789 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36790 The stub supports or does not support each returned @var{stubfeature},
36791 depending on the form of each @var{stubfeature} (see below for the
36794 An empty reply indicates that @samp{qSupported} is not recognized,
36795 or that no features needed to be reported to @value{GDBN}.
36798 The allowed forms for each feature (either a @var{gdbfeature} in the
36799 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36803 @item @var{name}=@var{value}
36804 The remote protocol feature @var{name} is supported, and associated
36805 with the specified @var{value}. The format of @var{value} depends
36806 on the feature, but it must not include a semicolon.
36808 The remote protocol feature @var{name} is supported, and does not
36809 need an associated value.
36811 The remote protocol feature @var{name} is not supported.
36813 The remote protocol feature @var{name} may be supported, and
36814 @value{GDBN} should auto-detect support in some other way when it is
36815 needed. This form will not be used for @var{gdbfeature} notifications,
36816 but may be used for @var{stubfeature} responses.
36819 Whenever the stub receives a @samp{qSupported} request, the
36820 supplied set of @value{GDBN} features should override any previous
36821 request. This allows @value{GDBN} to put the stub in a known
36822 state, even if the stub had previously been communicating with
36823 a different version of @value{GDBN}.
36825 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36830 This feature indicates whether @value{GDBN} supports multiprocess
36831 extensions to the remote protocol. @value{GDBN} does not use such
36832 extensions unless the stub also reports that it supports them by
36833 including @samp{multiprocess+} in its @samp{qSupported} reply.
36834 @xref{multiprocess extensions}, for details.
36837 This feature indicates that @value{GDBN} supports the XML target
36838 description. If the stub sees @samp{xmlRegisters=} with target
36839 specific strings separated by a comma, it will report register
36843 This feature indicates whether @value{GDBN} supports the
36844 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36845 instruction reply packet}).
36848 This feature indicates whether @value{GDBN} supports the swbreak stop
36849 reason in stop replies. @xref{swbreak stop reason}, for details.
36852 This feature indicates whether @value{GDBN} supports the hwbreak stop
36853 reason in stop replies. @xref{swbreak stop reason}, for details.
36856 This feature indicates whether @value{GDBN} supports fork event
36857 extensions to the remote protocol. @value{GDBN} does not use such
36858 extensions unless the stub also reports that it supports them by
36859 including @samp{fork-events+} in its @samp{qSupported} reply.
36862 This feature indicates whether @value{GDBN} supports vfork event
36863 extensions to the remote protocol. @value{GDBN} does not use such
36864 extensions unless the stub also reports that it supports them by
36865 including @samp{vfork-events+} in its @samp{qSupported} reply.
36868 This feature indicates whether @value{GDBN} supports exec event
36869 extensions to the remote protocol. @value{GDBN} does not use such
36870 extensions unless the stub also reports that it supports them by
36871 including @samp{exec-events+} in its @samp{qSupported} reply.
36873 @item vContSupported
36874 This feature indicates whether @value{GDBN} wants to know the
36875 supported actions in the reply to @samp{vCont?} packet.
36878 Stubs should ignore any unknown values for
36879 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36880 packet supports receiving packets of unlimited length (earlier
36881 versions of @value{GDBN} may reject overly long responses). Additional values
36882 for @var{gdbfeature} may be defined in the future to let the stub take
36883 advantage of new features in @value{GDBN}, e.g.@: incompatible
36884 improvements in the remote protocol---the @samp{multiprocess} feature is
36885 an example of such a feature. The stub's reply should be independent
36886 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36887 describes all the features it supports, and then the stub replies with
36888 all the features it supports.
36890 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36891 responses, as long as each response uses one of the standard forms.
36893 Some features are flags. A stub which supports a flag feature
36894 should respond with a @samp{+} form response. Other features
36895 require values, and the stub should respond with an @samp{=}
36898 Each feature has a default value, which @value{GDBN} will use if
36899 @samp{qSupported} is not available or if the feature is not mentioned
36900 in the @samp{qSupported} response. The default values are fixed; a
36901 stub is free to omit any feature responses that match the defaults.
36903 Not all features can be probed, but for those which can, the probing
36904 mechanism is useful: in some cases, a stub's internal
36905 architecture may not allow the protocol layer to know some information
36906 about the underlying target in advance. This is especially common in
36907 stubs which may be configured for multiple targets.
36909 These are the currently defined stub features and their properties:
36911 @multitable @columnfractions 0.35 0.2 0.12 0.2
36912 @c NOTE: The first row should be @headitem, but we do not yet require
36913 @c a new enough version of Texinfo (4.7) to use @headitem.
36915 @tab Value Required
36919 @item @samp{PacketSize}
36924 @item @samp{qXfer:auxv:read}
36929 @item @samp{qXfer:btrace:read}
36934 @item @samp{qXfer:btrace-conf:read}
36939 @item @samp{qXfer:exec-file:read}
36944 @item @samp{qXfer:features:read}
36949 @item @samp{qXfer:libraries:read}
36954 @item @samp{qXfer:libraries-svr4:read}
36959 @item @samp{augmented-libraries-svr4-read}
36964 @item @samp{qXfer:memory-map:read}
36969 @item @samp{qXfer:sdata:read}
36974 @item @samp{qXfer:spu:read}
36979 @item @samp{qXfer:spu:write}
36984 @item @samp{qXfer:siginfo:read}
36989 @item @samp{qXfer:siginfo:write}
36994 @item @samp{qXfer:threads:read}
36999 @item @samp{qXfer:traceframe-info:read}
37004 @item @samp{qXfer:uib:read}
37009 @item @samp{qXfer:fdpic:read}
37014 @item @samp{Qbtrace:off}
37019 @item @samp{Qbtrace:bts}
37024 @item @samp{Qbtrace:pt}
37029 @item @samp{Qbtrace-conf:bts:size}
37034 @item @samp{Qbtrace-conf:pt:size}
37039 @item @samp{QNonStop}
37044 @item @samp{QCatchSyscalls}
37049 @item @samp{QPassSignals}
37054 @item @samp{QStartNoAckMode}
37059 @item @samp{multiprocess}
37064 @item @samp{ConditionalBreakpoints}
37069 @item @samp{ConditionalTracepoints}
37074 @item @samp{ReverseContinue}
37079 @item @samp{ReverseStep}
37084 @item @samp{TracepointSource}
37089 @item @samp{QAgent}
37094 @item @samp{QAllow}
37099 @item @samp{QDisableRandomization}
37104 @item @samp{EnableDisableTracepoints}
37109 @item @samp{QTBuffer:size}
37114 @item @samp{tracenz}
37119 @item @samp{BreakpointCommands}
37124 @item @samp{swbreak}
37129 @item @samp{hwbreak}
37134 @item @samp{fork-events}
37139 @item @samp{vfork-events}
37144 @item @samp{exec-events}
37149 @item @samp{QThreadEvents}
37154 @item @samp{no-resumed}
37161 These are the currently defined stub features, in more detail:
37164 @cindex packet size, remote protocol
37165 @item PacketSize=@var{bytes}
37166 The remote stub can accept packets up to at least @var{bytes} in
37167 length. @value{GDBN} will send packets up to this size for bulk
37168 transfers, and will never send larger packets. This is a limit on the
37169 data characters in the packet, including the frame and checksum.
37170 There is no trailing NUL byte in a remote protocol packet; if the stub
37171 stores packets in a NUL-terminated format, it should allow an extra
37172 byte in its buffer for the NUL. If this stub feature is not supported,
37173 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37175 @item qXfer:auxv:read
37176 The remote stub understands the @samp{qXfer:auxv:read} packet
37177 (@pxref{qXfer auxiliary vector read}).
37179 @item qXfer:btrace:read
37180 The remote stub understands the @samp{qXfer:btrace:read}
37181 packet (@pxref{qXfer btrace read}).
37183 @item qXfer:btrace-conf:read
37184 The remote stub understands the @samp{qXfer:btrace-conf:read}
37185 packet (@pxref{qXfer btrace-conf read}).
37187 @item qXfer:exec-file:read
37188 The remote stub understands the @samp{qXfer:exec-file:read} packet
37189 (@pxref{qXfer executable filename read}).
37191 @item qXfer:features:read
37192 The remote stub understands the @samp{qXfer:features:read} packet
37193 (@pxref{qXfer target description read}).
37195 @item qXfer:libraries:read
37196 The remote stub understands the @samp{qXfer:libraries:read} packet
37197 (@pxref{qXfer library list read}).
37199 @item qXfer:libraries-svr4:read
37200 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37201 (@pxref{qXfer svr4 library list read}).
37203 @item augmented-libraries-svr4-read
37204 The remote stub understands the augmented form of the
37205 @samp{qXfer:libraries-svr4:read} packet
37206 (@pxref{qXfer svr4 library list read}).
37208 @item qXfer:memory-map:read
37209 The remote stub understands the @samp{qXfer:memory-map:read} packet
37210 (@pxref{qXfer memory map read}).
37212 @item qXfer:sdata:read
37213 The remote stub understands the @samp{qXfer:sdata:read} packet
37214 (@pxref{qXfer sdata read}).
37216 @item qXfer:spu:read
37217 The remote stub understands the @samp{qXfer:spu:read} packet
37218 (@pxref{qXfer spu read}).
37220 @item qXfer:spu:write
37221 The remote stub understands the @samp{qXfer:spu:write} packet
37222 (@pxref{qXfer spu write}).
37224 @item qXfer:siginfo:read
37225 The remote stub understands the @samp{qXfer:siginfo:read} packet
37226 (@pxref{qXfer siginfo read}).
37228 @item qXfer:siginfo:write
37229 The remote stub understands the @samp{qXfer:siginfo:write} packet
37230 (@pxref{qXfer siginfo write}).
37232 @item qXfer:threads:read
37233 The remote stub understands the @samp{qXfer:threads:read} packet
37234 (@pxref{qXfer threads read}).
37236 @item qXfer:traceframe-info:read
37237 The remote stub understands the @samp{qXfer:traceframe-info:read}
37238 packet (@pxref{qXfer traceframe info read}).
37240 @item qXfer:uib:read
37241 The remote stub understands the @samp{qXfer:uib:read}
37242 packet (@pxref{qXfer unwind info block}).
37244 @item qXfer:fdpic:read
37245 The remote stub understands the @samp{qXfer:fdpic:read}
37246 packet (@pxref{qXfer fdpic loadmap read}).
37249 The remote stub understands the @samp{QNonStop} packet
37250 (@pxref{QNonStop}).
37252 @item QCatchSyscalls
37253 The remote stub understands the @samp{QCatchSyscalls} packet
37254 (@pxref{QCatchSyscalls}).
37257 The remote stub understands the @samp{QPassSignals} packet
37258 (@pxref{QPassSignals}).
37260 @item QStartNoAckMode
37261 The remote stub understands the @samp{QStartNoAckMode} packet and
37262 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37265 @anchor{multiprocess extensions}
37266 @cindex multiprocess extensions, in remote protocol
37267 The remote stub understands the multiprocess extensions to the remote
37268 protocol syntax. The multiprocess extensions affect the syntax of
37269 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37270 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37271 replies. Note that reporting this feature indicates support for the
37272 syntactic extensions only, not that the stub necessarily supports
37273 debugging of more than one process at a time. The stub must not use
37274 multiprocess extensions in packet replies unless @value{GDBN} has also
37275 indicated it supports them in its @samp{qSupported} request.
37277 @item qXfer:osdata:read
37278 The remote stub understands the @samp{qXfer:osdata:read} packet
37279 ((@pxref{qXfer osdata read}).
37281 @item ConditionalBreakpoints
37282 The target accepts and implements evaluation of conditional expressions
37283 defined for breakpoints. The target will only report breakpoint triggers
37284 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37286 @item ConditionalTracepoints
37287 The remote stub accepts and implements conditional expressions defined
37288 for tracepoints (@pxref{Tracepoint Conditions}).
37290 @item ReverseContinue
37291 The remote stub accepts and implements the reverse continue packet
37295 The remote stub accepts and implements the reverse step packet
37298 @item TracepointSource
37299 The remote stub understands the @samp{QTDPsrc} packet that supplies
37300 the source form of tracepoint definitions.
37303 The remote stub understands the @samp{QAgent} packet.
37306 The remote stub understands the @samp{QAllow} packet.
37308 @item QDisableRandomization
37309 The remote stub understands the @samp{QDisableRandomization} packet.
37311 @item StaticTracepoint
37312 @cindex static tracepoints, in remote protocol
37313 The remote stub supports static tracepoints.
37315 @item InstallInTrace
37316 @anchor{install tracepoint in tracing}
37317 The remote stub supports installing tracepoint in tracing.
37319 @item EnableDisableTracepoints
37320 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37321 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37322 to be enabled and disabled while a trace experiment is running.
37324 @item QTBuffer:size
37325 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37326 packet that allows to change the size of the trace buffer.
37329 @cindex string tracing, in remote protocol
37330 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37331 See @ref{Bytecode Descriptions} for details about the bytecode.
37333 @item BreakpointCommands
37334 @cindex breakpoint commands, in remote protocol
37335 The remote stub supports running a breakpoint's command list itself,
37336 rather than reporting the hit to @value{GDBN}.
37339 The remote stub understands the @samp{Qbtrace:off} packet.
37342 The remote stub understands the @samp{Qbtrace:bts} packet.
37345 The remote stub understands the @samp{Qbtrace:pt} packet.
37347 @item Qbtrace-conf:bts:size
37348 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
37350 @item Qbtrace-conf:pt:size
37351 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
37354 The remote stub reports the @samp{swbreak} stop reason for memory
37358 The remote stub reports the @samp{hwbreak} stop reason for hardware
37362 The remote stub reports the @samp{fork} stop reason for fork events.
37365 The remote stub reports the @samp{vfork} stop reason for vfork events
37366 and vforkdone events.
37369 The remote stub reports the @samp{exec} stop reason for exec events.
37371 @item vContSupported
37372 The remote stub reports the supported actions in the reply to
37373 @samp{vCont?} packet.
37375 @item QThreadEvents
37376 The remote stub understands the @samp{QThreadEvents} packet.
37379 The remote stub reports the @samp{N} stop reply.
37384 @cindex symbol lookup, remote request
37385 @cindex @samp{qSymbol} packet
37386 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37387 requests. Accept requests from the target for the values of symbols.
37392 The target does not need to look up any (more) symbols.
37393 @item qSymbol:@var{sym_name}
37394 The target requests the value of symbol @var{sym_name} (hex encoded).
37395 @value{GDBN} may provide the value by using the
37396 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37400 @item qSymbol:@var{sym_value}:@var{sym_name}
37401 Set the value of @var{sym_name} to @var{sym_value}.
37403 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37404 target has previously requested.
37406 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37407 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37413 The target does not need to look up any (more) symbols.
37414 @item qSymbol:@var{sym_name}
37415 The target requests the value of a new symbol @var{sym_name} (hex
37416 encoded). @value{GDBN} will continue to supply the values of symbols
37417 (if available), until the target ceases to request them.
37422 @itemx QTDisconnected
37429 @itemx qTMinFTPILen
37431 @xref{Tracepoint Packets}.
37433 @item qThreadExtraInfo,@var{thread-id}
37434 @cindex thread attributes info, remote request
37435 @cindex @samp{qThreadExtraInfo} packet
37436 Obtain from the target OS a printable string description of thread
37437 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37438 for the forms of @var{thread-id}. This
37439 string may contain anything that the target OS thinks is interesting
37440 for @value{GDBN} to tell the user about the thread. The string is
37441 displayed in @value{GDBN}'s @code{info threads} display. Some
37442 examples of possible thread extra info strings are @samp{Runnable}, or
37443 @samp{Blocked on Mutex}.
37447 @item @var{XX}@dots{}
37448 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37449 comprising the printable string containing the extra information about
37450 the thread's attributes.
37453 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37454 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37455 conventions above. Please don't use this packet as a model for new
37474 @xref{Tracepoint Packets}.
37476 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37477 @cindex read special object, remote request
37478 @cindex @samp{qXfer} packet
37479 @anchor{qXfer read}
37480 Read uninterpreted bytes from the target's special data area
37481 identified by the keyword @var{object}. Request @var{length} bytes
37482 starting at @var{offset} bytes into the data. The content and
37483 encoding of @var{annex} is specific to @var{object}; it can supply
37484 additional details about what data to access.
37489 Data @var{data} (@pxref{Binary Data}) has been read from the
37490 target. There may be more data at a higher address (although
37491 it is permitted to return @samp{m} even for the last valid
37492 block of data, as long as at least one byte of data was read).
37493 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37497 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37498 There is no more data to be read. It is possible for @var{data} to
37499 have fewer bytes than the @var{length} in the request.
37502 The @var{offset} in the request is at the end of the data.
37503 There is no more data to be read.
37506 The request was malformed, or @var{annex} was invalid.
37509 The offset was invalid, or there was an error encountered reading the data.
37510 The @var{nn} part is a hex-encoded @code{errno} value.
37513 An empty reply indicates the @var{object} string was not recognized by
37514 the stub, or that the object does not support reading.
37517 Here are the specific requests of this form defined so far. All the
37518 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37519 formats, listed above.
37522 @item qXfer:auxv:read::@var{offset},@var{length}
37523 @anchor{qXfer auxiliary vector read}
37524 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37525 auxiliary vector}. Note @var{annex} must be empty.
37527 This packet is not probed by default; the remote stub must request it,
37528 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37530 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37531 @anchor{qXfer btrace read}
37533 Return a description of the current branch trace.
37534 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37535 packet may have one of the following values:
37539 Returns all available branch trace.
37542 Returns all available branch trace if the branch trace changed since
37543 the last read request.
37546 Returns the new branch trace since the last read request. Adds a new
37547 block to the end of the trace that begins at zero and ends at the source
37548 location of the first branch in the trace buffer. This extra block is
37549 used to stitch traces together.
37551 If the trace buffer overflowed, returns an error indicating the overflow.
37554 This packet is not probed by default; the remote stub must request it
37555 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37557 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37558 @anchor{qXfer btrace-conf read}
37560 Return a description of the current branch trace configuration.
37561 @xref{Branch Trace Configuration Format}.
37563 This packet is not probed by default; the remote stub must request it
37564 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37566 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37567 @anchor{qXfer executable filename read}
37568 Return the full absolute name of the file that was executed to create
37569 a process running on the remote system. The annex specifies the
37570 numeric process ID of the process to query, encoded as a hexadecimal
37571 number. If the annex part is empty the remote stub should return the
37572 filename corresponding to the currently executing process.
37574 This packet is not probed by default; the remote stub must request it,
37575 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37577 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37578 @anchor{qXfer target description read}
37579 Access the @dfn{target description}. @xref{Target Descriptions}. The
37580 annex specifies which XML document to access. The main description is
37581 always loaded from the @samp{target.xml} annex.
37583 This packet is not probed by default; the remote stub must request it,
37584 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37586 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37587 @anchor{qXfer library list read}
37588 Access the target's list of loaded libraries. @xref{Library List Format}.
37589 The annex part of the generic @samp{qXfer} packet must be empty
37590 (@pxref{qXfer read}).
37592 Targets which maintain a list of libraries in the program's memory do
37593 not need to implement this packet; it is designed for platforms where
37594 the operating system manages the list of loaded libraries.
37596 This packet is not probed by default; the remote stub must request it,
37597 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37599 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37600 @anchor{qXfer svr4 library list read}
37601 Access the target's list of loaded libraries when the target is an SVR4
37602 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37603 of the generic @samp{qXfer} packet must be empty unless the remote
37604 stub indicated it supports the augmented form of this packet
37605 by supplying an appropriate @samp{qSupported} response
37606 (@pxref{qXfer read}, @ref{qSupported}).
37608 This packet is optional for better performance on SVR4 targets.
37609 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37611 This packet is not probed by default; the remote stub must request it,
37612 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37614 If the remote stub indicates it supports the augmented form of this
37615 packet then the annex part of the generic @samp{qXfer} packet may
37616 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37617 arguments. The currently supported arguments are:
37620 @item start=@var{address}
37621 A hexadecimal number specifying the address of the @samp{struct
37622 link_map} to start reading the library list from. If unset or zero
37623 then the first @samp{struct link_map} in the library list will be
37624 chosen as the starting point.
37626 @item prev=@var{address}
37627 A hexadecimal number specifying the address of the @samp{struct
37628 link_map} immediately preceding the @samp{struct link_map}
37629 specified by the @samp{start} argument. If unset or zero then
37630 the remote stub will expect that no @samp{struct link_map}
37631 exists prior to the starting point.
37635 Arguments that are not understood by the remote stub will be silently
37638 @item qXfer:memory-map:read::@var{offset},@var{length}
37639 @anchor{qXfer memory map read}
37640 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37641 annex part of the generic @samp{qXfer} packet must be empty
37642 (@pxref{qXfer read}).
37644 This packet is not probed by default; the remote stub must request it,
37645 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37647 @item qXfer:sdata:read::@var{offset},@var{length}
37648 @anchor{qXfer sdata read}
37650 Read contents of the extra collected static tracepoint marker
37651 information. The annex part of the generic @samp{qXfer} packet must
37652 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37655 This packet is not probed by default; the remote stub must request it,
37656 by supplying an appropriate @samp{qSupported} response
37657 (@pxref{qSupported}).
37659 @item qXfer:siginfo:read::@var{offset},@var{length}
37660 @anchor{qXfer siginfo read}
37661 Read contents of the extra signal information on the target
37662 system. The annex part of the generic @samp{qXfer} packet must be
37663 empty (@pxref{qXfer read}).
37665 This packet is not probed by default; the remote stub must request it,
37666 by supplying an appropriate @samp{qSupported} response
37667 (@pxref{qSupported}).
37669 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37670 @anchor{qXfer spu read}
37671 Read contents of an @code{spufs} file on the target system. The
37672 annex specifies which file to read; it must be of the form
37673 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37674 in the target process, and @var{name} identifes the @code{spufs} file
37675 in that context to be accessed.
37677 This packet is not probed by default; the remote stub must request it,
37678 by supplying an appropriate @samp{qSupported} response
37679 (@pxref{qSupported}).
37681 @item qXfer:threads:read::@var{offset},@var{length}
37682 @anchor{qXfer threads read}
37683 Access the list of threads on target. @xref{Thread List Format}. The
37684 annex part of the generic @samp{qXfer} packet must be empty
37685 (@pxref{qXfer read}).
37687 This packet is not probed by default; the remote stub must request it,
37688 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37690 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37691 @anchor{qXfer traceframe info read}
37693 Return a description of the current traceframe's contents.
37694 @xref{Traceframe Info Format}. The annex part of the generic
37695 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37697 This packet is not probed by default; the remote stub must request it,
37698 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37700 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37701 @anchor{qXfer unwind info block}
37703 Return the unwind information block for @var{pc}. This packet is used
37704 on OpenVMS/ia64 to ask the kernel unwind information.
37706 This packet is not probed by default.
37708 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37709 @anchor{qXfer fdpic loadmap read}
37710 Read contents of @code{loadmap}s on the target system. The
37711 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37712 executable @code{loadmap} or interpreter @code{loadmap} to read.
37714 This packet is not probed by default; the remote stub must request it,
37715 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37717 @item qXfer:osdata:read::@var{offset},@var{length}
37718 @anchor{qXfer osdata read}
37719 Access the target's @dfn{operating system information}.
37720 @xref{Operating System Information}.
37724 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37725 @cindex write data into object, remote request
37726 @anchor{qXfer write}
37727 Write uninterpreted bytes into the target's special data area
37728 identified by the keyword @var{object}, starting at @var{offset} bytes
37729 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37730 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37731 is specific to @var{object}; it can supply additional details about what data
37737 @var{nn} (hex encoded) is the number of bytes written.
37738 This may be fewer bytes than supplied in the request.
37741 The request was malformed, or @var{annex} was invalid.
37744 The offset was invalid, or there was an error encountered writing the data.
37745 The @var{nn} part is a hex-encoded @code{errno} value.
37748 An empty reply indicates the @var{object} string was not
37749 recognized by the stub, or that the object does not support writing.
37752 Here are the specific requests of this form defined so far. All the
37753 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37754 formats, listed above.
37757 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37758 @anchor{qXfer siginfo write}
37759 Write @var{data} to the extra signal information on the target system.
37760 The annex part of the generic @samp{qXfer} packet must be
37761 empty (@pxref{qXfer write}).
37763 This packet is not probed by default; the remote stub must request it,
37764 by supplying an appropriate @samp{qSupported} response
37765 (@pxref{qSupported}).
37767 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37768 @anchor{qXfer spu write}
37769 Write @var{data} to an @code{spufs} file on the target system. The
37770 annex specifies which file to write; it must be of the form
37771 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37772 in the target process, and @var{name} identifes the @code{spufs} file
37773 in that context to be accessed.
37775 This packet is not probed by default; the remote stub must request it,
37776 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37779 @item qXfer:@var{object}:@var{operation}:@dots{}
37780 Requests of this form may be added in the future. When a stub does
37781 not recognize the @var{object} keyword, or its support for
37782 @var{object} does not recognize the @var{operation} keyword, the stub
37783 must respond with an empty packet.
37785 @item qAttached:@var{pid}
37786 @cindex query attached, remote request
37787 @cindex @samp{qAttached} packet
37788 Return an indication of whether the remote server attached to an
37789 existing process or created a new process. When the multiprocess
37790 protocol extensions are supported (@pxref{multiprocess extensions}),
37791 @var{pid} is an integer in hexadecimal format identifying the target
37792 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37793 the query packet will be simplified as @samp{qAttached}.
37795 This query is used, for example, to know whether the remote process
37796 should be detached or killed when a @value{GDBN} session is ended with
37797 the @code{quit} command.
37802 The remote server attached to an existing process.
37804 The remote server created a new process.
37806 A badly formed request or an error was encountered.
37810 Enable branch tracing for the current thread using Branch Trace Store.
37815 Branch tracing has been enabled.
37817 A badly formed request or an error was encountered.
37821 Enable branch tracing for the current thread using Intel Processor Trace.
37826 Branch tracing has been enabled.
37828 A badly formed request or an error was encountered.
37832 Disable branch tracing for the current thread.
37837 Branch tracing has been disabled.
37839 A badly formed request or an error was encountered.
37842 @item Qbtrace-conf:bts:size=@var{value}
37843 Set the requested ring buffer size for new threads that use the
37844 btrace recording method in bts format.
37849 The ring buffer size has been set.
37851 A badly formed request or an error was encountered.
37854 @item Qbtrace-conf:pt:size=@var{value}
37855 Set the requested ring buffer size for new threads that use the
37856 btrace recording method in pt format.
37861 The ring buffer size has been set.
37863 A badly formed request or an error was encountered.
37868 @node Architecture-Specific Protocol Details
37869 @section Architecture-Specific Protocol Details
37871 This section describes how the remote protocol is applied to specific
37872 target architectures. Also see @ref{Standard Target Features}, for
37873 details of XML target descriptions for each architecture.
37876 * ARM-Specific Protocol Details::
37877 * MIPS-Specific Protocol Details::
37880 @node ARM-Specific Protocol Details
37881 @subsection @acronym{ARM}-specific Protocol Details
37884 * ARM Breakpoint Kinds::
37887 @node ARM Breakpoint Kinds
37888 @subsubsection @acronym{ARM} Breakpoint Kinds
37889 @cindex breakpoint kinds, @acronym{ARM}
37891 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37896 16-bit Thumb mode breakpoint.
37899 32-bit Thumb mode (Thumb-2) breakpoint.
37902 32-bit @acronym{ARM} mode breakpoint.
37906 @node MIPS-Specific Protocol Details
37907 @subsection @acronym{MIPS}-specific Protocol Details
37910 * MIPS Register packet Format::
37911 * MIPS Breakpoint Kinds::
37914 @node MIPS Register packet Format
37915 @subsubsection @acronym{MIPS} Register Packet Format
37916 @cindex register packet format, @acronym{MIPS}
37918 The following @code{g}/@code{G} packets have previously been defined.
37919 In the below, some thirty-two bit registers are transferred as
37920 sixty-four bits. Those registers should be zero/sign extended (which?)
37921 to fill the space allocated. Register bytes are transferred in target
37922 byte order. The two nibbles within a register byte are transferred
37923 most-significant -- least-significant.
37928 All registers are transferred as thirty-two bit quantities in the order:
37929 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37930 registers; fsr; fir; fp.
37933 All registers are transferred as sixty-four bit quantities (including
37934 thirty-two bit registers such as @code{sr}). The ordering is the same
37939 @node MIPS Breakpoint Kinds
37940 @subsubsection @acronym{MIPS} Breakpoint Kinds
37941 @cindex breakpoint kinds, @acronym{MIPS}
37943 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37948 16-bit @acronym{MIPS16} mode breakpoint.
37951 16-bit @acronym{microMIPS} mode breakpoint.
37954 32-bit standard @acronym{MIPS} mode breakpoint.
37957 32-bit @acronym{microMIPS} mode breakpoint.
37961 @node Tracepoint Packets
37962 @section Tracepoint Packets
37963 @cindex tracepoint packets
37964 @cindex packets, tracepoint
37966 Here we describe the packets @value{GDBN} uses to implement
37967 tracepoints (@pxref{Tracepoints}).
37971 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37972 @cindex @samp{QTDP} packet
37973 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37974 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37975 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37976 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37977 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37978 the number of bytes that the target should copy elsewhere to make room
37979 for the tracepoint. If an @samp{X} is present, it introduces a
37980 tracepoint condition, which consists of a hexadecimal length, followed
37981 by a comma and hex-encoded bytes, in a manner similar to action
37982 encodings as described below. If the trailing @samp{-} is present,
37983 further @samp{QTDP} packets will follow to specify this tracepoint's
37989 The packet was understood and carried out.
37991 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37993 The packet was not recognized.
37996 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37997 Define actions to be taken when a tracepoint is hit. The @var{n} and
37998 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37999 this tracepoint. This packet may only be sent immediately after
38000 another @samp{QTDP} packet that ended with a @samp{-}. If the
38001 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38002 specifying more actions for this tracepoint.
38004 In the series of action packets for a given tracepoint, at most one
38005 can have an @samp{S} before its first @var{action}. If such a packet
38006 is sent, it and the following packets define ``while-stepping''
38007 actions. Any prior packets define ordinary actions --- that is, those
38008 taken when the tracepoint is first hit. If no action packet has an
38009 @samp{S}, then all the packets in the series specify ordinary
38010 tracepoint actions.
38012 The @samp{@var{action}@dots{}} portion of the packet is a series of
38013 actions, concatenated without separators. Each action has one of the
38019 Collect the registers whose bits are set in @var{mask},
38020 a hexadecimal number whose @var{i}'th bit is set if register number
38021 @var{i} should be collected. (The least significant bit is numbered
38022 zero.) Note that @var{mask} may be any number of digits long; it may
38023 not fit in a 32-bit word.
38025 @item M @var{basereg},@var{offset},@var{len}
38026 Collect @var{len} bytes of memory starting at the address in register
38027 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38028 @samp{-1}, then the range has a fixed address: @var{offset} is the
38029 address of the lowest byte to collect. The @var{basereg},
38030 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38031 values (the @samp{-1} value for @var{basereg} is a special case).
38033 @item X @var{len},@var{expr}
38034 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38035 it directs. The agent expression @var{expr} is as described in
38036 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38037 two-digit hex number in the packet; @var{len} is the number of bytes
38038 in the expression (and thus one-half the number of hex digits in the
38043 Any number of actions may be packed together in a single @samp{QTDP}
38044 packet, as long as the packet does not exceed the maximum packet
38045 length (400 bytes, for many stubs). There may be only one @samp{R}
38046 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38047 actions. Any registers referred to by @samp{M} and @samp{X} actions
38048 must be collected by a preceding @samp{R} action. (The
38049 ``while-stepping'' actions are treated as if they were attached to a
38050 separate tracepoint, as far as these restrictions are concerned.)
38055 The packet was understood and carried out.
38057 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38059 The packet was not recognized.
38062 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38063 @cindex @samp{QTDPsrc} packet
38064 Specify a source string of tracepoint @var{n} at address @var{addr}.
38065 This is useful to get accurate reproduction of the tracepoints
38066 originally downloaded at the beginning of the trace run. The @var{type}
38067 is the name of the tracepoint part, such as @samp{cond} for the
38068 tracepoint's conditional expression (see below for a list of types), while
38069 @var{bytes} is the string, encoded in hexadecimal.
38071 @var{start} is the offset of the @var{bytes} within the overall source
38072 string, while @var{slen} is the total length of the source string.
38073 This is intended for handling source strings that are longer than will
38074 fit in a single packet.
38075 @c Add detailed example when this info is moved into a dedicated
38076 @c tracepoint descriptions section.
38078 The available string types are @samp{at} for the location,
38079 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38080 @value{GDBN} sends a separate packet for each command in the action
38081 list, in the same order in which the commands are stored in the list.
38083 The target does not need to do anything with source strings except
38084 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38087 Although this packet is optional, and @value{GDBN} will only send it
38088 if the target replies with @samp{TracepointSource} @xref{General
38089 Query Packets}, it makes both disconnected tracing and trace files
38090 much easier to use. Otherwise the user must be careful that the
38091 tracepoints in effect while looking at trace frames are identical to
38092 the ones in effect during the trace run; even a small discrepancy
38093 could cause @samp{tdump} not to work, or a particular trace frame not
38096 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38097 @cindex define trace state variable, remote request
38098 @cindex @samp{QTDV} packet
38099 Create a new trace state variable, number @var{n}, with an initial
38100 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38101 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38102 the option of not using this packet for initial values of zero; the
38103 target should simply create the trace state variables as they are
38104 mentioned in expressions. The value @var{builtin} should be 1 (one)
38105 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38106 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38107 @samp{qTsV} packet had it set. The contents of @var{name} is the
38108 hex-encoded name (without the leading @samp{$}) of the trace state
38111 @item QTFrame:@var{n}
38112 @cindex @samp{QTFrame} packet
38113 Select the @var{n}'th tracepoint frame from the buffer, and use the
38114 register and memory contents recorded there to answer subsequent
38115 request packets from @value{GDBN}.
38117 A successful reply from the stub indicates that the stub has found the
38118 requested frame. The response is a series of parts, concatenated
38119 without separators, describing the frame we selected. Each part has
38120 one of the following forms:
38124 The selected frame is number @var{n} in the trace frame buffer;
38125 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38126 was no frame matching the criteria in the request packet.
38129 The selected trace frame records a hit of tracepoint number @var{t};
38130 @var{t} is a hexadecimal number.
38134 @item QTFrame:pc:@var{addr}
38135 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38136 currently selected frame whose PC is @var{addr};
38137 @var{addr} is a hexadecimal number.
38139 @item QTFrame:tdp:@var{t}
38140 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38141 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38142 is a hexadecimal number.
38144 @item QTFrame:range:@var{start}:@var{end}
38145 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38146 currently selected frame whose PC is between @var{start} (inclusive)
38147 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38150 @item QTFrame:outside:@var{start}:@var{end}
38151 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38152 frame @emph{outside} the given range of addresses (exclusive).
38155 @cindex @samp{qTMinFTPILen} packet
38156 This packet requests the minimum length of instruction at which a fast
38157 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38158 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38159 it depends on the target system being able to create trampolines in
38160 the first 64K of memory, which might or might not be possible for that
38161 system. So the reply to this packet will be 4 if it is able to
38168 The minimum instruction length is currently unknown.
38170 The minimum instruction length is @var{length}, where @var{length}
38171 is a hexadecimal number greater or equal to 1. A reply
38172 of 1 means that a fast tracepoint may be placed on any instruction
38173 regardless of size.
38175 An error has occurred.
38177 An empty reply indicates that the request is not supported by the stub.
38181 @cindex @samp{QTStart} packet
38182 Begin the tracepoint experiment. Begin collecting data from
38183 tracepoint hits in the trace frame buffer. This packet supports the
38184 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38185 instruction reply packet}).
38188 @cindex @samp{QTStop} packet
38189 End the tracepoint experiment. Stop collecting trace frames.
38191 @item QTEnable:@var{n}:@var{addr}
38193 @cindex @samp{QTEnable} packet
38194 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38195 experiment. If the tracepoint was previously disabled, then collection
38196 of data from it will resume.
38198 @item QTDisable:@var{n}:@var{addr}
38200 @cindex @samp{QTDisable} packet
38201 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38202 experiment. No more data will be collected from the tracepoint unless
38203 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38206 @cindex @samp{QTinit} packet
38207 Clear the table of tracepoints, and empty the trace frame buffer.
38209 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38210 @cindex @samp{QTro} packet
38211 Establish the given ranges of memory as ``transparent''. The stub
38212 will answer requests for these ranges from memory's current contents,
38213 if they were not collected as part of the tracepoint hit.
38215 @value{GDBN} uses this to mark read-only regions of memory, like those
38216 containing program code. Since these areas never change, they should
38217 still have the same contents they did when the tracepoint was hit, so
38218 there's no reason for the stub to refuse to provide their contents.
38220 @item QTDisconnected:@var{value}
38221 @cindex @samp{QTDisconnected} packet
38222 Set the choice to what to do with the tracing run when @value{GDBN}
38223 disconnects from the target. A @var{value} of 1 directs the target to
38224 continue the tracing run, while 0 tells the target to stop tracing if
38225 @value{GDBN} is no longer in the picture.
38228 @cindex @samp{qTStatus} packet
38229 Ask the stub if there is a trace experiment running right now.
38231 The reply has the form:
38235 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38236 @var{running} is a single digit @code{1} if the trace is presently
38237 running, or @code{0} if not. It is followed by semicolon-separated
38238 optional fields that an agent may use to report additional status.
38242 If the trace is not running, the agent may report any of several
38243 explanations as one of the optional fields:
38248 No trace has been run yet.
38250 @item tstop[:@var{text}]:0
38251 The trace was stopped by a user-originated stop command. The optional
38252 @var{text} field is a user-supplied string supplied as part of the
38253 stop command (for instance, an explanation of why the trace was
38254 stopped manually). It is hex-encoded.
38257 The trace stopped because the trace buffer filled up.
38259 @item tdisconnected:0
38260 The trace stopped because @value{GDBN} disconnected from the target.
38262 @item tpasscount:@var{tpnum}
38263 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38265 @item terror:@var{text}:@var{tpnum}
38266 The trace stopped because tracepoint @var{tpnum} had an error. The
38267 string @var{text} is available to describe the nature of the error
38268 (for instance, a divide by zero in the condition expression); it
38272 The trace stopped for some other reason.
38276 Additional optional fields supply statistical and other information.
38277 Although not required, they are extremely useful for users monitoring
38278 the progress of a trace run. If a trace has stopped, and these
38279 numbers are reported, they must reflect the state of the just-stopped
38284 @item tframes:@var{n}
38285 The number of trace frames in the buffer.
38287 @item tcreated:@var{n}
38288 The total number of trace frames created during the run. This may
38289 be larger than the trace frame count, if the buffer is circular.
38291 @item tsize:@var{n}
38292 The total size of the trace buffer, in bytes.
38294 @item tfree:@var{n}
38295 The number of bytes still unused in the buffer.
38297 @item circular:@var{n}
38298 The value of the circular trace buffer flag. @code{1} means that the
38299 trace buffer is circular and old trace frames will be discarded if
38300 necessary to make room, @code{0} means that the trace buffer is linear
38303 @item disconn:@var{n}
38304 The value of the disconnected tracing flag. @code{1} means that
38305 tracing will continue after @value{GDBN} disconnects, @code{0} means
38306 that the trace run will stop.
38310 @item qTP:@var{tp}:@var{addr}
38311 @cindex tracepoint status, remote request
38312 @cindex @samp{qTP} packet
38313 Ask the stub for the current state of tracepoint number @var{tp} at
38314 address @var{addr}.
38318 @item V@var{hits}:@var{usage}
38319 The tracepoint has been hit @var{hits} times so far during the trace
38320 run, and accounts for @var{usage} in the trace buffer. Note that
38321 @code{while-stepping} steps are not counted as separate hits, but the
38322 steps' space consumption is added into the usage number.
38326 @item qTV:@var{var}
38327 @cindex trace state variable value, remote request
38328 @cindex @samp{qTV} packet
38329 Ask the stub for the value of the trace state variable number @var{var}.
38334 The value of the variable is @var{value}. This will be the current
38335 value of the variable if the user is examining a running target, or a
38336 saved value if the variable was collected in the trace frame that the
38337 user is looking at. Note that multiple requests may result in
38338 different reply values, such as when requesting values while the
38339 program is running.
38342 The value of the variable is unknown. This would occur, for example,
38343 if the user is examining a trace frame in which the requested variable
38348 @cindex @samp{qTfP} packet
38350 @cindex @samp{qTsP} packet
38351 These packets request data about tracepoints that are being used by
38352 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38353 of data, and multiple @code{qTsP} to get additional pieces. Replies
38354 to these packets generally take the form of the @code{QTDP} packets
38355 that define tracepoints. (FIXME add detailed syntax)
38358 @cindex @samp{qTfV} packet
38360 @cindex @samp{qTsV} packet
38361 These packets request data about trace state variables that are on the
38362 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38363 and multiple @code{qTsV} to get additional variables. Replies to
38364 these packets follow the syntax of the @code{QTDV} packets that define
38365 trace state variables.
38371 @cindex @samp{qTfSTM} packet
38372 @cindex @samp{qTsSTM} packet
38373 These packets request data about static tracepoint markers that exist
38374 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38375 first piece of data, and multiple @code{qTsSTM} to get additional
38376 pieces. Replies to these packets take the following form:
38380 @item m @var{address}:@var{id}:@var{extra}
38382 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38383 a comma-separated list of markers
38385 (lower case letter @samp{L}) denotes end of list.
38387 An error occurred. The error number @var{nn} is given as hex digits.
38389 An empty reply indicates that the request is not supported by the
38393 The @var{address} is encoded in hex;
38394 @var{id} and @var{extra} are strings encoded in hex.
38396 In response to each query, the target will reply with a list of one or
38397 more markers, separated by commas. @value{GDBN} will respond to each
38398 reply with a request for more markers (using the @samp{qs} form of the
38399 query), until the target responds with @samp{l} (lower-case ell, for
38402 @item qTSTMat:@var{address}
38404 @cindex @samp{qTSTMat} packet
38405 This packets requests data about static tracepoint markers in the
38406 target program at @var{address}. Replies to this packet follow the
38407 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38408 tracepoint markers.
38410 @item QTSave:@var{filename}
38411 @cindex @samp{QTSave} packet
38412 This packet directs the target to save trace data to the file name
38413 @var{filename} in the target's filesystem. The @var{filename} is encoded
38414 as a hex string; the interpretation of the file name (relative vs
38415 absolute, wild cards, etc) is up to the target.
38417 @item qTBuffer:@var{offset},@var{len}
38418 @cindex @samp{qTBuffer} packet
38419 Return up to @var{len} bytes of the current contents of trace buffer,
38420 starting at @var{offset}. The trace buffer is treated as if it were
38421 a contiguous collection of traceframes, as per the trace file format.
38422 The reply consists as many hex-encoded bytes as the target can deliver
38423 in a packet; it is not an error to return fewer than were asked for.
38424 A reply consisting of just @code{l} indicates that no bytes are
38427 @item QTBuffer:circular:@var{value}
38428 This packet directs the target to use a circular trace buffer if
38429 @var{value} is 1, or a linear buffer if the value is 0.
38431 @item QTBuffer:size:@var{size}
38432 @anchor{QTBuffer-size}
38433 @cindex @samp{QTBuffer size} packet
38434 This packet directs the target to make the trace buffer be of size
38435 @var{size} if possible. A value of @code{-1} tells the target to
38436 use whatever size it prefers.
38438 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38439 @cindex @samp{QTNotes} packet
38440 This packet adds optional textual notes to the trace run. Allowable
38441 types include @code{user}, @code{notes}, and @code{tstop}, the
38442 @var{text} fields are arbitrary strings, hex-encoded.
38446 @subsection Relocate instruction reply packet
38447 When installing fast tracepoints in memory, the target may need to
38448 relocate the instruction currently at the tracepoint address to a
38449 different address in memory. For most instructions, a simple copy is
38450 enough, but, for example, call instructions that implicitly push the
38451 return address on the stack, and relative branches or other
38452 PC-relative instructions require offset adjustment, so that the effect
38453 of executing the instruction at a different address is the same as if
38454 it had executed in the original location.
38456 In response to several of the tracepoint packets, the target may also
38457 respond with a number of intermediate @samp{qRelocInsn} request
38458 packets before the final result packet, to have @value{GDBN} handle
38459 this relocation operation. If a packet supports this mechanism, its
38460 documentation will explicitly say so. See for example the above
38461 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38462 format of the request is:
38465 @item qRelocInsn:@var{from};@var{to}
38467 This requests @value{GDBN} to copy instruction at address @var{from}
38468 to address @var{to}, possibly adjusted so that executing the
38469 instruction at @var{to} has the same effect as executing it at
38470 @var{from}. @value{GDBN} writes the adjusted instruction to target
38471 memory starting at @var{to}.
38476 @item qRelocInsn:@var{adjusted_size}
38477 Informs the stub the relocation is complete. The @var{adjusted_size} is
38478 the length in bytes of resulting relocated instruction sequence.
38480 A badly formed request was detected, or an error was encountered while
38481 relocating the instruction.
38484 @node Host I/O Packets
38485 @section Host I/O Packets
38486 @cindex Host I/O, remote protocol
38487 @cindex file transfer, remote protocol
38489 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38490 operations on the far side of a remote link. For example, Host I/O is
38491 used to upload and download files to a remote target with its own
38492 filesystem. Host I/O uses the same constant values and data structure
38493 layout as the target-initiated File-I/O protocol. However, the
38494 Host I/O packets are structured differently. The target-initiated
38495 protocol relies on target memory to store parameters and buffers.
38496 Host I/O requests are initiated by @value{GDBN}, and the
38497 target's memory is not involved. @xref{File-I/O Remote Protocol
38498 Extension}, for more details on the target-initiated protocol.
38500 The Host I/O request packets all encode a single operation along with
38501 its arguments. They have this format:
38505 @item vFile:@var{operation}: @var{parameter}@dots{}
38506 @var{operation} is the name of the particular request; the target
38507 should compare the entire packet name up to the second colon when checking
38508 for a supported operation. The format of @var{parameter} depends on
38509 the operation. Numbers are always passed in hexadecimal. Negative
38510 numbers have an explicit minus sign (i.e.@: two's complement is not
38511 used). Strings (e.g.@: filenames) are encoded as a series of
38512 hexadecimal bytes. The last argument to a system call may be a
38513 buffer of escaped binary data (@pxref{Binary Data}).
38517 The valid responses to Host I/O packets are:
38521 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38522 @var{result} is the integer value returned by this operation, usually
38523 non-negative for success and -1 for errors. If an error has occured,
38524 @var{errno} will be included in the result specifying a
38525 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38526 operations which return data, @var{attachment} supplies the data as a
38527 binary buffer. Binary buffers in response packets are escaped in the
38528 normal way (@pxref{Binary Data}). See the individual packet
38529 documentation for the interpretation of @var{result} and
38533 An empty response indicates that this operation is not recognized.
38537 These are the supported Host I/O operations:
38540 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38541 Open a file at @var{filename} and return a file descriptor for it, or
38542 return -1 if an error occurs. The @var{filename} is a string,
38543 @var{flags} is an integer indicating a mask of open flags
38544 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38545 of mode bits to use if the file is created (@pxref{mode_t Values}).
38546 @xref{open}, for details of the open flags and mode values.
38548 @item vFile:close: @var{fd}
38549 Close the open file corresponding to @var{fd} and return 0, or
38550 -1 if an error occurs.
38552 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38553 Read data from the open file corresponding to @var{fd}. Up to
38554 @var{count} bytes will be read from the file, starting at @var{offset}
38555 relative to the start of the file. The target may read fewer bytes;
38556 common reasons include packet size limits and an end-of-file
38557 condition. The number of bytes read is returned. Zero should only be
38558 returned for a successful read at the end of the file, or if
38559 @var{count} was zero.
38561 The data read should be returned as a binary attachment on success.
38562 If zero bytes were read, the response should include an empty binary
38563 attachment (i.e.@: a trailing semicolon). The return value is the
38564 number of target bytes read; the binary attachment may be longer if
38565 some characters were escaped.
38567 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38568 Write @var{data} (a binary buffer) to the open file corresponding
38569 to @var{fd}. Start the write at @var{offset} from the start of the
38570 file. Unlike many @code{write} system calls, there is no
38571 separate @var{count} argument; the length of @var{data} in the
38572 packet is used. @samp{vFile:write} returns the number of bytes written,
38573 which may be shorter than the length of @var{data}, or -1 if an
38576 @item vFile:fstat: @var{fd}
38577 Get information about the open file corresponding to @var{fd}.
38578 On success the information is returned as a binary attachment
38579 and the return value is the size of this attachment in bytes.
38580 If an error occurs the return value is -1. The format of the
38581 returned binary attachment is as described in @ref{struct stat}.
38583 @item vFile:unlink: @var{filename}
38584 Delete the file at @var{filename} on the target. Return 0,
38585 or -1 if an error occurs. The @var{filename} is a string.
38587 @item vFile:readlink: @var{filename}
38588 Read value of symbolic link @var{filename} on the target. Return
38589 the number of bytes read, or -1 if an error occurs.
38591 The data read should be returned as a binary attachment on success.
38592 If zero bytes were read, the response should include an empty binary
38593 attachment (i.e.@: a trailing semicolon). The return value is the
38594 number of target bytes read; the binary attachment may be longer if
38595 some characters were escaped.
38597 @item vFile:setfs: @var{pid}
38598 Select the filesystem on which @code{vFile} operations with
38599 @var{filename} arguments will operate. This is required for
38600 @value{GDBN} to be able to access files on remote targets where
38601 the remote stub does not share a common filesystem with the
38604 If @var{pid} is nonzero, select the filesystem as seen by process
38605 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38606 the remote stub. Return 0 on success, or -1 if an error occurs.
38607 If @code{vFile:setfs:} indicates success, the selected filesystem
38608 remains selected until the next successful @code{vFile:setfs:}
38614 @section Interrupts
38615 @cindex interrupts (remote protocol)
38616 @anchor{interrupting remote targets}
38618 In all-stop mode, when a program on the remote target is running,
38619 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38620 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38621 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38623 The precise meaning of @code{BREAK} is defined by the transport
38624 mechanism and may, in fact, be undefined. @value{GDBN} does not
38625 currently define a @code{BREAK} mechanism for any of the network
38626 interfaces except for TCP, in which case @value{GDBN} sends the
38627 @code{telnet} BREAK sequence.
38629 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38630 transport mechanisms. It is represented by sending the single byte
38631 @code{0x03} without any of the usual packet overhead described in
38632 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38633 transmitted as part of a packet, it is considered to be packet data
38634 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38635 (@pxref{X packet}), used for binary downloads, may include an unescaped
38636 @code{0x03} as part of its packet.
38638 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38639 When Linux kernel receives this sequence from serial port,
38640 it stops execution and connects to gdb.
38642 In non-stop mode, because packet resumptions are asynchronous
38643 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38644 command to the remote stub, even when the target is running. For that
38645 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38646 packet}) with the usual packet framing instead of the single byte
38649 Stubs are not required to recognize these interrupt mechanisms and the
38650 precise meaning associated with receipt of the interrupt is
38651 implementation defined. If the target supports debugging of multiple
38652 threads and/or processes, it should attempt to interrupt all
38653 currently-executing threads and processes.
38654 If the stub is successful at interrupting the
38655 running program, it should send one of the stop
38656 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38657 of successfully stopping the program in all-stop mode, and a stop reply
38658 for each stopped thread in non-stop mode.
38659 Interrupts received while the
38660 program is stopped are queued and the program will be interrupted when
38661 it is resumed next time.
38663 @node Notification Packets
38664 @section Notification Packets
38665 @cindex notification packets
38666 @cindex packets, notification
38668 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38669 packets that require no acknowledgment. Both the GDB and the stub
38670 may send notifications (although the only notifications defined at
38671 present are sent by the stub). Notifications carry information
38672 without incurring the round-trip latency of an acknowledgment, and so
38673 are useful for low-impact communications where occasional packet loss
38676 A notification packet has the form @samp{% @var{data} #
38677 @var{checksum}}, where @var{data} is the content of the notification,
38678 and @var{checksum} is a checksum of @var{data}, computed and formatted
38679 as for ordinary @value{GDBN} packets. A notification's @var{data}
38680 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38681 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38682 to acknowledge the notification's receipt or to report its corruption.
38684 Every notification's @var{data} begins with a name, which contains no
38685 colon characters, followed by a colon character.
38687 Recipients should silently ignore corrupted notifications and
38688 notifications they do not understand. Recipients should restart
38689 timeout periods on receipt of a well-formed notification, whether or
38690 not they understand it.
38692 Senders should only send the notifications described here when this
38693 protocol description specifies that they are permitted. In the
38694 future, we may extend the protocol to permit existing notifications in
38695 new contexts; this rule helps older senders avoid confusing newer
38698 (Older versions of @value{GDBN} ignore bytes received until they see
38699 the @samp{$} byte that begins an ordinary packet, so new stubs may
38700 transmit notifications without fear of confusing older clients. There
38701 are no notifications defined for @value{GDBN} to send at the moment, but we
38702 assume that most older stubs would ignore them, as well.)
38704 Each notification is comprised of three parts:
38706 @item @var{name}:@var{event}
38707 The notification packet is sent by the side that initiates the
38708 exchange (currently, only the stub does that), with @var{event}
38709 carrying the specific information about the notification, and
38710 @var{name} specifying the name of the notification.
38712 The acknowledge sent by the other side, usually @value{GDBN}, to
38713 acknowledge the exchange and request the event.
38716 The purpose of an asynchronous notification mechanism is to report to
38717 @value{GDBN} that something interesting happened in the remote stub.
38719 The remote stub may send notification @var{name}:@var{event}
38720 at any time, but @value{GDBN} acknowledges the notification when
38721 appropriate. The notification event is pending before @value{GDBN}
38722 acknowledges. Only one notification at a time may be pending; if
38723 additional events occur before @value{GDBN} has acknowledged the
38724 previous notification, they must be queued by the stub for later
38725 synchronous transmission in response to @var{ack} packets from
38726 @value{GDBN}. Because the notification mechanism is unreliable,
38727 the stub is permitted to resend a notification if it believes
38728 @value{GDBN} may not have received it.
38730 Specifically, notifications may appear when @value{GDBN} is not
38731 otherwise reading input from the stub, or when @value{GDBN} is
38732 expecting to read a normal synchronous response or a
38733 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38734 Notification packets are distinct from any other communication from
38735 the stub so there is no ambiguity.
38737 After receiving a notification, @value{GDBN} shall acknowledge it by
38738 sending a @var{ack} packet as a regular, synchronous request to the
38739 stub. Such acknowledgment is not required to happen immediately, as
38740 @value{GDBN} is permitted to send other, unrelated packets to the
38741 stub first, which the stub should process normally.
38743 Upon receiving a @var{ack} packet, if the stub has other queued
38744 events to report to @value{GDBN}, it shall respond by sending a
38745 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38746 packet to solicit further responses; again, it is permitted to send
38747 other, unrelated packets as well which the stub should process
38750 If the stub receives a @var{ack} packet and there are no additional
38751 @var{event} to report, the stub shall return an @samp{OK} response.
38752 At this point, @value{GDBN} has finished processing a notification
38753 and the stub has completed sending any queued events. @value{GDBN}
38754 won't accept any new notifications until the final @samp{OK} is
38755 received . If further notification events occur, the stub shall send
38756 a new notification, @value{GDBN} shall accept the notification, and
38757 the process shall be repeated.
38759 The process of asynchronous notification can be illustrated by the
38762 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38765 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38767 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38772 The following notifications are defined:
38773 @multitable @columnfractions 0.12 0.12 0.38 0.38
38782 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38783 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38784 for information on how these notifications are acknowledged by
38786 @tab Report an asynchronous stop event in non-stop mode.
38790 @node Remote Non-Stop
38791 @section Remote Protocol Support for Non-Stop Mode
38793 @value{GDBN}'s remote protocol supports non-stop debugging of
38794 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38795 supports non-stop mode, it should report that to @value{GDBN} by including
38796 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38798 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38799 establishing a new connection with the stub. Entering non-stop mode
38800 does not alter the state of any currently-running threads, but targets
38801 must stop all threads in any already-attached processes when entering
38802 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38803 probe the target state after a mode change.
38805 In non-stop mode, when an attached process encounters an event that
38806 would otherwise be reported with a stop reply, it uses the
38807 asynchronous notification mechanism (@pxref{Notification Packets}) to
38808 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38809 in all processes are stopped when a stop reply is sent, in non-stop
38810 mode only the thread reporting the stop event is stopped. That is,
38811 when reporting a @samp{S} or @samp{T} response to indicate completion
38812 of a step operation, hitting a breakpoint, or a fault, only the
38813 affected thread is stopped; any other still-running threads continue
38814 to run. When reporting a @samp{W} or @samp{X} response, all running
38815 threads belonging to other attached processes continue to run.
38817 In non-stop mode, the target shall respond to the @samp{?} packet as
38818 follows. First, any incomplete stop reply notification/@samp{vStopped}
38819 sequence in progress is abandoned. The target must begin a new
38820 sequence reporting stop events for all stopped threads, whether or not
38821 it has previously reported those events to @value{GDBN}. The first
38822 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38823 subsequent stop replies are sent as responses to @samp{vStopped} packets
38824 using the mechanism described above. The target must not send
38825 asynchronous stop reply notifications until the sequence is complete.
38826 If all threads are running when the target receives the @samp{?} packet,
38827 or if the target is not attached to any process, it shall respond
38830 If the stub supports non-stop mode, it should also support the
38831 @samp{swbreak} stop reason if software breakpoints are supported, and
38832 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38833 (@pxref{swbreak stop reason}). This is because given the asynchronous
38834 nature of non-stop mode, between the time a thread hits a breakpoint
38835 and the time the event is finally processed by @value{GDBN}, the
38836 breakpoint may have already been removed from the target. Due to
38837 this, @value{GDBN} needs to be able to tell whether a trap stop was
38838 caused by a delayed breakpoint event, which should be ignored, as
38839 opposed to a random trap signal, which should be reported to the user.
38840 Note the @samp{swbreak} feature implies that the target is responsible
38841 for adjusting the PC when a software breakpoint triggers, if
38842 necessary, such as on the x86 architecture.
38844 @node Packet Acknowledgment
38845 @section Packet Acknowledgment
38847 @cindex acknowledgment, for @value{GDBN} remote
38848 @cindex packet acknowledgment, for @value{GDBN} remote
38849 By default, when either the host or the target machine receives a packet,
38850 the first response expected is an acknowledgment: either @samp{+} (to indicate
38851 the package was received correctly) or @samp{-} (to request retransmission).
38852 This mechanism allows the @value{GDBN} remote protocol to operate over
38853 unreliable transport mechanisms, such as a serial line.
38855 In cases where the transport mechanism is itself reliable (such as a pipe or
38856 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38857 It may be desirable to disable them in that case to reduce communication
38858 overhead, or for other reasons. This can be accomplished by means of the
38859 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38861 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38862 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38863 and response format still includes the normal checksum, as described in
38864 @ref{Overview}, but the checksum may be ignored by the receiver.
38866 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38867 no-acknowledgment mode, it should report that to @value{GDBN}
38868 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38869 @pxref{qSupported}.
38870 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38871 disabled via the @code{set remote noack-packet off} command
38872 (@pxref{Remote Configuration}),
38873 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38874 Only then may the stub actually turn off packet acknowledgments.
38875 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38876 response, which can be safely ignored by the stub.
38878 Note that @code{set remote noack-packet} command only affects negotiation
38879 between @value{GDBN} and the stub when subsequent connections are made;
38880 it does not affect the protocol acknowledgment state for any current
38882 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38883 new connection is established,
38884 there is also no protocol request to re-enable the acknowledgments
38885 for the current connection, once disabled.
38890 Example sequence of a target being re-started. Notice how the restart
38891 does not get any direct output:
38896 @emph{target restarts}
38899 <- @code{T001:1234123412341234}
38903 Example sequence of a target being stepped by a single instruction:
38906 -> @code{G1445@dots{}}
38911 <- @code{T001:1234123412341234}
38915 <- @code{1455@dots{}}
38919 @node File-I/O Remote Protocol Extension
38920 @section File-I/O Remote Protocol Extension
38921 @cindex File-I/O remote protocol extension
38924 * File-I/O Overview::
38925 * Protocol Basics::
38926 * The F Request Packet::
38927 * The F Reply Packet::
38928 * The Ctrl-C Message::
38930 * List of Supported Calls::
38931 * Protocol-specific Representation of Datatypes::
38933 * File-I/O Examples::
38936 @node File-I/O Overview
38937 @subsection File-I/O Overview
38938 @cindex file-i/o overview
38940 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38941 target to use the host's file system and console I/O to perform various
38942 system calls. System calls on the target system are translated into a
38943 remote protocol packet to the host system, which then performs the needed
38944 actions and returns a response packet to the target system.
38945 This simulates file system operations even on targets that lack file systems.
38947 The protocol is defined to be independent of both the host and target systems.
38948 It uses its own internal representation of datatypes and values. Both
38949 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38950 translating the system-dependent value representations into the internal
38951 protocol representations when data is transmitted.
38953 The communication is synchronous. A system call is possible only when
38954 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38955 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38956 the target is stopped to allow deterministic access to the target's
38957 memory. Therefore File-I/O is not interruptible by target signals. On
38958 the other hand, it is possible to interrupt File-I/O by a user interrupt
38959 (@samp{Ctrl-C}) within @value{GDBN}.
38961 The target's request to perform a host system call does not finish
38962 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38963 after finishing the system call, the target returns to continuing the
38964 previous activity (continue, step). No additional continue or step
38965 request from @value{GDBN} is required.
38968 (@value{GDBP}) continue
38969 <- target requests 'system call X'
38970 target is stopped, @value{GDBN} executes system call
38971 -> @value{GDBN} returns result
38972 ... target continues, @value{GDBN} returns to wait for the target
38973 <- target hits breakpoint and sends a Txx packet
38976 The protocol only supports I/O on the console and to regular files on
38977 the host file system. Character or block special devices, pipes,
38978 named pipes, sockets or any other communication method on the host
38979 system are not supported by this protocol.
38981 File I/O is not supported in non-stop mode.
38983 @node Protocol Basics
38984 @subsection Protocol Basics
38985 @cindex protocol basics, file-i/o
38987 The File-I/O protocol uses the @code{F} packet as the request as well
38988 as reply packet. Since a File-I/O system call can only occur when
38989 @value{GDBN} is waiting for a response from the continuing or stepping target,
38990 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38991 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38992 This @code{F} packet contains all information needed to allow @value{GDBN}
38993 to call the appropriate host system call:
38997 A unique identifier for the requested system call.
39000 All parameters to the system call. Pointers are given as addresses
39001 in the target memory address space. Pointers to strings are given as
39002 pointer/length pair. Numerical values are given as they are.
39003 Numerical control flags are given in a protocol-specific representation.
39007 At this point, @value{GDBN} has to perform the following actions.
39011 If the parameters include pointer values to data needed as input to a
39012 system call, @value{GDBN} requests this data from the target with a
39013 standard @code{m} packet request. This additional communication has to be
39014 expected by the target implementation and is handled as any other @code{m}
39018 @value{GDBN} translates all value from protocol representation to host
39019 representation as needed. Datatypes are coerced into the host types.
39022 @value{GDBN} calls the system call.
39025 It then coerces datatypes back to protocol representation.
39028 If the system call is expected to return data in buffer space specified
39029 by pointer parameters to the call, the data is transmitted to the
39030 target using a @code{M} or @code{X} packet. This packet has to be expected
39031 by the target implementation and is handled as any other @code{M} or @code{X}
39036 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39037 necessary information for the target to continue. This at least contains
39044 @code{errno}, if has been changed by the system call.
39051 After having done the needed type and value coercion, the target continues
39052 the latest continue or step action.
39054 @node The F Request Packet
39055 @subsection The @code{F} Request Packet
39056 @cindex file-i/o request packet
39057 @cindex @code{F} request packet
39059 The @code{F} request packet has the following format:
39062 @item F@var{call-id},@var{parameter@dots{}}
39064 @var{call-id} is the identifier to indicate the host system call to be called.
39065 This is just the name of the function.
39067 @var{parameter@dots{}} are the parameters to the system call.
39068 Parameters are hexadecimal integer values, either the actual values in case
39069 of scalar datatypes, pointers to target buffer space in case of compound
39070 datatypes and unspecified memory areas, or pointer/length pairs in case
39071 of string parameters. These are appended to the @var{call-id} as a
39072 comma-delimited list. All values are transmitted in ASCII
39073 string representation, pointer/length pairs separated by a slash.
39079 @node The F Reply Packet
39080 @subsection The @code{F} Reply Packet
39081 @cindex file-i/o reply packet
39082 @cindex @code{F} reply packet
39084 The @code{F} reply packet has the following format:
39088 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39090 @var{retcode} is the return code of the system call as hexadecimal value.
39092 @var{errno} is the @code{errno} set by the call, in protocol-specific
39094 This parameter can be omitted if the call was successful.
39096 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39097 case, @var{errno} must be sent as well, even if the call was successful.
39098 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39105 or, if the call was interrupted before the host call has been performed:
39112 assuming 4 is the protocol-specific representation of @code{EINTR}.
39117 @node The Ctrl-C Message
39118 @subsection The @samp{Ctrl-C} Message
39119 @cindex ctrl-c message, in file-i/o protocol
39121 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39122 reply packet (@pxref{The F Reply Packet}),
39123 the target should behave as if it had
39124 gotten a break message. The meaning for the target is ``system call
39125 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39126 (as with a break message) and return to @value{GDBN} with a @code{T02}
39129 It's important for the target to know in which
39130 state the system call was interrupted. There are two possible cases:
39134 The system call hasn't been performed on the host yet.
39137 The system call on the host has been finished.
39141 These two states can be distinguished by the target by the value of the
39142 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39143 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39144 on POSIX systems. In any other case, the target may presume that the
39145 system call has been finished --- successfully or not --- and should behave
39146 as if the break message arrived right after the system call.
39148 @value{GDBN} must behave reliably. If the system call has not been called
39149 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39150 @code{errno} in the packet. If the system call on the host has been finished
39151 before the user requests a break, the full action must be finished by
39152 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39153 The @code{F} packet may only be sent when either nothing has happened
39154 or the full action has been completed.
39157 @subsection Console I/O
39158 @cindex console i/o as part of file-i/o
39160 By default and if not explicitly closed by the target system, the file
39161 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39162 on the @value{GDBN} console is handled as any other file output operation
39163 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39164 by @value{GDBN} so that after the target read request from file descriptor
39165 0 all following typing is buffered until either one of the following
39170 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39172 system call is treated as finished.
39175 The user presses @key{RET}. This is treated as end of input with a trailing
39179 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39180 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39184 If the user has typed more characters than fit in the buffer given to
39185 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39186 either another @code{read(0, @dots{})} is requested by the target, or debugging
39187 is stopped at the user's request.
39190 @node List of Supported Calls
39191 @subsection List of Supported Calls
39192 @cindex list of supported file-i/o calls
39209 @unnumberedsubsubsec open
39210 @cindex open, file-i/o system call
39215 int open(const char *pathname, int flags);
39216 int open(const char *pathname, int flags, mode_t mode);
39220 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39223 @var{flags} is the bitwise @code{OR} of the following values:
39227 If the file does not exist it will be created. The host
39228 rules apply as far as file ownership and time stamps
39232 When used with @code{O_CREAT}, if the file already exists it is
39233 an error and open() fails.
39236 If the file already exists and the open mode allows
39237 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39238 truncated to zero length.
39241 The file is opened in append mode.
39244 The file is opened for reading only.
39247 The file is opened for writing only.
39250 The file is opened for reading and writing.
39254 Other bits are silently ignored.
39258 @var{mode} is the bitwise @code{OR} of the following values:
39262 User has read permission.
39265 User has write permission.
39268 Group has read permission.
39271 Group has write permission.
39274 Others have read permission.
39277 Others have write permission.
39281 Other bits are silently ignored.
39284 @item Return value:
39285 @code{open} returns the new file descriptor or -1 if an error
39292 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39295 @var{pathname} refers to a directory.
39298 The requested access is not allowed.
39301 @var{pathname} was too long.
39304 A directory component in @var{pathname} does not exist.
39307 @var{pathname} refers to a device, pipe, named pipe or socket.
39310 @var{pathname} refers to a file on a read-only filesystem and
39311 write access was requested.
39314 @var{pathname} is an invalid pointer value.
39317 No space on device to create the file.
39320 The process already has the maximum number of files open.
39323 The limit on the total number of files open on the system
39327 The call was interrupted by the user.
39333 @unnumberedsubsubsec close
39334 @cindex close, file-i/o system call
39343 @samp{Fclose,@var{fd}}
39345 @item Return value:
39346 @code{close} returns zero on success, or -1 if an error occurred.
39352 @var{fd} isn't a valid open file descriptor.
39355 The call was interrupted by the user.
39361 @unnumberedsubsubsec read
39362 @cindex read, file-i/o system call
39367 int read(int fd, void *buf, unsigned int count);
39371 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39373 @item Return value:
39374 On success, the number of bytes read is returned.
39375 Zero indicates end of file. If count is zero, read
39376 returns zero as well. On error, -1 is returned.
39382 @var{fd} is not a valid file descriptor or is not open for
39386 @var{bufptr} is an invalid pointer value.
39389 The call was interrupted by the user.
39395 @unnumberedsubsubsec write
39396 @cindex write, file-i/o system call
39401 int write(int fd, const void *buf, unsigned int count);
39405 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39407 @item Return value:
39408 On success, the number of bytes written are returned.
39409 Zero indicates nothing was written. On error, -1
39416 @var{fd} is not a valid file descriptor or is not open for
39420 @var{bufptr} is an invalid pointer value.
39423 An attempt was made to write a file that exceeds the
39424 host-specific maximum file size allowed.
39427 No space on device to write the data.
39430 The call was interrupted by the user.
39436 @unnumberedsubsubsec lseek
39437 @cindex lseek, file-i/o system call
39442 long lseek (int fd, long offset, int flag);
39446 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39448 @var{flag} is one of:
39452 The offset is set to @var{offset} bytes.
39455 The offset is set to its current location plus @var{offset}
39459 The offset is set to the size of the file plus @var{offset}
39463 @item Return value:
39464 On success, the resulting unsigned offset in bytes from
39465 the beginning of the file is returned. Otherwise, a
39466 value of -1 is returned.
39472 @var{fd} is not a valid open file descriptor.
39475 @var{fd} is associated with the @value{GDBN} console.
39478 @var{flag} is not a proper value.
39481 The call was interrupted by the user.
39487 @unnumberedsubsubsec rename
39488 @cindex rename, file-i/o system call
39493 int rename(const char *oldpath, const char *newpath);
39497 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39499 @item Return value:
39500 On success, zero is returned. On error, -1 is returned.
39506 @var{newpath} is an existing directory, but @var{oldpath} is not a
39510 @var{newpath} is a non-empty directory.
39513 @var{oldpath} or @var{newpath} is a directory that is in use by some
39517 An attempt was made to make a directory a subdirectory
39521 A component used as a directory in @var{oldpath} or new
39522 path is not a directory. Or @var{oldpath} is a directory
39523 and @var{newpath} exists but is not a directory.
39526 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39529 No access to the file or the path of the file.
39533 @var{oldpath} or @var{newpath} was too long.
39536 A directory component in @var{oldpath} or @var{newpath} does not exist.
39539 The file is on a read-only filesystem.
39542 The device containing the file has no room for the new
39546 The call was interrupted by the user.
39552 @unnumberedsubsubsec unlink
39553 @cindex unlink, file-i/o system call
39558 int unlink(const char *pathname);
39562 @samp{Funlink,@var{pathnameptr}/@var{len}}
39564 @item Return value:
39565 On success, zero is returned. On error, -1 is returned.
39571 No access to the file or the path of the file.
39574 The system does not allow unlinking of directories.
39577 The file @var{pathname} cannot be unlinked because it's
39578 being used by another process.
39581 @var{pathnameptr} is an invalid pointer value.
39584 @var{pathname} was too long.
39587 A directory component in @var{pathname} does not exist.
39590 A component of the path is not a directory.
39593 The file is on a read-only filesystem.
39596 The call was interrupted by the user.
39602 @unnumberedsubsubsec stat/fstat
39603 @cindex fstat, file-i/o system call
39604 @cindex stat, file-i/o system call
39609 int stat(const char *pathname, struct stat *buf);
39610 int fstat(int fd, struct stat *buf);
39614 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39615 @samp{Ffstat,@var{fd},@var{bufptr}}
39617 @item Return value:
39618 On success, zero is returned. On error, -1 is returned.
39624 @var{fd} is not a valid open file.
39627 A directory component in @var{pathname} does not exist or the
39628 path is an empty string.
39631 A component of the path is not a directory.
39634 @var{pathnameptr} is an invalid pointer value.
39637 No access to the file or the path of the file.
39640 @var{pathname} was too long.
39643 The call was interrupted by the user.
39649 @unnumberedsubsubsec gettimeofday
39650 @cindex gettimeofday, file-i/o system call
39655 int gettimeofday(struct timeval *tv, void *tz);
39659 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39661 @item Return value:
39662 On success, 0 is returned, -1 otherwise.
39668 @var{tz} is a non-NULL pointer.
39671 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39677 @unnumberedsubsubsec isatty
39678 @cindex isatty, file-i/o system call
39683 int isatty(int fd);
39687 @samp{Fisatty,@var{fd}}
39689 @item Return value:
39690 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39696 The call was interrupted by the user.
39701 Note that the @code{isatty} call is treated as a special case: it returns
39702 1 to the target if the file descriptor is attached
39703 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39704 would require implementing @code{ioctl} and would be more complex than
39709 @unnumberedsubsubsec system
39710 @cindex system, file-i/o system call
39715 int system(const char *command);
39719 @samp{Fsystem,@var{commandptr}/@var{len}}
39721 @item Return value:
39722 If @var{len} is zero, the return value indicates whether a shell is
39723 available. A zero return value indicates a shell is not available.
39724 For non-zero @var{len}, the value returned is -1 on error and the
39725 return status of the command otherwise. Only the exit status of the
39726 command is returned, which is extracted from the host's @code{system}
39727 return value by calling @code{WEXITSTATUS(retval)}. In case
39728 @file{/bin/sh} could not be executed, 127 is returned.
39734 The call was interrupted by the user.
39739 @value{GDBN} takes over the full task of calling the necessary host calls
39740 to perform the @code{system} call. The return value of @code{system} on
39741 the host is simplified before it's returned
39742 to the target. Any termination signal information from the child process
39743 is discarded, and the return value consists
39744 entirely of the exit status of the called command.
39746 Due to security concerns, the @code{system} call is by default refused
39747 by @value{GDBN}. The user has to allow this call explicitly with the
39748 @code{set remote system-call-allowed 1} command.
39751 @item set remote system-call-allowed
39752 @kindex set remote system-call-allowed
39753 Control whether to allow the @code{system} calls in the File I/O
39754 protocol for the remote target. The default is zero (disabled).
39756 @item show remote system-call-allowed
39757 @kindex show remote system-call-allowed
39758 Show whether the @code{system} calls are allowed in the File I/O
39762 @node Protocol-specific Representation of Datatypes
39763 @subsection Protocol-specific Representation of Datatypes
39764 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39767 * Integral Datatypes::
39769 * Memory Transfer::
39774 @node Integral Datatypes
39775 @unnumberedsubsubsec Integral Datatypes
39776 @cindex integral datatypes, in file-i/o protocol
39778 The integral datatypes used in the system calls are @code{int},
39779 @code{unsigned int}, @code{long}, @code{unsigned long},
39780 @code{mode_t}, and @code{time_t}.
39782 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39783 implemented as 32 bit values in this protocol.
39785 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39787 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39788 in @file{limits.h}) to allow range checking on host and target.
39790 @code{time_t} datatypes are defined as seconds since the Epoch.
39792 All integral datatypes transferred as part of a memory read or write of a
39793 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39796 @node Pointer Values
39797 @unnumberedsubsubsec Pointer Values
39798 @cindex pointer values, in file-i/o protocol
39800 Pointers to target data are transmitted as they are. An exception
39801 is made for pointers to buffers for which the length isn't
39802 transmitted as part of the function call, namely strings. Strings
39803 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39810 which is a pointer to data of length 18 bytes at position 0x1aaf.
39811 The length is defined as the full string length in bytes, including
39812 the trailing null byte. For example, the string @code{"hello world"}
39813 at address 0x123456 is transmitted as
39819 @node Memory Transfer
39820 @unnumberedsubsubsec Memory Transfer
39821 @cindex memory transfer, in file-i/o protocol
39823 Structured data which is transferred using a memory read or write (for
39824 example, a @code{struct stat}) is expected to be in a protocol-specific format
39825 with all scalar multibyte datatypes being big endian. Translation to
39826 this representation needs to be done both by the target before the @code{F}
39827 packet is sent, and by @value{GDBN} before
39828 it transfers memory to the target. Transferred pointers to structured
39829 data should point to the already-coerced data at any time.
39833 @unnumberedsubsubsec struct stat
39834 @cindex struct stat, in file-i/o protocol
39836 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39837 is defined as follows:
39841 unsigned int st_dev; /* device */
39842 unsigned int st_ino; /* inode */
39843 mode_t st_mode; /* protection */
39844 unsigned int st_nlink; /* number of hard links */
39845 unsigned int st_uid; /* user ID of owner */
39846 unsigned int st_gid; /* group ID of owner */
39847 unsigned int st_rdev; /* device type (if inode device) */
39848 unsigned long st_size; /* total size, in bytes */
39849 unsigned long st_blksize; /* blocksize for filesystem I/O */
39850 unsigned long st_blocks; /* number of blocks allocated */
39851 time_t st_atime; /* time of last access */
39852 time_t st_mtime; /* time of last modification */
39853 time_t st_ctime; /* time of last change */
39857 The integral datatypes conform to the definitions given in the
39858 appropriate section (see @ref{Integral Datatypes}, for details) so this
39859 structure is of size 64 bytes.
39861 The values of several fields have a restricted meaning and/or
39867 A value of 0 represents a file, 1 the console.
39870 No valid meaning for the target. Transmitted unchanged.
39873 Valid mode bits are described in @ref{Constants}. Any other
39874 bits have currently no meaning for the target.
39879 No valid meaning for the target. Transmitted unchanged.
39884 These values have a host and file system dependent
39885 accuracy. Especially on Windows hosts, the file system may not
39886 support exact timing values.
39889 The target gets a @code{struct stat} of the above representation and is
39890 responsible for coercing it to the target representation before
39893 Note that due to size differences between the host, target, and protocol
39894 representations of @code{struct stat} members, these members could eventually
39895 get truncated on the target.
39897 @node struct timeval
39898 @unnumberedsubsubsec struct timeval
39899 @cindex struct timeval, in file-i/o protocol
39901 The buffer of type @code{struct timeval} used by the File-I/O protocol
39902 is defined as follows:
39906 time_t tv_sec; /* second */
39907 long tv_usec; /* microsecond */
39911 The integral datatypes conform to the definitions given in the
39912 appropriate section (see @ref{Integral Datatypes}, for details) so this
39913 structure is of size 8 bytes.
39916 @subsection Constants
39917 @cindex constants, in file-i/o protocol
39919 The following values are used for the constants inside of the
39920 protocol. @value{GDBN} and target are responsible for translating these
39921 values before and after the call as needed.
39932 @unnumberedsubsubsec Open Flags
39933 @cindex open flags, in file-i/o protocol
39935 All values are given in hexadecimal representation.
39947 @node mode_t Values
39948 @unnumberedsubsubsec mode_t Values
39949 @cindex mode_t values, in file-i/o protocol
39951 All values are given in octal representation.
39968 @unnumberedsubsubsec Errno Values
39969 @cindex errno values, in file-i/o protocol
39971 All values are given in decimal representation.
39996 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39997 any error value not in the list of supported error numbers.
40000 @unnumberedsubsubsec Lseek Flags
40001 @cindex lseek flags, in file-i/o protocol
40010 @unnumberedsubsubsec Limits
40011 @cindex limits, in file-i/o protocol
40013 All values are given in decimal representation.
40016 INT_MIN -2147483648
40018 UINT_MAX 4294967295
40019 LONG_MIN -9223372036854775808
40020 LONG_MAX 9223372036854775807
40021 ULONG_MAX 18446744073709551615
40024 @node File-I/O Examples
40025 @subsection File-I/O Examples
40026 @cindex file-i/o examples
40028 Example sequence of a write call, file descriptor 3, buffer is at target
40029 address 0x1234, 6 bytes should be written:
40032 <- @code{Fwrite,3,1234,6}
40033 @emph{request memory read from target}
40036 @emph{return "6 bytes written"}
40040 Example sequence of a read call, file descriptor 3, buffer is at target
40041 address 0x1234, 6 bytes should be read:
40044 <- @code{Fread,3,1234,6}
40045 @emph{request memory write to target}
40046 -> @code{X1234,6:XXXXXX}
40047 @emph{return "6 bytes read"}
40051 Example sequence of a read call, call fails on the host due to invalid
40052 file descriptor (@code{EBADF}):
40055 <- @code{Fread,3,1234,6}
40059 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40063 <- @code{Fread,3,1234,6}
40068 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40072 <- @code{Fread,3,1234,6}
40073 -> @code{X1234,6:XXXXXX}
40077 @node Library List Format
40078 @section Library List Format
40079 @cindex library list format, remote protocol
40081 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40082 same process as your application to manage libraries. In this case,
40083 @value{GDBN} can use the loader's symbol table and normal memory
40084 operations to maintain a list of shared libraries. On other
40085 platforms, the operating system manages loaded libraries.
40086 @value{GDBN} can not retrieve the list of currently loaded libraries
40087 through memory operations, so it uses the @samp{qXfer:libraries:read}
40088 packet (@pxref{qXfer library list read}) instead. The remote stub
40089 queries the target's operating system and reports which libraries
40092 The @samp{qXfer:libraries:read} packet returns an XML document which
40093 lists loaded libraries and their offsets. Each library has an
40094 associated name and one or more segment or section base addresses,
40095 which report where the library was loaded in memory.
40097 For the common case of libraries that are fully linked binaries, the
40098 library should have a list of segments. If the target supports
40099 dynamic linking of a relocatable object file, its library XML element
40100 should instead include a list of allocated sections. The segment or
40101 section bases are start addresses, not relocation offsets; they do not
40102 depend on the library's link-time base addresses.
40104 @value{GDBN} must be linked with the Expat library to support XML
40105 library lists. @xref{Expat}.
40107 A simple memory map, with one loaded library relocated by a single
40108 offset, looks like this:
40112 <library name="/lib/libc.so.6">
40113 <segment address="0x10000000"/>
40118 Another simple memory map, with one loaded library with three
40119 allocated sections (.text, .data, .bss), looks like this:
40123 <library name="sharedlib.o">
40124 <section address="0x10000000"/>
40125 <section address="0x20000000"/>
40126 <section address="0x30000000"/>
40131 The format of a library list is described by this DTD:
40134 <!-- library-list: Root element with versioning -->
40135 <!ELEMENT library-list (library)*>
40136 <!ATTLIST library-list version CDATA #FIXED "1.0">
40137 <!ELEMENT library (segment*, section*)>
40138 <!ATTLIST library name CDATA #REQUIRED>
40139 <!ELEMENT segment EMPTY>
40140 <!ATTLIST segment address CDATA #REQUIRED>
40141 <!ELEMENT section EMPTY>
40142 <!ATTLIST section address CDATA #REQUIRED>
40145 In addition, segments and section descriptors cannot be mixed within a
40146 single library element, and you must supply at least one segment or
40147 section for each library.
40149 @node Library List Format for SVR4 Targets
40150 @section Library List Format for SVR4 Targets
40151 @cindex library list format, remote protocol
40153 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40154 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40155 shared libraries. Still a special library list provided by this packet is
40156 more efficient for the @value{GDBN} remote protocol.
40158 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40159 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40160 target, the following parameters are reported:
40164 @code{name}, the absolute file name from the @code{l_name} field of
40165 @code{struct link_map}.
40167 @code{lm} with address of @code{struct link_map} used for TLS
40168 (Thread Local Storage) access.
40170 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40171 @code{struct link_map}. For prelinked libraries this is not an absolute
40172 memory address. It is a displacement of absolute memory address against
40173 address the file was prelinked to during the library load.
40175 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40178 Additionally the single @code{main-lm} attribute specifies address of
40179 @code{struct link_map} used for the main executable. This parameter is used
40180 for TLS access and its presence is optional.
40182 @value{GDBN} must be linked with the Expat library to support XML
40183 SVR4 library lists. @xref{Expat}.
40185 A simple memory map, with two loaded libraries (which do not use prelink),
40189 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40190 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40192 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40194 </library-list-svr>
40197 The format of an SVR4 library list is described by this DTD:
40200 <!-- library-list-svr4: Root element with versioning -->
40201 <!ELEMENT library-list-svr4 (library)*>
40202 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40203 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40204 <!ELEMENT library EMPTY>
40205 <!ATTLIST library name CDATA #REQUIRED>
40206 <!ATTLIST library lm CDATA #REQUIRED>
40207 <!ATTLIST library l_addr CDATA #REQUIRED>
40208 <!ATTLIST library l_ld CDATA #REQUIRED>
40211 @node Memory Map Format
40212 @section Memory Map Format
40213 @cindex memory map format
40215 To be able to write into flash memory, @value{GDBN} needs to obtain a
40216 memory map from the target. This section describes the format of the
40219 The memory map is obtained using the @samp{qXfer:memory-map:read}
40220 (@pxref{qXfer memory map read}) packet and is an XML document that
40221 lists memory regions.
40223 @value{GDBN} must be linked with the Expat library to support XML
40224 memory maps. @xref{Expat}.
40226 The top-level structure of the document is shown below:
40229 <?xml version="1.0"?>
40230 <!DOCTYPE memory-map
40231 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40232 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40238 Each region can be either:
40243 A region of RAM starting at @var{addr} and extending for @var{length}
40247 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40252 A region of read-only memory:
40255 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40260 A region of flash memory, with erasure blocks @var{blocksize}
40264 <memory type="flash" start="@var{addr}" length="@var{length}">
40265 <property name="blocksize">@var{blocksize}</property>
40271 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40272 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40273 packets to write to addresses in such ranges.
40275 The formal DTD for memory map format is given below:
40278 <!-- ................................................... -->
40279 <!-- Memory Map XML DTD ................................ -->
40280 <!-- File: memory-map.dtd .............................. -->
40281 <!-- .................................... .............. -->
40282 <!-- memory-map.dtd -->
40283 <!-- memory-map: Root element with versioning -->
40284 <!ELEMENT memory-map (memory | property)>
40285 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40286 <!ELEMENT memory (property)>
40287 <!-- memory: Specifies a memory region,
40288 and its type, or device. -->
40289 <!ATTLIST memory type CDATA #REQUIRED
40290 start CDATA #REQUIRED
40291 length CDATA #REQUIRED
40292 device CDATA #IMPLIED>
40293 <!-- property: Generic attribute tag -->
40294 <!ELEMENT property (#PCDATA | property)*>
40295 <!ATTLIST property name CDATA #REQUIRED>
40298 @node Thread List Format
40299 @section Thread List Format
40300 @cindex thread list format
40302 To efficiently update the list of threads and their attributes,
40303 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40304 (@pxref{qXfer threads read}) and obtains the XML document with
40305 the following structure:
40308 <?xml version="1.0"?>
40310 <thread id="id" core="0" name="name">
40311 ... description ...
40316 Each @samp{thread} element must have the @samp{id} attribute that
40317 identifies the thread (@pxref{thread-id syntax}). The
40318 @samp{core} attribute, if present, specifies which processor core
40319 the thread was last executing on. The @samp{name} attribute, if
40320 present, specifies the human-readable name of the thread. The content
40321 of the of @samp{thread} element is interpreted as human-readable
40322 auxiliary information.
40324 @node Traceframe Info Format
40325 @section Traceframe Info Format
40326 @cindex traceframe info format
40328 To be able to know which objects in the inferior can be examined when
40329 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40330 memory ranges, registers and trace state variables that have been
40331 collected in a traceframe.
40333 This list is obtained using the @samp{qXfer:traceframe-info:read}
40334 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40336 @value{GDBN} must be linked with the Expat library to support XML
40337 traceframe info discovery. @xref{Expat}.
40339 The top-level structure of the document is shown below:
40342 <?xml version="1.0"?>
40343 <!DOCTYPE traceframe-info
40344 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40345 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40351 Each traceframe block can be either:
40356 A region of collected memory starting at @var{addr} and extending for
40357 @var{length} bytes from there:
40360 <memory start="@var{addr}" length="@var{length}"/>
40364 A block indicating trace state variable numbered @var{number} has been
40368 <tvar id="@var{number}"/>
40373 The formal DTD for the traceframe info format is given below:
40376 <!ELEMENT traceframe-info (memory | tvar)* >
40377 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40379 <!ELEMENT memory EMPTY>
40380 <!ATTLIST memory start CDATA #REQUIRED
40381 length CDATA #REQUIRED>
40383 <!ATTLIST tvar id CDATA #REQUIRED>
40386 @node Branch Trace Format
40387 @section Branch Trace Format
40388 @cindex branch trace format
40390 In order to display the branch trace of an inferior thread,
40391 @value{GDBN} needs to obtain the list of branches. This list is
40392 represented as list of sequential code blocks that are connected via
40393 branches. The code in each block has been executed sequentially.
40395 This list is obtained using the @samp{qXfer:btrace:read}
40396 (@pxref{qXfer btrace read}) packet and is an XML document.
40398 @value{GDBN} must be linked with the Expat library to support XML
40399 traceframe info discovery. @xref{Expat}.
40401 The top-level structure of the document is shown below:
40404 <?xml version="1.0"?>
40406 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40407 "http://sourceware.org/gdb/gdb-btrace.dtd">
40416 A block of sequentially executed instructions starting at @var{begin}
40417 and ending at @var{end}:
40420 <block begin="@var{begin}" end="@var{end}"/>
40425 The formal DTD for the branch trace format is given below:
40428 <!ELEMENT btrace (block* | pt) >
40429 <!ATTLIST btrace version CDATA #FIXED "1.0">
40431 <!ELEMENT block EMPTY>
40432 <!ATTLIST block begin CDATA #REQUIRED
40433 end CDATA #REQUIRED>
40435 <!ELEMENT pt (pt-config?, raw?)>
40437 <!ELEMENT pt-config (cpu?)>
40439 <!ELEMENT cpu EMPTY>
40440 <!ATTLIST cpu vendor CDATA #REQUIRED
40441 family CDATA #REQUIRED
40442 model CDATA #REQUIRED
40443 stepping CDATA #REQUIRED>
40445 <!ELEMENT raw (#PCDATA)>
40448 @node Branch Trace Configuration Format
40449 @section Branch Trace Configuration Format
40450 @cindex branch trace configuration format
40452 For each inferior thread, @value{GDBN} can obtain the branch trace
40453 configuration using the @samp{qXfer:btrace-conf:read}
40454 (@pxref{qXfer btrace-conf read}) packet.
40456 The configuration describes the branch trace format and configuration
40457 settings for that format. The following information is described:
40461 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40464 The size of the @acronym{BTS} ring buffer in bytes.
40467 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40471 The size of the @acronym{Intel PT} ring buffer in bytes.
40475 @value{GDBN} must be linked with the Expat library to support XML
40476 branch trace configuration discovery. @xref{Expat}.
40478 The formal DTD for the branch trace configuration format is given below:
40481 <!ELEMENT btrace-conf (bts?, pt?)>
40482 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40484 <!ELEMENT bts EMPTY>
40485 <!ATTLIST bts size CDATA #IMPLIED>
40487 <!ELEMENT pt EMPTY>
40488 <!ATTLIST pt size CDATA #IMPLIED>
40491 @include agentexpr.texi
40493 @node Target Descriptions
40494 @appendix Target Descriptions
40495 @cindex target descriptions
40497 One of the challenges of using @value{GDBN} to debug embedded systems
40498 is that there are so many minor variants of each processor
40499 architecture in use. It is common practice for vendors to start with
40500 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40501 and then make changes to adapt it to a particular market niche. Some
40502 architectures have hundreds of variants, available from dozens of
40503 vendors. This leads to a number of problems:
40507 With so many different customized processors, it is difficult for
40508 the @value{GDBN} maintainers to keep up with the changes.
40510 Since individual variants may have short lifetimes or limited
40511 audiences, it may not be worthwhile to carry information about every
40512 variant in the @value{GDBN} source tree.
40514 When @value{GDBN} does support the architecture of the embedded system
40515 at hand, the task of finding the correct architecture name to give the
40516 @command{set architecture} command can be error-prone.
40519 To address these problems, the @value{GDBN} remote protocol allows a
40520 target system to not only identify itself to @value{GDBN}, but to
40521 actually describe its own features. This lets @value{GDBN} support
40522 processor variants it has never seen before --- to the extent that the
40523 descriptions are accurate, and that @value{GDBN} understands them.
40525 @value{GDBN} must be linked with the Expat library to support XML
40526 target descriptions. @xref{Expat}.
40529 * Retrieving Descriptions:: How descriptions are fetched from a target.
40530 * Target Description Format:: The contents of a target description.
40531 * Predefined Target Types:: Standard types available for target
40533 * Enum Target Types:: How to define enum target types.
40534 * Standard Target Features:: Features @value{GDBN} knows about.
40537 @node Retrieving Descriptions
40538 @section Retrieving Descriptions
40540 Target descriptions can be read from the target automatically, or
40541 specified by the user manually. The default behavior is to read the
40542 description from the target. @value{GDBN} retrieves it via the remote
40543 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40544 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40545 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40546 XML document, of the form described in @ref{Target Description
40549 Alternatively, you can specify a file to read for the target description.
40550 If a file is set, the target will not be queried. The commands to
40551 specify a file are:
40554 @cindex set tdesc filename
40555 @item set tdesc filename @var{path}
40556 Read the target description from @var{path}.
40558 @cindex unset tdesc filename
40559 @item unset tdesc filename
40560 Do not read the XML target description from a file. @value{GDBN}
40561 will use the description supplied by the current target.
40563 @cindex show tdesc filename
40564 @item show tdesc filename
40565 Show the filename to read for a target description, if any.
40569 @node Target Description Format
40570 @section Target Description Format
40571 @cindex target descriptions, XML format
40573 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40574 document which complies with the Document Type Definition provided in
40575 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40576 means you can use generally available tools like @command{xmllint} to
40577 check that your feature descriptions are well-formed and valid.
40578 However, to help people unfamiliar with XML write descriptions for
40579 their targets, we also describe the grammar here.
40581 Target descriptions can identify the architecture of the remote target
40582 and (for some architectures) provide information about custom register
40583 sets. They can also identify the OS ABI of the remote target.
40584 @value{GDBN} can use this information to autoconfigure for your
40585 target, or to warn you if you connect to an unsupported target.
40587 Here is a simple target description:
40590 <target version="1.0">
40591 <architecture>i386:x86-64</architecture>
40596 This minimal description only says that the target uses
40597 the x86-64 architecture.
40599 A target description has the following overall form, with [ ] marking
40600 optional elements and @dots{} marking repeatable elements. The elements
40601 are explained further below.
40604 <?xml version="1.0"?>
40605 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40606 <target version="1.0">
40607 @r{[}@var{architecture}@r{]}
40608 @r{[}@var{osabi}@r{]}
40609 @r{[}@var{compatible}@r{]}
40610 @r{[}@var{feature}@dots{}@r{]}
40615 The description is generally insensitive to whitespace and line
40616 breaks, under the usual common-sense rules. The XML version
40617 declaration and document type declaration can generally be omitted
40618 (@value{GDBN} does not require them), but specifying them may be
40619 useful for XML validation tools. The @samp{version} attribute for
40620 @samp{<target>} may also be omitted, but we recommend
40621 including it; if future versions of @value{GDBN} use an incompatible
40622 revision of @file{gdb-target.dtd}, they will detect and report
40623 the version mismatch.
40625 @subsection Inclusion
40626 @cindex target descriptions, inclusion
40629 @cindex <xi:include>
40632 It can sometimes be valuable to split a target description up into
40633 several different annexes, either for organizational purposes, or to
40634 share files between different possible target descriptions. You can
40635 divide a description into multiple files by replacing any element of
40636 the target description with an inclusion directive of the form:
40639 <xi:include href="@var{document}"/>
40643 When @value{GDBN} encounters an element of this form, it will retrieve
40644 the named XML @var{document}, and replace the inclusion directive with
40645 the contents of that document. If the current description was read
40646 using @samp{qXfer}, then so will be the included document;
40647 @var{document} will be interpreted as the name of an annex. If the
40648 current description was read from a file, @value{GDBN} will look for
40649 @var{document} as a file in the same directory where it found the
40650 original description.
40652 @subsection Architecture
40653 @cindex <architecture>
40655 An @samp{<architecture>} element has this form:
40658 <architecture>@var{arch}</architecture>
40661 @var{arch} is one of the architectures from the set accepted by
40662 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40665 @cindex @code{<osabi>}
40667 This optional field was introduced in @value{GDBN} version 7.0.
40668 Previous versions of @value{GDBN} ignore it.
40670 An @samp{<osabi>} element has this form:
40673 <osabi>@var{abi-name}</osabi>
40676 @var{abi-name} is an OS ABI name from the same selection accepted by
40677 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40679 @subsection Compatible Architecture
40680 @cindex @code{<compatible>}
40682 This optional field was introduced in @value{GDBN} version 7.0.
40683 Previous versions of @value{GDBN} ignore it.
40685 A @samp{<compatible>} element has this form:
40688 <compatible>@var{arch}</compatible>
40691 @var{arch} is one of the architectures from the set accepted by
40692 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40694 A @samp{<compatible>} element is used to specify that the target
40695 is able to run binaries in some other than the main target architecture
40696 given by the @samp{<architecture>} element. For example, on the
40697 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40698 or @code{powerpc:common64}, but the system is able to run binaries
40699 in the @code{spu} architecture as well. The way to describe this
40700 capability with @samp{<compatible>} is as follows:
40703 <architecture>powerpc:common</architecture>
40704 <compatible>spu</compatible>
40707 @subsection Features
40710 Each @samp{<feature>} describes some logical portion of the target
40711 system. Features are currently used to describe available CPU
40712 registers and the types of their contents. A @samp{<feature>} element
40716 <feature name="@var{name}">
40717 @r{[}@var{type}@dots{}@r{]}
40723 Each feature's name should be unique within the description. The name
40724 of a feature does not matter unless @value{GDBN} has some special
40725 knowledge of the contents of that feature; if it does, the feature
40726 should have its standard name. @xref{Standard Target Features}.
40730 Any register's value is a collection of bits which @value{GDBN} must
40731 interpret. The default interpretation is a two's complement integer,
40732 but other types can be requested by name in the register description.
40733 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40734 Target Types}), and the description can define additional composite
40737 Each type element must have an @samp{id} attribute, which gives
40738 a unique (within the containing @samp{<feature>}) name to the type.
40739 Types must be defined before they are used.
40742 Some targets offer vector registers, which can be treated as arrays
40743 of scalar elements. These types are written as @samp{<vector>} elements,
40744 specifying the array element type, @var{type}, and the number of elements,
40748 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40752 If a register's value is usefully viewed in multiple ways, define it
40753 with a union type containing the useful representations. The
40754 @samp{<union>} element contains one or more @samp{<field>} elements,
40755 each of which has a @var{name} and a @var{type}:
40758 <union id="@var{id}">
40759 <field name="@var{name}" type="@var{type}"/>
40766 If a register's value is composed from several separate values, define
40767 it with either a structure type or a flags type.
40768 A flags type may only contain bitfields.
40769 A structure type may either contain only bitfields or contain no bitfields.
40770 If the value contains only bitfields, its total size in bytes must be
40773 Non-bitfield values have a @var{name} and @var{type}.
40776 <struct id="@var{id}">
40777 <field name="@var{name}" type="@var{type}"/>
40782 Both @var{name} and @var{type} values are required.
40783 No implicit padding is added.
40785 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
40788 <struct id="@var{id}" size="@var{size}">
40789 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40795 <flags id="@var{id}" size="@var{size}">
40796 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
40801 The @var{name} value is required.
40802 Bitfield values may be named with the empty string, @samp{""},
40803 in which case the field is ``filler'' and its value is not printed.
40804 Not all bits need to be specified, so ``filler'' fields are optional.
40806 The @var{start} and @var{end} values are required, and @var{type}
40808 The field's @var{start} must be less than or equal to its @var{end},
40809 and zero represents the least significant bit.
40811 The default value of @var{type} is @code{bool} for single bit fields,
40812 and an unsigned integer otherwise.
40814 Which to choose? Structures or flags?
40816 Registers defined with @samp{flags} have these advantages over
40817 defining them with @samp{struct}:
40821 Arithmetic may be performed on them as if they were integers.
40823 They are printed in a more readable fashion.
40826 Registers defined with @samp{struct} have one advantage over
40827 defining them with @samp{flags}:
40831 One can fetch individual fields like in @samp{C}.
40834 (gdb) print $my_struct_reg.field3
40840 @subsection Registers
40843 Each register is represented as an element with this form:
40846 <reg name="@var{name}"
40847 bitsize="@var{size}"
40848 @r{[}regnum="@var{num}"@r{]}
40849 @r{[}save-restore="@var{save-restore}"@r{]}
40850 @r{[}type="@var{type}"@r{]}
40851 @r{[}group="@var{group}"@r{]}/>
40855 The components are as follows:
40860 The register's name; it must be unique within the target description.
40863 The register's size, in bits.
40866 The register's number. If omitted, a register's number is one greater
40867 than that of the previous register (either in the current feature or in
40868 a preceding feature); the first register in the target description
40869 defaults to zero. This register number is used to read or write
40870 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40871 packets, and registers appear in the @code{g} and @code{G} packets
40872 in order of increasing register number.
40875 Whether the register should be preserved across inferior function
40876 calls; this must be either @code{yes} or @code{no}. The default is
40877 @code{yes}, which is appropriate for most registers except for
40878 some system control registers; this is not related to the target's
40882 The type of the register. It may be a predefined type, a type
40883 defined in the current feature, or one of the special types @code{int}
40884 and @code{float}. @code{int} is an integer type of the correct size
40885 for @var{bitsize}, and @code{float} is a floating point type (in the
40886 architecture's normal floating point format) of the correct size for
40887 @var{bitsize}. The default is @code{int}.
40890 The register group to which this register belongs. It must
40891 be either @code{general}, @code{float}, or @code{vector}. If no
40892 @var{group} is specified, @value{GDBN} will not display the register
40893 in @code{info registers}.
40897 @node Predefined Target Types
40898 @section Predefined Target Types
40899 @cindex target descriptions, predefined types
40901 Type definitions in the self-description can build up composite types
40902 from basic building blocks, but can not define fundamental types. Instead,
40903 standard identifiers are provided by @value{GDBN} for the fundamental
40904 types. The currently supported types are:
40909 Boolean type, occupying a single bit.
40916 Signed integer types holding the specified number of bits.
40923 Unsigned integer types holding the specified number of bits.
40927 Pointers to unspecified code and data. The program counter and
40928 any dedicated return address register may be marked as code
40929 pointers; printing a code pointer converts it into a symbolic
40930 address. The stack pointer and any dedicated address registers
40931 may be marked as data pointers.
40934 Single precision IEEE floating point.
40937 Double precision IEEE floating point.
40940 The 12-byte extended precision format used by ARM FPA registers.
40943 The 10-byte extended precision format used by x87 registers.
40946 32bit @sc{eflags} register used by x86.
40949 32bit @sc{mxcsr} register used by x86.
40953 @node Enum Target Types
40954 @section Enum Target Types
40955 @cindex target descriptions, enum types
40957 Enum target types are useful in @samp{struct} and @samp{flags}
40958 register descriptions. @xref{Target Description Format}.
40960 Enum types have a name, size and a list of name/value pairs.
40963 <enum id="@var{id}" size="@var{size}">
40964 <evalue name="@var{name}" value="@var{value}"/>
40969 Enums must be defined before they are used.
40972 <enum id="levels_type" size="4">
40973 <evalue name="low" value="0"/>
40974 <evalue name="high" value="1"/>
40976 <flags id="flags_type" size="4">
40977 <field name="X" start="0"/>
40978 <field name="LEVEL" start="1" end="1" type="levels_type"/>
40980 <reg name="flags" bitsize="32" type="flags_type"/>
40983 Given that description, a value of 3 for the @samp{flags} register
40984 would be printed as:
40987 (gdb) info register flags
40988 flags 0x3 [ X LEVEL=high ]
40991 @node Standard Target Features
40992 @section Standard Target Features
40993 @cindex target descriptions, standard features
40995 A target description must contain either no registers or all the
40996 target's registers. If the description contains no registers, then
40997 @value{GDBN} will assume a default register layout, selected based on
40998 the architecture. If the description contains any registers, the
40999 default layout will not be used; the standard registers must be
41000 described in the target description, in such a way that @value{GDBN}
41001 can recognize them.
41003 This is accomplished by giving specific names to feature elements
41004 which contain standard registers. @value{GDBN} will look for features
41005 with those names and verify that they contain the expected registers;
41006 if any known feature is missing required registers, or if any required
41007 feature is missing, @value{GDBN} will reject the target
41008 description. You can add additional registers to any of the
41009 standard features --- @value{GDBN} will display them just as if
41010 they were added to an unrecognized feature.
41012 This section lists the known features and their expected contents.
41013 Sample XML documents for these features are included in the
41014 @value{GDBN} source tree, in the directory @file{gdb/features}.
41016 Names recognized by @value{GDBN} should include the name of the
41017 company or organization which selected the name, and the overall
41018 architecture to which the feature applies; so e.g.@: the feature
41019 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41021 The names of registers are not case sensitive for the purpose
41022 of recognizing standard features, but @value{GDBN} will only display
41023 registers using the capitalization used in the description.
41026 * AArch64 Features::
41030 * MicroBlaze Features::
41034 * Nios II Features::
41035 * PowerPC Features::
41036 * S/390 and System z Features::
41042 @node AArch64 Features
41043 @subsection AArch64 Features
41044 @cindex target descriptions, AArch64 features
41046 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41047 targets. It should contain registers @samp{x0} through @samp{x30},
41048 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41050 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41051 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41055 @subsection ARC Features
41056 @cindex target descriptions, ARC Features
41058 ARC processors are highly configurable, so even core registers and their number
41059 are not completely predetermined. In addition flags and PC registers which are
41060 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41061 that one of the core registers features is present.
41062 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41064 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41065 targets with a normal register file. It should contain registers @samp{r0}
41066 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41067 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41068 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41069 @samp{ilink} and extension core registers are not available to read/write, when
41070 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41072 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41073 ARC HS targets with a reduced register file. It should contain registers
41074 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41075 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41076 This feature may contain register @samp{ilink} and any of extension core
41077 registers @samp{r32} through @samp{r59/acch}.
41079 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41080 targets with a normal register file. It should contain registers @samp{r0}
41081 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41082 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41083 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41084 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41085 registers are not available when debugging GNU/Linux applications. The only
41086 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41087 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41088 ARC v2, but @samp{ilink2} is optional on ARCompact.
41090 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41091 targets. It should contain registers @samp{pc} and @samp{status32}.
41094 @subsection ARM Features
41095 @cindex target descriptions, ARM features
41097 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41099 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41100 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41102 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41103 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41104 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41107 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41108 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41110 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41111 it should contain at least registers @samp{wR0} through @samp{wR15} and
41112 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41113 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41115 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41116 should contain at least registers @samp{d0} through @samp{d15}. If
41117 they are present, @samp{d16} through @samp{d31} should also be included.
41118 @value{GDBN} will synthesize the single-precision registers from
41119 halves of the double-precision registers.
41121 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41122 need to contain registers; it instructs @value{GDBN} to display the
41123 VFP double-precision registers as vectors and to synthesize the
41124 quad-precision registers from pairs of double-precision registers.
41125 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41126 be present and include 32 double-precision registers.
41128 @node i386 Features
41129 @subsection i386 Features
41130 @cindex target descriptions, i386 features
41132 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41133 targets. It should describe the following registers:
41137 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41139 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41141 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41142 @samp{fs}, @samp{gs}
41144 @samp{st0} through @samp{st7}
41146 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41147 @samp{foseg}, @samp{fooff} and @samp{fop}
41150 The register sets may be different, depending on the target.
41152 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41153 describe registers:
41157 @samp{xmm0} through @samp{xmm7} for i386
41159 @samp{xmm0} through @samp{xmm15} for amd64
41164 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41165 @samp{org.gnu.gdb.i386.sse} feature. It should
41166 describe the upper 128 bits of @sc{ymm} registers:
41170 @samp{ymm0h} through @samp{ymm7h} for i386
41172 @samp{ymm0h} through @samp{ymm15h} for amd64
41175 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
41176 Memory Protection Extension (MPX). It should describe the following registers:
41180 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
41182 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
41185 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41186 describe a single register, @samp{orig_eax}.
41188 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
41189 describe two system registers: @samp{fs_base} and @samp{gs_base}.
41191 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
41192 @samp{org.gnu.gdb.i386.avx} feature. It should
41193 describe additional @sc{xmm} registers:
41197 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
41200 It should describe the upper 128 bits of additional @sc{ymm} registers:
41204 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
41208 describe the upper 256 bits of @sc{zmm} registers:
41212 @samp{zmm0h} through @samp{zmm7h} for i386.
41214 @samp{zmm0h} through @samp{zmm15h} for amd64.
41218 describe the additional @sc{zmm} registers:
41222 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
41225 @node MicroBlaze Features
41226 @subsection MicroBlaze Features
41227 @cindex target descriptions, MicroBlaze features
41229 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
41230 targets. It should contain registers @samp{r0} through @samp{r31},
41231 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
41232 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
41233 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
41235 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
41236 If present, it should contain registers @samp{rshr} and @samp{rslr}
41238 @node MIPS Features
41239 @subsection @acronym{MIPS} Features
41240 @cindex target descriptions, @acronym{MIPS} features
41242 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41243 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41244 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41247 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41248 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41249 registers. They may be 32-bit or 64-bit depending on the target.
41251 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41252 it may be optional in a future version of @value{GDBN}. It should
41253 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41254 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41256 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41257 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41258 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41259 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41261 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41262 contain a single register, @samp{restart}, which is used by the
41263 Linux kernel to control restartable syscalls.
41265 @node M68K Features
41266 @subsection M68K Features
41267 @cindex target descriptions, M68K features
41270 @item @samp{org.gnu.gdb.m68k.core}
41271 @itemx @samp{org.gnu.gdb.coldfire.core}
41272 @itemx @samp{org.gnu.gdb.fido.core}
41273 One of those features must be always present.
41274 The feature that is present determines which flavor of m68k is
41275 used. The feature that is present should contain registers
41276 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41277 @samp{sp}, @samp{ps} and @samp{pc}.
41279 @item @samp{org.gnu.gdb.coldfire.fp}
41280 This feature is optional. If present, it should contain registers
41281 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41285 @node NDS32 Features
41286 @subsection NDS32 Features
41287 @cindex target descriptions, NDS32 features
41289 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
41290 targets. It should contain at least registers @samp{r0} through
41291 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
41294 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
41295 it should contain 64-bit double-precision floating-point registers
41296 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
41297 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
41299 @emph{Note:} The first sixteen 64-bit double-precision floating-point
41300 registers are overlapped with the thirty-two 32-bit single-precision
41301 floating-point registers. The 32-bit single-precision registers, if
41302 not being listed explicitly, will be synthesized from halves of the
41303 overlapping 64-bit double-precision registers. Listing 32-bit
41304 single-precision registers explicitly is deprecated, and the
41305 support to it could be totally removed some day.
41307 @node Nios II Features
41308 @subsection Nios II Features
41309 @cindex target descriptions, Nios II features
41311 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
41312 targets. It should contain the 32 core registers (@samp{zero},
41313 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
41314 @samp{pc}, and the 16 control registers (@samp{status} through
41317 @node PowerPC Features
41318 @subsection PowerPC Features
41319 @cindex target descriptions, PowerPC features
41321 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41322 targets. It should contain registers @samp{r0} through @samp{r31},
41323 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41324 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41326 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41327 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41329 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41330 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41333 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41334 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41335 will combine these registers with the floating point registers
41336 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41337 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41338 through @samp{vs63}, the set of vector registers for POWER7.
41340 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41341 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41342 @samp{spefscr}. SPE targets should provide 32-bit registers in
41343 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41344 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41345 these to present registers @samp{ev0} through @samp{ev31} to the
41348 @node S/390 and System z Features
41349 @subsection S/390 and System z Features
41350 @cindex target descriptions, S/390 features
41351 @cindex target descriptions, System z features
41353 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
41354 System z targets. It should contain the PSW and the 16 general
41355 registers. In particular, System z targets should provide the 64-bit
41356 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
41357 S/390 targets should provide the 32-bit versions of these registers.
41358 A System z target that runs in 31-bit addressing mode should provide
41359 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
41360 register's upper halves @samp{r0h} through @samp{r15h}, and their
41361 lower halves @samp{r0l} through @samp{r15l}.
41363 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
41364 contain the 64-bit registers @samp{f0} through @samp{f15}, and
41367 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
41368 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
41370 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
41371 contain the register @samp{orig_r2}, which is 64-bit wide on System z
41372 targets and 32-bit otherwise. In addition, the feature may contain
41373 the @samp{last_break} register, whose width depends on the addressing
41374 mode, as well as the @samp{system_call} register, which is always
41377 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
41378 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
41379 @samp{atia}, and @samp{tr0} through @samp{tr15}.
41381 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
41382 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
41383 combined by @value{GDBN} with the floating point registers @samp{f0}
41384 through @samp{f15} to present the 128-bit wide vector registers
41385 @samp{v0} through @samp{v15}. In addition, this feature should
41386 contain the 128-bit wide vector registers @samp{v16} through
41389 @node Sparc Features
41390 @subsection Sparc Features
41391 @cindex target descriptions, sparc32 features
41392 @cindex target descriptions, sparc64 features
41393 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
41394 targets. It should describe the following registers:
41398 @samp{g0} through @samp{g7}
41400 @samp{o0} through @samp{o7}
41402 @samp{l0} through @samp{l7}
41404 @samp{i0} through @samp{i7}
41407 They may be 32-bit or 64-bit depending on the target.
41409 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
41410 targets. It should describe the following registers:
41414 @samp{f0} through @samp{f31}
41416 @samp{f32} through @samp{f62} for sparc64
41419 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
41420 targets. It should describe the following registers:
41424 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
41425 @samp{fsr}, and @samp{csr} for sparc32
41427 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
41431 @node TIC6x Features
41432 @subsection TMS320C6x Features
41433 @cindex target descriptions, TIC6x features
41434 @cindex target descriptions, TMS320C6x features
41435 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41436 targets. It should contain registers @samp{A0} through @samp{A15},
41437 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41439 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41440 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41441 through @samp{B31}.
41443 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41444 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41446 @node Operating System Information
41447 @appendix Operating System Information
41448 @cindex operating system information
41454 Users of @value{GDBN} often wish to obtain information about the state of
41455 the operating system running on the target---for example the list of
41456 processes, or the list of open files. This section describes the
41457 mechanism that makes it possible. This mechanism is similar to the
41458 target features mechanism (@pxref{Target Descriptions}), but focuses
41459 on a different aspect of target.
41461 Operating system information is retrived from the target via the
41462 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41463 read}). The object name in the request should be @samp{osdata}, and
41464 the @var{annex} identifies the data to be fetched.
41467 @appendixsection Process list
41468 @cindex operating system information, process list
41470 When requesting the process list, the @var{annex} field in the
41471 @samp{qXfer} request should be @samp{processes}. The returned data is
41472 an XML document. The formal syntax of this document is defined in
41473 @file{gdb/features/osdata.dtd}.
41475 An example document is:
41478 <?xml version="1.0"?>
41479 <!DOCTYPE target SYSTEM "osdata.dtd">
41480 <osdata type="processes">
41482 <column name="pid">1</column>
41483 <column name="user">root</column>
41484 <column name="command">/sbin/init</column>
41485 <column name="cores">1,2,3</column>
41490 Each item should include a column whose name is @samp{pid}. The value
41491 of that column should identify the process on the target. The
41492 @samp{user} and @samp{command} columns are optional, and will be
41493 displayed by @value{GDBN}. The @samp{cores} column, if present,
41494 should contain a comma-separated list of cores that this process
41495 is running on. Target may provide additional columns,
41496 which @value{GDBN} currently ignores.
41498 @node Trace File Format
41499 @appendix Trace File Format
41500 @cindex trace file format
41502 The trace file comes in three parts: a header, a textual description
41503 section, and a trace frame section with binary data.
41505 The header has the form @code{\x7fTRACE0\n}. The first byte is
41506 @code{0x7f} so as to indicate that the file contains binary data,
41507 while the @code{0} is a version number that may have different values
41510 The description section consists of multiple lines of @sc{ascii} text
41511 separated by newline characters (@code{0xa}). The lines may include a
41512 variety of optional descriptive or context-setting information, such
41513 as tracepoint definitions or register set size. @value{GDBN} will
41514 ignore any line that it does not recognize. An empty line marks the end
41519 Specifies the size of a register block in bytes. This is equal to the
41520 size of a @code{g} packet payload in the remote protocol. @var{size}
41521 is an ascii decimal number. There should be only one such line in
41522 a single trace file.
41524 @item status @var{status}
41525 Trace status. @var{status} has the same format as a @code{qTStatus}
41526 remote packet reply. There should be only one such line in a single trace
41529 @item tp @var{payload}
41530 Tracepoint definition. The @var{payload} has the same format as
41531 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
41532 may take multiple lines of definition, corresponding to the multiple
41535 @item tsv @var{payload}
41536 Trace state variable definition. The @var{payload} has the same format as
41537 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
41538 may take multiple lines of definition, corresponding to the multiple
41541 @item tdesc @var{payload}
41542 Target description in XML format. The @var{payload} is a single line of
41543 the XML file. All such lines should be concatenated together to get
41544 the original XML file. This file is in the same format as @code{qXfer}
41545 @code{features} payload, and corresponds to the main @code{target.xml}
41546 file. Includes are not allowed.
41550 The trace frame section consists of a number of consecutive frames.
41551 Each frame begins with a two-byte tracepoint number, followed by a
41552 four-byte size giving the amount of data in the frame. The data in
41553 the frame consists of a number of blocks, each introduced by a
41554 character indicating its type (at least register, memory, and trace
41555 state variable). The data in this section is raw binary, not a
41556 hexadecimal or other encoding; its endianness matches the target's
41559 @c FIXME bi-arch may require endianness/arch info in description section
41562 @item R @var{bytes}
41563 Register block. The number and ordering of bytes matches that of a
41564 @code{g} packet in the remote protocol. Note that these are the
41565 actual bytes, in target order, not a hexadecimal encoding.
41567 @item M @var{address} @var{length} @var{bytes}...
41568 Memory block. This is a contiguous block of memory, at the 8-byte
41569 address @var{address}, with a 2-byte length @var{length}, followed by
41570 @var{length} bytes.
41572 @item V @var{number} @var{value}
41573 Trace state variable block. This records the 8-byte signed value
41574 @var{value} of trace state variable numbered @var{number}.
41578 Future enhancements of the trace file format may include additional types
41581 @node Index Section Format
41582 @appendix @code{.gdb_index} section format
41583 @cindex .gdb_index section format
41584 @cindex index section format
41586 This section documents the index section that is created by @code{save
41587 gdb-index} (@pxref{Index Files}). The index section is
41588 DWARF-specific; some knowledge of DWARF is assumed in this
41591 The mapped index file format is designed to be directly
41592 @code{mmap}able on any architecture. In most cases, a datum is
41593 represented using a little-endian 32-bit integer value, called an
41594 @code{offset_type}. Big endian machines must byte-swap the values
41595 before using them. Exceptions to this rule are noted. The data is
41596 laid out such that alignment is always respected.
41598 A mapped index consists of several areas, laid out in order.
41602 The file header. This is a sequence of values, of @code{offset_type}
41603 unless otherwise noted:
41607 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41608 Version 4 uses a different hashing function from versions 5 and 6.
41609 Version 6 includes symbols for inlined functions, whereas versions 4
41610 and 5 do not. Version 7 adds attributes to the CU indices in the
41611 symbol table. Version 8 specifies that symbols from DWARF type units
41612 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41613 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41615 @value{GDBN} will only read version 4, 5, or 6 indices
41616 by specifying @code{set use-deprecated-index-sections on}.
41617 GDB has a workaround for potentially broken version 7 indices so it is
41618 currently not flagged as deprecated.
41621 The offset, from the start of the file, of the CU list.
41624 The offset, from the start of the file, of the types CU list. Note
41625 that this area can be empty, in which case this offset will be equal
41626 to the next offset.
41629 The offset, from the start of the file, of the address area.
41632 The offset, from the start of the file, of the symbol table.
41635 The offset, from the start of the file, of the constant pool.
41639 The CU list. This is a sequence of pairs of 64-bit little-endian
41640 values, sorted by the CU offset. The first element in each pair is
41641 the offset of a CU in the @code{.debug_info} section. The second
41642 element in each pair is the length of that CU. References to a CU
41643 elsewhere in the map are done using a CU index, which is just the
41644 0-based index into this table. Note that if there are type CUs, then
41645 conceptually CUs and type CUs form a single list for the purposes of
41649 The types CU list. This is a sequence of triplets of 64-bit
41650 little-endian values. In a triplet, the first value is the CU offset,
41651 the second value is the type offset in the CU, and the third value is
41652 the type signature. The types CU list is not sorted.
41655 The address area. The address area consists of a sequence of address
41656 entries. Each address entry has three elements:
41660 The low address. This is a 64-bit little-endian value.
41663 The high address. This is a 64-bit little-endian value. Like
41664 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41667 The CU index. This is an @code{offset_type} value.
41671 The symbol table. This is an open-addressed hash table. The size of
41672 the hash table is always a power of 2.
41674 Each slot in the hash table consists of a pair of @code{offset_type}
41675 values. The first value is the offset of the symbol's name in the
41676 constant pool. The second value is the offset of the CU vector in the
41679 If both values are 0, then this slot in the hash table is empty. This
41680 is ok because while 0 is a valid constant pool index, it cannot be a
41681 valid index for both a string and a CU vector.
41683 The hash value for a table entry is computed by applying an
41684 iterative hash function to the symbol's name. Starting with an
41685 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41686 the string is incorporated into the hash using the formula depending on the
41691 The formula is @code{r = r * 67 + c - 113}.
41693 @item Versions 5 to 7
41694 The formula is @code{r = r * 67 + tolower (c) - 113}.
41697 The terminating @samp{\0} is not incorporated into the hash.
41699 The step size used in the hash table is computed via
41700 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41701 value, and @samp{size} is the size of the hash table. The step size
41702 is used to find the next candidate slot when handling a hash
41705 The names of C@t{++} symbols in the hash table are canonicalized. We
41706 don't currently have a simple description of the canonicalization
41707 algorithm; if you intend to create new index sections, you must read
41711 The constant pool. This is simply a bunch of bytes. It is organized
41712 so that alignment is correct: CU vectors are stored first, followed by
41715 A CU vector in the constant pool is a sequence of @code{offset_type}
41716 values. The first value is the number of CU indices in the vector.
41717 Each subsequent value is the index and symbol attributes of a CU in
41718 the CU list. This element in the hash table is used to indicate which
41719 CUs define the symbol and how the symbol is used.
41720 See below for the format of each CU index+attributes entry.
41722 A string in the constant pool is zero-terminated.
41725 Attributes were added to CU index values in @code{.gdb_index} version 7.
41726 If a symbol has multiple uses within a CU then there is one
41727 CU index+attributes value for each use.
41729 The format of each CU index+attributes entry is as follows
41735 This is the index of the CU in the CU list.
41737 These bits are reserved for future purposes and must be zero.
41739 The kind of the symbol in the CU.
41743 This value is reserved and should not be used.
41744 By reserving zero the full @code{offset_type} value is backwards compatible
41745 with previous versions of the index.
41747 The symbol is a type.
41749 The symbol is a variable or an enum value.
41751 The symbol is a function.
41753 Any other kind of symbol.
41755 These values are reserved.
41759 This bit is zero if the value is global and one if it is static.
41761 The determination of whether a symbol is global or static is complicated.
41762 The authorative reference is the file @file{dwarf2read.c} in
41763 @value{GDBN} sources.
41767 This pseudo-code describes the computation of a symbol's kind and
41768 global/static attributes in the index.
41771 is_external = get_attribute (die, DW_AT_external);
41772 language = get_attribute (cu_die, DW_AT_language);
41775 case DW_TAG_typedef:
41776 case DW_TAG_base_type:
41777 case DW_TAG_subrange_type:
41781 case DW_TAG_enumerator:
41783 is_static = language != CPLUS;
41785 case DW_TAG_subprogram:
41787 is_static = ! (is_external || language == ADA);
41789 case DW_TAG_constant:
41791 is_static = ! is_external;
41793 case DW_TAG_variable:
41795 is_static = ! is_external;
41797 case DW_TAG_namespace:
41801 case DW_TAG_class_type:
41802 case DW_TAG_interface_type:
41803 case DW_TAG_structure_type:
41804 case DW_TAG_union_type:
41805 case DW_TAG_enumeration_type:
41807 is_static = language != CPLUS;
41815 @appendix Manual pages
41819 * gdb man:: The GNU Debugger man page
41820 * gdbserver man:: Remote Server for the GNU Debugger man page
41821 * gcore man:: Generate a core file of a running program
41822 * gdbinit man:: gdbinit scripts
41828 @c man title gdb The GNU Debugger
41830 @c man begin SYNOPSIS gdb
41831 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41832 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41833 [@option{-b}@w{ }@var{bps}]
41834 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41835 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41836 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41837 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41838 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41841 @c man begin DESCRIPTION gdb
41842 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41843 going on ``inside'' another program while it executes -- or what another
41844 program was doing at the moment it crashed.
41846 @value{GDBN} can do four main kinds of things (plus other things in support of
41847 these) to help you catch bugs in the act:
41851 Start your program, specifying anything that might affect its behavior.
41854 Make your program stop on specified conditions.
41857 Examine what has happened, when your program has stopped.
41860 Change things in your program, so you can experiment with correcting the
41861 effects of one bug and go on to learn about another.
41864 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41867 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41868 commands from the terminal until you tell it to exit with the @value{GDBN}
41869 command @code{quit}. You can get online help from @value{GDBN} itself
41870 by using the command @code{help}.
41872 You can run @code{gdb} with no arguments or options; but the most
41873 usual way to start @value{GDBN} is with one argument or two, specifying an
41874 executable program as the argument:
41880 You can also start with both an executable program and a core file specified:
41886 You can, instead, specify a process ID as a second argument, if you want
41887 to debug a running process:
41895 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41896 named @file{1234}; @value{GDBN} does check for a core file first).
41897 With option @option{-p} you can omit the @var{program} filename.
41899 Here are some of the most frequently needed @value{GDBN} commands:
41901 @c pod2man highlights the right hand side of the @item lines.
41903 @item break [@var{file}:]@var{function}
41904 Set a breakpoint at @var{function} (in @var{file}).
41906 @item run [@var{arglist}]
41907 Start your program (with @var{arglist}, if specified).
41910 Backtrace: display the program stack.
41912 @item print @var{expr}
41913 Display the value of an expression.
41916 Continue running your program (after stopping, e.g. at a breakpoint).
41919 Execute next program line (after stopping); step @emph{over} any
41920 function calls in the line.
41922 @item edit [@var{file}:]@var{function}
41923 look at the program line where it is presently stopped.
41925 @item list [@var{file}:]@var{function}
41926 type the text of the program in the vicinity of where it is presently stopped.
41929 Execute next program line (after stopping); step @emph{into} any
41930 function calls in the line.
41932 @item help [@var{name}]
41933 Show information about @value{GDBN} command @var{name}, or general information
41934 about using @value{GDBN}.
41937 Exit from @value{GDBN}.
41941 For full details on @value{GDBN},
41942 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41943 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41944 as the @code{gdb} entry in the @code{info} program.
41948 @c man begin OPTIONS gdb
41949 Any arguments other than options specify an executable
41950 file and core file (or process ID); that is, the first argument
41951 encountered with no
41952 associated option flag is equivalent to a @option{-se} option, and the second,
41953 if any, is equivalent to a @option{-c} option if it's the name of a file.
41955 both long and short forms; both are shown here. The long forms are also
41956 recognized if you truncate them, so long as enough of the option is
41957 present to be unambiguous. (If you prefer, you can flag option
41958 arguments with @option{+} rather than @option{-}, though we illustrate the
41959 more usual convention.)
41961 All the options and command line arguments you give are processed
41962 in sequential order. The order makes a difference when the @option{-x}
41968 List all options, with brief explanations.
41970 @item -symbols=@var{file}
41971 @itemx -s @var{file}
41972 Read symbol table from file @var{file}.
41975 Enable writing into executable and core files.
41977 @item -exec=@var{file}
41978 @itemx -e @var{file}
41979 Use file @var{file} as the executable file to execute when
41980 appropriate, and for examining pure data in conjunction with a core
41983 @item -se=@var{file}
41984 Read symbol table from file @var{file} and use it as the executable
41987 @item -core=@var{file}
41988 @itemx -c @var{file}
41989 Use file @var{file} as a core dump to examine.
41991 @item -command=@var{file}
41992 @itemx -x @var{file}
41993 Execute @value{GDBN} commands from file @var{file}.
41995 @item -ex @var{command}
41996 Execute given @value{GDBN} @var{command}.
41998 @item -directory=@var{directory}
41999 @itemx -d @var{directory}
42000 Add @var{directory} to the path to search for source files.
42003 Do not execute commands from @file{~/.gdbinit}.
42007 Do not execute commands from any @file{.gdbinit} initialization files.
42011 ``Quiet''. Do not print the introductory and copyright messages. These
42012 messages are also suppressed in batch mode.
42015 Run in batch mode. Exit with status @code{0} after processing all the command
42016 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42017 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42018 commands in the command files.
42020 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42021 download and run a program on another computer; in order to make this
42022 more useful, the message
42025 Program exited normally.
42029 (which is ordinarily issued whenever a program running under @value{GDBN} control
42030 terminates) is not issued when running in batch mode.
42032 @item -cd=@var{directory}
42033 Run @value{GDBN} using @var{directory} as its working directory,
42034 instead of the current directory.
42038 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42039 @value{GDBN} to output the full file name and line number in a standard,
42040 recognizable fashion each time a stack frame is displayed (which
42041 includes each time the program stops). This recognizable format looks
42042 like two @samp{\032} characters, followed by the file name, line number
42043 and character position separated by colons, and a newline. The
42044 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42045 characters as a signal to display the source code for the frame.
42048 Set the line speed (baud rate or bits per second) of any serial
42049 interface used by @value{GDBN} for remote debugging.
42051 @item -tty=@var{device}
42052 Run using @var{device} for your program's standard input and output.
42056 @c man begin SEEALSO gdb
42058 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42059 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42060 documentation are properly installed at your site, the command
42067 should give you access to the complete manual.
42069 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42070 Richard M. Stallman and Roland H. Pesch, July 1991.
42074 @node gdbserver man
42075 @heading gdbserver man
42077 @c man title gdbserver Remote Server for the GNU Debugger
42079 @c man begin SYNOPSIS gdbserver
42080 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42082 gdbserver --attach @var{comm} @var{pid}
42084 gdbserver --multi @var{comm}
42088 @c man begin DESCRIPTION gdbserver
42089 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42090 than the one which is running the program being debugged.
42093 @subheading Usage (server (target) side)
42096 Usage (server (target) side):
42099 First, you need to have a copy of the program you want to debug put onto
42100 the target system. The program can be stripped to save space if needed, as
42101 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42102 the @value{GDBN} running on the host system.
42104 To use the server, you log on to the target system, and run the @command{gdbserver}
42105 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
42106 your program, and (c) its arguments. The general syntax is:
42109 target> gdbserver @var{comm} @var{program} [@var{args} ...]
42112 For example, using a serial port, you might say:
42116 @c @file would wrap it as F</dev/com1>.
42117 target> gdbserver /dev/com1 emacs foo.txt
42120 target> gdbserver @file{/dev/com1} emacs foo.txt
42124 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
42125 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
42126 waits patiently for the host @value{GDBN} to communicate with it.
42128 To use a TCP connection, you could say:
42131 target> gdbserver host:2345 emacs foo.txt
42134 This says pretty much the same thing as the last example, except that we are
42135 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
42136 that we are expecting to see a TCP connection from @code{host} to local TCP port
42137 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
42138 want for the port number as long as it does not conflict with any existing TCP
42139 ports on the target system. This same port number must be used in the host
42140 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
42141 you chose a port number that conflicts with another service, @command{gdbserver} will
42142 print an error message and exit.
42144 @command{gdbserver} can also attach to running programs.
42145 This is accomplished via the @option{--attach} argument. The syntax is:
42148 target> gdbserver --attach @var{comm} @var{pid}
42151 @var{pid} is the process ID of a currently running process. It isn't
42152 necessary to point @command{gdbserver} at a binary for the running process.
42154 To start @code{gdbserver} without supplying an initial command to run
42155 or process ID to attach, use the @option{--multi} command line option.
42156 In such case you should connect using @kbd{target extended-remote} to start
42157 the program you want to debug.
42160 target> gdbserver --multi @var{comm}
42164 @subheading Usage (host side)
42170 You need an unstripped copy of the target program on your host system, since
42171 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
42172 would, with the target program as the first argument. (You may need to use the
42173 @option{--baud} option if the serial line is running at anything except 9600 baud.)
42174 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
42175 new command you need to know about is @code{target remote}
42176 (or @code{target extended-remote}). Its argument is either
42177 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
42178 descriptor. For example:
42182 @c @file would wrap it as F</dev/ttyb>.
42183 (gdb) target remote /dev/ttyb
42186 (gdb) target remote @file{/dev/ttyb}
42191 communicates with the server via serial line @file{/dev/ttyb}, and:
42194 (gdb) target remote the-target:2345
42198 communicates via a TCP connection to port 2345 on host `the-target', where
42199 you previously started up @command{gdbserver} with the same port number. Note that for
42200 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
42201 command, otherwise you may get an error that looks something like
42202 `Connection refused'.
42204 @command{gdbserver} can also debug multiple inferiors at once,
42207 the @value{GDBN} manual in node @code{Inferiors and Programs}
42208 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
42211 @ref{Inferiors and Programs}.
42213 In such case use the @code{extended-remote} @value{GDBN} command variant:
42216 (gdb) target extended-remote the-target:2345
42219 The @command{gdbserver} option @option{--multi} may or may not be used in such
42223 @c man begin OPTIONS gdbserver
42224 There are three different modes for invoking @command{gdbserver}:
42229 Debug a specific program specified by its program name:
42232 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42235 The @var{comm} parameter specifies how should the server communicate
42236 with @value{GDBN}; it is either a device name (to use a serial line),
42237 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
42238 stdin/stdout of @code{gdbserver}. Specify the name of the program to
42239 debug in @var{prog}. Any remaining arguments will be passed to the
42240 program verbatim. When the program exits, @value{GDBN} will close the
42241 connection, and @code{gdbserver} will exit.
42244 Debug a specific program by specifying the process ID of a running
42248 gdbserver --attach @var{comm} @var{pid}
42251 The @var{comm} parameter is as described above. Supply the process ID
42252 of a running program in @var{pid}; @value{GDBN} will do everything
42253 else. Like with the previous mode, when the process @var{pid} exits,
42254 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
42257 Multi-process mode -- debug more than one program/process:
42260 gdbserver --multi @var{comm}
42263 In this mode, @value{GDBN} can instruct @command{gdbserver} which
42264 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
42265 close the connection when a process being debugged exits, so you can
42266 debug several processes in the same session.
42269 In each of the modes you may specify these options:
42274 List all options, with brief explanations.
42277 This option causes @command{gdbserver} to print its version number and exit.
42280 @command{gdbserver} will attach to a running program. The syntax is:
42283 target> gdbserver --attach @var{comm} @var{pid}
42286 @var{pid} is the process ID of a currently running process. It isn't
42287 necessary to point @command{gdbserver} at a binary for the running process.
42290 To start @code{gdbserver} without supplying an initial command to run
42291 or process ID to attach, use this command line option.
42292 Then you can connect using @kbd{target extended-remote} and start
42293 the program you want to debug. The syntax is:
42296 target> gdbserver --multi @var{comm}
42300 Instruct @code{gdbserver} to display extra status information about the debugging
42302 This option is intended for @code{gdbserver} development and for bug reports to
42305 @item --remote-debug
42306 Instruct @code{gdbserver} to display remote protocol debug output.
42307 This option is intended for @code{gdbserver} development and for bug reports to
42310 @item --debug-format=option1@r{[},option2,...@r{]}
42311 Instruct @code{gdbserver} to include extra information in each line
42312 of debugging output.
42313 @xref{Other Command-Line Arguments for gdbserver}.
42316 Specify a wrapper to launch programs
42317 for debugging. The option should be followed by the name of the
42318 wrapper, then any command-line arguments to pass to the wrapper, then
42319 @kbd{--} indicating the end of the wrapper arguments.
42322 By default, @command{gdbserver} keeps the listening TCP port open, so that
42323 additional connections are possible. However, if you start @code{gdbserver}
42324 with the @option{--once} option, it will stop listening for any further
42325 connection attempts after connecting to the first @value{GDBN} session.
42327 @c --disable-packet is not documented for users.
42329 @c --disable-randomization and --no-disable-randomization are superseded by
42330 @c QDisableRandomization.
42335 @c man begin SEEALSO gdbserver
42337 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42338 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42339 documentation are properly installed at your site, the command
42345 should give you access to the complete manual.
42347 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42348 Richard M. Stallman and Roland H. Pesch, July 1991.
42355 @c man title gcore Generate a core file of a running program
42358 @c man begin SYNOPSIS gcore
42359 gcore [-o @var{filename}] @var{pid}
42363 @c man begin DESCRIPTION gcore
42364 Generate a core dump of a running program with process ID @var{pid}.
42365 Produced file is equivalent to a kernel produced core file as if the process
42366 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
42367 limit). Unlike after a crash, after @command{gcore} the program remains
42368 running without any change.
42371 @c man begin OPTIONS gcore
42373 @item -o @var{filename}
42374 The optional argument
42375 @var{filename} specifies the file name where to put the core dump.
42376 If not specified, the file name defaults to @file{core.@var{pid}},
42377 where @var{pid} is the running program process ID.
42381 @c man begin SEEALSO gcore
42383 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42384 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42385 documentation are properly installed at your site, the command
42392 should give you access to the complete manual.
42394 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42395 Richard M. Stallman and Roland H. Pesch, July 1991.
42402 @c man title gdbinit GDB initialization scripts
42405 @c man begin SYNOPSIS gdbinit
42406 @ifset SYSTEM_GDBINIT
42407 @value{SYSTEM_GDBINIT}
42416 @c man begin DESCRIPTION gdbinit
42417 These files contain @value{GDBN} commands to automatically execute during
42418 @value{GDBN} startup. The lines of contents are canned sequences of commands,
42421 the @value{GDBN} manual in node @code{Sequences}
42422 -- shell command @code{info -f gdb -n Sequences}.
42428 Please read more in
42430 the @value{GDBN} manual in node @code{Startup}
42431 -- shell command @code{info -f gdb -n Startup}.
42438 @ifset SYSTEM_GDBINIT
42439 @item @value{SYSTEM_GDBINIT}
42441 @ifclear SYSTEM_GDBINIT
42442 @item (not enabled with @code{--with-system-gdbinit} during compilation)
42444 System-wide initialization file. It is executed unless user specified
42445 @value{GDBN} option @code{-nx} or @code{-n}.
42448 the @value{GDBN} manual in node @code{System-wide configuration}
42449 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
42452 @ref{System-wide configuration}.
42456 User initialization file. It is executed unless user specified
42457 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
42460 Initialization file for current directory. It may need to be enabled with
42461 @value{GDBN} security command @code{set auto-load local-gdbinit}.
42464 the @value{GDBN} manual in node @code{Init File in the Current Directory}
42465 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
42468 @ref{Init File in the Current Directory}.
42473 @c man begin SEEALSO gdbinit
42475 gdb(1), @code{info -f gdb -n Startup}
42477 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42478 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42479 documentation are properly installed at your site, the command
42485 should give you access to the complete manual.
42487 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42488 Richard M. Stallman and Roland H. Pesch, July 1991.
42494 @node GNU Free Documentation License
42495 @appendix GNU Free Documentation License
42498 @node Concept Index
42499 @unnumbered Concept Index
42503 @node Command and Variable Index
42504 @unnumbered Command, Variable, and Function Index
42509 % I think something like @@colophon should be in texinfo. In the
42511 \long\def\colophon{\hbox to0pt{}\vfill
42512 \centerline{The body of this manual is set in}
42513 \centerline{\fontname\tenrm,}
42514 \centerline{with headings in {\bf\fontname\tenbf}}
42515 \centerline{and examples in {\tt\fontname\tentt}.}
42516 \centerline{{\it\fontname\tenit\/},}
42517 \centerline{{\bf\fontname\tenbf}, and}
42518 \centerline{{\sl\fontname\tensl\/}}
42519 \centerline{are used for emphasis.}\vfill}
42521 % Blame: doc@@cygnus.com, 1991.