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.
549 The original port to the OpenRISC 1000 is believed to be due to
550 Alessandro Forin and Per Bothner. More recent ports have been the work
551 of Jeremy Bennett, Franck Jullien, Stefan Wallentowitz and
555 @chapter A Sample @value{GDBN} Session
557 You can use this manual at your leisure to read all about @value{GDBN}.
558 However, a handful of commands are enough to get started using the
559 debugger. This chapter illustrates those commands.
562 In this sample session, we emphasize user input like this: @b{input},
563 to make it easier to pick out from the surrounding output.
566 @c FIXME: this example may not be appropriate for some configs, where
567 @c FIXME...primary interest is in remote use.
569 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
570 processor) exhibits the following bug: sometimes, when we change its
571 quote strings from the default, the commands used to capture one macro
572 definition within another stop working. In the following short @code{m4}
573 session, we define a macro @code{foo} which expands to @code{0000}; we
574 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
575 same thing. However, when we change the open quote string to
576 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
577 procedure fails to define a new synonym @code{baz}:
586 @b{define(bar,defn(`foo'))}
590 @b{changequote(<QUOTE>,<UNQUOTE>)}
592 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
595 m4: End of input: 0: fatal error: EOF in string
599 Let us use @value{GDBN} to try to see what is going on.
602 $ @b{@value{GDBP} m4}
603 @c FIXME: this falsifies the exact text played out, to permit smallbook
604 @c FIXME... format to come out better.
605 @value{GDBN} is free software and you are welcome to distribute copies
606 of it under certain conditions; type "show copying" to see
608 There is absolutely no warranty for @value{GDBN}; type "show warranty"
611 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
616 @value{GDBN} reads only enough symbol data to know where to find the
617 rest when needed; as a result, the first prompt comes up very quickly.
618 We now tell @value{GDBN} to use a narrower display width than usual, so
619 that examples fit in this manual.
622 (@value{GDBP}) @b{set width 70}
626 We need to see how the @code{m4} built-in @code{changequote} works.
627 Having looked at the source, we know the relevant subroutine is
628 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
629 @code{break} command.
632 (@value{GDBP}) @b{break m4_changequote}
633 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
637 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
638 control; as long as control does not reach the @code{m4_changequote}
639 subroutine, the program runs as usual:
642 (@value{GDBP}) @b{run}
643 Starting program: /work/Editorial/gdb/gnu/m4/m4
651 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
652 suspends execution of @code{m4}, displaying information about the
653 context where it stops.
656 @b{changequote(<QUOTE>,<UNQUOTE>)}
658 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
660 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
664 Now we use the command @code{n} (@code{next}) to advance execution to
665 the next line of the current function.
669 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
674 @code{set_quotes} looks like a promising subroutine. We can go into it
675 by using the command @code{s} (@code{step}) instead of @code{next}.
676 @code{step} goes to the next line to be executed in @emph{any}
677 subroutine, so it steps into @code{set_quotes}.
681 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
683 530 if (lquote != def_lquote)
687 The display that shows the subroutine where @code{m4} is now
688 suspended (and its arguments) is called a stack frame display. It
689 shows a summary of the stack. We can use the @code{backtrace}
690 command (which can also be spelled @code{bt}), to see where we are
691 in the stack as a whole: the @code{backtrace} command displays a
692 stack frame for each active subroutine.
695 (@value{GDBP}) @b{bt}
696 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
698 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
700 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
701 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
703 #4 0x79dc in expand_input () at macro.c:40
704 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
708 We step through a few more lines to see what happens. The first two
709 times, we can use @samp{s}; the next two times we use @code{n} to avoid
710 falling into the @code{xstrdup} subroutine.
714 0x3b5c 532 if (rquote != def_rquote)
716 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
717 def_lquote : xstrdup(lq);
719 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
722 538 len_lquote = strlen(rquote);
726 The last line displayed looks a little odd; we can examine the variables
727 @code{lquote} and @code{rquote} to see if they are in fact the new left
728 and right quotes we specified. We use the command @code{p}
729 (@code{print}) to see their values.
732 (@value{GDBP}) @b{p lquote}
733 $1 = 0x35d40 "<QUOTE>"
734 (@value{GDBP}) @b{p rquote}
735 $2 = 0x35d50 "<UNQUOTE>"
739 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
740 To look at some context, we can display ten lines of source
741 surrounding the current line with the @code{l} (@code{list}) command.
747 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
749 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
752 538 len_lquote = strlen(rquote);
753 539 len_rquote = strlen(lquote);
760 Let us step past the two lines that set @code{len_lquote} and
761 @code{len_rquote}, and then examine the values of those variables.
765 539 len_rquote = strlen(lquote);
768 (@value{GDBP}) @b{p len_lquote}
770 (@value{GDBP}) @b{p len_rquote}
775 That certainly looks wrong, assuming @code{len_lquote} and
776 @code{len_rquote} are meant to be the lengths of @code{lquote} and
777 @code{rquote} respectively. We can set them to better values using
778 the @code{p} command, since it can print the value of
779 any expression---and that expression can include subroutine calls and
783 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
785 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
790 Is that enough to fix the problem of using the new quotes with the
791 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
792 executing with the @code{c} (@code{continue}) command, and then try the
793 example that caused trouble initially:
799 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
806 Success! The new quotes now work just as well as the default ones. The
807 problem seems to have been just the two typos defining the wrong
808 lengths. We allow @code{m4} exit by giving it an EOF as input:
812 Program exited normally.
816 The message @samp{Program exited normally.} is from @value{GDBN}; it
817 indicates @code{m4} has finished executing. We can end our @value{GDBN}
818 session with the @value{GDBN} @code{quit} command.
821 (@value{GDBP}) @b{quit}
825 @chapter Getting In and Out of @value{GDBN}
827 This chapter discusses how to start @value{GDBN}, and how to get out of it.
831 type @samp{@value{GDBP}} to start @value{GDBN}.
833 type @kbd{quit} or @kbd{Ctrl-d} to exit.
837 * Invoking GDB:: How to start @value{GDBN}
838 * Quitting GDB:: How to quit @value{GDBN}
839 * Shell Commands:: How to use shell commands inside @value{GDBN}
840 * Logging Output:: How to log @value{GDBN}'s output to a file
844 @section Invoking @value{GDBN}
846 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
847 @value{GDBN} reads commands from the terminal until you tell it to exit.
849 You can also run @code{@value{GDBP}} with a variety of arguments and options,
850 to specify more of your debugging environment at the outset.
852 The command-line options described here are designed
853 to cover a variety of situations; in some environments, some of these
854 options may effectively be unavailable.
856 The most usual way to start @value{GDBN} is with one argument,
857 specifying an executable program:
860 @value{GDBP} @var{program}
864 You can also start with both an executable program and a core file
868 @value{GDBP} @var{program} @var{core}
871 You can, instead, specify a process ID as a second argument, if you want
872 to debug a running process:
875 @value{GDBP} @var{program} 1234
879 would attach @value{GDBN} to process @code{1234} (unless you also have a file
880 named @file{1234}; @value{GDBN} does check for a core file first).
882 Taking advantage of the second command-line argument requires a fairly
883 complete operating system; when you use @value{GDBN} as a remote
884 debugger attached to a bare board, there may not be any notion of
885 ``process'', and there is often no way to get a core dump. @value{GDBN}
886 will warn you if it is unable to attach or to read core dumps.
888 You can optionally have @code{@value{GDBP}} pass any arguments after the
889 executable file to the inferior using @code{--args}. This option stops
892 @value{GDBP} --args gcc -O2 -c foo.c
894 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
895 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
897 You can run @code{@value{GDBP}} without printing the front material, which describes
898 @value{GDBN}'s non-warranty, by specifying @code{--silent}
899 (or @code{-q}/@code{--quiet}):
902 @value{GDBP} --silent
906 You can further control how @value{GDBN} starts up by using command-line
907 options. @value{GDBN} itself can remind you of the options available.
917 to display all available options and briefly describe their use
918 (@samp{@value{GDBP} -h} is a shorter equivalent).
920 All options and command line arguments you give are processed
921 in sequential order. The order makes a difference when the
922 @samp{-x} option is used.
926 * File Options:: Choosing files
927 * Mode Options:: Choosing modes
928 * Startup:: What @value{GDBN} does during startup
932 @subsection Choosing Files
934 When @value{GDBN} starts, it reads any arguments other than options as
935 specifying an executable file and core file (or process ID). This is
936 the same as if the arguments were specified by the @samp{-se} and
937 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
938 first argument that does not have an associated option flag as
939 equivalent to the @samp{-se} option followed by that argument; and the
940 second argument that does not have an associated option flag, if any, as
941 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
942 If the second argument begins with a decimal digit, @value{GDBN} will
943 first attempt to attach to it as a process, and if that fails, attempt
944 to open it as a corefile. If you have a corefile whose name begins with
945 a digit, you can prevent @value{GDBN} from treating it as a pid by
946 prefixing it with @file{./}, e.g.@: @file{./12345}.
948 If @value{GDBN} has not been configured to included core file support,
949 such as for most embedded targets, then it will complain about a second
950 argument and ignore it.
952 Many options have both long and short forms; both are shown in the
953 following list. @value{GDBN} also recognizes the long forms if you truncate
954 them, so long as enough of the option is present to be unambiguous.
955 (If you prefer, you can flag option arguments with @samp{--} rather
956 than @samp{-}, though we illustrate the more usual convention.)
958 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
959 @c way, both those who look for -foo and --foo in the index, will find
963 @item -symbols @var{file}
965 @cindex @code{--symbols}
967 Read symbol table from file @var{file}.
969 @item -exec @var{file}
971 @cindex @code{--exec}
973 Use file @var{file} as the executable file to execute when appropriate,
974 and for examining pure data in conjunction with a core dump.
978 Read symbol table from file @var{file} and use it as the executable
981 @item -core @var{file}
983 @cindex @code{--core}
985 Use file @var{file} as a core dump to examine.
987 @item -pid @var{number}
988 @itemx -p @var{number}
991 Connect to process ID @var{number}, as with the @code{attach} command.
993 @item -command @var{file}
995 @cindex @code{--command}
997 Execute commands from file @var{file}. The contents of this file is
998 evaluated exactly as the @code{source} command would.
999 @xref{Command Files,, Command files}.
1001 @item -eval-command @var{command}
1002 @itemx -ex @var{command}
1003 @cindex @code{--eval-command}
1005 Execute a single @value{GDBN} command.
1007 This option may be used multiple times to call multiple commands. It may
1008 also be interleaved with @samp{-command} as required.
1011 @value{GDBP} -ex 'target sim' -ex 'load' \
1012 -x setbreakpoints -ex 'run' a.out
1015 @item -init-command @var{file}
1016 @itemx -ix @var{file}
1017 @cindex @code{--init-command}
1019 Execute commands from file @var{file} before loading the inferior (but
1020 after loading gdbinit files).
1023 @item -init-eval-command @var{command}
1024 @itemx -iex @var{command}
1025 @cindex @code{--init-eval-command}
1027 Execute a single @value{GDBN} command before loading the inferior (but
1028 after loading gdbinit files).
1031 @item -directory @var{directory}
1032 @itemx -d @var{directory}
1033 @cindex @code{--directory}
1035 Add @var{directory} to the path to search for source and script files.
1039 @cindex @code{--readnow}
1041 Read each symbol file's entire symbol table immediately, rather than
1042 the default, which is to read it incrementally as it is needed.
1043 This makes startup slower, but makes future operations faster.
1046 @anchor{--readnever}
1047 @cindex @code{--readnever}, command-line option
1048 Do not read each symbol file's symbolic debug information. This makes
1049 startup faster but at the expense of not being able to perform
1050 symbolic debugging. DWARF unwind information is also not read,
1051 meaning backtraces may become incomplete or inaccurate. One use of
1052 this is when a user simply wants to do the following sequence: attach,
1053 dump core, detach. Loading the debugging information in this case is
1054 an unnecessary cause of delay.
1058 @subsection Choosing Modes
1060 You can run @value{GDBN} in various alternative modes---for example, in
1061 batch mode or quiet mode.
1069 Do not execute commands found in any initialization file.
1070 There are three init files, loaded in the following order:
1073 @item @file{system.gdbinit}
1074 This is the system-wide init file.
1075 Its location is specified with the @code{--with-system-gdbinit}
1076 configure option (@pxref{System-wide configuration}).
1077 It is loaded first when @value{GDBN} starts, before command line options
1078 have been processed.
1079 @item @file{~/.gdbinit}
1080 This is the init file in your home directory.
1081 It is loaded next, after @file{system.gdbinit}, and before
1082 command options have been processed.
1083 @item @file{./.gdbinit}
1084 This is the init file in the current directory.
1085 It is loaded last, after command line options other than @code{-x} and
1086 @code{-ex} have been processed. Command line options @code{-x} and
1087 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1090 For further documentation on startup processing, @xref{Startup}.
1091 For documentation on how to write command files,
1092 @xref{Command Files,,Command Files}.
1097 Do not execute commands found in @file{~/.gdbinit}, the init file
1098 in your home directory.
1104 @cindex @code{--quiet}
1105 @cindex @code{--silent}
1107 ``Quiet''. Do not print the introductory and copyright messages. These
1108 messages are also suppressed in batch mode.
1111 @cindex @code{--batch}
1112 Run in batch mode. Exit with status @code{0} after processing all the
1113 command files specified with @samp{-x} (and all commands from
1114 initialization files, if not inhibited with @samp{-n}). Exit with
1115 nonzero status if an error occurs in executing the @value{GDBN} commands
1116 in the command files. Batch mode also disables pagination, sets unlimited
1117 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1118 off} were in effect (@pxref{Messages/Warnings}).
1120 Batch mode may be useful for running @value{GDBN} as a filter, for
1121 example to download and run a program on another computer; in order to
1122 make this more useful, the message
1125 Program exited normally.
1129 (which is ordinarily issued whenever a program running under
1130 @value{GDBN} control terminates) is not issued when running in batch
1134 @cindex @code{--batch-silent}
1135 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1136 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1137 unaffected). This is much quieter than @samp{-silent} and would be useless
1138 for an interactive session.
1140 This is particularly useful when using targets that give @samp{Loading section}
1141 messages, for example.
1143 Note that targets that give their output via @value{GDBN}, as opposed to
1144 writing directly to @code{stdout}, will also be made silent.
1146 @item -return-child-result
1147 @cindex @code{--return-child-result}
1148 The return code from @value{GDBN} will be the return code from the child
1149 process (the process being debugged), with the following exceptions:
1153 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1154 internal error. In this case the exit code is the same as it would have been
1155 without @samp{-return-child-result}.
1157 The user quits with an explicit value. E.g., @samp{quit 1}.
1159 The child process never runs, or is not allowed to terminate, in which case
1160 the exit code will be -1.
1163 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1164 when @value{GDBN} is being used as a remote program loader or simulator
1169 @cindex @code{--nowindows}
1171 ``No windows''. If @value{GDBN} comes with a graphical user interface
1172 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1173 interface. If no GUI is available, this option has no effect.
1177 @cindex @code{--windows}
1179 If @value{GDBN} includes a GUI, then this option requires it to be
1182 @item -cd @var{directory}
1184 Run @value{GDBN} using @var{directory} as its working directory,
1185 instead of the current directory.
1187 @item -data-directory @var{directory}
1188 @itemx -D @var{directory}
1189 @cindex @code{--data-directory}
1191 Run @value{GDBN} using @var{directory} as its data directory.
1192 The data directory is where @value{GDBN} searches for its
1193 auxiliary files. @xref{Data Files}.
1197 @cindex @code{--fullname}
1199 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1200 subprocess. It tells @value{GDBN} to output the full file name and line
1201 number in a standard, recognizable fashion each time a stack frame is
1202 displayed (which includes each time your program stops). This
1203 recognizable format looks like two @samp{\032} characters, followed by
1204 the file name, line number and character position separated by colons,
1205 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1206 @samp{\032} characters as a signal to display the source code for the
1209 @item -annotate @var{level}
1210 @cindex @code{--annotate}
1211 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1212 effect is identical to using @samp{set annotate @var{level}}
1213 (@pxref{Annotations}). The annotation @var{level} controls how much
1214 information @value{GDBN} prints together with its prompt, values of
1215 expressions, source lines, and other types of output. Level 0 is the
1216 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1217 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1218 that control @value{GDBN}, and level 2 has been deprecated.
1220 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1224 @cindex @code{--args}
1225 Change interpretation of command line so that arguments following the
1226 executable file are passed as command line arguments to the inferior.
1227 This option stops option processing.
1229 @item -baud @var{bps}
1231 @cindex @code{--baud}
1233 Set the line speed (baud rate or bits per second) of any serial
1234 interface used by @value{GDBN} for remote debugging.
1236 @item -l @var{timeout}
1238 Set the timeout (in seconds) of any communication used by @value{GDBN}
1239 for remote debugging.
1241 @item -tty @var{device}
1242 @itemx -t @var{device}
1243 @cindex @code{--tty}
1245 Run using @var{device} for your program's standard input and output.
1246 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1248 @c resolve the situation of these eventually
1250 @cindex @code{--tui}
1251 Activate the @dfn{Text User Interface} when starting. The Text User
1252 Interface manages several text windows on the terminal, showing
1253 source, assembly, registers and @value{GDBN} command outputs
1254 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1255 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1256 Using @value{GDBN} under @sc{gnu} Emacs}).
1258 @item -interpreter @var{interp}
1259 @cindex @code{--interpreter}
1260 Use the interpreter @var{interp} for interface with the controlling
1261 program or device. This option is meant to be set by programs which
1262 communicate with @value{GDBN} using it as a back end.
1263 @xref{Interpreters, , Command Interpreters}.
1265 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1266 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1267 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1268 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1269 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1270 @sc{gdb/mi} interfaces are no longer supported.
1273 @cindex @code{--write}
1274 Open the executable and core files for both reading and writing. This
1275 is equivalent to the @samp{set write on} command inside @value{GDBN}
1279 @cindex @code{--statistics}
1280 This option causes @value{GDBN} to print statistics about time and
1281 memory usage after it completes each command and returns to the prompt.
1284 @cindex @code{--version}
1285 This option causes @value{GDBN} to print its version number and
1286 no-warranty blurb, and exit.
1288 @item -configuration
1289 @cindex @code{--configuration}
1290 This option causes @value{GDBN} to print details about its build-time
1291 configuration parameters, and then exit. These details can be
1292 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1297 @subsection What @value{GDBN} Does During Startup
1298 @cindex @value{GDBN} startup
1300 Here's the description of what @value{GDBN} does during session startup:
1304 Sets up the command interpreter as specified by the command line
1305 (@pxref{Mode Options, interpreter}).
1309 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1310 used when building @value{GDBN}; @pxref{System-wide configuration,
1311 ,System-wide configuration and settings}) and executes all the commands in
1314 @anchor{Home Directory Init File}
1316 Reads the init file (if any) in your home directory@footnote{On
1317 DOS/Windows systems, the home directory is the one pointed to by the
1318 @code{HOME} environment variable.} and executes all the commands in
1321 @anchor{Option -init-eval-command}
1323 Executes commands and command files specified by the @samp{-iex} and
1324 @samp{-ix} options in their specified order. Usually you should use the
1325 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1326 settings before @value{GDBN} init files get executed and before inferior
1330 Processes command line options and operands.
1332 @anchor{Init File in the Current Directory during Startup}
1334 Reads and executes the commands from init file (if any) in the current
1335 working directory as long as @samp{set auto-load local-gdbinit} is set to
1336 @samp{on} (@pxref{Init File in the Current Directory}).
1337 This is only done if the current directory is
1338 different from your home directory. Thus, you can have more than one
1339 init file, one generic in your home directory, and another, specific
1340 to the program you are debugging, in the directory where you invoke
1344 If the command line specified a program to debug, or a process to
1345 attach to, or a core file, @value{GDBN} loads any auto-loaded
1346 scripts provided for the program or for its loaded shared libraries.
1347 @xref{Auto-loading}.
1349 If you wish to disable the auto-loading during startup,
1350 you must do something like the following:
1353 $ gdb -iex "set auto-load python-scripts off" myprogram
1356 Option @samp{-ex} does not work because the auto-loading is then turned
1360 Executes commands and command files specified by the @samp{-ex} and
1361 @samp{-x} options in their specified order. @xref{Command Files}, for
1362 more details about @value{GDBN} command files.
1365 Reads the command history recorded in the @dfn{history file}.
1366 @xref{Command History}, for more details about the command history and the
1367 files where @value{GDBN} records it.
1370 Init files use the same syntax as @dfn{command files} (@pxref{Command
1371 Files}) and are processed by @value{GDBN} in the same way. The init
1372 file in your home directory can set options (such as @samp{set
1373 complaints}) that affect subsequent processing of command line options
1374 and operands. Init files are not executed if you use the @samp{-nx}
1375 option (@pxref{Mode Options, ,Choosing Modes}).
1377 To display the list of init files loaded by gdb at startup, you
1378 can use @kbd{gdb --help}.
1380 @cindex init file name
1381 @cindex @file{.gdbinit}
1382 @cindex @file{gdb.ini}
1383 The @value{GDBN} init files are normally called @file{.gdbinit}.
1384 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1385 the limitations of file names imposed by DOS filesystems. The Windows
1386 port of @value{GDBN} uses the standard name, but if it finds a
1387 @file{gdb.ini} file in your home directory, it warns you about that
1388 and suggests to rename the file to the standard name.
1392 @section Quitting @value{GDBN}
1393 @cindex exiting @value{GDBN}
1394 @cindex leaving @value{GDBN}
1397 @kindex quit @r{[}@var{expression}@r{]}
1398 @kindex q @r{(@code{quit})}
1399 @item quit @r{[}@var{expression}@r{]}
1401 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1402 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1403 do not supply @var{expression}, @value{GDBN} will terminate normally;
1404 otherwise it will terminate using the result of @var{expression} as the
1409 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1410 terminates the action of any @value{GDBN} command that is in progress and
1411 returns to @value{GDBN} command level. It is safe to type the interrupt
1412 character at any time because @value{GDBN} does not allow it to take effect
1413 until a time when it is safe.
1415 If you have been using @value{GDBN} to control an attached process or
1416 device, you can release it with the @code{detach} command
1417 (@pxref{Attach, ,Debugging an Already-running Process}).
1419 @node Shell Commands
1420 @section Shell Commands
1422 If you need to execute occasional shell commands during your
1423 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1424 just use the @code{shell} command.
1429 @cindex shell escape
1430 @item shell @var{command-string}
1431 @itemx !@var{command-string}
1432 Invoke a standard shell to execute @var{command-string}.
1433 Note that no space is needed between @code{!} and @var{command-string}.
1434 If it exists, the environment variable @code{SHELL} determines which
1435 shell to run. Otherwise @value{GDBN} uses the default shell
1436 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1439 The utility @code{make} is often needed in development environments.
1440 You do not have to use the @code{shell} command for this purpose in
1445 @cindex calling make
1446 @item make @var{make-args}
1447 Execute the @code{make} program with the specified
1448 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1451 @node Logging Output
1452 @section Logging Output
1453 @cindex logging @value{GDBN} output
1454 @cindex save @value{GDBN} output to a file
1456 You may want to save the output of @value{GDBN} commands to a file.
1457 There are several commands to control @value{GDBN}'s logging.
1461 @item set logging on
1463 @item set logging off
1465 @cindex logging file name
1466 @item set logging file @var{file}
1467 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1468 @item set logging overwrite [on|off]
1469 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1470 you want @code{set logging on} to overwrite the logfile instead.
1471 @item set logging redirect [on|off]
1472 By default, @value{GDBN} output will go to both the terminal and the logfile.
1473 Set @code{redirect} if you want output to go only to the log file.
1474 @kindex show logging
1476 Show the current values of the logging settings.
1480 @chapter @value{GDBN} Commands
1482 You can abbreviate a @value{GDBN} command to the first few letters of the command
1483 name, if that abbreviation is unambiguous; and you can repeat certain
1484 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1485 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1486 show you the alternatives available, if there is more than one possibility).
1489 * Command Syntax:: How to give commands to @value{GDBN}
1490 * Completion:: Command completion
1491 * Help:: How to ask @value{GDBN} for help
1494 @node Command Syntax
1495 @section Command Syntax
1497 A @value{GDBN} command is a single line of input. There is no limit on
1498 how long it can be. It starts with a command name, which is followed by
1499 arguments whose meaning depends on the command name. For example, the
1500 command @code{step} accepts an argument which is the number of times to
1501 step, as in @samp{step 5}. You can also use the @code{step} command
1502 with no arguments. Some commands do not allow any arguments.
1504 @cindex abbreviation
1505 @value{GDBN} command names may always be truncated if that abbreviation is
1506 unambiguous. Other possible command abbreviations are listed in the
1507 documentation for individual commands. In some cases, even ambiguous
1508 abbreviations are allowed; for example, @code{s} is specially defined as
1509 equivalent to @code{step} even though there are other commands whose
1510 names start with @code{s}. You can test abbreviations by using them as
1511 arguments to the @code{help} command.
1513 @cindex repeating commands
1514 @kindex RET @r{(repeat last command)}
1515 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1516 repeat the previous command. Certain commands (for example, @code{run})
1517 will not repeat this way; these are commands whose unintentional
1518 repetition might cause trouble and which you are unlikely to want to
1519 repeat. User-defined commands can disable this feature; see
1520 @ref{Define, dont-repeat}.
1522 The @code{list} and @code{x} commands, when you repeat them with
1523 @key{RET}, construct new arguments rather than repeating
1524 exactly as typed. This permits easy scanning of source or memory.
1526 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1527 output, in a way similar to the common utility @code{more}
1528 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1529 @key{RET} too many in this situation, @value{GDBN} disables command
1530 repetition after any command that generates this sort of display.
1532 @kindex # @r{(a comment)}
1534 Any text from a @kbd{#} to the end of the line is a comment; it does
1535 nothing. This is useful mainly in command files (@pxref{Command
1536 Files,,Command Files}).
1538 @cindex repeating command sequences
1539 @kindex Ctrl-o @r{(operate-and-get-next)}
1540 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1541 commands. This command accepts the current line, like @key{RET}, and
1542 then fetches the next line relative to the current line from the history
1546 @section Command Completion
1549 @cindex word completion
1550 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1551 only one possibility; it can also show you what the valid possibilities
1552 are for the next word in a command, at any time. This works for @value{GDBN}
1553 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1555 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1556 of a word. If there is only one possibility, @value{GDBN} fills in the
1557 word, and waits for you to finish the command (or press @key{RET} to
1558 enter it). For example, if you type
1560 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1561 @c complete accuracy in these examples; space introduced for clarity.
1562 @c If texinfo enhancements make it unnecessary, it would be nice to
1563 @c replace " @key" by "@key" in the following...
1565 (@value{GDBP}) info bre @key{TAB}
1569 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1570 the only @code{info} subcommand beginning with @samp{bre}:
1573 (@value{GDBP}) info breakpoints
1577 You can either press @key{RET} at this point, to run the @code{info
1578 breakpoints} command, or backspace and enter something else, if
1579 @samp{breakpoints} does not look like the command you expected. (If you
1580 were sure you wanted @code{info breakpoints} in the first place, you
1581 might as well just type @key{RET} immediately after @samp{info bre},
1582 to exploit command abbreviations rather than command completion).
1584 If there is more than one possibility for the next word when you press
1585 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1586 characters and try again, or just press @key{TAB} a second time;
1587 @value{GDBN} displays all the possible completions for that word. For
1588 example, you might want to set a breakpoint on a subroutine whose name
1589 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1590 just sounds the bell. Typing @key{TAB} again displays all the
1591 function names in your program that begin with those characters, for
1595 (@value{GDBP}) b make_ @key{TAB}
1596 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1597 make_a_section_from_file make_environ
1598 make_abs_section make_function_type
1599 make_blockvector make_pointer_type
1600 make_cleanup make_reference_type
1601 make_command make_symbol_completion_list
1602 (@value{GDBP}) b make_
1606 After displaying the available possibilities, @value{GDBN} copies your
1607 partial input (@samp{b make_} in the example) so you can finish the
1610 If you just want to see the list of alternatives in the first place, you
1611 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1612 means @kbd{@key{META} ?}. You can type this either by holding down a
1613 key designated as the @key{META} shift on your keyboard (if there is
1614 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1616 If the number of possible completions is large, @value{GDBN} will
1617 print as much of the list as it has collected, as well as a message
1618 indicating that the list may be truncated.
1621 (@value{GDBP}) b m@key{TAB}@key{TAB}
1623 <... the rest of the possible completions ...>
1624 *** List may be truncated, max-completions reached. ***
1629 This behavior can be controlled with the following commands:
1632 @kindex set max-completions
1633 @item set max-completions @var{limit}
1634 @itemx set max-completions unlimited
1635 Set the maximum number of completion candidates. @value{GDBN} will
1636 stop looking for more completions once it collects this many candidates.
1637 This is useful when completing on things like function names as collecting
1638 all the possible candidates can be time consuming.
1639 The default value is 200. A value of zero disables tab-completion.
1640 Note that setting either no limit or a very large limit can make
1642 @kindex show max-completions
1643 @item show max-completions
1644 Show the maximum number of candidates that @value{GDBN} will collect and show
1648 @cindex quotes in commands
1649 @cindex completion of quoted strings
1650 Sometimes the string you need, while logically a ``word'', may contain
1651 parentheses or other characters that @value{GDBN} normally excludes from
1652 its notion of a word. To permit word completion to work in this
1653 situation, you may enclose words in @code{'} (single quote marks) in
1654 @value{GDBN} commands.
1656 A likely situation where you might need this is in typing an
1657 expression that involves a C@t{++} symbol name with template
1658 parameters. This is because when completing expressions, GDB treats
1659 the @samp{<} character as word delimiter, assuming that it's the
1660 less-than comparison operator (@pxref{C Operators, , C and C@t{++}
1663 For example, when you want to call a C@t{++} template function
1664 interactively using the @code{print} or @code{call} commands, you may
1665 need to distinguish whether you mean the version of @code{name} that
1666 was specialized for @code{int}, @code{name<int>()}, or the version
1667 that was specialized for @code{float}, @code{name<float>()}. To use
1668 the word-completion facilities in this situation, type a single quote
1669 @code{'} at the beginning of the function name. This alerts
1670 @value{GDBN} that it may need to consider more information than usual
1671 when you press @key{TAB} or @kbd{M-?} to request word completion:
1674 (@value{GDBP}) p 'func< @kbd{M-?}
1675 func<int>() func<float>()
1676 (@value{GDBP}) p 'func<
1679 When setting breakpoints however (@pxref{Specify Location}), you don't
1680 usually need to type a quote before the function name, because
1681 @value{GDBN} understands that you want to set a breakpoint on a
1685 (@value{GDBP}) b func< @kbd{M-?}
1686 func<int>() func<float>()
1687 (@value{GDBP}) b func<
1690 This is true even in the case of typing the name of C@t{++} overloaded
1691 functions (multiple definitions of the same function, distinguished by
1692 argument type). For example, when you want to set a breakpoint you
1693 don't need to distinguish whether you mean the version of @code{name}
1694 that takes an @code{int} parameter, @code{name(int)}, or the version
1695 that takes a @code{float} parameter, @code{name(float)}.
1698 (@value{GDBP}) b bubble( @kbd{M-?}
1699 bubble(int) bubble(double)
1700 (@value{GDBP}) b bubble(dou @kbd{M-?}
1704 See @ref{quoting names} for a description of other scenarios that
1707 For more information about overloaded functions, see @ref{C Plus Plus
1708 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1709 overload-resolution off} to disable overload resolution;
1710 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1712 @cindex completion of structure field names
1713 @cindex structure field name completion
1714 @cindex completion of union field names
1715 @cindex union field name completion
1716 When completing in an expression which looks up a field in a
1717 structure, @value{GDBN} also tries@footnote{The completer can be
1718 confused by certain kinds of invalid expressions. Also, it only
1719 examines the static type of the expression, not the dynamic type.} to
1720 limit completions to the field names available in the type of the
1724 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1725 magic to_fputs to_rewind
1726 to_data to_isatty to_write
1727 to_delete to_put to_write_async_safe
1732 This is because the @code{gdb_stdout} is a variable of the type
1733 @code{struct ui_file} that is defined in @value{GDBN} sources as
1740 ui_file_flush_ftype *to_flush;
1741 ui_file_write_ftype *to_write;
1742 ui_file_write_async_safe_ftype *to_write_async_safe;
1743 ui_file_fputs_ftype *to_fputs;
1744 ui_file_read_ftype *to_read;
1745 ui_file_delete_ftype *to_delete;
1746 ui_file_isatty_ftype *to_isatty;
1747 ui_file_rewind_ftype *to_rewind;
1748 ui_file_put_ftype *to_put;
1755 @section Getting Help
1756 @cindex online documentation
1759 You can always ask @value{GDBN} itself for information on its commands,
1760 using the command @code{help}.
1763 @kindex h @r{(@code{help})}
1766 You can use @code{help} (abbreviated @code{h}) with no arguments to
1767 display a short list of named classes of commands:
1771 List of classes of commands:
1773 aliases -- Aliases of other commands
1774 breakpoints -- Making program stop at certain points
1775 data -- Examining data
1776 files -- Specifying and examining files
1777 internals -- Maintenance commands
1778 obscure -- Obscure features
1779 running -- Running the program
1780 stack -- Examining the stack
1781 status -- Status inquiries
1782 support -- Support facilities
1783 tracepoints -- Tracing of program execution without
1784 stopping the program
1785 user-defined -- User-defined commands
1787 Type "help" followed by a class name for a list of
1788 commands in that class.
1789 Type "help" followed by command name for full
1791 Command name abbreviations are allowed if unambiguous.
1794 @c the above line break eliminates huge line overfull...
1796 @item help @var{class}
1797 Using one of the general help classes as an argument, you can get a
1798 list of the individual commands in that class. For example, here is the
1799 help display for the class @code{status}:
1802 (@value{GDBP}) help status
1807 @c Line break in "show" line falsifies real output, but needed
1808 @c to fit in smallbook page size.
1809 info -- Generic command for showing things
1810 about the program being debugged
1811 show -- Generic command for showing things
1814 Type "help" followed by command name for full
1816 Command name abbreviations are allowed if unambiguous.
1820 @item help @var{command}
1821 With a command name as @code{help} argument, @value{GDBN} displays a
1822 short paragraph on how to use that command.
1825 @item apropos @var{args}
1826 The @code{apropos} command searches through all of the @value{GDBN}
1827 commands, and their documentation, for the regular expression specified in
1828 @var{args}. It prints out all matches found. For example:
1839 alias -- Define a new command that is an alias of an existing command
1840 aliases -- Aliases of other commands
1841 d -- Delete some breakpoints or auto-display expressions
1842 del -- Delete some breakpoints or auto-display expressions
1843 delete -- Delete some breakpoints or auto-display expressions
1848 @item complete @var{args}
1849 The @code{complete @var{args}} command lists all the possible completions
1850 for the beginning of a command. Use @var{args} to specify the beginning of the
1851 command you want completed. For example:
1857 @noindent results in:
1868 @noindent This is intended for use by @sc{gnu} Emacs.
1871 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1872 and @code{show} to inquire about the state of your program, or the state
1873 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1874 manual introduces each of them in the appropriate context. The listings
1875 under @code{info} and under @code{show} in the Command, Variable, and
1876 Function Index point to all the sub-commands. @xref{Command and Variable
1882 @kindex i @r{(@code{info})}
1884 This command (abbreviated @code{i}) is for describing the state of your
1885 program. For example, you can show the arguments passed to a function
1886 with @code{info args}, list the registers currently in use with @code{info
1887 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1888 You can get a complete list of the @code{info} sub-commands with
1889 @w{@code{help info}}.
1893 You can assign the result of an expression to an environment variable with
1894 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1895 @code{set prompt $}.
1899 In contrast to @code{info}, @code{show} is for describing the state of
1900 @value{GDBN} itself.
1901 You can change most of the things you can @code{show}, by using the
1902 related command @code{set}; for example, you can control what number
1903 system is used for displays with @code{set radix}, or simply inquire
1904 which is currently in use with @code{show radix}.
1907 To display all the settable parameters and their current
1908 values, you can use @code{show} with no arguments; you may also use
1909 @code{info set}. Both commands produce the same display.
1910 @c FIXME: "info set" violates the rule that "info" is for state of
1911 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1912 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1916 Here are several miscellaneous @code{show} subcommands, all of which are
1917 exceptional in lacking corresponding @code{set} commands:
1920 @kindex show version
1921 @cindex @value{GDBN} version number
1923 Show what version of @value{GDBN} is running. You should include this
1924 information in @value{GDBN} bug-reports. If multiple versions of
1925 @value{GDBN} are in use at your site, you may need to determine which
1926 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1927 commands are introduced, and old ones may wither away. Also, many
1928 system vendors ship variant versions of @value{GDBN}, and there are
1929 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1930 The version number is the same as the one announced when you start
1933 @kindex show copying
1934 @kindex info copying
1935 @cindex display @value{GDBN} copyright
1938 Display information about permission for copying @value{GDBN}.
1940 @kindex show warranty
1941 @kindex info warranty
1943 @itemx info warranty
1944 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1945 if your version of @value{GDBN} comes with one.
1947 @kindex show configuration
1948 @item show configuration
1949 Display detailed information about the way @value{GDBN} was configured
1950 when it was built. This displays the optional arguments passed to the
1951 @file{configure} script and also configuration parameters detected
1952 automatically by @command{configure}. When reporting a @value{GDBN}
1953 bug (@pxref{GDB Bugs}), it is important to include this information in
1959 @chapter Running Programs Under @value{GDBN}
1961 When you run a program under @value{GDBN}, you must first generate
1962 debugging information when you compile it.
1964 You may start @value{GDBN} with its arguments, if any, in an environment
1965 of your choice. If you are doing native debugging, you may redirect
1966 your program's input and output, debug an already running process, or
1967 kill a child process.
1970 * Compilation:: Compiling for debugging
1971 * Starting:: Starting your program
1972 * Arguments:: Your program's arguments
1973 * Environment:: Your program's environment
1975 * Working Directory:: Your program's working directory
1976 * Input/Output:: Your program's input and output
1977 * Attach:: Debugging an already-running process
1978 * Kill Process:: Killing the child process
1980 * Inferiors and Programs:: Debugging multiple inferiors and programs
1981 * Threads:: Debugging programs with multiple threads
1982 * Forks:: Debugging forks
1983 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1987 @section Compiling for Debugging
1989 In order to debug a program effectively, you need to generate
1990 debugging information when you compile it. This debugging information
1991 is stored in the object file; it describes the data type of each
1992 variable or function and the correspondence between source line numbers
1993 and addresses in the executable code.
1995 To request debugging information, specify the @samp{-g} option when you run
1998 Programs that are to be shipped to your customers are compiled with
1999 optimizations, using the @samp{-O} compiler option. However, some
2000 compilers are unable to handle the @samp{-g} and @samp{-O} options
2001 together. Using those compilers, you cannot generate optimized
2002 executables containing debugging information.
2004 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
2005 without @samp{-O}, making it possible to debug optimized code. We
2006 recommend that you @emph{always} use @samp{-g} whenever you compile a
2007 program. You may think your program is correct, but there is no sense
2008 in pushing your luck. For more information, see @ref{Optimized Code}.
2010 Older versions of the @sc{gnu} C compiler permitted a variant option
2011 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
2012 format; if your @sc{gnu} C compiler has this option, do not use it.
2014 @value{GDBN} knows about preprocessor macros and can show you their
2015 expansion (@pxref{Macros}). Most compilers do not include information
2016 about preprocessor macros in the debugging information if you specify
2017 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
2018 the @sc{gnu} C compiler, provides macro information if you are using
2019 the DWARF debugging format, and specify the option @option{-g3}.
2021 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
2022 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
2023 information on @value{NGCC} options affecting debug information.
2025 You will have the best debugging experience if you use the latest
2026 version of the DWARF debugging format that your compiler supports.
2027 DWARF is currently the most expressive and best supported debugging
2028 format in @value{GDBN}.
2032 @section Starting your Program
2038 @kindex r @r{(@code{run})}
2041 Use the @code{run} command to start your program under @value{GDBN}.
2042 You must first specify the program name with an argument to
2043 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2044 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2045 command (@pxref{Files, ,Commands to Specify Files}).
2049 If you are running your program in an execution environment that
2050 supports processes, @code{run} creates an inferior process and makes
2051 that process run your program. In some environments without processes,
2052 @code{run} jumps to the start of your program. Other targets,
2053 like @samp{remote}, are always running. If you get an error
2054 message like this one:
2057 The "remote" target does not support "run".
2058 Try "help target" or "continue".
2062 then use @code{continue} to run your program. You may need @code{load}
2063 first (@pxref{load}).
2065 The execution of a program is affected by certain information it
2066 receives from its superior. @value{GDBN} provides ways to specify this
2067 information, which you must do @emph{before} starting your program. (You
2068 can change it after starting your program, but such changes only affect
2069 your program the next time you start it.) This information may be
2070 divided into four categories:
2073 @item The @emph{arguments.}
2074 Specify the arguments to give your program as the arguments of the
2075 @code{run} command. If a shell is available on your target, the shell
2076 is used to pass the arguments, so that you may use normal conventions
2077 (such as wildcard expansion or variable substitution) in describing
2079 In Unix systems, you can control which shell is used with the
2080 @code{SHELL} environment variable. If you do not define @code{SHELL},
2081 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2082 use of any shell with the @code{set startup-with-shell} command (see
2085 @item The @emph{environment.}
2086 Your program normally inherits its environment from @value{GDBN}, but you can
2087 use the @value{GDBN} commands @code{set environment} and @code{unset
2088 environment} to change parts of the environment that affect
2089 your program. @xref{Environment, ,Your Program's Environment}.
2091 @item The @emph{working directory.}
2092 You can set your program's working directory with the command
2093 @kbd{set cwd}. If you do not set any working directory with this
2094 command, your program will inherit @value{GDBN}'s working directory if
2095 native debugging, or the remote server's working directory if remote
2096 debugging. @xref{Working Directory, ,Your Program's Working
2099 @item The @emph{standard input and output.}
2100 Your program normally uses the same device for standard input and
2101 standard output as @value{GDBN} is using. You can redirect input and output
2102 in the @code{run} command line, or you can use the @code{tty} command to
2103 set a different device for your program.
2104 @xref{Input/Output, ,Your Program's Input and Output}.
2107 @emph{Warning:} While input and output redirection work, you cannot use
2108 pipes to pass the output of the program you are debugging to another
2109 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2113 When you issue the @code{run} command, your program begins to execute
2114 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2115 of how to arrange for your program to stop. Once your program has
2116 stopped, you may call functions in your program, using the @code{print}
2117 or @code{call} commands. @xref{Data, ,Examining Data}.
2119 If the modification time of your symbol file has changed since the last
2120 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2121 table, and reads it again. When it does this, @value{GDBN} tries to retain
2122 your current breakpoints.
2127 @cindex run to main procedure
2128 The name of the main procedure can vary from language to language.
2129 With C or C@t{++}, the main procedure name is always @code{main}, but
2130 other languages such as Ada do not require a specific name for their
2131 main procedure. The debugger provides a convenient way to start the
2132 execution of the program and to stop at the beginning of the main
2133 procedure, depending on the language used.
2135 The @samp{start} command does the equivalent of setting a temporary
2136 breakpoint at the beginning of the main procedure and then invoking
2137 the @samp{run} command.
2139 @cindex elaboration phase
2140 Some programs contain an @dfn{elaboration} phase where some startup code is
2141 executed before the main procedure is called. This depends on the
2142 languages used to write your program. In C@t{++}, for instance,
2143 constructors for static and global objects are executed before
2144 @code{main} is called. It is therefore possible that the debugger stops
2145 before reaching the main procedure. However, the temporary breakpoint
2146 will remain to halt execution.
2148 Specify the arguments to give to your program as arguments to the
2149 @samp{start} command. These arguments will be given verbatim to the
2150 underlying @samp{run} command. Note that the same arguments will be
2151 reused if no argument is provided during subsequent calls to
2152 @samp{start} or @samp{run}.
2154 It is sometimes necessary to debug the program during elaboration. In
2155 these cases, using the @code{start} command would stop the execution
2156 of your program too late, as the program would have already completed
2157 the elaboration phase. Under these circumstances, either insert
2158 breakpoints in your elaboration code before running your program or
2159 use the @code{starti} command.
2163 @cindex run to first instruction
2164 The @samp{starti} command does the equivalent of setting a temporary
2165 breakpoint at the first instruction of a program's execution and then
2166 invoking the @samp{run} command. For programs containing an
2167 elaboration phase, the @code{starti} command will stop execution at
2168 the start of the elaboration phase.
2170 @anchor{set exec-wrapper}
2171 @kindex set exec-wrapper
2172 @item set exec-wrapper @var{wrapper}
2173 @itemx show exec-wrapper
2174 @itemx unset exec-wrapper
2175 When @samp{exec-wrapper} is set, the specified wrapper is used to
2176 launch programs for debugging. @value{GDBN} starts your program
2177 with a shell command of the form @kbd{exec @var{wrapper}
2178 @var{program}}. Quoting is added to @var{program} and its
2179 arguments, but not to @var{wrapper}, so you should add quotes if
2180 appropriate for your shell. The wrapper runs until it executes
2181 your program, and then @value{GDBN} takes control.
2183 You can use any program that eventually calls @code{execve} with
2184 its arguments as a wrapper. Several standard Unix utilities do
2185 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2186 with @code{exec "$@@"} will also work.
2188 For example, you can use @code{env} to pass an environment variable to
2189 the debugged program, without setting the variable in your shell's
2193 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2197 This command is available when debugging locally on most targets, excluding
2198 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2200 @kindex set startup-with-shell
2201 @anchor{set startup-with-shell}
2202 @item set startup-with-shell
2203 @itemx set startup-with-shell on
2204 @itemx set startup-with-shell off
2205 @itemx show startup-with-shell
2206 On Unix systems, by default, if a shell is available on your target,
2207 @value{GDBN}) uses it to start your program. Arguments of the
2208 @code{run} command are passed to the shell, which does variable
2209 substitution, expands wildcard characters and performs redirection of
2210 I/O. In some circumstances, it may be useful to disable such use of a
2211 shell, for example, when debugging the shell itself or diagnosing
2212 startup failures such as:
2216 Starting program: ./a.out
2217 During startup program terminated with signal SIGSEGV, Segmentation fault.
2221 which indicates the shell or the wrapper specified with
2222 @samp{exec-wrapper} crashed, not your program. Most often, this is
2223 caused by something odd in your shell's non-interactive mode
2224 initialization file---such as @file{.cshrc} for C-shell,
2225 $@file{.zshenv} for the Z shell, or the file specified in the
2226 @samp{BASH_ENV} environment variable for BASH.
2228 @anchor{set auto-connect-native-target}
2229 @kindex set auto-connect-native-target
2230 @item set auto-connect-native-target
2231 @itemx set auto-connect-native-target on
2232 @itemx set auto-connect-native-target off
2233 @itemx show auto-connect-native-target
2235 By default, if not connected to any target yet (e.g., with
2236 @code{target remote}), the @code{run} command starts your program as a
2237 native process under @value{GDBN}, on your local machine. If you're
2238 sure you don't want to debug programs on your local machine, you can
2239 tell @value{GDBN} to not connect to the native target automatically
2240 with the @code{set auto-connect-native-target off} command.
2242 If @code{on}, which is the default, and if @value{GDBN} is not
2243 connected to a target already, the @code{run} command automaticaly
2244 connects to the native target, if one is available.
2246 If @code{off}, and if @value{GDBN} is not connected to a target
2247 already, the @code{run} command fails with an error:
2251 Don't know how to run. Try "help target".
2254 If @value{GDBN} is already connected to a target, @value{GDBN} always
2255 uses it with the @code{run} command.
2257 In any case, you can explicitly connect to the native target with the
2258 @code{target native} command. For example,
2261 (@value{GDBP}) set auto-connect-native-target off
2263 Don't know how to run. Try "help target".
2264 (@value{GDBP}) target native
2266 Starting program: ./a.out
2267 [Inferior 1 (process 10421) exited normally]
2270 In case you connected explicitly to the @code{native} target,
2271 @value{GDBN} remains connected even if all inferiors exit, ready for
2272 the next @code{run} command. Use the @code{disconnect} command to
2275 Examples of other commands that likewise respect the
2276 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2277 proc}, @code{info os}.
2279 @kindex set disable-randomization
2280 @item set disable-randomization
2281 @itemx set disable-randomization on
2282 This option (enabled by default in @value{GDBN}) will turn off the native
2283 randomization of the virtual address space of the started program. This option
2284 is useful for multiple debugging sessions to make the execution better
2285 reproducible and memory addresses reusable across debugging sessions.
2287 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2288 On @sc{gnu}/Linux you can get the same behavior using
2291 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2294 @item set disable-randomization off
2295 Leave the behavior of the started executable unchanged. Some bugs rear their
2296 ugly heads only when the program is loaded at certain addresses. If your bug
2297 disappears when you run the program under @value{GDBN}, that might be because
2298 @value{GDBN} by default disables the address randomization on platforms, such
2299 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2300 disable-randomization off} to try to reproduce such elusive bugs.
2302 On targets where it is available, virtual address space randomization
2303 protects the programs against certain kinds of security attacks. In these
2304 cases the attacker needs to know the exact location of a concrete executable
2305 code. Randomizing its location makes it impossible to inject jumps misusing
2306 a code at its expected addresses.
2308 Prelinking shared libraries provides a startup performance advantage but it
2309 makes addresses in these libraries predictable for privileged processes by
2310 having just unprivileged access at the target system. Reading the shared
2311 library binary gives enough information for assembling the malicious code
2312 misusing it. Still even a prelinked shared library can get loaded at a new
2313 random address just requiring the regular relocation process during the
2314 startup. Shared libraries not already prelinked are always loaded at
2315 a randomly chosen address.
2317 Position independent executables (PIE) contain position independent code
2318 similar to the shared libraries and therefore such executables get loaded at
2319 a randomly chosen address upon startup. PIE executables always load even
2320 already prelinked shared libraries at a random address. You can build such
2321 executable using @command{gcc -fPIE -pie}.
2323 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2324 (as long as the randomization is enabled).
2326 @item show disable-randomization
2327 Show the current setting of the explicit disable of the native randomization of
2328 the virtual address space of the started program.
2333 @section Your Program's Arguments
2335 @cindex arguments (to your program)
2336 The arguments to your program can be specified by the arguments of the
2338 They are passed to a shell, which expands wildcard characters and
2339 performs redirection of I/O, and thence to your program. Your
2340 @code{SHELL} environment variable (if it exists) specifies what shell
2341 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2342 the default shell (@file{/bin/sh} on Unix).
2344 On non-Unix systems, the program is usually invoked directly by
2345 @value{GDBN}, which emulates I/O redirection via the appropriate system
2346 calls, and the wildcard characters are expanded by the startup code of
2347 the program, not by the shell.
2349 @code{run} with no arguments uses the same arguments used by the previous
2350 @code{run}, or those set by the @code{set args} command.
2355 Specify the arguments to be used the next time your program is run. If
2356 @code{set args} has no arguments, @code{run} executes your program
2357 with no arguments. Once you have run your program with arguments,
2358 using @code{set args} before the next @code{run} is the only way to run
2359 it again without arguments.
2363 Show the arguments to give your program when it is started.
2367 @section Your Program's Environment
2369 @cindex environment (of your program)
2370 The @dfn{environment} consists of a set of environment variables and
2371 their values. Environment variables conventionally record such things as
2372 your user name, your home directory, your terminal type, and your search
2373 path for programs to run. Usually you set up environment variables with
2374 the shell and they are inherited by all the other programs you run. When
2375 debugging, it can be useful to try running your program with a modified
2376 environment without having to start @value{GDBN} over again.
2380 @item path @var{directory}
2381 Add @var{directory} to the front of the @code{PATH} environment variable
2382 (the search path for executables) that will be passed to your program.
2383 The value of @code{PATH} used by @value{GDBN} does not change.
2384 You may specify several directory names, separated by whitespace or by a
2385 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2386 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2387 is moved to the front, so it is searched sooner.
2389 You can use the string @samp{$cwd} to refer to whatever is the current
2390 working directory at the time @value{GDBN} searches the path. If you
2391 use @samp{.} instead, it refers to the directory where you executed the
2392 @code{path} command. @value{GDBN} replaces @samp{.} in the
2393 @var{directory} argument (with the current path) before adding
2394 @var{directory} to the search path.
2395 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2396 @c document that, since repeating it would be a no-op.
2400 Display the list of search paths for executables (the @code{PATH}
2401 environment variable).
2403 @kindex show environment
2404 @item show environment @r{[}@var{varname}@r{]}
2405 Print the value of environment variable @var{varname} to be given to
2406 your program when it starts. If you do not supply @var{varname},
2407 print the names and values of all environment variables to be given to
2408 your program. You can abbreviate @code{environment} as @code{env}.
2410 @kindex set environment
2411 @anchor{set environment}
2412 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2413 Set environment variable @var{varname} to @var{value}. The value
2414 changes for your program (and the shell @value{GDBN} uses to launch
2415 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2416 values of environment variables are just strings, and any
2417 interpretation is supplied by your program itself. The @var{value}
2418 parameter is optional; if it is eliminated, the variable is set to a
2420 @c "any string" here does not include leading, trailing
2421 @c blanks. Gnu asks: does anyone care?
2423 For example, this command:
2430 tells the debugged program, when subsequently run, that its user is named
2431 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2432 are not actually required.)
2434 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2435 which also inherits the environment set with @code{set environment}.
2436 If necessary, you can avoid that by using the @samp{env} program as a
2437 wrapper instead of using @code{set environment}. @xref{set
2438 exec-wrapper}, for an example doing just that.
2440 Environment variables that are set by the user are also transmitted to
2441 @command{gdbserver} to be used when starting the remote inferior.
2442 @pxref{QEnvironmentHexEncoded}.
2444 @kindex unset environment
2445 @anchor{unset environment}
2446 @item unset environment @var{varname}
2447 Remove variable @var{varname} from the environment to be passed to your
2448 program. This is different from @samp{set env @var{varname} =};
2449 @code{unset environment} removes the variable from the environment,
2450 rather than assigning it an empty value.
2452 Environment variables that are unset by the user are also unset on
2453 @command{gdbserver} when starting the remote inferior.
2454 @pxref{QEnvironmentUnset}.
2457 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2458 the shell indicated by your @code{SHELL} environment variable if it
2459 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2460 names a shell that runs an initialization file when started
2461 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2462 for the Z shell, or the file specified in the @samp{BASH_ENV}
2463 environment variable for BASH---any variables you set in that file
2464 affect your program. You may wish to move setting of environment
2465 variables to files that are only run when you sign on, such as
2466 @file{.login} or @file{.profile}.
2468 @node Working Directory
2469 @section Your Program's Working Directory
2471 @cindex working directory (of your program)
2472 Each time you start your program with @code{run}, the inferior will be
2473 initialized with the current working directory specified by the
2474 @kbd{set cwd} command. If no directory has been specified by this
2475 command, then the inferior will inherit @value{GDBN}'s current working
2476 directory as its working directory if native debugging, or it will
2477 inherit the remote server's current working directory if remote
2482 @cindex change inferior's working directory
2483 @anchor{set cwd command}
2484 @item set cwd @r{[}@var{directory}@r{]}
2485 Set the inferior's working directory to @var{directory}, which will be
2486 @code{glob}-expanded in order to resolve tildes (@file{~}). If no
2487 argument has been specified, the command clears the setting and resets
2488 it to an empty state. This setting has no effect on @value{GDBN}'s
2489 working directory, and it only takes effect the next time you start
2490 the inferior. The @file{~} in @var{directory} is a short for the
2491 @dfn{home directory}, usually pointed to by the @env{HOME} environment
2492 variable. On MS-Windows, if @env{HOME} is not defined, @value{GDBN}
2493 uses the concatenation of @env{HOMEDRIVE} and @env{HOMEPATH} as
2496 You can also change @value{GDBN}'s current working directory by using
2497 the @code{cd} command.
2501 @cindex show inferior's working directory
2503 Show the inferior's working directory. If no directory has been
2504 specified by @kbd{set cwd}, then the default inferior's working
2505 directory is the same as @value{GDBN}'s working directory.
2508 @cindex change @value{GDBN}'s working directory
2510 @item cd @r{[}@var{directory}@r{]}
2511 Set the @value{GDBN} working directory to @var{directory}. If not
2512 given, @var{directory} uses @file{'~'}.
2514 The @value{GDBN} working directory serves as a default for the
2515 commands that specify files for @value{GDBN} to operate on.
2516 @xref{Files, ,Commands to Specify Files}.
2517 @xref{set cwd command}
2521 Print the @value{GDBN} working directory.
2524 It is generally impossible to find the current working directory of
2525 the process being debugged (since a program can change its directory
2526 during its run). If you work on a system where @value{GDBN} is
2527 configured with the @file{/proc} support, you can use the @code{info
2528 proc} command (@pxref{SVR4 Process Information}) to find out the
2529 current working directory of the debuggee.
2532 @section Your Program's Input and Output
2537 By default, the program you run under @value{GDBN} does input and output to
2538 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2539 to its own terminal modes to interact with you, but it records the terminal
2540 modes your program was using and switches back to them when you continue
2541 running your program.
2544 @kindex info terminal
2546 Displays information recorded by @value{GDBN} about the terminal modes your
2550 You can redirect your program's input and/or output using shell
2551 redirection with the @code{run} command. For example,
2558 starts your program, diverting its output to the file @file{outfile}.
2561 @cindex controlling terminal
2562 Another way to specify where your program should do input and output is
2563 with the @code{tty} command. This command accepts a file name as
2564 argument, and causes this file to be the default for future @code{run}
2565 commands. It also resets the controlling terminal for the child
2566 process, for future @code{run} commands. For example,
2573 directs that processes started with subsequent @code{run} commands
2574 default to do input and output on the terminal @file{/dev/ttyb} and have
2575 that as their controlling terminal.
2577 An explicit redirection in @code{run} overrides the @code{tty} command's
2578 effect on the input/output device, but not its effect on the controlling
2581 When you use the @code{tty} command or redirect input in the @code{run}
2582 command, only the input @emph{for your program} is affected. The input
2583 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2584 for @code{set inferior-tty}.
2586 @cindex inferior tty
2587 @cindex set inferior controlling terminal
2588 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2589 display the name of the terminal that will be used for future runs of your
2593 @item set inferior-tty [ @var{tty} ]
2594 @kindex set inferior-tty
2595 Set the tty for the program being debugged to @var{tty}. Omitting @var{tty}
2596 restores the default behavior, which is to use the same terminal as
2599 @item show inferior-tty
2600 @kindex show inferior-tty
2601 Show the current tty for the program being debugged.
2605 @section Debugging an Already-running Process
2610 @item attach @var{process-id}
2611 This command attaches to a running process---one that was started
2612 outside @value{GDBN}. (@code{info files} shows your active
2613 targets.) The command takes as argument a process ID. The usual way to
2614 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2615 or with the @samp{jobs -l} shell command.
2617 @code{attach} does not repeat if you press @key{RET} a second time after
2618 executing the command.
2621 To use @code{attach}, your program must be running in an environment
2622 which supports processes; for example, @code{attach} does not work for
2623 programs on bare-board targets that lack an operating system. You must
2624 also have permission to send the process a signal.
2626 When you use @code{attach}, the debugger finds the program running in
2627 the process first by looking in the current working directory, then (if
2628 the program is not found) by using the source file search path
2629 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2630 the @code{file} command to load the program. @xref{Files, ,Commands to
2633 The first thing @value{GDBN} does after arranging to debug the specified
2634 process is to stop it. You can examine and modify an attached process
2635 with all the @value{GDBN} commands that are ordinarily available when
2636 you start processes with @code{run}. You can insert breakpoints; you
2637 can step and continue; you can modify storage. If you would rather the
2638 process continue running, you may use the @code{continue} command after
2639 attaching @value{GDBN} to the process.
2644 When you have finished debugging the attached process, you can use the
2645 @code{detach} command to release it from @value{GDBN} control. Detaching
2646 the process continues its execution. After the @code{detach} command,
2647 that process and @value{GDBN} become completely independent once more, and you
2648 are ready to @code{attach} another process or start one with @code{run}.
2649 @code{detach} does not repeat if you press @key{RET} again after
2650 executing the command.
2653 If you exit @value{GDBN} while you have an attached process, you detach
2654 that process. If you use the @code{run} command, you kill that process.
2655 By default, @value{GDBN} asks for confirmation if you try to do either of these
2656 things; you can control whether or not you need to confirm by using the
2657 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2661 @section Killing the Child Process
2666 Kill the child process in which your program is running under @value{GDBN}.
2669 This command is useful if you wish to debug a core dump instead of a
2670 running process. @value{GDBN} ignores any core dump file while your program
2673 On some operating systems, a program cannot be executed outside @value{GDBN}
2674 while you have breakpoints set on it inside @value{GDBN}. You can use the
2675 @code{kill} command in this situation to permit running your program
2676 outside the debugger.
2678 The @code{kill} command is also useful if you wish to recompile and
2679 relink your program, since on many systems it is impossible to modify an
2680 executable file while it is running in a process. In this case, when you
2681 next type @code{run}, @value{GDBN} notices that the file has changed, and
2682 reads the symbol table again (while trying to preserve your current
2683 breakpoint settings).
2685 @node Inferiors and Programs
2686 @section Debugging Multiple Inferiors and Programs
2688 @value{GDBN} lets you run and debug multiple programs in a single
2689 session. In addition, @value{GDBN} on some systems may let you run
2690 several programs simultaneously (otherwise you have to exit from one
2691 before starting another). In the most general case, you can have
2692 multiple threads of execution in each of multiple processes, launched
2693 from multiple executables.
2696 @value{GDBN} represents the state of each program execution with an
2697 object called an @dfn{inferior}. An inferior typically corresponds to
2698 a process, but is more general and applies also to targets that do not
2699 have processes. Inferiors may be created before a process runs, and
2700 may be retained after a process exits. Inferiors have unique
2701 identifiers that are different from process ids. Usually each
2702 inferior will also have its own distinct address space, although some
2703 embedded targets may have several inferiors running in different parts
2704 of a single address space. Each inferior may in turn have multiple
2705 threads running in it.
2707 To find out what inferiors exist at any moment, use @w{@code{info
2711 @kindex info inferiors
2712 @item info inferiors
2713 Print a list of all inferiors currently being managed by @value{GDBN}.
2715 @value{GDBN} displays for each inferior (in this order):
2719 the inferior number assigned by @value{GDBN}
2722 the target system's inferior identifier
2725 the name of the executable the inferior is running.
2730 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2731 indicates the current inferior.
2735 @c end table here to get a little more width for example
2738 (@value{GDBP}) info inferiors
2739 Num Description Executable
2740 2 process 2307 hello
2741 * 1 process 3401 goodbye
2744 To switch focus between inferiors, use the @code{inferior} command:
2747 @kindex inferior @var{infno}
2748 @item inferior @var{infno}
2749 Make inferior number @var{infno} the current inferior. The argument
2750 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2751 in the first field of the @samp{info inferiors} display.
2754 @vindex $_inferior@r{, convenience variable}
2755 The debugger convenience variable @samp{$_inferior} contains the
2756 number of the current inferior. You may find this useful in writing
2757 breakpoint conditional expressions, command scripts, and so forth.
2758 @xref{Convenience Vars,, Convenience Variables}, for general
2759 information on convenience variables.
2761 You can get multiple executables into a debugging session via the
2762 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2763 systems @value{GDBN} can add inferiors to the debug session
2764 automatically by following calls to @code{fork} and @code{exec}. To
2765 remove inferiors from the debugging session use the
2766 @w{@code{remove-inferiors}} command.
2769 @kindex add-inferior
2770 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2771 Adds @var{n} inferiors to be run using @var{executable} as the
2772 executable; @var{n} defaults to 1. If no executable is specified,
2773 the inferiors begins empty, with no program. You can still assign or
2774 change the program assigned to the inferior at any time by using the
2775 @code{file} command with the executable name as its argument.
2777 @kindex clone-inferior
2778 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2779 Adds @var{n} inferiors ready to execute the same program as inferior
2780 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2781 number of the current inferior. This is a convenient command when you
2782 want to run another instance of the inferior you are debugging.
2785 (@value{GDBP}) info inferiors
2786 Num Description Executable
2787 * 1 process 29964 helloworld
2788 (@value{GDBP}) clone-inferior
2791 (@value{GDBP}) info inferiors
2792 Num Description Executable
2794 * 1 process 29964 helloworld
2797 You can now simply switch focus to inferior 2 and run it.
2799 @kindex remove-inferiors
2800 @item remove-inferiors @var{infno}@dots{}
2801 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2802 possible to remove an inferior that is running with this command. For
2803 those, use the @code{kill} or @code{detach} command first.
2807 To quit debugging one of the running inferiors that is not the current
2808 inferior, you can either detach from it by using the @w{@code{detach
2809 inferior}} command (allowing it to run independently), or kill it
2810 using the @w{@code{kill inferiors}} command:
2813 @kindex detach inferiors @var{infno}@dots{}
2814 @item detach inferior @var{infno}@dots{}
2815 Detach from the inferior or inferiors identified by @value{GDBN}
2816 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2817 still stays on the list of inferiors shown by @code{info inferiors},
2818 but its Description will show @samp{<null>}.
2820 @kindex kill inferiors @var{infno}@dots{}
2821 @item kill inferiors @var{infno}@dots{}
2822 Kill the inferior or inferiors identified by @value{GDBN} inferior
2823 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2824 stays on the list of inferiors shown by @code{info inferiors}, but its
2825 Description will show @samp{<null>}.
2828 After the successful completion of a command such as @code{detach},
2829 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2830 a normal process exit, the inferior is still valid and listed with
2831 @code{info inferiors}, ready to be restarted.
2834 To be notified when inferiors are started or exit under @value{GDBN}'s
2835 control use @w{@code{set print inferior-events}}:
2838 @kindex set print inferior-events
2839 @cindex print messages on inferior start and exit
2840 @item set print inferior-events
2841 @itemx set print inferior-events on
2842 @itemx set print inferior-events off
2843 The @code{set print inferior-events} command allows you to enable or
2844 disable printing of messages when @value{GDBN} notices that new
2845 inferiors have started or that inferiors have exited or have been
2846 detached. By default, these messages will not be printed.
2848 @kindex show print inferior-events
2849 @item show print inferior-events
2850 Show whether messages will be printed when @value{GDBN} detects that
2851 inferiors have started, exited or have been detached.
2854 Many commands will work the same with multiple programs as with a
2855 single program: e.g., @code{print myglobal} will simply display the
2856 value of @code{myglobal} in the current inferior.
2859 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2860 get more info about the relationship of inferiors, programs, address
2861 spaces in a debug session. You can do that with the @w{@code{maint
2862 info program-spaces}} command.
2865 @kindex maint info program-spaces
2866 @item maint info program-spaces
2867 Print a list of all program spaces currently being managed by
2870 @value{GDBN} displays for each program space (in this order):
2874 the program space number assigned by @value{GDBN}
2877 the name of the executable loaded into the program space, with e.g.,
2878 the @code{file} command.
2883 An asterisk @samp{*} preceding the @value{GDBN} program space number
2884 indicates the current program space.
2886 In addition, below each program space line, @value{GDBN} prints extra
2887 information that isn't suitable to display in tabular form. For
2888 example, the list of inferiors bound to the program space.
2891 (@value{GDBP}) maint info program-spaces
2895 Bound inferiors: ID 1 (process 21561)
2898 Here we can see that no inferior is running the program @code{hello},
2899 while @code{process 21561} is running the program @code{goodbye}. On
2900 some targets, it is possible that multiple inferiors are bound to the
2901 same program space. The most common example is that of debugging both
2902 the parent and child processes of a @code{vfork} call. For example,
2905 (@value{GDBP}) maint info program-spaces
2908 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2911 Here, both inferior 2 and inferior 1 are running in the same program
2912 space as a result of inferior 1 having executed a @code{vfork} call.
2916 @section Debugging Programs with Multiple Threads
2918 @cindex threads of execution
2919 @cindex multiple threads
2920 @cindex switching threads
2921 In some operating systems, such as GNU/Linux and Solaris, a single program
2922 may have more than one @dfn{thread} of execution. The precise semantics
2923 of threads differ from one operating system to another, but in general
2924 the threads of a single program are akin to multiple processes---except
2925 that they share one address space (that is, they can all examine and
2926 modify the same variables). On the other hand, each thread has its own
2927 registers and execution stack, and perhaps private memory.
2929 @value{GDBN} provides these facilities for debugging multi-thread
2933 @item automatic notification of new threads
2934 @item @samp{thread @var{thread-id}}, a command to switch among threads
2935 @item @samp{info threads}, a command to inquire about existing threads
2936 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2937 a command to apply a command to a list of threads
2938 @item thread-specific breakpoints
2939 @item @samp{set print thread-events}, which controls printing of
2940 messages on thread start and exit.
2941 @item @samp{set libthread-db-search-path @var{path}}, which lets
2942 the user specify which @code{libthread_db} to use if the default choice
2943 isn't compatible with the program.
2946 @cindex focus of debugging
2947 @cindex current thread
2948 The @value{GDBN} thread debugging facility allows you to observe all
2949 threads while your program runs---but whenever @value{GDBN} takes
2950 control, one thread in particular is always the focus of debugging.
2951 This thread is called the @dfn{current thread}. Debugging commands show
2952 program information from the perspective of the current thread.
2954 @cindex @code{New} @var{systag} message
2955 @cindex thread identifier (system)
2956 @c FIXME-implementors!! It would be more helpful if the [New...] message
2957 @c included GDB's numeric thread handle, so you could just go to that
2958 @c thread without first checking `info threads'.
2959 Whenever @value{GDBN} detects a new thread in your program, it displays
2960 the target system's identification for the thread with a message in the
2961 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2962 whose form varies depending on the particular system. For example, on
2963 @sc{gnu}/Linux, you might see
2966 [New Thread 0x41e02940 (LWP 25582)]
2970 when @value{GDBN} notices a new thread. In contrast, on other systems,
2971 the @var{systag} is simply something like @samp{process 368}, with no
2974 @c FIXME!! (1) Does the [New...] message appear even for the very first
2975 @c thread of a program, or does it only appear for the
2976 @c second---i.e.@: when it becomes obvious we have a multithread
2978 @c (2) *Is* there necessarily a first thread always? Or do some
2979 @c multithread systems permit starting a program with multiple
2980 @c threads ab initio?
2982 @anchor{thread numbers}
2983 @cindex thread number, per inferior
2984 @cindex thread identifier (GDB)
2985 For debugging purposes, @value{GDBN} associates its own thread number
2986 ---always a single integer---with each thread of an inferior. This
2987 number is unique between all threads of an inferior, but not unique
2988 between threads of different inferiors.
2990 @cindex qualified thread ID
2991 You can refer to a given thread in an inferior using the qualified
2992 @var{inferior-num}.@var{thread-num} syntax, also known as
2993 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2994 number and @var{thread-num} being the thread number of the given
2995 inferior. For example, thread @code{2.3} refers to thread number 3 of
2996 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2997 then @value{GDBN} infers you're referring to a thread of the current
3000 Until you create a second inferior, @value{GDBN} does not show the
3001 @var{inferior-num} part of thread IDs, even though you can always use
3002 the full @var{inferior-num}.@var{thread-num} form to refer to threads
3003 of inferior 1, the initial inferior.
3005 @anchor{thread ID lists}
3006 @cindex thread ID lists
3007 Some commands accept a space-separated @dfn{thread ID list} as
3008 argument. A list element can be:
3012 A thread ID as shown in the first field of the @samp{info threads}
3013 display, with or without an inferior qualifier. E.g., @samp{2.1} or
3017 A range of thread numbers, again with or without an inferior
3018 qualifier, as in @var{inf}.@var{thr1}-@var{thr2} or
3019 @var{thr1}-@var{thr2}. E.g., @samp{1.2-4} or @samp{2-4}.
3022 All threads of an inferior, specified with a star wildcard, with or
3023 without an inferior qualifier, as in @var{inf}.@code{*} (e.g.,
3024 @samp{1.*}) or @code{*}. The former refers to all threads of the
3025 given inferior, and the latter form without an inferior qualifier
3026 refers to all threads of the current inferior.
3030 For example, if the current inferior is 1, and inferior 7 has one
3031 thread with ID 7.1, the thread list @samp{1 2-3 4.5 6.7-9 7.*}
3032 includes threads 1 to 3 of inferior 1, thread 5 of inferior 4, threads
3033 7 to 9 of inferior 6 and all threads of inferior 7. That is, in
3034 expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5 6.7 6.8 6.9
3038 @anchor{global thread numbers}
3039 @cindex global thread number
3040 @cindex global thread identifier (GDB)
3041 In addition to a @emph{per-inferior} number, each thread is also
3042 assigned a unique @emph{global} number, also known as @dfn{global
3043 thread ID}, a single integer. Unlike the thread number component of
3044 the thread ID, no two threads have the same global ID, even when
3045 you're debugging multiple inferiors.
3047 From @value{GDBN}'s perspective, a process always has at least one
3048 thread. In other words, @value{GDBN} assigns a thread number to the
3049 program's ``main thread'' even if the program is not multi-threaded.
3051 @vindex $_thread@r{, convenience variable}
3052 @vindex $_gthread@r{, convenience variable}
3053 The debugger convenience variables @samp{$_thread} and
3054 @samp{$_gthread} contain, respectively, the per-inferior thread number
3055 and the global thread number of the current thread. You may find this
3056 useful in writing breakpoint conditional expressions, command scripts,
3057 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
3058 general information on convenience variables.
3060 If @value{GDBN} detects the program is multi-threaded, it augments the
3061 usual message about stopping at a breakpoint with the ID and name of
3062 the thread that hit the breakpoint.
3065 Thread 2 "client" hit Breakpoint 1, send_message () at client.c:68
3068 Likewise when the program receives a signal:
3071 Thread 1 "main" received signal SIGINT, Interrupt.
3075 @kindex info threads
3076 @item info threads @r{[}@var{thread-id-list}@r{]}
3078 Display information about one or more threads. With no arguments
3079 displays information about all threads. You can specify the list of
3080 threads that you want to display using the thread ID list syntax
3081 (@pxref{thread ID lists}).
3083 @value{GDBN} displays for each thread (in this order):
3087 the per-inferior thread number assigned by @value{GDBN}
3090 the global thread number assigned by @value{GDBN}, if the @samp{-gid}
3091 option was specified
3094 the target system's thread identifier (@var{systag})
3097 the thread's name, if one is known. A thread can either be named by
3098 the user (see @code{thread name}, below), or, in some cases, by the
3102 the current stack frame summary for that thread
3106 An asterisk @samp{*} to the left of the @value{GDBN} thread number
3107 indicates the current thread.
3111 @c end table here to get a little more width for example
3114 (@value{GDBP}) info threads
3116 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3117 2 process 35 thread 23 0x34e5 in sigpause ()
3118 3 process 35 thread 27 0x34e5 in sigpause ()
3122 If you're debugging multiple inferiors, @value{GDBN} displays thread
3123 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
3124 Otherwise, only @var{thread-num} is shown.
3126 If you specify the @samp{-gid} option, @value{GDBN} displays a column
3127 indicating each thread's global thread ID:
3130 (@value{GDBP}) info threads
3131 Id GId Target Id Frame
3132 1.1 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
3133 1.2 3 process 35 thread 23 0x34e5 in sigpause ()
3134 1.3 4 process 35 thread 27 0x34e5 in sigpause ()
3135 * 2.1 2 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3138 On Solaris, you can display more information about user threads with a
3139 Solaris-specific command:
3142 @item maint info sol-threads
3143 @kindex maint info sol-threads
3144 @cindex thread info (Solaris)
3145 Display info on Solaris user threads.
3149 @kindex thread @var{thread-id}
3150 @item thread @var{thread-id}
3151 Make thread ID @var{thread-id} the current thread. The command
3152 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3153 the first field of the @samp{info threads} display, with or without an
3154 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3156 @value{GDBN} responds by displaying the system identifier of the
3157 thread you selected, and its current stack frame summary:
3160 (@value{GDBP}) thread 2
3161 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3162 #0 some_function (ignore=0x0) at example.c:8
3163 8 printf ("hello\n");
3167 As with the @samp{[New @dots{}]} message, the form of the text after
3168 @samp{Switching to} depends on your system's conventions for identifying
3171 @kindex thread apply
3172 @cindex apply command to several threads
3173 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3174 The @code{thread apply} command allows you to apply the named
3175 @var{command} to one or more threads. Specify the threads that you
3176 want affected using the thread ID list syntax (@pxref{thread ID
3177 lists}), or specify @code{all} to apply to all threads. To apply a
3178 command to all threads in descending order, type @kbd{thread apply all
3179 @var{command}}. To apply a command to all threads in ascending order,
3180 type @kbd{thread apply all -ascending @var{command}}.
3184 @cindex name a thread
3185 @item thread name [@var{name}]
3186 This command assigns a name to the current thread. If no argument is
3187 given, any existing user-specified name is removed. The thread name
3188 appears in the @samp{info threads} display.
3190 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3191 determine the name of the thread as given by the OS. On these
3192 systems, a name specified with @samp{thread name} will override the
3193 system-give name, and removing the user-specified name will cause
3194 @value{GDBN} to once again display the system-specified name.
3197 @cindex search for a thread
3198 @item thread find [@var{regexp}]
3199 Search for and display thread ids whose name or @var{systag}
3200 matches the supplied regular expression.
3202 As well as being the complement to the @samp{thread name} command,
3203 this command also allows you to identify a thread by its target
3204 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3208 (@value{GDBN}) thread find 26688
3209 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3210 (@value{GDBN}) info thread 4
3212 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3215 @kindex set print thread-events
3216 @cindex print messages on thread start and exit
3217 @item set print thread-events
3218 @itemx set print thread-events on
3219 @itemx set print thread-events off
3220 The @code{set print thread-events} command allows you to enable or
3221 disable printing of messages when @value{GDBN} notices that new threads have
3222 started or that threads have exited. By default, these messages will
3223 be printed if detection of these events is supported by the target.
3224 Note that these messages cannot be disabled on all targets.
3226 @kindex show print thread-events
3227 @item show print thread-events
3228 Show whether messages will be printed when @value{GDBN} detects that threads
3229 have started and exited.
3232 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3233 more information about how @value{GDBN} behaves when you stop and start
3234 programs with multiple threads.
3236 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3237 watchpoints in programs with multiple threads.
3239 @anchor{set libthread-db-search-path}
3241 @kindex set libthread-db-search-path
3242 @cindex search path for @code{libthread_db}
3243 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3244 If this variable is set, @var{path} is a colon-separated list of
3245 directories @value{GDBN} will use to search for @code{libthread_db}.
3246 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3247 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3248 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3251 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3252 @code{libthread_db} library to obtain information about threads in the
3253 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3254 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3255 specific thread debugging library loading is enabled
3256 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3258 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3259 refers to the default system directories that are
3260 normally searched for loading shared libraries. The @samp{$sdir} entry
3261 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3262 (@pxref{libthread_db.so.1 file}).
3264 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3265 refers to the directory from which @code{libpthread}
3266 was loaded in the inferior process.
3268 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3269 @value{GDBN} attempts to initialize it with the current inferior process.
3270 If this initialization fails (which could happen because of a version
3271 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3272 will unload @code{libthread_db}, and continue with the next directory.
3273 If none of @code{libthread_db} libraries initialize successfully,
3274 @value{GDBN} will issue a warning and thread debugging will be disabled.
3276 Setting @code{libthread-db-search-path} is currently implemented
3277 only on some platforms.
3279 @kindex show libthread-db-search-path
3280 @item show libthread-db-search-path
3281 Display current libthread_db search path.
3283 @kindex set debug libthread-db
3284 @kindex show debug libthread-db
3285 @cindex debugging @code{libthread_db}
3286 @item set debug libthread-db
3287 @itemx show debug libthread-db
3288 Turns on or off display of @code{libthread_db}-related events.
3289 Use @code{1} to enable, @code{0} to disable.
3293 @section Debugging Forks
3295 @cindex fork, debugging programs which call
3296 @cindex multiple processes
3297 @cindex processes, multiple
3298 On most systems, @value{GDBN} has no special support for debugging
3299 programs which create additional processes using the @code{fork}
3300 function. When a program forks, @value{GDBN} will continue to debug the
3301 parent process and the child process will run unimpeded. If you have
3302 set a breakpoint in any code which the child then executes, the child
3303 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3304 will cause it to terminate.
3306 However, if you want to debug the child process there is a workaround
3307 which isn't too painful. Put a call to @code{sleep} in the code which
3308 the child process executes after the fork. It may be useful to sleep
3309 only if a certain environment variable is set, or a certain file exists,
3310 so that the delay need not occur when you don't want to run @value{GDBN}
3311 on the child. While the child is sleeping, use the @code{ps} program to
3312 get its process ID. Then tell @value{GDBN} (a new invocation of
3313 @value{GDBN} if you are also debugging the parent process) to attach to
3314 the child process (@pxref{Attach}). From that point on you can debug
3315 the child process just like any other process which you attached to.
3317 On some systems, @value{GDBN} provides support for debugging programs
3318 that create additional processes using the @code{fork} or @code{vfork}
3319 functions. On @sc{gnu}/Linux platforms, this feature is supported
3320 with kernel version 2.5.46 and later.
3322 The fork debugging commands are supported in native mode and when
3323 connected to @code{gdbserver} in either @code{target remote} mode or
3324 @code{target extended-remote} mode.
3326 By default, when a program forks, @value{GDBN} will continue to debug
3327 the parent process and the child process will run unimpeded.
3329 If you want to follow the child process instead of the parent process,
3330 use the command @w{@code{set follow-fork-mode}}.
3333 @kindex set follow-fork-mode
3334 @item set follow-fork-mode @var{mode}
3335 Set the debugger response to a program call of @code{fork} or
3336 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3337 process. The @var{mode} argument can be:
3341 The original process is debugged after a fork. The child process runs
3342 unimpeded. This is the default.
3345 The new process is debugged after a fork. The parent process runs
3350 @kindex show follow-fork-mode
3351 @item show follow-fork-mode
3352 Display the current debugger response to a @code{fork} or @code{vfork} call.
3355 @cindex debugging multiple processes
3356 On Linux, if you want to debug both the parent and child processes, use the
3357 command @w{@code{set detach-on-fork}}.
3360 @kindex set detach-on-fork
3361 @item set detach-on-fork @var{mode}
3362 Tells gdb whether to detach one of the processes after a fork, or
3363 retain debugger control over them both.
3367 The child process (or parent process, depending on the value of
3368 @code{follow-fork-mode}) will be detached and allowed to run
3369 independently. This is the default.
3372 Both processes will be held under the control of @value{GDBN}.
3373 One process (child or parent, depending on the value of
3374 @code{follow-fork-mode}) is debugged as usual, while the other
3379 @kindex show detach-on-fork
3380 @item show detach-on-fork
3381 Show whether detach-on-fork mode is on/off.
3384 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3385 will retain control of all forked processes (including nested forks).
3386 You can list the forked processes under the control of @value{GDBN} by
3387 using the @w{@code{info inferiors}} command, and switch from one fork
3388 to another by using the @code{inferior} command (@pxref{Inferiors and
3389 Programs, ,Debugging Multiple Inferiors and Programs}).
3391 To quit debugging one of the forked processes, you can either detach
3392 from it by using the @w{@code{detach inferiors}} command (allowing it
3393 to run independently), or kill it using the @w{@code{kill inferiors}}
3394 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3397 If you ask to debug a child process and a @code{vfork} is followed by an
3398 @code{exec}, @value{GDBN} executes the new target up to the first
3399 breakpoint in the new target. If you have a breakpoint set on
3400 @code{main} in your original program, the breakpoint will also be set on
3401 the child process's @code{main}.
3403 On some systems, when a child process is spawned by @code{vfork}, you
3404 cannot debug the child or parent until an @code{exec} call completes.
3406 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3407 call executes, the new target restarts. To restart the parent
3408 process, use the @code{file} command with the parent executable name
3409 as its argument. By default, after an @code{exec} call executes,
3410 @value{GDBN} discards the symbols of the previous executable image.
3411 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3415 @kindex set follow-exec-mode
3416 @item set follow-exec-mode @var{mode}
3418 Set debugger response to a program call of @code{exec}. An
3419 @code{exec} call replaces the program image of a process.
3421 @code{follow-exec-mode} can be:
3425 @value{GDBN} creates a new inferior and rebinds the process to this
3426 new inferior. The program the process was running before the
3427 @code{exec} call can be restarted afterwards by restarting the
3433 (@value{GDBP}) info inferiors
3435 Id Description Executable
3438 process 12020 is executing new program: prog2
3439 Program exited normally.
3440 (@value{GDBP}) info inferiors
3441 Id Description Executable
3447 @value{GDBN} keeps the process bound to the same inferior. The new
3448 executable image replaces the previous executable loaded in the
3449 inferior. Restarting the inferior after the @code{exec} call, with
3450 e.g., the @code{run} command, restarts the executable the process was
3451 running after the @code{exec} call. This is the default mode.
3456 (@value{GDBP}) info inferiors
3457 Id Description Executable
3460 process 12020 is executing new program: prog2
3461 Program exited normally.
3462 (@value{GDBP}) info inferiors
3463 Id Description Executable
3470 @code{follow-exec-mode} is supported in native mode and
3471 @code{target extended-remote} mode.
3473 You can use the @code{catch} command to make @value{GDBN} stop whenever
3474 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3475 Catchpoints, ,Setting Catchpoints}.
3477 @node Checkpoint/Restart
3478 @section Setting a @emph{Bookmark} to Return to Later
3483 @cindex snapshot of a process
3484 @cindex rewind program state
3486 On certain operating systems@footnote{Currently, only
3487 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3488 program's state, called a @dfn{checkpoint}, and come back to it
3491 Returning to a checkpoint effectively undoes everything that has
3492 happened in the program since the @code{checkpoint} was saved. This
3493 includes changes in memory, registers, and even (within some limits)
3494 system state. Effectively, it is like going back in time to the
3495 moment when the checkpoint was saved.
3497 Thus, if you're stepping thru a program and you think you're
3498 getting close to the point where things go wrong, you can save
3499 a checkpoint. Then, if you accidentally go too far and miss
3500 the critical statement, instead of having to restart your program
3501 from the beginning, you can just go back to the checkpoint and
3502 start again from there.
3504 This can be especially useful if it takes a lot of time or
3505 steps to reach the point where you think the bug occurs.
3507 To use the @code{checkpoint}/@code{restart} method of debugging:
3512 Save a snapshot of the debugged program's current execution state.
3513 The @code{checkpoint} command takes no arguments, but each checkpoint
3514 is assigned a small integer id, similar to a breakpoint id.
3516 @kindex info checkpoints
3517 @item info checkpoints
3518 List the checkpoints that have been saved in the current debugging
3519 session. For each checkpoint, the following information will be
3526 @item Source line, or label
3529 @kindex restart @var{checkpoint-id}
3530 @item restart @var{checkpoint-id}
3531 Restore the program state that was saved as checkpoint number
3532 @var{checkpoint-id}. All program variables, registers, stack frames
3533 etc.@: will be returned to the values that they had when the checkpoint
3534 was saved. In essence, gdb will ``wind back the clock'' to the point
3535 in time when the checkpoint was saved.
3537 Note that breakpoints, @value{GDBN} variables, command history etc.
3538 are not affected by restoring a checkpoint. In general, a checkpoint
3539 only restores things that reside in the program being debugged, not in
3542 @kindex delete checkpoint @var{checkpoint-id}
3543 @item delete checkpoint @var{checkpoint-id}
3544 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3548 Returning to a previously saved checkpoint will restore the user state
3549 of the program being debugged, plus a significant subset of the system
3550 (OS) state, including file pointers. It won't ``un-write'' data from
3551 a file, but it will rewind the file pointer to the previous location,
3552 so that the previously written data can be overwritten. For files
3553 opened in read mode, the pointer will also be restored so that the
3554 previously read data can be read again.
3556 Of course, characters that have been sent to a printer (or other
3557 external device) cannot be ``snatched back'', and characters received
3558 from eg.@: a serial device can be removed from internal program buffers,
3559 but they cannot be ``pushed back'' into the serial pipeline, ready to
3560 be received again. Similarly, the actual contents of files that have
3561 been changed cannot be restored (at this time).
3563 However, within those constraints, you actually can ``rewind'' your
3564 program to a previously saved point in time, and begin debugging it
3565 again --- and you can change the course of events so as to debug a
3566 different execution path this time.
3568 @cindex checkpoints and process id
3569 Finally, there is one bit of internal program state that will be
3570 different when you return to a checkpoint --- the program's process
3571 id. Each checkpoint will have a unique process id (or @var{pid}),
3572 and each will be different from the program's original @var{pid}.
3573 If your program has saved a local copy of its process id, this could
3574 potentially pose a problem.
3576 @subsection A Non-obvious Benefit of Using Checkpoints
3578 On some systems such as @sc{gnu}/Linux, address space randomization
3579 is performed on new processes for security reasons. This makes it
3580 difficult or impossible to set a breakpoint, or watchpoint, on an
3581 absolute address if you have to restart the program, since the
3582 absolute location of a symbol will change from one execution to the
3585 A checkpoint, however, is an @emph{identical} copy of a process.
3586 Therefore if you create a checkpoint at (eg.@:) the start of main,
3587 and simply return to that checkpoint instead of restarting the
3588 process, you can avoid the effects of address randomization and
3589 your symbols will all stay in the same place.
3592 @chapter Stopping and Continuing
3594 The principal purposes of using a debugger are so that you can stop your
3595 program before it terminates; or so that, if your program runs into
3596 trouble, you can investigate and find out why.
3598 Inside @value{GDBN}, your program may stop for any of several reasons,
3599 such as a signal, a breakpoint, or reaching a new line after a
3600 @value{GDBN} command such as @code{step}. You may then examine and
3601 change variables, set new breakpoints or remove old ones, and then
3602 continue execution. Usually, the messages shown by @value{GDBN} provide
3603 ample explanation of the status of your program---but you can also
3604 explicitly request this information at any time.
3607 @kindex info program
3609 Display information about the status of your program: whether it is
3610 running or not, what process it is, and why it stopped.
3614 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3615 * Continuing and Stepping:: Resuming execution
3616 * Skipping Over Functions and Files::
3617 Skipping over functions and files
3619 * Thread Stops:: Stopping and starting multi-thread programs
3623 @section Breakpoints, Watchpoints, and Catchpoints
3626 A @dfn{breakpoint} makes your program stop whenever a certain point in
3627 the program is reached. For each breakpoint, you can add conditions to
3628 control in finer detail whether your program stops. You can set
3629 breakpoints with the @code{break} command and its variants (@pxref{Set
3630 Breaks, ,Setting Breakpoints}), to specify the place where your program
3631 should stop by line number, function name or exact address in the
3634 On some systems, you can set breakpoints in shared libraries before
3635 the executable is run.
3638 @cindex data breakpoints
3639 @cindex memory tracing
3640 @cindex breakpoint on memory address
3641 @cindex breakpoint on variable modification
3642 A @dfn{watchpoint} is a special breakpoint that stops your program
3643 when the value of an expression changes. The expression may be a value
3644 of a variable, or it could involve values of one or more variables
3645 combined by operators, such as @samp{a + b}. This is sometimes called
3646 @dfn{data breakpoints}. You must use a different command to set
3647 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3648 from that, you can manage a watchpoint like any other breakpoint: you
3649 enable, disable, and delete both breakpoints and watchpoints using the
3652 You can arrange to have values from your program displayed automatically
3653 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3657 @cindex breakpoint on events
3658 A @dfn{catchpoint} is another special breakpoint that stops your program
3659 when a certain kind of event occurs, such as the throwing of a C@t{++}
3660 exception or the loading of a library. As with watchpoints, you use a
3661 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3662 Catchpoints}), but aside from that, you can manage a catchpoint like any
3663 other breakpoint. (To stop when your program receives a signal, use the
3664 @code{handle} command; see @ref{Signals, ,Signals}.)
3666 @cindex breakpoint numbers
3667 @cindex numbers for breakpoints
3668 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3669 catchpoint when you create it; these numbers are successive integers
3670 starting with one. In many of the commands for controlling various
3671 features of breakpoints you use the breakpoint number to say which
3672 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3673 @dfn{disabled}; if disabled, it has no effect on your program until you
3676 @cindex breakpoint ranges
3677 @cindex breakpoint lists
3678 @cindex ranges of breakpoints
3679 @cindex lists of breakpoints
3680 Some @value{GDBN} commands accept a space-separated list of breakpoints
3681 on which to operate. A list element can be either a single breakpoint number,
3682 like @samp{5}, or a range of such numbers, like @samp{5-7}.
3683 When a breakpoint list is given to a command, all breakpoints in that list
3687 * Set Breaks:: Setting breakpoints
3688 * Set Watchpoints:: Setting watchpoints
3689 * Set Catchpoints:: Setting catchpoints
3690 * Delete Breaks:: Deleting breakpoints
3691 * Disabling:: Disabling breakpoints
3692 * Conditions:: Break conditions
3693 * Break Commands:: Breakpoint command lists
3694 * Dynamic Printf:: Dynamic printf
3695 * Save Breakpoints:: How to save breakpoints in a file
3696 * Static Probe Points:: Listing static probe points
3697 * Error in Breakpoints:: ``Cannot insert breakpoints''
3698 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3702 @subsection Setting Breakpoints
3704 @c FIXME LMB what does GDB do if no code on line of breakpt?
3705 @c consider in particular declaration with/without initialization.
3707 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3710 @kindex b @r{(@code{break})}
3711 @vindex $bpnum@r{, convenience variable}
3712 @cindex latest breakpoint
3713 Breakpoints are set with the @code{break} command (abbreviated
3714 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3715 number of the breakpoint you've set most recently; see @ref{Convenience
3716 Vars,, Convenience Variables}, for a discussion of what you can do with
3717 convenience variables.
3720 @item break @var{location}
3721 Set a breakpoint at the given @var{location}, which can specify a
3722 function name, a line number, or an address of an instruction.
3723 (@xref{Specify Location}, for a list of all the possible ways to
3724 specify a @var{location}.) The breakpoint will stop your program just
3725 before it executes any of the code in the specified @var{location}.
3727 When using source languages that permit overloading of symbols, such as
3728 C@t{++}, a function name may refer to more than one possible place to break.
3729 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3732 It is also possible to insert a breakpoint that will stop the program
3733 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3734 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3737 When called without any arguments, @code{break} sets a breakpoint at
3738 the next instruction to be executed in the selected stack frame
3739 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3740 innermost, this makes your program stop as soon as control
3741 returns to that frame. This is similar to the effect of a
3742 @code{finish} command in the frame inside the selected frame---except
3743 that @code{finish} does not leave an active breakpoint. If you use
3744 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3745 the next time it reaches the current location; this may be useful
3748 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3749 least one instruction has been executed. If it did not do this, you
3750 would be unable to proceed past a breakpoint without first disabling the
3751 breakpoint. This rule applies whether or not the breakpoint already
3752 existed when your program stopped.
3754 @item break @dots{} if @var{cond}
3755 Set a breakpoint with condition @var{cond}; evaluate the expression
3756 @var{cond} each time the breakpoint is reached, and stop only if the
3757 value is nonzero---that is, if @var{cond} evaluates as true.
3758 @samp{@dots{}} stands for one of the possible arguments described
3759 above (or no argument) specifying where to break. @xref{Conditions,
3760 ,Break Conditions}, for more information on breakpoint conditions.
3763 @item tbreak @var{args}
3764 Set a breakpoint enabled only for one stop. The @var{args} are the
3765 same as for the @code{break} command, and the breakpoint is set in the same
3766 way, but the breakpoint is automatically deleted after the first time your
3767 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3770 @cindex hardware breakpoints
3771 @item hbreak @var{args}
3772 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3773 @code{break} command and the breakpoint is set in the same way, but the
3774 breakpoint requires hardware support and some target hardware may not
3775 have this support. The main purpose of this is EPROM/ROM code
3776 debugging, so you can set a breakpoint at an instruction without
3777 changing the instruction. This can be used with the new trap-generation
3778 provided by SPARClite DSU and most x86-based targets. These targets
3779 will generate traps when a program accesses some data or instruction
3780 address that is assigned to the debug registers. However the hardware
3781 breakpoint registers can take a limited number of breakpoints. For
3782 example, on the DSU, only two data breakpoints can be set at a time, and
3783 @value{GDBN} will reject this command if more than two are used. Delete
3784 or disable unused hardware breakpoints before setting new ones
3785 (@pxref{Disabling, ,Disabling Breakpoints}).
3786 @xref{Conditions, ,Break Conditions}.
3787 For remote targets, you can restrict the number of hardware
3788 breakpoints @value{GDBN} will use, see @ref{set remote
3789 hardware-breakpoint-limit}.
3792 @item thbreak @var{args}
3793 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3794 are the same as for the @code{hbreak} command and the breakpoint is set in
3795 the same way. However, like the @code{tbreak} command,
3796 the breakpoint is automatically deleted after the
3797 first time your program stops there. Also, like the @code{hbreak}
3798 command, the breakpoint requires hardware support and some target hardware
3799 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3800 See also @ref{Conditions, ,Break Conditions}.
3803 @cindex regular expression
3804 @cindex breakpoints at functions matching a regexp
3805 @cindex set breakpoints in many functions
3806 @item rbreak @var{regex}
3807 Set breakpoints on all functions matching the regular expression
3808 @var{regex}. This command sets an unconditional breakpoint on all
3809 matches, printing a list of all breakpoints it set. Once these
3810 breakpoints are set, they are treated just like the breakpoints set with
3811 the @code{break} command. You can delete them, disable them, or make
3812 them conditional the same way as any other breakpoint.
3814 The syntax of the regular expression is the standard one used with tools
3815 like @file{grep}. Note that this is different from the syntax used by
3816 shells, so for instance @code{foo*} matches all functions that include
3817 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3818 @code{.*} leading and trailing the regular expression you supply, so to
3819 match only functions that begin with @code{foo}, use @code{^foo}.
3821 @cindex non-member C@t{++} functions, set breakpoint in
3822 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3823 breakpoints on overloaded functions that are not members of any special
3826 @cindex set breakpoints on all functions
3827 The @code{rbreak} command can be used to set breakpoints in
3828 @strong{all} the functions in a program, like this:
3831 (@value{GDBP}) rbreak .
3834 @item rbreak @var{file}:@var{regex}
3835 If @code{rbreak} is called with a filename qualification, it limits
3836 the search for functions matching the given regular expression to the
3837 specified @var{file}. This can be used, for example, to set breakpoints on
3838 every function in a given file:
3841 (@value{GDBP}) rbreak file.c:.
3844 The colon separating the filename qualifier from the regex may
3845 optionally be surrounded by spaces.
3847 @kindex info breakpoints
3848 @cindex @code{$_} and @code{info breakpoints}
3849 @item info breakpoints @r{[}@var{list}@dots{}@r{]}
3850 @itemx info break @r{[}@var{list}@dots{}@r{]}
3851 Print a table of all breakpoints, watchpoints, and catchpoints set and
3852 not deleted. Optional argument @var{n} means print information only
3853 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3854 For each breakpoint, following columns are printed:
3857 @item Breakpoint Numbers
3859 Breakpoint, watchpoint, or catchpoint.
3861 Whether the breakpoint is marked to be disabled or deleted when hit.
3862 @item Enabled or Disabled
3863 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3864 that are not enabled.
3866 Where the breakpoint is in your program, as a memory address. For a
3867 pending breakpoint whose address is not yet known, this field will
3868 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3869 library that has the symbol or line referred by breakpoint is loaded.
3870 See below for details. A breakpoint with several locations will
3871 have @samp{<MULTIPLE>} in this field---see below for details.
3873 Where the breakpoint is in the source for your program, as a file and
3874 line number. For a pending breakpoint, the original string passed to
3875 the breakpoint command will be listed as it cannot be resolved until
3876 the appropriate shared library is loaded in the future.
3880 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3881 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3882 @value{GDBN} on the host's side. If it is ``target'', then the condition
3883 is evaluated by the target. The @code{info break} command shows
3884 the condition on the line following the affected breakpoint, together with
3885 its condition evaluation mode in between parentheses.
3887 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3888 allowed to have a condition specified for it. The condition is not parsed for
3889 validity until a shared library is loaded that allows the pending
3890 breakpoint to resolve to a valid location.
3893 @code{info break} with a breakpoint
3894 number @var{n} as argument lists only that breakpoint. The
3895 convenience variable @code{$_} and the default examining-address for
3896 the @code{x} command are set to the address of the last breakpoint
3897 listed (@pxref{Memory, ,Examining Memory}).
3900 @code{info break} displays a count of the number of times the breakpoint
3901 has been hit. This is especially useful in conjunction with the
3902 @code{ignore} command. You can ignore a large number of breakpoint
3903 hits, look at the breakpoint info to see how many times the breakpoint
3904 was hit, and then run again, ignoring one less than that number. This
3905 will get you quickly to the last hit of that breakpoint.
3908 For a breakpoints with an enable count (xref) greater than 1,
3909 @code{info break} also displays that count.
3913 @value{GDBN} allows you to set any number of breakpoints at the same place in
3914 your program. There is nothing silly or meaningless about this. When
3915 the breakpoints are conditional, this is even useful
3916 (@pxref{Conditions, ,Break Conditions}).
3918 @cindex multiple locations, breakpoints
3919 @cindex breakpoints, multiple locations
3920 It is possible that a breakpoint corresponds to several locations
3921 in your program. Examples of this situation are:
3925 Multiple functions in the program may have the same name.
3928 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3929 instances of the function body, used in different cases.
3932 For a C@t{++} template function, a given line in the function can
3933 correspond to any number of instantiations.
3936 For an inlined function, a given source line can correspond to
3937 several places where that function is inlined.
3940 In all those cases, @value{GDBN} will insert a breakpoint at all
3941 the relevant locations.
3943 A breakpoint with multiple locations is displayed in the breakpoint
3944 table using several rows---one header row, followed by one row for
3945 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3946 address column. The rows for individual locations contain the actual
3947 addresses for locations, and show the functions to which those
3948 locations belong. The number column for a location is of the form
3949 @var{breakpoint-number}.@var{location-number}.
3954 Num Type Disp Enb Address What
3955 1 breakpoint keep y <MULTIPLE>
3957 breakpoint already hit 1 time
3958 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3959 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3962 You cannot delete the individual locations from a breakpoint. However,
3963 each location can be individually enabled or disabled by passing
3964 @var{breakpoint-number}.@var{location-number} as argument to the
3965 @code{enable} and @code{disable} commands. It's also possible to
3966 @code{enable} and @code{disable} a range of @var{location-number}
3967 locations using a @var{breakpoint-number} and two @var{location-number}s,
3968 in increasing order, separated by a hyphen, like
3969 @kbd{@var{breakpoint-number}.@var{location-number1}-@var{location-number2}},
3970 in which case @value{GDBN} acts on all the locations in the range (inclusive).
3971 Disabling or enabling the parent breakpoint (@pxref{Disabling}) affects
3972 all of the locations that belong to that breakpoint.
3974 @cindex pending breakpoints
3975 It's quite common to have a breakpoint inside a shared library.
3976 Shared libraries can be loaded and unloaded explicitly,
3977 and possibly repeatedly, as the program is executed. To support
3978 this use case, @value{GDBN} updates breakpoint locations whenever
3979 any shared library is loaded or unloaded. Typically, you would
3980 set a breakpoint in a shared library at the beginning of your
3981 debugging session, when the library is not loaded, and when the
3982 symbols from the library are not available. When you try to set
3983 breakpoint, @value{GDBN} will ask you if you want to set
3984 a so called @dfn{pending breakpoint}---breakpoint whose address
3985 is not yet resolved.
3987 After the program is run, whenever a new shared library is loaded,
3988 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3989 shared library contains the symbol or line referred to by some
3990 pending breakpoint, that breakpoint is resolved and becomes an
3991 ordinary breakpoint. When a library is unloaded, all breakpoints
3992 that refer to its symbols or source lines become pending again.
3994 This logic works for breakpoints with multiple locations, too. For
3995 example, if you have a breakpoint in a C@t{++} template function, and
3996 a newly loaded shared library has an instantiation of that template,
3997 a new location is added to the list of locations for the breakpoint.
3999 Except for having unresolved address, pending breakpoints do not
4000 differ from regular breakpoints. You can set conditions or commands,
4001 enable and disable them and perform other breakpoint operations.
4003 @value{GDBN} provides some additional commands for controlling what
4004 happens when the @samp{break} command cannot resolve breakpoint
4005 address specification to an address:
4007 @kindex set breakpoint pending
4008 @kindex show breakpoint pending
4010 @item set breakpoint pending auto
4011 This is the default behavior. When @value{GDBN} cannot find the breakpoint
4012 location, it queries you whether a pending breakpoint should be created.
4014 @item set breakpoint pending on
4015 This indicates that an unrecognized breakpoint location should automatically
4016 result in a pending breakpoint being created.
4018 @item set breakpoint pending off
4019 This indicates that pending breakpoints are not to be created. Any
4020 unrecognized breakpoint location results in an error. This setting does
4021 not affect any pending breakpoints previously created.
4023 @item show breakpoint pending
4024 Show the current behavior setting for creating pending breakpoints.
4027 The settings above only affect the @code{break} command and its
4028 variants. Once breakpoint is set, it will be automatically updated
4029 as shared libraries are loaded and unloaded.
4031 @cindex automatic hardware breakpoints
4032 For some targets, @value{GDBN} can automatically decide if hardware or
4033 software breakpoints should be used, depending on whether the
4034 breakpoint address is read-only or read-write. This applies to
4035 breakpoints set with the @code{break} command as well as to internal
4036 breakpoints set by commands like @code{next} and @code{finish}. For
4037 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
4040 You can control this automatic behaviour with the following commands:
4042 @kindex set breakpoint auto-hw
4043 @kindex show breakpoint auto-hw
4045 @item set breakpoint auto-hw on
4046 This is the default behavior. When @value{GDBN} sets a breakpoint, it
4047 will try to use the target memory map to decide if software or hardware
4048 breakpoint must be used.
4050 @item set breakpoint auto-hw off
4051 This indicates @value{GDBN} should not automatically select breakpoint
4052 type. If the target provides a memory map, @value{GDBN} will warn when
4053 trying to set software breakpoint at a read-only address.
4056 @value{GDBN} normally implements breakpoints by replacing the program code
4057 at the breakpoint address with a special instruction, which, when
4058 executed, given control to the debugger. By default, the program
4059 code is so modified only when the program is resumed. As soon as
4060 the program stops, @value{GDBN} restores the original instructions. This
4061 behaviour guards against leaving breakpoints inserted in the
4062 target should gdb abrubptly disconnect. However, with slow remote
4063 targets, inserting and removing breakpoint can reduce the performance.
4064 This behavior can be controlled with the following commands::
4066 @kindex set breakpoint always-inserted
4067 @kindex show breakpoint always-inserted
4069 @item set breakpoint always-inserted off
4070 All breakpoints, including newly added by the user, are inserted in
4071 the target only when the target is resumed. All breakpoints are
4072 removed from the target when it stops. This is the default mode.
4074 @item set breakpoint always-inserted on
4075 Causes all breakpoints to be inserted in the target at all times. If
4076 the user adds a new breakpoint, or changes an existing breakpoint, the
4077 breakpoints in the target are updated immediately. A breakpoint is
4078 removed from the target only when breakpoint itself is deleted.
4081 @value{GDBN} handles conditional breakpoints by evaluating these conditions
4082 when a breakpoint breaks. If the condition is true, then the process being
4083 debugged stops, otherwise the process is resumed.
4085 If the target supports evaluating conditions on its end, @value{GDBN} may
4086 download the breakpoint, together with its conditions, to it.
4088 This feature can be controlled via the following commands:
4090 @kindex set breakpoint condition-evaluation
4091 @kindex show breakpoint condition-evaluation
4093 @item set breakpoint condition-evaluation host
4094 This option commands @value{GDBN} to evaluate the breakpoint
4095 conditions on the host's side. Unconditional breakpoints are sent to
4096 the target which in turn receives the triggers and reports them back to GDB
4097 for condition evaluation. This is the standard evaluation mode.
4099 @item set breakpoint condition-evaluation target
4100 This option commands @value{GDBN} to download breakpoint conditions
4101 to the target at the moment of their insertion. The target
4102 is responsible for evaluating the conditional expression and reporting
4103 breakpoint stop events back to @value{GDBN} whenever the condition
4104 is true. Due to limitations of target-side evaluation, some conditions
4105 cannot be evaluated there, e.g., conditions that depend on local data
4106 that is only known to the host. Examples include
4107 conditional expressions involving convenience variables, complex types
4108 that cannot be handled by the agent expression parser and expressions
4109 that are too long to be sent over to the target, specially when the
4110 target is a remote system. In these cases, the conditions will be
4111 evaluated by @value{GDBN}.
4113 @item set breakpoint condition-evaluation auto
4114 This is the default mode. If the target supports evaluating breakpoint
4115 conditions on its end, @value{GDBN} will download breakpoint conditions to
4116 the target (limitations mentioned previously apply). If the target does
4117 not support breakpoint condition evaluation, then @value{GDBN} will fallback
4118 to evaluating all these conditions on the host's side.
4122 @cindex negative breakpoint numbers
4123 @cindex internal @value{GDBN} breakpoints
4124 @value{GDBN} itself sometimes sets breakpoints in your program for
4125 special purposes, such as proper handling of @code{longjmp} (in C
4126 programs). These internal breakpoints are assigned negative numbers,
4127 starting with @code{-1}; @samp{info breakpoints} does not display them.
4128 You can see these breakpoints with the @value{GDBN} maintenance command
4129 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
4132 @node Set Watchpoints
4133 @subsection Setting Watchpoints
4135 @cindex setting watchpoints
4136 You can use a watchpoint to stop execution whenever the value of an
4137 expression changes, without having to predict a particular place where
4138 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4139 The expression may be as simple as the value of a single variable, or
4140 as complex as many variables combined by operators. Examples include:
4144 A reference to the value of a single variable.
4147 An address cast to an appropriate data type. For example,
4148 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4149 address (assuming an @code{int} occupies 4 bytes).
4152 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4153 expression can use any operators valid in the program's native
4154 language (@pxref{Languages}).
4157 You can set a watchpoint on an expression even if the expression can
4158 not be evaluated yet. For instance, you can set a watchpoint on
4159 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4160 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4161 the expression produces a valid value. If the expression becomes
4162 valid in some other way than changing a variable (e.g.@: if the memory
4163 pointed to by @samp{*global_ptr} becomes readable as the result of a
4164 @code{malloc} call), @value{GDBN} may not stop until the next time
4165 the expression changes.
4167 @cindex software watchpoints
4168 @cindex hardware watchpoints
4169 Depending on your system, watchpoints may be implemented in software or
4170 hardware. @value{GDBN} does software watchpointing by single-stepping your
4171 program and testing the variable's value each time, which is hundreds of
4172 times slower than normal execution. (But this may still be worth it, to
4173 catch errors where you have no clue what part of your program is the
4176 On some systems, such as most PowerPC or x86-based targets,
4177 @value{GDBN} includes support for hardware watchpoints, which do not
4178 slow down the running of your program.
4182 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4183 Set a watchpoint for an expression. @value{GDBN} will break when the
4184 expression @var{expr} is written into by the program and its value
4185 changes. The simplest (and the most popular) use of this command is
4186 to watch the value of a single variable:
4189 (@value{GDBP}) watch foo
4192 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4193 argument, @value{GDBN} breaks only when the thread identified by
4194 @var{thread-id} changes the value of @var{expr}. If any other threads
4195 change the value of @var{expr}, @value{GDBN} will not break. Note
4196 that watchpoints restricted to a single thread in this way only work
4197 with Hardware Watchpoints.
4199 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4200 (see below). The @code{-location} argument tells @value{GDBN} to
4201 instead watch the memory referred to by @var{expr}. In this case,
4202 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4203 and watch the memory at that address. The type of the result is used
4204 to determine the size of the watched memory. If the expression's
4205 result does not have an address, then @value{GDBN} will print an
4208 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4209 of masked watchpoints, if the current architecture supports this
4210 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4211 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4212 to an address to watch. The mask specifies that some bits of an address
4213 (the bits which are reset in the mask) should be ignored when matching
4214 the address accessed by the inferior against the watchpoint address.
4215 Thus, a masked watchpoint watches many addresses simultaneously---those
4216 addresses whose unmasked bits are identical to the unmasked bits in the
4217 watchpoint address. The @code{mask} argument implies @code{-location}.
4221 (@value{GDBP}) watch foo mask 0xffff00ff
4222 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4226 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4227 Set a watchpoint that will break when the value of @var{expr} is read
4231 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4232 Set a watchpoint that will break when @var{expr} is either read from
4233 or written into by the program.
4235 @kindex info watchpoints @r{[}@var{list}@dots{}@r{]}
4236 @item info watchpoints @r{[}@var{list}@dots{}@r{]}
4237 This command prints a list of watchpoints, using the same format as
4238 @code{info break} (@pxref{Set Breaks}).
4241 If you watch for a change in a numerically entered address you need to
4242 dereference it, as the address itself is just a constant number which will
4243 never change. @value{GDBN} refuses to create a watchpoint that watches
4244 a never-changing value:
4247 (@value{GDBP}) watch 0x600850
4248 Cannot watch constant value 0x600850.
4249 (@value{GDBP}) watch *(int *) 0x600850
4250 Watchpoint 1: *(int *) 6293584
4253 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4254 watchpoints execute very quickly, and the debugger reports a change in
4255 value at the exact instruction where the change occurs. If @value{GDBN}
4256 cannot set a hardware watchpoint, it sets a software watchpoint, which
4257 executes more slowly and reports the change in value at the next
4258 @emph{statement}, not the instruction, after the change occurs.
4260 @cindex use only software watchpoints
4261 You can force @value{GDBN} to use only software watchpoints with the
4262 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4263 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4264 the underlying system supports them. (Note that hardware-assisted
4265 watchpoints that were set @emph{before} setting
4266 @code{can-use-hw-watchpoints} to zero will still use the hardware
4267 mechanism of watching expression values.)
4270 @item set can-use-hw-watchpoints
4271 @kindex set can-use-hw-watchpoints
4272 Set whether or not to use hardware watchpoints.
4274 @item show can-use-hw-watchpoints
4275 @kindex show can-use-hw-watchpoints
4276 Show the current mode of using hardware watchpoints.
4279 For remote targets, you can restrict the number of hardware
4280 watchpoints @value{GDBN} will use, see @ref{set remote
4281 hardware-breakpoint-limit}.
4283 When you issue the @code{watch} command, @value{GDBN} reports
4286 Hardware watchpoint @var{num}: @var{expr}
4290 if it was able to set a hardware watchpoint.
4292 Currently, the @code{awatch} and @code{rwatch} commands can only set
4293 hardware watchpoints, because accesses to data that don't change the
4294 value of the watched expression cannot be detected without examining
4295 every instruction as it is being executed, and @value{GDBN} does not do
4296 that currently. If @value{GDBN} finds that it is unable to set a
4297 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4298 will print a message like this:
4301 Expression cannot be implemented with read/access watchpoint.
4304 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4305 data type of the watched expression is wider than what a hardware
4306 watchpoint on the target machine can handle. For example, some systems
4307 can only watch regions that are up to 4 bytes wide; on such systems you
4308 cannot set hardware watchpoints for an expression that yields a
4309 double-precision floating-point number (which is typically 8 bytes
4310 wide). As a work-around, it might be possible to break the large region
4311 into a series of smaller ones and watch them with separate watchpoints.
4313 If you set too many hardware watchpoints, @value{GDBN} might be unable
4314 to insert all of them when you resume the execution of your program.
4315 Since the precise number of active watchpoints is unknown until such
4316 time as the program is about to be resumed, @value{GDBN} might not be
4317 able to warn you about this when you set the watchpoints, and the
4318 warning will be printed only when the program is resumed:
4321 Hardware watchpoint @var{num}: Could not insert watchpoint
4325 If this happens, delete or disable some of the watchpoints.
4327 Watching complex expressions that reference many variables can also
4328 exhaust the resources available for hardware-assisted watchpoints.
4329 That's because @value{GDBN} needs to watch every variable in the
4330 expression with separately allocated resources.
4332 If you call a function interactively using @code{print} or @code{call},
4333 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4334 kind of breakpoint or the call completes.
4336 @value{GDBN} automatically deletes watchpoints that watch local
4337 (automatic) variables, or expressions that involve such variables, when
4338 they go out of scope, that is, when the execution leaves the block in
4339 which these variables were defined. In particular, when the program
4340 being debugged terminates, @emph{all} local variables go out of scope,
4341 and so only watchpoints that watch global variables remain set. If you
4342 rerun the program, you will need to set all such watchpoints again. One
4343 way of doing that would be to set a code breakpoint at the entry to the
4344 @code{main} function and when it breaks, set all the watchpoints.
4346 @cindex watchpoints and threads
4347 @cindex threads and watchpoints
4348 In multi-threaded programs, watchpoints will detect changes to the
4349 watched expression from every thread.
4352 @emph{Warning:} In multi-threaded programs, software watchpoints
4353 have only limited usefulness. If @value{GDBN} creates a software
4354 watchpoint, it can only watch the value of an expression @emph{in a
4355 single thread}. If you are confident that the expression can only
4356 change due to the current thread's activity (and if you are also
4357 confident that no other thread can become current), then you can use
4358 software watchpoints as usual. However, @value{GDBN} may not notice
4359 when a non-current thread's activity changes the expression. (Hardware
4360 watchpoints, in contrast, watch an expression in all threads.)
4363 @xref{set remote hardware-watchpoint-limit}.
4365 @node Set Catchpoints
4366 @subsection Setting Catchpoints
4367 @cindex catchpoints, setting
4368 @cindex exception handlers
4369 @cindex event handling
4371 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4372 kinds of program events, such as C@t{++} exceptions or the loading of a
4373 shared library. Use the @code{catch} command to set a catchpoint.
4377 @item catch @var{event}
4378 Stop when @var{event} occurs. The @var{event} can be any of the following:
4381 @item throw @r{[}@var{regexp}@r{]}
4382 @itemx rethrow @r{[}@var{regexp}@r{]}
4383 @itemx catch @r{[}@var{regexp}@r{]}
4385 @kindex catch rethrow
4387 @cindex stop on C@t{++} exceptions
4388 The throwing, re-throwing, or catching of a C@t{++} exception.
4390 If @var{regexp} is given, then only exceptions whose type matches the
4391 regular expression will be caught.
4393 @vindex $_exception@r{, convenience variable}
4394 The convenience variable @code{$_exception} is available at an
4395 exception-related catchpoint, on some systems. This holds the
4396 exception being thrown.
4398 There are currently some limitations to C@t{++} exception handling in
4403 The support for these commands is system-dependent. Currently, only
4404 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4408 The regular expression feature and the @code{$_exception} convenience
4409 variable rely on the presence of some SDT probes in @code{libstdc++}.
4410 If these probes are not present, then these features cannot be used.
4411 These probes were first available in the GCC 4.8 release, but whether
4412 or not they are available in your GCC also depends on how it was
4416 The @code{$_exception} convenience variable is only valid at the
4417 instruction at which an exception-related catchpoint is set.
4420 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4421 location in the system library which implements runtime exception
4422 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4423 (@pxref{Selection}) to get to your code.
4426 If you call a function interactively, @value{GDBN} normally returns
4427 control to you when the function has finished executing. If the call
4428 raises an exception, however, the call may bypass the mechanism that
4429 returns control to you and cause your program either to abort or to
4430 simply continue running until it hits a breakpoint, catches a signal
4431 that @value{GDBN} is listening for, or exits. This is the case even if
4432 you set a catchpoint for the exception; catchpoints on exceptions are
4433 disabled within interactive calls. @xref{Calling}, for information on
4434 controlling this with @code{set unwind-on-terminating-exception}.
4437 You cannot raise an exception interactively.
4440 You cannot install an exception handler interactively.
4444 @kindex catch exception
4445 @cindex Ada exception catching
4446 @cindex catch Ada exceptions
4447 An Ada exception being raised. If an exception name is specified
4448 at the end of the command (eg @code{catch exception Program_Error}),
4449 the debugger will stop only when this specific exception is raised.
4450 Otherwise, the debugger stops execution when any Ada exception is raised.
4452 When inserting an exception catchpoint on a user-defined exception whose
4453 name is identical to one of the exceptions defined by the language, the
4454 fully qualified name must be used as the exception name. Otherwise,
4455 @value{GDBN} will assume that it should stop on the pre-defined exception
4456 rather than the user-defined one. For instance, assuming an exception
4457 called @code{Constraint_Error} is defined in package @code{Pck}, then
4458 the command to use to catch such exceptions is @kbd{catch exception
4459 Pck.Constraint_Error}.
4461 @item exception unhandled
4462 @kindex catch exception unhandled
4463 An exception that was raised but is not handled by the program.
4466 @kindex catch assert
4467 A failed Ada assertion.
4471 @cindex break on fork/exec
4472 A call to @code{exec}.
4475 @itemx syscall @r{[}@var{name} @r{|} @var{number} @r{|} @r{group:}@var{groupname} @r{|} @r{g:}@var{groupname}@r{]} @dots{}
4476 @kindex catch syscall
4477 @cindex break on a system call.
4478 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4479 syscall is a mechanism for application programs to request a service
4480 from the operating system (OS) or one of the OS system services.
4481 @value{GDBN} can catch some or all of the syscalls issued by the
4482 debuggee, and show the related information for each syscall. If no
4483 argument is specified, calls to and returns from all system calls
4486 @var{name} can be any system call name that is valid for the
4487 underlying OS. Just what syscalls are valid depends on the OS. On
4488 GNU and Unix systems, you can find the full list of valid syscall
4489 names on @file{/usr/include/asm/unistd.h}.
4491 @c For MS-Windows, the syscall names and the corresponding numbers
4492 @c can be found, e.g., on this URL:
4493 @c http://www.metasploit.com/users/opcode/syscalls.html
4494 @c but we don't support Windows syscalls yet.
4496 Normally, @value{GDBN} knows in advance which syscalls are valid for
4497 each OS, so you can use the @value{GDBN} command-line completion
4498 facilities (@pxref{Completion,, command completion}) to list the
4501 You may also specify the system call numerically. A syscall's
4502 number is the value passed to the OS's syscall dispatcher to
4503 identify the requested service. When you specify the syscall by its
4504 name, @value{GDBN} uses its database of syscalls to convert the name
4505 into the corresponding numeric code, but using the number directly
4506 may be useful if @value{GDBN}'s database does not have the complete
4507 list of syscalls on your system (e.g., because @value{GDBN} lags
4508 behind the OS upgrades).
4510 You may specify a group of related syscalls to be caught at once using
4511 the @code{group:} syntax (@code{g:} is a shorter equivalent). For
4512 instance, on some platforms @value{GDBN} allows you to catch all
4513 network related syscalls, by passing the argument @code{group:network}
4514 to @code{catch syscall}. Note that not all syscall groups are
4515 available in every system. You can use the command completion
4516 facilities (@pxref{Completion,, command completion}) to list the
4517 syscall groups available on your environment.
4519 The example below illustrates how this command works if you don't provide
4523 (@value{GDBP}) catch syscall
4524 Catchpoint 1 (syscall)
4526 Starting program: /tmp/catch-syscall
4528 Catchpoint 1 (call to syscall 'close'), \
4529 0xffffe424 in __kernel_vsyscall ()
4533 Catchpoint 1 (returned from syscall 'close'), \
4534 0xffffe424 in __kernel_vsyscall ()
4538 Here is an example of catching a system call by name:
4541 (@value{GDBP}) catch syscall chroot
4542 Catchpoint 1 (syscall 'chroot' [61])
4544 Starting program: /tmp/catch-syscall
4546 Catchpoint 1 (call to syscall 'chroot'), \
4547 0xffffe424 in __kernel_vsyscall ()
4551 Catchpoint 1 (returned from syscall 'chroot'), \
4552 0xffffe424 in __kernel_vsyscall ()
4556 An example of specifying a system call numerically. In the case
4557 below, the syscall number has a corresponding entry in the XML
4558 file, so @value{GDBN} finds its name and prints it:
4561 (@value{GDBP}) catch syscall 252
4562 Catchpoint 1 (syscall(s) 'exit_group')
4564 Starting program: /tmp/catch-syscall
4566 Catchpoint 1 (call to syscall 'exit_group'), \
4567 0xffffe424 in __kernel_vsyscall ()
4571 Program exited normally.
4575 Here is an example of catching a syscall group:
4578 (@value{GDBP}) catch syscall group:process
4579 Catchpoint 1 (syscalls 'exit' [1] 'fork' [2] 'waitpid' [7]
4580 'execve' [11] 'wait4' [114] 'clone' [120] 'vfork' [190]
4581 'exit_group' [252] 'waitid' [284] 'unshare' [310])
4583 Starting program: /tmp/catch-syscall
4585 Catchpoint 1 (call to syscall fork), 0x00007ffff7df4e27 in open64 ()
4586 from /lib64/ld-linux-x86-64.so.2
4592 However, there can be situations when there is no corresponding name
4593 in XML file for that syscall number. In this case, @value{GDBN} prints
4594 a warning message saying that it was not able to find the syscall name,
4595 but the catchpoint will be set anyway. See the example below:
4598 (@value{GDBP}) catch syscall 764
4599 warning: The number '764' does not represent a known syscall.
4600 Catchpoint 2 (syscall 764)
4604 If you configure @value{GDBN} using the @samp{--without-expat} option,
4605 it will not be able to display syscall names. Also, if your
4606 architecture does not have an XML file describing its system calls,
4607 you will not be able to see the syscall names. It is important to
4608 notice that these two features are used for accessing the syscall
4609 name database. In either case, you will see a warning like this:
4612 (@value{GDBP}) catch syscall
4613 warning: Could not open "syscalls/i386-linux.xml"
4614 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4615 GDB will not be able to display syscall names.
4616 Catchpoint 1 (syscall)
4620 Of course, the file name will change depending on your architecture and system.
4622 Still using the example above, you can also try to catch a syscall by its
4623 number. In this case, you would see something like:
4626 (@value{GDBP}) catch syscall 252
4627 Catchpoint 1 (syscall(s) 252)
4630 Again, in this case @value{GDBN} would not be able to display syscall's names.
4634 A call to @code{fork}.
4638 A call to @code{vfork}.
4640 @item load @r{[}regexp@r{]}
4641 @itemx unload @r{[}regexp@r{]}
4643 @kindex catch unload
4644 The loading or unloading of a shared library. If @var{regexp} is
4645 given, then the catchpoint will stop only if the regular expression
4646 matches one of the affected libraries.
4648 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4649 @kindex catch signal
4650 The delivery of a signal.
4652 With no arguments, this catchpoint will catch any signal that is not
4653 used internally by @value{GDBN}, specifically, all signals except
4654 @samp{SIGTRAP} and @samp{SIGINT}.
4656 With the argument @samp{all}, all signals, including those used by
4657 @value{GDBN}, will be caught. This argument cannot be used with other
4660 Otherwise, the arguments are a list of signal names as given to
4661 @code{handle} (@pxref{Signals}). Only signals specified in this list
4664 One reason that @code{catch signal} can be more useful than
4665 @code{handle} is that you can attach commands and conditions to the
4668 When a signal is caught by a catchpoint, the signal's @code{stop} and
4669 @code{print} settings, as specified by @code{handle}, are ignored.
4670 However, whether the signal is still delivered to the inferior depends
4671 on the @code{pass} setting; this can be changed in the catchpoint's
4676 @item tcatch @var{event}
4678 Set a catchpoint that is enabled only for one stop. The catchpoint is
4679 automatically deleted after the first time the event is caught.
4683 Use the @code{info break} command to list the current catchpoints.
4687 @subsection Deleting Breakpoints
4689 @cindex clearing breakpoints, watchpoints, catchpoints
4690 @cindex deleting breakpoints, watchpoints, catchpoints
4691 It is often necessary to eliminate a breakpoint, watchpoint, or
4692 catchpoint once it has done its job and you no longer want your program
4693 to stop there. This is called @dfn{deleting} the breakpoint. A
4694 breakpoint that has been deleted no longer exists; it is forgotten.
4696 With the @code{clear} command you can delete breakpoints according to
4697 where they are in your program. With the @code{delete} command you can
4698 delete individual breakpoints, watchpoints, or catchpoints by specifying
4699 their breakpoint numbers.
4701 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4702 automatically ignores breakpoints on the first instruction to be executed
4703 when you continue execution without changing the execution address.
4708 Delete any breakpoints at the next instruction to be executed in the
4709 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4710 the innermost frame is selected, this is a good way to delete a
4711 breakpoint where your program just stopped.
4713 @item clear @var{location}
4714 Delete any breakpoints set at the specified @var{location}.
4715 @xref{Specify Location}, for the various forms of @var{location}; the
4716 most useful ones are listed below:
4719 @item clear @var{function}
4720 @itemx clear @var{filename}:@var{function}
4721 Delete any breakpoints set at entry to the named @var{function}.
4723 @item clear @var{linenum}
4724 @itemx clear @var{filename}:@var{linenum}
4725 Delete any breakpoints set at or within the code of the specified
4726 @var{linenum} of the specified @var{filename}.
4729 @cindex delete breakpoints
4731 @kindex d @r{(@code{delete})}
4732 @item delete @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4733 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4734 list specified as argument. If no argument is specified, delete all
4735 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4736 confirm off}). You can abbreviate this command as @code{d}.
4740 @subsection Disabling Breakpoints
4742 @cindex enable/disable a breakpoint
4743 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4744 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4745 it had been deleted, but remembers the information on the breakpoint so
4746 that you can @dfn{enable} it again later.
4748 You disable and enable breakpoints, watchpoints, and catchpoints with
4749 the @code{enable} and @code{disable} commands, optionally specifying
4750 one or more breakpoint numbers as arguments. Use @code{info break} to
4751 print a list of all breakpoints, watchpoints, and catchpoints if you
4752 do not know which numbers to use.
4754 Disabling and enabling a breakpoint that has multiple locations
4755 affects all of its locations.
4757 A breakpoint, watchpoint, or catchpoint can have any of several
4758 different states of enablement:
4762 Enabled. The breakpoint stops your program. A breakpoint set
4763 with the @code{break} command starts out in this state.
4765 Disabled. The breakpoint has no effect on your program.
4767 Enabled once. The breakpoint stops your program, but then becomes
4770 Enabled for a count. The breakpoint stops your program for the next
4771 N times, then becomes disabled.
4773 Enabled for deletion. The breakpoint stops your program, but
4774 immediately after it does so it is deleted permanently. A breakpoint
4775 set with the @code{tbreak} command starts out in this state.
4778 You can use the following commands to enable or disable breakpoints,
4779 watchpoints, and catchpoints:
4783 @kindex dis @r{(@code{disable})}
4784 @item disable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4785 Disable the specified breakpoints---or all breakpoints, if none are
4786 listed. A disabled breakpoint has no effect but is not forgotten. All
4787 options such as ignore-counts, conditions and commands are remembered in
4788 case the breakpoint is enabled again later. You may abbreviate
4789 @code{disable} as @code{dis}.
4792 @item enable @r{[}breakpoints@r{]} @r{[}@var{list}@dots{}@r{]}
4793 Enable the specified breakpoints (or all defined breakpoints). They
4794 become effective once again in stopping your program.
4796 @item enable @r{[}breakpoints@r{]} once @var{list}@dots{}
4797 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4798 of these breakpoints immediately after stopping your program.
4800 @item enable @r{[}breakpoints@r{]} count @var{count} @var{list}@dots{}
4801 Enable the specified breakpoints temporarily. @value{GDBN} records
4802 @var{count} with each of the specified breakpoints, and decrements a
4803 breakpoint's count when it is hit. When any count reaches 0,
4804 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4805 count (@pxref{Conditions, ,Break Conditions}), that will be
4806 decremented to 0 before @var{count} is affected.
4808 @item enable @r{[}breakpoints@r{]} delete @var{list}@dots{}
4809 Enable the specified breakpoints to work once, then die. @value{GDBN}
4810 deletes any of these breakpoints as soon as your program stops there.
4811 Breakpoints set by the @code{tbreak} command start out in this state.
4814 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4815 @c confusing: tbreak is also initially enabled.
4816 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4817 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4818 subsequently, they become disabled or enabled only when you use one of
4819 the commands above. (The command @code{until} can set and delete a
4820 breakpoint of its own, but it does not change the state of your other
4821 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4825 @subsection Break Conditions
4826 @cindex conditional breakpoints
4827 @cindex breakpoint conditions
4829 @c FIXME what is scope of break condition expr? Context where wanted?
4830 @c in particular for a watchpoint?
4831 The simplest sort of breakpoint breaks every time your program reaches a
4832 specified place. You can also specify a @dfn{condition} for a
4833 breakpoint. A condition is just a Boolean expression in your
4834 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4835 a condition evaluates the expression each time your program reaches it,
4836 and your program stops only if the condition is @emph{true}.
4838 This is the converse of using assertions for program validation; in that
4839 situation, you want to stop when the assertion is violated---that is,
4840 when the condition is false. In C, if you want to test an assertion expressed
4841 by the condition @var{assert}, you should set the condition
4842 @samp{! @var{assert}} on the appropriate breakpoint.
4844 Conditions are also accepted for watchpoints; you may not need them,
4845 since a watchpoint is inspecting the value of an expression anyhow---but
4846 it might be simpler, say, to just set a watchpoint on a variable name,
4847 and specify a condition that tests whether the new value is an interesting
4850 Break conditions can have side effects, and may even call functions in
4851 your program. This can be useful, for example, to activate functions
4852 that log program progress, or to use your own print functions to
4853 format special data structures. The effects are completely predictable
4854 unless there is another enabled breakpoint at the same address. (In
4855 that case, @value{GDBN} might see the other breakpoint first and stop your
4856 program without checking the condition of this one.) Note that
4857 breakpoint commands are usually more convenient and flexible than break
4859 purpose of performing side effects when a breakpoint is reached
4860 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4862 Breakpoint conditions can also be evaluated on the target's side if
4863 the target supports it. Instead of evaluating the conditions locally,
4864 @value{GDBN} encodes the expression into an agent expression
4865 (@pxref{Agent Expressions}) suitable for execution on the target,
4866 independently of @value{GDBN}. Global variables become raw memory
4867 locations, locals become stack accesses, and so forth.
4869 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4870 when its condition evaluates to true. This mechanism may provide faster
4871 response times depending on the performance characteristics of the target
4872 since it does not need to keep @value{GDBN} informed about
4873 every breakpoint trigger, even those with false conditions.
4875 Break conditions can be specified when a breakpoint is set, by using
4876 @samp{if} in the arguments to the @code{break} command. @xref{Set
4877 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4878 with the @code{condition} command.
4880 You can also use the @code{if} keyword with the @code{watch} command.
4881 The @code{catch} command does not recognize the @code{if} keyword;
4882 @code{condition} is the only way to impose a further condition on a
4887 @item condition @var{bnum} @var{expression}
4888 Specify @var{expression} as the break condition for breakpoint,
4889 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4890 breakpoint @var{bnum} stops your program only if the value of
4891 @var{expression} is true (nonzero, in C). When you use
4892 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4893 syntactic correctness, and to determine whether symbols in it have
4894 referents in the context of your breakpoint. If @var{expression} uses
4895 symbols not referenced in the context of the breakpoint, @value{GDBN}
4896 prints an error message:
4899 No symbol "foo" in current context.
4904 not actually evaluate @var{expression} at the time the @code{condition}
4905 command (or a command that sets a breakpoint with a condition, like
4906 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4908 @item condition @var{bnum}
4909 Remove the condition from breakpoint number @var{bnum}. It becomes
4910 an ordinary unconditional breakpoint.
4913 @cindex ignore count (of breakpoint)
4914 A special case of a breakpoint condition is to stop only when the
4915 breakpoint has been reached a certain number of times. This is so
4916 useful that there is a special way to do it, using the @dfn{ignore
4917 count} of the breakpoint. Every breakpoint has an ignore count, which
4918 is an integer. Most of the time, the ignore count is zero, and
4919 therefore has no effect. But if your program reaches a breakpoint whose
4920 ignore count is positive, then instead of stopping, it just decrements
4921 the ignore count by one and continues. As a result, if the ignore count
4922 value is @var{n}, the breakpoint does not stop the next @var{n} times
4923 your program reaches it.
4927 @item ignore @var{bnum} @var{count}
4928 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4929 The next @var{count} times the breakpoint is reached, your program's
4930 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4933 To make the breakpoint stop the next time it is reached, specify
4936 When you use @code{continue} to resume execution of your program from a
4937 breakpoint, you can specify an ignore count directly as an argument to
4938 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4939 Stepping,,Continuing and Stepping}.
4941 If a breakpoint has a positive ignore count and a condition, the
4942 condition is not checked. Once the ignore count reaches zero,
4943 @value{GDBN} resumes checking the condition.
4945 You could achieve the effect of the ignore count with a condition such
4946 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4947 is decremented each time. @xref{Convenience Vars, ,Convenience
4951 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4954 @node Break Commands
4955 @subsection Breakpoint Command Lists
4957 @cindex breakpoint commands
4958 You can give any breakpoint (or watchpoint or catchpoint) a series of
4959 commands to execute when your program stops due to that breakpoint. For
4960 example, you might want to print the values of certain expressions, or
4961 enable other breakpoints.
4965 @kindex end@r{ (breakpoint commands)}
4966 @item commands @r{[}@var{list}@dots{}@r{]}
4967 @itemx @dots{} @var{command-list} @dots{}
4969 Specify a list of commands for the given breakpoints. The commands
4970 themselves appear on the following lines. Type a line containing just
4971 @code{end} to terminate the commands.
4973 To remove all commands from a breakpoint, type @code{commands} and
4974 follow it immediately with @code{end}; that is, give no commands.
4976 With no argument, @code{commands} refers to the last breakpoint,
4977 watchpoint, or catchpoint set (not to the breakpoint most recently
4978 encountered). If the most recent breakpoints were set with a single
4979 command, then the @code{commands} will apply to all the breakpoints
4980 set by that command. This applies to breakpoints set by
4981 @code{rbreak}, and also applies when a single @code{break} command
4982 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4986 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4987 disabled within a @var{command-list}.
4989 You can use breakpoint commands to start your program up again. Simply
4990 use the @code{continue} command, or @code{step}, or any other command
4991 that resumes execution.
4993 Any other commands in the command list, after a command that resumes
4994 execution, are ignored. This is because any time you resume execution
4995 (even with a simple @code{next} or @code{step}), you may encounter
4996 another breakpoint---which could have its own command list, leading to
4997 ambiguities about which list to execute.
5000 If the first command you specify in a command list is @code{silent}, the
5001 usual message about stopping at a breakpoint is not printed. This may
5002 be desirable for breakpoints that are to print a specific message and
5003 then continue. If none of the remaining commands print anything, you
5004 see no sign that the breakpoint was reached. @code{silent} is
5005 meaningful only at the beginning of a breakpoint command list.
5007 The commands @code{echo}, @code{output}, and @code{printf} allow you to
5008 print precisely controlled output, and are often useful in silent
5009 breakpoints. @xref{Output, ,Commands for Controlled Output}.
5011 For example, here is how you could use breakpoint commands to print the
5012 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
5018 printf "x is %d\n",x
5023 One application for breakpoint commands is to compensate for one bug so
5024 you can test for another. Put a breakpoint just after the erroneous line
5025 of code, give it a condition to detect the case in which something
5026 erroneous has been done, and give it commands to assign correct values
5027 to any variables that need them. End with the @code{continue} command
5028 so that your program does not stop, and start with the @code{silent}
5029 command so that no output is produced. Here is an example:
5040 @node Dynamic Printf
5041 @subsection Dynamic Printf
5043 @cindex dynamic printf
5045 The dynamic printf command @code{dprintf} combines a breakpoint with
5046 formatted printing of your program's data to give you the effect of
5047 inserting @code{printf} calls into your program on-the-fly, without
5048 having to recompile it.
5050 In its most basic form, the output goes to the GDB console. However,
5051 you can set the variable @code{dprintf-style} for alternate handling.
5052 For instance, you can ask to format the output by calling your
5053 program's @code{printf} function. This has the advantage that the
5054 characters go to the program's output device, so they can recorded in
5055 redirects to files and so forth.
5057 If you are doing remote debugging with a stub or agent, you can also
5058 ask to have the printf handled by the remote agent. In addition to
5059 ensuring that the output goes to the remote program's device along
5060 with any other output the program might produce, you can also ask that
5061 the dprintf remain active even after disconnecting from the remote
5062 target. Using the stub/agent is also more efficient, as it can do
5063 everything without needing to communicate with @value{GDBN}.
5067 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
5068 Whenever execution reaches @var{location}, print the values of one or
5069 more @var{expressions} under the control of the string @var{template}.
5070 To print several values, separate them with commas.
5072 @item set dprintf-style @var{style}
5073 Set the dprintf output to be handled in one of several different
5074 styles enumerated below. A change of style affects all existing
5075 dynamic printfs immediately. (If you need individual control over the
5076 print commands, simply define normal breakpoints with
5077 explicitly-supplied command lists.)
5081 @kindex dprintf-style gdb
5082 Handle the output using the @value{GDBN} @code{printf} command.
5085 @kindex dprintf-style call
5086 Handle the output by calling a function in your program (normally
5090 @kindex dprintf-style agent
5091 Have the remote debugging agent (such as @code{gdbserver}) handle
5092 the output itself. This style is only available for agents that
5093 support running commands on the target.
5096 @item set dprintf-function @var{function}
5097 Set the function to call if the dprintf style is @code{call}. By
5098 default its value is @code{printf}. You may set it to any expression.
5099 that @value{GDBN} can evaluate to a function, as per the @code{call}
5102 @item set dprintf-channel @var{channel}
5103 Set a ``channel'' for dprintf. If set to a non-empty value,
5104 @value{GDBN} will evaluate it as an expression and pass the result as
5105 a first argument to the @code{dprintf-function}, in the manner of
5106 @code{fprintf} and similar functions. Otherwise, the dprintf format
5107 string will be the first argument, in the manner of @code{printf}.
5109 As an example, if you wanted @code{dprintf} output to go to a logfile
5110 that is a standard I/O stream assigned to the variable @code{mylog},
5111 you could do the following:
5114 (gdb) set dprintf-style call
5115 (gdb) set dprintf-function fprintf
5116 (gdb) set dprintf-channel mylog
5117 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
5118 Dprintf 1 at 0x123456: file main.c, line 25.
5120 1 dprintf keep y 0x00123456 in main at main.c:25
5121 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
5126 Note that the @code{info break} displays the dynamic printf commands
5127 as normal breakpoint commands; you can thus easily see the effect of
5128 the variable settings.
5130 @item set disconnected-dprintf on
5131 @itemx set disconnected-dprintf off
5132 @kindex set disconnected-dprintf
5133 Choose whether @code{dprintf} commands should continue to run if
5134 @value{GDBN} has disconnected from the target. This only applies
5135 if the @code{dprintf-style} is @code{agent}.
5137 @item show disconnected-dprintf off
5138 @kindex show disconnected-dprintf
5139 Show the current choice for disconnected @code{dprintf}.
5143 @value{GDBN} does not check the validity of function and channel,
5144 relying on you to supply values that are meaningful for the contexts
5145 in which they are being used. For instance, the function and channel
5146 may be the values of local variables, but if that is the case, then
5147 all enabled dynamic prints must be at locations within the scope of
5148 those locals. If evaluation fails, @value{GDBN} will report an error.
5150 @node Save Breakpoints
5151 @subsection How to save breakpoints to a file
5153 To save breakpoint definitions to a file use the @w{@code{save
5154 breakpoints}} command.
5157 @kindex save breakpoints
5158 @cindex save breakpoints to a file for future sessions
5159 @item save breakpoints [@var{filename}]
5160 This command saves all current breakpoint definitions together with
5161 their commands and ignore counts, into a file @file{@var{filename}}
5162 suitable for use in a later debugging session. This includes all
5163 types of breakpoints (breakpoints, watchpoints, catchpoints,
5164 tracepoints). To read the saved breakpoint definitions, use the
5165 @code{source} command (@pxref{Command Files}). Note that watchpoints
5166 with expressions involving local variables may fail to be recreated
5167 because it may not be possible to access the context where the
5168 watchpoint is valid anymore. Because the saved breakpoint definitions
5169 are simply a sequence of @value{GDBN} commands that recreate the
5170 breakpoints, you can edit the file in your favorite editing program,
5171 and remove the breakpoint definitions you're not interested in, or
5172 that can no longer be recreated.
5175 @node Static Probe Points
5176 @subsection Static Probe Points
5178 @cindex static probe point, SystemTap
5179 @cindex static probe point, DTrace
5180 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5181 for Statically Defined Tracing, and the probes are designed to have a tiny
5182 runtime code and data footprint, and no dynamic relocations.
5184 Currently, the following types of probes are supported on
5185 ELF-compatible systems:
5189 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5190 @acronym{SDT} probes@footnote{See
5191 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5192 for more information on how to add @code{SystemTap} @acronym{SDT}
5193 probes in your applications.}. @code{SystemTap} probes are usable
5194 from assembly, C and C@t{++} languages@footnote{See
5195 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5196 for a good reference on how the @acronym{SDT} probes are implemented.}.
5198 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5199 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5203 @cindex semaphores on static probe points
5204 Some @code{SystemTap} probes have an associated semaphore variable;
5205 for instance, this happens automatically if you defined your probe
5206 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5207 @value{GDBN} will automatically enable it when you specify a
5208 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5209 breakpoint at a probe's location by some other method (e.g.,
5210 @code{break file:line}), then @value{GDBN} will not automatically set
5211 the semaphore. @code{DTrace} probes do not support semaphores.
5213 You can examine the available static static probes using @code{info
5214 probes}, with optional arguments:
5218 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5219 If given, @var{type} is either @code{stap} for listing
5220 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5221 probes. If omitted all probes are listed regardless of their types.
5223 If given, @var{provider} is a regular expression used to match against provider
5224 names when selecting which probes to list. If omitted, probes by all
5225 probes from all providers are listed.
5227 If given, @var{name} is a regular expression to match against probe names
5228 when selecting which probes to list. If omitted, probe names are not
5229 considered when deciding whether to display them.
5231 If given, @var{objfile} is a regular expression used to select which
5232 object files (executable or shared libraries) to examine. If not
5233 given, all object files are considered.
5235 @item info probes all
5236 List the available static probes, from all types.
5239 @cindex enabling and disabling probes
5240 Some probe points can be enabled and/or disabled. The effect of
5241 enabling or disabling a probe depends on the type of probe being
5242 handled. Some @code{DTrace} probes can be enabled or
5243 disabled, but @code{SystemTap} probes cannot be disabled.
5245 You can enable (or disable) one or more probes using the following
5246 commands, with optional arguments:
5249 @kindex enable probes
5250 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5251 If given, @var{provider} is a regular expression used to match against
5252 provider names when selecting which probes to enable. If omitted,
5253 all probes from all providers are enabled.
5255 If given, @var{name} is a regular expression to match against probe
5256 names when selecting which probes to enable. If omitted, probe names
5257 are not considered when deciding whether to enable them.
5259 If given, @var{objfile} is a regular expression used to select which
5260 object files (executable or shared libraries) to examine. If not
5261 given, all object files are considered.
5263 @kindex disable probes
5264 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5265 See the @code{enable probes} command above for a description of the
5266 optional arguments accepted by this command.
5269 @vindex $_probe_arg@r{, convenience variable}
5270 A probe may specify up to twelve arguments. These are available at the
5271 point at which the probe is defined---that is, when the current PC is
5272 at the probe's location. The arguments are available using the
5273 convenience variables (@pxref{Convenience Vars})
5274 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5275 probes each probe argument is an integer of the appropriate size;
5276 types are not preserved. In @code{DTrace} probes types are preserved
5277 provided that they are recognized as such by @value{GDBN}; otherwise
5278 the value of the probe argument will be a long integer. The
5279 convenience variable @code{$_probe_argc} holds the number of arguments
5280 at the current probe point.
5282 These variables are always available, but attempts to access them at
5283 any location other than a probe point will cause @value{GDBN} to give
5287 @c @ifclear BARETARGET
5288 @node Error in Breakpoints
5289 @subsection ``Cannot insert breakpoints''
5291 If you request too many active hardware-assisted breakpoints and
5292 watchpoints, you will see this error message:
5294 @c FIXME: the precise wording of this message may change; the relevant
5295 @c source change is not committed yet (Sep 3, 1999).
5297 Stopped; cannot insert breakpoints.
5298 You may have requested too many hardware breakpoints and watchpoints.
5302 This message is printed when you attempt to resume the program, since
5303 only then @value{GDBN} knows exactly how many hardware breakpoints and
5304 watchpoints it needs to insert.
5306 When this message is printed, you need to disable or remove some of the
5307 hardware-assisted breakpoints and watchpoints, and then continue.
5309 @node Breakpoint-related Warnings
5310 @subsection ``Breakpoint address adjusted...''
5311 @cindex breakpoint address adjusted
5313 Some processor architectures place constraints on the addresses at
5314 which breakpoints may be placed. For architectures thus constrained,
5315 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5316 with the constraints dictated by the architecture.
5318 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5319 a VLIW architecture in which a number of RISC-like instructions may be
5320 bundled together for parallel execution. The FR-V architecture
5321 constrains the location of a breakpoint instruction within such a
5322 bundle to the instruction with the lowest address. @value{GDBN}
5323 honors this constraint by adjusting a breakpoint's address to the
5324 first in the bundle.
5326 It is not uncommon for optimized code to have bundles which contain
5327 instructions from different source statements, thus it may happen that
5328 a breakpoint's address will be adjusted from one source statement to
5329 another. Since this adjustment may significantly alter @value{GDBN}'s
5330 breakpoint related behavior from what the user expects, a warning is
5331 printed when the breakpoint is first set and also when the breakpoint
5334 A warning like the one below is printed when setting a breakpoint
5335 that's been subject to address adjustment:
5338 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5341 Such warnings are printed both for user settable and @value{GDBN}'s
5342 internal breakpoints. If you see one of these warnings, you should
5343 verify that a breakpoint set at the adjusted address will have the
5344 desired affect. If not, the breakpoint in question may be removed and
5345 other breakpoints may be set which will have the desired behavior.
5346 E.g., it may be sufficient to place the breakpoint at a later
5347 instruction. A conditional breakpoint may also be useful in some
5348 cases to prevent the breakpoint from triggering too often.
5350 @value{GDBN} will also issue a warning when stopping at one of these
5351 adjusted breakpoints:
5354 warning: Breakpoint 1 address previously adjusted from 0x00010414
5358 When this warning is encountered, it may be too late to take remedial
5359 action except in cases where the breakpoint is hit earlier or more
5360 frequently than expected.
5362 @node Continuing and Stepping
5363 @section Continuing and Stepping
5367 @cindex resuming execution
5368 @dfn{Continuing} means resuming program execution until your program
5369 completes normally. In contrast, @dfn{stepping} means executing just
5370 one more ``step'' of your program, where ``step'' may mean either one
5371 line of source code, or one machine instruction (depending on what
5372 particular command you use). Either when continuing or when stepping,
5373 your program may stop even sooner, due to a breakpoint or a signal. (If
5374 it stops due to a signal, you may want to use @code{handle}, or use
5375 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5376 or you may step into the signal's handler (@pxref{stepping and signal
5381 @kindex c @r{(@code{continue})}
5382 @kindex fg @r{(resume foreground execution)}
5383 @item continue @r{[}@var{ignore-count}@r{]}
5384 @itemx c @r{[}@var{ignore-count}@r{]}
5385 @itemx fg @r{[}@var{ignore-count}@r{]}
5386 Resume program execution, at the address where your program last stopped;
5387 any breakpoints set at that address are bypassed. The optional argument
5388 @var{ignore-count} allows you to specify a further number of times to
5389 ignore a breakpoint at this location; its effect is like that of
5390 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5392 The argument @var{ignore-count} is meaningful only when your program
5393 stopped due to a breakpoint. At other times, the argument to
5394 @code{continue} is ignored.
5396 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5397 debugged program is deemed to be the foreground program) are provided
5398 purely for convenience, and have exactly the same behavior as
5402 To resume execution at a different place, you can use @code{return}
5403 (@pxref{Returning, ,Returning from a Function}) to go back to the
5404 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5405 Different Address}) to go to an arbitrary location in your program.
5407 A typical technique for using stepping is to set a breakpoint
5408 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5409 beginning of the function or the section of your program where a problem
5410 is believed to lie, run your program until it stops at that breakpoint,
5411 and then step through the suspect area, examining the variables that are
5412 interesting, until you see the problem happen.
5416 @kindex s @r{(@code{step})}
5418 Continue running your program until control reaches a different source
5419 line, then stop it and return control to @value{GDBN}. This command is
5420 abbreviated @code{s}.
5423 @c "without debugging information" is imprecise; actually "without line
5424 @c numbers in the debugging information". (gcc -g1 has debugging info but
5425 @c not line numbers). But it seems complex to try to make that
5426 @c distinction here.
5427 @emph{Warning:} If you use the @code{step} command while control is
5428 within a function that was compiled without debugging information,
5429 execution proceeds until control reaches a function that does have
5430 debugging information. Likewise, it will not step into a function which
5431 is compiled without debugging information. To step through functions
5432 without debugging information, use the @code{stepi} command, described
5436 The @code{step} command only stops at the first instruction of a source
5437 line. This prevents the multiple stops that could otherwise occur in
5438 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5439 to stop if a function that has debugging information is called within
5440 the line. In other words, @code{step} @emph{steps inside} any functions
5441 called within the line.
5443 Also, the @code{step} command only enters a function if there is line
5444 number information for the function. Otherwise it acts like the
5445 @code{next} command. This avoids problems when using @code{cc -gl}
5446 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5447 was any debugging information about the routine.
5449 @item step @var{count}
5450 Continue running as in @code{step}, but do so @var{count} times. If a
5451 breakpoint is reached, or a signal not related to stepping occurs before
5452 @var{count} steps, stepping stops right away.
5455 @kindex n @r{(@code{next})}
5456 @item next @r{[}@var{count}@r{]}
5457 Continue to the next source line in the current (innermost) stack frame.
5458 This is similar to @code{step}, but function calls that appear within
5459 the line of code are executed without stopping. Execution stops when
5460 control reaches a different line of code at the original stack level
5461 that was executing when you gave the @code{next} command. This command
5462 is abbreviated @code{n}.
5464 An argument @var{count} is a repeat count, as for @code{step}.
5467 @c FIX ME!! Do we delete this, or is there a way it fits in with
5468 @c the following paragraph? --- Vctoria
5470 @c @code{next} within a function that lacks debugging information acts like
5471 @c @code{step}, but any function calls appearing within the code of the
5472 @c function are executed without stopping.
5474 The @code{next} command only stops at the first instruction of a
5475 source line. This prevents multiple stops that could otherwise occur in
5476 @code{switch} statements, @code{for} loops, etc.
5478 @kindex set step-mode
5480 @cindex functions without line info, and stepping
5481 @cindex stepping into functions with no line info
5482 @itemx set step-mode on
5483 The @code{set step-mode on} command causes the @code{step} command to
5484 stop at the first instruction of a function which contains no debug line
5485 information rather than stepping over it.
5487 This is useful in cases where you may be interested in inspecting the
5488 machine instructions of a function which has no symbolic info and do not
5489 want @value{GDBN} to automatically skip over this function.
5491 @item set step-mode off
5492 Causes the @code{step} command to step over any functions which contains no
5493 debug information. This is the default.
5495 @item show step-mode
5496 Show whether @value{GDBN} will stop in or step over functions without
5497 source line debug information.
5500 @kindex fin @r{(@code{finish})}
5502 Continue running until just after function in the selected stack frame
5503 returns. Print the returned value (if any). This command can be
5504 abbreviated as @code{fin}.
5506 Contrast this with the @code{return} command (@pxref{Returning,
5507 ,Returning from a Function}).
5510 @kindex u @r{(@code{until})}
5511 @cindex run until specified location
5514 Continue running until a source line past the current line, in the
5515 current stack frame, is reached. This command is used to avoid single
5516 stepping through a loop more than once. It is like the @code{next}
5517 command, except that when @code{until} encounters a jump, it
5518 automatically continues execution until the program counter is greater
5519 than the address of the jump.
5521 This means that when you reach the end of a loop after single stepping
5522 though it, @code{until} makes your program continue execution until it
5523 exits the loop. In contrast, a @code{next} command at the end of a loop
5524 simply steps back to the beginning of the loop, which forces you to step
5525 through the next iteration.
5527 @code{until} always stops your program if it attempts to exit the current
5530 @code{until} may produce somewhat counterintuitive results if the order
5531 of machine code does not match the order of the source lines. For
5532 example, in the following excerpt from a debugging session, the @code{f}
5533 (@code{frame}) command shows that execution is stopped at line
5534 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5538 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5540 (@value{GDBP}) until
5541 195 for ( ; argc > 0; NEXTARG) @{
5544 This happened because, for execution efficiency, the compiler had
5545 generated code for the loop closure test at the end, rather than the
5546 start, of the loop---even though the test in a C @code{for}-loop is
5547 written before the body of the loop. The @code{until} command appeared
5548 to step back to the beginning of the loop when it advanced to this
5549 expression; however, it has not really gone to an earlier
5550 statement---not in terms of the actual machine code.
5552 @code{until} with no argument works by means of single
5553 instruction stepping, and hence is slower than @code{until} with an
5556 @item until @var{location}
5557 @itemx u @var{location}
5558 Continue running your program until either the specified @var{location} is
5559 reached, or the current stack frame returns. The location is any of
5560 the forms described in @ref{Specify Location}.
5561 This form of the command uses temporary breakpoints, and
5562 hence is quicker than @code{until} without an argument. The specified
5563 location is actually reached only if it is in the current frame. This
5564 implies that @code{until} can be used to skip over recursive function
5565 invocations. For instance in the code below, if the current location is
5566 line @code{96}, issuing @code{until 99} will execute the program up to
5567 line @code{99} in the same invocation of factorial, i.e., after the inner
5568 invocations have returned.
5571 94 int factorial (int value)
5573 96 if (value > 1) @{
5574 97 value *= factorial (value - 1);
5581 @kindex advance @var{location}
5582 @item advance @var{location}
5583 Continue running the program up to the given @var{location}. An argument is
5584 required, which should be of one of the forms described in
5585 @ref{Specify Location}.
5586 Execution will also stop upon exit from the current stack
5587 frame. This command is similar to @code{until}, but @code{advance} will
5588 not skip over recursive function calls, and the target location doesn't
5589 have to be in the same frame as the current one.
5593 @kindex si @r{(@code{stepi})}
5595 @itemx stepi @var{arg}
5597 Execute one machine instruction, then stop and return to the debugger.
5599 It is often useful to do @samp{display/i $pc} when stepping by machine
5600 instructions. This makes @value{GDBN} automatically display the next
5601 instruction to be executed, each time your program stops. @xref{Auto
5602 Display,, Automatic Display}.
5604 An argument is a repeat count, as in @code{step}.
5608 @kindex ni @r{(@code{nexti})}
5610 @itemx nexti @var{arg}
5612 Execute one machine instruction, but if it is a function call,
5613 proceed until the function returns.
5615 An argument is a repeat count, as in @code{next}.
5619 @anchor{range stepping}
5620 @cindex range stepping
5621 @cindex target-assisted range stepping
5622 By default, and if available, @value{GDBN} makes use of
5623 target-assisted @dfn{range stepping}. In other words, whenever you
5624 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5625 tells the target to step the corresponding range of instruction
5626 addresses instead of issuing multiple single-steps. This speeds up
5627 line stepping, particularly for remote targets. Ideally, there should
5628 be no reason you would want to turn range stepping off. However, it's
5629 possible that a bug in the debug info, a bug in the remote stub (for
5630 remote targets), or even a bug in @value{GDBN} could make line
5631 stepping behave incorrectly when target-assisted range stepping is
5632 enabled. You can use the following command to turn off range stepping
5636 @kindex set range-stepping
5637 @kindex show range-stepping
5638 @item set range-stepping
5639 @itemx show range-stepping
5640 Control whether range stepping is enabled.
5642 If @code{on}, and the target supports it, @value{GDBN} tells the
5643 target to step a range of addresses itself, instead of issuing
5644 multiple single-steps. If @code{off}, @value{GDBN} always issues
5645 single-steps, even if range stepping is supported by the target. The
5646 default is @code{on}.
5650 @node Skipping Over Functions and Files
5651 @section Skipping Over Functions and Files
5652 @cindex skipping over functions and files
5654 The program you are debugging may contain some functions which are
5655 uninteresting to debug. The @code{skip} command lets you tell @value{GDBN} to
5656 skip a function, all functions in a file or a particular function in
5657 a particular file when stepping.
5659 For example, consider the following C function:
5670 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5671 are not interested in stepping through @code{boring}. If you run @code{step}
5672 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5673 step over both @code{foo} and @code{boring}!
5675 One solution is to @code{step} into @code{boring} and use the @code{finish}
5676 command to immediately exit it. But this can become tedious if @code{boring}
5677 is called from many places.
5679 A more flexible solution is to execute @kbd{skip boring}. This instructs
5680 @value{GDBN} never to step into @code{boring}. Now when you execute
5681 @code{step} at line 103, you'll step over @code{boring} and directly into
5684 Functions may be skipped by providing either a function name, linespec
5685 (@pxref{Specify Location}), regular expression that matches the function's
5686 name, file name or a @code{glob}-style pattern that matches the file name.
5688 On Posix systems the form of the regular expression is
5689 ``Extended Regular Expressions''. See for example @samp{man 7 regex}
5690 on @sc{gnu}/Linux systems. On non-Posix systems the form of the regular
5691 expression is whatever is provided by the @code{regcomp} function of
5692 the underlying system.
5693 See for example @samp{man 7 glob} on @sc{gnu}/Linux systems for a
5694 description of @code{glob}-style patterns.
5698 @item skip @r{[}@var{options}@r{]}
5699 The basic form of the @code{skip} command takes zero or more options
5700 that specify what to skip.
5701 The @var{options} argument is any useful combination of the following:
5704 @item -file @var{file}
5705 @itemx -fi @var{file}
5706 Functions in @var{file} will be skipped over when stepping.
5708 @item -gfile @var{file-glob-pattern}
5709 @itemx -gfi @var{file-glob-pattern}
5710 @cindex skipping over files via glob-style patterns
5711 Functions in files matching @var{file-glob-pattern} will be skipped
5715 (gdb) skip -gfi utils/*.c
5718 @item -function @var{linespec}
5719 @itemx -fu @var{linespec}
5720 Functions named by @var{linespec} or the function containing the line
5721 named by @var{linespec} will be skipped over when stepping.
5722 @xref{Specify Location}.
5724 @item -rfunction @var{regexp}
5725 @itemx -rfu @var{regexp}
5726 @cindex skipping over functions via regular expressions
5727 Functions whose name matches @var{regexp} will be skipped over when stepping.
5729 This form is useful for complex function names.
5730 For example, there is generally no need to step into C@t{++} @code{std::string}
5731 constructors or destructors. Plus with C@t{++} templates it can be hard to
5732 write out the full name of the function, and often it doesn't matter what
5733 the template arguments are. Specifying the function to be skipped as a
5734 regular expression makes this easier.
5737 (gdb) skip -rfu ^std::(allocator|basic_string)<.*>::~?\1 *\(
5740 If you want to skip every templated C@t{++} constructor and destructor
5741 in the @code{std} namespace you can do:
5744 (gdb) skip -rfu ^std::([a-zA-z0-9_]+)<.*>::~?\1 *\(
5748 If no options are specified, the function you're currently debugging
5751 @kindex skip function
5752 @item skip function @r{[}@var{linespec}@r{]}
5753 After running this command, the function named by @var{linespec} or the
5754 function containing the line named by @var{linespec} will be skipped over when
5755 stepping. @xref{Specify Location}.
5757 If you do not specify @var{linespec}, the function you're currently debugging
5760 (If you have a function called @code{file} that you want to skip, use
5761 @kbd{skip function file}.)
5764 @item skip file @r{[}@var{filename}@r{]}
5765 After running this command, any function whose source lives in @var{filename}
5766 will be skipped over when stepping.
5769 (gdb) skip file boring.c
5770 File boring.c will be skipped when stepping.
5773 If you do not specify @var{filename}, functions whose source lives in the file
5774 you're currently debugging will be skipped.
5777 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5778 These are the commands for managing your list of skips:
5782 @item info skip @r{[}@var{range}@r{]}
5783 Print details about the specified skip(s). If @var{range} is not specified,
5784 print a table with details about all functions and files marked for skipping.
5785 @code{info skip} prints the following information about each skip:
5789 A number identifying this skip.
5790 @item Enabled or Disabled
5791 Enabled skips are marked with @samp{y}.
5792 Disabled skips are marked with @samp{n}.
5794 If the file name is a @samp{glob} pattern this is @samp{y}.
5795 Otherwise it is @samp{n}.
5797 The name or @samp{glob} pattern of the file to be skipped.
5798 If no file is specified this is @samp{<none>}.
5800 If the function name is a @samp{regular expression} this is @samp{y}.
5801 Otherwise it is @samp{n}.
5803 The name or regular expression of the function to skip.
5804 If no function is specified this is @samp{<none>}.
5808 @item skip delete @r{[}@var{range}@r{]}
5809 Delete the specified skip(s). If @var{range} is not specified, delete all
5813 @item skip enable @r{[}@var{range}@r{]}
5814 Enable the specified skip(s). If @var{range} is not specified, enable all
5817 @kindex skip disable
5818 @item skip disable @r{[}@var{range}@r{]}
5819 Disable the specified skip(s). If @var{range} is not specified, disable all
5828 A signal is an asynchronous event that can happen in a program. The
5829 operating system defines the possible kinds of signals, and gives each
5830 kind a name and a number. For example, in Unix @code{SIGINT} is the
5831 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5832 @code{SIGSEGV} is the signal a program gets from referencing a place in
5833 memory far away from all the areas in use; @code{SIGALRM} occurs when
5834 the alarm clock timer goes off (which happens only if your program has
5835 requested an alarm).
5837 @cindex fatal signals
5838 Some signals, including @code{SIGALRM}, are a normal part of the
5839 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5840 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5841 program has not specified in advance some other way to handle the signal.
5842 @code{SIGINT} does not indicate an error in your program, but it is normally
5843 fatal so it can carry out the purpose of the interrupt: to kill the program.
5845 @value{GDBN} has the ability to detect any occurrence of a signal in your
5846 program. You can tell @value{GDBN} in advance what to do for each kind of
5849 @cindex handling signals
5850 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5851 @code{SIGALRM} be silently passed to your program
5852 (so as not to interfere with their role in the program's functioning)
5853 but to stop your program immediately whenever an error signal happens.
5854 You can change these settings with the @code{handle} command.
5857 @kindex info signals
5861 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5862 handle each one. You can use this to see the signal numbers of all
5863 the defined types of signals.
5865 @item info signals @var{sig}
5866 Similar, but print information only about the specified signal number.
5868 @code{info handle} is an alias for @code{info signals}.
5870 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5871 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5872 for details about this command.
5875 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5876 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5877 can be the number of a signal or its name (with or without the
5878 @samp{SIG} at the beginning); a list of signal numbers of the form
5879 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5880 known signals. Optional arguments @var{keywords}, described below,
5881 say what change to make.
5885 The keywords allowed by the @code{handle} command can be abbreviated.
5886 Their full names are:
5890 @value{GDBN} should not stop your program when this signal happens. It may
5891 still print a message telling you that the signal has come in.
5894 @value{GDBN} should stop your program when this signal happens. This implies
5895 the @code{print} keyword as well.
5898 @value{GDBN} should print a message when this signal happens.
5901 @value{GDBN} should not mention the occurrence of the signal at all. This
5902 implies the @code{nostop} keyword as well.
5906 @value{GDBN} should allow your program to see this signal; your program
5907 can handle the signal, or else it may terminate if the signal is fatal
5908 and not handled. @code{pass} and @code{noignore} are synonyms.
5912 @value{GDBN} should not allow your program to see this signal.
5913 @code{nopass} and @code{ignore} are synonyms.
5917 When a signal stops your program, the signal is not visible to the
5919 continue. Your program sees the signal then, if @code{pass} is in
5920 effect for the signal in question @emph{at that time}. In other words,
5921 after @value{GDBN} reports a signal, you can use the @code{handle}
5922 command with @code{pass} or @code{nopass} to control whether your
5923 program sees that signal when you continue.
5925 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5926 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5927 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5930 You can also use the @code{signal} command to prevent your program from
5931 seeing a signal, or cause it to see a signal it normally would not see,
5932 or to give it any signal at any time. For example, if your program stopped
5933 due to some sort of memory reference error, you might store correct
5934 values into the erroneous variables and continue, hoping to see more
5935 execution; but your program would probably terminate immediately as
5936 a result of the fatal signal once it saw the signal. To prevent this,
5937 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5940 @cindex stepping and signal handlers
5941 @anchor{stepping and signal handlers}
5943 @value{GDBN} optimizes for stepping the mainline code. If a signal
5944 that has @code{handle nostop} and @code{handle pass} set arrives while
5945 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5946 in progress, @value{GDBN} lets the signal handler run and then resumes
5947 stepping the mainline code once the signal handler returns. In other
5948 words, @value{GDBN} steps over the signal handler. This prevents
5949 signals that you've specified as not interesting (with @code{handle
5950 nostop}) from changing the focus of debugging unexpectedly. Note that
5951 the signal handler itself may still hit a breakpoint, stop for another
5952 signal that has @code{handle stop} in effect, or for any other event
5953 that normally results in stopping the stepping command sooner. Also
5954 note that @value{GDBN} still informs you that the program received a
5955 signal if @code{handle print} is set.
5957 @anchor{stepping into signal handlers}
5959 If you set @code{handle pass} for a signal, and your program sets up a
5960 handler for it, then issuing a stepping command, such as @code{step}
5961 or @code{stepi}, when your program is stopped due to the signal will
5962 step @emph{into} the signal handler (if the target supports that).
5964 Likewise, if you use the @code{queue-signal} command to queue a signal
5965 to be delivered to the current thread when execution of the thread
5966 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5967 stepping command will step into the signal handler.
5969 Here's an example, using @code{stepi} to step to the first instruction
5970 of @code{SIGUSR1}'s handler:
5973 (@value{GDBP}) handle SIGUSR1
5974 Signal Stop Print Pass to program Description
5975 SIGUSR1 Yes Yes Yes User defined signal 1
5979 Program received signal SIGUSR1, User defined signal 1.
5980 main () sigusr1.c:28
5983 sigusr1_handler () at sigusr1.c:9
5987 The same, but using @code{queue-signal} instead of waiting for the
5988 program to receive the signal first:
5993 (@value{GDBP}) queue-signal SIGUSR1
5995 sigusr1_handler () at sigusr1.c:9
6000 @cindex extra signal information
6001 @anchor{extra signal information}
6003 On some targets, @value{GDBN} can inspect extra signal information
6004 associated with the intercepted signal, before it is actually
6005 delivered to the program being debugged. This information is exported
6006 by the convenience variable @code{$_siginfo}, and consists of data
6007 that is passed by the kernel to the signal handler at the time of the
6008 receipt of a signal. The data type of the information itself is
6009 target dependent. You can see the data type using the @code{ptype
6010 $_siginfo} command. On Unix systems, it typically corresponds to the
6011 standard @code{siginfo_t} type, as defined in the @file{signal.h}
6014 Here's an example, on a @sc{gnu}/Linux system, printing the stray
6015 referenced address that raised a segmentation fault.
6019 (@value{GDBP}) continue
6020 Program received signal SIGSEGV, Segmentation fault.
6021 0x0000000000400766 in main ()
6023 (@value{GDBP}) ptype $_siginfo
6030 struct @{...@} _kill;
6031 struct @{...@} _timer;
6033 struct @{...@} _sigchld;
6034 struct @{...@} _sigfault;
6035 struct @{...@} _sigpoll;
6038 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
6042 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
6043 $1 = (void *) 0x7ffff7ff7000
6047 Depending on target support, @code{$_siginfo} may also be writable.
6049 @cindex Intel MPX boundary violations
6050 @cindex boundary violations, Intel MPX
6051 On some targets, a @code{SIGSEGV} can be caused by a boundary
6052 violation, i.e., accessing an address outside of the allowed range.
6053 In those cases @value{GDBN} may displays additional information,
6054 depending on how @value{GDBN} has been told to handle the signal.
6055 With @code{handle stop SIGSEGV}, @value{GDBN} displays the violation
6056 kind: "Upper" or "Lower", the memory address accessed and the
6057 bounds, while with @code{handle nostop SIGSEGV} no additional
6058 information is displayed.
6060 The usual output of a segfault is:
6062 Program received signal SIGSEGV, Segmentation fault
6063 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6064 68 value = *(p + len);
6067 While a bound violation is presented as:
6069 Program received signal SIGSEGV, Segmentation fault
6070 Upper bound violation while accessing address 0x7fffffffc3b3
6071 Bounds: [lower = 0x7fffffffc390, upper = 0x7fffffffc3a3]
6072 0x0000000000400d7c in upper () at i386-mpx-sigsegv.c:68
6073 68 value = *(p + len);
6077 @section Stopping and Starting Multi-thread Programs
6079 @cindex stopped threads
6080 @cindex threads, stopped
6082 @cindex continuing threads
6083 @cindex threads, continuing
6085 @value{GDBN} supports debugging programs with multiple threads
6086 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
6087 are two modes of controlling execution of your program within the
6088 debugger. In the default mode, referred to as @dfn{all-stop mode},
6089 when any thread in your program stops (for example, at a breakpoint
6090 or while being stepped), all other threads in the program are also stopped by
6091 @value{GDBN}. On some targets, @value{GDBN} also supports
6092 @dfn{non-stop mode}, in which other threads can continue to run freely while
6093 you examine the stopped thread in the debugger.
6096 * All-Stop Mode:: All threads stop when GDB takes control
6097 * Non-Stop Mode:: Other threads continue to execute
6098 * Background Execution:: Running your program asynchronously
6099 * Thread-Specific Breakpoints:: Controlling breakpoints
6100 * Interrupted System Calls:: GDB may interfere with system calls
6101 * Observer Mode:: GDB does not alter program behavior
6105 @subsection All-Stop Mode
6107 @cindex all-stop mode
6109 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
6110 @emph{all} threads of execution stop, not just the current thread. This
6111 allows you to examine the overall state of the program, including
6112 switching between threads, without worrying that things may change
6115 Conversely, whenever you restart the program, @emph{all} threads start
6116 executing. @emph{This is true even when single-stepping} with commands
6117 like @code{step} or @code{next}.
6119 In particular, @value{GDBN} cannot single-step all threads in lockstep.
6120 Since thread scheduling is up to your debugging target's operating
6121 system (not controlled by @value{GDBN}), other threads may
6122 execute more than one statement while the current thread completes a
6123 single step. Moreover, in general other threads stop in the middle of a
6124 statement, rather than at a clean statement boundary, when the program
6127 You might even find your program stopped in another thread after
6128 continuing or even single-stepping. This happens whenever some other
6129 thread runs into a breakpoint, a signal, or an exception before the
6130 first thread completes whatever you requested.
6132 @cindex automatic thread selection
6133 @cindex switching threads automatically
6134 @cindex threads, automatic switching
6135 Whenever @value{GDBN} stops your program, due to a breakpoint or a
6136 signal, it automatically selects the thread where that breakpoint or
6137 signal happened. @value{GDBN} alerts you to the context switch with a
6138 message such as @samp{[Switching to Thread @var{n}]} to identify the
6141 On some OSes, you can modify @value{GDBN}'s default behavior by
6142 locking the OS scheduler to allow only a single thread to run.
6145 @item set scheduler-locking @var{mode}
6146 @cindex scheduler locking mode
6147 @cindex lock scheduler
6148 Set the scheduler locking mode. It applies to normal execution,
6149 record mode, and replay mode. If it is @code{off}, then there is no
6150 locking and any thread may run at any time. If @code{on}, then only
6151 the current thread may run when the inferior is resumed. The
6152 @code{step} mode optimizes for single-stepping; it prevents other
6153 threads from preempting the current thread while you are stepping, so
6154 that the focus of debugging does not change unexpectedly. Other
6155 threads never get a chance to run when you step, and they are
6156 completely free to run when you use commands like @samp{continue},
6157 @samp{until}, or @samp{finish}. However, unless another thread hits a
6158 breakpoint during its timeslice, @value{GDBN} does not change the
6159 current thread away from the thread that you are debugging. The
6160 @code{replay} mode behaves like @code{off} in record mode and like
6161 @code{on} in replay mode.
6163 @item show scheduler-locking
6164 Display the current scheduler locking mode.
6167 @cindex resume threads of multiple processes simultaneously
6168 By default, when you issue one of the execution commands such as
6169 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
6170 threads of the current inferior to run. For example, if @value{GDBN}
6171 is attached to two inferiors, each with two threads, the
6172 @code{continue} command resumes only the two threads of the current
6173 inferior. This is useful, for example, when you debug a program that
6174 forks and you want to hold the parent stopped (so that, for instance,
6175 it doesn't run to exit), while you debug the child. In other
6176 situations, you may not be interested in inspecting the current state
6177 of any of the processes @value{GDBN} is attached to, and you may want
6178 to resume them all until some breakpoint is hit. In the latter case,
6179 you can instruct @value{GDBN} to allow all threads of all the
6180 inferiors to run with the @w{@code{set schedule-multiple}} command.
6183 @kindex set schedule-multiple
6184 @item set schedule-multiple
6185 Set the mode for allowing threads of multiple processes to be resumed
6186 when an execution command is issued. When @code{on}, all threads of
6187 all processes are allowed to run. When @code{off}, only the threads
6188 of the current process are resumed. The default is @code{off}. The
6189 @code{scheduler-locking} mode takes precedence when set to @code{on},
6190 or while you are stepping and set to @code{step}.
6192 @item show schedule-multiple
6193 Display the current mode for resuming the execution of threads of
6198 @subsection Non-Stop Mode
6200 @cindex non-stop mode
6202 @c This section is really only a place-holder, and needs to be expanded
6203 @c with more details.
6205 For some multi-threaded targets, @value{GDBN} supports an optional
6206 mode of operation in which you can examine stopped program threads in
6207 the debugger while other threads continue to execute freely. This
6208 minimizes intrusion when debugging live systems, such as programs
6209 where some threads have real-time constraints or must continue to
6210 respond to external events. This is referred to as @dfn{non-stop} mode.
6212 In non-stop mode, when a thread stops to report a debugging event,
6213 @emph{only} that thread is stopped; @value{GDBN} does not stop other
6214 threads as well, in contrast to the all-stop mode behavior. Additionally,
6215 execution commands such as @code{continue} and @code{step} apply by default
6216 only to the current thread in non-stop mode, rather than all threads as
6217 in all-stop mode. This allows you to control threads explicitly in
6218 ways that are not possible in all-stop mode --- for example, stepping
6219 one thread while allowing others to run freely, stepping
6220 one thread while holding all others stopped, or stepping several threads
6221 independently and simultaneously.
6223 To enter non-stop mode, use this sequence of commands before you run
6224 or attach to your program:
6227 # If using the CLI, pagination breaks non-stop.
6230 # Finally, turn it on!
6234 You can use these commands to manipulate the non-stop mode setting:
6237 @kindex set non-stop
6238 @item set non-stop on
6239 Enable selection of non-stop mode.
6240 @item set non-stop off
6241 Disable selection of non-stop mode.
6242 @kindex show non-stop
6244 Show the current non-stop enablement setting.
6247 Note these commands only reflect whether non-stop mode is enabled,
6248 not whether the currently-executing program is being run in non-stop mode.
6249 In particular, the @code{set non-stop} preference is only consulted when
6250 @value{GDBN} starts or connects to the target program, and it is generally
6251 not possible to switch modes once debugging has started. Furthermore,
6252 since not all targets support non-stop mode, even when you have enabled
6253 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
6256 In non-stop mode, all execution commands apply only to the current thread
6257 by default. That is, @code{continue} only continues one thread.
6258 To continue all threads, issue @code{continue -a} or @code{c -a}.
6260 You can use @value{GDBN}'s background execution commands
6261 (@pxref{Background Execution}) to run some threads in the background
6262 while you continue to examine or step others from @value{GDBN}.
6263 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6264 always executed asynchronously in non-stop mode.
6266 Suspending execution is done with the @code{interrupt} command when
6267 running in the background, or @kbd{Ctrl-c} during foreground execution.
6268 In all-stop mode, this stops the whole process;
6269 but in non-stop mode the interrupt applies only to the current thread.
6270 To stop the whole program, use @code{interrupt -a}.
6272 Other execution commands do not currently support the @code{-a} option.
6274 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6275 that thread current, as it does in all-stop mode. This is because the
6276 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6277 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6278 changed to a different thread just as you entered a command to operate on the
6279 previously current thread.
6281 @node Background Execution
6282 @subsection Background Execution
6284 @cindex foreground execution
6285 @cindex background execution
6286 @cindex asynchronous execution
6287 @cindex execution, foreground, background and asynchronous
6289 @value{GDBN}'s execution commands have two variants: the normal
6290 foreground (synchronous) behavior, and a background
6291 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6292 the program to report that some thread has stopped before prompting for
6293 another command. In background execution, @value{GDBN} immediately gives
6294 a command prompt so that you can issue other commands while your program runs.
6296 If the target doesn't support async mode, @value{GDBN} issues an error
6297 message if you attempt to use the background execution commands.
6299 To specify background execution, add a @code{&} to the command. For example,
6300 the background form of the @code{continue} command is @code{continue&}, or
6301 just @code{c&}. The execution commands that accept background execution
6307 @xref{Starting, , Starting your Program}.
6311 @xref{Attach, , Debugging an Already-running Process}.
6315 @xref{Continuing and Stepping, step}.
6319 @xref{Continuing and Stepping, stepi}.
6323 @xref{Continuing and Stepping, next}.
6327 @xref{Continuing and Stepping, nexti}.
6331 @xref{Continuing and Stepping, continue}.
6335 @xref{Continuing and Stepping, finish}.
6339 @xref{Continuing and Stepping, until}.
6343 Background execution is especially useful in conjunction with non-stop
6344 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6345 However, you can also use these commands in the normal all-stop mode with
6346 the restriction that you cannot issue another execution command until the
6347 previous one finishes. Examples of commands that are valid in all-stop
6348 mode while the program is running include @code{help} and @code{info break}.
6350 You can interrupt your program while it is running in the background by
6351 using the @code{interrupt} command.
6358 Suspend execution of the running program. In all-stop mode,
6359 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6360 only the current thread. To stop the whole program in non-stop mode,
6361 use @code{interrupt -a}.
6364 @node Thread-Specific Breakpoints
6365 @subsection Thread-Specific Breakpoints
6367 When your program has multiple threads (@pxref{Threads,, Debugging
6368 Programs with Multiple Threads}), you can choose whether to set
6369 breakpoints on all threads, or on a particular thread.
6372 @cindex breakpoints and threads
6373 @cindex thread breakpoints
6374 @kindex break @dots{} thread @var{thread-id}
6375 @item break @var{location} thread @var{thread-id}
6376 @itemx break @var{location} thread @var{thread-id} if @dots{}
6377 @var{location} specifies source lines; there are several ways of
6378 writing them (@pxref{Specify Location}), but the effect is always to
6379 specify some source line.
6381 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6382 to specify that you only want @value{GDBN} to stop the program when a
6383 particular thread reaches this breakpoint. The @var{thread-id} specifier
6384 is one of the thread identifiers assigned by @value{GDBN}, shown
6385 in the first column of the @samp{info threads} display.
6387 If you do not specify @samp{thread @var{thread-id}} when you set a
6388 breakpoint, the breakpoint applies to @emph{all} threads of your
6391 You can use the @code{thread} qualifier on conditional breakpoints as
6392 well; in this case, place @samp{thread @var{thread-id}} before or
6393 after the breakpoint condition, like this:
6396 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6401 Thread-specific breakpoints are automatically deleted when
6402 @value{GDBN} detects the corresponding thread is no longer in the
6403 thread list. For example:
6407 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6410 There are several ways for a thread to disappear, such as a regular
6411 thread exit, but also when you detach from the process with the
6412 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6413 Process}), or if @value{GDBN} loses the remote connection
6414 (@pxref{Remote Debugging}), etc. Note that with some targets,
6415 @value{GDBN} is only able to detect a thread has exited when the user
6416 explictly asks for the thread list with the @code{info threads}
6419 @node Interrupted System Calls
6420 @subsection Interrupted System Calls
6422 @cindex thread breakpoints and system calls
6423 @cindex system calls and thread breakpoints
6424 @cindex premature return from system calls
6425 There is an unfortunate side effect when using @value{GDBN} to debug
6426 multi-threaded programs. If one thread stops for a
6427 breakpoint, or for some other reason, and another thread is blocked in a
6428 system call, then the system call may return prematurely. This is a
6429 consequence of the interaction between multiple threads and the signals
6430 that @value{GDBN} uses to implement breakpoints and other events that
6433 To handle this problem, your program should check the return value of
6434 each system call and react appropriately. This is good programming
6437 For example, do not write code like this:
6443 The call to @code{sleep} will return early if a different thread stops
6444 at a breakpoint or for some other reason.
6446 Instead, write this:
6451 unslept = sleep (unslept);
6454 A system call is allowed to return early, so the system is still
6455 conforming to its specification. But @value{GDBN} does cause your
6456 multi-threaded program to behave differently than it would without
6459 Also, @value{GDBN} uses internal breakpoints in the thread library to
6460 monitor certain events such as thread creation and thread destruction.
6461 When such an event happens, a system call in another thread may return
6462 prematurely, even though your program does not appear to stop.
6465 @subsection Observer Mode
6467 If you want to build on non-stop mode and observe program behavior
6468 without any chance of disruption by @value{GDBN}, you can set
6469 variables to disable all of the debugger's attempts to modify state,
6470 whether by writing memory, inserting breakpoints, etc. These operate
6471 at a low level, intercepting operations from all commands.
6473 When all of these are set to @code{off}, then @value{GDBN} is said to
6474 be @dfn{observer mode}. As a convenience, the variable
6475 @code{observer} can be set to disable these, plus enable non-stop
6478 Note that @value{GDBN} will not prevent you from making nonsensical
6479 combinations of these settings. For instance, if you have enabled
6480 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6481 then breakpoints that work by writing trap instructions into the code
6482 stream will still not be able to be placed.
6487 @item set observer on
6488 @itemx set observer off
6489 When set to @code{on}, this disables all the permission variables
6490 below (except for @code{insert-fast-tracepoints}), plus enables
6491 non-stop debugging. Setting this to @code{off} switches back to
6492 normal debugging, though remaining in non-stop mode.
6495 Show whether observer mode is on or off.
6497 @kindex may-write-registers
6498 @item set may-write-registers on
6499 @itemx set may-write-registers off
6500 This controls whether @value{GDBN} will attempt to alter the values of
6501 registers, such as with assignment expressions in @code{print}, or the
6502 @code{jump} command. It defaults to @code{on}.
6504 @item show may-write-registers
6505 Show the current permission to write registers.
6507 @kindex may-write-memory
6508 @item set may-write-memory on
6509 @itemx set may-write-memory off
6510 This controls whether @value{GDBN} will attempt to alter the contents
6511 of memory, such as with assignment expressions in @code{print}. It
6512 defaults to @code{on}.
6514 @item show may-write-memory
6515 Show the current permission to write memory.
6517 @kindex may-insert-breakpoints
6518 @item set may-insert-breakpoints on
6519 @itemx set may-insert-breakpoints off
6520 This controls whether @value{GDBN} will attempt to insert breakpoints.
6521 This affects all breakpoints, including internal breakpoints defined
6522 by @value{GDBN}. It defaults to @code{on}.
6524 @item show may-insert-breakpoints
6525 Show the current permission to insert breakpoints.
6527 @kindex may-insert-tracepoints
6528 @item set may-insert-tracepoints on
6529 @itemx set may-insert-tracepoints off
6530 This controls whether @value{GDBN} will attempt to insert (regular)
6531 tracepoints at the beginning of a tracing experiment. It affects only
6532 non-fast tracepoints, fast tracepoints being under the control of
6533 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6535 @item show may-insert-tracepoints
6536 Show the current permission to insert tracepoints.
6538 @kindex may-insert-fast-tracepoints
6539 @item set may-insert-fast-tracepoints on
6540 @itemx set may-insert-fast-tracepoints off
6541 This controls whether @value{GDBN} will attempt to insert fast
6542 tracepoints at the beginning of a tracing experiment. It affects only
6543 fast tracepoints, regular (non-fast) tracepoints being under the
6544 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6546 @item show may-insert-fast-tracepoints
6547 Show the current permission to insert fast tracepoints.
6549 @kindex may-interrupt
6550 @item set may-interrupt on
6551 @itemx set may-interrupt off
6552 This controls whether @value{GDBN} will attempt to interrupt or stop
6553 program execution. When this variable is @code{off}, the
6554 @code{interrupt} command will have no effect, nor will
6555 @kbd{Ctrl-c}. It defaults to @code{on}.
6557 @item show may-interrupt
6558 Show the current permission to interrupt or stop the program.
6562 @node Reverse Execution
6563 @chapter Running programs backward
6564 @cindex reverse execution
6565 @cindex running programs backward
6567 When you are debugging a program, it is not unusual to realize that
6568 you have gone too far, and some event of interest has already happened.
6569 If the target environment supports it, @value{GDBN} can allow you to
6570 ``rewind'' the program by running it backward.
6572 A target environment that supports reverse execution should be able
6573 to ``undo'' the changes in machine state that have taken place as the
6574 program was executing normally. Variables, registers etc.@: should
6575 revert to their previous values. Obviously this requires a great
6576 deal of sophistication on the part of the target environment; not
6577 all target environments can support reverse execution.
6579 When a program is executed in reverse, the instructions that
6580 have most recently been executed are ``un-executed'', in reverse
6581 order. The program counter runs backward, following the previous
6582 thread of execution in reverse. As each instruction is ``un-executed'',
6583 the values of memory and/or registers that were changed by that
6584 instruction are reverted to their previous states. After executing
6585 a piece of source code in reverse, all side effects of that code
6586 should be ``undone'', and all variables should be returned to their
6587 prior values@footnote{
6588 Note that some side effects are easier to undo than others. For instance,
6589 memory and registers are relatively easy, but device I/O is hard. Some
6590 targets may be able undo things like device I/O, and some may not.
6592 The contract between @value{GDBN} and the reverse executing target
6593 requires only that the target do something reasonable when
6594 @value{GDBN} tells it to execute backwards, and then report the
6595 results back to @value{GDBN}. Whatever the target reports back to
6596 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6597 assumes that the memory and registers that the target reports are in a
6598 consistant state, but @value{GDBN} accepts whatever it is given.
6601 If you are debugging in a target environment that supports
6602 reverse execution, @value{GDBN} provides the following commands.
6605 @kindex reverse-continue
6606 @kindex rc @r{(@code{reverse-continue})}
6607 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6608 @itemx rc @r{[}@var{ignore-count}@r{]}
6609 Beginning at the point where your program last stopped, start executing
6610 in reverse. Reverse execution will stop for breakpoints and synchronous
6611 exceptions (signals), just like normal execution. Behavior of
6612 asynchronous signals depends on the target environment.
6614 @kindex reverse-step
6615 @kindex rs @r{(@code{step})}
6616 @item reverse-step @r{[}@var{count}@r{]}
6617 Run the program backward until control reaches the start of a
6618 different source line; then stop it, and return control to @value{GDBN}.
6620 Like the @code{step} command, @code{reverse-step} will only stop
6621 at the beginning of a source line. It ``un-executes'' the previously
6622 executed source line. If the previous source line included calls to
6623 debuggable functions, @code{reverse-step} will step (backward) into
6624 the called function, stopping at the beginning of the @emph{last}
6625 statement in the called function (typically a return statement).
6627 Also, as with the @code{step} command, if non-debuggable functions are
6628 called, @code{reverse-step} will run thru them backward without stopping.
6630 @kindex reverse-stepi
6631 @kindex rsi @r{(@code{reverse-stepi})}
6632 @item reverse-stepi @r{[}@var{count}@r{]}
6633 Reverse-execute one machine instruction. Note that the instruction
6634 to be reverse-executed is @emph{not} the one pointed to by the program
6635 counter, but the instruction executed prior to that one. For instance,
6636 if the last instruction was a jump, @code{reverse-stepi} will take you
6637 back from the destination of the jump to the jump instruction itself.
6639 @kindex reverse-next
6640 @kindex rn @r{(@code{reverse-next})}
6641 @item reverse-next @r{[}@var{count}@r{]}
6642 Run backward to the beginning of the previous line executed in
6643 the current (innermost) stack frame. If the line contains function
6644 calls, they will be ``un-executed'' without stopping. Starting from
6645 the first line of a function, @code{reverse-next} will take you back
6646 to the caller of that function, @emph{before} the function was called,
6647 just as the normal @code{next} command would take you from the last
6648 line of a function back to its return to its caller
6649 @footnote{Unless the code is too heavily optimized.}.
6651 @kindex reverse-nexti
6652 @kindex rni @r{(@code{reverse-nexti})}
6653 @item reverse-nexti @r{[}@var{count}@r{]}
6654 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6655 in reverse, except that called functions are ``un-executed'' atomically.
6656 That is, if the previously executed instruction was a return from
6657 another function, @code{reverse-nexti} will continue to execute
6658 in reverse until the call to that function (from the current stack
6661 @kindex reverse-finish
6662 @item reverse-finish
6663 Just as the @code{finish} command takes you to the point where the
6664 current function returns, @code{reverse-finish} takes you to the point
6665 where it was called. Instead of ending up at the end of the current
6666 function invocation, you end up at the beginning.
6668 @kindex set exec-direction
6669 @item set exec-direction
6670 Set the direction of target execution.
6671 @item set exec-direction reverse
6672 @cindex execute forward or backward in time
6673 @value{GDBN} will perform all execution commands in reverse, until the
6674 exec-direction mode is changed to ``forward''. Affected commands include
6675 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6676 command cannot be used in reverse mode.
6677 @item set exec-direction forward
6678 @value{GDBN} will perform all execution commands in the normal fashion.
6679 This is the default.
6683 @node Process Record and Replay
6684 @chapter Recording Inferior's Execution and Replaying It
6685 @cindex process record and replay
6686 @cindex recording inferior's execution and replaying it
6688 On some platforms, @value{GDBN} provides a special @dfn{process record
6689 and replay} target that can record a log of the process execution, and
6690 replay it later with both forward and reverse execution commands.
6693 When this target is in use, if the execution log includes the record
6694 for the next instruction, @value{GDBN} will debug in @dfn{replay
6695 mode}. In the replay mode, the inferior does not really execute code
6696 instructions. Instead, all the events that normally happen during
6697 code execution are taken from the execution log. While code is not
6698 really executed in replay mode, the values of registers (including the
6699 program counter register) and the memory of the inferior are still
6700 changed as they normally would. Their contents are taken from the
6704 If the record for the next instruction is not in the execution log,
6705 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6706 inferior executes normally, and @value{GDBN} records the execution log
6709 The process record and replay target supports reverse execution
6710 (@pxref{Reverse Execution}), even if the platform on which the
6711 inferior runs does not. However, the reverse execution is limited in
6712 this case by the range of the instructions recorded in the execution
6713 log. In other words, reverse execution on platforms that don't
6714 support it directly can only be done in the replay mode.
6716 When debugging in the reverse direction, @value{GDBN} will work in
6717 replay mode as long as the execution log includes the record for the
6718 previous instruction; otherwise, it will work in record mode, if the
6719 platform supports reverse execution, or stop if not.
6721 For architecture environments that support process record and replay,
6722 @value{GDBN} provides the following commands:
6725 @kindex target record
6726 @kindex target record-full
6727 @kindex target record-btrace
6730 @kindex record btrace
6731 @kindex record btrace bts
6732 @kindex record btrace pt
6738 @kindex rec btrace bts
6739 @kindex rec btrace pt
6742 @item record @var{method}
6743 This command starts the process record and replay target. The
6744 recording method can be specified as parameter. Without a parameter
6745 the command uses the @code{full} recording method. The following
6746 recording methods are available:
6750 Full record/replay recording using @value{GDBN}'s software record and
6751 replay implementation. This method allows replaying and reverse
6754 @item btrace @var{format}
6755 Hardware-supported instruction recording. This method does not record
6756 data. Further, the data is collected in a ring buffer so old data will
6757 be overwritten when the buffer is full. It allows limited reverse
6758 execution. Variables and registers are not available during reverse
6759 execution. In remote debugging, recording continues on disconnect.
6760 Recorded data can be inspected after reconnecting. The recording may
6761 be stopped using @code{record stop}.
6763 The recording format can be specified as parameter. Without a parameter
6764 the command chooses the recording format. The following recording
6765 formats are available:
6769 @cindex branch trace store
6770 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6771 this format, the processor stores a from/to record for each executed
6772 branch in the btrace ring buffer.
6775 @cindex Intel Processor Trace
6776 Use the @dfn{Intel Processor Trace} recording format. In this
6777 format, the processor stores the execution trace in a compressed form
6778 that is afterwards decoded by @value{GDBN}.
6780 The trace can be recorded with very low overhead. The compressed
6781 trace format also allows small trace buffers to already contain a big
6782 number of instructions compared to @acronym{BTS}.
6784 Decoding the recorded execution trace, on the other hand, is more
6785 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6786 increased number of instructions to process. You should increase the
6787 buffer-size with care.
6790 Not all recording formats may be available on all processors.
6793 The process record and replay target can only debug a process that is
6794 already running. Therefore, you need first to start the process with
6795 the @kbd{run} or @kbd{start} commands, and then start the recording
6796 with the @kbd{record @var{method}} command.
6798 @cindex displaced stepping, and process record and replay
6799 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6800 will be automatically disabled when process record and replay target
6801 is started. That's because the process record and replay target
6802 doesn't support displaced stepping.
6804 @cindex non-stop mode, and process record and replay
6805 @cindex asynchronous execution, and process record and replay
6806 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6807 the asynchronous execution mode (@pxref{Background Execution}), not
6808 all recording methods are available. The @code{full} recording method
6809 does not support these two modes.
6814 Stop the process record and replay target. When process record and
6815 replay target stops, the entire execution log will be deleted and the
6816 inferior will either be terminated, or will remain in its final state.
6818 When you stop the process record and replay target in record mode (at
6819 the end of the execution log), the inferior will be stopped at the
6820 next instruction that would have been recorded. In other words, if
6821 you record for a while and then stop recording, the inferior process
6822 will be left in the same state as if the recording never happened.
6824 On the other hand, if the process record and replay target is stopped
6825 while in replay mode (that is, not at the end of the execution log,
6826 but at some earlier point), the inferior process will become ``live''
6827 at that earlier state, and it will then be possible to continue the
6828 usual ``live'' debugging of the process from that state.
6830 When the inferior process exits, or @value{GDBN} detaches from it,
6831 process record and replay target will automatically stop itself.
6835 Go to a specific location in the execution log. There are several
6836 ways to specify the location to go to:
6839 @item record goto begin
6840 @itemx record goto start
6841 Go to the beginning of the execution log.
6843 @item record goto end
6844 Go to the end of the execution log.
6846 @item record goto @var{n}
6847 Go to instruction number @var{n} in the execution log.
6851 @item record save @var{filename}
6852 Save the execution log to a file @file{@var{filename}}.
6853 Default filename is @file{gdb_record.@var{process_id}}, where
6854 @var{process_id} is the process ID of the inferior.
6856 This command may not be available for all recording methods.
6858 @kindex record restore
6859 @item record restore @var{filename}
6860 Restore the execution log from a file @file{@var{filename}}.
6861 File must have been created with @code{record save}.
6863 @kindex set record full
6864 @item set record full insn-number-max @var{limit}
6865 @itemx set record full insn-number-max unlimited
6866 Set the limit of instructions to be recorded for the @code{full}
6867 recording method. Default value is 200000.
6869 If @var{limit} is a positive number, then @value{GDBN} will start
6870 deleting instructions from the log once the number of the record
6871 instructions becomes greater than @var{limit}. For every new recorded
6872 instruction, @value{GDBN} will delete the earliest recorded
6873 instruction to keep the number of recorded instructions at the limit.
6874 (Since deleting recorded instructions loses information, @value{GDBN}
6875 lets you control what happens when the limit is reached, by means of
6876 the @code{stop-at-limit} option, described below.)
6878 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6879 delete recorded instructions from the execution log. The number of
6880 recorded instructions is limited only by the available memory.
6882 @kindex show record full
6883 @item show record full insn-number-max
6884 Show the limit of instructions to be recorded with the @code{full}
6887 @item set record full stop-at-limit
6888 Control the behavior of the @code{full} recording method when the
6889 number of recorded instructions reaches the limit. If ON (the
6890 default), @value{GDBN} will stop when the limit is reached for the
6891 first time and ask you whether you want to stop the inferior or
6892 continue running it and recording the execution log. If you decide
6893 to continue recording, each new recorded instruction will cause the
6894 oldest one to be deleted.
6896 If this option is OFF, @value{GDBN} will automatically delete the
6897 oldest record to make room for each new one, without asking.
6899 @item show record full stop-at-limit
6900 Show the current setting of @code{stop-at-limit}.
6902 @item set record full memory-query
6903 Control the behavior when @value{GDBN} is unable to record memory
6904 changes caused by an instruction for the @code{full} recording method.
6905 If ON, @value{GDBN} will query whether to stop the inferior in that
6908 If this option is OFF (the default), @value{GDBN} will automatically
6909 ignore the effect of such instructions on memory. Later, when
6910 @value{GDBN} replays this execution log, it will mark the log of this
6911 instruction as not accessible, and it will not affect the replay
6914 @item show record full memory-query
6915 Show the current setting of @code{memory-query}.
6917 @kindex set record btrace
6918 The @code{btrace} record target does not trace data. As a
6919 convenience, when replaying, @value{GDBN} reads read-only memory off
6920 the live program directly, assuming that the addresses of the
6921 read-only areas don't change. This for example makes it possible to
6922 disassemble code while replaying, but not to print variables.
6923 In some cases, being able to inspect variables might be useful.
6924 You can use the following command for that:
6926 @item set record btrace replay-memory-access
6927 Control the behavior of the @code{btrace} recording method when
6928 accessing memory during replay. If @code{read-only} (the default),
6929 @value{GDBN} will only allow accesses to read-only memory.
6930 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6931 and to read-write memory. Beware that the accessed memory corresponds
6932 to the live target and not necessarily to the current replay
6935 @kindex show record btrace
6936 @item show record btrace replay-memory-access
6937 Show the current setting of @code{replay-memory-access}.
6939 @kindex set record btrace bts
6940 @item set record btrace bts buffer-size @var{size}
6941 @itemx set record btrace bts buffer-size unlimited
6942 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6943 format. Default is 64KB.
6945 If @var{size} is a positive number, then @value{GDBN} will try to
6946 allocate a buffer of at least @var{size} bytes for each new thread
6947 that uses the btrace recording method and the @acronym{BTS} format.
6948 The actually obtained buffer size may differ from the requested
6949 @var{size}. Use the @code{info record} command to see the actual
6950 buffer size for each thread that uses the btrace recording method and
6951 the @acronym{BTS} format.
6953 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6954 allocate a buffer of 4MB.
6956 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6957 also need longer to process the branch trace data before it can be used.
6959 @item show record btrace bts buffer-size @var{size}
6960 Show the current setting of the requested ring buffer size for branch
6961 tracing in @acronym{BTS} format.
6963 @kindex set record btrace pt
6964 @item set record btrace pt buffer-size @var{size}
6965 @itemx set record btrace pt buffer-size unlimited
6966 Set the requested ring buffer size for branch tracing in Intel
6967 Processor Trace format. Default is 16KB.
6969 If @var{size} is a positive number, then @value{GDBN} will try to
6970 allocate a buffer of at least @var{size} bytes for each new thread
6971 that uses the btrace recording method and the Intel Processor Trace
6972 format. The actually obtained buffer size may differ from the
6973 requested @var{size}. Use the @code{info record} command to see the
6974 actual buffer size for each thread.
6976 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6977 allocate a buffer of 4MB.
6979 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6980 also need longer to process the branch trace data before it can be used.
6982 @item show record btrace pt buffer-size @var{size}
6983 Show the current setting of the requested ring buffer size for branch
6984 tracing in Intel Processor Trace format.
6988 Show various statistics about the recording depending on the recording
6993 For the @code{full} recording method, it shows the state of process
6994 record and its in-memory execution log buffer, including:
6998 Whether in record mode or replay mode.
7000 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
7002 Highest recorded instruction number.
7004 Current instruction about to be replayed (if in replay mode).
7006 Number of instructions contained in the execution log.
7008 Maximum number of instructions that may be contained in the execution log.
7012 For the @code{btrace} recording method, it shows:
7018 Number of instructions that have been recorded.
7020 Number of blocks of sequential control-flow formed by the recorded
7023 Whether in record mode or replay mode.
7026 For the @code{bts} recording format, it also shows:
7029 Size of the perf ring buffer.
7032 For the @code{pt} recording format, it also shows:
7035 Size of the perf ring buffer.
7039 @kindex record delete
7042 When record target runs in replay mode (``in the past''), delete the
7043 subsequent execution log and begin to record a new execution log starting
7044 from the current address. This means you will abandon the previously
7045 recorded ``future'' and begin recording a new ``future''.
7047 @kindex record instruction-history
7048 @kindex rec instruction-history
7049 @item record instruction-history
7050 Disassembles instructions from the recorded execution log. By
7051 default, ten instructions are disassembled. This can be changed using
7052 the @code{set record instruction-history-size} command. Instructions
7053 are printed in execution order.
7055 It can also print mixed source+disassembly if you specify the the
7056 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
7057 as well as in symbolic form by specifying the @code{/r} modifier.
7059 The current position marker is printed for the instruction at the
7060 current program counter value. This instruction can appear multiple
7061 times in the trace and the current position marker will be printed
7062 every time. To omit the current position marker, specify the
7065 To better align the printed instructions when the trace contains
7066 instructions from more than one function, the function name may be
7067 omitted by specifying the @code{/f} modifier.
7069 Speculatively executed instructions are prefixed with @samp{?}. This
7070 feature is not available for all recording formats.
7072 There are several ways to specify what part of the execution log to
7076 @item record instruction-history @var{insn}
7077 Disassembles ten instructions starting from instruction number
7080 @item record instruction-history @var{insn}, +/-@var{n}
7081 Disassembles @var{n} instructions around instruction number
7082 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
7083 @var{n} instructions after instruction number @var{insn}. If
7084 @var{n} is preceded with @code{-}, disassembles @var{n}
7085 instructions before instruction number @var{insn}.
7087 @item record instruction-history
7088 Disassembles ten more instructions after the last disassembly.
7090 @item record instruction-history -
7091 Disassembles ten more instructions before the last disassembly.
7093 @item record instruction-history @var{begin}, @var{end}
7094 Disassembles instructions beginning with instruction number
7095 @var{begin} until instruction number @var{end}. The instruction
7096 number @var{end} is included.
7099 This command may not be available for all recording methods.
7102 @item set record instruction-history-size @var{size}
7103 @itemx set record instruction-history-size unlimited
7104 Define how many instructions to disassemble in the @code{record
7105 instruction-history} command. The default value is 10.
7106 A @var{size} of @code{unlimited} means unlimited instructions.
7109 @item show record instruction-history-size
7110 Show how many instructions to disassemble in the @code{record
7111 instruction-history} command.
7113 @kindex record function-call-history
7114 @kindex rec function-call-history
7115 @item record function-call-history
7116 Prints the execution history at function granularity. It prints one
7117 line for each sequence of instructions that belong to the same
7118 function giving the name of that function, the source lines
7119 for this instruction sequence (if the @code{/l} modifier is
7120 specified), and the instructions numbers that form the sequence (if
7121 the @code{/i} modifier is specified). The function names are indented
7122 to reflect the call stack depth if the @code{/c} modifier is
7123 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
7127 (@value{GDBP}) @b{list 1, 10}
7138 (@value{GDBP}) @b{record function-call-history /ilc}
7139 1 bar inst 1,4 at foo.c:6,8
7140 2 foo inst 5,10 at foo.c:2,3
7141 3 bar inst 11,13 at foo.c:9,10
7144 By default, ten lines are printed. This can be changed using the
7145 @code{set record function-call-history-size} command. Functions are
7146 printed in execution order. There are several ways to specify what
7150 @item record function-call-history @var{func}
7151 Prints ten functions starting from function number @var{func}.
7153 @item record function-call-history @var{func}, +/-@var{n}
7154 Prints @var{n} functions around function number @var{func}. If
7155 @var{n} is preceded with @code{+}, prints @var{n} functions after
7156 function number @var{func}. If @var{n} is preceded with @code{-},
7157 prints @var{n} functions before function number @var{func}.
7159 @item record function-call-history
7160 Prints ten more functions after the last ten-line print.
7162 @item record function-call-history -
7163 Prints ten more functions before the last ten-line print.
7165 @item record function-call-history @var{begin}, @var{end}
7166 Prints functions beginning with function number @var{begin} until
7167 function number @var{end}. The function number @var{end} is included.
7170 This command may not be available for all recording methods.
7172 @item set record function-call-history-size @var{size}
7173 @itemx set record function-call-history-size unlimited
7174 Define how many lines to print in the
7175 @code{record function-call-history} command. The default value is 10.
7176 A size of @code{unlimited} means unlimited lines.
7178 @item show record function-call-history-size
7179 Show how many lines to print in the
7180 @code{record function-call-history} command.
7185 @chapter Examining the Stack
7187 When your program has stopped, the first thing you need to know is where it
7188 stopped and how it got there.
7191 Each time your program performs a function call, information about the call
7193 That information includes the location of the call in your program,
7194 the arguments of the call,
7195 and the local variables of the function being called.
7196 The information is saved in a block of data called a @dfn{stack frame}.
7197 The stack frames are allocated in a region of memory called the @dfn{call
7200 When your program stops, the @value{GDBN} commands for examining the
7201 stack allow you to see all of this information.
7203 @cindex selected frame
7204 One of the stack frames is @dfn{selected} by @value{GDBN} and many
7205 @value{GDBN} commands refer implicitly to the selected frame. In
7206 particular, whenever you ask @value{GDBN} for the value of a variable in
7207 your program, the value is found in the selected frame. There are
7208 special @value{GDBN} commands to select whichever frame you are
7209 interested in. @xref{Selection, ,Selecting a Frame}.
7211 When your program stops, @value{GDBN} automatically selects the
7212 currently executing frame and describes it briefly, similar to the
7213 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
7216 * Frames:: Stack frames
7217 * Backtrace:: Backtraces
7218 * Selection:: Selecting a frame
7219 * Frame Info:: Information on a frame
7220 * Frame Filter Management:: Managing frame filters
7225 @section Stack Frames
7227 @cindex frame, definition
7229 The call stack is divided up into contiguous pieces called @dfn{stack
7230 frames}, or @dfn{frames} for short; each frame is the data associated
7231 with one call to one function. The frame contains the arguments given
7232 to the function, the function's local variables, and the address at
7233 which the function is executing.
7235 @cindex initial frame
7236 @cindex outermost frame
7237 @cindex innermost frame
7238 When your program is started, the stack has only one frame, that of the
7239 function @code{main}. This is called the @dfn{initial} frame or the
7240 @dfn{outermost} frame. Each time a function is called, a new frame is
7241 made. Each time a function returns, the frame for that function invocation
7242 is eliminated. If a function is recursive, there can be many frames for
7243 the same function. The frame for the function in which execution is
7244 actually occurring is called the @dfn{innermost} frame. This is the most
7245 recently created of all the stack frames that still exist.
7247 @cindex frame pointer
7248 Inside your program, stack frames are identified by their addresses. A
7249 stack frame consists of many bytes, each of which has its own address; each
7250 kind of computer has a convention for choosing one byte whose
7251 address serves as the address of the frame. Usually this address is kept
7252 in a register called the @dfn{frame pointer register}
7253 (@pxref{Registers, $fp}) while execution is going on in that frame.
7255 @cindex frame number
7256 @value{GDBN} assigns numbers to all existing stack frames, starting with
7257 zero for the innermost frame, one for the frame that called it,
7258 and so on upward. These numbers do not really exist in your program;
7259 they are assigned by @value{GDBN} to give you a way of designating stack
7260 frames in @value{GDBN} commands.
7262 @c The -fomit-frame-pointer below perennially causes hbox overflow
7263 @c underflow problems.
7264 @cindex frameless execution
7265 Some compilers provide a way to compile functions so that they operate
7266 without stack frames. (For example, the @value{NGCC} option
7268 @samp{-fomit-frame-pointer}
7270 generates functions without a frame.)
7271 This is occasionally done with heavily used library functions to save
7272 the frame setup time. @value{GDBN} has limited facilities for dealing
7273 with these function invocations. If the innermost function invocation
7274 has no stack frame, @value{GDBN} nevertheless regards it as though
7275 it had a separate frame, which is numbered zero as usual, allowing
7276 correct tracing of the function call chain. However, @value{GDBN} has
7277 no provision for frameless functions elsewhere in the stack.
7283 @cindex call stack traces
7284 A backtrace is a summary of how your program got where it is. It shows one
7285 line per frame, for many frames, starting with the currently executing
7286 frame (frame zero), followed by its caller (frame one), and on up the
7289 @anchor{backtrace-command}
7292 @kindex bt @r{(@code{backtrace})}
7295 Print a backtrace of the entire stack: one line per frame for all
7296 frames in the stack.
7298 You can stop the backtrace at any time by typing the system interrupt
7299 character, normally @kbd{Ctrl-c}.
7301 @item backtrace @var{n}
7303 Similar, but print only the innermost @var{n} frames.
7305 @item backtrace -@var{n}
7307 Similar, but print only the outermost @var{n} frames.
7309 @item backtrace full
7311 @itemx bt full @var{n}
7312 @itemx bt full -@var{n}
7313 Print the values of the local variables also. As described above,
7314 @var{n} specifies the number of frames to print.
7316 @item backtrace no-filters
7317 @itemx bt no-filters
7318 @itemx bt no-filters @var{n}
7319 @itemx bt no-filters -@var{n}
7320 @itemx bt no-filters full
7321 @itemx bt no-filters full @var{n}
7322 @itemx bt no-filters full -@var{n}
7323 Do not run Python frame filters on this backtrace. @xref{Frame
7324 Filter API}, for more information. Additionally use @ref{disable
7325 frame-filter all} to turn off all frame filters. This is only
7326 relevant when @value{GDBN} has been configured with @code{Python}
7332 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7333 are additional aliases for @code{backtrace}.
7335 @cindex multiple threads, backtrace
7336 In a multi-threaded program, @value{GDBN} by default shows the
7337 backtrace only for the current thread. To display the backtrace for
7338 several or all of the threads, use the command @code{thread apply}
7339 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7340 apply all backtrace}, @value{GDBN} will display the backtrace for all
7341 the threads; this is handy when you debug a core dump of a
7342 multi-threaded program.
7344 Each line in the backtrace shows the frame number and the function name.
7345 The program counter value is also shown---unless you use @code{set
7346 print address off}. The backtrace also shows the source file name and
7347 line number, as well as the arguments to the function. The program
7348 counter value is omitted if it is at the beginning of the code for that
7351 Here is an example of a backtrace. It was made with the command
7352 @samp{bt 3}, so it shows the innermost three frames.
7356 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7358 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7359 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7361 (More stack frames follow...)
7366 The display for frame zero does not begin with a program counter
7367 value, indicating that your program has stopped at the beginning of the
7368 code for line @code{993} of @code{builtin.c}.
7371 The value of parameter @code{data} in frame 1 has been replaced by
7372 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7373 only if it is a scalar (integer, pointer, enumeration, etc). See command
7374 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7375 on how to configure the way function parameter values are printed.
7377 @cindex optimized out, in backtrace
7378 @cindex function call arguments, optimized out
7379 If your program was compiled with optimizations, some compilers will
7380 optimize away arguments passed to functions if those arguments are
7381 never used after the call. Such optimizations generate code that
7382 passes arguments through registers, but doesn't store those arguments
7383 in the stack frame. @value{GDBN} has no way of displaying such
7384 arguments in stack frames other than the innermost one. Here's what
7385 such a backtrace might look like:
7389 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7391 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7392 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7394 (More stack frames follow...)
7399 The values of arguments that were not saved in their stack frames are
7400 shown as @samp{<optimized out>}.
7402 If you need to display the values of such optimized-out arguments,
7403 either deduce that from other variables whose values depend on the one
7404 you are interested in, or recompile without optimizations.
7406 @cindex backtrace beyond @code{main} function
7407 @cindex program entry point
7408 @cindex startup code, and backtrace
7409 Most programs have a standard user entry point---a place where system
7410 libraries and startup code transition into user code. For C this is
7411 @code{main}@footnote{
7412 Note that embedded programs (the so-called ``free-standing''
7413 environment) are not required to have a @code{main} function as the
7414 entry point. They could even have multiple entry points.}.
7415 When @value{GDBN} finds the entry function in a backtrace
7416 it will terminate the backtrace, to avoid tracing into highly
7417 system-specific (and generally uninteresting) code.
7419 If you need to examine the startup code, or limit the number of levels
7420 in a backtrace, you can change this behavior:
7423 @item set backtrace past-main
7424 @itemx set backtrace past-main on
7425 @kindex set backtrace
7426 Backtraces will continue past the user entry point.
7428 @item set backtrace past-main off
7429 Backtraces will stop when they encounter the user entry point. This is the
7432 @item show backtrace past-main
7433 @kindex show backtrace
7434 Display the current user entry point backtrace policy.
7436 @item set backtrace past-entry
7437 @itemx set backtrace past-entry on
7438 Backtraces will continue past the internal entry point of an application.
7439 This entry point is encoded by the linker when the application is built,
7440 and is likely before the user entry point @code{main} (or equivalent) is called.
7442 @item set backtrace past-entry off
7443 Backtraces will stop when they encounter the internal entry point of an
7444 application. This is the default.
7446 @item show backtrace past-entry
7447 Display the current internal entry point backtrace policy.
7449 @item set backtrace limit @var{n}
7450 @itemx set backtrace limit 0
7451 @itemx set backtrace limit unlimited
7452 @cindex backtrace limit
7453 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7454 or zero means unlimited levels.
7456 @item show backtrace limit
7457 Display the current limit on backtrace levels.
7460 You can control how file names are displayed.
7463 @item set filename-display
7464 @itemx set filename-display relative
7465 @cindex filename-display
7466 Display file names relative to the compilation directory. This is the default.
7468 @item set filename-display basename
7469 Display only basename of a filename.
7471 @item set filename-display absolute
7472 Display an absolute filename.
7474 @item show filename-display
7475 Show the current way to display filenames.
7479 @section Selecting a Frame
7481 Most commands for examining the stack and other data in your program work on
7482 whichever stack frame is selected at the moment. Here are the commands for
7483 selecting a stack frame; all of them finish by printing a brief description
7484 of the stack frame just selected.
7487 @kindex frame@r{, selecting}
7488 @kindex f @r{(@code{frame})}
7491 Select frame number @var{n}. Recall that frame zero is the innermost
7492 (currently executing) frame, frame one is the frame that called the
7493 innermost one, and so on. The highest-numbered frame is the one for
7496 @item frame @var{stack-addr} [ @var{pc-addr} ]
7497 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7498 Select the frame at address @var{stack-addr}. This is useful mainly if the
7499 chaining of stack frames has been damaged by a bug, making it
7500 impossible for @value{GDBN} to assign numbers properly to all frames. In
7501 addition, this can be useful when your program has multiple stacks and
7502 switches between them. The optional @var{pc-addr} can also be given to
7503 specify the value of PC for the stack frame.
7507 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7508 numbers @var{n}, this advances toward the outermost frame, to higher
7509 frame numbers, to frames that have existed longer.
7512 @kindex do @r{(@code{down})}
7514 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7515 positive numbers @var{n}, this advances toward the innermost frame, to
7516 lower frame numbers, to frames that were created more recently.
7517 You may abbreviate @code{down} as @code{do}.
7520 All of these commands end by printing two lines of output describing the
7521 frame. The first line shows the frame number, the function name, the
7522 arguments, and the source file and line number of execution in that
7523 frame. The second line shows the text of that source line.
7531 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7533 10 read_input_file (argv[i]);
7537 After such a printout, the @code{list} command with no arguments
7538 prints ten lines centered on the point of execution in the frame.
7539 You can also edit the program at the point of execution with your favorite
7540 editing program by typing @code{edit}.
7541 @xref{List, ,Printing Source Lines},
7545 @kindex select-frame
7547 The @code{select-frame} command is a variant of @code{frame} that does
7548 not display the new frame after selecting it. This command is
7549 intended primarily for use in @value{GDBN} command scripts, where the
7550 output might be unnecessary and distracting.
7552 @kindex down-silently
7554 @item up-silently @var{n}
7555 @itemx down-silently @var{n}
7556 These two commands are variants of @code{up} and @code{down},
7557 respectively; they differ in that they do their work silently, without
7558 causing display of the new frame. They are intended primarily for use
7559 in @value{GDBN} command scripts, where the output might be unnecessary and
7564 @section Information About a Frame
7566 There are several other commands to print information about the selected
7572 When used without any argument, this command does not change which
7573 frame is selected, but prints a brief description of the currently
7574 selected stack frame. It can be abbreviated @code{f}. With an
7575 argument, this command is used to select a stack frame.
7576 @xref{Selection, ,Selecting a Frame}.
7579 @kindex info f @r{(@code{info frame})}
7582 This command prints a verbose description of the selected stack frame,
7587 the address of the frame
7589 the address of the next frame down (called by this frame)
7591 the address of the next frame up (caller of this frame)
7593 the language in which the source code corresponding to this frame is written
7595 the address of the frame's arguments
7597 the address of the frame's local variables
7599 the program counter saved in it (the address of execution in the caller frame)
7601 which registers were saved in the frame
7604 @noindent The verbose description is useful when
7605 something has gone wrong that has made the stack format fail to fit
7606 the usual conventions.
7608 @item info frame @var{addr}
7609 @itemx info f @var{addr}
7610 Print a verbose description of the frame at address @var{addr}, without
7611 selecting that frame. The selected frame remains unchanged by this
7612 command. This requires the same kind of address (more than one for some
7613 architectures) that you specify in the @code{frame} command.
7614 @xref{Selection, ,Selecting a Frame}.
7618 Print the arguments of the selected frame, each on a separate line.
7622 Print the local variables of the selected frame, each on a separate
7623 line. These are all variables (declared either static or automatic)
7624 accessible at the point of execution of the selected frame.
7628 @node Frame Filter Management
7629 @section Management of Frame Filters.
7630 @cindex managing frame filters
7632 Frame filters are Python based utilities to manage and decorate the
7633 output of frames. @xref{Frame Filter API}, for further information.
7635 Managing frame filters is performed by several commands available
7636 within @value{GDBN}, detailed here.
7639 @kindex info frame-filter
7640 @item info frame-filter
7641 Print a list of installed frame filters from all dictionaries, showing
7642 their name, priority and enabled status.
7644 @kindex disable frame-filter
7645 @anchor{disable frame-filter all}
7646 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7647 Disable a frame filter in the dictionary matching
7648 @var{filter-dictionary} and @var{filter-name}. The
7649 @var{filter-dictionary} may be @code{all}, @code{global},
7650 @code{progspace}, or the name of the object file where the frame filter
7651 dictionary resides. When @code{all} is specified, all frame filters
7652 across all dictionaries are disabled. The @var{filter-name} is the name
7653 of the frame filter and is used when @code{all} is not the option for
7654 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7655 may be enabled again later.
7657 @kindex enable frame-filter
7658 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7659 Enable a frame filter in the dictionary matching
7660 @var{filter-dictionary} and @var{filter-name}. The
7661 @var{filter-dictionary} may be @code{all}, @code{global},
7662 @code{progspace} or the name of the object file where the frame filter
7663 dictionary resides. When @code{all} is specified, all frame filters across
7664 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7665 filter and is used when @code{all} is not the option for
7666 @var{filter-dictionary}.
7671 (gdb) info frame-filter
7673 global frame-filters:
7674 Priority Enabled Name
7675 1000 No PrimaryFunctionFilter
7678 progspace /build/test frame-filters:
7679 Priority Enabled Name
7680 100 Yes ProgspaceFilter
7682 objfile /build/test frame-filters:
7683 Priority Enabled Name
7684 999 Yes BuildProgra Filter
7686 (gdb) disable frame-filter /build/test BuildProgramFilter
7687 (gdb) info frame-filter
7689 global frame-filters:
7690 Priority Enabled Name
7691 1000 No PrimaryFunctionFilter
7694 progspace /build/test frame-filters:
7695 Priority Enabled Name
7696 100 Yes ProgspaceFilter
7698 objfile /build/test frame-filters:
7699 Priority Enabled Name
7700 999 No BuildProgramFilter
7702 (gdb) enable frame-filter global PrimaryFunctionFilter
7703 (gdb) info frame-filter
7705 global frame-filters:
7706 Priority Enabled Name
7707 1000 Yes PrimaryFunctionFilter
7710 progspace /build/test frame-filters:
7711 Priority Enabled Name
7712 100 Yes ProgspaceFilter
7714 objfile /build/test frame-filters:
7715 Priority Enabled Name
7716 999 No BuildProgramFilter
7719 @kindex set frame-filter priority
7720 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7721 Set the @var{priority} of a frame filter in the dictionary matching
7722 @var{filter-dictionary}, and the frame filter name matching
7723 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7724 @code{progspace} or the name of the object file where the frame filter
7725 dictionary resides. The @var{priority} is an integer.
7727 @kindex show frame-filter priority
7728 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7729 Show the @var{priority} of a frame filter in the dictionary matching
7730 @var{filter-dictionary}, and the frame filter name matching
7731 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7732 @code{progspace} or the name of the object file where the frame filter
7738 (gdb) info frame-filter
7740 global frame-filters:
7741 Priority Enabled Name
7742 1000 Yes PrimaryFunctionFilter
7745 progspace /build/test frame-filters:
7746 Priority Enabled Name
7747 100 Yes ProgspaceFilter
7749 objfile /build/test frame-filters:
7750 Priority Enabled Name
7751 999 No BuildProgramFilter
7753 (gdb) set frame-filter priority global Reverse 50
7754 (gdb) info frame-filter
7756 global frame-filters:
7757 Priority Enabled Name
7758 1000 Yes PrimaryFunctionFilter
7761 progspace /build/test frame-filters:
7762 Priority Enabled Name
7763 100 Yes ProgspaceFilter
7765 objfile /build/test frame-filters:
7766 Priority Enabled Name
7767 999 No BuildProgramFilter
7772 @chapter Examining Source Files
7774 @value{GDBN} can print parts of your program's source, since the debugging
7775 information recorded in the program tells @value{GDBN} what source files were
7776 used to build it. When your program stops, @value{GDBN} spontaneously prints
7777 the line where it stopped. Likewise, when you select a stack frame
7778 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7779 execution in that frame has stopped. You can print other portions of
7780 source files by explicit command.
7782 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7783 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7784 @value{GDBN} under @sc{gnu} Emacs}.
7787 * List:: Printing source lines
7788 * Specify Location:: How to specify code locations
7789 * Edit:: Editing source files
7790 * Search:: Searching source files
7791 * Source Path:: Specifying source directories
7792 * Machine Code:: Source and machine code
7796 @section Printing Source Lines
7799 @kindex l @r{(@code{list})}
7800 To print lines from a source file, use the @code{list} command
7801 (abbreviated @code{l}). By default, ten lines are printed.
7802 There are several ways to specify what part of the file you want to
7803 print; see @ref{Specify Location}, for the full list.
7805 Here are the forms of the @code{list} command most commonly used:
7808 @item list @var{linenum}
7809 Print lines centered around line number @var{linenum} in the
7810 current source file.
7812 @item list @var{function}
7813 Print lines centered around the beginning of function
7817 Print more lines. If the last lines printed were printed with a
7818 @code{list} command, this prints lines following the last lines
7819 printed; however, if the last line printed was a solitary line printed
7820 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7821 Stack}), this prints lines centered around that line.
7824 Print lines just before the lines last printed.
7827 @cindex @code{list}, how many lines to display
7828 By default, @value{GDBN} prints ten source lines with any of these forms of
7829 the @code{list} command. You can change this using @code{set listsize}:
7832 @kindex set listsize
7833 @item set listsize @var{count}
7834 @itemx set listsize unlimited
7835 Make the @code{list} command display @var{count} source lines (unless
7836 the @code{list} argument explicitly specifies some other number).
7837 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7839 @kindex show listsize
7841 Display the number of lines that @code{list} prints.
7844 Repeating a @code{list} command with @key{RET} discards the argument,
7845 so it is equivalent to typing just @code{list}. This is more useful
7846 than listing the same lines again. An exception is made for an
7847 argument of @samp{-}; that argument is preserved in repetition so that
7848 each repetition moves up in the source file.
7850 In general, the @code{list} command expects you to supply zero, one or two
7851 @dfn{locations}. Locations specify source lines; there are several ways
7852 of writing them (@pxref{Specify Location}), but the effect is always
7853 to specify some source line.
7855 Here is a complete description of the possible arguments for @code{list}:
7858 @item list @var{location}
7859 Print lines centered around the line specified by @var{location}.
7861 @item list @var{first},@var{last}
7862 Print lines from @var{first} to @var{last}. Both arguments are
7863 locations. When a @code{list} command has two locations, and the
7864 source file of the second location is omitted, this refers to
7865 the same source file as the first location.
7867 @item list ,@var{last}
7868 Print lines ending with @var{last}.
7870 @item list @var{first},
7871 Print lines starting with @var{first}.
7874 Print lines just after the lines last printed.
7877 Print lines just before the lines last printed.
7880 As described in the preceding table.
7883 @node Specify Location
7884 @section Specifying a Location
7885 @cindex specifying location
7887 @cindex source location
7890 * Linespec Locations:: Linespec locations
7891 * Explicit Locations:: Explicit locations
7892 * Address Locations:: Address locations
7895 Several @value{GDBN} commands accept arguments that specify a location
7896 of your program's code. Since @value{GDBN} is a source-level
7897 debugger, a location usually specifies some line in the source code.
7898 Locations may be specified using three different formats:
7899 linespec locations, explicit locations, or address locations.
7901 @node Linespec Locations
7902 @subsection Linespec Locations
7903 @cindex linespec locations
7905 A @dfn{linespec} is a colon-separated list of source location parameters such
7906 as file name, function name, etc. Here are all the different ways of
7907 specifying a linespec:
7911 Specifies the line number @var{linenum} of the current source file.
7914 @itemx +@var{offset}
7915 Specifies the line @var{offset} lines before or after the @dfn{current
7916 line}. For the @code{list} command, the current line is the last one
7917 printed; for the breakpoint commands, this is the line at which
7918 execution stopped in the currently selected @dfn{stack frame}
7919 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7920 used as the second of the two linespecs in a @code{list} command,
7921 this specifies the line @var{offset} lines up or down from the first
7924 @item @var{filename}:@var{linenum}
7925 Specifies the line @var{linenum} in the source file @var{filename}.
7926 If @var{filename} is a relative file name, then it will match any
7927 source file name with the same trailing components. For example, if
7928 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7929 name of @file{/build/trunk/gcc/expr.c}, but not
7930 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7932 @item @var{function}
7933 Specifies the line that begins the body of the function @var{function}.
7934 For example, in C, this is the line with the open brace.
7936 By default, in C@t{++} and Ada, @var{function} is interpreted as
7937 specifying all functions named @var{function} in all scopes. For
7938 C@t{++}, this means in all namespaces and classes. For Ada, this
7939 means in all packages.
7941 For example, assuming a program with C@t{++} symbols named
7942 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
7943 func}} and @w{@kbd{break B::func}} set a breakpoint on both symbols.
7945 Commands that accept a linespec let you override this with the
7946 @code{-qualified} option. For example, @w{@kbd{break -qualified
7947 func}} sets a breakpoint on a free-function named @code{func} ignoring
7948 any C@t{++} class methods and namespace functions called @code{func}.
7950 @xref{Explicit Locations}.
7952 @item @var{function}:@var{label}
7953 Specifies the line where @var{label} appears in @var{function}.
7955 @item @var{filename}:@var{function}
7956 Specifies the line that begins the body of the function @var{function}
7957 in the file @var{filename}. You only need the file name with a
7958 function name to avoid ambiguity when there are identically named
7959 functions in different source files.
7962 Specifies the line at which the label named @var{label} appears
7963 in the function corresponding to the currently selected stack frame.
7964 If there is no current selected stack frame (for instance, if the inferior
7965 is not running), then @value{GDBN} will not search for a label.
7967 @cindex breakpoint at static probe point
7968 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7969 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7970 applications to embed static probes. @xref{Static Probe Points}, for more
7971 information on finding and using static probes. This form of linespec
7972 specifies the location of such a static probe.
7974 If @var{objfile} is given, only probes coming from that shared library
7975 or executable matching @var{objfile} as a regular expression are considered.
7976 If @var{provider} is given, then only probes from that provider are considered.
7977 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7978 each one of those probes.
7981 @node Explicit Locations
7982 @subsection Explicit Locations
7983 @cindex explicit locations
7985 @dfn{Explicit locations} allow the user to directly specify the source
7986 location's parameters using option-value pairs.
7988 Explicit locations are useful when several functions, labels, or
7989 file names have the same name (base name for files) in the program's
7990 sources. In these cases, explicit locations point to the source
7991 line you meant more accurately and unambiguously. Also, using
7992 explicit locations might be faster in large programs.
7994 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7995 defined in the file named @file{foo} or the label @code{bar} in a function
7996 named @code{foo}. @value{GDBN} must search either the file system or
7997 the symbol table to know.
7999 The list of valid explicit location options is summarized in the
8003 @item -source @var{filename}
8004 The value specifies the source file name. To differentiate between
8005 files with the same base name, prepend as many directories as is necessary
8006 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
8007 @value{GDBN} will use the first file it finds with the given base
8008 name. This option requires the use of either @code{-function} or @code{-line}.
8010 @item -function @var{function}
8011 The value specifies the name of a function. Operations
8012 on function locations unmodified by other options (such as @code{-label}
8013 or @code{-line}) refer to the line that begins the body of the function.
8014 In C, for example, this is the line with the open brace.
8016 By default, in C@t{++} and Ada, @var{function} is interpreted as
8017 specifying all functions named @var{function} in all scopes. For
8018 C@t{++}, this means in all namespaces and classes. For Ada, this
8019 means in all packages.
8021 For example, assuming a program with C@t{++} symbols named
8022 @code{A::B::func} and @code{B::func}, both commands @w{@kbd{break
8023 -function func}} and @w{@kbd{break -function B::func}} set a
8024 breakpoint on both symbols.
8026 You can use the @kbd{-qualified} flag to override this (see below).
8030 This flag makes @value{GDBN} interpret a function name specified with
8031 @kbd{-function} as a complete fully-qualified name.
8033 For example, assuming a C@t{++} program with symbols named
8034 @code{A::B::func} and @code{B::func}, the @w{@kbd{break -qualified
8035 -function B::func}} command sets a breakpoint on @code{B::func}, only.
8037 (Note: the @kbd{-qualified} option can precede a linespec as well
8038 (@pxref{Linespec Locations}), so the particular example above could be
8039 simplified as @w{@kbd{break -qualified B::func}}.)
8041 @item -label @var{label}
8042 The value specifies the name of a label. When the function
8043 name is not specified, the label is searched in the function of the currently
8044 selected stack frame.
8046 @item -line @var{number}
8047 The value specifies a line offset for the location. The offset may either
8048 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
8049 the command. When specified without any other options, the line offset is
8050 relative to the current line.
8053 Explicit location options may be abbreviated by omitting any non-unique
8054 trailing characters from the option name, e.g., @w{@kbd{break -s main.c -li 3}}.
8056 @node Address Locations
8057 @subsection Address Locations
8058 @cindex address locations
8060 @dfn{Address locations} indicate a specific program address. They have
8061 the generalized form *@var{address}.
8063 For line-oriented commands, such as @code{list} and @code{edit}, this
8064 specifies a source line that contains @var{address}. For @code{break} and
8065 other breakpoint-oriented commands, this can be used to set breakpoints in
8066 parts of your program which do not have debugging information or
8069 Here @var{address} may be any expression valid in the current working
8070 language (@pxref{Languages, working language}) that specifies a code
8071 address. In addition, as a convenience, @value{GDBN} extends the
8072 semantics of expressions used in locations to cover several situations
8073 that frequently occur during debugging. Here are the various forms
8077 @item @var{expression}
8078 Any expression valid in the current working language.
8080 @item @var{funcaddr}
8081 An address of a function or procedure derived from its name. In C,
8082 C@t{++}, Objective-C, Fortran, minimal, and assembly, this is
8083 simply the function's name @var{function} (and actually a special case
8084 of a valid expression). In Pascal and Modula-2, this is
8085 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
8086 (although the Pascal form also works).
8088 This form specifies the address of the function's first instruction,
8089 before the stack frame and arguments have been set up.
8091 @item '@var{filename}':@var{funcaddr}
8092 Like @var{funcaddr} above, but also specifies the name of the source
8093 file explicitly. This is useful if the name of the function does not
8094 specify the function unambiguously, e.g., if there are several
8095 functions with identical names in different source files.
8099 @section Editing Source Files
8100 @cindex editing source files
8103 @kindex e @r{(@code{edit})}
8104 To edit the lines in a source file, use the @code{edit} command.
8105 The editing program of your choice
8106 is invoked with the current line set to
8107 the active line in the program.
8108 Alternatively, there are several ways to specify what part of the file you
8109 want to print if you want to see other parts of the program:
8112 @item edit @var{location}
8113 Edit the source file specified by @code{location}. Editing starts at
8114 that @var{location}, e.g., at the specified source line of the
8115 specified file. @xref{Specify Location}, for all the possible forms
8116 of the @var{location} argument; here are the forms of the @code{edit}
8117 command most commonly used:
8120 @item edit @var{number}
8121 Edit the current source file with @var{number} as the active line number.
8123 @item edit @var{function}
8124 Edit the file containing @var{function} at the beginning of its definition.
8129 @subsection Choosing your Editor
8130 You can customize @value{GDBN} to use any editor you want
8132 The only restriction is that your editor (say @code{ex}), recognizes the
8133 following command-line syntax:
8135 ex +@var{number} file
8137 The optional numeric value +@var{number} specifies the number of the line in
8138 the file where to start editing.}.
8139 By default, it is @file{@value{EDITOR}}, but you can change this
8140 by setting the environment variable @code{EDITOR} before using
8141 @value{GDBN}. For example, to configure @value{GDBN} to use the
8142 @code{vi} editor, you could use these commands with the @code{sh} shell:
8148 or in the @code{csh} shell,
8150 setenv EDITOR /usr/bin/vi
8155 @section Searching Source Files
8156 @cindex searching source files
8158 There are two commands for searching through the current source file for a
8163 @kindex forward-search
8164 @kindex fo @r{(@code{forward-search})}
8165 @item forward-search @var{regexp}
8166 @itemx search @var{regexp}
8167 The command @samp{forward-search @var{regexp}} checks each line,
8168 starting with the one following the last line listed, for a match for
8169 @var{regexp}. It lists the line that is found. You can use the
8170 synonym @samp{search @var{regexp}} or abbreviate the command name as
8173 @kindex reverse-search
8174 @item reverse-search @var{regexp}
8175 The command @samp{reverse-search @var{regexp}} checks each line, starting
8176 with the one before the last line listed and going backward, for a match
8177 for @var{regexp}. It lists the line that is found. You can abbreviate
8178 this command as @code{rev}.
8182 @section Specifying Source Directories
8185 @cindex directories for source files
8186 Executable programs sometimes do not record the directories of the source
8187 files from which they were compiled, just the names. Even when they do,
8188 the directories could be moved between the compilation and your debugging
8189 session. @value{GDBN} has a list of directories to search for source files;
8190 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
8191 it tries all the directories in the list, in the order they are present
8192 in the list, until it finds a file with the desired name.
8194 For example, suppose an executable references the file
8195 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
8196 @file{/mnt/cross}. The file is first looked up literally; if this
8197 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
8198 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
8199 message is printed. @value{GDBN} does not look up the parts of the
8200 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
8201 Likewise, the subdirectories of the source path are not searched: if
8202 the source path is @file{/mnt/cross}, and the binary refers to
8203 @file{foo.c}, @value{GDBN} would not find it under
8204 @file{/mnt/cross/usr/src/foo-1.0/lib}.
8206 Plain file names, relative file names with leading directories, file
8207 names containing dots, etc.@: are all treated as described above; for
8208 instance, if the source path is @file{/mnt/cross}, and the source file
8209 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
8210 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
8211 that---@file{/mnt/cross/foo.c}.
8213 Note that the executable search path is @emph{not} used to locate the
8216 Whenever you reset or rearrange the source path, @value{GDBN} clears out
8217 any information it has cached about where source files are found and where
8218 each line is in the file.
8222 When you start @value{GDBN}, its source path includes only @samp{cdir}
8223 and @samp{cwd}, in that order.
8224 To add other directories, use the @code{directory} command.
8226 The search path is used to find both program source files and @value{GDBN}
8227 script files (read using the @samp{-command} option and @samp{source} command).
8229 In addition to the source path, @value{GDBN} provides a set of commands
8230 that manage a list of source path substitution rules. A @dfn{substitution
8231 rule} specifies how to rewrite source directories stored in the program's
8232 debug information in case the sources were moved to a different
8233 directory between compilation and debugging. A rule is made of
8234 two strings, the first specifying what needs to be rewritten in
8235 the path, and the second specifying how it should be rewritten.
8236 In @ref{set substitute-path}, we name these two parts @var{from} and
8237 @var{to} respectively. @value{GDBN} does a simple string replacement
8238 of @var{from} with @var{to} at the start of the directory part of the
8239 source file name, and uses that result instead of the original file
8240 name to look up the sources.
8242 Using the previous example, suppose the @file{foo-1.0} tree has been
8243 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
8244 @value{GDBN} to replace @file{/usr/src} in all source path names with
8245 @file{/mnt/cross}. The first lookup will then be
8246 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
8247 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
8248 substitution rule, use the @code{set substitute-path} command
8249 (@pxref{set substitute-path}).
8251 To avoid unexpected substitution results, a rule is applied only if the
8252 @var{from} part of the directory name ends at a directory separator.
8253 For instance, a rule substituting @file{/usr/source} into
8254 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
8255 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
8256 is applied only at the beginning of the directory name, this rule will
8257 not be applied to @file{/root/usr/source/baz.c} either.
8259 In many cases, you can achieve the same result using the @code{directory}
8260 command. However, @code{set substitute-path} can be more efficient in
8261 the case where the sources are organized in a complex tree with multiple
8262 subdirectories. With the @code{directory} command, you need to add each
8263 subdirectory of your project. If you moved the entire tree while
8264 preserving its internal organization, then @code{set substitute-path}
8265 allows you to direct the debugger to all the sources with one single
8268 @code{set substitute-path} is also more than just a shortcut command.
8269 The source path is only used if the file at the original location no
8270 longer exists. On the other hand, @code{set substitute-path} modifies
8271 the debugger behavior to look at the rewritten location instead. So, if
8272 for any reason a source file that is not relevant to your executable is
8273 located at the original location, a substitution rule is the only
8274 method available to point @value{GDBN} at the new location.
8276 @cindex @samp{--with-relocated-sources}
8277 @cindex default source path substitution
8278 You can configure a default source path substitution rule by
8279 configuring @value{GDBN} with the
8280 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
8281 should be the name of a directory under @value{GDBN}'s configured
8282 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
8283 directory names in debug information under @var{dir} will be adjusted
8284 automatically if the installed @value{GDBN} is moved to a new
8285 location. This is useful if @value{GDBN}, libraries or executables
8286 with debug information and corresponding source code are being moved
8290 @item directory @var{dirname} @dots{}
8291 @item dir @var{dirname} @dots{}
8292 Add directory @var{dirname} to the front of the source path. Several
8293 directory names may be given to this command, separated by @samp{:}
8294 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
8295 part of absolute file names) or
8296 whitespace. You may specify a directory that is already in the source
8297 path; this moves it forward, so @value{GDBN} searches it sooner.
8301 @vindex $cdir@r{, convenience variable}
8302 @vindex $cwd@r{, convenience variable}
8303 @cindex compilation directory
8304 @cindex current directory
8305 @cindex working directory
8306 @cindex directory, current
8307 @cindex directory, compilation
8308 You can use the string @samp{$cdir} to refer to the compilation
8309 directory (if one is recorded), and @samp{$cwd} to refer to the current
8310 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8311 tracks the current working directory as it changes during your @value{GDBN}
8312 session, while the latter is immediately expanded to the current
8313 directory at the time you add an entry to the source path.
8316 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8318 @c RET-repeat for @code{directory} is explicitly disabled, but since
8319 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8321 @item set directories @var{path-list}
8322 @kindex set directories
8323 Set the source path to @var{path-list}.
8324 @samp{$cdir:$cwd} are added if missing.
8326 @item show directories
8327 @kindex show directories
8328 Print the source path: show which directories it contains.
8330 @anchor{set substitute-path}
8331 @item set substitute-path @var{from} @var{to}
8332 @kindex set substitute-path
8333 Define a source path substitution rule, and add it at the end of the
8334 current list of existing substitution rules. If a rule with the same
8335 @var{from} was already defined, then the old rule is also deleted.
8337 For example, if the file @file{/foo/bar/baz.c} was moved to
8338 @file{/mnt/cross/baz.c}, then the command
8341 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8345 will tell @value{GDBN} to replace @samp{/foo/bar} with
8346 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8347 @file{baz.c} even though it was moved.
8349 In the case when more than one substitution rule have been defined,
8350 the rules are evaluated one by one in the order where they have been
8351 defined. The first one matching, if any, is selected to perform
8354 For instance, if we had entered the following commands:
8357 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8358 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8362 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8363 @file{/mnt/include/defs.h} by using the first rule. However, it would
8364 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8365 @file{/mnt/src/lib/foo.c}.
8368 @item unset substitute-path [path]
8369 @kindex unset substitute-path
8370 If a path is specified, search the current list of substitution rules
8371 for a rule that would rewrite that path. Delete that rule if found.
8372 A warning is emitted by the debugger if no rule could be found.
8374 If no path is specified, then all substitution rules are deleted.
8376 @item show substitute-path [path]
8377 @kindex show substitute-path
8378 If a path is specified, then print the source path substitution rule
8379 which would rewrite that path, if any.
8381 If no path is specified, then print all existing source path substitution
8386 If your source path is cluttered with directories that are no longer of
8387 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8388 versions of source. You can correct the situation as follows:
8392 Use @code{directory} with no argument to reset the source path to its default value.
8395 Use @code{directory} with suitable arguments to reinstall the
8396 directories you want in the source path. You can add all the
8397 directories in one command.
8401 @section Source and Machine Code
8402 @cindex source line and its code address
8404 You can use the command @code{info line} to map source lines to program
8405 addresses (and vice versa), and the command @code{disassemble} to display
8406 a range of addresses as machine instructions. You can use the command
8407 @code{set disassemble-next-line} to set whether to disassemble next
8408 source line when execution stops. When run under @sc{gnu} Emacs
8409 mode, the @code{info line} command causes the arrow to point to the
8410 line specified. Also, @code{info line} prints addresses in symbolic form as
8415 @item info line @var{location}
8416 Print the starting and ending addresses of the compiled code for
8417 source line @var{location}. You can specify source lines in any of
8418 the ways documented in @ref{Specify Location}.
8421 For example, we can use @code{info line} to discover the location of
8422 the object code for the first line of function
8423 @code{m4_changequote}:
8425 @c FIXME: I think this example should also show the addresses in
8426 @c symbolic form, as they usually would be displayed.
8428 (@value{GDBP}) info line m4_changequote
8429 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8433 @cindex code address and its source line
8434 We can also inquire (using @code{*@var{addr}} as the form for
8435 @var{location}) what source line covers a particular address:
8437 (@value{GDBP}) info line *0x63ff
8438 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8441 @cindex @code{$_} and @code{info line}
8442 @cindex @code{x} command, default address
8443 @kindex x@r{(examine), and} info line
8444 After @code{info line}, the default address for the @code{x} command
8445 is changed to the starting address of the line, so that @samp{x/i} is
8446 sufficient to begin examining the machine code (@pxref{Memory,
8447 ,Examining Memory}). Also, this address is saved as the value of the
8448 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8453 @cindex assembly instructions
8454 @cindex instructions, assembly
8455 @cindex machine instructions
8456 @cindex listing machine instructions
8458 @itemx disassemble /m
8459 @itemx disassemble /s
8460 @itemx disassemble /r
8461 This specialized command dumps a range of memory as machine
8462 instructions. It can also print mixed source+disassembly by specifying
8463 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8464 as well as in symbolic form by specifying the @code{/r} modifier.
8465 The default memory range is the function surrounding the
8466 program counter of the selected frame. A single argument to this
8467 command is a program counter value; @value{GDBN} dumps the function
8468 surrounding this value. When two arguments are given, they should
8469 be separated by a comma, possibly surrounded by whitespace. The
8470 arguments specify a range of addresses to dump, in one of two forms:
8473 @item @var{start},@var{end}
8474 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8475 @item @var{start},+@var{length}
8476 the addresses from @var{start} (inclusive) to
8477 @code{@var{start}+@var{length}} (exclusive).
8481 When 2 arguments are specified, the name of the function is also
8482 printed (since there could be several functions in the given range).
8484 The argument(s) can be any expression yielding a numeric value, such as
8485 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8487 If the range of memory being disassembled contains current program counter,
8488 the instruction at that location is shown with a @code{=>} marker.
8491 The following example shows the disassembly of a range of addresses of
8492 HP PA-RISC 2.0 code:
8495 (@value{GDBP}) disas 0x32c4, 0x32e4
8496 Dump of assembler code from 0x32c4 to 0x32e4:
8497 0x32c4 <main+204>: addil 0,dp
8498 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8499 0x32cc <main+212>: ldil 0x3000,r31
8500 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8501 0x32d4 <main+220>: ldo 0(r31),rp
8502 0x32d8 <main+224>: addil -0x800,dp
8503 0x32dc <main+228>: ldo 0x588(r1),r26
8504 0x32e0 <main+232>: ldil 0x3000,r31
8505 End of assembler dump.
8508 Here is an example showing mixed source+assembly for Intel x86
8509 with @code{/m} or @code{/s}, when the program is stopped just after
8510 function prologue in a non-optimized function with no inline code.
8513 (@value{GDBP}) disas /m main
8514 Dump of assembler code for function main:
8516 0x08048330 <+0>: push %ebp
8517 0x08048331 <+1>: mov %esp,%ebp
8518 0x08048333 <+3>: sub $0x8,%esp
8519 0x08048336 <+6>: and $0xfffffff0,%esp
8520 0x08048339 <+9>: sub $0x10,%esp
8522 6 printf ("Hello.\n");
8523 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8524 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8528 0x08048348 <+24>: mov $0x0,%eax
8529 0x0804834d <+29>: leave
8530 0x0804834e <+30>: ret
8532 End of assembler dump.
8535 The @code{/m} option is deprecated as its output is not useful when
8536 there is either inlined code or re-ordered code.
8537 The @code{/s} option is the preferred choice.
8538 Here is an example for AMD x86-64 showing the difference between
8539 @code{/m} output and @code{/s} output.
8540 This example has one inline function defined in a header file,
8541 and the code is compiled with @samp{-O2} optimization.
8542 Note how the @code{/m} output is missing the disassembly of
8543 several instructions that are present in the @code{/s} output.
8573 (@value{GDBP}) disas /m main
8574 Dump of assembler code for function main:
8578 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8579 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8583 0x000000000040041d <+29>: xor %eax,%eax
8584 0x000000000040041f <+31>: retq
8585 0x0000000000400420 <+32>: add %eax,%eax
8586 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8588 End of assembler dump.
8589 (@value{GDBP}) disas /s main
8590 Dump of assembler code for function main:
8594 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8598 0x0000000000400406 <+6>: test %eax,%eax
8599 0x0000000000400408 <+8>: js 0x400420 <main+32>
8604 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8605 0x000000000040040d <+13>: test %eax,%eax
8606 0x000000000040040f <+15>: mov $0x1,%eax
8607 0x0000000000400414 <+20>: cmovne %edx,%eax
8611 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8615 0x000000000040041d <+29>: xor %eax,%eax
8616 0x000000000040041f <+31>: retq
8620 0x0000000000400420 <+32>: add %eax,%eax
8621 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8622 End of assembler dump.
8625 Here is another example showing raw instructions in hex for AMD x86-64,
8628 (gdb) disas /r 0x400281,+10
8629 Dump of assembler code from 0x400281 to 0x40028b:
8630 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8631 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8632 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8633 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8634 End of assembler dump.
8637 Addresses cannot be specified as a location (@pxref{Specify Location}).
8638 So, for example, if you want to disassemble function @code{bar}
8639 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8640 and not @samp{disassemble foo.c:bar}.
8642 Some architectures have more than one commonly-used set of instruction
8643 mnemonics or other syntax.
8645 For programs that were dynamically linked and use shared libraries,
8646 instructions that call functions or branch to locations in the shared
8647 libraries might show a seemingly bogus location---it's actually a
8648 location of the relocation table. On some architectures, @value{GDBN}
8649 might be able to resolve these to actual function names.
8652 @kindex set disassembler-options
8653 @cindex disassembler options
8654 @item set disassembler-options @var{option1}[,@var{option2}@dots{}]
8655 This command controls the passing of target specific information to
8656 the disassembler. For a list of valid options, please refer to the
8657 @code{-M}/@code{--disassembler-options} section of the @samp{objdump}
8658 manual and/or the output of @kbd{objdump --help}
8659 (@pxref{objdump,,objdump,binutils.info,The GNU Binary Utilities}).
8660 The default value is the empty string.
8662 If it is necessary to specify more than one disassembler option, then
8663 multiple options can be placed together into a comma separated list.
8664 Currently this command is only supported on targets ARM, PowerPC
8667 @kindex show disassembler-options
8668 @item show disassembler-options
8669 Show the current setting of the disassembler options.
8673 @kindex set disassembly-flavor
8674 @cindex Intel disassembly flavor
8675 @cindex AT&T disassembly flavor
8676 @item set disassembly-flavor @var{instruction-set}
8677 Select the instruction set to use when disassembling the
8678 program via the @code{disassemble} or @code{x/i} commands.
8680 Currently this command is only defined for the Intel x86 family. You
8681 can set @var{instruction-set} to either @code{intel} or @code{att}.
8682 The default is @code{att}, the AT&T flavor used by default by Unix
8683 assemblers for x86-based targets.
8685 @kindex show disassembly-flavor
8686 @item show disassembly-flavor
8687 Show the current setting of the disassembly flavor.
8691 @kindex set disassemble-next-line
8692 @kindex show disassemble-next-line
8693 @item set disassemble-next-line
8694 @itemx show disassemble-next-line
8695 Control whether or not @value{GDBN} will disassemble the next source
8696 line or instruction when execution stops. If ON, @value{GDBN} will
8697 display disassembly of the next source line when execution of the
8698 program being debugged stops. This is @emph{in addition} to
8699 displaying the source line itself, which @value{GDBN} always does if
8700 possible. If the next source line cannot be displayed for some reason
8701 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8702 info in the debug info), @value{GDBN} will display disassembly of the
8703 next @emph{instruction} instead of showing the next source line. If
8704 AUTO, @value{GDBN} will display disassembly of next instruction only
8705 if the source line cannot be displayed. This setting causes
8706 @value{GDBN} to display some feedback when you step through a function
8707 with no line info or whose source file is unavailable. The default is
8708 OFF, which means never display the disassembly of the next line or
8714 @chapter Examining Data
8716 @cindex printing data
8717 @cindex examining data
8720 The usual way to examine data in your program is with the @code{print}
8721 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8722 evaluates and prints the value of an expression of the language your
8723 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8724 Different Languages}). It may also print the expression using a
8725 Python-based pretty-printer (@pxref{Pretty Printing}).
8728 @item print @var{expr}
8729 @itemx print /@var{f} @var{expr}
8730 @var{expr} is an expression (in the source language). By default the
8731 value of @var{expr} is printed in a format appropriate to its data type;
8732 you can choose a different format by specifying @samp{/@var{f}}, where
8733 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8737 @itemx print /@var{f}
8738 @cindex reprint the last value
8739 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8740 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8741 conveniently inspect the same value in an alternative format.
8744 A more low-level way of examining data is with the @code{x} command.
8745 It examines data in memory at a specified address and prints it in a
8746 specified format. @xref{Memory, ,Examining Memory}.
8748 If you are interested in information about types, or about how the
8749 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8750 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8753 @cindex exploring hierarchical data structures
8755 Another way of examining values of expressions and type information is
8756 through the Python extension command @code{explore} (available only if
8757 the @value{GDBN} build is configured with @code{--with-python}). It
8758 offers an interactive way to start at the highest level (or, the most
8759 abstract level) of the data type of an expression (or, the data type
8760 itself) and explore all the way down to leaf scalar values/fields
8761 embedded in the higher level data types.
8764 @item explore @var{arg}
8765 @var{arg} is either an expression (in the source language), or a type
8766 visible in the current context of the program being debugged.
8769 The working of the @code{explore} command can be illustrated with an
8770 example. If a data type @code{struct ComplexStruct} is defined in your
8780 struct ComplexStruct
8782 struct SimpleStruct *ss_p;
8788 followed by variable declarations as
8791 struct SimpleStruct ss = @{ 10, 1.11 @};
8792 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8796 then, the value of the variable @code{cs} can be explored using the
8797 @code{explore} command as follows.
8801 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8802 the following fields:
8804 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8805 arr = <Enter 1 to explore this field of type `int [10]'>
8807 Enter the field number of choice:
8811 Since the fields of @code{cs} are not scalar values, you are being
8812 prompted to chose the field you want to explore. Let's say you choose
8813 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8814 pointer, you will be asked if it is pointing to a single value. From
8815 the declaration of @code{cs} above, it is indeed pointing to a single
8816 value, hence you enter @code{y}. If you enter @code{n}, then you will
8817 be asked if it were pointing to an array of values, in which case this
8818 field will be explored as if it were an array.
8821 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8822 Continue exploring it as a pointer to a single value [y/n]: y
8823 The value of `*(cs.ss_p)' is a struct/class of type `struct
8824 SimpleStruct' with the following fields:
8826 i = 10 .. (Value of type `int')
8827 d = 1.1100000000000001 .. (Value of type `double')
8829 Press enter to return to parent value:
8833 If the field @code{arr} of @code{cs} was chosen for exploration by
8834 entering @code{1} earlier, then since it is as array, you will be
8835 prompted to enter the index of the element in the array that you want
8839 `cs.arr' is an array of `int'.
8840 Enter the index of the element you want to explore in `cs.arr': 5
8842 `(cs.arr)[5]' is a scalar value of type `int'.
8846 Press enter to return to parent value:
8849 In general, at any stage of exploration, you can go deeper towards the
8850 leaf values by responding to the prompts appropriately, or hit the
8851 return key to return to the enclosing data structure (the @i{higher}
8852 level data structure).
8854 Similar to exploring values, you can use the @code{explore} command to
8855 explore types. Instead of specifying a value (which is typically a
8856 variable name or an expression valid in the current context of the
8857 program being debugged), you specify a type name. If you consider the
8858 same example as above, your can explore the type
8859 @code{struct ComplexStruct} by passing the argument
8860 @code{struct ComplexStruct} to the @code{explore} command.
8863 (gdb) explore struct ComplexStruct
8867 By responding to the prompts appropriately in the subsequent interactive
8868 session, you can explore the type @code{struct ComplexStruct} in a
8869 manner similar to how the value @code{cs} was explored in the above
8872 The @code{explore} command also has two sub-commands,
8873 @code{explore value} and @code{explore type}. The former sub-command is
8874 a way to explicitly specify that value exploration of the argument is
8875 being invoked, while the latter is a way to explicitly specify that type
8876 exploration of the argument is being invoked.
8879 @item explore value @var{expr}
8880 @cindex explore value
8881 This sub-command of @code{explore} explores the value of the
8882 expression @var{expr} (if @var{expr} is an expression valid in the
8883 current context of the program being debugged). The behavior of this
8884 command is identical to that of the behavior of the @code{explore}
8885 command being passed the argument @var{expr}.
8887 @item explore type @var{arg}
8888 @cindex explore type
8889 This sub-command of @code{explore} explores the type of @var{arg} (if
8890 @var{arg} is a type visible in the current context of program being
8891 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8892 is an expression valid in the current context of the program being
8893 debugged). If @var{arg} is a type, then the behavior of this command is
8894 identical to that of the @code{explore} command being passed the
8895 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8896 this command will be identical to that of the @code{explore} command
8897 being passed the type of @var{arg} as the argument.
8901 * Expressions:: Expressions
8902 * Ambiguous Expressions:: Ambiguous Expressions
8903 * Variables:: Program variables
8904 * Arrays:: Artificial arrays
8905 * Output Formats:: Output formats
8906 * Memory:: Examining memory
8907 * Auto Display:: Automatic display
8908 * Print Settings:: Print settings
8909 * Pretty Printing:: Python pretty printing
8910 * Value History:: Value history
8911 * Convenience Vars:: Convenience variables
8912 * Convenience Funs:: Convenience functions
8913 * Registers:: Registers
8914 * Floating Point Hardware:: Floating point hardware
8915 * Vector Unit:: Vector Unit
8916 * OS Information:: Auxiliary data provided by operating system
8917 * Memory Region Attributes:: Memory region attributes
8918 * Dump/Restore Files:: Copy between memory and a file
8919 * Core File Generation:: Cause a program dump its core
8920 * Character Sets:: Debugging programs that use a different
8921 character set than GDB does
8922 * Caching Target Data:: Data caching for targets
8923 * Searching Memory:: Searching memory for a sequence of bytes
8924 * Value Sizes:: Managing memory allocated for values
8928 @section Expressions
8931 @code{print} and many other @value{GDBN} commands accept an expression and
8932 compute its value. Any kind of constant, variable or operator defined
8933 by the programming language you are using is valid in an expression in
8934 @value{GDBN}. This includes conditional expressions, function calls,
8935 casts, and string constants. It also includes preprocessor macros, if
8936 you compiled your program to include this information; see
8939 @cindex arrays in expressions
8940 @value{GDBN} supports array constants in expressions input by
8941 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8942 you can use the command @code{print @{1, 2, 3@}} to create an array
8943 of three integers. If you pass an array to a function or assign it
8944 to a program variable, @value{GDBN} copies the array to memory that
8945 is @code{malloc}ed in the target program.
8947 Because C is so widespread, most of the expressions shown in examples in
8948 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8949 Languages}, for information on how to use expressions in other
8952 In this section, we discuss operators that you can use in @value{GDBN}
8953 expressions regardless of your programming language.
8955 @cindex casts, in expressions
8956 Casts are supported in all languages, not just in C, because it is so
8957 useful to cast a number into a pointer in order to examine a structure
8958 at that address in memory.
8959 @c FIXME: casts supported---Mod2 true?
8961 @value{GDBN} supports these operators, in addition to those common
8962 to programming languages:
8966 @samp{@@} is a binary operator for treating parts of memory as arrays.
8967 @xref{Arrays, ,Artificial Arrays}, for more information.
8970 @samp{::} allows you to specify a variable in terms of the file or
8971 function where it is defined. @xref{Variables, ,Program Variables}.
8973 @cindex @{@var{type}@}
8974 @cindex type casting memory
8975 @cindex memory, viewing as typed object
8976 @cindex casts, to view memory
8977 @item @{@var{type}@} @var{addr}
8978 Refers to an object of type @var{type} stored at address @var{addr} in
8979 memory. The address @var{addr} may be any expression whose value is
8980 an integer or pointer (but parentheses are required around binary
8981 operators, just as in a cast). This construct is allowed regardless
8982 of what kind of data is normally supposed to reside at @var{addr}.
8985 @node Ambiguous Expressions
8986 @section Ambiguous Expressions
8987 @cindex ambiguous expressions
8989 Expressions can sometimes contain some ambiguous elements. For instance,
8990 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8991 a single function name to be defined several times, for application in
8992 different contexts. This is called @dfn{overloading}. Another example
8993 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8994 templates and is typically instantiated several times, resulting in
8995 the same function name being defined in different contexts.
8997 In some cases and depending on the language, it is possible to adjust
8998 the expression to remove the ambiguity. For instance in C@t{++}, you
8999 can specify the signature of the function you want to break on, as in
9000 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
9001 qualified name of your function often makes the expression unambiguous
9004 When an ambiguity that needs to be resolved is detected, the debugger
9005 has the capability to display a menu of numbered choices for each
9006 possibility, and then waits for the selection with the prompt @samp{>}.
9007 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
9008 aborts the current command. If the command in which the expression was
9009 used allows more than one choice to be selected, the next option in the
9010 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
9013 For example, the following session excerpt shows an attempt to set a
9014 breakpoint at the overloaded symbol @code{String::after}.
9015 We choose three particular definitions of that function name:
9017 @c FIXME! This is likely to change to show arg type lists, at least
9020 (@value{GDBP}) b String::after
9023 [2] file:String.cc; line number:867
9024 [3] file:String.cc; line number:860
9025 [4] file:String.cc; line number:875
9026 [5] file:String.cc; line number:853
9027 [6] file:String.cc; line number:846
9028 [7] file:String.cc; line number:735
9030 Breakpoint 1 at 0xb26c: file String.cc, line 867.
9031 Breakpoint 2 at 0xb344: file String.cc, line 875.
9032 Breakpoint 3 at 0xafcc: file String.cc, line 846.
9033 Multiple breakpoints were set.
9034 Use the "delete" command to delete unwanted
9041 @kindex set multiple-symbols
9042 @item set multiple-symbols @var{mode}
9043 @cindex multiple-symbols menu
9045 This option allows you to adjust the debugger behavior when an expression
9048 By default, @var{mode} is set to @code{all}. If the command with which
9049 the expression is used allows more than one choice, then @value{GDBN}
9050 automatically selects all possible choices. For instance, inserting
9051 a breakpoint on a function using an ambiguous name results in a breakpoint
9052 inserted on each possible match. However, if a unique choice must be made,
9053 then @value{GDBN} uses the menu to help you disambiguate the expression.
9054 For instance, printing the address of an overloaded function will result
9055 in the use of the menu.
9057 When @var{mode} is set to @code{ask}, the debugger always uses the menu
9058 when an ambiguity is detected.
9060 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
9061 an error due to the ambiguity and the command is aborted.
9063 @kindex show multiple-symbols
9064 @item show multiple-symbols
9065 Show the current value of the @code{multiple-symbols} setting.
9069 @section Program Variables
9071 The most common kind of expression to use is the name of a variable
9074 Variables in expressions are understood in the selected stack frame
9075 (@pxref{Selection, ,Selecting a Frame}); they must be either:
9079 global (or file-static)
9086 visible according to the scope rules of the
9087 programming language from the point of execution in that frame
9090 @noindent This means that in the function
9105 you can examine and use the variable @code{a} whenever your program is
9106 executing within the function @code{foo}, but you can only use or
9107 examine the variable @code{b} while your program is executing inside
9108 the block where @code{b} is declared.
9110 @cindex variable name conflict
9111 There is an exception: you can refer to a variable or function whose
9112 scope is a single source file even if the current execution point is not
9113 in this file. But it is possible to have more than one such variable or
9114 function with the same name (in different source files). If that
9115 happens, referring to that name has unpredictable effects. If you wish,
9116 you can specify a static variable in a particular function or file by
9117 using the colon-colon (@code{::}) notation:
9119 @cindex colon-colon, context for variables/functions
9121 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
9122 @cindex @code{::}, context for variables/functions
9125 @var{file}::@var{variable}
9126 @var{function}::@var{variable}
9130 Here @var{file} or @var{function} is the name of the context for the
9131 static @var{variable}. In the case of file names, you can use quotes to
9132 make sure @value{GDBN} parses the file name as a single word---for example,
9133 to print a global value of @code{x} defined in @file{f2.c}:
9136 (@value{GDBP}) p 'f2.c'::x
9139 The @code{::} notation is normally used for referring to
9140 static variables, since you typically disambiguate uses of local variables
9141 in functions by selecting the appropriate frame and using the
9142 simple name of the variable. However, you may also use this notation
9143 to refer to local variables in frames enclosing the selected frame:
9152 process (a); /* Stop here */
9163 For example, if there is a breakpoint at the commented line,
9164 here is what you might see
9165 when the program stops after executing the call @code{bar(0)}:
9170 (@value{GDBP}) p bar::a
9173 #2 0x080483d0 in foo (a=5) at foobar.c:12
9176 (@value{GDBP}) p bar::a
9180 @cindex C@t{++} scope resolution
9181 These uses of @samp{::} are very rarely in conflict with the very
9182 similar use of the same notation in C@t{++}. When they are in
9183 conflict, the C@t{++} meaning takes precedence; however, this can be
9184 overridden by quoting the file or function name with single quotes.
9186 For example, suppose the program is stopped in a method of a class
9187 that has a field named @code{includefile}, and there is also an
9188 include file named @file{includefile} that defines a variable,
9192 (@value{GDBP}) p includefile
9194 (@value{GDBP}) p includefile::some_global
9195 A syntax error in expression, near `'.
9196 (@value{GDBP}) p 'includefile'::some_global
9200 @cindex wrong values
9201 @cindex variable values, wrong
9202 @cindex function entry/exit, wrong values of variables
9203 @cindex optimized code, wrong values of variables
9205 @emph{Warning:} Occasionally, a local variable may appear to have the
9206 wrong value at certain points in a function---just after entry to a new
9207 scope, and just before exit.
9209 You may see this problem when you are stepping by machine instructions.
9210 This is because, on most machines, it takes more than one instruction to
9211 set up a stack frame (including local variable definitions); if you are
9212 stepping by machine instructions, variables may appear to have the wrong
9213 values until the stack frame is completely built. On exit, it usually
9214 also takes more than one machine instruction to destroy a stack frame;
9215 after you begin stepping through that group of instructions, local
9216 variable definitions may be gone.
9218 This may also happen when the compiler does significant optimizations.
9219 To be sure of always seeing accurate values, turn off all optimization
9222 @cindex ``No symbol "foo" in current context''
9223 Another possible effect of compiler optimizations is to optimize
9224 unused variables out of existence, or assign variables to registers (as
9225 opposed to memory addresses). Depending on the support for such cases
9226 offered by the debug info format used by the compiler, @value{GDBN}
9227 might not be able to display values for such local variables. If that
9228 happens, @value{GDBN} will print a message like this:
9231 No symbol "foo" in current context.
9234 To solve such problems, either recompile without optimizations, or use a
9235 different debug info format, if the compiler supports several such
9236 formats. @xref{Compilation}, for more information on choosing compiler
9237 options. @xref{C, ,C and C@t{++}}, for more information about debug
9238 info formats that are best suited to C@t{++} programs.
9240 If you ask to print an object whose contents are unknown to
9241 @value{GDBN}, e.g., because its data type is not completely specified
9242 by the debug information, @value{GDBN} will say @samp{<incomplete
9243 type>}. @xref{Symbols, incomplete type}, for more about this.
9245 @cindex no debug info variables
9246 If you try to examine or use the value of a (global) variable for
9247 which @value{GDBN} has no type information, e.g., because the program
9248 includes no debug information, @value{GDBN} displays an error message.
9249 @xref{Symbols, unknown type}, for more about unknown types. If you
9250 cast the variable to its declared type, @value{GDBN} gets the
9251 variable's value using the cast-to type as the variable's type. For
9252 example, in a C program:
9255 (@value{GDBP}) p var
9256 'var' has unknown type; cast it to its declared type
9257 (@value{GDBP}) p (float) var
9261 If you append @kbd{@@entry} string to a function parameter name you get its
9262 value at the time the function got called. If the value is not available an
9263 error message is printed. Entry values are available only with some compilers.
9264 Entry values are normally also printed at the function parameter list according
9265 to @ref{set print entry-values}.
9268 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
9274 (gdb) print i@@entry
9278 Strings are identified as arrays of @code{char} values without specified
9279 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
9280 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
9281 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
9282 defines literal string type @code{"char"} as @code{char} without a sign.
9287 signed char var1[] = "A";
9290 You get during debugging
9295 $2 = @{65 'A', 0 '\0'@}
9299 @section Artificial Arrays
9301 @cindex artificial array
9303 @kindex @@@r{, referencing memory as an array}
9304 It is often useful to print out several successive objects of the
9305 same type in memory; a section of an array, or an array of
9306 dynamically determined size for which only a pointer exists in the
9309 You can do this by referring to a contiguous span of memory as an
9310 @dfn{artificial array}, using the binary operator @samp{@@}. The left
9311 operand of @samp{@@} should be the first element of the desired array
9312 and be an individual object. The right operand should be the desired length
9313 of the array. The result is an array value whose elements are all of
9314 the type of the left argument. The first element is actually the left
9315 argument; the second element comes from bytes of memory immediately
9316 following those that hold the first element, and so on. Here is an
9317 example. If a program says
9320 int *array = (int *) malloc (len * sizeof (int));
9324 you can print the contents of @code{array} with
9330 The left operand of @samp{@@} must reside in memory. Array values made
9331 with @samp{@@} in this way behave just like other arrays in terms of
9332 subscripting, and are coerced to pointers when used in expressions.
9333 Artificial arrays most often appear in expressions via the value history
9334 (@pxref{Value History, ,Value History}), after printing one out.
9336 Another way to create an artificial array is to use a cast.
9337 This re-interprets a value as if it were an array.
9338 The value need not be in memory:
9340 (@value{GDBP}) p/x (short[2])0x12345678
9341 $1 = @{0x1234, 0x5678@}
9344 As a convenience, if you leave the array length out (as in
9345 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9346 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9348 (@value{GDBP}) p/x (short[])0x12345678
9349 $2 = @{0x1234, 0x5678@}
9352 Sometimes the artificial array mechanism is not quite enough; in
9353 moderately complex data structures, the elements of interest may not
9354 actually be adjacent---for example, if you are interested in the values
9355 of pointers in an array. One useful work-around in this situation is
9356 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9357 Variables}) as a counter in an expression that prints the first
9358 interesting value, and then repeat that expression via @key{RET}. For
9359 instance, suppose you have an array @code{dtab} of pointers to
9360 structures, and you are interested in the values of a field @code{fv}
9361 in each structure. Here is an example of what you might type:
9371 @node Output Formats
9372 @section Output Formats
9374 @cindex formatted output
9375 @cindex output formats
9376 By default, @value{GDBN} prints a value according to its data type. Sometimes
9377 this is not what you want. For example, you might want to print a number
9378 in hex, or a pointer in decimal. Or you might want to view data in memory
9379 at a certain address as a character string or as an instruction. To do
9380 these things, specify an @dfn{output format} when you print a value.
9382 The simplest use of output formats is to say how to print a value
9383 already computed. This is done by starting the arguments of the
9384 @code{print} command with a slash and a format letter. The format
9385 letters supported are:
9389 Regard the bits of the value as an integer, and print the integer in
9393 Print as integer in signed decimal.
9396 Print as integer in unsigned decimal.
9399 Print as integer in octal.
9402 Print as integer in binary. The letter @samp{t} stands for ``two''.
9403 @footnote{@samp{b} cannot be used because these format letters are also
9404 used with the @code{x} command, where @samp{b} stands for ``byte'';
9405 see @ref{Memory,,Examining Memory}.}
9408 @cindex unknown address, locating
9409 @cindex locate address
9410 Print as an address, both absolute in hexadecimal and as an offset from
9411 the nearest preceding symbol. You can use this format used to discover
9412 where (in what function) an unknown address is located:
9415 (@value{GDBP}) p/a 0x54320
9416 $3 = 0x54320 <_initialize_vx+396>
9420 The command @code{info symbol 0x54320} yields similar results.
9421 @xref{Symbols, info symbol}.
9424 Regard as an integer and print it as a character constant. This
9425 prints both the numerical value and its character representation. The
9426 character representation is replaced with the octal escape @samp{\nnn}
9427 for characters outside the 7-bit @sc{ascii} range.
9429 Without this format, @value{GDBN} displays @code{char},
9430 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9431 constants. Single-byte members of vectors are displayed as integer
9435 Regard the bits of the value as a floating point number and print
9436 using typical floating point syntax.
9439 @cindex printing strings
9440 @cindex printing byte arrays
9441 Regard as a string, if possible. With this format, pointers to single-byte
9442 data are displayed as null-terminated strings and arrays of single-byte data
9443 are displayed as fixed-length strings. Other values are displayed in their
9446 Without this format, @value{GDBN} displays pointers to and arrays of
9447 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9448 strings. Single-byte members of a vector are displayed as an integer
9452 Like @samp{x} formatting, the value is treated as an integer and
9453 printed as hexadecimal, but leading zeros are printed to pad the value
9454 to the size of the integer type.
9457 @cindex raw printing
9458 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9459 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9460 Printing}). This typically results in a higher-level display of the
9461 value's contents. The @samp{r} format bypasses any Python
9462 pretty-printer which might exist.
9465 For example, to print the program counter in hex (@pxref{Registers}), type
9472 Note that no space is required before the slash; this is because command
9473 names in @value{GDBN} cannot contain a slash.
9475 To reprint the last value in the value history with a different format,
9476 you can use the @code{print} command with just a format and no
9477 expression. For example, @samp{p/x} reprints the last value in hex.
9480 @section Examining Memory
9482 You can use the command @code{x} (for ``examine'') to examine memory in
9483 any of several formats, independently of your program's data types.
9485 @cindex examining memory
9487 @kindex x @r{(examine memory)}
9488 @item x/@var{nfu} @var{addr}
9491 Use the @code{x} command to examine memory.
9494 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9495 much memory to display and how to format it; @var{addr} is an
9496 expression giving the address where you want to start displaying memory.
9497 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9498 Several commands set convenient defaults for @var{addr}.
9501 @item @var{n}, the repeat count
9502 The repeat count is a decimal integer; the default is 1. It specifies
9503 how much memory (counting by units @var{u}) to display. If a negative
9504 number is specified, memory is examined backward from @var{addr}.
9505 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9508 @item @var{f}, the display format
9509 The display format is one of the formats used by @code{print}
9510 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9511 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9512 The default is @samp{x} (hexadecimal) initially. The default changes
9513 each time you use either @code{x} or @code{print}.
9515 @item @var{u}, the unit size
9516 The unit size is any of
9522 Halfwords (two bytes).
9524 Words (four bytes). This is the initial default.
9526 Giant words (eight bytes).
9529 Each time you specify a unit size with @code{x}, that size becomes the
9530 default unit the next time you use @code{x}. For the @samp{i} format,
9531 the unit size is ignored and is normally not written. For the @samp{s} format,
9532 the unit size defaults to @samp{b}, unless it is explicitly given.
9533 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9534 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9535 Note that the results depend on the programming language of the
9536 current compilation unit. If the language is C, the @samp{s}
9537 modifier will use the UTF-16 encoding while @samp{w} will use
9538 UTF-32. The encoding is set by the programming language and cannot
9541 @item @var{addr}, starting display address
9542 @var{addr} is the address where you want @value{GDBN} to begin displaying
9543 memory. The expression need not have a pointer value (though it may);
9544 it is always interpreted as an integer address of a byte of memory.
9545 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9546 @var{addr} is usually just after the last address examined---but several
9547 other commands also set the default address: @code{info breakpoints} (to
9548 the address of the last breakpoint listed), @code{info line} (to the
9549 starting address of a line), and @code{print} (if you use it to display
9550 a value from memory).
9553 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9554 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9555 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9556 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9557 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9559 You can also specify a negative repeat count to examine memory backward
9560 from the given address. For example, @samp{x/-3uh 0x54320} prints three
9561 halfwords (@code{h}) at @code{0x54314}, @code{0x54328}, and @code{0x5431c}.
9563 Since the letters indicating unit sizes are all distinct from the
9564 letters specifying output formats, you do not have to remember whether
9565 unit size or format comes first; either order works. The output
9566 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9567 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9569 Even though the unit size @var{u} is ignored for the formats @samp{s}
9570 and @samp{i}, you might still want to use a count @var{n}; for example,
9571 @samp{3i} specifies that you want to see three machine instructions,
9572 including any operands. For convenience, especially when used with
9573 the @code{display} command, the @samp{i} format also prints branch delay
9574 slot instructions, if any, beyond the count specified, which immediately
9575 follow the last instruction that is within the count. The command
9576 @code{disassemble} gives an alternative way of inspecting machine
9577 instructions; see @ref{Machine Code,,Source and Machine Code}.
9579 If a negative repeat count is specified for the formats @samp{s} or @samp{i},
9580 the command displays null-terminated strings or instructions before the given
9581 address as many as the absolute value of the given number. For the @samp{i}
9582 format, we use line number information in the debug info to accurately locate
9583 instruction boundaries while disassembling backward. If line info is not
9584 available, the command stops examining memory with an error message.
9586 All the defaults for the arguments to @code{x} are designed to make it
9587 easy to continue scanning memory with minimal specifications each time
9588 you use @code{x}. For example, after you have inspected three machine
9589 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9590 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9591 the repeat count @var{n} is used again; the other arguments default as
9592 for successive uses of @code{x}.
9594 When examining machine instructions, the instruction at current program
9595 counter is shown with a @code{=>} marker. For example:
9598 (@value{GDBP}) x/5i $pc-6
9599 0x804837f <main+11>: mov %esp,%ebp
9600 0x8048381 <main+13>: push %ecx
9601 0x8048382 <main+14>: sub $0x4,%esp
9602 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9603 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9606 @cindex @code{$_}, @code{$__}, and value history
9607 The addresses and contents printed by the @code{x} command are not saved
9608 in the value history because there is often too much of them and they
9609 would get in the way. Instead, @value{GDBN} makes these values available for
9610 subsequent use in expressions as values of the convenience variables
9611 @code{$_} and @code{$__}. After an @code{x} command, the last address
9612 examined is available for use in expressions in the convenience variable
9613 @code{$_}. The contents of that address, as examined, are available in
9614 the convenience variable @code{$__}.
9616 If the @code{x} command has a repeat count, the address and contents saved
9617 are from the last memory unit printed; this is not the same as the last
9618 address printed if several units were printed on the last line of output.
9620 @anchor{addressable memory unit}
9621 @cindex addressable memory unit
9622 Most targets have an addressable memory unit size of 8 bits. This means
9623 that to each memory address are associated 8 bits of data. Some
9624 targets, however, have other addressable memory unit sizes.
9625 Within @value{GDBN} and this document, the term
9626 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9627 when explicitly referring to a chunk of data of that size. The word
9628 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9629 the addressable memory unit size of the target. For most systems,
9630 addressable memory unit is a synonym of byte.
9632 @cindex remote memory comparison
9633 @cindex target memory comparison
9634 @cindex verify remote memory image
9635 @cindex verify target memory image
9636 When you are debugging a program running on a remote target machine
9637 (@pxref{Remote Debugging}), you may wish to verify the program's image
9638 in the remote machine's memory against the executable file you
9639 downloaded to the target. Or, on any target, you may want to check
9640 whether the program has corrupted its own read-only sections. The
9641 @code{compare-sections} command is provided for such situations.
9644 @kindex compare-sections
9645 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9646 Compare the data of a loadable section @var{section-name} in the
9647 executable file of the program being debugged with the same section in
9648 the target machine's memory, and report any mismatches. With no
9649 arguments, compares all loadable sections. With an argument of
9650 @code{-r}, compares all loadable read-only sections.
9652 Note: for remote targets, this command can be accelerated if the
9653 target supports computing the CRC checksum of a block of memory
9654 (@pxref{qCRC packet}).
9658 @section Automatic Display
9659 @cindex automatic display
9660 @cindex display of expressions
9662 If you find that you want to print the value of an expression frequently
9663 (to see how it changes), you might want to add it to the @dfn{automatic
9664 display list} so that @value{GDBN} prints its value each time your program stops.
9665 Each expression added to the list is given a number to identify it;
9666 to remove an expression from the list, you specify that number.
9667 The automatic display looks like this:
9671 3: bar[5] = (struct hack *) 0x3804
9675 This display shows item numbers, expressions and their current values. As with
9676 displays you request manually using @code{x} or @code{print}, you can
9677 specify the output format you prefer; in fact, @code{display} decides
9678 whether to use @code{print} or @code{x} depending your format
9679 specification---it uses @code{x} if you specify either the @samp{i}
9680 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9684 @item display @var{expr}
9685 Add the expression @var{expr} to the list of expressions to display
9686 each time your program stops. @xref{Expressions, ,Expressions}.
9688 @code{display} does not repeat if you press @key{RET} again after using it.
9690 @item display/@var{fmt} @var{expr}
9691 For @var{fmt} specifying only a display format and not a size or
9692 count, add the expression @var{expr} to the auto-display list but
9693 arrange to display it each time in the specified format @var{fmt}.
9694 @xref{Output Formats,,Output Formats}.
9696 @item display/@var{fmt} @var{addr}
9697 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9698 number of units, add the expression @var{addr} as a memory address to
9699 be examined each time your program stops. Examining means in effect
9700 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9703 For example, @samp{display/i $pc} can be helpful, to see the machine
9704 instruction about to be executed each time execution stops (@samp{$pc}
9705 is a common name for the program counter; @pxref{Registers, ,Registers}).
9708 @kindex delete display
9710 @item undisplay @var{dnums}@dots{}
9711 @itemx delete display @var{dnums}@dots{}
9712 Remove items from the list of expressions to display. Specify the
9713 numbers of the displays that you want affected with the command
9714 argument @var{dnums}. It can be a single display number, one of the
9715 numbers shown in the first field of the @samp{info display} display;
9716 or it could be a range of display numbers, as in @code{2-4}.
9718 @code{undisplay} does not repeat if you press @key{RET} after using it.
9719 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9721 @kindex disable display
9722 @item disable display @var{dnums}@dots{}
9723 Disable the display of item numbers @var{dnums}. A disabled display
9724 item is not printed automatically, but is not forgotten. It may be
9725 enabled again later. Specify the numbers of the displays that you
9726 want affected with the command argument @var{dnums}. It can be a
9727 single display number, one of the numbers shown in the first field of
9728 the @samp{info display} display; or it could be a range of display
9729 numbers, as in @code{2-4}.
9731 @kindex enable display
9732 @item enable display @var{dnums}@dots{}
9733 Enable display of item numbers @var{dnums}. It becomes effective once
9734 again in auto display of its expression, until you specify otherwise.
9735 Specify the numbers of the displays that you want affected with the
9736 command argument @var{dnums}. It can be a single display number, one
9737 of the numbers shown in the first field of the @samp{info display}
9738 display; or it could be a range of display numbers, as in @code{2-4}.
9741 Display the current values of the expressions on the list, just as is
9742 done when your program stops.
9744 @kindex info display
9746 Print the list of expressions previously set up to display
9747 automatically, each one with its item number, but without showing the
9748 values. This includes disabled expressions, which are marked as such.
9749 It also includes expressions which would not be displayed right now
9750 because they refer to automatic variables not currently available.
9753 @cindex display disabled out of scope
9754 If a display expression refers to local variables, then it does not make
9755 sense outside the lexical context for which it was set up. Such an
9756 expression is disabled when execution enters a context where one of its
9757 variables is not defined. For example, if you give the command
9758 @code{display last_char} while inside a function with an argument
9759 @code{last_char}, @value{GDBN} displays this argument while your program
9760 continues to stop inside that function. When it stops elsewhere---where
9761 there is no variable @code{last_char}---the display is disabled
9762 automatically. The next time your program stops where @code{last_char}
9763 is meaningful, you can enable the display expression once again.
9765 @node Print Settings
9766 @section Print Settings
9768 @cindex format options
9769 @cindex print settings
9770 @value{GDBN} provides the following ways to control how arrays, structures,
9771 and symbols are printed.
9774 These settings are useful for debugging programs in any language:
9778 @item set print address
9779 @itemx set print address on
9780 @cindex print/don't print memory addresses
9781 @value{GDBN} prints memory addresses showing the location of stack
9782 traces, structure values, pointer values, breakpoints, and so forth,
9783 even when it also displays the contents of those addresses. The default
9784 is @code{on}. For example, this is what a stack frame display looks like with
9785 @code{set print address on}:
9790 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9792 530 if (lquote != def_lquote)
9796 @item set print address off
9797 Do not print addresses when displaying their contents. For example,
9798 this is the same stack frame displayed with @code{set print address off}:
9802 (@value{GDBP}) set print addr off
9804 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9805 530 if (lquote != def_lquote)
9809 You can use @samp{set print address off} to eliminate all machine
9810 dependent displays from the @value{GDBN} interface. For example, with
9811 @code{print address off}, you should get the same text for backtraces on
9812 all machines---whether or not they involve pointer arguments.
9815 @item show print address
9816 Show whether or not addresses are to be printed.
9819 When @value{GDBN} prints a symbolic address, it normally prints the
9820 closest earlier symbol plus an offset. If that symbol does not uniquely
9821 identify the address (for example, it is a name whose scope is a single
9822 source file), you may need to clarify. One way to do this is with
9823 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9824 you can set @value{GDBN} to print the source file and line number when
9825 it prints a symbolic address:
9828 @item set print symbol-filename on
9829 @cindex source file and line of a symbol
9830 @cindex symbol, source file and line
9831 Tell @value{GDBN} to print the source file name and line number of a
9832 symbol in the symbolic form of an address.
9834 @item set print symbol-filename off
9835 Do not print source file name and line number of a symbol. This is the
9838 @item show print symbol-filename
9839 Show whether or not @value{GDBN} will print the source file name and
9840 line number of a symbol in the symbolic form of an address.
9843 Another situation where it is helpful to show symbol filenames and line
9844 numbers is when disassembling code; @value{GDBN} shows you the line
9845 number and source file that corresponds to each instruction.
9847 Also, you may wish to see the symbolic form only if the address being
9848 printed is reasonably close to the closest earlier symbol:
9851 @item set print max-symbolic-offset @var{max-offset}
9852 @itemx set print max-symbolic-offset unlimited
9853 @cindex maximum value for offset of closest symbol
9854 Tell @value{GDBN} to only display the symbolic form of an address if the
9855 offset between the closest earlier symbol and the address is less than
9856 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9857 to always print the symbolic form of an address if any symbol precedes
9858 it. Zero is equivalent to @code{unlimited}.
9860 @item show print max-symbolic-offset
9861 Ask how large the maximum offset is that @value{GDBN} prints in a
9865 @cindex wild pointer, interpreting
9866 @cindex pointer, finding referent
9867 If you have a pointer and you are not sure where it points, try
9868 @samp{set print symbol-filename on}. Then you can determine the name
9869 and source file location of the variable where it points, using
9870 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9871 For example, here @value{GDBN} shows that a variable @code{ptt} points
9872 at another variable @code{t}, defined in @file{hi2.c}:
9875 (@value{GDBP}) set print symbol-filename on
9876 (@value{GDBP}) p/a ptt
9877 $4 = 0xe008 <t in hi2.c>
9881 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9882 does not show the symbol name and filename of the referent, even with
9883 the appropriate @code{set print} options turned on.
9886 You can also enable @samp{/a}-like formatting all the time using
9887 @samp{set print symbol on}:
9890 @item set print symbol on
9891 Tell @value{GDBN} to print the symbol corresponding to an address, if
9894 @item set print symbol off
9895 Tell @value{GDBN} not to print the symbol corresponding to an
9896 address. In this mode, @value{GDBN} will still print the symbol
9897 corresponding to pointers to functions. This is the default.
9899 @item show print symbol
9900 Show whether @value{GDBN} will display the symbol corresponding to an
9904 Other settings control how different kinds of objects are printed:
9907 @item set print array
9908 @itemx set print array on
9909 @cindex pretty print arrays
9910 Pretty print arrays. This format is more convenient to read,
9911 but uses more space. The default is off.
9913 @item set print array off
9914 Return to compressed format for arrays.
9916 @item show print array
9917 Show whether compressed or pretty format is selected for displaying
9920 @cindex print array indexes
9921 @item set print array-indexes
9922 @itemx set print array-indexes on
9923 Print the index of each element when displaying arrays. May be more
9924 convenient to locate a given element in the array or quickly find the
9925 index of a given element in that printed array. The default is off.
9927 @item set print array-indexes off
9928 Stop printing element indexes when displaying arrays.
9930 @item show print array-indexes
9931 Show whether the index of each element is printed when displaying
9934 @item set print elements @var{number-of-elements}
9935 @itemx set print elements unlimited
9936 @cindex number of array elements to print
9937 @cindex limit on number of printed array elements
9938 Set a limit on how many elements of an array @value{GDBN} will print.
9939 If @value{GDBN} is printing a large array, it stops printing after it has
9940 printed the number of elements set by the @code{set print elements} command.
9941 This limit also applies to the display of strings.
9942 When @value{GDBN} starts, this limit is set to 200.
9943 Setting @var{number-of-elements} to @code{unlimited} or zero means
9944 that the number of elements to print is unlimited.
9946 @item show print elements
9947 Display the number of elements of a large array that @value{GDBN} will print.
9948 If the number is 0, then the printing is unlimited.
9950 @item set print frame-arguments @var{value}
9951 @kindex set print frame-arguments
9952 @cindex printing frame argument values
9953 @cindex print all frame argument values
9954 @cindex print frame argument values for scalars only
9955 @cindex do not print frame argument values
9956 This command allows to control how the values of arguments are printed
9957 when the debugger prints a frame (@pxref{Frames}). The possible
9962 The values of all arguments are printed.
9965 Print the value of an argument only if it is a scalar. The value of more
9966 complex arguments such as arrays, structures, unions, etc, is replaced
9967 by @code{@dots{}}. This is the default. Here is an example where
9968 only scalar arguments are shown:
9971 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9976 None of the argument values are printed. Instead, the value of each argument
9977 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9980 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9985 By default, only scalar arguments are printed. This command can be used
9986 to configure the debugger to print the value of all arguments, regardless
9987 of their type. However, it is often advantageous to not print the value
9988 of more complex parameters. For instance, it reduces the amount of
9989 information printed in each frame, making the backtrace more readable.
9990 Also, it improves performance when displaying Ada frames, because
9991 the computation of large arguments can sometimes be CPU-intensive,
9992 especially in large applications. Setting @code{print frame-arguments}
9993 to @code{scalars} (the default) or @code{none} avoids this computation,
9994 thus speeding up the display of each Ada frame.
9996 @item show print frame-arguments
9997 Show how the value of arguments should be displayed when printing a frame.
9999 @item set print raw frame-arguments on
10000 Print frame arguments in raw, non pretty-printed, form.
10002 @item set print raw frame-arguments off
10003 Print frame arguments in pretty-printed form, if there is a pretty-printer
10004 for the value (@pxref{Pretty Printing}),
10005 otherwise print the value in raw form.
10006 This is the default.
10008 @item show print raw frame-arguments
10009 Show whether to print frame arguments in raw form.
10011 @anchor{set print entry-values}
10012 @item set print entry-values @var{value}
10013 @kindex set print entry-values
10014 Set printing of frame argument values at function entry. In some cases
10015 @value{GDBN} can determine the value of function argument which was passed by
10016 the function caller, even if the value was modified inside the called function
10017 and therefore is different. With optimized code, the current value could be
10018 unavailable, but the entry value may still be known.
10020 The default value is @code{default} (see below for its description). Older
10021 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
10022 this feature will behave in the @code{default} setting the same way as with the
10025 This functionality is currently supported only by DWARF 2 debugging format and
10026 the compiler has to produce @samp{DW_TAG_call_site} tags. With
10027 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10030 The @var{value} parameter can be one of the following:
10034 Print only actual parameter values, never print values from function entry
10038 #0 different (val=6)
10039 #0 lost (val=<optimized out>)
10041 #0 invalid (val=<optimized out>)
10045 Print only parameter values from function entry point. The actual parameter
10046 values are never printed.
10048 #0 equal (val@@entry=5)
10049 #0 different (val@@entry=5)
10050 #0 lost (val@@entry=5)
10051 #0 born (val@@entry=<optimized out>)
10052 #0 invalid (val@@entry=<optimized out>)
10056 Print only parameter values from function entry point. If value from function
10057 entry point is not known while the actual value is known, print the actual
10058 value for such parameter.
10060 #0 equal (val@@entry=5)
10061 #0 different (val@@entry=5)
10062 #0 lost (val@@entry=5)
10064 #0 invalid (val@@entry=<optimized out>)
10068 Print actual parameter values. If actual parameter value is not known while
10069 value from function entry point is known, print the entry point value for such
10073 #0 different (val=6)
10074 #0 lost (val@@entry=5)
10076 #0 invalid (val=<optimized out>)
10080 Always print both the actual parameter value and its value from function entry
10081 point, even if values of one or both are not available due to compiler
10084 #0 equal (val=5, val@@entry=5)
10085 #0 different (val=6, val@@entry=5)
10086 #0 lost (val=<optimized out>, val@@entry=5)
10087 #0 born (val=10, val@@entry=<optimized out>)
10088 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
10092 Print the actual parameter value if it is known and also its value from
10093 function entry point if it is known. If neither is known, print for the actual
10094 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
10095 values are known and identical, print the shortened
10096 @code{param=param@@entry=VALUE} notation.
10098 #0 equal (val=val@@entry=5)
10099 #0 different (val=6, val@@entry=5)
10100 #0 lost (val@@entry=5)
10102 #0 invalid (val=<optimized out>)
10106 Always print the actual parameter value. Print also its value from function
10107 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
10108 if both values are known and identical, print the shortened
10109 @code{param=param@@entry=VALUE} notation.
10111 #0 equal (val=val@@entry=5)
10112 #0 different (val=6, val@@entry=5)
10113 #0 lost (val=<optimized out>, val@@entry=5)
10115 #0 invalid (val=<optimized out>)
10119 For analysis messages on possible failures of frame argument values at function
10120 entry resolution see @ref{set debug entry-values}.
10122 @item show print entry-values
10123 Show the method being used for printing of frame argument values at function
10126 @item set print repeats @var{number-of-repeats}
10127 @itemx set print repeats unlimited
10128 @cindex repeated array elements
10129 Set the threshold for suppressing display of repeated array
10130 elements. When the number of consecutive identical elements of an
10131 array exceeds the threshold, @value{GDBN} prints the string
10132 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
10133 identical repetitions, instead of displaying the identical elements
10134 themselves. Setting the threshold to @code{unlimited} or zero will
10135 cause all elements to be individually printed. The default threshold
10138 @item show print repeats
10139 Display the current threshold for printing repeated identical
10142 @item set print null-stop
10143 @cindex @sc{null} elements in arrays
10144 Cause @value{GDBN} to stop printing the characters of an array when the first
10145 @sc{null} is encountered. This is useful when large arrays actually
10146 contain only short strings.
10147 The default is off.
10149 @item show print null-stop
10150 Show whether @value{GDBN} stops printing an array on the first
10151 @sc{null} character.
10153 @item set print pretty on
10154 @cindex print structures in indented form
10155 @cindex indentation in structure display
10156 Cause @value{GDBN} to print structures in an indented format with one member
10157 per line, like this:
10172 @item set print pretty off
10173 Cause @value{GDBN} to print structures in a compact format, like this:
10177 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
10178 meat = 0x54 "Pork"@}
10183 This is the default format.
10185 @item show print pretty
10186 Show which format @value{GDBN} is using to print structures.
10188 @item set print sevenbit-strings on
10189 @cindex eight-bit characters in strings
10190 @cindex octal escapes in strings
10191 Print using only seven-bit characters; if this option is set,
10192 @value{GDBN} displays any eight-bit characters (in strings or
10193 character values) using the notation @code{\}@var{nnn}. This setting is
10194 best if you are working in English (@sc{ascii}) and you use the
10195 high-order bit of characters as a marker or ``meta'' bit.
10197 @item set print sevenbit-strings off
10198 Print full eight-bit characters. This allows the use of more
10199 international character sets, and is the default.
10201 @item show print sevenbit-strings
10202 Show whether or not @value{GDBN} is printing only seven-bit characters.
10204 @item set print union on
10205 @cindex unions in structures, printing
10206 Tell @value{GDBN} to print unions which are contained in structures
10207 and other unions. This is the default setting.
10209 @item set print union off
10210 Tell @value{GDBN} not to print unions which are contained in
10211 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
10214 @item show print union
10215 Ask @value{GDBN} whether or not it will print unions which are contained in
10216 structures and other unions.
10218 For example, given the declarations
10221 typedef enum @{Tree, Bug@} Species;
10222 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
10223 typedef enum @{Caterpillar, Cocoon, Butterfly@}
10234 struct thing foo = @{Tree, @{Acorn@}@};
10238 with @code{set print union on} in effect @samp{p foo} would print
10241 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
10245 and with @code{set print union off} in effect it would print
10248 $1 = @{it = Tree, form = @{...@}@}
10252 @code{set print union} affects programs written in C-like languages
10258 These settings are of interest when debugging C@t{++} programs:
10261 @cindex demangling C@t{++} names
10262 @item set print demangle
10263 @itemx set print demangle on
10264 Print C@t{++} names in their source form rather than in the encoded
10265 (``mangled'') form passed to the assembler and linker for type-safe
10266 linkage. The default is on.
10268 @item show print demangle
10269 Show whether C@t{++} names are printed in mangled or demangled form.
10271 @item set print asm-demangle
10272 @itemx set print asm-demangle on
10273 Print C@t{++} names in their source form rather than their mangled form, even
10274 in assembler code printouts such as instruction disassemblies.
10275 The default is off.
10277 @item show print asm-demangle
10278 Show whether C@t{++} names in assembly listings are printed in mangled
10281 @cindex C@t{++} symbol decoding style
10282 @cindex symbol decoding style, C@t{++}
10283 @kindex set demangle-style
10284 @item set demangle-style @var{style}
10285 Choose among several encoding schemes used by different compilers to
10286 represent C@t{++} names. The choices for @var{style} are currently:
10290 Allow @value{GDBN} to choose a decoding style by inspecting your program.
10291 This is the default.
10294 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
10297 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
10300 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
10303 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
10304 @strong{Warning:} this setting alone is not sufficient to allow
10305 debugging @code{cfront}-generated executables. @value{GDBN} would
10306 require further enhancement to permit that.
10309 If you omit @var{style}, you will see a list of possible formats.
10311 @item show demangle-style
10312 Display the encoding style currently in use for decoding C@t{++} symbols.
10314 @item set print object
10315 @itemx set print object on
10316 @cindex derived type of an object, printing
10317 @cindex display derived types
10318 When displaying a pointer to an object, identify the @emph{actual}
10319 (derived) type of the object rather than the @emph{declared} type, using
10320 the virtual function table. Note that the virtual function table is
10321 required---this feature can only work for objects that have run-time
10322 type identification; a single virtual method in the object's declared
10323 type is sufficient. Note that this setting is also taken into account when
10324 working with variable objects via MI (@pxref{GDB/MI}).
10326 @item set print object off
10327 Display only the declared type of objects, without reference to the
10328 virtual function table. This is the default setting.
10330 @item show print object
10331 Show whether actual, or declared, object types are displayed.
10333 @item set print static-members
10334 @itemx set print static-members on
10335 @cindex static members of C@t{++} objects
10336 Print static members when displaying a C@t{++} object. The default is on.
10338 @item set print static-members off
10339 Do not print static members when displaying a C@t{++} object.
10341 @item show print static-members
10342 Show whether C@t{++} static members are printed or not.
10344 @item set print pascal_static-members
10345 @itemx set print pascal_static-members on
10346 @cindex static members of Pascal objects
10347 @cindex Pascal objects, static members display
10348 Print static members when displaying a Pascal object. The default is on.
10350 @item set print pascal_static-members off
10351 Do not print static members when displaying a Pascal object.
10353 @item show print pascal_static-members
10354 Show whether Pascal static members are printed or not.
10356 @c These don't work with HP ANSI C++ yet.
10357 @item set print vtbl
10358 @itemx set print vtbl on
10359 @cindex pretty print C@t{++} virtual function tables
10360 @cindex virtual functions (C@t{++}) display
10361 @cindex VTBL display
10362 Pretty print C@t{++} virtual function tables. The default is off.
10363 (The @code{vtbl} commands do not work on programs compiled with the HP
10364 ANSI C@t{++} compiler (@code{aCC}).)
10366 @item set print vtbl off
10367 Do not pretty print C@t{++} virtual function tables.
10369 @item show print vtbl
10370 Show whether C@t{++} virtual function tables are pretty printed, or not.
10373 @node Pretty Printing
10374 @section Pretty Printing
10376 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10377 Python code. It greatly simplifies the display of complex objects. This
10378 mechanism works for both MI and the CLI.
10381 * Pretty-Printer Introduction:: Introduction to pretty-printers
10382 * Pretty-Printer Example:: An example pretty-printer
10383 * Pretty-Printer Commands:: Pretty-printer commands
10386 @node Pretty-Printer Introduction
10387 @subsection Pretty-Printer Introduction
10389 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10390 registered for the value. If there is then @value{GDBN} invokes the
10391 pretty-printer to print the value. Otherwise the value is printed normally.
10393 Pretty-printers are normally named. This makes them easy to manage.
10394 The @samp{info pretty-printer} command will list all the installed
10395 pretty-printers with their names.
10396 If a pretty-printer can handle multiple data types, then its
10397 @dfn{subprinters} are the printers for the individual data types.
10398 Each such subprinter has its own name.
10399 The format of the name is @var{printer-name};@var{subprinter-name}.
10401 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10402 Typically they are automatically loaded and registered when the corresponding
10403 debug information is loaded, thus making them available without having to
10404 do anything special.
10406 There are three places where a pretty-printer can be registered.
10410 Pretty-printers registered globally are available when debugging
10414 Pretty-printers registered with a program space are available only
10415 when debugging that program.
10416 @xref{Progspaces In Python}, for more details on program spaces in Python.
10419 Pretty-printers registered with an objfile are loaded and unloaded
10420 with the corresponding objfile (e.g., shared library).
10421 @xref{Objfiles In Python}, for more details on objfiles in Python.
10424 @xref{Selecting Pretty-Printers}, for further information on how
10425 pretty-printers are selected,
10427 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10430 @node Pretty-Printer Example
10431 @subsection Pretty-Printer Example
10433 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10436 (@value{GDBP}) print s
10438 static npos = 4294967295,
10440 <std::allocator<char>> = @{
10441 <__gnu_cxx::new_allocator<char>> = @{
10442 <No data fields>@}, <No data fields>
10444 members of std::basic_string<char, std::char_traits<char>,
10445 std::allocator<char> >::_Alloc_hider:
10446 _M_p = 0x804a014 "abcd"
10451 With a pretty-printer for @code{std::string} only the contents are printed:
10454 (@value{GDBP}) print s
10458 @node Pretty-Printer Commands
10459 @subsection Pretty-Printer Commands
10460 @cindex pretty-printer commands
10463 @kindex info pretty-printer
10464 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10465 Print the list of installed pretty-printers.
10466 This includes disabled pretty-printers, which are marked as such.
10468 @var{object-regexp} is a regular expression matching the objects
10469 whose pretty-printers to list.
10470 Objects can be @code{global}, the program space's file
10471 (@pxref{Progspaces In Python}),
10472 and the object files within that program space (@pxref{Objfiles In Python}).
10473 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10474 looks up a printer from these three objects.
10476 @var{name-regexp} is a regular expression matching the name of the printers
10479 @kindex disable pretty-printer
10480 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10481 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10482 A disabled pretty-printer is not forgotten, it may be enabled again later.
10484 @kindex enable pretty-printer
10485 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10486 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10491 Suppose we have three pretty-printers installed: one from library1.so
10492 named @code{foo} that prints objects of type @code{foo}, and
10493 another from library2.so named @code{bar} that prints two types of objects,
10494 @code{bar1} and @code{bar2}.
10497 (gdb) info pretty-printer
10504 (gdb) info pretty-printer library2
10509 (gdb) disable pretty-printer library1
10511 2 of 3 printers enabled
10512 (gdb) info pretty-printer
10519 (gdb) disable pretty-printer library2 bar:bar1
10521 1 of 3 printers enabled
10522 (gdb) info pretty-printer library2
10529 (gdb) disable pretty-printer library2 bar
10531 0 of 3 printers enabled
10532 (gdb) info pretty-printer library2
10541 Note that for @code{bar} the entire printer can be disabled,
10542 as can each individual subprinter.
10544 @node Value History
10545 @section Value History
10547 @cindex value history
10548 @cindex history of values printed by @value{GDBN}
10549 Values printed by the @code{print} command are saved in the @value{GDBN}
10550 @dfn{value history}. This allows you to refer to them in other expressions.
10551 Values are kept until the symbol table is re-read or discarded
10552 (for example with the @code{file} or @code{symbol-file} commands).
10553 When the symbol table changes, the value history is discarded,
10554 since the values may contain pointers back to the types defined in the
10559 @cindex history number
10560 The values printed are given @dfn{history numbers} by which you can
10561 refer to them. These are successive integers starting with one.
10562 @code{print} shows you the history number assigned to a value by
10563 printing @samp{$@var{num} = } before the value; here @var{num} is the
10566 To refer to any previous value, use @samp{$} followed by the value's
10567 history number. The way @code{print} labels its output is designed to
10568 remind you of this. Just @code{$} refers to the most recent value in
10569 the history, and @code{$$} refers to the value before that.
10570 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10571 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10572 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10574 For example, suppose you have just printed a pointer to a structure and
10575 want to see the contents of the structure. It suffices to type
10581 If you have a chain of structures where the component @code{next} points
10582 to the next one, you can print the contents of the next one with this:
10589 You can print successive links in the chain by repeating this
10590 command---which you can do by just typing @key{RET}.
10592 Note that the history records values, not expressions. If the value of
10593 @code{x} is 4 and you type these commands:
10601 then the value recorded in the value history by the @code{print} command
10602 remains 4 even though the value of @code{x} has changed.
10605 @kindex show values
10607 Print the last ten values in the value history, with their item numbers.
10608 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10609 values} does not change the history.
10611 @item show values @var{n}
10612 Print ten history values centered on history item number @var{n}.
10614 @item show values +
10615 Print ten history values just after the values last printed. If no more
10616 values are available, @code{show values +} produces no display.
10619 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10620 same effect as @samp{show values +}.
10622 @node Convenience Vars
10623 @section Convenience Variables
10625 @cindex convenience variables
10626 @cindex user-defined variables
10627 @value{GDBN} provides @dfn{convenience variables} that you can use within
10628 @value{GDBN} to hold on to a value and refer to it later. These variables
10629 exist entirely within @value{GDBN}; they are not part of your program, and
10630 setting a convenience variable has no direct effect on further execution
10631 of your program. That is why you can use them freely.
10633 Convenience variables are prefixed with @samp{$}. Any name preceded by
10634 @samp{$} can be used for a convenience variable, unless it is one of
10635 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10636 (Value history references, in contrast, are @emph{numbers} preceded
10637 by @samp{$}. @xref{Value History, ,Value History}.)
10639 You can save a value in a convenience variable with an assignment
10640 expression, just as you would set a variable in your program.
10644 set $foo = *object_ptr
10648 would save in @code{$foo} the value contained in the object pointed to by
10651 Using a convenience variable for the first time creates it, but its
10652 value is @code{void} until you assign a new value. You can alter the
10653 value with another assignment at any time.
10655 Convenience variables have no fixed types. You can assign a convenience
10656 variable any type of value, including structures and arrays, even if
10657 that variable already has a value of a different type. The convenience
10658 variable, when used as an expression, has the type of its current value.
10661 @kindex show convenience
10662 @cindex show all user variables and functions
10663 @item show convenience
10664 Print a list of convenience variables used so far, and their values,
10665 as well as a list of the convenience functions.
10666 Abbreviated @code{show conv}.
10668 @kindex init-if-undefined
10669 @cindex convenience variables, initializing
10670 @item init-if-undefined $@var{variable} = @var{expression}
10671 Set a convenience variable if it has not already been set. This is useful
10672 for user-defined commands that keep some state. It is similar, in concept,
10673 to using local static variables with initializers in C (except that
10674 convenience variables are global). It can also be used to allow users to
10675 override default values used in a command script.
10677 If the variable is already defined then the expression is not evaluated so
10678 any side-effects do not occur.
10681 One of the ways to use a convenience variable is as a counter to be
10682 incremented or a pointer to be advanced. For example, to print
10683 a field from successive elements of an array of structures:
10687 print bar[$i++]->contents
10691 Repeat that command by typing @key{RET}.
10693 Some convenience variables are created automatically by @value{GDBN} and given
10694 values likely to be useful.
10697 @vindex $_@r{, convenience variable}
10699 The variable @code{$_} is automatically set by the @code{x} command to
10700 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10701 commands which provide a default address for @code{x} to examine also
10702 set @code{$_} to that address; these commands include @code{info line}
10703 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10704 except when set by the @code{x} command, in which case it is a pointer
10705 to the type of @code{$__}.
10707 @vindex $__@r{, convenience variable}
10709 The variable @code{$__} is automatically set by the @code{x} command
10710 to the value found in the last address examined. Its type is chosen
10711 to match the format in which the data was printed.
10714 @vindex $_exitcode@r{, convenience variable}
10715 When the program being debugged terminates normally, @value{GDBN}
10716 automatically sets this variable to the exit code of the program, and
10717 resets @code{$_exitsignal} to @code{void}.
10720 @vindex $_exitsignal@r{, convenience variable}
10721 When the program being debugged dies due to an uncaught signal,
10722 @value{GDBN} automatically sets this variable to that signal's number,
10723 and resets @code{$_exitcode} to @code{void}.
10725 To distinguish between whether the program being debugged has exited
10726 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10727 @code{$_exitsignal} is not @code{void}), the convenience function
10728 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10729 Functions}). For example, considering the following source code:
10732 #include <signal.h>
10735 main (int argc, char *argv[])
10742 A valid way of telling whether the program being debugged has exited
10743 or signalled would be:
10746 (@value{GDBP}) define has_exited_or_signalled
10747 Type commands for definition of ``has_exited_or_signalled''.
10748 End with a line saying just ``end''.
10749 >if $_isvoid ($_exitsignal)
10750 >echo The program has exited\n
10752 >echo The program has signalled\n
10758 Program terminated with signal SIGALRM, Alarm clock.
10759 The program no longer exists.
10760 (@value{GDBP}) has_exited_or_signalled
10761 The program has signalled
10764 As can be seen, @value{GDBN} correctly informs that the program being
10765 debugged has signalled, since it calls @code{raise} and raises a
10766 @code{SIGALRM} signal. If the program being debugged had not called
10767 @code{raise}, then @value{GDBN} would report a normal exit:
10770 (@value{GDBP}) has_exited_or_signalled
10771 The program has exited
10775 The variable @code{$_exception} is set to the exception object being
10776 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10779 @itemx $_probe_arg0@dots{}$_probe_arg11
10780 Arguments to a static probe. @xref{Static Probe Points}.
10783 @vindex $_sdata@r{, inspect, convenience variable}
10784 The variable @code{$_sdata} contains extra collected static tracepoint
10785 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10786 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10787 if extra static tracepoint data has not been collected.
10790 @vindex $_siginfo@r{, convenience variable}
10791 The variable @code{$_siginfo} contains extra signal information
10792 (@pxref{extra signal information}). Note that @code{$_siginfo}
10793 could be empty, if the application has not yet received any signals.
10794 For example, it will be empty before you execute the @code{run} command.
10797 @vindex $_tlb@r{, convenience variable}
10798 The variable @code{$_tlb} is automatically set when debugging
10799 applications running on MS-Windows in native mode or connected to
10800 gdbserver that supports the @code{qGetTIBAddr} request.
10801 @xref{General Query Packets}.
10802 This variable contains the address of the thread information block.
10805 The number of the current inferior. @xref{Inferiors and
10806 Programs, ,Debugging Multiple Inferiors and Programs}.
10809 The thread number of the current thread. @xref{thread numbers}.
10812 The global number of the current thread. @xref{global thread numbers}.
10816 @node Convenience Funs
10817 @section Convenience Functions
10819 @cindex convenience functions
10820 @value{GDBN} also supplies some @dfn{convenience functions}. These
10821 have a syntax similar to convenience variables. A convenience
10822 function can be used in an expression just like an ordinary function;
10823 however, a convenience function is implemented internally to
10826 These functions do not require @value{GDBN} to be configured with
10827 @code{Python} support, which means that they are always available.
10831 @item $_isvoid (@var{expr})
10832 @findex $_isvoid@r{, convenience function}
10833 Return one if the expression @var{expr} is @code{void}. Otherwise it
10836 A @code{void} expression is an expression where the type of the result
10837 is @code{void}. For example, you can examine a convenience variable
10838 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10842 (@value{GDBP}) print $_exitcode
10844 (@value{GDBP}) print $_isvoid ($_exitcode)
10847 Starting program: ./a.out
10848 [Inferior 1 (process 29572) exited normally]
10849 (@value{GDBP}) print $_exitcode
10851 (@value{GDBP}) print $_isvoid ($_exitcode)
10855 In the example above, we used @code{$_isvoid} to check whether
10856 @code{$_exitcode} is @code{void} before and after the execution of the
10857 program being debugged. Before the execution there is no exit code to
10858 be examined, therefore @code{$_exitcode} is @code{void}. After the
10859 execution the program being debugged returned zero, therefore
10860 @code{$_exitcode} is zero, which means that it is not @code{void}
10863 The @code{void} expression can also be a call of a function from the
10864 program being debugged. For example, given the following function:
10873 The result of calling it inside @value{GDBN} is @code{void}:
10876 (@value{GDBP}) print foo ()
10878 (@value{GDBP}) print $_isvoid (foo ())
10880 (@value{GDBP}) set $v = foo ()
10881 (@value{GDBP}) print $v
10883 (@value{GDBP}) print $_isvoid ($v)
10889 These functions require @value{GDBN} to be configured with
10890 @code{Python} support.
10894 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10895 @findex $_memeq@r{, convenience function}
10896 Returns one if the @var{length} bytes at the addresses given by
10897 @var{buf1} and @var{buf2} are equal.
10898 Otherwise it returns zero.
10900 @item $_regex(@var{str}, @var{regex})
10901 @findex $_regex@r{, convenience function}
10902 Returns one if the string @var{str} matches the regular expression
10903 @var{regex}. Otherwise it returns zero.
10904 The syntax of the regular expression is that specified by @code{Python}'s
10905 regular expression support.
10907 @item $_streq(@var{str1}, @var{str2})
10908 @findex $_streq@r{, convenience function}
10909 Returns one if the strings @var{str1} and @var{str2} are equal.
10910 Otherwise it returns zero.
10912 @item $_strlen(@var{str})
10913 @findex $_strlen@r{, convenience function}
10914 Returns the length of string @var{str}.
10916 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10917 @findex $_caller_is@r{, convenience function}
10918 Returns one if the calling function's name is equal to @var{name}.
10919 Otherwise it returns zero.
10921 If the optional argument @var{number_of_frames} is provided,
10922 it is the number of frames up in the stack to look.
10930 at testsuite/gdb.python/py-caller-is.c:21
10931 #1 0x00000000004005a0 in middle_func ()
10932 at testsuite/gdb.python/py-caller-is.c:27
10933 #2 0x00000000004005ab in top_func ()
10934 at testsuite/gdb.python/py-caller-is.c:33
10935 #3 0x00000000004005b6 in main ()
10936 at testsuite/gdb.python/py-caller-is.c:39
10937 (gdb) print $_caller_is ("middle_func")
10939 (gdb) print $_caller_is ("top_func", 2)
10943 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10944 @findex $_caller_matches@r{, convenience function}
10945 Returns one if the calling function's name matches the regular expression
10946 @var{regexp}. Otherwise it returns zero.
10948 If the optional argument @var{number_of_frames} is provided,
10949 it is the number of frames up in the stack to look.
10952 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10953 @findex $_any_caller_is@r{, convenience function}
10954 Returns one if any calling function's name is equal to @var{name}.
10955 Otherwise it returns zero.
10957 If the optional argument @var{number_of_frames} is provided,
10958 it is the number of frames up in the stack to look.
10961 This function differs from @code{$_caller_is} in that this function
10962 checks all stack frames from the immediate caller to the frame specified
10963 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10964 frame specified by @var{number_of_frames}.
10966 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10967 @findex $_any_caller_matches@r{, convenience function}
10968 Returns one if any calling function's name matches the regular expression
10969 @var{regexp}. Otherwise it returns zero.
10971 If the optional argument @var{number_of_frames} is provided,
10972 it is the number of frames up in the stack to look.
10975 This function differs from @code{$_caller_matches} in that this function
10976 checks all stack frames from the immediate caller to the frame specified
10977 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10978 frame specified by @var{number_of_frames}.
10980 @item $_as_string(@var{value})
10981 @findex $_as_string@r{, convenience function}
10982 Return the string representation of @var{value}.
10984 This function is useful to obtain the textual label (enumerator) of an
10985 enumeration value. For example, assuming the variable @var{node} is of
10986 an enumerated type:
10989 (gdb) printf "Visiting node of type %s\n", $_as_string(node)
10990 Visiting node of type NODE_INTEGER
10995 @value{GDBN} provides the ability to list and get help on
10996 convenience functions.
10999 @item help function
11000 @kindex help function
11001 @cindex show all convenience functions
11002 Print a list of all convenience functions.
11009 You can refer to machine register contents, in expressions, as variables
11010 with names starting with @samp{$}. The names of registers are different
11011 for each machine; use @code{info registers} to see the names used on
11015 @kindex info registers
11016 @item info registers
11017 Print the names and values of all registers except floating-point
11018 and vector registers (in the selected stack frame).
11020 @kindex info all-registers
11021 @cindex floating point registers
11022 @item info all-registers
11023 Print the names and values of all registers, including floating-point
11024 and vector registers (in the selected stack frame).
11026 @item info registers @var{reggroup} @dots{}
11027 Print the name and value of the registers in each of the specified
11028 @var{reggroup}s. The @var{reggoup} can be any of those returned by
11029 @code{maint print reggroups} (@pxref{Maintenance Commands}).
11031 @item info registers @var{regname} @dots{}
11032 Print the @dfn{relativized} value of each specified register @var{regname}.
11033 As discussed in detail below, register values are normally relative to
11034 the selected stack frame. The @var{regname} may be any register name valid on
11035 the machine you are using, with or without the initial @samp{$}.
11038 @anchor{standard registers}
11039 @cindex stack pointer register
11040 @cindex program counter register
11041 @cindex process status register
11042 @cindex frame pointer register
11043 @cindex standard registers
11044 @value{GDBN} has four ``standard'' register names that are available (in
11045 expressions) on most machines---whenever they do not conflict with an
11046 architecture's canonical mnemonics for registers. The register names
11047 @code{$pc} and @code{$sp} are used for the program counter register and
11048 the stack pointer. @code{$fp} is used for a register that contains a
11049 pointer to the current stack frame, and @code{$ps} is used for a
11050 register that contains the processor status. For example,
11051 you could print the program counter in hex with
11058 or print the instruction to be executed next with
11065 or add four to the stack pointer@footnote{This is a way of removing
11066 one word from the stack, on machines where stacks grow downward in
11067 memory (most machines, nowadays). This assumes that the innermost
11068 stack frame is selected; setting @code{$sp} is not allowed when other
11069 stack frames are selected. To pop entire frames off the stack,
11070 regardless of machine architecture, use @code{return};
11071 see @ref{Returning, ,Returning from a Function}.} with
11077 Whenever possible, these four standard register names are available on
11078 your machine even though the machine has different canonical mnemonics,
11079 so long as there is no conflict. The @code{info registers} command
11080 shows the canonical names. For example, on the SPARC, @code{info
11081 registers} displays the processor status register as @code{$psr} but you
11082 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
11083 is an alias for the @sc{eflags} register.
11085 @value{GDBN} always considers the contents of an ordinary register as an
11086 integer when the register is examined in this way. Some machines have
11087 special registers which can hold nothing but floating point; these
11088 registers are considered to have floating point values. There is no way
11089 to refer to the contents of an ordinary register as floating point value
11090 (although you can @emph{print} it as a floating point value with
11091 @samp{print/f $@var{regname}}).
11093 Some registers have distinct ``raw'' and ``virtual'' data formats. This
11094 means that the data format in which the register contents are saved by
11095 the operating system is not the same one that your program normally
11096 sees. For example, the registers of the 68881 floating point
11097 coprocessor are always saved in ``extended'' (raw) format, but all C
11098 programs expect to work with ``double'' (virtual) format. In such
11099 cases, @value{GDBN} normally works with the virtual format only (the format
11100 that makes sense for your program), but the @code{info registers} command
11101 prints the data in both formats.
11103 @cindex SSE registers (x86)
11104 @cindex MMX registers (x86)
11105 Some machines have special registers whose contents can be interpreted
11106 in several different ways. For example, modern x86-based machines
11107 have SSE and MMX registers that can hold several values packed
11108 together in several different formats. @value{GDBN} refers to such
11109 registers in @code{struct} notation:
11112 (@value{GDBP}) print $xmm1
11114 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
11115 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
11116 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
11117 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
11118 v4_int32 = @{0, 20657912, 11, 13@},
11119 v2_int64 = @{88725056443645952, 55834574859@},
11120 uint128 = 0x0000000d0000000b013b36f800000000
11125 To set values of such registers, you need to tell @value{GDBN} which
11126 view of the register you wish to change, as if you were assigning
11127 value to a @code{struct} member:
11130 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
11133 Normally, register values are relative to the selected stack frame
11134 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
11135 value that the register would contain if all stack frames farther in
11136 were exited and their saved registers restored. In order to see the
11137 true contents of hardware registers, you must select the innermost
11138 frame (with @samp{frame 0}).
11140 @cindex caller-saved registers
11141 @cindex call-clobbered registers
11142 @cindex volatile registers
11143 @cindex <not saved> values
11144 Usually ABIs reserve some registers as not needed to be saved by the
11145 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
11146 registers). It may therefore not be possible for @value{GDBN} to know
11147 the value a register had before the call (in other words, in the outer
11148 frame), if the register value has since been changed by the callee.
11149 @value{GDBN} tries to deduce where the inner frame saved
11150 (``callee-saved'') registers, from the debug info, unwind info, or the
11151 machine code generated by your compiler. If some register is not
11152 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
11153 its own knowledge of the ABI, or because the debug/unwind info
11154 explicitly says the register's value is undefined), @value{GDBN}
11155 displays @w{@samp{<not saved>}} as the register's value. With targets
11156 that @value{GDBN} has no knowledge of the register saving convention,
11157 if a register was not saved by the callee, then its value and location
11158 in the outer frame are assumed to be the same of the inner frame.
11159 This is usually harmless, because if the register is call-clobbered,
11160 the caller either does not care what is in the register after the
11161 call, or has code to restore the value that it does care about. Note,
11162 however, that if you change such a register in the outer frame, you
11163 may also be affecting the inner frame. Also, the more ``outer'' the
11164 frame is you're looking at, the more likely a call-clobbered
11165 register's value is to be wrong, in the sense that it doesn't actually
11166 represent the value the register had just before the call.
11168 @node Floating Point Hardware
11169 @section Floating Point Hardware
11170 @cindex floating point
11172 Depending on the configuration, @value{GDBN} may be able to give
11173 you more information about the status of the floating point hardware.
11178 Display hardware-dependent information about the floating
11179 point unit. The exact contents and layout vary depending on the
11180 floating point chip. Currently, @samp{info float} is supported on
11181 the ARM and x86 machines.
11185 @section Vector Unit
11186 @cindex vector unit
11188 Depending on the configuration, @value{GDBN} may be able to give you
11189 more information about the status of the vector unit.
11192 @kindex info vector
11194 Display information about the vector unit. The exact contents and
11195 layout vary depending on the hardware.
11198 @node OS Information
11199 @section Operating System Auxiliary Information
11200 @cindex OS information
11202 @value{GDBN} provides interfaces to useful OS facilities that can help
11203 you debug your program.
11205 @cindex auxiliary vector
11206 @cindex vector, auxiliary
11207 Some operating systems supply an @dfn{auxiliary vector} to programs at
11208 startup. This is akin to the arguments and environment that you
11209 specify for a program, but contains a system-dependent variety of
11210 binary values that tell system libraries important details about the
11211 hardware, operating system, and process. Each value's purpose is
11212 identified by an integer tag; the meanings are well-known but system-specific.
11213 Depending on the configuration and operating system facilities,
11214 @value{GDBN} may be able to show you this information. For remote
11215 targets, this functionality may further depend on the remote stub's
11216 support of the @samp{qXfer:auxv:read} packet, see
11217 @ref{qXfer auxiliary vector read}.
11222 Display the auxiliary vector of the inferior, which can be either a
11223 live process or a core dump file. @value{GDBN} prints each tag value
11224 numerically, and also shows names and text descriptions for recognized
11225 tags. Some values in the vector are numbers, some bit masks, and some
11226 pointers to strings or other data. @value{GDBN} displays each value in the
11227 most appropriate form for a recognized tag, and in hexadecimal for
11228 an unrecognized tag.
11231 On some targets, @value{GDBN} can access operating system-specific
11232 information and show it to you. The types of information available
11233 will differ depending on the type of operating system running on the
11234 target. The mechanism used to fetch the data is described in
11235 @ref{Operating System Information}. For remote targets, this
11236 functionality depends on the remote stub's support of the
11237 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
11241 @item info os @var{infotype}
11243 Display OS information of the requested type.
11245 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
11247 @anchor{linux info os infotypes}
11249 @kindex info os cpus
11251 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
11252 the available fields from /proc/cpuinfo. For each supported architecture
11253 different fields are available. Two common entries are processor which gives
11254 CPU number and bogomips; a system constant that is calculated during
11255 kernel initialization.
11257 @kindex info os files
11259 Display the list of open file descriptors on the target. For each
11260 file descriptor, @value{GDBN} prints the identifier of the process
11261 owning the descriptor, the command of the owning process, the value
11262 of the descriptor, and the target of the descriptor.
11264 @kindex info os modules
11266 Display the list of all loaded kernel modules on the target. For each
11267 module, @value{GDBN} prints the module name, the size of the module in
11268 bytes, the number of times the module is used, the dependencies of the
11269 module, the status of the module, and the address of the loaded module
11272 @kindex info os msg
11274 Display the list of all System V message queues on the target. For each
11275 message queue, @value{GDBN} prints the message queue key, the message
11276 queue identifier, the access permissions, the current number of bytes
11277 on the queue, the current number of messages on the queue, the processes
11278 that last sent and received a message on the queue, the user and group
11279 of the owner and creator of the message queue, the times at which a
11280 message was last sent and received on the queue, and the time at which
11281 the message queue was last changed.
11283 @kindex info os processes
11285 Display the list of processes on the target. For each process,
11286 @value{GDBN} prints the process identifier, the name of the user, the
11287 command corresponding to the process, and the list of processor cores
11288 that the process is currently running on. (To understand what these
11289 properties mean, for this and the following info types, please consult
11290 the general @sc{gnu}/Linux documentation.)
11292 @kindex info os procgroups
11294 Display the list of process groups on the target. For each process,
11295 @value{GDBN} prints the identifier of the process group that it belongs
11296 to, the command corresponding to the process group leader, the process
11297 identifier, and the command line of the process. The list is sorted
11298 first by the process group identifier, then by the process identifier,
11299 so that processes belonging to the same process group are grouped together
11300 and the process group leader is listed first.
11302 @kindex info os semaphores
11304 Display the list of all System V semaphore sets on the target. For each
11305 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
11306 set identifier, the access permissions, the number of semaphores in the
11307 set, the user and group of the owner and creator of the semaphore set,
11308 and the times at which the semaphore set was operated upon and changed.
11310 @kindex info os shm
11312 Display the list of all System V shared-memory regions on the target.
11313 For each shared-memory region, @value{GDBN} prints the region key,
11314 the shared-memory identifier, the access permissions, the size of the
11315 region, the process that created the region, the process that last
11316 attached to or detached from the region, the current number of live
11317 attaches to the region, and the times at which the region was last
11318 attached to, detach from, and changed.
11320 @kindex info os sockets
11322 Display the list of Internet-domain sockets on the target. For each
11323 socket, @value{GDBN} prints the address and port of the local and
11324 remote endpoints, the current state of the connection, the creator of
11325 the socket, the IP address family of the socket, and the type of the
11328 @kindex info os threads
11330 Display the list of threads running on the target. For each thread,
11331 @value{GDBN} prints the identifier of the process that the thread
11332 belongs to, the command of the process, the thread identifier, and the
11333 processor core that it is currently running on. The main thread of a
11334 process is not listed.
11338 If @var{infotype} is omitted, then list the possible values for
11339 @var{infotype} and the kind of OS information available for each
11340 @var{infotype}. If the target does not return a list of possible
11341 types, this command will report an error.
11344 @node Memory Region Attributes
11345 @section Memory Region Attributes
11346 @cindex memory region attributes
11348 @dfn{Memory region attributes} allow you to describe special handling
11349 required by regions of your target's memory. @value{GDBN} uses
11350 attributes to determine whether to allow certain types of memory
11351 accesses; whether to use specific width accesses; and whether to cache
11352 target memory. By default the description of memory regions is
11353 fetched from the target (if the current target supports this), but the
11354 user can override the fetched regions.
11356 Defined memory regions can be individually enabled and disabled. When a
11357 memory region is disabled, @value{GDBN} uses the default attributes when
11358 accessing memory in that region. Similarly, if no memory regions have
11359 been defined, @value{GDBN} uses the default attributes when accessing
11362 When a memory region is defined, it is given a number to identify it;
11363 to enable, disable, or remove a memory region, you specify that number.
11367 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
11368 Define a memory region bounded by @var{lower} and @var{upper} with
11369 attributes @var{attributes}@dots{}, and add it to the list of regions
11370 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
11371 case: it is treated as the target's maximum memory address.
11372 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
11375 Discard any user changes to the memory regions and use target-supplied
11376 regions, if available, or no regions if the target does not support.
11379 @item delete mem @var{nums}@dots{}
11380 Remove memory regions @var{nums}@dots{} from the list of regions
11381 monitored by @value{GDBN}.
11383 @kindex disable mem
11384 @item disable mem @var{nums}@dots{}
11385 Disable monitoring of memory regions @var{nums}@dots{}.
11386 A disabled memory region is not forgotten.
11387 It may be enabled again later.
11390 @item enable mem @var{nums}@dots{}
11391 Enable monitoring of memory regions @var{nums}@dots{}.
11395 Print a table of all defined memory regions, with the following columns
11399 @item Memory Region Number
11400 @item Enabled or Disabled.
11401 Enabled memory regions are marked with @samp{y}.
11402 Disabled memory regions are marked with @samp{n}.
11405 The address defining the inclusive lower bound of the memory region.
11408 The address defining the exclusive upper bound of the memory region.
11411 The list of attributes set for this memory region.
11416 @subsection Attributes
11418 @subsubsection Memory Access Mode
11419 The access mode attributes set whether @value{GDBN} may make read or
11420 write accesses to a memory region.
11422 While these attributes prevent @value{GDBN} from performing invalid
11423 memory accesses, they do nothing to prevent the target system, I/O DMA,
11424 etc.@: from accessing memory.
11428 Memory is read only.
11430 Memory is write only.
11432 Memory is read/write. This is the default.
11435 @subsubsection Memory Access Size
11436 The access size attribute tells @value{GDBN} to use specific sized
11437 accesses in the memory region. Often memory mapped device registers
11438 require specific sized accesses. If no access size attribute is
11439 specified, @value{GDBN} may use accesses of any size.
11443 Use 8 bit memory accesses.
11445 Use 16 bit memory accesses.
11447 Use 32 bit memory accesses.
11449 Use 64 bit memory accesses.
11452 @c @subsubsection Hardware/Software Breakpoints
11453 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11454 @c will use hardware or software breakpoints for the internal breakpoints
11455 @c used by the step, next, finish, until, etc. commands.
11459 @c Always use hardware breakpoints
11460 @c @item swbreak (default)
11463 @subsubsection Data Cache
11464 The data cache attributes set whether @value{GDBN} will cache target
11465 memory. While this generally improves performance by reducing debug
11466 protocol overhead, it can lead to incorrect results because @value{GDBN}
11467 does not know about volatile variables or memory mapped device
11472 Enable @value{GDBN} to cache target memory.
11474 Disable @value{GDBN} from caching target memory. This is the default.
11477 @subsection Memory Access Checking
11478 @value{GDBN} can be instructed to refuse accesses to memory that is
11479 not explicitly described. This can be useful if accessing such
11480 regions has undesired effects for a specific target, or to provide
11481 better error checking. The following commands control this behaviour.
11484 @kindex set mem inaccessible-by-default
11485 @item set mem inaccessible-by-default [on|off]
11486 If @code{on} is specified, make @value{GDBN} treat memory not
11487 explicitly described by the memory ranges as non-existent and refuse accesses
11488 to such memory. The checks are only performed if there's at least one
11489 memory range defined. If @code{off} is specified, make @value{GDBN}
11490 treat the memory not explicitly described by the memory ranges as RAM.
11491 The default value is @code{on}.
11492 @kindex show mem inaccessible-by-default
11493 @item show mem inaccessible-by-default
11494 Show the current handling of accesses to unknown memory.
11498 @c @subsubsection Memory Write Verification
11499 @c The memory write verification attributes set whether @value{GDBN}
11500 @c will re-reads data after each write to verify the write was successful.
11504 @c @item noverify (default)
11507 @node Dump/Restore Files
11508 @section Copy Between Memory and a File
11509 @cindex dump/restore files
11510 @cindex append data to a file
11511 @cindex dump data to a file
11512 @cindex restore data from a file
11514 You can use the commands @code{dump}, @code{append}, and
11515 @code{restore} to copy data between target memory and a file. The
11516 @code{dump} and @code{append} commands write data to a file, and the
11517 @code{restore} command reads data from a file back into the inferior's
11518 memory. Files may be in binary, Motorola S-record, Intel hex,
11519 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11520 append to binary files, and cannot read from Verilog Hex files.
11525 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11526 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11527 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11528 or the value of @var{expr}, to @var{filename} in the given format.
11530 The @var{format} parameter may be any one of:
11537 Motorola S-record format.
11539 Tektronix Hex format.
11541 Verilog Hex format.
11544 @value{GDBN} uses the same definitions of these formats as the
11545 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11546 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11550 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11551 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11552 Append the contents of memory from @var{start_addr} to @var{end_addr},
11553 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11554 (@value{GDBN} can only append data to files in raw binary form.)
11557 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11558 Restore the contents of file @var{filename} into memory. The
11559 @code{restore} command can automatically recognize any known @sc{bfd}
11560 file format, except for raw binary. To restore a raw binary file you
11561 must specify the optional keyword @code{binary} after the filename.
11563 If @var{bias} is non-zero, its value will be added to the addresses
11564 contained in the file. Binary files always start at address zero, so
11565 they will be restored at address @var{bias}. Other bfd files have
11566 a built-in location; they will be restored at offset @var{bias}
11567 from that location.
11569 If @var{start} and/or @var{end} are non-zero, then only data between
11570 file offset @var{start} and file offset @var{end} will be restored.
11571 These offsets are relative to the addresses in the file, before
11572 the @var{bias} argument is applied.
11576 @node Core File Generation
11577 @section How to Produce a Core File from Your Program
11578 @cindex dump core from inferior
11580 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11581 image of a running process and its process status (register values
11582 etc.). Its primary use is post-mortem debugging of a program that
11583 crashed while it ran outside a debugger. A program that crashes
11584 automatically produces a core file, unless this feature is disabled by
11585 the user. @xref{Files}, for information on invoking @value{GDBN} in
11586 the post-mortem debugging mode.
11588 Occasionally, you may wish to produce a core file of the program you
11589 are debugging in order to preserve a snapshot of its state.
11590 @value{GDBN} has a special command for that.
11594 @kindex generate-core-file
11595 @item generate-core-file [@var{file}]
11596 @itemx gcore [@var{file}]
11597 Produce a core dump of the inferior process. The optional argument
11598 @var{file} specifies the file name where to put the core dump. If not
11599 specified, the file name defaults to @file{core.@var{pid}}, where
11600 @var{pid} is the inferior process ID.
11602 Note that this command is implemented only for some systems (as of
11603 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11605 On @sc{gnu}/Linux, this command can take into account the value of the
11606 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11607 dump (@pxref{set use-coredump-filter}), and by default honors the
11608 @code{VM_DONTDUMP} flag for mappings where it is present in the file
11609 @file{/proc/@var{pid}/smaps} (@pxref{set dump-excluded-mappings}).
11611 @kindex set use-coredump-filter
11612 @anchor{set use-coredump-filter}
11613 @item set use-coredump-filter on
11614 @itemx set use-coredump-filter off
11615 Enable or disable the use of the file
11616 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11617 files. This file is used by the Linux kernel to decide what types of
11618 memory mappings will be dumped or ignored when generating a core dump
11619 file. @var{pid} is the process ID of a currently running process.
11621 To make use of this feature, you have to write in the
11622 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11623 which is a bit mask representing the memory mapping types. If a bit
11624 is set in the bit mask, then the memory mappings of the corresponding
11625 types will be dumped; otherwise, they will be ignored. This
11626 configuration is inherited by child processes. For more information
11627 about the bits that can be set in the
11628 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11629 manpage of @code{core(5)}.
11631 By default, this option is @code{on}. If this option is turned
11632 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11633 and instead uses the same default value as the Linux kernel in order
11634 to decide which pages will be dumped in the core dump file. This
11635 value is currently @code{0x33}, which means that bits @code{0}
11636 (anonymous private mappings), @code{1} (anonymous shared mappings),
11637 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11638 This will cause these memory mappings to be dumped automatically.
11640 @kindex set dump-excluded-mappings
11641 @anchor{set dump-excluded-mappings}
11642 @item set dump-excluded-mappings on
11643 @itemx set dump-excluded-mappings off
11644 If @code{on} is specified, @value{GDBN} will dump memory mappings
11645 marked with the @code{VM_DONTDUMP} flag. This flag is represented in
11646 the file @file{/proc/@var{pid}/smaps} with the acronym @code{dd}.
11648 The default value is @code{off}.
11651 @node Character Sets
11652 @section Character Sets
11653 @cindex character sets
11655 @cindex translating between character sets
11656 @cindex host character set
11657 @cindex target character set
11659 If the program you are debugging uses a different character set to
11660 represent characters and strings than the one @value{GDBN} uses itself,
11661 @value{GDBN} can automatically translate between the character sets for
11662 you. The character set @value{GDBN} uses we call the @dfn{host
11663 character set}; the one the inferior program uses we call the
11664 @dfn{target character set}.
11666 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11667 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11668 remote protocol (@pxref{Remote Debugging}) to debug a program
11669 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11670 then the host character set is Latin-1, and the target character set is
11671 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11672 target-charset EBCDIC-US}, then @value{GDBN} translates between
11673 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11674 character and string literals in expressions.
11676 @value{GDBN} has no way to automatically recognize which character set
11677 the inferior program uses; you must tell it, using the @code{set
11678 target-charset} command, described below.
11680 Here are the commands for controlling @value{GDBN}'s character set
11684 @item set target-charset @var{charset}
11685 @kindex set target-charset
11686 Set the current target character set to @var{charset}. To display the
11687 list of supported target character sets, type
11688 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11690 @item set host-charset @var{charset}
11691 @kindex set host-charset
11692 Set the current host character set to @var{charset}.
11694 By default, @value{GDBN} uses a host character set appropriate to the
11695 system it is running on; you can override that default using the
11696 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11697 automatically determine the appropriate host character set. In this
11698 case, @value{GDBN} uses @samp{UTF-8}.
11700 @value{GDBN} can only use certain character sets as its host character
11701 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11702 @value{GDBN} will list the host character sets it supports.
11704 @item set charset @var{charset}
11705 @kindex set charset
11706 Set the current host and target character sets to @var{charset}. As
11707 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11708 @value{GDBN} will list the names of the character sets that can be used
11709 for both host and target.
11712 @kindex show charset
11713 Show the names of the current host and target character sets.
11715 @item show host-charset
11716 @kindex show host-charset
11717 Show the name of the current host character set.
11719 @item show target-charset
11720 @kindex show target-charset
11721 Show the name of the current target character set.
11723 @item set target-wide-charset @var{charset}
11724 @kindex set target-wide-charset
11725 Set the current target's wide character set to @var{charset}. This is
11726 the character set used by the target's @code{wchar_t} type. To
11727 display the list of supported wide character sets, type
11728 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11730 @item show target-wide-charset
11731 @kindex show target-wide-charset
11732 Show the name of the current target's wide character set.
11735 Here is an example of @value{GDBN}'s character set support in action.
11736 Assume that the following source code has been placed in the file
11737 @file{charset-test.c}:
11743 = @{72, 101, 108, 108, 111, 44, 32, 119,
11744 111, 114, 108, 100, 33, 10, 0@};
11745 char ibm1047_hello[]
11746 = @{200, 133, 147, 147, 150, 107, 64, 166,
11747 150, 153, 147, 132, 90, 37, 0@};
11751 printf ("Hello, world!\n");
11755 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11756 containing the string @samp{Hello, world!} followed by a newline,
11757 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11759 We compile the program, and invoke the debugger on it:
11762 $ gcc -g charset-test.c -o charset-test
11763 $ gdb -nw charset-test
11764 GNU gdb 2001-12-19-cvs
11765 Copyright 2001 Free Software Foundation, Inc.
11770 We can use the @code{show charset} command to see what character sets
11771 @value{GDBN} is currently using to interpret and display characters and
11775 (@value{GDBP}) show charset
11776 The current host and target character set is `ISO-8859-1'.
11780 For the sake of printing this manual, let's use @sc{ascii} as our
11781 initial character set:
11783 (@value{GDBP}) set charset ASCII
11784 (@value{GDBP}) show charset
11785 The current host and target character set is `ASCII'.
11789 Let's assume that @sc{ascii} is indeed the correct character set for our
11790 host system --- in other words, let's assume that if @value{GDBN} prints
11791 characters using the @sc{ascii} character set, our terminal will display
11792 them properly. Since our current target character set is also
11793 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11796 (@value{GDBP}) print ascii_hello
11797 $1 = 0x401698 "Hello, world!\n"
11798 (@value{GDBP}) print ascii_hello[0]
11803 @value{GDBN} uses the target character set for character and string
11804 literals you use in expressions:
11807 (@value{GDBP}) print '+'
11812 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11815 @value{GDBN} relies on the user to tell it which character set the
11816 target program uses. If we print @code{ibm1047_hello} while our target
11817 character set is still @sc{ascii}, we get jibberish:
11820 (@value{GDBP}) print ibm1047_hello
11821 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11822 (@value{GDBP}) print ibm1047_hello[0]
11827 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11828 @value{GDBN} tells us the character sets it supports:
11831 (@value{GDBP}) set target-charset
11832 ASCII EBCDIC-US IBM1047 ISO-8859-1
11833 (@value{GDBP}) set target-charset
11836 We can select @sc{ibm1047} as our target character set, and examine the
11837 program's strings again. Now the @sc{ascii} string is wrong, but
11838 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11839 target character set, @sc{ibm1047}, to the host character set,
11840 @sc{ascii}, and they display correctly:
11843 (@value{GDBP}) set target-charset IBM1047
11844 (@value{GDBP}) show charset
11845 The current host character set is `ASCII'.
11846 The current target character set is `IBM1047'.
11847 (@value{GDBP}) print ascii_hello
11848 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11849 (@value{GDBP}) print ascii_hello[0]
11851 (@value{GDBP}) print ibm1047_hello
11852 $8 = 0x4016a8 "Hello, world!\n"
11853 (@value{GDBP}) print ibm1047_hello[0]
11858 As above, @value{GDBN} uses the target character set for character and
11859 string literals you use in expressions:
11862 (@value{GDBP}) print '+'
11867 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11870 @node Caching Target Data
11871 @section Caching Data of Targets
11872 @cindex caching data of targets
11874 @value{GDBN} caches data exchanged between the debugger and a target.
11875 Each cache is associated with the address space of the inferior.
11876 @xref{Inferiors and Programs}, about inferior and address space.
11877 Such caching generally improves performance in remote debugging
11878 (@pxref{Remote Debugging}), because it reduces the overhead of the
11879 remote protocol by bundling memory reads and writes into large chunks.
11880 Unfortunately, simply caching everything would lead to incorrect results,
11881 since @value{GDBN} does not necessarily know anything about volatile
11882 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11883 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11885 Therefore, by default, @value{GDBN} only caches data
11886 known to be on the stack@footnote{In non-stop mode, it is moderately
11887 rare for a running thread to modify the stack of a stopped thread
11888 in a way that would interfere with a backtrace, and caching of
11889 stack reads provides a significant speed up of remote backtraces.} or
11890 in the code segment.
11891 Other regions of memory can be explicitly marked as
11892 cacheable; @pxref{Memory Region Attributes}.
11895 @kindex set remotecache
11896 @item set remotecache on
11897 @itemx set remotecache off
11898 This option no longer does anything; it exists for compatibility
11901 @kindex show remotecache
11902 @item show remotecache
11903 Show the current state of the obsolete remotecache flag.
11905 @kindex set stack-cache
11906 @item set stack-cache on
11907 @itemx set stack-cache off
11908 Enable or disable caching of stack accesses. When @code{on}, use
11909 caching. By default, this option is @code{on}.
11911 @kindex show stack-cache
11912 @item show stack-cache
11913 Show the current state of data caching for memory accesses.
11915 @kindex set code-cache
11916 @item set code-cache on
11917 @itemx set code-cache off
11918 Enable or disable caching of code segment accesses. When @code{on},
11919 use caching. By default, this option is @code{on}. This improves
11920 performance of disassembly in remote debugging.
11922 @kindex show code-cache
11923 @item show code-cache
11924 Show the current state of target memory cache for code segment
11927 @kindex info dcache
11928 @item info dcache @r{[}line@r{]}
11929 Print the information about the performance of data cache of the
11930 current inferior's address space. The information displayed
11931 includes the dcache width and depth, and for each cache line, its
11932 number, address, and how many times it was referenced. This
11933 command is useful for debugging the data cache operation.
11935 If a line number is specified, the contents of that line will be
11938 @item set dcache size @var{size}
11939 @cindex dcache size
11940 @kindex set dcache size
11941 Set maximum number of entries in dcache (dcache depth above).
11943 @item set dcache line-size @var{line-size}
11944 @cindex dcache line-size
11945 @kindex set dcache line-size
11946 Set number of bytes each dcache entry caches (dcache width above).
11947 Must be a power of 2.
11949 @item show dcache size
11950 @kindex show dcache size
11951 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11953 @item show dcache line-size
11954 @kindex show dcache line-size
11955 Show default size of dcache lines.
11959 @node Searching Memory
11960 @section Search Memory
11961 @cindex searching memory
11963 Memory can be searched for a particular sequence of bytes with the
11964 @code{find} command.
11968 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11969 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11970 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11971 etc. The search begins at address @var{start_addr} and continues for either
11972 @var{len} bytes or through to @var{end_addr} inclusive.
11975 @var{s} and @var{n} are optional parameters.
11976 They may be specified in either order, apart or together.
11979 @item @var{s}, search query size
11980 The size of each search query value.
11986 halfwords (two bytes)
11990 giant words (eight bytes)
11993 All values are interpreted in the current language.
11994 This means, for example, that if the current source language is C/C@t{++}
11995 then searching for the string ``hello'' includes the trailing '\0'.
11996 The null terminator can be removed from searching by using casts,
11997 e.g.: @samp{@{char[5]@}"hello"}.
11999 If the value size is not specified, it is taken from the
12000 value's type in the current language.
12001 This is useful when one wants to specify the search
12002 pattern as a mixture of types.
12003 Note that this means, for example, that in the case of C-like languages
12004 a search for an untyped 0x42 will search for @samp{(int) 0x42}
12005 which is typically four bytes.
12007 @item @var{n}, maximum number of finds
12008 The maximum number of matches to print. The default is to print all finds.
12011 You can use strings as search values. Quote them with double-quotes
12013 The string value is copied into the search pattern byte by byte,
12014 regardless of the endianness of the target and the size specification.
12016 The address of each match found is printed as well as a count of the
12017 number of matches found.
12019 The address of the last value found is stored in convenience variable
12021 A count of the number of matches is stored in @samp{$numfound}.
12023 For example, if stopped at the @code{printf} in this function:
12029 static char hello[] = "hello-hello";
12030 static struct @{ char c; short s; int i; @}
12031 __attribute__ ((packed)) mixed
12032 = @{ 'c', 0x1234, 0x87654321 @};
12033 printf ("%s\n", hello);
12038 you get during debugging:
12041 (gdb) find &hello[0], +sizeof(hello), "hello"
12042 0x804956d <hello.1620+6>
12044 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
12045 0x8049567 <hello.1620>
12046 0x804956d <hello.1620+6>
12048 (gdb) find &hello[0], +sizeof(hello), @{char[5]@}"hello"
12049 0x8049567 <hello.1620>
12050 0x804956d <hello.1620+6>
12052 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
12053 0x8049567 <hello.1620>
12055 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
12056 0x8049560 <mixed.1625>
12058 (gdb) print $numfound
12061 $2 = (void *) 0x8049560
12065 @section Value Sizes
12067 Whenever @value{GDBN} prints a value memory will be allocated within
12068 @value{GDBN} to hold the contents of the value. It is possible in
12069 some languages with dynamic typing systems, that an invalid program
12070 may indicate a value that is incorrectly large, this in turn may cause
12071 @value{GDBN} to try and allocate an overly large ammount of memory.
12074 @kindex set max-value-size
12075 @item set max-value-size @var{bytes}
12076 @itemx set max-value-size unlimited
12077 Set the maximum size of memory that @value{GDBN} will allocate for the
12078 contents of a value to @var{bytes}, trying to display a value that
12079 requires more memory than that will result in an error.
12081 Setting this variable does not effect values that have already been
12082 allocated within @value{GDBN}, only future allocations.
12084 There's a minimum size that @code{max-value-size} can be set to in
12085 order that @value{GDBN} can still operate correctly, this minimum is
12086 currently 16 bytes.
12088 The limit applies to the results of some subexpressions as well as to
12089 complete expressions. For example, an expression denoting a simple
12090 integer component, such as @code{x.y.z}, may fail if the size of
12091 @var{x.y} is dynamic and exceeds @var{bytes}. On the other hand,
12092 @value{GDBN} is sometimes clever; the expression @code{A[i]}, where
12093 @var{A} is an array variable with non-constant size, will generally
12094 succeed regardless of the bounds on @var{A}, as long as the component
12095 size is less than @var{bytes}.
12097 The default value of @code{max-value-size} is currently 64k.
12099 @kindex show max-value-size
12100 @item show max-value-size
12101 Show the maximum size of memory, in bytes, that @value{GDBN} will
12102 allocate for the contents of a value.
12105 @node Optimized Code
12106 @chapter Debugging Optimized Code
12107 @cindex optimized code, debugging
12108 @cindex debugging optimized code
12110 Almost all compilers support optimization. With optimization
12111 disabled, the compiler generates assembly code that corresponds
12112 directly to your source code, in a simplistic way. As the compiler
12113 applies more powerful optimizations, the generated assembly code
12114 diverges from your original source code. With help from debugging
12115 information generated by the compiler, @value{GDBN} can map from
12116 the running program back to constructs from your original source.
12118 @value{GDBN} is more accurate with optimization disabled. If you
12119 can recompile without optimization, it is easier to follow the
12120 progress of your program during debugging. But, there are many cases
12121 where you may need to debug an optimized version.
12123 When you debug a program compiled with @samp{-g -O}, remember that the
12124 optimizer has rearranged your code; the debugger shows you what is
12125 really there. Do not be too surprised when the execution path does not
12126 exactly match your source file! An extreme example: if you define a
12127 variable, but never use it, @value{GDBN} never sees that
12128 variable---because the compiler optimizes it out of existence.
12130 Some things do not work as well with @samp{-g -O} as with just
12131 @samp{-g}, particularly on machines with instruction scheduling. If in
12132 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
12133 please report it to us as a bug (including a test case!).
12134 @xref{Variables}, for more information about debugging optimized code.
12137 * Inline Functions:: How @value{GDBN} presents inlining
12138 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
12141 @node Inline Functions
12142 @section Inline Functions
12143 @cindex inline functions, debugging
12145 @dfn{Inlining} is an optimization that inserts a copy of the function
12146 body directly at each call site, instead of jumping to a shared
12147 routine. @value{GDBN} displays inlined functions just like
12148 non-inlined functions. They appear in backtraces. You can view their
12149 arguments and local variables, step into them with @code{step}, skip
12150 them with @code{next}, and escape from them with @code{finish}.
12151 You can check whether a function was inlined by using the
12152 @code{info frame} command.
12154 For @value{GDBN} to support inlined functions, the compiler must
12155 record information about inlining in the debug information ---
12156 @value{NGCC} using the @sc{dwarf 2} format does this, and several
12157 other compilers do also. @value{GDBN} only supports inlined functions
12158 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
12159 do not emit two required attributes (@samp{DW_AT_call_file} and
12160 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
12161 function calls with earlier versions of @value{NGCC}. It instead
12162 displays the arguments and local variables of inlined functions as
12163 local variables in the caller.
12165 The body of an inlined function is directly included at its call site;
12166 unlike a non-inlined function, there are no instructions devoted to
12167 the call. @value{GDBN} still pretends that the call site and the
12168 start of the inlined function are different instructions. Stepping to
12169 the call site shows the call site, and then stepping again shows
12170 the first line of the inlined function, even though no additional
12171 instructions are executed.
12173 This makes source-level debugging much clearer; you can see both the
12174 context of the call and then the effect of the call. Only stepping by
12175 a single instruction using @code{stepi} or @code{nexti} does not do
12176 this; single instruction steps always show the inlined body.
12178 There are some ways that @value{GDBN} does not pretend that inlined
12179 function calls are the same as normal calls:
12183 Setting breakpoints at the call site of an inlined function may not
12184 work, because the call site does not contain any code. @value{GDBN}
12185 may incorrectly move the breakpoint to the next line of the enclosing
12186 function, after the call. This limitation will be removed in a future
12187 version of @value{GDBN}; until then, set a breakpoint on an earlier line
12188 or inside the inlined function instead.
12191 @value{GDBN} cannot locate the return value of inlined calls after
12192 using the @code{finish} command. This is a limitation of compiler-generated
12193 debugging information; after @code{finish}, you can step to the next line
12194 and print a variable where your program stored the return value.
12198 @node Tail Call Frames
12199 @section Tail Call Frames
12200 @cindex tail call frames, debugging
12202 Function @code{B} can call function @code{C} in its very last statement. In
12203 unoptimized compilation the call of @code{C} is immediately followed by return
12204 instruction at the end of @code{B} code. Optimizing compiler may replace the
12205 call and return in function @code{B} into one jump to function @code{C}
12206 instead. Such use of a jump instruction is called @dfn{tail call}.
12208 During execution of function @code{C}, there will be no indication in the
12209 function call stack frames that it was tail-called from @code{B}. If function
12210 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
12211 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
12212 some cases @value{GDBN} can determine that @code{C} was tail-called from
12213 @code{B}, and it will then create fictitious call frame for that, with the
12214 return address set up as if @code{B} called @code{C} normally.
12216 This functionality is currently supported only by DWARF 2 debugging format and
12217 the compiler has to produce @samp{DW_TAG_call_site} tags. With
12218 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
12221 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
12222 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
12226 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
12228 Stack level 1, frame at 0x7fffffffda30:
12229 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
12230 tail call frame, caller of frame at 0x7fffffffda30
12231 source language c++.
12232 Arglist at unknown address.
12233 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
12236 The detection of all the possible code path executions can find them ambiguous.
12237 There is no execution history stored (possible @ref{Reverse Execution} is never
12238 used for this purpose) and the last known caller could have reached the known
12239 callee by multiple different jump sequences. In such case @value{GDBN} still
12240 tries to show at least all the unambiguous top tail callers and all the
12241 unambiguous bottom tail calees, if any.
12244 @anchor{set debug entry-values}
12245 @item set debug entry-values
12246 @kindex set debug entry-values
12247 When set to on, enables printing of analysis messages for both frame argument
12248 values at function entry and tail calls. It will show all the possible valid
12249 tail calls code paths it has considered. It will also print the intersection
12250 of them with the final unambiguous (possibly partial or even empty) code path
12253 @item show debug entry-values
12254 @kindex show debug entry-values
12255 Show the current state of analysis messages printing for both frame argument
12256 values at function entry and tail calls.
12259 The analysis messages for tail calls can for example show why the virtual tail
12260 call frame for function @code{c} has not been recognized (due to the indirect
12261 reference by variable @code{x}):
12264 static void __attribute__((noinline, noclone)) c (void);
12265 void (*x) (void) = c;
12266 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12267 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
12268 int main (void) @{ x (); return 0; @}
12270 Breakpoint 1, DW_OP_entry_value resolving cannot find
12271 DW_TAG_call_site 0x40039a in main
12273 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
12276 #1 0x000000000040039a in main () at t.c:5
12279 Another possibility is an ambiguous virtual tail call frames resolution:
12283 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
12284 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
12285 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
12286 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
12287 static void __attribute__((noinline, noclone)) b (void)
12288 @{ if (i) c (); else e (); @}
12289 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
12290 int main (void) @{ a (); return 0; @}
12292 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
12293 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
12294 tailcall: reduced: 0x4004d2(a) |
12297 #1 0x00000000004004d2 in a () at t.c:8
12298 #2 0x0000000000400395 in main () at t.c:9
12301 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
12302 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
12304 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
12305 @ifset HAVE_MAKEINFO_CLICK
12306 @set ARROW @click{}
12307 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
12308 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
12310 @ifclear HAVE_MAKEINFO_CLICK
12312 @set CALLSEQ1B @value{CALLSEQ1A}
12313 @set CALLSEQ2B @value{CALLSEQ2A}
12316 Frames #0 and #2 are real, #1 is a virtual tail call frame.
12317 The code can have possible execution paths @value{CALLSEQ1B} or
12318 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
12320 @code{initial:} state shows some random possible calling sequence @value{GDBN}
12321 has found. It then finds another possible calling sequcen - that one is
12322 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
12323 printed as the @code{reduced:} calling sequence. That one could have many
12324 futher @code{compare:} and @code{reduced:} statements as long as there remain
12325 any non-ambiguous sequence entries.
12327 For the frame of function @code{b} in both cases there are different possible
12328 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
12329 also ambigous. The only non-ambiguous frame is the one for function @code{a},
12330 therefore this one is displayed to the user while the ambiguous frames are
12333 There can be also reasons why printing of frame argument values at function
12338 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
12339 static void __attribute__((noinline, noclone)) a (int i);
12340 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
12341 static void __attribute__((noinline, noclone)) a (int i)
12342 @{ if (i) b (i - 1); else c (0); @}
12343 int main (void) @{ a (5); return 0; @}
12346 #0 c (i=i@@entry=0) at t.c:2
12347 #1 0x0000000000400428 in a (DW_OP_entry_value resolving has found
12348 function "a" at 0x400420 can call itself via tail calls
12349 i=<optimized out>) at t.c:6
12350 #2 0x000000000040036e in main () at t.c:7
12353 @value{GDBN} cannot find out from the inferior state if and how many times did
12354 function @code{a} call itself (via function @code{b}) as these calls would be
12355 tail calls. Such tail calls would modify thue @code{i} variable, therefore
12356 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
12357 prints @code{<optimized out>} instead.
12360 @chapter C Preprocessor Macros
12362 Some languages, such as C and C@t{++}, provide a way to define and invoke
12363 ``preprocessor macros'' which expand into strings of tokens.
12364 @value{GDBN} can evaluate expressions containing macro invocations, show
12365 the result of macro expansion, and show a macro's definition, including
12366 where it was defined.
12368 You may need to compile your program specially to provide @value{GDBN}
12369 with information about preprocessor macros. Most compilers do not
12370 include macros in their debugging information, even when you compile
12371 with the @option{-g} flag. @xref{Compilation}.
12373 A program may define a macro at one point, remove that definition later,
12374 and then provide a different definition after that. Thus, at different
12375 points in the program, a macro may have different definitions, or have
12376 no definition at all. If there is a current stack frame, @value{GDBN}
12377 uses the macros in scope at that frame's source code line. Otherwise,
12378 @value{GDBN} uses the macros in scope at the current listing location;
12381 Whenever @value{GDBN} evaluates an expression, it always expands any
12382 macro invocations present in the expression. @value{GDBN} also provides
12383 the following commands for working with macros explicitly.
12387 @kindex macro expand
12388 @cindex macro expansion, showing the results of preprocessor
12389 @cindex preprocessor macro expansion, showing the results of
12390 @cindex expanding preprocessor macros
12391 @item macro expand @var{expression}
12392 @itemx macro exp @var{expression}
12393 Show the results of expanding all preprocessor macro invocations in
12394 @var{expression}. Since @value{GDBN} simply expands macros, but does
12395 not parse the result, @var{expression} need not be a valid expression;
12396 it can be any string of tokens.
12399 @item macro expand-once @var{expression}
12400 @itemx macro exp1 @var{expression}
12401 @cindex expand macro once
12402 @i{(This command is not yet implemented.)} Show the results of
12403 expanding those preprocessor macro invocations that appear explicitly in
12404 @var{expression}. Macro invocations appearing in that expansion are
12405 left unchanged. This command allows you to see the effect of a
12406 particular macro more clearly, without being confused by further
12407 expansions. Since @value{GDBN} simply expands macros, but does not
12408 parse the result, @var{expression} need not be a valid expression; it
12409 can be any string of tokens.
12412 @cindex macro definition, showing
12413 @cindex definition of a macro, showing
12414 @cindex macros, from debug info
12415 @item info macro [-a|-all] [--] @var{macro}
12416 Show the current definition or all definitions of the named @var{macro},
12417 and describe the source location or compiler command-line where that
12418 definition was established. The optional double dash is to signify the end of
12419 argument processing and the beginning of @var{macro} for non C-like macros where
12420 the macro may begin with a hyphen.
12422 @kindex info macros
12423 @item info macros @var{location}
12424 Show all macro definitions that are in effect at the location specified
12425 by @var{location}, and describe the source location or compiler
12426 command-line where those definitions were established.
12428 @kindex macro define
12429 @cindex user-defined macros
12430 @cindex defining macros interactively
12431 @cindex macros, user-defined
12432 @item macro define @var{macro} @var{replacement-list}
12433 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
12434 Introduce a definition for a preprocessor macro named @var{macro},
12435 invocations of which are replaced by the tokens given in
12436 @var{replacement-list}. The first form of this command defines an
12437 ``object-like'' macro, which takes no arguments; the second form
12438 defines a ``function-like'' macro, which takes the arguments given in
12441 A definition introduced by this command is in scope in every
12442 expression evaluated in @value{GDBN}, until it is removed with the
12443 @code{macro undef} command, described below. The definition overrides
12444 all definitions for @var{macro} present in the program being debugged,
12445 as well as any previous user-supplied definition.
12447 @kindex macro undef
12448 @item macro undef @var{macro}
12449 Remove any user-supplied definition for the macro named @var{macro}.
12450 This command only affects definitions provided with the @code{macro
12451 define} command, described above; it cannot remove definitions present
12452 in the program being debugged.
12456 List all the macros defined using the @code{macro define} command.
12459 @cindex macros, example of debugging with
12460 Here is a transcript showing the above commands in action. First, we
12461 show our source files:
12466 #include "sample.h"
12469 #define ADD(x) (M + x)
12474 printf ("Hello, world!\n");
12476 printf ("We're so creative.\n");
12478 printf ("Goodbye, world!\n");
12485 Now, we compile the program using the @sc{gnu} C compiler,
12486 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12487 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12488 and @option{-gdwarf-4}; we recommend always choosing the most recent
12489 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12490 includes information about preprocessor macros in the debugging
12494 $ gcc -gdwarf-2 -g3 sample.c -o sample
12498 Now, we start @value{GDBN} on our sample program:
12502 GNU gdb 2002-05-06-cvs
12503 Copyright 2002 Free Software Foundation, Inc.
12504 GDB is free software, @dots{}
12508 We can expand macros and examine their definitions, even when the
12509 program is not running. @value{GDBN} uses the current listing position
12510 to decide which macro definitions are in scope:
12513 (@value{GDBP}) list main
12516 5 #define ADD(x) (M + x)
12521 10 printf ("Hello, world!\n");
12523 12 printf ("We're so creative.\n");
12524 (@value{GDBP}) info macro ADD
12525 Defined at /home/jimb/gdb/macros/play/sample.c:5
12526 #define ADD(x) (M + x)
12527 (@value{GDBP}) info macro Q
12528 Defined at /home/jimb/gdb/macros/play/sample.h:1
12529 included at /home/jimb/gdb/macros/play/sample.c:2
12531 (@value{GDBP}) macro expand ADD(1)
12532 expands to: (42 + 1)
12533 (@value{GDBP}) macro expand-once ADD(1)
12534 expands to: once (M + 1)
12538 In the example above, note that @code{macro expand-once} expands only
12539 the macro invocation explicit in the original text --- the invocation of
12540 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12541 which was introduced by @code{ADD}.
12543 Once the program is running, @value{GDBN} uses the macro definitions in
12544 force at the source line of the current stack frame:
12547 (@value{GDBP}) break main
12548 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12550 Starting program: /home/jimb/gdb/macros/play/sample
12552 Breakpoint 1, main () at sample.c:10
12553 10 printf ("Hello, world!\n");
12557 At line 10, the definition of the macro @code{N} at line 9 is in force:
12560 (@value{GDBP}) info macro N
12561 Defined at /home/jimb/gdb/macros/play/sample.c:9
12563 (@value{GDBP}) macro expand N Q M
12564 expands to: 28 < 42
12565 (@value{GDBP}) print N Q M
12570 As we step over directives that remove @code{N}'s definition, and then
12571 give it a new definition, @value{GDBN} finds the definition (or lack
12572 thereof) in force at each point:
12575 (@value{GDBP}) next
12577 12 printf ("We're so creative.\n");
12578 (@value{GDBP}) info macro N
12579 The symbol `N' has no definition as a C/C++ preprocessor macro
12580 at /home/jimb/gdb/macros/play/sample.c:12
12581 (@value{GDBP}) next
12583 14 printf ("Goodbye, world!\n");
12584 (@value{GDBP}) info macro N
12585 Defined at /home/jimb/gdb/macros/play/sample.c:13
12587 (@value{GDBP}) macro expand N Q M
12588 expands to: 1729 < 42
12589 (@value{GDBP}) print N Q M
12594 In addition to source files, macros can be defined on the compilation command
12595 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12596 such a way, @value{GDBN} displays the location of their definition as line zero
12597 of the source file submitted to the compiler.
12600 (@value{GDBP}) info macro __STDC__
12601 Defined at /home/jimb/gdb/macros/play/sample.c:0
12608 @chapter Tracepoints
12609 @c This chapter is based on the documentation written by Michael
12610 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12612 @cindex tracepoints
12613 In some applications, it is not feasible for the debugger to interrupt
12614 the program's execution long enough for the developer to learn
12615 anything helpful about its behavior. If the program's correctness
12616 depends on its real-time behavior, delays introduced by a debugger
12617 might cause the program to change its behavior drastically, or perhaps
12618 fail, even when the code itself is correct. It is useful to be able
12619 to observe the program's behavior without interrupting it.
12621 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12622 specify locations in the program, called @dfn{tracepoints}, and
12623 arbitrary expressions to evaluate when those tracepoints are reached.
12624 Later, using the @code{tfind} command, you can examine the values
12625 those expressions had when the program hit the tracepoints. The
12626 expressions may also denote objects in memory---structures or arrays,
12627 for example---whose values @value{GDBN} should record; while visiting
12628 a particular tracepoint, you may inspect those objects as if they were
12629 in memory at that moment. However, because @value{GDBN} records these
12630 values without interacting with you, it can do so quickly and
12631 unobtrusively, hopefully not disturbing the program's behavior.
12633 The tracepoint facility is currently available only for remote
12634 targets. @xref{Targets}. In addition, your remote target must know
12635 how to collect trace data. This functionality is implemented in the
12636 remote stub; however, none of the stubs distributed with @value{GDBN}
12637 support tracepoints as of this writing. The format of the remote
12638 packets used to implement tracepoints are described in @ref{Tracepoint
12641 It is also possible to get trace data from a file, in a manner reminiscent
12642 of corefiles; you specify the filename, and use @code{tfind} to search
12643 through the file. @xref{Trace Files}, for more details.
12645 This chapter describes the tracepoint commands and features.
12648 * Set Tracepoints::
12649 * Analyze Collected Data::
12650 * Tracepoint Variables::
12654 @node Set Tracepoints
12655 @section Commands to Set Tracepoints
12657 Before running such a @dfn{trace experiment}, an arbitrary number of
12658 tracepoints can be set. A tracepoint is actually a special type of
12659 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12660 standard breakpoint commands. For instance, as with breakpoints,
12661 tracepoint numbers are successive integers starting from one, and many
12662 of the commands associated with tracepoints take the tracepoint number
12663 as their argument, to identify which tracepoint to work on.
12665 For each tracepoint, you can specify, in advance, some arbitrary set
12666 of data that you want the target to collect in the trace buffer when
12667 it hits that tracepoint. The collected data can include registers,
12668 local variables, or global data. Later, you can use @value{GDBN}
12669 commands to examine the values these data had at the time the
12670 tracepoint was hit.
12672 Tracepoints do not support every breakpoint feature. Ignore counts on
12673 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12674 commands when they are hit. Tracepoints may not be thread-specific
12677 @cindex fast tracepoints
12678 Some targets may support @dfn{fast tracepoints}, which are inserted in
12679 a different way (such as with a jump instead of a trap), that is
12680 faster but possibly restricted in where they may be installed.
12682 @cindex static tracepoints
12683 @cindex markers, static tracepoints
12684 @cindex probing markers, static tracepoints
12685 Regular and fast tracepoints are dynamic tracing facilities, meaning
12686 that they can be used to insert tracepoints at (almost) any location
12687 in the target. Some targets may also support controlling @dfn{static
12688 tracepoints} from @value{GDBN}. With static tracing, a set of
12689 instrumentation points, also known as @dfn{markers}, are embedded in
12690 the target program, and can be activated or deactivated by name or
12691 address. These are usually placed at locations which facilitate
12692 investigating what the target is actually doing. @value{GDBN}'s
12693 support for static tracing includes being able to list instrumentation
12694 points, and attach them with @value{GDBN} defined high level
12695 tracepoints that expose the whole range of convenience of
12696 @value{GDBN}'s tracepoints support. Namely, support for collecting
12697 registers values and values of global or local (to the instrumentation
12698 point) variables; tracepoint conditions and trace state variables.
12699 The act of installing a @value{GDBN} static tracepoint on an
12700 instrumentation point, or marker, is referred to as @dfn{probing} a
12701 static tracepoint marker.
12703 @code{gdbserver} supports tracepoints on some target systems.
12704 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12706 This section describes commands to set tracepoints and associated
12707 conditions and actions.
12710 * Create and Delete Tracepoints::
12711 * Enable and Disable Tracepoints::
12712 * Tracepoint Passcounts::
12713 * Tracepoint Conditions::
12714 * Trace State Variables::
12715 * Tracepoint Actions::
12716 * Listing Tracepoints::
12717 * Listing Static Tracepoint Markers::
12718 * Starting and Stopping Trace Experiments::
12719 * Tracepoint Restrictions::
12722 @node Create and Delete Tracepoints
12723 @subsection Create and Delete Tracepoints
12726 @cindex set tracepoint
12728 @item trace @var{location}
12729 The @code{trace} command is very similar to the @code{break} command.
12730 Its argument @var{location} can be any valid location.
12731 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12732 which is a point in the target program where the debugger will briefly stop,
12733 collect some data, and then allow the program to continue. Setting a tracepoint
12734 or changing its actions takes effect immediately if the remote stub
12735 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12737 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12738 these changes don't take effect until the next @code{tstart}
12739 command, and once a trace experiment is running, further changes will
12740 not have any effect until the next trace experiment starts. In addition,
12741 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12742 address is not yet resolved. (This is similar to pending breakpoints.)
12743 Pending tracepoints are not downloaded to the target and not installed
12744 until they are resolved. The resolution of pending tracepoints requires
12745 @value{GDBN} support---when debugging with the remote target, and
12746 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12747 tracing}), pending tracepoints can not be resolved (and downloaded to
12748 the remote stub) while @value{GDBN} is disconnected.
12750 Here are some examples of using the @code{trace} command:
12753 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12755 (@value{GDBP}) @b{trace +2} // 2 lines forward
12757 (@value{GDBP}) @b{trace my_function} // first source line of function
12759 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12761 (@value{GDBP}) @b{trace *0x2117c4} // an address
12765 You can abbreviate @code{trace} as @code{tr}.
12767 @item trace @var{location} if @var{cond}
12768 Set a tracepoint with condition @var{cond}; evaluate the expression
12769 @var{cond} each time the tracepoint is reached, and collect data only
12770 if the value is nonzero---that is, if @var{cond} evaluates as true.
12771 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12772 information on tracepoint conditions.
12774 @item ftrace @var{location} [ if @var{cond} ]
12775 @cindex set fast tracepoint
12776 @cindex fast tracepoints, setting
12778 The @code{ftrace} command sets a fast tracepoint. For targets that
12779 support them, fast tracepoints will use a more efficient but possibly
12780 less general technique to trigger data collection, such as a jump
12781 instruction instead of a trap, or some sort of hardware support. It
12782 may not be possible to create a fast tracepoint at the desired
12783 location, in which case the command will exit with an explanatory
12786 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12789 On 32-bit x86-architecture systems, fast tracepoints normally need to
12790 be placed at an instruction that is 5 bytes or longer, but can be
12791 placed at 4-byte instructions if the low 64K of memory of the target
12792 program is available to install trampolines. Some Unix-type systems,
12793 such as @sc{gnu}/Linux, exclude low addresses from the program's
12794 address space; but for instance with the Linux kernel it is possible
12795 to let @value{GDBN} use this area by doing a @command{sysctl} command
12796 to set the @code{mmap_min_addr} kernel parameter, as in
12799 sudo sysctl -w vm.mmap_min_addr=32768
12803 which sets the low address to 32K, which leaves plenty of room for
12804 trampolines. The minimum address should be set to a page boundary.
12806 @item strace @var{location} [ if @var{cond} ]
12807 @cindex set static tracepoint
12808 @cindex static tracepoints, setting
12809 @cindex probe static tracepoint marker
12811 The @code{strace} command sets a static tracepoint. For targets that
12812 support it, setting a static tracepoint probes a static
12813 instrumentation point, or marker, found at @var{location}. It may not
12814 be possible to set a static tracepoint at the desired location, in
12815 which case the command will exit with an explanatory message.
12817 @value{GDBN} handles arguments to @code{strace} exactly as for
12818 @code{trace}, with the addition that the user can also specify
12819 @code{-m @var{marker}} as @var{location}. This probes the marker
12820 identified by the @var{marker} string identifier. This identifier
12821 depends on the static tracepoint backend library your program is
12822 using. You can find all the marker identifiers in the @samp{ID} field
12823 of the @code{info static-tracepoint-markers} command output.
12824 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12825 Markers}. For example, in the following small program using the UST
12831 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12836 the marker id is composed of joining the first two arguments to the
12837 @code{trace_mark} call with a slash, which translates to:
12840 (@value{GDBP}) info static-tracepoint-markers
12841 Cnt Enb ID Address What
12842 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12848 so you may probe the marker above with:
12851 (@value{GDBP}) strace -m ust/bar33
12854 Static tracepoints accept an extra collect action --- @code{collect
12855 $_sdata}. This collects arbitrary user data passed in the probe point
12856 call to the tracing library. In the UST example above, you'll see
12857 that the third argument to @code{trace_mark} is a printf-like format
12858 string. The user data is then the result of running that formating
12859 string against the following arguments. Note that @code{info
12860 static-tracepoint-markers} command output lists that format string in
12861 the @samp{Data:} field.
12863 You can inspect this data when analyzing the trace buffer, by printing
12864 the $_sdata variable like any other variable available to
12865 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12868 @cindex last tracepoint number
12869 @cindex recent tracepoint number
12870 @cindex tracepoint number
12871 The convenience variable @code{$tpnum} records the tracepoint number
12872 of the most recently set tracepoint.
12874 @kindex delete tracepoint
12875 @cindex tracepoint deletion
12876 @item delete tracepoint @r{[}@var{num}@r{]}
12877 Permanently delete one or more tracepoints. With no argument, the
12878 default is to delete all tracepoints. Note that the regular
12879 @code{delete} command can remove tracepoints also.
12884 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12886 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12890 You can abbreviate this command as @code{del tr}.
12893 @node Enable and Disable Tracepoints
12894 @subsection Enable and Disable Tracepoints
12896 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12899 @kindex disable tracepoint
12900 @item disable tracepoint @r{[}@var{num}@r{]}
12901 Disable tracepoint @var{num}, or all tracepoints if no argument
12902 @var{num} is given. A disabled tracepoint will have no effect during
12903 a trace experiment, but it is not forgotten. You can re-enable
12904 a disabled tracepoint using the @code{enable tracepoint} command.
12905 If the command is issued during a trace experiment and the debug target
12906 has support for disabling tracepoints during a trace experiment, then the
12907 change will be effective immediately. Otherwise, it will be applied to the
12908 next trace experiment.
12910 @kindex enable tracepoint
12911 @item enable tracepoint @r{[}@var{num}@r{]}
12912 Enable tracepoint @var{num}, or all tracepoints. If this command is
12913 issued during a trace experiment and the debug target supports enabling
12914 tracepoints during a trace experiment, then the enabled tracepoints will
12915 become effective immediately. Otherwise, they will become effective the
12916 next time a trace experiment is run.
12919 @node Tracepoint Passcounts
12920 @subsection Tracepoint Passcounts
12924 @cindex tracepoint pass count
12925 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12926 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12927 automatically stop a trace experiment. If a tracepoint's passcount is
12928 @var{n}, then the trace experiment will be automatically stopped on
12929 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12930 @var{num} is not specified, the @code{passcount} command sets the
12931 passcount of the most recently defined tracepoint. If no passcount is
12932 given, the trace experiment will run until stopped explicitly by the
12938 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12939 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12941 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12942 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12943 (@value{GDBP}) @b{trace foo}
12944 (@value{GDBP}) @b{pass 3}
12945 (@value{GDBP}) @b{trace bar}
12946 (@value{GDBP}) @b{pass 2}
12947 (@value{GDBP}) @b{trace baz}
12948 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12949 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12950 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12951 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12955 @node Tracepoint Conditions
12956 @subsection Tracepoint Conditions
12957 @cindex conditional tracepoints
12958 @cindex tracepoint conditions
12960 The simplest sort of tracepoint collects data every time your program
12961 reaches a specified place. You can also specify a @dfn{condition} for
12962 a tracepoint. A condition is just a Boolean expression in your
12963 programming language (@pxref{Expressions, ,Expressions}). A
12964 tracepoint with a condition evaluates the expression each time your
12965 program reaches it, and data collection happens only if the condition
12968 Tracepoint conditions can be specified when a tracepoint is set, by
12969 using @samp{if} in the arguments to the @code{trace} command.
12970 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12971 also be set or changed at any time with the @code{condition} command,
12972 just as with breakpoints.
12974 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12975 the conditional expression itself. Instead, @value{GDBN} encodes the
12976 expression into an agent expression (@pxref{Agent Expressions})
12977 suitable for execution on the target, independently of @value{GDBN}.
12978 Global variables become raw memory locations, locals become stack
12979 accesses, and so forth.
12981 For instance, suppose you have a function that is usually called
12982 frequently, but should not be called after an error has occurred. You
12983 could use the following tracepoint command to collect data about calls
12984 of that function that happen while the error code is propagating
12985 through the program; an unconditional tracepoint could end up
12986 collecting thousands of useless trace frames that you would have to
12990 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12993 @node Trace State Variables
12994 @subsection Trace State Variables
12995 @cindex trace state variables
12997 A @dfn{trace state variable} is a special type of variable that is
12998 created and managed by target-side code. The syntax is the same as
12999 that for GDB's convenience variables (a string prefixed with ``$''),
13000 but they are stored on the target. They must be created explicitly,
13001 using a @code{tvariable} command. They are always 64-bit signed
13004 Trace state variables are remembered by @value{GDBN}, and downloaded
13005 to the target along with tracepoint information when the trace
13006 experiment starts. There are no intrinsic limits on the number of
13007 trace state variables, beyond memory limitations of the target.
13009 @cindex convenience variables, and trace state variables
13010 Although trace state variables are managed by the target, you can use
13011 them in print commands and expressions as if they were convenience
13012 variables; @value{GDBN} will get the current value from the target
13013 while the trace experiment is running. Trace state variables share
13014 the same namespace as other ``$'' variables, which means that you
13015 cannot have trace state variables with names like @code{$23} or
13016 @code{$pc}, nor can you have a trace state variable and a convenience
13017 variable with the same name.
13021 @item tvariable $@var{name} [ = @var{expression} ]
13023 The @code{tvariable} command creates a new trace state variable named
13024 @code{$@var{name}}, and optionally gives it an initial value of
13025 @var{expression}. The @var{expression} is evaluated when this command is
13026 entered; the result will be converted to an integer if possible,
13027 otherwise @value{GDBN} will report an error. A subsequent
13028 @code{tvariable} command specifying the same name does not create a
13029 variable, but instead assigns the supplied initial value to the
13030 existing variable of that name, overwriting any previous initial
13031 value. The default initial value is 0.
13033 @item info tvariables
13034 @kindex info tvariables
13035 List all the trace state variables along with their initial values.
13036 Their current values may also be displayed, if the trace experiment is
13039 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
13040 @kindex delete tvariable
13041 Delete the given trace state variables, or all of them if no arguments
13046 @node Tracepoint Actions
13047 @subsection Tracepoint Action Lists
13051 @cindex tracepoint actions
13052 @item actions @r{[}@var{num}@r{]}
13053 This command will prompt for a list of actions to be taken when the
13054 tracepoint is hit. If the tracepoint number @var{num} is not
13055 specified, this command sets the actions for the one that was most
13056 recently defined (so that you can define a tracepoint and then say
13057 @code{actions} without bothering about its number). You specify the
13058 actions themselves on the following lines, one action at a time, and
13059 terminate the actions list with a line containing just @code{end}. So
13060 far, the only defined actions are @code{collect}, @code{teval}, and
13061 @code{while-stepping}.
13063 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
13064 Commands, ,Breakpoint Command Lists}), except that only the defined
13065 actions are allowed; any other @value{GDBN} command is rejected.
13067 @cindex remove actions from a tracepoint
13068 To remove all actions from a tracepoint, type @samp{actions @var{num}}
13069 and follow it immediately with @samp{end}.
13072 (@value{GDBP}) @b{collect @var{data}} // collect some data
13074 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
13076 (@value{GDBP}) @b{end} // signals the end of actions.
13079 In the following example, the action list begins with @code{collect}
13080 commands indicating the things to be collected when the tracepoint is
13081 hit. Then, in order to single-step and collect additional data
13082 following the tracepoint, a @code{while-stepping} command is used,
13083 followed by the list of things to be collected after each step in a
13084 sequence of single steps. The @code{while-stepping} command is
13085 terminated by its own separate @code{end} command. Lastly, the action
13086 list is terminated by an @code{end} command.
13089 (@value{GDBP}) @b{trace foo}
13090 (@value{GDBP}) @b{actions}
13091 Enter actions for tracepoint 1, one per line:
13094 > while-stepping 12
13095 > collect $pc, arr[i]
13100 @kindex collect @r{(tracepoints)}
13101 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
13102 Collect values of the given expressions when the tracepoint is hit.
13103 This command accepts a comma-separated list of any valid expressions.
13104 In addition to global, static, or local variables, the following
13105 special arguments are supported:
13109 Collect all registers.
13112 Collect all function arguments.
13115 Collect all local variables.
13118 Collect the return address. This is helpful if you want to see more
13121 @emph{Note:} The return address location can not always be reliably
13122 determined up front, and the wrong address / registers may end up
13123 collected instead. On some architectures the reliability is higher
13124 for tracepoints at function entry, while on others it's the opposite.
13125 When this happens, backtracing will stop because the return address is
13126 found unavailable (unless another collect rule happened to match it).
13129 Collects the number of arguments from the static probe at which the
13130 tracepoint is located.
13131 @xref{Static Probe Points}.
13133 @item $_probe_arg@var{n}
13134 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
13135 from the static probe at which the tracepoint is located.
13136 @xref{Static Probe Points}.
13139 @vindex $_sdata@r{, collect}
13140 Collect static tracepoint marker specific data. Only available for
13141 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
13142 Lists}. On the UST static tracepoints library backend, an
13143 instrumentation point resembles a @code{printf} function call. The
13144 tracing library is able to collect user specified data formatted to a
13145 character string using the format provided by the programmer that
13146 instrumented the program. Other backends have similar mechanisms.
13147 Here's an example of a UST marker call:
13150 const char master_name[] = "$your_name";
13151 trace_mark(channel1, marker1, "hello %s", master_name)
13154 In this case, collecting @code{$_sdata} collects the string
13155 @samp{hello $yourname}. When analyzing the trace buffer, you can
13156 inspect @samp{$_sdata} like any other variable available to
13160 You can give several consecutive @code{collect} commands, each one
13161 with a single argument, or one @code{collect} command with several
13162 arguments separated by commas; the effect is the same.
13164 The optional @var{mods} changes the usual handling of the arguments.
13165 @code{s} requests that pointers to chars be handled as strings, in
13166 particular collecting the contents of the memory being pointed at, up
13167 to the first zero. The upper bound is by default the value of the
13168 @code{print elements} variable; if @code{s} is followed by a decimal
13169 number, that is the upper bound instead. So for instance
13170 @samp{collect/s25 mystr} collects as many as 25 characters at
13173 The command @code{info scope} (@pxref{Symbols, info scope}) is
13174 particularly useful for figuring out what data to collect.
13176 @kindex teval @r{(tracepoints)}
13177 @item teval @var{expr1}, @var{expr2}, @dots{}
13178 Evaluate the given expressions when the tracepoint is hit. This
13179 command accepts a comma-separated list of expressions. The results
13180 are discarded, so this is mainly useful for assigning values to trace
13181 state variables (@pxref{Trace State Variables}) without adding those
13182 values to the trace buffer, as would be the case if the @code{collect}
13185 @kindex while-stepping @r{(tracepoints)}
13186 @item while-stepping @var{n}
13187 Perform @var{n} single-step instruction traces after the tracepoint,
13188 collecting new data after each step. The @code{while-stepping}
13189 command is followed by the list of what to collect while stepping
13190 (followed by its own @code{end} command):
13193 > while-stepping 12
13194 > collect $regs, myglobal
13200 Note that @code{$pc} is not automatically collected by
13201 @code{while-stepping}; you need to explicitly collect that register if
13202 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
13205 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
13206 @kindex set default-collect
13207 @cindex default collection action
13208 This variable is a list of expressions to collect at each tracepoint
13209 hit. It is effectively an additional @code{collect} action prepended
13210 to every tracepoint action list. The expressions are parsed
13211 individually for each tracepoint, so for instance a variable named
13212 @code{xyz} may be interpreted as a global for one tracepoint, and a
13213 local for another, as appropriate to the tracepoint's location.
13215 @item show default-collect
13216 @kindex show default-collect
13217 Show the list of expressions that are collected by default at each
13222 @node Listing Tracepoints
13223 @subsection Listing Tracepoints
13226 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
13227 @kindex info tp @r{[}@var{n}@dots{}@r{]}
13228 @cindex information about tracepoints
13229 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
13230 Display information about the tracepoint @var{num}. If you don't
13231 specify a tracepoint number, displays information about all the
13232 tracepoints defined so far. The format is similar to that used for
13233 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
13234 command, simply restricting itself to tracepoints.
13236 A tracepoint's listing may include additional information specific to
13241 its passcount as given by the @code{passcount @var{n}} command
13244 the state about installed on target of each location
13248 (@value{GDBP}) @b{info trace}
13249 Num Type Disp Enb Address What
13250 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
13252 collect globfoo, $regs
13257 2 tracepoint keep y <MULTIPLE>
13259 2.1 y 0x0804859c in func4 at change-loc.h:35
13260 installed on target
13261 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
13262 installed on target
13263 2.3 y <PENDING> set_tracepoint
13264 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
13265 not installed on target
13270 This command can be abbreviated @code{info tp}.
13273 @node Listing Static Tracepoint Markers
13274 @subsection Listing Static Tracepoint Markers
13277 @kindex info static-tracepoint-markers
13278 @cindex information about static tracepoint markers
13279 @item info static-tracepoint-markers
13280 Display information about all static tracepoint markers defined in the
13283 For each marker, the following columns are printed:
13287 An incrementing counter, output to help readability. This is not a
13290 The marker ID, as reported by the target.
13291 @item Enabled or Disabled
13292 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
13293 that are not enabled.
13295 Where the marker is in your program, as a memory address.
13297 Where the marker is in the source for your program, as a file and line
13298 number. If the debug information included in the program does not
13299 allow @value{GDBN} to locate the source of the marker, this column
13300 will be left blank.
13304 In addition, the following information may be printed for each marker:
13308 User data passed to the tracing library by the marker call. In the
13309 UST backend, this is the format string passed as argument to the
13311 @item Static tracepoints probing the marker
13312 The list of static tracepoints attached to the marker.
13316 (@value{GDBP}) info static-tracepoint-markers
13317 Cnt ID Enb Address What
13318 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
13319 Data: number1 %d number2 %d
13320 Probed by static tracepoints: #2
13321 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
13327 @node Starting and Stopping Trace Experiments
13328 @subsection Starting and Stopping Trace Experiments
13331 @kindex tstart [ @var{notes} ]
13332 @cindex start a new trace experiment
13333 @cindex collected data discarded
13335 This command starts the trace experiment, and begins collecting data.
13336 It has the side effect of discarding all the data collected in the
13337 trace buffer during the previous trace experiment. If any arguments
13338 are supplied, they are taken as a note and stored with the trace
13339 experiment's state. The notes may be arbitrary text, and are
13340 especially useful with disconnected tracing in a multi-user context;
13341 the notes can explain what the trace is doing, supply user contact
13342 information, and so forth.
13344 @kindex tstop [ @var{notes} ]
13345 @cindex stop a running trace experiment
13347 This command stops the trace experiment. If any arguments are
13348 supplied, they are recorded with the experiment as a note. This is
13349 useful if you are stopping a trace started by someone else, for
13350 instance if the trace is interfering with the system's behavior and
13351 needs to be stopped quickly.
13353 @strong{Note}: a trace experiment and data collection may stop
13354 automatically if any tracepoint's passcount is reached
13355 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
13358 @cindex status of trace data collection
13359 @cindex trace experiment, status of
13361 This command displays the status of the current trace data
13365 Here is an example of the commands we described so far:
13368 (@value{GDBP}) @b{trace gdb_c_test}
13369 (@value{GDBP}) @b{actions}
13370 Enter actions for tracepoint #1, one per line.
13371 > collect $regs,$locals,$args
13372 > while-stepping 11
13376 (@value{GDBP}) @b{tstart}
13377 [time passes @dots{}]
13378 (@value{GDBP}) @b{tstop}
13381 @anchor{disconnected tracing}
13382 @cindex disconnected tracing
13383 You can choose to continue running the trace experiment even if
13384 @value{GDBN} disconnects from the target, voluntarily or
13385 involuntarily. For commands such as @code{detach}, the debugger will
13386 ask what you want to do with the trace. But for unexpected
13387 terminations (@value{GDBN} crash, network outage), it would be
13388 unfortunate to lose hard-won trace data, so the variable
13389 @code{disconnected-tracing} lets you decide whether the trace should
13390 continue running without @value{GDBN}.
13393 @item set disconnected-tracing on
13394 @itemx set disconnected-tracing off
13395 @kindex set disconnected-tracing
13396 Choose whether a tracing run should continue to run if @value{GDBN}
13397 has disconnected from the target. Note that @code{detach} or
13398 @code{quit} will ask you directly what to do about a running trace no
13399 matter what this variable's setting, so the variable is mainly useful
13400 for handling unexpected situations, such as loss of the network.
13402 @item show disconnected-tracing
13403 @kindex show disconnected-tracing
13404 Show the current choice for disconnected tracing.
13408 When you reconnect to the target, the trace experiment may or may not
13409 still be running; it might have filled the trace buffer in the
13410 meantime, or stopped for one of the other reasons. If it is running,
13411 it will continue after reconnection.
13413 Upon reconnection, the target will upload information about the
13414 tracepoints in effect. @value{GDBN} will then compare that
13415 information to the set of tracepoints currently defined, and attempt
13416 to match them up, allowing for the possibility that the numbers may
13417 have changed due to creation and deletion in the meantime. If one of
13418 the target's tracepoints does not match any in @value{GDBN}, the
13419 debugger will create a new tracepoint, so that you have a number with
13420 which to specify that tracepoint. This matching-up process is
13421 necessarily heuristic, and it may result in useless tracepoints being
13422 created; you may simply delete them if they are of no use.
13424 @cindex circular trace buffer
13425 If your target agent supports a @dfn{circular trace buffer}, then you
13426 can run a trace experiment indefinitely without filling the trace
13427 buffer; when space runs out, the agent deletes already-collected trace
13428 frames, oldest first, until there is enough room to continue
13429 collecting. This is especially useful if your tracepoints are being
13430 hit too often, and your trace gets terminated prematurely because the
13431 buffer is full. To ask for a circular trace buffer, simply set
13432 @samp{circular-trace-buffer} to on. You can set this at any time,
13433 including during tracing; if the agent can do it, it will change
13434 buffer handling on the fly, otherwise it will not take effect until
13438 @item set circular-trace-buffer on
13439 @itemx set circular-trace-buffer off
13440 @kindex set circular-trace-buffer
13441 Choose whether a tracing run should use a linear or circular buffer
13442 for trace data. A linear buffer will not lose any trace data, but may
13443 fill up prematurely, while a circular buffer will discard old trace
13444 data, but it will have always room for the latest tracepoint hits.
13446 @item show circular-trace-buffer
13447 @kindex show circular-trace-buffer
13448 Show the current choice for the trace buffer. Note that this may not
13449 match the agent's current buffer handling, nor is it guaranteed to
13450 match the setting that might have been in effect during a past run,
13451 for instance if you are looking at frames from a trace file.
13456 @item set trace-buffer-size @var{n}
13457 @itemx set trace-buffer-size unlimited
13458 @kindex set trace-buffer-size
13459 Request that the target use a trace buffer of @var{n} bytes. Not all
13460 targets will honor the request; they may have a compiled-in size for
13461 the trace buffer, or some other limitation. Set to a value of
13462 @code{unlimited} or @code{-1} to let the target use whatever size it
13463 likes. This is also the default.
13465 @item show trace-buffer-size
13466 @kindex show trace-buffer-size
13467 Show the current requested size for the trace buffer. Note that this
13468 will only match the actual size if the target supports size-setting,
13469 and was able to handle the requested size. For instance, if the
13470 target can only change buffer size between runs, this variable will
13471 not reflect the change until the next run starts. Use @code{tstatus}
13472 to get a report of the actual buffer size.
13476 @item set trace-user @var{text}
13477 @kindex set trace-user
13479 @item show trace-user
13480 @kindex show trace-user
13482 @item set trace-notes @var{text}
13483 @kindex set trace-notes
13484 Set the trace run's notes.
13486 @item show trace-notes
13487 @kindex show trace-notes
13488 Show the trace run's notes.
13490 @item set trace-stop-notes @var{text}
13491 @kindex set trace-stop-notes
13492 Set the trace run's stop notes. The handling of the note is as for
13493 @code{tstop} arguments; the set command is convenient way to fix a
13494 stop note that is mistaken or incomplete.
13496 @item show trace-stop-notes
13497 @kindex show trace-stop-notes
13498 Show the trace run's stop notes.
13502 @node Tracepoint Restrictions
13503 @subsection Tracepoint Restrictions
13505 @cindex tracepoint restrictions
13506 There are a number of restrictions on the use of tracepoints. As
13507 described above, tracepoint data gathering occurs on the target
13508 without interaction from @value{GDBN}. Thus the full capabilities of
13509 the debugger are not available during data gathering, and then at data
13510 examination time, you will be limited by only having what was
13511 collected. The following items describe some common problems, but it
13512 is not exhaustive, and you may run into additional difficulties not
13518 Tracepoint expressions are intended to gather objects (lvalues). Thus
13519 the full flexibility of GDB's expression evaluator is not available.
13520 You cannot call functions, cast objects to aggregate types, access
13521 convenience variables or modify values (except by assignment to trace
13522 state variables). Some language features may implicitly call
13523 functions (for instance Objective-C fields with accessors), and therefore
13524 cannot be collected either.
13527 Collection of local variables, either individually or in bulk with
13528 @code{$locals} or @code{$args}, during @code{while-stepping} may
13529 behave erratically. The stepping action may enter a new scope (for
13530 instance by stepping into a function), or the location of the variable
13531 may change (for instance it is loaded into a register). The
13532 tracepoint data recorded uses the location information for the
13533 variables that is correct for the tracepoint location. When the
13534 tracepoint is created, it is not possible, in general, to determine
13535 where the steps of a @code{while-stepping} sequence will advance the
13536 program---particularly if a conditional branch is stepped.
13539 Collection of an incompletely-initialized or partially-destroyed object
13540 may result in something that @value{GDBN} cannot display, or displays
13541 in a misleading way.
13544 When @value{GDBN} displays a pointer to character it automatically
13545 dereferences the pointer to also display characters of the string
13546 being pointed to. However, collecting the pointer during tracing does
13547 not automatically collect the string. You need to explicitly
13548 dereference the pointer and provide size information if you want to
13549 collect not only the pointer, but the memory pointed to. For example,
13550 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13554 It is not possible to collect a complete stack backtrace at a
13555 tracepoint. Instead, you may collect the registers and a few hundred
13556 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13557 (adjust to use the name of the actual stack pointer register on your
13558 target architecture, and the amount of stack you wish to capture).
13559 Then the @code{backtrace} command will show a partial backtrace when
13560 using a trace frame. The number of stack frames that can be examined
13561 depends on the sizes of the frames in the collected stack. Note that
13562 if you ask for a block so large that it goes past the bottom of the
13563 stack, the target agent may report an error trying to read from an
13567 If you do not collect registers at a tracepoint, @value{GDBN} can
13568 infer that the value of @code{$pc} must be the same as the address of
13569 the tracepoint and use that when you are looking at a trace frame
13570 for that tracepoint. However, this cannot work if the tracepoint has
13571 multiple locations (for instance if it was set in a function that was
13572 inlined), or if it has a @code{while-stepping} loop. In those cases
13573 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13578 @node Analyze Collected Data
13579 @section Using the Collected Data
13581 After the tracepoint experiment ends, you use @value{GDBN} commands
13582 for examining the trace data. The basic idea is that each tracepoint
13583 collects a trace @dfn{snapshot} every time it is hit and another
13584 snapshot every time it single-steps. All these snapshots are
13585 consecutively numbered from zero and go into a buffer, and you can
13586 examine them later. The way you examine them is to @dfn{focus} on a
13587 specific trace snapshot. When the remote stub is focused on a trace
13588 snapshot, it will respond to all @value{GDBN} requests for memory and
13589 registers by reading from the buffer which belongs to that snapshot,
13590 rather than from @emph{real} memory or registers of the program being
13591 debugged. This means that @strong{all} @value{GDBN} commands
13592 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13593 behave as if we were currently debugging the program state as it was
13594 when the tracepoint occurred. Any requests for data that are not in
13595 the buffer will fail.
13598 * tfind:: How to select a trace snapshot
13599 * tdump:: How to display all data for a snapshot
13600 * save tracepoints:: How to save tracepoints for a future run
13604 @subsection @code{tfind @var{n}}
13607 @cindex select trace snapshot
13608 @cindex find trace snapshot
13609 The basic command for selecting a trace snapshot from the buffer is
13610 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13611 counting from zero. If no argument @var{n} is given, the next
13612 snapshot is selected.
13614 Here are the various forms of using the @code{tfind} command.
13618 Find the first snapshot in the buffer. This is a synonym for
13619 @code{tfind 0} (since 0 is the number of the first snapshot).
13622 Stop debugging trace snapshots, resume @emph{live} debugging.
13625 Same as @samp{tfind none}.
13628 No argument means find the next trace snapshot or find the first
13629 one if no trace snapshot is selected.
13632 Find the previous trace snapshot before the current one. This permits
13633 retracing earlier steps.
13635 @item tfind tracepoint @var{num}
13636 Find the next snapshot associated with tracepoint @var{num}. Search
13637 proceeds forward from the last examined trace snapshot. If no
13638 argument @var{num} is given, it means find the next snapshot collected
13639 for the same tracepoint as the current snapshot.
13641 @item tfind pc @var{addr}
13642 Find the next snapshot associated with the value @var{addr} of the
13643 program counter. Search proceeds forward from the last examined trace
13644 snapshot. If no argument @var{addr} is given, it means find the next
13645 snapshot with the same value of PC as the current snapshot.
13647 @item tfind outside @var{addr1}, @var{addr2}
13648 Find the next snapshot whose PC is outside the given range of
13649 addresses (exclusive).
13651 @item tfind range @var{addr1}, @var{addr2}
13652 Find the next snapshot whose PC is between @var{addr1} and
13653 @var{addr2} (inclusive).
13655 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13656 Find the next snapshot associated with the source line @var{n}. If
13657 the optional argument @var{file} is given, refer to line @var{n} in
13658 that source file. Search proceeds forward from the last examined
13659 trace snapshot. If no argument @var{n} is given, it means find the
13660 next line other than the one currently being examined; thus saying
13661 @code{tfind line} repeatedly can appear to have the same effect as
13662 stepping from line to line in a @emph{live} debugging session.
13665 The default arguments for the @code{tfind} commands are specifically
13666 designed to make it easy to scan through the trace buffer. For
13667 instance, @code{tfind} with no argument selects the next trace
13668 snapshot, and @code{tfind -} with no argument selects the previous
13669 trace snapshot. So, by giving one @code{tfind} command, and then
13670 simply hitting @key{RET} repeatedly you can examine all the trace
13671 snapshots in order. Or, by saying @code{tfind -} and then hitting
13672 @key{RET} repeatedly you can examine the snapshots in reverse order.
13673 The @code{tfind line} command with no argument selects the snapshot
13674 for the next source line executed. The @code{tfind pc} command with
13675 no argument selects the next snapshot with the same program counter
13676 (PC) as the current frame. The @code{tfind tracepoint} command with
13677 no argument selects the next trace snapshot collected by the same
13678 tracepoint as the current one.
13680 In addition to letting you scan through the trace buffer manually,
13681 these commands make it easy to construct @value{GDBN} scripts that
13682 scan through the trace buffer and print out whatever collected data
13683 you are interested in. Thus, if we want to examine the PC, FP, and SP
13684 registers from each trace frame in the buffer, we can say this:
13687 (@value{GDBP}) @b{tfind start}
13688 (@value{GDBP}) @b{while ($trace_frame != -1)}
13689 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13690 $trace_frame, $pc, $sp, $fp
13694 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13695 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13696 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13697 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13698 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13699 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13700 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13701 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13702 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13703 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13704 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13707 Or, if we want to examine the variable @code{X} at each source line in
13711 (@value{GDBP}) @b{tfind start}
13712 (@value{GDBP}) @b{while ($trace_frame != -1)}
13713 > printf "Frame %d, X == %d\n", $trace_frame, X
13723 @subsection @code{tdump}
13725 @cindex dump all data collected at tracepoint
13726 @cindex tracepoint data, display
13728 This command takes no arguments. It prints all the data collected at
13729 the current trace snapshot.
13732 (@value{GDBP}) @b{trace 444}
13733 (@value{GDBP}) @b{actions}
13734 Enter actions for tracepoint #2, one per line:
13735 > collect $regs, $locals, $args, gdb_long_test
13738 (@value{GDBP}) @b{tstart}
13740 (@value{GDBP}) @b{tfind line 444}
13741 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13743 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13745 (@value{GDBP}) @b{tdump}
13746 Data collected at tracepoint 2, trace frame 1:
13747 d0 0xc4aa0085 -995491707
13751 d4 0x71aea3d 119204413
13754 d7 0x380035 3670069
13755 a0 0x19e24a 1696330
13756 a1 0x3000668 50333288
13758 a3 0x322000 3284992
13759 a4 0x3000698 50333336
13760 a5 0x1ad3cc 1758156
13761 fp 0x30bf3c 0x30bf3c
13762 sp 0x30bf34 0x30bf34
13764 pc 0x20b2c8 0x20b2c8
13768 p = 0x20e5b4 "gdb-test"
13775 gdb_long_test = 17 '\021'
13780 @code{tdump} works by scanning the tracepoint's current collection
13781 actions and printing the value of each expression listed. So
13782 @code{tdump} can fail, if after a run, you change the tracepoint's
13783 actions to mention variables that were not collected during the run.
13785 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13786 uses the collected value of @code{$pc} to distinguish between trace
13787 frames that were collected at the tracepoint hit, and frames that were
13788 collected while stepping. This allows it to correctly choose whether
13789 to display the basic list of collections, or the collections from the
13790 body of the while-stepping loop. However, if @code{$pc} was not collected,
13791 then @code{tdump} will always attempt to dump using the basic collection
13792 list, and may fail if a while-stepping frame does not include all the
13793 same data that is collected at the tracepoint hit.
13794 @c This is getting pretty arcane, example would be good.
13796 @node save tracepoints
13797 @subsection @code{save tracepoints @var{filename}}
13798 @kindex save tracepoints
13799 @kindex save-tracepoints
13800 @cindex save tracepoints for future sessions
13802 This command saves all current tracepoint definitions together with
13803 their actions and passcounts, into a file @file{@var{filename}}
13804 suitable for use in a later debugging session. To read the saved
13805 tracepoint definitions, use the @code{source} command (@pxref{Command
13806 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13807 alias for @w{@code{save tracepoints}}
13809 @node Tracepoint Variables
13810 @section Convenience Variables for Tracepoints
13811 @cindex tracepoint variables
13812 @cindex convenience variables for tracepoints
13815 @vindex $trace_frame
13816 @item (int) $trace_frame
13817 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13818 snapshot is selected.
13820 @vindex $tracepoint
13821 @item (int) $tracepoint
13822 The tracepoint for the current trace snapshot.
13824 @vindex $trace_line
13825 @item (int) $trace_line
13826 The line number for the current trace snapshot.
13828 @vindex $trace_file
13829 @item (char []) $trace_file
13830 The source file for the current trace snapshot.
13832 @vindex $trace_func
13833 @item (char []) $trace_func
13834 The name of the function containing @code{$tracepoint}.
13837 Note: @code{$trace_file} is not suitable for use in @code{printf},
13838 use @code{output} instead.
13840 Here's a simple example of using these convenience variables for
13841 stepping through all the trace snapshots and printing some of their
13842 data. Note that these are not the same as trace state variables,
13843 which are managed by the target.
13846 (@value{GDBP}) @b{tfind start}
13848 (@value{GDBP}) @b{while $trace_frame != -1}
13849 > output $trace_file
13850 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13856 @section Using Trace Files
13857 @cindex trace files
13859 In some situations, the target running a trace experiment may no
13860 longer be available; perhaps it crashed, or the hardware was needed
13861 for a different activity. To handle these cases, you can arrange to
13862 dump the trace data into a file, and later use that file as a source
13863 of trace data, via the @code{target tfile} command.
13868 @item tsave [ -r ] @var{filename}
13869 @itemx tsave [-ctf] @var{dirname}
13870 Save the trace data to @var{filename}. By default, this command
13871 assumes that @var{filename} refers to the host filesystem, so if
13872 necessary @value{GDBN} will copy raw trace data up from the target and
13873 then save it. If the target supports it, you can also supply the
13874 optional argument @code{-r} (``remote'') to direct the target to save
13875 the data directly into @var{filename} in its own filesystem, which may be
13876 more efficient if the trace buffer is very large. (Note, however, that
13877 @code{target tfile} can only read from files accessible to the host.)
13878 By default, this command will save trace frame in tfile format.
13879 You can supply the optional argument @code{-ctf} to save data in CTF
13880 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13881 that can be shared by multiple debugging and tracing tools. Please go to
13882 @indicateurl{http://www.efficios.com/ctf} to get more information.
13884 @kindex target tfile
13888 @item target tfile @var{filename}
13889 @itemx target ctf @var{dirname}
13890 Use the file named @var{filename} or directory named @var{dirname} as
13891 a source of trace data. Commands that examine data work as they do with
13892 a live target, but it is not possible to run any new trace experiments.
13893 @code{tstatus} will report the state of the trace run at the moment
13894 the data was saved, as well as the current trace frame you are examining.
13895 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13899 (@value{GDBP}) target ctf ctf.ctf
13900 (@value{GDBP}) tfind
13901 Found trace frame 0, tracepoint 2
13902 39 ++a; /* set tracepoint 1 here */
13903 (@value{GDBP}) tdump
13904 Data collected at tracepoint 2, trace frame 0:
13908 c = @{"123", "456", "789", "123", "456", "789"@}
13909 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13917 @chapter Debugging Programs That Use Overlays
13920 If your program is too large to fit completely in your target system's
13921 memory, you can sometimes use @dfn{overlays} to work around this
13922 problem. @value{GDBN} provides some support for debugging programs that
13926 * How Overlays Work:: A general explanation of overlays.
13927 * Overlay Commands:: Managing overlays in @value{GDBN}.
13928 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13929 mapped by asking the inferior.
13930 * Overlay Sample Program:: A sample program using overlays.
13933 @node How Overlays Work
13934 @section How Overlays Work
13935 @cindex mapped overlays
13936 @cindex unmapped overlays
13937 @cindex load address, overlay's
13938 @cindex mapped address
13939 @cindex overlay area
13941 Suppose you have a computer whose instruction address space is only 64
13942 kilobytes long, but which has much more memory which can be accessed by
13943 other means: special instructions, segment registers, or memory
13944 management hardware, for example. Suppose further that you want to
13945 adapt a program which is larger than 64 kilobytes to run on this system.
13947 One solution is to identify modules of your program which are relatively
13948 independent, and need not call each other directly; call these modules
13949 @dfn{overlays}. Separate the overlays from the main program, and place
13950 their machine code in the larger memory. Place your main program in
13951 instruction memory, but leave at least enough space there to hold the
13952 largest overlay as well.
13954 Now, to call a function located in an overlay, you must first copy that
13955 overlay's machine code from the large memory into the space set aside
13956 for it in the instruction memory, and then jump to its entry point
13959 @c NB: In the below the mapped area's size is greater or equal to the
13960 @c size of all overlays. This is intentional to remind the developer
13961 @c that overlays don't necessarily need to be the same size.
13965 Data Instruction Larger
13966 Address Space Address Space Address Space
13967 +-----------+ +-----------+ +-----------+
13969 +-----------+ +-----------+ +-----------+<-- overlay 1
13970 | program | | main | .----| overlay 1 | load address
13971 | variables | | program | | +-----------+
13972 | and heap | | | | | |
13973 +-----------+ | | | +-----------+<-- overlay 2
13974 | | +-----------+ | | | load address
13975 +-----------+ | | | .-| overlay 2 |
13977 mapped --->+-----------+ | | +-----------+
13978 address | | | | | |
13979 | overlay | <-' | | |
13980 | area | <---' +-----------+<-- overlay 3
13981 | | <---. | | load address
13982 +-----------+ `--| overlay 3 |
13989 @anchor{A code overlay}A code overlay
13993 The diagram (@pxref{A code overlay}) shows a system with separate data
13994 and instruction address spaces. To map an overlay, the program copies
13995 its code from the larger address space to the instruction address space.
13996 Since the overlays shown here all use the same mapped address, only one
13997 may be mapped at a time. For a system with a single address space for
13998 data and instructions, the diagram would be similar, except that the
13999 program variables and heap would share an address space with the main
14000 program and the overlay area.
14002 An overlay loaded into instruction memory and ready for use is called a
14003 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
14004 instruction memory. An overlay not present (or only partially present)
14005 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
14006 is its address in the larger memory. The mapped address is also called
14007 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
14008 called the @dfn{load memory address}, or @dfn{LMA}.
14010 Unfortunately, overlays are not a completely transparent way to adapt a
14011 program to limited instruction memory. They introduce a new set of
14012 global constraints you must keep in mind as you design your program:
14017 Before calling or returning to a function in an overlay, your program
14018 must make sure that overlay is actually mapped. Otherwise, the call or
14019 return will transfer control to the right address, but in the wrong
14020 overlay, and your program will probably crash.
14023 If the process of mapping an overlay is expensive on your system, you
14024 will need to choose your overlays carefully to minimize their effect on
14025 your program's performance.
14028 The executable file you load onto your system must contain each
14029 overlay's instructions, appearing at the overlay's load address, not its
14030 mapped address. However, each overlay's instructions must be relocated
14031 and its symbols defined as if the overlay were at its mapped address.
14032 You can use GNU linker scripts to specify different load and relocation
14033 addresses for pieces of your program; see @ref{Overlay Description,,,
14034 ld.info, Using ld: the GNU linker}.
14037 The procedure for loading executable files onto your system must be able
14038 to load their contents into the larger address space as well as the
14039 instruction and data spaces.
14043 The overlay system described above is rather simple, and could be
14044 improved in many ways:
14049 If your system has suitable bank switch registers or memory management
14050 hardware, you could use those facilities to make an overlay's load area
14051 contents simply appear at their mapped address in instruction space.
14052 This would probably be faster than copying the overlay to its mapped
14053 area in the usual way.
14056 If your overlays are small enough, you could set aside more than one
14057 overlay area, and have more than one overlay mapped at a time.
14060 You can use overlays to manage data, as well as instructions. In
14061 general, data overlays are even less transparent to your design than
14062 code overlays: whereas code overlays only require care when you call or
14063 return to functions, data overlays require care every time you access
14064 the data. Also, if you change the contents of a data overlay, you
14065 must copy its contents back out to its load address before you can copy a
14066 different data overlay into the same mapped area.
14071 @node Overlay Commands
14072 @section Overlay Commands
14074 To use @value{GDBN}'s overlay support, each overlay in your program must
14075 correspond to a separate section of the executable file. The section's
14076 virtual memory address and load memory address must be the overlay's
14077 mapped and load addresses. Identifying overlays with sections allows
14078 @value{GDBN} to determine the appropriate address of a function or
14079 variable, depending on whether the overlay is mapped or not.
14081 @value{GDBN}'s overlay commands all start with the word @code{overlay};
14082 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
14087 Disable @value{GDBN}'s overlay support. When overlay support is
14088 disabled, @value{GDBN} assumes that all functions and variables are
14089 always present at their mapped addresses. By default, @value{GDBN}'s
14090 overlay support is disabled.
14092 @item overlay manual
14093 @cindex manual overlay debugging
14094 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
14095 relies on you to tell it which overlays are mapped, and which are not,
14096 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
14097 commands described below.
14099 @item overlay map-overlay @var{overlay}
14100 @itemx overlay map @var{overlay}
14101 @cindex map an overlay
14102 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
14103 be the name of the object file section containing the overlay. When an
14104 overlay is mapped, @value{GDBN} assumes it can find the overlay's
14105 functions and variables at their mapped addresses. @value{GDBN} assumes
14106 that any other overlays whose mapped ranges overlap that of
14107 @var{overlay} are now unmapped.
14109 @item overlay unmap-overlay @var{overlay}
14110 @itemx overlay unmap @var{overlay}
14111 @cindex unmap an overlay
14112 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
14113 must be the name of the object file section containing the overlay.
14114 When an overlay is unmapped, @value{GDBN} assumes it can find the
14115 overlay's functions and variables at their load addresses.
14118 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
14119 consults a data structure the overlay manager maintains in the inferior
14120 to see which overlays are mapped. For details, see @ref{Automatic
14121 Overlay Debugging}.
14123 @item overlay load-target
14124 @itemx overlay load
14125 @cindex reloading the overlay table
14126 Re-read the overlay table from the inferior. Normally, @value{GDBN}
14127 re-reads the table @value{GDBN} automatically each time the inferior
14128 stops, so this command should only be necessary if you have changed the
14129 overlay mapping yourself using @value{GDBN}. This command is only
14130 useful when using automatic overlay debugging.
14132 @item overlay list-overlays
14133 @itemx overlay list
14134 @cindex listing mapped overlays
14135 Display a list of the overlays currently mapped, along with their mapped
14136 addresses, load addresses, and sizes.
14140 Normally, when @value{GDBN} prints a code address, it includes the name
14141 of the function the address falls in:
14144 (@value{GDBP}) print main
14145 $3 = @{int ()@} 0x11a0 <main>
14148 When overlay debugging is enabled, @value{GDBN} recognizes code in
14149 unmapped overlays, and prints the names of unmapped functions with
14150 asterisks around them. For example, if @code{foo} is a function in an
14151 unmapped overlay, @value{GDBN} prints it this way:
14154 (@value{GDBP}) overlay list
14155 No sections are mapped.
14156 (@value{GDBP}) print foo
14157 $5 = @{int (int)@} 0x100000 <*foo*>
14160 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
14164 (@value{GDBP}) overlay list
14165 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
14166 mapped at 0x1016 - 0x104a
14167 (@value{GDBP}) print foo
14168 $6 = @{int (int)@} 0x1016 <foo>
14171 When overlay debugging is enabled, @value{GDBN} can find the correct
14172 address for functions and variables in an overlay, whether or not the
14173 overlay is mapped. This allows most @value{GDBN} commands, like
14174 @code{break} and @code{disassemble}, to work normally, even on unmapped
14175 code. However, @value{GDBN}'s breakpoint support has some limitations:
14179 @cindex breakpoints in overlays
14180 @cindex overlays, setting breakpoints in
14181 You can set breakpoints in functions in unmapped overlays, as long as
14182 @value{GDBN} can write to the overlay at its load address.
14184 @value{GDBN} can not set hardware or simulator-based breakpoints in
14185 unmapped overlays. However, if you set a breakpoint at the end of your
14186 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
14187 you are using manual overlay management), @value{GDBN} will re-set its
14188 breakpoints properly.
14192 @node Automatic Overlay Debugging
14193 @section Automatic Overlay Debugging
14194 @cindex automatic overlay debugging
14196 @value{GDBN} can automatically track which overlays are mapped and which
14197 are not, given some simple co-operation from the overlay manager in the
14198 inferior. If you enable automatic overlay debugging with the
14199 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
14200 looks in the inferior's memory for certain variables describing the
14201 current state of the overlays.
14203 Here are the variables your overlay manager must define to support
14204 @value{GDBN}'s automatic overlay debugging:
14208 @item @code{_ovly_table}:
14209 This variable must be an array of the following structures:
14214 /* The overlay's mapped address. */
14217 /* The size of the overlay, in bytes. */
14218 unsigned long size;
14220 /* The overlay's load address. */
14223 /* Non-zero if the overlay is currently mapped;
14225 unsigned long mapped;
14229 @item @code{_novlys}:
14230 This variable must be a four-byte signed integer, holding the total
14231 number of elements in @code{_ovly_table}.
14235 To decide whether a particular overlay is mapped or not, @value{GDBN}
14236 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
14237 @code{lma} members equal the VMA and LMA of the overlay's section in the
14238 executable file. When @value{GDBN} finds a matching entry, it consults
14239 the entry's @code{mapped} member to determine whether the overlay is
14242 In addition, your overlay manager may define a function called
14243 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
14244 will silently set a breakpoint there. If the overlay manager then
14245 calls this function whenever it has changed the overlay table, this
14246 will enable @value{GDBN} to accurately keep track of which overlays
14247 are in program memory, and update any breakpoints that may be set
14248 in overlays. This will allow breakpoints to work even if the
14249 overlays are kept in ROM or other non-writable memory while they
14250 are not being executed.
14252 @node Overlay Sample Program
14253 @section Overlay Sample Program
14254 @cindex overlay example program
14256 When linking a program which uses overlays, you must place the overlays
14257 at their load addresses, while relocating them to run at their mapped
14258 addresses. To do this, you must write a linker script (@pxref{Overlay
14259 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
14260 since linker scripts are specific to a particular host system, target
14261 architecture, and target memory layout, this manual cannot provide
14262 portable sample code demonstrating @value{GDBN}'s overlay support.
14264 However, the @value{GDBN} source distribution does contain an overlaid
14265 program, with linker scripts for a few systems, as part of its test
14266 suite. The program consists of the following files from
14267 @file{gdb/testsuite/gdb.base}:
14271 The main program file.
14273 A simple overlay manager, used by @file{overlays.c}.
14278 Overlay modules, loaded and used by @file{overlays.c}.
14281 Linker scripts for linking the test program on the @code{d10v-elf}
14282 and @code{m32r-elf} targets.
14285 You can build the test program using the @code{d10v-elf} GCC
14286 cross-compiler like this:
14289 $ d10v-elf-gcc -g -c overlays.c
14290 $ d10v-elf-gcc -g -c ovlymgr.c
14291 $ d10v-elf-gcc -g -c foo.c
14292 $ d10v-elf-gcc -g -c bar.c
14293 $ d10v-elf-gcc -g -c baz.c
14294 $ d10v-elf-gcc -g -c grbx.c
14295 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
14296 baz.o grbx.o -Wl,-Td10v.ld -o overlays
14299 The build process is identical for any other architecture, except that
14300 you must substitute the appropriate compiler and linker script for the
14301 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
14305 @chapter Using @value{GDBN} with Different Languages
14308 Although programming languages generally have common aspects, they are
14309 rarely expressed in the same manner. For instance, in ANSI C,
14310 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
14311 Modula-2, it is accomplished by @code{p^}. Values can also be
14312 represented (and displayed) differently. Hex numbers in C appear as
14313 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
14315 @cindex working language
14316 Language-specific information is built into @value{GDBN} for some languages,
14317 allowing you to express operations like the above in your program's
14318 native language, and allowing @value{GDBN} to output values in a manner
14319 consistent with the syntax of your program's native language. The
14320 language you use to build expressions is called the @dfn{working
14324 * Setting:: Switching between source languages
14325 * Show:: Displaying the language
14326 * Checks:: Type and range checks
14327 * Supported Languages:: Supported languages
14328 * Unsupported Languages:: Unsupported languages
14332 @section Switching Between Source Languages
14334 There are two ways to control the working language---either have @value{GDBN}
14335 set it automatically, or select it manually yourself. You can use the
14336 @code{set language} command for either purpose. On startup, @value{GDBN}
14337 defaults to setting the language automatically. The working language is
14338 used to determine how expressions you type are interpreted, how values
14341 In addition to the working language, every source file that
14342 @value{GDBN} knows about has its own working language. For some object
14343 file formats, the compiler might indicate which language a particular
14344 source file is in. However, most of the time @value{GDBN} infers the
14345 language from the name of the file. The language of a source file
14346 controls whether C@t{++} names are demangled---this way @code{backtrace} can
14347 show each frame appropriately for its own language. There is no way to
14348 set the language of a source file from within @value{GDBN}, but you can
14349 set the language associated with a filename extension. @xref{Show, ,
14350 Displaying the Language}.
14352 This is most commonly a problem when you use a program, such
14353 as @code{cfront} or @code{f2c}, that generates C but is written in
14354 another language. In that case, make the
14355 program use @code{#line} directives in its C output; that way
14356 @value{GDBN} will know the correct language of the source code of the original
14357 program, and will display that source code, not the generated C code.
14360 * Filenames:: Filename extensions and languages.
14361 * Manually:: Setting the working language manually
14362 * Automatically:: Having @value{GDBN} infer the source language
14366 @subsection List of Filename Extensions and Languages
14368 If a source file name ends in one of the following extensions, then
14369 @value{GDBN} infers that its language is the one indicated.
14387 C@t{++} source file
14393 Objective-C source file
14397 Fortran source file
14400 Modula-2 source file
14404 Assembler source file. This actually behaves almost like C, but
14405 @value{GDBN} does not skip over function prologues when stepping.
14408 In addition, you may set the language associated with a filename
14409 extension. @xref{Show, , Displaying the Language}.
14412 @subsection Setting the Working Language
14414 If you allow @value{GDBN} to set the language automatically,
14415 expressions are interpreted the same way in your debugging session and
14418 @kindex set language
14419 If you wish, you may set the language manually. To do this, issue the
14420 command @samp{set language @var{lang}}, where @var{lang} is the name of
14421 a language, such as
14422 @code{c} or @code{modula-2}.
14423 For a list of the supported languages, type @samp{set language}.
14425 Setting the language manually prevents @value{GDBN} from updating the working
14426 language automatically. This can lead to confusion if you try
14427 to debug a program when the working language is not the same as the
14428 source language, when an expression is acceptable to both
14429 languages---but means different things. For instance, if the current
14430 source file were written in C, and @value{GDBN} was parsing Modula-2, a
14438 might not have the effect you intended. In C, this means to add
14439 @code{b} and @code{c} and place the result in @code{a}. The result
14440 printed would be the value of @code{a}. In Modula-2, this means to compare
14441 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
14443 @node Automatically
14444 @subsection Having @value{GDBN} Infer the Source Language
14446 To have @value{GDBN} set the working language automatically, use
14447 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14448 then infers the working language. That is, when your program stops in a
14449 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14450 working language to the language recorded for the function in that
14451 frame. If the language for a frame is unknown (that is, if the function
14452 or block corresponding to the frame was defined in a source file that
14453 does not have a recognized extension), the current working language is
14454 not changed, and @value{GDBN} issues a warning.
14456 This may not seem necessary for most programs, which are written
14457 entirely in one source language. However, program modules and libraries
14458 written in one source language can be used by a main program written in
14459 a different source language. Using @samp{set language auto} in this
14460 case frees you from having to set the working language manually.
14463 @section Displaying the Language
14465 The following commands help you find out which language is the
14466 working language, and also what language source files were written in.
14469 @item show language
14470 @anchor{show language}
14471 @kindex show language
14472 Display the current working language. This is the
14473 language you can use with commands such as @code{print} to
14474 build and compute expressions that may involve variables in your program.
14477 @kindex info frame@r{, show the source language}
14478 Display the source language for this frame. This language becomes the
14479 working language if you use an identifier from this frame.
14480 @xref{Frame Info, ,Information about a Frame}, to identify the other
14481 information listed here.
14484 @kindex info source@r{, show the source language}
14485 Display the source language of this source file.
14486 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14487 information listed here.
14490 In unusual circumstances, you may have source files with extensions
14491 not in the standard list. You can then set the extension associated
14492 with a language explicitly:
14495 @item set extension-language @var{ext} @var{language}
14496 @kindex set extension-language
14497 Tell @value{GDBN} that source files with extension @var{ext} are to be
14498 assumed as written in the source language @var{language}.
14500 @item info extensions
14501 @kindex info extensions
14502 List all the filename extensions and the associated languages.
14506 @section Type and Range Checking
14508 Some languages are designed to guard you against making seemingly common
14509 errors through a series of compile- and run-time checks. These include
14510 checking the type of arguments to functions and operators and making
14511 sure mathematical overflows are caught at run time. Checks such as
14512 these help to ensure a program's correctness once it has been compiled
14513 by eliminating type mismatches and providing active checks for range
14514 errors when your program is running.
14516 By default @value{GDBN} checks for these errors according to the
14517 rules of the current source language. Although @value{GDBN} does not check
14518 the statements in your program, it can check expressions entered directly
14519 into @value{GDBN} for evaluation via the @code{print} command, for example.
14522 * Type Checking:: An overview of type checking
14523 * Range Checking:: An overview of range checking
14526 @cindex type checking
14527 @cindex checks, type
14528 @node Type Checking
14529 @subsection An Overview of Type Checking
14531 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14532 arguments to operators and functions have to be of the correct type,
14533 otherwise an error occurs. These checks prevent type mismatch
14534 errors from ever causing any run-time problems. For example,
14537 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14539 (@value{GDBP}) print obj.my_method (0)
14542 (@value{GDBP}) print obj.my_method (0x1234)
14543 Cannot resolve method klass::my_method to any overloaded instance
14546 The second example fails because in C@t{++} the integer constant
14547 @samp{0x1234} is not type-compatible with the pointer parameter type.
14549 For the expressions you use in @value{GDBN} commands, you can tell
14550 @value{GDBN} to not enforce strict type checking or
14551 to treat any mismatches as errors and abandon the expression;
14552 When type checking is disabled, @value{GDBN} successfully evaluates
14553 expressions like the second example above.
14555 Even if type checking is off, there may be other reasons
14556 related to type that prevent @value{GDBN} from evaluating an expression.
14557 For instance, @value{GDBN} does not know how to add an @code{int} and
14558 a @code{struct foo}. These particular type errors have nothing to do
14559 with the language in use and usually arise from expressions which make
14560 little sense to evaluate anyway.
14562 @value{GDBN} provides some additional commands for controlling type checking:
14564 @kindex set check type
14565 @kindex show check type
14567 @item set check type on
14568 @itemx set check type off
14569 Set strict type checking on or off. If any type mismatches occur in
14570 evaluating an expression while type checking is on, @value{GDBN} prints a
14571 message and aborts evaluation of the expression.
14573 @item show check type
14574 Show the current setting of type checking and whether @value{GDBN}
14575 is enforcing strict type checking rules.
14578 @cindex range checking
14579 @cindex checks, range
14580 @node Range Checking
14581 @subsection An Overview of Range Checking
14583 In some languages (such as Modula-2), it is an error to exceed the
14584 bounds of a type; this is enforced with run-time checks. Such range
14585 checking is meant to ensure program correctness by making sure
14586 computations do not overflow, or indices on an array element access do
14587 not exceed the bounds of the array.
14589 For expressions you use in @value{GDBN} commands, you can tell
14590 @value{GDBN} to treat range errors in one of three ways: ignore them,
14591 always treat them as errors and abandon the expression, or issue
14592 warnings but evaluate the expression anyway.
14594 A range error can result from numerical overflow, from exceeding an
14595 array index bound, or when you type a constant that is not a member
14596 of any type. Some languages, however, do not treat overflows as an
14597 error. In many implementations of C, mathematical overflow causes the
14598 result to ``wrap around'' to lower values---for example, if @var{m} is
14599 the largest integer value, and @var{s} is the smallest, then
14602 @var{m} + 1 @result{} @var{s}
14605 This, too, is specific to individual languages, and in some cases
14606 specific to individual compilers or machines. @xref{Supported Languages, ,
14607 Supported Languages}, for further details on specific languages.
14609 @value{GDBN} provides some additional commands for controlling the range checker:
14611 @kindex set check range
14612 @kindex show check range
14614 @item set check range auto
14615 Set range checking on or off based on the current working language.
14616 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14619 @item set check range on
14620 @itemx set check range off
14621 Set range checking on or off, overriding the default setting for the
14622 current working language. A warning is issued if the setting does not
14623 match the language default. If a range error occurs and range checking is on,
14624 then a message is printed and evaluation of the expression is aborted.
14626 @item set check range warn
14627 Output messages when the @value{GDBN} range checker detects a range error,
14628 but attempt to evaluate the expression anyway. Evaluating the
14629 expression may still be impossible for other reasons, such as accessing
14630 memory that the process does not own (a typical example from many Unix
14634 Show the current setting of the range checker, and whether or not it is
14635 being set automatically by @value{GDBN}.
14638 @node Supported Languages
14639 @section Supported Languages
14641 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran,
14642 OpenCL C, Pascal, Rust, assembly, Modula-2, and Ada.
14643 @c This is false ...
14644 Some @value{GDBN} features may be used in expressions regardless of the
14645 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14646 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14647 ,Expressions}) can be used with the constructs of any supported
14650 The following sections detail to what degree each source language is
14651 supported by @value{GDBN}. These sections are not meant to be language
14652 tutorials or references, but serve only as a reference guide to what the
14653 @value{GDBN} expression parser accepts, and what input and output
14654 formats should look like for different languages. There are many good
14655 books written on each of these languages; please look to these for a
14656 language reference or tutorial.
14659 * C:: C and C@t{++}
14662 * Objective-C:: Objective-C
14663 * OpenCL C:: OpenCL C
14664 * Fortran:: Fortran
14667 * Modula-2:: Modula-2
14672 @subsection C and C@t{++}
14674 @cindex C and C@t{++}
14675 @cindex expressions in C or C@t{++}
14677 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14678 to both languages. Whenever this is the case, we discuss those languages
14682 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14683 @cindex @sc{gnu} C@t{++}
14684 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14685 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14686 effectively, you must compile your C@t{++} programs with a supported
14687 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14688 compiler (@code{aCC}).
14691 * C Operators:: C and C@t{++} operators
14692 * C Constants:: C and C@t{++} constants
14693 * C Plus Plus Expressions:: C@t{++} expressions
14694 * C Defaults:: Default settings for C and C@t{++}
14695 * C Checks:: C and C@t{++} type and range checks
14696 * Debugging C:: @value{GDBN} and C
14697 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14698 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14702 @subsubsection C and C@t{++} Operators
14704 @cindex C and C@t{++} operators
14706 Operators must be defined on values of specific types. For instance,
14707 @code{+} is defined on numbers, but not on structures. Operators are
14708 often defined on groups of types.
14710 For the purposes of C and C@t{++}, the following definitions hold:
14715 @emph{Integral types} include @code{int} with any of its storage-class
14716 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14719 @emph{Floating-point types} include @code{float}, @code{double}, and
14720 @code{long double} (if supported by the target platform).
14723 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14726 @emph{Scalar types} include all of the above.
14731 The following operators are supported. They are listed here
14732 in order of increasing precedence:
14736 The comma or sequencing operator. Expressions in a comma-separated list
14737 are evaluated from left to right, with the result of the entire
14738 expression being the last expression evaluated.
14741 Assignment. The value of an assignment expression is the value
14742 assigned. Defined on scalar types.
14745 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14746 and translated to @w{@code{@var{a} = @var{a op b}}}.
14747 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14748 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14749 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14752 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14753 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14754 should be of an integral type.
14757 Logical @sc{or}. Defined on integral types.
14760 Logical @sc{and}. Defined on integral types.
14763 Bitwise @sc{or}. Defined on integral types.
14766 Bitwise exclusive-@sc{or}. Defined on integral types.
14769 Bitwise @sc{and}. Defined on integral types.
14772 Equality and inequality. Defined on scalar types. The value of these
14773 expressions is 0 for false and non-zero for true.
14775 @item <@r{, }>@r{, }<=@r{, }>=
14776 Less than, greater than, less than or equal, greater than or equal.
14777 Defined on scalar types. The value of these expressions is 0 for false
14778 and non-zero for true.
14781 left shift, and right shift. Defined on integral types.
14784 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14787 Addition and subtraction. Defined on integral types, floating-point types and
14790 @item *@r{, }/@r{, }%
14791 Multiplication, division, and modulus. Multiplication and division are
14792 defined on integral and floating-point types. Modulus is defined on
14796 Increment and decrement. When appearing before a variable, the
14797 operation is performed before the variable is used in an expression;
14798 when appearing after it, the variable's value is used before the
14799 operation takes place.
14802 Pointer dereferencing. Defined on pointer types. Same precedence as
14806 Address operator. Defined on variables. Same precedence as @code{++}.
14808 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14809 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14810 to examine the address
14811 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14815 Negative. Defined on integral and floating-point types. Same
14816 precedence as @code{++}.
14819 Logical negation. Defined on integral types. Same precedence as
14823 Bitwise complement operator. Defined on integral types. Same precedence as
14828 Structure member, and pointer-to-structure member. For convenience,
14829 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14830 pointer based on the stored type information.
14831 Defined on @code{struct} and @code{union} data.
14834 Dereferences of pointers to members.
14837 Array indexing. @code{@var{a}[@var{i}]} is defined as
14838 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14841 Function parameter list. Same precedence as @code{->}.
14844 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14845 and @code{class} types.
14848 Doubled colons also represent the @value{GDBN} scope operator
14849 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14853 If an operator is redefined in the user code, @value{GDBN} usually
14854 attempts to invoke the redefined version instead of using the operator's
14855 predefined meaning.
14858 @subsubsection C and C@t{++} Constants
14860 @cindex C and C@t{++} constants
14862 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14867 Integer constants are a sequence of digits. Octal constants are
14868 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14869 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14870 @samp{l}, specifying that the constant should be treated as a
14874 Floating point constants are a sequence of digits, followed by a decimal
14875 point, followed by a sequence of digits, and optionally followed by an
14876 exponent. An exponent is of the form:
14877 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14878 sequence of digits. The @samp{+} is optional for positive exponents.
14879 A floating-point constant may also end with a letter @samp{f} or
14880 @samp{F}, specifying that the constant should be treated as being of
14881 the @code{float} (as opposed to the default @code{double}) type; or with
14882 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14886 Enumerated constants consist of enumerated identifiers, or their
14887 integral equivalents.
14890 Character constants are a single character surrounded by single quotes
14891 (@code{'}), or a number---the ordinal value of the corresponding character
14892 (usually its @sc{ascii} value). Within quotes, the single character may
14893 be represented by a letter or by @dfn{escape sequences}, which are of
14894 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14895 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14896 @samp{@var{x}} is a predefined special character---for example,
14897 @samp{\n} for newline.
14899 Wide character constants can be written by prefixing a character
14900 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14901 form of @samp{x}. The target wide character set is used when
14902 computing the value of this constant (@pxref{Character Sets}).
14905 String constants are a sequence of character constants surrounded by
14906 double quotes (@code{"}). Any valid character constant (as described
14907 above) may appear. Double quotes within the string must be preceded by
14908 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14911 Wide string constants can be written by prefixing a string constant
14912 with @samp{L}, as in C. The target wide character set is used when
14913 computing the value of this constant (@pxref{Character Sets}).
14916 Pointer constants are an integral value. You can also write pointers
14917 to constants using the C operator @samp{&}.
14920 Array constants are comma-separated lists surrounded by braces @samp{@{}
14921 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14922 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14923 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14926 @node C Plus Plus Expressions
14927 @subsubsection C@t{++} Expressions
14929 @cindex expressions in C@t{++}
14930 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14932 @cindex debugging C@t{++} programs
14933 @cindex C@t{++} compilers
14934 @cindex debug formats and C@t{++}
14935 @cindex @value{NGCC} and C@t{++}
14937 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14938 the proper compiler and the proper debug format. Currently,
14939 @value{GDBN} works best when debugging C@t{++} code that is compiled
14940 with the most recent version of @value{NGCC} possible. The DWARF
14941 debugging format is preferred; @value{NGCC} defaults to this on most
14942 popular platforms. Other compilers and/or debug formats are likely to
14943 work badly or not at all when using @value{GDBN} to debug C@t{++}
14944 code. @xref{Compilation}.
14949 @cindex member functions
14951 Member function calls are allowed; you can use expressions like
14954 count = aml->GetOriginal(x, y)
14957 @vindex this@r{, inside C@t{++} member functions}
14958 @cindex namespace in C@t{++}
14960 While a member function is active (in the selected stack frame), your
14961 expressions have the same namespace available as the member function;
14962 that is, @value{GDBN} allows implicit references to the class instance
14963 pointer @code{this} following the same rules as C@t{++}. @code{using}
14964 declarations in the current scope are also respected by @value{GDBN}.
14966 @cindex call overloaded functions
14967 @cindex overloaded functions, calling
14968 @cindex type conversions in C@t{++}
14970 You can call overloaded functions; @value{GDBN} resolves the function
14971 call to the right definition, with some restrictions. @value{GDBN} does not
14972 perform overload resolution involving user-defined type conversions,
14973 calls to constructors, or instantiations of templates that do not exist
14974 in the program. It also cannot handle ellipsis argument lists or
14977 It does perform integral conversions and promotions, floating-point
14978 promotions, arithmetic conversions, pointer conversions, conversions of
14979 class objects to base classes, and standard conversions such as those of
14980 functions or arrays to pointers; it requires an exact match on the
14981 number of function arguments.
14983 Overload resolution is always performed, unless you have specified
14984 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14985 ,@value{GDBN} Features for C@t{++}}.
14987 You must specify @code{set overload-resolution off} in order to use an
14988 explicit function signature to call an overloaded function, as in
14990 p 'foo(char,int)'('x', 13)
14993 The @value{GDBN} command-completion facility can simplify this;
14994 see @ref{Completion, ,Command Completion}.
14996 @cindex reference declarations
14998 @value{GDBN} understands variables declared as C@t{++} lvalue or rvalue
14999 references; you can use them in expressions just as you do in C@t{++}
15000 source---they are automatically dereferenced.
15002 In the parameter list shown when @value{GDBN} displays a frame, the values of
15003 reference variables are not displayed (unlike other variables); this
15004 avoids clutter, since references are often used for large structures.
15005 The @emph{address} of a reference variable is always shown, unless
15006 you have specified @samp{set print address off}.
15009 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
15010 expressions can use it just as expressions in your program do. Since
15011 one scope may be defined in another, you can use @code{::} repeatedly if
15012 necessary, for example in an expression like
15013 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
15014 resolving name scope by reference to source files, in both C and C@t{++}
15015 debugging (@pxref{Variables, ,Program Variables}).
15018 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
15023 @subsubsection C and C@t{++} Defaults
15025 @cindex C and C@t{++} defaults
15027 If you allow @value{GDBN} to set range checking automatically, it
15028 defaults to @code{off} whenever the working language changes to
15029 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
15030 selects the working language.
15032 If you allow @value{GDBN} to set the language automatically, it
15033 recognizes source files whose names end with @file{.c}, @file{.C}, or
15034 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
15035 these files, it sets the working language to C or C@t{++}.
15036 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
15037 for further details.
15040 @subsubsection C and C@t{++} Type and Range Checks
15042 @cindex C and C@t{++} checks
15044 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
15045 checking is used. However, if you turn type checking off, @value{GDBN}
15046 will allow certain non-standard conversions, such as promoting integer
15047 constants to pointers.
15049 Range checking, if turned on, is done on mathematical operations. Array
15050 indices are not checked, since they are often used to index a pointer
15051 that is not itself an array.
15054 @subsubsection @value{GDBN} and C
15056 The @code{set print union} and @code{show print union} commands apply to
15057 the @code{union} type. When set to @samp{on}, any @code{union} that is
15058 inside a @code{struct} or @code{class} is also printed. Otherwise, it
15059 appears as @samp{@{...@}}.
15061 The @code{@@} operator aids in the debugging of dynamic arrays, formed
15062 with pointers and a memory allocation function. @xref{Expressions,
15065 @node Debugging C Plus Plus
15066 @subsubsection @value{GDBN} Features for C@t{++}
15068 @cindex commands for C@t{++}
15070 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
15071 designed specifically for use with C@t{++}. Here is a summary:
15074 @cindex break in overloaded functions
15075 @item @r{breakpoint menus}
15076 When you want a breakpoint in a function whose name is overloaded,
15077 @value{GDBN} has the capability to display a menu of possible breakpoint
15078 locations to help you specify which function definition you want.
15079 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
15081 @cindex overloading in C@t{++}
15082 @item rbreak @var{regex}
15083 Setting breakpoints using regular expressions is helpful for setting
15084 breakpoints on overloaded functions that are not members of any special
15086 @xref{Set Breaks, ,Setting Breakpoints}.
15088 @cindex C@t{++} exception handling
15090 @itemx catch rethrow
15092 Debug C@t{++} exception handling using these commands. @xref{Set
15093 Catchpoints, , Setting Catchpoints}.
15095 @cindex inheritance
15096 @item ptype @var{typename}
15097 Print inheritance relationships as well as other information for type
15099 @xref{Symbols, ,Examining the Symbol Table}.
15101 @item info vtbl @var{expression}.
15102 The @code{info vtbl} command can be used to display the virtual
15103 method tables of the object computed by @var{expression}. This shows
15104 one entry per virtual table; there may be multiple virtual tables when
15105 multiple inheritance is in use.
15107 @cindex C@t{++} demangling
15108 @item demangle @var{name}
15109 Demangle @var{name}.
15110 @xref{Symbols}, for a more complete description of the @code{demangle} command.
15112 @cindex C@t{++} symbol display
15113 @item set print demangle
15114 @itemx show print demangle
15115 @itemx set print asm-demangle
15116 @itemx show print asm-demangle
15117 Control whether C@t{++} symbols display in their source form, both when
15118 displaying code as C@t{++} source and when displaying disassemblies.
15119 @xref{Print Settings, ,Print Settings}.
15121 @item set print object
15122 @itemx show print object
15123 Choose whether to print derived (actual) or declared types of objects.
15124 @xref{Print Settings, ,Print Settings}.
15126 @item set print vtbl
15127 @itemx show print vtbl
15128 Control the format for printing virtual function tables.
15129 @xref{Print Settings, ,Print Settings}.
15130 (The @code{vtbl} commands do not work on programs compiled with the HP
15131 ANSI C@t{++} compiler (@code{aCC}).)
15133 @kindex set overload-resolution
15134 @cindex overloaded functions, overload resolution
15135 @item set overload-resolution on
15136 Enable overload resolution for C@t{++} expression evaluation. The default
15137 is on. For overloaded functions, @value{GDBN} evaluates the arguments
15138 and searches for a function whose signature matches the argument types,
15139 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
15140 Expressions, ,C@t{++} Expressions}, for details).
15141 If it cannot find a match, it emits a message.
15143 @item set overload-resolution off
15144 Disable overload resolution for C@t{++} expression evaluation. For
15145 overloaded functions that are not class member functions, @value{GDBN}
15146 chooses the first function of the specified name that it finds in the
15147 symbol table, whether or not its arguments are of the correct type. For
15148 overloaded functions that are class member functions, @value{GDBN}
15149 searches for a function whose signature @emph{exactly} matches the
15152 @kindex show overload-resolution
15153 @item show overload-resolution
15154 Show the current setting of overload resolution.
15156 @item @r{Overloaded symbol names}
15157 You can specify a particular definition of an overloaded symbol, using
15158 the same notation that is used to declare such symbols in C@t{++}: type
15159 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
15160 also use the @value{GDBN} command-line word completion facilities to list the
15161 available choices, or to finish the type list for you.
15162 @xref{Completion,, Command Completion}, for details on how to do this.
15164 @item @r{Breakpoints in functions with ABI tags}
15166 The GNU C@t{++} compiler introduced the notion of ABI ``tags'', which
15167 correspond to changes in the ABI of a type, function, or variable that
15168 would not otherwise be reflected in a mangled name. See
15169 @url{https://developers.redhat.com/blog/2015/02/05/gcc5-and-the-c11-abi/}
15172 The ABI tags are visible in C@t{++} demangled names. For example, a
15173 function that returns a std::string:
15176 std::string function(int);
15180 when compiled for the C++11 ABI is marked with the @code{cxx11} ABI
15181 tag, and @value{GDBN} displays the symbol like this:
15184 function[abi:cxx11](int)
15187 You can set a breakpoint on such functions simply as if they had no
15191 (gdb) b function(int)
15192 Breakpoint 2 at 0x40060d: file main.cc, line 10.
15193 (gdb) info breakpoints
15194 Num Type Disp Enb Address What
15195 1 breakpoint keep y 0x0040060d in function[abi:cxx11](int)
15199 On the rare occasion you need to disambiguate between different ABI
15200 tags, you can do so by simply including the ABI tag in the function
15204 (@value{GDBP}) b ambiguous[abi:other_tag](int)
15208 @node Decimal Floating Point
15209 @subsubsection Decimal Floating Point format
15210 @cindex decimal floating point format
15212 @value{GDBN} can examine, set and perform computations with numbers in
15213 decimal floating point format, which in the C language correspond to the
15214 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
15215 specified by the extension to support decimal floating-point arithmetic.
15217 There are two encodings in use, depending on the architecture: BID (Binary
15218 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
15219 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
15222 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
15223 to manipulate decimal floating point numbers, it is not possible to convert
15224 (using a cast, for example) integers wider than 32-bit to decimal float.
15226 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
15227 point computations, error checking in decimal float operations ignores
15228 underflow, overflow and divide by zero exceptions.
15230 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
15231 to inspect @code{_Decimal128} values stored in floating point registers.
15232 See @ref{PowerPC,,PowerPC} for more details.
15238 @value{GDBN} can be used to debug programs written in D and compiled with
15239 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
15240 specific feature --- dynamic arrays.
15245 @cindex Go (programming language)
15246 @value{GDBN} can be used to debug programs written in Go and compiled with
15247 @file{gccgo} or @file{6g} compilers.
15249 Here is a summary of the Go-specific features and restrictions:
15252 @cindex current Go package
15253 @item The current Go package
15254 The name of the current package does not need to be specified when
15255 specifying global variables and functions.
15257 For example, given the program:
15261 var myglob = "Shall we?"
15267 When stopped inside @code{main} either of these work:
15271 (gdb) p main.myglob
15274 @cindex builtin Go types
15275 @item Builtin Go types
15276 The @code{string} type is recognized by @value{GDBN} and is printed
15279 @cindex builtin Go functions
15280 @item Builtin Go functions
15281 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
15282 function and handles it internally.
15284 @cindex restrictions on Go expressions
15285 @item Restrictions on Go expressions
15286 All Go operators are supported except @code{&^}.
15287 The Go @code{_} ``blank identifier'' is not supported.
15288 Automatic dereferencing of pointers is not supported.
15292 @subsection Objective-C
15294 @cindex Objective-C
15295 This section provides information about some commands and command
15296 options that are useful for debugging Objective-C code. See also
15297 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
15298 few more commands specific to Objective-C support.
15301 * Method Names in Commands::
15302 * The Print Command with Objective-C::
15305 @node Method Names in Commands
15306 @subsubsection Method Names in Commands
15308 The following commands have been extended to accept Objective-C method
15309 names as line specifications:
15311 @kindex clear@r{, and Objective-C}
15312 @kindex break@r{, and Objective-C}
15313 @kindex info line@r{, and Objective-C}
15314 @kindex jump@r{, and Objective-C}
15315 @kindex list@r{, and Objective-C}
15319 @item @code{info line}
15324 A fully qualified Objective-C method name is specified as
15327 -[@var{Class} @var{methodName}]
15330 where the minus sign is used to indicate an instance method and a
15331 plus sign (not shown) is used to indicate a class method. The class
15332 name @var{Class} and method name @var{methodName} are enclosed in
15333 brackets, similar to the way messages are specified in Objective-C
15334 source code. For example, to set a breakpoint at the @code{create}
15335 instance method of class @code{Fruit} in the program currently being
15339 break -[Fruit create]
15342 To list ten program lines around the @code{initialize} class method,
15346 list +[NSText initialize]
15349 In the current version of @value{GDBN}, the plus or minus sign is
15350 required. In future versions of @value{GDBN}, the plus or minus
15351 sign will be optional, but you can use it to narrow the search. It
15352 is also possible to specify just a method name:
15358 You must specify the complete method name, including any colons. If
15359 your program's source files contain more than one @code{create} method,
15360 you'll be presented with a numbered list of classes that implement that
15361 method. Indicate your choice by number, or type @samp{0} to exit if
15364 As another example, to clear a breakpoint established at the
15365 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
15368 clear -[NSWindow makeKeyAndOrderFront:]
15371 @node The Print Command with Objective-C
15372 @subsubsection The Print Command With Objective-C
15373 @cindex Objective-C, print objects
15374 @kindex print-object
15375 @kindex po @r{(@code{print-object})}
15377 The print command has also been extended to accept methods. For example:
15380 print -[@var{object} hash]
15383 @cindex print an Objective-C object description
15384 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
15386 will tell @value{GDBN} to send the @code{hash} message to @var{object}
15387 and print the result. Also, an additional command has been added,
15388 @code{print-object} or @code{po} for short, which is meant to print
15389 the description of an object. However, this command may only work
15390 with certain Objective-C libraries that have a particular hook
15391 function, @code{_NSPrintForDebugger}, defined.
15394 @subsection OpenCL C
15397 This section provides information about @value{GDBN}s OpenCL C support.
15400 * OpenCL C Datatypes::
15401 * OpenCL C Expressions::
15402 * OpenCL C Operators::
15405 @node OpenCL C Datatypes
15406 @subsubsection OpenCL C Datatypes
15408 @cindex OpenCL C Datatypes
15409 @value{GDBN} supports the builtin scalar and vector datatypes specified
15410 by OpenCL 1.1. In addition the half- and double-precision floating point
15411 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
15412 extensions are also known to @value{GDBN}.
15414 @node OpenCL C Expressions
15415 @subsubsection OpenCL C Expressions
15417 @cindex OpenCL C Expressions
15418 @value{GDBN} supports accesses to vector components including the access as
15419 lvalue where possible. Since OpenCL C is based on C99 most C expressions
15420 supported by @value{GDBN} can be used as well.
15422 @node OpenCL C Operators
15423 @subsubsection OpenCL C Operators
15425 @cindex OpenCL C Operators
15426 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
15430 @subsection Fortran
15431 @cindex Fortran-specific support in @value{GDBN}
15433 @value{GDBN} can be used to debug programs written in Fortran, but it
15434 currently supports only the features of Fortran 77 language.
15436 @cindex trailing underscore, in Fortran symbols
15437 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
15438 among them) append an underscore to the names of variables and
15439 functions. When you debug programs compiled by those compilers, you
15440 will need to refer to variables and functions with a trailing
15444 * Fortran Operators:: Fortran operators and expressions
15445 * Fortran Defaults:: Default settings for Fortran
15446 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
15449 @node Fortran Operators
15450 @subsubsection Fortran Operators and Expressions
15452 @cindex Fortran operators and expressions
15454 Operators must be defined on values of specific types. For instance,
15455 @code{+} is defined on numbers, but not on characters or other non-
15456 arithmetic types. Operators are often defined on groups of types.
15460 The exponentiation operator. It raises the first operand to the power
15464 The range operator. Normally used in the form of array(low:high) to
15465 represent a section of array.
15468 The access component operator. Normally used to access elements in derived
15469 types. Also suitable for unions. As unions aren't part of regular Fortran,
15470 this can only happen when accessing a register that uses a gdbarch-defined
15474 @node Fortran Defaults
15475 @subsubsection Fortran Defaults
15477 @cindex Fortran Defaults
15479 Fortran symbols are usually case-insensitive, so @value{GDBN} by
15480 default uses case-insensitive matches for Fortran symbols. You can
15481 change that with the @samp{set case-insensitive} command, see
15482 @ref{Symbols}, for the details.
15484 @node Special Fortran Commands
15485 @subsubsection Special Fortran Commands
15487 @cindex Special Fortran commands
15489 @value{GDBN} has some commands to support Fortran-specific features,
15490 such as displaying common blocks.
15493 @cindex @code{COMMON} blocks, Fortran
15494 @kindex info common
15495 @item info common @r{[}@var{common-name}@r{]}
15496 This command prints the values contained in the Fortran @code{COMMON}
15497 block whose name is @var{common-name}. With no argument, the names of
15498 all @code{COMMON} blocks visible at the current program location are
15505 @cindex Pascal support in @value{GDBN}, limitations
15506 Debugging Pascal programs which use sets, subranges, file variables, or
15507 nested functions does not currently work. @value{GDBN} does not support
15508 entering expressions, printing values, or similar features using Pascal
15511 The Pascal-specific command @code{set print pascal_static-members}
15512 controls whether static members of Pascal objects are displayed.
15513 @xref{Print Settings, pascal_static-members}.
15518 @value{GDBN} supports the @url{https://www.rust-lang.org/, Rust
15519 Programming Language}. Type- and value-printing, and expression
15520 parsing, are reasonably complete. However, there are a few
15521 peculiarities and holes to be aware of.
15525 Linespecs (@pxref{Specify Location}) are never relative to the current
15526 crate. Instead, they act as if there were a global namespace of
15527 crates, somewhat similar to the way @code{extern crate} behaves.
15529 That is, if @value{GDBN} is stopped at a breakpoint in a function in
15530 crate @samp{A}, module @samp{B}, then @code{break B::f} will attempt
15531 to set a breakpoint in a function named @samp{f} in a crate named
15534 As a consequence of this approach, linespecs also cannot refer to
15535 items using @samp{self::} or @samp{super::}.
15538 Because @value{GDBN} implements Rust name-lookup semantics in
15539 expressions, it will sometimes prepend the current crate to a name.
15540 For example, if @value{GDBN} is stopped at a breakpoint in the crate
15541 @samp{K}, then @code{print ::x::y} will try to find the symbol
15544 However, since it is useful to be able to refer to other crates when
15545 debugging, @value{GDBN} provides the @code{extern} extension to
15546 circumvent this. To use the extension, just put @code{extern} before
15547 a path expression to refer to the otherwise unavailable ``global''
15550 In the above example, if you wanted to refer to the symbol @samp{y} in
15551 the crate @samp{x}, you would use @code{print extern x::y}.
15554 The Rust expression evaluator does not support ``statement-like''
15555 expressions such as @code{if} or @code{match}, or lambda expressions.
15558 Tuple expressions are not implemented.
15561 The Rust expression evaluator does not currently implement the
15562 @code{Drop} trait. Objects that may be created by the evaluator will
15563 never be destroyed.
15566 @value{GDBN} does not implement type inference for generics. In order
15567 to call generic functions or otherwise refer to generic items, you
15568 will have to specify the type parameters manually.
15571 @value{GDBN} currently uses the C@t{++} demangler for Rust. In most
15572 cases this does not cause any problems. However, in an expression
15573 context, completing a generic function name will give syntactically
15574 invalid results. This happens because Rust requires the @samp{::}
15575 operator between the function name and its generic arguments. For
15576 example, @value{GDBN} might provide a completion like
15577 @code{crate::f<u32>}, where the parser would require
15578 @code{crate::f::<u32>}.
15581 As of this writing, the Rust compiler (version 1.8) has a few holes in
15582 the debugging information it generates. These holes prevent certain
15583 features from being implemented by @value{GDBN}:
15587 Method calls cannot be made via traits.
15590 Operator overloading is not implemented.
15593 When debugging in a monomorphized function, you cannot use the generic
15597 The type @code{Self} is not available.
15600 @code{use} statements are not available, so some names may not be
15601 available in the crate.
15606 @subsection Modula-2
15608 @cindex Modula-2, @value{GDBN} support
15610 The extensions made to @value{GDBN} to support Modula-2 only support
15611 output from the @sc{gnu} Modula-2 compiler (which is currently being
15612 developed). Other Modula-2 compilers are not currently supported, and
15613 attempting to debug executables produced by them is most likely
15614 to give an error as @value{GDBN} reads in the executable's symbol
15617 @cindex expressions in Modula-2
15619 * M2 Operators:: Built-in operators
15620 * Built-In Func/Proc:: Built-in functions and procedures
15621 * M2 Constants:: Modula-2 constants
15622 * M2 Types:: Modula-2 types
15623 * M2 Defaults:: Default settings for Modula-2
15624 * Deviations:: Deviations from standard Modula-2
15625 * M2 Checks:: Modula-2 type and range checks
15626 * M2 Scope:: The scope operators @code{::} and @code{.}
15627 * GDB/M2:: @value{GDBN} and Modula-2
15631 @subsubsection Operators
15632 @cindex Modula-2 operators
15634 Operators must be defined on values of specific types. For instance,
15635 @code{+} is defined on numbers, but not on structures. Operators are
15636 often defined on groups of types. For the purposes of Modula-2, the
15637 following definitions hold:
15642 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15646 @emph{Character types} consist of @code{CHAR} and its subranges.
15649 @emph{Floating-point types} consist of @code{REAL}.
15652 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15656 @emph{Scalar types} consist of all of the above.
15659 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15662 @emph{Boolean types} consist of @code{BOOLEAN}.
15666 The following operators are supported, and appear in order of
15667 increasing precedence:
15671 Function argument or array index separator.
15674 Assignment. The value of @var{var} @code{:=} @var{value} is
15678 Less than, greater than on integral, floating-point, or enumerated
15682 Less than or equal to, greater than or equal to
15683 on integral, floating-point and enumerated types, or set inclusion on
15684 set types. Same precedence as @code{<}.
15686 @item =@r{, }<>@r{, }#
15687 Equality and two ways of expressing inequality, valid on scalar types.
15688 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15689 available for inequality, since @code{#} conflicts with the script
15693 Set membership. Defined on set types and the types of their members.
15694 Same precedence as @code{<}.
15697 Boolean disjunction. Defined on boolean types.
15700 Boolean conjunction. Defined on boolean types.
15703 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15706 Addition and subtraction on integral and floating-point types, or union
15707 and difference on set types.
15710 Multiplication on integral and floating-point types, or set intersection
15714 Division on floating-point types, or symmetric set difference on set
15715 types. Same precedence as @code{*}.
15718 Integer division and remainder. Defined on integral types. Same
15719 precedence as @code{*}.
15722 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15725 Pointer dereferencing. Defined on pointer types.
15728 Boolean negation. Defined on boolean types. Same precedence as
15732 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15733 precedence as @code{^}.
15736 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15739 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15743 @value{GDBN} and Modula-2 scope operators.
15747 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15748 treats the use of the operator @code{IN}, or the use of operators
15749 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15750 @code{<=}, and @code{>=} on sets as an error.
15754 @node Built-In Func/Proc
15755 @subsubsection Built-in Functions and Procedures
15756 @cindex Modula-2 built-ins
15758 Modula-2 also makes available several built-in procedures and functions.
15759 In describing these, the following metavariables are used:
15764 represents an @code{ARRAY} variable.
15767 represents a @code{CHAR} constant or variable.
15770 represents a variable or constant of integral type.
15773 represents an identifier that belongs to a set. Generally used in the
15774 same function with the metavariable @var{s}. The type of @var{s} should
15775 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15778 represents a variable or constant of integral or floating-point type.
15781 represents a variable or constant of floating-point type.
15787 represents a variable.
15790 represents a variable or constant of one of many types. See the
15791 explanation of the function for details.
15794 All Modula-2 built-in procedures also return a result, described below.
15798 Returns the absolute value of @var{n}.
15801 If @var{c} is a lower case letter, it returns its upper case
15802 equivalent, otherwise it returns its argument.
15805 Returns the character whose ordinal value is @var{i}.
15808 Decrements the value in the variable @var{v} by one. Returns the new value.
15810 @item DEC(@var{v},@var{i})
15811 Decrements the value in the variable @var{v} by @var{i}. Returns the
15814 @item EXCL(@var{m},@var{s})
15815 Removes the element @var{m} from the set @var{s}. Returns the new
15818 @item FLOAT(@var{i})
15819 Returns the floating point equivalent of the integer @var{i}.
15821 @item HIGH(@var{a})
15822 Returns the index of the last member of @var{a}.
15825 Increments the value in the variable @var{v} by one. Returns the new value.
15827 @item INC(@var{v},@var{i})
15828 Increments the value in the variable @var{v} by @var{i}. Returns the
15831 @item INCL(@var{m},@var{s})
15832 Adds the element @var{m} to the set @var{s} if it is not already
15833 there. Returns the new set.
15836 Returns the maximum value of the type @var{t}.
15839 Returns the minimum value of the type @var{t}.
15842 Returns boolean TRUE if @var{i} is an odd number.
15845 Returns the ordinal value of its argument. For example, the ordinal
15846 value of a character is its @sc{ascii} value (on machines supporting
15847 the @sc{ascii} character set). The argument @var{x} must be of an
15848 ordered type, which include integral, character and enumerated types.
15850 @item SIZE(@var{x})
15851 Returns the size of its argument. The argument @var{x} can be a
15852 variable or a type.
15854 @item TRUNC(@var{r})
15855 Returns the integral part of @var{r}.
15857 @item TSIZE(@var{x})
15858 Returns the size of its argument. The argument @var{x} can be a
15859 variable or a type.
15861 @item VAL(@var{t},@var{i})
15862 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15866 @emph{Warning:} Sets and their operations are not yet supported, so
15867 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15871 @cindex Modula-2 constants
15873 @subsubsection Constants
15875 @value{GDBN} allows you to express the constants of Modula-2 in the following
15881 Integer constants are simply a sequence of digits. When used in an
15882 expression, a constant is interpreted to be type-compatible with the
15883 rest of the expression. Hexadecimal integers are specified by a
15884 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15887 Floating point constants appear as a sequence of digits, followed by a
15888 decimal point and another sequence of digits. An optional exponent can
15889 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15890 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15891 digits of the floating point constant must be valid decimal (base 10)
15895 Character constants consist of a single character enclosed by a pair of
15896 like quotes, either single (@code{'}) or double (@code{"}). They may
15897 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15898 followed by a @samp{C}.
15901 String constants consist of a sequence of characters enclosed by a
15902 pair of like quotes, either single (@code{'}) or double (@code{"}).
15903 Escape sequences in the style of C are also allowed. @xref{C
15904 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15908 Enumerated constants consist of an enumerated identifier.
15911 Boolean constants consist of the identifiers @code{TRUE} and
15915 Pointer constants consist of integral values only.
15918 Set constants are not yet supported.
15922 @subsubsection Modula-2 Types
15923 @cindex Modula-2 types
15925 Currently @value{GDBN} can print the following data types in Modula-2
15926 syntax: array types, record types, set types, pointer types, procedure
15927 types, enumerated types, subrange types and base types. You can also
15928 print the contents of variables declared using these type.
15929 This section gives a number of simple source code examples together with
15930 sample @value{GDBN} sessions.
15932 The first example contains the following section of code:
15941 and you can request @value{GDBN} to interrogate the type and value of
15942 @code{r} and @code{s}.
15945 (@value{GDBP}) print s
15947 (@value{GDBP}) ptype s
15949 (@value{GDBP}) print r
15951 (@value{GDBP}) ptype r
15956 Likewise if your source code declares @code{s} as:
15960 s: SET ['A'..'Z'] ;
15964 then you may query the type of @code{s} by:
15967 (@value{GDBP}) ptype s
15968 type = SET ['A'..'Z']
15972 Note that at present you cannot interactively manipulate set
15973 expressions using the debugger.
15975 The following example shows how you might declare an array in Modula-2
15976 and how you can interact with @value{GDBN} to print its type and contents:
15980 s: ARRAY [-10..10] OF CHAR ;
15984 (@value{GDBP}) ptype s
15985 ARRAY [-10..10] OF CHAR
15988 Note that the array handling is not yet complete and although the type
15989 is printed correctly, expression handling still assumes that all
15990 arrays have a lower bound of zero and not @code{-10} as in the example
15993 Here are some more type related Modula-2 examples:
15997 colour = (blue, red, yellow, green) ;
15998 t = [blue..yellow] ;
16006 The @value{GDBN} interaction shows how you can query the data type
16007 and value of a variable.
16010 (@value{GDBP}) print s
16012 (@value{GDBP}) ptype t
16013 type = [blue..yellow]
16017 In this example a Modula-2 array is declared and its contents
16018 displayed. Observe that the contents are written in the same way as
16019 their @code{C} counterparts.
16023 s: ARRAY [1..5] OF CARDINAL ;
16029 (@value{GDBP}) print s
16030 $1 = @{1, 0, 0, 0, 0@}
16031 (@value{GDBP}) ptype s
16032 type = ARRAY [1..5] OF CARDINAL
16035 The Modula-2 language interface to @value{GDBN} also understands
16036 pointer types as shown in this example:
16040 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
16047 and you can request that @value{GDBN} describes the type of @code{s}.
16050 (@value{GDBP}) ptype s
16051 type = POINTER TO ARRAY [1..5] OF CARDINAL
16054 @value{GDBN} handles compound types as we can see in this example.
16055 Here we combine array types, record types, pointer types and subrange
16066 myarray = ARRAY myrange OF CARDINAL ;
16067 myrange = [-2..2] ;
16069 s: POINTER TO ARRAY myrange OF foo ;
16073 and you can ask @value{GDBN} to describe the type of @code{s} as shown
16077 (@value{GDBP}) ptype s
16078 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
16081 f3 : ARRAY [-2..2] OF CARDINAL;
16086 @subsubsection Modula-2 Defaults
16087 @cindex Modula-2 defaults
16089 If type and range checking are set automatically by @value{GDBN}, they
16090 both default to @code{on} whenever the working language changes to
16091 Modula-2. This happens regardless of whether you or @value{GDBN}
16092 selected the working language.
16094 If you allow @value{GDBN} to set the language automatically, then entering
16095 code compiled from a file whose name ends with @file{.mod} sets the
16096 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
16097 Infer the Source Language}, for further details.
16100 @subsubsection Deviations from Standard Modula-2
16101 @cindex Modula-2, deviations from
16103 A few changes have been made to make Modula-2 programs easier to debug.
16104 This is done primarily via loosening its type strictness:
16108 Unlike in standard Modula-2, pointer constants can be formed by
16109 integers. This allows you to modify pointer variables during
16110 debugging. (In standard Modula-2, the actual address contained in a
16111 pointer variable is hidden from you; it can only be modified
16112 through direct assignment to another pointer variable or expression that
16113 returned a pointer.)
16116 C escape sequences can be used in strings and characters to represent
16117 non-printable characters. @value{GDBN} prints out strings with these
16118 escape sequences embedded. Single non-printable characters are
16119 printed using the @samp{CHR(@var{nnn})} format.
16122 The assignment operator (@code{:=}) returns the value of its right-hand
16126 All built-in procedures both modify @emph{and} return their argument.
16130 @subsubsection Modula-2 Type and Range Checks
16131 @cindex Modula-2 checks
16134 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
16137 @c FIXME remove warning when type/range checks added
16139 @value{GDBN} considers two Modula-2 variables type equivalent if:
16143 They are of types that have been declared equivalent via a @code{TYPE
16144 @var{t1} = @var{t2}} statement
16147 They have been declared on the same line. (Note: This is true of the
16148 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
16151 As long as type checking is enabled, any attempt to combine variables
16152 whose types are not equivalent is an error.
16154 Range checking is done on all mathematical operations, assignment, array
16155 index bounds, and all built-in functions and procedures.
16158 @subsubsection The Scope Operators @code{::} and @code{.}
16160 @cindex @code{.}, Modula-2 scope operator
16161 @cindex colon, doubled as scope operator
16163 @vindex colon-colon@r{, in Modula-2}
16164 @c Info cannot handle :: but TeX can.
16167 @vindex ::@r{, in Modula-2}
16170 There are a few subtle differences between the Modula-2 scope operator
16171 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
16176 @var{module} . @var{id}
16177 @var{scope} :: @var{id}
16181 where @var{scope} is the name of a module or a procedure,
16182 @var{module} the name of a module, and @var{id} is any declared
16183 identifier within your program, except another module.
16185 Using the @code{::} operator makes @value{GDBN} search the scope
16186 specified by @var{scope} for the identifier @var{id}. If it is not
16187 found in the specified scope, then @value{GDBN} searches all scopes
16188 enclosing the one specified by @var{scope}.
16190 Using the @code{.} operator makes @value{GDBN} search the current scope for
16191 the identifier specified by @var{id} that was imported from the
16192 definition module specified by @var{module}. With this operator, it is
16193 an error if the identifier @var{id} was not imported from definition
16194 module @var{module}, or if @var{id} is not an identifier in
16198 @subsubsection @value{GDBN} and Modula-2
16200 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
16201 Five subcommands of @code{set print} and @code{show print} apply
16202 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
16203 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
16204 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
16205 analogue in Modula-2.
16207 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
16208 with any language, is not useful with Modula-2. Its
16209 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
16210 created in Modula-2 as they can in C or C@t{++}. However, because an
16211 address can be specified by an integral constant, the construct
16212 @samp{@{@var{type}@}@var{adrexp}} is still useful.
16214 @cindex @code{#} in Modula-2
16215 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
16216 interpreted as the beginning of a comment. Use @code{<>} instead.
16222 The extensions made to @value{GDBN} for Ada only support
16223 output from the @sc{gnu} Ada (GNAT) compiler.
16224 Other Ada compilers are not currently supported, and
16225 attempting to debug executables produced by them is most likely
16229 @cindex expressions in Ada
16231 * Ada Mode Intro:: General remarks on the Ada syntax
16232 and semantics supported by Ada mode
16234 * Omissions from Ada:: Restrictions on the Ada expression syntax.
16235 * Additions to Ada:: Extensions of the Ada expression syntax.
16236 * Overloading support for Ada:: Support for expressions involving overloaded
16238 * Stopping Before Main Program:: Debugging the program during elaboration.
16239 * Ada Exceptions:: Ada Exceptions
16240 * Ada Tasks:: Listing and setting breakpoints in tasks.
16241 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
16242 * Ravenscar Profile:: Tasking Support when using the Ravenscar
16244 * Ada Glitches:: Known peculiarities of Ada mode.
16247 @node Ada Mode Intro
16248 @subsubsection Introduction
16249 @cindex Ada mode, general
16251 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
16252 syntax, with some extensions.
16253 The philosophy behind the design of this subset is
16257 That @value{GDBN} should provide basic literals and access to operations for
16258 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
16259 leaving more sophisticated computations to subprograms written into the
16260 program (which therefore may be called from @value{GDBN}).
16263 That type safety and strict adherence to Ada language restrictions
16264 are not particularly important to the @value{GDBN} user.
16267 That brevity is important to the @value{GDBN} user.
16270 Thus, for brevity, the debugger acts as if all names declared in
16271 user-written packages are directly visible, even if they are not visible
16272 according to Ada rules, thus making it unnecessary to fully qualify most
16273 names with their packages, regardless of context. Where this causes
16274 ambiguity, @value{GDBN} asks the user's intent.
16276 The debugger will start in Ada mode if it detects an Ada main program.
16277 As for other languages, it will enter Ada mode when stopped in a program that
16278 was translated from an Ada source file.
16280 While in Ada mode, you may use `@t{--}' for comments. This is useful
16281 mostly for documenting command files. The standard @value{GDBN} comment
16282 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
16283 middle (to allow based literals).
16285 @node Omissions from Ada
16286 @subsubsection Omissions from Ada
16287 @cindex Ada, omissions from
16289 Here are the notable omissions from the subset:
16293 Only a subset of the attributes are supported:
16297 @t{'First}, @t{'Last}, and @t{'Length}
16298 on array objects (not on types and subtypes).
16301 @t{'Min} and @t{'Max}.
16304 @t{'Pos} and @t{'Val}.
16310 @t{'Range} on array objects (not subtypes), but only as the right
16311 operand of the membership (@code{in}) operator.
16314 @t{'Access}, @t{'Unchecked_Access}, and
16315 @t{'Unrestricted_Access} (a GNAT extension).
16323 @code{Characters.Latin_1} are not available and
16324 concatenation is not implemented. Thus, escape characters in strings are
16325 not currently available.
16328 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
16329 equality of representations. They will generally work correctly
16330 for strings and arrays whose elements have integer or enumeration types.
16331 They may not work correctly for arrays whose element
16332 types have user-defined equality, for arrays of real values
16333 (in particular, IEEE-conformant floating point, because of negative
16334 zeroes and NaNs), and for arrays whose elements contain unused bits with
16335 indeterminate values.
16338 The other component-by-component array operations (@code{and}, @code{or},
16339 @code{xor}, @code{not}, and relational tests other than equality)
16340 are not implemented.
16343 @cindex array aggregates (Ada)
16344 @cindex record aggregates (Ada)
16345 @cindex aggregates (Ada)
16346 There is limited support for array and record aggregates. They are
16347 permitted only on the right sides of assignments, as in these examples:
16350 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
16351 (@value{GDBP}) set An_Array := (1, others => 0)
16352 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
16353 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
16354 (@value{GDBP}) set A_Record := (1, "Peter", True);
16355 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
16359 discriminant's value by assigning an aggregate has an
16360 undefined effect if that discriminant is used within the record.
16361 However, you can first modify discriminants by directly assigning to
16362 them (which normally would not be allowed in Ada), and then performing an
16363 aggregate assignment. For example, given a variable @code{A_Rec}
16364 declared to have a type such as:
16367 type Rec (Len : Small_Integer := 0) is record
16369 Vals : IntArray (1 .. Len);
16373 you can assign a value with a different size of @code{Vals} with two
16377 (@value{GDBP}) set A_Rec.Len := 4
16378 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
16381 As this example also illustrates, @value{GDBN} is very loose about the usual
16382 rules concerning aggregates. You may leave out some of the
16383 components of an array or record aggregate (such as the @code{Len}
16384 component in the assignment to @code{A_Rec} above); they will retain their
16385 original values upon assignment. You may freely use dynamic values as
16386 indices in component associations. You may even use overlapping or
16387 redundant component associations, although which component values are
16388 assigned in such cases is not defined.
16391 Calls to dispatching subprograms are not implemented.
16394 The overloading algorithm is much more limited (i.e., less selective)
16395 than that of real Ada. It makes only limited use of the context in
16396 which a subexpression appears to resolve its meaning, and it is much
16397 looser in its rules for allowing type matches. As a result, some
16398 function calls will be ambiguous, and the user will be asked to choose
16399 the proper resolution.
16402 The @code{new} operator is not implemented.
16405 Entry calls are not implemented.
16408 Aside from printing, arithmetic operations on the native VAX floating-point
16409 formats are not supported.
16412 It is not possible to slice a packed array.
16415 The names @code{True} and @code{False}, when not part of a qualified name,
16416 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
16418 Should your program
16419 redefine these names in a package or procedure (at best a dubious practice),
16420 you will have to use fully qualified names to access their new definitions.
16423 @node Additions to Ada
16424 @subsubsection Additions to Ada
16425 @cindex Ada, deviations from
16427 As it does for other languages, @value{GDBN} makes certain generic
16428 extensions to Ada (@pxref{Expressions}):
16432 If the expression @var{E} is a variable residing in memory (typically
16433 a local variable or array element) and @var{N} is a positive integer,
16434 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
16435 @var{N}-1 adjacent variables following it in memory as an array. In
16436 Ada, this operator is generally not necessary, since its prime use is
16437 in displaying parts of an array, and slicing will usually do this in
16438 Ada. However, there are occasional uses when debugging programs in
16439 which certain debugging information has been optimized away.
16442 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
16443 appears in function or file @var{B}.'' When @var{B} is a file name,
16444 you must typically surround it in single quotes.
16447 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
16448 @var{type} that appears at address @var{addr}.''
16451 A name starting with @samp{$} is a convenience variable
16452 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
16455 In addition, @value{GDBN} provides a few other shortcuts and outright
16456 additions specific to Ada:
16460 The assignment statement is allowed as an expression, returning
16461 its right-hand operand as its value. Thus, you may enter
16464 (@value{GDBP}) set x := y + 3
16465 (@value{GDBP}) print A(tmp := y + 1)
16469 The semicolon is allowed as an ``operator,'' returning as its value
16470 the value of its right-hand operand.
16471 This allows, for example,
16472 complex conditional breaks:
16475 (@value{GDBP}) break f
16476 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
16480 Rather than use catenation and symbolic character names to introduce special
16481 characters into strings, one may instead use a special bracket notation,
16482 which is also used to print strings. A sequence of characters of the form
16483 @samp{["@var{XX}"]} within a string or character literal denotes the
16484 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
16485 sequence of characters @samp{["""]} also denotes a single quotation mark
16486 in strings. For example,
16488 "One line.["0a"]Next line.["0a"]"
16491 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
16495 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
16496 @t{'Max} is optional (and is ignored in any case). For example, it is valid
16500 (@value{GDBP}) print 'max(x, y)
16504 When printing arrays, @value{GDBN} uses positional notation when the
16505 array has a lower bound of 1, and uses a modified named notation otherwise.
16506 For example, a one-dimensional array of three integers with a lower bound
16507 of 3 might print as
16514 That is, in contrast to valid Ada, only the first component has a @code{=>}
16518 You may abbreviate attributes in expressions with any unique,
16519 multi-character subsequence of
16520 their names (an exact match gets preference).
16521 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
16522 in place of @t{a'length}.
16525 @cindex quoting Ada internal identifiers
16526 Since Ada is case-insensitive, the debugger normally maps identifiers you type
16527 to lower case. The GNAT compiler uses upper-case characters for
16528 some of its internal identifiers, which are normally of no interest to users.
16529 For the rare occasions when you actually have to look at them,
16530 enclose them in angle brackets to avoid the lower-case mapping.
16533 (@value{GDBP}) print <JMPBUF_SAVE>[0]
16537 Printing an object of class-wide type or dereferencing an
16538 access-to-class-wide value will display all the components of the object's
16539 specific type (as indicated by its run-time tag). Likewise, component
16540 selection on such a value will operate on the specific type of the
16545 @node Overloading support for Ada
16546 @subsubsection Overloading support for Ada
16547 @cindex overloading, Ada
16549 The debugger supports limited overloading. Given a subprogram call in which
16550 the function symbol has multiple definitions, it will use the number of
16551 actual parameters and some information about their types to attempt to narrow
16552 the set of definitions. It also makes very limited use of context, preferring
16553 procedures to functions in the context of the @code{call} command, and
16554 functions to procedures elsewhere.
16556 If, after narrowing, the set of matching definitions still contains more than
16557 one definition, @value{GDBN} will display a menu to query which one it should
16561 (@value{GDBP}) print f(1)
16562 Multiple matches for f
16564 [1] foo.f (integer) return boolean at foo.adb:23
16565 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
16569 In this case, just select one menu entry either to cancel expression evaluation
16570 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
16571 instance (type the corresponding number and press @key{RET}).
16573 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16578 @kindex set ada print-signatures
16579 @item set ada print-signatures
16580 Control whether parameter types and return types are displayed in overloads
16581 selection menus. It is @code{on} by default.
16582 @xref{Overloading support for Ada}.
16584 @kindex show ada print-signatures
16585 @item show ada print-signatures
16586 Show the current setting for displaying parameter types and return types in
16587 overloads selection menu.
16588 @xref{Overloading support for Ada}.
16592 @node Stopping Before Main Program
16593 @subsubsection Stopping at the Very Beginning
16595 @cindex breakpointing Ada elaboration code
16596 It is sometimes necessary to debug the program during elaboration, and
16597 before reaching the main procedure.
16598 As defined in the Ada Reference
16599 Manual, the elaboration code is invoked from a procedure called
16600 @code{adainit}. To run your program up to the beginning of
16601 elaboration, simply use the following two commands:
16602 @code{tbreak adainit} and @code{run}.
16604 @node Ada Exceptions
16605 @subsubsection Ada Exceptions
16607 A command is provided to list all Ada exceptions:
16610 @kindex info exceptions
16611 @item info exceptions
16612 @itemx info exceptions @var{regexp}
16613 The @code{info exceptions} command allows you to list all Ada exceptions
16614 defined within the program being debugged, as well as their addresses.
16615 With a regular expression, @var{regexp}, as argument, only those exceptions
16616 whose names match @var{regexp} are listed.
16619 Below is a small example, showing how the command can be used, first
16620 without argument, and next with a regular expression passed as an
16624 (@value{GDBP}) info exceptions
16625 All defined Ada exceptions:
16626 constraint_error: 0x613da0
16627 program_error: 0x613d20
16628 storage_error: 0x613ce0
16629 tasking_error: 0x613ca0
16630 const.aint_global_e: 0x613b00
16631 (@value{GDBP}) info exceptions const.aint
16632 All Ada exceptions matching regular expression "const.aint":
16633 constraint_error: 0x613da0
16634 const.aint_global_e: 0x613b00
16637 It is also possible to ask @value{GDBN} to stop your program's execution
16638 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16641 @subsubsection Extensions for Ada Tasks
16642 @cindex Ada, tasking
16644 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16645 @value{GDBN} provides the following task-related commands:
16650 This command shows a list of current Ada tasks, as in the following example:
16657 (@value{GDBP}) info tasks
16658 ID TID P-ID Pri State Name
16659 1 8088000 0 15 Child Activation Wait main_task
16660 2 80a4000 1 15 Accept Statement b
16661 3 809a800 1 15 Child Activation Wait a
16662 * 4 80ae800 3 15 Runnable c
16667 In this listing, the asterisk before the last task indicates it to be the
16668 task currently being inspected.
16672 Represents @value{GDBN}'s internal task number.
16678 The parent's task ID (@value{GDBN}'s internal task number).
16681 The base priority of the task.
16684 Current state of the task.
16688 The task has been created but has not been activated. It cannot be
16692 The task is not blocked for any reason known to Ada. (It may be waiting
16693 for a mutex, though.) It is conceptually "executing" in normal mode.
16696 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16697 that were waiting on terminate alternatives have been awakened and have
16698 terminated themselves.
16700 @item Child Activation Wait
16701 The task is waiting for created tasks to complete activation.
16703 @item Accept Statement
16704 The task is waiting on an accept or selective wait statement.
16706 @item Waiting on entry call
16707 The task is waiting on an entry call.
16709 @item Async Select Wait
16710 The task is waiting to start the abortable part of an asynchronous
16714 The task is waiting on a select statement with only a delay
16717 @item Child Termination Wait
16718 The task is sleeping having completed a master within itself, and is
16719 waiting for the tasks dependent on that master to become terminated or
16720 waiting on a terminate Phase.
16722 @item Wait Child in Term Alt
16723 The task is sleeping waiting for tasks on terminate alternatives to
16724 finish terminating.
16726 @item Accepting RV with @var{taskno}
16727 The task is accepting a rendez-vous with the task @var{taskno}.
16731 Name of the task in the program.
16735 @kindex info task @var{taskno}
16736 @item info task @var{taskno}
16737 This command shows detailled informations on the specified task, as in
16738 the following example:
16743 (@value{GDBP}) info tasks
16744 ID TID P-ID Pri State Name
16745 1 8077880 0 15 Child Activation Wait main_task
16746 * 2 807c468 1 15 Runnable task_1
16747 (@value{GDBP}) info task 2
16748 Ada Task: 0x807c468
16751 Parent: 1 (main_task)
16757 @kindex task@r{ (Ada)}
16758 @cindex current Ada task ID
16759 This command prints the ID of the current task.
16765 (@value{GDBP}) info tasks
16766 ID TID P-ID Pri State Name
16767 1 8077870 0 15 Child Activation Wait main_task
16768 * 2 807c458 1 15 Runnable t
16769 (@value{GDBP}) task
16770 [Current task is 2]
16773 @item task @var{taskno}
16774 @cindex Ada task switching
16775 This command is like the @code{thread @var{thread-id}}
16776 command (@pxref{Threads}). It switches the context of debugging
16777 from the current task to the given task.
16783 (@value{GDBP}) info tasks
16784 ID TID P-ID Pri State Name
16785 1 8077870 0 15 Child Activation Wait main_task
16786 * 2 807c458 1 15 Runnable t
16787 (@value{GDBP}) task 1
16788 [Switching to task 1]
16789 #0 0x8067726 in pthread_cond_wait ()
16791 #0 0x8067726 in pthread_cond_wait ()
16792 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16793 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16794 #3 0x806153e in system.tasking.stages.activate_tasks ()
16795 #4 0x804aacc in un () at un.adb:5
16798 @item break @var{location} task @var{taskno}
16799 @itemx break @var{location} task @var{taskno} if @dots{}
16800 @cindex breakpoints and tasks, in Ada
16801 @cindex task breakpoints, in Ada
16802 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16803 These commands are like the @code{break @dots{} thread @dots{}}
16804 command (@pxref{Thread Stops}). The
16805 @var{location} argument specifies source lines, as described
16806 in @ref{Specify Location}.
16808 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16809 to specify that you only want @value{GDBN} to stop the program when a
16810 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16811 numeric task identifiers assigned by @value{GDBN}, shown in the first
16812 column of the @samp{info tasks} display.
16814 If you do not specify @samp{task @var{taskno}} when you set a
16815 breakpoint, the breakpoint applies to @emph{all} tasks of your
16818 You can use the @code{task} qualifier on conditional breakpoints as
16819 well; in this case, place @samp{task @var{taskno}} before the
16820 breakpoint condition (before the @code{if}).
16828 (@value{GDBP}) info tasks
16829 ID TID P-ID Pri State Name
16830 1 140022020 0 15 Child Activation Wait main_task
16831 2 140045060 1 15 Accept/Select Wait t2
16832 3 140044840 1 15 Runnable t1
16833 * 4 140056040 1 15 Runnable t3
16834 (@value{GDBP}) b 15 task 2
16835 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16836 (@value{GDBP}) cont
16841 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16843 (@value{GDBP}) info tasks
16844 ID TID P-ID Pri State Name
16845 1 140022020 0 15 Child Activation Wait main_task
16846 * 2 140045060 1 15 Runnable t2
16847 3 140044840 1 15 Runnable t1
16848 4 140056040 1 15 Delay Sleep t3
16852 @node Ada Tasks and Core Files
16853 @subsubsection Tasking Support when Debugging Core Files
16854 @cindex Ada tasking and core file debugging
16856 When inspecting a core file, as opposed to debugging a live program,
16857 tasking support may be limited or even unavailable, depending on
16858 the platform being used.
16859 For instance, on x86-linux, the list of tasks is available, but task
16860 switching is not supported.
16862 On certain platforms, the debugger needs to perform some
16863 memory writes in order to provide Ada tasking support. When inspecting
16864 a core file, this means that the core file must be opened with read-write
16865 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16866 Under these circumstances, you should make a backup copy of the core
16867 file before inspecting it with @value{GDBN}.
16869 @node Ravenscar Profile
16870 @subsubsection Tasking Support when using the Ravenscar Profile
16871 @cindex Ravenscar Profile
16873 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16874 specifically designed for systems with safety-critical real-time
16878 @kindex set ravenscar task-switching on
16879 @cindex task switching with program using Ravenscar Profile
16880 @item set ravenscar task-switching on
16881 Allows task switching when debugging a program that uses the Ravenscar
16882 Profile. This is the default.
16884 @kindex set ravenscar task-switching off
16885 @item set ravenscar task-switching off
16886 Turn off task switching when debugging a program that uses the Ravenscar
16887 Profile. This is mostly intended to disable the code that adds support
16888 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16889 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16890 To be effective, this command should be run before the program is started.
16892 @kindex show ravenscar task-switching
16893 @item show ravenscar task-switching
16894 Show whether it is possible to switch from task to task in a program
16895 using the Ravenscar Profile.
16900 @subsubsection Known Peculiarities of Ada Mode
16901 @cindex Ada, problems
16903 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16904 we know of several problems with and limitations of Ada mode in
16906 some of which will be fixed with planned future releases of the debugger
16907 and the GNU Ada compiler.
16911 Static constants that the compiler chooses not to materialize as objects in
16912 storage are invisible to the debugger.
16915 Named parameter associations in function argument lists are ignored (the
16916 argument lists are treated as positional).
16919 Many useful library packages are currently invisible to the debugger.
16922 Fixed-point arithmetic, conversions, input, and output is carried out using
16923 floating-point arithmetic, and may give results that only approximate those on
16927 The GNAT compiler never generates the prefix @code{Standard} for any of
16928 the standard symbols defined by the Ada language. @value{GDBN} knows about
16929 this: it will strip the prefix from names when you use it, and will never
16930 look for a name you have so qualified among local symbols, nor match against
16931 symbols in other packages or subprograms. If you have
16932 defined entities anywhere in your program other than parameters and
16933 local variables whose simple names match names in @code{Standard},
16934 GNAT's lack of qualification here can cause confusion. When this happens,
16935 you can usually resolve the confusion
16936 by qualifying the problematic names with package
16937 @code{Standard} explicitly.
16940 Older versions of the compiler sometimes generate erroneous debugging
16941 information, resulting in the debugger incorrectly printing the value
16942 of affected entities. In some cases, the debugger is able to work
16943 around an issue automatically. In other cases, the debugger is able
16944 to work around the issue, but the work-around has to be specifically
16947 @kindex set ada trust-PAD-over-XVS
16948 @kindex show ada trust-PAD-over-XVS
16951 @item set ada trust-PAD-over-XVS on
16952 Configure GDB to strictly follow the GNAT encoding when computing the
16953 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16954 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16955 a complete description of the encoding used by the GNAT compiler).
16956 This is the default.
16958 @item set ada trust-PAD-over-XVS off
16959 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16960 sometimes prints the wrong value for certain entities, changing @code{ada
16961 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16962 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16963 @code{off}, but this incurs a slight performance penalty, so it is
16964 recommended to leave this setting to @code{on} unless necessary.
16968 @cindex GNAT descriptive types
16969 @cindex GNAT encoding
16970 Internally, the debugger also relies on the compiler following a number
16971 of conventions known as the @samp{GNAT Encoding}, all documented in
16972 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16973 how the debugging information should be generated for certain types.
16974 In particular, this convention makes use of @dfn{descriptive types},
16975 which are artificial types generated purely to help the debugger.
16977 These encodings were defined at a time when the debugging information
16978 format used was not powerful enough to describe some of the more complex
16979 types available in Ada. Since DWARF allows us to express nearly all
16980 Ada features, the long-term goal is to slowly replace these descriptive
16981 types by their pure DWARF equivalent. To facilitate that transition,
16982 a new maintenance option is available to force the debugger to ignore
16983 those descriptive types. It allows the user to quickly evaluate how
16984 well @value{GDBN} works without them.
16988 @kindex maint ada set ignore-descriptive-types
16989 @item maintenance ada set ignore-descriptive-types [on|off]
16990 Control whether the debugger should ignore descriptive types.
16991 The default is not to ignore descriptives types (@code{off}).
16993 @kindex maint ada show ignore-descriptive-types
16994 @item maintenance ada show ignore-descriptive-types
16995 Show if descriptive types are ignored by @value{GDBN}.
16999 @node Unsupported Languages
17000 @section Unsupported Languages
17002 @cindex unsupported languages
17003 @cindex minimal language
17004 In addition to the other fully-supported programming languages,
17005 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
17006 It does not represent a real programming language, but provides a set
17007 of capabilities close to what the C or assembly languages provide.
17008 This should allow most simple operations to be performed while debugging
17009 an application that uses a language currently not supported by @value{GDBN}.
17011 If the language is set to @code{auto}, @value{GDBN} will automatically
17012 select this language if the current frame corresponds to an unsupported
17016 @chapter Examining the Symbol Table
17018 The commands described in this chapter allow you to inquire about the
17019 symbols (names of variables, functions and types) defined in your
17020 program. This information is inherent in the text of your program and
17021 does not change as your program executes. @value{GDBN} finds it in your
17022 program's symbol table, in the file indicated when you started @value{GDBN}
17023 (@pxref{File Options, ,Choosing Files}), or by one of the
17024 file-management commands (@pxref{Files, ,Commands to Specify Files}).
17026 @cindex symbol names
17027 @cindex names of symbols
17028 @cindex quoting names
17029 @anchor{quoting names}
17030 Occasionally, you may need to refer to symbols that contain unusual
17031 characters, which @value{GDBN} ordinarily treats as word delimiters. The
17032 most frequent case is in referring to static variables in other
17033 source files (@pxref{Variables,,Program Variables}). File names
17034 are recorded in object files as debugging symbols, but @value{GDBN} would
17035 ordinarily parse a typical file name, like @file{foo.c}, as the three words
17036 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
17037 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
17044 looks up the value of @code{x} in the scope of the file @file{foo.c}.
17047 @cindex case-insensitive symbol names
17048 @cindex case sensitivity in symbol names
17049 @kindex set case-sensitive
17050 @item set case-sensitive on
17051 @itemx set case-sensitive off
17052 @itemx set case-sensitive auto
17053 Normally, when @value{GDBN} looks up symbols, it matches their names
17054 with case sensitivity determined by the current source language.
17055 Occasionally, you may wish to control that. The command @code{set
17056 case-sensitive} lets you do that by specifying @code{on} for
17057 case-sensitive matches or @code{off} for case-insensitive ones. If
17058 you specify @code{auto}, case sensitivity is reset to the default
17059 suitable for the source language. The default is case-sensitive
17060 matches for all languages except for Fortran, for which the default is
17061 case-insensitive matches.
17063 @kindex show case-sensitive
17064 @item show case-sensitive
17065 This command shows the current setting of case sensitivity for symbols
17068 @kindex set print type methods
17069 @item set print type methods
17070 @itemx set print type methods on
17071 @itemx set print type methods off
17072 Normally, when @value{GDBN} prints a class, it displays any methods
17073 declared in that class. You can control this behavior either by
17074 passing the appropriate flag to @code{ptype}, or using @command{set
17075 print type methods}. Specifying @code{on} will cause @value{GDBN} to
17076 display the methods; this is the default. Specifying @code{off} will
17077 cause @value{GDBN} to omit the methods.
17079 @kindex show print type methods
17080 @item show print type methods
17081 This command shows the current setting of method display when printing
17084 @kindex set print type nested-type-limit
17085 @item set print type nested-type-limit @var{limit}
17086 @itemx set print type nested-type-limit unlimited
17087 Set the limit of displayed nested types that the type printer will
17088 show. A @var{limit} of @code{unlimited} or @code{-1} will show all
17089 nested definitions. By default, the type printer will not show any nested
17090 types defined in classes.
17092 @kindex show print type nested-type-limit
17093 @item show print type nested-type-limit
17094 This command shows the current display limit of nested types when
17097 @kindex set print type typedefs
17098 @item set print type typedefs
17099 @itemx set print type typedefs on
17100 @itemx set print type typedefs off
17102 Normally, when @value{GDBN} prints a class, it displays any typedefs
17103 defined in that class. You can control this behavior either by
17104 passing the appropriate flag to @code{ptype}, or using @command{set
17105 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
17106 display the typedef definitions; this is the default. Specifying
17107 @code{off} will cause @value{GDBN} to omit the typedef definitions.
17108 Note that this controls whether the typedef definition itself is
17109 printed, not whether typedef names are substituted when printing other
17112 @kindex show print type typedefs
17113 @item show print type typedefs
17114 This command shows the current setting of typedef display when
17117 @kindex info address
17118 @cindex address of a symbol
17119 @item info address @var{symbol}
17120 Describe where the data for @var{symbol} is stored. For a register
17121 variable, this says which register it is kept in. For a non-register
17122 local variable, this prints the stack-frame offset at which the variable
17125 Note the contrast with @samp{print &@var{symbol}}, which does not work
17126 at all for a register variable, and for a stack local variable prints
17127 the exact address of the current instantiation of the variable.
17129 @kindex info symbol
17130 @cindex symbol from address
17131 @cindex closest symbol and offset for an address
17132 @item info symbol @var{addr}
17133 Print the name of a symbol which is stored at the address @var{addr}.
17134 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
17135 nearest symbol and an offset from it:
17138 (@value{GDBP}) info symbol 0x54320
17139 _initialize_vx + 396 in section .text
17143 This is the opposite of the @code{info address} command. You can use
17144 it to find out the name of a variable or a function given its address.
17146 For dynamically linked executables, the name of executable or shared
17147 library containing the symbol is also printed:
17150 (@value{GDBP}) info symbol 0x400225
17151 _start + 5 in section .text of /tmp/a.out
17152 (@value{GDBP}) info symbol 0x2aaaac2811cf
17153 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
17158 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
17159 Demangle @var{name}.
17160 If @var{language} is provided it is the name of the language to demangle
17161 @var{name} in. Otherwise @var{name} is demangled in the current language.
17163 The @samp{--} option specifies the end of options,
17164 and is useful when @var{name} begins with a dash.
17166 The parameter @code{demangle-style} specifies how to interpret the kind
17167 of mangling used. @xref{Print Settings}.
17170 @item whatis[/@var{flags}] [@var{arg}]
17171 Print the data type of @var{arg}, which can be either an expression
17172 or a name of a data type. With no argument, print the data type of
17173 @code{$}, the last value in the value history.
17175 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
17176 is not actually evaluated, and any side-effecting operations (such as
17177 assignments or function calls) inside it do not take place.
17179 If @var{arg} is a variable or an expression, @code{whatis} prints its
17180 literal type as it is used in the source code. If the type was
17181 defined using a @code{typedef}, @code{whatis} will @emph{not} print
17182 the data type underlying the @code{typedef}. If the type of the
17183 variable or the expression is a compound data type, such as
17184 @code{struct} or @code{class}, @code{whatis} never prints their
17185 fields or methods. It just prints the @code{struct}/@code{class}
17186 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
17187 such a compound data type, use @code{ptype}.
17189 If @var{arg} is a type name that was defined using @code{typedef},
17190 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
17191 Unrolling means that @code{whatis} will show the underlying type used
17192 in the @code{typedef} declaration of @var{arg}. However, if that
17193 underlying type is also a @code{typedef}, @code{whatis} will not
17196 For C code, the type names may also have the form @samp{class
17197 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
17198 @var{union-tag}} or @samp{enum @var{enum-tag}}.
17200 @var{flags} can be used to modify how the type is displayed.
17201 Available flags are:
17205 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
17206 parameters and typedefs defined in a class when printing the class'
17207 members. The @code{/r} flag disables this.
17210 Do not print methods defined in the class.
17213 Print methods defined in the class. This is the default, but the flag
17214 exists in case you change the default with @command{set print type methods}.
17217 Do not print typedefs defined in the class. Note that this controls
17218 whether the typedef definition itself is printed, not whether typedef
17219 names are substituted when printing other types.
17222 Print typedefs defined in the class. This is the default, but the flag
17223 exists in case you change the default with @command{set print type typedefs}.
17226 Print the offsets and sizes of fields in a struct, similar to what the
17227 @command{pahole} tool does. This option implies the @code{/tm} flags.
17229 For example, given the following declarations:
17265 Issuing a @kbd{ptype /o struct tuv} command would print:
17268 (@value{GDBP}) ptype /o struct tuv
17269 /* offset | size */ type = struct tuv @{
17270 /* 0 | 4 */ int a1;
17271 /* XXX 4-byte hole */
17272 /* 8 | 8 */ char *a2;
17273 /* 16 | 4 */ int a3;
17275 /* total size (bytes): 24 */
17279 Notice the format of the first column of comments. There, you can
17280 find two parts separated by the @samp{|} character: the @emph{offset},
17281 which indicates where the field is located inside the struct, in
17282 bytes, and the @emph{size} of the field. Another interesting line is
17283 the marker of a @emph{hole} in the struct, indicating that it may be
17284 possible to pack the struct and make it use less space by reorganizing
17287 It is also possible to print offsets inside an union:
17290 (@value{GDBP}) ptype /o union qwe
17291 /* offset | size */ type = union qwe @{
17292 /* 24 */ struct tuv @{
17293 /* 0 | 4 */ int a1;
17294 /* XXX 4-byte hole */
17295 /* 8 | 8 */ char *a2;
17296 /* 16 | 4 */ int a3;
17298 /* total size (bytes): 24 */
17300 /* 40 */ struct xyz @{
17301 /* 0 | 4 */ int f1;
17302 /* 4 | 1 */ char f2;
17303 /* XXX 3-byte hole */
17304 /* 8 | 8 */ void *f3;
17305 /* 16 | 24 */ struct tuv @{
17306 /* 16 | 4 */ int a1;
17307 /* XXX 4-byte hole */
17308 /* 24 | 8 */ char *a2;
17309 /* 32 | 4 */ int a3;
17311 /* total size (bytes): 24 */
17314 /* total size (bytes): 40 */
17317 /* total size (bytes): 40 */
17321 In this case, since @code{struct tuv} and @code{struct xyz} occupy the
17322 same space (because we are dealing with an union), the offset is not
17323 printed for them. However, you can still examine the offset of each
17324 of these structures' fields.
17326 Another useful scenario is printing the offsets of a struct containing
17330 (@value{GDBP}) ptype /o struct tyu
17331 /* offset | size */ type = struct tyu @{
17332 /* 0:31 | 4 */ int a1 : 1;
17333 /* 0:28 | 4 */ int a2 : 3;
17334 /* 0: 5 | 4 */ int a3 : 23;
17335 /* 3: 3 | 1 */ signed char a4 : 2;
17336 /* XXX 3-bit hole */
17337 /* XXX 4-byte hole */
17338 /* 8 | 8 */ int64_t a5;
17339 /* 16:27 | 4 */ int a6 : 5;
17340 /* 16:56 | 8 */ int64_t a7 : 3;
17342 /* total size (bytes): 24 */
17346 Note how the offset information is now extended to also include how
17347 many bits are left to be used in each bitfield.
17351 @item ptype[/@var{flags}] [@var{arg}]
17352 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
17353 detailed description of the type, instead of just the name of the type.
17354 @xref{Expressions, ,Expressions}.
17356 Contrary to @code{whatis}, @code{ptype} always unrolls any
17357 @code{typedef}s in its argument declaration, whether the argument is
17358 a variable, expression, or a data type. This means that @code{ptype}
17359 of a variable or an expression will not print literally its type as
17360 present in the source code---use @code{whatis} for that. @code{typedef}s at
17361 the pointer or reference targets are also unrolled. Only @code{typedef}s of
17362 fields, methods and inner @code{class typedef}s of @code{struct}s,
17363 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
17365 For example, for this variable declaration:
17368 typedef double real_t;
17369 struct complex @{ real_t real; double imag; @};
17370 typedef struct complex complex_t;
17372 real_t *real_pointer_var;
17376 the two commands give this output:
17380 (@value{GDBP}) whatis var
17382 (@value{GDBP}) ptype var
17383 type = struct complex @{
17387 (@value{GDBP}) whatis complex_t
17388 type = struct complex
17389 (@value{GDBP}) whatis struct complex
17390 type = struct complex
17391 (@value{GDBP}) ptype struct complex
17392 type = struct complex @{
17396 (@value{GDBP}) whatis real_pointer_var
17398 (@value{GDBP}) ptype real_pointer_var
17404 As with @code{whatis}, using @code{ptype} without an argument refers to
17405 the type of @code{$}, the last value in the value history.
17407 @cindex incomplete type
17408 Sometimes, programs use opaque data types or incomplete specifications
17409 of complex data structure. If the debug information included in the
17410 program does not allow @value{GDBN} to display a full declaration of
17411 the data type, it will say @samp{<incomplete type>}. For example,
17412 given these declarations:
17416 struct foo *fooptr;
17420 but no definition for @code{struct foo} itself, @value{GDBN} will say:
17423 (@value{GDBP}) ptype foo
17424 $1 = <incomplete type>
17428 ``Incomplete type'' is C terminology for data types that are not
17429 completely specified.
17431 @cindex unknown type
17432 Othertimes, information about a variable's type is completely absent
17433 from the debug information included in the program. This most often
17434 happens when the program or library where the variable is defined
17435 includes no debug information at all. @value{GDBN} knows the variable
17436 exists from inspecting the linker/loader symbol table (e.g., the ELF
17437 dynamic symbol table), but such symbols do not contain type
17438 information. Inspecting the type of a (global) variable for which
17439 @value{GDBN} has no type information shows:
17442 (@value{GDBP}) ptype var
17443 type = <data variable, no debug info>
17446 @xref{Variables, no debug info variables}, for how to print the values
17450 @item info types @var{regexp}
17452 Print a brief description of all types whose names match the regular
17453 expression @var{regexp} (or all types in your program, if you supply
17454 no argument). Each complete typename is matched as though it were a
17455 complete line; thus, @samp{i type value} gives information on all
17456 types in your program whose names include the string @code{value}, but
17457 @samp{i type ^value$} gives information only on types whose complete
17458 name is @code{value}.
17460 This command differs from @code{ptype} in two ways: first, like
17461 @code{whatis}, it does not print a detailed description; second, it
17462 lists all source files where a type is defined.
17464 @kindex info type-printers
17465 @item info type-printers
17466 Versions of @value{GDBN} that ship with Python scripting enabled may
17467 have ``type printers'' available. When using @command{ptype} or
17468 @command{whatis}, these printers are consulted when the name of a type
17469 is needed. @xref{Type Printing API}, for more information on writing
17472 @code{info type-printers} displays all the available type printers.
17474 @kindex enable type-printer
17475 @kindex disable type-printer
17476 @item enable type-printer @var{name}@dots{}
17477 @item disable type-printer @var{name}@dots{}
17478 These commands can be used to enable or disable type printers.
17481 @cindex local variables
17482 @item info scope @var{location}
17483 List all the variables local to a particular scope. This command
17484 accepts a @var{location} argument---a function name, a source line, or
17485 an address preceded by a @samp{*}, and prints all the variables local
17486 to the scope defined by that location. (@xref{Specify Location}, for
17487 details about supported forms of @var{location}.) For example:
17490 (@value{GDBP}) @b{info scope command_line_handler}
17491 Scope for command_line_handler:
17492 Symbol rl is an argument at stack/frame offset 8, length 4.
17493 Symbol linebuffer is in static storage at address 0x150a18, length 4.
17494 Symbol linelength is in static storage at address 0x150a1c, length 4.
17495 Symbol p is a local variable in register $esi, length 4.
17496 Symbol p1 is a local variable in register $ebx, length 4.
17497 Symbol nline is a local variable in register $edx, length 4.
17498 Symbol repeat is a local variable at frame offset -8, length 4.
17502 This command is especially useful for determining what data to collect
17503 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
17506 @kindex info source
17508 Show information about the current source file---that is, the source file for
17509 the function containing the current point of execution:
17512 the name of the source file, and the directory containing it,
17514 the directory it was compiled in,
17516 its length, in lines,
17518 which programming language it is written in,
17520 if the debug information provides it, the program that compiled the file
17521 (which may include, e.g., the compiler version and command line arguments),
17523 whether the executable includes debugging information for that file, and
17524 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
17526 whether the debugging information includes information about
17527 preprocessor macros.
17531 @kindex info sources
17533 Print the names of all source files in your program for which there is
17534 debugging information, organized into two lists: files whose symbols
17535 have already been read, and files whose symbols will be read when needed.
17537 @kindex info functions
17538 @item info functions
17539 Print the names and data types of all defined functions.
17541 @item info functions @var{regexp}
17542 Print the names and data types of all defined functions
17543 whose names contain a match for regular expression @var{regexp}.
17544 Thus, @samp{info fun step} finds all functions whose names
17545 include @code{step}; @samp{info fun ^step} finds those whose names
17546 start with @code{step}. If a function name contains characters
17547 that conflict with the regular expression language (e.g.@:
17548 @samp{operator*()}), they may be quoted with a backslash.
17550 @kindex info variables
17551 @item info variables
17552 Print the names and data types of all variables that are defined
17553 outside of functions (i.e.@: excluding local variables).
17555 @item info variables @var{regexp}
17556 Print the names and data types of all variables (except for local
17557 variables) whose names contain a match for regular expression
17560 @kindex info classes
17561 @cindex Objective-C, classes and selectors
17563 @itemx info classes @var{regexp}
17564 Display all Objective-C classes in your program, or
17565 (with the @var{regexp} argument) all those matching a particular regular
17568 @kindex info selectors
17569 @item info selectors
17570 @itemx info selectors @var{regexp}
17571 Display all Objective-C selectors in your program, or
17572 (with the @var{regexp} argument) all those matching a particular regular
17576 This was never implemented.
17577 @kindex info methods
17579 @itemx info methods @var{regexp}
17580 The @code{info methods} command permits the user to examine all defined
17581 methods within C@t{++} program, or (with the @var{regexp} argument) a
17582 specific set of methods found in the various C@t{++} classes. Many
17583 C@t{++} classes provide a large number of methods. Thus, the output
17584 from the @code{ptype} command can be overwhelming and hard to use. The
17585 @code{info-methods} command filters the methods, printing only those
17586 which match the regular-expression @var{regexp}.
17589 @cindex opaque data types
17590 @kindex set opaque-type-resolution
17591 @item set opaque-type-resolution on
17592 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
17593 declared as a pointer to a @code{struct}, @code{class}, or
17594 @code{union}---for example, @code{struct MyType *}---that is used in one
17595 source file although the full declaration of @code{struct MyType} is in
17596 another source file. The default is on.
17598 A change in the setting of this subcommand will not take effect until
17599 the next time symbols for a file are loaded.
17601 @item set opaque-type-resolution off
17602 Tell @value{GDBN} not to resolve opaque types. In this case, the type
17603 is printed as follows:
17605 @{<no data fields>@}
17608 @kindex show opaque-type-resolution
17609 @item show opaque-type-resolution
17610 Show whether opaque types are resolved or not.
17612 @kindex set print symbol-loading
17613 @cindex print messages when symbols are loaded
17614 @item set print symbol-loading
17615 @itemx set print symbol-loading full
17616 @itemx set print symbol-loading brief
17617 @itemx set print symbol-loading off
17618 The @code{set print symbol-loading} command allows you to control the
17619 printing of messages when @value{GDBN} loads symbol information.
17620 By default a message is printed for the executable and one for each
17621 shared library, and normally this is what you want. However, when
17622 debugging apps with large numbers of shared libraries these messages
17624 When set to @code{brief} a message is printed for each executable,
17625 and when @value{GDBN} loads a collection of shared libraries at once
17626 it will only print one message regardless of the number of shared
17627 libraries. When set to @code{off} no messages are printed.
17629 @kindex show print symbol-loading
17630 @item show print symbol-loading
17631 Show whether messages will be printed when a @value{GDBN} command
17632 entered from the keyboard causes symbol information to be loaded.
17634 @kindex maint print symbols
17635 @cindex symbol dump
17636 @kindex maint print psymbols
17637 @cindex partial symbol dump
17638 @kindex maint print msymbols
17639 @cindex minimal symbol dump
17640 @item maint print symbols @r{[}-pc @var{address}@r{]} @r{[}@var{filename}@r{]}
17641 @itemx maint print symbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17642 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-pc @var{address}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17643 @itemx maint print psymbols @r{[}-objfile @var{objfile}@r{]} @r{[}-source @var{source}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17644 @itemx maint print msymbols @r{[}-objfile @var{objfile}@r{]} @r{[}--@r{]} @r{[}@var{filename}@r{]}
17645 Write a dump of debugging symbol data into the file @var{filename} or
17646 the terminal if @var{filename} is unspecified.
17647 If @code{-objfile @var{objfile}} is specified, only dump symbols for
17649 If @code{-pc @var{address}} is specified, only dump symbols for the file
17650 with code at that address. Note that @var{address} may be a symbol like
17652 If @code{-source @var{source}} is specified, only dump symbols for that
17655 These commands are used to debug the @value{GDBN} symbol-reading code.
17656 These commands do not modify internal @value{GDBN} state, therefore
17657 @samp{maint print symbols} will only print symbols for already expanded symbol
17659 You can use the command @code{info sources} to find out which files these are.
17660 If you use @samp{maint print psymbols} instead, the dump shows information
17661 about symbols that @value{GDBN} only knows partially---that is, symbols
17662 defined in files that @value{GDBN} has skimmed, but not yet read completely.
17663 Finally, @samp{maint print msymbols} just dumps ``minimal symbols'', e.g.,
17666 @xref{Files, ,Commands to Specify Files}, for a discussion of how
17667 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
17669 @kindex maint info symtabs
17670 @kindex maint info psymtabs
17671 @cindex listing @value{GDBN}'s internal symbol tables
17672 @cindex symbol tables, listing @value{GDBN}'s internal
17673 @cindex full symbol tables, listing @value{GDBN}'s internal
17674 @cindex partial symbol tables, listing @value{GDBN}'s internal
17675 @item maint info symtabs @r{[} @var{regexp} @r{]}
17676 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
17678 List the @code{struct symtab} or @code{struct partial_symtab}
17679 structures whose names match @var{regexp}. If @var{regexp} is not
17680 given, list them all. The output includes expressions which you can
17681 copy into a @value{GDBN} debugging this one to examine a particular
17682 structure in more detail. For example:
17685 (@value{GDBP}) maint info psymtabs dwarf2read
17686 @{ objfile /home/gnu/build/gdb/gdb
17687 ((struct objfile *) 0x82e69d0)
17688 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
17689 ((struct partial_symtab *) 0x8474b10)
17692 text addresses 0x814d3c8 -- 0x8158074
17693 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
17694 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
17695 dependencies (none)
17698 (@value{GDBP}) maint info symtabs
17702 We see that there is one partial symbol table whose filename contains
17703 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
17704 and we see that @value{GDBN} has not read in any symtabs yet at all.
17705 If we set a breakpoint on a function, that will cause @value{GDBN} to
17706 read the symtab for the compilation unit containing that function:
17709 (@value{GDBP}) break dwarf2_psymtab_to_symtab
17710 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
17712 (@value{GDBP}) maint info symtabs
17713 @{ objfile /home/gnu/build/gdb/gdb
17714 ((struct objfile *) 0x82e69d0)
17715 @{ symtab /home/gnu/src/gdb/dwarf2read.c
17716 ((struct symtab *) 0x86c1f38)
17719 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
17720 linetable ((struct linetable *) 0x8370fa0)
17721 debugformat DWARF 2
17727 @kindex maint info line-table
17728 @cindex listing @value{GDBN}'s internal line tables
17729 @cindex line tables, listing @value{GDBN}'s internal
17730 @item maint info line-table @r{[} @var{regexp} @r{]}
17732 List the @code{struct linetable} from all @code{struct symtab}
17733 instances whose name matches @var{regexp}. If @var{regexp} is not
17734 given, list the @code{struct linetable} from all @code{struct symtab}.
17736 @kindex maint set symbol-cache-size
17737 @cindex symbol cache size
17738 @item maint set symbol-cache-size @var{size}
17739 Set the size of the symbol cache to @var{size}.
17740 The default size is intended to be good enough for debugging
17741 most applications. This option exists to allow for experimenting
17742 with different sizes.
17744 @kindex maint show symbol-cache-size
17745 @item maint show symbol-cache-size
17746 Show the size of the symbol cache.
17748 @kindex maint print symbol-cache
17749 @cindex symbol cache, printing its contents
17750 @item maint print symbol-cache
17751 Print the contents of the symbol cache.
17752 This is useful when debugging symbol cache issues.
17754 @kindex maint print symbol-cache-statistics
17755 @cindex symbol cache, printing usage statistics
17756 @item maint print symbol-cache-statistics
17757 Print symbol cache usage statistics.
17758 This helps determine how well the cache is being utilized.
17760 @kindex maint flush-symbol-cache
17761 @cindex symbol cache, flushing
17762 @item maint flush-symbol-cache
17763 Flush the contents of the symbol cache, all entries are removed.
17764 This command is useful when debugging the symbol cache.
17765 It is also useful when collecting performance data.
17770 @chapter Altering Execution
17772 Once you think you have found an error in your program, you might want to
17773 find out for certain whether correcting the apparent error would lead to
17774 correct results in the rest of the run. You can find the answer by
17775 experiment, using the @value{GDBN} features for altering execution of the
17778 For example, you can store new values into variables or memory
17779 locations, give your program a signal, restart it at a different
17780 address, or even return prematurely from a function.
17783 * Assignment:: Assignment to variables
17784 * Jumping:: Continuing at a different address
17785 * Signaling:: Giving your program a signal
17786 * Returning:: Returning from a function
17787 * Calling:: Calling your program's functions
17788 * Patching:: Patching your program
17789 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17793 @section Assignment to Variables
17796 @cindex setting variables
17797 To alter the value of a variable, evaluate an assignment expression.
17798 @xref{Expressions, ,Expressions}. For example,
17805 stores the value 4 into the variable @code{x}, and then prints the
17806 value of the assignment expression (which is 4).
17807 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17808 information on operators in supported languages.
17810 @kindex set variable
17811 @cindex variables, setting
17812 If you are not interested in seeing the value of the assignment, use the
17813 @code{set} command instead of the @code{print} command. @code{set} is
17814 really the same as @code{print} except that the expression's value is
17815 not printed and is not put in the value history (@pxref{Value History,
17816 ,Value History}). The expression is evaluated only for its effects.
17818 If the beginning of the argument string of the @code{set} command
17819 appears identical to a @code{set} subcommand, use the @code{set
17820 variable} command instead of just @code{set}. This command is identical
17821 to @code{set} except for its lack of subcommands. For example, if your
17822 program has a variable @code{width}, you get an error if you try to set
17823 a new value with just @samp{set width=13}, because @value{GDBN} has the
17824 command @code{set width}:
17827 (@value{GDBP}) whatis width
17829 (@value{GDBP}) p width
17831 (@value{GDBP}) set width=47
17832 Invalid syntax in expression.
17836 The invalid expression, of course, is @samp{=47}. In
17837 order to actually set the program's variable @code{width}, use
17840 (@value{GDBP}) set var width=47
17843 Because the @code{set} command has many subcommands that can conflict
17844 with the names of program variables, it is a good idea to use the
17845 @code{set variable} command instead of just @code{set}. For example, if
17846 your program has a variable @code{g}, you run into problems if you try
17847 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17848 the command @code{set gnutarget}, abbreviated @code{set g}:
17852 (@value{GDBP}) whatis g
17856 (@value{GDBP}) set g=4
17860 The program being debugged has been started already.
17861 Start it from the beginning? (y or n) y
17862 Starting program: /home/smith/cc_progs/a.out
17863 "/home/smith/cc_progs/a.out": can't open to read symbols:
17864 Invalid bfd target.
17865 (@value{GDBP}) show g
17866 The current BFD target is "=4".
17871 The program variable @code{g} did not change, and you silently set the
17872 @code{gnutarget} to an invalid value. In order to set the variable
17876 (@value{GDBP}) set var g=4
17879 @value{GDBN} allows more implicit conversions in assignments than C; you can
17880 freely store an integer value into a pointer variable or vice versa,
17881 and you can convert any structure to any other structure that is the
17882 same length or shorter.
17883 @comment FIXME: how do structs align/pad in these conversions?
17884 @comment /doc@cygnus.com 18dec1990
17886 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17887 construct to generate a value of specified type at a specified address
17888 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17889 to memory location @code{0x83040} as an integer (which implies a certain size
17890 and representation in memory), and
17893 set @{int@}0x83040 = 4
17897 stores the value 4 into that memory location.
17900 @section Continuing at a Different Address
17902 Ordinarily, when you continue your program, you do so at the place where
17903 it stopped, with the @code{continue} command. You can instead continue at
17904 an address of your own choosing, with the following commands:
17908 @kindex j @r{(@code{jump})}
17909 @item jump @var{location}
17910 @itemx j @var{location}
17911 Resume execution at @var{location}. Execution stops again immediately
17912 if there is a breakpoint there. @xref{Specify Location}, for a description
17913 of the different forms of @var{location}. It is common
17914 practice to use the @code{tbreak} command in conjunction with
17915 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17917 The @code{jump} command does not change the current stack frame, or
17918 the stack pointer, or the contents of any memory location or any
17919 register other than the program counter. If @var{location} is in
17920 a different function from the one currently executing, the results may
17921 be bizarre if the two functions expect different patterns of arguments or
17922 of local variables. For this reason, the @code{jump} command requests
17923 confirmation if the specified line is not in the function currently
17924 executing. However, even bizarre results are predictable if you are
17925 well acquainted with the machine-language code of your program.
17928 On many systems, you can get much the same effect as the @code{jump}
17929 command by storing a new value into the register @code{$pc}. The
17930 difference is that this does not start your program running; it only
17931 changes the address of where it @emph{will} run when you continue. For
17939 makes the next @code{continue} command or stepping command execute at
17940 address @code{0x485}, rather than at the address where your program stopped.
17941 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17943 The most common occasion to use the @code{jump} command is to back
17944 up---perhaps with more breakpoints set---over a portion of a program
17945 that has already executed, in order to examine its execution in more
17950 @section Giving your Program a Signal
17951 @cindex deliver a signal to a program
17955 @item signal @var{signal}
17956 Resume execution where your program is stopped, but immediately give it the
17957 signal @var{signal}. The @var{signal} can be the name or the number of a
17958 signal. For example, on many systems @code{signal 2} and @code{signal
17959 SIGINT} are both ways of sending an interrupt signal.
17961 Alternatively, if @var{signal} is zero, continue execution without
17962 giving a signal. This is useful when your program stopped on account of
17963 a signal and would ordinarily see the signal when resumed with the
17964 @code{continue} command; @samp{signal 0} causes it to resume without a
17967 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17968 delivered to the currently selected thread, not the thread that last
17969 reported a stop. This includes the situation where a thread was
17970 stopped due to a signal. So if you want to continue execution
17971 suppressing the signal that stopped a thread, you should select that
17972 same thread before issuing the @samp{signal 0} command. If you issue
17973 the @samp{signal 0} command with another thread as the selected one,
17974 @value{GDBN} detects that and asks for confirmation.
17976 Invoking the @code{signal} command is not the same as invoking the
17977 @code{kill} utility from the shell. Sending a signal with @code{kill}
17978 causes @value{GDBN} to decide what to do with the signal depending on
17979 the signal handling tables (@pxref{Signals}). The @code{signal} command
17980 passes the signal directly to your program.
17982 @code{signal} does not repeat when you press @key{RET} a second time
17983 after executing the command.
17985 @kindex queue-signal
17986 @item queue-signal @var{signal}
17987 Queue @var{signal} to be delivered immediately to the current thread
17988 when execution of the thread resumes. The @var{signal} can be the name or
17989 the number of a signal. For example, on many systems @code{signal 2} and
17990 @code{signal SIGINT} are both ways of sending an interrupt signal.
17991 The handling of the signal must be set to pass the signal to the program,
17992 otherwise @value{GDBN} will report an error.
17993 You can control the handling of signals from @value{GDBN} with the
17994 @code{handle} command (@pxref{Signals}).
17996 Alternatively, if @var{signal} is zero, any currently queued signal
17997 for the current thread is discarded and when execution resumes no signal
17998 will be delivered. This is useful when your program stopped on account
17999 of a signal and would ordinarily see the signal when resumed with the
18000 @code{continue} command.
18002 This command differs from the @code{signal} command in that the signal
18003 is just queued, execution is not resumed. And @code{queue-signal} cannot
18004 be used to pass a signal whose handling state has been set to @code{nopass}
18009 @xref{stepping into signal handlers}, for information on how stepping
18010 commands behave when the thread has a signal queued.
18013 @section Returning from a Function
18016 @cindex returning from a function
18019 @itemx return @var{expression}
18020 You can cancel execution of a function call with the @code{return}
18021 command. If you give an
18022 @var{expression} argument, its value is used as the function's return
18026 When you use @code{return}, @value{GDBN} discards the selected stack frame
18027 (and all frames within it). You can think of this as making the
18028 discarded frame return prematurely. If you wish to specify a value to
18029 be returned, give that value as the argument to @code{return}.
18031 This pops the selected stack frame (@pxref{Selection, ,Selecting a
18032 Frame}), and any other frames inside of it, leaving its caller as the
18033 innermost remaining frame. That frame becomes selected. The
18034 specified value is stored in the registers used for returning values
18037 The @code{return} command does not resume execution; it leaves the
18038 program stopped in the state that would exist if the function had just
18039 returned. In contrast, the @code{finish} command (@pxref{Continuing
18040 and Stepping, ,Continuing and Stepping}) resumes execution until the
18041 selected stack frame returns naturally.
18043 @value{GDBN} needs to know how the @var{expression} argument should be set for
18044 the inferior. The concrete registers assignment depends on the OS ABI and the
18045 type being returned by the selected stack frame. For example it is common for
18046 OS ABI to return floating point values in FPU registers while integer values in
18047 CPU registers. Still some ABIs return even floating point values in CPU
18048 registers. Larger integer widths (such as @code{long long int}) also have
18049 specific placement rules. @value{GDBN} already knows the OS ABI from its
18050 current target so it needs to find out also the type being returned to make the
18051 assignment into the right register(s).
18053 Normally, the selected stack frame has debug info. @value{GDBN} will always
18054 use the debug info instead of the implicit type of @var{expression} when the
18055 debug info is available. For example, if you type @kbd{return -1}, and the
18056 function in the current stack frame is declared to return a @code{long long
18057 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
18058 into a @code{long long int}:
18061 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
18063 (@value{GDBP}) return -1
18064 Make func return now? (y or n) y
18065 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
18066 43 printf ("result=%lld\n", func ());
18070 However, if the selected stack frame does not have a debug info, e.g., if the
18071 function was compiled without debug info, @value{GDBN} has to find out the type
18072 to return from user. Specifying a different type by mistake may set the value
18073 in different inferior registers than the caller code expects. For example,
18074 typing @kbd{return -1} with its implicit type @code{int} would set only a part
18075 of a @code{long long int} result for a debug info less function (on 32-bit
18076 architectures). Therefore the user is required to specify the return type by
18077 an appropriate cast explicitly:
18080 Breakpoint 2, 0x0040050b in func ()
18081 (@value{GDBP}) return -1
18082 Return value type not available for selected stack frame.
18083 Please use an explicit cast of the value to return.
18084 (@value{GDBP}) return (long long int) -1
18085 Make selected stack frame return now? (y or n) y
18086 #0 0x00400526 in main ()
18091 @section Calling Program Functions
18094 @cindex calling functions
18095 @cindex inferior functions, calling
18096 @item print @var{expr}
18097 Evaluate the expression @var{expr} and display the resulting value.
18098 The expression may include calls to functions in the program being
18102 @item call @var{expr}
18103 Evaluate the expression @var{expr} without displaying @code{void}
18106 You can use this variant of the @code{print} command if you want to
18107 execute a function from your program that does not return anything
18108 (a.k.a.@: @dfn{a void function}), but without cluttering the output
18109 with @code{void} returned values that @value{GDBN} will otherwise
18110 print. If the result is not void, it is printed and saved in the
18114 It is possible for the function you call via the @code{print} or
18115 @code{call} command to generate a signal (e.g., if there's a bug in
18116 the function, or if you passed it incorrect arguments). What happens
18117 in that case is controlled by the @code{set unwindonsignal} command.
18119 Similarly, with a C@t{++} program it is possible for the function you
18120 call via the @code{print} or @code{call} command to generate an
18121 exception that is not handled due to the constraints of the dummy
18122 frame. In this case, any exception that is raised in the frame, but has
18123 an out-of-frame exception handler will not be found. GDB builds a
18124 dummy-frame for the inferior function call, and the unwinder cannot
18125 seek for exception handlers outside of this dummy-frame. What happens
18126 in that case is controlled by the
18127 @code{set unwind-on-terminating-exception} command.
18130 @item set unwindonsignal
18131 @kindex set unwindonsignal
18132 @cindex unwind stack in called functions
18133 @cindex call dummy stack unwinding
18134 Set unwinding of the stack if a signal is received while in a function
18135 that @value{GDBN} called in the program being debugged. If set to on,
18136 @value{GDBN} unwinds the stack it created for the call and restores
18137 the context to what it was before the call. If set to off (the
18138 default), @value{GDBN} stops in the frame where the signal was
18141 @item show unwindonsignal
18142 @kindex show unwindonsignal
18143 Show the current setting of stack unwinding in the functions called by
18146 @item set unwind-on-terminating-exception
18147 @kindex set unwind-on-terminating-exception
18148 @cindex unwind stack in called functions with unhandled exceptions
18149 @cindex call dummy stack unwinding on unhandled exception.
18150 Set unwinding of the stack if a C@t{++} exception is raised, but left
18151 unhandled while in a function that @value{GDBN} called in the program being
18152 debugged. If set to on (the default), @value{GDBN} unwinds the stack
18153 it created for the call and restores the context to what it was before
18154 the call. If set to off, @value{GDBN} the exception is delivered to
18155 the default C@t{++} exception handler and the inferior terminated.
18157 @item show unwind-on-terminating-exception
18158 @kindex show unwind-on-terminating-exception
18159 Show the current setting of stack unwinding in the functions called by
18164 @subsection Calling functions with no debug info
18166 @cindex no debug info functions
18167 Sometimes, a function you wish to call is missing debug information.
18168 In such case, @value{GDBN} does not know the type of the function,
18169 including the types of the function's parameters. To avoid calling
18170 the inferior function incorrectly, which could result in the called
18171 function functioning erroneously and even crash, @value{GDBN} refuses
18172 to call the function unless you tell it the type of the function.
18174 For prototyped (i.e.@: ANSI/ISO style) functions, there are two ways
18175 to do that. The simplest is to cast the call to the function's
18176 declared return type. For example:
18179 (@value{GDBP}) p getenv ("PATH")
18180 'getenv' has unknown return type; cast the call to its declared return type
18181 (@value{GDBP}) p (char *) getenv ("PATH")
18182 $1 = 0x7fffffffe7ba "/usr/local/bin:/"...
18185 Casting the return type of a no-debug function is equivalent to
18186 casting the function to a pointer to a prototyped function that has a
18187 prototype that matches the types of the passed-in arguments, and
18188 calling that. I.e., the call above is equivalent to:
18191 (@value{GDBP}) p ((char * (*) (const char *)) getenv) ("PATH")
18195 and given this prototyped C or C++ function with float parameters:
18198 float multiply (float v1, float v2) @{ return v1 * v2; @}
18202 these calls are equivalent:
18205 (@value{GDBP}) p (float) multiply (2.0f, 3.0f)
18206 (@value{GDBP}) p ((float (*) (float, float)) multiply) (2.0f, 3.0f)
18209 If the function you wish to call is declared as unprototyped (i.e.@:
18210 old K&R style), you must use the cast-to-function-pointer syntax, so
18211 that @value{GDBN} knows that it needs to apply default argument
18212 promotions (promote float arguments to double). @xref{ABI, float
18213 promotion}. For example, given this unprototyped C function with
18214 float parameters, and no debug info:
18218 multiply_noproto (v1, v2)
18226 you call it like this:
18229 (@value{GDBP}) p ((float (*) ()) multiply_noproto) (2.0f, 3.0f)
18233 @section Patching Programs
18235 @cindex patching binaries
18236 @cindex writing into executables
18237 @cindex writing into corefiles
18239 By default, @value{GDBN} opens the file containing your program's
18240 executable code (or the corefile) read-only. This prevents accidental
18241 alterations to machine code; but it also prevents you from intentionally
18242 patching your program's binary.
18244 If you'd like to be able to patch the binary, you can specify that
18245 explicitly with the @code{set write} command. For example, you might
18246 want to turn on internal debugging flags, or even to make emergency
18252 @itemx set write off
18253 If you specify @samp{set write on}, @value{GDBN} opens executable and
18254 core files for both reading and writing; if you specify @kbd{set write
18255 off} (the default), @value{GDBN} opens them read-only.
18257 If you have already loaded a file, you must load it again (using the
18258 @code{exec-file} or @code{core-file} command) after changing @code{set
18259 write}, for your new setting to take effect.
18263 Display whether executable files and core files are opened for writing
18264 as well as reading.
18267 @node Compiling and Injecting Code
18268 @section Compiling and injecting code in @value{GDBN}
18269 @cindex injecting code
18270 @cindex writing into executables
18271 @cindex compiling code
18273 @value{GDBN} supports on-demand compilation and code injection into
18274 programs running under @value{GDBN}. GCC 5.0 or higher built with
18275 @file{libcc1.so} must be installed for this functionality to be enabled.
18276 This functionality is implemented with the following commands.
18279 @kindex compile code
18280 @item compile code @var{source-code}
18281 @itemx compile code -raw @var{--} @var{source-code}
18282 Compile @var{source-code} with the compiler language found as the current
18283 language in @value{GDBN} (@pxref{Languages}). If compilation and
18284 injection is not supported with the current language specified in
18285 @value{GDBN}, or the compiler does not support this feature, an error
18286 message will be printed. If @var{source-code} compiles and links
18287 successfully, @value{GDBN} will load the object-code emitted,
18288 and execute it within the context of the currently selected inferior.
18289 It is important to note that the compiled code is executed immediately.
18290 After execution, the compiled code is removed from @value{GDBN} and any
18291 new types or variables you have defined will be deleted.
18293 The command allows you to specify @var{source-code} in two ways.
18294 The simplest method is to provide a single line of code to the command.
18298 compile code printf ("hello world\n");
18301 If you specify options on the command line as well as source code, they
18302 may conflict. The @samp{--} delimiter can be used to separate options
18303 from actual source code. E.g.:
18306 compile code -r -- printf ("hello world\n");
18309 Alternatively you can enter source code as multiple lines of text. To
18310 enter this mode, invoke the @samp{compile code} command without any text
18311 following the command. This will start the multiple-line editor and
18312 allow you to type as many lines of source code as required. When you
18313 have completed typing, enter @samp{end} on its own line to exit the
18318 >printf ("hello\n");
18319 >printf ("world\n");
18323 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
18324 provided @var{source-code} in a callable scope. In this case, you must
18325 specify the entry point of the code by defining a function named
18326 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
18327 inferior. Using @samp{-raw} option may be needed for example when
18328 @var{source-code} requires @samp{#include} lines which may conflict with
18329 inferior symbols otherwise.
18331 @kindex compile file
18332 @item compile file @var{filename}
18333 @itemx compile file -raw @var{filename}
18334 Like @code{compile code}, but take the source code from @var{filename}.
18337 compile file /home/user/example.c
18342 @item compile print @var{expr}
18343 @itemx compile print /@var{f} @var{expr}
18344 Compile and execute @var{expr} with the compiler language found as the
18345 current language in @value{GDBN} (@pxref{Languages}). By default the
18346 value of @var{expr} is printed in a format appropriate to its data type;
18347 you can choose a different format by specifying @samp{/@var{f}}, where
18348 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
18351 @item compile print
18352 @itemx compile print /@var{f}
18353 @cindex reprint the last value
18354 Alternatively you can enter the expression (source code producing it) as
18355 multiple lines of text. To enter this mode, invoke the @samp{compile print}
18356 command without any text following the command. This will start the
18357 multiple-line editor.
18361 The process of compiling and injecting the code can be inspected using:
18364 @anchor{set debug compile}
18365 @item set debug compile
18366 @cindex compile command debugging info
18367 Turns on or off display of @value{GDBN} process of compiling and
18368 injecting the code. The default is off.
18370 @item show debug compile
18371 Displays the current state of displaying @value{GDBN} process of
18372 compiling and injecting the code.
18375 @subsection Compilation options for the @code{compile} command
18377 @value{GDBN} needs to specify the right compilation options for the code
18378 to be injected, in part to make its ABI compatible with the inferior
18379 and in part to make the injected code compatible with @value{GDBN}'s
18383 The options used, in increasing precedence:
18386 @item target architecture and OS options (@code{gdbarch})
18387 These options depend on target processor type and target operating
18388 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
18389 (@code{-m64}) compilation option.
18391 @item compilation options recorded in the target
18392 @value{NGCC} (since version 4.7) stores the options used for compilation
18393 into @code{DW_AT_producer} part of DWARF debugging information according
18394 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
18395 explicitly specify @code{-g} during inferior compilation otherwise
18396 @value{NGCC} produces no DWARF. This feature is only relevant for
18397 platforms where @code{-g} produces DWARF by default, otherwise one may
18398 try to enforce DWARF by using @code{-gdwarf-4}.
18400 @item compilation options set by @code{set compile-args}
18404 You can override compilation options using the following command:
18407 @item set compile-args
18408 @cindex compile command options override
18409 Set compilation options used for compiling and injecting code with the
18410 @code{compile} commands. These options override any conflicting ones
18411 from the target architecture and/or options stored during inferior
18414 @item show compile-args
18415 Displays the current state of compilation options override.
18416 This does not show all the options actually used during compilation,
18417 use @ref{set debug compile} for that.
18420 @subsection Caveats when using the @code{compile} command
18422 There are a few caveats to keep in mind when using the @code{compile}
18423 command. As the caveats are different per language, the table below
18424 highlights specific issues on a per language basis.
18427 @item C code examples and caveats
18428 When the language in @value{GDBN} is set to @samp{C}, the compiler will
18429 attempt to compile the source code with a @samp{C} compiler. The source
18430 code provided to the @code{compile} command will have much the same
18431 access to variables and types as it normally would if it were part of
18432 the program currently being debugged in @value{GDBN}.
18434 Below is a sample program that forms the basis of the examples that
18435 follow. This program has been compiled and loaded into @value{GDBN},
18436 much like any other normal debugging session.
18439 void function1 (void)
18442 printf ("function 1\n");
18445 void function2 (void)
18460 For the purposes of the examples in this section, the program above has
18461 been compiled, loaded into @value{GDBN}, stopped at the function
18462 @code{main}, and @value{GDBN} is awaiting input from the user.
18464 To access variables and types for any program in @value{GDBN}, the
18465 program must be compiled and packaged with debug information. The
18466 @code{compile} command is not an exception to this rule. Without debug
18467 information, you can still use the @code{compile} command, but you will
18468 be very limited in what variables and types you can access.
18470 So with that in mind, the example above has been compiled with debug
18471 information enabled. The @code{compile} command will have access to
18472 all variables and types (except those that may have been optimized
18473 out). Currently, as @value{GDBN} has stopped the program in the
18474 @code{main} function, the @code{compile} command would have access to
18475 the variable @code{k}. You could invoke the @code{compile} command
18476 and type some source code to set the value of @code{k}. You can also
18477 read it, or do anything with that variable you would normally do in
18478 @code{C}. Be aware that changes to inferior variables in the
18479 @code{compile} command are persistent. In the following example:
18482 compile code k = 3;
18486 the variable @code{k} is now 3. It will retain that value until
18487 something else in the example program changes it, or another
18488 @code{compile} command changes it.
18490 Normal scope and access rules apply to source code compiled and
18491 injected by the @code{compile} command. In the example, the variables
18492 @code{j} and @code{k} are not accessible yet, because the program is
18493 currently stopped in the @code{main} function, where these variables
18494 are not in scope. Therefore, the following command
18497 compile code j = 3;
18501 will result in a compilation error message.
18503 Once the program is continued, execution will bring these variables in
18504 scope, and they will become accessible; then the code you specify via
18505 the @code{compile} command will be able to access them.
18507 You can create variables and types with the @code{compile} command as
18508 part of your source code. Variables and types that are created as part
18509 of the @code{compile} command are not visible to the rest of the program for
18510 the duration of its run. This example is valid:
18513 compile code int ff = 5; printf ("ff is %d\n", ff);
18516 However, if you were to type the following into @value{GDBN} after that
18517 command has completed:
18520 compile code printf ("ff is %d\n'', ff);
18524 a compiler error would be raised as the variable @code{ff} no longer
18525 exists. Object code generated and injected by the @code{compile}
18526 command is removed when its execution ends. Caution is advised
18527 when assigning to program variables values of variables created by the
18528 code submitted to the @code{compile} command. This example is valid:
18531 compile code int ff = 5; k = ff;
18534 The value of the variable @code{ff} is assigned to @code{k}. The variable
18535 @code{k} does not require the existence of @code{ff} to maintain the value
18536 it has been assigned. However, pointers require particular care in
18537 assignment. If the source code compiled with the @code{compile} command
18538 changed the address of a pointer in the example program, perhaps to a
18539 variable created in the @code{compile} command, that pointer would point
18540 to an invalid location when the command exits. The following example
18541 would likely cause issues with your debugged program:
18544 compile code int ff = 5; p = &ff;
18547 In this example, @code{p} would point to @code{ff} when the
18548 @code{compile} command is executing the source code provided to it.
18549 However, as variables in the (example) program persist with their
18550 assigned values, the variable @code{p} would point to an invalid
18551 location when the command exists. A general rule should be followed
18552 in that you should either assign @code{NULL} to any assigned pointers,
18553 or restore a valid location to the pointer before the command exits.
18555 Similar caution must be exercised with any structs, unions, and typedefs
18556 defined in @code{compile} command. Types defined in the @code{compile}
18557 command will no longer be available in the next @code{compile} command.
18558 Therefore, if you cast a variable to a type defined in the
18559 @code{compile} command, care must be taken to ensure that any future
18560 need to resolve the type can be achieved.
18563 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
18564 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
18565 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
18566 Compilation failed.
18567 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
18571 Variables that have been optimized away by the compiler are not
18572 accessible to the code submitted to the @code{compile} command.
18573 Access to those variables will generate a compiler error which @value{GDBN}
18574 will print to the console.
18577 @subsection Compiler search for the @code{compile} command
18579 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged
18580 which may not be obvious for remote targets of different architecture
18581 than where @value{GDBN} is running. Environment variable @code{PATH} on
18582 @value{GDBN} host is searched for @value{NGCC} binary matching the
18583 target architecture and operating system. This search can be overriden
18584 by @code{set compile-gcc} @value{GDBN} command below. @code{PATH} is
18585 taken from shell that executed @value{GDBN}, it is not the value set by
18586 @value{GDBN} command @code{set environment}). @xref{Environment}.
18589 Specifically @code{PATH} is searched for binaries matching regular expression
18590 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
18591 debugged. @var{arch} is processor name --- multiarch is supported, so for
18592 example both @code{i386} and @code{x86_64} targets look for pattern
18593 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
18594 for pattern @code{s390x?}. @var{os} is currently supported only for
18595 pattern @code{linux(-gnu)?}.
18597 On Posix hosts the compiler driver @value{GDBN} needs to find also
18598 shared library @file{libcc1.so} from the compiler. It is searched in
18599 default shared library search path (overridable with usual environment
18600 variable @code{LD_LIBRARY_PATH}), unrelated to @code{PATH} or @code{set
18601 compile-gcc} settings. Contrary to it @file{libcc1plugin.so} is found
18602 according to the installation of the found compiler --- as possibly
18603 specified by the @code{set compile-gcc} command.
18606 @item set compile-gcc
18607 @cindex compile command driver filename override
18608 Set compilation command used for compiling and injecting code with the
18609 @code{compile} commands. If this option is not set (it is set to
18610 an empty string), the search described above will occur --- that is the
18613 @item show compile-gcc
18614 Displays the current compile command @value{NGCC} driver filename.
18615 If set, it is the main command @command{gcc}, found usually for example
18616 under name @file{x86_64-linux-gnu-gcc}.
18620 @chapter @value{GDBN} Files
18622 @value{GDBN} needs to know the file name of the program to be debugged,
18623 both in order to read its symbol table and in order to start your
18624 program. To debug a core dump of a previous run, you must also tell
18625 @value{GDBN} the name of the core dump file.
18628 * Files:: Commands to specify files
18629 * File Caching:: Information about @value{GDBN}'s file caching
18630 * Separate Debug Files:: Debugging information in separate files
18631 * MiniDebugInfo:: Debugging information in a special section
18632 * Index Files:: Index files speed up GDB
18633 * Symbol Errors:: Errors reading symbol files
18634 * Data Files:: GDB data files
18638 @section Commands to Specify Files
18640 @cindex symbol table
18641 @cindex core dump file
18643 You may want to specify executable and core dump file names. The usual
18644 way to do this is at start-up time, using the arguments to
18645 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
18646 Out of @value{GDBN}}).
18648 Occasionally it is necessary to change to a different file during a
18649 @value{GDBN} session. Or you may run @value{GDBN} and forget to
18650 specify a file you want to use. Or you are debugging a remote target
18651 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
18652 Program}). In these situations the @value{GDBN} commands to specify
18653 new files are useful.
18656 @cindex executable file
18658 @item file @var{filename}
18659 Use @var{filename} as the program to be debugged. It is read for its
18660 symbols and for the contents of pure memory. It is also the program
18661 executed when you use the @code{run} command. If you do not specify a
18662 directory and the file is not found in the @value{GDBN} working directory,
18663 @value{GDBN} uses the environment variable @code{PATH} as a list of
18664 directories to search, just as the shell does when looking for a program
18665 to run. You can change the value of this variable, for both @value{GDBN}
18666 and your program, using the @code{path} command.
18668 @cindex unlinked object files
18669 @cindex patching object files
18670 You can load unlinked object @file{.o} files into @value{GDBN} using
18671 the @code{file} command. You will not be able to ``run'' an object
18672 file, but you can disassemble functions and inspect variables. Also,
18673 if the underlying BFD functionality supports it, you could use
18674 @kbd{gdb -write} to patch object files using this technique. Note
18675 that @value{GDBN} can neither interpret nor modify relocations in this
18676 case, so branches and some initialized variables will appear to go to
18677 the wrong place. But this feature is still handy from time to time.
18680 @code{file} with no argument makes @value{GDBN} discard any information it
18681 has on both executable file and the symbol table.
18684 @item exec-file @r{[} @var{filename} @r{]}
18685 Specify that the program to be run (but not the symbol table) is found
18686 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
18687 if necessary to locate your program. Omitting @var{filename} means to
18688 discard information on the executable file.
18690 @kindex symbol-file
18691 @item symbol-file @r{[} @var{filename} @r{]}
18692 Read symbol table information from file @var{filename}. @code{PATH} is
18693 searched when necessary. Use the @code{file} command to get both symbol
18694 table and program to run from the same file.
18696 @code{symbol-file} with no argument clears out @value{GDBN} information on your
18697 program's symbol table.
18699 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
18700 some breakpoints and auto-display expressions. This is because they may
18701 contain pointers to the internal data recording symbols and data types,
18702 which are part of the old symbol table data being discarded inside
18705 @code{symbol-file} does not repeat if you press @key{RET} again after
18708 When @value{GDBN} is configured for a particular environment, it
18709 understands debugging information in whatever format is the standard
18710 generated for that environment; you may use either a @sc{gnu} compiler, or
18711 other compilers that adhere to the local conventions.
18712 Best results are usually obtained from @sc{gnu} compilers; for example,
18713 using @code{@value{NGCC}} you can generate debugging information for
18716 For most kinds of object files, with the exception of old SVR3 systems
18717 using COFF, the @code{symbol-file} command does not normally read the
18718 symbol table in full right away. Instead, it scans the symbol table
18719 quickly to find which source files and which symbols are present. The
18720 details are read later, one source file at a time, as they are needed.
18722 The purpose of this two-stage reading strategy is to make @value{GDBN}
18723 start up faster. For the most part, it is invisible except for
18724 occasional pauses while the symbol table details for a particular source
18725 file are being read. (The @code{set verbose} command can turn these
18726 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
18727 Warnings and Messages}.)
18729 We have not implemented the two-stage strategy for COFF yet. When the
18730 symbol table is stored in COFF format, @code{symbol-file} reads the
18731 symbol table data in full right away. Note that ``stabs-in-COFF''
18732 still does the two-stage strategy, since the debug info is actually
18736 @cindex reading symbols immediately
18737 @cindex symbols, reading immediately
18738 @item symbol-file @r{[} -readnow @r{]} @var{filename}
18739 @itemx file @r{[} -readnow @r{]} @var{filename}
18740 You can override the @value{GDBN} two-stage strategy for reading symbol
18741 tables by using the @samp{-readnow} option with any of the commands that
18742 load symbol table information, if you want to be sure @value{GDBN} has the
18743 entire symbol table available.
18745 @cindex @code{-readnever}, option for symbol-file command
18746 @cindex never read symbols
18747 @cindex symbols, never read
18748 @item symbol-file @r{[} -readnever @r{]} @var{filename}
18749 @itemx file @r{[} -readnever @r{]} @var{filename}
18750 You can instruct @value{GDBN} to never read the symbolic information
18751 contained in @var{filename} by using the @samp{-readnever} option.
18752 @xref{--readnever}.
18754 @c FIXME: for now no mention of directories, since this seems to be in
18755 @c flux. 13mar1992 status is that in theory GDB would look either in
18756 @c current dir or in same dir as myprog; but issues like competing
18757 @c GDB's, or clutter in system dirs, mean that in practice right now
18758 @c only current dir is used. FFish says maybe a special GDB hierarchy
18759 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
18763 @item core-file @r{[}@var{filename}@r{]}
18765 Specify the whereabouts of a core dump file to be used as the ``contents
18766 of memory''. Traditionally, core files contain only some parts of the
18767 address space of the process that generated them; @value{GDBN} can access the
18768 executable file itself for other parts.
18770 @code{core-file} with no argument specifies that no core file is
18773 Note that the core file is ignored when your program is actually running
18774 under @value{GDBN}. So, if you have been running your program and you
18775 wish to debug a core file instead, you must kill the subprocess in which
18776 the program is running. To do this, use the @code{kill} command
18777 (@pxref{Kill Process, ,Killing the Child Process}).
18779 @kindex add-symbol-file
18780 @cindex dynamic linking
18781 @item add-symbol-file @var{filename} @var{address}
18782 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{|} -readnever @r{]}
18783 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
18784 The @code{add-symbol-file} command reads additional symbol table
18785 information from the file @var{filename}. You would use this command
18786 when @var{filename} has been dynamically loaded (by some other means)
18787 into the program that is running. The @var{address} should give the memory
18788 address at which the file has been loaded; @value{GDBN} cannot figure
18789 this out for itself. You can additionally specify an arbitrary number
18790 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
18791 section name and base address for that section. You can specify any
18792 @var{address} as an expression.
18794 The symbol table of the file @var{filename} is added to the symbol table
18795 originally read with the @code{symbol-file} command. You can use the
18796 @code{add-symbol-file} command any number of times; the new symbol data
18797 thus read is kept in addition to the old.
18799 Changes can be reverted using the command @code{remove-symbol-file}.
18801 @cindex relocatable object files, reading symbols from
18802 @cindex object files, relocatable, reading symbols from
18803 @cindex reading symbols from relocatable object files
18804 @cindex symbols, reading from relocatable object files
18805 @cindex @file{.o} files, reading symbols from
18806 Although @var{filename} is typically a shared library file, an
18807 executable file, or some other object file which has been fully
18808 relocated for loading into a process, you can also load symbolic
18809 information from relocatable @file{.o} files, as long as:
18813 the file's symbolic information refers only to linker symbols defined in
18814 that file, not to symbols defined by other object files,
18816 every section the file's symbolic information refers to has actually
18817 been loaded into the inferior, as it appears in the file, and
18819 you can determine the address at which every section was loaded, and
18820 provide these to the @code{add-symbol-file} command.
18824 Some embedded operating systems, like Sun Chorus and VxWorks, can load
18825 relocatable files into an already running program; such systems
18826 typically make the requirements above easy to meet. However, it's
18827 important to recognize that many native systems use complex link
18828 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
18829 assembly, for example) that make the requirements difficult to meet. In
18830 general, one cannot assume that using @code{add-symbol-file} to read a
18831 relocatable object file's symbolic information will have the same effect
18832 as linking the relocatable object file into the program in the normal
18835 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
18837 @kindex remove-symbol-file
18838 @item remove-symbol-file @var{filename}
18839 @item remove-symbol-file -a @var{address}
18840 Remove a symbol file added via the @code{add-symbol-file} command. The
18841 file to remove can be identified by its @var{filename} or by an @var{address}
18842 that lies within the boundaries of this symbol file in memory. Example:
18845 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18846 add symbol table from file "/home/user/gdb/mylib.so" at
18847 .text_addr = 0x7ffff7ff9480
18849 Reading symbols from /home/user/gdb/mylib.so...done.
18850 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18851 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18856 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18858 @kindex add-symbol-file-from-memory
18859 @cindex @code{syscall DSO}
18860 @cindex load symbols from memory
18861 @item add-symbol-file-from-memory @var{address}
18862 Load symbols from the given @var{address} in a dynamically loaded
18863 object file whose image is mapped directly into the inferior's memory.
18864 For example, the Linux kernel maps a @code{syscall DSO} into each
18865 process's address space; this DSO provides kernel-specific code for
18866 some system calls. The argument can be any expression whose
18867 evaluation yields the address of the file's shared object file header.
18868 For this command to work, you must have used @code{symbol-file} or
18869 @code{exec-file} commands in advance.
18872 @item section @var{section} @var{addr}
18873 The @code{section} command changes the base address of the named
18874 @var{section} of the exec file to @var{addr}. This can be used if the
18875 exec file does not contain section addresses, (such as in the
18876 @code{a.out} format), or when the addresses specified in the file
18877 itself are wrong. Each section must be changed separately. The
18878 @code{info files} command, described below, lists all the sections and
18882 @kindex info target
18885 @code{info files} and @code{info target} are synonymous; both print the
18886 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18887 including the names of the executable and core dump files currently in
18888 use by @value{GDBN}, and the files from which symbols were loaded. The
18889 command @code{help target} lists all possible targets rather than
18892 @kindex maint info sections
18893 @item maint info sections
18894 Another command that can give you extra information about program sections
18895 is @code{maint info sections}. In addition to the section information
18896 displayed by @code{info files}, this command displays the flags and file
18897 offset of each section in the executable and core dump files. In addition,
18898 @code{maint info sections} provides the following command options (which
18899 may be arbitrarily combined):
18903 Display sections for all loaded object files, including shared libraries.
18904 @item @var{sections}
18905 Display info only for named @var{sections}.
18906 @item @var{section-flags}
18907 Display info only for sections for which @var{section-flags} are true.
18908 The section flags that @value{GDBN} currently knows about are:
18911 Section will have space allocated in the process when loaded.
18912 Set for all sections except those containing debug information.
18914 Section will be loaded from the file into the child process memory.
18915 Set for pre-initialized code and data, clear for @code{.bss} sections.
18917 Section needs to be relocated before loading.
18919 Section cannot be modified by the child process.
18921 Section contains executable code only.
18923 Section contains data only (no executable code).
18925 Section will reside in ROM.
18927 Section contains data for constructor/destructor lists.
18929 Section is not empty.
18931 An instruction to the linker to not output the section.
18932 @item COFF_SHARED_LIBRARY
18933 A notification to the linker that the section contains
18934 COFF shared library information.
18936 Section contains common symbols.
18939 @kindex set trust-readonly-sections
18940 @cindex read-only sections
18941 @item set trust-readonly-sections on
18942 Tell @value{GDBN} that readonly sections in your object file
18943 really are read-only (i.e.@: that their contents will not change).
18944 In that case, @value{GDBN} can fetch values from these sections
18945 out of the object file, rather than from the target program.
18946 For some targets (notably embedded ones), this can be a significant
18947 enhancement to debugging performance.
18949 The default is off.
18951 @item set trust-readonly-sections off
18952 Tell @value{GDBN} not to trust readonly sections. This means that
18953 the contents of the section might change while the program is running,
18954 and must therefore be fetched from the target when needed.
18956 @item show trust-readonly-sections
18957 Show the current setting of trusting readonly sections.
18960 All file-specifying commands allow both absolute and relative file names
18961 as arguments. @value{GDBN} always converts the file name to an absolute file
18962 name and remembers it that way.
18964 @cindex shared libraries
18965 @anchor{Shared Libraries}
18966 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18967 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18968 DSBT (TIC6X) shared libraries.
18970 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18971 shared libraries. @xref{Expat}.
18973 @value{GDBN} automatically loads symbol definitions from shared libraries
18974 when you use the @code{run} command, or when you examine a core file.
18975 (Before you issue the @code{run} command, @value{GDBN} does not understand
18976 references to a function in a shared library, however---unless you are
18977 debugging a core file).
18979 @c FIXME: some @value{GDBN} release may permit some refs to undef
18980 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18981 @c FIXME...lib; check this from time to time when updating manual
18983 There are times, however, when you may wish to not automatically load
18984 symbol definitions from shared libraries, such as when they are
18985 particularly large or there are many of them.
18987 To control the automatic loading of shared library symbols, use the
18991 @kindex set auto-solib-add
18992 @item set auto-solib-add @var{mode}
18993 If @var{mode} is @code{on}, symbols from all shared object libraries
18994 will be loaded automatically when the inferior begins execution, you
18995 attach to an independently started inferior, or when the dynamic linker
18996 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18997 is @code{off}, symbols must be loaded manually, using the
18998 @code{sharedlibrary} command. The default value is @code{on}.
19000 @cindex memory used for symbol tables
19001 If your program uses lots of shared libraries with debug info that
19002 takes large amounts of memory, you can decrease the @value{GDBN}
19003 memory footprint by preventing it from automatically loading the
19004 symbols from shared libraries. To that end, type @kbd{set
19005 auto-solib-add off} before running the inferior, then load each
19006 library whose debug symbols you do need with @kbd{sharedlibrary
19007 @var{regexp}}, where @var{regexp} is a regular expression that matches
19008 the libraries whose symbols you want to be loaded.
19010 @kindex show auto-solib-add
19011 @item show auto-solib-add
19012 Display the current autoloading mode.
19015 @cindex load shared library
19016 To explicitly load shared library symbols, use the @code{sharedlibrary}
19020 @kindex info sharedlibrary
19022 @item info share @var{regex}
19023 @itemx info sharedlibrary @var{regex}
19024 Print the names of the shared libraries which are currently loaded
19025 that match @var{regex}. If @var{regex} is omitted then print
19026 all shared libraries that are loaded.
19029 @item info dll @var{regex}
19030 This is an alias of @code{info sharedlibrary}.
19032 @kindex sharedlibrary
19034 @item sharedlibrary @var{regex}
19035 @itemx share @var{regex}
19036 Load shared object library symbols for files matching a
19037 Unix regular expression.
19038 As with files loaded automatically, it only loads shared libraries
19039 required by your program for a core file or after typing @code{run}. If
19040 @var{regex} is omitted all shared libraries required by your program are
19043 @item nosharedlibrary
19044 @kindex nosharedlibrary
19045 @cindex unload symbols from shared libraries
19046 Unload all shared object library symbols. This discards all symbols
19047 that have been loaded from all shared libraries. Symbols from shared
19048 libraries that were loaded by explicit user requests are not
19052 Sometimes you may wish that @value{GDBN} stops and gives you control
19053 when any of shared library events happen. The best way to do this is
19054 to use @code{catch load} and @code{catch unload} (@pxref{Set
19057 @value{GDBN} also supports the the @code{set stop-on-solib-events}
19058 command for this. This command exists for historical reasons. It is
19059 less useful than setting a catchpoint, because it does not allow for
19060 conditions or commands as a catchpoint does.
19063 @item set stop-on-solib-events
19064 @kindex set stop-on-solib-events
19065 This command controls whether @value{GDBN} should give you control
19066 when the dynamic linker notifies it about some shared library event.
19067 The most common event of interest is loading or unloading of a new
19070 @item show stop-on-solib-events
19071 @kindex show stop-on-solib-events
19072 Show whether @value{GDBN} stops and gives you control when shared
19073 library events happen.
19076 Shared libraries are also supported in many cross or remote debugging
19077 configurations. @value{GDBN} needs to have access to the target's libraries;
19078 this can be accomplished either by providing copies of the libraries
19079 on the host system, or by asking @value{GDBN} to automatically retrieve the
19080 libraries from the target. If copies of the target libraries are
19081 provided, they need to be the same as the target libraries, although the
19082 copies on the target can be stripped as long as the copies on the host are
19085 @cindex where to look for shared libraries
19086 For remote debugging, you need to tell @value{GDBN} where the target
19087 libraries are, so that it can load the correct copies---otherwise, it
19088 may try to load the host's libraries. @value{GDBN} has two variables
19089 to specify the search directories for target libraries.
19092 @cindex prefix for executable and shared library file names
19093 @cindex system root, alternate
19094 @kindex set solib-absolute-prefix
19095 @kindex set sysroot
19096 @item set sysroot @var{path}
19097 Use @var{path} as the system root for the program being debugged. Any
19098 absolute shared library paths will be prefixed with @var{path}; many
19099 runtime loaders store the absolute paths to the shared library in the
19100 target program's memory. When starting processes remotely, and when
19101 attaching to already-running processes (local or remote), their
19102 executable filenames will be prefixed with @var{path} if reported to
19103 @value{GDBN} as absolute by the operating system. If you use
19104 @code{set sysroot} to find executables and shared libraries, they need
19105 to be laid out in the same way that they are on the target, with
19106 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
19109 If @var{path} starts with the sequence @file{target:} and the target
19110 system is remote then @value{GDBN} will retrieve the target binaries
19111 from the remote system. This is only supported when using a remote
19112 target that supports the @code{remote get} command (@pxref{File
19113 Transfer,,Sending files to a remote system}). The part of @var{path}
19114 following the initial @file{target:} (if present) is used as system
19115 root prefix on the remote file system. If @var{path} starts with the
19116 sequence @file{remote:} this is converted to the sequence
19117 @file{target:} by @code{set sysroot}@footnote{Historically the
19118 functionality to retrieve binaries from the remote system was
19119 provided by prefixing @var{path} with @file{remote:}}. If you want
19120 to specify a local system root using a directory that happens to be
19121 named @file{target:} or @file{remote:}, you need to use some
19122 equivalent variant of the name like @file{./target:}.
19124 For targets with an MS-DOS based filesystem, such as MS-Windows and
19125 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
19126 absolute file name with @var{path}. But first, on Unix hosts,
19127 @value{GDBN} converts all backslash directory separators into forward
19128 slashes, because the backslash is not a directory separator on Unix:
19131 c:\foo\bar.dll @result{} c:/foo/bar.dll
19134 Then, @value{GDBN} attempts prefixing the target file name with
19135 @var{path}, and looks for the resulting file name in the host file
19139 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
19142 If that does not find the binary, @value{GDBN} tries removing
19143 the @samp{:} character from the drive spec, both for convenience, and,
19144 for the case of the host file system not supporting file names with
19148 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
19151 This makes it possible to have a system root that mirrors a target
19152 with more than one drive. E.g., you may want to setup your local
19153 copies of the target system shared libraries like so (note @samp{c} vs
19157 @file{/path/to/sysroot/c/sys/bin/foo.dll}
19158 @file{/path/to/sysroot/c/sys/bin/bar.dll}
19159 @file{/path/to/sysroot/z/sys/bin/bar.dll}
19163 and point the system root at @file{/path/to/sysroot}, so that
19164 @value{GDBN} can find the correct copies of both
19165 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
19167 If that still does not find the binary, @value{GDBN} tries
19168 removing the whole drive spec from the target file name:
19171 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
19174 This last lookup makes it possible to not care about the drive name,
19175 if you don't want or need to.
19177 The @code{set solib-absolute-prefix} command is an alias for @code{set
19180 @cindex default system root
19181 @cindex @samp{--with-sysroot}
19182 You can set the default system root by using the configure-time
19183 @samp{--with-sysroot} option. If the system root is inside
19184 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19185 @samp{--exec-prefix}), then the default system root will be updated
19186 automatically if the installed @value{GDBN} is moved to a new
19189 @kindex show sysroot
19191 Display the current executable and shared library prefix.
19193 @kindex set solib-search-path
19194 @item set solib-search-path @var{path}
19195 If this variable is set, @var{path} is a colon-separated list of
19196 directories to search for shared libraries. @samp{solib-search-path}
19197 is used after @samp{sysroot} fails to locate the library, or if the
19198 path to the library is relative instead of absolute. If you want to
19199 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
19200 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
19201 finding your host's libraries. @samp{sysroot} is preferred; setting
19202 it to a nonexistent directory may interfere with automatic loading
19203 of shared library symbols.
19205 @kindex show solib-search-path
19206 @item show solib-search-path
19207 Display the current shared library search path.
19209 @cindex DOS file-name semantics of file names.
19210 @kindex set target-file-system-kind (unix|dos-based|auto)
19211 @kindex show target-file-system-kind
19212 @item set target-file-system-kind @var{kind}
19213 Set assumed file system kind for target reported file names.
19215 Shared library file names as reported by the target system may not
19216 make sense as is on the system @value{GDBN} is running on. For
19217 example, when remote debugging a target that has MS-DOS based file
19218 system semantics, from a Unix host, the target may be reporting to
19219 @value{GDBN} a list of loaded shared libraries with file names such as
19220 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
19221 drive letters, so the @samp{c:\} prefix is not normally understood as
19222 indicating an absolute file name, and neither is the backslash
19223 normally considered a directory separator character. In that case,
19224 the native file system would interpret this whole absolute file name
19225 as a relative file name with no directory components. This would make
19226 it impossible to point @value{GDBN} at a copy of the remote target's
19227 shared libraries on the host using @code{set sysroot}, and impractical
19228 with @code{set solib-search-path}. Setting
19229 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
19230 to interpret such file names similarly to how the target would, and to
19231 map them to file names valid on @value{GDBN}'s native file system
19232 semantics. The value of @var{kind} can be @code{"auto"}, in addition
19233 to one of the supported file system kinds. In that case, @value{GDBN}
19234 tries to determine the appropriate file system variant based on the
19235 current target's operating system (@pxref{ABI, ,Configuring the
19236 Current ABI}). The supported file system settings are:
19240 Instruct @value{GDBN} to assume the target file system is of Unix
19241 kind. Only file names starting the forward slash (@samp{/}) character
19242 are considered absolute, and the directory separator character is also
19246 Instruct @value{GDBN} to assume the target file system is DOS based.
19247 File names starting with either a forward slash, or a drive letter
19248 followed by a colon (e.g., @samp{c:}), are considered absolute, and
19249 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
19250 considered directory separators.
19253 Instruct @value{GDBN} to use the file system kind associated with the
19254 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
19255 This is the default.
19259 @cindex file name canonicalization
19260 @cindex base name differences
19261 When processing file names provided by the user, @value{GDBN}
19262 frequently needs to compare them to the file names recorded in the
19263 program's debug info. Normally, @value{GDBN} compares just the
19264 @dfn{base names} of the files as strings, which is reasonably fast
19265 even for very large programs. (The base name of a file is the last
19266 portion of its name, after stripping all the leading directories.)
19267 This shortcut in comparison is based upon the assumption that files
19268 cannot have more than one base name. This is usually true, but
19269 references to files that use symlinks or similar filesystem
19270 facilities violate that assumption. If your program records files
19271 using such facilities, or if you provide file names to @value{GDBN}
19272 using symlinks etc., you can set @code{basenames-may-differ} to
19273 @code{true} to instruct @value{GDBN} to completely canonicalize each
19274 pair of file names it needs to compare. This will make file-name
19275 comparisons accurate, but at a price of a significant slowdown.
19278 @item set basenames-may-differ
19279 @kindex set basenames-may-differ
19280 Set whether a source file may have multiple base names.
19282 @item show basenames-may-differ
19283 @kindex show basenames-may-differ
19284 Show whether a source file may have multiple base names.
19288 @section File Caching
19289 @cindex caching of opened files
19290 @cindex caching of bfd objects
19292 To speed up file loading, and reduce memory usage, @value{GDBN} will
19293 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
19294 BFD, bfd, The Binary File Descriptor Library}. The following commands
19295 allow visibility and control of the caching behavior.
19298 @kindex maint info bfds
19299 @item maint info bfds
19300 This prints information about each @code{bfd} object that is known to
19303 @kindex maint set bfd-sharing
19304 @kindex maint show bfd-sharing
19305 @kindex bfd caching
19306 @item maint set bfd-sharing
19307 @item maint show bfd-sharing
19308 Control whether @code{bfd} objects can be shared. When sharing is
19309 enabled @value{GDBN} reuses already open @code{bfd} objects rather
19310 than reopening the same file. Turning sharing off does not cause
19311 already shared @code{bfd} objects to be unshared, but all future files
19312 that are opened will create a new @code{bfd} object. Similarly,
19313 re-enabling sharing does not cause multiple existing @code{bfd}
19314 objects to be collapsed into a single shared @code{bfd} object.
19316 @kindex set debug bfd-cache @var{level}
19317 @kindex bfd caching
19318 @item set debug bfd-cache @var{level}
19319 Turns on debugging of the bfd cache, setting the level to @var{level}.
19321 @kindex show debug bfd-cache
19322 @kindex bfd caching
19323 @item show debug bfd-cache
19324 Show the current debugging level of the bfd cache.
19327 @node Separate Debug Files
19328 @section Debugging Information in Separate Files
19329 @cindex separate debugging information files
19330 @cindex debugging information in separate files
19331 @cindex @file{.debug} subdirectories
19332 @cindex debugging information directory, global
19333 @cindex global debugging information directories
19334 @cindex build ID, and separate debugging files
19335 @cindex @file{.build-id} directory
19337 @value{GDBN} allows you to put a program's debugging information in a
19338 file separate from the executable itself, in a way that allows
19339 @value{GDBN} to find and load the debugging information automatically.
19340 Since debugging information can be very large---sometimes larger
19341 than the executable code itself---some systems distribute debugging
19342 information for their executables in separate files, which users can
19343 install only when they need to debug a problem.
19345 @value{GDBN} supports two ways of specifying the separate debug info
19350 The executable contains a @dfn{debug link} that specifies the name of
19351 the separate debug info file. The separate debug file's name is
19352 usually @file{@var{executable}.debug}, where @var{executable} is the
19353 name of the corresponding executable file without leading directories
19354 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
19355 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
19356 checksum for the debug file, which @value{GDBN} uses to validate that
19357 the executable and the debug file came from the same build.
19360 The executable contains a @dfn{build ID}, a unique bit string that is
19361 also present in the corresponding debug info file. (This is supported
19362 only on some operating systems, when using the ELF or PE file formats
19363 for binary files and the @sc{gnu} Binutils.) For more details about
19364 this feature, see the description of the @option{--build-id}
19365 command-line option in @ref{Options, , Command Line Options, ld.info,
19366 The GNU Linker}. The debug info file's name is not specified
19367 explicitly by the build ID, but can be computed from the build ID, see
19371 Depending on the way the debug info file is specified, @value{GDBN}
19372 uses two different methods of looking for the debug file:
19376 For the ``debug link'' method, @value{GDBN} looks up the named file in
19377 the directory of the executable file, then in a subdirectory of that
19378 directory named @file{.debug}, and finally under each one of the global debug
19379 directories, in a subdirectory whose name is identical to the leading
19380 directories of the executable's absolute file name.
19383 For the ``build ID'' method, @value{GDBN} looks in the
19384 @file{.build-id} subdirectory of each one of the global debug directories for
19385 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
19386 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
19387 are the rest of the bit string. (Real build ID strings are 32 or more
19388 hex characters, not 10.)
19391 So, for example, suppose you ask @value{GDBN} to debug
19392 @file{/usr/bin/ls}, which has a debug link that specifies the
19393 file @file{ls.debug}, and a build ID whose value in hex is
19394 @code{abcdef1234}. If the list of the global debug directories includes
19395 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
19396 debug information files, in the indicated order:
19400 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
19402 @file{/usr/bin/ls.debug}
19404 @file{/usr/bin/.debug/ls.debug}
19406 @file{/usr/lib/debug/usr/bin/ls.debug}.
19409 @anchor{debug-file-directory}
19410 Global debugging info directories default to what is set by @value{GDBN}
19411 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
19412 you can also set the global debugging info directories, and view the list
19413 @value{GDBN} is currently using.
19417 @kindex set debug-file-directory
19418 @item set debug-file-directory @var{directories}
19419 Set the directories which @value{GDBN} searches for separate debugging
19420 information files to @var{directory}. Multiple path components can be set
19421 concatenating them by a path separator.
19423 @kindex show debug-file-directory
19424 @item show debug-file-directory
19425 Show the directories @value{GDBN} searches for separate debugging
19430 @cindex @code{.gnu_debuglink} sections
19431 @cindex debug link sections
19432 A debug link is a special section of the executable file named
19433 @code{.gnu_debuglink}. The section must contain:
19437 A filename, with any leading directory components removed, followed by
19440 zero to three bytes of padding, as needed to reach the next four-byte
19441 boundary within the section, and
19443 a four-byte CRC checksum, stored in the same endianness used for the
19444 executable file itself. The checksum is computed on the debugging
19445 information file's full contents by the function given below, passing
19446 zero as the @var{crc} argument.
19449 Any executable file format can carry a debug link, as long as it can
19450 contain a section named @code{.gnu_debuglink} with the contents
19453 @cindex @code{.note.gnu.build-id} sections
19454 @cindex build ID sections
19455 The build ID is a special section in the executable file (and in other
19456 ELF binary files that @value{GDBN} may consider). This section is
19457 often named @code{.note.gnu.build-id}, but that name is not mandatory.
19458 It contains unique identification for the built files---the ID remains
19459 the same across multiple builds of the same build tree. The default
19460 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
19461 content for the build ID string. The same section with an identical
19462 value is present in the original built binary with symbols, in its
19463 stripped variant, and in the separate debugging information file.
19465 The debugging information file itself should be an ordinary
19466 executable, containing a full set of linker symbols, sections, and
19467 debugging information. The sections of the debugging information file
19468 should have the same names, addresses, and sizes as the original file,
19469 but they need not contain any data---much like a @code{.bss} section
19470 in an ordinary executable.
19472 The @sc{gnu} binary utilities (Binutils) package includes the
19473 @samp{objcopy} utility that can produce
19474 the separated executable / debugging information file pairs using the
19475 following commands:
19478 @kbd{objcopy --only-keep-debug foo foo.debug}
19483 These commands remove the debugging
19484 information from the executable file @file{foo} and place it in the file
19485 @file{foo.debug}. You can use the first, second or both methods to link the
19490 The debug link method needs the following additional command to also leave
19491 behind a debug link in @file{foo}:
19494 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
19497 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
19498 a version of the @code{strip} command such that the command @kbd{strip foo -f
19499 foo.debug} has the same functionality as the two @code{objcopy} commands and
19500 the @code{ln -s} command above, together.
19503 Build ID gets embedded into the main executable using @code{ld --build-id} or
19504 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
19505 compatibility fixes for debug files separation are present in @sc{gnu} binary
19506 utilities (Binutils) package since version 2.18.
19511 @cindex CRC algorithm definition
19512 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
19513 IEEE 802.3 using the polynomial:
19515 @c TexInfo requires naked braces for multi-digit exponents for Tex
19516 @c output, but this causes HTML output to barf. HTML has to be set using
19517 @c raw commands. So we end up having to specify this equation in 2
19522 <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>
19523 + <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
19529 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
19530 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
19534 The function is computed byte at a time, taking the least
19535 significant bit of each byte first. The initial pattern
19536 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
19537 the final result is inverted to ensure trailing zeros also affect the
19540 @emph{Note:} This is the same CRC polynomial as used in handling the
19541 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
19542 However in the case of the Remote Serial Protocol, the CRC is computed
19543 @emph{most} significant bit first, and the result is not inverted, so
19544 trailing zeros have no effect on the CRC value.
19546 To complete the description, we show below the code of the function
19547 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
19548 initially supplied @code{crc} argument means that an initial call to
19549 this function passing in zero will start computing the CRC using
19552 @kindex gnu_debuglink_crc32
19555 gnu_debuglink_crc32 (unsigned long crc,
19556 unsigned char *buf, size_t len)
19558 static const unsigned long crc32_table[256] =
19560 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
19561 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
19562 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
19563 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
19564 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
19565 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
19566 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
19567 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
19568 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
19569 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
19570 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
19571 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
19572 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
19573 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
19574 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
19575 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
19576 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
19577 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
19578 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
19579 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
19580 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
19581 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
19582 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
19583 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
19584 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
19585 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
19586 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
19587 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
19588 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
19589 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
19590 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
19591 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
19592 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
19593 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
19594 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
19595 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
19596 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
19597 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
19598 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
19599 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
19600 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
19601 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
19602 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
19603 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
19604 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
19605 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
19606 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
19607 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
19608 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
19609 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
19610 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
19613 unsigned char *end;
19615 crc = ~crc & 0xffffffff;
19616 for (end = buf + len; buf < end; ++buf)
19617 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
19618 return ~crc & 0xffffffff;
19623 This computation does not apply to the ``build ID'' method.
19625 @node MiniDebugInfo
19626 @section Debugging information in a special section
19627 @cindex separate debug sections
19628 @cindex @samp{.gnu_debugdata} section
19630 Some systems ship pre-built executables and libraries that have a
19631 special @samp{.gnu_debugdata} section. This feature is called
19632 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
19633 is used to supply extra symbols for backtraces.
19635 The intent of this section is to provide extra minimal debugging
19636 information for use in simple backtraces. It is not intended to be a
19637 replacement for full separate debugging information (@pxref{Separate
19638 Debug Files}). The example below shows the intended use; however,
19639 @value{GDBN} does not currently put restrictions on what sort of
19640 debugging information might be included in the section.
19642 @value{GDBN} has support for this extension. If the section exists,
19643 then it is used provided that no other source of debugging information
19644 can be found, and that @value{GDBN} was configured with LZMA support.
19646 This section can be easily created using @command{objcopy} and other
19647 standard utilities:
19650 # Extract the dynamic symbols from the main binary, there is no need
19651 # to also have these in the normal symbol table.
19652 nm -D @var{binary} --format=posix --defined-only \
19653 | awk '@{ print $1 @}' | sort > dynsyms
19655 # Extract all the text (i.e. function) symbols from the debuginfo.
19656 # (Note that we actually also accept "D" symbols, for the benefit
19657 # of platforms like PowerPC64 that use function descriptors.)
19658 nm @var{binary} --format=posix --defined-only \
19659 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
19662 # Keep all the function symbols not already in the dynamic symbol
19664 comm -13 dynsyms funcsyms > keep_symbols
19666 # Separate full debug info into debug binary.
19667 objcopy --only-keep-debug @var{binary} debug
19669 # Copy the full debuginfo, keeping only a minimal set of symbols and
19670 # removing some unnecessary sections.
19671 objcopy -S --remove-section .gdb_index --remove-section .comment \
19672 --keep-symbols=keep_symbols debug mini_debuginfo
19674 # Drop the full debug info from the original binary.
19675 strip --strip-all -R .comment @var{binary}
19677 # Inject the compressed data into the .gnu_debugdata section of the
19680 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
19684 @section Index Files Speed Up @value{GDBN}
19685 @cindex index files
19686 @cindex @samp{.gdb_index} section
19688 When @value{GDBN} finds a symbol file, it scans the symbols in the
19689 file in order to construct an internal symbol table. This lets most
19690 @value{GDBN} operations work quickly---at the cost of a delay early
19691 on. For large programs, this delay can be quite lengthy, so
19692 @value{GDBN} provides a way to build an index, which speeds up
19695 The index is stored as a section in the symbol file. @value{GDBN} can
19696 write the index to a file, then you can put it into the symbol file
19697 using @command{objcopy}.
19699 To create an index file, use the @code{save gdb-index} command:
19702 @item save gdb-index [-dwarf-5] @var{directory}
19703 @kindex save gdb-index
19704 Create index files for all symbol files currently known by
19705 @value{GDBN}. For each known @var{symbol-file}, this command by
19706 default creates it produces a single file
19707 @file{@var{symbol-file}.gdb-index}. If you invoke this command with
19708 the @option{-dwarf-5} option, it produces 2 files:
19709 @file{@var{symbol-file}.debug_names} and
19710 @file{@var{symbol-file}.debug_str}. The files are created in the
19711 given @var{directory}.
19714 Once you have created an index file you can merge it into your symbol
19715 file, here named @file{symfile}, using @command{objcopy}:
19718 $ objcopy --add-section .gdb_index=symfile.gdb-index \
19719 --set-section-flags .gdb_index=readonly symfile symfile
19722 Or for @code{-dwarf-5}:
19725 $ objcopy --dump-section .debug_str=symfile.debug_str.new symfile
19726 $ cat symfile.debug_str >>symfile.debug_str.new
19727 $ objcopy --add-section .debug_names=symfile.gdb-index \
19728 --set-section-flags .debug_names=readonly \
19729 --update-section .debug_str=symfile.debug_str.new symfile symfile
19732 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
19733 sections that have been deprecated. Usually they are deprecated because
19734 they are missing a new feature or have performance issues.
19735 To tell @value{GDBN} to use a deprecated index section anyway
19736 specify @code{set use-deprecated-index-sections on}.
19737 The default is @code{off}.
19738 This can speed up startup, but may result in some functionality being lost.
19739 @xref{Index Section Format}.
19741 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
19742 must be done before gdb reads the file. The following will not work:
19745 $ gdb -ex "set use-deprecated-index-sections on" <program>
19748 Instead you must do, for example,
19751 $ gdb -iex "set use-deprecated-index-sections on" <program>
19754 There are currently some limitation on indices. They only work when
19755 for DWARF debugging information, not stabs. And, they do not
19756 currently work for programs using Ada.
19758 @node Symbol Errors
19759 @section Errors Reading Symbol Files
19761 While reading a symbol file, @value{GDBN} occasionally encounters problems,
19762 such as symbol types it does not recognize, or known bugs in compiler
19763 output. By default, @value{GDBN} does not notify you of such problems, since
19764 they are relatively common and primarily of interest to people
19765 debugging compilers. If you are interested in seeing information
19766 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
19767 only one message about each such type of problem, no matter how many
19768 times the problem occurs; or you can ask @value{GDBN} to print more messages,
19769 to see how many times the problems occur, with the @code{set
19770 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
19773 The messages currently printed, and their meanings, include:
19776 @item inner block not inside outer block in @var{symbol}
19778 The symbol information shows where symbol scopes begin and end
19779 (such as at the start of a function or a block of statements). This
19780 error indicates that an inner scope block is not fully contained
19781 in its outer scope blocks.
19783 @value{GDBN} circumvents the problem by treating the inner block as if it had
19784 the same scope as the outer block. In the error message, @var{symbol}
19785 may be shown as ``@code{(don't know)}'' if the outer block is not a
19788 @item block at @var{address} out of order
19790 The symbol information for symbol scope blocks should occur in
19791 order of increasing addresses. This error indicates that it does not
19794 @value{GDBN} does not circumvent this problem, and has trouble
19795 locating symbols in the source file whose symbols it is reading. (You
19796 can often determine what source file is affected by specifying
19797 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
19800 @item bad block start address patched
19802 The symbol information for a symbol scope block has a start address
19803 smaller than the address of the preceding source line. This is known
19804 to occur in the SunOS 4.1.1 (and earlier) C compiler.
19806 @value{GDBN} circumvents the problem by treating the symbol scope block as
19807 starting on the previous source line.
19809 @item bad string table offset in symbol @var{n}
19812 Symbol number @var{n} contains a pointer into the string table which is
19813 larger than the size of the string table.
19815 @value{GDBN} circumvents the problem by considering the symbol to have the
19816 name @code{foo}, which may cause other problems if many symbols end up
19819 @item unknown symbol type @code{0x@var{nn}}
19821 The symbol information contains new data types that @value{GDBN} does
19822 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
19823 uncomprehended information, in hexadecimal.
19825 @value{GDBN} circumvents the error by ignoring this symbol information.
19826 This usually allows you to debug your program, though certain symbols
19827 are not accessible. If you encounter such a problem and feel like
19828 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
19829 on @code{complain}, then go up to the function @code{read_dbx_symtab}
19830 and examine @code{*bufp} to see the symbol.
19832 @item stub type has NULL name
19834 @value{GDBN} could not find the full definition for a struct or class.
19836 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
19837 The symbol information for a C@t{++} member function is missing some
19838 information that recent versions of the compiler should have output for
19841 @item info mismatch between compiler and debugger
19843 @value{GDBN} could not parse a type specification output by the compiler.
19848 @section GDB Data Files
19850 @cindex prefix for data files
19851 @value{GDBN} will sometimes read an auxiliary data file. These files
19852 are kept in a directory known as the @dfn{data directory}.
19854 You can set the data directory's name, and view the name @value{GDBN}
19855 is currently using.
19858 @kindex set data-directory
19859 @item set data-directory @var{directory}
19860 Set the directory which @value{GDBN} searches for auxiliary data files
19861 to @var{directory}.
19863 @kindex show data-directory
19864 @item show data-directory
19865 Show the directory @value{GDBN} searches for auxiliary data files.
19868 @cindex default data directory
19869 @cindex @samp{--with-gdb-datadir}
19870 You can set the default data directory by using the configure-time
19871 @samp{--with-gdb-datadir} option. If the data directory is inside
19872 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19873 @samp{--exec-prefix}), then the default data directory will be updated
19874 automatically if the installed @value{GDBN} is moved to a new
19877 The data directory may also be specified with the
19878 @code{--data-directory} command line option.
19879 @xref{Mode Options}.
19882 @chapter Specifying a Debugging Target
19884 @cindex debugging target
19885 A @dfn{target} is the execution environment occupied by your program.
19887 Often, @value{GDBN} runs in the same host environment as your program;
19888 in that case, the debugging target is specified as a side effect when
19889 you use the @code{file} or @code{core} commands. When you need more
19890 flexibility---for example, running @value{GDBN} on a physically separate
19891 host, or controlling a standalone system over a serial port or a
19892 realtime system over a TCP/IP connection---you can use the @code{target}
19893 command to specify one of the target types configured for @value{GDBN}
19894 (@pxref{Target Commands, ,Commands for Managing Targets}).
19896 @cindex target architecture
19897 It is possible to build @value{GDBN} for several different @dfn{target
19898 architectures}. When @value{GDBN} is built like that, you can choose
19899 one of the available architectures with the @kbd{set architecture}
19903 @kindex set architecture
19904 @kindex show architecture
19905 @item set architecture @var{arch}
19906 This command sets the current target architecture to @var{arch}. The
19907 value of @var{arch} can be @code{"auto"}, in addition to one of the
19908 supported architectures.
19910 @item show architecture
19911 Show the current target architecture.
19913 @item set processor
19915 @kindex set processor
19916 @kindex show processor
19917 These are alias commands for, respectively, @code{set architecture}
19918 and @code{show architecture}.
19922 * Active Targets:: Active targets
19923 * Target Commands:: Commands for managing targets
19924 * Byte Order:: Choosing target byte order
19927 @node Active Targets
19928 @section Active Targets
19930 @cindex stacking targets
19931 @cindex active targets
19932 @cindex multiple targets
19934 There are multiple classes of targets such as: processes, executable files or
19935 recording sessions. Core files belong to the process class, making core file
19936 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19937 on multiple active targets, one in each class. This allows you to (for
19938 example) start a process and inspect its activity, while still having access to
19939 the executable file after the process finishes. Or if you start process
19940 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19941 presented a virtual layer of the recording target, while the process target
19942 remains stopped at the chronologically last point of the process execution.
19944 Use the @code{core-file} and @code{exec-file} commands to select a new core
19945 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19946 specify as a target a process that is already running, use the @code{attach}
19947 command (@pxref{Attach, ,Debugging an Already-running Process}).
19949 @node Target Commands
19950 @section Commands for Managing Targets
19953 @item target @var{type} @var{parameters}
19954 Connects the @value{GDBN} host environment to a target machine or
19955 process. A target is typically a protocol for talking to debugging
19956 facilities. You use the argument @var{type} to specify the type or
19957 protocol of the target machine.
19959 Further @var{parameters} are interpreted by the target protocol, but
19960 typically include things like device names or host names to connect
19961 with, process numbers, and baud rates.
19963 The @code{target} command does not repeat if you press @key{RET} again
19964 after executing the command.
19966 @kindex help target
19968 Displays the names of all targets available. To display targets
19969 currently selected, use either @code{info target} or @code{info files}
19970 (@pxref{Files, ,Commands to Specify Files}).
19972 @item help target @var{name}
19973 Describe a particular target, including any parameters necessary to
19976 @kindex set gnutarget
19977 @item set gnutarget @var{args}
19978 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19979 knows whether it is reading an @dfn{executable},
19980 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19981 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19982 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19985 @emph{Warning:} To specify a file format with @code{set gnutarget},
19986 you must know the actual BFD name.
19990 @xref{Files, , Commands to Specify Files}.
19992 @kindex show gnutarget
19993 @item show gnutarget
19994 Use the @code{show gnutarget} command to display what file format
19995 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19996 @value{GDBN} will determine the file format for each file automatically,
19997 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
20000 @cindex common targets
20001 Here are some common targets (available, or not, depending on the GDB
20006 @item target exec @var{program}
20007 @cindex executable file target
20008 An executable file. @samp{target exec @var{program}} is the same as
20009 @samp{exec-file @var{program}}.
20011 @item target core @var{filename}
20012 @cindex core dump file target
20013 A core dump file. @samp{target core @var{filename}} is the same as
20014 @samp{core-file @var{filename}}.
20016 @item target remote @var{medium}
20017 @cindex remote target
20018 A remote system connected to @value{GDBN} via a serial line or network
20019 connection. This command tells @value{GDBN} to use its own remote
20020 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
20022 For example, if you have a board connected to @file{/dev/ttya} on the
20023 machine running @value{GDBN}, you could say:
20026 target remote /dev/ttya
20029 @code{target remote} supports the @code{load} command. This is only
20030 useful if you have some other way of getting the stub to the target
20031 system, and you can put it somewhere in memory where it won't get
20032 clobbered by the download.
20034 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20035 @cindex built-in simulator target
20036 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
20044 works; however, you cannot assume that a specific memory map, device
20045 drivers, or even basic I/O is available, although some simulators do
20046 provide these. For info about any processor-specific simulator details,
20047 see the appropriate section in @ref{Embedded Processors, ,Embedded
20050 @item target native
20051 @cindex native target
20052 Setup for local/native process debugging. Useful to make the
20053 @code{run} command spawn native processes (likewise @code{attach},
20054 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
20055 (@pxref{set auto-connect-native-target}).
20059 Different targets are available on different configurations of @value{GDBN};
20060 your configuration may have more or fewer targets.
20062 Many remote targets require you to download the executable's code once
20063 you've successfully established a connection. You may wish to control
20064 various aspects of this process.
20069 @kindex set hash@r{, for remote monitors}
20070 @cindex hash mark while downloading
20071 This command controls whether a hash mark @samp{#} is displayed while
20072 downloading a file to the remote monitor. If on, a hash mark is
20073 displayed after each S-record is successfully downloaded to the
20077 @kindex show hash@r{, for remote monitors}
20078 Show the current status of displaying the hash mark.
20080 @item set debug monitor
20081 @kindex set debug monitor
20082 @cindex display remote monitor communications
20083 Enable or disable display of communications messages between
20084 @value{GDBN} and the remote monitor.
20086 @item show debug monitor
20087 @kindex show debug monitor
20088 Show the current status of displaying communications between
20089 @value{GDBN} and the remote monitor.
20094 @kindex load @var{filename} @var{offset}
20095 @item load @var{filename} @var{offset}
20097 Depending on what remote debugging facilities are configured into
20098 @value{GDBN}, the @code{load} command may be available. Where it exists, it
20099 is meant to make @var{filename} (an executable) available for debugging
20100 on the remote system---by downloading, or dynamic linking, for example.
20101 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
20102 the @code{add-symbol-file} command.
20104 If your @value{GDBN} does not have a @code{load} command, attempting to
20105 execute it gets the error message ``@code{You can't do that when your
20106 target is @dots{}}''
20108 The file is loaded at whatever address is specified in the executable.
20109 For some object file formats, you can specify the load address when you
20110 link the program; for other formats, like a.out, the object file format
20111 specifies a fixed address.
20112 @c FIXME! This would be a good place for an xref to the GNU linker doc.
20114 It is also possible to tell @value{GDBN} to load the executable file at a
20115 specific offset described by the optional argument @var{offset}. When
20116 @var{offset} is provided, @var{filename} must also be provided.
20118 Depending on the remote side capabilities, @value{GDBN} may be able to
20119 load programs into flash memory.
20121 @code{load} does not repeat if you press @key{RET} again after using it.
20126 @kindex flash-erase
20128 @anchor{flash-erase}
20130 Erases all known flash memory regions on the target.
20135 @section Choosing Target Byte Order
20137 @cindex choosing target byte order
20138 @cindex target byte order
20140 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
20141 offer the ability to run either big-endian or little-endian byte
20142 orders. Usually the executable or symbol will include a bit to
20143 designate the endian-ness, and you will not need to worry about
20144 which to use. However, you may still find it useful to adjust
20145 @value{GDBN}'s idea of processor endian-ness manually.
20149 @item set endian big
20150 Instruct @value{GDBN} to assume the target is big-endian.
20152 @item set endian little
20153 Instruct @value{GDBN} to assume the target is little-endian.
20155 @item set endian auto
20156 Instruct @value{GDBN} to use the byte order associated with the
20160 Display @value{GDBN}'s current idea of the target byte order.
20164 Note that these commands merely adjust interpretation of symbolic
20165 data on the host, and that they have absolutely no effect on the
20169 @node Remote Debugging
20170 @chapter Debugging Remote Programs
20171 @cindex remote debugging
20173 If you are trying to debug a program running on a machine that cannot run
20174 @value{GDBN} in the usual way, it is often useful to use remote debugging.
20175 For example, you might use remote debugging on an operating system kernel,
20176 or on a small system which does not have a general purpose operating system
20177 powerful enough to run a full-featured debugger.
20179 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
20180 to make this work with particular debugging targets. In addition,
20181 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
20182 but not specific to any particular target system) which you can use if you
20183 write the remote stubs---the code that runs on the remote system to
20184 communicate with @value{GDBN}.
20186 Other remote targets may be available in your
20187 configuration of @value{GDBN}; use @code{help target} to list them.
20190 * Connecting:: Connecting to a remote target
20191 * File Transfer:: Sending files to a remote system
20192 * Server:: Using the gdbserver program
20193 * Remote Configuration:: Remote configuration
20194 * Remote Stub:: Implementing a remote stub
20198 @section Connecting to a Remote Target
20199 @cindex remote debugging, connecting
20200 @cindex @code{gdbserver}, connecting
20201 @cindex remote debugging, types of connections
20202 @cindex @code{gdbserver}, types of connections
20203 @cindex @code{gdbserver}, @code{target remote} mode
20204 @cindex @code{gdbserver}, @code{target extended-remote} mode
20206 This section describes how to connect to a remote target, including the
20207 types of connections and their differences, how to set up executable and
20208 symbol files on the host and target, and the commands used for
20209 connecting to and disconnecting from the remote target.
20211 @subsection Types of Remote Connections
20213 @value{GDBN} supports two types of remote connections, @code{target remote}
20214 mode and @code{target extended-remote} mode. Note that many remote targets
20215 support only @code{target remote} mode. There are several major
20216 differences between the two types of connections, enumerated here:
20220 @cindex remote debugging, detach and program exit
20221 @item Result of detach or program exit
20222 @strong{With target remote mode:} When the debugged program exits or you
20223 detach from it, @value{GDBN} disconnects from the target. When using
20224 @code{gdbserver}, @code{gdbserver} will exit.
20226 @strong{With target extended-remote mode:} When the debugged program exits or
20227 you detach from it, @value{GDBN} remains connected to the target, even
20228 though no program is running. You can rerun the program, attach to a
20229 running program, or use @code{monitor} commands specific to the target.
20231 When using @code{gdbserver} in this case, it does not exit unless it was
20232 invoked using the @option{--once} option. If the @option{--once} option
20233 was not used, you can ask @code{gdbserver} to exit using the
20234 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
20236 @item Specifying the program to debug
20237 For both connection types you use the @code{file} command to specify the
20238 program on the host system. If you are using @code{gdbserver} there are
20239 some differences in how to specify the location of the program on the
20242 @strong{With target remote mode:} You must either specify the program to debug
20243 on the @code{gdbserver} command line or use the @option{--attach} option
20244 (@pxref{Attaching to a program,,Attaching to a Running Program}).
20246 @cindex @option{--multi}, @code{gdbserver} option
20247 @strong{With target extended-remote mode:} You may specify the program to debug
20248 on the @code{gdbserver} command line, or you can load the program or attach
20249 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
20251 @anchor{--multi Option in Types of Remote Connnections}
20252 You can start @code{gdbserver} without supplying an initial command to run
20253 or process ID to attach. To do this, use the @option{--multi} command line
20254 option. Then you can connect using @code{target extended-remote} and start
20255 the program you want to debug (see below for details on using the
20256 @code{run} command in this scenario). Note that the conditions under which
20257 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
20258 (@code{target remote} or @code{target extended-remote}). The
20259 @option{--multi} option to @code{gdbserver} has no influence on that.
20261 @item The @code{run} command
20262 @strong{With target remote mode:} The @code{run} command is not
20263 supported. Once a connection has been established, you can use all
20264 the usual @value{GDBN} commands to examine and change data. The
20265 remote program is already running, so you can use commands like
20266 @kbd{step} and @kbd{continue}.
20268 @strong{With target extended-remote mode:} The @code{run} command is
20269 supported. The @code{run} command uses the value set by
20270 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
20271 the program to run. Command line arguments are supported, except for
20272 wildcard expansion and I/O redirection (@pxref{Arguments}).
20274 If you specify the program to debug on the command line, then the
20275 @code{run} command is not required to start execution, and you can
20276 resume using commands like @kbd{step} and @kbd{continue} as with
20277 @code{target remote} mode.
20279 @anchor{Attaching in Types of Remote Connections}
20281 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
20282 not supported. To attach to a running program using @code{gdbserver}, you
20283 must use the @option{--attach} option (@pxref{Running gdbserver}).
20285 @strong{With target extended-remote mode:} To attach to a running program,
20286 you may use the @code{attach} command after the connection has been
20287 established. If you are using @code{gdbserver}, you may also invoke
20288 @code{gdbserver} using the @option{--attach} option
20289 (@pxref{Running gdbserver}).
20293 @anchor{Host and target files}
20294 @subsection Host and Target Files
20295 @cindex remote debugging, symbol files
20296 @cindex symbol files, remote debugging
20298 @value{GDBN}, running on the host, needs access to symbol and debugging
20299 information for your program running on the target. This requires
20300 access to an unstripped copy of your program, and possibly any associated
20301 symbol files. Note that this section applies equally to both @code{target
20302 remote} mode and @code{target extended-remote} mode.
20304 Some remote targets (@pxref{qXfer executable filename read}, and
20305 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
20306 the same connection used to communicate with @value{GDBN}. With such a
20307 target, if the remote program is unstripped, the only command you need is
20308 @code{target remote} (or @code{target extended-remote}).
20310 If the remote program is stripped, or the target does not support remote
20311 program file access, start up @value{GDBN} using the name of the local
20312 unstripped copy of your program as the first argument, or use the
20313 @code{file} command. Use @code{set sysroot} to specify the location (on
20314 the host) of target libraries (unless your @value{GDBN} was compiled with
20315 the correct sysroot using @code{--with-sysroot}). Alternatively, you
20316 may use @code{set solib-search-path} to specify how @value{GDBN} locates
20319 The symbol file and target libraries must exactly match the executable
20320 and libraries on the target, with one exception: the files on the host
20321 system should not be stripped, even if the files on the target system
20322 are. Mismatched or missing files will lead to confusing results
20323 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
20324 files may also prevent @code{gdbserver} from debugging multi-threaded
20327 @subsection Remote Connection Commands
20328 @cindex remote connection commands
20329 @value{GDBN} can communicate with the target over a serial line, or
20330 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
20331 each case, @value{GDBN} uses the same protocol for debugging your
20332 program; only the medium carrying the debugging packets varies. The
20333 @code{target remote} and @code{target extended-remote} commands
20334 establish a connection to the target. Both commands accept the same
20335 arguments, which indicate the medium to use:
20339 @item target remote @var{serial-device}
20340 @itemx target extended-remote @var{serial-device}
20341 @cindex serial line, @code{target remote}
20342 Use @var{serial-device} to communicate with the target. For example,
20343 to use a serial line connected to the device named @file{/dev/ttyb}:
20346 target remote /dev/ttyb
20349 If you're using a serial line, you may want to give @value{GDBN} the
20350 @samp{--baud} option, or use the @code{set serial baud} command
20351 (@pxref{Remote Configuration, set serial baud}) before the
20352 @code{target} command.
20354 @item target remote @code{@var{host}:@var{port}}
20355 @itemx target remote @code{tcp:@var{host}:@var{port}}
20356 @itemx target extended-remote @code{@var{host}:@var{port}}
20357 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
20358 @cindex @acronym{TCP} port, @code{target remote}
20359 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
20360 The @var{host} may be either a host name or a numeric @acronym{IP}
20361 address; @var{port} must be a decimal number. The @var{host} could be
20362 the target machine itself, if it is directly connected to the net, or
20363 it might be a terminal server which in turn has a serial line to the
20366 For example, to connect to port 2828 on a terminal server named
20370 target remote manyfarms:2828
20373 If your remote target is actually running on the same machine as your
20374 debugger session (e.g.@: a simulator for your target running on the
20375 same host), you can omit the hostname. For example, to connect to
20376 port 1234 on your local machine:
20379 target remote :1234
20383 Note that the colon is still required here.
20385 @item target remote @code{udp:@var{host}:@var{port}}
20386 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
20387 @cindex @acronym{UDP} port, @code{target remote}
20388 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
20389 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
20392 target remote udp:manyfarms:2828
20395 When using a @acronym{UDP} connection for remote debugging, you should
20396 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
20397 can silently drop packets on busy or unreliable networks, which will
20398 cause havoc with your debugging session.
20400 @item target remote | @var{command}
20401 @itemx target extended-remote | @var{command}
20402 @cindex pipe, @code{target remote} to
20403 Run @var{command} in the background and communicate with it using a
20404 pipe. The @var{command} is a shell command, to be parsed and expanded
20405 by the system's command shell, @code{/bin/sh}; it should expect remote
20406 protocol packets on its standard input, and send replies on its
20407 standard output. You could use this to run a stand-alone simulator
20408 that speaks the remote debugging protocol, to make net connections
20409 using programs like @code{ssh}, or for other similar tricks.
20411 If @var{command} closes its standard output (perhaps by exiting),
20412 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
20413 program has already exited, this will have no effect.)
20417 @cindex interrupting remote programs
20418 @cindex remote programs, interrupting
20419 Whenever @value{GDBN} is waiting for the remote program, if you type the
20420 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
20421 program. This may or may not succeed, depending in part on the hardware
20422 and the serial drivers the remote system uses. If you type the
20423 interrupt character once again, @value{GDBN} displays this prompt:
20426 Interrupted while waiting for the program.
20427 Give up (and stop debugging it)? (y or n)
20430 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
20431 the remote debugging session. (If you decide you want to try again later,
20432 you can use @kbd{target remote} again to connect once more.) If you type
20433 @kbd{n}, @value{GDBN} goes back to waiting.
20435 In @code{target extended-remote} mode, typing @kbd{n} will leave
20436 @value{GDBN} connected to the target.
20439 @kindex detach (remote)
20441 When you have finished debugging the remote program, you can use the
20442 @code{detach} command to release it from @value{GDBN} control.
20443 Detaching from the target normally resumes its execution, but the results
20444 will depend on your particular remote stub. After the @code{detach}
20445 command in @code{target remote} mode, @value{GDBN} is free to connect to
20446 another target. In @code{target extended-remote} mode, @value{GDBN} is
20447 still connected to the target.
20451 The @code{disconnect} command closes the connection to the target, and
20452 the target is generally not resumed. It will wait for @value{GDBN}
20453 (this instance or another one) to connect and continue debugging. After
20454 the @code{disconnect} command, @value{GDBN} is again free to connect to
20457 @cindex send command to remote monitor
20458 @cindex extend @value{GDBN} for remote targets
20459 @cindex add new commands for external monitor
20461 @item monitor @var{cmd}
20462 This command allows you to send arbitrary commands directly to the
20463 remote monitor. Since @value{GDBN} doesn't care about the commands it
20464 sends like this, this command is the way to extend @value{GDBN}---you
20465 can add new commands that only the external monitor will understand
20469 @node File Transfer
20470 @section Sending files to a remote system
20471 @cindex remote target, file transfer
20472 @cindex file transfer
20473 @cindex sending files to remote systems
20475 Some remote targets offer the ability to transfer files over the same
20476 connection used to communicate with @value{GDBN}. This is convenient
20477 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
20478 running @code{gdbserver} over a network interface. For other targets,
20479 e.g.@: embedded devices with only a single serial port, this may be
20480 the only way to upload or download files.
20482 Not all remote targets support these commands.
20486 @item remote put @var{hostfile} @var{targetfile}
20487 Copy file @var{hostfile} from the host system (the machine running
20488 @value{GDBN}) to @var{targetfile} on the target system.
20491 @item remote get @var{targetfile} @var{hostfile}
20492 Copy file @var{targetfile} from the target system to @var{hostfile}
20493 on the host system.
20495 @kindex remote delete
20496 @item remote delete @var{targetfile}
20497 Delete @var{targetfile} from the target system.
20502 @section Using the @code{gdbserver} Program
20505 @cindex remote connection without stubs
20506 @code{gdbserver} is a control program for Unix-like systems, which
20507 allows you to connect your program with a remote @value{GDBN} via
20508 @code{target remote} or @code{target extended-remote}---but without
20509 linking in the usual debugging stub.
20511 @code{gdbserver} is not a complete replacement for the debugging stubs,
20512 because it requires essentially the same operating-system facilities
20513 that @value{GDBN} itself does. In fact, a system that can run
20514 @code{gdbserver} to connect to a remote @value{GDBN} could also run
20515 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
20516 because it is a much smaller program than @value{GDBN} itself. It is
20517 also easier to port than all of @value{GDBN}, so you may be able to get
20518 started more quickly on a new system by using @code{gdbserver}.
20519 Finally, if you develop code for real-time systems, you may find that
20520 the tradeoffs involved in real-time operation make it more convenient to
20521 do as much development work as possible on another system, for example
20522 by cross-compiling. You can use @code{gdbserver} to make a similar
20523 choice for debugging.
20525 @value{GDBN} and @code{gdbserver} communicate via either a serial line
20526 or a TCP connection, using the standard @value{GDBN} remote serial
20530 @emph{Warning:} @code{gdbserver} does not have any built-in security.
20531 Do not run @code{gdbserver} connected to any public network; a
20532 @value{GDBN} connection to @code{gdbserver} provides access to the
20533 target system with the same privileges as the user running
20537 @anchor{Running gdbserver}
20538 @subsection Running @code{gdbserver}
20539 @cindex arguments, to @code{gdbserver}
20540 @cindex @code{gdbserver}, command-line arguments
20542 Run @code{gdbserver} on the target system. You need a copy of the
20543 program you want to debug, including any libraries it requires.
20544 @code{gdbserver} does not need your program's symbol table, so you can
20545 strip the program if necessary to save space. @value{GDBN} on the host
20546 system does all the symbol handling.
20548 To use the server, you must tell it how to communicate with @value{GDBN};
20549 the name of your program; and the arguments for your program. The usual
20553 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
20556 @var{comm} is either a device name (to use a serial line), or a TCP
20557 hostname and portnumber, or @code{-} or @code{stdio} to use
20558 stdin/stdout of @code{gdbserver}.
20559 For example, to debug Emacs with the argument
20560 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
20564 target> gdbserver /dev/com1 emacs foo.txt
20567 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
20570 To use a TCP connection instead of a serial line:
20573 target> gdbserver host:2345 emacs foo.txt
20576 The only difference from the previous example is the first argument,
20577 specifying that you are communicating with the host @value{GDBN} via
20578 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
20579 expect a TCP connection from machine @samp{host} to local TCP port 2345.
20580 (Currently, the @samp{host} part is ignored.) You can choose any number
20581 you want for the port number as long as it does not conflict with any
20582 TCP ports already in use on the target system (for example, @code{23} is
20583 reserved for @code{telnet}).@footnote{If you choose a port number that
20584 conflicts with another service, @code{gdbserver} prints an error message
20585 and exits.} You must use the same port number with the host @value{GDBN}
20586 @code{target remote} command.
20588 The @code{stdio} connection is useful when starting @code{gdbserver}
20592 (gdb) target remote | ssh -T hostname gdbserver - hello
20595 The @samp{-T} option to ssh is provided because we don't need a remote pty,
20596 and we don't want escape-character handling. Ssh does this by default when
20597 a command is provided, the flag is provided to make it explicit.
20598 You could elide it if you want to.
20600 Programs started with stdio-connected gdbserver have @file{/dev/null} for
20601 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
20602 display through a pipe connected to gdbserver.
20603 Both @code{stdout} and @code{stderr} use the same pipe.
20605 @anchor{Attaching to a program}
20606 @subsubsection Attaching to a Running Program
20607 @cindex attach to a program, @code{gdbserver}
20608 @cindex @option{--attach}, @code{gdbserver} option
20610 On some targets, @code{gdbserver} can also attach to running programs.
20611 This is accomplished via the @code{--attach} argument. The syntax is:
20614 target> gdbserver --attach @var{comm} @var{pid}
20617 @var{pid} is the process ID of a currently running process. It isn't
20618 necessary to point @code{gdbserver} at a binary for the running process.
20620 In @code{target extended-remote} mode, you can also attach using the
20621 @value{GDBN} attach command
20622 (@pxref{Attaching in Types of Remote Connections}).
20625 You can debug processes by name instead of process ID if your target has the
20626 @code{pidof} utility:
20629 target> gdbserver --attach @var{comm} `pidof @var{program}`
20632 In case more than one copy of @var{program} is running, or @var{program}
20633 has multiple threads, most versions of @code{pidof} support the
20634 @code{-s} option to only return the first process ID.
20636 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
20638 This section applies only when @code{gdbserver} is run to listen on a TCP
20641 @code{gdbserver} normally terminates after all of its debugged processes have
20642 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
20643 extended-remote}, @code{gdbserver} stays running even with no processes left.
20644 @value{GDBN} normally terminates the spawned debugged process on its exit,
20645 which normally also terminates @code{gdbserver} in the @kbd{target remote}
20646 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
20647 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
20648 stays running even in the @kbd{target remote} mode.
20650 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
20651 Such reconnecting is useful for features like @ref{disconnected tracing}. For
20652 completeness, at most one @value{GDBN} can be connected at a time.
20654 @cindex @option{--once}, @code{gdbserver} option
20655 By default, @code{gdbserver} keeps the listening TCP port open, so that
20656 subsequent connections are possible. However, if you start @code{gdbserver}
20657 with the @option{--once} option, it will stop listening for any further
20658 connection attempts after connecting to the first @value{GDBN} session. This
20659 means no further connections to @code{gdbserver} will be possible after the
20660 first one. It also means @code{gdbserver} will terminate after the first
20661 connection with remote @value{GDBN} has closed, even for unexpectedly closed
20662 connections and even in the @kbd{target extended-remote} mode. The
20663 @option{--once} option allows reusing the same port number for connecting to
20664 multiple instances of @code{gdbserver} running on the same host, since each
20665 instance closes its port after the first connection.
20667 @anchor{Other Command-Line Arguments for gdbserver}
20668 @subsubsection Other Command-Line Arguments for @code{gdbserver}
20670 You can use the @option{--multi} option to start @code{gdbserver} without
20671 specifying a program to debug or a process to attach to. Then you can
20672 attach in @code{target extended-remote} mode and run or attach to a
20673 program. For more information,
20674 @pxref{--multi Option in Types of Remote Connnections}.
20676 @cindex @option{--debug}, @code{gdbserver} option
20677 The @option{--debug} option tells @code{gdbserver} to display extra
20678 status information about the debugging process.
20679 @cindex @option{--remote-debug}, @code{gdbserver} option
20680 The @option{--remote-debug} option tells @code{gdbserver} to display
20681 remote protocol debug output. These options are intended for
20682 @code{gdbserver} development and for bug reports to the developers.
20684 @cindex @option{--debug-format}, @code{gdbserver} option
20685 The @option{--debug-format=option1[,option2,...]} option tells
20686 @code{gdbserver} to include additional information in each output.
20687 Possible options are:
20691 Turn off all extra information in debugging output.
20693 Turn on all extra information in debugging output.
20695 Include a timestamp in each line of debugging output.
20698 Options are processed in order. Thus, for example, if @option{none}
20699 appears last then no additional information is added to debugging output.
20701 @cindex @option{--wrapper}, @code{gdbserver} option
20702 The @option{--wrapper} option specifies a wrapper to launch programs
20703 for debugging. The option should be followed by the name of the
20704 wrapper, then any command-line arguments to pass to the wrapper, then
20705 @kbd{--} indicating the end of the wrapper arguments.
20707 @code{gdbserver} runs the specified wrapper program with a combined
20708 command line including the wrapper arguments, then the name of the
20709 program to debug, then any arguments to the program. The wrapper
20710 runs until it executes your program, and then @value{GDBN} gains control.
20712 You can use any program that eventually calls @code{execve} with
20713 its arguments as a wrapper. Several standard Unix utilities do
20714 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
20715 with @code{exec "$@@"} will also work.
20717 For example, you can use @code{env} to pass an environment variable to
20718 the debugged program, without setting the variable in @code{gdbserver}'s
20722 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
20725 @cindex @option{--selftest}
20726 The @option{--selftest} option runs the self tests in @code{gdbserver}:
20729 $ gdbserver --selftest
20730 Ran 2 unit tests, 0 failed
20733 These tests are disabled in release.
20734 @subsection Connecting to @code{gdbserver}
20736 The basic procedure for connecting to the remote target is:
20740 Run @value{GDBN} on the host system.
20743 Make sure you have the necessary symbol files
20744 (@pxref{Host and target files}).
20745 Load symbols for your application using the @code{file} command before you
20746 connect. Use @code{set sysroot} to locate target libraries (unless your
20747 @value{GDBN} was compiled with the correct sysroot using
20748 @code{--with-sysroot}).
20751 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
20752 For TCP connections, you must start up @code{gdbserver} prior to using
20753 the @code{target} command. Otherwise you may get an error whose
20754 text depends on the host system, but which usually looks something like
20755 @samp{Connection refused}. Don't use the @code{load}
20756 command in @value{GDBN} when using @code{target remote} mode, since the
20757 program is already on the target.
20761 @anchor{Monitor Commands for gdbserver}
20762 @subsection Monitor Commands for @code{gdbserver}
20763 @cindex monitor commands, for @code{gdbserver}
20765 During a @value{GDBN} session using @code{gdbserver}, you can use the
20766 @code{monitor} command to send special requests to @code{gdbserver}.
20767 Here are the available commands.
20771 List the available monitor commands.
20773 @item monitor set debug 0
20774 @itemx monitor set debug 1
20775 Disable or enable general debugging messages.
20777 @item monitor set remote-debug 0
20778 @itemx monitor set remote-debug 1
20779 Disable or enable specific debugging messages associated with the remote
20780 protocol (@pxref{Remote Protocol}).
20782 @item monitor set debug-format option1@r{[},option2,...@r{]}
20783 Specify additional text to add to debugging messages.
20784 Possible options are:
20788 Turn off all extra information in debugging output.
20790 Turn on all extra information in debugging output.
20792 Include a timestamp in each line of debugging output.
20795 Options are processed in order. Thus, for example, if @option{none}
20796 appears last then no additional information is added to debugging output.
20798 @item monitor set libthread-db-search-path [PATH]
20799 @cindex gdbserver, search path for @code{libthread_db}
20800 When this command is issued, @var{path} is a colon-separated list of
20801 directories to search for @code{libthread_db} (@pxref{Threads,,set
20802 libthread-db-search-path}). If you omit @var{path},
20803 @samp{libthread-db-search-path} will be reset to its default value.
20805 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
20806 not supported in @code{gdbserver}.
20809 Tell gdbserver to exit immediately. This command should be followed by
20810 @code{disconnect} to close the debugging session. @code{gdbserver} will
20811 detach from any attached processes and kill any processes it created.
20812 Use @code{monitor exit} to terminate @code{gdbserver} at the end
20813 of a multi-process mode debug session.
20817 @subsection Tracepoints support in @code{gdbserver}
20818 @cindex tracepoints support in @code{gdbserver}
20820 On some targets, @code{gdbserver} supports tracepoints, fast
20821 tracepoints and static tracepoints.
20823 For fast or static tracepoints to work, a special library called the
20824 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
20825 This library is built and distributed as an integral part of
20826 @code{gdbserver}. In addition, support for static tracepoints
20827 requires building the in-process agent library with static tracepoints
20828 support. At present, the UST (LTTng Userspace Tracer,
20829 @url{http://lttng.org/ust}) tracing engine is supported. This support
20830 is automatically available if UST development headers are found in the
20831 standard include path when @code{gdbserver} is built, or if
20832 @code{gdbserver} was explicitly configured using @option{--with-ust}
20833 to point at such headers. You can explicitly disable the support
20834 using @option{--with-ust=no}.
20836 There are several ways to load the in-process agent in your program:
20839 @item Specifying it as dependency at link time
20841 You can link your program dynamically with the in-process agent
20842 library. On most systems, this is accomplished by adding
20843 @code{-linproctrace} to the link command.
20845 @item Using the system's preloading mechanisms
20847 You can force loading the in-process agent at startup time by using
20848 your system's support for preloading shared libraries. Many Unixes
20849 support the concept of preloading user defined libraries. In most
20850 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
20851 in the environment. See also the description of @code{gdbserver}'s
20852 @option{--wrapper} command line option.
20854 @item Using @value{GDBN} to force loading the agent at run time
20856 On some systems, you can force the inferior to load a shared library,
20857 by calling a dynamic loader function in the inferior that takes care
20858 of dynamically looking up and loading a shared library. On most Unix
20859 systems, the function is @code{dlopen}. You'll use the @code{call}
20860 command for that. For example:
20863 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
20866 Note that on most Unix systems, for the @code{dlopen} function to be
20867 available, the program needs to be linked with @code{-ldl}.
20870 On systems that have a userspace dynamic loader, like most Unix
20871 systems, when you connect to @code{gdbserver} using @code{target
20872 remote}, you'll find that the program is stopped at the dynamic
20873 loader's entry point, and no shared library has been loaded in the
20874 program's address space yet, including the in-process agent. In that
20875 case, before being able to use any of the fast or static tracepoints
20876 features, you need to let the loader run and load the shared
20877 libraries. The simplest way to do that is to run the program to the
20878 main procedure. E.g., if debugging a C or C@t{++} program, start
20879 @code{gdbserver} like so:
20882 $ gdbserver :9999 myprogram
20885 Start GDB and connect to @code{gdbserver} like so, and run to main:
20889 (@value{GDBP}) target remote myhost:9999
20890 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20891 (@value{GDBP}) b main
20892 (@value{GDBP}) continue
20895 The in-process tracing agent library should now be loaded into the
20896 process; you can confirm it with the @code{info sharedlibrary}
20897 command, which will list @file{libinproctrace.so} as loaded in the
20898 process. You are now ready to install fast tracepoints, list static
20899 tracepoint markers, probe static tracepoints markers, and start
20902 @node Remote Configuration
20903 @section Remote Configuration
20906 @kindex show remote
20907 This section documents the configuration options available when
20908 debugging remote programs. For the options related to the File I/O
20909 extensions of the remote protocol, see @ref{system,
20910 system-call-allowed}.
20913 @item set remoteaddresssize @var{bits}
20914 @cindex address size for remote targets
20915 @cindex bits in remote address
20916 Set the maximum size of address in a memory packet to the specified
20917 number of bits. @value{GDBN} will mask off the address bits above
20918 that number, when it passes addresses to the remote target. The
20919 default value is the number of bits in the target's address.
20921 @item show remoteaddresssize
20922 Show the current value of remote address size in bits.
20924 @item set serial baud @var{n}
20925 @cindex baud rate for remote targets
20926 Set the baud rate for the remote serial I/O to @var{n} baud. The
20927 value is used to set the speed of the serial port used for debugging
20930 @item show serial baud
20931 Show the current speed of the remote connection.
20933 @item set serial parity @var{parity}
20934 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20935 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20937 @item show serial parity
20938 Show the current parity of the serial port.
20940 @item set remotebreak
20941 @cindex interrupt remote programs
20942 @cindex BREAK signal instead of Ctrl-C
20943 @anchor{set remotebreak}
20944 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20945 when you type @kbd{Ctrl-c} to interrupt the program running
20946 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20947 character instead. The default is off, since most remote systems
20948 expect to see @samp{Ctrl-C} as the interrupt signal.
20950 @item show remotebreak
20951 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20952 interrupt the remote program.
20954 @item set remoteflow on
20955 @itemx set remoteflow off
20956 @kindex set remoteflow
20957 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20958 on the serial port used to communicate to the remote target.
20960 @item show remoteflow
20961 @kindex show remoteflow
20962 Show the current setting of hardware flow control.
20964 @item set remotelogbase @var{base}
20965 Set the base (a.k.a.@: radix) of logging serial protocol
20966 communications to @var{base}. Supported values of @var{base} are:
20967 @code{ascii}, @code{octal}, and @code{hex}. The default is
20970 @item show remotelogbase
20971 Show the current setting of the radix for logging remote serial
20974 @item set remotelogfile @var{file}
20975 @cindex record serial communications on file
20976 Record remote serial communications on the named @var{file}. The
20977 default is not to record at all.
20979 @item show remotelogfile.
20980 Show the current setting of the file name on which to record the
20981 serial communications.
20983 @item set remotetimeout @var{num}
20984 @cindex timeout for serial communications
20985 @cindex remote timeout
20986 Set the timeout limit to wait for the remote target to respond to
20987 @var{num} seconds. The default is 2 seconds.
20989 @item show remotetimeout
20990 Show the current number of seconds to wait for the remote target
20993 @cindex limit hardware breakpoints and watchpoints
20994 @cindex remote target, limit break- and watchpoints
20995 @anchor{set remote hardware-watchpoint-limit}
20996 @anchor{set remote hardware-breakpoint-limit}
20997 @item set remote hardware-watchpoint-limit @var{limit}
20998 @itemx set remote hardware-breakpoint-limit @var{limit}
20999 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
21000 watchpoints. A limit of -1, the default, is treated as unlimited.
21002 @cindex limit hardware watchpoints length
21003 @cindex remote target, limit watchpoints length
21004 @anchor{set remote hardware-watchpoint-length-limit}
21005 @item set remote hardware-watchpoint-length-limit @var{limit}
21006 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
21007 a remote hardware watchpoint. A limit of -1, the default, is treated
21010 @item show remote hardware-watchpoint-length-limit
21011 Show the current limit (in bytes) of the maximum length of
21012 a remote hardware watchpoint.
21014 @item set remote exec-file @var{filename}
21015 @itemx show remote exec-file
21016 @anchor{set remote exec-file}
21017 @cindex executable file, for remote target
21018 Select the file used for @code{run} with @code{target
21019 extended-remote}. This should be set to a filename valid on the
21020 target system. If it is not set, the target will use a default
21021 filename (e.g.@: the last program run).
21023 @item set remote interrupt-sequence
21024 @cindex interrupt remote programs
21025 @cindex select Ctrl-C, BREAK or BREAK-g
21026 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
21027 @samp{BREAK-g} as the
21028 sequence to the remote target in order to interrupt the execution.
21029 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
21030 is high level of serial line for some certain time.
21031 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
21032 It is @code{BREAK} signal followed by character @code{g}.
21034 @item show interrupt-sequence
21035 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
21036 is sent by @value{GDBN} to interrupt the remote program.
21037 @code{BREAK-g} is BREAK signal followed by @code{g} and
21038 also known as Magic SysRq g.
21040 @item set remote interrupt-on-connect
21041 @cindex send interrupt-sequence on start
21042 Specify whether interrupt-sequence is sent to remote target when
21043 @value{GDBN} connects to it. This is mostly needed when you debug
21044 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
21045 which is known as Magic SysRq g in order to connect @value{GDBN}.
21047 @item show interrupt-on-connect
21048 Show whether interrupt-sequence is sent
21049 to remote target when @value{GDBN} connects to it.
21053 @item set tcp auto-retry on
21054 @cindex auto-retry, for remote TCP target
21055 Enable auto-retry for remote TCP connections. This is useful if the remote
21056 debugging agent is launched in parallel with @value{GDBN}; there is a race
21057 condition because the agent may not become ready to accept the connection
21058 before @value{GDBN} attempts to connect. When auto-retry is
21059 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
21060 to establish the connection using the timeout specified by
21061 @code{set tcp connect-timeout}.
21063 @item set tcp auto-retry off
21064 Do not auto-retry failed TCP connections.
21066 @item show tcp auto-retry
21067 Show the current auto-retry setting.
21069 @item set tcp connect-timeout @var{seconds}
21070 @itemx set tcp connect-timeout unlimited
21071 @cindex connection timeout, for remote TCP target
21072 @cindex timeout, for remote target connection
21073 Set the timeout for establishing a TCP connection to the remote target to
21074 @var{seconds}. The timeout affects both polling to retry failed connections
21075 (enabled by @code{set tcp auto-retry on}) and waiting for connections
21076 that are merely slow to complete, and represents an approximate cumulative
21077 value. If @var{seconds} is @code{unlimited}, there is no timeout and
21078 @value{GDBN} will keep attempting to establish a connection forever,
21079 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
21081 @item show tcp connect-timeout
21082 Show the current connection timeout setting.
21085 @cindex remote packets, enabling and disabling
21086 The @value{GDBN} remote protocol autodetects the packets supported by
21087 your debugging stub. If you need to override the autodetection, you
21088 can use these commands to enable or disable individual packets. Each
21089 packet can be set to @samp{on} (the remote target supports this
21090 packet), @samp{off} (the remote target does not support this packet),
21091 or @samp{auto} (detect remote target support for this packet). They
21092 all default to @samp{auto}. For more information about each packet,
21093 see @ref{Remote Protocol}.
21095 During normal use, you should not have to use any of these commands.
21096 If you do, that may be a bug in your remote debugging stub, or a bug
21097 in @value{GDBN}. You may want to report the problem to the
21098 @value{GDBN} developers.
21100 For each packet @var{name}, the command to enable or disable the
21101 packet is @code{set remote @var{name}-packet}. The available settings
21104 @multitable @columnfractions 0.28 0.32 0.25
21107 @tab Related Features
21109 @item @code{fetch-register}
21111 @tab @code{info registers}
21113 @item @code{set-register}
21117 @item @code{binary-download}
21119 @tab @code{load}, @code{set}
21121 @item @code{read-aux-vector}
21122 @tab @code{qXfer:auxv:read}
21123 @tab @code{info auxv}
21125 @item @code{symbol-lookup}
21126 @tab @code{qSymbol}
21127 @tab Detecting multiple threads
21129 @item @code{attach}
21130 @tab @code{vAttach}
21133 @item @code{verbose-resume}
21135 @tab Stepping or resuming multiple threads
21141 @item @code{software-breakpoint}
21145 @item @code{hardware-breakpoint}
21149 @item @code{write-watchpoint}
21153 @item @code{read-watchpoint}
21157 @item @code{access-watchpoint}
21161 @item @code{pid-to-exec-file}
21162 @tab @code{qXfer:exec-file:read}
21163 @tab @code{attach}, @code{run}
21165 @item @code{target-features}
21166 @tab @code{qXfer:features:read}
21167 @tab @code{set architecture}
21169 @item @code{library-info}
21170 @tab @code{qXfer:libraries:read}
21171 @tab @code{info sharedlibrary}
21173 @item @code{memory-map}
21174 @tab @code{qXfer:memory-map:read}
21175 @tab @code{info mem}
21177 @item @code{read-sdata-object}
21178 @tab @code{qXfer:sdata:read}
21179 @tab @code{print $_sdata}
21181 @item @code{read-spu-object}
21182 @tab @code{qXfer:spu:read}
21183 @tab @code{info spu}
21185 @item @code{write-spu-object}
21186 @tab @code{qXfer:spu:write}
21187 @tab @code{info spu}
21189 @item @code{read-siginfo-object}
21190 @tab @code{qXfer:siginfo:read}
21191 @tab @code{print $_siginfo}
21193 @item @code{write-siginfo-object}
21194 @tab @code{qXfer:siginfo:write}
21195 @tab @code{set $_siginfo}
21197 @item @code{threads}
21198 @tab @code{qXfer:threads:read}
21199 @tab @code{info threads}
21201 @item @code{get-thread-local-@*storage-address}
21202 @tab @code{qGetTLSAddr}
21203 @tab Displaying @code{__thread} variables
21205 @item @code{get-thread-information-block-address}
21206 @tab @code{qGetTIBAddr}
21207 @tab Display MS-Windows Thread Information Block.
21209 @item @code{search-memory}
21210 @tab @code{qSearch:memory}
21213 @item @code{supported-packets}
21214 @tab @code{qSupported}
21215 @tab Remote communications parameters
21217 @item @code{catch-syscalls}
21218 @tab @code{QCatchSyscalls}
21219 @tab @code{catch syscall}
21221 @item @code{pass-signals}
21222 @tab @code{QPassSignals}
21223 @tab @code{handle @var{signal}}
21225 @item @code{program-signals}
21226 @tab @code{QProgramSignals}
21227 @tab @code{handle @var{signal}}
21229 @item @code{hostio-close-packet}
21230 @tab @code{vFile:close}
21231 @tab @code{remote get}, @code{remote put}
21233 @item @code{hostio-open-packet}
21234 @tab @code{vFile:open}
21235 @tab @code{remote get}, @code{remote put}
21237 @item @code{hostio-pread-packet}
21238 @tab @code{vFile:pread}
21239 @tab @code{remote get}, @code{remote put}
21241 @item @code{hostio-pwrite-packet}
21242 @tab @code{vFile:pwrite}
21243 @tab @code{remote get}, @code{remote put}
21245 @item @code{hostio-unlink-packet}
21246 @tab @code{vFile:unlink}
21247 @tab @code{remote delete}
21249 @item @code{hostio-readlink-packet}
21250 @tab @code{vFile:readlink}
21253 @item @code{hostio-fstat-packet}
21254 @tab @code{vFile:fstat}
21257 @item @code{hostio-setfs-packet}
21258 @tab @code{vFile:setfs}
21261 @item @code{noack-packet}
21262 @tab @code{QStartNoAckMode}
21263 @tab Packet acknowledgment
21265 @item @code{osdata}
21266 @tab @code{qXfer:osdata:read}
21267 @tab @code{info os}
21269 @item @code{query-attached}
21270 @tab @code{qAttached}
21271 @tab Querying remote process attach state.
21273 @item @code{trace-buffer-size}
21274 @tab @code{QTBuffer:size}
21275 @tab @code{set trace-buffer-size}
21277 @item @code{trace-status}
21278 @tab @code{qTStatus}
21279 @tab @code{tstatus}
21281 @item @code{traceframe-info}
21282 @tab @code{qXfer:traceframe-info:read}
21283 @tab Traceframe info
21285 @item @code{install-in-trace}
21286 @tab @code{InstallInTrace}
21287 @tab Install tracepoint in tracing
21289 @item @code{disable-randomization}
21290 @tab @code{QDisableRandomization}
21291 @tab @code{set disable-randomization}
21293 @item @code{startup-with-shell}
21294 @tab @code{QStartupWithShell}
21295 @tab @code{set startup-with-shell}
21297 @item @code{environment-hex-encoded}
21298 @tab @code{QEnvironmentHexEncoded}
21299 @tab @code{set environment}
21301 @item @code{environment-unset}
21302 @tab @code{QEnvironmentUnset}
21303 @tab @code{unset environment}
21305 @item @code{environment-reset}
21306 @tab @code{QEnvironmentReset}
21307 @tab @code{Reset the inferior environment (i.e., unset user-set variables)}
21309 @item @code{set-working-dir}
21310 @tab @code{QSetWorkingDir}
21311 @tab @code{set cwd}
21313 @item @code{conditional-breakpoints-packet}
21314 @tab @code{Z0 and Z1}
21315 @tab @code{Support for target-side breakpoint condition evaluation}
21317 @item @code{multiprocess-extensions}
21318 @tab @code{multiprocess extensions}
21319 @tab Debug multiple processes and remote process PID awareness
21321 @item @code{swbreak-feature}
21322 @tab @code{swbreak stop reason}
21325 @item @code{hwbreak-feature}
21326 @tab @code{hwbreak stop reason}
21329 @item @code{fork-event-feature}
21330 @tab @code{fork stop reason}
21333 @item @code{vfork-event-feature}
21334 @tab @code{vfork stop reason}
21337 @item @code{exec-event-feature}
21338 @tab @code{exec stop reason}
21341 @item @code{thread-events}
21342 @tab @code{QThreadEvents}
21343 @tab Tracking thread lifetime.
21345 @item @code{no-resumed-stop-reply}
21346 @tab @code{no resumed thread left stop reply}
21347 @tab Tracking thread lifetime.
21352 @section Implementing a Remote Stub
21354 @cindex debugging stub, example
21355 @cindex remote stub, example
21356 @cindex stub example, remote debugging
21357 The stub files provided with @value{GDBN} implement the target side of the
21358 communication protocol, and the @value{GDBN} side is implemented in the
21359 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
21360 these subroutines to communicate, and ignore the details. (If you're
21361 implementing your own stub file, you can still ignore the details: start
21362 with one of the existing stub files. @file{sparc-stub.c} is the best
21363 organized, and therefore the easiest to read.)
21365 @cindex remote serial debugging, overview
21366 To debug a program running on another machine (the debugging
21367 @dfn{target} machine), you must first arrange for all the usual
21368 prerequisites for the program to run by itself. For example, for a C
21373 A startup routine to set up the C runtime environment; these usually
21374 have a name like @file{crt0}. The startup routine may be supplied by
21375 your hardware supplier, or you may have to write your own.
21378 A C subroutine library to support your program's
21379 subroutine calls, notably managing input and output.
21382 A way of getting your program to the other machine---for example, a
21383 download program. These are often supplied by the hardware
21384 manufacturer, but you may have to write your own from hardware
21388 The next step is to arrange for your program to use a serial port to
21389 communicate with the machine where @value{GDBN} is running (the @dfn{host}
21390 machine). In general terms, the scheme looks like this:
21394 @value{GDBN} already understands how to use this protocol; when everything
21395 else is set up, you can simply use the @samp{target remote} command
21396 (@pxref{Targets,,Specifying a Debugging Target}).
21398 @item On the target,
21399 you must link with your program a few special-purpose subroutines that
21400 implement the @value{GDBN} remote serial protocol. The file containing these
21401 subroutines is called a @dfn{debugging stub}.
21403 On certain remote targets, you can use an auxiliary program
21404 @code{gdbserver} instead of linking a stub into your program.
21405 @xref{Server,,Using the @code{gdbserver} Program}, for details.
21408 The debugging stub is specific to the architecture of the remote
21409 machine; for example, use @file{sparc-stub.c} to debug programs on
21412 @cindex remote serial stub list
21413 These working remote stubs are distributed with @value{GDBN}:
21418 @cindex @file{i386-stub.c}
21421 For Intel 386 and compatible architectures.
21424 @cindex @file{m68k-stub.c}
21425 @cindex Motorola 680x0
21427 For Motorola 680x0 architectures.
21430 @cindex @file{sh-stub.c}
21433 For Renesas SH architectures.
21436 @cindex @file{sparc-stub.c}
21438 For @sc{sparc} architectures.
21440 @item sparcl-stub.c
21441 @cindex @file{sparcl-stub.c}
21444 For Fujitsu @sc{sparclite} architectures.
21448 The @file{README} file in the @value{GDBN} distribution may list other
21449 recently added stubs.
21452 * Stub Contents:: What the stub can do for you
21453 * Bootstrapping:: What you must do for the stub
21454 * Debug Session:: Putting it all together
21457 @node Stub Contents
21458 @subsection What the Stub Can Do for You
21460 @cindex remote serial stub
21461 The debugging stub for your architecture supplies these three
21465 @item set_debug_traps
21466 @findex set_debug_traps
21467 @cindex remote serial stub, initialization
21468 This routine arranges for @code{handle_exception} to run when your
21469 program stops. You must call this subroutine explicitly in your
21470 program's startup code.
21472 @item handle_exception
21473 @findex handle_exception
21474 @cindex remote serial stub, main routine
21475 This is the central workhorse, but your program never calls it
21476 explicitly---the setup code arranges for @code{handle_exception} to
21477 run when a trap is triggered.
21479 @code{handle_exception} takes control when your program stops during
21480 execution (for example, on a breakpoint), and mediates communications
21481 with @value{GDBN} on the host machine. This is where the communications
21482 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
21483 representative on the target machine. It begins by sending summary
21484 information on the state of your program, then continues to execute,
21485 retrieving and transmitting any information @value{GDBN} needs, until you
21486 execute a @value{GDBN} command that makes your program resume; at that point,
21487 @code{handle_exception} returns control to your own code on the target
21491 @cindex @code{breakpoint} subroutine, remote
21492 Use this auxiliary subroutine to make your program contain a
21493 breakpoint. Depending on the particular situation, this may be the only
21494 way for @value{GDBN} to get control. For instance, if your target
21495 machine has some sort of interrupt button, you won't need to call this;
21496 pressing the interrupt button transfers control to
21497 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
21498 simply receiving characters on the serial port may also trigger a trap;
21499 again, in that situation, you don't need to call @code{breakpoint} from
21500 your own program---simply running @samp{target remote} from the host
21501 @value{GDBN} session gets control.
21503 Call @code{breakpoint} if none of these is true, or if you simply want
21504 to make certain your program stops at a predetermined point for the
21505 start of your debugging session.
21508 @node Bootstrapping
21509 @subsection What You Must Do for the Stub
21511 @cindex remote stub, support routines
21512 The debugging stubs that come with @value{GDBN} are set up for a particular
21513 chip architecture, but they have no information about the rest of your
21514 debugging target machine.
21516 First of all you need to tell the stub how to communicate with the
21520 @item int getDebugChar()
21521 @findex getDebugChar
21522 Write this subroutine to read a single character from the serial port.
21523 It may be identical to @code{getchar} for your target system; a
21524 different name is used to allow you to distinguish the two if you wish.
21526 @item void putDebugChar(int)
21527 @findex putDebugChar
21528 Write this subroutine to write a single character to the serial port.
21529 It may be identical to @code{putchar} for your target system; a
21530 different name is used to allow you to distinguish the two if you wish.
21533 @cindex control C, and remote debugging
21534 @cindex interrupting remote targets
21535 If you want @value{GDBN} to be able to stop your program while it is
21536 running, you need to use an interrupt-driven serial driver, and arrange
21537 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
21538 character). That is the character which @value{GDBN} uses to tell the
21539 remote system to stop.
21541 Getting the debugging target to return the proper status to @value{GDBN}
21542 probably requires changes to the standard stub; one quick and dirty way
21543 is to just execute a breakpoint instruction (the ``dirty'' part is that
21544 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
21546 Other routines you need to supply are:
21549 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
21550 @findex exceptionHandler
21551 Write this function to install @var{exception_address} in the exception
21552 handling tables. You need to do this because the stub does not have any
21553 way of knowing what the exception handling tables on your target system
21554 are like (for example, the processor's table might be in @sc{rom},
21555 containing entries which point to a table in @sc{ram}).
21556 The @var{exception_number} specifies the exception which should be changed;
21557 its meaning is architecture-dependent (for example, different numbers
21558 might represent divide by zero, misaligned access, etc). When this
21559 exception occurs, control should be transferred directly to
21560 @var{exception_address}, and the processor state (stack, registers,
21561 and so on) should be just as it is when a processor exception occurs. So if
21562 you want to use a jump instruction to reach @var{exception_address}, it
21563 should be a simple jump, not a jump to subroutine.
21565 For the 386, @var{exception_address} should be installed as an interrupt
21566 gate so that interrupts are masked while the handler runs. The gate
21567 should be at privilege level 0 (the most privileged level). The
21568 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
21569 help from @code{exceptionHandler}.
21571 @item void flush_i_cache()
21572 @findex flush_i_cache
21573 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
21574 instruction cache, if any, on your target machine. If there is no
21575 instruction cache, this subroutine may be a no-op.
21577 On target machines that have instruction caches, @value{GDBN} requires this
21578 function to make certain that the state of your program is stable.
21582 You must also make sure this library routine is available:
21585 @item void *memset(void *, int, int)
21587 This is the standard library function @code{memset} that sets an area of
21588 memory to a known value. If you have one of the free versions of
21589 @code{libc.a}, @code{memset} can be found there; otherwise, you must
21590 either obtain it from your hardware manufacturer, or write your own.
21593 If you do not use the GNU C compiler, you may need other standard
21594 library subroutines as well; this varies from one stub to another,
21595 but in general the stubs are likely to use any of the common library
21596 subroutines which @code{@value{NGCC}} generates as inline code.
21599 @node Debug Session
21600 @subsection Putting it All Together
21602 @cindex remote serial debugging summary
21603 In summary, when your program is ready to debug, you must follow these
21608 Make sure you have defined the supporting low-level routines
21609 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
21611 @code{getDebugChar}, @code{putDebugChar},
21612 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
21616 Insert these lines in your program's startup code, before the main
21617 procedure is called:
21624 On some machines, when a breakpoint trap is raised, the hardware
21625 automatically makes the PC point to the instruction after the
21626 breakpoint. If your machine doesn't do that, you may need to adjust
21627 @code{handle_exception} to arrange for it to return to the instruction
21628 after the breakpoint on this first invocation, so that your program
21629 doesn't keep hitting the initial breakpoint instead of making
21633 For the 680x0 stub only, you need to provide a variable called
21634 @code{exceptionHook}. Normally you just use:
21637 void (*exceptionHook)() = 0;
21641 but if before calling @code{set_debug_traps}, you set it to point to a
21642 function in your program, that function is called when
21643 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
21644 error). The function indicated by @code{exceptionHook} is called with
21645 one parameter: an @code{int} which is the exception number.
21648 Compile and link together: your program, the @value{GDBN} debugging stub for
21649 your target architecture, and the supporting subroutines.
21652 Make sure you have a serial connection between your target machine and
21653 the @value{GDBN} host, and identify the serial port on the host.
21656 @c The "remote" target now provides a `load' command, so we should
21657 @c document that. FIXME.
21658 Download your program to your target machine (or get it there by
21659 whatever means the manufacturer provides), and start it.
21662 Start @value{GDBN} on the host, and connect to the target
21663 (@pxref{Connecting,,Connecting to a Remote Target}).
21667 @node Configurations
21668 @chapter Configuration-Specific Information
21670 While nearly all @value{GDBN} commands are available for all native and
21671 cross versions of the debugger, there are some exceptions. This chapter
21672 describes things that are only available in certain configurations.
21674 There are three major categories of configurations: native
21675 configurations, where the host and target are the same, embedded
21676 operating system configurations, which are usually the same for several
21677 different processor architectures, and bare embedded processors, which
21678 are quite different from each other.
21683 * Embedded Processors::
21690 This section describes details specific to particular native
21694 * BSD libkvm Interface:: Debugging BSD kernel memory images
21695 * SVR4 Process Information:: SVR4 process information
21696 * DJGPP Native:: Features specific to the DJGPP port
21697 * Cygwin Native:: Features specific to the Cygwin port
21698 * Hurd Native:: Features specific to @sc{gnu} Hurd
21699 * Darwin:: Features specific to Darwin
21702 @node BSD libkvm Interface
21703 @subsection BSD libkvm Interface
21706 @cindex kernel memory image
21707 @cindex kernel crash dump
21709 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
21710 interface that provides a uniform interface for accessing kernel virtual
21711 memory images, including live systems and crash dumps. @value{GDBN}
21712 uses this interface to allow you to debug live kernels and kernel crash
21713 dumps on many native BSD configurations. This is implemented as a
21714 special @code{kvm} debugging target. For debugging a live system, load
21715 the currently running kernel into @value{GDBN} and connect to the
21719 (@value{GDBP}) @b{target kvm}
21722 For debugging crash dumps, provide the file name of the crash dump as an
21726 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
21729 Once connected to the @code{kvm} target, the following commands are
21735 Set current context from the @dfn{Process Control Block} (PCB) address.
21738 Set current context from proc address. This command isn't available on
21739 modern FreeBSD systems.
21742 @node SVR4 Process Information
21743 @subsection SVR4 Process Information
21745 @cindex examine process image
21746 @cindex process info via @file{/proc}
21748 Many versions of SVR4 and compatible systems provide a facility called
21749 @samp{/proc} that can be used to examine the image of a running
21750 process using file-system subroutines.
21752 If @value{GDBN} is configured for an operating system with this
21753 facility, the command @code{info proc} is available to report
21754 information about the process running your program, or about any
21755 process running on your system. This includes, as of this writing,
21756 @sc{gnu}/Linux and Solaris, for example.
21758 This command may also work on core files that were created on a system
21759 that has the @samp{/proc} facility.
21765 @itemx info proc @var{process-id}
21766 Summarize available information about any running process. If a
21767 process ID is specified by @var{process-id}, display information about
21768 that process; otherwise display information about the program being
21769 debugged. The summary includes the debugged process ID, the command
21770 line used to invoke it, its current working directory, and its
21771 executable file's absolute file name.
21773 On some systems, @var{process-id} can be of the form
21774 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
21775 within a process. If the optional @var{pid} part is missing, it means
21776 a thread from the process being debugged (the leading @samp{/} still
21777 needs to be present, or else @value{GDBN} will interpret the number as
21778 a process ID rather than a thread ID).
21780 @item info proc cmdline
21781 @cindex info proc cmdline
21782 Show the original command line of the process. This command is
21783 specific to @sc{gnu}/Linux.
21785 @item info proc cwd
21786 @cindex info proc cwd
21787 Show the current working directory of the process. This command is
21788 specific to @sc{gnu}/Linux.
21790 @item info proc exe
21791 @cindex info proc exe
21792 Show the name of executable of the process. This command is specific
21795 @item info proc mappings
21796 @cindex memory address space mappings
21797 Report the memory address space ranges accessible in the program, with
21798 information on whether the process has read, write, or execute access
21799 rights to each range. On @sc{gnu}/Linux systems, each memory range
21800 includes the object file which is mapped to that range, instead of the
21801 memory access rights to that range.
21803 @item info proc stat
21804 @itemx info proc status
21805 @cindex process detailed status information
21806 These subcommands are specific to @sc{gnu}/Linux systems. They show
21807 the process-related information, including the user ID and group ID;
21808 how many threads are there in the process; its virtual memory usage;
21809 the signals that are pending, blocked, and ignored; its TTY; its
21810 consumption of system and user time; its stack size; its @samp{nice}
21811 value; etc. For more information, see the @samp{proc} man page
21812 (type @kbd{man 5 proc} from your shell prompt).
21814 @item info proc all
21815 Show all the information about the process described under all of the
21816 above @code{info proc} subcommands.
21819 @comment These sub-options of 'info proc' were not included when
21820 @comment procfs.c was re-written. Keep their descriptions around
21821 @comment against the day when someone finds the time to put them back in.
21822 @kindex info proc times
21823 @item info proc times
21824 Starting time, user CPU time, and system CPU time for your program and
21827 @kindex info proc id
21829 Report on the process IDs related to your program: its own process ID,
21830 the ID of its parent, the process group ID, and the session ID.
21833 @item set procfs-trace
21834 @kindex set procfs-trace
21835 @cindex @code{procfs} API calls
21836 This command enables and disables tracing of @code{procfs} API calls.
21838 @item show procfs-trace
21839 @kindex show procfs-trace
21840 Show the current state of @code{procfs} API call tracing.
21842 @item set procfs-file @var{file}
21843 @kindex set procfs-file
21844 Tell @value{GDBN} to write @code{procfs} API trace to the named
21845 @var{file}. @value{GDBN} appends the trace info to the previous
21846 contents of the file. The default is to display the trace on the
21849 @item show procfs-file
21850 @kindex show procfs-file
21851 Show the file to which @code{procfs} API trace is written.
21853 @item proc-trace-entry
21854 @itemx proc-trace-exit
21855 @itemx proc-untrace-entry
21856 @itemx proc-untrace-exit
21857 @kindex proc-trace-entry
21858 @kindex proc-trace-exit
21859 @kindex proc-untrace-entry
21860 @kindex proc-untrace-exit
21861 These commands enable and disable tracing of entries into and exits
21862 from the @code{syscall} interface.
21865 @kindex info pidlist
21866 @cindex process list, QNX Neutrino
21867 For QNX Neutrino only, this command displays the list of all the
21868 processes and all the threads within each process.
21871 @kindex info meminfo
21872 @cindex mapinfo list, QNX Neutrino
21873 For QNX Neutrino only, this command displays the list of all mapinfos.
21877 @subsection Features for Debugging @sc{djgpp} Programs
21878 @cindex @sc{djgpp} debugging
21879 @cindex native @sc{djgpp} debugging
21880 @cindex MS-DOS-specific commands
21883 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
21884 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
21885 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
21886 top of real-mode DOS systems and their emulations.
21888 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
21889 defines a few commands specific to the @sc{djgpp} port. This
21890 subsection describes those commands.
21895 This is a prefix of @sc{djgpp}-specific commands which print
21896 information about the target system and important OS structures.
21899 @cindex MS-DOS system info
21900 @cindex free memory information (MS-DOS)
21901 @item info dos sysinfo
21902 This command displays assorted information about the underlying
21903 platform: the CPU type and features, the OS version and flavor, the
21904 DPMI version, and the available conventional and DPMI memory.
21909 @cindex segment descriptor tables
21910 @cindex descriptor tables display
21912 @itemx info dos ldt
21913 @itemx info dos idt
21914 These 3 commands display entries from, respectively, Global, Local,
21915 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21916 tables are data structures which store a descriptor for each segment
21917 that is currently in use. The segment's selector is an index into a
21918 descriptor table; the table entry for that index holds the
21919 descriptor's base address and limit, and its attributes and access
21922 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21923 segment (used for both data and the stack), and a DOS segment (which
21924 allows access to DOS/BIOS data structures and absolute addresses in
21925 conventional memory). However, the DPMI host will usually define
21926 additional segments in order to support the DPMI environment.
21928 @cindex garbled pointers
21929 These commands allow to display entries from the descriptor tables.
21930 Without an argument, all entries from the specified table are
21931 displayed. An argument, which should be an integer expression, means
21932 display a single entry whose index is given by the argument. For
21933 example, here's a convenient way to display information about the
21934 debugged program's data segment:
21937 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21938 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21942 This comes in handy when you want to see whether a pointer is outside
21943 the data segment's limit (i.e.@: @dfn{garbled}).
21945 @cindex page tables display (MS-DOS)
21947 @itemx info dos pte
21948 These two commands display entries from, respectively, the Page
21949 Directory and the Page Tables. Page Directories and Page Tables are
21950 data structures which control how virtual memory addresses are mapped
21951 into physical addresses. A Page Table includes an entry for every
21952 page of memory that is mapped into the program's address space; there
21953 may be several Page Tables, each one holding up to 4096 entries. A
21954 Page Directory has up to 4096 entries, one each for every Page Table
21955 that is currently in use.
21957 Without an argument, @kbd{info dos pde} displays the entire Page
21958 Directory, and @kbd{info dos pte} displays all the entries in all of
21959 the Page Tables. An argument, an integer expression, given to the
21960 @kbd{info dos pde} command means display only that entry from the Page
21961 Directory table. An argument given to the @kbd{info dos pte} command
21962 means display entries from a single Page Table, the one pointed to by
21963 the specified entry in the Page Directory.
21965 @cindex direct memory access (DMA) on MS-DOS
21966 These commands are useful when your program uses @dfn{DMA} (Direct
21967 Memory Access), which needs physical addresses to program the DMA
21970 These commands are supported only with some DPMI servers.
21972 @cindex physical address from linear address
21973 @item info dos address-pte @var{addr}
21974 This command displays the Page Table entry for a specified linear
21975 address. The argument @var{addr} is a linear address which should
21976 already have the appropriate segment's base address added to it,
21977 because this command accepts addresses which may belong to @emph{any}
21978 segment. For example, here's how to display the Page Table entry for
21979 the page where a variable @code{i} is stored:
21982 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21983 @exdent @code{Page Table entry for address 0x11a00d30:}
21984 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21988 This says that @code{i} is stored at offset @code{0xd30} from the page
21989 whose physical base address is @code{0x02698000}, and shows all the
21990 attributes of that page.
21992 Note that you must cast the addresses of variables to a @code{char *},
21993 since otherwise the value of @code{__djgpp_base_address}, the base
21994 address of all variables and functions in a @sc{djgpp} program, will
21995 be added using the rules of C pointer arithmetics: if @code{i} is
21996 declared an @code{int}, @value{GDBN} will add 4 times the value of
21997 @code{__djgpp_base_address} to the address of @code{i}.
21999 Here's another example, it displays the Page Table entry for the
22003 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
22004 @exdent @code{Page Table entry for address 0x29110:}
22005 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
22009 (The @code{+ 3} offset is because the transfer buffer's address is the
22010 3rd member of the @code{_go32_info_block} structure.) The output
22011 clearly shows that this DPMI server maps the addresses in conventional
22012 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
22013 linear (@code{0x29110}) addresses are identical.
22015 This command is supported only with some DPMI servers.
22018 @cindex DOS serial data link, remote debugging
22019 In addition to native debugging, the DJGPP port supports remote
22020 debugging via a serial data link. The following commands are specific
22021 to remote serial debugging in the DJGPP port of @value{GDBN}.
22024 @kindex set com1base
22025 @kindex set com1irq
22026 @kindex set com2base
22027 @kindex set com2irq
22028 @kindex set com3base
22029 @kindex set com3irq
22030 @kindex set com4base
22031 @kindex set com4irq
22032 @item set com1base @var{addr}
22033 This command sets the base I/O port address of the @file{COM1} serial
22036 @item set com1irq @var{irq}
22037 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
22038 for the @file{COM1} serial port.
22040 There are similar commands @samp{set com2base}, @samp{set com3irq},
22041 etc.@: for setting the port address and the @code{IRQ} lines for the
22044 @kindex show com1base
22045 @kindex show com1irq
22046 @kindex show com2base
22047 @kindex show com2irq
22048 @kindex show com3base
22049 @kindex show com3irq
22050 @kindex show com4base
22051 @kindex show com4irq
22052 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
22053 display the current settings of the base address and the @code{IRQ}
22054 lines used by the COM ports.
22057 @kindex info serial
22058 @cindex DOS serial port status
22059 This command prints the status of the 4 DOS serial ports. For each
22060 port, it prints whether it's active or not, its I/O base address and
22061 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
22062 counts of various errors encountered so far.
22066 @node Cygwin Native
22067 @subsection Features for Debugging MS Windows PE Executables
22068 @cindex MS Windows debugging
22069 @cindex native Cygwin debugging
22070 @cindex Cygwin-specific commands
22072 @value{GDBN} supports native debugging of MS Windows programs, including
22073 DLLs with and without symbolic debugging information.
22075 @cindex Ctrl-BREAK, MS-Windows
22076 @cindex interrupt debuggee on MS-Windows
22077 MS-Windows programs that call @code{SetConsoleMode} to switch off the
22078 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
22079 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
22080 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
22081 sequence, which can be used to interrupt the debuggee even if it
22084 There are various additional Cygwin-specific commands, described in
22085 this section. Working with DLLs that have no debugging symbols is
22086 described in @ref{Non-debug DLL Symbols}.
22091 This is a prefix of MS Windows-specific commands which print
22092 information about the target system and important OS structures.
22094 @item info w32 selector
22095 This command displays information returned by
22096 the Win32 API @code{GetThreadSelectorEntry} function.
22097 It takes an optional argument that is evaluated to
22098 a long value to give the information about this given selector.
22099 Without argument, this command displays information
22100 about the six segment registers.
22102 @item info w32 thread-information-block
22103 This command displays thread specific information stored in the
22104 Thread Information Block (readable on the X86 CPU family using @code{$fs}
22105 selector for 32-bit programs and @code{$gs} for 64-bit programs).
22107 @kindex signal-event
22108 @item signal-event @var{id}
22109 This command signals an event with user-provided @var{id}. Used to resume
22110 crashing process when attached to it using MS-Windows JIT debugging (AeDebug).
22112 To use it, create or edit the following keys in
22113 @code{HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\AeDebug} and/or
22114 @code{HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows NT\CurrentVersion\AeDebug}
22115 (for x86_64 versions):
22119 @code{Debugger} (REG_SZ) --- a command to launch the debugger.
22120 Suggested command is: @code{@var{fully-qualified-path-to-gdb.exe} -ex
22121 "attach %ld" -ex "signal-event %ld" -ex "continue"}.
22123 The first @code{%ld} will be replaced by the process ID of the
22124 crashing process, the second @code{%ld} will be replaced by the ID of
22125 the event that blocks the crashing process, waiting for @value{GDBN}
22129 @code{Auto} (REG_SZ) --- either @code{1} or @code{0}. @code{1} will
22130 make the system run debugger specified by the Debugger key
22131 automatically, @code{0} will cause a dialog box with ``OK'' and
22132 ``Cancel'' buttons to appear, which allows the user to either
22133 terminate the crashing process (OK) or debug it (Cancel).
22136 @kindex set cygwin-exceptions
22137 @cindex debugging the Cygwin DLL
22138 @cindex Cygwin DLL, debugging
22139 @item set cygwin-exceptions @var{mode}
22140 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
22141 happen inside the Cygwin DLL. If @var{mode} is @code{off},
22142 @value{GDBN} will delay recognition of exceptions, and may ignore some
22143 exceptions which seem to be caused by internal Cygwin DLL
22144 ``bookkeeping''. This option is meant primarily for debugging the
22145 Cygwin DLL itself; the default value is @code{off} to avoid annoying
22146 @value{GDBN} users with false @code{SIGSEGV} signals.
22148 @kindex show cygwin-exceptions
22149 @item show cygwin-exceptions
22150 Displays whether @value{GDBN} will break on exceptions that happen
22151 inside the Cygwin DLL itself.
22153 @kindex set new-console
22154 @item set new-console @var{mode}
22155 If @var{mode} is @code{on} the debuggee will
22156 be started in a new console on next start.
22157 If @var{mode} is @code{off}, the debuggee will
22158 be started in the same console as the debugger.
22160 @kindex show new-console
22161 @item show new-console
22162 Displays whether a new console is used
22163 when the debuggee is started.
22165 @kindex set new-group
22166 @item set new-group @var{mode}
22167 This boolean value controls whether the debuggee should
22168 start a new group or stay in the same group as the debugger.
22169 This affects the way the Windows OS handles
22172 @kindex show new-group
22173 @item show new-group
22174 Displays current value of new-group boolean.
22176 @kindex set debugevents
22177 @item set debugevents
22178 This boolean value adds debug output concerning kernel events related
22179 to the debuggee seen by the debugger. This includes events that
22180 signal thread and process creation and exit, DLL loading and
22181 unloading, console interrupts, and debugging messages produced by the
22182 Windows @code{OutputDebugString} API call.
22184 @kindex set debugexec
22185 @item set debugexec
22186 This boolean value adds debug output concerning execute events
22187 (such as resume thread) seen by the debugger.
22189 @kindex set debugexceptions
22190 @item set debugexceptions
22191 This boolean value adds debug output concerning exceptions in the
22192 debuggee seen by the debugger.
22194 @kindex set debugmemory
22195 @item set debugmemory
22196 This boolean value adds debug output concerning debuggee memory reads
22197 and writes by the debugger.
22201 This boolean values specifies whether the debuggee is called
22202 via a shell or directly (default value is on).
22206 Displays if the debuggee will be started with a shell.
22211 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
22214 @node Non-debug DLL Symbols
22215 @subsubsection Support for DLLs without Debugging Symbols
22216 @cindex DLLs with no debugging symbols
22217 @cindex Minimal symbols and DLLs
22219 Very often on windows, some of the DLLs that your program relies on do
22220 not include symbolic debugging information (for example,
22221 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
22222 symbols in a DLL, it relies on the minimal amount of symbolic
22223 information contained in the DLL's export table. This section
22224 describes working with such symbols, known internally to @value{GDBN} as
22225 ``minimal symbols''.
22227 Note that before the debugged program has started execution, no DLLs
22228 will have been loaded. The easiest way around this problem is simply to
22229 start the program --- either by setting a breakpoint or letting the
22230 program run once to completion.
22232 @subsubsection DLL Name Prefixes
22234 In keeping with the naming conventions used by the Microsoft debugging
22235 tools, DLL export symbols are made available with a prefix based on the
22236 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
22237 also entered into the symbol table, so @code{CreateFileA} is often
22238 sufficient. In some cases there will be name clashes within a program
22239 (particularly if the executable itself includes full debugging symbols)
22240 necessitating the use of the fully qualified name when referring to the
22241 contents of the DLL. Use single-quotes around the name to avoid the
22242 exclamation mark (``!'') being interpreted as a language operator.
22244 Note that the internal name of the DLL may be all upper-case, even
22245 though the file name of the DLL is lower-case, or vice-versa. Since
22246 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
22247 some confusion. If in doubt, try the @code{info functions} and
22248 @code{info variables} commands or even @code{maint print msymbols}
22249 (@pxref{Symbols}). Here's an example:
22252 (@value{GDBP}) info function CreateFileA
22253 All functions matching regular expression "CreateFileA":
22255 Non-debugging symbols:
22256 0x77e885f4 CreateFileA
22257 0x77e885f4 KERNEL32!CreateFileA
22261 (@value{GDBP}) info function !
22262 All functions matching regular expression "!":
22264 Non-debugging symbols:
22265 0x6100114c cygwin1!__assert
22266 0x61004034 cygwin1!_dll_crt0@@0
22267 0x61004240 cygwin1!dll_crt0(per_process *)
22271 @subsubsection Working with Minimal Symbols
22273 Symbols extracted from a DLL's export table do not contain very much
22274 type information. All that @value{GDBN} can do is guess whether a symbol
22275 refers to a function or variable depending on the linker section that
22276 contains the symbol. Also note that the actual contents of the memory
22277 contained in a DLL are not available unless the program is running. This
22278 means that you cannot examine the contents of a variable or disassemble
22279 a function within a DLL without a running program.
22281 Variables are generally treated as pointers and dereferenced
22282 automatically. For this reason, it is often necessary to prefix a
22283 variable name with the address-of operator (``&'') and provide explicit
22284 type information in the command. Here's an example of the type of
22288 (@value{GDBP}) print 'cygwin1!__argv'
22289 'cygwin1!__argv' has unknown type; cast it to its declared type
22293 (@value{GDBP}) x 'cygwin1!__argv'
22294 'cygwin1!__argv' has unknown type; cast it to its declared type
22297 And two possible solutions:
22300 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
22301 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
22305 (@value{GDBP}) x/2x &'cygwin1!__argv'
22306 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
22307 (@value{GDBP}) x/x 0x10021608
22308 0x10021608: 0x0022fd98
22309 (@value{GDBP}) x/s 0x0022fd98
22310 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
22313 Setting a break point within a DLL is possible even before the program
22314 starts execution. However, under these circumstances, @value{GDBN} can't
22315 examine the initial instructions of the function in order to skip the
22316 function's frame set-up code. You can work around this by using ``*&''
22317 to set the breakpoint at a raw memory address:
22320 (@value{GDBP}) break *&'python22!PyOS_Readline'
22321 Breakpoint 1 at 0x1e04eff0
22324 The author of these extensions is not entirely convinced that setting a
22325 break point within a shared DLL like @file{kernel32.dll} is completely
22329 @subsection Commands Specific to @sc{gnu} Hurd Systems
22330 @cindex @sc{gnu} Hurd debugging
22332 This subsection describes @value{GDBN} commands specific to the
22333 @sc{gnu} Hurd native debugging.
22338 @kindex set signals@r{, Hurd command}
22339 @kindex set sigs@r{, Hurd command}
22340 This command toggles the state of inferior signal interception by
22341 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
22342 affected by this command. @code{sigs} is a shorthand alias for
22347 @kindex show signals@r{, Hurd command}
22348 @kindex show sigs@r{, Hurd command}
22349 Show the current state of intercepting inferior's signals.
22351 @item set signal-thread
22352 @itemx set sigthread
22353 @kindex set signal-thread
22354 @kindex set sigthread
22355 This command tells @value{GDBN} which thread is the @code{libc} signal
22356 thread. That thread is run when a signal is delivered to a running
22357 process. @code{set sigthread} is the shorthand alias of @code{set
22360 @item show signal-thread
22361 @itemx show sigthread
22362 @kindex show signal-thread
22363 @kindex show sigthread
22364 These two commands show which thread will run when the inferior is
22365 delivered a signal.
22368 @kindex set stopped@r{, Hurd command}
22369 This commands tells @value{GDBN} that the inferior process is stopped,
22370 as with the @code{SIGSTOP} signal. The stopped process can be
22371 continued by delivering a signal to it.
22374 @kindex show stopped@r{, Hurd command}
22375 This command shows whether @value{GDBN} thinks the debuggee is
22378 @item set exceptions
22379 @kindex set exceptions@r{, Hurd command}
22380 Use this command to turn off trapping of exceptions in the inferior.
22381 When exception trapping is off, neither breakpoints nor
22382 single-stepping will work. To restore the default, set exception
22385 @item show exceptions
22386 @kindex show exceptions@r{, Hurd command}
22387 Show the current state of trapping exceptions in the inferior.
22389 @item set task pause
22390 @kindex set task@r{, Hurd commands}
22391 @cindex task attributes (@sc{gnu} Hurd)
22392 @cindex pause current task (@sc{gnu} Hurd)
22393 This command toggles task suspension when @value{GDBN} has control.
22394 Setting it to on takes effect immediately, and the task is suspended
22395 whenever @value{GDBN} gets control. Setting it to off will take
22396 effect the next time the inferior is continued. If this option is set
22397 to off, you can use @code{set thread default pause on} or @code{set
22398 thread pause on} (see below) to pause individual threads.
22400 @item show task pause
22401 @kindex show task@r{, Hurd commands}
22402 Show the current state of task suspension.
22404 @item set task detach-suspend-count
22405 @cindex task suspend count
22406 @cindex detach from task, @sc{gnu} Hurd
22407 This command sets the suspend count the task will be left with when
22408 @value{GDBN} detaches from it.
22410 @item show task detach-suspend-count
22411 Show the suspend count the task will be left with when detaching.
22413 @item set task exception-port
22414 @itemx set task excp
22415 @cindex task exception port, @sc{gnu} Hurd
22416 This command sets the task exception port to which @value{GDBN} will
22417 forward exceptions. The argument should be the value of the @dfn{send
22418 rights} of the task. @code{set task excp} is a shorthand alias.
22420 @item set noninvasive
22421 @cindex noninvasive task options
22422 This command switches @value{GDBN} to a mode that is the least
22423 invasive as far as interfering with the inferior is concerned. This
22424 is the same as using @code{set task pause}, @code{set exceptions}, and
22425 @code{set signals} to values opposite to the defaults.
22427 @item info send-rights
22428 @itemx info receive-rights
22429 @itemx info port-rights
22430 @itemx info port-sets
22431 @itemx info dead-names
22434 @cindex send rights, @sc{gnu} Hurd
22435 @cindex receive rights, @sc{gnu} Hurd
22436 @cindex port rights, @sc{gnu} Hurd
22437 @cindex port sets, @sc{gnu} Hurd
22438 @cindex dead names, @sc{gnu} Hurd
22439 These commands display information about, respectively, send rights,
22440 receive rights, port rights, port sets, and dead names of a task.
22441 There are also shorthand aliases: @code{info ports} for @code{info
22442 port-rights} and @code{info psets} for @code{info port-sets}.
22444 @item set thread pause
22445 @kindex set thread@r{, Hurd command}
22446 @cindex thread properties, @sc{gnu} Hurd
22447 @cindex pause current thread (@sc{gnu} Hurd)
22448 This command toggles current thread suspension when @value{GDBN} has
22449 control. Setting it to on takes effect immediately, and the current
22450 thread is suspended whenever @value{GDBN} gets control. Setting it to
22451 off will take effect the next time the inferior is continued.
22452 Normally, this command has no effect, since when @value{GDBN} has
22453 control, the whole task is suspended. However, if you used @code{set
22454 task pause off} (see above), this command comes in handy to suspend
22455 only the current thread.
22457 @item show thread pause
22458 @kindex show thread@r{, Hurd command}
22459 This command shows the state of current thread suspension.
22461 @item set thread run
22462 This command sets whether the current thread is allowed to run.
22464 @item show thread run
22465 Show whether the current thread is allowed to run.
22467 @item set thread detach-suspend-count
22468 @cindex thread suspend count, @sc{gnu} Hurd
22469 @cindex detach from thread, @sc{gnu} Hurd
22470 This command sets the suspend count @value{GDBN} will leave on a
22471 thread when detaching. This number is relative to the suspend count
22472 found by @value{GDBN} when it notices the thread; use @code{set thread
22473 takeover-suspend-count} to force it to an absolute value.
22475 @item show thread detach-suspend-count
22476 Show the suspend count @value{GDBN} will leave on the thread when
22479 @item set thread exception-port
22480 @itemx set thread excp
22481 Set the thread exception port to which to forward exceptions. This
22482 overrides the port set by @code{set task exception-port} (see above).
22483 @code{set thread excp} is the shorthand alias.
22485 @item set thread takeover-suspend-count
22486 Normally, @value{GDBN}'s thread suspend counts are relative to the
22487 value @value{GDBN} finds when it notices each thread. This command
22488 changes the suspend counts to be absolute instead.
22490 @item set thread default
22491 @itemx show thread default
22492 @cindex thread default settings, @sc{gnu} Hurd
22493 Each of the above @code{set thread} commands has a @code{set thread
22494 default} counterpart (e.g., @code{set thread default pause}, @code{set
22495 thread default exception-port}, etc.). The @code{thread default}
22496 variety of commands sets the default thread properties for all
22497 threads; you can then change the properties of individual threads with
22498 the non-default commands.
22505 @value{GDBN} provides the following commands specific to the Darwin target:
22508 @item set debug darwin @var{num}
22509 @kindex set debug darwin
22510 When set to a non zero value, enables debugging messages specific to
22511 the Darwin support. Higher values produce more verbose output.
22513 @item show debug darwin
22514 @kindex show debug darwin
22515 Show the current state of Darwin messages.
22517 @item set debug mach-o @var{num}
22518 @kindex set debug mach-o
22519 When set to a non zero value, enables debugging messages while
22520 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
22521 file format used on Darwin for object and executable files.) Higher
22522 values produce more verbose output. This is a command to diagnose
22523 problems internal to @value{GDBN} and should not be needed in normal
22526 @item show debug mach-o
22527 @kindex show debug mach-o
22528 Show the current state of Mach-O file messages.
22530 @item set mach-exceptions on
22531 @itemx set mach-exceptions off
22532 @kindex set mach-exceptions
22533 On Darwin, faults are first reported as a Mach exception and are then
22534 mapped to a Posix signal. Use this command to turn on trapping of
22535 Mach exceptions in the inferior. This might be sometimes useful to
22536 better understand the cause of a fault. The default is off.
22538 @item show mach-exceptions
22539 @kindex show mach-exceptions
22540 Show the current state of exceptions trapping.
22545 @section Embedded Operating Systems
22547 This section describes configurations involving the debugging of
22548 embedded operating systems that are available for several different
22551 @value{GDBN} includes the ability to debug programs running on
22552 various real-time operating systems.
22554 @node Embedded Processors
22555 @section Embedded Processors
22557 This section goes into details specific to particular embedded
22560 @cindex send command to simulator
22561 Whenever a specific embedded processor has a simulator, @value{GDBN}
22562 allows to send an arbitrary command to the simulator.
22565 @item sim @var{command}
22566 @kindex sim@r{, a command}
22567 Send an arbitrary @var{command} string to the simulator. Consult the
22568 documentation for the specific simulator in use for information about
22569 acceptable commands.
22574 * ARC:: Synopsys ARC
22576 * M68K:: Motorola M68K
22577 * MicroBlaze:: Xilinx MicroBlaze
22578 * MIPS Embedded:: MIPS Embedded
22579 * OpenRISC 1000:: OpenRISC 1000 (or1k)
22580 * PowerPC Embedded:: PowerPC Embedded
22583 * Super-H:: Renesas Super-H
22587 @subsection Synopsys ARC
22588 @cindex Synopsys ARC
22589 @cindex ARC specific commands
22595 @value{GDBN} provides the following ARC-specific commands:
22598 @item set debug arc
22599 @kindex set debug arc
22600 Control the level of ARC specific debug messages. Use 0 for no messages (the
22601 default), 1 for debug messages, and 2 for even more debug messages.
22603 @item show debug arc
22604 @kindex show debug arc
22605 Show the level of ARC specific debugging in operation.
22607 @item maint print arc arc-instruction @var{address}
22608 @kindex maint print arc arc-instruction
22609 Print internal disassembler information about instruction at a given address.
22616 @value{GDBN} provides the following ARM-specific commands:
22619 @item set arm disassembler
22621 This commands selects from a list of disassembly styles. The
22622 @code{"std"} style is the standard style.
22624 @item show arm disassembler
22626 Show the current disassembly style.
22628 @item set arm apcs32
22629 @cindex ARM 32-bit mode
22630 This command toggles ARM operation mode between 32-bit and 26-bit.
22632 @item show arm apcs32
22633 Display the current usage of the ARM 32-bit mode.
22635 @item set arm fpu @var{fputype}
22636 This command sets the ARM floating-point unit (FPU) type. The
22637 argument @var{fputype} can be one of these:
22641 Determine the FPU type by querying the OS ABI.
22643 Software FPU, with mixed-endian doubles on little-endian ARM
22646 GCC-compiled FPA co-processor.
22648 Software FPU with pure-endian doubles.
22654 Show the current type of the FPU.
22657 This command forces @value{GDBN} to use the specified ABI.
22660 Show the currently used ABI.
22662 @item set arm fallback-mode (arm|thumb|auto)
22663 @value{GDBN} uses the symbol table, when available, to determine
22664 whether instructions are ARM or Thumb. This command controls
22665 @value{GDBN}'s default behavior when the symbol table is not
22666 available. The default is @samp{auto}, which causes @value{GDBN} to
22667 use the current execution mode (from the @code{T} bit in the @code{CPSR}
22670 @item show arm fallback-mode
22671 Show the current fallback instruction mode.
22673 @item set arm force-mode (arm|thumb|auto)
22674 This command overrides use of the symbol table to determine whether
22675 instructions are ARM or Thumb. The default is @samp{auto}, which
22676 causes @value{GDBN} to use the symbol table and then the setting
22677 of @samp{set arm fallback-mode}.
22679 @item show arm force-mode
22680 Show the current forced instruction mode.
22682 @item set debug arm
22683 Toggle whether to display ARM-specific debugging messages from the ARM
22684 target support subsystem.
22686 @item show debug arm
22687 Show whether ARM-specific debugging messages are enabled.
22691 @item target sim @r{[}@var{simargs}@r{]} @dots{}
22692 The @value{GDBN} ARM simulator accepts the following optional arguments.
22695 @item --swi-support=@var{type}
22696 Tell the simulator which SWI interfaces to support. The argument
22697 @var{type} may be a comma separated list of the following values.
22698 The default value is @code{all}.
22713 The Motorola m68k configuration includes ColdFire support.
22716 @subsection MicroBlaze
22717 @cindex Xilinx MicroBlaze
22718 @cindex XMD, Xilinx Microprocessor Debugger
22720 The MicroBlaze is a soft-core processor supported on various Xilinx
22721 FPGAs, such as Spartan or Virtex series. Boards with these processors
22722 usually have JTAG ports which connect to a host system running the Xilinx
22723 Embedded Development Kit (EDK) or Software Development Kit (SDK).
22724 This host system is used to download the configuration bitstream to
22725 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
22726 communicates with the target board using the JTAG interface and
22727 presents a @code{gdbserver} interface to the board. By default
22728 @code{xmd} uses port @code{1234}. (While it is possible to change
22729 this default port, it requires the use of undocumented @code{xmd}
22730 commands. Contact Xilinx support if you need to do this.)
22732 Use these GDB commands to connect to the MicroBlaze target processor.
22735 @item target remote :1234
22736 Use this command to connect to the target if you are running @value{GDBN}
22737 on the same system as @code{xmd}.
22739 @item target remote @var{xmd-host}:1234
22740 Use this command to connect to the target if it is connected to @code{xmd}
22741 running on a different system named @var{xmd-host}.
22744 Use this command to download a program to the MicroBlaze target.
22746 @item set debug microblaze @var{n}
22747 Enable MicroBlaze-specific debugging messages if non-zero.
22749 @item show debug microblaze @var{n}
22750 Show MicroBlaze-specific debugging level.
22753 @node MIPS Embedded
22754 @subsection @acronym{MIPS} Embedded
22757 @value{GDBN} supports these special commands for @acronym{MIPS} targets:
22760 @item set mipsfpu double
22761 @itemx set mipsfpu single
22762 @itemx set mipsfpu none
22763 @itemx set mipsfpu auto
22764 @itemx show mipsfpu
22765 @kindex set mipsfpu
22766 @kindex show mipsfpu
22767 @cindex @acronym{MIPS} remote floating point
22768 @cindex floating point, @acronym{MIPS} remote
22769 If your target board does not support the @acronym{MIPS} floating point
22770 coprocessor, you should use the command @samp{set mipsfpu none} (if you
22771 need this, you may wish to put the command in your @value{GDBN} init
22772 file). This tells @value{GDBN} how to find the return value of
22773 functions which return floating point values. It also allows
22774 @value{GDBN} to avoid saving the floating point registers when calling
22775 functions on the board. If you are using a floating point coprocessor
22776 with only single precision floating point support, as on the @sc{r4650}
22777 processor, use the command @samp{set mipsfpu single}. The default
22778 double precision floating point coprocessor may be selected using
22779 @samp{set mipsfpu double}.
22781 In previous versions the only choices were double precision or no
22782 floating point, so @samp{set mipsfpu on} will select double precision
22783 and @samp{set mipsfpu off} will select no floating point.
22785 As usual, you can inquire about the @code{mipsfpu} variable with
22786 @samp{show mipsfpu}.
22789 @node OpenRISC 1000
22790 @subsection OpenRISC 1000
22791 @cindex OpenRISC 1000
22794 The OpenRISC 1000 provides a free RISC instruction set architecture. It is
22795 mainly provided as a soft-core which can run on Xilinx, Altera and other
22798 @value{GDBN} for OpenRISC supports the below commands when connecting to
22806 Runs the builtin CPU simulator which can run very basic
22807 programs but does not support most hardware functions like MMU.
22808 For more complex use cases the user is advised to run an external
22809 target, and connect using @samp{target remote}.
22811 Example: @code{target sim}
22813 @item set debug or1k
22814 Toggle whether to display OpenRISC-specific debugging messages from the
22815 OpenRISC target support subsystem.
22817 @item show debug or1k
22818 Show whether OpenRISC-specific debugging messages are enabled.
22821 @node PowerPC Embedded
22822 @subsection PowerPC Embedded
22824 @cindex DVC register
22825 @value{GDBN} supports using the DVC (Data Value Compare) register to
22826 implement in hardware simple hardware watchpoint conditions of the form:
22829 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
22830 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22833 The DVC register will be automatically used when @value{GDBN} detects
22834 such pattern in a condition expression, and the created watchpoint uses one
22835 debug register (either the @code{exact-watchpoints} option is on and the
22836 variable is scalar, or the variable has a length of one byte). This feature
22837 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22840 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22841 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22842 in which case watchpoints using only one debug register are created when
22843 watching variables of scalar types.
22845 You can create an artificial array to watch an arbitrary memory
22846 region using one of the following commands (@pxref{Expressions}):
22849 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22850 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22853 PowerPC embedded processors support masked watchpoints. See the discussion
22854 about the @code{mask} argument in @ref{Set Watchpoints}.
22856 @cindex ranged breakpoint
22857 PowerPC embedded processors support hardware accelerated
22858 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22859 the inferior whenever it executes an instruction at any address within
22860 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22861 use the @code{break-range} command.
22863 @value{GDBN} provides the following PowerPC-specific commands:
22866 @kindex break-range
22867 @item break-range @var{start-location}, @var{end-location}
22868 Set a breakpoint for an address range given by
22869 @var{start-location} and @var{end-location}, which can specify a function name,
22870 a line number, an offset of lines from the current line or from the start
22871 location, or an address of an instruction (see @ref{Specify Location},
22872 for a list of all the possible ways to specify a @var{location}.)
22873 The breakpoint will stop execution of the inferior whenever it
22874 executes an instruction at any address within the specified range,
22875 (including @var{start-location} and @var{end-location}.)
22877 @kindex set powerpc
22878 @item set powerpc soft-float
22879 @itemx show powerpc soft-float
22880 Force @value{GDBN} to use (or not use) a software floating point calling
22881 convention. By default, @value{GDBN} selects the calling convention based
22882 on the selected architecture and the provided executable file.
22884 @item set powerpc vector-abi
22885 @itemx show powerpc vector-abi
22886 Force @value{GDBN} to use the specified calling convention for vector
22887 arguments and return values. The valid options are @samp{auto};
22888 @samp{generic}, to avoid vector registers even if they are present;
22889 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22890 registers. By default, @value{GDBN} selects the calling convention
22891 based on the selected architecture and the provided executable file.
22893 @item set powerpc exact-watchpoints
22894 @itemx show powerpc exact-watchpoints
22895 Allow @value{GDBN} to use only one debug register when watching a variable
22896 of scalar type, thus assuming that the variable is accessed through the
22897 address of its first byte.
22902 @subsection Atmel AVR
22905 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22906 following AVR-specific commands:
22909 @item info io_registers
22910 @kindex info io_registers@r{, AVR}
22911 @cindex I/O registers (Atmel AVR)
22912 This command displays information about the AVR I/O registers. For
22913 each register, @value{GDBN} prints its number and value.
22920 When configured for debugging CRIS, @value{GDBN} provides the
22921 following CRIS-specific commands:
22924 @item set cris-version @var{ver}
22925 @cindex CRIS version
22926 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22927 The CRIS version affects register names and sizes. This command is useful in
22928 case autodetection of the CRIS version fails.
22930 @item show cris-version
22931 Show the current CRIS version.
22933 @item set cris-dwarf2-cfi
22934 @cindex DWARF-2 CFI and CRIS
22935 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22936 Change to @samp{off} when using @code{gcc-cris} whose version is below
22939 @item show cris-dwarf2-cfi
22940 Show the current state of using DWARF-2 CFI.
22942 @item set cris-mode @var{mode}
22944 Set the current CRIS mode to @var{mode}. It should only be changed when
22945 debugging in guru mode, in which case it should be set to
22946 @samp{guru} (the default is @samp{normal}).
22948 @item show cris-mode
22949 Show the current CRIS mode.
22953 @subsection Renesas Super-H
22956 For the Renesas Super-H processor, @value{GDBN} provides these
22960 @item set sh calling-convention @var{convention}
22961 @kindex set sh calling-convention
22962 Set the calling-convention used when calling functions from @value{GDBN}.
22963 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22964 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22965 convention. If the DWARF-2 information of the called function specifies
22966 that the function follows the Renesas calling convention, the function
22967 is called using the Renesas calling convention. If the calling convention
22968 is set to @samp{renesas}, the Renesas calling convention is always used,
22969 regardless of the DWARF-2 information. This can be used to override the
22970 default of @samp{gcc} if debug information is missing, or the compiler
22971 does not emit the DWARF-2 calling convention entry for a function.
22973 @item show sh calling-convention
22974 @kindex show sh calling-convention
22975 Show the current calling convention setting.
22980 @node Architectures
22981 @section Architectures
22983 This section describes characteristics of architectures that affect
22984 all uses of @value{GDBN} with the architecture, both native and cross.
22991 * HPPA:: HP PA architecture
22992 * SPU:: Cell Broadband Engine SPU architecture
22999 @subsection AArch64
23000 @cindex AArch64 support
23002 When @value{GDBN} is debugging the AArch64 architecture, it provides the
23003 following special commands:
23006 @item set debug aarch64
23007 @kindex set debug aarch64
23008 This command determines whether AArch64 architecture-specific debugging
23009 messages are to be displayed.
23011 @item show debug aarch64
23012 Show whether AArch64 debugging messages are displayed.
23017 @subsection x86 Architecture-specific Issues
23020 @item set struct-convention @var{mode}
23021 @kindex set struct-convention
23022 @cindex struct return convention
23023 @cindex struct/union returned in registers
23024 Set the convention used by the inferior to return @code{struct}s and
23025 @code{union}s from functions to @var{mode}. Possible values of
23026 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
23027 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
23028 are returned on the stack, while @code{"reg"} means that a
23029 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
23030 be returned in a register.
23032 @item show struct-convention
23033 @kindex show struct-convention
23034 Show the current setting of the convention to return @code{struct}s
23039 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
23040 @cindex Intel Memory Protection Extensions (MPX).
23042 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
23043 @footnote{The register named with capital letters represent the architecture
23044 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
23045 which are the lower bound and upper bound. Bounds are effective addresses or
23046 memory locations. The upper bounds are architecturally represented in 1's
23047 complement form. A bound having lower bound = 0, and upper bound = 0
23048 (1's complement of all bits set) will allow access to the entire address space.
23050 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
23051 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
23052 display the upper bound performing the complement of one operation on the
23053 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
23054 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
23055 can also be noted that the upper bounds are inclusive.
23057 As an example, assume that the register BND0 holds bounds for a pointer having
23058 access allowed for the range between 0x32 and 0x71. The values present on
23059 bnd0raw and bnd registers are presented as follows:
23062 bnd0raw = @{0x32, 0xffffffff8e@}
23063 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
23066 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
23067 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
23068 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
23069 Python, the display includes the memory size, in bits, accessible to
23072 Bounds can also be stored in bounds tables, which are stored in
23073 application memory. These tables store bounds for pointers by specifying
23074 the bounds pointer's value along with its bounds. Evaluating and changing
23075 bounds located in bound tables is therefore interesting while investigating
23076 bugs on MPX context. @value{GDBN} provides commands for this purpose:
23079 @item show mpx bound @var{pointer}
23080 @kindex show mpx bound
23081 Display bounds of the given @var{pointer}.
23083 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
23084 @kindex set mpx bound
23085 Set the bounds of a pointer in the bound table.
23086 This command takes three parameters: @var{pointer} is the pointers
23087 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
23088 for lower and upper bounds respectively.
23091 When you call an inferior function on an Intel MPX enabled program,
23092 GDB sets the inferior's bound registers to the init (disabled) state
23093 before calling the function. As a consequence, bounds checks for the
23094 pointer arguments passed to the function will always pass.
23096 This is necessary because when you call an inferior function, the
23097 program is usually in the middle of the execution of other function.
23098 Since at that point bound registers are in an arbitrary state, not
23099 clearing them would lead to random bound violations in the called
23102 You can still examine the influence of the bound registers on the
23103 execution of the called function by stopping the execution of the
23104 called function at its prologue, setting bound registers, and
23105 continuing the execution. For example:
23109 Breakpoint 2 at 0x4009de: file i386-mpx-call.c, line 47.
23110 $ print upper (a, b, c, d, 1)
23111 Breakpoint 2, upper (a=0x0, b=0x6e0000005b, c=0x0, d=0x0, len=48)....
23113 @{lbound = 0x0, ubound = ffffffff@} : size -1
23116 At this last step the value of bnd0 can be changed for investigation of bound
23117 violations caused along the execution of the call. In order to know how to
23118 set the bound registers or bound table for the call consult the ABI.
23123 See the following section.
23126 @subsection @acronym{MIPS}
23128 @cindex stack on Alpha
23129 @cindex stack on @acronym{MIPS}
23130 @cindex Alpha stack
23131 @cindex @acronym{MIPS} stack
23132 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
23133 sometimes requires @value{GDBN} to search backward in the object code to
23134 find the beginning of a function.
23136 @cindex response time, @acronym{MIPS} debugging
23137 To improve response time (especially for embedded applications, where
23138 @value{GDBN} may be restricted to a slow serial line for this search)
23139 you may want to limit the size of this search, using one of these
23143 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
23144 @item set heuristic-fence-post @var{limit}
23145 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
23146 search for the beginning of a function. A value of @var{0} (the
23147 default) means there is no limit. However, except for @var{0}, the
23148 larger the limit the more bytes @code{heuristic-fence-post} must search
23149 and therefore the longer it takes to run. You should only need to use
23150 this command when debugging a stripped executable.
23152 @item show heuristic-fence-post
23153 Display the current limit.
23157 These commands are available @emph{only} when @value{GDBN} is configured
23158 for debugging programs on Alpha or @acronym{MIPS} processors.
23160 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
23164 @item set mips abi @var{arg}
23165 @kindex set mips abi
23166 @cindex set ABI for @acronym{MIPS}
23167 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
23168 values of @var{arg} are:
23172 The default ABI associated with the current binary (this is the
23182 @item show mips abi
23183 @kindex show mips abi
23184 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
23186 @item set mips compression @var{arg}
23187 @kindex set mips compression
23188 @cindex code compression, @acronym{MIPS}
23189 Tell @value{GDBN} which @acronym{MIPS} compressed
23190 @acronym{ISA, Instruction Set Architecture} encoding is used by the
23191 inferior. @value{GDBN} uses this for code disassembly and other
23192 internal interpretation purposes. This setting is only referred to
23193 when no executable has been associated with the debugging session or
23194 the executable does not provide information about the encoding it uses.
23195 Otherwise this setting is automatically updated from information
23196 provided by the executable.
23198 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
23199 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
23200 executables containing @acronym{MIPS16} code frequently are not
23201 identified as such.
23203 This setting is ``sticky''; that is, it retains its value across
23204 debugging sessions until reset either explicitly with this command or
23205 implicitly from an executable.
23207 The compiler and/or assembler typically add symbol table annotations to
23208 identify functions compiled for the @acronym{MIPS16} or
23209 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
23210 are present, @value{GDBN} uses them in preference to the global
23211 compressed @acronym{ISA} encoding setting.
23213 @item show mips compression
23214 @kindex show mips compression
23215 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
23216 @value{GDBN} to debug the inferior.
23219 @itemx show mipsfpu
23220 @xref{MIPS Embedded, set mipsfpu}.
23222 @item set mips mask-address @var{arg}
23223 @kindex set mips mask-address
23224 @cindex @acronym{MIPS} addresses, masking
23225 This command determines whether the most-significant 32 bits of 64-bit
23226 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
23227 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
23228 setting, which lets @value{GDBN} determine the correct value.
23230 @item show mips mask-address
23231 @kindex show mips mask-address
23232 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
23235 @item set remote-mips64-transfers-32bit-regs
23236 @kindex set remote-mips64-transfers-32bit-regs
23237 This command controls compatibility with 64-bit @acronym{MIPS} targets that
23238 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
23239 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
23240 and 64 bits for other registers, set this option to @samp{on}.
23242 @item show remote-mips64-transfers-32bit-regs
23243 @kindex show remote-mips64-transfers-32bit-regs
23244 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
23246 @item set debug mips
23247 @kindex set debug mips
23248 This command turns on and off debugging messages for the @acronym{MIPS}-specific
23249 target code in @value{GDBN}.
23251 @item show debug mips
23252 @kindex show debug mips
23253 Show the current setting of @acronym{MIPS} debugging messages.
23259 @cindex HPPA support
23261 When @value{GDBN} is debugging the HP PA architecture, it provides the
23262 following special commands:
23265 @item set debug hppa
23266 @kindex set debug hppa
23267 This command determines whether HPPA architecture-specific debugging
23268 messages are to be displayed.
23270 @item show debug hppa
23271 Show whether HPPA debugging messages are displayed.
23273 @item maint print unwind @var{address}
23274 @kindex maint print unwind@r{, HPPA}
23275 This command displays the contents of the unwind table entry at the
23276 given @var{address}.
23282 @subsection Cell Broadband Engine SPU architecture
23283 @cindex Cell Broadband Engine
23286 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
23287 it provides the following special commands:
23290 @item info spu event
23292 Display SPU event facility status. Shows current event mask
23293 and pending event status.
23295 @item info spu signal
23296 Display SPU signal notification facility status. Shows pending
23297 signal-control word and signal notification mode of both signal
23298 notification channels.
23300 @item info spu mailbox
23301 Display SPU mailbox facility status. Shows all pending entries,
23302 in order of processing, in each of the SPU Write Outbound,
23303 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
23306 Display MFC DMA status. Shows all pending commands in the MFC
23307 DMA queue. For each entry, opcode, tag, class IDs, effective
23308 and local store addresses and transfer size are shown.
23310 @item info spu proxydma
23311 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
23312 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
23313 and local store addresses and transfer size are shown.
23317 When @value{GDBN} is debugging a combined PowerPC/SPU application
23318 on the Cell Broadband Engine, it provides in addition the following
23322 @item set spu stop-on-load @var{arg}
23324 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
23325 will give control to the user when a new SPE thread enters its @code{main}
23326 function. The default is @code{off}.
23328 @item show spu stop-on-load
23330 Show whether to stop for new SPE threads.
23332 @item set spu auto-flush-cache @var{arg}
23333 Set whether to automatically flush the software-managed cache. When set to
23334 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
23335 cache to be flushed whenever SPE execution stops. This provides a consistent
23336 view of PowerPC memory that is accessed via the cache. If an application
23337 does not use the software-managed cache, this option has no effect.
23339 @item show spu auto-flush-cache
23340 Show whether to automatically flush the software-managed cache.
23345 @subsection PowerPC
23346 @cindex PowerPC architecture
23348 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
23349 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
23350 numbers stored in the floating point registers. These values must be stored
23351 in two consecutive registers, always starting at an even register like
23352 @code{f0} or @code{f2}.
23354 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
23355 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
23356 @code{f2} and @code{f3} for @code{$dl1} and so on.
23358 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
23359 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
23362 @subsection Nios II
23363 @cindex Nios II architecture
23365 When @value{GDBN} is debugging the Nios II architecture,
23366 it provides the following special commands:
23370 @item set debug nios2
23371 @kindex set debug nios2
23372 This command turns on and off debugging messages for the Nios II
23373 target code in @value{GDBN}.
23375 @item show debug nios2
23376 @kindex show debug nios2
23377 Show the current setting of Nios II debugging messages.
23381 @subsection Sparc64
23382 @cindex Sparc64 support
23383 @cindex Application Data Integrity
23384 @subsubsection ADI Support
23386 The M7 processor supports an Application Data Integrity (ADI) feature that
23387 detects invalid data accesses. When software allocates memory and enables
23388 ADI on the allocated memory, it chooses a 4-bit version number, sets the
23389 version in the upper 4 bits of the 64-bit pointer to that data, and stores
23390 the 4-bit version in every cacheline of that data. Hardware saves the latter
23391 in spare bits in the cache and memory hierarchy. On each load and store,
23392 the processor compares the upper 4 VA (virtual address) bits to the
23393 cacheline's version. If there is a mismatch, the processor generates a
23394 version mismatch trap which can be either precise or disrupting. The trap
23395 is an error condition which the kernel delivers to the process as a SIGSEGV
23398 Note that only 64-bit applications can use ADI and need to be built with
23401 Values of the ADI version tags, which are in granularity of a
23402 cacheline (64 bytes), can be viewed or modified.
23406 @kindex adi examine
23407 @item adi (examine | x) [ / @var{n} ] @var{addr}
23409 The @code{adi examine} command displays the value of one ADI version tag per
23412 @var{n} is a decimal integer specifying the number in bytes; the default
23413 is 1. It specifies how much ADI version information, at the ratio of 1:ADI
23414 block size, to display.
23416 @var{addr} is the address in user address space where you want @value{GDBN}
23417 to begin displaying the ADI version tags.
23419 Below is an example of displaying ADI versions of variable "shmaddr".
23422 (@value{GDBP}) adi x/100 shmaddr
23423 0xfff800010002c000: 0 0
23427 @item adi (assign | a) [ / @var{n} ] @var{addr} = @var{tag}
23429 The @code{adi assign} command is used to assign new ADI version tag
23432 @var{n} is a decimal integer specifying the number in bytes;
23433 the default is 1. It specifies how much ADI version information, at the
23434 ratio of 1:ADI block size, to modify.
23436 @var{addr} is the address in user address space where you want @value{GDBN}
23437 to begin modifying the ADI version tags.
23439 @var{tag} is the new ADI version tag.
23441 For example, do the following to modify then verify ADI versions of
23442 variable "shmaddr":
23445 (@value{GDBP}) adi a/100 shmaddr = 7
23446 (@value{GDBP}) adi x/100 shmaddr
23447 0xfff800010002c000: 7 7
23452 @node Controlling GDB
23453 @chapter Controlling @value{GDBN}
23455 You can alter the way @value{GDBN} interacts with you by using the
23456 @code{set} command. For commands controlling how @value{GDBN} displays
23457 data, see @ref{Print Settings, ,Print Settings}. Other settings are
23462 * Editing:: Command editing
23463 * Command History:: Command history
23464 * Screen Size:: Screen size
23465 * Numbers:: Numbers
23466 * ABI:: Configuring the current ABI
23467 * Auto-loading:: Automatically loading associated files
23468 * Messages/Warnings:: Optional warnings and messages
23469 * Debugging Output:: Optional messages about internal happenings
23470 * Other Misc Settings:: Other Miscellaneous Settings
23478 @value{GDBN} indicates its readiness to read a command by printing a string
23479 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
23480 can change the prompt string with the @code{set prompt} command. For
23481 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
23482 the prompt in one of the @value{GDBN} sessions so that you can always tell
23483 which one you are talking to.
23485 @emph{Note:} @code{set prompt} does not add a space for you after the
23486 prompt you set. This allows you to set a prompt which ends in a space
23487 or a prompt that does not.
23491 @item set prompt @var{newprompt}
23492 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
23494 @kindex show prompt
23496 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
23499 Versions of @value{GDBN} that ship with Python scripting enabled have
23500 prompt extensions. The commands for interacting with these extensions
23504 @kindex set extended-prompt
23505 @item set extended-prompt @var{prompt}
23506 Set an extended prompt that allows for substitutions.
23507 @xref{gdb.prompt}, for a list of escape sequences that can be used for
23508 substitution. Any escape sequences specified as part of the prompt
23509 string are replaced with the corresponding strings each time the prompt
23515 set extended-prompt Current working directory: \w (gdb)
23518 Note that when an extended-prompt is set, it takes control of the
23519 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
23521 @kindex show extended-prompt
23522 @item show extended-prompt
23523 Prints the extended prompt. Any escape sequences specified as part of
23524 the prompt string with @code{set extended-prompt}, are replaced with the
23525 corresponding strings each time the prompt is displayed.
23529 @section Command Editing
23531 @cindex command line editing
23533 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
23534 @sc{gnu} library provides consistent behavior for programs which provide a
23535 command line interface to the user. Advantages are @sc{gnu} Emacs-style
23536 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
23537 substitution, and a storage and recall of command history across
23538 debugging sessions.
23540 You may control the behavior of command line editing in @value{GDBN} with the
23541 command @code{set}.
23544 @kindex set editing
23547 @itemx set editing on
23548 Enable command line editing (enabled by default).
23550 @item set editing off
23551 Disable command line editing.
23553 @kindex show editing
23555 Show whether command line editing is enabled.
23558 @ifset SYSTEM_READLINE
23559 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
23561 @ifclear SYSTEM_READLINE
23562 @xref{Command Line Editing},
23564 for more details about the Readline
23565 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
23566 encouraged to read that chapter.
23568 @node Command History
23569 @section Command History
23570 @cindex command history
23572 @value{GDBN} can keep track of the commands you type during your
23573 debugging sessions, so that you can be certain of precisely what
23574 happened. Use these commands to manage the @value{GDBN} command
23577 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
23578 package, to provide the history facility.
23579 @ifset SYSTEM_READLINE
23580 @xref{Using History Interactively, , , history, GNU History Library},
23582 @ifclear SYSTEM_READLINE
23583 @xref{Using History Interactively},
23585 for the detailed description of the History library.
23587 To issue a command to @value{GDBN} without affecting certain aspects of
23588 the state which is seen by users, prefix it with @samp{server }
23589 (@pxref{Server Prefix}). This
23590 means that this command will not affect the command history, nor will it
23591 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
23592 pressed on a line by itself.
23594 @cindex @code{server}, command prefix
23595 The server prefix does not affect the recording of values into the value
23596 history; to print a value without recording it into the value history,
23597 use the @code{output} command instead of the @code{print} command.
23599 Here is the description of @value{GDBN} commands related to command
23603 @cindex history substitution
23604 @cindex history file
23605 @kindex set history filename
23606 @cindex @env{GDBHISTFILE}, environment variable
23607 @item set history filename @var{fname}
23608 Set the name of the @value{GDBN} command history file to @var{fname}.
23609 This is the file where @value{GDBN} reads an initial command history
23610 list, and where it writes the command history from this session when it
23611 exits. You can access this list through history expansion or through
23612 the history command editing characters listed below. This file defaults
23613 to the value of the environment variable @code{GDBHISTFILE}, or to
23614 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
23617 @cindex save command history
23618 @kindex set history save
23619 @item set history save
23620 @itemx set history save on
23621 Record command history in a file, whose name may be specified with the
23622 @code{set history filename} command. By default, this option is disabled.
23624 @item set history save off
23625 Stop recording command history in a file.
23627 @cindex history size
23628 @kindex set history size
23629 @cindex @env{GDBHISTSIZE}, environment variable
23630 @item set history size @var{size}
23631 @itemx set history size unlimited
23632 Set the number of commands which @value{GDBN} keeps in its history list.
23633 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
23634 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
23635 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
23636 either a negative number or the empty string, then the number of commands
23637 @value{GDBN} keeps in the history list is unlimited.
23639 @cindex remove duplicate history
23640 @kindex set history remove-duplicates
23641 @item set history remove-duplicates @var{count}
23642 @itemx set history remove-duplicates unlimited
23643 Control the removal of duplicate history entries in the command history list.
23644 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
23645 history entries and remove the first entry that is a duplicate of the current
23646 entry being added to the command history list. If @var{count} is
23647 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
23648 removal of duplicate history entries is disabled.
23650 Only history entries added during the current session are considered for
23651 removal. This option is set to 0 by default.
23655 History expansion assigns special meaning to the character @kbd{!}.
23656 @ifset SYSTEM_READLINE
23657 @xref{Event Designators, , , history, GNU History Library},
23659 @ifclear SYSTEM_READLINE
23660 @xref{Event Designators},
23664 @cindex history expansion, turn on/off
23665 Since @kbd{!} is also the logical not operator in C, history expansion
23666 is off by default. If you decide to enable history expansion with the
23667 @code{set history expansion on} command, you may sometimes need to
23668 follow @kbd{!} (when it is used as logical not, in an expression) with
23669 a space or a tab to prevent it from being expanded. The readline
23670 history facilities do not attempt substitution on the strings
23671 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
23673 The commands to control history expansion are:
23676 @item set history expansion on
23677 @itemx set history expansion
23678 @kindex set history expansion
23679 Enable history expansion. History expansion is off by default.
23681 @item set history expansion off
23682 Disable history expansion.
23685 @kindex show history
23687 @itemx show history filename
23688 @itemx show history save
23689 @itemx show history size
23690 @itemx show history expansion
23691 These commands display the state of the @value{GDBN} history parameters.
23692 @code{show history} by itself displays all four states.
23697 @kindex show commands
23698 @cindex show last commands
23699 @cindex display command history
23700 @item show commands
23701 Display the last ten commands in the command history.
23703 @item show commands @var{n}
23704 Print ten commands centered on command number @var{n}.
23706 @item show commands +
23707 Print ten commands just after the commands last printed.
23711 @section Screen Size
23712 @cindex size of screen
23713 @cindex screen size
23716 @cindex pauses in output
23718 Certain commands to @value{GDBN} may produce large amounts of
23719 information output to the screen. To help you read all of it,
23720 @value{GDBN} pauses and asks you for input at the end of each page of
23721 output. Type @key{RET} when you want to continue the output, or @kbd{q}
23722 to discard the remaining output. Also, the screen width setting
23723 determines when to wrap lines of output. Depending on what is being
23724 printed, @value{GDBN} tries to break the line at a readable place,
23725 rather than simply letting it overflow onto the following line.
23727 Normally @value{GDBN} knows the size of the screen from the terminal
23728 driver software. For example, on Unix @value{GDBN} uses the termcap data base
23729 together with the value of the @code{TERM} environment variable and the
23730 @code{stty rows} and @code{stty cols} settings. If this is not correct,
23731 you can override it with the @code{set height} and @code{set
23738 @kindex show height
23739 @item set height @var{lpp}
23740 @itemx set height unlimited
23742 @itemx set width @var{cpl}
23743 @itemx set width unlimited
23745 These @code{set} commands specify a screen height of @var{lpp} lines and
23746 a screen width of @var{cpl} characters. The associated @code{show}
23747 commands display the current settings.
23749 If you specify a height of either @code{unlimited} or zero lines,
23750 @value{GDBN} does not pause during output no matter how long the
23751 output is. This is useful if output is to a file or to an editor
23754 Likewise, you can specify @samp{set width unlimited} or @samp{set
23755 width 0} to prevent @value{GDBN} from wrapping its output.
23757 @item set pagination on
23758 @itemx set pagination off
23759 @kindex set pagination
23760 Turn the output pagination on or off; the default is on. Turning
23761 pagination off is the alternative to @code{set height unlimited}. Note that
23762 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
23763 Options, -batch}) also automatically disables pagination.
23765 @item show pagination
23766 @kindex show pagination
23767 Show the current pagination mode.
23772 @cindex number representation
23773 @cindex entering numbers
23775 You can always enter numbers in octal, decimal, or hexadecimal in
23776 @value{GDBN} by the usual conventions: octal numbers begin with
23777 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
23778 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
23779 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
23780 10; likewise, the default display for numbers---when no particular
23781 format is specified---is base 10. You can change the default base for
23782 both input and output with the commands described below.
23785 @kindex set input-radix
23786 @item set input-radix @var{base}
23787 Set the default base for numeric input. Supported choices
23788 for @var{base} are decimal 8, 10, or 16. The base must itself be
23789 specified either unambiguously or using the current input radix; for
23793 set input-radix 012
23794 set input-radix 10.
23795 set input-radix 0xa
23799 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
23800 leaves the input radix unchanged, no matter what it was, since
23801 @samp{10}, being without any leading or trailing signs of its base, is
23802 interpreted in the current radix. Thus, if the current radix is 16,
23803 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
23806 @kindex set output-radix
23807 @item set output-radix @var{base}
23808 Set the default base for numeric display. Supported choices
23809 for @var{base} are decimal 8, 10, or 16. The base must itself be
23810 specified either unambiguously or using the current input radix.
23812 @kindex show input-radix
23813 @item show input-radix
23814 Display the current default base for numeric input.
23816 @kindex show output-radix
23817 @item show output-radix
23818 Display the current default base for numeric display.
23820 @item set radix @r{[}@var{base}@r{]}
23824 These commands set and show the default base for both input and output
23825 of numbers. @code{set radix} sets the radix of input and output to
23826 the same base; without an argument, it resets the radix back to its
23827 default value of 10.
23832 @section Configuring the Current ABI
23834 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
23835 application automatically. However, sometimes you need to override its
23836 conclusions. Use these commands to manage @value{GDBN}'s view of the
23842 @cindex Newlib OS ABI and its influence on the longjmp handling
23844 One @value{GDBN} configuration can debug binaries for multiple operating
23845 system targets, either via remote debugging or native emulation.
23846 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
23847 but you can override its conclusion using the @code{set osabi} command.
23848 One example where this is useful is in debugging of binaries which use
23849 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
23850 not have the same identifying marks that the standard C library for your
23853 When @value{GDBN} is debugging the AArch64 architecture, it provides a
23854 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
23855 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
23856 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
23860 Show the OS ABI currently in use.
23863 With no argument, show the list of registered available OS ABI's.
23865 @item set osabi @var{abi}
23866 Set the current OS ABI to @var{abi}.
23869 @cindex float promotion
23871 Generally, the way that an argument of type @code{float} is passed to a
23872 function depends on whether the function is prototyped. For a prototyped
23873 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
23874 according to the architecture's convention for @code{float}. For unprototyped
23875 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
23876 @code{double} and then passed.
23878 Unfortunately, some forms of debug information do not reliably indicate whether
23879 a function is prototyped. If @value{GDBN} calls a function that is not marked
23880 as prototyped, it consults @kbd{set coerce-float-to-double}.
23883 @kindex set coerce-float-to-double
23884 @item set coerce-float-to-double
23885 @itemx set coerce-float-to-double on
23886 Arguments of type @code{float} will be promoted to @code{double} when passed
23887 to an unprototyped function. This is the default setting.
23889 @item set coerce-float-to-double off
23890 Arguments of type @code{float} will be passed directly to unprototyped
23893 @kindex show coerce-float-to-double
23894 @item show coerce-float-to-double
23895 Show the current setting of promoting @code{float} to @code{double}.
23899 @kindex show cp-abi
23900 @value{GDBN} needs to know the ABI used for your program's C@t{++}
23901 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
23902 used to build your application. @value{GDBN} only fully supports
23903 programs with a single C@t{++} ABI; if your program contains code using
23904 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
23905 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
23906 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
23907 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
23908 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
23909 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
23914 Show the C@t{++} ABI currently in use.
23917 With no argument, show the list of supported C@t{++} ABI's.
23919 @item set cp-abi @var{abi}
23920 @itemx set cp-abi auto
23921 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
23925 @section Automatically loading associated files
23926 @cindex auto-loading
23928 @value{GDBN} sometimes reads files with commands and settings automatically,
23929 without being explicitly told so by the user. We call this feature
23930 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
23931 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
23932 results or introduce security risks (e.g., if the file comes from untrusted
23936 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23937 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23939 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23940 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23943 There are various kinds of files @value{GDBN} can automatically load.
23944 In addition to these files, @value{GDBN} supports auto-loading code written
23945 in various extension languages. @xref{Auto-loading extensions}.
23947 Note that loading of these associated files (including the local @file{.gdbinit}
23948 file) requires accordingly configured @code{auto-load safe-path}
23949 (@pxref{Auto-loading safe path}).
23951 For these reasons, @value{GDBN} includes commands and options to let you
23952 control when to auto-load files and which files should be auto-loaded.
23955 @anchor{set auto-load off}
23956 @kindex set auto-load off
23957 @item set auto-load off
23958 Globally disable loading of all auto-loaded files.
23959 You may want to use this command with the @samp{-iex} option
23960 (@pxref{Option -init-eval-command}) such as:
23962 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23965 Be aware that system init file (@pxref{System-wide configuration})
23966 and init files from your home directory (@pxref{Home Directory Init File})
23967 still get read (as they come from generally trusted directories).
23968 To prevent @value{GDBN} from auto-loading even those init files, use the
23969 @option{-nx} option (@pxref{Mode Options}), in addition to
23970 @code{set auto-load no}.
23972 @anchor{show auto-load}
23973 @kindex show auto-load
23974 @item show auto-load
23975 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23979 (gdb) show auto-load
23980 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23981 libthread-db: Auto-loading of inferior specific libthread_db is on.
23982 local-gdbinit: Auto-loading of .gdbinit script from current directory
23984 python-scripts: Auto-loading of Python scripts is on.
23985 safe-path: List of directories from which it is safe to auto-load files
23986 is $debugdir:$datadir/auto-load.
23987 scripts-directory: List of directories from which to load auto-loaded scripts
23988 is $debugdir:$datadir/auto-load.
23991 @anchor{info auto-load}
23992 @kindex info auto-load
23993 @item info auto-load
23994 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23998 (gdb) info auto-load
24001 Yes /home/user/gdb/gdb-gdb.gdb
24002 libthread-db: No auto-loaded libthread-db.
24003 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
24007 Yes /home/user/gdb/gdb-gdb.py
24011 These are @value{GDBN} control commands for the auto-loading:
24013 @multitable @columnfractions .5 .5
24014 @item @xref{set auto-load off}.
24015 @tab Disable auto-loading globally.
24016 @item @xref{show auto-load}.
24017 @tab Show setting of all kinds of files.
24018 @item @xref{info auto-load}.
24019 @tab Show state of all kinds of files.
24020 @item @xref{set auto-load gdb-scripts}.
24021 @tab Control for @value{GDBN} command scripts.
24022 @item @xref{show auto-load gdb-scripts}.
24023 @tab Show setting of @value{GDBN} command scripts.
24024 @item @xref{info auto-load gdb-scripts}.
24025 @tab Show state of @value{GDBN} command scripts.
24026 @item @xref{set auto-load python-scripts}.
24027 @tab Control for @value{GDBN} Python scripts.
24028 @item @xref{show auto-load python-scripts}.
24029 @tab Show setting of @value{GDBN} Python scripts.
24030 @item @xref{info auto-load python-scripts}.
24031 @tab Show state of @value{GDBN} Python scripts.
24032 @item @xref{set auto-load guile-scripts}.
24033 @tab Control for @value{GDBN} Guile scripts.
24034 @item @xref{show auto-load guile-scripts}.
24035 @tab Show setting of @value{GDBN} Guile scripts.
24036 @item @xref{info auto-load guile-scripts}.
24037 @tab Show state of @value{GDBN} Guile scripts.
24038 @item @xref{set auto-load scripts-directory}.
24039 @tab Control for @value{GDBN} auto-loaded scripts location.
24040 @item @xref{show auto-load scripts-directory}.
24041 @tab Show @value{GDBN} auto-loaded scripts location.
24042 @item @xref{add-auto-load-scripts-directory}.
24043 @tab Add directory for auto-loaded scripts location list.
24044 @item @xref{set auto-load local-gdbinit}.
24045 @tab Control for init file in the current directory.
24046 @item @xref{show auto-load local-gdbinit}.
24047 @tab Show setting of init file in the current directory.
24048 @item @xref{info auto-load local-gdbinit}.
24049 @tab Show state of init file in the current directory.
24050 @item @xref{set auto-load libthread-db}.
24051 @tab Control for thread debugging library.
24052 @item @xref{show auto-load libthread-db}.
24053 @tab Show setting of thread debugging library.
24054 @item @xref{info auto-load libthread-db}.
24055 @tab Show state of thread debugging library.
24056 @item @xref{set auto-load safe-path}.
24057 @tab Control directories trusted for automatic loading.
24058 @item @xref{show auto-load safe-path}.
24059 @tab Show directories trusted for automatic loading.
24060 @item @xref{add-auto-load-safe-path}.
24061 @tab Add directory trusted for automatic loading.
24064 @node Init File in the Current Directory
24065 @subsection Automatically loading init file in the current directory
24066 @cindex auto-loading init file in the current directory
24068 By default, @value{GDBN} reads and executes the canned sequences of commands
24069 from init file (if any) in the current working directory,
24070 see @ref{Init File in the Current Directory during Startup}.
24072 Note that loading of this local @file{.gdbinit} file also requires accordingly
24073 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24076 @anchor{set auto-load local-gdbinit}
24077 @kindex set auto-load local-gdbinit
24078 @item set auto-load local-gdbinit [on|off]
24079 Enable or disable the auto-loading of canned sequences of commands
24080 (@pxref{Sequences}) found in init file in the current directory.
24082 @anchor{show auto-load local-gdbinit}
24083 @kindex show auto-load local-gdbinit
24084 @item show auto-load local-gdbinit
24085 Show whether auto-loading of canned sequences of commands from init file in the
24086 current directory is enabled or disabled.
24088 @anchor{info auto-load local-gdbinit}
24089 @kindex info auto-load local-gdbinit
24090 @item info auto-load local-gdbinit
24091 Print whether canned sequences of commands from init file in the
24092 current directory have been auto-loaded.
24095 @node libthread_db.so.1 file
24096 @subsection Automatically loading thread debugging library
24097 @cindex auto-loading libthread_db.so.1
24099 This feature is currently present only on @sc{gnu}/Linux native hosts.
24101 @value{GDBN} reads in some cases thread debugging library from places specific
24102 to the inferior (@pxref{set libthread-db-search-path}).
24104 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
24105 without checking this @samp{set auto-load libthread-db} switch as system
24106 libraries have to be trusted in general. In all other cases of
24107 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
24108 auto-load libthread-db} is enabled before trying to open such thread debugging
24111 Note that loading of this debugging library also requires accordingly configured
24112 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24115 @anchor{set auto-load libthread-db}
24116 @kindex set auto-load libthread-db
24117 @item set auto-load libthread-db [on|off]
24118 Enable or disable the auto-loading of inferior specific thread debugging library.
24120 @anchor{show auto-load libthread-db}
24121 @kindex show auto-load libthread-db
24122 @item show auto-load libthread-db
24123 Show whether auto-loading of inferior specific thread debugging library is
24124 enabled or disabled.
24126 @anchor{info auto-load libthread-db}
24127 @kindex info auto-load libthread-db
24128 @item info auto-load libthread-db
24129 Print the list of all loaded inferior specific thread debugging libraries and
24130 for each such library print list of inferior @var{pid}s using it.
24133 @node Auto-loading safe path
24134 @subsection Security restriction for auto-loading
24135 @cindex auto-loading safe-path
24137 As the files of inferior can come from untrusted source (such as submitted by
24138 an application user) @value{GDBN} does not always load any files automatically.
24139 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
24140 directories trusted for loading files not explicitly requested by user.
24141 Each directory can also be a shell wildcard pattern.
24143 If the path is not set properly you will see a warning and the file will not
24148 Reading symbols from /home/user/gdb/gdb...done.
24149 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
24150 declined by your `auto-load safe-path' set
24151 to "$debugdir:$datadir/auto-load".
24152 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
24153 declined by your `auto-load safe-path' set
24154 to "$debugdir:$datadir/auto-load".
24158 To instruct @value{GDBN} to go ahead and use the init files anyway,
24159 invoke @value{GDBN} like this:
24162 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
24165 The list of trusted directories is controlled by the following commands:
24168 @anchor{set auto-load safe-path}
24169 @kindex set auto-load safe-path
24170 @item set auto-load safe-path @r{[}@var{directories}@r{]}
24171 Set the list of directories (and their subdirectories) trusted for automatic
24172 loading and execution of scripts. You can also enter a specific trusted file.
24173 Each directory can also be a shell wildcard pattern; wildcards do not match
24174 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
24175 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
24176 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
24177 its default value as specified during @value{GDBN} compilation.
24179 The list of directories uses path separator (@samp{:} on GNU and Unix
24180 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24181 to the @env{PATH} environment variable.
24183 @anchor{show auto-load safe-path}
24184 @kindex show auto-load safe-path
24185 @item show auto-load safe-path
24186 Show the list of directories trusted for automatic loading and execution of
24189 @anchor{add-auto-load-safe-path}
24190 @kindex add-auto-load-safe-path
24191 @item add-auto-load-safe-path
24192 Add an entry (or list of entries) to the list of directories trusted for
24193 automatic loading and execution of scripts. Multiple entries may be delimited
24194 by the host platform path separator in use.
24197 This variable defaults to what @code{--with-auto-load-dir} has been configured
24198 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
24199 substitution applies the same as for @ref{set auto-load scripts-directory}.
24200 The default @code{set auto-load safe-path} value can be also overriden by
24201 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
24203 Setting this variable to @file{/} disables this security protection,
24204 corresponding @value{GDBN} configuration option is
24205 @option{--without-auto-load-safe-path}.
24206 This variable is supposed to be set to the system directories writable by the
24207 system superuser only. Users can add their source directories in init files in
24208 their home directories (@pxref{Home Directory Init File}). See also deprecated
24209 init file in the current directory
24210 (@pxref{Init File in the Current Directory during Startup}).
24212 To force @value{GDBN} to load the files it declined to load in the previous
24213 example, you could use one of the following ways:
24216 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
24217 Specify this trusted directory (or a file) as additional component of the list.
24218 You have to specify also any existing directories displayed by
24219 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
24221 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
24222 Specify this directory as in the previous case but just for a single
24223 @value{GDBN} session.
24225 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
24226 Disable auto-loading safety for a single @value{GDBN} session.
24227 This assumes all the files you debug during this @value{GDBN} session will come
24228 from trusted sources.
24230 @item @kbd{./configure --without-auto-load-safe-path}
24231 During compilation of @value{GDBN} you may disable any auto-loading safety.
24232 This assumes all the files you will ever debug with this @value{GDBN} come from
24236 On the other hand you can also explicitly forbid automatic files loading which
24237 also suppresses any such warning messages:
24240 @item @kbd{gdb -iex "set auto-load no" @dots{}}
24241 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
24243 @item @file{~/.gdbinit}: @samp{set auto-load no}
24244 Disable auto-loading globally for the user
24245 (@pxref{Home Directory Init File}). While it is improbable, you could also
24246 use system init file instead (@pxref{System-wide configuration}).
24249 This setting applies to the file names as entered by user. If no entry matches
24250 @value{GDBN} tries as a last resort to also resolve all the file names into
24251 their canonical form (typically resolving symbolic links) and compare the
24252 entries again. @value{GDBN} already canonicalizes most of the filenames on its
24253 own before starting the comparison so a canonical form of directories is
24254 recommended to be entered.
24256 @node Auto-loading verbose mode
24257 @subsection Displaying files tried for auto-load
24258 @cindex auto-loading verbose mode
24260 For better visibility of all the file locations where you can place scripts to
24261 be auto-loaded with inferior --- or to protect yourself against accidental
24262 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
24263 all the files attempted to be loaded. Both existing and non-existing files may
24266 For example the list of directories from which it is safe to auto-load files
24267 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
24268 may not be too obvious while setting it up.
24271 (gdb) set debug auto-load on
24272 (gdb) file ~/src/t/true
24273 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
24274 for objfile "/tmp/true".
24275 auto-load: Updating directories of "/usr:/opt".
24276 auto-load: Using directory "/usr".
24277 auto-load: Using directory "/opt".
24278 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
24279 by your `auto-load safe-path' set to "/usr:/opt".
24283 @anchor{set debug auto-load}
24284 @kindex set debug auto-load
24285 @item set debug auto-load [on|off]
24286 Set whether to print the filenames attempted to be auto-loaded.
24288 @anchor{show debug auto-load}
24289 @kindex show debug auto-load
24290 @item show debug auto-load
24291 Show whether printing of the filenames attempted to be auto-loaded is turned
24295 @node Messages/Warnings
24296 @section Optional Warnings and Messages
24298 @cindex verbose operation
24299 @cindex optional warnings
24300 By default, @value{GDBN} is silent about its inner workings. If you are
24301 running on a slow machine, you may want to use the @code{set verbose}
24302 command. This makes @value{GDBN} tell you when it does a lengthy
24303 internal operation, so you will not think it has crashed.
24305 Currently, the messages controlled by @code{set verbose} are those
24306 which announce that the symbol table for a source file is being read;
24307 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
24310 @kindex set verbose
24311 @item set verbose on
24312 Enables @value{GDBN} output of certain informational messages.
24314 @item set verbose off
24315 Disables @value{GDBN} output of certain informational messages.
24317 @kindex show verbose
24319 Displays whether @code{set verbose} is on or off.
24322 By default, if @value{GDBN} encounters bugs in the symbol table of an
24323 object file, it is silent; but if you are debugging a compiler, you may
24324 find this information useful (@pxref{Symbol Errors, ,Errors Reading
24329 @kindex set complaints
24330 @item set complaints @var{limit}
24331 Permits @value{GDBN} to output @var{limit} complaints about each type of
24332 unusual symbols before becoming silent about the problem. Set
24333 @var{limit} to zero to suppress all complaints; set it to a large number
24334 to prevent complaints from being suppressed.
24336 @kindex show complaints
24337 @item show complaints
24338 Displays how many symbol complaints @value{GDBN} is permitted to produce.
24342 @anchor{confirmation requests}
24343 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
24344 lot of stupid questions to confirm certain commands. For example, if
24345 you try to run a program which is already running:
24349 The program being debugged has been started already.
24350 Start it from the beginning? (y or n)
24353 If you are willing to unflinchingly face the consequences of your own
24354 commands, you can disable this ``feature'':
24358 @kindex set confirm
24360 @cindex confirmation
24361 @cindex stupid questions
24362 @item set confirm off
24363 Disables confirmation requests. Note that running @value{GDBN} with
24364 the @option{--batch} option (@pxref{Mode Options, -batch}) also
24365 automatically disables confirmation requests.
24367 @item set confirm on
24368 Enables confirmation requests (the default).
24370 @kindex show confirm
24372 Displays state of confirmation requests.
24376 @cindex command tracing
24377 If you need to debug user-defined commands or sourced files you may find it
24378 useful to enable @dfn{command tracing}. In this mode each command will be
24379 printed as it is executed, prefixed with one or more @samp{+} symbols, the
24380 quantity denoting the call depth of each command.
24383 @kindex set trace-commands
24384 @cindex command scripts, debugging
24385 @item set trace-commands on
24386 Enable command tracing.
24387 @item set trace-commands off
24388 Disable command tracing.
24389 @item show trace-commands
24390 Display the current state of command tracing.
24393 @node Debugging Output
24394 @section Optional Messages about Internal Happenings
24395 @cindex optional debugging messages
24397 @value{GDBN} has commands that enable optional debugging messages from
24398 various @value{GDBN} subsystems; normally these commands are of
24399 interest to @value{GDBN} maintainers, or when reporting a bug. This
24400 section documents those commands.
24403 @kindex set exec-done-display
24404 @item set exec-done-display
24405 Turns on or off the notification of asynchronous commands'
24406 completion. When on, @value{GDBN} will print a message when an
24407 asynchronous command finishes its execution. The default is off.
24408 @kindex show exec-done-display
24409 @item show exec-done-display
24410 Displays the current setting of asynchronous command completion
24413 @cindex ARM AArch64
24414 @item set debug aarch64
24415 Turns on or off display of debugging messages related to ARM AArch64.
24416 The default is off.
24418 @item show debug aarch64
24419 Displays the current state of displaying debugging messages related to
24421 @cindex gdbarch debugging info
24422 @cindex architecture debugging info
24423 @item set debug arch
24424 Turns on or off display of gdbarch debugging info. The default is off
24425 @item show debug arch
24426 Displays the current state of displaying gdbarch debugging info.
24427 @item set debug aix-solib
24428 @cindex AIX shared library debugging
24429 Control display of debugging messages from the AIX shared library
24430 support module. The default is off.
24431 @item show debug aix-thread
24432 Show the current state of displaying AIX shared library debugging messages.
24433 @item set debug aix-thread
24434 @cindex AIX threads
24435 Display debugging messages about inner workings of the AIX thread
24437 @item show debug aix-thread
24438 Show the current state of AIX thread debugging info display.
24439 @item set debug check-physname
24441 Check the results of the ``physname'' computation. When reading DWARF
24442 debugging information for C@t{++}, @value{GDBN} attempts to compute
24443 each entity's name. @value{GDBN} can do this computation in two
24444 different ways, depending on exactly what information is present.
24445 When enabled, this setting causes @value{GDBN} to compute the names
24446 both ways and display any discrepancies.
24447 @item show debug check-physname
24448 Show the current state of ``physname'' checking.
24449 @item set debug coff-pe-read
24450 @cindex COFF/PE exported symbols
24451 Control display of debugging messages related to reading of COFF/PE
24452 exported symbols. The default is off.
24453 @item show debug coff-pe-read
24454 Displays the current state of displaying debugging messages related to
24455 reading of COFF/PE exported symbols.
24456 @item set debug dwarf-die
24458 Dump DWARF DIEs after they are read in.
24459 The value is the number of nesting levels to print.
24460 A value of zero turns off the display.
24461 @item show debug dwarf-die
24462 Show the current state of DWARF DIE debugging.
24463 @item set debug dwarf-line
24464 @cindex DWARF Line Tables
24465 Turns on or off display of debugging messages related to reading
24466 DWARF line tables. The default is 0 (off).
24467 A value of 1 provides basic information.
24468 A value greater than 1 provides more verbose information.
24469 @item show debug dwarf-line
24470 Show the current state of DWARF line table debugging.
24471 @item set debug dwarf-read
24472 @cindex DWARF Reading
24473 Turns on or off display of debugging messages related to reading
24474 DWARF debug info. The default is 0 (off).
24475 A value of 1 provides basic information.
24476 A value greater than 1 provides more verbose information.
24477 @item show debug dwarf-read
24478 Show the current state of DWARF reader debugging.
24479 @item set debug displaced
24480 @cindex displaced stepping debugging info
24481 Turns on or off display of @value{GDBN} debugging info for the
24482 displaced stepping support. The default is off.
24483 @item show debug displaced
24484 Displays the current state of displaying @value{GDBN} debugging info
24485 related to displaced stepping.
24486 @item set debug event
24487 @cindex event debugging info
24488 Turns on or off display of @value{GDBN} event debugging info. The
24490 @item show debug event
24491 Displays the current state of displaying @value{GDBN} event debugging
24493 @item set debug expression
24494 @cindex expression debugging info
24495 Turns on or off display of debugging info about @value{GDBN}
24496 expression parsing. The default is off.
24497 @item show debug expression
24498 Displays the current state of displaying debugging info about
24499 @value{GDBN} expression parsing.
24500 @item set debug fbsd-lwp
24501 @cindex FreeBSD LWP debug messages
24502 Turns on or off debugging messages from the FreeBSD LWP debug support.
24503 @item show debug fbsd-lwp
24504 Show the current state of FreeBSD LWP debugging messages.
24505 @item set debug frame
24506 @cindex frame debugging info
24507 Turns on or off display of @value{GDBN} frame debugging info. The
24509 @item show debug frame
24510 Displays the current state of displaying @value{GDBN} frame debugging
24512 @item set debug gnu-nat
24513 @cindex @sc{gnu}/Hurd debug messages
24514 Turn on or off debugging messages from the @sc{gnu}/Hurd debug support.
24515 @item show debug gnu-nat
24516 Show the current state of @sc{gnu}/Hurd debugging messages.
24517 @item set debug infrun
24518 @cindex inferior debugging info
24519 Turns on or off display of @value{GDBN} debugging info for running the inferior.
24520 The default is off. @file{infrun.c} contains GDB's runtime state machine used
24521 for implementing operations such as single-stepping the inferior.
24522 @item show debug infrun
24523 Displays the current state of @value{GDBN} inferior debugging.
24524 @item set debug jit
24525 @cindex just-in-time compilation, debugging messages
24526 Turn on or off debugging messages from JIT debug support.
24527 @item show debug jit
24528 Displays the current state of @value{GDBN} JIT debugging.
24529 @item set debug lin-lwp
24530 @cindex @sc{gnu}/Linux LWP debug messages
24531 @cindex Linux lightweight processes
24532 Turn on or off debugging messages from the Linux LWP debug support.
24533 @item show debug lin-lwp
24534 Show the current state of Linux LWP debugging messages.
24535 @item set debug linux-namespaces
24536 @cindex @sc{gnu}/Linux namespaces debug messages
24537 Turn on or off debugging messages from the Linux namespaces debug support.
24538 @item show debug linux-namespaces
24539 Show the current state of Linux namespaces debugging messages.
24540 @item set debug mach-o
24541 @cindex Mach-O symbols processing
24542 Control display of debugging messages related to Mach-O symbols
24543 processing. The default is off.
24544 @item show debug mach-o
24545 Displays the current state of displaying debugging messages related to
24546 reading of COFF/PE exported symbols.
24547 @item set debug notification
24548 @cindex remote async notification debugging info
24549 Turn on or off debugging messages about remote async notification.
24550 The default is off.
24551 @item show debug notification
24552 Displays the current state of remote async notification debugging messages.
24553 @item set debug observer
24554 @cindex observer debugging info
24555 Turns on or off display of @value{GDBN} observer debugging. This
24556 includes info such as the notification of observable events.
24557 @item show debug observer
24558 Displays the current state of observer debugging.
24559 @item set debug overload
24560 @cindex C@t{++} overload debugging info
24561 Turns on or off display of @value{GDBN} C@t{++} overload debugging
24562 info. This includes info such as ranking of functions, etc. The default
24564 @item show debug overload
24565 Displays the current state of displaying @value{GDBN} C@t{++} overload
24567 @cindex expression parser, debugging info
24568 @cindex debug expression parser
24569 @item set debug parser
24570 Turns on or off the display of expression parser debugging output.
24571 Internally, this sets the @code{yydebug} variable in the expression
24572 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
24573 details. The default is off.
24574 @item show debug parser
24575 Show the current state of expression parser debugging.
24576 @cindex packets, reporting on stdout
24577 @cindex serial connections, debugging
24578 @cindex debug remote protocol
24579 @cindex remote protocol debugging
24580 @cindex display remote packets
24581 @item set debug remote
24582 Turns on or off display of reports on all packets sent back and forth across
24583 the serial line to the remote machine. The info is printed on the
24584 @value{GDBN} standard output stream. The default is off.
24585 @item show debug remote
24586 Displays the state of display of remote packets.
24588 @item set debug separate-debug-file
24589 Turns on or off display of debug output about separate debug file search.
24590 @item show debug separate-debug-file
24591 Displays the state of separate debug file search debug output.
24593 @item set debug serial
24594 Turns on or off display of @value{GDBN} serial debugging info. The
24596 @item show debug serial
24597 Displays the current state of displaying @value{GDBN} serial debugging
24599 @item set debug solib-frv
24600 @cindex FR-V shared-library debugging
24601 Turn on or off debugging messages for FR-V shared-library code.
24602 @item show debug solib-frv
24603 Display the current state of FR-V shared-library code debugging
24605 @item set debug symbol-lookup
24606 @cindex symbol lookup
24607 Turns on or off display of debugging messages related to symbol lookup.
24608 The default is 0 (off).
24609 A value of 1 provides basic information.
24610 A value greater than 1 provides more verbose information.
24611 @item show debug symbol-lookup
24612 Show the current state of symbol lookup debugging messages.
24613 @item set debug symfile
24614 @cindex symbol file functions
24615 Turns on or off display of debugging messages related to symbol file functions.
24616 The default is off. @xref{Files}.
24617 @item show debug symfile
24618 Show the current state of symbol file debugging messages.
24619 @item set debug symtab-create
24620 @cindex symbol table creation
24621 Turns on or off display of debugging messages related to symbol table creation.
24622 The default is 0 (off).
24623 A value of 1 provides basic information.
24624 A value greater than 1 provides more verbose information.
24625 @item show debug symtab-create
24626 Show the current state of symbol table creation debugging.
24627 @item set debug target
24628 @cindex target debugging info
24629 Turns on or off display of @value{GDBN} target debugging info. This info
24630 includes what is going on at the target level of GDB, as it happens. The
24631 default is 0. Set it to 1 to track events, and to 2 to also track the
24632 value of large memory transfers.
24633 @item show debug target
24634 Displays the current state of displaying @value{GDBN} target debugging
24636 @item set debug timestamp
24637 @cindex timestampping debugging info
24638 Turns on or off display of timestamps with @value{GDBN} debugging info.
24639 When enabled, seconds and microseconds are displayed before each debugging
24641 @item show debug timestamp
24642 Displays the current state of displaying timestamps with @value{GDBN}
24644 @item set debug varobj
24645 @cindex variable object debugging info
24646 Turns on or off display of @value{GDBN} variable object debugging
24647 info. The default is off.
24648 @item show debug varobj
24649 Displays the current state of displaying @value{GDBN} variable object
24651 @item set debug xml
24652 @cindex XML parser debugging
24653 Turn on or off debugging messages for built-in XML parsers.
24654 @item show debug xml
24655 Displays the current state of XML debugging messages.
24658 @node Other Misc Settings
24659 @section Other Miscellaneous Settings
24660 @cindex miscellaneous settings
24663 @kindex set interactive-mode
24664 @item set interactive-mode
24665 If @code{on}, forces @value{GDBN} to assume that GDB was started
24666 in a terminal. In practice, this means that @value{GDBN} should wait
24667 for the user to answer queries generated by commands entered at
24668 the command prompt. If @code{off}, forces @value{GDBN} to operate
24669 in the opposite mode, and it uses the default answers to all queries.
24670 If @code{auto} (the default), @value{GDBN} tries to determine whether
24671 its standard input is a terminal, and works in interactive-mode if it
24672 is, non-interactively otherwise.
24674 In the vast majority of cases, the debugger should be able to guess
24675 correctly which mode should be used. But this setting can be useful
24676 in certain specific cases, such as running a MinGW @value{GDBN}
24677 inside a cygwin window.
24679 @kindex show interactive-mode
24680 @item show interactive-mode
24681 Displays whether the debugger is operating in interactive mode or not.
24684 @node Extending GDB
24685 @chapter Extending @value{GDBN}
24686 @cindex extending GDB
24688 @value{GDBN} provides several mechanisms for extension.
24689 @value{GDBN} also provides the ability to automatically load
24690 extensions when it reads a file for debugging. This allows the
24691 user to automatically customize @value{GDBN} for the program
24695 * Sequences:: Canned Sequences of @value{GDBN} Commands
24696 * Python:: Extending @value{GDBN} using Python
24697 * Guile:: Extending @value{GDBN} using Guile
24698 * Auto-loading extensions:: Automatically loading extensions
24699 * Multiple Extension Languages:: Working with multiple extension languages
24700 * Aliases:: Creating new spellings of existing commands
24703 To facilitate the use of extension languages, @value{GDBN} is capable
24704 of evaluating the contents of a file. When doing so, @value{GDBN}
24705 can recognize which extension language is being used by looking at
24706 the filename extension. Files with an unrecognized filename extension
24707 are always treated as a @value{GDBN} Command Files.
24708 @xref{Command Files,, Command files}.
24710 You can control how @value{GDBN} evaluates these files with the following
24714 @kindex set script-extension
24715 @kindex show script-extension
24716 @item set script-extension off
24717 All scripts are always evaluated as @value{GDBN} Command Files.
24719 @item set script-extension soft
24720 The debugger determines the scripting language based on filename
24721 extension. If this scripting language is supported, @value{GDBN}
24722 evaluates the script using that language. Otherwise, it evaluates
24723 the file as a @value{GDBN} Command File.
24725 @item set script-extension strict
24726 The debugger determines the scripting language based on filename
24727 extension, and evaluates the script using that language. If the
24728 language is not supported, then the evaluation fails.
24730 @item show script-extension
24731 Display the current value of the @code{script-extension} option.
24736 @section Canned Sequences of Commands
24738 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
24739 Command Lists}), @value{GDBN} provides two ways to store sequences of
24740 commands for execution as a unit: user-defined commands and command
24744 * Define:: How to define your own commands
24745 * Hooks:: Hooks for user-defined commands
24746 * Command Files:: How to write scripts of commands to be stored in a file
24747 * Output:: Commands for controlled output
24748 * Auto-loading sequences:: Controlling auto-loaded command files
24752 @subsection User-defined Commands
24754 @cindex user-defined command
24755 @cindex arguments, to user-defined commands
24756 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
24757 which you assign a new name as a command. This is done with the
24758 @code{define} command. User commands may accept an unlimited number of arguments
24759 separated by whitespace. Arguments are accessed within the user command
24760 via @code{$arg0@dots{}$argN}. A trivial example:
24764 print $arg0 + $arg1 + $arg2
24769 To execute the command use:
24776 This defines the command @code{adder}, which prints the sum of
24777 its three arguments. Note the arguments are text substitutions, so they may
24778 reference variables, use complex expressions, or even perform inferior
24781 @cindex argument count in user-defined commands
24782 @cindex how many arguments (user-defined commands)
24783 In addition, @code{$argc} may be used to find out how many arguments have
24789 print $arg0 + $arg1
24792 print $arg0 + $arg1 + $arg2
24797 Combining with the @code{eval} command (@pxref{eval}) makes it easier
24798 to process a variable number of arguments:
24805 eval "set $sum = $sum + $arg%d", $i
24815 @item define @var{commandname}
24816 Define a command named @var{commandname}. If there is already a command
24817 by that name, you are asked to confirm that you want to redefine it.
24818 The argument @var{commandname} may be a bare command name consisting of letters,
24819 numbers, dashes, and underscores. It may also start with any predefined
24820 prefix command. For example, @samp{define target my-target} creates
24821 a user-defined @samp{target my-target} command.
24823 The definition of the command is made up of other @value{GDBN} command lines,
24824 which are given following the @code{define} command. The end of these
24825 commands is marked by a line containing @code{end}.
24828 @kindex end@r{ (user-defined commands)}
24829 @item document @var{commandname}
24830 Document the user-defined command @var{commandname}, so that it can be
24831 accessed by @code{help}. The command @var{commandname} must already be
24832 defined. This command reads lines of documentation just as @code{define}
24833 reads the lines of the command definition, ending with @code{end}.
24834 After the @code{document} command is finished, @code{help} on command
24835 @var{commandname} displays the documentation you have written.
24837 You may use the @code{document} command again to change the
24838 documentation of a command. Redefining the command with @code{define}
24839 does not change the documentation.
24841 @kindex dont-repeat
24842 @cindex don't repeat command
24844 Used inside a user-defined command, this tells @value{GDBN} that this
24845 command should not be repeated when the user hits @key{RET}
24846 (@pxref{Command Syntax, repeat last command}).
24848 @kindex help user-defined
24849 @item help user-defined
24850 List all user-defined commands and all python commands defined in class
24851 COMAND_USER. The first line of the documentation or docstring is
24856 @itemx show user @var{commandname}
24857 Display the @value{GDBN} commands used to define @var{commandname} (but
24858 not its documentation). If no @var{commandname} is given, display the
24859 definitions for all user-defined commands.
24860 This does not work for user-defined python commands.
24862 @cindex infinite recursion in user-defined commands
24863 @kindex show max-user-call-depth
24864 @kindex set max-user-call-depth
24865 @item show max-user-call-depth
24866 @itemx set max-user-call-depth
24867 The value of @code{max-user-call-depth} controls how many recursion
24868 levels are allowed in user-defined commands before @value{GDBN} suspects an
24869 infinite recursion and aborts the command.
24870 This does not apply to user-defined python commands.
24873 In addition to the above commands, user-defined commands frequently
24874 use control flow commands, described in @ref{Command Files}.
24876 When user-defined commands are executed, the
24877 commands of the definition are not printed. An error in any command
24878 stops execution of the user-defined command.
24880 If used interactively, commands that would ask for confirmation proceed
24881 without asking when used inside a user-defined command. Many @value{GDBN}
24882 commands that normally print messages to say what they are doing omit the
24883 messages when used in a user-defined command.
24886 @subsection User-defined Command Hooks
24887 @cindex command hooks
24888 @cindex hooks, for commands
24889 @cindex hooks, pre-command
24892 You may define @dfn{hooks}, which are a special kind of user-defined
24893 command. Whenever you run the command @samp{foo}, if the user-defined
24894 command @samp{hook-foo} exists, it is executed (with no arguments)
24895 before that command.
24897 @cindex hooks, post-command
24899 A hook may also be defined which is run after the command you executed.
24900 Whenever you run the command @samp{foo}, if the user-defined command
24901 @samp{hookpost-foo} exists, it is executed (with no arguments) after
24902 that command. Post-execution hooks may exist simultaneously with
24903 pre-execution hooks, for the same command.
24905 It is valid for a hook to call the command which it hooks. If this
24906 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
24908 @c It would be nice if hookpost could be passed a parameter indicating
24909 @c if the command it hooks executed properly or not. FIXME!
24911 @kindex stop@r{, a pseudo-command}
24912 In addition, a pseudo-command, @samp{stop} exists. Defining
24913 (@samp{hook-stop}) makes the associated commands execute every time
24914 execution stops in your program: before breakpoint commands are run,
24915 displays are printed, or the stack frame is printed.
24917 For example, to ignore @code{SIGALRM} signals while
24918 single-stepping, but treat them normally during normal execution,
24923 handle SIGALRM nopass
24927 handle SIGALRM pass
24930 define hook-continue
24931 handle SIGALRM pass
24935 As a further example, to hook at the beginning and end of the @code{echo}
24936 command, and to add extra text to the beginning and end of the message,
24944 define hookpost-echo
24948 (@value{GDBP}) echo Hello World
24949 <<<---Hello World--->>>
24954 You can define a hook for any single-word command in @value{GDBN}, but
24955 not for command aliases; you should define a hook for the basic command
24956 name, e.g.@: @code{backtrace} rather than @code{bt}.
24957 @c FIXME! So how does Joe User discover whether a command is an alias
24959 You can hook a multi-word command by adding @code{hook-} or
24960 @code{hookpost-} to the last word of the command, e.g.@:
24961 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24963 If an error occurs during the execution of your hook, execution of
24964 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24965 (before the command that you actually typed had a chance to run).
24967 If you try to define a hook which does not match any known command, you
24968 get a warning from the @code{define} command.
24970 @node Command Files
24971 @subsection Command Files
24973 @cindex command files
24974 @cindex scripting commands
24975 A command file for @value{GDBN} is a text file made of lines that are
24976 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24977 also be included. An empty line in a command file does nothing; it
24978 does not mean to repeat the last command, as it would from the
24981 You can request the execution of a command file with the @code{source}
24982 command. Note that the @code{source} command is also used to evaluate
24983 scripts that are not Command Files. The exact behavior can be configured
24984 using the @code{script-extension} setting.
24985 @xref{Extending GDB,, Extending GDB}.
24989 @cindex execute commands from a file
24990 @item source [-s] [-v] @var{filename}
24991 Execute the command file @var{filename}.
24994 The lines in a command file are generally executed sequentially,
24995 unless the order of execution is changed by one of the
24996 @emph{flow-control commands} described below. The commands are not
24997 printed as they are executed. An error in any command terminates
24998 execution of the command file and control is returned to the console.
25000 @value{GDBN} first searches for @var{filename} in the current directory.
25001 If the file is not found there, and @var{filename} does not specify a
25002 directory, then @value{GDBN} also looks for the file on the source search path
25003 (specified with the @samp{directory} command);
25004 except that @file{$cdir} is not searched because the compilation directory
25005 is not relevant to scripts.
25007 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
25008 on the search path even if @var{filename} specifies a directory.
25009 The search is done by appending @var{filename} to each element of the
25010 search path. So, for example, if @var{filename} is @file{mylib/myscript}
25011 and the search path contains @file{/home/user} then @value{GDBN} will
25012 look for the script @file{/home/user/mylib/myscript}.
25013 The search is also done if @var{filename} is an absolute path.
25014 For example, if @var{filename} is @file{/tmp/myscript} and
25015 the search path contains @file{/home/user} then @value{GDBN} will
25016 look for the script @file{/home/user/tmp/myscript}.
25017 For DOS-like systems, if @var{filename} contains a drive specification,
25018 it is stripped before concatenation. For example, if @var{filename} is
25019 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
25020 will look for the script @file{c:/tmp/myscript}.
25022 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
25023 each command as it is executed. The option must be given before
25024 @var{filename}, and is interpreted as part of the filename anywhere else.
25026 Commands that would ask for confirmation if used interactively proceed
25027 without asking when used in a command file. Many @value{GDBN} commands that
25028 normally print messages to say what they are doing omit the messages
25029 when called from command files.
25031 @value{GDBN} also accepts command input from standard input. In this
25032 mode, normal output goes to standard output and error output goes to
25033 standard error. Errors in a command file supplied on standard input do
25034 not terminate execution of the command file---execution continues with
25038 gdb < cmds > log 2>&1
25041 (The syntax above will vary depending on the shell used.) This example
25042 will execute commands from the file @file{cmds}. All output and errors
25043 would be directed to @file{log}.
25045 Since commands stored on command files tend to be more general than
25046 commands typed interactively, they frequently need to deal with
25047 complicated situations, such as different or unexpected values of
25048 variables and symbols, changes in how the program being debugged is
25049 built, etc. @value{GDBN} provides a set of flow-control commands to
25050 deal with these complexities. Using these commands, you can write
25051 complex scripts that loop over data structures, execute commands
25052 conditionally, etc.
25059 This command allows to include in your script conditionally executed
25060 commands. The @code{if} command takes a single argument, which is an
25061 expression to evaluate. It is followed by a series of commands that
25062 are executed only if the expression is true (its value is nonzero).
25063 There can then optionally be an @code{else} line, followed by a series
25064 of commands that are only executed if the expression was false. The
25065 end of the list is marked by a line containing @code{end}.
25069 This command allows to write loops. Its syntax is similar to
25070 @code{if}: the command takes a single argument, which is an expression
25071 to evaluate, and must be followed by the commands to execute, one per
25072 line, terminated by an @code{end}. These commands are called the
25073 @dfn{body} of the loop. The commands in the body of @code{while} are
25074 executed repeatedly as long as the expression evaluates to true.
25078 This command exits the @code{while} loop in whose body it is included.
25079 Execution of the script continues after that @code{while}s @code{end}
25082 @kindex loop_continue
25083 @item loop_continue
25084 This command skips the execution of the rest of the body of commands
25085 in the @code{while} loop in whose body it is included. Execution
25086 branches to the beginning of the @code{while} loop, where it evaluates
25087 the controlling expression.
25089 @kindex end@r{ (if/else/while commands)}
25091 Terminate the block of commands that are the body of @code{if},
25092 @code{else}, or @code{while} flow-control commands.
25097 @subsection Commands for Controlled Output
25099 During the execution of a command file or a user-defined command, normal
25100 @value{GDBN} output is suppressed; the only output that appears is what is
25101 explicitly printed by the commands in the definition. This section
25102 describes three commands useful for generating exactly the output you
25107 @item echo @var{text}
25108 @c I do not consider backslash-space a standard C escape sequence
25109 @c because it is not in ANSI.
25110 Print @var{text}. Nonprinting characters can be included in
25111 @var{text} using C escape sequences, such as @samp{\n} to print a
25112 newline. @strong{No newline is printed unless you specify one.}
25113 In addition to the standard C escape sequences, a backslash followed
25114 by a space stands for a space. This is useful for displaying a
25115 string with spaces at the beginning or the end, since leading and
25116 trailing spaces are otherwise trimmed from all arguments.
25117 To print @samp{@w{ }and foo =@w{ }}, use the command
25118 @samp{echo \@w{ }and foo = \@w{ }}.
25120 A backslash at the end of @var{text} can be used, as in C, to continue
25121 the command onto subsequent lines. For example,
25124 echo This is some text\n\
25125 which is continued\n\
25126 onto several lines.\n
25129 produces the same output as
25132 echo This is some text\n
25133 echo which is continued\n
25134 echo onto several lines.\n
25138 @item output @var{expression}
25139 Print the value of @var{expression} and nothing but that value: no
25140 newlines, no @samp{$@var{nn} = }. The value is not entered in the
25141 value history either. @xref{Expressions, ,Expressions}, for more information
25144 @item output/@var{fmt} @var{expression}
25145 Print the value of @var{expression} in format @var{fmt}. You can use
25146 the same formats as for @code{print}. @xref{Output Formats,,Output
25147 Formats}, for more information.
25150 @item printf @var{template}, @var{expressions}@dots{}
25151 Print the values of one or more @var{expressions} under the control of
25152 the string @var{template}. To print several values, make
25153 @var{expressions} be a comma-separated list of individual expressions,
25154 which may be either numbers or pointers. Their values are printed as
25155 specified by @var{template}, exactly as a C program would do by
25156 executing the code below:
25159 printf (@var{template}, @var{expressions}@dots{});
25162 As in @code{C} @code{printf}, ordinary characters in @var{template}
25163 are printed verbatim, while @dfn{conversion specification} introduced
25164 by the @samp{%} character cause subsequent @var{expressions} to be
25165 evaluated, their values converted and formatted according to type and
25166 style information encoded in the conversion specifications, and then
25169 For example, you can print two values in hex like this:
25172 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
25175 @code{printf} supports all the standard @code{C} conversion
25176 specifications, including the flags and modifiers between the @samp{%}
25177 character and the conversion letter, with the following exceptions:
25181 The argument-ordering modifiers, such as @samp{2$}, are not supported.
25184 The modifier @samp{*} is not supported for specifying precision or
25188 The @samp{'} flag (for separation of digits into groups according to
25189 @code{LC_NUMERIC'}) is not supported.
25192 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
25196 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
25199 The conversion letters @samp{a} and @samp{A} are not supported.
25203 Note that the @samp{ll} type modifier is supported only if the
25204 underlying @code{C} implementation used to build @value{GDBN} supports
25205 the @code{long long int} type, and the @samp{L} type modifier is
25206 supported only if @code{long double} type is available.
25208 As in @code{C}, @code{printf} supports simple backslash-escape
25209 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
25210 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
25211 single character. Octal and hexadecimal escape sequences are not
25214 Additionally, @code{printf} supports conversion specifications for DFP
25215 (@dfn{Decimal Floating Point}) types using the following length modifiers
25216 together with a floating point specifier.
25221 @samp{H} for printing @code{Decimal32} types.
25224 @samp{D} for printing @code{Decimal64} types.
25227 @samp{DD} for printing @code{Decimal128} types.
25230 If the underlying @code{C} implementation used to build @value{GDBN} has
25231 support for the three length modifiers for DFP types, other modifiers
25232 such as width and precision will also be available for @value{GDBN} to use.
25234 In case there is no such @code{C} support, no additional modifiers will be
25235 available and the value will be printed in the standard way.
25237 Here's an example of printing DFP types using the above conversion letters:
25239 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
25244 @item eval @var{template}, @var{expressions}@dots{}
25245 Convert the values of one or more @var{expressions} under the control of
25246 the string @var{template} to a command line, and call it.
25250 @node Auto-loading sequences
25251 @subsection Controlling auto-loading native @value{GDBN} scripts
25252 @cindex native script auto-loading
25254 When a new object file is read (for example, due to the @code{file}
25255 command, or because the inferior has loaded a shared library),
25256 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
25257 @xref{Auto-loading extensions}.
25259 Auto-loading can be enabled or disabled,
25260 and the list of auto-loaded scripts can be printed.
25263 @anchor{set auto-load gdb-scripts}
25264 @kindex set auto-load gdb-scripts
25265 @item set auto-load gdb-scripts [on|off]
25266 Enable or disable the auto-loading of canned sequences of commands scripts.
25268 @anchor{show auto-load gdb-scripts}
25269 @kindex show auto-load gdb-scripts
25270 @item show auto-load gdb-scripts
25271 Show whether auto-loading of canned sequences of commands scripts is enabled or
25274 @anchor{info auto-load gdb-scripts}
25275 @kindex info auto-load gdb-scripts
25276 @cindex print list of auto-loaded canned sequences of commands scripts
25277 @item info auto-load gdb-scripts [@var{regexp}]
25278 Print the list of all canned sequences of commands scripts that @value{GDBN}
25282 If @var{regexp} is supplied only canned sequences of commands scripts with
25283 matching names are printed.
25285 @c Python docs live in a separate file.
25286 @include python.texi
25288 @c Guile docs live in a separate file.
25289 @include guile.texi
25291 @node Auto-loading extensions
25292 @section Auto-loading extensions
25293 @cindex auto-loading extensions
25295 @value{GDBN} provides two mechanisms for automatically loading extensions
25296 when a new object file is read (for example, due to the @code{file}
25297 command, or because the inferior has loaded a shared library):
25298 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
25299 section of modern file formats like ELF.
25302 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
25303 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
25304 * Which flavor to choose?::
25307 The auto-loading feature is useful for supplying application-specific
25308 debugging commands and features.
25310 Auto-loading can be enabled or disabled,
25311 and the list of auto-loaded scripts can be printed.
25312 See the @samp{auto-loading} section of each extension language
25313 for more information.
25314 For @value{GDBN} command files see @ref{Auto-loading sequences}.
25315 For Python files see @ref{Python Auto-loading}.
25317 Note that loading of this script file also requires accordingly configured
25318 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25320 @node objfile-gdbdotext file
25321 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
25322 @cindex @file{@var{objfile}-gdb.gdb}
25323 @cindex @file{@var{objfile}-gdb.py}
25324 @cindex @file{@var{objfile}-gdb.scm}
25326 When a new object file is read, @value{GDBN} looks for a file named
25327 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
25328 where @var{objfile} is the object file's name and
25329 where @var{ext} is the file extension for the extension language:
25332 @item @file{@var{objfile}-gdb.gdb}
25333 GDB's own command language
25334 @item @file{@var{objfile}-gdb.py}
25336 @item @file{@var{objfile}-gdb.scm}
25340 @var{script-name} is formed by ensuring that the file name of @var{objfile}
25341 is absolute, following all symlinks, and resolving @code{.} and @code{..}
25342 components, and appending the @file{-gdb.@var{ext}} suffix.
25343 If this file exists and is readable, @value{GDBN} will evaluate it as a
25344 script in the specified extension language.
25346 If this file does not exist, then @value{GDBN} will look for
25347 @var{script-name} file in all of the directories as specified below.
25349 Note that loading of these files requires an accordingly configured
25350 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25352 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
25353 scripts normally according to its @file{.exe} filename. But if no scripts are
25354 found @value{GDBN} also tries script filenames matching the object file without
25355 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
25356 is attempted on any platform. This makes the script filenames compatible
25357 between Unix and MS-Windows hosts.
25360 @anchor{set auto-load scripts-directory}
25361 @kindex set auto-load scripts-directory
25362 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
25363 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
25364 may be delimited by the host platform path separator in use
25365 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
25367 Each entry here needs to be covered also by the security setting
25368 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
25370 @anchor{with-auto-load-dir}
25371 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
25372 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
25373 configuration option @option{--with-auto-load-dir}.
25375 Any reference to @file{$debugdir} will get replaced by
25376 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
25377 reference to @file{$datadir} will get replaced by @var{data-directory} which is
25378 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
25379 @file{$datadir} must be placed as a directory component --- either alone or
25380 delimited by @file{/} or @file{\} directory separators, depending on the host
25383 The list of directories uses path separator (@samp{:} on GNU and Unix
25384 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
25385 to the @env{PATH} environment variable.
25387 @anchor{show auto-load scripts-directory}
25388 @kindex show auto-load scripts-directory
25389 @item show auto-load scripts-directory
25390 Show @value{GDBN} auto-loaded scripts location.
25392 @anchor{add-auto-load-scripts-directory}
25393 @kindex add-auto-load-scripts-directory
25394 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
25395 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
25396 Multiple entries may be delimited by the host platform path separator in use.
25399 @value{GDBN} does not track which files it has already auto-loaded this way.
25400 @value{GDBN} will load the associated script every time the corresponding
25401 @var{objfile} is opened.
25402 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
25403 is evaluated more than once.
25405 @node dotdebug_gdb_scripts section
25406 @subsection The @code{.debug_gdb_scripts} section
25407 @cindex @code{.debug_gdb_scripts} section
25409 For systems using file formats like ELF and COFF,
25410 when @value{GDBN} loads a new object file
25411 it will look for a special section named @code{.debug_gdb_scripts}.
25412 If this section exists, its contents is a list of null-terminated entries
25413 specifying scripts to load. Each entry begins with a non-null prefix byte that
25414 specifies the kind of entry, typically the extension language and whether the
25415 script is in a file or inlined in @code{.debug_gdb_scripts}.
25417 The following entries are supported:
25420 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
25421 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
25422 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
25423 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
25426 @subsubsection Script File Entries
25428 If the entry specifies a file, @value{GDBN} will look for the file first
25429 in the current directory and then along the source search path
25430 (@pxref{Source Path, ,Specifying Source Directories}),
25431 except that @file{$cdir} is not searched, since the compilation
25432 directory is not relevant to scripts.
25434 File entries can be placed in section @code{.debug_gdb_scripts} with,
25435 for example, this GCC macro for Python scripts.
25438 /* Note: The "MS" section flags are to remove duplicates. */
25439 #define DEFINE_GDB_PY_SCRIPT(script_name) \
25441 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
25442 .byte 1 /* Python */\n\
25443 .asciz \"" script_name "\"\n\
25449 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
25450 Then one can reference the macro in a header or source file like this:
25453 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
25456 The script name may include directories if desired.
25458 Note that loading of this script file also requires accordingly configured
25459 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25461 If the macro invocation is put in a header, any application or library
25462 using this header will get a reference to the specified script,
25463 and with the use of @code{"MS"} attributes on the section, the linker
25464 will remove duplicates.
25466 @subsubsection Script Text Entries
25468 Script text entries allow to put the executable script in the entry
25469 itself instead of loading it from a file.
25470 The first line of the entry, everything after the prefix byte and up to
25471 the first newline (@code{0xa}) character, is the script name, and must not
25472 contain any kind of space character, e.g., spaces or tabs.
25473 The rest of the entry, up to the trailing null byte, is the script to
25474 execute in the specified language. The name needs to be unique among
25475 all script names, as @value{GDBN} executes each script only once based
25478 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
25482 #include "symcat.h"
25483 #include "gdb/section-scripts.h"
25485 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
25486 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
25487 ".ascii \"gdb.inlined-script\\n\"\n"
25488 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
25489 ".ascii \" def __init__ (self):\\n\"\n"
25490 ".ascii \" super (test_cmd, self).__init__ ("
25491 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
25492 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
25493 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
25494 ".ascii \"test_cmd ()\\n\"\n"
25500 Loading of inlined scripts requires a properly configured
25501 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
25502 The path to specify in @code{auto-load safe-path} is the path of the file
25503 containing the @code{.debug_gdb_scripts} section.
25505 @node Which flavor to choose?
25506 @subsection Which flavor to choose?
25508 Given the multiple ways of auto-loading extensions, it might not always
25509 be clear which one to choose. This section provides some guidance.
25512 Benefits of the @file{-gdb.@var{ext}} way:
25516 Can be used with file formats that don't support multiple sections.
25519 Ease of finding scripts for public libraries.
25521 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
25522 in the source search path.
25523 For publicly installed libraries, e.g., @file{libstdc++}, there typically
25524 isn't a source directory in which to find the script.
25527 Doesn't require source code additions.
25531 Benefits of the @code{.debug_gdb_scripts} way:
25535 Works with static linking.
25537 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
25538 trigger their loading. When an application is statically linked the only
25539 objfile available is the executable, and it is cumbersome to attach all the
25540 scripts from all the input libraries to the executable's
25541 @file{-gdb.@var{ext}} script.
25544 Works with classes that are entirely inlined.
25546 Some classes can be entirely inlined, and thus there may not be an associated
25547 shared library to attach a @file{-gdb.@var{ext}} script to.
25550 Scripts needn't be copied out of the source tree.
25552 In some circumstances, apps can be built out of large collections of internal
25553 libraries, and the build infrastructure necessary to install the
25554 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
25555 cumbersome. It may be easier to specify the scripts in the
25556 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
25557 top of the source tree to the source search path.
25560 @node Multiple Extension Languages
25561 @section Multiple Extension Languages
25563 The Guile and Python extension languages do not share any state,
25564 and generally do not interfere with each other.
25565 There are some things to be aware of, however.
25567 @subsection Python comes first
25569 Python was @value{GDBN}'s first extension language, and to avoid breaking
25570 existing behaviour Python comes first. This is generally solved by the
25571 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
25572 extension languages, and when it makes a call to an extension language,
25573 (say to pretty-print a value), it tries each in turn until an extension
25574 language indicates it has performed the request (e.g., has returned the
25575 pretty-printed form of a value).
25576 This extends to errors while performing such requests: If an error happens
25577 while, for example, trying to pretty-print an object then the error is
25578 reported and any following extension languages are not tried.
25581 @section Creating new spellings of existing commands
25582 @cindex aliases for commands
25584 It is often useful to define alternate spellings of existing commands.
25585 For example, if a new @value{GDBN} command defined in Python has
25586 a long name to type, it is handy to have an abbreviated version of it
25587 that involves less typing.
25589 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25590 of the @samp{step} command even though it is otherwise an ambiguous
25591 abbreviation of other commands like @samp{set} and @samp{show}.
25593 Aliases are also used to provide shortened or more common versions
25594 of multi-word commands. For example, @value{GDBN} provides the
25595 @samp{tty} alias of the @samp{set inferior-tty} command.
25597 You can define a new alias with the @samp{alias} command.
25602 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25606 @var{ALIAS} specifies the name of the new alias.
25607 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25610 @var{COMMAND} specifies the name of an existing command
25611 that is being aliased.
25613 The @samp{-a} option specifies that the new alias is an abbreviation
25614 of the command. Abbreviations are not shown in command
25615 lists displayed by the @samp{help} command.
25617 The @samp{--} option specifies the end of options,
25618 and is useful when @var{ALIAS} begins with a dash.
25620 Here is a simple example showing how to make an abbreviation
25621 of a command so that there is less to type.
25622 Suppose you were tired of typing @samp{disas}, the current
25623 shortest unambiguous abbreviation of the @samp{disassemble} command
25624 and you wanted an even shorter version named @samp{di}.
25625 The following will accomplish this.
25628 (gdb) alias -a di = disas
25631 Note that aliases are different from user-defined commands.
25632 With a user-defined command, you also need to write documentation
25633 for it with the @samp{document} command.
25634 An alias automatically picks up the documentation of the existing command.
25636 Here is an example where we make @samp{elms} an abbreviation of
25637 @samp{elements} in the @samp{set print elements} command.
25638 This is to show that you can make an abbreviation of any part
25642 (gdb) alias -a set print elms = set print elements
25643 (gdb) alias -a show print elms = show print elements
25644 (gdb) set p elms 20
25646 Limit on string chars or array elements to print is 200.
25649 Note that if you are defining an alias of a @samp{set} command,
25650 and you want to have an alias for the corresponding @samp{show}
25651 command, then you need to define the latter separately.
25653 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25654 @var{ALIAS}, just as they are normally.
25657 (gdb) alias -a set pr elms = set p ele
25660 Finally, here is an example showing the creation of a one word
25661 alias for a more complex command.
25662 This creates alias @samp{spe} of the command @samp{set print elements}.
25665 (gdb) alias spe = set print elements
25670 @chapter Command Interpreters
25671 @cindex command interpreters
25673 @value{GDBN} supports multiple command interpreters, and some command
25674 infrastructure to allow users or user interface writers to switch
25675 between interpreters or run commands in other interpreters.
25677 @value{GDBN} currently supports two command interpreters, the console
25678 interpreter (sometimes called the command-line interpreter or @sc{cli})
25679 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25680 describes both of these interfaces in great detail.
25682 By default, @value{GDBN} will start with the console interpreter.
25683 However, the user may choose to start @value{GDBN} with another
25684 interpreter by specifying the @option{-i} or @option{--interpreter}
25685 startup options. Defined interpreters include:
25689 @cindex console interpreter
25690 The traditional console or command-line interpreter. This is the most often
25691 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25692 @value{GDBN} will use this interpreter.
25695 @cindex mi interpreter
25696 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25697 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25698 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25702 @cindex mi2 interpreter
25703 The current @sc{gdb/mi} interface.
25706 @cindex mi1 interpreter
25707 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25711 @cindex invoke another interpreter
25713 @kindex interpreter-exec
25714 You may execute commands in any interpreter from the current
25715 interpreter using the appropriate command. If you are running the
25716 console interpreter, simply use the @code{interpreter-exec} command:
25719 interpreter-exec mi "-data-list-register-names"
25722 @sc{gdb/mi} has a similar command, although it is only available in versions of
25723 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25725 Note that @code{interpreter-exec} only changes the interpreter for the
25726 duration of the specified command. It does not change the interpreter
25729 @cindex start a new independent interpreter
25731 Although you may only choose a single interpreter at startup, it is
25732 possible to run an independent interpreter on a specified input/output
25733 device (usually a tty).
25735 For example, consider a debugger GUI or IDE that wants to provide a
25736 @value{GDBN} console view. It may do so by embedding a terminal
25737 emulator widget in its GUI, starting @value{GDBN} in the traditional
25738 command-line mode with stdin/stdout/stderr redirected to that
25739 terminal, and then creating an MI interpreter running on a specified
25740 input/output device. The console interpreter created by @value{GDBN}
25741 at startup handles commands the user types in the terminal widget,
25742 while the GUI controls and synchronizes state with @value{GDBN} using
25743 the separate MI interpreter.
25745 To start a new secondary @dfn{user interface} running MI, use the
25746 @code{new-ui} command:
25749 @cindex new user interface
25751 new-ui @var{interpreter} @var{tty}
25754 The @var{interpreter} parameter specifies the interpreter to run.
25755 This accepts the same values as the @code{interpreter-exec} command.
25756 For example, @samp{console}, @samp{mi}, @samp{mi2}, etc. The
25757 @var{tty} parameter specifies the name of the bidirectional file the
25758 interpreter uses for input/output, usually the name of a
25759 pseudoterminal slave on Unix systems. For example:
25762 (@value{GDBP}) new-ui mi /dev/pts/9
25766 runs an MI interpreter on @file{/dev/pts/9}.
25769 @chapter @value{GDBN} Text User Interface
25771 @cindex Text User Interface
25774 * TUI Overview:: TUI overview
25775 * TUI Keys:: TUI key bindings
25776 * TUI Single Key Mode:: TUI single key mode
25777 * TUI Commands:: TUI-specific commands
25778 * TUI Configuration:: TUI configuration variables
25781 The @value{GDBN} Text User Interface (TUI) is a terminal
25782 interface which uses the @code{curses} library to show the source
25783 file, the assembly output, the program registers and @value{GDBN}
25784 commands in separate text windows. The TUI mode is supported only
25785 on platforms where a suitable version of the @code{curses} library
25788 The TUI mode is enabled by default when you invoke @value{GDBN} as
25789 @samp{@value{GDBP} -tui}.
25790 You can also switch in and out of TUI mode while @value{GDBN} runs by
25791 using various TUI commands and key bindings, such as @command{tui
25792 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
25793 @ref{TUI Keys, ,TUI Key Bindings}.
25796 @section TUI Overview
25798 In TUI mode, @value{GDBN} can display several text windows:
25802 This window is the @value{GDBN} command window with the @value{GDBN}
25803 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25804 managed using readline.
25807 The source window shows the source file of the program. The current
25808 line and active breakpoints are displayed in this window.
25811 The assembly window shows the disassembly output of the program.
25814 This window shows the processor registers. Registers are highlighted
25815 when their values change.
25818 The source and assembly windows show the current program position
25819 by highlighting the current line and marking it with a @samp{>} marker.
25820 Breakpoints are indicated with two markers. The first marker
25821 indicates the breakpoint type:
25825 Breakpoint which was hit at least once.
25828 Breakpoint which was never hit.
25831 Hardware breakpoint which was hit at least once.
25834 Hardware breakpoint which was never hit.
25837 The second marker indicates whether the breakpoint is enabled or not:
25841 Breakpoint is enabled.
25844 Breakpoint is disabled.
25847 The source, assembly and register windows are updated when the current
25848 thread changes, when the frame changes, or when the program counter
25851 These windows are not all visible at the same time. The command
25852 window is always visible. The others can be arranged in several
25863 source and assembly,
25866 source and registers, or
25869 assembly and registers.
25872 A status line above the command window shows the following information:
25876 Indicates the current @value{GDBN} target.
25877 (@pxref{Targets, ,Specifying a Debugging Target}).
25880 Gives the current process or thread number.
25881 When no process is being debugged, this field is set to @code{No process}.
25884 Gives the current function name for the selected frame.
25885 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25886 When there is no symbol corresponding to the current program counter,
25887 the string @code{??} is displayed.
25890 Indicates the current line number for the selected frame.
25891 When the current line number is not known, the string @code{??} is displayed.
25894 Indicates the current program counter address.
25898 @section TUI Key Bindings
25899 @cindex TUI key bindings
25901 The TUI installs several key bindings in the readline keymaps
25902 @ifset SYSTEM_READLINE
25903 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25905 @ifclear SYSTEM_READLINE
25906 (@pxref{Command Line Editing}).
25908 The following key bindings are installed for both TUI mode and the
25909 @value{GDBN} standard mode.
25918 Enter or leave the TUI mode. When leaving the TUI mode,
25919 the curses window management stops and @value{GDBN} operates using
25920 its standard mode, writing on the terminal directly. When reentering
25921 the TUI mode, control is given back to the curses windows.
25922 The screen is then refreshed.
25926 Use a TUI layout with only one window. The layout will
25927 either be @samp{source} or @samp{assembly}. When the TUI mode
25928 is not active, it will switch to the TUI mode.
25930 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25934 Use a TUI layout with at least two windows. When the current
25935 layout already has two windows, the next layout with two windows is used.
25936 When a new layout is chosen, one window will always be common to the
25937 previous layout and the new one.
25939 Think of it as the Emacs @kbd{C-x 2} binding.
25943 Change the active window. The TUI associates several key bindings
25944 (like scrolling and arrow keys) with the active window. This command
25945 gives the focus to the next TUI window.
25947 Think of it as the Emacs @kbd{C-x o} binding.
25951 Switch in and out of the TUI SingleKey mode that binds single
25952 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25955 The following key bindings only work in the TUI mode:
25960 Scroll the active window one page up.
25964 Scroll the active window one page down.
25968 Scroll the active window one line up.
25972 Scroll the active window one line down.
25976 Scroll the active window one column left.
25980 Scroll the active window one column right.
25984 Refresh the screen.
25987 Because the arrow keys scroll the active window in the TUI mode, they
25988 are not available for their normal use by readline unless the command
25989 window has the focus. When another window is active, you must use
25990 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25991 and @kbd{C-f} to control the command window.
25993 @node TUI Single Key Mode
25994 @section TUI Single Key Mode
25995 @cindex TUI single key mode
25997 The TUI also provides a @dfn{SingleKey} mode, which binds several
25998 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25999 switch into this mode, where the following key bindings are used:
26002 @kindex c @r{(SingleKey TUI key)}
26006 @kindex d @r{(SingleKey TUI key)}
26010 @kindex f @r{(SingleKey TUI key)}
26014 @kindex n @r{(SingleKey TUI key)}
26018 @kindex o @r{(SingleKey TUI key)}
26020 nexti. The shortcut letter @samp{o} stands for ``step Over''.
26022 @kindex q @r{(SingleKey TUI key)}
26024 exit the SingleKey mode.
26026 @kindex r @r{(SingleKey TUI key)}
26030 @kindex s @r{(SingleKey TUI key)}
26034 @kindex i @r{(SingleKey TUI key)}
26036 stepi. The shortcut letter @samp{i} stands for ``step Into''.
26038 @kindex u @r{(SingleKey TUI key)}
26042 @kindex v @r{(SingleKey TUI key)}
26046 @kindex w @r{(SingleKey TUI key)}
26051 Other keys temporarily switch to the @value{GDBN} command prompt.
26052 The key that was pressed is inserted in the editing buffer so that
26053 it is possible to type most @value{GDBN} commands without interaction
26054 with the TUI SingleKey mode. Once the command is entered the TUI
26055 SingleKey mode is restored. The only way to permanently leave
26056 this mode is by typing @kbd{q} or @kbd{C-x s}.
26060 @section TUI-specific Commands
26061 @cindex TUI commands
26063 The TUI has specific commands to control the text windows.
26064 These commands are always available, even when @value{GDBN} is not in
26065 the TUI mode. When @value{GDBN} is in the standard mode, most
26066 of these commands will automatically switch to the TUI mode.
26068 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26069 terminal, or @value{GDBN} has been started with the machine interface
26070 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26071 these commands will fail with an error, because it would not be
26072 possible or desirable to enable curses window management.
26077 Activate TUI mode. The last active TUI window layout will be used if
26078 TUI mode has prevsiouly been used in the current debugging session,
26079 otherwise a default layout is used.
26082 @kindex tui disable
26083 Disable TUI mode, returning to the console interpreter.
26087 List and give the size of all displayed windows.
26089 @item layout @var{name}
26091 Changes which TUI windows are displayed. In each layout the command
26092 window is always displayed, the @var{name} parameter controls which
26093 additional windows are displayed, and can be any of the following:
26097 Display the next layout.
26100 Display the previous layout.
26103 Display the source and command windows.
26106 Display the assembly and command windows.
26109 Display the source, assembly, and command windows.
26112 When in @code{src} layout display the register, source, and command
26113 windows. When in @code{asm} or @code{split} layout display the
26114 register, assembler, and command windows.
26117 @item focus @var{name}
26119 Changes which TUI window is currently active for scrolling. The
26120 @var{name} parameter can be any of the following:
26124 Make the next window active for scrolling.
26127 Make the previous window active for scrolling.
26130 Make the source window active for scrolling.
26133 Make the assembly window active for scrolling.
26136 Make the register window active for scrolling.
26139 Make the command window active for scrolling.
26144 Refresh the screen. This is similar to typing @kbd{C-L}.
26146 @item tui reg @var{group}
26148 Changes the register group displayed in the tui register window to
26149 @var{group}. If the register window is not currently displayed this
26150 command will cause the register window to be displayed. The list of
26151 register groups, as well as their order is target specific. The
26152 following groups are available on most targets:
26155 Repeatedly selecting this group will cause the display to cycle
26156 through all of the available register groups.
26159 Repeatedly selecting this group will cause the display to cycle
26160 through all of the available register groups in the reverse order to
26164 Display the general registers.
26166 Display the floating point registers.
26168 Display the system registers.
26170 Display the vector registers.
26172 Display all registers.
26177 Update the source window and the current execution point.
26179 @item winheight @var{name} +@var{count}
26180 @itemx winheight @var{name} -@var{count}
26182 Change the height of the window @var{name} by @var{count}
26183 lines. Positive counts increase the height, while negative counts
26184 decrease it. The @var{name} parameter can be one of @code{src} (the
26185 source window), @code{cmd} (the command window), @code{asm} (the
26186 disassembly window), or @code{regs} (the register display window).
26188 @item tabset @var{nchars}
26190 Set the width of tab stops to be @var{nchars} characters. This
26191 setting affects the display of TAB characters in the source and
26195 @node TUI Configuration
26196 @section TUI Configuration Variables
26197 @cindex TUI configuration variables
26199 Several configuration variables control the appearance of TUI windows.
26202 @item set tui border-kind @var{kind}
26203 @kindex set tui border-kind
26204 Select the border appearance for the source, assembly and register windows.
26205 The possible values are the following:
26208 Use a space character to draw the border.
26211 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
26214 Use the Alternate Character Set to draw the border. The border is
26215 drawn using character line graphics if the terminal supports them.
26218 @item set tui border-mode @var{mode}
26219 @kindex set tui border-mode
26220 @itemx set tui active-border-mode @var{mode}
26221 @kindex set tui active-border-mode
26222 Select the display attributes for the borders of the inactive windows
26223 or the active window. The @var{mode} can be one of the following:
26226 Use normal attributes to display the border.
26232 Use reverse video mode.
26235 Use half bright mode.
26237 @item half-standout
26238 Use half bright and standout mode.
26241 Use extra bright or bold mode.
26243 @item bold-standout
26244 Use extra bright or bold and standout mode.
26249 @chapter Using @value{GDBN} under @sc{gnu} Emacs
26252 @cindex @sc{gnu} Emacs
26253 A special interface allows you to use @sc{gnu} Emacs to view (and
26254 edit) the source files for the program you are debugging with
26257 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
26258 executable file you want to debug as an argument. This command starts
26259 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
26260 created Emacs buffer.
26261 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
26263 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
26268 All ``terminal'' input and output goes through an Emacs buffer, called
26271 This applies both to @value{GDBN} commands and their output, and to the input
26272 and output done by the program you are debugging.
26274 This is useful because it means that you can copy the text of previous
26275 commands and input them again; you can even use parts of the output
26278 All the facilities of Emacs' Shell mode are available for interacting
26279 with your program. In particular, you can send signals the usual
26280 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
26284 @value{GDBN} displays source code through Emacs.
26286 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
26287 source file for that frame and puts an arrow (@samp{=>}) at the
26288 left margin of the current line. Emacs uses a separate buffer for
26289 source display, and splits the screen to show both your @value{GDBN} session
26292 Explicit @value{GDBN} @code{list} or search commands still produce output as
26293 usual, but you probably have no reason to use them from Emacs.
26296 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
26297 a graphical mode, enabled by default, which provides further buffers
26298 that can control the execution and describe the state of your program.
26299 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
26301 If you specify an absolute file name when prompted for the @kbd{M-x
26302 gdb} argument, then Emacs sets your current working directory to where
26303 your program resides. If you only specify the file name, then Emacs
26304 sets your current working directory to the directory associated
26305 with the previous buffer. In this case, @value{GDBN} may find your
26306 program by searching your environment's @code{PATH} variable, but on
26307 some operating systems it might not find the source. So, although the
26308 @value{GDBN} input and output session proceeds normally, the auxiliary
26309 buffer does not display the current source and line of execution.
26311 The initial working directory of @value{GDBN} is printed on the top
26312 line of the GUD buffer and this serves as a default for the commands
26313 that specify files for @value{GDBN} to operate on. @xref{Files,
26314 ,Commands to Specify Files}.
26316 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
26317 need to call @value{GDBN} by a different name (for example, if you
26318 keep several configurations around, with different names) you can
26319 customize the Emacs variable @code{gud-gdb-command-name} to run the
26322 In the GUD buffer, you can use these special Emacs commands in
26323 addition to the standard Shell mode commands:
26327 Describe the features of Emacs' GUD Mode.
26330 Execute to another source line, like the @value{GDBN} @code{step} command; also
26331 update the display window to show the current file and location.
26334 Execute to next source line in this function, skipping all function
26335 calls, like the @value{GDBN} @code{next} command. Then update the display window
26336 to show the current file and location.
26339 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
26340 display window accordingly.
26343 Execute until exit from the selected stack frame, like the @value{GDBN}
26344 @code{finish} command.
26347 Continue execution of your program, like the @value{GDBN} @code{continue}
26351 Go up the number of frames indicated by the numeric argument
26352 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
26353 like the @value{GDBN} @code{up} command.
26356 Go down the number of frames indicated by the numeric argument, like the
26357 @value{GDBN} @code{down} command.
26360 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
26361 tells @value{GDBN} to set a breakpoint on the source line point is on.
26363 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
26364 separate frame which shows a backtrace when the GUD buffer is current.
26365 Move point to any frame in the stack and type @key{RET} to make it
26366 become the current frame and display the associated source in the
26367 source buffer. Alternatively, click @kbd{Mouse-2} to make the
26368 selected frame become the current one. In graphical mode, the
26369 speedbar displays watch expressions.
26371 If you accidentally delete the source-display buffer, an easy way to get
26372 it back is to type the command @code{f} in the @value{GDBN} buffer, to
26373 request a frame display; when you run under Emacs, this recreates
26374 the source buffer if necessary to show you the context of the current
26377 The source files displayed in Emacs are in ordinary Emacs buffers
26378 which are visiting the source files in the usual way. You can edit
26379 the files with these buffers if you wish; but keep in mind that @value{GDBN}
26380 communicates with Emacs in terms of line numbers. If you add or
26381 delete lines from the text, the line numbers that @value{GDBN} knows cease
26382 to correspond properly with the code.
26384 A more detailed description of Emacs' interaction with @value{GDBN} is
26385 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
26389 @chapter The @sc{gdb/mi} Interface
26391 @unnumberedsec Function and Purpose
26393 @cindex @sc{gdb/mi}, its purpose
26394 @sc{gdb/mi} is a line based machine oriented text interface to
26395 @value{GDBN} and is activated by specifying using the
26396 @option{--interpreter} command line option (@pxref{Mode Options}). It
26397 is specifically intended to support the development of systems which
26398 use the debugger as just one small component of a larger system.
26400 This chapter is a specification of the @sc{gdb/mi} interface. It is written
26401 in the form of a reference manual.
26403 Note that @sc{gdb/mi} is still under construction, so some of the
26404 features described below are incomplete and subject to change
26405 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
26407 @unnumberedsec Notation and Terminology
26409 @cindex notational conventions, for @sc{gdb/mi}
26410 This chapter uses the following notation:
26414 @code{|} separates two alternatives.
26417 @code{[ @var{something} ]} indicates that @var{something} is optional:
26418 it may or may not be given.
26421 @code{( @var{group} )*} means that @var{group} inside the parentheses
26422 may repeat zero or more times.
26425 @code{( @var{group} )+} means that @var{group} inside the parentheses
26426 may repeat one or more times.
26429 @code{"@var{string}"} means a literal @var{string}.
26433 @heading Dependencies
26437 * GDB/MI General Design::
26438 * GDB/MI Command Syntax::
26439 * GDB/MI Compatibility with CLI::
26440 * GDB/MI Development and Front Ends::
26441 * GDB/MI Output Records::
26442 * GDB/MI Simple Examples::
26443 * GDB/MI Command Description Format::
26444 * GDB/MI Breakpoint Commands::
26445 * GDB/MI Catchpoint Commands::
26446 * GDB/MI Program Context::
26447 * GDB/MI Thread Commands::
26448 * GDB/MI Ada Tasking Commands::
26449 * GDB/MI Program Execution::
26450 * GDB/MI Stack Manipulation::
26451 * GDB/MI Variable Objects::
26452 * GDB/MI Data Manipulation::
26453 * GDB/MI Tracepoint Commands::
26454 * GDB/MI Symbol Query::
26455 * GDB/MI File Commands::
26457 * GDB/MI Kod Commands::
26458 * GDB/MI Memory Overlay Commands::
26459 * GDB/MI Signal Handling Commands::
26461 * GDB/MI Target Manipulation::
26462 * GDB/MI File Transfer Commands::
26463 * GDB/MI Ada Exceptions Commands::
26464 * GDB/MI Support Commands::
26465 * GDB/MI Miscellaneous Commands::
26468 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26469 @node GDB/MI General Design
26470 @section @sc{gdb/mi} General Design
26471 @cindex GDB/MI General Design
26473 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
26474 parts---commands sent to @value{GDBN}, responses to those commands
26475 and notifications. Each command results in exactly one response,
26476 indicating either successful completion of the command, or an error.
26477 For the commands that do not resume the target, the response contains the
26478 requested information. For the commands that resume the target, the
26479 response only indicates whether the target was successfully resumed.
26480 Notifications is the mechanism for reporting changes in the state of the
26481 target, or in @value{GDBN} state, that cannot conveniently be associated with
26482 a command and reported as part of that command response.
26484 The important examples of notifications are:
26488 Exec notifications. These are used to report changes in
26489 target state---when a target is resumed, or stopped. It would not
26490 be feasible to include this information in response of resuming
26491 commands, because one resume commands can result in multiple events in
26492 different threads. Also, quite some time may pass before any event
26493 happens in the target, while a frontend needs to know whether the resuming
26494 command itself was successfully executed.
26497 Console output, and status notifications. Console output
26498 notifications are used to report output of CLI commands, as well as
26499 diagnostics for other commands. Status notifications are used to
26500 report the progress of a long-running operation. Naturally, including
26501 this information in command response would mean no output is produced
26502 until the command is finished, which is undesirable.
26505 General notifications. Commands may have various side effects on
26506 the @value{GDBN} or target state beyond their official purpose. For example,
26507 a command may change the selected thread. Although such changes can
26508 be included in command response, using notification allows for more
26509 orthogonal frontend design.
26513 There's no guarantee that whenever an MI command reports an error,
26514 @value{GDBN} or the target are in any specific state, and especially,
26515 the state is not reverted to the state before the MI command was
26516 processed. Therefore, whenever an MI command results in an error,
26517 we recommend that the frontend refreshes all the information shown in
26518 the user interface.
26522 * Context management::
26523 * Asynchronous and non-stop modes::
26527 @node Context management
26528 @subsection Context management
26530 @subsubsection Threads and Frames
26532 In most cases when @value{GDBN} accesses the target, this access is
26533 done in context of a specific thread and frame (@pxref{Frames}).
26534 Often, even when accessing global data, the target requires that a thread
26535 be specified. The CLI interface maintains the selected thread and frame,
26536 and supplies them to target on each command. This is convenient,
26537 because a command line user would not want to specify that information
26538 explicitly on each command, and because user interacts with
26539 @value{GDBN} via a single terminal, so no confusion is possible as
26540 to what thread and frame are the current ones.
26542 In the case of MI, the concept of selected thread and frame is less
26543 useful. First, a frontend can easily remember this information
26544 itself. Second, a graphical frontend can have more than one window,
26545 each one used for debugging a different thread, and the frontend might
26546 want to access additional threads for internal purposes. This
26547 increases the risk that by relying on implicitly selected thread, the
26548 frontend may be operating on a wrong one. Therefore, each MI command
26549 should explicitly specify which thread and frame to operate on. To
26550 make it possible, each MI command accepts the @samp{--thread} and
26551 @samp{--frame} options, the value to each is @value{GDBN} global
26552 identifier for thread and frame to operate on.
26554 Usually, each top-level window in a frontend allows the user to select
26555 a thread and a frame, and remembers the user selection for further
26556 operations. However, in some cases @value{GDBN} may suggest that the
26557 current thread or frame be changed. For example, when stopping on a
26558 breakpoint it is reasonable to switch to the thread where breakpoint is
26559 hit. For another example, if the user issues the CLI @samp{thread} or
26560 @samp{frame} commands via the frontend, it is desirable to change the
26561 frontend's selection to the one specified by user. @value{GDBN}
26562 communicates the suggestion to change current thread and frame using the
26563 @samp{=thread-selected} notification.
26565 Note that historically, MI shares the selected thread with CLI, so
26566 frontends used the @code{-thread-select} to execute commands in the
26567 right context. However, getting this to work right is cumbersome. The
26568 simplest way is for frontend to emit @code{-thread-select} command
26569 before every command. This doubles the number of commands that need
26570 to be sent. The alternative approach is to suppress @code{-thread-select}
26571 if the selected thread in @value{GDBN} is supposed to be identical to the
26572 thread the frontend wants to operate on. However, getting this
26573 optimization right can be tricky. In particular, if the frontend
26574 sends several commands to @value{GDBN}, and one of the commands changes the
26575 selected thread, then the behaviour of subsequent commands will
26576 change. So, a frontend should either wait for response from such
26577 problematic commands, or explicitly add @code{-thread-select} for
26578 all subsequent commands. No frontend is known to do this exactly
26579 right, so it is suggested to just always pass the @samp{--thread} and
26580 @samp{--frame} options.
26582 @subsubsection Language
26584 The execution of several commands depends on which language is selected.
26585 By default, the current language (@pxref{show language}) is used.
26586 But for commands known to be language-sensitive, it is recommended
26587 to use the @samp{--language} option. This option takes one argument,
26588 which is the name of the language to use while executing the command.
26592 -data-evaluate-expression --language c "sizeof (void*)"
26597 The valid language names are the same names accepted by the
26598 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
26599 @samp{local} or @samp{unknown}.
26601 @node Asynchronous and non-stop modes
26602 @subsection Asynchronous command execution and non-stop mode
26604 On some targets, @value{GDBN} is capable of processing MI commands
26605 even while the target is running. This is called @dfn{asynchronous
26606 command execution} (@pxref{Background Execution}). The frontend may
26607 specify a preferrence for asynchronous execution using the
26608 @code{-gdb-set mi-async 1} command, which should be emitted before
26609 either running the executable or attaching to the target. After the
26610 frontend has started the executable or attached to the target, it can
26611 find if asynchronous execution is enabled using the
26612 @code{-list-target-features} command.
26615 @item -gdb-set mi-async on
26616 @item -gdb-set mi-async off
26617 Set whether MI is in asynchronous mode.
26619 When @code{off}, which is the default, MI execution commands (e.g.,
26620 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
26621 for the program to stop before processing further commands.
26623 When @code{on}, MI execution commands are background execution
26624 commands (e.g., @code{-exec-continue} becomes the equivalent of the
26625 @code{c&} CLI command), and so @value{GDBN} is capable of processing
26626 MI commands even while the target is running.
26628 @item -gdb-show mi-async
26629 Show whether MI asynchronous mode is enabled.
26632 Note: In @value{GDBN} version 7.7 and earlier, this option was called
26633 @code{target-async} instead of @code{mi-async}, and it had the effect
26634 of both putting MI in asynchronous mode and making CLI background
26635 commands possible. CLI background commands are now always possible
26636 ``out of the box'' if the target supports them. The old spelling is
26637 kept as a deprecated alias for backwards compatibility.
26639 Even if @value{GDBN} can accept a command while target is running,
26640 many commands that access the target do not work when the target is
26641 running. Therefore, asynchronous command execution is most useful
26642 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
26643 it is possible to examine the state of one thread, while other threads
26646 When a given thread is running, MI commands that try to access the
26647 target in the context of that thread may not work, or may work only on
26648 some targets. In particular, commands that try to operate on thread's
26649 stack will not work, on any target. Commands that read memory, or
26650 modify breakpoints, may work or not work, depending on the target. Note
26651 that even commands that operate on global state, such as @code{print},
26652 @code{set}, and breakpoint commands, still access the target in the
26653 context of a specific thread, so frontend should try to find a
26654 stopped thread and perform the operation on that thread (using the
26655 @samp{--thread} option).
26657 Which commands will work in the context of a running thread is
26658 highly target dependent. However, the two commands
26659 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
26660 to find the state of a thread, will always work.
26662 @node Thread groups
26663 @subsection Thread groups
26664 @value{GDBN} may be used to debug several processes at the same time.
26665 On some platfroms, @value{GDBN} may support debugging of several
26666 hardware systems, each one having several cores with several different
26667 processes running on each core. This section describes the MI
26668 mechanism to support such debugging scenarios.
26670 The key observation is that regardless of the structure of the
26671 target, MI can have a global list of threads, because most commands that
26672 accept the @samp{--thread} option do not need to know what process that
26673 thread belongs to. Therefore, it is not necessary to introduce
26674 neither additional @samp{--process} option, nor an notion of the
26675 current process in the MI interface. The only strictly new feature
26676 that is required is the ability to find how the threads are grouped
26679 To allow the user to discover such grouping, and to support arbitrary
26680 hierarchy of machines/cores/processes, MI introduces the concept of a
26681 @dfn{thread group}. Thread group is a collection of threads and other
26682 thread groups. A thread group always has a string identifier, a type,
26683 and may have additional attributes specific to the type. A new
26684 command, @code{-list-thread-groups}, returns the list of top-level
26685 thread groups, which correspond to processes that @value{GDBN} is
26686 debugging at the moment. By passing an identifier of a thread group
26687 to the @code{-list-thread-groups} command, it is possible to obtain
26688 the members of specific thread group.
26690 To allow the user to easily discover processes, and other objects, he
26691 wishes to debug, a concept of @dfn{available thread group} is
26692 introduced. Available thread group is an thread group that
26693 @value{GDBN} is not debugging, but that can be attached to, using the
26694 @code{-target-attach} command. The list of available top-level thread
26695 groups can be obtained using @samp{-list-thread-groups --available}.
26696 In general, the content of a thread group may be only retrieved only
26697 after attaching to that thread group.
26699 Thread groups are related to inferiors (@pxref{Inferiors and
26700 Programs}). Each inferior corresponds to a thread group of a special
26701 type @samp{process}, and some additional operations are permitted on
26702 such thread groups.
26704 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26705 @node GDB/MI Command Syntax
26706 @section @sc{gdb/mi} Command Syntax
26709 * GDB/MI Input Syntax::
26710 * GDB/MI Output Syntax::
26713 @node GDB/MI Input Syntax
26714 @subsection @sc{gdb/mi} Input Syntax
26716 @cindex input syntax for @sc{gdb/mi}
26717 @cindex @sc{gdb/mi}, input syntax
26719 @item @var{command} @expansion{}
26720 @code{@var{cli-command} | @var{mi-command}}
26722 @item @var{cli-command} @expansion{}
26723 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26724 @var{cli-command} is any existing @value{GDBN} CLI command.
26726 @item @var{mi-command} @expansion{}
26727 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26728 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26730 @item @var{token} @expansion{}
26731 "any sequence of digits"
26733 @item @var{option} @expansion{}
26734 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26736 @item @var{parameter} @expansion{}
26737 @code{@var{non-blank-sequence} | @var{c-string}}
26739 @item @var{operation} @expansion{}
26740 @emph{any of the operations described in this chapter}
26742 @item @var{non-blank-sequence} @expansion{}
26743 @emph{anything, provided it doesn't contain special characters such as
26744 "-", @var{nl}, """ and of course " "}
26746 @item @var{c-string} @expansion{}
26747 @code{""" @var{seven-bit-iso-c-string-content} """}
26749 @item @var{nl} @expansion{}
26758 The CLI commands are still handled by the @sc{mi} interpreter; their
26759 output is described below.
26762 The @code{@var{token}}, when present, is passed back when the command
26766 Some @sc{mi} commands accept optional arguments as part of the parameter
26767 list. Each option is identified by a leading @samp{-} (dash) and may be
26768 followed by an optional argument parameter. Options occur first in the
26769 parameter list and can be delimited from normal parameters using
26770 @samp{--} (this is useful when some parameters begin with a dash).
26777 We want easy access to the existing CLI syntax (for debugging).
26780 We want it to be easy to spot a @sc{mi} operation.
26783 @node GDB/MI Output Syntax
26784 @subsection @sc{gdb/mi} Output Syntax
26786 @cindex output syntax of @sc{gdb/mi}
26787 @cindex @sc{gdb/mi}, output syntax
26788 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26789 followed, optionally, by a single result record. This result record
26790 is for the most recent command. The sequence of output records is
26791 terminated by @samp{(gdb)}.
26793 If an input command was prefixed with a @code{@var{token}} then the
26794 corresponding output for that command will also be prefixed by that same
26798 @item @var{output} @expansion{}
26799 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26801 @item @var{result-record} @expansion{}
26802 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26804 @item @var{out-of-band-record} @expansion{}
26805 @code{@var{async-record} | @var{stream-record}}
26807 @item @var{async-record} @expansion{}
26808 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26810 @item @var{exec-async-output} @expansion{}
26811 @code{[ @var{token} ] "*" @var{async-output nl}}
26813 @item @var{status-async-output} @expansion{}
26814 @code{[ @var{token} ] "+" @var{async-output nl}}
26816 @item @var{notify-async-output} @expansion{}
26817 @code{[ @var{token} ] "=" @var{async-output nl}}
26819 @item @var{async-output} @expansion{}
26820 @code{@var{async-class} ( "," @var{result} )*}
26822 @item @var{result-class} @expansion{}
26823 @code{"done" | "running" | "connected" | "error" | "exit"}
26825 @item @var{async-class} @expansion{}
26826 @code{"stopped" | @var{others}} (where @var{others} will be added
26827 depending on the needs---this is still in development).
26829 @item @var{result} @expansion{}
26830 @code{ @var{variable} "=" @var{value}}
26832 @item @var{variable} @expansion{}
26833 @code{ @var{string} }
26835 @item @var{value} @expansion{}
26836 @code{ @var{const} | @var{tuple} | @var{list} }
26838 @item @var{const} @expansion{}
26839 @code{@var{c-string}}
26841 @item @var{tuple} @expansion{}
26842 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26844 @item @var{list} @expansion{}
26845 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26846 @var{result} ( "," @var{result} )* "]" }
26848 @item @var{stream-record} @expansion{}
26849 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26851 @item @var{console-stream-output} @expansion{}
26852 @code{"~" @var{c-string nl}}
26854 @item @var{target-stream-output} @expansion{}
26855 @code{"@@" @var{c-string nl}}
26857 @item @var{log-stream-output} @expansion{}
26858 @code{"&" @var{c-string nl}}
26860 @item @var{nl} @expansion{}
26863 @item @var{token} @expansion{}
26864 @emph{any sequence of digits}.
26872 All output sequences end in a single line containing a period.
26875 The @code{@var{token}} is from the corresponding request. Note that
26876 for all async output, while the token is allowed by the grammar and
26877 may be output by future versions of @value{GDBN} for select async
26878 output messages, it is generally omitted. Frontends should treat
26879 all async output as reporting general changes in the state of the
26880 target and there should be no need to associate async output to any
26884 @cindex status output in @sc{gdb/mi}
26885 @var{status-async-output} contains on-going status information about the
26886 progress of a slow operation. It can be discarded. All status output is
26887 prefixed by @samp{+}.
26890 @cindex async output in @sc{gdb/mi}
26891 @var{exec-async-output} contains asynchronous state change on the target
26892 (stopped, started, disappeared). All async output is prefixed by
26896 @cindex notify output in @sc{gdb/mi}
26897 @var{notify-async-output} contains supplementary information that the
26898 client should handle (e.g., a new breakpoint information). All notify
26899 output is prefixed by @samp{=}.
26902 @cindex console output in @sc{gdb/mi}
26903 @var{console-stream-output} is output that should be displayed as is in the
26904 console. It is the textual response to a CLI command. All the console
26905 output is prefixed by @samp{~}.
26908 @cindex target output in @sc{gdb/mi}
26909 @var{target-stream-output} is the output produced by the target program.
26910 All the target output is prefixed by @samp{@@}.
26913 @cindex log output in @sc{gdb/mi}
26914 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26915 instance messages that should be displayed as part of an error log. All
26916 the log output is prefixed by @samp{&}.
26919 @cindex list output in @sc{gdb/mi}
26920 New @sc{gdb/mi} commands should only output @var{lists} containing
26926 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26927 details about the various output records.
26929 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26930 @node GDB/MI Compatibility with CLI
26931 @section @sc{gdb/mi} Compatibility with CLI
26933 @cindex compatibility, @sc{gdb/mi} and CLI
26934 @cindex @sc{gdb/mi}, compatibility with CLI
26936 For the developers convenience CLI commands can be entered directly,
26937 but there may be some unexpected behaviour. For example, commands
26938 that query the user will behave as if the user replied yes, breakpoint
26939 command lists are not executed and some CLI commands, such as
26940 @code{if}, @code{when} and @code{define}, prompt for further input with
26941 @samp{>}, which is not valid MI output.
26943 This feature may be removed at some stage in the future and it is
26944 recommended that front ends use the @code{-interpreter-exec} command
26945 (@pxref{-interpreter-exec}).
26947 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26948 @node GDB/MI Development and Front Ends
26949 @section @sc{gdb/mi} Development and Front Ends
26950 @cindex @sc{gdb/mi} development
26952 The application which takes the MI output and presents the state of the
26953 program being debugged to the user is called a @dfn{front end}.
26955 Although @sc{gdb/mi} is still incomplete, it is currently being used
26956 by a variety of front ends to @value{GDBN}. This makes it difficult
26957 to introduce new functionality without breaking existing usage. This
26958 section tries to minimize the problems by describing how the protocol
26961 Some changes in MI need not break a carefully designed front end, and
26962 for these the MI version will remain unchanged. The following is a
26963 list of changes that may occur within one level, so front ends should
26964 parse MI output in a way that can handle them:
26968 New MI commands may be added.
26971 New fields may be added to the output of any MI command.
26974 The range of values for fields with specified values, e.g.,
26975 @code{in_scope} (@pxref{-var-update}) may be extended.
26977 @c The format of field's content e.g type prefix, may change so parse it
26978 @c at your own risk. Yes, in general?
26980 @c The order of fields may change? Shouldn't really matter but it might
26981 @c resolve inconsistencies.
26984 If the changes are likely to break front ends, the MI version level
26985 will be increased by one. This will allow the front end to parse the
26986 output according to the MI version. Apart from mi0, new versions of
26987 @value{GDBN} will not support old versions of MI and it will be the
26988 responsibility of the front end to work with the new one.
26990 @c Starting with mi3, add a new command -mi-version that prints the MI
26993 The best way to avoid unexpected changes in MI that might break your front
26994 end is to make your project known to @value{GDBN} developers and
26995 follow development on @email{gdb@@sourceware.org} and
26996 @email{gdb-patches@@sourceware.org}.
26997 @cindex mailing lists
26999 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27000 @node GDB/MI Output Records
27001 @section @sc{gdb/mi} Output Records
27004 * GDB/MI Result Records::
27005 * GDB/MI Stream Records::
27006 * GDB/MI Async Records::
27007 * GDB/MI Breakpoint Information::
27008 * GDB/MI Frame Information::
27009 * GDB/MI Thread Information::
27010 * GDB/MI Ada Exception Information::
27013 @node GDB/MI Result Records
27014 @subsection @sc{gdb/mi} Result Records
27016 @cindex result records in @sc{gdb/mi}
27017 @cindex @sc{gdb/mi}, result records
27018 In addition to a number of out-of-band notifications, the response to a
27019 @sc{gdb/mi} command includes one of the following result indications:
27023 @item "^done" [ "," @var{results} ]
27024 The synchronous operation was successful, @code{@var{results}} are the return
27029 This result record is equivalent to @samp{^done}. Historically, it
27030 was output instead of @samp{^done} if the command has resumed the
27031 target. This behaviour is maintained for backward compatibility, but
27032 all frontends should treat @samp{^done} and @samp{^running}
27033 identically and rely on the @samp{*running} output record to determine
27034 which threads are resumed.
27038 @value{GDBN} has connected to a remote target.
27040 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
27042 The operation failed. The @code{msg=@var{c-string}} variable contains
27043 the corresponding error message.
27045 If present, the @code{code=@var{c-string}} variable provides an error
27046 code on which consumers can rely on to detect the corresponding
27047 error condition. At present, only one error code is defined:
27050 @item "undefined-command"
27051 Indicates that the command causing the error does not exist.
27056 @value{GDBN} has terminated.
27060 @node GDB/MI Stream Records
27061 @subsection @sc{gdb/mi} Stream Records
27063 @cindex @sc{gdb/mi}, stream records
27064 @cindex stream records in @sc{gdb/mi}
27065 @value{GDBN} internally maintains a number of output streams: the console, the
27066 target, and the log. The output intended for each of these streams is
27067 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27069 Each stream record begins with a unique @dfn{prefix character} which
27070 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27071 Syntax}). In addition to the prefix, each stream record contains a
27072 @code{@var{string-output}}. This is either raw text (with an implicit new
27073 line) or a quoted C string (which does not contain an implicit newline).
27076 @item "~" @var{string-output}
27077 The console output stream contains text that should be displayed in the
27078 CLI console window. It contains the textual responses to CLI commands.
27080 @item "@@" @var{string-output}
27081 The target output stream contains any textual output from the running
27082 target. This is only present when GDB's event loop is truly
27083 asynchronous, which is currently only the case for remote targets.
27085 @item "&" @var{string-output}
27086 The log stream contains debugging messages being produced by @value{GDBN}'s
27090 @node GDB/MI Async Records
27091 @subsection @sc{gdb/mi} Async Records
27093 @cindex async records in @sc{gdb/mi}
27094 @cindex @sc{gdb/mi}, async records
27095 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27096 additional changes that have occurred. Those changes can either be a
27097 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27098 target activity (e.g., target stopped).
27100 The following is the list of possible async records:
27104 @item *running,thread-id="@var{thread}"
27105 The target is now running. The @var{thread} field can be the global
27106 thread ID of the the thread that is now running, and it can be
27107 @samp{all} if all threads are running. The frontend should assume
27108 that no interaction with a running thread is possible after this
27109 notification is produced. The frontend should not assume that this
27110 notification is output only once for any command. @value{GDBN} may
27111 emit this notification several times, either for different threads,
27112 because it cannot resume all threads together, or even for a single
27113 thread, if the thread must be stepped though some code before letting
27116 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27117 The target has stopped. The @var{reason} field can have one of the
27121 @item breakpoint-hit
27122 A breakpoint was reached.
27123 @item watchpoint-trigger
27124 A watchpoint was triggered.
27125 @item read-watchpoint-trigger
27126 A read watchpoint was triggered.
27127 @item access-watchpoint-trigger
27128 An access watchpoint was triggered.
27129 @item function-finished
27130 An -exec-finish or similar CLI command was accomplished.
27131 @item location-reached
27132 An -exec-until or similar CLI command was accomplished.
27133 @item watchpoint-scope
27134 A watchpoint has gone out of scope.
27135 @item end-stepping-range
27136 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27137 similar CLI command was accomplished.
27138 @item exited-signalled
27139 The inferior exited because of a signal.
27141 The inferior exited.
27142 @item exited-normally
27143 The inferior exited normally.
27144 @item signal-received
27145 A signal was received by the inferior.
27147 The inferior has stopped due to a library being loaded or unloaded.
27148 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27149 set or when a @code{catch load} or @code{catch unload} catchpoint is
27150 in use (@pxref{Set Catchpoints}).
27152 The inferior has forked. This is reported when @code{catch fork}
27153 (@pxref{Set Catchpoints}) has been used.
27155 The inferior has vforked. This is reported in when @code{catch vfork}
27156 (@pxref{Set Catchpoints}) has been used.
27157 @item syscall-entry
27158 The inferior entered a system call. This is reported when @code{catch
27159 syscall} (@pxref{Set Catchpoints}) has been used.
27160 @item syscall-return
27161 The inferior returned from a system call. This is reported when
27162 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27164 The inferior called @code{exec}. This is reported when @code{catch exec}
27165 (@pxref{Set Catchpoints}) has been used.
27168 The @var{id} field identifies the global thread ID of the thread
27169 that directly caused the stop -- for example by hitting a breakpoint.
27170 Depending on whether all-stop
27171 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27172 stop all threads, or only the thread that directly triggered the stop.
27173 If all threads are stopped, the @var{stopped} field will have the
27174 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27175 field will be a list of thread identifiers. Presently, this list will
27176 always include a single thread, but frontend should be prepared to see
27177 several threads in the list. The @var{core} field reports the
27178 processor core on which the stop event has happened. This field may be absent
27179 if such information is not available.
27181 @item =thread-group-added,id="@var{id}"
27182 @itemx =thread-group-removed,id="@var{id}"
27183 A thread group was either added or removed. The @var{id} field
27184 contains the @value{GDBN} identifier of the thread group. When a thread
27185 group is added, it generally might not be associated with a running
27186 process. When a thread group is removed, its id becomes invalid and
27187 cannot be used in any way.
27189 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27190 A thread group became associated with a running program,
27191 either because the program was just started or the thread group
27192 was attached to a program. The @var{id} field contains the
27193 @value{GDBN} identifier of the thread group. The @var{pid} field
27194 contains process identifier, specific to the operating system.
27196 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27197 A thread group is no longer associated with a running program,
27198 either because the program has exited, or because it was detached
27199 from. The @var{id} field contains the @value{GDBN} identifier of the
27200 thread group. The @var{code} field is the exit code of the inferior; it exists
27201 only when the inferior exited with some code.
27203 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27204 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27205 A thread either was created, or has exited. The @var{id} field
27206 contains the global @value{GDBN} identifier of the thread. The @var{gid}
27207 field identifies the thread group this thread belongs to.
27209 @item =thread-selected,id="@var{id}"[,frame="@var{frame}"]
27210 Informs that the selected thread or frame were changed. This notification
27211 is not emitted as result of the @code{-thread-select} or
27212 @code{-stack-select-frame} commands, but is emitted whenever an MI command
27213 that is not documented to change the selected thread and frame actually
27214 changes them. In particular, invoking, directly or indirectly
27215 (via user-defined command), the CLI @code{thread} or @code{frame} commands,
27216 will generate this notification. Changing the thread or frame from another
27217 user interface (see @ref{Interpreters}) will also generate this notification.
27219 The @var{frame} field is only present if the newly selected thread is
27220 stopped. See @ref{GDB/MI Frame Information} for the format of its value.
27222 We suggest that in response to this notification, front ends
27223 highlight the selected thread and cause subsequent commands to apply to
27226 @item =library-loaded,...
27227 Reports that a new library file was loaded by the program. This
27228 notification has 5 fields---@var{id}, @var{target-name},
27229 @var{host-name}, @var{symbols-loaded} and @var{ranges}. The @var{id} field is an
27230 opaque identifier of the library. For remote debugging case,
27231 @var{target-name} and @var{host-name} fields give the name of the
27232 library file on the target, and on the host respectively. For native
27233 debugging, both those fields have the same value. The
27234 @var{symbols-loaded} field is emitted only for backward compatibility
27235 and should not be relied on to convey any useful information. The
27236 @var{thread-group} field, if present, specifies the id of the thread
27237 group in whose context the library was loaded. If the field is
27238 absent, it means the library was loaded in the context of all present
27239 thread groups. The @var{ranges} field specifies the ranges of addresses belonging
27242 @item =library-unloaded,...
27243 Reports that a library was unloaded by the program. This notification
27244 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27245 the same meaning as for the @code{=library-loaded} notification.
27246 The @var{thread-group} field, if present, specifies the id of the
27247 thread group in whose context the library was unloaded. If the field is
27248 absent, it means the library was unloaded in the context of all present
27251 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27252 @itemx =traceframe-changed,end
27253 Reports that the trace frame was changed and its new number is
27254 @var{tfnum}. The number of the tracepoint associated with this trace
27255 frame is @var{tpnum}.
27257 @item =tsv-created,name=@var{name},initial=@var{initial}
27258 Reports that the new trace state variable @var{name} is created with
27259 initial value @var{initial}.
27261 @item =tsv-deleted,name=@var{name}
27262 @itemx =tsv-deleted
27263 Reports that the trace state variable @var{name} is deleted or all
27264 trace state variables are deleted.
27266 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27267 Reports that the trace state variable @var{name} is modified with
27268 the initial value @var{initial}. The current value @var{current} of
27269 trace state variable is optional and is reported if the current
27270 value of trace state variable is known.
27272 @item =breakpoint-created,bkpt=@{...@}
27273 @itemx =breakpoint-modified,bkpt=@{...@}
27274 @itemx =breakpoint-deleted,id=@var{number}
27275 Reports that a breakpoint was created, modified, or deleted,
27276 respectively. Only user-visible breakpoints are reported to the MI
27279 The @var{bkpt} argument is of the same form as returned by the various
27280 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
27281 @var{number} is the ordinal number of the breakpoint.
27283 Note that if a breakpoint is emitted in the result record of a
27284 command, then it will not also be emitted in an async record.
27286 @item =record-started,thread-group="@var{id}",method="@var{method}"[,format="@var{format}"]
27287 @itemx =record-stopped,thread-group="@var{id}"
27288 Execution log recording was either started or stopped on an
27289 inferior. The @var{id} is the @value{GDBN} identifier of the thread
27290 group corresponding to the affected inferior.
27292 The @var{method} field indicates the method used to record execution. If the
27293 method in use supports multiple recording formats, @var{format} will be present
27294 and contain the currently used format. @xref{Process Record and Replay},
27295 for existing method and format values.
27297 @item =cmd-param-changed,param=@var{param},value=@var{value}
27298 Reports that a parameter of the command @code{set @var{param}} is
27299 changed to @var{value}. In the multi-word @code{set} command,
27300 the @var{param} is the whole parameter list to @code{set} command.
27301 For example, In command @code{set check type on}, @var{param}
27302 is @code{check type} and @var{value} is @code{on}.
27304 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
27305 Reports that bytes from @var{addr} to @var{data} + @var{len} were
27306 written in an inferior. The @var{id} is the identifier of the
27307 thread group corresponding to the affected inferior. The optional
27308 @code{type="code"} part is reported if the memory written to holds
27312 @node GDB/MI Breakpoint Information
27313 @subsection @sc{gdb/mi} Breakpoint Information
27315 When @value{GDBN} reports information about a breakpoint, a
27316 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
27321 The breakpoint number. For a breakpoint that represents one location
27322 of a multi-location breakpoint, this will be a dotted pair, like
27326 The type of the breakpoint. For ordinary breakpoints this will be
27327 @samp{breakpoint}, but many values are possible.
27330 If the type of the breakpoint is @samp{catchpoint}, then this
27331 indicates the exact type of catchpoint.
27334 This is the breakpoint disposition---either @samp{del}, meaning that
27335 the breakpoint will be deleted at the next stop, or @samp{keep},
27336 meaning that the breakpoint will not be deleted.
27339 This indicates whether the breakpoint is enabled, in which case the
27340 value is @samp{y}, or disabled, in which case the value is @samp{n}.
27341 Note that this is not the same as the field @code{enable}.
27344 The address of the breakpoint. This may be a hexidecimal number,
27345 giving the address; or the string @samp{<PENDING>}, for a pending
27346 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
27347 multiple locations. This field will not be present if no address can
27348 be determined. For example, a watchpoint does not have an address.
27351 If known, the function in which the breakpoint appears.
27352 If not known, this field is not present.
27355 The name of the source file which contains this function, if known.
27356 If not known, this field is not present.
27359 The full file name of the source file which contains this function, if
27360 known. If not known, this field is not present.
27363 The line number at which this breakpoint appears, if known.
27364 If not known, this field is not present.
27367 If the source file is not known, this field may be provided. If
27368 provided, this holds the address of the breakpoint, possibly followed
27372 If this breakpoint is pending, this field is present and holds the
27373 text used to set the breakpoint, as entered by the user.
27376 Where this breakpoint's condition is evaluated, either @samp{host} or
27380 If this is a thread-specific breakpoint, then this identifies the
27381 thread in which the breakpoint can trigger.
27384 If this breakpoint is restricted to a particular Ada task, then this
27385 field will hold the task identifier.
27388 If the breakpoint is conditional, this is the condition expression.
27391 The ignore count of the breakpoint.
27394 The enable count of the breakpoint.
27396 @item traceframe-usage
27399 @item static-tracepoint-marker-string-id
27400 For a static tracepoint, the name of the static tracepoint marker.
27403 For a masked watchpoint, this is the mask.
27406 A tracepoint's pass count.
27408 @item original-location
27409 The location of the breakpoint as originally specified by the user.
27410 This field is optional.
27413 The number of times the breakpoint has been hit.
27416 This field is only given for tracepoints. This is either @samp{y},
27417 meaning that the tracepoint is installed, or @samp{n}, meaning that it
27421 Some extra data, the exact contents of which are type-dependent.
27425 For example, here is what the output of @code{-break-insert}
27426 (@pxref{GDB/MI Breakpoint Commands}) might be:
27429 -> -break-insert main
27430 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27431 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27432 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27437 @node GDB/MI Frame Information
27438 @subsection @sc{gdb/mi} Frame Information
27440 Response from many MI commands includes an information about stack
27441 frame. This information is a tuple that may have the following
27446 The level of the stack frame. The innermost frame has the level of
27447 zero. This field is always present.
27450 The name of the function corresponding to the frame. This field may
27451 be absent if @value{GDBN} is unable to determine the function name.
27454 The code address for the frame. This field is always present.
27457 The name of the source files that correspond to the frame's code
27458 address. This field may be absent.
27461 The source line corresponding to the frames' code address. This field
27465 The name of the binary file (either executable or shared library) the
27466 corresponds to the frame's code address. This field may be absent.
27470 @node GDB/MI Thread Information
27471 @subsection @sc{gdb/mi} Thread Information
27473 Whenever @value{GDBN} has to report an information about a thread, it
27474 uses a tuple with the following fields. The fields are always present unless
27479 The global numeric id assigned to the thread by @value{GDBN}.
27482 The target-specific string identifying the thread.
27485 Additional information about the thread provided by the target.
27486 It is supposed to be human-readable and not interpreted by the
27487 frontend. This field is optional.
27490 The name of the thread. If the user specified a name using the
27491 @code{thread name} command, then this name is given. Otherwise, if
27492 @value{GDBN} can extract the thread name from the target, then that
27493 name is given. If @value{GDBN} cannot find the thread name, then this
27497 The execution state of the thread, either @samp{stopped} or @samp{running},
27498 depending on whether the thread is presently running.
27501 The stack frame currently executing in the thread. This field is only present
27502 if the thread is stopped. Its format is documented in
27503 @ref{GDB/MI Frame Information}.
27506 The value of this field is an integer number of the processor core the
27507 thread was last seen on. This field is optional.
27510 @node GDB/MI Ada Exception Information
27511 @subsection @sc{gdb/mi} Ada Exception Information
27513 Whenever a @code{*stopped} record is emitted because the program
27514 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
27515 @value{GDBN} provides the name of the exception that was raised via
27516 the @code{exception-name} field. Also, for exceptions that were raised
27517 with an exception message, @value{GDBN} provides that message via
27518 the @code{exception-message} field.
27520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27521 @node GDB/MI Simple Examples
27522 @section Simple Examples of @sc{gdb/mi} Interaction
27523 @cindex @sc{gdb/mi}, simple examples
27525 This subsection presents several simple examples of interaction using
27526 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
27527 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
27528 the output received from @sc{gdb/mi}.
27530 Note the line breaks shown in the examples are here only for
27531 readability, they don't appear in the real output.
27533 @subheading Setting a Breakpoint
27535 Setting a breakpoint generates synchronous output which contains detailed
27536 information of the breakpoint.
27539 -> -break-insert main
27540 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27541 enabled="y",addr="0x08048564",func="main",file="myprog.c",
27542 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
27547 @subheading Program Execution
27549 Program execution generates asynchronous records and MI gives the
27550 reason that execution stopped.
27556 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27557 frame=@{addr="0x08048564",func="main",
27558 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
27559 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
27564 <- *stopped,reason="exited-normally"
27568 @subheading Quitting @value{GDBN}
27570 Quitting @value{GDBN} just prints the result class @samp{^exit}.
27578 Please note that @samp{^exit} is printed immediately, but it might
27579 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
27580 performs necessary cleanups, including killing programs being debugged
27581 or disconnecting from debug hardware, so the frontend should wait till
27582 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
27583 fails to exit in reasonable time.
27585 @subheading A Bad Command
27587 Here's what happens if you pass a non-existent command:
27591 <- ^error,msg="Undefined MI command: rubbish"
27596 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27597 @node GDB/MI Command Description Format
27598 @section @sc{gdb/mi} Command Description Format
27600 The remaining sections describe blocks of commands. Each block of
27601 commands is laid out in a fashion similar to this section.
27603 @subheading Motivation
27605 The motivation for this collection of commands.
27607 @subheading Introduction
27609 A brief introduction to this collection of commands as a whole.
27611 @subheading Commands
27613 For each command in the block, the following is described:
27615 @subsubheading Synopsis
27618 -command @var{args}@dots{}
27621 @subsubheading Result
27623 @subsubheading @value{GDBN} Command
27625 The corresponding @value{GDBN} CLI command(s), if any.
27627 @subsubheading Example
27629 Example(s) formatted for readability. Some of the described commands have
27630 not been implemented yet and these are labeled N.A.@: (not available).
27633 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27634 @node GDB/MI Breakpoint Commands
27635 @section @sc{gdb/mi} Breakpoint Commands
27637 @cindex breakpoint commands for @sc{gdb/mi}
27638 @cindex @sc{gdb/mi}, breakpoint commands
27639 This section documents @sc{gdb/mi} commands for manipulating
27642 @subheading The @code{-break-after} Command
27643 @findex -break-after
27645 @subsubheading Synopsis
27648 -break-after @var{number} @var{count}
27651 The breakpoint number @var{number} is not in effect until it has been
27652 hit @var{count} times. To see how this is reflected in the output of
27653 the @samp{-break-list} command, see the description of the
27654 @samp{-break-list} command below.
27656 @subsubheading @value{GDBN} Command
27658 The corresponding @value{GDBN} command is @samp{ignore}.
27660 @subsubheading Example
27665 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27666 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27667 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27675 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27676 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27677 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27678 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27679 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27680 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27681 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27682 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27683 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27684 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
27689 @subheading The @code{-break-catch} Command
27690 @findex -break-catch
27693 @subheading The @code{-break-commands} Command
27694 @findex -break-commands
27696 @subsubheading Synopsis
27699 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
27702 Specifies the CLI commands that should be executed when breakpoint
27703 @var{number} is hit. The parameters @var{command1} to @var{commandN}
27704 are the commands. If no command is specified, any previously-set
27705 commands are cleared. @xref{Break Commands}. Typical use of this
27706 functionality is tracing a program, that is, printing of values of
27707 some variables whenever breakpoint is hit and then continuing.
27709 @subsubheading @value{GDBN} Command
27711 The corresponding @value{GDBN} command is @samp{commands}.
27713 @subsubheading Example
27718 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
27719 enabled="y",addr="0x000100d0",func="main",file="hello.c",
27720 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
27723 -break-commands 1 "print v" "continue"
27728 @subheading The @code{-break-condition} Command
27729 @findex -break-condition
27731 @subsubheading Synopsis
27734 -break-condition @var{number} @var{expr}
27737 Breakpoint @var{number} will stop the program only if the condition in
27738 @var{expr} is true. The condition becomes part of the
27739 @samp{-break-list} output (see the description of the @samp{-break-list}
27742 @subsubheading @value{GDBN} Command
27744 The corresponding @value{GDBN} command is @samp{condition}.
27746 @subsubheading Example
27750 -break-condition 1 1
27754 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27755 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27756 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27757 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27758 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27759 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27760 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27761 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27762 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27763 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
27767 @subheading The @code{-break-delete} Command
27768 @findex -break-delete
27770 @subsubheading Synopsis
27773 -break-delete ( @var{breakpoint} )+
27776 Delete the breakpoint(s) whose number(s) are specified in the argument
27777 list. This is obviously reflected in the breakpoint list.
27779 @subsubheading @value{GDBN} Command
27781 The corresponding @value{GDBN} command is @samp{delete}.
27783 @subsubheading Example
27791 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27792 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27793 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27794 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27795 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27796 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27797 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27802 @subheading The @code{-break-disable} Command
27803 @findex -break-disable
27805 @subsubheading Synopsis
27808 -break-disable ( @var{breakpoint} )+
27811 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
27812 break list is now set to @samp{n} for the named @var{breakpoint}(s).
27814 @subsubheading @value{GDBN} Command
27816 The corresponding @value{GDBN} command is @samp{disable}.
27818 @subsubheading Example
27826 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27827 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27828 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27829 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27830 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27831 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27832 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27833 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
27834 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27835 line="5",thread-groups=["i1"],times="0"@}]@}
27839 @subheading The @code{-break-enable} Command
27840 @findex -break-enable
27842 @subsubheading Synopsis
27845 -break-enable ( @var{breakpoint} )+
27848 Enable (previously disabled) @var{breakpoint}(s).
27850 @subsubheading @value{GDBN} Command
27852 The corresponding @value{GDBN} command is @samp{enable}.
27854 @subsubheading Example
27862 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27863 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27864 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27865 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27866 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27867 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27868 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27869 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27870 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
27871 line="5",thread-groups=["i1"],times="0"@}]@}
27875 @subheading The @code{-break-info} Command
27876 @findex -break-info
27878 @subsubheading Synopsis
27881 -break-info @var{breakpoint}
27885 Get information about a single breakpoint.
27887 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
27888 Information}, for details on the format of each breakpoint in the
27891 @subsubheading @value{GDBN} Command
27893 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
27895 @subsubheading Example
27898 @subheading The @code{-break-insert} Command
27899 @findex -break-insert
27900 @anchor{-break-insert}
27902 @subsubheading Synopsis
27905 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
27906 [ -c @var{condition} ] [ -i @var{ignore-count} ]
27907 [ -p @var{thread-id} ] [ @var{location} ]
27911 If specified, @var{location}, can be one of:
27914 @item linespec location
27915 A linespec location. @xref{Linespec Locations}.
27917 @item explicit location
27918 An explicit location. @sc{gdb/mi} explicit locations are
27919 analogous to the CLI's explicit locations using the option names
27920 listed below. @xref{Explicit Locations}.
27923 @item --source @var{filename}
27924 The source file name of the location. This option requires the use
27925 of either @samp{--function} or @samp{--line}.
27927 @item --function @var{function}
27928 The name of a function or method.
27930 @item --label @var{label}
27931 The name of a label.
27933 @item --line @var{lineoffset}
27934 An absolute or relative line offset from the start of the location.
27937 @item address location
27938 An address location, *@var{address}. @xref{Address Locations}.
27942 The possible optional parameters of this command are:
27946 Insert a temporary breakpoint.
27948 Insert a hardware breakpoint.
27950 If @var{location} cannot be parsed (for example if it
27951 refers to unknown files or functions), create a pending
27952 breakpoint. Without this flag, @value{GDBN} will report
27953 an error, and won't create a breakpoint, if @var{location}
27956 Create a disabled breakpoint.
27958 Create a tracepoint. @xref{Tracepoints}. When this parameter
27959 is used together with @samp{-h}, a fast tracepoint is created.
27960 @item -c @var{condition}
27961 Make the breakpoint conditional on @var{condition}.
27962 @item -i @var{ignore-count}
27963 Initialize the @var{ignore-count}.
27964 @item -p @var{thread-id}
27965 Restrict the breakpoint to the thread with the specified global
27969 @subsubheading Result
27971 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27972 resulting breakpoint.
27974 Note: this format is open to change.
27975 @c An out-of-band breakpoint instead of part of the result?
27977 @subsubheading @value{GDBN} Command
27979 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27980 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
27982 @subsubheading Example
27987 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27988 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
27991 -break-insert -t foo
27992 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27993 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
27997 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27998 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27999 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28000 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28001 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28002 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28003 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28004 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28005 addr="0x0001072c", func="main",file="recursive2.c",
28006 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28008 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28009 addr="0x00010774",func="foo",file="recursive2.c",
28010 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28013 @c -break-insert -r foo.*
28014 @c ~int foo(int, int);
28015 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28016 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28021 @subheading The @code{-dprintf-insert} Command
28022 @findex -dprintf-insert
28024 @subsubheading Synopsis
28027 -dprintf-insert [ -t ] [ -f ] [ -d ]
28028 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28029 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
28034 If supplied, @var{location} may be specified the same way as for
28035 the @code{-break-insert} command. @xref{-break-insert}.
28037 The possible optional parameters of this command are:
28041 Insert a temporary breakpoint.
28043 If @var{location} cannot be parsed (for example, if it
28044 refers to unknown files or functions), create a pending
28045 breakpoint. Without this flag, @value{GDBN} will report
28046 an error, and won't create a breakpoint, if @var{location}
28049 Create a disabled breakpoint.
28050 @item -c @var{condition}
28051 Make the breakpoint conditional on @var{condition}.
28052 @item -i @var{ignore-count}
28053 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
28054 to @var{ignore-count}.
28055 @item -p @var{thread-id}
28056 Restrict the breakpoint to the thread with the specified global
28060 @subsubheading Result
28062 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28063 resulting breakpoint.
28065 @c An out-of-band breakpoint instead of part of the result?
28067 @subsubheading @value{GDBN} Command
28069 The corresponding @value{GDBN} command is @samp{dprintf}.
28071 @subsubheading Example
28075 4-dprintf-insert foo "At foo entry\n"
28076 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
28077 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
28078 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
28079 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
28080 original-location="foo"@}
28082 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
28083 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
28084 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
28085 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
28086 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
28087 original-location="mi-dprintf.c:26"@}
28091 @subheading The @code{-break-list} Command
28092 @findex -break-list
28094 @subsubheading Synopsis
28100 Displays the list of inserted breakpoints, showing the following fields:
28104 number of the breakpoint
28106 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28108 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28111 is the breakpoint enabled or no: @samp{y} or @samp{n}
28113 memory location at which the breakpoint is set
28115 logical location of the breakpoint, expressed by function name, file
28117 @item Thread-groups
28118 list of thread groups to which this breakpoint applies
28120 number of times the breakpoint has been hit
28123 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28124 @code{body} field is an empty list.
28126 @subsubheading @value{GDBN} Command
28128 The corresponding @value{GDBN} command is @samp{info break}.
28130 @subsubheading Example
28135 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28136 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28137 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28138 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28139 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28140 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28141 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28142 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28143 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28145 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28146 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28147 line="13",thread-groups=["i1"],times="0"@}]@}
28151 Here's an example of the result when there are no breakpoints:
28156 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28157 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28158 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28159 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28160 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28161 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28162 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28167 @subheading The @code{-break-passcount} Command
28168 @findex -break-passcount
28170 @subsubheading Synopsis
28173 -break-passcount @var{tracepoint-number} @var{passcount}
28176 Set the passcount for tracepoint @var{tracepoint-number} to
28177 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28178 is not a tracepoint, error is emitted. This corresponds to CLI
28179 command @samp{passcount}.
28181 @subheading The @code{-break-watch} Command
28182 @findex -break-watch
28184 @subsubheading Synopsis
28187 -break-watch [ -a | -r ]
28190 Create a watchpoint. With the @samp{-a} option it will create an
28191 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28192 read from or on a write to the memory location. With the @samp{-r}
28193 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28194 trigger only when the memory location is accessed for reading. Without
28195 either of the options, the watchpoint created is a regular watchpoint,
28196 i.e., it will trigger when the memory location is accessed for writing.
28197 @xref{Set Watchpoints, , Setting Watchpoints}.
28199 Note that @samp{-break-list} will report a single list of watchpoints and
28200 breakpoints inserted.
28202 @subsubheading @value{GDBN} Command
28204 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28207 @subsubheading Example
28209 Setting a watchpoint on a variable in the @code{main} function:
28214 ^done,wpt=@{number="2",exp="x"@}
28219 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28220 value=@{old="-268439212",new="55"@},
28221 frame=@{func="main",args=[],file="recursive2.c",
28222 fullname="/home/foo/bar/recursive2.c",line="5"@}
28226 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28227 the program execution twice: first for the variable changing value, then
28228 for the watchpoint going out of scope.
28233 ^done,wpt=@{number="5",exp="C"@}
28238 *stopped,reason="watchpoint-trigger",
28239 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28240 frame=@{func="callee4",args=[],
28241 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28242 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28247 *stopped,reason="watchpoint-scope",wpnum="5",
28248 frame=@{func="callee3",args=[@{name="strarg",
28249 value="0x11940 \"A string argument.\""@}],
28250 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28251 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28255 Listing breakpoints and watchpoints, at different points in the program
28256 execution. Note that once the watchpoint goes out of scope, it is
28262 ^done,wpt=@{number="2",exp="C"@}
28265 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28266 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28267 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28268 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28269 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28270 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28271 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28272 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28273 addr="0x00010734",func="callee4",
28274 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28275 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28277 bkpt=@{number="2",type="watchpoint",disp="keep",
28278 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28283 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28284 value=@{old="-276895068",new="3"@},
28285 frame=@{func="callee4",args=[],
28286 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28287 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28290 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28291 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28292 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28293 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28294 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28295 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28296 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28297 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28298 addr="0x00010734",func="callee4",
28299 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28300 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28302 bkpt=@{number="2",type="watchpoint",disp="keep",
28303 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28307 ^done,reason="watchpoint-scope",wpnum="2",
28308 frame=@{func="callee3",args=[@{name="strarg",
28309 value="0x11940 \"A string argument.\""@}],
28310 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28311 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28314 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28315 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28316 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28317 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28318 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28319 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28320 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28321 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28322 addr="0x00010734",func="callee4",
28323 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28324 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28325 thread-groups=["i1"],times="1"@}]@}
28330 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28331 @node GDB/MI Catchpoint Commands
28332 @section @sc{gdb/mi} Catchpoint Commands
28334 This section documents @sc{gdb/mi} commands for manipulating
28338 * Shared Library GDB/MI Catchpoint Commands::
28339 * Ada Exception GDB/MI Catchpoint Commands::
28342 @node Shared Library GDB/MI Catchpoint Commands
28343 @subsection Shared Library @sc{gdb/mi} Catchpoints
28345 @subheading The @code{-catch-load} Command
28346 @findex -catch-load
28348 @subsubheading Synopsis
28351 -catch-load [ -t ] [ -d ] @var{regexp}
28354 Add a catchpoint for library load events. If the @samp{-t} option is used,
28355 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28356 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28357 in a disabled state. The @samp{regexp} argument is a regular
28358 expression used to match the name of the loaded library.
28361 @subsubheading @value{GDBN} Command
28363 The corresponding @value{GDBN} command is @samp{catch load}.
28365 @subsubheading Example
28368 -catch-load -t foo.so
28369 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28370 what="load of library matching foo.so",catch-type="load",times="0"@}
28375 @subheading The @code{-catch-unload} Command
28376 @findex -catch-unload
28378 @subsubheading Synopsis
28381 -catch-unload [ -t ] [ -d ] @var{regexp}
28384 Add a catchpoint for library unload events. If the @samp{-t} option is
28385 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28386 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28387 created in a disabled state. The @samp{regexp} argument is a regular
28388 expression used to match the name of the unloaded library.
28390 @subsubheading @value{GDBN} Command
28392 The corresponding @value{GDBN} command is @samp{catch unload}.
28394 @subsubheading Example
28397 -catch-unload -d bar.so
28398 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
28399 what="load of library matching bar.so",catch-type="unload",times="0"@}
28403 @node Ada Exception GDB/MI Catchpoint Commands
28404 @subsection Ada Exception @sc{gdb/mi} Catchpoints
28406 The following @sc{gdb/mi} commands can be used to create catchpoints
28407 that stop the execution when Ada exceptions are being raised.
28409 @subheading The @code{-catch-assert} Command
28410 @findex -catch-assert
28412 @subsubheading Synopsis
28415 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
28418 Add a catchpoint for failed Ada assertions.
28420 The possible optional parameters for this command are:
28423 @item -c @var{condition}
28424 Make the catchpoint conditional on @var{condition}.
28426 Create a disabled catchpoint.
28428 Create a temporary catchpoint.
28431 @subsubheading @value{GDBN} Command
28433 The corresponding @value{GDBN} command is @samp{catch assert}.
28435 @subsubheading Example
28439 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
28440 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
28441 thread-groups=["i1"],times="0",
28442 original-location="__gnat_debug_raise_assert_failure"@}
28446 @subheading The @code{-catch-exception} Command
28447 @findex -catch-exception
28449 @subsubheading Synopsis
28452 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
28456 Add a catchpoint stopping when Ada exceptions are raised.
28457 By default, the command stops the program when any Ada exception
28458 gets raised. But it is also possible, by using some of the
28459 optional parameters described below, to create more selective
28462 The possible optional parameters for this command are:
28465 @item -c @var{condition}
28466 Make the catchpoint conditional on @var{condition}.
28468 Create a disabled catchpoint.
28469 @item -e @var{exception-name}
28470 Only stop when @var{exception-name} is raised. This option cannot
28471 be used combined with @samp{-u}.
28473 Create a temporary catchpoint.
28475 Stop only when an unhandled exception gets raised. This option
28476 cannot be used combined with @samp{-e}.
28479 @subsubheading @value{GDBN} Command
28481 The corresponding @value{GDBN} commands are @samp{catch exception}
28482 and @samp{catch exception unhandled}.
28484 @subsubheading Example
28487 -catch-exception -e Program_Error
28488 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
28489 enabled="y",addr="0x0000000000404874",
28490 what="`Program_Error' Ada exception", thread-groups=["i1"],
28491 times="0",original-location="__gnat_debug_raise_exception"@}
28495 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28496 @node GDB/MI Program Context
28497 @section @sc{gdb/mi} Program Context
28499 @subheading The @code{-exec-arguments} Command
28500 @findex -exec-arguments
28503 @subsubheading Synopsis
28506 -exec-arguments @var{args}
28509 Set the inferior program arguments, to be used in the next
28512 @subsubheading @value{GDBN} Command
28514 The corresponding @value{GDBN} command is @samp{set args}.
28516 @subsubheading Example
28520 -exec-arguments -v word
28527 @subheading The @code{-exec-show-arguments} Command
28528 @findex -exec-show-arguments
28530 @subsubheading Synopsis
28533 -exec-show-arguments
28536 Print the arguments of the program.
28538 @subsubheading @value{GDBN} Command
28540 The corresponding @value{GDBN} command is @samp{show args}.
28542 @subsubheading Example
28547 @subheading The @code{-environment-cd} Command
28548 @findex -environment-cd
28550 @subsubheading Synopsis
28553 -environment-cd @var{pathdir}
28556 Set @value{GDBN}'s working directory.
28558 @subsubheading @value{GDBN} Command
28560 The corresponding @value{GDBN} command is @samp{cd}.
28562 @subsubheading Example
28566 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28572 @subheading The @code{-environment-directory} Command
28573 @findex -environment-directory
28575 @subsubheading Synopsis
28578 -environment-directory [ -r ] [ @var{pathdir} ]+
28581 Add directories @var{pathdir} to beginning of search path for source files.
28582 If the @samp{-r} option is used, the search path is reset to the default
28583 search path. If directories @var{pathdir} are supplied in addition to the
28584 @samp{-r} option, the search path is first reset and then addition
28586 Multiple directories may be specified, separated by blanks. Specifying
28587 multiple directories in a single command
28588 results in the directories added to the beginning of the
28589 search path in the same order they were presented in the command.
28590 If blanks are needed as
28591 part of a directory name, double-quotes should be used around
28592 the name. In the command output, the path will show up separated
28593 by the system directory-separator character. The directory-separator
28594 character must not be used
28595 in any directory name.
28596 If no directories are specified, the current search path is displayed.
28598 @subsubheading @value{GDBN} Command
28600 The corresponding @value{GDBN} command is @samp{dir}.
28602 @subsubheading Example
28606 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
28607 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28609 -environment-directory ""
28610 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
28612 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
28613 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
28615 -environment-directory -r
28616 ^done,source-path="$cdir:$cwd"
28621 @subheading The @code{-environment-path} Command
28622 @findex -environment-path
28624 @subsubheading Synopsis
28627 -environment-path [ -r ] [ @var{pathdir} ]+
28630 Add directories @var{pathdir} to beginning of search path for object files.
28631 If the @samp{-r} option is used, the search path is reset to the original
28632 search path that existed at gdb start-up. If directories @var{pathdir} are
28633 supplied in addition to the
28634 @samp{-r} option, the search path is first reset and then addition
28636 Multiple directories may be specified, separated by blanks. Specifying
28637 multiple directories in a single command
28638 results in the directories added to the beginning of the
28639 search path in the same order they were presented in the command.
28640 If blanks are needed as
28641 part of a directory name, double-quotes should be used around
28642 the name. In the command output, the path will show up separated
28643 by the system directory-separator character. The directory-separator
28644 character must not be used
28645 in any directory name.
28646 If no directories are specified, the current path is displayed.
28649 @subsubheading @value{GDBN} Command
28651 The corresponding @value{GDBN} command is @samp{path}.
28653 @subsubheading Example
28658 ^done,path="/usr/bin"
28660 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
28661 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
28663 -environment-path -r /usr/local/bin
28664 ^done,path="/usr/local/bin:/usr/bin"
28669 @subheading The @code{-environment-pwd} Command
28670 @findex -environment-pwd
28672 @subsubheading Synopsis
28678 Show the current working directory.
28680 @subsubheading @value{GDBN} Command
28682 The corresponding @value{GDBN} command is @samp{pwd}.
28684 @subsubheading Example
28689 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
28693 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28694 @node GDB/MI Thread Commands
28695 @section @sc{gdb/mi} Thread Commands
28698 @subheading The @code{-thread-info} Command
28699 @findex -thread-info
28701 @subsubheading Synopsis
28704 -thread-info [ @var{thread-id} ]
28707 Reports information about either a specific thread, if the
28708 @var{thread-id} parameter is present, or about all threads.
28709 @var{thread-id} is the thread's global thread ID. When printing
28710 information about all threads, also reports the global ID of the
28713 @subsubheading @value{GDBN} Command
28715 The @samp{info thread} command prints the same information
28718 @subsubheading Result
28720 The result contains the following attributes:
28724 A list of threads. The format of the elements of the list is described in
28725 @ref{GDB/MI Thread Information}.
28727 @item current-thread-id
28728 The global id of the currently selected thread. This field is omitted if there
28729 is no selected thread (for example, when the selected inferior is not running,
28730 and therefore has no threads) or if a @var{thread-id} argument was passed to
28735 @subsubheading Example
28740 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28741 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
28742 args=[]@},state="running"@},
28743 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28744 frame=@{level="0",addr="0x0804891f",func="foo",
28745 args=[@{name="i",value="10"@}],
28746 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
28747 state="running"@}],
28748 current-thread-id="1"
28752 @subheading The @code{-thread-list-ids} Command
28753 @findex -thread-list-ids
28755 @subsubheading Synopsis
28761 Produces a list of the currently known global @value{GDBN} thread ids.
28762 At the end of the list it also prints the total number of such
28765 This command is retained for historical reasons, the
28766 @code{-thread-info} command should be used instead.
28768 @subsubheading @value{GDBN} Command
28770 Part of @samp{info threads} supplies the same information.
28772 @subsubheading Example
28777 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28778 current-thread-id="1",number-of-threads="3"
28783 @subheading The @code{-thread-select} Command
28784 @findex -thread-select
28786 @subsubheading Synopsis
28789 -thread-select @var{thread-id}
28792 Make thread with global thread number @var{thread-id} the current
28793 thread. It prints the number of the new current thread, and the
28794 topmost frame for that thread.
28796 This command is deprecated in favor of explicitly using the
28797 @samp{--thread} option to each command.
28799 @subsubheading @value{GDBN} Command
28801 The corresponding @value{GDBN} command is @samp{thread}.
28803 @subsubheading Example
28810 *stopped,reason="end-stepping-range",thread-id="2",line="187",
28811 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
28815 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
28816 number-of-threads="3"
28819 ^done,new-thread-id="3",
28820 frame=@{level="0",func="vprintf",
28821 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
28822 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
28826 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28827 @node GDB/MI Ada Tasking Commands
28828 @section @sc{gdb/mi} Ada Tasking Commands
28830 @subheading The @code{-ada-task-info} Command
28831 @findex -ada-task-info
28833 @subsubheading Synopsis
28836 -ada-task-info [ @var{task-id} ]
28839 Reports information about either a specific Ada task, if the
28840 @var{task-id} parameter is present, or about all Ada tasks.
28842 @subsubheading @value{GDBN} Command
28844 The @samp{info tasks} command prints the same information
28845 about all Ada tasks (@pxref{Ada Tasks}).
28847 @subsubheading Result
28849 The result is a table of Ada tasks. The following columns are
28850 defined for each Ada task:
28854 This field exists only for the current thread. It has the value @samp{*}.
28857 The identifier that @value{GDBN} uses to refer to the Ada task.
28860 The identifier that the target uses to refer to the Ada task.
28863 The global thread identifier of the thread corresponding to the Ada
28866 This field should always exist, as Ada tasks are always implemented
28867 on top of a thread. But if @value{GDBN} cannot find this corresponding
28868 thread for any reason, the field is omitted.
28871 This field exists only when the task was created by another task.
28872 In this case, it provides the ID of the parent task.
28875 The base priority of the task.
28878 The current state of the task. For a detailed description of the
28879 possible states, see @ref{Ada Tasks}.
28882 The name of the task.
28886 @subsubheading Example
28890 ^done,tasks=@{nr_rows="3",nr_cols="8",
28891 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
28892 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
28893 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
28894 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
28895 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
28896 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
28897 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
28898 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
28899 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
28900 state="Child Termination Wait",name="main_task"@}]@}
28904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28905 @node GDB/MI Program Execution
28906 @section @sc{gdb/mi} Program Execution
28908 These are the asynchronous commands which generate the out-of-band
28909 record @samp{*stopped}. Currently @value{GDBN} only really executes
28910 asynchronously with remote targets and this interaction is mimicked in
28913 @subheading The @code{-exec-continue} Command
28914 @findex -exec-continue
28916 @subsubheading Synopsis
28919 -exec-continue [--reverse] [--all|--thread-group N]
28922 Resumes the execution of the inferior program, which will continue
28923 to execute until it reaches a debugger stop event. If the
28924 @samp{--reverse} option is specified, execution resumes in reverse until
28925 it reaches a stop event. Stop events may include
28928 breakpoints or watchpoints
28930 signals or exceptions
28932 the end of the process (or its beginning under @samp{--reverse})
28934 the end or beginning of a replay log if one is being used.
28936 In all-stop mode (@pxref{All-Stop
28937 Mode}), may resume only one thread, or all threads, depending on the
28938 value of the @samp{scheduler-locking} variable. If @samp{--all} is
28939 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
28940 ignored in all-stop mode. If the @samp{--thread-group} options is
28941 specified, then all threads in that thread group are resumed.
28943 @subsubheading @value{GDBN} Command
28945 The corresponding @value{GDBN} corresponding is @samp{continue}.
28947 @subsubheading Example
28954 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
28955 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
28961 @subheading The @code{-exec-finish} Command
28962 @findex -exec-finish
28964 @subsubheading Synopsis
28967 -exec-finish [--reverse]
28970 Resumes the execution of the inferior program until the current
28971 function is exited. Displays the results returned by the function.
28972 If the @samp{--reverse} option is specified, resumes the reverse
28973 execution of the inferior program until the point where current
28974 function was called.
28976 @subsubheading @value{GDBN} Command
28978 The corresponding @value{GDBN} command is @samp{finish}.
28980 @subsubheading Example
28982 Function returning @code{void}.
28989 *stopped,reason="function-finished",frame=@{func="main",args=[],
28990 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
28994 Function returning other than @code{void}. The name of the internal
28995 @value{GDBN} variable storing the result is printed, together with the
29002 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29003 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29004 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29005 gdb-result-var="$1",return-value="0"
29010 @subheading The @code{-exec-interrupt} Command
29011 @findex -exec-interrupt
29013 @subsubheading Synopsis
29016 -exec-interrupt [--all|--thread-group N]
29019 Interrupts the background execution of the target. Note how the token
29020 associated with the stop message is the one for the execution command
29021 that has been interrupted. The token for the interrupt itself only
29022 appears in the @samp{^done} output. If the user is trying to
29023 interrupt a non-running program, an error message will be printed.
29025 Note that when asynchronous execution is enabled, this command is
29026 asynchronous just like other execution commands. That is, first the
29027 @samp{^done} response will be printed, and the target stop will be
29028 reported after that using the @samp{*stopped} notification.
29030 In non-stop mode, only the context thread is interrupted by default.
29031 All threads (in all inferiors) will be interrupted if the
29032 @samp{--all} option is specified. If the @samp{--thread-group}
29033 option is specified, all threads in that group will be interrupted.
29035 @subsubheading @value{GDBN} Command
29037 The corresponding @value{GDBN} command is @samp{interrupt}.
29039 @subsubheading Example
29050 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29051 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29052 fullname="/home/foo/bar/try.c",line="13"@}
29057 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29061 @subheading The @code{-exec-jump} Command
29064 @subsubheading Synopsis
29067 -exec-jump @var{location}
29070 Resumes execution of the inferior program at the location specified by
29071 parameter. @xref{Specify Location}, for a description of the
29072 different forms of @var{location}.
29074 @subsubheading @value{GDBN} Command
29076 The corresponding @value{GDBN} command is @samp{jump}.
29078 @subsubheading Example
29081 -exec-jump foo.c:10
29082 *running,thread-id="all"
29087 @subheading The @code{-exec-next} Command
29090 @subsubheading Synopsis
29093 -exec-next [--reverse]
29096 Resumes execution of the inferior program, stopping when the beginning
29097 of the next source line is reached.
29099 If the @samp{--reverse} option is specified, resumes reverse execution
29100 of the inferior program, stopping at the beginning of the previous
29101 source line. If you issue this command on the first line of a
29102 function, it will take you back to the caller of that function, to the
29103 source line where the function was called.
29106 @subsubheading @value{GDBN} Command
29108 The corresponding @value{GDBN} command is @samp{next}.
29110 @subsubheading Example
29116 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29121 @subheading The @code{-exec-next-instruction} Command
29122 @findex -exec-next-instruction
29124 @subsubheading Synopsis
29127 -exec-next-instruction [--reverse]
29130 Executes one machine instruction. If the instruction is a function
29131 call, continues until the function returns. If the program stops at an
29132 instruction in the middle of a source line, the address will be
29135 If the @samp{--reverse} option is specified, resumes reverse execution
29136 of the inferior program, stopping at the previous instruction. If the
29137 previously executed instruction was a return from another function,
29138 it will continue to execute in reverse until the call to that function
29139 (from the current stack frame) is reached.
29141 @subsubheading @value{GDBN} Command
29143 The corresponding @value{GDBN} command is @samp{nexti}.
29145 @subsubheading Example
29149 -exec-next-instruction
29153 *stopped,reason="end-stepping-range",
29154 addr="0x000100d4",line="5",file="hello.c"
29159 @subheading The @code{-exec-return} Command
29160 @findex -exec-return
29162 @subsubheading Synopsis
29168 Makes current function return immediately. Doesn't execute the inferior.
29169 Displays the new current frame.
29171 @subsubheading @value{GDBN} Command
29173 The corresponding @value{GDBN} command is @samp{return}.
29175 @subsubheading Example
29179 200-break-insert callee4
29180 200^done,bkpt=@{number="1",addr="0x00010734",
29181 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29186 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29187 frame=@{func="callee4",args=[],
29188 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29189 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29195 111^done,frame=@{level="0",func="callee3",
29196 args=[@{name="strarg",
29197 value="0x11940 \"A string argument.\""@}],
29198 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29199 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29204 @subheading The @code{-exec-run} Command
29207 @subsubheading Synopsis
29210 -exec-run [ --all | --thread-group N ] [ --start ]
29213 Starts execution of the inferior from the beginning. The inferior
29214 executes until either a breakpoint is encountered or the program
29215 exits. In the latter case the output will include an exit code, if
29216 the program has exited exceptionally.
29218 When neither the @samp{--all} nor the @samp{--thread-group} option
29219 is specified, the current inferior is started. If the
29220 @samp{--thread-group} option is specified, it should refer to a thread
29221 group of type @samp{process}, and that thread group will be started.
29222 If the @samp{--all} option is specified, then all inferiors will be started.
29224 Using the @samp{--start} option instructs the debugger to stop
29225 the execution at the start of the inferior's main subprogram,
29226 following the same behavior as the @code{start} command
29227 (@pxref{Starting}).
29229 @subsubheading @value{GDBN} Command
29231 The corresponding @value{GDBN} command is @samp{run}.
29233 @subsubheading Examples
29238 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29243 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29244 frame=@{func="main",args=[],file="recursive2.c",
29245 fullname="/home/foo/bar/recursive2.c",line="4"@}
29250 Program exited normally:
29258 *stopped,reason="exited-normally"
29263 Program exited exceptionally:
29271 *stopped,reason="exited",exit-code="01"
29275 Another way the program can terminate is if it receives a signal such as
29276 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29280 *stopped,reason="exited-signalled",signal-name="SIGINT",
29281 signal-meaning="Interrupt"
29285 @c @subheading -exec-signal
29288 @subheading The @code{-exec-step} Command
29291 @subsubheading Synopsis
29294 -exec-step [--reverse]
29297 Resumes execution of the inferior program, stopping when the beginning
29298 of the next source line is reached, if the next source line is not a
29299 function call. If it is, stop at the first instruction of the called
29300 function. If the @samp{--reverse} option is specified, resumes reverse
29301 execution of the inferior program, stopping at the beginning of the
29302 previously executed source line.
29304 @subsubheading @value{GDBN} Command
29306 The corresponding @value{GDBN} command is @samp{step}.
29308 @subsubheading Example
29310 Stepping into a function:
29316 *stopped,reason="end-stepping-range",
29317 frame=@{func="foo",args=[@{name="a",value="10"@},
29318 @{name="b",value="0"@}],file="recursive2.c",
29319 fullname="/home/foo/bar/recursive2.c",line="11"@}
29329 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29334 @subheading The @code{-exec-step-instruction} Command
29335 @findex -exec-step-instruction
29337 @subsubheading Synopsis
29340 -exec-step-instruction [--reverse]
29343 Resumes the inferior which executes one machine instruction. If the
29344 @samp{--reverse} option is specified, resumes reverse execution of the
29345 inferior program, stopping at the previously executed instruction.
29346 The output, once @value{GDBN} has stopped, will vary depending on
29347 whether we have stopped in the middle of a source line or not. In the
29348 former case, the address at which the program stopped will be printed
29351 @subsubheading @value{GDBN} Command
29353 The corresponding @value{GDBN} command is @samp{stepi}.
29355 @subsubheading Example
29359 -exec-step-instruction
29363 *stopped,reason="end-stepping-range",
29364 frame=@{func="foo",args=[],file="try.c",
29365 fullname="/home/foo/bar/try.c",line="10"@}
29367 -exec-step-instruction
29371 *stopped,reason="end-stepping-range",
29372 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29373 fullname="/home/foo/bar/try.c",line="10"@}
29378 @subheading The @code{-exec-until} Command
29379 @findex -exec-until
29381 @subsubheading Synopsis
29384 -exec-until [ @var{location} ]
29387 Executes the inferior until the @var{location} specified in the
29388 argument is reached. If there is no argument, the inferior executes
29389 until a source line greater than the current one is reached. The
29390 reason for stopping in this case will be @samp{location-reached}.
29392 @subsubheading @value{GDBN} Command
29394 The corresponding @value{GDBN} command is @samp{until}.
29396 @subsubheading Example
29400 -exec-until recursive2.c:6
29404 *stopped,reason="location-reached",frame=@{func="main",args=[],
29405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29410 @subheading -file-clear
29411 Is this going away????
29414 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29415 @node GDB/MI Stack Manipulation
29416 @section @sc{gdb/mi} Stack Manipulation Commands
29418 @subheading The @code{-enable-frame-filters} Command
29419 @findex -enable-frame-filters
29422 -enable-frame-filters
29425 @value{GDBN} allows Python-based frame filters to affect the output of
29426 the MI commands relating to stack traces. As there is no way to
29427 implement this in a fully backward-compatible way, a front end must
29428 request that this functionality be enabled.
29430 Once enabled, this feature cannot be disabled.
29432 Note that if Python support has not been compiled into @value{GDBN},
29433 this command will still succeed (and do nothing).
29435 @subheading The @code{-stack-info-frame} Command
29436 @findex -stack-info-frame
29438 @subsubheading Synopsis
29444 Get info on the selected frame.
29446 @subsubheading @value{GDBN} Command
29448 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29449 (without arguments).
29451 @subsubheading Example
29456 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29457 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29458 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29462 @subheading The @code{-stack-info-depth} Command
29463 @findex -stack-info-depth
29465 @subsubheading Synopsis
29468 -stack-info-depth [ @var{max-depth} ]
29471 Return the depth of the stack. If the integer argument @var{max-depth}
29472 is specified, do not count beyond @var{max-depth} frames.
29474 @subsubheading @value{GDBN} Command
29476 There's no equivalent @value{GDBN} command.
29478 @subsubheading Example
29480 For a stack with frame levels 0 through 11:
29487 -stack-info-depth 4
29490 -stack-info-depth 12
29493 -stack-info-depth 11
29496 -stack-info-depth 13
29501 @anchor{-stack-list-arguments}
29502 @subheading The @code{-stack-list-arguments} Command
29503 @findex -stack-list-arguments
29505 @subsubheading Synopsis
29508 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29509 [ @var{low-frame} @var{high-frame} ]
29512 Display a list of the arguments for the frames between @var{low-frame}
29513 and @var{high-frame} (inclusive). If @var{low-frame} and
29514 @var{high-frame} are not provided, list the arguments for the whole
29515 call stack. If the two arguments are equal, show the single frame
29516 at the corresponding level. It is an error if @var{low-frame} is
29517 larger than the actual number of frames. On the other hand,
29518 @var{high-frame} may be larger than the actual number of frames, in
29519 which case only existing frames will be returned.
29521 If @var{print-values} is 0 or @code{--no-values}, print only the names of
29522 the variables; if it is 1 or @code{--all-values}, print also their
29523 values; and if it is 2 or @code{--simple-values}, print the name,
29524 type and value for simple data types, and the name and type for arrays,
29525 structures and unions. If the option @code{--no-frame-filters} is
29526 supplied, then Python frame filters will not be executed.
29528 If the @code{--skip-unavailable} option is specified, arguments that
29529 are not available are not listed. Partially available arguments
29530 are still displayed, however.
29532 Use of this command to obtain arguments in a single frame is
29533 deprecated in favor of the @samp{-stack-list-variables} command.
29535 @subsubheading @value{GDBN} Command
29537 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
29538 @samp{gdb_get_args} command which partially overlaps with the
29539 functionality of @samp{-stack-list-arguments}.
29541 @subsubheading Example
29548 frame=@{level="0",addr="0x00010734",func="callee4",
29549 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29550 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
29551 frame=@{level="1",addr="0x0001076c",func="callee3",
29552 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29553 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
29554 frame=@{level="2",addr="0x0001078c",func="callee2",
29555 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29556 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
29557 frame=@{level="3",addr="0x000107b4",func="callee1",
29558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29559 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
29560 frame=@{level="4",addr="0x000107e0",func="main",
29561 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29562 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
29564 -stack-list-arguments 0
29567 frame=@{level="0",args=[]@},
29568 frame=@{level="1",args=[name="strarg"]@},
29569 frame=@{level="2",args=[name="intarg",name="strarg"]@},
29570 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
29571 frame=@{level="4",args=[]@}]
29573 -stack-list-arguments 1
29576 frame=@{level="0",args=[]@},
29578 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29579 frame=@{level="2",args=[
29580 @{name="intarg",value="2"@},
29581 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
29582 @{frame=@{level="3",args=[
29583 @{name="intarg",value="2"@},
29584 @{name="strarg",value="0x11940 \"A string argument.\""@},
29585 @{name="fltarg",value="3.5"@}]@},
29586 frame=@{level="4",args=[]@}]
29588 -stack-list-arguments 0 2 2
29589 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
29591 -stack-list-arguments 1 2 2
29592 ^done,stack-args=[frame=@{level="2",
29593 args=[@{name="intarg",value="2"@},
29594 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
29598 @c @subheading -stack-list-exception-handlers
29601 @anchor{-stack-list-frames}
29602 @subheading The @code{-stack-list-frames} Command
29603 @findex -stack-list-frames
29605 @subsubheading Synopsis
29608 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
29611 List the frames currently on the stack. For each frame it displays the
29616 The frame number, 0 being the topmost frame, i.e., the innermost function.
29618 The @code{$pc} value for that frame.
29622 File name of the source file where the function lives.
29623 @item @var{fullname}
29624 The full file name of the source file where the function lives.
29626 Line number corresponding to the @code{$pc}.
29628 The shared library where this function is defined. This is only given
29629 if the frame's function is not known.
29632 If invoked without arguments, this command prints a backtrace for the
29633 whole stack. If given two integer arguments, it shows the frames whose
29634 levels are between the two arguments (inclusive). If the two arguments
29635 are equal, it shows the single frame at the corresponding level. It is
29636 an error if @var{low-frame} is larger than the actual number of
29637 frames. On the other hand, @var{high-frame} may be larger than the
29638 actual number of frames, in which case only existing frames will be
29639 returned. If the option @code{--no-frame-filters} is supplied, then
29640 Python frame filters will not be executed.
29642 @subsubheading @value{GDBN} Command
29644 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
29646 @subsubheading Example
29648 Full stack backtrace:
29654 [frame=@{level="0",addr="0x0001076c",func="foo",
29655 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
29656 frame=@{level="1",addr="0x000107a4",func="foo",
29657 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29658 frame=@{level="2",addr="0x000107a4",func="foo",
29659 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29660 frame=@{level="3",addr="0x000107a4",func="foo",
29661 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29662 frame=@{level="4",addr="0x000107a4",func="foo",
29663 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29664 frame=@{level="5",addr="0x000107a4",func="foo",
29665 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29666 frame=@{level="6",addr="0x000107a4",func="foo",
29667 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29668 frame=@{level="7",addr="0x000107a4",func="foo",
29669 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29670 frame=@{level="8",addr="0x000107a4",func="foo",
29671 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29672 frame=@{level="9",addr="0x000107a4",func="foo",
29673 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29674 frame=@{level="10",addr="0x000107a4",func="foo",
29675 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29676 frame=@{level="11",addr="0x00010738",func="main",
29677 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
29681 Show frames between @var{low_frame} and @var{high_frame}:
29685 -stack-list-frames 3 5
29687 [frame=@{level="3",addr="0x000107a4",func="foo",
29688 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29689 frame=@{level="4",addr="0x000107a4",func="foo",
29690 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29691 frame=@{level="5",addr="0x000107a4",func="foo",
29692 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29696 Show a single frame:
29700 -stack-list-frames 3 3
29702 [frame=@{level="3",addr="0x000107a4",func="foo",
29703 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
29708 @subheading The @code{-stack-list-locals} Command
29709 @findex -stack-list-locals
29710 @anchor{-stack-list-locals}
29712 @subsubheading Synopsis
29715 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29718 Display the local variable names for the selected frame. If
29719 @var{print-values} is 0 or @code{--no-values}, print only the names of
29720 the variables; if it is 1 or @code{--all-values}, print also their
29721 values; and if it is 2 or @code{--simple-values}, print the name,
29722 type and value for simple data types, and the name and type for arrays,
29723 structures and unions. In this last case, a frontend can immediately
29724 display the value of simple data types and create variable objects for
29725 other data types when the user wishes to explore their values in
29726 more detail. If the option @code{--no-frame-filters} is supplied, then
29727 Python frame filters will not be executed.
29729 If the @code{--skip-unavailable} option is specified, local variables
29730 that are not available are not listed. Partially available local
29731 variables are still displayed, however.
29733 This command is deprecated in favor of the
29734 @samp{-stack-list-variables} command.
29736 @subsubheading @value{GDBN} Command
29738 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
29740 @subsubheading Example
29744 -stack-list-locals 0
29745 ^done,locals=[name="A",name="B",name="C"]
29747 -stack-list-locals --all-values
29748 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
29749 @{name="C",value="@{1, 2, 3@}"@}]
29750 -stack-list-locals --simple-values
29751 ^done,locals=[@{name="A",type="int",value="1"@},
29752 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
29756 @anchor{-stack-list-variables}
29757 @subheading The @code{-stack-list-variables} Command
29758 @findex -stack-list-variables
29760 @subsubheading Synopsis
29763 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
29766 Display the names of local variables and function arguments for the selected frame. If
29767 @var{print-values} is 0 or @code{--no-values}, print only the names of
29768 the variables; if it is 1 or @code{--all-values}, print also their
29769 values; and if it is 2 or @code{--simple-values}, print the name,
29770 type and value for simple data types, and the name and type for arrays,
29771 structures and unions. If the option @code{--no-frame-filters} is
29772 supplied, then Python frame filters will not be executed.
29774 If the @code{--skip-unavailable} option is specified, local variables
29775 and arguments that are not available are not listed. Partially
29776 available arguments and local variables are still displayed, however.
29778 @subsubheading Example
29782 -stack-list-variables --thread 1 --frame 0 --all-values
29783 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
29788 @subheading The @code{-stack-select-frame} Command
29789 @findex -stack-select-frame
29791 @subsubheading Synopsis
29794 -stack-select-frame @var{framenum}
29797 Change the selected frame. Select a different frame @var{framenum} on
29800 This command in deprecated in favor of passing the @samp{--frame}
29801 option to every command.
29803 @subsubheading @value{GDBN} Command
29805 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
29806 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
29808 @subsubheading Example
29812 -stack-select-frame 2
29817 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29818 @node GDB/MI Variable Objects
29819 @section @sc{gdb/mi} Variable Objects
29823 @subheading Motivation for Variable Objects in @sc{gdb/mi}
29825 For the implementation of a variable debugger window (locals, watched
29826 expressions, etc.), we are proposing the adaptation of the existing code
29827 used by @code{Insight}.
29829 The two main reasons for that are:
29833 It has been proven in practice (it is already on its second generation).
29836 It will shorten development time (needless to say how important it is
29840 The original interface was designed to be used by Tcl code, so it was
29841 slightly changed so it could be used through @sc{gdb/mi}. This section
29842 describes the @sc{gdb/mi} operations that will be available and gives some
29843 hints about their use.
29845 @emph{Note}: In addition to the set of operations described here, we
29846 expect the @sc{gui} implementation of a variable window to require, at
29847 least, the following operations:
29850 @item @code{-gdb-show} @code{output-radix}
29851 @item @code{-stack-list-arguments}
29852 @item @code{-stack-list-locals}
29853 @item @code{-stack-select-frame}
29858 @subheading Introduction to Variable Objects
29860 @cindex variable objects in @sc{gdb/mi}
29862 Variable objects are "object-oriented" MI interface for examining and
29863 changing values of expressions. Unlike some other MI interfaces that
29864 work with expressions, variable objects are specifically designed for
29865 simple and efficient presentation in the frontend. A variable object
29866 is identified by string name. When a variable object is created, the
29867 frontend specifies the expression for that variable object. The
29868 expression can be a simple variable, or it can be an arbitrary complex
29869 expression, and can even involve CPU registers. After creating a
29870 variable object, the frontend can invoke other variable object
29871 operations---for example to obtain or change the value of a variable
29872 object, or to change display format.
29874 Variable objects have hierarchical tree structure. Any variable object
29875 that corresponds to a composite type, such as structure in C, has
29876 a number of child variable objects, for example corresponding to each
29877 element of a structure. A child variable object can itself have
29878 children, recursively. Recursion ends when we reach
29879 leaf variable objects, which always have built-in types. Child variable
29880 objects are created only by explicit request, so if a frontend
29881 is not interested in the children of a particular variable object, no
29882 child will be created.
29884 For a leaf variable object it is possible to obtain its value as a
29885 string, or set the value from a string. String value can be also
29886 obtained for a non-leaf variable object, but it's generally a string
29887 that only indicates the type of the object, and does not list its
29888 contents. Assignment to a non-leaf variable object is not allowed.
29890 A frontend does not need to read the values of all variable objects each time
29891 the program stops. Instead, MI provides an update command that lists all
29892 variable objects whose values has changed since the last update
29893 operation. This considerably reduces the amount of data that must
29894 be transferred to the frontend. As noted above, children variable
29895 objects are created on demand, and only leaf variable objects have a
29896 real value. As result, gdb will read target memory only for leaf
29897 variables that frontend has created.
29899 The automatic update is not always desirable. For example, a frontend
29900 might want to keep a value of some expression for future reference,
29901 and never update it. For another example, fetching memory is
29902 relatively slow for embedded targets, so a frontend might want
29903 to disable automatic update for the variables that are either not
29904 visible on the screen, or ``closed''. This is possible using so
29905 called ``frozen variable objects''. Such variable objects are never
29906 implicitly updated.
29908 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
29909 fixed variable object, the expression is parsed when the variable
29910 object is created, including associating identifiers to specific
29911 variables. The meaning of expression never changes. For a floating
29912 variable object the values of variables whose names appear in the
29913 expressions are re-evaluated every time in the context of the current
29914 frame. Consider this example:
29919 struct work_state state;
29926 If a fixed variable object for the @code{state} variable is created in
29927 this function, and we enter the recursive call, the variable
29928 object will report the value of @code{state} in the top-level
29929 @code{do_work} invocation. On the other hand, a floating variable
29930 object will report the value of @code{state} in the current frame.
29932 If an expression specified when creating a fixed variable object
29933 refers to a local variable, the variable object becomes bound to the
29934 thread and frame in which the variable object is created. When such
29935 variable object is updated, @value{GDBN} makes sure that the
29936 thread/frame combination the variable object is bound to still exists,
29937 and re-evaluates the variable object in context of that thread/frame.
29939 The following is the complete set of @sc{gdb/mi} operations defined to
29940 access this functionality:
29942 @multitable @columnfractions .4 .6
29943 @item @strong{Operation}
29944 @tab @strong{Description}
29946 @item @code{-enable-pretty-printing}
29947 @tab enable Python-based pretty-printing
29948 @item @code{-var-create}
29949 @tab create a variable object
29950 @item @code{-var-delete}
29951 @tab delete the variable object and/or its children
29952 @item @code{-var-set-format}
29953 @tab set the display format of this variable
29954 @item @code{-var-show-format}
29955 @tab show the display format of this variable
29956 @item @code{-var-info-num-children}
29957 @tab tells how many children this object has
29958 @item @code{-var-list-children}
29959 @tab return a list of the object's children
29960 @item @code{-var-info-type}
29961 @tab show the type of this variable object
29962 @item @code{-var-info-expression}
29963 @tab print parent-relative expression that this variable object represents
29964 @item @code{-var-info-path-expression}
29965 @tab print full expression that this variable object represents
29966 @item @code{-var-show-attributes}
29967 @tab is this variable editable? does it exist here?
29968 @item @code{-var-evaluate-expression}
29969 @tab get the value of this variable
29970 @item @code{-var-assign}
29971 @tab set the value of this variable
29972 @item @code{-var-update}
29973 @tab update the variable and its children
29974 @item @code{-var-set-frozen}
29975 @tab set frozeness attribute
29976 @item @code{-var-set-update-range}
29977 @tab set range of children to display on update
29980 In the next subsection we describe each operation in detail and suggest
29981 how it can be used.
29983 @subheading Description And Use of Operations on Variable Objects
29985 @subheading The @code{-enable-pretty-printing} Command
29986 @findex -enable-pretty-printing
29989 -enable-pretty-printing
29992 @value{GDBN} allows Python-based visualizers to affect the output of the
29993 MI variable object commands. However, because there was no way to
29994 implement this in a fully backward-compatible way, a front end must
29995 request that this functionality be enabled.
29997 Once enabled, this feature cannot be disabled.
29999 Note that if Python support has not been compiled into @value{GDBN},
30000 this command will still succeed (and do nothing).
30002 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30003 may work differently in future versions of @value{GDBN}.
30005 @subheading The @code{-var-create} Command
30006 @findex -var-create
30008 @subsubheading Synopsis
30011 -var-create @{@var{name} | "-"@}
30012 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30015 This operation creates a variable object, which allows the monitoring of
30016 a variable, the result of an expression, a memory cell or a CPU
30019 The @var{name} parameter is the string by which the object can be
30020 referenced. It must be unique. If @samp{-} is specified, the varobj
30021 system will generate a string ``varNNNNNN'' automatically. It will be
30022 unique provided that one does not specify @var{name} of that format.
30023 The command fails if a duplicate name is found.
30025 The frame under which the expression should be evaluated can be
30026 specified by @var{frame-addr}. A @samp{*} indicates that the current
30027 frame should be used. A @samp{@@} indicates that a floating variable
30028 object must be created.
30030 @var{expression} is any expression valid on the current language set (must not
30031 begin with a @samp{*}), or one of the following:
30035 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30038 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30041 @samp{$@var{regname}} --- a CPU register name
30044 @cindex dynamic varobj
30045 A varobj's contents may be provided by a Python-based pretty-printer. In this
30046 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30047 have slightly different semantics in some cases. If the
30048 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30049 will never create a dynamic varobj. This ensures backward
30050 compatibility for existing clients.
30052 @subsubheading Result
30054 This operation returns attributes of the newly-created varobj. These
30059 The name of the varobj.
30062 The number of children of the varobj. This number is not necessarily
30063 reliable for a dynamic varobj. Instead, you must examine the
30064 @samp{has_more} attribute.
30067 The varobj's scalar value. For a varobj whose type is some sort of
30068 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30069 will not be interesting.
30072 The varobj's type. This is a string representation of the type, as
30073 would be printed by the @value{GDBN} CLI. If @samp{print object}
30074 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30075 @emph{actual} (derived) type of the object is shown rather than the
30076 @emph{declared} one.
30079 If a variable object is bound to a specific thread, then this is the
30080 thread's global identifier.
30083 For a dynamic varobj, this indicates whether there appear to be any
30084 children available. For a non-dynamic varobj, this will be 0.
30087 This attribute will be present and have the value @samp{1} if the
30088 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30089 then this attribute will not be present.
30092 A dynamic varobj can supply a display hint to the front end. The
30093 value comes directly from the Python pretty-printer object's
30094 @code{display_hint} method. @xref{Pretty Printing API}.
30097 Typical output will look like this:
30100 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30101 has_more="@var{has_more}"
30105 @subheading The @code{-var-delete} Command
30106 @findex -var-delete
30108 @subsubheading Synopsis
30111 -var-delete [ -c ] @var{name}
30114 Deletes a previously created variable object and all of its children.
30115 With the @samp{-c} option, just deletes the children.
30117 Returns an error if the object @var{name} is not found.
30120 @subheading The @code{-var-set-format} Command
30121 @findex -var-set-format
30123 @subsubheading Synopsis
30126 -var-set-format @var{name} @var{format-spec}
30129 Sets the output format for the value of the object @var{name} to be
30132 @anchor{-var-set-format}
30133 The syntax for the @var{format-spec} is as follows:
30136 @var{format-spec} @expansion{}
30137 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
30140 The natural format is the default format choosen automatically
30141 based on the variable type (like decimal for an @code{int}, hex
30142 for pointers, etc.).
30144 The zero-hexadecimal format has a representation similar to hexadecimal
30145 but with padding zeroes to the left of the value. For example, a 32-bit
30146 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
30147 zero-hexadecimal format.
30149 For a variable with children, the format is set only on the
30150 variable itself, and the children are not affected.
30152 @subheading The @code{-var-show-format} Command
30153 @findex -var-show-format
30155 @subsubheading Synopsis
30158 -var-show-format @var{name}
30161 Returns the format used to display the value of the object @var{name}.
30164 @var{format} @expansion{}
30169 @subheading The @code{-var-info-num-children} Command
30170 @findex -var-info-num-children
30172 @subsubheading Synopsis
30175 -var-info-num-children @var{name}
30178 Returns the number of children of a variable object @var{name}:
30184 Note that this number is not completely reliable for a dynamic varobj.
30185 It will return the current number of children, but more children may
30189 @subheading The @code{-var-list-children} Command
30190 @findex -var-list-children
30192 @subsubheading Synopsis
30195 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30197 @anchor{-var-list-children}
30199 Return a list of the children of the specified variable object and
30200 create variable objects for them, if they do not already exist. With
30201 a single argument or if @var{print-values} has a value of 0 or
30202 @code{--no-values}, print only the names of the variables; if
30203 @var{print-values} is 1 or @code{--all-values}, also print their
30204 values; and if it is 2 or @code{--simple-values} print the name and
30205 value for simple data types and just the name for arrays, structures
30208 @var{from} and @var{to}, if specified, indicate the range of children
30209 to report. If @var{from} or @var{to} is less than zero, the range is
30210 reset and all children will be reported. Otherwise, children starting
30211 at @var{from} (zero-based) and up to and excluding @var{to} will be
30214 If a child range is requested, it will only affect the current call to
30215 @code{-var-list-children}, but not future calls to @code{-var-update}.
30216 For this, you must instead use @code{-var-set-update-range}. The
30217 intent of this approach is to enable a front end to implement any
30218 update approach it likes; for example, scrolling a view may cause the
30219 front end to request more children with @code{-var-list-children}, and
30220 then the front end could call @code{-var-set-update-range} with a
30221 different range to ensure that future updates are restricted to just
30224 For each child the following results are returned:
30229 Name of the variable object created for this child.
30232 The expression to be shown to the user by the front end to designate this child.
30233 For example this may be the name of a structure member.
30235 For a dynamic varobj, this value cannot be used to form an
30236 expression. There is no way to do this at all with a dynamic varobj.
30238 For C/C@t{++} structures there are several pseudo children returned to
30239 designate access qualifiers. For these pseudo children @var{exp} is
30240 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30241 type and value are not present.
30243 A dynamic varobj will not report the access qualifying
30244 pseudo-children, regardless of the language. This information is not
30245 available at all with a dynamic varobj.
30248 Number of children this child has. For a dynamic varobj, this will be
30252 The type of the child. If @samp{print object}
30253 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30254 @emph{actual} (derived) type of the object is shown rather than the
30255 @emph{declared} one.
30258 If values were requested, this is the value.
30261 If this variable object is associated with a thread, this is the
30262 thread's global thread id. Otherwise this result is not present.
30265 If the variable object is frozen, this variable will be present with a value of 1.
30268 A dynamic varobj can supply a display hint to the front end. The
30269 value comes directly from the Python pretty-printer object's
30270 @code{display_hint} method. @xref{Pretty Printing API}.
30273 This attribute will be present and have the value @samp{1} if the
30274 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30275 then this attribute will not be present.
30279 The result may have its own attributes:
30283 A dynamic varobj can supply a display hint to the front end. The
30284 value comes directly from the Python pretty-printer object's
30285 @code{display_hint} method. @xref{Pretty Printing API}.
30288 This is an integer attribute which is nonzero if there are children
30289 remaining after the end of the selected range.
30292 @subsubheading Example
30296 -var-list-children n
30297 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30298 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30300 -var-list-children --all-values n
30301 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30302 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30306 @subheading The @code{-var-info-type} Command
30307 @findex -var-info-type
30309 @subsubheading Synopsis
30312 -var-info-type @var{name}
30315 Returns the type of the specified variable @var{name}. The type is
30316 returned as a string in the same format as it is output by the
30320 type=@var{typename}
30324 @subheading The @code{-var-info-expression} Command
30325 @findex -var-info-expression
30327 @subsubheading Synopsis
30330 -var-info-expression @var{name}
30333 Returns a string that is suitable for presenting this
30334 variable object in user interface. The string is generally
30335 not valid expression in the current language, and cannot be evaluated.
30337 For example, if @code{a} is an array, and variable object
30338 @code{A} was created for @code{a}, then we'll get this output:
30341 (gdb) -var-info-expression A.1
30342 ^done,lang="C",exp="1"
30346 Here, the value of @code{lang} is the language name, which can be
30347 found in @ref{Supported Languages}.
30349 Note that the output of the @code{-var-list-children} command also
30350 includes those expressions, so the @code{-var-info-expression} command
30353 @subheading The @code{-var-info-path-expression} Command
30354 @findex -var-info-path-expression
30356 @subsubheading Synopsis
30359 -var-info-path-expression @var{name}
30362 Returns an expression that can be evaluated in the current
30363 context and will yield the same value that a variable object has.
30364 Compare this with the @code{-var-info-expression} command, which
30365 result can be used only for UI presentation. Typical use of
30366 the @code{-var-info-path-expression} command is creating a
30367 watchpoint from a variable object.
30369 This command is currently not valid for children of a dynamic varobj,
30370 and will give an error when invoked on one.
30372 For example, suppose @code{C} is a C@t{++} class, derived from class
30373 @code{Base}, and that the @code{Base} class has a member called
30374 @code{m_size}. Assume a variable @code{c} is has the type of
30375 @code{C} and a variable object @code{C} was created for variable
30376 @code{c}. Then, we'll get this output:
30378 (gdb) -var-info-path-expression C.Base.public.m_size
30379 ^done,path_expr=((Base)c).m_size)
30382 @subheading The @code{-var-show-attributes} Command
30383 @findex -var-show-attributes
30385 @subsubheading Synopsis
30388 -var-show-attributes @var{name}
30391 List attributes of the specified variable object @var{name}:
30394 status=@var{attr} [ ( ,@var{attr} )* ]
30398 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30400 @subheading The @code{-var-evaluate-expression} Command
30401 @findex -var-evaluate-expression
30403 @subsubheading Synopsis
30406 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30409 Evaluates the expression that is represented by the specified variable
30410 object and returns its value as a string. The format of the string
30411 can be specified with the @samp{-f} option. The possible values of
30412 this option are the same as for @code{-var-set-format}
30413 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30414 the current display format will be used. The current display format
30415 can be changed using the @code{-var-set-format} command.
30421 Note that one must invoke @code{-var-list-children} for a variable
30422 before the value of a child variable can be evaluated.
30424 @subheading The @code{-var-assign} Command
30425 @findex -var-assign
30427 @subsubheading Synopsis
30430 -var-assign @var{name} @var{expression}
30433 Assigns the value of @var{expression} to the variable object specified
30434 by @var{name}. The object must be @samp{editable}. If the variable's
30435 value is altered by the assign, the variable will show up in any
30436 subsequent @code{-var-update} list.
30438 @subsubheading Example
30446 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30450 @subheading The @code{-var-update} Command
30451 @findex -var-update
30453 @subsubheading Synopsis
30456 -var-update [@var{print-values}] @{@var{name} | "*"@}
30459 Reevaluate the expressions corresponding to the variable object
30460 @var{name} and all its direct and indirect children, and return the
30461 list of variable objects whose values have changed; @var{name} must
30462 be a root variable object. Here, ``changed'' means that the result of
30463 @code{-var-evaluate-expression} before and after the
30464 @code{-var-update} is different. If @samp{*} is used as the variable
30465 object names, all existing variable objects are updated, except
30466 for frozen ones (@pxref{-var-set-frozen}). The option
30467 @var{print-values} determines whether both names and values, or just
30468 names are printed. The possible values of this option are the same
30469 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30470 recommended to use the @samp{--all-values} option, to reduce the
30471 number of MI commands needed on each program stop.
30473 With the @samp{*} parameter, if a variable object is bound to a
30474 currently running thread, it will not be updated, without any
30477 If @code{-var-set-update-range} was previously used on a varobj, then
30478 only the selected range of children will be reported.
30480 @code{-var-update} reports all the changed varobjs in a tuple named
30483 Each item in the change list is itself a tuple holding:
30487 The name of the varobj.
30490 If values were requested for this update, then this field will be
30491 present and will hold the value of the varobj.
30494 @anchor{-var-update}
30495 This field is a string which may take one of three values:
30499 The variable object's current value is valid.
30502 The variable object does not currently hold a valid value but it may
30503 hold one in the future if its associated expression comes back into
30507 The variable object no longer holds a valid value.
30508 This can occur when the executable file being debugged has changed,
30509 either through recompilation or by using the @value{GDBN} @code{file}
30510 command. The front end should normally choose to delete these variable
30514 In the future new values may be added to this list so the front should
30515 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
30518 This is only present if the varobj is still valid. If the type
30519 changed, then this will be the string @samp{true}; otherwise it will
30522 When a varobj's type changes, its children are also likely to have
30523 become incorrect. Therefore, the varobj's children are automatically
30524 deleted when this attribute is @samp{true}. Also, the varobj's update
30525 range, when set using the @code{-var-set-update-range} command, is
30529 If the varobj's type changed, then this field will be present and will
30532 @item new_num_children
30533 For a dynamic varobj, if the number of children changed, or if the
30534 type changed, this will be the new number of children.
30536 The @samp{numchild} field in other varobj responses is generally not
30537 valid for a dynamic varobj -- it will show the number of children that
30538 @value{GDBN} knows about, but because dynamic varobjs lazily
30539 instantiate their children, this will not reflect the number of
30540 children which may be available.
30542 The @samp{new_num_children} attribute only reports changes to the
30543 number of children known by @value{GDBN}. This is the only way to
30544 detect whether an update has removed children (which necessarily can
30545 only happen at the end of the update range).
30548 The display hint, if any.
30551 This is an integer value, which will be 1 if there are more children
30552 available outside the varobj's update range.
30555 This attribute will be present and have the value @samp{1} if the
30556 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30557 then this attribute will not be present.
30560 If new children were added to a dynamic varobj within the selected
30561 update range (as set by @code{-var-set-update-range}), then they will
30562 be listed in this attribute.
30565 @subsubheading Example
30572 -var-update --all-values var1
30573 ^done,changelist=[@{name="var1",value="3",in_scope="true",
30574 type_changed="false"@}]
30578 @subheading The @code{-var-set-frozen} Command
30579 @findex -var-set-frozen
30580 @anchor{-var-set-frozen}
30582 @subsubheading Synopsis
30585 -var-set-frozen @var{name} @var{flag}
30588 Set the frozenness flag on the variable object @var{name}. The
30589 @var{flag} parameter should be either @samp{1} to make the variable
30590 frozen or @samp{0} to make it unfrozen. If a variable object is
30591 frozen, then neither itself, nor any of its children, are
30592 implicitly updated by @code{-var-update} of
30593 a parent variable or by @code{-var-update *}. Only
30594 @code{-var-update} of the variable itself will update its value and
30595 values of its children. After a variable object is unfrozen, it is
30596 implicitly updated by all subsequent @code{-var-update} operations.
30597 Unfreezing a variable does not update it, only subsequent
30598 @code{-var-update} does.
30600 @subsubheading Example
30604 -var-set-frozen V 1
30609 @subheading The @code{-var-set-update-range} command
30610 @findex -var-set-update-range
30611 @anchor{-var-set-update-range}
30613 @subsubheading Synopsis
30616 -var-set-update-range @var{name} @var{from} @var{to}
30619 Set the range of children to be returned by future invocations of
30620 @code{-var-update}.
30622 @var{from} and @var{to} indicate the range of children to report. If
30623 @var{from} or @var{to} is less than zero, the range is reset and all
30624 children will be reported. Otherwise, children starting at @var{from}
30625 (zero-based) and up to and excluding @var{to} will be reported.
30627 @subsubheading Example
30631 -var-set-update-range V 1 2
30635 @subheading The @code{-var-set-visualizer} command
30636 @findex -var-set-visualizer
30637 @anchor{-var-set-visualizer}
30639 @subsubheading Synopsis
30642 -var-set-visualizer @var{name} @var{visualizer}
30645 Set a visualizer for the variable object @var{name}.
30647 @var{visualizer} is the visualizer to use. The special value
30648 @samp{None} means to disable any visualizer in use.
30650 If not @samp{None}, @var{visualizer} must be a Python expression.
30651 This expression must evaluate to a callable object which accepts a
30652 single argument. @value{GDBN} will call this object with the value of
30653 the varobj @var{name} as an argument (this is done so that the same
30654 Python pretty-printing code can be used for both the CLI and MI).
30655 When called, this object must return an object which conforms to the
30656 pretty-printing interface (@pxref{Pretty Printing API}).
30658 The pre-defined function @code{gdb.default_visualizer} may be used to
30659 select a visualizer by following the built-in process
30660 (@pxref{Selecting Pretty-Printers}). This is done automatically when
30661 a varobj is created, and so ordinarily is not needed.
30663 This feature is only available if Python support is enabled. The MI
30664 command @code{-list-features} (@pxref{GDB/MI Support Commands})
30665 can be used to check this.
30667 @subsubheading Example
30669 Resetting the visualizer:
30673 -var-set-visualizer V None
30677 Reselecting the default (type-based) visualizer:
30681 -var-set-visualizer V gdb.default_visualizer
30685 Suppose @code{SomeClass} is a visualizer class. A lambda expression
30686 can be used to instantiate this class for a varobj:
30690 -var-set-visualizer V "lambda val: SomeClass()"
30694 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30695 @node GDB/MI Data Manipulation
30696 @section @sc{gdb/mi} Data Manipulation
30698 @cindex data manipulation, in @sc{gdb/mi}
30699 @cindex @sc{gdb/mi}, data manipulation
30700 This section describes the @sc{gdb/mi} commands that manipulate data:
30701 examine memory and registers, evaluate expressions, etc.
30703 For details about what an addressable memory unit is,
30704 @pxref{addressable memory unit}.
30706 @c REMOVED FROM THE INTERFACE.
30707 @c @subheading -data-assign
30708 @c Change the value of a program variable. Plenty of side effects.
30709 @c @subsubheading GDB Command
30711 @c @subsubheading Example
30714 @subheading The @code{-data-disassemble} Command
30715 @findex -data-disassemble
30717 @subsubheading Synopsis
30721 [ -s @var{start-addr} -e @var{end-addr} ]
30722 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
30730 @item @var{start-addr}
30731 is the beginning address (or @code{$pc})
30732 @item @var{end-addr}
30734 @item @var{filename}
30735 is the name of the file to disassemble
30736 @item @var{linenum}
30737 is the line number to disassemble around
30739 is the number of disassembly lines to be produced. If it is -1,
30740 the whole function will be disassembled, in case no @var{end-addr} is
30741 specified. If @var{end-addr} is specified as a non-zero value, and
30742 @var{lines} is lower than the number of disassembly lines between
30743 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
30744 displayed; if @var{lines} is higher than the number of lines between
30745 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
30750 @item 0 disassembly only
30751 @item 1 mixed source and disassembly (deprecated)
30752 @item 2 disassembly with raw opcodes
30753 @item 3 mixed source and disassembly with raw opcodes (deprecated)
30754 @item 4 mixed source and disassembly
30755 @item 5 mixed source and disassembly with raw opcodes
30758 Modes 1 and 3 are deprecated. The output is ``source centric''
30759 which hasn't proved useful in practice.
30760 @xref{Machine Code}, for a discussion of the difference between
30761 @code{/m} and @code{/s} output of the @code{disassemble} command.
30764 @subsubheading Result
30766 The result of the @code{-data-disassemble} command will be a list named
30767 @samp{asm_insns}, the contents of this list depend on the @var{mode}
30768 used with the @code{-data-disassemble} command.
30770 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
30775 The address at which this instruction was disassembled.
30778 The name of the function this instruction is within.
30781 The decimal offset in bytes from the start of @samp{func-name}.
30784 The text disassembly for this @samp{address}.
30787 This field is only present for modes 2, 3 and 5. This contains the raw opcode
30788 bytes for the @samp{inst} field.
30792 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
30793 @samp{src_and_asm_line}, each of which has the following fields:
30797 The line number within @samp{file}.
30800 The file name from the compilation unit. This might be an absolute
30801 file name or a relative file name depending on the compile command
30805 Absolute file name of @samp{file}. It is converted to a canonical form
30806 using the source file search path
30807 (@pxref{Source Path, ,Specifying Source Directories})
30808 and after resolving all the symbolic links.
30810 If the source file is not found this field will contain the path as
30811 present in the debug information.
30813 @item line_asm_insn
30814 This is a list of tuples containing the disassembly for @samp{line} in
30815 @samp{file}. The fields of each tuple are the same as for
30816 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
30817 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
30822 Note that whatever included in the @samp{inst} field, is not
30823 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
30826 @subsubheading @value{GDBN} Command
30828 The corresponding @value{GDBN} command is @samp{disassemble}.
30830 @subsubheading Example
30832 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
30836 -data-disassemble -s $pc -e "$pc + 20" -- 0
30839 @{address="0x000107c0",func-name="main",offset="4",
30840 inst="mov 2, %o0"@},
30841 @{address="0x000107c4",func-name="main",offset="8",
30842 inst="sethi %hi(0x11800), %o2"@},
30843 @{address="0x000107c8",func-name="main",offset="12",
30844 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
30845 @{address="0x000107cc",func-name="main",offset="16",
30846 inst="sethi %hi(0x11800), %o2"@},
30847 @{address="0x000107d0",func-name="main",offset="20",
30848 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
30852 Disassemble the whole @code{main} function. Line 32 is part of
30856 -data-disassemble -f basics.c -l 32 -- 0
30858 @{address="0x000107bc",func-name="main",offset="0",
30859 inst="save %sp, -112, %sp"@},
30860 @{address="0x000107c0",func-name="main",offset="4",
30861 inst="mov 2, %o0"@},
30862 @{address="0x000107c4",func-name="main",offset="8",
30863 inst="sethi %hi(0x11800), %o2"@},
30865 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
30866 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
30870 Disassemble 3 instructions from the start of @code{main}:
30874 -data-disassemble -f basics.c -l 32 -n 3 -- 0
30876 @{address="0x000107bc",func-name="main",offset="0",
30877 inst="save %sp, -112, %sp"@},
30878 @{address="0x000107c0",func-name="main",offset="4",
30879 inst="mov 2, %o0"@},
30880 @{address="0x000107c4",func-name="main",offset="8",
30881 inst="sethi %hi(0x11800), %o2"@}]
30885 Disassemble 3 instructions from the start of @code{main} in mixed mode:
30889 -data-disassemble -f basics.c -l 32 -n 3 -- 1
30891 src_and_asm_line=@{line="31",
30892 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30893 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30894 line_asm_insn=[@{address="0x000107bc",
30895 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
30896 src_and_asm_line=@{line="32",
30897 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
30898 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
30899 line_asm_insn=[@{address="0x000107c0",
30900 func-name="main",offset="4",inst="mov 2, %o0"@},
30901 @{address="0x000107c4",func-name="main",offset="8",
30902 inst="sethi %hi(0x11800), %o2"@}]@}]
30907 @subheading The @code{-data-evaluate-expression} Command
30908 @findex -data-evaluate-expression
30910 @subsubheading Synopsis
30913 -data-evaluate-expression @var{expr}
30916 Evaluate @var{expr} as an expression. The expression could contain an
30917 inferior function call. The function call will execute synchronously.
30918 If the expression contains spaces, it must be enclosed in double quotes.
30920 @subsubheading @value{GDBN} Command
30922 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
30923 @samp{call}. In @code{gdbtk} only, there's a corresponding
30924 @samp{gdb_eval} command.
30926 @subsubheading Example
30928 In the following example, the numbers that precede the commands are the
30929 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
30930 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
30934 211-data-evaluate-expression A
30937 311-data-evaluate-expression &A
30938 311^done,value="0xefffeb7c"
30940 411-data-evaluate-expression A+3
30943 511-data-evaluate-expression "A + 3"
30949 @subheading The @code{-data-list-changed-registers} Command
30950 @findex -data-list-changed-registers
30952 @subsubheading Synopsis
30955 -data-list-changed-registers
30958 Display a list of the registers that have changed.
30960 @subsubheading @value{GDBN} Command
30962 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
30963 has the corresponding command @samp{gdb_changed_register_list}.
30965 @subsubheading Example
30967 On a PPC MBX board:
30975 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
30976 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
30979 -data-list-changed-registers
30980 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
30981 "10","11","13","14","15","16","17","18","19","20","21","22","23",
30982 "24","25","26","27","28","30","31","64","65","66","67","69"]
30987 @subheading The @code{-data-list-register-names} Command
30988 @findex -data-list-register-names
30990 @subsubheading Synopsis
30993 -data-list-register-names [ ( @var{regno} )+ ]
30996 Show a list of register names for the current target. If no arguments
30997 are given, it shows a list of the names of all the registers. If
30998 integer numbers are given as arguments, it will print a list of the
30999 names of the registers corresponding to the arguments. To ensure
31000 consistency between a register name and its number, the output list may
31001 include empty register names.
31003 @subsubheading @value{GDBN} Command
31005 @value{GDBN} does not have a command which corresponds to
31006 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31007 corresponding command @samp{gdb_regnames}.
31009 @subsubheading Example
31011 For the PPC MBX board:
31014 -data-list-register-names
31015 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31016 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31017 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31018 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31019 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31020 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31021 "", "pc","ps","cr","lr","ctr","xer"]
31023 -data-list-register-names 1 2 3
31024 ^done,register-names=["r1","r2","r3"]
31028 @subheading The @code{-data-list-register-values} Command
31029 @findex -data-list-register-values
31031 @subsubheading Synopsis
31034 -data-list-register-values
31035 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
31038 Display the registers' contents. The format according to which the
31039 registers' contents are to be returned is given by @var{fmt}, followed
31040 by an optional list of numbers specifying the registers to display. A
31041 missing list of numbers indicates that the contents of all the
31042 registers must be returned. The @code{--skip-unavailable} option
31043 indicates that only the available registers are to be returned.
31045 Allowed formats for @var{fmt} are:
31062 @subsubheading @value{GDBN} Command
31064 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31065 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31067 @subsubheading Example
31069 For a PPC MBX board (note: line breaks are for readability only, they
31070 don't appear in the actual output):
31074 -data-list-register-values r 64 65
31075 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31076 @{number="65",value="0x00029002"@}]
31078 -data-list-register-values x
31079 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31080 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31081 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31082 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31083 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31084 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31085 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31086 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31087 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31088 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31089 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31090 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31091 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31092 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31093 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31094 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31095 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31096 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31097 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31098 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31099 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31100 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31101 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31102 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31103 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31104 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31105 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31106 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31107 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31108 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31109 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31110 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31111 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31112 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31113 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31114 @{number="69",value="0x20002b03"@}]
31119 @subheading The @code{-data-read-memory} Command
31120 @findex -data-read-memory
31122 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31124 @subsubheading Synopsis
31127 -data-read-memory [ -o @var{byte-offset} ]
31128 @var{address} @var{word-format} @var{word-size}
31129 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31136 @item @var{address}
31137 An expression specifying the address of the first memory word to be
31138 read. Complex expressions containing embedded white space should be
31139 quoted using the C convention.
31141 @item @var{word-format}
31142 The format to be used to print the memory words. The notation is the
31143 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31146 @item @var{word-size}
31147 The size of each memory word in bytes.
31149 @item @var{nr-rows}
31150 The number of rows in the output table.
31152 @item @var{nr-cols}
31153 The number of columns in the output table.
31156 If present, indicates that each row should include an @sc{ascii} dump. The
31157 value of @var{aschar} is used as a padding character when a byte is not a
31158 member of the printable @sc{ascii} character set (printable @sc{ascii}
31159 characters are those whose code is between 32 and 126, inclusively).
31161 @item @var{byte-offset}
31162 An offset to add to the @var{address} before fetching memory.
31165 This command displays memory contents as a table of @var{nr-rows} by
31166 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31167 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31168 (returned as @samp{total-bytes}). Should less than the requested number
31169 of bytes be returned by the target, the missing words are identified
31170 using @samp{N/A}. The number of bytes read from the target is returned
31171 in @samp{nr-bytes} and the starting address used to read memory in
31174 The address of the next/previous row or page is available in
31175 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31178 @subsubheading @value{GDBN} Command
31180 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31181 @samp{gdb_get_mem} memory read command.
31183 @subsubheading Example
31185 Read six bytes of memory starting at @code{bytes+6} but then offset by
31186 @code{-6} bytes. Format as three rows of two columns. One byte per
31187 word. Display each word in hex.
31191 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31192 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31193 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31194 prev-page="0x0000138a",memory=[
31195 @{addr="0x00001390",data=["0x00","0x01"]@},
31196 @{addr="0x00001392",data=["0x02","0x03"]@},
31197 @{addr="0x00001394",data=["0x04","0x05"]@}]
31201 Read two bytes of memory starting at address @code{shorts + 64} and
31202 display as a single word formatted in decimal.
31206 5-data-read-memory shorts+64 d 2 1 1
31207 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31208 next-row="0x00001512",prev-row="0x0000150e",
31209 next-page="0x00001512",prev-page="0x0000150e",memory=[
31210 @{addr="0x00001510",data=["128"]@}]
31214 Read thirty two bytes of memory starting at @code{bytes+16} and format
31215 as eight rows of four columns. Include a string encoding with @samp{x}
31216 used as the non-printable character.
31220 4-data-read-memory bytes+16 x 1 8 4 x
31221 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31222 next-row="0x000013c0",prev-row="0x0000139c",
31223 next-page="0x000013c0",prev-page="0x00001380",memory=[
31224 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31225 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31226 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31227 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31228 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31229 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31230 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31231 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31235 @subheading The @code{-data-read-memory-bytes} Command
31236 @findex -data-read-memory-bytes
31238 @subsubheading Synopsis
31241 -data-read-memory-bytes [ -o @var{offset} ]
31242 @var{address} @var{count}
31249 @item @var{address}
31250 An expression specifying the address of the first addressable memory unit
31251 to be read. Complex expressions containing embedded white space should be
31252 quoted using the C convention.
31255 The number of addressable memory units to read. This should be an integer
31259 The offset relative to @var{address} at which to start reading. This
31260 should be an integer literal. This option is provided so that a frontend
31261 is not required to first evaluate address and then perform address
31262 arithmetics itself.
31266 This command attempts to read all accessible memory regions in the
31267 specified range. First, all regions marked as unreadable in the memory
31268 map (if one is defined) will be skipped. @xref{Memory Region
31269 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31270 regions. For each one, if reading full region results in an errors,
31271 @value{GDBN} will try to read a subset of the region.
31273 In general, every single memory unit in the region may be readable or not,
31274 and the only way to read every readable unit is to try a read at
31275 every address, which is not practical. Therefore, @value{GDBN} will
31276 attempt to read all accessible memory units at either beginning or the end
31277 of the region, using a binary division scheme. This heuristic works
31278 well for reading accross a memory map boundary. Note that if a region
31279 has a readable range that is neither at the beginning or the end,
31280 @value{GDBN} will not read it.
31282 The result record (@pxref{GDB/MI Result Records}) that is output of
31283 the command includes a field named @samp{memory} whose content is a
31284 list of tuples. Each tuple represent a successfully read memory block
31285 and has the following fields:
31289 The start address of the memory block, as hexadecimal literal.
31292 The end address of the memory block, as hexadecimal literal.
31295 The offset of the memory block, as hexadecimal literal, relative to
31296 the start address passed to @code{-data-read-memory-bytes}.
31299 The contents of the memory block, in hex.
31305 @subsubheading @value{GDBN} Command
31307 The corresponding @value{GDBN} command is @samp{x}.
31309 @subsubheading Example
31313 -data-read-memory-bytes &a 10
31314 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31316 contents="01000000020000000300"@}]
31321 @subheading The @code{-data-write-memory-bytes} Command
31322 @findex -data-write-memory-bytes
31324 @subsubheading Synopsis
31327 -data-write-memory-bytes @var{address} @var{contents}
31328 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31335 @item @var{address}
31336 An expression specifying the address of the first addressable memory unit
31337 to be written. Complex expressions containing embedded white space should
31338 be quoted using the C convention.
31340 @item @var{contents}
31341 The hex-encoded data to write. It is an error if @var{contents} does
31342 not represent an integral number of addressable memory units.
31345 Optional argument indicating the number of addressable memory units to be
31346 written. If @var{count} is greater than @var{contents}' length,
31347 @value{GDBN} will repeatedly write @var{contents} until it fills
31348 @var{count} memory units.
31352 @subsubheading @value{GDBN} Command
31354 There's no corresponding @value{GDBN} command.
31356 @subsubheading Example
31360 -data-write-memory-bytes &a "aabbccdd"
31367 -data-write-memory-bytes &a "aabbccdd" 16e
31372 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31373 @node GDB/MI Tracepoint Commands
31374 @section @sc{gdb/mi} Tracepoint Commands
31376 The commands defined in this section implement MI support for
31377 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31379 @subheading The @code{-trace-find} Command
31380 @findex -trace-find
31382 @subsubheading Synopsis
31385 -trace-find @var{mode} [@var{parameters}@dots{}]
31388 Find a trace frame using criteria defined by @var{mode} and
31389 @var{parameters}. The following table lists permissible
31390 modes and their parameters. For details of operation, see @ref{tfind}.
31395 No parameters are required. Stops examining trace frames.
31398 An integer is required as parameter. Selects tracepoint frame with
31401 @item tracepoint-number
31402 An integer is required as parameter. Finds next
31403 trace frame that corresponds to tracepoint with the specified number.
31406 An address is required as parameter. Finds
31407 next trace frame that corresponds to any tracepoint at the specified
31410 @item pc-inside-range
31411 Two addresses are required as parameters. Finds next trace
31412 frame that corresponds to a tracepoint at an address inside the
31413 specified range. Both bounds are considered to be inside the range.
31415 @item pc-outside-range
31416 Two addresses are required as parameters. Finds
31417 next trace frame that corresponds to a tracepoint at an address outside
31418 the specified range. Both bounds are considered to be inside the range.
31421 Line specification is required as parameter. @xref{Specify Location}.
31422 Finds next trace frame that corresponds to a tracepoint at
31423 the specified location.
31427 If @samp{none} was passed as @var{mode}, the response does not
31428 have fields. Otherwise, the response may have the following fields:
31432 This field has either @samp{0} or @samp{1} as the value, depending
31433 on whether a matching tracepoint was found.
31436 The index of the found traceframe. This field is present iff
31437 the @samp{found} field has value of @samp{1}.
31440 The index of the found tracepoint. This field is present iff
31441 the @samp{found} field has value of @samp{1}.
31444 The information about the frame corresponding to the found trace
31445 frame. This field is present only if a trace frame was found.
31446 @xref{GDB/MI Frame Information}, for description of this field.
31450 @subsubheading @value{GDBN} Command
31452 The corresponding @value{GDBN} command is @samp{tfind}.
31454 @subheading -trace-define-variable
31455 @findex -trace-define-variable
31457 @subsubheading Synopsis
31460 -trace-define-variable @var{name} [ @var{value} ]
31463 Create trace variable @var{name} if it does not exist. If
31464 @var{value} is specified, sets the initial value of the specified
31465 trace variable to that value. Note that the @var{name} should start
31466 with the @samp{$} character.
31468 @subsubheading @value{GDBN} Command
31470 The corresponding @value{GDBN} command is @samp{tvariable}.
31472 @subheading The @code{-trace-frame-collected} Command
31473 @findex -trace-frame-collected
31475 @subsubheading Synopsis
31478 -trace-frame-collected
31479 [--var-print-values @var{var_pval}]
31480 [--comp-print-values @var{comp_pval}]
31481 [--registers-format @var{regformat}]
31482 [--memory-contents]
31485 This command returns the set of collected objects, register names,
31486 trace state variable names, memory ranges and computed expressions
31487 that have been collected at a particular trace frame. The optional
31488 parameters to the command affect the output format in different ways.
31489 See the output description table below for more details.
31491 The reported names can be used in the normal manner to create
31492 varobjs and inspect the objects themselves. The items returned by
31493 this command are categorized so that it is clear which is a variable,
31494 which is a register, which is a trace state variable, which is a
31495 memory range and which is a computed expression.
31497 For instance, if the actions were
31499 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
31500 collect *(int*)0xaf02bef0@@40
31504 the object collected in its entirety would be @code{myVar}. The
31505 object @code{myArray} would be partially collected, because only the
31506 element at index @code{myIndex} would be collected. The remaining
31507 objects would be computed expressions.
31509 An example output would be:
31513 -trace-frame-collected
31515 explicit-variables=[@{name="myVar",value="1"@}],
31516 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
31517 @{name="myObj.field",value="0"@},
31518 @{name="myPtr->field",value="1"@},
31519 @{name="myCount + 2",value="3"@},
31520 @{name="$tvar1 + 1",value="43970027"@}],
31521 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
31522 @{number="1",value="0x0"@},
31523 @{number="2",value="0x4"@},
31525 @{number="125",value="0x0"@}],
31526 tvars=[@{name="$tvar1",current="43970026"@}],
31527 memory=[@{address="0x0000000000602264",length="4"@},
31528 @{address="0x0000000000615bc0",length="4"@}]
31535 @item explicit-variables
31536 The set of objects that have been collected in their entirety (as
31537 opposed to collecting just a few elements of an array or a few struct
31538 members). For each object, its name and value are printed.
31539 The @code{--var-print-values} option affects how or whether the value
31540 field is output. If @var{var_pval} is 0, then print only the names;
31541 if it is 1, print also their values; and if it is 2, print the name,
31542 type and value for simple data types, and the name and type for
31543 arrays, structures and unions.
31545 @item computed-expressions
31546 The set of computed expressions that have been collected at the
31547 current trace frame. The @code{--comp-print-values} option affects
31548 this set like the @code{--var-print-values} option affects the
31549 @code{explicit-variables} set. See above.
31552 The registers that have been collected at the current trace frame.
31553 For each register collected, the name and current value are returned.
31554 The value is formatted according to the @code{--registers-format}
31555 option. See the @command{-data-list-register-values} command for a
31556 list of the allowed formats. The default is @samp{x}.
31559 The trace state variables that have been collected at the current
31560 trace frame. For each trace state variable collected, the name and
31561 current value are returned.
31564 The set of memory ranges that have been collected at the current trace
31565 frame. Its content is a list of tuples. Each tuple represents a
31566 collected memory range and has the following fields:
31570 The start address of the memory range, as hexadecimal literal.
31573 The length of the memory range, as decimal literal.
31576 The contents of the memory block, in hex. This field is only present
31577 if the @code{--memory-contents} option is specified.
31583 @subsubheading @value{GDBN} Command
31585 There is no corresponding @value{GDBN} command.
31587 @subsubheading Example
31589 @subheading -trace-list-variables
31590 @findex -trace-list-variables
31592 @subsubheading Synopsis
31595 -trace-list-variables
31598 Return a table of all defined trace variables. Each element of the
31599 table has the following fields:
31603 The name of the trace variable. This field is always present.
31606 The initial value. This is a 64-bit signed integer. This
31607 field is always present.
31610 The value the trace variable has at the moment. This is a 64-bit
31611 signed integer. This field is absent iff current value is
31612 not defined, for example if the trace was never run, or is
31617 @subsubheading @value{GDBN} Command
31619 The corresponding @value{GDBN} command is @samp{tvariables}.
31621 @subsubheading Example
31625 -trace-list-variables
31626 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31627 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31628 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31629 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31630 body=[variable=@{name="$trace_timestamp",initial="0"@}
31631 variable=@{name="$foo",initial="10",current="15"@}]@}
31635 @subheading -trace-save
31636 @findex -trace-save
31638 @subsubheading Synopsis
31641 -trace-save [ -r ] [ -ctf ] @var{filename}
31644 Saves the collected trace data to @var{filename}. Without the
31645 @samp{-r} option, the data is downloaded from the target and saved
31646 in a local file. With the @samp{-r} option the target is asked
31647 to perform the save.
31649 By default, this command will save the trace in the tfile format. You can
31650 supply the optional @samp{-ctf} argument to save it the CTF format. See
31651 @ref{Trace Files} for more information about CTF.
31653 @subsubheading @value{GDBN} Command
31655 The corresponding @value{GDBN} command is @samp{tsave}.
31658 @subheading -trace-start
31659 @findex -trace-start
31661 @subsubheading Synopsis
31667 Starts a tracing experiment. The result of this command does not
31670 @subsubheading @value{GDBN} Command
31672 The corresponding @value{GDBN} command is @samp{tstart}.
31674 @subheading -trace-status
31675 @findex -trace-status
31677 @subsubheading Synopsis
31683 Obtains the status of a tracing experiment. The result may include
31684 the following fields:
31689 May have a value of either @samp{0}, when no tracing operations are
31690 supported, @samp{1}, when all tracing operations are supported, or
31691 @samp{file} when examining trace file. In the latter case, examining
31692 of trace frame is possible but new tracing experiement cannot be
31693 started. This field is always present.
31696 May have a value of either @samp{0} or @samp{1} depending on whether
31697 tracing experiement is in progress on target. This field is present
31698 if @samp{supported} field is not @samp{0}.
31701 Report the reason why the tracing was stopped last time. This field
31702 may be absent iff tracing was never stopped on target yet. The
31703 value of @samp{request} means the tracing was stopped as result of
31704 the @code{-trace-stop} command. The value of @samp{overflow} means
31705 the tracing buffer is full. The value of @samp{disconnection} means
31706 tracing was automatically stopped when @value{GDBN} has disconnected.
31707 The value of @samp{passcount} means tracing was stopped when a
31708 tracepoint was passed a maximal number of times for that tracepoint.
31709 This field is present if @samp{supported} field is not @samp{0}.
31711 @item stopping-tracepoint
31712 The number of tracepoint whose passcount as exceeded. This field is
31713 present iff the @samp{stop-reason} field has the value of
31717 @itemx frames-created
31718 The @samp{frames} field is a count of the total number of trace frames
31719 in the trace buffer, while @samp{frames-created} is the total created
31720 during the run, including ones that were discarded, such as when a
31721 circular trace buffer filled up. Both fields are optional.
31725 These fields tell the current size of the tracing buffer and the
31726 remaining space. These fields are optional.
31729 The value of the circular trace buffer flag. @code{1} means that the
31730 trace buffer is circular and old trace frames will be discarded if
31731 necessary to make room, @code{0} means that the trace buffer is linear
31735 The value of the disconnected tracing flag. @code{1} means that
31736 tracing will continue after @value{GDBN} disconnects, @code{0} means
31737 that the trace run will stop.
31740 The filename of the trace file being examined. This field is
31741 optional, and only present when examining a trace file.
31745 @subsubheading @value{GDBN} Command
31747 The corresponding @value{GDBN} command is @samp{tstatus}.
31749 @subheading -trace-stop
31750 @findex -trace-stop
31752 @subsubheading Synopsis
31758 Stops a tracing experiment. The result of this command has the same
31759 fields as @code{-trace-status}, except that the @samp{supported} and
31760 @samp{running} fields are not output.
31762 @subsubheading @value{GDBN} Command
31764 The corresponding @value{GDBN} command is @samp{tstop}.
31767 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31768 @node GDB/MI Symbol Query
31769 @section @sc{gdb/mi} Symbol Query Commands
31773 @subheading The @code{-symbol-info-address} Command
31774 @findex -symbol-info-address
31776 @subsubheading Synopsis
31779 -symbol-info-address @var{symbol}
31782 Describe where @var{symbol} is stored.
31784 @subsubheading @value{GDBN} Command
31786 The corresponding @value{GDBN} command is @samp{info address}.
31788 @subsubheading Example
31792 @subheading The @code{-symbol-info-file} Command
31793 @findex -symbol-info-file
31795 @subsubheading Synopsis
31801 Show the file for the symbol.
31803 @subsubheading @value{GDBN} Command
31805 There's no equivalent @value{GDBN} command. @code{gdbtk} has
31806 @samp{gdb_find_file}.
31808 @subsubheading Example
31812 @subheading The @code{-symbol-info-function} Command
31813 @findex -symbol-info-function
31815 @subsubheading Synopsis
31818 -symbol-info-function
31821 Show which function the symbol lives in.
31823 @subsubheading @value{GDBN} Command
31825 @samp{gdb_get_function} in @code{gdbtk}.
31827 @subsubheading Example
31831 @subheading The @code{-symbol-info-line} Command
31832 @findex -symbol-info-line
31834 @subsubheading Synopsis
31840 Show the core addresses of the code for a source line.
31842 @subsubheading @value{GDBN} Command
31844 The corresponding @value{GDBN} command is @samp{info line}.
31845 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
31847 @subsubheading Example
31851 @subheading The @code{-symbol-info-symbol} Command
31852 @findex -symbol-info-symbol
31854 @subsubheading Synopsis
31857 -symbol-info-symbol @var{addr}
31860 Describe what symbol is at location @var{addr}.
31862 @subsubheading @value{GDBN} Command
31864 The corresponding @value{GDBN} command is @samp{info symbol}.
31866 @subsubheading Example
31870 @subheading The @code{-symbol-list-functions} Command
31871 @findex -symbol-list-functions
31873 @subsubheading Synopsis
31876 -symbol-list-functions
31879 List the functions in the executable.
31881 @subsubheading @value{GDBN} Command
31883 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
31884 @samp{gdb_search} in @code{gdbtk}.
31886 @subsubheading Example
31891 @subheading The @code{-symbol-list-lines} Command
31892 @findex -symbol-list-lines
31894 @subsubheading Synopsis
31897 -symbol-list-lines @var{filename}
31900 Print the list of lines that contain code and their associated program
31901 addresses for the given source filename. The entries are sorted in
31902 ascending PC order.
31904 @subsubheading @value{GDBN} Command
31906 There is no corresponding @value{GDBN} command.
31908 @subsubheading Example
31911 -symbol-list-lines basics.c
31912 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
31918 @subheading The @code{-symbol-list-types} Command
31919 @findex -symbol-list-types
31921 @subsubheading Synopsis
31927 List all the type names.
31929 @subsubheading @value{GDBN} Command
31931 The corresponding commands are @samp{info types} in @value{GDBN},
31932 @samp{gdb_search} in @code{gdbtk}.
31934 @subsubheading Example
31938 @subheading The @code{-symbol-list-variables} Command
31939 @findex -symbol-list-variables
31941 @subsubheading Synopsis
31944 -symbol-list-variables
31947 List all the global and static variable names.
31949 @subsubheading @value{GDBN} Command
31951 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
31953 @subsubheading Example
31957 @subheading The @code{-symbol-locate} Command
31958 @findex -symbol-locate
31960 @subsubheading Synopsis
31966 @subsubheading @value{GDBN} Command
31968 @samp{gdb_loc} in @code{gdbtk}.
31970 @subsubheading Example
31974 @subheading The @code{-symbol-type} Command
31975 @findex -symbol-type
31977 @subsubheading Synopsis
31980 -symbol-type @var{variable}
31983 Show type of @var{variable}.
31985 @subsubheading @value{GDBN} Command
31987 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
31988 @samp{gdb_obj_variable}.
31990 @subsubheading Example
31995 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31996 @node GDB/MI File Commands
31997 @section @sc{gdb/mi} File Commands
31999 This section describes the GDB/MI commands to specify executable file names
32000 and to read in and obtain symbol table information.
32002 @subheading The @code{-file-exec-and-symbols} Command
32003 @findex -file-exec-and-symbols
32005 @subsubheading Synopsis
32008 -file-exec-and-symbols @var{file}
32011 Specify the executable file to be debugged. This file is the one from
32012 which the symbol table is also read. If no file is specified, the
32013 command clears the executable and symbol information. If breakpoints
32014 are set when using this command with no arguments, @value{GDBN} will produce
32015 error messages. Otherwise, no output is produced, except a completion
32018 @subsubheading @value{GDBN} Command
32020 The corresponding @value{GDBN} command is @samp{file}.
32022 @subsubheading Example
32026 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32032 @subheading The @code{-file-exec-file} Command
32033 @findex -file-exec-file
32035 @subsubheading Synopsis
32038 -file-exec-file @var{file}
32041 Specify the executable file to be debugged. Unlike
32042 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32043 from this file. If used without argument, @value{GDBN} clears the information
32044 about the executable file. No output is produced, except a completion
32047 @subsubheading @value{GDBN} Command
32049 The corresponding @value{GDBN} command is @samp{exec-file}.
32051 @subsubheading Example
32055 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32062 @subheading The @code{-file-list-exec-sections} Command
32063 @findex -file-list-exec-sections
32065 @subsubheading Synopsis
32068 -file-list-exec-sections
32071 List the sections of the current executable file.
32073 @subsubheading @value{GDBN} Command
32075 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32076 information as this command. @code{gdbtk} has a corresponding command
32077 @samp{gdb_load_info}.
32079 @subsubheading Example
32084 @subheading The @code{-file-list-exec-source-file} Command
32085 @findex -file-list-exec-source-file
32087 @subsubheading Synopsis
32090 -file-list-exec-source-file
32093 List the line number, the current source file, and the absolute path
32094 to the current source file for the current executable. The macro
32095 information field has a value of @samp{1} or @samp{0} depending on
32096 whether or not the file includes preprocessor macro information.
32098 @subsubheading @value{GDBN} Command
32100 The @value{GDBN} equivalent is @samp{info source}
32102 @subsubheading Example
32106 123-file-list-exec-source-file
32107 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32112 @subheading The @code{-file-list-exec-source-files} Command
32113 @findex -file-list-exec-source-files
32115 @subsubheading Synopsis
32118 -file-list-exec-source-files
32121 List the source files for the current executable.
32123 It will always output both the filename and fullname (absolute file
32124 name) of a source file.
32126 @subsubheading @value{GDBN} Command
32128 The @value{GDBN} equivalent is @samp{info sources}.
32129 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32131 @subsubheading Example
32134 -file-list-exec-source-files
32136 @{file=foo.c,fullname=/home/foo.c@},
32137 @{file=/home/bar.c,fullname=/home/bar.c@},
32138 @{file=gdb_could_not_find_fullpath.c@}]
32142 @subheading The @code{-file-list-shared-libraries} Command
32143 @findex -file-list-shared-libraries
32145 @subsubheading Synopsis
32148 -file-list-shared-libraries [ @var{regexp} ]
32151 List the shared libraries in the program.
32152 With a regular expression @var{regexp}, only those libraries whose
32153 names match @var{regexp} are listed.
32155 @subsubheading @value{GDBN} Command
32157 The corresponding @value{GDBN} command is @samp{info shared}. The fields
32158 have a similar meaning to the @code{=library-loaded} notification.
32159 The @code{ranges} field specifies the multiple segments belonging to this
32160 library. Each range has the following fields:
32164 The address defining the inclusive lower bound of the segment.
32166 The address defining the exclusive upper bound of the segment.
32169 @subsubheading Example
32172 -file-list-exec-source-files
32173 ^done,shared-libraries=[
32174 @{id="/lib/libfoo.so",target-name="/lib/libfoo.so",host-name="/lib/libfoo.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x72815989",to="0x728162c0"@}]@},
32175 @{id="/lib/libbar.so",target-name="/lib/libbar.so",host-name="/lib/libbar.so",symbols-loaded="1",thread-group="i1",ranges=[@{from="0x76ee48c0",to="0x76ee9160"@}]@}]
32181 @subheading The @code{-file-list-symbol-files} Command
32182 @findex -file-list-symbol-files
32184 @subsubheading Synopsis
32187 -file-list-symbol-files
32192 @subsubheading @value{GDBN} Command
32194 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32196 @subsubheading Example
32201 @subheading The @code{-file-symbol-file} Command
32202 @findex -file-symbol-file
32204 @subsubheading Synopsis
32207 -file-symbol-file @var{file}
32210 Read symbol table info from the specified @var{file} argument. When
32211 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32212 produced, except for a completion notification.
32214 @subsubheading @value{GDBN} Command
32216 The corresponding @value{GDBN} command is @samp{symbol-file}.
32218 @subsubheading Example
32222 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32228 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32229 @node GDB/MI Memory Overlay Commands
32230 @section @sc{gdb/mi} Memory Overlay Commands
32232 The memory overlay commands are not implemented.
32234 @c @subheading -overlay-auto
32236 @c @subheading -overlay-list-mapping-state
32238 @c @subheading -overlay-list-overlays
32240 @c @subheading -overlay-map
32242 @c @subheading -overlay-off
32244 @c @subheading -overlay-on
32246 @c @subheading -overlay-unmap
32248 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32249 @node GDB/MI Signal Handling Commands
32250 @section @sc{gdb/mi} Signal Handling Commands
32252 Signal handling commands are not implemented.
32254 @c @subheading -signal-handle
32256 @c @subheading -signal-list-handle-actions
32258 @c @subheading -signal-list-signal-types
32262 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32263 @node GDB/MI Target Manipulation
32264 @section @sc{gdb/mi} Target Manipulation Commands
32267 @subheading The @code{-target-attach} Command
32268 @findex -target-attach
32270 @subsubheading Synopsis
32273 -target-attach @var{pid} | @var{gid} | @var{file}
32276 Attach to a process @var{pid} or a file @var{file} outside of
32277 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32278 group, the id previously returned by
32279 @samp{-list-thread-groups --available} must be used.
32281 @subsubheading @value{GDBN} Command
32283 The corresponding @value{GDBN} command is @samp{attach}.
32285 @subsubheading Example
32289 =thread-created,id="1"
32290 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32296 @subheading The @code{-target-compare-sections} Command
32297 @findex -target-compare-sections
32299 @subsubheading Synopsis
32302 -target-compare-sections [ @var{section} ]
32305 Compare data of section @var{section} on target to the exec file.
32306 Without the argument, all sections are compared.
32308 @subsubheading @value{GDBN} Command
32310 The @value{GDBN} equivalent is @samp{compare-sections}.
32312 @subsubheading Example
32317 @subheading The @code{-target-detach} Command
32318 @findex -target-detach
32320 @subsubheading Synopsis
32323 -target-detach [ @var{pid} | @var{gid} ]
32326 Detach from the remote target which normally resumes its execution.
32327 If either @var{pid} or @var{gid} is specified, detaches from either
32328 the specified process, or specified thread group. There's no output.
32330 @subsubheading @value{GDBN} Command
32332 The corresponding @value{GDBN} command is @samp{detach}.
32334 @subsubheading Example
32344 @subheading The @code{-target-disconnect} Command
32345 @findex -target-disconnect
32347 @subsubheading Synopsis
32353 Disconnect from the remote target. There's no output and the target is
32354 generally not resumed.
32356 @subsubheading @value{GDBN} Command
32358 The corresponding @value{GDBN} command is @samp{disconnect}.
32360 @subsubheading Example
32370 @subheading The @code{-target-download} Command
32371 @findex -target-download
32373 @subsubheading Synopsis
32379 Loads the executable onto the remote target.
32380 It prints out an update message every half second, which includes the fields:
32384 The name of the section.
32386 The size of what has been sent so far for that section.
32388 The size of the section.
32390 The total size of what was sent so far (the current and the previous sections).
32392 The size of the overall executable to download.
32396 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32397 @sc{gdb/mi} Output Syntax}).
32399 In addition, it prints the name and size of the sections, as they are
32400 downloaded. These messages include the following fields:
32404 The name of the section.
32406 The size of the section.
32408 The size of the overall executable to download.
32412 At the end, a summary is printed.
32414 @subsubheading @value{GDBN} Command
32416 The corresponding @value{GDBN} command is @samp{load}.
32418 @subsubheading Example
32420 Note: each status message appears on a single line. Here the messages
32421 have been broken down so that they can fit onto a page.
32426 +download,@{section=".text",section-size="6668",total-size="9880"@}
32427 +download,@{section=".text",section-sent="512",section-size="6668",
32428 total-sent="512",total-size="9880"@}
32429 +download,@{section=".text",section-sent="1024",section-size="6668",
32430 total-sent="1024",total-size="9880"@}
32431 +download,@{section=".text",section-sent="1536",section-size="6668",
32432 total-sent="1536",total-size="9880"@}
32433 +download,@{section=".text",section-sent="2048",section-size="6668",
32434 total-sent="2048",total-size="9880"@}
32435 +download,@{section=".text",section-sent="2560",section-size="6668",
32436 total-sent="2560",total-size="9880"@}
32437 +download,@{section=".text",section-sent="3072",section-size="6668",
32438 total-sent="3072",total-size="9880"@}
32439 +download,@{section=".text",section-sent="3584",section-size="6668",
32440 total-sent="3584",total-size="9880"@}
32441 +download,@{section=".text",section-sent="4096",section-size="6668",
32442 total-sent="4096",total-size="9880"@}
32443 +download,@{section=".text",section-sent="4608",section-size="6668",
32444 total-sent="4608",total-size="9880"@}
32445 +download,@{section=".text",section-sent="5120",section-size="6668",
32446 total-sent="5120",total-size="9880"@}
32447 +download,@{section=".text",section-sent="5632",section-size="6668",
32448 total-sent="5632",total-size="9880"@}
32449 +download,@{section=".text",section-sent="6144",section-size="6668",
32450 total-sent="6144",total-size="9880"@}
32451 +download,@{section=".text",section-sent="6656",section-size="6668",
32452 total-sent="6656",total-size="9880"@}
32453 +download,@{section=".init",section-size="28",total-size="9880"@}
32454 +download,@{section=".fini",section-size="28",total-size="9880"@}
32455 +download,@{section=".data",section-size="3156",total-size="9880"@}
32456 +download,@{section=".data",section-sent="512",section-size="3156",
32457 total-sent="7236",total-size="9880"@}
32458 +download,@{section=".data",section-sent="1024",section-size="3156",
32459 total-sent="7748",total-size="9880"@}
32460 +download,@{section=".data",section-sent="1536",section-size="3156",
32461 total-sent="8260",total-size="9880"@}
32462 +download,@{section=".data",section-sent="2048",section-size="3156",
32463 total-sent="8772",total-size="9880"@}
32464 +download,@{section=".data",section-sent="2560",section-size="3156",
32465 total-sent="9284",total-size="9880"@}
32466 +download,@{section=".data",section-sent="3072",section-size="3156",
32467 total-sent="9796",total-size="9880"@}
32468 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32475 @subheading The @code{-target-exec-status} Command
32476 @findex -target-exec-status
32478 @subsubheading Synopsis
32481 -target-exec-status
32484 Provide information on the state of the target (whether it is running or
32485 not, for instance).
32487 @subsubheading @value{GDBN} Command
32489 There's no equivalent @value{GDBN} command.
32491 @subsubheading Example
32495 @subheading The @code{-target-list-available-targets} Command
32496 @findex -target-list-available-targets
32498 @subsubheading Synopsis
32501 -target-list-available-targets
32504 List the possible targets to connect to.
32506 @subsubheading @value{GDBN} Command
32508 The corresponding @value{GDBN} command is @samp{help target}.
32510 @subsubheading Example
32514 @subheading The @code{-target-list-current-targets} Command
32515 @findex -target-list-current-targets
32517 @subsubheading Synopsis
32520 -target-list-current-targets
32523 Describe the current target.
32525 @subsubheading @value{GDBN} Command
32527 The corresponding information is printed by @samp{info file} (among
32530 @subsubheading Example
32534 @subheading The @code{-target-list-parameters} Command
32535 @findex -target-list-parameters
32537 @subsubheading Synopsis
32540 -target-list-parameters
32546 @subsubheading @value{GDBN} Command
32550 @subsubheading Example
32553 @subheading The @code{-target-flash-erase} Command
32554 @findex -target-flash-erase
32556 @subsubheading Synopsis
32559 -target-flash-erase
32562 Erases all known flash memory regions on the target.
32564 The corresponding @value{GDBN} command is @samp{flash-erase}.
32566 The output is a list of flash regions that have been erased, with starting
32567 addresses and memory region sizes.
32571 -target-flash-erase
32572 ^done,erased-regions=@{address="0x0",size="0x40000"@}
32576 @subheading The @code{-target-select} Command
32577 @findex -target-select
32579 @subsubheading Synopsis
32582 -target-select @var{type} @var{parameters @dots{}}
32585 Connect @value{GDBN} to the remote target. This command takes two args:
32589 The type of target, for instance @samp{remote}, etc.
32590 @item @var{parameters}
32591 Device names, host names and the like. @xref{Target Commands, ,
32592 Commands for Managing Targets}, for more details.
32595 The output is a connection notification, followed by the address at
32596 which the target program is, in the following form:
32599 ^connected,addr="@var{address}",func="@var{function name}",
32600 args=[@var{arg list}]
32603 @subsubheading @value{GDBN} Command
32605 The corresponding @value{GDBN} command is @samp{target}.
32607 @subsubheading Example
32611 -target-select remote /dev/ttya
32612 ^connected,addr="0xfe00a300",func="??",args=[]
32616 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32617 @node GDB/MI File Transfer Commands
32618 @section @sc{gdb/mi} File Transfer Commands
32621 @subheading The @code{-target-file-put} Command
32622 @findex -target-file-put
32624 @subsubheading Synopsis
32627 -target-file-put @var{hostfile} @var{targetfile}
32630 Copy file @var{hostfile} from the host system (the machine running
32631 @value{GDBN}) to @var{targetfile} on the target system.
32633 @subsubheading @value{GDBN} Command
32635 The corresponding @value{GDBN} command is @samp{remote put}.
32637 @subsubheading Example
32641 -target-file-put localfile remotefile
32647 @subheading The @code{-target-file-get} Command
32648 @findex -target-file-get
32650 @subsubheading Synopsis
32653 -target-file-get @var{targetfile} @var{hostfile}
32656 Copy file @var{targetfile} from the target system to @var{hostfile}
32657 on the host system.
32659 @subsubheading @value{GDBN} Command
32661 The corresponding @value{GDBN} command is @samp{remote get}.
32663 @subsubheading Example
32667 -target-file-get remotefile localfile
32673 @subheading The @code{-target-file-delete} Command
32674 @findex -target-file-delete
32676 @subsubheading Synopsis
32679 -target-file-delete @var{targetfile}
32682 Delete @var{targetfile} from the target system.
32684 @subsubheading @value{GDBN} Command
32686 The corresponding @value{GDBN} command is @samp{remote delete}.
32688 @subsubheading Example
32692 -target-file-delete remotefile
32698 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32699 @node GDB/MI Ada Exceptions Commands
32700 @section Ada Exceptions @sc{gdb/mi} Commands
32702 @subheading The @code{-info-ada-exceptions} Command
32703 @findex -info-ada-exceptions
32705 @subsubheading Synopsis
32708 -info-ada-exceptions [ @var{regexp}]
32711 List all Ada exceptions defined within the program being debugged.
32712 With a regular expression @var{regexp}, only those exceptions whose
32713 names match @var{regexp} are listed.
32715 @subsubheading @value{GDBN} Command
32717 The corresponding @value{GDBN} command is @samp{info exceptions}.
32719 @subsubheading Result
32721 The result is a table of Ada exceptions. The following columns are
32722 defined for each exception:
32726 The name of the exception.
32729 The address of the exception.
32733 @subsubheading Example
32736 -info-ada-exceptions aint
32737 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
32738 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
32739 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
32740 body=[@{name="constraint_error",address="0x0000000000613da0"@},
32741 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
32744 @subheading Catching Ada Exceptions
32746 The commands describing how to ask @value{GDBN} to stop when a program
32747 raises an exception are described at @ref{Ada Exception GDB/MI
32748 Catchpoint Commands}.
32751 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32752 @node GDB/MI Support Commands
32753 @section @sc{gdb/mi} Support Commands
32755 Since new commands and features get regularly added to @sc{gdb/mi},
32756 some commands are available to help front-ends query the debugger
32757 about support for these capabilities. Similarly, it is also possible
32758 to query @value{GDBN} about target support of certain features.
32760 @subheading The @code{-info-gdb-mi-command} Command
32761 @cindex @code{-info-gdb-mi-command}
32762 @findex -info-gdb-mi-command
32764 @subsubheading Synopsis
32767 -info-gdb-mi-command @var{cmd_name}
32770 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
32772 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
32773 is technically not part of the command name (@pxref{GDB/MI Input
32774 Syntax}), and thus should be omitted in @var{cmd_name}. However,
32775 for ease of use, this command also accepts the form with the leading
32778 @subsubheading @value{GDBN} Command
32780 There is no corresponding @value{GDBN} command.
32782 @subsubheading Result
32784 The result is a tuple. There is currently only one field:
32788 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
32789 @code{"false"} otherwise.
32793 @subsubheading Example
32795 Here is an example where the @sc{gdb/mi} command does not exist:
32798 -info-gdb-mi-command unsupported-command
32799 ^done,command=@{exists="false"@}
32803 And here is an example where the @sc{gdb/mi} command is known
32807 -info-gdb-mi-command symbol-list-lines
32808 ^done,command=@{exists="true"@}
32811 @subheading The @code{-list-features} Command
32812 @findex -list-features
32813 @cindex supported @sc{gdb/mi} features, list
32815 Returns a list of particular features of the MI protocol that
32816 this version of gdb implements. A feature can be a command,
32817 or a new field in an output of some command, or even an
32818 important bugfix. While a frontend can sometimes detect presence
32819 of a feature at runtime, it is easier to perform detection at debugger
32822 The command returns a list of strings, with each string naming an
32823 available feature. Each returned string is just a name, it does not
32824 have any internal structure. The list of possible feature names
32830 (gdb) -list-features
32831 ^done,result=["feature1","feature2"]
32834 The current list of features is:
32837 @item frozen-varobjs
32838 Indicates support for the @code{-var-set-frozen} command, as well
32839 as possible presense of the @code{frozen} field in the output
32840 of @code{-varobj-create}.
32841 @item pending-breakpoints
32842 Indicates support for the @option{-f} option to the @code{-break-insert}
32845 Indicates Python scripting support, Python-based
32846 pretty-printing commands, and possible presence of the
32847 @samp{display_hint} field in the output of @code{-var-list-children}
32849 Indicates support for the @code{-thread-info} command.
32850 @item data-read-memory-bytes
32851 Indicates support for the @code{-data-read-memory-bytes} and the
32852 @code{-data-write-memory-bytes} commands.
32853 @item breakpoint-notifications
32854 Indicates that changes to breakpoints and breakpoints created via the
32855 CLI will be announced via async records.
32856 @item ada-task-info
32857 Indicates support for the @code{-ada-task-info} command.
32858 @item language-option
32859 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
32860 option (@pxref{Context management}).
32861 @item info-gdb-mi-command
32862 Indicates support for the @code{-info-gdb-mi-command} command.
32863 @item undefined-command-error-code
32864 Indicates support for the "undefined-command" error code in error result
32865 records, produced when trying to execute an undefined @sc{gdb/mi} command
32866 (@pxref{GDB/MI Result Records}).
32867 @item exec-run-start-option
32868 Indicates that the @code{-exec-run} command supports the @option{--start}
32869 option (@pxref{GDB/MI Program Execution}).
32872 @subheading The @code{-list-target-features} Command
32873 @findex -list-target-features
32875 Returns a list of particular features that are supported by the
32876 target. Those features affect the permitted MI commands, but
32877 unlike the features reported by the @code{-list-features} command, the
32878 features depend on which target GDB is using at the moment. Whenever
32879 a target can change, due to commands such as @code{-target-select},
32880 @code{-target-attach} or @code{-exec-run}, the list of target features
32881 may change, and the frontend should obtain it again.
32885 (gdb) -list-target-features
32886 ^done,result=["async"]
32889 The current list of features is:
32893 Indicates that the target is capable of asynchronous command
32894 execution, which means that @value{GDBN} will accept further commands
32895 while the target is running.
32898 Indicates that the target is capable of reverse execution.
32899 @xref{Reverse Execution}, for more information.
32903 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32904 @node GDB/MI Miscellaneous Commands
32905 @section Miscellaneous @sc{gdb/mi} Commands
32907 @c @subheading -gdb-complete
32909 @subheading The @code{-gdb-exit} Command
32912 @subsubheading Synopsis
32918 Exit @value{GDBN} immediately.
32920 @subsubheading @value{GDBN} Command
32922 Approximately corresponds to @samp{quit}.
32924 @subsubheading Example
32934 @subheading The @code{-exec-abort} Command
32935 @findex -exec-abort
32937 @subsubheading Synopsis
32943 Kill the inferior running program.
32945 @subsubheading @value{GDBN} Command
32947 The corresponding @value{GDBN} command is @samp{kill}.
32949 @subsubheading Example
32954 @subheading The @code{-gdb-set} Command
32957 @subsubheading Synopsis
32963 Set an internal @value{GDBN} variable.
32964 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
32966 @subsubheading @value{GDBN} Command
32968 The corresponding @value{GDBN} command is @samp{set}.
32970 @subsubheading Example
32980 @subheading The @code{-gdb-show} Command
32983 @subsubheading Synopsis
32989 Show the current value of a @value{GDBN} variable.
32991 @subsubheading @value{GDBN} Command
32993 The corresponding @value{GDBN} command is @samp{show}.
32995 @subsubheading Example
33004 @c @subheading -gdb-source
33007 @subheading The @code{-gdb-version} Command
33008 @findex -gdb-version
33010 @subsubheading Synopsis
33016 Show version information for @value{GDBN}. Used mostly in testing.
33018 @subsubheading @value{GDBN} Command
33020 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33021 default shows this information when you start an interactive session.
33023 @subsubheading Example
33025 @c This example modifies the actual output from GDB to avoid overfull
33031 ~Copyright 2000 Free Software Foundation, Inc.
33032 ~GDB is free software, covered by the GNU General Public License, and
33033 ~you are welcome to change it and/or distribute copies of it under
33034 ~ certain conditions.
33035 ~Type "show copying" to see the conditions.
33036 ~There is absolutely no warranty for GDB. Type "show warranty" for
33038 ~This GDB was configured as
33039 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33044 @subheading The @code{-list-thread-groups} Command
33045 @findex -list-thread-groups
33047 @subheading Synopsis
33050 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33053 Lists thread groups (@pxref{Thread groups}). When a single thread
33054 group is passed as the argument, lists the children of that group.
33055 When several thread group are passed, lists information about those
33056 thread groups. Without any parameters, lists information about all
33057 top-level thread groups.
33059 Normally, thread groups that are being debugged are reported.
33060 With the @samp{--available} option, @value{GDBN} reports thread groups
33061 available on the target.
33063 The output of this command may have either a @samp{threads} result or
33064 a @samp{groups} result. The @samp{thread} result has a list of tuples
33065 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33066 Information}). The @samp{groups} result has a list of tuples as value,
33067 each tuple describing a thread group. If top-level groups are
33068 requested (that is, no parameter is passed), or when several groups
33069 are passed, the output always has a @samp{groups} result. The format
33070 of the @samp{group} result is described below.
33072 To reduce the number of roundtrips it's possible to list thread groups
33073 together with their children, by passing the @samp{--recurse} option
33074 and the recursion depth. Presently, only recursion depth of 1 is
33075 permitted. If this option is present, then every reported thread group
33076 will also include its children, either as @samp{group} or
33077 @samp{threads} field.
33079 In general, any combination of option and parameters is permitted, with
33080 the following caveats:
33084 When a single thread group is passed, the output will typically
33085 be the @samp{threads} result. Because threads may not contain
33086 anything, the @samp{recurse} option will be ignored.
33089 When the @samp{--available} option is passed, limited information may
33090 be available. In particular, the list of threads of a process might
33091 be inaccessible. Further, specifying specific thread groups might
33092 not give any performance advantage over listing all thread groups.
33093 The frontend should assume that @samp{-list-thread-groups --available}
33094 is always an expensive operation and cache the results.
33098 The @samp{groups} result is a list of tuples, where each tuple may
33099 have the following fields:
33103 Identifier of the thread group. This field is always present.
33104 The identifier is an opaque string; frontends should not try to
33105 convert it to an integer, even though it might look like one.
33108 The type of the thread group. At present, only @samp{process} is a
33112 The target-specific process identifier. This field is only present
33113 for thread groups of type @samp{process} and only if the process exists.
33116 The exit code of this group's last exited thread, formatted in octal.
33117 This field is only present for thread groups of type @samp{process} and
33118 only if the process is not running.
33121 The number of children this thread group has. This field may be
33122 absent for an available thread group.
33125 This field has a list of tuples as value, each tuple describing a
33126 thread. It may be present if the @samp{--recurse} option is
33127 specified, and it's actually possible to obtain the threads.
33130 This field is a list of integers, each identifying a core that one
33131 thread of the group is running on. This field may be absent if
33132 such information is not available.
33135 The name of the executable file that corresponds to this thread group.
33136 The field is only present for thread groups of type @samp{process},
33137 and only if there is a corresponding executable file.
33141 @subheading Example
33145 -list-thread-groups
33146 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33147 -list-thread-groups 17
33148 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33149 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33150 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33151 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33152 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33153 -list-thread-groups --available
33154 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33155 -list-thread-groups --available --recurse 1
33156 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33157 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33158 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33159 -list-thread-groups --available --recurse 1 17 18
33160 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33161 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33162 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33165 @subheading The @code{-info-os} Command
33168 @subsubheading Synopsis
33171 -info-os [ @var{type} ]
33174 If no argument is supplied, the command returns a table of available
33175 operating-system-specific information types. If one of these types is
33176 supplied as an argument @var{type}, then the command returns a table
33177 of data of that type.
33179 The types of information available depend on the target operating
33182 @subsubheading @value{GDBN} Command
33184 The corresponding @value{GDBN} command is @samp{info os}.
33186 @subsubheading Example
33188 When run on a @sc{gnu}/Linux system, the output will look something
33194 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
33195 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33196 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33197 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33198 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
33200 item=@{col0="files",col1="Listing of all file descriptors",
33201 col2="File descriptors"@},
33202 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33203 col2="Kernel modules"@},
33204 item=@{col0="msg",col1="Listing of all message queues",
33205 col2="Message queues"@},
33206 item=@{col0="processes",col1="Listing of all processes",
33207 col2="Processes"@},
33208 item=@{col0="procgroups",col1="Listing of all process groups",
33209 col2="Process groups"@},
33210 item=@{col0="semaphores",col1="Listing of all semaphores",
33211 col2="Semaphores"@},
33212 item=@{col0="shm",col1="Listing of all shared-memory regions",
33213 col2="Shared-memory regions"@},
33214 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33216 item=@{col0="threads",col1="Listing of all threads",
33220 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33221 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33222 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33223 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33224 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33225 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33226 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33227 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33229 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33230 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33234 (Note that the MI output here includes a @code{"Title"} column that
33235 does not appear in command-line @code{info os}; this column is useful
33236 for MI clients that want to enumerate the types of data, such as in a
33237 popup menu, but is needless clutter on the command line, and
33238 @code{info os} omits it.)
33240 @subheading The @code{-add-inferior} Command
33241 @findex -add-inferior
33243 @subheading Synopsis
33249 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33250 inferior is not associated with any executable. Such association may
33251 be established with the @samp{-file-exec-and-symbols} command
33252 (@pxref{GDB/MI File Commands}). The command response has a single
33253 field, @samp{inferior}, whose value is the identifier of the
33254 thread group corresponding to the new inferior.
33256 @subheading Example
33261 ^done,inferior="i3"
33264 @subheading The @code{-interpreter-exec} Command
33265 @findex -interpreter-exec
33267 @subheading Synopsis
33270 -interpreter-exec @var{interpreter} @var{command}
33272 @anchor{-interpreter-exec}
33274 Execute the specified @var{command} in the given @var{interpreter}.
33276 @subheading @value{GDBN} Command
33278 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33280 @subheading Example
33284 -interpreter-exec console "break main"
33285 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33286 &"During symbol reading, bad structure-type format.\n"
33287 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33292 @subheading The @code{-inferior-tty-set} Command
33293 @findex -inferior-tty-set
33295 @subheading Synopsis
33298 -inferior-tty-set /dev/pts/1
33301 Set terminal for future runs of the program being debugged.
33303 @subheading @value{GDBN} Command
33305 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33307 @subheading Example
33311 -inferior-tty-set /dev/pts/1
33316 @subheading The @code{-inferior-tty-show} Command
33317 @findex -inferior-tty-show
33319 @subheading Synopsis
33325 Show terminal for future runs of program being debugged.
33327 @subheading @value{GDBN} Command
33329 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33331 @subheading Example
33335 -inferior-tty-set /dev/pts/1
33339 ^done,inferior_tty_terminal="/dev/pts/1"
33343 @subheading The @code{-enable-timings} Command
33344 @findex -enable-timings
33346 @subheading Synopsis
33349 -enable-timings [yes | no]
33352 Toggle the printing of the wallclock, user and system times for an MI
33353 command as a field in its output. This command is to help frontend
33354 developers optimize the performance of their code. No argument is
33355 equivalent to @samp{yes}.
33357 @subheading @value{GDBN} Command
33361 @subheading Example
33369 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33370 addr="0x080484ed",func="main",file="myprog.c",
33371 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33373 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33381 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33382 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33383 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33384 fullname="/home/nickrob/myprog.c",line="73"@}
33389 @chapter @value{GDBN} Annotations
33391 This chapter describes annotations in @value{GDBN}. Annotations were
33392 designed to interface @value{GDBN} to graphical user interfaces or other
33393 similar programs which want to interact with @value{GDBN} at a
33394 relatively high level.
33396 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33400 This is Edition @value{EDITION}, @value{DATE}.
33404 * Annotations Overview:: What annotations are; the general syntax.
33405 * Server Prefix:: Issuing a command without affecting user state.
33406 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33407 * Errors:: Annotations for error messages.
33408 * Invalidation:: Some annotations describe things now invalid.
33409 * Annotations for Running::
33410 Whether the program is running, how it stopped, etc.
33411 * Source Annotations:: Annotations describing source code.
33414 @node Annotations Overview
33415 @section What is an Annotation?
33416 @cindex annotations
33418 Annotations start with a newline character, two @samp{control-z}
33419 characters, and the name of the annotation. If there is no additional
33420 information associated with this annotation, the name of the annotation
33421 is followed immediately by a newline. If there is additional
33422 information, the name of the annotation is followed by a space, the
33423 additional information, and a newline. The additional information
33424 cannot contain newline characters.
33426 Any output not beginning with a newline and two @samp{control-z}
33427 characters denotes literal output from @value{GDBN}. Currently there is
33428 no need for @value{GDBN} to output a newline followed by two
33429 @samp{control-z} characters, but if there was such a need, the
33430 annotations could be extended with an @samp{escape} annotation which
33431 means those three characters as output.
33433 The annotation @var{level}, which is specified using the
33434 @option{--annotate} command line option (@pxref{Mode Options}), controls
33435 how much information @value{GDBN} prints together with its prompt,
33436 values of expressions, source lines, and other types of output. Level 0
33437 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33438 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33439 for programs that control @value{GDBN}, and level 2 annotations have
33440 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33441 Interface, annotate, GDB's Obsolete Annotations}).
33444 @kindex set annotate
33445 @item set annotate @var{level}
33446 The @value{GDBN} command @code{set annotate} sets the level of
33447 annotations to the specified @var{level}.
33449 @item show annotate
33450 @kindex show annotate
33451 Show the current annotation level.
33454 This chapter describes level 3 annotations.
33456 A simple example of starting up @value{GDBN} with annotations is:
33459 $ @kbd{gdb --annotate=3}
33461 Copyright 2003 Free Software Foundation, Inc.
33462 GDB is free software, covered by the GNU General Public License,
33463 and you are welcome to change it and/or distribute copies of it
33464 under certain conditions.
33465 Type "show copying" to see the conditions.
33466 There is absolutely no warranty for GDB. Type "show warranty"
33468 This GDB was configured as "i386-pc-linux-gnu"
33479 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33480 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33481 denotes a @samp{control-z} character) are annotations; the rest is
33482 output from @value{GDBN}.
33484 @node Server Prefix
33485 @section The Server Prefix
33486 @cindex server prefix
33488 If you prefix a command with @samp{server } then it will not affect
33489 the command history, nor will it affect @value{GDBN}'s notion of which
33490 command to repeat if @key{RET} is pressed on a line by itself. This
33491 means that commands can be run behind a user's back by a front-end in
33492 a transparent manner.
33494 The @code{server } prefix does not affect the recording of values into
33495 the value history; to print a value without recording it into the
33496 value history, use the @code{output} command instead of the
33497 @code{print} command.
33499 Using this prefix also disables confirmation requests
33500 (@pxref{confirmation requests}).
33503 @section Annotation for @value{GDBN} Input
33505 @cindex annotations for prompts
33506 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33507 to know when to send output, when the output from a given command is
33510 Different kinds of input each have a different @dfn{input type}. Each
33511 input type has three annotations: a @code{pre-} annotation, which
33512 denotes the beginning of any prompt which is being output, a plain
33513 annotation, which denotes the end of the prompt, and then a @code{post-}
33514 annotation which denotes the end of any echo which may (or may not) be
33515 associated with the input. For example, the @code{prompt} input type
33516 features the following annotations:
33524 The input types are
33527 @findex pre-prompt annotation
33528 @findex prompt annotation
33529 @findex post-prompt annotation
33531 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33533 @findex pre-commands annotation
33534 @findex commands annotation
33535 @findex post-commands annotation
33537 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33538 command. The annotations are repeated for each command which is input.
33540 @findex pre-overload-choice annotation
33541 @findex overload-choice annotation
33542 @findex post-overload-choice annotation
33543 @item overload-choice
33544 When @value{GDBN} wants the user to select between various overloaded functions.
33546 @findex pre-query annotation
33547 @findex query annotation
33548 @findex post-query annotation
33550 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33552 @findex pre-prompt-for-continue annotation
33553 @findex prompt-for-continue annotation
33554 @findex post-prompt-for-continue annotation
33555 @item prompt-for-continue
33556 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33557 expect this to work well; instead use @code{set height 0} to disable
33558 prompting. This is because the counting of lines is buggy in the
33559 presence of annotations.
33564 @cindex annotations for errors, warnings and interrupts
33566 @findex quit annotation
33571 This annotation occurs right before @value{GDBN} responds to an interrupt.
33573 @findex error annotation
33578 This annotation occurs right before @value{GDBN} responds to an error.
33580 Quit and error annotations indicate that any annotations which @value{GDBN} was
33581 in the middle of may end abruptly. For example, if a
33582 @code{value-history-begin} annotation is followed by a @code{error}, one
33583 cannot expect to receive the matching @code{value-history-end}. One
33584 cannot expect not to receive it either, however; an error annotation
33585 does not necessarily mean that @value{GDBN} is immediately returning all the way
33588 @findex error-begin annotation
33589 A quit or error annotation may be preceded by
33595 Any output between that and the quit or error annotation is the error
33598 Warning messages are not yet annotated.
33599 @c If we want to change that, need to fix warning(), type_error(),
33600 @c range_error(), and possibly other places.
33603 @section Invalidation Notices
33605 @cindex annotations for invalidation messages
33606 The following annotations say that certain pieces of state may have
33610 @findex frames-invalid annotation
33611 @item ^Z^Zframes-invalid
33613 The frames (for example, output from the @code{backtrace} command) may
33616 @findex breakpoints-invalid annotation
33617 @item ^Z^Zbreakpoints-invalid
33619 The breakpoints may have changed. For example, the user just added or
33620 deleted a breakpoint.
33623 @node Annotations for Running
33624 @section Running the Program
33625 @cindex annotations for running programs
33627 @findex starting annotation
33628 @findex stopping annotation
33629 When the program starts executing due to a @value{GDBN} command such as
33630 @code{step} or @code{continue},
33636 is output. When the program stops,
33642 is output. Before the @code{stopped} annotation, a variety of
33643 annotations describe how the program stopped.
33646 @findex exited annotation
33647 @item ^Z^Zexited @var{exit-status}
33648 The program exited, and @var{exit-status} is the exit status (zero for
33649 successful exit, otherwise nonzero).
33651 @findex signalled annotation
33652 @findex signal-name annotation
33653 @findex signal-name-end annotation
33654 @findex signal-string annotation
33655 @findex signal-string-end annotation
33656 @item ^Z^Zsignalled
33657 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33658 annotation continues:
33664 ^Z^Zsignal-name-end
33668 ^Z^Zsignal-string-end
33673 where @var{name} is the name of the signal, such as @code{SIGILL} or
33674 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33675 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
33676 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33677 user's benefit and have no particular format.
33679 @findex signal annotation
33681 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33682 just saying that the program received the signal, not that it was
33683 terminated with it.
33685 @findex breakpoint annotation
33686 @item ^Z^Zbreakpoint @var{number}
33687 The program hit breakpoint number @var{number}.
33689 @findex watchpoint annotation
33690 @item ^Z^Zwatchpoint @var{number}
33691 The program hit watchpoint number @var{number}.
33694 @node Source Annotations
33695 @section Displaying Source
33696 @cindex annotations for source display
33698 @findex source annotation
33699 The following annotation is used instead of displaying source code:
33702 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33705 where @var{filename} is an absolute file name indicating which source
33706 file, @var{line} is the line number within that file (where 1 is the
33707 first line in the file), @var{character} is the character position
33708 within the file (where 0 is the first character in the file) (for most
33709 debug formats this will necessarily point to the beginning of a line),
33710 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33711 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33712 @var{addr} is the address in the target program associated with the
33713 source which is being displayed. The @var{addr} is in the form @samp{0x}
33714 followed by one or more lowercase hex digits (note that this does not
33715 depend on the language).
33717 @node JIT Interface
33718 @chapter JIT Compilation Interface
33719 @cindex just-in-time compilation
33720 @cindex JIT compilation interface
33722 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33723 interface. A JIT compiler is a program or library that generates native
33724 executable code at runtime and executes it, usually in order to achieve good
33725 performance while maintaining platform independence.
33727 Programs that use JIT compilation are normally difficult to debug because
33728 portions of their code are generated at runtime, instead of being loaded from
33729 object files, which is where @value{GDBN} normally finds the program's symbols
33730 and debug information. In order to debug programs that use JIT compilation,
33731 @value{GDBN} has an interface that allows the program to register in-memory
33732 symbol files with @value{GDBN} at runtime.
33734 If you are using @value{GDBN} to debug a program that uses this interface, then
33735 it should work transparently so long as you have not stripped the binary. If
33736 you are developing a JIT compiler, then the interface is documented in the rest
33737 of this chapter. At this time, the only known client of this interface is the
33740 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33741 JIT compiler communicates with @value{GDBN} by writing data into a global
33742 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33743 attaches, it reads a linked list of symbol files from the global variable to
33744 find existing code, and puts a breakpoint in the function so that it can find
33745 out about additional code.
33748 * Declarations:: Relevant C struct declarations
33749 * Registering Code:: Steps to register code
33750 * Unregistering Code:: Steps to unregister code
33751 * Custom Debug Info:: Emit debug information in a custom format
33755 @section JIT Declarations
33757 These are the relevant struct declarations that a C program should include to
33758 implement the interface:
33768 struct jit_code_entry
33770 struct jit_code_entry *next_entry;
33771 struct jit_code_entry *prev_entry;
33772 const char *symfile_addr;
33773 uint64_t symfile_size;
33776 struct jit_descriptor
33779 /* This type should be jit_actions_t, but we use uint32_t
33780 to be explicit about the bitwidth. */
33781 uint32_t action_flag;
33782 struct jit_code_entry *relevant_entry;
33783 struct jit_code_entry *first_entry;
33786 /* GDB puts a breakpoint in this function. */
33787 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33789 /* Make sure to specify the version statically, because the
33790 debugger may check the version before we can set it. */
33791 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33794 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33795 modifications to this global data properly, which can easily be done by putting
33796 a global mutex around modifications to these structures.
33798 @node Registering Code
33799 @section Registering Code
33801 To register code with @value{GDBN}, the JIT should follow this protocol:
33805 Generate an object file in memory with symbols and other desired debug
33806 information. The file must include the virtual addresses of the sections.
33809 Create a code entry for the file, which gives the start and size of the symbol
33813 Add it to the linked list in the JIT descriptor.
33816 Point the relevant_entry field of the descriptor at the entry.
33819 Set @code{action_flag} to @code{JIT_REGISTER} and call
33820 @code{__jit_debug_register_code}.
33823 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33824 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33825 new code. However, the linked list must still be maintained in order to allow
33826 @value{GDBN} to attach to a running process and still find the symbol files.
33828 @node Unregistering Code
33829 @section Unregistering Code
33831 If code is freed, then the JIT should use the following protocol:
33835 Remove the code entry corresponding to the code from the linked list.
33838 Point the @code{relevant_entry} field of the descriptor at the code entry.
33841 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
33842 @code{__jit_debug_register_code}.
33845 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
33846 and the JIT will leak the memory used for the associated symbol files.
33848 @node Custom Debug Info
33849 @section Custom Debug Info
33850 @cindex custom JIT debug info
33851 @cindex JIT debug info reader
33853 Generating debug information in platform-native file formats (like ELF
33854 or COFF) may be an overkill for JIT compilers; especially if all the
33855 debug info is used for is displaying a meaningful backtrace. The
33856 issue can be resolved by having the JIT writers decide on a debug info
33857 format and also provide a reader that parses the debug info generated
33858 by the JIT compiler. This section gives a brief overview on writing
33859 such a parser. More specific details can be found in the source file
33860 @file{gdb/jit-reader.in}, which is also installed as a header at
33861 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
33863 The reader is implemented as a shared object (so this functionality is
33864 not available on platforms which don't allow loading shared objects at
33865 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
33866 @code{jit-reader-unload} are provided, to be used to load and unload
33867 the readers from a preconfigured directory. Once loaded, the shared
33868 object is used the parse the debug information emitted by the JIT
33872 * Using JIT Debug Info Readers:: How to use supplied readers correctly
33873 * Writing JIT Debug Info Readers:: Creating a debug-info reader
33876 @node Using JIT Debug Info Readers
33877 @subsection Using JIT Debug Info Readers
33878 @kindex jit-reader-load
33879 @kindex jit-reader-unload
33881 Readers can be loaded and unloaded using the @code{jit-reader-load}
33882 and @code{jit-reader-unload} commands.
33885 @item jit-reader-load @var{reader}
33886 Load the JIT reader named @var{reader}, which is a shared
33887 object specified as either an absolute or a relative file name. In
33888 the latter case, @value{GDBN} will try to load the reader from a
33889 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
33890 system (here @var{libdir} is the system library directory, often
33891 @file{/usr/local/lib}).
33893 Only one reader can be active at a time; trying to load a second
33894 reader when one is already loaded will result in @value{GDBN}
33895 reporting an error. A new JIT reader can be loaded by first unloading
33896 the current one using @code{jit-reader-unload} and then invoking
33897 @code{jit-reader-load}.
33899 @item jit-reader-unload
33900 Unload the currently loaded JIT reader.
33904 @node Writing JIT Debug Info Readers
33905 @subsection Writing JIT Debug Info Readers
33906 @cindex writing JIT debug info readers
33908 As mentioned, a reader is essentially a shared object conforming to a
33909 certain ABI. This ABI is described in @file{jit-reader.h}.
33911 @file{jit-reader.h} defines the structures, macros and functions
33912 required to write a reader. It is installed (along with
33913 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
33914 the system include directory.
33916 Readers need to be released under a GPL compatible license. A reader
33917 can be declared as released under such a license by placing the macro
33918 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
33920 The entry point for readers is the symbol @code{gdb_init_reader},
33921 which is expected to be a function with the prototype
33923 @findex gdb_init_reader
33925 extern struct gdb_reader_funcs *gdb_init_reader (void);
33928 @cindex @code{struct gdb_reader_funcs}
33930 @code{struct gdb_reader_funcs} contains a set of pointers to callback
33931 functions. These functions are executed to read the debug info
33932 generated by the JIT compiler (@code{read}), to unwind stack frames
33933 (@code{unwind}) and to create canonical frame IDs
33934 (@code{get_Frame_id}). It also has a callback that is called when the
33935 reader is being unloaded (@code{destroy}). The struct looks like this
33938 struct gdb_reader_funcs
33940 /* Must be set to GDB_READER_INTERFACE_VERSION. */
33941 int reader_version;
33943 /* For use by the reader. */
33946 gdb_read_debug_info *read;
33947 gdb_unwind_frame *unwind;
33948 gdb_get_frame_id *get_frame_id;
33949 gdb_destroy_reader *destroy;
33953 @cindex @code{struct gdb_symbol_callbacks}
33954 @cindex @code{struct gdb_unwind_callbacks}
33956 The callbacks are provided with another set of callbacks by
33957 @value{GDBN} to do their job. For @code{read}, these callbacks are
33958 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
33959 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
33960 @code{struct gdb_symbol_callbacks} has callbacks to create new object
33961 files and new symbol tables inside those object files. @code{struct
33962 gdb_unwind_callbacks} has callbacks to read registers off the current
33963 frame and to write out the values of the registers in the previous
33964 frame. Both have a callback (@code{target_read}) to read bytes off the
33965 target's address space.
33967 @node In-Process Agent
33968 @chapter In-Process Agent
33969 @cindex debugging agent
33970 The traditional debugging model is conceptually low-speed, but works fine,
33971 because most bugs can be reproduced in debugging-mode execution. However,
33972 as multi-core or many-core processors are becoming mainstream, and
33973 multi-threaded programs become more and more popular, there should be more
33974 and more bugs that only manifest themselves at normal-mode execution, for
33975 example, thread races, because debugger's interference with the program's
33976 timing may conceal the bugs. On the other hand, in some applications,
33977 it is not feasible for the debugger to interrupt the program's execution
33978 long enough for the developer to learn anything helpful about its behavior.
33979 If the program's correctness depends on its real-time behavior, delays
33980 introduced by a debugger might cause the program to fail, even when the
33981 code itself is correct. It is useful to be able to observe the program's
33982 behavior without interrupting it.
33984 Therefore, traditional debugging model is too intrusive to reproduce
33985 some bugs. In order to reduce the interference with the program, we can
33986 reduce the number of operations performed by debugger. The
33987 @dfn{In-Process Agent}, a shared library, is running within the same
33988 process with inferior, and is able to perform some debugging operations
33989 itself. As a result, debugger is only involved when necessary, and
33990 performance of debugging can be improved accordingly. Note that
33991 interference with program can be reduced but can't be removed completely,
33992 because the in-process agent will still stop or slow down the program.
33994 The in-process agent can interpret and execute Agent Expressions
33995 (@pxref{Agent Expressions}) during performing debugging operations. The
33996 agent expressions can be used for different purposes, such as collecting
33997 data in tracepoints, and condition evaluation in breakpoints.
33999 @anchor{Control Agent}
34000 You can control whether the in-process agent is used as an aid for
34001 debugging with the following commands:
34004 @kindex set agent on
34006 Causes the in-process agent to perform some operations on behalf of the
34007 debugger. Just which operations requested by the user will be done
34008 by the in-process agent depends on the its capabilities. For example,
34009 if you request to evaluate breakpoint conditions in the in-process agent,
34010 and the in-process agent has such capability as well, then breakpoint
34011 conditions will be evaluated in the in-process agent.
34013 @kindex set agent off
34014 @item set agent off
34015 Disables execution of debugging operations by the in-process agent. All
34016 of the operations will be performed by @value{GDBN}.
34020 Display the current setting of execution of debugging operations by
34021 the in-process agent.
34025 * In-Process Agent Protocol::
34028 @node In-Process Agent Protocol
34029 @section In-Process Agent Protocol
34030 @cindex in-process agent protocol
34032 The in-process agent is able to communicate with both @value{GDBN} and
34033 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34034 used for communications between @value{GDBN} or GDBserver and the IPA.
34035 In general, @value{GDBN} or GDBserver sends commands
34036 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34037 in-process agent replies back with the return result of the command, or
34038 some other information. The data sent to in-process agent is composed
34039 of primitive data types, such as 4-byte or 8-byte type, and composite
34040 types, which are called objects (@pxref{IPA Protocol Objects}).
34043 * IPA Protocol Objects::
34044 * IPA Protocol Commands::
34047 @node IPA Protocol Objects
34048 @subsection IPA Protocol Objects
34049 @cindex ipa protocol objects
34051 The commands sent to and results received from agent may contain some
34052 complex data types called @dfn{objects}.
34054 The in-process agent is running on the same machine with @value{GDBN}
34055 or GDBserver, so it doesn't have to handle as much differences between
34056 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34057 However, there are still some differences of two ends in two processes:
34061 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34062 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34064 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34065 GDBserver is compiled with one, and in-process agent is compiled with
34069 Here are the IPA Protocol Objects:
34073 agent expression object. It represents an agent expression
34074 (@pxref{Agent Expressions}).
34075 @anchor{agent expression object}
34077 tracepoint action object. It represents a tracepoint action
34078 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34079 memory, static trace data and to evaluate expression.
34080 @anchor{tracepoint action object}
34082 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34083 @anchor{tracepoint object}
34087 The following table describes important attributes of each IPA protocol
34090 @multitable @columnfractions .30 .20 .50
34091 @headitem Name @tab Size @tab Description
34092 @item @emph{agent expression object} @tab @tab
34093 @item length @tab 4 @tab length of bytes code
34094 @item byte code @tab @var{length} @tab contents of byte code
34095 @item @emph{tracepoint action for collecting memory} @tab @tab
34096 @item 'M' @tab 1 @tab type of tracepoint action
34097 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34098 address of the lowest byte to collect, otherwise @var{addr} is the offset
34099 of @var{basereg} for memory collecting.
34100 @item len @tab 8 @tab length of memory for collecting
34101 @item basereg @tab 4 @tab the register number containing the starting
34102 memory address for collecting.
34103 @item @emph{tracepoint action for collecting registers} @tab @tab
34104 @item 'R' @tab 1 @tab type of tracepoint action
34105 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34106 @item 'L' @tab 1 @tab type of tracepoint action
34107 @item @emph{tracepoint action for expression evaluation} @tab @tab
34108 @item 'X' @tab 1 @tab type of tracepoint action
34109 @item agent expression @tab length of @tab @ref{agent expression object}
34110 @item @emph{tracepoint object} @tab @tab
34111 @item number @tab 4 @tab number of tracepoint
34112 @item address @tab 8 @tab address of tracepoint inserted on
34113 @item type @tab 4 @tab type of tracepoint
34114 @item enabled @tab 1 @tab enable or disable of tracepoint
34115 @item step_count @tab 8 @tab step
34116 @item pass_count @tab 8 @tab pass
34117 @item numactions @tab 4 @tab number of tracepoint actions
34118 @item hit count @tab 8 @tab hit count
34119 @item trace frame usage @tab 8 @tab trace frame usage
34120 @item compiled_cond @tab 8 @tab compiled condition
34121 @item orig_size @tab 8 @tab orig size
34122 @item condition @tab 4 if condition is NULL otherwise length of
34123 @ref{agent expression object}
34124 @tab zero if condition is NULL, otherwise is
34125 @ref{agent expression object}
34126 @item actions @tab variable
34127 @tab numactions number of @ref{tracepoint action object}
34130 @node IPA Protocol Commands
34131 @subsection IPA Protocol Commands
34132 @cindex ipa protocol commands
34134 The spaces in each command are delimiters to ease reading this commands
34135 specification. They don't exist in real commands.
34139 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34140 Installs a new fast tracepoint described by @var{tracepoint_object}
34141 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
34142 head of @dfn{jumppad}, which is used to jump to data collection routine
34147 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34148 @var{target_address} is address of tracepoint in the inferior.
34149 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34150 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34151 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
34152 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34159 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34160 is about to kill inferiors.
34168 @item probe_marker_at:@var{address}
34169 Asks in-process agent to probe the marker at @var{address}.
34176 @item unprobe_marker_at:@var{address}
34177 Asks in-process agent to unprobe the marker at @var{address}.
34181 @chapter Reporting Bugs in @value{GDBN}
34182 @cindex bugs in @value{GDBN}
34183 @cindex reporting bugs in @value{GDBN}
34185 Your bug reports play an essential role in making @value{GDBN} reliable.
34187 Reporting a bug may help you by bringing a solution to your problem, or it
34188 may not. But in any case the principal function of a bug report is to help
34189 the entire community by making the next version of @value{GDBN} work better. Bug
34190 reports are your contribution to the maintenance of @value{GDBN}.
34192 In order for a bug report to serve its purpose, you must include the
34193 information that enables us to fix the bug.
34196 * Bug Criteria:: Have you found a bug?
34197 * Bug Reporting:: How to report bugs
34201 @section Have You Found a Bug?
34202 @cindex bug criteria
34204 If you are not sure whether you have found a bug, here are some guidelines:
34207 @cindex fatal signal
34208 @cindex debugger crash
34209 @cindex crash of debugger
34211 If the debugger gets a fatal signal, for any input whatever, that is a
34212 @value{GDBN} bug. Reliable debuggers never crash.
34214 @cindex error on valid input
34216 If @value{GDBN} produces an error message for valid input, that is a
34217 bug. (Note that if you're cross debugging, the problem may also be
34218 somewhere in the connection to the target.)
34220 @cindex invalid input
34222 If @value{GDBN} does not produce an error message for invalid input,
34223 that is a bug. However, you should note that your idea of
34224 ``invalid input'' might be our idea of ``an extension'' or ``support
34225 for traditional practice''.
34228 If you are an experienced user of debugging tools, your suggestions
34229 for improvement of @value{GDBN} are welcome in any case.
34232 @node Bug Reporting
34233 @section How to Report Bugs
34234 @cindex bug reports
34235 @cindex @value{GDBN} bugs, reporting
34237 A number of companies and individuals offer support for @sc{gnu} products.
34238 If you obtained @value{GDBN} from a support organization, we recommend you
34239 contact that organization first.
34241 You can find contact information for many support companies and
34242 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34244 @c should add a web page ref...
34247 @ifset BUGURL_DEFAULT
34248 In any event, we also recommend that you submit bug reports for
34249 @value{GDBN}. The preferred method is to submit them directly using
34250 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34251 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34254 @strong{Do not send bug reports to @samp{info-gdb}, or to
34255 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34256 not want to receive bug reports. Those that do have arranged to receive
34259 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34260 serves as a repeater. The mailing list and the newsgroup carry exactly
34261 the same messages. Often people think of posting bug reports to the
34262 newsgroup instead of mailing them. This appears to work, but it has one
34263 problem which can be crucial: a newsgroup posting often lacks a mail
34264 path back to the sender. Thus, if we need to ask for more information,
34265 we may be unable to reach you. For this reason, it is better to send
34266 bug reports to the mailing list.
34268 @ifclear BUGURL_DEFAULT
34269 In any event, we also recommend that you submit bug reports for
34270 @value{GDBN} to @value{BUGURL}.
34274 The fundamental principle of reporting bugs usefully is this:
34275 @strong{report all the facts}. If you are not sure whether to state a
34276 fact or leave it out, state it!
34278 Often people omit facts because they think they know what causes the
34279 problem and assume that some details do not matter. Thus, you might
34280 assume that the name of the variable you use in an example does not matter.
34281 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34282 stray memory reference which happens to fetch from the location where that
34283 name is stored in memory; perhaps, if the name were different, the contents
34284 of that location would fool the debugger into doing the right thing despite
34285 the bug. Play it safe and give a specific, complete example. That is the
34286 easiest thing for you to do, and the most helpful.
34288 Keep in mind that the purpose of a bug report is to enable us to fix the
34289 bug. It may be that the bug has been reported previously, but neither
34290 you nor we can know that unless your bug report is complete and
34293 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34294 bell?'' Those bug reports are useless, and we urge everyone to
34295 @emph{refuse to respond to them} except to chide the sender to report
34298 To enable us to fix the bug, you should include all these things:
34302 The version of @value{GDBN}. @value{GDBN} announces it if you start
34303 with no arguments; you can also print it at any time using @code{show
34306 Without this, we will not know whether there is any point in looking for
34307 the bug in the current version of @value{GDBN}.
34310 The type of machine you are using, and the operating system name and
34314 The details of the @value{GDBN} build-time configuration.
34315 @value{GDBN} shows these details if you invoke it with the
34316 @option{--configuration} command-line option, or if you type
34317 @code{show configuration} at @value{GDBN}'s prompt.
34320 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34321 ``@value{GCC}--2.8.1''.
34324 What compiler (and its version) was used to compile the program you are
34325 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34326 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34327 to get this information; for other compilers, see the documentation for
34331 The command arguments you gave the compiler to compile your example and
34332 observe the bug. For example, did you use @samp{-O}? To guarantee
34333 you will not omit something important, list them all. A copy of the
34334 Makefile (or the output from make) is sufficient.
34336 If we were to try to guess the arguments, we would probably guess wrong
34337 and then we might not encounter the bug.
34340 A complete input script, and all necessary source files, that will
34344 A description of what behavior you observe that you believe is
34345 incorrect. For example, ``It gets a fatal signal.''
34347 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34348 will certainly notice it. But if the bug is incorrect output, we might
34349 not notice unless it is glaringly wrong. You might as well not give us
34350 a chance to make a mistake.
34352 Even if the problem you experience is a fatal signal, you should still
34353 say so explicitly. Suppose something strange is going on, such as, your
34354 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34355 the C library on your system. (This has happened!) Your copy might
34356 crash and ours would not. If you told us to expect a crash, then when
34357 ours fails to crash, we would know that the bug was not happening for
34358 us. If you had not told us to expect a crash, then we would not be able
34359 to draw any conclusion from our observations.
34362 @cindex recording a session script
34363 To collect all this information, you can use a session recording program
34364 such as @command{script}, which is available on many Unix systems.
34365 Just run your @value{GDBN} session inside @command{script} and then
34366 include the @file{typescript} file with your bug report.
34368 Another way to record a @value{GDBN} session is to run @value{GDBN}
34369 inside Emacs and then save the entire buffer to a file.
34372 If you wish to suggest changes to the @value{GDBN} source, send us context
34373 diffs. If you even discuss something in the @value{GDBN} source, refer to
34374 it by context, not by line number.
34376 The line numbers in our development sources will not match those in your
34377 sources. Your line numbers would convey no useful information to us.
34381 Here are some things that are not necessary:
34385 A description of the envelope of the bug.
34387 Often people who encounter a bug spend a lot of time investigating
34388 which changes to the input file will make the bug go away and which
34389 changes will not affect it.
34391 This is often time consuming and not very useful, because the way we
34392 will find the bug is by running a single example under the debugger
34393 with breakpoints, not by pure deduction from a series of examples.
34394 We recommend that you save your time for something else.
34396 Of course, if you can find a simpler example to report @emph{instead}
34397 of the original one, that is a convenience for us. Errors in the
34398 output will be easier to spot, running under the debugger will take
34399 less time, and so on.
34401 However, simplification is not vital; if you do not want to do this,
34402 report the bug anyway and send us the entire test case you used.
34405 A patch for the bug.
34407 A patch for the bug does help us if it is a good one. But do not omit
34408 the necessary information, such as the test case, on the assumption that
34409 a patch is all we need. We might see problems with your patch and decide
34410 to fix the problem another way, or we might not understand it at all.
34412 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34413 construct an example that will make the program follow a certain path
34414 through the code. If you do not send us the example, we will not be able
34415 to construct one, so we will not be able to verify that the bug is fixed.
34417 And if we cannot understand what bug you are trying to fix, or why your
34418 patch should be an improvement, we will not install it. A test case will
34419 help us to understand.
34422 A guess about what the bug is or what it depends on.
34424 Such guesses are usually wrong. Even we cannot guess right about such
34425 things without first using the debugger to find the facts.
34428 @c The readline documentation is distributed with the readline code
34429 @c and consists of the two following files:
34432 @c Use -I with makeinfo to point to the appropriate directory,
34433 @c environment var TEXINPUTS with TeX.
34434 @ifclear SYSTEM_READLINE
34435 @include rluser.texi
34436 @include hsuser.texi
34440 @appendix In Memoriam
34442 The @value{GDBN} project mourns the loss of the following long-time
34447 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34448 to Free Software in general. Outside of @value{GDBN}, he was known in
34449 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34451 @item Michael Snyder
34452 Michael was one of the Global Maintainers of the @value{GDBN} project,
34453 with contributions recorded as early as 1996, until 2011. In addition
34454 to his day to day participation, he was a large driving force behind
34455 adding Reverse Debugging to @value{GDBN}.
34458 Beyond their technical contributions to the project, they were also
34459 enjoyable members of the Free Software Community. We will miss them.
34461 @node Formatting Documentation
34462 @appendix Formatting Documentation
34464 @cindex @value{GDBN} reference card
34465 @cindex reference card
34466 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34467 for printing with PostScript or Ghostscript, in the @file{gdb}
34468 subdirectory of the main source directory@footnote{In
34469 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34470 release.}. If you can use PostScript or Ghostscript with your printer,
34471 you can print the reference card immediately with @file{refcard.ps}.
34473 The release also includes the source for the reference card. You
34474 can format it, using @TeX{}, by typing:
34480 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34481 mode on US ``letter'' size paper;
34482 that is, on a sheet 11 inches wide by 8.5 inches
34483 high. You will need to specify this form of printing as an option to
34484 your @sc{dvi} output program.
34486 @cindex documentation
34488 All the documentation for @value{GDBN} comes as part of the machine-readable
34489 distribution. The documentation is written in Texinfo format, which is
34490 a documentation system that uses a single source file to produce both
34491 on-line information and a printed manual. You can use one of the Info
34492 formatting commands to create the on-line version of the documentation
34493 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34495 @value{GDBN} includes an already formatted copy of the on-line Info
34496 version of this manual in the @file{gdb} subdirectory. The main Info
34497 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34498 subordinate files matching @samp{gdb.info*} in the same directory. If
34499 necessary, you can print out these files, or read them with any editor;
34500 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34501 Emacs or the standalone @code{info} program, available as part of the
34502 @sc{gnu} Texinfo distribution.
34504 If you want to format these Info files yourself, you need one of the
34505 Info formatting programs, such as @code{texinfo-format-buffer} or
34508 If you have @code{makeinfo} installed, and are in the top level
34509 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34510 version @value{GDBVN}), you can make the Info file by typing:
34517 If you want to typeset and print copies of this manual, you need @TeX{},
34518 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34519 Texinfo definitions file.
34521 @TeX{} is a typesetting program; it does not print files directly, but
34522 produces output files called @sc{dvi} files. To print a typeset
34523 document, you need a program to print @sc{dvi} files. If your system
34524 has @TeX{} installed, chances are it has such a program. The precise
34525 command to use depends on your system; @kbd{lpr -d} is common; another
34526 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34527 require a file name without any extension or a @samp{.dvi} extension.
34529 @TeX{} also requires a macro definitions file called
34530 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34531 written in Texinfo format. On its own, @TeX{} cannot either read or
34532 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34533 and is located in the @file{gdb-@var{version-number}/texinfo}
34536 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34537 typeset and print this manual. First switch to the @file{gdb}
34538 subdirectory of the main source directory (for example, to
34539 @file{gdb-@value{GDBVN}/gdb}) and type:
34545 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34547 @node Installing GDB
34548 @appendix Installing @value{GDBN}
34549 @cindex installation
34552 * Requirements:: Requirements for building @value{GDBN}
34553 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34554 * Separate Objdir:: Compiling @value{GDBN} in another directory
34555 * Config Names:: Specifying names for hosts and targets
34556 * Configure Options:: Summary of options for configure
34557 * System-wide configuration:: Having a system-wide init file
34561 @section Requirements for Building @value{GDBN}
34562 @cindex building @value{GDBN}, requirements for
34564 Building @value{GDBN} requires various tools and packages to be available.
34565 Other packages will be used only if they are found.
34567 @heading Tools/Packages Necessary for Building @value{GDBN}
34569 @item ISO C90 compiler
34570 @value{GDBN} is written in ISO C90. It should be buildable with any
34571 working C90 compiler, e.g.@: GCC.
34575 @heading Tools/Packages Optional for Building @value{GDBN}
34579 @value{GDBN} can use the Expat XML parsing library. This library may be
34580 included with your operating system distribution; if it is not, you
34581 can get the latest version from @url{http://expat.sourceforge.net}.
34582 The @file{configure} script will search for this library in several
34583 standard locations; if it is installed in an unusual path, you can
34584 use the @option{--with-libexpat-prefix} option to specify its location.
34590 Remote protocol memory maps (@pxref{Memory Map Format})
34592 Target descriptions (@pxref{Target Descriptions})
34594 Remote shared library lists (@xref{Library List Format},
34595 or alternatively @pxref{Library List Format for SVR4 Targets})
34597 MS-Windows shared libraries (@pxref{Shared Libraries})
34599 Traceframe info (@pxref{Traceframe Info Format})
34601 Branch trace (@pxref{Branch Trace Format},
34602 @pxref{Branch Trace Configuration Format})
34607 @value{GDBN} can use the GNU MPFR multiple-precision floating-point
34608 library. This library may be included with your operating system
34609 distribution; if it is not, you can get the latest version from
34610 @url{http://www.mpfr.org}. The @file{configure} script will search
34611 for this library in several standard locations; if it is installed
34612 in an unusual path, you can use the @option{--with-libmpfr-prefix}
34613 option to specify its location.
34615 GNU MPFR is used to emulate target floating-point arithmetic during
34616 expression evaluation when the target uses different floating-point
34617 formats than the host. If GNU MPFR it is not available, @value{GDBN}
34618 will fall back to using host floating-point arithmetic.
34621 @cindex compressed debug sections
34622 @value{GDBN} will use the @samp{zlib} library, if available, to read
34623 compressed debug sections. Some linkers, such as GNU gold, are capable
34624 of producing binaries with compressed debug sections. If @value{GDBN}
34625 is compiled with @samp{zlib}, it will be able to read the debug
34626 information in such binaries.
34628 The @samp{zlib} library is likely included with your operating system
34629 distribution; if it is not, you can get the latest version from
34630 @url{http://zlib.net}.
34633 @value{GDBN}'s features related to character sets (@pxref{Character
34634 Sets}) require a functioning @code{iconv} implementation. If you are
34635 on a GNU system, then this is provided by the GNU C Library. Some
34636 other systems also provide a working @code{iconv}.
34638 If @value{GDBN} is using the @code{iconv} program which is installed
34639 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34640 This is done with @option{--with-iconv-bin} which specifies the
34641 directory that contains the @code{iconv} program.
34643 On systems without @code{iconv}, you can install GNU Libiconv. If you
34644 have previously installed Libiconv, you can use the
34645 @option{--with-libiconv-prefix} option to configure.
34647 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34648 arrange to build Libiconv if a directory named @file{libiconv} appears
34649 in the top-most source directory. If Libiconv is built this way, and
34650 if the operating system does not provide a suitable @code{iconv}
34651 implementation, then the just-built library will automatically be used
34652 by @value{GDBN}. One easy way to set this up is to download GNU
34653 Libiconv, unpack it, and then rename the directory holding the
34654 Libiconv source code to @samp{libiconv}.
34657 @node Running Configure
34658 @section Invoking the @value{GDBN} @file{configure} Script
34659 @cindex configuring @value{GDBN}
34660 @value{GDBN} comes with a @file{configure} script that automates the process
34661 of preparing @value{GDBN} for installation; you can then use @code{make} to
34662 build the @code{gdb} program.
34664 @c irrelevant in info file; it's as current as the code it lives with.
34665 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34666 look at the @file{README} file in the sources; we may have improved the
34667 installation procedures since publishing this manual.}
34670 The @value{GDBN} distribution includes all the source code you need for
34671 @value{GDBN} in a single directory, whose name is usually composed by
34672 appending the version number to @samp{gdb}.
34674 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34675 @file{gdb-@value{GDBVN}} directory. That directory contains:
34678 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34679 script for configuring @value{GDBN} and all its supporting libraries
34681 @item gdb-@value{GDBVN}/gdb
34682 the source specific to @value{GDBN} itself
34684 @item gdb-@value{GDBVN}/bfd
34685 source for the Binary File Descriptor library
34687 @item gdb-@value{GDBVN}/include
34688 @sc{gnu} include files
34690 @item gdb-@value{GDBVN}/libiberty
34691 source for the @samp{-liberty} free software library
34693 @item gdb-@value{GDBVN}/opcodes
34694 source for the library of opcode tables and disassemblers
34696 @item gdb-@value{GDBVN}/readline
34697 source for the @sc{gnu} command-line interface
34699 @item gdb-@value{GDBVN}/glob
34700 source for the @sc{gnu} filename pattern-matching subroutine
34702 @item gdb-@value{GDBVN}/mmalloc
34703 source for the @sc{gnu} memory-mapped malloc package
34706 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34707 from the @file{gdb-@var{version-number}} source directory, which in
34708 this example is the @file{gdb-@value{GDBVN}} directory.
34710 First switch to the @file{gdb-@var{version-number}} source directory
34711 if you are not already in it; then run @file{configure}. Pass the
34712 identifier for the platform on which @value{GDBN} will run as an
34718 cd gdb-@value{GDBVN}
34719 ./configure @var{host}
34724 where @var{host} is an identifier such as @samp{sun4} or
34725 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34726 (You can often leave off @var{host}; @file{configure} tries to guess the
34727 correct value by examining your system.)
34729 Running @samp{configure @var{host}} and then running @code{make} builds the
34730 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34731 libraries, then @code{gdb} itself. The configured source files, and the
34732 binaries, are left in the corresponding source directories.
34735 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34736 system does not recognize this automatically when you run a different
34737 shell, you may need to run @code{sh} on it explicitly:
34740 sh configure @var{host}
34743 If you run @file{configure} from a directory that contains source
34744 directories for multiple libraries or programs, such as the
34745 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34747 creates configuration files for every directory level underneath (unless
34748 you tell it not to, with the @samp{--norecursion} option).
34750 You should run the @file{configure} script from the top directory in the
34751 source tree, the @file{gdb-@var{version-number}} directory. If you run
34752 @file{configure} from one of the subdirectories, you will configure only
34753 that subdirectory. That is usually not what you want. In particular,
34754 if you run the first @file{configure} from the @file{gdb} subdirectory
34755 of the @file{gdb-@var{version-number}} directory, you will omit the
34756 configuration of @file{bfd}, @file{readline}, and other sibling
34757 directories of the @file{gdb} subdirectory. This leads to build errors
34758 about missing include files such as @file{bfd/bfd.h}.
34760 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34761 However, you should make sure that the shell on your path (named by
34762 the @samp{SHELL} environment variable) is publicly readable. Remember
34763 that @value{GDBN} uses the shell to start your program---some systems refuse to
34764 let @value{GDBN} debug child processes whose programs are not readable.
34766 @node Separate Objdir
34767 @section Compiling @value{GDBN} in Another Directory
34769 If you want to run @value{GDBN} versions for several host or target machines,
34770 you need a different @code{gdb} compiled for each combination of
34771 host and target. @file{configure} is designed to make this easy by
34772 allowing you to generate each configuration in a separate subdirectory,
34773 rather than in the source directory. If your @code{make} program
34774 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34775 @code{make} in each of these directories builds the @code{gdb}
34776 program specified there.
34778 To build @code{gdb} in a separate directory, run @file{configure}
34779 with the @samp{--srcdir} option to specify where to find the source.
34780 (You also need to specify a path to find @file{configure}
34781 itself from your working directory. If the path to @file{configure}
34782 would be the same as the argument to @samp{--srcdir}, you can leave out
34783 the @samp{--srcdir} option; it is assumed.)
34785 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34786 separate directory for a Sun 4 like this:
34790 cd gdb-@value{GDBVN}
34793 ../gdb-@value{GDBVN}/configure sun4
34798 When @file{configure} builds a configuration using a remote source
34799 directory, it creates a tree for the binaries with the same structure
34800 (and using the same names) as the tree under the source directory. In
34801 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34802 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34803 @file{gdb-sun4/gdb}.
34805 Make sure that your path to the @file{configure} script has just one
34806 instance of @file{gdb} in it. If your path to @file{configure} looks
34807 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34808 one subdirectory of @value{GDBN}, not the whole package. This leads to
34809 build errors about missing include files such as @file{bfd/bfd.h}.
34811 One popular reason to build several @value{GDBN} configurations in separate
34812 directories is to configure @value{GDBN} for cross-compiling (where
34813 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34814 programs that run on another machine---the @dfn{target}).
34815 You specify a cross-debugging target by
34816 giving the @samp{--target=@var{target}} option to @file{configure}.
34818 When you run @code{make} to build a program or library, you must run
34819 it in a configured directory---whatever directory you were in when you
34820 called @file{configure} (or one of its subdirectories).
34822 The @code{Makefile} that @file{configure} generates in each source
34823 directory also runs recursively. If you type @code{make} in a source
34824 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34825 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34826 will build all the required libraries, and then build GDB.
34828 When you have multiple hosts or targets configured in separate
34829 directories, you can run @code{make} on them in parallel (for example,
34830 if they are NFS-mounted on each of the hosts); they will not interfere
34834 @section Specifying Names for Hosts and Targets
34836 The specifications used for hosts and targets in the @file{configure}
34837 script are based on a three-part naming scheme, but some short predefined
34838 aliases are also supported. The full naming scheme encodes three pieces
34839 of information in the following pattern:
34842 @var{architecture}-@var{vendor}-@var{os}
34845 For example, you can use the alias @code{sun4} as a @var{host} argument,
34846 or as the value for @var{target} in a @code{--target=@var{target}}
34847 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34849 The @file{configure} script accompanying @value{GDBN} does not provide
34850 any query facility to list all supported host and target names or
34851 aliases. @file{configure} calls the Bourne shell script
34852 @code{config.sub} to map abbreviations to full names; you can read the
34853 script, if you wish, or you can use it to test your guesses on
34854 abbreviations---for example:
34857 % sh config.sub i386-linux
34859 % sh config.sub alpha-linux
34860 alpha-unknown-linux-gnu
34861 % sh config.sub hp9k700
34863 % sh config.sub sun4
34864 sparc-sun-sunos4.1.1
34865 % sh config.sub sun3
34866 m68k-sun-sunos4.1.1
34867 % sh config.sub i986v
34868 Invalid configuration `i986v': machine `i986v' not recognized
34872 @code{config.sub} is also distributed in the @value{GDBN} source
34873 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
34875 @node Configure Options
34876 @section @file{configure} Options
34878 Here is a summary of the @file{configure} options and arguments that
34879 are most often useful for building @value{GDBN}. @file{configure} also has
34880 several other options not listed here. @inforef{What Configure
34881 Does,,configure.info}, for a full explanation of @file{configure}.
34884 configure @r{[}--help@r{]}
34885 @r{[}--prefix=@var{dir}@r{]}
34886 @r{[}--exec-prefix=@var{dir}@r{]}
34887 @r{[}--srcdir=@var{dirname}@r{]}
34888 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
34889 @r{[}--target=@var{target}@r{]}
34894 You may introduce options with a single @samp{-} rather than
34895 @samp{--} if you prefer; but you may abbreviate option names if you use
34900 Display a quick summary of how to invoke @file{configure}.
34902 @item --prefix=@var{dir}
34903 Configure the source to install programs and files under directory
34906 @item --exec-prefix=@var{dir}
34907 Configure the source to install programs under directory
34910 @c avoid splitting the warning from the explanation:
34912 @item --srcdir=@var{dirname}
34913 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
34914 @code{make} that implements the @code{VPATH} feature.}@*
34915 Use this option to make configurations in directories separate from the
34916 @value{GDBN} source directories. Among other things, you can use this to
34917 build (or maintain) several configurations simultaneously, in separate
34918 directories. @file{configure} writes configuration-specific files in
34919 the current directory, but arranges for them to use the source in the
34920 directory @var{dirname}. @file{configure} creates directories under
34921 the working directory in parallel to the source directories below
34924 @item --norecursion
34925 Configure only the directory level where @file{configure} is executed; do not
34926 propagate configuration to subdirectories.
34928 @item --target=@var{target}
34929 Configure @value{GDBN} for cross-debugging programs running on the specified
34930 @var{target}. Without this option, @value{GDBN} is configured to debug
34931 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
34933 There is no convenient way to generate a list of all available targets.
34935 @item @var{host} @dots{}
34936 Configure @value{GDBN} to run on the specified @var{host}.
34938 There is no convenient way to generate a list of all available hosts.
34941 There are many other options available as well, but they are generally
34942 needed for special purposes only.
34944 @node System-wide configuration
34945 @section System-wide configuration and settings
34946 @cindex system-wide init file
34948 @value{GDBN} can be configured to have a system-wide init file;
34949 this file will be read and executed at startup (@pxref{Startup, , What
34950 @value{GDBN} does during startup}).
34952 Here is the corresponding configure option:
34955 @item --with-system-gdbinit=@var{file}
34956 Specify that the default location of the system-wide init file is
34960 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
34961 it may be subject to relocation. Two possible cases:
34965 If the default location of this init file contains @file{$prefix},
34966 it will be subject to relocation. Suppose that the configure options
34967 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
34968 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
34969 init file is looked for as @file{$install/etc/gdbinit} instead of
34970 @file{$prefix/etc/gdbinit}.
34973 By contrast, if the default location does not contain the prefix,
34974 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
34975 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
34976 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
34977 wherever @value{GDBN} is installed.
34980 If the configured location of the system-wide init file (as given by the
34981 @option{--with-system-gdbinit} option at configure time) is in the
34982 data-directory (as specified by @option{--with-gdb-datadir} at configure
34983 time) or in one of its subdirectories, then @value{GDBN} will look for the
34984 system-wide init file in the directory specified by the
34985 @option{--data-directory} command-line option.
34986 Note that the system-wide init file is only read once, during @value{GDBN}
34987 initialization. If the data-directory is changed after @value{GDBN} has
34988 started with the @code{set data-directory} command, the file will not be
34992 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
34995 @node System-wide Configuration Scripts
34996 @subsection Installed System-wide Configuration Scripts
34997 @cindex system-wide configuration scripts
34999 The @file{system-gdbinit} directory, located inside the data-directory
35000 (as specified by @option{--with-gdb-datadir} at configure time) contains
35001 a number of scripts which can be used as system-wide init files. To
35002 automatically source those scripts at startup, @value{GDBN} should be
35003 configured with @option{--with-system-gdbinit}. Otherwise, any user
35004 should be able to source them by hand as needed.
35006 The following scripts are currently available:
35009 @item @file{elinos.py}
35011 @cindex ELinOS system-wide configuration script
35012 This script is useful when debugging a program on an ELinOS target.
35013 It takes advantage of the environment variables defined in a standard
35014 ELinOS environment in order to determine the location of the system
35015 shared libraries, and then sets the @samp{solib-absolute-prefix}
35016 and @samp{solib-search-path} variables appropriately.
35018 @item @file{wrs-linux.py}
35019 @pindex wrs-linux.py
35020 @cindex Wind River Linux system-wide configuration script
35021 This script is useful when debugging a program on a target running
35022 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
35023 the host-side sysroot used by the target system.
35027 @node Maintenance Commands
35028 @appendix Maintenance Commands
35029 @cindex maintenance commands
35030 @cindex internal commands
35032 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35033 includes a number of commands intended for @value{GDBN} developers,
35034 that are not documented elsewhere in this manual. These commands are
35035 provided here for reference. (For commands that turn on debugging
35036 messages, see @ref{Debugging Output}.)
35039 @kindex maint agent
35040 @kindex maint agent-eval
35041 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35042 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35043 Translate the given @var{expression} into remote agent bytecodes.
35044 This command is useful for debugging the Agent Expression mechanism
35045 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35046 expression useful for data collection, such as by tracepoints, while
35047 @samp{maint agent-eval} produces an expression that evaluates directly
35048 to a result. For instance, a collection expression for @code{globa +
35049 globb} will include bytecodes to record four bytes of memory at each
35050 of the addresses of @code{globa} and @code{globb}, while discarding
35051 the result of the addition, while an evaluation expression will do the
35052 addition and return the sum.
35053 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35054 If not, generate remote agent bytecode for current frame PC address.
35056 @kindex maint agent-printf
35057 @item maint agent-printf @var{format},@var{expr},...
35058 Translate the given format string and list of argument expressions
35059 into remote agent bytecodes and display them as a disassembled list.
35060 This command is useful for debugging the agent version of dynamic
35061 printf (@pxref{Dynamic Printf}).
35063 @kindex maint info breakpoints
35064 @item @anchor{maint info breakpoints}maint info breakpoints
35065 Using the same format as @samp{info breakpoints}, display both the
35066 breakpoints you've set explicitly, and those @value{GDBN} is using for
35067 internal purposes. Internal breakpoints are shown with negative
35068 breakpoint numbers. The type column identifies what kind of breakpoint
35073 Normal, explicitly set breakpoint.
35076 Normal, explicitly set watchpoint.
35079 Internal breakpoint, used to handle correctly stepping through
35080 @code{longjmp} calls.
35082 @item longjmp resume
35083 Internal breakpoint at the target of a @code{longjmp}.
35086 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35089 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35092 Shared library events.
35096 @kindex maint info btrace
35097 @item maint info btrace
35098 Pint information about raw branch tracing data.
35100 @kindex maint btrace packet-history
35101 @item maint btrace packet-history
35102 Print the raw branch trace packets that are used to compute the
35103 execution history for the @samp{record btrace} command. Both the
35104 information and the format in which it is printed depend on the btrace
35109 For the BTS recording format, print a list of blocks of sequential
35110 code. For each block, the following information is printed:
35114 Newer blocks have higher numbers. The oldest block has number zero.
35115 @item Lowest @samp{PC}
35116 @item Highest @samp{PC}
35120 For the Intel Processor Trace recording format, print a list of
35121 Intel Processor Trace packets. For each packet, the following
35122 information is printed:
35125 @item Packet number
35126 Newer packets have higher numbers. The oldest packet has number zero.
35128 The packet's offset in the trace stream.
35129 @item Packet opcode and payload
35133 @kindex maint btrace clear-packet-history
35134 @item maint btrace clear-packet-history
35135 Discards the cached packet history printed by the @samp{maint btrace
35136 packet-history} command. The history will be computed again when
35139 @kindex maint btrace clear
35140 @item maint btrace clear
35141 Discard the branch trace data. The data will be fetched anew and the
35142 branch trace will be recomputed when needed.
35144 This implicitly truncates the branch trace to a single branch trace
35145 buffer. When updating branch trace incrementally, the branch trace
35146 available to @value{GDBN} may be bigger than a single branch trace
35149 @kindex maint set btrace pt skip-pad
35150 @item maint set btrace pt skip-pad
35151 @kindex maint show btrace pt skip-pad
35152 @item maint show btrace pt skip-pad
35153 Control whether @value{GDBN} will skip PAD packets when computing the
35156 @kindex set displaced-stepping
35157 @kindex show displaced-stepping
35158 @cindex displaced stepping support
35159 @cindex out-of-line single-stepping
35160 @item set displaced-stepping
35161 @itemx show displaced-stepping
35162 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35163 if the target supports it. Displaced stepping is a way to single-step
35164 over breakpoints without removing them from the inferior, by executing
35165 an out-of-line copy of the instruction that was originally at the
35166 breakpoint location. It is also known as out-of-line single-stepping.
35169 @item set displaced-stepping on
35170 If the target architecture supports it, @value{GDBN} will use
35171 displaced stepping to step over breakpoints.
35173 @item set displaced-stepping off
35174 @value{GDBN} will not use displaced stepping to step over breakpoints,
35175 even if such is supported by the target architecture.
35177 @cindex non-stop mode, and @samp{set displaced-stepping}
35178 @item set displaced-stepping auto
35179 This is the default mode. @value{GDBN} will use displaced stepping
35180 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35181 architecture supports displaced stepping.
35184 @kindex maint check-psymtabs
35185 @item maint check-psymtabs
35186 Check the consistency of currently expanded psymtabs versus symtabs.
35187 Use this to check, for example, whether a symbol is in one but not the other.
35189 @kindex maint check-symtabs
35190 @item maint check-symtabs
35191 Check the consistency of currently expanded symtabs.
35193 @kindex maint expand-symtabs
35194 @item maint expand-symtabs [@var{regexp}]
35195 Expand symbol tables.
35196 If @var{regexp} is specified, only expand symbol tables for file
35197 names matching @var{regexp}.
35199 @kindex maint set catch-demangler-crashes
35200 @kindex maint show catch-demangler-crashes
35201 @cindex demangler crashes
35202 @item maint set catch-demangler-crashes [on|off]
35203 @itemx maint show catch-demangler-crashes
35204 Control whether @value{GDBN} should attempt to catch crashes in the
35205 symbol name demangler. The default is to attempt to catch crashes.
35206 If enabled, the first time a crash is caught, a core file is created,
35207 the offending symbol is displayed and the user is presented with the
35208 option to terminate the current session.
35210 @kindex maint cplus first_component
35211 @item maint cplus first_component @var{name}
35212 Print the first C@t{++} class/namespace component of @var{name}.
35214 @kindex maint cplus namespace
35215 @item maint cplus namespace
35216 Print the list of possible C@t{++} namespaces.
35218 @kindex maint deprecate
35219 @kindex maint undeprecate
35220 @cindex deprecated commands
35221 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35222 @itemx maint undeprecate @var{command}
35223 Deprecate or undeprecate the named @var{command}. Deprecated commands
35224 cause @value{GDBN} to issue a warning when you use them. The optional
35225 argument @var{replacement} says which newer command should be used in
35226 favor of the deprecated one; if it is given, @value{GDBN} will mention
35227 the replacement as part of the warning.
35229 @kindex maint dump-me
35230 @item maint dump-me
35231 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35232 Cause a fatal signal in the debugger and force it to dump its core.
35233 This is supported only on systems which support aborting a program
35234 with the @code{SIGQUIT} signal.
35236 @kindex maint internal-error
35237 @kindex maint internal-warning
35238 @kindex maint demangler-warning
35239 @cindex demangler crashes
35240 @item maint internal-error @r{[}@var{message-text}@r{]}
35241 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35242 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
35244 Cause @value{GDBN} to call the internal function @code{internal_error},
35245 @code{internal_warning} or @code{demangler_warning} and hence behave
35246 as though an internal problem has been detected. In addition to
35247 reporting the internal problem, these functions give the user the
35248 opportunity to either quit @value{GDBN} or (for @code{internal_error}
35249 and @code{internal_warning}) create a core file of the current
35250 @value{GDBN} session.
35252 These commands take an optional parameter @var{message-text} that is
35253 used as the text of the error or warning message.
35255 Here's an example of using @code{internal-error}:
35258 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35259 @dots{}/maint.c:121: internal-error: testing, 1, 2
35260 A problem internal to GDB has been detected. Further
35261 debugging may prove unreliable.
35262 Quit this debugging session? (y or n) @kbd{n}
35263 Create a core file? (y or n) @kbd{n}
35267 @cindex @value{GDBN} internal error
35268 @cindex internal errors, control of @value{GDBN} behavior
35269 @cindex demangler crashes
35271 @kindex maint set internal-error
35272 @kindex maint show internal-error
35273 @kindex maint set internal-warning
35274 @kindex maint show internal-warning
35275 @kindex maint set demangler-warning
35276 @kindex maint show demangler-warning
35277 @item maint set internal-error @var{action} [ask|yes|no]
35278 @itemx maint show internal-error @var{action}
35279 @itemx maint set internal-warning @var{action} [ask|yes|no]
35280 @itemx maint show internal-warning @var{action}
35281 @itemx maint set demangler-warning @var{action} [ask|yes|no]
35282 @itemx maint show demangler-warning @var{action}
35283 When @value{GDBN} reports an internal problem (error or warning) it
35284 gives the user the opportunity to both quit @value{GDBN} and create a
35285 core file of the current @value{GDBN} session. These commands let you
35286 override the default behaviour for each particular @var{action},
35287 described in the table below.
35291 You can specify that @value{GDBN} should always (yes) or never (no)
35292 quit. The default is to ask the user what to do.
35295 You can specify that @value{GDBN} should always (yes) or never (no)
35296 create a core file. The default is to ask the user what to do. Note
35297 that there is no @code{corefile} option for @code{demangler-warning}:
35298 demangler warnings always create a core file and this cannot be
35302 @kindex maint packet
35303 @item maint packet @var{text}
35304 If @value{GDBN} is talking to an inferior via the serial protocol,
35305 then this command sends the string @var{text} to the inferior, and
35306 displays the response packet. @value{GDBN} supplies the initial
35307 @samp{$} character, the terminating @samp{#} character, and the
35310 @kindex maint print architecture
35311 @item maint print architecture @r{[}@var{file}@r{]}
35312 Print the entire architecture configuration. The optional argument
35313 @var{file} names the file where the output goes.
35315 @kindex maint print c-tdesc @r{[}@var{file}@r{]}
35316 @item maint print c-tdesc
35317 Print the target description (@pxref{Target Descriptions}) as
35318 a C source file. By default, the target description is for the current
35319 target, but if the optional argument @var{file} is provided, that file
35320 is used to produce the description. The @var{file} should be an XML
35321 document, of the form described in @ref{Target Description Format}.
35322 The created source file is built into @value{GDBN} when @value{GDBN} is
35323 built again. This command is used by developers after they add or
35324 modify XML target descriptions.
35326 @kindex maint check xml-descriptions
35327 @item maint check xml-descriptions @var{dir}
35328 Check that the target descriptions dynamically created by @value{GDBN}
35329 equal the descriptions created from XML files found in @var{dir}.
35331 @kindex maint print dummy-frames
35332 @item maint print dummy-frames
35333 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35336 (@value{GDBP}) @kbd{b add}
35338 (@value{GDBP}) @kbd{print add(2,3)}
35339 Breakpoint 2, add (a=2, b=3) at @dots{}
35341 The program being debugged stopped while in a function called from GDB.
35343 (@value{GDBP}) @kbd{maint print dummy-frames}
35344 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
35348 Takes an optional file parameter.
35350 @kindex maint print registers
35351 @kindex maint print raw-registers
35352 @kindex maint print cooked-registers
35353 @kindex maint print register-groups
35354 @kindex maint print remote-registers
35355 @item maint print registers @r{[}@var{file}@r{]}
35356 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35357 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35358 @itemx maint print register-groups @r{[}@var{file}@r{]}
35359 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35360 Print @value{GDBN}'s internal register data structures.
35362 The command @code{maint print raw-registers} includes the contents of
35363 the raw register cache; the command @code{maint print
35364 cooked-registers} includes the (cooked) value of all registers,
35365 including registers which aren't available on the target nor visible
35366 to user; the command @code{maint print register-groups} includes the
35367 groups that each register is a member of; and the command @code{maint
35368 print remote-registers} includes the remote target's register numbers
35369 and offsets in the `G' packets.
35371 These commands take an optional parameter, a file name to which to
35372 write the information.
35374 @kindex maint print reggroups
35375 @item maint print reggroups @r{[}@var{file}@r{]}
35376 Print @value{GDBN}'s internal register group data structures. The
35377 optional argument @var{file} tells to what file to write the
35380 The register groups info looks like this:
35383 (@value{GDBP}) @kbd{maint print reggroups}
35396 This command forces @value{GDBN} to flush its internal register cache.
35398 @kindex maint print objfiles
35399 @cindex info for known object files
35400 @item maint print objfiles @r{[}@var{regexp}@r{]}
35401 Print a dump of all known object files.
35402 If @var{regexp} is specified, only print object files whose names
35403 match @var{regexp}. For each object file, this command prints its name,
35404 address in memory, and all of its psymtabs and symtabs.
35406 @kindex maint print user-registers
35407 @cindex user registers
35408 @item maint print user-registers
35409 List all currently available @dfn{user registers}. User registers
35410 typically provide alternate names for actual hardware registers. They
35411 include the four ``standard'' registers @code{$fp}, @code{$pc},
35412 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
35413 registers can be used in expressions in the same way as the canonical
35414 register names, but only the latter are listed by the @code{info
35415 registers} and @code{maint print registers} commands.
35417 @kindex maint print section-scripts
35418 @cindex info for known .debug_gdb_scripts-loaded scripts
35419 @item maint print section-scripts [@var{regexp}]
35420 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35421 If @var{regexp} is specified, only print scripts loaded by object files
35422 matching @var{regexp}.
35423 For each script, this command prints its name as specified in the objfile,
35424 and the full path if known.
35425 @xref{dotdebug_gdb_scripts section}.
35427 @kindex maint print statistics
35428 @cindex bcache statistics
35429 @item maint print statistics
35430 This command prints, for each object file in the program, various data
35431 about that object file followed by the byte cache (@dfn{bcache})
35432 statistics for the object file. The objfile data includes the number
35433 of minimal, partial, full, and stabs symbols, the number of types
35434 defined by the objfile, the number of as yet unexpanded psym tables,
35435 the number of line tables and string tables, and the amount of memory
35436 used by the various tables. The bcache statistics include the counts,
35437 sizes, and counts of duplicates of all and unique objects, max,
35438 average, and median entry size, total memory used and its overhead and
35439 savings, and various measures of the hash table size and chain
35442 @kindex maint print target-stack
35443 @cindex target stack description
35444 @item maint print target-stack
35445 A @dfn{target} is an interface between the debugger and a particular
35446 kind of file or process. Targets can be stacked in @dfn{strata},
35447 so that more than one target can potentially respond to a request.
35448 In particular, memory accesses will walk down the stack of targets
35449 until they find a target that is interested in handling that particular
35452 This command prints a short description of each layer that was pushed on
35453 the @dfn{target stack}, starting from the top layer down to the bottom one.
35455 @kindex maint print type
35456 @cindex type chain of a data type
35457 @item maint print type @var{expr}
35458 Print the type chain for a type specified by @var{expr}. The argument
35459 can be either a type name or a symbol. If it is a symbol, the type of
35460 that symbol is described. The type chain produced by this command is
35461 a recursive definition of the data type as stored in @value{GDBN}'s
35462 data structures, including its flags and contained types.
35464 @kindex maint selftest
35466 @item maint selftest @r{[}@var{filter}@r{]}
35467 Run any self tests that were compiled in to @value{GDBN}. This will
35468 print a message showing how many tests were run, and how many failed.
35469 If a @var{filter} is passed, only the tests with @var{filter} in their
35472 @kindex "maint info selftests"
35474 @item maint info selftests
35475 List the selftests compiled in to @value{GDBN}.
35477 @kindex maint set dwarf always-disassemble
35478 @kindex maint show dwarf always-disassemble
35479 @item maint set dwarf always-disassemble
35480 @item maint show dwarf always-disassemble
35481 Control the behavior of @code{info address} when using DWARF debugging
35484 The default is @code{off}, which means that @value{GDBN} should try to
35485 describe a variable's location in an easily readable format. When
35486 @code{on}, @value{GDBN} will instead display the DWARF location
35487 expression in an assembly-like format. Note that some locations are
35488 too complex for @value{GDBN} to describe simply; in this case you will
35489 always see the disassembly form.
35491 Here is an example of the resulting disassembly:
35494 (gdb) info addr argc
35495 Symbol "argc" is a complex DWARF expression:
35499 For more information on these expressions, see
35500 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35502 @kindex maint set dwarf max-cache-age
35503 @kindex maint show dwarf max-cache-age
35504 @item maint set dwarf max-cache-age
35505 @itemx maint show dwarf max-cache-age
35506 Control the DWARF compilation unit cache.
35508 @cindex DWARF compilation units cache
35509 In object files with inter-compilation-unit references, such as those
35510 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
35511 reader needs to frequently refer to previously read compilation units.
35512 This setting controls how long a compilation unit will remain in the
35513 cache if it is not referenced. A higher limit means that cached
35514 compilation units will be stored in memory longer, and more total
35515 memory will be used. Setting it to zero disables caching, which will
35516 slow down @value{GDBN} startup, but reduce memory consumption.
35518 @kindex maint set profile
35519 @kindex maint show profile
35520 @cindex profiling GDB
35521 @item maint set profile
35522 @itemx maint show profile
35523 Control profiling of @value{GDBN}.
35525 Profiling will be disabled until you use the @samp{maint set profile}
35526 command to enable it. When you enable profiling, the system will begin
35527 collecting timing and execution count data; when you disable profiling or
35528 exit @value{GDBN}, the results will be written to a log file. Remember that
35529 if you use profiling, @value{GDBN} will overwrite the profiling log file
35530 (often called @file{gmon.out}). If you have a record of important profiling
35531 data in a @file{gmon.out} file, be sure to move it to a safe location.
35533 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35534 compiled with the @samp{-pg} compiler option.
35536 @kindex maint set show-debug-regs
35537 @kindex maint show show-debug-regs
35538 @cindex hardware debug registers
35539 @item maint set show-debug-regs
35540 @itemx maint show show-debug-regs
35541 Control whether to show variables that mirror the hardware debug
35542 registers. Use @code{on} to enable, @code{off} to disable. If
35543 enabled, the debug registers values are shown when @value{GDBN} inserts or
35544 removes a hardware breakpoint or watchpoint, and when the inferior
35545 triggers a hardware-assisted breakpoint or watchpoint.
35547 @kindex maint set show-all-tib
35548 @kindex maint show show-all-tib
35549 @item maint set show-all-tib
35550 @itemx maint show show-all-tib
35551 Control whether to show all non zero areas within a 1k block starting
35552 at thread local base, when using the @samp{info w32 thread-information-block}
35555 @kindex maint set target-async
35556 @kindex maint show target-async
35557 @item maint set target-async
35558 @itemx maint show target-async
35559 This controls whether @value{GDBN} targets operate in synchronous or
35560 asynchronous mode (@pxref{Background Execution}). Normally the
35561 default is asynchronous, if it is available; but this can be changed
35562 to more easily debug problems occurring only in synchronous mode.
35564 @kindex maint set target-non-stop @var{mode} [on|off|auto]
35565 @kindex maint show target-non-stop
35566 @item maint set target-non-stop
35567 @itemx maint show target-non-stop
35569 This controls whether @value{GDBN} targets always operate in non-stop
35570 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
35571 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
35572 if supported by the target.
35575 @item maint set target-non-stop auto
35576 This is the default mode. @value{GDBN} controls the target in
35577 non-stop mode if the target supports it.
35579 @item maint set target-non-stop on
35580 @value{GDBN} controls the target in non-stop mode even if the target
35581 does not indicate support.
35583 @item maint set target-non-stop off
35584 @value{GDBN} does not control the target in non-stop mode even if the
35585 target supports it.
35588 @kindex maint set per-command
35589 @kindex maint show per-command
35590 @item maint set per-command
35591 @itemx maint show per-command
35592 @cindex resources used by commands
35594 @value{GDBN} can display the resources used by each command.
35595 This is useful in debugging performance problems.
35598 @item maint set per-command space [on|off]
35599 @itemx maint show per-command space
35600 Enable or disable the printing of the memory used by GDB for each command.
35601 If enabled, @value{GDBN} will display how much memory each command
35602 took, following the command's own output.
35603 This can also be requested by invoking @value{GDBN} with the
35604 @option{--statistics} command-line switch (@pxref{Mode Options}).
35606 @item maint set per-command time [on|off]
35607 @itemx maint show per-command time
35608 Enable or disable the printing of the execution time of @value{GDBN}
35610 If enabled, @value{GDBN} will display how much time it
35611 took to execute each command, following the command's own output.
35612 Both CPU time and wallclock time are printed.
35613 Printing both is useful when trying to determine whether the cost is
35614 CPU or, e.g., disk/network latency.
35615 Note that the CPU time printed is for @value{GDBN} only, it does not include
35616 the execution time of the inferior because there's no mechanism currently
35617 to compute how much time was spent by @value{GDBN} and how much time was
35618 spent by the program been debugged.
35619 This can also be requested by invoking @value{GDBN} with the
35620 @option{--statistics} command-line switch (@pxref{Mode Options}).
35622 @item maint set per-command symtab [on|off]
35623 @itemx maint show per-command symtab
35624 Enable or disable the printing of basic symbol table statistics
35626 If enabled, @value{GDBN} will display the following information:
35630 number of symbol tables
35632 number of primary symbol tables
35634 number of blocks in the blockvector
35638 @kindex maint space
35639 @cindex memory used by commands
35640 @item maint space @var{value}
35641 An alias for @code{maint set per-command space}.
35642 A non-zero value enables it, zero disables it.
35645 @cindex time of command execution
35646 @item maint time @var{value}
35647 An alias for @code{maint set per-command time}.
35648 A non-zero value enables it, zero disables it.
35650 @kindex maint translate-address
35651 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35652 Find the symbol stored at the location specified by the address
35653 @var{addr} and an optional section name @var{section}. If found,
35654 @value{GDBN} prints the name of the closest symbol and an offset from
35655 the symbol's location to the specified address. This is similar to
35656 the @code{info address} command (@pxref{Symbols}), except that this
35657 command also allows to find symbols in other sections.
35659 If section was not specified, the section in which the symbol was found
35660 is also printed. For dynamically linked executables, the name of
35661 executable or shared library containing the symbol is printed as well.
35665 The following command is useful for non-interactive invocations of
35666 @value{GDBN}, such as in the test suite.
35669 @item set watchdog @var{nsec}
35670 @kindex set watchdog
35671 @cindex watchdog timer
35672 @cindex timeout for commands
35673 Set the maximum number of seconds @value{GDBN} will wait for the
35674 target operation to finish. If this time expires, @value{GDBN}
35675 reports and error and the command is aborted.
35677 @item show watchdog
35678 Show the current setting of the target wait timeout.
35681 @node Remote Protocol
35682 @appendix @value{GDBN} Remote Serial Protocol
35687 * Stop Reply Packets::
35688 * General Query Packets::
35689 * Architecture-Specific Protocol Details::
35690 * Tracepoint Packets::
35691 * Host I/O Packets::
35693 * Notification Packets::
35694 * Remote Non-Stop::
35695 * Packet Acknowledgment::
35697 * File-I/O Remote Protocol Extension::
35698 * Library List Format::
35699 * Library List Format for SVR4 Targets::
35700 * Memory Map Format::
35701 * Thread List Format::
35702 * Traceframe Info Format::
35703 * Branch Trace Format::
35704 * Branch Trace Configuration Format::
35710 There may be occasions when you need to know something about the
35711 protocol---for example, if there is only one serial port to your target
35712 machine, you might want your program to do something special if it
35713 recognizes a packet meant for @value{GDBN}.
35715 In the examples below, @samp{->} and @samp{<-} are used to indicate
35716 transmitted and received data, respectively.
35718 @cindex protocol, @value{GDBN} remote serial
35719 @cindex serial protocol, @value{GDBN} remote
35720 @cindex remote serial protocol
35721 All @value{GDBN} commands and responses (other than acknowledgments
35722 and notifications, see @ref{Notification Packets}) are sent as a
35723 @var{packet}. A @var{packet} is introduced with the character
35724 @samp{$}, the actual @var{packet-data}, and the terminating character
35725 @samp{#} followed by a two-digit @var{checksum}:
35728 @code{$}@var{packet-data}@code{#}@var{checksum}
35732 @cindex checksum, for @value{GDBN} remote
35734 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35735 characters between the leading @samp{$} and the trailing @samp{#} (an
35736 eight bit unsigned checksum).
35738 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35739 specification also included an optional two-digit @var{sequence-id}:
35742 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35745 @cindex sequence-id, for @value{GDBN} remote
35747 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35748 has never output @var{sequence-id}s. Stubs that handle packets added
35749 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35751 When either the host or the target machine receives a packet, the first
35752 response expected is an acknowledgment: either @samp{+} (to indicate
35753 the package was received correctly) or @samp{-} (to request
35757 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35762 The @samp{+}/@samp{-} acknowledgments can be disabled
35763 once a connection is established.
35764 @xref{Packet Acknowledgment}, for details.
35766 The host (@value{GDBN}) sends @var{command}s, and the target (the
35767 debugging stub incorporated in your program) sends a @var{response}. In
35768 the case of step and continue @var{command}s, the response is only sent
35769 when the operation has completed, and the target has again stopped all
35770 threads in all attached processes. This is the default all-stop mode
35771 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35772 execution mode; see @ref{Remote Non-Stop}, for details.
35774 @var{packet-data} consists of a sequence of characters with the
35775 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35778 @cindex remote protocol, field separator
35779 Fields within the packet should be separated using @samp{,} @samp{;} or
35780 @samp{:}. Except where otherwise noted all numbers are represented in
35781 @sc{hex} with leading zeros suppressed.
35783 Implementors should note that prior to @value{GDBN} 5.0, the character
35784 @samp{:} could not appear as the third character in a packet (as it
35785 would potentially conflict with the @var{sequence-id}).
35787 @cindex remote protocol, binary data
35788 @anchor{Binary Data}
35789 Binary data in most packets is encoded either as two hexadecimal
35790 digits per byte of binary data. This allowed the traditional remote
35791 protocol to work over connections which were only seven-bit clean.
35792 Some packets designed more recently assume an eight-bit clean
35793 connection, and use a more efficient encoding to send and receive
35796 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35797 as an escape character. Any escaped byte is transmitted as the escape
35798 character followed by the original character XORed with @code{0x20}.
35799 For example, the byte @code{0x7d} would be transmitted as the two
35800 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35801 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35802 @samp{@}}) must always be escaped. Responses sent by the stub
35803 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35804 is not interpreted as the start of a run-length encoded sequence
35807 Response @var{data} can be run-length encoded to save space.
35808 Run-length encoding replaces runs of identical characters with one
35809 instance of the repeated character, followed by a @samp{*} and a
35810 repeat count. The repeat count is itself sent encoded, to avoid
35811 binary characters in @var{data}: a value of @var{n} is sent as
35812 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35813 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35814 code 32) for a repeat count of 3. (This is because run-length
35815 encoding starts to win for counts 3 or more.) Thus, for example,
35816 @samp{0* } is a run-length encoding of ``0000'': the space character
35817 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35820 The printable characters @samp{#} and @samp{$} or with a numeric value
35821 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35822 seven repeats (@samp{$}) can be expanded using a repeat count of only
35823 five (@samp{"}). For example, @samp{00000000} can be encoded as
35826 The error response returned for some packets includes a two character
35827 error number. That number is not well defined.
35829 @cindex empty response, for unsupported packets
35830 For any @var{command} not supported by the stub, an empty response
35831 (@samp{$#00}) should be returned. That way it is possible to extend the
35832 protocol. A newer @value{GDBN} can tell if a packet is supported based
35835 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35836 commands for register access, and the @samp{m} and @samp{M} commands
35837 for memory access. Stubs that only control single-threaded targets
35838 can implement run control with the @samp{c} (continue), and @samp{s}
35839 (step) commands. Stubs that support multi-threading targets should
35840 support the @samp{vCont} command. All other commands are optional.
35845 The following table provides a complete list of all currently defined
35846 @var{command}s and their corresponding response @var{data}.
35847 @xref{File-I/O Remote Protocol Extension}, for details about the File
35848 I/O extension of the remote protocol.
35850 Each packet's description has a template showing the packet's overall
35851 syntax, followed by an explanation of the packet's meaning. We
35852 include spaces in some of the templates for clarity; these are not
35853 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35854 separate its components. For example, a template like @samp{foo
35855 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35856 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35857 @var{baz}. @value{GDBN} does not transmit a space character between the
35858 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35861 @cindex @var{thread-id}, in remote protocol
35862 @anchor{thread-id syntax}
35863 Several packets and replies include a @var{thread-id} field to identify
35864 a thread. Normally these are positive numbers with a target-specific
35865 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35866 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35869 In addition, the remote protocol supports a multiprocess feature in
35870 which the @var{thread-id} syntax is extended to optionally include both
35871 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35872 The @var{pid} (process) and @var{tid} (thread) components each have the
35873 format described above: a positive number with target-specific
35874 interpretation formatted as a big-endian hex string, literal @samp{-1}
35875 to indicate all processes or threads (respectively), or @samp{0} to
35876 indicate an arbitrary process or thread. Specifying just a process, as
35877 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35878 error to specify all processes but a specific thread, such as
35879 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35880 for those packets and replies explicitly documented to include a process
35881 ID, rather than a @var{thread-id}.
35883 The multiprocess @var{thread-id} syntax extensions are only used if both
35884 @value{GDBN} and the stub report support for the @samp{multiprocess}
35885 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35888 Note that all packet forms beginning with an upper- or lower-case
35889 letter, other than those described here, are reserved for future use.
35891 Here are the packet descriptions.
35896 @cindex @samp{!} packet
35897 @anchor{extended mode}
35898 Enable extended mode. In extended mode, the remote server is made
35899 persistent. The @samp{R} packet is used to restart the program being
35905 The remote target both supports and has enabled extended mode.
35909 @cindex @samp{?} packet
35911 Indicate the reason the target halted. The reply is the same as for
35912 step and continue. This packet has a special interpretation when the
35913 target is in non-stop mode; see @ref{Remote Non-Stop}.
35916 @xref{Stop Reply Packets}, for the reply specifications.
35918 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35919 @cindex @samp{A} packet
35920 Initialized @code{argv[]} array passed into program. @var{arglen}
35921 specifies the number of bytes in the hex encoded byte stream
35922 @var{arg}. See @code{gdbserver} for more details.
35927 The arguments were set.
35933 @cindex @samp{b} packet
35934 (Don't use this packet; its behavior is not well-defined.)
35935 Change the serial line speed to @var{baud}.
35937 JTC: @emph{When does the transport layer state change? When it's
35938 received, or after the ACK is transmitted. In either case, there are
35939 problems if the command or the acknowledgment packet is dropped.}
35941 Stan: @emph{If people really wanted to add something like this, and get
35942 it working for the first time, they ought to modify ser-unix.c to send
35943 some kind of out-of-band message to a specially-setup stub and have the
35944 switch happen "in between" packets, so that from remote protocol's point
35945 of view, nothing actually happened.}
35947 @item B @var{addr},@var{mode}
35948 @cindex @samp{B} packet
35949 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35950 breakpoint at @var{addr}.
35952 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35953 (@pxref{insert breakpoint or watchpoint packet}).
35955 @cindex @samp{bc} packet
35958 Backward continue. Execute the target system in reverse. No parameter.
35959 @xref{Reverse Execution}, for more information.
35962 @xref{Stop Reply Packets}, for the reply specifications.
35964 @cindex @samp{bs} packet
35967 Backward single step. Execute one instruction in reverse. No parameter.
35968 @xref{Reverse Execution}, for more information.
35971 @xref{Stop Reply Packets}, for the reply specifications.
35973 @item c @r{[}@var{addr}@r{]}
35974 @cindex @samp{c} packet
35975 Continue at @var{addr}, which is the address to resume. If @var{addr}
35976 is omitted, resume at current address.
35978 This packet is deprecated for multi-threading support. @xref{vCont
35982 @xref{Stop Reply Packets}, for the reply specifications.
35984 @item C @var{sig}@r{[};@var{addr}@r{]}
35985 @cindex @samp{C} packet
35986 Continue with signal @var{sig} (hex signal number). If
35987 @samp{;@var{addr}} is omitted, resume at same address.
35989 This packet is deprecated for multi-threading support. @xref{vCont
35993 @xref{Stop Reply Packets}, for the reply specifications.
35996 @cindex @samp{d} packet
35999 Don't use this packet; instead, define a general set packet
36000 (@pxref{General Query Packets}).
36004 @cindex @samp{D} packet
36005 The first form of the packet is used to detach @value{GDBN} from the
36006 remote system. It is sent to the remote target
36007 before @value{GDBN} disconnects via the @code{detach} command.
36009 The second form, including a process ID, is used when multiprocess
36010 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36011 detach only a specific process. The @var{pid} is specified as a
36012 big-endian hex string.
36022 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36023 @cindex @samp{F} packet
36024 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36025 This is part of the File-I/O protocol extension. @xref{File-I/O
36026 Remote Protocol Extension}, for the specification.
36029 @anchor{read registers packet}
36030 @cindex @samp{g} packet
36031 Read general registers.
36035 @item @var{XX@dots{}}
36036 Each byte of register data is described by two hex digits. The bytes
36037 with the register are transmitted in target byte order. The size of
36038 each register and their position within the @samp{g} packet are
36039 determined by the @value{GDBN} internal gdbarch functions
36040 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}.
36042 When reading registers from a trace frame (@pxref{Analyze Collected
36043 Data,,Using the Collected Data}), the stub may also return a string of
36044 literal @samp{x}'s in place of the register data digits, to indicate
36045 that the corresponding register has not been collected, thus its value
36046 is unavailable. For example, for an architecture with 4 registers of
36047 4 bytes each, the following reply indicates to @value{GDBN} that
36048 registers 0 and 2 have not been collected, while registers 1 and 3
36049 have been collected, and both have zero value:
36053 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36060 @item G @var{XX@dots{}}
36061 @cindex @samp{G} packet
36062 Write general registers. @xref{read registers packet}, for a
36063 description of the @var{XX@dots{}} data.
36073 @item H @var{op} @var{thread-id}
36074 @cindex @samp{H} packet
36075 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36076 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
36077 should be @samp{c} for step and continue operations (note that this
36078 is deprecated, supporting the @samp{vCont} command is a better
36079 option), and @samp{g} for other operations. The thread designator
36080 @var{thread-id} has the format and interpretation described in
36081 @ref{thread-id syntax}.
36092 @c 'H': How restrictive (or permissive) is the thread model. If a
36093 @c thread is selected and stopped, are other threads allowed
36094 @c to continue to execute? As I mentioned above, I think the
36095 @c semantics of each command when a thread is selected must be
36096 @c described. For example:
36098 @c 'g': If the stub supports threads and a specific thread is
36099 @c selected, returns the register block from that thread;
36100 @c otherwise returns current registers.
36102 @c 'G' If the stub supports threads and a specific thread is
36103 @c selected, sets the registers of the register block of
36104 @c that thread; otherwise sets current registers.
36106 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36107 @anchor{cycle step packet}
36108 @cindex @samp{i} packet
36109 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36110 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36111 step starting at that address.
36114 @cindex @samp{I} packet
36115 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36119 @cindex @samp{k} packet
36122 The exact effect of this packet is not specified.
36124 For a bare-metal target, it may power cycle or reset the target
36125 system. For that reason, the @samp{k} packet has no reply.
36127 For a single-process target, it may kill that process if possible.
36129 A multiple-process target may choose to kill just one process, or all
36130 that are under @value{GDBN}'s control. For more precise control, use
36131 the vKill packet (@pxref{vKill packet}).
36133 If the target system immediately closes the connection in response to
36134 @samp{k}, @value{GDBN} does not consider the lack of packet
36135 acknowledgment to be an error, and assumes the kill was successful.
36137 If connected using @kbd{target extended-remote}, and the target does
36138 not close the connection in response to a kill request, @value{GDBN}
36139 probes the target state as if a new connection was opened
36140 (@pxref{? packet}).
36142 @item m @var{addr},@var{length}
36143 @cindex @samp{m} packet
36144 Read @var{length} addressable memory units starting at address @var{addr}
36145 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
36146 any particular boundary.
36148 The stub need not use any particular size or alignment when gathering
36149 data from memory for the response; even if @var{addr} is word-aligned
36150 and @var{length} is a multiple of the word size, the stub is free to
36151 use byte accesses, or not. For this reason, this packet may not be
36152 suitable for accessing memory-mapped I/O devices.
36153 @cindex alignment of remote memory accesses
36154 @cindex size of remote memory accesses
36155 @cindex memory, alignment and size of remote accesses
36159 @item @var{XX@dots{}}
36160 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
36161 The reply may contain fewer addressable memory units than requested if the
36162 server was able to read only part of the region of memory.
36167 @item M @var{addr},@var{length}:@var{XX@dots{}}
36168 @cindex @samp{M} packet
36169 Write @var{length} addressable memory units starting at address @var{addr}
36170 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
36171 byte is transmitted as a two-digit hexadecimal number.
36178 for an error (this includes the case where only part of the data was
36183 @cindex @samp{p} packet
36184 Read the value of register @var{n}; @var{n} is in hex.
36185 @xref{read registers packet}, for a description of how the returned
36186 register value is encoded.
36190 @item @var{XX@dots{}}
36191 the register's value
36195 Indicating an unrecognized @var{query}.
36198 @item P @var{n@dots{}}=@var{r@dots{}}
36199 @anchor{write register packet}
36200 @cindex @samp{P} packet
36201 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36202 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36203 digits for each byte in the register (target byte order).
36213 @item q @var{name} @var{params}@dots{}
36214 @itemx Q @var{name} @var{params}@dots{}
36215 @cindex @samp{q} packet
36216 @cindex @samp{Q} packet
36217 General query (@samp{q}) and set (@samp{Q}). These packets are
36218 described fully in @ref{General Query Packets}.
36221 @cindex @samp{r} packet
36222 Reset the entire system.
36224 Don't use this packet; use the @samp{R} packet instead.
36227 @cindex @samp{R} packet
36228 Restart the program being debugged. The @var{XX}, while needed, is ignored.
36229 This packet is only available in extended mode (@pxref{extended mode}).
36231 The @samp{R} packet has no reply.
36233 @item s @r{[}@var{addr}@r{]}
36234 @cindex @samp{s} packet
36235 Single step, resuming at @var{addr}. If
36236 @var{addr} is omitted, resume at same address.
36238 This packet is deprecated for multi-threading support. @xref{vCont
36242 @xref{Stop Reply Packets}, for the reply specifications.
36244 @item S @var{sig}@r{[};@var{addr}@r{]}
36245 @anchor{step with signal packet}
36246 @cindex @samp{S} packet
36247 Step with signal. This is analogous to the @samp{C} packet, but
36248 requests a single-step, rather than a normal resumption of execution.
36250 This packet is deprecated for multi-threading support. @xref{vCont
36254 @xref{Stop Reply Packets}, for the reply specifications.
36256 @item t @var{addr}:@var{PP},@var{MM}
36257 @cindex @samp{t} packet
36258 Search backwards starting at address @var{addr} for a match with pattern
36259 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
36260 There must be at least 3 digits in @var{addr}.
36262 @item T @var{thread-id}
36263 @cindex @samp{T} packet
36264 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36269 thread is still alive
36275 Packets starting with @samp{v} are identified by a multi-letter name,
36276 up to the first @samp{;} or @samp{?} (or the end of the packet).
36278 @item vAttach;@var{pid}
36279 @cindex @samp{vAttach} packet
36280 Attach to a new process with the specified process ID @var{pid}.
36281 The process ID is a
36282 hexadecimal integer identifying the process. In all-stop mode, all
36283 threads in the attached process are stopped; in non-stop mode, it may be
36284 attached without being stopped if that is supported by the target.
36286 @c In non-stop mode, on a successful vAttach, the stub should set the
36287 @c current thread to a thread of the newly-attached process. After
36288 @c attaching, GDB queries for the attached process's thread ID with qC.
36289 @c Also note that, from a user perspective, whether or not the
36290 @c target is stopped on attach in non-stop mode depends on whether you
36291 @c use the foreground or background version of the attach command, not
36292 @c on what vAttach does; GDB does the right thing with respect to either
36293 @c stopping or restarting threads.
36295 This packet is only available in extended mode (@pxref{extended mode}).
36301 @item @r{Any stop packet}
36302 for success in all-stop mode (@pxref{Stop Reply Packets})
36304 for success in non-stop mode (@pxref{Remote Non-Stop})
36307 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36308 @cindex @samp{vCont} packet
36309 @anchor{vCont packet}
36310 Resume the inferior, specifying different actions for each thread.
36312 For each inferior thread, the leftmost action with a matching
36313 @var{thread-id} is applied. Threads that don't match any action
36314 remain in their current state. Thread IDs are specified using the
36315 syntax described in @ref{thread-id syntax}. If multiprocess
36316 extensions (@pxref{multiprocess extensions}) are supported, actions
36317 can be specified to match all threads in a process by using the
36318 @samp{p@var{pid}.-1} form of the @var{thread-id}. An action with no
36319 @var{thread-id} matches all threads. Specifying no actions is an
36322 Currently supported actions are:
36328 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36332 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36335 @item r @var{start},@var{end}
36336 Step once, and then keep stepping as long as the thread stops at
36337 addresses between @var{start} (inclusive) and @var{end} (exclusive).
36338 The remote stub reports a stop reply when either the thread goes out
36339 of the range or is stopped due to an unrelated reason, such as hitting
36340 a breakpoint. @xref{range stepping}.
36342 If the range is empty (@var{start} == @var{end}), then the action
36343 becomes equivalent to the @samp{s} action. In other words,
36344 single-step once, and report the stop (even if the stepped instruction
36345 jumps to @var{start}).
36347 (A stop reply may be sent at any point even if the PC is still within
36348 the stepping range; for example, it is valid to implement this packet
36349 in a degenerate way as a single instruction step operation.)
36353 The optional argument @var{addr} normally associated with the
36354 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36355 not supported in @samp{vCont}.
36357 The @samp{t} action is only relevant in non-stop mode
36358 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36359 A stop reply should be generated for any affected thread not already stopped.
36360 When a thread is stopped by means of a @samp{t} action,
36361 the corresponding stop reply should indicate that the thread has stopped with
36362 signal @samp{0}, regardless of whether the target uses some other signal
36363 as an implementation detail.
36365 The server must ignore @samp{c}, @samp{C}, @samp{s}, @samp{S}, and
36366 @samp{r} actions for threads that are already running. Conversely,
36367 the server must ignore @samp{t} actions for threads that are already
36370 @emph{Note:} In non-stop mode, a thread is considered running until
36371 @value{GDBN} acknowleges an asynchronous stop notification for it with
36372 the @samp{vStopped} packet (@pxref{Remote Non-Stop}).
36374 The stub must support @samp{vCont} if it reports support for
36375 multiprocess extensions (@pxref{multiprocess extensions}).
36378 @xref{Stop Reply Packets}, for the reply specifications.
36381 @cindex @samp{vCont?} packet
36382 Request a list of actions supported by the @samp{vCont} packet.
36386 @item vCont@r{[};@var{action}@dots{}@r{]}
36387 The @samp{vCont} packet is supported. Each @var{action} is a supported
36388 command in the @samp{vCont} packet.
36390 The @samp{vCont} packet is not supported.
36393 @anchor{vCtrlC packet}
36395 @cindex @samp{vCtrlC} packet
36396 Interrupt remote target as if a control-C was pressed on the remote
36397 terminal. This is the equivalent to reacting to the @code{^C}
36398 (@samp{\003}, the control-C character) character in all-stop mode
36399 while the target is running, except this works in non-stop mode.
36400 @xref{interrupting remote targets}, for more info on the all-stop
36411 @item vFile:@var{operation}:@var{parameter}@dots{}
36412 @cindex @samp{vFile} packet
36413 Perform a file operation on the target system. For details,
36414 see @ref{Host I/O Packets}.
36416 @item vFlashErase:@var{addr},@var{length}
36417 @cindex @samp{vFlashErase} packet
36418 Direct the stub to erase @var{length} bytes of flash starting at
36419 @var{addr}. The region may enclose any number of flash blocks, but
36420 its start and end must fall on block boundaries, as indicated by the
36421 flash block size appearing in the memory map (@pxref{Memory Map
36422 Format}). @value{GDBN} groups flash memory programming operations
36423 together, and sends a @samp{vFlashDone} request after each group; the
36424 stub is allowed to delay erase operation until the @samp{vFlashDone}
36425 packet is received.
36435 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36436 @cindex @samp{vFlashWrite} packet
36437 Direct the stub to write data to flash address @var{addr}. The data
36438 is passed in binary form using the same encoding as for the @samp{X}
36439 packet (@pxref{Binary Data}). The memory ranges specified by
36440 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36441 not overlap, and must appear in order of increasing addresses
36442 (although @samp{vFlashErase} packets for higher addresses may already
36443 have been received; the ordering is guaranteed only between
36444 @samp{vFlashWrite} packets). If a packet writes to an address that was
36445 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36446 target-specific method, the results are unpredictable.
36454 for vFlashWrite addressing non-flash memory
36460 @cindex @samp{vFlashDone} packet
36461 Indicate to the stub that flash programming operation is finished.
36462 The stub is permitted to delay or batch the effects of a group of
36463 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36464 @samp{vFlashDone} packet is received. The contents of the affected
36465 regions of flash memory are unpredictable until the @samp{vFlashDone}
36466 request is completed.
36468 @item vKill;@var{pid}
36469 @cindex @samp{vKill} packet
36470 @anchor{vKill packet}
36471 Kill the process with the specified process ID @var{pid}, which is a
36472 hexadecimal integer identifying the process. This packet is used in
36473 preference to @samp{k} when multiprocess protocol extensions are
36474 supported; see @ref{multiprocess extensions}.
36484 @item vMustReplyEmpty
36485 @cindex @samp{vMustReplyEmpty} packet
36486 The correct reply to an unknown @samp{v} packet is to return the empty
36487 string, however, some older versions of @command{gdbserver} would
36488 incorrectly return @samp{OK} for unknown @samp{v} packets.
36490 The @samp{vMustReplyEmpty} is used as a feature test to check how
36491 @command{gdbserver} handles unknown packets, it is important that this
36492 packet be handled in the same way as other unknown @samp{v} packets.
36493 If this packet is handled differently to other unknown @samp{v}
36494 packets then it is possile that @value{GDBN} may run into problems in
36495 other areas, specifically around use of @samp{vFile:setfs:}.
36497 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36498 @cindex @samp{vRun} packet
36499 Run the program @var{filename}, passing it each @var{argument} on its
36500 command line. The file and arguments are hex-encoded strings. If
36501 @var{filename} is an empty string, the stub may use a default program
36502 (e.g.@: the last program run). The program is created in the stopped
36505 @c FIXME: What about non-stop mode?
36507 This packet is only available in extended mode (@pxref{extended mode}).
36513 @item @r{Any stop packet}
36514 for success (@pxref{Stop Reply Packets})
36518 @cindex @samp{vStopped} packet
36519 @xref{Notification Packets}.
36521 @item X @var{addr},@var{length}:@var{XX@dots{}}
36523 @cindex @samp{X} packet
36524 Write data to memory, where the data is transmitted in binary.
36525 Memory is specified by its address @var{addr} and number of addressable memory
36526 units @var{length} (@pxref{addressable memory unit});
36527 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36537 @item z @var{type},@var{addr},@var{kind}
36538 @itemx Z @var{type},@var{addr},@var{kind}
36539 @anchor{insert breakpoint or watchpoint packet}
36540 @cindex @samp{z} packet
36541 @cindex @samp{Z} packets
36542 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36543 watchpoint starting at address @var{address} of kind @var{kind}.
36545 Each breakpoint and watchpoint packet @var{type} is documented
36548 @emph{Implementation notes: A remote target shall return an empty string
36549 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36550 remote target shall support either both or neither of a given
36551 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36552 avoid potential problems with duplicate packets, the operations should
36553 be implemented in an idempotent way.}
36555 @item z0,@var{addr},@var{kind}
36556 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36557 @cindex @samp{z0} packet
36558 @cindex @samp{Z0} packet
36559 Insert (@samp{Z0}) or remove (@samp{z0}) a software breakpoint at address
36560 @var{addr} of type @var{kind}.
36562 A software breakpoint is implemented by replacing the instruction at
36563 @var{addr} with a software breakpoint or trap instruction. The
36564 @var{kind} is target-specific and typically indicates the size of the
36565 breakpoint in bytes that should be inserted. E.g., the @sc{arm} and
36566 @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36567 architectures have additional meanings for @var{kind}
36568 (@pxref{Architecture-Specific Protocol Details}); if no
36569 architecture-specific value is being used, it should be @samp{0}.
36570 @var{kind} is hex-encoded. @var{cond_list} is an optional list of
36571 conditional expressions in bytecode form that should be evaluated on
36572 the target's side. These are the conditions that should be taken into
36573 consideration when deciding if the breakpoint trigger should be
36574 reported back to @value{GDBN}.
36576 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
36577 for how to best report a software breakpoint event to @value{GDBN}.
36579 The @var{cond_list} parameter is comprised of a series of expressions,
36580 concatenated without separators. Each expression has the following form:
36584 @item X @var{len},@var{expr}
36585 @var{len} is the length of the bytecode expression and @var{expr} is the
36586 actual conditional expression in bytecode form.
36590 The optional @var{cmd_list} parameter introduces commands that may be
36591 run on the target, rather than being reported back to @value{GDBN}.
36592 The parameter starts with a numeric flag @var{persist}; if the flag is
36593 nonzero, then the breakpoint may remain active and the commands
36594 continue to be run even when @value{GDBN} disconnects from the target.
36595 Following this flag is a series of expressions concatenated with no
36596 separators. Each expression has the following form:
36600 @item X @var{len},@var{expr}
36601 @var{len} is the length of the bytecode expression and @var{expr} is the
36602 actual commands expression in bytecode form.
36606 @emph{Implementation note: It is possible for a target to copy or move
36607 code that contains software breakpoints (e.g., when implementing
36608 overlays). The behavior of this packet, in the presence of such a
36609 target, is not defined.}
36621 @item z1,@var{addr},@var{kind}
36622 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36623 @cindex @samp{z1} packet
36624 @cindex @samp{Z1} packet
36625 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36626 address @var{addr}.
36628 A hardware breakpoint is implemented using a mechanism that is not
36629 dependent on being able to modify the target's memory. The
36630 @var{kind}, @var{cond_list}, and @var{cmd_list} arguments have the
36631 same meaning as in @samp{Z0} packets.
36633 @emph{Implementation note: A hardware breakpoint is not affected by code
36646 @item z2,@var{addr},@var{kind}
36647 @itemx Z2,@var{addr},@var{kind}
36648 @cindex @samp{z2} packet
36649 @cindex @samp{Z2} packet
36650 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36651 The number of bytes to watch is specified by @var{kind}.
36663 @item z3,@var{addr},@var{kind}
36664 @itemx Z3,@var{addr},@var{kind}
36665 @cindex @samp{z3} packet
36666 @cindex @samp{Z3} packet
36667 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36668 The number of bytes to watch is specified by @var{kind}.
36680 @item z4,@var{addr},@var{kind}
36681 @itemx Z4,@var{addr},@var{kind}
36682 @cindex @samp{z4} packet
36683 @cindex @samp{Z4} packet
36684 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36685 The number of bytes to watch is specified by @var{kind}.
36699 @node Stop Reply Packets
36700 @section Stop Reply Packets
36701 @cindex stop reply packets
36703 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36704 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36705 receive any of the below as a reply. Except for @samp{?}
36706 and @samp{vStopped}, that reply is only returned
36707 when the target halts. In the below the exact meaning of @dfn{signal
36708 number} is defined by the header @file{include/gdb/signals.h} in the
36709 @value{GDBN} source code.
36711 In non-stop mode, the server will simply reply @samp{OK} to commands
36712 such as @samp{vCont}; any stop will be the subject of a future
36713 notification. @xref{Remote Non-Stop}.
36715 As in the description of request packets, we include spaces in the
36716 reply templates for clarity; these are not part of the reply packet's
36717 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36723 The program received signal number @var{AA} (a two-digit hexadecimal
36724 number). This is equivalent to a @samp{T} response with no
36725 @var{n}:@var{r} pairs.
36727 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36728 @cindex @samp{T} packet reply
36729 The program received signal number @var{AA} (a two-digit hexadecimal
36730 number). This is equivalent to an @samp{S} response, except that the
36731 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36732 and other information directly in the stop reply packet, reducing
36733 round-trip latency. Single-step and breakpoint traps are reported
36734 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36738 If @var{n} is a hexadecimal number, it is a register number, and the
36739 corresponding @var{r} gives that register's value. The data @var{r} is a
36740 series of bytes in target byte order, with each byte given by a
36741 two-digit hex number.
36744 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36745 the stopped thread, as specified in @ref{thread-id syntax}.
36748 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36749 the core on which the stop event was detected.
36752 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36753 specific event that stopped the target. The currently defined stop
36754 reasons are listed below. The @var{aa} should be @samp{05}, the trap
36755 signal. At most one stop reason should be present.
36758 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36759 and go on to the next; this allows us to extend the protocol in the
36763 The currently defined stop reasons are:
36769 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36772 @item syscall_entry
36773 @itemx syscall_return
36774 The packet indicates a syscall entry or return, and @var{r} is the
36775 syscall number, in hex.
36777 @cindex shared library events, remote reply
36779 The packet indicates that the loaded libraries have changed.
36780 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36781 list of loaded libraries. The @var{r} part is ignored.
36783 @cindex replay log events, remote reply
36785 The packet indicates that the target cannot continue replaying
36786 logged execution events, because it has reached the end (or the
36787 beginning when executing backward) of the log. The value of @var{r}
36788 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36789 for more information.
36792 @anchor{swbreak stop reason}
36793 The packet indicates a software breakpoint instruction was executed,
36794 irrespective of whether it was @value{GDBN} that planted the
36795 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
36796 part must be left empty.
36798 On some architectures, such as x86, at the architecture level, when a
36799 breakpoint instruction executes the program counter points at the
36800 breakpoint address plus an offset. On such targets, the stub is
36801 responsible for adjusting the PC to point back at the breakpoint
36804 This packet should not be sent by default; older @value{GDBN} versions
36805 did not support it. @value{GDBN} requests it, by supplying an
36806 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36807 remote stub must also supply the appropriate @samp{qSupported} feature
36808 indicating support.
36810 This packet is required for correct non-stop mode operation.
36813 The packet indicates the target stopped for a hardware breakpoint.
36814 The @var{r} part must be left empty.
36816 The same remarks about @samp{qSupported} and non-stop mode above
36819 @cindex fork events, remote reply
36821 The packet indicates that @code{fork} was called, and @var{r}
36822 is the thread ID of the new child process. Refer to
36823 @ref{thread-id syntax} for the format of the @var{thread-id}
36824 field. This packet is only applicable to targets that support
36827 This packet should not be sent by default; older @value{GDBN} versions
36828 did not support it. @value{GDBN} requests it, by supplying an
36829 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36830 remote stub must also supply the appropriate @samp{qSupported} feature
36831 indicating support.
36833 @cindex vfork events, remote reply
36835 The packet indicates that @code{vfork} was called, and @var{r}
36836 is the thread ID of the new child process. Refer to
36837 @ref{thread-id syntax} for the format of the @var{thread-id}
36838 field. This packet is only applicable to targets that support
36841 This packet should not be sent by default; older @value{GDBN} versions
36842 did not support it. @value{GDBN} requests it, by supplying an
36843 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36844 remote stub must also supply the appropriate @samp{qSupported} feature
36845 indicating support.
36847 @cindex vforkdone events, remote reply
36849 The packet indicates that a child process created by a vfork
36850 has either called @code{exec} or terminated, so that the
36851 address spaces of the parent and child process are no longer
36852 shared. The @var{r} part is ignored. This packet is only
36853 applicable to targets that support vforkdone events.
36855 This packet should not be sent by default; older @value{GDBN} versions
36856 did not support it. @value{GDBN} requests it, by supplying an
36857 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36858 remote stub must also supply the appropriate @samp{qSupported} feature
36859 indicating support.
36861 @cindex exec events, remote reply
36863 The packet indicates that @code{execve} was called, and @var{r}
36864 is the absolute pathname of the file that was executed, in hex.
36865 This packet is only applicable to targets that support exec events.
36867 This packet should not be sent by default; older @value{GDBN} versions
36868 did not support it. @value{GDBN} requests it, by supplying an
36869 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
36870 remote stub must also supply the appropriate @samp{qSupported} feature
36871 indicating support.
36873 @cindex thread create event, remote reply
36874 @anchor{thread create event}
36876 The packet indicates that the thread was just created. The new thread
36877 is stopped until @value{GDBN} sets it running with a resumption packet
36878 (@pxref{vCont packet}). This packet should not be sent by default;
36879 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
36880 also the @samp{w} (@pxref{thread exit event}) remote reply below. The
36881 @var{r} part is ignored.
36886 @itemx W @var{AA} ; process:@var{pid}
36887 The process exited, and @var{AA} is the exit status. This is only
36888 applicable to certain targets.
36890 The second form of the response, including the process ID of the
36891 exited process, can be used only when @value{GDBN} has reported
36892 support for multiprocess protocol extensions; see @ref{multiprocess
36893 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36897 @itemx X @var{AA} ; process:@var{pid}
36898 The process terminated with signal @var{AA}.
36900 The second form of the response, including the process ID of the
36901 terminated process, can be used only when @value{GDBN} has reported
36902 support for multiprocess protocol extensions; see @ref{multiprocess
36903 extensions}. Both @var{AA} and @var{pid} are formatted as big-endian
36906 @anchor{thread exit event}
36907 @cindex thread exit event, remote reply
36908 @item w @var{AA} ; @var{tid}
36910 The thread exited, and @var{AA} is the exit status. This response
36911 should not be sent by default; @value{GDBN} requests it with the
36912 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
36913 @var{AA} is formatted as a big-endian hex string.
36916 There are no resumed threads left in the target. In other words, even
36917 though the process is alive, the last resumed thread has exited. For
36918 example, say the target process has two threads: thread 1 and thread
36919 2. The client leaves thread 1 stopped, and resumes thread 2, which
36920 subsequently exits. At this point, even though the process is still
36921 alive, and thus no @samp{W} stop reply is sent, no thread is actually
36922 executing either. The @samp{N} stop reply thus informs the client
36923 that it can stop waiting for stop replies. This packet should not be
36924 sent by default; older @value{GDBN} versions did not support it.
36925 @value{GDBN} requests it, by supplying an appropriate
36926 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
36927 also supply the appropriate @samp{qSupported} feature indicating
36930 @item O @var{XX}@dots{}
36931 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36932 written as the program's console output. This can happen at any time
36933 while the program is running and the debugger should continue to wait
36934 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36936 @item F @var{call-id},@var{parameter}@dots{}
36937 @var{call-id} is the identifier which says which host system call should
36938 be called. This is just the name of the function. Translation into the
36939 correct system call is only applicable as it's defined in @value{GDBN}.
36940 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36943 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36944 this very system call.
36946 The target replies with this packet when it expects @value{GDBN} to
36947 call a host system call on behalf of the target. @value{GDBN} replies
36948 with an appropriate @samp{F} packet and keeps up waiting for the next
36949 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36950 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36951 Protocol Extension}, for more details.
36955 @node General Query Packets
36956 @section General Query Packets
36957 @cindex remote query requests
36959 Packets starting with @samp{q} are @dfn{general query packets};
36960 packets starting with @samp{Q} are @dfn{general set packets}. General
36961 query and set packets are a semi-unified form for retrieving and
36962 sending information to and from the stub.
36964 The initial letter of a query or set packet is followed by a name
36965 indicating what sort of thing the packet applies to. For example,
36966 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36967 definitions with the stub. These packet names follow some
36972 The name must not contain commas, colons or semicolons.
36974 Most @value{GDBN} query and set packets have a leading upper case
36977 The names of custom vendor packets should use a company prefix, in
36978 lower case, followed by a period. For example, packets designed at
36979 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36980 foos) or @samp{Qacme.bar} (for setting bars).
36983 The name of a query or set packet should be separated from any
36984 parameters by a @samp{:}; the parameters themselves should be
36985 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36986 full packet name, and check for a separator or the end of the packet,
36987 in case two packet names share a common prefix. New packets should not begin
36988 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36989 packets predate these conventions, and have arguments without any terminator
36990 for the packet name; we suspect they are in widespread use in places that
36991 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36992 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36995 Like the descriptions of the other packets, each description here
36996 has a template showing the packet's overall syntax, followed by an
36997 explanation of the packet's meaning. We include spaces in some of the
36998 templates for clarity; these are not part of the packet's syntax. No
36999 @value{GDBN} packet uses spaces to separate its components.
37001 Here are the currently defined query and set packets:
37007 Turn on or off the agent as a helper to perform some debugging operations
37008 delegated from @value{GDBN} (@pxref{Control Agent}).
37010 @item QAllow:@var{op}:@var{val}@dots{}
37011 @cindex @samp{QAllow} packet
37012 Specify which operations @value{GDBN} expects to request of the
37013 target, as a semicolon-separated list of operation name and value
37014 pairs. Possible values for @var{op} include @samp{WriteReg},
37015 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
37016 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
37017 indicating that @value{GDBN} will not request the operation, or 1,
37018 indicating that it may. (The target can then use this to set up its
37019 own internals optimally, for instance if the debugger never expects to
37020 insert breakpoints, it may not need to install its own trap handler.)
37023 @cindex current thread, remote request
37024 @cindex @samp{qC} packet
37025 Return the current thread ID.
37029 @item QC @var{thread-id}
37030 Where @var{thread-id} is a thread ID as documented in
37031 @ref{thread-id syntax}.
37032 @item @r{(anything else)}
37033 Any other reply implies the old thread ID.
37036 @item qCRC:@var{addr},@var{length}
37037 @cindex CRC of memory block, remote request
37038 @cindex @samp{qCRC} packet
37039 @anchor{qCRC packet}
37040 Compute the CRC checksum of a block of memory using CRC-32 defined in
37041 IEEE 802.3. The CRC is computed byte at a time, taking the most
37042 significant bit of each byte first. The initial pattern code
37043 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
37045 @emph{Note:} This is the same CRC used in validating separate debug
37046 files (@pxref{Separate Debug Files, , Debugging Information in Separate
37047 Files}). However the algorithm is slightly different. When validating
37048 separate debug files, the CRC is computed taking the @emph{least}
37049 significant bit of each byte first, and the final result is inverted to
37050 detect trailing zeros.
37055 An error (such as memory fault)
37056 @item C @var{crc32}
37057 The specified memory region's checksum is @var{crc32}.
37060 @item QDisableRandomization:@var{value}
37061 @cindex disable address space randomization, remote request
37062 @cindex @samp{QDisableRandomization} packet
37063 Some target operating systems will randomize the virtual address space
37064 of the inferior process as a security feature, but provide a feature
37065 to disable such randomization, e.g.@: to allow for a more deterministic
37066 debugging experience. On such systems, this packet with a @var{value}
37067 of 1 directs the target to disable address space randomization for
37068 processes subsequently started via @samp{vRun} packets, while a packet
37069 with a @var{value} of 0 tells the target to enable address space
37072 This packet is only available in extended mode (@pxref{extended mode}).
37077 The request succeeded.
37080 An error occurred. The error number @var{nn} is given as hex digits.
37083 An empty reply indicates that @samp{QDisableRandomization} is not supported
37087 This packet is not probed by default; the remote stub must request it,
37088 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37089 This should only be done on targets that actually support disabling
37090 address space randomization.
37092 @item QStartupWithShell:@var{value}
37093 @cindex startup with shell, remote request
37094 @cindex @samp{QStartupWithShell} packet
37095 On UNIX-like targets, it is possible to start the inferior using a
37096 shell program. This is the default behavior on both @value{GDBN} and
37097 @command{gdbserver} (@pxref{set startup-with-shell}). This packet is
37098 used to inform @command{gdbserver} whether it should start the
37099 inferior using a shell or not.
37101 If @var{value} is @samp{0}, @command{gdbserver} will not use a shell
37102 to start the inferior. If @var{value} is @samp{1},
37103 @command{gdbserver} will use a shell to start the inferior. All other
37104 values are considered an error.
37106 This packet is only available in extended mode (@pxref{extended
37112 The request succeeded.
37115 An error occurred. The error number @var{nn} is given as hex digits.
37118 This packet is not probed by default; the remote stub must request it,
37119 by supplying an appropriate @samp{qSupported} response
37120 (@pxref{qSupported}). This should only be done on targets that
37121 actually support starting the inferior using a shell.
37123 Use of this packet is controlled by the @code{set startup-with-shell}
37124 command; @pxref{set startup-with-shell}.
37126 @item QEnvironmentHexEncoded:@var{hex-value}
37127 @anchor{QEnvironmentHexEncoded}
37128 @cindex set environment variable, remote request
37129 @cindex @samp{QEnvironmentHexEncoded} packet
37130 On UNIX-like targets, it is possible to set environment variables that
37131 will be passed to the inferior during the startup process. This
37132 packet is used to inform @command{gdbserver} of an environment
37133 variable that has been defined by the user on @value{GDBN} (@pxref{set
37136 The packet is composed by @var{hex-value}, an hex encoded
37137 representation of the @var{name=value} format representing an
37138 environment variable. The name of the environment variable is
37139 represented by @var{name}, and the value to be assigned to the
37140 environment variable is represented by @var{value}. If the variable
37141 has no value (i.e., the value is @code{null}), then @var{value} will
37144 This packet is only available in extended mode (@pxref{extended
37150 The request succeeded.
37153 This packet is not probed by default; the remote stub must request it,
37154 by supplying an appropriate @samp{qSupported} response
37155 (@pxref{qSupported}). This should only be done on targets that
37156 actually support passing environment variables to the starting
37159 This packet is related to the @code{set environment} command;
37160 @pxref{set environment}.
37162 @item QEnvironmentUnset:@var{hex-value}
37163 @anchor{QEnvironmentUnset}
37164 @cindex unset environment variable, remote request
37165 @cindex @samp{QEnvironmentUnset} packet
37166 On UNIX-like targets, it is possible to unset environment variables
37167 before starting the inferior in the remote target. This packet is
37168 used to inform @command{gdbserver} of an environment variable that has
37169 been unset by the user on @value{GDBN} (@pxref{unset environment}).
37171 The packet is composed by @var{hex-value}, an hex encoded
37172 representation of the name of the environment variable to be unset.
37174 This packet is only available in extended mode (@pxref{extended
37180 The request succeeded.
37183 This packet is not probed by default; the remote stub must request it,
37184 by supplying an appropriate @samp{qSupported} response
37185 (@pxref{qSupported}). This should only be done on targets that
37186 actually support passing environment variables to the starting
37189 This packet is related to the @code{unset environment} command;
37190 @pxref{unset environment}.
37192 @item QEnvironmentReset
37193 @anchor{QEnvironmentReset}
37194 @cindex reset environment, remote request
37195 @cindex @samp{QEnvironmentReset} packet
37196 On UNIX-like targets, this packet is used to reset the state of
37197 environment variables in the remote target before starting the
37198 inferior. In this context, reset means unsetting all environment
37199 variables that were previously set by the user (i.e., were not
37200 initially present in the environment). It is sent to
37201 @command{gdbserver} before the @samp{QEnvironmentHexEncoded}
37202 (@pxref{QEnvironmentHexEncoded}) and the @samp{QEnvironmentUnset}
37203 (@pxref{QEnvironmentUnset}) packets.
37205 This packet is only available in extended mode (@pxref{extended
37211 The request succeeded.
37214 This packet is not probed by default; the remote stub must request it,
37215 by supplying an appropriate @samp{qSupported} response
37216 (@pxref{qSupported}). This should only be done on targets that
37217 actually support passing environment variables to the starting
37220 @item QSetWorkingDir:@r{[}@var{directory}@r{]}
37221 @anchor{QSetWorkingDir packet}
37222 @cindex set working directory, remote request
37223 @cindex @samp{QSetWorkingDir} packet
37224 This packet is used to inform the remote server of the intended
37225 current working directory for programs that are going to be executed.
37227 The packet is composed by @var{directory}, an hex encoded
37228 representation of the directory that the remote inferior will use as
37229 its current working directory. If @var{directory} is an empty string,
37230 the remote server should reset the inferior's current working
37231 directory to its original, empty value.
37233 This packet is only available in extended mode (@pxref{extended
37239 The request succeeded.
37243 @itemx qsThreadInfo
37244 @cindex list active threads, remote request
37245 @cindex @samp{qfThreadInfo} packet
37246 @cindex @samp{qsThreadInfo} packet
37247 Obtain a list of all active thread IDs from the target (OS). Since there
37248 may be too many active threads to fit into one reply packet, this query
37249 works iteratively: it may require more than one query/reply sequence to
37250 obtain the entire list of threads. The first query of the sequence will
37251 be the @samp{qfThreadInfo} query; subsequent queries in the
37252 sequence will be the @samp{qsThreadInfo} query.
37254 NOTE: This packet replaces the @samp{qL} query (see below).
37258 @item m @var{thread-id}
37260 @item m @var{thread-id},@var{thread-id}@dots{}
37261 a comma-separated list of thread IDs
37263 (lower case letter @samp{L}) denotes end of list.
37266 In response to each query, the target will reply with a list of one or
37267 more thread IDs, separated by commas.
37268 @value{GDBN} will respond to each reply with a request for more thread
37269 ids (using the @samp{qs} form of the query), until the target responds
37270 with @samp{l} (lower-case ell, for @dfn{last}).
37271 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37274 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
37275 initial connection with the remote target, and the very first thread ID
37276 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
37277 message. Therefore, the stub should ensure that the first thread ID in
37278 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
37280 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37281 @cindex get thread-local storage address, remote request
37282 @cindex @samp{qGetTLSAddr} packet
37283 Fetch the address associated with thread local storage specified
37284 by @var{thread-id}, @var{offset}, and @var{lm}.
37286 @var{thread-id} is the thread ID associated with the
37287 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37289 @var{offset} is the (big endian, hex encoded) offset associated with the
37290 thread local variable. (This offset is obtained from the debug
37291 information associated with the variable.)
37293 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37294 load module associated with the thread local storage. For example,
37295 a @sc{gnu}/Linux system will pass the link map address of the shared
37296 object associated with the thread local storage under consideration.
37297 Other operating environments may choose to represent the load module
37298 differently, so the precise meaning of this parameter will vary.
37302 @item @var{XX}@dots{}
37303 Hex encoded (big endian) bytes representing the address of the thread
37304 local storage requested.
37307 An error occurred. The error number @var{nn} is given as hex digits.
37310 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37313 @item qGetTIBAddr:@var{thread-id}
37314 @cindex get thread information block address
37315 @cindex @samp{qGetTIBAddr} packet
37316 Fetch address of the Windows OS specific Thread Information Block.
37318 @var{thread-id} is the thread ID associated with the thread.
37322 @item @var{XX}@dots{}
37323 Hex encoded (big endian) bytes representing the linear address of the
37324 thread information block.
37327 An error occured. This means that either the thread was not found, or the
37328 address could not be retrieved.
37331 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37334 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37335 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37336 digit) is one to indicate the first query and zero to indicate a
37337 subsequent query; @var{threadcount} (two hex digits) is the maximum
37338 number of threads the response packet can contain; and @var{nextthread}
37339 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37340 returned in the response as @var{argthread}.
37342 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37346 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37347 Where: @var{count} (two hex digits) is the number of threads being
37348 returned; @var{done} (one hex digit) is zero to indicate more threads
37349 and one indicates no further threads; @var{argthreadid} (eight hex
37350 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37351 is a sequence of thread IDs, @var{threadid} (eight hex
37352 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
37356 @cindex section offsets, remote request
37357 @cindex @samp{qOffsets} packet
37358 Get section offsets that the target used when relocating the downloaded
37363 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37364 Relocate the @code{Text} section by @var{xxx} from its original address.
37365 Relocate the @code{Data} section by @var{yyy} from its original address.
37366 If the object file format provides segment information (e.g.@: @sc{elf}
37367 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37368 segments by the supplied offsets.
37370 @emph{Note: while a @code{Bss} offset may be included in the response,
37371 @value{GDBN} ignores this and instead applies the @code{Data} offset
37372 to the @code{Bss} section.}
37374 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37375 Relocate the first segment of the object file, which conventionally
37376 contains program code, to a starting address of @var{xxx}. If
37377 @samp{DataSeg} is specified, relocate the second segment, which
37378 conventionally contains modifiable data, to a starting address of
37379 @var{yyy}. @value{GDBN} will report an error if the object file
37380 does not contain segment information, or does not contain at least
37381 as many segments as mentioned in the reply. Extra segments are
37382 kept at fixed offsets relative to the last relocated segment.
37385 @item qP @var{mode} @var{thread-id}
37386 @cindex thread information, remote request
37387 @cindex @samp{qP} packet
37388 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37389 encoded 32 bit mode; @var{thread-id} is a thread ID
37390 (@pxref{thread-id syntax}).
37392 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37395 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37399 @cindex non-stop mode, remote request
37400 @cindex @samp{QNonStop} packet
37402 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37403 @xref{Remote Non-Stop}, for more information.
37408 The request succeeded.
37411 An error occurred. The error number @var{nn} is given as hex digits.
37414 An empty reply indicates that @samp{QNonStop} is not supported by
37418 This packet is not probed by default; the remote stub must request it,
37419 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37420 Use of this packet is controlled by the @code{set non-stop} command;
37421 @pxref{Non-Stop Mode}.
37423 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
37424 @itemx QCatchSyscalls:0
37425 @cindex catch syscalls from inferior, remote request
37426 @cindex @samp{QCatchSyscalls} packet
37427 @anchor{QCatchSyscalls}
37428 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
37429 catching syscalls from the inferior process.
37431 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
37432 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
37433 is listed, every system call should be reported.
37435 Note that if a syscall not in the list is reported, @value{GDBN} will
37436 still filter the event according to its own list from all corresponding
37437 @code{catch syscall} commands. However, it is more efficient to only
37438 report the requested syscalls.
37440 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
37441 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
37443 If the inferior process execs, the state of @samp{QCatchSyscalls} is
37444 kept for the new process too. On targets where exec may affect syscall
37445 numbers, for example with exec between 32 and 64-bit processes, the
37446 client should send a new packet with the new syscall list.
37451 The request succeeded.
37454 An error occurred. @var{nn} are hex digits.
37457 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
37461 Use of this packet is controlled by the @code{set remote catch-syscalls}
37462 command (@pxref{Remote Configuration, set remote catch-syscalls}).
37463 This packet is not probed by default; the remote stub must request it,
37464 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37466 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37467 @cindex pass signals to inferior, remote request
37468 @cindex @samp{QPassSignals} packet
37469 @anchor{QPassSignals}
37470 Each listed @var{signal} should be passed directly to the inferior process.
37471 Signals are numbered identically to continue packets and stop replies
37472 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37473 strictly greater than the previous item. These signals do not need to stop
37474 the inferior, or be reported to @value{GDBN}. All other signals should be
37475 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37476 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37477 new list. This packet improves performance when using @samp{handle
37478 @var{signal} nostop noprint pass}.
37483 The request succeeded.
37486 An error occurred. The error number @var{nn} is given as hex digits.
37489 An empty reply indicates that @samp{QPassSignals} is not supported by
37493 Use of this packet is controlled by the @code{set remote pass-signals}
37494 command (@pxref{Remote Configuration, set remote pass-signals}).
37495 This packet is not probed by default; the remote stub must request it,
37496 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37498 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37499 @cindex signals the inferior may see, remote request
37500 @cindex @samp{QProgramSignals} packet
37501 @anchor{QProgramSignals}
37502 Each listed @var{signal} may be delivered to the inferior process.
37503 Others should be silently discarded.
37505 In some cases, the remote stub may need to decide whether to deliver a
37506 signal to the program or not without @value{GDBN} involvement. One
37507 example of that is while detaching --- the program's threads may have
37508 stopped for signals that haven't yet had a chance of being reported to
37509 @value{GDBN}, and so the remote stub can use the signal list specified
37510 by this packet to know whether to deliver or ignore those pending
37513 This does not influence whether to deliver a signal as requested by a
37514 resumption packet (@pxref{vCont packet}).
37516 Signals are numbered identically to continue packets and stop replies
37517 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37518 strictly greater than the previous item. Multiple
37519 @samp{QProgramSignals} packets do not combine; any earlier
37520 @samp{QProgramSignals} list is completely replaced by the new list.
37525 The request succeeded.
37528 An error occurred. The error number @var{nn} is given as hex digits.
37531 An empty reply indicates that @samp{QProgramSignals} is not supported
37535 Use of this packet is controlled by the @code{set remote program-signals}
37536 command (@pxref{Remote Configuration, set remote program-signals}).
37537 This packet is not probed by default; the remote stub must request it,
37538 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37540 @anchor{QThreadEvents}
37541 @item QThreadEvents:1
37542 @itemx QThreadEvents:0
37543 @cindex thread create/exit events, remote request
37544 @cindex @samp{QThreadEvents} packet
37546 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
37547 reporting of thread create and exit events. @xref{thread create
37548 event}, for the reply specifications. For example, this is used in
37549 non-stop mode when @value{GDBN} stops a set of threads and
37550 synchronously waits for the their corresponding stop replies. Without
37551 exit events, if one of the threads exits, @value{GDBN} would hang
37552 forever not knowing that it should no longer expect a stop for that
37553 same thread. @value{GDBN} does not enable this feature unless the
37554 stub reports that it supports it by including @samp{QThreadEvents+} in
37555 its @samp{qSupported} reply.
37560 The request succeeded.
37563 An error occurred. The error number @var{nn} is given as hex digits.
37566 An empty reply indicates that @samp{QThreadEvents} is not supported by
37570 Use of this packet is controlled by the @code{set remote thread-events}
37571 command (@pxref{Remote Configuration, set remote thread-events}).
37573 @item qRcmd,@var{command}
37574 @cindex execute remote command, remote request
37575 @cindex @samp{qRcmd} packet
37576 @var{command} (hex encoded) is passed to the local interpreter for
37577 execution. Invalid commands should be reported using the output
37578 string. Before the final result packet, the target may also respond
37579 with a number of intermediate @samp{O@var{output}} console output
37580 packets. @emph{Implementors should note that providing access to a
37581 stubs's interpreter may have security implications}.
37586 A command response with no output.
37588 A command response with the hex encoded output string @var{OUTPUT}.
37590 Indicate a badly formed request.
37592 An empty reply indicates that @samp{qRcmd} is not recognized.
37595 (Note that the @code{qRcmd} packet's name is separated from the
37596 command by a @samp{,}, not a @samp{:}, contrary to the naming
37597 conventions above. Please don't use this packet as a model for new
37600 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37601 @cindex searching memory, in remote debugging
37603 @cindex @samp{qSearch:memory} packet
37605 @cindex @samp{qSearch memory} packet
37606 @anchor{qSearch memory}
37607 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37608 Both @var{address} and @var{length} are encoded in hex;
37609 @var{search-pattern} is a sequence of bytes, also hex encoded.
37614 The pattern was not found.
37616 The pattern was found at @var{address}.
37618 A badly formed request or an error was encountered while searching memory.
37620 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37623 @item QStartNoAckMode
37624 @cindex @samp{QStartNoAckMode} packet
37625 @anchor{QStartNoAckMode}
37626 Request that the remote stub disable the normal @samp{+}/@samp{-}
37627 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37632 The stub has switched to no-acknowledgment mode.
37633 @value{GDBN} acknowledges this reponse,
37634 but neither the stub nor @value{GDBN} shall send or expect further
37635 @samp{+}/@samp{-} acknowledgments in the current connection.
37637 An empty reply indicates that the stub does not support no-acknowledgment mode.
37640 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37641 @cindex supported packets, remote query
37642 @cindex features of the remote protocol
37643 @cindex @samp{qSupported} packet
37644 @anchor{qSupported}
37645 Tell the remote stub about features supported by @value{GDBN}, and
37646 query the stub for features it supports. This packet allows
37647 @value{GDBN} and the remote stub to take advantage of each others'
37648 features. @samp{qSupported} also consolidates multiple feature probes
37649 at startup, to improve @value{GDBN} performance---a single larger
37650 packet performs better than multiple smaller probe packets on
37651 high-latency links. Some features may enable behavior which must not
37652 be on by default, e.g.@: because it would confuse older clients or
37653 stubs. Other features may describe packets which could be
37654 automatically probed for, but are not. These features must be
37655 reported before @value{GDBN} will use them. This ``default
37656 unsupported'' behavior is not appropriate for all packets, but it
37657 helps to keep the initial connection time under control with new
37658 versions of @value{GDBN} which support increasing numbers of packets.
37662 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37663 The stub supports or does not support each returned @var{stubfeature},
37664 depending on the form of each @var{stubfeature} (see below for the
37667 An empty reply indicates that @samp{qSupported} is not recognized,
37668 or that no features needed to be reported to @value{GDBN}.
37671 The allowed forms for each feature (either a @var{gdbfeature} in the
37672 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37676 @item @var{name}=@var{value}
37677 The remote protocol feature @var{name} is supported, and associated
37678 with the specified @var{value}. The format of @var{value} depends
37679 on the feature, but it must not include a semicolon.
37681 The remote protocol feature @var{name} is supported, and does not
37682 need an associated value.
37684 The remote protocol feature @var{name} is not supported.
37686 The remote protocol feature @var{name} may be supported, and
37687 @value{GDBN} should auto-detect support in some other way when it is
37688 needed. This form will not be used for @var{gdbfeature} notifications,
37689 but may be used for @var{stubfeature} responses.
37692 Whenever the stub receives a @samp{qSupported} request, the
37693 supplied set of @value{GDBN} features should override any previous
37694 request. This allows @value{GDBN} to put the stub in a known
37695 state, even if the stub had previously been communicating with
37696 a different version of @value{GDBN}.
37698 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37703 This feature indicates whether @value{GDBN} supports multiprocess
37704 extensions to the remote protocol. @value{GDBN} does not use such
37705 extensions unless the stub also reports that it supports them by
37706 including @samp{multiprocess+} in its @samp{qSupported} reply.
37707 @xref{multiprocess extensions}, for details.
37710 This feature indicates that @value{GDBN} supports the XML target
37711 description. If the stub sees @samp{xmlRegisters=} with target
37712 specific strings separated by a comma, it will report register
37716 This feature indicates whether @value{GDBN} supports the
37717 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37718 instruction reply packet}).
37721 This feature indicates whether @value{GDBN} supports the swbreak stop
37722 reason in stop replies. @xref{swbreak stop reason}, for details.
37725 This feature indicates whether @value{GDBN} supports the hwbreak stop
37726 reason in stop replies. @xref{swbreak stop reason}, for details.
37729 This feature indicates whether @value{GDBN} supports fork event
37730 extensions to the remote protocol. @value{GDBN} does not use such
37731 extensions unless the stub also reports that it supports them by
37732 including @samp{fork-events+} in its @samp{qSupported} reply.
37735 This feature indicates whether @value{GDBN} supports vfork event
37736 extensions to the remote protocol. @value{GDBN} does not use such
37737 extensions unless the stub also reports that it supports them by
37738 including @samp{vfork-events+} in its @samp{qSupported} reply.
37741 This feature indicates whether @value{GDBN} supports exec event
37742 extensions to the remote protocol. @value{GDBN} does not use such
37743 extensions unless the stub also reports that it supports them by
37744 including @samp{exec-events+} in its @samp{qSupported} reply.
37746 @item vContSupported
37747 This feature indicates whether @value{GDBN} wants to know the
37748 supported actions in the reply to @samp{vCont?} packet.
37751 Stubs should ignore any unknown values for
37752 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37753 packet supports receiving packets of unlimited length (earlier
37754 versions of @value{GDBN} may reject overly long responses). Additional values
37755 for @var{gdbfeature} may be defined in the future to let the stub take
37756 advantage of new features in @value{GDBN}, e.g.@: incompatible
37757 improvements in the remote protocol---the @samp{multiprocess} feature is
37758 an example of such a feature. The stub's reply should be independent
37759 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37760 describes all the features it supports, and then the stub replies with
37761 all the features it supports.
37763 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37764 responses, as long as each response uses one of the standard forms.
37766 Some features are flags. A stub which supports a flag feature
37767 should respond with a @samp{+} form response. Other features
37768 require values, and the stub should respond with an @samp{=}
37771 Each feature has a default value, which @value{GDBN} will use if
37772 @samp{qSupported} is not available or if the feature is not mentioned
37773 in the @samp{qSupported} response. The default values are fixed; a
37774 stub is free to omit any feature responses that match the defaults.
37776 Not all features can be probed, but for those which can, the probing
37777 mechanism is useful: in some cases, a stub's internal
37778 architecture may not allow the protocol layer to know some information
37779 about the underlying target in advance. This is especially common in
37780 stubs which may be configured for multiple targets.
37782 These are the currently defined stub features and their properties:
37784 @multitable @columnfractions 0.35 0.2 0.12 0.2
37785 @c NOTE: The first row should be @headitem, but we do not yet require
37786 @c a new enough version of Texinfo (4.7) to use @headitem.
37788 @tab Value Required
37792 @item @samp{PacketSize}
37797 @item @samp{qXfer:auxv:read}
37802 @item @samp{qXfer:btrace:read}
37807 @item @samp{qXfer:btrace-conf:read}
37812 @item @samp{qXfer:exec-file:read}
37817 @item @samp{qXfer:features:read}
37822 @item @samp{qXfer:libraries:read}
37827 @item @samp{qXfer:libraries-svr4:read}
37832 @item @samp{augmented-libraries-svr4-read}
37837 @item @samp{qXfer:memory-map:read}
37842 @item @samp{qXfer:sdata:read}
37847 @item @samp{qXfer:spu:read}
37852 @item @samp{qXfer:spu:write}
37857 @item @samp{qXfer:siginfo:read}
37862 @item @samp{qXfer:siginfo:write}
37867 @item @samp{qXfer:threads:read}
37872 @item @samp{qXfer:traceframe-info:read}
37877 @item @samp{qXfer:uib:read}
37882 @item @samp{qXfer:fdpic:read}
37887 @item @samp{Qbtrace:off}
37892 @item @samp{Qbtrace:bts}
37897 @item @samp{Qbtrace:pt}
37902 @item @samp{Qbtrace-conf:bts:size}
37907 @item @samp{Qbtrace-conf:pt:size}
37912 @item @samp{QNonStop}
37917 @item @samp{QCatchSyscalls}
37922 @item @samp{QPassSignals}
37927 @item @samp{QStartNoAckMode}
37932 @item @samp{multiprocess}
37937 @item @samp{ConditionalBreakpoints}
37942 @item @samp{ConditionalTracepoints}
37947 @item @samp{ReverseContinue}
37952 @item @samp{ReverseStep}
37957 @item @samp{TracepointSource}
37962 @item @samp{QAgent}
37967 @item @samp{QAllow}
37972 @item @samp{QDisableRandomization}
37977 @item @samp{EnableDisableTracepoints}
37982 @item @samp{QTBuffer:size}
37987 @item @samp{tracenz}
37992 @item @samp{BreakpointCommands}
37997 @item @samp{swbreak}
38002 @item @samp{hwbreak}
38007 @item @samp{fork-events}
38012 @item @samp{vfork-events}
38017 @item @samp{exec-events}
38022 @item @samp{QThreadEvents}
38027 @item @samp{no-resumed}
38034 These are the currently defined stub features, in more detail:
38037 @cindex packet size, remote protocol
38038 @item PacketSize=@var{bytes}
38039 The remote stub can accept packets up to at least @var{bytes} in
38040 length. @value{GDBN} will send packets up to this size for bulk
38041 transfers, and will never send larger packets. This is a limit on the
38042 data characters in the packet, including the frame and checksum.
38043 There is no trailing NUL byte in a remote protocol packet; if the stub
38044 stores packets in a NUL-terminated format, it should allow an extra
38045 byte in its buffer for the NUL. If this stub feature is not supported,
38046 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38048 @item qXfer:auxv:read
38049 The remote stub understands the @samp{qXfer:auxv:read} packet
38050 (@pxref{qXfer auxiliary vector read}).
38052 @item qXfer:btrace:read
38053 The remote stub understands the @samp{qXfer:btrace:read}
38054 packet (@pxref{qXfer btrace read}).
38056 @item qXfer:btrace-conf:read
38057 The remote stub understands the @samp{qXfer:btrace-conf:read}
38058 packet (@pxref{qXfer btrace-conf read}).
38060 @item qXfer:exec-file:read
38061 The remote stub understands the @samp{qXfer:exec-file:read} packet
38062 (@pxref{qXfer executable filename read}).
38064 @item qXfer:features:read
38065 The remote stub understands the @samp{qXfer:features:read} packet
38066 (@pxref{qXfer target description read}).
38068 @item qXfer:libraries:read
38069 The remote stub understands the @samp{qXfer:libraries:read} packet
38070 (@pxref{qXfer library list read}).
38072 @item qXfer:libraries-svr4:read
38073 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38074 (@pxref{qXfer svr4 library list read}).
38076 @item augmented-libraries-svr4-read
38077 The remote stub understands the augmented form of the
38078 @samp{qXfer:libraries-svr4:read} packet
38079 (@pxref{qXfer svr4 library list read}).
38081 @item qXfer:memory-map:read
38082 The remote stub understands the @samp{qXfer:memory-map:read} packet
38083 (@pxref{qXfer memory map read}).
38085 @item qXfer:sdata:read
38086 The remote stub understands the @samp{qXfer:sdata:read} packet
38087 (@pxref{qXfer sdata read}).
38089 @item qXfer:spu:read
38090 The remote stub understands the @samp{qXfer:spu:read} packet
38091 (@pxref{qXfer spu read}).
38093 @item qXfer:spu:write
38094 The remote stub understands the @samp{qXfer:spu:write} packet
38095 (@pxref{qXfer spu write}).
38097 @item qXfer:siginfo:read
38098 The remote stub understands the @samp{qXfer:siginfo:read} packet
38099 (@pxref{qXfer siginfo read}).
38101 @item qXfer:siginfo:write
38102 The remote stub understands the @samp{qXfer:siginfo:write} packet
38103 (@pxref{qXfer siginfo write}).
38105 @item qXfer:threads:read
38106 The remote stub understands the @samp{qXfer:threads:read} packet
38107 (@pxref{qXfer threads read}).
38109 @item qXfer:traceframe-info:read
38110 The remote stub understands the @samp{qXfer:traceframe-info:read}
38111 packet (@pxref{qXfer traceframe info read}).
38113 @item qXfer:uib:read
38114 The remote stub understands the @samp{qXfer:uib:read}
38115 packet (@pxref{qXfer unwind info block}).
38117 @item qXfer:fdpic:read
38118 The remote stub understands the @samp{qXfer:fdpic:read}
38119 packet (@pxref{qXfer fdpic loadmap read}).
38122 The remote stub understands the @samp{QNonStop} packet
38123 (@pxref{QNonStop}).
38125 @item QCatchSyscalls
38126 The remote stub understands the @samp{QCatchSyscalls} packet
38127 (@pxref{QCatchSyscalls}).
38130 The remote stub understands the @samp{QPassSignals} packet
38131 (@pxref{QPassSignals}).
38133 @item QStartNoAckMode
38134 The remote stub understands the @samp{QStartNoAckMode} packet and
38135 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38138 @anchor{multiprocess extensions}
38139 @cindex multiprocess extensions, in remote protocol
38140 The remote stub understands the multiprocess extensions to the remote
38141 protocol syntax. The multiprocess extensions affect the syntax of
38142 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38143 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38144 replies. Note that reporting this feature indicates support for the
38145 syntactic extensions only, not that the stub necessarily supports
38146 debugging of more than one process at a time. The stub must not use
38147 multiprocess extensions in packet replies unless @value{GDBN} has also
38148 indicated it supports them in its @samp{qSupported} request.
38150 @item qXfer:osdata:read
38151 The remote stub understands the @samp{qXfer:osdata:read} packet
38152 ((@pxref{qXfer osdata read}).
38154 @item ConditionalBreakpoints
38155 The target accepts and implements evaluation of conditional expressions
38156 defined for breakpoints. The target will only report breakpoint triggers
38157 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38159 @item ConditionalTracepoints
38160 The remote stub accepts and implements conditional expressions defined
38161 for tracepoints (@pxref{Tracepoint Conditions}).
38163 @item ReverseContinue
38164 The remote stub accepts and implements the reverse continue packet
38168 The remote stub accepts and implements the reverse step packet
38171 @item TracepointSource
38172 The remote stub understands the @samp{QTDPsrc} packet that supplies
38173 the source form of tracepoint definitions.
38176 The remote stub understands the @samp{QAgent} packet.
38179 The remote stub understands the @samp{QAllow} packet.
38181 @item QDisableRandomization
38182 The remote stub understands the @samp{QDisableRandomization} packet.
38184 @item StaticTracepoint
38185 @cindex static tracepoints, in remote protocol
38186 The remote stub supports static tracepoints.
38188 @item InstallInTrace
38189 @anchor{install tracepoint in tracing}
38190 The remote stub supports installing tracepoint in tracing.
38192 @item EnableDisableTracepoints
38193 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
38194 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
38195 to be enabled and disabled while a trace experiment is running.
38197 @item QTBuffer:size
38198 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
38199 packet that allows to change the size of the trace buffer.
38202 @cindex string tracing, in remote protocol
38203 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
38204 See @ref{Bytecode Descriptions} for details about the bytecode.
38206 @item BreakpointCommands
38207 @cindex breakpoint commands, in remote protocol
38208 The remote stub supports running a breakpoint's command list itself,
38209 rather than reporting the hit to @value{GDBN}.
38212 The remote stub understands the @samp{Qbtrace:off} packet.
38215 The remote stub understands the @samp{Qbtrace:bts} packet.
38218 The remote stub understands the @samp{Qbtrace:pt} packet.
38220 @item Qbtrace-conf:bts:size
38221 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
38223 @item Qbtrace-conf:pt:size
38224 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
38227 The remote stub reports the @samp{swbreak} stop reason for memory
38231 The remote stub reports the @samp{hwbreak} stop reason for hardware
38235 The remote stub reports the @samp{fork} stop reason for fork events.
38238 The remote stub reports the @samp{vfork} stop reason for vfork events
38239 and vforkdone events.
38242 The remote stub reports the @samp{exec} stop reason for exec events.
38244 @item vContSupported
38245 The remote stub reports the supported actions in the reply to
38246 @samp{vCont?} packet.
38248 @item QThreadEvents
38249 The remote stub understands the @samp{QThreadEvents} packet.
38252 The remote stub reports the @samp{N} stop reply.
38257 @cindex symbol lookup, remote request
38258 @cindex @samp{qSymbol} packet
38259 Notify the target that @value{GDBN} is prepared to serve symbol lookup
38260 requests. Accept requests from the target for the values of symbols.
38265 The target does not need to look up any (more) symbols.
38266 @item qSymbol:@var{sym_name}
38267 The target requests the value of symbol @var{sym_name} (hex encoded).
38268 @value{GDBN} may provide the value by using the
38269 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
38273 @item qSymbol:@var{sym_value}:@var{sym_name}
38274 Set the value of @var{sym_name} to @var{sym_value}.
38276 @var{sym_name} (hex encoded) is the name of a symbol whose value the
38277 target has previously requested.
38279 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
38280 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
38286 The target does not need to look up any (more) symbols.
38287 @item qSymbol:@var{sym_name}
38288 The target requests the value of a new symbol @var{sym_name} (hex
38289 encoded). @value{GDBN} will continue to supply the values of symbols
38290 (if available), until the target ceases to request them.
38295 @itemx QTDisconnected
38302 @itemx qTMinFTPILen
38304 @xref{Tracepoint Packets}.
38306 @item qThreadExtraInfo,@var{thread-id}
38307 @cindex thread attributes info, remote request
38308 @cindex @samp{qThreadExtraInfo} packet
38309 Obtain from the target OS a printable string description of thread
38310 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
38311 for the forms of @var{thread-id}. This
38312 string may contain anything that the target OS thinks is interesting
38313 for @value{GDBN} to tell the user about the thread. The string is
38314 displayed in @value{GDBN}'s @code{info threads} display. Some
38315 examples of possible thread extra info strings are @samp{Runnable}, or
38316 @samp{Blocked on Mutex}.
38320 @item @var{XX}@dots{}
38321 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
38322 comprising the printable string containing the extra information about
38323 the thread's attributes.
38326 (Note that the @code{qThreadExtraInfo} packet's name is separated from
38327 the command by a @samp{,}, not a @samp{:}, contrary to the naming
38328 conventions above. Please don't use this packet as a model for new
38347 @xref{Tracepoint Packets}.
38349 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
38350 @cindex read special object, remote request
38351 @cindex @samp{qXfer} packet
38352 @anchor{qXfer read}
38353 Read uninterpreted bytes from the target's special data area
38354 identified by the keyword @var{object}. Request @var{length} bytes
38355 starting at @var{offset} bytes into the data. The content and
38356 encoding of @var{annex} is specific to @var{object}; it can supply
38357 additional details about what data to access.
38362 Data @var{data} (@pxref{Binary Data}) has been read from the
38363 target. There may be more data at a higher address (although
38364 it is permitted to return @samp{m} even for the last valid
38365 block of data, as long as at least one byte of data was read).
38366 It is possible for @var{data} to have fewer bytes than the @var{length} in the
38370 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38371 There is no more data to be read. It is possible for @var{data} to
38372 have fewer bytes than the @var{length} in the request.
38375 The @var{offset} in the request is at the end of the data.
38376 There is no more data to be read.
38379 The request was malformed, or @var{annex} was invalid.
38382 The offset was invalid, or there was an error encountered reading the data.
38383 The @var{nn} part is a hex-encoded @code{errno} value.
38386 An empty reply indicates the @var{object} string was not recognized by
38387 the stub, or that the object does not support reading.
38390 Here are the specific requests of this form defined so far. All the
38391 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
38392 formats, listed above.
38395 @item qXfer:auxv:read::@var{offset},@var{length}
38396 @anchor{qXfer auxiliary vector read}
38397 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
38398 auxiliary vector}. Note @var{annex} must be empty.
38400 This packet is not probed by default; the remote stub must request it,
38401 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38403 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
38404 @anchor{qXfer btrace read}
38406 Return a description of the current branch trace.
38407 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
38408 packet may have one of the following values:
38412 Returns all available branch trace.
38415 Returns all available branch trace if the branch trace changed since
38416 the last read request.
38419 Returns the new branch trace since the last read request. Adds a new
38420 block to the end of the trace that begins at zero and ends at the source
38421 location of the first branch in the trace buffer. This extra block is
38422 used to stitch traces together.
38424 If the trace buffer overflowed, returns an error indicating the overflow.
38427 This packet is not probed by default; the remote stub must request it
38428 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38430 @item qXfer:btrace-conf:read::@var{offset},@var{length}
38431 @anchor{qXfer btrace-conf read}
38433 Return a description of the current branch trace configuration.
38434 @xref{Branch Trace Configuration Format}.
38436 This packet is not probed by default; the remote stub must request it
38437 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38439 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
38440 @anchor{qXfer executable filename read}
38441 Return the full absolute name of the file that was executed to create
38442 a process running on the remote system. The annex specifies the
38443 numeric process ID of the process to query, encoded as a hexadecimal
38444 number. If the annex part is empty the remote stub should return the
38445 filename corresponding to the currently executing process.
38447 This packet is not probed by default; the remote stub must request it,
38448 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38450 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
38451 @anchor{qXfer target description read}
38452 Access the @dfn{target description}. @xref{Target Descriptions}. The
38453 annex specifies which XML document to access. The main description is
38454 always loaded from the @samp{target.xml} annex.
38456 This packet is not probed by default; the remote stub must request it,
38457 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38459 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
38460 @anchor{qXfer library list read}
38461 Access the target's list of loaded libraries. @xref{Library List Format}.
38462 The annex part of the generic @samp{qXfer} packet must be empty
38463 (@pxref{qXfer read}).
38465 Targets which maintain a list of libraries in the program's memory do
38466 not need to implement this packet; it is designed for platforms where
38467 the operating system manages the list of loaded libraries.
38469 This packet is not probed by default; the remote stub must request it,
38470 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38472 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
38473 @anchor{qXfer svr4 library list read}
38474 Access the target's list of loaded libraries when the target is an SVR4
38475 platform. @xref{Library List Format for SVR4 Targets}. The annex part
38476 of the generic @samp{qXfer} packet must be empty unless the remote
38477 stub indicated it supports the augmented form of this packet
38478 by supplying an appropriate @samp{qSupported} response
38479 (@pxref{qXfer read}, @ref{qSupported}).
38481 This packet is optional for better performance on SVR4 targets.
38482 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
38484 This packet is not probed by default; the remote stub must request it,
38485 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38487 If the remote stub indicates it supports the augmented form of this
38488 packet then the annex part of the generic @samp{qXfer} packet may
38489 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
38490 arguments. The currently supported arguments are:
38493 @item start=@var{address}
38494 A hexadecimal number specifying the address of the @samp{struct
38495 link_map} to start reading the library list from. If unset or zero
38496 then the first @samp{struct link_map} in the library list will be
38497 chosen as the starting point.
38499 @item prev=@var{address}
38500 A hexadecimal number specifying the address of the @samp{struct
38501 link_map} immediately preceding the @samp{struct link_map}
38502 specified by the @samp{start} argument. If unset or zero then
38503 the remote stub will expect that no @samp{struct link_map}
38504 exists prior to the starting point.
38508 Arguments that are not understood by the remote stub will be silently
38511 @item qXfer:memory-map:read::@var{offset},@var{length}
38512 @anchor{qXfer memory map read}
38513 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
38514 annex part of the generic @samp{qXfer} packet must be empty
38515 (@pxref{qXfer read}).
38517 This packet is not probed by default; the remote stub must request it,
38518 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38520 @item qXfer:sdata:read::@var{offset},@var{length}
38521 @anchor{qXfer sdata read}
38523 Read contents of the extra collected static tracepoint marker
38524 information. The annex part of the generic @samp{qXfer} packet must
38525 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
38528 This packet is not probed by default; the remote stub must request it,
38529 by supplying an appropriate @samp{qSupported} response
38530 (@pxref{qSupported}).
38532 @item qXfer:siginfo:read::@var{offset},@var{length}
38533 @anchor{qXfer siginfo read}
38534 Read contents of the extra signal information on the target
38535 system. The annex part of the generic @samp{qXfer} packet must be
38536 empty (@pxref{qXfer read}).
38538 This packet is not probed by default; the remote stub must request it,
38539 by supplying an appropriate @samp{qSupported} response
38540 (@pxref{qSupported}).
38542 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
38543 @anchor{qXfer spu read}
38544 Read contents of an @code{spufs} file on the target system. The
38545 annex specifies which file to read; it must be of the form
38546 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38547 in the target process, and @var{name} identifes the @code{spufs} file
38548 in that context to be accessed.
38550 This packet is not probed by default; the remote stub must request it,
38551 by supplying an appropriate @samp{qSupported} response
38552 (@pxref{qSupported}).
38554 @item qXfer:threads:read::@var{offset},@var{length}
38555 @anchor{qXfer threads read}
38556 Access the list of threads on target. @xref{Thread List Format}. The
38557 annex part of the generic @samp{qXfer} packet must be empty
38558 (@pxref{qXfer read}).
38560 This packet is not probed by default; the remote stub must request it,
38561 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38563 @item qXfer:traceframe-info:read::@var{offset},@var{length}
38564 @anchor{qXfer traceframe info read}
38566 Return a description of the current traceframe's contents.
38567 @xref{Traceframe Info Format}. The annex part of the generic
38568 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
38570 This packet is not probed by default; the remote stub must request it,
38571 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38573 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
38574 @anchor{qXfer unwind info block}
38576 Return the unwind information block for @var{pc}. This packet is used
38577 on OpenVMS/ia64 to ask the kernel unwind information.
38579 This packet is not probed by default.
38581 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
38582 @anchor{qXfer fdpic loadmap read}
38583 Read contents of @code{loadmap}s on the target system. The
38584 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
38585 executable @code{loadmap} or interpreter @code{loadmap} to read.
38587 This packet is not probed by default; the remote stub must request it,
38588 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38590 @item qXfer:osdata:read::@var{offset},@var{length}
38591 @anchor{qXfer osdata read}
38592 Access the target's @dfn{operating system information}.
38593 @xref{Operating System Information}.
38597 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38598 @cindex write data into object, remote request
38599 @anchor{qXfer write}
38600 Write uninterpreted bytes into the target's special data area
38601 identified by the keyword @var{object}, starting at @var{offset} bytes
38602 into the data. The binary-encoded data (@pxref{Binary Data}) to be
38603 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
38604 is specific to @var{object}; it can supply additional details about what data
38610 @var{nn} (hex encoded) is the number of bytes written.
38611 This may be fewer bytes than supplied in the request.
38614 The request was malformed, or @var{annex} was invalid.
38617 The offset was invalid, or there was an error encountered writing the data.
38618 The @var{nn} part is a hex-encoded @code{errno} value.
38621 An empty reply indicates the @var{object} string was not
38622 recognized by the stub, or that the object does not support writing.
38625 Here are the specific requests of this form defined so far. All the
38626 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38627 formats, listed above.
38630 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38631 @anchor{qXfer siginfo write}
38632 Write @var{data} to the extra signal information on the target system.
38633 The annex part of the generic @samp{qXfer} packet must be
38634 empty (@pxref{qXfer write}).
38636 This packet is not probed by default; the remote stub must request it,
38637 by supplying an appropriate @samp{qSupported} response
38638 (@pxref{qSupported}).
38640 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38641 @anchor{qXfer spu write}
38642 Write @var{data} to an @code{spufs} file on the target system. The
38643 annex specifies which file to write; it must be of the form
38644 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38645 in the target process, and @var{name} identifes the @code{spufs} file
38646 in that context to be accessed.
38648 This packet is not probed by default; the remote stub must request it,
38649 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38652 @item qXfer:@var{object}:@var{operation}:@dots{}
38653 Requests of this form may be added in the future. When a stub does
38654 not recognize the @var{object} keyword, or its support for
38655 @var{object} does not recognize the @var{operation} keyword, the stub
38656 must respond with an empty packet.
38658 @item qAttached:@var{pid}
38659 @cindex query attached, remote request
38660 @cindex @samp{qAttached} packet
38661 Return an indication of whether the remote server attached to an
38662 existing process or created a new process. When the multiprocess
38663 protocol extensions are supported (@pxref{multiprocess extensions}),
38664 @var{pid} is an integer in hexadecimal format identifying the target
38665 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38666 the query packet will be simplified as @samp{qAttached}.
38668 This query is used, for example, to know whether the remote process
38669 should be detached or killed when a @value{GDBN} session is ended with
38670 the @code{quit} command.
38675 The remote server attached to an existing process.
38677 The remote server created a new process.
38679 A badly formed request or an error was encountered.
38683 Enable branch tracing for the current thread using Branch Trace Store.
38688 Branch tracing has been enabled.
38690 A badly formed request or an error was encountered.
38694 Enable branch tracing for the current thread using Intel Processor Trace.
38699 Branch tracing has been enabled.
38701 A badly formed request or an error was encountered.
38705 Disable branch tracing for the current thread.
38710 Branch tracing has been disabled.
38712 A badly formed request or an error was encountered.
38715 @item Qbtrace-conf:bts:size=@var{value}
38716 Set the requested ring buffer size for new threads that use the
38717 btrace recording method in bts format.
38722 The ring buffer size has been set.
38724 A badly formed request or an error was encountered.
38727 @item Qbtrace-conf:pt:size=@var{value}
38728 Set the requested ring buffer size for new threads that use the
38729 btrace recording method in pt format.
38734 The ring buffer size has been set.
38736 A badly formed request or an error was encountered.
38741 @node Architecture-Specific Protocol Details
38742 @section Architecture-Specific Protocol Details
38744 This section describes how the remote protocol is applied to specific
38745 target architectures. Also see @ref{Standard Target Features}, for
38746 details of XML target descriptions for each architecture.
38749 * ARM-Specific Protocol Details::
38750 * MIPS-Specific Protocol Details::
38753 @node ARM-Specific Protocol Details
38754 @subsection @acronym{ARM}-specific Protocol Details
38757 * ARM Breakpoint Kinds::
38760 @node ARM Breakpoint Kinds
38761 @subsubsection @acronym{ARM} Breakpoint Kinds
38762 @cindex breakpoint kinds, @acronym{ARM}
38764 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38769 16-bit Thumb mode breakpoint.
38772 32-bit Thumb mode (Thumb-2) breakpoint.
38775 32-bit @acronym{ARM} mode breakpoint.
38779 @node MIPS-Specific Protocol Details
38780 @subsection @acronym{MIPS}-specific Protocol Details
38783 * MIPS Register packet Format::
38784 * MIPS Breakpoint Kinds::
38787 @node MIPS Register packet Format
38788 @subsubsection @acronym{MIPS} Register Packet Format
38789 @cindex register packet format, @acronym{MIPS}
38791 The following @code{g}/@code{G} packets have previously been defined.
38792 In the below, some thirty-two bit registers are transferred as
38793 sixty-four bits. Those registers should be zero/sign extended (which?)
38794 to fill the space allocated. Register bytes are transferred in target
38795 byte order. The two nibbles within a register byte are transferred
38796 most-significant -- least-significant.
38801 All registers are transferred as thirty-two bit quantities in the order:
38802 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38803 registers; fsr; fir; fp.
38806 All registers are transferred as sixty-four bit quantities (including
38807 thirty-two bit registers such as @code{sr}). The ordering is the same
38812 @node MIPS Breakpoint Kinds
38813 @subsubsection @acronym{MIPS} Breakpoint Kinds
38814 @cindex breakpoint kinds, @acronym{MIPS}
38816 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38821 16-bit @acronym{MIPS16} mode breakpoint.
38824 16-bit @acronym{microMIPS} mode breakpoint.
38827 32-bit standard @acronym{MIPS} mode breakpoint.
38830 32-bit @acronym{microMIPS} mode breakpoint.
38834 @node Tracepoint Packets
38835 @section Tracepoint Packets
38836 @cindex tracepoint packets
38837 @cindex packets, tracepoint
38839 Here we describe the packets @value{GDBN} uses to implement
38840 tracepoints (@pxref{Tracepoints}).
38844 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38845 @cindex @samp{QTDP} packet
38846 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38847 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38848 the tracepoint is disabled. The @var{step} gives the tracepoint's step
38849 count, and @var{pass} gives its pass count. If an @samp{F} is present,
38850 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38851 the number of bytes that the target should copy elsewhere to make room
38852 for the tracepoint. If an @samp{X} is present, it introduces a
38853 tracepoint condition, which consists of a hexadecimal length, followed
38854 by a comma and hex-encoded bytes, in a manner similar to action
38855 encodings as described below. If the trailing @samp{-} is present,
38856 further @samp{QTDP} packets will follow to specify this tracepoint's
38862 The packet was understood and carried out.
38864 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38866 The packet was not recognized.
38869 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38870 Define actions to be taken when a tracepoint is hit. The @var{n} and
38871 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38872 this tracepoint. This packet may only be sent immediately after
38873 another @samp{QTDP} packet that ended with a @samp{-}. If the
38874 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38875 specifying more actions for this tracepoint.
38877 In the series of action packets for a given tracepoint, at most one
38878 can have an @samp{S} before its first @var{action}. If such a packet
38879 is sent, it and the following packets define ``while-stepping''
38880 actions. Any prior packets define ordinary actions --- that is, those
38881 taken when the tracepoint is first hit. If no action packet has an
38882 @samp{S}, then all the packets in the series specify ordinary
38883 tracepoint actions.
38885 The @samp{@var{action}@dots{}} portion of the packet is a series of
38886 actions, concatenated without separators. Each action has one of the
38892 Collect the registers whose bits are set in @var{mask},
38893 a hexadecimal number whose @var{i}'th bit is set if register number
38894 @var{i} should be collected. (The least significant bit is numbered
38895 zero.) Note that @var{mask} may be any number of digits long; it may
38896 not fit in a 32-bit word.
38898 @item M @var{basereg},@var{offset},@var{len}
38899 Collect @var{len} bytes of memory starting at the address in register
38900 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38901 @samp{-1}, then the range has a fixed address: @var{offset} is the
38902 address of the lowest byte to collect. The @var{basereg},
38903 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38904 values (the @samp{-1} value for @var{basereg} is a special case).
38906 @item X @var{len},@var{expr}
38907 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38908 it directs. The agent expression @var{expr} is as described in
38909 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38910 two-digit hex number in the packet; @var{len} is the number of bytes
38911 in the expression (and thus one-half the number of hex digits in the
38916 Any number of actions may be packed together in a single @samp{QTDP}
38917 packet, as long as the packet does not exceed the maximum packet
38918 length (400 bytes, for many stubs). There may be only one @samp{R}
38919 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38920 actions. Any registers referred to by @samp{M} and @samp{X} actions
38921 must be collected by a preceding @samp{R} action. (The
38922 ``while-stepping'' actions are treated as if they were attached to a
38923 separate tracepoint, as far as these restrictions are concerned.)
38928 The packet was understood and carried out.
38930 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38932 The packet was not recognized.
38935 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38936 @cindex @samp{QTDPsrc} packet
38937 Specify a source string of tracepoint @var{n} at address @var{addr}.
38938 This is useful to get accurate reproduction of the tracepoints
38939 originally downloaded at the beginning of the trace run. The @var{type}
38940 is the name of the tracepoint part, such as @samp{cond} for the
38941 tracepoint's conditional expression (see below for a list of types), while
38942 @var{bytes} is the string, encoded in hexadecimal.
38944 @var{start} is the offset of the @var{bytes} within the overall source
38945 string, while @var{slen} is the total length of the source string.
38946 This is intended for handling source strings that are longer than will
38947 fit in a single packet.
38948 @c Add detailed example when this info is moved into a dedicated
38949 @c tracepoint descriptions section.
38951 The available string types are @samp{at} for the location,
38952 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38953 @value{GDBN} sends a separate packet for each command in the action
38954 list, in the same order in which the commands are stored in the list.
38956 The target does not need to do anything with source strings except
38957 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38960 Although this packet is optional, and @value{GDBN} will only send it
38961 if the target replies with @samp{TracepointSource} @xref{General
38962 Query Packets}, it makes both disconnected tracing and trace files
38963 much easier to use. Otherwise the user must be careful that the
38964 tracepoints in effect while looking at trace frames are identical to
38965 the ones in effect during the trace run; even a small discrepancy
38966 could cause @samp{tdump} not to work, or a particular trace frame not
38969 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
38970 @cindex define trace state variable, remote request
38971 @cindex @samp{QTDV} packet
38972 Create a new trace state variable, number @var{n}, with an initial
38973 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38974 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38975 the option of not using this packet for initial values of zero; the
38976 target should simply create the trace state variables as they are
38977 mentioned in expressions. The value @var{builtin} should be 1 (one)
38978 if the trace state variable is builtin and 0 (zero) if it is not builtin.
38979 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
38980 @samp{qTsV} packet had it set. The contents of @var{name} is the
38981 hex-encoded name (without the leading @samp{$}) of the trace state
38984 @item QTFrame:@var{n}
38985 @cindex @samp{QTFrame} packet
38986 Select the @var{n}'th tracepoint frame from the buffer, and use the
38987 register and memory contents recorded there to answer subsequent
38988 request packets from @value{GDBN}.
38990 A successful reply from the stub indicates that the stub has found the
38991 requested frame. The response is a series of parts, concatenated
38992 without separators, describing the frame we selected. Each part has
38993 one of the following forms:
38997 The selected frame is number @var{n} in the trace frame buffer;
38998 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38999 was no frame matching the criteria in the request packet.
39002 The selected trace frame records a hit of tracepoint number @var{t};
39003 @var{t} is a hexadecimal number.
39007 @item QTFrame:pc:@var{addr}
39008 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39009 currently selected frame whose PC is @var{addr};
39010 @var{addr} is a hexadecimal number.
39012 @item QTFrame:tdp:@var{t}
39013 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39014 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39015 is a hexadecimal number.
39017 @item QTFrame:range:@var{start}:@var{end}
39018 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39019 currently selected frame whose PC is between @var{start} (inclusive)
39020 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39023 @item QTFrame:outside:@var{start}:@var{end}
39024 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39025 frame @emph{outside} the given range of addresses (exclusive).
39028 @cindex @samp{qTMinFTPILen} packet
39029 This packet requests the minimum length of instruction at which a fast
39030 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39031 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39032 it depends on the target system being able to create trampolines in
39033 the first 64K of memory, which might or might not be possible for that
39034 system. So the reply to this packet will be 4 if it is able to
39041 The minimum instruction length is currently unknown.
39043 The minimum instruction length is @var{length}, where @var{length}
39044 is a hexadecimal number greater or equal to 1. A reply
39045 of 1 means that a fast tracepoint may be placed on any instruction
39046 regardless of size.
39048 An error has occurred.
39050 An empty reply indicates that the request is not supported by the stub.
39054 @cindex @samp{QTStart} packet
39055 Begin the tracepoint experiment. Begin collecting data from
39056 tracepoint hits in the trace frame buffer. This packet supports the
39057 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39058 instruction reply packet}).
39061 @cindex @samp{QTStop} packet
39062 End the tracepoint experiment. Stop collecting trace frames.
39064 @item QTEnable:@var{n}:@var{addr}
39066 @cindex @samp{QTEnable} packet
39067 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39068 experiment. If the tracepoint was previously disabled, then collection
39069 of data from it will resume.
39071 @item QTDisable:@var{n}:@var{addr}
39073 @cindex @samp{QTDisable} packet
39074 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39075 experiment. No more data will be collected from the tracepoint unless
39076 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39079 @cindex @samp{QTinit} packet
39080 Clear the table of tracepoints, and empty the trace frame buffer.
39082 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39083 @cindex @samp{QTro} packet
39084 Establish the given ranges of memory as ``transparent''. The stub
39085 will answer requests for these ranges from memory's current contents,
39086 if they were not collected as part of the tracepoint hit.
39088 @value{GDBN} uses this to mark read-only regions of memory, like those
39089 containing program code. Since these areas never change, they should
39090 still have the same contents they did when the tracepoint was hit, so
39091 there's no reason for the stub to refuse to provide their contents.
39093 @item QTDisconnected:@var{value}
39094 @cindex @samp{QTDisconnected} packet
39095 Set the choice to what to do with the tracing run when @value{GDBN}
39096 disconnects from the target. A @var{value} of 1 directs the target to
39097 continue the tracing run, while 0 tells the target to stop tracing if
39098 @value{GDBN} is no longer in the picture.
39101 @cindex @samp{qTStatus} packet
39102 Ask the stub if there is a trace experiment running right now.
39104 The reply has the form:
39108 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39109 @var{running} is a single digit @code{1} if the trace is presently
39110 running, or @code{0} if not. It is followed by semicolon-separated
39111 optional fields that an agent may use to report additional status.
39115 If the trace is not running, the agent may report any of several
39116 explanations as one of the optional fields:
39121 No trace has been run yet.
39123 @item tstop[:@var{text}]:0
39124 The trace was stopped by a user-originated stop command. The optional
39125 @var{text} field is a user-supplied string supplied as part of the
39126 stop command (for instance, an explanation of why the trace was
39127 stopped manually). It is hex-encoded.
39130 The trace stopped because the trace buffer filled up.
39132 @item tdisconnected:0
39133 The trace stopped because @value{GDBN} disconnected from the target.
39135 @item tpasscount:@var{tpnum}
39136 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39138 @item terror:@var{text}:@var{tpnum}
39139 The trace stopped because tracepoint @var{tpnum} had an error. The
39140 string @var{text} is available to describe the nature of the error
39141 (for instance, a divide by zero in the condition expression); it
39145 The trace stopped for some other reason.
39149 Additional optional fields supply statistical and other information.
39150 Although not required, they are extremely useful for users monitoring
39151 the progress of a trace run. If a trace has stopped, and these
39152 numbers are reported, they must reflect the state of the just-stopped
39157 @item tframes:@var{n}
39158 The number of trace frames in the buffer.
39160 @item tcreated:@var{n}
39161 The total number of trace frames created during the run. This may
39162 be larger than the trace frame count, if the buffer is circular.
39164 @item tsize:@var{n}
39165 The total size of the trace buffer, in bytes.
39167 @item tfree:@var{n}
39168 The number of bytes still unused in the buffer.
39170 @item circular:@var{n}
39171 The value of the circular trace buffer flag. @code{1} means that the
39172 trace buffer is circular and old trace frames will be discarded if
39173 necessary to make room, @code{0} means that the trace buffer is linear
39176 @item disconn:@var{n}
39177 The value of the disconnected tracing flag. @code{1} means that
39178 tracing will continue after @value{GDBN} disconnects, @code{0} means
39179 that the trace run will stop.
39183 @item qTP:@var{tp}:@var{addr}
39184 @cindex tracepoint status, remote request
39185 @cindex @samp{qTP} packet
39186 Ask the stub for the current state of tracepoint number @var{tp} at
39187 address @var{addr}.
39191 @item V@var{hits}:@var{usage}
39192 The tracepoint has been hit @var{hits} times so far during the trace
39193 run, and accounts for @var{usage} in the trace buffer. Note that
39194 @code{while-stepping} steps are not counted as separate hits, but the
39195 steps' space consumption is added into the usage number.
39199 @item qTV:@var{var}
39200 @cindex trace state variable value, remote request
39201 @cindex @samp{qTV} packet
39202 Ask the stub for the value of the trace state variable number @var{var}.
39207 The value of the variable is @var{value}. This will be the current
39208 value of the variable if the user is examining a running target, or a
39209 saved value if the variable was collected in the trace frame that the
39210 user is looking at. Note that multiple requests may result in
39211 different reply values, such as when requesting values while the
39212 program is running.
39215 The value of the variable is unknown. This would occur, for example,
39216 if the user is examining a trace frame in which the requested variable
39221 @cindex @samp{qTfP} packet
39223 @cindex @samp{qTsP} packet
39224 These packets request data about tracepoints that are being used by
39225 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39226 of data, and multiple @code{qTsP} to get additional pieces. Replies
39227 to these packets generally take the form of the @code{QTDP} packets
39228 that define tracepoints. (FIXME add detailed syntax)
39231 @cindex @samp{qTfV} packet
39233 @cindex @samp{qTsV} packet
39234 These packets request data about trace state variables that are on the
39235 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39236 and multiple @code{qTsV} to get additional variables. Replies to
39237 these packets follow the syntax of the @code{QTDV} packets that define
39238 trace state variables.
39244 @cindex @samp{qTfSTM} packet
39245 @cindex @samp{qTsSTM} packet
39246 These packets request data about static tracepoint markers that exist
39247 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39248 first piece of data, and multiple @code{qTsSTM} to get additional
39249 pieces. Replies to these packets take the following form:
39253 @item m @var{address}:@var{id}:@var{extra}
39255 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39256 a comma-separated list of markers
39258 (lower case letter @samp{L}) denotes end of list.
39260 An error occurred. The error number @var{nn} is given as hex digits.
39262 An empty reply indicates that the request is not supported by the
39266 The @var{address} is encoded in hex;
39267 @var{id} and @var{extra} are strings encoded in hex.
39269 In response to each query, the target will reply with a list of one or
39270 more markers, separated by commas. @value{GDBN} will respond to each
39271 reply with a request for more markers (using the @samp{qs} form of the
39272 query), until the target responds with @samp{l} (lower-case ell, for
39275 @item qTSTMat:@var{address}
39277 @cindex @samp{qTSTMat} packet
39278 This packets requests data about static tracepoint markers in the
39279 target program at @var{address}. Replies to this packet follow the
39280 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
39281 tracepoint markers.
39283 @item QTSave:@var{filename}
39284 @cindex @samp{QTSave} packet
39285 This packet directs the target to save trace data to the file name
39286 @var{filename} in the target's filesystem. The @var{filename} is encoded
39287 as a hex string; the interpretation of the file name (relative vs
39288 absolute, wild cards, etc) is up to the target.
39290 @item qTBuffer:@var{offset},@var{len}
39291 @cindex @samp{qTBuffer} packet
39292 Return up to @var{len} bytes of the current contents of trace buffer,
39293 starting at @var{offset}. The trace buffer is treated as if it were
39294 a contiguous collection of traceframes, as per the trace file format.
39295 The reply consists as many hex-encoded bytes as the target can deliver
39296 in a packet; it is not an error to return fewer than were asked for.
39297 A reply consisting of just @code{l} indicates that no bytes are
39300 @item QTBuffer:circular:@var{value}
39301 This packet directs the target to use a circular trace buffer if
39302 @var{value} is 1, or a linear buffer if the value is 0.
39304 @item QTBuffer:size:@var{size}
39305 @anchor{QTBuffer-size}
39306 @cindex @samp{QTBuffer size} packet
39307 This packet directs the target to make the trace buffer be of size
39308 @var{size} if possible. A value of @code{-1} tells the target to
39309 use whatever size it prefers.
39311 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
39312 @cindex @samp{QTNotes} packet
39313 This packet adds optional textual notes to the trace run. Allowable
39314 types include @code{user}, @code{notes}, and @code{tstop}, the
39315 @var{text} fields are arbitrary strings, hex-encoded.
39319 @subsection Relocate instruction reply packet
39320 When installing fast tracepoints in memory, the target may need to
39321 relocate the instruction currently at the tracepoint address to a
39322 different address in memory. For most instructions, a simple copy is
39323 enough, but, for example, call instructions that implicitly push the
39324 return address on the stack, and relative branches or other
39325 PC-relative instructions require offset adjustment, so that the effect
39326 of executing the instruction at a different address is the same as if
39327 it had executed in the original location.
39329 In response to several of the tracepoint packets, the target may also
39330 respond with a number of intermediate @samp{qRelocInsn} request
39331 packets before the final result packet, to have @value{GDBN} handle
39332 this relocation operation. If a packet supports this mechanism, its
39333 documentation will explicitly say so. See for example the above
39334 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
39335 format of the request is:
39338 @item qRelocInsn:@var{from};@var{to}
39340 This requests @value{GDBN} to copy instruction at address @var{from}
39341 to address @var{to}, possibly adjusted so that executing the
39342 instruction at @var{to} has the same effect as executing it at
39343 @var{from}. @value{GDBN} writes the adjusted instruction to target
39344 memory starting at @var{to}.
39349 @item qRelocInsn:@var{adjusted_size}
39350 Informs the stub the relocation is complete. The @var{adjusted_size} is
39351 the length in bytes of resulting relocated instruction sequence.
39353 A badly formed request was detected, or an error was encountered while
39354 relocating the instruction.
39357 @node Host I/O Packets
39358 @section Host I/O Packets
39359 @cindex Host I/O, remote protocol
39360 @cindex file transfer, remote protocol
39362 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
39363 operations on the far side of a remote link. For example, Host I/O is
39364 used to upload and download files to a remote target with its own
39365 filesystem. Host I/O uses the same constant values and data structure
39366 layout as the target-initiated File-I/O protocol. However, the
39367 Host I/O packets are structured differently. The target-initiated
39368 protocol relies on target memory to store parameters and buffers.
39369 Host I/O requests are initiated by @value{GDBN}, and the
39370 target's memory is not involved. @xref{File-I/O Remote Protocol
39371 Extension}, for more details on the target-initiated protocol.
39373 The Host I/O request packets all encode a single operation along with
39374 its arguments. They have this format:
39378 @item vFile:@var{operation}: @var{parameter}@dots{}
39379 @var{operation} is the name of the particular request; the target
39380 should compare the entire packet name up to the second colon when checking
39381 for a supported operation. The format of @var{parameter} depends on
39382 the operation. Numbers are always passed in hexadecimal. Negative
39383 numbers have an explicit minus sign (i.e.@: two's complement is not
39384 used). Strings (e.g.@: filenames) are encoded as a series of
39385 hexadecimal bytes. The last argument to a system call may be a
39386 buffer of escaped binary data (@pxref{Binary Data}).
39390 The valid responses to Host I/O packets are:
39394 @item F @var{result} [, @var{errno}] [; @var{attachment}]
39395 @var{result} is the integer value returned by this operation, usually
39396 non-negative for success and -1 for errors. If an error has occured,
39397 @var{errno} will be included in the result specifying a
39398 value defined by the File-I/O protocol (@pxref{Errno Values}). For
39399 operations which return data, @var{attachment} supplies the data as a
39400 binary buffer. Binary buffers in response packets are escaped in the
39401 normal way (@pxref{Binary Data}). See the individual packet
39402 documentation for the interpretation of @var{result} and
39406 An empty response indicates that this operation is not recognized.
39410 These are the supported Host I/O operations:
39413 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
39414 Open a file at @var{filename} and return a file descriptor for it, or
39415 return -1 if an error occurs. The @var{filename} is a string,
39416 @var{flags} is an integer indicating a mask of open flags
39417 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
39418 of mode bits to use if the file is created (@pxref{mode_t Values}).
39419 @xref{open}, for details of the open flags and mode values.
39421 @item vFile:close: @var{fd}
39422 Close the open file corresponding to @var{fd} and return 0, or
39423 -1 if an error occurs.
39425 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
39426 Read data from the open file corresponding to @var{fd}. Up to
39427 @var{count} bytes will be read from the file, starting at @var{offset}
39428 relative to the start of the file. The target may read fewer bytes;
39429 common reasons include packet size limits and an end-of-file
39430 condition. The number of bytes read is returned. Zero should only be
39431 returned for a successful read at the end of the file, or if
39432 @var{count} was zero.
39434 The data read should be returned as a binary attachment on success.
39435 If zero bytes were read, the response should include an empty binary
39436 attachment (i.e.@: a trailing semicolon). The return value is the
39437 number of target bytes read; the binary attachment may be longer if
39438 some characters were escaped.
39440 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
39441 Write @var{data} (a binary buffer) to the open file corresponding
39442 to @var{fd}. Start the write at @var{offset} from the start of the
39443 file. Unlike many @code{write} system calls, there is no
39444 separate @var{count} argument; the length of @var{data} in the
39445 packet is used. @samp{vFile:write} returns the number of bytes written,
39446 which may be shorter than the length of @var{data}, or -1 if an
39449 @item vFile:fstat: @var{fd}
39450 Get information about the open file corresponding to @var{fd}.
39451 On success the information is returned as a binary attachment
39452 and the return value is the size of this attachment in bytes.
39453 If an error occurs the return value is -1. The format of the
39454 returned binary attachment is as described in @ref{struct stat}.
39456 @item vFile:unlink: @var{filename}
39457 Delete the file at @var{filename} on the target. Return 0,
39458 or -1 if an error occurs. The @var{filename} is a string.
39460 @item vFile:readlink: @var{filename}
39461 Read value of symbolic link @var{filename} on the target. Return
39462 the number of bytes read, or -1 if an error occurs.
39464 The data read should be returned as a binary attachment on success.
39465 If zero bytes were read, the response should include an empty binary
39466 attachment (i.e.@: a trailing semicolon). The return value is the
39467 number of target bytes read; the binary attachment may be longer if
39468 some characters were escaped.
39470 @item vFile:setfs: @var{pid}
39471 Select the filesystem on which @code{vFile} operations with
39472 @var{filename} arguments will operate. This is required for
39473 @value{GDBN} to be able to access files on remote targets where
39474 the remote stub does not share a common filesystem with the
39477 If @var{pid} is nonzero, select the filesystem as seen by process
39478 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
39479 the remote stub. Return 0 on success, or -1 if an error occurs.
39480 If @code{vFile:setfs:} indicates success, the selected filesystem
39481 remains selected until the next successful @code{vFile:setfs:}
39487 @section Interrupts
39488 @cindex interrupts (remote protocol)
39489 @anchor{interrupting remote targets}
39491 In all-stop mode, when a program on the remote target is running,
39492 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
39493 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
39494 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
39496 The precise meaning of @code{BREAK} is defined by the transport
39497 mechanism and may, in fact, be undefined. @value{GDBN} does not
39498 currently define a @code{BREAK} mechanism for any of the network
39499 interfaces except for TCP, in which case @value{GDBN} sends the
39500 @code{telnet} BREAK sequence.
39502 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
39503 transport mechanisms. It is represented by sending the single byte
39504 @code{0x03} without any of the usual packet overhead described in
39505 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
39506 transmitted as part of a packet, it is considered to be packet data
39507 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
39508 (@pxref{X packet}), used for binary downloads, may include an unescaped
39509 @code{0x03} as part of its packet.
39511 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
39512 When Linux kernel receives this sequence from serial port,
39513 it stops execution and connects to gdb.
39515 In non-stop mode, because packet resumptions are asynchronous
39516 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
39517 command to the remote stub, even when the target is running. For that
39518 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
39519 packet}) with the usual packet framing instead of the single byte
39522 Stubs are not required to recognize these interrupt mechanisms and the
39523 precise meaning associated with receipt of the interrupt is
39524 implementation defined. If the target supports debugging of multiple
39525 threads and/or processes, it should attempt to interrupt all
39526 currently-executing threads and processes.
39527 If the stub is successful at interrupting the
39528 running program, it should send one of the stop
39529 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
39530 of successfully stopping the program in all-stop mode, and a stop reply
39531 for each stopped thread in non-stop mode.
39532 Interrupts received while the
39533 program is stopped are queued and the program will be interrupted when
39534 it is resumed next time.
39536 @node Notification Packets
39537 @section Notification Packets
39538 @cindex notification packets
39539 @cindex packets, notification
39541 The @value{GDBN} remote serial protocol includes @dfn{notifications},
39542 packets that require no acknowledgment. Both the GDB and the stub
39543 may send notifications (although the only notifications defined at
39544 present are sent by the stub). Notifications carry information
39545 without incurring the round-trip latency of an acknowledgment, and so
39546 are useful for low-impact communications where occasional packet loss
39549 A notification packet has the form @samp{% @var{data} #
39550 @var{checksum}}, where @var{data} is the content of the notification,
39551 and @var{checksum} is a checksum of @var{data}, computed and formatted
39552 as for ordinary @value{GDBN} packets. A notification's @var{data}
39553 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
39554 receiving a notification, the recipient sends no @samp{+} or @samp{-}
39555 to acknowledge the notification's receipt or to report its corruption.
39557 Every notification's @var{data} begins with a name, which contains no
39558 colon characters, followed by a colon character.
39560 Recipients should silently ignore corrupted notifications and
39561 notifications they do not understand. Recipients should restart
39562 timeout periods on receipt of a well-formed notification, whether or
39563 not they understand it.
39565 Senders should only send the notifications described here when this
39566 protocol description specifies that they are permitted. In the
39567 future, we may extend the protocol to permit existing notifications in
39568 new contexts; this rule helps older senders avoid confusing newer
39571 (Older versions of @value{GDBN} ignore bytes received until they see
39572 the @samp{$} byte that begins an ordinary packet, so new stubs may
39573 transmit notifications without fear of confusing older clients. There
39574 are no notifications defined for @value{GDBN} to send at the moment, but we
39575 assume that most older stubs would ignore them, as well.)
39577 Each notification is comprised of three parts:
39579 @item @var{name}:@var{event}
39580 The notification packet is sent by the side that initiates the
39581 exchange (currently, only the stub does that), with @var{event}
39582 carrying the specific information about the notification, and
39583 @var{name} specifying the name of the notification.
39585 The acknowledge sent by the other side, usually @value{GDBN}, to
39586 acknowledge the exchange and request the event.
39589 The purpose of an asynchronous notification mechanism is to report to
39590 @value{GDBN} that something interesting happened in the remote stub.
39592 The remote stub may send notification @var{name}:@var{event}
39593 at any time, but @value{GDBN} acknowledges the notification when
39594 appropriate. The notification event is pending before @value{GDBN}
39595 acknowledges. Only one notification at a time may be pending; if
39596 additional events occur before @value{GDBN} has acknowledged the
39597 previous notification, they must be queued by the stub for later
39598 synchronous transmission in response to @var{ack} packets from
39599 @value{GDBN}. Because the notification mechanism is unreliable,
39600 the stub is permitted to resend a notification if it believes
39601 @value{GDBN} may not have received it.
39603 Specifically, notifications may appear when @value{GDBN} is not
39604 otherwise reading input from the stub, or when @value{GDBN} is
39605 expecting to read a normal synchronous response or a
39606 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
39607 Notification packets are distinct from any other communication from
39608 the stub so there is no ambiguity.
39610 After receiving a notification, @value{GDBN} shall acknowledge it by
39611 sending a @var{ack} packet as a regular, synchronous request to the
39612 stub. Such acknowledgment is not required to happen immediately, as
39613 @value{GDBN} is permitted to send other, unrelated packets to the
39614 stub first, which the stub should process normally.
39616 Upon receiving a @var{ack} packet, if the stub has other queued
39617 events to report to @value{GDBN}, it shall respond by sending a
39618 normal @var{event}. @value{GDBN} shall then send another @var{ack}
39619 packet to solicit further responses; again, it is permitted to send
39620 other, unrelated packets as well which the stub should process
39623 If the stub receives a @var{ack} packet and there are no additional
39624 @var{event} to report, the stub shall return an @samp{OK} response.
39625 At this point, @value{GDBN} has finished processing a notification
39626 and the stub has completed sending any queued events. @value{GDBN}
39627 won't accept any new notifications until the final @samp{OK} is
39628 received . If further notification events occur, the stub shall send
39629 a new notification, @value{GDBN} shall accept the notification, and
39630 the process shall be repeated.
39632 The process of asynchronous notification can be illustrated by the
39635 <- @code{%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39638 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39640 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39645 The following notifications are defined:
39646 @multitable @columnfractions 0.12 0.12 0.38 0.38
39655 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39656 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39657 for information on how these notifications are acknowledged by
39659 @tab Report an asynchronous stop event in non-stop mode.
39663 @node Remote Non-Stop
39664 @section Remote Protocol Support for Non-Stop Mode
39666 @value{GDBN}'s remote protocol supports non-stop debugging of
39667 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39668 supports non-stop mode, it should report that to @value{GDBN} by including
39669 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39671 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39672 establishing a new connection with the stub. Entering non-stop mode
39673 does not alter the state of any currently-running threads, but targets
39674 must stop all threads in any already-attached processes when entering
39675 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39676 probe the target state after a mode change.
39678 In non-stop mode, when an attached process encounters an event that
39679 would otherwise be reported with a stop reply, it uses the
39680 asynchronous notification mechanism (@pxref{Notification Packets}) to
39681 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39682 in all processes are stopped when a stop reply is sent, in non-stop
39683 mode only the thread reporting the stop event is stopped. That is,
39684 when reporting a @samp{S} or @samp{T} response to indicate completion
39685 of a step operation, hitting a breakpoint, or a fault, only the
39686 affected thread is stopped; any other still-running threads continue
39687 to run. When reporting a @samp{W} or @samp{X} response, all running
39688 threads belonging to other attached processes continue to run.
39690 In non-stop mode, the target shall respond to the @samp{?} packet as
39691 follows. First, any incomplete stop reply notification/@samp{vStopped}
39692 sequence in progress is abandoned. The target must begin a new
39693 sequence reporting stop events for all stopped threads, whether or not
39694 it has previously reported those events to @value{GDBN}. The first
39695 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39696 subsequent stop replies are sent as responses to @samp{vStopped} packets
39697 using the mechanism described above. The target must not send
39698 asynchronous stop reply notifications until the sequence is complete.
39699 If all threads are running when the target receives the @samp{?} packet,
39700 or if the target is not attached to any process, it shall respond
39703 If the stub supports non-stop mode, it should also support the
39704 @samp{swbreak} stop reason if software breakpoints are supported, and
39705 the @samp{hwbreak} stop reason if hardware breakpoints are supported
39706 (@pxref{swbreak stop reason}). This is because given the asynchronous
39707 nature of non-stop mode, between the time a thread hits a breakpoint
39708 and the time the event is finally processed by @value{GDBN}, the
39709 breakpoint may have already been removed from the target. Due to
39710 this, @value{GDBN} needs to be able to tell whether a trap stop was
39711 caused by a delayed breakpoint event, which should be ignored, as
39712 opposed to a random trap signal, which should be reported to the user.
39713 Note the @samp{swbreak} feature implies that the target is responsible
39714 for adjusting the PC when a software breakpoint triggers, if
39715 necessary, such as on the x86 architecture.
39717 @node Packet Acknowledgment
39718 @section Packet Acknowledgment
39720 @cindex acknowledgment, for @value{GDBN} remote
39721 @cindex packet acknowledgment, for @value{GDBN} remote
39722 By default, when either the host or the target machine receives a packet,
39723 the first response expected is an acknowledgment: either @samp{+} (to indicate
39724 the package was received correctly) or @samp{-} (to request retransmission).
39725 This mechanism allows the @value{GDBN} remote protocol to operate over
39726 unreliable transport mechanisms, such as a serial line.
39728 In cases where the transport mechanism is itself reliable (such as a pipe or
39729 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39730 It may be desirable to disable them in that case to reduce communication
39731 overhead, or for other reasons. This can be accomplished by means of the
39732 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39734 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39735 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39736 and response format still includes the normal checksum, as described in
39737 @ref{Overview}, but the checksum may be ignored by the receiver.
39739 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39740 no-acknowledgment mode, it should report that to @value{GDBN}
39741 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39742 @pxref{qSupported}.
39743 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39744 disabled via the @code{set remote noack-packet off} command
39745 (@pxref{Remote Configuration}),
39746 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39747 Only then may the stub actually turn off packet acknowledgments.
39748 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39749 response, which can be safely ignored by the stub.
39751 Note that @code{set remote noack-packet} command only affects negotiation
39752 between @value{GDBN} and the stub when subsequent connections are made;
39753 it does not affect the protocol acknowledgment state for any current
39755 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39756 new connection is established,
39757 there is also no protocol request to re-enable the acknowledgments
39758 for the current connection, once disabled.
39763 Example sequence of a target being re-started. Notice how the restart
39764 does not get any direct output:
39769 @emph{target restarts}
39772 <- @code{T001:1234123412341234}
39776 Example sequence of a target being stepped by a single instruction:
39779 -> @code{G1445@dots{}}
39784 <- @code{T001:1234123412341234}
39788 <- @code{1455@dots{}}
39792 @node File-I/O Remote Protocol Extension
39793 @section File-I/O Remote Protocol Extension
39794 @cindex File-I/O remote protocol extension
39797 * File-I/O Overview::
39798 * Protocol Basics::
39799 * The F Request Packet::
39800 * The F Reply Packet::
39801 * The Ctrl-C Message::
39803 * List of Supported Calls::
39804 * Protocol-specific Representation of Datatypes::
39806 * File-I/O Examples::
39809 @node File-I/O Overview
39810 @subsection File-I/O Overview
39811 @cindex file-i/o overview
39813 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39814 target to use the host's file system and console I/O to perform various
39815 system calls. System calls on the target system are translated into a
39816 remote protocol packet to the host system, which then performs the needed
39817 actions and returns a response packet to the target system.
39818 This simulates file system operations even on targets that lack file systems.
39820 The protocol is defined to be independent of both the host and target systems.
39821 It uses its own internal representation of datatypes and values. Both
39822 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39823 translating the system-dependent value representations into the internal
39824 protocol representations when data is transmitted.
39826 The communication is synchronous. A system call is possible only when
39827 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39828 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39829 the target is stopped to allow deterministic access to the target's
39830 memory. Therefore File-I/O is not interruptible by target signals. On
39831 the other hand, it is possible to interrupt File-I/O by a user interrupt
39832 (@samp{Ctrl-C}) within @value{GDBN}.
39834 The target's request to perform a host system call does not finish
39835 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39836 after finishing the system call, the target returns to continuing the
39837 previous activity (continue, step). No additional continue or step
39838 request from @value{GDBN} is required.
39841 (@value{GDBP}) continue
39842 <- target requests 'system call X'
39843 target is stopped, @value{GDBN} executes system call
39844 -> @value{GDBN} returns result
39845 ... target continues, @value{GDBN} returns to wait for the target
39846 <- target hits breakpoint and sends a Txx packet
39849 The protocol only supports I/O on the console and to regular files on
39850 the host file system. Character or block special devices, pipes,
39851 named pipes, sockets or any other communication method on the host
39852 system are not supported by this protocol.
39854 File I/O is not supported in non-stop mode.
39856 @node Protocol Basics
39857 @subsection Protocol Basics
39858 @cindex protocol basics, file-i/o
39860 The File-I/O protocol uses the @code{F} packet as the request as well
39861 as reply packet. Since a File-I/O system call can only occur when
39862 @value{GDBN} is waiting for a response from the continuing or stepping target,
39863 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39864 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39865 This @code{F} packet contains all information needed to allow @value{GDBN}
39866 to call the appropriate host system call:
39870 A unique identifier for the requested system call.
39873 All parameters to the system call. Pointers are given as addresses
39874 in the target memory address space. Pointers to strings are given as
39875 pointer/length pair. Numerical values are given as they are.
39876 Numerical control flags are given in a protocol-specific representation.
39880 At this point, @value{GDBN} has to perform the following actions.
39884 If the parameters include pointer values to data needed as input to a
39885 system call, @value{GDBN} requests this data from the target with a
39886 standard @code{m} packet request. This additional communication has to be
39887 expected by the target implementation and is handled as any other @code{m}
39891 @value{GDBN} translates all value from protocol representation to host
39892 representation as needed. Datatypes are coerced into the host types.
39895 @value{GDBN} calls the system call.
39898 It then coerces datatypes back to protocol representation.
39901 If the system call is expected to return data in buffer space specified
39902 by pointer parameters to the call, the data is transmitted to the
39903 target using a @code{M} or @code{X} packet. This packet has to be expected
39904 by the target implementation and is handled as any other @code{M} or @code{X}
39909 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39910 necessary information for the target to continue. This at least contains
39917 @code{errno}, if has been changed by the system call.
39924 After having done the needed type and value coercion, the target continues
39925 the latest continue or step action.
39927 @node The F Request Packet
39928 @subsection The @code{F} Request Packet
39929 @cindex file-i/o request packet
39930 @cindex @code{F} request packet
39932 The @code{F} request packet has the following format:
39935 @item F@var{call-id},@var{parameter@dots{}}
39937 @var{call-id} is the identifier to indicate the host system call to be called.
39938 This is just the name of the function.
39940 @var{parameter@dots{}} are the parameters to the system call.
39941 Parameters are hexadecimal integer values, either the actual values in case
39942 of scalar datatypes, pointers to target buffer space in case of compound
39943 datatypes and unspecified memory areas, or pointer/length pairs in case
39944 of string parameters. These are appended to the @var{call-id} as a
39945 comma-delimited list. All values are transmitted in ASCII
39946 string representation, pointer/length pairs separated by a slash.
39952 @node The F Reply Packet
39953 @subsection The @code{F} Reply Packet
39954 @cindex file-i/o reply packet
39955 @cindex @code{F} reply packet
39957 The @code{F} reply packet has the following format:
39961 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39963 @var{retcode} is the return code of the system call as hexadecimal value.
39965 @var{errno} is the @code{errno} set by the call, in protocol-specific
39967 This parameter can be omitted if the call was successful.
39969 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39970 case, @var{errno} must be sent as well, even if the call was successful.
39971 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39978 or, if the call was interrupted before the host call has been performed:
39985 assuming 4 is the protocol-specific representation of @code{EINTR}.
39990 @node The Ctrl-C Message
39991 @subsection The @samp{Ctrl-C} Message
39992 @cindex ctrl-c message, in file-i/o protocol
39994 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39995 reply packet (@pxref{The F Reply Packet}),
39996 the target should behave as if it had
39997 gotten a break message. The meaning for the target is ``system call
39998 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39999 (as with a break message) and return to @value{GDBN} with a @code{T02}
40002 It's important for the target to know in which
40003 state the system call was interrupted. There are two possible cases:
40007 The system call hasn't been performed on the host yet.
40010 The system call on the host has been finished.
40014 These two states can be distinguished by the target by the value of the
40015 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40016 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40017 on POSIX systems. In any other case, the target may presume that the
40018 system call has been finished --- successfully or not --- and should behave
40019 as if the break message arrived right after the system call.
40021 @value{GDBN} must behave reliably. If the system call has not been called
40022 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40023 @code{errno} in the packet. If the system call on the host has been finished
40024 before the user requests a break, the full action must be finished by
40025 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40026 The @code{F} packet may only be sent when either nothing has happened
40027 or the full action has been completed.
40030 @subsection Console I/O
40031 @cindex console i/o as part of file-i/o
40033 By default and if not explicitly closed by the target system, the file
40034 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40035 on the @value{GDBN} console is handled as any other file output operation
40036 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40037 by @value{GDBN} so that after the target read request from file descriptor
40038 0 all following typing is buffered until either one of the following
40043 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40045 system call is treated as finished.
40048 The user presses @key{RET}. This is treated as end of input with a trailing
40052 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40053 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40057 If the user has typed more characters than fit in the buffer given to
40058 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40059 either another @code{read(0, @dots{})} is requested by the target, or debugging
40060 is stopped at the user's request.
40063 @node List of Supported Calls
40064 @subsection List of Supported Calls
40065 @cindex list of supported file-i/o calls
40082 @unnumberedsubsubsec open
40083 @cindex open, file-i/o system call
40088 int open(const char *pathname, int flags);
40089 int open(const char *pathname, int flags, mode_t mode);
40093 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40096 @var{flags} is the bitwise @code{OR} of the following values:
40100 If the file does not exist it will be created. The host
40101 rules apply as far as file ownership and time stamps
40105 When used with @code{O_CREAT}, if the file already exists it is
40106 an error and open() fails.
40109 If the file already exists and the open mode allows
40110 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40111 truncated to zero length.
40114 The file is opened in append mode.
40117 The file is opened for reading only.
40120 The file is opened for writing only.
40123 The file is opened for reading and writing.
40127 Other bits are silently ignored.
40131 @var{mode} is the bitwise @code{OR} of the following values:
40135 User has read permission.
40138 User has write permission.
40141 Group has read permission.
40144 Group has write permission.
40147 Others have read permission.
40150 Others have write permission.
40154 Other bits are silently ignored.
40157 @item Return value:
40158 @code{open} returns the new file descriptor or -1 if an error
40165 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40168 @var{pathname} refers to a directory.
40171 The requested access is not allowed.
40174 @var{pathname} was too long.
40177 A directory component in @var{pathname} does not exist.
40180 @var{pathname} refers to a device, pipe, named pipe or socket.
40183 @var{pathname} refers to a file on a read-only filesystem and
40184 write access was requested.
40187 @var{pathname} is an invalid pointer value.
40190 No space on device to create the file.
40193 The process already has the maximum number of files open.
40196 The limit on the total number of files open on the system
40200 The call was interrupted by the user.
40206 @unnumberedsubsubsec close
40207 @cindex close, file-i/o system call
40216 @samp{Fclose,@var{fd}}
40218 @item Return value:
40219 @code{close} returns zero on success, or -1 if an error occurred.
40225 @var{fd} isn't a valid open file descriptor.
40228 The call was interrupted by the user.
40234 @unnumberedsubsubsec read
40235 @cindex read, file-i/o system call
40240 int read(int fd, void *buf, unsigned int count);
40244 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40246 @item Return value:
40247 On success, the number of bytes read is returned.
40248 Zero indicates end of file. If count is zero, read
40249 returns zero as well. On error, -1 is returned.
40255 @var{fd} is not a valid file descriptor or is not open for
40259 @var{bufptr} is an invalid pointer value.
40262 The call was interrupted by the user.
40268 @unnumberedsubsubsec write
40269 @cindex write, file-i/o system call
40274 int write(int fd, const void *buf, unsigned int count);
40278 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40280 @item Return value:
40281 On success, the number of bytes written are returned.
40282 Zero indicates nothing was written. On error, -1
40289 @var{fd} is not a valid file descriptor or is not open for
40293 @var{bufptr} is an invalid pointer value.
40296 An attempt was made to write a file that exceeds the
40297 host-specific maximum file size allowed.
40300 No space on device to write the data.
40303 The call was interrupted by the user.
40309 @unnumberedsubsubsec lseek
40310 @cindex lseek, file-i/o system call
40315 long lseek (int fd, long offset, int flag);
40319 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40321 @var{flag} is one of:
40325 The offset is set to @var{offset} bytes.
40328 The offset is set to its current location plus @var{offset}
40332 The offset is set to the size of the file plus @var{offset}
40336 @item Return value:
40337 On success, the resulting unsigned offset in bytes from
40338 the beginning of the file is returned. Otherwise, a
40339 value of -1 is returned.
40345 @var{fd} is not a valid open file descriptor.
40348 @var{fd} is associated with the @value{GDBN} console.
40351 @var{flag} is not a proper value.
40354 The call was interrupted by the user.
40360 @unnumberedsubsubsec rename
40361 @cindex rename, file-i/o system call
40366 int rename(const char *oldpath, const char *newpath);
40370 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
40372 @item Return value:
40373 On success, zero is returned. On error, -1 is returned.
40379 @var{newpath} is an existing directory, but @var{oldpath} is not a
40383 @var{newpath} is a non-empty directory.
40386 @var{oldpath} or @var{newpath} is a directory that is in use by some
40390 An attempt was made to make a directory a subdirectory
40394 A component used as a directory in @var{oldpath} or new
40395 path is not a directory. Or @var{oldpath} is a directory
40396 and @var{newpath} exists but is not a directory.
40399 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
40402 No access to the file or the path of the file.
40406 @var{oldpath} or @var{newpath} was too long.
40409 A directory component in @var{oldpath} or @var{newpath} does not exist.
40412 The file is on a read-only filesystem.
40415 The device containing the file has no room for the new
40419 The call was interrupted by the user.
40425 @unnumberedsubsubsec unlink
40426 @cindex unlink, file-i/o system call
40431 int unlink(const char *pathname);
40435 @samp{Funlink,@var{pathnameptr}/@var{len}}
40437 @item Return value:
40438 On success, zero is returned. On error, -1 is returned.
40444 No access to the file or the path of the file.
40447 The system does not allow unlinking of directories.
40450 The file @var{pathname} cannot be unlinked because it's
40451 being used by another process.
40454 @var{pathnameptr} is an invalid pointer value.
40457 @var{pathname} was too long.
40460 A directory component in @var{pathname} does not exist.
40463 A component of the path is not a directory.
40466 The file is on a read-only filesystem.
40469 The call was interrupted by the user.
40475 @unnumberedsubsubsec stat/fstat
40476 @cindex fstat, file-i/o system call
40477 @cindex stat, file-i/o system call
40482 int stat(const char *pathname, struct stat *buf);
40483 int fstat(int fd, struct stat *buf);
40487 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
40488 @samp{Ffstat,@var{fd},@var{bufptr}}
40490 @item Return value:
40491 On success, zero is returned. On error, -1 is returned.
40497 @var{fd} is not a valid open file.
40500 A directory component in @var{pathname} does not exist or the
40501 path is an empty string.
40504 A component of the path is not a directory.
40507 @var{pathnameptr} is an invalid pointer value.
40510 No access to the file or the path of the file.
40513 @var{pathname} was too long.
40516 The call was interrupted by the user.
40522 @unnumberedsubsubsec gettimeofday
40523 @cindex gettimeofday, file-i/o system call
40528 int gettimeofday(struct timeval *tv, void *tz);
40532 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
40534 @item Return value:
40535 On success, 0 is returned, -1 otherwise.
40541 @var{tz} is a non-NULL pointer.
40544 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
40550 @unnumberedsubsubsec isatty
40551 @cindex isatty, file-i/o system call
40556 int isatty(int fd);
40560 @samp{Fisatty,@var{fd}}
40562 @item Return value:
40563 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
40569 The call was interrupted by the user.
40574 Note that the @code{isatty} call is treated as a special case: it returns
40575 1 to the target if the file descriptor is attached
40576 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
40577 would require implementing @code{ioctl} and would be more complex than
40582 @unnumberedsubsubsec system
40583 @cindex system, file-i/o system call
40588 int system(const char *command);
40592 @samp{Fsystem,@var{commandptr}/@var{len}}
40594 @item Return value:
40595 If @var{len} is zero, the return value indicates whether a shell is
40596 available. A zero return value indicates a shell is not available.
40597 For non-zero @var{len}, the value returned is -1 on error and the
40598 return status of the command otherwise. Only the exit status of the
40599 command is returned, which is extracted from the host's @code{system}
40600 return value by calling @code{WEXITSTATUS(retval)}. In case
40601 @file{/bin/sh} could not be executed, 127 is returned.
40607 The call was interrupted by the user.
40612 @value{GDBN} takes over the full task of calling the necessary host calls
40613 to perform the @code{system} call. The return value of @code{system} on
40614 the host is simplified before it's returned
40615 to the target. Any termination signal information from the child process
40616 is discarded, and the return value consists
40617 entirely of the exit status of the called command.
40619 Due to security concerns, the @code{system} call is by default refused
40620 by @value{GDBN}. The user has to allow this call explicitly with the
40621 @code{set remote system-call-allowed 1} command.
40624 @item set remote system-call-allowed
40625 @kindex set remote system-call-allowed
40626 Control whether to allow the @code{system} calls in the File I/O
40627 protocol for the remote target. The default is zero (disabled).
40629 @item show remote system-call-allowed
40630 @kindex show remote system-call-allowed
40631 Show whether the @code{system} calls are allowed in the File I/O
40635 @node Protocol-specific Representation of Datatypes
40636 @subsection Protocol-specific Representation of Datatypes
40637 @cindex protocol-specific representation of datatypes, in file-i/o protocol
40640 * Integral Datatypes::
40642 * Memory Transfer::
40647 @node Integral Datatypes
40648 @unnumberedsubsubsec Integral Datatypes
40649 @cindex integral datatypes, in file-i/o protocol
40651 The integral datatypes used in the system calls are @code{int},
40652 @code{unsigned int}, @code{long}, @code{unsigned long},
40653 @code{mode_t}, and @code{time_t}.
40655 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40656 implemented as 32 bit values in this protocol.
40658 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40660 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40661 in @file{limits.h}) to allow range checking on host and target.
40663 @code{time_t} datatypes are defined as seconds since the Epoch.
40665 All integral datatypes transferred as part of a memory read or write of a
40666 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40669 @node Pointer Values
40670 @unnumberedsubsubsec Pointer Values
40671 @cindex pointer values, in file-i/o protocol
40673 Pointers to target data are transmitted as they are. An exception
40674 is made for pointers to buffers for which the length isn't
40675 transmitted as part of the function call, namely strings. Strings
40676 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40683 which is a pointer to data of length 18 bytes at position 0x1aaf.
40684 The length is defined as the full string length in bytes, including
40685 the trailing null byte. For example, the string @code{"hello world"}
40686 at address 0x123456 is transmitted as
40692 @node Memory Transfer
40693 @unnumberedsubsubsec Memory Transfer
40694 @cindex memory transfer, in file-i/o protocol
40696 Structured data which is transferred using a memory read or write (for
40697 example, a @code{struct stat}) is expected to be in a protocol-specific format
40698 with all scalar multibyte datatypes being big endian. Translation to
40699 this representation needs to be done both by the target before the @code{F}
40700 packet is sent, and by @value{GDBN} before
40701 it transfers memory to the target. Transferred pointers to structured
40702 data should point to the already-coerced data at any time.
40706 @unnumberedsubsubsec struct stat
40707 @cindex struct stat, in file-i/o protocol
40709 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40710 is defined as follows:
40714 unsigned int st_dev; /* device */
40715 unsigned int st_ino; /* inode */
40716 mode_t st_mode; /* protection */
40717 unsigned int st_nlink; /* number of hard links */
40718 unsigned int st_uid; /* user ID of owner */
40719 unsigned int st_gid; /* group ID of owner */
40720 unsigned int st_rdev; /* device type (if inode device) */
40721 unsigned long st_size; /* total size, in bytes */
40722 unsigned long st_blksize; /* blocksize for filesystem I/O */
40723 unsigned long st_blocks; /* number of blocks allocated */
40724 time_t st_atime; /* time of last access */
40725 time_t st_mtime; /* time of last modification */
40726 time_t st_ctime; /* time of last change */
40730 The integral datatypes conform to the definitions given in the
40731 appropriate section (see @ref{Integral Datatypes}, for details) so this
40732 structure is of size 64 bytes.
40734 The values of several fields have a restricted meaning and/or
40740 A value of 0 represents a file, 1 the console.
40743 No valid meaning for the target. Transmitted unchanged.
40746 Valid mode bits are described in @ref{Constants}. Any other
40747 bits have currently no meaning for the target.
40752 No valid meaning for the target. Transmitted unchanged.
40757 These values have a host and file system dependent
40758 accuracy. Especially on Windows hosts, the file system may not
40759 support exact timing values.
40762 The target gets a @code{struct stat} of the above representation and is
40763 responsible for coercing it to the target representation before
40766 Note that due to size differences between the host, target, and protocol
40767 representations of @code{struct stat} members, these members could eventually
40768 get truncated on the target.
40770 @node struct timeval
40771 @unnumberedsubsubsec struct timeval
40772 @cindex struct timeval, in file-i/o protocol
40774 The buffer of type @code{struct timeval} used by the File-I/O protocol
40775 is defined as follows:
40779 time_t tv_sec; /* second */
40780 long tv_usec; /* microsecond */
40784 The integral datatypes conform to the definitions given in the
40785 appropriate section (see @ref{Integral Datatypes}, for details) so this
40786 structure is of size 8 bytes.
40789 @subsection Constants
40790 @cindex constants, in file-i/o protocol
40792 The following values are used for the constants inside of the
40793 protocol. @value{GDBN} and target are responsible for translating these
40794 values before and after the call as needed.
40805 @unnumberedsubsubsec Open Flags
40806 @cindex open flags, in file-i/o protocol
40808 All values are given in hexadecimal representation.
40820 @node mode_t Values
40821 @unnumberedsubsubsec mode_t Values
40822 @cindex mode_t values, in file-i/o protocol
40824 All values are given in octal representation.
40841 @unnumberedsubsubsec Errno Values
40842 @cindex errno values, in file-i/o protocol
40844 All values are given in decimal representation.
40869 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40870 any error value not in the list of supported error numbers.
40873 @unnumberedsubsubsec Lseek Flags
40874 @cindex lseek flags, in file-i/o protocol
40883 @unnumberedsubsubsec Limits
40884 @cindex limits, in file-i/o protocol
40886 All values are given in decimal representation.
40889 INT_MIN -2147483648
40891 UINT_MAX 4294967295
40892 LONG_MIN -9223372036854775808
40893 LONG_MAX 9223372036854775807
40894 ULONG_MAX 18446744073709551615
40897 @node File-I/O Examples
40898 @subsection File-I/O Examples
40899 @cindex file-i/o examples
40901 Example sequence of a write call, file descriptor 3, buffer is at target
40902 address 0x1234, 6 bytes should be written:
40905 <- @code{Fwrite,3,1234,6}
40906 @emph{request memory read from target}
40909 @emph{return "6 bytes written"}
40913 Example sequence of a read call, file descriptor 3, buffer is at target
40914 address 0x1234, 6 bytes should be read:
40917 <- @code{Fread,3,1234,6}
40918 @emph{request memory write to target}
40919 -> @code{X1234,6:XXXXXX}
40920 @emph{return "6 bytes read"}
40924 Example sequence of a read call, call fails on the host due to invalid
40925 file descriptor (@code{EBADF}):
40928 <- @code{Fread,3,1234,6}
40932 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40936 <- @code{Fread,3,1234,6}
40941 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40945 <- @code{Fread,3,1234,6}
40946 -> @code{X1234,6:XXXXXX}
40950 @node Library List Format
40951 @section Library List Format
40952 @cindex library list format, remote protocol
40954 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40955 same process as your application to manage libraries. In this case,
40956 @value{GDBN} can use the loader's symbol table and normal memory
40957 operations to maintain a list of shared libraries. On other
40958 platforms, the operating system manages loaded libraries.
40959 @value{GDBN} can not retrieve the list of currently loaded libraries
40960 through memory operations, so it uses the @samp{qXfer:libraries:read}
40961 packet (@pxref{qXfer library list read}) instead. The remote stub
40962 queries the target's operating system and reports which libraries
40965 The @samp{qXfer:libraries:read} packet returns an XML document which
40966 lists loaded libraries and their offsets. Each library has an
40967 associated name and one or more segment or section base addresses,
40968 which report where the library was loaded in memory.
40970 For the common case of libraries that are fully linked binaries, the
40971 library should have a list of segments. If the target supports
40972 dynamic linking of a relocatable object file, its library XML element
40973 should instead include a list of allocated sections. The segment or
40974 section bases are start addresses, not relocation offsets; they do not
40975 depend on the library's link-time base addresses.
40977 @value{GDBN} must be linked with the Expat library to support XML
40978 library lists. @xref{Expat}.
40980 A simple memory map, with one loaded library relocated by a single
40981 offset, looks like this:
40985 <library name="/lib/libc.so.6">
40986 <segment address="0x10000000"/>
40991 Another simple memory map, with one loaded library with three
40992 allocated sections (.text, .data, .bss), looks like this:
40996 <library name="sharedlib.o">
40997 <section address="0x10000000"/>
40998 <section address="0x20000000"/>
40999 <section address="0x30000000"/>
41004 The format of a library list is described by this DTD:
41007 <!-- library-list: Root element with versioning -->
41008 <!ELEMENT library-list (library)*>
41009 <!ATTLIST library-list version CDATA #FIXED "1.0">
41010 <!ELEMENT library (segment*, section*)>
41011 <!ATTLIST library name CDATA #REQUIRED>
41012 <!ELEMENT segment EMPTY>
41013 <!ATTLIST segment address CDATA #REQUIRED>
41014 <!ELEMENT section EMPTY>
41015 <!ATTLIST section address CDATA #REQUIRED>
41018 In addition, segments and section descriptors cannot be mixed within a
41019 single library element, and you must supply at least one segment or
41020 section for each library.
41022 @node Library List Format for SVR4 Targets
41023 @section Library List Format for SVR4 Targets
41024 @cindex library list format, remote protocol
41026 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41027 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41028 shared libraries. Still a special library list provided by this packet is
41029 more efficient for the @value{GDBN} remote protocol.
41031 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41032 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41033 target, the following parameters are reported:
41037 @code{name}, the absolute file name from the @code{l_name} field of
41038 @code{struct link_map}.
41040 @code{lm} with address of @code{struct link_map} used for TLS
41041 (Thread Local Storage) access.
41043 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41044 @code{struct link_map}. For prelinked libraries this is not an absolute
41045 memory address. It is a displacement of absolute memory address against
41046 address the file was prelinked to during the library load.
41048 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41051 Additionally the single @code{main-lm} attribute specifies address of
41052 @code{struct link_map} used for the main executable. This parameter is used
41053 for TLS access and its presence is optional.
41055 @value{GDBN} must be linked with the Expat library to support XML
41056 SVR4 library lists. @xref{Expat}.
41058 A simple memory map, with two loaded libraries (which do not use prelink),
41062 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41063 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41065 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41067 </library-list-svr>
41070 The format of an SVR4 library list is described by this DTD:
41073 <!-- library-list-svr4: Root element with versioning -->
41074 <!ELEMENT library-list-svr4 (library)*>
41075 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41076 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41077 <!ELEMENT library EMPTY>
41078 <!ATTLIST library name CDATA #REQUIRED>
41079 <!ATTLIST library lm CDATA #REQUIRED>
41080 <!ATTLIST library l_addr CDATA #REQUIRED>
41081 <!ATTLIST library l_ld CDATA #REQUIRED>
41084 @node Memory Map Format
41085 @section Memory Map Format
41086 @cindex memory map format
41088 To be able to write into flash memory, @value{GDBN} needs to obtain a
41089 memory map from the target. This section describes the format of the
41092 The memory map is obtained using the @samp{qXfer:memory-map:read}
41093 (@pxref{qXfer memory map read}) packet and is an XML document that
41094 lists memory regions.
41096 @value{GDBN} must be linked with the Expat library to support XML
41097 memory maps. @xref{Expat}.
41099 The top-level structure of the document is shown below:
41102 <?xml version="1.0"?>
41103 <!DOCTYPE memory-map
41104 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41105 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41111 Each region can be either:
41116 A region of RAM starting at @var{addr} and extending for @var{length}
41120 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41125 A region of read-only memory:
41128 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41133 A region of flash memory, with erasure blocks @var{blocksize}
41137 <memory type="flash" start="@var{addr}" length="@var{length}">
41138 <property name="blocksize">@var{blocksize}</property>
41144 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41145 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41146 packets to write to addresses in such ranges.
41148 The formal DTD for memory map format is given below:
41151 <!-- ................................................... -->
41152 <!-- Memory Map XML DTD ................................ -->
41153 <!-- File: memory-map.dtd .............................. -->
41154 <!-- .................................... .............. -->
41155 <!-- memory-map.dtd -->
41156 <!-- memory-map: Root element with versioning -->
41157 <!ELEMENT memory-map (memory)*>
41158 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41159 <!ELEMENT memory (property)*>
41160 <!-- memory: Specifies a memory region,
41161 and its type, or device. -->
41162 <!ATTLIST memory type (ram|rom|flash) #REQUIRED
41163 start CDATA #REQUIRED
41164 length CDATA #REQUIRED>
41165 <!-- property: Generic attribute tag -->
41166 <!ELEMENT property (#PCDATA | property)*>
41167 <!ATTLIST property name (blocksize) #REQUIRED>
41170 @node Thread List Format
41171 @section Thread List Format
41172 @cindex thread list format
41174 To efficiently update the list of threads and their attributes,
41175 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41176 (@pxref{qXfer threads read}) and obtains the XML document with
41177 the following structure:
41180 <?xml version="1.0"?>
41182 <thread id="id" core="0" name="name">
41183 ... description ...
41188 Each @samp{thread} element must have the @samp{id} attribute that
41189 identifies the thread (@pxref{thread-id syntax}). The
41190 @samp{core} attribute, if present, specifies which processor core
41191 the thread was last executing on. The @samp{name} attribute, if
41192 present, specifies the human-readable name of the thread. The content
41193 of the of @samp{thread} element is interpreted as human-readable
41194 auxiliary information. The @samp{handle} attribute, if present,
41195 is a hex encoded representation of the thread handle.
41198 @node Traceframe Info Format
41199 @section Traceframe Info Format
41200 @cindex traceframe info format
41202 To be able to know which objects in the inferior can be examined when
41203 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41204 memory ranges, registers and trace state variables that have been
41205 collected in a traceframe.
41207 This list is obtained using the @samp{qXfer:traceframe-info:read}
41208 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41210 @value{GDBN} must be linked with the Expat library to support XML
41211 traceframe info discovery. @xref{Expat}.
41213 The top-level structure of the document is shown below:
41216 <?xml version="1.0"?>
41217 <!DOCTYPE traceframe-info
41218 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41219 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41225 Each traceframe block can be either:
41230 A region of collected memory starting at @var{addr} and extending for
41231 @var{length} bytes from there:
41234 <memory start="@var{addr}" length="@var{length}"/>
41238 A block indicating trace state variable numbered @var{number} has been
41242 <tvar id="@var{number}"/>
41247 The formal DTD for the traceframe info format is given below:
41250 <!ELEMENT traceframe-info (memory | tvar)* >
41251 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41253 <!ELEMENT memory EMPTY>
41254 <!ATTLIST memory start CDATA #REQUIRED
41255 length CDATA #REQUIRED>
41257 <!ATTLIST tvar id CDATA #REQUIRED>
41260 @node Branch Trace Format
41261 @section Branch Trace Format
41262 @cindex branch trace format
41264 In order to display the branch trace of an inferior thread,
41265 @value{GDBN} needs to obtain the list of branches. This list is
41266 represented as list of sequential code blocks that are connected via
41267 branches. The code in each block has been executed sequentially.
41269 This list is obtained using the @samp{qXfer:btrace:read}
41270 (@pxref{qXfer btrace read}) packet and is an XML document.
41272 @value{GDBN} must be linked with the Expat library to support XML
41273 traceframe info discovery. @xref{Expat}.
41275 The top-level structure of the document is shown below:
41278 <?xml version="1.0"?>
41280 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41281 "http://sourceware.org/gdb/gdb-btrace.dtd">
41290 A block of sequentially executed instructions starting at @var{begin}
41291 and ending at @var{end}:
41294 <block begin="@var{begin}" end="@var{end}"/>
41299 The formal DTD for the branch trace format is given below:
41302 <!ELEMENT btrace (block* | pt) >
41303 <!ATTLIST btrace version CDATA #FIXED "1.0">
41305 <!ELEMENT block EMPTY>
41306 <!ATTLIST block begin CDATA #REQUIRED
41307 end CDATA #REQUIRED>
41309 <!ELEMENT pt (pt-config?, raw?)>
41311 <!ELEMENT pt-config (cpu?)>
41313 <!ELEMENT cpu EMPTY>
41314 <!ATTLIST cpu vendor CDATA #REQUIRED
41315 family CDATA #REQUIRED
41316 model CDATA #REQUIRED
41317 stepping CDATA #REQUIRED>
41319 <!ELEMENT raw (#PCDATA)>
41322 @node Branch Trace Configuration Format
41323 @section Branch Trace Configuration Format
41324 @cindex branch trace configuration format
41326 For each inferior thread, @value{GDBN} can obtain the branch trace
41327 configuration using the @samp{qXfer:btrace-conf:read}
41328 (@pxref{qXfer btrace-conf read}) packet.
41330 The configuration describes the branch trace format and configuration
41331 settings for that format. The following information is described:
41335 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
41338 The size of the @acronym{BTS} ring buffer in bytes.
41341 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
41345 The size of the @acronym{Intel PT} ring buffer in bytes.
41349 @value{GDBN} must be linked with the Expat library to support XML
41350 branch trace configuration discovery. @xref{Expat}.
41352 The formal DTD for the branch trace configuration format is given below:
41355 <!ELEMENT btrace-conf (bts?, pt?)>
41356 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
41358 <!ELEMENT bts EMPTY>
41359 <!ATTLIST bts size CDATA #IMPLIED>
41361 <!ELEMENT pt EMPTY>
41362 <!ATTLIST pt size CDATA #IMPLIED>
41365 @include agentexpr.texi
41367 @node Target Descriptions
41368 @appendix Target Descriptions
41369 @cindex target descriptions
41371 One of the challenges of using @value{GDBN} to debug embedded systems
41372 is that there are so many minor variants of each processor
41373 architecture in use. It is common practice for vendors to start with
41374 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41375 and then make changes to adapt it to a particular market niche. Some
41376 architectures have hundreds of variants, available from dozens of
41377 vendors. This leads to a number of problems:
41381 With so many different customized processors, it is difficult for
41382 the @value{GDBN} maintainers to keep up with the changes.
41384 Since individual variants may have short lifetimes or limited
41385 audiences, it may not be worthwhile to carry information about every
41386 variant in the @value{GDBN} source tree.
41388 When @value{GDBN} does support the architecture of the embedded system
41389 at hand, the task of finding the correct architecture name to give the
41390 @command{set architecture} command can be error-prone.
41393 To address these problems, the @value{GDBN} remote protocol allows a
41394 target system to not only identify itself to @value{GDBN}, but to
41395 actually describe its own features. This lets @value{GDBN} support
41396 processor variants it has never seen before --- to the extent that the
41397 descriptions are accurate, and that @value{GDBN} understands them.
41399 @value{GDBN} must be linked with the Expat library to support XML
41400 target descriptions. @xref{Expat}.
41403 * Retrieving Descriptions:: How descriptions are fetched from a target.
41404 * Target Description Format:: The contents of a target description.
41405 * Predefined Target Types:: Standard types available for target
41407 * Enum Target Types:: How to define enum target types.
41408 * Standard Target Features:: Features @value{GDBN} knows about.
41411 @node Retrieving Descriptions
41412 @section Retrieving Descriptions
41414 Target descriptions can be read from the target automatically, or
41415 specified by the user manually. The default behavior is to read the
41416 description from the target. @value{GDBN} retrieves it via the remote
41417 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
41418 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
41419 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
41420 XML document, of the form described in @ref{Target Description
41423 Alternatively, you can specify a file to read for the target description.
41424 If a file is set, the target will not be queried. The commands to
41425 specify a file are:
41428 @cindex set tdesc filename
41429 @item set tdesc filename @var{path}
41430 Read the target description from @var{path}.
41432 @cindex unset tdesc filename
41433 @item unset tdesc filename
41434 Do not read the XML target description from a file. @value{GDBN}
41435 will use the description supplied by the current target.
41437 @cindex show tdesc filename
41438 @item show tdesc filename
41439 Show the filename to read for a target description, if any.
41443 @node Target Description Format
41444 @section Target Description Format
41445 @cindex target descriptions, XML format
41447 A target description annex is an @uref{http://www.w3.org/XML/, XML}
41448 document which complies with the Document Type Definition provided in
41449 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
41450 means you can use generally available tools like @command{xmllint} to
41451 check that your feature descriptions are well-formed and valid.
41452 However, to help people unfamiliar with XML write descriptions for
41453 their targets, we also describe the grammar here.
41455 Target descriptions can identify the architecture of the remote target
41456 and (for some architectures) provide information about custom register
41457 sets. They can also identify the OS ABI of the remote target.
41458 @value{GDBN} can use this information to autoconfigure for your
41459 target, or to warn you if you connect to an unsupported target.
41461 Here is a simple target description:
41464 <target version="1.0">
41465 <architecture>i386:x86-64</architecture>
41470 This minimal description only says that the target uses
41471 the x86-64 architecture.
41473 A target description has the following overall form, with [ ] marking
41474 optional elements and @dots{} marking repeatable elements. The elements
41475 are explained further below.
41478 <?xml version="1.0"?>
41479 <!DOCTYPE target SYSTEM "gdb-target.dtd">
41480 <target version="1.0">
41481 @r{[}@var{architecture}@r{]}
41482 @r{[}@var{osabi}@r{]}
41483 @r{[}@var{compatible}@r{]}
41484 @r{[}@var{feature}@dots{}@r{]}
41489 The description is generally insensitive to whitespace and line
41490 breaks, under the usual common-sense rules. The XML version
41491 declaration and document type declaration can generally be omitted
41492 (@value{GDBN} does not require them), but specifying them may be
41493 useful for XML validation tools. The @samp{version} attribute for
41494 @samp{<target>} may also be omitted, but we recommend
41495 including it; if future versions of @value{GDBN} use an incompatible
41496 revision of @file{gdb-target.dtd}, they will detect and report
41497 the version mismatch.
41499 @subsection Inclusion
41500 @cindex target descriptions, inclusion
41503 @cindex <xi:include>
41506 It can sometimes be valuable to split a target description up into
41507 several different annexes, either for organizational purposes, or to
41508 share files between different possible target descriptions. You can
41509 divide a description into multiple files by replacing any element of
41510 the target description with an inclusion directive of the form:
41513 <xi:include href="@var{document}"/>
41517 When @value{GDBN} encounters an element of this form, it will retrieve
41518 the named XML @var{document}, and replace the inclusion directive with
41519 the contents of that document. If the current description was read
41520 using @samp{qXfer}, then so will be the included document;
41521 @var{document} will be interpreted as the name of an annex. If the
41522 current description was read from a file, @value{GDBN} will look for
41523 @var{document} as a file in the same directory where it found the
41524 original description.
41526 @subsection Architecture
41527 @cindex <architecture>
41529 An @samp{<architecture>} element has this form:
41532 <architecture>@var{arch}</architecture>
41535 @var{arch} is one of the architectures from the set accepted by
41536 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41539 @cindex @code{<osabi>}
41541 This optional field was introduced in @value{GDBN} version 7.0.
41542 Previous versions of @value{GDBN} ignore it.
41544 An @samp{<osabi>} element has this form:
41547 <osabi>@var{abi-name}</osabi>
41550 @var{abi-name} is an OS ABI name from the same selection accepted by
41551 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
41553 @subsection Compatible Architecture
41554 @cindex @code{<compatible>}
41556 This optional field was introduced in @value{GDBN} version 7.0.
41557 Previous versions of @value{GDBN} ignore it.
41559 A @samp{<compatible>} element has this form:
41562 <compatible>@var{arch}</compatible>
41565 @var{arch} is one of the architectures from the set accepted by
41566 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
41568 A @samp{<compatible>} element is used to specify that the target
41569 is able to run binaries in some other than the main target architecture
41570 given by the @samp{<architecture>} element. For example, on the
41571 Cell Broadband Engine, the main architecture is @code{powerpc:common}
41572 or @code{powerpc:common64}, but the system is able to run binaries
41573 in the @code{spu} architecture as well. The way to describe this
41574 capability with @samp{<compatible>} is as follows:
41577 <architecture>powerpc:common</architecture>
41578 <compatible>spu</compatible>
41581 @subsection Features
41584 Each @samp{<feature>} describes some logical portion of the target
41585 system. Features are currently used to describe available CPU
41586 registers and the types of their contents. A @samp{<feature>} element
41590 <feature name="@var{name}">
41591 @r{[}@var{type}@dots{}@r{]}
41597 Each feature's name should be unique within the description. The name
41598 of a feature does not matter unless @value{GDBN} has some special
41599 knowledge of the contents of that feature; if it does, the feature
41600 should have its standard name. @xref{Standard Target Features}.
41604 Any register's value is a collection of bits which @value{GDBN} must
41605 interpret. The default interpretation is a two's complement integer,
41606 but other types can be requested by name in the register description.
41607 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
41608 Target Types}), and the description can define additional composite
41611 Each type element must have an @samp{id} attribute, which gives
41612 a unique (within the containing @samp{<feature>}) name to the type.
41613 Types must be defined before they are used.
41616 Some targets offer vector registers, which can be treated as arrays
41617 of scalar elements. These types are written as @samp{<vector>} elements,
41618 specifying the array element type, @var{type}, and the number of elements,
41622 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
41626 If a register's value is usefully viewed in multiple ways, define it
41627 with a union type containing the useful representations. The
41628 @samp{<union>} element contains one or more @samp{<field>} elements,
41629 each of which has a @var{name} and a @var{type}:
41632 <union id="@var{id}">
41633 <field name="@var{name}" type="@var{type}"/>
41640 If a register's value is composed from several separate values, define
41641 it with either a structure type or a flags type.
41642 A flags type may only contain bitfields.
41643 A structure type may either contain only bitfields or contain no bitfields.
41644 If the value contains only bitfields, its total size in bytes must be
41647 Non-bitfield values have a @var{name} and @var{type}.
41650 <struct id="@var{id}">
41651 <field name="@var{name}" type="@var{type}"/>
41656 Both @var{name} and @var{type} values are required.
41657 No implicit padding is added.
41659 Bitfield values have a @var{name}, @var{start}, @var{end} and @var{type}.
41662 <struct id="@var{id}" size="@var{size}">
41663 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41669 <flags id="@var{id}" size="@var{size}">
41670 <field name="@var{name}" start="@var{start}" end="@var{end}" type="@var{type}"/>
41675 The @var{name} value is required.
41676 Bitfield values may be named with the empty string, @samp{""},
41677 in which case the field is ``filler'' and its value is not printed.
41678 Not all bits need to be specified, so ``filler'' fields are optional.
41680 The @var{start} and @var{end} values are required, and @var{type}
41682 The field's @var{start} must be less than or equal to its @var{end},
41683 and zero represents the least significant bit.
41685 The default value of @var{type} is @code{bool} for single bit fields,
41686 and an unsigned integer otherwise.
41688 Which to choose? Structures or flags?
41690 Registers defined with @samp{flags} have these advantages over
41691 defining them with @samp{struct}:
41695 Arithmetic may be performed on them as if they were integers.
41697 They are printed in a more readable fashion.
41700 Registers defined with @samp{struct} have one advantage over
41701 defining them with @samp{flags}:
41705 One can fetch individual fields like in @samp{C}.
41708 (gdb) print $my_struct_reg.field3
41714 @subsection Registers
41717 Each register is represented as an element with this form:
41720 <reg name="@var{name}"
41721 bitsize="@var{size}"
41722 @r{[}regnum="@var{num}"@r{]}
41723 @r{[}save-restore="@var{save-restore}"@r{]}
41724 @r{[}type="@var{type}"@r{]}
41725 @r{[}group="@var{group}"@r{]}/>
41729 The components are as follows:
41734 The register's name; it must be unique within the target description.
41737 The register's size, in bits.
41740 The register's number. If omitted, a register's number is one greater
41741 than that of the previous register (either in the current feature or in
41742 a preceding feature); the first register in the target description
41743 defaults to zero. This register number is used to read or write
41744 the register; e.g.@: it is used in the remote @code{p} and @code{P}
41745 packets, and registers appear in the @code{g} and @code{G} packets
41746 in order of increasing register number.
41749 Whether the register should be preserved across inferior function
41750 calls; this must be either @code{yes} or @code{no}. The default is
41751 @code{yes}, which is appropriate for most registers except for
41752 some system control registers; this is not related to the target's
41756 The type of the register. It may be a predefined type, a type
41757 defined in the current feature, or one of the special types @code{int}
41758 and @code{float}. @code{int} is an integer type of the correct size
41759 for @var{bitsize}, and @code{float} is a floating point type (in the
41760 architecture's normal floating point format) of the correct size for
41761 @var{bitsize}. The default is @code{int}.
41764 The register group to which this register belongs. It must
41765 be either @code{general}, @code{float}, or @code{vector}. If no
41766 @var{group} is specified, @value{GDBN} will not display the register
41767 in @code{info registers}.
41771 @node Predefined Target Types
41772 @section Predefined Target Types
41773 @cindex target descriptions, predefined types
41775 Type definitions in the self-description can build up composite types
41776 from basic building blocks, but can not define fundamental types. Instead,
41777 standard identifiers are provided by @value{GDBN} for the fundamental
41778 types. The currently supported types are:
41783 Boolean type, occupying a single bit.
41790 Signed integer types holding the specified number of bits.
41797 Unsigned integer types holding the specified number of bits.
41801 Pointers to unspecified code and data. The program counter and
41802 any dedicated return address register may be marked as code
41803 pointers; printing a code pointer converts it into a symbolic
41804 address. The stack pointer and any dedicated address registers
41805 may be marked as data pointers.
41808 Single precision IEEE floating point.
41811 Double precision IEEE floating point.
41814 The 12-byte extended precision format used by ARM FPA registers.
41817 The 10-byte extended precision format used by x87 registers.
41820 32bit @sc{eflags} register used by x86.
41823 32bit @sc{mxcsr} register used by x86.
41827 @node Enum Target Types
41828 @section Enum Target Types
41829 @cindex target descriptions, enum types
41831 Enum target types are useful in @samp{struct} and @samp{flags}
41832 register descriptions. @xref{Target Description Format}.
41834 Enum types have a name, size and a list of name/value pairs.
41837 <enum id="@var{id}" size="@var{size}">
41838 <evalue name="@var{name}" value="@var{value}"/>
41843 Enums must be defined before they are used.
41846 <enum id="levels_type" size="4">
41847 <evalue name="low" value="0"/>
41848 <evalue name="high" value="1"/>
41850 <flags id="flags_type" size="4">
41851 <field name="X" start="0"/>
41852 <field name="LEVEL" start="1" end="1" type="levels_type"/>
41854 <reg name="flags" bitsize="32" type="flags_type"/>
41857 Given that description, a value of 3 for the @samp{flags} register
41858 would be printed as:
41861 (gdb) info register flags
41862 flags 0x3 [ X LEVEL=high ]
41865 @node Standard Target Features
41866 @section Standard Target Features
41867 @cindex target descriptions, standard features
41869 A target description must contain either no registers or all the
41870 target's registers. If the description contains no registers, then
41871 @value{GDBN} will assume a default register layout, selected based on
41872 the architecture. If the description contains any registers, the
41873 default layout will not be used; the standard registers must be
41874 described in the target description, in such a way that @value{GDBN}
41875 can recognize them.
41877 This is accomplished by giving specific names to feature elements
41878 which contain standard registers. @value{GDBN} will look for features
41879 with those names and verify that they contain the expected registers;
41880 if any known feature is missing required registers, or if any required
41881 feature is missing, @value{GDBN} will reject the target
41882 description. You can add additional registers to any of the
41883 standard features --- @value{GDBN} will display them just as if
41884 they were added to an unrecognized feature.
41886 This section lists the known features and their expected contents.
41887 Sample XML documents for these features are included in the
41888 @value{GDBN} source tree, in the directory @file{gdb/features}.
41890 Names recognized by @value{GDBN} should include the name of the
41891 company or organization which selected the name, and the overall
41892 architecture to which the feature applies; so e.g.@: the feature
41893 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41895 The names of registers are not case sensitive for the purpose
41896 of recognizing standard features, but @value{GDBN} will only display
41897 registers using the capitalization used in the description.
41900 * AArch64 Features::
41904 * MicroBlaze Features::
41908 * Nios II Features::
41909 * OpenRISC 1000 Features::
41910 * PowerPC Features::
41911 * S/390 and System z Features::
41917 @node AArch64 Features
41918 @subsection AArch64 Features
41919 @cindex target descriptions, AArch64 features
41921 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41922 targets. It should contain registers @samp{x0} through @samp{x30},
41923 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41925 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41926 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41930 @subsection ARC Features
41931 @cindex target descriptions, ARC Features
41933 ARC processors are highly configurable, so even core registers and their number
41934 are not completely predetermined. In addition flags and PC registers which are
41935 important to @value{GDBN} are not ``core'' registers in ARC. It is required
41936 that one of the core registers features is present.
41937 @samp{org.gnu.gdb.arc.aux-minimal} feature is mandatory.
41939 The @samp{org.gnu.gdb.arc.core.v2} feature is required for ARC EM and ARC HS
41940 targets with a normal register file. It should contain registers @samp{r0}
41941 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41942 @samp{lp_count} and @samp{pcl}. This feature may contain register @samp{ilink}
41943 and any of extension core registers @samp{r32} through @samp{r59/acch}.
41944 @samp{ilink} and extension core registers are not available to read/write, when
41945 debugging GNU/Linux applications, thus @samp{ilink} is made optional.
41947 The @samp{org.gnu.gdb.arc.core-reduced.v2} feature is required for ARC EM and
41948 ARC HS targets with a reduced register file. It should contain registers
41949 @samp{r0} through @samp{r3}, @samp{r10} through @samp{r15}, @samp{gp},
41950 @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink}, @samp{lp_count} and @samp{pcl}.
41951 This feature may contain register @samp{ilink} and any of extension core
41952 registers @samp{r32} through @samp{r59/acch}.
41954 The @samp{org.gnu.gdb.arc.core.arcompact} feature is required for ARCompact
41955 targets with a normal register file. It should contain registers @samp{r0}
41956 through @samp{r25}, @samp{gp}, @samp{fp}, @samp{sp}, @samp{r30}, @samp{blink},
41957 @samp{lp_count} and @samp{pcl}. This feature may contain registers
41958 @samp{ilink1}, @samp{ilink2} and any of extension core registers @samp{r32}
41959 through @samp{r59/acch}. @samp{ilink1} and @samp{ilink2} and extension core
41960 registers are not available when debugging GNU/Linux applications. The only
41961 difference with @samp{org.gnu.gdb.arc.core.v2} feature is in the names of
41962 @samp{ilink1} and @samp{ilink2} registers and that @samp{r30} is mandatory in
41963 ARC v2, but @samp{ilink2} is optional on ARCompact.
41965 The @samp{org.gnu.gdb.arc.aux-minimal} feature is required for all ARC
41966 targets. It should contain registers @samp{pc} and @samp{status32}.
41969 @subsection ARM Features
41970 @cindex target descriptions, ARM features
41972 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41974 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41975 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41977 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41978 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41979 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41982 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41983 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41985 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41986 it should contain at least registers @samp{wR0} through @samp{wR15} and
41987 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41988 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41990 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41991 should contain at least registers @samp{d0} through @samp{d15}. If
41992 they are present, @samp{d16} through @samp{d31} should also be included.
41993 @value{GDBN} will synthesize the single-precision registers from
41994 halves of the double-precision registers.
41996 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41997 need to contain registers; it instructs @value{GDBN} to display the
41998 VFP double-precision registers as vectors and to synthesize the
41999 quad-precision registers from pairs of double-precision registers.
42000 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42001 be present and include 32 double-precision registers.
42003 @node i386 Features
42004 @subsection i386 Features
42005 @cindex target descriptions, i386 features
42007 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42008 targets. It should describe the following registers:
42012 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42014 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42016 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42017 @samp{fs}, @samp{gs}
42019 @samp{st0} through @samp{st7}
42021 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42022 @samp{foseg}, @samp{fooff} and @samp{fop}
42025 The register sets may be different, depending on the target.
42027 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42028 describe registers:
42032 @samp{xmm0} through @samp{xmm7} for i386
42034 @samp{xmm0} through @samp{xmm15} for amd64
42039 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42040 @samp{org.gnu.gdb.i386.sse} feature. It should
42041 describe the upper 128 bits of @sc{ymm} registers:
42045 @samp{ymm0h} through @samp{ymm7h} for i386
42047 @samp{ymm0h} through @samp{ymm15h} for amd64
42050 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
42051 Memory Protection Extension (MPX). It should describe the following registers:
42055 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
42057 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
42060 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42061 describe a single register, @samp{orig_eax}.
42063 The @samp{org.gnu.gdb.i386.segments} feature is optional. It should
42064 describe two system registers: @samp{fs_base} and @samp{gs_base}.
42066 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
42067 @samp{org.gnu.gdb.i386.avx} feature. It should
42068 describe additional @sc{xmm} registers:
42072 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
42075 It should describe the upper 128 bits of additional @sc{ymm} registers:
42079 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
42083 describe the upper 256 bits of @sc{zmm} registers:
42087 @samp{zmm0h} through @samp{zmm7h} for i386.
42089 @samp{zmm0h} through @samp{zmm15h} for amd64.
42093 describe the additional @sc{zmm} registers:
42097 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
42100 The @samp{org.gnu.gdb.i386.pkeys} feature is optional. It should
42101 describe a single register, @samp{pkru}. It is a 32-bit register
42102 valid for i386 and amd64.
42104 @node MicroBlaze Features
42105 @subsection MicroBlaze Features
42106 @cindex target descriptions, MicroBlaze features
42108 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
42109 targets. It should contain registers @samp{r0} through @samp{r31},
42110 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
42111 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
42112 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
42114 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
42115 If present, it should contain registers @samp{rshr} and @samp{rslr}
42117 @node MIPS Features
42118 @subsection @acronym{MIPS} Features
42119 @cindex target descriptions, @acronym{MIPS} features
42121 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42122 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42123 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42126 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42127 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42128 registers. They may be 32-bit or 64-bit depending on the target.
42130 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42131 it may be optional in a future version of @value{GDBN}. It should
42132 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42133 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42135 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42136 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42137 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42138 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42140 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42141 contain a single register, @samp{restart}, which is used by the
42142 Linux kernel to control restartable syscalls.
42144 @node M68K Features
42145 @subsection M68K Features
42146 @cindex target descriptions, M68K features
42149 @item @samp{org.gnu.gdb.m68k.core}
42150 @itemx @samp{org.gnu.gdb.coldfire.core}
42151 @itemx @samp{org.gnu.gdb.fido.core}
42152 One of those features must be always present.
42153 The feature that is present determines which flavor of m68k is
42154 used. The feature that is present should contain registers
42155 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42156 @samp{sp}, @samp{ps} and @samp{pc}.
42158 @item @samp{org.gnu.gdb.coldfire.fp}
42159 This feature is optional. If present, it should contain registers
42160 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42164 @node NDS32 Features
42165 @subsection NDS32 Features
42166 @cindex target descriptions, NDS32 features
42168 The @samp{org.gnu.gdb.nds32.core} feature is required for NDS32
42169 targets. It should contain at least registers @samp{r0} through
42170 @samp{r10}, @samp{r15}, @samp{fp}, @samp{gp}, @samp{lp}, @samp{sp},
42173 The @samp{org.gnu.gdb.nds32.fpu} feature is optional. If present,
42174 it should contain 64-bit double-precision floating-point registers
42175 @samp{fd0} through @emph{fdN}, which should be @samp{fd3}, @samp{fd7},
42176 @samp{fd15}, or @samp{fd31} based on the FPU configuration implemented.
42178 @emph{Note:} The first sixteen 64-bit double-precision floating-point
42179 registers are overlapped with the thirty-two 32-bit single-precision
42180 floating-point registers. The 32-bit single-precision registers, if
42181 not being listed explicitly, will be synthesized from halves of the
42182 overlapping 64-bit double-precision registers. Listing 32-bit
42183 single-precision registers explicitly is deprecated, and the
42184 support to it could be totally removed some day.
42186 @node Nios II Features
42187 @subsection Nios II Features
42188 @cindex target descriptions, Nios II features
42190 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42191 targets. It should contain the 32 core registers (@samp{zero},
42192 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42193 @samp{pc}, and the 16 control registers (@samp{status} through
42196 @node OpenRISC 1000 Features
42197 @subsection Openrisc 1000 Features
42198 @cindex target descriptions, OpenRISC 1000 features
42200 The @samp{org.gnu.gdb.or1k.group0} feature is required for OpenRISC 1000
42201 targets. It should contain the 32 general purpose registers (@samp{r0}
42202 through @samp{r31}), @samp{ppc}, @samp{npc} and @samp{sr}.
42204 @node PowerPC Features
42205 @subsection PowerPC Features
42206 @cindex target descriptions, PowerPC features
42208 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42209 targets. It should contain registers @samp{r0} through @samp{r31},
42210 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42211 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42213 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42214 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42216 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42217 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42220 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42221 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42222 will combine these registers with the floating point registers
42223 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42224 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42225 through @samp{vs63}, the set of vector registers for POWER7.
42227 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42228 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42229 @samp{spefscr}. SPE targets should provide 32-bit registers in
42230 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42231 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42232 these to present registers @samp{ev0} through @samp{ev31} to the
42235 @node S/390 and System z Features
42236 @subsection S/390 and System z Features
42237 @cindex target descriptions, S/390 features
42238 @cindex target descriptions, System z features
42240 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42241 System z targets. It should contain the PSW and the 16 general
42242 registers. In particular, System z targets should provide the 64-bit
42243 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42244 S/390 targets should provide the 32-bit versions of these registers.
42245 A System z target that runs in 31-bit addressing mode should provide
42246 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42247 register's upper halves @samp{r0h} through @samp{r15h}, and their
42248 lower halves @samp{r0l} through @samp{r15l}.
42250 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42251 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42254 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42255 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42257 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42258 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42259 targets and 32-bit otherwise. In addition, the feature may contain
42260 the @samp{last_break} register, whose width depends on the addressing
42261 mode, as well as the @samp{system_call} register, which is always
42264 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42265 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42266 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42268 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
42269 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
42270 combined by @value{GDBN} with the floating point registers @samp{f0}
42271 through @samp{f15} to present the 128-bit wide vector registers
42272 @samp{v0} through @samp{v15}. In addition, this feature should
42273 contain the 128-bit wide vector registers @samp{v16} through
42276 The @samp{org.gnu.gdb.s390.gs} feature is optional. It should contain
42277 the 64-bit wide guarded-storage-control registers @samp{gsd},
42278 @samp{gssm}, and @samp{gsepla}.
42280 The @samp{org.gnu.gdb.s390.gsbc} feature is optional. It should contain
42281 the 64-bit wide guarded-storage broadcast control registers
42282 @samp{bc_gsd}, @samp{bc_gssm}, and @samp{bc_gsepla}.
42284 @node Sparc Features
42285 @subsection Sparc Features
42286 @cindex target descriptions, sparc32 features
42287 @cindex target descriptions, sparc64 features
42288 The @samp{org.gnu.gdb.sparc.cpu} feature is required for sparc32/sparc64
42289 targets. It should describe the following registers:
42293 @samp{g0} through @samp{g7}
42295 @samp{o0} through @samp{o7}
42297 @samp{l0} through @samp{l7}
42299 @samp{i0} through @samp{i7}
42302 They may be 32-bit or 64-bit depending on the target.
42304 Also the @samp{org.gnu.gdb.sparc.fpu} feature is required for sparc32/sparc64
42305 targets. It should describe the following registers:
42309 @samp{f0} through @samp{f31}
42311 @samp{f32} through @samp{f62} for sparc64
42314 The @samp{org.gnu.gdb.sparc.cp0} feature is required for sparc32/sparc64
42315 targets. It should describe the following registers:
42319 @samp{y}, @samp{psr}, @samp{wim}, @samp{tbr}, @samp{pc}, @samp{npc},
42320 @samp{fsr}, and @samp{csr} for sparc32
42322 @samp{pc}, @samp{npc}, @samp{state}, @samp{fsr}, @samp{fprs}, and @samp{y}
42326 @node TIC6x Features
42327 @subsection TMS320C6x Features
42328 @cindex target descriptions, TIC6x features
42329 @cindex target descriptions, TMS320C6x features
42330 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42331 targets. It should contain registers @samp{A0} through @samp{A15},
42332 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42334 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42335 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42336 through @samp{B31}.
42338 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42339 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42341 @node Operating System Information
42342 @appendix Operating System Information
42343 @cindex operating system information
42349 Users of @value{GDBN} often wish to obtain information about the state of
42350 the operating system running on the target---for example the list of
42351 processes, or the list of open files. This section describes the
42352 mechanism that makes it possible. This mechanism is similar to the
42353 target features mechanism (@pxref{Target Descriptions}), but focuses
42354 on a different aspect of target.
42356 Operating system information is retrived from the target via the
42357 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42358 read}). The object name in the request should be @samp{osdata}, and
42359 the @var{annex} identifies the data to be fetched.
42362 @appendixsection Process list
42363 @cindex operating system information, process list
42365 When requesting the process list, the @var{annex} field in the
42366 @samp{qXfer} request should be @samp{processes}. The returned data is
42367 an XML document. The formal syntax of this document is defined in
42368 @file{gdb/features/osdata.dtd}.
42370 An example document is:
42373 <?xml version="1.0"?>
42374 <!DOCTYPE target SYSTEM "osdata.dtd">
42375 <osdata type="processes">
42377 <column name="pid">1</column>
42378 <column name="user">root</column>
42379 <column name="command">/sbin/init</column>
42380 <column name="cores">1,2,3</column>
42385 Each item should include a column whose name is @samp{pid}. The value
42386 of that column should identify the process on the target. The
42387 @samp{user} and @samp{command} columns are optional, and will be
42388 displayed by @value{GDBN}. The @samp{cores} column, if present,
42389 should contain a comma-separated list of cores that this process
42390 is running on. Target may provide additional columns,
42391 which @value{GDBN} currently ignores.
42393 @node Trace File Format
42394 @appendix Trace File Format
42395 @cindex trace file format
42397 The trace file comes in three parts: a header, a textual description
42398 section, and a trace frame section with binary data.
42400 The header has the form @code{\x7fTRACE0\n}. The first byte is
42401 @code{0x7f} so as to indicate that the file contains binary data,
42402 while the @code{0} is a version number that may have different values
42405 The description section consists of multiple lines of @sc{ascii} text
42406 separated by newline characters (@code{0xa}). The lines may include a
42407 variety of optional descriptive or context-setting information, such
42408 as tracepoint definitions or register set size. @value{GDBN} will
42409 ignore any line that it does not recognize. An empty line marks the end
42414 Specifies the size of a register block in bytes. This is equal to the
42415 size of a @code{g} packet payload in the remote protocol. @var{size}
42416 is an ascii decimal number. There should be only one such line in
42417 a single trace file.
42419 @item status @var{status}
42420 Trace status. @var{status} has the same format as a @code{qTStatus}
42421 remote packet reply. There should be only one such line in a single trace
42424 @item tp @var{payload}
42425 Tracepoint definition. The @var{payload} has the same format as
42426 @code{qTfP}/@code{qTsP} remote packet reply payload. A single tracepoint
42427 may take multiple lines of definition, corresponding to the multiple
42430 @item tsv @var{payload}
42431 Trace state variable definition. The @var{payload} has the same format as
42432 @code{qTfV}/@code{qTsV} remote packet reply payload. A single variable
42433 may take multiple lines of definition, corresponding to the multiple
42436 @item tdesc @var{payload}
42437 Target description in XML format. The @var{payload} is a single line of
42438 the XML file. All such lines should be concatenated together to get
42439 the original XML file. This file is in the same format as @code{qXfer}
42440 @code{features} payload, and corresponds to the main @code{target.xml}
42441 file. Includes are not allowed.
42445 The trace frame section consists of a number of consecutive frames.
42446 Each frame begins with a two-byte tracepoint number, followed by a
42447 four-byte size giving the amount of data in the frame. The data in
42448 the frame consists of a number of blocks, each introduced by a
42449 character indicating its type (at least register, memory, and trace
42450 state variable). The data in this section is raw binary, not a
42451 hexadecimal or other encoding; its endianness matches the target's
42454 @c FIXME bi-arch may require endianness/arch info in description section
42457 @item R @var{bytes}
42458 Register block. The number and ordering of bytes matches that of a
42459 @code{g} packet in the remote protocol. Note that these are the
42460 actual bytes, in target order, not a hexadecimal encoding.
42462 @item M @var{address} @var{length} @var{bytes}...
42463 Memory block. This is a contiguous block of memory, at the 8-byte
42464 address @var{address}, with a 2-byte length @var{length}, followed by
42465 @var{length} bytes.
42467 @item V @var{number} @var{value}
42468 Trace state variable block. This records the 8-byte signed value
42469 @var{value} of trace state variable numbered @var{number}.
42473 Future enhancements of the trace file format may include additional types
42476 @node Index Section Format
42477 @appendix @code{.gdb_index} section format
42478 @cindex .gdb_index section format
42479 @cindex index section format
42481 This section documents the index section that is created by @code{save
42482 gdb-index} (@pxref{Index Files}). The index section is
42483 DWARF-specific; some knowledge of DWARF is assumed in this
42486 The mapped index file format is designed to be directly
42487 @code{mmap}able on any architecture. In most cases, a datum is
42488 represented using a little-endian 32-bit integer value, called an
42489 @code{offset_type}. Big endian machines must byte-swap the values
42490 before using them. Exceptions to this rule are noted. The data is
42491 laid out such that alignment is always respected.
42493 A mapped index consists of several areas, laid out in order.
42497 The file header. This is a sequence of values, of @code{offset_type}
42498 unless otherwise noted:
42502 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42503 Version 4 uses a different hashing function from versions 5 and 6.
42504 Version 6 includes symbols for inlined functions, whereas versions 4
42505 and 5 do not. Version 7 adds attributes to the CU indices in the
42506 symbol table. Version 8 specifies that symbols from DWARF type units
42507 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42508 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42510 @value{GDBN} will only read version 4, 5, or 6 indices
42511 by specifying @code{set use-deprecated-index-sections on}.
42512 GDB has a workaround for potentially broken version 7 indices so it is
42513 currently not flagged as deprecated.
42516 The offset, from the start of the file, of the CU list.
42519 The offset, from the start of the file, of the types CU list. Note
42520 that this area can be empty, in which case this offset will be equal
42521 to the next offset.
42524 The offset, from the start of the file, of the address area.
42527 The offset, from the start of the file, of the symbol table.
42530 The offset, from the start of the file, of the constant pool.
42534 The CU list. This is a sequence of pairs of 64-bit little-endian
42535 values, sorted by the CU offset. The first element in each pair is
42536 the offset of a CU in the @code{.debug_info} section. The second
42537 element in each pair is the length of that CU. References to a CU
42538 elsewhere in the map are done using a CU index, which is just the
42539 0-based index into this table. Note that if there are type CUs, then
42540 conceptually CUs and type CUs form a single list for the purposes of
42544 The types CU list. This is a sequence of triplets of 64-bit
42545 little-endian values. In a triplet, the first value is the CU offset,
42546 the second value is the type offset in the CU, and the third value is
42547 the type signature. The types CU list is not sorted.
42550 The address area. The address area consists of a sequence of address
42551 entries. Each address entry has three elements:
42555 The low address. This is a 64-bit little-endian value.
42558 The high address. This is a 64-bit little-endian value. Like
42559 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42562 The CU index. This is an @code{offset_type} value.
42566 The symbol table. This is an open-addressed hash table. The size of
42567 the hash table is always a power of 2.
42569 Each slot in the hash table consists of a pair of @code{offset_type}
42570 values. The first value is the offset of the symbol's name in the
42571 constant pool. The second value is the offset of the CU vector in the
42574 If both values are 0, then this slot in the hash table is empty. This
42575 is ok because while 0 is a valid constant pool index, it cannot be a
42576 valid index for both a string and a CU vector.
42578 The hash value for a table entry is computed by applying an
42579 iterative hash function to the symbol's name. Starting with an
42580 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42581 the string is incorporated into the hash using the formula depending on the
42586 The formula is @code{r = r * 67 + c - 113}.
42588 @item Versions 5 to 7
42589 The formula is @code{r = r * 67 + tolower (c) - 113}.
42592 The terminating @samp{\0} is not incorporated into the hash.
42594 The step size used in the hash table is computed via
42595 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42596 value, and @samp{size} is the size of the hash table. The step size
42597 is used to find the next candidate slot when handling a hash
42600 The names of C@t{++} symbols in the hash table are canonicalized. We
42601 don't currently have a simple description of the canonicalization
42602 algorithm; if you intend to create new index sections, you must read
42606 The constant pool. This is simply a bunch of bytes. It is organized
42607 so that alignment is correct: CU vectors are stored first, followed by
42610 A CU vector in the constant pool is a sequence of @code{offset_type}
42611 values. The first value is the number of CU indices in the vector.
42612 Each subsequent value is the index and symbol attributes of a CU in
42613 the CU list. This element in the hash table is used to indicate which
42614 CUs define the symbol and how the symbol is used.
42615 See below for the format of each CU index+attributes entry.
42617 A string in the constant pool is zero-terminated.
42620 Attributes were added to CU index values in @code{.gdb_index} version 7.
42621 If a symbol has multiple uses within a CU then there is one
42622 CU index+attributes value for each use.
42624 The format of each CU index+attributes entry is as follows
42630 This is the index of the CU in the CU list.
42632 These bits are reserved for future purposes and must be zero.
42634 The kind of the symbol in the CU.
42638 This value is reserved and should not be used.
42639 By reserving zero the full @code{offset_type} value is backwards compatible
42640 with previous versions of the index.
42642 The symbol is a type.
42644 The symbol is a variable or an enum value.
42646 The symbol is a function.
42648 Any other kind of symbol.
42650 These values are reserved.
42654 This bit is zero if the value is global and one if it is static.
42656 The determination of whether a symbol is global or static is complicated.
42657 The authorative reference is the file @file{dwarf2read.c} in
42658 @value{GDBN} sources.
42662 This pseudo-code describes the computation of a symbol's kind and
42663 global/static attributes in the index.
42666 is_external = get_attribute (die, DW_AT_external);
42667 language = get_attribute (cu_die, DW_AT_language);
42670 case DW_TAG_typedef:
42671 case DW_TAG_base_type:
42672 case DW_TAG_subrange_type:
42676 case DW_TAG_enumerator:
42678 is_static = language != CPLUS;
42680 case DW_TAG_subprogram:
42682 is_static = ! (is_external || language == ADA);
42684 case DW_TAG_constant:
42686 is_static = ! is_external;
42688 case DW_TAG_variable:
42690 is_static = ! is_external;
42692 case DW_TAG_namespace:
42696 case DW_TAG_class_type:
42697 case DW_TAG_interface_type:
42698 case DW_TAG_structure_type:
42699 case DW_TAG_union_type:
42700 case DW_TAG_enumeration_type:
42702 is_static = language != CPLUS;
42710 @appendix Manual pages
42714 * gdb man:: The GNU Debugger man page
42715 * gdbserver man:: Remote Server for the GNU Debugger man page
42716 * gcore man:: Generate a core file of a running program
42717 * gdbinit man:: gdbinit scripts
42723 @c man title gdb The GNU Debugger
42725 @c man begin SYNOPSIS gdb
42726 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
42727 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
42728 [@option{-b}@w{ }@var{bps}]
42729 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
42730 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
42731 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
42732 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
42733 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
42736 @c man begin DESCRIPTION gdb
42737 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
42738 going on ``inside'' another program while it executes -- or what another
42739 program was doing at the moment it crashed.
42741 @value{GDBN} can do four main kinds of things (plus other things in support of
42742 these) to help you catch bugs in the act:
42746 Start your program, specifying anything that might affect its behavior.
42749 Make your program stop on specified conditions.
42752 Examine what has happened, when your program has stopped.
42755 Change things in your program, so you can experiment with correcting the
42756 effects of one bug and go on to learn about another.
42759 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
42762 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
42763 commands from the terminal until you tell it to exit with the @value{GDBN}
42764 command @code{quit}. You can get online help from @value{GDBN} itself
42765 by using the command @code{help}.
42767 You can run @code{gdb} with no arguments or options; but the most
42768 usual way to start @value{GDBN} is with one argument or two, specifying an
42769 executable program as the argument:
42775 You can also start with both an executable program and a core file specified:
42781 You can, instead, specify a process ID as a second argument, if you want
42782 to debug a running process:
42790 would attach @value{GDBN} to process @code{1234} (unless you also have a file
42791 named @file{1234}; @value{GDBN} does check for a core file first).
42792 With option @option{-p} you can omit the @var{program} filename.
42794 Here are some of the most frequently needed @value{GDBN} commands:
42796 @c pod2man highlights the right hand side of the @item lines.
42798 @item break [@var{file}:]@var{function}
42799 Set a breakpoint at @var{function} (in @var{file}).
42801 @item run [@var{arglist}]
42802 Start your program (with @var{arglist}, if specified).
42805 Backtrace: display the program stack.
42807 @item print @var{expr}
42808 Display the value of an expression.
42811 Continue running your program (after stopping, e.g. at a breakpoint).
42814 Execute next program line (after stopping); step @emph{over} any
42815 function calls in the line.
42817 @item edit [@var{file}:]@var{function}
42818 look at the program line where it is presently stopped.
42820 @item list [@var{file}:]@var{function}
42821 type the text of the program in the vicinity of where it is presently stopped.
42824 Execute next program line (after stopping); step @emph{into} any
42825 function calls in the line.
42827 @item help [@var{name}]
42828 Show information about @value{GDBN} command @var{name}, or general information
42829 about using @value{GDBN}.
42832 Exit from @value{GDBN}.
42836 For full details on @value{GDBN},
42837 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42838 by Richard M. Stallman and Roland H. Pesch. The same text is available online
42839 as the @code{gdb} entry in the @code{info} program.
42843 @c man begin OPTIONS gdb
42844 Any arguments other than options specify an executable
42845 file and core file (or process ID); that is, the first argument
42846 encountered with no
42847 associated option flag is equivalent to a @option{-se} option, and the second,
42848 if any, is equivalent to a @option{-c} option if it's the name of a file.
42850 both long and short forms; both are shown here. The long forms are also
42851 recognized if you truncate them, so long as enough of the option is
42852 present to be unambiguous. (If you prefer, you can flag option
42853 arguments with @option{+} rather than @option{-}, though we illustrate the
42854 more usual convention.)
42856 All the options and command line arguments you give are processed
42857 in sequential order. The order makes a difference when the @option{-x}
42863 List all options, with brief explanations.
42865 @item -symbols=@var{file}
42866 @itemx -s @var{file}
42867 Read symbol table from file @var{file}.
42870 Enable writing into executable and core files.
42872 @item -exec=@var{file}
42873 @itemx -e @var{file}
42874 Use file @var{file} as the executable file to execute when
42875 appropriate, and for examining pure data in conjunction with a core
42878 @item -se=@var{file}
42879 Read symbol table from file @var{file} and use it as the executable
42882 @item -core=@var{file}
42883 @itemx -c @var{file}
42884 Use file @var{file} as a core dump to examine.
42886 @item -command=@var{file}
42887 @itemx -x @var{file}
42888 Execute @value{GDBN} commands from file @var{file}.
42890 @item -ex @var{command}
42891 Execute given @value{GDBN} @var{command}.
42893 @item -directory=@var{directory}
42894 @itemx -d @var{directory}
42895 Add @var{directory} to the path to search for source files.
42898 Do not execute commands from @file{~/.gdbinit}.
42902 Do not execute commands from any @file{.gdbinit} initialization files.
42906 ``Quiet''. Do not print the introductory and copyright messages. These
42907 messages are also suppressed in batch mode.
42910 Run in batch mode. Exit with status @code{0} after processing all the command
42911 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
42912 Exit with nonzero status if an error occurs in executing the @value{GDBN}
42913 commands in the command files.
42915 Batch mode may be useful for running @value{GDBN} as a filter, for example to
42916 download and run a program on another computer; in order to make this
42917 more useful, the message
42920 Program exited normally.
42924 (which is ordinarily issued whenever a program running under @value{GDBN} control
42925 terminates) is not issued when running in batch mode.
42927 @item -cd=@var{directory}
42928 Run @value{GDBN} using @var{directory} as its working directory,
42929 instead of the current directory.
42933 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
42934 @value{GDBN} to output the full file name and line number in a standard,
42935 recognizable fashion each time a stack frame is displayed (which
42936 includes each time the program stops). This recognizable format looks
42937 like two @samp{\032} characters, followed by the file name, line number
42938 and character position separated by colons, and a newline. The
42939 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
42940 characters as a signal to display the source code for the frame.
42943 Set the line speed (baud rate or bits per second) of any serial
42944 interface used by @value{GDBN} for remote debugging.
42946 @item -tty=@var{device}
42947 Run using @var{device} for your program's standard input and output.
42951 @c man begin SEEALSO gdb
42953 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
42954 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
42955 documentation are properly installed at your site, the command
42962 should give you access to the complete manual.
42964 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
42965 Richard M. Stallman and Roland H. Pesch, July 1991.
42969 @node gdbserver man
42970 @heading gdbserver man
42972 @c man title gdbserver Remote Server for the GNU Debugger
42974 @c man begin SYNOPSIS gdbserver
42975 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
42977 gdbserver --attach @var{comm} @var{pid}
42979 gdbserver --multi @var{comm}
42983 @c man begin DESCRIPTION gdbserver
42984 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
42985 than the one which is running the program being debugged.
42988 @subheading Usage (server (target) side)
42991 Usage (server (target) side):
42994 First, you need to have a copy of the program you want to debug put onto
42995 the target system. The program can be stripped to save space if needed, as
42996 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
42997 the @value{GDBN} running on the host system.
42999 To use the server, you log on to the target system, and run the @command{gdbserver}
43000 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43001 your program, and (c) its arguments. The general syntax is:
43004 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43007 For example, using a serial port, you might say:
43011 @c @file would wrap it as F</dev/com1>.
43012 target> gdbserver /dev/com1 emacs foo.txt
43015 target> gdbserver @file{/dev/com1} emacs foo.txt
43019 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43020 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43021 waits patiently for the host @value{GDBN} to communicate with it.
43023 To use a TCP connection, you could say:
43026 target> gdbserver host:2345 emacs foo.txt
43029 This says pretty much the same thing as the last example, except that we are
43030 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43031 that we are expecting to see a TCP connection from @code{host} to local TCP port
43032 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43033 want for the port number as long as it does not conflict with any existing TCP
43034 ports on the target system. This same port number must be used in the host
43035 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43036 you chose a port number that conflicts with another service, @command{gdbserver} will
43037 print an error message and exit.
43039 @command{gdbserver} can also attach to running programs.
43040 This is accomplished via the @option{--attach} argument. The syntax is:
43043 target> gdbserver --attach @var{comm} @var{pid}
43046 @var{pid} is the process ID of a currently running process. It isn't
43047 necessary to point @command{gdbserver} at a binary for the running process.
43049 To start @code{gdbserver} without supplying an initial command to run
43050 or process ID to attach, use the @option{--multi} command line option.
43051 In such case you should connect using @kbd{target extended-remote} to start
43052 the program you want to debug.
43055 target> gdbserver --multi @var{comm}
43059 @subheading Usage (host side)
43065 You need an unstripped copy of the target program on your host system, since
43066 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43067 would, with the target program as the first argument. (You may need to use the
43068 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43069 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43070 new command you need to know about is @code{target remote}
43071 (or @code{target extended-remote}). Its argument is either
43072 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43073 descriptor. For example:
43077 @c @file would wrap it as F</dev/ttyb>.
43078 (gdb) target remote /dev/ttyb
43081 (gdb) target remote @file{/dev/ttyb}
43086 communicates with the server via serial line @file{/dev/ttyb}, and:
43089 (gdb) target remote the-target:2345
43093 communicates via a TCP connection to port 2345 on host `the-target', where
43094 you previously started up @command{gdbserver} with the same port number. Note that for
43095 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43096 command, otherwise you may get an error that looks something like
43097 `Connection refused'.
43099 @command{gdbserver} can also debug multiple inferiors at once,
43102 the @value{GDBN} manual in node @code{Inferiors and Programs}
43103 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43106 @ref{Inferiors and Programs}.
43108 In such case use the @code{extended-remote} @value{GDBN} command variant:
43111 (gdb) target extended-remote the-target:2345
43114 The @command{gdbserver} option @option{--multi} may or may not be used in such
43118 @c man begin OPTIONS gdbserver
43119 There are three different modes for invoking @command{gdbserver}:
43124 Debug a specific program specified by its program name:
43127 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43130 The @var{comm} parameter specifies how should the server communicate
43131 with @value{GDBN}; it is either a device name (to use a serial line),
43132 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43133 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43134 debug in @var{prog}. Any remaining arguments will be passed to the
43135 program verbatim. When the program exits, @value{GDBN} will close the
43136 connection, and @code{gdbserver} will exit.
43139 Debug a specific program by specifying the process ID of a running
43143 gdbserver --attach @var{comm} @var{pid}
43146 The @var{comm} parameter is as described above. Supply the process ID
43147 of a running program in @var{pid}; @value{GDBN} will do everything
43148 else. Like with the previous mode, when the process @var{pid} exits,
43149 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43152 Multi-process mode -- debug more than one program/process:
43155 gdbserver --multi @var{comm}
43158 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43159 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43160 close the connection when a process being debugged exits, so you can
43161 debug several processes in the same session.
43164 In each of the modes you may specify these options:
43169 List all options, with brief explanations.
43172 This option causes @command{gdbserver} to print its version number and exit.
43175 @command{gdbserver} will attach to a running program. The syntax is:
43178 target> gdbserver --attach @var{comm} @var{pid}
43181 @var{pid} is the process ID of a currently running process. It isn't
43182 necessary to point @command{gdbserver} at a binary for the running process.
43185 To start @code{gdbserver} without supplying an initial command to run
43186 or process ID to attach, use this command line option.
43187 Then you can connect using @kbd{target extended-remote} and start
43188 the program you want to debug. The syntax is:
43191 target> gdbserver --multi @var{comm}
43195 Instruct @code{gdbserver} to display extra status information about the debugging
43197 This option is intended for @code{gdbserver} development and for bug reports to
43200 @item --remote-debug
43201 Instruct @code{gdbserver} to display remote protocol debug output.
43202 This option is intended for @code{gdbserver} development and for bug reports to
43205 @item --debug-format=option1@r{[},option2,...@r{]}
43206 Instruct @code{gdbserver} to include extra information in each line
43207 of debugging output.
43208 @xref{Other Command-Line Arguments for gdbserver}.
43211 Specify a wrapper to launch programs
43212 for debugging. The option should be followed by the name of the
43213 wrapper, then any command-line arguments to pass to the wrapper, then
43214 @kbd{--} indicating the end of the wrapper arguments.
43217 By default, @command{gdbserver} keeps the listening TCP port open, so that
43218 additional connections are possible. However, if you start @code{gdbserver}
43219 with the @option{--once} option, it will stop listening for any further
43220 connection attempts after connecting to the first @value{GDBN} session.
43222 @c --disable-packet is not documented for users.
43224 @c --disable-randomization and --no-disable-randomization are superseded by
43225 @c QDisableRandomization.
43230 @c man begin SEEALSO gdbserver
43232 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43233 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43234 documentation are properly installed at your site, the command
43240 should give you access to the complete manual.
43242 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43243 Richard M. Stallman and Roland H. Pesch, July 1991.
43250 @c man title gcore Generate a core file of a running program
43253 @c man begin SYNOPSIS gcore
43254 gcore [-a] [-o @var{filename}] @var{pid}
43258 @c man begin DESCRIPTION gcore
43259 Generate a core dump of a running program with process ID @var{pid}.
43260 Produced file is equivalent to a kernel produced core file as if the process
43261 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43262 limit). Unlike after a crash, after @command{gcore} the program remains
43263 running without any change.
43266 @c man begin OPTIONS gcore
43269 Dump all memory mappings. The actual effect of this option depends on
43270 the Operating System. On @sc{gnu}/Linux, it will disable
43271 @code{use-coredump-filter} (@pxref{set use-coredump-filter}) and
43272 enable @code{dump-excluded-mappings} (@pxref{set
43273 dump-excluded-mappings}).
43275 @item -o @var{filename}
43276 The optional argument
43277 @var{filename} specifies the file name where to put the core dump.
43278 If not specified, the file name defaults to @file{core.@var{pid}},
43279 where @var{pid} is the running program process ID.
43283 @c man begin SEEALSO gcore
43285 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43286 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43287 documentation are properly installed at your site, the command
43294 should give you access to the complete manual.
43296 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43297 Richard M. Stallman and Roland H. Pesch, July 1991.
43304 @c man title gdbinit GDB initialization scripts
43307 @c man begin SYNOPSIS gdbinit
43308 @ifset SYSTEM_GDBINIT
43309 @value{SYSTEM_GDBINIT}
43318 @c man begin DESCRIPTION gdbinit
43319 These files contain @value{GDBN} commands to automatically execute during
43320 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43323 the @value{GDBN} manual in node @code{Sequences}
43324 -- shell command @code{info -f gdb -n Sequences}.
43330 Please read more in
43332 the @value{GDBN} manual in node @code{Startup}
43333 -- shell command @code{info -f gdb -n Startup}.
43340 @ifset SYSTEM_GDBINIT
43341 @item @value{SYSTEM_GDBINIT}
43343 @ifclear SYSTEM_GDBINIT
43344 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43346 System-wide initialization file. It is executed unless user specified
43347 @value{GDBN} option @code{-nx} or @code{-n}.
43350 the @value{GDBN} manual in node @code{System-wide configuration}
43351 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43354 @ref{System-wide configuration}.
43358 User initialization file. It is executed unless user specified
43359 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43362 Initialization file for current directory. It may need to be enabled with
43363 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43366 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43367 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43370 @ref{Init File in the Current Directory}.
43375 @c man begin SEEALSO gdbinit
43377 gdb(1), @code{info -f gdb -n Startup}
43379 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43380 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43381 documentation are properly installed at your site, the command
43387 should give you access to the complete manual.
43389 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43390 Richard M. Stallman and Roland H. Pesch, July 1991.
43396 @node GNU Free Documentation License
43397 @appendix GNU Free Documentation License
43400 @node Concept Index
43401 @unnumbered Concept Index
43405 @node Command and Variable Index
43406 @unnumbered Command, Variable, and Function Index
43411 % I think something like @@colophon should be in texinfo. In the
43413 \long\def\colophon{\hbox to0pt{}\vfill
43414 \centerline{The body of this manual is set in}
43415 \centerline{\fontname\tenrm,}
43416 \centerline{with headings in {\bf\fontname\tenbf}}
43417 \centerline{and examples in {\tt\fontname\tentt}.}
43418 \centerline{{\it\fontname\tenit\/},}
43419 \centerline{{\bf\fontname\tenbf}, and}
43420 \centerline{{\sl\fontname\tensl\/}}
43421 \centerline{are used for emphasis.}\vfill}
43423 % Blame: doc@@cygnus.com, 1991.